Title:
CAVITATION-DETERRING ENERGY-EFFICIENT FLUID PUMP SYSTEM AND METHOD OF OPERATION
Kind Code:
A1


Abstract:
A variable nozzle area jet pump is provided having a nozzle-sealing member resiliently urged to form a sealing closure. The sealing member is part of a normally non-passing pressure control valve that recirculates excess fluid back to the inlet of a positive displacement fluid pump. The fluid is recirculated with elevated pressure after a threshold fluid pressure is exceeded. The disclosed system provides for energy conservation and pump cavitation speed increase. The system may be integrated with an engine balance shaft module so as to provide low cost robustness to low speed gear noise emissions by application of the oil pump's drive torque to at lease one gearset.



Inventors:
Killion, David L. (Clarkston, MI, US)
Application Number:
12/113592
Publication Date:
11/06/2008
Filing Date:
05/01/2008
Assignee:
METALDYNE COMPANY LLC. (Plymouth, MI, US)
Primary Class:
Other Classes:
123/90.33, 123/196R, 417/186, 417/189, 417/190
International Classes:
F04F5/44; F01M1/02; F04F5/50
View Patent Images:
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Primary Examiner:
LETTMAN, BRYAN MATTHEW
Attorney, Agent or Firm:
CANTOR COLBURN, LLP (20 Church Street, 22nd Floor, Hartford, CT, 06103, US)
Claims:
What is claimed is:

1. A pump system comprising: a first positive displacement pump having an inlet passage and a discharge passage; and an adjustable nozzle jet pump valve having: a supply chamber fluidly coupled to said discharge passage, said supply chamber further having a port with a seat surface; a movable valve member having a sealing surface in sealing contact with said seat surface when in a first position, and a body portion, said body portion further having a first face sealingly positioned within said supply chamber, and an opposing second face, said first face having a first surface area; an urging member coupled to said second face; a suction chamber fluidly coupled to said port; a throat passage fluidly coupled to said suction chamber and said inlet passage wherein said port, said suction chamber and said throat passage are arranged in a continuous serial fluid connection to said inlet passage.

2. The pump system of claim 1 wherein said adjustable nozzle jet pump valve includes an orifice fluidly coupled to said second face.

3. The pump system of claim 2 wherein said orifice is vented to atmospheric pressure.

4. The pump system of claim 2 wherein said venting to atmospheric pressure is by means of fluid coupling with an oil reservoir exposed to atmospheric pressure.

5. The pump system of claim 1 wherein said urging member is a spring arranged to bias said movable valve member sealing surface against said seat.

6. The pump system of claim 1 wherein said urging member is an electromechanical actuator.

7. The pump system of claim 1 further comprising: an uptake passage fluidly coupled to said suction chamber and to a fluid reservoir; and, a one-way check valve fluidly coupled between a fluid reservoir and said inlet passage.

8. The pump system of claim 1 wherein said throat passage comprises an entry bell for smoothing the acceleration of flows entering said throat passage, said entry bell having outside diameter larger than an outside diameter circumscribing said throat passage.

9. The pump system of claim 1 wherein said adjustable nozzle jet pump valve includes a diaphragm member coupled to said body portion.

10. The pump system of claim 1 wherein said adjustable nozzle jet pump valve includes a bellows member coupled to said body portion.

11. The pump system of claim 1 further comprising: a fluid reservoir fluidly coupled to said suction chamber; and, a second positive displacement pump fluidly coupled between said fluid reservoir and said discharge passage.

12. The pump system of claim 1 wherein said adjustable nozzle jet pump valve further comprises a pilot chamber positioned between said body member and said supply chamber.

13. A pump system for a variable consumptive load, said system comprising: a first positive displacement pump, said pump having an inlet passage and a discharge passage, wherein said discharge passage is arranged to couple with said variable consumptive load; a jet pump valve having a variable nozzle opening area fluidly coupled between said discharge passage and said inlet passage, said jet pump valve including means for changing the area of said variable nozzle opening in direct response to changes in fluid pressure in said discharge passage, said jet pump valve further including an urging member arranged to bias a member to close said variable nozzle opening; said jet pump valve further having a suction chamber adjacent said variable nozzle opening and arranged to receive fluid from said variable nozzle opening and from a fluid reservoir; said jet pump valve further having a throat passage coupled to said suction chamber, said throat passage being fluidly coupled to receive fluid from said reservoir and from said variable valve opening, and to transfer said received fluid to said inlet passage.

14. The pump system of claim 13 wherein: said means for changing the size of said variable nozzle opening comprises: a supply chamber in direct fluid connection to said discharge line; and, a valve body movable between a first position and a second position, said valve body having a sealing member with a first cross sectional area and a first face with a second surface, where in said second surface's area is greater than said first cross sectional area, and wherein said sealing member is in contact with and closes said variable nozzle opening when said valve body is in said first position.

15. The pump system of claim 14 further comprising a damping chamber, wherein a portion of said valve body forms a portion of one side of said damping chamber.

16. The pump system of claim 15 further comprising a damping orifice fluidly coupled to said damping chamber.

17. The pump system of claim 16 wherein said damping orifice is vented to atmospheric pressure by means of fluid coupling with an oil reservoir exposed to atmospheric pressure.

18. The pump system of claim 13 further comprising: a fluid reservoir fluidly coupled to said first positive displacement pump; and, a second positive displacement pump fluidly coupled between to said fluid reservoir and said discharge passage.

19. The pump system of claim 18 further comprising a bypass passage fluidly coupled to said supply chamber when said valve body is in said second position.

20. The pump system of claim 13 further comprising a one way check valve fluidly coupled between said reservoir and said inlet passage adjacent one end of said throat passage opposite said inlet transition region.

21. The pump system of claim 20 wherein said valve is a ball and seat type valve or a reed type valve.

22. The pump system of claim 20 wherein said valve includes a member having a substantially cup-shaped cross-section, and a seat, said cup shape having sides which slidingly engage a pilot member for locating of a face area of said cup-shaped member in sealable proximity to said seat.

23. The pump system of claim 13 wherein said urging member is a compression spring.

24. The pump system of claim 13 wherein said urging member is an electromechanical actuator.

25. The pump system of claim 14 further comprising a pilot pressure chamber adjacent said first face, wherein said pilot pressure chamber having a partition wall that inhibits flow from said supply chamber to said pilot pressure chamber.

26. The pump system of claim 25 further comprising a seal arranged between said supply chamber and said pilot pressure chamber.

27. The pump system of claim 13 wherein said throat passage further includes an inlet transition region coupled to said suction chamber.

28. The pump system of claim 13 wherein said means for changing the area of said variable nozzle opening is in direct response to changes in fluid pressure in said consumptive load.

29. The pump system of claim 13 further comprising an actuator movable between a first position and a second position, said actuator being coupled to said urging member, wherein said urging member provides a first force when said actuator is in said first position and a second force when said actuator is in said second position.

30. A method of operating a pump system comprising: pressurizing a fluid with a positive displacement pump; discharging said fluid into a discharge passage; flowing a portion of said fluid from said discharge passage directly into a valve supply chamber; applying pressure to a valve body face; moving said valve body; opening a port in said valve supply chamber; ejecting said fluid into a suction chamber; and, increasing the fluid pressure at an inlet to said displacement pump by injecting said fluid across a suction chamber into a throat passage which also receives fluid from a reservoir by means of said suction chamber.

31. The method of claim 30 further comprising the step of varying the opening area of said port in direct response to changes in pressure of said fluid in said outlet passage.

32. The method of claim 31 further comprising the steps of: adducting fluid in said suction chamber towards said injected fluid; flowing said adducted fluid and said injected fluid into a throat passage; flowing said adducted and injected fluids to said displacement pump inlet.

33. The method of claim 30 further comprising the step of biasing said valve body towards said port.

34. The method of claim 33 wherein said step of moving said valve body occurs if the pressure in said discharge passage increases beyond a first threshold.

35. The method of claim 34 further comprising the step of opening a one-way valve fluidly coupled to said inlet if pressure at said inlet is less than a second threshold.

36. The method of claim 30 further comprising the step of powering said positive displacement pump by driving connectivity with a balance shaft for an internal combustion engine having at least one piston and connecting rod assembly.

37. The method of claim 36 further comprising the step of transferring said fluid to said internal combustion engine.

38. The method of claim 29 further comprising the steps of: applying a force with an urging member to said valve body; and, changing the magnitude of said force in response to a switching event.

39. An internal combustion engine comprising: a balance shaft assembly; a first positive displacement pump, said pump having an inlet passage and a discharge passage, wherein said discharge passage is arranged to fluidly couple with said balance shaft assembly; a jet pump valve having a variable nozzle opening area fluidly coupled between said discharge passage and said inlet passage, said jet pump valve including means for changing the area of said variable nozzle opening in direct response to changes in fluid pressure in said discharge passage, said jet pump valve further including an urging member arranged to bias a member to close said variable nozzle opening; said jet pump valve further having a suction chamber adjacent said variable nozzle opening and arranged to receive fluid from said variable nozzle opening and a fluid reservoir; and, said jet pump valve further having a throat passage coupled to said suction chamber, said throat passage being fluidly coupled to receive fluid from said reservoir and said variable valve opening and transfer said received fluid to said inlet passage.

40. The internal combustion engine of claim 39 wherein said means for changing the area of said variable nozzle opening is in direct response to changes in fluid pressure in said internal combustion engine.

41. The internal combustion engine of claim 39 further comprising an actuator movable between a first position and a second position, said actuator being operably coupled to said urging member wherein said urging member provides a first force when said actuator is in said first position and a second force when said actuator is in said second position.

Description:

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit of U.S. Provisional Application Ser. No. 60/927,484 filed May 3, 2007, and entitled “Energy Efficient Fluid Pump System.” which is incorporated by reference herein in its entirety.

FIELD OF ART

The present invention relates generally to a fluid pump system for an engine or other system, and more particularly, to the provision of low cost increases in the cavitation speeds of positive displacement fluid pumps, concurrent with useful power consumption reductions over a wide range of operational speeds, in applications offering limited packaging space.

BACKGROUND

The use of an adjustable nozzle area jet pump having normally non-passing pressure control valve functionality to conserve energy by delivering pressurized recirculation flow back to the inlet of a positive displacement fluid pump under widely varying load conditions is known in the art. The use of a positive displacement pump to reduce the timing gear noise emissions of an engine balance shaft module at low cost by applying the oil pump's driving torque to minimize gear tooth separation is also known. These types of engine balance shaft module applications typically drive the pump at twice engine speed by means of a driving connection with a twice engine speed balance shaft. This arrangement is beneficial in terms of both pump volumetric efficiency at low speeds and required pump packaging space claim. However, such applications often represent significant challenge when an operating speed range that is often greater than an order of magnitude in breadth is combined with a requirement for copious low speed flow volume. This is due to increased-displacement pumps generally suffering from reduced cavitation speeds, those where pump filling becomes challenged for lack of sufficient inlet passage pressure. This challenging combination is becoming increasingly commonplace with marketplace demands for ever-improving engine performance. These demands result in engine applications having both oil flow resistance-lowering features such as variable valve timing, and increased peak operating speeds.

Jet pump recirculation of unused flow volumes has proven to be an effective means of both reducing power consumption and increasing pump cavitation speeds in case of high speed applications utilizing positive displacement pumps. The energy efficiency benefits of jet pump recirculation are extendable into the lower portions of an operating speed range by means of the efficiency-broadening character of adjustable nozzle jet pumps. Additionally, the elimination of the upstream-of-jet pump pressure drop of a separate flow control valve, by integrating normally non-passing pressure control valve functionality into an adjustable nozzle jet pump offers the potential of improved recycling efficiency. However, current art systems typically require a differential control valve means, responsive to the difference between the inlet pressure and the discharge pressure of the positive displacement pump. This arrangement is much more costly and space-consumptive than necessary to achieve the desired functionality of optimized energy efficiencies and cavitation speeds in fluid pump systems that for avoidance of cost, complexity, or packaging space claim require positive displacement pumps to function over a wide range of speeds. Other prior art adjustable nozzle jet pumps having normally non-passing pressure control valve functionality similarly define much more costly and complex structures than are necessary for the purpose of achieving the above-cited desired functionality.

Accordingly, while existing pump systems are adequate for their intended purposes, there exists a need for a simpler, lower cost, and less space claim-consumptive fluid pump system for improving both cavitation speed and normal speed range power consumption. There is further need for these improvements in applications where in order to minimize cost, complexity, and/or packaging spaceclaim, positive displacement pumps are required to function over a wide range of speeds.

SUMMARY OF THE INVENTION

A pump system is provided having a positive displacement pump. The positive displacement pump includes an inlet passage and a discharge passage. The pump system further includes an adjustable nozzle jet pump valve. The adjustable nozzle jet pump valve includes a supply chamber fluidly coupled to the first positive displacement pump discharge passage. The supply chamber includes a port with a seat surface. A movable valve member having a sealing surface and a body portion is arranged in the adjustable nozzle jet. The sealing surface is arranged in sealing contact with the seat surface when in a first position. The body portion has a first face sealingly positioned within the supply chamber, and an opposing second face. The first face has a first surface area. The adjustable nozzle jet pump valve further includes an urging member, a suction chamber and a throat passage. The urging member is arranged and coupled to the second face. The suction chamber is fluidly coupled to the port. The throat passage fluidly is coupled to the suction chamber and the inlet passage. The port, the suction chamber and the throat passage are arranged in a continuous serial fluid connection to the inlet passage.

Another embodiment pump system for a variable consumptive load is also provided. The pump system includes a first positive displacement pump having an inlet passage and a discharge passage, wherein the discharge passage is arranged to couple with the variable consumptive load. A jet pump valve is provided having a variable nozzle opening area directly fluidly coupled between the discharge passage and the inlet passage. The jet pump valve also includes means for changing the area of the variable nozzle opening in direct response to changes in a fluid pressure such as that in the discharge passage. The jet pump valve further includes an urging member arranged to bias a member to close the variable nozzle opening. The jet pump valve further also includes a suction chamber adjacent the variable nozzle opening and arranged to receive fluid from the variable nozzle opening and from a fluid reservoir. A throat passage is provided in the jet pump valve and is coupled to the suction chamber. The throat passage is further fluidly coupled to receive fluid from the reservoir and from the variable valve opening. The throat passage transfers the received fluid to the inlet passage.

A method of operating a pump system is also provided. The method includes pressurizing a fluid with a positive displacement pump. The fluid is discharged into a discharge passage and a portion of the fluid is flowed from the discharge passage into a valve supply chamber. Pressure is applied to a valve body face. The valve body is moved to open a port in the valve supply chamber. Fluid is ejected into a suction chamber. Finally, the fluid pressure is increased at an inlet to the displacement pump by injecting the fluid across a suction chamber and into a throat passage. The throat passage further receives fluid from a reservoir by means of the suction chamber.

An internal combustion engine having a balance shaft assembly is also provided. A first positive displacement pump having an inlet and a discharge passage is arranged such that the discharge passage is fluidly coupled with the balance shaft assembly. A jet pump valve having a variable nozzle opening area is provided where the variable nozzle opening is fluidly coupled between the discharge and the inlet passage. The jet pump valve includes means for changing the area of the variable nozzle opening in direct response to changes in fluid pressure in the discharge passage. The jet pump valve further includes an urging member arranged to bias a member to close the variable nozzle opening. A suction chamber is arranged in the jet pump valve adjacent the variable nozzle opening to receive fluid from the variable nozzle opening and a fluid reservoir. The jet pump valve further includes a throat passage coupled to the suction chamber. The throat passage is fluidly coupled to receive fluid from the reservoir and the variable valve opening and transfer the received fluid to the inlet passage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an exemplary embodiment cavitation-deterring energy-efficient pump system;

FIG. 2 is a schematic illustration of the pump system of FIG. 1 with the nozzle sealing member having been moved, by system pressure, for jet pump pressurization of the positive displacement pump's inlet;

FIG. 3 is a schematic illustration of the pump system of FIG. 1 having an alternate embodiment supplemental pump that adds its flow volume to that of the energy efficient pumping system to circumvent a “throat restriction at pre-boost operating conditions” issue;

FIG. 4 is a schematic illustration of the pump system of FIG. 3 with the nozzle sealing member at a “bypass threshold” position;

FIG. 5 is a schematic illustration of the pump system of FIG. 3 with the “full bypass” nozzle sealing member position;

FIG. 6 is a schematic illustration of the pump system of FIG. 1 with an alternate embodiment arrangement of circumventing the “throat restriction at pre-boost operating conditions” issue;

FIG. 7 is a schematic illustration of the pump system of FIG. 6 at a system pressure that has moved the nozzle sealing member and initiated boost pressure, or reduction in vacuum magnitude, in the throat-to-pump inlet passage or diffuser, wherein the check valve ball is shown seated;

FIG. 8 is a schematic illustration of the pump system of FIG. 1 having an alternate embodiment, a low cost, low mass, and vibration-robust check valve in the throat-bypassing supply passage;

FIG. 9 is a schematic illustration of the pump system of FIG. 1 with another alternate embodiment check valve arrangement, a so-called reed valve assembly check valve in the throat-bypassing supply passage;

FIG. 10 is a schematic illustration of the pump system of FIG. 1 with an alternate embodiment wherein a nozzle supply cavity sealing partition isolates the sealingly mobile pressure area of the nozzle sealing member for control of system pressure at a location downstream of a flow resistance, by means of a separate remote pilot pressure control passage;

FIG. 11 is a schematic illustration of the pump system of FIG. 10 having a positive seal between the nozzle sealing member and the nozzle supply cavity sealing partition;

FIG. 12 is a schematic illustration of the pump system having an alternate embodiment electronic actuator as a control device whereby system delivery pressure may be electronically controlled in response to a signal;

FIG. 13 is a schematic illustration of a pump system with a combination of remote pilot and electronic pressure controls, whereby system pressure is passively managed to maintain threshold downstream-of-resistance pressure targets, and may additionally be actively managed;

FIG. 14 is a schematic illustration of the pump system providing for direct movement of the nozzle sealing member by an electronic pressure control;

FIG. 15 illustrates the pump system of FIG. 1 with a leakage-proof nozzle sealing member;

FIG. 16 illustrates another alternate embodiment pump system having an alternate embodiment leakage-proof nozzle sealing member;

FIG. 17 illustrates a graphical comparison between the empirical pressure curves of a conventional positive displacement pump system and the exemplary embodiment, for the satisfaction of a hypothetical high speed pressure target with the same positive displacement pump;

FIG. 18 illustrates a graphical comparison between the drive system power consumptions of the conventional positive displacement pump system and the exemplary embodiment, including a percentage difference curve; and,

FIG. 19 illustrates a schematic illustration of the pump system of FIG. 1 coupled to a modular balance shaft assembly and internal combustion engine.

DETAILED DESCRIPTION OF THE INVENTION

Adjustable nozzle jet pumps are known for substantially extended efficiency range in comparison with fixed nozzle area jet pumps. In the exemplary embodiment, a consistently high velocity of nozzle exit flow enables an automatically-adjusted variable nozzle area jet pump to provide this performance advantage more or less continually in the case of variable operating conditions. Substantial further efficiency range advantages are gained over fixed area ratio jet pump-assisted positive displacement pumping systems by means of the exemplary embodiment's low cost, compact integration of normally non-passing pressure control valve functionality with an adjustable nozzle-type jet pump.

The exemplary embodiment utilizes this simple normally non-passing pressure-controlling adjustable nozzle jet pump valve (hereafter referred to as a “Jet Pump Valve” or “JPV”) to captively recirculate unused flow volumes back to a positive displacement pump's inlet with pressure boost (or reduction of vacuum) when the operating system pressure exceeds a predetermined threshold. The integration provided in the exemplary embodiment effectively eliminates all of the flow energy losses customarily incurred with a so-called “bypass valve,” or “pressure-relief valve,” hereafter called a “PRV,” upstream of the nozzle supply passage. The JPV's “pressure relief” restriction itself is used as the means for efficiently propelling the unused flow volumes to high velocity in a useful direction. This elimination of a separate PRV thus increases the energy available to accelerate nozzle flow to high velocities and thereby enables peak efficiency to be achieved at reduced cost in comparison with current art systems.

The elimination of a separate PRV provides, by means of the consistently high energy of nozzle discharge flow, the energy-saving benefit of pressure enhancement to the inlet passage of the positive displacement pump to commence immediately upon the achievement of the predetermined threshold pressure and the associated onset of nozzle discharge flow. This greatly extends the range of operating conditions wherein useful efficiency advantages are provided, in comparison with fixed nozzle jet pump recirculation systems.

Referring now to FIG. 1, the exemplary embodiment cavitation-deterring energy-efficient fluid pump system 10 is illustrated. The arrows illustrated in the Figures represent the direction of flow of fluid to and from system 10, etc. The system 10 includes a pressure-controlled nozzle sealing member 30 which is continuously moveable between a first closed position and a second fully open position. As used herein, the terms “closed” and “open” refer to the extent of sealing. The nozzle sealing member includes an axisymmetric tapered seat region 34 of the nozzle sealing member 30 which contacts an axisymmetric seat region 38 adjacent the radially inner and preferably longitudinal extremity of the jet pump nozzle. The seat region 38 is formed in a first end of a nozzle supply chamber 32. The nozzle sealing member's 30 travel away from the first position towards the second position is resisted by a resilient urging member 44, and motivated by fluid pressure acting upon at least one reaction face 42. An annular area of the nozzle sealing member 30's seat region 34 has a diameter greater than that of the nozzle seat 38.

During operation, a predetermined threshold of fluid pressure is required to overcome a predetermined force exerted by the resilient urging member 44 to open the nozzle. This provides control over the pressure of the discharge-to-load portion of the present fluid pump system 10. In the exemplary embodiment, the resilient urging member 44 is a compression spring. The nozzle sealing member includes a sealing mobility portion 36 comprising a valve body portion 40 adjacent to the spring 44 and opposite the seat region 34. The spring side of the body 40 may include a captured volume, 46 within the body 40. In the exemplary embodiment, the spring 44 is positioned within the volume 46 and a chamber 50. The volume 46 and chamber 50 are collectively referred to herein as a “spring pocket” or damping chamber 54.

In the exemplary embodiment, the chamber 54 is vented to atmospheric pressure through one or more damping orifice(s) 48 that are positioned so as to allow escape of air. In one embodiment the damping orifice 48 is in communication with a damping orifice oil reservoir 52 (FIGS. 10-14) having volume greater than the displacement of the nozzle sealing member's 30 travel. Any rapid movement of the nozzle sealing member 30 is thus resisted by oil viscosity in the damping orifice 48 after the spring pocket 54 has been substantially purged of air and the damping orifice reservoir filled by oil. The resulting motion damping of nozzle sealing member 30 serves to smooth system pressure vis-à-vis positive pump inherent displacement “ripple” and the tendency for structures involving springs and masses to exhibit resonance. The venting to atmosphere enables the system pressure to be controlled by the force from urging member 44. Flow resistance characteristics of the damping orifice 48 may be such that any leakage flow from the nozzle supply chamber 32 to the spring pocket 54 is discharged to the reservoir without pressure buildup in the spring pocket 54. The nozzle sealing member 30 motion is allowed to be sufficiently rapid, such as under cold startup conditions for example, to avoid excessively high transient system pressure.

In the exemplary embodiment, the member body portion 40 and the chamber 50 are cylindrical in shape. The body portion 40 and chamber 50 thus form a piston and cylinder arrangement. It should be appreciated, however, that the shape of the body portion 40 and the corresponding chamber 50 may be altered, or alternative means of sealing mobility with respect to the nozzle supply chamber may be provided, without deviating from the scope of the claimed invention.

The nozzle sealing member 30 is sealingly mobile with respect to the second end of the nozzle supply chamber 32, and positioned opposite the nozzle seat 38. This allows the fluid pressure to act on the nozzle sealing member 30. When the fluid pressure within the nozzle supply chamber 32 is below a first threshold, the sealing member seat region 34 is in contact with the nozzle seat 38. By maintaining the seal at low speeds, the desired fluid pressure is maintained in the discharge passage 72 of a positive displacement pump fluid 70, such as an internal tip sealing rotor pump, commonly known as a gerotor pump. In one embodiment, this sealing mobility may be provided by the aforementioned piston and cylinder arrangement, but for embodiments where sealing must be complete, or at least relatively leak-free, alternative means of sealing mobility, such as a diaphragm or bellows-type diaphragm apparatus for example, may be used. Nozzle sealing member 30 position, and thus system pressure, automatically adjusts in response to recirculation flow rate and viscosity of fluid from the discharge passage 72 after exceeding the predetermined threshold of fluid pressure. The nozzle sealing member 30 is therefore independent of inlet pressure, or lack thereof, with an advantageous reduction in complexity, size, and cost.

JPV nozzle discharge flow, when present as illustrated by the partially opened JPV of FIG. 2, is directed at consistently high velocity by the axisymmetrically variable opening area between the nozzle sealing member 30 and the nozzle seat 38, across an annular gap or suction chamber 56 between the nozzle and a jet pump throat passage 60 having adjacent throat inlet transition region 62. The throat passage 60 is also being fed, in this suction chamber 56 region, by an uptake supply passage 66 referred to as a “throat supply passage.”

Fluid from the sump 64 is drawn into the suction chamber region and adducted towards the nozzle discharge flow stream when present, drawn into the throat inlet transition region, and then into the throat itself where the two flows combine and momentums are averaged as is characteristic of jet pump operation. The jet pump throat passage 60 is in fluid communication with the inlet passage 68 to the positive displacement oil pump 70, so as to apply fluid pressure to this positive displacement pump's inlet passage 68 when the jet pump nozzle opens and delivers pressurized oil at high velocity to the jet pump throat 60. The pressurization of the positive displacement pump's inlet 68 provides advantages in driving energy savings via so-called “hydraulic unloading,” i.e. the reduction of the pressure differential between the positive displacement pump's inlet 68 and discharge passages 72. Additionally, further advantages are gained in cavitation deterrence, i.e. increase in the positive displacement pump's pre-cavitation operating speed, via the enhanced pump filling that the inlet passage's elevated fluid pressure motivates. At operating conditions such as idle speed, and especially with hot oil, when the system pressure is below the threshold required to open the JPV, the positive displacement pump 70 draws its inlet flow from the sump 64, through the jet pump's throat supply passage 66 and the throat inlet transition region 62, and then the throat passage 60 itself, without the jet pump valve injecting fluid and thus providing pressure increase.

The positive displacement pump's discharge passage 72 is in captive fluid communication with both a consumptive load 74 and the JPV's nozzle supply passage 76. This allows a recirculation circuit to be formed from the pump's discharge 72, through the JPV nozzle supply passage 76, nozzle supply chamber 32 and nozzle 38 and throat 60, and then back to the pump's inlet passage 68. This fluid circuit feeds unused pump output flow volumes forcibly back to the pump's inlet 68 under pressure. The fluid circuit thus efficiently “recycles” much of the pressure energy of the unused flow volumes, in terms of the hydraulic work required of the pump. The exemplary embodiment includes an appropriately proportioned diffuser 78 downstream of the JPV throat, for the recovery of velocity pressure to the increase of static pressure, between the throat and the pump inlet. However, an abbreviated diffuser, or no diffuser, are to be understood as included in the scope of the claimed invention.

The spatial requirements for packaging flow-efficient configurations of the JPV's nozzle supply chamber are preferably minimized, along with side-loading of the JPV's sealingly mobile interface, by providing a necked down portion 58 of the nozzle sealing member 30 between its seat portion 34 and its sealingly mobile or body portion 40. In this arrangement the nozzle supply flow area in the nozzle supply chamber 32 is locally increased, to locally reduce flow velocity, and thereby also the area exposed to the incoming nozzle supply flow velocity is reduced. These area and flow velocity differences result in reduced side-loading on the nozzle sealing member 30 due to flow impingement, and consequently wear may thereby be reduced.

While these embodiments offer efficiency advantages by virtue of adjustable nozzle jet pump efficiency benefits and the elimination of pressure losses across a separate flow control valve, some application conditions will require measures to avoid throat flow restriction at pre-boost operating conditions. In the case of JPV applications that specify relatively high system pressure before “cracking” or beginning of recirculation flow (hereafter “high JPV cracking pressure systems”), the jet pump's throat area may need to be larger than optimal for boost efficiency in order to pass the entire inlet flow volume under atmospheric pressure motivation alone prior to the onset of nozzle discharge.

This throat size based efficiency limitation renders current art fixed nozzle area single pump systems highly ineffective because of the oversized jet pump throats necessary to avoid choking their respective positive displacement pumps under some operating conditions. Additionally, throat size based efficiency limitation further renders current art fixed nozzle area single pump systems highly ineffective because of the appreciable recirculation flow volumes needed to achieve nozzle discharge velocity dependent benefit from a fixed nozzle area jet pump.

In the case of high JPV cracking pressure systems, maximal system efficiency over broad ranges of operating conditions may be achieved, by means whereby the jet pump's throat can be allowed to pass less than the entirety of system flow volume. This permits the throat to be sized for efficiency rather than in light of pre-boost flow velocity limitations. Two alternate embodiments provide a means of circumventing this “throat restriction at pre-boost operating conditions” issue, and thereby enabling optimal JPV throat sizing. A first embodiment provides a parallel combination of the single positive displacement pump with JPV recirculation circuit arrangement as discussed above with a supplemental positive displacement pump, whose supply passage is separate and independent of the JPV's throat area. A second embodiment provides an introduction of additional inlet supply flow capacity downstream of the JPV's throat 60, between the jet pump's throat and the positive displacement pump's inlet 68, hereafter the “throat-to-pump inlet passage,” through at least one one-way check valve to provide the high flow capacity and low pressure drop characteristics needed to sufficiently minimize inlet vacuum and thus avoid cavitation.

In case of the first embodiment including a supplemental positive displacement pump, and referring now to the cavitation-deterring energy-efficient fluid pump system 12 as illustrated in FIG. 3, the flow volume from the sump 64 through supplemental pump inlet passage 82 to supplemental pump 80, being discharged to load 74 through supplemental pump discharge passage 84 acts to reduce the operating speeds at which unused oil becomes available to “power” the JPV, thus lowering the critical speed for which the jet pump throat passage 60 must be sized, an efficiency advantage over the larger-than-optimal throat sizes of prior art single pump systems. In this exemplary dual pump embodiment, the JPV may also incorporate an integral pressure relief or “bypass” port 86, which opens before the nozzle sealing member 30 has reached its fully open second position. This allows an additional flow route for the supplemental pump's flow volumes. This additional flow route may be advantageous when operating at cold or “deadhead” flow restriction conditions, or to avoid issues such as overpressurizing seals, that of an oil filter for example. In the exemplary embodiment, this integrated bypass port 86 is formed by at least one opening or port in the wall of a cylindrical valve bore 88 which maintains concentric location between the circular cross-section nozzle sealing member's tapered sealing portion's sealing area 34, and its conical seat region 38 in the nozzle portion of the supply chamber 32. The bypass port 86 is positioned so that it is only opened at the high pressure end of the nozzle sealing member's 30 travel range. It should be appreciated that sealing portion 34 and seat region 38 are described for exemplary purposes as having a particular conical shape, however, other shape types, such as a concave, convex or spherical surface for example, could be used without deviating from the intended scope of the claimed invention.

FIG. 4 schematically illustrates the cavitation-deterring energy-efficient fluid pump system 12 illustrated in FIG. 3 with nozzle sealing member 30 at a bypass threshold position where further displacement from the first closed position towards the second open position would enable fluid to escape through bypass port (74) and return either to the reservoir 64 or, alternatively, to the throat supply passage 66.

FIG. 5 schematically illustrates the system 12 with nozzle sealing member 30 in the second fully open position whereby bypass flow in bypass port 74 is enabled. The need for such pressure relief functionality in a given system is not certain because the unused portion of the supplemental pump's flow volume may be able to escape through the JPV's nozzle, thus creating backflow out its throat supply passage without exceeding engineering design limitations on system pressure.

Another embodiment for avoiding having the entirety of system supply flow volume to pass through the JPV throat 60 in high JPV cracking pressure systems is illustrated in FIGS. 6-9. These embodiments have one or more one-way (or check) valve(s) that may be used to provide supplemental (i.e. in addition to that which passes through the JPV's throat) intake flow to the positive displacement pump 70 if needed prior to pressurization of the throat-to-pump inlet passage. After pressurization of the positive displacement pump's inlet 68 passage by jet pump action commences, the one-way valve automatically closes to maintain the pressurization, for “hydraulic unloading” energy savings and cavitation speed increase.

FIG. 6 schematically illustrates a cavitation-deterring energy-efficient fluid pump system 14 which enables optimal throat sizing in a high JPV cracking pressure single pump system, namely the addition of one or more one-way check valve inlet bypass passage(s), such as a ball-type check valve 90 for example, having inlet 96 that draws from the sump 64, and outlet 98 that discharges to the throat-to-pump inlet passage 78 for introduction of supply flow downstream of the JPV's throat 60. In this figure the system pressure has not yet opened the JPV, yet the pump's inlet flow rate is such that without flow through the check valve 90, the flow rate through an optimally-sized jet pump's throat 60 might be high enough to create substantial enough pressure drop across the throat 60 as to cause premature cavitation in the pump 70. The ball 92 is shown in an elevated or open position above its valve seat 94 to provide low resistance inlet flow to bypass the jet pump's throat passage 60, thus reducing the vacuum magnitude of the positive displacement pump's inlet passage 68 and thus avoiding premature pump cavitation at times prior to the opening of the JPV.

FIG. 7 illustrates the same system with the ball 92 in a seated or closed position, to resist loss of inlet boost pressure after JPV opening. Such ball-type check valves are available both with and without spring assist, the latter utilizing gravity to seat the ball as illustrated in FIG. 7. While normally offering more than adequate sealing performance, the employment of the customary solid balls in this valve type may not be well suited to highly vibratory applications such as balance shaft modules due to the appreciable inertia forces associated with the mass of a solid ball when confronted by aggressive vibration. The location and configuration of the check-valved supply passage's union with the positive displacement pump's throat-to-pump inlet passage are arranged to minimize flow resistance while representing minimal interruption of diffuser functionality, such as utilization of Coanda effect shielded merging for example.

FIG. 8 illustrates the cavitation-deterring energy-efficient fluid pump system 16 with a second alternate embodiment one-way check valve 100 in the throat-bypassing supply passage 96, utilizing a low cost, low mass, and vibration resistant type of valve having a cup-shaped valve member 102 including a substantially cup-shaped cross section. The cup shaped valve member 102 has sides that slidingly engage a cup piloting spring seat member 104 for wear resistant locating of the bottom area of the cup-shaped valve member 102. This provides for one-way sealing of a substantially flat perimeter sealing surface 106 of the inlet bypass passage 96. An optional cup-shaped valve member urging member or spring 108 may aid gravity in urging the cup-shaped valve member 102 gently towards closure or sealing without greatly resisting bypass flow, when needed by certain applications. The proportions and spring rate of this valve 100 configuration can be tailored to provide very high flow capacity at very low pressure drop. The cup-shaped valve member's 102 sides may be circumferentially continuous or interrupted without departing from their radial positioning functionality in interaction with the cup piloting spring seat member 104.

FIG. 9 illustrates the cavitation-deterring energy-efficient fluid pump system 18 with a third alternate embodiment check valved inlet bypass having a so-called reed valve assembly check valve 110 positioned in the throat-bypassing supply passage 96. This kind of multiple reed assembly 110 is used in the intake ports of high performance two-stroke cycle engines and is capable of high flow capacity concurrent with relatively low pressure drop. In one embodiment, reed valves 112 are sealingly mounted to a sealing reed frame member 114 that may also include reed travel stops 116. The stops 116 provide motion control for the reed valves 112, including the extent of their opening.

In some applications the predetermined threshold of pilot pressure needed to open the JPV is allowed to be relatively low. In these applications, the throat flow volume prior to commencement of inlet pressurization is also commensurately low. Therefore, the throat choking issue and the need for its avoidance, may be irrelevant. Energy savings are maximized in this case because after fully meeting an engine's hot idle flow requirements, only gradual increase in engine system pressure with RPM is needed to overcome the increased centripetal forces acting on the oil in crankshaft oil passages. Any more than this gradual increase is typically unnecessary for basic engine system performance. Therefore any incremental increase in pressure, pump hydraulic loading and driving torque, over that which is needed to assure this basic system performance, represents wasted energy except where justified by consumptive load devices that can more than make up for the driving torque increase by their contributions to engine performance.

Referring now to FIG. 10, an alternate cavitation-deterring energy-efficient fluid pump system 20 is illustrated. In cases where the pressure drop across an oil filter and/or other consumptive load flow resistance is considered to have a larger than desired deviation between the system delivery pressure as managed by the JPV, and the system pressure downstream of this resistance, the introduction of a cavitation-deterring energy-efficient fluid pump system 20 with a nozzle supply chamber sealing partition 118 is provided. This nozzle supply chamber sealing partition 118 allows sealing mobility of the cylindrical nozzle sealing member support 120 that is arranged between the seat 34 of nozzle sealing member 30 and its body portion 40. The partition 118 separates the sealingly mobile pressure reaction face area 42 of the nozzle sealing member 30 from the nozzle supply chamber 32. This allows the exposure of face 42 to a pilot pressure chamber 122. The pilot pressure chamber 122 provides exposure of the face 42 to the downstream of resistance pilot pressure 124 rather than the fluid pressure from the discharge passage 72. The downstream of resistance pilot pressure 124 may be represented by an engine's oil gallery downstream of its filter system flow resistance for example. The use of the pilot pressure chamber 122 to actuate the nozzle sealing member 30 may be referred to as “remote pilot” control.

The cavitation-deterring energy-efficient fluid pump system is advantageous when integrated into engine applications such as Lanchester-type balance shaft modules where pump driving torques offer cost-effective drive system noise control synergies, and yet where packaging space constraints prohibit the use of more complex variable-displacement pump configurations. The embodiments disclosed herein, such as the positive displacement pump 70, the diffuser 66, and the JPV, form a fluid circuit “chain.” This chain provides considerable packaging flexibility in comparison with the substantially more complex variable-displacement pump configurations, which require mechanical proximity of all key elements.

At least one embodiment thus combines the cavitation-deterring energy-efficient fluid pump system with at least one engine balancing shaft to form a balance shaft/oil pump apparatus (FIG. 19) for control of gear noise emissions at minimum cost. Such balance shaft/oil pump modules are typically very highly constrained, in terms of available packaging space, because they are usually housed below the engine's crankshaft, and therefore compete for available space with the engine's oil volume in the oil pan or wet sump, the oil level needing to stay below the level of the spinning crankshaft and its connecting rods in order to avoid needless oil aeration, oil heating, and power consumption. The spatial requirements for packaging flow-efficient configurations of a jet pump's typically largest diameter feature, namely its suction chamber, are a function of the advantages of smooth acceleration of the radially inward adduction flow approaching the throat 60. This is conventionally significant, diameter-wise, in order to establish the substantially axisymmetric adduction flow pattern for most efficient energy transfer between nozzle discharge flow and suction chamber flow as they enter, past the throat inlet transition region, into the throat passage itself.

FIG. 10 illustrates an embodiment for minimizing the diameter of the suction chamber in order to facilitate compact packaging. In this embodiment, the throat supply passage 66 is located adjacent to a necked-down region 126 behind (i.e. remote from the suction chamber) a throat entry horn. The throat passage 60 includes a throat inlet transition region 62 such that substantially uniform axial flow can supply the perimeter of the horn. The flow in this region 62 is substantially free from “crosswind” effects from throat supply passage 66 flow velocity. The necked down region circumscribing the throat passage 60 lowers the velocity of the flow from the throat supply passage 66. This allows the throat supply passage 66 to be a low restriction “elbow” that aligns the flow from the throat supply passage 66 towards the suction chamber 56 into being substantially coaxial with the throat passage 60.

In this embodiment, the substantially uniform gap around the bell of the throat entry horn acts to produce substantially uniform flow velocity all around its periphery. This is advantageous in providing the desired axisymmetric flow pattern approaching the throat supply passage 66. Even if the throat supply passage 66 is not entirely behind the throat entry horn 62, such a necked down region can be helpful towards reducing crosswind asymmetry of throat inlet transition region flow by increasing flow area without a corresponding increase in suction chamber diameter. In adverse packaging space conditions where fully axisymmetric suction chamber designs are impractical, such flow area improvements as necking behind a throat entry horn 62 can be of particular value in a compromise solution optimized by numerical methods, such as computational fluid dynamics methods for example. The embodiment of FIG. 10 further includes a vented-to-atmospheric damping reservoir 52 in fluid communication with the nozzle sealing member 30 motion control means of damping orifice 48.

FIG. 11 illustrates the cavitation-deterring energy-efficient fluid pump system 20 with the addition of an optional pilot pressure chamber seal 128 that may be utilized to minimize leakage between the cylindrical nozzle sealing member support 120 of the nozzle sealing member 30 and the nozzle supply sealing partition 118. Such a seal, if desired, may be oriented to withstand the always-higher pressure of the nozzle supply chamber 32.

In some applications, electronic or other logic based automated control of system pressure may be desired in order to increase system delivery flow rates under certain operating conditions, such as the opening of a piston cooling jet manifold valve for example. The nozzle-closing force of the resilient urging member 44 may be supplied, or else supplemented, by a control apparatus such as an electronic or electromechanical actuation device for example. FIG. 12 illustrates a cavitation-deterring energy-efficient fluid pump system 22 having such an electronic control means 130 as supplementation to a resilient urging member 44. It should be appreciated that the electronic control means 130 may be coupled to one or more sensors (not shown) that provide feedback signals indicating operating conditions such as pressure of the fluid either within the cavitation-deterring energy-efficient fluid pump system 22 or the consumptive load for example. The electronic control means 130 is responsive to these signals in actuating the nozzle sealing member 30. The electronic control means 130 may be further responsive to pressure on the face 42 and activate based on the amount of pressure in supply chamber 32. Also shown is the necked down portion 58 of the nozzle sealing member 30 between the seat portion 34 and the body portion 40 as discussed above. It should be appreciated that such a control device 130 maybe used alone as the urging member. Typically electromagnetic solenoids are used for electronic actuation, however, their continual power draw when exerting a control force is counterproductive to net energy efficiency. Therefore, the use of alternative devices may be desirable.

FIG. 13 illustrates a cavitation-deterring energy-efficient fluid pump system 24 with the optional combination of both remote pilot pressure 124 and electronic pressure control means 130, whereby system pressure is passively managed to maintain threshold downstream-of-resistance targets, and may additionally be actively managed for specific purposes when desired.

FIG. 14 illustrates an alternate embodiment cavitation-deterring energy—efficient fluid pump system 25 having actuation of the nozzle sealing member 30 by the electronic control means 130 without the assistance of spring 44. In this embodiment, the electronic control means 130 includes a plunger 132. The plunger 132 is coupled to the body portion 40 and arranged to be moved linearly along an axis parallel to the axis of the nozzle sealing member 30. This movement causes the sealing seat 34 of member 30 to move into and out of contact with nozzle seat 38.

[In applications where the sealingly mobile functionality of the nozzle sealing member 30 with respect to the nozzle supply chamber 32 must be nearly leak-free, a piston and cylinder type apparatus may be fitted with at least one o-ring or other sealing device. In other applications where the sealingly mobile functionality of the nozzle sealing member 30 and chamber 32 must be completely leak-free, a sealing mobility portion 36 comprising a diaphragm-type apparatus, including bellows-type diaphragm may also be used. FIG. 15 illustrates such a sealingly mobile diaphragm type cavitation-deterring energy-efficient fluid pump system 26. In this embodiment, a sealing tip 136 is coupled to the body portion 142 of the nozzle sealing member 30. The sealing tip 136 includes a seat area 138 that contacts the nozzle seat 38 when the sealing member 30 is in the first position. A diaphragm member 140 is also coupled to the body portion 142. The diaphragm member 140 provides the reaction surface upon which the fluid pressure from discharge passage 72 acts. The spring 44 biases the sealing tip 136 into contact with the nozzle seat 38.

It should be appreciated that other types and constructions of sealing mobility portion 36's diaphragm type cavitation-deterring energy-efficient fluid pump system 26 may be used. For example, the diaphragm member 140 may be bonded to the sealing tip 136, or a formed protrusion of the diaphragm may be press fit onto the sealing tip 136. This would allow the elimination of the spring guide. Further, the diaphragm member 140 may be used itself as the urging member allowing the elimination of the separate spring.

FIG. 16 illustrates a cavitation-deterring energy-efficient fluid pump system 28 wherein leak-free sealing mobility of the JPV's nozzle sealing member with respect to the nozzle supply cavity is provided by a bellows type diaphragm. In this embodiment, the spring 44 acts upon a body portion 142 as described herein above. The body portion 142 is coupled to a sealing body 144. Sealing body 144 includes a seat region 146 that contacts the nozzle seat 38 when the sealing member 30 is in the first position. The sealing body 144 is generally cone shaped and includes a pilot flange portion 148 that is axially mobile within a pilot diameter 150. A bellows member 152 is coupled to the body portion 142. The bellows member's 152 minor diameter represents the outside of the functional area of pressure reaction face 42, so this diameter is sized in conjunction with mating component properties such as nozzle seat diameter, urging member static force and rate of force change (e.g. spring rate), in light of desired system fluid pressure range. A damping orifice 154 is arranged in the spring pocket 54 opposite the body portion 142. During operation, the bellows member 152 compresses and expands axially to enable nozzle sealing member 30 motion within nozzle supply chamber 32. During this motion, the large pilot flange 148 is able to “leak” oil back and forth to the diaphragm OD region.

FIG. 17 illustrates a cavitation-deterring energy-efficient fluid pump system 29 having an electronic control means 156 similar to control means 130 discussed above in reference to FIG. 12. Control means 156 acts on the spring 44 instead of acting directly on the nozzle sealing member 30. The control means 156 includes an actuator, such as a solenoid or a stepper motor for example, that actuates a spring support 158. The spring support 158 has a spring support face 160 that may be moved linearly by the control means 156 from a first or initial position to a second position in response to a switching event. The movement of the spring support 158 changes the amount of compression of spring 44, and thus the magnitude of the force provided by spring 44. In the exemplary embodiment, the spring support 158 may be held at the second position without further energy expenditure. The spring support 158 may remain in this position until another switching event, such as the closing of a piston cooling jet manifold valve for example, causes the control means 156 to restores the spring support 158 to the initial position. This embodiment provides the advantage of using a normally passive type electronic control 156 such as a stepping motor instead of an electronic control such as a solenoid that continually draws power in order to exert an axial force. Such a normally passive electronic control 156 may be activated when a significant change to engine permeability occurs, such as the opening of a piston cooling jet manifold valve for example. This type of activation may result in a desired new degree of spring 44 preload that may be used to maintain system pressure under such a higher permeability condition. This preload of the spring 44 may then be maintained without need for the control 156 to actively respond to system pressure changes. This use of a normally passive type electronic control provides the advantage of increased energy savings in comparison with an electronic control that requires continual electrical power to exert a force.

FIG. 18 illustrates empirical test data comparing the pressure curves of a conventional PRV-regulated single positive displacement pump and a FIG. 1 cavitation-deterring energy-efficient fluid pump system (“C-dE-EFPS”) 10. The test setup between the two tests differed only in respective hydraulics, as needed to achieve a hypothetical high-speed pressure requirement. The PRV testing results are defined by dashed-line 158, while that of the exemplary embodiment fluid pump system 10 is defined by line 160. The PRV system recirculates its bypass oil directly back to the pump's inlet, merging with sump uptake oil in a favorable direction within 1 cm of the pump, in a routing commonly termed “supercharging.” As can be seen from curve 158, the PRV-regulated system pressure begins to falter at point 166 due to cavitation beginning around 5200 rpm, while the inlet pressurization benefit of the C-dE-EFPS 10 enables its outlet pressure to rise steadily to nearly 8000 rpm.

FIG. 19 compares empirical drive system power consumption curves for the FIG. 17 test conditions. The PRV test results are defined by dashed-line 168, while those of the fluid pump system 10 is defined by line 170. The approximately 19% average difference in drive system power consumption over the most frequently-used speed range understates the actual pump power consumption difference, because the drive system friction losses (from spindle bearings, spindle seals, chain, sprockets, chain tensioner and chain guide) are also included in these curves.

The cavitation-deterring energy-efficient fluid pump system may be used in a number of applications. FIG. 20 illustrates one such application where the cavitation-deterring energy-efficient pump system 172, including a positive displacement pump 174 arranged with an adjustable nozzle jet pump valve 178 and reservoir 180 as described embodiments illustrated in FIGS. 1-16, is coupled to a balance shaft modular assembly 184. The positive displacement pump 174 includes a discharge passage 182 that transfers fluid, such as a petroleum-based lubricant, to the engine 186 through a filter 194. The positive displacement pump 174 is drivingly connected to the engine 186 that provides the energy for operation of the positive displacement pump 174. In the connection 176 the positive displacement pump 174 is mechanically connected.

The modular assembly 184 delivers the fluid to an engine 186, such as an internal combustion engine for example. In the exemplary embodiment, the engine 186 includes one or more pistons 188, each with a connecting rod assembly 190. The delivered fluid is cleaned by filter 194 and then used within both engine 186 and modular assembly 184 before being returned to reservoir 180 via at least one return passage 192.

The embodiments described herein provide a cavitation-deterring energy-efficient fluid pump system that provides advantages in extending the working speed range of a positive displacement pump. The cavitation-deterring energy-efficient fluid pump system further provides advantages in reducing the driving power consumption of a positive displacement pump over its typical operating speed range. Additional advantages are made in minimizing the packaging space claim of a positive displacement pump system having jet pump-assisted recirculation, and to enable its design flexibility with regards to application packaging constraints. Additional advantages are provided to minimize manufacturing costs. The cavitation-deterring energy-efficient fluid pump system also provides advantages in enabling control by means remote from the positive displacement pump's output pressure where so desired.

The embodiments described herein provide further improvements in that the aforementioned differential control means of prior art valve mechanisms are larger, and thus disadvantaged in terms of packageability and cost, for any given combination of urging force and nozzle flow capacity. In comparison, the embodiments provided herein include further advantages because the valve motion motivating pressure area of prior art mechanisms is reduced by both the nozzle seat area and that of the smaller of two piston diameters. Further, the fluid pressure acting on this reduced pressure area is only the net difference between the output pressure and the input pressure, with the input pressure typically being positive. In comparison, the valve motion motivating pressure area of the embodiments provided herein is reduced by only the nozzle seat area, and the fluid pressure acting on this pressure area is not influenced by inlet pressure.

While the present invention has been described with reference to preferred embodiments, obviously other embodiments, modifications, and alternations could be envisioned by one skilled in the art upon reading the present disclosure. The present invention is intended to cover these other embodiments, modifications, and alterations that fall within the scope of the invention upon reading and understanding this specification with its appended claims.