Title:
Electrically driven motors and pumps having such motors
Kind Code:
A1


Abstract:
A motor, possibly for a pump, has a housing, a first member disposed within the housing and mounted on an inner wall of the housing, and a second member rotatably disposed within the housing and having a rotary shaft. A thrust bearing is mounted within the housing in order to support a first end of the rotary shaft in an axial direction of the rotary shaft. A core and coils wound around the core are provided on one of the first and second members. A set of magnets is provided on the other of the first and second members. The core and the set of magnets are positioned such that a magnetic force is produced in an area where a magnetic flux is generated between the core and the set of magnets. The magnetic force causes the second member to move toward the thrust bearing.



Inventors:
Naito, Hiroaki (Aichi-ken, JP)
Application Number:
10/956368
Publication Date:
04/07/2005
Filing Date:
10/04/2004
Assignee:
Aisan Kogyo Kabushiki Kaisha
Primary Class:
Other Classes:
417/365, 417/423.14
International Classes:
H02K29/00; F04D5/00; H02K5/12; H02K5/167; H02K5/24; H02K7/08; H02K7/14; H02K21/12; H02K21/16; H02K5/15; (IPC1-7): F04B17/00; F04B35/00; F04B35/04
View Patent Images:
Related US Applications:
20080199336Outdoor EquipmentAugust, 2008Brensinger
20050047930System for controlling a hydraulic variable-displacement pumpMarch, 2005Schmid
20060045774Fans and fan framesMarch, 2006Lu et al.
20060120892Hydraulic system for mining equipment and method of adjusting power of rock drill machineJune, 2006Muona et al.
20070196213Metering pump with self-calibration and health predictionAugust, 2007Parsons et al.
20040119430Power fan speed controllerJune, 2004Lai
20090208353Motorized fan with whimsical figure appearanceAugust, 2009Weiser
20090304528Electrical Signal Input Type Displacement Control Device and Hydraulic EquipmentDecember, 2009Shimazaki et al.
20100003135BLANK CONFIGURABLE AS A MANUALLY OPERABLE FAN OR DISPLAYJanuary, 2010Meyerratken
20090148315Circulation pumpJune, 2009Laing
20090204205Platinum-cobalt-boron blood pump elementAugust, 2009Larose et al.



Primary Examiner:
KIM, JOHN K
Attorney, Agent or Firm:
Arlington/LADAS & PARRY LLP (ALEXANDRIA, VA, US)
Claims:
1. A motor comprising: a housing; a first member disposed within the housing and mounted on an inner wall of the housing; a second member rotatably disposed within the housing and having a rotary shaft, wherein at least a part of the second member opposes at least a part of the first member in a radial direction of the rotary shaft; a thrust bearing mounted within the housing and arranged and constructed to support a first end of the rotary shaft in an axial direction of the rotary shaft; and a core and coils wound around the core provided on one of the first and second members and a set of magnets provided on the other of the first and second members, so that a rotation force for rotating the second member relative to the first member is produced by exciting the coils; wherein, the core and the set of magnets are positioned such that a magnetic force is produced in an area where a magnetic flux is generated between the core and the set of magnets, to move the second member toward the thrust bearing.

2. The motor as in claim 1, wherein the core and the set of magnets are offset from each other in the axial direction of the rotary shaft.

3. The motor as in claim 2, wherein the motor is configured as a brush-less motor, and wherein the first member comprises a stator having the core and the coils, and wherein the second member comprises a rotor having the set of magnets.

4. The motor as in claim 3, wherein the set of magnets is offset relative to the core in a direction away from the thrust bearing.

5. The motor as in claim 4, wherein the core and the set of magnets have different lengths in the axial direction of the rotary shaft, and wherein the set of magnets extends beyond the core in a direction away from the thrust bearing.

6. The motor as in claim 2, wherein the motor is configured as a DC motor, and wherein the first member comprises the set of magnets, and wherein the second member comprises an armature having the core and the coils.

7. The motor as in claim 6, wherein the core is offset relative to the set of magnets in a direction away from the thrust bearing.

8. The motor as in claim 7, wherein the core and the set of magnets have different lengths in the axial direction of the rotary shaft, so that the core extends beyond the set of magnets in a direction away from the thrust bearing.

9. The motor as in claim 1, further comprising: a first end cover disposed on one end of the housing in a direction opposite to the thrust bearing; and a second end cover disposed on the other end of the housing on the side of the thrust bearing, wherein the first end cover is formed integrally with the housing.

10. The motor as in claim 9, wherein the rotary shaft has second end opposite to the first end, and wherein the second end is rotatably supported by the first end cover.

11. The motor as in claim 10, wherein the thrust bearing is mounted on the second end cover.

12. The motor as in claim 9, further comprising an electric control circuit electrically connected to the coils in order to control the supply of current to the coils, and wherein the electrical control circuit is disposed within a substantially closed space formed within the first end cover.

13. A pump comprising: a housing; a motor section disposed within the housing and comprising: a first member disposed within the housing and mounted on an inner wall of the housing; and a second member rotatably disposed within the housing and having a rotary shaft, wherein at least a part of the second member opposes at least a part of the first member in a radial direction of the rotary shaft; and a core and coils wound around the core provided on one of the first and second members and a set of magnets provided on the other of the first and second members, so that a rotation force for rotating the second member relative to the first member is produced when the coils are excited; a thrust bearing mounted within the housing and arranged and constructed to support a first end of the rotary shaft in an axial direction of the rotary shaft; and a pump section disposed within the housing and arranged and constructed to be driven by the motor section; wherein, the core and the set of magnets are positioned such that a magnetic force is produced in an area where a magnetic flux is generated between the core and the set of magnets, to move the second member towards the thrust bearing.

14. The pump as in claim 13, wherein the core and the set of magnets are offset from each other in the axial direction of the rotary shaft.

15. The pump as in claim 14, wherein the motor section is configured as a brush-less motor, and wherein the first member comprises a stator having the core and the coils, and wherein the second member comprises a rotor having the set of magnets.

16. The pump as in claim 15, wherein the set of magnets is offset relative to the core in a direction away from the thrust bearing.

17. The pump as in claim 16, wherein the core and the set of magnets have different lengths in the axial direction of the rotary shaft, so that the set of magnets extends beyond the core in an axial direction away from the thrust bearing.

18. The pump as in claim 14, wherein the motor section is configured as a DC motor, and wherein the first member comprises the set of magnets; and wherein the second member comprises an armature having the core and the coils.

19. The pump as in claim 18, wherein the core is offset relative to the set of magnets in a direction away from the thrust bearing.

20. The pump as in claim 19, wherein the core and the set of magnets have different lengths in the axial direction of the rotary shaft, so that the core extends beyond the set of magnets in a direction away from the thrust bearing.

21. The pump as in claim 13, further comprising: a first end cover disposed on one end of the housing in an axial direction opposite to the thrust bearing; and a second end cover disposed on the other end of the housing on the side of the thrust bearing, wherein the first end cover is formed integrally with the housing.

22. The pump as in claim 21, wherein the rotary shaft has a second end opposite to the first end, and wherein the second end is rotatably supported by the first end cover.

23. The pump as in claim 22, wherein the thrust bearing is mounted on the second end cover.

24. The pump as in claim 21, further comprising an electric control circuit electrically connected to the coils in order to control the supply of current to the coils, wherein the electrical control circuit is disposed within a substantially closed space formed within the first end cover.

25. The pump as in claim 13, wherein the pump is used for pumping a liquid.

Description:

This application claims priority to Japanese patent application serial number 2003-344431, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrically driven motors and pumps having such motors.

2. Description of the Related Art

Various types of electrically driven motors are known. For example, Japanese Laid-Open Patent Publication No. 2000-102210 teaches a brush-less electrically driven motor having a housing, a stator, a rotor, magnets, a thrust bearing, and a spring. The rotor has a rotor shaft that is rotatably supported by the housing. The magnets are provided on the rotor and oppose the stator via a predetermined space. The thrust bearing is mounted to the housing and supports the one end of the rotor shaft with respect to a thrust direction. The spring biases the rotor in a direction toward the thrust bearing, so that the one end of the rotor is pressed against the thrust bearing.

Because the motor of the above publication requires a spring to bias the rotor toward the thrust bearing, there has been a problem with the relatively large number of parts and the relatively large number of assembly steps for assembling the motor. These problems have been a limitation in attempts to downsize the motors.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to teach improved techniques for minimizing the number of parts and the number of assembly steps of electrically driven motors.

According to one aspect of the present teachings, motors are taught that include a housing, a first member disposed within the housing and mounted on an inner wall of the housing, and a second member rotatably disposed within the housing and having a rotary shaft. The second member opposes the first member in a radial direction of the rotary shaft. A thrust bearing is mounted within the housing in order to support a first end of the rotary shaft in an axial direction of the rotary shaft. A core and coils wound around the core are provided on one of the first and second members. A set of magnets is provided on the other of the first and second members so that when the coils are excited a rotation force is produced for rotating the second member relative to the first member. The core and the set of magnets are positioned such that a magnetic force is produced in an area where a magnetic flux is generated between the core and the set of magnets, causing the second member to move towards the thrust bearing.

Therefore, it is not necessary to incorporate a spring in order to bias the rotary shaft toward the thrust bearing. As a result, the number of parts and the number of assembly steps of the motor can be reduced.

In another aspect of the present teachings, the core and the set of magnets are offset from each other in the axial direction of the rotary shaft. This allows the biasing force to be easily produced by primarily determining the position of the core relative to the set of magnets.

In another aspect of the present teachings, the motor is configured as a brush-less motor. Therefore, the first member is a stator having a core and coils and the second member is a rotor having a set of magnets.

In the case of the brush-less motor, the set of magnets may be offset relative to the core in a direction away from the thrust bearing. In addition, the core and the set of magnets may have different lengths in the axial direction of the rotary shaft. The set of magnets may extend beyond the core in a direction away from the thrust bearing.

In another aspect of the present teachings, the motor is configured as a DC motor. Therefore, the first member is a set of magnets and the second member is an armature having a core and coils.

In the case of the DC motor, the core may be offset relative to the set of magnets in a direction away from the thrust bearing. In addition, the core and the set of magnets may have different lengths in the axial direction of the rotary shaft. The core may extend beyond the set of magnets in a direction away from the thrust bearing.

In another aspect of the present teachings, the motor further includes a first end cover and a second end cover. The first end cover is disposed on one end of the housing in a direction opposite to the thrust bearing. The second end cover is disposed on the other end of the housing, on the side containing the thrust bearing. The first end cover may be formed integrally with the housing. Therefore, the number of parts and the number of assembly steps of the motor may be further reduced.

In another aspect of the present teachings, the rotary shaft has a second end (in an axial direction) opposite to the first end. The first end cover rotatably supports the second end of the rotary shaft.

In another aspect of the present teachings, the thrust bearing is mounted on the second end cover.

In another aspect of the present teachings, the motor further includes an electric control circuit electrically connected to the coils in order to control the supply of current to the coils. The electrical control circuit is disposed within a substantially closed space formed within the first end cover. The substantially closed space reliably prevents the possible short-circuiting or breakage of the electrical connection.

In another aspect of the present teachings, pumps are taught that have a motor section and a pump section. The motor in the various aspects described above may be incorporated as the motor section. The housing of the motor section may also serve as the housing of the pump section. The pumps may pump liquids, such as water, oils and fuels. For example, the pumps may be fuel pumps for pumping fuel from a fuel tank of an automobile in order to deliver the fuel to an internal combustion engine of the automobile.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of a fuel pump according to a first representative embodiment; and

FIG. 2 is a vertical sectional view of a fuel pump according to a second representative embodiment; and

FIG. 3 is a vertical sectional view of a fuel pump according to a third representative embodiment; and

FIG. 4 is a vertical sectional view of a stator in FIG. 3 with an integral housing member shown by dotted lines; and

FIG. 5 is a vertical sectional view of a fuel pump according to a fourth representative embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Each of the additional features and teachings disclosed above and below may be utilized separately or in conjunction with other features and teachings to provide improved motors and pumps for reducing the number of parts and the number of assembly steps. Representative examples of the present invention, which examples utilize many of these additional features and teachings both separately and in conjunction with one another, will now be described in detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Only the claims define the scope of the claimed invention. Therefore, combinations of features and steps disclosed in the following detailed description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the invention. Moreover, various features of the representative examples and the dependent claims may be combined in ways that are not specifically enumerated in order to provide additional useful embodiments of the present teachings.

Various representative embodiments of the present invention will now be described with reference to FIGS. 1 to 5.

First Representative Embodiment

Referring to FIG. 1, a fuel pump 1 according to a first representative embodiment is mountable on an automobile (not shown) and has a brush-less DC motor as a motor section 10. As shown in a vertical sectional view in FIG. 1, the fuel pump 1 includes a pump section 50 in addition to the motor section 10. The pump section 50 is disposed on the lower side of the motor section 10.

The motor section 10 will now be described. The motor section 10 generally includes a housing 11, a rotor 20 rotatably supported within the housing 11, and a stator 30 fixedly mounted within the housing 11. The housing 11 has a substantially cylindrical housing tube 13, an upper end cover 15 mounted to the upper end of the housing tube 13, and a pump casing 51 and a pump cover 53 mounted to the lower end of the housing tube 13. An axial support hole 16 is formed in an inner wall of the upper end cover 15 (the lower wall as viewed in FIG. 1) and extends substantially along the central axis of the housing tube 13. A substantially cylindrical discharge port 17 is defined in the upper end cover 15 in order to allow communication between inside and outside of the upper end cover 15. The discharge port 17 extends parallel to the central axis of the housing tube 13 but is displaced therefrom by a small distance.

The rotor 20 has a rotor shaft 21, a pair of upper and lower retainers 23 press-fitted onto the rotor shaft 21, a cylindrical yoke 25 press-fitted on the retainers 23, and a permanent magnet 27 bonded to the outer periphery of the yoke 25 by means of an adhesive made of resin. The retainers 23 may be made of stainless steel. The yoke 25 is also made of stainless steel but can be electrically magnetized. The permanent magnet 27 opposes the stator 30 via a predetermined clearance. The permanent magnet 27 has four magnetic poles arranged in the circumferential direction.

The pump casing 51 rotatably supports the lower portion of the rotor shaft 21 via a bearing 28. On the other hand, the axial support hole 16 rotatably supports the upper end of the rotor shaft 21 via a bearing 29. The rotor shaft 21 has a lower end 21a that extends further downward, beyond the bearing 28. The lower end 21a has a substantially D-shaped cross section and is inserted into a corresponding D-shaped cavity 59a formed in an impeller 59. In addition, the lower end 21 has a spherical lower end surface 21b that contacts with the upper surface of a thrust bearing 57. The thrust bearing 57 is mounted within the pump cover 53.

Each of the upper and lower retainers 23 has respective flange portions 23a. The flange portion 23a of the upper retainer 23 may be bonded to the upper end of the yoke 25 and the upper end of the magnet 27 by means of an adhesive made of resin. Similarly, the flange portion 23a of the lower retainer 23 may be bonded to the lower end of the yoke 25 and the lower end of the magnet 27 by means of an adhesive made of resin.

The stator 30 has a stator core 31, a holder 32 made of resin and serving to hold the stator core 31, and a stator coil 33 wound around the stator core 31. The stator 30 is closely fitted into the housing tube 13. A terminal end 33a of the stator coil 33 is electrically connected to a lower end of a terminal 35 by means of fusion welding or like measure. The upper end of the terminal 35 is inserted into a terminal receiving hole 15a formed in the upper end cover 15 so as to extend into a recess 18. The recess 18 is formed in the upper end cover 15 for receiving a control circuit 40. Then, the upper end of the terminal 35 is electrically connected to a connecting circuit board 38 that is also disposed within the recess 18. The connecting circuit board 38 is supported within the recess 18 via a suitable support (not shown).

The recess 18 is configured as a bottomed recess and opens at an upper external surface of the upper end cover 15. The control circuit 40 also is supported within the recess 18 via a suitable support (not shown) and serves to control the supply of current to the stator coil 33 of the stator 30. The control circuit 40 includes a coil-side circuit board 41 having a connecting terminal 42 and a cover-side circuit board 43 having an input terminal 44. One end (the lower end as viewed in FIG. 1) of the connecting terminal 42 is connected to the connecting circuit board 38. One end (the upper end as viewed in FIG. 1) of the input terminal 44 extends from the open upper end of the recess 18 to the outside of the fuel pump 1 via an auxiliary cover 46 that closes the open upper end of the recess 18. Although not shown in the drawings, the control circuit 40 may include power MOS-FETs and a drive circuit. The MOS-FETs permit and interrupt the supply of the current to a U-phase portion, a V-phase portion, and a W-phase portion of the stator coil 33. The drive circuit serves to control the operation of the MOS-FETs. More specifically, with predetermined overlapping turning periods, the drive circuit in turn activates the MOS-FETs in order to excite the respective phase portions of the stator coil 33.

The auxiliary cover 46 is attached to the upper end cover 15 by means of an appropriate attaching means, such as adhesion, heat crimping, and mechanical fastening by screws or other fastening devices (not shown), so that the open upper end of the recess 18 is sealingly closed. A terminal insertion hole 46a is formed in the auxiliary cover 46, so that the upper end (as viewed in FIG. 1) of the input terminal 44 of the control circuit 40 extends to the outside of the pump 1 through the terminal insertion hole 46a.

The upper end cover 15 is press-fitted into the housing tube 13 via an open upper end 13b as the upper end cover 15 is prevented from rotating relative to the housing tube 13. The open upper end 13b of the housing tube 13 is then heated and inwardly crimped against the lower end of the upper end cover 15. As a result, the upper end cover 15 is reliably prevented from being removed from the housing tube 13 and the upper end cover 15 sealingly closes the upper opening of the housing tube 13. In addition, a ring-like upper spacer 19 is fitted into the housing tube 13 so as to be interposed between opposing portions of the upper end cover 15 and the holder 32 of the stator 30.

As shown in FIG. 1, the permanent magnet 27 is displaced from the stator 30 by a predetermined distance in an axial direction away from the pump section 50. Therefore, in the area of the stator 30 and the magnet 27 where the magnetic flux comes in or out, a magnetic force is produced to equalize the imbalance of the resulting magnetic flux. Such a magnetic force may urge the rotor 20 to move in an axial direction towards the pump section 50 (the downward direction as viewed in FIG. 1). Consequently, the spherical end surface 21b of the rotor shaft 21 of the rotor 20 may be pressed against the thrust bearing 57. As a result, wobbling of the rotor 20 during rotation can be prevented or minimized. In other words, the rotor 20 and the impeller 59 can rotate in a stable and consistent manner.

The magnitude of the magnetic force that forces the rotor 20 may be adjusted by changing the amount of the distance of the displacement between the stator 30 and the permanent magnet 27. Alternatively, the magnitude of the magnetic force may also be adjusted by changing the length of the stator 30 or the length of the permanent magnet 27 relative to one another. For example, increasing the distance that the upper end of the permanent magnet 27 extends beyond the upper end of the stator 30 may increase the magnitude of the magnetic force. However, the displacement distance between the permanent magnet 27 and the stator 30 and the distance that the permanent magnet 27 extends beyond the stator 30 must be chosen so as to ensure the generation of the necessary rotational force for the rotor 20.

The pump section 50 will now be described. As shown in FIG. 1, the pump section 50 has the pump casing 51 (disposed directly below the bottom of the motor section 10), the pump cover 53, and the impeller 59. The pump casing 51 is press-fitted into the housing tube 13 via a lower open end 13a while the pump casing 51 is prevented from rotating relative to the housing tube 13. Subsequent to the fitting of the pump casing 51, the pump cover 53 is also press-fitted into the housing tube 13 via the lower open end 13a while the pump cover 53 is prevented from rotating relative to the housing tube 13. A pump chamber 56 is defined between the pump casing 51 and the pump cover 53. After the pump cover 53 has been fitted into the housing tube 13, the lower open end 13a is heated and inwardly crimped so that the pump cover 53 may be held pressed against the pump casing 51. The crimping also may prevent the pump casing 51 and the pump cover 53 from being inadvertently removed from the housing tube 13. In addition, the pump chamber may be sealed from unintentional communication with the environment outside of the pump 1.

A suction port 54 is defined in the pump cover 53 and communicates with the discharge side of the pump chamber 56. A discharge port 52 is defined in the pump casing 51 and communicates with the discharge side of the pump chamber 56. The pump casing 51 also serves as a lower end cover of the motor section 10. A substantially ring-shaped lower spacer 39 is fitted into the housing tube 13 so as to be interposed between opposing portions of the pump casing 51 and the holder 32 of the stator 30.

As previously described, the pump casing 51 rotatably supports the lower end of the rotor shaft 21 of the rotor 20 via the bearing 28. The impeller 59 is disposed between the pump casing 51 and the pump cover 53. A D-shaped cavity 59a is formed in a central portion of the impeller 59. The lower end 21a of the rotor shaft 21, having a corresponding D-shaped cross section, is engagingly inserted into the D-shaped cavity 59a, so that the impeller 59 rotates together with the rotor shaft 21. The thrust bearing 57 is press-fitted into an axial hole formed in an inner wall (the upper wall as viewed in FIG. 1) of the pump cover 53. As already described, the spherical end surface 21b of the rotor shaft 21 contacts the upper surface of the thrust bearing 57.

The operation of the fuel pump 1 will now be described. In the practical application of the fuel pump 1 of the current invention, although not shown in the drawings, a filter may interface with the suction port 54 and a fuel delivery pipe may be connected to the discharge port 17. A practical application of the fuel pump 1 may be to deliver fuel to a fuel injection device of the automobile. The whole fuel pump 1 may be supported within a fuel tank via an appropriate support device, preferably such as stays or any other type of mechanical or chemical (e.g. adhesive) support devices.

When power is supplied to the input terminal 44 of the control circuit 40, the drive portion of the control circuit 40 operates in turn to activate the MOS-FETs with a predetermined overlapping time, so that the respective phase portions of the stator coil 33 are appropriately excited. The rotor 20 may rotate as a result of this three-phase half-wave driving operation. As the rotor 20 rotates, the impeller 59 also rotates-so as to draw the fuel from within the fuel tank into the pump chamber 56 via the suction port 54. The fuel may then be discharged from the discharge side of the pump chamber 56 into the housing 11 via the discharge port 52 of the pump casing 51. The fuel discharged into the housing 11 may flow through the clearance located between the stator 30 and the rotor 20 and may be ultimately discharged to the outside via the discharge port 17 of the upper end cover 15.

According to the fuel pump 1 of the first representative embodiment, the motor section 10 is configured as a brush-less motor assembled into the fuel pump 1. As previously described, in the area of the stator 30 and the magnet 27 where the magnetic flux comes in or out, a magnetic force is produced so as to force the rotor 20 to press the spherical end surface 21b of the rotor shaft 21 against the thrust bearing 57. This configuration may eliminate a separate spring that is required in a conventional brush-less motor to bias the rotor 20 toward the thrust bearing 57. Consequently, the number of parts and the number of assembly steps of the motor may be reduced. As a result, the motor section can be downsized and the assembly operation of the motor section can be performed effectively.

In addition, because a separate spring for biasing the rotor 20 toward the thrust bearing 57 may be eliminated, the possible loss of torque due to the contact of the spring with the rotor shaft 21 may also be eliminated. Further, because no spring is disposed around the rotor shaft 21, the space required for such a spring may be eliminated. Therefore, the motor section 10 may be downsized.

The second to fourth representative embodiments will now be described with reference to FIGS. 2 through 5. The second to fourth representative embodiments are modifications of the first representative embodiment. Therefore, in FIGS. 2 to 5, like members are given the same reference numerals as in FIG. 1, and the explanation of these members may not be repeated.

Second Representative Embodiment

The second representative embodiment will now be described with reference to FIG. 2. The second representative embodiment is different from the first representative embodiment only in that the connecting circuit board 38 is disposed within the housing 11. Therefore, the connecting circuit board 38 is connected to the terminal 35 at a location within the housing 11. In this case, the connecting terminal 42 of the coil-side circuit board 41 extends through the terminal hole 15a formed in the upper end cover 15 so as to be electrically connected to the connecting circuit board 38. Also with this second representative embodiment, substantially the same operation and advantages may be attained as with the first representative embodiment.

Third Representative Embodiment

The third representative embodiment will now be described with reference to FIG. 3. The third representative embodiment is different from the first representative embodiment in that the housing tube 13 and the upper end cover 15 of the housing 11 are molded integrally with each other into an integral housing member 12 via a resin molding process. In addition, the upper spacer 19 and the lower spacer 39 are also molded integrally with the housing member 12. Further, the stator 30, including the terminal end 33a of the stator coil 33 connected to the terminal 35, is integrated within the housing tube 13, i.e., the housing member 12, using an insertion molding process. For example, the stator 30 may be set into a cavity of the mold used for molding the housing member 12. A resin material may then be injected into the cavity, consequently integrating the stator 30 with the housing member 12. FIG. 4 shows a vertical sectional view of the stator 30 prior to the molding process. The dotted lines indicate where the housing member 12 will be molded. This embodiment may result in a reduction of the number of parts of the motor section 10 and may also result in a reduction of the number of assembly steps for the motor section 10.

Also with the third representative embodiment, in addition to the same advantages as with the first representative embodiment, the number of parts of the motor section 10 and the number of assembly steps for the motor section 10 can be further reduced. The motor section 10 can be further downsized. Thus, it is not necessary to separately manufacture the housing tube 13 and the upper end cover 15 because the stator 30 is molded integrally with the integral housing member 12, which includes both the housing tube 13 and the upper end cover 15. Therefore the assembly operation step of pressing the upper end cover 15 into the housing tube 13 may be eliminated. In addition, because the stator 30, having the stator coil 33 wound around the stator core 31, is molded with the integral housing member 12 via an insert molding process, the assembly operation step of closely fitting the stator 30 into the housing tube 13 may be eliminated. As a result, the steps required in the first representative embodiment of assembling the upper end cover 15 and the stator 30 to the housing tube 13 can be eliminated.

The fuel pump 1, assembled with the previously described motor section 10, may have the same advantages as detailed in connection with the motor section 10. In addition, according to the fuel pump 1 of this representative embodiment, the stator coil 33 of the stator 30, the terminal 35, and the control circuit 40, are disposed such that they will not be exposed to fuel. Therefore, potential faults may be eliminated such as short-circuiting and the breakage of electrical connections that may be caused due to the electric corrosion of these parts.

Further, because the housing member 12 is molded with resin, it is advantageous in regard to providing a lightweight construction and noise reduction. Furthermore, the recess 18 for accommodating the control circuit 40 (used to control the supply of power to the stator coil 33), can be formed simultaneously with the molding process of the integral housing member 12.

Fourth Representative Embodiment

The fourth representative embodiment will now be described with reference to FIG. 5. The fourth representative embodiment is different from the first representative embodiment in that the motor section 10 is configured as a motor having a brush. In other words, the motor section 10 of the fourth representative embodiment is configured as a DC motor. As shown in FIG. 5, in this representative embodiment an armature 60 replaces the rotor 20 of the first representative embodiment. The armature 60 is rotatably supported within the housing 11. A predetermined number of permanent magnets 70 are secured to the inner wall of the housing 11 and radially opposed via a predetermined clearance to an armature core 62 of the armature 60.

The armature 60 includes an armature shaft 61 and a commutator 64 in addition to the armature core 62. Coils (not shown) are wound around the armature core 62. In the same manner as with the rotor shaft 21 of the first representative embodiment, the pump casing 51 rotatably supports the lower portion of the armature shaft 61 via the bearing 28. Conversely, the axial support hole 16 of the upper end cover 15 rotatably supports the upper end of the armature shaft via the bearing 29. In addition, the armature shaft 61 has a lower end 61a configured to have a substantially D-shaped cross section similar to the lower end 21a of the rotor shaft 21 of the first representative embodiment. The lower end 61a of the armature shaft 61 is inserted into a corresponding D-shaped cavity 59a of the impeller 59. Further, the lower end 61a has a spherical lower end surface 61b similar to the spherical lower end surface 21b of the rotor shaft 21 of the first representative embodiment. The lower end surface 61b of the armature shaft 61 contacts the upper surface of the thrust bearing 57 mounted to the pump cover 53.

A brush 65 and a spring 66 are mounted within the upper end cover 15. The brush 65 slidably contacts with the commutator 64 of the armature 60 and established an electrical connection therebetween. The spring 66 serves to bias the brush so as to have the brush press against the commutator 64. One end of a choke coil 67 is electrically connected to the brush 65. The other end of the choke coil 67 is connected to a terminal for further connection with an external circuit (not shown). A check valve 72 is fitted into the discharge port 17 of the upper end cover 15. The recess 18 of the upper end cover 15, the control circuit 40 accommodated within the recess 18, the upper spacer 19, the lower spacer 39, and the auxiliary cover 46, are not incorporated into the fourth representative embodiment.

As shown in FIG. 5, the armature core 62 of the armature 60 is displaced from the permanent magnets 70 by a predetermined distance in an axial direction away from the pump section 50. Therefore, in the area of the armature core 62 and the permanent magnets 70 where the magnetic flux comes in or out, a magnetic force is produced to equalize the imbalance of the resultant magnetic flux. Such a magnetic force may force the armature 60 to move towards the pump section 50 (downward direction as viewed in FIG. 5). Therefore, the spherical end surface 61b of the armature shaft 61 of the armature 60 may be pressed against the thrust bearing 57. As a result, wobbling of the armature 60 during rotation or operation of the motor may be minimized or prevented.

Therefore, in the fourth representative embodiment it is not necessary to provide a separate spring for biasing the armature 60 toward the thrust bearing 57. As a result, the number of parts of and the number of assembly steps of the motor can be reduced, the motor section can be downsized, and the assembly operation of the motor section can be more effectively performed.

(Possible Alternative Arrangements of the First to Fourth Representative Embodiments)

The present invention may not be limited to the above representative embodiments but may be modified in various ways. For example, although the motor section 10 of the above representative embodiments is adapted to drive a pump section 50 of a fuel pump 1, the motor section 10 can be used as a driving device for any other mechanism. Although the integral housing member 12 is molded with resin in the third representative embodiment, in place of resin, any other moldable material may be used to mold the integral housing member 12. In addition, the recess 18 of the upper end cover 15 of the third representative embodiment may be eliminated as in the second representative embodiment. Further, although the pump section 50 is adapted to pump fuel in the above representative embodiments, the pump section 50 may be used for pumping any other fluid in place of fuel, such as water. Furthermore, although the pump section 50 has been configured as an impeller pump of a type known as a Westco pump or a regenerative pump, the pump section 50 may be replaced with any other type of pump.