Title:
HYDRAULIC PUMP OR HYDRAULIC MOTOR HAVING A ROTATION SPEED SENSOR
Kind Code:
A1


Abstract:
The invention relates to a hydraulic pump or hydraulic motor having a rotating shaft, which is mounted in a fixed position in a housing and on which a pulse generator is provided, and having a rotation speed sensor, which is fixed to the housing and comprises a sensor element associated with the pulse generator, the sensor element being fitted eccentrically and offset with respect to the insertion axis of the rotation speed sensor.



Inventors:
Reimer, Markus (Klein Nordende, DE)
Application Number:
11/307944
Publication Date:
11/16/2006
Filing Date:
02/28/2006
Assignee:
SAUER-DANFOSS INC. (Ames, IA, US)
Primary Class:
International Classes:
F04B27/08
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Primary Examiner:
YOUNGER, SEAN JERRARD
Attorney, Agent or Firm:
ZARLEY LAW FIRM P.L.C. (DES MOINES, IA, US)
Claims:
What is claimed is:

1. Hydraulic pump or hydraulic motor having a rotating shaft (5), which is mounted in a fixed position in a housing (6a, 6b) and on which a pulse generator (4) is provided, and having a rotation speed sensor (1a), which is fixed to the housing (6a, 6b) and comprises a sensor element (3) associated with the pulse generator (4), characterized in that the sensor element (3) is fitted eccentrically and offset with respect to the insertion axis (2) of the rotation speed sensor (1a).

2. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the rotation speed sensor (1a) is in the form of an L-shaped built-in part, on whose first limb (14) the sensor element (3) is provided, and on whose second limb (15) fixing means (11), intended for installation in the housing (6a, 6b), and a plug element (12), for electrically connecting the sensor element (3) to electronics fitted outside the housing (6a, 6b), are provided.

3. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the offset of the sensor element (3) with respect to the insertion axis (2) of the rotation speed sensor (1a) is greater than the radius of the housing hole, which extends around the insertion axis (2), for the purpose of accommodating the second limb (15) of the rotation speed sensor (1a).

4. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the sensor element (3) is in the form of a Hall probe.

5. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the sensor element (3) is in the form of a GMR sensor.

6. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the sensor element (3) is in the form of an AMR sensor.

7. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the sensor element (3) is in the form of an inductive sensor.

8. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the pulse generator (4) is in the form of a magnet element.

9. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the pulse generator (4) is in the form of an annular gear.

10. Hydraulic pump or hydraulic motor according to claim 2, characterized in that the first limb (14), bearing the sensor element (3), of the L-shaped rotation speed sensor (1a) is longer than the second limb (15).

11. Hydraulic pump or hydraulic motor according to claim 2, characterized in that the first limb (14) of the L-shaped rotation speed sensor (1a) comprises a printed circuit board (13), which bears the sensor element (3).

12. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the second limb (15) of the rotation speed sensor (1a) is designed such that it closes off the wall of the housing (6a, 6b) in a sealing manner once it has been installed in said housing (6a, 6b).

13. Hydraulic pump or hydraulic motor according to claim 1, characterized in that the rotation speed sensor is combined with a temperature sensor.

Description:

BACKGROUND OF THE INVENTION

The invention relates to a hydraulic pump or hydraulic motor having a rotation speed sensor in accordance with the features of claim 1. Such hydraulic machines, which are used as a pump or a motor, have a rotating shaft, which is mounted in a fixed position in the housing, and a device for the purpose of determining its speed of revolution, which is required, for example, in the case of inclined-axis motors for the detection of the vehicle speed. In this case, the rotation speed is tapped off from the rotating parts via a sensor, in which case annular gears or magnet rings are often used which are fitted to the rotating parts and have the task of producing pulses for a sensor fixed to the housing.

The shaft is an option for the positioning of the pulse generator. The sensor in this case needs to be provided opposite on the housing. Owing to the different installation conditions of the machines, there is not always the desired amount of space available for this. Inclined-axis motors, for example, are often installed in extremely short wheel-hub drives. This requires a housing version (cartridge), in which a large proportion of the rotating parts are located in the region of the gear mechanism. There is then no longer sufficient space available for the rotation speed sensor and its fixing parts in order to be able to mount it perpendicularly with respect to the shaft along an axis parallel to the attachment flange. In this case, individual solutions need to be found in each case for the various housing designs. These circumstances will be explained briefly below with reference to FIGS. 3 and 4:

FIG. 3 shows an inclined-axis motor having a conventional rotation speed sensor 1b with a linear alignment. The insertion axis 2 can in this case extend parallel to the attachment flange of the housing variant 6a shown since the gear mechanism 7 is set back relatively far. To this extent, in this case the sensor 2 and the sensor element 3 can easily be arranged in a straight line opposite the pulse generator 4 fitted on the shaft 5.

FIG. 4 illustrate a second housing variant 6b. In this case, the shaft 5 is located to a considerable extent within the gear mechanism 7, of which only individual elements which overlap on the outside are illustrated. The insertion axis 2 of the rotation speed sensor 1b conventionally extends obliquely in order that the sensor element 3 can be arranged opposite the pulse generator 4. In addition, the pulse generator 4 for its part needs to be oriented towards the sensor element 3 in order to produce a reliable signal on rotation of the shaft 5. This means additional complexity in terms of production and assembly. In addition, various embodiments of rotation speed sensors need to be provided for different housing shapes.

SUMMARY OF THE INVENTION

The present invention aims to provide a hydraulic pump or a hydraulic motor having improved rotation speed sensing.

This object is achieved by the measures in accordance with claim 1. Developments of the invention are included in the dependent claims.

The hydraulic pump or the hydraulic motor according to the invention has a rotating shaft, which is mounted in a fixed position in a housing and on which a pulse generator is provided. A rotation speed sensor, which is fixed to the housing, comprises a sensor element, which is associated with the pulse generator and fitted eccentrically and offset with respect to the insertion axis of the rotation speed sensor. It is thus possible for the outwardly leading main part of the rotation speed sensor to be displaced into a region where there is free space available in the housing variants in question, while the sensor element can be fitted within the housing with optimum proximity and alignment with respect to the pulse generator. This makes sensing of the rotation speed possible even in regions within the housing of hydraulic pumps and motors which are otherwise not accessible or are only accessible with difficulty.

The rotation speed sensor is preferably in the form of an L-shaped built-in part, on whose first limb the sensor element is provided, and on whose second limb fixing means, intended for installation in the housing, and a plug element, for electrically connecting the sensor element to electronics fitted outside the housing, are provided. Owing to the L shape, the sensor element can be displaced eccentrically to quite a considerable extent, given a corresponding length of the limb, with the result that the sensor can be adapted to quite different installation requirements. The distance between the sensor element and the insertion axis (central axis of the accommodating hole) may in this case be greater than the radius of the housing hole, provided around this axis, for the purpose of accommodating the rotation speed sensor.

The sensor element is preferably in the form of a Hall probe, and the pulse generator is preferably in the form of a magnet element. Inductive sensor elements, GMR sensors (giant magnetoresistive sensors) or AMR sensors (anisotropic magnetoresistive sensors) can advantageously be used. The pulse generator may be in the form of, for example, an annular gear.

It is advantageous if the first limb, bearing the sensor element, of the L-shaped rotation speed sensor is considerably longer than the second, outwardly pointing limb. The design engineer therefore has additional freedom in optimizing the offset of the sensor element with respect to the insertion axis and the process of passing the plug part through the housing wall and fixing it. The first limb of the L-shaped rotation speed sensor in this case preferably comprises a printed circuit board, which bears the sensor element and makes a particularly space-saving solution possible. The second limb of the rotation speed sensor is designed such that it closes off the wall of the housing in a sealing manner once it has been installed in said housing. The connection to the outside takes place merely via the plug connection. Components which protrude far out of the pump contour and are thus unprotected are avoided.

One further advantage results from the fact that the rotation speed sensor can be combined with a temperature sensor, with the result that only one built-in part is required for both measurements. Further features and advantages of the invention result from the description below relating to the exemplary embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a first housing variant having the L-shaped rotation speed sensor.

FIG. 2 shows a second housing variant having the L-shaped rotation speed sensor.

FIG. 3 shows the first housing variant having a conventional rotation speed sensor.

FIG. 4 shows the second housing variant having a conventional rotation speed sensor.

FIG. 5 shows an overall view of the L-shaped rotation speed sensor.

FIG. 6 shows a partial section through the rotation speed sensor shown in FIG. 5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an inclined-axis motor having a first housing variant 6a, in which the rotation speed sensor 1a according to the invention is installed. The housing 6a is connected to the gear mechanism 7 via a flange, only housing parts of said gear mechanism 7 being indicated here. The drive mechanism of the inclined-axis motor comprises in a known manner a cylinder block 8 and a pivoting mechanism 9, which are arranged in the region of the end housing 10.

The rotation speed is tapped off from the shaft 5, which is mounted in a fixed position in the housing 6a and on which an annular, magnetic pulse generator 4 is fixed, said pulse generator 4 producing corresponding pulses in the sensor element 3, a Hall probe, on rotation of the shaft 5. The Hall probe 3 is arranged on a printed circuit board 13, which extends along a first limb 14 of the L-shaped rotation speed sensor 1a. The limb 14 requires very little physical space. It can be matched optimally to the free space between the shaft 5 and the housing wall, with the result that the sensor element lies precisely opposite the pulse generator 4 in the immediate vicinity thereof.

The second limb 15 of the L-shaped rotation speed sensor 1a, which is designed to be inserted into the housing wall along the insertion axis 2, closes off the housing to the outside with a corresponding sealing element. Protruding parts and the resulting risk of damage are thus avoided.

The L shape of the sensor makes it possible to select the eccentric offset of the sensor element 3 in relation to the insertion axis 2 to be so great that the sensor element 3 lies outside the accommodating hole, which is provided for the limb 15, or the sealing element located there. The point at which the plug part is passed through the housing wall can thus be displaced into a suitable region, which is largely independent of where the sensor element needs to be fitted.

FIG. 2 shows the sensor 1a installed in a second housing variant 6b. The inclined-axis motor is in this case installed in a very short wheel-hub drive, of which only the housing parts 7 which overlap on the outside are illustrated. The shaft 5 thus lies virtually within the gear mechanism 7. A pulse generator 4 fitted there, if need be, can only be reached along an obliquely extending insertion axis, as described initially. The other rotating parts of the drive mechanism are likewise not very suitable for tapping off the rotation speed since they can be displaced and are thus not fixed in position. The solution here is the same L-shaped rotation speed sensor 1a from FIG. 1, which is inserted into the housing wall with its outwardly pointing second limb 15 along an offset insertion axis 2 and engages far under the housing wall with its first limb 14. “Far” in this case means that the sensor element 3 is further removed from the central axis 2 of the housing hole than this housing hole has as a radius. The sensor element 3 fitted on the printed circuit board 13 can thus be placed with suitable assignment with respect to the pulse generator 4, no particular measures needing to be taken for the alignment of said pulse generator 4.

At the same time, the problem of having to find in each case individual solutions for rotation speed sensing for different installation conditions is reduced to a single design which can be applied to different cases.

FIGS. 5 and 6 show the L-shaped rotation speed sensor 1a according to the invention in an overall view and in a partially sectioned illustration. The printed circuit board 13 having conductor tracks and the sensor element 3, which has, as a result, a considerable offset with respect to the axis of the second limb 15, is arranged in the first limb 14 of the L-shaped sensor 1a. This second limb 15 comprises the plug element 12 and fixing means 11, which produce the electrical connection to the outside, for the rotation speed sensor 1a, which is fixed to the housing with its flange-like edging and a suitable sealing element. The rotation speed sensor does not have any parts which protrude to a considerable extent beyond the housing; it ends practically flush with the housing wall; the plug pins 12 lie protected in a pot-like depression in order to minimize the risk of damage.

The design of the rotation speed sensor with a considerably eccentric arrangement of the sensor element in relation to the insertion axis also allows for a very cost-effective, automated production of the compact arrangement including the printed circuit board, conductor tracks and plug connectors by omitting flexible conductor connections and cables.