EP0071529A1 - Motor-pump unit, especially for a power steering system of an automotive vehicle - Google Patents

Abstract

1. A motor-pump unit for a device assisting the steering of a motor vehicle, said unit comprising a hydraulic pump and a driving DC motor assembled in such manner as to constitute a unit, in which the assembly between the motor (2) and the pump (3) is achieved by means of a single assembling element (4) forming at the same time one of the end walls of the electric motor (2), a throughway passage (15) for the transmission (10) of the movement of rotation between the motor and pump, and the housing (14) of a safety valve (31), this motor-pump unit being characterised in that the assembling element has a recess for a sealing element (17) providing the seal between the cavity of the pump (3) and the electric motor (2), and a single machined surface (22) located adjacent to the pump, in which surface there is formed a peripheral groove for a sealing element providing the seal with the housing of the pump (10) and there being provided inside the perimeter defined by the groove (23) two orifices (26, 27) respectively communicating, on one hand, directly with the suction and delivery chambers of said pump (10) and, on the other hand, with the upstream and downstream sides of said safety valve (31).

Description

The present invention relates to motor-pump groups composed of a hydraulic pump and an electric drive motor assembled so as to form a mono-block unit. More particularly, the invention relates to an improved motor-pump group in which the hydraulic pump, preferably of the gear type, is intended to supply the hydraulic circuit of the steering assistance device of a motor vehicle.

The current trend in the construction of motor vehicles is to provide the driver with maximum comfort and safety and manufacturers therefore seek to equip vehicles (even those called "low end") with equipment to obtain this result. This is particularly the case with the direction to which we tend to add more and more assistance allowing the driver to maneuver easily, especially at low speed and when stationary. If these are "low-end" vehicles, it is naturally essential that these additional equipment does not excessively increase the cost price of the vehicle as a whole and we therefore seek as far as possible to reduce manufacturing costs. In GB 987 587, there is already described a motor-pump unit comprising a gear pump and an electric drive motor, these two components being connected together by means of an assembly part which in what relates to the electric motor constitutes a flange thereof supporting a bearing of its shaft.

In the intermediate room there is a relatively complex network of pipes, the pipes being intended to establish the various communications between the suction and discharge cavities of the pump and of the control valves which are arranged in this same intermediate part. One of the valves constitutes a safety against pressures exceeding a certain predetermined value.

The network of pipes of the intermediate piece can only be produced by machining, which obviously gives rise to this expensive intermediate piece which is hardly compatible with the requirements mentioned above concerning the automobile industry. Furthermore, this prior pumping unit is intended to be immersed in an oil tank and therefore does not require any sealing at the level of the joint plane between the pump and the intermediate part.

The object of the invention is to provide a motor-pump unit recalling the known construction of the aforementioned patent, but which can be manufactured at a much lower cost price, while ensuring a perfect seal at the joint plane between the intermediate part. assembly and pump.

The subject of the invention is therefore a motor-pump group for a steering assistance device of a motor vehicle, this group being composed of a hydraulic pump and an electric DC drive motor assembled from so as to form a unit, in which the assembly between motor and pump is carried out using a single assembly part forming at the same time one of the flanges of the electric motor, a bushing for the transmission of the movement of rotation between motor and pump and the casing of a safety valve, this motor-pump unit being characterized in that the assembly part has a housing for a seal ensuring the seal between the pump cavity and the electric motor, as well as a single machined surface located on the side of the pump, surface in which is made a peripheral groove for a seal forming a seal with the pump housing and in that inside the perimeter defined by the groove are located two orifices communicating respectively on the one hand directly with the chambers suction and discharge of said pump and on the other hand with the upstream and downstream sides of said safety valve.

Thanks to these characteristics, the casing of the safety valve communicates through simple orifices with the corresponding chambers of the pump, so that the intermediate assembly part can be manufactured for an inexpensive molding process while sealing is ensured by a seal which is housed in a groove in the end surface on the pump side of this part, a groove with respect to which said orifices are judiciously arranged.

It should be noted that other compact motor-pump groups are described in the prior art, for example, in FR 2 242 885 and FR 2 436 895. However, in the first of these documents, the group comprises a motor electric drive built autonomously so that the intermediate piece disposed between the motor and the pump does not constitute the flange of this motor. Furthermore, the intermediate piece has no arrangement for mounting a safety valve.

The group described in FR 2,436,895 comprises an intermediate piece of _e assemblag which is a simple flange of the electric motor, but which is not to convey the pumped fluid.

• - la Fig. 1 est une vue en perspective partielle et avec arrachement partiel d'un groupe moto-pompe suivant l'invention;
• - la Fig. 2 est une vue en perspective schématique de la partie d'extrémité, côté pompe, de la pièce d'assemblage du groupe moto-pompe;
• - la Fig. 3 montre une vue à plus grande échelle et en coupe axiale du clapet de sécurité à montage inviolable;
• - la Fig.4 est une vue schématique en coupe d'un autre dispositif utilisé comme bouchon inviolable du clapet de sécurité;
• - la Fig. 5 est une vue en perspective schématique du bouchon de la Fig.4.

The invention will be described below with reference to the accompanying drawings given solely by way of example and in which:

• - Fig. 1 is a partial perspective view with partial cutaway of a motor-pump unit according to the invention;
• - Fig. 2 is a schematic perspective view of the end part, pump side, of the assembly part of the motor-pump group;
• - Fig. 3 shows a view on a larger scale and in axial section of the tamper-evident mounting safety valve;
• - Fig.4 is a schematic sectional view of another device used as a tamper-evident cap of the safety valve;
• - Fig. 5 is a schematic perspective view of the plug of FIG. 4.

We first refer to FIG. 1 on which it can be seen that the motor-pump unit 1 comprises an electric motor 2,, a hydraulic pump 3 as well as an assembly part 4, the assembly forming a monobloc unit. The electric motor 2 which will not be described in detail in the present description, can be of any type, but it can advantageously consist of the motor described in the patent application filed on the same day in the name of the Applicant, for : "Electric motor in particular for driving a hydraulic gear pump". It suffices to note here that this motor comprises an output shaft 5 driven in rotation by a rotor 6 which is rotatably mounted in a stator 7 with permanent magnets itself arranged in a casing 8.

The hydraulic pump 3 is preferably of the A type. gears 9a, 9b (see Fig.2) mounted in a pump housing 10 from which emerges a stud 11 integral in rotation with the gear 9a.

Motor 2 and pump 3 are assembled using of the assembly part 4 which is in the general form of a circular disc constituting one of the flanges of the motor 2. The assembly part is fixed to the casing of the latter by means of crimped lugs 12 penetrating respectively in notches 13 formed at the periphery of the assembly part. This comprises a central body 14 whose cross section is adapted to the shape of the pump body and which protrudes on either side of the faces of the disc forming a flange. This central body has a passage 15 of generally cylindrical section centered on the axis XX of the shaft 5 of the electric motor 2. The passage 15 is stepped and first receives a bearing 16 of the shaft 5, a seal d seal 17, an Oldham seal 18 as well as the pin 11 of the gear 9a. The Oldham seal 18 is of known type making it possible to absorb the geometric alignment defects between the shaft 5 of the electric motor, on the one hand, and the equipment formed by the pin 11 and the gear 9a, d 'somewhere else.

The casing 10 of the pump 3 is attached to the body 14 of the assembly part 4 by means of four screws 19. The gear 9b which is rotatably mounted in the casing 10 comprises a cylindrical end piece 20 which is received with play in a cavity 21 whose axis is parallel to the axis XX and which is formed in the body 14.

The casing 10 of the pump 3 is pressed against a flat end surface 22 of the assembly part 4, this surface being the only element machined with precision on this part. A groove 23 is formed in this surface and bypasses the cylindrical passage 15 and the cavity 21. A seal 24 disposed in this groove seals the cavity of the pump 3 from the outside.

The body 14 of the assembly part 4 has also a transverse blind hole 25 (Fig.3) located above the passage 15. This hole is stepped and comprises two parts 25a, 25b of diameters increasing from the inside to the outside and separated by a radial shoulder 25c. The rear part 25a communicates with an oblong light 26 which opens directly into the cavity of the pump 3 on the delivery side (high pressure), while the front part 25b is in communication with an oblong light 27 which also opens directly in the cavity of the pump, but on the suction side.

A sleeve 28 of circular section is mounted by screwing in the blind hole 25 and stopped against the radial shoulder 25c. It comprises a radial end neck 29 which forms a seat for a needle 30 of a safety valve 31, the central hole delimited by the neck 29 establishing communication between the part 25a (discharge side of the pump- and the delimited chamber by the sleeve 28 which, through orifices 32 is connected to the part 25b, when the needle is lifted from its seat.

This needle is kept pressed on its seat thanks to a calibrated spring 33 which is supported on a plug 34 retained in an enlarged front part 28a of the sleeve 28 while being tightened against a radial shoulder 28b formed therein. The plug 34 is held in place by a circular plate 35 which is itself blocked by an annular rim crimped 28c of the sleeve 28. The latter is in turn blocked by a flange 36 of the body 14 crimped against the annular rim 28c. It is understood that thanks to this construction the safety valve 31 can only be disassembled by destroying the collar 36, the plug 34 can only be removed by deforming the annular rim 28c. The whole is therefore tamper-proof and intervention on valve 31 by unauthorized persons is not possible.

Figs. 4 and 5 representing an alternative mounting of the safety valve 31. In this case, the body 14 of the connecting piece 4 has a cavity 37 which opens to the outside by a rectangular opening 38 through which the valve 31 can to be placed. A blocking wedge 39 is inserted into the cavity 37 is held in position by crimped lugs 40a and 40b which are molded with the body 14.

In Fig. l, it can be seen that the assembly part also comprises two fixing plates 41a and 41b which have come from molding and which extend outwards from two reinforcement wings 42 extending between the body 14 and the periphery of the assembly part.

Each sole 41a, 41b has a housing 43 for a screw 44, two opposite walls of this housing being formed by deformable lugs 45 make it possible to make the screw 44 captive while maintaining it! against any rotation. The rod of the screw passes through the bottom of the housing 43. Of course, instead of the screws 44, it is possible to provide in the housings 43 nuts of the same dimensions as the heads of these screws.

The assembly part 4 can thus be produced entirely by molding. It is preferable to use for this part the die-cast Zamac, only the face 22 contiguous to the pump requiring precise machining.

The Oldham seal 18 is lubricated in operation by the oil transported by the pump 3 which fills the bore 15 thanks to a voluntary leak from this pump.

Claims (7)

1. Motor-pump unit for a motor vehicle steering assistance device, this group being composed of a hydraulic pump and an electric DC drive motor assembled so as to form a unit, in which the assembly between motor (2) and pump (3) is carried out using a single assembly part (4) forming at the same time one of the flanges of the electric motor (2), a bushing (15 ) for the transmission (10) of the rotational movement between motor and pump, and the casing (14) of a safety valve (31), this motor-pump unit being characterized in that the assembly part has a housing (15) for a seal (17) sealing between the pump cavity (3) and the electric motor (2), as well as a single machined surface (22) located on the side of the pump, surface in which a peripheral groove is made for a seal forming a seal with the pump housing (10) and in that inside the perimeter defined by the rain ure (23) are located two orifices (26,27) communicating respectively on the one hand directly with the suction and discharge chambers of said pump (10) and on the other hand with the upstream and downstream sides of said safety valve (31). 2. motor-pump unit according to claim 1, characterized in that the assembly part (4) has the general shape of a disc at the center of which is provided a body (14) which extends axially from this disc and whose section corresponds to that of the body (10) of the pump (3), the latter being fitted against said machined end face (22) of the body (14) of the assembly part (4). 3. motor-pump unit according to claim 2, characterized in that said assembly part (4) has come entirely from molding. 4. Motor-pump unit according to any one of claims 1 to 3, characterized in that the casing of said safety valve (31) is delimited by a blind hole (25) provided in the body (14) of the part d assembly (4) and in that this safety valve (31) is locked in this hole using a blocking device comprising as blocking element at least a part (36; 40a, 40b) of the material of said body (14) of the assembly part (4). 5. motor-pump unit according to claim 4, characterized in that said blocking element (36) is an annular lip surrounding the opening of the blind hole (25) forming the casing of the safety valve (31) and retaining it- here in the blind hole (25). 6. motor-pump unit according to claim 4, characterized in that said blocking device comprises a wedge (39) disposed in a cavity formed in the body (14) of the assembly part (4) in front of the hole (25 ) forming the casing of the safety valve (31) and in that the wedge is retained in this cavity by means of deformed lugs (40a, 40b) of the body (14) which have formed therewith. 7. motor-pump unit according to any one of claims 1 to 6, characterized in that the assembly part (4) comprises fixing plates (41a, 41b) coming from forming with it and intended to ensure the fixing of the group as a whole.

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