Liquid pump, in particular for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle

A liquid pump for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle, having a pump housing wherein a pump chamber and a pump rotor are arranged, wherein the pump housing has at least one intake opening, wherein a filter plate which covers at least one intake opening is attached to the pump housing.

The invention relates to a liquid pump, in particular for providing a supply to a transmission of an electric or hybrid drive module of a motor vehicle, having a pump housing in which a pump chamber and a pump rotor are arranged, wherein the pump housing has at least one intake opening.

Such a liquid pump may be used for supplying oil to a transmission or other components in a drive train. The liquid pump may, for example, be arranged on a housing of the transmission in such a way that the intake opening is arranged below the level of an oil reservoir in the transmission housing.

The object of the invention is to prevent, with little outlay, passing of impurities into the pump and possibly also to the lubrication points supplied with oil by the pump.

For the purpose of achieving said object, it is provided according to the invention, in the case of a liquid pump of the type mentioned in the introduction, that a filter plate which covers the at least one intake opening is attached to the pump housing. The invention is based on the fundamental concept of performing the filtering function with a single component which, on the one hand, can be produced with little outlay (by being provided with suitable filter openings) and which, on the other hand, can be mounted with very little outlay, specifically can be simply screwed to the housing.

Preferably, the filter plate has a multiplicity of filter openings which have an opening width of at most 0.4 mm, preferably at most 0.3 mm, and in particular at most 0.2 mm. In this way, the filtering action can be very easily set in the desired manner during the production of the filter plate.

In order to increase the overall available flow cross section, provision may additionally be made of filter slots through which oil can be sucked in. Said filter slots are provided between the filter plate and the pump housing and have dimensions which are comparable to those of the filter openings.

It is furthermore possible for the filter plate to be of planar form, if provision is made in the pump housing of recessed portions such that the filter slots are delimited between said recessed portions and the filter plate.

The filter plate may consist of a sheet metal, that is to say of a material which can be machined very well. Moreover, there is no risk of wear.

The filter plate may be etched, laser-cut or water jet-cut. By way of these machining processes, the filter openings can be produced with very high accuracy.

It is also possible for the filter plate to be a punched part, which leads to particularly low production costs.

In the case of a punched part, the filter openings may be formed between material portions of the filter plate that are bent relative to one another. This makes it possible to produce different filter plates, that is to say filter plates which differ with regard to the opening width of the filter openings, using an intrinsically identical production process. For this purpose, it is merely necessary for the material portions to be deformed relative to one another to a greater or lesser extent.

The filter plate may also be an injection-moulded part, with the result that it can be produced with little outlay, low costs and high precision.

Preferably, the filter openings are formed in an undercut-free manner, as viewed in a direction perpendicular to the plane of the filter plate. This makes it possible for the filter plate to be producible in an injection mould without slides.

According to one embodiment of the invention, it is provided that the filter plate is provided with at least one latching lug, by way of which it can be locked to the pump housing. This makes it possible for said filter plate to be pre-mounted on the pump housing such that the assembly composed of pump housing and filter plate can be checked in advance. It is thereby possible for any malfunctions to be detected before the liquid pump is completely assembled.

According to one configuration of the invention, provision is made of a pressure-limiting valve, which has a valve body and a spring, wherein the spring is supported against the filter plate. On account of its strength, the filter plate is suitable for acting as a counter bearing for the spring of the pressure-limiting valve. Consequently, no additional components are required for mounting the pressure-limiting valve.

According to one configuration of the invention, it is provided that the filter plate has a spring-centering means. This prevents inadvertent jamming of the spring during the opening and/or closing of the valve body.

The spring-centering means may be formed in particular by a plastically deformed portion of the filter plate. In this configuration too, no additional components are required. It is sufficient for the filter plate to be plastically deformed in such a way that, for the support of the spring, there is formed either a wall, in which the spring is received, or a projection, which extends into the spring.

According to the preferred embodiment of the invention, provision is made of multiple mounting screws by way of which at least one bearing body and the pump housing are screwed to one another, wherein the mounting screws have screw heads which bear directly on the filter plate. On account of its mechanical strength, the filter plate acts in the manner of shims such that separate shims can be dispensed with, which simplifies the mounting and reduces the costs.

FIGS.1and2show a liquid pump10, which is provided for being attached to a transmission of an electric or hybrid drive module of a motor vehicle. Of the transmission, a part of the transmission housing12is schematically shown here.

The liquid pump10has an electric motor, which has a stator14and a rotor16, wherein the rotation of the rotor16of the electric motor is transmitted to a pump rotor18by means of a shaft17. The pump rotor18is part of a toothed ring pump, which has an outer ring20in which the pump rotor18meshes. The outer ring20slides in a pump housing22. This pump type is also known as a gerotor pump.

The liquid pump sucks in via an intake opening24, which is provided here in a bearing body26which serves for mounting the shaft17. The discharge is realized via an outlet opening28, which is likewise formed in the bearing body26. From there, the oil flows to a connection piece30.

The outlet opening28is assigned a pressure-limiting valve32, which has a valve body34and a spring36.

The pressure-limiting valve32opens if the pressure on the delivery side of the liquid pump becomes excessively high. In this case, delivered oil flows directly back to the suction side.

Here, the valve body34is accommodated displaceably in a suitable opening of the bearing body26.

The spring36is supported against a filter plate40, which covers the intake opening24at the outside and is attached to the pump housing22. Specifically, in the embodiment shown, the filter plate40is attached on that side of the bearing body26facing away from the electric motor. Any oil which is sucked in through the intake opening24by the liquid pump must therefore first pass through the filter openings42, which are provided in the filter plate40.

The filter plate consists of sheet metal.

The filter openings may be formed by different processes according to requirements and desired accuracy. For example, the filter openings42may be etched, laser-cut or water jet-cut. It is also possible for the filter openings42to be punched.

In order to connect the filter plate40to the liquid pump, multiple mounting screws44are provided (see in particularFIGS.1and3). These extend through the filter plate40and the bearing body26at least into the pump housing22. Since the filter plate40consists of metal, it has sufficient strength to serve as a “shim” for the mounting screws44.

FIGS.5and6show a second embodiment. The same reference signs are used for the components known from the first embodiment, and, in this respect, reference is made to the explanations above.

The difference between the first and second embodiments lies in the configuration of the filter plate40.

A first difference is that, in the second embodiment, a spring-centering means46is provided for the spring36of the pressure-limiting valve32. Said spring-centering means is formed here as a projection of the filter plate40that is directed towards the pressure-limiting valve32. At this position, the filter plate40may be deformed plastically in the manner of a deep-drawn formation.

As an alternative to the projection shown, it is also possible to use a well, that is to say a depression, in which the spring36is seated.

A second difference in comparison with the first embodiment is that, in the second embodiment, the filter openings42are formed not by cut-away regions of the material of the filter plate40, but by plastically deformed material portions of the filter plate that are bent relative to one another (see in particularFIG.6). This can be obtained by way of a combined punching and embossing step.

Irrespective of the manner in which the filter openings42are produced, the opening width of the filter openings can be set to a desired value. Said value depends on the size of dirt particles which are considered to be still permissible. Common values lie in the range from 0.2 mm to 0.4 mm.

FIGS.7to11show a sub-assembly of a liquid pump10according to a third embodiment. The same reference signs are used for the components known from the first two embodiments, and, in this respect, reference is made to the explanations above.

The sub-assembly shown inFIGS.7to11consists of a part of the pump housing, specifically the bearing body26, and the filter plate40.

As in the second embodiment, the filter plate40is formed from metal, and the filter openings42are formed by plastically deformed material portions of the filter plate40that are bent relative to one another.

The difference between the second and third embodiments is on the one hand that, in the third embodiment, provision is made of additional filter openings, specifically in the form of filter slots43, which are provided between the filter plate40and the bearing body26. The filter slots43increase the available throughflow cross section.

In order to form the filter slots43, the bearing body is provided with multiple recessed portions45in the abutment surface at which the filter plate40bears against said bearing body (see in particularFIG.8), with the result that, there, a flow cross section is formed between the bottom side of the filter plate40and the base of the recessed portions45.

The dimensions of the filter slots correspond to the dimensions of the filter openings42, and so the same filtering action is obtained. The recessed portions45are thus set back by 0.2 to 0.4 mm in comparison with the level of the abutment surface for the filter plate40.

The difference between the second and third embodiments is on the other hand that, in the third embodiment, provision is made of multiple latching lugs50by way of which the filter plate40can be locked to the pump body.

In the exemplary embodiment shown, the latching lugs50are provided on the filter plate40, and they interact with latching noses52on the bearing body42.

By means of the latching lugs50, the filter plate40can be pre-mounted on the pump body (on the bearing body26in this case) such that the sub-assembly formed in this way can be tested for proper functioning thereof. For example, the functioning of the pressure-limiting valve32can be tested before the liquid pump10is completely assembled.

Also provided on the filter plate40are multiple centering lugs54, which engage into suitable cutouts in the bearing body26. This facilitates the mounting of the filter plate40on the bearing body26and ensures that the filter plate40, in its mounted state, is precisely in position.

FIGS.12to14show a liquid pump according to a fourth embodiment. The same reference signs are used for the components known from the preceding embodiments, and, in this respect, reference is made to the explanations above.

The most substantial difference between the fourth embodiment and the preceding embodiments is that, in the fourth embodiment, the filter plate40does not consist of sheet metal, but is a plastic component.

The filter plate40is injection-moulded, wherein all the geometrical features (for example the spring-centering means46and the centering lugs54) can be moulded. Latching lugs may also be formed, in order to be able to pre-mount the filter plate on the pump body in the same manner as in the third embodiment.

As can be seen in particular inFIG.14, the filter plate40may be designed in an undercut-free manner. The filter openings42are formed between two layers of webs60, which, in view of the demouldability, have a trapeziform cross section (which is illustrated in a slightly exaggerated manner here).

The mutually facing surfaces62of the webs60lie in planes which are at a distance H from one another.

The filter plate is therefore designed in an undercut-free manner (as viewed in a direction B which is perpendicular to the plane of the filter plate40). It can therefore be injection moulded without the necessity of slides in the injection mould for this purpose. It is merely necessary that the parting surface between the two mould halves has a tooth-like engagement formation in the region of the filter openings42.