FLUID PUMP

Abstract

An electromagnetic actuating device for a torque transmission system includes a shell arranged around an axis X, the shell being fixed relative to the axis X. The shell includes walls defining an annular cavity which houses a coil and at least partially a plunger which is able to move axially along the axis X to actuate a coupling device.

Description

The invention relates to a fluid pump, in particular an oil pump for supplying a clutch actuator, a gearbox actuator, a lubrication system and/or a cooling system of a drive train, with an electric drive unit which comprises a stator and a rotor which is arranged inside the stator and can rotate about a rotor axis.

Such fluid pumps and methods are known from the prior art. An example can be found in DE 10 2019 130 722 A1. Such fluid pumps are often fitted in motor vehicles, in particular cars. The electric drive units of such fluid pumps are here usually controlled via control units provided inside the fluid pump.

Here, the fluid pumps must firstly function reliably in aggressive environments, i.e. environments with high temperatures and/or shaking or vibrations, over their entire useful life. Furthermore, it is desirable that the fluid pumps can be produced with the lowest possible cost. There is often a conflict of objectives here between low production costs, on one hand, and high reliability over a long period.

So that the fluid pump can be produced simply and at the same time functions reliably even under adverse environmental conditions over its entire useful life, it is known from the abovementioned document that the control unit and the stator are embedded in the drive housing by means of a casting compound. The whole housing is here filled with the casting compound. Relative movements between the stator, the control unit and the drive housing are prevented by the casting compound over the entire useful life of the fluid pump and the penetration of dirt, moisture, etc can also be prevented. The robustness is further increased by the rigid housing which is present in addition to the casting compound. The fluid pump consequently also functions reliably under adverse conditions. At the same time, the casting of the control unit and the stator is relatively simple such that the fluid pump can be produced simply and cost-effectively.

It has, however, been established that electronic power components which are part of the control unit generate a relatively large amount of waste heat under certain operating conditions. In terms of the useful life of the electronic components, it is desirable that this waste heat is reliably dissipated.

The object of the invention consists in providing a fluid pump in which the waste heat from electronic power components of the control unit can be dissipated reliably without a great deal of effort being required for this purpose.

In order to achieve this object, a fluid pump is provided according to the invention, in particular an oil pump for supplying a clutch actuator, a gearbox actuator, a lubrication system and/or a cooling system of a drive train, with a housing, a stator, a control unit which is arranged at one end of the housing, and a heat-conducting element with a plate-like base body, wherein the stator, the control unit and the plate-like base body are embedded in a casting compound. The invention is based on the fundamental concept of distributing the locally occurring waste heat over a larger surface area by means of the heat-conducting element such that it can then be emitted to the outside through the casting compound and no hot spots occur. It has namely proven to be the case that if the waste heat which occurs is distributed over a large surface area, the thermal conductivity of the casting compound is sufficient to dissipate quickly the waste heat which occurs such that the electronic power components cannot heat up to undesirably high temperatures. The particular advantage of the construction according to the invention consists in the fact that the whole of the plate-like base body is embedded inside the casting compound such that the front side of the cast body formed by the casting compound is designed as closed. A closed outer face of the cast body is particularly advantageous in terms of thermal expansion which occurs during operation in the case of temperature differences.

According to an embodiment of the invention, it is provided that the base body has a surface area which is more than 50% of the internal cross-section. As a result, it is ensured that the waste heat occurring at the control unit is dissipated over a large surface area. In principle, the base body should have a surface area which is as large as possible and preferably in the order of 80% or alternatively more than 90% of the internal cross-section. In order to make production simpler or when other components have to be arranged laterally next to the heat-conducting element, it can be necessary to design the base body with a slightly smaller surface area.

The base body can be provided with support tabs which bear elastically against the inner surface of the housing. Heat can be emitted directly to the housing of the fluid pump via the support tabs such that an additional “heat exchange surface” with the environment can be used here.

According to one embodiment, it is provided that the heat-conducting element and the housing are electrically conductive. As a result, the emission of electromagnetic radiation to the outside is reduced. Moreover, the effect of EMV radiation externally is reduced and the interference resistance improved. Better EMV compatibility results in this way. The materials from which the heat-conducting element and the housing are made are then not only optimized in terms of thermal conductivity but also in terms of electrical conductivity and hence in terms of the capacity to act as a shield for electromagnetic radiation in both directions. The housing and hence also the heat-conducting element are connected to each other capacitively or galvanically via a suitable connection depending on requirements with regard to EMV.

It is preferably provided that the base body bears directly against at least one electronic component of the control unit such that a direct transfer of heat is ensured.

It can alternatively also be provided that a thin layer of casting compound is situated between at least one electronic component of the control unit and the base body. It has been proven to be the case that such a thin layer of casting compound does not significantly impede the heat conductance because the conventional casting compounds have a thermal conductivity of a similar magnitude to that of heat-conducting pastes that are used to attach heat sinks to electronic components.

The base body can be provided with a plurality of spacers which bear against a printed circuit board of the control unit, wherein the spacers are designed in particular as beads. The spacers ensure that the heat-conducting element is situated in a precise position relative to the printed circuit board before the interior of the housing is filled with the casting compound.

The base body can be provided with a plurality of through openings such that material bridges are formed from the casting compound between those sections of the cast body which lie on opposite sides of the base body. This is advantageous with respect to the resulting strength of the cast body.

The base body can have at least one embossed raised/depressed portion which has a different spacing from the printed circuit board of the control unit than the remainder of the base body. By means of the raised/depressed portions which can, for example, be embossed, the height profile of the base body can be adapted to the different height of different electronic power components such that optimal heat dissipation into the base body is ensured for each power component.

The base body can be made of an aluminium alloy such that a high thermal conductivity with a low weight results. Alternative possible materials are steel, copper or brass. It is also conceivable to use a plastic that is a good conductor of heat.

The housing can be made of an aluminium alloy too, which is advantageous for the total weight of the fluid pump. Other materials, for example plastic, are, however, also suitable in principle. Depending on the requirements for the thermal conductivity, the latter can be optimized such that it has high thermal conductivity.

The invention will be described below on the basis of two embodiments which are illustrated in the appended drawings, in which:

FIG. 1 shows a fluid pump according to the invention in a perspective view;

FIG. 2 shows a cross-section through the fluid pump from FIG. 1;

FIG. 3 shows a plan view of the cast body of the fluid pump in FIGS. 1 and 2;

FIG. 4 shows a section along the plane IV-IV of FIG. 3;

FIG. 5 shows a heat-conducting element of the fluid pump according to a first embodiment in a perspective view;

FIG. 6 shows a schematic exploded view of a fluid pump according to the first embodiment, wherein the cast body is illustrated in section;

FIG. 7 shows a heat-conducting element of a fluid pump according to a second embodiment in a perspective view; and

FIG. 8 shows a schematic exploded view of the fluid pump according to the second embodiment.

A fluid pump 10, which has a housing 12 in which a stator 14 (see FIG. 2) and a control unit 16 are arranged, is shown in FIG. 1. The control unit 16 is used to activate the stator such that a rotor 18 can be set in rotation in a desired fashion.

The rotor 18 is part of a pump module which has a pump unit 20, driven by the rotor 18, by means of which a fluid can be pumped through suction and pressure ports 22 shown schematically in FIG. 1.

The pump module with the pump unit 20 and the rotor 18 is attached to the housing 12 from outside such that the rotor 18 lies inside the stator 14.

A cap 24 which delimits the space relative to the rotor 18 is arranged inside the housing 12. The internal volume between the wall of the housing 12 and the cap 24 is filled with a casting compound 26. In addition to the stator 14 and the control unit 16, a heat-conducting element 30 is also embedded in the casting compound 26 and thus in the cast body 28 formed by the set casting compound 26.

The heat-conducting element 30 (see in particular FIG. 5) has a plate-like base body 32 which is here designed as plane.

Provided in the vicinity of the outer rim of the base body 32 are a plurality of spacers 34 which are here designed in the form of beads which extend along almost the whole outer circumference of the base body.

The heat-conducting element 30 here extends over almost the whole cross-section of the housing 12.

Provided at the outer rim of the base body 32 of the heat-conducting element 30 are a plurality of support tabs 36 which are provided and dimensioned so as to bear against the inner side of the housing 12 under pretension (see FIG. 2).

The heat-conducting element 30 is attached to a printed circuit board 38 of the control unit 16 before the housing 12 is filled with the casting compound 26, and to be precise such that the spacers 34 are supported on the printed circuit board 38. It is consequently ensured that the base body 32 of the heat-conducting element 30 is situated with a desired predefined spacing from electronic power components 40 which are part of the control unit 16.

As can be seen in FIG. 2, the heat-conducting element 30 is arranged on that side of the printed circuit board 38 which faces away from the stator 14.

The support tabs 36 can be used to install the heat-conducting element 30 at the desired position inside the housing 12 and bearing against the printed circuit board 38 of the control unit 16. Depending on the component heights of the electronic power components 40 of the control unit 16 (and also depending on any raised/depressed portions which are embossed in the base body 32 of the heat-conducting element 30), the electronic power components 40 bear directly against the heat-conducting element 30 or a small gap is present between the upper side of the power components 40 and the underside of the base body 32 of the heat-conducting element 30.

If the interior of the housing 12 is filled with the casting compound 26, the space between the printed circuit board 38 and the heat-conducting element 30 is also filled. A quantity of casting compound 26 is added here such that the level of the casting compound is above the heat-conducting element 30 such that the latter is completely embedded. As can be seen in FIGS. 1 and 2, however, the heat-conducting element 30 is situated with a slight spacing below the end face of the cast body 28 thus formed.

Heat from the electronic power components 40 is transmitted into the base body 32 either by direct contact with the base body 32 (see the relieved portion, labelled with the reference sign 50 in FIG. 6, in the cast body 28) or via a residual thin layer of casting compound 26 (see the relieved portion, labelled with the reference sign 52 in FIG. 6, of a power component).

The heat introduced locally from the power components 40 is transmitted over the whole surface area of the heat-conducting element 30 by virtue of the high thermal conductivity of the heat-conducting element 30. Some of the heat is emitted into the environment via the outer end side of the cast body 28, and some of the heat is emitted into the housing 12 via the support tabs 36. Relatively large amounts of heat can be effectively dissipated into the environment without there being any need for heat sinks to be provided which have to extend through the cast body 28 to the outside.

A further advantage of the heat-conducting element 30 which is electrically conductively connected to the housing 12 is that it improves the EMV properties of the pump because it serves as a shield.

FIGS. 7 and 8 show a second embodiment. The same reference signs are used for the features and components known from the first embodiment, and to this extent reference is made to the explanations above.

The difference between the first and the second embodiment is that, in the second embodiment, the base body 32 is designed as not closed and instead has a plurality of perforations or through openings 60. Material bridges of casting compound extend through the through openings 60 such that those sections of the cast body 28 which are situated above and below the heat-conducting element 30 are connected directly to one another. This is advantageous for the strength of the cast body 28.

In terms of avoiding notch effects, the rims of the through openings 60 are designed as very smooth and in particular with a rounded bevel.

Claims

1. An electromagnetic actuating device for a torque transmission system, the electromagnetic actuating device comprising: a shell arranged around an axis X, the shell being fixed relative to the axis X and comprising walls defining an annular cavity which houses a coil and at least partially a plunger which is able to move axially along the axis X to actuate a coupling device, the actuating device being characterized in that the shell also comprises a recess and the actuating device comprises a detection lug fixed to the plunger and passing through this recess, wherein the detection lug is able to be detected by a sensor so as to generate a signal representative of the axial position of the plunger.

2. The electromagnetic actuating device as claimed in claim 1, wherein the relative rotation of the plunger relative to the shell along the axis X is prevented or limited by the cooperation of the detection lug and the recess.

3. The electromagnetic actuating device as claimed in claim 1, wherein the plunger is arranged radially outside the coil.

4. The electromagnetic actuating device as claimed in claim 1, wherein the plunger is situated axially facing the coil.

5. The electromagnetic actuating device as claimed in claim 1, wherein the shell comprises, viewed in a plane containing the axis X: a first side wall arranged around the axis X,a second side wall arranged around the axis X and axially spaced from the first side wall,a radially inner wall arranged around the axis X and connecting the first side wall to the second side wall,at least one radially outer wall arranged around the axis X and extending axially from the at least one of the first side wall and the second side wall, the plunger being arranged radially inside the radially outer wall and radially outside the radially inner wall.

6. The electromagnetic actuating device as claimed in claim 5, wherein the recess is situated on the radially outer wall.

7. The electromagnetic actuating device as claimed in claim 5, wherein the second side wall is situated, relative to the coil, on the side of the coupling device actuated by the axial movement of the plunger, and the first side wall is situated on the other side, the recess being situated at least partly in the first side wall.

8. The electromagnetic actuating device as claimed in claim 1, wherein the plunger is centred by its outer circumference on the shell.

9. The electromagnetic actuating device as claimed in claim 1, wherein the detection lug is able to be detected by a magnetic sensor, and the electromagnetic actuating device comprises a screen arranged between the sensor and the coil, the screen being carried by the detection lug.

10. The electromagnetic actuating device as claimed in claim 1, wherein the electromagnetic actuating device comprises a non-magnetic connecting ring fixed to the axial end of the plunger, on the side of the coupling device actuated by the axial movement of the plunger.

11. A transmission system for a motor vehicle, comprising: the electromagnetic actuating device according to claim 1,a first element and a second element, the second element being able to rotate relative to the first element around the axis X, the at least one of the first element and the second element being able to transmit a torque between a motor and a vehicle wheel,a coupling device which is actuatable by the electromagnetic actuating device; the coupling device comprising a first coupling part able to be axially pressed by the plunger of the electromagnetic actuating device, and a second coupling part; the first coupling part being fixed in rotation about the axis X relative to the first element, and the second coupling part being fixed in rotation about the axis X relative to the second element; the first coupling part being axially movable between a coupled position in which the first coupling part is coupled to the second coupling part so as to prevent a relative rotation of the first element and second element about the axis X, and a decoupled position in which the first coupling part and the second coupling part are decoupled so as to allow a relative rotation of the first element and second element about the axis X,a sensor cooperating with the detection lug to supply a signal representative of the axial position of the plunger, so as to determine whether the first coupling part is in the decoupled position, the coupled position, or an intermediate position between the decoupled position and the coupled position.

12. The transmission system as claimed in claim 11, wherein the transmission system comprises a differential drive device, and the first element comprises a casing inside which the second coupling part is housed; the first coupling part comprising an inner portion which is housed inside the casing, an outer portion which is positioned outside the casing, and a plurality of connecting portions which axially connect the inner portion and the outer portion of the first coupling part, each of the connecting portions passing through a corresponding through-opening made in the casing.

13. The transmission system as claimed in claim 11, wherein the second element comprises a supporting ring which is guided in rotation about the axis X inside the casing, two planet pinions which are mounted to rotate on the supporting ring about an axis Z perpendicular to the axis X, and two sun gears which are movable in rotation about the axis X and each in mesh with the two planet pinions and each intended to be rotationally fixed to a wheel drive shaft; the second coupling part of the coupling device being rotationally fixed to the supporting ring about the axis X.

14. The transmission system as claimed in claim 11, wherein the transmission system is housed in a housing comprising a non-magnetic wall, for example of aluminum, and the sensor is mounted on the housing wall outside the housing, the sensor being able to detect the detection zone of the detection lug through the housing wall.

15. The transmission system as claimed in claim 11, wherein a pivot joint kinematically links the plunger and the first coupling part so as to allow a relative rotation of the plunger and the first coupling part about the axis X.

16. The transmission system as claimed in claim 15, wherein the connecting ring and the first coupling part each comprise a groove, the two grooves being arranged radially opposite one another, and a retaining ring is arranged inside the two grooves.

17. A power train, in particular electrified, comprising a motor, in particular electric, at least one drive wheel, and a transmission system as claimed in claim 11, the transmission system being configured to transmit a torque between the motor and said at least one drive wheel.

18. The electromagnetic actuating device as claimed in claim 2, wherein the plunger is arranged radially outside the coil.

19. The electromagnetic actuating device as claimed in claim 2, wherein the plunger is situated axially facing the coil.

20. The electromagnetic actuating device as claimed in claim 2, wherein the shell comprises, viewed in a plane containing the axis X: a first side wall arranged around the axis X,a second side wall arranged around the axis X and axially spaced from the first side wall,a radially inner wall arranged around the axis X and connecting the first side wall to the second side wall,at least one radially outer wall arranged around the axis X and extending axially from the at least one of the first side wall and the second side wall, the plunger being arranged radially inside the radially outer wall and radially outside the radially inner wall.