Patent Application
20240271619
The present disclosure relates to a hydraulic pump unit, in particular for use in hydraulic actuation systems for motor vehicles, and an assembly method for a hydraulic pump unit. It deals in particular with the connection of a pillow block for a pump of the hydraulic pump unit to a housing of the hydraulic pump unit.
Hydraulic actuation systems are known for actuating actuators in automotive technology, for example for actuating clutches, parking locks or the like. A hydraulic system requires a pump to build up the necessary pressure of the hydraulic medium. The pump is normally mounted using pillow blocks, which must be secured against rotation in order to be able to absorb the frictional torques between the pump gear and the pillow block. It is assumed to be known that this takes place via a cross pin in the pillow block on a recess in the housing. Furthermore, a press fit between the pillow block and the housing is normally formed in a blind hole that has a ventilation opening. If the housing—as is assumed to be known—is made from an aluminum material, an additional processing step is required for this, in which the risk of chip formation is high. The ventilation opening regularly leads to a misalignment of the pillow block, which reduces the positioning accuracy and thus the efficiency of the pump and its accuracy.
Proceeding therefrom, the object of the present disclosure is to at least partially overcome the problems known from the prior art.
This object is achieved with the features described herein. The features can be combined with one another in a technologically meaningful manner and can define further embodiments of the disclosure.
The hydraulic pump unit according to the disclosure comprises a pump, at least one pillow block for mounting the pump, and a housing. The housing includes a receptacle for each pillow block, and the receptacle has a first region of a first length which is shaped as a blind hole. The pillow block has a second region of a second length that is smaller than the first length. The second region is formed in the first region of the receptacle, and the second region has a peripheral knurl around its circumference that extends at least over a subregion of the second length with the knurl pressed into the first region.
Both the first region and the second region can be of cylindrical design. The knurl is formed on the outer circumference of the second region and has structures that effect a larger diameter in the region of the knurl than in the first region. As a result, when pressed into the first region, the knurl intersects a corresponding counter-structure, for example a serration, and an intimate connection is formed between the receptacle and the pillow block in the region of the knurl. This absorbs the torque generated during operation of the pump and braces it in the first region and thus in the housing. Due to the shorter design of the second region compared to the first region, a dead space is created in a press-in direction after the pressing-in operation, which is bounded by the base of the blind hole on the one hand and by an end face of the second region on the other hand (and peripherally by the first region). On the one hand, this dead space is useful during assembly, i.e. when pressing the pillow block into the receptacle, since the air present when the intimate connection between the knurl and the first region is formed does not need to escape and a ventilation opening can therefore be dispensed with. Thus, the air is compressed in the dead space but does not need to be removed. On the other hand, the dead space can also serve as a chip space, which receives the chips produced when the knurl is pressed into the first region. This is the case in particular when the knurl is formed at the tip of the second region in the press-in direction or is connected to the tip, for example via a corresponding chamfer.
The pillow block can thus be installed easily, in particular requiring no additional elements to absorb the torques. The pump is precisely positioned so that precise dosing or precise pressure build-up by the pump is possible without further measures.
The second region can have a press-fit region which is cylindrical and is press-fitted with the first region. In this way, centering and positioning of the pillow block in the receptacle can be further facilitated and improved.
The receptacle can have a recess in which the diameter of the receptacle increases from a first diameter in the first region to a third diameter and thus defines a third region of the receptacle. The pillow block has a projection in which the diameter of the pillow block increases from a second diameter in the second region to a fourth diameter, thus defining a fourth region of the pillow block. The fourth region is positioned in the third region of the receptacle, and the projection of the pillow block rests against the recess of the receptacle. The interaction of the projection, which serves as a collar, and the recess can thus further improve the containment of the chips produced, since the projection and the recess by their interaction form an effective barrier to the migration of chips.
The fourth region can have a press-fit region which is cylindrical and is press-fitted with the third region. In this way, centering and positioning of the pillow block in the receptacle can be further facilitated and improved.
The housing is made of a first material with a first Brinell hardness and the pillow block is made of a second material with a second Brinell hardness and the second Brinell hardness is greater than the first Brinell hardness. The knurl can be hardened, so that its Brinell hardness is well above the first Brinell hardness, in order to reduce the necessary press-in forces.
The housing can be made of a first material with a first tensile strength and the pillow block is made of a second material with a second tensile strength and a quotient of the second tensile strength divided by the first tensile strength is greater than 2.5. The housing is made of a first material with a first yield point Rp0,2 and the pillow block is made of a second material with a second yield point Rp0,2 and a quotient of the second yield point divided by the first yield point is greater than 2.5. A quotient or ratio of the second tensile strength to the first tensile strength and/or of the second yield point to the first yield point of 2.5 or more, in particular 3.0 or more, define exemplary embodiments that promote chip formation and thus a defined formation of the knurl structures can take place.
The housing can be made of an aluminum material and the pillow block can be made of steel. In particular, the knurl and in particular its profile is hardened further in order to make it easier to press the knurl into the first region or to reduce the press-in forces to be applied.
The first region designed as a blind hole has a base which is opposite an end face of the second region. The region between the base and the end face being designed as a chip space which receives chips produced when the knurl is pressed into the first region. The knurl and the chip space being connected to one another by a chamfer, through which the chips can pass from the knurl into the chip space. As a result, the chips produced when the knurl is pressed into the first region can be reliably collected without being able to move them in the direction of the pump.
In an example embodiment, a press-in direction of the pillow block into the receptacle is defined, and the second region has a groove, adjacent to the knurl in the press-in direction, which serves as a chip space which receives chips produced when the knurl is pressed into the first region. This enables a chip space to be formed remote from the dead space between the first region and the second region and increases the flexibility of the design of the hydraulic pump unit. At the same time, the chip space also enables the chips that are produced to be securely collected.
According to a further aspect of the disclosure, a method for assembling a hydraulic pump unit, in particular according to the present disclosure, is proposed. The hydraulic pump unit includes a pump, at least one pillow block for mounting the pump, and a housing. The housing includes a receptacle for each pillow block, and the receptacle has a first region of a first length, which is shaped as a blind hole. The pillow block has a second region of a second length that is smaller than the first length. The second region includes a circumferential knurl that extends at least over a subregion of the second length. The pillow block is first pressed into the receptacle so that the knurl is pressed into the first region and the second region of the pillow block is pressed into the first region of the receptacle. The pump is then mounted on the pillow block and is connected to this and the housing.
The details and advantages disclosed for the hydraulic pump unit can be transferred and applied to the assembly method and vice versa.
As a precaution, it should be noted that the numerical designations used here (“first”, “second”, etc.) serve primarily (only) to distinguish between several similar objects, sizes, or processes, and in particular no necessary dependency and/or sequence of these objects, sizes, or processes to each other is indicated. If a dependency and/or sequence is necessary, this is explicitly stated here or results in a manner obvious to the person skilled in the art when studying the specifically described configuration.
Both the disclosure and the technical field are explained in more detail below with reference to the figures. It should be noted that the disclosure is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the subject matter outlined in the figures and to combine them with other components and knowledge from the present description and/or figures. In particular, it should be noted that the figures and in particular the size relationships shown are only schematic in nature. Identical reference symbols indicate the same objects, so that, where applicable, explanations from other figures can also be used.
During assembly, the pillow block 3 is pressed into the receptacle 5 in a press-in direction 25. The second region 9 has a peripheral knurl 13 around its circumference, which is pressed into the first region 6 of the housing 4. The chips (not shown) produced during pressing are collected in the chip space 12. Since this is closed, they cannot escape from it and in particular cannot enter the pump 2 or a hydraulic line and cause damage there. In the present example, the pillow block 3 and thus also the knurl 13 are made of steel, while the housing 4 and thus also the first region 6 is made of an aluminum material, in particular an aluminum alloy, so that pressing in is possible with a comparatively little effort. The second region 9 has a circumferential chamfer 14, which on the one hand serves to center the pillow block 3 during assembly. At the same time, the chamfer 14 connects the knurl 13 to a chip space 12. This is formed between a base 23 of the first region 6 designed as a blind hole and an end face 24 of the second region 9 opposite the base 23. The chip space 12 accommodates chips produced when the knurl 13 is pressed into the first region 6, the chips being able to pass from the knurl 13 into the chip space 12 via the chamfer 14.
Furthermore, the receptacle 5 has a recess 15 in which the diameter of the receptacle 5 increases from the first diameter 8 in the first region 6 to a third diameter 16 and thus defines a third region 17 of the receptacle 5. The third region 17 has a chamfer 27 which facilitates assembly and causes the third region 17 to be centered. The third region 17 is cylindrical. The pillow block 3 has a projection 18, in which the diameter of the pillow block 3 increases from the second diameter 11 in the second region 10 to a fourth diameter 19 and thus defines a fourth region 20 of the pillow block 4. The fourth region is positioned in the third region 17 of the receptacle 5, wherein the projection 18 of the pillow block 3 rests against the recess 15 of the receptacle 5. This creates a further barrier if a chip or chips is/are not pressed into the chip space 12 when the knurl 13 is pressed into the first region 6. A movement of the chip or chips in the direction of the pump 2 is reliably prevented by this barrier.
In the present example, the fourth region 20 has a press-fit region 21 which is cylindrical and is press-fitted with the third region 17. For this purpose, when the pillow block 3 is pressed into the receptacle 5 of the housing 4, the press-fit region 21 has a diameter that is larger than the third diameter 16. The press-fit region 21 can form part or all of the fourth region 20 viewed in the direction of a longitudinal axis 22 of the pillow block 3. The formation of a press fit between the press-fit region 21 and the third region 17 and the design of this region in the form of a cylinder achieves a high level of accuracy in the positioning of the pillow block 3 in the receptacle 5 of the housing 4. The pillow block 3, in particular the press-fit region 21 and the knurl 13, and the receptacle 5 are designed such that when the pillow block 3 is mounted in the receptacle 5, the press-fit region 21 comes into contact with the third region 17 first and only then does the knurl 13 come into contact with the first region 6. This can effectively prevent chips from entering the press-fit region.
The pre-centering via the press-fit region 21 allows the height of the knurl 13 in the direction of the longitudinal axis 22 to be kept small. This height of the knurl 13 is can be 30% of the diameter of the knurl 13 and more. As a result, the reshaping force to be applied during manufacture of the knurl 13 can be reduced, and at the same time the press-in forces during the assembly of the pillow block 3 in the receptacle 5 are reduced. At the same time, the tooth size of the knurl 13 in the direction of the longitudinal axis 22 is designed such that different temperature expansions of the housing 4 and the pillow block 3 are compensated for, so that the knurl 13 does not break off from the first region 6 even under extreme temperature conditions. In particular, tooth sizes of 0.2 mm and less, in particular 0.16 mm and less, are possible.
The knurl 13 allows the torque acting on the pillow block 3 to be absorbed and the pillow block to be supported on the housing 4. At the same time, simple assembly is ensured without chips being able to escape from the chip space 12.
The difference between the first length 7 and the second length 10 also creates a space that is large enough that the compression of the air present in the receptacle 5 during the assembly of the pillow block 3 is possible without causing excessive heating of the air or an excessive increase in air pressure and a resulting counterforce. Here, in particular, the difference between the first length 7 and the second length 10 is dimensioned such that the ratio of a first volume, which is the air-filled volume in the first region 6 and third region 17 of the receptacle 5 when the lower edge of the fourth region 20 rests against the upper edge of the third region 17, and a second volume, which corresponds to the air volume in the first region 6 in the assembled state (in this example identical to the volume of the chip space 12), is greater than about four. As a result, the counterforce created by the compression of the air in the first volume is limited and at the same time the heating of the air due to the compression is reduced.
A knurl 13 connects a pillow block 3 for a pump 2 to a housing 4 to form a hydraulic pump unit 1, in which the knurl 13 is pressed into a first region 6 of a receptacle 4 for the pillow block 3. The resulting chips can be accommodated in a chip space 12, which is further secured by a projection 18 of the pillow block 3 so that a movement of the chips towards the pump 3 can be prevented. The hydraulic pump unit 1 is simple to assemble, the torque of the pump 2 is absorbed by the knurl 13 and the pump is supported in the housing 4, so that precise operation of the pump 2 is possible. Furthermore, an anti-turn mechanism for the pillow block 3 is achieved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 114 712.3 | Jun 2021 | DE | national |
This application is the U.S. National Phase of PCT Application No. PCT/DE2022/100327 filed on May 2, 2022, which claims priority to DE 10 2021 114 712.3 filed on Jun. 8, 2021, the entire disclosures of which are incorporated by reference herein.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/DE2022/100327 | 5/2/2022 | WO |
