DE102024100329A1 - Piston unit and radial piston device with piston unit - Google Patents

Abstract

The present disclosure relates to a piston unit (1) for a radial piston device (1), comprising a radial piston (6) and a cylindrical roller (7), wherein the roller (7) is displaceable in the radial direction by actuation of the radial piston (6) and is designed to be in rolling contact with a cam contour (4) on a housing (3) of the radial piston device (2), wherein the piston unit (1) has a ball bearing device (8) which is arranged radially between the radial piston (6) and the roller (7) and has a plurality of balls (9) rotating around the ball bearing device (8) for supporting the roller (7) in the radial piston (6). Furthermore, the present disclosure relates to a radial piston device (2) having a plurality of such piston units (1).

Description

The present disclosure relates to a piston unit for a radial piston device, in particular a radial piston pump or a radial piston motor, for a vehicle, for example, a motor vehicle, a tractor, or a construction machine. The piston unit comprises a radial piston and a cylindrical roller. The roller is displaceable in the radial direction by actuation of the radial piston and is designed to be in rolling contact with a cam contour of the radial piston device formed on a housing inner circumference.

Furthermore, the present disclosure relates to a radial piston device, in particular a radial piston pump or a radial piston engine, for a vehicle, for example for a motor vehicle, a tractor, or a construction machine. The radial piston device has a housing having a cam contour on its inner circumference. The radial piston device has a cylinder block that is arranged radially within the housing and is rotatable relative to the housing about an axis of rotation of the radial piston device. The radial piston device has a plurality of such piston units that are arranged in a star shape in the cylinder block. The rollers of the piston units are in rolling contact with the cam contour.

Through the actuation of the radial pistons and the rolling contact between the roller and the cam contour, the radial movement of the radial pistons is converted into a rotary movement of the cylinder block relative to the housing.

The problem is that the rollers in prior art radial piston devices are mounted directly in the radial piston, meaning that although the rollers roll on the cam contour, they slide along the contact surface with the radial piston. This causes friction and wear between the radial piston and the rollers, particularly during start-up. This results in high levels of wear, particularly in stop-and-go operation of the radial piston device. To reduce friction and wear, prior art methods include designing the rollers with a particularly smooth/fine surface or providing the roller surface with a friction-reducing coating. However, these solutions are cost-intensive and cannot completely resolve the underlying problem of friction and wear.

Against this background, the present disclosure is based on the object of avoiding or at least mitigating the disadvantages of the prior art. In particular, a piston unit for a radial piston device and a radial piston device comprising a plurality of such piston units are to be provided, in which the friction arising during operation of the radial piston device, in particular between the radial piston and the roller, is eliminated or at least significantly reduced. At the same time, a cost-effective and simply constructed piston unit is to be provided.

This object is achieved by a piston unit having the features of the independent patent claim and by a radial piston device having the features of the independent patent claim. Advantageous further developments are the subject of the dependent claims.

Accordingly, the present disclosure relates to a piston unit for a radial piston device, in particular a radial piston pump or a radial piston motor. The radial piston device is particularly suitable for use in a vehicle, for example in a motor vehicle, a tractor, or a construction machine. The piston unit has a radial piston (movable radially like a piston) and a cylindrical roller (cylindrical roller). A longitudinal axis of the roller preferably corresponds to an axial direction of the piston unit (or an axial direction of the radial piston device or preferably runs along the axis of rotation of the radial piston device). Preferably, the roller and the radial piston are connected to one another in the circumferential direction of the piston unit (or in the circumferential direction of the radial piston device), i.e., they are not rotatable relative to one another in the circumferential direction of the piston unit. The roller can be displaced in the radial direction, i.e., radially outwards and inwards, by actuating the radial piston. The roller is designed to be in rolling contact with a cam contour of the radial piston device formed on the inner circumference of the housing or to roll on the cam contour.

According to the present disclosure, the piston unit comprises a ball bearing device arranged radially between the radial piston and the roller and having a plurality of balls rotating around the ball bearing device for (rolling) supporting the roller in the radial piston. This means that a separate device is provided in the radial piston that enables rolling support of the roller in the radial piston.

According to a preferred embodiment, the piston unit may have a raceway formed by the roller and the ball bearing device, on/in which the balls are arranged. This provides suitable guidance for the balls.

According to a preferred embodiment, the raceway can be circular in cross-section (in particular, corresponding to a diameter of the balls). This provides a particularly low-friction arrangement. Alternatively, the raceway can be rectangular or square in cross-section.

According to a preferred embodiment, the raceway can be formed by a first radial groove in the roller and a second radial groove in the ball bearing device. This provides suitable guidance for the balls, both in the roller and in the ball bearing device.

According to a preferred embodiment, the piston unit can have a first raceway in which a first set of balls is arranged, and a second raceway in which a second set of balls is arranged. In particular, the first raceway and the second raceway can be offset in the axial direction of the piston unit (or in the axial direction of the radial piston device or along the rotational axis of the radial piston device). This ensures stable mounting of the roller.

The first raceway and the second raceway can form an O-bearing arrangement or an X-bearing arrangement.

According to a preferred embodiment, the ball bearing device can be accommodated in the radial piston, preloaded radially toward the roller, i.e., radially outward. For this purpose, the ball bearing device can preferably comprise a spring. The spring can be arranged, in particular, in a radial recess in the radial piston in the region of contact with the ball bearing device. This ensures that the roller is pressed into contact with the cam contour. Furthermore, smooth running of the balls is ensured and the balls are prevented from falling out.

The roller can have a cam contour running surface. The cam contour running surface is formed in particular by a radial outer circumference or a portion of the radial outer circumference of the roller. The cam contour running surface is in rolling contact with the cam contour or can be brought into rolling contact with the cam contour. According to a preferred embodiment, the cam contour running surface can be ground and/or honed.

The roller may have a ball raceway. The ball raceway is formed, in particular, by a surface in the region of the first radial groove of the roller. The ball raceway is in rolling contact with the balls of the ball bearing device. According to a preferred embodiment, the ball raceway may be ground and/or honed.

The ball bearing device can have a radial contact surface with the radial piston. According to a preferred embodiment, the radial contact surface can be flat. This allows for a particularly simple design of the ball bearing device.

According to an alternative preferred embodiment, the radial contact surface can be curved. According to a further development of the alternative preferred embodiment, the radial contact surface can extend along a radius that has its center in the axial direction in the center of the cam contour running surface. This can prevent assembly errors and achieve a high level of smooth running.

According to a preferred embodiment, the balls of the ball bearing device may have a contact angle of 45° or less than 45°.

According to a preferred embodiment, the radial piston can have a claw portion that protrudes toward the roller. The claw portion can preferably abut the roller in the axial direction and/or in the circumferential direction, in particular on both sides. This enables a suitable receptacle. The claw portion can also be formed as a separate component from the radial piston.

The present disclosure also relates to a radial piston device, in particular a radial piston pump or a radial piston motor. The radial piston device is particularly suitable for use in a vehicle, for example in a motor vehicle, a tractor, or a construction machine. The radial piston device has a housing having a cam contour on its inner circumference. This means that the inner circumference of the housing is not circular, but rather extends in a wave-like manner in the circumferential direction, i.e., has a diameter that changes continuously in the circumferential direction and is smaller in the region of the radially projecting cams than in the region between the cams. The radial piston device has a cylinder block that is arranged radially inside the housing and is rotatable relative to the housing about a rotational axis of the radial piston device. The radial piston device has a plurality of the described piston units that are arranged in a star shape in the cylinder block. The piston units are rotatable with the cylinder block about the rotational axis of the radial piston device, i.e., No relative rotation occurs between the cylinder block and the piston units. The rollers of the piston units are in rolling contact with the cam contour. Through the actuation of the radial pistons and the rolling contact between the roller and the cam contour, the radial movement of the radial pistons is converted into a rotational movement of the cylinder block relative to the housing.

In other words, the present disclosure relates to radial piston pumps or radial piston motors that use rollers for each piston. On the cam side, the roller rotates with rolling contact, and on the piston side, the roller rotates with sliding contact. The advantage over the axial piston pump is the high efficiency during operation (steady operating state). However, the disadvantage of the radial piston pump or radial piston motor is the low efficiency during start-up. This disadvantage has a particularly negative impact on radial piston engines for tractors or other construction machinery that frequently operate in stop-and-go mode. The reason for the low efficiency is two sliding contact surfaces: the piston-side contact surface and the end surfaces of rollers and axial covers. Wear of the contact surfaces can also be a problem, so countermeasures are necessary. In the prior art, to improve starting efficiency, a very fine roughness roller is used for the radial piston engine. The actual measured value is approximately 0.003 to 0.004 Ra for the rolling surface and approximately 0.005 to 0.009 Ra for the side surfaces, which is about 10 times finer/smoother than a standard roller. This allows the roller to easily retain the oil film in the sliding contact areas and improve efficiency. Another prior art solution is the use of a DLC-coated (diamond-like carbon coated) roller, in which the DLC coating is also applied to the roller. This can reduce friction in the sliding areas. However, the problem is that achieving a fine roughness is very expensive and the cause of sliding contact remains, requiring attention to the wear on the sliding contact surfaces. According to the present disclosure, the piston has a separate device containing revolving balls on which the rollers can roll. Instead of a plain bearing, a separate device with recesses for the balls is used. Each roller has two recesses for the ball guide. The roller is supported by rolling balls instead of sliding contact. This reduces friction and wear. In particular, the starting torque is significantly reduced, which is advantageous for tractors and other construction machines that frequently operate in stop-and-go mode.

In particular, the raceway in the load area and in the recess of the roller can be ground, or ground and honed. The cross-section of the path outside the load area can preferably be circular. Alternatively, a rectangular or square design is also possible. A claw area, which preferably serves to radially hold the rollers, can be a separate part. Not only the separate device, but also a region of the piston where the separate device contacts the piston can be used as the raceway outside the load area. The separate device has a spring on the underside to maintain contact between the roller and the cam (or the cam contour), to ensure smooth running of the balls and to prevent the balls from slipping and falling out. The separate device can have a rounded bottom so that a center of the radius is in the middle of a contact area between the roller and the cam, viewed in the axial direction. This can compensate for manufacturing errors and ensure smooth running. In this case, a raceway on the piston can be designed to be wide to accommodate or compensate for displacement caused by the oscillation of the separate device. The balls can preferably have a contact angle of 45 degrees or less. Both an O-arrangement and an X-arrangement of the balls are possible.

• 1 zeigt einen grundsätzlichen Aufbau einer Radialkolbenvorrichtung mit einer Vielzahl von Kolbeneinheiten,
• 2 und 3 zeigen eine Frontansicht bzw. eine Seitenansicht einer Kolbeneinheit gemäß einer ersten Ausführungsform der vorliegenden Offenbarung,
• 4 zeigt eine perspektivische Ansicht einer Kugellagervorrichtung der Kolbeneinheit,
• 5 zeigt eine perspektivische Ansicht einer Rolle der Kolbeneinheit,
• 6 und 7 zeigen eine Frontansicht bzw. eine Seitenansicht eines Radialkolbens der Kolbeneinheit,
• 8 und 9 zeigen eine Frontansicht bzw. eine Seitenansicht der Kolbeneinheit,
• 10 zeigt eine Seitenansicht der Kolbeneinheit gemäß einer zweiten Ausführungsform, und
• 11 und 12 zeigen eine Seitenansicht der Kolbeneinheit mit verschiedenen Lageranordnungen.

The disclosure is explained below with the help of drawings:

• 1 shows a basic structure of a radial piston device with a large number of piston units,
• 2 and 3 show a front view and a side view of a piston unit according to a first embodiment of the present disclosure,
• 4 shows a perspective view of a ball bearing device of the piston unit,
• 5 shows a perspective view of a roller of the piston unit,
• 6 and 7 show a front view and a side view of a radial piston of the piston unit,
• 8 and 9 show a front view and a side view of the piston unit,
• 10 shows a side view of the piston unit according to a second embodiment, and
• 11 and 12 show a side view of the piston unit with different bearing arrangements.

The figures are merely schematic in nature and are intended solely for the purpose of understanding the present disclosure.

1 shows a basic structure of a piston unit 1 and a radial piston device 2.

The radial piston device 2 is designed, in particular, as a radial piston pump or as a radial piston motor. The radial piston device 2 is particularly suitable for use in a vehicle, for example, in a motor vehicle, a tractor, or a construction machine.

The radial piston device 2 comprises a housing 3 having a cam contour 4 on its inner circumference. This means that the inner circumference of the housing 3 is not circular, but rather extends in a wave-like manner in the circumferential direction, i.e., it has a diameter that continuously changes in the circumferential direction and is smaller in the region of the radially projecting cams than in the region between the cams.

The radial piston device 2 has a cylinder block 5. The cylinder block 5 is arranged or mounted radially within the housing 3. The cylinder block 5 is rotatable relative to the housing 3 about a rotation axis of the radial piston device 2.

The radial piston device 2 comprises a plurality of piston units 1. The piston units 1 are preferably arranged in a star shape in the cylinder block 5. The piston units 1 are rotatable with the cylinder block 5 about the rotation axis of the radial piston device 2, i.e., there is no relative rotation between the cylinder block 5 and the piston units 1.

The or each piston unit 1 has a radial piston 6 and a cylindrical roller 7 (cylindrical roller). The radial piston 6 is accommodated in the cylinder block 4 so as to be movable in the radial direction like a piston. A longitudinal axis of the (or each) roller 7 preferably corresponds to an axial direction of the piston unit 1 or an axial direction of the radial piston device 2 or preferably runs along the axis of rotation of the radial piston device 2. The (or each) roller 7 can be displaced in the radial direction, i.e., radially outwards and inwards, by actuating the (associated) radial piston 6. The (or each) roller 7 is (radially outside) in rolling contact with the cam contour 4 or can be brought into rolling contact with the cam contour 4 or is designed to be in rolling contact with the cam contour 4.

By actuating the radial piston 6 or the radial pistons 6 and the rolling contact between the roller 7 or the rollers 7 and the cam contour 4, the radial movement of the radial piston 6 or the radial pistons 6 is converted into a rotational movement of the cylinder block 5 relative to the housing 3 about the axis of rotation of the radial piston device 2.

The piston unit 1 is based on 2 to 12 described. According to the present disclosure, the or each piston unit 1 has a ball bearing device 8. The ball bearing device 8 is arranged radially between the radial piston 6 and the roller 7. The ball bearing device 8 has a plurality of balls 9. The balls 9 rotate around the ball bearing device 8 or are mounted such that they can rotate around the ball bearing device 8. The balls 9 serve to support the roller 7 (in a rolling and non-sliding manner) in the radial piston 6. This means that a separate device in the form of the ball bearing device 8 is provided in the radial piston 6, which enables the roller 7 to be supported in a rolling manner in the radial piston 6.

Preferably, the piston unit 1 may have a raceway 10 formed by the roller 7 and the ball bearing device 8, in which the balls 9 are arranged.

In particular, the raceway 10 can be circular in cross-section (in particular corresponding to a diameter of the balls 9). Alternatively, the raceway 10 can be rectangular or square in cross-section.

Preferably, the raceway 10 can be formed by a first radial groove 11 in the roller 7 and a second radial groove 12 in the ball bearing device 8.

Preferably, the or each piston unit 1 may have a first raceway 13 in which a first set of balls 9 is arranged, and a second raceway 14 in which a second set of balls 9 is arranged. In particular, the first raceway 13 and the second raceway 14 may be arranged offset in the axial direction of the piston unit 1 or in the axial direction of the radial piston device 2.

The first raceway 13 and the second raceway 14 can have an O-bearing arrangement (cf. 11 ) or an X-bearing arrangement (cf. 12 ) form.

The roller 7 can have a cam contour running surface 15. The cam contour running surface 15 is formed in particular by a radial outer circumference catch or part of the radial outer circumference of the roller 7. The cam contour running surface 15 is in rolling contact with the cam contour 4.

The roller 7 can have a ball raceway 16. The ball raceway 16 is formed in particular by a surface in the region of the first radial groove 11 of the roller 7. The ball raceway 16 is in rolling contact with the balls 9 of the ball bearing device 8.

Preferably, the cam contour running surface 15 can be ground and/or honed. Preferably, the ball running surface 16 can be ground and/or honed.

Preferably, the ball bearing device 8 can be accommodated in the radial piston 6, preloaded radially in the direction of the roller 7, i.e., radially outward. Preferably, the ball bearing device 8 can have a spring 17 for this purpose. The spring 17 can be arranged, in particular, in a radial recess 18 in the radial piston 6 in the region of contact with the ball bearing device 8.

The radial piston 6 can preferably have a claw portion 19 that protrudes toward the roller 7. The claw portion 19 can preferably abut the roller 19 in the axial direction and/or in the circumferential direction, in particular on both sides. This enables a suitable receptacle. The claw portion 19 can also be formed as a separate component from the radial piston 6.

In 6 and 7 A contact surface 20 of the radial piston 6 to the ball bearing device 8 is shown. Not only the ball bearing device 8, but also the contact surface 20 can serve as a running surface for the balls 9 of the ball bearing device 8.

The ball bearing device 8 can have a radial contact surface 21 to the radial piston 6. In a first preferred embodiment, the radial contact surface 21 can be flat (cf. 3 , 4 and 9 ). In a second preferred embodiment, the radial contact surface 21 can be curved (cf. 10 ). In particular, the radial contact surface 21 can extend along a radius R which has its center M in the axial direction in the center of the cam contour running surface 15.

In addition, as in 10 As shown, each of the two contact surfaces 20 of the radial piston 6 has a greater curvature in side view than the balls 9 in order to absorb axial movements due to vibrations between the radial piston 6 and the roller 7. In other words, a running surface of the radial piston 6 that comes into contact with the balls 9 is larger in the axial direction than a ball diameter of the balls 9.

Furthermore, each of the two contact surfaces 20 of the radial piston 6 can have a flat surface on the underside in side view to provide sufficient space for the balls 9. In other words, the running surface of the radial piston 6 is formed in a straight line (uncurved/unbent) in the axial direction, at least in a central region in the axial direction.

Preferably, the balls 9 of the ball bearing device 8 may have a contact angle of 45° or less than 45°.

List of reference symbols

1

Piston unit

2

Radial piston device

3

Housing

4

Cam contour

5

cylinder block

6

Radial piston

7

role

8

ball bearing device

9

Bullet

10

career

11

first radial groove

12

second radial groove

13

first career

14

second career

15

Cam contour running surface

16

Ball bearing surface

17

Feather

18

Radial recess

19

claw

20

Contact surface

21

radial contact surface

Claims (10)

Piston unit (1) for a radial piston device (1), with a radial piston (6) and a cylindrical roller (7), wherein the roller (7) is displaceable in the radial direction by actuation of the radial piston (6) and is designed to be in rolling contact with a cam contour (4) on a housing (3) of the radial piston device (2), characterized in that the piston unit (1) has a ball bearing device (8) which is arranged radially between the radial piston (6) and the roller (7) and has a plurality of balls (9) rotating around the ball bearing device (8) for supporting the roller (7) in the radial piston (6). Piston unit (1) after Claim 1 , characterized in that the piston unit (1) has a raceway (10) formed by the roller (7) and the ball bearing device (8), in which the balls (9) are arranged. Piston unit (1) after Claim 2 , characterized in that the track (10) is circular in cross-section. Piston unit (1) after Claim 2 or 3 , characterized in that the raceway (10) is formed by a first radial groove (11) in the roller (7) and a second radial groove (12) in the ball bearing device (8). Piston unit (1) according to one of the Claims 1 until 4 , characterized in that the piston unit (5) has a first raceway (13) in which a first set of balls (9) is arranged, and a second raceway (14) in which a second set of balls (9) is arranged, wherein the first raceway (13) and the second raceway (14) are arranged offset in the axial direction of the piston unit (1). Piston unit (1) after Claim 5 , characterized in that the first raceway (13) and the second raceway (14) form an O-bearing arrangement or an X-bearing arrangement. Piston unit (1) according to one of the Claims 1 until 6 , characterized in that the ball bearing device (8) is accommodated in the radial piston (6) in a radially preloaded manner in the direction of the roller (7). Piston unit (1) according to one of the Claims 1 until 7 , characterized in that a cam contour running surface (15) of the roller (7) and/or a ball running surface (16) of the roller (7) are ground and/or honed Piston unit (1) after Claim 8 , characterized in that the ball bearing device (8) is curved at its radial contact surface (21) to the radial piston (6), wherein the contact surface (21) runs along a radius (R) which has its center point (M) in the axial direction in the center of the cam contour running surface (15). Radial piston device (2) for a vehicle, comprising a housing (3) which has a cam contour (4) on its inner circumference, a cylinder block (5) which is arranged radially inside the housing (3) and is rotatable relative to the housing (3) about a rotational axis of the radial piston device (2), and a plurality of piston units (1) according to one of the Claims 1 until 9 , wherein the piston units (1) are arranged in a star shape in the cylinder block (5) and the rollers (7) of the piston units (1) are in rolling contact with the cam contour (4).

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