Hydrostatic radial piston unit with cam lobe

Abstract

The present application provides a hydrostatic radial piston unit with a cam lobe structure, comprising: a shaft, which defines the rotation axis of the hydrostatic radial piston unit and extends from a non-rotating, fixed rear housing to a front end portion of a front housing, a cylinder body is accommodated in the front housing and is connected to the front end portion of the shaft in a torsion-proof manner, in the cylinder body, a radially reciprocating working piston is arranged in a radial cylinder hole, and hydraulic fluid is introduced into and discharged from the cylinder hole through a distributor, the distributor is fixed relative to the front housing in the rotation direction and freely rotates relative to the shaft, and a circumferential cam lobe surface with which the working piston can interact is integrally formed on the radial inner side of the front housing.

Description

Technical Field

[0001] The present application relates to a hydrostatic radial piston unit, and more specifically to a cam lobe motor or pump, or a gerotor motor or pump. Specifically, the present application relates to a housing of a hydrostatic radial piston unit with a cam lobe structure. Background Art

[0002] Radial piston units, i.e. radial piston pumps and radial piston motors, are widely used in the art, for example in heavy-duty applications. For example, radial piston units are used in the field of construction, agriculture or forestry equipment. Radial piston units are characterized in that, when supplied with pressurized hydraulic fluid (in the case of radial piston motors), their working pistons move in radial direction relative to the central longitudinal / rotational axis. Typically, radial piston units are used in hydraulic applications that do not require high rotational speeds but do require high torques. Radial piston units show advantages over axial piston units (with reduced axial construction space).

[0003] A specific application of radial piston units is the travel of working vehicles (e.g., crawler loaders). Often, a radial piston unit is mounted on either side of the frame / body of the working vehicle. Therefore, the geometry of the frame and the propulsion mechanism is significantly affected by the size of the radial piston unit. In many applications, the position at which the radial piston unit transmits torque to the drive mechanism is pre-set by other components, rather than by the radial piston unit that interacts with the drive mechanism. However, the radial piston unit in the known technology presents a relatively large length and a relatively large diameter in the axial direction. Since the radial piston unit that drives the working vehicle must be integrated into the vehicle frame, the frame must be designed to accommodate the fixed parts (e.g., fixed housing) of the radial piston unit so as to support the torque generated / applied under operating conditions. Therefore, it is desirable to reduce the size of the radial piston unit used (especially the size in the axial direction) as much as possible to reduce the design adaptation of the frame on which the radial piston unit is mounted. Summary of the invention

[0004] The object of the present application is to provide a radial piston unit with reduced dimensions, in particular reduced axial length, and reduced radial dimensions / diameter. At the same time, the radial piston unit provided should be easy to assemble and should have a cost-effective and robust design.

[0005] To achieve the above-mentioned purpose, the hydrostatic radial piston unit with a cam lobe structure provided in the present application includes: a shaft, which defines the rotation axis of the hydrostatic radial piston unit and extends from a non-rotating, fixed rear housing to a front end portion of a front housing, a cylinder body is accommodated in the front housing and connected to the front end portion of the shaft in a torsion-proof manner, in the cylinder body, a radially reciprocating working piston is arranged in a radial cylinder hole, and the hydraulic fluid is introduced into and discharged from the cylinder hole through a distributor, and the distributor is fixed relative to the front housing in the rotation direction and freely rotates relative to the shaft, wherein the circumferential cam lobe surface with which the working piston can interact is integrally formed on the radial inner side of the front housing.

[0006] The hydrostatic radial piston unit according to the present application comprises a shaft defining a longitudinal axis which is also the rotation axis of the hydrostatic radial piston unit.In the description of the present application, the terms "radial" and "axial" refer to directions relative to the longitudinal axis of the shaft.

[0007] The fixed rear housing accommodates the shaft in the rear end section. The fixed rear housing is therefore arranged to be connected to the frame of the work vehicle, for example, in the meaning of the present application description, the fixed part of the radial piston unit according to the present application forms a rear end region, which can be fixed to a frame or a bracket, for example, in the present application description, the term "fixed" means not rotating around the longitudinal / rotational axis of the hydrostatic radial piston unit.

[0008] According to the present application, two optional basic design principles are provided. The shaft can be connected to the fixed rear housing in a torsion-proof manner, meaning that the fixed shaft and the fixed rear housing cannot rotate relative to each other. Alternatively, the shaft can rotate, i.e. the shaft can rotate relative to the fixed rear housing.

[0009] At the front end portion of the shaft protruding from the fixed rear housing, the cylinder is arranged to be connected to the shaft in a torsionally fixed manner. Thus, according to the basic principle, if a rotating shaft is provided, the cylinder is rotating; if a fixed shaft is provided, the cylinder is fixed. The front housing surrounds the cylinder at the protruding front end portion of the shaft. Thus, the rear end portion of the front housing is sealed to the front end portion of the fixed rear housing. The sealing between the front housing and the fixed rear housing is carried out in such a way that the two housings together form a closed, liquid-tight chamber.

[0010] Typically, the axial position of the sealing body between the fixed rear housing and the front housing defines a sealing surface, which is orthogonal to the longitudinal axis of rotation. Thus, seen from the outside, the sealing surface divides the housing of the hydrostatic radial piston device into a rear housing on one side of the sealing surface and a front housing on the other side of the sealing surface. In the case of the fixed shaft design, the front housing is rotating and the rear housing is fixed. In the case of the rotating shaft design, the rotating shaft is used for power output or driving a radial piston unit at any time.

[0011] In each case, the cylinder body includes a plurality of cylinder bores extending radially inward from the circumferential surface of the cylinder body. A plurality of working plungers are arranged in the cylinder bores in a radially reciprocating manner, wherein each cylinder bore accommodates a working plunger. Each working plunger seals a pressure chamber in the cylinder bore, which can provide pressurized hydraulic fluid through a hydraulic channel to generate a force on the head of the working plunger, thereby moving the working plunger radially outward. In the case of mechanically driving the working plunger to move inward, the hydraulic fluid can also be discharged from the cylinder bore through the hydraulic channel.

[0012] The front housing includes an internal cam lobe surface. When pressurized fluid is supplied to the pressure chamber, the working plunger is pushed against the cam lobe surface. The radially outward movement of the working plunger generates a force on the cam lobe surface, thereby causing relative rotation between the front housing and the cylinder body. According to the basic design principle, that is, whether the shaft is fixed or rotating, the front housing rotates when the cylinder body is fixed, or the front housing is fixed when the cylinder body rotates with the shaft.

[0013] In order to provide a pressurized fluid to the pressure chamber, a distributor is provided, the distributor comprising a hollow shaft part and a disc-shaped part, preferably, the disc-shaped part and the hollow shaft part are formed integrally, but can also be connected to each other, for example in a fluid-tight manner. In a preferred embodiment, the disc-shaped part of the distributor shows a radial protrusion, which matches the cam of the cam surface. Therefore, the disc-shaped part is anti-twistly connected to the front housing. Therefore, the distributor rotates when the front housing rotates, and the distributor is fixed when the front housing is fixed. The distributor includes a timing hole in the disc-shaped part for supplying hydraulic fluid to the cylinder bore in the cylinder body and discharging hydraulic fluid from the cylinder bore through a hydraulic channel. The operating principle of the radial piston unit is well known to those skilled in the relevant art, so the function of the radial piston unit here does not need to be described in more detail.

[0014] According to the present application, the cam lobe surface is formed integrally with the front housing, i.e. it is not provided by a separate cam ring or similar component as is common in the prior art. If the housing is assembled from multiple components, connections and sealing are necessary, which will require additional radial and axial space. The cam lobe surface is formed integrally with the front housing to reduce the complexity of the entire assembly process of the radial piston unit. In addition, this integrated concept can reduce the diameter of the hydrostatic radial piston unit, i.e. the radial dimension, because the connection between the components can be eliminated.

[0015] In addition, by the one-piece design, the manufacturing work of the front housing and the cam lobe surface is reduced because the guiding, centering and / or connection, etc. can be omitted. In the case of a separately provided cam lobe surface, strict manufacturing tolerances must also be met to ensure accurate interaction between the cam lobe surface and the working plunger, with precise timing and low wear. In order to ensure that such strict manufacturing tolerances are met, it is necessary to accurately machine the surfaces of the front housing and the cam lobe surface that interact. In contrast, if the cam lobe surface is formed integrally with the front housing, only the cam lobe surface needs to be accurately machined, because the same is true for a separate cam ring, and therefore, this does not result in any additional machining. Therefore, the integrally formed cam lobe surface saves manufacturing, machining and assembly costs by avoiding accurate machining of the connecting surface and additional assembly steps. In addition, the size of the radial piston unit according to the present application can be reduced because no additional space is required for assembly, centering or fixing.

[0016] According to one embodiment of the present application, the front housing is a single-piece design, which further reduces the precise processing and assembly steps of the connection surface. The single-piece front housing can be manufactured using appropriate manufacturing techniques, such as casting, forging, turning or 3D milling or 3D printing or different manufacturing methods or a combination of these technologies.

[0017] The first cylinder block may include more than one row of cylinder bores with radially reciprocating working plungers, each row of cylinder bores being arranged to be axially spaced from an adjacent row. The cylinder bores and corresponding working plungers may be arranged to be adjacent in adjacent circumferential directions (i.e., have the same rotational direction), or staggered with each other, and may interact with the first cam lobe surface.

[0018] According to the application, the hydrostatic radial piston unit may also include a second cylinder whose working piston interacts with the same cam lobe surface or another cam lobe surface arranged parallel to the first cam lobe surface. The second cylinder is arranged axially parallel to the first cylinder on the shaft. Providing a cylinder or a second cylinder with more than one row of cylinder bores significantly increases the potential working volume, wherein the diameter of the hydrostatic radial piston unit remains the same.

[0019] In order to adapt the performance of the hydrostatic radial piston unit to a specific application, the number of axially spaced cylinder bores or cylinder bores of the second cylinder block and the number of radially reciprocating working pistons may be different from the number of cylinder bores of the first cylinder block and the number of radially reciprocating working pistons. In this case, a second circumferential cam lobe surface may be provided radially inwardly of the rotating front housing. The working pistons of the second cylinder block or the second or more rows of cylinder bores may interact with the second cam lobe surface. In one embodiment, the second circumferential cam lobe surface is formed integrally with the front housing.

[0020] According to a preferred embodiment of the present application, the shaft is designed to be non-rotating, i.e., fixed and connected to the fixed rear housing in a torsion-proof manner. The front housing can rotate relative to the fixed rear housing and relative to the fixed shaft around the axis of rotation of the radial piston unit. The disc-shaped part of the rotating distributor is connected to the rotating front housing in a torsion-proof manner, so the distributor rotates relative to the fixed shaft and the fixed rear housing.

[0021] In the following, only for the sake of simplifying the readability and traceability of the concept of the present application, the features of the present application are explained by a hydrostatic radial piston unit with a fixed shaft and a rotating front housing. However, a person skilled in the relevant art will easily transfer the following description, features and functions of the concept of the present application to a hydrostatic radial piston unit including a fixed front housing and a rotating shaft.

[0022] A synchronization pin can be housed in an axial hole of the front housing, preferably in the extension of the cam, and engages with a corresponding hole in one of the radial protrusions of the disc-shaped part of the distributor. The synchronization pin is thus able to interact simultaneously with the rotating front housing and the rotating distributor. Thus, the synchronization pin ensures that the distributor (or more precisely, the disc-shaped part of the rotating distributor) is correctly oriented when the distributor is mounted in the rotating front housing. In addition, the synchronization pin synchronizes the rotation of the distributor with the rotation of the rotating housing, i.e. prevents relative movement between the two parts.

[0023] According to the present application, the radial piston unit may further comprise: a distributor spring to press the disc-shaped part of the rotating distributor towards the cylinder body. According to the present application, these distributor springs are preferably accommodated in axially extending holes in the rotating front housing at the axial extension of the cam. Preferably, the disc-shaped part of the rotating distributor shows a profile complementary to the surface of the cam cam. The distributor spring presses the rotating distributor towards the cylinder body. Thereby, the front surface of the disc-shaped part of the rotating distributor and the adjacent front surface of the cylinder body form a hydrostatic bearing between the disc-shaped part of the rotating distributor and the fixed cylinder body.

[0024] The hydrostatic bearing is supplied with pressurized fluid by means of a timing hole arranged in the front surface of the disc-shaped portion of the rotating distributor, through which the hydraulic fluid can be supplied to or discharged from the cylinder bore in the cylinder block. The arrangement of the distributor spring in the rotating front housing, which is in anti-twist connection with the distributor, ensures that there is no relative movement in the circumferential direction between the distributor spring and the distributor. If there would be relative movement between the two components, the spring would be likely to be susceptible to severe wear and / or would experience deformation. Furthermore, axially accommodating the distributor spring in the elongated portion / extension of the cam lobe surface reduces the loads and stresses on the synchronization pins generated by the friction resistance between the rotating distributor and the fixed shaft.

[0025] Another benefit is achieved when the spring is located within the axial thickness of the distributor, which further reduces the axial length of the hydrostatic radial piston motor because the axial hole in the front housing for accommodating the spring is moved to the distributor, thereby reducing the axial length of the front housing.

[0026] According to one embodiment of the present application, the hollow shaft portion of the rotating distributor includes a second internal groove, which together with a second groove on the outer surface of the non-rotating shaft forms a second annular passage, and the second groove on the outer surface of the non-rotating shaft is connected to the first annular passage through a channel in the shaft.

[0027] According to a preferred design, a pair of roller bearings rotatably supports the rotating front housing on the fixed rear housing. According to another aspect of the present application, the roller bearings can be arranged radially outside the hollow shaft portion of the rotating distributor, and at substantially the same position axially as the hollow shaft portion of the distributor, close to the rear end portion of the rotating front housing and close to the front end portion of the fixed rear housing. In other words, the roller bearings that enable relative movement between the rotating front housing and the fixed rear housing are arranged near or close to the sealing surface to avoid a large overturning moment between the two housings, which is also beneficial to the sealing of the two housings.

[0028] Roller bearings according to the present application are arranged in pairs, and in one embodiment are preferably close to or adjacent to each other, and are approximately in the same position axially as the hollow shaft portion of the rotating distributor, and the bearings are arranged in an axial region close to the cylinder side facing the fixed rear housing. In this region, the fixed rear housing and the rotating front housing overlap or overlap axially when at least the extension or protrusion of one or two housings are coaxially arranged. Paired bearings may include an axial length different from that of the distributor. When the bearing is arranged radially (relative to the longitudinal axis) outside the hollow shaft portion of the distributor rather than axially adjacent to it, the axial length of the hydrostatic radial piston unit is reduced. Those skilled in the relevant art will understand that the use of roller bearings is only a preferred embodiment. However, the present application also covers the following scheme: a sliding bearing is used to support the rotating front housing rotatably relative to the fixed rear housing.

[0029] According to a preferred embodiment of the present application, the fixed rear housing of the radial piston unit may include: a fixed extension portion, which extends in the axial direction beyond the sealing surface into the volume of the rotating front housing and has a generally cylindrical shape. The extension portion is, for example, an inner shell for mounting a bearing. When the paired bearings are accommodated in the space between the rotating front housing and the hollow shaft portion of the rotating distributor, the extension portion provides fixed support for the pair of bearings, for example, radially outside the hollow shaft portion of the rotating distributor. Therefore, the extension portion is radially arranged in the space between the two rotating parts (rotating distributor and rotating front housing).

[0030] In one embodiment according to the present application, the extension can be formed integrally with the fixed rear housing. However, in another embodiment according to the present application, the extension is set as an additional component and attached to the fixed rear housing. The extension can be attached to the fixed rear housing, for example, by screwing, welding, bonding, press-fitting, heat shrinking, clamping, crimping or plastic deformation. The connection between the fixed rear housing and the additional extension needs to be a torsion-proof connection so that the supporting force of the bearing can be statically transmitted to the fixed rear housing via the extension. This increases the feasibility of the design and assembly of the radial piston unit according to the present application. Preferably, the extension includes: a hollow cylindrical sleeve shape, wherein its outer surface is suitable for mounting a pair of bearings (preferably in an O-type arrangement). In order to support the bearing in the axial direction, the extension may include a fixing mechanism for the bearing on the outer surface of the extension, such as a shoulder for supporting the bearing in the axial direction, a groove for receiving a retaining ring, and / or a thread that can be screwed on a shaft nut.

[0031] According to the present application, the paired roller bearings can be located not only at the same axial position or near the hollow shaft portion of the distributor, but also at the same axial position as the flange, sprocket or similar torque transmission device on the outer peripheral surface of the rotating front housing. In the motor operation mode, the rotating part (such as a wheel or sprocket) can be driven by the hydrostatic radial piston unit. In the pump operation mode, the rotating part can drive the hydrostatic radial piston unit. The torque transmission device is used as an interface, and the rotating part or track / track or chain can be fixed to the interface. When the bearing is arranged in the same axial position as the torque transmission device, there is no or at least a reduction in the tilting moment related to the position of the paired bearings generated by the rotating front housing relative to the longitudinal axis. Therefore, the bearing can be designed to be smaller and have a lower load factor. This makes the bearing have a lower cost and further reduces the production cost of the hydrostatic radial piston unit. At the same time, this reduces the axial distance between the torque transmission point and the fixing device of the fixed rear housing (the radial piston unit can be installed to the frame of a vehicle, for example).

[0032] According to the present application, the radial piston unit may include a parking brake mechanism with a brake disc, which is radially arranged between the fixed rear housing and the rotating front housing, in the axial overlapping area of ​​the two housings. The brake discs are alternately fixed to the fixed rear housing and the rotating front housing. The parking brake mechanism includes a blocking position, in which the brake discs are pressed against each other and the rotating front housing is fixed relative to the fixed rear housing. According to one embodiment of the present application, the brake disc can be arranged in the axial overlapping area between the fixed rear housing and the rotating front housing, axially close to the bearing arrangement, for example on the other side of the sealing surface.

[0033] The parking brake mechanism may be preloaded toward its blocking position by means of a disc spring which provides a preload force acting on the brake piston in an axial direction and is supported, for example, by an end cap fixed to the rear end of the fixed rear housing.

[0034] The axial preload of the disc spring can be transmitted to the brake disc via a brake piston arranged near the disc spring. The brake pin extends axially between the brake piston and the brake disc. Therefore, the brake piston transmits the preload of the disc spring to the brake pin, which presses the brake discs against each other.

[0035] Different solutions can be used to switch the parking brake mechanism into the open position. As a first solution, the brake pin seals a chamber formed, for example, in the fixed part of the housing at the rear end of the radial piston unit. The chamber can also be formed by multiple parts, for example by the shaft, by the fixed rear housing, the brake pin and by the brake piston.

[0036] In one possibility, the rear end of the brake pin is accommodated in the brake piston in a liquid-tight manner. An additional seal is provided between the front end of the brake pin and the fixed rear housing. Thus, a pressure chamber is formed by the fixed rear housing in conjunction with the front end of the rear end of the fixed shaft, the brake pin guide hole and the brake piston. If pressurized hydraulic fluid is supplied to this pressure chamber, a force is generated on the release surface of the brake piston to balance the preload of the disc spring and release the brake.

[0037] Preferably, the rear end of the brake pin facing the direction of the brake piston has a larger diameter than the front end of the brake pin. If pressurized hydraulic fluid is supplied to the previously mentioned pressure chamber to generate a force on the release face of the brake piston, the same pressure is applied to the end surface of the brake pin. Since the diameter of the rear end of the brake pin is larger, a greater force will be generated on this side. Therefore, the brake pin moves in the direction of the brake piston until it contacts the brake piston. The brake pin then remains in contact with the brake piston even when the brake piston moves in the direction toward the disc spring (i.e., in the direction of the end cap to which the rear housing is fixed).

[0038] For the second scheme embodying the optional embodiment of the present application, a pressure chamber is formed in an axial hole (in which the brake pin is arranged and guided in the axial direction). Seals are provided at the front and rear ends of the brake pin to close the pressure chamber. Preferably, also in this embodiment, the rear end of the brake pin facing the brake piston direction has a larger diameter than the front end of the brake pin. If pressure is supplied to the pressure chamber, a greater force will be generated at the rear end of the brake pin due to the larger diameter. Therefore, the brake pin moves in the direction of the rear end of the hydrostatic radial piston unit (i.e., in the direction of the brake piston). If there is a gap between the brake pin and the brake piston, the brake pin will move toward the rear side until it contacts the brake piston. Then, the force generated by the pressure in the pressure chamber is transmitted to the brake piston by the brake pin. If the force generated is large enough to overcome the preload of the disc spring, the disc spring is compressed and the parking brake mechanism is released.

[0039] In a preferred embodiment, the end cap closes the non-rotating fixed rear housing on the side of the fixed rear housing opposite to the arrangement position of the brake disc and supports the disc spring in the axial direction. The disc spring generates an axial force on the disc brake piston. As a result, the brake pin (for example, arranged in an axial hole of the fixed rear housing) moves towards the brake disc so as to press the brake discs against each other.

[0040] The brake design according to one embodiment mentioned above allows the positioning of a centrally arranged brake disc close to the area where the rotating part and the fixed part of the hydrostatic radial piston unit overlap. At the same time, the hydraulic connection required to provide the pressure chamber of the brake device with hydraulic fluid to release the brake can be arranged in the fixed part of the hydrostatic radial piston unit and the mechanical part of the parking brake mechanism, except for the rotating brake disc fixed to the rotating part. The brake pin provides a functional connection between the brake disc in the overlapping area / close to the rotating part and the pressure chamber of the fixed part. Therefore, there is no need to send hydraulic fluid with brake release pressure from the fixed part to the rotating part. Therefore, fewer sealing connections are required, and the complexity of assembly and processing of the hydrostatic radial piston unit according to the present application is reduced. In addition, the number of potential leakage points is also reduced.

[0041] According to one embodiment of the present application, the non-rotating rear housing comprises an annular groove at the inner surface, which together with the first groove at the outer circumferential surface of the non-rotating fixed shaft forms a first annular passage. According to the present application, the brake pin is used to bridge the axial gap between the brake piston and the brake disc (which can be arranged in the axial overlap area). Preferably, the axial hole with the brake pin is arranged radially outside the first annular passage in the fixed rear housing, which ensures that sufficient space can be provided for the annular groove on the outer surface of the shaft and sufficient space can be provided for the first groove on the inner surface of the fixed rear housing.

[0042] In another embodiment according to the present application, the hydrostatic radial piston unit includes a fixed (non-rotating) two-speed, three-speed, or multi-speed control valve. The control valve (for example, in a two-speed embodiment) can be switched between a first position and a second position. In the first position, for example, all cylinder bores are used to generate torque on the rotating front housing, that is, fluid under high pressure (for example, operating pressure) can be supplied to the cylinder bores. This means that high-pressure hydraulic fluid is supplied to the cylinder bores, forcing the plungers arranged in the cylinder bores to move radially outward. When the plungers move radially inward due to the cam shape following the cam lobe surface, the corresponding cylinder bores are connected to the outlet timing holes, and the hydraulic fluid is discharged from the cylinder bores. In the second position, for example, only a portion of the cylinder bores presents the same operating behavior as in the first position, that is, only a portion of the cylinder bores can be supplied with high-pressure hydraulic fluid via the inlet timing holes. However, another portion of the cylinder bores are supplied with hydraulic fluid of reduced pressure (for example, oil filling pressure), regardless of the movement of the working plunger. Here, for example, the grouped cylinder bores can also be hydraulically short-circuited under reduced hydraulic pressure.

[0043] In other words, in the first position of the control valve, the working volume of the hydrostatic radial piston unit is the sum of all the working volumes enclosed between the cylinder bores and their corresponding working cylinders. In the second position, only a portion of the cylinder bores is supplied with high-pressure fluid. Therefore, only this portion of the working pistons and the corresponding cylinder bores contribute to the working volume of the radial piston unit. The other working pistons are provided with a reduced pressure, which is sufficient to ensure that the piston rollers are in contact with the cam lobe surface of the rotating front housing, and they do not contribute to the actual working volume of the radial piston unit because the corresponding pressure chambers are not supplied with high-pressure hydraulic fluid. In the event of a short circuit, the volume of hydraulic fluid necessary to move one piston outward is replaced by another piston moving inward.

[0044] In a further embodiment according to the present application, a reinforced disc-shaped cover is attached to the front end of the rotating front housing (also the front end of the hydrostatic radial piston unit). The cover closes and preferably seals the rotating front housing, for example with an O-ring, thereby preventing leakage of hydraulic fluid from the cavity formed by the rotating front housing and the fixed rear housing. Furthermore, the front end and the reinforced cover are designed such that the reinforced cover is able to absorb radial forces acting on the rotating front housing due to the working principle of the cam lobe.

[0045] In another embodiment, the reinforcing cover comprises a sleeve-shaped collar portion and the rotating front housing comprises a complementary shoulder, or vice versa. The sleeve-shaped collar portion can be arranged in a form of closed connection with the complementary shoulder at least in the radial direction. Thus, the rotating front housing can be enhanced in the radial direction. Preferably, the thickness of the reinforcing cover is designed so that: the reinforcing cover includes a low rotational mass when it rotates with the rotating front housing, but provides high radial stiffness. The higher radial stiffness of the reinforcing rotating front housing reduces the possible deviation between the cam lobe surface and the working plunger (which interacts with the cam lobe surface). The reinforcing cover thus ensures better contact between the cam lobe surface and the working plunger, and thereby prevents increased wear of the components, because it is beneficial for the plunger roller to press against the cam lobe surface with line contact during the operation of the radial piston unit.

[0046] In a preferred embodiment according to the present application, the hydrostatic radial piston unit operates as a hydraulic motor. The hydraulic motor drives the track drive or the wheels of a working machine, such as a crawler loader, for example, by means of a torque transmission. In particular in the field of track drives, it is important that the axial length of the radial piston unit is small, so that the design of the working machine can be selected as flexibly as possible. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In the following figures, exemplary embodiments of a hydrostatic radial piston unit according to the present application and specific subassemblies of a hydrostatic radial piston unit according to the present application are described. The presented embodiments do not limit the scope of the present application. The figures show:

[0048] Figure 1 A first sectional view along the axis of rotation of a hydrostatic radial piston unit according to the present application is shown;

[0049] Figure 2 A second sectional view along the axis of rotation of the hydrostatic radial piston unit according to the present application is shown;

[0050] Figure 3 A third sectional view showing a hydrostatic radial piston unit according to the present application;

[0051] Figure 4 An isometric view showing a rotating front housing of a hydrostatic radial piston unit according to the present application;

[0052] Figure 5 An isometric cutaway view showing the rotating front housing (with the distributor mounted) of a hydrostatic radial piston unit according to the present application;

[0053] Figure 6 A partial sectional view of the front end of a hydrostatic radial piston unit according to the application is shown.

[0054] For purposes of illustration and readability only, identical functional parts are indicated by identical reference numerals in all the presented figures.

[0055] Description of Reference Numerals

[0056] 1-Hydrostatic radial piston unit; 3-Casing; 10-Axis of rotation; 12-Non-rotating fixed shaft; 13-First groove; 14-Second groove; 15-Axial hole; 17-Front end region of fixed shaft; 20-Non-rotating fixed rear housing; 22-Annular groove; 24-End side; 25-Extension; 26-Through hole; 28-Axial hole for brake pin; 30-Axial overlap region; 33-First annular passage; 35-Sealing surface; 37-Seal body; 40-Rotating front housing; 42-Front end; 43-Second annular passage; 44-Torque transmission device; 45-Reinforced front cover; 46-Collar portion; 47-step / shoulder; 48-peripheral surface; 49-screw; 50-cylinder body; 55-cylinder bore; 60-working plunger; 65-roller; 70-rotating distributor; 71-disc portion; 72-distributor spring; 73-second internal groove; 74-hollow shaft portion; 75-axial hole; 77-timing hole; 78-synchronizing pin; 80-first cam lobe surface; 90-roller bearing; 100-parking brake mechanism; 112-brake disc; 114-brake pin; 116-brake piston; 117-release surface; 118-disc spring; 120-dual-speed valve / multi-speed control valve; 130-end cover. DETAILED DESCRIPTION

[0057] Figure 1A hydrostatic radial piston unit 1 according to the present application is disclosed. The hydrostatic radial piston unit 1 comprises: a fixed non-rotating rear housing 20, the non-rotating rear housing 20 comprising a through hole 26 defining a rotation axis 10. The non-rotating rear housing 20 accommodates a fixed shaft 12, which is coaxially arranged with the rotation axis 10 and is anti-twist connected to the non-rotating rear housing 20. The rotating front housing 40 is supported by a pair of roller bearings 90 so that it can rotate relative to the fixed rear housing 20 around the rotation axis 10. Therefore, the rear end portion of the rotating front housing 40 is sealed with the front end portion of the fixed rear housing 20 by a sealing body 37. The axial position of the sealing body 37 is defined by a sealing surface 35 orthogonal to the rotation axis 10. From the outside, the sealing surface 35 divides the housing 3 of the radial piston unit 1 into a rotating front housing portion 40 on one side of the sealing surface 35, and a fixed rear housing portion 20 on the other side of the sealing surface 35.

[0058] The pair of roller bearings 90 are arranged on the extension 25 of the fixed rear housing 20, wherein according to Figure 1 The extension 25 of the embodiment shown in FIG. 1 is provided as an additional extension portion. The extension 25 extends through the sealing surface 35 into the cavity formed by the rotating front housing 40. Figure 1 In the embodiment shown, the roller bearings 90 are arranged in pairs (i.e., substantially adjacent to each other in the direction of the axis of rotation) and in an O-type configuration. If the bearing support spacing is to be increased (e.g., if the component should be guided with a small tilting gap) or if large tilting forces must be supported, then the O-type configuration of the bearing is preferred. Otherwise, an X-type configuration or a locating / non-locating bearing arrangement may be selected.

[0059] According to the present application, the pair of bearings 90 is arranged in an axial overlap region 30, in which the fixed non-rotating rear housing 20 and the rotating front housing 40 overlap. In other words: in the overlap region 30, the fixed rear housing 20 is arranged coaxially with the rotating front housing 40, and vice versa. However, both the fixed rear housing 20 and the rotating front housing 40 are radially spaced apart from each other. This means that the rotating front housing 40 surrounds the fixed rear housing 20, as it is the case in the example presented, or vice versa.

[0060] The rotating front housing 40 includes a torque transmission device 44, i.e., a flange at the outer peripheral surface 48 of the rotating front housing. Depending on the application, components can be attached to the flange 44, the flange 44 can be driven by the hydrostatic radial piston unit 1, or the flange 44 can drive the hydrostatic radial piston unit 1. The torque transmission device 44 is preferably arranged at the same axial position as the pair of bearings 90 to reduce axial prying between the bearings 90 and the torque transmission device 49 and thereby eliminate the tilting moment that would otherwise be generated.

[0061] The rotating front housing 40 includes an inwardly facing cam lobe surface 80 against which the working plunger 60 can be pressed (see also Figure 3 ). In the embodiment presented, the cam lobe surface 80 is formed integrally with the rotating front housing 40, for example by three-dimensional milling, casting, turning, forging or other different manufacturing methods. The working plunger 60 is accommodated in the cylinder bore 55 of the cylinder block 50. The cylinder block 50 is designed to be fixed relative to the fixed shaft 12 and the fixed rear housing 20. Therefore, the working plunger 60 is pushed / pressed against the cam lobe surface 80, generating a force on the cam lobe surface 80 supported by the fixed cylinder block 50. Due to the shape of the cam lobe, this force causes the rotating front housing 40 to rotate.

[0062] To drive the working piston 60 against the cam lobe surface 80, pressurized fluid is supplied to the cylinder bore 55 of the cylinder block 50. If, in the opposite case, the working piston 60 is driven radially inward due to following the shape of the cam lobe surface (i.e., cam), the hydraulic fluid is discharged from the corresponding cylinder bore 55. Therefore, the cylinder bore 55 must be alternately connected to the hydrostatic radial piston unit 1 inlet and the hydrostatic radial piston unit 1 outlet, which is achieved by the rotary distributor 70.

[0063] The rotary distributor 70 (having a T-shaped cross section) having the disk-shaped portion 711 and the hollow shaft portion 74 is partially arranged in the axial overlap region 30. Therefore, the pair of bearings 90 can be arranged axially at the same position as the rotary distributor 70 and arranged radially outside the region with a smaller diameter of the hollow shaft portion 74 of the rotary distributor 70. However, in some designs, the pair of bearings 90 can also be arranged radially inside the hollow shaft portion 74 of the rotary distributor 70.

[0064] Preferably, the rotating front housing 40 and the fixed rear housing 20 seal out the inner cavity. To this end, in order to facilitate the manufacture and installation of the components of the radial piston unit 1 according to the present application, the end caps 45, 130 are arranged at the rear end side 24 and the front end 42 of the radial piston unit 1. In addition to its function of closing the housing cavity, the front cover 45 is designed to enhance the rotating front housing 40 in the radial direction and thereby enhance the cam lobe surface 80. The front cover 45 includes a substantially flat disc-shaped substrate, and a hollow cylindrical collar portion 46 extends from the substrate. Complementarily to the collar portion 46, a step 47 is provided on the outer peripheral surface 48 of the rotating front housing 40. After the front cover 45 is attached to the rotating front housing 40, the collar portion 46 provides support for the step 47 in the radial direction. This additional support ensures that the cam lobe surface 80 maintains its shape, even if the working plunger 60 presses against the cam lobe surface 80. The thickness of the collar portion 46 and the base plate can be selected according to the desired stability increase.

[0065] In addition, the front cover 45 may include a lightweight structure, for example by providing reinforcing ribs in the main stress-bearing areas and cutouts / recesses in the lower stress areas. A person skilled in the art will recognize that the functional principles of the collar portion 46 provided on the front cover 45 and the step provided on the housing 40 can be reversed, so that the front cover 45 may include a step 47 and the housing 40 may include a collar portion 46. However, other stability-increasing designs capable of absorbing forces acting on the rotating front housing 40 in the radial direction are also covered by the scope of the present application. For example, a dowel connection is provided between the generally flat front cover 45 and the rotating front housing 40.

[0066] In addition to the function of closing the rear end side 24 of the cavity of the two-part housing of the radial piston unit 1, the end cover 130 is part of the parking brake mechanism 100 (whose actuating mechanism is arranged in the fixed rear housing 20). The parking brake mechanism 100 includes at least two brake discs 112, one of which is attached to the rotating front housing 40 in a torsion-proof manner and the other is non-rotatably attached to the fixed rear housing 20. The brake disc 112 can move axially relative to the fixed rear housing 20 and the rotating front housing 40. If the parking brake mechanism 100 includes more than two brake discs 112, each brake disc 112 is connected to the fixed rear housing 20 and the rotating front housing 40 in an alternating sequence. The disc spring 118 is supported by the end cover 130 and provides a preload to the brake piston 116. As long as the brake piston 116 is not pressed at its release surface 117, the elastic force is transmitted to at least one brake pin 114 (the brake pin 114 is arranged in the axial hole 28 in the fixed rear housing 20) via the brake piston 116.

[0067] Preferably, in order to provide a more balanced brake disc actuation, more than one brake pin 114 is provided. Each brake pin 114 is arranged in one of the circumferentially distributed axial holes 28. At least one brake pin 114 applies / transmits the preload force of the disc spring 118 to the brake disc 112, which are pressed against each other and supported, for example, by a shoulder of the fixed rear housing 20 or the extension 25. Thereby, relative movement between the rotating front housing 40 and the fixed rear housing 20 can be prevented, for example, when the work vehicle is stopped.

[0068] If the relative movement between the rotating front housing 40 and the fixed rear housing 20 is allowed, hydraulic pressure is applied to the release surface 117 of the brake piston 116 on the opposite side of the disc spring 118. The hydraulic pressure generates a force on the release surface 117 in the direction toward the rear side of the fixed rear housing 20 (i.e., in the direction of the disc spring 118). Since the generated force is opposite to the preload force of the disc spring 118, the brake pin 114 is released from the brake disc 112. In this way, the brake discs 112 can move relative to each other, and thus, the fixed rear housing 20 and the rotating front housing 40 can move relative to each other.

[0069] Preferably, the brake pin 114 comprises a specific geometry. The end of the brake pin 114 facing the direction of the brake piston 116 comprises a larger diameter than the end facing the direction of the brake disc 112. In addition, the brake pin 114 is sealed relative to the fixed rear housing 20 and the fixed shaft 12. Therefore, a pressure chamber is formed between the end face of the brake pin 114 and the housing 20 of the hydrostatic radial piston unit 1. If the brake piston 116 is driven in the direction of the brake disc 112, the brake piston 116 pushes the brake pin 114 against the brake disc 112. In other cases, if pressure is applied to the sealed pressure chamber, a force is generated on the end face of the brake pin 114. Due to the different diameters of the end faces, the pressure generates a force that pushes the brake pin 114 in the direction of the brake piston 116. After the brake pin 114 contacts the brake piston 116, the brake pin 114 presses the brake piston 116 against the disc spring 118, thereby releasing the axial force of the brake disc 112.

[0070] However, the idea according to the present application also encompasses the following: the specific design of the brake pin 114 ensures that the pin 114 always contacts the brake piston 116, regardless of whether the release surface is pressed. In this embodiment, the brake pin 114 is sealed relative to the fixed rear housing 20 on the end away from the brake piston 116. The rear end of the brake pin 114 with a larger diameter is received in the brake piston 116, and a seal is provided between the rear end of the brake pin 114 and the brake piston 116. Thus, when the brake piston 116 is moved by the force generated by the hydraulic pressure in the pressure chamber (which is formed by the brake piston 116, the shaft 12, the front end of the brake pin 114 and the fixed rear housing 20), the hydraulic pressure may exist at the rear face / end face of the brake pin 114. Due to the larger diameter of the end face facing the brake piston 116, the hydraulic pressure generates a greater force on the side away from the brake piston 116, and the brake pin 114 is kept in contact with the brake piston 116.

[0071] Figure 2 Shows the basis Figure 1 Sectional views of the hydrostatic radial piston unit 1 in different sections. Figure 2 , showing some of the multiple hydraulic passages of the hydrostatic radial piston unit 1 according to the present application. In the center of the hydrostatic radial piston unit 1, a non-rotating fixed shaft 12 is provided, the fixed shaft 12 comprising: a first group of grooves 13, the first group of grooves 13 in the area facing the end side 24 of the hydrostatic radial piston unit 1 according to the present application. The fixed shaft 12 further comprises: a second group of grooves 14, the second group of grooves 14 in the area facing the front end 42 of the hydrostatic radial piston unit 1. The first group of grooves 13, together with the annular groove 22 provided in the non-rotating fixed rear housing, form a first annular passage 33. These first annular passages 33 are used to distribute the hydraulic fluid entering from the inlet of the hydrostatic radial piston unit 1 and flowing to the outlet of the hydrostatic radial piston unit 1.

[0072] The second annular passage 43 is formed by combining the second groove 14 with the second inner groove groove 73 in the hollow shaft portion 74 of the rotary distributor 70. The first annular passage 33 is formed by a channel ( Figure 2 The fluid (not visible) is connected to the second annular passage 43.

[0073] The internal structure of the rotary distributor 70 is Figure 1 and 2 The rotary distributor 70 is able to selectively connect the second annular passage 43 to the appropriate cylinder bore 55 , depending on whether a high pressure should be supplied to a particular cylinder bore 55 via a timing hole or whether hydraulic fluid should be exhausted from the particular cylinder bore 55 .

[0074] In the illustrated embodiment of the present application, the extension 25 is provided as an additional component attached to the fixed rear housing 20. In addition to supporting the paired bearings 90, the extension 25 is also provided with a shoulder against which the brake disc 112 can be pressed. Both functions require strict manufacturing tolerances to ensure reliable support and braking of the hydrostatic radial piston unit 1. Realizing these two functions on a relatively small additional component includes the following advantages: only a relatively small additional component needs to be machined, and a large part of the fixed rear housing 20 does not need to undergo such complex machining, which would be required if the fixed rear housing 20 should provide shoulders and / or bearing surfaces.

[0075] The non-rotating fixed shaft 12 further comprises: an axial hole 15, which is arranged coaxially with the axis of rotation 10 in the presented example. A two-speed valve 120 is arranged in the axial hole 15. The two-speed valve 120 comprises two positions. In the first position, all cylinder bores 55 can be supplied with hydraulic fluid under high pressure. In the second position, only a portion of the cylinder bores 55 can be supplied with hydraulic fluid under high pressure. The other cylinder bores 55 are supplied with a lower pressure, which is sufficient to force the rollers of the working plunger 60 to follow the cam lobe surface. At the same time, the cylinder bores 55 supplied with a lower pressure can be hydraulically short-circuited. Therefore, in the first position, all cylinder bores 55 contribute to the working volume of the hydrostatic radial piston unit 1. In the second position, the short-circuited cylinder bores 55 do not contribute to the working volume of the hydrostatic radial piston unit 1, because for each working plunger 60 that moves to the outside, another plunger moves to the inside of its associated cylinder bore 55.

[0076] In the embodiment presented, the two-speed valve 120 is hydraulically operated. However, the two-speed valve 120 can also be mechanically operated or electromechanically operated. In other embodiments, as those skilled in the art will appreciate, the two-speed valve 120 can be a multi-speed valve 120 providing more positions to change the rotational speed and torque of the hydrostatic radial piston unit 1 in a wider range.

[0077] Figure 3A sectional view of a hydrostatic radial piston unit 1 according to the present application is shown in a plane orthogonal to the axis of rotation 10 . Figure 3 The fixed shaft 12 shown in the middle is connected to the cylinder body 50 in a torsion-proof manner. Therefore, the cylinder body 50 is also fixed. The cylinder body 50 includes: cylinder holes 55 arranged in the radial direction, which are equidistantly distributed on the circumferential surface of the cylinder body 50. Each cylinder hole 55 receives a working plunger 60 so that the working plunger 60 can slide in the cylinder hole 55 in the radial direction. The working plunger 60 includes a roller 65 at the outer end in the radial direction. When pressure is supplied to the cylinder hole 55, the roller 65 is pushed to contact the cam lobe surface 80 formed on the radial inner side of the rotating front housing 40. The pressure forms a force in the radial outward direction on the working plunger 60. If the rotating front housing 40 is driven to rotate, the roller 65 interacts with the cam lobe surface 80, depending on whether the roller 65 moves from the lobe to the cam or vice versa. If the roller 65 travels from the lobe to the cam (i.e., the cam lobe surface shape is in the radially inward direction), the roller 65 and the corresponding plunger 60 are driven in the inward direction by the shape of the cam lobe surface 80, and the hydraulic fluid is discharged from the associated cylinder bore 55. In the opposite case, i.e., if the roller travels from the cam to the lobe, which means that the cam lobe surface 80 shape is in the radially outward direction in this area, the roller and the corresponding plunger 60 are driven outward by the pressure in the cylinder bore 55 to follow the cam lobe surface.

[0078] Figure 4 1 shows an isometric view of a rotating front housing 40 for a hydrostatic radial piston unit 1 in one embodiment according to the present application. In addition to the features already mentioned above, Figure 4 An axial hole 75 is shown, which is arranged radially inside the cam lobe surface 80, at a surface perpendicular to the rotation axis 10. The axial hole 75 receives a distributor spring 72, which provides a preload force to the adjacently arranged rotating distributor 70. The disc-shaped portion 71 of the rotating distributor 70 and the rotating front housing 40, in combination with the axial hole 75 and the accommodated distributor spring 72, can be rotatably coupled using a synchronization pin 78 arranged in one axial hole 75 of the rotating front housing 40. Therefore, the rotating distributor 70 and the distributor spring 72 rotate at the same rotation rate.

[0079] according to Figure 1 or Figure 2 , technical personnel in the relevant field from Figure 4 Found in, axial hole 75 can also be moved to distributor 70, to abut the bottom surface of relevant convex angle. Placing distributor spring 72 in hole 75 of distributor 70 can realize the same function: the disc-shaped component 71 of distributor 70 is pressed against the front surface of cylinder body 50.

[0080] exist Figure 4Also shown is a timing pin 78, which is arranged on a larger diameter in a conventional manner in the art, which reduces the shear torque acting on the timing pin 78. These shear forces are generated during the operation of the hydraulic motor by the friction between the outer peripheral surface of the shaft 12 and the inner peripheral surface of the distributor 70, which is sealed with the surface of the shaft 12 to form an annular distribution channel (see also Figure 1 or Figure 2 Here, the synchronization pin 78 is installed in the axial hole 75 in the front housing 40 and the corresponding hole in the distributor 70.

[0081] Figure 5 A cross-sectional view of a rotating front housing 40 is disclosed, in which a rotating distributor 70 is arranged. The outer surface of the disc-shaped portion 71 of the rotating distributor 70 is formed to be complementary to the cam lobe surface 80 to support the function of a synchronization pin 78 accommodated in the rotating front housing 40. The synchronization pin 78 ensures that the rotational orientation of the distributor 70 is correct when the distributor 70 is received in the rotating front housing 40. In addition, the synchronization pin 78 synchronizes the rotation of the distributor 70 with the rotation of the rotating front housing 40. In addition, it is shown how the distributor spring 72 abuts against the bottom of the axial hole 75 and thereby moves in the direction of the front end 42 (i.e., toward the cylinder 50 ( Figure 5 The rotary distributor 70 includes a lightweight design to reduce the moment of inertia of the assembly. To this end, a gap is partially provided at the radially extending disc-shaped portion 71 of the distributor 70. In addition, a second internal groove 73 formed at the radial inner side of the distributor 70 is shown. The second internal groove 73 includes an annular shape and is capable of guiding the fluid in and out of the timing hole 77 arranged in the front surface of the distributor 70.

[0082] Figure 6 It is illustrated how the enhanced front cover 45 is attached to the rotating front housing 40 using screws that are equally spaced along an imaginary arc. The combination of the collar portion in the front cover 45 and the step in the rotating front housing 40 explained above not only enhances the cam lobe surface 80, but also ensures that the cover 45 is properly centered relative to the rotating front housing 40. It should be recognized that other techniques for attaching the cover to the rotating front housing 40 are also within the common knowledge of those skilled in the art.

[0083] Based on the above disclosure and the accompanying drawings and claims, it should be recognized that the hydrostatic radial piston unit 1 according to the present application provides a variety of feasible solutions and advantages over the prior art. Those skilled in the art should further recognize that, without departing from the spirit of the present application, further modifications and changes known in the prior art may be made to the radial piston unit 1 according to the present application. Therefore, all these modifications and changes are within the scope of the claims and are covered by the claims. It should be further understood that the above examples and embodiments are for illustrative purposes only, and various modifications, changes or combinations of the embodiments made therefrom (which will be suggested by those skilled in the art) are included in the spirit and scope of the present application.

Claims

1. A hydrostatic radial piston unit (1) with a cam lobe structure, comprising: A non-rotating shaft (12) defining an axis of rotation (10) of the hydrostatic radial piston unit (1), and a front end (17) of the shaft (12) extending from a non-rotating, fixed rear housing (20) to a front housing (40) rotating about the axis of rotation (10), a cylinder (50) being accommodated in the front housing (40) and connected to the front end (17) of the shaft (12) in a torsionally fixed manner, in which a radially reciprocating A moving working piston (60) is arranged in a radial cylinder hole (55), and hydraulic fluid is introduced into and discharged from the cylinder hole (55) through a distributor (70), wherein the distributor (70) is fixed relative to the front housing (40) in the rotational direction and freely rotates relative to the shaft (12), wherein the front housing (40) is a single-piece design, and a circumferential cam lobe surface (80) that can interact with the working piston (60) is integrally formed on the radial inner side of the front housing (40).

2. The hydrostatic radial piston unit (1) according to claim 1, wherein: The cylinder block (50) includes more than one row of cylinder holes (55) and radially reciprocating working plungers (60), which are arranged adjacent to or staggered with each other in the circumferential direction and are capable of interacting with the cam lobe surface (80).

3. The hydrostatic radial piston unit (1) according to claim 1, wherein: The second cylinder body is fixedly arranged and axially parallel to the cylinder body (50) on the front end (17) of the shaft (12), and the second cylinder body has a radially reciprocating working plunger (60) that interacts with the cylinder hole (55) and the cam lobe surface (80).

4. The hydrostatic radial piston unit (1) according to claim 3, wherein: The number of cylinder holes (55) and the number of radially reciprocating working plungers (60) of the second cylinder body are different from the number of cylinder holes (55) and the number of radially reciprocating working plungers of the cylinder body (50), and a second circumferential cam lobe surface (82) capable of interacting with the working plungers (60) of the second cylinder body is arranged on the radial inner side of the front housing (40).

5. The hydrostatic radial piston unit (1) according to claim 4, wherein: The second circumferential cam lobe surface (82) is integrally formed with the front housing (40).

6. The hydrostatic radial piston unit according to claim 1 comprises a multi-speed control valve, which is a two-speed valve capable of switching between a first position and a second position, in which, in the first position, all cylinder holes (55) can be supplied with high-pressure hydraulic fluid from a high-pressure inlet of the hydrostatic radial piston unit (1), and in the second position, only a portion of the cylinder holes (55) can be supplied with high-pressure fluid, and in the second position, the grouped cylinder holes (55) are hydraulically short-circuited.

7. The hydrostatic radial piston unit according to claim 1 comprises a multi-speed control valve which can be switched between a first position in which all cylinder bores (55) can be supplied with hydraulic fluid and a plurality of intermediate positions in which a different number of cylinder bores (55) are supplied with high-pressure hydraulic fluid.

8. The hydrostatic radial piston unit according to claim 6 or 7, wherein: The multi-speed control valve is arranged in a first axial hole (15) of the shaft (12), wherein the first axial hole (15) is arranged coaxially with the rotation axis (10).

9. A hydrostatic radial piston unit (1) according to any one of claims 1 to 7, wherein the distributor (70) is axially biased against the side surface of the cylinder body (50) by a distributor spring (72) and / or a distributor plunger, and the distributor spring (72) and the distributor plunger are both axially accommodated in the front housing (40) or in the disc-shaped portion (71) of the distributor (70).

10. The hydrostatic radial piston unit (1) according to claim 9, wherein: The distributor spring (72) is received in a third axial hole (75) of the front housing (40) or the disc-shaped portion (71) of the rotary distributor (70), at the axial extension of the lobe of the cam lobe surface (80).

11. A hydrostatic radial piston unit according to any one of claims 1 to 7, wherein a reinforced front cover (45) is attached to the front end (42) of the front housing (40) and closes the front housing (40), wherein the front end (42) of the front housing (40) and the reinforced front cover (45) are arranged so that the reinforced front cover (45) can at least partially absorb the force acting on the front housing (40) in the radial direction.

12. The hydrostatic radial piston unit (1) according to claim 11, wherein the reinforced front cover (45) comprises a sleeve-like collar portion (46) and the front housing (40) comprises a complementary shoulder (47) on which the sleeve-like collar portion (46) can be placed, or the front housing (40) comprises a sleeve-like collar portion and the reinforced front cover (45) comprises a complementary shoulder on which the sleeve-like collar portion (46) can be placed.

13. The hydrostatic radial piston unit (1) according to claim 8, wherein a pair of roller bearings (90) for rotatably mounting the front housing (40) to the rear housing (20) are located in an axial overlap region (30) where a front end portion of the rear housing (20) and a rear end portion of the front housing (40) overlap.

14. The hydrostatic radial piston unit (1) according to claim 13, wherein: The paired roller bearings (90) are mounted on an extension portion (25), which is integrally formed on or attached to the front end of the rear housing (20), protrudes beyond the sealing surface (35) into the volume of the front housing (40), and extends radially between the hollow shaft portion (74) of the distributor (70) and the front housing (40), wherein the extension portion (25) is configured to fit the inner shell of the roller bearing (90).

15. The hydrostatic radial piston unit (1) according to any one of claims 1 to 7, comprising a parking brake mechanism (100), the parking brake mechanism (100) comprising at least two brake discs (112), wherein: One brake disc (112) is fixed relative to the rear housing (20) in the rotational direction, and the other brake disc (112) is fixed relative to the front housing (40) in the rotational direction. It also includes at least one brake pin (114), a disc brake piston (116) and a disc spring (118) arranged in the rear housing (20), wherein, in a non-hydraulic state, the disc spring (118) supported by the end cover (130) of the rear housing (20) expands toward the brake piston (116) and offsets the brake piston (116) toward the brake pin (114), and the brake pin (114) causes the brake discs (112) to be pressed against each other in the axial direction.

16. The hydrostatic radial piston unit (1) according to claim 15, wherein: The at least one brake pin (114) has a portion with a larger diameter at an end facing the brake piston (116).

17. The hydrostatic radial piston unit (1) according to claim 16, wherein: The front and rear ends of the at least one brake pin (114) seal a pressure chamber in the second axial hole (28) of the rear housing (20), and the pressure chamber can be pressurized to push the brake pin (114) in the direction toward the end cover (130) and cause the brake piston (116) to compress the disc spring (118), thereby releasing the clamping force from the brake disc (112).

18. The hydrostatic radial piston unit (1) according to claim 16, wherein: The brake piston (116), the at least one brake pin (114), the non-rotating shaft (12), and the rear housing (20) seal a pressure chamber that can be pressurized to offset the brake piston (116) along the axis toward the disc spring (118) and compress the disc spring (118), thereby releasing the clamping force of the brake pin (114) from the brake disc (112).

19. The hydrostatic radial piston unit (1) according to claim 15, the brake disc (112) being arranged in an axial overlapping area (30), in which a front end portion of the rear housing (20) and a rear end portion of the front housing (40) overlap.

Images