Hydrostatic Radial Piston Unit

Abstract

The hydrostatic radial piston unit of cam lobe type construction comprises a non-rotating stationary casing. The stationary casing comprises a through hole defining the rotation axis of the hydrostatic radial piston unit. The rotating casing is rotatably mounted to the non-rotating stationary casing in an axial overlapping region. The parking brake mechanism comprises at least two brake discs arranged adjacent to each other in the overlapping region. An end cover closes the non-rotating casing at a rear end side of the hydrostatic radial piston unit facing away from the rotating casing. The end cover pretensions a disc spring against a disc-shaped brake piston, both of which are arranged in the rear end portion of the stationary casing, to generate an axially directed spring force. When the brake piston on the opposite face of the disc spring is not forced to move towards the end cover, a force can be transmitted by the brake piston to at least one brake pin arranged in an axially directed bore of the stationary casing to press the brake discs against each other.

Description

[Technical Field]

[0001] The present invention relates to a hydrostatic radial piston unit, and more particularly to a cam lobe or orbital motor or pump. In particular, the present invention relates to a brake mechanism for a hydrostatic radial piston unit of cam lobe type construction. [Background technology]

[0002] Radial piston units, i.e., radial piston pumps and radial piston motors, are widely used in the art, for example, for heavy-duty applications. For example, radial piston units are used in the fields of construction machinery, agricultural equipment, or forestry machinery. Radial piston units are characterized by their working pistons moving radially relative to a central longitudinal / rotational axis when supplied with pressurized hydraulic fluid, in the case of radial piston motors. Radial piston units are generally used in hydraulic applications that do not require high rotational speeds but do require high torque. Radial piston units offer the advantage over axial piston units of reduced axial construction space.

[0003] One particular application of radial piston units is the propulsion of work vehicles, such as track loaders. In many cases, one radial piston unit is installed on either side of the frame / body of the work vehicle. Therefore, the geometry of the frame and the propulsion mechanism is significantly influenced by the size of the radial piston unit. In many applications, the position at which the radial piston unit transmits torque to the drive means is predetermined by other components, other than the radial piston unit, that interact with the drive means. However, known technical radial piston units exhibit relatively large axial lengths and relatively large diameters. Because the radial piston unit driving the work vehicle must be integrated into the vehicle frame, the frame must be designed to receive the fixed portion of the radial piston unit, e.g., the fixed casing, to support the torque generated / applied during operation. Therefore, it is desirable to minimize the size of the radial piston unit used, particularly in the axial direction, in order to minimize the need for modifications to the design of the frame on which the radial piston unit is installed.

[0004] When a hydrostatic radial piston unit is used in a propulsion application, a parking brake is often required to ensure fail-safe operation of the hydrostatic radial piston unit. In this case, the brake only allows the vehicle to move when actively released. In the inactive state of the parking brake, movement of the hydrostatic radial piston unit, and therefore of the vehicle, is prevented. In the prior art, different concepts are available for providing a parking brake mechanism for a hydrostatic radial piston unit, such as a disc brake mounted on the outside of the casing of the hydrostatic radial piston unit. As an alternative, the brake can be arranged inside the casing of the hydrostatic radial piston unit, where it is protected from dust and similar negative influences. Unfortunately, this arrangement significantly increases the axial length of the hydrostatic radial piston unit.

[0005] WO 2013 / 160145 A2 discloses a radial piston engine having a rotating output shaft. To reduce the axial length of the radial piston engine, at least a portion of a parking brake is arranged between the housing and a portion of the output shaft. The output shaft is designed to rotate, for example, to drive a wheel that can be fastened to an output flange on the output shaft. Summary of the Invention [Problem to be solved by the invention]

[0006] The object of the present invention is to provide a radial piston unit having a reduced size, in particular a reduced axial length, but also a reduced radial size / diameter, and at the same time, the radial piston unit is provided with a parking brake mechanism that is arranged inside the casing of the radial piston unit so that neither the axial nor the radial size of the radial piston unit increases significantly. [Means for solving the problem]

[0007] This object is achieved by a hydrostatic radial piston unit according to claim 1. Preferred embodiments are set forth in the dependent claims.

[0008] The hydrostatic radial piston unit according to the invention comprises a stationary casing with a through-hole defining a longitudinal axis, which is also the axis of rotation of the hydrostatic radial piston unit, and which is provided for connection to the frame of the work vehicle, i.e., in the sense of this specification, the stationary part of the radial piston unit according to the invention forms, for example, a rear end region that can be fixedly fastened to a frame or a support.

[0009] In this specification, the terms "radial" and "axial" refer to directions relative to the longitudinal axis of a fixed shaft. In the context of this application, "fixed" means that the radial piston unit does not rotate about the longitudinal axis, for example, when installed in a work vehicle.

[0010] The cylindrical rotating casing is rotatably mounted to the non-rotating stationary casing in an axial overlap region. In this region, the front end portion of the non-rotating casing and the rear end portion of the rotating casing overlap axially. As a result, in the overlap region, at least a portion of the rotating casing is disposed radially outside or inside the stationary casing. Thereby, the rear end portion of the rotating casing is sealed against the front end portion of the stationary casing when the rotating casing can rotate relative to the stationary casing around the rotation axis of the radial piston unit. The sealing between the rotating casing and the stationary casing is performed so that both casings together form a closed, fluid-tight cavity. The connection between the rotating casing and the stationary casing allows the rotating casing to rotate relative to the stationary casing around the rotation axis, i.e., the longitudinal axis.

[0011] Essentially, the axial position of the seal between the stationary casing and the rotating casing defines a sealing surface perpendicular to the axis of rotation. As a result, in a view from the outside, the sealing surface divides the casing of the hydrostatic radial piston unit into a stationary part (rear end) on one side of the sealing surface and a rotating part (front end) on the other side of the sealing surface.

[0012] In a preferred embodiment of the present invention, the stationary casing accommodates the stationary shaft in a torque-resistant manner at its rear end portion, meaning that neither the stationary shaft nor the stationary casing rotates relative to each other. The stationary shaft is arranged coaxially with the rotation axis within the internal cavity formed by the stationary casing and the rotating casing. A stationary cylinder block is arranged in torque-resistant connection with the stationary shaft at the front end portion of the stationary shaft protruding from the stationary casing. The cylinder block has a plurality of cylinder bores extending radially inward from the circumferential surface of the cylinder block.

[0013] The hydrostatic radial piston unit according to the present invention further comprises a parking brake mechanism comprising at least two brake discs arranged adjacent to each other in an overlapping region, one brake disc rotatably fixed to the non-rotating casing and the other brake disc rotatably fixed to the rotating casing, whereby at least one brake disc is axially movable. If the hydrostatic radial piston unit comprises more than two brake discs, the brake discs must be rotatably fixed alternately to the stationary and rotating casings, and axial mobility must be provided to achieve the braking effect by (fully) pressing the brake discs together, and to release the brake by reducing the compression force. According to the present invention, the rotatably fixed parts cannot rotate relative to each other.

[0014] The parking brake mechanism includes a blocking position in which the brake discs are pressed against each other and the rotational position of the rotating casing is fixed relative to the stationary casing. According to a preferred embodiment of the present invention, the brake discs can be arranged in the axial overlap region between the stationary casing and the rotating casing, axially adjacent to the sealing surface.

[0015] The parking brake mechanism can be pretensioned towards its blocking position by a disc spring that provides a pretensioning force acting axially on the brake piston and can be supported, for example, by an end cap / end cover fixed to the rear end of the stationary casing, which closes the non-rotating stationary casing on the end side of the hydrostatic radial piston unit that faces away from the rotating casing, i.e., away from the axial overlap area where the rotating casing is attached to the stationary casing.

[0016] The axial pretensioning force of the disc spring can be transmitted to the brake disc via the brake piston by at least one brake pin extending axially between the brake piston and the brake disc. The at least one brake pin is preferably disposed in an axially oriented bore in the non-rotating stationary casing on the opposite side of the brake piston from the disc spring. As a result, the brake piston transmits the pretensioning force of the disc spring to the brake pin, which presses the brake disc against each other.

[0017] Those skilled in the art will select the number, shape, and arrangement of the brake pins and corresponding axially oriented bores according to the requirements of the specific application. For example, it may be preferable to arrange at least three brake pins equidistantly distributed on a circular arc having the axis of rotation as its center.

[0018] Different options are available for switching the parking brake into the open / release position. For the first option, the brake pin seals a chamber formed, for example, in the fixed part of the casing at the rear end of the radial piston unit. The chamber can also be formed by several parts, for example, by the shaft, the fixed casing, the brake pin and the brake piston.

[0019] Thus, the rear end of the brake pin is preferably attached fluid-tight to the brake piston. Additional sealing is provided between the front end of the brake pin and the fixed casing. A pressure chamber is thus formed by the fixed casing together with the fixed shaft, the brake pin guide hole, and the rear end front surface of the brake piston. When pressurized hydraulic fluid is supplied to this pressure chamber, a force is generated on the release surface of the brake piston to counteract the pretensioning force of the disc spring and release the brake. The compressive force of the brake pin is thereby released from the brake disc, allowing the rotating casing to rotate relative to the fixed casing. The release pressure required to release the brake depends on the size of the release surface of the brake piston compared to the pretensioning force provided by the disc spring. The pretensioning force of the spring may be adjustable by adjusting the relative position of the brake piston to the end cover, for example, with an adjustable shoulder or adjustment screw on the end cap / end cover. Alternatively, the length of the brake pack, i.e., the number of brake discs, may also be adjusted.

[0020] Preferably, the rear end of the brake pin, which faces the brake piston, has a larger diameter than the front end of the brake pin. This design of the brake pin ensures that the pin is always in contact with the brake piston, whether or not the brake is preventing the relative rotation of the stationary casing and the rotating casing. In the blocking position, or when the hydrostatic radial piston unit is moved towards the blocking position, the brake piston presses the brake pin against the brake disc, for example against the shoulder of the stationary casing, which presses against it.

[0021] When pressurized hydraulic fluid is supplied to the aforementioned pressure chamber to generate a force on the release face of the brake piston, the same pressure is applied to the end face of the brake pin. This pressure generates a force acting on the end face of the brake pin. Due to the larger diameter of the rear end of the brake pin, a larger force is generated on this side. The brake pin therefore moves towards the brake piston until it comes into contact with the brake piston. In that case, the brake pin remains in contact with the brake piston even if the brake piston moves towards the disc spring, i.e. towards the end cap of the fixed casing.

[0022] In a second option representing an alternative embodiment of the present invention, a pressure chamber is formed in an axially oriented bore in which a brake pin is disposed and guided axially. Sealings 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, which faces the brake piston, has a larger diameter than the front end of the brake pin. When pressure is applied to the pressure chamber, a larger force is generated at the rear end of the brake pin due to the larger diameter. Therefore, the brake pin moves toward the rear end of the hydrostatic radial piston unit, i.e., toward the brake piston. If there is a gap between the brake pin and the brake piston, the brake pin moves rearward until it contacts the brake pin. The force generated by the pressure in the pressure chamber is then transmitted by the brake pin to the brake piston. If the generated force is large enough to overcome the pretensioning force of the disc spring, the disc spring is compressed and the parking brake is released.

[0023] In one embodiment of the present invention, the non-rotating stationary casing includes an annular groove on the inner surface of the through hole, which, together with a first groove on the outer circumferential surface of the non-rotating stationary shaft, forms a first circular guide. According to the present invention, a brake pin is used to fill the axial gap between the brake piston and the brake disc, which may be located in the axial overlap area. Preferably, the axially oriented bore containing the brake pin is located radially outside the first circular guide of the stationary casing. This ensures that there is sufficient space on the outer surface of the shaft for the annular groove and sufficient space on the inner surface of the stationary casing for the first groove.

[0024] The brake design of the present invention allows a centrally located brake disc to be positioned adjacent to the area where the rotating portion of the hydrostatic radial piston unit overlaps with the stationary portion. At the same time, the hydraulic connections needed to provide hydraulic fluid to the pressure chamber of the brake device to release the brake can be located in the stationary portion of the hydrostatic radial piston unit and in the mechanical portion of the parking brake, excluding the rotating brake disc, which is fixed to the rotating portion. A brake pin provides a functional connection between the brake disc in the overlap area / near the rotating portion and the pressure chamber in the stationary portion. Therefore, it is not necessary to provide hydraulic fluid at brake release pressure to the rotating portion from the stationary portion. As a result, fewer sealed joints are required, reducing the complexity of assembling and machining the hydrostatic radial piston unit of the present invention. Furthermore, the number of potential leak points is reduced.

[0025] The stationary cylinder block at the forward end portion of the radial piston unit includes a plurality of cylinder bores extending radially inward from the circumferential surface of the cylinder block. A plurality of actuating pistons can be arranged to be radially movable within the cylinder bores, with each cylinder bore housing one actuating piston. Each actuating piston seals a pressure chamber within the cylinder bore to which pressurized hydraulic fluid can be supplied via a hydraulic channel to generate a force on the head of the associated actuating piston that moves the actuating piston radially outward. Hydraulic fluid can also be evacuated from the cylinder bore via the hydraulic channel when the actuating piston is mechanically urged inward, for example by a cam.

[0026] The rotating casing includes an internal cam lobe surface. When pressurized fluid is supplied to the pressure chamber, the working piston is urged against the cam lobe surface. Because the cylinder block is fixed and supported on the stationary casing via a fixed shaft, radially outward movement of the working piston generates a force on the cam lobe surface that rotates the rotating casing relative to the stationary casing.

[0027] To guide pressurized fluid into the pressure chamber, a rotary distributor is provided according to the present invention, comprising a hollow shaft portion and a disk-shaped portion, preferably integrally formed with each other, but which may be, for example, fluid-tightly attached to each other. The disk-shaped portion is torque-resistantly connected to the rotating casing, i.e., rotates together with the rotating casing. In a preferred embodiment, the disk-shaped portion of the distributor exhibits a radial height that matches the lobes of the cam lobe surface. The rotary distributor further comprises timing holes in the disk-shaped portion for supplying hydraulic fluid to and discharging hydraulic fluid from the cylinder bores of the cylinder block via hydraulic channels. Furthermore, the rotary distributor comprises a second internal groove that, together with a second groove in the outer surface of the non-rotating, fixed shaft, forms a second circular guide. The second groove in the outer surface of the non-rotating shaft is connected to the first circular guide by an internal channel in the shaft. Those skilled in the art are familiar with the operating principle of radial piston units, and therefore further details of the function of radial piston units are not necessary here.

[0028] According to the present invention, a pair of roller bearings supports the rotating casing so that it rotates relative to the stationary casing. According to the present invention, the roller bearings are arranged radially outside the rotating distributor, but near the front end portion of the stationary casing, and near the rear end portion of the rotating casing, respectively, at substantially the same axial position as the hollow shaft portion of the distributor. In other words, the roller bearings are arranged adjacent to or near the sealing surfaces to allow relative movement between the rotating casing and the stationary casing and to avoid large tilting moments of both casings. This also facilitates sealing of both casings.

[0029] The roller bearings according to the present invention are arranged in pairs, preferably next to or adjacent to each other in one embodiment. Arranging the bearings substantially in the same axial position as the hollow shaft portion of the rotary distributor means that the bearings are disposed in an axial region adjacent to the side of the cylinder block facing the stationary casing, for example, at least partially surrounding the rotary distributor in its cylindrical portion. Even in this region, the stationary casing and the rotating casing overlap, or at least extensions or protrusions of one or both casings overlap axially, while being coaxially arranged so that a rotating part, such as the rotating casing or the rotary distributor, can rotate relative to a fixed part, such as the stationary casing or the stationary shaft. The pair of bearings may have an axial length different from that of the distributor. Since the bearings are arranged radially outside (with respect to the longitudinal axis) the hollow shaft portion of the distributor and at least partially overlap the distributor in the axial direction instead of being axially adjacent to it, the axial length of the hydrostatic radial piston unit is reduced. Those skilled in the art will appreciate that the use of roller bearings is only a preferred embodiment, however, the use of journal bearings to rotatably support the rotating casing relative to the stationary casing is also encompassed by the present invention.

[0030] According to one preferred embodiment of the present invention, the stationary casing of the radial piston unit may include a fixed extension having a generally cylindrical shape, extending axially beyond the sealing surface into the volume of the rotating casing. The extension may, for example, accommodate the inner shells of bearings. Since the pair of bearings is received in the space between the rotating casing and the rotary distributor, the extension may, for example, provide fixed support for the pair of bearings radially outside the rotary distributor. Thus, the extension is disposed in the radial space between the two rotating parts, the rotary distributor and the rotating casing.

[0031] In one embodiment according to the present invention, the extension may be integrally formed with the stationary casing. However, in another embodiment according to the present invention, the extension is provided as an additional part and attached to the stationary casing. The extension may be attached to the stationary casing, for example, by threading, welding, joining, press-fitting, heat-shrinking, clamping, crimping, or plastic deformation. The connection between the stationary casing and the additional extension must be a torque-resistant connection, so that the bearing's support force can be statically transmitted to the stationary casing via the extension. This separate component design increases the possibilities for designing and assembling the radial piston unit according to the present invention. Preferably, the extension has a hollow cylindrical sleeve-like shape, the outer surface of which is adapted to accommodate a pair of bearings, preferably O-type devices. To support the bearings axially, the extension may have fixing means for the bearings on its outer surface, such as a shoulder for axially supporting the bearings, a groove for receiving a retaining ring, and / or a thread onto which a shaft nut can be threaded.

[0032] According to the present invention, the pair of roller bearings can be positioned not only at substantially the same axial position or near the distributor, but also at substantially the same axial position on the outer circumferential surface of the rotating casing as a flange, sprocket, or similar torque transmission device. In the motor operation mode, a 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 serves as an interface to which the rotating part, or a track or chain, can be fixed. Because the bearings are essentially positioned at the same axial position as the torque transmission device, a tilting moment is not generated by the rotating casing with respect to the longitudinal axis, or at least is reduced, with respect to the position of the pair of bearings. Therefore, the bearings can be designed to be smaller and with a smaller load coefficient. This leads to a reduction in the cost of the bearings and, further, to a reduction in the manufacturing cost of the hydrostatic radial piston unit. At the same time, the bearing device according to the invention reduces the axial length of the radial piston unit and reduces the distance required between the torque transmission point and the fixing means of a fixed casing on which the radial piston unit can be mounted, for example on the frame of a vehicle.

[0033] In another embodiment according to the present invention, the hydrostatic radial piston unit includes a fixed (non-rotating) two-speed, three-speed, or multi-speed control valve. For example, in a two-speed embodiment, the control valve is switchable 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 casing, i.e., the cylinder bores can be supplied with fluid under high pressure, e.g., working pressure. This means that hydraulic fluid is supplied to the cylinder bores under high pressure, which moves pistons located in the cylinder bores radially outward. When the pistons move radially inward to follow the shape of the cam on the cam lobe surface, the corresponding cylinder bores are connected to the outlet timing holes, and hydraulic fluid is discharged from the cylinder bores. In the second position, for example, only some of the cylinder bores exhibit the same operating behavior as in the first position, i.e., only some of the cylinder bores can be supplied with hydraulic fluid under high pressure via the inlet timing holes. However, other parts of the cylinder bores are supplied with hydraulic fluid at a lower pressure, e.g., charge pressure, independent of the movement of the working pistons. Here, for example, groups of cylinder bores can also be hydraulically short-circuited under low water pressure.

[0034] 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 their corresponding cylinder bores contribute to the working volume of the radial piston unit. The other working pistons are supplied with a pressure low enough to ensure contact of the piston rollers with the cam lobe surfaces of the rotating casing. Since the corresponding pressure chambers are not supplied with high-pressure hydraulic fluid, they do not contribute to the actual working volume of the radial piston unit. When short-circuited, the hydraulic fluid volume required to move one piston outward is displaced by another piston moving inward.

[0035] In another preferred embodiment according to the present invention, the cam lobe surfaces are integrally formed with the rotating casing. When the casing is assembled from multiple parts, the necessary connections and seals require additional radial and axial space. By integrally forming the rotating casing together with the cam lobe surfaces, the complexity of the assembly process is reduced. Furthermore, this integral concept can eliminate connections between parts, thereby reducing the diameter, i.e., the radial dimension, of the hydrostatic radial piston unit. This also reduces manufacturing and assembly costs, as precisely machined connection surfaces and additional assembly steps are avoided.

[0036] The synchronizing pin can be accommodated in an axially oriented hole in the rotating casing, preferably in the extension of the lobe, and engages with a corresponding hole in one of the radial heights of the disk-shaped part of the distributor. This allows the synchronizing pin to interact simultaneously with the rotating casing and the rotating distributor. The synchronizing pin thereby ensures that the distributor, or rather the disk-shaped part of the rotating distributor, is correctly oriented when the distributor is installed in the rotating casing. Furthermore, the synchronizing pin synchronizes the rotation of the distributor with that of the rotating casing, i.e. prevents relative movement between these two parts.

[0037] According to the present invention, the radial piston unit may further comprise distributor springs that press the rotary distributor with its disk-shaped portion toward the cylinder block. According to the present invention, these distributor springs are preferably received in the axially extending bore of the rotary casing in the axial extension direction of the lobes. Preferably, the disk-shaped portion of the rotary distributor presents a profile complementary to the cam lobe surface. The distributor springs urge the rotary distributor toward the cylinder block. The front surface of the disk-shaped portion of the rotary distributor and the adjacent front surface of the cylinder block thereby form a hydrostatic bearing between the disk-shaped portion of the rotary distributor and the fixed cylinder block.

[0038] The hydrostatic bearing is located in front of the disk-shaped portion of the rotary distributor and is supplied with pressurized fluid by timing holes that allow hydraulic fluid to be supplied to and discharged from the cylinder bores of the cylinder block. The location of the distributor spring in the rotating casing, which has a torque-resistant connection with the distributor, ensures that there is no relative circumferential movement between the distributor spring and the distributor. If there were relative movement between the two components, the spring would likely be prone to concentrated wear and / or buckling. Furthermore, the axial accommodation of the distributor spring in the lobe extension / extension of the cam lobe face reduces the load and stress on the synchronizer pin resulting from frictional resistance between the rotary distributor and the fixed shaft.

[0039] When the spring is housed within the axial thickness of the distributor, another benefit is realized: the axially oriented bore in the front housing for housing the spring is moved toward the distributor, thereby reducing the axial length of the front housing, further reducing the axial length of the hydrostatic radial piston motor.

[0040] The first cylinder block may include more than one row of cylinder bores with radially reciprocating actuating pistons, each row of cylinder bores spaced axially from an adjacent row, and the cylinder bores and corresponding actuating pistons may be circumferentially adjacent, i.e., in the same rotational direction, or may be staggered and may interact with a first cam lobe surface.

[0041] According to the present invention, the hydrostatic radial piston unit can further comprise a second cylinder block, the working pistons of which interact with the same cam lobe surface or with another cam lobe surface arranged parallel to the first cylinder block. The second cylinder block is arranged axially parallel to the first cylinder block on a non-rotating shaft. By providing the cylinder block or second cylinder block with more than one row of cylinder bores, the potential working volume can be significantly increased while the diameter of the hydrostatic radial piston unit remains the same.

[0042] To tailor the operation of the hydrostatic radial piston unit to a particular application, the number of cylinder bores and the number of radially reciprocating working pistons in the axially spaced rows of cylinder bores or in the second cylinder block may be different from the number of cylinder bores and the number of radially reciprocating working pistons in the first cylinder block. In this case, a second peripheral cam lobe surface may be provided radially inward of the rotating casing. The working pistons of the second cylinder block or of the second or further rows of cylinder bores may interact with the second cam lobe surface. In one embodiment, the second peripheral cam lobe surface is integrally formed with the rotating casing.

[0043] In a further embodiment according to the invention, a reinforced disk-shaped cover is attached to the front end of the rotating casing, which is also the front end of the hydrostatic radial piston unit. The cover closes the rotating casing and preferably seals it, for example by an O-ring, thereby preventing leakage of hydraulic fluid from inside the cavity formed by the rotating casing and the stationary casing. Furthermore, the front end and the reinforced cover are designed so that the reinforced cover can absorb radial forces acting on the rotating casing due to the cam lobe operating principle.

[0044] In another embodiment, the reinforcing cover comprises a sleeve-like collar and the rotating casing comprises a complementary shoulder, or vice versa. The sleeve-like collar can be arranged to be form-lockingly connected to the complementary shoulder at least in the radial direction, thereby reinforcing the rotating casing in the radial direction. Preferably, the reinforcing cover rotates with the rotating casing, but the thickness of the reinforcing cover is designed so that the reinforcing cover has a small rotating mass because it provides high radial rigidity. The higher radial rigidity of the reinforced rotating casing reduces possible slippage between the cam lobe surface and the working piston interacting with the cam lobe surface. Thus, the reinforcing cover ensures better contact between the cam lobe surface and the working piston, which prevents increased wear of the components since being pressed against the cam lobe surface during operation of the radial piston unit is advantageous for line contact of the piston roller, thereby preventing increased wear of the components.

[0045] In one preferred embodiment according to the invention, a hydrostatic radial piston unit operates as a hydraulic motor, which drives, for example, the track drive or wheels of a work machine, for example a track loader, by means of a torque transmission device. Particularly in the field of track drives, it is important that the radial piston unit has a small axial length in order to allow as much flexibility as possible in the design of the work machine.

[0046] In the accompanying drawings, exemplary embodiments of a hydrostatic radial piston unit according to the invention as well as specific subassemblies of a hydrostatic radial piston unit according to the invention are illustrated, the embodiments shown not limiting the scope of the invention. [Brief explanation of the drawings]

[0047] [Figure 1] 1 shows a first cross-sectional view along the axis of rotation of a hydrostatic radial piston unit according to the invention; [Figure 2] 2 shows a second cross-sectional view along the axis of rotation of a hydrostatic radial piston unit according to the invention; FIG. [Figure 3] 3 shows a third cross-sectional view perpendicular to the axis of rotation of a hydrostatic radial piston unit according to the invention; FIG. [Figure 4] 1 shows an isometric view of the rotating casing of a hydrostatic radial piston unit according to the present invention; FIG. [Figure 5] 1 shows an isometric cross-sectional view of a rotating casing with a distributor mounted thereon of a hydrostatic radial piston unit according to the present invention; [Figure 6] 1 shows a partial cross-sectional view of the front end of a hydrostatic radial piston unit according to the present invention; DETAILED DESCRIPTION OF THE INVENTION

[0048] For ease of explanation and visibility only, the same functional parts are designated by the same reference numerals in all the illustrated figures.

[0049] FIG. 1 shows a hydrostatic radial piston unit 1 according to the present invention. The hydrostatic radial piston unit 1 includes a stationary, non-rotating casing 20 with a through-hole 26 defining a rotation axis 10. The non-rotating casing 20 houses a stationary shaft 12 coaxially disposed about the rotation axis 10 and is connected to the non-rotating casing 20 in a torque-resistant manner. A rotating casing 40 is supported by a pair of roller bearings 90 so as to be rotatable about the rotation axis 10 relative to the stationary casing 20. The rear end portion of the rotating casing 40 is thereby sealed against the front end portion of the stationary casing 20 by a seal 37. The axial position of the seal 37 is defined by a sealing surface 35 that is perpendicular to the rotation axis 10. When viewed from the outside, the sealing surface 35 divides the housing 3 of the radial piston unit 1 into a rotating casing portion 40 on one side of the sealing surface 35 and a stationary casing portion 20 on the other side of the sealing surface 35.

[0050] A pair of roller bearings 90 is arranged on the extension 25 of the stationary casing 20, the extension 25 according to the embodiment shown in FIG. 1 being provided as an additional extension part. The extension 25 protrudes across the sealing surface 35 into the cavity formed by the rotating casing 40. In the embodiment shown in FIG. 1, the roller bearings 90 are arranged in pairs, i.e., substantially directly next to each other in an O-arrangement in the direction of the rotation axis. The O-arrangement of the bearings is preferred when the bearing support spacing is increased, for example, when components are guided with small tilting clearances or when large tilting forces must be supported. In other cases, an X-arrangement or a locating / non-locating bearing arrangement may be selected.

[0051] According to the present invention, a pair of bearings 90 are arranged in the axial overlap region 30 where the stationary non-rotating casing part 20 and the rotating casing 40 overlap. In other words, in the overlap region 30, the stationary casing 20 is arranged coaxially with the rotating casing 40, and vice versa. However, both the stationary casing 20 and the rotating casing 40 are radially spaced apart from each other. This means that in the case of the example shown, the rotating casing 40 surrounds the stationary casing 20, or vice versa.

[0052] The rotating casing 40 comprises a torque transmission device 44, i.e. a flange at its outer circumferential surface 48. Depending on the application, components that can be driven by or that can drive the hydrostatic radial piston unit 1 can be mounted on the flange 44. The torque transmission device 44 is preferably arranged in the same axial position as the pair of bearings 90 in order to reduce the axial lever between the bearing 90 and the torque transmission device 44 and thereby eliminate the tilting moment that would otherwise occur.

[0053] The rotating casing 40 comprises an inwardly facing cam lobe surface 80 against which the working piston 60 can press (see also FIG. 3 ). In the embodiment shown, the cam lobe surface 80 is formed integrally with the rotating casing 40, for example by 3D milling, casting, turning, forging, or a different manufacturing method. The working piston 60 is accommodated in a cylinder bore 55 of the cylinder block 50. The cylinder block 50 is designed to be stationary relative to the fixed shaft 12 and the fixed casing 20. Thus, biasing / pressing the working piston 60 against the cam lobe surface 80 generates 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 casing 40 to rotate.

[0054] Pressurized fluid is supplied to the cylinder bores 55 of the cylinder block 50 in order to urge the working pistons 60 against the cam lobe surfaces 80. In the opposite case, when the working pistons 60 are driven radially inward to follow the shape of the cam lobe surfaces, i.e., the cams, hydraulic fluid is discharged from the corresponding cylinder bores 55. Therefore, the cylinder bores 55 must be alternately connected to the inlets of the hydrostatic radial piston units 1 and to the outlets of the hydrostatic radial piston units 1. This is achieved by the rotary distributor 70.

[0055] The rotary distributor 70, which has a T-shaped cross section due to the disk-shaped portion 71 and the hollow shaft portion 74, is partially disposed in the axial overlap region 30. As a result, the pair of bearings 90 can be disposed axially at the same position as the hollow shaft portion 74 of the rotary distributor 70, but radially outside the hollow shaft portion 74 of the rotary distributor 70 in a region exhibiting a smaller diameter. However, in some designs, the pair of bearings 90 may also be disposed radially inside the hollow shaft portion 74 of the rotary distributor 70.

[0056] Preferably, the rotating casing 40 and the stationary casing 20 seal the internal cavity. To this end, end covers 45, 130 are provided at the rear end side 24 and the front end 42 of the radial piston unit 1 to facilitate the manufacturing and installation of the components of the radial piston unit 1 according to the present invention. In addition to its function of closing the casing cavity, the front cover 45 is designed to radially reinforce the rotating casing 40 and, with it, the cam lobe surface 80. The front cover 45 comprises a substantially flat, disk-shaped base from which a hollow cylindrical collar 46 extends. A step 47, complementary to the collar 46, is provided on the outer peripheral surface 48 of the rotating casing 40. After the front cover 45 is attached to the rotating casing 40, the collar 46 provides support for the radial step 47. This additional support ensures that the cam lobe surface 80 maintains its shape even when the working piston 55 is pressed against it. The thickness of the collar 46 and base plate can be selected depending on the increased stability required.

[0057] Furthermore, the front cover 45 may be provided with a lightweight structure, for example by means of reinforcing ribs in areas subject to primary stress and cutouts / recesses in areas subject to lesser stress. Those skilled in the art will understand that the functional principles of the front cover 45 providing the collar 46 and the casing 40 providing the step may be reversed, such that the front cover 45 may be provided with a step 47 and the casing 40 may be provided with the collar 46. However, other stability-increasing designs capable of absorbing radial forces acting on the rotating casing 40 are also within the scope of the present invention, for example providing a dowel joint between the substantially flat front cover 45 and the rotating front casing 40.

[0058] In addition to its function of closing the rear end side 24 of the two-part casing cavity of the radial piston unit 1, the end cover 130 is part of the parking brake mechanism 100, whose actuation mechanism is arranged in the stationary casing 20. The parking brake mechanism 100 comprises at least two brake discs 112, one of which is torque-resistantly attached to the rotating casing 40 and the other of which is non-rotatably attached to the stationary casing 20. The brake discs 112 are axially movable relative to the stationary casing 20 and the rotating casing 40. If the parking brake mechanism 100 comprises more than two brake discs 112, the discs 112 are connected to the stationary casing 20 and the rotating casing 40 in alternating order. A disc spring 118 supported by the end cover 130 provides a pretensioning force on the brake piston 116. Unless the brake piston 116 is pressurized with its release face 117, the spring force is transmitted via the brake piston 116 to at least one brake pin 114 arranged in an axially oriented bore 28 in the stationary casing 20.

[0059] Preferably, more than one brake pin 114 is provided to provide a more balanced operation of the brake disc. Each brake pin 114 is arranged in one of the circumferentially distributed axial bores 28. At least one brake pin 114 applies / transmits the pretensioning force of the disc spring 118 onto the brake disc 112 that is pressed against each other and supported, for example, by a shoulder or extension 25 of the stationary casing 20. This makes it possible to prevent relative movement between the rotating casing 40 and the stationary casing 20, for example, when the work vehicle is stopped.

[0060] If relative movement between the rotating casing 40 and the stationary casing 20 is permitted, hydraulic pressure is applied to a release surface 117 of the brake piston 116, which is arranged opposite the disc spring 118. The hydraulic pressure generates a force on the release surface 117, which is directed towards the rear side of the stationary casing 20, i.e., in the direction of the disc spring 118. As the generated force is directed against the pretensioning force of the disc spring 118, the brake pin 114 is released from the brake disc 112. Thus, relative movement between the brake discs 112, and therefore between the stationary casing 20 and the rotating casing 40, is possible.

[0061] Preferably, the brake pin 114 has a specific geometric shape. The end of the brake pin 114 facing the brake piston 116 has a larger diameter than the end facing the brake disc 112. Furthermore, the brake pin 114 is sealed relative to the fixed casing 20 and the fixed shaft 12. A pressure chamber is therefore formed between the brake pin 114 and the end face of the casing 20 of the hydrostatic radial piston unit 1. When the brake piston 116 is urged towards the brake disc 112, the brake piston 116 presses the brake pin 114 against the brake disc 112. When pressure is otherwise supplied to the sealed pressure chamber and 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 urges the brake pin 114 towards 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 relieving the axial force from the brake disc 112 .

[0062] However, it is also within the concept of the present invention that a specific design of the brake pin 114 ensures that the pin 114 is always in contact with the brake piston 116, regardless of whether the release face is pressurized or not. In this embodiment, the brake pin 114 is sealed to the stationary casing 20 at the end facing away from the brake piston 116. The rear end of the brake pin 114, which has 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. In that case, hydraulic pressure can be present on the rear / end face of the brake pin 114 when the brake piston 116 moves due to the force generated by hydraulic pressure in the pressure chamber formed by the brake piston 116 together with the shaft 12, the front end of the brake pin 114, and the stationary casing 20. Due to the larger diameter of the end face facing towards the brake piston 116, a greater force is generated by hydraulic pressure on the side facing away from the brake piston 116, and the brake pin 114 is held in contact with the brake piston 116.

[0063] FIG. 2 shows cross-sectional views of the hydrostatic radial piston unit 1 according to FIG. 1 in different cross sections. In the view according to FIG. 2, several hydraulic guides of the hydrostatic radial piston unit 1 according to the invention are shown. A fixed, non-rotating shaft 12 is provided in the center of the hydrostatic radial piston unit 1, which is provided with a first group of grooves 13 in the region towards the end side 24 of the hydrostatic radial piston unit 1 according to the invention. The fixed shaft 12 further comprises a second group of grooves 14 in the region towards the front end 42 of the hydrostatic radial piston unit 1. The first group of grooves 13, together with the annular grooves 22 provided in the fixed, non-rotating casing, form first circular guides 33. These first circular guides 33 are used to distribute the hydraulic fluid guided from the inlet of the hydrostatic radial piston unit 1 towards the outlet of the hydrostatic radial piston unit 1.

[0064] The second circular guide 43 is formed by the second groove 14 together with the second internal groove 73 of the hollow shaft portion 74 of the rotary distributor 70. The first circular guide 33 is fluidly connected to the second circular guide 43 by a channel (not visible in FIG. 2) located in the fixed shaft 12.

[0065] 1 and 2 reveal the internal structure of the rotary distributor 70. The rotary distributor 70 can selectively connect the second circular guide 43 to the appropriate cylinder bore 55 via a timing hole depending on whether high pressure is to be supplied to the particular cylinder bore 55 or whether hydraulic fluid is to be discharged from the particular cylinder bore 55.

[0066] In the illustrated embodiment of the invention, the extension 25 is provided as an additional part that is attached to the stationary casing 20. In addition to supporting the pair of bearings 90, the extension 25 provides a shoulder against which the brake disc 112 can press. Both functions require close manufacturing tolerances to ensure reliable bearing and braking of the hydrostatic radial piston unit 1. The realization of both of these functions with a relatively small additional part includes the advantage that only a relatively small additional part has to be machined, while if the stationary casing 20 had to provide a shoulder and / or bearing surface, a larger part of the stationary casing 20 would not require such complex machining as would be done in this regard.

[0067] The stationary, non-rotating shaft 12 further comprises an axial bore 15, which in the illustrated example is arranged coaxially with the rotating shaft 10. A two-speed valve 120 is arranged in the axial bore 15. The two-speed valve 120 has two positions. In the first position, all cylinder bores 55 can be supplied with hydraulic fluid at high pressure. In the second position, only some of the cylinder bores 55 can be supplied with hydraulic fluid at high pressure. The other cylinder bores 55 are supplied with hydraulic fluid at a lower pressure sufficient to cause the rollers of the working pistons 60 to follow the cam lobe surfaces. At the same time, the cylinder bores 55 supplied with the lower pressure can be hydraulically short-circuited. Thus, in the first position, all cylinder bores 55 comprise 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, and when all working pistons 60 move outward, another piston moves inward in its associated cylinder bore 55.

[0068] In the embodiment shown, the two-speed valve 120 is hydraulically actuated. However, the two-speed valve 120 may also be mechanically or electromechanically actuated. In other embodiments, as one skilled in the art will recognize, the two-speed valve 120 may be a multi-speed valve 120 that provides additional positions to vary the rotational speed and torque of the hydrostatic radial piston unit 1 over a larger range.

[0069] FIG. 3 shows a cross-sectional view of a hydrostatic radial piston unit 1 according to the present invention in a plane arranged perpendicular to the rotation axis 10. The fixed shaft 12, shown in the center of FIG. 3, is torque-resistantly connected to a cylinder block 50, which is therefore also stationary. The cylinder block 50 has radially arranged cylinder bores 55 distributed equidistantly around the periphery of the cylinder block 50. All cylinder bores 55 receive working pistons 60 so that the working pistons 60 can slide radially within the cylinder bores 55. At their radially outer ends, the working pistons 60 have rollers 65. When pressure is applied to the cylinder bores 55, the rollers 65 are forced into contact with cam lobe surfaces 80 formed on the radially inner side of the rotating casing 40. The pressure generates a force on the working pistons 60 that is directed radially outward. When the rotating casing is forced to rotate, the rollers 65 interact with the cam lobe surfaces 80, or vice versa, depending on whether the rollers 65 are moving from a lobe to a cam. If the rollers 65 move from a lobe to a cam, i.e., if the cam lobe surface profile is directed radially inward, the rollers 65 and corresponding pistons 60 are forced inward by the profile of the cam lobe surfaces 80, and hydraulic fluid is expelled from the associated cylinder bores 55. In the opposite case, i.e., if the rollers move from a cam to a lobe, which means that the profile of the cam lobe surfaces 80 in this section is directed radially outward, the rollers and corresponding pistons 60 are forced outward and follow the cam lobe surfaces due to the pressure inside the cylinder bores 55.

[0070] FIG. 4 shows an isometric view of the rotating casing 40 used in one embodiment of the hydrostatic radial piston unit 1 according to the present invention. In addition to the features already mentioned above, FIG. 4 shows axially oriented holes 75 arranged radially inward of the cam lobe surface 80 in a plane perpendicular to the rotation axis 10. The axially oriented holes 75 receive distributor springs 72 that can provide a pretensioning force on the adjacently arranged rotary distributor 70. The disk-shaped portion 71 of the rotary distributor 70 and the rotating casing 40 can be rotatably coupled by a synchronizing pin 78 arranged in one of the axially extending holes 75 of the rotating casing 40 in combination with the axially oriented holes 75 and the housed distributor spring 72. As a result, the rotary distributor 70 and the distributor spring 72 rotate at the same rotational speed.

[0071] 1 or 2, one skilled in the art will see from FIG. 4 that the axially oriented holes 75 can also move towards the distributor 70 and abut against the bottom surface of the associated lobe. Placing a distributor spring 72 in the holes 75 of the distributor 70 achieves the same function, pressing the disk-shaped portion 71 of the distributor 70 against the front face of the cylinder block 50.

[0072] Also shown in Figure 4 is a synchronizing pin 78 positioned on a larger diameter than is conventional in the art. This reduces the shear moment acting on the synchronizing pin 78. These shear forces are generated in the operation of the hydraulic motor by friction forces between the outer circumferential surface of the shaft 12 and the inner circumferential surface of the distributor 70, which seals between the surface of the shaft 12 and the circular distribution channel (see also Figures 1 or 2). Here, the synchronizing pin 78 is received in an axial bore 75 in the front housing 40 and a corresponding hole in the distributor 70.

[0073] FIG. 5 shows a cross-sectional view of the rotary casing 40 in which the rotary distributor 70 is disposed. The outer surface of the disk-shaped portion 71 of the distributor 70 is formed complementary to the cam lobe surface 80 to support the function of the synchronizing pin 78 housed in the rotary casing 40. The synchronizing pin 78 ensures that the rotational direction of the distributor 70 is correct when the distributor 70 is received in the rotary casing 40. Furthermore, the synchronizing pin 78 synchronizes the rotation of the distributor 70 with the rotation of the rotary casing 40. It is also shown (not shown in FIG. 5 ) how the distributor spring 72 abuts against the base of the axially oriented hole 75, thereby pushing the distributor 70 toward the front end 42, i.e., toward the cylinder block 50. The rotary distributor 70 has a lightweight design, reducing the rotational inertia of the assembly. For this purpose, a gap is partially provided in the radially extending plate-like part 71 of the distributor 70. Also shown is a second internal groove 73 formed on the radially inner side of the distributor 70. The groove 73 has an annular shape and can guide fluid to and from a timing hole 77 located on the front surface of the distributor 70.

[0074] 6 shows how the stiffening front cover 45 is attached to the rotating casing 40 by threads that are equidistantly distributed along an imaginary arc. The above-described combination of the collar of the front cover 45 and the step of the rotating casing 40 not only stiffens the cam lobe face 80, but also ensures that the cover 45 is accurately centered relative to the rotating casing 40. It will be understood that other techniques for attaching the cover to the rotating casing are within the knowledge of one skilled in the art.

[0075] From the above disclosure and the accompanying drawings, as well as the claims, it will be understood that the hydrostatic radial piston unit 1 according to the present invention offers many possibilities and advantages over the prior art. Furthermore, it will be apparent to those skilled in the art that further modifications and variations known in the art may be made to the radial piston unit 1 according to the present invention without departing from the spirit of the present invention. Accordingly, all such modifications and variations are within the scope of the claims and are intended to be encompassed thereby. It should be further understood that the above-described examples and embodiments are for illustrative purposes only, and that various modifications, variations, or combinations of the embodiments will be suggested to those skilled in the art in light of the same and are within the spirit and scope of the present application. [Explanation of symbols]

[0076] 1 Hydrostatic radial piston unit 3. Housing 10 Rotation axis 12 Fixed non-rotating shaft 13 First Groove 14 Second Groove 15 axial bore 20 Fixed non-rotating casing part 22 Annular groove 24 End side 25 Extension 26 through holes 28 Axially oriented bore for brake pin 30 Axial overlap area 33 First circular guide 35 Sealing surface 37 Seals 40 Rotating Casing 42 Front end 43 Second circular guide 44 Torque transmission device 45 Reinforced front cover 46 Color 47 Step / Shoulder 48 Outer surface 49 Screws 50 Cylinder block 55 cylinder bore 60 working piston 65 Laura 70 rpm distributor 71 Disk-shaped part 72 Distributor spring 73 Second internal groove 74 Hollow shaft section 75 axially oriented holes 77 Timing Hole 78 Sync Pin 80 First cam lobe surface 90 Roller bearing pair 100 Parking brake mechanism 112 Brake disc 114 Brake pin 116 Brake piston 117 Release plane 118 Disc Spring 120 Two-speed valve / multiple-speed control valve 130 End cover

Claims

1. A hydrostatic radial piston unit (1) of cam lobe type construction, a non-rotating stationary casing (20) with a through hole (26) defining the axis of rotation (10) of said hydrostatic radial piston unit (1); a cylindrical rotating casing (40) that is rotatably mounted on the non-rotating, stationary casing (20) in an axial overlap region (30) where a front end portion of the non-rotating, stationary casing (20) and a rear end portion of the rotating casing (40) overlap such that the rotating casing (40) can rotate relative to the non-rotating, stationary casing (20) around the rotation axis (10); a parking brake mechanism (100) comprising at least two brake discs (112) arranged adjacent to each other in the overlapping region (30), one brake disc (112) being rotatably fixed to the non-rotating stationary casing (20) and the other brake disc (112) being rotatably fixed to the rotating casing (40); an end cover (130) closing the non-rotating stationary casing (20) on the rear end side (24) of the hydrostatic radial piston unit (1) facing away from the rotating casing (40), the end cover (130) pretensioning a disc spring (118) against a disc-shaped brake piston (116) both of which are arranged in the rear end part of the non-rotating stationary casing (20) to generate an axially directed spring force; A hydrostatic radial piston unit (1) comprising: a fixed shaft (12) is arranged coaxially with the rotating shaft (10) in an internal cavity formed by the non-rotating fixed casing (20), the rotating casing (40), the end cover (130) and the front cover (45), and a cylinder block (50) non-rotatingly accommodated in the front end portion of the rotating casing (40) is in torque-resistant connection with the fixed shaft (12); - said rotating casing (40) comprises an internal cam lobe surface (80) on which a working piston (60) housed in said cylinder block (50) can act; - when the brake piston (116) on the opposite face of the disc spring (118) is not forced to move towards the end cover (130), the axially directed spring force can be transmitted by the brake piston (116) to at least one brake pin (114) arranged in an axially directed bore (28) in the non-rotating fixed casing (20) in order to press the brake discs (112) against each other, characterized in that Hydrostatic radial piston unit (1).

2. 2. The hydrostatic radial piston unit (1) of claim 1, wherein a front end and a rear end of the at least one brake pin (114) seal a pressure chamber within the axially oriented bore (28) that can be pressurized, thereby urging the brake pin (114) toward the end cover (130) to cause the brake piston (116) to compress the disc spring (118), thereby relieving compression force from the brake disc (112).

3. 2. The hydrostatic radial piston unit (1) of claim 1, wherein the brake piston (116), the at least one brake pin (114), the fixed shaft (12), and the non-rotating fixed casing (20) seal a pressure chamber that can be pressurized, whereby the brake piston (116) is forced toward the end cover (130) to compress the disc spring (118), thereby relieving compression force from the brake disc (112).

4. 2. A hydrostatic radial piston unit (1) according to claim 1, wherein the at least one brake pin (114) comprises, at an end facing the brake piston (116), a portion with a larger diameter.

5. 2. A hydrostatic radial piston unit (1) according to claim 1, wherein the non-rotating stationary casing (20) comprises an inner annular groove (22) which, together with a first groove (13) on the outer surface of the stationary shaft (12), forms a first circular guide (33).

6. The rotary distributor (70) has a disk-shaped portion (71) and a hollow shaft portion (74), by which the distributor (70) is disposed around the front end portion of the fixed shaft (12) and is rotatably received by the rotary casing (40) while being fixed to the disk-shaped portion (71), and the rotary distributor (70) is adapted to transmit power to an operating piston (60) of the cylinder block (50) through a timing hole (78) in the disk-shaped portion (71).

6. A hydrostatic radial piston unit (1) according to claim 5, wherein the hollow shaft portion (74) has a second internal groove (73) for guiding hydraulic fluid to and from the working piston (60) of the cylinder block (50), the second internal groove (73) forming a second circular guide (43) together with a second groove (14) on the outer surface of the fixed shaft (12), the second circular guide (43) being connected to the first circular guide (33) by a fluid channel arranged in the fixed shaft (12).

7. 7. The hydrostatic radial piston unit (1) of claim 6, further comprising a pair of roller bearings (90) for rotatably mounting the rotating casing (40) to the non-rotating stationary casing (20), the pair of roller bearings (90) being arranged in the overlapping region (30) between the rotating casing (40) and the non-rotating stationary casing (20) radially outward of the hollow shaft portion (74) of the rotary distributor (70).

8. 8. The hydrostatic radial piston unit according to claim 7, wherein the overlapping area (30) of the front end portion of the radial piston unit (1) is defined by an extension (25) of the non-rotating, stationary casing (20), the extension extending axially beyond a sealing surface (35) into the volume of the rotating casing (40) and extending radially between the hollow shaft portion (74) of the rotating distributor (70) and the rotating casing (40), the extension (25) being provided to accommodate inner shells of the pair of roller bearings (90) and being provided as an additional part and attached to the non-rotating, stationary casing (20) or being formed integrally with the non-rotating, stationary casing (20).

9. 9. The hydrostatic radial piston unit (1) according to claim 1, comprising a fixed multi-speed control valve (120) switchable between a first position in which all of the cylinder bores (55) can be supplied with hydraulic fluid under high pressure from a high-pressure inlet of the hydrostatic radial piston unit (1) and a second position in which only some of the cylinder bores (55) can be supplied with fluid under high pressure, and pairs of the cylinder bores (55) are hydraulically short-circuited.

10. 10. The hydrostatic radial piston unit (1) according to claim 9, wherein the fixed multi-speed control valve (120) is arranged in an axial bore (15) of the fixed shaft (12), the axial bore (15) being preferably arranged coaxially with the rotation axis (10), and the multi-speed control valve (120) is a two-speed control valve (120) or a three-speed control valve (120).

11. 2. The hydrostatic radial piston unit (1) according to claim 1, wherein the cam lobe surface (80) is integrally formed with the rotating casing (40).

12. 8. The hydrostatic radial piston unit (1) according to claim 7, wherein the rotary distributor (70) is biased together with the disk-shaped region (71) against the outer surface of the cylinder block (50) by a distributor spring (72) and / or a distributor piston that are both housed in an axially oriented manner in the disk-shaped region (71) of the rotary casing (40) or the rotary distributor (70), and the distributor spring (72) and / or the distributor piston are received in an axially oriented hole (75) of the rotary casing that is arranged in a recess in the cam lobe surface (80).

13. A hydrostatic radial piston unit (1) as described in claim 1, wherein the first cylinder block (52) has more than one row of cylinder bores (55) arranged adjacent to each other in the circumferential direction or arranged alternately and capable of interacting with the cam lobe surface (80), the cylinder bores having radially reciprocating working pistons (62).

14. A hydrostatic radial piston unit (1) as described in claim 13, wherein a second cylinder block, the working piston (60) of which interacts with the first cylinder block (52) and the cam lobe surface (80), is positioned parallel to the first cylinder block (50) on the fixed shaft (12).

15. the number of cylinder bores (55) and radially reciprocating working pistons (60) of the second cylinder block is different from the number of cylinder bores (55) and radially reciprocating working pistons (60) of the first cylinder block (50), and a second peripheral cam lobe surface (82) with which the working pistons (60) of the second cylinder block can interact is disposed on the forward casing (40) radially inward thereof; A hydrostatic radial piston unit (1) according to claim 14.

16. 2. The hydrostatic radial piston unit (1) according to claim 1, wherein the front cover (45) is attached to a front end (42) of the rotating casing (40) facing away from the non-rotating stationary casing (20) to close the rotating casing (40), and the front end (42) of the rotating casing (40) and the front cover (45) are designed so that the front cover (45) can at least partially absorb forces acting on the rotating casing (40), in particular in the radial direction.

17. 17. A hydrostatic radial piston unit (1) according to claim 16, wherein the front cover (45) comprises a sleeve-like collar (46) and the rotating casing (40) comprises a complementary shoulder (48), or vice versa.

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