CN116265737A

CN116265737A - Hydrostatic radial plunger unit of cam lobe configuration

Info

Publication number: CN116265737A
Application number: CN202111547232.5A
Authority: CN
Inventors: 克里斯·斯芮芙; 万延江; 陈晓元
Original assignee: Danfoss Power Solutions Jiangsu Co Ltd
Current assignee: Danfoss AS
Priority date: 2021-12-16
Filing date: 2021-12-16
Publication date: 2023-06-20

Abstract

The present application provides a hydrostatic radial plunger unit of cam lobe configuration, comprising: a non-rotating stationary housing including a through bore defining an axis of rotation of the hydrostatic radial plunger unit; a rotary housing rotatably mounted to the stationary housing at an axial overlap region; a parking brake mechanism comprising at least two brake discs arranged adjacently in the overlap region; an end cap pre-tightening a disc spring against a disc brake piston to generate an elastic force in an axial direction, the disc spring and the brake piston being both located in a rear end portion of the stationary housing, the elastic force being transmittable through the brake piston to at least one brake pin disposed in an axial hole in the stationary housing to press the brake discs against each other when the brake piston opposite the disc spring is not driven to move toward the end cap.

Description

Hydrostatic radial plunger unit of cam lobe configuration

Technical Field

The present application relates to hydrostatic radial plunger units, and more particularly to cam lobe motors or pumps, or gerotor motors or pumps. In particular, the present application relates to a braking mechanism for a hydrostatic radial plunger unit of cam lobe construction.

Background

Radial plunger units, i.e. radial plunger pumps and radial plunger motors, are widely used in the art, e.g. in heavy duty applications. Radial plug units are used, for example, in the field of construction, agriculture or forestry equipment. Radial plunger units are characterized in that when supplied with pressurized hydraulic fluid (in the case of radial plunger motors), their working plungers move in a radial direction with respect to a central longitudinal/rotational axis. Typically, radial plunger units are used in hydraulic applications that do not require high rotational speeds but require high torque. Radial plunger units show advantages over axial plunger units (with reduced axial space).

One particular application of the radial plunger unit is: the travel of a work vehicle (e.g., a track loader). Often, one radial plunger unit is mounted to the work vehicle at either side of the frame/body. Thus, the geometry of the frame and propulsion mechanism is significantly affected by the radial plunger unit size. In many applications, the location at which the radial piston unit transmits torque to the drive mechanism is preset by other components than the radial piston unit that interacts with the drive mechanism. However, the radial plunger units of the known art exhibit a relatively large length in the axial direction and a relatively large diameter. Since the radial plug unit driving the work vehicle must be integrated into the vehicle frame, the frame must be designed to be able to receive the fixed components (e.g. the fixed housing) of the radial plug unit in order to be able to support the torque generated/applied under operating conditions. It is therefore desirable to reduce the size of the radial plug units used (in particular in the axial direction) as much as possible in order to reduce the design adaptations of the frame on which the radial plug units are mounted.

If the hydrostatic radial plug unit is used in propulsion applications, it is often necessary for the parking brake to ensure failsafe operation of the hydrostatic radial plug unit. In this case, the brakes allow the vehicle to move only when they are actively released. In the inactive state of the parking brake, the hydrostatic radial plunger unit and the movement of the vehicle are prevented. In the state of the art, there are different ideas available for providing a parking brake mechanism for a hydrostatic radial plunger unit, such as a disc brake attached to the outside of the hydrostatic radial plunger unit housing. As an alternative, the brake may be arranged inside the hydrostatic radial plunger unit housing, wherein the brake is protected from dirt or the like. Disadvantageously, this arrangement significantly increases the axial length of the hydrostatic radial plunger unit.

WO 2013/160145 A2 discloses a radial piston machine with a rotating output shaft. In order to reduce the axial length of the radial piston machine, at least a portion of the parking brake is arranged between the housing and a portion of the output shaft. The output shaft is designed to rotate, for example for driving wheels, which can be fastened to an output flange at the output shaft.

Disclosure of Invention

The purpose of the present application is: a radial plunger unit is provided which has a reduced dimension, in particular an axial length, and a reduced radial dimension/diameter. Meanwhile, the provided radial plunger unit will include: a parking brake mechanism disposed within the radial plunger unit housing such that neither the axial nor radial dimensions of the radial plunger unit are significantly increased.

To achieve the above object, the present application provides a hydrostatic radial plunger unit of a cam lobe structure, comprising:

a non-rotating stationary housing including a through bore defining an axis of rotation of the hydrostatic radial plunger unit;

a cylindrical rotary housing rotatably mounted to the non-rotary stationary housing at an axial overlap region where a front end portion of the non-rotary stationary housing and a rear end portion of the rotary housing overlap, enabling the rotary housing to rotate about the rotational axis relative to the stationary housing;

a parking brake mechanism including at least two brake discs adjacently arranged in the overlap region, wherein one brake disc is fixed with respect to the stationary housing in a rotational direction and the other brake disc is fixed with respect to the rotary housing in a rotational direction;

An end cap closing the stationary housing on a rear end side of the hydrostatic radial plunger unit facing away from the rotary housing;

wherein the end cap pre-biases a disc spring against a disc brake piston to generate an elastic force in an axial direction, the disc spring and the brake piston being both located in the rear end portion of the stationary housing, the elastic force being transmittable by the brake piston to at least one brake pin arranged in an axial hole in the stationary housing to press the brake discs against each other when the brake piston facing the disc spring is not driven to move toward the end cap.

The hydrostatic radial plunger unit according to the present application comprises a stationary housing comprising a through bore defining a longitudinal axis, which is also the rotational axis of the hydrostatic radial plunger unit. The stationary housing is arranged to be connected to the frame of the work vehicle, i.e. in the sense of the present description the stationary part of the radial plunger unit according to the present application forms a rear end region which can be fixedly fastened to, for example, a frame or a support.

In this specification, the terms "radial" and "axial" refer to directions relative to the longitudinal axis of the stationary shaft. Within the scope of the present application, "fixed" means: not rotating about the longitudinal axis, for example when the radial plunger unit is mounted to a work vehicle.

The cylindrical rotating housing is rotatably mounted to the non-rotating stationary housing in an axially overlapping region. In this region, the front end portion of the stationary housing and the rear end portion of the rotary housing overlap in the axial direction. Thus, at least a portion of the rotary housing is arranged radially outside or inside the stationary housing in the overlap region. Thereby, when the rotary housing is rotatable relative to the stationary housing about the radial plunger unit rotation axis, the rear end portion of the rotary housing is sealed to the front end portion of the stationary housing. The sealing between the rotating housing and the stationary housing is performed in such a way that: the two housings together form a closed fluid-tight chamber. The connection between the rotating housing and the stationary housing allows the rotating housing to rotate relative to the stationary housing about a rotational axis (i.e., a longitudinal axis).

Basically, an axial position of the sealing body between the stationary housing and the rotary housing defines a sealing surface orthogonal to the axis of rotation. Thus, the sealing surface divides the hydrostatic radial plug unit housing, seen from the outside, into a stationary part (rear end part) on one side of the sealing surface and a rotating part (front end part) on the other side of the sealing surface.

In a preferred embodiment of the present application, the stationary housing accommodates the stationary shaft at the rear end portion in a torsion-proof manner. This means that neither the stationary shaft nor the stationary housing rotates relative to each other. The stationary shaft is arranged coaxially with the rotation axis in an inner cavity formed by the stationary housing and the rotation housing. At a front end portion of the fixed shaft protruding from the fixed housing, a fixed cylinder connected with the fixed shaft in a torque-proof manner is disposed. The cylinder block includes a plurality of cylinder bores, each cylinder bore extending radially inward from a circumferential surface of the cylinder block.

The hydrostatic radial plunger unit according to the present application further comprises: a parking brake mechanism comprising at least two brake discs arranged adjacently in an overlap region, wherein one brake disc is fixed to a stationary housing in a rotational direction and the other brake disc is fixed to the rotary housing in the rotational direction, whereby the at least one brake disc is movable in an axial direction. If the hydrostatic radial plunger unit comprises more than two brake discs, each brake disc is alternately fixed to the stationary housing and the rotary housing in the direction of rotation, wherein it is provided to be axially movable such that: the braking effect can be achieved by pressing the brake discs (compression) together and releasing the brake by reducing the pressing force. According to the present application, the parts fixed in the direction of rotation cannot rotate relative to each other.

The parking brake mechanism includes a blocking position in which the brake discs are pressed against each other, and a rotational position in which the rotary housing is fixed relative to the stationary housing. According to a preferred embodiment of the present application, the brake disc may be arranged in an axial overlap region between the stationary housing and the rotary housing, axially close to the sealing surface.

The parking brake mechanism may be preloaded towards its blocking position by means of a disc spring providing a preload force acting on the brake piston in the axial direction and supported for example by an end cap/end cover fixed to the rear end of the stationary housing. The end cap encloses the non-rotating stationary housing on the end side of the hydrostatic radial plunger unit facing away from the rotating housing (i.e., away from the axial overlap region where the rotating housing is mounted to the stationary housing).

The axial pretensioning force of the disc spring can be transmitted via the brake piston with at least one brake pin (which extends in the axial direction between the brake piston and the brake disc) to the brake disc. The at least one brake pin is preferably arranged in an axial bore in the non-rotating stationary housing, which axial bore is located on the side of the brake piston opposite the disc spring. The brake piston thus transmits the preload of the disc spring to the brake pins, which press the brake discs against one another.

The number, shape and arrangement of the detent pins and corresponding axial holes will be selected by those skilled in the art according to the different application requirements. For example, it may be preferable to arrange at least three brake pins, equally distributed over an arc centered on the rotation axis.

Different schemes may be used to switch the parking brake mechanism to the on/off position. As a first solution, the brake pin seals a chamber formed in the fixed part of the housing, for example at the rear end of the radial plunger unit. The chamber may also be formed by several parts, for example by a shaft, by a stationary housing, a brake pin and by a brake piston.

Thus, the rear end of the brake pin is preferably attached to the brake piston in a liquid-tight manner. An additional seal is provided between the front end of the brake pin and the stationary housing. Accordingly, the pressure chamber is formed by the fixed housing combining the rear end front face of the fixed shaft, the brake pin guide hole, and the brake piston. If pressurized hydraulic fluid is supplied to the pressure chamber, a force is generated on the release surface of the brake piston to counteract the preload of the disc spring and release the brake. Thereby, the pressing force of the brake pin is released from the brake disc, and the rotary housing can rotate relative to the stationary housing. The opening pressure required to release the brake is dependent on the size of the brake cylinder piston release surface (compared to the preload provided by the disc spring). The spring preload may be adjustable, for example, by adjusting the relative position of the brake piston and the end cap (by an adjustable shoulder or adjustment screw in the end cap/end cap). Alternatively, the length of the brake assembly, i.e. the number of brake discs, may be adjusted.

Preferably, the rear end of the brake pin facing in the direction of 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 always contacts the brake piston, whether or not the brake prevents relative rotation of the stationary housing and the rotary housing. In the blocking position or when the hydrostatic radial plunger unit is moved towards the blocking position, the brake piston pushes the brake pin against the brake disc, which is pressed, for example against a shoulder of the stationary housing.

If pressurized hydraulic fluid is supplied to the previously mentioned pressure chamber to create a force on the release surface of the brake piston, the same pressure is applied to the end surface of the brake pin. This pressure creates a force on the end surface of the brake pin. Due to the larger diameter of the rear end of the brake pin, a larger force will be generated on this side. Thus, 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 is moved in a direction toward the disc spring (i.e., in a direction of the stationary housing end cap).

For a second version embodying an alternative embodiment of the present application, the pressure chamber is formed within an axial bore (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 in the direction of the brake piston 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 greater diameter. Thus, the brake pin moves in the direction of the rear end of the hydrostatic radial plunger 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 towards the rear side until it contacts the brake piston. The force generated by the pressure in the pressure chamber is then transmitted to the brake piston by means of 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 is released.

In one embodiment according to the present application, the non-rotating stationary housing comprises an annular groove at the inner surface of the through bore, the annular groove together with a first groove at the outer circumferential surface of the non-rotating stationary shaft forming a first annular passage. According to the present application, the brake pin serves to bridge an axial gap between the brake piston and the brake disc (which may be arranged in an axial overlap region). Preferably, the axial bore with the brake pin is arranged radially outside the first annular passage in the stationary housing. This ensures that sufficient space is provided for the annular groove on the outer surface of the shaft and for the first groove on the inner surface of the stationary housing.

The braking design according to the present application allows a centrally arranged brake disc to be positioned close to the area where the rotating part and the stationary part of the hydrostatic radial plunger unit overlap. At the same time, the hydraulic connections required for supplying the pressure chambers of the brake device with hydraulic fluid for releasing the brake can be arranged in the stationary part of the hydrostatic radial plunger unit as well as in the mechanical part of the parking brake mechanism, except for the rotating brake disc which is fixed on the rotating part. The brake pin provides a functional connection between the overlap area/brake disc close to the rotating part and the pressure chamber of the stationary part. Thus, it is not necessary to send hydraulic fluid having brake release pressure from the stationary member to the rotating member. Thus, fewer sealing connections are required and the complexity of assembly and machining of the hydrostatic radial plunger unit according to the invention is reduced. In addition, the number of potential leak points is reduced.

The fixed cylinder block at the front end portion of the radial plunger unit includes a plurality of cylinder bores extending radially inward from a circumferential surface of the cylinder block. A plurality of working plungers may be arranged in a radially movable manner in cylinder bores, wherein each cylinder bore accommodates one working plunger. Each working ram seals a pressure chamber in the cylinder bore, which may be supplied with pressurized hydraulic fluid via a hydraulic passage to generate a force on the head of the associated working ram that moves the working ram radially outward. Moreover, in the event that the working plunger is mechanically driven into inward movement (e.g., with a cam), hydraulic fluid may be discharged from the cylinder bore via the hydraulic passage.

The rotary housing includes an inner cam lobe surface. When pressurized fluid is supplied to the pressure chamber, the working plunger is driven against the cam lobe surface. When the cylinder is fixed and supported by the fixed housing via the fixed shaft, movement of the working plunger radially outward generates a force on the cam lobe surface that rotates the rotating housing relative to the fixed housing.

In order to direct the pressurized fluid to the pressure chamber, according to the present application, a rotary distributor is provided, comprising a hollow shaft portion and a disc-shaped portion, which are integrally formed, but which can also be connected to each other, for example in a fluid-tight manner. The disc-shaped portion is connected to the rotary housing in a torque-proof manner, i.e. is connected to the rotary housing for rotation therewith. In a preferred embodiment, the disc-shaped portion of the rotary distributor exhibits a radial protrusion that mates with a lobe of the cam lobe surface, the rotary distributor further comprising: timing holes in the disc-shaped portion for discharging hydraulic fluid to and from the cylinders Kong Gongying in the cylinder block through the hydraulic passages. In addition, the rotary distributor includes a second internal groove that forms a second annular passage with a second groove on an outer surface of the non-rotating stationary shaft. The second groove of the outer surface of the stationary shaft is connected to the first annular passage by an internal passage in the shaft. The principle of operation of a radial plunger unit is well known to those skilled in the art, and thus the function of the radial plunger unit herein need not be described in more detail.

According to the present application, the pair of roller bearings rotatably support the rotary housing to the stationary housing. According to the present application, the roller bearings are arranged radially outside the rotary distributor, but near the rear end portion of the rotary housing and near the front end portion of the stationary housing, respectively, at substantially the same position in the axial direction as the hollow shaft portion of the distributor. In other words, the roller bearing enables a relative movement between the rotating housing and the stationary housing and is arranged near or close to the sealing surface to avoid large tilting moments between the two housings, which is also advantageous for the sealing of the two housings.

The roller bearings according to the present application are arranged in pairs and in one embodiment are preferably close or in close proximity to each other. Arranging at substantially the same position in the axial direction as the hollow shaft portion of the rotary distributor means: the bearing is arranged in the axial direction in a region adjacent to the side of the cylinder body facing the stationary housing and at least partially encloses the rotary distributor (for example in the cylindrical part of the rotary distributor). Also in this region, the stationary housing and the rotary housing overlap, or at least the extensions or protrusions of one or both housings overlap each other in the axial direction, while being coaxially arranged such that the rotary part (e.g. rotary housing or rotary distributor) is rotatable relative to the stationary part (e.g. stationary housing or stationary shaft). The pair of bearings may comprise a different axial length than the distributor. When the bearing is arranged radially (with respect to the longitudinal axis) outside said hollow shaft portion of the distributor and at least partially overlaps the distributor in the axial direction (rather than being axially adjacent thereto), the axial length of the hydrostatic radial plunger unit is reduced. Those skilled in the art will appreciate that the use of roller bearings is only a preferred embodiment. However, the present application also covers the following schemes: a sliding bearing is used to rotatably support the rotary housing with respect to the stationary housing.

According to a preferred embodiment of the present application, the stationary housing of the radial plunger unit may comprise: a stationary extension extending beyond the sealing surface in an axial direction into the volume of the rotary housing and having a substantially cylindrical shape. The extension is for example provided with an inner housing for the bearing. The extensions provide a fixed support for the pair of bearings, for example, radially outward of the rotary distributor, when the pair of bearings are received in the space between the rotary housing and the rotary distributor. Thus, the extension is provided in the space between the two rotating parts (the rotating distributor and the rotating housing) in the radial direction.

In one embodiment according to the present application, the extension may be integrally formed with the stationary housing. In yet another embodiment according to the present application, the extension is provided as an additional component and is attached to the stationary housing. The extension may be attached to the stationary housing, for example, using screwing, welding, bonding, press fitting, heat shrinking, clamping, crimping, or plastic deformation. The connection between the stationary housing and the additional extension needs to be a torsion-proof connection, so that the supporting forces of the bearing can be transferred statically to the stationary housing via the extension. This split design increases the feasibility of design and assembly of the radial plug unit according to the present application. Preferably, the extension comprises: a hollow cylindrical sleeve shape with an outer surface adapted to mount a pair of bearings (preferably in an O-ring arrangement). In order to support the bearing in the axial direction, the extension may include: a fixing means 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 on which a spindle nut can be screwed.

According to the present application, the pair of roller bearings may be located not only at or near substantially the same axial position as the distributor, but also at substantially the same axial position as a flange, sprocket or similar torque transmitting device of the outer peripheral surface of the rotary housing. In the motor mode of operation, the rotating portion (e.g., wheel or sprocket) may be driven by a hydrostatic radial plunger unit. In the pump mode of operation, the rotating portion may drive the hydrostatic radial plunger unit. The torque transmitting device serves as an interface to which the rotating parts or tracks/tracks or chains may be fixed. When the bearings are arranged in substantially the same axial position as the torque transmitting means, there is no or at least reduced tilting moment generated by the rotating housing relative to the longitudinal axis, which moment is related to the position of the pair of bearings. Thus, the bearing can be designed smaller and with a lower load factor. This allows for a lower cost bearing and further reduces the production costs of the hydrostatic radial plunger unit. At the same time, the bearing arrangement according to the present application reduces the axial length of the radial piston unit and reduces the distance required between the torque transmission site and the fixing means of the stationary housing (the radial piston unit can thereby be mounted to, for example, the frame of a vehicle).

In another embodiment according to the present application, the hydrostatic radial plunger unit includes a fixed (non-rotating) two-speed, three-speed, or multi-speed control valve. The control valve (e.g., in a two-speed embodiment) is switchable between a first position and a second position. In the first position, for example, all cylinder bores are used for generating torque on the rotary housing, i.e. fluid at high pressure (e.g. working pressure) can be supplied to the cylinder bores. This means that high-pressure hydraulic fluid is supplied to the cylinder bore forcing the plunger arranged in the cylinder bore to move radially outwards. When the plunger moves radially inward as it follows the cam shape of the cam lobe surface, the corresponding cylinder bore is connected to the outlet timing bore from which hydraulic fluid is discharged. In the second position, for example, only a part of the cylinder bores exhibit the same working behaviour as in the first position, i.e. only a part of the cylinder bores may be supplied with high-pressure hydraulic fluid via the inlet timing hole. However, another portion of the cylinder bores are supplied with hydraulic fluid at reduced pressure (e.g., charge pressure) regardless of the movement of the working ram. Here, for example, groups of cylinder bores can also be hydraulically short-circuited under reduced hydraulic pressure.

In other words, in the first position of the control valve, the working volume of the hydrostatic radial plunger unit is the sum of all working volumes enclosed between each cylinder bore and its corresponding working cylinder. In the second position, only a portion of the cylinder bores are supplied with high-pressure fluid. Thus, only this part of the working ram and the corresponding cylinder bore contributes to the working volume of the radial ram unit. Other working plungers are provided with a reduced pressure sufficient to ensure that the plunger rollers are in contact with the cam lobe surface of the rotary housing, they do not contribute to the actual working volume of the radial plunger unit, since the corresponding pressure chambers are not supplied with high pressure hydraulic fluid. In the event of a short circuit, the hydraulic fluid volume necessary to move one plunger outward is replaced by the other plunger that moves inward.

In another preferred embodiment according to the present application, the cam lobe surface is integrally formed with the rotary housing. If the housing is to be assembled from multiple parts, the necessary connections and seals will require additional radial and axial space. Integrating the rotating housing with the cam lobe surface reduces the complexity of the assembly process. Furthermore, this integrated idea enables to reduce the diameter, i.e. the radial dimension, of the hydrostatic radial plug unit, since the connection between the parts can be dispensed with. This also saves manufacturing and assembly costs, as precision machined connection surfaces and additional assembly steps are avoided.

The synchronizing pin may be housed in an axial hole of the rotary housing, preferably in an extension of the lobe, and engages with a corresponding hole in one of the radial projections of the disc-shaped portion of the distributor. Thereby, the synchronizing pin is able to interact with the rotary housing and the rotary distributor simultaneously. Thus, when the dispenser is mounted in the rotary housing, the synchronizing pin ensures that the dispenser (or rather the disc-shaped portion of the rotary dispenser) is oriented correctly. Furthermore, the synchronizing pin synchronizes the rotation of the dispenser with the rotation of the rotary housing, i.e. prevents relative movement between the two parts.

According to the present application, the radial plunger unit may further comprise: a distributor spring to press the disc-shaped portion of the rotary distributor toward the cylinder. According to the present application, these dispenser springs are preferably received in axially extending holes in the rotary housing at the axial extension of the lobes (lobes). Preferably, said disc-shaped portion of the rotary distributor exhibits a disc-shaped extension facing the fixed cylinder and exhibits a profile complementary to the cam lobe surface. The distributor spring urges the rotary distributor toward the cylinder. Thereby, the front surface of the disc-shaped portion of the rotary distributor and the adjacent front surface of the cylinder form a hydrostatic bearing between the disc-shaped portion of the rotary distributor and the stationary cylinder.

The hydrostatic bearing is supplied with pressurized fluid using timing holes (which are arranged in the front surface of the disc-shaped portion of the rotary distributor, via which hydraulic fluid can be supplied to or discharged from cylinder bores in the cylinder block). The arrangement of the dispenser spring in the rotary housing, which is in torque-proof connection with the dispenser, ensures that there is no relative movement between the dispenser spring and the dispenser in the circumferential direction. If there were to be relative movement between the two components, the springs would likely be prone to severe wear and/or would experience deformation. In addition, axially receiving the distributor spring in the extension/extension of the lobe of the cam lobe surface reduces the load and stress on the synchronizing pin caused by frictional resistance between the rotating distributor and the stationary shaft.

Another benefit is realized when the spring is located within the axial thickness of the dispenser, which further reduces the axial length of the hydrostatic radial plunger motor, since the axial bore in the front housing for receiving the spring is moved to the dispenser, which may reduce the axial length of the front housing.

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

According to the present application, the hydrostatic radial plunger unit may further comprise: a second cylinder with a working plunger that interacts with the same cam lobe surface or another cam lobe surface disposed parallel to the first cam lobe surface. The second cylinder is arranged on the non-rotating shaft in parallel with the first cylinder in the axial direction. Providing a cylinder block or a second cylinder block having more than one row of cylinder bores significantly increases the potential working volume, wherein the hydrostatic radial plunger unit diameter remains the same.

In order to tailor the behaviour of the hydrostatic radial piston unit for a particular 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 inward of the rotary housing. The working plungers of the second cylinder bores 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 integrally formed with the rotary housing.

In a further embodiment according to the present application, a reinforced disc-shaped cover is attached to the front end of the rotary housing (also the front end of the hydrostatic radial plunger unit). The cover encloses and preferably seals the rotating housing, for example with an O-ring, thereby preventing hydraulic fluid from leaking from the cavity formed by the rotating housing and the stationary housing. Furthermore, the front end and the reinforcing cover are designed such that: the reinforcing cover is capable of absorbing radial forces acting on the rotary housing due to the cam lobe operating principle.

In another embodiment, the reinforcing cover comprises a sleeve-like collar portion and the swivel housing comprises a complementary shoulder, or vice versa. The sleeve-like collar portion may be arranged in a form that forms a closed connection with the complementary shoulder portion at least in the radial direction. Thereby, the rotary housing may be reinforced in the radial direction. Preferably, the thickness of the reinforcing cover is designed such that: the reinforcing cover includes a low rotational mass as it rotates with the rotating housing, but provides a high radial stiffness. Enhancing the higher radial stiffness of the rotating housing reduces possible misalignment 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, as it is beneficial for the plunger rollers to press against the cam lobe surface in line contact during operation of the radial plunger unit.

In a preferred embodiment according to the present application, the hydrostatic radial plunger unit operates as a hydraulic motor. The hydraulic motor drives a track drive or wheel of a work machine (e.g., a track loader), for example, using a torque transfer device. In particular in the field of track drives, it is important that the axial length of the radial plunger unit is small, so that the design of the work machine can be chosen as flexibly as possible.

Drawings

In the following figures, exemplary embodiments of a hydrostatic radial plunger unit according to the present application and specific sub-assemblies of a hydrostatic radial plunger unit according to the present application are described. The presented embodiments do not limit the scope of the present application. The figure shows:

FIG. 1 shows a first cross-sectional view along the rotational axis of a hydrostatic radial plunger unit according to the present application;

FIG. 2 shows a second cross-sectional view along the rotational axis of a hydrostatic radial plunger unit according to the present application;

FIG. 3 shows a third cross-sectional view perpendicular to the axis of rotation of a hydrostatic radial plunger unit according to the present application;

FIG. 4 shows an isometric view of a rotating housing of a hydrostatic radial plunger unit according to the present application;

FIG. 5 shows an isometric cross-sectional view of a rotating housing (with a dispenser mounted) of a hydrostatic radial plunger unit according to the present application;

Fig. 6 shows a partial cross-sectional view of the front end of a hydrostatic radial plunger unit according to the present application.

For purposes of illustration and legibility only, like functional parts are indicated with like reference numerals throughout the figures presented.

Description of the reference numerals

1-a hydrostatic radial plunger unit; 3-a housing; 10-axis of rotation; 12-a non-rotating fixed shaft; 13-a first groove; 14-a second groove; 15-an axial bore; 20-a non-rotating stationary housing; 22-an annular groove; 24-terminal side; 25-extension; 26-through holes; 28-an axial bore for a brake pin; 30-an axial overlap region; 33-a first annular passage; 35-sealing surface; 37-a seal; 40-rotating the housing; 42-front end; 43-a second annular passage; 44-a torque transmitting device; 45-reinforcing the front cover; 46-collar portion; 47-step/shoulder; 48-an outer peripheral surface; 49-screw; 50-cylinder body; 55-cylinder holes; 60-working plunger; 65-roller; 70-a rotary distributor; 71-a disc-shaped portion; 72-dispenser spring; 73-a second internal groove; 74-a hollow shaft portion; 75-axial holes; 77-timing hole; 78-synchronizing pins; 80-a first cam lobe surface; 90-roller bearings; 100 parking brake mechanism; 112-brake disc; 114-a brake pin; 116-braking the piston; 117-release surface; 118-disc springs; 120-two-speed valve/multi-speed control valve; 130 end caps.

Detailed Description

Fig. 1 discloses a hydrostatic radial plunger unit 1 according to the present application. The hydrostatic radial plunger unit 1 comprises: a stationary non-rotating housing 20, the non-rotating housing 20 comprising a through bore 26 defining the axis of rotation 10. The non-rotating housing 20 accommodates a stationary shaft 12, the stationary shaft 12 being arranged coaxially with the rotational axis 10 and being connected to the non-rotating housing 20 in a torque-proof manner. The rotary housing 40 is supported by means of a pair of roller bearings 90 such that it can rotate about the rotation axis 10 relative to the stationary housing 20. Therefore, the rear end portion of the rotary housing 40 is sealed with the front end portion of the stationary housing 20 by the sealing body 37. The axial position of the sealing body 37 is defined by a sealing surface 35 orthogonal to the rotation axis 10. The sealing surface 35 divides the housing 3 of the radial plug unit 1, seen from the outside, into a rotating housing part 40 on one side of the sealing surface 35 and a stationary housing part 20 on the other side of the sealing surface 35.

Pairs of roller bearings 90 are arranged on the extensions 25 of the stationary housing 20, wherein the extensions 25 according to the embodiment shown in fig. 1 are provided as additional extensions. The extension 25 protrudes through the sealing surface 35 into the cavity formed by the rotary housing 40. In the embodiment shown in FIG. 1, the roller bearings 90 are arranged in pairs (i.e., substantially immediately adjacent to each other in the direction of the rotational axis) and take an O-shaped configuration. The O-configuration of the bearing is preferred if the support interval of the bearing is to be increased (e.g. if the component should be guided with a small tilting gap) or if a large tilting force has to be supported. Otherwise, an X-type configuration or a locating/non-locating bearing arrangement may be selected.

According to the present application, the pair of bearings 90 are arranged in the axial overlap region 30, and the stationary portion 20 of the non-rotating housing and the rotating housing 40 overlap in the overlap region 30. In other words: in the overlap region 30, the stationary housing 20 is arranged coaxially with the rotary housing 40 and vice versa. However, both the stationary housing 20 and the rotary housing 40 are radially spaced apart from each other. This means that the rotary housing 40 encloses the stationary housing 20, as it is the case in the presented example, or vice versa.

The rotary housing 40 includes: the torque transfer device 44, i.e., the flange at the outer peripheral surface 48 of the rotating housing. Depending on the application, the components may be attached to the flange 44, the flange 44 may be driven by the hydrostatic radial plunger unit 1, or the flange 44 may drive the hydrostatic radial plunger unit 1. The torque transfer devices 44 are preferably disposed at the same axial location as the pair of bearings 90 to reduce axial prying between the bearings 90 and the torque transfer devices 49 and thereby eliminate tilting moments that would otherwise occur.

The rotary housing 40 includes: toward the inboard cam lobe surface 80, the working plunger 60 may press against the cam lobe surface 80 (see also fig. 3). In the embodiment presented, cam lobe surface 80 is integrally formed with rotary housing 40, such as by three-dimensional milling, casting, turning, forging, or other different manufacturing methods. The working plunger 60 is accommodated in the cylinder hole 55 of the cylinder block 50. The cylinder 50 is designed to be fixed with respect to the fixed shaft 12 and the fixed housing 20. Thus, pushing/abutting working plunger 60 against cam lobe surface 80 creates a force on cam lobe surface 80 supported by fixed cylinder 50. This force causes the rotary housing 40 to rotate due to the shape of the cam lobes.

To drive the working plunger 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 plunger 60 is driven radially inward by following the shape of the cam lobe surface (i.e., cam), hydraulic fluid is discharged from the corresponding cylinder bore 55. Thus, the cylinder bores 55 must be alternately connected to the hydrostatic radial plug unit 1 inlet and the hydrostatic radial plug unit 1 outlet, which is accomplished by rotating the distributor 70.

A rotary distributor 70 (having a T-shaped cross section) having a disc-shaped portion 711 and a hollow shaft portion 74 is partially arranged in the axial overlap region 30. Accordingly, the pair of bearings 90 may be disposed at the same position as the rotary distributor 70 in the axial direction and radially outside the smaller diameter region of the hollow shaft portion 74 of the rotary distributor 70. However, in some designs, the pair of bearings 90 may also be disposed radially inward of the hollow shaft portion 74 of the rotary distributor 70.

Preferably, the rotary housing 40 and the stationary housing 20 seal off the inner cavity. In this regard, for ease of manufacture and installation of the components of the radial plug unit 1 according to the present application, end caps 45, 130 are provided at the rear end side 24 and at the front end 42 of the radial plug unit 1. In addition to its function of closing the housing cavity, the front cover 45 is designed to strengthen the rotary housing 40 and thereby the cam lobe surface 80 in the radial direction. The front cover 45 comprises a substantially flat disc-shaped base body from which a hollow cylindrical collar portion 46 extends. Complementary to the collar portion 46, a step 47 is provided on an outer circumferential surface 48 of the rotary housing 40. After the front cover 45 is attached to the rotary housing 40, the collar portion 46 provides support for the step 47 in the radial direction. This additional support ensures that cam lobe surface 80 retains its shape even if working plunger 60 presses against cam lobe surface 80. The thickness of collar portion 46 and the base plate may be selected based on the desired stability increase.

Furthermore, the front cover 45 may comprise a lightweight structure, for example by providing reinforcing ribs in the main stress area and cut-outs/recesses in the lower stress area. Those of ordinary skill in the art will recognize that the functional principles of the collar portion 46 provided to the front cover 45 and the step provided to the housing 40 may be reversed such that the front cover 45 may include the step 47 and the housing 40 may include the collar portion 46. However, other stability augmentation designs capable of absorbing forces acting on the rotating housing 40 in a radial direction are also contemplated by the scope of the present application. For example, a dowel connection is provided between the generally planar front cover 45 and the rotating front housing 40.

In addition to the function for closing the rear end side 24 of the cavity of the two-part housing of the radial plunger unit 1, the end cap 130 is part of the parking brake mechanism 100 (the brake mechanism of which is arranged in the stationary housing 20). The parking brake mechanism 100 includes at least two brake discs 112, one of which is attached to the rotary housing 40 in a torque-proof manner and the other of which is non-rotatably attached to the stationary housing 20. The brake disc 112 is axially movable relative to the stationary housing 20 and the rotary housing 40. If the parking brake mechanism 100 includes more than two brake discs 112, each brake disc 112 is connected to the stationary housing 20 and the rotary housing 40 in an alternating sequence. Disc spring 118 is supported by end cap 130 and provides a preload force to brake piston 116. As long as the brake piston 116 is not pressed at its release surface 117, the spring force is transmitted via the brake piston 116 to the at least one brake pin 114 (the brake pin 114 is arranged in the axial bore 28 in the stationary housing 20).

Preferably, more than one brake pin 114 is provided in order to provide a more balanced brake disc actuation. Each detent pin 114 is disposed 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 to the brake discs 112, the brake discs 112 pressing against each other and being supported, for example, by the shoulder of the stationary housing 20 or the extension 25. Thus, for example, when the work vehicle is stopped, the relative movement between the rotary case 40 and the stationary case 20 can be prevented.

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

Preferably, the detent 114 comprises a particular geometry. The end of the brake pin 114 facing in the direction of the brake piston 116 comprises a larger diameter than the end facing in the direction of the brake disc 112. Further, the brake pin 114 is sealed with respect to the stationary housing 20 and the stationary shaft 12. Thus, a pressure chamber is formed between the end face of the brake pin 114 and the housing 20 of the hydrostatic radial plunger 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 pushing 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.

However, the concepts according to the present application also cover the following: the particular design of the brake pin 114 ensures that the pin 114 always contacts the brake piston 116 regardless of whether the release surface is pressurized or not. In this embodiment, the brake pin 114 is sealed against the stationary housing 20 at the end remote 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. Thus, when the brake piston 116 moves by a force generated by hydraulic pressure in a pressure chamber (which is formed by the brake piston 116, the shaft 12, the front end of the brake pin 114, and the stationary housing 20 together), hydraulic pressure may exist at the rear/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 larger force on the side facing away from the brake piston 116, the brake pin 114 remaining in contact with the brake piston 116.

Fig. 2 shows a cross-section of the hydrostatic radial plunger unit 1 according to fig. 1 in a different cross-section. According to the view of fig. 2, some of the plurality of hydraulic passages of the hydrostatic radial plunger unit 1 according to the present application are shown. In the center of the hydrostatic radial plunger unit 1, a non-rotating stationary shaft 12 is provided, the stationary shaft 12 comprising: the first set of grooves 13, the first set of grooves 13 being in a region facing the end side 24 of the hydrostatic radial plunger unit 1 according to the present application. The stationary shaft 12 additionally includes: a second set of grooves 14, the second set of grooves 14 being in a region towards the front end 42 of the hydrostatic radial plunger unit 1. The first set of grooves 13 forms a first annular passage 33 together with an annular groove 22 provided in the non-rotating stationary housing. These first annular passages 33 serve to distribute hydraulic fluid entering from the inlet of the hydrostatic radial plug unit 1 and flowing towards the outlet of the hydrostatic radial plug unit 1.

The second annular passageway 43 is formed by the second groove 14 in combination with a second internal groove 73 in a hollow shaft portion 74 of the rotary distributor 70. The first annular passage 33 is fluidly connected to the second annular passage 43 by a channel (not visible in fig. 2) disposed in the stationary shaft 12.

The internal structure of the rotary distributor 70 is evident from figures 1 and 2. The rotary distributor 70 can selectively connect the second annular passage 43 to the appropriate cylinder bore 55 depending on whether high pressure should be supplied to the particular cylinder bore 55 via the timing bore or whether hydraulic fluid should be discharged from the particular cylinder bore 55.

In the illustrated embodiment of the present application, the extension 25 is provided as an additional component attached to the stationary housing 20. In addition to supporting the pair of bearings 90, the extension 25 is provided with a shoulder against which the brake disc 112 may be pressed. Both functions require strict manufacturing tolerances to ensure reliable support and braking of the hydrostatic radial plunger unit 1. Implementing both functions on a relatively small additional component includes the following advantages: only relatively small additional parts need to be machined, and a large portion of the stationary housing 20 need not be so complex machined, as would be required if the stationary housing 20 were to provide a shoulder and/or bearing surface.

The non-rotating stationary shaft 12 further includes: an axial bore 15, which in the example presented is arranged coaxially with the axis of rotation 10. Two-speed valve 120 is disposed in axial bore 15. Two-speed valve 120 includes 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 bore 55 is supplied with a lower pressure sufficient to force the roller of the working plunger 60 to follow the cam lobe surface. At the same time, the cylinder bore 55 supplied at a lower pressure may be hydraulically shorted. Thus, in the first position, all cylinder bores 55 contribute to the working volume of the hydrostatic radial plunger unit 1. In the second position, the shorted cylinder bore 55 does not contribute to the working volume of the hydrostatic radial piston unit 1, since for each working piston 60 moving to the outside, the other piston moves to the inside of its associated cylinder bore 55.

In the embodiment presented, two-speed valve 120 is hydraulically operated. However, two-speed valve 120 may also be mechanically or electro-mechanically operated. In other embodiments, as will be appreciated by those skilled in the art, two-speed valve 120 may be a multi-speed valve 120 that provides more positions to vary the rotational speed and torque of hydrostatic radial plunger unit 1 over a greater range.

Fig. 3 shows a cross-section of the hydrostatic radial plunger unit 1 according to the present application in a plane orthogonal to the rotation axis 10. The stationary shaft 12 shown in the middle of fig. 3 is connected with the cylinder 50 in a torque proof manner. Thus, the cylinder 50 is also stationary. The cylinder 50 includes: the cylinder bores 55 are arranged in the radial direction, and they are equally distributed on the circumferential surface of the cylinder block 50. Each cylinder bore 55 receives a working plunger 60 such that the working plunger 60 is slidable in the cylinder bore 55 in a radial direction. The working plunger 60 includes a roller 65 at the radially outer end. When pressure is supplied to the cylinder bore 55, the roller 65 is urged into contact with a cam lobe surface 80 formed radially inward of the rotary housing 40. The pressure creates a force on the working plunger 60 in a radially outward direction. If the rotating housing is driven into rotation, the rollers 65 interact with the cam lobe surface 80, depending on whether the rollers 65 are moving from lobe to cam or vice versa. If the roller travels from the lobe to the cam (i.e., the cam lobe surface shape is in a radially inward direction), the roller 65 and corresponding plunger 60 are driven in an inward direction by the cam lobe surface 80 shape and 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 is shaped in a radially outward direction in this region, the roller and corresponding plunger 60 are driven outwardly by the pressure within the cylinder bore 55 to follow the cam lobe surface.

Fig. 4 shows an isometric view of a rotary housing 40 for a hydrostatic radial plunger unit 1 according to one embodiment of the application. In addition to the features already mentioned above, fig. 4 shows an axial bore 75, the axial bore 75 being arranged radially inside the cam lobe surface 80, at a surface perpendicular to the rotation axis 10. The axial bore 75 receives the distributor spring 72, the distributor spring 72 providing a preload to the adjacently disposed rotary distributor 70. The disc-shaped portion 71 of the rotary distributor 70 and the rotary housing 40, in combination with the axial hole 75 and the received distributor spring 72, can be coupled in a rotatable manner with a synchronizing pin 78 arranged in one axial hole 75 of the rotary housing 40. Thus, the rotary distributor 70 and the distributor spring 72 rotate at the same rotation rate.

From fig. 1 or 2, one skilled in the relevant art will recognize from fig. 4 that the axial bore 75 may also be moved to the distributor 70 to abut against the bottom surface of the relevant lobe. The same function is achieved by placing the dispenser spring 72 in the aperture 75 of the dispenser 70: the disc-shaped member 71 of the dispenser 70 is pressed against the front surface of the cylinder 50.

In fig. 4, the synchronizing pin 78 is also shown, arranged on a larger diameter in a manner conventional in the art, which reduces the shear moment acting on the synchronizing pin 78. These shear forces are generated by frictional forces between the outer peripheral surface of the shaft 12 and the inner peripheral surface of the distributor 70 during operation of the hydraulic motor, the distributor 70 being surface-sealed to the shaft 12 to form an annular distribution channel (see also fig. 1 or 2). Here, the synchronizing pin 78 is mounted in an axial hole 75 in the front housing 40 and a corresponding hole in the dispenser 70.

Fig. 5 discloses a cross-sectional view of the rotary housing 40, in which rotary distributor 70 is arranged in the rotary housing 40. The outer surface of the disc-shaped portion 71 of the rotary distributor 70 is formed complementary to the cam lobe surface 80 to support the function of the synchronizing pin 78 housed in the rotary housing 40. The synchronizing pin 78 ensures that: the rotational orientation of the dispenser 70 is correct when the dispenser 70 is received in the rotary housing 40. In addition, the synchronizing pin 78 synchronizes the rotation of the dispenser 70 with the rotation of the rotary housing 40. In addition, it is also shown how the dispenser spring 72 abuts against the bottom of the axial bore 75 and thereby presses the dispenser 70 in the direction of the front end 42, i.e. towards the cylinder 50 (not shown in fig. 5). The rotary distributor 70 includes a lightweight design to reduce the moment of inertia of the assembly. For this purpose, a recess is provided in part at the radially extending disk-shaped portion of the distributor 70. Also shown is a second internal groove 73 formed at the radially inner side of the dispenser 70. The second internal groove 73 comprises an annular shape and is capable of directing fluid into and out of a timing hole 77 disposed in the front surface of the dispenser 70.

Fig. 6 illustrates how the reinforced front cover 45 is attached to the swivel housing 40 with screws (they are equally distributed along an imaginary circular arc). The combination of the collar portion in the front cover 45 and the step in the rotary housing 40 explained earlier not only strengthen the cam lobe surface 80, but also ensure that the cover 45 is exactly centered relative to the rotary housing 40. It should be appreciated that other techniques for attaching the cover to the rotating housing are within the purview of one skilled in the art.

Based on the above disclosure and the drawings and claims, it should be appreciated that the hydrostatic radial plunger unit 1 according to the present application provides a number of possible solutions and advantages with respect to the prior art. Those skilled in the art will further appreciate that further modifications and variations known in the art may be made to the radial plunger unit 1 according to the present application without departing from the spirit of the present application. Accordingly, all such modifications and changes are within the scope of the claims and are intended to be covered by the claims. It should be further understood that the above examples and embodiments are for illustrative purposes only and that various modifications, changes, or combinations of embodiments (as would be suggested by one skilled in the art) are to be included within the spirit and purview of this application.

Claims

1. A hydrostatic radial plunger unit (1) of cam lobe construction, comprising:

a non-rotating stationary housing (20), the stationary housing (20) comprising a through bore (26), the through bore (26) defining a rotational axis (10) of the hydrostatic radial plunger unit (1);

a cylindrical rotary housing (40), the rotary housing (40) being rotatably mounted to the stationary housing (20) in an axial overlap region (30), a front end portion of the stationary housing (20) and a rear end portion of the rotary housing (40) overlapping in the axial overlap region (30) such that the rotary housing (40) is rotatable about the rotational axis (10) relative to the stationary housing (20);

-a parking brake mechanism (100), the parking brake mechanism (100) comprising at least two brake discs (112) arranged adjacently in the overlap region (30), wherein one brake disc (112) is fixed in a rotational direction with respect to the stationary housing (20) and the other brake disc (112) is fixed in a rotational direction with respect to the rotary housing (40);

an end cap (130), the end cap (130) closing the stationary housing (20) on a rear end side (24) of the hydrostatic radial plunger unit (1) facing away from the rotary housing (40);

wherein the end cap (130) pre-biases a disc spring (118) against a disc brake piston (116) to create an axial spring force, the disc spring (118) and the brake piston (116) both being located in a rear end portion of the stationary housing (20), the spring force being transmittable by the brake piston (116) to at least one brake pin (114) arranged in an axial bore (28) in the stationary housing (20) to press the brake discs (112) against each other when the brake piston (116) opposite the disc spring (118) is not driven for movement towards the end cap (130).

2. The hydrostatic radial plunger unit (1) according to claim 1, further comprising: -a stationary shaft (12), the stationary shaft (12) being arranged coaxially with the rotational axis (10) in an inner cavity formed by the stationary housing (20), the rotational housing (40), the end cap (130) and a front cover (45), wherein a cylinder (50) non-rotatably accommodated in a front end portion of the rotational housing (40) is connected with the stationary shaft (12) against torsion.

3. The hydrostatic radial plunger unit (1) according to claim 2, wherein the front and rear ends of the at least one brake pin (114) seal a pressure chamber in the axial bore (28), the pressure chamber being pressurizable to push the brake pin (114) in a direction towards the end cap (130) and cause the brake piston (116) to compress the disc spring (118), thereby releasing the compression force from the brake disc (112).

4. The hydrostatic radial plunger unit (1) according to claim 2, wherein the brake piston (116), the at least one brake pin (114), the stationary shaft (12), and the stationary housing (20) seal out a pressure chamber that can be pressurized to push the brake piston (116) towards the end cap (130) and compress the disc spring (118), thereby releasing the compression force from the brake disc (112).

5. The hydrostatic radial plunger unit (1) according to any one of claims 1 to 4, wherein the end of the at least one brake pin (114) facing the brake piston (116) has a larger diameter portion.

6. The hydrostatic radial plunger unit (1) according to any one of claims 2 to 5, wherein the stationary housing (20) comprises an annular groove (22) at an inner surface, the annular groove (22) forming a first annular passage (33) together with a first groove (13) at an outer surface of the stationary shaft (12).

7. The hydrostatic radial plunger unit (1) according to any one of claims 2 to 6, further comprising: a rotary distributor (70), the rotary distributor (70) having a disc-shaped portion (71) and a hollow shaft portion (74), the rotary distributor (70) being arranged around a front end portion of the fixed shaft (12) with the hollow shaft portion (74) and being fixedly accommodated in the rotary housing (40) in a rotational direction with the disc-shaped portion (71), the rotary distributor (70) guiding and guiding hydraulic fluid out of a working plunger (60) in the cylinder (50) through a timing hole (78), and the rotary distributor (70) comprising a second inner groove (73) inside the hollow shaft portion (74), the second inner groove (73) forming a second annular passage (43) together with a second groove (14) at an outer surface of the fixed shaft (12), the second annular passage (43) being connected to the first annular passage (33) with a fluid passage located in the fixed shaft (12).

8. The hydrostatic radial plunger unit (1) according to any one of claims 1 to 7, comprising: -a pair of roller bearings (90) for rotatably mounting the rotary housing (40) to the stationary housing (20), wherein the pair of roller bearings (90) is arranged at the overlap region (30) between the rotary housing (40) and the stationary housing (20) radially outside the hollow shaft portion (74) of the rotary distributor (70).

9. Hydrostatic radial piston unit (1) according to claim 8, wherein the overlap region (30) of the front end portion of the radial piston unit (1) is defined by an extension (25) of the stationary housing (20), which extension (25) extends in axial direction beyond a sealing surface (35) into the volume of the rotary housing (40) and radially between the hollow shaft portion (74) of the rotary distributor (70) and the rotary housing (40), wherein the extension (25) is arranged to cooperate with an inner shell of the roller bearing (90).

10. The hydrostatic radial plunger unit (1) according to claim 9, wherein the extension (25) is provided as an additional component and is attached to the stationary housing (20).

11. The hydrostatic radial plunger unit (1) according to any one of claims 1 to 10, further comprising: -a fixed multi-speed control valve (120), the fixed multi-speed control valve (120) being switchable between a first position in which all cylinder bores (55) can be supplied with high pressure hydraulic fluid from a high pressure inlet of the hydrostatic radial plunger unit (1), and a second position in which only a part of the cylinder bores (55) can be supplied with high pressure fluid, and in which a pair of cylinder bores (55) are hydraulically short circuited.

12. Hydrostatic radial plunger unit (1) according to claim 11, wherein the fixed multi-speed control valve (120) is arranged in an axial bore (15) in the fixed shaft (12), wherein the axial bore (15) is preferably arranged coaxially with the rotation axis (10).

13. The hydrostatic radial plunger unit (1) according to any one of claims 11 to 12, wherein the multi-speed control valve (120) is a two-speed control valve (120) or a three-speed control valve (120).

14. The hydrostatic radial plunger unit (1) according to any one of claims 1 to 13, wherein a cam lobe surface (80) upon which the working plunger (60) is able to act is integrally formed with the rotary housing (40).

15. The hydrostatic radial plunger unit (1) according to any one of claims 7 to 14, wherein a disc-shaped portion (71) of the rotary distributor (70) is biased against a side surface of the cylinder (50) by a distributor spring (72) and/or a distributor plunger (74), both the distributor spring (72) and the distributor plunger (74) being axially accommodated in the rotary housing (40) or in the disc-shaped portion (71) of the rotary distributor (70).

16. The hydrostatic radial plunger unit (1) according to claim 15, wherein the distributor spring (72) and/or the distributor plunger (74) are accommodated in an axial bore (75) in the rotary housing, the axial bore (75) being arranged at a recess of the cam lobe surface (80).

17. The hydrostatic radial plunger unit (1) according to any one of claims 1 to 16, wherein the first cylinder block (52) comprises more than one row of cylinder bores having cylinder bores (55) and radially reciprocating working plungers (62), the radially reciprocating working plungers (62) being circumferentially adjacent or staggered with respect to each other and being capable of interacting with the cam lobe surface (80).

18. The hydrostatic radial plunger unit (1) according to any one of claims 1 to 17, wherein a second cylinder is arranged parallel to the first cylinder (50) on the stationary shaft (12), a working plunger (60) of the second cylinder interacting with the first cam lobe surface (80).

19. The hydrostatic radial piston unit (1) according to claim 18, wherein the number of cylinder bores (55) and the number of radially reciprocating working pistons (60) of the second cylinder block are different from the number of cylinder bores (55) and the number of radially reciprocating working pistons (60) of the first cylinder block (50), a second cam lobe surface (82) capable of interacting with the working pistons (60) of the second cylinder block being arranged radially inside the front housing (40).

20. The hydrostatic radial plunger unit (1) according to any one of claims 1 to 19, wherein,

A reinforcing front cover (45) is attached to a front end (42) of the rotary housing (40) facing away from the stationary housing (20) and encloses the rotary housing (40), wherein the front end (42) of the rotary housing (40) and the reinforcing front cover (45) are arranged such that the reinforcing front cover (45) can at least partially absorb forces acting on the rotary housing (40), in particular forces in a radial direction.

21. The hydrostatic radial plunger unit (1) according to claim 19, wherein the reinforcing front cover (45) comprises a sleeve-like collar portion (46) and the rotary housing (40) comprises a complementary shoulder (48), or the rotary housing (40) comprises a sleeve-like collar portion, the reinforcing front cover (45) comprising a complementary shoulder.