Displacement volume setting device and hydrostatic variable displacement axial piston machine

Abstract

A displacement volume setting device for a hydrostatic variable displacement axial piston machine is disclosed, which includes an input device for providing a displacement command. A displacement volume adjusting device sets the tilt angle of a displacement element according to the displacement command. A connecting rod element includes: an input coupling element connected to the input device, an output coupling element connected to the displacement volume adjusting device, and a connecting element. The input coupling element and the output coupling element are connected by the connecting element, and the connecting element is elastically deformable if the force generated by the high pressure level existing in the hydrostatic axial piston machine and acting on the output coupling element exceeds a predetermined threshold. A hydrostatic variable displacement axial piston machine is also disclosed.

Description

Field of the Invention

[0001] The present invention relates to a hydrostatic variable displacement axial piston machine. More specifically, the present invention relates to a displacement volume setting device for a hydrostatic variable displacement axial piston machine. Background Art

[0002] Hydraulic work vehicles are usually equipped with a hydrostatic variable displacement axial piston machine that is driven by an internal combustion engine in order to generate hydraulic pressure, which can be converted into a driving force for the vehicle, for example, by a hydraulic motor. In most cases, the displacement volume of the hydraulic motor that drives the vehicle or actuates a work function is constant. The speed of the hydraulic motor and / or (auxiliary) work device is controlled by controlling the displacement volume of the hydrostatic axial piston machine. Therefore, it can be concluded that the tilt angle of the displacement element of the hydrostatic variable displacement axial piston machine must be adjustable.

[0003] The tilt angle of the displacement element is adjusted according to an input command from the vehicle operator, and the input command is transmitted to the displacement element of the hydrostatic variable displacement axial piston machine via certain interfaces (such as a pedal or a control lever) by setting a rigid mechanical connection element. A hydrostatic variable displacement axial piston machine equipped with a rigid link element is usually referred to as a direct displacement control unit.

[0004] Since the link between the axial displacement unit and the operator input device is rigid, the load acting on the displacement unit increases the force required to hold the link in place and also provides an unwanted mechanical feedback signal to the input device.

[0005] If the vehicle operator increases the force on the input command device, the hydraulic power generated by the hydrostatic variable displacement axial piston machine should also increase. If the tilt angle of the displacement element cannot adapt to the new load situation (which is the normal behavior of a hydrostatic variable displacement unit), the rotational speed of the internal combustion engine is forced to decrease, which may cause the engine to stall, especially if the operator's input command prevents the hydrostatic variable displacement unit from adapting to the increasing load on the work vehicle. Then, the internal combustion engine is required to provide more power to the hydrostatic axial piston machine, and thus the internal combustion engine is forced to operate at a different torque-speed ratio, which in turn deviates from the designed torque / speed ratio. At this different torque-speed ratio, the efficiency of the internal combustion engine is worse than when operating in the target operating state. Since the internal combustion engine may not be able to provide sufficient power for the deviated system state, system overload may occur. This not only results in increased fuel consumption; if the required torque exceeds the torque that the internal combustion engine can provide, it may also cause the engine to stall. Summary of the Invention

[0006] Accordingly, an object of the present invention is to provide a displacement volume setting device that enables a direct mechanical connection between an operator input device and a displacement element of a hydrostatic variable displacement axial piston machine, wherein the displacement volume setting device is configured to invalidate an operator input command when necessary to maintain a target operating state or to avoid stalling of an internal combustion engine.

[0007] This object is solved by a displacement volume setting device according to an embodiment of the present invention and by a hydrostatic variable displacement axial piston machine according to an embodiment of the present invention.

[0008] According to the present invention, a displacement volume setting device of a hydrostatic variable displacement axial piston machine includes an input device for providing a displacement command. Preferably, the input device is a mechanical device that is moved to adjust the displacement volume of the axial piston machine and the consequent volume flow. For example, in the operator's cab of a work vehicle, the input device may be arranged remote from the hydrostatic variable displacement axial piston machine.

[0009] The displacement volume setting device according to the present invention further includes a displacement volume adjusting device for setting an inclination angle of the displacement element according to the displacement command provided via the input device. According to the present invention, the movement of the displacement volume adjusting device causes a change in the inclination angle of the displacement element and ultimately a change in the displacement volume of the axial piston machine. Preferably, the displacement volume adjusting device is also provided as a mechanical device that is attached to the displacement element and is capable of transferring a force acting on the displacement volume adjusting device to the displacement element and vice versa, transferring a force from the displacement element towards the input device. The displacement volume adjusting device may be, for example, a control rod or lever connected to the displacement element, and the displacement element may be, for example, a swash plate or a yoke.

[0010] According to the present invention, the displacement volume setting device includes a link element having an input coupling element connected to the input device, an output coupling element connected to the displacement volume adjusting device, and a connecting element connecting the input coupling element and the output coupling element. The connecting element transfers the displacement command from the input device transmitted via the input coupling element to the output coupling element and further via the output coupling element to the displacement volume adjusting device. The connecting element generally exhibits an inelastic behavior, but is capable of elastic deformation if the force generated by a high pressure level present at / in the hydrostatic variable displacement axial piston machine exceeds a predetermined threshold.

[0011] A hydrostatic variable displacement axial piston machine can be, for example, a hydrostatic pump which is connected via a high-pressure line to a hydraulic consumer (e.g., a hydraulic motor). If the load counteracting the force / movement of the hydraulic consumer increases, the pressure level in the high-pressure line rises, thereby increasing the pressure difference which the hydrostatic variable displacement axial piston pump has to generate between its inlet and outlet. This can occur if a vehicle driven hydraulically by a hydraulic motor drives uphill or overcomes an obstacle while driving / pushing / pulling. In response to the increased load on the high-pressure side, the displacement element of the axial piston machine tilts towards a smaller displacement volume, thereby reducing the volume flow through the pump and increasing the pressure difference between the pump's inlet and outlet. For example, if the speed of the work vehicle is to be maintained in such a case, the input command must be adjusted. In the case of a hydraulically pump with direct displacement control, this can only be done by commanding the displacement element to obtain a greater tilt angle. However, a greater tilt angle causes the drive engine to provide a greater torque, the negative consequences of which have already been mentioned above.

[0012] For a command to increase the displacement volume which generates a relatively small pressure change at the high-pressure side of the hydrostatic axial piston machine, the displacement command is transferred directly and rigidly to the displacement volume regulating element, and the load feedback is transferred directly and rigidly in the opposite way from the displacement volume regulating device back to the input device.

[0013] If the force generated by a higher pressure level acting on the displacement element (and on the output coupling element) of the hydrostatic axial piston machine is greater than a predefined threshold, the connecting element according to the invention decouples the input coupling element from the output coupling element by elastic deformation. Thus, the tilt angle of the displacement element is no longer directly controlled by the input device. This elastic deformation allows the output coupling element to move relative to the input coupling element and enables the displacement element to rotate back to a lower tilt angle by allowing the displacement volume regulating element to retract, thereby avoiding an overload of the drive engine.

[0014] This elastic deformation limits the force generated by the high-pressure side of the hydraulic axial piston machine to a predefined threshold. The magnitude of the load acting on the hydraulic axial piston machine below the predefined threshold allows the drive engine to maintain an economic operating state range and / or prevents the engine from being damaged. In addition, a direct feedback of the load acting on the displacement element can be transferred to the input device. On the other hand, if an adjustment of the tilt angle is required due to an external load representative value being higher than the threshold, a mechanically non-feedback behavior is provided.

[0015] A pre-determined threshold can be set by a pre-tension force on the connecting element. If the force applied to the connecting element is less than the pre-tension force, the pre-tensioned connecting element will act rigidly when transferring the load from the input coupling element to the output coupling element (and vice versa). Thus, it can be concluded that if the pre-tensioned connecting element is capable of elastic deformation, the connecting element can be set such that, for example, if the load acting on a hydraulic axial piston machine is greater than the threshold set by the pre-tension force, the connecting element deforms.

[0016] According to the invention, the pre-tension force of the connecting element can be adjusted. The magnitude of the pre-tension force affects the behavior of the hydraulic working machine (vehicle). If the pre-tension force is high, a rigid feedback will be provided between the input coupling element and the output coupling element even when the external load is high. If the pre-tension force and thus the resulting threshold are low, the displacement volume setting device will react more smoothly to the external load and the displacement command provided via the input device (if it would result in a high pressure level above the threshold).

[0017] To achieve this, the connecting element can include a spring or another type of elastically deformable element. The material selection for the elastically deformable element can be wide, including but not limited to metals, plastics, or reinforced plastics. Thereby, the elastically deformable element can have any form, such as a tension spring, a compression spring, a torsion spring, or any other type of spring. The connecting element can also be designed as an elastic washer, a lock washer, a bursting disc, a screw or a bolt, or a similar device.

[0018] What the concept of the present invention covers is to provide a partially elastic element, which includes: a component that is rigid in any operating state; and an elastically deformable component that deforms when the force generated by a high pressure level and acting on the output coupling element exceeds a pre-determined threshold set by the pre-tension force of the elastically deformable element.

[0019] The elastically deformable element can also be designed as a pre-tensioned rope, cable, rod, or column with a small diameter, such that if the force acting on these elements exceeds the pre-determined threshold, these elements are elastically deformable. Depending on the design of the connecting rod element, the elastic connecting element can be capable of transmitting tensile and / or compressive forces. As described, the connecting element can also include a combination of the said components.

[0020] In addition, the connecting rod element may include end stops that limit the elastic deformation of the connecting element, where the damping element may be arranged at the end stops. By providing the end stops, a force range for the elastic behavior of the connecting element is defined. The lower end of this range is defined by the magnitude of a predefined threshold, and the upper end of this range is defined by the position of the higher end stop and the consequent corresponding maximum elastic deformation force. If the force acting on the output coupling element is within this force range, the connecting element acts elastically. If the force is outside this force range, the connecting element serves as a rigid force transmission device. If the force is less than the pre-tensioning force, a rigid transmission is provided without causing elastic deformation of the connecting element. If the force is greater than the pre-tensioning force, the connecting rod element elastically transmits the displacement command until it contacts the end stop.

[0021] The damping element, such as a shock absorber, crane buffer, foam rubber or similar element, can make the elastic behavior of the connecting element smoothly transition to the rigid behavior of the connecting element. Additionally, the damping element can eliminate vibrations, thus providing a more comfortable load feedback to the operator of the variable displacement axial piston machine.

[0022] The input device for providing the displacement command can be a joystick, control lever, pedal or similar device for providing a mechanical input command. Preferably, the movement of the input device is transmitted to the displacement element via a mechanical transmission device (such as a connecting rod element) that defines a movement / transmission ratio, so that a comfortable / economical operation of the axial piston machine can be achieved.

[0023] The displacement command can also be an electrical signal or a hydraulic pressure that is mechanically converted onto the input coupling element via a solenoid or a servo mechanism. As described, the mechanical movement of the input coupling element can thus be transmitted to the displacement element. The load feedback acting on the high-pressure side of the hydrostatic axial piston machine is transmitted to the input device via the connecting rod element, where this load feedback can be used as feedback to the system operator or the system control unit, for example to adjust the engine drive speed.

[0024] As previously mentioned, the connecting rod element can transmit linear motion and / or rotational motion. Also covered by the spirit of the present invention is that the connecting rod element transmits a combination of linear motion and / or rotational motion.

[0025] The hydrostatic variable displacement piston machine can be of the swashplate or bent axis type. It is common knowledge to those skilled in the art that in the first case, the displacement element is a tiltable swashplate, also called a rotating element, and in the second case, the displacement element is a yoke.

[0026] Although the concept of the present invention has been described using a hydraulic axial piston pump, any hydrostatic axial piston machine can be equipped with a displacement volume setting device according to the present invention. Thus, a hydrostatic axial piston machine equipped with a displacement volume setting device according to the present invention can be part of a hydrostatic motor, a hydrostatic pump, and / or a hydrostatic transmission. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In the following drawings, exemplary embodiments of a displacement volume setting device for a hydrostatic variable displacement axial piston machine according to the present invention are shown. Without departing from the spirit of the concept of the present invention, the proposed embodiments can be combined with each other. Combinations and alternatives of embodiments that are not shown in the drawings or the above description but are within the knowledge of those skilled in the art are also covered by the spirit of the present invention. The proposed embodiments do not limit the scope of the present invention. The following figures show:

[0028] Figure 1 A first embodiment of a displacement volume setting device according to the present invention is shown in a side view;

[0029] Figure 2 is shown in a cross-sectional view Figure 1 of the embodiment;

[0030] Figure 3 A second embodiment of a displacement volume setting device according to the present invention is shown in a side view;

[0031] Figure 4 is shown in a cross-sectional view Figure 3 of the embodiment;

[0032] Figure 5 A third embodiment of a displacement volume setting device according to the present invention is shown in a cross-sectional view.

[0033] Although the following drawings show different embodiments of the present invention, the same reference numerals are used for corresponding components, regardless of the specific embodiment. DETAILED DESCRIPTION

[0034] Figure 1Shows a side view of a first embodiment of a connecting rod element 10 of a displacement volume setting device 1 according to the present invention. The connecting rod element 10 includes an input coupling element 15 and an output coupling element 20, both the input coupling element 15 and the output coupling element 20 being provided as separate components. The input coupling element 15 and the output coupling element 20 are rotatable relative to each other about a pivot axis 28, wherein both the input coupling element 15 and the output coupling element 20 are connected to a pivot pin 25 serving as a common center of rotation. The input coupling element 15 is connected to an input device 6, and the output coupling element 20 is connected to a displacement volume adjustment device 8. The relative rotation between the output coupling element 20 and the input coupling element 15 is restricted by a connecting element 30 which is arranged in the force path between the input coupling element 15 and the output coupling element 20.

[0035] As shown in more detail in Figure 2 the connecting element 30 includes a guide rod 32 on which a spring 38 is movably arranged. One side of the spring 38 abuts against a spring seat 40, while the other side abuts against a washer 34 which is held in place by a nut 36. The guide rod 32 is inserted into an opening 48 formed in the input coupling element 15 and the output coupling element 20. A rod end pin 42 is fixed to the end of the guide rod 32 opposite the spring 38 and protruding through the opening 48, such that the relative position of the input coupling element 15 and the output coupling element 20 is restricted in one direction by the rod end pin 42. In the other direction, the mobility of the pin 32 is restricted by the spring seat 40. As in this embodiment, the convex surfaces on the spring seat 40 and the rod end pin 42 can be received by concave grooves which are also formed in the input coupling element 15 and the output coupling element 20. The paired arrangement of the convex and concave surfaces ensures that when the input coupling element 15 and / or the output coupling element 20 rotates about the pivot pin 25, the guide rod axis 26 can remain stationary. As Figure 2 shown in the embodiment of

[0036] As shown in Figure 1 and Figure 2In the embodiment, the displacement volume setting device 1 can be installed on a variable displacement axial piston machine. Before starting the operation of the variable displacement axial piston machine, the spring 38 can be pre-tensioned by adjusting the position of the adjusting nut 36 on the guide rod 32. If the nut 36 is screwed towards the spring seat 40, the pre-tensioning force of the spring 38 increases, and if the nut 36 is screwed in the opposite direction, the pre-tensioning force decreases.

[0037] In the rated operating state, an input command, such as the movement of an input control lever, is provided, and this input command is set via the input device 6. The input command causes the input coupling element 15 to rotate, and this rotation is indicated by the double-headed arrow 60. The rotational input command is transmitted via the input coupling element 15 to the spring seat 40 or the rod end pin 42 (depending on the rotational direction of the input coupling element 15). If the force applied to the spring seat 40 or the rod end pin 42 by the rotational movement of the input coupling element 15 is less than the pre-tensioning force of the spring 38, the rotation of the input coupling element 15 will be transmitted inelastically towards the output coupling element 20, which rotates about the pivot pin 25 in the same direction as the input coupling element 15 and transmits this rotation to the displacement volume adjusting device 8, thereby causing a change in the tilt angle of the displacement element of the axial piston machine (not shown).

[0038] If the direction of the force is opposite, i.e., if a force is applied to the output coupling element 20 by the displacement volume adjusting device 8 such that the output coupling element 20 rotates about the pivot pin 25 (see the double-headed arrow 65), the principle described above applies vice versa. If the force applied to the spring seat 40 or the rod end pin 42 by the rotation of the output coupling element 20 is less than the pre-tensioning force of the spring 38 (which represents a predefined threshold for a high pressure level), the connecting element 30 exhibits rigid behavior and directly transmits the rotation of the output coupling element 20 to the input coupling element 15. The input coupling element 15 is connected to the input device 6, thereby providing a direct (mechanical) feedback of the load acting on the displacement volume adjusting device 8 to the input device 6.

[0039] This means that the operator of the hydrostatic variable displacement axial piston machine can feel the load acting on the working machine (vehicle) transmitted via the displacement volume adjusting device 8. For example, if an obstacle appears in the driving path of a vehicle pushed by the axial piston machine according to the present invention, after the operator feels an increase in the load at the input device 6, the operator can, if necessary, react to the increased load.

[0040] However, if the load acting on the displacement volume adjusting device 8 exceeds the amplitude of the threshold value set by the pre-tensioning force of the spring 38, the rotation of the output coupling element 20 results in a force on the rod end pin 42 or the spring seat 40 that is greater than the pre-tensioning force of the spring 38. This means that the spring 38 is compressed and that relative rotation between the input coupling element 15 and the output coupling element 20 is allowed because the connecting element 30 exhibits elastic behavior.

[0041] The elastic behavior of the connecting element 30 enables decoupling of the movement of the input coupling element 15 and the input device 6 from the movement of the output coupling element 20 and the displacement volume adjusting device 8 connected to the output coupling element 20. Thus, the hydraulic unit controlled by the input device 6 can adjust its tilt angle independently of the input command. Thereby, a stable and efficient operating point can be maintained for the internal combustion engine, and the internal combustion engine will not operate in a torque range where there is a very low efficiency or a risk of stalling the engine. According to the invention, if a high load present on the high-pressure side of a hydrostatic variable displacement axial piston machine exceeds a threshold value, the displacement element will tilt back and reduce the displacement, and the displacement volume adjusting device 8 will transfer the reduction in the tilt angle to the output coupling element 20. As the displacement volume decreases, the torque required by the internal combustion engine also decreases.

[0042] Those skilled in the art are aware of many devices equivalent to the spring 38 and can be pre-tensioned in a similar manner. For example, a tension spring, a torsion spring, or any other type of spring or other elastically deformable device and / or material can be applied. Moreover, a different device for pre-tensioning the elastically deformable device can be provided compared to the nut 36 in combination with the washer 34, for example, by means of a clip or a latch device. The invention also encompasses transforming the concept shown in the embodiments of Figure 1 and Figure 2 from a range mainly of rotational motion to a range of linear motion.

[0043] Figure 3 and Figure 4 shows a second embodiment of the link element 10 of the displacement volume setting device 1 of a hydrostatic variable displacement axial piston machine, which link element 10 is suitable for transmitting the relative rotational movement between the input device 6 and the displacement volume adjusting element 8. The input device 6 is connected to an input coupling element designed as a first pin 15. The displacement volume adjusting device 8 is connected to another second pin 20 serving as an output coupling element. The first pin 15 and the second pin 20 are connected by a rotary spring 38 serving as a connecting element 30. The spring 38, the input device 6, and the displacement volume adjusting element 8 share a common center of rotation 39, which is defined by a guide rod (shaft) 32. The input device 6 and the displacement volume adjusting device 8 are movably arranged (at least in the rotational direction) on the shaft 32.

[0044] In accordance withFigure 3 and Figure 4 In the embodiment of Figure 4 , the rotational movement and the corresponding torque acting on the displacement volume adjustment device 8 are transmitted via the second pin 20 to the connecting element 30, which acts rigidly when the force balance between the input coupling element 15 and the output coupling element 20 is less than its pre-tensioning force. Then, the torque of the displacement volume adjustment device 8 is rigidly transmitted to the input device 6 and vice versa. If the force balance between the input coupling element 15 and the output coupling element 20 is higher than the pre-tensioning force (predetermined threshold), the connecting element 30 is elastic and thus the torque of the displacement volume adjustment device 8 is decoupled from the input device 6, allowing the axial piston machine to react load-dependently.

[0045] Figure 5 A cross-sectional view of the link element 10 applying the linear motion principle is shown. The link element 10 includes a guide rod 32, which is part of the connecting element 30. The guide rod 32 is actuated at its free end by the input coupling element 15. At the opposite end of the guide rod 32 in the embodiment according to Figure 5 a spring 38 is movably arranged and fixed between a first washer 34 and a second washer 35. The first washer 34 and the second washer 35 are arranged between a first nut 36 and a second nut 37 and are held in place by the first nut 36 and the second nut 37 respectively. The washers 34, 35 abut against a first shoulder 46 and a second shoulder 47 of the housing 20 serving as the output coupling element on the side facing away from the spring. The housing 20 includes a first opening 48 and a second opening 49 and circumferentially surrounds the spring assembly. The guide rod 32 projects from the first opening 48 towards the input coupling element 15. The second opening 49 of the output coupling element 20 is closed by an end stop 44 of the end cap.

[0046] The pre-tensioning force of the spring 38 can be adjusted by screwing the nuts 36, 37 onto the guide rod 32 and thus changing the distance between the first nut 36 and the second nut 37 and the two corresponding washers 34, 35. If the distance between the first nut 36 and the second nut 37 is greater than the distance between the shoulders 46, 47, the washers 34, 35 will be pressed against the shoulders 46, 47 by the action of the spring 38. In the case where the distance between the two nuts 36, 37 is less than the distance between the two shoulders 46, 47, the washers 34, 35 are arranged with a gap from the shoulders 46, 47 and are freely movable on the rod 32 for at least a certain distance. Preferably, in the starting position, the distances between the nuts 36, 37 and between the shoulders 46, 47 are substantially the same, such that the washers 34, 35 abut against the nuts 36, 37 and against the shoulders 46, 47 simultaneously.

[0047] If the force balance between the force applied by the input coupling element 15 towards the housing 20 (representing the output coupling element) and the force applied by the displacement volume adjusting element in the opposite direction on the housing 20 is less than the pre-tensioning force of the spring 38, the connecting element 30 acts inelastically and transfers the force directly from the housing 20 (output coupling element) to the input coupling element 15 and vice versa, where the force is transmitted via the first shoulder 46 to the first washer 34, to the spring 38, to the second washer 35, to the nut 37 on the guide rod 32 and vice versa.

[0048] If the difference between the forces at the input coupling element 15 and the output coupling element 20 is greater than the threshold value predetermined by the pre-tensioning force, the spring 38 is compressed so that relative movement between the output coupling element 20 (housing 20) and the input coupling element 15 becomes possible. For example, if the output coupling element 20 is pushed towards the input coupling element 15 held in place and the displacement force at the output coupling element 20 is greater than the pre-tensioning force of the spring 38, the spring 38 is compressed towards the input coupling element 15 and the distance between the output coupling element 20 and the input coupling element 15 is reduced. If the spring 38 has a linear characteristic, the distance between the input coupling element 15 and the output coupling element 20 is proportional to the displacement force.

[0049] End stops 44 are provided which limit the relative movement between the output coupling element 20 and the input coupling element 15 in the case of very high displacement forces. If the end stop 44 contacts the first nut 36, the force of the output coupling element 20 is transmitted directly towards the input coupling element 15 compared to the inelastic case. Thus, when the displacement force is greater than a first threshold value defined by the pre-tensioning force and less than a predetermined second threshold value defined by the force required for the end stop 44 to contact the first nut 36, the connecting element 30 does exhibit elastic behavior.

[0050] From the above disclosure as well as the drawings and the claims, it will be recognized that, compared to the prior art, the displacement volume setting device according to the invention and the hydrostatic variable displacement axial piston machine according to the invention offer many possibilities and advantages. Those skilled in the art will further recognize that further modifications and changes can be made to the displacement volume setting device and the hydrostatic variable displacement axial piston machine according to the invention without departing from the spirit and scope of the invention. Therefore, such modifications and changes are within the scope of the claims and are covered by the claims. It should be further understood that the examples in the above-described embodiments are for illustrative purposes only, and various modifications, changes or combinations according to these examples and embodiments that would occur to those skilled in the art are included in the spirit and scope of this application.

[0051] List of reference numerals

[0052] 1 Displacement volume setting device

[0053] 6 Input device

[0054] 8 Displacement volume adjustment device

[0055] 10 Link element

[0056] 15 Input coupling element / First pin

[0057] 20 Output coupling element / Second pin / Housing

[0058] 25 Pivot pin

[0059] 26 Guide rod axis

[0060] 28 Pivot axis

[0061] 30 Connecting element

[0062] 32 Guide rod

[0063] 34 Washer / First washer

[0064] 35 Second washer

[0065] 36 Nut / First nut

[0066] 37 Second nut

[0067] 38 Spring

[0068] 39 Center of rotation

[0069] 40 Spring seat

[0070] 42 Rod end pin

[0071] 44 End stop / End cover

[0072] 46 First shoulder

[0073] 47 Second shoulder

[0074] 48 First opening

[0075] 49 Second opening

[0076] 60 Double-headed arrow

[0077] 65 Double-headed arrow

Claims

1. A displacement volume setting device (1) for a hydrostatic variable displacement axial piston machine, comprising: - an input device (6) for providing a displacement command, - a displacement volume adjusting device (8) for setting the tilt angle of a displacement element according to the displacement command, - a connecting rod element (10) having: i) an input coupling element (15) connected to the input device (6), ii) an output coupling element (20) connected to the displacement volume adjusting device (8), and iii) a connecting element (30) connecting the input coupling element (15) to the output coupling element (20), wherein when the force generated by the high pressure level present in the hydrostatic variable displacement axial piston machine and acting on the output coupling element (20) exceeds a predetermined threshold, the connecting element (30) can elastically deform to decouple the input coupling element (15) from the output coupling element (20), such that the tilt angle of the displacement element is no longer directly controlled by the input device (6), and the elastic deformation limits the force generated by the high pressure side of the hydrostatic variable displacement axial piston machine to the predetermined threshold.

2. The displacement volume setting device according to claim 1, wherein the predetermined threshold is set by a pre-tensioning force on the connecting element (30).

3. The displacement volume setting device according to claim 2, wherein the pre-tensioning force on the connecting element is adjustable.

4. The displacement volume setting device according to any one of claims 1 to 3, wherein the connecting element comprises a spring (38) or an elastically deformable element.

5. The displacement volume setting device according to claim 4, wherein the spring (38) is a tension spring, a compression spring, a torsion spring or any other type of spring.

6. The displacement volume setting device according to any one of claims 1 to 3 and 5, wherein the connecting rod element (10) comprises end stops (44) that limit the elastic deformation of the connecting element (30), and a damping element can be arranged at the end stops (44).

7. The displacement volume setting device according to any one of claims 1 to 3 and 5, wherein the input device (6) is a joystick, a control lever or a pedal.

8. The displacement volume setting device according to any one of claims 1 to 3 and 5, wherein the displacement command is an electrical signal or a hydraulic pressure mechanically converted onto the input coupling element (15) via a solenoid or a servo mechanism.

9. The displacement volume setting device according to any one of claims 1 to 3 and 5, wherein the connecting rod element (10) transmits linear motion and / or rotational motion.

10. A hydrostatic variable displacement axial piston machine, the hydrostatic variable displacement axial piston machine being equipped with a displacement volume setting device (1) according to any one of claims 1 to 9, wherein, the hydrostatic variable displacement axial piston machine is of the swash plate type or the bent axis type.

11. The hydrostatic variable displacement axial piston machine according to claim 10, wherein, the hydrostatic variable displacement axial piston machine is part of a hydrostatic motor, a hydrostatic pump and / or a hydrostatic transmission.

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