Hydrostatic axial piston machine

Abstract

The invention relates to a hydrostatic axial piston machine (1), comprising: a hydraulic control cylinder (10), which has a control piston (8), on which a first control piston surface (12) and a second control piston surface (14) acting opposite the first control piston surface are formed; and having an actuator (10) which is movably coupled to the actuating piston (8), the stroke volume of the axial piston machine (1) being dependent on the position thereof; and a control valve (28), which can be actuated by means of a control signal (Ir) as a function of the detected actual position (Sist) and target position (Ssoll) of the control piston (8) or of the actuator element, such that the control piston surfaces (12, 14) can form a throttled pressure medium connection to the control pressure medium source (pst) and the control pressure medium outlet (R) by means of the control valve (28) as a function of the control signal (Ir), as a result, the adjusting piston (8) can be actuated on both sides of an intermediate position or zero position in which the stroke volume is zero.

Description

Technical Field

[0001] The present disclosure relates to a hydrostatic axial piston machine according to the preamble of claim 1 . Background Art

[0002] The axial piston machine that can be used in a closed hydraulic circuit has a stroke volume that can be adjusted through zero, so that four-quadrant operation can be achieved. In pump operation, a change in direction of the pressure medium volume flow can be achieved by adjusting the delivery volume from the positive adjustment range, through zero to the negative adjustment range, or vice versa from negative to positive, without having to change the direction of rotation of the drive shaft for this purpose. In motor operation, a change in direction of the torque can be achieved by the above-mentioned adjustment without having to change the direction of the pressure medium volume flow. For adjustment, a double-acting adjustment cylinder is provided, which can be hydraulically actuated on both sides of its zero position, and is coupled to an actuator of the axial piston machine, the stroke volume being related to the position of the actuator. The actuator is, for example, a swash plate that can be adjusted in terms of its pivot angle, on which the working piston is slidably supported.

[0003] The hydraulic actuation of the double-acting control cylinder is achieved by a control valve. Here, the high-cost mechanical feedback of the actual position of the actuator (swash plate) to the control valve is omitted, and as an alternative, the control loop is electronically closed.

[0004] The applicant's data sheet RD92076-01-B_2022-04-22 shows a hydrostatic axial piston machine with a swash plate design, which has a double-acting adjusting cylinder, which is coupled to the swash plate for adjusting the stroke volume. The adjusting piston is preloaded to a zero position, in which the stroke volume is zero, by means of a return spring inside the adjusting piston of the adjusting cylinder. Adjusting screws are provided at the ends of the adjusting cylinder that are located opposite one another, by means of which the zero position can be adjusted. The springs are subject to fatigue processes, so that the zero position preset by the springs can change over time.

[0005] Since the actual position and therefore the actual displacement volume are always detected and regulated to the target value during fault-free operation, the required zero position or the required zero pressure medium volume flow can be reliably set despite the fatigue process.

[0006] The return spring is used for returning to zero, in particular in the pressure-free state, and in particular for regulating and adjusting work. In order to achieve high pivoting dynamics and a small construction space requirement, the return spring is designed with a relatively small return torque. However, this has the consequence that, at high operating pressures, a return to zero cannot be ensured in a process-reliable manner. In the event of a fault in the regulating device, a residual pressure medium volume flow may occur due to a faulty zero position. Summary of the invention

[0007] The object of the disclosure is to provide a hydrostatic axial piston machine, the regulated stroke volume of which can be regulated to zero precisely and repeatedly, in particular in the event of a failure of the regulating device.

[0008] This object is achieved by a hydrostatic axial piston machine having the feature combination of claim 1 .

[0009] The hydrostatic axial piston machine is designed in particular in the form of a swash plate and according to the disclosure has a hydraulic, in particular double-acting adjusting cylinder with an adjusting piston, in particular axially movable, on which a first adjusting piston surface and a second adjusting piston surface acting in opposition thereto are formed. Preferably, the adjusting piston surfaces are of the same size, that is, the adjusting cylinder is designed as a synchronous cylinder, which makes adjustment easier. An actuator is coupled to the adjusting piston in a movement, and the stroke volume of the axial piston machine is dependent on the position of the actuator. The actuator is in particular a swash plate, on which a hydrostatic working piston of a cylinder-piston unit of a cylinder barrel rotatably supported in the housing of the axial piston machine is slidably supported. According to the disclosure, the axial piston machine has a regulating valve that can be particularly electromagnetically controlled and manipulated, which is preferably used to adjust the position of the actuator and thus the stroke volume; according to the disclosure, the regulating valve can be controlled according to the detected actual position of the regulating piston or the actuator and according to the preferably required and detected target position of the regulating piston or the actuator using an especially electrical control signal, so that the regulating piston surface can form a throttled pressure medium connection with the regulating pressure medium source and the regulating pressure medium outlet through the regulating valve according to the control signal. In this way, the regulating piston can be manipulated on both sides of the intermediate position or zero position, in which the stroke volume of the axial piston machine and therefore especially its pressure medium volume flow are also zero. By enabling the stroke volume to pass through zero, the axial piston machine is designed in particular in a closed hydraulic circuit and in particular in an operating mode that can operate in four quadrants. According to the invention, the axial piston machine has a hydraulic auxiliary cylinder which is preferably arranged coaxially with the adjusting cylinder and / or aligned therewith, the auxiliary cylinder having an auxiliary piston which is particularly axially displaceable, the auxiliary piston having a first auxiliary piston surface which is particularly fluidically connected to a pressure medium source and acts in an actuation direction of the auxiliary piston directed toward the adjusting piston and further directed toward a first stroke limiter of the auxiliary cylinder. If the auxiliary piston is actuated toward the first stroke limiter, i.e. abuts against it, an intermediate stop for the adjusting piston is formed by the auxiliary piston, preferably by the end surface of the auxiliary piston directed toward the adjusting piston, the adjusting piston can be actuated or tensioned, particularly actuated or tensioned, toward the intermediate stop, so that the adjusting piston can be actuated or tensioned, particularly actuated or tensioned, into its intermediate position or zero position.

[0010] In this way, a hydrostatic axial piston machine with an adjusted stroke volume is achieved, whose stroke volume and therefore the pressure medium volume flow can be adjusted to zero reliably and repeatedly with high precision, especially in the event of a fault. According to the disclosure, this is achieved only by means of a fluid-mechanical method, i.e. without necessary adjustment, in that, on the one hand, the auxiliary piston is actuated in the direction of the regulating piston and is caused to collide with the first stroke limit of the auxiliary piston, and on the other hand, the regulating piston is actuated so that it collide with the auxiliary piston. In other words, according to the disclosure, the fluid-mechanical design and activation of the intermediate stop of the regulating piston are not subject to the typical disadvantages of the hydromechanical zero-position adjustment of the stroke volume, which are demonstrated, for example, in terms of hysteresis. According to the disclosure, the fluid-mechanical design and activation of the intermediate stop are advantageous in particular when the axial piston machine is used in a reliability-related manner, wherein, in particular in the event of a failure of the regulating device, it must be ensured with extremely high reliability that the pressure medium volume flow is zero.

[0011] According to an improved solution, the first auxiliary piston surface is larger than the second regulating piston surface, which acts in the actuation direction of the regulating piston toward the auxiliary piston, that is, presses the regulating piston onto the auxiliary piston. This ensures that when the same pressure is applied to the first auxiliary piston surface and the second regulating piston surface, the auxiliary piston is always in contact with the first stroke limiter and remains in contact, even when the regulating piston is pressed against the auxiliary piston. Therefore, the intermediate position or zero position of the regulating piston is ensured in an extremely simple manner.

[0012] According to a further development, the axial piston machine has a valve device, which is designed to connect the first auxiliary piston surface and the second regulating piston surface to the regulating pressure medium source and to connect the first regulating piston surface to the regulating pressure medium outlet in the event of a fault. In this way, it is ensured that the force generated at the first regulating piston surface and acting on the regulating piston in the direction away from the auxiliary piston is smaller than the force generated at the second regulating piston surface and acting on the regulating piston in the direction of the auxiliary piston.

[0013] The valve device can be formed by a regulating valve, for example by means of a valve position, or by a separate logic valve or switching valve.

[0014] In particular, fault situations are defined in which the control signal is outside the specification, outside a prescribed range, is interrupted, is a fault signal, has excessively strong or too high frequency fluctuations or there is a signal loss, so that the control fails.

[0015] According to an improved solution, the auxiliary piston has a second auxiliary piston surface, which acts in opposition to the first auxiliary piston surface. As a result, the auxiliary piston can be lifted, in particular moved in, from its first stroke limit by applying pressure medium to the second auxiliary piston surface, in particular by connecting it to a pressure medium regulating source.

[0016] In a preferred improvement, the second auxiliary piston surface acts in the actuation direction of the auxiliary piston toward the second stroke limitation of the auxiliary cylinder. In this way, the auxiliary piston can be actuated in a defined manner from a position defined by its intermediate stop into a second end position.

[0017] According to a variant according to the disclosure, the auxiliary cylinder is an auxiliary cylinder bore formed on the housing section of the axial piston machine, in which the auxiliary piston is received axially displaceably. At least the first stroke limitation and thus the intermediate stop are then fixed. The position of the intermediate stop formed by the auxiliary piston is then dependent on the manufacturing dimensions of the housing section and the auxiliary piston and cannot be adjusted.

[0018] According to an improved scheme, the first regulating piston surface and the second regulating piston surface limit separate pressure chambers or cylinder chambers. As already explained, the first regulating piston surface acts in the operating direction of the regulating piston away from the auxiliary piston. As already explained, the second regulating piston surface acts in the opposite direction to the first auxiliary piston surface and acts in the operating direction of the auxiliary piston away from the regulating piston. These pressure chambers or cylinder chambers can therefore be independently and optionally connected to a regulating pressure medium source and a regulating pressure medium outlet, so that flexibility in the operation of the regulating piston is achieved regardless of the operation of the auxiliary piston.

[0019] According to a variant according to the disclosure, the auxiliary cylinder is received in a housing section of the axial piston machine in such a way that it can be axially displaced in the actuating direction of the regulating piston. In this way, the position of the auxiliary cylinder on the axial piston machine, in particular relative to the regulating piston, is variable and the intermediate stop can be changed. The auxiliary cylinder is in particular formed by a cylinder sleeve which is received in the housing section in such a way that it can be axially displaced.

[0020] Particularly preferably, an adjusting device, in particular an adjusting screw, which is accessible from outside the housing, is provided, by means of which the position of the auxiliary cylinder can be adjusted so that at least the first stroke limitation and therefore in particular the intermediate stop is adjustable. Thus, the hydraulically actuatable intermediate stop for the adjusting piston can be adjusted precisely so that it adjusts the pressure medium volume flow of the axial piston machine to exactly zero in the intermediate position or zero position.

[0021] According to an improved solution, the first regulating piston surface and the second auxiliary piston surface are continuously fluidly connected, as mentioned, the first regulating piston surface acts in the operating direction of the regulating piston away from the auxiliary piston, as mentioned, the second auxiliary piston surface acts opposite to the first auxiliary piston surface and acts in the operating direction of the auxiliary piston away from the regulating piston. In this way, they can not be connected to the regulating pressure medium source and the regulating pressure medium outlet independently of each other. Instead, they always have the same pressure or are at least connected to the same pressure level. Therefore, the flexibility of the operating aspect of the regulating piston is limited independently of the operation of the auxiliary piston. However, the advantage obtained is that the pressure chamber is limited by the two piston surfaces in this way, and the pressure chamber makes the auxiliary piston away from the regulating piston and operated toward its second stroke limit when connected to the pressure medium source.

[0022] According to a preferred development, the regulating valve has a basic position into which it is prestressed, in particular by means of a spring, and in which the first regulating piston surface is connected to the pressure medium outlet and the second regulating piston surface is connected to the regulating pressure medium source via the regulating valve. Thus, in the event of a fault, the regulating piston can be actuated in a process-reliable manner in the direction of the auxiliary piston even without auxiliary electrical energy.

[0023] According to a preferred development, the axial piston machine further comprises a switching valve with a basic position, into which the switching valve is preloaded, in particular by means of a spring, and in which the first auxiliary piston surface is connected to a source of regulating pressure medium via the switching valve. Thus, in the event of a fault, the auxiliary piston can be actuated in a process-reliable manner in the direction of the regulating piston and the first stroke limiter even without auxiliary electrical energy, so that the intermediate stop for the regulating piston is designed to be process-reliable without auxiliary electrical energy.

[0024] According to a development, the axial piston machine has a supplementary switching valve with a basic position, which is prestressed into the basic position, in particular by means of a spring, and in which the second auxiliary piston surface is connected to the control pressure medium outlet via the supplementary switching valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 shows a hydraulic circuit diagram of a hydrostatic axial piston machine according to a first embodiment of the present disclosure;

[0026] Figure 2 A hydrostatic axial piston machine according to a first embodiment is shown in a top view;

[0027] Figure 3 The longitudinal section shows the Figure 1 and Figure 2An adjusting cylinder of the axial piston machine having an auxiliary cylinder, which is in an adjusting position close to the zero position;

[0028] Figure 4 The longitudinal section shows the Figure 3 An adjusting cylinder with an auxiliary cylinder, wherein the adjusting cylinder abuts against the left end stop;

[0029] Figure 5 The longitudinal section shows the Figure 3 and Figure 4 an adjusting cylinder which is fixed in its zero position by means of a hydraulically actuated auxiliary cylinder; and

[0030] Figure 6 An adjusting cylinder with an auxiliary cylinder of an axial piston machine according to a second exemplary embodiment is shown in a detailed longitudinal section. DETAILED DESCRIPTION

[0031] Two embodiments of the present disclosure are described below based on the relevant drawings. Regarding these embodiments, the same components are provided with the same reference numerals.

[0032] Figure 1 The hydraulic circuit diagram of a hydrostatic axial piston machine 1 according to a first embodiment of the disclosure is shown. The axial piston machine 1 is designed in a swash plate construction, has an adjustable stroke volume, and has a drive shaft 2, with which a drive device 4 is in operative connection. The drive device 4 has a cylinder barrel (not shown) which is connected to the drive shaft 2 in a rotationally fixed manner, and has a plurality of cylinder-piston units, the working pistons of which are supported in sliding on a swash plate 6, which is adjustable in terms of its pivot angle. The swash plate 6 determines the stroke of the working piston, i.e. the stroke volume of the axial piston machine 1, and thus determines the pressure medium volume flow of the axial piston machine 1 as a function of the rotation speed of the drive shaft 2 within its set pivot angle range. According to the disclosure, the pivot angle can be adjusted on both sides of the zero stroke volume, i.e. in a positive adjustment range and a negative adjustment range. In other words, the axial piston machine 1 is constructed in a "through-rotating" manner. The axial piston machine 1 has two working ports A, B and, due to its design with a “rotatable” swash plate 6 , can be operated in a closed hydraulic circuit as a hydraulic pump and as a hydraulic motor in four-quadrant operation.

[0033] In order to adjust the pivot angle of the swash plate 6 and thus the stroke volume of the axial piston machine 1, the adjusting piston 8 of the adjusting cylinder 10 is coupled to the swash plate 6. The adjusting cylinder 10 is designed as a synchronous cylinder, wherein two adjusting piston surfaces of the same size and acting in opposition to each other are formed on the adjusting piston 8: a first adjusting piston surface 12 and a second adjusting piston surface 14, which each delimit an adjusting cylinder chamber of the adjusting cylinder 10.

[0034] The adjusting cylinder 10 has an adjustable first end stop 16 and a second end stop fixed to the housing (at Figure 1 Not shown, see 74, Figures 3 to 5 ), the second regulating piston surface 14 and the first end stop portion are in contact with each other when the regulating piston 8 has the maximum positive stroke, and the radial flange of the regulating piston 8 (at Figure 1 Not shown, see 72, Figures 3 to 5 ) and the second end stop come into contact with each other at the maximum negative stroke of the adjusting piston 8. Therefore, the maximum pivot angle of the swash plate 6 and thus the maximum stroke volume of the axial piston machine 1 are defined by the first end stop 16 and the second end stop in two adjustment ranges.

[0035] The second end stop is formed by an end face fixed to the housing and with which the radial collar forms a stop.

[0036] According to the disclosure, the auxiliary cylinder 22 is provided for forming a hydraulically actuatable intermediate stop (18', see the following description) of the regulating piston 8 when necessary, in particular in the event of a fault when the regulating device fails. Figure 5 When the auxiliary piston 20 of the auxiliary cylinder 22 is actuated toward the regulating piston 8, the intermediate stop 18' (see in particular Figure 5 ) is formed by the end face 18 of the auxiliary cylinder 20 , more precisely by the end face 18 of the piston rod of the auxiliary piston 20 .

[0037] The auxiliary piston 20 has a first auxiliary piston surface 24, which acts in the direction of the displacement of the auxiliary piston 20 toward the regulating piston 8. On the piston rod side, the auxiliary piston 20 has a second auxiliary piston surface (for reasons of clarity, in the figure) which acts in opposition to the first auxiliary piston surface 24. Figure 1 ), which second auxiliary piston surface acts in the direction in which the auxiliary piston 20 moves away from the regulating piston 8.

[0038] The auxiliary cylinder 22 has a first stroke limiter 26 which can be adjusted by means of an adjusting device 25 and which limits the stroke of the auxiliary piston 20 in the direction of the regulating piston 8 when the second auxiliary piston surface comes into contact with the first stroke limiter 26. The auxiliary cylinder 22 has a second stroke limiter in the opposite direction (for reasons of clarity) Figure 1 When the first auxiliary piston surface 24 comes into contact with the second stroke limiter, the second stroke limiter limits the stroke of the auxiliary piston 20 in the direction away from the regulating piston 8. The second stroke limiter can also be adjusted by the adjusting device 25, wherein its adjustment is linked to the adjustment of the first stroke limiter 26 and thus to the adjustment of the intermediate stop.

[0039] In order to actuate the regulating piston 8 and thus to adjust the stroke volume of the axial piston machine 1, a regulating valve 28 is provided, whose first supply connection T is connected to the regulating pressure medium outlet R and whose second supply connection P is connected to the regulating pressure medium source pst. In addition, the regulating valve 28 has two working connections A, B, wherein the first working connection A is connected to the first regulating cylinder chamber bounded by the first regulating piston surface 12, and the second working connection B is connected to the second regulating cylinder chamber bounded by the second regulating piston surface 14.

[0040] The regulating valve 28 can be electromagnetically actuated and is signal-connected to a control unit 30 of the axial piston machine 1. The control unit 30 controls the electromagnet of the regulating valve 28 with a control signal Ir, which is obtained by a regulating device of the control unit 30 as a function of a control deviation between an actual signal Sist and a target signal Ssoll. The actual signal Sist represents the actual stroke of the regulating piston 8 and thus the actual stroke volume of the axial piston machine 1, wherein the actual stroke is detected by a displacement detection unit 11 of the axial piston machine 1, which reports the actual signal Sist to the control unit 30. The target signal Ssoll represents the target stroke of the regulating piston 8 and thus the target stroke volume of the axial piston machine 1.

[0041] The regulating valve 28 has a basic position 28 b preloaded by a spring 32, in which the first regulating piston surface 12 is fluidically connected to the regulating pressure medium outlet R via the first working connection A and the first supply connection T of the regulating valve 28, and in which the second regulating piston surface 14 is fluidically connected to the regulating pressure medium source pst via the second working connection B and the second supply connection P of the regulating valve 28. In the basic position 28 b, a force is thus generated on the regulating piston 8, which moves the regulating piston 8 in the direction of its maximum negative stroke in the direction of the second end stop, so that the stroke volume of the axial piston machine 1 is set in the direction of its negative maximum value.

[0042] The regulating valve 28 has an end position 28a which can be actuated by an electromagnet, in which the second regulating piston surface 14 is connected to the regulating pressure medium outlet R via the second working connection B and the first supply connection T of the regulating valve 28, and in which the first regulating piston surface 12 is connected to the regulating pressure medium source pst via the first working connection A and the second supply connection P of the regulating valve 28. In the end position 28a, a force is thus generated on the regulating piston 8, which moves the regulating piston 8 in the direction of its maximum positive stroke in the direction of the first end stop 16, so that the stroke volume of the axial piston machine 1 is set in the direction of its positive maximum value.

[0043] Between the basic position 28b and the end position 28a, the regulating valve 28 occupies the regulating position 28c according to the control signal Ir, the electromagnetic force generated thereby and the reaction spring force of the spring 32, in which the two regulating cylinder chambers are in a throttling pressure medium connection with the regulating pressure medium outlet R and the regulating pressure medium source pst, respectively.

[0044] According to the disclosure, the auxiliary cylinder 22 has the following function: forming an intermediate stop for the regulating piston 8, which can be hydraulically operated and can be activated repeatedly and accurately in the event of a fault. When the first auxiliary piston surface 24 is connected to the pressure medium of the regulating pressure medium source pst, the auxiliary piston 20 is operated in the direction of the regulating piston 8 until it forms abutment with the first stroke limiter 26 with its second auxiliary piston surface and stops its movement. In this state, the end face 18 of the piston rod of the auxiliary piston 20 engages with the regulating piston 8 and thus limits its stroke, or forms an intermediate stop (see in particular 18', Figure 5 ).

[0045] The last-mentioned pressure medium connection of the first auxiliary piston surface 24 must not be permanent, but must be controlled or switched, otherwise the intermediate stop is permanently activated. For this purpose, the axial piston machine 1 has an electromagnetically actuated 3 / 2-way valve 34, which has an electromagnetically actuated switching position 34a, in which the first auxiliary piston surface 24 is connected to the regulating pressure medium outlet R, i.e., pressure relief, and a basic position 34b preloaded by a spring 33, and in which the first auxiliary piston surface 24 is connected to the regulating pressure medium source pst, i.e., pressure loading. In a proper, fault-free operation, the electromagnet of the switching valve 34 is actuated by the control signal Is used by the control unit 30.

[0046] For the basic positions 28b and 34b, the first auxiliary piston surface 24 and the second control piston surface 14 are connected to the control pressure medium source pst, and the first control piston surface 12 and the second auxiliary piston surface that reacts against the first auxiliary piston surface 24 are connected to the control pressure medium outlet R. This causes the auxiliary piston 20 to move out toward the control piston 8 and the control piston 8 to move to the left in the direction of the auxiliary piston 20. Figure 1 The end face 18 of the piston rod is an intermediate stop (18', see Figure 5 ), the regulating piston 8 can be actuated towards this intermediate stop. Here, the first auxiliary piston surface 24 is larger than the second regulating piston surface 14, thereby ensuring that the regulating piston 8 is reliably actuated towards its intermediate position or zero position.

[0047] Figure 2 The top view shows the Figure 1An axial piston machine 1 is provided, which has a housing 36, from which the drive shaft 2 protrudes at the front. The housing 34 has an approximately square housing section 36 on the upper side, which extends with a longitudinal axis 38 at a right angle to the rotation axis 40 of the drive shaft 2. The above-described regulating piston is accommodated in the housing section 36. Figures 3 to 5 36. Figure 2 An auxiliary cylinder housing 42 is installed on the left side in which an auxiliary piston ( Figure 1 and Figures 3 to 5 20 of them; Figure 6 120 in). Except for the adjusting cylinder and the auxiliary cylinder, a detailed description of the housing 34 and the remaining components of the axial piston machine 1 is omitted here, because they are sufficiently known in the prior art.

[0048] according to Figure 3 , reference Figure 1 The design structure and interaction of the regulating piston 10 and the auxiliary piston 22 according to the first embodiment are described. Figure 3 The regulating piston 8 is shown in its regulating position close to its middle position or zero position. Figure 4 The adjusting piston 8 is shown against its fixed part on the housing. Figure 4 The left end stop is at the second end stop, ie, it has its maximum possible negative travel. Figure 5 The control piston 8 is shown being actuated into its center position or zero position by means of the auxiliary cylinder 22 .

[0049] according to Figure 3 The housing section 36 has a cylinder bore 44 extending coaxially with the longitudinal axis 38 and closed on one side by the auxiliary cylinder housing 42 and on the opposite side by an end cap 46. The auxiliary cylinder housing 42 and the end cap 46 extend into the cylinder bore 44 in sections with corresponding guide necks, wherein the regulating piston 8 is guided in an axially displaceable manner with corresponding end sections in the associated guide necks.

[0050] The first control cylinder chamber 48 is delimited in sections by the first control piston surface 12 and the inner circumference of the guide neck of the auxiliary cylinder housing 42, and the second control cylinder chamber 50 is delimited in sections by the second control piston surface 14 and the inner circumference of the guide neck of the end cap 46. The first control cylinder chamber 48 is in a continuous pressure medium connection with the first working connection A of the control valve 28, and the second control cylinder chamber 50 is in a continuous pressure medium connection with the second working connection B of the control valve 28 (see accordingly). Figure 1 ).

[0051] The auxiliary cylinder housing 42 has a continuous stepped bore, the radially tapering section of which forms the inner circumference of the aforementioned guide neck, on which an end section of the regulating piston 8 with the first regulating piston surface 12 at the end side is guided.

[0052] An auxiliary cylinder sleeve 54 of the auxiliary cylinder 22 is accommodated in an axially displaceable manner in the radially widened section 52 of the stepped bore. The auxiliary piston 20 is in turn accommodated in the auxiliary cylinder sleeve 54 in an axially displaceable manner.

[0053] The auxiliary piston 20 has a piston rod 56 which penetrates the auxiliary cylinder bottom forming the first stroke limiter 26 and enters the first adjustment cylinder chamber 48. Therefore, the end face 18 of the piston rod 56 in the first adjustment cylinder chamber 48 points toward the first adjustment piston surface 12.

[0054] The auxiliary cylinder casing 54 is closed at the rear by an auxiliary cylinder cover 58 .

[0055] In the illustrated, non-actuated position of the auxiliary piston 20 , the first auxiliary piston surface 24 abuts against the inner side of the auxiliary cylinder cover. Figure 3 The auxiliary piston 20 moves in until it touches the auxiliary cylinder cover 58.

[0056] The adjusting screw 60 of the adjusting device 25 abuts against the outer side of the auxiliary cylinder cover 58. By operating this rotatable adjusting screw 60, the auxiliary cylinder 22 can be positioned as a whole, that is, together with the auxiliary cylinder cover 58, the auxiliary cylinder sleeve 52 and the auxiliary piston 20 arranged therein, and the first stroke limiter 26 formed on the auxiliary cylinder sleeve 52, so that the intermediate stop described above can be adjusted when the adjusting piston 20 is operated (see 18 ', Figure 5 ).

[0057] In order to actuate the auxiliary piston 20 by pressure medium loading of the first auxiliary piston surface 24, the auxiliary cylinder sleeve 54 has a radial bore 62 approximately at the level of the inner side of the auxiliary cylinder cover 58, which radial bore overlaps with an inner circumferential groove 70 of the auxiliary cylinder housing 42 regardless of the setting position of the auxiliary cylinder sleeve 54. In the illustrated embodiment, the inner circumferential groove 70 has a width in the adjustment direction of the auxiliary cylinder sleeve 54 that corresponds approximately to 2.5 times the diameter of the radial bore 62. The radial bore 64 that penetrates the auxiliary cylinder housing 42 opens into the inner circumferential groove 70 from the radial outside.

[0058] Reference Figure 1 It is shown that the radial bore 64 is connected to a working port of the switching valve 34 which connects the first auxiliary piston surface 24 either to the control pressure medium source pst or to the control pressure medium outlet in the manner described above, depending on the control signal Is.

[0059] exist Figure 3and Figure 4 In the state shown in , the switching valve 34 is controlled by the control signal Is and actuated into the switching position 34 a and the first auxiliary piston surface 24 is thus relieved of pressure. The regulating valve 28 is active and is acted upon by the control unit 30 with the control signal Ir.

[0060] As stated, Figure 3 The regulating piston 8 is shown in its regulated zero position region. The regulating valve thus assumes its regulating position 28c.

[0061] In contrast, Figure 4 The regulating piston 8 is shown in its maximum possible left position, i.e. with its maximum negative stroke, wherein the radial flange 72 in the middle of the regulating piston 8 abuts against a second end stop 74 fixed to the housing. The second end stop 74 is formed by the end face of the guide neck of the auxiliary cylinder housing 42. This maximum negative stroke is achieved in that the regulating valve 28 is actuated by means of the control signal Ir and under the elastic force of the spring 32 into its basic position 28b, in which the first regulating cylinder chamber 48 is connected to the regulating pressure medium outlet R and the second regulating cylinder chamber 50 is connected to the regulating pressure medium source pst. Here, a minimum residual gap still remains between the first regulating piston face 12 and the end face 18 of the piston rod 56.

[0062] therefore, Figure 3 and Figure 4 The control piston 8 is shown in a correct, fault-free operation of the axial piston machine 1 and therefore in a control mode of the control unit 30. In this respect, the control unit 30 applies a control signal Ir to the control valve 28, so that the pressure conditions at the control piston 8 are regulated via the control valve 28 and the control piston 8 accordingly maintains or adjusts the stroke volume of the axial piston machine 1. The switching valve 34 is continuously actuated with the control signal Is, so that the first auxiliary piston surface 24 is relieved of pressure and the auxiliary piston 20 is moved in.

[0063] according to Figures 3 to 5 Reference Figure 1 In the illustrated embodiment, the bottom of the auxiliary cylinder sleeve 54 forming the first stroke limiter 26 has a through-cut 68, through which the first control piston surface 12 and the second auxiliary piston surface 66 mentioned above are continuously connected to the pressure medium. Figure 3 and Figure 4As shown in the figure, if the regulating pressure pst acts on the first working interface A of the regulating valve 28, then the regulating pressure not only acts on the first regulating piston surface 12 of the end surface 18 of the driving regulating piston 8 away from the auxiliary piston rod 56, but also always acts on the second auxiliary piston surface 66 of the driving auxiliary piston 20 away from the regulating piston 8 and forming a stop with the inner side of the auxiliary cylinder cover 58 through the through-recessed portion 68.

[0064] Figure 5 In particular, a fault situation is shown in which the control unit 30 fails so that the control signals Ir and Is are missing. Here, some reference numerals are omitted for reasons of clarity. Figure 5 The components shown in Figure 3 and Figure 4 Those parts shown are the same.

[0065] For the fault situation it is assumed that neither the regulating valve 28 nor the switching valve 34 is energized and therefore the control signals Ir and Ir are missing or have signal values ​​that are specified as faults. Figure 1 In its basic position 28b or 34b. Accordingly, via the basic position 28b, the first working connection A of the control valve 28 is connected to the control pressure medium outlet R, and the second working connection B of the control valve 28 is connected to the control pressure medium source pst. Figure 1 ), the radial hole 64 of the auxiliary cylinder housing 42 (see Figure 1 and Figures 3 to 5 ) is connected to the regulating pressure medium source pst. Figure 5 , the auxiliary piston 20 is completely moved out and abuts against its first stroke limiter 26, and the regulating piston 8 moves toward the auxiliary piston 20, Figure 5 Since the first auxiliary piston surface 24 is larger than the second regulating piston surface 14 acting against it and since the two surfaces 14, 24 are subject to the same regulating pressure pst, it is ensured that the regulating piston 20 remains in contact with the first stroke limiter 26, while the regulating piston 8 is tensioned towards the intermediate stop 18' formed by the regulating piston 20.

[0066] according to Figure 5 The intermediate position or zero position of the regulating piston 8 shown in the figure indicates that the intermediate position or zero position of the regulating piston 8 can be adjusted by means of the adjusting screw 60 of the adjusting device 25, wherein the adjusting screw 60 is adjusted until a pressure medium volume flow of zero can be observed or measured. Then, the adjusting screw 60 is reversed (kontern) and the intermediate position or zero position of the regulating piston 8 is set and can be reproduced repeatedly, precisely and reliably, especially in the event of a fault.

[0067] Figure 6 A second exemplary embodiment of an axial piston machine 101 is shown in a highly schematic, simplified illustration, with the already known control cylinder 10 and control piston 8, but with an auxiliary cylinder 122 and an auxiliary piston 120 which are designed and controlled in a different manner. Figures 1 to 5 In the first embodiment, the auxiliary cylinder 122 cannot be adjusted in its position, and the auxiliary piston 120 is not received in an auxiliary cylinder sleeve that can be axially displaced, but is directly received in an auxiliary cylinder bore 152 that is constructed in the auxiliary cylinder housing 142. Therefore, the first stroke limiter 126 is not adjustable, but fixed and is only related to the manufacturing dimensions. Therefore, when the auxiliary piston 120 is moved out, the intermediate stop 118' formed by its end face 118 is also only related to the manufacturing dimensions and cannot be changed. In addition, unlike the first embodiment, the first regulating piston surface 12 and the second auxiliary piston surface 166 both limit separate pressure chambers 48 or 148 respectively and can therefore be loaded with pressure medium and pressure-unloaded independently of each other. In order to provide an independently controllable pressure medium supply to them, the switching valve 34 described above is provided and a supplementary switching valve 134 is also provided.

[0068] List of reference numerals:

[0069] 1;101 Axial piston machine

[0070] 2 Drive shaft

[0071] 4 Drive device

[0072] 6 Swash plate

[0073] 8 Adjusting piston

[0074] 10 Adjustment cylinder

[0075] 11 Displacement detection unit

[0076] 12 First regulating piston surface

[0077] 14 Second regulating piston surface

[0078] 16 First end stop

[0079] 18; 118 end face

[0080] 18'; 118' Intermediate stop

[0081] 20; 120 Auxiliary piston

[0082] 22; 122 Auxiliary cylinder

[0083] 24;124 First auxiliary piston surface

[0084] 25 Adjustment device

[0085] 26; 126 First stroke limiter

[0086] 28 Control valve

[0087] 28a End position

[0088] 28b Adjustment position

[0089] 28c Basic Position

[0090] 30 Control unit

[0091] 32 Spring

[0092] 33 Spring

[0093] 34; 134 Directional valve

[0094] 34a; 134a Switch position

[0095] 34b; 134b Basic position

[0096] 36 Shell section

[0097] 38 Cylinder - longitudinal axis

[0098] 40 Rotation axis

[0099] 42 Auxiliary cylinder housing

[0100] 44 Adjustment cylinder bore

[0101] 46 End cap

[0102] 48 First adjustment cylinder chamber

[0103] 148 Second auxiliary cylinder chamber

[0104] 50 First adjustment cylinder chamber

[0105] 52; 152 Auxiliary cylinder hole

[0106] 54 Auxiliary cylinder sleeve

[0107] 56 Piston rod

[0108] 58; 158 Auxiliary cylinder head

[0109] 60 Adjustment thread

[0110] 62 Radial holes

[0111] 64 Radial holes

[0112] 66; 166 Second auxiliary piston surface

[0113] 68 Through-hole section

[0114] 70 slots

[0115] 72 Radial flange

[0116] 74 second end stop

[0117] A, B working interface

[0118] P Adjustment pressure medium connection

[0119] T Tank, tank interface

[0120] R Regulating pressure medium outlet

[0121] Pst regulates the pressure medium source

[0122] Ssoll target value

[0123] Sist actual value

[0124] Ir control valve control signal

[0125] Is Reversing valve control signal

Claims

1. A hydrostatic axial piston machine (1; 101), comprising: a hydraulic control cylinder (10), the control cylinder having a control piston (8), on which a first control piston surface (12) and a second control piston surface (14) acting in opposition to the first control piston surface are formed; and an actuator (10) which is coupled to the control piston (8) in a displacement manner, the stroke volume of the axial piston machine (1; 101) being dependent on the position of the actuator; and a control valve (28) which can be controlled by means of a control signal (Ir) in accordance with a detected actual position (Sist) and a target position (Ssoll) of the control piston (8) or of the actuator, so that the control piston surface (12, 14) can be connected to a control pressure medium source (pst) and a control pressure medium outlet (R) via the control valve (28) in accordance with the control signal (Ir), thereby enabling the control piston (8) to be actuated on both sides of an intermediate position or a zero position at which the stroke volume is zero, characterized in that The axial piston machine (1; 101) has a hydraulic auxiliary cylinder (22; 122), which has an auxiliary piston (20; 120), which has a first auxiliary piston surface (24; 124), which acts on a first stroke limiter (26; 126) of the auxiliary cylinder (22; 122) in the actuation direction of the auxiliary piston (20; 120) toward the regulating piston (8), and an intermediate stop (18') is formed by the auxiliary piston (20; 120) actuated toward the first stroke limiter (26; 126). 118'), the regulating piston (8) can be actuated towards the intermediate stop into its center position or zero position.

2. The axial piston machine (1; 101) according to claim 1, characterized in that The first auxiliary piston surface (24; 124) is larger than the second regulating piston surface (14), which acts in an actuating direction of the regulating piston (8) towards the auxiliary piston (20; 120).

3. The axial piston machine (1; 101) according to claim 1 or 2, characterized in that The axial piston machine (1; 101) has a valve device (28, 34; 28, 34, 134), through which, in the event of a fault, the first auxiliary piston surface (24; 124) and the second regulating piston surface (14) acting in the actuating direction of the regulating piston (8) toward the auxiliary piston (20; 120) are connected to the regulating pressure medium source (pst), and the first regulating piston surface (12) is connected to the regulating pressure medium outlet (R).

4. An axial piston machine (1; 101) according to any one of the preceding claims, characterized in that The auxiliary piston (20; 120) has a second auxiliary piston surface (66; 166), which acts in opposition to the first auxiliary piston surface (24; 124) and acts in the actuation direction of a second stroke limitation of the auxiliary piston (20; 120) toward the auxiliary cylinder (22; 122).

5. The axial piston machine (101) according to any one of the preceding claims, characterized in that The auxiliary cylinder (122) is formed by an auxiliary cylinder bore (152) which is formed on a housing section (142) of the axial piston machine (101), so that at least the first stroke limitation (126) and therefore in particular the intermediate stop (118') are fixed.

6. An axial piston machine (101) according to any one of the preceding claims, characterized in that A first regulating piston surface (12) acting in an actuating direction of the regulating piston (8) away from an auxiliary piston (120) and a second auxiliary piston surface (166) acting in opposition to the first auxiliary piston surface (124) each delimit separate pressure chambers (48, 148).

7. An axial piston machine (1) according to any one of claims 1 to 4, characterized in that The auxiliary cylinder (22) is received in a housing section (42) of the axial piston machine (1) in a manner that allows it to be moved in the actuating direction of the regulating piston (8), and the position of the auxiliary cylinder (22) in the housing section (42) can be adjusted by means of an adjusting device (25) of the axial piston machine (1), so that at least the first stroke limiting portion (26) is adjustable and therefore in particular the intermediate stop portion (18') is adjustable.

8. Axial piston machine (1) according to any one of the preceding claims 1 to 4 or according to claim 7, characterized in that A first regulating piston surface (12) acting in an actuating direction of the regulating piston (8) away from an auxiliary piston (20) and a second auxiliary piston surface (66) acting in opposition to the first auxiliary piston surface (24) are continuously fluidically connected. The second auxiliary piston surface acts in an actuating direction of the auxiliary piston (20) away from the regulating piston (8).

9. An axial piston machine (1; 101) according to any one of the preceding claims, characterised in that The regulating valve (28) has a basic position (28b), into which it is preloaded, in particular, by means of a spring (32), and in which the first regulating piston surface (12) is connected to a pressure medium outlet (R) and the second regulating piston surface (14) is connected to a regulating pressure medium source (pst) via the regulating valve (28).

10. An axial piston machine (1; 101) according to any one of the preceding claims, characterised in that The axial piston machine (1; 101) has a switching valve (34) having a basic position (34b), the switching valve being preloaded into the basic position in particular by means of a spring (33), and in the basic position the first auxiliary piston surface (24; 124) is connected to the regulating pressure medium source (pst) via the switching valve (34).

11. The axial piston machine (101) according to claim 10, characterized in that The axial piston machine (101) has a supplementary switching valve (134) having a basic position (134b), the supplementary switching valve being preloaded into the basic position in particular by means of a spring (33), and in the basic position the second auxiliary piston surface (166) is connected to the regulating pressure medium outlet (R) via the supplementary switching valve (134).

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