Adjustment of an axial piston machine via reversing valves with switchable relief

Abstract

The present invention teaches an axial piston machine with a housing, a cylindrical drum rotatable about an axis of rotation, and a pivoting cradle. A first and a second tap opening are arranged in the region of the first and second control gaps, respectively. The first tap opening can be connected to a pressure fluid sink (19) or a pressure fluid source (18) via a first throttle (27, 28, 37, 38), and the second tap opening via a second throttle (27, 28, 37, 38). A position controller (32) is provided, which adjusts the actual value to a predetermined setpoint by adjusting the first and / or the second throttle (27, 28, 37, 38). According to the invention, the pivoting cradle (6) is supported on the housing via at least one hydrostatic relief pocket (4), wherein at least one adjustable third throttle (1A to 1G) is provided, via which at least one associated relief pocket can be connected to a pressure fluid source. Furthermore, the third throttle (1A to 1G) is adjustable by the position controller (32) such that it is at least temporarily open when the actual value deviates from the target value by more than a predetermined threshold, and such that the third throttle (1A to 1G) limits pressure build-up in the relief pocket (4A to 4G) when the actual value deviates from the target value by less than the predetermined threshold. Furthermore, the invention also teaches a method for using the axial piston machine.

Description

Technical field

[0001] The present disclosure relates to a novel adjustment mechanism for an axial piston machine. Axial piston machines, in particular positive displacement pumps that convey fluid via a rotary drive, and conversely, working machines that drive a shaft based on pressure reduction, are generally known. In such machines, the working stroke of the piston, and thus the delivery volume, can be changed by means of a so-called pivoting cradle, which determines the working stroke by being adjusted relative to a plane perpendicular to the axis of rotation. This adjustment of the pivoting cradle is therefore referred to below as the "adjustment of the axial piston machine".

[0002] Such pivoting cradles are preferably adjusted by building up fluid pressure in a control kidney between the bearing and the pivoting cradle. This allows the pivoting cradle to slide more easily on its bearing and thus be adjusted relatively easily. An example of such an arrangement can be found in US 5,554,007 A1 or its related patent DE 19,538,494 A1, which is currently considered the closest prior art.

[0003] Further developments of this idea can also be found in US 11 946 462 A1, DE 10 2022 107 860 A1, and DE 10 2016 214 422 A1. The latter, for example, discloses a pivoting cradle on whose sliding surface working pistons are supported. The pivoting cradle is mounted on a housing-fixed sliding bearing so that it can pivot about a pivot axis for adjusting the displacement volume. This pivot axis is typically perpendicular to the axis of rotation of the axial piston engine. A hydrostatic pressure relief field is formed between the sliding bearing and the pivoting cradle. This pressure field is maintained by fluid that is introduced into control kidneys and can exit at control pockets as soon as it reaches them. On its way from the control kidneys to the control pockets, the fluid reduces friction between the sliding bearing and the pivoting cradle.

[0004] As long as the control kidneys are continuously supplied with suitable pressures via reversing valves, a pivoting torque can be generated that holds the pivoting cradle in the desired position by adjusting the center of force.

[0005] This type of adjustment requires appropriate sensors for the controlled variables (e.g., swivel angle sensor, pressure sensor, depending on the control strategy), whose actual values ​​are fed into a control system stored on a control unit. The control is then carried out electronically via the control unit, which actuates the reversing valves.

[0006] One disadvantage of this type of adjustability is the susceptibility to disturbances that must be regulated at high frequencies, because the low friction desired for adjustment also leads to increased sensitivity to corresponding disturbances.

[0007] Therefore, it is an object of the present invention to eliminate or at least mitigate this disadvantage. This object is achieved by the features specified in claim 1 and in method claim 10. Advantageous further developments are the subject of the dependent claims.

[0008] According to the invention, an axial piston machine is provided with a housing and a cylindrical drum rotatable with respect to an axis of rotation. Several pistons are linearly movable within the drum, each forming a cylinder chamber together with the drum. The cylindrical drum has a sealing surface oriented towards the axis of rotation. Each cylinder chamber opens at the sealing surface of the cylindrical drum via a terminal opening. The sealing surface abuts a counter-sealing surface, which is stationary relative to the housing. A first and a second control element are arranged in the counter-sealing surface such that, during rotation of the cylindrical drum, the respective terminal openings can be brought into fluid exchange with either the first or the second control element. The first and second control elements are spaced apart circumferentially with respect to the axis of rotation by means of a first and a second control gap.The pistons are supported on their side facing away from the respective cylinder chamber by a pivoting cradle. The pivoting cradle is pivotable about a pivot axis. The pivot axis is preferably oriented perpendicular to the axis of rotation. The first and second control orifices are arranged in alignment along a transverse axis on opposite sides of the axis of rotation. The transverse axis is perpendicular to the axis of rotation and preferably perpendicular to the pivot axis. A first and a second tap opening are arranged in the region of the first and second control orifices, respectively. The first tap opening can be connected to a pressure fluid sink (low pressure cardioid) or a pressure fluid source (high pressure cardioid) via a first throttle, and the second tap opening can be connected to a pressure fluid sink (low pressure cardioid) or a pressure fluid source (high pressure cardioid) via a second throttle. The axial piston machine includes at least one sensor with which an actual value can be measured.A position controller is provided which, by adjusting the first and / or the second throttle, regulates the actual value to a predetermined target value.

[0009] According to the invention, the pivoting cradle is also supported on the housing via at least one hydrostatic relief pocket. At least one adjustable third throttle is provided, through which at least one associated relief pocket can be connected to a pressure fluid source (e.g., high pressure). The third throttle is adjustable by the positioner such that it is at least temporarily open when the actual value deviates from the target value by more than a predetermined threshold. The third throttle limits pressure build-up in the relief pocket when the actual value deviates from the target value by less than the predetermined threshold.

[0010] If the third throttle restricts pressure build-up in the relief pocket—in other words, if the third throttle is essentially closed because the actual value (approximately) corresponds to the setpoint—then the slewing cradle is largely in contact with the housing. This limits unwanted adjustment of the slewing cradle by disturbances, thus increasing control stability. Furthermore, there are no, or at least significantly reduced, leakage losses via the relief pockets as long as the slewing angle does not need to be changed, thus increasing efficiency. If the deviation is large, opening the third throttle reduces friction, so that essentially comparable effects regarding reduced friction can be achieved during the adjustment process as in the prior art.

[0011] In a preferred embodiment, the sensor is a swivel angle sensor, with which the swivel angle of the swivel cradle relative to the swivel axis can be measured as a measured value. Alternatively, the sensor is a pressure sensor, with which the higher pressure resulting from the pressure at the first control kidney and the pressure at the second control kidney can be measured as a measured value. Another alternative would be a speed sensor and / or a torque sensor, with which the rotational speed and / or torque of the axial piston machine can be measured as a measured value. Furthermore, several different (or even identical) sensors can be used simultaneously.

[0012] As discussed above, various sensors can be used to detect deviations between the target and actual states. Examples include measuring the swivel angle, measuring the pressures in the control valves, and measuring the rotational speed of the axial piston engine. Furthermore, a combination of such sensors can be used to increase measurement accuracy, provide fail-safe operation, or select a suitable sensor for different conditions.

[0013] In a preferred embodiment of the axial piston machine, the pivot axis and the rotary axis intersect. While it is generally possible for the pivot and rotary axes to be skew to each other, intersecting the rotary and pivot axes facilitates an approximately symmetrical design of the axial piston machine.

[0014] Preferably, the pressure fluid source is formed by the first control kidney and the pressure fluid sink by the second control kidney. Conversely, one of, for example, two control kidneys can also be defined as the "first" control kidney by being connected to the pressure fluid source.

[0015] In a further embodiment, the axial piston machine is also connected to a fourth and a fifth throttle valve for the pressure fluid source. This allows the reduction of the actuating force and friction, as well as the generation of a torque about the pivot axis, to be even more precisely tailored to the identified requirements, in particular the results of the sensor evaluations.

[0016] In a further embodiment, the axial piston machine is also connected to a sixth and a seventh throttle valve for the pressure fluid sink. With such an arrangement, not only the supply but also the discharge of the fluid to the pressure fluid sink can be precisely controlled. Consequently, a smoother "engagement" of the pivot cradle in the bearing is enabled when the pressure is released.

[0017] Finally, the invention also discloses a method for using the swivel cradle according to the invention. Brief description of the characters Fig. Figure 1 is a representation illustrating a system setup according to the known state of the art from the aforementioned US 5 554 007 A1; Fig. Figure 2 is a representation illustrating an example of a control system for the pivoting cradle according to the invention; and Fig. 3 is a representation similar to that of the Fig. 2, in which, in a further embodiment, several chokes are used. Description of the exemplary implementations

[0018] An embodiment of the present disclosure is described below on the basis of the accompanying figures.

[0019] First, the state of the art is used as a basis for analysis according to the Fig. Figure 1 outlines the basic concept of friction reduction and torque generation for the pivoting cradle. As can be seen in the figure, four 2 / 2-way valves 27, 28, 37, and 38 are provided, which establish or interrupt a connection between control valves 18, 19 and control pockets 21, 22 arranged between the control valves 18, 19. The valves 27, 28, 37, and 38 are controlled by a controller 32, which receives signals from various sensors 33, 24, 36, and 41, and a command signal generator 29. The valves 27, 28, 37, and 38 in this illustration are shown as exemplary electrohydraulic valves. Pistons (not shown) are movable up and down in piston bores that terminate in (dashed lines) openings 13. The pistons are moved up and down by rotating them relative to a (not shown) swivel plate. In doing so, they take in fluid from the control kidneys and control pockets 18 to 22 and discharge it there as well.

[0020] The pump's flow rate is determined by both the tilt angle of the swivel plate, detected by an angle sensor 33, and the rotational speed of a cylindrical drum with piston bores 13. If the pump is driven by a variable-speed power source, such as an internal combustion engine, a speed signal comparable to or corresponding to the rotational speed of the cylindrical drum is output by a speed sensor 36 and processed by the controller 32, so that both the angle signal and the speed signal can be used to determine when the desired or target flow rate is reached.

[0021] In another operating mode, the operating parameter is a predetermined pressure level in the control valve 19. The controller processes the command signal described above, as well as the sensor data, to tilt the swivel plate in the desired direction. The controller processes the pressure signal to determine when the swivel plate reaches an angle at which the pressure in the control valve 18 and / or 19 matches the set pressure, and then modifies the control signals to the valves 27, 28, 37, and 38 to modulate the flow rate through these valves. This holds the swivel plate at the desired angle.

[0022] The control unit processes the command signal from the command signal generator 29 and initially outputs suitable control signals to the valves 27 and 28 to control the fluid flow from the control pocket 21 to the control kidney 18 and from the control kidney 19 to the control pocket 22, thereby controlling the pressure in the control pockets. This modifies the torque applied to the pivot plate by the pressure fluid acting on the piston, causing the pivot plate to tilt in the desired direction. This tilt occurs when the pivot plate is also tilted in a first direction with respect to its position without displacement, where the passage 18 is the inlet passage and the passage 19 is the outlet passage. In this state, the valves 27 and 28 control the pivot and tilt angles of the pivot plate.

[0023] However, if the pivoting plate is tilted in the second direction relative to the position without displacement, where the control kidney 19 is the inlet and the control kidney 18 is the outlet, the valves 37 and 38 are used in combination to control the tilt angle of the pivoting plate. More precisely, valve 37 controls the flow of fluid between the control pocket 21 and the control kidney 19 to control the pressure in the control pocket 21, while valve 38 controls the flow of fluid between the control kidney 18 and the control pocket 22 to control the pressure in the control pocket 22. The highest pressure in the control kidneys 18 and 19 is transmitted to the pressure detector 34 via a resolver 41.

[0024] Thus, according to this state of the art, the inclination of the swivel plate is always regulated by means of suitable pressure via the valves, by reducing friction and generating a torque for the swivel cradle as explained above.

[0025] As from the Fig. As can be seen in Figure 2, according to the invention, a valve 1 is provided in a connection 2 between a pressure source 3 and a relief pocket 4 in the bearing 5 of the pivoting cradle 6. The pivoting cradle 6 corresponds to the pivot plate from the prior art described above. If a change in the pivot angle is desired by the control system, the valve 1 can be opened and thus the pressure source 3 can be activated to perform the relief. In this way, the frictional torque in the bearing 5 of the pivoting cradle is significantly reduced. The required actuating force is reduced. Essentially, this results in a situation already known from the prior art; the valve 1 of the invention is installed in such a way that it controls the fluid supply to the valves 27, 28 and 37, 38 from the prior art (not shown here), which are provided in the connection 2 of the invention.These valves operate similarly to those in the prior art, which is why they are omitted for the purpose of illustrating the present invention.

[0026] In the Fig. In the sectional view, the end pieces of two pistons of the drive unit are indicated to the right of the pivoting cradle 6. These pistons slide on a surface 6A of the pivoting cradle 6 when driven by a drive unit (not shown) to rotate around the axis 7 of the axial piston pump (as an example of an axial piston machine) (or, as an axial piston drive, to drive a corresponding shaft due to pressure differences). At the pivot angle of approximately "zero" shown for the pivoting cradle 6, the axial piston machine is idling, and consequently, the pump is not delivering any hydraulic fluid.

[0027] If the control point, i.e., a pivot angle of the pivoting cradle 6, is to be maintained, the connection to the pressure source 3 is interrupted according to the invention. As a result, the pivoting cradle 6 rests on a pivot bearing 7 because it is no longer relieved of the load, but still experiences the force acting on it from the axial pistons, and the frictional torque becomes high. In this way, external disturbances can only very difficult to disturb the system.

[0028] Fig. Figure 3 schematically shows another embodiment with several valves 1A to 1G, shown here as throttle valves, and several relief pockets 4A to 4G. In the following, when no valve or relief pocket is to be specifically designated, the terms "the valve" 1 and "the relief pocket 4" are used generally. Each relief pocket 4 is assigned a corresponding valve 1, and thus each relief pocket 4 can be pressurized with fluid separately. This allows for more precise control of the frictional force distribution by applying varying degrees of pressure or lifting to a support surface 6B of the pivoting cradle 6 at different points using the hydraulic fluid in the relief pockets 4A to 4G. Furthermore, the pivot angle α of the pivoting cradle 6 can be influenced by correspondingly different pressures, which generate a tilting moment of the pivoting cradle 6, as indicated by an arrow.

[0029] Although the figures generally show simplified directional control valves 1, the present invention is not limited to these. The connection between the pressure source 3 and the relief pocket 4 can be established and interrupted, for example, via proportional valves or as shown in Fig. 3 shown by means of throttles. The valves 1 are therefore referred to as "throttles 1" in the claims. The essential feature of the invention is that, in contrast to the prior art, the fluid supply is interrupted when the pivoting cradle is in a desired position, so that it remains in the desired position with frictional support and less control effort. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 5 554 007 A1 [0002, 0017] DE 19 538 494 A1

[0002] US 11 946 462 A1

[0003] DE 10 2022 107 860 A1

[0003] DE 10 2016 214 422 A1

[0003]

Claims

[1] Axial piston machine with a housing and a cylinder drum rotatable with respect to an axis of rotation (7), in which several pistons are each linearly movable in such a way that they each together with the cylinder drum define a cylinder space in the cylinder drum, wherein the cylinder drum has a sealing surface pointing in the direction of the axis of rotation, wherein each cylinder chamber opens with a mouth opening (13) at the sealing surface of the cylinder drum, wherein the sealing surface rests against a counter-sealing surface which is stationary with respect to the housing, wherein at least a first and a second control kidney (18, 19) are arranged in the counter-sealing surface such that the respective outlet openings (13) can be brought into fluid exchange contact with the first or with the second control kidney (18, 19) alternately when the cylinder drum is rotated, wherein the first and the second control kidney (18, 19) are spaced apart from each other in the circumferential direction with respect to the axis of rotation by a first and a second control gap, wherein the pistons are supported on a pivot cradle (6) on the side facing away from the respective cylinder chamber, wherein the pivoting cradle (6) is pivotable with respect to a pivoting axis, wherein the pivoting axis is preferably aligned perpendicular to the axis of rotation, wherein the first and the second control gap are arranged in the direction of a transverse axis in an alignment on opposite sides of the axis of rotation (7), wherein the transverse axis is oriented perpendicular to the axis of rotation (7) and preferably perpendicular to the pivot axis, wherein in the area of ​​the first and second control gap a first and a second tap opening (21, 22) is arranged, wherein the first tap opening (21) can be connected to a pressure fluid sink (19) or a pressure fluid source (18) via a first and the second tap opening (22) via a second throttle (27, 28, 37, 38), wherein at least one sensor (29, 33, 34, 36, 41) is provided with which an actual value can be measured, wherein a position controller (32) is provided which adjusts the actual value to a predetermined target value by adjusting the first and / or the second throttle (27, 28, 37, 38), characterized by , that the pivoting cradle (6) is supported on the housing via at least one hydrostatic relief pocket (4), wherein at least one adjustable third throttle (1; 1A to 1G) is provided, via which at least one associated relief pocket (4A to 4G) can be connected to a pressure fluid source (3), that the third throttle (1; 1A to 1G) is adjustable by the positioner (32) such that it is at least temporarily open when the actual value deviates from the target value by more than a predetermined threshold value, and that the third throttle (1; 1A to 1G) limits pressure build-up in the relief pocket (4A to 4G) if the actual size deviates from the target size by less than the specified threshold. [2] Axial piston machine according to claim 1, wherein the sensor is a swivel angle sensor (33) with which a swivel angle (α) of the swivel cradle (6) with respect to the swivel axis (7) can be measured as an actual value. [3] Axial piston machine according to claim 1, wherein the sensor is a pressure sensor with which the higher pressure from the pressure at the first control kidney (18) and the pressure at the second control kidney (19) can be measured as an actual value. [4] Axial piston machine according to claim 1, wherein the sensor is a speed sensor (36) and / or a torque sensor with which the speed and / or torque of the axial piston machine can be measured as an actual quantity. [5] Axial piston machine according to one of the preceding claims, wherein the sensor (29, 33, 34, 36, 41) comprises a combination of several sensors (29, 33, 34, 36, 41). [6] Axial piston machine according to one of the preceding claims, wherein the pivot axis and the rotary axis (7) intersect. [7] Axial piston machine according to one of the preceding claims, wherein the pressure fluid source in the axial piston machine is formed by the first control kidney (18) and the pressure fluid sink by the second control kidney (19). [8] Axial piston machine according to one of the preceding claims, further comprising a fourth and a fifth throttle to the pressure fluid source (3). [9] Axial piston machine according to one of the preceding claims, further comprising a sixth and a seventh throttle to a pressure fluid sink. [10] Method for operating an axial piston machine according to one of the preceding claims, comprising the steps Supporting the pivot cradle (6) via at least one hydrostatic relief pocket (4) on the housing, Connecting the hydrostatic relief pocket (4) to a pressure fluid source via the third throttle (1; 1A to 1G) of the axial piston machine, characterized by the step Adjusting the third throttle (1; 1A to 1G) by the position controller (32) such that it is at least temporarily open when an actual value measured by a sensor deviates from a corresponding target value by more than a predetermined threshold value, and such that the third throttle (1; 1A to 1G) limits pressure build-up when the actual value deviates from the target value by less than the specified threshold.

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