Neutral setting device for an adjustable hydraulic unit

Abstract

A manual displacement control device (MDC) for a hydraulic unit includes an input shaft that is rotatably mounted about an input shaft axis in an input shaft block. The input shaft projects from the input shaft block with a first end to which a rotational torque can be applied. The MDC further includes a control spool accommodated in a control housing, the control spool being movable by rotating the input shaft to control a servo pressure. The control device includes a positioning device for adjusting and fixing the lateral position of the input shaft relative to the control housing in a direction perpendicular to the input shaft axis and perpendicular to the direction of the restoring force applied to the input shaft. The hydraulic unit can be adjusted to its neutral position by means of a servo spring bracket that provides an end stop surface for a servo spring seat facing the displacement element. The servo spring bracket can be variably fixed to the hydraulic unit housing such that the orientation of the end stop surface can be adjusted parallel to the neutral position of the displacement element.

Description

Technical Field

[0001] The present invention relates to a variable displacement hydraulic unit, and more particularly to a manual displacement control device for a variable displacement hydraulic unit. Background Art

[0002] A hydrostatic unit equipped with a manual displacement control device generally includes a rotatable input shaft on which a torque can be applied by a system operator to adjust the displacement volume of the hydrostatic unit. A variety of different manual displacement control devices and mechanisms can be applied to convert the rotational movement of the input shaft into hydraulic pressure acting on a servo unit, thereby tilting the displacement element of the hydrostatic unit. If the operator's displacement command changes, the servo pressure increases or decreases, and the tilt angle of the displacement element changes. When the displacement of the pump is consistent with the input signal applied to the input shaft, mechanical position feedback is provided to indicate to the operator that the desired adaptation of the tilt angle of the displacement element has been achieved.

[0003] Due to the manufacturing tolerances of the components of the hydraulic unit, particularly the components of the displacement control device of the hydraulic unit, when the hydraulic unit is in its neutral position, the relative positions of the mechanical feedback element of the control unit for supplying servo pressure to the servo unit and the input shaft must consistently be in the zero position. Since the manual displacement control device is installed on the variable displacement hydraulic unit after its assembly, the zero position of this manual displacement control may not be consistent with the neutral position of the hydraulic unit. Subsequently, the mechanical relationship in the feedback chain results in an asymmetric behavior of the manual displacement control unit. This can even lead to the input operating lever being in a non-centered starting position, which as a result has a negative impact on the control behavior of the hydraulic unit. This may also lead to an asymmetric rotational angle of the input shaft, even with an adjustable centering mechanism for bringing the input shaft to its rotational zero position. Summary of the Invention

[0004] Therefore, an object of the present invention is to provide a manual displacement control device that can be adjusted to the neutral position of a variable displacement hydraulic unit after being assembled and installed, and that exhibits a symmetric rotational behavior when setting the displacement of the hydraulic unit.

[0005] The manual displacement control device according to the invention is applicable to a variable displacement hydraulic unit which is equipped with a servo unit capable of operating a variable tilt displacement element to set the displacement volume of the variable displacement hydraulic unit. The control device according to the invention comprises an input shaft which is rotatably mounted about an input shaft axis in an input shaft block. The input shaft projects from the input shaft block with a first end, and a rotational torque can be applied to this first end. The control device further comprises a control spool accommodated in a control housing. The control spool can be displaced by means of the rotation of the input shaft to control a servo pressure which can be directed to and from the servo unit. Depending on this servo pressure, the servo unit interacts with the displacement element of the variable displacement hydraulic unit and thereby controls the displacement of the hydraulic unit. A feedback transmission element is provided to transmit the displacement element position to the control unit and the input shaft. The feedback transmission element can pivot about a feedback pivot axis which is oriented substantially parallel to the input shaft axis. The feedback transmission element comprises a first end and a second end, the first end being for interacting with the control spool, and the second end being for receiving a mechanical feedback signal from a feedback element connected to the displacement element of the hydraulic unit, such that a mechanical feedback chain is provided between the feedback element and the control spool of the control unit. The actuation signal sensed at the first end of the input shaft displaces the control spool, thereby changing the pressure in the servo unit, which results in a change in the tilt angle of the displacement element, which causes a displacement of the feedback element, and this displacement is transmitted back to the control spool by the pivoting movement of the feedback transmission element.

[0006] According to the invention, a positioning device is provided which is capable of adjusting and fixing the lateral position of the input shaft relative to the control housing in a direction substantially perpendicular to the input shaft axis and substantially perpendicular to the direction of a centering force applied to the input shaft. The centering force is applied by a centering mechanism in order to bring the input shaft to a zero rotation position when no rotational torque is applied to the first end of the input shaft. This lateral adjustability of the position of the input shaft minimizes the asymmetrical behavior when controlling the displacement of the hydraulic unit, since all manufacturing and / or assembly tolerances of the components involved can be compensated.

[0007] Compared to rotational or angular compensation of tolerances, the lateral movement of the input shaft can adjust the geometric relationship between the control spool and the feedback element via the feedback transfer element, without superimposing the lateral adjustment movement and the rotational control movement. In other words, the feedback pivot axis does not move on a circular path, which would superimpose control actions that are later applied to the input shaft and thus result in an asymmetrical control behavior. According to the invention, the feedback transfer element moves on a straight path due to the lateral movement of the input shaft, thus obtaining a symmetrical behavior when controlling the displacement of the hydraulic unit. A person skilled in the art understands that a lateral deviation of the input shaft, for example caused by manufacturing and / or assembly tolerances of the input shaft block relative to the control housing and / or the hydraulic unit housing, will cause a displacement of the control spool, because the rotational centering mechanism acting on the input shaft is designed to rotate the input shaft to a position with less torque. This is typically done in the art by means of elastic restoring forces. Thus, a lateral deviation of the input shaft causes an increased restoring force at the centering mechanism, which can be released by rotating the input shaft, resulting in an asymmetrical rotational position of the input shaft in both rotational directions. According to the invention, such a lateral deviation can be compensated by providing a positioning device that allows correcting the lateral position of the input shaft relative to the input shaft block / housing.

[0008] In a specific embodiment, inclined surfaces are formed on opposite sides of the input shaft block such that the wedge surfaces of the wedge-shaped part of the positioning device having through-holes can be pressed against the inclined surfaces by fixing bolts, thereby fixing the input shaft block to the control housing. Preferably, the wedge surfaces of the wedge-shaped parts face each other and thus, if the wedge-shaped part is pressed against the inclined surface of the input shaft block, a force is applied in the direction towards the opposite wedge-shaped part. According to the invention, one of the fixing bolts can be loosened while the other fixing bolt is tightened to move the input shaft block in the direction towards the loosened fixing bolt and relative to the control housing. The loosened fixing bolt allows an upward movement of the corresponding wedge-shaped part, thus providing space for the movement of the input shaft block (especially the inclined surface on the input shaft block). The tightened fixing bolt exerts a force on the input shaft block towards the other side where the fixing bolt is loosened. When the corresponding correct tolerance compensation position of the input shaft is reached, both fixing bolts are tightened and the input shaft block is fixed / locked in this position. Such a lateral adjustment of the input shaft block can be performed in a direction substantially perpendicular to the force for centering the input shaft to its zero rotational position and substantially perpendicular to the input shaft axis.

[0009] Preferably, the control housing includes guiding means adjacent to the threaded holes for screwing in the fixing bolts. When loosening or tightening one of the fixing bolts, the guiding means keeps the distance between the wedge-shaped parts constant in the direction of the lateral movement of the input shaft block. Thus, the guiding means not only prevents the lateral movement of the wedge-shaped parts, but also can prevent the inclination of the wedge-shaped parts, the inclination of which may cause the blocking of the wedge-shaped parts on the inclined surface of the input shaft block, which will offset the function of the control device according to the present invention.

[0010] The wedge-shaped parts may exhibit a circular base surface, and the guiding means may include an annular groove formed in the control housing. By this geometric arrangement, the wedge-shaped parts are guided in all directions except in the direction towards or away from the input shaft block. This means that when loosening or tightening one of the fixing bolts, the wedge-shaped parts can only slide on the inclined surface towards or away from the input shaft block, thereby forcing the input shaft block to move in a direction perpendicular to the input shaft axis and perpendicular to the rotational centering force (i.e., the input shaft rotational restoring force).

[0011] Preferably, in one embodiment of the present invention, the direction and / or magnitude of the centering force of the centering mechanism can be adjusted by an adjusting means. Thus, the restoring force that causes the input shaft to rotate back to its zero position after being rotated can be adapted to the desired movement behavior and to the tolerance compensation position of the input shaft.

[0012] In another embodiment, the feedback pivot axis can be defined by an eccentric pin positioned eccentrically at the second end of the input shaft. This means that the feedback pivot axis is displaced when the input shaft rotates. In a specific embodiment according to the present invention, this causes the feedback transmission element to laterally displace the control spool, thereby opening and closing the control edge to change the servo pressure acting in the servo unit to adjust the angular position of the displacement element.

[0013] In an alternative embodiment, the feedback pivot axis can be defined by a support pin that is eccentrically positioned on an adjustment pin, and the adjustment pin is rotatably received in the control housing parallel to the input shaft axis. In this embodiment, the input shaft does not have to move / transfer the cylindrical control spool, but rather rotates a control sleeve to direct hydraulic pressure to and from the servo unit, and the control sleeve is mechanically connected to the feedback transmission device and is arranged around the input shaft in the servo unit.

[0014] The feedback transmission element may include an elongated hole for receiving a feedback pin, which is attached to the displacement element of the hydraulic unit and indicates the position of the displacement element. Since the displacement element rotates about its tilt axis and the feedback pin is eccentrically attached to the displacement element to perform its function, the free end of the feedback pin describes a circular path when the displacement element tilts. To allow for such circular movement, the elongated hole is provided in the feedback transmission element.

[0015] Preferably, the centering mechanism for the input shaft is accommodated in the input shaft block. In this configuration, there is no need to provide a separate angle adjustment device for the centering mechanism, as is the case when the centering mechanism is not arranged within the input shaft block. When the input shaft block is laterally displaced, for example, by a wedge-shaped portion, the centering mechanism moves accordingly, and the relative position between the input shaft block and the centering mechanism does not change. In contrast, if the centering mechanism and the input shaft block are arranged separately, the relative position of the two parts changes when calibrating / adjusting the position of the input shaft axis to eliminate assembly tolerances. The centering mechanism then has to be readjusted afterwards in order to correctly perform the function of the centering mechanism.

[0016] According to the invention, the hydraulic unit may be equipped with a manual displacement control device according to the invention as described above. In one embodiment, the control housing of the manual displacement control device is preferably part of the hydraulic unit housing, where the positioning device is located close to the first end of the input shaft, for example in order to be able to adjust / change the lateral position of the input shaft relative to the hydraulic unit housing and / or the neutral position of the displacement element.

[0017] According to the invention, the wedge-shaped portion of the positioning device may be guided by guiding means on the hydraulic unit housing in a direction perpendicular to the rotational restoring force. This means that the guiding means prevents the wedge-shaped portion from moving in the direction of the restoring force.

[0018] The hydraulic unit may include a tiltable displacement element having a feedback pin attached to the tiltable displacement element. One end of the feedback pin is received by the second end portion of the feedback transmission element. Thereby, a mechanical feedback chain is established between the displacement element and the control spool via the feedback transmission element, where the feedback transmission element may rotate about an eccentric pin arranged at the second end of the input shaft in one embodiment of the invention. Thus, the movement of the feedback pin causes the displacement of the control spool. Since the feedback transmission element can rotate about the feedback pin, when the input shaft is rotated, the feedback transmission element is displaced by the eccentric pin, thereby displacing the control spool.

[0019] In a preferred embodiment of the present invention, a servo unit having at least one servo piston and at least one servo spring is used to ensure the neutral position of the displacement element, wherein these two parts of the servo unit are arranged on opposite sides of the displacement element relative to the sliding surface on which the reciprocating piston is supported. When the servo unit is without pressure, the accurate setting of the neutral position of the displacement element is a safety issue for the hydraulic unit, because for example, no hydraulic pressure should be generated in the idling condition to stop the vehicle from moving. In order to set / find the accurate true neutral position of the displacement element, the hydraulic unit is frequently calibrated on a test bench to compensate for the manufacturing and assembly tolerances that affect the neutral position of the displacement element. Another object of the present invention is to provide a device by which the neutral position of the displacement element can be set / calibrated already during the assembly of the hydraulic unit.

[0020] To ensure that a servo unit in a pressure-balanced or pressureless state does not exert any spring restoring force on the displacement element in the neutral position of the displacement element, according to the present invention, a variable / adjustable fixable servo spring bracket is provided, which has end stop surfaces for each servo spring of the servo unit. During the assembly of the hydraulic unit, the true neutral position deviating from the theoretical neutral position can be temporarily blocked by means of an auxiliary blocking device. The end stop surfaces of the servo spring bracket can be aligned with the blocked neutral position of the displacement element, such that the end stop surfaces (i.e., the servo spring bracket) are parallel to the sliding surface on the displacement element on which the working piston of the rotating group of the hydraulic unit is supported. In other words, the servo spring bracket is aligned with the true neutral position of the displacement element with the end stop surfaces of the servo spring bracket. On these end stop surfaces, the servo springs can preferably abut against the servo spring seats, and the further (full) extension of the servo springs is restricted by means of these end stop surfaces. The servo spring rod is attached to the servo spring seat at a first end, and the servo spring rod passes through the servo spring bracket towards the displacement element, where, in the neutral position of the displacement element, the servo spring rod abuts at the placement point without any clearance and without spring force, because the end stop surfaces abutting against the servo spring seats restrict the servo spring travel path.

[0021] In a preferred embodiment, a servo spring is arranged on either side of the tilt axis of the displacement element such that the neutral position of the displacement element is reliably held by the servo spring rod, since each movement of the displacement element causes one of the servo springs to be compressed. To this end, the second end of the servo spring rod is shaped such that the second end of the servo spring rod can exert a thrust force rather than a tensile force on the displacement element. In one embodiment, the second end of the servo spring rod may exhibit a semi-circular shape so that the servo spring rod can follow the circular movement of the placement point when the displacement element is deflected by the servo piston force applied on the opposite side of the displacement element. To this end, in one embodiment, the connection between the second end of the servo spring rod and the placement point of the displacement element is shaped as a type of pivot connection.

[0022] To adjust the servo spring bracket to the neutral position of the displacement element, those skilled in the art will find various different possibilities. However, in the preferred embodiment of the present invention, a combination of a fixed bolt and an adjustable threaded sleeve is used. Thus, it is equivalent whether the threaded sleeve is screwed into the bracket to adjust the distance between the servo spring bracket and the housing of the hydraulic unit and to keep this distance constant, or whether the threaded sleeve is screwed onto the fixed bolt to maintain the desired distance of the servo spring bracket to the housing of the hydraulic unit. In both of these alternative scenarios, the servo spring bracket is fixed to the housing of the hydraulic unit by means of the fixed bolt. Needless to say, for those skilled in the relevant art, when tightening the fixed bolt, the threaded sleeve must be fixed to prevent rotation so as not to change the adjusted distance, and the threaded sleeve must support the servo spring bracket with the end stop surface parallel to the orientation of the sliding surface on the displacement element when the displacement element is in its neutral position.

[0023] This neutral position adjustment according to the present invention is applicable to any hydraulic unit and is independent of the number of servo springs and servo pistons installed for changing the displacement of a variable displacement hydraulic unit. It is conceivable that the present invention is applicable to two types of hydraulic units, a hydraulic unit that can be deflected only in one direction or a hydraulic unit that can be deflected in two directions. Thus, a displacement force can be exerted on the displacement element by at least one servo piston, as described above, with the at least one servo piston on one side of the displacement element and supported by at least one servo spring device on the other side.

[0024] Once the neutral position of the displacement element is adjusted according to the present invention and the transfer assembly is used to install a manual displacement device (MDC), since the neutral position of the displacement element has been adjusted / calibrated, the lateral adjustment of the input shaft of the MDC can be directly completed on the assembly line. Therefore, according to the present invention, it is not necessary to calibrate the neutral position on the test bench and then adjust the lateral position of the input shaft of the manual displacement controller (MDC). In other words, the neutral position calibration adjusted by means of the servo spring bracket described above provides a prerequisite for the lateral position adjustment / calibration of the input shaft of the manual displacement controller (MDC).

[0025] The hydraulic unit to which the present invention can be applied can be of the axial piston type or the radial piston type. Specifically, in the case of selecting an axial piston design, the hydraulic unit can be of the swash plate type or the bent-axis type. Brief Description of the Drawings

[0026] The present invention generally described above will now be described in further detail with the aid of the drawings, in which preferred embodiments and preferred design possibilities are shown. However, these preferred embodiments do not limit the scope of the inventive concept. The preferred embodiments shown can be combined with each other without departing from the spirit of the present invention. In addition, modifications within the knowledge of those skilled in the relevant art can be implemented without departing from the spirit of the present invention. In the drawings, shown are:

[0027] Figure 1 is a top view of a manual displacement control device according to the present invention;

[0028] Figure 2 is of an embodiment according to Figure 1 the first cross-sectional view along the section line A-A;

[0029] Figure 3 is of an embodiment according to Figure 1 the second cross-sectional view along the section line B-B;

[0030] Figure 4 is of an embodiment according to Figure 1 the third cross-sectional view along the section line C-C;

[0031] Figure 5 is a cross-sectional view of a servo spring device according to the present invention;

[0032] Figure 6 is a top view of a servo spring bracket according to the present invention;

[0033] Figure 7 is of the servo spring device according to Figure 6 the cross-sectional view along the section line A-A in;

[0034] Figure 8 is a sectional view taken along section line B-B of a servo spring device Figure 6 . DETAILED DESCRIPTION

[0035] Figure 1 There is shown a manual displacement control device 1 for setting the displacement of a hydraulic unit (not shown). The manual displacement control device 1 includes an operating lever 6, for example, on which an operator can apply a corresponding force or torque. The operating lever 6 transmits the input torque to the first end 11 of an input shaft 10. The input shaft 10 is received in an input shaft block 15 which, according to the invention, is laterally displaceable along the direction of the operating lever 6 - as exemplarily shown in the embodiment of Figure 1 . Those skilled in the art will find that the orientation of the operating lever 6 can be any other orientation, where the direction of the lateral adjustment of the input shaft will remain parallel to the section line Figure 1 indicated.

[0036] A centering mechanism 35 is provided at the input shaft block 15 to force / restore the input shaft 10 and the operating lever 6 to their starting positions when no torque is applied to the operating lever 6. The centering force / torque of the centering mechanism 35 can be adjusted via an adjusting device 50 (for example, an eccentric mechanism and / or a pre-tensioned spring). The input shaft block 15 is fixed to the control housing 20 via a fixing bolt 42 pressing on a wedge portion 44 which exerts a holding force on the input shaft block 15. When one of the fixing bolts 42 is loosened and the other fixing bolt 42 is tightened, lateral adjustability of the input shaft block 15 is provided. A gap 49 can be seen between the input shaft block 15 and the wedge portion 44 which restricts the lateral mobility of the input shaft block 15. If the input shaft block 15 moves in the Figure 1 plane in a leftward or rightward direction, one of the corresponding gaps 49 will become smaller while another gap 49 between the tightened fixing bolt 42 and the assembly of the wedge portion 44 and the input shaft block 15 will increase.

[0037] In Figure 1 there are shown three cross-lines labeled with letters A to C. In Figures 2 to 4 a corresponding sectional view is presented.

[0038] Figure 2 is according to Figure 1Cross-sectional view taken along line A-A of an embodiment of the manual displacement control device 1. The input shaft block 15 is attached to the control housing 20 by means of fixing bolts 42 and a wedge portion 44. The wedge portion 44 includes a wedge / inclined surface 47 which contacts the inclined surface 17 on the input shaft block 15, wherein the inclined surface 17 includes an outward-facing normal vector and the wedge surface 47 of the wedge portion 44 includes an inward-facing normal vector, i.e., in a direction opposite to the normal vector of the inclined surface 17. The head of the fixing bolt 42 contacts the base surface 46 on the wedge portion 44 such that (in Figure 2 the view) the vertical force applied by tightening one of the fixing bolts 42 is converted via the base surface 46 and the wedge surface 47 of the wedge portion 44 into an inclined force on the assigned inclined surface 17. A guiding device 48 is provided to constrain the movement of the wedge portion 44 (in Figure 2 the view) to upward or downward movement since the outward-facing surface of the wedge portion 44 is in circular contact with a circumferential groove in the control housing 20 which serves as the guiding device 48.

[0039] Hereinafter, the function of the positioning device 40 according to the present invention will be explained with a leftward movement as representative in Figure 2 the view. However, those skilled in the art are aware of the fact that movement in the opposite direction can be accomplished in a similar manner. If adjustment of the position of the input shaft 10 relative to the control housing 20 is necessary, for example due to elimination of manufacturing tolerances, the left fixing bolt 42 is loosened, for example by turning it half a turn, which means that the head of the fixing bolt 42 moves slightly away from the control housing 20 and no longer contacts the base surface 46. When the opposite fixing bolt 42 on the right side is tightened, the head of this fixing bolt 42 approaches the control housing 20 and exerts a force on the wedge portion 44 towards the control housing 20. Since the guiding device 48 constrains the lateral movement of the wedge portion 44 to only upward and downward movement, the wedge portion 44 will move downward towards the control housing 20, thereby applying an inclined force on the inclined surface 17 of the input shaft block 15 which is perpendicular to the wedge surface 47. The horizontal portion of this inclined force vector forces the input shaft block 15 to move leftward since upward movement is prohibited by the inclined surface of the tightened right wedge portion 44. Thereby the left wedge portion 44 is lifted in the direction towards the head of the fixing bolt 42 on the left. The movement ends when the wedge portion 44 on the left side of the input shaft block 15 again contacts the head of the fixing bolt 42 via the base surface 46. With this movement of the input shaft block 15, the input shaft 10 also moves leftward, which allows adjustment of the lateral position of the input shaft 10 in order to compensate for position tolerances during the assembly of the hydraulic unit. In fact, after the initial assembly of the input shaft block 15, the operating lever 6 will not be as Figure 1oriented perfectly horizontally as shown, because the operating lever 6 will show an angular deviation when the displacement element 4 is blocked in the neutral position of the displacement element. This deviation is caused, for example, by component, manufacturing and assembly tolerances. At the same time, the centering mechanism 35 will be compressed more compared to the theoretical zero position of the input shaft 10. Therefore, according to the present invention, the input shaft 10 can be laterally displaced to a position in which the neutral position of the displacement element 4 is blocked and the operating lever is rotated to its designated position. Another indication of the proper position of the input shaft 10 (where all tolerances are compensated) is that the restoring force of the centering mechanism is at the point where this restoring force is minimal.

[0040] As shown Figure 3 in Figure 1 a perspective cross-sectional view taken along line B - B indicated. Since the viewing direction is the same as Figure 2 that, the fixing bolts 42, the wedge-shaped part 44 with the wedge-shaped surface 47, and the inclined surface 17 of the input shaft block 15 are also visible. Additionally, the input shaft axis 13 is marked, which is the central axis of the input shaft 10. The first end 11 of the input shaft 10 is in a torque-proof connection with the operating lever 6. The second end 12 of the input shaft 10 includes an eccentric pin 16 that defines the center of rotation of the feedback transmission element 30, and the first end 31 of this feedback transmission element 30 is visible Figure 3 in

[0041] In the specific embodiment shown in the drawing, the rotation of the input shaft 10 about the input shaft axis 13 causes a lateral displacement of the eccentric pin 16, as Figure 4This is best visible in [description], which causes the deflection of the feedback transmission element 30 and consequently the displacement of the control spool 5. On the second end 12 of the input shaft 10, the eccentric pin 16 is arranged radially offset from the input shaft axis 13. The eccentric pin 16 defines a feedback pivot axis 33, which serves as the center of rotation of the feedback transmission element 30. The second end 32 of the feedback transmission element 30 is provided with an elongated hole 34, which can receive the feedback element 3 of the hydraulic unit. The first end 31 of the feedback transmission element 30 is in operative connection with the control spool 5. This means that if the operating lever 6 rotates, the eccentric pin 16 arranged at the second end 12 of the input shaft 10 will be laterally displaced, and the feedback transmission element 30 will be forced to rotate around the feedback element 3, which provides the center of rotation of the feedback transmission element 30 in this case. Accordingly, the first end 31 of the feedback transmission element 30 is also forced to rotate around the feedback element 3 and, accordingly, moves the control spool 5. Thereby, the servo pressure guided to the servo unit is changed, and the displacement element 4 of the hydraulic unit changes its tilt angle. As a result, the feedback element 3 attached to the displacement element 4 moves, and consequently the second end 32 of the feedback transmission element 30 also moves. Since the input shaft 10 is held in a constant position, the feedback transmission element 30 rotates around the feedback pivot axis 33, so that the control spool 5 disables the pressure flow to the servo unit and thereby stops the movement of the displacement element 4 of the hydraulic unit.

[0042] Manufacturing and installation tolerances have a negative impact on the function of this mechanical feedback chain, and therefore, after the manual displacement control device 1 has been assembled, the manufacturing and installation tolerances must be eliminated by adjusting the position of the eccentric pin 16 and consequently the position of the feedback pivot axis 33. At the same time, since the neutral position is the starting point for the tolerance compensation of the hydraulic unit, the neutral position of the hydraulic unit must be accurately defined. In other words, the calibration of the input shaft 10 should be carried out when the displacement element 4 is held in its neutral position, preferably in the true neutral position where the manufacturing and assembly tolerances affecting the neutral position are compensated.

[0043] According to the invention, the adjustment of the lateral position of the input shaft 10 relative to the neutral position of the displacement element 4 and consequently the adjustment of the lateral position of the eccentric pin 16 are achieved by the combination of the inclined surface 17 at the input shaft block 15 and the wedge surface 47 at the wedge portion 44. Thereby, as described in detail above, the lateral mobility of the input shaft axis 13 and the feedback pivot axis 33 in the direction perpendicular to the section line C-C is provided.

[0044] Figure 4The function of the centering mechanism 35 is also shown, which is additionally equipped with an adjusting device 50 for adjusting the restoring force on the input shaft 10. If the input shaft 10 rotates away from the starting position of the input shaft, the centering mechanism 35 exerts a reaction torque on the input shaft 10, and if the torque acting on the operating lever 6 decreases, this reaction torque causes the input shaft 10 to rotate / return to the starting position of the input shaft.

[0045] Figures 5 to 8 An embodiment for adjusting the neutral position of the displacement element 4 according to the invention is shown. In Figure 5 it, the displacement element 4 is shown in the neutral position, in which the hydraulic unit does not exhibit any displacement volume. The servo spring bracket 68 is arranged parallel to the displacement element 4, such that the end stop surfaces 69 are respectively parallel to the displacement element, parallel to the sliding surface on the displacement element 4 on which the working piston (not shown) of the hydraulic unit is supported. These end stop surfaces 69 serve as spring expansion path limiters for the servo spring 63. In one embodiment of the invention, the servo spring 63 is held by means of a servo spring seat 64 which abuts the end stop surfaces 69. Thus, by means of the servo spring bracket 68, the servo spring 63 can be held in a pre-compressed state, for example against the hydraulic unit end cap. The servo spring rod 65 is attached at its first end 66 to the servo spring seat 64 and passes through the servo spring bracket 68 towards the displacement element 4, and the servo spring rod 65 is supported at its second end 67 on the displacement element 4. Since the servo force application point undergoes a bending-like movement when the displacement element is deflected, the second end 67 of the servo spring rod 65 Figure 5 is shown in the form of a half-shell in the embodiment shown, in order to achieve the associated rotational movement of the displacement element 4 related to the linear movement when one of the servo springs in the servo spring 63 is compressed.

[0046] According to the invention, the orientation / positioning of the servo spring bracket 68 can be adjusted by means of a variably adjustable fixing system. In Figures 5 to 8In the illustrated embodiment, such a variable adjustable fixing system is realized by means of a threaded sleeve 72, which may be adjustably fixed to a fixing bolt 70 or adjustably fixed to a servo spring bracket 68. By means of adjusting the screwing-in depth of the threaded sleeve 72, the position of the servo spring bracket 68 is adjusted such that the servo spring rod 65 shows neither a clearance from the displacement element 4 nor a clearance from the servo spring seat 64, nor does it lift the servo spring seat 64 from the end stop surface 69. By means of this adjustment of the position of the servo spring bracket 68, the displacement element 4 is safely held in the neutral position of the displacement element, because each rotation movement of the displacement element 4 causes the compression of one of the servo springs in the servo spring 63. By restricting the servo spring travel by means of the servo spring bracket 68, the servo unit 60 (not shown in its entirety) can adapt to the neutral position of the displacement element 4 while compensating for all the manufacturing and assembly tolerances of all the components involved that affect the neutral position of the displacement element 4.

[0047] In Figures 6 to 8 the details of the servo spring bracket 68 are depicted ( Figure 6 is a top view of the servo spring bracket 68) and the details of the preferred variable adjustable fixing system of the servo spring bracket 68 to the housing 120 of the hydraulic unit 100. Thus, Figure 7 the threaded sleeve 72 screwed onto the fixing bolt 70 is shown, and Figure 8 the threaded sleeve 72 screwed into the corresponding thread in the servo spring bracket 68 is shown, where the fixing bolt 70 passes through the threaded sleeve 72. Those skilled in the art will find other ways to provide variable adjustable fixing possibilities for positioning the servo spring bracket 68 according to the invention and adapting to the true neutral position of the displacement element 4 of the hydraulic unit 100.

[0048] List of reference numerals

[0049] 1 Manual displacement control device

[0050] 3 Feedback element

[0051] 4 Displacement element

[0052] 5 Control spool

[0053] 6 Operating lever

[0054] 8 Sliding element

[0055] 10 Input shaft

[0056] 11 First end of the input shaft

[0057] 12 Second end of the input shaft

[0058] 13 Input shaft axis

[0059] 14 concave part

[0060] 15 input shaft block

[0061] 16 eccentric pin

[0062] 17 inclined surface

[0063] 20 control housing

[0064] 21 screw hole

[0065] 30 feedback transmission element

[0066] 31 first end of the feedback transmission element

[0067] 32 second end of the feedback transmission element

[0068] 33 feedback pivot axis

[0069] 34 elongated hole

[0070] 35 centering mechanism

[0071] 37 spring

[0072] 38 sliding element

[0073] 40 positioning device

[0074] 42 fixing bolt

[0075] 43 slot hole

[0076] 44 wedge part

[0077] 46 base surface

[0078] 47 wedge surface

[0079] 48 guiding device

[0080] 49 clearance

[0081] 50 adjusting device

[0082] 60 servo unit

[0083] 63 servo spring

[0084] 64 servo spring seat

[0085] 65 servo spring rod

[0086] 66 first end of the servo spring rod

[0087] 67 second end of the servo spring rod

[0088] 68 servo spring bracket

[0089] 69 end stop surface

[0090] 70 Fixed bolt

[0091] 72 Threaded sleeve

[0092] 120 Hydraulic unit housing

[0093] F Centripetal force.

Claims

1. A manual displacement control device (1) for a variable displacement hydraulic unit, the variable displacement hydraulic unit being equipped with a servo unit (60) capable of operating a displacement element (4) to set a displacement volume, the control device (1) comprising: - an input shaft (10) rotatably mounted about an input shaft axis (13) in an input shaft block (15), and with a first end (11) of the input shaft (10) protruding from the input shaft block (15), a rotational torque being applicable to the first end (11); - a control spool (5) housed in a control housing (20) and movable by rotation of the input shaft (10) to control a servo pressure which can be directed to and from the servo unit (60); - a feedback transfer element (30) pivotable about a feedback pivot axis (33) parallel to the input shaft axis (13), the feedback transfer element (30) having a first end (31) and a second end (32), the first end (31) for interacting with the control spool (5), and the second end (32) for receiving a mechanical feedback signal from a feedback element (3) connected to the displacement element (4) of the hydraulic unit; - a positioning device (40) for adjusting and fixing a lateral position of the input shaft (10) relative to the control housing (20) in a direction perpendicular to the input shaft axis (13) and perpendicular to a centering force (F), the centering force (F) being applied to the input shaft (10) by a centering mechanism (35) so as to return the input shaft (10) to a zero position when no rotational torque is applied to the first end (11) of the input shaft (10); wherein inclined surfaces (17) are formed on opposite sides of the input shaft block (15) in a direction of adjusting the position of the input shaft (10), such that a wedge surface (47) of a wedge portion (44) of the positioning device (40) having a through hole (43) can be pressed against the inclined surface (17) by a fixing bolt (42), thereby fixing the input shaft block (15) to the control housing (20).

2. The control device (1) according to claim 1, wherein the control housing (20) includes a guiding device (48) adjacent to a threaded hole (21) for screwing in the fixing bolt (42), wherein when one or two fixing bolts (42) are loosened or tightened, the guiding device (48) keeps a distance between the wedge portions (44) constant in a direction of lateral movement of the input shaft block (15).

3. The control device (1) according to claim 1 or 2, wherein the wedge portion (44) exhibits a circular base surface (46), and the guiding device (48) is an annular groove formed in the control housing (20).

4. The control device (1) according to claim 1 or 2, wherein, the direction and / or height of the centering force (F) of the centering mechanism (35) can be adjusted by an adjusting device (50).

5. The control device (1) according to claim 1 or 2, wherein, the feedback pivot axis (33) is defined by an eccentric pin (16) which is eccentrically located at the second end (12) of the input shaft (10).

6. The control device (1) according to claim 1 or 2, wherein, the feedback pivot axis (33) is defined by a support pin which is eccentrically located on an adjustment pin, and the adjustment pin is rotatably received in the control housing (20) parallel to the input shaft axis (13).

7. The control device (1) according to claim 1 or 2, wherein, the feedback transmission element (30) includes an elongated hole (34) for receiving a feedback pin of the hydraulic unit indicating the position of the displacement element (4).

8. The control device (1) according to claim 1 or 2, wherein, the centering mechanism (35) is accommodated in the input shaft block (15).

9. A hydraulic unit having a manual displacement control device (1) according to any one of claims 1 to 8.

10. The hydraulic unit according to claim 9, wherein, the control housing (20) of the manual displacement control device (1) is part of a hydraulic unit housing (120), and the positioning device (40) is located near the first end (11) of the input shaft (10) so as to be able to adjust the lateral position of the input shaft (10) relative to the hydraulic unit housing (120).

11. The hydraulic unit according to claim 9 or 10, wherein, the wedge-shaped portion (44) of the positioning device (40) can be guided by a guiding device (48) on the hydraulic unit housing (120) in a direction towards the control spool (5).

12. The hydraulic unit according to claim 9 or 10, wherein, the hydraulic unit includes a tiltable displacement element (4), the tiltable displacement element (4) has a feedback pin attached thereto, and one end of the feedback pin is received by the second end portion (32) of the feedback transmission element (30).

13. The hydraulic unit according to claim 12, wherein, The servo unit (60) includes a servo piston (62) and a servo spring (63) located on opposite sides of the displacement element (4), wherein a servo spring bracket (68) that provides an end stop surface (69) for a servo spring seat (64) facing the displacement element (4) can be variably fixed to the hydraulic unit housing (120) such that the orientation of the end stop surface (69) can be adjusted parallel to the neutral position of the displacement element (4), wherein a servo spring rod (65) contacts the servo spring seat (64) with a first end (66) and contacts the displacement element (4) with a second end (67) such that when the displacement element (4) is tilted away from the neutral position, the servo spring rod (65) can compress the servo spring (63) via the servo spring seat (64).

14. The hydraulic unit according to claim 13, wherein, the second end (67) of the servo spring rod (65) abuts the displacement element (4) in a manner that can rotate about an axis parallel to the tilt axis of the displacement element (4).

15. The hydraulic unit according to claim 13, wherein, the second end (67) of the servo spring rod (65) is of an annular shape.

16. The hydraulic unit according to claim 13, wherein, the relative position of the servo spring bracket (68) in the hydraulic unit housing (120) can be adjusted by means of a threaded sleeve (72) having an internal or external thread, and wherein the relative position of the servo spring bracket (68) is fixed to the hydraulic unit housing (120) by means of a fixing bolt (70).

17. The hydraulic unit according to claim 13, wherein, at least one servo unit (60) is arranged on either side of the displacement element (4) relative to the tilt axis of the displacement element.

18. The hydraulic unit according to claim 9 or 10, wherein, the hydraulic unit is of an axial piston type or a radial piston type.

19. The hydraulic unit according to claim 18, wherein, the hydraulic unit is of a swash plate type or a bent axis type.

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