Neutral setting device of an adjustable hydraulic unit

Abstract

Manual displacement control device (MDC) for hydraulic units has an input shaft mounted rotatably about an input shaft axis in an input shaft block. The input shaft protrudes from the input shaft block with a first end, onto which a rotating torque can be applied. The MDC further includes a control spool housed in a control housing, which is moveable by rotating the input shaft for controlling a servo pressure. The control device is configured for adjusting and fixing the lateral position of the input shaft with respect to the control housing in a direction perpendicular to the input shaft axis and perpendicular to the direction of a restoring force exerted on the input shaft.

Claims

1. A manual displacement control device for variable displacement hydraulic units equipped with a servo unit capable of operating a displacement element in order to set a displacement volume, the control device comprising: an input shaft mounted rotatable about an input shaft axis in an input shaft block and protruding from the input shaft block with a first end on which a rotating torque is configured to be applied; a control spool housed in a control housing and moveable by means of rotation of the input shaft for controlling a servo pressure which is configured to be guided to and from a servo unit; a feedback transmitting element pivotable about a feedback pivot axis parallel to the input shaft axis, having a first end portion for interacting with the control spool, and a second end portion for receiving a mechanical feedback signal of a feedback element connected to a displacement element of a hydraulic unit; positioning means for adjusting and fixing a lateral position of the input shaft with respect to the control housing in a direction perpendicular to the input shaft axis and perpendicular to the direction of a centering force exerted on the input shaft by a centering mechanism in order to restore the input shaft to a zero position when no rotating torque is applied to the first end of the input shaft.

2. The control device according to claim 1, wherein the direction and/or the magnitude of the centering force of the centering mechanism is adjustable by an adjustment means.

3. The control device according to claim 1, wherein the feedback pivot axis is defined by an eccentric pin located eccentrically at the second end of the input shaft.

4. The control device according to claim 1, wherein the feedback transmitting element comprises an elongated hole for receiving the feedback element of the hydraulic unit indicating a position of the displacement element.

5. The control device according to claim 1, wherein the centering mechanism is housed in the input shaft block.

6. A hydraulic unit comprising: a displacement element; a servo unit configured to operate the displacement element to set a displacement volume; and a manual displacement control device comprising: an input shaft mounted rotatable about an input shaft axis in an input shaft block and protruding from the input shaft block with a first end on which a rotating torque is configured to be applied; a control spool housed in a control housing and moveable by means of rotation of the input shaft to control a servo pressure which is configured to be guided to and from the servo unit; a feedback transmitting element pivotable about a feedback pivot axis which is parallel to the input shaft axis, having a first end portion that interacts with the control spool and a second end portion that receives a mechanical feedback signal of a feedback element connected to the displacement element of the hydraulic unit; and positioning means for adjusting and fixing a lateral position of the input shaft with respect to the control housing in a direction perpendicular to the input shaft axis and perpendicular to the direction of a centering force exerted on the input shaft by a centering mechanism in order to restore the input shaft to a zero position when no rotating torque is applied to the first end of the input shaft.

7. The hydraulic unit according to claim 6, wherein the control housing of the manual displacement control device is part of a hydraulic unit housing, wherein the positioning means is located at the first end of the input shaft in order to be able to adjust the lateral position of the input shaft relative to the hydraulic unit housing.

8. The hydraulic unit according to claim 6, wherein wedge surface parts of the positioning means are configured to be guided by guiding means on the hydraulic unit housing.

9. The hydraulic unit according to claim 6, wherein the feedback element is in the form of a feedback pin, wherein the displacement element of the hydraulic unit is tiltable and has the feedback pin attached thereto, and wherein one end of the feedback pin is received by the second end portion of the feedback transmitting element.

10. The hydraulic unit according to claim 9, wherein the servo unit comprises a servo piston and a servo spring, which are located on opposite sides of the displacement element, wherein a servo spring bracket providing an end stop surface for a servo spring seat is variably fixable to the hydraulic unit housing in such a manner that the orientation of the end stop surface is adjustable parallel to the displacement element in a neutral position, and wherein a first end of a servo spring rod is arranged contacting the servo spring seat and a second end of the servo spring rod is arranged contacting the displacement element such that the servo spring rod is capable of compressing the servo spring via the servo spring seat when the displacement element is tilted out of the neutral position.

11. The hydraulic unit according to claim 9, wherein the servo unit comprises a servo piston and a servo spring, which are located on opposite sides of the displacement element, wherein a servo spring bracket providing an end stop surface for a servo spring seat is variably fixable to the hydraulic unit housing in such a manner that the orientation of the end stop surface is adjustable parallel to the displacement element in a neutral position, wherein a first end of a servo spring rod is arranged contacting the servo spring seat and a second end of the servo spring rod is arranged contacting the displacement element such that the servo spring rod is capable of compressing the servo spring via the servo spring seat when the displacement element is tilted out of the neutral position, and wherein the second end of the servo spring rod abuts against the displacement element in a rotatable manner with respect to an axis parallel to a tilt axis of the displacement element.

12. The hydraulic unit according to claim 9, wherein the servo unit comprises a servo piston and a servo spring which are located on opposite sides of the displacement element, wherein a servo spring bracket providing an end stop surface for a servo spring seat is variably fixable to the hydraulic unit housing in such a manner that the orientation of the end stop surface is adjustable parallel to the displacement element in a neutral position, and wherein a first end of a servo spring rod is arranged contacting the servo spring seat and a second end of the servo spring rod is arranged contacting the displacement element such that the servo spring rod is capable of compressing the servo spring via the servo spring seat when the displacement element is tilted out of the neutral position, wherein the second end of the servo spring rod is annular shaped.

13. The hydraulic unit according to claim 9, wherein the servo unit comprises a servo piston and a servo spring which are located on opposite sides of the displacement element, wherein a servo spring bracket providing an end stop surface for a servo spring seat is variably fixable to the hydraulic unit housing in such a manner that the orientation of the end stop surface is adjustable parallel to the displacement element in a neutral position, and wherein a first end of a servo spring rod is arranged contacting the servo spring seat and a second end of the servo spring rod is arranged contacting the displacement element such that the servo spring rod is capable of compressing the servo spring via the servo spring seat when the displacement element is tilted out of the neutral position, wherein a relative position of the servo spring bracket in the hydraulic unit housing is configured to be adjusted by means of threaded sleeves having an internal or an external thread, and wherein the position of the servo spring bracket is fixed to the hydraulic unit housing by means of fixation bolts.

14. The hydraulic unit according to claim 9, wherein the servo unit comprises a servo piston and a servo spring which are located on opposite sides of the displacement element, wherein a servo spring bracket providing an end stop surface for a servo spring seat is variably fixable to the hydraulic unit housing in such a manner that the orientation of the end stop surface is adjustable parallel to the displacement element in a neutral position, and wherein a first end of a servo spring rod is arranged contacting the servo spring seat and a second end of the servo spring rod is arranged contacting the displacement element such that the servo spring rod is capable of compressing the servo spring via the servo spring seat when the displacement element is tilted out of the neutral position, wherein, with respect to a displacement element tilt axis, at either side of the displacement element at least one servo unit is arranged.

15. The hydraulic unit according to claim 6, wherein the hydraulic unit is of the axial or radial piston type.

16. The hydraulic unit according to claim 15, wherein the hydraulic unit is of the swashplate or bent axis type.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention described above in general is now detailed further with the help of annexed Figures, in which preferred embodiments and preferred design possibilities are shown. However, these preferred embodiments do not limit the scope of the inventive idea. The shown preferred embodiments can be combined with one another without leaving the spirit of the invention. Furthermore, modifications within the possibilities of the knowledge of a person with skills in the relevant art can be implemented without leaving the spirit of the invention. In the Figures, it is shown:

(2) FIG. 1 is a top view of a manual displacement control device according to the invention;

(3) FIG. 2 is a first sectional view of the embodiment according to section line A-A of FIG. 1;

(4) FIG. 3 is a second sectional view of the embodiment according to section line B-B of FIG. 1;

(5) FIG. 4 is a third sectional view of the embodiment according to section line C-C of FIG. 1;

(6) FIG. 5 is a sectional view of a servo spring arrangement according to the invention;

(7) FIG. 6 is a top view of a servo spring bracket according to the invention;

(8) FIG. 7 is a sectional view of a servo spring arrangement according to section line A-A in FIG. 6; and

(9) FIG. 8 is a sectional view of a servo spring arrangement according to section line B-B in FIG. 6.

DETAILED DESCRIPTION

(10) FIG. 1 shows a manual displacement control device 1 for setting the displacement of a hydraulic unit (not shown). The manual displacement control device 1 comprises a lever 6, on which a force or a torque, respectively, can be applied by an operator, for example. The lever 6 transmits the input torque to the first end 11 of an input shaft 10. The input shaft 10 is housed in an input shaft block 15, which according to the invention is laterally movable along the direction of lever 6as exemplarily shown in the embodiment with FIG. 1 for illustration purposes only. A person skilled in the relevant art will detect that the orientation of the lever 6 can be any other, wherein the direction of lateral adjustment of the input shaft will remain parallel to the section lines as indicated in FIG. 1.

(11) A centering mechanism 35 is provided at the input shaft block 15 in order to force/restore the input shaft 10 and the lever 6 back to the starting position, when no torque is applied to the lever 6. The centering force/torque of the centering mechanism 35 can be adjusted via adjustment means 50, e.g., an eccentric mechanism and/or a pre-tensioned spring. Input shaft block 15 is fixed to a control housing 20 via fixation bolts 42 pressing onto wedge-shaped parts 44, which exert a holding force on the input shaft block 15. A lateral adjustability of the input shaft block 15 is provided, when one of the fixation bolts 42 is loosened and the other fixation bolt 42 is tightened. Gaps 49, which are visible between the input shaft block 15 and the wedge-shaped parts 44, restrict the lateral movability of the input shaft block 15. If the input shaft block 15 is moved either to the left or right direction in the plane of FIG. 1, one of the corresponding gaps 49 will become smaller, whereas the other gap 49 between the input shaft block 15 and the tightened fixation bolt 42 and wedge-shaped part 44 assembly will increase.

(12) Three intersection lines, marked with the letters A to C are shown with FIG. 1. The corresponding sectional views are presented in FIGS. 2 to 4.

(13) FIG. 2 is a sectional view along line A-A of the embodiment of the manual displacement control device 1 according to FIG. 1. The input shaft block 15 is attached to the control housing 20 by means of fixation bolts 42 and wedge-shaped parts 44. The wedge-shaped parts 44 comprise wedge/inclined surfaces 47, which are in contact with inclined surfaces 17 on the input shaft block 15, wherein the inclined surfaces 17 comprise an outwardly facing normal vector and the wedge surfaces 47 of the wedge-shaped parts 44 comprise an inwardly facing normal vector, i.e., in the opposite direction of the normal vector of the inclined surfaces 17. The heads of the fixation bolts 42 are in contact with base surfaces 46 on the wedge-shaped parts 44, such that (in the view of FIG. 2) a vertical force applied by tightening one of the fixation bolts 42 is converted to an inclined force on the allocated inclined surface 17 via the base surface 46 and the wedge surface 47 of the wedge-shaped part 44. Guiding means 48 are provided to restrict the movement of the wedge-shaped parts 44 (in the view of FIG. 2) to an up or down movement, as the outwardly facing surfaces of the wedge-shaped parts 44 are in circular contact with circumferential grooves in the control housing 20 serving as guiding means 48.

(14) In the following, the functionality of the positioning means 40 according to the invention is explained on behalf of a movement to the left in the view of FIG. 2. However, a person with skills in the relevant art is aware of the fact that a movement in the opposite direction can done in an analogous way. If an adjustment of the position of the input shaft 10 relative to the control housing 20 is necessary, e.g., due to elimination of manufacturing tolerances, the left fixation bolt 42 is loosened, e.g., by half turn, which means that the head of the fixation bolt 42 is moved slightly away from the control housing 20 and is no longer in contact with the base surface 46.

(15) When the opposite fixation bolt 42 on the right side is tightened, the head of the fixation bolt 42 approaches the control housing 20 and forces the wedge-shaped part 44 towards the control housing 20. As the guiding means 48 restrict the lateral movement of the wedge-shaped part 44 to a up and down movement only, the wedge-shaped part 44 will move downwards towards the control housing 20, thereby exerting an inclined force, which is perpendicular to the wedge surface 47 on the inclined surface 25 of the input shaft block 15. The horizontal part of this inclined force vector forces the input shaft block 15 to move to the left, as an upward movement is prohibited by the inclined surface of the tightened right wedge-shaped part 44. Thereby the left wedge-shaped part 44 is lifted in the direction of the bolt head of the left fixation bolt 42. The movement ends when the wedge-shaped part 44 on the left side of input shaft block 15 is again in contact with the head of the fixation bolt 42 via the base surface 46. With this movement of the input shaft block 15 the input shaft 10 is moved also towards left, which allows to adjust the lateral position of the input shaft 10 in order to compensate position tolerances during the assembly of a hydraulic unit. In practice, after the initial assembly of the input shaft block 15 the lever 6 will not be oriented perfectly horizontal as shown in FIG. 1, since will show an angular deviation, when the displacement element 4 is blocked in its neutral position. This deviation is caused by part, manufacturing and assembly tolerances, e.g. At the same time the centering mechanism 35 will be compressed more than in a theoretical zero position of the input shaft 10. Hence, according to the invention, the input shaft 10 can be moved laterally to a position in which, with blocked neutral position of the displacement element 4, the lever turns to his designated position. Another indication of the correct position of the input shaft 10, in which all tolerances are compensated is the point at which the restoring forces of the centering mechanism are at its minimum.

(16) In FIG. 3 a perspective sectional view along the line B-B as indicated in FIG. 1 is shown. As the viewing direction is the same as in FIG. 2, the fixation bolts 42, the wedge-shaped parts 44 with wedge surfaces 47 and the inclined surfaces 25 of the input shaft block 15 are visible also. Additionally, the input shaft axis 13, which is the central axis of the input shaft 10 is marked. The first end 11 of input shaft 10 is in a torque-proof connection with the lever 6. The second end 12 of the input shaft 10 comprises an eccentric pin 16, defining the center of rotation of a feedback transmitting element 30, whose first end 31 is visible in FIG. 3 and is in contact with a control spool 5. Control spool 5 is capable of guiding servo pressure to the pressure surfaces of a servo spool mechanically tilting a displacement element 4 of a hydraulic unit.

(17) In the specific embodiment shown with the Figures, a rotation of the input shaft 10 around the input shaft axis 13 leads to a lateral displacement of the eccentric pin 16, which causesas best can be seen in FIG. 4a deflection of feedback transmitting element 30 and therewith a shifting of control spool 5. On the second end 12 of input shaft 10, the eccentric pin 16 is arranged with a radial offset to the input shaft axis 13. The eccentric pin 16 defines the feedback pivot axis 33, which serves as a center of rotation of the feedback transmitting element 30. The second end 32 of the feedback transmitting element 30 provides an elongated hole 34, which can receive a feedback element 3 of a hydraulic unit. The first end 31 of the feedback transmitting element 30 is in operative connection with the control spool 5. This means, if the lever 6 is rotated, that the eccentric pin 16 arranged at the second end 12 of input shaft 10 will be laterally displaced and the feedback transmitting element 30 will be forced to rotate around the feedback element 3 providing in this case the center of rotation of the feedback transmitting element 30. Accordingly, the first end 31 of feedback transmitting element 30 is forced to rotate also around the feedback element 3 and the control spool 5 is moved correspondingly. Thereby, servo pressure guided to the servo unit, is changed and the displacement element 4 of the hydraulic unit changes its inclination angle. As a result, the feedback element 3, which is attached to the displacement element 4, moves and therewith the second end 32 of feedback transmitting element 30 also. As the input shaft 10 is held in a constant position, the feedback transmitting element 30 rotates around the feedback pivot axis 33, causing the control spool 5 to disable the pressure flow towards the servo unit and thereby stopping the movement of the displacement element 4 of the hydraulic unit.

(18) Manufacturing and mounting tolerances negatively influence the functionality of this mechanical feedback chain and, therefore, have to be eliminated by adjusting the position of the eccentric pin 16 and therewith the position of the feedback pivot axis 33 after the manual displacement control device 1 has been assembled. Simultaneously, the neutral position of the hydraulic unit has to be defined accurately as this neutral position is the initial point for tolerance compensation of a hydraulic unit. In other words, a calibration of the input shaft 10 should be done when the displacement element 4 is held in its neutral position, preferably in the real neutral position in which manufacturing and assembly tolerances influencing the neutral position are compensated.

(19) According to the invention, the adjustment of the lateral position of the input shaft 10 and therewith of the eccentric pin 16 to the neutral position of the displacement element 4 is achieved by the combination of inclined surfaces 17 at the input shaft block 15 and the wedge surfaces 47 at the wedge-shaped parts 44. Thereby, a lateral movability of the input shaft axis 13 and the feedback pivot axis 33 in a direction perpendicular to the sectional line C-C is provided as descript in detail above.

(20) FIG. 4 also shows the functionality of the centering mechanism 35, which is additionally equipped with adjustment means 50 for adjusting the restoring force on the input shaft 10. If the input shaft 10 is rotated out of its starting position, the centering mechanism 35 applies a counteracting torque on the input shaft 10, which rotates/restores the input shaft 10 back to its starting position if a torque acting on lever 6 is lowered.

(21) With FIGS. 5 to 8 an embodiment for adjusting the neutral position of the displacement element 4 according to the invention is shown. In FIG. 5 the displacement element 4 is shown in the neutral position in which the hydraulic unit do not show any displacement volume. A servo spring bracket 68 is arranged parallel to the displacement element 4 such that the end stop surfaces 69 are parallel to the displacement element, respectively, parallel to a sliding surface on the displacement element 4 on which working pistons of the hydraulic unit are supported (not shown). These end stop surfaces 69 serve as spring expansion path limitations for the servo springs 63 which in one embodiment of the invention are held by means of servo spring seats 64 which abut against the end stop surfaces 69. Hence by means of the servo spring bracket 68 the servo springs 63 can be held in a pre-compressed state, e.g., against a hydraulic unit end cap. To the servo spring seats 64 servo spring rods 65 are attached with a first end 66 and traverse the servo spring bracket 68 towards the displacement element 4 on which they are supported with their second ends 67. As the servo force application point fulfills a curvature like movement when the displacement element is deflected, the second ends 67 of the servo spring rods 65 show in the embodiment shown with FIG. 5 a semi-shell form to enable a relative rotational movement of the displacement element 4 with regard to the linear movement when one of the servo springs 63 is compressed.

(22) According to the invention the orientation/positioning of the servo spring bracket 68 can be adjusted by means of a variable adjustable fixing system. In the embodiment shown in the FIGS. 5 to 8 such a variable adjustable fixing system is realized by means of threaded sleeves 72 which can be adjustably fixed to fixation bolts 70 or adjustably fixed to the servo spring bracket 68. By means of adjusting the screw-in depth of the threaded sleeves 72 the position of the servo spring bracket 68 is adjusted in such a manner that the servo spring rods 65 neither show a gap with the displacement element 4 nor with the servo spring seats 64 nor lift up the servo spring seats 64 from the end stop surfaces 69. By means of this adjustment of the position of the servo spring bracket 68 the displacement element 4 is hold safely in its neutral position as every rotational movement of the displacement element 4 would cause a compression of one of the servo springs 63. By this kind of limiting the servo spring travel by means of the servo spring bracket 68 a servo unit (not shown as a whole) can be adapted to the neutral position of displacement element 4 while compensating all manufacturing and assembly tolerances of all involved parts influencing the neutral position of the displacement element 4.

(23) In FIGS. 6 to 8 details of the servo spring bracket 68 (FIG. 6 is a top view of the servo spring bracket 68) and of the preferred variable adjustable fixation system of the servo spring bracket 68 to a housing 120 of a hydraulic unit is depicted. Thereby FIG. 7 shows a threaded sleeve 72 screwed-on the fixation bolt 70, and FIG. 8 show a threaded sleeve 72 screwed-in in a corresponding thread in the servo spring bracket 68, wherein the fixation bolt 70 traverses the threaded sleeve 72. A person skilled in the relevant art will find other ways for providing a variable adjustable fixation possibility for positioning the servo spring bracket 68 according to the invention and adapted to the real neutral position of a displacement element 4 of a hydraulic unit.

(24) While the present disclosure has been illustrated and described with respect to a particular embodiment thereof, it should be appreciated by those of ordinary skill in the art that various modifications to this disclosure may be made without departing from the spirit and scope of the present disclosure.