JP5060213B2 - Servo regulator - Google Patents

Description

  The present invention relates to a servo regulator in which a servo piston moves in an axial direction by operating hydraulic pressure.

  Conventionally, for example, a variable displacement swash plate type piston pump provided in a construction machine or a work machine tilts the swash plate of a piston pump via a servo regulator in order to control the hydraulic pressure discharged from the piston pump. It has become.

  This type of servo regulator is designed to control the tilt angle of the swash plate by mechanical feedback control that mechanically feeds back the movement of the swash plate, and the tilt angle of the swash plate detected by a potentiometer. There is an electrical feedback control method to bring it close to.

  A highly reliable mechanical feedback control method is often used for a piston pump used in a hydrostatic continuously variable transmission (HST) that supplies and discharges hydraulic oil to and from a vehicle running motor.

  As this type of servo regulator, Japanese Patent Application Laid-Open No. H10-228688 discloses a servo regulator that tilts a swash plate of a piston pump in two directions to change a displacement volume and a discharge direction of the piston pump.

  In this servo regulator, two proportional solenoids are connected to both ends of one pilot spool, respectively, and two pressure chambers are defined by both ends (pistons) of one control spool. The control spool is operated by the pilot pressure guided to the pressure chamber. As a mechanism for performing mechanical feedback control, a pin that protrudes in the radial direction from the outer periphery of the control spool, a pair of links that engage with the pin, and a spring that is interposed between the links are provided. The movement of the piston is transmitted to the control spool.

  Another mechanism is provided with two proportional solenoids for applying thrust to both ends of the control spool.

Regardless of the method, the control spool moves to a position where the biasing force of the spring corresponding to the axial position of the servo piston and the exciting force of the proportional solenoid are balanced, and the axial position of the servo piston is controlled and set in advance. The tilt angle of the swash plate is obtained.
USP 4,756,157

  However, in such a conventional servo regulator, since the link applies a driving force to the pin protruding from the outer periphery of the control spool, a bending load acts on the control spool, and the control spool slides smoothly. There is a problem that hysteresis that occurs in the control characteristics of the servo regulator increases.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce hysteresis generated in the control characteristics of a servo regulator.

The present invention is a servo regulator in which a servo piston is moved in the axial direction by operating hydraulic pressure, two hydraulic chambers to which hydraulic pressure for moving the servo piston in both directions from the neutral position in the axial direction is guided, and the hydraulic chambers are guided to the respective hydraulic chambers. Two control spools for adjusting the hydraulic pressure applied according to the respective axial positions, a spring holder that is slidably supported coaxially with the control spool, and a compression between the spring holder and each control spool and two feedback spring interposed by the two proportional solenoid for driving the control spool against the respective feedback spring in the axial direction, the spring holder with in the servo piston to move in the axial direction And a feedback link that contracts the feedback spring when pressed, Control spool in a position where the biasing force of the feedback spring in accordance with the axial position of the piston and the exciting force of each proportional solenoid are balanced is assumed, characterized in that it has a structure to be moved.

  According to the present invention, since the feedback link pushes and moves the spring holder in the axial direction and the feedback spring expands and contracts, the force from the feedback link does not act directly on the control spool, so that no bending load acts on the control spool. The friction of the control spool is reduced. Thereby, the control spool slides smoothly, the hydraulic pressure guided to the servo piston by the control spool is accurately controlled, and the hysteresis generated in the control characteristics of the servo regulator can be reduced.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  A pump 10 shown in FIG. 1 is used, for example, in a hydrostatic continuously variable transmission (HST) that supplies and discharges hydraulic oil to and from a vehicle running motor.

  1 is a transverse sectional view of the servo regulator 20 and the pump 10, FIG. 2 is a longitudinal sectional view of the servo regulator 20, and FIG. 1 is a sectional view taken along the line AA of FIG.

  The variable capacity swash plate type pump 10 includes a swash plate 12 supported by a pump housing 11 so as to be tiltable by a pair of trunnion shafts 13, and a cylinder block 14 is driven to rotate with respect to the swash plate 12. Engine rotation is transmitted to the cylinder block 14 via a shaft (not shown).

  The cylinder block 14 is provided with a plurality of cylinders arranged in the circumferential direction, and a piston is slidably interposed in each cylinder. A volume chamber is defined between each piston and each cylinder, and each volume chamber communicates alternately with the suction port and the discharge port as the cylinder block 14 rotates.

  Each revolution of the cylinder block 14 causes each piston to reciprocate the cylinder once. In the suction stroke in which the volume chamber between the piston and the cylinder expands, the hydraulic oil is sucked into the volume chamber through the suction port. In the discharge stroke in which the volume chamber contracts, hydraulic oil is discharged from the volume chamber through the discharge port.

  The displacement of the pump 10 is changed by changing the tilt angle of the swash plate 12 with respect to the rotation axis O of the cylinder block 14. Thus, the rotational speed of the traveling motor is changed by increasing or decreasing the hydraulic oil discharge amount of the pump 10.

  If the tilt angle at which the swash plate 12 is orthogonal to the rotation axis O of the cylinder block 14 is at a neutral position where the tilt angle is 0 °, the hydraulic oil discharge amount of the pump 10 becomes 0, and the rotation of the travel motor is stopped.

  The pump 10 is a two-way discharge type, and by switching the tilting direction of the swash plate 12 with respect to the rotation axis O of the cylinder block 14, the port where the hydraulic oil is sucked and discharged is switched. By switching the hydraulic oil discharge direction of the pump 10 in this way, the rotation direction of the traveling motor is switched, and the vehicle is switched between forward and reverse.

  The servo regulator 20 generates a force that is proportional to the drive current output from a controller (not shown) for the hydraulic oil discharge amount and the hydraulic oil discharge direction of the pump 10.

  As shown in FIG. 2, the servo regulator 20 includes a servo piston 30 that tilts and drives the swash plate 12 by operating hydraulic pressure, a pair of control spools 40 and 50 that adjust the operating hydraulic pressure guided to the servo piston 30, Proportional solenoids 2 and 3 for displacing the control spools 40 and 50 by a drive current and a feedback link 90 for transmitting the displacement of the servo piston 30 to the control spools 40 and 50 are provided.

  As a transmission mechanism for transmitting the displacement of the servo piston 30 to the swash plate 12 of the pump 10, a slide metal 22 that engages with the servo piston 30 and an operation arm 23 that rotates the swash plate 12 by the displacement of the slide metal 22 are provided. .

  The operation arm 23 is fixedly coupled to the trunnion shaft 13 of the swash plate 12 at its base end. As a result, the operation arm 23 rotates together with the swash plate 12.

  The slide metal 22 is rotatably connected to the distal end portion of the operation arm 23 via a pin 24 and engages with an annular recess 31 formed at the center of the servo piston 30. Accordingly, as the servo piston 30 moves, the slide metal 22 moves together with the servo piston 30 and the operation arm 23 rotates together with the slide metal 22.

  FIG. 2 shows a state in which the servo piston 30 is in a neutral position. In this neutral state, the swash plate 12 is in a neutral position where the tilt angle is 0 °. Thereby, the discharge amount of the pump 10 becomes zero, and the traveling motor is not driven to rotate.

  When the servo piston 30 moves to the left in FIG. 2 from the neutral position, the operating arm 23 rotates counterclockwise as the slide metal 22 is displaced to the left together with the servo piston 30, and the swash plate 12 is moved. Tilt to one side. As a result, the traveling motor rotates forward to advance the vehicle.

  When the servo piston 30 moves to the right in FIG. 2 from the neutral position, the operating arm 23 rotates clockwise as the slide metal 22 is displaced to the right together with the servo piston 30, and the swash plate 12 is moved. Tilt to the other. As a result, the traveling motor reverses to reverse the vehicle.

  A servo cylinder 26 in which a servo piston 30 is slidably interposed is formed in a casing 25 of the servo regulator 20, and covers 27 and 28 that close both ends of the servo cylinder 26 are fastened. In the servo cylinder 26, hydraulic chambers 32 and 33 are defined between the servo piston 30 and the covers 27 and 28, respectively.

  Two return springs 34 and 35 for urging the servo piston 30 to be held at the neutral position are provided. A rod 36 is fastened to one cover 27, and a pair of first and second retainers 37 and 38 are slidably fitted to the rod 36, and each return spring is interposed between the first and second retainers 37 and 38. 34 and 35 are compressed and interposed.

  As shown in FIG. 2, when the servo piston 30 is in the neutral position, the first retainer 37 contacts the stopper ring 40 and the second retainer 38 contacts the stopper surface 39 of the servo piston 30.

  The distance between the first and second retainers 37 and 38 is adjusted so as to be substantially equal to the distance between the stopper ring 40 and the stopper surface 39 so that the servo piston 30 does not rattle.

  The neutral position adjustment of the servo piston 30 is performed by adjusting the fastening position of the rod 36 with respect to the cover 27.

  When the servo piston 30 moves to the left in FIG. 2 from the neutral position, the second retainer 38 slides with respect to the rod 36 and moves away from the stopper ring 40, whereby the urging force of the return springs 34, 35 is applied to the servo piston 30. In contrast, it acts only in the right direction, and becomes a force that returns the servo piston 30 to the neutral position.

  On the other hand, when the servo piston 30 moves rightward in FIG. 2 from the neutral position, the first retainer 37 slides with respect to the rod 36 and moves away from the stopper surface 39, thereby compressing the return springs 34 and 35 and servoing them. The piston 30 is urged only in the left direction in FIG. 2, and the servo piston 30 is returned to the neutral position.

  Sleeves 60 and 70 are press-fitted into holes formed in the casing 25, and the control spools 40 and 50 are slidably inserted into the sleeves 60 and 70, respectively. The cylindrical sleeves 60 and 70 are arranged coaxially with each other.

  However, the present invention is not limited to this, and the control spools 40 and 50 may be directly inserted into holes formed in the casing 25.

  The feedback link 90 is rotatably connected to the casing 25 via a pin 91. Thereby, the feedback link 90 is supported so as to rotate around the center point e (see FIG. 4) of the pin 91.

  A pin 29 is fixed to the operation arm 23, and a recess 92 that engages with the pin 29 is formed at the base end of the feedback link 90. Thus, when the operation arm 23 rotates together with the swash plate 12, the feedback link 90 rotates in the same direction via the pin 29.

  In order to transmit the movement of the feedback link 90 to each control spool 40, 50, each feedback spring 45, 55 and each spring holder 46, 56 are provided between the rotation tip of the feedback link 90 and each control spool 40, 50. Are intervened.

  Holes 47 and 57 are formed in the casing 25, and spring holders 46 and 56 are slidably inserted into the holes 47 and 57, respectively.

  As shown in FIG. 4, the holes 47 and 57 are formed on the same center line c, and the spring holders 46 and 56 are arranged on the same axis.

  Each spring holder 46, 56 is formed in a bottomed cylindrical shape, and the end of each feedback spring 45, 55 is accommodated inside thereof.

  Each spring holder 46, 56 has end faces 49, 59 facing the feedback link 90, and has convex faces 48, 58 bulging from each end face 49, 59. Each end surface 49, 59 and each convex surface 48, 58 are formed in a planar shape orthogonal to the center line c.

  A cam portion 93 that engages with each of the spring holders 46 and 56 is formed at the rotating tip of the feedback link 90.

  The cam portion 93 is formed in a disc shape at the rotating tip portion of the feedback link 90, and a portion that contacts the convex surfaces 48 and 58 of the spring holders 46 and 56 is formed in a cylindrical surface centered on the point d. As a result, the cam portion 93 linearly contacts the convex surfaces 48 and 58 of the spring holders 46 and 56, and wear of the cam portion 93 and the convex surfaces 48 and 58 can be suppressed.

  However, the present invention is not limited to this, and the cam portion 93 may be formed in a spherical shape with the point d as a center at the portion that contacts the convex surfaces 48 and 58 of the spring holders 46 and 56. In this case, the cam portion 93 comes into contact with the convex surfaces 48 and 58 of the spring holders 46 and 56 in the form of dots.

  As shown in FIG. 4, the cam portion 93 has an arc-shaped cross section centered on the point d, and the center point d of the cam portion 93 is that the feedback link 90 rotates about the pin 91 to the center point e. Accordingly, the spring holders 46 and 56 are arranged so as to intersect with the center line c.

  As shown by a solid line in FIG. 4, in the state where the feedback link 90 is in the neutral position, the center point d of the cam portion 93 is positioned below the center line c of the spring holders 46 and 56 by a distance a in FIG. 4.

  As indicated by a two-dot chain line in FIG. 4, in the state where the feedback link 90 rotates at the maximum stroke (when the swash plate 12 is at the maximum tilt), the center point d of the cam portion 93 is the position of each spring holder 46, 56. It is located above the center line c by a distance b in FIG.

  When the dimensions of the respective parts are set so that the distance a and the distance b are substantially equal, and the feedback link 90 moves the spring holders 46 and 56, the cam part 93 has the convex surfaces 48 of the spring holders 46 and 56, The center of 58 is in sliding contact.

  Thereby, the bending load which acts on each spring holder 46,56 can be made small, and the friction which arises when each spring holder 46,56 slidably contacts each hole 47,57 of the casing 25 can be reduced.

  As shown in FIG. 1, a stopper pin 97 is fixedly attached to the casing 25, and this stopper pin 97 is provided between the spring holders 46 and 56. When the stopper pin 97 abuts against the end faces 49 and 59 of the spring holders 46 and 56, the stroke of the spring holders 46 and 56 is restricted, and the spring holders 46 and 56 exceed the neutral position of the feedback link 90. It does not move.

  As shown by the solid line in FIG. 4, in the state where the feedback link 90 is in the neutral position, the end surfaces 49 and 59 of the spring holders 46 and 56 abut against the stopper pin 97, and the convex surfaces 48 of the spring holders 46 and 56, 58 abuts on the cam portion 93.

  As indicated by a two-dot chain line in FIG. 4, as the feedback link 90 rotates in one direction, the end surface 59 of the spring holder 56 is separated from the stopper pin 97 and the cam portion 93 is separated from the convex surface 48 of the spring holder 46. Leave.

  Conversely, as the feedback link 90 rotates to the other side, the end surface 49 of the spring holder 46 moves away from the stopper pin 97 and the cam portion 93 moves away from the convex surface 58 of the spring holder 56.

  The base end portions of the control spools 40 and 50 are in contact with the plungers 9 of the proportional solenoids 2 and 3. The proportional solenoids 2 and 3 are moved by the plunger 9 against the feedback springs 45 and 55 by the exciting force generated by the current sent from the controller (not shown) through the lead wires 6 and 7. .

  A hydraulic pressure source pump 4 is provided as a hydraulic pressure source for driving the servo piston 30. The discharge pressure of the hydraulic source pump 4 is selectively guided to the hydraulic chambers 32 and 33 of the servo piston 30 by the control spools 40 and 50, so that the servo piston 30 moves against the return springs 34 and 35. It is supposed to be.

  Each control spool 40, 50 has an operation position for guiding the discharge pressure of the hydraulic source pump 4 to each hydraulic chamber 32, 33, a drain position for guiding the drain pressure of the tank 5 to each hydraulic chamber 32, 33, and each hydraulic chamber 32. , 33 is switched to the closing position for closing.

  As shown in FIG. 3, each sleeve 60, 70 has ports 61, 71 communicating with the hydraulic power source pump 4, ports 62, 72 communicating with the respective hydraulic chambers 32, 33, ports 63 communicating with the tank 5, 73.

  Each of the control spools 40 and 50 has grooves 41 and 51 that are recessed in an annular shape with respect to their outer peripheral surfaces.

  Each groove 41, 51 communicates each port 61, 71 and each port 62, 72 at the operating position to guide the discharge pressure of the hydraulic source pump 4 to each hydraulic chamber 32, 33, and each port at the drain position. The drain pressure of the tank 5 is guided to the hydraulic chambers 32 and 33 through communication between the ports 61 and 71 and the ports 63 and 73.

  The operation of the servo regulator 20 configured as described above will be described.

  When the vehicle stops traveling, the proportional solenoids 2 and 3 are not energized, and the thrust of the plunger 9 of each proportional solenoid 2 and 3 becomes zero.

  As a result, as shown in FIGS. 2 and 3, the control spools 40 and 50 are pushed by the feedback springs 45 and 55 and are held at the drain position.

  As a result, the drain pressure of the tank 5 is guided to the hydraulic chambers 32 and 33, the servo piston 30 is held at the neutral position where it abuts against the stopper pin 97 by the urging force of the return springs 34 and 35, and the swash plate 12 is tilted. While being held at the neutral position where the angle is 0 °, the feedback link 90 is held at the neutral position sandwiched between the spring holders 46 and 56.

  When the vehicle moves forward, one proportional solenoid 3 is energized, and the control spool 50 is pushed by the plunger 9 of the proportional solenoid 3 to switch to the operating position.

  As a result, the discharge pressure of the hydraulic source pump 4 is guided to the hydraulic chamber 33, the servo piston 30 moves to the left in FIG. 2 from the neutral position against the urging force of the return springs 34, 35, and the swash plate 12 In addition to tilting, the feedback link 90 rotates counterclockwise in FIG. 2 from the neutral position to a position indicated by a two-dot chain line in FIG.

  Thus, as the feedback link 90 rotates, the cam portion 93 moves the spring holder 56 to the right in FIG. 2 and compresses the feedback spring 55. Eventually, the biasing force of the feedback spring 55 and the exciting force of the proportional solenoid 3 are balanced, whereby each control spool 50 is switched to the closing position where the hydraulic chamber 33 is closed, and the movement of the servo piston 30 is stopped.

  When the vehicle moves backward, the other proportional solenoid 2 is energized, and the control spool 40 is pushed by the plunger 9 of the proportional solenoid 2 to switch to the operating position.

  As a result, the discharge pressure of the hydraulic source pump 4 is guided to the hydraulic chamber 32, the servo piston 30 moves to the right in FIG. 2 from the neutral position against the urging force of the return springs 34, 35, and the swash plate 12 moves. While tilting in the opposite direction, the feedback link 90 rotates in the clockwise direction in FIG. 2 from the neutral position.

  Thus, as the feedback link 90 rotates, the cam portion 93 moves the spring holder 46 leftward in FIG. 2 and compresses the feedback spring 45. Eventually, the biasing force of the feedback spring 45 and the exciting force of the proportional solenoid 2 are balanced, whereby the control spool 40 is switched to the closing position where the hydraulic chamber 32 is closed, and the movement of the servo piston 30 is stopped.

  In this way, the servo regulator 20 changes the moving direction and stop position of the servo piston 30 by the drive currents of the proportional solenoids 2 and 3 to switch the vehicle forward and backward, and adjust the vehicle traveling speed. .

  As described above, the pump 10 is of the two-direction discharge type, and the servo regulator 20 is such that the servo piston 30 moves in both directions from the neutral position in the axial direction. A directional discharge type may be used, and the servo piston 30 may move in only one direction from the neutral position in the axial direction. In that case, for example, the hydraulic chamber 33, the control spool 50, the feedback spring 55, the spring holder 56, and the like provided in the servo regulator 20 are eliminated.

  In the present embodiment, the servo regulator 20 is configured such that the servo piston 30 moves in the axial direction by the operating hydraulic pressure, and the hydraulic chamber 32 to which the hydraulic pressure for moving the servo piston 30 is guided, and the hydraulic pressure guided to the hydraulic chamber 32 to the axis thereof. A control spool 40 that is adjusted according to the position in the direction, a spring holder 46 that is slidably supported coaxially with the control spool 40, and that is compressed and interposed between the spring holder 46 and the control spool 40. Feedback spring 45, the proportional solenoid 2 that drives the control spool 40 in the axial direction against the feedback spring 45, and feedback by pressing the spring holder 46 as the servo piston 30 moves in the axial direction. A feedback link 90 for contracting the spring 45; Since the control spool 40 is moved to a position where the biasing force of the feedback spring 45 and the exciting force of the proportional solenoid 2 are balanced according to the axial position of the vobo piston 30, the feedback link 90 moves the spring holder 46 in the axial direction. By extending and contracting the feedback spring 45, the force from the feedback link 90 does not act directly on the control spool 40, so that the bending load acting on the control spool 40 does not act, and the friction of the control spool 40 is reduced. By smoothly sliding the control spool 40 in this way, the movement of the servo piston 30 is accurately controlled by the hydraulic pressure adjusted via the control spool 40, and the hysteresis generated in the control characteristics of the servo regulator 20 is reduced. can do.

  In this embodiment, the feedback link 90 is configured to rotate as the servo piston 30 moves in the axial direction, and a cam portion 93 that presses the end surface 48 of the spring holder 46 is formed at the rotating tip of the feedback link 90. Therefore, when the feedback link 90 rotates and moves each spring holder 46, the cam portion 93 is slidably pressed against the end surface 48 of the spring holder 46, and the control spool 40 is pressed via the spring 45, thereby controlling The bending load acting on the spool 40 is reduced, and the friction of the control spool 40 is reduced. In this way, the sliding of the control spool 40 is performed smoothly, so that hysteresis occurring in the control characteristics of the servo regulator 20 can be reduced.

  In the present embodiment, the cam portion 93 has an arc-shaped cross section centered on the point d, and the center point d of the cam portion 93 and the center line c of the spring holder 46 as the feedback link 90 rotates. Since the cam portions 93 push the spring holder 46 along the center line c of the spring holder 46, the amount of eccentricity can be reduced and the bending load acting on the spring holder 46 can be reduced. Friction is reduced. Thus, the smooth sliding of the spring holder 46 can reduce the hysteresis generated in the control characteristics of the servo regulator 20.

  In the present embodiment, the two hydraulic chambers 32 and 33 to which the hydraulic pressure for moving the servo piston 30 in both directions from the neutral position in the axial direction is guided, and the hydraulic pressure guided to the hydraulic chambers 32 and 33 are set to the respective axial positions. Two control spools 40, 50 to be adjusted in response, two spring holders 46, 56 slidably supported coaxially with each control spool 40, 50, each spring holder 46, 56 and each control Two feedback springs 45, 55 that are compressed and interposed between the spools 40, 50, and two proportionalities that drive the control spools 40, 50 in the axial direction against the feedback springs 45, 55. As the solenoids 2 and 3 and the servo piston 30 move in the axial direction, the spring holders 46 and 56 move in the axial direction. Due to a over-back link 90 is switched to the discharge direction of the pump 10.

  In the present embodiment, the spring holders 46 and 56 are brought into contact with each other at the neutral position, and the stopper pins 97 that restrict the stroke ranges of the spring holders 46 and 56 are provided. The spring holder 46 is smoothly slid.

  In the present embodiment, since the control spools 40 and 50 are provided independently, it is possible to adopt a configuration that guides the drain pressure to the hydraulic chambers 32 and 33 at the neutral position. For this reason, the control spool neutral position adjustment, which is necessary when a conventional control spool is provided, becomes unnecessary.

  Further, with the above-described configuration, it is possible to reduce the accuracy with which the control spools 40 and 50 are arranged coaxially, and the control spools 40 and 50 can be accommodated in the casing 25 via the sleeves 60 and 70. .

  In the present embodiment, a casing 25 that accommodates the control spools 40 and 50 is provided, and two sleeves 60 and 70 into which the control spools 40 and 50 are slidably inserted are provided in the casing 25. Since the ports 61 to 63 and 71 to 73 are formed in the ports 60 and 70, it is easy to secure the performance of the servo regulator 20 by increasing the processing accuracy of the ports 61 to 63 and 71 to 73, and the casing 25 The processing accuracy required for the oil passage is reduced, and the cost of the product can be reduced.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The servo regulator of the present invention is not limited to driving a swash plate of a variable capacity swash plate type piston pump, but also drives a swash plate of a variable capacity type swash plate type piston motor, and drives other machines and equipment. Can be used for what to do.

FIG. 3 is a cross-sectional view of the servo regulator and the pump along the line AA in FIG. 2 according to the embodiment of the present invention. Similarly, a sectional view of a servo regulator. Sectional drawing of a control spool, a spring holder, etc. similarly. Sectional drawing of a spring holder etc. similarly.

Explanation of symbols

2, 3 proportional solenoid 10 pump 12 swash plate 20 servo regulator 25 casing 30 servo piston 40, 50 control spool 45, 55 feedback spring 46, 56 spring holder 60, 70 sleeve 90 feedback link 93 cam section

Claims (7)

A servo regulator in which the servo piston moves in the axial direction by hydraulic pressure,
Two hydraulic chambers to which hydraulic pressure is guided to move the servo piston in both directions from the neutral position in the axial direction ;
Two control spools for adjusting the hydraulic pressure guided to each of the hydraulic chambers according to the respective axial positions;
A spring holder slidably supported coaxially with the control spool;
Two feedback springs compressed and interposed between the spring holder and each control spool;
Two proportional solenoid for driving the respective control spool in the axial direction against the Each feedback spring,
A feedback link that contracts the feedback spring by pushing the spring holder as the servo piston moves in the axial direction;
A servo regulator characterized in that the control spool moves to a position where the biasing force of the feedback spring and the exciting force of each proportional solenoid are balanced in accordance with the position of the servo piston in the axial direction. The feedback link rotates as the servo piston moves in the axial direction.
The servo regulator according to claim 1, wherein a cam portion that presses an end surface of the spring holder is formed at a rotation tip portion of the feedback link. The cam portion has an arc-shaped cross section,
The servo regulator according to claim 2, wherein a center point of the cam portion is arranged so as to intersect a center line of the spring holder as the feedback link rotates. And two of the spring holder slidably supported by the respective control spool coaxially,
4. The feedback link according to claim 1, further comprising: the one feedback link that moves the spring holders in the axial direction as the servo piston moves in the axial direction. 5. Servo regulator.   5. The servo regulator according to claim 4, further comprising a stopper pin that restricts a stroke range of each spring holder by contacting each spring holder at a neutral position.   6. The servo regulator according to claim 4, wherein each of the control spools is configured to guide a drain pressure to each of the hydraulic chambers at a neutral position. A casing for housing each control spool;
The servo regulator according to any one of claims 4 to 6, wherein the casing is provided with two sleeves into which the control spools are slidably inserted.

Images