JP2009243663A - Servo regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce hysteresis caused in control characteristics of a servo regulator. <P>SOLUTION: In the servo regulator 20, a servo piston 30 moves in both directions from a neutral position in regard to an axial direction, and it is equipped with a cylindrical spring box 80 provided away from a casing 25, a feedback spring 44 interposed in the spring box 80 in a pre-compressed state and between first and second control spools 40, 50, first and second rear springs 48, 58 energizing the first and second control spools 40, 50 against each other, and a feedback link 90 transmitting movement of the servo piston 30 to the spring box 80. It is composed such that the first and second control spools 40, 50 are moved to a balancing position of energizing force of the feedback spring 44, energizing force of the first and second rear springs 48, 58, and thrust of first and second proportional solenoids 2, 3. <P>COPYRIGHT: (C)2010,JPO&INPIT

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 uses a mechanical feedback control method that mechanically feeds back the movement of the swash plate as a method for controlling the tilt angle of the swash plate, and a set value for 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.

  This servo regulator is provided with two proportional solenoids for applying thrust to both ends of one pilot spool, and two pressure chambers are defined by both ends of one control spool. The control spool is operated by a pilot pressure introduced to each 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. The control spool moves to a position where the biasing force of the spring according to the position of the servo piston in the axial direction and the thrust of the proportional solenoid are balanced to control the position of the servo piston in the axial direction. A corner is obtained.
USP 4,756,157

  However, in such a conventional servo regulator, a bending load (squeezing force) acts on the control spool because the link applies a driving force to a position off the axis of the pin protruding from the control spool. The control spool cannot slide smoothly, and there is a problem that the hysteresis generated in the control characteristics of the servo regulator is increased.

  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 both directions from a neutral position in the axial direction by operating hydraulic pressure, and first and second hydraulic chambers to which hydraulic pressure for moving the servo piston in both directions in the axial direction is guided, The first and second control spools that adjust the hydraulic pressure guided to the first and second hydraulic chambers according to the respective axial positions, and the cylinders that are provided apart from the casing that houses the first and second control spools -Shaped spring box, a feedback spring that is preliminarily compressed in the spring box and sandwiched between the first and second control spools, and the first and second control spools against the feedback spring Drive the first and second back springs and the first and second control spools in the axial direction to urge them so that they press against each other. First and second proportional solenoids, and a feedback link that moves the spring box in the axial direction as the servo piston moves in the axial direction, and the first and second control spools are biased by the feedback spring. The urging force of the first and second back springs and the thrust of the first and second proportional solenoids are moved to a position that balances.

  According to the present invention, since the force from the feedback link is transmitted to the first and second control spools via the spring box and the feedback spring, it is possible to suppress the bending load (twisting force) from acting on the first and second control spools. Thus, the friction of the first and second control spools is reduced. Thereby, since the control spool slides smoothly, the movement of the servo piston is accurately controlled by the hydraulic pressure adjusted via the control spool, and the occurrence of hysteresis in the control characteristics of the servo regulator can be suppressed.

  Since the feedback spring is preliminarily compressed and interposed, the first and second control spools are prevented from moving due to inertial force or the like when the first and second proportional solenoids are not excited. The first and second control spools operate accurately when the proportional solenoid is excited.

  The spring box is provided away from the casing, and is supported by the first and second control spools via the feedback spring, so that even if the coaxiality between the first and second control spools decreases, the first, The second control spool can slide smoothly, and an increase in friction of the first and second control spools can be suppressed.

  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.

  In the variable capacity swash plate type pump 10, a cylinder block 14 and a swash plate 12 are accommodated in a pump housing 11. The rotation of the engine 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 swash plate 12 is supported by a pair of trunnion shafts 13 so as to be tiltable. 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 traveling motor stops.

  The pump 10 is of a two-way discharge type, and suction and discharge of hydraulic oil is performed by switching the tilt direction of the swash plate 12 with respect to the rotation axis O of the cylinder block 14 at a tilt angle of 0 °. The port is switched. Thus, by switching the direction in which the pump 10 discharges the hydraulic oil, the rotation direction of the travel motor is switched, and the vehicle is switched between forward and reverse.

  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, and first and second control spools 40 and 50 that adjust the operating hydraulic pressure guided to the servo piston 30. The first and second proportional solenoids 2 and 3 for displacing the first and second control spools 40 and 50 by the drive current and the feedback for transmitting the displacement of the servo piston 30 to the first and second control spools 40 and 50. And a link 90.

  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 casing 25 of the servo regulator 20 is formed with a servo cylinder 26 in which a servo piston 30 is slidably interposed, and a cover 27 that closes both ends of the servo cylinder 26 is fastened. In the servo cylinder 26, first and second hydraulic chambers 32 and 33 are defined between the servo piston 30 and the covers 27, 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 abuts against the stopper ring 94 and the nut 99, and the second retainer 38 includes the stopper surface 39 of the servo piston 30 and the rod 36. It abuts on the stepped portion 36a.

  The neutral position adjustment of the servo piston 30 is performed by first adjusting the positions of the two nuts 99 screwed to the rod 36 and the first and second retainers 37 contacting the nut 99 and the step portion 36a of the rod 36, 38 is adjusted so as to contact the stopper ring 94 and the stopper surface 39 without rattling, and then the fastening position of the rod 36 with respect to the cover 27 is adjusted, and the two nuts 98 screwed to the rod 36 are adjusted. Tighten and fix.

  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 surface 39, 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 to the right in FIG. 2 from the neutral position, the first retainer 37 slides with respect to the rod 36 and moves away from the stopper ring 94, 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.

  A sleeve 60 is interposed in a hole formed in the casing 25, and the first and second control spools 40 and 50 are slidably inserted into the sleeve 60. The cylindrical sleeves 60 are arranged coaxially with each other.

  However, the present invention is not limited to this, and the first and second 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 91a of the support shaft 91. Thereby, the feedback link 90 is supported so as to rotate about the center point e of the pin 91a.

  The support shaft 91 has a shaft portion 91b that fits into a hole in the casing 25, and a screw portion 91c that protrudes from the base end of the shaft 91b to the outside of the casing 25, and a nut 96 that is screwed into the screw portion 91c. It is fastened to the casing 25 via

  The center point e of the pin 91a is offset by a predetermined distance with respect to the center line of the shaft portion 91b, and the position of the center point e of the pin 91a is changed by rotating the shaft portion 91b with respect to the hole of the casing 25. As a result, neutral position adjustment of the first and second control spools 40 and 50 is performed as will be described later.

  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 the first and second control spools 40, 50, a spring box 80 that moves following the rotation tip of the feedback link 90 is provided. It is arrange | positioned in the space in the casing 25 away from.

  A cam pin 95 protruding from the rotating tip of the feedback link 90 is provided, and a long hole 81 is formed at the center of the spring box 80, and the cam pin 95 engages with the long hole 81. The cam pin 95 comes into contact with the side surface of the elongated hole 81, and the spring box 80 moves in the axial direction via the cam pin 95 as the servo piston 30 moves and the feedback link 90 rotates. Since the outer peripheral surface of the cam pin 95 comes into linear contact with the side surface of the long hole 81, wear of both can be suppressed.

  In the present embodiment, the feedback link 90 is arranged offset to the side of the spring box 80.

  The spring box 80 is formed in a hollow cylindrical shape, and the first and second control spools 40 and 50, the first and second retainers 45 and 55, and the coiled feedback spring 44 are accommodated therein.

  The spring box 80, the first and second retainers 45, 55, the feedback spring 44, and the first and second control spools 40, 50 are arranged on the same axis.

  The first and second retainers 45 and 55 are formed in a ring shape having an L-shaped cross section, and both end portions of the feedback spring 44 are in contact with the respective flange portions, and the outer peripheral surfaces of the respective flange portions are the inner peripheral surfaces of the spring box 80. The inner peripheral surfaces of the first and second control spools 40 and 50 are slidably fitted to the outer peripheral surfaces 47 and 57, respectively.

  The first and second retainers 45 and 55 are not limited to this, and the first and second retainers 45 and 55 have a gap between one of the inner peripheral surface of the spring box 80 and the outer peripheral surfaces 47 and 57 of the first and second control spools 40 and 50. It may be provided to have.

  First and second stopper rings 86 and 87 are fitted on the inner peripheral surface of the spring box 80, and the sliding range of the first and second retainers 45 and 55 is limited by the first and second stopper rings 86 and 87. The The first and second stopper rings 86 and 87 are respectively locked at predetermined positions of the spring box 80 via snap rings 88.

  The feedback spring 44 is interposed between the first and second retainers 45 and 55 in a compressed state. The first and second retainers 45 and 55 are urged away from each other by the feedback spring 44.

  The first and second control spools 40 and 50 are formed with first and second step portions 42 and 52, and the first and second retainers 45 and 55 abut against the first and second step portions 42 and 52. The movement of the feedback link 90 is transmitted to the first and second control spools 40 and 50 via the feedback spring 44.

  The first and second control spools 40, 50 have front end surfaces 40a, 50a that come into contact with each other. Each of the front end surfaces 40a and 50a is formed in a planar shape perpendicular to the center line of the first and second control spools 40 and 50, respectively.

  When the servo piston 30 is in the neutral position, as shown in FIG. 2, the front end surfaces 40a and 50a of the first and second control spools 40 and 50 are in contact with each other, and the first and second retainers 45 and 55 are in contact with each other. The first and second stopper rings 86 and 87 are in contact with each other, and the first and second control spools 40 and 50 are in contact with the first and second step portions 42 and 52, respectively. At this time, the distance between the first and second stopper rings 86 and 87 is equal to the distance between the first and second step portions 42 and 52. Accordingly, the biasing force of the feedback spring 44 does not act on the first and second control spools 40 and 50 at the neutral position of the servo regulator 20.

  The servo regulator 20 urges the first and second control spools 40 and 50 so that the first and second control spools 40 and 50 are not separated from each other in the axial direction so that they are pressed against each other. First and second back springs 48 and 58 are provided.

  Retainers 49 and 59 are fitted and attached in the middle of the first and second control spools 40 and 50, and coiled between the retainers 49 and 59 and the first and second proportional solenoids 2 and 3. The first and second rear springs 48 and 58 are respectively compressed and interposed. The first and second control spools 40 and 50 are urged in a direction approaching each other by the first and second rear springs 48 and 58.

  The base ends of the first and second control spools 40 and 50 are in contact with the plungers 9 of the first and second proportional solenoids 2 and 3. A current is sent to the first and second proportional solenoids 2 and 3 from a controller (not shown) via a lead wire 6, and the plunger 9 is caused to protrude by a thrust generated by the current. The first and second control spools 40 and 50 are moved in the axial direction against the feedback spring 44 by being pushed by the plungers 9.

  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 first and second hydraulic chambers 32 and 33 of the servo piston 30 by the first and second control spools 40 and 50, so that the servo piston 30 is connected to each return spring. The tilting angle of the swash plate 12 is changed by moving against the movements 34 and 35 and rotating the operation arm 23.

  The first and second control spools 40 and 50 move in the axial direction thereof, thereby operating positions for guiding the discharge pressure of the hydraulic source pump 4 to the first and second hydraulic chambers 32 and 33, and the first and second The position is switched between a closing position for closing the hydraulic chambers 32 and 33 and a drain position for guiding the drain pressure of the tank 5 to the first and second hydraulic chambers 32 and 33.

  Each sleeve 60 has a pump port 61 that communicates with the hydraulic source pump 4, a supply / discharge port 62 that communicates with the first and second hydraulic chambers 32 and 33, and a drain port 63 that communicates with the tank 5.

  The first and second control spools 40 and 50 have grooves 41 and 51 that are recessed in an annular shape with respect to the respective outer peripheral surfaces. Each groove 41, 51 communicates each pump port 61 and each supply / discharge port 62 at the operating position to guide the discharge pressure of the hydraulic source pump 4 to the first and second hydraulic chambers 32, 33, and to the drain position. Thus, each supply / discharge port 62 and each drain port 63 communicate with each other to guide the drain pressure of the tank 5 to the first and second hydraulic chambers 32 and 33.

  The first and second control spools 40 and 50 move so that they are not separated from each other in the axial direction by the urging force of the first and second rear springs 48 and 58, so when one of them moves in the direction to open the drain port 63. The other moves in the direction of opening the pump port 61.

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

  When the vehicle stops traveling, the first and second proportional solenoids 2 and 3 are in a non-energized state, and the thrust of the plunger 9 of the first and second proportional solenoids 2 and 3 becomes zero.

  As a result, the first and second control spools 40 and 50 are urged by the feedback spring 44 and the first and second rear springs 48 and 58, and as shown in FIG. And the first and second step portions 42 and 52 are held at neutral positions where they abut against the first and second retainers 45 and 55, respectively.

  In the neutral position, the feedback spring 44 is provided with an initial load by being interposed between the first and second stopper rings 86 and 87 in a pre-compressed state. The second control spools 40 and 50 are supported with respect to the spring box 80, and the first and second control spools 40 and 50 are prevented from moving due to an inertia load or the like, and are kept in the neutral position. The initial load of the feedback spring 44 is larger than the urging force of the first and second rear springs 48 and 58.

  In the neutral position, the first and second control spools 40 and 50 are held at the drain position where each drain port 63 is slightly opened, and the drain pressure of the tank 5 is guided to the first and second hydraulic chambers 32 and 33, and the servo The piston 30 is held at the neutral position by the urging force of the return springs 34 and 35, the swash plate 12 is held at the neutral position where the tilt angle is 0 °, and the feedback link 90 is held at the neutral position.

  When the vehicle advances, only the second proportional solenoid 3 is energized, the second control spool 50 is pushed by the plunger 9 of the proportional solenoid 3 to open the pump port 61, and the first control spool 40 is connected to the second control spool 50. When pressed, the drain port 63 is opened.

  When pushed by the plunger 9 of the second proportional solenoid 3, the tip surface 50a of the second control spool 50 and the tip surface 40a of the first control spool 40 are in contact with each other, so that the first control spool 40 is accurately moved. .

  As a result, the discharge pressure of the hydraulic source pump 4 is guided to the second hydraulic chamber 33, while the drain pressure is guided to the first hydraulic chamber 32, and the servo piston 30 is neutral against the urging force of the return springs 34 and 35. 2, the swash plate 12 tilts and the feedback link 90 rotates counterclockwise in FIG. 2 from the neutral position.

  Thus, as the feedback link 90 rotates, the cam pin 95 moves the spring box 80 to the right in FIG. 2, and the feedback spring 44 contracts. Eventually, the urging force of the feedback spring 44, the urging force of the first and second rear springs 48, 58 and the thrust of the second proportional solenoid 3 are balanced, whereby the first and second control spools 40, 50 are moved to the neutral position. Returning, the supply of hydraulic oil to the second hydraulic chamber 33 stops, and the movement of the servo piston 30 stops at a position corresponding to the thrust of the second proportional solenoid 3. As a result, the servo regulator 20 adjusts the tilt angle of the swash plate 12 of the pump 10, the running motor is rotated by the hydraulic oil discharged from the pump 10 at a predetermined flow rate, and the vehicle advances at a predetermined speed.

  When the vehicle is moving backward, only the first proportional solenoid 2 is energized, the first control spool 40 is pushed by the plunger 9 of the first proportional solenoid 2 to open the pump port 61, and the second control spool 50 is the first control spool. 40 is pushed to open the drain port 63.

  When pushed by the plunger 9 of the first proportional solenoid 2, the tip surface 40a of the first control spool 40 and the tip surface 50a of the second control spool 50 are in contact with each other, so that the second control spool 50 is accurately moved. .

  As a result, the discharge pressure of the hydraulic source pump 4 is guided to the first hydraulic chamber 32, while the drain pressure is guided to the second hydraulic chamber 33, and the servo piston 30 is neutral against the urging force of the return springs 34 and 35. 2, the swash plate 12 is tilted in the opposite direction, and the feedback link 90 is rotated clockwise from the neutral position in FIG.

  Thus, as the feedback link 90 rotates, the cam pin 95 moves the spring box 80 leftward in FIG. 2 and the feedback spring 44 contracts. Eventually, the urging force of the feedback spring 44, the urging force of the first and second rear springs 48, 58 and the thrust of the first proportional solenoid 2 are balanced, so that the first and second control spools 40, 50 are in the neutral position. Returning, the supply of hydraulic oil to the first oil chamber 32 stops, and the movement of the servo piston 30 stops at a position corresponding to the thrust of the first proportional solenoid 2. As a result, the servo regulator 20 adjusts the tilt angle of the swash plate 12 of the pump 10, the driving motor rotates by the hydraulic oil discharged from the pump 10 at a predetermined flow rate, and the vehicle moves backward at a predetermined speed.

  In this way, the servo regulator 20 changes the moving direction and the stop position of the servo piston 30 by the drive currents of the first and second proportional solenoids 2 and 3, and switches between forward and reverse travel of the vehicle and travel of the vehicle. Adjust the speed.

  By the way, for example, when the vehicle is driven downhill or decelerated, when the traveling motor is rotationally driven by the wheels, a force in the direction in which the tilt angle of the swash plate 12 is increased by the hydraulic pressure sent from the traveling motor to the pump 10 works. . In such a situation, the first and second control spools 40 and 50 are not separated from each other by the urging force of the first and second rear springs 48 and 58, so that as the tilt angle of the swash plate 12 increases, Moves in the direction in which the drain port 63 is opened, the other moves in the direction in which the pump port 61 is opened, and the servo piston 30 applies a force in a direction in which the tilt angle of the swash plate 12 decreases, and the tilt of the swash plate 12 An increase in angle is suppressed.

  This operation will be described in detail. For example, when the vehicle travels downhill or decelerates, when the tilt angle of the swash plate 12 increases from the set value by the hydraulic pressure sent from the traveling motor driven by the wheels to the pump 10, feedback is performed. The link 90 rotates counterclockwise in FIG. 2 from the neutral position, the cam pin 95 moves the spring box 80 to the right in FIG. 2, the feedback spring 44 contracts, and the second control is performed by the biasing force of the feedback spring 44. The spool 50 moves in the direction to open the drain port 63, and the first control spool 40 moves in the direction to open the pump port 61 by the urging force of the first back spring 48, thereby increasing the pressure in the first hydraulic chamber 32 to increase the servo. The piston 30 applies a force in the direction in which the tilt angle of the swash plate 12 decreases, It is suppressed that the rolling angle is increased.

  Thereby, for example, when the vehicle travels downhill or decelerates, the tilt angle of the swash plate 12 is maintained at the set value, and the traveling speed of the vehicle can be adjusted.

  On the other hand, when the first and second rear springs 48 and 58 are not provided and the first and second control spools 40 and 50 are separated from each other, the first control spool 40 does not move rightward. Since the pressure cannot be guided to the first hydraulic chamber 32, it is not possible to prevent the tilt angle of the swash plate 12 from increasing beyond the set value, and the vehicle may not be able to decelerate as controlled or may run away.

  In the present embodiment, the servo regulator 20 moves the servo piston 30 in both directions from the neutral position in the axial direction by operating hydraulic pressure, and the first and second hydraulic pressures to which the hydraulic pressure that moves the servo piston 30 in both directions in the axial direction is guided. Chambers 32, 33, first and second control spools 40, 50 for adjusting the hydraulic pressure guided to the first and second hydraulic chambers 32, 33 according to the respective axial positions, and the first, first A cylindrical spring box 80 provided apart from the casing 25 that accommodates the two control spools 40, 50, and a compression box interposed in advance in the spring box 80 and between the first and second control spools 40, 50 A feedback spring 44 sandwiched between the first and second control spools 40 and 50 against the feedback spring 44 First and second rear springs 48 and 58 that urge the two to press against each other; first and second proportional solenoids 2 and 3 that drive the first and second control spools 40 and 50 in the axial direction; A feedback link 90 for moving the spring box 80 in the axial direction as the servo piston 30 moves in the axial direction, and the first and second control spools 40, 50 are connected to the biasing force of the feedback spring 44 and the first, The configuration is such that the urging force of the second rear springs 48 and 58 and the thrust of the first and second proportional solenoids 2 and 3 are moved to a position where they are balanced.

  Since the force from the feedback link 90 is transmitted to the first and second control spools 40 and 50 via the spring box 80 and the feedback spring 44 based on the above configuration, the force from the feedback link 90 is controlled in the first and second controls. It acts on the same axis as the spools 40 and 50, suppresses the bending load (squeezing force) from acting on the first and second control spools 40 and 50, and reduces the friction of the first and second control spools 40 and 50. The As a result, the first and second control spools 40 and 50 slide smoothly, so that the movement of the servo piston 30 is accurately controlled by the hydraulic pressure adjusted via the first and second control spools 40 and 50. The occurrence of hysteresis in the control characteristics of the servo regulator 20 can be suppressed.

  Since the feedback spring 44 is preliminarily compressed and interposed, it is possible to prevent the first and second control spools 40 and 50 from moving due to an inertial force or the like when the first and second proportional solenoids 2 and 3 are not excited. At the same time, the first and second control spools 40 and 50 operate accurately when the first and second proportional solenoids 2 and 3 are excited.

  Since the spring box 80 does not slide on the casing 25, the friction can be kept low.

  The spring box 80 is provided apart from the casing 25 and is supported by the first and second control spools 40 and 50 via the feedback spring 44, whereby the first and second control spools 40 and 50 are coaxial. The first and second control spools 40 and 50 can slide smoothly even if the first and second control spools 40 and 50 are reduced, and the increase in friction of the first and second control spools 40 and 50 is suppressed. This makes it possible to reduce the accuracy with which the first and second control spools 40 and 50 are arranged coaxially, and the first and second control spools 40 and 50 are accommodated in the casing 25 via the sleeves 60. be able to.

  In the present embodiment, the first and second control spools 40, 50 are connected to the first and second hydraulic chambers 32, 33 and the first and second hydraulic chambers 32, 33. The drain port 63 is switched to a drain position that guides the drain pressure of the drain port 63, and one of the first and second control spools 40, 50 moves in the direction to open the drain port 63, and the other opens the pump port 61. It was set as the structure which moves to.

  Based on the above configuration, when the swash plate 12 tries to move beyond the control range in the tilt angle increasing direction due to the force acting on the servo regulator 20 from the swash plate 12, the first and second back springs 48, 58 are attached. When the first and second control spools 40 and 50 move together so as not to be separated from each other by the force, when one of the first and second control spools 40 and 50 moves in the direction of opening the drain port 63, the other is the pump port. 61 is moved in the opening direction, and the servo piston 30 applies a force in a direction in which the tilt angle of the swash plate 12 decreases, and the tilt angle of the swash plate 12 is prevented from increasing.

  In the present embodiment, front end surfaces 40a and 50a that are in contact with the first and second control spools 40 and 50 are formed, and the front end surfaces 40a and 50a are respectively connected to the center lines of the first and second control spools 40 and 50. It was formed in an orthogonal plane shape.

  Based on the above configuration, the first and second control spools 40 and 50 are allowed to be displaced in the radial direction, and no bending load is applied to the first and second control spools 40 and 50. The friction of the two control spools 40, 50 is reduced.

  In addition, based on the above configuration, it is possible to reduce the accuracy with which the first and second control spools 40 and 50 are arranged on the same axis, and the first and second control spools 40 and 50 are casings through the sleeves 60. 25.

  In the present embodiment, two sleeves 60 into which the first and second control spools 40 and 50 are slidably inserted are disposed in the casing 25, and ports 61 to 63 for guiding hydraulic oil to the respective sleeves 60 are formed. did.

  Based on the above configuration, it is easy to secure the performance of the servo regulator 20 by increasing the processing accuracy of each of the ports 61 to 63, and the processing accuracy required for the oil passage of the casing 25 is reduced. Cost reduction is planned.

  In the present embodiment, the feedback link 90 is offset with respect to the spring box 80. However, the present invention is not limited to this, and the feedback link 90 is disposed in the radial direction of the spring box 80 as shown in FIG. May be. In this case, a cylindrical cam pin portion 98 is formed at the rotating tip of the feedback link 90, and the cam pin portion 98 engages with the groove 89 of the servo piston 30. The cam pin portion 98 abuts the side surface of the groove 89, and the spring box 80 moves in the axial direction via the cam pin portion 98 as the servo piston 30 moves and the feedback link 90 rotates. Since the outer peripheral surface of the cam pin portion 98 comes into linear contact with the side surface of the groove 89, wear of the both can be suppressed.

  In the present embodiment, the servo regulator 20 is provided with a feedback link 90 at a substantially central portion thereof, and is formed substantially symmetrically with respect to the center line of the feedback link 90. Can do.

  Further, in the present embodiment, as a configuration in which the feedback link 90 is engaged with the spring box 80, the elongated hole 81 is formed in the spring box 80. However, the present invention is not limited to this, and the spring box 80 opens to the outer peripheral surface. An annular groove may be formed.

  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, or drives other machines, equipment, etc. Available for things.

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. 1 is a cross-sectional view of a servo regulator showing an embodiment of the present invention.

Explanation of symbols

2, 3 First, second proportional solenoid 10 Pump 12 Swash plate 20 Servo regulator 25 Casing 30 Servo piston 32, 33 First, second hydraulic chamber 40, 50 First, second control spool 45, 55 First, first Two feedback springs 48, 58 First and second rear springs 60 Sleeve 80 Spring box 90 Feedback link 95 Cam pin

Claims (4)

A servo regulator in which the servo piston moves in both directions from the neutral position in the axial direction by operating hydraulic pressure,
First and second hydraulic chambers to which hydraulic pressure for moving the servo piston in both directions in the axial direction is guided;
First and second control spools for adjusting the hydraulic pressure guided to the first and second hydraulic chambers according to the respective axial positions;
A cylindrical spring box provided apart from the casing containing the first and second control spools;
A feedback spring that is pre-compressed and interposed in the spring box and is sandwiched between the first and second control spools;
First and second back springs that bias the first and second control spools against each other against the feedback springs,
The first and second proportional solenoids for driving the first and second control spools in the axial direction;
A feedback link that moves the spring box in the axial direction as the servo piston moves in the axial direction;
The first and second control spools are configured to move to a position where the biasing force of the feedback spring, the biasing force of the first and second back springs, and the thrust of the first and second proportional solenoids are balanced. Features servo regulator. The first and second control spools are
An operating position for guiding the hydraulic pressure of the pump port to the first and second hydraulic chambers;
Switch to the drain position that guides the drain pressure of the drain port to the first and second hydraulic chambers,
2. The servo according to claim 1, wherein one of the first and second control spools moves in a direction to open the drain port and the other moves in a direction to open the pump port. regulator. Forming a front end surface that contacts the first and second control spools;
The servo regulator according to claim 1 or 2, wherein each of the front end surfaces (a) is formed in a planar shape perpendicular to the center lines of the first and second control spools. Two sleeves in which the first and second control spools are slidably inserted into the casing are interposed,
The servo regulator according to claim 2 or 3, wherein the pump port and the drain port for guiding the hydraulic pressure to each sleeve are formed.

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