JP2009243409A - Servo regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce hysteresis to occur in the control characteristics of a servo regulator. <P>SOLUTION: The servo regulator 20, wherein a servo piston 30 is moved from a neutral position in both axial directions with operating hydraulic pressure, includes a hollow cylindrical spring holder 80 slidably supported coaxially with first and second control spools 40, 50, and first and second feedback springs 45, 55 compressed and mounted between the spring holder 80 and each of the first and second control spools 40, 50. The first and second control spools 40, 50 are moved to positions where the energizing force of the first and second feedback springs 45, 55 and the thrust of first and second proportional solenoids 2, 3 are balanced with each other. <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 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 are slidably supported coaxially with the first and second control spools. A hollow cylindrical spring holder, first and second feedback springs compressed and interposed between the spring holder and the first and second control spools, and the first and second feedback springs. The first and second proportional solenoids that drive the first and second control spools in the axial direction against the force and the spring holder as the servo piston moves in the axial direction The first and second control spools are connected to each other so that they are not separated from each other in the axial direction by the urging force of the first and second feedback springs. And a coupling that allows displacement in the radial direction, and the first and second control spools are moved to a position where the biasing forces of the first and second feedback springs and the thrust of the first and second proportional solenoids are balanced. It was characterized by having a configuration.

  According to the present invention, since the force from the feedback link is transmitted to the first and second control spools via the hollow cylindrical spring holder and the first and second feedback springs, the bending load is applied to the first and second control spools. It is possible to suppress the (twisting force) from acting and to reduce the friction of the first and second control spools. As a result, since the control spool slides smoothly, the movement of the servo piston is accurately controlled by the hydraulic pressure adjusted via the first and second control spools, and hysteresis occurs in the control characteristics of the servo regulator. It can be suppressed.

  The coupling allows the shaft centers of the first and second control spools to be displaced, prevents the bending load acting on the first and second control spools from acting, and reduces the friction of the first and second control spools.

  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 traveling motor is stopped.

  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 around the center point e (see FIG. 3) 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 holder 80 that moves following the rotation tip of the feedback link 90 is provided. First and second feedback springs 45 and 55 are interposed between the two control spools 40 and 50, respectively.

  As shown in FIG. 3, a hole 28 is formed in the casing 25, and a spring holder 80 is slidably inserted into the hole 28.

  The spring holder 80 is formed in a hollow cylindrical shape, and the end portions of the first and second feedback springs 45 and 55 are accommodated inside thereof.

  The spring holder 80, the first and second feedback springs 45 and 55, and the first and second control spools 40 and 50 are disposed on the same axis.

  A cam pin 95 protruding from the rotating tip of the feedback link 90 is provided, while the spring holder 80 is formed with an annular recess 81 at the center thereof, and the cam pin 95 engages with the recess 81. The cam pin 95 abuts against the side surface of the recess 81, and the spring holder 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 recess 81, wear of both can be suppressed.

  2 and 3, since the feedback link 90 rotates about the center point e of the pin 91, the cam pin 95 has an arc locus with respect to the center line (axis line) of the spring holder 80. When the center of the cam pin 95 is made to coincide with the center line (axis line) of the spring holder 80 in the neutral state of the feedback link 90, when the feedback link 90 rotates and reaches the maximum stroke, the deviation is larger than the center line (axis line). Thus, the friction increases due to the twisting force acting on the spring holder 80. In order to minimize the distance that the cam pin 95 is displaced (disengaged) from the center line (axis), the cam pin 95 is in a neutral state so as to contact the recess 81 at a position displaced (disengaged) below the center line (axis). The neutral position and the amount of deviation (displacement distance) at the time of the maximum stroke are substantially matched.

  2 and 3, the cam pin 95 is in sliding contact with the vicinity of the central portion of the recess 81, so that the bending load acting on the spring holder 80 is reduced, and the friction generated when the spring holder 80 is in sliding contact with the hole 28 of the casing 25. Can be reduced.

  A hole 82 is formed in the bottom of the recess 81 of the spring holder 80, and the inside and outside of the spring holder 80 communicate with each other through this hole 82.

  Retainers 47 and 57 are fitted and attached in the middle of the first and second control spools 40 and 50. Between the retainers 47 and 57 and the spring holder 80, coil-shaped first and second feedback springs 45, 55 are respectively compressed and interposed.

  The spring holder 80 is formed with a pair of annular step portions 83 at the center, and one end of each of the first and second feedback springs 45 and 55 is seated on each annular step portion 83. An annular recess 81 is formed between each annular step 83.

  The first and second control spools 40 and 50 are urged away from each other by the first and second feedback springs 45 and 55.

  As shown in FIG. 4, the end surface 40a and the receiving surface 40b of the first spool 40 are formed with a step. Similarly, the second control spool 50 is formed with a step between the end surface 50a and the receiving surface 50b. The end surfaces 40a and 50a and the receiving surfaces 40b and 50b are formed in a planar shape orthogonal to the center lines of the first and second control spools 40 and 50, respectively.

  The first and second control spools 40 and 50 include a joint 46 that connects the two so as not to be separated from each other in the axial direction.

  As shown in FIG. 4, as the joint 46, the first and second control spools 40, 50 are formed with hook portions 43, 53 that engage with each other at their tips. The hooks 43 and 53 have engagement surfaces 43a and 53a that are bent into a key shape in cross section and abut against each other. Each engagement surface 43a, 53a is formed in a planar shape orthogonal to the center line of the first and second control spools 40, 50, respectively.

  The first and second control spools 40, 50 are urged away from each other by the first and second feedback springs 45, 55, and only the engagement surfaces 43a, 53a abut against each other.

  When the first control spool 40 moves in the left-right direction in FIG. 4, only the engagement surfaces 43a and 53a are kept in contact with the urging force of the first and second feedback springs 45 and 55, and the second control spool 50 Moves together with the first control spool 40.

  As a means for allowing the joint 46 to displace the first and second control spools 40 and 50 in the radial direction, gaps 44 and 54 are formed between the hook portions 43 and 53. As the first and second control spools 40, 50 are displaced from each other in the radial direction (vertical front-rear direction in FIG. 4), the gaps 44, 54 are expanded or contracted.

  In the first and second control spools 40, 50, a gap 48 is formed between each end face 40a and the receiving face 50b, and a gap 58 is formed between each end face 50a and the receiving face 40b. .

  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 first and second feedback springs 45 and 55 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 changes as the operating arm 23 rotates against the movements 34 and 35 and rotates.

  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.

  As shown in FIG. 3, each sleeve 60 includes 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 that communicates with the tank 5. 63.

  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, the intake / exhaust ports 62 and the drain ports 63 are communicated to guide the drain pressure of the tank 5 to the first and second hydraulic chambers 32 and 33.

  Since the first and second control spools 40 and 50 are connected via the joint 46 so that they are not separated in the axial direction, when one moves in the direction to open the drain port 63, the other opens the pump port 61. Move in the direction.

  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 first and second feedback springs 45 and 55 and are held in the neutral positions as shown in FIGS. Held in the drain position.

  As a result, the drain pressure of the tank 5 is guided to the first and second hydraulic chambers 32 and 33, the servo piston 30 is held at the neutral position by the urging force of the return springs 34 and 35, and the tilt angle of the swash plate 12 is increased. While being held at the neutral position of 0 °, the feedback link 90 is held at the neutral position.

  When the vehicle moves forward, only the second proportional solenoid 3 is energized, the second control spool 50 is pushed by the plunger 9 of the second proportional solenoid 3 to open the pump port 61, and the first control spool 40 is The engagement surfaces 43a and 53a are kept in contact with each other by the urging force of the second feedback springs 45 and 55, and the second control spool 50 is pushed together to open the drain port 63.

  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 holder 80 to the right in FIG. 2, the second feedback spring 55 contracts, and the first feedback spring 45 expands. Eventually, when the urging forces of the first and second feedback springs 45 and 55 balance with the thrust of the second proportional solenoid 3, the first and second control spools 40 and 50 return to the neutral position, and the first hydraulic chamber 32. The supply of hydraulic oil to the engine 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 reverses, 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 engagement surfaces 43a and 53a are kept in contact with each other by the urging force of the second feedback springs 45 and 55, and the first control spool 40 is pushed together to open the drain port 63.

  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 holder 80 leftward in FIG. 2 to contract the first feedback spring 45 and extend the second feedback spring 55. Eventually, when the urging forces of the first and second feedback springs 45 and 55 balance with the thrust of the first proportional solenoid 2, the first and second control spools 40 and 50 return to the neutral position, and the second hydraulic chamber 33. The supply of hydraulic oil to the engine 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, a tilting moment (operation moment) is generated in the swash plate 12. When this tilting moment acts in the neutral return direction, the tilt angle can be controlled on the excitation side of the control spools 40 and 50. However, when the tilting moment works in the direction of increasing the tilt angle, the tilt angle cannot be controlled only on the excitation side of the control spools 40 and 50.

  In a hydrostatic continuously variable transmission (HST) that is generally used for running a vehicle, the tilting moment for returning the swash plate 12 to the neutral position increases as the driving pressure of the motor increases. In such a setting, when the solenoid is de-energized, the motor is driven by the wheel, so-called engine braking state is established, the direction of the load pressure is reversed and the direction of the tilting moment is also reversed. Increase moment works. In such a situation, the first and second control spools 40 and 50 are connected so as not to be separated from each other via the joint 46, so that the side that has been excited as the tilt angle of the swash plate 12 increases. The control spool moves in the direction to open the drain port 63, and the other control spool is pulled by the joint to move in the direction to open the pump port 61, so that the tilt angle of the swash plate 12 decreases in the servo piston 30. A directional force is applied, and the swash plate 12 is returned to the neutral position as controlled.

  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 holder 80 rightward in FIG. 2, the second feedback spring 55 contracts, and the first feedback spring 45 extends. The second control spool 50 is moved in the direction to open the drain port 63 by the urging force of the first and second feedback springs 45 and 55, and the first control spool 40 is connected to the second control spool 50 via the joint 46. Pulled to move in the direction of opening the pump port 61, Servo piston 30 is imparted a force to be reduced tilting angle of the swash plate 12 to increase the force, to return to the neutral position swash plate 12 as controlled.

  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 joint 46 is 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 in FIG. Since the pressure of 32 cannot be controlled, an increase in the tilt angle of the swash plate 12 from the set value cannot be suppressed, and the vehicle may not 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 hollow cylindrical spring holder 80 slidably supported coaxially with the two control spools 40, 50, and compressed between the spring holder 80 and the first and second control spools 40, 50. First and second feedback springs 45 and 55, and first and second control spools 40 against the biasing force of the first and second feedback springs 45 and 55, First and second proportional solenoids 2 and 3 for driving 0 in the axial direction, a feedback link 90 for moving the spring holder 80 in the axial direction as the servo piston 30 moves in the axial direction, and first and second The two control spools 40, 50 are connected so that they are not separated from each other in the axial direction by the urging force of the first and second feedback springs 45, 55, and the first and second control spools 40, 50 are displaced in the radial direction. A joint 46 that allows the first and second control spools 40 and 50 to have a biasing force of the first and second feedback springs 45 and 55 and a thrust of the first and second proportional solenoids 2 and 3. It was set as the structure which moves to the position which balances.

  Since the force from the feedback link 90 is transmitted to the first and second control spools 40 and 50 via the hollow cylindrical spring holder 80 and the first and second feedback springs 45 and 55 based on the above configuration, the feedback link The force from 90 acts on the same axis as the first and second control spools 40 and 50, and it is possible to suppress the bending load (the twisting force) from acting on the first and second control spools 40 and 50. The friction of the two control spools 40, 50 is reduced. 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.

  The joint 46 allows the axial centers of the first and second control spools 40 and 50 to be displaced, and the bending load acting on the first and second control spools 40 and 50 does not act. , 50 friction is reduced.

  Further, it is possible to reduce the accuracy of coaxial arrangement with the first and second control spools 40 and 50, and the first and second control spools 40 and 50 are accommodated in the casing 25 via the sleeves 60. Can do.

In the present embodiment, the hook portions 43 and 53 that are engaged with each other are formed as the joints 46 at the tips of the first and second control spools 40 and 50, so when assembling the servo regulator 20,
By inserting the first and second control spools 40 and 50 from both sides of the casing 25 and then engaging the hook portions 43 and 53, the first and second control spools 40 and 50 can be easily assembled.

  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 as one moves in the direction to open the drain port 63, the other moves in the direction to open the pump port 61 via the joint 46. .

  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 pressures against this force are the first and second pressures. This movement is suppressed by being guided to one of the hydraulic chambers 32 and 33.

  In this embodiment, the casing 25 which accommodates the 1st, 2nd control spools 40 and 50 is provided, The two sleeves 60 by which the 1st and 2nd control spools 40 and 50 are slidably inserted in this casing 25 are provided. Each port 61-63 which interposes and guides hydraulic oil to each sleeve 60 was formed.

  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.

  The servo regulator 20 may use a working fluid such as a water-soluble alternative liquid instead of oil as the working oil.

  In the present embodiment, since the feedback link 90 is provided in the substantially central portion of the servo regulator 20, the servo regulator 20 can be compactly mounted when mounted on the pump 10.

  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. Sectional drawing of a 1st, 2nd control spool, a spring holder, etc. similarly. Sectional drawing of a 1st, 2nd control spool similarly.

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 Double feedback spring 60 Sleeve 80 Spring holder 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 hollow cylindrical spring holder that is slidably supported coaxially with the first and second control spools;
First and second feedback springs that are compressed and interposed between the spring holder and the first and second control spools;
First and second proportional solenoids for driving the first and second control spools in the axial direction against the biasing force of the first and second feedback springs;
A feedback link for moving the spring holder in the axial direction as the servo piston moves in the axial direction;
The first and second control spools are connected so that they are not separated from each other in the axial direction by the urging force of the first and second feedback springs, and the first and second control spools are displaced in the radial direction. With fittings that allow
A servo regulator characterized in that the first and second control spools are moved to a position where the biasing forces of the first and second feedback springs and the thrust of the first and second proportional solenoids are balanced.   2. The servo regulator according to claim 1, wherein a hook portion that engages with each other is formed at the tip of the first and second control spools as the joint. 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;
The first and second hydraulic chambers are switched to the drain position for guiding the drain pressure of the drain port,
3. The servo regulator according to claim 1, wherein one side moves in the direction to open the drain port, and the other side moves in the direction to open the pump port via the joint. A casing for housing the first and second control spools;
Two sleeves in which the first and second control spools are slidably inserted in this casing are interposed,
The servo regulator according to claim 3, wherein the pump port and the drain port are formed in each sleeve.

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