JP2021195918A - Servo mechanism - Google Patents

Abstract

To provide a servo mechanism that improves responsivity at tilting of a variable swash place of a variable displacement liquid pressure rotary machine.SOLUTION: A servo mechanism 2 is equipped with a first regulator 21, a second regulator 22, and an actuator 23. The actuator has a servo piston 233 coupled to the variable swash plate 18, and a first pressure chamber 231 and a second pressure chamber 232 defined at one end and the other end of the servo piston. The first regulator switches a supply destination and a discharge source of working fluid between the first pressure chamber and the second pressure chamber. The second regulator switches the discharge source of the working fluid to the first pressure chamber, when the pressure of a working fluid of the first pressure chamber becomes lower than a pressure of working fluid of the second pressure chamber, and switches the discharge source of the working fluid to the second pressure chamber when the pressure of the working fluid of the second pressure chamber becomes lower than the pressure of the working fluid of the first pressure chamber. Therefore, the second regulator discharges the working fluid from the first pressure chamber or the second pressure chamber.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to a servo mechanism for tilting a variable swash plate of a variable displacement hydraulic rotary machine.

Conventionally, inventions relating to a regulator of a variable displacement hydraulic rotary machine mounted on a construction machine such as a hydraulic excavator and used as a variable displacement hydraulic pump or a hydraulic motor have been known (see Patent Document 1 below). .. This conventional regulator is provided with a tubular regulator casing, a spool, and a feedback link in order to tilt-drive the variable capacitance portion of the variable displacement hydraulic rotary machine by a tilting actuator (the same document, claim). Item 1 and paragraph 0007, etc.).

The spool is provided in the regulator casing so as to be relatively displaceable via a control sleeve, and supplies and discharges the tilt control pressure to the servo piston of the tilt actuator. A feedback link is provided between the servo piston of the tilting actuator and the control sleeve to convey the displacement of the servo piston to the control sleeve. The regulator casing is provided with a position adjusting mechanism. The position adjusting mechanism is arranged at a position different from that of the control sleeve, and adjusts the neutral position of the spool as a relative position to the control sleeve.

In this conventional regulator, the neutral position of the spool can be adjusted as a relative position to the control sleeve by the position adjusting mechanism provided in the regulator casing forming the outer shell. That is, by operating the position adjustment mechanism on the regulator casing side during maintenance work of the variable displacement hydraulic rotary machine, it is easy to perform the adjustment work to hold the swash plate in the neutral position (neutral position) with a tilt angle of zero. (Ibid., Paragraph 0008, etc.).

Japanese Unexamined Patent Publication No. 2017-376713

Like the conventional regulator, the servo mechanism that tilts the variable swash plate of the variable displacement hydraulic swash plate is required to further improve the responsiveness when the variable swash plate is tilted. The present disclosure provides a servo mechanism capable of improving the responsiveness when the variable swash plate of the variable displacement hydraulic rotary machine is tilted.

One aspect of the present disclosure is a servo mechanism for tilting a variable swash plate of a variable displacement hydraulic rotary machine, which is defined at one end and the other end of a servo piston connected to the variable swash plate and the servo piston. The actuator having the first pressure chamber and the second pressure chamber, and the operation to the first pressure chamber by switching the supply destination and the discharge source of the hydraulic oil between the first pressure chamber and the second pressure chamber. A first regulator that discharges the hydraulic oil from the second pressure chamber when the oil is supplied and discharges the hydraulic oil from the first pressure chamber when the hydraulic oil is supplied to the second pressure chamber, and the first regulator. When the pressure of the hydraulic oil in the pressure chamber becomes lower than the pressure of the hydraulic oil in the second pressure chamber, the discharge source of the hydraulic oil is switched to the first pressure chamber and the pressure of the hydraulic oil in the second pressure chamber. Is lower than the pressure of the hydraulic oil in the first pressure chamber, the discharge source of the hydraulic oil is switched to the second pressure chamber, and the hydraulic oil is discharged from the first pressure chamber or the second pressure chamber. It is a servo mechanism characterized by having two regulators.

According to the above aspect of the present disclosure, it is possible to provide a servo mechanism capable of improving the responsiveness when the variable swash plate of the variable displacement hydraulic rotary machine is tilted.

FIG. 3 is a cross-sectional view showing an embodiment of a variable displacement hydraulic rotary machine. Sectional drawing of the variable capacity type hydraulic rotary machine along the line II-II of FIG. The conceptual diagram which shows one Embodiment of the servo mechanism which concerns on this disclosure. The conceptual diagram explaining the operation of the servo mechanism shown in FIG. The conceptual diagram explaining the operation of the servo mechanism shown in FIG. The conceptual diagram explaining the operation of the servo mechanism shown in FIG. The graph of the flow rate of the hydraulic oil discharged from the actuator of the servo mechanism of FIG.

Hereinafter, an embodiment of the servo mechanism according to the present disclosure will be described with reference to the drawings.

FIG. 1 is a cross-sectional view showing an embodiment of a variable displacement hydraulic rotary machine including the servo mechanism according to the present disclosure. FIG. 2 is a cross-sectional view of the variable displacement hydraulic rotary machine along the line II-II of FIG. FIG. 3 is a conceptual diagram showing an embodiment of the servo mechanism according to the present disclosure.

The variable-capacity hydraulic rotary machine shown in FIGS. 1 and 2 is, for example, a variable-capacity hydraulic pump 1 constituting a hydraulic device such as a hydrostatic continuously variable transmission (HST). The variable displacement hydraulic rotary machine to which the servo mechanism according to the present disclosure is applied is not limited to the hydraulic pump 1 as long as it has a variable swash plate.

As shown in FIGS. 1 and 2, the hydraulic pump 1 of the present embodiment has, for example, a casing 11, a shaft 12, a cylinder block 13, a piston 14, a shoe 15, a valve plate 16, and a support 17. A variable swash plate 18 and a supply / discharge passage 19 are provided. Further, as shown in FIG. 3, the hydraulic pump 1 of the present embodiment includes a servo mechanism 2. The servo mechanism 2 includes a first regulator 21, a second regulator 22, and an actuator 23, and tilts the variable swash plate 18 of the hydraulic pump 1.

The casing 11 has, for example, a front casing 111 and a rear casing 112. The casing 11 houses each part of the hydraulic pump 1 and the servo piston 233 that constitutes the actuator 23 of the servo mechanism 2. Further, the casing 11 constitutes, for example, a part of the actuator 23 of the servo mechanism 2. Further, the rear casing 112 is provided with a part of a supply / discharge passage 19 for sucking and discharging hydraulic oil.

For example, as shown in FIG. 1, one end of the shaft 12 is supported by a recess of the rear casing 112 via a bearing, and the other end penetrates the front casing 111 and projects to the outside of the casing 11 and is front via the bearing. It is supported by the casing 111. The end of the shaft 12 protruding from the casing 11 is connected to the prime mover of the work machine, for example, via a power transmission mechanism (not shown). As a result, the shaft 12 is rotated by the power of the prime mover, for example.

The cylinder block 13 is, for example, a disk-shaped or cylindrical member having a through hole through which the shaft 12 penetrates. The cylinder block 13 is, for example, spline-coupled to the outer periphery of the shaft 12 and rotates integrally with the shaft 12 inside the casing 11. The cylinder block 13 is provided with a plurality of cylinders 131 and a part of a supply / discharge passage 19 communicating with the bottom of the cylinder 131.

As shown in FIG. 2, the cylinder 131 is a cylindrical hole provided at equal intervals in the circumferential direction of the cylinder block 13. As shown in FIG. 1, the axial direction of the cylinder 131 is parallel to the axial direction of the shaft 12. Each cylinder 131 houses a cylindrical piston 14.

The piston 14 is slidably fitted to each cylinder 131 of the cylinder block 13 in the axial direction, and one end thereof protrudes from the cylinder 131. The tip of the piston 14 protruding from the cylinder 131 faces the variable swash plate 18 via the shoe 15. The piston 14 and the shoe 15 rotate with respect to the variable swash plate 18 together with the cylinder block 13 due to the rotation of the shaft 12.

The valve plate 16 is fixed to the rear casing 112 of the casing 11. The valve plate 16 has a pair of through holes provided in an arc shape around the shaft 12. The through hole of the valve plate 16 constitutes a part of the supply / discharge passage 19.

The support 17 is a disk-shaped member fixed to the front casing 111 of the casing 11. The support 17 has a pair of sliding surfaces 171 that support the variable swash plate 18 so as to be tiltable. The pair of sliding surfaces 171 are concave curved surfaces arranged apart from each other in the radial direction of the shaft 12.

The variable swash plate 18 is provided in the casing 11 so as to be tiltable. The variable swash plate 18 is attached to the front casing 111 via a support 17 and has a smooth surface 181 facing the shoe 15. The variable swash plate 18 has a through hole through which the shaft 12 is inserted. A gap is formed between the inner peripheral surface of the through hole of the variable swash plate 18 and the outer peripheral surface of the shaft 12. The variable swash plate 18 is connected to the servo piston 233 constituting the actuator 23 of the servo mechanism 2 via the lever 182, the pin 183 and the slide plate 184, and is tilted by the actuator 23.

The pair of supply / discharge passages 19 are provided in the rear casing 112 of the casing 11, the valve plate 16, and the cylinder block 13. The hydraulic pump 1 sucks hydraulic oil from one of the supply / discharge passages 19 of the pair of supply / discharge passages 19, and discharges the hydraulic oil whose pressure has increased from the other supply / discharge passage 19.

More specifically, for example, when the shaft 12 is rotated by the power of the prime mover, the cylinder block 13, the piston 14, and the shoe 15 rotate together with the shaft 12. The tip of the piston 14 protruding from the cylinder 131 of the cylinder block 13 is pressed against the smooth surface 181 of the variable swash plate 18 via the shoe 15 by the pressure of the hydraulic oil, and is variablely inclined together with the cylinder block 13 and the shoe 15. It rotates with respect to the plate 18.

As a result, the piston 14 reciprocates in the axial direction between the bottom dead center position extending from the inside of the cylinder 131 toward the variable swash plate 18 and the top dead center position contracted toward the bottom of the cylinder 131. In the suction stroke of the piston 14, which corresponds to half a rotation of the cylinder block 13, hydraulic oil is sucked into the cylinder 131 from one of the supply / discharge passages 19. Further, in the discharge stroke of the piston 14 corresponding to the remaining half rotation of the cylinder block 13, the piston 14 compresses the hydraulic oil in each cylinder 131 and discharges it from the other supply / discharge passage 19 to the outside of the hydraulic pump 1. Let me.

The actuator 23 of the servo mechanism 2 moves the servo piston 233 and tilts the variable swash plate 18 connected to the servo piston 233. As a result, the amplitude of the piston 14 changes according to the tilt angle of the variable swash plate 18, and the discharge capacity of the hydraulic pump 1 changes. Further, by tilting the variable swash plate 18 from the position where the tilt angle shown in FIG. 2 is zero to one direction D1 or the opposite direction D2, in one supply / discharge passage 19 and the other supply / discharge passage 19. The suction and discharge are reversed, and the discharge direction of the hydraulic oil in the hydraulic pump 1 is reversed. The hydraulic pump 1 constitutes, for example, the HST of a work machine and drives a hydraulic motor (not shown). Therefore, the servo mechanism 2 that tilts the variable swash plate 18 is required to further improve the responsiveness of the actuator 23.

Hereinafter, the configuration of the servo mechanism 2 of the present embodiment will be described in detail with reference to FIG. As described above, the servo mechanism 2 includes the first regulator 21, the second regulator 22, and the actuator 23, and tilts the variable swash plate 18 of the hydraulic pump 1. The actuator 23 includes, for example, a cylindrical or cylindrical servo piston 233 connected to a variable swash plate 18, and a cylindrical first pressure chamber 231 and a second pressure defined at one end and the other end of the servo piston 233. It has a chamber 232.

As described above, the servo piston 233 is connected to the variable swash plate 18 via, for example, a lever 182, a pin 183, and a slide plate 184. The servo piston 233 moves axially, that is, to the right or left in FIGS. 2 and 3, depending on the pressure of the hydraulic oil supplied to the first pressure chamber 231 or the second pressure chamber 232 via the first regulator 21. Will be done. As a result, the servo piston 233 tilts the variable swash plate 18 in one direction D1 or the opposite direction D2 shown in FIG. 2 via the lever 182.

The first pressure chamber 231 and the second pressure chamber 232 are defined by, for example, a servo piston 233 and a casing 11 of the hydraulic pump 1. More specifically, the casing 11 defines, for example, a cylindrical servo cylinder 234 that houses the servo piston 233, and the servo piston 233 and the servo cylinder 234 define the first pressure chamber 231 and the second pressure chamber 232. Will be done. Further, in the example shown in FIGS. 2 and 3, the casing 11 includes a pair of lid plates 113 that close both ends of the servo cylinder 234 and define the first pressure chamber 231 and the second pressure chamber 232.

Although not shown, the actuator 23 may include a casing for accommodating the servo piston 233 in addition to the casing 11 of the hydraulic pump 1. In this case, the casing of the actuator 23 and the servo piston 233 can define the first pressure chamber 231 and the second pressure chamber 232. More specifically, the casing of the actuator 23 defines, for example, a cylindrical servo cylinder 234 that houses the servo piston 233, with the servo piston 233 and the servo cylinder 234 to provide a first pressure chamber 231 and a second pressure chamber 232. Demarcated.

The first regulator 21 switches between the supply destination and the discharge source of the hydraulic oil between the first pressure chamber 231 and the second pressure chamber 232. That is, the first regulator 21 discharges the hydraulic oil from the second pressure chamber 232 when the hydraulic oil is supplied to the first pressure chamber 231 and the first pressure chamber when the hydraulic oil is supplied to the second pressure chamber 232. The hydraulic oil is discharged from 231. The first regulator 21 is, for example, an electromagnetically driven directional control valve. The first regulator 21 includes, for example, a main body portion 211, a sleeve 212, a feedback lever 213, a spool 214, an urging portion 215, a spring 216, and a solenoid actuator 217.

The main body 211 has, for example, a cylindrical internal space that slidably accommodates the cylindrical sleeve 212 in the axial direction. The internal space of the main body 211 has larger diameters at both ends in the axial direction than the intermediate portion accommodating the sleeve 212. The main body portion 211 accommodates the urging portion 215 and the spring 216 at both ends of the cylindrical internal space. The main body 211 defines, for example, the A port, the B port, the P port, and the T port of the first regulator 21. Further, the main body portion 211 has a bypass passage 211b in which one end and the other end in the axial direction of the intermediate portion are communicated with each other in the cylindrical internal space.

The A port and the B port of the first regulator 21 are connected to the first pressure chamber 231 and the second pressure chamber 232, respectively, via the hydraulic oil pipeline. The P port of the first regulator 21 is connected to an external pilot pump 3 for pumping hydraulic oil via a hydraulic oil pipeline. The T port of the first regulator 21 is connected to the hydraulic oil tank, for example, via the hydraulic oil pipeline.

The sleeve 212 is a cylindrical member that is slidably housed in an intermediate portion of the cylindrical internal space of the main body portion 211 in the axial direction. The sleeve 212 has a plurality of through holes. The state of each through hole at the neutral position of the sleeve 212 shown in FIG. 3 is as follows. The vertical, horizontal, and horizontal directions in the following description are convenient directions for explaining the state of the first regulator 21 in FIG. 3, and do not limit the posture of the first regulator 21.

In the sleeve 212 in the neutral position shown in FIG. 3, the upper through hole at the left end communicates with the left end of the bypass passage 211b, and the lower through hole at the left end is closed. Further, the upper through hole second from the left is closed, and the lower through hole second from the left communicates with the A port. Further, the upper through hole at the right end is closed, and the lower through hole at the right end communicates with the B port. Further, the upper through hole second from the right is closed, and the lower through hole second from the right communicates with the P port.

The feedback lever 213 is, for example, an elongated plate-shaped or rod-shaped member extending in one direction. One end and the other end of the feedback lever 213 are pivotally connected to the sleeve 212 and the servo piston 233, respectively. The feedback lever 213 is provided with a rotation shaft in the middle portion, and rotates about the rotation shaft. For example, when the servo piston 233 moves to the right, the feedback lever 213 rotates counterclockwise around the axis of rotation, causing the sleeve 212 to move to the left. Further, when the servo piston 233 moves to the left, the feedback lever 213 rotates clockwise around the rotation axis to move the sleeve 212 to the right.

The spool 214 is, for example, a round bar-shaped, columnar or shaft-shaped member extending in one direction. The spool 214 has two lands in the middle portion in the axial direction. The two lands of the spool 214 are, for example, larger in diameter than the other parts of the spool 214 and project radially. Each land of the spool 214 is provided corresponding to the position of the through hole of the sleeve 212, and selectively opens and closes the through hole of the sleeve 212.

In the neutral position of the sleeve 212 and the spool 214 shown in FIG. 3, the land on the left side of the spool 214 closes most of the lower through hole second from the left of the sleeve 212, and opens a small gap. The port and the A port are communicated with each other. Further, the land on the right side of the spool 214 closes most of the through hole on the lower side of the right end of the sleeve 212, and allows the P port and the B port to communicate with each other with a small gap. As a result, the pilot pump 3, the first pressure chamber 231 and the second pressure chamber 232 communicate with each other, and the hydraulic oil pressures in the first pressure chamber 231 and the second pressure chamber 232 become equal.

The urging portion 215 is, for example, a cylindrical or flange-shaped member, and has a large-diameter portion adjacent to the spool 214 and a small-diameter portion on the opposite side of the spool 214, which is smaller in diameter than the large-diameter portion. There is. The central axis of the cylindrical urging portion 215 coincides with, for example, the central axis of the cylindrical spool 214. The urging portion 215 has a through hole along the central axis in the center.

The spring 216 is arranged around the small diameter portion of the urging portion 215 and is compressed between the large diameter portion of the urging portion 215 and the solenoid actuator 217 at the neutral position shown in FIG. As a result, in the neutral position shown in FIG. 3, the urging portion 215 is urged toward the spool 214 by the spring 216, and the end face facing the spool 214 of the large diameter portion is an intermediate portion of the internal space of the main body portion 211. It is pressed against the step between the and both ends.

The solenoid actuator 217 has, for example, a frame 217a, a coil 217b, a fixed iron core 217c, and a plunger 217d. The frame 217a is made of, for example, a magnetic material and houses a coil 217b, a fixed iron core 217c and a plunger 217d. The coil 217b generates a magnetic field by passing an electric current. In the fixed iron core 217c, a magnetic flux passes when a magnetic field is generated in the coil 217b. The plunger 217d penetrates the through hole of the urging portion 215, and when the magnetic flux passes through the fixed iron core 217c, it is attracted by the fixed iron core 217c and protrudes toward the spool 214.

When the pressure of the hydraulic oil in the first pressure chamber 231 becomes lower than the pressure of the hydraulic oil in the second pressure chamber 232, the second regulator 22 switches the discharge source of the hydraulic oil to the first pressure chamber 231. Further, when the pressure of the hydraulic oil in the second pressure chamber 232 drops below the pressure of the hydraulic oil in the first pressure chamber 231, the second regulator 22 switches the discharge source of the hydraulic oil to the second pressure chamber 232. .. As a result, the second regulator 22 discharges the hydraulic oil from the first pressure chamber 231 or the second pressure chamber 232.

The second regulator 22 is, for example, a differential pressure drive type 3-port, 3-position, closed center valve. More specifically, the second regulator 22 has, for example, a direction switching unit 221 and an urging unit 222. The direction switching unit 221 has, for example, a main body portion 211 similar to the main body portion 211 and the spool 214 of the first regulator 21, and a spool, and switches the discharge source of the hydraulic oil according to the position of the spool.

The direction switching unit 221 is connected to, for example, the A port connected to the first pressure chamber 231 via the hydraulic oil pipe and the second pressure chamber 232 via the hydraulic oil pipe. It has three ports, a B port and a T port connected to the hydraulic oil tank via a hydraulic oil pipeline. Further, the direction switching unit 221 takes three positions: a neutral position shown in FIG. 3, a right position moved to the right from the neutral position, and a left position moved to the left from the neutral position.

The direction switching unit 221 is a closed center valve in which the space between the A port and the B port and the T port is closed at the neutral position in the center. Further, in the direction switching unit 221 at the right position, the B port and the T port are connected, and the A port is closed. Further, in the direction switching unit 221 at the left position, the A port and the T port are connected, and the B port is closed.

A pilot pipeline that causes the pressure of the hydraulic oil in the first pressure chamber 231 to act on the left end of the direction switching unit 221 is connected to the left end of the direction switching unit 221. Further, a pilot pipeline that causes the pressure of the hydraulic oil in the second pressure chamber 232 to act on the right end of the direction switching unit 221 is connected to the right end of the direction switching unit 221.

The pair of urging portions 222 are arranged on both sides of the direction switching portion 221 in the moving direction so as to face the direction switching portion 221 and urge the direction switching portions 221 in directions facing each other. For example, the urging unit 222 urges the plunger 222b toward the direction switching unit 221 by the elastic force of the spring 222a, and urges the direction switching unit 221 by the plunger 222b. The urging force exerted by the pair of urging portions 222 on the direction switching portion 221 is set according to, for example, the threshold value of the differential pressure of the hydraulic oil between the first pressure chamber 231 and the second pressure chamber 232. There is.

Specifically, in the urging force of the pair of urging portions 222, for example, the pressure of the hydraulic oil in the first pressure chamber 231 becomes higher than the pressure of the hydraulic oil in the second pressure chamber 232, and these differential pressures are generated. When the threshold value is exceeded, the direction switching unit 221 is set to move to the right position. Further, in the urging force of the pair of urging portions 222, for example, the pressure of the hydraulic oil in the second pressure chamber 232 becomes higher than the pressure of the hydraulic oil in the first pressure chamber 231, and these differential pressures set a threshold value. When it exceeds, the direction switching unit 221 is set to move to the left position.

Here, the flow rate of the hydraulic oil discharged via the second regulator 22 is larger than the flow rate of the hydraulic oil discharged via the first regulator 21, for example. More specifically, the minimum cross-sectional area in the hydraulic oil flow path from the first pressure chamber 231 to the hydraulic oil tank via the second regulator 22 is from the first pressure chamber 231 via the first regulator 21. It is larger than the minimum cross-sectional area in the hydraulic fluid flow path to the hydraulic fluid tank. Similarly, the minimum cross-sectional area in the hydraulic oil flow path from the second pressure chamber 232 to the hydraulic oil tank via the second regulator 22 is the hydraulic oil from the second pressure chamber 232 via the first regulator 21. Greater than the minimum cross-sectional area in the hydraulic flow path to the tank.

Further, the differential pressure of the hydraulic oil between the first pressure chamber 231 and the second pressure chamber 232 for the second regulator 22 to switch the discharge source of the hydraulic oil is, for example, the first pressure at the start of the servo piston 233. It is made larger than the differential pressure of the hydraulic oil between the chamber 231 and the second pressure chamber 232. The discharge source of the hydraulic oil switched by the second regulator 22 is the first pressure chamber 231 and the second pressure chamber 232.

Next, the operation of the servo mechanism 2 of the present embodiment will be described with reference to FIGS. 3 to 7. 4 to 6 are conceptual diagrams illustrating the operation of the servo mechanism 2 shown in FIG. FIG. 7 is a graph showing an example of the time change of the flow rate of the hydraulic oil discharged from the first pressure chamber 231 or the second pressure chamber 232 of the actuator 23 to the tank.

For example, the servo mechanism 2 can switch the supply destination of the hydraulic oil pumped from the external pilot pump 3 to the first pressure chamber 231 of the actuator 23 by the first regulator 21. Further, the servo mechanism 2 can switch the discharge source of the hydraulic oil discharged from the actuator 23 to the tank to the second pressure chamber 232 by the first regulator 21. Specifically, in the state shown in FIG. 3, the servo mechanism 2 operates, for example, the solenoid actuator 217 on the right side of the first regulator 21, and the plunger 217d moves the spool 214 to the left.

As a result, as shown in FIG. 4, the P port and the A port of the first regulator 21 communicate with each other, and the pilot pump 3 and the first pressure chamber 231 communicate with each other via the first regulator 21. Further, the B port and the T port of the first regulator 21 communicate with each other, and the second pressure chamber 232 and the hydraulic oil tank communicate with each other via the first regulator 21. In this state, when the hydraulic oil is pumped from the pilot pump 3 and supplied to the first pressure chamber 231 of the actuator 23, the pressure P1 of the hydraulic oil in the first pressure chamber 231 becomes the pressure of the hydraulic oil in the second pressure chamber 232. It will be higher than P2.

When the hydraulic oil is supplied from the pilot pump 3 to the first pressure chamber 231, the pressure P1 of the hydraulic oil in the first pressure chamber 231 rises with the passage of time. Then, when the differential pressure of the hydraulic oil between the first pressure chamber 231 and the second pressure chamber 232 reaches the force required to start the servo piston 233, the servo piston 233 starts moving to the right. .. As a result, the volume of the second pressure chamber 232 is reduced, the hydraulic oil is discharged from the second pressure chamber 232 to the B port of the first regulator 21, and the hydraulic oil flowing into the first regulator 21 is discharged from the T port to the tank. Will be done.

At this time, the increase in the flow rate of the hydraulic oil discharged from the second pressure chamber 232 to the tank via the first regulator 21 is the hydraulic oil including the hydraulic oil pipeline and the B port and the T port of the first regulator 21. Limited by the cross-sectional area of the flow path. Therefore, the pressure of the hydraulic oil in the first pressure chamber 231 increases with the passage of time, and the moving speed of the servo piston 233 gradually increases. Further, as shown in FIG. 7, the flow rate of the hydraulic oil discharged from the second pressure chamber 232 to the tank via the first regulator 21 is gradual with the passage of time from the time t0 when the discharge of the hydraulic oil is started. Increase to.

After that, the pressure P1 of the hydraulic oil in the first pressure chamber 231 further increases, and the pressure P2 of the hydraulic oil in the second pressure chamber 232 further decreases than the pressure P1 of the hydraulic oil in the first pressure chamber 231 to provide a differential pressure. The second regulator 22 shown in FIG. 3 switches the discharge source of the hydraulic oil to the second pressure chamber 232. Specifically, for example, the differential pressure between the hydraulic oil pressure P1 in the first pressure chamber 231 and the hydraulic oil pressure P2 in the second pressure chamber 232 increases, and the threshold set in advance in the second regulator 22 increases. Exceed the value. Then, the direction switching unit 221 of the second regulator 22 moves to the right against the urging force of the urging unit 222.

As a result, as shown in FIG. 5, the B port of the second regulator 22 communicates with the T port, the discharge source of the hydraulic oil is switched to the second pressure chamber 232, and the hydraulic oil is second from the second pressure chamber 232. It is discharged to the tank via the regulator 22. As a result, as shown in FIG. 7, after the time t1 when the second regulator 22 switches the discharge source of the hydraulic oil to the second pressure chamber 232, the hydraulic oil in the second pressure chamber 232 becomes the first regulator 21 and the second regulator 21 and the second. It is discharged to the tank via the regulator 22.

As a result, as shown in FIG. 7, after time t1, the rate of increase in the flow rate of the hydraulic oil discharged from the second pressure chamber 232 increases, and the servo piston is compared with the case where the second regulator 22 is not provided. The 233 moves to the right at a higher speed. As a result, the variable swash plate 18 is tilted at a higher speed by the servo piston 233 of the actuator 23, and the responsiveness of the variable swash plate 18 at the time of tilting in the hydraulic pump 1 is improved.

Further, as shown in FIG. 6, when the servo piston 233 moves to the right, the feedback lever 213 connecting the servo piston 233 and the sleeve 212 of the first regulator 21 rotates counterclockwise, and the sleeve 212 rotates to the left. Move to. As a result, the P port, the A port, and the B port of the first regulator 21 communicate with each other by a slight gap between the sleeve 212 and the land of the spool 214.

As a result, the differential pressure of the hydraulic oil between the first pressure chamber 231 and the second pressure chamber 232 of the actuator 23 becomes equal to or less than the threshold value set in the second regulator 22, and the direction switching portion of the second regulator 22 The 221 returns to the central closed position by the urging force of the urging portion 222. As described above, in the servo mechanism 2, a series of operations of moving the servo piston 233 of the actuator 23 to the right and tilting the variable swash plate 18 in one direction D1 are completed.

Further, the servo mechanism 2 can switch, for example, the supply destination of the hydraulic oil pumped from the external pilot pump 3 to the second pressure chamber 232 of the actuator 23 by the first regulator 21. Further, the servo mechanism 2 can switch the discharge source of the hydraulic oil discharged from the second pressure chamber 232 of the actuator 23 to the first pressure chamber 231 by the first regulator 21. Specifically, the servo mechanism 2 operates, for example, the solenoid actuator 217 on the left side of the first regulator 21, and the plunger 217d moves the spool 214 to the right.

As a result, the P port and the B port of the first regulator 21 communicate with each other, and the pilot pump 3 and the second pressure chamber 232 communicate with each other via the first regulator 21. Further, the A port and the T port of the first regulator 21 communicate with each other via the bypass passage 211b, and the first pressure chamber 231 and the hydraulic oil tank communicate with each other via the first regulator 21. In this state, when the hydraulic oil is pumped from the pilot pump 3 and supplied to the second pressure chamber 232 of the actuator 23, the pressure P2 of the hydraulic oil in the second pressure chamber 232 becomes the pressure of the hydraulic oil in the first pressure chamber 231. It will be higher than P1.

When the hydraulic oil is supplied from the pilot pump 3 to the second pressure chamber 232, the pressure P2 of the hydraulic oil in the second pressure chamber 232 rises with the passage of time. Then, when the differential pressure of the hydraulic oil between the second pressure chamber 232 and the first pressure chamber 231 reaches the force required to start the servo piston 233, the servo piston 233 starts moving to the left. .. As a result, the volume of the first pressure chamber 231 is reduced, the hydraulic oil is discharged from the first pressure chamber 231 to the A port of the first regulator 21, and the hydraulic oil flowing into the first regulator 21 is discharged from the T port to the tank. Will be done.

At this time, the increase in the flow rate of the hydraulic oil discharged from the first pressure chamber 231 to the tank via the first regulator 21 causes the hydraulic oil pipeline, the A port of the first regulator 21, the bypass passage 211b, and the T port. It is limited by the cross-sectional area of the flow path of the hydraulic oil it contains. Therefore, the pressure of the hydraulic oil in the second pressure chamber 232 increases with the passage of time, and the moving speed of the servo piston 233 gradually increases. Further, as shown in FIG. 7, the flow rate of the hydraulic oil discharged from the first pressure chamber 231 to the tank via the first regulator 21 is gradual with the passage of time from the time t0 when the discharge of the hydraulic oil is started. Increase to.

After that, the pressure P2 of the hydraulic oil in the second pressure chamber 232 further increases, and the pressure P1 of the hydraulic oil in the first pressure chamber 231 further decreases than the pressure P2 of the hydraulic oil in the second pressure chamber 232, resulting in a differential pressure. The second regulator 22 switches the discharge source of the hydraulic oil to the first pressure chamber 231. Specifically, for example, the differential pressure between the hydraulic oil pressure P2 in the second pressure chamber 232 and the hydraulic oil pressure P1 in the first pressure chamber 231 increases, and the threshold set in advance in the second regulator 22 increases. Exceed the value. Then, the direction switching unit 221 of the second regulator 22 moves to the left against the urging force of the urging unit 222.

As a result, the A port of the second regulator 22 communicates with the T port, the discharge source of the hydraulic oil is switched to the first pressure chamber 231 and the hydraulic oil from the first pressure chamber 231 to the tank via the second regulator 22. It is discharged. As a result, as shown in FIG. 7, after the time t1 when the second regulator 22 switches the discharge source of the hydraulic oil to the first pressure chamber 231, the hydraulic oil in the first pressure chamber 231 becomes the first regulator 21 and the second regulator 21. It is discharged to the tank via the regulator 22.

As a result, as shown in FIG. 7, after time t1, the rate of increase in the flow rate of the hydraulic oil discharged from the first pressure chamber 231 increases, and the servo piston is compared with the case where the second regulator 22 is not provided. The 233 moves to the left faster. As a result, the variable swash plate 18 is tilted at a higher speed by the servo piston 233 of the actuator 23, and the responsiveness of the variable swash plate 18 at the time of tilting in the hydraulic pump 1 is improved.

Further, when the servo piston 233 moves to the left, the feedback lever 213 connecting the servo piston 233 and the sleeve 212 of the first regulator 21 rotates clockwise, and the sleeve 212 moves to the right. As a result, the P port, the A port, and the B port of the first regulator 21 communicate with each other by a slight gap between the sleeve 212 and the land of the spool 214.

As a result, the differential pressure of the hydraulic oil between the first pressure chamber 231 and the second pressure chamber 232 of the actuator 23 becomes equal to or less than the threshold value set in the second regulator 22, and the direction switching portion of the second regulator 22 The 221 returns to the central closed position by the urging force of the urging portion 222. As described above, in the servo mechanism 2, a series of operations of moving the servo piston 233 of the actuator 23 to the left and tilting the variable swash plate 18 in the direction D2 opposite to the one direction D1 is completed.

Hereinafter, the operation of the servo mechanism 2 of the present embodiment will be described.

In recent years, energy saving has been promoted in various fields including hydraulic systems such as HST mounted on work machines. In order to save energy in the hydraulic system, it is effective not only to improve the efficiency of the hydraulic pump and suppress the leakage of hydraulic oil from the actuator, but also to improve the efficiency of the work cycle in the work machine equipped with the hydraulic system. In order to realize such efficiency of the work cycle, it is necessary to improve not only the position accuracy of the actuator but also the responsiveness of the actuator. For that purpose, in addition to the responsiveness of the control valve, it is required to improve the responsiveness of the variable displacement hydraulic rotary machine including the hydraulic pump and the hydraulic motor.

The servo mechanism 2 of the present embodiment is a servo mechanism that tilts the variable swash plate 18 of the variable capacitance type hydraulic rotary machine as described above, and as described above, the first regulator 21 and the second regulator 22 , And an actuator 23. The actuator 23 has a servo piston 233 connected to a variable swash plate 18 and a first pressure chamber 231 and a second pressure chamber 232 defined at one end and the other end of the servo piston 233. The first regulator 21 switches between the supply destination and the discharge source of the hydraulic oil between the first pressure chamber 231 and the second pressure chamber 232, and the second pressure chamber 232 when the hydraulic oil is supplied to the first pressure chamber 231. The hydraulic oil is discharged from the first pressure chamber 231 when the hydraulic oil is supplied to the second pressure chamber 232. When the pressure of the hydraulic oil in the first pressure chamber 231 drops below the pressure of the hydraulic oil in the second pressure chamber 232, the second regulator 22 switches the discharge source of the hydraulic oil to the first pressure chamber 231 and switches the second pressure chamber to the first pressure chamber 231. When the pressure of the hydraulic oil in 232 becomes lower than the pressure of the hydraulic oil in the first pressure chamber 231, the discharge source of the hydraulic oil is switched to the second pressure chamber 232. As a result, the second regulator 22 discharges the hydraulic oil from the first pressure chamber 231 or the second pressure chamber 232.

With such a configuration, according to the servo mechanism 2 of the present embodiment, as described above, it is possible to improve the responsiveness of the variable swash plate 18 of the variable displacement hydraulic swash plate 18 at the time of tilting. More specifically, the servo mechanism 2 switches the supply destination of the hydraulic oil via the first regulator 21 to the first pressure chamber 231 of the actuator 23, and discharges the hydraulic oil via the first regulator 21 to the actuator 23. It is possible to switch to the second pressure chamber 232. As a result, when the pressure of the hydraulic oil in the second pressure chamber 232 becomes lower than the pressure of the hydraulic oil in the first pressure chamber 231, the second regulator 22 switches the discharge source of the hydraulic oil to the second pressure chamber 232. As a result, the servo mechanism 2 determines the flow rate of the hydraulic oil discharged from the second pressure chamber 232 when, for example, the servo piston 233 is moved to the right and the variable swash plate 18 is tilted in one direction D1. It can be increased as compared with the case where the second regulator 22 is not provided. Therefore, the moving speed of the servo piston 233 to the right can be increased, and the responsiveness of the variable swash plate 18 when tilted can be improved.

Further, with the configuration as described above, the servo mechanism 2 of the present embodiment switches the supply destination of the hydraulic oil via the first regulator 21 to the second pressure chamber 232 of the actuator 23, and operates via the first regulator 21. The oil discharge source can be switched to the first pressure chamber 231 of the actuator 23. As a result, when the pressure of the hydraulic oil in the first pressure chamber 231 becomes lower than the pressure of the hydraulic oil in the second pressure chamber 232, the second regulator 22 switches the discharge source of the hydraulic oil to the first pressure chamber 231. As a result, the servo mechanism 2 is discharged from the first pressure chamber 231 when, for example, the servo piston 233 is moved to the left and the variable swash plate 18 is tilted in the direction D2 opposite to the one direction D1. The flow rate of oil can be increased as compared with the case without the second regulator 22. Therefore, the moving speed of the servo piston 233 to the left can be increased, and the responsiveness when the variable swash plate 18 is tilted can be improved.

Further, in the servo mechanism 2 of the present embodiment, the flow rate of the hydraulic oil discharged via the second regulator 22 is larger than the flow rate of the hydraulic oil discharged via the first regulator 21. With such a configuration, the moving speed of the servo piston 233 is higher than when the flow rate of the hydraulic oil discharged through the second regulator 22 is equal to or less than the flow rate of the hydraulic oil discharged via the first regulator 21. It is possible to improve the responsiveness of the variable swash plate 18 when it is tilted.

In the servo mechanism 2 of the present embodiment, the flow rate of the hydraulic oil discharged via the second regulator 22 may be equal to or less than the flow rate of the hydraulic oil discharged via the first regulator 21. With such a configuration, the position accuracy of the servo piston 233 is higher than that in the case where the flow rate of the hydraulic oil discharged through the second regulator 22 is larger than the flow rate of the hydraulic oil discharged through the first regulator 21. It is possible to improve the position accuracy when the variable swash plate 18 is tilted.

Further, in the servo mechanism 2 of the present embodiment, the differential pressure of the hydraulic oil between the first pressure chamber 231 and the second pressure chamber 232 for the second regulator 22 to switch the discharge source of the hydraulic oil is the servo piston 233. It is made larger than the differential pressure between the first pressure chamber 231 and the second pressure chamber 232 at the time of starting. With such a configuration, as shown in FIG. 7, at the time t1 when a predetermined time elapses from the time t0 when the servo piston 233 starts, the first pressure chamber 231 or the second pressure chamber 232 passes through the second regulator 22. The discharge of hydraulic oil can be started. As a result, the servo piston 233 is prevented from moving at high speed at the same time as the start, the sudden tilting of the variable swash plate 18 is prevented, and the safety of the hydraulic system including the hydraulic pump 1 and the hydraulic motor can be improved. can.

Further, in the servo mechanism 2 of the present embodiment, the second regulator 22 is a differential pressure drive type 3-port, 3-position, closed center valve. With such a configuration, when the pressure of the hydraulic oil in the first pressure chamber 231 becomes lower than the pressure of the hydraulic oil in the second pressure chamber 232, the second regulator 22 sets the discharge source of the hydraulic oil to the first pressure chamber 231. Can be switched. Further, the second regulator 22 can switch the discharge source of the hydraulic oil to the second pressure chamber 232 when the pressure of the hydraulic oil in the second pressure chamber 232 becomes lower than the pressure of the hydraulic oil in the first pressure chamber 231. ..

Further, in the servo mechanism 2 of the present embodiment, the first regulator 21 is an electromagnetically driven directional control valve. With such a configuration, the first regulator 21 can be miniaturized and the servo mechanism 2 can be miniaturized.

Although the embodiments of the servo mechanism according to the present disclosure have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and design changes and the like are not deviated from the gist of the present disclosure. If any, they are included in this disclosure.

1 Hydraulic pump (variable capacity hydraulic rotary machine)
18 Variable swash plate 2 Servo mechanism 21 1st regulator 22 2nd regulator 23 Actuator 231 1st pressure chamber 232 2nd pressure chamber 233 Servo piston

Claims (5)

A servo mechanism that tilts the variable swash plate of a variable displacement hydraulic rotary machine.
A servo piston connected to the variable swash plate, an actuator having a first pressure chamber and a second pressure chamber defined at one end and the other end of the servo piston, and an actuator.
The hydraulic oil is discharged from the second pressure chamber when the hydraulic oil is supplied to the first pressure chamber by switching the supply destination and the discharge source of the hydraulic oil between the first pressure chamber and the second pressure chamber. A first regulator that discharges the hydraulic oil from the first pressure chamber when the hydraulic oil is supplied to the second pressure chamber.
When the pressure of the hydraulic oil in the first pressure chamber becomes lower than the pressure of the hydraulic oil in the second pressure chamber, the discharge source of the hydraulic oil is switched to the first pressure chamber and the operation of the second pressure chamber is performed. When the pressure of the oil drops below the pressure of the hydraulic oil in the first pressure chamber, the discharge source of the hydraulic oil is switched to the second pressure chamber, and the hydraulic oil is discharged from the first pressure chamber or the second pressure chamber. A servo mechanism characterized by having a second regulator for discharging. The servo according to claim 1, wherein the flow rate of the hydraulic oil discharged through the second regulator is larger than the flow rate of the hydraulic oil discharged through the first regulator. mechanism. The differential pressure of the hydraulic oil between the first pressure chamber and the second pressure chamber for the second regulator to switch the discharge source of the hydraulic oil is larger than the differential pressure at the start of the servo piston. The servo mechanism according to claim 1, wherein the servo mechanism is enlarged. The servo mechanism according to claim 1, wherein the second regulator is a differential pressure drive type 3-port, 3-position, closed center valve. The servo mechanism according to claim 1, wherein the first regulator is an electromagnetically driven directional control valve.

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