JP5604051B2 - Counter balance valve - Google Patents

Description

  The present invention relates to a counter balance valve that restricts the flow of working fluid flowing out from an actuator in accordance with the load pressure of the actuator.

  The counter balance valve uses, for example, the load pressure of the actuator generated by the suspended load of the winch as a pilot pressure, and prevents the actuator from operating more than the control speed (see Patent Document 1).

  Conventionally, as this type of fluid pressure circuit, for example, there is one shown in FIG. Explaining this, the motor 5 that drives the winch 1 includes two ports (entrances / exits) through which hydraulic oil is supplied and discharged, and a first supply / discharge passage 11 and a second supply / discharge passage 12 are provided in each port. Connected. The first supply / discharge passage 11 and the second supply / discharge passage 12 are selectively communicated with a pump 15 and a tank 16 via a direction switching valve 14.

  A counter balance valve 50 is interposed in the first supply / discharge passage 11. The counter balance valve 50 restricts the flow of hydraulic oil flowing out from the motor 5 to the first supply / discharge passage 11 using the load pressure of the motor 5 generated in the second supply / discharge passage 12 as a pilot pressure.

  The counter balance valve 50 includes an annular seat 58 formed on the valve body 51, a spool 61 having a land portion 62 fitted to the seat 58, and a spool 61 so that the land portion 62 is fitted to the seat 58. And a return spring 57 for biasing.

  A check valve 55 is interposed in the unit of the counter balance valve 50 in parallel with the seat 58.

  When the winch 1 operates to raise the workpiece 4, the direction switching valve 14 is switched to the winding position a. As a result, the hydraulic oil discharged from the pump 15 is supplied to the motor 5 through the check valve 55 of the first supply / discharge passage 11, the motor 5 rotates in the forward direction, and the hydraulic oil flowing out from the motor 5 is discharged. It returns to the tank 16 through the second supply / discharge passage 12. Thereby, the winch 1 operates and the workpiece | work 4 raises.

  When the winch 1 operates to lower the workpiece 4, the direction switching valve 14 is switched to the feeding position b. As a result, the hydraulic oil discharged from the pump 15 is supplied to the motor 5 through the second supply / discharge passage 12, the motor 5 rotates in the reverse direction, and the hydraulic oil flowing out of the motor 5 is supplied to the first supply / discharge. It returns to the tank 16 through the counter balance valve 50 in the passage 11. Thereby, the winch 1 operates and the work 4 descends.

  When the winch 1 operates to lower the workpiece 4, the counter balance valve 50 displaces the spool 61 when the pilot pressure guided from the second supply / discharge passage 12 to the pilot pressure chamber 56 through the orifice 63 becomes higher than a predetermined value. Then, the flow of hydraulic oil flowing out from the motor 5 is throttled by the opening formed by the seat 58 and the land portion 62, and the operating speed of the motor 5 is adjusted.

  When the pilot pressure is lower than a predetermined value, the spool 61 fits the land portion 62 to the seat 58 and blocks the first supply / discharge passage 11. As a result, the motor 5 is held at the stop position.

JP 2001-89079 A

  However, in such a conventional counterbalance valve 50, the cylindrical land portion 62 is fitted to the seat 58 with a gap, so that a sufficient sealing performance to block the flow of hydraulic oil is obtained. It may not be possible. For example, when a working fluid such as water having low viscosity is used instead of the working oil, the working fluid leaks from the gap between the land portion 62 and the seat 58, so the motor 5 is held at the stop position for a long time. Can not do it.

  In addition, since the counter balance valve 50 unit is provided with the check valve 55 in parallel with the seat 58, a space for the check valve 55 is required, which increases the size of the counter balance valve 50 unit. There was a problem.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a counterbalance valve with high sealing performance that blocks the flow of working fluid.

In the present invention, when the actuator is normally operated, the working fluid is supplied from the pressure source to the actuator through the first supply / discharge passage, and the working fluid flows out from the actuator through the second supply / discharge passage. In operation, the working fluid is supplied from the pressure source to the actuator through the second supply / discharge passage, and the working fluid flows out from the actuator through the first supply / discharge passage. A valve body having an annular seat opened in the passage, a poppet having a poppet valve portion that sits on the seat and forms a variable throttle portion between the seat, and a return that biases the poppet in the valve closing direction A spring, a piston provided side by side with the poppet, and a piston, which is arranged in the axial direction , are generated closer to the pressure source than the seat of the first supply / discharge passage when the actuator is normally operated. Is supplied to the actuator from the second supply / discharge passage during reverse operation of the actuator, and a first pilot pressure chamber that is guided as a pilot pressure that drives the poppet through the communication passage branched from the first supply / discharge passage. And a second pilot pressure chamber that is guided as a pilot pressure that drives the poppet in the valve opening direction. The poppet has a cylindrical large land portion that is slidably fitted to the valve body, and a valve body. A cylindrical small land portion having a smaller outer diameter than the large land portion, and a poppet valve portion is formed between the large land portion and the small land portion. while the first pilot pressure chamber is defined between the small land portion of the poppet, thereby opening the first supply-discharge passage in accordance with the supply pressure derived from the pressure source during forward operation of the actuator The throttling the flow of hydraulic fluid flowing through the first supply-discharge passage from the actuator in response from the second supply and discharge passage during the reverse operation of the actuator to the load pressure supplied to the actuator and shall be characterized.

  According to the present invention, when the load pressure of the actuator is lower than a predetermined value, the poppet seats the poppet valve portion on the seat and blocks the passage through which the working fluid flowing out from the actuator passes. At this time, since the poppet valve portion is in contact with the seat without any gap, the sealing performance for blocking the flow of the working fluid can be improved. As a result, even when a low-viscosity liquid such as water is used as the working fluid, the working fluid is prevented from leaking from the contact portion between the poppet valve portion and the seat, and the actuator is stopped for a long time. Can be held in position.

1 is a fluid pressure circuit diagram showing an embodiment of the present invention. The partial cross section figure of the counter balance valve which shows other embodiment of this invention. The partial cross section figure of the counter balance valve which shows other embodiment of this invention. The diagram which similarly shows the valve opening characteristic of a counter balance valve. The partial cross section figure of the counter balance valve which shows other embodiment of this invention. The hydraulic circuit diagram which shows a prior art example.

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

  FIG. 1 shows a fluid pressure circuit provided in the winch 1. The winch 1 includes a drum 2 that is rotationally driven by a motor 5, and suspends a work (suspended load) 4 via a rope 3 wound around the drum 2. The drum 2 is rotationally driven in both forward and reverse directions by a motor 5 to raise and lower the workpiece 4.

  As the working fluid, for example, a liquid such as oil (working oil) or water is used.

  The motor 5 includes two ports (inlet / outlet) through which working fluid is supplied and discharged, and a first supply / discharge passage 11 and a second supply / discharge passage 12 are connected to the respective ports. The first supply / discharge passage 11 and the second supply / discharge passage 12 are selectively communicated with a pump 15 and a tank 16 via a direction switching valve 14.

  A counter balance valve 20 is interposed in the first supply / discharge passage 11. The counter balance valve 20 adjusts the descending speed of the work 4 by restricting the flow of the working fluid flowing out from the motor 5 (actuator) according to the load pressure guided from the second supply / discharge passage 12 when the winch 1 is extended. To do.

  The counter balance valve 20 includes an annular seat 28 formed in the valve body 21, a poppet 31 interposed so as to be displaceable in the axial direction with respect to the seat 28, and a return spring that presses the poppet 31 against the seat 28. 41 and a piston 30 that drives the poppet 31 in the valve opening direction against the return spring 41 by a pilot pressure (load pressure of the motor 5) described later.

  In the poppet 31, a large land portion 32 having a cylindrical shape with an outer diameter D and a small land portion 33 having a cylindrical shape with an outer diameter d smaller than the outer diameter D are formed on the same axis. A conical poppet valve portion 34 is formed coaxially with the land portion 33.

  The valve body 21 is formed with a large cylinder 22 in which the large land portion 32 is slidably fitted, and a small cylinder 23 in which the small land portion 33 is slidably fitted. The opening diameter of the large cylinder 22 is set so as to have a predetermined gap between the outer diameter D of the large land portion 32. The opening diameter of the small cylinder 23 is set so as to have a predetermined gap between the outer diameter d of the small land portion 33. The large cylinder 22 and the small cylinder 23 are formed on the same axis, and the poppet 31 is supported so as to be slidable in the axial direction.

  In the valve body 21, a valve hole 24 is formed between the large cylinder 22 and the small cylinder 23, and annular grooves 25 and 26 are formed so as to sandwich the valve hole 24. The annular groove 25 communicates with a port (entrance / exit) of the motor 5, and the annular groove 26 communicates with a port (entrance / exit) of the direction switching valve 14. Thus, the annular groove 25, the valve hole 24, and the annular groove 26 constitute the first supply / discharge passage 11.

  In the valve body 21, an annular seat 28 is formed at the opening edge of the valve hole 24, and the seat 28 and the poppet valve portion 34 of the poppet 31 are seated.

  The opening diameters of the valve hole 24 and the seat 28 are formed to be equal to the opening diameter of the small cylinder 23. The maximum outer diameter of the poppet valve portion 34 is formed larger than the opening diameter of the seat 28. The counter balance valve 20 is closed when the poppet valve portion 34 is seated on the seat 28, and the first supply / discharge passage 11 is shut off.

  When the poppet 31 moves in the axial direction of the counter balance valve 20 and the poppet valve portion 34 of the poppet 31 is separated from the seat 28, a variable restricting portion is defined as a channel having an annular cross section therebetween. The counter balance valve 20 adjusts the flow rate of the working fluid passing through the first supply / discharge passage 11 by the poppet valve portion 34 being displaced in the axial direction with respect to the seat 28 so that the cross-sectional area of the variable throttle portion increases or decreases. To do.

  The piston 30 has an outer diameter smaller than the small land portion 33. The piston 30 is formed separately from the poppet 31 and is provided so as to be slidably fitted to the valve body 21 along with the poppet 31.

The valve body 21 includes a cylinder 27 for a piston 30 slidably fitted is formed. Thus, the piston 30 is supported so as to be displaceable in the axial direction.

  A coiled return spring 41 that biases the poppet 31 in the left direction in the drawing is interposed in the valve body 21 while being compressed, and the poppet 31 is biased in the right direction in the drawing through the piston 30. A coiled spring 42 is compressed and interposed. The spring force of the return spring 41 is set to be larger than the spring force of the spring 42. Accordingly, the poppet valve portion 34 is urged to be seated on the seat 28 by the spring force of the return spring 41 and the spring 42.

  In the valve body 21, a second pilot pressure chamber 36, a first pilot pressure chamber 37, a pressure chamber 38, and a back pressure chamber 39 are formed coaxially with the poppet 31.

  The back pressure chamber 39 is defined behind the large land portion 32 and a return spring 41 is interposed. An atmospheric pressure is introduced into the back pressure chamber 39 as a back pressure acting on the large land portion 32. Further, the back pressure chamber 39 may be communicated with the tank 16.

  The pressure chamber 38 is defined between the large land portion 32 and the small land portion 33. The pressure chamber 38 defines the first supply / discharge passage 11 closer to the direction switching valve 14 than the seat 28, and the working fluid supplied to and discharged from the motor 5 flows therethrough.

  An annular seal 29 is provided on the outer periphery of the large land portion 32. The seal 29 is an O-ring. The seal 29 is interposed in an annular groove 44 formed on the outer periphery of the large land portion 32 and is in sliding contact with the large cylinder 22. A seal 29 seals between the pressure chamber 38 and the back pressure chamber 39.

  The second pilot pressure chamber 36 and the first pilot pressure chamber 37 are partitioned by the piston 30.

  The second pilot pressure chamber 36 is defined by the cylinder 27 and the base end portion (end face) of the piston 30. As a pilot pressure, the load pressure in the second supply / discharge passage 12 is guided to the second pilot pressure chamber 36 through the orifice 35. When the load pressure guided from the second supply / discharge passage 12 to the second pilot pressure chamber 36 rises above a predetermined value, the poppet 31 moves to the right in the figure against the spring force of the return spring 41 and the spring 42. The first supply / discharge passage 11 is opened.

  The orifice 35 serves to stabilize the operation of the counter balance valve 20 by imparting a viscous damping force to the working fluid passing through the orifice 35, suppressing vibrations of the poppet 31 caused by pressure fluctuations and disturbances.

  The first pilot pressure chamber 37 is defined by the small cylinder 23, the end face of the small land portion 33, and the tip portion of the piston 30. The first pilot pressure chamber 37 communicates with the pressure chamber 38 via the communication passage 13, and the pressure on the direction switching valve 14 side is guided from the seat 28 of the first supply / discharge passage 11.

  Next, the operation will be described.

  At the time of winding operation of the winch 1 (at the time of normal operation of the actuator), the direction switching valve 14 is switched to the winding position a. As a result, the discharge pressure of the pump 15 is guided to the first pilot pressure chamber 37 and the pressure chamber 38, and the fluid pressure acting on the pressure receiving portion of the poppet 31 facing the first pilot pressure chamber 37 and the biasing force of the spring 42 are used. The poppet 31 moves to the right in the figure against the return spring 41, and the poppet valve portion 34 moves away from the seat 28 and opens the first supply / discharge passage 11. At this time, since the pressure of the tank 16 is guided to the second pilot pressure chamber 36 via the second supply / discharge passage 12, the poppet 31 is opened only depending on the pressure of the first pilot pressure chamber 37. Move in the direction. Along with this, the pressurized working fluid discharged from the pump 15 is supplied to the motor 5 through the first supply / discharge passage 11, the motor 5 rotates in the forward direction, and the working fluid flowing out from the motor 5 becomes the first. It returns to the tank 16 through the two supply / discharge passages 12. Thereby, the winch 1 rotates the drum 2 in the winding direction by the operation of the motor 5, winds the rope 3 around the drum 2, and raises the work 4.

  Thus, the counter balance valve 20 functions as a check valve that opens the first supply / discharge passage 11 as its pressure increases.

  When the winch 1 is extended (when the actuator is reversely operated), the direction switching valve 14 is switched to the extended position b. As a result, the discharge pressure of the pump 15 (load pressure of the motor 5) is guided to the second pilot pressure chamber 36 through the orifice 35, and the fluid pressure acting on the pressure receiving portion of the piston 30 facing the second pilot pressure chamber 36. The urging force of the spring 42 moves the poppet 31 to the right in the drawing against the return spring 41, and the poppet valve portion 34 moves away from the seat 28 and opens the first supply / discharge passage 11. Along with this, the pressurized working fluid discharged from the pump 15 is supplied to the motor 5 through the second supply / discharge passage 12, the motor 5 rotates in the reverse direction, and the working fluid flowing out of the motor 5 becomes the first. It returns to the tank 16 through the one supply / discharge passage 11. Accordingly, the winch 1 is driven to rotate the drum 2 in the feeding direction by the operation of the motor 5, and the rope 3 is fed out from the drum 2 to lower the work 4.

  When the pilot pressure led to the second pilot pressure chamber 36 from the second supply / discharge passage 12 through the orifice 35 is lowered from a predetermined value during the above-described winch 1 feeding operation, the spring 42 is applied to the spring 42 by the urging force of the return spring 41. Accordingly, the poppet 31 moves to the left in the figure, and the flow passage cross-sectional area of the variable throttle portion defined between the poppet valve portion 34 and the seat 28 decreases, and passes through the first supply / discharge passage 11. The flow rate of the working fluid returned to the tank 16 decreases. Thus, the counter balance valve 20 appropriately adjusts the rotational speed of the motor 5 in accordance with the pilot pressure (load pressure of the motor 5) guided from the second supply / discharge passage 12 to the second pilot pressure chamber 36. At this time, since the pressure of the tank 16 is guided to the first pilot pressure chamber 37 via the first supply / discharge passage 11, the poppet 31 is opened only depending on the pressure of the second pilot pressure chamber 36. Move in the direction. The operating position of the poppet 31 can be changed by adjusting the balance between the opening area of the orifice 35 and the urging force of the return springs 41 and 42. Thereby, the descending speed of the workpiece 4 is adjusted moderately.

  When the pilot pressure (load pressure of the motor 5) is lower than a predetermined value when the winch 1 is extended, the poppet 31 moves to the left in the figure against the spring 42 by the biasing force of the return spring 41. Then, the poppet valve portion 34 sits on the seat 28 and blocks the first supply / discharge passage 11. At this time, since the conical poppet valve portion 34 contacts the seat 28 without a gap, the sealing performance for blocking the first supply / discharge passage 11 is ensured. As a result, the working fluid is prevented from leaking from the contact portion between the poppet valve portion 34 and the seat 28, the rotation of the motor 5 is stopped for a long time, and the workpiece 4 can be held at the stop position.

  Thus, when the winch 1 is fed out, the counter balance valve 20 performs a speed adjusting function for limiting the descending speed of the work 4 and a function for preventing the work 4 from dropping according to the pilot pressure (load pressure of the motor 5).

  When the winch 1 is stopped, the direction switching valve 14 is switched to the neutral position c. As a result, the first supply / discharge passage 11 and the second supply / discharge passage 12 are blocked, and supply / discharge of the working fluid to the motor 5 is stopped. Thereby, the rotation of the drum 2 is stopped and the work 4 is held at the stop position.

  As described above, in the present embodiment, when the actuator (motor 5) is normally operated, the working fluid is supplied from the pressure source (pump 15) through the first supply / discharge passage 11 to the actuator (motor 5). While the working fluid flows out from the (motor 5) through the second supply / discharge passage 12, the actuator (motor 5) passes from the pressure source (pump 15) through the second supply / discharge passage 12 when the actuator (motor 5) operates in reverse. ) In the working fluid pressure circuit in which the working fluid flows out from the actuator (motor 5) through the first supply / discharge passage 11 and is annularly disposed in the first supply / discharge passage 11 A poppet 31 having a poppet valve portion 34 that is seated on the seat 28 and that forms a variable throttle portion between the seat 28 and the poppet 31 is closed. The return spring 41 that biases in the direction and the pilot pressure that drives the poppet 31 in the valve opening direction due to the pressure generated on the pressure source (pump 15) side from the seat 28 of the first supply / discharge passage 11 when the actuator (motor 5) is normally operated A pilot piloted to drive the poppet 31 in the valve opening direction by the first pilot pressure chamber 37 guided as pressure and the load pressure supplied to the actuator (motor 5) from the second supply / discharge passage 12 when the actuator (motor 5) is reversely operated. A second pilot pressure chamber 36 guided as pressure, and opens the first supply / discharge passage 11 in accordance with the supply pressure guided from the pressure source (pump 15) when the actuator (motor 5) is normally operated. According to the load pressure supplied from the second supply / discharge passage 12 to the actuator (motor 5) during reverse operation of the motor 5) Actuator and configured to narrow the flow of hydraulic fluid flowing through the first supply-discharge passage 11 from (motor 5).

  Based on the above configuration, when the actuator (motor 5) is normally operated, the poppet 31 is moved to the return spring 41 according to the pilot pressure guided from the upstream side of the seat 28 of the first supply / discharge passage 11 to the first pilot pressure chamber 37. As a result, the poppet valve portion 34 moves away from the seat 28 and supplies the working fluid to the actuator (motor 5).

When the pressure generated on the pressure source (pump 15) side from the seat 28 of the first supply / discharge passage 11 is lower than a predetermined value during the normal operation of the actuator (motor 5), the poppet 31 moves the poppet valve portion 34 to the seat 28. The first supply / discharge passage 11 is blocked by being seated.

  At this time, since the poppet valve portion 34 abuts the seat 28 without a gap, the sealing performance for blocking the flow of the working fluid can be improved. As a result, even when a low-viscosity liquid such as water is used as the working fluid, it is possible to prevent the working fluid from leaking from the contact portion between the poppet valve portion 34 and the seat 28, and the actuator can be used for a long time. (Motor 5) can be held at the stop position.

  Thus, the counter balance valve 20 functions as a check valve that opens according to the pressure of the working fluid supplied to the actuator (motor 5). Accordingly, there is no need to provide a check valve interposed in parallel with the spool unlike the conventional counter balance valve unit, the structure of the counter balance valve 20 unit is simplified, and the counter balance valve 20 unit is made compact. Is peeled off.

  When the load pressure of the actuator (motor 5) is higher than a predetermined value during the reverse operation of the actuator (motor 5), the poppet valve portion 34 is separated from the seat 28, and the load pressure of the actuator (motor 5) increases. Accordingly, the flow passage cross-sectional area of the variable throttle portion defined between the seat 28 and the poppet valve portion 34 is increased. In other words, the counter balance valve 20 restricts the flow of the working fluid flowing out from the actuator (motor 5) when the poppet valve portion 34 approaches the seat 28 as the load pressure of the actuator (motor 5) decreases. The operating speed of (motor 5) is adjusted.

  During reverse operation of the actuator (motor 5), if the load pressure of the actuator (motor 5) is lower than a predetermined value, the poppet 31 seats the poppet valve portion 34 on the seat 28 and blocks the first supply / discharge passage 11. .

  In the present embodiment, a piston 30 is provided which is provided side by side with the poppet 31 in the axial direction. The first pilot pressure chamber 37 is defined by the distal end portion of the piston 30 and the poppet 31, and the proximal end portion of the piston 30 Two pilot pressure chambers 36 are defined.

  Based on the above configuration, the pilot pressure guided to the first pilot pressure chamber 37 from the upstream side of the seat 28 of the first supply / discharge passage 11 during the normal operation of the actuator (motor 5) is the tip of the piston 30 and the end face of the poppet 31. The poppet 31 moves in the valve opening direction according to the pilot pressure and supplies the working fluid to the actuator (motor 5). Thus, the counter balance valve 20 functions as a check valve that opens with respect to the flow of the working fluid supplied to the actuator (motor 5).

  In the present embodiment, the valve body 21 having the seat 28 opened is provided, and the poppet 31 is slidably fitted to the valve body 21 and the cylindrical large land portion 32 that is slidably fitted to the valve body 21. The large land portion 32 has a cylindrical small land portion 33 having an outer diameter smaller than that of the large land portion 32, and the poppet valve portion 34 is formed between the large land portion 32 and the small land portion 33.

  Based on the above configuration, when the large land portion 32 and the small land portion 33 are slidably fitted to the valve body 21, the poppet valve portion 34 is displaced coaxially with the seat 28, and the poppet valve portion 34 is moved to the seat. 28 can be brought into contact with no gap, and the sealing performance for blocking the flow of the working fluid can be improved.

  In the present embodiment, a pressure chamber 38 through which the working fluid flowing out from the actuator (motor 5) flows is defined between the large land portion 32 and the small land portion 33, and the back pressure chamber 39 is located behind the large land portion 32. The annular seal 29 is provided on the outer periphery of the large land portion 32, and the seal 29 is in sliding contact with the valve body 21 so that the space between the pressure chamber 38 and the back pressure chamber 39 is sealed.

  Based on the above configuration, the sealing performance of the pressure chamber 38 can be enhanced by the seal 29. Thus, even when a low-viscosity liquid such as water is used as the working fluid, the working fluid is prevented from leaking from the pressure chamber 38 to the back pressure chamber 39.

  Next, another embodiment shown in FIG. 2 will be described. This basically has the same configuration as that of the embodiment of FIG. 1, and only different portions will be described. In addition, the same code | symbol is used for the same structure part as the said embodiment.

  In the valve body 21, a conical sheet 28 is formed at the opening edge of the valve hole 24.

  The poppet valve portion 34 of the poppet 31 includes a conical poppet taper portion 71 and an annular poppet seat portion 72 that extends from the conical poppet taper portion 71 in the outer diameter direction.

  The poppet sheet portion 72 is formed in a curved surface whose longitudinal section including the center line O of the poppet 31 is curved in an arc shape.

  The counter balance valve 20 is closed when the poppet seat 72 is seated on the seat 28, and the first supply / discharge passage 11 is shut off. When the poppet seat portion 72 having an arcuate cross section is seated on the conical surface seat 28, the surface pressure of the contact portion between the poppet 31 and the seat 28 is reduced. Thereby, even if the counter balance valve 20 is repeatedly opened and closed, the contact portion between the poppet 31 and the seat 28 is suppressed from being worn, and the durability is enhanced.

  When the poppet 31 moves in the axial direction and the poppet sheet portion 72 is separated from the sheet 28, a variable restricting portion is defined as a channel having an annular cross section between the sheet 28 and the conical poppet taper portion 71.

  In the present embodiment, the poppet valve portion 34 includes a poppet taper portion 71 that defines a variable throttle portion between the poppet valve portion 34 and an annular poppet that extends from the poppet taper portion 71 in the outer diameter direction and sits on the seat 28. The sheet portion 72 is formed on the same axis.

  Based on the above configuration, the annular poppet seat portion 72 extending from the poppet taper portion 71 in the outer diameter direction is seated on the seat 28, whereby the surface pressure of the contact portion between the poppet 31 and the seat 28 is reduced. Thereby, even if the counter balance valve 20 is repeatedly opened and closed, the contact portion between the poppet 31 and the seat 28 is suppressed from being worn, and the durability is enhanced.

  In the present embodiment, the poppet seat portion 72 is formed in a curved surface that is curved in a cross-sectional arc shape, and the seat 28 on which the poppet seat portion 72 is seated is formed in a conical surface shape.

  Based on the above configuration, the poppet seat portion 72 having an arcuate cross section is seated on the conical surface seat 28, whereby the surface pressure of the contact portion between the poppet 31 and the seat 28 is reduced. Thereby, even if the counter balance valve 20 is repeatedly opened and closed, the contact portion between the poppet 31 and the seat 28 is suppressed from being worn, and the durability is enhanced.

  Next, another embodiment shown in FIG. 3 will be described. This basically has the same configuration as that of the embodiment of FIG. 1, and only different portions will be described. In addition, the same code | symbol is used for the same structure part as the said embodiment.

  The poppet valve portion 34 of the poppet 31 includes a poppet taper portion 73 whose longitudinal section including the center line O of the poppet 31 is curved in a parabolic shape, and a poppet seat portion 74 that extends from the poppet taper portion 73 in a planar shape in the outer diameter direction. Are formed on the same axis.

  The poppet taper portion 73 gradually decreases in size as the outer diameter thereof moves away from the poppet sheet portion 74, and the rate of change in the outer diameter (the degree to which the outer diameter of the poppet taper portion 73 decreases in the axial direction of the poppet 31). It is formed so as to gradually increase as the distance from the sheet portion 74 increases.

  The poppet sheet portion 74 is formed in a planar shape orthogonal to the center line O of the poppet 31.

  In the valve body 21, a flat sheet 28 is formed at the opening edge of the valve hole 24. The sheet 28 is formed in a planar shape orthogonal to the center line O of the poppet 31 and faces the poppet sheet portion 74 in parallel.

  In addition to this, as shown in FIG. 2, as shown in FIG. 2, the poppet seat portion 74 is formed in a curved surface in which a longitudinal section including the center line O of the poppet 31 is curved in an arc shape, and the seat 28 on which the poppet seat portion 74 is seated. May be formed in a conical shape.

  The poppet valve portion 34 of the poppet 31 includes a conical poppet taper portion 71 and an annular poppet seat portion 72 that extends from the conical poppet taper portion 71 in the outer diameter direction.

  The poppet sheet portion 72 is formed in a curved surface whose longitudinal section including the center line O of the poppet 31 is curved in an arc shape.

  When the poppet seat portion 74 of the poppet valve portion 34 is seated on the seat 28, the valve is closed and the first supply / discharge passage 11 is shut off.

  When the poppet 31 moves in the axial direction and the poppet seat portion 74 of the poppet valve portion 34 is separated from the seat 28, a variable throttle portion is defined as a flow path having an annular cross section between the seat 28 and the poppet taper portion 73. The

  FIG. 4 is a characteristic diagram showing the relationship between the displacement (stroke) of the poppet 31 and the opening area of the variable aperture portion defined between the sheet 28 and the poppet taper portion 73. Since the change in the opening area of the variable throttle portion with respect to the displacement of the poppet 31 is reduced when the work 4 is lowered at a low speed, the change in pressure proportional to the square of the opening area is reduced, and the counter at the time of low-speed winding is reduced. The controllability of the balance valve 20 can be improved. Since the change of the opening area of the variable throttle portion with respect to the displacement of the poppet 31 becomes large at the time of high-speed winding when the unwinding operation of the winch 1 is performed at high speed without the work 4, the counter balance valve 20 is operated with a large flow rate. Flows and the lowering speed is increased.

  In the present embodiment, the poppet valve portion 34 has a configuration having a poppet taper portion 73 whose section is curved in a parabolic shape.

  Based on the above configuration, it is possible to improve both controllability during low-speed operation of the actuator (motor 5) and ensure high-speed operability.

  Next, another embodiment shown in FIG. 5 will be described. This basically has the same configuration as that of the embodiment of FIG. 1, and only different portions will be described. In addition, the same code | symbol is used for the same structure part as the said embodiment.

  As means for guiding the load pressure of the second supply / discharge passage 12 to the second pilot pressure chamber 36, the upstream pressure chamber 81 communicating with the second supply / discharge passage 12 and the upstream pressure chamber 81 communicated with the second pilot pressure chamber 36. The intermediate pressure chamber 83, the upstream orifice 82 interposed between the upstream pressure chamber 81 and the intermediate pressure chamber 83, and the intermediate orifice 84 interposed between the intermediate pressure chamber 83 and the second pilot pressure chamber 36. With.

  The intermediate pressure chamber 83 has a volume necessary for recovering the dynamic pressure from the upstream pressure chamber 81 through the upstream orifice 82 to the static pressure.

  In this case, the load pressure in the second supply / exhaust passage 12 as the pilot pressure for driving the piston 30 is guided to the second pilot pressure chamber 36 via the upstream pressure chamber 81, the upstream orifice 82, the intermediate pressure chamber 83, and the intermediate orifice 84. It is burned. The upstream orifice 82 gives a viscous damping force to the working fluid passing therethrough, and after the dynamic pressure recovers to the static pressure when passing through the upstream orifice 82 in the intermediate pressure chamber 83, the intermediate orifice 84 passes therethrough. A viscous damping force is applied to the working fluid. As a result, even when a low-viscosity working fluid such as water is used, the upstream orifice 82 and the intermediate orifice 84 impart a viscous damping force to the working fluid passing therethrough, and are generated due to pressure fluctuations or disturbances. This function serves to suppress the vibration of the poppet 31 and stabilize the operation of the counter balance valve 20.

  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.

1 winch 2 drum 3 rope 4 work 5 motor 11 first supply / discharge passage 12 second supply / discharge passage 13 communication passage 14 direction switching valve 15 pump 16 tank 20 counter balance valve 21 valve body 22 large cylinder 23 small cylinder 24 valve hole 25 Annular groove 26 Annular groove 27 Cylinder 28 Seat 29 Seal 30 Piston 31 Poppet 32 Large land portion 33 Small land portion 34 Poppet valve portion 35 Orifice 36 Second pilot pressure chamber 37 First pilot pressure chamber 38 Pressure chamber 39 Back pressure chamber 41 Return Spring 42 Spring 71 Poppet taper portion 72 Poppet seat portion 73 Poppet taper portion 74 Poppet seat portion 81 Upstream pressure chamber 82 Upstream orifice 83 Intermediate pressure chamber 84 Intermediate orifice

Claims (7)

When the actuator is normally operated, the working fluid is supplied from the pressure source to the actuator through the first supply / discharge passage, and the working fluid flows out from the actuator through the second supply / discharge passage, while the actuator is reversely operated. A working fluid pressure circuit in which a working fluid is sometimes supplied from the pressure source through the second supply / discharge passage to the actuator and the working fluid flows out from the actuator through the first supply / discharge passage;
A valve body having an annular seat opened in the first supply / discharge passage;
A poppet having a poppet valve portion that sits on the seat and forms a variable throttle portion with the seat;
A return spring for urging the poppet in the valve closing direction;
A piston provided side by side in the axial direction with the poppet;
The pressure generated on the pressure source side from the seat of the first supply / discharge passage during normal operation of the actuator is guided as a pilot pressure for driving the poppet in the valve opening direction through a communication passage branched from the first supply / discharge passage. A first pilot pressure chamber;
A second pilot pressure chamber in which a load pressure supplied from the second supply / discharge passage to the actuator during reverse operation of the actuator is guided as a pilot pressure for driving the poppet in a valve opening direction;
The poppet is
A cylindrical large land portion slidably fitted to the valve body;
A cylindrical small land portion that is slidably fitted to the valve body and has a smaller outer diameter than the large land portion,
The poppet valve portion is formed between the large land portion and the small land portion,
A first pilot pressure chamber is defined between a tip portion of the piston and the small land portion of the poppet;
The first supply / discharge passage is opened according to the supply pressure introduced from the pressure source during the normal operation of the actuator, while the load pressure supplied to the actuator from the second supply / discharge passage is reversed during the reverse operation of the actuator. Accordingly, the counter balance valve is configured to restrict the flow of the working fluid flowing out from the actuator through the first supply / discharge passage. Counterbalance valve according to claim 1, characterized in that where the structure defining said second pilot pressure chamber by the base end portion of the front Symbol piston. A pressure chamber through which a working fluid flowing out from the actuator flows is defined between the large land portion and the small land portion,
A back pressure chamber is defined behind the large land,
An annular seal is provided on the outer periphery of the large land portion,
3. The counterbalance valve according to claim 1, wherein a space between the pressure chamber and the back pressure chamber is sealed by sliding the seal against the valve body. 4.   The poppet valve portion is coaxially formed with a poppet taper portion that defines the variable throttle portion between the poppet valve portion and an annular poppet seat portion that extends from the poppet taper portion in an outer diameter direction and is seated on the seat. The counter balance valve according to claim 1, wherein the counter balance valve is formed. The poppet sheet portion is formed in a curved surface that is curved in a cross-section arc shape,
The counter balance valve according to claim 4, wherein the seat is formed in a conical shape.   6. The counter balance valve according to claim 4, wherein the poppet valve portion includes the poppet taper portion whose cross section is curved in a parabolic shape. As means for guiding the load pressure of the second supply / discharge passage to the second pilot pressure chamber,
An intermediate pressure chamber communicating the upstream pressure chamber with the second pilot pressure chamber;
An upstream orifice interposed between the upstream pressure chamber and the intermediate pressure chamber;
The counterbalance valve according to claim 1, further comprising an intermediate orifice interposed between the intermediate pressure chamber and the second pilot pressure chamber.