JP2012137134A - Flow rate control valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flow rate control valve that reduces pressure loss while reducing descending speed of a loading platform or the like connected to a lift cylinder.SOLUTION: The flow rate control valve is provided between a lift cylinder 2 constituting an actuator which drives the loading platform to lift or lower the loading platform that receives supplied working liquid, and a working liquid supply passage 6 which supplies the working liquid to the lift cylinder 2. The flow rate control valve includes: a body 71 having an inner passage 71x communicating with the working liquid supply passage 6; a piston 72 which projects to and retracts from the body 71, has an opening whose size changes according to projecting/retracting operations, and has a working liquid circulating hole 72x communicating with the inside of the lift cylinder 2; a spring 73 which is a biasing means that biases the piston 72 to the side where the opening of the working liquid circulating hole 72x is increased; a bypass passage 74 which connects the inner passage 71x with the lift cylinder 2; and a check valve 75 which shuts off the bypass passage 74 when the loading platform is lowered.

Description

  The present invention relates to a flow control valve connected to an actuator that operates by hydraulic pressure.

  2. Description of the Related Art Conventionally, in industrial vehicles such as forklifts, a cargo handling operation for raising and lowering a loading platform as a driving target is performed by supplying pressure generated in a hydraulic circuit to a cylinder of a hydraulic actuator. At this time, a flow control valve may be provided between a cylinder constituting the hydraulic actuator and a hydraulic fluid supply path for supplying the hydraulic fluid to the cylinder in order to prevent a sudden drop of the cargo bed (for example, a patent Reference 1).

  An example of such a flow control valve is a flow control valve mounted on a lift cylinder of a forklift. As shown in FIG. 4, the flow control valve includes a body c having an internal passage c1 communicating with a hydraulic fluid supply passage b for supplying hydraulic fluid to the lift cylinder a, and a projecting / recessing to the body c. A piston d provided with a hydraulic fluid flow hole d1 that is possible and the size of the opening changes depending on the protrusion and subtraction operation, and this piston d is urged toward the side where the size of the hydraulic fluid flow hole d1 increases. And a spring e as an urging means.

  In the normal state, when the fork is raised, the working fluid passes through the working fluid circulation hole d1 via the internal passage c1 of the body c, and freely flows into the lift cylinder bottom portion without being controlled by the flow rate. On the other hand, when the fork is lowered, the working fluid is returned from the lift cylinder a to the tank (not shown) through the working fluid circulation hole d1 and the internal passage c1 of the body c. The descending speed of the lift cylinder at this time is controlled by another flow control valve (not shown) provided separately.

  On the other hand, when the lowering speed cannot be controlled by the other flow control valve when the fork is lowered, for example, when a large pressure difference occurs between the internal passage c1 of the body c and the inside of the lift cylinder a due to, for example, breakage of the pipe, Due to the hydraulic pressure from the lift cylinder a side, the piston d is immersed in the body c against the urging force of the spring e, and the size of the opening portion of the hydraulic fluid circulation hole d1 is reduced or closed. The hydraulic fluid flow hole d1 functions as a throttle, and a rapid lowering of the fork is suppressed.

  That is, the set flow rate of the flow rate control valve for determining the maximum flow rate of the hydraulic fluid flowing out from the cylinder when descending is defined by the size of the hydraulic fluid flow hole d1 and the spring constant of the spring e. That is, in order to suppress the flow rate of the hydraulic fluid that flows out when descending, it is necessary to reduce the size of the hydraulic fluid circulation hole d1 or set the spring constant of the spring e low. That is, since the hydraulic fluid circulation hole d1 is determined by the control flow rate on the descending side, the pressure loss at the time of ascent is also determined by this.

  Such a problem is not limited to the actuator used for raising and lowering the loading platform, but a large pressure difference is generated between the cylinder and the hydraulic fluid supply path due to piping breakage or the like, and the hydraulic fluid is rapidly discharged from the cylinder. It exists in general when it is necessary to suppress the rapid movement of the driven object.

JP 7-179300 A

  The present invention focuses on the above points, and an object of the present invention is to realize a structure of a flow rate control valve with a small pressure loss while suppressing a moving speed of a driving object connected to a cylinder.

  That is, the flow control valve according to the present invention is a flow control valve provided between a cylinder that constitutes an actuator that receives supply of hydraulic fluid and a hydraulic fluid supply passage that supplies hydraulic fluid to the cylinder. A body provided with an internal passage communicating with the liquid supply path, and a hydraulic fluid circulation hole that can project and retract with respect to the body and change the size of the opening according to the projecting and retracting operation and communicate with the inside of the cylinder. A piston, a biasing means for biasing the piston toward the side where the size of the opening of the hydraulic fluid circulation hole is increased, a bypass passage communicating the internal passage and the cylinder, and the hydraulic fluid is discharged from the cylinder And a check valve that shuts off the bypass passage.

  If it is such, since a bypass channel | path will be interrupted | blocked in the case of a downward movement and a hydraulic fluid will go to a tank through only a hydraulic fluid circulation hole, a downward speed can be suppressed. On the other hand, during the ascending operation, the working fluid flows through both the working fluid circulation hole and the bypass passage and is supplied to the cylinder, so that a larger passage toward the cylinder can be secured. That is, the pressure loss generated before and after the flow control valve can be suppressed, and the increase in the temperature of the hydraulic fluid can be suppressed.

  In particular, if the bypass passage is formed in the piston and the check valve is housed in the piston, such a flow control valve can be realized with a simple configuration.

  As a preferred example of using such a flow control valve, there is one that functions as a down safety valve provided at the bottom portion of a lift cylinder that constitutes an actuator that drives the loading platform up and down by hydraulic pressure.

  ADVANTAGE OF THE INVENTION According to this invention, the structure of the flow control valve with a small pressure loss is realizable, suppressing the moving speed of the drive target connected to the cylinder.

1 is a schematic circuit diagram of a hydraulic system according to an embodiment of the present invention. The figure which shows schematically the flow control valve which concerns on the same embodiment. The figure which shows schematically the forklift provided with the hydraulic circuit which concerns on the same embodiment. The figure which shows the conventional flow control valve schematically.

  An embodiment of the present invention will be described below with reference to FIGS.

  The hydraulic system according to the present embodiment is attached to the lowermost part of a mast 1 of a forklift F as shown in FIG. 3, and raises and lowers a fork 3 as a loading platform by supplying hydraulic pressure to a lift cylinder 2. Here, in the present embodiment, the forklift F is operated by electric power supplied from a battery or power supplied from an internal combustion engine.

  As shown in FIG. 1, the hydraulic pressure system is operated from a hydraulic pressure supply source 4 such as a pump, a control valve 5 that receives hydraulic fluid from the hydraulic pressure supply source 4, and an output port 5a of the control valve 5. A hydraulic fluid supply path 6 for receiving hydraulic fluid and supplying hydraulic fluid to the lift cylinder 2, and a book provided between the hydraulic fluid supply path 6 and the lift cylinder 2 to suppress a sudden drop of the fork 3. And a flow control valve 7 of the invention. Here, the lift cylinder 2 constitutes an actuator that drives the fork 3 to move the fork 3 up and down.

  The control valve 5 is a directional control valve having a spool 52 that is connected to an operation lever 51 and receives an operation on the operation lever 51 and takes any one of a raised position U, a neutral position S, and a lowered position D. It is used. When the spool 52 assumes the raised position U, hydraulic fluid is supplied from the hydraulic pressure supply source 4 to the lift cylinder 2 via the output port 5a. On the other hand, when the spool 52 assumes the lowered position D, the hydraulic fluid is returned from the lift cylinder 2 to the tank 8 via the output port 5a. When the spool 52 takes the neutral position S, the lift cylinder 2 is held at that position.

  Thus, the flow control valve 7 includes a body 71 having an internal passage 71x communicating with the hydraulic fluid supply passage 6 therein, and can project and retract with respect to the body 71 and has a size corresponding to the projecting and retracting operation. The piston 72 provided with the hydraulic fluid circulation hole 72x constituting the variable throttle communicating with the inside of the lift cylinder to which the hydraulic fluid is changed and the opening of the hydraulic fluid circulation hole 72x increases. A spring 73 as a biasing means for biasing to the side, a bypass chamber 74 communicating with the internal passage 71x and the lift cylinder 2, and provided in the bypass chamber 74 so as to be able to advance and retreat. A check valve 75 is provided to block between the bypass chamber 74 and the internal passage 71x.

  The check valve 75 includes a valve body 751 capable of advancing and retreating in the bypass chamber 74, and a valve seat 752 provided at a boundary between the bypass chamber 74 and the internal passage 71x to block them when the valve body 751 is seated. And a spring 753 as an urging means for urging the valve body 751 toward the valve seat 752 side. The outer wall of the bypass chamber 74 is provided with a second hydraulic fluid circulation hole 74 x that communicates the inside of the bypass chamber 74 and the outside of the flow control valve 7. On the other hand, the valve body 751 is provided with an orifice 751x that communicates the inside and the outside.

  Here, when the spool 52 of the control valve 5 takes the raised position U, the hydraulic fluid is guided from the output port 5 a of the control valve 5 to the flow rate control valve 7 through the hydraulic fluid supply path 6. The hydraulic fluid that has reached the flow control valve 7 first circulates in the internal passage 71x. Next, the piston 72 moves in a direction away from the body 71 due to the hydraulic pressure and the urging force of the spring 73. At this time, the entire hydraulic fluid circulation hole 72 x is exposed to the outside of the body 71. Further, the valve body 751 of the check valve 75 is acted in the direction away from the valve seat 752 against the urging force of the spring 753 due to the hydraulic pressure of the hydraulic fluid. At this time, the internal passage 71x communicates with the bypass chamber 74 and the second hydraulic fluid circulation hole 74x. Thereafter, the hydraulic fluid reaches the lift cylinder 2 through the hydraulic fluid circulation hole 72x and the second hydraulic fluid circulation hole 74x.

  On the other hand, when the control valve 5 takes the lowered position D or a pressure difference is generated between the lift cylinder 2 and the internal passage 71x due to piping breakage or the like, the valve body 751 of the check valve 75 is released from the spring 753. Therefore, the valve body 751 is seated on the valve seat 752. That is, the bypass chamber 74 and the second hydraulic fluid circulation hole 74 x are blocked from the internal passage 71. Further, the piston 72 is acted by the hydraulic pressure in a direction approaching the body 71 against the urging force of the spring 73, and the area of the portion where the hydraulic fluid circulation hole 72x is exposed is reduced. At this time, the working fluid from the lift cylinder 2 flows through the working fluid circulation hole 72 x and the internal passage 71 and is guided in the direction toward the tank 8. Here, the hydraulic fluid circulation hole 72x functions as a throttle for controlling the flow rate of the hydraulic fluid toward the internal passage, and the descending speed of the lift cylinder 2 is suppressed. The lowering speed of the lift cylinder 2 is controlled by another flow control valve A provided separately.

  That is, by providing the flow rate control valve 7 according to the present embodiment, the bypass passage 74 is blocked during the lowering operation, and the hydraulic fluid is directed to the tank 8 only through the hydraulic fluid circulation hole 72x. Speed can be suppressed. On the other hand, during the ascending operation, the hydraulic fluid flows through both the hydraulic fluid circulation hole 72x and the bypass passage 74 and is supplied to the lift cylinder 2, so that a flow rate toward the lift cylinder 2 can be secured. That is, the pressure loss generated before and after the flow control valve 7 can be suppressed, and the increase in the temperature of the hydraulic fluid can be suppressed. Therefore, the fuel efficiency of the forklift F provided with such a flow control valve 7 can be improved.

  In particular, in this embodiment, the bypass passage 74 is formed in the piston 72 and the check valve 75 is housed in the piston 72. Therefore, such a flow control valve 7 has a simple configuration. Can be realized.

  The present invention is not limited to the embodiment described above.

  For example, in the above-described embodiment, the valve body of the check valve is accommodated in the piston, but a bypass passage that communicates the internal passage of the body and the inside of the lift cylinder is separately provided outside, and the bypass passage is provided. A mode may be adopted in which a check valve is provided to suppress the flow of hydraulic fluid from the lift cylinder to the output port of the direction control valve.

  Further, the present invention may be applied to, for example, an actuator for controlling the inclination of a forklift mast, an actuator used for a tailgate raising / lowering mechanism of a vehicle having a tailgate, and the like other than an actuator used for raising / lowering a forklift platform.

  In addition, various modifications may be made without departing from the spirit of the present invention.

7 ... Flow control valve 71 ... Body 71x ... Internal passage 72 ... Piston 72x ... Hydraulic fluid supply path 73 ... Spring (biasing means)
74 ... Bypass passage 75 ... Check valve

Claims (3)

A flow rate control valve provided between a cylinder that constitutes an actuator that receives the supply of hydraulic fluid and a hydraulic fluid supply passage that supplies the hydraulic fluid to the cylinder, and an internal passage that communicates with the hydraulic fluid supply passage A body provided with a hydraulic fluid passage hole that can project and retract with respect to the body and has an opening that changes in response to the motion of the body and communicates with the inside of the cylinder. An urging means for urging the opening of the hole toward the larger side, a bypass passage communicating the internal passage and the cylinder, and shutting off the bypass passage when hydraulic fluid is discharged from the cylinder A flow rate control valve comprising a check valve. The flow control valve according to claim 1, wherein the bypass passage is formed in the piston and the check valve is housed in the piston. The flow control valve according to claim 1 or 2, wherein the flow control valve functions as a down safety valve provided at a bottom portion of a lift cylinder that constitutes an actuator that lifts and lowers a cargo bed by hydraulic pressure.

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