JP2010031983A - Counter balance device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make return oil quickly flow into a working fluid tank when surge pressure may be generated, and to prevent occurrence of hunting when pressure difference between both end face of a spool is small, with simple structure. <P>SOLUTION: The valve casing 11 of a counter balance valve 10 is provided with a working fluid chamber 30 with grease sealed therein. The working fluid chamber 30 is disposed to an end part on an oil chamber 13A side opposed to a side provided with a spring 14 for applying an urging force to the spool 12. A movable partition wall 31 is disposed to the inside of the working fluid chamber 30 to partition the chamber into chambers A, B. A throttle passage 35 connects between the chambers A, B, and rods 32a, 32b are continuously disposed to the movable partition wall 31. The rod 32a passes through a through-hole 33a formed in the casing of the working fluid chamber 30, is extended, and is connected and fixed to an end face on a side facing the oil chamber 13A of the spool 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a counter balance device for controlling a movement speed according to a load and giving a desired holding pressure when a load is driven up and down by a hydraulic motor, such as a hydraulic circuit of a hydraulic crane. is there.

  The hydraulic crane has a hydraulic circuit with a winch, and the winch is for lifting and lowering a suspended load. This hydraulic circuit is provided with a direction switching valve. By operating the direction switching valve, a hydraulic motor for driving the winch is operated. In order to prevent the suspended load from falling, a counter balance device is provided in the hydraulic circuit. The counter balance valve constituting the counter balance device is for controlling the operating speed of the winch unwinding operation.

  The counter balance valve is equipped with a spool in the valve casing so that both ends of the spool face the oil chamber, and a return flow passage area variable portion is provided at the return side portion during the lowering operation. I have to. Further, a spring is applied to the spool in the direction in which the return flow path area variable portion is closed. The oil chambers on both sides of the valve casing are connected to a pair of flow paths connected to the direction switching valve via a throttle.

  When winding up the winch, the damping function is not required, so the counter balance valve does not act specially. On the other hand, when unwinding the winch, by controlling the return flow rate of the flow path of the return flow area variable section, the back pressure is applied to the hydraulic motor to exert the damping function, so the falling speed of the suspended load by the winch To control.

  When operating the directional control valve in the unwinding direction during sudden operation, unless the spool is moved quickly and the flow passage area is quickly increased, a large surge pressure is generated on the return side of the hydraulic motor, and the hydraulic circuit is There is a risk of damaging the equipment including the hydraulic motor to be configured. On the other hand, at the time of fine operation, due to the balance of forces acting on the spool of the counter balance valve, the stability of the spool in the valve casing is impaired, and a hunting phenomenon may occur due to the minute reciprocation of the spool. . When hunting occurs in this way, the suspended load will swing, resulting in lack of operational stability. For this reason, at the time of unwinding operation, it is desirable to change the flow rate of the hydraulic oil flowing from the oil chamber provided with the spring toward the hydraulic oil tank among the oil chambers facing the spool, depending on the operation conditions.

Patent Document 1 discloses a configuration in which a throttle adjusting device is provided in a drain channel connected to an oil chamber equipped with a spring so that the channel area of the throttle provided in the drain channel is variable. In Patent Document 1, the throttle amount is changed in accordance with the viscosity of the hydraulic oil, that is, in accordance with the hydraulic oil temperature. Therefore, it can be used as a throttle adjusting mechanism according to the weight of the suspended load.
JP-A-6-159316

  In Patent Document 1 described above, in order to perform the throttle adjustment of the drain flow path according to the pressure acting in the hydraulic circuit, not the hydraulic oil temperature, the pressure in the hydraulic circuit must be detected. Therefore, when the hydraulic circuit of Patent Document 1 is used as a mechanism for adjusting the flow rate on the return side according to the weight of the suspended load when the direction switching valve is operated in the direction of unwinding the winch, The configuration of the counter balance device becomes extremely complicated, such as requiring a complicated throttle adjusting mechanism including a path adjusting unit and providing a detection mechanism and a control device for the pressure on the return side of the hydraulic motor.

  The present invention has been made in view of the above points, and the object of the present invention is to allow the return oil to quickly flow out to the hydraulic oil tank when there is a possibility that surge pressure may occur due to a simple configuration. The object is to prevent the occurrence of hunting when the pressure difference acting on both end faces of the spool is small.

  In order to achieve the above-described object, the present invention is provided in a hydraulic circuit that drives a load up and down by a hydraulic motor, and a spool is provided in a valve casing, and the hydraulic motor is provided between the valve casing and the spool. A counter balance device provided with a counter balance valve that is provided with a return side flow path and changes the flow area of the return side flow path to change the return side holding pressure in accordance with the load variation. The valve casing is provided with a working fluid chamber that is partitioned into two chambers by a movable partition wall. The working fluid chamber contains a Bingham fluid therein, and the space between the two chambers is reduced. The structure is characterized in that the movable partition wall and the spool are connected by a connecting member in communication with each other by a passage.

  In the present invention, instead of using a variable throttle that changes the opening area of the throttle provided in the drain channel, the throttle itself is a fixed throttle. In the valve casing, the moving speed of the spool is changed according to the pressure on the return side. Thereby, the area change degree of the return flow path in the return flow path area variable portion is controlled. That is, when an excessive back pressure is applied to the return flow path side, the spool is moved at a high speed. As a result, the flow passage area of the return flow passage area variable portion increases rapidly, so that it is possible to prevent the occurrence of surge pressure that causes damage to each device constituting the hydraulic circuit such as a hydraulic motor. On the other hand, when the pressure difference between the oil chambers on both sides of the spool is small, even if the pressure balance between them is slightly lost, the spool will switch, and the spool will switch frequently, resulting in stable operation. Lack of sex. At this time, the movement of the spool is suppressed, and the switching of the spool based on the pressure fluctuation is suppressed, thereby preventing the occurrence of hunting.

  This hydraulic circuit can be used, for example, as a rotary drive for a winch that lifts and lowers a suspended load. In this case, a directional switching valve is provided between the hydraulic motor and both ports of the hydraulic motor between the hydraulic pump and the hydraulic oil tank to perform flow path switching control. The directional switching valve and the hydraulic motor A counter balance valve is inserted between the two. In the valve casing, a pair of oil chambers connected to the flow path between the direction switching valve and the hydraulic motor via respective throttles are formed. These oil chambers are arranged so that both end faces of the spool face each other, and a return passage area variable section for changing the passage area of the return passage from the hydraulic motor is provided between the inner surface of the valve casing and the spool. Further, the spool is provided with a spring having an urging force in a direction to reduce the flow channel area of the return flow channel area variable portion. In this case, the connecting member is connected to the end surface of the spool opposite to the end surface on which the spring acts.

  Here, the Bingham fluid enclosed in the working fluid chamber is a so-called thixotropic non-Newtonian fluid whose viscosity changes according to the magnitude of the external force. Typical examples include grease, silicon oil, etc. Can also be used. When a large external force is applied to the movable partition wall in the working fluid chamber in which the Bingham fluid is sealed and formed into two chambers by the movable partition wall, the fluid is solated, that is, fluidized, and the shear rate of the fluid Becomes larger. The resistance to the movement of the movable partition is reduced, and a quick movement is possible. On the other hand, when the external force acting on the movable partition wall is small, the fluid is in a gel state and the shear rate is reduced. As a result, the resistance to movement of the movable partition increases.

  In a situation where surge pressure is likely to occur without providing pressure detection means or a control device, the return oil is allowed to flow quickly to the hydraulic oil tank so that surge pressure is not generated. When the pressure difference acting on both end faces of the spool is small, the operation of the spool can be stably maintained, and the occurrence of hunting can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. First, FIG. 1 shows a configuration of a hydraulic circuit for driving a hydraulic crane n winch as an example of a hydraulic circuit including a counter balance valve constituting the counter balance device.

  In the figure, 1 indicates a winch, a rope 2 is wound around the winch 1, a suspended load 3 is connected to the tip of the rope 2, and the rope 2 is wound around the winch 1, or from the winch 1 By rewinding the rope 2, the suspended load 3 as a load can be lifted and lowered. There are various types of suspended loads 3, which may be heavy or light.

  A hydraulic motor 4 is used to rotationally drive the winch 1, and when the winch 1 is rotationally driven in one direction by the hydraulic motor 4, the rope 2 is caught and the suspended load 3 is lifted (winding operation of the winch 1). When the hydraulic motor 4 is rotationally driven in the opposite direction, the rope 2 is unwound and the suspended load 3 is lowered (the operation for lowering the winch 1). The hydraulic motor 4 is driven by a hydraulic pump 5, and the hydraulic motor 4 is switched and connected to the hydraulic pump 5 and the hydraulic oil tank 7 via a direction switching valve 6. The counter balance valve 10 is interposed between the hydraulic motor 4 and the direction switching valve 6.

  The counter balance valve 10 is constituted by a valve casing 11 in which a spool 12 is slidably provided. Both ends of the spool 12 face oil chambers 13A and 13B provided in the valve casing 11, and the pressures of these oil chambers 13A and 13B act. A spring 14 is provided in the oil chamber 13B, and this spring 14 biases the spool 12 so as to press the spool 12 in the direction toward the oil chamber 13A. The spool 12 is formed with three land portions 15, 16 and 17. An annular oil passage 18 between the land portions 15 and 16 and an annular oil passage 19 between the land portions 16 and 17 are formed in the valve casing 11 by these land portions 15, 16 and 17.

  The flow paths 20 and 21 connected to the two ports of the hydraulic motor 4 are connected to the annular oil paths 18 and 19, respectively. The annular oil passages 18 and 19 and the direction switching valve 6 are connected by flow passages 22 and 23. A check valve 24 is provided in the middle of the flow path 23 to allow the hydraulic oil to flow from the direction switching valve 6 side toward the annular oil path 19 but to prevent the flow in the reverse direction. ing. Accordingly, the flow path 23 functions only when pressure oil is supplied to the hydraulic motor 4, and return oil from the hydraulic motor 4 is not supplied to the flow path 23.

  The return oil from the hydraulic motor 4 is returned to the hydraulic oil tank 7 via the return flow area variable unit 25, and at this time, the damping according to the flow area of the return flow area variable unit 25 is performed. Characteristics are obtained. For this purpose, an annular oil chamber 26 is formed in the land portion 18 of the spool 12, and a return flow path 27 to the direction switching valve 6 is connected to the annular oil chamber 26. Further, the left portion of the land portion 18 of the spool 12 in the drawing is tapered, and when the spool 12 is slid to the right in the drawing, that is, in the direction in which the spring 14 is compressed, the annular oil chamber 26 is formed. The area of the flow path to changes. Accordingly, the inflow portion from the tapered portion formed in the land portion 18 of the spool 12 to the annular oil chamber 26 functions as the return flow path area variable portion 25.

  Further, throttle passages 28 and 29 are formed in the spool 12 to communicate between the annular oil passage 18 and the oil chamber 13A and between the annular oil passage 26 and the oil chamber 13B. 28 and 29 have fixed stops 28t and 29t, respectively. Accordingly, the pressures in the annular oil passages 18 and 26 act on the oil chambers 13A and 13B, respectively.

  Further, in the valve casing 11, a working fluid chamber 30 is provided at an end portion on the side where the oil chamber 13A is provided. A movable partition wall 31 is provided in the casing of the working fluid chamber 30, and rod portions 32 a and 32 b are connected to the movable partition wall 31. The rod portion 32a extends through a through hole 33a provided in the casing of the working fluid chamber 30, and is connected and fixed to an end surface of the spool 12 facing the oil chamber 13A. Accordingly, the rod portion 32 a constitutes a connecting member provided between the movable partition wall 31 and the spool 12. On the other hand, the rod portion 32b has the same diameter as the rod portion 32a, and is inserted into a through hole 33b formed on the opposite side of the through hole 33a through which the rod portion 32a of the working fluid chamber 30 is inserted. Seal members 34 are interposed between the through holes 33a and the rod portions 32a and between the through holes 33b and the rod portions 32b, respectively.

  The movable partition wall 31 provided in the working fluid chamber 30 divides the working fluid chamber 30 into two chambers A and B, and the movable partition wall 31 communicates the chamber A and the chamber B with each other. 35 is provided. Accordingly, when an external force is applied to the rod portion 33a, the movable partition wall 31 is slidably displaced in the working fluid chamber 30.

  The working fluid chamber 30 is filled with grease as a Bingham fluid which is a non-Newtonian fluid having thixotropy. FIG. 2 shows the relationship between the shearing force and the shearing force between a grease and a general hydraulic oil (mineral oil) that is a Newtonian fluid. In general hydraulic oil, the shear rate changes proportionally according to the magnitude of the shearing force, whereas when the shearing force is as small as level L or less, the change in shear rate is small. When the shearing force is equal to or higher than the level L, the shearing speed changes almost proportionally to the shearing force. In short, when the external force acting on the grease is small, the grease gels and has a low fluidity. And when a big external force acts on grease, this grease will be in the state of sol, and fluidity | liquidity will become high. Therefore, the damping characteristic does not change proportionally like hydraulic oil.

  As described above, the working fluid chamber 30 is attached to the valve casing 11 of the counter balance valve 10, and the rod portion 32 a of the movable partition wall 31 extending from the working fluid chamber 30 is connected and fixed to the spool 12. By filling the working fluid chamber 30 with grease as a Bingham fluid, optimum damping characteristics are exhibited according to the weight of the suspended load 3 when the winch 1 is lowered. Here, the return side of the flow path 21 of the hydraulic motor 4, that is, the outflow side that exhibits the pump function when the suspended load 3 is suspended from the rope 2.

  Now, when the direction switching valve 6 is in the neutral position, the oil chambers 13A and 13B facing both ends of the spool 12 are in substantially the same pressure state, so that the spool 12 is displaced to the left in the figure by the action of the spring 14. become. At this time, if a heavy load 3 at the tip of the rope 2 is suspended, a load due to the weight of the suspended load 3 acts on the hydraulic motor 4 and the pressure in the flow path 21 increases. However, since the check valve 24 is provided in the flow path 23 connected to the hydraulic oil tank 7 and the return flow path area variable portion 25 is closed, the hydraulic motor 4 cannot immediately rotate. Absent. Therefore, the suspended load 3 is held at that position.

  When winding the suspended load 3, the direction switching valve 6 is switched to the position (A). As a result, the pressure oil from the hydraulic pump 5 is supplied to the hydraulic motor 4 from the flow path 23, the annular oil path 19 and the flow path 21 by the direction switching valve 6, and another flow path 20 connected to the hydraulic motor 4. Is communicated with the hydraulic oil tank 7 from the annular oil passage 18 and the passage 22, so that the hydraulic motor 4 is rotationally driven, the rope 2 is wound around the winch 1, and the suspended load 3 is wound up.

  When the direction switching valve 6 is switched to the position (b), pressure oil is supplied from the flow path 22 to the one port of the hydraulic motor 4 through the annular oil path 18 and the flow path 20, and a check valve 24 is provided. The flow path 23 and the return flow path 27 are connected to the hydraulic oil tank 7. However, the flow path 23 does not allow the return oil from the hydraulic motor 4 to flow out by the action of the check valve 24. On the other hand, the return flow path 27 is connected to the hydraulic motor 4 via the return flow path area variable section 25, and the flow path is not opened unless the spool 12 moves to the right in FIG.

  In the oil chambers 13A and 13B facing both ends of the spool 12, the oil chamber 13A side becomes the pump pressure and the oil chamber 13B side becomes the tank pressure, so that the spool 12 resists the urging force of the spring 14 to the right in FIG. As a result, the return flow path area variable section 25 is opened, and the other flow path 21 connected to the hydraulic motor 4 has an annular oil path 19 and a return flow path variable. The tank 25 is connected to the hydraulic oil tank 7 via the part 25 and the return flow path 27 in order, and becomes a tank pressure. Accordingly, the winch 1 rotates in the direction in which the suspended load 3 is wound down.

  Here, in order to start the operation of the hydraulic motor 4 when the winch 1 is operated in the lowering direction, it is necessary to open the return flow path area variable section 25. It must be slid along the casing 11 to the right in FIG. The displacement of the spool 12 is based on the differential pressure between the oil chambers 13A and 13B. The oil chamber 13A is connected to the annular oil passage 18 via the throttle passage 28 having the fixed throttle 28t, and the oil chamber. 13B is connected to the annular oil chamber 26 via a throttle channel 29 having a fixed throttle 29t. Therefore, the responsiveness of the operation of the winch 1 to the operation of the direction switching valve 6 is determined based on the passage areas of the fixed throttles 28t and 29t. The rotation speed is determined.

  If the passage areas of the fixed throttles 28t and 29t are reduced, the response of the spool 12 to the operation of the direction switching valve 6 is delayed. Therefore, if the suspended load 3 is heavy, an excessive load, ie, surge pressure, is applied to the hydraulic motor 4. Works. In order to reduce this surge pressure, the passage area of the fixed throttles 28t and 29t may be increased. However, when the lightweight suspended load 3 is suspended, the differential pressure between the oil chambers 13A and 13B is reduced. Since the spool 12 becomes smaller, the spool 12 is not stabilized, chattering occurs, and the suspended load 3 is shaken. In short, when the suspended load 3 is lowered, the load acting on the hydraulic motor 4 differs depending on whether the suspended load 3 is a heavy object or a light object.

  Therefore, the working fluid chamber 30 is attached to the counter balance valve 10 to reduce the surge pressure and prevent chattering during the damping operation. The rod portion 32 a connected and fixed to the spool 12 is connected to a movable partition wall 31 provided in the working fluid chamber 30, and the movable partition wall 31 moves in conjunction with the movement of the spool 12. Grease that is a Bingham fluid is sealed in the working fluid chamber 30, and when the movable partition wall 31 slides in the working fluid chamber 30, the grease passes through the throttle passage 35 provided in the movable partition wall 31, and the chamber A , B, and flow resistance occurs at this time.

  Since the grease has the characteristics shown in FIG. 2, when the external force acting on the movable partition wall 31 is small, that is, when the suspended load 3 is a lightweight object, the circle connected to the oil chamber 13A via the throttle channel 28 is used. Since the pressure in the annular oil passage 18 does not increase so much, the force for moving the spool 12 to the right in FIG. 1 is small, so that only a small shearing force acts on the grease in the working fluid chamber 30. For this reason, the shear rate of the grease is suppressed, and the resistance to the movement of the spool 12 is increased. Therefore, even if an instantaneous differential pressure occurs between the oil chambers 13A and 13B, the spool 12 does not move. In this way, chattering of the spool 12 is eliminated, so that the hydraulic motor 4 operates stably and there is no fear that the suspended load 3 swings.

  On the other hand, when the lifting operation of the winch 1 is performed when the suspended load 3 is heavy, a high pressure is applied to the return side of the hydraulic motor 4. Need to be released. That is, the spool 12 must be moved quickly. A pump pressure is applied to the oil chamber 13A facing the spool 12, and the other oil chamber 13B is a tank pressure. Therefore, a large driving force is applied based on a large differential pressure acting on both ends of the spool 12. It will be. Since this driving force is transmitted to the movable partition wall 31 through the rod portion 32a, a strong external force acts on the movable partition wall 31. For this reason, the movable partition wall 31 moves at a high speed, the spool 12 moves quickly, and the generation of surge pressure can be suppressed. As a result, there is no possibility of damaging each component constituting the hydraulic circuit.

  As described above, the working fluid chamber 30 is effective for optimizing the damping characteristics when the winch 1 is lowered, that is, for reducing the surge pressure and preventing chattering of the spool 12. Does not act only when the winch 1 is lowered, but also acts when the winch 1 is rolled up. Although the fluid enclosed in the working fluid chamber 30 is a viscous fluid, it has fluidity, so that it does not have a special influence even when the winch 1 is wound up or stopped.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory diagram of a crane hydraulic circuit showing an embodiment of the present invention. It is a diagram which shows the relationship between the shear force of a Bingham fluid, and a shear rate compared with the case of steel oil.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Winch 3 Suspended load 4 Hydraulic motor 5 Hydraulic pump 10 Counter balance valve 11 Valve casings 13A and 13B Oil chamber 25 Return passage area variable portions 28 and 29 Restricted passage 30 Working fluid chamber 31 Movable partition walls 32a and 32b Rod portion 35 Restriction aisle

Claims (3)

Provided in a hydraulic circuit that drives the load up and down by a hydraulic motor, a spool is provided in the valve casing, and a return-side flow path from the hydraulic motor is provided between the valve casing and the spool. In the counter balance device provided with a counter balance valve that changes the return-side holding pressure in accordance with the change in the load by changing the flow path area of
The valve casing is provided with a working fluid chamber partitioned into two chambers by a movable partition wall,
In this working fluid chamber, Bingham fluid is housed, and the two chambers communicate with each other through a throttle passage,
A counter balance device characterized in that the movable partition and the spool are connected by a connecting member. 2. The counter balance device according to claim 1, wherein the Bingham fluid is grease. The hydraulic circuit rotationally drives a winch that lifts and lowers a suspended load, and the counter balance valve is a directional switching valve that switches the hydraulic motor and both ports of the hydraulic motor between a hydraulic pump and a hydraulic oil tank. A pair of oil chambers connected to the flow path between the direction switching valve and the hydraulic motor and the respective throttles are formed in the valve casing. Is provided so that both end faces of the spool face each other, and a return flow area variable section for changing the flow area of the return flow path from the hydraulic motor is provided between the inner surface of the valve casing and the spool. Further, a spring having an urging force is provided in the spool in a direction to reduce the flow passage area of the return flow passage area variable portion, and the connection member is connected because the spring of the spool acts. Counterbalancing apparatus according to claim 1 or claim 2, wherein it is a surface opposite to the.

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