JP2000291604A - Valve device in work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To miniaturize a valve device by assembling a check valve freely moving in the axial direction for preventing lowering due to self-weight which opens a discharge oil passage at the time of meter-out control of a spool valve, and closes the discharge oil passage at not the time of the control. SOLUTION: A first check valve 19 preventing discharge of oil from an ascent side oil chamber 8a of a boom cylinder 8 in a condition in which an operation device 16 is not operated onto a descent side and a spool valve 18 metering discharge oil from the ascent side oil chamber 8a based on the operation of the operation device 16 onto the descent side are provided in a logic valve 17. The drop of a boom 5 due to its self-weight is prevented by the first check valve 19 and meter out control can be done at the time of descent of the boom 5 by the spool valve 18, but the logic valve 17 is assembled on an outer peripheral side of the spool valve 18 and is constituted. As a result, it is possible to miniaturize the logic valve 17 when compared with a device in which the spool valve 18 and the first check valve 19 are assembled individually.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of a valve device for a working machine such as a hydraulic shovel.

[0002]

2. Description of the Related Art In general, a working machine such as a hydraulic excavator is provided with a hydraulic cylinder such as a boom cylinder or an arm cylinder for vertically moving a heavy object such as a boom or an arm. Is controlled by a control valve that operates based on operation of an operating tool. In this case, if an accident such as leakage occurs in the hydraulic oil supply / discharge path of the hydraulic cylinder during operation and the control of the hydraulic cylinder by the control valve cannot be performed, there is a risk that the heavy object may drop due to its own weight. is there. Therefore, conventionally, a check valve that closes a discharge oil passage on the descending side of the hydraulic cylinder when the operating tool is not operated on the descending side is incorporated in a valve device directly attached to the hydraulic cylinder, and the weight of the check valve is reduced by the check valve. The structure was designed to prevent the object from falling by its own weight. However, when the control valve cannot control the hydraulic cylinder, the above-described check valve can prevent the weight from dropping by its own weight. However, it is necessary to lower the weight until it contacts the ground in order to perform repair or the like. Therefore, it has been proposed to incorporate a valve for performing a descending control (meter-out control) until a heavy object comes into contact with the ground in a valve device together with the check valve.

[0003]

The valve device in which the check valve for preventing the self-weight descent and the valve for the descent control are assembled is mounted directly on the hydraulic cylinder as described above. It is required to be as small as possible. However, the conventionally proposed one has a problem that the valve device is inevitably increased in size because the check valve for preventing the self-weight descent and the valve for the descent control are separate. There was a problem to be solved.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been made to solve these problems, and has a hydraulic cylinder for vertically moving a heavy object. In a work machine, a valve having a self-weight drop prevention function for preventing a heavy object from falling due to its own weight in a discharge oil passage from a hydraulic cylinder when a heavy object descends, and a meter-out control function when the heavy object descends In providing the device, the valve device controls the spool valve that performs meter-out control to open the drain oil passage when the spool valve is meter-out controlled, but closes the drain oil passage when the spool valve is not controlled. The valve is configured so as to be freely movable in the axial direction. By doing so, the size of the valve device can be reduced. In this case, the check valve for preventing the weight from falling can be made highly sealable by using a poppet type valve element. Further, the valve device may further be provided with a check valve that allows the flow of oil on the heavy-weight rising side to the hydraulic cylinder, but prevents the flow in the opposite direction. The valve device of the present invention is useful as a device directly mounted on a hydraulic cylinder.

[0005]

Next, an embodiment of the present invention will be described with reference to the drawings. In the drawings, reference numeral 1 denotes a hydraulic excavator. The hydraulic excavator 1 is mounted on a crawler-type lower traveling body 2, an upper revolving body 3 rotatably supported by the lower traveling body 2, and the upper revolving body 3. Further, the front attachment 4 includes a boom 5 whose base end is supported by the upper swing body 2 so as to be able to swing up and down, and a front end of the boom that swings back and forth. An arm 6, which is freely supported, a bucket 7, which is supported at the tip of the arm 6 so as to be able to swing back and forth, a boom cylinder 8, an arm cylinder 9, and a bucket for causing the boom 5, the arm 6, and the bucket 7 to swing. Cylinder 10
Although a member device such as is provided, in the present embodiment,
The present invention is applied to a hydraulic circuit of the boom cylinder 8 and the arm cylinder 9.

Since the hydraulic circuits of the boom cylinder 8 and the arm cylinder 9 are similar, the boom cylinder 8 will be described with reference to FIG. 2. In FIG. 2, reference numeral 11 denotes a main pump, and 12 denotes a pilot pump. , 13 is an oil tank, 14 is a control valve, 15
Denotes a pilot valve, and 16 denotes an operating tool for a boom. These member devices 11 to 16 are mounted on the upper swing body 2. Reference numeral 17 denotes a logic valve, which is directly attached to the boom cylinder 8.

The control valve 14 is a three-position switching valve having first to fourth ports 14a to 14d and pilot ports 14e and 14f on the ascending and descending sides.
The second port 14b is connected to the oil tank 13 and the third port 1
4c is the boom cylinder 8 via the logic valve 17
The fourth port 14d is connected to the lower oil chamber 8b of the boom cylinder 8, respectively. When the pilot pressure is not input to both pilot ports 14e and 14f, the control valve 14 is located at the neutral position N in which the supply and discharge of the pressure oil to the boom cylinder 8 is not performed. When the pilot pressure is input to the part 14e, the pressure oil from the main pump 11 is supplied to the rising oil chamber 8a of the boom cylinder 8 via the logic valve 17, while the oil discharged from the falling oil chamber 8b is supplied. Is switched to the ascending side position X in which the oil flows into the oil tank 13, whereby the boom cylinder 8 is extended and the boom 5 is raised. When the pilot pressure is input to the descending pilot part 14f, the control valve 14
The boom cylinder 8 is contracted and the boom 5 is lowered by switching to the lower position Y in which the pressurized oil from the pressure chamber is supplied to the lower oil chamber 8b. The oil discharged from the rising oil chamber 8a when the boom 5 descends flows to the oil tank 13 via the logic valve 17 as described later.

The pilot valve 15 includes an ascending pilot valve 15A and a descending pilot valve 1A.
5B. By operating the operating tool 16 to the ascending side or the descending side, pilot pressure is output from the operated pilot valve 15A or 15B, and the pilot pressure is applied to the ascending or descending pilot valve of the control valve 14. Ports 14e, 14
f, respectively.
The pilot pressure output from the descending pilot valve 15B is configured to be input also to the logic valve 17 as described later.

On the other hand, regarding the logic valve 17, FIG.
Referring to FIGS. 3 to 8, a housing 17a of the logic valve 17 includes a spool valve 18 for meter-out control at the time of boom lowering, a first check valve 19 for preventing own weight descent, and a first check valve 19 for boom raising. A second check valve 20, first, second, and third ammunition units 21, 22, and 23 for urging the valves 18, 19, and 20, respectively, are incorporated and connected to the rising oil chamber 8a of the boom cylinder 8. Cylinder-side oil chamber 17b, tank-side oil chamber 17c connected to oil tank 13, pilot oil chamber 17d connected to descending pilot valve 15B, drain oil chamber 17e connected to oil tank 13, control valve 14 Third port 14 of
c, a control valve side oil chamber 17f connected to the control valve side oil chamber 17f, a supply oil chamber 17g communicated with the control valve side oil chamber 17f via the second check valve 20, and a connection between the supply oil chamber 17g and the cylinder side oil chamber 17b. A communication oil chamber 17h and the like provided therebetween are formed. In the following description, up, down, left, and right indicate positions and directions in FIGS. 3 to 8, but do not indicate actual positions and directions.

The spool valve 18 for meter-out control when the boom is lowered is supported by the housing 17a so as to be freely movable in the axial direction (left and right directions). The left end of the spool valve 18 is opposed to the pilot oil chamber 17d, and the right end is the drain oil. It is stored in the chamber 17e. A groove-shaped first oil passage 18a facing in the axial direction is formed on the upper outer peripheral surface of the spool valve 18.
Further, on the left side of the first oil passage 18a, a second oil passage 18b recessed in the circumferential direction is formed. When the pilot pressure is not input to the pilot oil chamber 17d, the spool valve 18 receives the urging force of the first elastic machine 21 housed in the drain oil chamber 17e, and causes the flange portion 18c to move to the wall surface of the housing 17a. Is located at the leftmost position (hereinafter, this position is referred to as a neutral position of the spool valve 18) at which further movement to the left is restricted, and the metering oil passages 17i and Although the drain oil passage 17j is closed, the pilot pressure is input to the pilot oil chamber 17d, so that the first
It is configured to move to the right against the urging force of No. 1 to open the metering oil passage 17i and the drain oil passage 17j. Here, the metering oil passage 17i is connected to the tank-side oil chamber 17c and the communication oil chamber 1
7h through the second oil passage 18b of the spool valve 18, and the opening degree of the metering oil passage 17i is determined by the pilot pressure input to the pilot oil chamber 17d, that is, the operating tool 16 Is adjusted in accordance with the pilot pressure output from the descending pilot valve 15B based on the above operation. Then, as described later, when the boom 5 is lowered, the discharged oil from the rising oil chamber 8a passes through the metering oil passage 17i whose opening is adjusted, and the oil tank 1
3 so that meter-out control (flow rate control of discharged oil) is performed when the boom is lowered. The drain oil passage 17j is an oil passage that connects the drain oil chamber 17e and a later-described second machine chamber 17k via a first oil passage 18a of the spool valve 18.

On the other hand, the first check valve 1 for preventing the self-weight drop
9 is a poppet type in which a tapered surface portion 19a is formed on the left side, which has a cylindrical shape,
The spool valve 18 is externally fitted to the outer peripheral side of the spool valve 18 so as to be slidable in the axial direction. A cylinder side oil chamber 17b is provided above the first check valve 19, and a supply oil chamber 1 is provided below the first check valve 19.
7g, a communication oil chamber 17h is arranged on the left side, and a second machine chamber 17k is arranged on the right side. In the second machine chamber 17k, the first check valve 19 is directed to the left. A second ammunition 22 that is energized is stored. Further, the upper outer peripheral surface portion of the first check valve 19 has a concave-shaped first oil passage 19b facing in the axial direction, and the outer periphery of the first check valve 19 communicates from the right end of the first oil passage 19b. A second oil passage 19c penetrating from the side to the inner peripheral side and a third oil passage 19d located to the left of the first oil passage 19b and penetrating from the outer peripheral side to the inner peripheral side of the first check valve 19 are formed. Have been. The first check valve 19 is located at the leftmost position where the tapered surface portion 19a contacts the step 17m formed on the housing 17a and further movement to the left is restricted (the position is hereinafter referred to as the first position). (Referred to as the seal position of the one check valve 19), the cylinder side oil chamber 17b and the communication oil chamber 17h, and the communication oil chamber 17h and the supply oil chamber 17g are sealed. However, by moving to the right from the seal position, the cylinder oil chamber 17b, the communication oil chamber 17h, and the supply oil chamber 17g are configured to be open. The first oil passage 19b of the first check valve 19 communicates with the cylinder-side oil chamber 17b when the first check valve 19 is located at the sealing position. It is set so that it is shut off from the cylinder side oil chamber 17b when moved to the right end position. The second oil passage 19c is connected to the first oil passage 1
It communicates with the cylinder side oil chamber 17b via 9b. The third oil passage 19d is connected to the first check valve 19
Is set so as to communicate with the cylinder side oil chamber 17b regardless of the position of the cylinder oil chamber 17b.

Next, the operation of the spool valve 18 and the first check valve 19 will be described with reference to FIGS. 4 to 8. First, when the operating tool 16 is not operated, as shown in FIG. The spool valve 18 is located at a neutral position that closes the metering oil passage 17i and the drain oil passage 17j, and the first check valve 19 is connected to the cylinder-side oil chamber 17.
b and the communication oil chamber 17h are located at a sealing position for sealing.
The second oil passages 19b and 19c communicate with the cylinder-side oil chamber 17b. Further, the second oil passage 19c of the first check valve 19 and the second machine chamber 17k are connected to the first oil passage 18a of the spool valve 18.
Is communicated through. Thus, the pressure oil in the cylinder side oil chamber 17b is supplied to the first and second oil passages 19b of the first check valve 19,
19c, the oil is introduced into the second machine chamber 17k via the first oil passage 18a of the spool valve 18, and the pressure oil introduced into the second machine chamber 17k moves the first check valve 19 to the left. It acts as a force to press. The pressing force is such that the pressure oil in the cylinder-side oil chamber 17 b is applied to the tapered surface 19 a of the first check valve 19.
Is greater than the force acting to move the first check valve 19 to the right.
9 is held in the sealing position. That is, when the operating tool 16 is not operated, the spool valve 18 is located at the neutral position for closing the metering oil passage 17i and the drain oil passage 17j, and the first check valve 19 is in the cylinder side oil chamber 1
The cylinder oil chamber 17b and the communication oil chamber 17h are sealed, and the drain oil passage 17j is closed. In the state, there is no oil discharge path from the cylinder-side oil chamber 17b, so that pressure oil can be prevented from flowing out from the rising-side oil chamber 8a of the boom cylinder 8 connected to the cylinder-side oil chamber 17b. Have been.

On the other hand, when the operating tool 16 is operated on the lower side, the pilot pressure output from the lower pilot valve 15B is input into the pilot oil chamber 17d, and the spool valve 18 is moved rightward as shown in FIG. In a metering state in which the metering oil passage 17i and the drain oil passage 17j are opened. In this state, the pressure oil introduced into the second machine chamber 17k flows to the oil tank 13 via the drain oil passage 17j and the drain oil chamber 17e, and moves the first check valve 19 to the left. There is no pressing force, so the first check valve 19 is connected to the cylinder side oil chamber 1.
The pressure oil 7b moves to the rightmost end position by the force acting on the tapered surface portion 19a of the first check valve 19, and is brought into an open state in which the cylinder side oil chamber 17b and the communication oil chamber 17h are communicated. When the first check valve 19 has moved to the rightmost position, the first and second oil passages 19b and 19c are shut off from the cylinder side oil chamber 17b, and the third oil passage 19d is connected to the outer peripheral surface of the spool valve 18. The oil in the cylinder side oil chamber 17b is transferred from the second oil chamber 17k to the drain oil chamber 1 via the first to third oil passages 19b to 19d.
7e. That is, the spool valve 18 is controlled based on the descending operation of the operating tool 16.
Is in the metering state, the first check valve 19 is opened accordingly. In this state, the oil in the cylinder side oil chamber 17b flows through the communication oil chamber 17h and the metering oil passage 17i. It will flow to the tank side oil chamber 17c. Thus, when the boom 5 is lowered, the oil discharged from the rising oil chamber 8a of the boom cylinder 8 is supplied to the spool valve 18a.
Thus, the oil flows into the oil tank 13 in a state of being meter-out controlled.

When the operating tool 16 operated to the lower side is returned to the neutral side, the pressure input to the pilot oil chamber 17d decreases, and the spool valve 18 is moved leftward by the urging force of the first elastic machine 21. In this case, as shown in FIG. 6, at a position slightly before the spool valve 18 returns to the neutral position, the metering oil passage 17i is closed first, and then the drain oil passage 17j is closed. When the spool valve 18 further moves leftward from this state to the neutral position, as shown in FIG. 7, the third oil passage 19d of the first check valve 19 becomes the second oil passage through the first oil passage 18a of the spool valve 18. Second shot room 17
Communicate with k. Thereby, the pressure oil in the cylinder-side oil chamber 17b is introduced into the second machine chamber 17k.
The pressure oil introduced into 7k acts as a force for pressing the first check valve 19 leftward because the drain oil passage 17j is closed, and moves the first check valve 19 leftward, that is, toward the seal position. Press toward. And the first check valve 1
When the cylinder 9 moves to the left and reaches the position shown in FIG. 8, the pressure oil in the cylinder-side oil chamber 17 b is supplied to the first and second oil passages 19 b and 19 c of the first check valve 19 and the second It is introduced into the second machine chamber 17k via one oil passage 18a, and presses the first check valve 19 further leftward, so that the first check valve 19 moves to the sealing position, The oil chamber 17b and the communication oil chamber 17h are sealed. In this state, as described above, the first check valve 19 is held at the seal position.

The second check valve 20 for raising the boom includes a control side oil chamber 17f and a supply oil chamber 17g.
, And is configured to allow the flow of oil from the control valve side oil chamber 17f to the supply oil chamber 17g, but to prevent the flow in the reverse direction. When the pressure oil is not supplied to the control-side oil chamber 17f, the second check valve 20 shuts off the control valve-side oil chamber 17f and the supply oil chamber 17g by the urging force of the third shell 23. Although it is located at the position, the pressure oil from the control valve 14 at the ascending side position X is supplied to the control valve side oil chamber 17f along with the ascending side operation of the operating tool 16, so that the It is configured such that it moves against the urging force and becomes a supply position for supplying pressure oil from the control valve side oil chamber 17f to the supply oil chamber 17g. Further, the pressure oil supplied to the supply oil chamber 17g via the second check valve 20 at the supply position acts on the tapered surface portion 19a of the first check valve 19 and presses the first check valve 19 rightward. As a result, the first check valve 19
Is opened to communicate the cylinder-side oil chamber 17b, the communication oil chamber 17h, and the supply oil chamber 17g. Thus, the operating tool 16
Is supplied from the control valve 14 at the ascending side position X based on the ascending side operation of the control oil chamber 1.
7b, the second check valve 20, the supply oil chamber 17g, the communication oil chamber 17h, and the cylinder-side oil chamber 17b are supplied to the upward oil chamber 8a of the boom cylinder 8.

In the apparatus constructed as described above, when the boom 6 is moved up and down, pilot pressure oil is output from the ascending or descending pilot valve 15A or 15B based on the operation of the operating tool 16, whereby the control valve 14 is controlled. Is switched to the ascending side or descending position X or Y, and the pressure oil from the control valve 14 is supplied to the ascending oil chamber 8a or the descending oil chamber 8b of the boom cylinder 8 by the pressurized oil. But in this one,
Even if an accident such as leakage occurs in a pipe or the like from the control valve 14 to the boom cylinder 8, and the control valve 14 cannot control the boom cylinder 8, the boom cylinder 8 can be directly mounted. The attached logic valve 17 can prevent the boom 5 from lowering its own weight, and can control the lowering of the boom 5. That is, the logic valve 17 includes a first check valve 19 for preventing oil from being discharged from the rising oil chamber 8a of the boom cylinder 8 when the operating tool 16 is not operated on the lower side, and an operating tool 16 And a spool valve 18 for metering the discharged oil from the ascending oil chamber 8a based on the operation of the boom 5 on the descending side. The spool valve 18 can perform meter-out control when the boom 5 is lowered. The logic valve 17 includes a first check valve 19 on the outer peripheral side of the spool valve 18.
Are slidably assembled in the axial direction. As a result, the size of the logic valve 18 can be reduced as compared with the case where the spool valve and the first check valve are separately installed, and the logic valve 18 can be mounted directly on the boom cylinder 8 so that the mountability is excellent.

In this case, the first check valve 19 of the poppet type having a high sealing property is used to prevent the weight from dropping.
And the meter-out control is performed using the spool valve 18 having good controllability, so that a highly reliable valve device can be provided. The present invention is not limited to a boom cylinder or an arm cylinder, but can be applied to valve devices for various hydraulic cylinders that move a heavy object up and down.

[Brief description of the drawings]

FIG. 1 is a perspective view of a hydraulic shovel.

FIG. 2 is a hydraulic circuit diagram of a boom cylinder.

FIG. 3 is a diagram showing a structure of a logic valve.

FIG. 4 is an explanatory diagram showing operations of a spool valve and a first check valve.

FIG. 5 is an explanatory diagram showing operations of a spool valve and a first check valve.

FIG. 6 is an explanatory diagram showing operations of a spool valve and a first check valve.

FIG. 7 is an explanatory diagram showing operations of a spool valve and a first check valve.

FIG. 8 is an explanatory diagram showing operations of a spool valve and a first check valve.

[Explanation of symbols]

 5 Boom 8 Boom cylinder 17 Logic valve 18 Spool valve 19 First check valve 20 Second check valve

Claims (4)

[Claims] 1. A work machine equipped with a hydraulic cylinder for vertically moving a heavy object, which prevents a heavy object from descending due to its own weight in an oil passage discharged from the hydraulic cylinder when the heavy object descends. In providing a valve device having a function and a meter-out control function when a heavy object is lowered, the valve device opens a discharge oil passage at a spool valve that performs meter-out control and at the time of meter-out control of the spool valve. However, a valve device for a working machine configured to incorporate a check valve for preventing its own weight descent that closes a discharge oil passage when not being controlled so as to be movable in the axial direction. 2. A valve device for a working machine according to claim 1, wherein the check valve for preventing the weight from dropping is formed by using a poppet type valve element. 3. The valve device according to claim 1, further comprising a check valve that allows the flow of the oil on the heavy-weight rising side to the hydraulic cylinder, but prevents the flow in the reverse direction. Valve equipment in work machines. 4. The valve device according to claim 1, 2 or 3, wherein the valve device is a working machine mounted directly on a hydraulic cylinder.