JP3248080B2 - Directional switching valve for preventing runaway of actuator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a directional control valve for preventing runaway of an actuator, in particular, a careless running or turning of a hydraulic excavator equipped with a remote control type steering device, other civil engineering or construction equipment, or the like. The present invention relates to a direction switching valve for preventing runaway of an actuator which can be driven without causing runaway.

[0002]

2. Description of the Related Art A conventional hydraulic excavator and other actuators such as hydraulic motors for traveling and turning of civil engineering and construction machines are operated by a remote control type steering device. There is something like that shown in

[0003] A variable displacement type pump as a hydraulic source (reference numeral "1" in FIG. 3 showing an embodiment of the present invention) is supplied to a hydraulic motor 12 as a travel actuator of a construction machine.
The pilot oil (operation signal) from the pilot valve 16, which is operated by the operating lever of the joystick 15 (see reference numeral “15a” in FIG. 4), is used as the pilot oil. Roads 16a, 16
b, the spool 3 of the directional control valve 2 is alternately applied to the left and right (FIG. 7) ends of the spool 3 of the remote control type directional control valve 2 to move the spool 3 to the left or right to remove the pressure oil. The oil is supplied from the P port (pressure port) 6 through the A port (cylinder port) 7a or the B port (cylinder port) 7b, and the pressure oil is discharged to the tank 8a through the tank port (return port) 8. In addition, pressure oil is supplied to the pump chamber 4 as a hydraulic source side port of the remote control type directional switching valve 2 and an actuator such as a traveling hydraulic motor 12 of a construction machine through the A port 7a or the B port 7b. A load check valve 5 that is released at a required pressure is provided between the load check valve 5 and a P port 6 for the load.

The remote control type directional control valve 2
When a pressure exceeding the pressure set by the compression spring 5c of the load check valve 5 is generated in the hydraulic circuit of the construction machine or the like having the above, the valve element 5a of the load check valve 5 moves backward (in FIG. The pressure oil exceeding the pressure is supplied to the pressure oil motor 12 via the P port 6, the B port 7b (or the A port 7a) and the like. In addition, 11 is a counter balancing valve.

[0005] A spring chamber 5b of the load check valve 5 of the remote control type directional control valve 2 includes:
Since it is always in communication with the P port 6, its spring chamber 5
b The hydraulic _{P 2} and the hydraulic _{P 3} P-port match. P ₂ = P ₃

On the other hand, the pump chamber 4 and the spring chamber 5b of the direction switching valve 2 are always shut off as shown in FIG. 7 by the valve element 5a of the load check valve 5 which is resiliently pressed by the compression spring 5c. if the compressive force of the spring 5c of the load check valve 5 Fs, the area of the contact portion between the valve body 5a and the valve seat and _S, when the condition of _{P 1> P 3 + Fs /} S is satisfied, the The valve body 5a is a compression spring 5
c (FIG. 7), and the pressure oil in the pump chamber 4 is supplied to the P port 6 via the load check valve 5.

Therefore, the joystick 1 as described above
5, the spool 3 of the remote control type directional control valve 2 is switched through pilot oil passages 16a and 16b in accordance with an operation signal of a pilot valve 16 operated by an operation lever 15a of the control lever 15a. Excavators, other civil engineering, construction machinery, etc., which drive by supplying and discharging air, as long as each part installed in the hydraulic circuit operates normally, the pressure oil supplied from the variable discharge type pump 1 is used. The traveling hydraulic motor 12 can be driven through the remote control type directional switching valve 2 in accordance with the operation command of the operation lever 15a of the joystick 15.

[0008]

However, in this case, an actuator such as the traveling motor 12 is used.
Operation lever 1 of joystick 15 as a control device
5A, the spool 3 of the pilot-type remote control type directional control valve 2 is moved and driven in a required direction, and then the operation lever 15a of the joystick 15 is operated.
Is returned to the neutral position, temporarily, the spool 3 of the remote control type directional control valve 2 is, for example,
For some reason, such as generation of thermal shock or catching of cutting chips (iron pieces), the joystick 1
5, the directional control valve 2 does not respond (retreat) according to the return operation command signal by the operation lever 15a, or does not respond at all to the return command signal, and the spool 3 of the remote control type directional control valve 2 returns the return command signal. The position before transmission, that is, the sticking state is maintained, and the traveling hydraulic motor 12 continues to rotate. As a result, there is a possibility that the construction machine or the like may inadvertently travel or turn, that is, even runaway. Was.

For this reason, an operator who operates a conventional construction machine or the like having the remote control type directional control valve 2 as described above requires an actuator such as the hydraulic motor 12 to cause the above-described inadvertent runaway. Great care had to be taken at all times to prevent it.

[0010]

According to the present invention, a load check valve 21 is provided on a valve body 20a of a remote control type directional control valve 20 of a construction machine or the like in order to solve the above-mentioned problems of the prior art. The valve body 22 of the load check valve 21 is provided with an oil passage 22a with a throttle 22b that communicates the pump chamber 4 of the remote control type directional control valve 20 with the spring chamber 23 of the valve body 22. The spring chamber 23 of the switching valve 20 and the P ports 6, 6 are connected by a bypass 26 with a switching valve 27, and the actuator 12 such as a hydraulic motor of the construction machine is connected to the remote control type directional switching valve 2.
The switching valve 27 is switched by the operation signal detected by the detectors 32 and 34 provided between the pilot valve 16 or the operating lever 15a thereof and the switching valve 27, which are operated by the control device 15, and the bypass 26 is switched. This is a direction switching valve for preventing runaway of the actuator, which is configured to open the load check valve 21 at a predetermined pressure when opened.

[0011]

Since the present invention has the above-described structure,
A remote control type directional control valve is switched by an operation signal of a control device such as a construction machine to drive an actuator such as a hydraulic motor, and the spool of the directional control valve is duplicated to a neutral position by an operation signal of the control device. In addition to stopping the operation of the actuator such as the hydraulic motor in the same manner as in the conventional example, when the double return command signal to the neutral position of the directional control valve is transmitted by the control device, the operation signal is transmitted to the construction. An actuator 12 such as a hydraulic motor of a machine
The bypass valve 16 is operated in response to a detection signal detected by detectors 32 and 34 provided between the pilot valve 16 or the operation lever 15a of the direction switching valve 20 and the operation lever 15a and the switching valve 27. Switching valve 27
Is closed, the hydraulic spring chamber 23 and the P port 6,
6 is shut off, no oil flow occurs in the throttled flow path 22a, so that the pressure before and after the throttle 22b is the same, the load check valve 21 is closed, and the control device is temporarily stopped. In the state where the double return command signal to the neutral position of the remote control type directional control valve 20 by the control unit 15 is transmitted, if an abnormality occurs in which the spool of the directional control valve does not return to the neutral position for some reason. Also, the actuator 12 such as the hydraulic motor
The supply of pressurized oil to the actuator 12 is stopped to prevent or alleviate runaway such as careless running and turning of the actuator 12.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a directional control valve for preventing runaway of an actuator according to the present invention will be described below with reference to FIGS. Note that the same parts as those of the conventional example shown in FIG.

[0013]

First Embodiment FIGS. 1 to 3 (note that FIG. 4 which schematically shows a drive command signal extraction unit in a schematic diagram will be described later).
1 is a schematic explanatory view of a first embodiment of a directional control valve for preventing runaway of an actuator according to the present invention. FIG. 1 shows a load check valve 21 which is a main part of the directional control valve for preventing runaway of the actuator. FIG. 2 is an enlarged schematic vertical cross-sectional explanatory view, FIG.
FIG. 3 is a schematic vertical sectional view showing the (remote control type) directional control valve 20, and FIG. 3 is a schematic explanatory view of a hydraulic circuit for driving a hydraulic motor by the runaway preventing directional control valve 20.

1 to 3, reference numeral 1 denotes a variable discharge type pump as a hydraulic pressure source, 1a denotes a pilot pump for generating pilot pressure, 20 denotes a remote control type directional control valve, and 3 denotes a remote type directional control valve 20. Spool, 4
Is a pump chamber on the hydraulic pressure source side, and 6 is a P port (JIS, hydraulic terminology, JIS B 0118-) as a pressure port for supplying pressure oil to an A port or a B port (cylinder port) described later.
1970 Japanese Industrial Standards Committee deliberations, February 1, 1970
Japan Standards Association, issued on July 31, 1970, see), 7a and 7b are A port and B port (cylinder port) (refer to JIS, hydraulic terminology), 8 is tank port (return port: JIS, hydraulic terms, JIS B
0118-1970), 8a is a tank, 11 is a counter balancing valve, 12 is a traveling hydraulic motor as an actuator, 15 is a joystick as a control device of a construction machine such as a power shovel (not shown), 16
Is an operation lever (operation unit) of the joystick 15 (reference numeral "15" in FIG. 4 showing the runaway prevention device of the first embodiment of the present invention).
a), pilot valves 16a and 1
Reference numeral 6b denotes a pilot oil passage, and the pilot oil passages 16a, 1
6b transmits a pilot signal transmitted from a pilot valve 16 switched by operating the operation lever 15a of the joystick 15 to both sides of the spool 3 of the remote control type directional switching valve 20 of the hydraulic circuit of the construction machine or the like. 3 is moved to the right or left in FIG. 2 to supply the pressure oil from the variable displacement pump 1 to the hydraulic motor 12 via the same-direction switching valve 20, and to supply the pressure oil of the hydraulic motor 12 to the same-direction switching valve It is discharged to the tank 8a through the P port 20 and the tank port 8.

When the pilot valve 16 is switched by operating the operating lever (operating portion) 15a of the joystick 15, an operation signal transmitted to the remote control type directional switching valve 20 via the pilot oil passages 16a and 16b is transmitted to the remote controller. A voltage is applied to the spool 3 of the control type directional control valve 20, and the spool 3 is moved to the right or left to drive an actuator such as the hydraulic motor 12;
A point is provided in which the pressure oil on the pump chamber 4 side of the same-way switching valve 20 is released to the P port 6 side via the load check valve 21 (however, the valve body 22 of the load check valve 21).
However, except that an oil passage 22a with a throttle 22b described later is provided)
Then, the first embodiment is almost the same as the conventional remote control type directional control valve 2 shown in FIG.

Reference numeral 20 denotes a remote control type directional control valve capable of preventing runaway of the hydraulic motor 12 as an actuator, reference numeral 20a denotes a valve body of the directional control valve 20, reference numeral 21 denotes a load check valve provided on the valve main body 20a, and reference numeral 22 denotes a load. The valve body of the check valve 21, 22 a is an oil passage provided in the length direction of the central portion of the valve body 22 (the vertical direction in FIG. 1), 22 b is a throttle provided in the oil passage 22 a, and 23 is the load check valve 21.
, A compression spring provided in the spring chamber 23, a bypass 26, which connects the pump chamber 4 of the directional control valve 20 to the spring chamber 23, whereby the pump of the directional control valve 20 The chamber 4 and the P port 6 are connected to the oil passage 22 of the valve body 22 of the load check valve 21.
a, through the spring chamber 23 and the bypass 26.

Reference numeral 27 denotes a switching valve provided in the bypass 26. The switching valve 27 is switched by operating an operation lever 15a (see FIG. 4) of the joystick 15 as a control device for a construction machine such as a power shovel (not shown). In response to an operation signal transmitted from the pilot valve 16 via the pilot oil passage 16c, the bypass 26 is switched between open and closed so as to communicate or shut off. Specifically, the switching valve 27 is used for traveling of the construction machine. The hydraulic motor 12 is closed in a stopped state, that is, in a state where the spool 3 of the direction switching valve 20 has returned to the neutral position.

[0018]

First, the pressure oil of the hydraulic pressure P1 of the variable discharge type pump ₁ is supplied to the remote control type directional control valve 2
The hydraulic motor 1 is supplied to the traveling hydraulic motor 12 as an actuator (not shown) of a construction machine or the like via the pump chamber 4, the A or B port 7a or 7b, etc.
The second pressure oil is discharged to the tank 8a via the direction switching valve 20.

At this time, the pump chamber 4 of the direction switching valve 20 and P
Since the bypass 26 communicates with the port 6, the load
2 that is resiliently pressed by the compression spring 24 of the check valve 21
2 so that they can communicate with each other.
The switching valve 27 is opened as long as
In the state, the hydraulic pressure P of the pressure oil in the pump chamber 4₁Is P
Oil pressure P of port 6₃taller than. P₁> P₃  Note that this action is achieved by the load check valve 21
Hydraulic pressure equal to or higher than the set pressure of the spring 24 provided in the
The conventional example shown in FIG.
It is almost the same as the direction switching valve 2.

Next, when the operating lever 15a of the joystick 15 is operated and an operation command signal for returning the spool 3 of the remote control type directional control valve 20 to the neutral position is transmitted from the pilot valve 16, the signal is transmitted to the pilot oil passage 16a. , 16b of the directional control valve 20 via the
And the spool 3 returns to the neutral position. Simultaneously with the return signal of the spool 3 to the neutral position, a signal transmitted from the pilot valve 16 is transmitted to the switching valve 27 via the pilot oil passage 16c, and the switching valve 27 is brought into the state of FIG. The bypass 26 is shut off, and the hydraulic pressure P of the spring chamber 23 of the load check valve 21 is reduced.
_2, the hydraulic _{P 1} of the pump chamber ₄ matches. P ₁ = P ₂

Therefore, in this state, the force of the load check valve 21 in the opening direction of the valve body 22 is determined by setting the diameter of the contact portion of the valve seat of the valve body 22 of the load check valve 21 to a, Assuming that the diameter is b and b> a as in the load check valve 21 shown in FIG. 1, (a / 2) ² π × P ₁ + ｛(b / 2) ² π- (a / 2) ² a π} × _{P 3.}

On the other hand, the force in the closing direction of the load check valve 21 in this state is (b / 2) ² π × P ₂ + F, where F is the elastic force of the compression spring 24 in the spring chamber 23.

The load check valve 21 has a valve body.
The condition for opening the valve 22 is that the force in the opening direction of the valve body 22 is closed.
(A / 2)²π × P₁+ [B / 2)²π × P₃  -(A / 2)²π × P₃-(B / 2)²π × P₂−F> 0...

In the state where the switching valve 27 moves to the right from the state shown in FIGS. 1 and 2 and the bypass 26 communicates, P ₂ = P _{3. In} this state, P ₁ is obtained from the above equation. When the condition of> P ₃ + F / (a / 2) ² π is satisfied, the valve body 22 rises against the compression spring 24 (FIG. 1), the load check valve 21 is opened, and the pump chamber 4 is opened. Flows out to the P port 6 side through the opened load check valve 21.

The operating state of the traveling hydraulic motor 12 is described below.
The switching valve 27 is in the closed position in FIGS.
The bypass 26 is shut off by the switching valve 27
However, the spring chamber 23 of the directional control valve 20 is
Hydraulic pressure P of the pump chamber 4 via the oil passage 22a with₁of
Since the pressurized oil is introduced, the oil pressure in the spring chamber 23 is set to P₂
Then P₃<P₂= P₁  Becomes

Therefore, in this state, the above equation becomes (P ₃ −P ₁ ) × {(b / 2) ² π− (a / 2) ² π} −F> 0...

On the other hand, from the pump chamber 4 to the hydraulic motor 12 side
In its driving state of supplying pressurized oil, the pump chamber 4
Hydraulic pressure P₁And hydraulic pressure P of P port 6₃Is related to P₁> P₃  ∴ P₃−P₁<0, the above equation does not hold in this state.
Pressure oil cannot be supplied to the hydraulic motor 12.

On the other hand, the operating lever of the joystick 15
15a, the pilot motor 16
At the same time that the drive command signal is transmitted,
Open signal for switching the switching valve 27 from 6c to the open position (FIG. 1)
Is transmitted and the switching valve 27 is switched to the open state.₃= P₂  This load check valve 21 is
Check valve (see symbol "5" in FIG. 7)
You.

In the above description, an example is described in which the directional control valve 20 for preventing runaway of an actuator is applied to a hydraulic circuit including a hydraulic motor 12 for traveling as an actuator of a construction machine. Although not shown, the directional control valve 20 can be implemented as a directional control valve for preventing runaway of a hydraulic motor as a hydraulic actuator, including a turning hydraulic motor for a revolving structure of a crane vehicle, not shown.

[0030]

[Drive Command Signal Extraction Unit] FIG. 4 shows a drive command signal extraction unit according to the first embodiment of the present invention, that is, a switching valve 27 provided in a bypass 26 of the remote control type directional switching valve 20 and a construction machine or the like. FIG. 3 is a schematic explanatory view showing a relationship with a steering device (joystick) 15. FIG.
In addition, the same names and reference numerals are used for portions common to the embodiment schematically shown in FIG.

In FIG. 4, 1a is a pilot pump,
8a is a tank, 15 is a joystick as a control device of a construction machine or the like, 15a is an operation lever of the joystick 15, 16 is a pilot valve switched by operating the operation lever 15a, and 16a and 16b are operation commands transmitted from the pilot valve 16. A pilot oil passage for transmitting a signal to the directional control valve 20, 16d is a pilot oil passage 16a, 16b
Instruction signal (detection signal) detected by the detection unit 30 from
Is transmitted to a switching valve 27, and 26 is a remote control type directional switching valve 20 (see FIGS. 1 to 3).
The switching valve 27 is provided in the bypass 26 for connecting the spring chamber 23 and the P port 6.

Operation lever 15a of joystick 15
1 and 2, the spool 3 of the remote control type directional control valve 20 is moved to drive the traveling hydraulic motor 12 in the same manner as described above, and the operating lever 15a of the joystick 15 is operated. Is transmitted from the pilot valve 16 and the pilot oil passage 1
The detection unit 30 detects whether or not an operation command signal transmitted to the spool 3 of the remote control type directional control valve 20 via 6a and 16b, that is, a signal for operating the remote control type directional control valve 20 is output. The detection signal from the detection unit 30 is transmitted via the pilot oil passage 16c to the spring chamber 23 of the load check valve 21 having the oil passage 22a and the throttle 22b, and the P port 6
Is transmitted to a switching valve 27 provided in a bypass 26 that communicates with the joystick 15, and the switching valve 27 is automatically switched to open or closed in accordance with the operation of the operation lever 15a of the joystick 15.

[0033]

Second Embodiment FIG. 5 shows a second embodiment of a directional control valve for preventing runaway of an actuator according to the present invention, in which a directional control valve 27 provided on a bypass 26 of a remote control type directional control valve 20 and a construction machine. FIG. 5 is a schematic explanatory view showing a relationship with a joystick 15 as a control device for the vehicle. Parts common to those of the first embodiment shown in FIGS. 1 to 4 have the same names and the same reference numerals.

In FIG. 5, 1a is a pilot pump,
8a is a tank, 15 is a joystick as a control device for construction equipment, etc., 15a is its operation lever, 20 is a remote control type directional control valve, and these structures are the first embodiment schematically shown in FIGS. It is almost the same as the directional control valve 20 of the example. 26 is a bypass connecting the spring chamber 23 of the remote control type directional control valve 20 to the P port 6, 27 is a switching valve provided in the bypass 26, and 32 is a detector for detecting the operation angle of the operation lever 15a of the joystick 15. is there.

[0035]

Operation of the Second Embodiment An operation signal transmitted from the pilot valve 16 by operating the operation lever 15a of the joystick 15 is sent to the remote control type directional control valve 20 via the pilot oil passages 16a and 16b, and the spool 3 In the second embodiment, the joystick 15 is moved.
The operation state of the operation lever 15a is detected by, for example, a detector 32 of the operation angle, and the switching valve 27 of the bypass 26 is switched to open or closed by a detection signal of the detector 32. Other configurations and operations are substantially the same as those of the first embodiment. In the second embodiment, it is possible to cope with a case where either the spool 3 of the remote control type directional control valve 20 or the spool (not shown) of the pilot valve 16 sticks.

[0036]

Third Embodiment FIG. 6 shows a third embodiment of a directional control valve for preventing runaway of an actuator according to the present invention, which is a directional control valve 27 provided in a bypass 26 of a directional control valve 20 of a remote control type, and a construction machine. FIG. 4 is a schematic explanatory view schematically showing a relationship with an electric joystick 15 ′ as a control device of the present invention. Parts common to those of the first embodiment shown in FIGS. 1 to 4 have the same names and the same reference numerals.

In FIG. 6, 15 'is an electric joystick as a control device, and 15a' is a joystick 1
5 'operating lever, 16' operating signal output unit, 16
a ′ and 16b ′ are operation signal lines;
a ′ and 16b ′ represent operation signals of the operation signal output unit 16 ′,
It has substantially the same structure as the remote control type directional control valve 20 of the first embodiment shown in FIGS.
26 is the spring chamber 23 of the directional control valve 20 and the P port 6
27 is a switching valve provided in the bypass 26, and 34 is the operating lever 15 of the joystick 15 '.
A detector 36 for electrically detecting the operation state of a ′ is a power supply for driving the operation signal output unit 16 ′ so as to be proportional to the operation angle of the operation lever 15a ′.

[0038]

[Operation of Third Embodiment] By operating the operation lever 15a 'of the electric joystick 15, the operation signal output section 16' is operated.
To transmit an operation signal, and the operation signal lines 16a ', 1a
In addition to moving the spool 3 of the remote control type directional switching valve 20 as shown in FIGS. 1 and 2 through the 6b 'and driving the traveling hydraulic motor 12, the electric joystick in the third embodiment The operation state of the operation lever 15a '15' is detected by the electric detector 34 as a voltage value, for example, and a detection signal (voltage value) is applied to the switching valve 27, and the switching valve 27 is switched between open and closed. , And automatically switches the bypass 26 between open and closed. Other operations are almost the same as those of the first embodiment.
In this case, due to the failure of the operation signal output unit 16 ',
This also applies when a signal is output.

[0039]

(1) A load check valve is provided on a valve body of a remote control type directional control valve of a construction machine or the like,
The valve body of the load check valve is provided with an oil passage with a throttle that communicates the pump chamber of the remote control type directional switching valve with the spring chamber of the valve body. The port is connected with a bypass with a switching valve, and an actuator such as a hydraulic motor of the construction machine or the like, a pilot valve operated by a remote control type directional control valve operating device or an operation lever thereof and the switching valve. Since the load check valve is opened at a predetermined pressure by switching the switching valve and opening the bypass according to an operation signal detected by a detector provided therebetween, the steering device of the construction machine or the like is used. As long as is in the operating state, the pump chamber of the direction switching valve and the P port are connected by the operation signal of the operating device. The bypass valve is opened by the switching valve, the pressure oil in the pump chamber is discharged to the P port, and in addition to performing the same function as the conventional directional switching valve, if the control device is returned to the neutral position, it can be used for traveling and turning. Supply of pressure oil from the pump chamber to an actuator such as a hydraulic motor is cut off, and the switching valve of the bypass is shut off in response to a return operation signal to the neutral position of the control device. Even when a stick state in which the spool of the switching valve does not respond to the return command signal of the control device occurs, the actuator continues running or turning carelessly,
There is no fear of runaway.

(2) The operating state of the steering device of the remote control type directional control valve is detected by a detector or the like, and the detection signal is used to switch the bypass directional control valve bypass valve.
Since the operation is automatically switched so as to respond to the operation state, the operation procedure itself of the operator of the construction machine or the like can be operated without substantially changing the operation procedure of the existing apparatus of the same type. Since normal operation can be expected without paying special attention to the vehicle, it is possible to continue driving for a long time without causing special fatigue and maintaining required effects.

(3) An oil passage with a throttle is provided in the valve body of the load check valve of the existing remote control type directional control valve, and the spring chamber and the P port are connected to each other in accordance with the operation state of the control device of the actuator. And the actuator such as a hydraulic motor of the construction machine is operated by a pilot valve operated by a remote control type directional control valve operating device or the operating lever thereof and the switching valve. The present invention can be easily applied to an existing directional control valve by a simple modification in which only a detector provided between them is provided.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic longitudinal sectional view showing a load check valve portion, which is an essential part of a first embodiment of a direction changeover valve for preventing runaway of an actuator according to the present invention.

FIG. 2 is a schematic longitudinal sectional view showing the direction change valve for preventing runaway from running.

FIG. 3 is an explanatory diagram of a hydraulic circuit for driving a hydraulic motor by the runaway prevention direction switching valve.

FIG. 4 is a schematic explanatory view of a connection structure between a switching valve provided in a bypass of a runaway prevention direction switching valve according to the first embodiment of the present invention and a steering device such as a construction machine.

FIG. 5 is a schematic explanatory view showing a relationship between a control device, a detector, a switching valve, and the like of a runaway prevention direction switching valve according to a second embodiment of the present invention.

FIG. 6 is a schematic explanatory view showing a relationship between a steering device, a detector, a switching valve, and the like of a runaway prevention direction switching valve according to a third embodiment of the present invention.

FIG. 7 is a schematic longitudinal sectional view of a conventional directional control valve of a hydraulic actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Variable discharge type pump 3 ... Spool 4 ... Pump chamber 6 ... P port 7a ... A port 7b ... B port 8 ... Tank port 12 ... Hydraulic motor 15 ... Joystick (steering device) 15 '... voltage joystick (steering device) 15a ... operating lever 16 ... pilot valve 16a, 16b ... pilot oil passage 16a', 16b '... electric operation signal circuit 20 ... remote control type directional control valve 21 ... … Load check valve 22… valve body 22 a… oil passage 22 b… throttle 23… spring chamber 24… spring 26… bypass 27… switching valve 30… detector 32… detector 34… detection vessel

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-61734 (JP, A) JP-A-1-203702 (JP, A) JP-A-2-8502 (JP, A) JP-A-2- 134402 (JP, A) JP-A-1-145401 (JP, A) JP-A-1-206181 (JP, A) JP-A-58-113605 (JP, A) JP-A-2-31085 (JP, A) JP-A-1-158803 (JP, U) JP-A-3-57507 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F15B 11/08 F15B 20/00 E02F 9/24

Claims (1)

(57) [Claims] 1. A load check valve 21 is provided on a valve body 20a of a remote control type directional control valve 20 of a construction machine or the like, and a pump chamber 4 of the remote control type directional control valve 20 is provided on a valve body 22 of the load check valve 21. And an oil passage 22a with a throttle 22b that communicates with the spring chamber 23 of the valve body 22 and connects the spring chamber 23 of the remote control type directional switching valve 20 and the P ports 6, 6 to a bypass 26 with a switching valve 27. And an actuator 12 such as a hydraulic motor of the construction machine or the like, and a pilot valve 16 operated by a steering device 15 of the remote control type directional switching valve 20 or its operating lever 1.
The load check valve 21 is opened at a predetermined pressure by switching the switch valve 27 and opening the bypass 26 in accordance with an operation signal detected by detectors 32 and 34 provided between the switch 5a and the switch valve 27. A directional control valve for preventing runaway of an actuator characterized by having such a configuration.