JP3387733B2 - Hydraulic valve control device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic valve control device for a hydraulic actuator, which is mainly installed in construction machines such as hydraulic excavators and work vehicles.

[0002]

2. Description of the Related Art FIG. 6 is a hydraulic circuit diagram of a construction machine described in JP-A-5-187409. In the hydraulic circuit shown in FIG. 6, a pilot opening / closing valve 4 is provided in a pipe line that connects the rod side oil chamber 2 of the arm cylinder 1 and the arm cylinder control pilot switching valve 3 to each other. The pilot port 5 and the pilot valve 6 on the arm pulling operation side are communicated with each other via the pressure reducing valve 7. When the pressure in the bottom side oil chamber 8 of the arm cylinder 1 falls to a predetermined low pressure, the pilot pressure derived from the pressure reducing valve 7 is reduced to narrow the opening degree of the discharge passage of the pilot opening / closing valve 4. I chose As a result, when the pressure in the bottom side oil chamber 8 of the arm cylinder 1 falls to a low pressure that causes cavitation, the reduced pilot pressure causes the pilot opening / closing valve 4
Of the pilot opening / closing valve 4 narrows the return circuit communicating with the rod side oil chamber 2. That is, the arm cylinder 1 prevents the arm 31 and the bucket 32 from expanding due to the weight of the arm 31 and the bucket 32. Therefore, it is possible to prevent the cavitation. Further, when the operation of the arm cylinder 1 is stopped, the holes of the pilot opening / closing valve 4 and the check valve 33 act as holding valves, so that the arm 31 can be prevented from being lowered naturally.

FIG. 7 is a hydraulic circuit diagram of a main part of an arm cylinder 9 conventionally equipped in a hydraulic excavator (not shown). In the figure, 10 is a boom of a work attachment (not shown in the overall view) attached to the front part of the hydraulic excavator, and 11 is a boom 10.
Arm 12 rotatably connected to the tip of the
1, a bucket rotatably connected to the tip of 1, a control valve 13 for controlling the arm cylinder 9, a hydraulic pump 14 for discharging main pressure oil, a relief valve 15
Is an oil tank, 17 is an arm hydraulic remote control valve, 18 is an operating lever of the arm hydraulic remote control valve 17, 19 _F , 19
_R is a pilot valve of the arm hydraulic remote control valve 17, and 20 is a pilot hydraulic pressure source. In the hydraulic circuit shown in FIG. 7, when the operating lever 18 is tilted from the neutral position n toward the position i, the pilot primary pressure from the pilot hydraulic power source 20 is derived from the pilot valve 19 _{F as the} pilot secondary pressure and is supplied through the pipe line 21. Control valve 13
To the pilot port 22 of the. Since the control valve 13 is switched from the neutral position to the c position, the main pressure oil from the hydraulic pump 14 is supplied to the rod side oil chamber 23 of the arm cylinder 9 through the c position of the control valve 13 and the bottom side oil chamber 24. The return oil from is returned to the oil tank 16 through the control valve 13 c position. That is, since the arm cylinder 9 is reduced, the arm pushing operation of the arm 11 can be performed.
Next, when the operation lever 18 is tilted from the neutral position n toward the position b, the pilot secondary pressure is derived from the pilot valve 19 _R , and the control valve 13 is supplied through the conduit 25.
To the pilot port 26 of the. Since the control valve 13 is switched from the neutral position to the two position, the main pressure oil from the hydraulic pump 14 is supplied to the bottom side oil chamber 24 of the arm cylinder 9 through the two positions of the control valve 13, and the rod side oil chamber 23. Return oil from the oil tank 16 passes through the two positions of the control valve 13 described above.
Returned to. That is, since the arm cylinder 9 is extended, the arm pulling operation of the arm 11 can be performed.

[0004]

The work contents of the hydraulic excavator include leveling work (so-called horizontal pulling work) performed by moving the bucket 12 shown in FIG. 7 in the horizontal direction. When the horizontal pulling operation is performed, the main spool (not shown) of the control valve 13 for controlling the arm 11 starts to move and the meter-out opening (the rod-side oil chamber 23) is started.
From the oil tank 16 to the oil tank 16)
Operate by squeezing extremely. This is to prevent the arm 11 from moving ahead of the boom 10 when the pulling operation of the arm 11 is started, and the toes of the bucket 12 are difficult to get into the ground (GL). However, in a state where the arm 11 is pushed and fully extended to the operation end (in this case, the arm cylinder 9
When the arm pulling operation is performed from the relief valve 15 operates to perform the arm pulling operation), the high residual pressure during the relief operation, that is, the internal mist pressure is trapped in the rod side oil chamber 23. Therefore, in order to release the internal pressure of the muffle, it is necessary to pull the operation lever 18 more than necessary (operation in the B position direction), and the main supply pressure to the bottom side oil chamber 24 depends on the tilting depth of the operation lever 18. Will increase. Therefore, the internal pressure of the muffled inside the rod-side oil chamber 23 is released and the arm cylinder 9
At the timing at which the arm 11 starts to move, the arm 11 starts to move in a situation where the arm 11 is pushed away by the main pressure pushed into the rod-side oil chamber 24, and so-called "arm stone drop" occurs. Since the toe of the bucket 12 is pushed into the sloping portion of the ground shown in FIG. 7, there was a problem in horizontal pulling operation. In the hydraulic circuit according to the embodiment of the related art shown in FIG. 6, a pilot opening / closing valve 4 is provided in a pipe line communicating with the rod side oil chamber 2 in a supply / discharge circuit communicating with the arm cylinder 1 to prevent cavitation of the bottom side oil chamber 8. Although this is prevented, no means is provided to release the internal pressure of the muffled trapped in the oil chamber of the hydraulic actuator at the start of the operation of the operation lever. In order to prevent the stone from dropping when the arm 11 starts moving in FIG. 7, the present invention instantaneously meters out at the minimum tilt start region of the operating lever 18, that is, at the minimum stroke start region of the main spool of the control valve 13. An object of the present invention is to provide a hydraulic valve control device that sets an opening and enables internal pressure release of the rod-side oil chamber 23 of the arm cylinder 9.

[0005]

According to the present invention, a boom, an arm, and a bucket are sequentially rotatably connected to a front portion of a vehicle body, and the pushing / pulling operation of the arm is performed by a contracting / extending operation of an arm cylinder. In addition, the pilot secondary pressure is derived from the arm hydraulic remote control valve according to the operation amount of the operating lever, and the pilot secondary pressure is applied to the pilot port of the arm control valve for arm cylinder control to The control valve is operated to be switched, and a means for detecting the pilot secondary pressure and a means for detecting the main pressure of the hydraulic pump are provided, and a signal from the detecting means is input to the controller. In the electric circuit, the number of supply / discharge circuits leading from the arm control valve to the arm cylinder is reduced. Also, connect the electromagnetic switching valve for releasing the internal pressure of the muffle trapped in the oil chamber of the arm cylinder to the required pipeline on one side, and set the minimum tilt angle around the neutral position of the operating lever of the hydraulic remote control valve for arm. The pilot secondary pressure detection signal derived in the zone operation state and the main pressure signal discharged from the hydraulic pump are input to the controller, and the electromagnetic switching valve is switched by the command signal output from the controller based on the detection signal. By operating, the oil chamber and the oil tank having the above-mentioned muffled internal pressure,
The electromagnetic switching valve is allowed to communicate through the position with the throttle portion, and is not communicated after the internal pressure is released.
Then, in the above case, the oil chamber on the side where the inner pressure of the arm cylinder is generated is set to the rod side oil chamber, and the oil supply and discharge pipe line leading to the rod side oil chamber and the oil tank are connected via the electromagnetic switching valve. The main pressure discharged from the hydraulic pump is set to the relief set pressure or the relief pressure while the pilot secondary pressure derived from the arm pushing operation side pilot valve of the hydraulic remote control valve for the arm is lowered to near 0 (zero). The electromagnetic switching valve is actuated by the detection means detecting the state in which the pilot secondary pressure is started to be derived from the arm pulling operation side pilot valve after a short time of seconds from the time of a high pressure state close to the set pressure. I tried to blame you.

In the hydraulic valve control device of the present invention, the arm pushing operation side of the hydraulic remote control valve for the arm is in a state where the internal pressure of the muffle remains in the rod-side oil chamber of the arm cylinder, or even when the internal pressure does not remain. The pilot secondary pressure signal from the arm pulling operation side pilot valve and the main pressure signal from the hydraulic pump are input to the controller. And the operating state of the operating lever of the hydraulic remote control valve for the arm is
A minimum tilt angle range centered on the neutral position of the operating lever, that is, when the operating lever is in the angular range immediately before returning to the neutral position after the main pressure is relieved by the arm pushing operation or when the arm pulling operation is started. , When the pilot secondary pressure derived from the arm pushing operation side pilot valve is in a state of decrease close to 0 (zero), the main pressure discharged from the hydraulic pump is set to the relief setting pressure or a high pressure state close to the relief setting pressure for a second. When the detecting means detects a state in which the pilot secondary pressure has been started to be derived from the arm pulling operation side pilot valve after a short period of time, the detection signal is input to the controller. The controller makes a determination based on the detection signal and outputs a short-time switching command signal to the electromagnetic switching valve. The solenoid of the solenoid operated directional control valve energizes for a short time, the solenoid operated directional control valve is instantly switched from the shutoff oil passage position to the throttled position (the same as the throttled oil passage position), and immediately after that, the shutoff oil is again released. Return to the road position. That is, during the switching operation of the electromagnetic switching valve, the rod-side oil chamber of the arm cylinder momentarily communicates with the oil tank via the position with the throttle portion. Therefore, it is possible to instantaneously release the internal pressure of the rod-side oil chamber of the arm cylinder within the mist in the minimum tilting angle range from the end of the relief operation in the arm pushing operation of the operation lever to the start of the arm pulling operation. It is possible to prevent a so-called arm drop phenomenon that occurs when performing.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a circuit diagram of essential parts showing a hydraulic valve control device of the present invention. In the figure, components using the same components as those of the conventional hydraulic circuit shown in FIG. 7 are designated by the same reference numerals. 27 is an electromagnetic switching valve, 28
Is a solenoid of the electromagnetic switching valve 27, E is an oil passage position with a throttle portion of the electromagnetic switching valve 27 (same as the position with a throttle portion), 29 is an oil passage position with an aperture portion of E, and a closed oil passage position is F. ,
Reference numeral 30 is a check valve provided inside the shutoff oil passage position for ensuring oil tightness, and 34 and 35 are arm hydraulic remote control valves 1
7 of the arm pulling operation side pilot valve 19 _R and the arm pushing operation side pilot valve 19 _F, which are detection means for detecting the pilot secondary pressure, pressure sensors, pressure switches, etc. Of the pressure sensor, pressure switch, etc. for detecting the main pressure discharged from the pump 14, for example, a pressure sensor, 37 is a controller.

FIG. 2 shows an arm control valve 13
FIG. 4 is a cross-sectional view of a main part showing (hereinafter referred to as a control valve 13). 2 is a view showing a state when the operation lever 18 in FIG. 1 is operated in the direction of the position b (that is, an arm pulling operation), but when the operation lever 18 shown in FIG. 1 is in the neutral position n, FIG. The main spool 38 of the control valve 13 shown in is in the neutral position. At that time, the pressure oil discharged from the hydraulic pump 14 is
9 through the main pressure inflow port (hereinafter referred to as P port) of the control valve 13 and the center bypass oil passage N to the oil tank 16. Next, when the operation lever 18 in FIG. 1 is operated in the low position direction, it acts on the arm pulling operation side pilot valve 19 _R. That is, it acts on the pilot port 26 shown in FIG. The main spool 38 moves in the direction of arrow C, and the oil flowing out toward the center bypass oil passage N is squeezed. At the same time, the flow path opens from the spool notch portion, the pressure oil that has flowed into the P port flows in the direction of the arrow N, and the bottom side oil chamber communication port C ₁ (hereinafter, referred to as C ₁ port) It is supplied to the bottom side oil chamber 24 of the arm cylinder 9 through 40. And the return oil from the rod side oil chamber 23 is
The oil flows from the pipe line 41 and the rod-side oil chamber communication port C ₂ (hereinafter referred to as C ₂ port) in the direction of the arrow and is returned to the oil tank 16 from the tank communication port T (hereinafter referred to as T port). Therefore, since the arm cylinder 9 extends, the pulling operation of the arm 11 can be performed. Also, in FIG.
6 is a chart showing the relationship between the arm pulling operation time and the opening area of the flow path opened by the stroke movement of the main spool 38. In the table, P, C ₁ , C ₂ , T are respective ports, and N is a center bypass oil passage, but the symbols connected by arrows in parentheses indicate curved passages. Although the switching spool is not shown, the electromagnetic switching valve 27
It is a spool for switching inside.

Next, the structure of the hydraulic valve control device of the present invention will be described with reference to FIGS. In the present invention, the oil chamber on the side that produces the internal pressure of the arm cylinder 9 is set as the rod-side oil chamber 23.
, The oil passage 16 is communicated with the oil tank 16 from the control valve 13 to the rod-side oil chamber 23 via the electromagnetic switching valve 27, and the arm hydraulic remote control valve 17 is set.
Of the arm pulling operation side pilot valve 19 _R and the arm pushing operation side pilot valve 19 _F, which are detection means for detecting the pilot secondary pressure, respectively.
35 and a pressure sensor 36 which is a detecting means for detecting the main pressure discharged from the hydraulic pump 14, and the detection signals from the pressure sensors 34, 35 and 36 are input to the controller 37. Then, the pilot secondary pressure derived from the arm pushing operation side pilot valve 19 _F is 0 in the minimum tilting angle range operating state around the neutral position n of the operating lever 18 of the arm hydraulic remote control valve 17.
When the main pressure discharged from the hydraulic pump 14 is in a lowering state close to (zero), the main pressure discharged from the relief set pressure (relief set pressure of the relief valve 15 in FIG. 1) to a high pressure state close to the relief set pressure is a short time in seconds. When the pressure sensors 34, 35, 36 detect the state in which the pilot secondary pressure has started to be derived from the arm pulling operation side pilot valve 19 _R after a lapse of time and the detection signal is input to the controller 37,
By switching the electromagnetic switching valve 27 in response to a command signal output from the controller 37, the rod-side oil chamber 23 and the oil tank 16 having a muffled internal pressure are passed through the throttle-equipped position E of the electromagnetic switching valve 27. Communication is possible for a short time.

Next, the operation of the hydraulic valve control device of the present invention will be described. According to the present invention, the arm pushing operation side and the arm pulling operation side of the arm hydraulic remote control valve 17 are performed even when the internal pressure of the muffled remains in the rod side oil chamber 23 of the arm cylinder 9, or even when the internal pressure does not remain. The pilot secondary pressure signal from the pilot valves (19 _F and 19 _R ) and the main pressure signal from the hydraulic pump 14 are input to the controller 37. And hydraulic remote control valve for arm 17
The operating state of the operating lever 18 is a minimum tilting angle range around the neutral position n of the operating lever 18, that is, immediately before returning the operating lever 18 to the neutral position n after the main pressure is relieved by the arm pushing operation. Alternatively, when the arm is in the angular range at the time of starting the arm pulling operation, the pilot secondary pressure derived from the arm pushing operation side pilot valve 19 _F is 0.
With the descent state close to (zero), the main pressure discharged from the hydraulic pump 14 is the relief set pressure (for example, 350 kg / cm).
² ) to a high pressure state close to the relief set pressure (for example, 30
0 kg / cm ² ) from the time point, a state in which the pilot secondary pressure is started to be derived from the arm pulling operation side pilot valve 19 _R after a short time of several seconds, for example, several seconds, is detected.
When 35 and 36 detect, the detection signal is input to the controller 37. The controller 37 makes a determination based on the detection signal, and determines the solenoid 2 of the electromagnetic switching valve 27.
A command signal is output to 8. The solenoid 28 is energized for a short time (for example, 0.5 sec), the electromagnetic switching valve 27 is instantaneously switched from the cutoff oil passage position to the oil passage position E with a throttle portion, and immediately after that, the cutoff oil is again provided. Return to the road position. That is, during the switching operation of the electromagnetic switching valve 27,
The rod-side oil chamber 23 of the arm cylinder 9 momentarily communicates with the oil tank 16 via the oil passage position E with the throttle portion.
Therefore, the internal pressure of the rod-side oil chamber 23 of the arm cylinder 9 can be instantaneously released in the minimum tilt angle range from the end of the relief operation in the arm pushing operation of the operation lever 18 to the start of the arm pulling operation. It is possible to prevent a so-called stone drop phenomenon of the arm 11 that occurs when the pulling operation is performed.

FIG. 4 is a flow chart showing the operation of the hydraulic valve control device of the present invention. In step A2 of the flowchart shown in FIG. 4, the arm pulling operation is not first performed (FL0 = 0), and the arm pushing operation is not performed (F0).
L1 = 0) state. Next, at step A3, there is an arm pushing operation (control valve 1 shown in FIG.
Pilot pressure P _r acting on the pilot port 22 of No. 3
≧ 5 kg / cm ² ) and the main pressure P _o discharged from the hydraulic pump 14 is ≧ 300 kg / cm ² (relief setting pressure is 350 kg / cm ² ), the arm pushing operation is performed as shown in step A4. ing. Next, the operation lever 18 for the arm pushing operation is returned to the neutral position n, and the arm pulling operation is started. Operation lever 18 shown in step A5
In the minimum tilting angle range of, the pilot pressure P _h acting on the pilot port 26 of the control valve 13 is, for example, 5 kg / cm ² , so that the arm pulling operation is performed as shown in step A6 (FL0 = 1), but FIG. As shown in FIG. 2, the stroke amount of the main spool 38 is equal to or smaller than the dimension Sα (for example, 3.0 mm), and therefore the flow path from the C ₁ port to the T port shown in FIG. 2 is not open. In this state, the command signal output from the controller 37 energizes the solenoid 28 of the electromagnetic switching valve 27 for a short time, for example, 0.5 seconds, as shown in step A7. The electromagnetic switching valve 27 instantaneously switches from the cutoff oil passage position to the oil passage position E with the throttle portion, and immediately thereafter returns to the cutoff oil passage position again. That is, during the switching operation of the electromagnetic switching valve 27, the internal pressure of the rod-side oil chamber 23 of the arm cylinder 9 can be instantaneously released via the oil passage position E with the throttle portion. By providing step B1, when the ground leveling work is performed by repeating the arm pushing operation and the arm pulling operation, if the arm pulling operation is not performed even if, for example, one minute or more has elapsed after the arm pushing operation is completed. The controller 37 can judge and cancel the control.

FIG. 5 is a flow chart of another embodiment showing the operation of the hydraulic valve control device of the present invention. In step A′2 of the flowchart shown in FIG. 5, the arm is not first pushed (FL1 = 0). Next, at step A′3, there is an arm pushing operation (pilot pressure P _r acting on the pilot port 22 of the control valve 13 shown in FIG. 1 ≧ 5 kg / cm ² ), and the main discharge from the hydraulic pump 14 is performed. Pressure P _o ≧ 300kg /
When the pressure is cm ² (the relief setting pressure is 350 kg / cm ² for example), the arm pushing operation is performed as shown in step A′4. Next, when the operation lever 18 for pushing the arm is returned to the neutral position n, the pilot pressure acting on the pilot port 22 of the control valve 13 is set in the minimum tilt angle range close to the neutral position n as shown in step A'5. P _r decreases, and P _r ≦ 3 kg / cm ² , for example.
In this state, the command signal output from the controller 37 causes the electromagnetic switching valve 27 to operate as shown in step A′6.
The solenoid 28 is energized for a short time, for example, 0.5 seconds. The electromagnetic switching valve 27 instantaneously switches from the shutoff oil passage position to the throttle-equipped oil passage position E, and immediately thereafter returns to the shutoff oil passage position again. That is, in the flowchart shown in FIG. 5, the internal pressure of the muffled body is not released in the minimum tilt angle range of the operation lever 18 at the start of the arm pulling operation, but at the time point after the main pressure relief in the arm pushing operation is completed
The internal pressure of the muffled rod-side oil chamber 23 is instantaneously released.

[0013]

According to the hydraulic valve control device of the present invention, the arm pushing operation of the hydraulic remote control valve for the arm is performed even if the internal pressure of the muffled rod remains in the rod side oil chamber of the arm cylinder, or even if the internal pressure does not remain. A pilot secondary pressure signal from the operating side and arm pulling operating side pilot valves and a main pressure signal from the hydraulic pump are input to the controller. The operating state of the operating lever of the hydraulic remote control valve for the arm is in a very small tilting angle range centered on the neutral position of the operating lever, that is, immediately before returning the operating lever to the neutral position after the main pressure is relieved by pushing the arm. , Or in the angular range at the time of starting the arm pulling operation, the main secondary pressure discharged from the hydraulic pump is relieved while the pilot secondary pressure derived from the arm pushing operation side pilot valve drops close to 0 (zero). When the detection means detects the state where the pilot secondary pressure is started to be derived from the arm pulling operation side pilot valve after a short time of seconds from the time of the high pressure state close to the set pressure or the relief set pressure, the detection signal is the controller. Entered in. The controller makes a determination based on the detection signal and outputs a short-time switching command signal to the electromagnetic switching valve. The solenoid of the solenoid operated directional control valve energizes for a short time, the solenoid operated directional control valve is instantly switched from the shutoff oil passage position to the throttled position (the same as the throttled oil passage position), and immediately after that, the shutoff oil is again released. Return to the road position. That is, during the switching operation of the electromagnetic switching valve, the rod-side oil chamber of the arm cylinder momentarily communicates with the oil tank via the position with the throttle portion. Therefore, it is possible to instantaneously release the internal pressure of the rod-side oil chamber of the arm cylinder within the mist in the minimum tilting angle range from the end of the relief operation in the arm pushing operation of the operation lever to the start of the arm pulling operation. It is possible to prevent a so-called arm drop phenomenon that occurs when performing. Therefore, in a construction machine or work vehicle equipped with the hydraulic valve control device of the present invention, so-called horizontal pulling work such as leveling work can be accurately performed, and thus horizontal pulling operability and work precision can be improved.

[Brief description of drawings]

FIG. 1 is a main circuit diagram showing a hydraulic valve control device of the present invention.

FIG. 2 is a sectional view of an essential part showing a control valve for an arm.

FIG. 3 is a chart showing a relationship between an arm pulling operation time and an opening area of a flow path opened by a stroke movement of a main spool.

FIG. 4 is a flowchart showing the operation of the hydraulic valve control device of the present invention.

FIG. 5 is a flowchart of another embodiment showing the operation of the hydraulic valve control device of the present invention.

FIG. 6 is a hydraulic circuit diagram of an embodiment of the prior art.

FIG. 7 is a hydraulic circuit diagram of a main part of another embodiment of an arm cylinder that is conventionally equipped in a hydraulic excavator.

[Explanation of symbols]

1, 9 Arm cylinder 2, 23 Rod side oil chamber 6, 19 _F , 19 _R Pilot valve 8, 24 Bottom side oil chamber 11, 31 Arm 12, 32 Bucket 13 Control valve 14 Hydraulic pump 15 Relief valve 16 Oil tank 17 Arm Hydraulic remote control valve 18 Control lever 22, 26 Pilot port 27 Electromagnetic switching valve 34, 35, 36 Pressure sensor 37 Controller 38 Main spool

Front page continuation (58) Fields surveyed (Int.Cl. ⁷ , DB name) E02F 9/20-9/22 E02F 3/43 F15B 11/028 F15B 11/08

Claims (6)

(57) [Claims] 1. A pilot secondary pressure is derived from a hydraulic remote control valve according to an operation amount of an operation lever, and the pilot secondary pressure is applied to a pilot port of a hydraulic valve for controlling a hydraulic actuator to switch the hydraulic valve. And means for detecting the pilot secondary pressure and means for detecting the main pressure of the hydraulic pump,
In the hydraulic / electric circuit for inputting the signal from the detection means to the controller, the hydraulic chamber is confined in the oil chamber of the hydraulic actuator in at least one of the conduits of the supply / discharge circuit leading from the hydraulic valve to the hydraulic actuator. By connecting an electromagnetic switching valve for releasing the internal pressure of the thigh and switching the electromagnetic switching valve in response to a command signal output from the controller, the oil chamber and the oil tank having the internal pressure of the mist are connected to the electromagnetic switching valve. A hydraulic valve control device characterized in that the hydraulic valve control device is capable of communicating through a position with a throttle portion. 2. The hydraulic valve control device according to claim 1, wherein communication between the oil chamber having the internal pressure of the muffle and the oil tank becomes non-communication after the internal pressure is released. 3. A boom, an arm, and a bucket are sequentially rotatably connected to a front portion of a vehicle body so that the pushing / pulling operation of the arm is performed by a contracting / extending operation of an arm cylinder, and an operation amount of an operating lever. According to the above, the pilot secondary pressure is derived from the hydraulic remote control valve for the arm, and the pilot secondary pressure is applied to the pilot port of the arm control valve for controlling the arm cylinder to switch the control valve for the arm. ,
Further, in the hydraulic / electric circuit having means for detecting the pilot secondary pressure and means for detecting the main pressure of the hydraulic pump, and inputting a signal from the detecting means to the controller, the arm control valve Connect the electromagnetic switching valve for releasing the internal pressure of the muffled oil trapped in the oil chamber of the arm cylinder to the required pipe line of at least one of the supply and discharge circuits leading to the arm cylinder, and operate the hydraulic remote control valve for the arm. The detection signal of the pilot secondary pressure derived in the operating state of the minimum tilt angle centered on the neutral position and the main pressure signal discharged from the hydraulic pump are input to the controller and output from the controller based on the detection signal. By switching the electromagnetic switching valve in response to the command signal generated, the oil chamber and the oil tank having the above-mentioned internal pressure of the mist are Preparative, hydraulic valve control apparatus being characterized in that to enable communicating via a throttle portion with the position of the electromagnetic switching valve. 4. The hydraulic valve control device according to claim 3, wherein communication between the oil chamber having the internal pressure of the muffle and the oil tank becomes non-communication after the internal pressure is released. 5. The hydraulic valve control device according to claim 3, wherein the oil chamber on the side where the internal pressure of the boom of the arm cylinder is generated is set to a rod-side oil chamber, and the supply / discharge is communicated to the rod-side oil chamber. A hydraulic valve control device characterized in that a pipeline for oil and an oil tank are communicated with each other via the electromagnetic switching valve. 6. The hydraulic valve control device according to claims 3 and 5, wherein the pilot secondary pressure derived from the arm pushing operation side pilot valve of the arm hydraulic remote control valve is 0 (zero). When the main pressure discharged from the hydraulic pump is at a high pressure close to the relief setting pressure or the relief setting pressure in a descending state close to, the pilot secondary pressure is derived from the arm pulling operation side pilot valve after a short time in seconds. A hydraulic valve control device, wherein the electromagnetic switching valve is actuated by the detection means detecting the started state.