JP2003028101A - Hydraulic control device of construction machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic control device for a construction machine capable of precluding a breathing phenomenon when an inertial load is applied to an actuator and reducing the pressure loss on the meter-out side in any work requiring a positive drive of the actuator such as excavation to decrease the energy loss. SOLUTION: The hydraulic control device of the construction machine is equipped with a meter-out control valve 42 and a selector valve 43 to make changeover control of the meter-out control valve 42. The valve 42 is installed on a meter-out branch line 41 leading to a tank 33 branching from an actuator line 35 on the meter-out side when an arm cloud command is issued, while the selector valve 43 is installed on a signal pressure line 44 which connects a pilot line 38 on the arm cloud command side with a pressure reception part 42b of the meter-out control valve 42. A pressure reception part 43b of the selector valve 43 is connected to an actuator line 34 on the meter-in side when the arm cloud command is issued through another signal pressure line 45.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic control device for a construction machine such as a hydraulic excavator, and more particularly to a hydraulic control device for a construction machine capable of reducing energy loss when an actuator is driven.

[0002]

2. Description of the Related Art Construction machines such as hydraulic excavators are generally
A hydraulic pump, an actuator driven by pressure oil discharged from the hydraulic pump, and a flow control valve are provided. For example, in the case of a hydraulic excavator, the actuator is a boom cylinder that drives the boom of the front working machine, an arm cylinder that drives the arm, a bucket cylinder that drives the bucket, and a flow control valve is provided for each actuator. . The flow control valve has a meter-in throttle and a meter-out throttle.The meter-in throttle controls the flow rate of pressure oil supplied from the hydraulic pump to the actuator, and the meter-out throttle controls the flow rate of pressure oil returned from the actuator to the tank. Control. This type of hydraulic circuit is disclosed, for example, in Japanese Patent Laid-Open No. 2000-220168.
It is described in Japanese Patent Publication No.

[0003]

As described above, a construction machine such as a hydraulic excavator is provided with a flow control valve having a meter-in throttle and a meter-out throttle. Here, the meter-out diaphragm is provided separately from the meter-in diaphragm.
This is for speed control and prevention of breathing phenomenon (cavitation) when an inertial load acts on the actuator.

For example, in the case of an arm cylinder of a hydraulic excavator, when the arm is clouded above the ground, that is, in the air, the flow control valve for the arm controls the return oil of the arm cylinder by a meter-out throttle to control the arm cylinder. While controlling the speed of the (arm) and preventing the breathing phenomenon (cavitation) due to the free fall of the arm, work above the ground, such as leveling work,
It is possible to improve the operability of dusting work.

As described above, the meter-out throttle is an essential function for improving operability when an inertial load acts on the actuator. However, the meter-out aperture is not necessary for work that requires active drive of the actuator, such as excavation work, traveling, and turning. For example, when excavating with a hydraulic excavator, the front working machine is in contact with the ground, and therefore the above-described arm drop or breathing phenomenon does not occur. Therefore, it is not necessary to narrow down the meter-out side, which causes energy loss and the like. On the contrary, since the meter-out side is narrowed, unnecessary pressure loss occurs, causing energy loss and lowering cylinder thrust. Similar problems also exist in other actuator operations such as bucket cloud operation.

The present invention prevents the breathing phenomenon when an inertial load acts on the actuator, and reduces the pressure loss on the meter-out side in the work that requires active driving of the actuator, such as during excavation, to reduce energy loss. It is to provide a hydraulic control device for a construction machine capable of performing the above.

[0007]

(1) In order to achieve the above object, the present invention provides a hydraulic pump, an actuator driven by pressure oil discharged from the hydraulic pump,
A flow rate control valve, wherein the flow rate control valve controls a flow rate of the pressure oil supplied from the hydraulic pump to the actuator, and a meter out throttle control the flow rate of the pressure oil returned from the actuator to the tank. A hydraulic control device for a construction machine, including: an operating condition detecting unit that detects an operating condition of the actuator; and a meter-out controlling unit that releases a meter-out throttle of the flow control valve according to an operating condition of the actuator. Shall have.

By thus providing the operation status detecting means and the meter-out control means and releasing the meter-out throttle of the flow control valve according to the operation status of the actuator,
When an inertial load is applied to the actuator, the meter-out throttle of the flow control valve is enabled to prevent breathing, and the meter-out throttle of the flow control valve is released for work that requires active drive of the actuator, such as during excavation. By doing so, the pressure loss on the meter-out side can be reduced and the energy loss can be reduced. Further, the driving force of the actuator can be increased by decreasing the pressure that has been increased due to the pressure loss on the meter-out side.

(2) In the above (1), preferably,
The operation status detecting means is a pressure detecting means for detecting a drive pressure on the meter-in side of the actuator.

In the work which requires the positive drive of the actuator, the drive pressure on the meter-in side of the hydraulic cylinder becomes high,
When an inertial load acts on the actuator, the drive pressure on the meter-in side drops to near the tank pressure. For this reason,
The operating condition of the actuator can be detected by detecting the drive pressure on the meter-in side of the hydraulic cylinder.

(3) Further, in the above (1) or (2), preferably, the meter-out control means is a meter provided in a branch line connecting the upstream side of the meter-out throttle of the flow rate control valve to the tank. An out control valve and a switching control means for switching the meter-out control means in the opening direction according to the detection result of the operation status detection means.

By configuring the meter-out control means by the meter-out control valve and the switching control means in this way,
When the meter-out control valve is closed, the meter-out throttle of the flow control valve becomes effective, and when the meter-out control valve is opened, the meter-out throttle of the flow control valve is released. The aperture can be released.

(4) Further, in the above (3), preferably, the meter-out control valve has a metering characteristic.

This makes it possible to suppress pressure fluctuations on the meter-out side when the meter-out control valve is switched.

(5) Further, in the above (3), preferably, the meter-out control valve has a pressure receiving portion at an end portion on the operating side in the opening direction, and the switching control means sets the command pilot pressure of the actuator to the command pilot pressure. It has a signal pressure line leading to the pressure receiving section and a switching valve arranged in this signal pressure line, and switches the switching valve according to the operating condition of the actuator to selectively guide the command pilot pressure to the pressure receiving section. .

As a result, the switching control means can be constructed hydraulically.

(6) Further, in the above (3), preferably, the meter-out control valve has a pressure receiving portion at an end portion on the operating side in the opening direction, and the switching control means detects the command pilot pressure of the actuator. Pressure detection means, a proportional solenoid valve that outputs a signal pressure to the pressure receiving portion, and the detection signals of the operating condition detection means and the pressure detection means are input, and predetermined arithmetic processing is performed to output a command current to the proportional solenoid valve. And a controller for outputting a signal pressure to the pressure receiving portion by driving the proportional solenoid valve according to the calculation result of the controller.

Thus, the switching control means can be electrically constructed.

(7) In the above (3), the meter-out control valve has a pressure receiving portion at an opening-side operation side end, and the switching control means uses the command pilot pressure of the actuator as a primary pressure to receive the pressure. A proportional solenoid valve that outputs a signal pressure to the section, and input the detection signal of the operating condition detection means,
A controller for performing a predetermined calculation process and outputting a command current to the proportional solenoid valve, driving the proportional solenoid valve according to a calculation result of the controller, and guiding a signal pressure to the pressure receiving portion. May be.

Thus, a part of the switching control means can be hydraulically constructed and the other part can be electrically constructed.

(8) In the above (1) to (7), the actuator is an arm cylinder for driving the arm of the hydraulic excavator or a bucket cylinder for driving the bucket.

Thus, in the operation of the arm cloud or the bucket cloud, the breathing phenomenon is prevented when the inertial load acts on the actuator, and the pressure loss on the meter-out side is reduced in the work requiring the active drive of the actuator such as during excavation. Energy loss can be reduced.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 schematically shows a hydraulic circuit portion related to an arm cylinder of a hydraulic excavator in a hydraulic control device according to a first embodiment of the present invention.

In FIG. 1, a hydraulic control system according to the present embodiment is connected to a prime mover (engine) 1, a hydraulic pump 2 driven by the prime mover 1, a discharge line 3 of the hydraulic pump 2, and an arm cylinder. 4 is provided with a valve device 5 having an arm flow rate control valve 31 for controlling the flow (flow rate and supply direction) of the pressure oil supplied to 4, and an arm operation lever device 6.

The hydraulic pump 2 is of a variable displacement type and has a displacement volume variable member, for example, a swash plate 2a. The swash plate 2a reduces horsepower so as to reduce tilting (capacity) as the discharge pressure of the hydraulic pump 2 increases. It is controlled by the control actuator 2b.

The flow control valve 31 is a center bypass type, and the center bypass section 21 has a center bypass line 32.
Located on top. The center bypass line 32 has an upstream side connected to the discharge line 3 of the hydraulic pump 2 and a downstream side connected to the tank 33. The flow control valve 31 has a pump port 31a, a tank port 31b, and actuator ports 31c and 31d.
a is connected to the center bypass line 32, tank port 31b is connected to the tank 33, and actuator ports 31c and 31d are connected to the bottom side and rod side of the arm cylinder 4 via actuator lines 34 and 35.

The operation lever device 6 has an operation lever 36 and a command pilot pressure generator 37 having a pair of pressure reducing valves (not shown) built therein. The command pilot pressure generator 37 is connected via pilot lines 38 and 39. Is connected to the pilot pressure receiving portions 31e and 31f of the flow control valve 31. When the operation lever 36 is operated, the command pilot pressure generator 37 activates one of the pair of pressure reducing valves according to the operation direction,
A command pilot pressure corresponding to the manipulated variable is output to one of the pilot lines 38, 39.

Here, the flow control valve 31 has a neutral position A and switching positions B and C, and when the command pilot pressure is applied to the pressure receiving portion 31e from the pilot line 38, it is switched to the position B on the left side in the drawing, and the actuator. The line 34 is on the meter-in side and the actuator line 35 is on the meter-out side, pressure oil is supplied to the bottom side of the arm cylinder 4 and the arm cylinder 4 extends, and the pilot line 39
When the command pilot pressure is applied to the pressure receiving portion 31f, the position is switched to the position C on the right side in the drawing, the actuator line 35 is on the meter-in side, the actuator line 34 is on the meter-out side, and pressure oil is supplied to the rod side of the arm cylinder 4. The arm cylinder 4 contracts. The extension of the arm cylinder 4 corresponds to the arm crowd operation, and the contraction of the arm cylinder 4 corresponds to the arm dump operation. That is, the pilot line 38, the pressure receiving portion 31e and the command pilot pressure thereof are on the arm cloud command side, the actuator line 34 is on the meter-in side actuator line when the arm cloud command is issued, and the actuator line 35 is on the meter out side when the arm cloud command is issued. Actuator line.

Further, the flow control valve 31 is a meter-in throttle 2
2a, 22b and meter-out throttles 23a, 23b. When the flow rate control valve 31 is in the switching position B, the meter-in throttle 22a controls the flow rate of the pressure oil supplied to the arm cylinder 4, and the meter-out throttle 23a. The flow rate of return oil from the arm cylinder 4 is controlled by the flow rate control valve 3
When 1 is in the switching position C, the flow rate of the pressure oil supplied to the arm cylinder 4 is controlled by the meter-in throttle 22b,
The flow rate of return oil from the arm cylinder 4 is controlled by the meter-out throttle 23b.

The valve device 5 for the arm according to the present embodiment is characterized by its meter-out control valve 42.
And a switching valve 43 for switching and controlling the meter-out control valve 42, and the meter-out control valve 42 is the actuator line 3 on the meter-out side at the time of arm cloud command.
It is arranged on a meter-out branch line 41 that branches from 5 to the tank 33.

The meter-out control valve 42 is a two-port, two-position valve having a spring 42a for operating in the closing direction and a pressure receiving portion 42b for operating in the opening direction at both ends of the valve body, and the pressure receiving portion 42b is connected via a signal pressure line 44. Connected to the pilot line 38 on the arm cloud command side. The switching valve 43 is an on-off valve arranged in the signal pressure line 44, and has a closing direction actuating spring 43a and an opening direction actuating pressure receiving portion 43b at both ends of the valve body, and the pressure receiving portion 43b passes through the signal pressure line 45. Is connected to the actuator line 34 on the meter-in side when the arm cloud command is issued. That is, when the pressure on the bottom side of the arm cylinder 4 is introduced to the pressure receiving portion 43b of the switching valve 43 and the switching valve 43 whose pressure becomes high is switched to the open position,
The flow rate control valve 4 is attached to the pressure receiving portion 42b of the meter-out control valve 42.
The same arm-cloud command pilot pressure as that introduced to the first pressure receiving portion 31e is introduced and switched to the opening direction.

The metering characteristic of the meter-out control valve 42 is shown in FIG. In the figure, the solid line A is the meter-out control valve 4
2 is a metering characteristic when the arm crowd command pilot pressure is applied to the armature 2, and a wavy line B is a metering characteristic of the meter-out throttle 23a when the arm cloud command pilot pressure is applied to the arm flow control valve 31. is there. The metering characteristic of the meter-out control valve 42, that is, the relationship between the stroke (arm cloud command pilot pressure) and the opening area is such that the opening area increases as the stroke increases, and the same arm cloud command as the flow control valve 31 is used. The pilot pressure is set to be larger than the opening area of the meter-out throttle 23a of the flow control valve 31.

FIG. 3 shows the appearance of a hydraulic excavator equipped with a hydraulic control device. The hydraulic excavator has a traveling body 100, a revolving body 101, and a front working machine 102.
0 is the left and right traveling motors 50a, 50b (only one is shown)
Drive the left and right crawlers 100a and 100b (only one is shown), and the revolving structure 101 revolves on the traveling structure 100 by the revolving motor 51. The front working machine 102 has a multi-joint structure including a boom 103, an arm 104, and a bucket 105, and is rotationally driven in a vertical plane by a boom cylinder 106, an arm cylinder 4, and a bucket cylinder 107, respectively.

In addition to the arm valve device 5 shown in FIG. 1, the hydraulic control device according to the present embodiment includes left and right traveling motors 50a and 50b, a swing motor 51, and a boom cylinder 10.
6. A valve device (not shown) for the bucket cylinder 107 is provided. Regarding the entire hydraulic circuit including these valve devices, for example, the above-mentioned Japanese Patent Laid-Open No. 2000-2201.
This is shown in FIG. 1 of the '68 publication.

Next, the operation of this embodiment will be described in comparison with the conventional example.

FIG. 4 is a view showing a hydraulic circuit portion related to an arm cylinder similar to FIG. 1 of a conventional hydraulic control device.
In the conventional hydraulic control device, the valve device 150 for the arm is not provided with the meter-out control valve 42 or the switching valve 43.

Now, in the conventional hydraulic control apparatus, it is assumed that the arm flow control valve 31 is switched to the position B in FIG. 4 in order to cloud the arm 104 above the ground, that is, in the air as shown in FIG. At this time, the flow control valve 31
Is the meter-out throttle 23 for the return oil of the arm cylinder 4.
a by controlling the arm cylinder 4 (arm 10
In addition to the speed control of 4), the breathing phenomenon (cavitation) due to the free fall of the arm 104 is prevented. That is, the pressure on the rod side of the arm cylinder 4 is increased by squeezing the meter-out side of the arm cloud,
A force that resists the pressure on the bottom side due to the weight of the arm is generated. This makes it possible to improve the operability of work above the ground, such as leveling work and dusting work.

However, in the work requiring the positive drive of the arm cylinder 4, for example, the excavation work shown in FIG. 6, the front working machine 104 is grounded,
The drop or breathing phenomenon of the arm 104 as described above does not occur. Therefore, it is not necessary to reduce the meter-out side as described above. On the contrary, since the meter-out side is narrowed, unnecessary pressure loss occurs, causing energy loss and lowering cylinder thrust. Similar problems exist in bucket cloud operations.

FIG. 7 and FIG. 8 show calculation results for energy loss and cylinder thrust reduction.

FIG. 7A is a calculation result of the input energy to the arm cylinder 4 and the pressure loss energy by the meter-out throttle 23a of the arm cloud of the flow control valve 31 when the pump discharge pressure is changed, and FIG. Shows the calculation result of FIG. 7A replaced with the loss energy ratio (%). Here, loss energy ratio (%) =
(Pressure loss energy / input energy) × 100 (%). As can be seen from these figures, since the discharge flow rate of the hydraulic pump 1 is large in the region where the pump discharge pressure is low due to the horsepower control of the actuator 2b, the pressure loss energy due to the meter-out throttle 23a is large in the region where the pump discharge pressure is low, and the loss Higher energy ratio.

FIG. 8A shows the calculation results of the apparent thrust and the actual thrust of the arm cylinder 4 when the pump discharge pressure is changed, and FIG. 8B shows the calculation results of FIG. 8A lost. It is replaced with the thrust ratio. Here, the apparent thrust of the arm cylinder 4 is the thrust when the pressure on the meter-out side is 0, and the actual thrust is calculated based on the actual pressure by the meter-out throttle 23a of the arm cloud of the flow control valve 31. It is the thrust. Also, the loss thrust ratio (%) =
((Apparent thrust-actual thrust) / apparent thrust) x 100
(%). As can be seen from these figures, the discharge flow rate of the hydraulic pump 1 is large especially in the region where the pump discharge pressure is low due to the horsepower control of the actuator 2b. Therefore, the actual thrust force is reduced by the meter-out throttle 23a particularly in the region where the pump discharge pressure is low. It is large and the loss thrust ratio is high.

In contrast to the prior art as described above, in the present embodiment configured as described above, when the front working machine 102 is moved in the air, that is, when the arm crowd is performed in the air as shown in FIG. Since the pressure on the bottom side of the cylinder 4 is not high, the pressure is used as the signal pressure in the switching valve 43.
The switching valve 43 does not operate even if it is guided to the pressure receiving portion 43b.
Therefore, the meter-out control valve 42 also does not operate and is held in the illustrated closed position. That is, as in the prior art, the meter-out throttle 23a of the flow control valve 31 operates, and the breathing phenomenon (cavitation) due to the free fall of the arm 104 is prevented.

Next, it is assumed that the state shown in FIG. 5 is changed to the excavation state shown in FIG. At this time, the pressure on the bottom side of the arm cylinder 4 rises and this pressure is introduced as a signal pressure to the pressure receiving portion 43b of the switching valve 43, so that the switching valve 43 is switched from the closed position to the open position. As a result, the arm cloud command pilot pressure is guided to the pressure receiving portion 42b of the meter-out control valve 42, and the meter-out control valve 42 switches to the stroke position corresponding to the command pilot pressure. As described above, the metering characteristic of the meter-out control valve 42 is larger than the opening area of the meter-out throttle 23a of the flow control valve 31 at the same arm cloud command pilot pressure as compared with the meter-out throttle 23a of the flow control valve 31. Is set to. Therefore, for example, assuming that the arm cloud command pilot pressure is equivalent to the stroke X1 in FIG. 2, most of the return oil from the rod side of the arm cylinder 4 is not the meter-out throttle valve 23a of the flow control valve 31 but the meter-out control valve. The pressure loss due to meter-out can be reduced.

Therefore, according to the present embodiment, it is possible to reduce the pressure loss on the meter-out side at the time of excavation (when operating the arm crowd) and reduce the energy loss. Also,
By reducing the pressure on the rod side of the arm cylinder 4 that has been increased due to the pressure loss on the meter-out side, the thrust of the arm cylinder 4 can be increased.

Further, in this embodiment, since the meter-out control valve 42 has the metering characteristic as shown in FIG. 2, when the meter-out control valve 42 is switched from the closed position shown in the drawing to the opening direction. It is possible to suppress pressure fluctuations of the return oil when the meter-out control valve 42 is switched, such as a sudden increase in the pressure of the return oil, and obtain good operability.

In the above embodiment, the switching valve 43
Is a switching valve, but this switching valve 43 may also have metering characteristics. In this case, when the switching valve 43 is switched due to pressure fluctuation on the bottom side of the arm cylinder 4, the pressure received by the metering control valve 42 is received. The on / off switching of the metering control valve 42 due to the arm cloud command pilot pressure acting on / off the portion 42b is prevented, so that the pressure fluctuation of the return oil can be more effectively suppressed, and further. Good operability can be obtained.

A second embodiment of the present invention is shown in FIGS. 9 and 1.
This will be described with reference to 0. 9, the same members as those shown in FIG. 1 are designated by the same reference numerals. In this embodiment, the meter-out control valve is electrically controlled.

In FIG. 9, the valve device 5A for the arm having the flow rate control valve 31 does not include the switching valve 43 which is included in the valve device 5 of FIG. Instead, the hydraulic control device according to the present embodiment is provided in the pilot line 38 on the arm cloud command side, and has a pressure sensor 51 for detecting the arm cloud command pilot pressure and an actuator line on the meter-in side at the time of the arm cloud command. 34, which has a pressure sensor 52 for detecting the pressure on the bottom side of the arm cylinder 4, a controller 53, and a proportional solenoid valve 54. Detection signals of the pressure sensors 51, 52 are input to the controller 53, and the controller 53 53 to proportional solenoid valve 5
The command current is output to 4. The secondary side (output side) of the proportional solenoid valve 54 is connected to the pressure receiving portion 42b of the meter-out control valve 43 via the signal pressure line 55, and the secondary pressure of the proportional solenoid valve 54 is applied to the pressure receiving portion 43b as a signal pressure. To be As is well known, the primary side of the proportional solenoid valve 54 has a pilot hydraulic power source 5
Connected to 6.

FIG. 10 is a functional block diagram showing the processing functions of the controller 53. The controller 53 includes a solenoid current calculator 53a, a control coefficient calculator 53b, and a multiplier 53.
have c. The solenoid current calculation unit 53a calculates the solenoid current value according to the arm cloud command pilot pressure using a table as shown in the figure. The control coefficient calculator 53b uses a table as shown in the figure to
Control coefficient k according to the pressure on the bottom side of the arm cylinder 4
Is calculated. In the table of the solenoid current calculation unit 53a, the relationship between the two is set so that the solenoid current also increases as the arm cloud command pilot pressure increases. The solenoid current value calculated using this table corresponds to the arm cloud command pilot pressure guided to the signal pressure line 44 of FIG. 1 according to the first embodiment. In the table of the control coefficient calculation unit 53b, the relationship between the two is set so that the control coefficient k increases from 0 to 1 with a certain inclination (proportional characteristic) as the pressure on the bottom side of the arm cylinder 4 increases. The slope is the first
This is equivalent to providing the switching valve 43 shown in FIG. 2 according to the embodiment with the metering characteristic. Calculation unit 53a
The solenoid current value calculated in (3) and the control coefficient k calculated in the calculation unit 53b are multiplied by the multiplication unit 53c to obtain the target solenoid current value. This target solenoid current value is output to the proportional solenoid valve 54 as a command current.

Even in the present embodiment configured as described above, the same operation as that of the first embodiment can be obtained when the arm 104 is clouded in the air and excavated by the arm cloud. The pressure loss on the meter-out side (during cloud operation) can be reduced to reduce the energy loss, and the pressure on the rod side of the arm cylinder 4 which has been increased by the pressure loss on the meter-out side can be reduced to reduce the arm cylinder 4's It is possible to increase the thrust.

Further, in the present embodiment, it is equivalent to that the control coefficient computing unit 53b has a proportional characteristic and the switching valve 43 shown in FIG. 2 according to the first embodiment has a metering characteristic. With this configuration, the output of the proportional solenoid valve (the signal pressure line 5
Since the on / off switching of the meter-out control valve 42 due to the on / off change of the signal pressure of No. 5) is suppressed, the pressure fluctuation of the return oil is further effectively suppressed, and a better operation is achieved. You can get sex.

A third embodiment of the present invention will be described with reference to FIG. In the figure, the same members as those shown in FIGS. 1 and 9 are designated by the same reference numerals. The present embodiment shows another example of electrically controlling the meter-out control valve.

In FIG. 11, the hydraulic control system according to the present embodiment is provided with an arm valve device 5A similar to that of the second embodiment of FIG. 9, but in the second embodiment. It does not have a pressure sensor to detect arm cloud command pilot pressure. Instead, the primary side of the proportional solenoid valve 54 is connected to the pilot line 38 on the arm cloud command side via the signal pressure line 44A. That is, in the present embodiment, the arm cloud command pilot pressure of the pilot line 38 is used as the hydraulic pressure source of the proportional solenoid valve 54. This corresponds to the solenoid current calculator 53a and the multiplier 5 of FIG. 10 according to the second embodiment.
This is equivalent to hydraulically configuring the configuration of 3c.

The controller 53A has a solenoid current calculator 53d as shown in FIG. 12, and calculates a target solenoid current value according to the pressure on the bottom side of the arm cylinder 4 using a table as shown. The relationship between the pressure on the bottom side of the arm cylinder 4 set in the table of the solenoid current calculation unit 53d and the target solenoid current is as follows. The pressure and the control coefficient on the bottom side of the arm cylinder 4 of the control coefficient calculation unit 53b shown in FIG. It is equivalent to the relationship with k, and the relationship between the two is set so that the target solenoid current increases from 0 to the maximum value with a certain inclination (proportional characteristic) as the pressure on the bottom side of the arm cylinder 4 increases.

Also according to this embodiment, the same effect as that of the first embodiment can be obtained, and the solenoid current calculation unit 53 is provided with the proportional characteristic so that FIG. 2 relating to the first embodiment can be obtained. Since a configuration equivalent to giving the metering characteristic to the switching valve 43 shown can be obtained, the output of the proportional solenoid valve (the signal pressure of the signal pressure line 55) is turned on when the pressure on the bottom side of the arm cylinder 4 changes. Since the switching of the meter-out control valve 42 from ON to OFF due to the change in the OFF state is suppressed, it is possible to further effectively suppress the pressure fluctuation of the return oil and obtain better operability.

The above-described embodiment is a case where the present invention is applied to the valve device of the arm cylinder of the hydraulic excavator, but there is a similar problem in the bucket cloud operation as described above. May be applied to the valve device of the bucket cylinder. In this case, for example, in the hydraulic circuit shown in FIG. 1, the arm cylinder is replaced with a bucket cylinder, the arm flow control valve is replaced with a bucket flow control valve, and the arm operation lever device is replaced with a bucket operation lever device. Good. In addition, the present invention provides an actuator other than an arm cylinder or a bucket cylinder of a hydraulic excavator, or a construction machine other than a hydraulic excavator, such as a wheel loader, as long as the same actuator performs a work in which an inertial load acts and a work that requires positive drive. Similarly, it can be applied to valve devices of actuators such as cranes.

[0058]

According to the present invention, the following effects can be obtained.

(1) The breathing phenomenon can be prevented when an inertial load acts on the actuator, and the
In the work that requires the positive drive of the actuator, the pressure loss on the meter-out side can be reduced and the energy loss can be reduced.

(2) It is possible to increase the driving force of the actuator by decreasing the pressure that has risen due to the pressure loss on the meter-out side.

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a hydraulic circuit portion related to an arm cylinder of a hydraulic excavator in a hydraulic control device for a construction machine according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a metering characteristic of a meter-out control valve 42.

FIG. 3 is a diagram showing an external appearance of a hydraulic excavator on which a hydraulic control device is mounted.

FIG. 4 is a diagram showing a hydraulic circuit portion related to an arm cylinder similar to FIG. 1 of a conventional hydraulic control device.

FIG. 5 is a diagram showing an operation of clouding the arm of the hydraulic excavator in the air.

FIG. 6 is a diagram showing an excavation work using an arm cloud of a hydraulic excavator.

FIG. 7A is a diagram showing calculation results of input energy to the arm cylinder and pressure loss energy by the meter-out side throttle of the arm cloud of the flow control valve when the pump discharge pressure is changed, and FIG. It is the figure which replaced the calculation result of (a) with the loss energy ratio (%).

FIG. 8A is a diagram showing the calculation results of the apparent thrust and the actual thrust of the arm cylinder when the pump discharge pressure is changed, and FIG. 8B is the calculation result of FIG. FIG.

FIG. 9 is a diagram schematically showing a hydraulic circuit portion related to an arm cylinder of a hydraulic excavator in a hydraulic control device for a construction machine according to a second embodiment of the present invention.

FIG. 10 is a functional block diagram showing processing functions of a controller according to the second embodiment.

FIG. 11 is a diagram schematically showing a hydraulic circuit portion related to an arm cylinder of a hydraulic excavator in a hydraulic control device for a construction machine according to a third embodiment of the present invention.

FIG. 12 is a functional block diagram showing processing functions of a controller according to the third embodiment.

[Explanation of symbols]

1 prime mover (engine) 2 hydraulic pump 2a Displacement variable member (swash plate) 2b Horsepower control actuator 3 discharge lines 4 arm cylinder 5,5A valve device 6 Control lever device 21 Center bypass section 22a, 22b Meter-in diaphragm 23a, 23b Meter-out aperture 31 Flow control valve 31e, 31f Pressure receiving part 32 center bypass line 33 tanks 34,35 actuator line 36 Operation lever 37 Command pilot pressure generator 38,39 Pilot line 41 branch line 42 meter-out control valve 42b Pressure receiving part 43 switching valve 43b Pressure receiving part 44,44A Signal pressure line 51,52 Pressure sensor 53 Controller 53a Solenoid current calculation unit 53b Control coefficient calculator 53c Multiplier 53d Solenoid current calculator 54 Proportional solenoid valve 55 Signal pressure line 100 running bodies 101 revolving structure 102 front working machine 103 boom 104 arm 105 buckets

Continued front page    F-term (reference) 2D003 AA01 AB03 AC09 BA01 BA05                       BB02 CA02 DA02 DA03 DA04                       DB02 FA02                 3H089 AA22 AA23 BB02 BB11 CC01                       DA03 DA13 DB12 DB33 DB47                       DB49 EE16 EE31 EE36 FF07                       GG02 JJ02

Claims (8)

[Claims] 1. A hydraulic pump, an actuator driven by pressure oil discharged from the hydraulic pump, and a flow rate control valve, wherein the flow rate control valve controls the pressure oil supplied from the hydraulic pump to the actuator. In a hydraulic control device for a construction machine having a meter-in throttle that controls a flow rate and a meter-out throttle that controls a flow rate of pressure oil returned from the actuator to the tank, an operation status detecting unit that detects an operation status of the actuator, A hydraulic control device for a construction machine, comprising: a meter-out control unit that releases a meter-out throttle of the flow control valve according to an operating state of the actuator. 2. The hydraulic control system for a construction machine according to claim 1, wherein the operation status detection means is a pressure detection means for detecting a drive pressure on the meter-in side of the actuator. Control device. 3. The hydraulic control device for a construction machine according to claim 1 or 2, wherein the meter-out control means is provided in a branch line that connects an upstream side of a meter-out throttle of the flow control valve to a tank. A hydraulic control device for a construction machine, comprising: a control valve; and a switching control means for switching the meter-out control means in an opening direction according to a detection result of the operation status detection means. 4. The hydraulic control device for a construction machine according to claim 3, wherein the meter-out control valve has a metering characteristic. 5. The hydraulic control device for a construction machine according to claim 3, wherein the meter-out control valve has a pressure receiving portion at an end portion on the operating side in the opening direction, and the switching control means controls the command pilot pressure of the actuator. A signal pressure line leading to the pressure receiving section and a switching valve arranged on the signal pressure line are provided, and the switching valve is switched according to the operating condition of the actuator to selectively supply a command pilot pressure to the pressure receiving section. A hydraulic control device for a construction machine characterized by leading. 6. A hydraulic control device for a construction machine according to claim 3, wherein the meter-out control valve has a pressure receiving portion at an end portion on the operating side in the opening direction, and the switching control means controls the command pilot pressure of the actuator. The pressure detecting means for detecting, the proportional solenoid valve for outputting a signal pressure to the pressure receiving portion, the detection signals of the operating condition detecting means and the pressure detecting means are inputted, predetermined arithmetic processing is performed, and the proportional solenoid valve is commanded. A hydraulic control device for a construction machine, comprising: a controller that outputs a current; and driving the proportional solenoid valve according to a calculation result of the controller to guide a signal pressure to the pressure receiving portion. 7. The hydraulic control device for a construction machine according to claim 3, wherein the meter-out control valve has a pressure receiving portion at an end portion on the opening direction operating side, and the switching control means includes a command pilot pressure of the actuator. A proportional solenoid valve that outputs a signal pressure to the pressure receiving portion as a primary pressure, and a controller that inputs a detection signal of the operating condition detection means, performs a predetermined arithmetic process, and outputs a command current to the proportional solenoid valve. A hydraulic control device for a construction machine, comprising: driving the proportional solenoid valve according to a calculation result of the controller to guide a signal pressure to the pressure receiving portion. 8. The hydraulic control device for a construction machine according to claim 1, wherein the actuator is an arm cylinder that drives an arm of a hydraulic excavator or a bucket cylinder that drives a bucket. Hydraulic control device for construction machinery.