JPH07331705A - Oil hydraulic circuit for turning of construction machine - Google Patents

Abstract

PURPOSE:To provide an effective means instead of a check valve having problems of pressure loss. as a means preventing generation of negative pressure in an oil hydraulic circuit at inertial turning of a hydraulic shovel. CONSTITUTION:A lever operation returning a turning changeover valve 7 to a neutral position is detected by neutral detecting sensors 26a, 26b, and rotation of a turning hydraulic motor 17 is detected by a rotating speed sensor 25. The detected signals are processed by a NOR logic element 27 and a AND logic element 28. and a condition in which an upper turning body is rotated by inertia even if a lever 20 is returned to the neutral position is detected. A controller 29 outputs control current corresponding to the inertial rotating speed detected by the sensor 25 to an electromagnetic proportional pressure reducing valve 30, and controls to restrict a variable flow metering valve 37 in response to the inertial rotating speed. As the metering valve 37 is restricted, the return oil from a directional control valve 5 is supplied to the negative pressure side of the hydraulic motor 17 so as to prevent generation of negative pressure due to inertial rotation. In the case of no inertial rotation, the valve 37 is in full opening condition so as to minimize pressure loss in a return oil passage 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swing hydraulic circuit for a construction machine, which prevents a vacuum pressure generated in the swing hydraulic circuit by inertial turning when the swing of a hydraulic excavator or the like is stopped.

[0002]

2. Description of the Related Art FIG. 5 shows a hydraulic circuit (partially omitted) of a conventional hydraulic excavator.

Hydraulic power source 1 driven by an in-vehicle engine
Is provided with a pair of main pumps 2a, 2b and a pilot pump 3 on a plurality of gear shafts, and swash plate control devices 4a, 4b are provided on a swash plate for controlling the discharge amount of the main pumps 2a, 2b.

Each pressure oil supply line drawn from the discharge ports of the main pumps 2a and 2b is connected to the direction control valve 5 and a similar parallel circuit (not shown), and is maintained at a set pressure by a main relief valve 41. . The directional control valve 5 corresponding to the one main pump 2a is composed of a traveling motor (left) switching valve 6, a swing motor switching valve 7 and a stick cylinder switching valve 8. The directional control valve (not shown) corresponding to the other main pump 2b includes a traveling motor (right) switching valve, a boom cylinder switching valve, and a bucket cylinder switching valve.

The oil discharge line of the directional control valve 5 comprises a return oil passage 23 and a return oil passage 24. The return oil passage 24 communicates with the oil tank 10 via the slow return check valve 15 and the oil cooler 9. .

The pilot line drawn out from the discharge port of the pilot pump 3 passes through a pilot relief valve 11 and communicates with a travel motor (left) operation valve 12, a swing motor operation valve 13 and a stick cylinder operation valve 14. Has been done. Each of these operation valves is provided with an operation lever. For example, the turning operation valve 13 has an operation lever 20
Is provided.

The output port of the swing switching valve 7 is connected to a swing motor circuit 16. This swing motor circuit 16
Is a turning hydraulic motor (hereinafter referred to as a turning motor) 17 for turning the upper turning body of the construction machine, and the turning motor.
Main oil passages 22a, 22b connected to the hydraulic ports at 17 doorways
And crossover relief valves 18a, 18b and check valves 19a, 19b provided between the main oil passages 22a, 22b. The drain oil inside the swing motor 17 is drain oil passage 36.
After that, drain to the oil tank 10.

A make-up line 21 is drawn from the swing motor circuit 16, and the make-up line 21 and the return oil passage 23 from the directional control valve 5 merge to form a main return oil passage 24. The passage 24 is connected to the oil tank 10 via the check valve 15 and the oil cooler 9.

Since the upper revolving structure (not shown) of the hydraulic excavator has a large inertia, when the operating lever 20 is returned to the neutral position when the revolving operation is stopped, it revolves by a considerable angle by inertia. When the operating lever 20 is in the neutral position, the turning switching valve 7 is in the neutral position (N), and the all ports are closed. Therefore, the main circuits 22a and 22b of the swing motor 17 are
Then, the supply and discharge of hydraulic oil are cut off at both the inlet port and the outlet port when the swing motor 17 is driven. The swing motor 17 is driven by an upper swing body that inertially swings due to inertia,
It acts as a pump and the outlet side becomes high pressure due to the hydraulic oil discharged into the closed circuit, and pushes open the check valves 19a and 19b through the crossover relief valve 18a or 18b to open the swing motor.
It flows into the entrance side of 17. However, the outlet side is high pressure,
The amount of oil flowing out to the drain oil passage 36 increases due to the leakage, and the amount of oil on the inlet side becomes insufficient by this amount, resulting in vacuum.

In the swing motor circuit 16, the makeup line 21 and the return oil passage 24 are provided between the check valves 19a and 19b provided between the main oil passages 22a and 22b connected to the inlet port and the outlet port of the swing motor 17, respectively. Since it is connected to the oil tank 10, if there is no slow return check valve 15 described later, the vacuum phenomenon is eliminated by a so-called prefill circuit that sucks the working oil of the oil tank 10 by the vacuum pressure of the inlet side circuit.

On the other hand, as shown in FIG. 5, the return oil passage 24 connected to the oil tank 10 is conventionally used to assist the suction of the hydraulic oil into the inlet side circuit of the swing motor 17 which is producing a vacuum pressure. Slow return check valve 15 in the middle of
Is provided, and the oil tank 10 is connected from the return oil passage 23 of the directional control valve 5.
To the return oil passage 24 by increasing the pressure difference between the inlet side circuit and the vacuum of the directional control valve 5.
The hydraulic oil is sent from the return oil passage 23 through the makeup line 21 to the inlet side circuit. From this,
The check valve 15 is called a "push check valve".

[0012]

However, the check valve 15 is provided in the main return oil passage 24 which merges with the return oil passage 23 of the directional control valve 5 to the oil tank 10, and is used in addition to the hydraulic excavator. Since the return hydraulic oil to the tank 10 when the actuator of is operated is in a position to flow through,
The cracking pressure is always generated. This always causes a pressure loss of only the cracking pressure, resulting in energy loss, which is also an undesirable problem.

The present invention has been made in view of the above circumstances, and as a means for preventing the generation of vacuum pressure in the swing hydraulic circuit due to inertial swing when the swing of a construction machine such as a hydraulic excavator is stopped, swing stop is performed. It is an object of the present invention to provide an effective means in place of a push-in check valve which has a problem of pressure loss and energy loss due to cracking pressure in cases other than time.

[0014]

According to a first aspect of the present invention, a turning hydraulic motor is driven by a hydraulic pressure supplied from a hydraulic source via a turning switching valve, and an upper turning body is provided with respect to a lower traveling body. In the swing hydraulic circuit of the construction machine to swing,
When stopping the turning hydraulic motor in the return oil passage on the downstream side where the makeup line of the turning hydraulic motor circuit is joined to the return oil passages from the plurality of directional control valves including the turning switching valve 1 is a swing hydraulic circuit of a construction machine having a variable throttle valve that is throttle-controlled by inertial rotation of an upper swing body.

According to a second aspect of the present invention, the turning of the construction machine is performed in which the turning hydraulic motor is driven by the hydraulic pressure supplied from the hydraulic source through the turning switching valve to turn the upper turning body with respect to the lower traveling body. In the hydraulic circuit, a variable throttle valve provided in the return oil passage on the downstream side where the make-up line of the turning hydraulic motor circuit is joined to the return oil passages from the plurality of directional control valves including the turning switching valve, A sensor for detecting inertial rotation due to inertia of the upper revolving structure when stopping the turning hydraulic motor, and a controller for receiving a throttle command to the variable throttle valve upon detection of inertial rotation by the sensor It is a swing hydraulic circuit of a construction machine.

According to a third aspect of the present invention, the turning of the construction machine is performed in which the turning hydraulic motor is driven by the hydraulic pressure supplied from the hydraulic power source through the turning switching valve to turn the upper turning body with respect to the lower traveling body. In the hydraulic circuit, a variable throttle valve provided in the return oil passage on the downstream side where the make-up line of the turning hydraulic motor circuit is joined to the return oil passages from the plurality of directional control valves including the turning switching valve, A neutral detection sensor that detects an operation of returning the turning switching valve to the neutral position, a rotation speed sensor that detects the rotation of the turning hydraulic motor, and a turning hydraulic pressure based on detection signals from the neutral detection sensor and the rotation speed sensor. A logic element circuit that detects inertial rotation due to inertia of the upper swing body when the motor is stopped, and the inertial rotation state detected by this logic element circuit In a swing hydraulic circuit of a construction machine configured to include a controller that outputs a control current value according to the inertial rotation speed and an electromagnetic proportional pressure reducing valve that gives a throttle command to the variable throttle valve according to the output from the controller. is there.

According to a fourth aspect of the present invention, the swing of the construction machine, in which the swing hydraulic motor is driven by the hydraulic pressure supplied from the hydraulic source through the swing switching valve to swing the upper swing body with respect to the lower traveling body. In the hydraulic circuit, a variable throttle valve provided in the return oil passage on the downstream side where the make-up line of the turning hydraulic motor circuit is joined to the return oil passages from the plurality of directional control valves including the turning switching valve, A inertial rotation sensor that detects inertial rotation due to inertia of the upper revolving superstructure when stopping the turning hydraulic motor, and a pressure that is inserted into a return oil passage upstream from the variable throttle valve to detect the pressure on the upstream side. A construction machine having a sensor, and a controller for receiving a detection of inertial rotation by the inertial rotation sensor and a detection of upstream pressure by the pressure sensor to give a throttle command to the variable throttle valve. Times is a hydraulic circuit.

[0018]

According to the first aspect of the present invention, the upper swing body is swung with respect to the lower traveling body by supplying pressure oil from the hydraulic source to the swing hydraulic motor through the swing switching valve. At this time, open the variable throttle valve to reduce the resistance of the return oil passage to the oil tank. When the turning hydraulic motor is stopped, the variable throttle valve is throttled by inertial rotation due to the inertia of the upper swing body, and the return oil from the directional control valve is passed through the makeup line to the negative pressure side of the turning hydraulic motor. To prevent the vacuum pressure generated in the swing hydraulic circuit due to the inertia swing of the upper swing body.

According to a second aspect of the present invention, the inertial rotation of the upper revolving superstructure when the turning hydraulic motor is stopped is detected by the sensor, and the variable throttle valve is throttled by the controller. The return oil is supplied to the negative pressure side of the turning hydraulic motor through the make-up line to prevent the vacuum pressure due to inertial turning.

According to the third aspect of the present invention, the neutral detection sensor detects the operation of returning the turning switching valve to the neutral position, and at the same time, the rotation of the turning hydraulic motor is detected by the rotation speed sensor. The signal is processed by the logic element circuit to detect inertial rotation due to inertia of the upper swing body when stopping the swing hydraulic motor. The controller receiving the detection of this inertial rotation state outputs a control current value corresponding to the inertial rotation speed detected from the rotation speed sensor to the electromagnetic proportional pressure reducing valve, and this electromagnetic proportional pressure reducing valve changes the variable throttle valve to the inertial rotational speed. According to the throttle control, the return oil from the directional control valve is replenished to the negative pressure side of the turning hydraulic motor through the make-up line to prevent the vacuum pressure due to the inertia turning.

According to a fourth aspect of the present invention, the pressure sensor detects the pressure in the return oil passage upstream of the variable throttle valve,
By controlling the throttle opening of the variable throttle valve via the controller by the pressure in the return oil passage, the throttle amount can be set according to the flow rate in the return oil passage. Normally, the pressure in the return oil passage is kept to a minimum, and when the pushing hydraulic pressure during inertial rotation is required, the opening of the variable throttle valve is reduced to obtain the proper pushing hydraulic pressure according to the rotation speed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention described in claims 1 to 3 will be described below with reference to the embodiments shown in FIGS. 1 and 2, and the invention described in claim 4 will be described in FIGS. 3 and 4. It will be described with reference to the embodiment.

FIG. 1 shows a swing hydraulic circuit (partially omitted) of a hydraulic excavator as a construction machine according to the present invention.
In FIG. 1, the same parts as those in the conventional example shown in FIG. 5 are designated by the same reference numerals and the description thereof will be omitted.

A rotation speed sensor 25, which outputs a positive level signal proportional to the rotation speed of the swing motor 17, is provided on the rotation axis of the swing hydraulic motor (hereinafter referred to as the swing motor) 17.

Below the turning operation lever 20, there are two neutral detection sensors which detect the operation of returning the operation lever 20 to the neutral position by detecting the movement of the operation lever 20 in the turning operation direction. Switches 26a and 26b are provided, and these switches 26a and 26b are connected to communication cables 33a and 33b.
And the ON / OFF signals of the switches 26a and 26b are input to the NOR logic element 27 via the input terminal of the NOR logic element 27.

This NOR logic element 27 receives (0,1) (1,0) when there is an input to at least one of the two input sections.
Outputs an ON signal when there is no output signal and there is no input to either of the two input sections (0, 0). That is, when the operation lever 20 is returned to the neutral position, the switch 26
Since the signals from a and 26b are (0,0), this NO
An ON signal is output from the R logic element 27.

The rotation speed sensor 25 is connected to one input of the AND logic element 28 via the communication cable 34, and the output of the NOR logic element 27 is connected to the AND logic element 28.
Connect to the other input of. Then, the signal from the rotation speed sensor 25 is processed as a binary signal of significant value or zero
The OFF signal is sent to the AND logic element 28 via the communication cable 34.
The output of the NOR logic element 27 is connected to one input side of
It is put in the other input side of the D logic element 28, respectively.

The output section of the AND logic element 28 and the communication cable 35 branched from the communication cable 34 of the rotation speed sensor 25 are connected to the input section of the controller 29, and the output section of the controller 29 is connected to the electromagnetic proportional pressure reducing valve 30. Connect to the control section (solenoid).

The rotation speed sensor 25 and the neutral detection sensor
Reference numerals 26a and 26b constitute inertial rotation sensors that detect inertial rotation due to inertia of the upper swing body when the swing operation lever 20 is returned to the neutral position and the swing hydraulic motor 17 is stopped.

When the operating lever 20 is neutral in the turning operation direction and the turning motor 17 inertially rotates due to the inertia of the upper turning body, the circuit of the AND logic element 28 is turned on.
Since the signal is output, the controller 29 receiving the ON signal is preset as shown in FIG. 2 based on the rotation speed level signal obtained from the rotation speed sensor 25 via the communication cables 34 and 35. The current value calculated by the functions 1 and 2 is output as a control signal for the electromagnetic proportional pressure reducing valve 30.

The primary side of the electromagnetic proportional pressure reducing valve 30 communicates with the pilot pump 3 via the oil passage 31, and the secondary side of the electromagnetic proportional pressure reducing valve 30 is provided in the return oil passage 24 via the oil passage 32. It communicates with the pilot pressure part of the variable throttle valve 37.

The electromagnetic proportional pressure reducing valve 30 has a pilot pressure introduced from the pilot pump 3 to the primary side, and receives a control signal from the controller 29 to detect a rotation speed sensor.
A pressure proportional to the level signal of 25 is output to the secondary side, and this output pressure is guided to the pilot pressure section of the variable throttle valve 37 via the oil passage 32.

Next, the operation of this embodiment will be described.

The pilot pressure generated by the pilot pump 3 and regulated to a constant pressure by the pilot relief valve 11 is introduced to the primary side of the electromagnetic proportional pressure reducing valve 30 through the oil passage 31. The operation lever 20 is provided with switches 26a and 26b for detecting a turning operation, which are turned on and off.
A signal is sent to the NOR logic element 27 through the communication cables 33a and 33b to determine whether or not the turning operation is being performed.

A rotation speed sensor 25 is attached to the swing motor 16 and outputs a positive level signal proportional to the rotation speed regardless of whether the rotation is normal or reverse. This level signal is processed as a significant value or zero ON / OFF signal, and is input to one of the inputs of the AND logic element 28 through the communication cable 34, and the output signal of the NOR logic element 27 is input to the other of the AND logic element 28. Put it in the input and judge.

As a result, in the logic element circuit composed of the above-mentioned logic elements 27 and 28, the turning motor 17 performs inertial rotation by the inertia of the upper turning body while the operating lever 20 is returned from the turning operation to the neutral position. While it is ON, the AND logic element 28 outputs an ON signal to the controller 29.

Next, the operation in the controller 29 including the above-mentioned logic element circuit will be shown by the flowchart of FIG. The circled numbers in this flowchart are step numbers indicating the processing procedure.

The step indicates the judgment made by the NOR logic element 27, and it is judged by the switches 26a and 26b whether the turning operation lever 20 is in the neutral state, that is, whether the turning switching valve 7 is in the neutral state. To be done.

The step shows the judgment made by the AND logic element 28, and only when the step is YES, the rotational speed sensor 25 provided in the turning motor 17 judges whether or not the upper revolving superstructure is inertially rotated.

In the step, when an output signal is output from the AND logic element 28 to the controller 29 as described above, a positive level signal proportional to the rotation speed detected by the rotation speed sensor 25 is transmitted through the communication cables 34 and 35 to the controller 29. Then, the pushing hydraulic pressure value with respect to the turning speed (coasting speed) is calculated based on the relationship of the function 1 which is set in advance based on the characteristics of the turning motor circuit 16, and this value is sent to the function 2 shown in the step.

In the step, the control current value to be given to the electromagnetic proportional pressure reducing valve 30 necessary for generating the predetermined pushing oil pressure is calculated by the function 2. The control current value is instructed by the controller 29, and the opening of the electromagnetic proportional pressure reducing valve 30 is determined as shown in step.

A constant pilot hydraulic pressure is introduced from the oil passage 31 to the primary side of the electromagnetic proportional pressure reducing valve 30 as described above, and is generated on the secondary side of the electromagnetic proportional pressure reducing valve 30 by the pressure reduction based on the opening degree. By adjusting the opening degree (throttle amount) of the variable throttle valve 37 by the pressure, the return oil from the return oil passage 23 is passed through the makeup line 21 to the vacuum generation side of the turning hydraulic circuit to a predetermined amount according to the inertia rotation speed. Supply as pushing oil pressure.

That is, even if the turning operation lever 20 is returned to the neutral position, the opening degree of the variable throttle valve 37 is set to the rotation speed of the turning motor 17 while the turning motor 17 is rotating by inertia of the upper turning body. Accordingly, the hydraulic pressure is controlled to be small so that the flow path resistance is large, so that the make-up line 21 is supplied with the pushing hydraulic pressure corresponding to the inertial rotation speed.

On the other hand, under other conditions (lever 20 is non-neutral, or swing motor 17 is non-rotating), variable throttle valve 37
Is set to the maximum, and the pressure loss and energy loss in the variable throttle valve 37 are suppressed to the minimum.

The embodiment based on FIG. 1 and FIG.
The rotation speed sensor 25 regardless of the flow rate (pressure) of the return oil passage 24
Since a corresponding throttle is added in relation to the number of revolutions detected in, when the flow rate of the return oil passage 24 is high, the throttle will be excessively throttled.
The pushing hydraulic pressure may be too high. Therefore, the throttle amount must be set so as to be equal to or lower than the allowable pressure at the expected maximum flow rate, and therefore, when the flow rate is low, a sufficient pushing hydraulic pressure may not be obtained.

Therefore, in the embodiment shown in FIG. 3, the pressure sensor 38 is provided in the return oil passage 24 upstream of the variable throttle valve 37.
The pressure sensor 38 detects the return oil passage pressure on the upstream side of the variable throttle valve 37, and the pressure sensor 38
By connecting the output part of the controller 29 to the input part of the controller 29 by the signal cable 39 and inputting the pressure information of the return oil passage 24 detected by the pressure sensor 38 to the controller 29 for controlling the variable throttle valve, The throttle opening of the throttle valve 37 is controlled to a throttle amount according to the flow rate (pressure) of the return oil passage 24. In addition,
The embodiment shown in FIG. 3 is different from the embodiment shown in FIG. 1 only in that the pressure sensor 38 is added, and the other parts are the same, so the illustration and description of the other parts will be omitted. Omit it.

FIG. 4 is a flow chart showing a processing procedure in the controller 29 of FIG. It is determined whether or not (step 11), and in such a normal state (NO in step 11), the opening of the variable throttle valve 37 is controlled to be fully opened to minimize the pressure in the return oil passage 24. Try to keep it (step 12).

On the other hand, during inertial rotation (YES in step 11), the return oil passage 24 needs a pushing oil pressure, but the pressure in the return oil passage 24 detected by the pressure sensor 38 is larger than the required pushing oil pressure. At this time (YES in step 13), the opening of the variable throttle valve 37 is increased to reduce the throttle pressure of the return oil passage 24 to the required pushing oil pressure (step 14).

The return oil passage 24 detected by the pressure sensor 38
Is less than the required pushing oil pressure (NO in step 13
In the case of), the opening of the variable throttle valve 37 is throttled to raise the throttle pressure of the return oil passage 24 to the required pushing oil pressure (step
15).

In this way, normally, the pressure in the return oil passage 24 is kept to a minimum (throttle fully opened), and when a required pushing oil pressure is required in the return oil passage 24, such as during inertial rotation, Not only the rotation speed of the upper revolving structure but also the pressure in the return oil passage 24 is detected,
Since the throttle opening of the variable throttle valve 37 is controlled, an appropriate pushing hydraulic pressure can be supplied to the makeup line 21.

The inventions of claims 2 and 4 are
The variable throttle valve 37 may be directly controlled by an electric signal output from the controller 29. In that case, the variable throttle valve 37 uses an electromagnetic actuation type.

[0052]

According to the invention as set forth in claim 1, the variable throttle is provided only when the turning hydraulic valve circuit causes a vacuum in the turning hydraulic motor circuit due to inertial rotation due to inertia of the upper turning body during the turning stop operation of the turning switching valve. The throttle valve is controlled to supply the required pushing oil pressure to the negative pressure side of the swing hydraulic motor from the return oil passage from the directional control valve through the make-up line, preventing the occurrence of vacuum pressure due to inertial swing of the upper swing structure. In addition to that, the variable throttle valve can be opened to minimize the resistance of the return oil passage to the oil tank when this is not the case (when the rotation is not stopped), so the return oil passage can be reduced when the conventional push-in check valve is used. Since the pressure loss due to the cracking pressure that has always been generated in 1 is eliminated, energy loss can be avoided. Further, by thus restricting the variable throttle valve only during inertial rotation and supplying a more appropriate hydraulic pressure than the conventional natural suction method, it is possible to effectively prevent the occurrence of vacuum.
A smooth turning stop operation can be obtained.

According to the second aspect of the invention, the inertial rotation due to the inertia of the upper swing body is detected by the sensor, and the throttle of the variable throttle valve can be appropriately controlled by the controller.

According to the third aspect of the present invention, the neutral rotation sensor, the rotation speed sensor and the logic element circuit can accurately detect the inertial rotation state due to the inertia of the upper swing body, and the controller responds to the inertial rotation speed. The control current value is output to the electromagnetic proportional pressure reducing valve, and the variable throttle valve is throttle-controlled according to the inertia rotation speed by this electromagnetic proportional pressure reducing valve.
The return oil from the directional control valve can be replenished to the negative pressure side of the turning hydraulic motor according to the inertia rotation speed, and the vacuum pressure can be appropriately canceled according to the inertia rotation speed.

According to the fourth aspect of the present invention, a pressure sensor is inserted into the return oil passage upstream of the variable throttle valve, and the controller changes the variable throttle valve based on the upstream pressure detected by the pressure sensor. Since the throttle command is given, normally, the throttle amount is fully opened to minimize the pressure loss, and when braking to brake inertial rotation, the throttle amount can be set according to the return oil amount, so it is optimal. Pushing hydraulic pressure is obtained. It is also possible to prevent the equipment from being damaged due to excessive pushing oil pressure.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a swing hydraulic circuit according to the invention described in claims 1 to 3. FIG.

FIG. 2 is a flowchart showing a processing procedure of a pushing hydraulic pressure control system for the turning hydraulic circuit.

FIG. 3 is a partial circuit diagram showing an embodiment of a swing hydraulic circuit according to the invention described in claim 4.

FIG. 4 is a flowchart showing a processing procedure in the controller shown in FIG.

FIG. 5 is a circuit diagram showing a swing hydraulic circuit of a conventional construction machine.

[Explanation of symbols]

 1 Hydraulic power source 5 Directional control valve 7 Turning switching valve 10 Oil tank 17 Turning hydraulic motor (swing motor) 21 Makeup line 23 Return oil passage 24 Return oil passage 25 Rotation speed sensor 26a, 26b Switch as neutral detection sensor 27 NOR logic element 28 AND logic element 29 Controller 30 Electromagnetic proportional pressure reducing valve 37 Variable throttle valve 38 Pressure sensor

Claims (4)

[Claims] 1. A swing hydraulic circuit of a construction machine, wherein a swing hydraulic motor is driven by a hydraulic pressure supplied from a hydraulic source through a swing switching valve to swing an upper swing body with respect to a lower traveling body. An upper swing body for stopping the swing hydraulic motor in the downstream return oil passage where the make-up line of the swing hydraulic motor circuit is joined to the return oil passages from the plurality of directional control valves including the switching valve A swing hydraulic circuit for a construction machine, which is provided with a variable throttle valve that is throttle-controlled by inertial rotation due to inertia of the. 2. A swing hydraulic circuit of a construction machine, wherein a swing hydraulic motor is driven by a hydraulic pressure supplied from a hydraulic source through a swing switching valve to swing an upper swing body with respect to a lower traveling body. A variable throttle valve provided in the return oil passage on the downstream side where the make-up line of the turning hydraulic motor circuit is joined to the return oil passages from the plurality of directional control valves including the switching valve, and the turning hydraulic motor is stopped. An inertial rotation sensor that detects inertial rotation due to inertia of the upper revolving structure when the rotation is performed, and a controller that receives the inertial rotation detection by the inertial rotation sensor and gives a throttle command to the variable throttle valve. Swing hydraulic circuit of construction machinery. 3. A swing hydraulic circuit of a construction machine for driving a swing hydraulic motor by a hydraulic pressure supplied from a hydraulic source through a swing switching valve to swing an upper swing body with respect to a lower traveling body. A variable throttle valve provided in the return oil passage on the downstream side where the make-up line of the turning hydraulic motor circuit is joined to the return oil passages from the plurality of directional control valves including the switching valve, and the turning switching valve is neutral. A neutral detection sensor that detects an operation of returning to a position and a rotation speed sensor that detects the rotation of the turning hydraulic motor, and an upper portion when the turning hydraulic motor is stopped by detection signals from the neutral detection sensor and the rotation speed sensor. A logic element circuit that detects inertial rotation due to inertia of the revolving structure, and a inertial rotation speed detected by the rotation speed sensor in response to detection of an inertial rotation state by the logic element circuit. A controller for outputting a control current value, turning hydraulic circuit for a construction machine characterized by comprising an electromagnetic proportional pressure reducing valve that gives a command throttle the variable throttle valve in accordance with an output from this controller. 4. A swing hydraulic circuit of a construction machine, wherein a hydraulic motor for swing is driven by a hydraulic pressure supplied from a hydraulic source through a swing switching valve to swing an upper swing body with respect to a lower traveling body. A variable throttle valve provided in the return oil passage on the downstream side where the make-up line of the turning hydraulic motor circuit is joined to the return oil passages from the plurality of directional control valves including the switching valve, and the turning hydraulic motor is stopped. An inertial rotation sensor that detects inertial rotation due to inertia of the upper revolving structure when it is caused to move, a pressure sensor that is inserted into a return oil passage on the upstream side of the variable throttle valve to detect pressure on the upstream side, and the inertial rotation sensor. And a controller for giving a throttle command to the variable throttle valve in response to detection of inertial rotation by the pressure sensor and detection of upstream pressure by the pressure sensor. .