JPH078360Y2 - Running control circuit for construction machinery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention is provided in a construction machine such as a hydraulic excavator, and is suitable for use in driving and controlling a variable displacement hydraulic motor for traveling. Related to the traveling control circuit.

[Conventional technology]

Generally, in a traveling hydraulic motor such as a hydraulic excavator, when the load is small or when traveling on a level ground, there is a demand for high torque traveling, but a small torque is required.In this case, reduce the capacity of the hydraulic motor. Corresponding with high speed rotation. On the other hand, when climbing a slope or loading cargo, the traveling speed may be slow, but there is a demand for a large torque. In this case, the hydraulic motor is switched to a large capacity to cope with it.

Therefore, FIG. 6 shows a travel control circuit of a hydraulic excavator according to this type of prior art.

In FIG. 6, "A" is attached to the left traveling device element, and "B" is attached to the right traveling device element. In FIG. 6, 1A and 1B are left portions provided on the lower traveling body. , The right hydraulic motor for traveling, the hydraulic motors 1A and 1B are, for example, swash plate type and swash shaft type variable displacement hydraulic motors, and the displacement variable parts 2A and 2B such as the swash plate and the valve plate are tilted. By driving it, the motor capacity can be made variable. 3A and 3B are servo actuators attached to the hydraulic motors 1A and 1B.
For example, a servo cylinder mechanism is used as A and 3B, and by displacing in the X direction indicated by the arrow, the hydraulic motors 1A and 1B are rotated at low torque and high speed with a small capacity, and are displaced in the Y direction indicated by the arrow. The motors 1A and 1B have a large capacity to rotate at high torque and low speed. Reference numerals 4A and 4B denote brake devices including negative brakes attached to the hydraulic motors 1A and 1B.

5 is a variable displacement hydraulic pump that is provided on the upper revolving structure side and is driven by a prime mover 6 such as an engine, 7 is a tank, and the left hydraulic motor 1A is a hydraulic pump via main pipelines 8, 9, 10A, 11A. Connected to the pump 5 and the tank 7, the hydraulic motor 1B on the right side is connected to the hydraulic pump 5 and the tank 7 through the main pipes 8, 9, 10B and 11B, and the main pipes 10A, 10B, 11A and 11B are turned. A center joint 12 provided in the device divides the upper revolving structure side and the lower traveling structure side. 13 is the main pipeline
8 and 9 show a control valve provided between the main pipes 10A, 10B, 11A and 11B on the upper revolving structure side, and the control valve 13 is provided by an operating lever (not shown) provided in the operator's cab. It is operated to control the flow rate of the pressure oil supplied from the hydraulic pump 5 to the hydraulic motors 1A and 1B, and to control the rotation direction of the hydraulic motors 1A and 1B to move the hydraulic excavator forward, backward and stop. .

14A, 14B are located on the undercarriage side, and main pipelines 10A, 10B, 11A,
Shows a shuttle valve as a high-pressure selection valve provided between 11B, the shuttle valve 14A, 14B, among the pressure oil flowing in the main pipeline 10A, 10B, 11A, 11B of the hydraulic motor 1A, 1B on the high pressure side. Select the driving pressure and lead it into the brake lines 15A, 15B,
This is supplied to the brake devices 4A and 4B as brake release pressure. 16A and 16B are located between the hydraulic motors 1A and 1B and the shuttle valves 14A and 14B, and the main pipelines 10A, 10B, 11A and 1
The brake valve provided in the middle of 1B is shown.

17A, 17B are shuttle valves as other high pressure selection valves provided between the hydraulic motors 1A, 1B and the brake valves 16A, 16B and provided between the main pipelines 10A, 10B, 11A, 11B. Valve 17
A, 17B selects the pressure oil on the high pressure side like the shuttle valves 14A, 14B, and guides this pressure oil to the servo actuators 3A, 3B via the capacity control valves 18A, 18B described later. There is. 18A and 18B are displacement control valves attached to the hydraulic motors 1A and 1B, respectively, in order to supply the driving pressure to the servo actuators 3A and 3B, and the displacement control valves 18A and 18B are arranged so that the spring and the hydraulic pilot portion are opposed to each other. A 4-port 2-position spool switching valve of spring offset / hydraulic pilot type is used, and is switched between a large capacity constant large capacity position (a) and a small capacity constant small capacity position (b) by a pilot pressure described later.

Reference numeral 19 denotes a pilot pump driven by the prime mover 6 together with the hydraulic pump 5, and the pilot pump 19 is connected to the hydraulic pilot portions of the capacity control valves 18A, 18B via control pipelines 20, 20A, 20B, and these It is designed to supply pilot pressure. 21 is located on the side of the upper revolving structure and is a control line
20 shows a switching valve provided in the middle of 20. The switching valve 21 is switched to the switching positions (a) and (b) by the operating lever in the operator's cab, and the pilot pressure is brought to the tank pressure state at the switching position (a). At the switching position (B), the pilot pressure is increased to the set pressure P _A by the relief valve 22.
Here, the displacement control valves 18A, 18B are normally urged to a large displacement position (a) by a spring to displace the servo actuators 3A, 3B in the Y direction shown by the arrow, and the pilot pressure is changed to the displacement control valves 18A, 18B. Switching pressure P _B (P _B <P _B <
P _A ) or more, switch to the small capacity position (b),
The servo actuators 3A and 3B are displaced in the X direction shown by the arrow.

Further, 23A and 23B are motor assemblies showing the whole of the traveling motor assembly, and the motor assemblies 23A and 23B are configured with a range enclosed in the drawing.

In the traveling control circuit of the hydraulic excavator configured as described above, it is assumed that the control valve 13 is switched to a desired switching position in order to drive the hydraulic excavator. Now, looking at the traveling circuit on the left side, the pressure oil from the hydraulic pump 5 is supplied to the main pipeline 10
Of A and 11A, for example, the main joint 10A to the center joint 1
2, supplied to the hydraulic motor 1A via the brake valve 16A, the return oil is the main pipe line 11A, the brake valve 16A, the center joint 1
2. Returned to the tank 7 via the control valve 13 and the hydraulic motor 1A
To rotate. On the other hand, the same applies to the traveling circuit on the right side. At this time, the pressure oil flowing in the main pipelines 10A, 10B on the high pressure side is supplied from the shuttle valves 14A, 14B to the brake devices 4A, 4B via the brake pipelines 15A, 15B to release the brakes.

Further, when the switching valve 21 is set to the switching position (a) as shown in the figure, the pilot pressures in the control lines 20A and 20B are in the tank pressure state, so the capacity control valves 18A and 18B are in the large capacity position (as shown). B) The hydraulic motors 1A and 1B are kept in a large capacity and are rotated at a low speed with a high torque. When the switching valve 21 is switched to the switching position (b), the pilot pressure in the control lines 20A, 20B is increased to the set pressure P _A of the relief valve 22,
The set pressure P _A displacement control valve 18A, since higher than 18B of switching pressure P _B, capacitive control valve 18A, 18B is switched to the small volume position (b), the hydraulic motor 1A, and 1B and small volume constant , Rotate at high speed with low torque.

[Problems to be solved by the device]

By the way, in the above-mentioned conventional technique, the drive pressure of the hydraulic motors 1A and 1B is guided to the brake devices 4A and 4B as the brake release pressure via the shuttle valves 14A and 14B and the brake lines 15A and 15B. When the drive pressure of 1A, 1B increases depending on the load when climbing a slope, the brake release pressure also increases correspondingly. However, the braking device 4
Since brakes A and 4B need to be released before the hydraulic motors 1A and 1B are activated, the brake release pressure is set to a low pressure of, for example, about 15 kg / cm ² .

Therefore, in the related art, it is necessary to increase the pressure resistance of the brake devices 4A and 4B in an extra amount, which causes a problem that the brake devices 4A and 4B become large in size and heavy in weight, resulting in an increase in cost.

Further, since the capacity of the hydraulic motors 1A and 1B is switched from a large capacity to a small capacity by manually operating the switching valve 21, for example, when the hydraulic excavator is run in a place with many ups and downs, the switching valve There is a problem that the manual operation becomes troublesome because the manual operation must be switched from the large capacity to the small capacity and from the small capacity to the large capacity by repeating the manual operation 21.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention can automatically switch the motor capacity according to the load during traveling, improve the operability and stability, and further, the braking device. The present invention provides a traveling control circuit for a construction machine, which can be reduced in size and weight and can be reduced in cost.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention provides a variable displacement traveling hydraulic motor having a variable displacement portion, a servo actuator for driving the variable displacement portion of the hydraulic motor, and a pilot pressure supplied to the hydraulic pilot portion. A capacity control valve for switching and controlling pressure oil supplied to the servo actuator according to the above, a brake device for braking the hydraulic motor when the rotation of the hydraulic motor is stopped, and a connection between the hydraulic motor and the hydraulic pump. A main pipeline, a control valve provided in the middle of the main pipeline to control the flow rate of the pressure oil supplied from the hydraulic pump to the hydraulic motor, and to control the rotation direction of the hydraulic motor, and a pilot pressure from the pilot pump. A control line connecting between a hydraulic pilot section of the displacement control valve and a pilot pump for switching control of the displacement control valve by It applies the driving control circuit for a construction machine comprising a.

The features of the configuration adopted by the present invention are a first signal generator that outputs a signal corresponding to the driving pressure of the hydraulic motor, and a second signal generator that outputs a signal corresponding to the operating state of the control valve. A solenoid valve that is provided between the generator and the hydraulic pilot section of the displacement control valve and the pilot pump, is provided in the middle of the control line, and switches the pilot pressure in at least three stages; A brake line connected to the control line between the hydraulic pilot portion of the control valve and supplying pilot pressure from the pilot pump to the brake device as a brake release pressure, and the first and second signal generations. A controller that outputs a control signal to the solenoid valve to switch and control the solenoid valve based on a signal from the controller. A first stage pressure value lower than the brake release pressure of the brake device, and a second stage pressure value higher than the brake release pressure of the brake device and lower than the set pressure of the displacement control valve; It is configured to selectively switch to the pressure value of the third stage which is higher than the set pressure of the displacement control valve.

[Action]

With the above configuration, the controller generates the pilot pressure by the solenoid valve based on the signals from the first and second signal generators.
At least the first stage pressure value, the second stage pressure value, or the third stage pressure value is selectively switched.
Based on the signal from the second signal generator (the driving pressure of the hydraulic motor and the operating state of the control valve), the braking by the brake device can be automatically released, and the capacity of the hydraulic motor can be automatically switched and controlled. .

That is, when the control valve is in the neutral position and the hydraulic motor is stopped, the controller controls the switching of the solenoid valve based on the signals from the first and second signal generators, and the pilot pressure by the solenoid valve is controlled. Can be switched to the first stage pressure value. Since the pressure value in the first stage is lower than the brake release pressure of the brake device,
In this case, braking can be applied to the hydraulic motor by the brake device, and the hydraulic motor can be held in a stopped state.

Further, when the control valve is finely operated and the hydraulic motor is driven to rotate at a low speed, the controller controls the switching of the solenoid valve based on the signals from the first and second signal generators, and the solenoid valve is controlled. The pilot pressure can be switched to the second stage pressure value. Since the second stage pressure value is higher than the brake release pressure of the brake device and lower than the set pressure of the displacement control valve, in this case, the braking of the hydraulic motor by the brake device can be automatically released. By making the motor capacity of the motor large, for example, the hydraulic motor can be rotated at a relatively slow speed.

Further, when the control valve is largely operated and the driving pressure of the hydraulic motor is in a relatively low pressure state, the pilot pressure by the solenoid valve is switched to a third stage pressure value higher than the set pressure of the displacement control valve. As a result, the motor capacity can be automatically switched to the smaller capacity side, and the hydraulic motor can be rotated at a high speed with a small torque. On the other hand, when the driving pressure of the hydraulic motor becomes a high pressure state, the motor capacity can be automatically switched to the large capacity side by switching the pilot pressure by the solenoid valve to the pressure value of the second stage,
It is possible to rotate the hydraulic motor with a large torque at a low speed.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. In the embodiment, the same components as those of the prior art shown in FIG. 6 described above are designated by the same reference numerals and the description thereof will be omitted.

1 to 4 show the first embodiment of the present invention.

In the figure, 31 indicates a pressure sensor as a first signal generator that outputs a signal corresponding to the driving pressure of the hydraulic motors 1A and 1B. The pressure sensor 31 is located between the hydraulic pump 5 and the control valve 13. Then, it is provided in the middle of the main pipe line 8 and detects the pressure of the pressure oil discharged from the hydraulic pump 5 as a driving pressure and outputs a signal P corresponding to this. Reference numeral 32 denotes a position sensor as a second signal generator that outputs a signal corresponding to the operating state of the control valve 13, and the position sensor 32 is provided at one end side of the control valve 13 or the like, for example, the spool of the control valve 13. The position is detected as the stroke of this spool, and a signal S corresponding to this is output to the controller 38 described later.

Reference numeral 33 denotes an electromagnetic valve located on the upper revolving structure side and provided in the middle of the control line 20. The electromagnetic valve 33 has solenoids 34 and 35 on both left and right ends, and the solenoids 34 and 35 are controlled by the controller. 38
It is possible to switch from the neutral position (a) to the left and right switching positions (b) and (c) by exciting and deactivating the control signal from.

Here, when the solenoid valve 33 is placed in the neutral position (a), the pilot pressure in the control lines 20, 20A, 20B is brought to the tank pressure state as the pressure value of the first stage. Also, the solenoid valve
When the switch 33 is switched to the switching position (b), the pilot pressure from the pilot pump 19 is reduced by the pressure reducing valve 36, and this pilot pressure is switched to the switching pressure P _{B of the} capacity control valves 18A, 18B.
It is set to a set pressure P _C (P _B > P _C > P _D ) as a second-stage pressure value that is lower than the brake release pressure P _D described later (see FIGS. 2 and 3). Then, the solenoid valve 33 raises the pilot pressure to the set pressure P _A (P _A > P _B ) of the relief valve 22 as the pressure value of the third stage at the switching position (C), and the capacity control valves 18A and 18B are increased. The capacity position (a) is switched to the small capacity position (b).

Further, 37A and 37B indicate brake lines connected to the control lines 20A and 20B between the solenoid valve 33 and the hydraulic pilot portions of the displacement control valves 18A and 18B, and the brake lines 37A and 37B are pilot pumps. The pilot pressure supplied from 19 via the control lines 20A, 20B, etc. is applied to the brake devices 4A, 4B, and the braking force applied from the brake devices 4A, 4B to the hydraulic motors 1A, 1B is applied to the hydraulic motors 1A, 1B. It is designed to be released when 1B is activated. Here, the brake release pressure P _{D of the} brake devices 4A and 4B is lower than the set pressures P _A and P _C , for example, set to about 15 kg / cm ² , and the solenoid valve 33 is switched from the neutral position (a). The braking force is released when the position is changed to (b) or (c).

Further, 38 indicates a controller constituted by a microcomputer or the like, the controller 38 has an input side connected to the pressure sensor 31, the position sensor 32, etc., an output side connected to the solenoid 34, 35 of the solenoid valve 33, as a power source. Is connected to a battery (not shown) as a DC power source. Then, the controller 38 has a fourth memory in its memory circuit.
The program shown in the figure is stored, and switching control processing of the solenoid valve 33 is performed by outputting a control signal to the solenoids 34 and 35 based on the signals P and S from the pressure sensor 31 and the position sensor 32. There is. In the storage area 38A of the controller 38, the stroke amount S ₁ (second stroke) for determining whether the operating state of the control valve 13 (spool stroke amount) is within the play (dead zone) range. (See the figure), and the stroke amount S ₂ for determining whether the control valve 13 exceeds the fine operation region and is in the operation region close to the full state, and the drive pressure of the hydraulic motors 1A and 1B is at a predetermined high pressure level. The pressure value P ₁ (see FIG. 3) for determining whether or not the pressure is exceeded is stored.

The traveling control circuit of the hydraulic excavator according to the present embodiment has the above-mentioned configuration, and its basic operation is not particularly different from that of the prior art.

Therefore, the control processing operation by the controller 38 will be described with reference to FIGS.

First, when the processing operation is started, the signal S from the position sensor 32 is read in step 1 and this signal S is read in step 2.
Is greater than the stroke amount S _1, and when it is determined to be “NO”, the operating state of the control valve 13 is within the play range, so the process proceeds to step 3 and the solenoids 34, 3 of the solenoid valve 33 are moved.
Demagnetize 5 and put it in the neutral position (a), and control lines 20A, 20B,
The pilot pressure in the brake lines 37A, 37B is set to the tank pressure state, the capacity control valves 18A, 18B are held in the large capacity position (a), and the hydraulic motors 1A, 1B are set by the brake devices 4A, 4B.
Apply braking force to. This ensures safety when an operator accidentally touches the operation lever of the control valve 13 or shakes the operation lever due to vibration or the like, and prevents malfunction.

Further, when it is determined to be "YES" in step 2, the control valve 1
Since 3 is operating beyond the stroke amount S ₁ , it proceeds to step 4 to determine whether the signal S exceeds the stroke amount S _2, and when it is determined to be "NO", the control valve 13 is finely operated. Since it is in the state, the process proceeds to step 5 to excite the solenoid 34 of the solenoid valve 33 to demagnetize the solenoid 35 and switch the solenoid valve 33 to the switching position (b) to set the pilot pressure to the set pressure P _C by the pressure reducing valve 36. Brake device 4
Release the braking force of hydraulic motors 1A and 1B by A and 4B. In this state, the pilot pressure becomes the set pressure P _C and the capacity control valve
Since it is lower than the switching valves P _B (P _B > P _C ) of 18A and 18B, the capacity control valves 18A and 18B are held in the large capacity position (a). In this case, since the control valve 13 is in a state of squeezing the pressure oil from the hydraulic pump 5 to rotate the hydraulic motors 1A, 1B,
By keeping 1B having a large capacity and constantly rotating at a low speed and a high torque, it is suitable, for example, for slowly and safely traveling on a narrow road or for mounting a hydraulic excavator on a trailer or the like.

Further, when it is determined to be "YES" in step 4, the control valve 1
Since 3 exceeds the stroke amount S ₂ and is operating in a state close to full operation (including full operation), the process moves to step 6 and the signal P from the pressure sensor 31 is read, and in step 7, the hydraulic pressure based on this signal P is read. It is determined whether or not the drive pressure (load pressure) of the motors 1A and 1B is lower than a predetermined pressure P _1, and when the determination is “YES”, the drive pressure is relatively low and the load acting on the hydraulic excavator is low. Since it is small and can be run at high speed on flat ground, for example, the process moves to step 8 to demagnetize the solenoid 34 of the solenoid valve 33 to excite the solenoid 35 and switch the solenoid valve 33 to the switching position (c). As a result, the pilot pressure is increased to the set pressure P _A of the relief valve 22, so that the displacement control valves 18A, 18B are switched to the small displacement position (b), and the hydraulic motors 1A, 1B can be controlled to a constant small displacement, and the low displacement can be controlled. It can be rotated at high speed with torque.

Then, when it is determined to be "NO" in step 7, the drive pressure becomes equal to or higher than the pressure value P _1, and the load acting on the hydraulic excavator is increased, for example, when climbing a slope. Therefore, the process proceeds to step 9 and the solenoid valve 33 is stepped. Switch to the switching position (B) in the same manner as in 5, and lower the pilot pressure to the set pressure P _C as shown in FIGS. 3 (A) and (B) to set the hydraulic motors 1A, 1B to a large capacity,
Rotate with high torque at a low speed so that you can climb uphill smoothly.

Thus, in the present embodiment, the solenoid valve 33 is provided in the middle of the control line 20, and the solenoid valve 33 is operated by the controller 38 so that the pressure sensor 31,
The signals P and S from the position sensor 32 control the switching from the neutral position (a) to the switching positions (b) and (c), and connect the brake conduits 37A and 37B to the downstream sides of the control conduits 20A and 20B. Then, since the pilot pressure of the pilot pump 19 and the like is supplied to the brake devices 4A, 4B as brake release pressure, the brake devices 4A, 4B can be operated at a pilot pressure significantly lower than the driving pressure, Brake device 4
It is possible to reduce the size and weight of A and 4B, and to reduce the cost by designing the pressure resistance to be low pressure.

In addition, the solenoid valve 33 is switched to the switching position (b) according to the driving pressure or the like.
Since it can be automatically switched to (c), the capacity of the hydraulic motors 1A and 1B can be automatically switched and controlled according to the load of the hydraulic excavator, and it is not necessary to repeat the operation of the operation lever as in the prior art, and operability is improved. Can be improved. And the control line 20
Since it is possible to release the braking force by the braking device 4A, 4B and switch the motor capacity with the pilot pressure from A, 20B,
For example, the left and right hydraulic motors 1A and 1B can be prevented from causing a meandering or the like due to a speed difference at the time of capacity switching, and various effects such as stable traveling can be realized.

Next, FIG. 5 shows a second embodiment of the present invention. In this embodiment, the same components as those of the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. The feature of this embodiment is that the branch pipelines 41A, 41B branched from the control pipelines 20A, 20B are connected to the inlet side ports of the capacity control valves 18A, 18B, and the control pipeline 2
The configuration is such that the servo actuators 3A, 3B are operated by the pilot pressure from 0A, 20B via the branch pipes 41A, 41B and the capacity control valves 18A, 18B.

Thus, in this embodiment having such a structure, it is possible to obtain substantially the same operational effects as those of the first embodiment.

In each of the above embodiments, the pressure sensor 31 is used to detect the driving pressure of the hydraulic pressure sensors 1A and 1B, and the corresponding signal P is detected.
However, instead of this, a tilt angle sensor that detects the tilt angle of the variable displacement hydraulic pump 5 may be used as the first signal generator. In case of hydraulic pump 5
Since the discharge amount of is controlled by changing the tilt angle,
The tilt angle signal can be output as a signal corresponding to the driving pressure.

Further, in each of the above embodiments, the position sensor 32 is used to control the valve.
Although it has been described that the operation state of 13 is detected, in place of this, the operation lever of the control valve 13 is provided with a detector for detecting the operation amount of this operation lever to form the second signal generator. Alternatively, when the control valve 13 is composed of a hydraulic pilot type directional control valve or the like, the second signal generator may be composed by detecting this pilot pressure with a pressure sensor or the like.

Furthermore, in each of the above-described embodiments, the hydraulic excavator has been described as an example, but the present invention is not limited to this, and can be applied to other construction machines having a traveling hydraulic motor such as a hydraulic crane.

[Effect of device]

As described above in detail, according to the present invention, the controller controls the switching of the solenoid valve based on the signals from the first and second signal generators (the driving pressure of the hydraulic motor and the operating state of the control valve).
Since the pilot pressure by the solenoid valve is selectively switched to at least the first-stage pressure value, the second-stage pressure value, or the third-stage pressure value, braking by the brake device is automatically performed by this pilot pressure. Therefore, the pressure resistance of the brake device can be designed to be low pressure, and the brake device can be reduced in size and weight.

Further, the controller controls the switching of the solenoid valve based on the signals from the first and second signal generators, so that the displacement of the hydraulic motor is automatically adjusted according to the driving pressure of the hydraulic motor and the operating state of the control valve. It is possible to perform various switching effects, and it is possible to surely improve operability and stability during traveling, and various effects are achieved.

[Brief description of drawings]

1 to 4 show a first embodiment of the present invention, and FIG. 1 is a travel control circuit diagram of a hydraulic excavator, FIG. 2 (a),
(B) is a characteristic diagram of the motor capacity and pilot pressure with respect to the stroke of the control valve, FIGS. 3 (a) and (b) are characteristic diagrams of the motor capacity and pilot pressure with respect to the driving pressure of the hydraulic motor, and FIG. 4 is FIG. 5 is a flow chart showing a solenoid valve switching control process, FIG. 5 is a travel control circuit diagram of a hydraulic excavator showing a second embodiment, and FIG. 6 is a travel control circuit diagram of a hydraulic excavator showing a conventional technique. 1A, 1B …… hydraulic motor, 3A, 3B servo actuator, 4
A, 4B brake device, 5 ... hydraulic pump, 6 ... prime mover,
7 ... Tank, 8,9,10A, 10B, 11A, 11B ... Main pipeline, 13 ...
… Control valve, 18A, 18B… Capacity control valve, 19… Pilot pump, 20, 20A, 20B… Control line, 22… Relief valve,
31 ... Pressure sensor (first signal generator), 32 ... Position sensor (second signal generator), 33 ... Solenoid valve, 36 ... Pressure reducing valve, 37A, 37B ... Brake pipeline, 38 ...... Controller, 4
1A, 41B …… Branch pipeline.

Claims (1)

[Scope of utility model registration request] 1. A variable displacement traveling hydraulic motor having a variable displacement portion, a servo actuator for driving the variable displacement portion of the hydraulic motor, and a servo actuator for the servo actuator according to pilot pressure supplied to a hydraulic pilot portion. A capacity control valve for switching and controlling the pressure oil to be supplied, a brake device for braking the hydraulic motor when the rotation of the hydraulic motor is stopped, a main pipeline connecting the hydraulic motor and the hydraulic pump, and the main pipeline. Which is provided in the middle of the hydraulic pump, controls the flow rate of the pressure oil supplied from the hydraulic pump to the hydraulic motor and controls the rotational direction of the hydraulic motor, and switches the capacity control valve by the pilot pressure from the pilot pump. In order to control, the traveling control of the construction machine, which consists of the hydraulic pilot section of the displacement control valve and a control line connected between the pilot pump In the circuit, a first signal generator that outputs a signal corresponding to the driving pressure of the hydraulic motor, a second signal generator that outputs a signal corresponding to the operating state of the control valve, and a capacity control valve Between a solenoid valve provided between the hydraulic pilot section and the pilot pump and provided in the middle of the control line for switching the pilot pressure in at least three stages, and between the solenoid valve and the hydraulic pilot section of the displacement control valve. On the basis of signals from the first and second signal generators, which are connected to the control pipeline by means of which a pilot pressure from the pilot pump is supplied to the brake device as a brake release pressure. A controller for outputting a control signal to the solenoid valve for switching control of the valve, the controller at least applying a pilot pressure by the solenoid valve to the brake device. Pressure value of the first stage lower than the brake release pressure of the stationary device, a second stage pressure value higher than the brake release pressure of the brake device and lower than the set pressure of the displacement control valve, and the setting of the displacement control valve. Third higher than pressure
A traveling control circuit for a construction machine, characterized in that it is configured to selectively switch to a pressure value in stages.