JPH05156666A - Travel and drive gear for construction machine - Google Patents

Abstract

PURPOSE:To enable pivot turn at high speed while preventing corotation by controlling the displacement of right and left variable displacement hydraulic travel motors according to the traveling state of a construction machine. CONSTITUTION:Of a cylinder 20 for controlling the displacement of a variable displacement hydraulic travel motor 3, 4, a two-position switching valve 21, a cylinder 26, and a two-position switching valve 27, the switching valves 21, 27 are actuated independently in response to command signals from a controller 45. When the controller 25 recognizes the action of pivot turn according to values detected by pressure switches P1-P4 for detecting the controlling states of control valves 9, 13 controlling driving of the variable displacement hydraulic travel motor 3, 4 and to a value detected by a delivery pressure sensor P5 for detecting the load pressure of the motor 3, 4, the switching valve related to the motor being stopped is actuated to increase the displacement of the motor in order to increase braking forces. Unnecessary corotation can thus be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling drive device for a construction machine, which controls the displacement volumes of two left and right variable displacement hydraulic traveling motors according to the traveling state.

[0002]

2. Description of the Related Art A construction machine such as a hydraulic excavator capable of traveling includes hydraulic traveling motors on the left and right, and the crawler belts on the left and right are driven by these hydraulic traveling motors for traveling. A traveling drive device for such a construction machine will be described with reference to FIG.

FIG. 2 is a hydraulic circuit diagram of a conventional traveling drive system for a construction machine. In this figure, reference numeral 1 is a main hydraulic pump, which supplies pressure oil to the main circuit 2. 3 is a variable displacement hydraulic traveling motor installed on one side of the construction machine, for example, the left side, and 4 is a variable displacement hydraulic traveling motor installed on the other side of the construction machine, for example, the right side. It is driven by the supplied pressure oil. The variable displacement hydraulic traveling motors 3 and 4 are connected in parallel to the main hydraulic pump 1. Reference numerals 3a and 4a respectively denote a displacement volume variable mechanism (hereinafter, represented by a swash plate) of the variable displacement hydraulic traveling motors 3 and 4. Reference numeral 5 is a direction switching valve for controlling the direction and flow rate of pressure oil supplied to the variable displacement hydraulic traveling motor 3, and 6 is a direction switching valve for controlling direction and flow rate of the pressure oil supplied to the variable displacement hydraulic traveling motor 4. is there. Reference numeral 7 denotes a pilot pump, which supplies pilot pressure to a pilot circuit 8 shown by a broken line in the figure. An operation valve 9 supplies pilot pressure to the pilot line 11 or 12 to operate the directional control valve 5 during operation. Reference numeral 13 is also an operation valve similar to the operation valve 9, and the pilot line 1 is operated at the time of operation.
Directional switching valve 6 by supplying pilot pressure to 4 or 15
Control the operation of. These operation valves 9 and 13 are connected in parallel to the pilot pump 7.

Reference numeral 17 denotes a shuttle valve, which takes out the pressure oil on the high pressure side from the pressure oil in the pipe lines 18 and 19 connected to the variable displacement hydraulic traveling motor 3. Reference numeral 20 is a cylinder that tilts and drives the swash plate 3a. Reference numeral 21 denotes a two-position switching valve, which supplies the pressure oil from the shuttle valve 17 to the bottom side of the cylinder 20 when switched to the position on the A side in the drawing, and the cylinder 20 when switched to the position on the B side in the drawing. Oil in the bottom of the tank 2
Discharge to 2. Also on the variable displacement hydraulic traveling motor 4 side, a shuttle valve 23, a cylinder 26, and a two-position switching valve 27 having the same functions as the shuttle valve 17, the cylinder 20, and the two-position switching valve 21 are provided. Incidentally, reference numerals 24 and 25 denote pipe lines of the variable displacement hydraulic traveling motor 4. Reference numeral 29 is a solenoid valve, which controls the supply and cutoff of pilot pressure from the pilot pump 7 to the two-position switching valves 21 and 27.

P ₁ is a pressure switch for detecting the left forward movement, and detects the pilot pressure into the pilot conduit 11 when the operating valve 9 is operated to the A side (left forward side) in the figure. P
Reference numeral ₂ is a pressure switch for detecting the left backward movement, which is the pilot line 1 when the operation valve 9 is operated to the B side (left backward movement side) in the figure.
Detect the pilot pressure into 2. P ₃ is a pressure switch for detecting the right forward movement, and detects the pilot pressure into the pilot conduit 14 when the operating valve 13 is operated to the A side (right forward side) in the figure. P ₄ is a pressure switch for detecting the right reverse movement, and detects the pilot pressure into the pilot conduit 15 when the operation valve 13 is operated to the B side (right reverse movement side) in the figure. P ₅ is a discharge pressure sensor, which detects the pressure value of the pump discharge pressure in the main circuit 2 and outputs an electric signal in response to this. A controller 36 outputs a command signal to the solenoid valve 29 according to the states of the output signals output by the pressure switches P _{1 to} P ₄ and the pressure signal output by the discharge pressure sensor P ₅ .

The tilt amounts of the swash plates 3a and 4a of the variable displacement hydraulic traveling motors 3 and 4 are, for example, cylinders 20 and 26.
Shall be minimum when expanded and maximum when contracted.

In the above traveling drive device, for example, when the main hydraulic pump 1 and the pilot pump 7 are driven,
When both the operation valves 9 and 13 are operated to the positions on the side A in the drawing,
Since both the direction switching valves 5 and 6 are switched to the positions on the A side in the drawing, both the variable displacement hydraulic traveling motors 3 and 4 are normally rotated. Therefore, the construction machine runs straight. Controller 36
Recognizes the straight traveling by the output signals from the pressure switches P ₁ and P ₃ , and judges the traveling load level by the pressure signal from the discharge sensor P ₅ . If the load pressure of each of the variable displacement hydraulic traveling motors 3 and 4 is low, such as when traveling on level ground, the controller 36 outputs a command signal to the solenoid valve 29 to turn off the solenoid valve 29. Therefore, the two-position switching valves 21 and 27 are both in the position on the side A in the figure due to the spring force, and the cylinders 20 and 26 are both in the extended state. Therefore, the swash plates 3a of the variable displacement hydraulic traveling motors 3 and 4 are
Both the tilting amounts of 4a are controlled to be minimum, and high speed is exhibited in straight running. On the other hand, when the traveling load is high, such as when climbing a slope, the controller 36 receives the pressure signal from the discharge sensor P ₅ and recognizes that the load pressure of the variable displacement hydraulic traveling motors 3 and 4 is high. , Does not output a command signal to the solenoid valve 29, and makes it conductive. Therefore, the two-position switching valves 21 and 27 are both switched to the position on the B side in the drawing by the pilot pressure, and both the cylinders 20 and 26 are contracted.
Therefore, the displacement volumes of the variable displacement hydraulic traveling motors 3 and 4 are both controlled to the maximum, and the traveling speed is reduced but the traveling force is increased.

[0008]

By the way, in the above-mentioned prior art, the switching control of the two-position switching valves 21 and 27 is set to 1.
Since the two solenoid valves 29 perform the same operation at the same time,
When one of the variable displacement hydraulic traveling motors is stopped and only the other variable displacement hydraulic traveling motor is used for turning, the following problems are likely to occur during a so-called pivot turn.

That is, when only one of the variable displacement hydraulic traveling motors 3 is stopped in a state where the variable displacement hydraulic traveling motors 3 and 4 are equally driven with a small displacement, such as when traveling straight on flat ground, Since the variable displacement hydraulic traveling motor 4 on the drive side has a slightly higher load, but is lower than when the vehicle is climbing uphill, the controller 36 tilts so that a signal is output to the solenoid valve 29 at the load pressure in this case. When the switching load pressure is set, in the above case, the tilt amount is small, so that the pivot turn can be performed at high speed. But,
At this time, since the tilt amount of the variable displacement hydraulic traveling motor 3 on the stop side is also controlled to be small, the braking force of the variable displacement hydraulic traveling motor 3 on the stop side (because the front and rear pipes of the motor are closed). The hydraulic braking force generated at) is weak and tends to be accompanied by an external force and rotate together. Needless to say, if such a turnaround occurs,
The pivot turn fulcrum will move continuously,
Disables the pivot turn in the normal trajectory intended by the operator. Therefore, the maneuverability is extremely deteriorated. In consideration of this phenomenon, if the set value of the tilt switching load in the controller 36 is lowered and the tilt amount is controlled to be large during the pivot turn, the brake of the variable displacement hydraulic traveling motor 3 on the stop side is hydraulically braked. Since the force is increased, it is possible to prevent the entrainment, but with this, the variable displacement hydraulic traveling motor 4 on the drive side cannot obtain a sufficient drive speed, and the pivot turn cannot be performed at a high speed.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a traveling drive device for a construction machine capable of performing a pivot turn at a high speed while preventing a turn around.

[0011]

In order to achieve the above object, the present invention provides a hydraulic pump, a first variable displacement hydraulic traveling motor driven by pressure oil from the hydraulic pump, and a second variable displacement. Type hydraulic traveling motor, a first displacement control means for controlling the displacement of the first variable displacement hydraulic traveling motor, and a second displacement controlling volume of the second variable displacement hydraulic traveling motor. The displacement control means, the first direction switching means for controlling the supply of pressure oil to the first variable displacement hydraulic traveling motor, and the supply of pressure oil to the second variable displacement hydraulic traveling motor are provided. Second to control
Direction switching means, first operating means for operating the operation of the first direction switching means, second operating means for operating the operation of the second direction switching means, and the first operating means. In the traveling drive device for a construction machine, comprising: and an operation state detection unit that detects an operation state of each of the second operation units, the operation state detection unit controls the first operation unit and the second operation unit. When it is detected that one of them is in the non-operation state and the other one is in the operation state, the displacement volume control means corresponding to the operation means in the non-operation state is selected to increase the displacement volume. It is characterized in that selection driving means for driving is provided.

[0012]

In the state where the first and second variable displacement hydraulic traveling motors are equally driven with a small displacement (straight traveling), only one of the operating valves, for example, the first operating valve is made non-operating. When only one variable displacement hydraulic traveling motor is stopped, the controller causes the first variable displacement hydraulic traveling motor to be in the stopped state based on the detection value from the operation state detecting means, and the second variable displacement hydraulic traveling motor. Recognizing that the motor is in a driving state, the first solenoid valve operates the first displacement control means corresponding to the first variable displacement hydraulic traveling motor to increase the displacement.
Therefore, the displacement volume of the second variable displacement hydraulic traveling motor on the drive side remains controlled to be small, while the displacement volume of the first variable displacement hydraulic traveling motor on the stop side is largely controlled, The second variable displacement hydraulic traveling motor on the drive side can be driven at high speed with a small displacement, while the first variable displacement hydraulic traveling motor on the stop side can continue to stop with a strong braking force. Therefore, the operator can perform a high-speed pivot turn on the trajectory intended by the operator, and the maneuverability is improved.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments. FIG. 1 is a hydraulic circuit diagram of a traveling drive device for a construction machine according to an embodiment of the present invention. In this figure, the same parts as those shown in FIG.
Reference numeral 41 is a pilot line, which branches from the pilot circuit 8 and is connected to the pilot port of the two-position switching valve 21. Reference numeral 42 is a solenoid valve for connecting and disconnecting the pilot conduit 41. Reference numeral 43 is a pilot line, which branches from the pilot circuit 8 and is connected to the pilot port of the two-position switching valve 27. Reference numeral 44 is a solenoid valve for connecting and disconnecting the pilot conduit 43. Reference numeral 45 denotes a controller, which outputs a command signal S to the solenoid valve 42 according to the states (ON, OFF) of the output signals output by the pressure switches P _{1 to} P ₄ and the pressure signal output by the discharge pressure sensor P ₅ . And a command signal T to the solenoid valve 44. The controller 45 has a pressure setting means for setting a preset pressure and a comparing means for comparing the pressure set in the pressure setting means with the pressure signal of the discharge pressure sensor P ₅ , and the pressure signal is When the pressure is lower than the set pressure, the command signals S and T are output to the determined solenoid valve.

In the traveling drive system of the present embodiment, for example, the operation valves 9 and 13 are equally operated to the A side in the figure, and the variable displacement hydraulic traveling motors 3 and 4 are equally driven in the forward direction. When the traveling load is lower than the set pressure in the state where the pressure is on, the controller 45 uses the output signals of the ON state from the pressure switches P ₁ and P ₃ and the pressure signal of the low pressure (L) state from the discharge pressure sensor P _5. Command signals S and T are output to the solenoid valves 42 and 44. Therefore, the solenoid valve 42,
Both 44 operate on the shutoff side and the pilot line 4
Since the valves 1 and 43 are shut off, the two-position switching valves 21 and 27 are not supplied with the pilot pressure and are in the position on the side A in the figure due to the spring force, and the cylinders 20 and 26 are both in the extended state.
Therefore, the tilt amounts of the swash plates 3a and 4a are minimized, and the variable displacement hydraulic traveling motors 3 and 4 are both driven at high speed with the minimum displacement.

On the other hand, in this state, for example, when only the operation valve 9 is not operated and the variable displacement hydraulic traveling motor 3 is stopped, the controller 45 causes the pressure switch P ₁
As a result of changing the output signal from the
It is recognized that only the variable displacement hydraulic traveling motor 3 is stopped by the output signal in the FF state and the output signal in the ON state from the pressure switch P ₃ to shift from the straight traveling to the pivot turn to the left, and the pressure switch P 3 _The command signal T to the solenoid valve 44 is output based on the pressure signal in the L state of ₅ , but the output of the command signal S to the solenoid valve 42 is cut off. Therefore, the two-position switching valve 27 continues to maintain the position on the A side in the figure by the spring force, while the two-position switching valve 21 operates the solenoid valve 42 toward the conduction side to operate the pilot pressure supplied from the pilot conduit 41. Is switched to the position on the B side in the figure, and the cylinder 20 is contracted. Therefore, the tilt amount of the swash plate 4a is minimum,
The tilt amount of the swash plate 3a becomes maximum, and the variable displacement hydraulic traveling motor 4 continues to drive at high speed with the minimum displacement volume, while the variable displacement hydraulic traveling motor 3 is controlled to have the maximum displacement volume and is strong. It keeps stopping while securing the braking force.

Similarly, the variable displacement hydraulic traveling motors 3, 4
When only the variable displacement hydraulic traveling motor 3 is stopped in a state where they are driving each other, and the traveling load pressure rises above a set value due to, for example, a change in the terrain, the controller 45 switches the pressure switch P ₁ from the pressure switch P _1. The output signal of the OFF state and the output signal of the ON state from the pressure switch P ₃ recognize the shift from the straight traveling to the pivot turn to the left, and at the same time, the pressure in the high pressure (H) state from the discharge pressure sensor P ₅ is recognized. By recognizing that the displacement volume should be changed by the signal, the output of the command signal S to the solenoid valve 42 is cut off, and the output of the command signal T to the solenoid valve 44 is also cut off. Therefore, since the solenoid valves 42 and 44 are operated to the conduction side, both of the two-position switching valves 21 and 27 are switched to the positions on the B side in the drawing by the pilot pressures supplied from the pilot conduits 41 and 43, respectively. The cylinders 20 and 26 are contracted. Therefore, the tilting amounts of the swash plates 3a and 4a are maximized, the variable displacement hydraulic traveling motor 4 is controlled to have the maximum displacement and continues to be driven while increasing the traveling force, and the variable displacement hydraulic traveling motor 3 has the maximum displacement. It is controlled by the displacement volume and keeps stopping while securing a strong braking force.

The operation of pivoting to the right also follows the above-described operation.

Thus, in this embodiment, the two-position switching valve 2
The operation of No. 1 is controlled by the solenoid valve 42 that moves by the command signal S from the controller 45, and the operation of the two-position switching valve 27 is controlled by the solenoid valve 44 that moves by the command signal T from the controller 45. During the pivot turn, the displacement volume of the variable displacement hydraulic traveling motor on the traveling side can be controlled to the maximum while keeping the displacement volume of the variable displacement hydraulic traveling motor on the traveling side to a minimum, thus preventing unnecessary entrainment. be able to. Therefore, the pivot turn can be performed at high speed within the normal trajectory range intended by the operator, and the maneuverability can be improved. Also,
At the time of pivot turn, in addition to controlling the displacement volume of the variable displacement hydraulic drive motor on the stop side to the maximum, the displacement volume of the variable displacement hydraulic drive motor on the drive side is set to the maximum or minimum depending on the level of the load pressure. Since it can be freely controlled to the side, it is possible to obtain a running force that responds to changes in the road surface and terrain.

In this embodiment, the displacement volume of the variable displacement hydraulic traveling motors 3 and 4 is controlled to the maximum or minimum side, but the present invention is not limited to this. Instead, it is also possible to configure so as to perform control with an appropriate displacement volume in between.

[0020]

According to the present invention, the displacement control means of each variable displacement hydraulic traveling motor can be operated independently of each other on the basis of a command from the controller. It is possible to increase the displacement volume of the variable displacement type hydraulic traveling motor, and to prevent unnecessary accompanying rotation. Therefore, at the time of the pivot turn, it is easy and reliable to increase the speed within the regular trajectory range, and the maneuverability can be improved. During the pivot turn, in addition to increasing the displacement volume of the variable displacement hydraulic traveling motor on the stop side, the displacement volume of the variable displacement hydraulic traveling motor on the drive side can be controlled freely according to changes in load pressure. Since it has been obtained, it is possible to cope with changes in the road surface and terrain, and to improve power and workability.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a traveling drive device for a construction machine according to an embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of a conventional traveling drive device for a construction machine.

[Explanation of symbols]

 1 Main hydraulic pump 3 Variable displacement hydraulic traveling motor 4 Variable displacement hydraulic traveling motor 5 Directional switching valve 6 Directional switching valve 9 Operation valve 13 Operation valve 17 Shuttle valve 20 Cylinder 21 2 Position switching valve 23 Shuttle valve 26 Cylinder 27 2 Position Switching valve 42 Solenoid valve 44 Solenoid valve 45 Controller

Claims (3)

[Claims] 1. A hydraulic pump, a first variable displacement hydraulic traveling motor driven by pressure oil from the hydraulic pump, a second variable displacement hydraulic traveling motor, and the first variable displacement hydraulic traveling. First displacement volume control means for controlling displacement volume of the motor, second displacement displacement hydraulic control means for controlling displacement volume of the second variable displacement hydraulic drive, and first displacement displacement hydraulic travel First direction switching means for controlling the supply of pressure oil to the motor, and second for controlling the supply of pressure oil to the second variable displacement hydraulic traveling motor.
Direction switching means, first operating means for operating the operation of the first direction switching means, second operating means for operating the operation of the second direction switching means, and the first operating means. In the traveling drive device for a construction machine, comprising: and an operation state detection unit that detects an operation state of each of the second operation units, the operation state detection unit controls the first operation unit and the second operation unit. When it is detected that one of them is in the non-operation state and the other one is in the operation state, the displacement volume control means corresponding to the operation means in the non-operation state is selected to increase the displacement volume. A traveling drive device for a construction machine, comprising a selection drive means for driving. 2. The selection drive means according to claim 1, wherein the first solenoid valve inserted into a pilot circuit for supplying pilot pressure oil to the first displacement volume control means and the second displacement volume. It comprises a second solenoid valve inserted in a pilot circuit for supplying pilot pressure oil to the control means, and an output means for selectively outputting an operation signal to the first solenoid valve or the second solenoid valve. A traveling drive device for a construction machine, which is characterized in that 3. The traveling drive device for a construction machine according to claim 1, wherein load pressure detection means for detecting drive load pressures of the first variable displacement hydraulic traveling motor and the second variable displacement hydraulic traveling motor. And a control means for controlling the displacement volume control means of the variable displacement hydraulic traveling motor on the drive side according to the detection value of the load pressure detection means when the selective drive means is operating. A drive device for a construction machine.