JP2880365B2 - Hydraulic motor drive circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic circuit for a construction machine, and more particularly to a drive circuit for a hydraulic motor capable of switching speed between high and low.

[0002]

2. Description of the Related Art There is known a hydraulic motor used in a hydraulic circuit of a construction machine, in which a tilting angle is changed by an adjusting cylinder so that a speed can be switched between high and low. FIG. 4 shows a drive circuit of a hydraulic motor of a conventional construction machine capable of switching a speed mode between a low speed and a high speed. A directional control valve 5 and a counterbalance valve 6 are provided in main pipelines 3 and 4 connecting the hydraulic pump 1 and the traveling hydraulic motor 2. The directional control valve 5 is controlled by a pilot pressure operating unit 7, the directional control valve 5 is switched in conjunction with the movement of the operating lever 8, and the discharge oil of the hydraulic pump 1 is discharged through the directional control valve 5 and the counterbalance valve 6.
It is led out to the hydraulic motor 2 from the main line 3 or the main line 4. The hydraulic motor 2 can change the tilt angle by the operation of the tilt angle adjusting cylinder 9, and the state shown is the low speed mode, and the rod 9 is biased by the bias of the spring 9 b built in the tilt angle adjusting cylinder 9. 9a contracts into the cylinder, and the tilt angle of the hydraulic motor 2 becomes large. That is, the flow rate per rotation of the hydraulic motor 2 is large and the torque is high.

Further, relief valves 10 and 11 acting in the respective directions are provided between the two main pipelines 3 and 4 in a crossover, and a shuttle valve 14 is provided between bypass oil passages 12 and 13. Then, a speed switching valve 15 that operates in the opening direction by the pilot pressure is provided, and an oil path to the back pressure chamber 9c of the tilt angle adjusting cylinder 9 is connected to the secondary side of the speed switching valve 15, and the speed switching is performed. The outlet oil passage of the shuttle valve 14 and the return tank 16 are connected to the primary side of the valve 15. Further, a solenoid valve 17 which is operated in the opening direction by energizing the solenoid is provided, and a pilot oil passage 18 is provided on the secondary side of the solenoid valve 17 so as to be connected to a pilot port 15c of the speed switching valve 15 and a solenoid valve is provided. The pilot pump 19 and the return tank 16 are connected to the primary side of the pump 17.

When a high-speed switching signal is supplied to the solenoid 17c of the solenoid valve 17 from the illustrated state, the spool is switched from the position 17a to the position 17b, the solenoid valve is opened, and the spool is discharged from the pilot pump 19. The pilot oil is led to a pilot port 15c of the speed switching valve 15 through a pilot oil passage 18. For this reason, the spool of the speed switching valve 15 switches from the position 15a to the position 15b, the speed switching valve 15 is opened, and the hydraulic oil from the outlet oil passage of the shuttle valve 14 is subjected to the back pressure of the tilt angle adjusting cylinder 9. After flowing into the chamber 9c, the rod 9a extends out of the cylinder 9 against the spring 9b built in the cylinder 9 for adjusting the tilt angle, and the tilt angle of the hydraulic motor 2 is reduced.
That is, the flow rate per rotation of the hydraulic motor 2 is small and the torque is low, and the high-speed mode is set.

When the hydraulic motor is braked in the high-speed mode, the torque is low because the tilt angle of the hydraulic motor 2 is small, and the relief valves 10 and 11 provided between the main pipelines 3 and 4 are operated. By the action, the increase in the hydraulic pressure of one main pipeline is reduced, and the shock at the time of braking is reduced.

[0006]

As described above, in the conventional construction machine, the shock at the time of braking the hydraulic motor in the high-speed mode is reduced. However, in the low-speed mode, the torque is high due to the large tilt angle of the hydraulic motor, and a large flow of hydraulic oil is discharged in a short time during the braking operation of the hydraulic motor, so that the braking pressure sharply increases. Therefore, the shock at the time of braking the hydraulic motor becomes large, and the fatigue of the operator increases, which causes a decrease in work efficiency.

Therefore, technical problems to be solved in order to improve the operability by reducing the shock at the time of braking the hydraulic motor even in the low-speed mode and to improve the work efficiency by reducing the physical burden on the operator. The present invention aims to solve this problem.

[0008]

DISCLOSURE OF THE INVENTION The present invention has been proposed to achieve the above object, and the tilt angle of a hydraulic motor can be freely changed by a tilt angle adjusting cylinder, and the speed can be switched between high and low. In the operable construction machine, when a speed switching circuit for controlling oil supply to the tilt angle adjusting cylinder is provided, and a means for detecting an operation state of the directional control valve is provided, and sudden braking is performed in a low speed mode. Provides a hydraulic motor drive circuit that controls the tilt angle of the hydraulic motor to switch to a high-speed mode.

[0009]

When the tilt angle of the hydraulic motor is switched to the low speed mode by the speed switching circuit, the means for detecting the operation state of the directional control valve detects whether or not the directional control valve is operated. When the directional control valve is operated, it is determined whether the operating state is decelerating or accelerating or has been operated to a steady position. When the directional control valve is being accelerated or in the steady position, the low speed mode is maintained.

When it is determined that the directional control valve has been suddenly decelerated, the tilt angle of the hydraulic motor is switched to a high-speed mode by a speed switching circuit to reduce the torque, and the braking pressure is reduced to rapidly brake in a low-speed mode. Reduce shock in case.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to FIGS. For convenience of description, the same components as those described in the related art are denoted by the same reference numerals, and redundant description will be omitted. In FIG. 1, a shuttle valve 22 is provided between the pilot oil passages 20 and 21 of the pilot pressure operating section 7,
A pressure sensor 23 is provided in an outlet oil passage of the shuttle valve 22 to detect an operation state of the direction control valve 5. Pressure sensor 2
The signal detected at 3 is sent to the control unit 24, and the position of the spool of the directional control valve 5 has been operated, is being operated, or is neutral due to a change in the pilot pressure of the pilot oil passages 20 and 21. The control unit 24 determines whether or not it is quickly returned to the position. In this embodiment, the pressure sensor 23 is used as a means for detecting the operation state of the direction control valve 5. However, various detection means such as attaching an encoder to the operation lever 8 can be used.

A speed changeover switch 25 is connected to the control unit 24 in addition to the pressure sensor 23, and the speed changeover switch 25 outputs either a high-speed mode signal or a low-speed mode signal. Based on the output signal of the speed changeover switch 25, the control unit 24 turns on / off an electric signal to the solenoid 17c of the solenoid valve 17. Next, the operation of the drive circuit of the hydraulic motor according to the present invention will be described. First, the control unit 24 determines the operation state of the speed changeover switch 25, and when the speed changeover switch 25 is at the high speed position, supplies a high speed changeover signal to the solenoid 17c of the solenoid valve 17. In such a case, as shown in FIG.
The pilot oil from the pilot pump 19 passes through the solenoid valve 17 and is led out to the pilot oil passage 18 after being moved to the position b and opened. Therefore, pilot pressure is applied to the pilot port 15c of the speed switching valve 15, and the spool moves to the position 15b to be in an open state.

In this state, if the operation lever 8 is operated to either the left or right, the pilot pressure is led out to the pilot oil 20 or 21, and the direction control valve 5 and the counter balance valve 6 are switched. Then, hydraulic oil is discharged from the hydraulic pump 1 to the main pipeline 3 or 4, a drive pressure is applied to the hydraulic motor 2, and the speed switching valve 1 is transmitted from the shuttle valve 14.
5, a part of the hydraulic oil is led out to the back pressure chamber 9c of the tilt angle adjusting cylinder 9. Accordingly, as shown in the figure, the rod 9a extends against the pressure of the spring 9b, the tilt angle of the hydraulic motor 2 changes to a small value, and the low-torque high-speed mode is set.

On the other hand, when the speed changeover switch 25 is at the low speed position, the control unit 24 does not output an electric signal to the solenoid 17c of the solenoid valve 17, and the solenoid valve 17 is closed as shown in FIG. Therefore, the pilot pressure is not applied to the pilot port 15c of the speed switching valve 15. Therefore,
The speed switching valve 15 is also closed, the hydraulic oil does not flow into the back pressure chamber 9c of the tilt angle adjusting cylinder 9, the tilt angle of the hydraulic motor 2 increases, and a low torque mode with high torque is set.

In the high-speed mode shown in FIG.
When the operation lever 8 is returned to the neutral position to apply braking while the directional control valve 5 and the counterbalance valve 6 are returned to the neutral position and the main pipe opposite to the main pipe from which the driving pressure was discharged, is being driven. A braking pressure is generated in the road 3 or 4, and the hydraulic motor 2
Until stops, the relief pressure of the relief valve 10 or 11 on the braking side is set to a high pressure. At that time, since the hydraulic motor is in the low-torque high-speed mode, the shock at the time of braking is reduced.

In the low-speed mode shown in FIG.
When the brake is applied by returning the operation lever 8 to the neutral position while the brake is being driven, the relief pressure on the braking side increases and the hydraulic motor 2 stops, as in the case of braking in the high-speed mode. In the mode, since the hydraulic motor 2 has a high torque, the shock at the time of braking is large. Therefore, during braking in the low-speed mode, the shock is reduced by the procedure shown in the flowchart of FIG.

As shown in the steps of the flowchart, the control unit 24 determines whether the speed changeover switch 25 is at the high speed position or the low speed position, and outputs an electric signal to the solenoid 17c of the solenoid valve 17 if the speed changeover switch 25 is at the high speed position. Then, the hydraulic motor 2 is switched to the high-speed mode (step). When the speed changeover switch 25 is at the low speed position, the pressure sensor 23 detects the pilot pressure of the pilot oil passages 20 and 21 and determines whether the directional control valve 5 is at the neutral position or has been operated to any position. The operation state of the direction control valve 5 is detected (step). Here, when the speed changeover switch 25 is at the low speed position and the pilot pressure operating unit 7 is not operated, that is, when the direction control valve 5 is in the neutral position and the machine is stopped, the solenoid 17 of the solenoid valve 17 is stopped.
Output an electric signal to c (step →).

When the pilot pressure in the pilot oil passage 20 or 21 has reached a previously known maximum value, the spool of the directional control valve 5 moves to the stroke end,
The state is switched to any position, and the hydraulic motor 2 is in a steady operation. If so, the control unit 24 stops the electric signal to the solenoid 17c of the solenoid valve 17, and switches the hydraulic motor 2 to the low-speed mode (Step →
). Alternatively, when the mode is already the low-speed mode, the low-speed mode is maintained as it is.

When the pilot pressure in the pilot oil passage 20 or 21 is increasing, the spool of the directional control valve 5 is in the process of switching from the neutral position to any position, and the machine is started up to the steady operation. It is in an accelerating operation state.
Further, when the pilot pressure is substantially unchanged, the machine is started and is in a low-speed operation state. When the machine is in an accelerating operation state or a low-speed operation state, the control unit 24 stops the electric signal to the solenoid 17c of the solenoid valve 17, and stops the hydraulic motor 2
To low speed mode (step →). Alternatively, when the mode is already the low-speed mode, the low-speed mode is maintained as it is.

When the pilot pressure in the pilot oil passage 20 or 21 is falling, the spool of the directional control valve 5 is in the process of switching from any position to the neutral position, and the machine is operated from steady operation to stop. In the deceleration operation state. When the decrease of the pilot pressure is within a certain range, the control unit 24 stops the electric signal to the solenoid 17c of the solenoid valve 17 and switches the hydraulic motor 2 to the low-speed mode, assuming normal deceleration operation. Step →
). Alternatively, when the mode is already the low-speed mode, the low-speed mode is maintained as it is.

When the pilot pressure in the pilot oil passage 20 or 21 drops rapidly, the machine is being rapidly decelerated. If so, the control unit 24 sends the electromagnetic valve 1
7 outputs an electric signal to the solenoid 17c, and switches the hydraulic motor 2 to the high-speed mode (step →). Therefore, as described above, the tilt angle of the hydraulic motor 2 becomes small, the torque becomes low, and the shock at the time of sudden braking in the low-speed mode is reduced.

The present invention can be variously modified without departing from the spirit of the present invention, and it goes without saying that the present invention extends to the modified ones.

[0023]

As described in detail in the above-described embodiment, the present invention controls the speed switching circuit while constantly detecting the operation state of the direction control valve. Switch the turning angle to high-speed mode. Accordingly, the hydraulic motor has a low torque, minimizes the shock at the time of sudden braking, improves operability, reduces the degree of operator fatigue, and contributes to improvement of workability.

[Brief description of the drawings]

FIG. 1 is a drive circuit diagram of a hydraulic motor in a low speed mode according to an embodiment of the present invention.

FIG. 2 is a drive circuit diagram of a hydraulic motor in a high-speed mode.

FIG. 3 is a flowchart showing an operation procedure.

FIG. 4 is a drive circuit diagram of a conventional hydraulic motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Hydraulic pump 2 Hydraulic motor 3, 4 Main line 5 Direction control valve 9 Cylinder for adjusting tilt angle 15 Speed switching valve 17 Solenoid valve 23 Pressure sensor 24 Control part 25 Speed switching switch

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) E02F 9/22 F15B 11/00 F15B 11/02

Claims (1)

(57) [Claims] In a construction machine in which the tilt angle of a hydraulic motor is made variable by a tilt angle adjusting cylinder and the speed can be switched between high and low, oil supplied to the tilt angle adjusting cylinder is supplied. In addition to providing a speed switching circuit for controlling, a means for detecting the operation state of the directional control valve is provided, and in the case of sudden braking in the low speed mode, control is performed so that the tilt angle of the hydraulic motor is switched to the high speed mode. The drive circuit of the hydraulic motor.