JP2567613Y2 - Hydraulic motor drive circuit for hydraulic traveling vehicle - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a hydraulic motor driving circuit in a hydraulic traveling vehicle.

[0002]

2. Description of the Related Art In a hydraulic traveling vehicle capable of switching the speed between low and high speeds (or automatic switching), high-speed running is relieved.
The shock at stopping has been considerably reduced by the improvement of the valve. However, low-speed running is slow but high-torque, so even if a braking pressure equivalent to that at high-speed is generated, the braking torque is larger than at high-speed, causing the vehicle to stop immediately. It was causing shock.

A known circuit will be described with reference to FIG.
FIG. 1 is a drive circuit diagram of a conventional hydraulic traveling vehicle having a function of switching between first and second speeds. 1 is a main pump, 2 and 3 are downstream main pipelines, 4 is a traveling valve, and 5 is a counterbalance valve.
6 is a traveling motor, 7 and 8 are upstream main pipelines, 9 is an oil passage, 1
Reference numerals 0 and 11 are cross-over relief valves. 12 is a solenoid valve, 13 is a speed switching valve, 14 is a tilt angle adjusting cylinder, 15 is a shuttle valve, 16 is a pilot pump, 17
Is a pilot oilway. In FIG. 1, the position of the piston 14a of the tilt angle adjusting cylinder 14 indicates that the amount of absorption per rotation of the traveling motor 6 is set to a large capacity side, that is, a low speed. When pressure oil is supplied to the back pressure chamber 14b of the piston 14a, the piston 14a overcomes the spring force and moves to the left, minimizing the tilt angle, and switches to the small capacity side, that is, high speed.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to reduce shock when a low-speed traveling is stopped in a hydraulic traveling vehicle having a low / high speed switching of a traveling speed or an automatic second speed function.

[0005]

According to a second aspect of the present invention, a two-speed switching signal is used to set a second speed.
A shuttle valve 15 connected to the position-switchable solenoid valve 12 and disposed between the main lines 2 and 3; a speed switching valve 13 connected to the tank; and a tilt angle adjusting device connected to the speed switching valve 13. An operation detection valve 19 is provided in a hydraulic traveling vehicle having a cylinder 14 and having a traveling speed switching function in which the tilt angle of the traveling motor 6 is changed by the cylinder 14, and switching of the detection valve 19. Is performed with the main line pressure upstream of the counterbalance valve 5 or the pilot pressure for switching the traveling valve 4, and the main line pressure downstream of the counterbalance valve 5 is led to the inlet port of the operation detection valve 19. The outlet port is connected to a shuttle valve 20 connected to a pilot oil passage from the speed switching solenoid valve 12, and the shuttle valve 20
Is connected to the pilot oil chamber of the speed switching valve 13, and the traveling motor 6 is set to a high speed during braking at a low speed.
The braking torque was minimized.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. In FIG. 2, the description of the parts common to FIG. 1 is omitted. 18 is a shuttle valve, 19 is an operation detection valve, and 20 is a shuttle valve. The shuttle valve 18 is provided between the upstream main pipelines 7 and 8, and the operation detection valve 19 is provided between the shuttle valve 18, the oil valve 9 connecting the shuttle valve 15 and the speed switching valve 13. The shuttle valve 20 is provided between the operation detection valve 19 and the solenoid valve 12,
Thus, the speed switching valve 13 is configured to operate by switching the pilot pressure. The operation detecting valve 19 is switched when the main line 7 or 8 reaches ²⁰ to 30 kgf / cm ² .

[0007]

When the second speed is switched to the second speed by the second speed switching signal, the solenoid valve 12 is always at the B position, and the pilot pressure from the pilot pump 16 is applied to the pilot port of the speed switching valve 13. The switching valve 13 to B
Hold in position. The pressure oil from the main line 2 or 3 is supplied via the shuttle valve 15 to the back pressure chamber 14b of the tilt angle adjusting cylinder 14.
And the traveling motor 6 is set to the second speed (high speed).

When the traveling valve 4 is switched to, for example, the B side, the pressure oil from the main pump 1 switches the counterbalance valve 5 from the main pipe 7 and the downstream main pipe 2 The motor 6 is reached.
The motor 6 is driven. At the same time, the pressure oil acts on the pilot port of the operation detection valve 19 via the shuttle valve 18 and switches the operation detection valve 19 to B. At this time, since the solenoid valve 12 is at the position A and the pilot port of the speed switching valve 13 has the tank pressure, the switching valve 13 holds the position A and the shuttle valve 15
Pressure oil from the main line 2 through the cylinder 1 for tilt angle adjustment
4 does not act on the back pressure chamber 14b, and the traveling motor 6 is started with the first speed (low speed) set.

When stopped: When the traveling valve 4 is returned to A, the main pipeline 7,
8 becomes the tank pressure, and the counter balance valve returns to the state shown in the figure. The traveling motor 6 rotates due to the inertial force, and the pressure oil is discharged to the main line 3, and a braking pressure is generated in the main line 3, whereby the braking of the machine body proceeds. At the same time, since the pilot chamber of the operation detection valve 19 becomes the tank pressure, the detection valve 19 returns to A, and the braking pressure via the shuttle valve 15 is transferred from the detection valve 19 to the pilot chamber of the speed switching valve 13 via the shuttle valve 20. Acts to switch the switching valve 13 to B. As a result, the braking pressure generated in the main pipeline 3 is also supplied to the back pressure chamber of the cylinder 14 for adjusting the tilt angle to minimize the tilt angle and switch the traveling motor 6 to the second speed (high speed) to advance the braking. . At this time, since the braking torque of the motor 6 is minimized, the shock at the time of braking can be minimized.

When decelerating by inching, the operation detecting valve 19 is set not to return to the position A until the circuit pressure in the main line 7 or 8 becomes low. The position is switched to the position, the tilt angle adjusting cylinder 14 moves to the small tilt side, and there is no problem that the speed is set to the second speed (high speed) and accelerated.

[0011]

[Effect] In a hydraulic traveling vehicle, an operation detection valve 19 is provided,
The detection valve 19 is switched at a main line pressure upstream of the counterbalance valve 5 or at a pilot pressure at which the traveling valve 4 is switched. The inlet port of the operation detection valve 19 is located downstream of the counterbalance valve 5. Guide the main pipeline pressure, and
The shuttle port is connected to a shuttle valve 20 connected to a pilot oil passage from the speed switching solenoid valve 12, and an outlet port of the shuttle valve 20 is connected to a pilot oil chamber of the speed switching valve 13.
At the time of braking at a low speed, the traveling motor 6 is set at a high speed so that the braking torque is minimized.

When the travel valve 4 is returned to A when stopped, the main pipelines 7 and 8 become tank pressure, and the counter balance valve returns to the state shown in FIG. The traveling motor 6 is rotated by the inertial force, and the pressure oil is discharged to the main line 3 and the main line 3
, A braking pressure is generated inside the vehicle, and thereby the braking of the airframe advances. At the same time, since the pilot chamber of the operation detection valve 19 becomes the tank pressure, the detection valve 19 returns to A, and the braking pressure via the shuttle valve 15 is transferred from the detection valve 19 to the pilot chamber of the speed switching valve 13 via the shuttle valve 20. Acts to switch the switching valve 13 to B. As a result, the braking pressure generated in the main pipeline 3 is also supplied to the back pressure chamber of the cylinder 14 for adjusting the tilt angle to minimize the tilt angle and switch the traveling motor 6 to the second speed (high speed) to advance the braking. . At this time, since the braking torque of the motor 6 is minimized, the shock at the time of braking can be minimized.

[Brief description of the drawings]

FIG. 1 is a known hydraulic circuit diagram.

FIG. 2 is a hydraulic circuit diagram according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Main pump 2, 3 Downstream main pipeline 4 Travel valve 5 Counter balance valve 6 Travel motor 7, 8 Upstream main pipeline 9 Oil passage 10, 11 Cross-over
Barrel relief valve 12 Solenoid valve 13 Speed switching valve 14 Cylinder for adjusting tilt angle 14a Piston 14b Back pressure chamber 15 Shuttle valve 16 Pilot pump 17 Pilot oil passage 18 Shuttle valve 19 Operation detection valve 20 Shuttle valve

Claims (1)

(57) [Scope of request for utility model registration] 1. A shuttle valve (15) connected between a solenoid valve (12) that can be switched between two positions by a two-speed switching signal and disposed between main pipes (2 and 3) and a speed switching valve connected to a tank. (13)
And a tilt angle adjusting cylinder (14) in which a back pressure chamber (14b) is connected to the speed switching valve (13). In a hydraulic traveling vehicle having a traveling speed switching function that changes the operation speed, an operation detection valve (19)
And a counterbalance valve for switching the detection valve (19).
(5) The main pipeline pressure upstream of the counterbalance valve (5) is provided at the inlet port of the operation detection valve (19) at the main port pressure upstream of the counterbalance valve (5). The outlet port is connected to a shuttle valve (20) connected to a pilot oil passage from a speed switching solenoid valve (12), and the outlet port of the shuttle valve (20) is connected to a speed switching valve ( 13) The hydraulic motor drive in a hydraulic traveling vehicle, characterized in that the traveling motor (6) is set to a high speed at the time of braking at a low speed while the braking torque is minimized. circuit.