JP2860728B2 - Hydraulic circuit of industrial vehicle - 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 an industrial vehicle having improved steering operability.

[0002]

2. Description of the Related Art As shown in FIG. 1, there is a conventional industrial vehicle equipped with a hydraulic power steering device having a large-capacity pump a for working equipment and a small-capacity pump b for steering. The discharge pressure of the displacement pump b is divided by the two flow dividers c and d and supplied to the brake booster e and the clutch booster f, and the remainder is supplied to the power steering cylinder g. Is supplied to the working machine cylinder i. For this reason, when the engine speed is low and the oil temperature is high and the pump efficiency is reduced, the amount of oil supplied to the power steering cylinder g is insufficient and a large steering force is required. There was a problem of lowering.

As shown in FIG. 2, the discharge pressure of the small-capacity pump b is diverted by the flow divider c to the brake booster e, the clutch booster f and the working machine cylinder i as shown in FIG. There has also been proposed a circuit in which the discharge pressure is divided by a flow divider d and supplied to a working machine cylinder i and a power steering cylinder g (see Japanese Patent Publication No. 3-38142).

[0004]

However, in the above-mentioned conventional hydraulic circuit, when the work machine i is operated, a sufficient flow rate can be obtained with only one pump a, but two pumps a and b are provided. Since the operating pressure is generated, a large load is applied to the engine, and the engine is inadvertently stopped, and power loss is large. Further, since the high pressure of the working machine cylinder i acts on the small capacity pump b, there is a problem that the load acting on the engine is increased and the fuel efficiency is deteriorated. SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described conventional problems, and has as its object to provide a hydraulic circuit for an industrial vehicle in which power steering operability does not decrease even when the engine is running at a low speed.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and the invention according to claim 1 is provided with a large capacity pump and a small capacity pump driven by an engine. The discharge pressure of the displacement pump is diverted by the flow divider and supplied to hydraulic equipment of the traveling system other than the steering system such as the work machine and clutch booster,
The discharge pressure of the small-capacity pump is diverted by the flow divider and supplied to the power steering cylinder and traveling hydraulic equipment other than the steering system, and the return oil of the power steering cylinder and clutch booster is supplied to the oil clutch. It is designed to drain directly.

With the above structure, a sufficient amount of oil can be ensured on the steering cylinder side. Therefore, even if the engine speed is reduced and the flow rate of the small capacity pump is reduced, the steering force is not increased, and the steering operability is improved. I can plan.

[0007]

An embodiment of the present invention will be described in detail with reference to the drawing shown in FIG. In FIG. 3, 1 is a large capacity pump driven by an engine (not shown), 2 is a small capacity pump,
After the discharge pressure of the large-capacity pump 1 is divided by the flow divider 3, a part of the discharge pressure is transmitted from a work machine operation valve 4 to a tilt cylinder 5 or a lift cylinder 6 provided in a work machine (not shown).
And the rest is supplied to the clutch booster 7. The discharge pressure of the small-capacity pump 2 is divided by a flow divider 8, and a part of the discharge pressure is supplied to a brake booster 9 and the remaining part is supplied to a power steering cylinder 11 via a power steering valve 10.

The return oil from the power steering cylinder 11 and the clutch booster 7 is supplied to an oil clutch 12
Is supplied to the oil clutch 12 and used for cooling the oil clutch 12, and is drained to the tank 13 when there is no oil clutch 12. The flow divider 3 for diverting the discharge pressure of the large-capacity pump 1 may be provided inside the working machine operation valve 4.

Next, the operation will be described. The discharge pressure discharged from the large-capacity pump 1 is diverted to the flow divider 3 and a part is supplied to the tilt cylinder 5 and the lift cylinder 6 of the working machine. The remainder is used to drive the lift cylinder 6 and the remainder is supplied to the clutch booster 7 to reduce the pedaling force when the clutch pedal 7a is depressed. The discharge pressure of the small-capacity pump 2 is divided by the flow divider 8 and partly supplied to the brake booster 9, which is used to reduce the depression force when the brake pedal 9 a is depressed, and the remaining power is supplied from the power steering valve 10. It is supplied to the steering cylinder 11 and used for steering operation.

[0010]

As described above in detail, the present invention divides the discharge pressure of the large capacity pump by the flow divider to supply the discharge pressure of the small capacity pump to the traveling system hydraulic equipment other than the working machine cylinder and the steering system. Since the flow is divided by the flow divider and supplied to the hydraulic system other than the power steering cylinder and the steering system, the discharge pressure of the conventional small-capacity pump is compared with that when the flow is divided by two flow dividers. Since the amount of oil supplied to the power steering cylinder increases, the steering force does not increase even if the rotation speed of the engine decreases, so that the steering operability can be improved. In addition, since the load and the high pressure on the working machine cylinder side do not act on the small capacity pump side, it is possible to prevent the engine from being stopped carelessly and reduce the power loss.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a hydraulic circuit of a conventional industrial vehicle.

FIG. 2 is a circuit diagram showing a hydraulic circuit of a conventional industrial vehicle.

FIG. 3 is a circuit diagram showing a hydraulic circuit of an industrial vehicle according to one embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Large capacity pump 2 Small capacity pump 3 Flow divider 5 Work machine 6 Work machine 7 Clutch booster 8 Flow divider 9 Brake booster 11 Power steering cylinder 12 Oil clutch 13 Tank

Claims (1)

(57) [Claims] A large-capacity pump (1) and a small-capacity pump (2) driven by an engine are provided, and the discharge pressure of the large-capacity pump (1) is divided by a flow divider (3) to divide it into a work machine (5). ), (6) and hydraulic equipment of the traveling system other than the steering system such as the clutch booster (7), and the discharge pressure of the small capacity pump (2) is divided by the flow divider (8) to be Steering cylinder (1
1) and supply to the traveling hydraulic device (9) other than the steering system, and return oil from the power steering cylinder (11) and the clutch booster (7) is supplied to the oil clutch (12) or directly to the drain (13). A hydraulic circuit for an industrial vehicle.