JPH1160189A - Hydraulic circuit for industrial vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic circuit which can improve work speed even in an industrial vehicle in which pump size is selected by load balance which does not cause an engine failure even at the time of low idling by setting a flow rate in a control circuit in such a manner that the flow rate is larger than a pump discharge amount of a second pump and after in a low idling condition of an engine and constituting the hydraulic circuit in such a way that an excess circuit which makes oil pressure which changes the controlled flow rate escape meets a hydraulic operation circuit on a discharge side of a first pump. SOLUTION: In a hydraulic circuit for industrial vehicle provided with a multiple pump having two or more pumps, a flow divider 4 is provided on a pump discharge side of a second pump 2 and after, a flow rate in a control circuit 7 is set in such a manner that it is larger than a pump discharge amount of the second pump 2 and after in a low idling condition of an engine 3, and an excess circuit 8 which makes oil pressure exceeding the controlled flow rate escape meets a hydraulic operation circuit, 6 on a discharge side of a first pump 1 to constitute the hydraulic circuit for industrial vehicle.

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.

[0002]

2. Description of the Related Art In the prior art, in a vehicle equipped with a dual pump or more multiple pumps, a pump size is determined by a total discharge amount of two or more pumps corresponding to an engine low idle output. We have selected and decided. However, depending on how much load balance between engine output and pump size is available, an engine idle-up device may be added as necessary, or an engine stall prevention valve that releases oil from the high-pressure circuit may be added. .

[0003]

However, if the pump size is selected so as to match the general engine output as described above, there is almost no danger of engine stall during low idling of the engine. The working speed of the hydraulic equipment and the like used in the cargo handling work during high idle is determined by the selected pump size, and it is difficult to seek a further increase in performance. However, in order for industrial vehicles to compete for work performance with each other, pump sizes that are full for the low idle output of the engine and have no margin are being selected.
The engine will stall when the engine is in low idling state, and the engine idle-up device is installed, and the possibility of engine stall due to a response delay is great. Speed loss. Therefore, it is an object of the present invention to provide a hydraulic circuit capable of improving the working speed even in an industrial vehicle having a hydraulic circuit in which a pump size is selected with a load balance that does not cause engine stall.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and is intended for a hydraulic circuit for an industrial vehicle having a double pump or more multiple pumps. A flow divider is provided on the discharge side of the subsequent pump, and the flow rate of the control circuit is set to be larger than the discharge rate of the pump after the second pump in the low idle state of the engine. The circuit constitutes a hydraulic circuit so as to join the hydraulic operation circuit on the discharge side of the first pump.

With the above-described hydraulic circuit configuration, when the engine is in a low idling state, the load balance between the engine output and the pump size is always stable, there is no possibility of engine stall, and the load handling machine is operated. With the increase in engine speed and the high idle state, among the discharge amounts of the second and subsequent pumps, the constant amount of hydraulic pressure sent to the control circuit always maintains the function of the hydraulic device, while the excess discharge amount is reduced by the flow divider. Is added to the operation circuit of the discharge amount of the first pump through the surplus circuit, and is sent to the control valve of the hydraulic equipment for the cargo handling machine to be used. Up is measured.

Accordingly, the hydraulic pressure, which has conventionally been unloaded from the increase in engine speed to the high idle state, or wasted and discharged as an excessive discharge amount, can be efficiently used for cargo handling work. This will help to improve energy consumption and reduce energy loss.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a pressure circuit diagram of an industrial vehicle showing one embodiment, and uses a dual pump. The hydraulic pressure of the operation circuit 6 discharged from the first pump 1 and driven by the engine 3 passes through the control valve 5 that controls the cargo handling machine and the like, and is used as a hydraulic device for the cargo handling machine such as a lift cylinder or a tilt cylinder. Sent to 51.
The hydraulic pressure discharged from the second pump 2 is sent to a control hydraulic device 71 such as a brake booster to form a control circuit 7.

A flow divider 4 is provided in the middle of the path of the control circuit 7 to which the hydraulic pressure discharged from the second pump 2 is sent.
The flow rate is set to be sent to 71. The set flow rate is set by the second pump discharge oil amount when the engine 3 is in a low idle state.

On the other hand, the discharge amount of the second pump 2 increases until the rotation side of the flow divider 4, that is, the rotation of the engine 3 rises from low idle to a high idle state, and the set flow rate of the flow divider 4 is reduced. The excess surplus oil amount is connected to the hydraulic circuit of the operation circuit 6 discharged from the first pump 1 in the middle of the hydraulic path so as to be merged, and forms a hydraulic circuit as the surplus circuit 8.

By configuring the hydraulic circuit as described above, it is easy to set a pump load corresponding to the engine output when the engine 3 is in a low idle state.
In order to eliminate the risk of engine stall and to carry out cargo handling work, the surplus oil pressure of the second pump 2 is added to the operation oil pressure of the first pump 1 until the rotation of the engine 3 rises and reaches a high idle state. Thus, the speed of the cargo handling work is increased, which contributes to the improvement of the work efficiency and contributes to the effective use of energy.

[Brief description of the drawings]

FIG. 1 is a hydraulic circuit diagram showing an embodiment provided with a double pump according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st pump 2 2nd pump 3 Engine 4 Flow divider 6 Operation circuit 7 Control circuit 8 Surplus circuit

Claims (1)

[Claims] In an industrial vehicle equipped with a dual pump or multiple pumps, a flow divider (4) is provided in a hydraulic circuit on the pump discharge side after the second pump (2), and the flow divider (4) is provided. ) Is controlled by the engine
The second pump (2) when (3) is in the low idle state
A control circuit (7) set to be larger than the subsequent discharge amount is formed, and a surplus circuit (8) for releasing the hydraulic pressure exceeding the control flow rate from the flow divider (4) is operated by the hydraulic operation of the discharge side of the first pump (1). A hydraulic circuit for an industrial vehicle, wherein the hydraulic circuit is configured to join the circuit (6).