JPH0524441A - Hydraulic circuit for industrial vehicle - Google Patents

Abstract

PURPOSE:To always keep the number of rotations of a cooling fan constant even if the oil temperature is varied. CONSTITUTION:In an industrial vehicle in which a delivery oil under pressure from a hydraulic pump 1 is divided by a flow divider 2, and a part of it is fed to a hydraulic motor 4 for driving a cooling fan 5 and the remaining is fed to a work machine, a flow control valve 10 is provided between a line 3 for feeding oil pressure to the hydraulic motor 4 and a tank 8. The flow control valve 10 is controlled by signals from a rotational speed detector 11 for detecting the number of rotations of the cooling fan 5 so that the number of rotations of the cooling fan 5 is always kept at a constant. Thus the number of rotations of the cooling fan 5 can be kept always constant even if the oil temperature is varied.

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 a hydraulically driven cooling fan.

[0002]

2. Description of the Related Art A conventional hydraulic circuit for an industrial vehicle having a hydraulically driven cooling fan is shown in FIG. In the conventional hydraulic circuit described above, the discharge pressure of the hydraulic pump a is divided by the flow divider b to supply a constant hydraulic pressure to the hydraulic motor c, and the hydraulic motor c drives the cooling fan f for cooling the radiator e. It has become. The remaining flow rate divided by the flow divider b is
Is supplied to a working machine (not shown) to drive the working machine.

[0003]

However, in the hydraulic motor c that drives the cooling fan f, the volumetric efficiency decreases as the oil temperature rises. For this reason, in a conventional hydraulic circuit in which a constant hydraulic pressure divided by the flow divider b is supplied to the hydraulic motor c, as the oil temperature rises, the rotation speed of the cooling fan f becomes the curve B in FIG. As shown in the figure, there was a problem such as a drop in engine temperature and overheating. The present invention has been made for the purpose of improving the above problems, and an object of the present invention is to provide a hydraulic circuit for an industrial vehicle in which the rotation speed of a cooling fan can be maintained constant regardless of the oil temperature.

[0004]

In order to achieve the above object, the present invention divides the discharge pressure of a hydraulic pump by a flow divider and supplies a part of the discharge pressure to a hydraulic motor that drives a cooling fan, and the remaining flow rate. In the hydraulic circuit of the industrial vehicle that supplies the hydraulic fluid to the working machine, a flow control valve is provided between the tank for supplying the hydraulic pressure to the hydraulic motor and the tank, and the flow control valve detects the rotational speed of the cooling fan. The rotation speed of the cooling fan is controlled to be always constant by the signal from the rotation speed detector.

[0005]

With the above structure, even if the oil temperature of the working oil rises during work and the volumetric efficiency of the hydraulic motor decreases, the flow rate supplied to the hydraulic motor increases, so the rotation speed of the cooling fan is always kept constant. it can.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the drawing shown in FIG. In FIG. 1, reference numeral 1 denotes a hydraulic pump mounted on an industrial vehicle (not shown). The discharge pressure of the hydraulic pump 1 is diverted by a flow divider 2, a part of which is supplied to a hydraulic motor 4 by a pipeline 3, and the rest is a pipe. It is adapted to be supplied to a working machine (not shown) through the path 5.

In consideration of the volumetric efficiency of the hydraulic motor 4 in which the flow rate of the hydraulic pressure supplied to the hydraulic motor 4 decreases as the oil temperature rises, a predetermined rotational speed is obtained when the oil temperature rises most. The flow rate is set too high. Further, a cooling fan 5 is attached to the hydraulic motor 4 so that the radiator 6 for radiating engine cooling water is cooled by the cooling fan 5, and the oil discharged from the hydraulic motor 4 is supplied to the conduit 7 Is to be drained to the tank 8.

On the other hand, a pipeline 3 for supplying hydraulic pressure to the hydraulic motor 4
A flow rate control valve 10 is provided midway between the tank 8 and the tank 8. The flow rate control valve 10 has its opening controlled by a signal from a rotation speed detector 11 which detects the rotation speed of the cooling fan 5. It is like this.

The operation will now be described. When the oil temperature of the hydraulic oil is low, such as immediately after the start of work, the opening degree of the flow control valve 10 is large. As a result, a part of the hydraulic pressure divided by the flow divider 2 is drained to the tank 8 from the flow control valve 10, so that even if the flow divider 2 divides a larger amount than the specified amount, the hydraulic motor 4 is not supplied with the specified amount of flow. Is supplied, and the cooling fan 5 is rotated at a constant rotation speed to cool the radiator 6.

After that, when the oil temperature rises with the lapse of time and the volumetric efficiency of the hydraulic motor 4 decreases, the rotation speed of the cooling fan 5 also decreases. When the number of rotations of the cooling fan 5 becomes equal to or lower than the set number of rotations, the opening of the flow rate control valve 10 is throttled by the signal from the number of rotations detector 11, so that the flow rate of the hydraulic pressure supplied to the hydraulic motor 4 increases and the cooling is performed. The rotation speed of the fan 5 is maintained constant.

As a result, the rotational speed of the cooling fan 5 can be maintained constant even if the oil temperature of the operating oil changes, so that overheating of the engine can be prevented. The relationship between the oil temperature and the rotation speed of the cooling fan by the hydraulic circuit of the present invention is shown by the curve A in FIG. For comparison, a curve B shows the relationship between the oil temperature of the conventional hydraulic circuit and the rotation speed of the cooling fan.

[0012]

As described above in detail, the present invention provides a flow rate control valve whose opening is controlled in accordance with the number of rotations of a cooling fan in the middle of a pipeline for supplying hydraulic pressure to a hydraulic motor for driving a cooling fan. Since the above is provided, even if the temperature of the working oil rises during work, the rotation of the cooling fan is kept constant, so that overheating of the engine can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a hydraulic circuit of an industrial vehicle according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an oil temperature and a rotation speed of a cooling fan.

FIG. 3 is a circuit diagram showing a hydraulic circuit of a conventional industrial vehicle.

[Explanation of symbols] 1 hydraulic pump 2 flow divider 3 pipe line 4 hydraulic motor 5 cooling fan 8 tank 10 flow control valve 11 rotation speed detector

Claims (1)

Claim: What is claimed is: 1. A discharge pressure of a hydraulic pump (1) is diverted by a flow divider (2) to supply a part of the discharge pressure to a hydraulic motor (4) driving a cooling fan (5) and a remaining flow rate to a working machine. In the hydraulic circuit of the industrial vehicle configured as described above, a flow rate control valve 10 is provided between the pipeline 3 that supplies the hydraulic pressure to the hydraulic motor 4 and the tank 8, and the flow rate control valve 10 controls the rotation speed of the cooling fan 5. A hydraulic circuit for an industrial vehicle in which a rotation speed of the cooling fan 5 is controlled to be always constant by a signal from a rotation speed detector 11 that detects the rotation speed.