JPS64570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic cooling fan control device for cooling an engine and a retarder brake mounted on a construction machine such as a dump truck.

In order to operate the engine of a dump truck or the like efficiently, it is necessary to maintain the cooling water temperature at an appropriate temperature. Therefore, while the cooling water is circulated through the path from radiator to engine to radiator, a cooling fan is connected to the output shaft of the engine via a fan belt, and this fan is rotated to blow air to the radiator to cool the cooling water. I have to.

However, in the conventional cooling device that rotates the fan via a fan belt, the fan rotates according to the rotational speed of the engine, so it is not possible to control the air volume to the radiator depending on the cooling water temperature. cannot be maintained at an appropriate value. For this reason, the engine could not be operated efficiently, resulting in a large horsepower loss.

Further, when a dump truck used for transporting ore in a mine or the like goes downhill, the driver manually operates a retarder control lever to control the speed. The effectiveness of the retarder brake varies greatly depending on changes in the slope of the road, the weight and weight of the load, and the retarder brake control is performed at the discretion of the driver each time. For this reason, it is difficult to perform optimal control according to road conditions, loading conditions, etc., and when traveling long distances downhill, there is a risk of overheating and damage to the brake disc.

Therefore, in order to prevent such accidents, the brake cooling oil temperature is detected, and if the oil temperature exceeds a dangerous temperature, an alarm or the like is issued to warn the driver. This warning causes the driver to stop the vehicle and wait until the oil temperature drops.

However, such warning devices do not actively prevent brake seizure, and take countermeasures after the oil temperature has risen, which may damage the brakes. Furthermore, if the driver ignores the warning and continues driving, there is no effect, and as a result, there is a risk of overusing the brakes or causing an accident. Furthermore, if the vehicle is stopped every time the oil temperature rises, work efficiency will decrease accordingly.

The present invention has been made to solve the above-mentioned disadvantages, and its purpose is to provide automatic cooling fan control that can prevent the retarder brake from seizing and maintain the engine cooling water temperature at an appropriate value. It is about providing.

The present invention will be described in detail below based on one embodiment of the accompanying drawings.

In Fig. 1, the engine cooling water circulates in the path of radiator 1 → engine 3 → brake oil cooler 4 → radiator 1, and the hydraulic oil for the retarder brake is circulated through the oil tank 5 → left and right retarder brakes 6, 7 → The brake oil is circulated along a path from the brake oil cooler 4 to the oil tank 5.
The cooling water cooled by the radiator 1 cools the engine 3, and then further cools the retarder brake hydraulic oil in the brake oil cooler 4. In the process of cooling the engine 3 and the brake hydraulic oil, the cooling water whose temperature has increased is cooled again in the radiator 1.

On the other hand, the shaft 2a of the cooling fan 2 is connected to the drive section 2.
0 hydraulic motor 21, and is rotationally driven by this hydraulic motor 21. The hydraulic motor 21 is rotationally driven by oil discharged from a variable displacement hydraulic pump 22. The variable displacement hydraulic pump 22 is, for example, a swash plate type hydraulic pump, and the swash plate angle is controlled by a servo valve 23, and the discharge capacity is controlled accordingly. This hydraulic pump 22
is adapted to be driven by an engine 3, and the load on the engine 3 changes depending on the discharge amount of the hydraulic pump 22. The rotational speed of the hydraulic motor 21 changes depending on the discharge amount of the hydraulic pump 22. According to the rotation of this hydraulic motor, the cooling fan 2
rotates and blows air to the radiator 1 to cool the radiator 1.

The water temperature sensor 15 is the cooling water inlet 1 of the radiator 1.
It is disposed at a predetermined position near point a, detects the temperature of the cooling water flowing into the radiator 1, outputs a corresponding temperature signal Vt, and applies it to the control circuit 10. This water temperature sensor 10 is composed of, for example, a thermistor. A reference temperature setter 11 of the control circuit 10 is for setting a reference cooling water temperature T, and outputs a temperature signal V _T corresponding to a preset water temperature T. This reference temperature T is set to a value that optimizes engine efficiency. Reference temperature signal V _T and actual cooling water temperature
The deviation ε from Vt is amplified by an amplifier 12 with a gain of −K ₁ and output as a signal −K ₁ ε. Here amplifier 1
Since the gain of 2 is negative, the polarity of the output signal -K ₁ ε is opposite to the polarity of the deviation ε. This signal -K ₁ ε is applied to the contact 13B of the control signal changeover switch 13. Further, the maximum rotation command signal Vm is applied to the contact 13A of the control signal changeover switch 13.
This command signal Vm is for setting the rotational speed of the cooling fan 2 to the maximum rotational speed when the retarder brake is used. The control signal changeover switch 13 is interlocked with, for example, a retarder brake lever (not shown), and is turned on when the retarder brake is used, with the contact 13A turned on and the contact 13B turned off. During normal driving without using the retarder brake, the switch is off and contact 1
3A is turned off and contact 13B is turned on. and,
The control signal changeover switch 13 selectively outputs the command signal Vm or the input signal -K ₁ ε and applies it to the servo valve drive circuit 14 .

When the input signal is polar, the servo valve drive circuit 14 generates a control signal according to the magnitude of the input signal.
Output Vs. Furthermore, if the input signal is polar, no control signal is output (Vs=0). The servo valve 23 operates according to the input control signal Vs to control the swash plate angle of the hydraulic pump 22. This hydraulic pump 2
The swash plate angle of No. 2 is at its minimum when the control signal Vs is 0, and the discharge amount is accordingly at its minimum. The discharge amount at this time is so small that the hydraulic pump 22 itself does not seize.

First, the case when the control signal changeover switch 13 is off, that is, the case during normal operation will be described.

When the cooling water temperature is lower than the reference water temperature, Vt<
V _T , the deviation ε becomes the polarity, and the output signal −K ₁ ε of the amplifier 12 becomes the polarity. Therefore, the control signal Vs becomes 0, and the discharge amount of the hydraulic pump 22 becomes the minimum. However, the input/output characteristics of the drive circuit 14 are as shown in FIG. Therefore, the rotational speed of the hydraulic motor 21 becomes the lowest, and the rotational speed of the cooling fan 2 also becomes the lowest. Further, the load caused by the cooling fan of the engine 3 is also minimized. In this state, the amount of air blown to the radiator 1 is almost zero. If the cooling water temperature is lower than the standard water temperature, radiator 1
There is no need to blow air to.

When the temperature of the engine 3 rises, the cooling water temperature rises accordingly, and when Vt > V _T , the deviation ε (=
V _T -Vt) has a polarity, and the output signal of the amplifier 12 -K ₁ ε has a polarity. The drive circuit 14 outputs a control signal Vs corresponding to the input signal -K ₁ ε and applies it to the servo valve 23 . The input/output characteristics of this drive circuit 14 are shown in FIG. The servo valve 23 controls the swash plate angle of the hydraulic pump 22 in response to this control signal, thereby controlling the discharge amount. The hydraulic motor 21 rotates the cooling fan 2 at a rotational speed according to the discharge amount of the hydraulic pump 22 and blows air to the radiator 1.
to cool down. Then, the temperature of the cooling water flowing into the radiator 1 is controlled to the reference water temperature T. In this way, radiator 1 → engine 3 → oil cooler 4
→The temperature of the cooling water flowing in the path of the radiator 1 is maintained at the reference water temperature T, and the engine 3 is operated at maximum efficiency.

Incidentally, the relationship between the swash plate angle of the hydraulic pump 22 and the cooling water temperature is expressed as shown in FIG.

In addition, when using the retarder brake, when the control signal changeover switch 13 is turned on, the signal -
The maximum rotation command signal Vm is used as the drive circuit 1 instead of K ₁ ε.
4 is input. When the input signal Vm is applied, the drive circuit 14 outputs the maximum value Vsm of the control signal, controls the swash plate angle of the hydraulic pump 22 to the maximum, and maximizes the pump discharge amount. Therefore, the rotational speed of the cooling fan 2 becomes the highest, and the amount of air blown to the radiator 1 becomes the largest. Accordingly, the effect of cooling the brake hydraulic fluid in the oil cooler 4 is maximized, and a rise in temperature of the brake hydraulic fluid can be suppressed. Of course, the cooling effect of the engine 3 is also increased.
Note that at this time, the load of the cooling fan 2 on the engine 3 becomes maximum.

In this embodiment, a case has been described in which the retarder brake hydraulic oil is also cooled, but the present invention is not limited to this, and it goes without saying that only the engine may be cooled. Therefore, depending on the purpose, the water temperature sensor 15 may be installed near the engine outlet.

As explained above, according to the present invention, by controlling the amount of air blown to the radiator according to the engine cooling water temperature and maintaining the cooling water temperature at a predetermined temperature,
The engine can always be operated at maximum efficiency, reducing engine horsepower loss and making effective use of energy. Furthermore, since the cooling fan is driven by a hydraulic motor, there are advantages such as improved maintainability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the automatic cooling fan control device according to the present invention, and FIG. 2 is a diagram showing the relationship between the swash plate angle of the hydraulic pump of the device shown in FIG. 1 and the cooling water temperature. . Further, FIG. 3 shows the input/output characteristics of the drive circuit 14. 1...Radiator, 2...Cooling fan, 3...
Engine, 4... Brake oil cooler, 5...
Oil tank, 6, 7... Retarder brake, 1
2...Amplifier, 13...Control signal changeover switch, 14...Drive circuit, 15...Water temperature sensor, 2
1...Hydraulic motor, 22...Hydraulic pump, 23...
...servo valve.

Claims (1)

[Scope of Claims] 1. A cooling waterway through which cooling water circulates to cool the engine and the retarder brake; a cooling fan that blows air to a radiator provided in the cooling waterway to cool the cooling water; a hydraulic motor that drives the cooling fan; a variable displacement hydraulic pump that is driven by the engine and rotates the hydraulic motor according to a discharge amount; a water temperature sensor that detects the temperature of the cooling water; and a target of the cooling water. a setting device for setting a temperature; and, when the temperature detected by the water temperature sensor is larger than the target temperature, outputting a first control signal according to the temperature difference; control signal output means for outputting a second control signal for making the swash plate angle of the variable displacement hydraulic pump zero when the temperature is below the target temperature; and depending on whether or not the retarder brake is used. , control signal switching for selectively outputting either a third control signal for maximizing the swash plate angle of the variable displacement hydraulic pump or the first and second control signals output from the control signal output means; and means for controlling a swash plate angle of the variable displacement hydraulic pump based on the output of the control signal switching means, the cooling fan cooling the retarder brake and controlling the temperature of the cooling water to a target temperature. Automatic control device.