JPH0543876B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control device for a hydraulic pump driven by a prime mover in a construction machine.

Hydraulic pumps used in construction machinery are driven by a prime mover mounted on the construction machine, but in this case, the average output of the prime mover that drives the hydraulic pump is about 70 to 80% of its maximum output. By the way, construction machines that use hydraulic pumps rarely perform constant work at constant temperatures, and in rare cases, they drive large loads at high temperatures. Therefore, the capacity of the cooling system of the prime mover that drives the hydraulic pump is designed in accordance with the worst usage conditions of the hydraulic pump. For example, in the case of construction machinery such as hydraulic excavators and cranes, there is work that requires the prime mover to maintain its maximum output for a relatively long period of time in high-temperature locations. and continued maximum output.

The capacity of a cooling system installed to meet the worst usage conditions that rarely occur has the disadvantage that it occupies too much space compared to normal usage conditions and requires high costs. Ta.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic pump control device that can reduce the capacity of a cooling system for a prime mover that drives a hydraulic pump, without causing any problems in driving the prime mover even in high-temperature regions. .

In order to achieve this object, the present invention provides a detection device that detects the temperature of cooling water of a prime mover, inputs the detected temperature, outputs a control signal according to a predetermined function, and outputs a control signal according to a predetermined function. The system is characterized by controlling the operation of a variable displacement mechanism that controls the discharge capacity of the hydraulic pump according to the temperature of the cooling water, so that when the temperature of the cooling water is high, the discharge capacity of the hydraulic pump is reduced to reduce the load on the prime mover. do.

The present invention will be explained below based on the embodiment shown in FIG.

In the figure, 1 is a prime mover such as an engine, and is equipped with a cooling system such as a radiator, a water pump, and cooling water piping. Reference numeral 2 denotes a variable displacement hydraulic pump connected to and driven by a prime mover, and 2a denotes a variable displacement mechanism for controlling the discharge displacement of the hydraulic pump 2.
3 is a regulator for operating the variable displacement mechanism, which includes a cylinder 3a, a servo valve 3b, a piston 3c, springs 3d and 3e, a chamber 3f, and a link mechanism 3.
It is composed of g. The cylinder 3a has a piston coupled to a variable displacement mechanism 2a and a link mechanism 3g. The servo valve 3b inputs the discharge pressure _Pd of the hydraulic pump 2, and when the springs 3d, 3e and the pressure _Pd become unbalanced, the cylinder 3a is driven accordingly and the displacement variable displacement mechanism 2a is activated.
This operation takes a new neutral position via the link mechanism 3g. Piston 3c is chamber 3
The forces of the springs 3d and 3e are changed according to the oil pressure in f.

Reference numeral 4 denotes a hydraulic pressure source for hydraulic pressure supplied to the regulator 3. Reference numeral 5 denotes a temperature detection device that detects the temperature of the cooling water of the prime mover and outputs a signal θ corresponding to this temperature. 6 is an arithmetic unit which, as shown, has a predetermined function and outputs a signal i corresponding to the input temperature signal θ. For example, the above function outputs a temperature signal i ₀ having a low constant value until the temperature signal θ ₀ , but after the temperature signal exceeds θ ₀ , it outputs a signal i proportional to the temperature signal. 7
is an electromagnetic proportional valve operated by the output signal i of the arithmetic unit 6;
and a port communicating with the tank 8, and the pressure P _e of the chamber 3f is introduced.

Here, the operation of this embodiment shown in FIG. 1 will be explained.

It is now assumed that the hydraulic pump 2 is driving a load in a normal working state under a normal environment.
In this case, the output of prime mover 1 is 70% of its maximum output.
Within the range of ~80%, the temperature of the cooling water is kept at a low temperature. Therefore, the value of the output signal of the detection device 5 is less than or equal to θ ₀ and the output signal i of the arithmetic device 6 is at a low value i ₀ . For this reason, the electromagnetic proportional valve 7
The pressure P _c in the chamber 3f controlled by the operation of is also small, and the piston 3c is at a constant position determined by the springs 3e, 3d and the pressure P _c in the chamber 3f. In this state,
For example, when the pressure P _d of the hydraulic pump 2 increases, this pressure is transmitted to the servo valve 3 b, and the servo valve 3 b moves to the left against the springs 3 e and 3 d to connect the right chamber of the cylinder 3 a to the tank 8 . As a result, the piston of the cylinder 3a moves to the right, reducing the tilting angle of the variable displacement mechanism 2a and reducing the displacement of the hydraulic pump 2. This operation is transmitted to the servo valve 3b via the link mechanism 3g, and a new equilibrium state is established with the servo valve 3b in the neutral position. The relationship between the discharge pressure P and the discharge capacity Q of the hydraulic pump 2 in this case is shown by a curve A in FIG. As is clear from curve A, when the pressure P decreases, the regulator 3 operates in the opposite manner as described above, and the displacement variable mechanism 2
The displacement angle of a is increased to increase the discharge capacity of the hydraulic pump 2.

Next, it is assumed that the hydraulic pump 2 is driving a load that causes the prime mover 1 to have maximum output for a relatively long period of time in a high temperature environment. In this case, since the temperature of the cooling water of the prime mover 1 naturally increases, the output signal θ of the detection device 5 becomes a large value exceeding θ ₀ . Therefore, the output signal i of the arithmetic unit 6 also has a proportionally large value. Furthermore, the electromagnetic proportional valve 7 is also operated in proportion to this output signal i, and the pressure in the chamber 3f also increases. As a result, the piston 3c moves to the left, compressing the spring 3e and expanding the spring 3d, thereby weakening the spring force of the spring 3d against the servo valve 3b. In this state, compared to the above-mentioned normal case, even if the pressure P _d of the hydraulic pump 2 is the same, the servo valve 3b is moved further to the left, so that the tilting of the variable displacement mechanism 2a is The reduction in the angle also becomes large, and the reduction in the discharge capacity of the hydraulic pump 2 also becomes large. That is, when the prime mover 1 is in an operating state where its cooling water becomes high temperature, the hydraulic pump 2
This reduces the load on the prime mover 1 by increasing the reduction in discharge capacity. Pressure P _d of hydraulic pump 2
decreases, the servo valve 3b increases the tilt angle of the variable displacement mechanism 2a that has moved to the right, and tries to increase the discharge capacity, but since the spring 3d is in an extended state, the degree of movement of the servo valve 3b to the right is is smaller than in the normal case, suppressing an increase in discharge capacity. The relationship between the discharge pressure and discharge capacity of the hydraulic pump 2 using the temperature of the cooling water detected by the detection device 5 as a parameter is shown by curves B, C, and D in FIG. In the figure, each temperature signal θ ₀ to _{θ 3} has the following relationship: θ ₀ < θ ₁ < θ ₂ <
There is a relationship of θ ₃ . As is clear from FIG. 2, if the pressure P _d of the hydraulic pump 2 is the same, its discharge capacity decreases as the temperature increases, and the pump operates to reduce the load on the prime mover 1.

In this way, in this embodiment, the temperature of the cooling water of the prime mover is detected, the arithmetic unit outputs a signal corresponding to this temperature, and this signal excites the electromagnetic proportional valve to operate the piston provided in the regulator. Since the spring force of the servo valve of the regulator is changed, the capacity of the cooling system of the prime mover that drives the hydraulic pump can be reduced, saving space and reducing costs. Moreover, even if the capacity is reduced in this way, the prime mover will not overheat when used in high temperature regions. Furthermore, even if an abnormality occurs in the cooling system, such as a slip in the cooling fan or dirt on the radiation fins, overheating of the prime mover can be alleviated.

As described above, in the present invention, the temperature of the cooling water of the prime mover is detected, a signal corresponding to this temperature is output according to a predetermined function, and the operation of the variable displacement mechanism is controlled in accordance with this signal. This makes it possible to reduce the capacity of the cooling system for the prime mover that drives the hydraulic pump, saving space and reducing costs. Moreover, even if the capacity is reduced in this way, the prime mover will not overheat when used in high temperature regions.
Furthermore, even if an abnormality occurs in the cooling system, such as a slip in the cooling fan or dirt on the heat dissipation fins, overheating of the prime mover can be alleviated.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a hydraulic pump control device according to an embodiment of the present invention, and FIG. 2 is a characteristic diagram showing the relationship between pressure and capacity of the hydraulic pump shown in FIG. 1. 1... Prime mover, 2... Variable displacement hydraulic pump, 2
a... variable displacement mechanism, 3... regulator, 3a... cylinder, 3b... servo valve, 3c
...Piston, 3d, 3e...Spring, 3f...
Chamber, 3g... Link mechanism, 5... Detection device, 6...
...Arithmetic unit, 7...Solenoid proportional valve.

Claims (1)

[Claims] 1. A hydraulic pump driven by a prime mover and a variable displacement mechanism for controlling the discharge capacity of the hydraulic pump, which includes a temperature detection device that detects the temperature of the cooling water of the prime mover, and a temperature detection device that detects the temperature of the cooling water of the prime mover, and a control signal generating means for outputting a control signal having a characteristic of reducing the input torque of the hydraulic pump in response to the detected temperature increase;
A control device for a hydraulic pump, comprising: control means for controlling the operation of the variable displacement mechanism in response to a control signal from the control signal generation means.