JPH09242624A - Fuel cooling device for construction equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To operate a fuel cooling fan only when required by a simple structure. SOLUTION: Excess fuel from an engine 2 is passed through a fuel cooler 6 arranged in a fuel reflux pipe 5 and refluxed in a fuel tank l, however, the fuel cooler 6 is cooled by cooling wind from a fan 8 driven by a hydraulic motor 9. A temperature switch 20 for detecting fuel temperature is arranged in the fuel tank 1, and a selector valve 21 is arranged in an unload piping 23 which is diverged from an oil pressure piping 10 between an oil pressure pump 11 and the hydraulic motor 9, and connected to an operating oil tank 22. When detected temperature by the temperature switch 20 is at a set temperature or more, the selector valve 21 is retained in a switching position (a) by the action of a return spring 21a, and when fuel temperature is low and the detected temperature by the temperature switch 20 is at the set temperature or below, the selector valve 21 is changed over to a switching position (b) against the return spring 21a when a solenoid 21b is energized, and the hydraulic pump 11 is unloaded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cooling device for cooling fuel supplied to a prime mover of a construction machine.

[0002]

Fuel for operating a prime mover is supplied from a fuel tank to a carburetor through a fuel supply pipe.
Excess fuel in this vaporizer is returned to the fuel tank. In this way, the fuel circulates between the fuel tank and the prime mover, while the temperature of the fuel rises due to the heat of combustion. Since the fuel is highly volatile, if the fuel temperature rises too much, the shaft output of the prime mover will decrease, and if the fuel temperature rises significantly, the fuel will partially become vapor and accumulate in the piping etc. As a result, problems such as a so-called vapor lock phenomenon that hinders fuel supply and a so-called forming phenomenon that a large amount of bubbles are generated in the fuel tank occur.

In order to prevent the temperature of the fuel from rising and causing vapor lock or forming phenomenon, a cooling mechanism is provided in the fuel circulation system to cool the fuel. Here, a construction machine such as a hydraulic excavator is equipped with a hydraulic pump, and hydraulic oil supplied from the hydraulic pump drives hydraulic actuators such as a hydraulic cylinder and a hydraulic motor to drive respective parts constituting the machine. It Therefore,
As the fuel cooling mechanism, a fan driven by a hydraulic motor is used, a hydraulic pump is connected to the prime mover, and the hydraulic motor is driven by the pressure oil supplied from the hydraulic pump. It is also rational.

Therefore, an example of a conventional fuel cooling device is shown in FIG. In the figure, 1 is a fuel tank and 2 is an engine. The engine 2 includes a fuel pump 2a, a governor 2b, and an injector 2c. The fuel pressure-fed from the fuel pump 2a is supplied to the injector 2c after the pressure is adjusted by the governor 2b according to the rotation speed and load of the engine 2. A fuel supply pipe 3 is connected between the fuel tank 1 and the engine 2, and a fuel filter 4 is provided in the middle of the fuel supply pipe 3. Of the fuel supplied to the engine 2, excess fuel that is not injected from the injector 2c is recirculated to the fuel tank 1 via the fuel recirculation pipe 5.

During operation of the engine 2, the temperature of the engine 2 rises, so that the temperature of the surplus fuel returned to the fuel tank 1 also rises. In order to suppress an increase in the fuel temperature, the fuel recirculation pipe 5 is provided with a fuel cooler 6 to cool the excess fuel recirculated to the fuel tank 1. In addition,
Reference numeral 7 is a fuel relief valve for preventing the pressure on the upstream side of the fuel cooler 6 in the fuel return pipe 5 from becoming abnormally high.

In order to supply cooling air to the fuel cooler 6,
A fan 8 is provided, and the fan 8 is driven by a hydraulic motor 9. The hydraulic motor 9 is a hydraulic pipe 10.
Is connected to the hydraulic pump 11 via the hydraulic pump 11, and the hydraulic motor 9 is operated by the pressure oil supplied from the hydraulic pump 11. The hydraulic pump 11 is driven by the engine 2. Further, in the figure, 12 is a relief valve that functions as a safety valve that limits the pressure of the circuit that drives the hydraulic motor 9, and 13 is for making up so that the hydraulic motor 9 does not become a load when the engine 2 is rapidly decelerated. The make-up valve 14 is a low-pressure relief valve for producing a predetermined pressure in the outlet pipe of the hydraulic motor 9 to enable make-up. And in the figure,
Reference numerals 15 and 15 are main pumps for driving a hydraulic actuator including a hydraulic motor and a hydraulic cylinder that constitute the machine.

With the above structure, when fuel is supplied to the engine 2 to operate the engine 2, the hydraulic pump 11 operates and pressure oil is supplied to the hydraulic motor 9. The fan 8 connected to 9 rotates and the cooling air is supplied to the fuel cooler 6. Therefore, while the surplus fuel from the engine 2 is returned to the fuel tank 1 through the fuel recirculation pipe 5, it is cooled by the fuel cooler 6, and the fuel temperature is so high as to cause vapor lock and forming phenomenon. You can prevent it from rising.

[0008]

The construction machine is for working outdoors, and the outside air temperature is not constant. For example, when working in the daytime in the summer, the fuel temperature can become extremely high, and therefore, the excess fuel must be cooled by the fuel cooler when it is recirculated. However, when the outside air temperature is low, such as in cold regions or winter nights, the fuel temperature does not rise much even if the construction machine continues to operate for a long time, and the cooling air is supplied by the fan. There are good things to do. Even in such a case, driving the fan is a waste of energy. Especially,
When the outside air temperature is extremely low, for example, below freezing, the viscosity of the fuel becomes high, the pressure loss in the supply path from the fuel tank to the fuel pump in the engine becomes large, and the suction pressure of the fuel pump becomes low. Therefore, there is a disadvantage that the fuel suction efficiency of the engine is reduced, so it is better not to cool the fuel.

The present invention has been made in view of the above points, and it is an object of the present invention to operate a fan for cooling fuel only when necessary by a simple structure.

[0010]

In order to achieve the above object, the present invention provides a prime mover, a fuel tank for supplying fuel to the prime mover, fuel from the fuel tank to the prime mover, and a surplus from the prime mover. A fuel circulation pipe for circulating the fuel in the fuel tank, a fan arranged in the middle of the fuel circulation pipe to cool the fuel flowing in the pipe, and a hydraulic motor for driving the fan. In the above configuration, a temperature switch is provided in the fuel tank or the fuel circulation pipe, and when the temperature of the fuel is equal to or lower than a predetermined set temperature, the pressure oil is stopped from being supplied to the hydraulic motor. It is characterized by that.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A fan is used to cool fuel, and this fan is driven by a hydraulic motor, but when the fuel temperature is low, the rotation of the fan is stopped. This rotation of the fan can be stopped by unloading the hydraulic pump, which puts the hydraulic pump in a virtually unloaded state without consuming unnecessary energy and cooling the fuel too much. Things will disappear. For this purpose, it is necessary to detect the fuel temperature, but the fuel temperature may be detected by detecting whether or not a predetermined set value is exceeded. Therefore, a temperature switch that has a simple structure and outputs an ON / OFF signal is used. This temperature switch can be provided in the fuel tank or in the fuel circulation pipe. It is most preferable to provide the temperature switch on the fuel tank because the fuel temperature is substantially equal on the fuel supply pipe side from the fuel tank, the capacity of the fuel tank is large, and there is a space for providing the temperature switch.

As a setting temperature of the temperature switch, it is necessary to prevent the viscosity of the fuel from becoming abnormally low at a minimum, but if the fan is continuously driven even though it is not necessary,
Energy loss increases. In order to avoid this, the set temperature is raised to some extent and set to a temperature condition, for example, 60 ° C., which can surely prevent inconveniences such as vapor lock and forming. If the fuel temperature is equal to or lower than this set temperature, no particular problem will occur and energy consumption can be suppressed to a minimum.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, and FIG.
Members that are the same as or equivalent to those of the related art shown in FIG.

In FIG. 1, reference numeral 20 denotes a temperature switch, and the temperature switch 20 is provided in the fuel tank 1.
The fuel temperature in the fuel tank 1 is detected. The temperature switch 20 is opened when the temperature is higher than the set temperature and closed when the temperature is lower than the set temperature. Also, 21
Is a switching valve, and this switching valve 21 is
Is provided in the middle of the unload pipe 23 connected to the hydraulic oil tank 22 and branched from the hydraulic pipe 10 connected between the hydraulic oil tank 22 and the hydraulic motor 9.

The switching valve 21 has a switching position (a) for blocking the communication between the hydraulic pipe 10 and the hydraulic oil tank 22, and a switching position (b) for connecting the hydraulic pipe 10 and the hydraulic oil tank 22.
It switches between and. Then, the return spring 21a is always held in the switching position (a) by the action of the return spring 21a, and when the solenoid 21b is excited, the return spring 21a is held.
It switches to the switching position (b) against a. This switching valve 2
The switching from the switching position (1) to the switching position (2) of 1 is performed by the temperature switch 20. Temperature switch 2
When 0 is closed, that is, when the temperature in the fuel tank 1 becomes equal to or lower than the set value, power is supplied from the power source 24 including a battery to the solenoid 21b of the switching valve 21, and the switching valve 21 is at the switching position (b). To the hydraulic pump 11
Is unloaded.

When the engine 2 is started, the fuel is supplied from the fuel tank 1 to the engine 2 and the main pump 15 is driven. As a result, pressure oil is discharged from the main pump 15 and each hydraulic actuator is driven. The fuel supplied to the engine 2 is not entirely consumed by the engine 2, but some excess fuel is generated. This surplus fuel is recirculated into the fuel tank 1 through the fuel recirculation pipe 5, and the surplus fuel thus recirculated is the engine 2
When the surplus fuel heated in this way is recirculated to the fuel tank 1 as it is, the temperature of the fuel in the fuel tank 1 rises.

When the engine 2 is started, the hydraulic pump 11 is driven, and pressure oil is supplied from the discharge port of the hydraulic pump 11. When the fuel temperature in the fuel tank 1 is equal to or higher than the set value, the temperature switch 20 is opened, so that the switching valve 21 is actuated by the return spring 21a.
And the hydraulic oil tank 22 are kept in the switching position (a). Therefore, the pressure oil from the hydraulic pump 11 is supplied to the hydraulic motor 9 via the hydraulic pipe 10, so that the hydraulic motor 9 operates and the fan 8 rotates. The fan 8 faces the fuel cooler 6, and when the fan 8 rotates, cooling air is supplied toward the fuel cooler 6. Therefore, when the surplus fuel is recirculated from the fuel recirculation pipe 5 to the fuel tank 1, it is cooled by the fuel cooler 6, so that the surplus fuel is efficiently cooled and the temperature in the fuel tank 1 becomes abnormally high. Can be prevented.

By the way, depending on the outside air temperature and the like, the fuel temperature may not increase remarkably even if the construction machine is continuously operated. Further, for example, when working in an outside air temperature below the freezing point, such as in a cold region, cooling the fuel may be rather harmful. When the fuel temperature in the fuel tank 1 is below the set value, the temperature switch 20 is closed, so that the switching valve 2 is powered by the power source 24.
The solenoid 21b of No. 1 is excited, the switching valve 21 is switched from the switching position (a) to the switching position (b), and the hydraulic pump 11 is unloaded. As a result, the operation of the hydraulic motor 9 is stopped, the fan 8 is in a non-rotating state, and when excess fuel flows back from the fuel recirculation pipe 5 to the fuel tank 1, even if it passes through the fuel cooler 6, The cooler 6 has no cooling effect. And the hydraulic pump 11
Is not loaded, it is virtually unloaded,
There is no waste of energy.

As described above, by controlling the operation of the fan 8 according to the temperature of the fuel in the fuel tank 1, the fuel does not rise abnormally to the extent that the vapor lock phenomenon or the forming phenomenon occurs, and Viscosity does not become abnormally low. Moreover, by setting the set temperature of the temperature switch 20 to an appropriate value, the hydraulic motor 9 operates unnecessarily, so that energy consumption does not increase.

Next, FIG. 2 shows a second embodiment of the present invention. In this embodiment, the same or equivalent members as those in the first embodiment described above are designated by the same reference numerals. The description thereof will be omitted.

In the second embodiment, the relief valve 30 that functions as a safety valve that limits the pressure of the circuit that drives the hydraulic motor 9 is utilized to unload the hydraulic pump 11. That is, the relief valve 30 is configured as a pilot operated relief valve. Therefore, the relief valve 30 is provided with the hydraulic pilot portion 30b in addition to the spring 30a that serves as the set pressure. When this hydraulic pilot portion 30b is connected to the hydraulic oil tank 22, it exerts its original function as a relief valve based on the pressure set by the spring 30a, and when pressure oil is supplied to the hydraulic pilot portion 30b, the relief valve 30 is forced. And the hydraulic pump 11 is unloaded.

The pressure oil is supplied to the hydraulic pilot portion 30b from the auxiliary hydraulic pump 31. Here, in the construction machine, a hydraulic actuator including a hydraulic motor and a hydraulic cylinder is provided in order to drive and turn each part of the machine, for example, a vehicle, operate a front working mechanism, and the like. A main pump is provided for supplying pressure oil to the hydraulic actuators, and a directional control valve is provided for controlling supply of pressure oil from the main pumps to the hydraulic actuators. This directional control valve is switched by a hydraulic pilot system, and is equipped with an auxiliary hydraulic pump for supplying pilot pressure to each hydraulic pilot section. Therefore, this auxiliary hydraulic pump is used as a supply source of the pressure oil to the hydraulic pilot portion 30b of the relief valve 30.

The hydraulic pilot portion 30b of the relief valve 30
Is connected to the hydraulic oil tank 22 and to the state connected to the auxiliary hydraulic pump 31.
The switching valve 32 is always held at the switching position (a) where the hydraulic pilot portion 30b is connected to the hydraulic oil tank 22 by the return spring 32a. Further, the solenoid 32 is arranged so as to face the return spring 32a.
b is provided, and when this solenoid 32b is excited, the switching valve 32 switches to the switching position (b) where the hydraulic pilot portion 30b is connected to the auxiliary hydraulic pump 31.

The switching of the switching valve 32 is performed based on the temperature switch 20 provided in the fuel tank 1. That is, when the fuel temperature of the fuel tank 1 is higher than the set value, the solenoid 32b of the switching valve 32 is kept in the demagnetized state, and therefore the switching valve 32 is in the switching position (a) by the action of the return spring 32a. Hydraulic pilot section 3 of relief valve 30
Since 0b is the tank pressure, the relief valve 30 functions as an original safety valve. On the other hand, when the fuel temperature is lower than the set value of the temperature switch 20, the switching valve 32
Since the solenoid 32b is supplied with power and becomes excited, the switching valve 32 is switched from the switching position (a) to the switching position (b). As a result, the pilot pressure from the auxiliary hydraulic pump 31 is supplied to the hydraulic pilot portion 30b of the relief valve 30, and the relief valve 30 is opened.

Therefore, when the fuel temperature is higher than the set value of the temperature switch 20, the hydraulic pump 11 to the hydraulic motor 9
A pressure is generated in the hydraulic pipe 10 to drive the hydraulic motor 9, the fan 8 rotates, and the fuel cooler 6 cools the fuel. When the fuel temperature is lower than the set value of the temperature switch 20, the hydraulic pump 11 is connected to the hydraulic oil tank 22 via the relief valve 30,
It will be in the unload state. Therefore, substantially the same operation as that of the first embodiment described above is performed.

Here, comparing the first embodiment and the second embodiment, in the first embodiment, the switching valve 21 is provided in the circuit from the hydraulic pump 11, and the pressure oil from the hydraulic pump 11 is provided. Is configured to be directly unloaded via the switching valve 21. On the other hand, in the second embodiment, the function of unloading the hydraulic pump 11 is constituted by the pilot-operated relief valve 30 provided in the circuit as a safety valve, and the signal hydraulic pressure is supplied to the hydraulic pilot portion 30b. The unload function is demonstrated by doing. Further, in the second embodiment, the switching valve 32 is provided to supply the pressure oil to the hydraulic pilot portion 30b of the relief valve 30, but this pressure oil is supplied from the auxiliary hydraulic pump 31, and the signal pressure is reduced. Therefore, the pressure acting on the switching valve 32 is significantly lower than the pressure acting on the switching valve 21. Therefore, the switching valve 32 can be smaller than the switching valve 21.

[0027]

As described above, according to the present invention, the temperature switch is provided in the fuel tank or the fuel circulation pipe, and when the temperature of the fuel is equal to or lower than the predetermined set temperature, the pressure applied to the hydraulic motor is controlled by the temperature switch. The oil supply is stopped, the fan rotation is stopped, and the fuel is not cooled.Therefore, when the fuel temperature is low, energy is not unnecessarily consumed and the fuel is too cold. It has the effect of preventing the viscosity from extremely decreasing.

[Brief description of drawings]

FIG. 1 is a hydraulic circuit diagram of a fuel cooling device showing a first embodiment of the present invention.

FIG. 2 is a hydraulic circuit diagram of a fuel cooling device showing a second embodiment of the present invention.

FIG. 3 is a hydraulic circuit diagram of a conventional fuel cooling device.

[Explanation of symbols]

 1 Fuel Tank 2 Engine 5 Fuel Return Pipe 6 Fuel Cooler 8 Fan 9 Hydraulic Motor 10 Hydraulic Pipe 11 Hydraulic Pump 20 Temperature Switch 21, 32 Switching Valve 22 Hydraulic Oil Tank 23 Unload Pipe 30 Relief Valve 31 Auxiliary Hydraulic Pump

Claims (3)

[Claims] 1. A prime mover, a fuel tank for supplying fuel to the prime mover, a fuel circulation pipe for feeding fuel from the fuel tank to the prime mover and circulating excess fuel from the prime mover to the fuel tank, and A fuel cooler arranged in the middle of the fuel circulation pipe, a fan for supplying cooling air to the fuel cooler, and a hydraulic motor for driving the fan are provided with a temperature switch in the fuel tank or the fuel circulation pipe. A fuel cooling device for a construction machine, wherein when the temperature of the fuel is equal to or lower than a predetermined set temperature by the temperature switch, the supply of the pressure oil to the hydraulic motor is stopped. 2. A switching valve is provided between a pipe for supplying pressure oil to the hydraulic motor and a hydraulic oil tank, and when the temperature switch falls below a set temperature, the switching valve unloads the hydraulic pump. The fuel cooling device for a construction machine according to claim 1, wherein the fuel cooling device has a configuration. 3. When the temperature switch falls below a preset temperature, the temperature switch is unloaded via a relief valve provided in a pipe line between the hydraulic pump and the hydraulic motor. 2. A fuel cooling device for a construction machine according to 2.