JPH0316526B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat exchange device for a hydraulic system that warms hydraulic fluid when the system starts up in cold weather.

When starting a hydraulic system in cold weather, the viscosity of the hydraulic oil is high, so if the system is suddenly started, various problems will occur in the hydraulic system. Therefore, in the case of startup in cold weather, a so-called warm-up operation is required to raise the oil temperature of the entire circuit of the hydraulic system in advance.

Conventionally, this warm-up operation involves gradually rotating the hydraulic pump to suck in oil from the hydraulic oil tank, and then returning this oil to the hydraulic oil tank through the relief valve through a predetermined operation, thereby reducing the heat generated in the relief valve. This was done by applying a loss to the oil and raising the temperature of the oil.

However, such warm-up operation has disadvantages in that energy loss is large and warm-up takes a long time, resulting in a significant drop in work efficiency.

An object of the present invention is to provide a hydraulic system that can effectively utilize energy during warm-up operation, shorten the warm-up operation time, and improve work efficiency, while eliminating the above-mentioned conventional drawbacks. To provide heat exchange equipment.

In order to achieve the above object, the present invention provides a heat engine, a cooling system that circulates a cooling medium for cooling the heat engine through a cooler, and a hydraulic device driven by the heat engine. , a heat exchanger that is disposed in an oil supply section of the hydraulic system and heats oil in the oil supply section with the cooling medium; and a first temperature detector that detects the temperature of the cooling medium from the heat engine; a second temperature detector that detects the temperature of oil in the oil supply section; a first path that directly introduces the cooling medium from the heat engine into the cooler; a second path introduced into the cooler via an exchanger; a switching valve that selectively switches between the first path and the second path; and an oil detected by the second temperature sensor. a control unit that switches the switching valve to the second path only when the temperature of the cooling medium is lower than a preset predetermined temperature and the temperature of the cooling medium detected by the first temperature sensor exceeds the temperature of the oil; It is characterized by having the following.

In the above configuration, the temperature of the cooling medium of a heat engine such as an engine that drives the hydraulic device and the temperature of the hydraulic oil of the hydraulic device are detected, and if the oil temperature is less than a predetermined temperature and the cooling medium is Only when the temperature of the hydraulic fluid is higher than that of the hydraulic fluid, the switching valve is switched to the second path to warm the hydraulic fluid with all the cooling medium; in other cases, the switching valve is switched to the first path to completely cool the hydraulic fluid. The medium is cooled by a cooler.

The present invention will be explained below based on the embodiments shown in FIGS. 1 and 3.

FIG. 1 is a system diagram of a heat exchange circuit of a hydraulic system according to a first embodiment of the present invention. In the figure, 1 is an internal combustion engine such as an engine, and this internal combustion engine 1 drives a hydraulic pump (not shown). 2 is a cooler such as a radiator, and the coolant heated by removing the heat generated in the internal combustion engine 1 is passed through the pipe a.
This is to dissipate the heat of the cooling medium. The coolant cooled by the cooler 2 is sent to the internal combustion engine 1 again and circulated, thereby forming a cooling system. Reference numeral 3 designates a hydraulic oil tank for storing the hydraulic oil of the hydraulic system, and 4 designates a heat exchanger installed at an appropriate location in the hydraulic oil tank 3 to warm the hydraulic oil therein. The heat exchanger 4 is configured to introduce the cooling medium heated by the internal combustion engine 1 through a pipe b. Reference numeral 5 denotes a directional switching valve composed of a solenoid valve, etc. When this directional switching valve is located on the right side in the figure, the cooling medium that has passed through the internal combustion engine 1 is guided to the pipe a, and is placed on the left side in the figure. When switched, internal combustion engine 1
The cooling medium passing through is guided to pipe b. 6 is a temperature sensor installed in a pipe through which the coolant heated by the internal combustion engine 1 passes, and detects its temperature; 7 is a temperature sensor installed at an appropriate location in the hydraulic oil tank to detect the temperature of the hydraulic oil. be. 8 inputs a signal Tw corresponding to the temperature detected by the temperature sensor 6 and a signal To corresponding to the temperature detected by the temperature sensor 7;
This is a control section that controls switching of the directional switching valve 5 based on these signals.

The operation of this embodiment will be explained with reference to the flowchart shown in FIG. When starting the hydraulic system in cold weather, the internal combustion engine 1 is first warmed up by appropriate means to enable normal operation, and then the internal combustion engine 1 rotates the hydraulic pump of the hydraulic system. As described above, the oil discharged from the hydraulic pump is returned to the hydraulic oil tank 3 through the relief valve by a predetermined operation, and at this time, the hydraulic oil is warmed by the heat generated in the relief valve. On the other hand, the directional control valve 5 is located on the right side as shown, and the internal combustion engine 1 being operated is cooled by a cooling medium such as cooling water. The temperature of the cooling medium increases due to heat exchange with the internal combustion engine 1, and this temperature is detected by the temperature sensor 6, which outputs a signal Tw according to the detected temperature. Further, the temperature sensor 7 detects the temperature of the hydraulic oil in the hydraulic oil tank 3 and outputs a signal To corresponding to this temperature. The control unit 8 takes in these signals Tw and To, and first compares the signal To with a certain predetermined setting value Tc. This set value is, for example, a value corresponding to the lowest temperature of the hydraulic oil that does not interfere with normal operation of the hydraulic system. As a result of the comparison, if the signal To is above the set value,
The directional control valve 5 is kept in the OFF state, that is, in the right position as shown in the figure. Therefore, during normal operation of the hydraulic system, the cooling medium passes through the pipe a and is cooled by the cooler 2, thereby providing a normal cooling system for cooling the internal combustion engine 1.

In the previous comparison, the signal To is less than the set value Tc, that is,
If it is determined that the temperature of the hydraulic oil is too low to operate the hydraulic system, then the signal To and the signal Tw are compared. As a result of this comparison, the signal To becomes the signal
If the value is higher than Tw, that is, if the temperature of the hydraulic oil is higher than the temperature of the cooling medium, it is impossible to warm the hydraulic oil with the cooling medium, so the directional control valve 5 is turned off. . Conversely, signal Tw is
If it is determined that the temperature of the cooling medium exceeds the value of To, that is, if it is determined that the temperature of the cooling medium exceeds the oil temperature and it is possible to heat the hydraulic oil with the cooling medium, the control unit 8 An output is generated to turn on the switching valve 5. As a result, the directional control valve 5 is switched from the illustrated state to the left position, and the coolant heated through the internal combustion engine 1 is introduced into the heat exchanger 4 through the pipe b, where its heat is After being discharged into the hydraulic oil, it enters the cooler 2. As a result, the hydraulic fluid is warmed up more quickly than in conventional warm-up operations, where it is only heated through the relief valve, reducing relief time and reducing energy loss at the relief valve. This also shortens the time it takes to be able to start work.

In this way, in this embodiment, the heat exchanger is installed in the hydraulic oil tank, and the temperature of the hydraulic oil is lower than a predetermined temperature, and the temperature of the cooling medium that cools the internal combustion engine is lower than the temperature of the hydraulic oil. Since the directional control valve is switched to guide the cooling medium to the heat exchanger only when the temperature exceeds In addition, warm-up operation time can be shortened and work efficiency can be improved. Furthermore, the heat of the cooling medium, which was previously wasted in the cooler, can be effectively used as heat to warm the hydraulic oil, so energy loss can be reduced from this point of view as well. The reduction in energy loss is large.

FIG. 3 is a system diagram of a heat exchange circuit of a hydraulic system according to a second embodiment of the present invention. In the figure, the same parts as those shown in FIG. 1 are given the same reference numerals. 9
is a hydraulic pump of a hydraulic system, and is driven by an internal combustion engine 1. 10 is a heat exchanger provided in a pipe line between the hydraulic oil tank 3 and the hydraulic pump 9;
Similar to the heat exchanger 4 in the previous embodiment, the internal combustion engine 1
The cooling medium whose temperature has been raised is introduced through pipe b. This embodiment differs from the previous embodiment only in the installation location of the heat exchanger 10, and its operation is the same as that of the previous embodiment, so a description thereof will be omitted.

In this way, in this embodiment, a heat exchanger is installed in the pipe line between the hydraulic pump and the hydraulic oil tank, and the heat exchanger is installed in the pipe line between the hydraulic pump and the hydraulic oil tank to ensure that the oil temperature of the hydraulic oil is below a predetermined temperature and that the heat exchanger is used as a cooling device to cool the internal combustion engine. Since the directional control valve is switched to guide the cooling medium to the heat exchanger only when the temperature of the medium exceeds the temperature of the hydraulic oil, the same effect as in the previous embodiment is achieved. Furthermore, by installing a heat exchanger in the suction circuit of the hydraulic pump, the temperature of the hydraulic oil sucked into the hydraulic pump is increased, and the hydraulic pump can be driven smoothly during warm-up operation. .

Note that the control section 8 can be configured using a microcomputer, or can also be configured using a normal analog circuit or logic circuit.

As described above, in the present invention, the cooling medium is used only when the temperature of the hydraulic oil is below a predetermined temperature and the temperature of the cooling medium that cools the heat engine exceeds the oil temperature. Since the hydraulic oil is heated, it is possible to quickly warm up the hydraulic oil during warm-up operation, reduce energy loss, and shorten the warm-up operation time to improve work efficiency. .

[Brief explanation of drawings]

FIG. 1 is a system diagram of a heat exchange circuit of a hydraulic device according to a first embodiment of the present invention, FIG. 2 is a flowchart explaining the operation of the device shown in FIG. 1, and FIG. FIG. 2 is a system diagram of a heat exchange circuit of a hydraulic system according to a second embodiment. DESCRIPTION OF SYMBOLS 1... Internal combustion engine, 2... Cooler, 3... Hydraulic oil tank, 4, 10... Heat exchanger, 5... Directional switching valve, 6, 7... Temperature sensor, 8... Control unit, 9 …
…Hydraulic pump.

Claims (1)

[Scope of Claims] 1. A heat engine, a cooling system that circulates a cooling medium for cooling the heat engine through a cooler, and a hydraulic device driven by the heat engine, wherein the hydraulic device a heat exchanger that is disposed in the oil supply section and heats the oil in the oil supply section with the cooling medium; a first temperature detector that detects the temperature of the cooling medium from the heat engine; and a first temperature detector that detects the temperature of the cooling medium from the heat engine; a second temperature detector for detecting the temperature of the oil; a first path for directly introducing the cooling medium from the heat engine into the cooler; and a first path for introducing the cooling medium from the heat engine through the heat exchanger. a second path through which the oil is introduced into the cooler, a switching valve that selectively switches between the first path and the second path; and a control unit that switches the switching valve to the second path only when the temperature of the cooling medium detected by the first temperature detector exceeds the temperature of the oil and is lower than a predetermined temperature. A heat exchange device for a hydraulic system characterized by: 2. The heat exchange device for a hydraulic system according to claim 1, wherein the heat exchanger is installed in a hydraulic oil tank of the hydraulic system. 3. The heat exchange device for a hydraulic system according to claim 1, wherein the heat exchanger is installed in a suction side piping of a hydraulic pump of the hydraulic system.