JP2653290B2 - Engine cooling system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-cooled cooling system for an automobile engine or the like, and more particularly to an improvement in a cooling system for optimally controlling a pressure in a cooling system.

[0002]

2. Description of the Related Art FIG. 5 schematically shows the structure of a water-cooled cooling device generally used in a conventional automobile engine or the like. Reference numeral 21 denotes an engine body having a water jacket formed therein; Is a radiator, 23 is a water pump driven by engine output,
The cooling water flowing out of the water jacket of the engine body 21 flows into the upper part of the radiator 22 through the inlet passage 24 and exchanges heat there. Then, the cooling water passes through the outlet passage 25 from the lower part of the radiator 22 and is sucked by the water pump 23. And forced circulation in the water jacket.

In such a cooling device that relies on forced convection heat transfer, if cavitation occurs in the water pump 23 and the amount of circulating cooling water is reduced, the cooling performance is reduced, resulting in a so-called overheat state. Therefore, by maintaining the pressure in the cooling system in a predetermined pressurized state via the reservoir tank 27 by the pressure regulating function of the pressure valve and the negative pressure valve of the radiator cap 26, the saturation temperature of the cooling water is ensured to be high. I have.

[0004] However, the normal operating range of the cooling water temperature is generally around 85 to 90 ° C, so that the closing pressure of the pressurizing valve of the radiator cap 26 is 0.9 kg / normal as described above.
If kept at about cm ² atg, a considerable degree of subcooling (difference between the saturation temperature and the actual cooling temperature) will be given. Therefore, the generation rate of subcooling boiling in the water jacket is reduced due to the large subcooling degree, so that the heat transferability is reduced and the combustion chamber wall temperature cannot be sufficiently reduced. That is, the heat transfer coefficient in the water jacket has a subcooling degree of about 30 as shown in FIG.
As the temperature approaches 0 ° C from 0 ° C, it increases,
When the temperature is higher than ℃, the characteristic is extremely small.

Accordingly, the present applicant has already proposed a technique for controlling the opening pressure of the pressurizing valve of the radiator cap in accordance with a change in the temperature of the cooling water to solve the above-mentioned problem. That is, when the temperature of the cooling water is relatively low, the closing pressure of the pressurizing valve of the radiator cap 26 is controlled to be low to lower the internal pressure of the cooling system. Thereby, the degree of subcooling is 5 ° C to 20 ° C.
The temperature of the combustion chamber wall is reduced by obtaining an efficient heat transfer property by subcool boiling at a portion that becomes a heat spot. On the other hand, when the temperature of the cooling water rises, the opening pressure of the pressurizing valve is controlled to be high by the action of the thermowax to secure an appropriate degree of subcooling, thereby preventing overheating. -151932).

[0006]

However, in the conventional cooling device described in the above publication, the subcooling is performed by changing the valve opening pressure of the pressurizing valve of the radiator cap according to the cooling water temperature as described above. Although the degree of heat transfer is controlled by controlling the degree of cooling within a range of about 15 to 20 ° C., the degree of subcooling cannot be further reduced. This is because, if the subcool degree is further reduced, cavitation is likely to occur in the water pump, and the pump efficiency will be significantly reduced. Therefore, as shown in FIG. 4, it is difficult to effectively use a region having a smaller subcool degree that further enhances the heat transfer efficiency.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art. It is intended to control the degree to a small degree.

That is, a cooling system mainly including a water jacket and a radiator in an engine body, a water pump for forcibly circulating cooling water in the cooling system, and a pressure for pressurizing or depressurizing the cooling system. It is characterized by comprising a control valve and control means for controlling the pressure control valve based on a relative information signal between a pressure difference between an inlet and an outlet of the water pump and an engine speed.

[0009]

[Action] The water pump cavitation limit range is determined by the difference between the pressure difference between the suction port and the discharge port of the water pump and the rotation speed of the water pump replaced with the engine rotation speed if the specifications of the water pump are determined. It is determined experimentally by the relative relationship. Therefore, the function value of the differential pressure and the engine speed is stored in the control means in advance. Then, by comparing the relative relationship between the actual differential pressure value and the engine speed value after the engine is started, it is possible to detect the limit of occurrence of cavitation during operation. Accordingly, if the control means controls the internal pressure of the cooling system by controlling the pressure control valve to the limit of the occurrence of cavitation, the degree of subcooling can be reduced to an area as small as 15 ° C. or less. Therefore, it is possible to improve the heat transfer efficiency in the water jacket while securing a good pump efficiency of the water pump.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 schematically shows an embodiment of a cooling device according to the present invention, wherein 1 is an engine body having a water jacket formed therein, 2 is a water pump driven by the engine output, 3 Is a radiator. Cooling water that has exited the water jacket of the engine body 1 flows into the radiator 3 through the inlet passage 4 and exchanges heat there, and is then sucked by the water pump 2 through the outlet passage 5. Forced circulation in the water jacket. A thermostat 6 is disposed in the inlet passage 4. When the temperature of the cooling water is low, the thermostat 6 opens the bypass passage 7, shuts off the inlet passage 4 and circulates the cooling water without passing through the radiator 3. It is configured to be.

Reference numeral 8 denotes a water inlet cap provided on the upper part of the radiator 3, 9 denotes a reservoir tank, and 10 denotes an opening of the cooling system when the pressure in the cooling system becomes 1.5 kg / cm ^2. A reservoir tank cap having a relief valve, wherein the reservoir tank 9 is provided at the highest position in a cooling system, and has a lower end connected to the inside of the radiator 3 via a cooling water passage 11 and the inlet cap 8. On the other hand, the downstream end of the pressure passage 12 is connected to the upper end.

A pressure pump 13 is provided at an upstream end of the pressure passage 12, and a three-way solenoid valve 14 as a pressure control valve is provided downstream of the pressure pump 13. The pressurizing pump 13 has a structure driven by the output of the engine and has a maximum pressure of 0.9 kg / in the cooling system.
It has the ability to pressurize to about ² cm2. The three-way solenoid valve 14 is provided with a flow path that connects the pressurizing pump 13 and the reservoir tank 9 through the pressure passage 12 or that opens the three-way to the atmosphere and communicates the atmosphere with the reservoir tank 9. Is switched.

Reference numeral 15 denotes a differential pressure detection sensor for detecting a differential pressure between the suction port 2a and the discharge port 2b of the water pump 2. Reference numeral 16 denotes a crank angle sensor for detecting the number of revolutions of the engine. The information signal output from the crankshaft angle sensor 15 and the crank angle sensor 16 is input to a control unit 17 as control means via an input circuit.

The control unit 17 has a built-in microcomputer which detects cavitation generated inside the water pump 2 based on the differential pressure signal and the engine speed signal, and according to the detected value, By switching the three-way solenoid valve 14 to shut off the atmosphere side and pressurize the cooling system by the pressurizing pump 13 or
It is controlled to open the cooling system to reduce the pressure inside the cooling system.

More specifically, if the specification of the water pump 2 is determined as described above, the rotation speed of the water pump 2 is determined by the solid line in FIG. Is obtained experimentally from the relative relationship between the pressure difference between the suction port 2a and the discharge port 2b, and the characteristics do not significantly change under the influence of the cooling water temperature. Here, since the rotation speed of the water pump 2 is generally substantially proportional to the engine speed, it can be replaced with the engine speed. When the actual differential pressure value is lower than a predetermined differential pressure value in relation to a predetermined engine speed, it is considered that cavitation occurs.

Therefore, in the control unit 17, the function map of the engine speed and the differential pressure value shown in FIG. 2 is stored in advance, and the relationship between the engine speed and the actual engine speed and the differential pressure is compared. It is possible to detect the limit of the occurrence of the teasion. If the reference differential pressure value shown by the solid line in the figure is set to a slightly smaller value as shown by the broken line, the occurrence of cavitation can be detected more reliably. Hereinafter, the actual control of the control unit 17 will be described with reference to the flowchart of FIG.

First, after the engine is started in section S1, the current engine speed and the differential pressure value between the suction port 2a and the discharge port 2b are read in section S2. Next, in section S3, it is determined from the function map whether or not the current differential pressure value is smaller than the reference differential pressure value based on the relative relationship with the engine speed. Here, YES, that is, when it is determined that it is smaller than the reference differential pressure value (below the broken line in FIG. 2)
Since the cavitation may occur in the water pump 2, the air side of the three-way solenoid valve 14 is shut off in the section S4. Therefore, the pressure fed from the pressurizing pump 13 is supplied into the cooling system via the pressure passage 12 and the reservoir tank 9 to increase the internal pressure of the cooling system.
For this reason, the subcool degree becomes moderately high, and the occurrence of cavitation in the water pump 2 can be reliably prevented. In other words, the degree of subcooling can be reduced as much as possible to the limit of cavitation.

On the other hand, when it is determined in the section S3 that the current differential pressure value is larger than the reference differential pressure value (above the broken line in FIG. 2), there is little possibility that cavitation will occur. All three sides of the three-way solenoid valve 13 are released to the atmosphere. Therefore, the pressure in the cooling system is reduced, and the degree of subcooling becomes sufficiently small. That is, the inside of the cooling system is depressurized to the limit of the occurrence of cavitation, so that the degree of subcooling can be reduced as much as possible.

After controlling the three-way solenoid valve 13 in the sections S4 and S5, the process returns to the section S2.

As described above, in this embodiment, the degree of subcooling is set to 15 ° C. until the occurrence of cavitation in the water pump 2 in any engine operating state.
Because it can be controlled as small as possible below, it is possible to improve the heat transfer efficiency inside the water jacket while improving the pump efficiency, further improve the cooling performance of the engine, and improve the output and fuel efficiency Can be achieved.

The present invention is not limited to the above embodiment. For example, the pressurizing pump may be an electric pump.
Further, in a diesel engine vehicle, a vacuum pump for brake master back can be used, and in an engine having a supercharger such as a turbocharger, the supercharger can be used.

[0023]

As is apparent from the above description, in the engine cooling device according to the present invention, the control means utilizes the engine speed and the differential pressure between the suction port and the discharge port of the water pump. In addition to detecting the cavitation occurrence limit of the water pump and controlling the internal pressure of the cooling system via the pressure control valve based on the detected value, the subcooling degree is reduced to the cavitation occurrence limit of the water pump as much as possible. It can be controlled small. As a result, it is possible to improve both the water pump efficiency and the heat transfer efficiency due to active subcool boiling in the water jacket.

In particular, by reducing the degree of subcooling as much as possible and improving the heat transfer, heat spots are eliminated, the wall temperature of the combustion chamber is reduced, abnormal combustion can be prevented, and the output due to an increase in the mechanical octane number. And fuel efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram schematically showing one embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a water pump rotation speed and a differential pressure between a pump suction port and a discharge port.

FIG. 3 is a flowchart of a control unit according to the embodiment.

FIG. 4 is a characteristic diagram showing a relationship between a degree of subcooling and a heat transfer coefficient.

FIG. 5 is an overall configuration diagram schematically showing a conventional cooling device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine main body, 2 ... Water pump, 3 ... Radiator, 14 ... 3-way solenoid valve (pressure control valve), 15 ... Differential pressure detection sensor, 16 ... Crank angle sensor, 17 ... Control unit (control means).

Claims (1)

(57) [Claims] 1. A cooling system mainly comprising a water jacket and a radiator in an engine body, a water pump for forcibly circulating cooling water in the cooling system, and a pressure for increasing or decreasing the pressure in the cooling system. An engine cooling system comprising: a control valve; and control means for controlling the pressure control valve based on a relative information signal between a pressure difference between an intake port and a discharge port of the water pump and an engine speed. apparatus.