JPH0141813B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a boiling cooling device that cools an engine using latent heat of boiling vaporization of a coolant.

b Technical background It is well known that in terms of thermal efficiency of an engine, it is preferable to increase the wall temperature of the combustion chamber as much as possible without affecting the durability and knock resistance of the material. The type engine had a simple configuration in which the cooling water was circulated between the engine's cooling water jacket and the radiator, and the cooling water circulation path was switched by a thermostat that opened and closed depending on the temperature of the cooling water. In other words, it was difficult to control the maximum temperature according to the operating conditions.

From this point of view, for example, as seen in Japanese Patent Application Laid-open No. 58-5449, the wall temperature of the combustion chamber is detected and fed back to the electric motor for driving the cooling water pump, so that the temperature can be set appropriately depending on the operating condition. A device has been proposed that continuously variable controls the amount of coolant circulated to achieve this goal, but this type of device is fundamentally a liquid-based system that cools the engine by returning the coolant that has been radiated to the outside air in the radiator to the water jacket. Since it is still a phase circulation cooling system, there is no choice between conventional and common-sense water cooling methods in terms of heat dissipation efficiency.In other words, the cooling water pump has a large drive loss due to the need to circulate a large amount of cooling water, and Problems remain, such as that it is difficult to control the temperature in a responsive manner for automobile engines, etc., which undergo rapid changes in operating conditions.

In response to this, a boiling cooling device as seen in Japanese Patent Publication No. 57-57608, for example, has been proposed as a device that uses the latent heat of boiling vaporization of the cooling water to ensure the required amount of heat radiation with a small amount of cooling water. .

As shown in Fig. 1, the water jacket 2 of the engine 1 and the lower part of the radiator 3 are connected through a passage 4 so that the level of the cooling water filled inside is the same in each. Then, the cooling water vapor boiled and vaporized by the combustion heat is sent to the radiator 3 through the upper space 5 of the jacket 2 and the steam passage 6.
The amount of condensed and liquefied steam introduced into the water jacket 2 and cooled by the radiator 3 is passed through the passage 4 to the water jacket 2.
A natural circulation cooling system is formed in which cooling water returns to the tank.

According to such a cooling system, heat is absorbed from the cylinder wall etc. by the latent heat of boiling and vaporization of the cooling water, so the cooling water capacity is lower than that of general circulation cooling which depends on the heat capacity of the cooling water in the liquid phase. Since boiling starts from the high-temperature parts of the engine, even multi-cylinder engines can be cooled evenly.

However, on the other hand, in this type of cooling system, the radiator 3 is filled with cooling water at the same level as the water jacket 2, and heat exchange occurs between the liquid phase cooling water and the outside air, so the cooling system The heat dissipation efficiency of the system does not necessarily improve, and since the pressure inside the system is always kept constant, it has been difficult to variably control the cooling performance.

Furthermore, in this device, in order to stabilize the boiling point of the cooling water, that is, the amount of cooling heat, the pressure in the system is kept constant as described above, and for this purpose, only gas passes between the steam passage 6 and the atmosphere. Pressure is exchanged through a permselective filter 7 that allows the water to flow, but as a result, when the pressure inside the system increases due to boiling and vaporization of the cooling water, some of the steam escapes to the outside. As the cooling water escapes, it becomes necessary to periodically replenish the cooling water, and when the pressure inside the system decreases as the temperature drops after the engine stops, air is sucked in from the outside, causing problems such as deterioration of cooling performance. It is possible that

c. Purpose of the Invention The present invention was devised against this technical background, and aims to improve thermal efficiency by controlling the optimum cooling state in response to changes in engine operating conditions, and also to improve the efficiency of the cooling system. The purpose of the present invention is to provide a boiling-cooled engine that meets the demand for a lighter, more compact engine and requires no maintenance.

d Disclosure of the Invention In order to achieve the above object, the present invention includes a condenser that cools and liquefies the refrigerant vapor generated in the water jacket of the engine, a lower tank that temporarily stores the refrigerant liquefied by the condenser, and a lower tank that stores the liquefied refrigerant in the lower tank. An electric pump that returns the refrigerant to the water jacket and an electric fan that supplies forced cooling air to the condenser are installed, and the electric pump is controlled so that the liquid level of the refrigerant sealed in the water jacket reaches a predetermined value. In this method, the heat dissipation efficiency is increased by exchanging heat between the refrigerant vapor and the outside air, which has a large temperature difference, and the amount of refrigerant condensed in the condenser, that is, the pressure in the system and the boiling point of the refrigerant, is changed via an electric fan. In addition, an auxiliary tank that stores refrigerant is installed outside to prevent outside air from entering the cooling system between the water jacket and the condenser. When the engine is stopped, liquid refrigerant from the auxiliary tank is introduced to fill the system with refrigerant, thereby discharging intruding air and ensuring that the cooling system always delivers the desired performance.

Embodiments of the present invention will be described below based on the drawings.

e Example In FIG. 2 or 3, 21 is the engine (main body), 22 is its water jacket, 23 is a condenser, 24 is a lower tank communicating with the lower part of the condenser 23, 25 is an electric pump, and 26 is an electric fan. It is.

The water jacket 22 is formed over the cylinder block 21a and the cylinder head 21b so as to surround the outer periphery of the cylinder and combustion chamber of the engine 21, and has an appropriate space (vapor phase space) filled upwardly with refrigerant vapor inside the water jacket 22. Liquid phase refrigerant is sealed to the extent that 22a remains. In a multi-cylinder engine, the gas phase space 22a communicates with each other between cylinders.

The water jacket 22 has a refrigerant injection pipe 22b and a steam passage 27 connected to the water jacket 22 facing the gas phase space.
It communicates with the condenser inlet section 23a via the condenser inlet section 23a. The refrigerant injection pipe 22b is located at the top of the path through which the refrigerant circulates, and the injection port 2 rises upward.
2c is sealed with a cap 22d.

The lower tank 24 is connected to a refrigerant inlet portion 22e at the bottom of the water jacket 22 via a refrigerant passage 28 having an electric pump 25 interposed therebetween.

The condenser 23 is provided at a position through which air flows when the vehicle is running, and the electric fan 26 is located on the front or back side of the condenser 23 to supply forced cooling air to the condenser 23.

30 is the electric pump 25 and the electric fan 2
6 (Fig. 3), which controls the operation of the liquid level sensor 31 provided in the cylinder head 21b.
Similarly, the temperature sensor 32 and other detection means (not shown) for detecting the engine operating state form a control system.

The output of the liquid level sensor 31 changes on and off depending on whether the detection part is immersed in the refrigerant liquid or exposed to the gas phase space 22a, and the control circuit 30 determines whether the refrigerant liquid level is high based on this change in output. When the liquid level falls below a predetermined value depending on the position of the liquid level sensor 31, the electric pump 25 is driven to replenish the water jacket 22 with the refrigerant stored in the lower tank 24 until the liquid level reaches the predetermined level again. Therefore, a predetermined amount of refrigerant is always ensured within the water jacket 22. Note that the total capacity of the liquid phase refrigerant injected into the cooling system is such that the inside of the condenser 23 is almost in the gas phase state while the refrigerant is secured to the predetermined liquid level in the water jacket 22 as described above. It is set to the extent that

On the other hand, the temperature sensor 32 detects the engine temperature from the temperature or pressure of the refrigerant, and provides an output corresponding to the engine temperature as an actual temperature signal to the control circuit 30. Along with the detected value, engine rotation, throttle opening, fuel supply amount, etc. are detected through well-known sensors to determine the engine operating condition, and based on comparison with the actual temperature, the appropriate temperature is determined according to the operating condition. The operation or stopping of the electric fan 26 is controlled so that the engine temperature is maintained.

It goes without saying that the relationship between the engine operating state and the control temperature value can be set freely depending on the engine specifications, purpose, and application, but generally speaking, automobile engines are used in urban driving areas where the load and engine speed are relatively low. , and other high-speed or high-load areas, the temperature is raised in urban driving areas to improve thermal efficiency, and the temperature is lowered in high-speed/high-load areas to prevent abnormal combustion.

To explain the basic function of the cooling system based on the above, when the liquid phase refrigerant in the water jacket 22 is heated by the engine combustion heat, it reaches a boiling point according to the pressure in the system at that time. At that point, it starts boiling, takes away the latent heat of vaporization, and evaporates. At this time, the refrigerant boils more actively in the higher temperature parts of the engine 21 and cools the combustion chamber and the cylinder wall by the amount equivalent to the latent heat of vaporization. Since hot spots are less likely to occur, it is possible to raise the overall temperature of the combustion chamber, etc.

The refrigerant vapor generated as a result of the boiling cooling action enters the condenser 23 through the vapor passage 27,
It is cooled and liquefied by heat exchange with the outside air, and is sequentially stored in the lower tank 24. In this case, as mentioned above, the inside of the capacitor 23 is maintained in a gaseous state,
Since the high-temperature refrigerant vapor is cooled by the outside air while maintaining good heat transfer between it and the metal surface that constitutes the condenser 23, the heat radiation efficiency is greatly improved compared to the case where heat is radiated in the liquid phase. capacitor 2
3 and electric fans that are significantly smaller than conventional ones can be used.

Then, it is liquefied in the condenser 23 and lower tank 2
The refrigerant stored in the water jacket 22
As the liquid level decreases, the electric pump 25 operates to return the liquid to the water jacket 22, and the boiling cooling continues by repeating the above process.

By the way, when a gasoline engine with a total displacement of 1,800 c.c. is operated at full throttle at 4,000 rpm, the required amount of heat radiation is more than 400 kcal per minute, and this can be achieved by liquid phase circulation cooling of the cooling water. The required circulation amount of water Q is as follows: assuming the radiator inlet temperature is 88℃, the radiator outlet temperature is 84℃, and the specific heat of water is 1, Q=
400/(88-84)×1≒110Kg, or approximately 110 kg/min. On the other hand, in boiling cooling, when water is used as the refrigerant, the latent heat of vaporization is approximately 539kcal/Kg.
Therefore, the required circulation rate of liquid phase refrigerant is several hundred cc per minute.
It's nothing more than that. As a result, the electric pump 25 can be small and driven with a small current, making it easy to control, and in particular, driving loss is significantly reduced compared to an engine-driven water pump in water circulation cooling, so even under the same temperature. This results in a significant improvement in fuel efficiency.

Next, in explaining the operation of the cooling system associated with temperature control, an example of the operational concept of the control system will first be explained.

As mentioned earlier, the control system is based on the electric fan 26.
By controlling the operation of the engine, the engine temperature ultimately reaches the target value according to the operating condition at that time.To do this, the operating condition must first be determined from the relationship between the engine speed and the load. In urban driving areas where the rotational speed and load are relatively low, a preset high-temperature target value T _H (for example, equivalent to T _H = 110°C) is selected as the control temperature target value T ₀ , and in other high-speed Or the same in high load range
The low temperature target value T _L (for example, T _L = equivalent to 90°C) is selected as T ₀ .

Next, the final target value T ₀ is compared with the actual engine temperature Ta, and when TaT is ₀ , the electric fan 26 is driven to supply cooling air to the condenser 23 to actively cool it. . On the contrary, Ta
<To, the electric fan 26 is stopped and the condenser 23 is left in a natural cooling state. The control system repeatedly executes such operations periodically or continuously to control the engine temperature, and in response, the cooling system operates as follows.

That is, in the present invention, since the inside of the condenser 23 is kept in the gas phase to improve heat dissipation efficiency, when forced cooling air is supplied by the electric fan 26, the refrigerant vapor in the condenser 23 is quickly reacted to the forced cooling air. Liquefaction is promoted, and as a result, the pressure within the system decreases, the boiling point of the liquid refrigerant also decreases, and the engine temperature accordingly decreases accordingly. On the other hand, electric fan 26
When the condenser 23 stops, the amount of heat dissipated from the condenser 23 decreases, and the amount of heat dissipated from the water jacket 22 is greater than the amount of liquefied refrigerant inside the condenser 23, especially when the vehicle speed is low and there is insufficient airflow, such as when driving in a city. Since the amount of boiling and vaporization exceeds the amount, the pressure in the system increases and the engine temperature increases.

In this way, the engine 21 changes its temperature in a responsive manner such that it is high in low speed/low load ranges and low in high speed/high load ranges. Not only can abnormal combustion such as knocking and detonation be avoided by suppressing the engine temperature at high speeds and high load ranges, but also by keeping the engine at an appropriate high temperature in commonly used city driving ranges, cooling loss is reduced and fuel consumption is reduced. It goes without saying that effects such as being enhanced can be obtained. In particular, in diesel engines, by keeping the combustion chamber at a high temperature during low-speed rotation such as when idling, the ignition delay period of the injected fuel is reduced.In other words, the proportion of premixed combustion is reduced, so the rise in cylinder internal pressure is made more gradual. As a result, noise and vibration are reduced, and the average effective pressure is increased, leading to further improvements in fuel efficiency.

The present invention provides such a boiling cooling device,
Another feature is that liquid refrigerant is introduced from the outside when the engine is stopped, with the direct purpose of eliminating air that has entered the system.This point will be explained next.

In FIG. 2 or 3, 50 indicates the water jacket 22 and lower tank 2 during engine operation.
51 is a first auxiliary passage that communicates the auxiliary tank 50 with the refrigerant passage 28 of the cooling system; A second tank that communicates between the auxiliary tank 50 and the engine water jacket 22
An auxiliary passage 53 connects the suction side of the electric pump 25 to the passage 28 on the lower tank 24 side or the first auxiliary passage 51.
a first solenoid valve (three-way valve), 54, which selectively communicates with the
55 is a second solenoid valve that opens and closes the second auxiliary passage 52;
is a third solenoid valve that opens or closes the vicinity of the top of the gas phase space 22a to the atmosphere.

The inside of the auxiliary tank 50 is maintained at atmospheric pressure via a cap with a filter 50a having a ventilation function, and the third solenoid valve 55 is connected to the auxiliary tank 5.
An air passage 5 that communicates between the internal upper space of 0 and the refrigerant inlet 22c at the top of the gas phase space 22a.
Intervened in the middle of 6.

Further, the first solenoid valve 53 communicates the lower tank 24 and the electric pump 25 when not energized, but when energized, connects the auxiliary tank 50 to the suction side of the electric pump 25 via the first auxiliary passage 51. . On the other hand, the second solenoid valve 54 is held open when not energized;
The valve is closed when energized, and the third solenoid valve 55 is set to remain closed when energized and open when energized.

In addition, 57 is the second solenoid valve 54 and the auxiliary tank 50.
This is a manual cock inserted in the middle of the second auxiliary passage 52 so as to be located between the engine and the cap 22.
d, and inject liquid refrigerant until the mouth of the injection port 22c is almost full. After injecting the refrigerant, tighten the cap 22d and leave the manual pot 57 open.

The control system that controls the opening, closing, or switching of each of the electromagnetic valves 53 to 55 includes the liquid level sensor 31 described above.
In addition to the temperature sensor 32, a second liquid level sensor 58 detects the refrigerant liquid level position in the lower tank 24, and a third liquid level sensor 59 detects the amount of refrigerant at the injection port 22c when the engine is stopped. The control circuit performs the following control operations based on signals from each of the sensors.

That is, when the engine is cold, the cooling system is filled with liquid refrigerant as described above, but when the engine 21 is started from this state, the refrigerant in the water jacket 22 is heated by the heat of combustion. It gradually begins to vaporize. During this time, the control circuit 30 cuts off the power to each of the solenoid valves 53 to 55, that is, the first solenoid valve 53 connects the lower tank 24 and the electric pump 25, and the second solenoid valve 54 opens.
The third solenoid valve 55 is closed. Therefore, as the refrigerant vaporizes, the pressure within the system increases, and as a result, the liquid refrigerant in the water jacket 22 flows into the second tank.
It is pushed out to the auxiliary tank 50 via the auxiliary passage 52.

In this way, when the engine 21 is started, the refrigerant liquid level in the water jacket 22 gradually decreases, but when the liquid level falls below the position detected by the first liquid level sensor 31, Since the electric pump 25 operates to replenish the refrigerant from the lower tank 24, the refrigerant level in the water jacket 22 does not drop any further, and the refrigerant on the condenser 23 side is apparently pushed out to the auxiliary tank 50. As a result, the liquid level decreases.

Then, when the liquid level in the capacitor 23 further decreases to the point where the second liquid level sensor 58 is facing the space, the control circuit 30 detects this and energizes the second solenoid valve 54. , close this. As a result, the cooling system is filled with a standard amount of refrigerant as shown in FIG. 2, and thereafter performs its cooling function in accordance with the temperature control operation described above.

Note that during startup, as the refrigerant level in the system decreases as described above, the capacitor 2
Since the inside of 3 is in a liquid phase, the amount of heat released is significantly reduced compared to when it is in a gas phase (FIG. 2). Therefore, the heat generated by the engine 21 does not wastefully escape to the outside, and warm-up is completed in a short time.

Next, when the engine 21 is stopped from the state shown in FIG. 2, the control circuit 30 stops energizing the second solenoid valve 54 when the engine temperature drops to, for example, 50° C. or less based on the signal from the temperature sensor 32. to open the second auxiliary passage 52.

On the other hand, at this time, in the system, the refrigerant vapor condenses and liquefies as the temperature decreases after the engine is stopped, and the internal pressure decreases, so when the second auxiliary passage 52 opens, the refrigerant stored in the auxiliary tank 50 flows into the water jacket. 22
Eventually, the system will be filled with liquid refrigerant up to approximately the level of the third liquid level sensor 59 unless outside air enters the system.

On the other hand, if a certain amount of outside air has entered the system, negative pressure in the system will be hindered by that amount, so the refrigerant should be introduced from the auxiliary tank 50 until its liquid level The process ends before the liquid level sensor 59 is reached.

In such a case, the control circuit 30 determines that the engine 21 has reached normal temperature based on, for example, that the signal value from the temperature sensor 32 has stopped changing, or immediately after a cold start, the control circuit 30 starts the third fluid. It is detected through the surface sensor 59 that the liquid level in the system has not reached the specified value, and the first solenoid valve 53 is activated.
is energized to switch and connect the first auxiliary passage 51 to the suction side of the electric pump 25 and drive the electric pump 25 to force-feed the liquid refrigerant in the auxiliary tank 50 to the water jacket 22. At this time, the second and third solenoid valves 54 and 55 are also energized, and the second
The auxiliary passage 52 is closed to prevent the refrigerant from flowing back from the water jacket 22 to the auxiliary tank 50, and the inlet portion 22 at the top of the gas phase space is closed.
c is opened to the space of the auxiliary tank 50, that is, to the atmosphere side. As a result, the liquid level in the system gradually rises and the intruding air is forced to the outside (auxiliary tank 50).
is discharged to. This air bleeding control continues until the liquid level in the system reaches a specified value, that is, when it reaches the level detected by the third liquid level sensor 59, each electromagnetic valve 53 to 55 and the electric pump 2
The process ends by cutting off the power to 5.

In this way, if harmful air has entered the cooling system, it will be automatically removed after the engine is stopped or immediately after starting, and the performance of the cooling system will therefore be subject to special maintenance. It is guaranteed for a long time without any work required.

f. Effects of the Invention As explained above, according to the present invention, the interior of the condenser that liquefies refrigerant vapor is basically maintained in a gas phase state to improve heat dissipation efficiency, and to provide cooling to this highly efficient condenser. Since the boiling point of the refrigerant liquid is controlled by changing the air volume via an electric fan, the engine system can be significantly reduced in weight and size, and the temperature can be quickly controlled to the appropriate temperature according to the operating conditions. Therefore, fuel efficiency can be effectively improved.

Furthermore, the present invention prevents outside air from entering the system by introducing liquid refrigerant from an external auxiliary tank to fill the cooling system with refrigerant when the engine is stopped, and also prevents outside air from entering the system. Since this is eliminated, the reliability and stability of the cooling device are further improved, and maintenance is also facilitated.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a conventional example. FIG. 2 is a schematic configuration diagram of an embodiment of the present invention, and FIG. 3 is a schematic configuration diagram also including the configuration of a control system and showing different operating states. 21... Engine (main body), 22... Water jacket, 22a... Gas phase space, 22b... Refrigerant injection pipe, 23... Condenser, 24... Lower tank, 25
...Electric pump, 26...Electric fan, 28...Refrigerant passage, 30...Control circuit, 31, 58, 59...Liquid level sensor, 32...Temperature sensor, 50...Auxiliary tank, 5
1...first auxiliary passage, 52...second auxiliary passage, 53...
First solenoid valve, 54...second solenoid valve, 55...third solenoid valve.

Claims (1)

[Claims] 1 A condenser that cools and liquefies refrigerant vapor from the engine water jacket, a lower tank that temporarily stores the liquefied refrigerant from this condenser, an electric pump that returns the liquefied refrigerant from the lower tank to the water jacket, and supplies forced cooling air to the condenser. A circuit that detects the engine temperature and drives the electric fan at a predetermined high temperature, and a circuit that detects the refrigerant liquid level in the water jacket and drives the electric pump until the liquid level reaches a predetermined level when the liquid level drops. A control system with a control system is provided, and the liquid refrigerant is sealed in an amount such that the upper part of the water jacket and almost the entire inside of the condenser become a gas phase space under the condition that a predetermined liquid level is satisfied. The device includes: an auxiliary tank that stores liquid refrigerant with a capacity at least as large as that of the gas phase space; a first auxiliary passage that introduces the liquid refrigerant in the auxiliary tank into the refrigerant passage between the electric pump and the lower tank; A first solenoid valve that selectively communicates the suction side with either the refrigerant passage on the lower tank side or the first auxiliary passage, a second auxiliary passage that introduces liquid refrigerant from the auxiliary tank into the water jacket, and a second auxiliary passage. A second solenoid valve that opens and closes, and a third solenoid valve that opens or closes the top portion of the gas phase space to the atmosphere is provided, and each of the solenoid valves is switched and controlled according to the engine condition and the amount of liquid refrigerant in the cooling system. 1. A boiling cooling device for an engine, characterized by forming a control system for controlling the engine.