JPH03111617A - Cooling system for engine - Google Patents

Abstract

PURPOSE:To most properly control the temperature of cooling water by switching a change-over valve to a main water passage side under a torrid condition during a low load operation after a high load operation is continued and to a bypass water passage side under a cold condition. CONSTITUTION:A control unit 33 outputs a valve position switching command to an actuator 28 based on input signals of a water temperature sensor 24, a temperature sensor 25 and an air flow meter 27 and an operating state of an idle contact 34 and a heater switch 35. In an idle operation immediately after a high load operation is continued under a torrid condition, the actuator 28 is turned off and a change-over valve 23 is switched to a main water passage 31 side. In an idle operation immediately after the high load operation is continued under a cold condition, the actuator 28 is turned on and the change-over valve 23 is switched to a bypass water passage 30 side. Thus, overheat under the torrid condition or deterioration in a heater performance under the cold condition is prevented and the temperature of cooling water can be most properly controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to an engine cooling system, and in particular has a bypass water passage that bypasses a radiator and returns cooling water to a water pump, and switches the cooling water passage. The present invention relates to a cooling water device that controls cooling water temperature.

Conventional technology In automobile engines, a water-cooled cooling system is generally used that uses a water pump to forcibly circulate cooling water between the engine's water jacket and radiator. However, depending on the operating conditions and operating environment, it is difficult to control the cooling water temperature to the optimum temperature.

Therefore, in order to control the cooling water temperature according to the operating conditions, a water passage that bypasses the radiator is provided, and the amount of water flowing through the bypass water passage is controlled based on the cooling water temperature and the front surface temperature of the radiator. , Utsukai Showa 61-
55121 (Japanese Unexamined Patent Publication No. 58-74824), which controls the drive of a cooling fan and a water pump in addition to the water flow rate control described above, has been proposed.

Problems to be Solved by the Invention Under hot geological conditions, when the engine suddenly shifts to idling after high-load operation such as driving on steep slopes or accelerating, the amount of heat accumulated in the engine is released into the engine room.
The temperature in the engine room becomes very high and the heat dissipation efficiency of the radiator decreases, so it is necessary to lower the cooling water as soon as possible before the temperature rises further.However,
In the conventional example described above, the water flow to the bypass is not stopped until the temperature of the cooling water becomes quite high (for example, 90 to 95° C.), so the temperature of the cooling water does not easily decrease to an appropriate temperature.

On the other hand, under cold region conditions, it is better not to cool the engine too much in order to secure a heat source for the heater, but there is a problem in that the temperature of the cooling water drops suddenly if water is passed through the radiator.

Means for Solving the Problems This invention provides a water pump 1 as shown in FIG.
The cooling system that forcibly circulates cooling water between the water jacket 2 and the radiator 3 of the engine is provided with a bypass water passage 4 that bypasses the radiator 3 and returns the cooling water to the water pump 1. In an engine cooling system that is equipped with a switching valve 6 that switches between the path 4 and the main water flow path 5 toward the radiator 5 according to the cooling water temperature, a low-load system detects a change from high-load operation to low-load operation. transition detection means 7; high load duration determination means 8 for determining whether or not the previous high load duration time is longer than a predetermined time during this transition to low load operation; and temperature detection for detecting the front temperature of the radiator 3. means 9; an operating environment determining means 10 for determining whether the radiator front surface temperature is in a hot region condition or a cold region condition; Switching valve control means 1 for switching the switching valve 6 to the main water flow path 5 side if the condition is present, or to the bypass water flow path 4 side if the condition is in a cold region, and forcibly holding the switching position for a predetermined time.
It is characterized by having the following.

When the low load transition detecting means 7 detects a change from high load operation to low load operation, the high load continuation time determining means 8 determines whether the previous high load continuation is 17fl or more than a predetermined time. will judge. Further, the driving environment determining means 10 determines whether the radiator front temperature is detected by the temperature detecting means 9 as a hot region condition or a cold region condition,
If the high load duration is longer than the predetermined time,
Said hot ground 9
fTI+ Yoichi9shiIIM-! The switching valve 6 is switched to the λ5 side of the urakere 13 and forcibly held in that position for a predetermined period of time. Through this operation, cooling water is passed through the radiator for a predetermined period of time, and the temperature of the cooling water is rapidly reduced. Under cold region conditions, the switching valve control means 11 switches the switching valve 6 to the bypass water flow path 4 side and forcibly maintains the switching position for a predetermined period of time. With this operation, the cooling water is circulated bypassing the radiator 3 for a predetermined period of time, making it difficult for the cooling water temperature to drop.

Embodiment FIG. 2 is a schematic explanatory diagram showing the structure of an embodiment in which the present invention is applied to an automobile engine. First, the configuration of an embodiment of this invention will be explained based on FIG.

20 is an engine body with a water jacket formed inside, 21 is a radiator disposed at the front of the vehicle body, 22
is a water pump driven by an engine, 23
is a switching valve for switching the cooling water flow path.

Also, 24 is a watch
n--1 10n→shi mountain r+ I+ :G sea
Base Quantity 7 Pattern Tag - One temperature sensor, 25 is a temperature sensor for detecting the temperature on the front surface of the radiator with a temperature sensing part arranged near the front part of the radiator 21, 26 is a crank angle sensor for detecting the engine rotation speed , 27 is an air meter 70 for detecting the intake air amount of the engine.

The above-mentioned switching valve 23 is a butterfly valve equipped with a valve body 23a whose rotation is controlled by an electromagnetic actuator 28 consisting of a solenoid or the like, as shown in FIG. 3, for example, and has a main water flow path 29 and a bypass water flow path. 30 to either one. When the actuator 28 is off and the valve body 4a is in the solid line position, the cooling water coming out of the water jacket enters the radiator 21 from the main water passage 31, is cooled by heat exchange, and then is switched from the main water passage 29. The water enters the water pump 22 via the valve 23 and the water flow path 32, and is forcedly circulated through this path. When the actuator 28 is on and the valve body 23a is in the two-dot chain line position, the water enters the bypass water passage 30 from the main water passage 31 and returns to the water pump 22 via the switching valve 23 and the water passage 32. , cooling water is forcedly circulated.

33 is a control unit that gives a valve body position switching command to the actuator 28 so that the valve body 23a is switched between the two positions described above.

The valve body position switching command is given by the water temperature sensor 24° temperature sensor 25. It is output based on the signals input from each sensor of the air flow meter 27 and the operating states of the idle contact 34 and the heater switch 35.

Next, based on the flowcharts shown in Figures 4 to 6,
The operation of this embodiment will be explained. 4 to 6 show the control operation of the control unit 33.

When the engine is started, the engine speed NE is 20
High rotation determination flag KN indicating whether it is below or above 0 Orpm
set to "0" (if KN=Q, then 2000 rpm+
Hereinafter, if KN=1, it indicates 2000 rpn+ or more), and initialization is performed to turn off the actuator 28 (step Sl).

Note that this initialization is executed only when the engine is started.

In this state, as mentioned above, the cooling water is flowing to the radiator 21.
water is passed through.

Next, the engine speed NE, idle contact signal SA, and cooling water temperature TW are read (step S2).
. Then, it is determined whether the high rotation determination flag KN is "0" or not, and when KN=O, the engine rotation speed NE is 200.
It is determined whether Orpm or less (steps S3 and S4
). When NE is 2000 rpm or less, it is determined whether the idle contact signal SA is on or off (the idle contact signal SA is turned on when the engine is running at idle), and when the idle contact signal SA is on, the cooling water temperature TW is determined. is 85
It is determined whether the temperature is higher than or equal to 0.degree. C. (steps S5, S6). For example, when the engine is idling immediately after starting, step S6 is executed, and when the cooling water temperature TW is 85°C or higher, the cooling water set temperature TS is set to a slightly lower 75°C, and when it is 85°C or lower, the cooling water set temperature TS is set to 75°C or lower. The cooling water set temperature TS is set to a slightly higher value of 85° C. (steps S7 and S8).

If the engine is being warmed up, the process proceeds to step S8, and warm-up is promoted.

In step S3 described above, when the high rotation determination flag KN is rlJ, that is, when the engine rotation speed NE was 200 Orpm or more in the previous data reading, the engine rotation speed NE is set to 200 Orpm in step S9.
It is determined whether or not it is equal to or greater than pm, and if it is equal to or less than 200 orpm, a high rotation determination flag KN is set to "0" in step SIO. In addition, in step S4 described above, when the engine rotation speed NE is 2000 rp■, that is, when it was less than 200 Orpm in the previous data reading and became more than 200 Orpm in the current data reading, the high rotation determination flag KN is set. It is set to "1" (step 5ll).

When the engine speed NE is 200 Orpm or more, or when the idle contact signal SA is off, the intake air amount, that is, the output signal of the air flow meter 27, is read, and the intake air flow downstream of the throttle valve is adjusted based on this air flow meter signal. Pressure PB is calculated (step S12, 513).

When the suction negative pressure PB is -300+zHg or more, that is, during high-load operation such as climbing or accelerating, the cooling water set temperature TS is set to 75°C, and the suction negative pressure PB is -3001
x Hg or less, that is, during medium-low load operation, it is determined whether the high rotation determination flag KN is "0" (or whether the engine rotation speed NE is 200 Orpm or less) (steps s14.s15. 516). High rotation determination flag K
When N is "1", that is, during medium-load operation such as high-speed constant speed driving, the cooling water set temperature TS is set to 80 degrees Celsius, and when the high rotation determination flag KN is "0", that is, during medium-speed constant speed driving During low load operation such as, the cooling water set temperature TS is set to 85° C. (steps 817, 518).

Now, when the high rotation determination flag KN is changed from "1" to [0] in step SIO mentioned above, that is, when the engine rotation speed NE is changed from a medium-high load operating state of 2000 rpm or more to a low-load operating state of 200 rpm or less. 5, the process advances to step 319 shown in FIG.

In step S19, a timer that measures the time for forcibly switching the switching valve 23 is cleared and starts counting. Then, in the next step S20, the engine speed NE
It is determined whether the duration when is 2000 rpm or more, that is, the duration of medium/high load operation is 10 minutes or more, and if it is 10 minutes or less, the process returns to step S2.

When the medium/high load operation duration time is 10 minutes or more, it is determined in the next step 321 whether the idle contact signal SA is on or off, and when it is off, the process returns to step S2. When the idle contact signal SA is on, next the cooling water temperature TW and the radiator front temperature TA based on the input signal of the temperature sensor 25 are read (step 522). Then, it is determined whether or not the radiator front temperature TA is 10°C or less (this judgment determines whether or not it is a cold region condition). When it is 10°C or less, that is, in a cold region condition, the cooling water set temperature TS is 1
The temperature is set to a sufficiently high temperature of 00°C (step S23,
524). Further, when the radiator front surface temperature TA is 10° C. or higher, the process proceeds to step S25, where it is determined whether the radiator front surface temperature TA is 25° C. or higher (this determination determines whether or not the hot ground condition is met); When the temperature is 25° C. or higher, the cooling water set temperature is set to a sufficiently low temperature of `1''S/+470° C. in step 926, and when the temperature is 10° C. or higher and 225° C. or lower, the process returns to step S2.

Step S24. When the cooling water set temperature 'rS is set in S20, the actual cooling water temperature '1'W and its cooling water set temperature 'rS are compared, and 'I' W >'l
' If S, a valve body position switching command is output so that the actuator 28 is turned off (step S27.8).
28). Also, if 'r w <'t' s te,
Conversely, a valve body position switching command is output so that the actuator 28 is turned on (steps 827 and 529).

In other words, here, when the actual cooling water temperature 'rW is higher than the set temperature 'rS, the cooling water is passed through the radiator for two days to facilitate heat dissipation, and conversely, when it is lower, the cooling water is not passed through the radiator 21. Make it difficult for heat to be dissipated. Therefore, under hot geological conditions, the set cooling water temperature 'i' s is set sufficiently lower than the actual temperature 1' W , 1 - so the cooling water temperature 1' W begins to drop immediately by 4°, and vice versa. Under cold region conditions, TS is set sufficiently higher than TW, so the cooling water temperature TW is less likely to drop.

In the next step S30, it is determined whether or not 20 minutes have passed since the time started in step S19. If it is within 20 minutes, the process returns to step S21, and if 20 minutes have elapsed, the process returns to step S2. return. In other words, the idle contact signal S
Steps S22 to S29 are repeated for 20 minutes unless A is on and the radiator front surface temperature TA is within the range of 10°C or more and 25°C or less. Here, the above process is repeated for the same amount of time even under different conditions, but the times may be set separately for cold region conditions and hot region conditions.

Step 37 above. S8. S15. After S17 and S18 are executed and the coolant set temperature TS is set, the radiator front temperature TA is read as shown in FIG. The TS is reset (steps S31-337). +5℃ if TA is below 10℃,
If it is 25°C or higher, it is corrected by -5°C, and if it is within 10°C to 25°C and the heater switch 35 is on, it is corrected by +5°C and reset. In other words, when the radiator front temperature TA, which corresponds to the outside air temperature, is relatively low, the cooling water set temperature TS is slightly raised to promote warm-up and improve heater performance, and when TA is relatively high, the heat dissipation of the radiator 21 is reduced. In order to promote this, the TS is set a little lower. Furthermore, even if the outside air temperature is relatively high, when the heater switch 35 is on, TS is set a little higher to improve the heater performance.

When the cooling water set temperature TS is reset, the set temperature TS and the actual cooling water temperature TW are compared, and TW>TS
If so, the actuator 30 is turned on, and conversely, TW<T
If S, the actuator 30 is turned on, and the valve body position of the switching valve 23 is controlled so that the cooling water temperature TW becomes the set temperature TS (steps 338 to 540). Step S
39° After S40 is executed, the process returns to step S2.

As described above, in this embodiment, the switching valve 23 is controlled to switch based on each of the input signals described above, so that the optimum cooling water temperature can be set depending on the operating conditions and the operating environment such as cold region conditions or hot region conditions. Control takes place. In particular, if the transition to idle operation occurs after medium-high load operation continues for 10 minutes or more under hot region conditions or cold region conditions, step S19
The operations from ~S30 are executed, and optimal control corresponding to the environment is performed.

During idling operation immediately after continued high-load operation under hot ground conditions, heat is accumulated in the engine, so the hot air that has passed through the radiator 21 receives heat from the engine and is returned to the radiator 21 with a further temperature rise. state, and the heat dissipation performance of the radiator 21 is significantly reduced. However, in this embodiment, the cooling water set temperature TS is set to 70°C, which is sufficiently low compared to the actual cooling water temperature TW, regardless of the operating conditions. Cooling water is constantly passed through the radiator 21, and the cooling capacity of the cooling device is utilized to the maximum.

In addition, under cold region conditions, in order to ensure heater performance, it is necessary to prevent the heat accumulated in the cooling water from escaping as much as possible. If water is being used, the cooling water temperature TW will drop suddenly. In this embodiment, in such a case, the cooling water set temperature TS is set in advance to 100°C, which is sufficiently higher than the actual cooling water temperature, so that the radiator 21
Since cooling water is not passed through the heater, the heater performance can be maintained as much as possible.

FIG. 7 and FIG. 8 are graphs showing experimental results by the present inventor. FIG. 7 shows the change in cooling water temperature under hot geological conditions, where the solid line is the result in this example and the broken line is the conventional result. Figure 8 shows similar results under cold region conditions. As is clear from these graphs, under hot region conditions, the cooling water temperature decreases more rapidly than in the past, and under cold region conditions, the cooling water temperature decreases more rapidly than in the past ( It has become.

In the above embodiment, the cooling water set temperature TS is set to 70°C under hot region conditions, and the cooling water set temperature TS is set to 1°C under cold region conditions.
00°C and compares it with the actual cooling water temperature TW to control switching of the switching valve 23. However, under these conditions, when transitioning to idle operation after continuing medium to high load operation, the cooling water temperature Regardless of TW, switching control of the switching valve 23 may be performed such that water is forcibly passed through the radiator 21 under hot region conditions and bypassed under cold region conditions.

Effects of the Invention As is clear from the above explanation, according to the engine cooling device according to the present invention, when the high load operation is continued for a predetermined period and then the low load operation is started, the radiator front temperature changes from the hot ground temperature. The control valve determines whether the conditions are cold or cold, and controls the switching valve so that water passes through the radiator under hot conditions and bypasses the radiator under cold conditions, thereby preventing overheating or cold conditions. It is possible to optimally control the cooling water temperature while preventing a decrease in heater performance under underground conditions.

[Brief explanation of drawings]

FIG. 1 is a diagram corresponding to the claims of the present invention, FIG. 2 is a structural explanatory diagram briefly showing the configuration of an embodiment in which the present invention is applied to an automobile engine, and FIG. 3 is a structural explanatory diagram of the switching valve 23.
4 to 6 are flowcharts showing control operations of the control unit 33, FIG. 7 is a graph showing changes in cooling water temperature under hot region conditions, and FIG. 8 is a graph showing changes in cooling water temperature under cold region conditions. It is a graph. 1...Water pump, 2...Water jacket, 3...Radiator, 4...Bypass water passage, 5...Main water passage, 6...Switching valve, 7...Low Load shift detection means, 8... High load duration determination means, 9
...Temperature detection means, 10...Operating environment determination means, 1
1...Switching valve control means. 4 BA 4 Y S j J1 Water pregnancy path 2 J Figure 3 〕1〉S A fu ni 5L ding≧-(0C)

Claims (1)

[Claims] (1) A cooling system that forcibly circulates cooling water between the engine water jacket and the radiator using a water pump is equipped with a bypass water passage that bypasses the radiator and returns the cooling water to the water pump, and this bypass water passage A low-load transition detection means for detecting a change from high-load operation to low-load operation in an engine cooling system equipped with a switching valve that switches between the main water flow path and the main water flow path toward the radiator according to the temperature of the cooling water. , high load duration determination means for determining whether or not the previous high load duration time is equal to or longer than a predetermined time during this transition to low load operation; temperature detection means for detecting the front surface temperature of the radiator; and the detected front surface temperature of the radiator. an operating environment determining means for determining whether it is a hot region condition or a cold region condition from the temperature; An engine cooling device characterized by comprising: switching valve control means for switching the switching valve to the bypass water flow path side if the cold region condition exists, and forcibly maintaining the switching position for a predetermined period of time.