JPH0526259Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a radiator water temperature detection device that predicts the water temperature of a radiator provided in a water-cooled engine based on the engine water temperature.

(Prior art) Conventionally, there are engines for automobiles that detect the water temperature in the radiator in addition to the water temperature in the water jacket, and control the engine based on the detected value. 58−
Japanese Patent No. 152157 discloses an engine equipped with an exhaust gas recirculation device for reducing NOx, in which the amount of exhaust gas recirculation is controlled based on both engine water temperature and radiator water temperature.
According to this device, it is possible to improve the operating performance of the engine.

In other words, the amount of exhaust gas recirculation is generally controlled according to the engine temperature, but in addition to the engine temperature, the radiator water temperature can also affect the operating conditions, such as the outside air temperature and When the corresponding radiator water temperature is extremely low, the driving performance tends to deteriorate, and control based only on the engine water temperature may cause problems. Therefore, in the above device, when the radiator water temperature is low, exhaust gas recirculation is suppressed to maintain excellent operating performance.

However, in the case of such a device, it is necessary to install a new water temperature sensor to the radiator, which has the disadvantage of increasing costs.Moreover, the sensor can be corroded by water droplets, etc., causing failure. There was a possibility.

(Purpose of the invention) In view of the above circumstances, the present invention is a radiator water temperature detection device for a water-cooled engine that can determine whether the radiator water temperature is above a reference value without using a means to directly detect the radiator water temperature. The purpose is to provide

(Structure of the invention) The present invention has a water jacket, a radiator is connected to the water jacket, and an engine water temperature in the water jacket is set in advance between the radiator and the water jacket. In a water-cooled engine equipped with a thermostat that opens when the opening/closing set temperature is higher than the opening/closing set temperature, the water temperature detecting means detects the engine water temperature, and the radiator water temperature is set to be lower than the opening/closing set temperature based on the detected engine water temperature. and determining means for determining whether or not the engine water temperature is at least the low reference value, and at least when the engine water temperature at the time of engine startup is lower than the reference value, the engine water temperature thereafter becomes the opening/closing set temperature. The radiator water temperature is determined to be equal to or higher than the reference value when the temperature becomes higher than the reference value.

According to such a configuration, the radiator water temperature is indirectly detected based on the detected value of the water temperature sensor. More specifically, if the engine water temperature at the time of engine startup is lower than a preset reference value, then when the engine water temperature rises and becomes higher than the thermostat opening/closing temperature setting, which is higher than the reference value, That is, when the thermostat is opened, it is assumed that the engine water temperature and the radiator water temperature are equalized, and it is only at this point that it is determined that the radiator water temperature is equal to or higher than the reference value.
Therefore, when only the engine water temperature is rising with the thermostat closed, there is no possibility of erroneously determining that the radiator water temperature is above the reference value.

(Example) Embodiments of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 1 denotes a water-cooled engine. The engine 1 has a piston 2 in a cylinder, and a combustion chamber 3 is formed above the piston 2. As shown in FIG. An intake valve 4, an exhaust valve 5, and a spark plug (not shown) are arranged to face the combustion chamber 3, and an ignition control section 6 is connected to the spark plug.

An intake passage 7 and an exhaust passage 8 communicate with the combustion chamber 3 via the intake valve 4 and exhaust valve 5. In the intake passage 7, an air flow meter 9,
A throttle valve 10, a fuel injection valve 11, etc. are provided, and the exhaust passage 8 is provided with an O ₂ sensor 12 for detecting the air-fuel ratio of exhaust gas. The intake passage 7 and the exhaust passage 8 communicate with each other.
An EGR (exhaust gas recirculation) passage 13 is provided, and an EGR valve 14 is provided in the middle thereof.

The engine 1 has a water jacket 15, and a radiator 18 is connected to the water jacket 15 via a thermostat 16 and a water pump 17. thermostat 1
6 is provided on the upstream side of the radiator 18, and is opened when the engine water temperature in the water jacket 15 is equal to or higher than the opening/closing set temperature (here, 80°C), and the thermostat 16 is in the open state. Only in this case is a water flow flowing through the water jacket 15 and the radiator 18 formed.

The water jacket 15 is provided with a water temperature sensor (water temperature detection means) 19 for detecting engine water temperature. The water temperature sensor 19 is connected to a control unit (judgment means) 20 that performs drive control of the fuel injection valve 11 and EGR control, and the water temperature sensor 19 and control unit 20 predict the radiator water temperature. A water temperature detection device is configured.

The control unit 20 receives detection signals output from the air flow meter 9, O ₂ sensor 12, water temperature sensor 19, and a throttle sensor provided in the throttle valve 14, and an ignition signal output from the ignition control section 6. The engine is controlled by outputting control signals to the fuel injection valve 11 and the EGR valve 14 in response to these signals.

The control unit 20 controls the radiator water temperature to a preset reference value (here,
17°C) or higher, and the criteria for this judgment can be divided into the following three cases.

1 When starting the engine (control unit 20
When the radiator water temperature receives the ignition signal from the ignition control section) is higher than 80℃ (the temperature set for opening/closing the thermostat 16), it is determined that the radiator water temperature is already above the reference value (17℃) when the engine starts. , set the memory flag to 1.

2 If the engine water temperature at engine start is above 17℃ (standard value) and below 80℃ If the memory flag when the engine was stopped in the previous operation was 1, the radiator water temperature was already at the standard when the engine was started. It is determined that the value is greater than or equal to the value, and the memory flag is set to 1. If the memory flag was 0 when the engine was last stopped, the radiator water temperature is determined to be below the reference value when the engine is started, and the memory flag is set to 0, and the engine water temperature is set to 80℃ after the engine starts. When the temperature rises, it is determined that the radiator water temperature has exceeded the reference value, and the memory flag is set to 1.

3 If the engine water temperature is lower than 17℃ when the engine is started, it is determined that the radiator water temperature is below the standard value and the memory flag is set to 0, and the engine water temperature rises to below 80℃. When the value increases, it is determined that the value has exceeded the reference value, and the memory flag is set to 1.

The control operation of this control unit 20 is
This will be explained based on the flowchart shown in FIG. In the figure, when the engine ₁ is started in step S1, the control unit 20 calls out the previous memory flag in step _S2 . And step S ₃
If it is determined in step _S4 that the engine water temperature is 80°C or lower, and if it is determined in step S4 that the engine water temperature is 17°C or higher, the recalled memory flag serves as the criterion for determination. If it is determined in step _S3 that the engine water temperature is higher than 80°C, the memory flag is set to 1 in step _S5 regardless of the memory flag that was recalled. If it is determined in step _S3 that the engine water temperature is 80°C or lower, and if it is further determined in step _S4 that it is lower than 17°C, the memory flag is set to 0 in step _S6 .

Based on the memory flag set in this way, the radiator water temperature is determined in step _S7 . That is, if the memory flag is 1, it is determined that the radiator water temperature is 17°C or higher and the EGR valve 14 is opened to perform normal EGR in step _S8 , and if the memory flag is 0, the radiator water temperature is 17
℃, and the EGR valve 14 is throttled to reduce the EGR in step _S9 .

The above operations are executed while engine 1 is running, but if it is determined in step _S10 that engine 1 has stopped, the memory flag at the time of stopping is memorized in step _S11 , and the memory flag is used when starting the engine next time. Call it again at some point.

FIG. 3 shows actual engine water temperature and radiator water temperature fluctuations as the engine 1 is stopped and started, respectively, shown by a solid line 30 and a two-dot chain line 31, below which are changes set by the control unit 20. It describes the value of the memory flag.

The left side of the figure shows a case where the outside air temperature is 17°C or higher. As shown in the figure, while the engine 1 is operating, the engine water temperature is higher than 80°C, so the thermostat 16 is open, and the engine water temperature and the radiator water temperature are equal. When the engine 1 stops, both water temperatures drop, and the thermostat 16 is closed when the engine water temperature falls below 80°C, but after that, both water temperatures continue to fall at the same rate, and a parallel state occurs at a temperature of 17°C or higher. becomes.

When the engine 1 is started again from this state, the engine water temperature rises, but the radiator water temperature does not rise because the thermostat 16 is closed, and the thermostat 16 opens when the engine water temperature becomes higher than 80°C. It begins to rise when it is lowered. Therefore, when the outside temperature is 17°C or higher, the radiator water temperature is always 17°C or higher.

On the other hand, the control unit 20 stores the memory flag set to 1 when the engine 1 is stopped, and calls the same memory flag when the engine 1 is restarted, so the memory flag remains in the state of 1 from beginning to end. , the radiator water temperature is always determined to be 17℃ or higher.

The right side of Figure 3 shows the case where the outside air temperature is lower than 17°C. When the engine 1 stops, the engine water temperature and the radiator water temperature decrease in the same way as described above, but since the outside air temperature is lower than 17°C, both water temperatures reach an equilibrium state at a temperature lower than 17°C.

When the engine 1 is restarted from this state, only the engine water temperature increases because the thermostat 16 is closed. Then, when the engine water temperature becomes higher than 80°C, the thermostat 16 opens and the radiator water temperature starts to rise, and reaches 17°C or more after time t has elapsed since the start of the rise.

On the other hand, the control unit 20 stores the memory flag set to 1 when the engine 1 is stopped, but sets the memory flag to 0 when the engine 1 is restarted because the engine water temperature is lower than 17°C. Then, when the engine water temperature rises and the water temperature becomes higher than 80℃, the memory flag is set to 1.
Set to . That is, control unit 2
0 means that the radiator water temperature is 17 before engine 1 stops.
℃ or higher, but when engine 1 is restarted, it is determined to be 17℃ or lower, and after engine 1 is restarted, the radiator water temperature is determined to be 17℃ or higher when the radiator water temperature actually starts to rise. .

Therefore, according to the above configuration, the outside temperature is
When the temperature is 17°C or higher, the same judgment can be made as when the actual radiator water temperature is detected, and even if the outside temperature is lower than 17°C, the time when the radiator water temperature reaches 17°C or higher after engine 1 is restarted. can be determined almost reliably except for a slight difference in time t. Therefore, without providing a new water temperature sensor to the radiator 18, accurate engine control can be performed only by detecting the engine water temperature.

Note that in this embodiment, the memory flag is stored when the engine is stopped and recalled when the engine is started, but the same determination as above may be made even if the configuration is such that the memory flag continues to be set even when the engine is stopped. (See the dotted line in Figure 3).

Furthermore, in the same embodiment, if the engine water temperature at the time of engine startup is 17°C or higher and 80°C or lower, the radiator water temperature is determined based on the memory flag stored when the engine was stopped last time.
Even if such a memory flag is not used and the configuration is configured such that when the engine water temperature is 17°C or higher and 80°C or lower, it is immediately determined that the radiator water temperature is 17°C or higher, the same judgment as above can be made. can. However, if you use the above memory flag,
Accurate judgment can be made even when a special engine operation as shown in FIG. 4 is performed.

In other words, when the outside air temperature is lower than 17°C, if engine 1 is stopped with the engine water temperature (solid line 40) between 17°C and 80°C, and engine 1 is started again before the engine temperature of engine 1 has dropped to 17°C, the actual radiator water temperature (two-dot chain line 41) at engine start will be lower than 17°C, but a judgment that does not rely on the memory flag would result in a judgment that the temperature is 17°C or higher. However, if the memory flag is used, the memory flag that was set to 0 when the engine was stopped is called up when the engine is restarted, so that an accurate judgment that the radiator water temperature is lower than 17°C will be made.

In the present invention, the opening/closing set temperature of the thermostat 16 and the reference value for determining the radiator temperature may be set as appropriate. Furthermore, the present invention may be applied to other controls that require detection of radiator water temperature, in addition to the EGR amount control as described above.

(Effects of the invention) As described above, the present invention judges the radiator water temperature based on the engine water temperature in the water jacket.Moreover, if the engine water temperature at the time of engine startup is lower than the reference value, The radiator water temperature is determined to be above the above reference value only when the engine water temperature becomes higher than the thermostat's opening/closing set temperature, which is higher than the above reference value. This eliminates the possibility of incorrectly determining that the radiator water temperature is higher than the above reference value when only the radiator water temperature is rising, and thus the radiator water temperature can be accurately determined without installing a new sensor etc. on the radiator. effective.

[Brief explanation of drawings]

Fig. 1 is a structural diagram of an engine to which the radiator water temperature detection device of the present invention is applied, Fig. 2 is a flowchart showing the control operation of the control unit in the device, and Figs. 3 and 4 show actual engine water temperature. 3 is a graph showing changes in the radiator and values of memory flags set accordingly. 1...Engine, 15...Water jacket, 16...Thermostat, 18...Radiator, 19...Water temperature sensor (water temperature detection means), 20
...Control unit (judgment means).

Claims (1)

[Scope of utility model registration request] It has a water jacket, a radiator is connected to the water jacket, and between the radiator and the water jacket,
In a water-cooled engine equipped with a thermostat that opens when the engine water temperature in the water jacket exceeds a preset opening/closing temperature,
The water temperature detecting means detects the engine water temperature, and the determining means determines whether the radiator water temperature is equal to or higher than a reference value lower than the opening/closing set temperature based on the detected engine water temperature, and the judgment means At least when the engine water temperature at the time of engine startup is lower than the above reference value,
A radiator water temperature detection device for a water-cooled engine, characterized in that the radiator water temperature is determined to be equal to or higher than the reference value when the engine water temperature subsequently becomes higher than the opening/closing set temperature.