JPH0415366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a cooling device for a water-cooled engine, and particularly to a cooling device that appropriately controls cooling according to the temperature of inflow cooling water flowing into the engine.

(Prior art) As an engine cooling method, low-temperature cooling water is supplied to the water jacket around the cylinder, and cooling water that has become high temperature by cooling the cylinder is supplied to the radiator. A cooling water circulation system is widely used, in which the cooling water is cooled to a low temperature by water and then supplied to the water jacket again.

In this cooling method, a thermostatic on-off valve, for example, is provided at the engine outlet of the coolant circulation passage, and the amount of circulating water is controlled by increasing or decreasing the opening of the on-off valve according to the coolant temperature. Therefore, the cooling water temperature at the engine outlet is maintained at a predetermined value, but such cooling water temperature control has problems of so-called response delay and hunting, resulting in the following problems. In other words, in order to reduce the response delay, the operation speed of the above-mentioned on-off valve should be increased, and when the cooling water temperature is higher than a predetermined value, the circulating amount of cooling water can be quickly increased. Then, if the temperature of the cooling water flowing into the engine is low in relation to the outside temperature, etc., the engine will be cooled down rapidly and the cooling water temperature will significantly undershoot below the predetermined value. Hunting will occur. In addition, in order to reduce this hunting, it is possible to slow down the operating speed of the on-off valve, but in that case, the response delay of the control becomes significant, and it takes a long time for the cooling water temperature to drop to a predetermined value when it is high. Therefore, for example, when the engine is under high load and generates a large amount of heat, there is a risk that the engine will overheat.

By the way, regarding cooling control of a water-cooled engine, there is an invention disclosed in, for example, Japanese Patent Laid-Open No. 168017/1983. This focuses on the problem that even if the cooling water temperature is controlled at a constant level, the amount of heat generated by the engine changes depending on the operating conditions, resulting in the engine becoming overcooled during low loads when the amount of heat generated is low. , a cooling regulating device such as a flow control valve that regulates the cooling capacity of the cooling system, a sensor that outputs a signal correlated to the cylinder wall temperature, and a control circuit that drives the cooling regulating device according to the output of this sensor. and the control circuit controls the cooling regulating device based on a preset table depending on the operating state, or directly detects the cylinder wall temperature and feedbacks the cooling regulating device so that the temperature becomes a predetermined value. It was designed to be controlled. However, even in this invention, there is a delay in response when the cooling water temperature or cylinder wall temperature changes to a predetermined value after the cooling regulating device is activated. In some cases, the above-mentioned problem of significant hunting occurs.

(Object of the Invention) The present invention addresses the above-mentioned problems in a cooling device that controls cooling water temperature by adjusting the amount of cooling water circulated between a radiator and a water jacket. By changing the operating speed or amount of operation of a regulating device such as an on-off valve that adjusts the circulating amount of cooling water in accordance with the temperature of the inflowing cooling water flowing into the engine, the inflowing cooling water temperature can be adjusted without impeding control responsiveness. The purpose is to effectively suppress hunting when the temperature is low.

(Configuration of the Invention) A cooling device according to the present invention is configured as follows for the above purpose.

That is, in a water-cooled engine that includes a radiator, a water jacket provided around a cylinder of the engine, and a cooling water passage that circulates cooling water between the radiator and the jacket, a signal related to the cooling water temperature is transmitted. A cooling water temperature detection means to output, an adjustment device such as an on-off valve that adjusts the amount of circulation of cooling water between the radiator and the water jacket, and an adjustment device operated in accordance with the output of the cooling water temperature detection means. A cooling water temperature control means for controlling the amount of circulation of cooling water is provided, and the cooling water temperature is controlled to be below a predetermined value by these means. In addition to these configurations, there is also an inflow cooling water temperature detection means that directly or indirectly detects the temperature of the inflow cooling water flowing into the engine, and the cooling water temperature control described above when the inflow cooling water temperature is low based on the output of the detection means. and control gain control means for reducing the control gain for the adjustment device by the means. The inflow cooling water temperature detection means may be, for example, a sensor that directly detects the inflow cooling water temperature, a sensor that detects the outside air temperature that affects the inflow cooling water temperature, or a sensor that predicts the inflow cooling water temperature based on the elapsed time from the time the engine is started. A timer or the like is used at startup.

According to such a configuration, when the inflow cooling water temperature is low, the operating speed or operating amount of the adjustment device that adjusts the circulating amount of cooling water becomes smaller, so that hunting of the cooling water temperature can be suppressed without causing a response delay during normal times. will be suppressed.

In addition to electrically controlling the opening degree of the adjusting device, a conventionally used thermostatic on-off valve can also be used. In this case, the control gain of the cooling water circulation amount control is changed by increasing or decreasing the passage area depending on the inflow cooling water temperature, for example.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

As shown in FIG. 1, the engine 1 is provided with a water jacket 3 around the cylinders 2...2, and the outlet 3a of the jacket 3 is connected to the inlet 4a of a radiator 4 provided near the engine 1. The inlet 3b of the jacket 3 is connected to the outlet 4b of the radiator 4 via pipes 5 and 6, respectively, and a cooling water circulation passage 7 is formed between the jacket 3 and the radiator 4. Further, a cooling water pump 10 driven by the crankshaft 8 of the engine 1 via a belt 9 is provided near the inlet 3b of the water jacket 3, and a cooling water pump 10 is provided at the outlet 3a of the water jacket 3. An on-off valve 11 is provided as an adjustment device for increasing or decreasing the amount of cooling water flowing out (circulating amount) from the outlet 3a to the pipe 5 or radiator 4 side. Here, cooling water is supplied to the radiator 4 between the outlet 3a and the inlet 3b of the water jacket 3 when the on-off valve 11 is closed.
Bypass passage 12 for circulating without supplying
is provided.

Further, a water temperature sensor 13 is provided at a position immediately upstream of the on-off valve 11 in the water jacket 3 to detect the cooling water temperature at the engine outlet, and a water temperature signal A outputted from the sensor 13 is inputted to the control circuit 14. It is becoming more and more like this. The control circuit 14 receives the water temperature signal A and compares its voltage level with the voltage level corresponding to the target cooling water temperature output from the set voltage generation circuit 15, and when the former voltage level is higher than the latter, A comparison circuit 16 that outputs a signal B of “1” and an integration circuit 1 that integrates the output signal B of this comparison circuit 16
7 and an amplifier circuit 18 for amplifying the output signal C of the integrating circuit 17, and the output signal of the amplifier circuit 18 is sent as a control signal D to the on-off valve 11. The on-off valve 11 is lifted in accordance with the value of the control signal D to increase or decrease the degree of opening of the passage leading from the water jacket 3 to the pipe 5 or radiator 4.

However, in this embodiment, in addition to the above-described configuration, an outside temperature sensor 19 is provided to indirectly detect the temperature of the inflowing cooling water flowing into the water jacket 3 from the inlet 3b. The engine 1 includes a rotation speed sensor 20 that detects the rotation speed of the engine 1, and a load sensor 21 that detects the magnitude of the load on the engine 1 from the opening degree of the throttle valve, intake negative pressure, and the like. These sensors 19
~21 output signals E, F, G are the first to third output signals, respectively.
The signals are input to function circuits 22-24 and converted into function values with characteristics as shown in FIG. 2 1-3. In other words,
The first function circuit 22 outputs a function value that increases as the outside temperature indicated by the output signal E of the sensor 19 increases, and the second function circuit 23 outputs a function value that increases as the outside temperature indicated by the output signal F of the sensor 20 increases. The third function circuit 24 outputs a function value that becomes smaller as the output signal G of the sensor 21 becomes higher, and the third function circuit 24 outputs a function value that becomes larger as the engine load indicated by the output signal G of the sensor 21 becomes larger. Then, a signal E′ indicating these function values,
F' and G' are input to an arithmetic circuit 25, and after predetermined arithmetic processing is performed, they are input from the arithmetic circuit 25 to an integral constant setting circuit 26 as a signal H. As shown in FIG. 3, this integral constant setting circuit 26 has an integral constant that increases as the output signal H of the arithmetic circuit 25 increases; An integral constant that increases as the engine load increases is set, and this is applied as a signal to the integrating circuit 7 in the control circuit 14. This integral constant is used in the integrating circuit 17 as an integral constant when integrating the output signal B of the comparator circuit 16.

In addition, the above-mentioned integration circuit 17 and integration constant setting circuit 26
For example, as shown in FIG. 4, the capacitor 28 is composed of a resistor 27 and a capacitor 28, and the capacitor 28 is a variable capacitor whose capacitance changes according to the output signal H of the arithmetic circuit 25. The constants are set to change as shown above.

Next, the operation of the above embodiment will be explained.

Now, when the engine 1 is started, the cooling water pump 10 is driven by the crankshaft 8 via the belt 9, and the cooling water in the water jacket 3 is pumped from the inlet 3b side to each cylinder 2. ...It passes around 2 and flows toward the exit 3a, but
Since the cooling water temperature is low immediately after starting, the control circuit 1 receives the water temperature signal A from the water temperature sensor 13 provided near the outlet 3a of the jacket 3.
4, the output of the comparison circuit 16 is "0", and therefore the control signal D sent from the control circuit 14 to the on-off valve 11 is also "0", and the on-off valve 11 closes the outlet 3a. in a state. Therefore, at this point, the cooling water is not supplied to the radiator 4, but instead circulates through the bypass passage 12.

In this state, as time elapses from the start of the engine, the cooling water temperature rises as shown by the solid line a in Fig. 5, and the water temperature reaches the set value T ₀ (e.g., 85°C). At this point, the voltage level of the water temperature signal A from the water temperature sensor 13 becomes equal to or higher than the output voltage level of the set voltage generation circuit 15 in the control circuit 14. Therefore, the output signal B of the comparison circuit 16 is
The signal changes to "1" as indicated by the symbol b in FIG. 2, and in conjunction with this, the output signal C of the integrating circuit 17 rises at a certain slope as indicated by the symbol c in FIG. 3. Then, the output signal C of this integrating circuit 17 is transmitted to the amplifier circuit 1.
8 to the on-off valve 11 as a control signal D, and the opening degree of the on-off valve 11 increases as the output value of the control signal D (output signal C of the integrating circuit 17) increases. This allows water jacket 3
The cooling water inside is supplied to the radiator 4 in accordance with the opening degree of the on-off valve 111, and the amount of circulating water passing through the radiator 4 gradually increases.

When the amount of circulating water passing through the radiator 4 increases in this way, the temperature of the cooling water stops increasing, and then the water temperature begins to decrease. Then, when the output signal B of the comparison circuit 16 in the control circuit 14 decreases to the set value T ₀ , the output signal B of the comparison circuit 16 in the control circuit 14 shows the sign shown in FIG.
As shown by b', the output signal C or the control signal D of the integrating circuit 17 changes from this point to "0".
The value of starts to decrease as shown by the symbol c′ in Figure 3,
Along with this, the opening degree of the on-off valve 11, that is, the amount of circulating cooling water passing through the radiator 4 decreases. Therefore, the cooling water temperature decreases to a constant temperature and then rises again, and as a result, the cooling water temperature at the water jacket outlet 3a fluctuates up and down around the set value _T0 , as shown by the solid line a in FIG. , hunting will occur.

By the way, in controlling the cooling water temperature as described above, when the temperature of the cooling water flowing from the radiator 4 into the water jacket 3 is low because the outside temperature is low, the engine 1 is cooled more quickly, and the cooling water temperature at the water jacket outlet 3a decreases rapidly. Therefore, as shown by the chain line a' in FIG. 5, the cooling water temperature significantly undershoots below the set value _T0 , and hunting becomes significant as a result. However, when the outside temperature becomes low, the sensor 1 that indicates this
The output E' of the first function circuit 22 to which the output signal E of 9 is input becomes small as shown in FIG. 2, and the integral constant set by the integral constant circuit 26 becomes small accordingly. Therefore, the signal C output from the integrating circuit 17 of the control circuit 14 is shown by the dotted line in FIG.
The slope becomes gentler as shown by c″. This means that
This means that the control gain of the control circuit 14 for the on-off valve 11 becomes smaller, and the opening speed of the on-off valve 11 becomes slower when the cooling water temperature exceeds the set value T ₀ . As a result, even though the inflow cooling water temperature is low, the water jacket outlet 3a
The cooling water temperature decreases more slowly in Figure 5-1.
As shown by the solid line a, undershoot or hunting is reduced.

Further, in this embodiment, the outside temperature sensor 19
In addition, a rotation speed sensor 20 and a load sensor 21 are provided, and the control gain changes depending on the engine rotation speed and engine load detected by these sensors 20 and 21. In other words, when the engine speed is high, the cooling water pump 1
0 also increases, the flow rate of the cooling water supplied to the water jacket 3 increases, and as a result, the cooling water temperature rapidly decreases for a constant valve opening speed of the on-off valve 11, as shown in FIG. In this case, hunting becomes significant as shown by the dashed line a′, but in this case,
As shown in FIGS. 2 and 3, as the integral constant set in the integral constant setting circuit 26 becomes smaller, as in the case where the inflow cooling water temperature is low,
The opening speed of the on-off valve 11 becomes slower, and hunting is suppressed.

Also, when the load on engine 1 is large and therefore the engine heat generation is large, the cooling water temperature is set to T ₀
If the opening speed of the on-off valve 11 is slow when the temperature exceeds T0, the cooling water temperature will greatly overshoot the set value _T0 , as shown by the chain line a'' in FIG. 5, and the response will be delayed. It will take a long time to drop to the set value T ₀ , and there is a risk that the engine 1 will overheat during this time.However, in this case, as shown in Figs. Since the integral constant set by the integral constant setting circuit 26 increases, the output signal C of the integrating circuit 17 in the control circuit 14 rises at a steep slope as shown by the symbol c in FIG. Accordingly, the opening degree of the on-off valve 11 increases rapidly, and the amount of circulating water passing through the radiator 4 is rapidly increased, so that overheating is prevented regardless of the increase in engine heat generation amount.

In the above embodiment, the outside air temperature sensor 19 was used to detect the temperature of the inflowing cooling water flowing into the engine, but instead of this, the inflowing cooling water temperature could be directly detected at the inlet 3b of the water jacket 3, etc. A sensor may be provided to detect this, or a starting timer may be used to measure this elapsed time by taking advantage of the fact that the inflow cooling water temperature rises up to a certain temperature approximately corresponding to the elapsed time from the start of the engine 1. The inflow cooling water temperature may be detected indirectly.

(Effects of the Invention) As described above, according to the present invention, in a cooling device for a water-cooled engine that controls the temperature of cooling water by adjusting the amount of circulating water between a radiator and a water jacket, Since the control gain for the regulating device that adjusts the amount of circulating water is reduced when the temperature of the inflowing cooling water is low, the response delay in controlling the cooling water temperature during normal times and overheating especially when the engine heat output is large are reduced. Hunting of the cooling water temperature when the inflow cooling water temperature is low can be suppressed without causing such problems. In this way, the cooling water temperature will always be well controlled.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a control system diagram, FIGS. 2 1 to 3 are output characteristic diagrams of the first to third function circuits in FIG. 1, and FIG.
Output characteristics diagram of the integral constant setting circuit in Fig. 4.
This figure is an electric circuit diagram showing a specific example of the integrating circuit and integral constant setting circuit in FIG. 1, and FIG. 5 is a time chart showing the operation. 1...Engine, 3...Water jacket, 4...Radiator, 7...Cooling water passage (circulation passage), 11...Adjusting device (on/off valve), 13...Cooling water temperature detection means (water temperature sensor), 14...Cooling water temperature control means (control circuit), 19...Inflow cooling water temperature detection means (outside temperature sensor), 26...Control gain control means (integral constant setting circuit).

Claims (1)

[Claims] 1. A radiator, a water jacket of the engine, a cooling water passage that circulates cooling water between the radiator and the jacket, a cooling water temperature detection means that outputs a signal related to the cooling water temperature, and a cooling water jacket between the radiator and the jacket. a cooling water temperature adjusting device that adjusts the amount of circulating water between the two; and a cooling water temperature controlling device that operates the regulating device according to the output of the cooling water temperature detection means to control the circulating amount of the cooling water so that the cooling water temperature is below a predetermined value. a control means, an inflow cooling water temperature detection means for outputting a signal related to the temperature of the inflow cooling water flowing into the engine, and an amount of cooling water circulated by the cooling water temperature control means when the inflow cooling water temperature is low in response to the output of the detection means; A cooling device for a water-cooled engine comprising a control gain control means for reducing a control gain.