JP2754902B2 - Cooling fan rotation speed control device for internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to the rotation of a cooling fan of an internal combustion engine, such as an internal combustion engine of an automobile, which is cooled via a heat exchanger supplied with cooling air by a cooling fan. The present invention relates to a speed control device.

The (prior art) automotive internal combustion engine cooling system, conventionally, a cooling fan rotational speed N _F controlled continuously to follow the temperature of the system have been proposed.

For example, in Japanese Utility Model Laid-Open No. 63-82026, the water temperature and the outputs of the air conditioner operation switch and the refrigerant pressure sensor are used as input information,
In principle, the fan speed is controlled in proportion to the water temperature.
When the air conditioner operation switch is ON or when the refrigerant pressure detected by the refrigerant pressure sensor is high, the fan is lower than when the air conditioner operation switch is OFF or when the refrigerant pressure by the refrigerant pressure sensor is low. It is described that the number of rotations is increased.

(Problems to be Solved by the Invention) By the way, the cooling water temperature characteristic under running conditions such as climbing up and downhill from a general road such as an urban road as a mountain road, as shown in FIG. It is constantly changing in response to the ups and downs of the road. FIG. 6 shows the temperature characteristics of the cooling water of the internal combustion engine in an automobile, the vertical axis represents the temperature of the cooling water, and the horizontal axis represents time. ~t ₁ and t ₃ ~ corresponds to the general traveling section, t ₁ ~
t ₂ is in pitched interval, t ₂ ~t ₃ correspond respectively to the downhill section. In the general traveling section, the characteristic shows a characteristic of drifting near a certain temperature in a low temperature region during normal operation, and rises in an uphill section and returns to the characteristic in general traveling in a downhill section. This is proportional to the heat load of the internal combustion engine.

Since the temperature characteristics of the cooling water are as shown in FIG. 6, in the conventional internal combustion engine cooling system as described in the above publication, the heat load fluctuation such as an uphill section or a downhill section is abrupt. A control pattern emphasizing the water temperature control at the time, that is, a control pattern in which the control curve of the rotational speed (called a tilt characteristic) is steep is set.

However, according to the above control pattern, for example, in a general traveling section, every time the water temperature drifts relatively large, the same control as that for the control of a mountain road or the like is performed. There has been a problem that power and heat dissipation are increased, and fuel economy and silence are sacrificed.

Contrary to the above, it is possible to set a control pattern such that the cooling fan drive loss power and the amount of heat radiation in a general traveling section are reduced, but this time, control in a mountain road section cannot be performed well.

SUMMARY OF THE INVENTION An object of the present invention is to provide a cooling fan control system that reduces fan driving power for improving fuel efficiency in a general traveling section, which is the most common section, and satisfies cooling performance in a mountain climbing section.

(Means for Solving the Problems) Cooling water of an internal combustion engine is circulated between the heat exchanger and a cooling fan whose rotation speed is controlled by a predetermined driving means, and water temperature is controlled via the heat exchanger. In a cooling fan rotation speed control device for an internal combustion engine, a water temperature sensor for detecting a temperature of cooling water for the internal combustion engine, and first means for inputting an output from the water temperature sensor every predetermined time to obtain a temperature change rate, The control tilt characteristic of the rotation speed is changed in accordance with the temperature change rate, and the changed control tilt characteristic is set in the driving means, and the current control tilt characteristic is changed in accordance with an increase or decrease in the temperature change rate. Second means for increasing the degree of change to the next control tilt characteristic is provided.

(Operation) According to the present invention, in an operating condition in which a sudden change in water temperature occurs, such as a mountainous road section, the change from the current control tilt characteristic to the next control tilt characteristic greatly changes the degree of change in the control tilt characteristic. In a driving situation where the water temperature change drifts in the vicinity of a substantially constant value, such as in a general traveling section, a small change is made in which the degree of change to the next control tilt characteristic according to the drift is small. As a result, it is possible to reduce the fan driving power in a general traveling section without impairing the cooling performance under an operating condition in which the thermal load fluctuates greatly, such as a mountain road section. As a result, it is possible to reduce the fan drive power in the general traveling section without impairing the cooling performance under exercise conditions in which the thermal load fluctuates severely, such as a mountain road section.

(Example) Hereinafter, an example in which the present invention is applied to an internal combustion engine of an automobile will be described in detail.

FIG. 1 is a configuration diagram showing one embodiment of a cooling fan rotation speed control device for an internal combustion engine according to the present invention, and FIG. 2 is an internal view of an ECU (electric control unit) used in the configuration of the above embodiment. FIG. 2 is a configuration diagram schematically showing a configuration.

In FIG. 1, reference numeral 10 denotes an internal combustion engine, 11 denotes a radiator, and 12 denotes a cooling fan for supplying cooling air to the radiator 11.

In the internal combustion engine 10, cooling water in a water jacket is circulated through cooling water pads 14 and 15 provided to reciprocate with the radiator 11. The cooling water from the cooling water pipe 15 on the outward path is pumped into the water jacket by the water pump 16.

The cooling fan 12 is driven to rotate by a hydraulic motor 17, and the hydraulic motor 17 is connected to a pump 19 by a conduit 18 at a working liquid inlet, and the pump 19 pumps the working liquid. Has become. The pump 19 is connected to a reserve tank 21 by a conduit 20, and sucks the working liquid from the reserve tank 21.

The hydraulic motor 17 has a working liquid outlet connected to a reserve tank 21 by a conduit 22 so as to transfer the working liquid to the reserve tank.
It is designed to be discharged to 21.

The conduits 18 and 20 are connected by a bypass conduit 24 having a flow control valve 28 in the middle. The flow control valve 23 is, for example, an electromagnetically operated valve, and controls the flow rate of the working liquid flowing through the bypass conduit 24 based on a pulse width modulation signal 25a from the ECU 25. Pulse width modulation signal 25
“a” is a signal obtained by modulating a carrier signal with a modulation control signal having a certain tilt characteristic and having a continuously variable pulse duty. In this embodiment, the flow rate of the working liquid flowing through the bypass conduit 24 is reduced in accordance with the increase in the pulse duty ratio of the pulse width modulation signal 25a to increase the flow rate of the working liquid flowing through the hydraulic motor 17. I have.

The radiator 11 is provided with a water temperature sensor 26 for detecting the temperature of the cooling water of the internal combustion engine 10. The detection output 26a from the water temperature sensor 26 is input to the EUC 25.

As shown in FIG. 2, the EUC 25 inputs a detection output 26a from the water temperature sensor 26 at regular small time intervals, and obtains a temperature change rate K at each minute time, a first circuit 31 and a circuit 31.
Of the pulse width modulation signals having different pulse width modulation tilt characteristics depending on the increase or decrease of the temperature change rate K indicated by the signal from
A second circuit 32 for selecting one of the two, and when the detection output 26a from the water temperature sensor 26 indicates a predetermined high temperature value or more, the flow control valve 2
And a circuit 33 for forcibly switching the second circuit 32 to a signal having a maximum tilt characteristic as a pulse width modulation signal to be given to the third circuit. Here, the second circuit 32 stores, for example, a plurality of ramp waveform data corresponding to the magnitude of the tilt characteristic in a waveform memory, and selectively reads out these data to obtain the modulation tilt of the pulse width modulation signal 25a. Characteristics can be selected.

The cooling fan rotation speed control device of this embodiment is configured as described above, and its operation will be described next with reference to the flowchart shown in FIG. 4 and 5 to be referred to.
4 is a characteristic diagram for explaining a control pattern, and FIG. 5 is an explanatory diagram for explaining a temperature change rate.

In the flowchart shown in FIG. 3, the control pattern is determined by switching the temperature at which the cooling fan 12 rotates at the maximum speed. Generally, when controlling the fan rotation speed in proportion to the water temperature, the maximum rotation speed is when the water temperature reaches a high temperature. Therefore, the maximum rotation speed is not reached even though the water temperature is low. Therefore, in this embodiment, a control pattern is created such that the rotation speed is maximized even when the water temperature is low. That is, the temperature at which the fan rotation speed is maximized is virtually determined, and the control characteristic (control pattern) is set according to the temperature.

According to the method of creating the control pattern, two methods can be considered for the high temperature side and the low temperature side of the virtual temperature range. In this embodiment, the low water temperature side is set to a fixed value _TL , and the high water temperature side temperature T _H is variable. By changing the set value _TH to various values, the modulation tilt characteristics of the pulse width modulation signal 25a are changed. Pulse width modulation signal 25a
In the configuration using the waveform memory, the set value _TH is a read address of the memory.

Now, when the starter switch is turned on by step 100, in step 101, T _H is tentatively set to a predetermined register in the ECU 25. In this temporary set step, T _H
= Set to T _MID . As shown in FIG. 4, T _MID is substantially equal to the high water temperature set value T _MIN in the control pattern 27 in which the tilt characteristic is the maximum and the high water temperature side set value T _{MAX in} the control pattern 29 having the minimum tilt characteristic. It has an intermediate temperature value.
Therefore, the control pattern set when starting the engine is:
As shown in FIG. 28, the tilt characteristic is a characteristic having a substantially intermediate magnitude. The vertical axis in FIG. 4 represents the fan rotational speed N _F, the horizontal axis represents the temperature T _W.

Next, at step 102, the detection output 2 from the water temperature sensor 26
This is a process of reading 6a by the first circuit 31. Further, the first circuit 31 proceeds to step 103, where the minute time Δt
The output 26a of the water temperature sensor 26 after two seconds is read as current water temperature information.

After step 103, in step 104, for example, 100 degrees Celsius
In the third circuit 33, the alarm temperature T _K set in ゜ and the current water temperature T _W2 read in step 103 are compared. The third circuit 33, when the T _W2 is larger than T _K (NO), executes the step 105, the second circuit 32, the modulation tilt characteristic, the inclination of the fan rotational speed N _F for temperature T _W Pulse width modulation signal 25a exhibiting a control pattern 27 in which
Is sent out. The pulse width modulation signal 25a controls the flow control valve 23 so that the bypass conduit 24 is completely closed in a very short time, for example, in order to rotate the cooling fan 12 at the lowest water temperature. Otherwise, there is a risk of overheating.

Thus, the first circuit 31 performs the step 106 calculates the following equation by dividing the difference between T _W2 read in T _W1 and step 103 read at step 102 at Delta] t, obtaining the temperature change rate K .

Such temperature change rate K is the temperature characteristics shown in FIG. 6 corresponds to the derivative of the temperature characteristic at time t _A neighborhood.

After the step 106, the steps 107 to 117 correspond to the second circuit 3
This is the process performed in 2.

The temperature change value K calculated in step 106 is
The step 107 and 108, the absolute value | K | is a positive value K _1, K
Compared to ₂ . K ₁ and K ₂ have a relationship of K ₁ <K ₂ . Step 107 | K | ≧ K ₁ it is determined whether the true made, step 10
8 | K | <K ₂ determines whether true becomes.

FIG. 5 is a diagram schematically illustrating the range of | K | corresponding to the branches of the determination steps 107 and 108. NO in step 107
In the case of (1), K is in the range of -K ₁ <K <K ₁ shown by Q in FIG. This means that the temperature change rate K is extremely small and the control pattern of T _H = T _MID is continued.

YES and in step 107, if NO in step 108, in the range of _{K <-K 2, K 2 <} K shown by R, in this case, the performance of step 110 → 111 or step 110 → 112 Thereafter, the process proceeds to step 109. Step 110 → 111 or step 110 → 112 is, | K | because is excessive, suppress K to K ₂ or -K _2, the tilt difference to the next control tilt characteristic from the current control tilt characteristics (degree of change) is to some extent I try not to grow. As a result, the play of the control can be suppressed, and the stability can be obtained.

By the way, in the case of YES at step 108 (or at steps 112 and 11
(After 1 is suppressed to ± K ₂ ), that is, K is in the range P of K ₁ ≦ | K | ≦ K ₂ , and then step 109 is executed.
Step 109 is a process to replace the T _H provisionally set in step 101, the _{T H1 = T H -K · C} ...... comprising calculating a go T _H1. C is a constant and is determined by the heat load characteristics of each vehicle and the like. From the above equation, the high water temperature set value T _H1 for creating a control pattern other than the control patterns 27, 28 and 29 is obtained.

After step 109, step 113 is performed.
The tilt characteristics of the control pattern created in
It is determined whether or not it is true that the tilt characteristic is larger than the tilt characteristic.
In the case of NO in step 113, by executing step 117, the pattern 29 having the smallest tilt characteristic is selected as the control pattern to be set in the flow control valve 23. Y at step 113
In the case of ES, the process proceeds to step 114, and it is determined whether or not it is true that the tilt characteristic of the control pattern created in step 109 is smaller than the tilt characteristic of the control pattern 27. Steps
If NO in step 114, execute step 116 to
As the control pattern to be set to 13, the pattern 27 having the largest tilt characteristic is selected. Also, if YES in step 114, it selects a control pattern having a high temperature side set value T _H1 generated in step 109 (step 115).

Now, if K is K ₁ is greater than positive, when the determination in step 114 is YES, thereby newly set monkey T _H1,
Is smaller than the previous set value T _H, the tilt characteristic is greater control pattern is selected. That is, when the heat load increases and the water temperature rises, control is performed to change in the direction A from the T _MID pattern, and the rise in the water temperature is dealt with. Note that the control direction in the new control pattern is a direction in which the fan rotation speed is increased.

In the case K is negative large in absolute value than -K _1, when the determination is YES in step 114, thereby newly set monkey T _H1 is larger than the previous set value T _H, the tilt characteristic A smaller control pattern is selected. In other words, when the heat load decreases and the water temperature decreases, control is performed to shift in the B direction from the T _MID pattern, and control appropriate to the decrease in the water temperature is performed. In this case, the control with the new control pattern works in the direction of decreasing the fan rotation speed.

After selecting the control pattern, go to step 10
Jump to 2 and enter a new control cycle. step 1
The same is true for 05.

According to such a flowchart, when the instantaneous water temperature change becomes equal to or more than a certain value, it is possible to perform control such that the fan rotation speed varies depending on the water temperature change rate even at the same water temperature.

For example, when entering an uphill in a mountain road section, K suddenly shows a large positive value, and the degree of change in which the control tilt characteristic is changed increases in proportion to the value of K, and the heat load increases sharply. The control pattern changes immediately in response to the increasing uphill. Such a control pattern acts in a direction in which the bypass conduit 24 is closed by a pattern in which the pulse duty changes with the characteristic 27 when viewed in terms of the modulation tilt characteristic of the loose width modulation signal 25a of the embodiment, so that the cooling fan 12
Reaches the maximum rotation speed at low water temperature and exhibits sufficient cooling performance. On a downhill, K suddenly shows a large negative value. In this case as well, the degree of change in the next control tilt characteristic is large, and a response suitable for a descending slope is obtained, and since the polarity is negative, the tilt characteristic is small and the pulse duty takes a pattern in which the pulse duty changes gradually. A control pattern based on the water temperature drop characteristic shown in FIG. 6 is exhibited. That is, the control pattern is a standby control pattern for the next general traveling section.

Further, in the general traveling section, since the change in the temperature change rate K is small, the switching operation of the small control pattern having a small change degree to the next control tilt characteristic is performed, and the cooling fan is switched.
There is no need to increase or decrease the rotation speed of the 12 in vain. Therefore, the rotation speed of the fan is reduced, so that the fuel consumption can be improved and the quietness can be improved by reducing the power loss.

As another example, as the setting method of the control pattern, instead of switching the high temperature side set value T _H, also be T _H switches the fixed lower temperature side set value T _L, to create a control pattern be able to.

In addition, the rotation driving means of the cooling fan is not limited to the hydraulic motor, but may be a method in which the fan is directly driven by an electric coater.

Further, although the function of the control pattern in the embodiment is shown as a linear function, a secondary, tertiary or other special function may be used.

(Effect of the Invention) As described above, according to the present invention, it is possible to reduce the fan rotation loss power by precisely selecting a control pattern in a general traveling section, and to select a control pattern in a mountain road section. The transition width is large, and the cooling performance is not impaired under an operating condition in which the thermal load varies greatly.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of a cooling fan rotation speed control device for an internal combustion engine according to the present invention, FIG. 2 is a block diagram showing a circuit configuration of an ECU used in the configuration of FIG. 1, and FIG. Is a flowchart illustrating an example of the operation of the present invention, FIG. 4 is a characteristic diagram illustrating a control pattern selection operation, FIG. 5 is a schematic diagram for setting a determination range of a temperature change rate, and FIG. FIG. 3 is a characteristic diagram showing temperature characteristics. 10 internal combustion engine, 11 radiator, 12 cooling fan, 14, 15 cooling water pipe, 16 water pump, 17 hydraulic motor, 23 flow control valve, 24 bypass Conduit, 25 ... ECU, 26 ... Water temperature sensor, 31 ... First
Circuit, 32... Second circuit, 33... Third circuit, 25a.
... Pulse width modulation signal.

Claims (1)

(57) [Claims] The cooling water of an internal combustion engine is circulated between the internal combustion engine and a heat exchanger, and the cooling temperature of the internal combustion engine is controlled by a cooling fan whose rotation speed is controlled by a predetermined driving means. In the fan rotation speed control device, a water temperature sensor for detecting a temperature of cooling water of the internal combustion engine; first means for inputting an output from the water temperature sensor at predetermined time intervals to obtain a temperature change rate; Means for changing the control tilt characteristic of the rotational speed in accordance with the control tilt characteristic, and setting the changed control tilt characteristic in the drive means. A second means for increasing the degree of change to the tilt characteristic. A cooling fan rotation speed control device for an internal combustion engine, comprising: