JP2000220454A - Cooling fan control device in engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control the rotation of a radiator cooling fan based on the temperature of water in a radiator exit to be detected by a second water temperature sensor even when the second sensor is broken down. SOLUTION: The water temperature TWE in an engine is detected by a first water temperature sensor (S1) and the water temperature TWR at an radiator exit is detected by a second water temperature sensor (S2). The decision is made if the second water temperature sensor has any trouble or not (S3). And when these is no trouble, for each engine driving condition, the temperature difference ΔTW between the water temperature TWE in the engine and the water temperature TWR at the radiator exit is learned and stored (S5-S7). While the rotation of a cooling fan is controlled based on the detected value of the water temperature TWR at the radiator exit (S11). When troubles are detected, the water temperature TWR at the radiator exit is estimated by the water temperature TWE in the engine and the learned value of the temperature difference ΔTW for each engine driving condition (S8-S10). The radiation of the cooling fan is controlled based on the estimated value of the water temperature TWR at the radiator exit (S11).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an engine cooling fan control device.

[0002]

2. Description of the Related Art Conventionally, in an engine cooling fan control device, apart from a first water temperature sensor disposed on a water jacket of the engine and detecting an engine water temperature,
A second sensor disposed in a cooling water passage from the radiator to the engine to detect a radiator outlet water temperature (engine inlet water temperature);
A water temperature sensor is provided, and the rotation of the radiator cooling fan is controlled based on the radiator outlet water temperature detected by the second water temperature sensor so that the radiator outlet water temperature becomes the target temperature.

[0003]

However, in such a conventional cooling fan control device, if the second water temperature sensor for detecting the radiator outlet water temperature fails, the temperature cannot be controlled to the target temperature. Could lead to

[0004] Further, when a failure of the second water temperature sensor for detecting the radiator outlet water temperature is detected, a method of fixing the detected value of the radiator outlet water temperature to a predetermined value is conceivable, but in this case, overheating prevention is given priority. Therefore, the number of rotations of the cooling fan is increased more than necessary, which may cause an increase in fan noise.

The present invention has been made in view of such conventional problems, and provides a cooling fan control device capable of controlling a radiator outlet water temperature to a target temperature even when a second water temperature sensor for detecting a radiator outlet water temperature fails. The purpose is to do.

[0006]

In order to achieve the above object, the present invention (the invention according to claim 1) is configured as shown in FIG.

That is, a second water temperature sensor disposed in a cooling water passage from the radiator to the engine to detect a radiator outlet water temperature, separately from the first water temperature sensor disposed in the water jacket of the engine and detecting the engine water temperature. And a cooling fan control device for an engine including cooling fan rotation control means for controlling rotation of the radiator cooling fan based on the radiator outlet water temperature detected by the second water temperature sensor.

[0008] Here, second water temperature sensor failure detecting means for detecting the presence or absence of a failure in the second water temperature sensor, and when no failure is detected by the failure detecting means, the first water temperature sensor is provided for each engine operating condition. Temperature difference learning means for learning and storing a temperature difference between the detected engine water temperature and the radiator outlet water temperature detected by the second water temperature sensor; and The radiator outlet water temperature estimating means for estimating the radiator outlet water temperature based on the engine water temperature detected by the first water temperature sensor and the temperature difference learning value for each engine operating condition by the learning means, and a failure is detected by the failure detecting means. The radiator outlet water temperature detected by the second water temperature sensor, Based on the radiator outlet water temperature, characterized in that a, a switching means for causing the rotation control of the radiator cooling fan by the cooling fan rotation control means.

In the invention according to a second aspect, the temperature difference learning means learns the temperature difference for each engine operating condition using the engine load and the vehicle speed as parameters of the engine operating conditions. .

The invention according to claim 3 is characterized in that the temperature difference learning means learns an average value of the temperature difference for each engine operating condition. The invention according to claim 4 is characterized in that the temperature difference learning means learns on condition that the engine has been warmed up as a learning condition.

[0011] In the invention according to claim 5, the radiator outlet temperature estimating means includes learning value correcting means for correcting the temperature difference learning value according to an elapsed time after starting, and the corrected temperature difference learning value is calculated. It is characterized by using.

[0012]

According to the first aspect of the present invention, when the second water temperature sensor for detecting the radiator outlet water temperature is normal, the engine water temperature detected by the first water temperature sensor and the second water temperature sensor for each engine operating condition are used. The temperature difference between the detected radiator outlet water temperature and the radiator outlet water temperature are learned and stored, and when the second water temperature sensor fails, the engine water temperature detected by the first water temperature sensor and the temperature difference learning value for each engine operating condition are compared. Accordingly, the radiator outlet water temperature is estimated, and the rotation control of the radiator cooling fan is performed based on the radiator outlet water temperature. Therefore, even when the second water temperature sensor for detecting the radiator outlet water temperature fails, the radiator outlet water temperature can be controlled to the target temperature. Thus, the effect that the fan noise can be suppressed low can be obtained.

According to the second aspect of the present invention, the learning accuracy can be improved by learning the temperature difference for each engine operating condition using the engine load and the vehicle speed as parameters of the engine operating conditions.

According to the third aspect of the present invention, the learning accuracy can be improved by learning the average value of the temperature difference for each engine operating condition. According to the fourth aspect of the present invention, learning is performed under the condition that the engine has been warmed up as a learning condition, so that learning accuracy can be improved.

According to the fifth aspect of the present invention, the temperature difference learning value is corrected according to the elapsed time after the start and used.
Accurate control is possible even immediately after starting.

[0016]

Embodiments of the present invention will be described below. FIG. 2 is a system diagram of an engine cooling system showing one embodiment of the present invention.

A water jacket (not shown) is formed in the engine 1. Cooling water cooled by the cooling fan 3 in the radiator 2 is supplied to a water jacket in the engine 1 through a cooling water passage 4 by a water pump (not shown). Through the cooling water passage 5 on the outlet side,
It returns to the radiator 2.

Here, the cooling fan 3 is driven by an electric motor or a hydraulic motor, and its rotation is controlled by a signal from the control unit 6. Further, a first water temperature sensor 7 disposed on a water jacket of the engine 1 to detect an engine water temperature TWE, and a radiator outlet water temperature (engine inlet water temperature) TWR disposed on a cooling water passage 4 from the radiator 2 to the engine 1. And a second water temperature sensor 8 for detecting the temperature of the control unit 6.
Has been entered.

The control unit 6 also receives an engine load signal from a load sensor, a vehicle speed signal from a vehicle speed sensor, and the like. Here, based on the radiator outlet water temperature TWR detected by the second water temperature sensor 8, the control unit 6 controls the rotation of the radiator cooling fan 3 and detects whether the second water temperature sensor 8 has failed. The learning control and the fail-safe control are performed in response to this.

The control contents of the control unit 6 are shown in the flowchart of FIG. In step 1 (referred to as S1 in the figure, the same applies hereinafter), the engine coolant temperature TWE is detected based on a signal from the first coolant temperature sensor 7.

In step 2, the radiator outlet water temperature TWR is detected based on the signal from the second water temperature sensor 8. In step 3, it is determined whether or not the second water temperature sensor 8 has failed. Specifically, when the output voltage of the second water temperature sensor 8 is out of the predetermined range, it is determined that a failure such as disconnection has occurred. This part corresponds to a second water temperature sensor failure detecting means.

If there is no failure in the second water temperature sensor 8, the process proceeds to step 4. In step 4, it is determined whether or not a learning condition has been reached, specifically, whether or not the engine has been warmed up (the engine water temperature TWE is equal to or greater than a predetermined value or a predetermined time has elapsed since startup).
In the case of the learning condition, steps 5 to 7 are executed.

In step 5, a temperature difference Δ between the engine coolant temperature TWE detected by the first coolant temperature sensor 7 and the radiator outlet coolant temperature TER detected by the second coolant temperature sensor 8.
TW0 = TWE-TWR is calculated.

In step 6, the engine load and the vehicle speed are used as parameters of the engine operating conditions, and a learning map on the backup RAM storing the temperature difference learning value ΔTW for each engine operating condition is referred to. The temperature difference learning value ΔTW corresponding to the condition is read.

In step 7, the temperature difference learning value ΔTW is updated by taking the weighted average of the current temperature difference learning value ΔTW and the current temperature difference ΔTW0, and the data in the backup RAM is rewritten as shown in the following equation. You.

ΔTW = ΔTW × (1−K) + ΔTW0 × K where K is a weighted average weighting constant (0 <K <
1). Here, the steps 5 to 7 correspond to the temperature difference learning means.

Finally, the process proceeds to step 11. Step 1
In step 1, the radiator outlet temperature TWR detected by the second water temperature sensor 8 is compared with the target temperature, and the rotation of the radiator cooling fan 3 is controlled so that TWR = target temperature. That is, when TWR <target temperature, the rotation of the radiator cooling fan 3 is reduced, and when TWR> target temperature, the rotation of the radiator cooling fan 3 is increased.
This part corresponds to the cooling fan rotation control means.

If there is a failure in the second water temperature sensor 8, the process proceeds to step 8. In step 8, the engine load and the vehicle speed are used as parameters of the engine operating conditions, and the learning map on the backup RAM that stores the temperature difference learning value ΔTW is referred to for each engine operating condition to correspond to the current engine operating condition. The temperature difference learning value ΔTW to be read is read.

In step 9, the correction coefficient TRM is set in accordance with the elapsed time after the start by referring to a table in which the correction coefficient TRM is set in advance using the elapsed time after the start as a parameter. Here, the correction coefficient TRM increases from 0 to 1.0 in accordance with the elapsed time after the start, and is set to be 1.0 after the time corresponding to the completion of the warm-up. This is because the temperature difference between the engine water temperature TWE and the radiator outlet water temperature TWR is small immediately after the start.

In step 10, from the engine coolant temperature TWE detected by the first coolant temperature sensor 7,
The radiator outlet water temperature TWR is estimated by subtracting a value obtained by correcting the temperature difference learning value ΔTW by the correction coefficient TRM.

TWR = TWE-(. DELTA.TW.times.TRM) Steps 8 to 10 correspond to the radiator outlet water temperature estimating means. Finally, proceed to Step 11.

In step 11, the estimated radiator outlet temperature TWR is compared with the target temperature, and the rotation of the radiator cooling fan 3 is controlled so that TWR = target temperature. That is, when TWR <target temperature, the rotation of the radiator cooling fan 3 is reduced, and when TWR> target temperature, the rotation of the radiator cooling fan 3 is increased.
This part corresponds to the cooling fan rotation control means.

Here, from step 3 to step 8,
After executing Steps 9 and 10, the part for executing Step 11 is the radiator outlet water temperature T detected by the second water temperature sensor 7.
Instead of WR, it corresponds to switching means for controlling the rotation of the radiator cooling fan 3 by the cooling fan rotation control means based on the radiator outlet water temperature TWR estimated by the estimation means.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a configuration of the present invention.

FIG. 2 is a system diagram of an engine cooling system showing one embodiment of the present invention.

FIG. 3 is a flowchart of cooling fan rotation control.

[Explanation of symbols]

 Reference Signs List 1 engine 2 radiator 3 cooling fan 4, 5 cooling water passage 6 control unit 7 first water temperature sensor (for detecting engine water temperature) 8 second water temperature sensor (for detecting radiator outlet water temperature)

Claims (5)

[Claims] 1. A second water temperature sensor disposed in a cooling water passage from a radiator to an engine to detect a radiator outlet water temperature, separately from a first water temperature sensor disposed in a water jacket of the engine and detecting an engine water temperature. And a cooling fan control device for controlling the rotation of the radiator cooling fan based on the radiator outlet water temperature detected by the second water temperature sensor. A second water temperature sensor failure detecting means for detecting the presence or absence of an engine water temperature detected by the first water temperature sensor and the second water temperature sensor for each engine operating condition when no failure is detected by the failure detecting means. Temperature difference learning means for learning and storing and retaining the temperature difference between the radiator outlet water temperature and When a fault is detected by the serial fault detection means, the engine coolant temperature detected by the first temperature sensor and,
A radiator outlet water temperature estimating means for estimating a radiator outlet water temperature based on a temperature difference learning value for each engine operating condition by the learning means; and a second water temperature sensor detecting when a failure is detected by the failure detecting means. Switching means for controlling the rotation of the radiator cooling fan by the cooling fan rotation control means based on the radiator outlet water temperature estimated by the estimation means, instead of the radiator outlet water temperature. Cooling fan control device. 2. The engine according to claim 1, wherein the temperature difference learning means learns the temperature difference for each engine operating condition using an engine load and a vehicle speed as parameters of the engine operating condition. Cooling fan control device. 3. The engine cooling fan control device according to claim 1, wherein said temperature difference learning means learns an average value of said temperature differences for each engine operating condition. 4. The engine according to claim 1, wherein said temperature difference learning means learns on condition that the engine has been warmed up as a learning condition. Cooling fan control device. 5. The radiator outlet temperature estimating means includes learning value correcting means for correcting the temperature difference learning value according to an elapsed time after starting, and using the corrected temperature difference learning value. An engine cooling fan control device according to claim 4.