JPH06207513A - Method of electronically controlling engine fan and analog electronic fan control circuit - Google Patents

Abstract

PURPOSE: To effectively control a cooling fan by receiving threshold temperature signals from coolant temperature signals and invalid signals showing if the vehicle speed is slower than a predetermined speed, and controlling on-off of a vehicle fan clutch based on the speed signals and the engine load signals. CONSTITUTION: A control circuit 10 has a thermistor 12, a load sensor 14, and a vehicle-to-road speed sensor 16. Temperature detectors 18, 20 receiving coolant temperature signals of the thermistor 12 respectively generate signals showing if the speed over a predetermined speed, a temperature detector 22 generates invalid signals showing if action of the thermistor 22 is correct, and a switch 24 generates invalid signals while the vehicle-to-road is slower than the determined speed. These signals are input into a judgment comparator 26, and vehicle fan clutch 28 and cooling fan 30 are turned on or turned off corresponding to the coolant temperature, the vehicle-to-road speed and the engine load conditions. By this manner, the cooling fan is effectively controlled.

Description

Detailed Description of the Invention

Cross Reference of Related Applications
Ongoing US patent application filed March 26, 992
It is a continuation-in-part application of 857,900, both applications being owned by the same person.

[0002]

FIELD OF THE INVENTION This invention relates generally to the operation of cooling fans in motor vehicles, and more particularly to methods and electronic circuits for controlling the operation of engine fans.

[0003]

2. Description of the Related Art Conventional motor vehicles are generally provided with an engine cooling system which circulates a liquid coolant around an engine block for heat exchange so as to remove heat from the engine during operation. The cooling system generally includes a radiator to dissipate the heat absorbed by the liquid coolant. Many automobiles are also equipped with air conditioning systems that include condensers using Freon gas that also act to dissipate heat. To facilitate the distribution of heat from the vehicle engine cooling and air conditioning systems,
Vehicles are commonly equipped with fans to force air through the radiator and condenser at low speeds such that the air flow through the radiator and condenser is minimized. The fan can be connected to a fan clutch that responds separately to either engine coolant temperature or the pressure of freon gas in the condenser.

However, such a design can cause various problems during operation. For example, only if the engine temperature or condenser pressure exceeds a given set point,
Fans are generally connected. The fan is then disconnected and the engine temperature or condenser pressure rises to the point of reconnecting the fan. During low speed operation of the vehicle,
Especially during idling, not only frequent failures of temperature and freon pressure switches, but also excessive periodic movement of the fan mechanism occurs. The problem of such excessive cyclic operation is generally exacerbated during operation of the air conditioning system if either engine temperature or condenser pressure may connect cooling fans separately.

Not only the failure of the temperature or pressure sensor,
A switch failure can result in the engine or air conditioning system overheating in a short period of time. If the fan mechanism operates excessively periodically, the life of the fan mechanism may be shortened, the fuel efficiency of the entire engine may be deteriorated, and system troubleshooting may become more difficult. Inadequate cooling can secondarily result in unreliable system components. Finally, conventional engine fans lacked the controlled responsiveness to the cooling conditions of other vehicle systems including transmission oils, power steering oils, and especially air-to-air intercoolers.

To date, various systems have been proposed to address some of these problems. One such system is disclosed in US Pat. No. 4,425,766 to Claypole. The Clay Paul patent is for a vehicle cooling fan with a microprocessor-based electronic control unit for controlling the engine fan in response to engine temperature, engine speed, road vehicle speed and on / off states of the air conditioning system. A power management system is disclosed. The length of the low voltage signal sent to the engine cooling fan is varied via the pulse width modulator as needed to cool the engine. This voltage signal can be directly actuated to drive the engine cooling fan at a variable speed.

However, the Claypole patent does not solve the problem of overheating associated with temperature or pressure switch and detector failures. Also, the Clay Paul patent does not address the control of cooling conditions for other vehicle systems including transmission oils, power steering oils and air-to-air intercoolers. Moreover, the use of a microprocessor increases the cost of the system and the lack of additional logic circuits limits the number of input signals for controlling fan operation based on other vehicle operating systems. The use of a microprocessor also increases the electromagnetic emissions of the system, thus increasing the likelihood of interfering with other electronic vehicle systems.

In addition, the Claypole patented system discloses an engine fan that is driven directly by a voltage signal from a pulse width modulator. As a result, the Clay pole system can only operate in small vehicles, such as passenger cars, that do not use engine cooling fans that require significant horsepower. In a large automobile having an engine cooling fan that requires a large horsepower, for example, a large truck, when the engine cooling fan is operated by the clay pole system, the efficiency of the engine is significantly reduced. Finally, such a pulse width modulation system is neither suitable for efficient control of engine fan clutches,
Nor is it intended for this.

US Pat. No. 4,546,742 to Sturges discloses a temperature control system for an internal combustion engine having a variable speed cooling fan. The Starges system utilizes a pulse width modulated voltage signal generator to alternately open and close solenoid valves, thus actuating a cooling fan to control the fluid pressure level. However, as a result of this, the Stargues system is not adapted to or targeted at the efficient control of engine fan clutches.

British Patent Application No. 2,142,445A discloses a vehicle cooling fan drive control system utilizing an electronic control unit for controlling engine fan clutch and fan operation in response to engine coolant temperature, engine speed and engine load. Is disclosed. This system utilizes digital logic circuitry that connects the engine fan when the coolant temperature exceeds a predetermined high temperature and disconnects the engine fan when the cooling temperature drops below a predetermined low temperature. When the coolant temperature is between the predetermined high temperature and the predetermined low temperature, the engine fan is controlled only in response to the engine speed and the engine load.

US Pat. No. 4, assigned to Bier,
No. 804,139 is used to control engine fan operation.
A cooling system for a water-cooled engine utilizing one engine coolant temperature sensor and a reactive device responsive to temperature sensor failure is disclosed. However, this beer system is a microprocessor-based system, and the use of this microprocessor causes problems such as increased cost, limited input signals, and increased radiation of electromagnetic waves.

US Pat. No. 4, assigned to Ide et al.,
No. 930,320 discloses a cooling fan control device for an automobile equipped with an air conditioner. The IDE patent uses a digital electronic control unit responsive to the vehicle air conditioning system to control the operation of the engine fan. Nova (No
U.S. Pat. No. 4,651,922 and Japanese Patent No. 58-39513 to Ba) disclose engine fan control systems utilizing two cooling fans to increase cooling capacity. U.S. Pat. No. 4,848,100 issued to Barthel et al. Discloses a system for controlling the flow of refrigerant in an air conditioning system.

The above-mentioned conventional device provides a general background for controlling an engine cooling fan. These devices have various problems such as lack of universal responsiveness to a large number of vehicle systems requiring cooling, lack of compatibility with various automobile cooling systems, and complicated parts. .

Accordingly, it is an object of the present invention to provide a method for efficiently controlling a vehicle engine in response to various vehicle systems requiring cooling and an electronic controller for implementing the method. It is in.

Another object of the present invention is that the structure is simple,
Easy to manufacture, manufactured from traditional parts, easy to maintain, durable, easy to troubleshoot, compatible with direct drive or clutch driven engine cooling fan, no cooling required A method and apparatus for efficiently controlling a vehicle engine cooling fan in response to a variety of vehicle systems.

Yet another object of the present invention is to efficiently control a vehicle engine cooling fan in response to various vehicle systems requiring cooling that extend the life of the fan mechanism and improve engine fuel economy. To provide a method and an apparatus therefor.

Yet another object of the present invention is to provide a vehicle engine cooling fan in response to various vehicle systems requiring cooling which improves the reliability of both the vehicle system requiring cooling and the control system itself. It is to provide a method and an apparatus for controlling efficiently.

Yet another object of the present invention is to efficiently control a vehicle engine cooling fan in response to various vehicle systems that require cooling having a defeat mechanism that operates in the event of a component failure. A method and apparatus are provided.

[0019]

To achieve the above objects, the electronic control circuit of the present invention is generally comprised of components that operate as follows.

Heat detection means is provided for detecting the temperature of the engine coolant and generating a coolant temperature signal proportional to this temperature. Threshold temperature signal generating means is used to receive the coolant temperature signal and generate a threshold temperature signal indicating whether the coolant temperature has exceeded a predetermined temperature.

Further, a road speed detecting means for detecting the road speed of the vehicle and a load detecting means for detecting the operation of a predetermined vehicle operating system are provided. As described in more detail herein, the speed detecting means generates a speed signal proportional to the road speed of the vehicle, and similarly the load detecting means generates a load signal corresponding to the detected load on the engine. To do.

In addition, an invalidation signal is received which receives the speed signal and the load signal and which indicates whether the speed of the vehicle on the road is slower than the predetermined speed when the predetermined vehicle operating system is connected. Signal generating means is also provided. In addition, it receives a threshold temperature signal and an invalid signal to generate a control signal that operates to connect and disconnect the vehicle fan clutch or cooling fan in response to a predetermined temperature, vehicle road speed and engine load conditions. Control signal generating means is also provided.

The following detailed description of the best mode for carrying out the present invention will be read with reference to the accompanying drawings,
The above and other objects, features and advantages of the present invention will be readily apparent.

[0024]

【Example】

BEST MODE FOR CARRYING OUT THE INVENTION Electronic Fan Control Circuit Next, referring to FIG. The control circuit of the present invention is shown in the block diagram and is generally designated by the numeral 10.
This circuit includes a thermistor 12, a load sensor 14, and an on-road vehicle speed sensor 16.

The thermistor 12 is a heat detecting means for detecting the temperature of the coolant of the engine and generating a coolant temperature signal proportional to this temperature. Although the thermistor 12 is of conventional design, it preferably has a negative temperature coefficient with a resistance value that gradually decreases as the engine coolant temperature increases. However, it should be noted that, of course, other types of thermistors 12 known to those skilled in the art could easily be substituted.

The load sensor 14 has a conventional design and serves as a load detecting means for detecting the operation of a predetermined vehicle operating system which applies a combined load to the engine.
For example, in the case of an air conditioning system, sensor 14 is used to detect the operation of this air conditioning system and generate a load signal when the air conditioning system is connected. Applicants have found that load sensor 14 not only detects the presence of engine load,
It is recognized that it can also be used to generate a measurement signal proportional to the combined load on the engine.

The vehicle speed sensor 16 is a speed detecting means for detecting the speed of the vehicle with respect to the road and generating a speed signal proportional to this speed. The road speed sensor 16 is a conventional variable reluctance sensor, but is preferably provided at the rear of the vehicle's transmission system.

Still referring to FIG. 1, the electronic control circuit 10 of the present invention is shown to include a first temperature detector 18. The temperature detector 18 receives the coolant temperature signal of the thermistor 12 and produces a first temperature signal for indicating whether or not the coolant temperature exceeds a _first predetermined temperature T _1. It is a means of generation. The temperature T ₁ may be any temperature as long as it is a predetermined temperature determined by the vehicle and engine specifications. As shown in FIG. 2, this first temperature detector 18 is preferably a comparator of known design, for example a conventional operational amplifier.

Still referring to FIG. The electronic fan control circuit 10 of the present invention further includes a second temperature detector 20.
The temperature detector 20 receives a coolant temperature signal from the thermistor 12 and produces a second temperature signal for generating a second temperature signal indicating whether the engine coolant temperature exceeds a _second predetermined temperature T _2. It is a means of generation. As shown in FIG. 2, this second temperature detector 20 is also preferably a comparator of known design, for example a conventional operational amplifier.

In operation, Applicants have found that T ₂ is preferably higher than T ₁ . However, it has been found that this temperature T ₂ can be a temperature that depends on the particular vehicle and its associated engine. In practice, it is the object of measurement, and depending on the parameters to be responded, only one threshold type temperature detector needs to be used to generate the input signal to the circuit.

Referring again to FIG. 1, the electronic fan control circuit 10 of the present invention further comprises an optional malfunction detector 22. The detector 22 constitutes a first invalid signal generating means for receiving the coolant temperature signal of the thermistor 12 and generating a first invalid signal indicating whether the thermistor 12 is operating properly. As the malfunction of the thermistor 12, the thermistor is short-circuited,
Or there is an operational failure in either the open state. As shown in FIG. 2, the malfunction detector 22 is also a conventional operational amplifier type.

The electronic fan control circuit 10 also includes a programmable frequency-voltage switch 24. This switch 2
Reference numeral 4 constitutes a second invalid signal generating means for receiving a load signal and a speed signal from the load sensor 14 and the vehicle speed sensor 16, respectively, and generating a second invalid signal under a specific condition. For example, when used to detect the connected air conditioning system, the switch 24 generates a second override signal when the air conditioning system is connected and the vehicle speed to the road becomes slower than the predetermined speed V. Of course, the speed V can vary depending on the particular vehicle and the associated engine. However, the vehicle speed V is equal to or higher than the minimum speed at which the airflow passing through the condenser caused by the movement of the vehicle is sufficient to cool the required condenser without separately cooling the engine fan of the vehicle. There must be.

Programmable frequency-voltage switch 2
For 4, any number of conventional circuits known to those skilled in the art can be used. As shown in FIG. 2, in the present invention, LM29
It uses a circuit chip labeled 07. It will be appreciated that the programmable frequency switch 24 can also be set to generate another or alternative override signal under various other air conditioning load and vehicle speed operating conditions. This programmable frequency switch 24
Can be replaced by a conventional timing mechanism 25 known to those skilled in the art that stores the above or another engine load and road vehicle speed operating conditions.

Still referring to FIG. The electronic fan control circuit 10 of the present invention also includes a discrimination comparator 26. This discriminating comparator 26 not only provides the first invalid signal from the detector 22 and the second invalid signal from the programmable frequency switch 24, but also the temperature detectors 18 and 2.
It constitutes a control signal generating means for also receiving the first and second temperature signals from 0. The determination comparator 26 is responsive to a predetermined engine coolant temperature, road vehicle speed and engine load conditions to generate a control signal that operates to connect and disconnect the vehicle fan clutch 28 and the cooling fan 30. It is a control signal generating means. Any number of conventional comparators known to those skilled in the art, such as conventional operational amplifiers, can be used for the discrimination comparator 26. As shown in FIG.
The present invention uses a circuit chip labeled LM2902.

Circuit Operation The operation of the electronic fan control circuit 10 of the present invention will now be described with reference generally to FIGS. 1-4 and particularly with reference to FIG.

First, in the preferred embodiment of the present invention, the fan clutch 28 and fan 30 are automatically engaged to allow air to pass through the vehicle condenser and radiator, regardless of other operating conditions. It is recognized that there are two independent null conditions.

Referring to FIG. 5, when the thermistor 12 malfunctions and produces a coolant temperature signal indicating a condition on the malfunction detector 22, there is always a first invalid condition. In this situation, the engine cooling system must operate without the benefit of temperature information feedback and cannot determine whether the engine coolant temperature is within normal operating parameters. In order to eliminate the possibility that the engine will overheat, the malfunction detector 22 generates a first invalid signal to the discrimination comparator 26. The discriminator comparator 26 then generates a control signal which operates to engage the fan clutch 28 and fan 30 until the thermistor 12 is enabled to operate properly or is replaced.

(1) When the load sensor detects that the air conditioning system is connected and a load signal indicating this state is generated at the programmable frequency switch 24, and (2) the vehicle speed is slower than the predetermined speed V. Whenever the vehicle speed sensor 16 detects that a speed signal has been generated by the sensor on the programmable frequency switch 24 indicating this condition, a second invalid condition exists. As mentioned above, the predetermined speed V is the road speed, below which the air flow through the condenser caused by the movement of the vehicle is insufficient to provide the necessary cooling capacity for the condenser. In such a situation, programmable frequency switch 24 produces a second invalid signal to discrimination comparator 26. The discrimination comparator 26 generates a control signal that operates to connect the fan clutch 28 and the fan 35 until the air conditioning system is turned off or the roadway speed becomes higher than the predetermined speed V.

It should be appreciated that the invalid conditions are detected separately from each other and are responded to separately. Therefore, in explaining the operation of the other components of the present invention, it is assumed that none of the above invalid conditions exist. Also, when the coolant temperature is higher than the predetermined temperature T ₁ and T _2, 2 which are used respectively to generate the respective temperature signal
The operation of the circuit will be described with reference to two temperature detectors. T ₁ is also used as a reference point where T ₁ <T ₂ .

When the thermistor 12 generates a coolant temperature signal indicating that the engine coolant temperature has exceeded the first predetermined temperature T ₁ , the first temperature detector 18 receives the coolant temperature signal received by the discrimination comparator 26. To generate a first temperature signal corresponding to Similarly, when the thermistor 12 generates a coolant temperature signal indicating that the engine coolant temperature has exceeded the second predetermined temperature T ₂ , the second temperature detector 20 outputs a second temperature signal corresponding to this signal. The generated second temperature signal is received by the discrimination comparator 26. Importantly, since there are two coolant temperature inputs, the discrimination comparator 26 generates a control signal after the comparator has probed both temperature detectors 18 and 20 and received and analyzed the corresponding temperature signals. Just do. Therefore, the control circuit of the present invention is a continuous input circuit that continuously monitors a specific temperature, road speed and load condition.

Therefore, during operation, the discrimination comparator 26
Generates a control signal that operates to maintain the engagement of the fan clutch 28 and the fan 30 when the detected engine coolant temperature rises above T ₂ . However, when the detected engine coolant temperature becomes lower than T ₁ , the discrimination comparator 2
6 generates a control signal for operating the fan clutch 28 and the fan 30 until the engine coolant temperature becomes higher than T ₂ . FIG. 4 shows a more detailed logic sequence of the control circuit of the present invention.

As mentioned above, the control circuit 10 of the present invention.
Is a continuous probe, an analog circuit. Such a design has a number of inherent advantages over control circuits based on digital technology. One such advantage is that the control circuit 10 of the present invention can accept an infinite number of input signals from various vehicle operating systems. In contrast, similar digital control circuits always require a separate microprocessor unit to accept the input signals of the additional vehicle operating system. In addition, digital control circuits typically emit high levels of electromagnetic waves that can interfere with the operation of other electronic based vehicle systems. The analog nature of the control circuit of the present invention reduces the amount of electromagnetic radiation from the circuit, thus reducing interference with the operation of other electronic vehicle systems.

Parts Next, refer to FIG. A detailed view of the electronic fan control circuit 10 of the present invention is shown in this figure. as mentioned above,
Both temperature detectors 18 and 20 and malfunction detector 22 are shown as conventional op amp type. Further, the programmable frequency switch 24 and the discrimination comparator 26 are respectively provided in the circuit chip LM29.
It is shown as a conventional comparator in the form of a standard op amp labeled 07 and LM2902. Figure 2
Is a frequency switch 24 with programmable electrical components necessary to prevent excessive engagement and disengagement, or hunting, of fan clutch 28 at a selected vehicle speed for a given speed V with a hysteresis of about 5 mph. It shows with. FIG. 2 further shows a power amplifier 2 for amplifying the power of the control signal generated by the discrimination comparator 26 as well as the voltage regulator 17 for regulating the vehicle battery voltage to a constant DC 8V.
7 is also shown.

Logic Sequence of Control Circuit Next, refer to FIG. 3 and FIG. These figures show
Electronic fan control with logical sequence table summarizing motion
A simplified diagram of the circuit is shown. Shown in FIGS. 3 and 4
So that the operational amplifier (ie temperature detector 18 and
20 and malfunction detector 22) at each common output point
The voltage has the reference symbol E_kIs displayed. Discrimination comparator
The base reference voltage and output voltage of the
Like, E _fAnd E₀Is displayed.

As mentioned above, it is assumed that this logic sequence does not have either the malfunctioning thermistor 12 or the two null conditions associated with the presence of the air conditioning load at low speed. In the first scenario shown in FIG. 4, the temperature of the engine coolant is lower than the first predetermined temperature T ₁ .
This temperature is the temperature of the base reference point described above.

Under these conditions, both the first temperature detector 18 and the second temperature detector 20 generate an "off" signal (ie 0 volts). Therefore, the voltage at E _k is 0 volts. With a 47 kilohm series resistor divider, the reference voltage E _f will be about 4 volts (ie 5.3 volts). When E _k is lower than E _f , the discrimination comparator 26 generates an ON signal, and the output voltage E _o becomes 8 volts. Since the electronic fan control device 10 is designed to be inverted, the ON signal generated by the discrimination comparator corresponds to the disengaged state between the fan clutch 28 and the fan 30.

As the temperature of the engine coolant increases to a value between the first predetermined temperature T ₁ and the second predetermined temperature T ₂ , the first temperature detector 18 will turn on the ON signal (ie 8
Volt) while the second temperature detector 20 continues to generate an off signal (ie 0 volt). Therefore E _k
The voltage at is raised to 4 volts by a 100 kilohm series connected voltage divider resistor. E _k is the reference voltage E
_Since it is still lower than _f, the output voltage E of the discrimination comparator is
_o remains at 8 volts and the fan clutch 28 and fan 30 remain disengaged.

When the temperature of the engine coolant exceeds the second predetermined temperature T ₂ , both the first temperature detector 18 and the second temperature detector 20 generate an ON signal (that is, 8 volts). The voltage at E _k is 8 volts due to the 100 kOhm series connected voltage divider resistors. E
_{When k} exceeds E _f , the output voltage E _o is converted to 0 volt according to the function of the discrimination comparator 26. Therefore, the fan clutch 28 and the fan 30 are connected. Further E
The voltage at _f is reduced to about 2 volts (or 2.7 volts) by a 47k ohm series connected voltage divider resistor.

When the temperature of the engine coolant drops to a value between the first predetermined temperature T ₁ and the second predetermined temperature T ₂ , the second temperature detector 20 produces an off signal (ie 0 volt). Meanwhile, the first temperature detector 18 continues to generate an ON signal (ie 8 volts). Therefore, the voltage at E _k returns to 4 volts. As E _k continues to exceed E _f , the output voltage E _o remains at 0 volts and the fan clutch 28 and fan 30 remain engaged.

Finally, the temperature of the engine coolant is the first
Predetermined temperature T₁Lower than the first temperature detector 1
8 and the second temperature detector 20 both have an off signal (ie,
0 volt) is generated. As a result, E_kVoltage at
Drops to 0 volts. E _kIs E_fWhen lower than
The output voltage E_oFollows the function of the discrimination comparator 26.
Converted to 8 volts, fan clutch 28 and fan
Separated from 30. Furthermore, E_fThe voltage at is 47
Approximately 4 volts with a voltage-dividing resistor connected in series of kilo ohms
Up to 5 volts (ie 5.3 volts) and based on state
Return to the reference point state.

FIG. 3 also shows the programmable frequency switch 24 in a simplified state. The programmable frequency switch 24 is isolated from the voltage E _{k at the} common output point by a conventional diode 32. When the programmable frequency switch 24 produces a second invalid signal, the diode 32 is free to pass this signal to the common output. However, when the programmable frequency switch 24 does not generate the second invalid signal, the diode 32 disables the electrical connection between the programmable frequency switch 24 and the common output point.

Still referring to FIG. The generic detector 34 is also shown in this figure. This global detector 34
It constitutes third invalid signal generating means for generating a third invalid signal in response to other vehicle systems 35 that may require cooling capacity, such as transmission oil, power steering oil or air-to-air intercoolers. . As will be appreciated, any number of global detectors 34 needed to handle any of the various vehicle systems 35 that may require cooling capacity can be incorporated. This global detector 34 produces a third invalidation signal whenever the temperature of the corresponding vehicle operating system exceeds a _third predetermined temperature T ₃ . The generic detector 34 is of the conventional op amp type, and like the programmable frequency switch 24, the generic detector 34 is also isolated from the common output point by a conventional diode 32.

In the preceding description of the electronic control circuit 10, its operation, components and logic sequence of the present invention, the circuit 10 has been described in connection with the fan clutch 28 and fan 30. It should be noted that the fan clutch 28 may be either magnetic driven or air driven. In either configuration, the control signal generated by the circuit 10 of the present invention is operable to energize the solenoid.
In the case of an air driven clutch, the solenoid actuates a valve (not shown) to release the pressurized air needed to actuate the fan clutch 28. In the magnetic clutch, the solenoid directly operates the fan clutch 28. In either configuration, the fan clutch 28 is the fan 30.
Is driven to drive at a constant speed.

It is clear that the control circuit 10 of the present invention can also directly drive the fan 30 without using the fan clutch 28. In such a configuration, the fan can be controlled electrically or hydraulically. When using an electric fan, the control signal generated by the circuit 10 is the fan 3
It can only act to directly force 0. In the case of a hydraulic fan, the control signal generated by the circuit 10 energizes a solenoid valve (not shown) to release the fluid required to operate the hydraulic fan motor to drive the fan 30. Further, in any configuration, the fan 30 is driven at a constant speed.

While the best mode for carrying out the invention has been described in detail above, those skilled in the art will be able to conceive of alternative designs and embodiments for carrying out the claimed invention. I can do it.

[Brief description of drawings]

FIG. 1 is a simplified logic diagram of the operation of the electronic control circuit of the present invention.

FIG. 2 is a detailed diagram of an electronic control circuit of the present invention.

FIG. 3 is a simplified diagram of an electronic control circuit of the present invention.

FIG. 4 is a logic sequence diagram of the electronic control circuit of the present invention.

FIG. 5 is a block diagram showing the steps of the method of the present invention.

[Explanation of symbols]

 10 Fan Control Circuit 14 Load Sensor 18, 20 Temperature Detector 22 Malfunction Eliminator 24 Programmable Frequency Switch 26 Discrimination Comparator 28 Fan Clutch 30 Cooling Fan

Claims (20)

[Claims] 1. A heat detecting means for detecting a temperature of the coolant and generating a coolant temperature signal proportional to the temperature in an automobile having an engine, a coolant system and a fan, and the heat detecting means. It is electrically connected and receives the coolant temperature signal, and when the coolant temperature exceeds the specified temperature,
The threshold temperature signal generating means for generating the threshold temperature signal, the speed detecting means for detecting the on-road vehicle speed and generating a speed signal proportional to this speed, and the existence of a predetermined engine load A load detecting unit for detecting and generating a load signal corresponding to the load detecting unit and the load detecting unit and the speed detecting unit are electrically connected to each other. And an invalid signal generating means for generating an invalid signal when a predetermined engine load is present later than the threshold temperature signal generating means and the invalid means generating means. A signal and an input signal, including the null signal, to distinguish between them and to respond to at least one of the input signals to obtain the required error. An analog electronic fan control circuit comprising: a control signal generating means for generating a control signal operable to connect and drive the fan at a constant speed to achieve cooling of the engine. 2. The fan is electrically driven.
The described control circuit. 3. The control circuit according to claim 1, wherein the fan is driven by fluid pressure. 4. The control circuit according to claim 1, wherein the load detecting means includes a sensor of an air conditioning system. 5. The control circuit according to claim 1, wherein the heat detecting means includes a thermistor. 6. The control circuit according to claim 1, wherein the speed detecting means includes a variable reluctance type road speed sensor. 7. The control circuit according to claim 1, wherein said invalid signal generating means comprises a programmable frequency switch. 8. The control circuit according to claim 1, wherein the control signal generating means includes a discrimination comparator. 9. The control circuit according to claim 1, wherein said threshold signal generating means comprises an operational amplifier. 10. A voltage for electrically converting the input voltage into 8 V DC, which is electrically connected to the heat detecting means, the threshold temperature signal generating means, the invalid signal generating means, and the control signal generating means. The controller is electrically connected to the control signal generating means, detects the temperature of a predetermined vehicle operating system, and when the temperature of the predetermined system exceeds a second predetermined temperature, the control signal generating means. 2. The control circuit of claim 1, further comprising second heat detection means for generating a second invalid signal received by. 11. The control circuit according to claim 10, wherein the second heat detecting means includes a temperature detector of a power steering fluid. 12. The control circuit according to claim 10, wherein the second heat detecting means includes a temperature detector for a transmission fluid. 13. The control circuit according to claim 10, wherein the second heat detecting means comprises an air-to-air intercooler temperature detector. 14. A third invalid signal generating means which is electrically connected to the control signal generating means, receives the coolant temperature signal, and generates a third invalid signal when the heat detecting means malfunctions. The control circuit according to claim 10, further comprising: 15. A heavy load indicating vehicle having an engine, a coolant system, an air conditioning system, a fan and a fan clutch, and heat detecting means for detecting the temperature of the coolant and generating a coolant temperature signal proportional to the temperature. First temperature signal generating means for electrically connecting with the heat detecting means, receiving a coolant temperature signal, and generating a first temperature signal when the coolant temperature exceeds a first predetermined temperature, Second temperature signal generating means electrically connected to the heat detecting means, receiving a coolant temperature signal, and generating a second temperature signal when the coolant temperature exceeds a second predetermined temperature. A speed detecting means for detecting a vehicle speed to the road and generating a speed signal proportional to the speed, and an operation of the air conditioning system to detect a corresponding load. Load detecting means for generating a signal, and for receiving a coolant temperature signal electrically connected to the heat detecting means and generating a first invalid signal when the heat detecting means malfunctions. The first invalid signal generating means is electrically connected to the speed detecting means and the load detecting means, receives the speed signal and the load signal, the vehicle speed is lower than a predetermined speed, and the air conditioning system is connected. Second invalid signal generating means for generating a second invalid signal when the first temperature signal generating means and the first and second temperature signal generating means and the first
And an input signal including the first and second temperature signals and the first and second invalid signals, which are electrically connected to the second invalid signal generating means and are distinguished from each other. Analog electronic fan control circuit for generating a control signal responsive to at least one of them to operate and drive the fan at a constant speed to achieve the required engine cooling. . 16. The control circuit of claim 15, wherein the fan clutch is air driven. 17. The control circuit according to claim 15, wherein the fan clutch is of a magnetic type. 18. An input voltage which is electrically connected to said heat detecting means, said first and second temperature signal generating means, said first and second invalid signal generating means and said control signal generating means. Is electrically connected to the control signal generating means and a voltage regulator for converting DC into 8 V, and detects the temperature of a predetermined operating system, and the temperature of the predetermined system is determined to be a third predetermined value. 16. The control circuit of claim 15, further comprising second heat detection means for generating a third invalid signal received by the control signal generation means when the temperature is exceeded. 19. A method for electronically controlling an engine fan in a heavy duty vehicle having an engine, an engine coolant system, an air conditioning system and a fan, the method comprising: detecting a temperature of the engine coolant; Generates a coolant temperature signal proportional to the first coolant temperature signal and compares the coolant temperature signal with a first predetermined temperature. When the coolant temperature exceeds the first predetermined temperature,
A temperature signal is generated, the coolant temperature signal is compared with a second predetermined temperature, and when the coolant temperature exceeds the second predetermined temperature,
A second temperature signal is generated, a speed of the vehicle with respect to a road is detected, a speed signal proportional to the vehicle speed is generated, it is detected whether the air conditioning system is connected, and a load of the air conditioning system on the engine. Generating a load signal corresponding to, comparing the speed signal with a predetermined speed, when the vehicle speed is slower than the predetermined speed, and the air conditioning system is operating, generates an invalid signal, A control signal generating means is provided for receiving and comparing the input signals including the first and second temperature signals and said invalid signal, and the fan is connected to keep the fan running at a constant speed to achieve the required engine cooling. A method for electronically controlling an engine fan comprising the steps of generating a control signal operable to drive in response to at least one of the input signals. 20. A temperature of a predetermined vehicle operating system is detected, the temperature of the predetermined operating system is compared with a third predetermined temperature, and when the temperature of the operating system exceeds the third predetermined temperature, 20. The method of claim 19, further comprising the step of generating a second invalid signal received by said control signal generating means.