JP2004052645A - Analog control circuit for driving fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an analog control circuit for driving a fan, easy in troubleshooting and maintenance, and efficiently cooling the liquid with a simple constitution by continuously rotating the fan by using an inexpensive analog circuit. <P>SOLUTION: This analog control circuit for driving the fan comprises a DC power source, a temperature sensor detecting a temperature of a liquid to be cooled by the fan, and outputting a temperature signal in proportion to the temperature, a temperature determining circuit receiving the temperature signal and outputting a first command current corresponding to the temperature, a differential amplification circuit for amplifying the first command current and outputting the same as a second command current, a drive circuit receiving the second command current and the DC current and outputting the drive command current to an electromagnetic proportional valve, and the electromagnetic proportional valve receiving the drive command current and controlling a rotating speed of the fan. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fan drive analog control circuit, and more particularly to a fan drive analog control circuit that cools liquid by continuously and continuously rotating the fan.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a vehicle driven by an engine, cooling air is sent by rotating a fan to cool the engine and cool lubricating oil. There are two types of fan rotation: a type in which the belt is driven by the engine, and a type in which the fan is rotated by an electric motor or a hydraulic motor independent of the engine.
In the type in which the fan is driven by the electric motor or the hydraulic motor, the temperature of the cooling water or the lubricating oil of the engine is measured, and the electric motor or the hydraulic motor is turned on / off according to the temperature, or the rotational speed is gradually increased. The engine cooling water or lubricating oil is controlled so as to fall within an appropriate range. In this control, the temperature of engine cooling water or lubricating oil is detected by a thermistor thermometer, and the temperature set by the analog circuit is compared with the measured temperature. When the set temperature is reached, the electric motor or hydraulic motor is used. Is turned ON-OFF or stepwise changed as shown in FIG.
In recent years, the temperature of engine cooling water or lubricating oil detected by a thermistor thermometer is sent to the controller, and the controller changes the rotation of the electric motor or hydraulic motor in a stepless manner, and the temperature of the engine cooling water or lubricating oil is adjusted appropriately. It is controlled so that it falls within the proper range. In this control, the rotation of the electric motor or the hydraulic motor is continuously changed by a command from a controller using a digital circuit.
[0003]
[Problems to be solved by the invention]
However, in the above-described analog circuit, when the rotation speed of the electric motor or the hydraulic motor reaches a set temperature, it changes stepwise, so that a loud noise is generated at a change point (points Ya and Yb shown in FIG. 6). The problem of noisy arises. In addition, since the rotation speed of the electric motor or the hydraulic motor is changed stepwise, there is a problem that efficiency is not good.
Compared with the analog circuit, a digital circuit such as a digital controller using a microprocessor has a higher cost. Also, the complexity of the circuit makes troubleshooting and maintenance difficult.
[0004]
The present invention has been made in view of the above problems, and relates to an analog control circuit for driving a fan. In particular, it is easy to troubleshoot and maintain, and continuously rotates a fan using an inexpensive analog circuit. It is another object of the present invention to provide an analog control circuit for driving a fan that efficiently cools a liquid with a simple configuration.
[0005]
Means for Solving the Problems, Functions and Effects
In order to achieve the above object, in the invention of the analog control circuit for driving a fan according to the present invention, the temperature of the liquid is formed by an analog circuit, the temperature of the liquid is detected by a temperature sensor, and the fan is continuously operated continuously in accordance with the temperature signal. Then, the liquid is rotated and cooled, and the temperature of the liquid is controlled to fall within a predetermined range.
[0006]
In this case, the fan drive analog control circuit includes a DC power supply, a temperature sensor that detects a temperature of the liquid cooled by the fan, and outputs a temperature signal proportional to the temperature, and receives the temperature signal, A temperature determination circuit that outputs a first command current corresponding to the above, a differential amplifier circuit that amplifies the first command current and outputs the same as a second command current, It is preferable to include a drive circuit that outputs a drive command current and an electromagnetic proportional valve that receives the drive command current and controls the rotation speed of the fan.
[0007]
Also, a feedback circuit that detects a drive command current output to the electromagnetic proportional valve and outputs a feedback current to a differential amplifier circuit, adds and subtracts the first command current and the feedback current, and multiplies the gain to output a second command current. It is preferable that a differential amplifier circuit is provided.
It is preferable to provide an overcurrent protection circuit between the DC power supply and the drive circuit.
Further, it is preferable to provide a dither circuit that dithers the first command current output from the temperature determination circuit.
[0008]
According to the above configuration, the fan drive analog control circuit detects the temperature of the liquid cooled by the fan with the temperature sensor, and outputs a temperature signal proportional to this temperature to the temperature determination circuit of the analog control main unit. . In the temperature determination circuit, the temperature detection amplifier obtains the drive command current by comparing the temperature of the liquid with the set low temperature and high temperature based on the input temperature signal. The drive command current is output to the electromagnetic proportional valve via the dither circuit, the differential amplifier circuit and the drive circuit of the analog control main body.
[0009]
The electromagnetic proportional valve operates upon receiving a drive command current from the analog control main body, and sends the pressure oil of the hydraulic pump to the flow control valve, and returns it to the tank while adjusting the flow using the flow control valve. When the temperature of the liquid is lower than the low temperature, the solenoid proportional valve increases the flow returning to the tank, reduces the pressure oil supplied from the hydraulic pump to the hydraulic motor, and reduces the rotation speed of the cooling fan to the lower limit fan rotation speed Is adjusted as follows.
Conversely, when the temperature of the liquid exceeds the high temperature, the flow rate returned to the tank is reduced, the pressure oil supplied from the hydraulic pump to the hydraulic motor is increased, and the rotation speed of the cooling fan is set to the upper limit fan rotation speed. Has been adjusted.
[0010]
When the temperature of the liquid is equal to or higher than the low temperature and equal to or lower than the high temperature, the flow rate returned to the tank is adjusted according to the temperature of the liquid, and the pressure oil supplied from the hydraulic pump to the hydraulic motor is variable according to the temperature of the liquid. The rotation speed of the fan changes continuously and continuously between the upper limit fan rotation speed and the lower limit fan rotation speed.
As a result, the fan drive analog control circuit continuously changes and rotates the fan in a stepless manner, so that noise such as abnormal noise generated at the time of conventional switching does not occur, and the fan rotates quietly. The efficiency is improved because it continuously changes in a stepless manner. In addition, since the analog control main body is formed by an analog circuit, troubleshooting and maintenance are facilitated, heat resistance is high, and the apparatus can be simplified and inexpensive.
[0011]
The analog control main unit is provided with a feedback circuit, detects the load current flowing through the electromagnetic proportional valve, returns the feedback current to the differential amplifier circuit, adds and subtracts the drive command current with the differential amplifier circuit, and multiplies the gain by the gain. Output to the drive circuit to operate the solenoid proportional valve.
As a result, an accurate current is supplied from the drive circuit to the proportional solenoid valve, so that accurate pressure oil is supplied from the proportional solenoid valve to the flow regulating valve, and the fan is rotated at an accurate rotational speed according to the temperature of the liquid. And the required cooling air can be sent.
[0012]
Since the analog control main unit has an overcurrent protection circuit between the DC power supply and the drive circuit, overcurrent is not supplied to the drive circuit, and the drive circuit and the solenoid proportional valve are reliably protected. No failure.
Further, the analog control main unit is provided with a dither circuit, dithers the first command current output from the temperature determination circuit, and outputs the first command current to the electromagnetic proportional valve as a drive command current. And the dither amplitude, the solenoid is finely moved even at the neutral point, so that it operates reliably in accordance with the drive command current. Accordingly, the electromagnetic proportional valve can be reliably operated even when the flow rate is high or the oil temperature is high, and a circuit suitable for a large flow rate can be formed.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of a fan drive analog control circuit according to the present invention will be described with reference to the drawings.
First, a fan driving analog control circuit according to an embodiment will be described with reference to FIGS. FIG. 1 is a circuit diagram of a fan drive analog control circuit, FIG. 2 is a circuit diagram of a fan drive analog control main body, FIG. 3 is a diagram illustrating the relationship between liquid temperature, fan rotation speed, and drive command current, and FIG. FIG. 5 is a diagram illustrating an example of calibrating a value to an output target value, and FIG. 5 is a diagram illustrating an example of switching by comparing a triangular wave with a command current.
[0014]
FIG. 1 is a diagram showing an example of a fan drive analog control circuit 1. The fan drive analog control circuit 1 mainly includes a temperature sensor 3, an analog control main body 5, a cooling fan 7, an engine 11, a hydraulic pump 12 , A hydraulic motor 13 and a flow rate adjusting unit 15.
The fan drive analog control circuit 1 outputs the temperature T of the cooling water detected by the temperature sensor 3 to the analog control main body 5 as a temperature signal Te, and the analog control main body 5 responds to the cooling fan temperature T according to the cooling water temperature T. 7 is continuously rotated in a stepless manner so that the temperature T of the cooling water is controlled to fall within a predetermined range (between the liquid temperature Tr and Th in FIG. 3). This rotation control is performed as follows. I have.
[0015]
A hydraulic pump 12 driven by the engine 11 discharges hydraulic oil to a hydraulic motor 13 and rotates a cooling fan 7 connected to the hydraulic motor 13. The hydraulic motor 13 rotates at a rotation speed according to the flow rate, when the pressure oil discharged from the hydraulic pump 12 is adjusted by the flow rate adjusting unit 15.
The flow control unit 15 is formed by the throttle 17, the flow control valve 18, the electromagnetic proportional valve 19, and the analog control main unit 5, and controls the flow. A throttle 17 is disposed between the hydraulic pump 12 and the hydraulic motor 13, and the throttle 17 throttles the hydraulic oil of the hydraulic pump 12 to generate different pilot pressures on the upstream side and the downstream side. It is supplied to the regulating valve 18.
[0016]
The flow control valve 18 is disposed in a first pipe 21 branched upstream of the throttle 17, and has one end receiving the upstream pilot pressure of the throttle 17 and the other end thereof receiving the downstream pilot pressure and the electromagnetic proportional valve 19. In response to the pressure oil, the spool (not shown) moves and returns the pressure oil of the hydraulic pump 12 to the tank 22.
The electromagnetic proportional valve 19 is disposed in a second pipe 23 branched from between the hydraulic pump 12 and the throttle 17, operates according to the drive command current If of the analog control main unit 5, and controls the hydraulic oil from the hydraulic pump 12. Is supplied to the flow control valve 18 and returned to the tank 22 while adjusting the discharge amount of the hydraulic pump 12 by the flow control valve 18.
[0017]
For example, when the drive command current If of the analog control main unit 5 is small, the electromagnetic proportional valve 19 reduces the opening degree and sends low-pressure hydraulic oil to the flow control valve 18, and the electromagnetic pressure from the flow control valve 18 to the tank 22 is reduced. The rotation speed of the hydraulic motor 13 is increased by reducing the return amount. At this time, when the temperature T of the cooling water is higher than the high temperature Th in FIG. 3, the fan rotation speed is kept at the upper limit fan rotation speed Nh.
Conversely, when the drive command current If of the analog control main unit 5 is large, the electromagnetic proportional valve 19 increases the opening degree and sends high-pressure hydraulic oil to the flow control valve 18, and the electromagnetic pressure is supplied from the flow control valve 18 to the tank 22. The rotation amount of the hydraulic motor 13 is reduced by increasing the return amount. At this time, when the temperature T of the cooling water is lower than the low temperature Tr in FIG. 3, the fan rotation speed is kept at the lower limit fan rotation speed Nr.
[0018]
When the temperature T of the cooling water is between the high temperature Th and the low temperature Tr in FIG. 3, the fan rotation speed is between the upper limit fan rotation speed Nh and the lower limit fan rotation speed Nr, It changes continuously and continuously according to the rotation.
As described above, the discharge amount of the hydraulic pump 12 is supplied to the hydraulic motor 13 after being made to have a variable flow rate by the flow control valve 18 so that the rotation speed of the hydraulic motor 13 is variable, and the cooling fan 7 connected thereto is stepless. To make a continuous variable rotation speed.
[0019]
The cooling fan 7 driven by the hydraulic motor 13 supplies cooling air to the radiator 25 to cool the cooling water flowing inside. The rotation speed of the cooling fan 7 is continuously variable according to the temperature T of the cooling water flowing inside the radiator 25 so that the temperature T of the cooling water falls within a predetermined temperature range.
The cooling water of the radiator 25 is measured by the temperature sensor 3, and the measured temperature T is output to the analog control main unit 5 as a temperature signal Te. The temperature sensor 3 outputs a current that changes in accordance with the level of the measured temperature T, and the temperature sensor 3 is preferably a thermistor thermometer whose resistance decreases as the temperature T of the cooling water increases.
[0020]
The analog control main unit 5 outputs a drive command current If according to the temperature T of the cooling water to the electromagnetic proportional valve 19, reduces the pressure oil from the hydraulic pump 12 and sends it to the flow regulating valve 18, 12 is adjusted by the flow control valve 18 and returned to the tank 22.
Thus, the analog control main unit 5 variably rotates the cooling fan 7 in a stepless manner according to the temperature T of the cooling water, and controls the temperature of the cooling water to fall within a predetermined range.
[0021]
The analog control main unit 5 is formed as follows. The analog control main unit 5 mainly includes a temperature determination circuit 31, a dither circuit 33, a differential amplifier circuit 35, a drive circuit 37, an overcurrent protection circuit 39, an abnormal voltage protection circuit 41, and a feedback circuit 43.
The temperature determination circuit 31 is formed by a temperature detection amplifier 46 and a temperature comparator 47. The temperature detection amplifier 46 compares the low temperature Tr set in response to the temperature signal Te of the cooling water from the temperature sensor 3 with the high temperature Th set higher than the low temperature Tr, and compares the first command current Iq. Output to the temperature comparator 47.
[0022]
At this time, the temperature detection amplifier 46 outputs the first command low current Iqr if the temperature signal Te of the temperature sensor 3 is lower than the set low temperature Tr, and if the temperature signal Te exceeds the set high temperature Th. Outputs the first command high current Iqh. Further, when the temperature signal Te is between the set low temperature Tr and the high temperature Th, a variable first command current Iq corresponding to the cooling water temperature signal Te is output.
The temperature comparator 47 calibrates the input voltage from the temperature sensor 3 and outputs a correction command current Iqm. In the temperature comparator 47, as shown in FIG. 2, the first command current Iq is corrected by the W signal, for example, by performing current output characteristic offset adjustment and current output characteristic gain adjustment as shown by a dotted line to a solid line in FIG. Calibrated to Iqm.
[0023]
The dither circuit 33 includes a dither generation circuit 49 and a dither adder 50. The dither generation circuit 49 generates a dither waveform in which the dither frequency and the dither amplitude are adjusted, and outputs the generated dither waveform to the dither adder 50. The dither adder 50 adds the correction command current Iqm from the temperature comparator 47 to the dither waveform from the dither generation circuit 49 and outputs the result.
The differential amplifier circuit 35 adds and subtracts the feedback current from the feedback circuit 43 to the correction command current Iqm from the dither adder 50 by the differential amplifier 35a, and multiplies by a gain K (Vo = K (Vr-Vf)). The signal is amplified and output as the second command current In to the drive circuit 37.
[0024]
The drive circuit 37 is formed by a triangular wave generator 51, a drive comparator 52, and a drive current output circuit 53. The triangular wave generator 51 generates, for example, a triangular wave having a predetermined shape as shown by a solid line (Y) shown in FIG.
The drive comparator 52 performs switching by comparing the triangular wave from the triangular wave generator 51 with the second command current In (Z) from the differential amplifier circuit 35, and outputs the switching to the drive current output circuit 53. The drive current output circuit 53 adjusts the current from the DC power supply DC to the drive command current If by the second command current In from the drive comparator 52 and outputs the drive command current If to the electromagnetic proportional valve 19.
[0025]
The overcurrent protection circuit 39 is formed by an overcurrent detection resistor 57 and an overcurrent prevention circuit 58. The overcurrent detection resistor 57 detects a direct current flowing from the DC power supply DC into the drive current output circuit 53. In the case of an overcurrent, the overcurrent prevention circuit 58 prevents the current from flowing to the electromagnetic proportional valve 19.
The abnormal voltage protection circuit 41 protects the circuit by preventing an abnormal voltage from entering the overcurrent protection circuit 39 from the DC power supply DC.
The feedback circuit 43 is formed by a current detection resistor 55 and a current detection amplifier 56. The current detection resistor 55 detects a load current flowing through the electromagnetic proportional valve 19, outputs the load current to the current detection amplifier 56, amplifies the current with the current detection amplifier 56, and returns the amplified current to the differential amplifier 35a as a feedback current.
[0026]
Next, the operation of the fan drive analog control circuit 1 will be described. The cooling water flowing inside the radiator 25 is measured by the temperature sensor 3, and the measured temperature T is input to the temperature determination circuit 31 of the analog control main unit 5 as a temperature signal Te.
The temperature determination circuit 31 compares the temperature T of the cooling water with the temperature detection amplifier 46 based on the input temperature signal Te and detects the temperature T. When the temperature is lower than the low temperature Tr, the low drive command current Ifr is changed to the state shown in FIG. As shown, the cooling fan 7 is output to the electromagnetic proportional valve 19 via the dither circuit 33, the differential amplifier circuit 35, and the drive circuit 37 so as to rotate at the lower limit rotation speed Nr.
[0027]
When the temperature signal Te exceeds the high temperature Th, the dither circuit 33, the differential amplifier circuit 35, and the drive circuit cause the high drive command current Ifh to rotate the cooling fan 7 at the upper limit rotation speed Nh as shown in FIG. The signal is output to the electromagnetic proportional valve 19 via 37.
When the temperature signal Te is between the low temperature Tr and the high temperature Th, as shown in FIG. 3, the low drive command current Ifr and the high drive speed are set so that the cooling fan 7 rotates at a rotation speed corresponding to the temperature. A variable drive command current If is output to the electromagnetic proportional valve 19 with respect to the command current Ifh. As a result, the cooling fan 7 continuously changes and rotates between the low temperature Tr and the high temperature Th in a stepless manner and sends cooling air to the radiator 25 so that the cooling water enters a required temperature range. I have.
[0028]
In the dither circuit 33, a dither frequency and a dither amplitude are given to the drive command current If, and a solenoid 19a (shown in FIG. 1) of the electromagnetic proportional valve 19 and a spool (not shown) of the electromagnetic proportional valve 19 connected to the solenoid are neutralized. It is also slightly moving at the point, so that it operates reliably according to the command current.
Accordingly, the electromagnetic proportional valve 19 can be reliably operated even when the flow rate increases, and a circuit suitable for a large flow rate can be formed.
[0029]
The differential amplifier circuit 35 and the feedback circuit 43 detect the load current flowing through the electromagnetic proportional valve 19 by the feedback circuit 43 and return it to the differential amplifier circuit 35 as a feedback current. The addition / subtraction and multiplication by the gain are output to the drive circuit 37 to operate the electromagnetic proportional valve 19.
As a result, an accurate current is supplied from the drive circuit 37 to the electromagnetic proportional valve 19, so that accurate pressure oil is supplied from the electromagnetic proportional valve 19 to the flow regulating valve 18. Therefore, the flow regulating valve 18 can accurately return the pressure oil of the hydraulic pump 12 to the tank 22, and the hydraulic motor 13 receiving the pressure oil of the hydraulic pump 12 rotates the cooling fan 7 accurately according to the temperature T of the cooling water. It can rotate at a speed and can send required cooling air to the radiator 25.
[0030]
Further, since the fan drive analog control circuit 1 is provided with the abnormal voltage protection circuit 41 and the overcurrent protection circuit 39, the drive current output circuit 53 is not supplied with an abnormal voltage and an overcurrent. The current output circuit 53 and the proportional solenoid valve 19 are securely protected, so that no failure occurs.
[0031]
As described below, the analog control main unit 5 outputs to the electromagnetic proportional valve 19 a drive command current If that continuously rotates in a stepless manner and that is adapted to the temperature of the cooling water measured by the temperature sensor 3.
The electromagnetic proportional valve 19 is actuated by receiving a drive command current If from the analog control main unit 5 to supply the pressure oil from the hydraulic pump 12 to the flow control valve 18 and to adjust the discharge amount of the hydraulic pump 12 to the flow control valve 18. The tank is returned to the tank 22 while being adjusted.
For example, when the temperature T of the cooling water is lower than the low temperature Tr, the electromagnetic proportional valve 19 increases the flow returning from the flow regulating valve 18 to the tank 22 and reduces the pressure oil supplied from the hydraulic pump 12 to the hydraulic motor 13. Then, the rotation speed of the cooling fan 7 is adjusted to be the lower limit fan rotation speed Nr.
[0032]
Conversely, when the temperature T of the cooling water exceeds the high temperature Th, the flow returning from the flow regulating valve 18 to the tank 22 is reduced, and the pressure oil supplied from the hydraulic pump 12 to the hydraulic motor 13 is increased to increase the cooling fan. 7 is adjusted to be the upper limit fan rotation speed Nh.
When the temperature T of the cooling water is equal to or higher than the low temperature Tr and equal to or lower than the high temperature Th, the flow returning from the flow control valve 18 to the tank 22 is adjusted in accordance with the temperature T of the cooling water, and the hydraulic pump 12 The pressure oil supplied to 13 is also adjusted according to the temperature T of the cooling water, and the rotation speed of the cooling fan 7 is steplessly changed between the upper limit fan rotation speed Nh and the lower limit fan rotation speed Nr as shown by a curve Rv in FIG. Is adjusted to rotate continuously. This change in the curve Rv may be a straight line.
[0033]
As described above, the cooling fan 7 is configured such that the electromagnetic proportional valve 19 receives the analog signal from the analog control main unit 5, adjusts the discharge amount of the hydraulic pump 12 by the flow control valve 18, and supplies it to the hydraulic motor 13. Is continuously and continuously rotated as the rotation speed is continuously changed. Thus, since the cooling fan 7 continuously rotates in a stepless manner, noise such as abnormal noise generated at the time of conventional switching is not generated, and the efficiency is improved.
[0034]
In the above-described embodiment, the cooling water of the engine is described to be in a predetermined temperature range. However, liquid such as lubricating oil or hydraulic oil may be controlled to be in a predetermined temperature range.
The discharge amount of the hydraulic pump 12 is supplied to the hydraulic motor 13 after being adjusted to a variable flow rate by the flow control valve 18, and the rotation speed of the hydraulic motor 13 is variable. However, the swash plate is controlled by the electromagnetic valve to change the discharge volume. A variable displacement hydraulic pump or a variable displacement hydraulic motor may be used.
The temperature detection amplifier calculates the drive command current by comparing the liquid temperature with the set low temperature and high temperature from the input temperature signal, but the temperature detection amplifier drives the temperature signal from the temperature sensor The current is output to the solenoid valve, and the solenoid valve rotates the fan at the upper limit fan speed and the lower limit fan speed, and continuously and continuously changes between the upper limit fan speed and the lower limit fan speed. You may do it.
[Brief description of the drawings]
FIG. 1 is a fan drive analog control circuit diagram according to the present invention.
FIG. 2 is a circuit diagram of a fan drive analog control main unit according to the present invention.
FIG. 3 is a diagram illustrating a relationship between a liquid temperature, a fan rotation speed, and a drive command current.
FIG. 4 is a diagram illustrating an example of calibrating an input value to an output target value.
FIG. 5 is a diagram illustrating an example in which switching is performed by comparing a triangular wave with a command current.
FIG. 6 is a diagram illustrating a conventional relationship between liquid temperature and fan rotation speed.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Analog control circuit for fan drive, 3 ... Temperature sensor, 5 ... Analog control main unit, 7 ... Cooling fan, 11 ... Engine, 12 ... Hydraulic pump, 13 ... Hydraulic motor, 15 ... Flow rate adjusting unit, 17 ... Throttle, 18: Flow control valve, 19: Electromagnetic proportional valve, 22: Tank, 25: Radiator, 31: Temperature determination circuit, 33: Dither circuit, 35: Differential amplifier circuit, 37: Drive circuit, 39: Overcurrent protection circuit, 41: abnormal voltage protection circuit, 43: feedback circuit, 46: temperature detection amplifier, 47: temperature comparator, 49: dither generation circuit, 50: dither adder, 51: triangular wave generator, 51: drive comparator, 53 ... Drive current output circuit, 55 ... Current detection resistor, 56 ... Current detection amplifier, 57 ... Overcurrent detection resistor, 58 ... Overcurrent prevention circuit.

Claims (5)

Forming an analog circuit, detecting the temperature of the liquid with a temperature sensor, cooling the fan by continuously rotating the fan continuously according to the temperature signal, and controlling the temperature of the liquid to be within a predetermined range. An analog control circuit for driving a fan. An analog control circuit for driving a fan,
DC power supply,
A temperature sensor that detects the temperature of the liquid cooled by the fan and outputs a temperature signal proportional to this temperature;
A temperature determination circuit that receives the temperature signal and outputs a first command current corresponding to the temperature;
A differential amplifier circuit for amplifying the first command current and outputting the amplified second command current as a second command current;
A drive circuit that receives a second command current and a DC current and outputs a drive command current to an electromagnetic proportional valve;
An analog control circuit for driving a fan, comprising: an electromagnetic proportional valve that receives a drive command current and controls a rotation speed of the fan. A feedback circuit that detects a drive command current output to the electromagnetic proportional valve and outputs a feedback current to the differential amplifier circuit;
The fan drive analog control circuit according to claim 2, further comprising a differential amplifier circuit that adds and subtracts the first command current and the feedback current, multiplies the gain, and outputs a second command current. 4. The fan drive analog control circuit according to claim 2, wherein an overcurrent protection circuit is provided between the DC power supply and the drive circuit. The fan drive analog control circuit according to any one of claims 2 to 4, further comprising a dither circuit that dithers the first command current output from the temperature determination circuit.

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