JPH07243918A - Water temperature detecting device for controlling air conditioner - Google Patents

Abstract

PURPOSE:To accurately detect the water temperature detection signal for controlling an air conditioner by using a water temperature sensor for displaying the water temperature of the engine cooling water in common even when the DC power voltage has a fluctuation. CONSTITUTION:A water temperature sensor 1 is connected to the output terminal V1 of an on-vehicle battery in series to a water temperature display meter 2. A control circuit 3 detects the terminal voltage VIG from the output terminal V1 and the terminal voltage VB from the water temperature sensor 1. The terminal voltage VIG is divided by voltage dividing resistors 4, 5 to obtain the detection voltage VC. The detection voltage VC is outputted by a correcting circuit 6 as the correction detection voltage VC. When the fluctuation of the terminal voltage VB of the water temperature sensor 1 due to the fluctuation of the terminal voltage VIG becomes the change point voltage VD or above of the characteristic approximated with a polygonal line, the correcting circuit 6 feeds a current via a shunt resistor 8 to obtain the correction detection voltage VC. The detection signal in response to the cooling water temperature is obtained based on the terminal voltage VB of the water temperature sensor 1 and the correction detection voltage VC.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water temperature detecting device for air conditioning control which can accurately detect a temperature signal for air conditioning control by utilizing a terminal voltage of a water temperature sensor connected in series with a water temperature display circuit. Regarding

[0002]

2. Description of the Related Art In a vehicle engine, for example, a water temperature sensor is provided at the outlet of cooling water to detect the temperature of the cooling water. In this case, the water temperature sensor has a structure in which, for example, a coil-type water temperature display meter is connected in series and is connected to the output terminal of the vehicle-mounted battery to display the detected temperature on the driver's seat section. The water temperature sensor has the characteristic that the resistance value changes according to the temperature of the cooling water, and changes the direction and magnitude of the current flowing through the coil bridge that constitutes the water temperature display meter according to the temperature, thereby The shake is changed and displayed. As a result, when the temperature of the cooling water has risen to the temperature of the overheated state, it can be recognized by the large swing of the pointer of the water temperature display meter.

By the way, in an air conditioner for an automobile,
Although the air conditioning operation control is performed using the heat of the engine cooling water, it is necessary to detect this when the engine overheats and stop the air conditioning operation. Therefore, in the past,
A water temperature sensor is separately provided to detect the temperature of the cooling water. In this case, the water temperature sensor is provided with a predetermined voltage for control from a control circuit for air conditioning control through a voltage dividing resistor and the temperature is detected by comparing the output voltage with a reference voltage, or A temperature switch that operates at a predetermined temperature is provided, and an overheat is detected by receiving an operation signal from the temperature switch.

[0004]

However, providing two water temperature sensors in order to detect the temperature of the cooling water of the engine in this way has a difficulty in mounting space, and it is troublesome to mount them. Therefore, there is a problem that the cost increases. Therefore, it is demanded that one water temperature sensor be commonly used for the detection operation. However, it is difficult to have a configuration in which one water temperature sensor is shared, because of the following problems due to the difference in the respective water temperature detection configurations.

That is, the temperature of the engine cooling water is detected by the separate water temperature sensor as described above, whereas the water temperature display by the water temperature display meter may be a relatively rough value display. This is because high detection accuracy is required in water temperature detection for air conditioning control. That is,
The output voltage of a battery as a power source generally fluctuates within a range of, for example, about 11 V to 14 V depending on its use condition, whereas the water temperature sensor is connected via a water temperature display meter, and therefore its terminal Although the voltage will fluctuate according to the fluctuation of the power supply voltage, the characteristic of the water temperature sensor is that the resistance characteristic does not change linearly with the output voltage of the battery due to heat generation of the element itself due to the energized current. is there.

Therefore, in order to obtain an accurate temperature signal for air-conditioning control, it is necessary to correct the terminal voltage generated in the water temperature sensor in response to fluctuations in the output voltage of the battery and use it as the detection signal. There is a circumstance that the resistance characteristic of the water temperature sensor cannot be corrected with a simple configuration because the theoretical elucidation has not been clarified. Therefore, it is difficult to accurately detect the temperature when the water temperature sensor for displaying the water temperature is shared and the overheat state in the air conditioning control is detected from the terminal voltage.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method even when there is a fluctuation in the DC power supply voltage.
An object of the present invention is to provide a water temperature detection device for air conditioning control, which can share a water temperature sensor for displaying the water temperature of engine cooling water and can accurately perform temperature detection for overheat detection during air conditioning control.

[0008]

A water temperature detecting device for air conditioning control according to the present invention includes a water temperature sensor provided so that a resistance value changes according to a temperature of cooling water of an engine, and the cooling according to an applied voltage. A water temperature display circuit for displaying water temperature is connected in series to a DC power supply, and two characteristics of the terminal voltage change of the water temperature sensor are provided corresponding to a change in the terminal voltage of the DC power supply. Correction means for outputting as a correction detection voltage so as to follow the approximated characteristics obtained by the line approximation by the above straight line, and for the air conditioning control based on the terminal voltage of the water temperature sensor and the correction detection voltage from the correction means. It is characterized in that it is configured by being provided with water temperature detecting means for outputting a temperature signal.

A power supply voltage detecting means for detecting the terminal voltage of the DC power supply by dividing the correcting means with a voltage dividing resistor, and a changing point voltage for setting a changing point voltage corresponding to a changing point of the approximate characteristic. When the generation means, the shunt resistance connected to the output terminal of the power supply voltage detection means, and the detection voltage of the power supply voltage detection means exceed the change point voltage, the voltage value obtained via the shunt resistance is changed. It may be configured by a voltage adjusting unit that outputs the correction detection voltage by causing a current to flow through the shunt resistance so as to be held at the point voltage.

Further, the correction means is connected to the power source voltage detecting means for detecting the terminal voltage of the DC power source by dividing the terminal voltage with a plurality of voltage dividing resistors, and is connected in parallel to the voltage dividing resistors at the change point of the approximate characteristic. It is also possible to provide a constant voltage diode in which a breakdown voltage value equal to the corresponding change point voltage is set.

Further, the correction means stores the data of the correction detection voltage set so as to follow the approximate characteristic corresponding to the terminal voltage of the DC power supply, and the terminal voltage of the DC power supply. May be detected and the data corresponding to the detected voltage is read from the storage means and set as the corrected detection voltage.

[0012]

According to the water temperature detecting device for air conditioning control of the first aspect, the correcting means corrects the terminal voltage of the DC power source in accordance with a change in the terminal voltage and outputs it as a corrected detection voltage. The temperature signal for air conditioning control is detected based on the terminal voltage of the sensor and the correction detection voltage. In this case, the correction detection voltage is corrected so as to follow the approximation characteristic obtained by the line approximation of the variation characteristic of the terminal voltage of the water temperature sensor corresponding to the variation of the terminal voltage of the DC power supply with two or more straight lines. This is because the change characteristic of the terminal voltage of the water temperature sensor with respect to the fluctuation of the terminal voltage of the DC power supply generally has a non-linear characteristic.

As a result, even if the terminal voltage of the water temperature sensor fluctuates in response to the fluctuation of the terminal voltage of the DC power source, the voltage value of the difference between the two can be obtained as a voltage signal corresponding to the temperature of the cooling water. Therefore, the temperature of the cooling water can be accurately detected regardless of the fluctuation of the terminal voltage of the DC power supply, and it is used for the water temperature display even in the air conditioning control that requires the detection accuracy of the water temperature. By using the terminal voltage of the water temperature sensor, the temperature of the cooling water can be accurately detected, and the air conditioning control can be performed accurately.

According to the water temperature detecting device for air conditioning control of the second aspect, the voltage adjusting means, when the detected voltage from the power source voltage detecting means exceeds the change point voltage, the voltage value obtained through the shunt resistor. The current flows through the shunt resistor so that the voltage is held at the change point voltage, and the corrected voltage is output as a corrected detection voltage. At this time, the change point voltage is set to a voltage corresponding to a change point when the change characteristic of the terminal voltage of the water temperature sensor with respect to the change of the terminal voltage of the DC power source is approximated to a polygonal line by two or more straight lines. As a result, it is possible to obtain a corrected detection voltage by correcting the terminal voltage of the DC power supply in accordance with the approximate characteristics of the water temperature sensor, and to accurately detect the temperature of the cooling water by comparing it with the terminal voltage of the water temperature sensor. Will be able to.

According to the water temperature detecting device for air conditioning control of the third aspect, when the voltage detected by the power supply voltage detecting means exceeds the change point voltage, the voltage shared by the voltage dividing resistors to which the constant voltage diodes are connected in parallel is changed. When the breakdown voltage value of the constant voltage diode is reached and the terminal voltage of the DC power supply rises higher than that, the voltage detected by the power supply voltage detection means is the voltage value obtained by subtracting the breakdown voltage of the constant voltage diode from the terminal voltage of the DC power supply. Is corrected to the voltage value when the voltage is divided by the remaining voltage dividing resistance. As a result, the corrected detection voltage becomes a voltage output that follows the approximate characteristic when the variation characteristic of the terminal voltage of the water temperature sensor with respect to the fluctuation of the terminal voltage of the DC power source is approximated by a polygonal line with two or more straight lines, and the terminal voltage of the water temperature sensor. By comparing with, it becomes possible to accurately detect the temperature of the cooling water.

According to the water temperature detecting device for air conditioning control of the fourth aspect, the setting means detects the terminal voltage of the DC power source, reads the data corresponding to the terminal voltage from the storage means, and sets the correction detection voltage. . At this time, the correction detection voltage is stored as data to be corrected so as to follow the approximation characteristic when the variation characteristic of the terminal voltage of the water temperature sensor along with the variation of the terminal voltage of the DC power supply is approximated by a polygonal line. Therefore, the temperature of the cooling water can be accurately detected based on the corrected detection voltage and the terminal voltage of the water temperature sensor.

[0017]

The first embodiment of the present invention applied to an automobile will be described below.
An embodiment of the above will be described with reference to FIGS. In FIG. 1 showing the electrical configuration, the water temperature sensor 1 is
For example, the thermistor has a characteristic that its resistance value changes according to the temperature, and is arranged so as to detect the temperature TW of the cooling water of the engine (not shown). The water temperature sensor 1 is connected to an output terminal V1 of an on-vehicle battery as a DC power supply via a coil-type water temperature display meter 2 as a water temperature display circuit, and is supplied with a DC power supply voltage VIG.

The water temperature indicating meter 2 is constructed by combining two coils, a resistor and a Zener diode, and a bridge circuit is formed by connecting the water temperature sensor 1. And the water temperature sensor 1
When the resistance value of the current changes, the magnitude or direction of the current flowing through the Zener diode changes, so that the current flowing through one of the coils changes, and the indicator needle moves to a position corresponding to the temperature TW, thereby changing the water temperature. Is configured to display.

The control circuit 3 controls the terminal voltage V of the water temperature sensor 1.
A circuit that detects the water temperature for air conditioning control based on B, and is configured as follows. The input terminal A is the output terminal V of the battery
1 (terminal voltage VIG), and the input terminal B is connected to a common connection point between the water temperature sensor 1 and the water temperature display meter 2. The input terminal A is grounded via two voltage dividing resistors 4 and 5 in series. An output terminal C, which is a common connection point of the voltage dividing resistors 4 and 5, is connected to a correction circuit 6 as a correction means.

In the correction circuit 6, the inverting input terminal of the operational amplifier 7 as the voltage adjusting means is connected to the output terminal C via the shunt resistor 8 and to the output terminal of the operational amplifier 7 via the diode 9 in the forward direction. It is connected. The change point voltage generation circuit 10 is formed by connecting two resistors 11 and 12 in series, and is connected between the constant voltage output terminal V2 and the ground. The non-inverting input terminal of the operational amplifier 7 is connected to the change point voltage output terminal D which is a common connection point of the resistors 11 and 12, and the change point voltage VD is input. An output obtained by converting the output voltage of the battery into a constant voltage VCC by a constant voltage circuit (not shown) is applied to the constant voltage output terminal V2.

The operational amplifier 7 outputs an "H" level signal when the input voltage Va at the inverting input terminal is lower than the change point voltage VD, and when the input voltage Va at the inverting input terminal becomes equal to the change point voltage VD. When the output is inverted and thereafter the input voltage Va at the inverting input terminal is about to increase, a current is caused to flow through the diode 9 so that the input voltage V
It operates so as to hold a at the change point voltage VD.

An output terminal C, which is a common connection point of the voltage dividing resistors 4 and 5, is connected to a non-inverting input of an operational amplifier 16 as a water temperature detecting means via an input resistor 13, an impedance converting operational amplifier 14, and an input resistor 15. It is connected to the terminal. The output terminal of the operational amplifier 14 is also connected to the inverting input terminal. The input terminal B is grounded via the Zener diode 18 having the polarity shown in the figure through the protection resistor 17, and is also connected to the inverting input terminal of the operational amplifier 16. The non-inverting input terminal of the operational amplifier 16 is grounded via the resistor 19, and the noise absorbing capacitor 2
It is connected to the inverting input terminal through 0 and is also connected to the output terminal of the operational amplifier 16 through the feedback resistor 21 for adding hysteresis.

The output terminal of the operational amplifier 16 is connected to the inverting input terminal of the operational amplifier 22 for waveform shaping. The non-inverting input terminal of the operational amplifier 22 is connected to the constant voltage output terminal VCC via the voltage dividing resistor 23 and is also grounded via the voltage dividing resistor 24. The output terminal of the operational amplifier 22 is connected to the non-inverting input terminal via the feedback resistor 25 and the output terminal P. The operational amplifier 1
Reference numeral 4 is for converting the impedance in order to prevent the detected voltage at the output terminal C from fluctuating due to the effect of hysteresis caused by the feedback resistor 19 connected to the operational amplifier 16.

Next, the operation of this embodiment will be described with reference to FIGS. 2 and 3. First, the electrical characteristics of the water temperature sensor 1 will be described. The water temperature sensor 1 has a negative temperature characteristic that its resistance value decreases as the temperature rises, and is provided so that its resistance value changes according to the temperature TW of the engine cooling water. The water temperature sensor 1 has a characteristic that the terminal voltage VB of the battery fluctuates when the terminal voltage VIG of the battery fluctuates, and is, for example, as shown in FIG. In this case, the terminal voltage VB of the water temperature sensor 1 has a non-linear characteristic with respect to the terminal voltage VIG of the battery.

Therefore, when the terminal voltage VIG of the battery fluctuates, the terminal voltage VB of the water temperature sensor 1 changes non-linearly, so that the voltage value deviates from the voltage value corresponding to the temperature TW of the cooling water. The accurate water temperature TW cannot be detected from the terminal voltage VB of the sensor 1. Therefore, in the present embodiment, the terminal voltage VIG of the battery is detected via the voltage dividing resistor 4, and the detected voltage VC changes, for example, according to the terminal voltage VB of the water temperature sensor 1 depending on the terminal voltage VIG of the battery. Correct so as to follow.
At this time, the characteristic of the terminal voltage VB of the water temperature sensor shown in FIG. 3 is set, for example, as a broken line by two straight lines, as shown by the solid line in FIG.

First, in the changing point voltage generating circuit 10, as the changing point voltage VD at the changing point voltage output terminal D, detection is made corresponding to the intersection point of two straight lines having the characteristics approximate to the broken line, that is, the changing point M of the broken line. It is set to be equal to the voltage VCM. When the detection voltage VC is smaller than the change point voltage VD (VC <VD), the level of the voltage signal input to the inverting input terminal of the operational amplifier 7 via the shunt resistor 8 is smaller than the change point voltage VD. Therefore, since the operational amplifier 7 outputs a signal of "H" level, the current to the side of the shunt resistor 8 is blocked, and the detection voltage VC increases as the terminal voltage VIG of the battery increases. .

When the detected voltage VC becomes equal to the change point voltage VD, the output of the operational amplifier 7 is inverted. When the detected voltage VC becomes larger than the change point voltage VD thereafter, the operational amplifier 7 receives the input voltage of the inverting input terminal. The shunt resistor 8 is connected from the output terminal C so that the level becomes equal to the change point voltage VD.
And a detection voltage VC by passing a current through the diode 9
Will be corrected.

That is, until the detected voltage VC reaches the change point voltage VD, the detected voltage VC is divided by the voltage dividing resistors 4 and 5 as the value of the terminal voltage VIG of the battery rises. The value is output to the output terminal C (value along the straight line p in FIG. 2), and when the detection voltage VC becomes equal to or higher than the change point voltage VD, the detection voltage VC increases with the increase in the value of the terminal voltage VIG. The voltage value divided by the resistors 4 and 5 and the shunt resistor 8 is output to the output terminal C (value along the straight line q in FIG. 2). As a result, the voltage corresponding to the terminal voltage VIG that appears at the detection terminal C is output as the corrected detection voltage VC that follows the characteristic approximated by the broken line.

When the correction detection voltage VC is input to the operational amplifier 14 via the resistor 13, it is output as a voltage signal whose impedance is converted here, and this voltage signal is divided by the resistors 15 and 19 to be operational amplifier 16.
The reference voltage VS is input to the non-inverting input terminal of the. This reference voltage VS is a voltage value obtained by dividing the correction detection voltage VC, as indicated by the straight lines r and s in FIG. 2, and the operational amplifier 1 is used as a reference voltage when water temperature detection is performed.
6 is input. In addition, this reference voltage VS
Is divided by resistors 15 and 19 so as to be set as a reference voltage value corresponding to the temperature at which the temperature TW of the cooling water reaches or exceeds a predetermined temperature to cause overheating.

The terminal voltage VB of the water temperature sensor 1 is input to the inverting input terminal of the operational amplifier 16 via the resistor 17. When the terminal voltage VB exceeds the reference voltage VS, it is output as a low level signal. Become. When the terminal voltage VB shifts from a state higher than the reference voltage VS to a state lower than the reference voltage VS, hysteresis is imparted by the action of the feedback resistor 21.
The output is inverted when B becomes smaller than the reference voltage VS by a predetermined voltage.

The waveform shaping operational amplifier 22 inverts the output of the operational amplifier 16 and outputs it to the output terminal P. As a result, when the terminal voltage VB of the water temperature sensor 1 drops below the reference voltage VS by a certain value or more, a low level signal is output to the output terminal P. That is, the water temperature sensor 1
When the temperature TW of the cooling water detected by the temperature exceeds the temperature of the overheat state, the terminal voltage VB is
That is, it becomes lower than S, and the detection signal is output to the output terminal P. As a result, in the air conditioner, measures such as stopping the air conditioning operation can be properly implemented.

According to this embodiment, the correction circuit 6
Thus, the terminal voltage VIG of the battery is corrected so that the voltage characteristic of the water temperature sensor 1 follows the approximated characteristic obtained by the broken line approximation, and the corrected voltage is output from the output terminal C as the corrected detection voltage VC. Set VS,
Since the comparison is made with the terminal voltage VB of the water temperature sensor 1, the accurate reference voltage VS follows the terminal voltage VB of the water temperature sensor 1 which varies non-linearly with respect to the fluctuation of the terminal voltage VIG of the battery. Therefore, even if the terminal voltage fluctuates like a battery, it is necessary to always accurately detect the temperature TW of the cooling water by using the water temperature sensor 1 used for displaying the water temperature and accurately perform the air conditioning control. Will be able to.

FIG. 4 shows a second embodiment of the present invention. The difference from the first embodiment is that the voltage dividing resistors 4,
In addition to 5, the voltage dividing resistor 26 is connected in series, and at the portion of the voltage dividing resistor 26, instead of the correction circuit 6,
A zener diode 27, which is a constant voltage diode, is connected in parallel with the polarity shown. That is,
The Zener voltage VZ of the Zener diode 27 is set to be a voltage corresponding to the change point voltage VD described above, that is, the terminal voltage VE at the common connection point E between the voltage dividing resistors 5 and 26 becomes the Zener voltage VZ. When it reaches, the terminal voltage VC of the output terminal C is set to reach the change point voltage VD.

According to such a configuration, when the terminal voltage VIG of the battery fluctuates and the detection voltage VC at the detection terminal C becomes equal to or higher than the change point voltage VD, the terminal voltage V of the voltage dividing resistor 26.
Since E reaches the Zener voltage VZ, this voltage dividing resistor 26
Does not rise any further, and thereafter, as the terminal voltage VIG rises, the detection voltage VC becomes a voltage value (= the terminal voltage VIG minus the Zener voltage VZ (=
VIG-VZ) increases as the terminal voltage when the voltage is divided by the voltage dividing resistors 4 and 5.

As a result, as in the first embodiment,
Corrected detection voltage V that follows the approximate characteristics when the detection voltage VC approximates the characteristics of the terminal voltage VB of the water temperature sensor 1 by the broken line approximation.
You can get it as C. Therefore, according to the second embodiment as described above, it is possible to obtain the same effect as that of the first embodiment.

5 and 6 show a third embodiment of the present invention. The difference from the first embodiment is that the control circuit 3 is replaced by a microcomputer, ROM, R.
A control circuit 28 including an AM and A / D conversion circuit is provided. In this case, the ROM 28a provided in the control circuit 28 stores a control program to be described later and also has a function as a storage means, and stores terminal voltage data corresponding to the detected temperature TW of the water temperature sensor 1. Data stored in advance is stored as characteristic data obtained by approximating the terminal voltage data corresponding to the terminal voltage VIG of the battery by a plurality of broken line approximations.

When the terminal voltage VIG of the battery and the terminal voltage VB of the water temperature sensor 1 are input, the control circuit 28 detects the water temperature and outputs a detection signal according to the flow chart of the program shown in FIG. Like That is, the control circuit 28 controls the terminal voltage VIG.
When VB and VB are input (step S1), A / D conversion is performed to generate a digital signal (step S2), and then it is determined whether the air conditioner is currently in operation (step S3).

When the air conditioner is in operation, the control circuit 28 judges "YES" and proceeds to step S4, where the detected terminal voltage V of the battery is detected.
Data corresponding to the off condition of the correction detection voltage VC corresponding to IG is read from the ROM 28a and set as the correction detection voltage VCoff of the off condition. In this case, since the air conditioner is operating, the correction detection of the off condition is performed to determine whether the terminal voltage VB of the water temperature sensor 1 has reached the temperature at which the air conditioner is stopped, that is, the overheat temperature. The voltage VCoff is read.

Next, the control circuit 28 controls the correction detection voltage VCoff of the set off condition and the terminal voltage V of the water temperature sensor 1.
B is compared (step S5), and if the terminal voltage VB is smaller than the correction detection voltage VCoff in the off condition, that is, if the temperature TW of the cooling water is higher than the temperature in the overheat state, it is determined to be “YES”. Then, the air conditioning control is stopped (step S6), and then the program is ended. If the control circuit 28 determines “NO” in step S6, that is, if the temperature TW of the cooling water is equal to or lower than the temperature of the overheat state, the control circuit 28 ends the program as it is.

On the other hand, if it is determined to be "NO" in step S3, that is, if the air conditioner is stopped, the control circuit 28 proceeds to step S7 to set the detected battery terminal voltage VIG. Corresponding correction detection voltage VC
Of these, the data corresponding to the ON condition is read from the ROM 28a and set as the ON condition correction detection voltage VCon. In this case, since the operation of the air conditioner is stopped, the correction detection voltage VCon of the ON condition is used to determine whether the terminal voltage VB of the water temperature sensor 1 is in a state of allowing the operation of the air conditioner. Is read.

Then, the control circuit 28 controls the correction detection voltage VCon of the set ON condition and the terminal voltage V of the water temperature sensor 1.
Compared with B (step S8), when the terminal voltage VB is larger than the correction detection voltage VCon of the ON condition, that is, when the temperature TW of the cooling water is lower than the temperature of the overheat state, it is determined to be “YES”. Then, the operation of the air conditioner is permitted (step S9), and this program ends. Also,
When the control circuit 28 determines "NO" in step S8, that is, when the temperature TW of the cooling water is still in the overheat state, the control circuit 28 ends the program while maintaining the stopped state of the air conditioning operation. .

According to such a third embodiment, the ROM
28a is provided to detect the characteristic that the terminal voltage VB of the water temperature sensor 1 changes non-linearly according to the change of the terminal voltage VIG of the battery so as to follow the approximate characteristic when the line approximation is performed by a plurality of straight lines. Corrected detection voltages VCon and VCof of the ON condition and the OFF condition corresponding to the terminal voltage VIG
f is stored, and the control circuit 28 reads the data of the correction detection voltages VCon and VCoff according to the operating state of the air conditioner and the terminal voltage VIG at that time to read the water temperature sensor 1.
Since the terminal voltage VB is compared with the terminal voltage VB, the temperature TW can be accurately detected based on the terminal voltage VB of the water temperature sensor 1 for displaying the water temperature even when the terminal voltage VIG of the battery varies. Therefore, the air conditioning control can be surely performed.

The present invention is not limited to the above embodiment, but can be modified or expanded as follows. In the first and second embodiments, the approximate characteristics of the water temperature sensor 1 are
The characteristic may be a polygonal line approximation with three or more straight lines.
In this case, in the first embodiment, it can be realized by providing a plurality of stages of correction circuits, and in the second embodiment, the one in which the Zener diode is connected in parallel to the voltage dividing resistor is added. Can be realized by

Further, in the third embodiment, the water temperature sensor 1
By storing data in the ROM 28a as a characteristic obtained by approximating the approximated characteristic of the above with a plurality of straight lines, the correction detection voltage VC set according to the terminal voltage VIG of the battery is stored.
The on and VCoff can be made to have almost no error with respect to the terminal voltage VB of the water temperature sensor 1, and the temperature TW of the cooling water can be detected with higher accuracy.

When the characteristic curve showing the variation characteristic of the terminal voltage VB of the water temperature sensor 1 corresponding to the variation of the terminal voltage VIG of the battery is approximated by the polygonal line approximation, the tangent line is drawn on the characteristic curve. There is a method of approximation, or a method of approximation by drawing so that the distance difference between the characteristic curve and a straight line is minimized.

In the second embodiment, when the actual fluctuation region of the battery terminal voltage VIG is a region above the change point voltage of the approximate characteristics of the terminal voltage VB of the water temperature sensor 1, the Zener diode 27 is used. The voltage dividing resistor 26 provided in parallel with the above can be omitted.

[0047]

As described above, according to the water temperature detecting device for air conditioning control of the present invention, the following effects can be obtained. That is, according to the water temperature detecting device for air conditioning control of claim 1, the correction means approximates the change characteristic of the terminal voltage of the water temperature sensor to a polygonal line approximation by two or more straight lines in response to the change of the terminal voltage of the DC power supply. Output as a correction detection voltage so as to follow the obtained approximate characteristics, and the water temperature detection means outputs a temperature signal for air conditioning control based on the terminal voltage of the water temperature sensor and the correction detection voltage from the correction means. Therefore, even when the terminal voltage of the water temperature sensor fluctuates in response to the fluctuation of the terminal voltage of the DC power source, the voltage value of the difference between the two can be obtained as a voltage signal according to the temperature of the cooling water. The temperature of the cooling water can now be detected accurately regardless of the fluctuations in the terminal voltage of the water temperature. Utilizing the terminal voltage of the capacitors and the cooling water temperature accurately detected by an excellent effect that the air-conditioning control can be performed reliably with.

According to the water temperature detecting device for air conditioning control of the second aspect, the correcting means comprises the power source voltage detecting means, the change point voltage generating means, the shunt resistance and the voltage adjusting means, and the voltage adjusting means causes the power source to be supplied. When the detected voltage from the voltage detecting means exceeds the change-point voltage, the voltage value obtained via the shunt resistance is held at the change-point voltage so that the detected voltage is corrected by flowing a current through the shunt resistance. Since it is output as a detection voltage, it is possible to obtain a corrected detection voltage in which the terminal voltage of the DC power supply is corrected by following the approximate characteristics of the water temperature sensor, and as a result, by comparing with the terminal voltage of the water temperature sensor, It has an excellent effect that the temperature of the cooling water can be accurately detected.

According to the water temperature detecting device for air conditioning control of the third aspect, the correcting means comprises the power source voltage detecting means, the voltage dividing resistor and the constant voltage diode, and the voltage detected by the power source voltage detecting means is the change point voltage. When it exceeds, the divided voltage of the voltage dividing resistor reaches the breakdown voltage value of the constant voltage diode so that it becomes a constant divided voltage, so the change characteristic of the terminal voltage of the water temperature sensor against the fluctuation of the terminal voltage of the DC power supply It becomes possible to obtain a corrected detection voltage that follows the approximate characteristics when the line approximation is performed by two or more straight lines, and it is possible to accurately detect the temperature of the cooling water by comparing it with the terminal voltage of the water temperature sensor. It has an excellent effect that it can be done.

According to the water temperature detecting device for air conditioning control of the fourth aspect, the correcting means comprises the storing means and the setting means, the setting means detects the terminal voltage of the DC power source, and the terminal voltage is detected from the storing means. Since the data corresponding to is read and the correction detection voltage is set, there is an excellent effect that the temperature of the cooling water can be accurately detected based on the correction detection voltage and the terminal voltage of the water temperature sensor. .

[Brief description of drawings]

FIG. 1 is an electrical configuration diagram showing a first embodiment of the present invention.

FIG. 2 is a correlation diagram of the correction detection voltage with respect to the terminal voltage of the battery.

FIG. 3 is a correlation diagram of the terminal voltage of the water temperature sensor with respect to the terminal voltage of the battery.

FIG. 4 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 5 is a diagram corresponding to FIG. 1 showing a third embodiment of the present invention.

FIG. 6 is a flowchart of a control program

[Explanation of symbols]

1 is a water temperature sensor, 2 is a water temperature display meter (water temperature display circuit), 3 is a control circuit, 4 and 5 are voltage dividing resistors, 6 is a correction circuit (correction means), 7 is an operational amplifier (voltage adjustment means), and 8 is Shunt resistance, 9 is a diode, 10 is a change point voltage generating circuit, 14 is an operational amplifier for impedance conversion, 16 is an operational amplifier (water temperature detecting means), 18 is a Zener diode, 20 is a capacitor for absorbing noise, 21 is a feedback resistor, 22 is an operational amplifier for waveform shaping, 25 is a feedback resistor,
Reference numeral 26 is a voltage dividing resistor, 27 is a zener diode (constant voltage diode), 28 is a control circuit, and 28a is a ROM (storage means).

Claims (4)

[Claims] 1. A DC power source comprising a water temperature sensor provided so that a resistance value changes according to the temperature of cooling water of an engine, and a water temperature display circuit for displaying the temperature of the cooling water according to an applied voltage. When connected in series with each other, the change characteristic of the terminal voltage of the water temperature sensor follows the approximate characteristic obtained by the line approximation with two or more straight lines in response to the change of the terminal voltage of the DC power supply. As described above, it is provided with a correction unit that outputs a correction detection voltage, and a water temperature detection unit that outputs a temperature signal for air conditioning control based on the terminal voltage of the water temperature sensor and the correction detection voltage from the correction unit. Water temperature detection device for air conditioning control. 2. The power supply voltage detection means for detecting the terminal voltage of the DC power supply by dividing the terminal voltage of the DC power supply with a voltage dividing resistor, and a change for setting a change point voltage corresponding to a change point of the approximate characteristic. Point voltage generation means, shunt resistance connected to the output terminal of the power supply voltage detection means, when the detection voltage of the power supply voltage detection means exceeds the change point voltage, the voltage value obtained via the shunt resistance The water temperature detection for air conditioning control according to claim 1, further comprising voltage adjusting means for outputting the correction detection voltage by causing a current to flow through the shunt resistance so as to be held at the change point voltage. apparatus. 3. The power supply voltage detection means for detecting the terminal voltage of the DC power supply by dividing the terminal voltage of the DC power supply with a plurality of voltage dividing resistors, and the correction means connected in parallel to the voltage dividing resistors at a change point of the approximate characteristic. 2. A constant voltage diode in which a breakdown voltage value equal to the corresponding change point voltage is set.
The water temperature detection device for air conditioning control described. 4. The correcting means stores the data of the correction detection voltage set so as to follow the approximate characteristic corresponding to the terminal voltage of the DC power supply, and the terminal voltage of the DC power supply. The water temperature detecting device for air conditioning control according to claim 1, further comprising: a setting unit configured to detect the temperature and read data corresponding to the detected voltage from the storage unit to set the detected voltage as a corrected detection voltage.