JP3329055B2 - Water temperature detector for air conditioning control - Google Patents

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 using a terminal voltage of a water temperature sensor connected in series with a circuit for displaying a water temperature. About.

[0002]

2. Description of the Related Art In an engine of an automobile, for example, a water temperature sensor is provided at an outlet of a cooling water to detect a temperature of the cooling water. In this case, the water temperature sensor is configured such that, for example, a coil-type water temperature display meter is connected in series and connected to an output terminal of a vehicle-mounted battery, and the detected temperature is displayed on a driver's seat. The water temperature sensor has a characteristic that the resistance value changes according to the temperature of the cooling water, and changes the direction and the magnitude of the current flowing through the coil bridge constituting the water temperature display meter according to the temperature. The vibration is changed and displayed. Thereby, when the temperature of the cooling water has risen to the temperature in the overheat state, it is possible to recognize this by a large swing of the pointer of the water temperature display meter.

[0003] By the way, in an air conditioner of an automobile,
The air-conditioning operation control is performed using the heat of the cooling water of the engine. However, it is necessary to detect the overheating and stop the air-conditioning operation when overheating occurs. For this reason, conventionally,
A separate water temperature sensor is provided to detect the temperature of the cooling water. In this case, the water temperature sensor is configured to detect a temperature by giving a predetermined voltage for control from a control circuit for air conditioning control via a voltage dividing resistor and 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 in response to the operation signal.

[0004]

However, providing two water temperature sensors for detecting the temperature of the cooling water for the engine as described above is difficult in terms of installation space, and is troublesome in installation. Therefore, there is a problem that the cost increases. Therefore, it is demanded that a single water temperature sensor performs the detection operation in common. However, it has been difficult to adopt a configuration in which a single water temperature sensor is shared because of the following disadvantages due to differences in the configuration of each water temperature detection.

That is, the reason that the temperature of the engine cooling water is detected by the separate water temperature sensor is that the display of the water temperature 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 supply generally varies within a range of, for example, about 11 V to about 14 V depending on the usage state. On the other hand, since a water temperature sensor is connected via a water temperature display meter, its terminal Although the voltage fluctuates according to the fluctuation of the power supply voltage, the characteristics of the water temperature sensor are such that the resistance characteristics do not change linearly with respect to the output voltage of the battery because the element itself generates heat due to the supplied current. is there.

Therefore, in order to obtain an accurate temperature signal for air conditioning control, it is necessary to correct a terminal voltage generated at the water temperature sensor in response to a change in the output voltage of the battery to obtain a detection signal. There is a situation that the resistance characteristics of the water temperature sensor cannot be corrected with a simple configuration because the theoretical characteristics have not been clarified. For this reason, it has been difficult to detect an accurate temperature when an overheat state in air-conditioning control is detected from the terminal voltage by sharing a water temperature sensor for displaying the water temperature.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to solve the problem even when the DC power supply voltage fluctuates.
It is an object of the present invention to provide an air-conditioning control water temperature detection device that can accurately perform temperature detection for overheating detection during air-conditioning control by sharing a water temperature sensor for displaying a temperature of engine cooling water.

[0008]

According to the present invention, there is provided a water temperature detecting device for air conditioning control, comprising: a water temperature sensor provided so that a resistance value changes according to a temperature of cooling water of an engine; A water temperature display circuit for displaying water temperature is connected in series to a DC power supply, and two terminal voltage change characteristics of the water temperature sensor corresponding to a change in terminal voltage of the DC power supply are provided. Correction means for outputting as a correction detection voltage so as to follow an approximation characteristic obtained by polygonal line approximation by the straight line, and 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 provided with a water temperature detecting means for outputting a temperature signal.

Power supply voltage detecting means for detecting the correction means by dividing the terminal voltage of the DC power supply with a voltage dividing resistor, and a change point voltage for setting a change point voltage corresponding to a change point of the approximate characteristic Generating means, a shunt resistor connected to an output terminal of the power supply voltage detecting means, and a voltage value obtained via the shunt resistance when the detection voltage of the power supply voltage detecting means exceeds the change point voltage. It is preferable to include a voltage adjusting unit that outputs the correction detection voltage by flowing a current through the shunt resistance so as to be maintained at the point voltage.

In addition, the correction means includes a power supply voltage detection means for detecting the terminal voltage of the DC power supply by dividing the terminal voltage with a plurality of voltage dividing resistors, and a power supply voltage detecting means connected in parallel with the voltage dividing resistance to a 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 includes a storage means for storing data of the correction detection voltage set so as to follow the approximation characteristic in accordance with a terminal voltage of the DC power supply, and a terminal voltage of the DC power supply. And a setting means for reading out data corresponding to the detected voltage from the storage means and setting it as a corrected detection voltage.

[0012]

According to the first aspect of the present invention, the correction means corrects the terminal voltage of the DC power supply in response to a change in the terminal voltage and outputs the corrected voltage as a correction detection voltage. Based on the terminal voltage of the sensor and the correction detection voltage, it is detected as a temperature signal for air conditioning control. In this case, the correction detection voltage is corrected so as to follow an approximation characteristic obtained by approximating the change characteristic of the terminal voltage of the water temperature sensor with two or more straight lines in accordance with the change in the terminal voltage of the DC power supply. 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.

Thus, even when the terminal voltage of the water temperature sensor fluctuates in response to the fluctuation of the terminal voltage of the DC power supply, the voltage value of the difference between the two can be obtained as a voltage signal corresponding to the temperature of the cooling water. This makes it possible to accurately detect the temperature of the cooling water irrespective of fluctuations in the terminal voltage of the DC power supply, and is used for displaying the water temperature even in air conditioning control that requires detection accuracy of the water temperature. 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 accurately performed.

According to the second aspect of the present invention, when the detected voltage from the power supply voltage detecting means exceeds the change point voltage, the voltage adjusting means controls the voltage value obtained via the shunt resistor. The current flows through the shunt resistor so that the detected voltage is maintained at the change point voltage, whereby the detected voltage is output as a corrected detected 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 supply is approximated by a broken line using two or more straight lines. This makes it possible to obtain a corrected detection voltage obtained by correcting the terminal voltage of the DC power supply following the approximate characteristics of the water temperature sensor, and to accurately detect the temperature of the cooling water by comparing with the terminal voltage of the water temperature sensor. Will be able to

According to the third aspect of the present invention, when the voltage detected by the power supply voltage detecting means exceeds the change point voltage, the shared voltage of the voltage dividing resistor connected in parallel with the constant voltage diode is adjusted. When the breakdown voltage of the constant voltage diode is reached and the terminal voltage of the DC power supply rises further, 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 resistors. As a result, the corrected detection voltage becomes a voltage output that follows the approximation characteristic when 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 is approximated by two or more straight lines. As a result, the temperature of the cooling water can be accurately detected.

According to the fourth aspect of the present invention, the setting means detects a terminal voltage of the DC power supply, reads data corresponding to the terminal voltage from the storage means, and sets a correction detection voltage. . At this time, the correction detection voltage is stored as data for correcting the change characteristic of the terminal voltage of the water temperature sensor in accordance with the change of the terminal voltage of the DC power supply so as to follow the approximation characteristic obtained by approximating the change characteristic of the water temperature sensor with a number of straight lines. 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]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
Will be described with reference to FIGS. 1 to 3. FIG. In FIG. 1 showing an electrical configuration, a water temperature sensor 1 is
For example, it has a characteristic that the resistance value changes according to the temperature of the thermistor or the like, and is provided so as to detect the temperature TW of the engine coolant (not shown). The water temperature sensor 1 is connected to an output terminal V1 of a vehicle-mounted battery as a DC power supply via a coil-type water temperature display meter 2 as a water temperature display circuit, and supplied with a DC power supply voltage VIG.

The water temperature display meter 2 is formed by combining two coils, a resistor and a Zener diode, and forms a bridge circuit by connecting the water temperature sensor 1. And the water temperature sensor 1
When the resistance value of the coil changes, the magnitude and direction of the current flowing through the Zener diode changes, and the current flowing through one of the coils changes to move the indicating needle to a position corresponding to the temperature TW. It is configured to display.

The control circuit 3 controls the terminal voltage V of the water temperature sensor 1.
A circuit for detecting a 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 correction means.

In the correction circuit 6, an inverting input terminal of an operational amplifier 7 as a voltage adjusting means is connected to an output terminal C via a shunt resistor 8, and to an output terminal of the operational amplifier 7 via a diode 9 in a 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 a transition point voltage output terminal D, which is a common connection point of the resistors 11 and 12, and receives the transition point voltage VD. The constant voltage output terminal V2 is provided with an output obtained by converting the output voltage of the battery to a constant voltage VCC by a constant voltage circuit (not shown).

When the input voltage Va at the inverting input terminal is lower than the change point voltage VD, the operational amplifier 7 outputs an "H" level signal, 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 the input voltage Va at the inverting input terminal is about to increase thereafter, a current flows through the diode 9 to thereby reduce the input voltage V
The operation is performed so as to maintain “a” at the transition voltage VD.

An output terminal C, which is a common connection point between 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 operational amplifier 14 for impedance conversion, and an input resistor 15. Connected to terminal. The output terminal of the operational amplifier 14 is also connected to the inverting input terminal. The input terminal B is connected to the inverting input terminal of the operational amplifier 16 while being grounded via a Zener diode 18 of the illustrated polarity while passing through a protection resistor 17. 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 an inverting input terminal via a zero and to an output terminal of the operational amplifier 16 via a feedback resistor 21 for providing 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 a constant voltage output terminal VCC via a voltage dividing resistor 23 and is grounded via a 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 to the output terminal P. The operational amplifier 1
Reference numeral 4 denotes an impedance converter for preventing the detection 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. First, the electrical characteristics of the water temperature sensor 1 will be described. The water temperature sensor 1 has a negative temperature characteristic in which the resistance value decreases as the temperature increases, and is provided so that the resistance value changes according to the temperature TW of the engine cooling water. The water temperature sensor 1 has such a characteristic that the terminal voltage VB fluctuates when the terminal voltage VIG of the battery fluctuates, 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, and thus deviates from a voltage value corresponding to the cooling water temperature TW. This makes it impossible to accurately detect the water temperature TW 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, the terminal voltage VB of the water temperature sensor 1 changes according to the terminal voltage VIG of the battery. It is corrected so that it follows.
At this time, the characteristic of the terminal voltage VB of the water temperature sensor shown in FIG. 3 is set, for example, as shown by a solid line in FIG.

First, in the transition point voltage generation circuit 10, the transition point voltage VD is applied to the transition point voltage output terminal D, and the detection point corresponding to the intersection point of the two straight lines having the above-described broken line approximation characteristic, that is, the transition point M of the broken line. The setting is made 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 the signal of the “H” level, the current to the shunt resistor 8 is blocked, and the detection voltage VC increases as the terminal voltage VIG of the battery increases. .

When the detection voltage VC becomes equal to the change point voltage VD, the output of the operational amplifier 7 is inverted. When the detection voltage VC becomes higher than the change point voltage VD, the operational amplifier 7 changes 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 transition point voltage VD.
And a current flows through the diode 9 to detect the detection voltage VC.
Will be corrected.

That is, until the detection voltage VC reaches the change point voltage VD, the detection voltage VC is divided by the voltage dividing resistors 4 and 5 as the value of the battery terminal voltage VIG increases. 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 value of the terminal voltage VIG. This is output to the output terminal C as a voltage value divided by 4, 5, and the shunt resistor 8 (a value along the straight line q in FIG. 2). As a result, the voltage corresponding to the terminal voltage VIG appearing at the detection terminal C is output as the corrected detection voltage VC along 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 has been converted. The voltage signal is divided by the resistors 15 and 19 and
Is input as the reference voltage VS to the non-inverting input terminal. The reference voltage VS is a voltage value obtained by dividing the correction detection voltage VC, as shown by the straight lines r and s in FIG. 2, and is used as the reference voltage for detecting the water temperature.
6 is input. Also, this reference voltage VS
Is divided by the resistors 15 and 19 so as to be set as a reference voltage value corresponding to a temperature when the temperature TW of the cooling water reaches a predetermined temperature or higher and causes 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 lowering the same, the hysteresis is given by the operation of the feedback resistor 21, so that the terminal voltage VB
When B becomes smaller than the reference voltage VS by a predetermined voltage, the output is inverted.

The waveform shaping operational amplifier 22 inverts the output of the operational amplifier 16 and outputs the inverted output to the output terminal P. Thus, when the terminal voltage VB of the water temperature sensor 1 is lower than 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 above becomes equal to or higher than the temperature in the overheat state, the terminal voltage VB is changed to the reference voltage V
That is, the detection signal is output to the output terminal P below S. Thus, in the air conditioner, measures such as stopping the air conditioning operation can be appropriately performed.

According to the present embodiment, the correction circuit 6
Accordingly, the terminal voltage VIG of the battery is corrected so as to follow the approximation characteristic obtained by approximating the voltage characteristic of the water temperature sensor 1 with a polygonal line, and is output from the output terminal C as a correction detection voltage VC. Set VS,
Since the comparison with the terminal voltage VB of the water temperature sensor 1 is performed, the accurate reference voltage VS follows the terminal voltage VB of the water temperature sensor 1 which fluctuates nonlinearly with the fluctuation of the terminal voltage VIG of the battery. Therefore, even when the terminal voltage fluctuates like a battery, the temperature TW of the cooling water is always accurately detected using the water temperature sensor 1 used for displaying the water temperature, and the air conditioning control is accurately performed. 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,
5 and a voltage dividing resistor 26 connected in series and provided.
The zener diode 27, which is a constant voltage diode, is provided 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 equal to the Zener voltage VZ. When the output voltage reaches the terminal voltage VC, the terminal voltage VC of the output terminal C reaches the change point voltage VD.

According to such a configuration, when the terminal voltage VIG of the battery fluctuates and the detection voltage VC of the detection terminal C becomes higher than the change point voltage VD, the terminal voltage V
Since E reaches the Zener voltage VZ, the voltage dividing resistor 26
No longer rises, and as the terminal voltage VIG rises thereafter, the detection voltage VC becomes the voltage value (== the terminal voltage VIG minus the Zener voltage VZ).
VIG-VZ) as a terminal voltage when the voltage is divided by the voltage dividing resistors 4 and 5.

Thus, in the same manner as in the first embodiment,
The corrected detection voltage V is such that the detection voltage VC follows the approximation characteristic when the characteristic of the terminal voltage VB of the water temperature sensor 1 is approximated by a polygonal line.
C can be obtained. Therefore, according to the second embodiment, the same operation and effect as those of the first embodiment can be obtained.

FIGS. 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 an 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 has a function as a storage unit, and stores terminal voltage data corresponding to the detected temperature TW of the water temperature sensor 1. In this case, data measured in advance is stored as the characteristic data when the characteristic corresponding to the terminal voltage VIG of the battery is approximated by a plurality of broken line approximations.

When the control circuit 28 receives the terminal voltage VIG of the battery and the terminal voltage VB of the water temperature sensor 1, it detects the water temperature and outputs a detection signal in accordance with the flow chart of the program shown in FIG. Become like That is, the control circuit 28 outputs the terminal voltage VIG
After inputting VB and VB (step S1), A / D conversion is performed to generate a digital signal (step S2), and then it is determined whether or not the air conditioner is currently operating (step S3).

When the air conditioner is operating, the control circuit 28 determines "YES" and shifts to step S4 to detect the terminal voltage V of the detected battery.
Data corresponding to the off condition among the correction detection voltages VC corresponding to the IG is read from the ROM 28a and set as the correction detection voltage VCoff for the off condition. In this case, since the air conditioner is operating, the OFF condition correction detection 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 temperature at the time of overheating. The voltage VCoff is read.

Next, the control circuit 28 determines the correction detection voltage VCoff of the set OFF condition and the terminal voltage V of the water temperature sensor 1.
B (step S5), if the terminal voltage VB is lower 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 thereafter, the program ends. When the control circuit 28 determines “NO” in step S6, that is, when 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 "NO" is determined in the step S3, that is, if the air conditioner is in a stopped state, the control circuit 28 proceeds to a step S7, where the detected terminal voltage VIG of the battery is reduced. Corresponding correction detection voltage VC
Among them, the data corresponding to the ON condition is read from the ROM 28a and set as the correction detection voltage VCon for the ON condition. In this case, since the operation of the air conditioner is stopped, the ON-condition correction detection voltage VCon is used to determine whether the terminal voltage VB of the water temperature sensor 1 is in a state allowing the operation of the air conditioner. Is read.

Then, the control circuit 28 determines the correction detection voltage VCon of the set ON condition and the terminal voltage V of the water temperature sensor 1.
B (step S8), when the terminal voltage VB is higher than the on-condition correction detection voltage VCon, that is, when the temperature TW of the cooling water is lower than the temperature in the overheat state, it is determined to be “YES”. Then, the operation of the air conditioner is permitted (step S9), and the 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 the temperature of the overheating state, the control circuit 28 ends the program while maintaining the stop state of the air conditioning operation. .

According to the third embodiment, the ROM
28a is provided so that the characteristic in which the terminal voltage VB of the water temperature sensor 1 changes nonlinearly in response to the change in the terminal voltage VIG of the battery is detected so as to follow the approximation characteristic obtained when a plurality of straight lines approximate the broken line. Correction 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 out the data of the correction detection voltages VCon and VCoff in accordance with the operating state of the air conditioner and the terminal voltage VIG at that time, and reads out the water temperature sensor 1.
, 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 fluctuates. Thus, the air conditioning control can be reliably 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 as follows:
A characteristic obtained by approximating a broken line with three or more straight lines may be used.
In this case, in the first embodiment, this can be realized by providing a plurality of stages of correction circuits. In the second embodiment, a circuit in which a Zener diode is connected in parallel to a voltage dividing resistor is added. Can be realized by:

In the third embodiment, the water temperature sensor 1
Is stored in the ROM 28a as a characteristic obtained by approximating the approximation characteristic by a plurality of straight lines, and the correction detection voltage VC set in accordance with the terminal voltage VIG of the battery.
On and VCoff can be made so that there is 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 a characteristic curve indicating a change characteristic of the terminal voltage VB of the water temperature sensor 1 corresponding to a change in the terminal voltage VIG of the battery is approximated by a polygonal line approximation, the approximation method is to draw a tangent line on the characteristic curve. There is a method of approximation by drawing, or a method of approximating by drawing so that the difference in distance from a straight line superimposed on the characteristic curve is minimized.

In the second embodiment, when the actual fluctuation region of the terminal voltage VIG of the battery is a region of the approximate characteristic of the terminal voltage VB of the water temperature sensor 1 which is equal to or higher than the change point voltage, the Zener diode 27 is used. , The voltage dividing resistor 26 provided in parallel can be omitted.

[0047]

As described above, according to the air-conditioning control water temperature detecting device of the present invention, the following effects can be obtained. That is, according to the water temperature detecting device for air-conditioning control of the first aspect, the correcting means approximates the change characteristic of the terminal voltage of the water temperature sensor by two or more straight lines in accordance with the change of the terminal voltage of the DC power supply. A correction detection voltage is output so as to follow the obtained approximate characteristic, 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 supply, the voltage value of the difference between the two can be obtained as a voltage signal corresponding to the temperature of the cooling water. The temperature of the cooling water can be accurately detected irrespective of the fluctuation of the terminal voltage of the cooling water. 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 second aspect of the present invention, the correcting means comprises the power supply voltage detecting means, the change point voltage generating means, the shunt resistor and the voltage adjusting means, and the voltage adjusting means controls the power supply. When the detected voltage from the voltage detecting means exceeds the change point voltage, the correction is performed by correcting the detection voltage by flowing a current through the shunt resistance so that the voltage value obtained through the shunt resistance is maintained at the change point voltage. Since the detection voltage is output, a corrected detection voltage obtained by correcting the terminal voltage of the DC power supply following the approximation characteristics of the water temperature sensor can be obtained. As a result, by comparing with the terminal voltage of the water temperature sensor, There is an excellent effect that the temperature of the cooling water can be accurately detected.

According to the third aspect of the present invention, the correcting means comprises the power supply voltage detecting means, the voltage dividing resistor and the constant voltage diode, and the voltage detected by the power supply voltage detecting means is the change point voltage. When the voltage exceeds, the shared voltage of the voltage dividing resistor reaches the breakdown voltage value of the constant voltage diode and becomes a constant shared voltage, so 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 is It is possible to obtain a correction detection voltage that follows the approximation characteristic when the polygonal line is approximated by two or more straight lines, and to accurately detect the temperature of the cooling water by comparing with the terminal voltage of the water temperature sensor. It has an excellent effect that it can be done.

According to the fourth aspect of the present invention, the correction means comprises a storage means and a setting means, the setting means detects a terminal voltage of the DC power supply, and the storage means detects the terminal voltage from the storage means. Is read and the correction detection voltage is set, so that 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 the drawings]

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

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

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

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

FIG. 5 is a view 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 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,
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).

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01K 7/25 G01K 7/20 G01K 7/00 321

Claims (4)

(57) [Claims] 1. A DC power supply comprising: a water temperature sensor provided so that a resistance value changes according to the temperature of cooling water of an engine; and a circuit for displaying a temperature of the cooling water according to an applied voltage. In addition, in accordance with a change in the terminal voltage of the DC power supply, a change characteristic of the terminal voltage of the water temperature sensor follows an approximate characteristic obtained by approximating the change characteristic of the water temperature sensor with two or more straight lines. And a water temperature detection means for outputting 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. Water temperature detection device for air conditioning control. 2. A power supply voltage detecting means for detecting a terminal voltage of the DC power supply by dividing the terminal voltage with a voltage dividing resistor, and a change for setting a change point voltage corresponding to a change point of the approximate characteristic. A point voltage generator, a shunt resistor connected to an output terminal of the power supply voltage detector, and a voltage value obtained through the shunt resistor when the detection voltage of the power supply voltage detector exceeds the change point voltage. 2. The air-conditioning control water temperature detection device according to claim 1, further comprising voltage adjustment means for outputting the correction detection voltage by passing a current through the shunt resistance so as to be maintained at the change point voltage. apparatus. 3. The power supply voltage detection means for detecting a terminal voltage of the DC power supply by dividing the terminal voltage with a plurality of voltage-dividing resistors; 2. A constant voltage diode having a breakdown voltage value equal to a corresponding change point voltage.
A water temperature detection device for air conditioning control as described in the above. 4. A storage unit for storing data of the correction detection voltage set so as to follow the approximate characteristic in accordance with a terminal voltage of the DC power supply, and a terminal voltage of the DC power supply. 2. The air-conditioning control water temperature detecting device according to claim 1, further comprising setting means for detecting the detected voltage and reading data corresponding to the detected voltage from the storage means and setting the data as a corrected detection voltage.