JPH089617Y2 - Electric circuit of cross coil type water thermometer - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric circuit of a cross-coil type water thermometer for detecting water temperature, and more specifically, it has a stable range with a constant width in a medium temperature range, and measures the water temperature of engine cooling water for vehicles. The present invention relates to an electric circuit of a cross-coil type water thermometer.

[0002]

2. Description of the Related Art Conventionally, a cross-coil type water thermometer has been usually used as an analog meter for measuring an engine temperature of a vehicle or the like. In the water temperature gauge, a permanent magnet having a pointer attached is arranged in two sets of coils wound in an intersecting manner, and the permanent magnet is rotated by a synthetic magnetic field generated in the coil based on a sensor signal to indicate the water temperature. It is a thing. By the way, the proper operating temperature of the engine is generally around 80 ° C to 100 ° C, but if the water temperature gauge is linearly displayed in proportion to the water temperature, the rise of the pointer will be slow in the low temperature range,
If the pointer indicates a high temperature range, for example, around the upper limit of 100 ° C., it may be mistaken for overheating.

For this reason, a cross-coil type water thermometer has been proposed which has a stable range with a constant width in the medium temperature range. The electric circuit of the water thermometer is configured in a bridge with respect to a power source, as shown in FIG. 4, for example.

That is, a circuit in which the coil L ₃ , which is one of the cross coils, and the coil L ₂ are connected in series is formed, and the circuit in which the resistor R and the sensor R _x are connected in series is connected in parallel to the circuit. The sensor R _x is composed of a thermistor and its resistance value decreases as the temperature rises. Further, the coil L ₁ is arranged so as to cross the coils L ₃ and L _2, and one end of the coil L ₁ is connected to the connection point between the coil L ₃ and the coil L ₂ . Further, the other end of the coil L ₁ is connected to the connection point between the resistor R and the sensor R _x via a Zener diode Z _D. Then, the coil L ₃ and the coil L ₂
Both ends of a circuit in which and are connected in series are used as power supply points.
The coils L ₃ and L ₂ are wound so that the magnetic field generation directions are differential.

The operation of this electric circuit will be described with reference to FIG. 4. First, the water temperature is low and the resistance value of the sensor R _x is large.
When the voltage V _B (= V ₁ −V ₂ ) across the series circuit of the Zener diode Z _D and the coil L ₁ is larger than the Zener voltage V _Z of the diode Z _D , that is, when V _B > V _Z , the coil A current I ₁ flows in L ₁ in the direction of arrow A, and a magnetic field is generated in the + F ₁ direction, which is the left direction in FIG. The combined magnetic field of this magnetic field and the magnetic fields F _3,2 generated by the coils L ₃ , L ₂ is on the C (Cold) point side, and the pointer of the water thermometer indicates this direction.

Further, water temperature continue to become smaller the resistance value of the sensor R _x and rise, V _B is less than V _Z, and turn-on voltage V _F (V _F of the Zener diode Z _D is the Zener diode Z _D when greater than a value obtained with the negative sign of the voltage) which current flows when forward biased, that is, when the V _Z> V _B> -V _F, a coil L ₁
A current does not flow in and no magnetic field is generated. Therefore, the generated magnetic field is only based on the coils L ₃ and L ₂ , and the direction thereof is the F _3,2 direction shown in FIG. 5, and the pointer indicates the middle temperature.

As shown in FIG. 6, the medium temperature stable range, which is the range of change of V _B indicating the medium temperature, is shown in FIG.
_It is equivalent to the change of _X , and the deflection angle θ of the pointer does not change even if the resistance value of the sensor R _X changes at a temperature within a certain range, and indicates a middle temperature. Therefore, the medium temperature stable region can be arbitrarily set, as compared with the one having the characteristic of linearly following the change of the water temperature, which makes it easier to visually recognize. Since the width of the middle temperature stable region can be adjusted by changing V _Z , the width can be adjusted by changing the Zener diode Z _D.

When the water temperature further rises and V _B becomes smaller than −V _F , that is, when V _B <−V _F , the coil L
_A current I ₁ flows in ₁ in the arrow B direction, and a magnetic field is generated in the −F ₁ direction which is the right direction in FIG. This magnetic field and coil L
₃ , the combined magnetic field with the magnetic field F _3,2 generated by L ₂ is H
It becomes the (Hot) point side, and the pointer of the water temperature indicator indicates this direction.

[0009]

However, when the medium temperature stable region is created by using the Zener diode Z _D in this way, it is very good when the power supply voltage is stable at a constant value, but once If there is voltage fluctuation, coil L ₁
Is connected in series with the Zener diode Z _D ,
The rate of change of the voltage applied to the coil L ₁ and the rate of change of the voltage applied to the coils L ₃ and L ₂ are different, and the characteristic with respect to the voltage fluctuation of the power supply may be worse than that of the water temperature gauge having the linear characteristic.

For example, as shown in FIG. 7, the power supply voltage is 1
Assuming that the composite magnetic field F ₁₆ of the coil L ₁ and the coils L ₃ and L ₂ is pointing to the point C at 6V, when the power supply voltage becomes 10V, the voltage applied to the coils L ₃ and L ₂ is 16V to 1V.
Although it became 0V, the voltage applied to the coil L ₁ was
Since the Zener voltage V _Z of the Zener diode Z _D is a constant value, it becomes larger than this change rate, and the magnetomotive force decreases at a large rate, and the combined magnetic field F ₁₀ becomes that shown in the figure, and it deviates by the angle θ _1. become.

Similarly, assuming that the composite magnetic field F ₁₆ points to the point H and the power supply voltage becomes 10 V, the coil L ₃ ,
The voltage applied to L ₂ has changed from 16V to 10V, but the voltage applied to the coil L ₁ is
_Since it is affected by the turn-on voltage V _{F of D,} the ratio becomes larger than this ratio, and the composite magnetic field F ₁₀ becomes as shown in the figure, which is offset by the angle θ ₂ . As described above, there may be a problem that the indication of the water thermometer is different due to the difference in the supplied power source voltage, and in particular, the Zener voltage V _Z
The larger this is, the greater this tendency is.

Therefore, an object of the present invention is to provide an electric circuit of a cross-coil type water thermometer which has a medium temperature stable region and has a small change in the pointing position of the pointer even if the supply voltage varies.

[0013]

An electric circuit of a cross-coil type water thermometer according to the present invention comprises a circuit composed of second and third coils connected in series, a first resistor, a second resistor and a sensor. A circuit connected in series in this order and connected in parallel with the circuit,
A first coil having one end connected to a connection point between the second coil and the third coil and wound by intersecting these coils, the other end of the first coil and both ends of the second resistor. It is characterized in that it is composed of first and second current direction control elements connected to each other and having different current passing directions, and that both ends of the circuit are power supply points.

[0014]

Based on the above structure, referring to FIG. 1, when the water temperature is low and the resistance value of the sensor is large, the magnetic fields generated by the second and third coils and the second current direction control element are shown. The combined magnetic field with the magnetic field generated by the current flowing through the first coil passes through the direction in which the pointer of the water thermometer is directed to the point C side.

When the water temperature becomes medium, the resistance value becomes medium and the second current direction control element is turned off. At this time, the first current direction control element is still off since it is connected to the other end of the second resistor, so that no current flows in the first coil and no magnetic field is generated. Therefore, the magnetic field is only the magnetic fields generated by the second and third coils, and causes the pointer of the water thermometer to indicate a medium temperature.

When the water temperature further rises, the first current direction control element is turned on, and a current flows in the first coil in the opposite direction to the above direction to generate a magnetic field, which is generated by the second and third coils. The combined magnetic field with the magnetic field to be turned is in the direction of pointing the pointer of the water temperature gauge to the H point side.

In this electric circuit, since it is not the zener diode of the constant voltage element but the current direction control element made of the silicon diode that is in series with the first coil, even if the supply voltage varies, Since there is no influence of the Zener voltage as in the conventional case and only the turn-on voltage of the silicon diode has an influence, there is little indication error due to the voltage fluctuation of the water thermometer.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of an electric circuit of a cross-coil type water thermometer of the present invention. Second coil L
Make a circuit in which ₂ and the third coil L ₃ are connected in series,
The first resistor R, the second resistor R _A and the sensor R _X are sequentially connected in series and connected in parallel with the circuit. The sensor R _X is composed of a thermistor, and its resistance value decreases as the temperature rises.

Further, one end of the first coil L ₁ wound so as to intersect with these is connected to the connection point of L ₂ and L ₃ . The other end of L ₁ is connected to one end of the second resistor R _A via the silicon diode D ₁ which is the first current direction control element. D ₁ should be in the forward direction from the L ₁ side to the _RA side. Similarly, the other end of L ₁ has a second resistor R 2 via a silicon diode D ₂ which is a second current direction control element.
Connect to the other end of _A. D ₂ should be in the opposite direction from the L ₁ side to the _RA side. Then, the coils L ₂ and L of this circuit
_A parallel connection point between the resistor ₃ , the resistor R, and the sensor R _X is used as a power supply point.

The operating principle of this circuit will be described below.
The difference from the conventional example shown in FIG. 4 is that instead of the Zener diode, diodes D ₁ and D ₂ and a resistor R are used.
_{Since A} is used, the description of the same operation principle may be omitted in some cases.

As shown in FIG. 2, the operating principle is that when the water temperature is low and the resistance value of the sensor R _X is large within the range shown by the symbol a, the voltage V _B across the series circuit of the diode D ₂ and the coil L ₁ is increased. (= V ₁ −V ₂ ) is larger than the turn-on voltage V _f2 of the diode D ₂ , that is, V _B > V _f2 ,
The equivalent circuit shown by the symbol a is formed, and the current I ₁ flows through the coil L ₁ in the direction of arrow A. Therefore, the coil L ₂ ,
The pointer of the water thermometer is C due to the combined magnetic field of L ₃ and coil L _1.
The point side is shown.

When the water temperature is medium and the resistance value of the sensor R _X is the symbol b.
, That is, V _f2 > V _B and V _B > −
When it becomes (V _f1 + V _Ra ), it becomes an equivalent circuit shown by symbol b, and no current flows through the coil L ₁ . For this reason,
Only the magnetic field generated by the coils L ₂ and L ₃ becomes, and the pointer of the water thermometer indicates medium temperature. Note that V _f1 is the turn-on voltage of the diode D ₁ and V _Ra is the voltage across the resistor _RA . Therefore, the width of the medium temperature can be freely adjusted by changing the value of the resistance R _A.

Further, when the water temperature rises and the resistance value of the sensor R _{X is in} the range indicated by the symbol c, that is, V _B <-(V _f1 + V
_Ra ), the equivalent circuit is shown by the symbol c,
A current I ₁ flows through the coil L ₁ in the direction of arrow B. Therefore, guidance water thermometer by the combined magnetic field of the coil L _2, L ₃ and the coil L ₁ represents H point side.

In this circuit, when the supply voltage fluctuates, the magnetomotive force generated by the coils L ₂ and L ₃ changes according to the rate of change of the voltage. Since the diode D ₁ or D ₂ is in series with the coil L ₁ , its turn-on voltages V _f1 and V _f2 affect the coil L _{1 so} that the coil L ₁ and D ₃ do not have the same effect as the coils L ₂ and L ₃ , but a silicon diode is used. Since this turn-on voltage is about 0.7 V, the influence can be reduced as compared with the case where a Zener diode is used.

As shown in FIG. 3, the diode D ₁
The resistor R _{1 is connected} to the diode D ₂ , the resistor R _{2 is connected} to the coil L _1, and the resistor R ₃ is connected in series to adjust the C point side, the H point side, and CH.
If the point side adjustment is made possible, the inclination of the indicating characteristic curve shown in FIG. 3 can be changed variously. It is also possible to use elements such as transistors instead of diodes.

[0027]

As described above, according to the present invention,
Of the circuits in which the first resistor, the second resistor, and the sensor are connected in series in this order, the width of the intermediate temperature range can be freely adjusted by changing the resistance value of the second resistor. Further, even if the supplied power supply voltage fluctuates, there is little difference between the rate of change in magnetomotive force due to the second and third coils and the rate of change in magnetomotive force due to the first coil. .

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing an equivalent circuit of an electric circuit based on a change in a resistance value of a sensor and a pointing position of a pointer of a water thermometer.

FIG. 3 is a diagram showing a main part of another embodiment.

FIG. 4 is a diagram showing an electric circuit of a conventional cross coil type water thermometer.

5 is a diagram showing directions of magnetomotive forces of respective coils of the circuit of FIG. 4 and a synthetic magnetic field.

6 is a diagram showing a deflection angle of a pointer due to a change in sensor resistance value of the circuit of FIG.

7 is a diagram showing the magnitude of the magnetomotive force of each coil and the direction of the combined magnetic field when the supply voltage of the circuit of FIG. 4 changes.

[Explanation of symbols]

L ₁ 1st coil L ₂ 2nd coil L ₃ 3rd coil R 1st resistance R _A 2nd resistance R _X sensor D ₁ 1st current control element (diode) D ₂ 2nd current control Element (diode)

Claims (1)

[Scope of utility model registration request] 1. A circuit composed of second and third coils connected in series, a circuit in which a first resistor, a second resistor, and a sensor are connected in series in this order and connected in parallel with the circuit, and A first coil having one end connected to a connection point between the second coil and the third coil and wound by intersecting these coils; and the other end of the first coil and both ends of the second resistor. An electric circuit of a cross-coil type water thermometer, comprising: first and second current direction control elements connected to each other and having different current passing directions, wherein both ends of the circuit are power supply points.