JPH0664165U - Driving circuit for cross coil type instrument - Google Patents

Abstract

(57) [Abstract] [Purpose] Suppresses self-heating of the sensor itself, is highly accurate,
It is an object of the present invention to provide a drive circuit for a cross coil type instrument that can be applied to various vehicle types. [Arrangement] An odd-shaped triangular wave generating circuit 1 for generating a combined wave of a triangular wave and a square wave, a signal generating circuit in which a resistor R and a thermistor sensor R _X are connected in series, and power is applied to both ends thereof, and the odd-shaped triangular wave is generated. A comparator 2 that inputs and outputs the output of the circuit and the signal voltage at the connection point A between the resistance of the signal generating circuit and the sensor, and a first output that receives the output waveform of the comparator via the first transistor. Coil L
₁ and an inverted waveform of the output waveform of the comparator 2 as an input via the second transistor, and a second coil wound so as to cross the first coil.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a drive circuit for a cross-coil type instrument, more specifically, a cross-coil type instrument having a stable range with a constant width in the indicated middle range of the instrument, which is suitable for measuring the engine coolant temperature of a vehicle. Drive circuit.

[0002]

[Prior art]

 Conventionally, a large number of cross-coil type water gauges have been used as instruments for vehicles and the like. Generally, for example, a cross-coil water temperature gauge is often used as an analog instrument for measuring the engine temperature of vehicles and the like. This water thermometer has a magnet with a pointer attached inside two sets of coils wound in an intersecting manner, and the magnet rotates due to the action of the combined magnetic field of the coil generated based on the signal of the sensor, The pointer indicates the water temperature. By the way, the appropriate temperature of the engine is generally around 80 ° C to 100 ° C, but if the pointer of the water temperature gauge is displayed linearly with respect to the water temperature, the rising of the pointer in the low temperature range is slow and If the pointer indicates around 100 ° C, it may be mistaken for overheating.

Therefore, a cross-coil type water thermometer has been proposed which has a stable range with a constant width in the medium temperature range. The drive circuit of the water thermometer is configured in a bridge with respect to the power source, as shown in FIG. 5, for example.

That is, a circuit in which the coil L ₃ and the coil L ₂ which are one of the cross coils are connected in series is formed, and a circuit in which a resistor R and a sensor R _{x including a} thermistor are connected in series is connected to the circuit. They are connected in parallel. The sensor R _x comprises 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 the Zener diode Z _D. Both ends of the circuit in which the coil L ₃ and the coil L ₂ 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 direction is differential.

The operation of this electric circuit will be described. First, when the water temperature is low and the sensor R_xThe resistance of zener diode Z is large._DAnd coil L₁Voltage V across the series circuit_B(= V ₁ -V₂) Is the diode Z_DZener voltage V_ZGreater than, ie V _B > V_ZWhen, coil L₁Current I in the direction of arrow A₁Flows to the left in FIG. 6 and is -F.₁A magnetic field is generated in the direction. This magnetic field and coil L₃, L₂Magnetic field F generated by_3,2The combined magnetic field of and is on the C (Cold) point side, and the pointer of the water temperature indicator points in this direction.

Further, the water temperature rises and the sensor R_xThe resistance value of_BIs V_ZSmaller and Zener diode Z_DTurn-on voltage V_F(V_FIs a Zener diode Z_DWhen a forward bias is applied to the current, the voltage at which the current flows out) is greater than the value with a negative sign, that is, V_Z> V_B> -V_FWhen, coil L₁ A current does not flow in and no magnetic field is generated. Therefore, the magnetic field generated is the coil L₃, L ₂ Based on F, and the direction is F shown in FIG._3,2As a result, the pointer indicates a medium temperature.

As shown in FIG. 6, the middle temperature stable region, which is the change range of V _B indicating the middle temperature, is equivalent to the change of the sensor R _X due to the change of the water temperature, and the sensor has a certain range of temperature. Even if the resistance value of R _X changes, the deflection angle θ of the pointer does not change and indicates a medium temperature. Therefore, it is easier to see because the middle temperature stable range can be set arbitrarily compared to the one that has the characteristic of linearly following changes in water temperature.

When the water temperature further rises, V_BIs -V_FIs smaller than, that is, V_B<-V _F When, coil L₁Current I in the direction of arrow B₁Is flowing to the right in FIG. 6 + F₁A magnetic field is generated in the direction. This magnetic field and coil L₃, L₂Magnetic field F generated by_3,2The combined magnetic field of and is on the H (Hot) point side, and the pointer of the water temperature indicator points in this direction. Thus sensor R_XChanges the coil L₁, L₂, L₃The direction of the composite magnetization changes due to_XAnd the rotation angle of the pointer attached to the magnet in the coil are as shown in FIG.

[0009]

[Problems to be solved by the device]

However, in the drive circuit of the cross coil type water thermometer as described above, the resistance value of the sensor R _X becomes smaller as the water temperature rises, so that the current flowing from the power source becomes large and the heat generated by the resistance R and the sensor R _X is generated. As a result, the sensor R _X self-heats, causing a problem such as characteristic deviation. In this case, the value of the resistance R cannot be increased due to the relationship with the coils L ₂ and L ₃ . In addition, the Zener voltage V _Z of the Zener diode Z _D has variations, so it may appear as an instruction error, and it is necessary to replace the Zener diode Z _D when changing the middle temperature range depending on the vehicle model. It's also annoying. An object of the present invention is to provide a drive circuit for a cross-coil type instrument that suppresses self-heating of the sensor itself, has high accuracy, and can be applied to various vehicle types.

[0010]

[Means for Solving the Problems]

 The driving circuit of the cross-coil type instrument according to the present invention is a variant triangular wave generating circuit that generates a composite wave of a triangular wave and a square wave, and a resistor and a thermistor sensor are connected in series to generate a signal with power applied to both ends. A circuit, a comparator for inputting and outputting the output of the odd-shaped triangular wave generating circuit, the signal voltage at the connection point between the resistance of the signal generating circuit and the sensor, and a first input for receiving the output waveform of the comparator. It is characterized by comprising a coil and a second coil which is wound with the inverted waveform of the output waveform of the comparator or a reference voltage as an input and which intersects the first coil and is wound.

[0011]

[Action]

 Based on the above configuration, the operation will be described with reference to FIG. _X When the resistance value of is low and the signal voltage at the connection point between the resistor and the sensor is located on the hypotenuse of the base of the odd-shaped triangular wave, the output of the comparator becomes a square wave with a large duty to drive the first transistor, A large current is passed through the first coil. On the other hand, an inverted version of this square wave drives the second transistor, causing a small current to flow through the second coil. The indication of the water thermometer appears in the combined magnetic field of both coils, in this case the direction of the magnetic field generated by the first coil, ie in the high temperature range. If the water temperature is medium and the signal voltage at the connection point between the resistor and the sensor is in the vertical range of the odd-shaped triangular wave, the output of the comparator is constant in this range and the direction of the synthetic magnetic field generated by both coils does not change. . That is, the water temperature indicator indicates the middle temperature range. Next, the water temperature becomes low and the sensor R_XIf the resistance value of is large and the signal voltage at the connection point between the resistor and the sensor is located on the upper slope of the irregular triangular wave, the output of the comparator becomes a square wave with a small duty and drives the first transistor, Apply a small electric current to the coil. On the other hand, by inverting the square wave, the second transistor is driven, and a large current flows through the second coil. The indication of the water thermometer appears in the combined magnetic field of both coils, in this case the direction of the magnetic field generated by the second coil, ie in the low temperature range.

[0012]

【Example】

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

As shown in FIG. 1, the drive circuit of the cross-coil type instrument according to the embodiment of the present invention has a modified triangular wave generation circuit 1. This odd-shaped triangular wave generating circuit 1 outputs the output waveforms of a triangular wave generating circuit 1a which generates a triangular wave of a constant frequency and a square wave generating circuit 1b which generates a square wave of the same frequency as this triangular wave and a duty of 50%. This is a circuit that generates a synthesized waveform.

The output of the odd-shaped triangular wave generating circuit 1 is input to the non-inverting input terminal of the comparator 2 and the inverting input terminal of the comparator 2 is connected in series with a resistor R and a thermistor sensor R _X. The signal voltage at the connection point A between the resistor R and the sensor R _{X of} the signal generating circuit to which the power is applied is input to.

The output B of the comparator 2 is the first coil L₁Transistor TR with load₁Applied to the base of. On the other hand, the output B of the comparator 2 has its waveform inverted by the inverting circuit 3 and the second coil L₂Second transistor TR with load ₂ Is configured to be applied to the base of the.

Next, the operation when this circuit is used as a drive circuit for a water temperature gauge of a vehicle or the like will be described with reference to FIGS. As the water temperature becomes high, the resistance value of the sensor R _X becomes small, and the signal voltage at the connection point A between the resistance R and the sensor R _X is located at the hypotenuse of the bottom of the odd-shaped triangular wave as shown in FIG. When positioned, the output B of the comparator is a square wave with a large duty. This square wave drives the first transistor TR ₁ shown in FIG. 1 and causes a large current to flow through the first coil L ₁ . On the other hand, the output B of the comparator 2 is inverted by the inverting circuit 3 into a square wave with a small duty to drive the second transistor TR ₂ , and a small current is passed through the second coil L ₂ . The pointer of the water thermometer swings in the direction of the combined magnetic field of both coils, in this case the magnetic field generated by the first carp L ₁ , that is, in the high temperature range.

When the water temperature is medium and the signal voltage at the connection point A between the resistor R and the sensor _X is located in the vertical region of the waveform of the irregular triangular wave, that is, in this range, the output of the comparator 2 has a constant duty. Therefore, the direction of the synthetic magnetic field generated by both coils L ₁ and L ₂ does not change. That is, the instruction of the water thermometer indicates the medium temperature range.

Next, when the water temperature becomes low and the resistance value of the sensor R _X is large, and the signal voltage at the connection point A between the resistance R and the sensor R _X is located at the upper slope of the irregular triangular wave, that is, the comparator 2 Output becomes a square wave with a small duty to drive the first transistor TR ₁ , and a small current flows through the first coil L ₁ . On the other hand, by inverting this square wave, the second transistor TR ₂ is driven, and a large current flows through the second coil L ₂ . The pointer of the water thermometer is swung in the direction of the magnetic field generated by the two coils L ₁ and L ₂ , in this case the magnetic field generated by the second coil L ₂ , that is, in the low temperature range.

In this embodiment, since the PWM signal is generated by combining the odd-shaped triangular wave generating circuit 1 and the comparator 2 in this way and the water temperature gauge is driven by a digital signal, heat generation is reduced. be able to. Further, the value of the resistor R can be changed by adjusting the output voltage of the odd-shaped triangular wave generating circuit 1, so that the current flowing into the sensor R _X can be reduced and the problem of characteristic deviation due to self-heating can be solved. be able to. Further, by adjusting the inclination of the triangular wave of the odd-shaped triangular wave generating circuit 1 and the duty of the square wave, it is possible to correct the variation in the accuracy of the parts and to make the driving circuit of various characteristics, so that various types of driving circuits can be produced. It can be adapted to the vehicle type.

In the present embodiment, the waveform obtained by inverting the output of the comparator 2 is input to the second transistor TR ₁ so that the current flows through the second coil L ₂ . The reference voltage may be applied to the second transistor TR _{1 or the} reference voltage may be directly applied to the second coil L ₂ . Further, in the present embodiment, the drive circuit is used for the water temperature gauge, but the drive circuit is not limited to this, and can be used as a drive circuit for various instruments requiring a medium temperature stable range.

[0021]

[Effect of device]

 As described above, according to the present invention, the heat generation of the drive circuit of the cross-coil type instrument can be reduced, so that the problem of the characteristic deviation due to the self-heating of the sensor can be solved and the triangular wave generation circuit of the odd-shaped triangular wave generation circuit can be solved. By changing the duty of the slope and the square wave, it is possible to create a drive circuit with various characteristics, so that it can be used for various instruments.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a drive circuit for a cross coil type instrument of the present invention.

FIG. 2 is a diagram illustrating an operation in a high temperature range of the circuit shown in FIG.

FIG. 3 is a diagram for explaining the operation in the medium temperature range of the circuit shown in FIG.

FIG. 4 is a diagram illustrating an operation in a low temperature range of the circuit shown in FIG.

FIG. 5 is a diagram showing a drive circuit of a conventional cross-coil type water thermometer.

FIG. 6 is a diagram showing a direction of magnetomotive force of each coil and a synthetic magnetic field.

FIG. 7 is a diagram showing a resistance value of a sensor and a swing angle of a water thermometer.

[Explanation of symbols]

 1 Variant triangular wave generation circuit 2 Comparator 3 Inversion circuit

Claims (1)

[Scope of utility model registration request] 1. A deformed triangular wave generating circuit for generating a combined wave of a triangular wave and a square wave, a signal generating circuit in which a resistor and a thermistor sensor are connected in series and a power source is applied to both ends, and the deformed triangular wave generating circuit. A comparator that inputs and outputs an output and a signal voltage at a connection point between the resistance of the signal generating circuit and the sensor, a first coil that receives an output waveform of the comparator, and an inversion of the output waveform of the comparator. A drive circuit for a cross-coil type instrument, characterized by comprising a second coil wound by intersecting the first coil with a waveform or a reference voltage as an input.