JPH0618562A - Cross coil type meter driving device - Google Patents

Abstract

PURPOSE:To reduce the cost of the title device and make the device compact by remarkably reducing the number of mechanical parts used in the device. CONSTITUTION:Cross coils 1A and 1B which are wound in orthogonal directions are connected to the transistor 22 of a conducting circuit 2 and generate a variable magnetic field when the coils 1A and 1B are excited with an electric current corresponding to a detecting signal Vin. An auxiliary coil 3 wound around the coils 1A and 1B in an overlapping state is connected to the transistor 42 of another conducting circuit 4 and generates a steady magnetic field having a fixed magnitude when the soil 3 is excited with a constant current. The pointer of a meter rotates in the direction of the resultant magnetic field of the variable and steady magnetic fields. Since the auxiliary coil 3 is used for generating the steady magnetic field, the winding process of the coil 3 can be automated together with the coils 1A and 1B and the manufacturing cost of this meter driving device can be reduced. In addition, the circuit 4 can be integrally formed on a printed board, etc., and the device can be made compact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cross coil type meter driving device, and more particularly to a structural improvement thereof.

[0002]

13 and 14 show an example of a conventional cross coil type meter driving device. In the figure, a rotary shaft 62 of a meter pointer 61 is supported in a vertical posture at the center of a meter housing 5, and a permanent magnet (movable magnet) having different magnetic poles formed at symmetrical positions in the radial direction is provided on the outer periphery of an intermediate portion thereof. 63 is fixed.

A pair of coils 1A and 1B are wound around the outer circumference of the bobbin 51 provided so as to cover the movable magnet 63, and these coils 1A and 1B are arranged orthogonally to each other. A permanent magnet (external magnet) 8 is provided on the inner circumference of the outer wall of the meter housing 5 which is separated from the crossing coils 1A and 1B.

The crossing coils 1A and 1B are energized in accordance with a detection signal, and the movable magnet 63 rotates in the combined vector direction of the variable magnetic field generated by the crossing coils 1A and 1B and the stationary magnetic field generated by the external magnet 8. The meter pointer 61 indicates a predetermined scale.

Such a structure is disclosed in, for example, Japanese Patent Publication No. 2543.

[0006]

By the way, the above-mentioned conventional structure using the external magnet 8 requires a relatively large number of mechanical parts such as a magnet body, a magnet housing for holding the magnet body, and if necessary a holding leaf spring. Therefore, it takes time and labor to manufacture and store, and it is difficult to automate the assembling, resulting in cost increase and various problems that it is difficult to reduce the size of the apparatus.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a cross-coil type meter driving device which can significantly reduce the number of mechanical parts, reduce the cost and make the device compact.

[0008]

The structure of the present invention will be described. A meter driving device includes cross coils 1A and 1B wound so as to intersect each other at right angles, and these cross coils 1A and 1B.
The first energizing means 2 for generating a variable magnetic field that is energized according to the detection signal to change its magnitude, and the crossing coil 1
Auxiliary coil 3 wound on A and 1B in a superposed manner, and second energizing means 4 for energizing the auxiliary coil 3 in a constant amount to generate a steady magnetic field having a constant magnitude are provided. The meter pointer can be rotated in the direction of the combined magnetic field of the magnetic field and the stationary magnetic field.

As another configuration, there is further provided a means 5 for offsetting the detection signal voltage by a certain amount, and the first energizing means 2 is provided with an exciting current proportional to the offset voltage value. It is set to supply to 1B.

[0010]

In the above construction, in order to generate a steady magnetic field, the auxiliary coil 3 wound on the crossing coils 1A, 1B in a superposed manner is used in place of the external magnet. It is easy to automate the process and reduce the manufacturing cost.

Since the energizing means 4 can be constituted by electric parts, it can be integrated on a printed circuit board or the like, is compact and can be manufactured and stored easily.

According to another configuration of the present invention, when the maximum exciting current has a certain limit, the voltage value of the detection signal is offset, so that the proportional constant of the offset voltage value and the exciting current can be increased. Even when the change range of the detection signal voltage is small, the change range of the exciting current is sufficiently large, and the indication resolution of the meter pointer can be increased.

[0013]

[Embodiment 1] In FIG. 1 (1), crossing coils 1A, 1
As already described in the conventional example, Bs are arranged so as to cross each other at right angles, and are connected in series with each other on the collector side of the transistor 22 constituting the energizing circuit 2. An output terminal of an operational amplifier (op-amp) 21 is connected to the base of the transistor 22, and a detection signal voltage Vin such as engine boost pressure is input to the non-inverting input terminal of the op-amp. The feedback voltage from the current detection resistor 23 connected to the emitter side of the transistor 22 is input to the inverting input terminal of the comparator 21.

The feedback voltage is the detection signal voltage V
changes in accordance with in, and as a result, the crossing coils 1A, 1
An exciting current corresponding to the detection signal voltage Vin is supplied to B. In the figure, 24 is a flywheel diode.

The energizing circuit 4 for the auxiliary coil 3 is shown in FIG. The operational amplifier 41, the transistor 42, and the current detection resistor 43 correspond to the operational amplifier 21, the transistor 22, and the current detection resistor 23 of FIG. 1A, respectively. The non-inverting input terminal of the operational amplifier 41 has voltage dividing resistors 45 and 46.
The constant voltage Vc created by is input. As a result, a constant exciting current is always supplied to the auxiliary coil 3. In addition, 44 is a flywheel diode.

As shown in FIG. 2, the magnetic field vector T4 obtained by the crossing coils 1A and 1B orthogonal to each other is 45 ° with respect to the magnetic field vectors T1 and T2 of the individual coils 1A and 1B.
When the magnitudes of the magnetic field vectors T1 and T2 change according to the magnitude of the detection signal voltage Vin, the magnitude of the composite magnetic field vector T4 also changes.

The magnetic field vector T3 of the auxiliary coil 3 is opposite in direction to the magnetic field vector T1 and has a constant magnitude, and the synthetic magnetic field vector T5 of the magnetic field vector T3 and the synthetic magnetic field vector T4 is the magnitude of the synthetic magnetic field vector T4. As the white arrow in the figure changes, the direction of the change changes.

Therefore, the movable magnet of the rotary shaft of the pointer described in the prior art is made to rotate and coincide in the direction of the composite magnetic field vector T5, and the pointer shows a predetermined scale.

The auxiliary coil 3 of this embodiment is the cross coil 1
It is possible to wind the bobbin together with A and 1B by an automatic machine, and the assembling work is greatly reduced.

Since the energizing circuits 2 and 4 can be integrally formed on the printed circuit board, they are compact and easy to manufacture.

[0021]

Second Embodiment Instead of the current driving of the first embodiment, voltage driving may be used, which is shown in FIG. In FIG. 3 (1), the crossing coils 1A and 1B are connected in series to the emitter side of the transistor 22 that constitutes the energizing circuit 2, and the voltage applied to the crossing coils 1A and 1B is fed back to the inverting terminal of the operational amplifier 21. , The detection signal voltage Vin is made to follow. The energizing circuit 4 of the auxiliary coil 3 is shown in FIG.
As shown in (2), the constant voltage of the Zener diode 47 connected in series with the current limiting resistor 48 is applied to the auxiliary coil 3.

According to this embodiment, in particular, the energizing circuit 4 of the auxiliary coil 3 can be simplified and the cost can be further reduced.

[0023]

Third Embodiment By the way, taking a boost meter as an example,
As shown in FIG. 4, in order to obtain good visibility, -200
It is necessary to swing the pointer 7 within a pressure range of mmHg to 400 mmHg within an angle range of 80 °. In this case, the voltage range of the detection signal for each pressure value is 1.89V to 3.06V as shown in FIG. 5, and the crossing coils 1A and 1B are
If the maximum exciting current IM of the above is set to about 50 mA,
1 is set to 62Ω, the coil current becomes 30.5 mA to 49.4 mA. In this case, the change in the exciting current is relatively small at 6.3 mA with respect to the change in pressure of 200 mmHg, and conventionally, the current range is expanded by the amplifier circuit to secure the indication resolution of the pointer.
However, this amplifier circuit requires various auxiliary circuits such as drift compensation in order to accurately expand and amplify a weak current range, and there is a problem in that the overall configuration becomes complicated.

In this embodiment, the exciting current range is expanded with an extremely simple structure without using an amplifier circuit. An example of the circuit is shown in FIG. In the figure, a voltage offset circuit 5 is provided on the input side of an operational amplifier 21 that constitutes the energizing circuit 2 for the crossing coils 1A and 1B described above, and the circuit 5 includes a resistor 51 and a resistor 51 provided on the input line of the detection signal Vin. It is composed of a diode 52, a resistor 55 and a pair of transistors 53 and 54 that form a current mirror circuit.

The current flowing through the resistor 55 I1 is to the resistance value RA, the base-emitter voltage of the transistor 53 as VBE, is constant at _{I 1 = (Vc-VBE)} / RA. On the other hand, the input voltage of the operational amplifier 21 is the collector-emitter voltage VCE of the transistor 54, and the resistor 51
The resistance value RB, the current through this forward voltage drop of I _2, the diode 52 as VF, VCE = Vin-
(I ₂ RB + VF). From the characteristics of the current mirror circuit, VCE is zero while I ₂ ≤I ₁ , and I ₂ is I ₁
Is saturated with. This is shown in FIG.

Here, after I ₂ is saturated with I ₁ , (I
The value of ( ₂ RB + VF) is set to 1.4V, and the value of the current detection resistor 23 is set to 33Ω which is about half of the above 62Ω. According to this, the crossing coils 1A, 1B
The exciting current value IM becomes IM = (Vin-1.4) / 33, and while the detection signal Vin voltage changes from 1.89V to 3.06V, IM becomes 14.8mA to 50.3mA,
The change range can be expanded to about twice.

The diode 52 shown in FIG. 6 cancels the temperature characteristic of VBE. Also, operational amplifier 2
The capacitor 7 provided on the first input line is for absorbing noise and is not particularly required.

[0028]

Fourth Embodiment By the way, as shown in FIG. 8, a detection signal from a booster pressure detecting device 91 composed of a booster pressure sensor 911 and an amplifier 912 is connected to another device in parallel with the energizing circuits 2 and 4 of the boost meter. It may be input to the control circuit 923 and the control circuit 923 may detect disconnection.
In this case, if the offset circuit 5 is composed of a current mirror circuit having a small input impedance as in the third embodiment, a problem may occur.

That is, in FIG. 8, the control circuit 923
Input line 924 has a pull-up resistor 9 between it and a 5V power supply.
21 is provided, and the voltage of the input line 924 (detection signal Vin voltage) is compared with the constant voltage of 4.5 V by the comparator 922. Then, for example, if the line is broken at the point x in the figure, the input line voltage becomes 5V and the comparator 9
Although the disconnection signal is issued from 22, if the input impedance of the energizing circuits 2 and 4 is small, the voltage of the input line 924 does not rise at the time of disconnection and the disconnection signal is not issued.

Therefore, as shown in FIG. 9, energizing circuits 2 and 4 are provided.
A high-impedance operational amplifier 21 directly receives the detection signal Vin input to the circuit 22. On the other hand, a diode 56 having a forward voltage drop of about 0.7 V is provided in series with the current detection resistor 23 connected to the emitter of the transistor 22.
A resistor 58 for current supply is provided between the emitter and the power source to form the voltage offset circuit 5.

However, if a voltage of 0.7 V is generated in the resistor 23 by the current supplied through the resistor 58, the offset voltage Vf (emitter voltage) becomes 1.4 V, and the detection signal voltage exceeds this. First cross coil 1
Current is supplied to A and 1B (FIG. 10). The resistance 7
2 and the capacitor 73 are RC filters.

[0032]

Fifth Embodiment Instead of the diode 56 and the current supply resistor 58 of the fourth embodiment, the voltage offset circuit 5 can be constituted by a constant current source 59 as shown in FIG.

[0033]

Sixth Embodiment Further, when the temperature characteristics of the diode are not a problem, as shown in FIG. 12, the diodes 56 and 57 having a forward voltage drop of 0.7 V are connected in series to simplify the voltage offset circuit. Can be configured to.

The resistor 71 is for absorbing a bias current.

[0035]

As described above, the cross-coil type meter driving device of the present invention is simple to manufacture, compact and inexpensive.

[Brief description of drawings]

FIG. 1 is a conduction circuit diagram of an apparatus according to a first embodiment of the present invention.

FIG. 2 is a magnetic field vector diagram.

FIG. 3 is a conduction circuit diagram of an apparatus according to a second embodiment of the present invention.

FIG. 4 is a schematic front view of a boost meter according to a third embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the detection signal voltage and the deflection angle of the pointer.

FIG. 6 is an energization circuit diagram of the device.

FIG. 7 is a graph showing a relationship between a detection signal voltage and a collector-emitter voltage.

FIG. 8 is a circuit diagram of a disconnection detection circuit of a control circuit provided in the energizing circuit according to a fourth embodiment of the present invention.

FIG. 9 is an energization circuit diagram of the device.

FIG. 10 is a graph showing the relationship between the detection signal voltage and the current supplied to the cross coil.

FIG. 11 is an energization circuit diagram of the device according to the fifth exemplary embodiment of the present invention.

FIG. 12 is a conduction circuit diagram of an apparatus according to a sixth embodiment of the present invention.

13 is a vertical cross-sectional view of the conventional device, which is taken along line XIII-XIII in FIG.
It is a line sectional view.

FIG. 14 is a plan view of a conventional device.

[Explanation of symbols]

 1A, 1B Crossing coil 2 Energizing circuit (first energizing means) 3 Auxiliary coil 4 Energizing circuit (second energizing means) 5 Voltage offset circuit

Claims (2)

[Claims] 1. A crossing coil wound so as to cross each other at right angles, a first energizing means for generating a variable magnetic field whose magnitude changes by energizing these crossing coils according to a detection signal, and the crossing coil. An auxiliary coil wound on top of the other and a second energizing means for energizing the auxiliary coil with a constant amount to generate a stationary magnetic field having a constant size are provided, and the variable magnetic field and the stationary magnetic field are combined. A cross-coil type meter drive device that rotates the meter pointer in the direction of the magnetic field. 2. The cross-coil type meter driving device further comprises means for offsetting the detection signal voltage by a fixed amount, and the first energizing means applies an exciting current proportional to the offset voltage value to the crossing current. The cross-coil type meter driving device according to claim 1, wherein the cross-coil type meter driving device is set to supply the coil.