JPH09159697A - Meter drive circuit for cross-coil type meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a pointer from swinging out by connecting one coil of a meter drive circuit in parallel with a Zener diode to provide a bypass circuit operating at a voltage higher than a predetermined level. SOLUTION: Coils L1, L2 are wound around a coil bobbin while intersecting perpendicularly. The coil L1 is connected through a resistor R with a power supply voltage Vcc and fed with a constant current I. The coil L2 is connected with a current type sensor providing a current corresponding to the power supply voltage Vcc and a measurement and a current Ic flows through the coil L2 when a current Is is provided from the current type sensor. A bypass circuit 2 comprises a Zener diode and connected in parallel with the coil L2 in the direction for blocking passage of current under normal voltage. When the resistance Rc of coil L2, the current Ih of coil L2 at full-scale, and the Zener voltage Vz are set to satisfy a relationship Vz<=Rc×Ih, the pointer does not swing out for any magnitude of current Is being fed from the sensor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a cross-coil meter, and more particularly to a meter drive circuit for a cross-coil meter that can prevent the pointer from swinging out.

[0002]

2. Description of the Related Art Conventionally, there is a cross-coil type meter as a meter used for a vehicle. In this meter, a disk-shaped magnet rotor is rotatably arranged in a coil bobbin, and a pointer shaft is fixed to the central portion of the magnet rotor. The pointer shaft projects from the coil bobbin and is provided at its tip. Is attached with a pointer. In the coil bobbin, the coils L1 and L2 are wound orthogonally, forming a meter drive circuit as shown in FIG.
The coil bobbin is housed in a case, and a scale plate is attached to the case body. Further, a meter stopper for preventing the pointer from swinging out is provided.

The cross-coil type meter constructed as described above is connected to a current type sensor for giving a current according to the measured quantity as shown in FIG. 4, and when the meter is switched on, the coil L1 is connected to the coil L1. Is supplied with a power supply voltage Vcc via a resistor R, and a constant current I flows. FIG. 5 is a vector diagram for explaining the operation of the pointer of this conventional cross-coil type meter, and the current I causes the coil L1 to generate a constant magnetic field φ1 (vector OL) as shown in the vector diagram of FIG. On the other hand, when the current of the current sensor is is, the current is flows through the coil L2. That is, as shown in the vector diagram of FIG. 5, the coil L2 generates the magnetic field φ2 in accordance with the magnitude of the current is, for example, as the vector OS1, OS2, OS3 from the smaller current to the larger current. The combined vector direction of φ2 and φ1 due to this current is is the direction of the pointer. When the sensor current is is zero, the magnetic field φ2 is zero and the pointer is at the OL position. When the sensor current is increases and the magnetic field φ2 is OS1, the pointer occupies the center position OM of the scale.・ The sensor current is is further increased and the magnetic field φ2 becomes OS2.
Then, the pointer indicates the full scale (OH position).

When such a cross-coil type meter is used for a vehicle, the output capability of the sensor is usually larger than the scale of the meter. Therefore, when the sensor current is is further increased, the magnetic field φ2 becomes O
At S3, the pointer will be shaken out, but the conventional device is provided with a meter stopper, and since it touches the meter stopper, it does not shake more than the stopper position. However, when the IGN is turned on, the loads in the vehicle start at the same time, so a current larger than the full scale of the meter may flow, the pointer may be shaken out, and it may hit the meter stopper strongly, causing idling between the pointer and the drive shaft.

Therefore, if the large current flowing when the IGN is turned on is set to the full-scale scale, then the deflection of the pointer becomes small during normal use, which is difficult to read and difficult to read.

[0006]

As described above, in the conventional vehicle-mounted cross-coil meter, when the ignition key is turned on and a large current flows, the pointer is shaken and hits the meter stopper strongly, and the drive shaft of the pointer is driven. There is a problem that the fixed position to the position is displaced, and in order to avoid it, the scale is difficult to read and difficult to read. According to the present invention, it is possible to provide a drive circuit for a cross-coil meter in which the scale is large and easy to read, and the pointer does not swing out.

[0007]

As a means for solving the above-mentioned problems, the present invention provides one coil with a bypass circuit which operates at a predetermined voltage or higher,
Specifically, the Zener diode is connected to one coil in parallel.

[0008]

With this structure, a current of full scale or more does not flow in the second coil, so that the fixed position of the pointer with respect to the drive shaft is displaced when the pointer strongly hits the meter stopper. It will never happen. Of course, the scale can be as large as the conventional one.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention.
3 will be described with reference to FIG. In FIG. 1, reference numeral 1 denotes a meter driving circuit of a cross coil type meter, and a coil L1 and a coil L2 are wound around a coil bobbin so as to be orthogonal to each other. The coil L1 is connected to the power supply voltage Vcc via the resistor R, and a constant current I flows through the coil L1. The coil L2 is connected to a current type sensor that gives a current according to the power supply voltage Vcc and the measured amount. When the current type sensor gives the current is, the current ic flows through the coil L2.
The bypass circuit 2 is composed of a Zener diode, and is connected in parallel to the coil L2 in a direction in which the passage of current is blocked at a normal voltage.

As described above, the Zener voltage of the Zener diode forming the bypass circuit of the meter drive circuit connected to the current type sensor is determined as follows. That is, the resistance of the coil L2 is Rc, the current is given by the current type sensor, and the coil L when the pointer indicates the full case.
If the current flowing through 2 is iH and the Zener voltage of the Zener diode is Vz, the current ic flowing through the coil L2 is
It becomes as shown in the following table.

[0011]

[Table 1]

Therefore, the Zener voltage Vz is Vz≤Rc
If xiH is set, no matter how large i _S becomes, ic will not exceed iH and the pointer will not rotate beyond the full scale.

Further, if the current flowing through the coil L2 when the pointer rotates until it comes into contact with the meter stopper is iA, if the zener voltage Vz is set to Vz≤Rc × iA, is becomes large. Even if ic is iA
The above never occurs, and the pointer does not come into contact with the meter stopper. From the above, if the Zener voltage V _Z is set to Rc × iH ≦ Vz ≦ Rc × iA (4), no matter how large is,
Since the pointer occupies a position between the full scale and the meter stopper, it is possible to avoid the pointer from colliding with the meter stopper. Therefore, the Zener voltage Vz of the Zener diode forming the bypass circuit
Is preferably set to satisfy equation (4). In particular, if the zener voltage Vz is set to Vz = Rc × iH, the pointer does not swing beyond the full scale no matter how large is.

FIG. 3 shows a second embodiment of the present invention. This embodiment is a meter drive circuit when the sensor is a voltage type sensor. 1 is a meter drive circuit, which is a coil L1
And that the coil L2 is wound around a coil bobbin at right angles to each other, and the bypass circuit 2 formed of a Zener diode is connected in parallel to the coil L2.
Is the same as A resistor RI is connected in series with the parallel circuit of the bypass circuit 2 and the coil L2. A voltage sensor is connected to one end of the coil L2 via a resistor RI, and the other end is grounded. This voltage type sensor provides a voltage vs according to the measured amount.

The operation of the Zener diode which constitutes the meter driving circuit constructed as described above is the same as that of FIG. 1, so the following explanation of the operation will be omitted.
The current ic flowing through the zener voltage is Vz ≦ Rc × i
If you set A, no matter how big vs becomes, i
c does not exceed iA and the pointer does not contact the meter stopper. Therefore, the Zener voltage is changed to Rci
If H ≦ Vz ≦ Rc × iA is selected, the pointer occupies a position between the full scale and the meter stopper regardless of how large vs becomes, and the pointer can be prevented from colliding with the meter stopper. .

[0016]

As described above, according to the present invention, in the meter drive circuit of the cross coil type meter having the cross coil composed of the first coil and the second coil, the one coil is operated at a predetermined voltage or more. Since a bypass circuit is provided, even if the sensor detects an excessive current or voltage, excessive current does not flow in the coil. It is possible to solve the drawback that the fixed position on the drive shaft is displaced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a meter drive circuit of a cross coil type meter that is a first embodiment of the present invention.

FIG. 2 is an is-ic diagram of the meter drive circuit of FIG.

FIG. 3 is a configuration diagram of a meter drive circuit of a cross-coil type meter that is a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a meter drive circuit of a conventional cross coil meter.

FIG. 5 is a vector diagram for explaining the operation of a pointer of a conventional cross coil meter.

[Explanation of Codes] 1 Meter drive circuit 2 Bypass circuit L1 by Zener diode First coil of cross coil L2 Second coil of cross coil

Claims (4)

[Claims] 1. A meter drive circuit of a cross coil type meter having a cross coil composed of a first coil and a second coil, wherein a bypass circuit operating at a predetermined voltage or more is provided in the one coil. A meter drive circuit for a cross coil meter. 2. The meter drive circuit for a cross coil meter according to claim 1, wherein the bypass circuit is a circuit in which a Zener diode is connected in parallel to the one coil. 3. The meter drive circuit for a cross-coil type meter according to claim 2, wherein the Zener voltage Vz of the Zener diode is Rc × iH ≦ Vz ≦ Rc × iA. 4. The meter drive circuit for a cross-coil meter according to claim 2, wherein the zener voltage Vz of the zener diode is Vz = Rc × iH.