JPH0638593A - Indicating instrument - Google Patents

Abstract

PURPOSE:To provide an indication device with an improved indication accuracy by preventing accumulation of indication errors. CONSTITUTION:An indication device is an analog-type speedometer 2 having a needle 11, and uses a stepping motor 12 as a drive source. A motor driving circuit 13 is connected to the motor 12. Based on a pulse signal from a control circuit 10, the motor driving circuit 13 operates to rotate the motor 12 to cause an indication by the needle 11. A signal produced by a rotation sensor 1 is input to an A-D converter 5 through a filter 3, and a resulting DC signal is input to the control circuit 10. In addition to the conventional functions, the control circuit 10 has a function of inputting, to the motor driving circuit 13 at the power-on of the indication device, a control signal that corresponds an angle larger than a maximum graduation angle of the needle 11 and serves to rotate the motor 12 toward the zero-point position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indicating instrument using a stepping motor, and more particularly to an indicating instrument in which a pointer is forcibly placed at a zero position when power is turned on.

[0002]

2. Description of the Related Art Conventionally, there is an indicator instrument that uses a stepping motor for the movement of a pointer.
With the recent development of digital technology, various control devices have been digitized, and a servo system is also digitized and used as an operating device for the stepping motor. The stepping motor is driven by a pulse signal, and a rotation angle according to the number of pulses is obtained based on the operating principle of the stepping motor, so sufficient accuracy can be obtained without providing feedback control. It is used.

FIG. 2 shows an example of a conventional indicating instrument for a vehicle using a stepping motor as a movement. As shown in the figure, the indicating instrument is an analog type speedometer 2 having a pointer 11, and a stepping motor 12 is used as a movement. A motor drive circuit 13 is connected to the stepping motor 12,
The motor drive circuit 13 is activated by the pulse signal from the control circuit 10, whereby the stepping motor 12 is activated.
Is rotated and displayed as an instruction of the pointer 11.

Further, the rotation sensor 1 is provided in the transmission (not shown).
Are arranged, and the signal obtained by the sensor 1 is input to the AD converter 5 via the filter 3.
The signal converted into direct current by the A / D converter 5 becomes an input signal to the control circuit 10.

In this state, the ignition switch (I
When GN) is turned on, the value detected by the sensor 1 is converted into a DC voltage by the AD converter 5 via the filter 3 and input to the control circuit 10. The control circuit 1
0 sends an output signal of the number of pulses corresponding to the input DC voltage value to the motor drive circuit 13, and the motor drive circuit 13 rotates the shaft 12a of the stepping motor 12 by an angle corresponding to the number of pulse signals. Therefore, the shaft 1 of the motor 12
Pointer 1 attached to 2a directly or via gears
1 is a character on the dial 15 corresponding to the detection value of the sensor 1.
Specify the scale, etc.

Then, when there is no change in the input signal value to the control circuit 10 once the pointer 11 is displayed as described above, a signal is sent from the control circuit 10 to the motor drive circuit 13, With the exciting coil of the stepping motor 12 excited, the stepping motor 12
I'm trying to hold it at that position. Especially when the stepping motor is a variable reluctance type, unless it is held, the rotor may rotate due to some cause such as slight vibration or moment of the pointer connected to the rotation shaft of the motor. is there.

When the input signal to the control circuit 10 changes,
The control circuit 10 obtains the difference between the display angle displayed by the pointer 11 at that time and the input signal value, and the number of pulses and the rotation direction required to move the pointer to the angle corresponding to the input signal value. Is calculated, and a pulse signal including the number of pulses and the rotation direction is supplied to the motor drive circuit 13. The motor drive circuit 13 drives the stepping motor 12 according to the number of supplied signal pulses and the rotation direction, and the pointer 1
Move 1 to the angle corresponding to the input signal value. Then, when the ignition switch is turned off and the power is turned off, the shaft 12a of the motor 12 is rotated by the action of the return spring or the like and stopped by the stoppers 16 and 17. At this position, the pointer 11 indicates the zero point position.

[0008]

However, in the above-mentioned structure, if the friction between the motor and the shaft increases, or if there is a catch for some reason, a step-out occurs and, for example, in a speedometer or the like. In some cases, the pointer indicates an incorrect number even though the actual speed becomes zero at the end of driving the vehicle. In this state, even if the power is turned off, the pointer may not be able to return to the zero position by the urging force of the return spring or the like. If the pointer is not returned to the zero position and the power is turned on and a new input pulse signal is applied to the motor, there is a problem that the motor operates with that position as the origin and an instruction error occurs.

An object of the present invention is to provide an indicating instrument which prevents the accumulation of pointing errors and improves pointing accuracy.

[0010]

According to the present invention, there is provided a stepping motor, a pointer interlocked with the rotating operation of the stepping motor, a motor drive circuit for inputting a pulse signal to the stepping motor to drive the rotation, and an input signal value. A control circuit for inputting a control signal to the motor drive circuit to rotate the motor forward and backward based on the above, and further, a stopper for stopping the rotation of the motor is provided at a position where the pointer indicates a zero point position. In the provided indicating instrument, when the indicating instrument is powered on, the control circuit outputs a control signal corresponding to an angle equal to or larger than the maximum scale angle indicated by the pointer and rotating the motor in the zero point position direction to the motor. The feature is that the input is made to the drive circuit.

[0011]

With the above-described structure, when a pulse signal is input from the control circuit to the motor through the motor drive circuit, the shaft of the motor rotates a predetermined angle according to the number of input pulse signals, and this movement In conjunction with this, the pointer indicates a scale or the like according to the number of input pulse signals. From this state, when the operation of the instrument ends, that is, when the power is turned off, the pointer is returned to the zero point position by the zero-returning means such as a return spring.
When the pointer reaches the zero position, it stops with the stopper.

[0012] Newly, when the power of the indicating instrument is turned on, the control circuit outputs a control signal corresponding to an angle equal to or larger than the maximum scale angle indicated by the pointer and rotating the motor in the direction of the zero point position. Input to the motor drive circuit. Therefore, even if the pointer does not return to the zero point position for some reason, it is forcibly returned to the zero point position.
Accumulation of instruction errors can be prevented.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. Note that the same or corresponding parts as those described in the related art are designated by the same reference numerals.

FIG. 1 is a block diagram of an indicating instrument according to an embodiment of the present invention. As shown in the figure, the indicator is an analog type speedometer 2 having a pointer 11.
Therefore, the stepping motor 12 is used as a movement. A motor drive circuit 13 is connected to the stepping motor 12, and the motor drive circuit 13 is actuated by a pulse signal from the control circuit 10, whereby the stepping motor 12 is rotated and displayed as an indication of a pointer 11. It

Further, a rotation sensor 1 is provided in a transmission device (not shown).
Are arranged, and the signal obtained by the sensor 1 is input to the AD converter 5 via the filter 3.
The signal converted into direct current by the A / D converter 5 becomes an input signal to the control circuit 10. In addition to the conventional function, the control circuit 10 has
A control signal that corresponds to an angle equal to or larger than the maximum scale angle indicated by the pointer 11 and that causes the motor 12 to rotate in the direction of the zero point is
Input is made to the motor drive circuit 13.

Therefore, the ignition switch (I
GN) is turned on and the indicating instrument is powered on, the motor 12 first reverses in the direction of the zero point position of the pointer 11, and the stopper 1
Stopping by 6 and 17, the pointer surely returns to the zero position. Next, the value detected by the sensor 1 is converted into a DC voltage by the AD converter 5 via the filter 3 and input to the control circuit 10. The control circuit 10 sends an output signal having a pulse number corresponding to the input DC voltage value to the motor drive circuit 13, and the motor drive circuit 13 rotates the shaft 12a of the stepping motor 12 by an angle corresponding to the pulse signal number. Therefore, the pointer 11 attached to the shaft 12a of the motor 12 directly or via a gear or the like is the sensor 1
The character, scale, etc. on the dial 15 corresponding to the detected value of are accurately designated. In this way, even if the pointer does not return to the zero point position for some reason, it is forcibly returned to the zero point position, and thus it is possible to prevent accumulation of pointing errors.

[0017]

As described above, according to the present invention,
Accumulation of pointing error of the pointing instrument due to open loop control can be prevented, so that pointing accuracy can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram of an indicating instrument according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional indicating instrument. 〇

[Explanation of symbols]

 10 Control Circuit 11 Pointer 12 Stepping Motor 13 Motor Drive Circuit 16, 17 Stopper

Claims (1)

[Claims] 1. A stepping motor, a pointer interlocked with the rotation operation of the stepping motor, a motor drive circuit for inputting a pulse signal to the stepping motor to drive the stepping motor, and a control for the motor drive circuit based on an input signal value. A control circuit for inputting a signal to rotate the motor forward and backward, further comprising a stopper for stopping the rotation of the motor at a position where the pointer indicates a zero point position, When the power of the indicating instrument is turned on, the control circuit inputs to the motor drive circuit a control signal corresponding to an angle equal to or larger than the maximum scale angle indicated by the pointer and rotating the motor in the direction of the zero point position. Indicating instrument characterized by the fact that