JPH0638597A - Indicating instrument - Google Patents

Abstract

PURPOSE:To provide an indicating instrument having a needle rotation detecting section. CONSTITUTION:An indicating instrument is an analog-type speedometer 2, 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. When the motor 12 rotates based on the pulse signal, a waveform of a current flowing through a coil of the motor 12 assumes a rectangular wave that corresponds to a waveform of an input pulse signal, and has peaks at shoulders. These peaks are extracted by a clipping circuit 15 and input to a detection circuit 16. Based on a resulting detection signal, it is judged whether the motor 12 is rotating correctly.

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 adapted to detect a rotational position of a rotating shaft of a motor based on a waveform component of a coil current of the stepping motor. .

[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. 3 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.
The rotating shaft 12a of 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, when an ignition switch (IGN) (not shown) is turned on, the value detected by the sensor 1 is converted into a DC voltage by the A / D converter 5 via the filter 3 and sent to the control circuit 10. Is entered. 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 motor 1
A pointer 11 attached to the second shaft 12a directly or via a gear or the like indicates a character, a scale, or the like on the dial 15 corresponding to the detection value of the sensor 1.

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 a slight vibration or a moment of a pointer or the like connected to the rotating shaft. .

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 rotation required to move the pointer to the angle corresponding to the input signal value. The direction 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.

[0008]

A stepping motor driven by such open loop control is released when the rotation of the stepping motor is temporarily stopped due to some physical factor such as a decrease in driving voltage or dust. The tone will occur. When the step-out occurs, there is a problem that the initial value of the control device is deviated and the pointer error of the instrument occurs.

An object of the present invention is to provide an indicating instrument equipped with a rotation detecting portion for a pointer.

[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. Based on, a control circuit for inputting a control signal to the motor drive circuit to rotate the motor in forward and reverse directions,
It is characterized in that the peak-shaped protrusion generated in the current waveform of the motor is clipped by a clipping circuit and input to a detection circuit to detect the rotational position of the rotary shaft of the motor.

Further, in addition to the above-mentioned configuration, the indicating instrument according to the present invention clips a peak-like protrusion generated in the current waveform of the motor with a clip circuit and inputs it to a detection circuit,
It is characterized in that the detected value obtained by detecting the rotational position of the rotary shaft of the motor is fed back to the control circuit to control the rotation of the motor.

[0012]

With the above configuration, when a pulse signal is input from the control circuit to the stepping motor via the motor drive circuit, the shaft of the motor rotates by a predetermined angle in accordance with the number of input pulse signals. In conjunction with the movement, the pointer indicates a scale or the like according to the number of input pulse signals. At this time, if the waveform of the pulse signal output from the control circuit is a square wave as shown in FIG. 2 (A), the waveform of the current flowing through the coil of the motor when the motor rotates is as shown in FIG. 2 (B). A peak-shaped protrusion is formed on the shoulder of the square wave. The projection is taken out by the clip circuit and input to the detection circuit to determine whether or not the rotation shaft of the motor has rotated by a predetermined angle. Furthermore, if this detected value is fed back to the control circuit, closed loop control can be performed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. In addition, the same reference numerals are given to the same or corresponding portions as those described in the related art.

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. From the control circuit 10 to the motor drive circuit 13, the stepping motor 12
The pulse signal input to is a square wave as shown in FIG. Note that FIG. 2A shows a sequence of the two-phase excitation method.

When the motor 12 is rotated by this input signal, the waveform of the current flowing through the coil of the motor 12 is shown in FIG.
As shown in (B), it becomes a similar square wave corresponding to the waveform of the input pulse signal, and a peak-shaped protrusion is generated on the shoulder of the waveform. As shown in FIG. 1, the clip circuit 15 inputs this protrusion to the detection circuit 16 to determine whether or not the rotary shaft 12a of the motor 12 has rotated by a predetermined angle.
Further, if the detected value obtained here is fed back to the control circuit 10, closed loop control can be performed.

In the present embodiment, a speedometer is described as the indicating instrument, but other than this, it can be applied to various things such as a tachometer, a thermometer, and a fuel gauge.

[0018]

As described above, according to the present invention,
Accumulation of pointing error of the pointing instrument 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. 2A is a diagram showing a sequence of input signal waveforms to the stepping motor, and FIG. 2B is a diagram showing a sequence of motor current waveforms corresponding to the input waveforms.

FIG. 3 is a block diagram of a conventional indicating instrument.

[Explanation of symbols]

 10 control circuit 11 pointer 12 stepping motor 13 motor drive circuit 15 clip circuit 16 detection circuit

Claims (2)

[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. In a indicating instrument equipped with a control circuit for inputting a signal to rotate the motor forward and reverse, a peak-shaped protrusion generated in the current waveform of the motor is clipped by a clipping circuit and input to a detection circuit to rotate the motor. An indicating instrument characterized in that the rotational position of the shaft is detected. 2. A stepping motor, a pointer interlocking 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 controlling the motor drive circuit based on an input signal value. In a indicating instrument equipped with a control circuit for inputting a signal to rotate the motor forward and reverse, a peak-shaped protrusion generated in the current waveform of the motor is clipped by a clipping circuit and input to a detection circuit to rotate the motor. An indicating instrument characterized in that the rotational position of the shaft is detected and the detected value is fed back to the control circuit to control the rotation of the motor.