JPH06109487A - Zero point returning mechanism of step motor type measuring instrument - Google Patents

Abstract

PURPOSE:To perform an accurate indication by starting a step motor from a zero point returning position constantly even if re-throwing after breaking during instruction of a power supply to a measuring instrument is performed halfway during returning to the zero point of a needle. CONSTITUTION:The mechanism is provided with a delay circuit 14 for delaying the excitation of a step motor type measuring instrument 1 with a whisper spring 6 for returning to zero point to a step motor 2 by the amount of time exceeding a returning time TM to the zero point or a point near it of a needle 5 from the power-off during instruction and then starting excitation to the step motor 2 for the first time after returning to the zero point even if the power is rethrown halfway during returning to the zero point of the needle 5 after the power-off.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an indicating instrument suitable for, for example, an automobile engine tachometer or a speedometer, which changes a measured quantity by indicating an angle of a pointer, and more particularly to a step motor type using a step motor as a drive source. It relates to a mechanism for returning the origin of the pointer of the instrument.

[0002]

2. Description of the Related Art Conventionally, in the zero-reset method in a step motor type instrument, that is, the pointer return-to-origin method, the step motor is rotated in the direction of a decrease instruction when the power switch is turned off, and the pointer stopper contacts the origin. The return to the origin is stopped by contact, and for example, the method disclosed in Japanese Patent Publication No. 62-462 or Japanese Patent Laid-Open No. 3-31722 is used. For example, as in Japanese Utility Model Laid-Open No. 64-2158, when the power switch is turned off or on, the step motor is subtractively rotated to return to zero by the full scale, and when the stopper is stopped at the origin position, it is installed at the origin position. The pointer is detected by the photo sensor and the initial position of the step motor drive circuit is reset with the position as the origin.

[0003]

By the way, in the above-mentioned conventional zero-reset system, a backup power-supply system for driving the step motor in reverse after the power-off is required as the zero-return operation accompanying the power switch being turned off. Instead, a circuit for zeroing is needed. Also, if such a zeroing is not performed when the power switch is turned off, and the initial setting operation that returns the full scale when the switch is turned on is performed, when the power switch is turned off when the instrument is instructing in the middle / high instruction range, the indicated position. There is a problem that the pointer will give meaningless instructions until the initial setting when the power is turned on again.

Instead of such an electric zeroing system, a zeroing structure using a simple whisker spring is conceivable. For example, the origin return spring disclosed in Japanese Utility Model Publication No. 3-10402 is used in the control field other than the instrument mechanism. It has been proposed to use it, but when it is used as an instrument, the power switch may be repeatedly turned on and off particularly as an instrument for automobiles (for example, at engine start at engine stall or while driving). When the power switch is turned on during zero return, the step motor control circuit resets the origin when the power is turned on. Becomes an indefinite part of the instruction range, and there is a problem that the instruction becomes inaccurate.

According to the present invention, the whistle spring is used to perform the origin return when the power of the step motor type instrument is turned off, and the reset operation when the power of the step motor control circuit is turned on does not work before the origin return. , Regardless of the timing of turning the power switch on and off, the reset at the origin position always works when the power is turned on.
The purpose is to be able to always give an accurate instruction from the origin position.

[0006]

SUMMARY OF THE INVENTION The present invention is a step motor type instrument for returning to the origin by means of a beard spring, which has a return time TM to the origin or near the origin by the beard spring when the power supply to the instrument drive circuit is turned off. When the return time TM from the predetermined indicated angle of the instrument is set, the power supply to the drive circuit or the signal supply from the drive circuit to the step motor is delayed for at least the return time TM after the power is turned on at least in the pointer return process after the power is turned off. It is characterized in that it is provided with a delay circuit.

[0007]

The step motor can be driven with a delay of the recovery time TM or more after the power is turned on, so that even if the power is turned on while the power switch is turned off and the whisker spring returns to zero while instructing. , The step motor does not operate until it returns to the origin by the delay circuit, and gives an accurate instruction with the origin as the instruction base point.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, an indicating instrument 1 has a well-known pointer rotating type graduation reading structure, in which a rotary output shaft 3 of a PM type step motor 2 is passed through a through hole of a graduated dial 4, and Stick the pointer 5 to the tip. The rotation output shaft 3 of the motor 2 has its outer end connected to the inner end of a whisker spring 6 fixed to the motor case so that the rotation output shaft 3 can be biased counterclockwise.

A pointer stopper 7 is placed at an arbitrary position on the dial 3 preceding the returning position of the rotation output shaft 3 by the beard spring 6.
Is erected and sets the rotation base point of the pointer 5. Beard spring 6
The return torque of the step motor 2 is larger than the detent torque of the step motor 2 and may be set so as not to impair the drive torque of the step motor 2 due to the exciting current. Since it is linked to the speed, the return time T of the pointer 5 to the origin, that is, the contact position with the pointer stopper 7 or the vicinity thereof is
It can be determined relatively easily and experimentally by the selection conditions of each part when designing the instrument.

Although the PM type of the step motor 2 is easy to control and understand, the internal structure thereof such as the yoke shape and the number of poles of the magnet may be arbitrarily selected. The step motor drive system is also the required level of the indicator characteristic of the instrument. You can choose freely. That is, in the case of a structure in which the number of yokes in the motor, that is, the number of steps per rotation is set finely in terms of mechanical structure, or a structure in which a reduction gear is provided internally to smoothly rotate the rotation output shaft 3, The drive signal system can also be controlled by simple phase control with a rectangular pulse. Also, the rotary output shaft 3
Is not limited to the number of structural steps depending on the number of yokes, and circuit processing for smoother movement, for example, JP-A-61-61
It can also be controlled by the so-called microstep drive disclosed in Japanese Patent No. 39,899.

In FIG. 1, a drive circuit 8 including an output transistor for supplying an excitation signal to a two-phase excitation coil in the step motor 2 is provided, and the drive circuit 8 is provided.
Is a phase control circuit for supplying a microstep signal to the exciting coil, an up-down counter or sin
A control circuit 9 including a wave ROM, a cos wave ROM, etc. is connected. As a basic operation, for example, when using this as a speedometer of an automobile, the frequency pulse signal from the vehicle speed sensor 10 is input and this is counted in a predetermined gate cycle, or the input signal cycle of the high frequency clock is counted. Then, the vehicle speed data for a predetermined period is obtained, the increase / decrease is compared with the vehicle speed data in the next cycle, and the step motor 2 is driven based on the ROM data corresponding to the difference.

A power supply voltage from a power supply 11 is supplied to a control circuit 9 and a drive circuit 8 for executing the above step drive through a power switch 12, and a pulse signal having a frequency proportional to a traveling speed from a vehicle speed sensor 10 is used. The vehicle speed is detected, the step motor 2 is driven, and the dial 4 is set by the pointer 5.
It is indicated by contrasting the scale above.

When the power supply voltage is turned off by turning off the power switch 12, the control circuit 9 and the drive circuit 8 are turned on.
Stops its operation, and the energization control of the step motor 2 is not performed either. In particular, the control circuit 9 is configured to perform an initial reset and normalize the operation when the power is turned on again because the logic circuit including the internal counter becomes indefinite.

When the control circuit 9 is composed of a microcomputer, the power switch 12 is controlled to be turned off by judging the off operation of the power switch 12 by continuously maintaining the operation with a temporary backup power source such as a capacitor. However, in order to make the operation thereof easy to understand, the control circuit 9 will be described as functioning only for the step drive of the step motor 2.

That is, in FIG. 2, on the negative side of the power switch 12, the state of the presence or absence of the power supply voltage is discriminated to determine the power switch.
A power supply detection circuit 13 that detects an on / off operation of 12 is connected. This power supply detection circuit 13 can be composed of a simple voltage comparison circuit using transistors or operational amplifiers, and a backup with a capacitor and a power supply 16
Supply by direct connection to.

When the power supply detection circuit 13 detects that the power supply switch 12 is off, a signal indicating that the power supply is off is generated and supplied to the delay circuit 14. The delay circuit 14 includes a power switch 12
Connected to the power supply line to the control circuit 9 and the drive circuit 8 from the power supply circuit 12, and is configured to supply the power supply voltage due to the ON operation of the power supply switch 12 to each of the circuits 8 and 9 with a delay of a fixed time. It can be composed of a combination of capacitors, transistors and relays.

The delay operation of the delay circuit 14 is performed by the power supply detection circuit 13
It is activated by the input of a power-off detection signal from, the internal transistor turns on the internal transistor after a certain period of time, for example, and the power supply voltage through the power switch 12 is supplied to the control circuit 9 and the drive circuit 8. This delay circuit 14
If the power supply detection circuit 13 is configured to be digitally judged by an AD conversion circuit, for example, a ladder resistor, as described above, it can be incorporated in the control circuit 9 in FIG. it can.

Further, the delay time by the delay circuit 14 may be appropriately determined depending on the use of the indicating instrument 1 and the restoring force of the whisker spring 6, and when it is used as a speedometer for an automobile, a steady use speed range, for example, 60 km / If it is set to the origin return by the whisker spring 6 from the indicated position of H by turning off the power, that is, the return time until reaching the pointer stopper 7, the power switch 12 is turned off to save gasoline at least during normal driving on a general road. Even if the power switch 12 is turned on by inertial driving or by causing an engine stall, the delay circuit 14 supplies the power supply voltage to the control circuit 9 from the power-off state until the pointer 5 returns to the origin. Is not performed and it can be supplied and driven only after returning to the home position, so the count process starting from the home position is always performed and So that the correct instruction is given.

That is, when the return time to the origin by the beard spring 6 due to the power off is T, the power supply voltage is supplied by the delay circuit 14 by at least the return time TM from the indicated angle of the normal use range of the instrument 1. By delaying the operation, the instruction error of the meter 1 caused by at least power-off for some reason in the normal use range and the subsequent power-on again, that is, a deviation of the instruction origin due to restarting during the return to the origin of the pointer 5 Can be prevented.

Further, the delay time (above the time TM) in the delay circuit 14 is set to the maximum deflection angle if it can occur in the maximum deflection angle range of the indicating instrument 1 based on the cause of the power supply being turned off. The time required to return to the origin by the beard spring 6 after the power is turned off is longer than that, and may be selected according to the purpose of use.

Further, in the above embodiment, the delay circuit
The power switch 12 and the control circuit 9 and the drive circuit 8 are provided with the power supply line 14 interposed therebetween. For example, an excitation signal supply line from the drive circuit 8 to the step motor 2 or a signal from the control circuit 9 to the drive circuit 8 is provided. By arranging a signal gate circuit in the line and configuring this circuit as a delay circuit that delays the signal transmission to the step motor 2 for a certain period of time, it is possible to similarly start the instrument after completion of the origin return. is there.

That is, in the returning operation by the whisker spring 6 when the power is turned off, even if the power is turned on again before the pointer 5 is returned to the origin of the pointer stopper 7, the counting operation and the frequency dividing operation in the control circuit 9 are performed. A signal is not supplied to the step motor 2 only by performing it, and the step motor 2 is excited only after the delay time TM. As a result, an accurate instruction by a correct step operation starting from the origin is obtained. . In this case, if the number of mechanical structural steps of the step motor 2, that is, the number of yokes is small, it is easy to give a step instruction up to a measurement value by microstep operation at the step interval, and the number of yokes is large and simple. In the case of a structure in which a mechanical pulse step is performed, the input signal count value at the time of exciting the step motor 2 in the control circuit 9 may be directly supplied as the number of steps without performing difference calculation processing by comparison. Good. In the case of such pulse step driving, it is preferable that the rotation output shaft 3 and the pointer 5 are connected by a reduction gear.

The delay time by the delay circuit 14 after the power is turned off reaches the origin by setting the yoke of the step motor 2 in addition to the setting based on the return time of the pointer stopper 7 to the origin position as in the above embodiment. It may be based on the return time to the vicinity of the previous origin. That is, it is preferable that the yoke position of the step motor 2 is arranged in synchronism with the origin position of the pointer 5 by the pointer stopper 7 on the dial plate 4. In this case, the pointer 5 starts from the origin and the control circuit 9 is started.
The starting point required to be activated by means of is only necessary to make a return rotation to a position where the magnetic pole of the rotary magnet in the step motor 2 is attracted by the yoke located at a position synchronized with the origin. If the return to a position close to the former yoke between the synchronized yokes and the adjacent yokes on the rising side is achieved, immediately after that, for example, the power is turned off and then back on completely. Even if it is done, since the starting point of the step motor 2 is the origin, the delay time from when the power is turned off until the step motor 2 is re-excited is the return time T from when the power is turned off until the pointer 5 returns to the origin or near the origin.
It is sufficient to set M or more.

[0024]

According to the home-return mechanism of the present invention, the power supply voltage to the control drive circuit in the step motor type instrument is turned off for some reason and the power is turned on again while the pointer returns to its home position by the whisker spring. Even if it becomes a state, it is possible to always start with the origin of the instrument as the starting point without shifting to the step operation with that position peculiar to the step motor as a base point, and unexpected power supply interruption or re-input occurs. Also, there is an effect that an accurate instruction can be given without causing a large error in the instrument instruction.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of the present invention.

FIG. 2 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1 indicator 2 step motor 3 rotation output shaft 4 dial 5 pointer 6 whisker spring 7 pointer stopper 8 drive circuit 9 control circuit 10 vehicle speed sensor 11 power supply 12 power switch 13 power supply detection circuit 14 delay circuit

Claims (3)

[Claims] 1. A rotation angle of a pointer, comprising a drive circuit for bidirectionally driving a step motor according to an increase / decrease of an input signal, and a pointer fixed to an output shaft of the step motor directly or through a reduction mechanism. In a step motor type instrument that indicates the magnitude of the input signal by means of a whisker spring, connect both ends of the step motor output shaft to the fixed side of the motor housing, etc., and return to the origin of rotation of the pointer together with the output shaft. And a return time TM from a predetermined indicated angle of the instrument having a return time T to the origin or near the origin due to the whisker spring accompanying the power-off to the instrument drive circuit,
A step motor type characterized by including a delay circuit for delaying the power supply to the drive circuit or the signal supply from the drive circuit to the step motor for at least the recovery time TM at least after the power is turned on in the pointer return process after the power is turned off. Return-to-origin mechanism for instruments. 2. The predetermined indication angle is the maximum indication angle of the instrument, and the delay time from power-on at least in the needle return process after power-off is set to be equal to or longer than the return time TM from the maximum indication angle. The return-to-origin mechanism of a step motor type instrument according to claim 1. 3. An origin of rotation of the pointer in the instrument and one of the excitation magnetic poles of the step motor are made to substantially coincide with each other, and up to an intermediate angle between the adjacent excitation magnetic pole on the pointer raising side and the origin side magnetic pole. 2. The origin return mechanism for a step motor type instrument according to claim 1, wherein power supply to the drive circuit or signal supply from the drive circuit to the step motor is delayed for a recovery time TM or more.