JP4825588B2 - Stepper motor device and stepper motor control method - Google Patents

Description

  The present invention relates to a stepper motor device and a stepper motor control method, and more particularly to a stepper motor device that drives a pointer and a stepper motor control method.

  2. Description of the Related Art Conventionally, for example, a vehicle indicating device is known as a device using the above-described stepper motor device. This indicating device includes a dial plate provided with a scale indicating the measurement values of various sensors such as a speed sensor, and a pointer indicating the scale on the dial plate, and a stepper motor is used as a movement for driving the pointer. ing.

  This stepper motor device supplies a drive signal that changes periodically, and periodically changes the excitation state of the excitation coil in the stepper motor, thereby generating rotational torque in the magnet rotor surrounded by the excitation coil. Rotate the stepper motor.

  Specifically, the stepper motor device supplies a drive signal for a phase corresponding to a movement amount (θ−θ ′), which is the difference between the current position θ ′ of the pointer and the target indication position θ, to the stepper motor, and the movement amount The stepper motor is rotated by (θ−θ ′). The current position θ ′ of the pointer and the target indication position θ are stored in a memory in the stepper motor device. The stepper motor device updates the current position θ ′ of the pointer based on the drive signal supplied to the stepper motor, and updates the target indication position θ based on the measurement values from various sensors. As a result, the pointer indicates the measured value on the dial.

  By the way, the above-described pointing device has a movement amount (θ−θ ′) to which the pointer should move due to the input of measurement values from various sensors on which vehicle vibration or noise is superimposed, and the actual movement. It may cause a step-out with a different amount. If this step-out is repeated, the current position θ ′ of the pointer stored in the memory is different from the current position of the pointer on the dial plate, and an accurate instruction cannot be performed.

  Therefore, in order to solve such a problem, a stepper motor is provided with a piece and a stopper. The piece is, for example, a convex portion provided on a gear on the pointer side for transmitting the rotation of the stepper motor to the pointer, and rotates in conjunction with the stepper motor. The stopper abuts against the piece and mechanically stops the rotation of the stepper motor. This stopper is provided so that the pointer indicates the measured value 0 (= initialization position) when it comes into contact with the piece.

  Then, each time the power is turned on, the stepper motor device supplies a drive signal to the stepper motor so that the stepper motor rotates in the return direction toward the stopper, thereby forcing the piece into contact with the stopper. Perform initialization. This forcibly stops the pointer at the measured value 0. The stepper motor device also resets the current position θ ′ in the memory to the measured value 0.

  By the above initialization operation, when the current position θ ′ stored in the memory is reset to the measured value 0, the pointer on the dial also indicates the measured value 0. Therefore, the pointer stored in the memory The error between the current position θ ′ and the current position of the pointer on the dial can be reset. In addition, the operation of the pointer can be started from the measured value 0 every time the power is turned on.

  By the way, the timing when the power supply to the stepper motor device is started is not only when the ignition switch is turned on. In addition, there is a timing at which the power-on is temporarily interrupted due to a decrease in the battery voltage accompanying the cranking, and then the battery voltage is restored and the power is turned on again. Immediately before the momentary power interruption due to cranking, the guidelines used in fuel gauges and the like often already indicate a somewhat large measured value.

Therefore, conventionally, the current position θ ′ of the pointer stored in the memory is held immediately before the momentary power interruption due to cranking, and the measured value 0 from the current position θ ′ of the pointer is restored when the power is turned on thereafter. It is considered that the stepper motor is rotated in the return direction by the difference up to (for example, Patent Documents 1 and 2). Thereby, the operation of the pointer can be started from the measured value 0 even when the power is turned on after the instantaneous interruption.
JP 2003-189694 A JP 2004-53553 A

  However, as shown in FIG. 4, when the stepper motor rotates at a high speed in the forward rotation direction opposite to the return direction, an instantaneous power interruption occurs, and the drive signal supply to the stepper motor is interrupted. Then, the rotation of the stepper motor does not stop immediately, but stops after a positive rotation for a while due to the inertial force.

  That is, as the current position θ ′ of the pointer stored in the memory, the pointer indicating position θ1 when the power supply is interrupted and the supply of the drive signal to the stepper motor is interrupted is stored. On the other hand, the indication position of the pointer on the dial plate is a position (θ1 + Δθ) on the forward rotation direction side from the indication position θ1 by the error angle Δθ rotated by the inertial force.

  Therefore, as described above, even if the stepper motor is rotated in the return direction by the difference from the current position θ ′ of the pointer stored in the memory immediately before the momentary interruption to the measured value 0, the pointer remains at the measured value 0. There is a problem in that the movement of the pointer cannot be started from the measured value 0 because it stops at the position where the measured value 0 is rotated forward by the error angle Δθ without reaching.

  Further, as a countermeasure for the above problem, for example, a method of supplying a drive signal for rotating the stepper motor in the return direction by the maximum deflection angle of the pointer after the return from the momentary interruption can be considered. However, if the position of the pointer on the dial plate immediately before the momentary break is close to the measured value 0, even if the pointer reaches the measured value 0, the drive signal in the return direction continues to be supplied to the stepper motor and the pointer bounces. The time to do will become longer, and the appearance will deteriorate.

  Therefore, the present invention pays attention to the above-described problems, and a stepper motor device capable of reliably returning the pointer to the initialization position where the piece and the stopper come into contact with each other even when the power is restored after a momentary power interruption. It is an object of the present invention to provide a method for controlling a stepper motor.

  In order to solve the above-mentioned problem, the invention according to claim 1 is in contact with a stepper motor that rotates in response to a drive signal to drive a pointer, and a driven member that interlocks with the rotation of the stepper motor. In a stepper motor device comprising a stopper for mechanically stopping the rotation of the stepper motor to forcibly stop the pointer at an initialization position, and a memory means for storing the current position of the pointer, An acquisition means for acquiring the current position of the pointer stored in the memory means immediately before, and an initial position of the pointer and the initial position of the pointer acquired by the acquisition means when the power is turned on again after the instantaneous power interruption. A first initialization for supplying the drive signal to the stepper motor so that the driven member rotates in a return direction in which the driven member moves toward the stopper by a difference from the shift position. And a speed detecting means for detecting the rotational speed or rotational acceleration of the stepper motor immediately before the momentary power interruption, and the rotational speed or the rotation when the power is turned on again after the momentary power interruption. A stepper motor apparatus comprising: a second initialization drive unit that supplies the drive signal to the stepper motor so that the stepper motor rotates in the return direction by a correction amount corresponding to an acceleration.

  According to the first aspect of the present invention, the second initialization drive means includes a stepper motor in the return direction by a correction amount corresponding to the rotational speed or rotational acceleration in addition to the difference between the current position of the pointer and the initialization position of the pointer. Since the drive signal is supplied to the stepper motor so as to rotate, the error angle caused by the inertia after the recovery from the momentary interruption can be corrected by the correction amount corresponding to the rotation speed or the rotation acceleration.

  According to a second aspect of the present invention, there is provided a rotation direction detecting means for detecting a rotation direction of the stepper motor immediately before the instantaneous power interruption, and a second initialization driving means when a return direction is detected by the rotation direction detecting means. The stepper motor device according to claim 1, further comprising stop means for stopping the supply of the drive signal.

  According to the second aspect of the present invention, since the stop means stops the supply of the drive signal by the second initialization drive means when the return direction is detected by the rotation direction detection means, the driven member and the stopper are in contact with each other. It is possible to shorten the time during which the drive signal in the return direction is continuously supplied after the contact.

  According to a third aspect of the present invention, the rotation of the stepper motor starts when the second initialization drive means stops supplying the drive signal to the stepper motor rotating at the detected rotational speed or rotational acceleration. 3. The stepper motor device according to claim 1, further comprising a correction amount setting unit that sets the movement amount of the pointer until the stop is set to the correction amount. 4.

  According to the third aspect of the present invention, the rotation of the stepper motor is started when the correction amount setting means stops supplying the drive signal to the stepper motor that rotates in the direction opposite to the return direction based on the rotational speed or the rotational acceleration. Estimate the movement amount of the pointer until it stops, and set the estimated movement amount as the correction amount, so that the error angle caused by the inertia that occurs after recovery from the momentary interruption is corrected with the correction amount. Can do.

  According to a fourth aspect of the present invention, when the power is turned on again after the instantaneous power interruption, the drive signal is supplied to the stepper motor so that the stepper motor further rotates in the return direction by a predetermined angle. The stepper motor device according to claim 1, further comprising a drive unit.

  According to the invention described in claim 4, the third initialization drive means is configured so that the stepper motor rotates in the return direction by a predetermined angle in addition to the difference between the current position of the pointer and the initialization position of the pointer and the correction amount. Since the drive signal is supplied to the stepper motor, even if the pointer has stepped out due to vibration or the like, the stepping out part is canceled by the rotation of the stepper motor in the return direction by a predetermined angle.

  The invention according to claim 5 is a method for controlling a stepper motor that drives a pointer by supplying a drive signal, and is stored in the memory means immediately before the instantaneous power interruption when the power is turned on again after the instantaneous power interruption. The difference between the current position of the pointer and the initialization position that is the indicated position of the pointer at the contact position with the stopper of the driven member interlocked with the rotation of the stepper motor, and the stepper immediately before the instantaneous power interruption A setting step of setting a value obtained by adding a correction amount corresponding to the rotational speed or rotational acceleration of the motor as a return movement amount, and the stepper in the return direction in which the driven member moves toward the stopper by the return movement amount. The stepper motor control method further includes an initialization drive step of sequentially supplying the drive signal to the stepper motor so that the motor rotates.

  According to the fifth aspect of the present invention, the stepper motor rotates in the return direction by the return movement amount set to the value obtained by adding the difference between the current position of the pointer and the initialization position of the pointer and the correction amount. Since the drive signal is supplied to the stepper motor, it is possible to correct the error angle caused by the inertia generated after the recovery from the momentary interruption by the correction amount corresponding to the rotation speed or the rotation acceleration.

  As described above, according to the inventions of claims 1 and 5, the error angle caused by the inertia generated after the recovery from the momentary interruption can be corrected by the correction amount according to the rotational speed or the rotational acceleration. Even when the power is restored after a momentary power interruption, the pointer can be reliably restored to the initialization position where the piece and the stopper come into contact.

  According to the second aspect of the present invention, it is possible to shorten the time during which the drive signal is continuously supplied in the return direction after the driven member and the stopper come into contact with each other, so that an unnatural behavior of the pointer occurs. There is no.

  According to the third aspect of the invention, the error angle caused by the inertia generated after the recovery from the momentary interruption can be reliably corrected by the correction amount. The pointer can be returned to the initialization position where the piece and the stopper abut.

  According to the fourth aspect of the present invention, even if there is a step out of the pointer due to vibration or the like, the step out is canceled by the rotation of the stepper motor in the return direction by a predetermined angle. Even if it occurs, the pointer can be returned to the initialization position where the piece and the stopper abut without using the position detecting means for detecting the abutment between the stopper and the pointer.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an electric circuit diagram showing a pointing device incorporating a stepper motor device that implements the stepper motor control method of the present invention. 2 is an exploded perspective view of the pointing device shown in FIG. The pointing device includes a pointer 1 and a stepper motor device 2 that drives the pointer 1. The pointer 1 is provided on a dial (see FIG. 2) provided with a scale indicating a measurement value of a sensor such as a speed sensor.

  The stepper motor device 2 includes a stepper motor 3 and a driving device 4 that rotates the stepper motor 3. The stepper motor 3 described above includes two excitation coils 5 and 6, a magnet rotor 7 that rotates following changes in the excitation state of the excitation coils 5 and 6, and a gear 8 that transmits the driving force of the magnet rotor 7 to the pointer 1. And a case (not shown).

  The magnet rotor 7 is provided in a disk shape, and N poles and S poles are alternately magnetized by 5 poles along the outer periphery thereof. The gear 8 includes three gears that mesh with each other. One of the three gears 8 is fixed to the rotating shaft of the magnet rotor 7, and one is fixed to the rotating shaft of the pointer 1. The remaining one is provided between the gear fixed to the magnet rotor 7 and the gear fixed to the pointer 1.

  The stepper motor device 2 includes a piece 9 as a driven member that interlocks with the rotation of the stepper motor 3 and a stopper 10 that abuts the piece 9 and mechanically stops the rotation of the stepper motor 3. The piece 9 is protrudingly provided on the other side of the gear 8 that is fixed to the rotating shaft of the pointer 1. The stopper 10 is protruded from the case. The pointer 1 is driven into the rotary shaft of the stepper motor 3 so that the pointer 1 indicates a measured value 0 (initialization position) on the scale provided on the dial when the piece 9 and the stopper 10 are in contact with each other. It is.

  Hereinafter, the rotation of the stepper motor 3 in which the piece 9 faces the stopper 10 is defined as a return direction. On the other hand, the direction opposite to the return direction, that is, the rotation of the stepper motor 3 in which the piece 9 is separated from the stopper 10 is defined as the forward rotation direction.

  Next, the configuration of the driving device 4 will be described. The drive device 4 includes a microcomputer 11 (hereinafter referred to as μCOM 11) connected to the excitation coils 5 and 6. The μCOM 11 includes a central processing unit (CPU) 12 that performs various processes according to a program, a ROM 13 that is a read-only memory that stores a processing program performed by the CPU 12, a work area that is used in various processing processes in the CPU 12, The RAM 14 is a readable / writable memory having a data storage area for storing various data.

  The above-described μCOM 11 rotates the stepper motor 3 by supplying pulsed drive signals whose duty changes periodically to the excitation coils 5 and 6, respectively. The drive signals supplied to the excitation coils 5 and 6 are 90 degrees out of phase with each other.

  Further, the above-described μCOM 11 is connected to an EEPROM 15 which is a nonvolatile memory means and an ignition switch (not shown). Further, the above-described μCOM 11 is inputted with a target indication position θi which is a sensor measurement value.

  In the above-described EEPROM 15 or ROM 13, an error angle generated due to inertia is stored for each frequency of the drive signal that is a value corresponding to the rotation speed or the rotation acceleration. The error angle refers to the pointer 1 from when the supply of the drive signal to the stepper motor 3 rotating at the rotational speed or rotational acceleration is stopped until the rotation of the stepper motor 3 due to the inertia of the pointer 1 or the gear 8 is stopped. The amount of movement.

  The error angle generated by cutting off the drive signal for the stepper motor 3 during low-speed rotation is small. On the other hand, the error angle generated by blocking the drive signal for the stepper motor 3 during high-speed rotation is large. Therefore, as the error angle, a larger value is stored as the frequency of the drive signal is higher.

  The operation of the pointing device having the above-described configuration will be described. As already described in the background art, the CPU 12 supplies a drive signal to the stepper motor 3 so that the stepper motor 3 rotates in the return direction in response to power-on in response to turning on the ignition switch. 9 is forcibly brought into contact with the stopper 10 and an initializing operation at the time of resetting the current position θ ′ of the pointer 1 in the memory (RAM 14 or EEPROM 15) to the measured value 0 is performed.

  Thereafter, the CPU 12 performs a normal driving process to instruct the pointer 1 to measure the value on the dial scale. In the normal drive process, the CPU 12 outputs a drive signal for a phase corresponding to a movement amount (θi−θ ′), which is a difference between the current position θ ′ of the pointer 1 and the target indication position θi stored in the RAM 14. 3 and the stepper motor 3 is rotated by the amount of movement (θi−θ ′).

  At the same time, the CPU 12 functions as an updating means, and updates the current position θ ′ of the pointer 1 in the memory (RAM 14 or EEPROM 15) based on the drive signal supplied to the stepper motor 3 every predetermined time. Note that the current position θ ′ of the pointer 1 is represented by the difference between the current position of the pointer 1 and the measured value 0. As a result, the pointer 1 indicates the measured value on the dial.

  At the same time, the CPU 12 updates the frequency of the drive signal supplied to the stepper motor 3 every predetermined time as the current frequency stored in the memory (RAM 14 or EEPROM 15). The frequency of the drive signal is a value corresponding to the rotational speed or rotational acceleration of the stepper motor 3.

  Thereafter, when the ignition switch is turned off, the CPU 12 ends the normal driving process and supplies a drive signal to the stepper motor 3 so that the stepper motor 3 rotates in the return direction, forcing the piece 9 into the stopper 10. And an initialization operation at the time of shut-off that resets the current position θ ′ of the pointer 1 in the memory (RAM 14 or EEPROM 15) to the measured value 0, and then the power is shut off. If there is a momentary interruption due to cranking, this shut-down initialization operation is not performed.

  In addition, the CPU 12 starts the initialization process at the time of return in response to the power return from the power interruption due to cranking. Note that the distinction between the power-on by ignition-on and the recovery from the momentary interruption is made based on the current position θ ′ of the pointer 1 stored in the memory (RAM 14 or EEPROM 15) at the time of power-on, for example. That is, when the current position θ ′ of the pointer 1 stored in the memory (RAM 14 or EEPROM 15) is not the measured value 0, it is determined that the return from the momentary interruption.

  The operation of the pointer device in the return initialization process described above will be described below with reference to FIG. FIG. 3 is a flowchart showing a processing procedure in the return initialization process of the CPU 12 constituting the pointing device shown in FIG. First, the CPU 12 functions as an acquisition unit, and acquires the current position θ ′ of the pointer 1 stored in the memory (RAM 14 or EEPROM 15) as the current position θ ′ of the pointer 1 stored in the EEPROM 15 immediately before the momentary power interruption. An acquisition process is performed (step S1).

  Next, the CPU 12 functions as a rotation direction detection unit, and performs rotation direction detection processing for detecting the rotation direction of the stepper motor 3 immediately before the momentary power interruption (step S2). The CPU 12 detects the rotational direction based on the comparison between the current position θ ′ of the pointer 1 and the target position θi of the pointer 1 stored in the memory (RAM 14 or EEPROM 15). If the target position θi is on the forward direction side with respect to the current position θ ′, the CPU 12 detects rotation in the forward direction. If the target position θi is on the return direction side of the current position θ ′, the CPU 12 detects rotation in the return direction.

  Next, the CPU 12 functions as speed detection means, and performs speed detection processing for detecting the current frequency stored in the memory (RAM 14 or EEPROM 15) as the rotation speed or the rotation acceleration of the stepper motor 3 immediately before the momentary power interruption ( Step S3).

  Next, when the CPU 12 detects the rotation in the return direction by the rotation direction detection process (Y in step S4), the CPU 12 stores the pointer 1 stored in the memory (RAM 14 or EEPROM 15) immediately before the instantaneous power interruption acquired in the acquisition process. After the current position θ ′ is set to the reverse rotation angle (step S5), the process proceeds to the next step S6.

  On the other hand, when the CPU 12 detects the rotation in the forward rotation direction by the rotation direction detection process (N in step S4), the memory detected as the rotation speed or the rotation acceleration of the stepper motor 3 immediately before the instantaneous power interruption in the speed detection process ( It is determined whether or not the current frequency stored in the RAM 14 or the EEPROM 15) is below a predetermined value (step S7). The predetermined value is set to a fraction of the maximum response frequency of the stepper motor 3, for example, 1/2 or 1/3 (for example, 100 to 200 ° / sec).

  If the CPU 12 determines that the value is equal to or less than the predetermined value (Y in step S7), the rotation speed or the rotation acceleration of the stepper motor 3 immediately before the momentary power interruption is very slow, so that an error angle due to inertia has not occurred, and step S5 is performed. Proceed to

  On the other hand, if it is determined that the value is larger than the predetermined value (N in step S7), the CPU 12 functions as a correction amount setting means, and an error caused by inertia corresponding to the current frequency that is a value corresponding to the rotational speed or rotational acceleration. A correction value setting process for reading the angle from the memory (RAM 14 or EEPROM 15) and setting it as the correction amount Δθ is performed (step S8).

  Next, the CPU 12 adds the amount obtained by adding the current position θ ′ of the pointer 1 stored in the memory (RAM 14 or EEPROM 15) and the correction amount Δθ acquired immediately before the instantaneous power interruption acquired in the acquisition process to the reverse rotation angle (= return). After performing the setting process to set (movement amount) (step S9), the process proceeds to step S6.

  In step S <b> 6, the CPU 12 supplies a return direction driving signal to the stepper motor 3. Then, the CPU 12 determines whether or not it has rotated in the return direction by the reverse rotation angle set in steps S5 and S9 (step S10). The CPU 12 waits for the rotation in the return direction corresponding to the reverse rotation angle to end (Y in step S10), and then proceeds to step S11.

  In step S11, the CPU 12 functions as a third initialization drive unit, performs a third initialization drive process for supplying a drive signal so that the stepper motor 3 rotates in the return direction by a predetermined angle, and then performs the normal drive process. Is started (step S12), and the return initialization drive process is terminated.

  According to the above operation, when the process proceeds from step S5 to steps S6 and S10, the CPU 12 sets the current position θ ′ of the pointer 1 stored in the memory (RAM 14 or EEPROM 15) immediately before the instantaneous power interruption as the reverse rotation angle. The stepper motor 3 rotates in the return direction by the current position θ ′ of the pointer 1. As described above, the current position θ ′ of the pointer 1 is represented by the difference between the current position of the pointer 1 and the measured value 0 that is the initialization position of the pointer 1. That is, the CPU 12 supplies a drive signal to the stepper motor 3 so that the stepper motor 3 rotates in the return direction by the difference between the current position of the pointer 1 and the measured value 0 which is the initialization position of the pointer 1. It works as the first initialization drive means in the section.

  On the other hand, when proceeding from steps S7 to S9 to steps S6 and S10, the CPU 12 adds the current position θ ′ of the pointer 1 stored in the memory (RAM 14 or EEPROM 15) immediately before the instantaneous power interruption and the correction amount Δθ. (Θ ′ + Δθ) is set as the reverse rotation angle, and the stepper motor 3 rotates in the return direction by (θ ′ + Δθ). That is, the CPU 12 supplies a drive signal for rotating the stepper motor 3 in the return direction by the current position θ ′ of the pointer 1, and a drive signal for rotating the stepper motor 3 in the return direction by the correction amount Δθ. Supply is also performed, and the first and second initialization driving means in the claims are served.

  According to the above instruction device, the drive signal is sent to the stepper motor 3 so that the CPU 12 rotates the stepper motor 3 in the return direction by the correction amount Δθ corresponding to the rotational speed or rotational acceleration in addition to the current position θ ′ of the pointer 1. Therefore, the error angle Δθ due to the inertia generated after the recovery from the momentary interruption can be canceled by the correction amount Δθ corresponding to the rotation speed or the rotation acceleration. Therefore, if there is no out-of-step of the pointer 1 due to vibration or the like, the pointer 1 can be returned to the measured value 0 at which the piece 9 and the stopper 10 come into contact with each other at the time of Y in step S10. As a result, the pointer 1 is not completely returned to the measured value 0, and the display of the pointer 1 is not shifted, thereby causing no discomfort.

  Further, when a momentary interruption occurs while the stepper motor 3 is rotating in the return direction and the drive signal is interrupted, an error angle Δθ due to inertia occurs in the return direction. For this reason, if the rotation direction of the stepper motor 3 immediately before the momentary power interruption is the return direction, a drive signal for rotating the stepper motor 3 in the return direction by the amount of (θ ′ + Δθ) after the return from the momentary interruption is output. After the piece 9 and the stopper 10 come into contact with each other and the rotation of the stepper motor 3 is mechanically stopped, a drive signal in the return direction of 2Δθ is further supplied. For this reason, after the piece 9 and the stopper 10 contact | abut, the time which the drive signal in a return direction continues being supplied becomes long.

  Therefore, in the present embodiment, the CPU 12 functions as a stop unit, and stops supplying the drive signal in the return direction by the correction amount Δθ when the return direction is detected by the rotation direction detection process. For this reason, the time during which the drive signal in the return direction continues to be supplied after the piece 9 and the stopper 10 abut can be shortened, and an unnatural behavior occurs in which the pointer 1 swings around the measured value 0. There is no.

  Further, the CPU 12 supplies a drive signal to the stepper motor 3 so that the stepper motor 3 rotates in the return direction by a predetermined angle (for example, about 10 °) in addition to the current position θ ′ of the pointer 1 and the correction amount Δθ. Even if the pointer 1 is out of step due to vibration or the like, the step out is canceled by the rotation of the stepper motor 3 in the return direction by a predetermined angle. For this reason, an expensive mechanical (optical) sensor is provided to detect the contact between the piece 9 and the stopper 10, or the rotation of the stepper motor 3 is detected based on the presence or absence of an induced voltage generated in the excitation coils 5 and 6. The pointer 1 can be returned to the measured value 0 at which the piece 9 and the stopper 10 come into contact with each other.

  In the above-described embodiment, when the rotation direction of the stepper motor 3 immediately before the instantaneous power interruption is the return direction, the supply of the drive signal in the return direction corresponding to the correction amount Δθ is stopped. Is not limited to this. For example, a drive signal in the return direction corresponding to the correction amount Δθ may be supplied regardless of whether the rotation direction of the stepper motor 3 immediately before the momentary power interruption is the return direction or the normal rotation direction.

  In the above-described embodiment, in addition to the current position θ ′ of the pointer 1 and the correction amount Δθ, a drive signal is supplied to the stepper motor 3 so that the stepper motor 3 rotates in the return direction by a predetermined angle, and vibration is generated. Although the generated step-out portion has been canceled, the present invention is not limited to this. For example, after the rotation of the stepper motor 3 in the return direction by the current position θ ′ of the pointer 1 and the correction amount Δθ is completed, the piece 9 and the stopper 10 are moved based on the presence or absence of the induced voltage generated in the exciting coils 5 and 6. The step-out portion may be canceled by continuing to supply the drive signal in the return direction until the contact is detected.

  Further, in the above-described embodiment, the initialization position that is the indicated position of the pointer 1 when the piece 9 and the stopper 10 are in contact with the measurement value 0 that is the reference position on the scale is provided at the same position. However, the present invention is not limited to this. For example, the initialization position of the pointer 1 may be provided on the return direction side by a certain angle from the measured value 0. In this case, the difference between the current position of the pointer 1 and the initialization position of the pointer 1 is a value obtained by adding the current position θ ′ of the pointer 1 stored in the memory (RAM 14 or EEPROM 15) and the certain angle.

  Further, the above-described embodiments are merely representative forms of the present invention, and the present invention is not limited to the embodiments. That is, various modifications can be made without departing from the scope of the present invention.

It is an electric circuit diagram which shows the instruction | indication apparatus incorporating the stepper motor apparatus which implemented the control method of the stepper motor of this invention. FIG. 2 is an exploded perspective view of the pointing device shown in FIG. 1. It is a flowchart which shows the process sequence in the initialization process at the time of return of CPU12 which comprises the instruction | indication apparatus shown in FIG. It is explanatory drawing for demonstrating the conventional problem.

Explanation of symbols

1 Pointer 3 Stepper motor 9 Piece (Driven member)
10 Stopper 12 CPU (Update means, acquisition means, first initialization drive means, speed detection means, second initialization drive means, rotation direction detection means, stop means, correction amount setting means, third initialization drive means)
15 EEPROM (memory means)

Claims (5)

A stepper motor that rotates in response to the supply of a drive signal to drive the pointer, and a driven member that interlocks with the rotation of the stepper motor, and mechanically stops the rotation of the stepper motor to initialize the pointer. In a stepper motor device provided with a stopper forcibly stopping at a position and memory means for storing the current position of the pointer,
Obtaining means for obtaining the current position of the pointer stored in the memory means immediately before the momentary power interruption;
When the power is turned on again after the momentary power interruption, the stepper motor moves in the return direction in which the driven member moves toward the stopper by the difference between the current position of the pointer acquired by the acquisition means and the initialization position of the pointer. And a first initialization drive means for supplying the drive signal to the stepper motor so as to rotate.
Speed detecting means for detecting the rotational speed or rotational acceleration of the stepper motor immediately before the instantaneous power interruption;
When the power is turned on again after the instantaneous power interruption, the drive signal is supplied to the stepper motor so that the stepper motor further rotates in the return direction by a correction amount corresponding to the rotational speed or the rotational acceleration. A stepper motor device comprising: 2 initialization driving means; Rotation direction detection means for detecting the rotation direction of the stepper motor immediately before the instantaneous power interruption;
2. The stepper motor device according to claim 1, further comprising: a stop unit that stops the supply of the drive signal by the second initialization drive unit when a return direction is detected by the rotation direction detection unit.   The pointer from the time when the second initialization drive means stops supplying the drive signal to the stepper motor rotating at the detected rotational speed or rotational acceleration until the rotation of the stepper motor stops The stepper motor apparatus according to claim 1, further comprising a correction amount setting unit that sets a movement amount of the second movement amount to the correction amount.   And a third initialization drive means for supplying the drive signal to the stepper motor so that the stepper motor rotates in the return direction by a predetermined angle when the power is turned on again after the instantaneous power interruption. The stepper motor device according to any one of claims 1 to 3, wherein A stepper motor control method for driving a pointer by supplying a drive signal,
When the power is turned on again after a momentary power interruption, the current position of the pointer stored in the memory means immediately before the momentary power interruption and the contact position between the stopper of the driven member interlocked with the rotation of the stepper motor A setting for setting a value obtained by adding the difference between the initialization position, which is the indicated position of the pointer, and the correction amount according to the rotation speed or rotation acceleration of the stepper motor immediately before the instantaneous power interruption as the return movement amount Process,
And an initialization driving step of sequentially supplying the drive signal to the stepper motor so that the driven member rotates in the return direction of the driven member toward the stopper by an amount corresponding to the return movement amount. Stepper motor control method.

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