JP2005045852A - Driver of stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driver of a stepping motor in which erroneous detection of zero position can be prevented by settling rotation of the stepping motor during zero position detection and obtaining a settled induction voltage during rotation. <P>SOLUTION: The driver of a stepping motor comprises a driven member 2, a stopper 5, a control means 41a, an element 1a1 for detecting an induction voltage, and a zero position detecting means 41d. During normal operation, the control means 41a generates a first excitation pattern for constituting one electric cycle by a plurality of excitation steps for rotating a rotor 1b forward and reversely by microstep drive system based on an inputted angular data signal and provides the first excitation pattern to exciting coils 1a1 and 1a2. During zero position detection for returning the driven member 2 back to a zero position, the control means 41a generates a second excitation pattern by converting a part of the plurality of excitation steps in the first excitation pattern into an excitation step for detecting the induction voltage and provides the second excitation pattern to the exciting coils 1a1 and 1a2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a stepper motor drive device, and more particularly to a stepper motor drive device with improved initialization processing for a stepper motor used in a vehicle-mounted meter or the like.
[0002]
[Prior art]
In-vehicle meters such as a speedometer that displays the vehicle speed and a tachometer that displays the number of revolutions of the engine, stepper motors have been frequently used in recent years for indication accuracy and price reasons.
[0003]
However, in a vehicle equipped with an in-vehicle meter using such a stepper motor, the amount of movement of the pointer that is linked to the rotation of the stepper motor due to an erroneous drive signal generated due to vibration or noise of the vehicle, etc. And there may be a difference between the actual movement amount.
[0004]
Therefore, in an in-vehicle meter using such a stepper motor, for example, when the ignition switch is turned on, an initialization process is performed to reverse the stepper motor in the stopper direction and return the pointer to the zero position determined by the stopper. It has been broken.
[0005]
In this initialization process, in order to detect whether or not the display pointer whose position is controlled by the stepper motor has come into contact with the stopper that determines the zero position, an induced voltage generated by the rotation of the rotor of the stepper motor is detected. When the detected induced voltage falls below a predetermined threshold value, zero position detection processing is performed in which it is determined that the display pointer has stopped by hitting the stopper set at the zero position.
[0006]
Hereinafter, the zero position detection process will be described with reference to FIGS. 19 and 20.
[0007]
FIG. 19 is a diagram showing the relationship among each excitation step, zero position detection excitation pattern, detection timing signal, and induced voltage in the zero position detection process. FIG. 20 is a diagram showing the relationship between each excitation step of FIG. 19 and the rotation pattern of the rotor. The number in the rectangle indicates the step number. In these figures, it is assumed that the rotor of the stepper motor rotates in the direction indicated by the arrow during the zero position detection process. In this rotor, three N poles and S poles are alternately and evenly magnetized.
[0008]
The excitation signal for rotating the rotor is composed of excitation signals (excitation pulses) P1, P2, P3 and P4, which are constituted by a combination of H (high level) and L (low level). For example, H is 5 volts, and L is 0 volts. Excitation pulses P1 and P2 are supplied to both ends a and b of one excitation coil 1a1. The excitation pulses P3 and P4 are supplied to both ends a and b of the other excitation coil 1a2.
[0009]
One cycle of the zero position detection excitation pattern for reversely rotating the rotor so that the pointer geared to the rotor moves in the zero position direction determined by the stopper is 8 excitations each assigned an equal time. Steps 3, 2, 1, 8, 7, 6, 5, and 4 are configured, and the stepper motor is driven by a half-step driving method.
[0010]
The excitation signal (P1, P2, P3 and P4) of excitation step 1 and the corresponding rotor rotation pattern are synchronized, and the excitation steps are in the order of 3, 2, 1, 8, 7, 6, 5 and 4. As the movement proceeds, the rotor rotates 15 degrees each as shown in FIG. For example, when transitioning from excitation step 3 to excitation step 2, the rotor changes its angle from 0 degrees to 15 degrees according to the excitation signals (P1, P2, P3, and P4). Similarly, the amount of angular displacement between the following excitation steps is also 15 degrees. It should be noted that the angle shift amount at the time of transition from excitation step 4 to excitation step 3 of the next cycle is also 15 degrees.
[0011]
Such a cycle consisting of eight excitation steps is repeated until the pointer contacts the stopper, that is, until the rotor cannot rotate and the induced voltage value detected by the excitation coil falls below the threshold value.
[0012]
The detection timing signal for detecting the zero position is the timing at which the excitation coil 1a1 is in the non-excitation state, that is, the excitation step 1 at which the excitation pulses P1 and P2 supplied to both ends a and b of the excitation coil 1a1 become L (zero volts). And 5 and excitation steps 3 and 7 at which excitation pulses P3 and P4 supplied to both ends a and b of the excitation coil C2 become L (zero volt) are set to H. In response to this detection timing signal, the induced voltage detected by exciting coils 1a1 and 1a2 having one end grounded and the other end open is compared with a threshold value (reference voltage V). When the rotor is rotated so that the pointer moves in the zero position direction determined by the stopper, if the pointer contacts the stopper, the induced voltage should theoretically be zero, so it will fall below the threshold, At this time, zero position detection is performed.
[0013]
[Problems to be solved by the invention]
In the zero position detection process described above, the induction voltage detection cycle is a half-step drive system, and as shown in the vector diagram of FIG. 21, the coil A phase (excitation coil 1a1) and the coil B phase (excitation coil 1a2). Since the magnitude of the drive torque varies between the one-phase excitation step and the two-phase excitation step in FIG. 2, the drive torque is not constant, and the rotation speed of the rotor changes, resulting in non-smooth rotation, as shown in FIG. As described above, the detected induced voltage value fluctuates with a considerable fluctuation range, and there is a possibility that the zero position is erroneously detected.
[0014]
Therefore, in view of the above-described conventional problems, the present invention stabilizes the rotation of the stepper motor during the zero position detection process, obtains a stable induced voltage during rotation, and prevents erroneous detection of the zero position. The object is to provide a drive device.
[0015]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an invention according to claim 1 is directed to a stepper motor having an excitation coil and a rotor that rotates in accordance with a change in an excitation state of the excitation coil, and a stepper motor that is interlocked with the rotation of the rotor. A driving member, a stopper for mechanically stopping the driven member at a zero position, a control means for controlling the excitation state of the excitation coil, and an induced voltage generated by a change in magnetic flux according to the rotation of the rotor And a zero position detecting means for detecting whether or not the driven member is stopped at the zero position by the stopper based on the induced voltage detected by the detecting element, and the control means In normal operation, an electrical cycle is performed in a plurality of excitation steps for rotating the rotor forward and reverse by a microstep drive system based on the input angle data signal. In the zero position detection process for generating the first excitation pattern that constitutes the source and supplying the excitation pattern to the excitation coil and returning the driven member to the zero position, one of the plurality of excitation steps in the first excitation pattern A stepper motor driving apparatus is characterized in that a second excitation pattern obtained by converting the portion into an excitation step for detecting an induced voltage is generated and supplied to the excitation coil.
[0016]
According to the first aspect of the present invention, a stepper motor drive device includes an excitation coil and a stepper motor having a rotor that rotates in accordance with a change in the excitation state of the excitation coil, and a driven member that is interlocked with the rotation of the rotor. A stopper that mechanically stops the driven member at the zero position, a control unit that controls the excitation state of the excitation coil, a detection element that detects an induced voltage generated by a magnetic flux change according to the rotation of the rotor, And zero position detecting means for detecting whether or not the driven member is stopped at the zero position by the stopper based on the induced voltage detected by the detecting element, and the control means receives angle data inputted during normal operation. Based on the signal, a first excitation pattern is generated in which one electrical cycle is constituted by a plurality of excitation steps for forward and reverse rotation of the rotor by the microstep drive method. In the zero position detection process for supplying the excitation coil and returning the driven member to the zero position, the second excitation pattern obtained by converting a part of the plurality of excitation steps in the first excitation pattern to the excitation step for detecting the induced voltage is used. Since it is generated and supplied to the exciting coil, the rotation of the stepper motor can be stabilized and the sampling time for detecting the induction voltage can be secured during the zero position detection process, thereby obtaining a stable induction voltage during rotation. And erroneous detection of the zero position can be prevented.
[0017]
According to a second aspect of the present invention, the plurality of excitation steps in the first excitation pattern are configured so that the duty ratio increases or decreases stepwise between 0% and 100%. 2. The stepper motor according to claim 1, further comprising: an excitation signal that is PWM-controlled, and the excitation step for detecting the induced voltage in the second excitation pattern includes an excitation signal having a duty ratio of 0% or 100%. Lies in the drive.
[0018]
According to the second aspect of the present invention, the plurality of excitation steps in the first excitation pattern include an excitation signal that is PWM controlled so that the duty ratio increases or decreases stepwise between 0% and 100%. Since the excitation step for detecting the induced voltage in the second excitation pattern includes an excitation signal with a duty ratio of 0% or 100%, a sampling time for detecting the induced voltage can be secured during the zero position detection process. Thus, a more stable induced voltage during rotation can be obtained.
[0019]
In order to solve the above-mentioned problem, the invention according to claim 3 is characterized in that the second excitation pattern is such that the electrical 90 degrees in the one cycle has a first predetermined time length for detecting the induced voltage. 3. The stepper motor drive according to claim 1, further comprising: an excitation step for detecting the induced voltage, and a rotation excitation step having a second predetermined time length longer than the first predetermined time length. Exists in the device.
[0020]
According to the third aspect of the present invention, the second excitation pattern includes the excitation step for detecting the induced voltage, wherein the electrical 90 degrees in one cycle has a first predetermined time length for detecting the induced voltage; And a rotation excitation step having a second predetermined time length longer than the first predetermined time length, so that the induced voltage during rotation can be stably obtained during the zero position detection processing, and erroneous detection of the zero position can be achieved. Can be prevented.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
FIG. 1 is a configuration diagram of an in-vehicle meter using an embodiment of a stepper motor driving apparatus according to the present invention. The in-vehicle meter is, for example, a speedometer, and two exciting coils 1a1 and 1a2 arranged at positions orthogonal to each other on a stator (not shown), and N poles and S poles are alternately magnetized by three poles, and excited. A stepper motor 1 having a rotor 1b that rotates following a change in the excitation state of the coils 1a1 and 1a2 and a drive circuit 4 for driving and controlling the stepper motor 1 are provided.
[0023]
The on-vehicle meter further contacts the pointer 2 as a driven member interlocked with the rotational drive of the rotor 1b, the gear 3 for transmitting the rotational drive of the rotor 1b to the pointer 2, and the pointer 2 at a mechanical zero position. And a stopper 5 to be stopped. Instead of setting the zero position by contact between the stopper 5 and the pointer 2, contact between a stopper piece 6 as a driven member protruding from the gear 3 and a stopper 5 'provided separately at a position corresponding to the zero position. A configuration may be adopted in which the zero position is set by.
[0024]
As shown in FIG. 2, the drive circuit 4 includes a microcomputer 41 (hereinafter referred to as a microcomputer 41) as control means. The microcomputer 41 includes a central processing unit (CPU) 41a that performs various processes according to a program, a memory 41b, a motor drive circuit 41c, and a zero position detection circuit 41d.
[0025]
The CPU 41a receives an angle data signal D1 calculated based on speed information from a vehicle speed sensor (not shown) and an H-level initialization command signal S1 based on an ignition-on operation of an ignition switch (not shown) to drive the motor. Excitation signals S1, S2, S3 and S4 are output from the circuit 41c to both ends a and b of the excitation coils 1a1 and 1a2.
[0026]
The zero position detection open circuit 41d receives induced voltages V1, V2, V3 and V4 via I / F (interface) circuits 42a, 42b, 42c and 42d connected to one ends a or b of the exciting coils 1a1 and 1a2, respectively. The zero position determination signal is input to the CPU 41a.
[0027]
During normal operation, the CPU 41a generates a first excitation pattern in which one electrical cycle is composed of a plurality of excitation steps for rotating the rotor 1b in the forward and reverse directions by the microstep drive method according to the angle data signal D1. By supplying the excitation coils 1a1 and 1a2 and controlling the excitation state of the excitation coils 1a1 and 1a2, the rotor 1b is moved in the forward direction (Y2) or the reverse direction (Y1) in accordance with the angle data signal D1. The stepper motor 1 is driven and controlled to rotate in the reverse direction. In addition, during the initialization processing operation, the CPU 41a applies a second excitation pattern obtained by converting a part of the plurality of excitation steps in the first excitation pattern to an induction voltage detection excitation step in response to the initialization command signal S1. By generating and supplying the exciting coils 1a1 and 1a2 and controlling the exciting state of the exciting coils 1a1 and 1a2 by the microstep driving method, the rotor 1b is moved in the direction in which the pointer 2 faces the stopper 5 (ie, the Y1 direction). The stepper motor 1 is driven and controlled to reversely rotate so as to move to.
[0028]
This micro-step driving method uses 1 / n (n ≧ 3) micro-steps. In this embodiment, for example, a micro-step that divides one electrical cycle into 64 is used, and is divided into 16 at 90 degrees electrical. The
[0029]
FIG. 3 shows a current vector diagram of the excitation signal during normal operation. In FIG. 3, as an example, a current vector at 90 degrees corresponding to excitation steps 0 to 16 in one electrical cycle is shown.
[0030]
FIG. 4 is a waveform diagram showing, in time series, current vectors of excitation signals supplied to the excitation coils 1a1 and 1a2 of the microstep drive system during normal operation. As shown in FIG. 4, during normal operation, each excitation coil 1a1, 1a2 is supplied with an excitation signal PWM-controlled so that the duty ratio increases or decreases stepwise between 0% and 100%. .
[0031]
During the initialization processing operation, the zero position detection circuit 41d has induced voltages V1, V2, V3, and V4 generated at both ends of the excitation coils 1a1, 1a2 in the non-excitation state whose one ends are opened according to the detection timing signal. When the input voltage V1, V2, V3, or V4, which is input via the / F circuit, falls below the threshold value, it is determined that the pointer 2 is in contact with the stopper 5 and is at the zero position. A zero position determination signal is output to the CPU 41a. That is, the above-described exciting coils 1a1 and 1a2 function as an induction voltage detecting element when one end is opened.
[0032]
As shown in FIG. 5, when the drive circuit 4 reversely rotates the stepper motor 1 during the initialization processing operation, first, excitation pulses P1, P2, P3 having excitation patterns for accelerating the stepper motor 1 for a predetermined time. , P4 are supplied to the exciting coils 1a1 and 1a2 to accelerate the stepper motor 1 from the start of reverse rotation, and thereafter, zero position detection processing is performed.
[0033]
In the zero position detection process, the drive circuit 4 is an excitation pattern in which one electrical cycle is constituted by a plurality of excitation steps that reversely rotate the rotor 1b by the micro-step driving method, that is, the first excitation during normal operation. Excitation signals S1, S2, S3 and S4 having a second excitation pattern in which a part of a plurality of excitation steps in the pattern is converted into an excitation step for detecting an induced voltage are generated. An induction voltage detecting excitation step in which the electrical 90 degrees has a first predetermined time length for detecting the induced voltage, and a second predetermined time longer than the first predetermined time length of the induced voltage detecting excitation step. Long excitation step.
[0034]
As shown in FIG. 6, the micro-step driving method at the time of the zero position detection process outputs a predetermined excitation step that is divided into 16 at 90 electrical degrees in one cycle.
[0035]
Specifically, the excitation coils 1a1 and 1a2 are excited in the excitation step indicated by an arrow (with numerals) in one cycle in FIG. That is, if the exciting coil 1a1 corresponds to the A phase (SIN +) and -A phase (SIN-), and the exciting coil 1a2 corresponds to the B phase (COS +) and -B phase (COS-), When the element is rotated in the reverse direction, the excitation steps for detecting the induced voltage are STEP-0 (converting steps 58 to 64 in normal operation), 16 (converting steps 10 to 16 in normal operation), 32 (in normal operation) Steps 26 to 32 are converted) and 48 (Steps 42 to 48 in normal operation are converted), and the excitation steps for rotation are STEP-2, 5, 7, 9, 18, 21, 23, 25, 34, 37. , 39, 41, 50, 53, 55 and 57 are used.
[0036]
And the output time of excitation signal S1, S2, S3, S4 in each excitation step is set as follows.
Induction voltage detection excitation step = STEP-0, 16, 32 and 48 are 3 (ms; milliseconds)
Excitation step for rotation = STEP-2, 5, 7, 9, 18, 21, 23, 25, 34, 37, 39, 41, 50, 53, 55 and 57 are each 1 (ms; millisecond)
[0037]
Therefore, within each electrical 90 degree, the length of time of the excitation step for detecting the induced voltage (first predetermined time length) and the length of time of the excitation step for rotation (second predetermined time length) )
Induction voltage detection excitation step 3 (ms) <rotation excitation step 4 (ms)
It has become.
[0038]
Next, the operation of the vehicle-mounted meter having the above-described configuration will be described below with reference to the flowchart showing the zero position detection procedure of the CPU 41a shown in FIG. When the initialization process is started, the excitation step is updated at a predetermined update interval (step S1), and then it is determined whether or not a predetermined time has passed (step S2). Specifically, as shown in FIG. 5, the step S2 causes the rotor 1b to follow (synchronize) the excitation signal while removing (shifting) the backlash of the gear 3 from the start of the zero position detection process, Rotate (accelerate) to a predetermined speed. If the predetermined time has passed, next, the induced voltage detection process is started (step S3). That is, since the induced voltage is not stable until a predetermined time has elapsed immediately after the start of rotation of the rotor 1b, the induced voltage detection process is not performed. (For example, refer to JP 2001-298993 A.)
[0039]
Next, the induction voltage measuring coil is switched from PWM output to Hi-Z output (high impedance output) in accordance with the detection timing signal (step S4). The Hi-Z output is a state in which one end of an excitation coil corresponding to an induction voltage measurement coil is opened in a non-excited state for a sampling time (3 ms in this embodiment) in an excitation step for detecting an induced voltage. It means that an induced voltage is output from the exciting coil during the sampling time.
[0040]
Next, the induced voltage that appears during the detection excitation step is sampled from the induced voltage measuring coil a plurality of times (step S5). That is, the induced voltages V1, V2, V3 and V4 generated at both ends of the exciting coils 1a1 and 1a2 are sampled through the respective I / F circuits and input to the zero position detecting circuit 41d. Next, it is determined whether or not the number of times that the sampled induced voltage value is determined to exceed the threshold is less than a preset contact determination number (step S6).
[0041]
If the answer to step S6 is yes, the output excitation phase is held for a certain time (step S8), and then the initialization process is normally terminated.
[0042]
On the other hand, if the answer to step S6 is no, it is next determined whether or not the rotor 1b has rotated 360 degrees (step S9). If the answer is yes, then the output excitation phase is held for a certain period of time (step S9). S10) Next, the initialization process ends abnormally. On the other hand, if the answer to step S9 is no, the reverse rotation process is executed in microsteps until the next detection excitation step (step S11), and then the process returns to step S4.
[0043]
8 shows a drive waveform at the time of the initialization process of the stepper motor, FIG. 9 shows an enlarged view of the drive waveform at the time of the acceleration process in FIG. 8, and FIGS. 10 (A) and 10 (B) are diagrams respectively. 9 shows the PWM output waveforms of the first half and the latter half of the acceleration process in FIG. 9, FIG. 11 shows an enlarged view of the drive waveform during the induced voltage detection process, and FIG. 12 shows an enlarged view of the induced voltage detection cycle (excitation by PWM drive). FIG. 13 shows an enlarged waveform of the reverse processing portion in FIG. 12, and FIGS. 14 (A), (B), (C), and (D) show the rotation excitation step 41, FIG. The enlarged waveforms at 39, 37, and 34 are shown.
[0044]
FIG. 15 shows a current vector diagram of the excitation signal during the above-described induced voltage detection process, that is, the zero position detection process. In FIG. 15, as an example, a current vector at 90 degrees corresponding to excitation steps 0 to 16 in one electrical cycle is shown.
[0045]
FIG. 16 is a waveform diagram showing, in time series, current vectors of excitation signals supplied to the microstep drive excitation coils 1a1 and 1a2 during the zero position detection process. As shown in FIG. 16, during the zero position detection process, the excitation coils 1a1 and 1a2 have the same excitation pattern as that in the normal operation, but the excitation steps are reversed, and the duty ratio ranges from 0% to 100%. The PWM control is performed so as to increase or decrease stepwise between 1% and the duty ratio during a sampling time (3 ms in this embodiment) in which a part of each excitation step is adjusted to the detection timing of the induced voltage. An excitation signal converted (or replaced) into an induction voltage detection excitation step of 0% or 100% is supplied. Excitation steps other than the induction voltage detection excitation step are rotation excitation steps that are longer than the sampling time of the induction voltage detection excitation step (3 ms in this embodiment) at each electrical 90 ° in one cycle. (In this embodiment, 4 ms), the rotation of the rotor 1b is stabilized.
[0046]
FIG. 17 is a diagram showing the rotation angle of the rotor in time series in order to explain the drive waveforms of the excitation coils 1a1 and 1a2 and the timing for applying excitation. In order to completely capture the induced voltage of the stepper motor, it is necessary to set the detection time (sampling time) so that the maximum value of the induced voltage generated in the exciting coils 1a1 and 1a2 can be sampled. (This is because it may be difficult to determine the zero position when the induced voltage before the peak occurs is captured.)
[0047]
When the rotor 1b is rotating at a certain speed and excitation is performed to stop rotation without performing deceleration processing (that is, an excitation signal with a duty ratio of 0% is applied in the excitation step for detecting the induction voltage) (Indicated by A in FIG. 17), the rotor 1b overshoots (indicated by B in FIG. 17) unless the excitation of the next rotational excitation step is applied (this is indicated by B in FIG. 17). After overshooting, a peak value of the induced voltage is generated), and then reaches a stop angle corresponding to the excitation output while vibrating. At this time, when excitation in the rotational direction by the next excitation step for rotation is given at the timing of C in FIG. 17 or at the timing of D when the rotor 1b is reversed, the rotation of the rotor 1b becomes unstable and smooth. Therefore, the level of the induced voltage after the next induced voltage detection point (indicated by F in FIG. 17) becomes unstable.
[0048]
In order to avoid this, immediately after passing through point B (that is, immediately after the peak value of the induced voltage is generated), the excitation signal in the rotation direction by the excitation step for rotation is output again. The excitation waveform output position at this time outputs an excitation signal corresponding to the rotation angle E that should be output when the stepper motor continues to rotate at a constant speed without stopping at the point A. That is, as shown in FIG. 16, the excitation signal in the excitation step for rotation next to the excitation step for detecting the induced voltage with a duty ratio of 0% (that is, steps 9, 57, 41, and 25) is a drive waveform during normal operation. Is supplied again from the portion having the duty ratio along the line.
[0049]
FIG. 18 shows a time chart of the detected induced voltage. From this figure, it can be seen that the fluctuation range of the detected induced voltage values V1 to V4 is smaller than that of the conventional one and the time until stabilization is short.
[0050]
Thus, during the zero position detection process, the excitation coil is excited with the excitation signal having the second excitation pattern obtained by converting a part of the plurality of excitation steps in the first excitation pattern during normal operation into the induction voltage detection excitation step. In addition, the rotation of the excitation step for rotation (second predetermined time length) is set longer than the time of the excitation step for detecting induced voltage (first predetermined time length) at 90 degrees in one electrical cycle. Since the rotation excitation time of the child is long and the rotation is smooth, a stable induction voltage can be obtained, and erroneous detection of the zero position can be prevented.
[0051]
As described above, the embodiment of the present invention has been described. However, the present invention is not limited to this, and various modifications and applications are possible.
[0052]
【The invention's effect】
According to the first aspect of the present invention, during the zero position detection process, the rotation of the stepper motor can be stabilized and the sampling time for detecting the induced voltage can be secured, thereby obtaining a stable induced voltage during rotation. And erroneous detection of the zero position can be prevented.
[0053]
According to the second aspect of the present invention, it is possible to secure a sampling time for detecting the induced voltage during the zero position detecting process, thereby obtaining a stable rotational induced voltage.
[0054]
According to the third aspect of the present invention, the induced voltage during rotation can be stably obtained during the zero position detection process, and erroneous detection of the zero position can be prevented.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of an in-vehicle meter using an embodiment of a stepper motor driving apparatus according to the present invention.
FIG. 2 is a diagram showing a configuration of a drive device in the in-vehicle meter of FIG.
FIG. 3 shows a current vector diagram of excitation signals during normal operation.
FIG. 4 is a waveform diagram showing, in time series, current vectors of excitation signals supplied to each microstep drive excitation coil during normal operation.
FIG. 5 is a diagram for explaining the outline of the operation of the drive circuit of FIG. 2;
FIG. 6 is a diagram illustrating a specific example of a microstep driving method.
FIG. 7 is a flowchart showing a processing procedure of the CPU of the drive circuit.
FIG. 8 shows a drive waveform at the time of initialization processing of a stepper motor.
9 shows an enlarged view of a drive waveform during the acceleration process in FIG. 8. FIG.
10A and 10B show PWM output waveforms in the first half and second half of the acceleration processing in FIG. 9, respectively.
FIG. 11 is an enlarged view of a drive waveform at the time of induced voltage detection processing.
FIG. 12 is an enlarged view of an induction voltage detection cycle (excitation by PWM drive).
FIG. 13 shows an enlarged waveform of the reverse processing portion in FIG. 12;
14 (A), (B), (C), and (D) show enlarged waveforms at rotation excitation steps 41, 39, 37, and 34 in FIG. 13, respectively.
FIG. 15 is a current vector diagram of an excitation signal during induction voltage detection processing (zero position detection processing).
FIG. 16 is a waveform diagram showing, in time series, current vectors of excitation signals supplied to each excitation coil of the microstep drive method during zero position detection processing.
FIG. 17 is a diagram showing the rotation angle of the rotor in time series in order to explain the drive waveform of the excitation coil and the timing for applying excitation.
FIG. 18 is a time chart of induced voltages detected by the position detection circuit.
FIG. 19 is a diagram showing the relationship among each excitation step, zero position detection excitation pattern, detection timing signal, and induced voltage in zero position detection processing in a vehicle-mounted meter using a conventional stepper motor.
20 is a diagram showing the relationship between each excitation step of FIG. 19 and the rotation pattern of the rotor.
FIG. 21 shows a vector diagram of drive torque in the half-step drive method.
FIG. 22 is a time chart of induced voltage detected in a zero position detection process in a vehicle-mounted meter using a conventional stepper motor.
[Explanation of symbols]
1 Stepper motor 1a1 Excitation coil 1a2 Excitation coil 1b Rotor 2 Pointer (driven member)
4 Drive circuit 41a CPU (control means)
41b Memory 41c Motor drive circuit 41d Zero position detection circuit (zero position detection means)
5 Stopper

Claims (3)

A stepper motor having an excitation coil and a rotor that rotates in response to a change in the excitation state of the excitation coil;
A driven member interlocked with the rotation of the rotor;
A stopper that mechanically stops the driven member at a zero position;
Control means for controlling the excitation state of the excitation coil;
A detection element for detecting an induced voltage generated by a magnetic flux change according to the rotation of the rotor;
Zero position detecting means for detecting whether or not the driven member is stopped at the zero position by the stopper based on the induced voltage detected by the detection element;
In the normal operation, the control means has a first excitation pattern in which one electrical cycle is composed of a plurality of excitation steps for rotating the rotor forward and reverse by a microstep drive system based on an input angle data signal. Is generated, supplied to the excitation coil, and at the time of zero position detection processing for returning the driven member to the zero position, a part of the plurality of excitation steps in the first excitation pattern is converted into an excitation step for detecting an induced voltage. A stepper motor driving apparatus, wherein the second excitation pattern is generated and supplied to the excitation coil. The plurality of excitation steps in the first excitation pattern include an excitation signal PWM-controlled so that the duty ratio increases or decreases stepwise between 0% and 100%, and the excitation step in the second excitation pattern 2. The stepper motor driving apparatus according to claim 1, wherein the excitation step for detecting the induced voltage includes an excitation signal having a duty ratio of 0% or 100%. The second excitation pattern includes the induced voltage detecting excitation step in which the electrical 90 degrees in the one cycle has a first predetermined time length for detecting the induced voltage, and the first predetermined time length. 3. A stepper motor driving apparatus according to claim 1, further comprising a rotating excitation step having a longer second predetermined time length.

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