JP2007159274A - Step motor drive device - Google Patents

Abstract

A rotor is efficiently rotated even under various conditions.
Stator magnetic poles 2p and 2q are formed such that an angle θ between a dynamic magnetic center line L2 and a static stable line L1 is 45 ° or more and 90 ° or less in a forward rotation direction. The magnetic sensor 3 is disposed in the vicinity of the rotor 1 of the step motor 11. The magnetic sensor 3 detects the rotation direction of the rotor 1. The control circuit 14 variably sets the pulse width of the drive pulse signal while determining the rotation of the rotor 1 based on the detection signal of the magnetic sensor 3.
[Selection] Figure 1

Description

  The present invention relates to a step motor driving device.

  As a timepiece motor, there is a single-phase two-pole step motor capable of forward and reverse rotation (see, for example, Patent Document 1).

In this step motor, the static stable position of the rotor in the non-excited state is at a position displaced by approximately 90 degrees with respect to the dynamic magnetic center of the stator magnetic pole in the excited state. The controller that drives the step motor generates a single polarity initialization pulse having a sufficiently large pulse width at the time of initial movement. Thereafter, a drive pulse signal for normal driving is output to drive the step motor in a desired rotation direction.
Japanese Patent No. 2614769

  However, in order to drive the step motor with certainty, it is necessary to consider the usage environment, power supply voltage, and component variations. It is also necessary to consider that there is a difference in output torque between forward rotation and reverse rotation. In addition, it is necessary to output a drive pulse having a sufficient pulse width so as to operate reliably. In the conventional step motor driving device, the driving energy more than necessary is consumed, and the efficiency is lowered.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a step motor driving device capable of rotating efficiently.

In order to achieve this object, a step motor driving device according to the first aspect of the present invention includes:
A step motor for a clock that rotates intermittently;
A control unit for driving the step motor,
The step motor is
A rotor in which N and S poles are magnetized in two poles;
A stator comprising a pair of stator magnetic poles for driving the rotor and having a hole through which the rotor passes;
A drive coil for exciting the stator;
A magnetic sensor disposed near the shaft surface of the rotor and detecting a magnetic pole of the rotor close to the magnetic sensor and outputting a detection signal;
The control unit variably sets a pulse width of a drive pulse signal for controlling energization to the drive coil based on a detection signal output from the magnetic sensor to determine whether the rotor is rotated or not rotated by a previous pulse. It is characterized by doing.

In the stator, the angle of the static stability line indicating the direction in which the rotor is stationary in a non-excited state with respect to the dynamic magnetic center line of the stator magnetic pole is 45 ° or more and 90 ° or less in the forward rotation direction. The pair of stator magnetic poles is formed on
The magnetic sensor may be arranged in the vicinity of a position shifted by 90 ° with respect to the dynamic magnetic center line.

  The control unit may include a storage unit that stores pulse width data necessary for the rotation of the rotor during forward rotation and reverse rotation of the rotor.

  The control unit may update the pulse width data stored in the storage unit when the rotor rotates normally by a fixed number of pulses.

  According to the present invention, it is possible to rotate efficiently.

Hereinafter, a step motor driving device according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows the configuration of the step motor according to this embodiment.
As shown in FIG. 1A, the step motor 11 includes a rotor 1, a stator 2, a magnetic sensor 3, a coil core 5, and a drive coil 6.

  The rotor 1 is constituted by a disk-shaped permanent magnet, and both ends of the diameter of the rotor 1 are magnetized to two poles of N pole and S pole, respectively.

  The stator 2 is formed by integrating stator magnetic poles 2p and 2q, and a circular hole 2a for inserting the rotor 1 is provided at the center.

  Narrows 2b and 2c are provided on the upper and lower sides of the stator 2 on the straight line Y, where Y is a straight line extending in the vertical direction through the center of the circular hole 2a. The cross-sectional area of the stator 2 is reduced at the narrow portions 2b and 2c, and the magnetic resistance is increased. Accordingly, the stator 2 is magnetically divided into left and right with the straight line Y as a boundary.

  A coil core 5 is provided at the lower end of the stator 2, and a drive coil 6 is wound around the coil core 5. Input terminals 6 a and 6 b are provided at both ends of the drive coil 6. A magnetic circuit is formed with a straight line extending through the center of the circular hole 2a as a dynamic magnetic center line L2. The pair of stator magnetic poles 2p and 2q are formed on both sides of the circular hole 2a on the dynamic magnetic center line L2.

  When a drive pulse is applied to the drive coil 6 via the input terminals 6a and 6b, the stator magnetic poles 2p and 2q are excited through the coil core 5 to become N and S poles.

  The circular hole 2a is provided with a pair of arc-shaped notches 2d and 2e. The notches 2d and 2e are provided on the notch center line L3 through the center of the circular hole 2a.

  The notches 2d and 2e have a shape symmetrical with respect to the notch center line L3. For this reason, when the stator 2 is in a non-excited state, the N pole and S pole of the rotor 1 are located at equal distances from the two notches, and the rotor 1 is stationary in this state.

  That is, the rotor 1 stands still in a state where the straight line connecting the N pole and S pole of the rotor 1 and the static stability line L1 coincide. The static stability line L1 is a line indicating the direction in which the rotor 1 is stationary in the non-excited state, and this position is the static stable position.

  The angle formed by the static stability line L1 and the notch center line L3 is 90 °. The stator magnetic poles 2p and 2q are formed such that the angle θ is 45 ° or more and 90 ° or less in the forward rotation direction, where θ is the angle of the static stability line L1 with respect to the dynamic magnetic center line L2. The fact that the angle θ is approximately 90 ° is effective for reducing the difference in characteristics between forward rotation and reverse rotation.

  In addition, the angle θ formed by the dynamic magnetic center line L2 and the static stability line L1 may be set to approximately 45 °, whereby the most efficient motor can be obtained in the case of normal rotation. In this case, in order to reverse, it is necessary to input a drive pulse with higher energy (specifically, a pulse having a long pulse width or a combination of two or more kinds of pulses having different polarities).

  However, in the case of a watch, in general, since the motor is normally rotated for most of the time, setting the angle θ to approximately 45 ° is effective for obtaining a highly efficient watch having a long battery life. It is also effective in preventing reverse rotation during normal times. Further, the angle θ formed by the dynamic magnetic center line L2 and the static stability line L1 may be determined within a range of 45 ° or more and 90 ° or less, taking into account the respective advantages.

  The magnetic sensor 3 detects the strength of the magnetic field to be measured and the like, as shown in FIG. 1B, in the vicinity of the rotor 1 and facing the pole of the rotor 1 in a non-excited state. Is arranged. As the magnetic sensor 3, a semiconductor magnetoresistive element, Hall element, ferromagnetic thin film element, coil pickup, or the like is used.

  The magnetic sensor 3 is disposed in the vicinity of a position shifted by 90 ° with respect to the dynamic center line L2, that is, a position shifted by 90 ° and an error range set in advance around this position. For this reason, the position of the magnetic sensor 3 is shifted by 0 to 45 ° with respect to the pole of the rotor 1 located at the static stable position, and the magnetic sensor 3 determines the direction when the rotor 1 is stationary. To obtain the strength of the magnetic field required to

  At the same time, if the magnetic sensor 3 is disposed in the vicinity of a position shifted by 90 ° with respect to the dynamic center line L2, the timing of switching the polarity of the drive pulse signal during non-intermittent high-speed rotation of the pulse motor 11 described later. And the timing at which the signal of the magnetic sensor 3 crosses zero. For this reason, when the magnetic sensor 3 is also used for drive pulse control during high-speed rotation, control of the drive pulse signal during high-speed rotation is facilitated.

  The magnetic sensor 3 of the present embodiment outputs an L_HIGH detection signal when approaching the N pole of the rotor 1, and outputs an L_LOW detection signal when approaching the S pole of the rotor 1.

The motor drive circuit shown in FIG. 2 drives the step motor 11.
The motor drive circuit includes a crystal oscillator 12, a frequency divider 13, a control circuit 14, a driver 15, a forward / reverse selector switch 16, and a magnetic sensor 3.

The crystal oscillator 12 outputs a signal having a constant frequency.
The frequency divider 13 divides the frequency of the signal output from the crystal oscillator 12.

  The forward / reverse selector switch 16 is a switch for switching forward / reverse rotation of the step motor 11 manually by supplying a rotation direction switching signal to the control circuit 14. The magnetic sensor 3 described above supplies a detection signal to the control circuit 14.

  The control circuit 14 drives the step motor 11 by supplying drive pulse signals O1 and O2 to the driver 15. The control circuit 14 includes a CPU, a ROM, a RAM, a nonvolatile memory, and the like (not shown), and determines the rotation direction of the rotor 1 based on the rotation direction switching signal supplied from the forward / reverse selector switch 16. Further, the control circuit 14 supplies the drive pulse signals O1 and O2 to the driver 15 based on the detection signal supplied from the magnetic sensor 3 before the drive pulse signal OUT is output.

  Further, the control circuit 14 determines the pulse widths of the drive pulse signals O1 and O2 for controlling energization to the drive coil 6 based on the detection signal output from the magnetic sensor 3 before the drive pulse signal is output. The rotor 1 is variably set while discriminating the rotation and non-rotation of the rotor 1 with the pulse width.

  Specifically, the control circuit 14 stores data of the pulse widths of the drive pulse signals O1 and O2 in the nonvolatile memory for each rotation direction of the rotor 1 and each direction of the rotor 1. The pulse width may be the same for each rotation direction of the rotor 1 and each direction of the rotor 1 or may be different. In the present embodiment, the pulse width will be described as different for each rotation direction of the rotor 1 and each direction of the rotor 1.

  The control circuit 14 generates drive pulse signals O1 and O2 based on the respective pulse widths during forward rotation and reverse rotation, and outputs the drive pulse signals O1 and O2.

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal supplied from the magnetic sensor 3 after the drive pulse signals O1 and O2 are stopped, and compares it with the orientation of the rotor 1 before the output of the drive pulse signals O1 and O2. Thus, it is determined whether the rotor 1 is rotating or not.

  When it is determined that the rotor 1 can be rotated by the previous drive pulse signals O1 and O2, the control circuit 14 can vary the pulse widths of the drive pulse signals O1 and O2 depending on the rotation direction of the rotor 1 and the direction of the rotor 1. To do. The control circuit 14 updates the pulse width data necessary for the rotation of the rotor 1 when it rotates normally for a fixed number of times.

  The driver 15 amplifies the drive pulse signals O1 and O2 supplied from the control circuit 14, and supplies the drive pulse signals OUT1 and OUT2 to the step motor 11. In this embodiment, when the drive pulse OUT1 is supplied to the input terminal 6a and the drive pulse OUT2 is supplied to the input terminal 6b, and the drive pulse signal O1 = LOW and O2 = HIGH, the driver 15 uses the drive pulse OUT1 = LOW, Assume that OUT2 = HIGH, and a drive current is supplied to the step motor 11 so that the stator magnetic pole 2p is magnetized to the N pole and the stator magnetic pole 2q is magnetized to the S pole.

Next, operations of the step motor 11 and the motor drive circuit according to the embodiment will be described.
The crystal oscillator 12 outputs a signal having a constant frequency to the frequency divider 13, and the frequency divider 13 outputs the frequency-divided signal to the control circuit 14.

  The control circuit 14 executes the drive control process according to the flowchart shown in FIG. 3 and supplies the drive pulse signals O1 and O2 to the driver 15 at each timing of moving hands.

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 before outputting the drive pulse signal (step S11).

  When it is determined in step S11 that the orientation of the rotor 1 is N-pole, the control circuit 14 determines whether the direction of rotation is normal or reverse based on the rotation direction switching signal supplied from the forward / reverse selector switch 16 ( Step S12). If it is determined in step S12 that the rotation direction is the forward rotation direction, the control circuit 14 executes the pulse width setting process (1) according to the flowchart shown in FIG. 4 (step S13).

The control circuit 14 reads out the pulse width N1 of the drive pulse signals O1 and O2 from the nonvolatile memory (step S21).
The control circuit 14 outputs drive pulse signals O1 = LOW and O2 = HIGH, and the driver 15 outputs OUT1 = LOW and OUT2 = HIGH (step S22).

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 (step S23).

  When the signal level of the detection signal of the magnetic sensor 3 is L_HIGH, the control circuit 14 determines that the magnetic pole of the rotor 1 is the N pole (“HIGH” in step S23). In this case, it is determined that the rotor 1 could not rotate with the pulse width N1, and the control circuit 14 increases the pulse width N1 by 1 ms (step S24).

The control circuit 14 sets the pulse width to N0 (step S25). Here, N0 is set to a sufficient pulse width that can reliably rotate the rotor 1.
The control circuit 14 sets M1 to 0 (step S26).
The control circuit 14 outputs the drive pulse signals O1 and O2 again (step S22).

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 (step S23). When the orientation of the rotor 1 is determined to be the S pole (“L_LOW” in step S23), M1 is incremented. (Step S27).

  The control circuit 14 determines whether or not M1 has reached 300 (step S28).

  When it is determined that M1 has not reached 300 (No in step S28), the control circuit 14 returns to the drive control process.

  When it is determined that M1 has reached 300 (Yes in step S28), the control circuit 14 shortens the pulse width N1 by 1 ms (step S29).

  The control circuit 14 sets M1 to 0 (step S30). Then, the control circuit 14 returns to the drive control process. After returning to the drive control process, the control circuit 14 ends the drive control process.

  On the other hand, when it is determined in step S12 that the rotation direction is the reverse rotation direction (“reverse rotation” in step S12), the control circuit 14 executes the pulse width setting process (2) according to the flowchart shown in FIG. 5 (step S14).

The control circuit 14 reads out the pulse width N2 of the drive pulse signals O1 and O2 from the nonvolatile memory (step S41).
The control circuit 14 outputs drive pulse signals O1 = HIGH and O2 = LOW, and the driver 15 outputs drive pulse signals OUT1 = HIGH and OUT2 = LOW (step S42).

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 (step S43).

  When the signal level of the detection signal of the magnetic sensor 3 is L_LOW, the control circuit 14 determines that the magnetic pole is the N pole (“L_LOW” in step S43). In this case, the control circuit 14 increases the pulse width N2 by 1 ms (step S44).

The control circuit 14 sets the pulse width to N0 (step S45).
The control circuit 14 sets M2 to 0 (step S46).
The control circuit 14 outputs the drive pulse signals O1 and O2 again (step S42).

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 (step S43). When the orientation of the rotor 1 is determined to be the S pole (“L_LOW” in step S43), M2 is incremented. (Step S47).

  The control circuit 14 determines whether M2 has reached 300 (step S48).

  If it is determined that M2 has not reached 300 (No in step S48), the control circuit 14 returns to the drive control process.

  If it is determined that M2 has reached 300 (Yes in step S48), the control circuit 14 shortens the pulse width N2 by 1 ms (step S49).

  The control circuit 14 sets M2 to 0 (step S50). Then, the control circuit 14 returns to the drive control process. After returning to the drive control process, the control circuit 14 ends the drive control process.

  Next, when it is determined in step S11 that the orientation of the rotor 1 is the south pole, the control circuit 14 is rotated in the normal rotation direction or the reverse rotation direction based on the rotation direction switching signal supplied from the forward / reverse selector switch 16. Is determined (step S15). If it is determined in step S15 that the rotation direction is the normal rotation direction, the control circuit 14 executes a pulse width setting process (3) according to the flowchart shown in FIG. 6 (step S16).

The control circuit 14 reads the pulse width N3 of the drive pulse signal from the nonvolatile memory (step S61).
The control circuit 14 outputs drive pulse signals O1 = HIGH and O2 = LOW, and the driver 15 outputs drive pulse signals OUT1 = HIGH and OUT2 = LOW (step S62).

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 (step S63).

  When the signal level of the detection signal of the magnetic sensor 3 is L_LOW, the control circuit 14 determines that the magnetic pole of the rotor 1 is the S pole (“L_LOW” in step S63). In this case, the control circuit 14 increases the pulse width N3 by 1 ms (step S64).

The control circuit 14 sets the pulse width to N0 (step S65).
The control circuit 14 sets M3 to 0 (step S66).
The control circuit 14 outputs the drive pulse signals O1 and O2 again (step S62).

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 (step S63), and when it is determined that the orientation of the rotor 1 is N pole (“L_LOW” in step S63), M3 is incremented. (Step S67).

  The control circuit 14 determines whether M3 has reached 300 (step S68).

  When it is determined that M3 has not reached 300 (No in step S68), the control circuit 14 returns to the drive control process.

  When it is determined that M3 has reached 300 (Yes in step S68), the control circuit 14 shortens the pulse width N3 by 1 ms (step S69).

  The control circuit 14 sets M3 to 0 (step S70). Then, the control circuit 14 returns to the drive control process. After returning to the drive control process, the control circuit 14 ends the drive control process.

  On the other hand, when it is determined in step S15 that the rotation direction is the reverse rotation direction (“reverse rotation” in step S15), the control circuit 14 executes the pulse width setting process (4) according to the flowchart shown in FIG. 7 (step S17).

The control circuit 14 reads the pulse width N4 of the drive pulse signal from the nonvolatile memory (step S81).
The control circuit 14 outputs drive pulse signals O1 = LOW and O2 = HIGH, and the driver 15 outputs drive pulse signals OUT1 = LOW and OUT2 = HIGH (step S82).

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 (step S83).

  When the signal level of the detection signal of the magnetic sensor 3 is L_LOW, the control circuit 14 determines that the magnetic pole of the rotor 1 is the S pole (“L_LOW” in step S83). In this case, the control circuit 14 increases the pulse width N4 by 1 ms (step S84).

The control circuit 14 sets the pulse width to N0 (step S85).
The control circuit 14 sets M4 to 0 (step S86).
The control circuit 14 outputs the drive pulse signals O1 and O2 again (step S82).

  The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3 (step S83). If the orientation of the rotor 1 is determined to be N pole (“L_HIGH” in step S83), the control circuit 14 increments M4. (Step S87).

  The control circuit 14 determines whether or not M4 has reached 300 (step S88).

  If it is determined that M4 has not reached 300 (No in step S88), the control circuit 14 returns to the drive control process.

  When it is determined that M4 has reached 300 (Yes in step S88), the control circuit 14 shortens the pulse width N4 by 1 ms (step S89).

  The control circuit 14 sets M4 to 0 (step S90). Then, the control circuit 14 returns to the drive control process. After returning to the drive control process, the control circuit 14 ends the drive control process.

  As described above, according to this embodiment, the step motor 11 is driven with a short pulse width, and the pulse width is gradually increased when the step motor 11 cannot be driven.

  Therefore, the step motor 11 can be driven by the drive pulse signal having the minimum pulse width necessary for driving, and the minimum pulse width necessary for the rotation of the rotor 1 can be selected according to various conditions. And efficiency can be improved.

  In addition, when the required pulse width is different between forward rotation and reverse rotation, the minimum pulse width necessary for each condition can be selected.

  Even when the load is suddenly increased, the pulse width is reviewed after a certain period of time even if the pulse width is temporarily set longer, so that the step motor 11 can be driven efficiently.

  According to the present embodiment, since the orientation of the rotor 1 can be easily recognized by the magnetic sensor 3, it is possible to easily select the polarity of the pulse according to the rotation direction, and to make sure whether the rotor 1 has rotated after the pulse is output. Can be judged. Further, since the rotation and non-rotation of the rotor 1 can be detected without using the induced voltage during rotation, it is possible to prevent the efficiency of the step motor 11 from being lowered.

  Further, when the step motor 11 is used in a timepiece, the rotor 1 can be rotated at high speed in a non-intermittent manner when correcting the display of the timepiece. The operation in this case will be described.

  Hereinafter, the case where the N pole of the rotor 1 is close to the magnetic sensor 3 and is stationary and rotated in the forward rotation direction will be described.

The control circuit 14 determines the orientation of the rotor 1 based on the detection signal of the magnetic sensor 3.
When determining that the direction of the rotor 1 is N pole, the control circuit 14 determines whether the rotation direction is the normal rotation direction or the reverse rotation direction based on the rotation direction switching signal supplied from the forward / reverse selector switch 16.

  When it is determined that the rotation direction is the forward rotation direction, the control circuit 14 outputs drive pulse signals O1 = LOW and O2 = HIGH to be output, as indicated by Pos31 in FIG.

  The driver 15 amplifies the drive pulse signals O1 and O2, outputs a drive pulse signal of OUT1 = LOW, OUT2 = HIGH, and supplies a drive current to the drive coil 6. When a drive current flows through the drive coil 6, the stator magnetic pole 2p is magnetized to the N pole and the stator magnetic pole 2q is magnetized to the S pole.

  When the stator magnetic poles 2p and 2q are magnetized, the rotor 1 rotates forward in the direction of the arrow shown after Pos32 in FIG.

  The magnetic sensor 3 always outputs a detection signal to the control circuit 14 while rotating the rotor 1 at a high speed. Since the magnetic sensor 3 is disposed in the vicinity of a position shifted by 90 ° with respect to the dynamic magnetic center line L2, if the straight line connecting the N pole and S pole of the rotor 1 coincides with the dynamic magnetic center line L2, the magnetic The detection signal of the sensor 3 becomes zero.

  As indicated by Pos32 in FIG. 8, at the timing when the detection signal becomes zero, that is, when the straight line connecting the N pole and S pole of the rotor 1 coincides with the dynamic magnetic center line L2, the control circuit 14 Switch to O1 = HIGH and O2 = LOW.

  As shown by Pos33 in FIG. 8, the stator magnetic pole 2p is magnetized to the S pole and the stator magnetic pole 2q is magnetized to the N pole, and the rotor 1 continues to rotate further due to its inertia and magnetic force.

  As shown by Pos34 in FIG. 8, when the straight line connecting the N pole and S pole of the rotor 1 again coincides with the dynamic magnetic center line L2, and the detection signal of the magnetic sensor 3 becomes zero, the control circuit 14 generates a drive pulse signal. Repeatedly switch to O1 = LOW and O2 = HIGH.

  By disposing the magnetic sensor 3 in the vicinity of the position shifted by 90 ° with respect to the dynamic magnetic center line L2 in this way, it is synchronized with the phase of the rotor 1 by the detection signal of the magnetic sensor 3 without newly providing a detection means. By switching the drive pulse signal, it is possible to perform non-intermittent high-speed rotation with higher speed and efficiency.

It is a figure which shows the structure of the step motor which concerns on embodiment of this invention. It is a block diagram of the circuit which drives the step motor shown in FIG. 3 is a flowchart showing drive control processing executed by the control circuit shown in FIG. 2. It is a flowchart which shows the pulse width setting process (1) which the control circuit shown in FIG. 2 performs. It is a flowchart which shows the pulse width setting process (2) which the control circuit shown in FIG. 2 performs. It is a flowchart which shows the pulse width setting process (3) which the control circuit shown in FIG. 2 performs. It is a flowchart which shows the pulse width setting process (4) which the control circuit shown in FIG. 2 performs. It is a timing chart which shows the operation | movement at the time of rotating a rotor at high speed (forward direction) non-intermittently.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor 2 Stator 3 Magnetic sensor 11 Step motor 14 Control circuit

Claims (4)

A step motor for a clock that rotates intermittently;
A control unit for driving the step motor,
The step motor is
A rotor in which N and S poles are magnetized in two poles;
A stator comprising a pair of stator magnetic poles for driving the rotor and having a hole through which the rotor passes;
A drive coil for exciting the stator;
A magnetic sensor disposed near the shaft surface of the rotor and detecting a magnetic pole of the rotor close to the magnetic sensor and outputting a detection signal;
The control unit variably sets a pulse width of a drive pulse signal for controlling energization to the drive coil based on a detection signal output from the magnetic sensor to determine whether the rotor is rotated or not rotated by a previous pulse. To
A step motor driving device characterized by the above. In the stator, the angle of the static stability line indicating the direction in which the rotor is stationary in a non-excited state with respect to the dynamic magnetic center line of the stator magnetic pole is 45 ° or more and 90 ° or less in the forward rotation direction. The pair of stator magnetic poles is formed on
The magnetic sensor is disposed in the vicinity of a position shifted by 90 ° with respect to the dynamic magnetic center line.
The step motor driving device according to claim 1. The control unit includes a storage unit that stores pulse width data necessary for the rotation of the rotor at the time of forward rotation and reverse rotation of the rotor, respectively.
The step motor driving device according to claim 1, wherein the step motor driving device is provided. The control unit updates the pulse width data stored in the storage unit when the rotor rotates normally for a certain number of pulses.
The step motor drive device according to claim 3.

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