JP2005027370A - Rotor state detector and detecting method of stepping motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide rotor state detector and detecting method capable of detecting the rotor state directly regardless of variation in a current being fed to a coil. <P>SOLUTION: The rotor state detector of a stepping motor being driven through switching control of power supply (30) to each coil (A, B) comprises a means (40) for setting a detection state where one coil (A) out of two coils becomes conductible state and the other coil (B) becomes interrupted state, a means (51) for detecting a voltage being induced in the other coil under the detection state, and a means (52) for judging the rotor state based on the induction voltage detected by the induction voltage detecting means. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rotor state detection apparatus and method for a stepping motor, and more particularly to a rotor state detection apparatus and method for detecting whether a rotor of a stepping motor is in a rotating state or a stopped state.
[0002]
[Prior art]
For example, in a camera lens driving apparatus using a stepping motor, it is necessary to detect that the lens has reached the end position. By using an optical or mechanical sensor, it is possible to detect that the mechanical component (lens) moved by such a stepping motor has reached the end position. In addition, a method for detecting the end position of a mechanical component that is moved by the stepping motor without using such a sensor dedicated to position detection has been proposed (for example, Patent Document 1). In this method, when the mechanical component reaches the end position while the coil of the stepping motor is energized and the rotor is forcibly stopped, the mechanical component is The end position is detected.
[0003]
[Patent Document 1]
[Patent Document 1] Japanese Patent Application Laid-Open No. 62-1000019 [Problems to be Solved by the Invention]
However, in the conventional method, when the mechanical component reaches the end and the rotor is forcibly stopped, the rotor stopped state is detected based on the change in the current flowing through the coil. It is necessary to increase the current capacity of the drive circuit that performs the above and the detection circuit that performs the current detection.
[0004]
In addition, the conventional method estimates the state of the rotor based on a change in the current flowing through the coil, and does not directly detect the state of the rotor. If the current changes, the rotor state may be erroneously detected.
[0005]
The present invention has been made to solve the above-described drawbacks of the prior art, and the state of the rotor in the stepping motor capable of directly detecting the state of the rotor regardless of the change in the current supplied to the coil. A detection apparatus and method are provided.
[0006]
[Means for Solving the Problems]
A rotor state detection device in a stepping motor according to the present invention is a rotor state detection device in a stepping motor that has at least two coils and is driven by switching control of energization of each coil from a power source. Detection state setting means for setting a detection state in which one of the coils is energized and the other coil is in an energization cut-off state, and when the one coil is energized in the detection state, An induced voltage detection unit that detects a voltage induced in the other coil and a rotor state determination unit that determines the state of the rotor based on the induced voltage detected by the induced voltage detection unit.
[0007]
According to such a configuration, when the rotor is in the rotating state, in the detection state, the energization of the one coil contributes to the rotation of the rotor, while the other coil in the energization cut-off state is caused by the magnetic flux change. A voltage is induced. Therefore, the rotational state of the rotor can be determined based on the induced voltage. For example, when the mechanical component driven by the stepping motor reaches the end position and the rotor is forcibly stopped, the magnetic flux change in the other rotor disappears in the detection state, and the other coil There is no induced voltage. Therefore, the rotor stop state can be determined based on the induced voltage.
[0008]
Further, the rotor state detection device in the stepping motor according to the present invention may be configured such that the detection state setting means includes a switch means for switching connection and disconnection of the other coil to the power source.
[0009]
According to such a configuration, it is possible to easily set the detection state by setting the other coil to a cut-off state by the switch means.
[0010]
Furthermore, the detection state detection device for the rotor of the stepping motor according to the present invention is configured such that the detection state setting means sets the detection state at a timing when the drive pulse energization with a predetermined polarity is applied to the one coil. be able to.
[0011]
With such a configuration, the detection state can be easily set in the process of performing energization switching control on each coil.
[0012]
In the rotor state detection apparatus for a stepping motor according to the present invention, the detection state setting means includes a first switch means for switching between connection and disconnection of the one coil with respect to the power supply, and a state of the other coil with respect to the power supply. It can be set as the structure which has the 2nd switch means which switches connection and disconnection.
[0013]
According to such a configuration, switching between energization and energization interruption with respect to the one coil and switching between energization and energization interruption with respect to the other coil can be performed independently, so that the detection state can be performed at an arbitrary timing. It can be easily set.
[0014]
In the rotor state detection apparatus for a stepping motor according to the present invention, the detection state setting means sets the detection state after the coils are energized and shuts off, and in the detection state, the one coil is set to a predetermined state. It is possible to adopt a configuration in which a polarity pulse energization is performed.
[0015]
With such a configuration, the detection state can be set at an arbitrary timing in the process of performing energization switching control on each coil.
[0016]
The magnitude and time of pulse energization with respect to the one coil may be the same as or different from the magnitude and time of energization performed in normal drive control. From the viewpoint of not overloading the driving of the rotor, it is preferable that the magnitude and time of the pulse energization for the one coil are smaller than the magnitude and time of the energization performed in normal drive control.
[0017]
The rotor state detection apparatus in the stepping motor according to the present invention may be configured such that the induced voltage detection means includes voltage rectification means for rectifying the voltage induced in the other coil.
[0018]
With such a configuration, it is possible to evaluate the voltage induced in the other coil as a voltage level obtained by the rectifying means.
[0019]
Further, in the rotor state detection apparatus in the stepping motor according to the present invention, the rotor state determination unit includes a comparison unit that compares the rectified voltage obtained by the voltage rectification unit with a predetermined reference voltage. The rotor state can be determined based on the comparison result obtained in the above.
[0020]
According to such a configuration, by appropriately setting the reference voltage, the rotor is stopped by the magnitude relationship between the rectified voltage obtained by rectifying the voltage induced in the other coil and the reference voltage. The rotation state can be easily determined.
[0021]
A rotor state detection method in a stepping motor according to the present invention is a rotor state detection method in a stepping motor that has at least two coils and is driven by switching control of energization of each coil from a power source. A detection state setting step for setting a detection state in which one of the coils is energized and the other coil is in an energization cut-off state, and in the detection state, a voltage induced in the other coil is detected The configuration includes an induced voltage detection step and a rotor state determination step for determining the state of the rotor based on the induced voltage detected by the induced voltage detection means.
[0022]
Further, the rotor state detection method in the stepping motor according to the present invention is configured such that the detection state setting step sets the detection state at a timing when the drive pulse energization with a predetermined polarity is applied to the one coil. Can do.
[0023]
Furthermore, in the rotor state detection method in the stepping motor according to the present invention, the detection state setting step sets the detection state after the coils are turned off and the predetermined state is set in the one coil in the detection state. It can be configured to perform polarity pulse energization.
[0024]
Embodiment
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0025]
The basic configuration of the rotor state detection device in the stepping motor according to the embodiment of the present invention is as shown in FIG.
[0026]
In FIG. 1, the stepping motor 10 is driven by applying a pulse to each coil from a drive signal generator 30 (power source). The rotor state detection apparatus in the stepping motor 10 has a switching circuit 40 and a voltage detection circuit 50. The switching circuit 40 switches between connection and disconnection of a predetermined coil of the stepping motor 10 with respect to the drive signal generator 30 under the control of the CPU (control unit) 20. The voltage detection circuit 50 detects a voltage induced in a predetermined coil of the stepping motor 10 and sends a detection signal based on the induced voltage to the CPU 20. The CPU (control unit) 20 controls the drive signal generator 30 and the switching circuit 40 and is a mechanical component (for example, a camera lens) driven by the stepping motor 10 based on the detection signal from the voltage detection circuit 50. It is determined whether or not the terminal position has been reached.
[0027]
A specific configuration of the rotor state detection device in the stepping motor 10 (first embodiment of the present invention) is as shown in FIG. The stepping motor 10 includes stators 11a, 11b, 11c, 11d and a rotor 12, as shown in FIG. Further, the stepping motor 10 includes a coil A that magnetizes the opposing stators 11a and 11c and a coil B that magnetizes the opposing stators 11b and 11d.
[0028]
In FIG. 2, the drive signal generator 30 includes a pulse generation circuit 31 and a drive circuit 32, and the drive circuit 32 uses each pulse of the stepping motor 10 based on a pulse signal having a predetermined period from the pulse circuit generator 30. Drive pulse currents for A and B are output. The switching circuit 40 has a switch 41 and maintains the drive circuit 32 and the coil A of the stepping motor 10 in a constantly connected state. The switch 41 switches between connection and disconnection of the coil B in the stepping motor 10 with respect to the drive circuit 32 in accordance with a control signal from the CPU 20.
[0029]
The voltage detection circuit 50 includes a diode bridge circuit 51 and a comparison circuit 52. The diode bridge circuit 51 rectifies the voltage induced in the coil B of the stepping motor 10 and outputs a detection voltage that becomes a DC voltage. The comparison circuit 52 compares the detection voltage from the diode bridge circuit 51 with the reference voltage Vth and outputs an induced voltage detection signal having a level corresponding to the magnitude relationship between them. For example, when the detection voltage is equal to or higher than the reference voltage Vth, the induced voltage detection signal is at a high level, and when the detection voltage is lower than the reference voltage Vth, the induced voltage detection signal is at a low level. .
[0030]
When the stepping motor 10 is normally operated, the switch 41 is closed and the coil B is connected to the drive circuit 32. In this state, as shown in FIG. 3, the coil A from the drive circuit 32 based on the pulse signal from the pulse generator 31 so that the rotor 12 rotates once in four phases (I, II, III, IV). And the polarity of the drive pulse current for the coil B is sequentially switched. Thereby, the rotor 12 rotates continuously.
[0031]
When detecting the state of the rotor 12, the CPU 20 executes processing according to the procedure shown in FIG.
[0032]
In FIG. 4, when the detection routine is started, the CPU 20 supplies a drive pulse current having a phase I (I phase) polarity from the drive circuit 32 to the coil A (S1), and then controls the switch 41 by a control signal. It is opened (OFF) (S2). Thereby, the detection state is set. In this detection state, the coil B is disconnected from the drive circuit 32 and enters a high impedance state. Next, the CPU 20 causes the coil A to supply a drive pulse current having a phase II (II phase) polarity. At this time, if the rotor 12 is rotating, the magnetic field with respect to the coil B changes, and the change in the magnetic field causes a comparison with the coil B in phase II (II phase) as shown in FIG. Large voltage is induced. On the other hand, if the rotor 12 is stopped, there is no change (small) in the magnetic field with respect to the coil B, and the voltage induced in the coil B in phase II (II phase) is very small as shown in FIG. Become.
[0033]
The voltage induced in the coil B as described above is converted into a DC detection voltage by the diode bridge 51, and an induced voltage detection signal having a level corresponding to the magnitude relationship between the detection voltage and the reference voltage Vth is a comparison circuit 52. Is output from. After supplying the phase II (II phase) driving pulse current to the coil A (S3), the CPU 20 acquires the induced voltage detection signal from the comparison circuit 52 at a predetermined timing, and sets the level of the induced voltage detection signal. Based on this, it is determined whether or not the mechanical component driven by the stepping motor 10 has reached the end position (S4). For example, if the induced voltage detection signal is at a high level (the detected voltage is equal to or higher than the reference voltage Vth), it is determined that the component has not yet reached the end position (the rotor 12 is in a rotating state), and the induced voltage detection is performed. If the signal is at a low level (the detected voltage is smaller than the reference voltage Vth), it is determined that the mechanical component has reached the end position.
[0034]
When the processing of the detection routine as described above is completed when the rotor 12 is in a rotating state, the CPU 20 closes (ON) the switch 41 by a control signal to cancel the detection state, and thereafter, the coil A and the coil B In contrast, supply control of the drive pulse current from phase III (phase III) is performed. On the other hand, when the rotor 12 is in a stopped state, when the processing in the detection routine as described above is completed, the CPU 20 closes (ON) the switch 41 by a control signal to cancel the detection state, and each coil A, B The subsequent supply of the drive pulse current to is stopped.
[0035]
According to such a state detection device for the rotor 12 in the stepping motor 10, it is possible to detect the rotation state and the stop state of the rotor 12 without using a special sensor. Since the state of the rotor 12 is directly detected based on the induced voltage of the coil B, the state of the rotor 12 can be detected with high accuracy even if the supply current to the coil A changes due to power supply fluctuation or the like. it can.
[0036]
Further, since the rotation state and the stop state of the rotor 12 are detected based on the voltage induced in the coil B in a state of being separated from the drive circuit 32 (detection state), even if the rotor 12 is stopped, Current does not flow through the voltage detection circuit 50, and the current capacity of the voltage detection circuit 50 does not need to be designed to be particularly large. Furthermore, since the coil B is disconnected from the drive circuit 32 when the rotor 12 is stopped, there is no current supplied from the drive circuit 32 to the coil B, and the current capacity of the drive circuit 32 is the same as that of the conventional apparatus. It can be made smaller.
[0037]
Next, another specific configuration (second embodiment of the present invention) of the rotor state detection device in the stepping motor 10 is as shown in FIG. Also in this case, the configuration of the stepping motor 10 is the same as that shown in FIG. The apparatus according to the second embodiment of the present invention is different from the apparatus according to the first embodiment of the present invention described above in that the coil A can be connected to and disconnected from the drive circuit 32 as well. In FIG. 7, the same parts as those shown in FIG. 3 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0038]
In FIG. 7, the switching circuit 40 has a first switch 41a and a second switch 41b. The first switch 41 a switches between connection and disconnection of the coil A to the drive circuit 32 in the stepping motor 10 according to the control signal 1 from the CPU 20. The second switch 41b switches between connection and disconnection of the coil B to the drive circuit 32 in the stepping motor 10 according to the control signal 2 from the CPU 20.
[0039]
When the stepping motor 10 is normally operated, the first switch 41 a and the second switch 41 b are both closed, and the coil A and the coil B are connected to the drive circuit 32. In this state, as in the case of the first embodiment described above, as shown in FIG. 3, from the drive circuit 32, the rotor 12 rotates once in four phases (I, II, III, IV). The polarity of the drive pulse current for the coils A and B is sequentially switched.
[0040]
When detecting the state of the rotor 12, the CPU 20 executes processing according to the procedure shown in FIG.
[0041]
In FIG. 8, the CPU 20 opens (turns off) the first switch 41 a and the second switch 41 b with the control signal 1 and the control signal 2 at the start of the detection routine. In this state (see phase I in FIG. 9), the coil A and the coil B are in a high impedance state. Thereafter, the CPU 20 closes (ON) the first switch 41a by the control signal 1 to connect the coil A to the drive circuit 32 (S11). Thereby, the detection state is set. In this detection state, the CPU 20 supplies a short pulse current having a predetermined polarity from the drive circuit 32 to the coil A as in phase II shown in FIG. 9 (S12). Note that the polarity of the short pulse current is set to a polarity that does not hinder the rotation of the rotor 12.
[0042]
Thus, when the short pulse current is supplied to the coil A, if the rotor 12 is rotating, the magnetic field with respect to the coil B will change, and as shown in FIG. In addition, a relatively large voltage is induced in the coil B (see Phase II). On the other hand, if the rotor 12 is stopped, there is no change (less) in the magnetic field with respect to the coil B, and the voltage induced in the coil B is very small as shown in FIG. 10 (see Phase II). The CPU 20 generates the induced voltage output from the voltage detection circuit 50 (including the diode bridge 51 and the comparison circuit 52) based on the voltage induced in the coil B as in the case of the first embodiment described above. A detection signal is acquired at a predetermined timing. Then, the CPU 20 determines whether or not the mechanical component driven by the stepping motor 10 has reached the end position based on the level of the induced voltage detection signal (S13).
[0043]
After the determination, the CPU 20 opens (OFF) the first switch 41a again by the control signal 1 to disconnect the coil A from the drive circuit 32 (S14).
If the rotor 12 is in a rotating state, the CPU 20 closes (ON) the first switch 41a and the second switch 42 by the control signal 1 and the control signal 2 at a predetermined timing, and the coil A and the coil B Is connected to the drive circuit 32 (S15). Thereafter, the CPU 20 controls the supply of the drive pulse current from the phase III (phase III) to the coil A and the coil B (see FIG. 9).
On the other hand, if the rotor is in a stopped state (when the mechanical component has reached the end position), the CPU 20 stops the supply control of the drive pulse current to the coils A and B as it is.
[0044]
According to such a state detection device for the rotor 12 in the stepping motor 10, the same operation and effect as those of the first embodiment described above can be obtained, and the rotation control of the rotor 12 can be performed. The detection state for detecting the induced voltage of the coil B can be set at an arbitrary timing. Further, since the current to be supplied to the coil A in this detection state is a short pulse current, the overload with respect to the rotation of the rotor 12 due to the supplied current can be minimized.
[0045]
In the second embodiment, when only the coil A is connected to the drive circuit 32 from the state where the coil A and the coil B are disconnected from the drive circuit 32 (when switching to the detection state), or The stepping motor 12 is devised so that the rotor 12 does not reversely rotate when the coil A and the coil B are connected to the drive circuit 32 from the state where the coil B is disconnected from the drive circuit 32 (shift to normal drive). Has been. Specifically, as shown in FIG. 11, a protrusion is formed at a portion facing the rotor 12 at the downstream end in the rotation direction of each of the stators 11 a, 11 b, 11 c, and 11 d around which the coil A and the coil B are wound. As a result, the magnetic poles (N pole and S pole) of the rotor 12 always rotate in the direction approaching the protrusion, that is, the magnetic poles of the rotor 12 do not face each stator in each phase, but always slightly in the rotational direction. Since they face each other at an angle, reverse rotation of the rotor 12 can be prevented.
[0046]
Whether the above-mentioned mechanical component has reached the end is determined in the manufacturing process of the device on which the mechanical component is mounted, or in the initial setting operation when the device is turned on. It may be performed constantly in the process of using the device. Further, if the end position of the mechanical component (end position on one side or both sides) is detected at that time, the position of the mechanical component (for example, a camera lens) based on the number of pulses applied to the stepping motor 10 based on the position. Can be estimated.
[0047]
The above-described stepping motor 10 has two coils A and B. However, even a stepping motor having three or more coils determines the coil for detecting the induced voltage. The state of the rotor can be detected by the above-described apparatus.
[0048]
Further, even in the apparatus having the configuration shown in FIG. 7, the state of the rotor 12 can be detected using a regular drive pulse current, as in the case of the first embodiment. In this case, the coil for detecting the induced voltage can be set to either the coil A or the coil B by the first switch 41a and the second switch 41b.
[0049]
【The invention's effect】
As described above, according to the present invention, the state of the rotor is determined based on the voltage induced in the other coil that is in the power shut-off state while one coil is energized. Therefore, it is possible to realize a rotor state detection apparatus and method in a stepping motor that can directly detect the state of the rotor regardless of changes in the current supplied to the coil.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a basic configuration example of a rotor state detection device in a stepping motor according to an embodiment of the present invention.
FIG. 2 is a diagram showing an apparatus according to the first embodiment of the present invention.
FIG. 3 is a diagram showing an energization state of each coil during normal driving and a corresponding rotation state of a rotor.
FIG. 4 is a diagram illustrating an example of a processing procedure in a CPU.
5 is a diagram showing a voltage induced in a coil B in a detection state set when the rotor rotates in the apparatus shown in FIG. 2. FIG.
6 is a diagram showing a voltage induced in a coil B in a detection state set when the rotor is stopped in the apparatus shown in FIG. 2;
FIG. 7 is a diagram showing an apparatus according to a second embodiment of the present invention.
FIG. 8 is a diagram illustrating another example of a processing procedure in the CPU.
9 is a diagram showing a voltage induced in a coil B in a detection state set when the rotor rotates in the apparatus shown in FIG.
10 is a diagram showing a voltage induced in coil B in the detection state set when the rotor is stopped in the apparatus shown in FIG. 7;
FIG. 11 is a view showing a structural example of each stator in a stepping motor.
[Explanation of symbols]
10 Stepping motors 11a, 11b, 11c, 11c Stator 12 Rotor 20 CPU (control unit)
30 drive signal generator 31 pulse generation circuit 32 drive circuit 40 switching circuit 41 switch 50 voltage detection circuit 51 diode bridge circuit 52 comparison circuit

Claims (10)

A rotor state detection device in a stepping motor having at least two coils and driven by switching control of energization of each coil from a power source,
Detection state setting means for setting a detection state in which one of the two coils is energized and the other coil is energized;
In the detection state, induced voltage detection means for detecting a voltage induced in the other coil when the one coil is energized;
A rotor state detection apparatus in a stepping motor, comprising: a rotor state determination unit that determines a state of the rotor based on an induced voltage detected by the induced voltage detection unit. 2. The rotor state detection apparatus for a stepping motor according to claim 1, wherein the detection state setting means includes switch means for switching connection and disconnection of the other coil with respect to the power source. 3. The rotor state detection device for a stepping motor according to claim 1, wherein the detection state setting means sets the detection state at a timing when a drive pulse energization with a predetermined polarity is applied to the one coil. . The detection state setting means includes a first switch means for switching between connection and disconnection of the one coil to the power source,
2. The rotor state detection apparatus for a stepping motor according to claim 1, further comprising second switch means for switching connection and disconnection of the other coil to and from the power source. The detection state setting means sets the detection state after putting each of the coils into an energization cut-off state, and applies a pulse of a predetermined polarity to the one coil in the detection state. Rotor state detection device in the stepping motor of the present invention. 6. The rotor state detection device for a stepping motor according to claim 1, wherein the induced voltage detection means includes voltage rectification means for rectifying a voltage induced in the other coil. The rotor state determination unit includes a comparison unit that compares the rectified voltage obtained by the voltage rectification unit with a predetermined reference voltage, and performs rotor state determination based on the comparison result obtained by the comparison unit. 7. The rotor state detection apparatus according to claim 6, wherein the rotor state detection apparatus is configured as described above. A rotor state detection method in a stepping motor having at least two coils and driven by switching control of energization of each coil from a power source,
A detection state setting step of setting a detection state in which one of the two coils is energized and the other coil is in an energization cut-off state;
An induced voltage detecting step of detecting a voltage induced in the other coil in the detection state;
A rotor state detection method in a stepping motor, comprising: a rotor state determination step for determining a state of the rotor based on an induced voltage detected by the induced voltage detection means. 9. The method for detecting a rotor state in a stepping motor according to claim 8, wherein the detection state setting step sets the detection state at a timing when a drive pulse energization with a predetermined polarity is applied to the one coil. 9. The detection state setting step, wherein the detection state is set after each of the coils is turned off, and a pulse of a predetermined polarity is applied to the one coil in the detection state. A method for detecting the state of a rotor in a stepping motor.

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