JP2007094076A - Rotation detector of two-phase step motor, lens driving device, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve downsizing and high-speed rotation by eliminating the need of a rotation detection coil for detecting rotation of a rotor exclusively and to precisely discriminate the rotating state and the non-rotating state of the rotor to apply a discrimination result to lens reference position setting or the like. <P>SOLUTION: A rotation detector 4 detects rotation of a two-phase step motor having a rotor magnetized to two poles and a stator having two-phase coils wound around a yoke and includes: a pulse applying means 50 for applying a driving pulse to each coil; a detection means 51 for detecting an induced voltage generated between both terminals of at lest one coil, within a rotation angle range wherein the induced voltage is maximum; and a determination means 52 for comparing the detected induced voltage with a preliminarily set reference voltage to determine whether the rotor is rotating or not. The pulse applying means applies the driving pulse so as to produce a certain opening time, and the detection means detects the induced voltage within the certain opening period. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotation detection device for detecting the rotation of a two-phase step motor used as a driving source for driving a lens of a digital camera, a mobile phone with a camera, etc., a lens driving device having the rotation detecting device, and an electronic apparatus having the same It is about.

An electronic device having a camera mechanism such as a digital camera incorporates a lens driving device to perform an autofocus and zoom function. A two-phase step motor is generally used as a driving source for driving the lens driving device. Has been.
As this type of two-phase step motor, for example, it has a rotor magnetized in two poles, a stator around which a two-phase coil is wound, and a notch provided in an opposing portion of the stator. There is known a motor capable of rotating forward and backward by 180 degrees (step angle 180 °) so that a magnetically stable state can be maintained at a certain angle (see, for example, Patent Document 1).

By the way, in this kind of two-phase step motor, in order to realize low power consumption, it is necessary to keep input power to a minimum. However, if the rotor cannot rotate due to factors such as load fluctuations and disturbances, accurate position feed cannot be realized. Therefore, in order to realize accurate position feed, some rotation detection devices for detecting the rotation of the rotor are separately provided.
Such a rotation detection device detects the rotation of the rotor by various methods. For example, the current is detected by a detection resistor, and after the drive pulse is applied, the rotation is detected from the change in the counter electromotive force caused by the vibration of the rotor. (For example, see Patent Document 2), a method for detecting a voltage by opening a terminal and detecting a rotation from a change in counter electromotive force due to vibration of a rotor after applying a driving pulse (for example, see Patent Document 3). ) And a method of simultaneously detecting the rotation of the rotor and the rotation of the rotor using a detection coil (for example, see Patent Document 4).
JP-A-57-15662 JP 61-94598 A JP 2001-51076 A JP 2001-289972 A

However, the following problems remain in the conventional method.
That is, in the method of detecting the current using the detection resistor or the method of detecting the voltage by opening the terminal, the rotation detection time is required every time one step driving (rotating 180 °), so the driving is continuously performed. It was difficult to apply a pulse. Therefore, the rotor could not be rotated at a high speed.
Further, in the method of simultaneously performing the rotor driving and the rotor rotation detection by the detection coil, the detection coil has to be provided separately, so that a dedicated space for that is required, which hinders downsizing.

  The present invention has been made in view of such circumstances, and the object thereof is to eliminate the need for a rotation detection coil that exclusively detects the rotation of the rotor, which can be miniaturized and can perform high-speed rotation. To provide a rotation detecting device for a two-phase step motor, a lens driving device having the same, and an electronic device having the same.

Here, an example in which a conventional two-phase step motor and rotation detection device are applied to a lens driving device will be described.
The lens driving device is built in electronic devices such as digital cameras and camera-equipped mobile phones, and enables focusing and zooming by moving the lens in the optical axis direction and changing the distance from the image sensor. It is what is letting. This lens driving device is, for example, arranged in a direction parallel to the optical axis, and a lead screw that is rotationally driven by a two-phase step motor, and is screwed into the lead screw, and in the optical axis direction as the lead screw rotates. A moving nut and a lens frame for fixing the lens and having one end fixed to the nut are provided.

  According to the lens driving device configured as described above, the lead screw can be rotated in an arbitrary direction by the two-phase step motor, and the nut can be moved along the lead screw, that is, along the optical axis direction. As a result, the lens can be moved in the optical axis direction via the lens frame, and focus, zoom, and the like can be performed by changing the focal point.

By the way, in order to accurately control the movement of the lens and perform focusing, zooming, and the like with high accuracy, it is necessary to set the position of the lens in advance as a reference position. That is, the reference position needs to be set before lens driving. Several methods are known for setting the reference position. For example, as shown in FIGS. 18A and 18B, a lens frame is detected by a position detection sensor such as a photo interrupter or an electrical contact. A method is known in which a detection member attached to the sensor is detected and the detected position is used as a reference position.
That is, in the method using the photo interrupter shown in FIG. 18A, the position where the detection member approaches and blocks light is the reference position. In the method using the electrical contact shown in FIG. 18B, the position where the detection member (conductive member) is brought into contact and conducted is the reference position.

However, the method using the position detection sensor requires a space for the sensor and the detection member, which hinders downsizing. Further, since the number of parts increases, there is a disadvantage that the cost increases.
Therefore, without using such a position detection sensor, for example, as shown in FIG. 18 (c), the rotor of the step motor has a predetermined number of predetermined steps (for example, 100 steps; maximum movement in which the nut can move). There is known a method in which the nut is moved to a position where it is mechanically stopped by rotating it by an amount corresponding to the amount), and that position is used as a reference position.

  However, in this method, when the nut is positioned at the extreme end side of the movable range, when the nut is rotated by the specified number of steps, the nut comes into contact with the contact portion and becomes mechanically stationary. When the nut is positioned in the middle of the movable range, the nut comes into contact with the contact portion in the middle and becomes stationary. However, since the lead screw is forcibly rotated by a predetermined number of steps regardless of the position of the nut, a drive pulse is input and the motor continues to rotate even after the nut is stationary. As a result, the nut may be bitten by the lead screw, or may be worn out and cause malfunction. Further, since the nut is merely rotated unnecessarily after the nut is stationary, the power consumption is increased and the detection time is increased.

  Further, as shown in FIG. 18 (d), a shaft having a smaller diameter than that of the lead screw is also known. By doing this, when the nut reaches the small-diameter shaft part, the engagement is disengaged, so that direct contact between the nut and the contact part is prevented, and it is possible to prevent the nut from being caught or malfunctioning due to wear. Although it is possible, since the lead screw is rotated by a predetermined number of steps regardless of the position of the nut, power consumption and detection time are increased.

   Therefore, if the rotation detection device can be used to set the reference point by detecting that the motor is not rotating when the nut contacts the contact portion, the power consumption and detection time at the time of detecting the reference point Can be reduced. However, as described above, in the conventionally proposed rotation detection device, various problems such as the fact that the rotor cannot be rotated at a high speed and a detection coil needs to be provided separately have occurred.

  Therefore, as another object of the present invention, there is provided a rotation detection device for a two-phase step motor capable of discriminating the rotation state and non-rotation state of the rotor with high accuracy and applied to the reference position setting of the lens and the like A lens driving device, and further an electronic apparatus having the lens driving device.

The present invention provides the following means in order to solve the above problems.
The rotation detection device for a two-phase step motor of the present invention is a rotation detection device for a two-phase step motor having a rotor magnetized in two poles and a stator having a two-phase coil wound around a yoke, A pulse applying means for applying a driving pulse to each of the two-phase coils, and an induced voltage generated between both terminals of at least one of the two-phase coils, the rotation of the rotor that maximizes the induced voltage. Detection means for detecting within an angle range; and judgment means for judging whether the rotor is rotating by comparing the detected induced voltage with a preset reference voltage; and the pulse applying means When the rotor reaches the rotation angle range, the drive pulse is applied to the coil from which the induced voltage is detected so that a certain open time is available, and the detection means It is characterized in detecting the induced voltage within a certain open time.

In the rotation detecting device for a two-phase step motor according to the present invention, a predetermined drive pulse is applied to each coil by the pulse applying means, thereby generating S and N pole magnetic fields in the stator. Thereby, the rotor magnetized to two poles of the S pole and the N pole rotates by receiving the repulsion / attraction force of the magnetic field generated in the stator. As a result, the rotor can be rotated at a step angle of 180 °, for example (it is also possible to rotate at a step angle of 90 °).
Here, when the rotor is rotating, an induced voltage is generated between the terminals of the two-phase coils, which is proportional to the amount of time variation of the rotor magnetic flux linked to the coils. When the rotor is in a non-rotating state, the change in magnetic flux is “0” and no induced voltage is generated. The induced voltage changes in magnitude according to the rotation angle and the rotation speed of the rotor, and a rotation angle range that has a maximum value (peak) during normal rotation is determined in advance.

  Therefore, the detecting means detects the induced voltage generated in at least one of the rotors when the rotor reaches the rotation angle range in which the induced voltage is maximum. At this time, the pulse applying means applies a driving pulse to the coil in which the induced voltage is detected so that a certain open time is available when the rotor reaches the rotation angle range. And a detection means detects an induced voltage within this fixed open time. Thereby, the detection means can reliably detect the maximum induced voltage generated in the coil.

  Then, the determination means determines whether the rotor is rotating by comparing the detected induced voltage with a preset reference voltage. That is, if the induced voltage is larger than the reference voltage, it is determined that the rotor is rotating, and if the induced voltage is smaller, it is determined that the rotor is stopped. Thus, by detecting the induced voltage generated in the coil, it is possible to accurately grasp the rotation state of the rotor. Therefore, there is no need to provide a dedicated rotation detection coil for detecting the rotation of the rotor as in the prior art. Therefore, it is possible to reduce the size.

In addition, since the detecting means detects the induced voltage only within a certain open time, it is possible to detect rotation simultaneously with the driving while driving the rotor. Further, since the application of the drive pulse is stopped only during a certain opening time, the influence on the rotational speed of the rotor can be reduced as much as possible, and high-speed rotation can be achieved.
In particular, since the detecting means detects an induced voltage generated in at least one of the coils, when the detection is performed for one coil, the other coil is continuously in a state without a certain open time. A drive pulse is applied to. Therefore, in this case, the rotational speed of the rotor is hardly affected.
The induced voltage generated in both coils may be detected. In this case, in addition to detecting the rotation of the rotor, the rotation direction of the rotor can also be confirmed.

As described above, according to the rotation detection device for the two-phase step motor of the present embodiment, the coil for detecting the rotation of the rotor is not required and the size can be reduced, and the rotation detection of the rotor can be performed without reducing the rotation speed of the rotor. It can be performed.
Further, since it is possible to detect with high accuracy whether or not the rotor is rotating based on the detected induced voltage, when the two-phase step motor is applied to, for example, a lens driving device, the reference position setting of the lens, etc. Can be easily performed.

  In addition, the two-phase step motor rotation detection device of the present invention is the two-phase step motor rotation detection device of the present invention, wherein the pulse applying means is fixed when the rotor reaches the rotation angle range. The drive pulse is applied in a state where the opening time is repeated a plurality of times at each time interval.

In the rotation detecting device for a two-phase step motor according to the present invention, when the rotor reaches the rotation angle range in which the induced voltage is maximum, the pulse applying means repeats the opening time a plurality of times at regular time intervals. Apply drive pulses. Accordingly, it is possible to detect the induced voltage in a wide range while the rotor reaches the rotation angle range in which the induced voltage becomes maximum, instead of detecting the induced voltage in one opening time. Therefore, the detection of the induced voltage becomes more accurate and the rotation can be detected more accurately.
Moreover, since the opening time of one time can be shortened, a decrease in the rotational speed of the rotor can be further suppressed, leading to prevention of torque reduction.

  Further, the rotation detection device for a two-phase step motor of the present invention is the rotation detection device for a two-phase step motor of the present invention described above, wherein each time the detection device rotates the rotor one step, A terminal is provided for detecting each terminal voltage generated, and for calculating the induced voltage from the difference between the two terminal voltages.

  In the rotation detection device for a two-phase step motor according to the present invention, when the rotor reaches a rotation angle range in which the induced voltage is maximum every time the rotor rotates by one step, the calculation unit first determines the coil Terminal voltages (voltages with respect to the ground) generated at both terminals are detected. And a calculation part calculates an induced voltage from the difference of these detected both terminal voltages. Thus, since it has a calculation part, an induced voltage can be easily calculated from the both terminal voltages of a coil.

  Further, the rotation detection device for a two-phase step motor of the present invention is the rotation detection device for a two-phase step motor of the present invention, wherein the pulse applying means has a diode connected to one terminal of the coil, The detection means has a resistor connected between the other terminal of the coil and the ground, and the voltage generated between the diode and the resistor every time the rotor rotates two steps. Based on this, the induced voltage is detected.

  In the rotation detecting device for a two-phase stepping motor according to the present invention, the induced voltage can be detected by using a diode normally included in pulse applying means such as a motor driver. Therefore, the components for detecting the induced voltage can be minimized, and the configuration can be simplified.

  The lens driving device of the present invention is movable along the optical axis, the rotation detecting device of any of the above two-phase step motors of the present invention, the two-phase step motor whose rotation is detected by the rotation detecting device, and And a driving means for moving the lens body along the optical axis in accordance with the driving of the two-phase step motor to vary the distance from the image sensor. To do.

  In the lens driving device according to the present invention, when the rotor of the two-phase step motor is rotated, the driving means is operated to move the lens body along the optical axis. Accordingly, the distance between the lens body and the image sensor can be adjusted to be an arbitrary distance. As a result, the focus can be changed, and focus and zoom can be performed.

  In particular, since it has a rotation detection device that can detect with high accuracy whether or not the rotor is rotating, the reference position setting for setting the lens body at a predetermined reference position can be performed easily and reliably. . For example, when a lens body is brought into contact with each other and mechanically stopped, it is forcibly limited to a predetermined number of predetermined steps even if the nut screwed into the rotor is in contact with each other. In the present invention, it is possible to detect whether or not the rotor is rotating. Therefore, the application of the drive pulse can be stopped when the rotation of the rotor is stopped. Therefore, the detection time can be shortened and the power consumption can be reduced. Further, it is possible to prevent wear of the nut and the like, and to eliminate malfunction as much as possible.

  Further, the lens driving device of the present invention is the lens driving device of the present invention, wherein the lens driving device is provided at a moving end of the lens body and contacts the moving lens body to stop the movement of the lens body and the rotor. A contact portion for stopping the rotation of the lens body, and when the determination means determines that the rotor is in a non-rotating state, a position where the lens body contacts the contact portion is set as a lens reference position. It is characterized by.

In the lens driving device according to the present invention, since the moving end of the lens body (the end of the moving stroke) has a contact portion, when the lens body is moved to the full stroke by the rotation of the rotor, the lens body However, the movement stops due to mechanical contact with the contact portion. Further, since the movement of the lens body is regulated by contacting the contact portion, the rotation of the rotor is loaded and starts to stop.
Here, the determining means determines that the rotor is in a non-rotating state based on the detected induced voltage, and determines that the lens body has come into contact with the contact portion and stopped. Then, this contact position is set as the lens reference position of the lens body. Thus, the lens reference position can be set accurately in a short time.

  An electronic apparatus according to the present invention includes the lens driving device according to the present invention.

  The electronic apparatus according to the present invention includes a lens driving device that performs the setting of the reference position of the lens in a state where there is little malfunction and the power consumption is reduced in a short time, so that it is easy to use and excellent in convenience. , Quality and reliability can be improved.

  According to the rotation detection device for a two-phase step motor of the present invention, it is possible to reduce the size and reduce the size of the rotor without reducing the rotation speed of the rotor. it can. Further, since rotation or non-rotation of the rotor can be detected with high accuracy, it can be applied to various devices.

In addition, according to the lens driving device of the present invention, since the rotation detection device that can detect with high accuracy whether or not the rotor is rotating is provided, the reference position setting of the lens can be performed in a short time. It can be performed accurately with little power consumption.
In addition, according to the electronic apparatus of the present invention, it is possible to set the reference position promptly before performing focusing, zooming, or the like, and perform operations such as focusing accurately. Therefore, it is easy to use and excellent in convenience, and it is difficult to cause malfunctions with low consumption, so that quality and reliability can be improved.

Hereinafter, an embodiment of a rotation detection device for a two-phase step motor, a lens driving device, and an electronic apparatus according to the present invention will be described with reference to FIGS.
As shown in FIG. 1, a camera-equipped mobile phone (electronic device) 1 according to the present embodiment includes a lens driving device 2 incorporated in a housing (not shown). The lens driving device 2 includes a two-phase step motor 3, a rotation detection device 4 that detects the rotation of the two-phase step motor 3, a lens body 5 that is movably disposed along the optical axis L1, and a two-phase motor. A driving means 7 is provided for moving the lens body 5 along the optical axis L <b> 1 as the step motor 3 is driven to vary the distance from the image sensor 6.

As shown in FIG. 2, the two-phase step motor 3 includes a rotor 10 magnetized in two poles with a step angle of 180 °, a stator 13 in which two-phase coils A and B are wound around yokes 11 and 12, and have. The stator 13 is formed with elongated holes 14 and 15 that serve as spaces for winding the coils A and B. A region extending from the elongated holes 14 and 15 to one side surface of the stator 13 is the yokes 11 and 12. It has become. Coils A and B are wound around the yokes 11 and 12, respectively.
Further, the stator 13 has a rotor insertion hole 10a through which the rotor 10 is inserted, an insertion hole 10b through which a lead screw 35 described later is inserted, and a fixing insertion hole (not shown) through which a fixing screw 20 for fixing the stator 13 is inserted. Is formed.

Furthermore, two notches 16 for stabilizing the stop position of the rotor 10 are formed in the stator 13 around the axis L2 of the rotor 10 with an interval of 180 °. A recess for cutting the magnetic path is formed in the upper portion of the stator 13. And between this dent and the rotor insertion hole 10a, between the two long holes 14 and 15 and the rotor insertion hole 10a, it is the pole part 17 magnetically cut | disconnected.
In the two-phase stepping motor 3 configured as described above, the rotor 10 rotates at a step angle of 180 ° by a magnetic action generated by applying a predetermined driving pulse by a motor driver 50 described later. . This rotation principle will be described in detail later.

  A terminal on one end side of the coil A is a1, a terminal on the other end side is a2, a terminal on one end side of the coil B is b1, and a terminal on the other end side is b2. Also, drive pulses applied to the terminals a1 and a2 are A1 and A2, and drive pulses applied to the terminals b1 and b2 are B1 and B2.

As shown in FIG. 1, the two-phase stepping motor 3 configured as described above is supported with the bottom surface of the stator 13 being placed on the support member 21 and disposed above the stator 13. The cover 22 is fixed by the fixing screw 20.
The support member 21 is made of, for example, a non-magnetic material, and functions as a gear support that rotatably supports various gears described later in addition to supporting the two-phase step motor 3. The support member 21 is fixed on the base member 23. The base member 23 is formed, for example, in a rectangular shape when viewed from above, and is fixed by a fixing screw 25 while being placed on the upper surface of the circuit board 24. At this time, the fixing screw 25 also fixes the hard support plate 26 laminated in an insulating state on the back surface of the circuit board 24.

  On the circuit board 24, the rotation detection device 4 and the image sensor 6 (for example, a semiconductor device such as a CCD or a CMOS) are mounted. The image sensor 6 is mounted so as to be accommodated in an opening 23 a formed in a step shape on the base member 23. The circuit board 24 is bent at approximately 90 ° at one end side, and is fastened together with the fixing screw 20 that fixes the two-phase step motor 3. At this time, the fixing screw 20 fixes the circuit board 24 with the coil block 27 sandwiched between the circuit board 24 and the stator 13. This facilitates the wiring work of a motor lead (not shown) between the circuit board 24 and the coils A and B.

  The cover portion 22 is formed so as to cover the upper portions of the two-phase step motor 3, the support member 21, the base member 23, and the like described above, and these are built in a space between the circuit board 24. In the cover portion 22, a daylighting hole 22 a that becomes incident light of the lens body 5 is formed at a position corresponding to the upper side of the image sensor 6.

The lens body 5 is disposed above the image sensor 6 and includes a cylindrical lens holder portion 30 and one or more lenses R fixed to the inner peripheral surface of the lens holder portion 30. Has been. Note that the installation positions of the image pickup device 6 and the daylighting hole 22a are adjusted so as to be arranged on the optical axis L1 of the lens R.
A pair of sliding portions 31 and 32 are provided on the outer periphery of the lens holder portion 30 so as to face each other with the optical axis L1 in between. The pair of sliding portions 31 and 32 are respectively formed with guide holes 31a and 32a such as through holes and grooves through which the pair of guide shafts 33 and 34 can be inserted.

  The pair of guide shafts 33 and 34 are, for example, round bars and are arranged in parallel with the optical axis L1 at a position sandwiching the lens body 5 therebetween, and both ends are fixed to the cover portion 22 and the base member 23, respectively. ing. That is, the lens body 5 is supported in a state of being spanned between the pair of guide shafts 33 and 34, and is disposed so as to be positioned between the imaging element 6 and the daylighting hole 22a. The pair of guide shafts 33, 34 and the pair of guide holes 31a, 32a are slidable. As a result, the lens body 5 is movable along the pair of guide shafts 33 and 34 in the direction of the optical axis L1.

Further, of the pair of sliding portions 31 and 32, one sliding portion 31 is formed so as to extend in a direction away from the lens body 5, and is screwed to the screw portion 35 a of the lead screw 35 at the tip thereof. The nut 36 to be pressed is provided in a press-fit state.
The lead screw 35 is disposed so as to be parallel to the optical axis L <b> 1 at a position adjacent to one of the pair of guide shafts 33, 34. At this time, the lead screw 35 is arranged in a state of passing through the insertion hole 10 b formed in the stator 13 of the two-phase step motor 3. Further, both ends of the lead screw 35 are rotatably supported by the cover portion 22 and the base member 23, respectively. As a result, the lead screw 35 can rotate about an axis L3 parallel to the optical axis L1.

Note that the bottom surface of one sliding portion 31 is a contact portion 31b (the same as the bottom surface of the nut 36), and when the lens body 5 is moved closest to the image sensor 6, the contact portion 31b and the upper surface of the base member 23 are in contact with each other. In this embodiment, the position at this time is set as the reference position of the lens R.
That is, the base member 23 is provided at the moving end of the lens body 5 and functions as a contact portion that contacts the moving lens body 5 to stop the movement of the lens body 5 and stop the rotation of the rotor 10. It is supposed to be.

  A driven gear 35b integrally formed with the lead screw 35 is formed on the cover portion 22 side of the lead screw 35, and a thread groove is formed on the outer peripheral surface on the base member 23 side beyond the insertion hole 10b. Thus, the thread portion 35a is formed. As described above, the nut 36 press-fitted into the one sliding portion 31 is screwed into the screw portion 35a. At this time, since the lens body 5 is supported by the pair of guide shafts 33, 34, the nut 36 is rotated by the lead screw 35 without rotating when the lead screw 35 is rotated around the axis L 3. It moves in the L3 direction. That is, the rotational motion is converted into a linear motion.

The driven gear 35b of the lead screw 35 is connected to a drive gear 41 fixed to the rotor 10 of the two-phase step motor 3 via the reduction gear mechanism 40, and rotates around the axis L2 as the rotor 10 rotates. It is designed to rotate.
More specifically, first, the rotor 10 of the two-phase step motor 3 is rotatably supported at both ends by the cover portion 22 and the support member 21, and the driving gear 41 is integrally molded on the outer peripheral surface, for example. ing. The drive gear 41 is meshed with a first reduction gear 42 whose both ends are rotatably supported by the cover portion 22 and the support member 21. Further, the first reduction gear 42 is integrally formed with a second reduction gear 43 having a small diameter. The driven gear 35 b is engaged with the second reduction gear 43. Thus, the rotational force of the rotor 10 is transmitted to the lead screw 35 after being decelerated by the drive gear 41, the first reduction gear 42, the second reduction gear 43, and the driven gear 35b.

  That is, the first reduction gear 42 and the second reduction gear 43 constitute the reduction gear mechanism 40. The drive gear 41, the reduction gear mechanism 40, the lead screw 35, and the nut 36 constitute the drive means 7 that moves the lens body 5 as the rotor 10 rotates.

As shown in FIG. 3, the rotation detecting device 4 includes a motor driver (pulse applying means) 50 for applying a driving pulse to each of the two-phase coils A and B, and at least one of the two-phase coils A and B. Detecting means 51 for detecting an induced voltage generated between both terminals a1, a2 or b1, b2 of the coil within a rotation angle range of the rotor 10 at which the induced voltage is maximum, and the detected induced voltage is preset. A DSP (digital signal processor) (determination means) 52 that determines whether or not the rotor 10 is rotating as compared with the reference voltage is provided. When the DSP 52 determines that the rotor 10 is in a non-rotating state, the DSP 52 sets the position where the lens body 5 is in contact with the base member 23 that is the contact portion as the lens reference position.
In addition, when the rotor 10 reaches the rotation angle range described above, the motor driver 50 sends a drive pulse to the coils A and B in which the induced voltage is detected with a certain open time t _OFF. It is designed to be applied. Further, the detection means 51 detects the induced voltage within the certain open time t _OFF .

The detecting means 51 detects the terminal voltage generated at both terminals a1, a2 or b1, b2 of the coils A, B each time the rotor 10 rotates by one step, and the induced voltage is calculated from the difference between the two terminal voltages. An A / D conversion circuit (calculation unit) 53 for calculation is provided.
The DSP 52 includes a CPU 54 and a ROM 55 and a RAM 56 that store the above-described reference voltage, various programs, fixed data, and the like.
In the present embodiment, an A / D conversion circuit 53 is built in the DSP 52. The CPU 54, ROM 55, RAM 56, and A / D conversion circuit 53 are electrically connected to each other via a bus.

The principle of detecting the rotation of the rotor 10 by the thus configured rotation detection device 4 will be described in detail later.
First, the rotation principle of the two-phase step motor 3 will be described below with reference to FIGS. 4 and 5. First, a case where the rotor 10 is rotated clockwise (CW direction) will be described. 4 and 5, the polarities of the drive pulses applied to the coils A and B are illustrated.

First, as shown in FIG. 4A, in the state where the rotation angle of the rotor 10 is 0 °, a driving pulse having the polarity shown in FIG. As a result of this application, a magnetic field is generated in the stator 13 so as to have an N pole on the upper left and an S pole on the upper right. As a result, the S pole and N pole of the rotor 10 rotate in the clockwise direction by receiving a repulsive force / attraction force from the S pole and N pole of the magnetic field generated in the stator 13.
Next, when the rotor 10 rotates 90 °, the polarity of the drive pulse applied to the coil B is reversed as shown in FIG. As a result, a magnetic field is generated in the stator 13 such that the middle part of the yokes 11 and 12 is the S pole and the upper left and right sides of the stator 13 are the N poles. As a result, the rotor 10 is further rotated in the clockwise direction, and the rotor 10 is rotated 180 ° as shown in FIG.

  When the rotor 10 rotates 180 °, the drive pulse applied to the coil A is reversed as shown in FIG. If the drive pulse applied to the coil A is not reversed when the rotor 10 rotates 180 °, the rotation gradually converges around the notch 16 as shown in FIG. Stopped. On the other hand, as described above, when the drive pulse is inverted, a magnetic field is generated in the stator 13 such that the upper left side is the S pole and the upper right side is the N pole, as shown in FIG. To do. As a result, the S pole and N pole of the rotor 10 receive repulsive force and attractive force from the S pole and N pole of the stator 13, respectively, and further rotate in the clockwise direction.

  Next, when the rotor 10 rotates 270 °, the drive pulse applied to the coil B is reversed as shown in FIG. As a result, a magnetic field is generated in the stator 13 such that the middle part of both yokes 11 and 12 has an N pole and the upper left and right sides of the stator 13 have an S pole. As a result, as shown in FIG. 4F, the rotor 10 further rotates and makes one rotation. Thus, the rotor 10 can be rotated clockwise by changing the drive pulse applied to each of the coils A and B in a timely manner according to the rotation angle of the rotor 10.

  When the rotor 10 rotates 360 ° (one rotation), the drive pulse applied to the coil A is changed to the state shown in FIG. If not changed, as shown in FIG. 4 (f), the rotation gradually converges around the notch 16 as in the case of 180 ° rotation, and a stop state is reached.

Next, the case where the rotor 10 is rotated counterclockwise (CCW direction) will be described with reference to FIG. In this case, the basic principle is the same as in the case of rotating clockwise as described above, except that the polarity and order of the applied pulses are different.
That is, as shown in FIG. 5A, in the state where the rotation angle of the rotor 10 is 0 °, a drive pulse having the polarity shown in FIG. As a result of this application, a magnetic field is generated in the stator 13 so as to have an S pole on the upper left and an N pole on the upper right. As a result, the S pole and N pole of the rotor 10 are rotated counterclockwise by receiving a repulsive force / attraction force from the S pole and N pole of the magnetic field generated in the stator 13.

  Next, when the rotor 10 rotates 90 °, the polarity of the drive pulse applied to the coil A is reversed as shown in FIG. As a result, a magnetic field is generated in the stator 13 such that the middle part of the yokes 11 and 12 is the S pole and the upper left and right sides of the stator 13 are the N poles. As a result, the rotor 10 is further rotated counterclockwise, and the rotor 10 rotates 180 ° as shown in FIG.

Then, when the rotor 10 rotates 180 °, the drive pulse applied to the coil B is reversed as shown in FIG. As a result, a magnetic field is generated in the stator 13 such that the upper left side is the N pole and the upper right side is the S pole. As a result, the S pole and N pole of the rotor 10 receive repulsive force / attraction force from the S pole and N pole of the stator 13, respectively, and further rotate counterclockwise.
If the drive pulse applied to the coil B is not reversed when the rotor 10 rotates 180 °, the rotation gradually converges around the notch 16 as shown in FIG. Stop.

Next, when the rotor 10 rotates 270 °, the polarity of the drive pulse applied to the coil A is reversed as shown in FIG. As a result, a magnetic field is generated in the stator 13 such that the middle part of both yokes 11 and 12 has an N pole and the upper left and right sides of the stator 13 have an S pole. As a result, as shown in FIG. 5F, the rotor 10 further rotates and makes one rotation. Thus, the rotor 10 can be rotated counterclockwise by changing the drive pulses applied to the coils A and B in a timely manner according to the rotation angle of the rotor 10.
When the rotor 10 rotates 360 degrees (one rotation), the drive pulse can be further rotated by setting the drive pulse to the state shown in FIG. 5A, and the drive pulse applied to the coil B can be increased. When the reversal is not performed, as shown in FIG. 5 (f), a stop state is gradually started around the notch 16 as in the case of the clockwise rotation.

  In the case of 90 ° step driving, it is possible to keep the rotor 10 stationary at rotor rotation angles of 90 ° and 270 ° by continuously inputting drive pulses P1 and P3 described later.

Next, the principle of detecting the rotation of the rotor 10 by the rotation detection device 4 will be described.
First, the induced voltage generated in the coils A and B will be described below. Since this induced voltage is derived by the rotational speed of the rotor 10 and the coil linkage magnetic flux, these will be described first with reference to FIGS. Note that the case where the rotor 10 is rotated counterclockwise (CCW direction) as shown in FIG. 10 will be described as an example.

  Here, the interlinkage magnetic flux of each of the coils A and B (the magnetic flux received from the rotor 10 when the coils A and B are not excited) with respect to the rotation angle of the rotor 10 is shown in FIG. FIG. 7 shows the rotation speed of the rotor 10 with respect to the above, and FIG. At this time, the magnetic flux in the arrow direction shown in FIG. 10 is positive.

First, as shown in FIG. 6, it can be seen that the flux linkages generated in both coils A and B are out of phase by 60 °. Further, it can be seen that the range in which the amount of change in the interlinkage magnetic flux is large, that is, the range in which the inclination is large, is within the range of the rotor rotation angle of approximately 90 ° to 210 ° and the range of 270 ° to 10 °.
Next, as shown in FIG. 7, it can be seen that the rotational speed of the rotor 10 is increased every 90 °, starting from 0 °. This is because, as shown in FIGS. 8 and 9, the drive pulse is switched at the rotation angle (every 90 °) at which the torque is maximized, so that the rotation speed immediately after the pulse switch is maximized.

That is, as shown in FIG. 8, the range where the rotor rotation angle is 0 ° to 90 ° is P1 pulse, the range where the rotor rotation angle is 90 ° to 180 ° is P2 pulse, and the range where the rotor rotation angle is 180 ° to 270 °. Is a P3 pulse, and a rotor rotation angle of 270 ° to 360 ° is a P4 pulse. As shown in FIG. 9, the torque waveform of the rotor 10 is the same as that of the P1 pulse and the P3 pulse. The P4 pulse has the same waveform.
As described above, since the drive pulses are sequentially switched at the position where each torque is the largest (position where the rotor rotation angle is every 90 °), the rotation speed immediately after the pulse switching is increased, and the rotation speed of the rotor 10 is The waveform is shown in FIG.

Next, the induced voltage generated in the coil A is shown in FIG. The voltage in the direction of the arrow shown in FIG. 12 is positive. As shown in FIG. 11, the induced voltage has a negative peak in the vicinity of the rotor rotation angle of approximately 90 ° to 150 °, and a positive peak in the vicinity of the rotor rotation angle of 270 ° to 330 °. I know that. That is, the induced voltage is a value obtained by multiplying the gradient of the coil linkage magnetic flux by the rotation speed of the rotor 10, so that the induced voltage is most in the above range where the gradient of the coil linkage flux is large and the rotation speed of the rotor 10 is fast. A large induced voltage is generated.
Here, when the rotor 10 is not rotating, since the rotation speed is “0”, no induced voltage is generated. That is, whether or not the rotor 10 is rotating can be determined based on whether or not the induced voltage is generated.

The rotation detection device 4 according to the present embodiment performs rotation detection based on such a principle to determine whether or not the rotor 10 is rotating from the induced voltage. Further, in order to detect the induced voltage with high accuracy, detection is performed within a rotation angle range where the induced voltage reaches a peak. That is, the rotation angle range of the rotor 10 in which the induced voltage is maximum is in the vicinity of 90 ° to 150 ° and in the vicinity of 270 ° to 330 °. Therefore, detection is performed in this range.
Then, as shown in FIG. 13A, the motor driver 50 drives the drive pulse in a state in which the above-described constant opening time t _OFF is released (opened) when the rotor 10 reaches within this rotation angle range. Is adjusted to apply.
In the present embodiment, by applying a driving pulse spaced only open time t _OFF in coil A, and an example of the case of applying a continuous drive pulse is not open time t _OFF the coil B.

  Next, a case will be described in which the two-phase step motor 3 configured as described above is operated to move the lens driving device 2 of the camera-equipped mobile phone 1 and, for example, an image of a subject (not shown) is zoomed. . In the present embodiment, when the rotor 10 is rotated clockwise (CW direction), the lens R approaches the image sensor 6 and is rotated counterclockwise (CCW direction), so that the lens R is image sensor. It is assumed that it is adjusted so as to be separated from 6.

  First, when the user turns on the power supply (not shown) of the camera-equipped mobile phone 1, a reference position setting operation for temporarily setting the position of the lens R to the reference position is started in order to accurately perform the zoom operation. Here, when the power is turned on, the position of the lens R is in the middle of the movable range, that is, the contact portion 31b located on the lower surface of one sliding portion 31 is the contact portion of the base member 23. A case where the upper surface is not in contact is described as an example.

In order to perform the reference position setting, the motor driver 50 is in a state in which a predetermined opening time t _OFF is set as shown in FIG. 13A within a rotation angle range in which the induced voltage reaches a peak. Then, the drive pulses shown in FIG. 4 are sequentially applied. By applying this drive pulse, the rotor 10 rotates clockwise (CW direction). When the rotor 10 rotates, the drive gear 41 molded integrally with the rotor 10 similarly rotates around the axis L2. This rotational force is transmitted to the lead screw 35 via the drive gear 41, the first reduction gear 42, the second reduction gear 43, and the driven gear 35b. As a result, the lead screw 35 rotates around the axis L3 while being decelerated to a predetermined rotational speed.

  As the lead screw 35 rotates, the nut 36 screwed into the threaded portion 35a of the lead screw 35 moves toward the image sensor 6 along the direction of the axis L3. As a result, the entire lens body 5 fixed to one sliding portion 31 gradually moves toward the image sensor 6 along the optical axis L1. As a result, the contact portion 31b provided on the lower surface of one sliding portion 31 begins to approach the upper surface of the base member 23, and finally comes into contact with each other. This contact restricts the movement of the lens body 5 and stops the rotation of the rotor 10.

On the other hand, as shown in FIG. 14, the rotation detection device 4 detects the induced voltage every time it rotates by one step (step 1: S1) when the rotor 10 starts rotating by setting the reference position (step 2: S1). S2). That is, the A / D conversion circuit 53 causes the coil A to reach the coil A within a certain open time t _OFF when the rotor 10 reaches the rotation angle of 90 ° to 150 ° or the vicinity of 270 ° to 330 °. Terminal voltage (with respect to the ground) generated at both terminals a1 and a2 is detected, and an induced voltage is calculated from the difference between the detected terminal voltages and output to the DSP 52.

The CPU 54 of the DSP 52 determines whether or not the rotor 10 is rotating based on the induced voltage sent (step 3: S3). That is, comparing the induced voltage with a preset reference voltage, if the reference voltage is smaller than the induced voltage (that is, if the induced voltage is larger), it is determined that the rotor 10 is rotating. (Step 4: S4), the motor drive is controlled so that the drive pulse is continuously applied.
If the reference voltage is higher than the induced voltage (that is, if the induced voltage is smaller), it is determined that the rotor 10 is starting to be non-rotating (step 5: S5), and the drive pulse is applied. Control the motor drive to stop.

As a result, the rotation of the rotor 10 and the lead screw 35 stops when the contact portion 31b comes into contact with the upper surface of the base member 23 that is the contact portion, and the movement of the lens body 5 stops. Then, the DSP 52 sets the position of the lens body 5 at this time as the lens reference position, and stores it in the ROM 55 and RAM 56. Thereby, the position of the lens R can be reliably set to the reference position in a state where excessive contact is prevented. In this way, unlike the conventional one in which the rotor 10 is forcibly rotated by a predetermined number of steps regardless of the position of the lens R, the non-rotation of the rotor 10 is detected based on the induced voltage, and the drive pulse is detected. Therefore, it is not necessary to perform useless rotation.
Therefore, it is possible to shorten the time taken for setting the reference position and reduce power consumption. Further, wear between the nut 36 and the threaded portion 35a of the lead screw 35 can be prevented, and malfunctions can be eliminated as much as possible.

As described above, when the camera-equipped cellular phone 1 is turned on, the rotation detection device 4 quickly performs the reference position setting operation for setting the position of the lens R to the reference position. When this setting is completed, the setting of the motor driver 50 is changed so that the drive pulse is applied to the coil A without leaving a certain opening time t _OFF .
Next, when the user performs a zoom operation while confirming the subject on the display panel (not shown) of the camera-equipped cellular phone 1, the motor driver 50 applies the drive pulse shown in FIG. Rotate counterclockwise (CCW direction).

  As the rotor 10 rotates, the lead screw 35 rotates around the axis L3 while being decelerated to a predetermined rotation speed, and the nut 36 moves away from the image sensor 6 along the direction of the axis L2. . As a result, the lens R can be separated from the image sensor 6 and focusing can be performed freely, and the subject can be imaged in a zoomed state. In particular, since the position of the lens R is accurately set as the reference position and the possibility of malfunction is small, zooming can be performed with high accuracy.

In particular, since the rotation detection device 4 of the present embodiment can reliably grasp the rotation state of the rotor 10 by detecting the induced voltage generated in the coil A, a dedicated rotation for detecting the rotation of the rotor 10. There is no need to provide a detection coil. Therefore, it is possible to reduce the size.
Further, since the detecting means 51 detects the induced voltage only within a certain open time t _OFF , rotation detection can be performed simultaneously with the driving while the rotor 10 is being driven.
Further, since the application of the drive pulse is stopped only during the fixed opening time t _OFF , the influence on the rotational speed of the rotor 10 can be reduced as much as possible, and high-speed rotation can be enabled. Therefore, the reference position can be set in a short time. In particular, in the present embodiment, since the drive pulse is continuously applied to the coil B in a state where there is no fixed opening time t _OFF , the rotational speed of the rotor 10 is hardly affected.

  In addition, according to the camera-equipped cellular phone 1 of the present embodiment, the lens driving device 2 that can accurately set the reference position of the lens R in a state where there are few malfunctions and the power consumption is reduced in a short time. Therefore, it is easy to use and excellent in convenience, and quality and reliability can be improved.

  The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

For example, in the above embodiment, the induced voltage is detected within one opening time t _OFF , but for example, as shown in FIG. 13B, the motor driver 50 sets a plurality of opening times t _OFF at regular time intervals. The driving pulse may be applied in a repeated state. By doing so, it is possible to detect the induced voltage in a wide range while the rotor 10 reaches the rotation angle range in which the induced voltage is maximized. Therefore, the detection of the induced voltage becomes more accurate and the rotation can be detected more accurately. In addition, since the one opening time t _OFF can be shortened, a decrease in the rotational speed of the rotor 10 can be further suppressed, leading to prevention of torque reduction.

In the above embodiment, the induced voltage is detected by using the A / D conversion circuit 53. For example, as shown in FIG. 15, the induced voltage is detected by using a subtracting circuit (calculation unit) 60. It doesn't matter. Further, the detected induced voltage may be compared with a reference voltage by a comparator (determination means) 61 provided between the subtraction circuit 60 and the DSP 52 to determine whether or not the rotor 10 is rotating. Absent. Even in this case, the same effects as those of the above embodiment can be obtained.
The determination result determined by the comparator 61 is output to an input / output interface (I / F) 63 built in the DSP 52. The arithmetic circuit 60 and the comparator 63 may be built in the DSP 52.

In the above embodiment, the A / D conversion circuit 53 detects the induced voltage for each step. However, the A / D conversion circuit 53 is not used, but the induction is performed using the diode 65 that the motor driver 50 normally has. The voltage may be detected.
That is, as shown in FIG. 16, the motor driver 50 includes a diode 65 connected to one terminal a1 of the coil A. The detection means 51 has a resistor 66 connected between the other terminal a2 of the coil A and the ground G. Each time the rotor 10 rotates two steps, the diode 65 and the resistor 66 The induced voltage is detected based on the voltage flowing between the two.
Note that the comparator 61 serves as a determination unit, and determines whether or not the rotor 10 is rotating by comparing the detected induced voltage with a reference voltage. As a result of the determination, the fact is sent to an input / output interface (I / F) 63 arranged in the DSP 52.

In this case, there are three possible circuit operations when the terminal is opened within a certain opening time t _OFF . That is, the case of (V _A2 −V _A1 )> (Vcc + V _D ) shown in FIG. 17A, the case of −V _D ≦ (V _A2 −V _A1 ) ≦ V _D shown in FIG. This is divided into the case of (V _A2 −V _A1 ) <− V _D shown in FIG.
Here, (V _A2 −V _A1 ) indicates an induced voltage, Vcc indicates a power supply voltage, and V _D indicates an ON voltage of the diode 65.

First, in the case of the condition shown in FIG. 17A, since a current flows from the resistor 66 to the diode 65, the voltage V _det generated in the comparator 61 is V _det = Vcc + V _D − (V _A2 −V _A1 ) and a positive voltage is generated.
In the case of the condition shown in FIG. 17B, no current flows, and the voltage V _det generated in the comparator 61 is “0 V”. Further, in the case of the condition shown in FIG. 17C, a current flows from the diode 65 toward the resistor 66, and the voltage V _det generated in the comparator 61 is V _det = GND−V _D + (V _A2 − V _A1 ) and a negative voltage is generated.

Then, the comparator 61 compares the voltage V _det with the reference voltage to determine whether or not the rotor 10 is rotating. In particular, the induced voltage can be detected using the diode 65 that the motor driver 50 normally uses without using the A / D conversion circuit 53 as in the above embodiment, so that the number of components can be minimized. Can do. Therefore, cost reduction and size reduction can be achieved. The comparator 61 may be built in the motor driver 50 or the DSP 52.

Further, when setting the reference position, the induced voltage generated in the coil A is detected and the rotation or non-rotation of the rotor 10 is determined. However, the induced voltage generated in the coil B may be detected. In this case, the position where the lens R is farthest from the image sensor 6 may be set as the reference position.
Further, the induced voltage generated in both coils A and B may be detected simultaneously. By doing so, in addition to the rotation state of the rotor 10, the rotation direction of the rotor 10 can also be determined from the phase difference of the induced voltage.

  Moreover, in the said embodiment, although the mobile telephone 1 with a camera which has the lens drive device 2 was taken as an example as an electronic device, it is not restricted to this case, For example, a digital camera etc. may be sufficient.

It is sectional drawing which shows one Embodiment of the mobile telephone with a camera which has a rotation detection apparatus of the two-phase step motor which concerns on this invention, and a lens drive device. It is a top view of the two-phase step motor which the mobile phone with a camera shown in FIG. 1 has. It is a block diagram of the rotation detection apparatus shown in FIG. It is explanatory drawing which shows the clockwise rotation operation | movement of the two-phase step motor shown in FIG. It is explanatory drawing which shows the rotation operation | movement of the counterclockwise direction of the two-phase step motor shown in FIG. In the two-phase step motor shown in FIG. 2, it is the figure which showed the relationship between a rotor rotational angle and the coil linkage magnetic flux received from a rotor. In the two-phase step motor shown in FIG. 2, it is the figure which showed the relationship between the rotor rotation angle at the time of normal rotation, and the rotational speed of a rotor. FIG. 3 is a diagram showing a relationship between a rotor rotation angle and a drive pulse applied to each coil in the two-phase step motor shown in FIG. 2. FIG. 3 is a diagram showing a relationship between a rotor rotation angle and torque in the two-phase step motor shown in FIG. 2. FIG. 10 is a diagram for defining the direction of magnetic flux in FIGS. In the two-phase step motor shown in FIG. 2, it is the figure which showed the relationship between the rotor rotation angle at the time of normal rotation, and the induced voltage generate | occur | produced between coil terminals. In FIG. 11, it is a figure for defining the direction of a voltage. (A) is the figure which showed the waveform of the drive pulse applied to a coil in the state which left the fixed open time within the range where an induced voltage becomes a peak by the rotation detection apparatus shown in FIG. ) Is a diagram showing a waveform of a driving pulse applied to the coil in a state where a certain opening time is repeated. It is a flowchart at the time of performing rotation detection of a two-phase step motor by the rotation detection apparatus shown in FIG. It is the block diagram which showed the other example of the rotation detection apparatus which concerns on this invention. It is the block diagram which showed the further another example of the rotation detection apparatus which concerns on this invention. It is the figure which showed the circuit operation | movement at the time of the terminal open | release in the rotation detection apparatus shown in FIG. It is the figure which showed an example of the conventional reference position detection mechanism.

Explanation of symbols

A, B Coil L1 Optical axis t _OFF constant opening time 1 Mobile phone with camera (electronic equipment)
DESCRIPTION OF SYMBOLS 2 Lens drive device 3 Two-phase step motor 4 Rotation detection apparatus 5 Lens body 6 Image pick-up element 7 Drive means 10 Rotor 11, 12 Yoke 13 Stator 23 degrees contact part (base member)
50 Motor driver (pulse application means)
51 Detection means 52 DSP (judgment means)
53 A / D conversion circuit (calculation unit)
60 arithmetic circuit (calculation unit)
61 Comparator (Judgment means)
65 Diode 66 Resistor

Claims (7)

A rotation detection device for a two-phase step motor having a rotor magnetized in two poles and a stator having a two-phase coil wound around a yoke,
Pulse applying means for applying a driving pulse to each of the two-phase coils;
Detecting means for detecting an induced voltage generated between both terminals of at least one of the two-phase coils within a rotation angle range of the rotor at which the induced voltage is maximized;
Comparing the detected induced voltage with a preset reference voltage, and determining means for determining whether the rotor is rotating,
The pulse applying means applies the drive pulse so that a certain opening time is vacant with respect to the coil from which the induced voltage is detected when the rotor reaches the rotation angle range,
The two-phase stepping motor rotation detecting device, wherein the detecting means detects the induced voltage within the fixed opening time. The rotation detection device for a two-phase step motor according to claim 1,
The pulse applying means applies the driving pulse in a state where the opening time is repeated a plurality of times at regular time intervals when the rotor reaches the rotation angle range. Rotation detection device. In the rotation detection device of the two-phase step motor according to claim 1 or 2,
The detection means includes a calculation unit that detects a terminal voltage generated at both terminals of the coil each time the rotor rotates by one step and calculates the induced voltage from a difference between the two terminal voltages. A rotation detection device for a two-phase step motor. In the rotation detection device of the two-phase step motor according to claim 1 or 2,
The pulse applying means has a diode connected to one terminal of the coil,
The detection means includes a resistor connected between the other terminal of the coil and the ground, and generates a voltage generated between the diode and the resistor every time the rotor rotates two steps. Based on this, the induced voltage is detected, and a rotation detecting device for a two-phase step motor. A rotation detection device for a two-phase step motor according to any one of claims 1 to 4,
A two-phase step motor whose rotation is detected by the rotation detector;
A lens body arranged to be movable along the optical axis;
A lens driving device comprising: a driving unit configured to move the lens body along the optical axis in accordance with the driving of the two-phase step motor, and to change a distance from the imaging device. The lens driving device according to claim 5,
Provided at the moving end of the lens body, provided with a contact portion that contacts the moving lens body and stops the movement of the lens body and stops the rotation of the rotor,
The determination means sets the position where the lens body is in contact with the contact portion as a lens reference position when determining that the rotor is in a non-rotating state.   An electronic apparatus comprising the lens driving device according to claim 5.

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