JP5631023B2 - Imaging device - Google Patents

Description

The present invention relates to an imaging apparatus that drives a mirror member by a motor.

  In a single-lens reflex camera having a high-speed continuous shooting function, the occurrence of bounce and impact sound at the time of up / down of a mirror member that operates at high speed by a motor drive is a problem. For example, the subject image formed on the imaging surface is shaken due to the bounce generated when the mirror member is down, and the autofocus for the next imaging cannot be started, thereby reducing the continuous shooting speed. In addition, the impact sound hinders silence.

  In order to suppress the occurrence of such bounces and impact sounds, Patent Document 1 discloses that the mirror member motor is decelerated (brake control such as reverse energization and short circuit) by performing mirror deceleration control before the down position. A camera has been disclosed that mitigates bouncing and impact sounds when down.

Japanese Patent Laid-Open No. 05-181194

  As the mirror driving motor, a DC motor or a stepping motor can be used. However, the DC motor has a structure with no clear detent torque, so that the position controllability is low, or the speed depends on the driving load, and thus the speed controllability is low. For this reason, when the DC motor is used as the mirror driving motor, the variation in the operation speed of the mirror member and the start / stop position of the operation increases, and there is a high possibility that the deceleration control does not function sufficiently.

  It is possible to improve position controllability and speed controllability by providing a sensor and a pulse generator for detecting the rotational position of the DC motor and performing feedback control based on the detected rotational position. However, it is particularly difficult to sufficiently improve the stop position accuracy due to rotational position detection errors caused by sensors and pulse generators.

  Further, the stepping motor can be driven by pulses by open loop control, and is superior in position and speed controllability compared to a DC motor. However, if it is attempted to drive at the same high speed as a DC motor, there is a possibility that a step-out occurs, so that it is not suitable for high-speed driving of the mirror member.

  Thus, it is difficult to ensure both high-speed driving of the mirror member and high stop position accuracy, regardless of which of the DC motor and the stepping motor is used, and it cannot be said that it is suitable for a mirror driving motor.

  The present invention provides an imaging apparatus capable of suppressing the bounce of a mirror member and the generation of impact sound while enabling high-speed driving of the mirror member.

An imaging apparatus according to an aspect of the present invention includes a motor capable of driving by open loop control and feedback control using a signal based on rotation of a rotor, driving by the open loop control, and driving by the feedback control. Using control means for selectively switching, a mirror member movable between a first position arranged inside the optical path and a second position retracted outside the optical path, and a driving force from the motor A mirror driving mechanism for moving the mirror member, a stopper with which the mirror member moved from the second position to the first position abuts, and a first photographing mode or a second photographing mode selectively. has a photographing mode setting means for setting, and when moving the mirror member to the first position from the second position, wherein, prior to The drive of the motor is started by the feedback control from the state where the mirror member is in the second position, and when the mirror member reaches a predetermined position before coming into contact with the stopper, from the feedback control to the open loop control. The predetermined position is different when the first shooting mode is set by the shooting mode setting means and when the second shooting mode is set by the shooting mode setting means. It is characterized by.

According to the present invention, while enabling high-speed driving motion of the mirror member, the occurrence of bounce and impact sound of the mirror member can be suppressed.

1 is an external perspective view of a camera that is an embodiment of the present invention. The perspective view which shows the mirror drive mechanism of the camera of an Example. The front view which shows the imaging | photography standby state of the said mirror drive mechanism. The top view and side view which show the imaging | photography standby state of the said mirror drive mechanism. The front view which shows the mirror up state immediately after release of the said mirror drive mechanism. The front view which shows the mirror down start state after imaging | photography of the said mirror drive mechanism. The front view and side view which show the state immediately before the mirror down completion of the said mirror drive mechanism. The front view which shows the mirror down completion state of the said mirror drive mechanism. FIG. 2 is a block diagram illustrating an electrical configuration of the camera of the embodiment. The perspective view which shows the structure of the motor for a mirror drive in the camera of an Example, and the rotation sensor. FIG. 11 is a cross-sectional view illustrating a phase relationship among a yoke, a rotation sensor, and a rotor of the motor illustrated in FIG. 10. The graph which shows the relationship between the rotation angle of the rotor of the motor shown in FIG. 10, motor torque, and sensor output. The circuit diagram which shows the structure of the advance angle circuit provided in the camera of the Example. Sectional drawing which shows the feedback control operation | movement in the camera of an Example. The graph which shows the output of the motor at the time of the open loop control and feedback control in the camera of an Example. The flowchart which shows operation | movement of the camera of an Example. The flowchart which shows operation | movement of the camera of an Example. 6 is a timing chart showing the operation of the camera of the embodiment. The cam diagram of the mirror cam of the said mirror drive mechanism.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIGS. 1A and 1B show the appearance of a single-lens reflex digital camera (hereinafter simply referred to as a camera) as an imaging apparatus according to an embodiment of the present invention. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7 and FIG. 8 show the configuration and operation of a mirror driving mechanism provided in the camera. FIG. 9 shows the electrical configuration of the camera.

  In these drawings, reference numeral 1 denotes a camera body, and 2 denotes an interchangeable lens that can be attached to and detached from the camera body 1. Reference numeral 3 denotes a release button for instructing the start of photometry and AF (autofocus) or instructing photographing. Metering and AF are started by pressing the release button 3 halfway (SW1-ON). Further, when the release button 3 is fully pressed (SW2-ON), the shutter 4 is driven, the image sensor 10 is exposed, and photographing is performed.

  A motor 5 is capable of step driving by open loop control and driving by feedback control using a signal output from a rotation sensor (rotation detecting means) 6 to be described later according to the rotation of the rotor. The motor 5 starts operating in response to the full-pressing operation of the release button 3 and moves the quick return mirror (mirror member: hereinafter simply referred to as a mirror) 30 by driving the mirror cam gear 33 via the gear train 42. Let

  The mirror 30 has a down position (first position) disposed inside an optical path (hereinafter referred to as a photographing optical path) from the interchangeable lens 2 toward the image sensor 10 and an up position (second position) retracted upward from the photographing optical path. It is possible to move (rotate). That is, the mirror 30 is movable so as to advance and retract with respect to the photographing optical path.

  The rotation sensor 6 outputs a signal corresponding to the rotational position of the rotor of the motor 5. The rotation sensor 6 includes a first hall element 207 and a second hall element 208 provided in the motor 5. The first and second Hall elements 207 and 208 output signals (voltages) that change in accordance with the positional relationship between their positions and the magnetic poles of the rotor, and have a phase difference from each other. By using these two-phase signals, the rotational position of the rotor can be detected.

  Reference numeral 7 denotes an optical finder. Reference numeral 8 denotes a plurality of optical lenses constituting a photographing optical system disposed in the interchangeable lens 2, and 9 denotes a stop. An image sensor 10 provided in the camera body 1 converts a subject image formed by the photographing optical system into an electrical signal. A signal processing unit 11 includes an A / D conversion unit that converts an analog imaging signal output from the imaging element 10 into a digital imaging signal, an image processing unit that performs various image processing on the digital imaging signal to generate image data, and the like. Circuit.

  Reference numeral 14 denotes a system control unit. The system control unit 14 includes a microcomputer unit including a CPU, and controls the camera body 1 and the interchangeable lens 2 by executing a built-in computer program. The system control unit 14 receives an output of a photo reflector (initial position detection means) 36 that detects an initial position of the mirror cam gear 33 and determines whether or not the mirror drive mechanism is at a predetermined standby position.

  Further, the system control unit 14 selectively performs step driving by open loop control of the motor 5 through the first driver 22 and driving by feedback control of the motor 5 through the second driver 25. Specifically, the motor is driven in response to the rotation amount (rotation count value) of the motor 5 counted by a rotation counter 16 described later based on a signal from the rotation sensor 6 reaching a predetermined amount (predetermined count value). Switch the method between open loop control and feedback control. The system control unit 14 and the first and second drivers 22 and 25 constitute a control means.

  Reference numeral 15 denotes a memory for storing constants, variables, programs and the like for operation of the system control unit 14. The memory 15 also stores the predetermined count value that is different for each shooting mode described later.

  The rotation counter 16 is provided inside the system control unit 14. The rotation counter 16 is based on a reference clock from a clock generation circuit (not shown), and is based on a signal from the rotation sensor 6 (first and second Hall elements 207 and 208). Count the amount of rotation. The rotation amount (rotation count value) referred to here is the rotation amount from the start of the motor 5 in the up operation and the down operation of the mirror 30.

  Here, in this embodiment, 8 poles (4 N poles and 4 S poles) are formed on the rotor of the motor 5. For this reason, a signal having eight peaks per one rotation of the rotor is output from one Hall element. That is, the first and second Hall elements 207 and 208 output two-phase signals having a total of 16 peaks per one rotation of the rotor. Therefore, by counting the number of peaks from the start of the motor 5, the rotation amount from the start of the motor 5 can be detected.

  The rotation amount from the start of the motor 5 matches the rotation angle of the mirror cam gear 33 that is gear-coupled to the motor 5. As will be described in detail later, the mirror cam gear 33 causes the mirror 30 to perform an up operation and a down operation (hereinafter also referred to as a mirror up operation and a mirror down operation) in one rotation.

  Reference numeral 17 denotes a shooting mode button (operation means) which is operated by the user to select a shooting mode to be used (set) from a plurality of shooting modes provided in the camera of this embodiment.

  The camera according to the present embodiment has selectable shooting modes such as a single shooting mode (single shooting mode) in which only one frame image (still image) is shot when the release button 3 is fully pressed, and the release button 3. The camera has a continuous shooting mode that keeps shooting continuously while the button is fully pressed. Furthermore, the continuous shooting mode includes a low-speed continuous shooting mode (first continuous shooting mode) that enables continuous shooting of about 2 frames per second, and a continuous shooting speed of about 5 frames per second (that is, the continuous shooting speed is lower than the low-speed continuous shooting mode). There is a high-speed continuous shooting mode (second continuous shooting mode) that enables continuous shooting. In this embodiment, deceleration control is performed during mirror down operation according to the shooting mode. The single shooting mode, the low-speed continuous shooting mode, and the high-speed continuous shooting mode can be said to be shooting modes in which the number of shot images per unit time is different.

  Reference numeral 18 denotes a recording medium for recording image data generated by photographing, and is composed of a nonvolatile memory such as a flash memory. The recording medium 18 is detachable from the camera body 1.

  A shutter control unit 21 controls the opening / closing operation of the shutter 4 by controlling the supply of electric power to the electromagnets (front curtain coil and rear curtain coil) provided in the shutter drive mechanism.

  The first driver 22 performs step driving (hereinafter referred to as OP driving) by open loop control of the motor 5 in accordance with a driving control signal output from the system control unit 14. Details of the OP drive will be described later.

  The second driver 25 has an advance angle circuit (not shown) that generates an advance angle signal having a predetermined phase difference with respect to the signal from the position sensor 6. The second driver 25 is driven by feedback control of the motor 5 according to the drive control signal and the advance angle signal output from the system control unit 14 (that is, based on the signal from the position sensor 6) (hereinafter referred to as FB drive). )I do. Details of the FB drive will also be described later.

  The system control unit 14 drives the motor 5 at high speed by the FB movement through the second driver 25 at the start of the mirror down operation. Then, in response to the rotation count value of the motor 5 reaching a predetermined count value in the second half of the mirror down operation (during the mirror down operation), the motor drive system is switched to OP drive through the first driver 22 and the motor 5 is decelerated. Take control. Reference numeral 32 shown in FIGS. 2 and 3 denotes a locking pin. The locking pin 32 functions as a stopper for stabilizing the mirror 30 at the down position while preventing the mirror 30 that has been rotated from the up position to the down position and preventing further rotation. The speed at which the mirror 30 abuts against the locking pin 32 can be sufficiently reduced by the deceleration control by the OP drive toward the down position, so that the bounce of the mirror 30 and the generation of impact sound at the down position can be suppressed. Can do.

  In this embodiment, acceleration / deceleration can be freely performed in the medium / low speed driving range, and the OP driving which is a step driving which is easy to drive at a constant speed and the FB driving which can be driven at a high speed without being affected by a load fluctuation are used. doing. The high speed driving in this embodiment means driving at, for example, 5000 rpm or more, and the low speed driving means driving at, for example, 3000 rpm or less.

  In this embodiment, in order to reliably and sufficiently reduce the speed of the motor 5 toward the down position during OP driving, the timing at which OP driving is started in the second half of the mirror down operation is changed according to the photographing mode. . This is done by making the “predetermined count value” different in at least two shooting modes.

  Reference numeral 23 denotes an aperture control unit that controls the aperture 9, and reference numeral 24 denotes an AF control unit that controls focusing of the interchangeable lens 2.

  Hereinafter, the shutter driving mechanism and the mirror driving mechanism will be described. As shown in FIGS. 2 to 4, a ground plate 29 fixed to the camera body 1 is provided with a shutter drive mechanism that drives a front curtain shutter blade group and a rear curtain shutter blade group (not shown) and a mirror drive that drives a mirror 30. Parts constituting each mechanism are attached.

  The mirror 30 advances and retreats with respect to the imaging optical path by rotating around the shaft portion 30 a held by the base plate 29. The mirror 30 is always pressed against the mirror drive lever (lever member) 31 by the mirror spring 34. For this reason, the mirror 30 rotates following the movement of the mirror drive lever 31.

  The mirror drive lever 31 is rotatably supported by the shaft portion 29 a of the main plate 29. A lever spring 35, which is a torsion coil spring, is disposed on the outer periphery of the shaft portion 29a. The lever spring 35 urges the mirror drive lever 31 in the clockwise direction (mirror up direction) to bring the shaft portion 31 b of the mirror drive lever 31 into contact with the shaft portion (driven portion) 30 b of the mirror 30. .

  Further, the mirror drive lever 31 abuts on the cam surface 33a of the mirror cam gear 33, which is a cam member, at the shaft portion 31a by the biasing force of the lever spring 35. On the back surface of the mirror cam gear 33, a reflecting portion 33d formed of a thin metal plate such as aluminum is provided. The reflecting portion 33d faces the photo reflector 36 in a state where the mirror cam gear 33 is located at the initial position. In this state, the photo reflector 36 receives the light irradiated and reflected on the reflecting portion 33d, and outputs a signal indicating that the mirror cam gear 33 is located at the initial position. The mirror drive lever 31 and the mirror cam gear 33 transmit the driving force from the motor 5 to the mirror 30 and drive it.

  The mirror cam gear 33 is supported by the base plate 29 so as to be rotatable about an axis extending in the same direction as the direction in which the photographing optical path extends. The mirror cam gear 33 receives the driving force from the motor 5 having the output shaft extending in the same direction as the direction in which the photographing optical path extends, and rotates only in the clockwise direction through the reduction gear train 42. The mirror cam gear 33 rotates once in a photographing sequence for acquiring one image data.

  A cam surface 33 a formed on the mirror cam gear 33 is in contact with the shaft portion 31 a of the mirror drive lever 31. As the mirror cam gear 33 rotates in the clockwise direction, the mirror drive lever 31 rotates about the shaft portion 31c. As a result, the mirror 30 is rotated and moved forward and backward with respect to the photographing optical path. Specifically, the cam surface 33a performs the charging operation by rotating the mirror drive lever 31 in the counterclockwise direction in FIG. 5 from the state where the mirror 30 is in the up position.

  Next, the configuration of the motor 5 will be described. FIG. 10 shows the configuration of the motor 5 and the position sensor 6. In FIG. 10, some parts are shown broken away.

  The motor 5 includes a rotor 202 having a magnet 201, a first coil 203, a second coil 204, a first yoke 205, a second yoke 206, a first Hall element 207, a second The Hall element 208 is configured. The first coil 203, the second coil 204, the first yoke 205, and the second yoke 206 constitute a stator, and the first and second Hall elements 207, 208 are fixed to the stator.

  The magnet 201 is a cylindrical permanent magnet whose outer peripheral surface is multipolarly magnetized. The magnet 201 has a magnetization pattern in which the strength of the magnetic force in the radial direction changes in a sine wave shape as the rotation angle (rotation position) changes. As the magnet 201, it is preferable to use a neodymium magnet having a high magnetic flux density.

  The rotor 202 is rotatably supported with respect to the stator and is integrally fixed to the magnet 201.

  The first yoke 205 has a plurality of magnetic pole teeth excited by the first coil 203. The torque applied to the rotor 202 can be changed by switching the excited poles. The second yoke 206 has a plurality of magnetic pole teeth excited by the second coil 204. The torque applied to the rotor 202 can be changed by switching the excited poles.

  The first Hall element 207 and the second Hall element 208 output a signal whose signal value (voltage) changes according to the change of the magnetic flux from the magnet 201. As described above, the first and second Hall elements 207 and 208 constitute the position sensor 6 shown in FIG.

  In this embodiment, the Hall element is used as the rotation detection means for detecting the rotation of the rotor 202, but other rotation detection means may be used. For example, the rotation may be detected by reading, with an optical sensor, reflection areas (or transmission areas) and non-reflection areas (or light-shielding areas) alternately formed on a scale that rotates integrally with the rotor. Further, the position sensor 6 may be integrally fixed to the motor 5 as in the present embodiment, or may be provided separately from the motor.

  Next, OP driving of the motor 5 will be described. The OP driving is a driving method similar to the open loop control in a normal stepping motor, and the so-called step driving is performed by switching the energization state of the first and second coils 203 and 204 at a predetermined time interval. It is a method. The first driver 22 sequentially switches energization to the first and second coils 203 and 204 according to the drive pulse interval (drive frequency) indicated by the drive control signal input from the system control unit 14 and the rotation direction, The rotor 202 is rotated at a speed corresponding to the driving frequency. This is called speed control of the motor 5 by OP driving.

  In addition, the first driver 22 gives the first and second coils 203 and 204 a drive pulse signal having a number of pulses corresponding to the rotation amount indicated by the drive control signal input from the system control unit 14, so that the rotor 202 Can be rotated by an amount corresponding to the number of drive pulses. This is called position control of the motor 5 by OP driving.

  In the OP drive, the energization switching timing for the first and second coils 203 and 204 can be controlled without being affected by the change in the output of the position sensor 6. By the OP drive, the motor 5 becomes a motor capable of accurate speed control and highly accurate position control from the low speed range to the medium speed range.

  However, if the driving speed of the motor 5 is increased (the driving pulse interval is shortened), the rotor 202 cannot respond to switching of energization to the first and second coils 203 and 204, and the possibility of causing step-out increases. . For this reason, it is necessary to set a lower limit for the drive pulse interval. As a result, there is a limit to the high-speed driving of the motor 5 by OP driving.

  Next, FB driving of the motor 5 will be described. The FB drive is a drive system that switches the energized state of the first and second coils 203 and 204 in accordance with the output of the position sensor 6. The second driver 25 includes the first and second coils 203, in accordance with the number of drive pulses input from the system control unit 14, the rotation direction, and the advance angle signal generated based on the signal output from the position sensor 6. The energization to 204 is sequentially switched. Thereby, the rotor 202 can be rotated by the amount of rotation corresponding to the number of drive pulses. Further, the torque of the rotor 202 can be controlled by controlling the currents flowing through the first and second coils 203 and 204. This is called current control of the motor 5.

  In the FB drive, since the energization switching to the first and second coils 203 and 204 is performed in accordance with the output of the position sensor 6 (rotational position of the rotor 202), occurrence of step-out due to a response delay of the rotor 202 can be suppressed. High-speed driving according to the driving load becomes possible. In other words, by performing FB driving on the motor 5, the motor can be used up to a high speed range.

  Next, the phase relationship between the first and second yokes 205 and 206 and the position sensor 6 in the motor 5 will be described with reference to FIG. In FIG. 11, the clockwise direction is the positive direction. 205a to 205d are magnetic pole teeth of the first yoke 205. 206 a to 206 d are magnetic pole teeth of the second yoke 206. In this embodiment, the magnet 201 has 8 poles and the magnetization angle P is 45 °. With reference to the first yoke 205, the phase P / 2 of the second yoke 206 is −22.5 °, the phase β1 of the first Hall element 207 is + 22.5 °, and the second The phase β2 of the Hall element 208 is −45 °.

In the following description of the operation of the motor 5, “electrical angle” is used. The electrical angle represents one period of the magnetic force of the magnet as 360 °. When the number of poles of the rotor 202 is M and the actual angle is θ ₀ , the electrical angle θ is
θ = θ ₀ × M / 2 (Formula 1-1)
It is expressed.

  The phase difference between the first yoke 205 and the second yoke 206, the phase difference between the first Hall element 207 and the second Hall element 208, and the phase difference between the first yoke 205 and the first Hall element 207 are all. The electrical angle is 90 °. In FIG. 11, the center of each magnetic pole tooth of the first yoke 205 faces the center of the N pole of the magnet 201. This state is the initial state of the rotor 202, and the electrical angle is 0 °.

  Here, regarding the relationship between the rotation position (rotation angle) of the rotor 202 in the motor 5 and the motor torque, and the relationship between the rotation position of the rotor 202 and the signals output from the first and second Hall elements 207 and 208, This will be described with reference to FIG.

  FIG. 12A is a graph showing the relationship between the rotational position of the rotor 202 and the motor torque, where the horizontal axis represents the electrical angle and the vertical axis represents the motor torque. The motor torque is a positive torque that rotates the rotor 202 in the clockwise direction.

  When a positive current is passed through the first coil 203, the first yoke 205 is magnetized to the N pole, and an electromagnetic force is generated between the magnetic pole of the magnet 201. When a positive current is passed through the second coil 204, the second yoke 206 is magnetized to the N pole, and an electromagnetic force is generated between the magnetic pole of the magnet 201. When the two electromagnetic forces are combined, a sinusoidal torque curve (A + B +) is obtained as the rotor 202 rotates. Similarly, in other energized states, sinusoidal torque curves (A + B−, AB−, AB−) are obtained. Since the first yoke 205 is arranged with a phase of 90 ° in electrical angle with respect to the second yoke 206, the four torque curves have a phase difference of 90 ° in electrical angle.

  FIG. 12 (2) is a graph showing the relationship between the rotational position of the rotor 202 and the signals output from the first and second Hall elements 207 and 208, where the horizontal axis represents the electrical angle and the vertical axis represents each hole. The output signal from an element is shown.

  The strength of the magnetic force in the radial direction of the magnet 201 changes sinusoidally with respect to the electrical angle. Therefore, a sinusoidal signal (position sensor signal A) is output from the first hall element 207 by the rotation of the rotor 202. In the present embodiment, the first Hall element 207 outputs a positive value signal (+ A) when facing the north pole of the magnet 201.

  The second hall element 208 has a phase difference of 90 ° in electrical angle with respect to the first hall element 207. Therefore, a cosine wave signal (position sensor signal B) is output from the second hall element 208 as the rotor 202 rotates. In the present embodiment, since the polarity of the second Hall element 208 is reversed with respect to the first Hall element 207, a positive value signal (+ B) when facing the S pole of the magnet 201. Is output.

  The above-described advance angle circuit (not shown) performs a predetermined calculation based on the outputs of the first Hall element 207 and the second Hall element 208, and the first advance signal and the first advance signal having a predetermined advance angle. 2 lead angle signal is output. Hereinafter, a method for calculating the advance angle signal will be described.

When the electrical angle is θ, the output of the first Hall element 207 is HE1, and the output of the second Hall element 208 is HE2, HE1 and HE2 are expressed as follows.
HE1 = sinθ
HE2 = cos θ (Formula 2-1)
Also, assuming that the first advance signal advanced by the advance angle α is PS1, and the second advance signal advanced by the advance angle α is PS2, PS1, PS2 use HE1, HE2, α, respectively. It can be calculated as follows.
PS1 = sin (θ + α) = HE1 × cosα + HE2 × sinα (Formula 3-1)
PS2 = cos (θ + α) = HE2 × cos α−HE1 × sin α (Formula 3-2)
FIG. 13 shows the configuration of the advance circuit. The above calculation can be realized by configuring the advance circuit in this embodiment with an analog circuit as shown in FIG. 13, for example. First, a signal obtained by amplifying each position sensor output by a predetermined amplification factor C and signals (Csinθ, Ccosθ, −Csinθ, −Ccosθ) obtained by inverting them are generated. An advance angle signal is generated by multiplying them by appropriate resistance values R1 and R2 and adding them. The first advance signal PS1 and the second advance signal PS2 are expressed as follows.
PS1 = C × (R / R1) × sin θ + C × (R / R2) cos θ (Formula 4-1)
PS2 = C × (R / R1) × cos θ−C × (R / R2) sin θ (Formula 4-2)
By selecting the variable resistors R, R1, and R2 in the circuit as follows, an advance angle signal advanced by an arbitrary advance angle α can be generated.
R / R1 = cos α
R / R2 = sin α (Formula 5-1)
Further, a binarized signal (first binarized signal A and second binarized signal B) obtained by binarizing the first advance signal PS1 and the second advance signal PS2 using a comparator. ) Is output.

  The method for generating the advance angle signal described above is merely an example, and the advance angle signal may be generated by another method. For example, the advance angle signal may be generated by a digital circuit that performs the above calculation, or the advance angle signal may be generated by adjusting a pulse interval for switching energization using a high-resolution encoder.

  Next, switching of energization in the FB drive of the motor 5 will be described. First, switching of energization in the FB drive when the advance angle of the advance signal output from the advance circuit is zero will be described.

  The first advance angle signal PS1 and the second advance angle signal PS2 are signals obtained by performing the advance angle calculation on the first position sensor signal A and the second position sensor signal B, respectively, and giving an advance angle. It is. Here, since the advance angle is zero, the first sensor signal A and the first advance signal PS1 coincide, and the second sensor signal B and the second advance signal B also coincide. ing. The first binarized signal A and the second binarized signal B are signals obtained by binarizing the advance angle signal A and the advance angle signal B using a comparator, respectively.

  In the FB drive, energization to the first coil 203 is switched based on the first binarized signal A, and energization to the second coil 204 is switched based on the second binarized signal B. That is, when the first binarized signal A shows a positive value, a current in the positive direction is passed through the first coil 203, and when the first binarized signal A shows a negative value, the first A negative current flows through the coil 203. Further, when the second binarized signal B shows a positive value, the second coil 204 is energized in the positive direction, and when the second binarized signal B shows a negative value, the second value is supplied. The coil 204 is energized in the negative direction.

FIG. 14 shows a cross section of the motor 5 in the FB drive. FIG. 14A shows a state in which the rotor 202 is rotated 135 degrees in electrical angle. Each advance angle signal indicates the value shown in (a) of FIG. 12 (2). The first binarized signal A has a positive value, and the second binarized signal B has a negative value. Show. Accordingly, a positive current flows through the first coil 203 and the first yoke 205 is magnetized to the N pole, and a negative current flows through the second coil 204 and the second yoke 206 is the S pole. Is magnetized. In this case, FIG. 12 (1) torque curve A + B- acts torque corresponding clockwise, the rotor 202 is rotated by the rotational force of the theta ₀ direction.

  FIG. 14B shows a state where the rotor 202 is rotated by 180 ° in electrical angle. The first Hall element 207 is located at the boundary between the N pole and the S pole of the magnet 201. For this reason, the first binarized signal A is switched from a positive value to a negative value at an electrical angle of 180 °, and the energization direction of the first coil 203 is switched from the positive direction to the negative direction. This electrical angle coincides with the electrical angle at the intersection of the torque curve A + B− and the torque curve AB−.

FIG. 14B ′ shows a state in which the rotor 202 has rotated 180 ° in electrical angle and the energization direction of the first coil 203 has been switched. A negative current flows through the first coil 203 and the first yoke 205 is magnetized to the south pole, and a negative current flows through the second coil 204 and the second yoke 206 is also magnetized to the south pole. To do. In this case, FIG. 12 (1) torque curve A-B- working torque corresponding clockwise, the rotor 202 is rotated by the rotational force of the theta ₀ direction.

FIG. 14C shows a state in which the rotor 202 is rotated by 225 ° in electrical angle. Each advance angle signal shows the value shown in (c) of FIG. 12 (2). The first binarized signal A has a negative value, and the second binarized signal B has a negative value. Show. Therefore, a negative current flows through the first coil 203, the first yoke 205 is magnetized to the south pole, a negative current flows through the second coil 204, and the second yoke 206 passes through the S yoke. Magnetized to the pole. In this case, FIG. 12 (1) torque curve A-B- working torque corresponding clockwise, the rotor 202 is rotated by the rotational force of the theta ₀ direction.

  FIG. 14D shows a state in which the rotor 202 is rotated by 270 ° in electrical angle. The second hall element 208 is located at the boundary between the north pole and the south pole of the magnet 201. For this reason, the second binarized signal B is switched from a negative value to a positive value at an electrical angle of 270 °, and the energization direction of the second coil 204 is switched from the negative direction to the positive direction. This electrical angle coincides with the electrical angle at the intersection of the torque curve AB- and the torque curve AB +.

FIG. 14D ′ shows a state in which the rotor 202 is rotated by 270 ° in electrical angle and the energization direction of the second coil 204 is switched. A positive current flows through the second coil 204 and the second yoke 206 is magnetized in the N pole, and a negative current flows through the first coil 203 and the first yoke 205 is magnetized in the S pole. To do. In this case, FIG. 12 (1) acts a torque clockwise direction corresponding to the torque curve A-B + of the rotor 202 is rotated by the rotational force of the theta ₀ direction.

  By repeating the above state, the rotor 202 can be continuously rotated. Further, if the positive and negative of the first and second binarized signals A and B are reversed, reverse rotation is also possible.

  In the FB drive, the rotor 202 can be rotated by a desired angle by inputting the number of drive pulses and the rotation direction. Further, by controlling the current flowing through the coils 203 and 204, the magnetic force between the magnetic pole teeth of the yokes 205 and 206 and the magnetic pole of the magnet 201 is changed, and the rotational force acting on the rotor 202 is controlled to control the rotor 202. It is possible to rotate at a desired speed.

  In the FB drive, energization is switched at an electrical angle that coincides with the intersection of each torque curve, so that the torque obtained from the motor 5 can be maximized (torque curve T in FIG. 12A).

  In the OP drive, when the speed increases, the rotation of the rotor 202 cannot catch up with the energization switching, and the step-out may occur. However, in the FB drive, since the energization is switched while detecting the rotational position of the rotor 202, the step-out can be suppressed. For this reason, it is not necessary to provide a lower limit for the drive pulse interval as in OP driving, and the motor 5 can be driven at a higher speed than in OP driving.

  In the FB drive, speed control can be performed by controlling the current flowing through the coils 203 and 204, but since it is affected by load torque fluctuation, it is difficult to control the speed with high accuracy. In addition, the current value must be lowered during low-speed driving, and the torque is reduced. For this reason, the positioning accuracy at the time of low speed driving is lowered.

  The relationship between the output of the motor 5 in the OP drive and the FB drive is summarized as follows. FIG. 15 is a graph showing the output of the motor 5 in OP driving and FB driving, in which the horizontal axis indicates the driving frequency PPS and the vertical axis indicates the output torque T. T1 represents the maximum output torque of the motor 5.

  In the OP drive and the FB drive, the energization switching to the coils 203 and 204 is performed at an ideal timing, and the output of the motor 5 itself is equivalent to the maximum output torque T1 when no step-out occurs. However, if the driving speed is increased in the OP driving (the driving frequency is increased), the rotor 202 cannot respond to the energization switching of the coils 203 and 204, and the possibility of causing a step-out increases. For this reason, the OP drive is used under a torque range that allows for a certain safety factor with respect to the maximum output torque T1.

  On the other hand, in the FB drive, the energization is switched while detecting the rotational position of the rotor 202 to suppress the step-out, so that it can be used in the torque range up to the maximum output torque T1. Therefore, the FB drive can be said to be a drive system that can stably extract a substantially large output torque, and has high efficiency and low power consumption, compared to the OP drive.

  Next, the operation of the mirror drive mechanism when shooting is performed with the camera will be described with reference to the flowcharts of FIGS. 16 and 17, the timing chart of FIG. 18, and the cam gear diagram of FIG.

  FIG. 18 is a timing chart showing switching of the driving method of the motor 5 when the shooting mode is the single shooting mode, the low speed continuous shooting mode, and the high speed continuous shooting mode. The current drive system is represented by the position in the height direction, and the horizontal axis represents the elapsed time. FB indicates FB driving, and OP indicates OP driving. Characters enclosed by a rectangular frame represent an instruction from the system control unit 14 and a rotation count value (count number) in the rotation counter 16.

  The cam diagram in FIG. 19 represents the cam lift in one rotation of the mirror cam gear 33 from the standby state to the end of photographing of one image data. The horizontal axis indicates the angle from 0 ° at the SW2-ON time to 360 ° at the time of one rotation, and the vertical axis indicates the cam top and the cam bottom.

  Further, characters enclosed by a rectangular frame indicate a rotation count value (count number) in the rotation counter 16 and are different for each photographing mode.

  The count number of the motor 5 matches the angle phase on the mirror cam gear 33 due to the gear connection of the motor 5 and the mirror cam gear 33. Here, the size (rotation amount) of each count number is approximately the magnitude relationship shown in FIG. The next sequence is started in response to reaching each count number.

  In FIG. 16, when the camera is turned on, the system control unit 14 starts operation (step S101). First, the system control unit 14 determines whether or not the mirror cam gear 33 is in the initial position based on the signal from the photo reflector 36 (step S102). When the mirror cam gear 33 is not in the initial position, the system control unit 14 rotates the motor 5 in the clockwise (CW) direction or the counterclockwise (CCW) direction by a predetermined amount as a cam reset operation to initialize the mirror cam gear 33. The position is reset (step S103). If the mirror cam gear 33 is at the initial position, the process proceeds to step S104.

  In step S104, the system control unit 14 determines the shooting mode (one of the single shooting mode, the low speed continuous shooting mode, and the high speed continuous shooting mode) selected by the user through the shooting mode button 17. In the case of the single shooting mode, the process proceeds to step S107, in the case of the low speed continuous shooting mode, the process proceeds to step S105, and in the case of the high speed continuous shooting mode, the process proceeds to step 106.

(Single-shot mode)
In the single shooting mode, the count number at which the up operation of the mirror 30 ends and the motor 5 stops is set to A. When the opening / closing operation of the shutter 4 (exposure of the image sensor 10) is completed (SH completion), the system control unit 14 activates the motor 5 to start the mirror down operation. Thereafter, the count number (predetermined count value) of the start position of the deceleration control of the motor 5 is set to B. Furthermore, the count number of the energization switching position for the mirror drive mechanism to move to the standby position (the mirror cam gear 33 is the initial position) after the mirror down operation is completed is set to C. The last stop position of the motor 5 is common to all photographing modes, and is set to a count number D.
2, 3 and 4 show the standby state of the mirror drive mechanism. In FIGS. 5, 6, 7 and 8, the spring is not shown.

  When the release button 3 is pressed halfway to turn on SW1-ON (step S107), the system control unit 14 performs photometry and AF and resets the rotation counter 16 (step S108). Subsequently, when the release button 3 is fully pressed to turn on SW2-ON (step S109), the system control unit 14 starts energizing a front curtain coil and a rear curtain coil (not shown) of the shutter drive mechanism. At the same time, the FB drive of the motor 5 through the second driver 25 is performed to rotate the motor 5 at high speed (step S110). As a result, the mirror cam gear 33 rotates in the clockwise direction and the rotation counter 16 starts counting.

  When the mirror cam gear 33 rotates clockwise, the shaft portion 31a of the mirror drive lever 31 urged clockwise by the lever spring 35 moves from the cam top end of the cam surface 33a of the mirror cam gear 33 to the cam bottom. drop down. As a result, the mirror drive lever 31 rotates in the clockwise direction, and the mirror drive lever 31 drives the shaft portion 30b of the mirror 30 to flip up the mirror 30 (step S111). The cam top is an outer peripheral surface having the largest radius among the cam surfaces 33a, and the cam bottom is an outer peripheral surface having the smallest radius among the cam surfaces 33a.

  Thereafter, in step S112, the system control unit 14 stops the driving of the motor 5 in response to the count number of the rotation counter 16 reaching A (FIG. 5). As a result, the mirror 30 stops at the up position. In addition, so far, the mirror cam gear 33 has rotated 110 degrees.

  Next, the system control unit 14 opens and closes the shutter 4 to expose the image sensor 10 (step S113). After a predetermined exposure time has elapsed, the system control unit 14 closes the shutter 4 and ends the exposure.

  When the exposure is completed, the system control unit 14 performs FB driving of the motor 5 through the second driver 25 to rotate (accelerate) the motor 5 at a high speed (step S114). Thereby, the mirror cam gear 33 starts to rotate in the clockwise direction, and the cam surface 33a of the mirror cam gear 33 starts to push the shaft portion 31a of the mirror drive lever 31 as shown in FIG. Up to this point, the mirror cam gear 33 has rotated 128 degrees.

  At this time, since the mirror drive lever 31 rotates counterclockwise, the shaft portion 30b of the mirror 30 is also interlocked with the lowering of the shaft portion 31b, and the mirror 30 rapidly moves down toward the down position (step S115). ).

  During the mirror down operation (FIG. 7), when the count value of the rotation counter 16 reaches B which is a predetermined count value, the system control unit 14 changes the motor drive system from FB drive to OP through the first driver 22. Switching to driving (step S116). The system control unit 14 decelerates the motor 5 by step driving to reduce the down speed of the mirror 30, and finally causes the mirror 30 to gently contact the locking pin 32 (FIG. 8). Up to this point, the mirror cam gear 33 has rotated 251 degrees.

  Thereafter, when the count number of the rotation counter 16 reaches C, the system control unit 14 switches the motor drive method to FB drive (step S117). As a result, the mirror cam gear 33 rotates toward the initial position, and when the count number of the rotation counter 16 reaches D, the system control unit 14 stops the motor 5 (step S118). Up to this point, the mirror cam gear 33 has rotated 360 degrees.

  The shaft portion 31b of the mirror drive lever 31 has already detached from the shaft portion 30b of the mirror 30, but the mirror 30 is stabilized in the down position by the biasing force of the mirror spring 34. As described above, all the mechanisms return to the standby position, and the shooting sequence in the single shooting mode ends (step S119).

In the single shooting mode, there is a deceleration period of the motor 5 by OP driving in step S116.
Although the time until the end of the photographing sequence becomes longer, it is possible to suppress the occurrence of bounce and impact sound when the mirror 30 is moved down.

(Low-speed continuous shooting mode)
In the low-speed continuous shooting mode, the count number at which the up operation of the mirror 30 ends and the motor 5 stops is set to A. Also, the count number (predetermined count value) of the start position of the deceleration control of the motor 5 after starting the mirror 5 by starting the motor 5 upon completion of the opening / closing operation of the shutter 4 (SH completion) is set to E. ing. Note that E may be the same as B in the single-shot mode, or may be slightly different. Further, after the mirror down operation is completed, the count number of the energization switching position for moving the mirror drive mechanism to the standby position is set to F. The count number of the stop position of the last motor 5 is D.

  When the low-speed continuous shooting mode is set, the process proceeds to step S105 as described above, and the operations of steps S201 to S213 shown in FIG. 17 are performed. Here, the operations from step S201 to step S213 are the same as the operations from step S107 to step S119 except that the count numbers E and F described above are different. For this reason, operation | movement after step S210 is demonstrated here.

  In the middle of the mirror down operation by the FB driving of the motor 5 started in step S208 (FIG. 7), when the count number of the rotation counter 16 reaches E which is a predetermined count value, the system control unit 14 changes the motor driving method. Switching from the FB drive to the OP drive (step S210). The system control unit 14 decelerates the motor 5 by step driving to lower the down speed of the mirror 30, and finally brings the mirror 30 into contact with the locking pin 32 (FIG. 8). In the low-speed continuous shooting mode, the time for decelerating until the motor 5 stops is set shorter than that in the single-shot mode described above. For this reason, the mirror 30 cannot be brought into contact with the locking pin 32 at a lower speed as in the single-shot mode, but the occurrence of bounce and impact sound during the mirror down operation can be considerably suppressed. Up to this point, the mirror cam gear 33 has rotated 251 degrees.

  Thereafter, when the count number of the rotation counter 16 reaches F, the system control unit 14 switches the motor drive method to FB drive (step S211). Thereby, the mirror cam gear 33 rotates toward the initial position, and when the count number of the rotation counter 16 reaches D, the system control unit 14 stops the motor 5 (step S212). Up to this point, the mirror cam gear 33 has rotated 360 degrees.

  The shaft portion 31b of the mirror drive lever 31 has already detached from the shaft portion 30b of the mirror 30, but the mirror 30 is stabilized in the down position by the biasing force of the mirror spring 34. As described above, all the mechanisms are returned to the standby position, and the shooting sequence in the low-speed continuous shooting mode is completed (step S213).

(High-speed continuous shooting mode)
In the high-speed continuous shooting mode, the count number at which the up operation of the mirror 30 ends and the motor 5 stops is set to A. Also, the count number (predetermined count value) of the start position of the deceleration control of the motor 5 after starting the mirror 5 by starting the motor 5 upon completion of the opening / closing operation of the shutter 4 (SH completion) is set to G. ing. G is a value larger than B in the single shooting mode and E in the low-speed continuous shooting mode. Further, after the mirror down operation is completed, the count number of the energization switching position for moving the mirror drive mechanism to the standby position is set to F. The count number of the stop position of the last motor 5 is D.

  When the high-speed continuous shooting mode is set, the process proceeds to step S106 as described above, and the operations of steps S301 to S313 shown in FIG. 17 are performed. Here, the operations from step S301 to step S313 are the same as the operations from step S107 to step S119 except that the count numbers G and F described above are different. For this reason, operation | movement of step S310 is demonstrated here.

  During the mirror-down operation by the FB driving of the motor 5 started in step S308 (a state closer to the down position than the state shown in FIG. 7), the count number of the rotation counter 16 reaches G, which is a predetermined count value. Thereby, the system control unit 14 switches the motor drive method from the FB drive to the OP drive (step S310). The system control unit 14 decelerates the motor 5 by step driving to lower the down speed of the mirror 30, and finally brings the mirror 30 into contact with the locking pin 32 (FIG. 8). In the high-speed continuous shooting mode, the time for deceleration until the motor 5 stops is set shorter than that in the low-speed continuous shooting mode described above. For this reason, the mirror 30 cannot be brought into contact with the locking pin 32 at a lower speed as in the low-speed continuous shooting mode. Finished to enable high-speed continuous shooting. Up to this point, the mirror cam gear 33 has rotated 251 degrees.

  Subsequent steps S311 to S313 are the same as steps S211 to S213 in the low-speed continuous shooting mode.

  According to this embodiment, a motor capable of OP drive and FB drive is used, and the motor drive system is switched from FB drive to OP drive while the mirror 30 is moving to the down position, so that the speed of the mirror down operation is sufficiently increased. Slow down. Thereby, generation | occurrence | production of the bounce and impact sound in the down position of the mirror 30 can be suppressed effectively.

  Moreover, in a camera having a plurality of shooting modes with different numbers of shot images per unit time, the rotation amount (predetermined amount) of the motor 5 that switches from the FB drive to the OP drive is changed during the mirror down operation according to the shooting mode. Thereby, the speed of the mirror down operation can be set to a speed suitable for each shooting mode. For this reason, both suppression of bounce and impact sound and realization of a desired continuous shooting speed (high-speed continuous shooting) are possible.

  The embodiments described above are merely representative examples, and various modifications and changes can be made to the above-described embodiments when implementing the present invention.

  For example, in the above embodiment, the rotation amount of the motor 5 is detected based on the signal from the rotation sensor 6 provided in the motor 5, and the motor drive system is changed to the FB drive in response to the rotation amount reaching a predetermined amount. The case of switching from OP to OP drive has been described. However, a sensor for directly detecting the rotation position of the mirror 30 is provided, and the motor drive system is switched from the FB drive to the OP drive when the rotation position of the mirror 30 obtained from the sensor reaches a predetermined position. Also good.

  In the above-described embodiment, the case where the low-speed continuous shooting mode and the high-speed continuous shooting mode are provided as the continuous shooting mode has been described. However, the first and second continuous shooting modes are limited to two continuous shooting modes. Does not mean that That is, you may have three or more continuous shooting modes including other continuous shooting modes, such as medium-speed continuous shooting mode.

  It is possible to provide an imaging apparatus capable of suppressing the bounce of a mirror member and the generation of impact sound while enabling high-speed continuous shooting.

DESCRIPTION OF SYMBOLS 1 Camera body 2 Interchangeable lens 5 Motor 6 Position sensor 14 System control part 22 1st driver 25 2nd driver 30 Quick return mirror 31 Mirror drive lever 32 Locking pin 33 Mirror cam gear

Claims (4)

A motor capable of driving by open loop control and feedback control using a signal based on rotation of the rotor;
Control means for selectively switching between driving by the open loop control and driving by the feedback control;
A mirror member movable between a first position arranged inside the optical path and a second position retracted outside the optical path;
A mirror driving mechanism for moving the mirror member using a driving force from the motor;
A stopper with which the mirror member moved from the second position to the first position contacts;
Photographing mode setting means for selectively setting the first photographing mode or the second photographing mode,
When moving the mirror member from the second position to the first position, the control means starts driving the motor by the feedback control from a state where the mirror member is in the second position. When the mirror member reaches a predetermined position before contacting the stopper, the feedback control is switched to the open loop control,
The predetermined position differs between when the first shooting mode is set by the shooting mode setting means and when the second shooting mode is set by the shooting mode setting means. An imaging device. The shooting mode setting means sets any one of a single shooting mode, a first continuous shooting mode, and a second continuous shooting mode having a continuous shooting speed higher than that of the first continuous shooting mode.
The imaging apparatus according to claim 1, wherein the predetermined position is different in at least two shooting modes among the single shooting mode, the first continuous shooting mode, and the second continuous shooting mode. The motor includes rotation detection means for detecting a rotation amount of the rotor,
The imaging apparatus according to claim 1, wherein it is determined whether the mirror member reaches the predetermined position based on a rotation amount of the rotor detected by the rotation detection unit. When the mirror member is moved from the first position to the second position, the control means has the mirror member in the second position from the state in which the mirror member is in the first position. state until the without switching to open-loop control, the imaging apparatus according to any one of claims 1 to 3, wherein that you drive the motor by the feedback control.