JP2019066870A - Drive device and lens unit using the same - Google Patents

Abstract

To provide a drive device that meets quietness required when photographing motion images, and can drive a heavier lens without increasing a size of a motor.SOLUTION: A drive device comprises: a lead screw part 5; a rack member 4 that has a rack tooth engaging with a lead screw provided and freely moves back and forth in an optical axis direction; a spring member 7 that presses the rack tooth against a lead screw side; a lens holding member 2 that is guided by the lead screw, and is movable back and forth in the optical axis direction; a main shaft 81 and a sub shaft 82 that guide the lens holding member in the optical axis direction, in which the lens holding member has a hole engaging with the main shaft, a guide engaging with the sub shaft, and a pair of rack member supporting parts to be arranged with an interval in the optical axis direction; a motor 6 that moves back and forth the lens holding member in the optical axis direction; and an urging spring that is disposed in the lens holding member, and urges the sub shaft in an abutting direction with respect to the lens holding member. Urging force of the urging spring is set to force equal to or more than lifting a total weight of a structure to be driven by the motor.SELECTED DRAWING: Figure 1

Description

  The present invention relates to lens driving of an optical device that moves a lens using a lead screw.

  In recent years, digital cameras capable of shooting not only still images but also moving images have been commercialized. The photographing lens used in the camera performs focusing and zooming by electrically driving a movable frame holding an optical element such as a movable lens. When the user operates focusing and zooming along with shooting, the movable frame is required to move at high speed and with high precision in order to accurately capture a shooting opportunity.

  Conventionally, as a mechanism for driving a movable frame, a method by combination of a lead screw and a nut and a method by combination of a lead screw and a rack are known. These are because they are advantageous for converting rotational displacement of a motor or the like into linear displacement. Especially when combined with the stepping motor, this advantage is more realized. This means that if the screw thread is single, the nut or rack moves back and forth one pitch for one rotation of the lead screw. In the case of a stepping motor, since rotation is performed by step driving, it is possible to easily control advancing and retracting of the nut or the rack by pulse-controlling this rotation. Therefore, it is easy to set the amount of movement of the nut or rack. As an example in which a movable lens which is a movable frame is directly driven by a stepping motor, there are those disclosed in JP 2012-150234 A and JP 2007-298718 A. Also, instead of the stepping motor, a DC motor or an ultrasonic motor may be used.

JP 2012-150234 A JP 2007-298718 A

  In the case of a mechanism for driving a moving lens using a lead screw and a nut, it is movable forward and backward along the first and second guide shafts in the optical axis direction. With only the first guide shaft, the movable frame rotates about the first guide shaft when the driving operation by the stepping motor such as rotation and stop of the motor, forward rotation and reverse rotation is added. Therefore, the second guide shaft is used to prevent the movable frame from rotating about the first guide shaft. However, since the engaging portion of the second guide shaft of the movable frame has a clearance, there is a problem that rattling occurs due to this clearance and vibration and noise occur.

  Therefore, in order to prevent these vibrations and noises, the drive device described in Patent Document 1 is provided with a spring to bias the movable frame to the guide shaft. However, this method has problems. Assuming that the position at which the spring for biasing the movable frame to the guide shaft is the shortest is the initial position, when the movable frame moves back and forth in the optical axis direction from the initial position, it is perpendicular to the optical axis for biasing the movable frame to the guide shaft In addition to the direction, the force of the spring acts also in the direction that prevents the movable frame from moving back and forth in the optical axis direction. As a result, an extra load is applied to the motor for moving the lens.

  Further, in the case of a mechanism for driving a moving lens using a lead screw and a rack, unlike a mechanism for driving a moving lens using a lead screw and a nut, a spring for biasing the movable frame is not used. Therefore, even if the movable frame moves back and forth in the direction of the optical axis from the initial position, no force acts on the movable frame in a direction that hinders the movement in the direction of the optical axis. However, since the spring for biasing the movable frame is not used, there is a problem that the engagement portion between the movable frame and the second guide shaft causes rattling by the amount of the clearance and vibration and noise occur.

  The present invention has been made in view of such a situation, and by providing an urging mechanism to the lens holding member, it is possible to suppress the vibration at the time of movement of the lens and at the same time suppress the vibration due to the difference in posture. In addition, since the vibration can be suppressed also at the time of high speed driving, the quietness at the time of lens movement is enhanced. In addition, there is no force that prevents the lens from moving back and forth in the optical axis direction. As a result, it is an object of the present invention to provide a lens capable of driving a heavier lens or driving a lens at high speed without upsizing a driving motor while satisfying the quietness required for moving image shooting.

  According to a first aspect of the present invention, which is a means for solving the above problems, a lead screw portion disposed parallel to an optical axis and rotationally driven, and rack teeth meshing with the lead screw are provided, and the lead screw is rotated by rotation. A rack member that moves forward and backward in the optical axis direction, a spring member that presses the rack teeth toward the lead screw, a lens holding member that is guided by the lead screw and is movable forward and backward in the optical axis direction, and the optical axis A main shaft and a secondary shaft which are disposed in parallel and guide the lens holding member back and forth in the optical axis direction, and the lens holding member is provided with a hole engaged with the main shaft and a guide and light engaged with the secondary shaft And a pair of rack member support portions arranged at intervals in the axial direction, and the lens holding member is moved back and forth in the optical axis direction along the lead screw via the rack member And a biasing spring disposed on the lens holding member and biasing the sub shaft in a direction to abut the lens holding member, and a biasing force of the biasing spring is driven by the motor. The driving device is characterized in that it is set to a force that raises the total weight of the structure to be carried out.

  According to the present invention, by providing the biasing mechanism to the lens holding member, it is possible to suppress the vibration at the time of movement of the lens and at the same time suppress the vibration due to the difference in posture. In addition, since the vibration can be suppressed also at the time of high speed driving, the quietness at the time of lens movement is enhanced. In addition, there is no force that prevents the lens from moving back and forth in the optical axis direction. As a result, it is possible to provide a lens capable of driving a heavier lens or driving the lens at high speed without upsizing a driving motor while satisfying the quietness required for moving image shooting.

A perspective view of the lens driving device of the present invention in the close-range object focusing state A perspective view of a conventional lens drive in a close-range object focusing state A perspective view of a conventional lens drive in an infinite object focusing state Front view of lens drive

  Hereinafter, the best mode for carrying out the present invention will be described according to the attached drawings. The present invention is not limited by the embodiment.

  FIG. 1 shows an example of a lens driving device according to an embodiment of the present invention. The lens holding frame 2 will be described. A first protrusion 21 and a second protrusion 22 are extended on the outer peripheral portion of the lens holding frame 2 with the optical axis of the lens (group) 1 interposed therebetween. The first protrusion 21 and the second protrusion 22 have a predetermined length in the optical axis direction, and a hole 211 for inserting the main shaft into the inside of the first protrusion 21, and a second protrusion Guides 222 for inserting the sub shaft are provided in the inside of the projection 22 respectively. The holes 211 may be either round holes or rectangular holes. In addition, a U-shaped hole or the like may be used as long as the lens holding frame 2 is restricted so as to be detached in the direction perpendicular to the optical axis. The guide 222 may be capable of holding the countershaft.

  Specifically, the structure driven by the motor 6 is such that the lens (group) 1 is attached to the lens holding frame 2 and the lens holding frame 2 is mounted on the lens (group) 1. The main shaft 81 is engaged with the hole 211 formed in the first protrusion 21 with the optical axis interposed, and the sub shaft 82 is engaged with the guide 222 formed in the second protrusion 22. The lens holding frame 2 is movable in the optical axis direction along the main axis 81 and the sub axis 82 by being provided parallel to the optical axis.

  At this time, the lens holding frame 2 moves along with the lens (group) 1 along the main axis 81 and the sub axis 82 while sliding smoothly in the optical axis direction.

  In addition to the first protrusion 21 and the second protrusion 22, an engagement portion 23 is provided on the outer peripheral portion of the lens holding frame 2. The engagement portion 23 is engaged with the nut member 4. The nut member 4 is screwed with the lead screw 5.

  Further, by rotating the lead screw 5 of the motor 6 for moving the lens (group) 1 forward or backward, the nut member 4 screwed with the lead screw 5 is engaged with the engaging portion 23 of the lens holding frame 2 There is no driven rotation due to this. That is, when the nut member 4 moves to the front side in the optical axis direction, the lens holding frame 2 moves to the front side in the optical axis direction while being in contact with the nut member 4 by the biasing of the spring 7. When the nut member 4 moves rearward in the optical axis direction, the lens holding frame 2 similarly moves rearward in the optical axis direction. Accordingly, the lead screw 5 moves the lens holding frame 2 and the lens (group) 1 back and forth in the optical axis direction via the nut member 4.

  Further, as long as the lens holding frame 2 can urge the lens holding frame 2 in the optical axis direction, the engagement position of the lens holding frame 2 and the spring 7 may be any position. Further, one of the springs 7 is engaged with the lens holding frame 2 and the other is engaged with a fixed barrel (not shown).

  Although the lead screw 5 and the nut member 4 are used in the present embodiment of the present invention, the lead screw 5 and the rack which are already known in the prior art document 2 may be used.

  Specifically, the nut 4 may be replaced with a rack, and the engagement portion 23 may be replaced with a spring for pressing the rack portion against the lead screw and a rack support portion.

  Even in the configuration using the lead screw 5 and the rack, since the clearance is provided around the auxiliary shaft, rattling occurs and vibration and noise occur.

  Next, FIG. 2 and FIG. 3 show an example of the conventional lens drive device.

  The same reference numerals as in FIG. 1 denote the same parts, and a description thereof will be omitted.

  The conventional lens drive device biases the lens holding frame by the spring 71 and two springs in addition to the spring 7. Specifically, the lens holding frame 2 is biased by the spring 7 in a direction parallel to the optical axis. On the other hand, the biasing direction of the spring 71 differs depending on the position of the lens (group) 1. FIG. 2 shows the case where the position of the lens (group) 1 is at a close distance, and FIG. 3 shows the case where the position of the lens (group) 1 is at infinity.

  The case where the position of the lens (group) 1 in FIG. 2 is at infinity will be described. The biasing force of the spring 71 (vector a in the drawing) can be decomposed into two types of force: a force in the direction parallel to the optical axis (the same vector b) and a force in the direction perpendicular to the optical axis (the same vector c). At this time, the force in the direction perpendicular to the optical axis (the vector c) urges the lens holding frame 2 to the sub shaft 82. On the other hand, the force in the direction parallel to the optical axis (the vector b) is the load of the motor 6. Further, even when the position of the lens (group) 1 in FIG. 3 is a close distance, the biasing force of the spring 71 can be similarly decomposed into two forces in the direction perpendicular to the optical axis and in the direction parallel to the optical axis. From the above, in the conventional lens driving device, a force is generated which applies a load to the motor 6 in the range from the infinite distance to the close distance of the lens (group) 1. Further, since the biasing force (the same vector a) of the spring 71 changes depending on the position of the lens (group) 1, it is understood that both the force in the direction perpendicular to the optical axis and the force in the direction parallel to the optical axis change. Therefore, when controlling the driving force of the motor 6, it was necessary to consider the position of the lens (group) 1.

  On the other hand, in the lens holding frame 2 of the present invention, the biasing spring 31 disposed on the lens holding frame 2 biases the lens holding frame 2 in the direction perpendicular to the optical axis. Therefore, the lens holding frame 2 is always kept in contact with the countershaft 82 inserted in the guide 222 provided on the second projection 22. Therefore, problems such as vibration and sound caused by the clearance between the guide 222 and the countershaft 82 do not occur. Furthermore, since the biasing spring 31 of the present application always biases the lens holding frame 2 only in the direction perpendicular to the optical axis regardless of the position of the lens holding frame 2, the force of the biasing spring 31 causes the lens holding frame 2 to It does not work in the direction that hinders forward and backward movement in the optical axis direction. As a result, it is not necessary to apply an extra load to the motor 6 for moving the lens.

  Further, according to the present invention, regardless of the position of the lens (group) 1, a constant force can be obtained in which the biasing spring 31 biases the lens holding frame 2 to the countershaft 82.

  Next, FIG. 4 is a front view of a lens drive device according to an embodiment of the present invention.

  The front view of the lens driving device of FIG. 4 is a front view of the lens driving device with the cover 3 removed from FIG. The same reference numerals as in FIG. 1 denote the same parts, and a description thereof will be omitted. The biasing spring 31 biases the lens holding frame 2 to the countershaft 82 via the biasing arm 32. As a result, the vibration generated from the guide 222 and the auxiliary shaft 82 at the time of focus driving can be suppressed, and the quietness is enhanced. Furthermore, since the biasing spring 31 is disposed in the lens holding unit 2 when driven by the motor, it together with the lens (group) 1 and the lens holding frame 2 or the like. The biasing direction of the biasing spring 31 is limited to the direction perpendicular to the optical axis. That is, it does not bias in a direction parallel to the optical axis.

  In the embodiment of the present invention, the biasing arm 32 is inserted. By inserting the biasing arm 32, the slidability with the countershaft 82 is improved. However, the biasing spring 31 may directly bias the lens holding frame 2 to the countershaft 82 without inserting the biasing arm 32.

  Further, it is desirable that the biasing force of the biasing spring 31 be a force that raises the total weight of the structure moving in the optical axis direction together with the lens holding frame 2 by the drive of the motor 6. When the biasing force of the biasing spring 31 is less than the total weight of the structure moving in the optical axis direction together with the lens holding frame 2 by the motor 6, the movement according to the attitude of the lens holding frame 2, that is, the attitude of the biasing spring 31 If the total weight of the structure to be mounted is in the direction opposite to the direction in which the biasing spring 31 biases, the biasing force is canceled and a clearance is generated between the guide 222 and the countershaft 82, causing problems such as vibration or sound. Sometimes.

  The structure moving in the optical axis direction with the lens holding frame 2 by the drive of the motor 6 becomes the lens (group) 1, the lens holding frame 2, the biasing spring 31, the biasing arm 32, and the cover 3 in the case of FIG. Therefore, the biasing force of the biasing spring 31 is a set value that is greater than the weight that raises the total weight of these. However, as described above, the present invention can obtain the effect without providing the biasing arm 32. Therefore, in the case where the biasing arm 32 is not provided, the biasing force of the biasing spring 31 is more than the force that raises the total weight of the lens (group) 1, the lens holding frame 2, the biasing spring 31, and the cover 3. It becomes a setting value.

  The cover 3 is also similar to the biasing arm 32. Even if the cover 3 is not provided, the effects of the present invention can be obtained. Therefore, when the cover 3 is not provided, it is not included in the structure moving in the optical axis direction together with the lens holding frame 2 by the drive of the motor 6, and therefore, it is not necessary to add to the biasing force of the biasing spring 31.

  In the present embodiment of the present invention, the spring 7 biases the lens holding frame 2 in the optical axis direction, and the biasing spring 31 biases the lens holding frame 2 in the direction perpendicular to the optical axis. It is carried out. Therefore, in either the lead screw or rack configuration, even if only the biasing spring 31 is used without using the spring 7, it has an effect of suppressing vibration and noise caused by having a clearance around the auxiliary shaft.

1 lens (group)
Reference Signs List 2 lens holding frame 21 first projection 211 hole 22 second projection 222 guide 3 cover 31 biasing spring 32 biasing arm 4 nut member 5 lead screw 6 motor 7 spring 71 spring 81 main shaft 82 secondary shaft

Claims (1)

A lead screw portion disposed parallel to the optical axis and rotationally driven;
A rack member that is provided with a rack tooth that meshes with the lead screw and that moves forward and backward in the optical axis direction by rotation of the lead screw;
A spring member pressing the rack teeth toward the lead screw;
A lens holding member guided by the lead screw and movable back and forth in the optical axis direction;
A main axis and an auxiliary axis disposed parallel to the optical axis and guiding the lens holding member back and forth in the optical axis direction;
The lens holding member has a hole engaged with the main shaft, a guide engaged with the counter shaft, and a pair of rack member support portions arranged at intervals in the optical axis direction.
A motor for advancing and retracting the lens holding member along the lead screw via the rack member in the optical axis direction;
An urging spring disposed in the lens holding member and urging the auxiliary shaft in a direction in which the auxiliary shaft abuts on the lens holding member;
The biasing force of the biasing spring is set to a force that raises the total weight of the structure driven by the motor.

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