JP2008058894A - Linear driving device, lens driving device, and lens unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact linear driving device capable of smoothly moving a mobile object holding a lens or the like, and to provide an imaging device that uses the linear driving device. <P>SOLUTION: The device for linearly driving a mobile object is constituted to drive the mobile object linearly along the drive shaft, while controlling the rotation of the mobile object, by using a spherical part disposed at a section of the moving shaft and a guide part having a groove parallel to the drive shaft. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a rectilinear drive device that moves a moving body straight, and more particularly to a rectilinear drive device and a lens unit for moving a lens frame that holds a lens in the optical axis direction.

  In recent years, many electronic devices such as a mobile phone and a personal digital assistant (PDA) have a lens unit and have a camera function. As electronic devices become smaller and more functional, smaller lens units and zoom functions are desired.

  As a small lens unit having a zoom function, for example, as shown in the perspective view of FIG. 1, friction lens actuators 10a and 10b that transmit a driving force via a frictional force are used to separate the ball frames 50 and 60 from each other. Thus, a lens driving device 104 for driving is proposed.

In the actuators 10a and 10b, the bases 1a and 1b and the drive shafts 3a and 3b are respectively fixed to both ends of the piezoelectric elements 2a and 2b in the expansion / contraction direction. The drive shafts 3a and 3b are biased by the leaf springs 4b (only one shown) in the grooves 52 and 56 of the ball frames 50 and 60 as lens holding frames, and are frictionally coupled to the ball frames 50 and 60. . Then, a drive voltage having a sawtooth pulse waveform, for example, is applied to the piezoelectric elements 2a and 2b, and as indicated by arrows 90 and 92, the drive shafts 3a and 3b are vibrated at different speeds depending on the direction of the axial direction. , 60 are moved along the drive shafts 3a, 3b. The ball frames 50 and 60 are engaged with the drive shaft 80 by U-shaped grooves 90a and 90b as rotation restricting means for restricting rotation about the drive shafts 3a and 3b. The ball frames 50 and 60 are guided in the optical axis direction, and an image sensor 70 is disposed on the image plane of the optical system (see Patent Document 1).
JP 2002-189165 A

  However, with the rotation restricting means in Patent Document 1, if an impact or the like is applied to the image pickup apparatus when the ball frame is driven, there may be a problem that a twist occurs between the U-shaped groove portion and the guide shaft. In particular, when the imaging device is downsized, the contact width between the U-shaped groove portion and the guide shaft is reduced, and even a slight gap between the U-shaped groove and the guide shaft causes twisting due to the vibration of the ball frame, and smooth lens movement is achieved. There is a problem that you can't.

  Therefore, a technical problem to be solved by the present invention is to provide a small linear drive device that can smoothly move a moving body holding a lens and the like, and an imaging device using the linear drive device.

  This invention can achieve the said subject with the following structures.

1.
A drive shaft for moving the moving body straight;
Positioning means for allowing the movable body to move along the drive shaft;
A drive source for moving the movable body along the drive shaft;
In a rectilinear drive device comprising a rotation restricting means for restricting the rotation of the movable body on a plane orthogonal to the drive shaft,
The rotation restricting means includes a spherical portion provided on the movable body;
A rectilinear drive device comprising a guide portion that engages with the spherical portion and has a groove parallel to the drive shaft.

2.
A drive shaft for moving the lens holding frame for holding the lens straight;
Positioning means for moving the lens holding frame along the optical axis;
A drive source for moving the lens holding frame along the optical axis;
A lens driving device comprising: a rotation restricting means for restricting the rotation of the lens holding frame on a plane perpendicular to the drive shaft;
The rotation restricting means includes a spherical portion provided on the lens holding frame;
A lens driving device comprising a guide portion engaging with the spherical portion and having a groove parallel to the drive shaft.

3.
The lens holding frame has a contact portion in contact with the drive shaft,
The positioning means includes
A pressing plate disposed at a position facing the contact portion and the drive shaft;
A biasing means for biasing the contact portion and the pressing plate in a direction of pulling each other;
3. The lens driving device according to 2, wherein the lens driving device is configured as follows.

4).
4. The lens driving device according to 2 or 3, wherein the driving source has a piezoelectric element.

5.
A lens unit using the lens driving device according to any one of 2 to 4.

  According to the present invention, in a device that drives a moving body in a straight line, the rotation of the moving body is regulated using a spherical portion provided in a part of the moving shaft and a guide portion having a groove parallel to the driving shaft. Since the moving body is driven linearly along the drive shaft, even if an impact is applied from the outside, there is no twisting between the guide groove and the spherical portion of the moving body, and it moves smoothly. The body can be driven. In particular, in a lens driving device in which the moving body is a lens holding frame, even if an impact or the like is applied from the outside, no twisting occurs between the groove of the guide portion and the spherical portion of the lens holding frame, and the moving body can be smoothly moved. Since it can be driven, a lens unit capable of forming a high-quality image can be provided.

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

  2 shows a lens unit 1 according to an embodiment of the present invention, and FIG. 3 shows a cross section taken along the line AA of FIG. In the lens unit 1, a lens frame 4 as a lens holding frame for holding a plurality of lenses 3 is accommodated in a housing 2.

  An optical path regulating device 5 is fixed to the ball frame 4 so as to be partially inserted. The lens 3 held by the ball frame 4 forms an image on the image sensor 6. The ball frame 4 is slidably engaged with a guide portion 7 having a U-shaped groove provided in the housing 2 and a spherical portion 40 which is a part of the ball frame 4, and is perpendicular to the optical axis x. Rotation restricting means for restricting rotation on a smooth surface is configured. FIG. 4 shows an enlarged perspective view of the spherical portion 40 of the ball frame 4.

  In addition, the ball frame 4 has a driven portion 8 that extends so as to overlap the optical path regulating device 5. The driven portion 8 is frictionally engaged with a piezoelectric actuator 9 using a piezoelectric element as a driving source, and is moved in parallel with the optical axis x. Furthermore, the position of the ball frame 4 is detected by the position sensor 10 in the optical axis x direction.

  One end of the optical path regulating device 5 is inserted into the ball frame 4, and the optical path is narrowed or blocked by an optical path regulating member described later inside the ball frame 4. The optical path regulating device 5 has two optical path regulating drive units 11 and 12 positioned outside the ball frame 4 in order to drive the optical path regulating member. The optical path regulation drive units 11 and 12 are arranged with a gap therebetween in a direction perpendicular to the radial direction of the lens 3. The optical path control device 5 is formed in a shape in which the space between the optical path control drive units 11 and 12 is cut out in accordance with the arrangement of the optical path control drive units 11 and 12.

  The piezoelectric actuator 9 is disposed so as to penetrate the notch portion of the optical path regulating device 5 between the two optical path regulating drive units 11 and 12. The piezoelectric actuator 9 includes a weight 13 fixed to the housing 2, a piezoelectric element 14 having one end fixed to the weight 13, a columnar drive shaft 15 having one end fixed to the other end of the piezoelectric element 14, and a ball frame. 4 and a driven plate 8 and a pressing plate 16 that sandwiches the driving shaft 15 and frictionally engages the driven portion 8 with the driving shaft 15. The pressing plate 16 is biased by a helical spring 17 so as to sandwich the drive shaft 15 between the driven portion 8 and the driven plate 8. The pressing plate 16 and the helical spring 17 that is an urging unit constitute a positioning unit.

  The piezoelectric actuator 9 expands and contracts the piezoelectric element 14 at an asymmetric speed in the optical axis x direction by applying an asymmetric fluctuation voltage to the piezoelectric element 14, and the expansion and contraction of the piezoelectric element 14 moves the drive shaft 15 in the optical axis x direction. Vibrate asymmetrically. When the drive shaft 15 moves slowly, the driven member 8 moves together with the drive shaft 15 in frictional engagement. However, when the drive shaft 15 moves steeply, the driven member 8 remains in place due to its own inertia. It tries to slide and moves relative to the drive shaft 15. By changing the waveform of the voltage applied to the piezoelectric element 14, it is possible to control the movement direction and the movement amount of the driven part 8 with respect to the drive shaft 15. In this way, the piezoelectric actuator 9 can move the ball frame 4 having the lens 3 through the driven portion 8 together with the optical path regulating device 5 in the optical axis x direction.

  FIG. 5 simply shows the internal configuration of the optical path regulating device 5 of the lens unit 1. The optical path control device 5 includes two shutter blades (optical path control members) 18 and 19 that can block the optical path, and aperture blades (optical path control members) 20 that can control the optical path finely. The optical path regulation drive unit 11 of the optical path regulation device 5 is a shutter drive unit made of, for example, a solenoid that drives the shutter blades 18 and 19, and the optical path regulation drive unit 12 drives the diaphragm blades 20, for example, an aperture drive unit made of, for example, a solenoid. It is.

  Then, the effect by having comprised the lens unit 1 as mentioned above is demonstrated compared with a prior art example.

  FIG. 6 shows a configuration diagram of a conventional lens unit 100. The rotation restricting means for the lens frame 4 in the conventional lens unit 100 is adapted to engage with a cylindrical guide part 700 with a U-shaped groove forming part 400 in which a part of the lens frame 4 is formed with a U-shaped groove. . FIGS. 7 (a), 7 (b) and 7 (c) schematically show the state of occurrence of twisting when an external impact is applied in such a configuration. FIG. 7B shows a normal state of the conventional example. However, when an impact is applied from the outside, the U-shaped groove portion is inclined with respect to the guide portion 700 as shown in FIG. May occur and stop in an oblique state. In this state, smooth driving becomes difficult, and in severe cases, it will not move.

  On the other hand, the case of the lens unit 1 according to the present invention is schematically shown in FIGS. 8 (a), (b) and (c). As shown in FIG. 8 (c), even when an external impact is applied and the ball frame 4 is tilted, the twisting as shown in FIG. It can be seen that the ball frame 4 can be smoothly driven along.

  As described above, according to the present invention, it is possible to provide a lens driving device that is small in size and can be smoothly driven even when an impact is applied from the outside, and a lens unit using the driving device.

  Needless to say, this lens driving device can be used not only for a lens unit but also for a linear driving device that needs to move a moving body smoothly.

Schematic diagram of a lens unit showing a conventional example. The schematic diagram of the lens unit of one Embodiment in this invention. 1 is a cross-sectional view of a lens unit according to an embodiment of the present invention. The perspective view which shows the spherical part of the ball frame which is a moving body in this invention. The schematic diagram which shows the internal structure of the optical path control apparatus of a lens unit. Schematic diagram of a lens unit showing a conventional example. The schematic diagram which shows the condition when the external impact in a prior art example is added. The schematic diagram which shows the condition when the external impact is added in this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,100 Lens unit 2 Housing 3 Lens 4 Ball frame 5 Optical path control apparatus 6 Imaging element 7, 700 Guide part 8 Driven part 9 Piezoelectric actuator 11 Shutter drive part (optical path control drive part)
12 Aperture drive unit (optical path regulation drive unit)
13 Weight 14 Piezoelectric element 15 Drive shaft 16 Press plate 17 Helical spring 18, 19 Shutter blade (light path regulating member)
20 Aperture blade (optical path regulating member)
40 Spherical part 400 U-shaped groove forming part

Claims (5)

A drive shaft for moving the moving body straight;
Positioning means for allowing the movable body to move along the drive shaft;
A drive source for moving the movable body along the drive shaft;
In a rectilinear drive device comprising a rotation restricting means for restricting the rotation of the movable body on a plane orthogonal to the drive shaft,
The rotation restricting means includes a spherical portion provided on the movable body;
A rectilinear drive device comprising a guide portion that engages with the spherical portion and has a groove parallel to the drive shaft. A drive shaft for moving the lens holding frame for holding the lens straight;
Positioning means for moving the lens holding frame along the optical axis;
A drive source for moving the lens holding frame along the optical axis;
A lens driving device comprising: a rotation restricting means for restricting the rotation of the lens holding frame on a plane perpendicular to the drive shaft;
The rotation restricting means includes a spherical portion provided on the lens holding frame;
A lens driving device comprising a guide portion engaging with the spherical portion and having a groove parallel to the drive shaft. The lens holding frame has a contact portion in contact with the drive shaft,
The positioning means includes
A pressing plate disposed at a position facing the contact portion and the drive shaft;
A biasing means for biasing the contact portion and the pressing plate in a direction of pulling each other;
The lens driving device according to claim 2, comprising: The lens driving device according to claim 2, wherein the driving source has a piezoelectric element. A lens unit comprising the lens driving device according to claim 2.

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