JP2011125097A - Linear drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear drive unit that obtains a high driving force and reduced an installation space around a drive shaft. <P>SOLUTION: The linear drive unit 7 includes a vibration member 17, a drive shaft 21 whose base end is fixed on the vibration member 17, and a support member 41a that supports the drive shaft 21 so as to be vibrated. The drive shaft 21 is vibrated in the direction of the axial line by vibration of the vibration member 17 and a moving body 5 frictionally engaged with the drive shaft 21 is thereby slid along the direction of the axial line of the drive shaft 21. The vibration member 17 includes a piezoelectric element 23 expanded and contracted by energization and a plate-like elastic vibrator 19. The vibrator 19 is fixed on one side face of the piezoelectric element 23 with its plate face being stacked, and the drive shaft 21 is fixed off the center position of the vibration member 17 as viewed in a plane. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a linear drive device that linearly moves a moving body.

  In Patent Document 1, the base end of a drive shaft is fixed to a vibration member in which a plate-like vibrator having elasticity is overlapped and fixed on a piezoelectric element, and the drive shaft is vibrated in the axial direction thereof. A linear drive device that linearly moves a moving body in frictional contact is disclosed. In this linear drive device, on the surface of the vibration member that fixes the base end of the drive shaft, the drive shaft is fixed at the center of the surface.

JP 2009-273303 A

In such a linear drive device, a pulse current having a predetermined current value is passed through the piezoelectric element at a predetermined frequency to vibrate the drive shaft at a predetermined frequency (drive frequency). The increase in the amplitude and the elastic restoring force by the vibrator are required.
On the other hand, conventionally, the drive shaft fixing surface of the vibration member has been considered to have a stable central position as a drive shaft mounting position and a large vibration amplitude. Also, in the vibration member, it has been considered that a drive shaft fixing surface having diagonal lines and radii of equal length from the center position such as a square or a circle is effective.

However, such a conventional linear drive device has a limit in increasing the amplitude and elastic restoring force of the vibration member without increasing the size of the device.
Further, there is a high demand for miniaturization of the linear drive device, and in particular, there is a high demand for reducing the installation space of the linear drive device around the drive shaft.

  Accordingly, an object of the present invention is to provide a linear drive device that can obtain a high driving force and can reduce the installation space around the drive shaft.

  The invention according to claim 1 includes a vibration member, a drive shaft having a base end fixed to the vibration member, and a support member that holds the drive shaft in a freely oscillating manner. In the linear drive device in which the moving body frictionally engaged with the drive shaft slides along the axial direction of the drive shaft by vibrating, the vibration member includes a piezoelectric element that expands and contracts when energized, and an elastic plate-like vibration. The vibrator is fixed by overlapping a plate surface on one side surface of the piezoelectric element, and the drive shaft is fixed at a position shifted from the center position of the vibration member on the plane.

  According to a second aspect of the invention, in the first aspect of the invention, the vibration member is formed such that one dimension is longer than the other dimension in a two-dimensional plane in which the base end of the drive shaft is fixed. The drive shaft is fixed to the longitudinal end of the vibration member.

  The invention described in claim 3 is characterized in that, in the invention described in claim 2, one dimension has a length that is at least twice as long as the other dimension.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the moving body is a lens support that holds the lens, and the lens support is made to be light of the lens by vibration of the vibration member. It is characterized by moving in the axial direction.

As a result of research and experiments, the inventors have found that the drive shaft fixing surface of the vibration member has a larger amplitude at a position shifted from the center position than at the center position. In particular, it has been found that when the periphery of the vibration member is in a substantially free state without being fixed, the vibration amplitude is larger at the periphery than at the center position. When the amplitude of the vibration member increases, the elastic restoring force of the vibrator also increases, and a high driving force can be obtained.
Therefore, by fixing the drive shaft at a position shifted from the center position of the vibration member on the drive shaft fixing surface of the vibration member, the amplitude of the vibration member acting on the drive shaft can be increased without increasing the area of the vibration member. Since the elastic restoring force of the vibrator is increased, a large driving force can be obtained.

  According to the second aspect of the present invention, the function and effect of the first aspect can be achieved, and the drive shaft fixing surface of the vibration member can be set to a two-dimensional plane (X-Y plane) with one dimension (X) being set. A longer driving force can be obtained with a smaller area than a square or a circle by making it longer than the other dimension (Y), for example, by making it a rectangle or an ellipse and attaching a drive shaft to its longitudinal end. .

  According to the invention described in claim 3, the effect of the invention described in claim 2 is achieved, and as a result of the experiment, the amplitude of the vibration member increases as the distance from the center of the vibration member increases. It is not proportional to the distance, but synergistically increases. Therefore, by making the long side (X) at least twice the short side (Y) on the drive shaft fixed surface of the vibration member, at the end position, it is possible to obtain at least four times the amplitude at the center, High practicality. In addition, since the vibration member can be elongated in a band shape, the plate-like vibration member can be disposed in the dead space of the housing on which the near drive device is mounted, except for the drive shaft fixed position, and the area required for the installation of the linear drive device Can be small.

  According to invention of Claim 4, it can use as a lens drive device of the camera which show | plays the effect as described in any one of Claims 1-3.

It is a figure which shows schematic structure of the linear drive device which concerns on 1st Embodiment, (a) is a side view, (b) is the top view seen from the front end side of the drive shaft. It is a longitudinal cross-sectional view of the camera using the linear drive device which concerns on 1st Embodiment. It is AA sectional drawing shown in FIG. It is a figure explaining the effect | action of the linear drive device concerning this Embodiment, and is a side view which shows the relationship between the drive shaft attachment position and amplitude in a vibration member. It is a side view which shows schematic structure of the linear drive device concerning 2nd Embodiment. It is a figure which shows schematic structure of the linear drive device concerning the modification of this invention, (a) is a side view, (b) is the top view seen from the front end side of the drive shaft.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. The linear drive device according to the present embodiment is a linear drive device 7 that drives a lens of an autofocus camera 1 with an optical zoom incorporated in a mobile phone.

  As shown in FIG. 2, the camera 1 according to the present embodiment includes a zoom lens holder (moving body) 3, a focus lens holder 5 (moving body), and a zoom that drives the zoom lens holder 3 in a housing 2. A lens holder driving means (linear driving device) 7, a focus lens holder driving means (linear driving device) 9 for driving the focus lens holder 5, and a substrate 4 on which an image sensor 11 is provided. Further, as shown in FIG. 3, in the housing 2, a zoom lens position detection unit 43 that detects the position of the zoom lens holder 3 and a focus lens position detection unit 45 that detects the position of the focus lens holder 5 are provided. It is provided.

  The zoom lens holder 3 holds an optical zoom lens 14, the focus lens holder 5 holds a focus lens 16, and the optical zoom lens 14 and the focus lens 16 have the same optical axis 0. An image sensor 11 is provided at a joint position on the optical axis 0. Further, the casing 2 is provided with a subject side lens 18 and an imaging side lens 20 with the zoom lens 14, the focus lens 16 and the optical axis 0 aligned. In this embodiment, the subject side is the telephoto side of the optical zoom, and the imaging side is the enlargement side of the optical zoom.

  Since the zoom lens driving means (linear driving device) 7 and the focus lens driving means (linear driving device) 9 have substantially the same configuration, the zoom lens driving means 7 will be described and the same effect as the focus lens driving means 9 will be described. The same reference numerals are given to the parts having the above description, and the description thereof is omitted.

  The zoom lens driving means 7 includes a vibration member 17 disposed on the base 2a of the housing 2 and a drive shaft 21 (22) disposed in the optical axis direction. The base end of the drive shaft 21 (22) is The vibration member 17 is fixed.

  As shown in FIG. 1, the vibrating member 17 includes a piezoelectric element 23 and a vibrator 19 that is bonded and fixed to one side surface of the piezoelectric element 23 (the front end side surface of the drive shaft 21).

  The piezoelectric element 23 has a rectangular shape in plan view, and a terminal of a power control unit 27 is connected to the piezoelectric element 23. The thickness of the piezoelectric element is about 0.25 mm.

The vibrator 19 has a rectangular shape in plan view (see FIG. 1B) having a slightly larger area than the piezoelectric element 23, and is bonded and fixed to the piezoelectric element 23 so that one surface is overlapped. The vibrator 19 is a metal plate having elasticity. In the present embodiment, the vibrator 19 is a copper plate formed with a substantially uniform thickness (about 0.25 mm) throughout. The vibrator 19 is connected to a terminal of the power control unit 27.
As shown in FIG. 1B, the vibration member 17 (in other words, the vibrator 19) has a dimension in which the length L in the X direction on the XY plane is larger than the length W in the Y direction. Yes. L is preferably at least twice W, but in this embodiment, for example, W is 1.1 to 1.2 mm, and L is about 9 mm. Therefore, in the present embodiment, L has a size of about 8 times W.

As shown in FIG. 1, the base end 26 of the drive shaft 21 is bonded and fixed to one side of the vibrator 19 with an adhesive 30, and the base end 26 of the drive shaft 21 contacts and is fixed to the vibrator 19. Has been. The fixed position of the drive shaft 21 in the vibration member 17 is a position shifted from the center T in the longitudinal direction (X direction) of the vibration member 17 in the rectangular vibration member 17. It is fixed at the end position. Exactly, it is located away from the center of the vibration member 17 in the longitudinal direction (X direction), and the distance S is better as it is away from the center T. However, the arrangement of the adhesive 30 for fixing, the electrode for power supply, etc. It is arranged at the end as much as possible. The distance S is about 3 to 4 times the width W.
The drive shaft 21 is made of carbon and has a long cylindrical shape in the axial direction. The zoom lens holder (moving body) 3 slides and moves on the body 25.

As shown in FIGS. 2 and 1, the distal end portion of the drive shaft 21 is inserted into a support member 41a fixed to the housing 2 and held by the housing 2, and the vibration member 17 is also supported by the support member 41b. It is supported by. On the other hand, the support member 41a supports the drive shaft 21 so as to vibrate, and is a rubber bush in the present embodiment. The support member 41b is made of rubber and covers the entire vibration member 17. However, the vibration member 17 is covered with a gel-like adhesive on the base 2a of the housing 2 of the camera 1 without covering the vibration member 17 with a rubber material. The periphery of 17 may be fixed so that it can vibrate freely.
Further, as shown in FIG. 3, the vibrating member 17 has a length L in the X direction that is long along one side of the rectangular base 2a on the rectangular base 2a of the housing 2 of the camera 1. .

  One end portion of the zoom lens holder 3 is provided with a resin or metal pressure contact portion 51 that is in pressure contact with the body portion 25 (see FIG. 1A) of the drive shaft 21, and the pressure contact portion 51 is shown in FIG. As shown, an opening 53 is formed on one side surrounding the drive shaft 21, and the opening 53 adjusts the clearance of the opening 53 with a screw 55, and friction between the pressure contact portion 51 and the drive shaft 21 is shown. (Pressing force) is adjustable. In addition, without providing the screw 55, a predetermined friction may be applied using the elasticity of the pressure contact portion 51, or the screw may be brought into pressure contact with the drive shaft 21. Also good.

  The inner peripheral surface of the press contact portion 51 has a polygonal cross section in the present embodiment, and a square hole in the present embodiment, and is in point contact with the drive shaft 21 having a circular cross section on the inner peripheral surface. In this way, the point contact makes it possible to release powder, dust, and the like caused by friction between the drive shaft 21 and the pressure contact portion 51 of the zoom lens holder 3 to a non-contact location, so that driving reliability is high. it can.

  The other end portion of the zoom lens holder 3 is provided with an engagement portion 33 with the drive shaft 22 of the focus lens holder 5, and the engagement portion 33 is engaged with and supported by the drive shaft 22 of the focus lens holder. The movement of the zoom lens holder 3 is guided. The engaging portion 33 has a substantially U-shaped cross section, and the drive shaft 22 of the focus lens holder 5 is inserted into the U-shape.

  The configuration of the focus lens holder 5 is the same as that of the zoom lens holder 3, and the drive shaft 22 of the focus lens holder 5 is attached to the vibrating member 17 in the same manner as the drive shaft 21 of the zoom lens holder 3.

  Here, with reference to FIG. 3, the zoom lens position detecting means 43 for detecting the position of the zoom lens holder 3 and the focus lens position detecting means 45 for detecting the position of the optical focus lens holder 5 will be described. The zoom lens position detecting means 43 and the focus lens position detector 45 have the same configuration, and magnetic pole members 57 in which different magnetic poles (S pole and N pole) are alternately arranged along the optical axis 0 direction of the lens, The MR sensor 59 detects the magnetic field strength. The MR sensor 59 is fixed to the holders 3 and 5, and moves together with the holders 3 and 5 so that the movement amount and the movement direction of each holder from the reference position (or initial position) can be detected. The position information signal of each MR sensor 59 is sent to the position control unit by the flexible wiring board 60.

  Next, operations and effects of the first embodiment will be described. In this embodiment, the zoom lens holder 3 is moved to change the magnification by optical zoom, and the focus lens holder 5 is moved to adjust the focal length.

When the zoom lens holder 3 is moved to the telephoto side (subject side), a pulse current having a predetermined frequency and a predetermined current value is supplied to the piezoelectric element 23 of the vibration member 17 to vibrate the expansion and contraction of the piezoelectric element 23. Amplified by the child 19 and vibrated.
That is, as shown by the solid line in FIG. 4, when a pulse current is supplied to the piezoelectric element 23, the piezoelectric element 23 extends in the longitudinal direction and projects along with the vibrator 19 at the center in the longitudinal direction. The part is deformed so as to protrude to the front side, and the drive shaft 21 protrudes to the front side. As a result, the zoom lens holder 3 moves to the front side because there is a frictional force with the drive shaft 21 at the press contact portion 51. Next, as indicated by a two-dot chain line, when the piezoelectric element 23 contracts, the vibrator 19 suddenly returns to the original position due to the elastically deformed reaction force, but is deformed into a dent shape by inertial force, and the drive shaft 21 is The fixed end moves rapidly backwards. The zoom lens holder 3 moves forward along the drive shaft 21 by repeating such deformation operation of the vibrator 19.

  In this case, as apparent from FIG. 4, there is a difference in amplitude between the center position AA in the longitudinal direction (X) of the vibration member 17 and the longitudinal end BB where the drive shaft 21 is fixed. The amplitude of the longitudinal end portion BB is larger than the amplitude AA of the center position. As a result of the experiment, it was not possible to obtain a predetermined mathematical expression regarding the relationship between the distance and the amplitude from the center position, but this embodiment is compared with the case where the drive shaft is attached to the central portion of a square having a side of 4 mm. Then, the driving force could be increased by about 15 times compared with the conventional one.

  This is because not only the amplitude of the drive shaft fixing portion in the vibration member 17 is increased, but also the amplitude of the vibration member 17 in the drive shaft fixing portion is increased. It seems that 15 times as much driving force (propulsive force) could be obtained by these synergistic effects.

  According to the present embodiment, by fixing the drive shaft 21 at a position displaced from the center position of the XY plane of the vibration member 17 on the fixed surface of the drive shaft 21 of the vibration member 17, The amplitude of the vibrating member 17 to be increased can be made larger than before, and the elastic restoring force of the vibrator 19 is thereby increased, so that a large driving force can be obtained.

  Since the drive shaft fixing surface of the vibration member 17 is elongated in a band shape, that is, in the two-dimensional plane (XY plane), one dimension (X) is made longer than the other dimension (Y), Since the drive shaft is attached to the end portion in the longitudinal direction, a large driving force can be obtained with a small area on the two-dimensional plane of the vibration member.

By making the long side (X) at least twice the short side (Y), the vibration member 17 can obtain at least four times the amplitude at the center in the longitudinal direction end position. A high driving force can be obtained in synergy with the elastic restoring force.
In addition, the vibration member 17 has a long side (X) that is at least twice as long as the short side (Y), so that the vibration member 17 is arranged in a long band in the dead space of the housing 2a except at the drive shaft fixing position. Thus, the area required for the installation of the linear drive device 1 can be substantially reduced.

  When the zoom lens holder 3 is moved to the enlargement side (imaging side), if a pulse current in the opposite direction is supplied to the piezoelectric element 23 of the vibration member 17, vibration is accompanied by amplification of vibration by the vibrator 19. Then, the zoom lens holder 3 moves backward.

  Similarly to the zoom lens holder 3, the focus lens holder 5 can also be driven forward or backward along the drive shaft 22 by supplying a predetermined pulse current to the vibration member 17.

Next, other embodiments of the present invention will be described. In the embodiments described below, parts having the same effects as those of the first embodiment are denoted by the same reference numerals. A detailed description of this part will be omitted, and in the description of other embodiments described below, differences from the first embodiment will be mainly described.
FIG. 5 shows a second embodiment of the present invention. In the second embodiment, a weight 35 that balances the drive shaft 21 is provided on the surface of the vibration member 17 opposite to the surface on which the drive shaft 21 is fixed. Other configurations are substantially the same as those of the first embodiment. The weight 35 is a metal having a specific gravity greater than that of the drive shaft 21, and is intended to suspend a load acting on the vibration member 17 with a smaller volume than the drive shaft 21.

In the second embodiment, the load acting on the vibration member 17 is balanced to balance the load acting on the amplitude direction of the vibrator 19, and the increase in amplitude and force (elastic restoring force) of the vibration member 17 are achieved. ) Can be increased. Accordingly, it is possible to prevent variation in the vibration amount in the same type of linear drive device, obtain a stable vibration amount, and increase the vibration amount.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the drive shaft 21 is not limited to directly fixing the base end 26 to the vibrator 19, and a hole 34 is formed in the center of the vibrator 19 as shown in FIG. A base end 26 may be inserted and fixed to the piezoelectric element 23.
In the vibrating member 17, the size and shape of the vibrator 19 with respect to the piezoelectric element 23 are not limited, but it is desirable that both have substantially the same size and shape, or the piezoelectric element 23 is slightly smaller than the vibrator 19.
In the second embodiment, the weight member 26 may be one in which solder is mounted.

3 Zoom lens holder (moving body)
5 Focus lens holder (moving body)
7 Zoom lens holder drive means (linear drive)
9 Focus lens holder driving means (linear driving device)
17 Vibrating member 19 Vibrator 21 Zoom lens holder drive shaft (drive shaft)
22 Focus lens holder drive shaft (drive shaft)
26 Base end (fixed surface)

Claims (4)

A vibration member, a drive shaft whose base end is fixed to the vibration member, and a support member that holds the drive shaft in a freely vibrating manner, and the vibration of the vibration member causes the drive shaft to vibrate in the axial direction, thereby causing friction to the drive shaft. In the linear drive device in which the engaged moving body slides along the axial direction of the drive shaft,
The vibration member includes a piezoelectric element that expands and contracts when energized, and a plate-like vibrator having elasticity, and the vibrator is fixed by overlapping a plate surface on one side surface of the piezoelectric element, and the drive shaft is a vibration in a plane. A linear drive device, wherein the linear drive device is fixed at a position shifted from a center position of the member.   In the two-dimensional plane where the base end of the drive shaft is fixed, the vibration member is formed so that one dimension is longer than the other dimension, and the drive shaft is fixed to the longitudinal end of the vibration member. The linear drive device according to claim 1.   3. The linear driving apparatus according to claim 2, wherein one dimension has a length that is at least twice as long as the other dimension.   The linear drive according to any one of claims 1 to 3, wherein the moving body is a lens support that holds the lens, and the lens support is moved in the optical axis direction of the lens by vibration of the vibration member. apparatus.

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