JP2011120414A - Linear drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear drive device, capable of obtaining a stable amount of vibration, by preventing variations in the amount of vibration in the same type of linear drive devices, and capable of increasing the amount of vibration. <P>SOLUTION: In the linear drive device including an oscillating member 17 and a drive shaft 21 having a base end 26 fixed to the oscillating member 17, wherein a moving body friction-engaging with the drive shaft 21 slides along the axial direction of the drive shaft 21 when the drive shaft 21 vibrates in the axial direction thereof by vibration of the oscillating member 17, the oscillating member 17 has a piezoelectric element 23 which expands and contracts by energization and a planar elastic vibrator 19, the vibrator 19 is fixed by superimposing the plate surface on one side surface of the piezoelectric element 23, and a weight member 32 is fixed to the surface of the oscillating member 17 on the reverse side of the surface where the drive shaft 21 is fixed. <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.

JP 2009-273303 A

  In such a linear drive device, a pulse current having a predetermined current value is supplied to the piezoelectric element at a predetermined frequency to vibrate the drive shaft at a predetermined frequency (drive frequency). The drive frequency is set according to the type (size and type) of the linear drive device so as to drive with the optimum amount of vibration (amplitude and force), but the pulse of the same current value is applied to the same type of linear drive device. In some cases, the optimum amount of vibration could not be obtained even when a current was applied (variation in vibration amount).

  Furthermore, there is a case where a stable vibration amount cannot be obtained even when a pulse current having the same current value is passed through the same type of linear drive device.

  On the other hand, in such a linear drive device, it is desired to increase the vibration amount with a pulse current having the same current value at the same frequency.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a linear drive device that can prevent variation in vibration amount in the same type of linear drive device, obtain a stable vibration amount, and increase the vibration amount. .

  The invention according to claim 1 includes a vibration member and a drive shaft having a base end fixed to the vibration member, and the drive shaft vibrates in the axial direction by the vibration of the vibration member, thereby frictionally engaging the drive shaft. In the linear drive device in which the movable 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 a piezoelectric element. A plate surface is overlapped and fixed to one side surface, and a weight member is fixed to the surface opposite to the side on which the drive shaft is fixed to the vibration member.

  The invention according to claim 2 is characterized in that, in the invention according to claim 1, the weight member has a specific gravity greater than the specific gravity of the drive shaft.

  The invention according to claim 3 is the invention according to claim 2, wherein the weight member is fixed at a position that is the same area as the fixed surface of the drive shaft and faces the fixed surface of the drive shaft. And

  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 experiment, the inventors have found that in a linear drive device in which a drive shaft is fixed to one side surface of a vibration member, the drive shaft is fixed to one side of the vibration member. I found out that I have received it. Therefore, in the vibration member, by providing a weight member that balances the load on the surface opposite to the one side on which the drive shaft is fixed, by balancing the load acting on the vibration member, the amplitude direction of the vibrator It is possible to balance the load acting on the vibration member and increase the amplitude and force (elastic return force) of the vibration member. 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.

  According to the second aspect of the present invention, the effect of the first aspect is achieved, and the weight member having a large specific gravity is used to balance the mass with the drive shaft with a small weight member. Therefore, the apparatus can be reduced in size.

According to the third aspect of the present invention, the vibration member is obtained by fixing the weight member at a position opposite to the fixed surface of the drive shaft with the same area as that of the drive shaft while exhibiting the operational effect of the second aspect. The balance with the drive shaft can be optimized.

  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 base 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 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 3rd Embodiment, (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 supply 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 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. 1A, a base end 26 of the drive shaft 21 is bonded and fixed to the vibrator 19 at a substantially central portion of one side surface with an adhesive 30, and the base end 26 of the drive shaft 21 is It is fixed in contact with the vibrator 19.

  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.

  A weight member 32 is fixed to the other side surface of the piezoelectric element 23 (base end side surface of the drive shaft 21) by an adhesive 30. The weight member 32 has a mass balance with the drive shaft 21 fixed to the tip side surface (one side surface) of the vibration member 17.

  The weight member 32 is a metal member whose specific gravity is heavier than that of the drive shaft 21, and has a dimension shorter than that of the drive shaft 21 and substantially the same mass as the drive shaft 21. Thus, the weight member 32 can be prevented from projecting greatly toward the base end side while achieving a mass balance with the drive shaft 21, and the apparatus can be downsized. As the weight member 32, for example, silver, copper, ceramics, or lead is used.

  In the present embodiment, the weight member 32 is fixed at a position that is the same as the area of the base end (fixed surface) 26 of the drive shaft 21 and faces the drive shaft 21, and the drive shaft 21 in the vibration member 17. The mass balance with respect to the drive shaft 21 is optimized by using the same position where the load is applied.

  As shown in FIG. 2, the distal end portion of the drive shaft 21 is inserted into a holder 41a fixed to the casing 2 and held by the casing 2, and the vibration member 17 is also held by the casing 2 by the holder 41b. ing.

  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 a two-dot chain line in FIG. 1A, when a pulse current is supplied to the piezoelectric element 23, the piezoelectric element 23 is deformed so as to protrude forward together with the vibrator 19, and the drive shaft 21 Is deformed toward the front side, and the zoom 1 lens holder 3 moves forward because there is a frictional force with the drive shaft 21 at the press contact portion 51. Next, when the piezoelectric element 23 contracts, the vibrator 19 suddenly returns to the original position due to the elastically deformed reaction force, but deforms into a dent shape due to the inertial force and rapidly moves backward. The zoom lens holder 3 moves forward along the drive shaft 21 by repeating such deformation operation of the vibrator 19.

  In such an elastic deformation of the vibrator 19 and the return by the reaction force, in the present embodiment, as shown in FIG. 1A, the vibrator 19 has a drive shaft fixed to one side surface (tip side surface). Since the weight member 32 is fixed to the other side surface (base end side surface) in order to balance the mass with the mass 21, the balance of the load acting on the vibration member 17 is balanced, so that the deformation of the vibrator 19 in the amplitude direction is achieved. It is possible to balance the load acting on (see the two-dot chain line in FIG. 1A), and to increase the amplitude and force (elastic return force) of the vibration member. In particular, unlike the conventional case, the vibrator 19 can be prevented from being deformed biased toward the drive shaft 21 (one side surface) or a biased load acting on the vibrator 19, so that the vibrator 19 can be evenly deformed, amplitude and reaction force. The return (force) due to can be obtained, thereby increasing the amount of vibration.

  That is, by supplying a pulse current having the same current value and the same frequency to the vibrating member 17, it is possible to prevent variation in vibration amount in the linear drive device of the same type (same type and size) and to be stable compared to the conventional case. The amount of vibration can be obtained.

  By using the weight member 32 having a specific gravity greater than that of the drive shaft 21, it is possible to balance the mass with the drive shaft with the small weight member 32, and thus the linear drive device 7 can be downsized. .

  In particular, in the present embodiment, the weight member 32 is fixed at a position opposite to the drive shaft 21 with the same area as the drive shaft 21 fixed to the vibration member 17. The member 17 can be obtained.

  Note that the current supplied to the vibrating member 17 was stable at a voltage V of several tens of volts and a frequency H of several tens of kilohertz, and could be moved smoothly and smoothly.

  When the zoom lens holder 3 is moved to the enlargement side (imaging side), when a pulse current in the opposite direction is supplied to the piezoelectric element 23 of the vibration member 17, it vibrates with amplification of vibration by the vibrator 19. 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. 4 shows a second embodiment of the present invention. In the second embodiment, the base end 26 of the drive shaft 21 is made thinner so that the area of the base end 26 where the drive shaft 21 is fixed in contact with the vibrator 19 is reduced. In this way, by reducing the fixed area of the drive shaft 21 with respect to the vibrator 19, the area that the vibrator 19 contributes to elastic deformation can be relatively increased, so that the elastic deformation and restoring force can be increased with a larger amplitude. (Force) can be increased.

  In the second embodiment, the weight member 23 is fixed at a position corresponding to the base end 26 with the same area M as the base end (fixed surface) 26 of the drive shaft 21 in the vibrator 19.

  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.

  The weight member 26 may be one in which solder is placed.

  For example, the piezoelectric element 23 and the vibrator 19 are not limited to a rectangular shape in plan view, but may be a polygonal shape such as a circular shape or a hexagonal shape in plan view, and the shapes are not limited.

  The material and shape of the weight member 32 are not specified, and it is only necessary to achieve a mass balance with the drive shaft.

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)
32 Weight member

Claims (4)

A vibration member and a drive shaft having a base end fixed to the vibration member. The drive shaft vibrates in the axial direction due to vibration of the vibration member, so that the movable body frictionally engaged with the drive shaft is moved in the axial direction of the drive shaft. In a linear drive that slides along
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. A linear drive device, characterized in that a weight member is fixed to a surface opposite to the surface on which the is fixed.   The linear drive device according to claim 1, wherein the weight member has a specific gravity greater than that of the drive shaft.   The linear drive device according to claim 2, wherein the weight member is fixed at a position having the same area as the fixed surface of the drive shaft and facing the fixed surface of the drive shaft.   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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