JP2010246277A - Linear drive unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized linear drive unit which can increase drive torque without changing a magnitude of drive power and a characteristic of a piezoelectric element. <P>SOLUTION: In the linear drive unit in which moving bodies 3, 5 friction-contacting with a drive shaft 21 linearly move by an effect that the drive shaft 21 vibrates in the axial direction due to the vibration of a vibration member 17, the vibration member 17 comprises the piezoelectric element 23 which elongates and contracts by being applied with electricity, and a vibrator 19 which has elasticity and is formed of a steel plate. The vibrator 19 is fixed to the piezoelectric element 23 with its plate faces superimposed on each other, and the base end of the drive shaft 21 is fixed to the vibrator 19 or the piezoelectric element 23 at the center of the vibrator 19. A mass addition part 28 for increasing a mass is formed at the external peripheral part 19a of the vibrator 19. <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 metal 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 2008-259345 A

  In recent years, in this type of linear drive device, it is required to increase the drive torque without changing the magnitude of the drive power and the characteristics of the piezoelectric element.

  As a result of research and experiments, the inventors have found that, in a vibration member composed of a piezoelectric element and a vibrator, the vibration torque acting on the drive shaft is a vibrator that elastically deforms due to expansion and contraction of the piezoelectric element. It was clarified that it depends on.

  The torque F acting on the drive shaft by vibration is generally obtained by the equation F = ma. Here, m is mass and a is acceleration.

  Accordingly, when the mass of the vibrator is m, the acceleration a becomes an acceleration when the vibrator is elastically deformed. Therefore, the vibration torque F acting on the drive shaft is increased by increasing the mass of only the vibrator. Can do it.

  In this case, it is conceivable to increase the thickness of the vibrator to increase the mass of the vibrator. However, when the thickness of the vibrator is increased, there is a disadvantage in that the elasticity of the vibrator is reduced.

  Further, when the area of the vibrator is increased, there is a problem that the vibration member is enlarged.

  Therefore, an object of the present invention is to provide a small linear drive device that can increase the drive torque without changing the magnitude of the drive power and the characteristics of the piezoelectric element.

  The invention according to claim 1 is provided with 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 moving in frictional contact with the drive shaft. In a linear drive device in which the body moves linearly, the vibration member has a piezoelectric element that expands and contracts when energized, and a vibrator made of an elastic metal plate, and the vibrator is fixed by overlapping the plate surface on the piezoelectric element. In addition, the base end of the drive shaft is fixed to the vibrator or the piezoelectric element at the center position of the vibrator, and a mass adding portion for increasing the mass is provided on the outer periphery of the vibrator.

  The invention according to claim 2 is the invention according to claim 1, wherein the mass adding portion is a frame member having the same shape as the contour of the vibrator, and the frame member is fixed to the outer peripheral surface of the vibrator. It is characterized by.

  The invention according to claim 3 is the invention according to claim 1, wherein the mass adding portion is a thickness increasing portion in which the thickness of the outer peripheral portion of the vibrator is increased.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the mass adding portion is 5 to 15% of the mass of the vibrator.

  According to the first aspect of the present invention, since the mass adding portion is provided in the vibrator, the driving torque of the vibrating member can be increased without changing the characteristics of the piezoelectric element or increasing the driving power.

  Since the mass adding portion is provided on the outer peripheral portion of the vibrator, the mass of the vibrator can be increased without affecting the elasticity of the central portion where the vibrator is mainly elastically deformed, and the driving torque of the vibrating member can be increased. it can.

  Since the area of the vibrator is not increased, the vibration member does not increase in size even when the vibration torque increases.

  According to the second aspect of the present invention, the effect of the first aspect is achieved and the frame member is fixed to the vibrator. Therefore, it can be easily manufactured by retrofitting the vibrator. In addition, it is possible to easily adjust the increasing mass.

  According to the third aspect of the present invention, since the effect of the first aspect is achieved and only the thickness of the outer peripheral portion of the vibrator is changed, the mass of the vibrator can be reduced without increasing the number of parts. Can be increased.

  According to invention of Claim 4, while having the effect as described in any one of Claims 1-3, as shown in FIG. 3, as a result of experiment, the mass which increases is 5 to 15%. In this case, an effective increase torque can be obtained.

It is a figure which shows schematic structure of the linear drive device which concerns on embodiment of this invention, (a) is a longitudinal cross-sectional view, (b) is the top view seen from the front end side of the drive shaft. It is a figure which shows the effect | action of the linear drive device shown in FIG. In the linear drive device shown in FIG. 1, it is a graph which shows the relationship between the increase mass of the outer peripheral part in a vibrator | oscillator, and the increase torque which acts on a drive shaft. It is a longitudinal cross-sectional view which shows the structure of the camera which concerns on this Embodiment. It is AA sectional drawing shown in FIG. It is a longitudinal cross-sectional view which shows the schematic structure of the linear drive which concerns on 2nd Embodiment. It is a longitudinal cross-sectional view which shows schematic structure of the linear drive which concerns on 3rd Embodiment.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the first embodiment of the present invention will be described with reference to FIGS. The linear drive device according to the first 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. 4, the camera 1 includes a zoom lens holder (moving body) 3, a focus lens holder 5 (moving body), and a zoom lens holder driving unit (linear) that drives the zoom lens holder 3. Drive device) 7, focus lens holder drive means (linear drive 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. 5, 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 in the housing 2. 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 fixed to the base 2a of the housing 2 and a drive shaft 21 (22) arranged 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 vibration member 17 includes a piezoelectric element 23 and a vibrator 19 that is bonded and fixed to the subject side surface (drive shaft side surface) of the piezoelectric element 23.

  The piezoelectric element 23 has a rectangular shape in plan view. An electrode layer is formed on the piezoelectric element 23 on the surface opposite to the vibrator 19, and a terminal of the 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 substantially the same dimensions as the piezoelectric element 23, and is bonded and fixed to the piezoelectric element 23 in an overlapping manner. 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.

  The base end of the drive shaft 21 is bonded and fixed to a substantially central portion on the inner peripheral side of the vibrator 19, and a square ring-shaped frame member (mass added) is attached to the outer peripheral portion 19a on the surface on the drive shaft 21 side. Part) 28 is overlapped and fixed. The frame member 28 is made of copper having the same material and thickness as the vibrator 19, and has a mass of about 10% with respect to the mass of the vibrator 19.

  As shown in FIG. 4, 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 holder 2 by the holder 41b. ing.

  One end portion of the zoom lens holder 3 is provided with a resin-made or metal-made pressure contact portion 51 that is in pressure contact with the drive shaft 21, and the pressure contact portion 51 opens on one side surrounding the drive shaft 21 as shown in FIG. 5. A portion 53 is formed, and the opening 53 adjusts a gap between the opening 53 with a screw 55 so that friction (pressure contact force) between the pressure contact portion 51 and the drive shaft 21 can be adjusted. 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 pressure contact portion 51 has a polygonal cross section in the present embodiment, and a rectangular 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.

  Next, 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 predetermined pulse current is supplied to the piezoelectric element 23 of the vibration member 17, and the expansion and contraction of the piezoelectric element 25 is amplified by the vibrator 19 to vibrate. Let When a pulse current is supplied to the piezoelectric element 23 from the state shown in FIG. 2A, the piezoelectric element 23 is deformed so as to project forward as shown in FIG. Is moved toward the front by a dimension h, and the zoom 1 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 shown in FIG. 2 (c), when the piezoelectric element 23 contracts, the vibrator 19 suddenly returns to its original position due to the elastically deformed reaction force. Move backward by h dimension. By repeating such an operation, the zoom lens holder 3 moves forward along the drive shaft 21.

  The current supplied to the vibrating member 17 was able to move smoothly when the voltage V was several tens V and the frequency H was several tens KHz.

  Here, the frame member 28 in the first embodiment having variously changed masses is attached to the vibrator 19, and the relationship between the increased mass of the vibrator 19 and the torque received by the drive shaft 21 is measured. The results are shown in FIG. As a result of the experiment, when the mass of the vibrator 19 was increased by about 10%, the increasing torque was maximized, but when the mass was increased beyond 10%, the gradually increasing torque was increased. Reduced. This is presumably because when the increasing mass becomes larger than a predetermined value, the elasticity of the vibrator 19 is affected, and the acceleration of the vibrator during elastic deformation decreases.

  In this experiment, as is apparent from the graph of FIG. 3, it is clear that the increasing mass is preferably 5 to 15% and most preferably 8 to 12% in relation to the obtained increase torque.

  Similarly, when the zoom lens holder 3 is moved to the enlargement side (imaging side), supplying a pulse current in the opposite direction to the piezoelectric element 23 of the vibrating member 17 is accompanied by amplification of vibration by the vibrator 19. It vibrates and the zoom lens holder 3 moves backward.

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

  According to the first embodiment, only the mass of the vibrator 19 is increased, so that the zoom lens holder driving means (linear driving device) 7 and the focus are not changed without changing the characteristics of the piezoelectric element 23 or increasing the driving power. The driving torque of the lens holder driving means (linear driving device) can be increased.

  Since the mass of the outer peripheral portion 19a of the vibrator 19 is larger than that of the central portion, the mass of the vibrator is increased and driven without substantially affecting the elasticity of the central portion where the vibrator 19 is mainly elastically deformed. Torque can be increased.

  Moreover, since the area of the vibrator 19 is not increased, the vibration member 17 does not increase in size even when the vibration torque increases.

  Since only the frame member 28 is fixed to the vibrator 19, it can be easily attached to the ready-made vibrator 19. In addition, the mass can be easily adjusted by cutting the frame member 28 or preparing a plurality of types of frame members 19 having different masses.

  In addition, since the driving torque of the drive shafts 21 and 22 can be increased, it is possible to drive larger lenses (zoom lenses and focus lenses) than before, and use large lenses without increasing the size. This can improve the image quality of the camera and increase the zoom magnification.

  Even if the driving torque acting on the drive shafts 21 and 22 is increased and the moving speed of the zoom lens holder (moving body) 3 and the furcus lens holder (moving body) 5 is increased, the position detecting means 43 and 45 are arranged in the optical axis. Since it is arranged along the magnetic pole member 57 in the O direction and is detected by the MR sensor 59 that moves together with the lens holders 3 and 5, the positions of the lens holders 3 and 5 can be detected continuously and with high accuracy. Excellent.

  Other embodiments of the present invention will be described below. In the embodiments described below, the same reference numerals are given to the portions having the same effects as the first embodiment described above. Therefore, detailed description of the portion is omitted, and in the following description, differences from the first embodiment will be mainly described.

  A second embodiment of the present invention will be described with reference to FIG. In the second embodiment, in the vibration member 17, the mass adding portion 29 is provided by increasing the thickness of the outer peripheral portion 19a of the vibrator 19, thereby increasing the mass of the outer peripheral portion 19a. In the second embodiment, the base end of the drive shaft 21 is bonded and fixed to the piezoelectric element 23.

  According to the second embodiment, the same effect as the first embodiment described above can be obtained, and the mass adding portion 29 for adding mass to the vibrator 19 is formed integrally with the vibrator 19. As compared with the case where the frame member 28 is bonded as in the first embodiment described above, the number of parts is small and the assembly can be facilitated.

  A third embodiment of the present invention will be described with reference to FIG. In the third embodiment, two piezoelectric elements 23a and 23b are arranged so as to sandwich the vibrator 19 from both sides in the axial direction of the drive shaft 21, and the outer peripheral portion 19a of the vibrator 19 is arranged on both sides in the axial direction of the drive shaft. The mass adding portions 29a and 29b are formed by projecting from each other. In the third embodiment, the base end of the drive shaft 21 is bonded and fixed to the piezoelectric element 23a.

  According to the third embodiment, the same effects as those of the second embodiment described above can be achieved, and pulse powers in different directions can be simultaneously applied to one piezoelectric element 23a and the other piezoelectric element 23b. The amplitude of vibration can be made larger than that in the first embodiment.

  Further, since the mass adding portions 29a and 29b also serve as positioning portions that determine the storage positions of the piezoelectric elements 23a and 23b, it is easy to assemble.

  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 piezoelectric elements 23, 23 a, 23 b 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 shape is not limited.

  The frame member 28 and the mass adding portions 29, 29 a, and 29 b are not limited to being provided continuously in the circumferential direction on the outer periphery of the vibrator 19, and may be provided at intervals in the circumferential direction.

  In the first embodiment, the frame member 28 may be made of a material different from that of the vibrator 19.

  In the first embodiment, a hole is formed in the central portion of the vibrator 19, and the drive shaft 21 is inserted into the hole of the vibrator 19 and the base end of the drive shaft is fixed to the piezoelectric element 23. good.

  In the first embodiment, the outer peripheral portion of the vibrator 19 may protrude from the outer periphery of the piezoelectric element 23.

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)
23, 23a, 23b Electric element 28 Frame member (mass addition part)
29a, 29b Mass addition part

Claims (4)

In a linear drive device that includes a vibrating member and a drive shaft having a base end fixed to the vibrating member, and the moving body that is in frictional contact with the drive shaft linearly moves when the drive shaft vibrates in the axial direction due to vibration of the vibration member ,
The vibration member includes a piezoelectric element that expands and contracts when energized and a vibrator made of a metal plate having elasticity, and the vibrator is fixed by overlapping the plate surface on the piezoelectric element and the base end of the drive shaft is a vibrator. A linear drive device characterized by being fixed to a vibrator or a piezoelectric element at a central position of and having a mass adding portion for increasing the mass at the outer periphery of the vibrator.   The linear drive device according to claim 1, wherein the mass adding portion is a frame member having the same shape as the contour of the vibrator, and the frame member is fixed to the outer peripheral surface of the vibrator.   The linear drive device according to claim 1, wherein the mass adding portion is a thickness increasing portion in which a thickness of an outer peripheral portion of the vibrator is increased.   The linear drive device according to claim 1, wherein the mass adding unit is 5 to 15% of the mass of the vibrator.

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