JP3640534B2 - Drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a drive device that drives a driven body by bringing a holding member holding the driven body into sliding contact with a drive shaft and vibrating the drive shaft in the axial direction.
[0002]
[Prior art]
The holding member holding the driven body is pressed against the driving shaft with an appropriate force, the driving shaft is vibrated in the axial direction while the displacement speed is different between one direction and the opposite direction, and the holding member is slid. There is a drive device that drives a drive body. An example of such a drive device is shown in FIG. This driving device drives a lens L, and includes a piezoelectric actuator 11 that is a driving element, a driving shaft 12, a guide shaft 13, support walls 14 and 15, and a lens frame 51 that is a holding member.
[0003]
The piezoelectric actuator 11 has a rear end surface fixed to an apparatus body (not shown), and expands and contracts in the front-rear direction according to the applied voltage. The drive shaft 12 has a rear end fixed to the front end face of the piezoelectric actuator 11 and is displaced in the axial direction as the piezoelectric actuator 11 expands and contracts. When a voltage is periodically applied to the piezoelectric actuator 11, the drive shaft 12 vibrates. The guide shaft 13 is disposed in parallel with the drive shaft 12.
[0004]
The support walls 14 and 15 are arranged in parallel and are fixed to the apparatus main body. The support wall 14 has a through hole 14a that supports the tip end portion thereof through the drive shaft 12, a fixing hole 14b that fixes the tip end portion of the guide shaft 13, and a large-diameter opening 14c that guides light from the front to the lens L. ing. The support wall 15 has a through hole 15a for supporting the rear portion thereof through the drive shaft 12, a fixing hole 15b for fixing the rear end portion of the guide shaft 13, and a large-diameter opening 15c for guiding the light transmitted through the lens L rearward. doing. The inner wall surfaces of the through holes 14a and 15a are in light contact with the outer peripheral surface of the drive shaft 12, and support the drive shaft 12 slidably in the axial direction.
[0005]
A front view of the lens frame 51 is shown in FIG. The lens frame 51 includes an annular holding portion 52 for fixing the lens L, a protrusion 53 formed on the upper portion of the holding portion 52, a plate-like contact portion 54 having a bent portion fixed to the protrusion 53 and in contact with the drive shaft 12, and holding A protrusion 55 having a groove formed in the lower portion of the portion 52 and through which the guide shaft 13 passes is provided. A leaf spring 56 is fixed to the protrusion 53 with a screw 57, and the drive shaft 12 is sandwiched between the contact portion 54 and the leaf spring 56, and slidably contacts the contact portion 54 and the leaf spring 56 by the elastic force of the leaf spring 56. Yes. The guide shaft 13 is in light contact with the left and right side walls of the groove of the protrusion 55 and restricts the movement of the lens frame 51 around the drive shaft 12.
[0006]
An example of the voltage applied to the piezoelectric actuator 11 is shown in FIG. When the applied voltage changes abruptly, the piezoelectric actuator 11 rapidly expands or contracts, and when the applied voltage changes gradually, the piezoelectric actuator 11 gradually expands or contracts. The lens frame 51 that is merely in sliding contact with the drive shaft 12 slides on the drive shaft 12. However, if the displacement of the drive shaft 12 is low, the lens frame 51 is displaced following the displacement by frictional force. If the displacement is high, the displacement cannot be followed and the original position is maintained.
[0007]
Therefore, the lens L can be driven in one direction by repeatedly increasing the voltage applied to the piezoelectric actuator 11 rapidly and slowly decreasing as shown in FIG. The lens L can be driven in the reverse direction by repeating the gentle rise and the rapid fall as shown in FIG. The driving speed of the lens L can be adjusted by the magnitude and period of the applied voltage.
[0008]
[Problems to be solved by the invention]
The driving device drives the lens frame 51 by the frictional force between the drive shaft 12, the contact portion 54, and the leaf spring 56. When the frictional force is too large, the lens frame 51 follows the displacement even if the displacement of the drive shaft 12 is high speed. Conversely, when the frictional force is too small, the displacement of the drive shaft 12 is reduced. Even at a low speed, the lens frame 51 cannot follow the displacement, and the lens L cannot be driven efficiently. Therefore, it is necessary to appropriately set the frictional force so that the lens frame 51 reliably follows the low-speed displacement of the drive shaft 12 and does not reliably follow the high-speed displacement.
[0009]
The frictional force between the drive shaft 12 and the contact portion 54 and the leaf spring 56 depends on the elastic force of the leaf spring 56. On the other hand, the elastic force of the leaf spring 56 depends on the thickness, width, length from the fixed portion to the contact portion with the drive shaft 12, and the amount of bending due to contact with the drive shaft 12, but these are errors in processing and assembly. Varies depending on However, since the leaf spring 56 is formed so as to be fixed to the protrusion 53 close to the drive shaft 12, the spring constant is large and a slight error appears as a large difference in elastic force.
[0010]
For this reason, in the conventional drive device, it is not easy to set the elastic force of the leaf spring 56, and hence the friction force between the drive shaft 12, the contact portion 54, and the leaf spring 56 to an appropriate value, and the drive efficiency varies. It was easy. In order to improve the driving efficiency, it is necessary to perform processing and assembly with high accuracy, and it takes a long time to manufacture the apparatus, resulting in an increase in cost.
[0011]
If the spring constant of the leaf spring 56 is reduced, it is possible to reduce the influence of processing and assembly errors on the elastic force. This can be easily achieved by lengthening the leaf spring 56 together with the contact portion 54. Can do. However, when the contact portion 54 and the leaf spring 56 are lengthened, a new problem arises that the drive device becomes large.
[0012]
The present invention has been made in view of the above problems, and is a compact drive in which the elastic force of a leaf spring for pressing a holding member that holds a driven body against a drive shaft is unlikely to fluctuate due to errors in processing or assembly. An object is to provide an apparatus.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, in the present invention, a drive shaft, a drive element that vibrates the drive shaft in the axial direction, a holding member that holds a driven body, a holding member that is fixed to the holding member and is in contact with the driving shaft In a drive device that drives a driven body by vibrating the drive shaft and sliding the holding member, from a fixed part of the plate spring to a part in contact with the drive shaft Is longer than the distance from the fixed part to the drive shaft, the part of the holding member that holds the driven body is annular, the leaf spring is bent outwardly of the plate surface, and the annular part of the holding member is It is set as the structure arrange | positioned along the outer peripheral surface of a site | part substantially.
[0014]
The minimum length of the leaf spring required to press the holding member against the drive shaft is equal to the distance from the fixed portion to the drive shaft (the length of the perpendicular line extending from the fixed portion to the drive shaft). However, by making the length along the spring surface from the fixed part to the part in contact with the drive shaft, that is, the length of the flexible part longer than the necessary shortest distance, the spring constant of the leaf spring can be reduced. If the spring constant is reduced, the elastic force of the leaf spring will be less, even if there is some error in the thickness, width, distance from the fixed part to the drive shaft, or the amount of deflection due to contact with the drive shaft. Without change, the holding member can be pressed against the drive shaft with a substantially constant force.
[0015]
Further, since the arranged substantially along the outer peripheral surface of the portion of the annular holding member by bending a leaf spring plate surface outward, drive shaft length of the flexible portion of the leaf spring, from a fixed site Much longer than the distance up to, and the spring constant can be greatly reduced. Moreover, it is not necessary to enlarge the device in any direction. Further, the length of the leaf spring can be freely set, the degree of freedom in setting the spring constant is increased, and an elastic force suitable for driving can be easily obtained.
[0016]
In order to achieve the above object, the present invention also provides a drive shaft, a drive element that vibrates the drive shaft in the axial direction, a holding member that holds a driven body, and a holding member that is fixed to the holding member and is in contact with the driving shaft. In a drive device that includes a leaf spring that presses a member against a drive shaft, and drives the driven body by vibrating the drive shaft and sliding the holding member, the portion that contacts the drive shaft from the fixed portion of the leaf spring lengths up is longer than the distance from said fixed portion to the drive shaft, the plate spring is L-shaped bent in the plate plane, substantially parallel to the to the bending sites drive shaft from a fixed site It is set as the structure arrange | positioned . In this configuration, the spring constant can be reduced without increasing the device in the direction perpendicular to the drive shaft.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a drive device of the present invention will be described with reference to the drawings. The driving device of each embodiment is for driving the lens L as in the device shown in FIG. 3, but only the structure of the lens frame and the leaf spring for holding the lens L is different, and the overall configuration and driving of the device are different. Since the principle is the same, redundant description is omitted.
[0018]
FIG. 1 shows a front view of a lens frame and its peripheral portion of the driving apparatus of the first embodiment. The lens frame 21 includes an annular holding portion 22 for fixing the lens L, a protrusion 23 formed on the upper portion of the holding portion 22, a plate-like contact portion 24 having a bent portion fixed to the protrusion 23 and in contact with the drive shaft 12, And the protrusion 25 which has the groove | channel which is formed in the lower part of the holding | maintenance part 22 and lets the guide shaft 13 pass is provided.
[0019]
A leaf spring 26 bent according to the shape of the holding portion 22 is disposed on the outer peripheral surface of the holding portion 22, and one end of the leaf spring 26 is fixed to the holding portion 22 with a screw 27. The other end of the leaf spring 26 faces the contact portion 24. The drive shaft 12 is sandwiched between the contact portion 24 and the leaf spring 26, and is in sliding contact with the contact portion 24 and the leaf spring 26 by the elastic force of the leaf spring 26. Since the leaf spring 26 is bent, the length from the fixed part by the screw 27 to the part in contact with the drive shaft 12 is longer than the distance from the fixed part to the drive shaft 12.
[0020]
The force applied to the leaf spring 26 by contact with the drive shaft 12 is transmitted from the contact portion to the fixed portion, and this entire range becomes the flexible portion of the leaf spring 26. Therefore, the spring constant of the leaf spring 26 is much smaller than that of the leaf spring 56 of FIG. 4 even if the material, thickness, and width are the same. For this reason, even if there is an error in the processing or attachment of the contact portion 24, the protrusion 23, and the leaf spring 26, there is almost no influence on the elastic force of the leaf spring 26 applied to the drive shaft 12. The frictional force with the leaf spring 26 is substantially constant.
[0021]
By simply designing the length of the flexible portion of the leaf spring 26 in consideration of various factors relating to driving, including the voltage applied to the piezoelectric actuator 11, the lens frame 21 can be reliably displaced against the low-speed displacement of the drive shaft 12. The frictional force can be set so as to follow and not reliably follow the high-speed displacement, and the lens L can always be driven efficiently. In addition, since the leaf spring 26 is arranged along the outer peripheral surface of the holding portion 22 of the lens frame 21, the influence of the length of the leaf spring 26 on the size of the driving device is any of the front-rear direction, the left-right direction, and the upper-lower direction. There is nothing at all.
[0022]
The leaf spring 26 does not need to be in contact with the outer peripheral surface of the holding portion 22 of the lens frame 21 except for an end portion to be fixed, and the bent shape is not necessarily the same as the outer peripheral surface of the holding portion 22. Although the leaf spring 26 is fixed to the holding portion 22 here, it may be extended as necessary and fixed to the protrusion 23.
[0023]
FIG. 2 is a perspective view of the lens frame and its peripheral portion of the driving apparatus of the second embodiment. The lens frame 31 includes an annular holding portion 32 for fixing the lens L, a protrusion 33 formed on the upper portion of the holding portion 32, a plate-like contact portion 34 having a bent portion fixed to the protrusion 33 and in contact with the drive shaft 12, And a protrusion 35 having a groove formed in the lower portion of the holding portion 32 and through which the guide shaft 13 passes.
[0024]
The protrusion 33 is formed longer than the rear end surface of the holding portion 32. The rear portion 33 a of the protrusion 33 is formed thicker than the front portion, and one end of an L-shaped leaf spring 36 is fixed thereto by a screw 37. From the bent portion of the leaf spring 36 to one end fixed, the leaf spring 36 is disposed in parallel with the drive shaft 12, and the other end faces the contact portion 34. The drive shaft 12 is sandwiched between the contact portion 34 and the leaf spring 36 and is in sliding contact with the contact portion 34 and the leaf spring 36 by the elastic force of the leaf spring 36. Since the leaf spring 36 has a portion parallel to the drive shaft 12, the length from the fixed portion by the screw 37 to the portion in contact with the drive shaft 12 is longer than the distance from the fixed portion to the drive shaft 12.
[0025]
The force applied to the leaf spring 36 by the contact with the drive shaft 12 is transmitted from the contact portion to the fixed portion through the bent portion, and this entire range becomes the flexible portion of the leaf spring 36. Therefore, the spring constant of the leaf spring 36 is smaller than that of the leaf spring 56 of FIG. For this reason, even if there is an error in the processing or attachment of each part, the influence on the elastic force of the leaf spring 36 applied to the drive shaft 12 is small, and the friction force between the drive shaft 12 and the contact portion 34 and the leaf spring 36 is approximately. Thus, the lens L can be driven efficiently.
[0026]
In the configuration of the present embodiment, since the protrusion 33 and the leaf spring 36 are lengthened in the front-rear direction, the drive device is slightly longer in the front-rear direction, but the size in the vertical and horizontal directions is not affected. Here, although the holding portion 32 is annular, the holding portion 32 is not involved in fixing the leaf spring 36, and therefore the holding portion 32 can have any shape as long as the lens L can be held.
[0027]
The drive device of the present invention has been described with reference to two examples. However, the drive device of the present invention is not limited to the exemplified lens, and can be applied to drive any object. Here, the piezoelectric actuator is used as the drive element for vibrating the drive shaft, but the drive shaft may be vibrated by other methods. For example, it is possible to employ a method in which the drive shaft is elastically biased in the axial direction and the drive shaft is displaced against an urging force by an eccentric cam attached to the rotating shaft of the motor.
[0028]
【The invention's effect】
In the drive device of the present invention, the length of the flexible portion of the leaf spring is made larger than the minimum length necessary for pressing the holding member against the drive shaft to reduce the spring constant. Variations in the elastic force of the leaf spring due to errors can be suppressed. For this reason, the frictional force between the holding member and the drive shaft is stabilized, and the driven body can be driven efficiently. In addition, it is not necessary to perform processing and assembly with particularly high accuracy, so that manufacturing efficiency can be improved and the cost of the apparatus can be reduced.
[0029]
In particular, in the configuration in which the leaf spring is arranged along the outer peripheral surface of the annular holding member, it is easy to set a spring constant for efficiently driving the driven body, and the apparatus is not enlarged at all. Moreover, the structure which arrange | positions an L-shaped leaf | plate spring substantially parallel to a drive shaft can make the to-be-driven body holding | maintenance part of a holding member arbitrary shapes, and has a wide use.
[Brief description of the drawings]
FIG. 1 is a front view of a lens frame and a peripheral portion of a driving apparatus according to a first embodiment.
FIG. 2 is a perspective view of a lens frame and a peripheral portion of a driving apparatus according to a second embodiment.
FIG. 3 is a perspective view of a conventional drive device.
FIG. 4 is a front view of a lens frame and a peripheral portion of a conventional driving device.
FIG. 5 is a diagram illustrating an example of a voltage applied to a piezoelectric actuator.
[Explanation of symbols]
11 Piezoelectric actuator (drive element)
12 Drive shaft 13 Guide shafts 14 and 15 Support walls 21 and 31 Lens frame (holding member)
22, 32 Holding portion 23, 33 Protrusion 24, 34 Contact portion 25, 35 Protrusion portion 26, 36 Leaf spring 27, 37 Screw L Lens (driven body)

Claims (2)

A driving shaft, a driving element that vibrates the driving shaft in the axial direction, a holding member that holds the driven body, and a leaf spring that is fixed to the holding member and contacts the driving shaft and presses the holding member against the driving shaft; In the drive device that drives the driven body by vibrating the drive shaft and sliding the holding member,
The length from the fixed part of the leaf spring to the part in contact with the drive shaft is longer than the distance from the fixed part to the drive shaft,
Site for holding the driven body of the holding member is annular, the plate spring is bent in the plate surface outward, the driving apparatus characterized by being arranged substantially along the outer peripheral surface of the annular portion of the holding member . A driving shaft, a driving element that vibrates the driving shaft in the axial direction, a holding member that holds the driven body, and a leaf spring that is fixed to the holding member and contacts the driving shaft and presses the holding member against the driving shaft; In the drive device that drives the driven body by vibrating the drive shaft and sliding the holding member,
The length from the fixed part of the leaf spring to the part in contact with the drive shaft is longer than the distance from the fixed part to the drive shaft,
The leaf spring is L-shaped bent in the plate surface, the drive apparatus characterized by until the bent portion is disposed substantially parallel to the drive shaft from a fixed site.

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