JP2014212591A - Linear driving unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear driving unit which reduces an amount of abrasion powder generated in a linear actuator and diffusing to a driven member side space of a dust-proof wall through a through hole.SOLUTION: A linear driving unit includes: a linear actuator 1 which enables driving in a straight manner; a wall member 5 which isolates a region where the linear actuator is driven in the straight manner from other regions; and a guide shaft 3 having a transmission portion 4 connected with the linear actuator and a driven member. The wall member is provided with bearing parts 5a, 5b which support the guide shaft extending in a straight driving direction; a through hole 5c through which the transmission portion penetrates; and a surface 5d contacting with the guide shaft at a part of or an entire periphery of the through hole.

Description

The present invention relates to a linear drive unit having a linear actuator, and in particular, is a linear drive unit applied to a linear actuator that easily generates wear powder, an optical device that dislikes foreign matters, and the like.

FIG. 4 is a diagram for explaining a lens barrel using a conventional linear drive unit. FIG. 4A is a front view and a side view (partial cross section) of the lens barrel. In FIG. 4A, 101 is an outer frame, 102 is a focus lens, 103 is a focus lens holder, and 104 and 105 are guide shafts that support the focus lens holder 103 and guide it in the optical axis direction (A in the figure). Reference numeral 106 denotes a linear drive unit that drives the focus lens holder 103 in the optical axis direction. When the linear drive unit 106 moves a considerable distance in accordance with a movement command from a microcomputer (not shown), the focus lens 102 held by the focus lens holder 103 can reach the in-focus position. FIG. 4B is an enlarged view of the linear drive unit 106. In FIG. 4B, 201 is a linear actuator having a vibrator having two protrusions that vibrate ultrasonically, 202 is a vibrator holder, 203 is a spring that pressurizes the vibrator 201, and 204 is a protrusion of the vibrator. It is a slider that contacts and frictionally drives. Reference numeral 205 denotes a roller that rotates and slides on the back surface of the slider 204, 206 denotes a sheet metal member that receives the reaction force of the spring 203 and the roller 205, and 207 denotes a drive transmission portion connected to the lens holder 103. The vibrator 201 is ultrasonically vibrated by a high-frequency power supply means (not shown), and friction drive can be performed along the slider 204.

FIG. 4C is a plan view and a front view (partial cross section) of the vibrator 201 and the vibrator holder 202. 4C, reference numeral 301 denotes a guide shaft that linearly guides the vibrator holder 202 in the optical axis direction, and 302 denotes a bearing portion of the guide shaft 301 formed on the vibrator holder 202. Reference numeral 303 denotes a piezoelectric element attached to the back surface of the vibrator 201, and 304 denotes a pressure plate provided between the piezoelectric element 303 and the spring 203. Although the straightness of the vibrator cannot be guaranteed with the slider 204 alone, the vibrator 201 and the vibrator holder 202 can be linearly driven by the guide action of the guide shaft 301. The details of the operation and function of the linear drive unit as described above are disclosed in Patent Document 1.

A linear actuator using ultrasonic vibration of a piezoelectric element is an excellent actuator that is small in size, has a high driving force, can be used in a wide speed range, and has low noise. However, there is a potential problem that abrasion powder is generated due to friction drive. This problem can be a serious problem in an apparatus that dislikes foreign matter, particularly in an optical apparatus such as a lens barrel. Examples of such defects include the case where a foreign object adheres to the lens, which may cause a defect in a photographed image, and that the quality of a product is degraded when the foreign object is visible from the outside. In order to cope with this problem, a dustproof wall has been conventionally provided. In FIG. 4B, 208 is a dustproof wall.

FIG. 5 illustrates the vibrator 201, the vibrator holder 202, the transmission portion 207, the guide shaft 301, the dust-proof wall 208, and the like in the BB cross section of FIG. 4B. (A) is a diagram in a state in which the vibrator 201 and the transducer holder 202 have reached the lowermost side of the paper surface, (b) is a diagram in a state in which the vibrator 201 and the vibrator holder 202 have reached the uppermost side of the paper surface, (C) is the side view seen from the right of a dust-proof wall. As shown in the drawing, since the transmission part 207 cannot transmit the straight drive unless it passes through the dust-proof wall 208 and is connected to the lens holder 103, a hole like C shown in the drawing is necessary. Therefore, although the dustproof wall 208 has a certain degree of dustproof effect, it cannot be said that it is a sufficient dustproof measure.

Further, as shown in FIGS. 5D, 5E, and 5F, even if a wall 207a that moves integrally with the transmission portion 207 is provided, the dustproof effect is improved to some extent, but the gap Since E exists, it is still not a sufficient dustproof measure. Although it is possible to seal the gap E with an elastic body, the frictional load increases and wear powder of the friction member is generated, which is not an appropriate dustproof measure. Further, as an example of a sufficient dust-proof measure, there is an example described in Patent Document 2 in which a bellows-like cover is provided.

Japanese Patent Laid-Open No. 2001-292584 JP 2006-202654 A

Therefore, the fact that sufficient dust prevention cannot be achieved is a potential problem of a linear drive unit that employs a linear actuator that utilizes ultrasonic vibrations of a piezoelectric element. This was a major problem for optical instruments such as a lens barrel.

In order to solve the above-described problems, a linear drive unit according to the present invention spatially separates a linear actuator that can be driven in a straight line, a region that is provided adjacent to the linear actuator and that drives the linear actuator, and another region. And a guide shaft extending in the rectilinear drive direction having a transmission portion connected to the linear actuator and a driven member of the linear drive unit. The wall member is provided with a bearing portion that supports the guide shaft, a through-hole through which the transmission portion passes, and a surface that contacts the guide shaft in part or all of the periphery of the through-hole. Yes.

In the linear drive unit of the present invention, the guide shaft that is provided integrally with the linear actuator via the transmission portion and extends in the straight drive direction is guided straight by the bearing portion of the wall member, and around the through hole of the wall member. It touches the surface provided in part or all of the. As a result, the through hole is sealed. With this sealing configuration, it is possible to reduce or drastically reduce the amount of wear powder generated by the linear actuator diffusing into the space on the driven member side of the wall member through the through hole.

Explanatory drawing of the Example of the linear drive unit of this invention. Explanatory drawing of the Example of the linear drive unit of this invention. Explanatory drawing of the Example of the linear drive unit of this invention. Explanatory drawing of the conventional linear drive unit. Explanatory drawing of the conventional linear drive unit.

The present invention includes a linear actuator that can be linearly driven, a guide shaft that is integrated with the linear actuator by a transmission portion, and a wall member that spatially separates the region where the linear actuator is linearly driven from the other region. The wall member is provided with a bearing portion that supports the guide shaft, a through-hole through which the transmission site passes, and a surface that contacts the guide shaft in part or all of the periphery of the through-hole. The surface in contact with the guide shaft has a shape that matches the surface shape of the guide shaft so that the through hole is effectively sealed. For example, if the guide shaft is cylindrical, the surface in contact with the guide shaft is a cylindrical surface. Since the cross section of the guide shaft may have various shapes such as an ellipse, the surface in contact with the guide shaft may have various shapes in accordance with the shape. However, in order to keep the sliding resistance of the guide shaft in a straight drive, the cross section of the guide shaft is preferably a curved shape such as a circle. In the embodiments described later, the guide shaft and the bearing portion are provided on the surface of the wall member on the linear actuator side, but may be provided on the surface of the driven member side. In addition, the surface in contact with the guide shaft is preferably provided in the entire periphery of the through hole from the viewpoint of sealing, but the sealing function can be improved even if it is provided in a part of the periphery of the through hole.

Hereinafter, modes for carrying out the invention will be described.
FIG. 1 is a diagram of a linear drive unit according to an embodiment of the present invention. (A) is a diagram in a state where the vibrator 1 and the transducer holder 2 have reached the lowermost side of the paper surface, (b) is a diagram in a state where the vibrator 1 and the vibrator holder 2 have reached the uppermost side of the paper surface, (C) is the side view seen from the right of a dust-proof wall, and is a figure equivalent to FIG. 5 of a prior art example. In FIG. 1, 1 is a vibrator of an ultrasonic motor that is a linear actuator, 2 is a vibrator holder, and 5 is a dust-proof wall that is a wall member provided adjacent to the linear actuator. Since these operations and functions are the same as those of the conventional example, description thereof will be omitted.

FIGS. 2A and 2B are views for showing the structure of the transmission portion 4 connected to the vibrator holder 2, the guide shaft 3, the linear actuator, and the driven member of the linear drive unit. Is a single view, and (b) is an integrated view. As shown in the figure, by inserting and fixing the transmission portion 5 in the direction of the arrow in the hole (broken line) of the guide shaft 3 extending in the linear driving direction and the hole (broken line) of the vibrator holder 2, the three parts are It can be fixed integrally as shown in (b). FIG.2 (c) is a figure which shows the shape of the dust-proof wall 5, and the left view from the left, a front view, a right view, and sectional drawing of AC are shown. 2C, 5a and 5b are bearing portions of the guide shaft 3, 5c is a through-hole through which the transmission site 4 passes, and 5d is a cylindrical surface formed around the through-hole 5c and in contact with the guide shaft. It is. Here, the cylindrical surface 5d has a radius that is in contact with the half circumferential surface of the guide shaft 3 without a gap. The guide shaft has a circular cross section, and the surface in contact with the guide shaft forms a part of a cylindrical surface, and a part of this cylindrical surface and the cylindrical surface of the bearing portions 5a and 5b form the same cylindrical surface. Yes.

FIG. 3A is a diagram showing the assembly order. As shown in the drawing, after the guide shaft 3 is inserted into the bearings 5a and 5b, the transmission part 4 is inserted and fixed in the direction of the arrow through the through-hole 5c, and can be assembled as shown in (b). FIG. 3C is a diagram showing the relationship between the assembled guide shaft 3 and the bearing portions 5a and 5b, the through hole 5c, and the cylindrical surface 5d of the dust-proof wall 3. As illustrated, the bearing portions 5a and 5b of the dust-proof wall 5 and the cylindrical surface 5d are in contact with the guide shaft 3 in the entire range. Here, since the guide shaft 3 is manufactured by cutting, and the bearing portions 5a and 5b of the protective wall 5 and the cylindrical surface 5d are manufactured by injection molding, a gap of 10 μm to 30 μm can be formed.

As described above, in the linear drive unit of the present invention, the guide shaft provided integrally with the linear actuator and extending in the straight drive direction is guided straight by the bearing portion of the wall member, and the through hole of the wall member is provided. The through-hole is sealed by contacting the surrounding surface. Furthermore, as described above, the gap between the guide shaft, the bearing portion, and the surface around the through hole is 10 μm to 30 μm, and the contacting width can be set to 1 mm or more. Accordingly, there is no possibility that wear powder having a size exceeding 30 μm and particularly harmful will flow out of the wall member. Moreover, the possibility that the wear powder of about 1 μm will flow out to the outside through this gap is very low as compared with the conventional example. Further, since it is common to apply grease or oil for lubrication to this gap in order to improve slidability, the outflow of wear powder is also prevented by the grease or oil. Therefore, the possibility that the wear powder flows out of the wall member through this gap is extremely low in reality.

With the above configuration, the guide shaft is linearly guided by the bearing portion of the dust-proof wall, so that an effect of suppressing the sliding resistance of the linear drive can be obtained. At the same time, since the guide shaft is in contact with the surface around the through-hole of the dust-proof wall, an effect of effectively sealing the through-hole and making the dust-proof function sufficient can be obtained.

The present invention is applicable to an apparatus having a linear drive unit such as a lens barrel.

1 .. Vibrator (Linear actuator) 2 .... Vibrator holder 3 .... Guide shaft 4 .... Transmission member 5 .... Protective wall (wall member) 5a, 5b ... Bearing part 5c ... Through-hole, 5d ・ ・ A surface in contact with the guide shaft

Claims (3)

A linear actuator that can be driven straight,
A wall member that is provided adjacent to the linear actuator and spatially separates an area in which the linear actuator is linearly driven from another area;
A guide shaft extending in a straight drive direction having a transmission portion coupled to the linear actuator and a driven member of the linear drive unit;
A linear drive unit comprising:
The wall member is provided with a bearing portion that supports the guide shaft, a through-hole through which the transmission site passes, and a surface that contacts the guide shaft in part or all of the periphery of the through-hole. A linear drive unit characterized by The guide shaft has a circular cross section, a surface in contact with the guide shaft forms a part of a cylindrical surface, and a part of the cylindrical surface and the cylindrical surface of the bearing portion form the same cylindrical surface. The linear drive unit according to claim 1. The linear drive unit, wherein the linear actuator is an ultrasonic motor.

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