JP2004205556A - Focus adjusting device, optical equipment and manufacturing method for driving shaft - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize the smooth movement of an optical lens part from the outside of moving tolerance to the moving tolerance in focusing. <P>SOLUTION: The focusing device 1 is equipped with a driven and rotated lead screw 5, a nut 35 and the optical lens part 3, and performs focus adjusting by moving the lens part 3 in an optical axis direction by the movement of the nut 35. In the device 1, a gap Ga is formed between the screw 5 and the nut 35 at the edge part 13 of the screw 5. Since backlash occurs at the edge part 13 of the screw 5 by the gap Ga, frictional resistance and clamping torque between the screw 5 and the nut 35 are reduced and the biting of the screw 5 and the nut 35 is softened. Therefore, in the case of moving the lens part 3 from the edge part 13 of the screw 5 to the middle part 16 thereof, the lens part 3 is restored to the middle part 16 in a state where the nut 35 is screwed on the screw 5. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a focus adjustment device that adjusts focus by moving an optical lens unit in an optical axis direction by moving a driven member screwed to a drive shaft, an optical device, and a method of manufacturing a drive shaft.
[0002]
[Prior art]
As shown in FIG. 10, a focus adjustment device 100 for adjusting a focus by moving an optical lens unit 103 in an optical axis direction is conventionally mounted on an optical device such as a camera. In the focus adjustment device 100, since a high driving accuracy is required particularly for a digital still camera or a digital video camera, a stepping motor 101 is used rather than a DC motor. The output shaft 105 of the stepping motor 101 is provided with a lead screw 102 provided with a thread groove and supported by a bearing 104 so that the lead screw 102 rotates together with the output shaft 105. The optical lens unit 103 includes an optical lens 109, a lens holding unit 110 that holds the optical lens 109, and a nut 111. The nut 111 is supported by the lens holder 110 and screwed to the lead screw 102. Therefore, when the lead screw 102 rotates by the driving of the stepping motor 101, the optical lens unit 103 moves in the axial direction of the output shaft 105, that is, in the optical axis direction of the optical lens 109.
[0003]
Further, as a conventional technique, a lens frame guided by a guide shaft so as to be movable in an optical axis direction, a driving source for driving the lens frame along the optical axis direction, and a lead screw attached to the driving source A nut that is screwed into the lead screw, is restricted in rotation by a rotation restricting unit, and moves only in the optical axis direction with the rotation of the lead screw, and the lens frame follows the movement of the nut. And a biasing spring for pressing a part of the lens frame against the nut portion, wherein a tip portion and a root portion of the lead screw have a diameter smaller than a diameter of a root of the screw portion. There is disclosed an optical device in which a coil spring which is formed as a screw portion and is urged so as to push the nut stuck in the root portion toward the distal end of the screw is inserted in the vicinity of the root portion (for example, see Patent Document 1). ).
[0004]
[Patent Document 1]
JP-A-11-84207
[0005]
[Problems to be solved by the invention]
In the mechanism shown in FIG. 10, the moving range of the nut 111 is limited by giving a predetermined drive pulse to the stepping motor 101 from a control unit (not shown). However, if an excessive drive pulse is given due to a malfunction of the control unit, the nut 111 may run away to the tip end portion 106 of the lead screw 102 as shown in FIG.
[0006]
In this case, as shown in FIG. 12, when the nut 111 is screwed into the distal end portion 106 of the lead screw 102, the end surface 112 of the nut 111 comes into contact with the bearing 104, and the distal end portion 106 of the lead screw 102 and the nut 111 are fastened. As a result, biting between the nut 111 and the lead screw 102 occurs.
[0007]
Similarly, when the nut 111 runs away to the rear end 107 of the lead screw 102 as shown in FIG. 13, the nut 111 is screwed into the rear end 107 of the lead screw 102 as shown in FIG. The contact 110 comes into contact with the support plate 113, and the distal end portion 106 of the lead screw 102 and the nut 111 are fastened, so that the nut 111 bites into the lead screw 102.
[0008]
Therefore, even if the stepping motor 101 is rotated in the reverse direction from such a biting state, the driving torque of the stepping motor 101 is lower than the tightening torque of the lead screw 102 and the nut 111, resulting in insufficient torque. There is a case where the nut 111 does not return from the 106 and 107 to the intermediate portion 108. In this case, the optical lens unit 103 stays at both ends 106 and 107 of the lead screw 102, and the focus cannot be adjusted.
[0009]
Also, in Patent Document 1 described above, the same lead screw and nut as those in FIG. 12 are used, and biting occurs at the leading end and the root of the lead screw. In some cases, the optical lens unit does not return, and the optical lens unit stays at the distal end and the root of the lead screw.
[0010]
Further, in Patent Document 1, since the coil spring for pushing the nut to the tip side of the lead screw and the biasing spring for biasing the lens frame to the nut are provided, the moving range of the optical lens unit is reduced. As a result, the number of parts increases, and the size of the optical device increases.
[0011]
In Patent Document 1, since both springs are constantly biased in the optical axis direction of the lens, the driving torque of the stepping motor must be increased in order to move the nut. Therefore, in order to obtain the required torque, it is necessary to increase the size of the motor or increase the power consumption.
[0012]
The present invention solves the above-mentioned problems caused by the prior art, and the present invention uses a simple configuration to smoothly move an optical lens unit in focus adjustment from outside the allowable movement range to within the allowable movement range. The purpose is to: It is another object of the present invention to reduce the size of the focus adjustment device by adopting this simple configuration. It is another object of the present invention to provide such a focus adjustment mechanism to reduce the size of an optical device. It is another object of the present invention to provide a method of manufacturing a drive shaft capable of mass-producing the drive shaft by increasing the efficiency of the manufacturing operation of the drive shaft.
[0013]
[Means for Solving the Problems]
In order to solve the above-mentioned problems and achieve the object, a focus adjustment device according to the first aspect of the present invention is provided with a drive shaft that is driven to rotate, a driven member screwed to the drive shaft, and the driven member. An optical lens unit, comprising: a focus adjustment device that adjusts focus by moving the optical lens unit in the optical axis direction by movement of the driven member within a movement allowable range in which movement of the driven member is allowed, A gap is provided between the drive shaft and the driven member outside the movement allowable range to create play between the drive shaft and the driven member.
[0014]
According to the first aspect of the present invention, the frictional resistance and the tightening torque between the drive shaft and the driven member are reduced outside the allowable movement range, and the biting between the drive shaft and the driven member is reduced.
[0015]
According to a second aspect of the present invention, there is provided a focus adjustment device comprising: a drive shaft that is driven to rotate; a driven member screwed to the drive shaft; and an optical lens unit provided on the driven member. A focus adjustment device for adjusting the focus by moving the optical lens unit in the optical axis direction by moving the drive shaft, wherein the drive shaft moves more than the effective diameter in a movement allowable range in which the movement of the driven member is allowed. It is characterized by having a small diameter region having a small effective diameter outside the allowable range.
[0016]
According to the second aspect of the present invention, when the driven member is located outside the allowable movement range, a gap is formed between the drive shaft and the driven member, thereby causing play. Accordingly, the frictional resistance and the tightening torque between the drive shaft and the driven member are reduced outside the allowable movement range, and the biting between the drive shaft and the driven member is reduced.
[0017]
The focus adjusting device according to a third aspect of the present invention is the focus adjusting device according to the second aspect, wherein an outer diameter of the drive shaft in the small-diameter region is larger than an inner diameter of the driven member. .
[0018]
According to the third aspect of the present invention, when the driven member is located outside the allowable movement range, a gap is formed between the drive shaft and the driven member, and the drive shaft and the driven member are screwed together. Rattling occurs. Accordingly, the frictional resistance and the tightening torque between the drive shaft and the driven member are reduced outside the allowable movement range, and the biting between the drive shaft and the driven member is reduced.
[0019]
A focus adjusting device according to a fourth aspect of the present invention is the focus adjusting device according to the second or third aspect, wherein the small-diameter region is narrower than a thickness of the driven member.
[0020]
According to the fourth aspect, the drive shaft and the driven member partially bite out of the movement allowable range, so that the optical lens unit can be moved in a stable state even outside the movement allowable range. Further, since a gap is formed between the drive shaft and the driven member outside the allowable movement range, play occurs. Accordingly, the frictional resistance and the tightening torque between the drive shaft and the driven member are reduced outside the allowable movement range, and the biting between the drive shaft and the driven member is reduced.
[0021]
The focus adjusting device according to a fifth aspect of the present invention is the focus adjusting device according to any one of the second to fourth aspects, wherein the small-diameter region is provided at a front end portion and / or a rear end portion of the drive shaft. It is characterized by being provided.
[0022]
According to the fifth aspect of the invention, when the driven member is located at the front end and / or the rear end of the drive shaft, a gap is formed between the drive shaft and the driven member, thereby causing play. Thereby, at the front end and / or the rear end of the drive shaft, the frictional resistance and the tightening torque between the drive shaft and the driven member are reduced, and the biting between the drive shaft and the driven member is reduced.
[0023]
Further, like the focus adjusting device according to the invention of claim 6, the focus adjusting device according to any one of claims 1 to 5, further comprising a drive required for moving the optical lens unit on the drive shaft. Transmission means for transmitting torque may be provided. Further, like the focus adjusting device according to the seventh aspect of the present invention, in the focus adjusting device according to the sixth aspect, it is preferable that a stepping motor is provided as the transmission unit.
[0024]
According to the seventh aspect of the invention, the drive shaft vibrates due to the step-out of the stepping motor, so that the bite is released against the tightening torque of the drive shaft and the driven member. Therefore, when the optical lens portion is moved from the movement restriction range to the movement allowable range, play is generated simply by transmitting the necessary driving torque, and the driven member is easily returned to the movement allowable range in a state where the driven member is screwed with the drive shaft. Can be.
[0025]
An optical apparatus according to an eighth aspect of the present invention includes the focus adjustment device according to any one of the first to seventh aspects.
[0026]
According to the invention of claim 8, it is possible to save space inside the optical device.
[0027]
A method for manufacturing a drive shaft according to a ninth aspect of the present invention is a method for manufacturing a drive shaft for moving an optical lens in an optical axis direction, wherein a diameter of an end portion of the drive shaft is set to be smaller than a diameter of an intermediate portion in advance. The drive shaft is machined to be small, and a thread groove is formed on a peripheral surface of the machined drive shaft.
[0028]
According to the ninth aspect of the present invention, it is possible to manufacture a drive shaft capable of causing backlash by a simple method. In addition, the end of the drive shaft may be formed into a tapered shape. According to this, only the end of the drive shaft is formed into a tapered shape in advance, so as to cause looseness between the driven member and the driven member. A thread groove that forms a gap can be formed. The thread groove formed on the peripheral surface of the drive shaft may be formed by rolling. According to this, it is possible to simultaneously form the screw grooves at both the middle part and the end part of the drive shaft.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of a focus adjustment device according to the present invention will be described in detail with reference to the accompanying drawings. This focus adjustment device is applied to various optical devices such as a film camera, a digital camera, a video camera, a telescope, and a microscope.
[0030]
1 to 3 are schematic partial side sectional views showing a focus adjustment device 1 of the present embodiment. This focus adjustment device 1 is substantially constituted by a drive unit 2 and an optical lens unit 3.
[0031]
The drive unit 2 is generally constituted by an AF motor 4 as a transmission means, a lead screw 5 as a drive shaft, a bearing 6, a support plate 7, and a guide shaft 8.
[0032]
The AF motor 4 is, for example, a stepping motor or a DC motor, and includes a motor body 10 and an output shaft 11. The AF motor 4 rotates the output shaft 11 based on a drive command from a control unit (not shown). It is preferable to use a stepping motor as the AF motor 4, so that the size of the AF motor 4 can be reduced and power consumption can be reduced.
[0033]
The lead screw 5 is driven to rotate by the torque transmitted from the output shaft 11 of the AF motor 4. A thread groove is formed on the peripheral surface of the lead screw 5. Both ends 17, 20 of both ends 13, 14 of the lead screw 5 are formed in a substantially tapered shape. A protruding shaft 22 coaxial with the lead screw 5 is provided on the end surface (tip surface 18) of the distal end portion 13 of the lead screw 5, and is fitted to the bearing 6. That is, the lead screw 5 is held so as not to rotate relative to the output shaft 11. A protruding portion 23 is also provided in the axial direction from the end surface (rear end surface 21) of the rear end portion 14 of the lead screw 5. A fitting hole 15 is formed coaxially between the protrusion 23 and the rear end 14 of the lead screw 5 so that the output shaft 11 of the AF motor 4 is fitted.
[0034]
The bearing 6 is provided on the tip 13 side of the lead screw 5. The end face 24 of the bearing 6 faces the tip face 18 of the lead screw 5. A concave portion 25 is formed in the end face 24 so as to fit with the protruding shaft 22.
[0035]
The support plate 7 is made of, for example, metal, and has a substantially U-shape with both ends bent. The horizontal plate portion 26 of the support plate 7 is substantially equal to the length of the lead screw 5. Both ends of the support plate 7 are vertical plate portions 27, 28 perpendicular to the horizontal plate portion 26, and the vertical plate portion 27 on the leading end 13 side of the lead screw 5 is on the rear end 14 side of the lead screw 5. Are formed shorter than the vertical plate portion 28 of FIG. An opening 30 is formed in the vertical plate portion 27 on the tip end portion 13 side of the lead screw 5 to hold the bearing 6. An opening 31 is also formed in the vertical plate portion 28 on the rear end portion 14 side of the lead screw 5, and the protruding portion 23 of the rear end surface 21 is fitted. A through hole 32 is formed below the opening 31 so that the guide shaft 8 can pass therethrough. The guide shaft 8 is parallel to the center axis C of the lead screw 5 (see FIGS. 4 to 6). The guide shaft 8 is held inside the optical device. Thus, the drive unit 2 is configured such that the lead screw 5 also rotates around its own axis with the rotation of the output shaft 11.
[0036]
The optical lens unit 3 is substantially constituted by a photographing lens 33, a lens holding unit 34, a nut 35 as a driven member, and a rotation restricting shaft 36.
[0037]
The taking lens 33 receives incident light from the front thereof and guides it to the image sensor. In the present embodiment, the optical axis of the photographing lens 33 is parallel to the central axis C of the lead screw 5.
[0038]
A lens frame 37 is formed to project from a lower portion of the lens holding portion 34 so as to hold the periphery of the taking lens 33. A through hole 38 is formed in the lens holding portion 34 in the optical axis direction of the photographing lens 33 so that the guide shaft 8 can pass therethrough. Further, a pair of vertical pieces 40 and 41 are provided above the lens holding unit 34. A substantially U-shaped notch 43 is formed at the tip of one of the vertical pieces 40, and the lead screw 5 is loosely inserted into the notch 43. The front surface 44 of one vertical piece 40 is flush with the side surface 42 on the AF motor 4 side.
[0039]
A nut 35 as a driven member is provided on a back surface 45 of one of the vertical pieces 40. The nut 35 is screwed to the lead screw 5. The front surface 46 of the nut 35 is in close contact with the back surface 45 of one vertical piece 40.
[0040]
A pair of insertion holes 50, 51 are formed in both vertical pieces 40, 41, and the rotation regulating shaft 36 is supported. The rotation restricting shaft 36 penetrates a through hole 47 formed in the nut 35 and prevents the rotation of the nut 35 accompanying the rotation of the lead screw 5.
[0041]
In the focus adjustment device 1, when the lead screw 5 is rotated in one direction (for example, clockwise), the optical lens unit 3 is guided by the nut 35 and the guide shaft 8 and moves to the distal end portion 13 side. As shown, the nut 35 and the distal end portion 13 of the lead screw 5 are screwed together, and the back surface 48 of the nut 35 contacts the end surface 24 of the bearing 6. In the present embodiment, at the position where the nut 35 is screwed with the distal end 13 of the lead screw 5, the movement of the nut 35 and the lead screw 5 toward the distal end 13 is regulated by the end face 24 of the bearing 6. That is, at this position, the movement of the lead screw 5 in the direction of the distal end portion 13 is not allowed, and the movement is out of the movement allowable range.
[0042]
Similarly, when the lead screw 5 is rotated in the other direction (for example, counterclockwise), the optical lens portion 3 is guided by the nut 35 and the guide shaft 8 and moves toward the rear end portion 14, as shown in FIG. Then, the nut 35 and the rear end portion 14 of the lead screw 5 are screwed together, and the front surface 44 of the vertical piece 40 of the lens holding portion 34 comes into contact with the support plate 7. In the present embodiment, the position at which the nut 35 and the rear end 14 of the lead screw 5 are screwed together is also restricted by the support plate 7 from moving the nut 35 to the rear end 14 of the lead screw 5. That is, at this position, movement in the direction of the rear end portion 14 of the lead screw 5 is not allowed, and the movement is out of the movement allowable range.
[0043]
On the other hand, when the nut 35 is located at a position where the movement of the lead screw 5 in any direction is not restricted, the nut 35 is allowed to move in the direction of the center axis C of the lead screw 5. For example, as shown in FIG. 1, when the nut 35 is located in the middle portion 16 of the lead screw 5, the nut 35 can be moved in any direction of the center axis C. Therefore, in the state of FIG. It will be located in the movement allowable range.
[0044]
Next, both ends 13, 14 of the lead screw 5, which is a feature of the present embodiment, will be described. As shown in FIGS. 4 and 5, the effective diameters r (r ₁ ~ R ₁₆ ) Is formed smaller than the effective diameter R of the intermediate portion 16 of the lead screw 5. The area where the effective diameter r is small is the small diameter area. The effective diameter r decreases as the distance from the intermediate portion 16 of the lead screw 5 increases (R> r ₁ > R _Two > R _Three > R _Four > R _Five > R ₆ > R ₇ > R ₈ , R> r ₉ > R _Ten > R ₁₁ > R ₁₂ > R ₁₃ > R ₁₄ > R _Fifteen > R ₁₆ ). That is, the virtual curved surface formed by the effective diameter r of both ends 13 and 14 of the lead screw 5 is a tapered surface.
[0045]
The screw outer diameters s (s ₁ ~ S ₁₆ ) Is formed larger than the screw inner diameter S of the nut 35. The screw outer diameter s also decreases as the distance from the intermediate portion 16 of the lead screw 5 increases (S> s). ₁ > S _Two > S _Three > S _Four > S _Five > S ₆ > S ₇ > S ₈ , S> s ₉ > S _Ten > S ₁₁ > S ₁₂ > S ₁₃ > S ₁₄ > S _Fifteen > S ₁₆ ). Accordingly, at the tip 13 of the lead screw 5, the thread of the nut 35 enters the thread groove of the both ends 13, 14 of the lead screw 5, so that the both ends 13, 14 of the lead screw 5 and the nut 35 are screwed. However, the outer peripheral surfaces of both ends 13 and 14 of the lead screw 5 do not come into contact with the inner peripheral surface of the nut 35, and the gaps Ga and Gb in which the gaps of the leads are continuous are formed. . For this reason, the frictional resistance and the tightening torque between both ends 13 and 14 of the lead screw 5 and the nut 35 are reduced, and the biting between the lead screw 5 and the nut 35 is reduced.
[0046]
Therefore, when the AF motor 4 is driven in a direction in which the nut 35 is returned to the intermediate portion 16 of the lead screw 5 in a state where the both ends 13 and 14 of the lead screw 13 and the nut 35 shown in FIGS. Ga and Gb cause rattling between the lead screw 5 and the nut 35. In addition, since the tightening torque and the frictional resistance are smaller than the drive torque, the drive torque of the AF motor 4 resists the tightening torque and the frictional resistance. Thereby, the nut 35 can be smoothly moved to the middle portion 16 side of the lead screw 5, and the optical lens unit 3 can be smoothly moved.
[0047]
Here, a method of manufacturing the lead screw 5 will be described. First, a lead screw before forming a screw groove, that is, both end edges of a screw blank are chamfered in advance. Thereby, both end edges of the screw blank can be tapered. Then, the screw blank having the tapered surface is rolled. Various rolling methods, such as a flat die type, a planetary type, and a round die type, can be adopted as a rolling method. Thereby, the thread groove can be formed in the peripheral surface of the middle part of the screw blank and the tapered surfaces at both ends by a single rolling process, and the lead screw 5 can be manufactured. Thereby, processing efficiency and mass productivity can be improved.
[0048]
Further, as long as the effective diameter r of both ends 13 and 14 of the lead screw 5 is formed smaller than the effective diameter R of the middle part 16 of the lead screw 5, the shape is not limited to the shape shown in FIGS. , FIG. 6 and FIG. As shown in FIGS. 6 and 7, at both ends 13 and 14 of the lead screw 5, the virtual curved surface formed by the effective diameter r is the peripheral surface of the cylinder. Even in the case of this shape, corrugated gaps Gc and Gd are formed between the peripheral surfaces of both ends 13 and 14 of the lead screw 5 and the inner peripheral surface of the nut 35. For this reason, the frictional resistance and the tightening torque between both end portions 13 and 14 of the lead screw 5 and the inner peripheral surface of the nut 35 are reduced, and the biting between the lead screw 5 and the nut 35 is reduced.
[0049]
Accordingly, when the AF motor 4 is driven in a direction in which the nut 35 is returned to the intermediate portion 16 of the lead screw 5 in a state where the both ends 13 and 14 of the lead screw illustrated in FIGS. Gc and Gd cause rattling between the lead screw 5 and the nut 35. Further, since the tightening torque and the frictional resistance are smaller than the drive torque, the drive torque of the AF motor 4 resists the tightening torque and the frictional resistance. Thereby, the nut 35 can be smoothly moved to the middle portion 16 side of the lead screw 5, and the optical lens unit 3 can be smoothly moved.
[0050]
4 to 7, an example is described in which the length t of the small-diameter region of the both ends 13 and 14 of the lead screw 5 is longer than the length T of the nut 35, but is shown in FIGS. 8 and 9. As described above, the length t of the small-diameter region of both ends 13 and 14 of the lead screw 5 may be formed shorter than the length T of the nut 35. According to this, a part of the nut 35 is not screwed with the small diameter area of the both ends 13 and 14 of the lead screw 5, but is screwed in a state of being in close contact with the large diameter area having the same effective diameter as the middle part 16 of the lead screw 5. Will be combined. The ratio between the length t of the small diameter region and the length u of the large diameter region may be adjusted so that the driving torque of the AF motor 4 is smaller than the tightening torque and the frictional resistance in the large diameter region. According to this, when the nut 35 is moved from the middle portion 16 of the lead screw 5 to the both ends 13 and 14, even if the nut 35 is located at the leading end 13 or the rear end 14 of the lead screw 5, the nut 35 is moved by the large diameter region. By the screwing, the focus adjustment can be performed without blurring the optical lens unit 3 even at the front end portion 13 or the rear end portion 14 of the lead screw 5.
[0051]
In addition, biting occurs due to frictional resistance and tightening torque in the large-diameter region. If such biting occurs, the stepping motor loses synchronism by using a stepping motor as the AF motor 4. Due to this step-out, the lead screw 5 vibrates, causing play, and the bite between the lead screw 5 and the nut 35 is released. Therefore, when the optical lens portion 3 is moved from the both ends 13 and 14 of the lead screw 5 to the intermediate portion 16, the nut 35 is easily screwed into the lead screw 5 only by transmitting the driving torque. Can be returned to the midway section 16.
[0052]
In the above-described embodiment, the positions outside the movement allowable range are the both ends 13 and 14 of the lead screw 5, but may be either the leading end 13 or the rear end 14. If the movement of the nut 35 is restricted to only one of the directions of the center axis C, the position outside the allowable movement range is limited to the front end 13 and / or the rear end 14 of the lead screw 5. There is no. For example, by providing a regulating member (not shown) for regulating the movement of the nut 35 in the vicinity of the middle portion 16 of the lead screw 5, a part of the middle portion 16 of the lead screw 5 can be out of the allowable movement range.
[0053]
According to the focus adjustment device 1 of the present embodiment, even when the optical lens unit 3 moves from the middle part 16 of the lead screw 5 to the front end part 13 and / or the rear end part 14 during the focus adjustment. The gap between the lead screw 5 and the nut 35 causes play, and even if the nut 35 and the lead screw 5 are screwed together, the tightening torque is weak, and the biting between the nut 35 and the lead screw 5 is reduced. Thereby, when returning the optical lens part 3 from the front end part 13 and / or the rear end part 14 of the lead screw 5 to the intermediate part 16, the optical lens part 3 can be moved smoothly.
[0054]
Further, since the optical lens portion 3 can be returned from the front end portion 13 and / or the rear end portion 14 of the lead screw 5 to the intermediate portion 16 only by the driving torque of the AF motor 4, a spring or the like for releasing biting can be used. There is no need to separately attach an urging member, and the number of components can be reduced. This makes it possible to secure a long moving range of the optical lens unit 3, facilitate manufacturing, and provide an inexpensive device.
[0055]
Further, since it is not necessary to increase the driving torque of the AF motor 4, a small-sized AF motor 4 can be employed, and the power consumption of the AF motor 4 can be reduced.
[0056]
Further, even if the nut 35 runs away due to a malfunction of the control unit, the bite between the lead screw 5 and the nut 35 is reduced, so that even if a stepping motor with a relatively small driving torque is used, the optical lens The part 3 can be smoothly moved from both ends 13 and 14 of the lead screw 5 to the halfway part 16.
[0057]
Further, when the focus adjustment device 1 is incorporated in an optical device, an urging member such as a spring for releasing biting is unnecessary, and the AF motor 4 can be reduced in size, thereby saving space in the optical device. be able to.
[0058]
【The invention's effect】
As described above, according to the focus adjustment device of the present invention, there is an effect that the optical lens unit can be smoothly moved from outside the allowable movement range to the allowable movement range. Further, the simple configuration provides an effect that the size of the focus adjustment device can be reduced. Furthermore, there is an effect that the size of the optical device can be reduced by applying the focus adjustment device. Further, according to the manufacturing method of the drive shaft of the present invention, it is possible to easily manufacture the drive shaft for smoothly moving the optical lens unit by processing the end of the drive shaft in advance, thereby improving the efficiency of the manufacturing operation. Can be planned. This produces an effect that the drive shaft can be mass-produced.
[Brief description of the drawings]
FIG. 1 is a partial sectional side view of a focus adjustment device according to an embodiment of the present invention.
FIG. 2 is a partial side cross-sectional view of the focus adjustment device according to the embodiment of the present invention, showing a state where an optical lens unit has moved to a tip end of a drive shaft.
FIG. 3 is a partial side cross-sectional view of the focus adjustment device according to the embodiment of the present invention, when the optical lens unit has moved to the rear end of the drive shaft.
FIG. 4 is an enlarged side sectional view in which a distal end portion of a drive shaft in FIG. 2 is enlarged.
FIG. 5 is an enlarged side sectional view in which a rear end portion of the drive shaft in FIG. 3 is enlarged.
FIG. 6 is an enlarged side sectional view showing a modified example of a tip portion of a drive shaft.
FIG. 7 is an enlarged sectional side view showing a modified example of the rear end of the drive shaft.
FIG. 8 is an enlarged side sectional view showing another modified example of the distal end portion of the drive shaft.
FIG. 9 is an enlarged side sectional view showing another modified example of the rear end of the drive shaft.
FIG. 10 is a partial side sectional view showing a conventional focus adjustment device.
FIG. 11 is a partial sectional side view of a conventional focus adjustment device, showing a state where an optical lens unit has moved to a distal end of a drive shaft.
FIG. 12 is an enlarged side sectional view in which a distal end portion of a drive shaft in FIG. 11 is enlarged.
FIG. 13 is a partial side cross-sectional view of a conventional focus adjustment device when an optical lens unit has moved to a rear end of a driving shaft.
FIG. 14 is an enlarged side sectional view in which a rear end portion of the drive shaft in FIG. 13 is enlarged.
[Explanation of symbols]
1 Focus adjustment device
3 Optical lens unit
4 Transmission means (AF motor, stepping motor)
5 Drive shaft (lead screw)
13 Tip
14 Rear end
35 Follower (nut)
Ga, Gb, Gc, Gd void
r (r ₁ ~ R ₁₆ ) Effective diameter of both ends of drive shaft (lead screw)
s (s ₁ ~ S ₁₆ ) Screw outer diameter at both ends of drive shaft (lead screw)
R Effective diameter in the middle of drive shaft (lead screw)
S Inner diameter of screw of driven member (nut)

Claims (9)

A driven shaft that is driven to rotate, a driven member screwed to the driven shaft, and an optical lens unit provided on the driven member, wherein the driven member is within a movement allowable range in which the movement of the driven member is allowed. Focus adjustment device for moving the optical lens unit in the optical axis direction by moving the focus adjustment.
A focus adjustment device, wherein a gap is formed between the drive shaft and the driven member outside the movement allowable range to generate play. A drive shaft that is driven to rotate, a driven member screwed to the drive shaft, and an optical lens unit provided on the driven member, wherein the movement of the driven member moves the optical lens unit in the optical axis direction. A focus adjustment device for adjusting focus by
The focus adjustment device, wherein the drive shaft has a small-diameter region in which the effective diameter outside the movement allowable range is smaller than the effective diameter in the movement allowable range in which the movement of the driven member is allowed. The focus adjusting device according to claim 2, wherein an outer diameter of the drive shaft in the small diameter region is larger than an inner diameter of the driven member. The focus adjusting device according to claim 2, wherein a length of the small diameter region is shorter than a length of the driven member. The focus adjusting device according to claim 2, wherein the small-diameter region is provided at a front end and / or a rear end of the drive shaft. The focus adjustment device according to claim 1, further comprising a transmission unit configured to transmit a drive torque required for moving the optical lens unit to the drive shaft. 7. The focus adjustment device according to claim 6, wherein the transmission unit is a stepping motor. An optical apparatus comprising the focus adjustment device according to claim 1. A method of manufacturing a drive shaft for moving an optical lens in an optical axis direction,
A first step of processing in advance so that the diameter of the end portion of the drive shaft is smaller than the diameter of the halfway portion;
A second step of forming a thread groove on the peripheral surface of the drive shaft after the processing,
A method for manufacturing a drive shaft, comprising:

Images