Lens barrel and imaging device

Abstract

To provide a lens barrel which can control a position of a lens with high accuracy.SOLUTION: A lens barrel comprises: a drive source; a lead screw which is formed with a first thread groove and is rotationally driven by the drive source; a nut which has a first engagement part in which a second thread groove to be engaged with the first thread groove is formed, a second engagement part in which a third thread groove to be engaged with the first thread groove is formed, and an auxiliary part in which a fourth thread groove is formed, and moves in an axial direction of the lead screw following the rotation of the lead screw; a rotation regulation shaft which regulates the rotation of the nut; a first lens holding frame which holds a first lens; and a first biasing part which biases the nut so as to bring the nut into contact with the first lens holding frame. The phase of the second thread groove is different from the phase of the third thread groove. The fourth thread groove is disengaged from the first thread groove while the nut is moving following the rotation of the lead screw.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a lens barrel and an imaging device. [Background technology]

[0002] In order to move the lens in the optical axis direction, for example, a drive device including a lead screw attached to a motor and a nut having a thread groove that engages with the lead screw is used (for example, Patent Document 1). Highly accurate position control of the lens is desired. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2011-7938 A Summary of the Invention

[0004] According to a first aspect, a lens barrel has a drive source, a lead screw having a first thread groove formed therein and rotatably driven by the drive source, a first engagement portion having a second thread groove formed therein and engaging with the first thread groove, a second engagement portion having a third thread groove formed therein and engaging with the first thread groove, and an auxiliary portion having a fourth thread groove formed therein, and further comprises a nut that moves in the axial direction of the lead screw as the lead screw rotates, a rotation regulating shaft that regulates the rotation of the nut, a first lens holding frame that holds a first lens, and a first urging portion that urges the nut so that the nut abuts against the first lens holding frame, wherein a phase of the second thread groove is different from a phase of the third thread groove, and the fourth thread groove is spaced apart from the first thread groove while the nut moves in the axial direction of the lead screw as the lead screw rotates. Cage , In the nut, the auxiliary portion is disposed at a position different from the first engagement portion and the second engagement portion in the axial direction of the lead screw, and when the nut is viewed from the axial direction of the lead screw, the first engagement portion and the second engagement portion do not surround a portion of the lead screw, and the auxiliary portion surrounds at least the portion of the lead screw. .

[0005] According to a second aspect, an imaging device includes the above-described lens barrel.

[0006] The configurations of the embodiments described below may be appropriately improved, and at least a part of them may be replaced with other components. Furthermore, components that are not particularly limited in terms of their location may be located in any location that achieves their function, not limited to the location disclosed in the embodiments. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a cross-sectional view showing a camera equipped with a lens barrel and a camera body according to an embodiment. [Diagram 2] Figure 2(A) is an oblique view showing the fifth lens retaining frame and the drive source unit, and Figure 2(B) is a view of the fifth lens retaining frame and the drive source unit as viewed from the direction indicated by arrow A1 in Figure 2(A). [Diagram 3] FIG. 3(A) is a cross-sectional view showing the relationship between the fifth lens retaining frame and each component of the drive source unit, FIG. 3(B) is an oblique view of a spring, and FIG. 3(C) is a cross-sectional view taken along line AA of FIG. 3(A). [Figure 4] 4(A) and 4(B) are perspective views of the nut, FIG. 4(C) is a partial cross-sectional view of FIG. 4(A), and FIG. 4(D) is a cross-sectional view of the nut as viewed from the axial direction of the lead screw. [Diagram 5] FIG. 5 is a cross-sectional view showing an engagement state between the thread groove of the lead screw, the thread groove of the first engagement portion, the thread groove of the second engagement portion, and the thread groove of the auxiliary portion. [Figure 6] Fig. 6(A) is a diagram showing the positional relationship between the fourth lens holding frame and the fifth lens holding frame in a state where the lens is focused on a close subject in a zoom state, and Fig. 6(B) is a diagram showing the state of the fifth lens holding frame in the state of Fig. 6(A). Fig. 6(C) is a diagram showing the positional relationship between the fourth lens holding frame and the fifth lens holding frame when the camera is switched to a wide-angle state by operating the zoom operation ring after the power supply to the camera is turned off in the state of Fig. 6(A), and Fig. 6(D) is a diagram showing the state of the fifth lens holding frame in the state of Fig. 6(C). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a lens barrel according to an embodiment will be described in detail with reference to the drawings. Note that the scale of the shape, length, thickness, etc. of each part shown in the embodiment does not necessarily match the actual one, and in each drawing, some elements may be omitted to facilitate understanding. Also, in the cross-sectional view, hatching of some elements may be omitted.

[0009] Fig. 1 is a cross-sectional view showing a camera 1 equipped with a lens barrel 2 according to this embodiment and a camera body 3. In Fig. 1, the wide (wide-angle) state is shown above the center line, and the telephoto state is shown below.

[0010] The camera 1 includes a camera body 3 and a lens barrel 2. The lens barrel 2 is provided with a lens mount LM at the rear (base end) thereof, and is detachably attached to the camera body 3 by engaging with a body mount (not shown) of the camera body 3. Note that in this embodiment, the lens barrel 2 is detachable from the camera body 3, but is not limited to this, and the lens barrel 2 and the camera body 3 may be integrated.

[0011] The camera body 3 includes an image sensor IS and a control unit (not shown) inside. The image sensor IS is composed of a photoelectric conversion element such as a CCD (Charge Coupled Device), and converts the subject image formed by the imaging optical system (the lens barrel 2 attached to the camera body 3) into an electrical signal.

[0012] The control unit is equipped with a CPU (Central Processing Unit) and the like, and controls the overall operation of the camera 1 related to photography, including focusing drive in the camera body 3 and the attached lens barrel 2, and blur correction of captured images caused by camera shake, etc.

[0013] As shown in Fig. 1, the lens barrel 2 according to this embodiment includes a first lens group L1 to a seventh lens group L7 arranged in sequence along a common optical axis OA, and is a so-called zoom lens with a variable focal length. Note that the lens barrel 2 is not limited to a zoom lens, and may be a fixed-focus lens with an unchangeable focal length. Also, each of the first lens group L1 to the seventh lens group L7 may be composed of a single lens or multiple lenses.

[0014] The first lens group L1 to the seventh lens group L7 move in the direction of the optical axis OA during zooming. The fifth lens group L5 is a focus lens group that moves during focusing. There may be multiple focus lens groups. For example, the sixth lens group L6 may also be a focus lens group.

[0015] The first lens group L1 is held in the first lens holding frame F1, the second lens group L2 is held in the second lens holding frame F2, the third lens group L3 is held in the third lens holding frame F3, the fourth lens group L4 is held in the fourth lens holding frame F4, the fifth lens group L5 is held in the fifth lens holding frame F5, the sixth lens group L6 is held in the sixth lens holding frame F6, and the seventh lens group L7 is held in the seventh lens holding frame F7.

[0016] The lens barrel 2 includes an outer fixed barrel 21 and a zoom operation ring 22 provided on the outer periphery of the outer fixed barrel 21. On the inner periphery of the zoom operation ring 22, in order from the outer periphery, there are arranged a zoom linkage ring 23, a first group barrel 24 that holds the first lens group L1 (first lens holding frame F1), a cam barrel 25, and an inner fixed barrel 26.

[0017] A pin (not shown) is provided on the outer periphery of the zoom interlocking ring 23, and the pin engages with a groove formed in the optical axis direction on the inner periphery of the zoom operation ring 22. As a result, the rotation of the zoom operation ring 22 is transmitted to the zoom interlocking ring 23.

[0018] A pin (not shown) is provided on the outer periphery of the cam barrel 25, and the cam barrel 25 and the zoom interlock ring 23 are fixed by the pin. Also, a cam groove 25a that rotates and advances the cam barrel 25 itself is formed in the cam barrel 25, and engages with a pin 32b fixed to the inner fixed barrel 26. As a result, when the zoom operation ring 22 rotates, the zoom interlock ring 23 and the cam barrel 25 move in the direction of the optical axis OA while rotating around the optical axis OA.

[0019] In addition to cam groove 25a, multiple cam grooves are formed in cam barrel 25. A pin (not shown) is provided on the inner peripheral side of first group barrel 24, and this pin engages with both a linear groove provided in inner fixed barrel 26 and a cam groove provided in cam barrel 25. Therefore, first group barrel 24 moves linearly in the direction of the optical axis OA in conjunction with the rotation of cam barrel 25.

[0020] Furthermore, a pin P2 provided on the outer periphery of the third lens retaining frame F3 and a pin P3 provided on the outer periphery of the fourth lens retaining frame F4 are engaged with both a rectilinear groove provided in the inner fixed barrel 26 and a cam groove provided in the cam barrel 25. As a result, in conjunction with the rotation of the cam barrel 25, the third lens retaining frame F3 and the fourth lens retaining frame F4 move rectilinearly in the direction of the optical axis OA without rotating around the optical axis OA.

[0021] The fifth lens retaining frame F5 is driven by a drive source unit 200. The fifth lens retaining frame F5 and the drive source unit 200 will be described in detail below.

[0022] Fig. 2(A) is a perspective view showing the fifth lens retaining frame F5 and the drive source unit 200, and Fig. 2(B) is a view showing the fifth lens retaining frame F5 and the drive source unit 200 from the direction indicated by the arrow A1 in Fig. 2(A). Fig. 3(A) is a cross-sectional view showing the relationship between the fifth lens retaining frame F5 and each component of the drive source unit 200, Fig. 3(B) is a perspective view of a spring 310, and Fig. 3(C) is a cross-sectional view taken along the line AA in Fig. 3(A).

[0023] First, the configuration of the fifth lens holding frame F5 will be described. As shown in Fig. 2(A) and Fig. 2(B), the fifth lens holding frame F5 has a cylinder portion 240 that holds the fifth lens group L5, and the outer periphery of the cylinder portion 240 is provided with a first guide portion 210 for guiding the fifth lens holding frame F5 in the optical axis OA direction and a second guide portion 220 for suppressing the movement of the fifth lens holding frame F5 in the rotational direction.

[0024] 2B, the first guide portion 210 extends in the optical axis OA direction and has a first end portion 210a and a second end portion 210b that face each other in the optical axis OA direction. A through hole 210c is formed in the first end portion 210a and the second end portion 210b. The guide bar 301 is inserted through the through hole 210c.

[0025] The guide bar 301 is fixed to the third lens retaining frame F3 in parallel with the optical axis OA. The through hole 210c slides, thereby guiding the fifth lens retaining frame F5 in the direction of the optical axis OA.

[0026] On the other hand, the second guide portion 220 engages with the sub guide bar 302. The sub guide bar 302 is fixed to the third lens retaining frame F3 and restricts the movement of the fifth lens retaining frame F5 in the rotational direction.

[0027] 2(B), the fifth lens retaining frame F5 has a rotation restriction bar support portion 211. The rotation restriction bar support portion 211 has a first support portion 211a and a second support portion 211b that protrude from the first guide portion 210 in the circumferential direction of a circle centered on the optical axis OA. The first support portion 211a and the second support portion 211b support a rotation restriction bar 206 provided in the drive source unit 200 described later.

[0028] Next, a description will be given of the driving source unit 200. As shown in Figures 2(A) and 2(B), the driving source unit 200 includes a stepping motor 201, a lead screw 202, a nut 203, an attachment member 205, and a rotation restriction bar 206.

[0029] The mounting member 205 is fixed to the stepping motor 201, and rotatably supports the lead screw 202. A plurality of holes 205a are formed in the mounting member 205 as shown in Fig. 2(B), and the drive source unit 200 is fixed to the third lens retaining frame F3 by fastening the mounting member 205 to the third lens retaining frame F3 with screws or the like.

[0030] The lead screw 202 is directly connected to the output shaft of the stepping motor 201, and is rotationally driven by the stepping motor 201. The lead screw 202 extends in the direction of the optical axis OA, and has a screw groove 202a formed on its outer periphery.

[0031] A nut 203 is engaged with the lead screw 202. Figures 4(A) and 4(B) are perspective views of the nut 203, Figure 4(C) is a partial cross-sectional view of Figure 4(A), and Figure 4(D) is a cross-sectional view of the nut 203 as viewed from the axis AX1 direction of the lead screw 202.

[0032] The nut 203 is, for example, a one-piece molded product made of resin, and has a first engagement portion 231 having a thread groove 231a formed therein that engages with the thread groove 202a of the lead screw 202, and a second engagement portion 232 having a thread groove 232a formed therein that engages with the thread groove 202a.

[0033] The first engaging portion 231 and the second engaging portion 232 are in the shape of a half nut. That is, the first engaging portion 231 and the second engaging portion 232 are in the shape of a C (semi-annular) when viewed from the axis AX1 direction of the lead screw 202, and the screw grooves 231a and 232a are formed on the inner circumferential surfaces thereof, respectively. Therefore, the screw grooves 231a and 232a extend in an arc shape centered on the axis AX1 of the lead screw 202. More specifically, in this embodiment, the screw grooves 231a and 232a extend in an arc shape so as to surround half the circumference of the lead screw 202.

[0034] The nut 203 also has an auxiliary part 233 in which a screw groove 233a is formed. The screw groove 233a of the auxiliary part 233 is configured not to engage with the lead screw 202 (to maintain a spaced state) when the nut 203 moves in the axis AX1 direction of the lead screw 202 with the rotation of the lead screw 202. Note that the screw groove 233a may be formed, for example, so as to surround half the circumference of the lead screw 202, or so as to surround the entire circumference.

[0035] In this embodiment, the phase of the thread groove 231a of the first engagement portion 231 is different from the phase of the thread groove 232a of the second engagement portion 232. This point will be described. Fig. 5 is a cross-sectional view showing an engagement state between the thread groove 202a of the lead screw 202 and the thread groove 231a of the first engagement portion 231, the thread groove 232a of the second engagement portion 232, and the thread groove 233a of the auxiliary portion 233.

[0036] 5, in this embodiment, the thread groove 202a of the lead screw 202 has a first flank surface 204a and a second flank surface 204b that face each other in the optical axis OA direction. The thread groove 231a of the first engagement portion 231 abuts against the second flank surface 204b, and the thread groove 232a of the second engagement portion 232 abuts against the first flank surface 204a. In other words, the surface of the thread groove 231a of the first engagement portion 231 that faces the camera body 3 contacts the thread groove 202a, and the surface of the thread groove 232a of the second engagement portion 232 that faces the subject contacts the thread groove 202a.

[0037] For example, consider a case where the nut 203 moves from the camera body 3 side to the subject side in the optical axis OA direction, and then moves from the subject side to the camera body 3 side. In this case, if the phase of the screw groove 231a of the first engagement portion 231 and the phase of the screw groove 232a of the second engagement portion 232 are in phase, when the moving direction of the nut 203 changes, there is a gap between the lead screw 202 and the first engagement portion 231 and the second engagement portion 232, so a delay occurs before the nut 203 follows the lead screw 202. In other words, if the phase of the screw groove 231a and the phase of the screw groove 232a are in phase, a backlash occurs between the lead screw 202 and the first engagement portion 231 and the second engagement portion 232, so that a delay equivalent to the backlash occurs when the moving direction of the nut 203 is reversed.

[0038] On the other hand, in this embodiment, the screw groove 231a of the first engagement portion 231 is formed so that the surface on the camera body 3 side contacts the screw groove 202a, and the screw groove 232a of the second engagement portion 232 is formed so that the surface on the subject side contacts the screw groove 202a. Therefore, when the nut 203 moves in either the subject side or the camera body 3 side in the optical axis OA direction, either the screw groove 231a of the first engagement portion 231 or the screw groove 232a of the second engagement portion 232 contacts the screw groove 202a of the lead screw 202 (because no gap is generated between the screw groove 202a of the lead screw 202), so there is no delay before the nut 203 follows the lead screw 202. This improves the movement accuracy of the fifth lens holding frame F5 in the optical axis OA direction, and improves the position control accuracy of the fifth lens group L5.

[0039] In this embodiment, in order to avoid excessive constraint, the thread groove 233a of the auxiliary part 233 is formed so that neither the surface on the subject side nor the surface on the camera body 3 side comes into contact with the thread groove 202a. For this reason, the phase of the thread groove 231a of the first engagement part 231, the phase of the thread groove 232a of the second engagement part 232, and the phase of the thread groove 233a of the auxiliary part 233 are different from each other.

[0040] Although the screw groove 233a of the auxiliary part 233 is not normally in contact with the screw groove 202a, it is in contact with the screw groove 202a when, for example, an impact is applied to the nut 203 or the fifth lens holding frame F5 and the nut 203 and the lead screw 202 move relatively in the direction of the axis AX1. As a result, in addition to the screw grooves 231a and 232a, the screw groove 233a also comes into contact with the lead screw 202, so that the nut 203 can withstand the force received from the lead screw 202, and it is possible to prevent the nut 203 from skipping teeth due to an impact or the like.

[0041] 4(A) and 4(B), the nut 203 has a fork portion 234 that engages with the rotation restriction bar 206. The fork portion 234 is bifurcated and, as shown in Fig. 2(B), clamps the rotation restriction bar 206. As a result, the rotation of the nut 203 is restricted by the rotation restriction bar 206, and when the lead screw 202 is rotated by the stepping motor 201, the nut 203 moves linearly in the direction of the optical axis OA.

[0042] 2(A) and 2(B), a spring 310 is provided between the fork portion 234 of the nut 203 and the second support portion 211b of the fifth lens retaining frame F5. The rotation restriction bar 206 is inserted into the spring 310.

[0043] As shown in FIG. 3(B), the spring 310 includes a compression coil spring portion 310b and a torsion spring portion 310a.

[0044] The compression coil spring portion 310b biases the second support portion 211b and the nut 203 in a direction separating the second support portion 211b and the nut 203 from each other. As a result, the first support portion 211a is pressed against the nut 203, and the nut 203 is pressed toward the first support portion 211a by the compression load of the compression coil spring portion 310b.

[0045] Since the nut 203 is pressed against the first support portion 211a, when the nut 203 moves in the optical axis OA direction, the fifth lens retaining frame F5 moves in the optical axis OA direction together with the nut 203. This allows the fifth lens retaining frame F5 to be driven in the optical axis OA direction by rotating the lead screw 202.

[0046] As shown in Fig. 2(B), a locking portion 311 is provided between the spring 310 and the nut 203, and as shown in Fig. 3(C), a torsion spring portion 310a of the spring 310 is locked to the locking portion 311. As shown in Fig. 3(C), a portion of the locking portion 311 is housed in a housing portion 203b formed in the nut 203.

[0047] As shown in FIG. 3C, the torsion spring portion 310a biases the locking portion 311 in the direction of the arrow A11. As a result, the nut 203 is biased in the direction of the arrow A13. As a result, the screw groove 231a of the first engaging portion 231 and the screw groove 232a of the second engaging portion 232 are in close contact with the screw groove 202a of the lead screw 202, so that the rattle between the lead screw 202 and the nut 203 is suppressed. The torsion spring portion 310a biases the nut 203 toward the lead screw 202 in a direction perpendicular to the axis AX1 via the locking portion 311, so that no load is applied to the nut 203 in the direction of the optical axis OA. As a result, the rattle between the lead screw 202 and the nut 203 can be suppressed without increasing the load on the stepping motor 201.

[0048] Next, a description will be given of the rotation restriction bar 206. As shown in Fig. 3(A), one end of the rotation restriction bar 206 is supported by the first support portion 211a of the fifth lens retaining frame F5 and the other end is supported by the second support portion 211b so as to be parallel to the lead screw 202, i.e., so as to extend in the direction of the optical axis OA.

[0049] In this embodiment, the length of the rotation restricting bar 206 in the optical axis OA direction is substantially equal to the length of the lead screw 202 in the optical axis OA direction. The reason for this will be explained with reference to Figures 6(A) to 6(D).

[0050] Fig. 6(A) is a diagram showing the positional relationship between the fourth lens holding frame F4 and the fifth lens holding frame F5 in a state where the zoom lens is focused on a close subject, and Fig. 6(B) is a diagram showing the state of the fifth lens holding frame F5 in the state of Fig. 6(A). Fig. 6(C) is a diagram showing the positional relationship between the fourth lens holding frame F4 and the fifth lens holding frame F5 when the camera body 3 is switched to a wide-angle state by operating the zoom operation ring 22 after the power supply to the camera body 3 is turned off in the state of Fig. 6(A), and Fig. 6(D) is a diagram showing the state of the fifth lens holding frame F5 in the state of Fig. 6(C).

[0051] As shown in Fig. 6(A), when the zoom lens is in focus at a close distance, the fourth lens retaining frame F4 and the fifth lens retaining frame F5 do not come into contact with each other. Therefore, as shown in Fig. 6(B), the nut 203 is biased by the spring 310 to come into contact with the first support portion 211a of the fifth lens retaining frame F5.

[0052] 6(A), suppose that after the power of the camera body 3 is turned off, the zoom ring 22 is operated to switch to the wide-angle state. In this case, the amount of movement of the fourth lens retaining frame F4, which is moved by the cam barrel 25 that rotates in conjunction with the operation of the zoom ring 22, is greater than the amount of movement of the fifth lens retaining frame F5, so the fourth lens retaining frame F4 collides with the fifth lens retaining frame F5. The fifth lens retaining frame F5 is pushed by the fourth lens retaining frame F4 and moves toward the camera body 3.

[0053] At this time, since the power is off, the position of the nut 203 engaged with the lead screw 202 does not move from the position when the power is off. Therefore, as the fifth lens holding frame F5 moves toward the camera body 3, the second support portion 211b of the fifth lens holding frame F5 approaches the nut 203. At this time, if the rotation restriction bar 206 is short, the nut 203 and the second support portion 211b of the fifth lens holding frame F5 may collide with each other, and the fifth lens holding frame F5 may be damaged. Therefore, in this embodiment, the rotation restriction bar 206 is made to have approximately the same length as the lead screw 202 so that the nut 203 does not collide with the second support portion 211b even when the fourth lens holding frame F4 and the fifth lens holding frame F5 collide with each other. This makes it possible to prevent the fifth lens holding frame F5 from being damaged even when the fourth lens holding frame F4 and the fifth lens holding frame F5 collide with each other due to the operation of the zoom operation ring 22 after the power is turned off.

[0054] Incidentally, when the fifth lens retaining frame F5 moves toward the camera body 3 while the position of the nut 203 engaged with the lead screw 202 is maintained at the position when the power is off, the spring 310 between the nut 203 and the second support portion 211b is compressed. Since the spring 310 has a stronger biasing force as it is compressed, a strong biasing force is applied to the nut 203 in the optical axis OA direction in the state of FIG. 6(D).

[0055] Here, for example, when a rack is used instead of the nut 203 of this embodiment, the screw groove of the rack and the screw groove 202a of the lead screw 202 are in line contact, and therefore the contact area is small. Therefore, when a large biasing force in the optical axis OA direction is applied to the rack, the biasing force cannot be received by the screw groove of the rack, and there is a risk that the rack will jump teeth and generate abnormal noise.

[0056] On the other hand, in this embodiment, the thread grooves 231a and 232a of the nut 203 engage with the thread groove 202a of the lead screw 202 over half a circumference of the lead screw 202. This makes the area of ​​contact between the thread grooves 231a and 232a and the thread groove 202a larger than in the case of a rack. Therefore, even when a large biasing force is applied in the optical axis OA direction, the nut 203 can maintain the position when the power is off, and it is possible to prevent the nut 203 from skipping teeth and generating abnormal noise.

[0057] As described above in detail, according to this embodiment, the lens barrel 2 includes the stepping motor 201, the lead screw 202 in which the screw groove 202a is formed and which is rotationally driven by the stepping motor 201, the nut 203 which moves in the axis AX1 direction of the lead screw 202 with the rotation of the lead screw 202, the rotation restriction bar 206 which restricts the rotation of the nut 203, the fifth lens holding frame F5 which holds the fifth lens group L5, and the spring 310 which biases the nut 203 so that the nut 203 abuts against the fifth lens holding frame F5. The nut 203 includes a first engagement portion 231 in which a screw groove 231a which engages with the screw groove 202a is formed, a second engagement portion 232 in which a screw groove 232a which engages with the screw groove 202a is formed, and an auxiliary portion 233 in which a screw groove 233a is formed. The thread groove 202a of the lead screw 202 has a first flank surface 204a and a second flank surface 204b that face each other in the optical axis OA direction. The thread groove 231a of the first engagement portion 231 abuts against the second flank surface 204b, and the thread groove 232a of the second engagement portion 232 abuts against the first flank surface 204a. The thread groove 233a of the auxiliary portion 233 is separated from the thread groove 202a of the lead screw 202 while the nut 203 moves in the axis AX1 direction of the lead screw with the rotation of the lead screw 202. As a result, whether the nut 203 moves toward the camera body 3 side or the subject side, a surface that exists in the direction in which the nut 203 moves contacts the thread groove 202a of the lead screw 202 at either the first engagement portion 231 or the second engagement portion 232. As a result, there is no delay before the nut 203 follows the lead screw 202, and the accuracy of movement of the fifth lens retaining frame F5 in the direction of the optical axis OA can be improved, thereby improving the accuracy of position control of the fifth lens group L5.

[0058] In this embodiment, the torsion spring portion 310a of the spring 310 biases the first engagement portion 231 and the second engagement portion 232 toward the lead screw 202 in a direction perpendicular to the axis AX1 direction of the lead screw 202. As a result, no load is applied to the nut 203 in the optical axis OA direction, and therefore, rattle between the lead screw 202 and the nut 203 can be suppressed without increasing the load on the stepping motor 201.

[0059] In the present embodiment, the phase of the screw groove 231a, the phase of the screw groove 232a, and the phase of the screw groove 233a are different from each other. This makes it possible to prevent the lead screw 202 from being excessively restricted by the nut 203.

[0060] In this embodiment, the nut 203 is integrally molded, which makes it possible to obtain the nut 203 having the required strength.

[0061] In this embodiment, the screw grooves 231a and 232a extend in an arc shape centered on the axis AX1 of the lead screw 202. This allows the contact area between the screw grooves 231a and 232a and the screw groove 202a of the lead screw 202 to be larger than that of a rack, making it possible to suppress tooth skipping compared to a rack.

[0062] In this embodiment, the lens barrel 2 includes a zoom operation ring 22 and a fourth lens holding frame F4 that holds the fourth lens group L4 and is movable in the optical axis OA direction by operating the zoom operation ring 22, and the fifth lens holding frame F5 and the fourth lens holding frame F4 may come into contact with each other when power is not supplied to the stepping motor 201. The rotation restriction bar 206 is held by the fifth lens holding frame F5, and the length of the rotation restriction bar 206 is approximately equal to the length of the lead screw 202. This makes it possible to prevent the fifth lens holding frame F5 from being damaged even when the fifth lens holding frame F5 and the fourth lens holding frame F4 come into contact with each other by operating the zoom operation ring 22 when the power is off.

[0063] In the above embodiment, the thread groove 231a of the first engagement portion 231 abuts against the second flank surface 204b of the thread groove 202a of the lead screw 202, and the thread groove 232a of the second engagement portion 232 abuts against the first flank surface 204a of the thread groove 202a of the lead screw 202, but this is not limited thereto. For example, the thread groove 231a of the first engagement portion 231 may abut against the first flank surface 204a of the thread groove 202a of the lead screw 202, and the thread groove 232a of the second engagement portion 232 may abut against the second flank surface 204b of the thread groove 202a of the lead screw 202. In other words, the surface of the thread groove 231a of the first engagement portion 231 on the subject side may be in contact with the thread groove 202a, and the surface of the thread groove 232a of the second engagement portion 232 on the camera body 3 side may be in contact with the thread groove 202a.

[0064] In the above embodiment, the thread groove 231a of the first engagement portion 231 and the thread groove 232a of the second engagement portion 232 are in contact with the thread groove 202a of the lead screw 202, but the thread groove 231a of the first engagement portion 231 and the thread groove 232a of the second engagement portion 232 may not be in contact with the thread groove 202a of the lead screw 202. In the case of such a configuration, since the phase of the thread groove 231a and the phase of the thread groove 232a are different, for example, the distance between the thread groove 231a and the first flank surface 204a of the thread groove 202a of the lead screw 202 is shorter than the distance between the thread groove 232a and the first flank surface 204a, and the distance between the thread groove 231a and the second flank surface 204b is longer than the distance between the thread groove 232a and the second flank surface 204b. Therefore, whether the nut 203 moves toward the camera body 3 side or toward the subject side, one of the first engagement portion 231 and the second engagement portion 232 comes into contact with the thread groove 202a of the lead screw 202 before the other. This shortens the time it takes for the nut 203 to follow the lead screw 202, improving the movement accuracy of the fifth lens holding frame F5 in the optical axis OA direction, and ultimately improving the position control accuracy of the fifth lens group L5.

[0065] In the above embodiment, the spring 310 has the torsion spring portion 310a and the compression coil spring portion 310b, but this is not limited to the above. The torsion spring portion 310a and the compression coil spring portion 310b may be separate members.

[0066] In the above embodiment, the screw groove 231a of the first engagement portion 231 and the screw groove 232a of the second engagement portion 232 of the nut 203 extend in an arc shape so as to surround half the circumference of the lead screw 202, but this is not limited thereto. As described in Figs. 6(A) to 6(D), even if a strong urging force in the optical axis OA direction is applied to the nut 203, it is only necessary to ensure a contact area between the screw groove 231a and the screw groove 232a and the screw groove 202a of the lead screw 202 to an extent that the urging force can be received and the teeth of the nut 203 can be prevented from jumping. For example, the screw groove 231a and the screw groove 232a may extend in an arc shape so as to surround a quarter circumference of the lead screw 202, or may extend in an arc shape so as to surround a one-eighth circumference.

[0067] The above-described embodiment is a preferred example, but is not limited thereto, and various modifications are possible without departing from the scope of the present invention, and any combination of components may be used. [Explanation of symbols]

[0068] 1 Camera 2 Lens barrel 3. Camera body 22 Zoom ring L4 4th lens group L5 Fifth lens group F4 4th lens holder F5 5th lens holder 200 Drive unit 201 Stepping motor 202 Lead screw 202a Thread groove 203 Nut 204a 1st flank surface 204b 2nd flank surface 206 Rotation restriction bar 231 First engagement part 231a Thread groove 232 Second engagement part 232a Thread groove 233 Auxiliary section 233a Thread groove 310 Spring 310a Torsion spring part 310b Compression coil spring part

Claims

1. A driving source; a lead screw having a first screw groove formed therein and being rotated by the drive source; a nut having a first engagement portion having a second thread groove that engages with the first thread groove, a second engagement portion having a third thread groove that engages with the first thread groove, and an auxiliary portion having a fourth thread groove, the nut moving in the axial direction of the lead screw as the lead screw rotates; A rotation restricting shaft that restricts rotation of the nut; a first lens holding frame that holds a first lens; a first biasing portion that biases the nut so that the nut abuts against the first lens holding frame; Equipped with The phase of the second thread groove is different from the phase of the third thread groove, the fourth thread groove is spaced from the first thread groove while the nut moves in the axial direction of the lead screw in accordance with the rotation of the lead screw, In the nut, the auxiliary portion is disposed at a position different from the first engagement portion and the second engagement portion in an axial direction of the lead screw, When the nut is viewed from an axial direction of the lead screw, the first engagement portion and the second engagement portion do not surround a portion of the lead screw, and the auxiliary portion surrounds at least the portion of the lead screw. Lens barrel.

2. a second biasing portion that biases the first engagement portion and the second engagement portion toward the lead screw in a direction perpendicular to an axial direction of the lead screw; 2. The lens barrel according to claim 1.

3. A locking portion that locks the second biasing portion is disposed between the nut and the second biasing portion, The second biasing portion biases the first engagement portion and the second engagement portion via the locking portion. The lens barrel according to claim 2 .

4. The phase of the second thread groove, the phase of the third thread groove, and the phase of the fourth thread groove are different from each other. The lens barrel according to any one of claims 1 to 3.

5. The first engagement portion, the auxiliary portion, and the second engagement portion are arranged in this order along an optical axis: the first engagement portion, the auxiliary portion, and the second engagement portion. The lens barrel according to any one of claims 1 to 4.

6. When the nut is viewed from the axial direction of the lead screw, the nut, together with the first engaging portion, the second engaging portion, and the auxiliary portion, surrounds the entire circumference of the lead screw. The lens barrel according to any one of claims 1 to 5.

7. The nut is integrally molded. The lens barrel according to any one of claims 1 to 6.

8. The first thread groove has a first flank surface and a second flank surface opposed to each other in the optical axis direction, the second thread groove abuts against the first flank surface, and the third thread groove abuts against the second flank surface. The lens barrel according to any one of claims 1 to 7.

9. The second screw groove and the third screw groove extend in an arc shape centered on the axis of the lead screw. The lens barrel according to any one of claims 1 to 8.

10. The second thread groove and the third thread groove engage with the first thread groove in a circumferential surface contact. The lens barrel according to any one of claims 1 to 9.

11. The second thread groove and the third thread groove engage with the first thread groove over half a circumference of the lead screw. The lens barrel according to any one of claims 1 to 10.

12. the rotation restriction shaft is held by the first lens holding frame, The length of the rotation restriction shaft is approximately equal to the length of the lead screw. The lens barrel according to any one of claims 1 to 11.

13. The first lens holding frame has a support portion that protrudes in a circumferential direction of a circle centered on the optical axis and supports the rotation regulating shaft, The support portion is disposed at an end portion of the rotation restriction shaft. The lens barrel according to claim 12.

14. The first biasing portion biases the nut in a direction in which the nut and the support portion move away from each other. The lens barrel according to claim 13.

15. An operating ring; a second lens holding frame that holds a second lens and is movable in the optical axis direction by operating the operation ring, when the second lens holding frame is moved by operating the operation ring in a state where power is not supplied to the driving source, even if the first lens holding frame and the second lens holding frame come into contact with each other, the support portion and the nut do not collide with each other. The lens barrel according to claim 13 or 14.

16. An imaging device comprising the lens barrel according to any one of claims 1 to 15.

Images