JP5515595B2 - Mirror holding mechanism and camera equipped with mirror holding mechanism - Google Patents

Description

  The present invention relates to a mirror holding mechanism and a camera including the mirror holding mechanism.

  In a single-lens reflex camera, a mirror holding mechanism including a sub mirror that swings together with a main mirror is known as a mechanism for guiding a subject light beam to an AF sensor below the camera body. In such a mirror holding mechanism, when the main mirror is inclined with respect to the subject light beam, the sub mirror is also inclined with a different angle, and when the main mirror is retracted from the subject light beam, the sub mirror is also retracted. These operations are repeatedly executed in synchronization with the photographing operation.

JP-A-9-274250

  In particular, when repeated at high speed in the continuous shooting mode, the damped vibration time required for the sub mirror to stop at a predetermined position becomes a problem. Therefore, a mechanism using a catch pin that stops the sub mirror holding member is known. However, in such a mechanism, wear occurs in the sliding portion, which changes the oblique angle of the sub-mirror over time, which adversely affects AF detection accuracy.

  In order to solve the above-described problem, the mirror holding mechanism installed in the camera body in the first aspect of the present invention includes a swingable main mirror portion (31, 32) and a swingable support on the main mirror portion. A sub-mirror portion (37, 38), a cam portion (56) provided in the sub-mirror portion, and a cam pin (57) that contacts the cam portion and swings the sub-mirror in conjunction with the swing of the main mirror portion. And a support portion (53) that supports the cam pin, and the cam pin is supported by the support portion so as to rotate around the axis of the cam pin by contact with the cam portion.

  In order to solve the above problem, a camera according to a second aspect of the present invention includes the above mirror holding mechanism.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is principal part sectional drawing of a single-lens reflex camera. It is a side view which shows the mode of the mirror holding mechanism in an oblique installation state. It is a side view which shows the mode of the mirror holding mechanism in a retracted state. It is a figure which shows the operation | movement progress of the mirror holding mechanism from a retracted state to a diagonal installation state. It is a figure which shows the operation | movement progress of the mirror holding mechanism from a retracted state to a diagonal installation state. It is an enlarged view of a cam part and a turning pin. It is sectional drawing which shows the periphery structure of a turning pin. It is sectional drawing which shows the periphery structure of the turning pin of another example. It is sectional drawing which shows the periphery structure of the turning pin of another example.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a cross-sectional view of a main part of a single-lens reflex camera 10. The single-lens reflex camera 10 functions as an imaging device by combining the lens unit 20 and the camera unit 30.

  The lens unit 20 includes a lens group 21 arranged along the optical axis 11. The lens group 21 guides the incident subject luminous flux to the camera unit 30. The lens group 21 includes a focus lens, a zoom lens, and the like, and is configured to be movable in the optical axis direction in response to instructions for focus adjustment and field angle adjustment. The lens unit 20 includes a lens mount 22 at a connection portion with the camera unit 30, engages with a camera mount 46 included in the camera unit 30, and is integrated with the camera unit 30.

  The camera unit 30 includes a main mirror 31 that reflects the subject light beam incident from the lens unit 20 and a focus plate 34 on which the subject light beam reflected by the main mirror 31 forms an image. The main mirror 31 is held by the main mirror holding frame 32 and swings around the main mirror rotation shaft 33 so that the main mirror 31 is obliquely installed in the subject light flux centered on the optical axis 11 and retracted from the subject light flux. Can take. When the subject image is guided to the focus plate 34 side, the main mirror 31 is provided obliquely in the subject light flux. The focus plate 34 is disposed at a position conjugate with the light receiving surface of the image sensor 42. The subject image formed on the focus plate 34 is converted into an erect image by the pentaprism 35 and observed by the user through the eyepiece optical system 36.

  A region near the optical axis 11 of the main mirror 31 in the oblique state is formed as a half mirror, and a part of the incident subject luminous flux is transmitted therethrough. The transmitted subject light flux is reflected by the sub mirror 37 held by the sub mirror holding frame 38 that swings in conjunction with the main mirror 31, and is guided to the AF optical system 39. The subject light flux that has passed through the AF optical system 39 enters the AF sensor 40. The AF sensor 40 detects a phase difference signal from the received subject light beam. The sub mirror 37 retracts from the subject light beam in conjunction with the main mirror 31 when the main mirror 31 retracts from the subject light beam. This operation will be described in detail later.

  A focal plane shutter 41 and an image sensor 42 are arranged along the optical axis 11 behind the oblique main mirror 31. The focal plane shutter 41 is in an open state when the subject light flux is guided to the image sensor 42 and is in a shielded state at other times. The imaging element 42 is a photoelectric conversion element such as a CMOS sensor, for example, and converts the subject image formed on the light receiving surface into an electrical signal.

  The electrical signal photoelectrically converted by the image sensor 42 is processed into image data by an image processing unit 44 which is a DSP mounted on the main board 43. In addition to the image processing unit 44, a camera system control unit 45 that is an MPU that integrally controls the system of the camera unit 30 is mounted on the main board 43. The camera system control unit 45 manages the camera sequence accompanied by the operations of the main mirror 31 and the sub mirror 37 and performs focusing control from the phase difference signal output from the AF sensor 40, etc. I do.

  FIG. 2 is a side view of the mirror holding mechanism centering on the main mirror holding frame 32 holding the main mirror 31 and the sub mirror holding frame 38 holding the sub mirror 37. In particular, the state of the mirror holding mechanism in an oblique state in which the main mirror 31 is obliquely arranged with respect to the subject light beam is shown. As described above, the mirror holding mechanism is installed on the camera body of the camera unit 30.

  The main mirror holding frame 32 is pivotally supported by the camera body so as to be swingable around the main mirror rotation shaft 33, and by the action of the mirror return spring 51 hung between the camera body and the main mirror holding frame 32, The eccentric pin 52 is biased counterclockwise. That is, the main mirror holding frame 32 is urged so that the main mirror 31 is inclined with respect to the subject light flux. The eccentric pin 52 is installed so that it can be rotationally adjusted with respect to the support plate 53 fixed to the side surface of the mirror box. The eccentric pin 52 can adjust the position where it abuts on the main mirror holding frame 32 by rotating, and the oblique angle of the main mirror 31 can be accurately set.

  The sub mirror holding frame 38 is supported by a sub mirror rotating shaft 54 provided integrally with the main mirror holding frame 32, and can swing with respect to the main mirror holding frame 32. When the main mirror 31 is in an oblique state by the action of the toggle spring 55 that is hung between the main mirror holding frame 32 and the sub mirror holding frame 38, the subject light flux incident on the sub mirror 37 is directed to the AF optical system 39. Energize in the guiding direction. Further, when the main mirror 31 is in the retracted state, the sub mirror holding frame 38 is biased in a direction in which the sub mirror holding frame 38 is superimposed on the main mirror holding frame 32.

  The sub mirror holding frame 38 is provided with a cam portion 56 so as to operate in conjunction with the main mirror holding frame 32. The cam portion 56 contacts the turning pin 57 that is a cam pin supported by the support plate 53 in accordance with the operation of the main mirror holding frame 32, and reverses the biasing direction of the toggle spring 55.

  The sub mirror holding frame 38 has a U-shaped portion 58 at the tip. The U-shaped portion 58 is fitted with a catch pin 59 supported by the support plate 53 in a tilted state in which the sub mirror 37 guides the subject light beam to the AF optical system 39, and the sub mirror holding frame 38 is stopped at an optimal position. Let When the sub mirror holding frame 38 moves to the retracted position in conjunction with the swinging of the main mirror holding frame 32, the U-shaped portion 58 is adjusted so as to be disengaged from the catch pin 59. In FIG. 2, in order to show the arrangement relationship of the elements and the like, a part of the configuration is displayed in an overlapping manner, and a part of the configuration is simplified.

  FIG. 3 is a side view showing a state of the mirror holding mechanism in the retracted state. In this state, the main mirror 31 is in a state of facing the focusing plate 34, and the sub mirror 37 is in a state of being superimposed on the back side of the main mirror 31. The operation from the oblique state to the retracted state is realized by a motor (not shown) lifting the main mirror holding frame 32 against the urging force of the mirror return spring 51. 3 is maintained by electromagnetic adsorption until the exposure operation is completed.

  4 and 5 are views showing the operation progress of the mirror holding mechanism from the retracted state in FIG. 3 to the obliquely installed state in FIG. When the exposure operation is completed and the electromagnetic attraction is released in the retracted state of FIG. 3, the main mirror holding frame 32 attempts to return to the obliquely installed state by the urging force of the mirror return spring 51. In the process in which the main mirror holding frame 32 returns to the oblique state, the turning pin 57 contacts the cam portion 56 of the sub mirror holding frame 38. Then, since the sub mirror holding frame 38 has the sub mirror rotation shaft 54 with respect to the main mirror holding frame 32, the cam surface of the cam portion 56 is fixed to the support plate 53 as the main mirror holding frame 32 swings. Follow the turning pin 57. When the sub mirror holding frame 38 is rotated counterclockwise by the copying operation with respect to the turning pin 57, the biasing direction of the toggle spring 55 is reversed at a certain time. Thereafter, the sub mirror holding frame 38 is swung in the direction of the catch pin 59 by the urging force of the toggle spring 55 regardless of the action of the cam portion 56. The U-shaped portion 58 of the sub-mirror holding frame 38 is shaped according to this locus, and the catch pin 59 stops the swinging of the sub-mirror holding frame 38 instantaneously by fitting the U-shaped portion 58. Let

  Here, the operation of the turning pin 57 and the cam portion 56 will be further described. Switching of the mirror holding mechanism between the oblique state and the retracted state is repeated at high speed in, for example, the continuous shooting mode. As described above, the turning pin 57 contacts and slides with respect to the cam portion 56 at least until the urging force of the toggle spring 55 is reversed. Will wear out. When the cam trajectory changes due to wear, the point in time when the toggle spring 55 reverses with respect to the swing angle of the main mirror holding frame 32 changes, and accordingly, the swing motion of the sub mirror holding frame 38 changes with respect to the original trajectory. Since the U-shaped portion 58 of the sub mirror holding frame 38 is formed so as to receive the catch pin 59 in a tangential direction with respect to the initial locus, when the locus of the swinging motion changes due to wear of the contact portion, The movement direction and the opening direction of the U-shaped portion 58 are displaced, and an impact is generated when the U-shaped portion 58 and the catch pin 59 come into contact with each other. The impact at the time of contact between the U-shaped portion 58 and the catch pin 59 newly causes wear on both. Since the sub mirror holding frame 38 has an oblique angle defined by the catch pin 59, if the U-shaped portion 58 or the catch pin 59 is worn, the oblique angle changes. The change in the oblique angle of the sub-mirror holding frame 38 means changing the incident angle of the subject light flux on the AF optical system 39, and thus adversely affects the AF detection accuracy.

  Therefore, it is effective to reduce wear of the turning pin 57 and the cam portion 56 as one measure for maintaining the AF detection accuracy. Therefore, in the present embodiment, the turning pin 57 that contacts the cam surface of the cam portion 56 is configured to rotate around the axis of the turning pin 57 by contact with the cam portion 56. FIG. 6 is an enlarged view of the cam portion 56 and the turning pin 57. The turning pin 57 has a rotating shaft supported by the bearing portion 61 and rotates by receiving friction with the cam portion 56. As described above, the cam portion 56 only needs to contact the turning pin 57 at least until the urging force of the toggle spring 55 is reversed. Therefore, the cam surface required as a cam function is formed in an annular shape as shown in the figure. do not have to. However, considering that the contact between the cam portion 56 and the turning pin 57 is repeated at a high speed, it is effective to increase the rigidity of the cam portion 56. Therefore, in this embodiment, the cam portion 56 is formed in an annular shape.

  FIG. 7 is a cross-sectional view showing the peripheral structure of the turning pin 57. The bearing portion 61 is fixed through the through hole 531 formed in the support plate 53 that is a plate-like substrate. Specifically, the bearing portion 61 is inserted from the inside of the mirror box, and is fixed by pressing the flange portion 611 against the support plate 53 and caulking the crimping portion 612 against the support plate 53 from the opposite side. The

  The turning pin 57 includes a contact portion 571 that comes into contact with the cam surface of the cam portion 56 and a through portion 572 serving as a rotation shaft connected to the contact portion 571. As illustrated, the radius around the axis of the contact portion 571 is larger than the radius around the axis of the penetrating portion 572. By such a configuration of the shaft radius, smooth rotation of the turning pin 57 is realized.

  The turning pin 57 has a through portion 572 inserted into the bearing portion 61 from the inside of the mirror box and passes therethrough, and an E ring 62 is press-fitted into a groove portion 575 provided in a portion protruding from the bearing portion 61 and fixed. The penetrating portion 572 has fitting portions 573 and 574 at two locations separated in the axial direction, and the turning pin 57 is fitted to the inner periphery of the bearing portion 61 at two locations of the fitting portions 573 and 574. Thereby, the turning pin 57 is rotationally slidably fitted to the bearing portion 61. The fitting portions 573 and 574 are provided in the vicinity of the inner peripheral opening end of the bearing portion 61, respectively. In particular, when the fitting portion 574 is provided at a position as far as possible in the axial direction from the contact portion 571, the turning pin 57 rotates smoothly due to contact with the cam surface.

  Lubricating oil 63 is injected and held in the space surrounded by the fitting portions 573 and 574 and the inner periphery of the bearing portion 61. Specifically, the lubricating oil 63 is applied to the corresponding portion of the penetrating portion 572 in advance, and then the penetrating portion 572 is inserted into the bearing portion 61. The turning pin 57 rotates smoothly by the lubricating oil 63, and the lubricating oil 63 is held in the space by the fitting portions 573 and 574, so that the smooth rotation continues. The locations where the lubricating oil 63 is applied have been the contact portion 571 and the cam portion 56 in the conventional mirror box, but in this embodiment, the amount of the lubricating oil 63 scattered in the mirror box by being inside the bearing portion 61. Can be reduced.

  The outer peripheral portion of the bearing portion 61 on the side of the contact portion 571 from the flange portion 611 has a circular cross section. In particular, a tapered portion 613 is provided in the vicinity of the opening end on the contact portion 571 side, and is configured such that the radius of the outer circumferential circle of the cross section gradually decreases toward the opening end. The radius at the open end is formed to be equal to or smaller than the radius of the contact portion 571 of the turning pin 57. That is, the opening end surface of the bearing portion 61 is formed to be hidden by the contact portion 571 when the contact portion 571 is viewed from the surface opposite to the surface facing the opening end surface of the bearing portion 61. Such a configuration is preferable because the opening end surface of the bearing portion 61 does not cause the subject luminous flux to diffusely reflect in the mirror box and cause stray light. On the other hand, since the bearing portion 61 is required to have rigidity sufficient to allow the turning pin 57 to rotate, the outer peripheral radius of the cross section near the flange portion 611 is larger than the outer peripheral radius of the opening end surface with respect to the contact portion 571. Is desirable.

  As a countermeasure against stray light, it is also effective to apply an antireflection coating to the turning pin 57 by plating. In consideration of the rotation of the turning pin 57, the coating process is more preferable than the coating process because there is a fear of peeling in the coating process. In addition, the flocked paper 64 is arrange | positioned so that the flange part 611 may be covered in the opposite side to the support plate 53 of the flange part 611. FIG. Instead of the flocked paper 64, the side surface of the mirror box subjected to the stray light treatment may be arranged.

  FIG. 8 is a cross-sectional view showing a peripheral structure of another example of the turning pin. Unlike the taper portion 613 in FIG. 7, the taper portion 614 has a taper from the vicinity of the flange portion 611 to the opening end surface with respect to the contact portion 571. In other words, the tip of the flange portion 611 has a truncated cone shape. Even if comprised in this way, the rigidity requested | required of prevention of a stray light and a bearing part can be satisfy | filled simultaneously. Furthermore, since there are no corners on the outer periphery, an effect of preventing stray light from being generated can be expected.

  FIG. 9 is a cross-sectional view showing a peripheral structure of a turning pin of still another example. Although the taper portion 614 in FIG. 8 is a straight line in the cross section, the taper portion 615 is curved. Even if comprised in this way, the rigidity requested | required of prevention of a stray light and a bearing part can be satisfy | filled simultaneously. Furthermore, since there are no corners on the outer periphery, an effect of preventing stray light from being generated can be expected.

  According to the configuration of the present embodiment as described above, since the turning pin 57 rotates around its axis in contact with the cam portion, wear can be suppressed. Thereby, it is possible to maintain the AF detection accuracy. At the same time, since generation of wear powder can be suppressed, scattering of wear powder in the camera body can be suppressed, and adhesion to the light receiving surface of the image sensor 42 can be avoided as much as possible. Furthermore, since the structure of the turning pin 57 and the bearing portion 61 is taken into consideration, stray light in the mirror box can be suppressed and the influence of ghost or the like on the subject optical image received by the image sensor 42 can be suppressed.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

10 single lens reflex camera, 11 optical axis, 20 lens unit, 21 lens group, 22 lens mount, 30 camera unit, 31 main mirror, 32 main mirror holding frame, 33 main mirror rotation axis, 34 focus plate, 35 penta prism, 36 Eyepiece optical system, 37 sub mirror, 38 sub mirror holding frame, 39 AF optical system, 40 AF sensor, 41 focal plane shutter, 42 image sensor, 43 main substrate, 44 image processing unit, 45 camera system control unit, 46 camera mount, 51 Mirror return spring, 52 Eccentric pin, 53 Support plate, 54 Sub mirror rotation shaft, 55 Toggle spring, 56 Cam part, 57 Turning pin, 58 U-shaped part, 59 Catch pin, 61 Bearing part, 62 E-ring, 63 Lubricating oil, 64 Flocking paper, 531 through hole, 71 contact portion 572 through portion, 573 and 574 fitting portion 612 caulking portion, 575 groove, 611 flanges, 612 caulking portion, 613, 614, and 615 taper portion

Claims (6)

A mirror holding mechanism installed in the camera body,
A swingable main mirror,
A sub-mirror part supported swingably on the main mirror part;
A cam portion provided in the sub-mirror portion;
A cam pin that contacts the cam portion and swings the sub mirror in conjunction with the swing of the main mirror portion;
A plate-like substrate, and a support part for supporting the cam pin;
A bearing portion fixed through the substrate;
With
The cam pin is a mirror holding mechanism that is supported by the support portion via the bearing portion so as to rotate around the axis of the cam pin by contact with the cam portion. The cam pin is composed of a penetrating portion that penetrates the bearing portion and a contact portion that contacts the cam portion,
The radius around the axis of the contact portion, the mirror holding mechanism according to a radius greater than claim 1 about the axis of the through section. 3. The mirror holding mechanism according to claim 2 , wherein the penetrating portion and the bearing portion are rotationally slidably fitted at two locations separated in the axial direction of the cam pin, and the lubricating oil is held in a space sandwiched between the two locations. . The end face which faces the contact portion of the cam pin of the bearing unit, when the contact portion as viewed from the surface opposite to the end surface which faces, claim 2 or claim 3 hidden to the contact portion The mirror holding mechanism described in 1. Of the bearing portion, the contact portion side of the flange portion in contact with the support portion has a circular cross-sectional outer peripheral shape with respect to the axial direction of the cam pin, and the radius in the vicinity of the flange portion is larger than the radius of the end surface facing the contact portion. The mirror holding mechanism according to any one of claims 2 to 4 , wherein the mirror holding mechanism is large. A camera comprising the mirror holding mechanism according to any one of claims 1 to 5 .

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