JPH08110587A - Variable power mechanism - Google Patents

Abstract

PURPOSE: To prevent the deformation of respective parts such as a link means and a mirror base unit at the time of varying power by independenly providing the engaging surface of a variable power cam means with the link means corresponding to the variable power operation such as enlargement and reduction. CONSTITUTION: A positive cam 1 being the variable power means is provided with a rib-like cam projection part 3 functioning as the engaging surface with the link means 2 near an outer peripheral surface, and the engaging parts 2a and 2b of the link means 2 are arranged to be engaged to interpose the cam projection part 3 on the inner and outer peripheral surface sides of the cam projection part 3. As for the operation of a lens unit 35, the positive cam 1 and the link means 2 corresponding to respective variable power modes, the lens unit 35 is necessarily moved and stopped from a right direction to a left direction in any mode in order to prevent the backlash of the gear means of an optical driving system, improve the accuracy of the stopping position of the lens unit 35, and prevent the lowering of the accuracy of the stopping position of the mirror base unit 40 caused by the difference of the engaging surface between the positive cam 1 and the link means 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zooming mechanism using zooming cam means in an optical system such as a copying or printing apparatus.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an optical system such as a copying or printing apparatus, as one of the image forming functions, image information is formed not in the same size but in a reduced or enlarged size. The scaling function is widely used.
Two technical means for achieving this are a zoom lens mechanism and a mirror zoom mechanism. Regarding the zoom lens mechanism, the fixed lens group and the movable lens group are arranged in the lens unit of the optical system, and the movable lens group is moved to a predetermined position at the same time as the movement of the lens unit by the cam means arranged outside. By changing the focal length f of the lens, the zooming operation can be performed in principle. With this method, it is possible to achieve the zooming function only with the lens unit and the parts in the vicinity of it, but the number of expensive optical parts of the lens increases and the cost increases, and the amount of light that passes through the lens increases accordingly. Also has the drawback of decreasing.

In contrast to the above zoom lens mechanism, the mirror zoom mechanism achieves a variable power function by changing the optical path length by combining the positions of the single focus lens unit and the moving mirror system. Therefore, it is possible to provide a variable magnification function which is more advantageous in light quantity and cheaper than the zoom lens mechanism method. A conventional example of this type of mirror zoom mechanism is shown in FIGS.

A lens unit 135 and a mirror base unit 140 are arranged at appropriate positions in the optical path of the apparatus.
The lens unit 135 applies the driving force of the drive motor means 130 to the gear / wire systems 131, 132, 133, 13
It is transmitted via the wire fastening portions of 134a and 134b via 4 and can be moved / stopped in the arrow E'direction in the expansion mode and in the arrow R'direction in the reduction mode.

At the same time, the driving force is transmitted to the gear 136 and the variable magnification cam 137 integrated with the gear 136 via the gear 132, and the link means 13 abuts on the outer peripheral surface of the variable magnification cam.
The driving force is transmitted to the mirror base unit 140 via the switch 8. As a result, the mirror base unit 140 moves in the direction of the arrow E'a or R'a (the lens unit 13 described above).
5 corresponds to the moving directions E ′ and R ′. ) To
It is possible to stop. In this system, the relative position between the lens unit 135 and the mirror base unit 140 is finely adjusted by the connecting portion 139 between the link means 138 and the mirror base unit 140.

[0006]

However, in such a conventional example, the variable magnification cam 137 and the link means 138 are provided.
The following problems have occurred in the contacting method with.

As a method for contacting the variable power cam 137 and the link means 138, the method shown in FIGS. 6 (a) and 6 (b) is generally used. In FIG. 6A, the link plate 142 is in contact with the outer peripheral surface of the variable power cam 141 by the spring means 143. In this type, the tension force by the spring means 143 changes at each magnification change, and the contact force becomes maximum especially at the maximum magnification change (maximum value in the E or R direction), which causes the link means 138 to move. Due to deformation, tilt (tilt) of the mirror base unit 140 with respect to the optical axis, and the like, distortion and abnormal magnification occur in the final scaled image. Therefore, in order to solve these problems, it is necessary to review the design of the spring means 143 (adopt a spring means having a smaller spring constant) and to reinforce the mirror base unit moving rail portion (not shown). .

With these measures, it is unavoidable that the apparatus becomes large and the economic cost rises. Further, the increase of the contact force at the time of zooming promotes the wear of the cam surface or the contact portion of the link plate, which is also disadvantageous in durability.

Further, FIG. 6 (b) shows that the variable-magnification cam 144 is a positive-acting cam provided with a protrusion means 145 in the vicinity of the cam circumference, and an engaging portion 147 of the link means 146 which engages with the protrusion means 145 is arranged. The mirror stand unit 140
It is possible to move. In this method, since there is no spring means, the above-mentioned problem does not occur, but as shown in FIG. 6C, a gap e ′ is formed between the projection means 145 and the engaging portion 147 due to the structure. , A large cam cannot be adopted in consideration of the amount of backlash due to the clearance e ′, that is, the accuracy of zooming of the zooming function. Therefore, it is not possible to provide the mirror base unit with a large zooming range, and the zooming amount is limited, which is unattractive in terms of device specifications.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The object of the present invention is not to deform each part such as the link means and the mirror base unit at the time of changing the magnification, and to change the magnification. It suppresses wear and rattling of the engagement part between the cam surface and the link means at the time, and solves the problem of reduction in zooming accuracy due to backlash, that is, the problem of stop position accuracy of the mirror base unit, and a large zooming ratio can be obtained. A zooming mechanism using an inexpensive zoom mirror mechanism is provided.

[0011]

In order to achieve the above object, in the present invention, the lens unit is moved by the lens moving means, and in synchronization with this, the mirror base unit is moved by the mirror base moving means. In a scaling mechanism for performing a scaling operation of enlarging and reducing by moving to a proper position relative to a unit, the mirror base moving means includes a scaling cam means and a link means, and the link of the scaling cam means. The engaging surface with the means is provided independently corresponding to each of the scaling operation of enlargement and reduction.

Further, the variable-magnification cam means is a positive-moving cam, and the engaging surface of the positive-moving cam with the link means is composed of a plurality of engaging surfaces that differ in the cam rotation direction. It is also preferable that only a specific engagement surface of the plurality of engagement surfaces is engaged when determining the position.

Further, the lens unit and the mirror base unit may be stopped from a state in which they are moving in a specific one direction when determining the position of the zooming operation.

Further, the specific engagement surface which is engaged when the position of the mirror base unit of the positive movement cam is determined can be provided on different continuous engagement surfaces at the time of contraction and at the time of expansion. An engaging surface switching portion for reducing backlash of the engaging portion with the link means may be provided at a position where the surfaces are switched.

The engagement surface switching portion may be formed by forming a discontinuous step portion on the cam surface or by changing the cam width.

[0016]

According to the present invention having the above-described structure, when the position of the zooming operation is determined, the link means engages only with a specific engaging surface of the plurality of engaging surfaces of the zooming cam means so that the mirror base is engaged. The position of the unit is determined and it is stopped from moving in a particular one direction.

Further, when the link means passes through the engagement surface switching portion, the engagement portion and the engagement surface of the link means can be smoothly and quickly switched.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to illustrated embodiments.

(First Embodiment) FIG. 1 is an explanatory view of a main portion of a variable power mechanism to which the present invention is applied.

In FIG. 1, a lens unit 35 and a mirror base unit 40 are arranged at appropriate positions on the image optical path. The lens unit 35 applies the driving force from the drive motor 30 as the lens moving means to the gear / wire system 31, 3
It is transmitted via the wire fastening portions 34a and 34b via 2, 33 and 34, and can be moved / stopped in the arrow E direction in the expansion mode and in the arrow R direction in the reduction mode.

At the same time, the driving force is transmitted to the gear 36 and the positive cam 1 as variable magnification cam means integrated with the gear 36 via the gear 32, and the driving surface abuts on the cam surface as an engaging surface of the positive cam 1. The driving force is transmitted to the mirror base unit 40 via the link means 2 in contact with each other. As a result, the mirror base unit 40 can be moved in the arrow Ea or Ra direction (corresponding to the moving directions E and R of the lens unit 35 described above) and stopped.

In this system, the relative position between the lens unit 35 and the mirror base unit 40 is finely adjusted by the connecting portion 39 between the link means 2 and the mirror base unit 40.

FIG. 2 is an enlarged view of the positive cam 1 for driving the mirror base unit 40 of FIG. Here, the drive transmission system of the lens unit 35 and the mirror base unit 40 is the same as that described above. The positive cam 1 of the present invention shown in FIG. 2 is provided with a rib-shaped cam projection 3 as an engaging surface with the link means 2 in the vicinity of the outer peripheral surface,
Engaging portions 2a and 2b of the link means 2 are arranged on the inner and outer peripheral surfaces of the cam protrusion 3 so as to be engaged with the cam protrusion 3 so as to sandwich the cam protrusion 3.

Here, the operation of the lens unit 35, the positive cam 1 and the link means 2 corresponding to each variable power mode of the present invention will be described with reference to FIG. In the present invention, in order to prevent backlash of the gear means of the optical drive system, such as backlash, to improve the stop position accuracy of the lens unit 35, and for the mirror base unit 40 due to the difference between the engaging surfaces of the positive cam 1 and the link means 2. In order to prevent the stop position accuracy from deteriorating, the lens unit 35 is always moved from the right direction to the left direction and stopped in any mode.

In FIG. 3, in the variable magnification mode A for moving from the position of equal magnification to the position of enlargement, the lens unit is moved leftward from the position of equal magnification of the white circle and at the position of predetermined magnification. Stop. In the case of the variable magnification mode B in which the magnification is changed from enlargement a to enlargement b, the lens unit is once returned to the right side from the stop position (position of enlargement b) and then moved from right to left to enlarge. It is stopped at position b.

In the variable magnification mode C in which the lens unit is moved from the same-magnification position to the reduction position, the lens unit is moved to the rightward position from the same-magnification position of the white circle, and then moved from the rightward direction to the leftward direction. Then, the lens unit is stopped at the position of the predetermined reduction magnification. In the variable magnification mode D in which the magnification is changed from reduction a to reduction b, the lens unit is moved from the right direction to the left direction and stopped at the position of reduction b. When the position of the reduction b is on the left side of the position of the reduction a, the lens unit is once moved to the right of the position of the reduction b, and from that position the lens unit is moved from the right direction to the left direction to reduce the size of the reduction b. Stop in position.

With the above movement, the engagement surface between the zooming cam and the link means is located on the outer peripheral surface side of the rib-like projection in the expansion mode when determining the position of the mirror base unit 40, and in the reduction mode. Switch to a specific engagement surface corresponding to each mode on the surface side. (Note that the contact surface at the same magnification can be set appropriately on either the inner or outer peripheral surface.) Therefore, as shown in FIG. At the time of enlargement, the outer peripheral surface side indicated by the thick arrow Ea of the lower half portion is used to abut the engagement portion 2b, and at the time of contraction, the inner peripheral surface side indicated by the thick arrow Ra of the substantially upper half portion is used. And abuts on the engaging portion 2a. The thin one-dot chain lines Eb and Rb are engagement surfaces that engage with the engagement portions 2a and 2b when the lens unit is moved from the left direction to the right direction, and are surfaces that are not engaged when the position of the lens unit is determined.

In FIG. 2, reference numeral 3a is an engagement surface switching between the engagement portions 2a and 2b of the link means 2 and a plurality of engagement surfaces Ea, Eb, Ra and Rb formed by the cam projections 3 of the positive cam 1. It is an engagement surface switching portion for reducing backlash in the portion. Further, HP is a home position in which the lens unit is at the same size position, and is a portion of the portion where the engagement surface shown by the thick arrow Ra that engages with the engagement portion 2a when the inner peripheral surface side is contracted is in contact. At one end.

In the engagement surface switching portion 3a, the cam protrusion 3 forms a discontinuous step portion, and in the case of this embodiment, a thick arrow Ra is applied when the lens unit home position HP is changed to the enlargement mode. From the state in which the engagement surface on the inner peripheral surface side is in contact with the engagement portion 2a to the state in which the engagement surface on the outer peripheral surface side is in contact with the engagement portion 2b shown by the thick arrow Ea. When switching, the thin chain line R of the positive cam 1
Even if there is a gap e between the engaging surface indicated by b and the engaging portion 2b of the link means 2, the switching is performed smoothly and quickly.

With this structure, the cam protrusion 3 and the engaging portion 2
A gap e between a and 2b can be appropriately determined according to the contour shape of the positive cam 1, and the positional accuracy of the mirror base unit can be guaranteed, and at the same time, it is possible to prevent an extra load from being generated during zooming. It was

In the present embodiment, the lens unit is brought closer to the stop position from the right side and stopped. However, also in the reverse configuration, the shape of the projection of the variable-magnification cam is in the enlargement mode, the inner peripheral surface is in the reduction mode. Needless to say, it is possible to deal with this by simply using the outer peripheral surface.

Further, the positive cam 1 according to the present invention and the embodiment has a rib-shaped cam projection 3 formed on the peripheral portion thereof, and a zooming operation is performed by a combination with the link means 2 engaging with the cam projection 3. However, the combination of forming the groove portion on the cam means side and the protrusion portion that engages with the groove means side on the side of the link means does not depart from the idea of the present invention due to the space of the apparatus or the convenience of fabrication. .

(Second Embodiment) FIG. 4 shows a second embodiment to which the present invention is applied. 4, reference numeral 3b denotes an engagement surface switching portion 3a shown in FIG. 1, in which the width of the cam projection 3 is widened to make the engagement surface of the positive movement cam 1 and the engagement portion 2 of the link means 2.
The gap e2 between a and 2b is narrowed to reduce backlash. In this embodiment, when moving from the position of the lens unit of the same size to the reduction or enlargement,
Even if the engagement surface of the positive-moving cam 1 is changed and the engagement portion of the link means 2 is changed, the gap e2 is small and backlash is small, so that the change can be made smoothly and quickly. Further, the width of the cam projection 3 of the positive cam 1 is constant at any engagement state where the clearance e2 between the engaging surface of the positive cam 1 and the engaging portions 2a, 2b of the link means 2 is a predetermined small value. May be narrowed as it moves away from the central axis of rotation of the positive cam 1.

[0034]

The present invention is a zooming mechanism for an optical system having the above-described structure and action. An optical system that can move without load fluctuation during zooming can be realized, and a mirror that requires conventional spring means and rigidity. It is possible to provide a highly reliable device that does not require a stand rail or the like, realizes low cost and space saving, and at the same time has no distortion or tilt of the image.

Further, since no extra load is generated as described above, the driving torque can be suppressed low, and energy saving and low noise can be achieved.

Further, since the contact pressure between the above-mentioned zooming cam and the link means can be reduced as much as possible, wear of the engagement surfaces of both means can be suppressed and durable positioning accuracy is almost unchanged from the initial stage. The mechanism can be achieved.

Further, it is possible to solve the problem of reduction of the precision of magnification due to backlash, that is, the problem of precision of the stop position of the mirror base unit, and a large magnification of magnification can be obtained with high precision.

[Brief description of drawings]

FIG. 1 is an operation explanatory view of a variable power mechanism of an optical system to which the present invention is applied.

FIG. 2 is an engagement relationship diagram of a variable power cam and link means of the variable power mechanism in the first embodiment of the present invention.

FIG. 3 is an operation diagram in a variable power mode in which a lens unit, a variable power cam, and a link means are engaged with each other.

FIG. 4 is an engagement relationship diagram of a variable power cam and link means of a variable power mechanism according to a second embodiment of the present invention.

FIG. 5 is an operation explanatory diagram of a conventional variable power mechanism of an optical system.

FIG. 6 is an explanatory view of an engagement relationship between a variable power cam and a link means of a conventional optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive movement cam (variable-magnification cam means) 2 Link means 2a, 2b Engagement portion 3 Cam projection portion 35 Lens unit 40 Mirror base unit e, e2 Gap

Claims (7)

[Claims] 1. A lens unit is moved by a lens moving unit, and in synchronization therewith, a mirror base unit is moved by a mirror base moving unit to an appropriate position relative to the lens unit, and the magnification is changed between enlargement and reduction. In the zooming mechanism for performing the operation, the mirror base moving means is composed of a zooming cam means and a link means, and an engaging surface of the zooming cam means with the link means corresponds to each zooming operation of enlargement and reduction. A variable magnification mechanism characterized by being independently provided. 2. The zooming cam means is a positive-moving cam, and an engaging surface of the positive-moving cam with the link means is composed of a plurality of engaging surfaces that differ in the cam rotation direction. 2. The variable power mechanism according to claim 1, wherein only the specific engagement surface of the plurality of engagement surfaces is engaged when the position is determined. 3. The variable power mechanism according to claim 1, wherein the lens unit and the mirror base unit are stopped from a state of moving in a specific one direction when determining the position of the variable power operation. . 4. The specific engagement surface that is engaged when the position of the mirror base unit of the positive cam is determined is provided on different continuous engagement surfaces when contracting and when expanding. The variable power mechanism described in 2 or 3. 5. A linking means is provided at a position where a specific engagement surface of the positive cam which is engaged when determining the position of the mirror base unit is switched to a different continuous engagement surface at the time of contraction and at the time of expansion. 5. The variable power mechanism according to claim 4, further comprising an engagement surface switching portion for reducing backlash of the joint portion. 6. The variable power mechanism according to claim 5, wherein the engagement surface switching portion forms a step portion having a discontinuous cam surface. 7. The variable power mechanism according to claim 5, wherein the engagement surface switching portion changes a cam width of the positive movement cam.