JPS59228237A - Variable magnification exposure device of copying machine - Google Patents

Abstract

PURPOSE:To perform scanning exposure at a stable speed even during reduction copying operation whose scanning speed is fast by varying the preliminary scan distance of a scanning part for scanning according to the variation in copy magnification. CONSTITUTION:The 1st mirror unit frame 4 and the 2nd mirror unit frame 5 starts a preliminary scan at a position a0 in unmagnification copying and at a position a1 (a1>a0) in reduction copying, and an exposure lamp 2 and the 1st mirror 3 moves in scanning to right until a specific position where the projection of an original 1 is completed, and then return to left to stop at the original position. Thus, the starting positions are changed easily by moving and setting a driving means frame at a specific position corresponding to copy magnification M, and the preliminary scan starts at the position a1 farther than the a0 in case of the reduction copying wherein the speed of the 1st mirror unit frame 4 is switched to a high speed, so the speed of projection scanning is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a variable magnification exposure device for a copying machine such as an electrophotographic copying machine. The present invention relates to a variable-magnification exposure device for a copying machine in which a variable-magnification copy is performed by cutting off the image.

[Prior art]

A conventional copying machine equipped with a variable magnification exposure device as described above performs variable magnification copying without changing the starting position of the scanning movement member of the exposure optical system. On the other hand, there is a strong desire to increase the copying speed of copying machines, and the same holds true for copying machines that perform variable-magnification copying.

The copying speed of a copying machine equipped with a variable magnification exposure device as described above is also determined by the speed of the photoreceptor, similar to the copying speed of a copying machine that only performs reproduction at the same magnification.

Therefore, even at the same copying speed, the scanning speed of the exposure optical system becomes faster as the copying magnification decreases. For this reason, in conventional copying machines capable of variable magnification copying, in which the starting position of the scanning movement member of the exposure optical system remains unchanged, when the copying speed is increased, the scan run-up distance becomes insufficient, especially in the case of reduction copying. Therefore, there is a problem in that the projection scanning of the document is performed before the speed of the scanning movement member becomes stable, and therefore a flow image is likely to be generated in the portion that was exposed first. This problem becomes even more pronounced when a means for shortening the scan run-up distance is adopted in order to increase the copying speed and to reduce the size of the copying machine.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned problems with conventional photocopying machines capable of variable-magnification copying. The present invention provides a double exposure device.

[Structure of the invention]

The present invention provides a variable magnification exposure apparatus for copying, in which scanning exposure is performed and the moving speed of the scanning section of the exposure optical system changes during magnification change, in which the scanning section of the scanning section changes in accordance with changes in copying magnification. A variable magnification exposure device for a copying machine, characterized by having means for changing a run-up distance.

〔Example〕

Hereinafter, the present invention will be explained in detail based on illustrated examples.

FIG. 1 is a schematic partial side view of a copying machine showing an example of a variable-magnification exposure apparatus of the present invention using an exposure optical system in which the optical path length from the original surface to the photoreceptor surface changes during variable-magnification copying; B is a state in which reduction copying is performed, and FIG. 2 is a schematic perspective view of the exposure optical system scanning drive means.

In the figure, 1 is a document placed at a predetermined position on a fixed document table, 2 is an exposure lamp, 3 is a first mirror, 4 is a first mirror unit frame to which the exposure lamp 2 and first mirror 3 are attached, and 5 is a first mirror unit frame. is the second mirror, 6 is the third mirror, 7 is the second mirror 5
and a second mirror unit frame to which a third mirror 6 is attached, 8 is a lens, 9 is a fixed mirror, and 10 is a photosensitive drum having a photosensitive member on its surface and rotating in the direction of the arrow at a constant speed.

The first mirror unit frame 4 and the second mirror unit frame 7 are
In the case of full-size copying, the run-up distance shown in Figure 1A is a. In the case of reduced copying, the exposure lamp 2 and the first mirror 3 completely project the original 1 from the position shown in FIG. It scans to the right until it reaches a certain position, then returns to the left and stops when it returns to its original position. In the starting position shown in FIGS.
, second mirror5. The optical path length from the surface of the original 1 that enters the surface of the photoreceptor drum 10 via the third mirror 6, the lens 8, and the fixed mirror 9 to the surface of the photoreceptor drum 10, that is, from the placement surface of the document placement table to the photoreceptor drum 10 The optical path length U to the surface of the body drum 100 is set so as to satisfy the relationship U=(M+1/M)f+2f, and the reciprocating movement of the first mirror unit frame 4 and the second mirror unit frame 7 is The speed V of the unit frame 4 is V+''7Ml, the speed v2 of the second mirror unit frame 7 is v2 = v, /2, and the return movement of the first mirror unit frame 4 and the second mirror unit frame 7 is performed. The stoppage of is carried out by the switch 11 provided on the first mirror unit frame 4 with the speed of vl coming into contact with the switch actuating part 12 provided on the second mirror unit frame 7 with the speed of 1/2. be exposed. Here, )11
: Copying magnification, f is the focal length of the lens 8, and ■ is the surface speed of the photosensitive drum 1. Further, a switch 11 is provided on the second mirror unit frame 7, and a switch actuating section 12 is provided on the second mirror unit frame 7.
It may also be provided in the mirror unit frame 4.

In addition, even in enlarged copying, as shown in the above relational expression,
The optical path length U is longer than when copying at full size, and as far as the optical path length is concerned, it is similar to the case of reduced copying. Enlarged copying is also possible by moving the second mirror unit frames 4, 7 as shown in FIG. 1B. However, in the case of enlarged copying, the position of the lens 8 changes to the position shown by the two-dot chain line in FIG. 1B.

The above-mentioned starting position setting and reciprocating movement of the first mirror unit frame 4 and the second mirror unit frame 7 are performed by a scanning driving means as shown in FIG.

In FIG. 2, the same reference numerals as in FIG. 1 indicate the same ladder function members, 13 is a wire extending from the first mirror unit frame 4, and 14 and 15 are wire tensioning members provided on the drive means frame. The members 16 and 17 are driven wheels similarly provided on the driving means frame, and 18 and 19 are moving wheels rotatably fitted on a shaft integral with the second mirror unit head 7;
0 is a drive wheel, and the shaft end integral with the second mirror unit frame 7 is slidably engaged with the drive means frame. Here, although the driving means frame is omitted in the figure, as will be explained later, it is moved when changing magnification and loss, but when scanning for the end of exposure, it can be used for full-size reproduction or variable-magnification copying. Fixed regardless of money. -Then, the wire 13 goes around the movable wheel 18 and the driven wheel 16 from the wire tensioning member 4 provided in the drive means frame, and then turns around the outer periphery of the drive wheel 20 at least once, and then turns around the driven wheel 16 at least once. 17 and the moving wheel 19 are stretched around half a length, and the other end is stretched by a wire tensioning member 15. Further, the drive wheel 20 is capable of transmitting rotation in conjunction with the rotation of the photosensitive drum 10 through a rotation transmission means including a conventionally known transmission means 2 rotation direction switching means and an engagement/disengagement clutch. Preferably, it is supported by a fixed bearing similar to the shaft of the body drum 10,
This simplifies the construction of the rotation transmission means. If the shaft is supported by a fixed bearing, the wires 13 should be stretched so that the tension direction of the wires 13 at the front and rear of the drive wheel 20 is as parallel as possible to the moving direction of the first mirror unit frame 4 and the second mirror unit frame 7. Stretch it. This is done by moving the driving means frame provided with wire tensioning members 14.15, driven wheels 16.17, etc. parallel to the placement surface of the document placement table, and then moving the first mirror unit frame 4 and the second mirror unit frame 7. This is to prevent the wire 13 from loosening due to movement of the drive means frame and becoming under excessive tension when bringing the wire 13 to the starting position shown in FIG. 1A or 1-1:B. In this regard, when the shaft of the drive wheel 20 is supported on the drive means frame, the wires 1 at the front and rear of the drive wheel 20
The tension directions in step 3 do not have to be parallel. However, in that case, the structure of the rotation transmitting means becomes more complicated than when it is supported by a fixed bearing.

When changing the copying magnification M, the first mirror unit frame 4 and the second mirror unit frame 7 are brought to the starting position shown in FIG. 1A or B by moving the drive means frame fUj as described above. You can simply do it. That is, as shown in the example shown, the optical path length U is changed to increase the copying magnification (
In a copying machine that uses an exposure optical system that changes the
From the relationship = (M+1/M)f + 2f, j(=
The optical path length U is the shortest in the case of equal-size copying of 1, and the optical path length U is lengthened in the case of reduced or enlarged copying, so the speed ■ of the first mirror unit frame 4 is particularly high at v/14. In the case of reduced copying that is switched to , the run-up distance is set to a to stabilize the speed during projection scanning. The starting position is changed from Al to a longer one by moving and setting the drive means frame to a predetermined position corresponding to the copying magnification M, as described above. When changing the copying magnification of 1.1, the 1st digit of lens 8 must also be moved to the position shown in Figure 1 A and B, but even if it is set to move relative to the frame of the copying machine. , may be set to move relative to the drive means frame.

When changing the copying magnification M, as described above, set the starting position to the position shown in FIG. The outer peripheral speed of the drive wheel 20 is changed to v/'M. Therefore, when copying is started, the connection/disconnection clutch of the rotation transmission means is connected, and the drive wheel 20 rotates in the direction of the arrow to move the first mirror unit frame 4 at a speed of V.
1=:v/'M, the speed of the second mirror unit frame 7 is v1
/2, and when the first mirror unit frame 4 or the second mirror unit frame 7 reaches a predetermined position, the rotation direction switching means of the rotation transmission means is switched and the drive wheel 20 is reversely rotated. 1st mirror unit frame 4
Then, the second mirror unit frame 7 returns to the opposite direction. Note that the rotation direction switching means may increase the reverse rotation speed of the drive wheel 20 and switch the rotation direction. 1st
The mirror unit frame 4 and the second mirror unit frame 7 move back at speeds v1 and v1/2, respectively, and return to the starting position,
At this time, the switch actuator 12 operates the switch 11 to disengage the engagement/disengagement clutch of the rotation transmission means, and if necessary, a brake is applied to the drive wheel 2° side of the engagement/disengagement clutch, thereby causing the first Mirror unit frame 4
Then, the second mirror unit frame 7 is stopped.

〔Effect of the invention〕

As described above, in the variable magnification exposure apparatus of the present invention,
Because the scan run-up distance of the exposure optical system is changed during variable-magnification copying, exposure scanning is performed at a stable speed even in reduction copying, where the scanning speed is faster, making it possible to always make uniform copies. Excellent effects can be obtained.

Note that the present invention is not limited to the illustrated example, but can also be applied to an exposure optical system that uses an exposure optical system in which the optical path length from the document surface to the photoreceptor surface is not changed by changing the lens during variable magnification copying. In that case, the run-up distance ψ can be changed by, for example, shifting the mounting position of the switch 11 on the first mirror unit 4 in FIG. 1 in the moving direction of the frame.

[Brief explanation of drawings]

FIG. 1 is a schematic partial side view of a copying machine showing an example of a variable-magnification exposure apparatus of the present invention using an exposure optical system in which the optical path length from the original surface to the photoreceptor surface changes during variable-magnification copying; 2 is a schematic perspective view of the scanning driving means of the exposure optical system. 1... Original, 2... Exposure lamp, 3...
...first mirror, 4...first mirror unit frame, 5, 6...second, iλ3 mirror -
, 7... Second mirror unit frame, 8... Lens, 9... Fixed mirror, 1
0...Photosensitive drum, 11...Switch, 12...
・Switch operating part, 13...Wire, 14, 15
... Wire tensioning member, 16, 17... Driven wheel, 18, 19... Moving wheel, 20... Driving wheel, ao, a,... Run-up distance.

Claims (1)

[Scope of Claims] 1. In a variable magnification exposure device for a copying machine that performs scanning exposure and changes the moving speed of the scanning section of the exposure optical system when changing magnification,
A variable magnification exposure device for a copying machine, comprising means for changing an approach distance of the scanning section for scanning in accordance with a change in copying magnification. 2. The copying machine according to claim 1, wherein the means for changing the run-up distance includes at least means for setting the run-up distance for scanning to be longer than when the copy magnification is smaller than 1x, compared to when the copy magnification is 1x. Variable magnification exposure device. 3. A variable magnification exposure device for a copying machine according to claim 1 or 2, wherein the exposure optical system is an exposure optical system in which the optical path length from the document surface to the photoreceptor surface changes during variable magnification copying. . 4. A variable magnification exposure apparatus for copying as claimed in claim 1 or 2, wherein an exposure optical system whose focal length remains unchanged during variable magnification copying is used as the exposure optical system. 5. The scanning section of the exposure optical system is composed of a mirror unit that moves at a speed of vl and a mirror unit that moves at a speed of v,/2, and a switch provided on one of both mirror units and a switch provided on the other. A variable magnification of a copying machine according to Claim 1@Claim 5, wherein means for changing the run-up distance is constituted by a switch operating section, and when the switch operating section acts on the switch, the return movement of the scanning section is stopped. Exposure equipment.