JPS6019495B2 - Exposure slit opening/closing mechanism of variable magnification copying machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an exposure slit opening/closing mechanism for a variable magnification copying machine.

In some types of variable magnification copying machines, when copying at a magnification, the scanning speed of the optical scanning system including the first moving mirror and the second moving mirror is changed, and at the same time the third mirror is moved. Change the axial distance.

Therefore, the position at which the document irradiation light is projected onto the photosensitive drum differs depending on the magnification, and therefore the exposure slit is provided with a plurality of slit openings corresponding to the magnification. When such an exposure slit is used, for a certain magnification, the light incident from the slit opening that is not being used will affect the light that is projected onto the photoreceptor through the slit that is being used, and the developed image will be affected. The density changes and uniform density cannot be obtained, and a band with a bright slit width appears in the image. The present invention provides exposure slit opening/closing for closing unused slit openings or opening only used slit openings in connection with the movement of a mirror in a variable magnification copying machine using an exposure slit having a plurality of slit openings. Provide a mechanism.

The exposure slit opening/closing mechanism preferably includes a shutter plate that closes each slit opening by a spring or its own weight, and an actuation plate that is driven by the mirror support and opens the shutter plate of a particular slit opening to be used. The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a schematic diagram of the optical path of a variable magnification copying machine,
The light reflected from the document surface 2 by the irradiation lamp passes through the first mirror 3 , the second mirror 4 , the lens 5 , the third mirror 6 , the exposure slit 7 , and is projected onto the photoreceptor drum 8 . Form an electrostatic port image. At the time of magnification copying, the scanning speed of the optical scanning system including the first mirror 3 and the second mirror 4 is changed, and at the same time, the third mirror 6 is moved to the position a when copying at the same magnification.
, and moves to positions b and c according to the magnification. 3rd mirror 6
As the position of the third mirror 6 shifts from a, the position where the reflected light is projected onto the photoreceptor drum 8 gradually shifts.
Three slit openings d, e, and f corresponding to the openings b and c are formed, and each slit opening is partitioned by partition walls 7a and 7b. In a conventional copying machine, the slit openings d, e, and f of the exposure slit 7 are all open, so for example, when the slit opening e is used for copying at a certain magnification, part of the light reflected from the third mirror 6 is The light may be projected onto the photoreceptor 9 from the slit opening f, and as a result, the original reflected light projected through the slit row e is affected and the image density changes, causing a bright band with the slit width f to appear in the image. appear. In order to prevent such a phenomenon, in the present invention, only the slit opening to be used is opened and all other slit openings are closed with shirt flap plates. One embodiment will be described with reference to FIG. In FIG. 2, a shutter plate 10d for shielding the slit openings d, e, and f of the exposure slit 7,
10e and 10f are outer walls 7' of the exposure slit 7, respectively;
The slit rods d, e, f are attached to the partition walls 7a, 7b so as to be constantly biased in a direction to close them by springs 11d, 11e, 11f.

These shirt plates 10d, 10e, 10f extend across the width direction of the photoreceptor drum 8, and one side edge thereof has an arm 12d, 12e, 1 which can rotate about 0 as a fulcrum.
It is fixed to one end of 2f. Arms 12d, 12e,
Rollers 13d, 13e, and 13f are rotatably provided at the other end of 12f. On the other hand, the third mirror 6 is
4, and is moved by moving the mirror support stand 14 along the guide bar 15 by an appropriate driving means (not shown).

A protrusion 16 is formed on the lower surface of the support base 14, and when the support base 14 is moved along the guide rod 15, it comes into contact with the rollers 13d, 13e, and 13f and is pushed down. FIG. 2 shows the state in which the fog light slit IJ 7 is used when copying at the same magnification.The irradiated light that has passed through the lens is reflected by the third mirror 6, passes through the slit opening d, and passes through the slit opening d onto the photoreceptor 9. forming an image. When the support stand 14 is in the illustrated position, the protrusion 16 pushes down the roller 13d provided at one end of the arm 12d, thereby moving the arm 12d to the fulcrum 0.
Rotate counterclockwise around the center. As a result, arm 12d
The shirt plate 10d fixed to the other end is a spring 11d.
The slit rod d is lifted vertically upward as shown by the solid line against the clockwise bias caused by the slit rod d. At this time, the other slit rows e and f are both shielded by the spring-biased shutter plates 10e and 10f, so the third slit row
It is completely possible to prevent the reflected light from the mirror 6 from passing through the slits e and f and entering the photoreceptor 9. Next, during magnification copying, the support stand 14 is moved to the position shown by the chain line in order to change the optical axis distance, and as a result, the slit opening e is used.

At this time, the arm 12d is disengaged from the protrusion 16 of the support base 14, so the shirt shirt plate 10d returns to the position shown by the dashed line in the figure due to the biasing action of the spring 11d.
while completely shielding the roller 13 of the arm 12e.
The slit opening e is pressed down by the protrusion 16 of e.
Since the shirt flap plate 10e is raised to the vertical position against the biasing action of the spring 11e, the slit lock c is opened. As a result, the reflected light from the third mirror 6 can form a static exposure latent image on the photoreceptor 9 through the slit e. At this time, the other two slit openings d and f are completely blocked by the shutter plates 10d and 10f, respectively, so that the reflected light from the third mirror 6 passes through these slit openings d and f and onto the photoreceptor 9. There is no incident. Similarly, even when copying at different magnifications when the slit f is used, only the shirt flap plate 10f is opened due to the action of the protrusion 16 of the support base 14, and the other two slit openings d and e are opened, respectively. 10e, the reflected light does not pass through those slits.

In this way, by providing a shutter plate that constantly shields each slit opening of the exposure slit and opening only the slit opening used in connection with the movement of the third mirror, stray light can enter the photoreceptor from the slit opening that is not used. It is possible to completely eliminate the adverse effects on image quality, such as uneven image density caused by this and bright bands of slit width that appear in the image. The illustrated embodiment is only an example of an exposure slit opening/closing mechanism, and for example, a structure in which a light shielding plate having one closing opening is moved in conjunction with the movement of the third mirror so that its opening coincides only with the slit opening to be used. Various other options are possible.

[Brief explanation of the drawing]

FIG. 1 of the accompanying drawings is a schematic view of an optical path of a variable magnification copying machine, and FIG. 2 is a schematic side view showing an embodiment of an exposure slit opening/closing mechanism according to the present invention. 1...Irradiation lamp, 2...Document surface, 3...
....First mif, 4...Second mirror, 5...Lens, 6...Third mirror, 7...Exposure slit, 8...Photoconductor drum , 9... Photoreceptor, 10d, 10e, 10f... Shaft plate, 11d, 1
1ellf...'Imitation, 12d, 12e, 12f...Arm, 13d, 13e, 13f...Roller, 14...
...Support stand, 15...Guide bar, 16...Protrusion. Figure 1 Sei Figure 2

Claims (1)

[Claims] 1. In a variable magnification copying machine with a fixed lens equipped with an exposure slit having a plurality of slit openings, a slit corresponding to each copying magnification is connected to the movement of a mirror that is moved to different positions corresponding to the copying magnification. An exposure slit opening/closing mechanism characterized by having a means for opening only the mouth.