JPS6045435B2 - Registration correction method for variable magnification type copying machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is equipped with a variable magnification device, and forms an electrostatic latent image by projecting a document onto a fixed position on a moving photoreceptor surface by slit exposure. The present invention relates to a copying machine in which a document scanning speed is changed according to a selection of a magnification.

For example, in the case of a copying machine of the above type that has a restriction on the position where a latent image is formed on the surface of the photoreceptor, such as when using a photoreceptor with a seam, and is equipped with a variable magnification device, It is necessary to synchronize the movement of the photoreceptor with the exposure work, and to perform so-called registration, in which copying is performed by aligning the leading edge of the original image on the surface of the photoreceptor with the leading edge of the fed transfer paper. If the moving speed of the photoreceptor is held constant when changing the magnification of the variable magnification device, the document scanning speed will be changed in accordance with the change in magnification, resulting in the above-mentioned registration being disturbed. To deal with this, a leading edge detection means for the moving document is provided, and the document is temporarily stopped based on its detection signal, and the stopped document is restarted after a certain period of time based on the detection signal from the reference position detection means of the photoreceptor, and then The present inventor has already proposed that the above-mentioned misregistration be corrected by feeding the transfer paper after another certain period of time. In this proposal, the time from the restart of a stopped original until the same original passes the reference position of the original exposure slit differs depending on the magnification, and this difference must be taken into account when correcting the registration. It is inevitable that it will present the above difficulties. The above-mentioned reference position within the slit is a position corresponding to one ray in the optical path that does not change at all even if the projection slit width changes due to movement of lenses, mirrors, etc. for zooming. For example, in FIG. 1, the document leading edge detection switch 20 is arranged upstream of the exposure slit 4, and in this case, the distance from the document leading edge detection to the reference position 4a in the exposure slit 4 is set to 1.

If the document moving speed at the reference magnification m1 is V, then the document moving speed at other magnifications M2 is as follows.

Therefore, if the time it takes for the document to travel a distance of 1 when the magnification is m1 is the time it takes for the document to travel a distance of 1 when the magnification is M2, then the following equation holds true. Therefore, the time lag is .

Since the moving speed of the photoreceptor is Mlv, the registration shift is .

For example, if the standard magnification m1=1 and M2=0.71 (this corresponds to the magnification that changes A3 to A4), then 1=20
The amount of deviation in the above registration is given by the formula (
1) It becomes better.

The present invention focuses on the fact that the amount of registration deviation is 0 when 1=0 according to equation (1), and attempts to arrange and place the document leading edge detection means at a reference position within the document exposure slit. .

Embodiments of the present invention will be described below with reference to FIG. 2 and subsequent figures.
The electrophotographic copying machine shown in FIG. 2 is equipped with a transparent glass 2 for placing thick originals and a sheet original feeding device 3 on the upper side wall of its casing 1, and has an original exposure slit in the sheet original conveyance path. 4 is provided.

In this case, the sheet document 5 is fed in the direction of the arrow either manually or by an automatic document feeder. An exposure device consisting of a light source 6, reflecting mirrors 7, 8, 9, and a lens system 10 is provided in the casing 1. When copying a thick original placed on the glass 2, the light source 6 and the reflecting mirror are used to scan the original. 7 and 8 move. In addition, the lens system 10 and the reflecting mirror 9 are
It is possible to move between the positions shown by the solid line and the dashed line to change the magnification ratio. A photoreceptor drum 11 provided with a seamed photoreceptor sheet as described later is rotatably mounted in the direction of the arrow, and around it are a charging device 12, seven exposure positions 21, . A developing device 13, a transfer device 14, a static eliminator F5, and a cleaning device 16 are arranged.

17 is a paper feeding device, 18 is a feeding roller (registration roller)
, and 19 is a fixing device.

The paper feeding device 17 has two forces for feeding paper of two different sizes.
A set 22 is provided, and each cassette has a feed roller 23.
are attached to each. In FIG. 3, a photoreceptor sheet 24 is wound around the photoreceptor drum 11, and the photoreceptor sheet 24 has a slit 11A in the longitudinal direction of the photoreceptor drum.
It passes through the drum and is wound around a take-up spool 25 and an unwind spool 26.

By rewinding the photoreceptor sheet 24 from the unwinding spool 26 and winding it up with the take-up spool 25, the photoreceptor drum 1
The photoreceptor sheet 24 on the circumferential surface of the photoreceptor sheet 24 can be replaced with a new part. The cam 27 is fixed to the shaft of the photoreceptor drum 11, and the roller-equipped actuator 28A of the fixed detection switch 28 comes into contact with the protrusion of the cam 27, thereby opening the slit 11A1 of the photoreceptor drum 11, that is, the photoreceptor sheet 24.
Detects seams. In the above-mentioned apparatus, when a sheet original is fed by the sheet original feeding device 3 and copied, the leading edge of the original image and the leading edge of the transfer paper are aligned and copied, that is, in order to match the registration, 1. As shown in FIG. 4, means 27 and 28 for detecting the seam of the photoreceptor sheet 24 are provided, and as shown in FIG.
A document insertion detection switch 29 is installed on the upstream side of the exposure slit 4 in the document conveyance path, and a reference position 4a in the exposure slit is provided.
A document leading edge detection device 30 is disposed at.

The leading edge of the sheet document 5 sent by the feed roller pair 3a is detected by the detection switch 29, and as shown in the time chart of FIG.
The document stops at the dirt position. Next, the reference position (slit 11A) of the rotating photoreceptor drum 11 is detected by the photoreceptor reference position detection switch 28. In response to this detection signal, the document conveying device is moved again to restart the stopped document, the rotation of one of the feed rollers 23 is started, the light source 6 is turned on, and the charger 12 is powered. The transfer paper on the cassette 22, which is fed by the rotation of the feeding roller 23, comes into contact with the feeding roller 18, which is still stopped at this time, and stops, and assumes a standby position at (a). The feed roller 2 is activated by the detection signal of the document insertion detection switch 29.
It is also possible to trigger the start of rotation of 3 and so on. The original 5 then reaches the exposure slit 4 and is irradiated by the light source 6, and the detection device 30 is located at a reference position within the slit.
The tip is detected by As shown in FIG. 5, the time it takes for the leading edge of the document 5 to be detected by the detection switch 29 and again by the detection device 30 varies depending on the magnification, but the time required for the leading edge of the document 5 to be detected by the detection device 30 at each magnification is The time T from when the detection signal is sent to when the transfer paper is fed. is always constant. In other words, the feeding roller 18 waits for a fixed time T after the detection device 30 detects the leading edge of the document. After that, the rotation is restarted and the waiting transfer paper is sent out. The thus-fed transfer paper receives the light image of the original 5 at the exposure position 21 and passes through the transfer position while being superimposed on the visible image on the photosensitive drum 11, which is made visible by the developing device 13. Time T above. is set so that the image on the photosensitive drum 11 and the transfer paper fed by the feeding roller 18 match at the transfer position. Document leading edge detection device 3
A timer device, a digital control circuit, etc. can be used as a means for rotationally driving the feed roller 18 after the predetermined sawing time TO when the detection signal is 0. Next, an example of a mechanical delay device will be shown. In FIG. 6, the solenoid 31 is energized by the detection signal of the detection device 30, and the plunger 3
2, the control lever 33 is pivoted clockwise about its fulcrum 33A against the action of the spring 34.

As a result, the pawl 36 of the control lever 33 that is engaged with the stop portion 35A of the cam 35 is released, and the cam 35 is rotated in the direction of the arrow due to friction with the drive shaft 37.
The protrusion 38 provided on the cam 35 lasts for a certain period of time T. actuator of switch 39, thereby triggering rotation of feed roller 18. After one rotation, the cam 35 is stopped again by the claw 36. Since a glass plate is installed in the original exposure slit, it is difficult to detect the paper thickness using a microswitch, and it is impossible to use a photoelectric element because this position is flooded with illumination light. It is.

Therefore, the detection device 30 uses an ultrasonic oscillator and a microphone to detect the leading edge of the document by utilizing the difference in ultrasonic reflectance between glass and the document. In this case, in order to distinguish between a failure of the oscillator and reflection from the original, the detection device 30 needs to have the following three levels of detection ability.
Reflection from the glass Reflection from the original No reflection By doing this, it is possible to detect the leading edge of the original without being affected by the glass or even if there is a lot of light.

As another method, it is possible to use a combination of a member that generates light of wavelengths that are not included in the illumination light, such as ultraviolet rays and infrared rays, and an element that responds only to these lights.

The present invention can be advantageously applied not only to a copying machine using a sheet document transport method as described above, but also to a copying machine using a document table moving method or an optical system moving method.

An example of how to apply each method of optical system movement and document platen movement is shown below.
Shown in FIGS. 7 and 8. In FIG. 7, a thick original 41 is placed on the original placing glass 40, and the moving optical system 4
2 scans a document 41. A light source 743, a reflecting mirror 44, and an actuating piece 45 are fixed to the moving optical system, and the reflecting mirror 46 moves at half the speed of the optical system 42. 47 is a variable magnification optical system.

The document placement glass 45 serves as the traveling path of the moving optical system 42.
A third detection switch 49 is installed on the upper side wall of the casing that supports the
8 and a first detection switch 49 are arranged. Third
The detection switch 48 is equivalent to the document insertion detection switch 29 shown in FIG. 4, and when this detection switch 48 is activated by the operating piece 45 of the optical system, it feeds the transfer paper and supplies power to the charger and light source. . The first detection switch 49
It corresponds to the detection device 30 shown in the figure, and is arranged at a position corresponding to the start of exposure of the original 41. The third and first detection switches 48 and 49 are actuated by the actuation piece 45 when the optical system 42 travels. In the embodiment shown in FIG. 8, an actuating protrusion 52 is provided on the document table 51 on which a document 50 is placed and moves, and a third detection switch 53 and a 1
A detection switch 54 is arranged. In FIGS. 7 and 8 above, the third detection switches 48 and 53 are omitted, and the optical system 42 and document table 51 perform the scanning movement after a certain period of time after the detection signal from the photoconductor reference position detection switch 28. It is also possible to set it to start.

As described above, the correction method according to the present invention reliably guarantees that the leading edge of the original image and the leading edge of the copy paper match, that is, the registration matches, even if the scanning speed of the original changes depending on the magnification. It is.

Note that the fixed time described in the claims includes O time, in which the document or the optical system is run together with the detection signal of the second detection means, and the document feed signal is sent simultaneously with the detection signal of the fourth detection means. It is also possible to emit it.

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the conventional sheet original exposure slit range.
Figure 2 is an explanatory diagram of a variable magnification type copying machine to which the present invention is applied;
The figure is an explanatory diagram of a drum equipped with a seamed photoreceptor, the fourth
The figure is a schematic diagram of the sheet original exposure slit range of the copying machine shown in Figure 2, Figure 5 is an example of a time chart in the case of implementing the method of the present invention, Figure 6 is an explanatory diagram of the time delay mechanism, 7
The figure shows the main parts of an embodiment in which the present invention is applied to a copying machine with a moving optical system, and FIG. 3...Sheet document feeder, 4...Document exposure slit, 5, 41, 50...Document, 6
, 7, 8; 42...Moving optical system, 9, 10...
...Variable magnification optical system, 11...Photosensitive drum, 12
...Charger, 18...Transfer paper feeding roller,
23... Transfer paper feeding roller, 29, 48, 53...
...Third detection switch, 30, 49, 54...
...First detection device, 28...Second detection switch.

Claims (1)

[Claims] 1. A variable magnification device is provided, and an electrostatic latent image is formed by projecting a document onto a substantially constant position on a moving photoreceptor surface by slit exposure, in which case the magnification of the variable magnification can be selected. In a copying machine in which the document scanning speed is changed according to 1st for
A detection means is provided, a second detection means is provided for detecting the reference position of the photoreceptor, a third detection means is arranged upstream of the first detection means for detecting insertion of a document or start of the optical system, and this detection means The original or the optical system is temporarily stopped by the detection signal of the second detection means, and the original or the optical system, which is stopped after a certain period of time from the detection signal of the second detection means, is caused to run for exposure scanning;
A registration correction method characterized in that a transfer paper feeding signal is emitted after a predetermined period of time from the signal detected by the first detection means of the traveling original or the optical system. 2. The registration correction method according to claim 1, wherein power is supplied to at least one of a light source, a charger, and a transfer paper feeding device based on the detection signal of the second detection means. 3. The registration correction method according to claim 1, wherein power is supplied to at least one of a light source, a charger, and a transfer paper feeding device based on the detection signal of the third detection means. 4. The registration correction method according to claim 1, wherein the first detection means comprises an electromagnetic wave generator of a specific wavelength and a sensitive member sensitive to the electromagnetic wave. 5. The registration correction method according to claim 1, wherein the first detection means comprises an ultrasonic oscillator and a microphone.