JPS60111236A - Image forming method of variable magnification copying machine - Google Patents

Abstract

PURPOSE:To register plural monochromatic copies constantly, and obtain a color copy of good quality without any color blurring by keeping the scan starting position of an optical scanner for image formation invariably constant. CONSTITUTION:A scan for image formation is started invariably at the optical scan starting position. Namely, even when a selection of variable magnification is necessary, the image forming scan is started not in a magnification selected state, but after the optical scanner is returned to the scan starting position by a scanning motor temporarily. Consequently, the scan is started invariably in the state where the optical scanner is returned to the scan starting position by the scan return motor, thereby preventing color blurring on a color copy and a failure in the registration of plural monochromatic copies of the same original.

Description

Description: TECHNICAL FIELD The present invention relates to an image forming method using optical scanning for an electrophotographic copying machine capable of variable magnification copying, particularly for a color electrophotographic copying machine using a three-color superposition transfer system.

Prior Art In an electrophotographic copying machine, for example, as shown in FIG. 5. The second mirror 6, the third mirror 7, the imaging lens 8, and the fourth mirror 9 form an image on the photosensitive drum 1o at a certain position and expose it to light. In the same-magnification slit exposure using the above-mentioned optical device, as is well known, the light source 4 and the first mirror 5 are moved integrally in the scanning direction at the same speed V as the circumferential speed (2) of the photoreceptor drum 10, and the second mirror 6 and This is done by moving the six mirrors 7 and 7 in synchronization at a speed of μ·V in the same direction.

Now, in a slit exposure scanning type copying machine, when copying a document by changing the magnification such as same size, reduction and/or enlargement, the lens and mirror of the exposure optical device are displaced according to the copying magnification, and It is sometimes necessary to change the document scanning speed inversely proportional to the magnification.

When changing the magnification in the vertical direction with the aperture system shown in FIG. It is displaced from the same magnification position shown by, for example, to the position shown by the chain line in the figure, depending on the change ratio. In that case, the second mirror 6 and the third mirror 7 are placed at positions farther from the first mirror 5 than at the same magnification (for example, 6', 7') during reduction and enlargement.
When zooming out, the lens 8 is moved closer to the fourth mirror 9, for example, at a position 8', and during enlargement, it is moved closer to the sixth mirror 7, for example, at a position 8N.

FIG. 2 shows an example of a lens and mirror moving device that moves the second and sixth mirrors 6.7 and lens 8 in relation to each other in accordance with the magnification ratio as described above and scans an original. FIG. 2(a) shows a lens/mirror displacement mechanism for varying magnification, in which a lens drive stepping motor 22 rotates a screw shaft 24 via a gear train 23, and a lens bracket 25 to which a lens 8 is fixed is shown. When the lens is moved to the left in the figure when zooming out, and to the right when zooming in, by an amount corresponding to the magnification ratio, the cam plate 26 integrally attached to the lens bracket 25 also moves left and right at the same time. An arc-shaped slit cam 26a is formed on the cam plate 26, and a cam follower 28a provided at one end of an L-shaped variable power drive lever 28 that is swingably supported on a fulcrum 27 engages with this cam. are doing. The engagement position of the cam 26a at the same magnification is at the most downwardly protruding position in the figure, and the amount of protrusion decreases from there to the left and right. Therefore, even if the lens bracket 25 moves to the left or right during reduction or enlargement, the cam follower 28a is displaced upward in the figure, and accordingly, when the variable power drive lever 28 is turned back, the cam follower 28a moves upward. It rotates in one direction, and its upper end is displaced to the left from its original magnification position. As a result, when the light source 4 and the first mirror 5 are fixed by the wire rope and pulley arrangement shown in FIG. 2(b), the second and sixth mirrors 6.7 are displaced to the left in the figure. .

(Note that the arrangement of lenses and mirrors in FIG. 2(b) is reversed from that in FIG. 1.) In this state, the lens drive stepping motor 22 is stopped, and the scan drive pulley 60
By rotating the light source 4 and the first mirror 5, the light source 4 and the first mirror 5 are synchronously displaced in the same direction at a certain speed, and the second and sixth mirrors 6.7 are moved at half the speed, thereby performing exposure scanning.

Since the circumferential speed of the photosensitive drum cannot be changed by the process speed, it must be maintained at a constant speed regardless of the copying magnification. Therefore, the scanning speed of the light source 4 and the first mirror 5 is set to V
By setting the speed of the second and third mirrors to 772 m, the magnification in the scanning direction of the document is adjusted to η. For this purpose, the scan drive shaft 6 shown in FIG. 2(b)
The drive boob IJ3'0 fixed at 6 is driven by a control device (not shown) at a rotational speed inversely proportional to the magnification of the belly image during scanning, and is controlled so that the clutch is disengaged and rotates freely at the same time as scanning is completed. Therefore, the scanning return is shown in Figure 2 (b
) is carried out by a scan return servo motor indicated by the reference numeral 29.

Now, in the variable magnification, scanning, and return mechanism configured as described above, the scanning return servo motor 29 moves the driving wire rope during scanning return in the direction of the arrow shown by the broken line in FIG. 2(b), and the wire rope has tension in that direction. On the other hand, when the magnification is changed from the same magnification to reduction or enlargement, tension is applied to the wire lobe in the direction of the solid arrow shown in FIG. 2(b).

In a scanning, return, and variable magnification drive device using a wire lobe, in order to apply a predetermined tension to the wire lobe, the wire lobe is attached to a tension pulley (reference numeral 5o in the example of Fig. 2(b)) attached to the machine frame via a tension spring. ).

Therefore, if tension is applied to the wire lobe as described above during the scan return and the magnification change operation, the scanning device (7) 'R, :i
: Due to inertia and friction, the wire lobe becomes slack on the drive direction side from the wire rope drive point, and at the end of the scan return, the scan return motor 2
A slack is created in the wire lobe between the pulley 29-1 of No. 9 and the drive pulley 60, and the reference position A on the wire lobe (indicated by a white circle in FIG. It stops at a position shifted counterclockwise by Δt1 from the position indicated by the black circle inside.

On the other hand, when the magnification change operation is completed, the reference position A on the wire rope stops at a position shifted by Δt2 in the hour direction from the scanning start reference position B of the drive pulley 60, as shown in FIG. .

During image formation, that is, during mirror scanning, the reference position B on the pulley 60
Whether or not the reference position A on the wire lobe always corresponds with the reference position A on the wire lobe during the copy cycle operation, or even if they do not match, as long as the amount of deviation between the two reference positions A and B is always constant and there is no variation, the photoreceptor is always Since image formation starts from the same position, if the copying device is a color copying device that uses a multicolor toner image overlapping transfer method, a color copy without color shift can be obtained, and if it is a monochrome copying device, a color copy can be obtained. , it is possible to obtain copies with constant registration for each copy.

However, in a copying apparatus having the variable magnification, scanning, and return mechanism configured as described above, the variable magnification operation is performed at
It starts from a position shifted by 2 in the scanning direction. When the same image is created continuously, the magnification change operation is not performed each time, so that the reference position A of the wire lobe is △ with respect to the reference position B of the scanning drive pulley 60, as shown in FIG. Start from a position shifted by one step in the anti-scanning direction.

As a result, the first image and the second and subsequent images are formed at positions shifted by Δt1+Δt2 on the transfer paper. Therefore, if the copying apparatus is a color copying apparatus of an overlay transfer type, a double image is created in which the image of the first color is shifted from the image of the second color [ ] and the following colors. Furthermore, monochrome copying machines have the problem of producing copies with inconsistent registration.

In view of the above-mentioned drawbacks of the conventional variable-magnification copying device having a variable-magnification optical device configured as described in 2. Even when creating an image, it is possible to create the same image continuously under the same starting conditions.This makes it possible to create color copies without color shift, or to create multiple single-color copies with uniform registration. It is an object of the present invention to provide an image forming method in an 8 variable magnification copying apparatus that provides the following.

The above object is achieved by always starting scanning for image formation from the state where the optical scanning device has returned to the scanning starting position. In other words, even when a variable magnification selection is required, the scanning return motor 2 is immediately activated without starting the image forming scan from the state where the variable magnification selection has been made.
9, the optical scanning device may be returned to the scanning start position, and scanning for image formation may be started from that state.

Examples of specific image forming methods of the present invention will be described below.

FIG. 5 is a flowchart of an embodiment of the image forming method of the present invention. In this image forming method, during the final scanning cycle of a series of scanning cycles for the same document, the scanning device is stopped at the scanning end position and held in this state. When the power switch is turned on for the next copy, it is detected whether the scanning device is at the scan end position or not, and if it is not at that position, it is moved to the scan end position and the copy start switch can be pressed. If scaling is required, first press the scaling selection switch, and if scaling is not required, press the copy start switch immediately; if scaling selection switch is pressed, the scaling device operates first. After that, if the variable magnification selection switch is not pressed, the optical scanning device immediately returns to the scanning start position (home position) and scanning for image formation is started.

By doing this, scanning always starts with the optical scanning device returned to the scanning start position by the scan return motor, which prevents color misregistration in color copies or registration of multiple monochrome copies from the same original. Inconsistent rations (1) can be prevented.

In the above embodiment, the optical scanning device is stopped and held at the scan end position during the final scan cycle, but the return motor is used to return it to a position halfway between the scan end position and the scan start position. Even if you look dumbfounded (S).

In addition, in the 70-chart of the embodiment shown in FIG. 5, when the copying machine is turned on, it is confirmed that the scanning device is at the scanning end position, and if the scanning device is not at that position, the scanning device is turned off. Since the scanning device is moved by that distance, even if the scanning device is at a position different from the scanning end position, such as the scanning start position, due to jam removal, maintenance inspection, etc., it will always be returned to the scanning end position. Since the magnification change operation is performed at that position, no problem occurs. The same applies when the scanning device is held at an intermediate position between the scan end position and the scan start position after the final scan is completed.

In another embodiment of the image forming method, the flowchart of which is shown in FIG. The copy inhibiting force of 1M is removed only after the scanner returns to the scanning start position. Thereby, scanning for image formation is always started with the optical scanning device returning to the scanning starting position.

In still another embodiment, the flowchart of which is shown in FIG. 7, when the variable magnification selection switch is pressed, the variable magnification operation is performed, and when the copy start switch is pressed, -simultaneous scanning is performed. Scanning for post-imaging is performed. If the magnification selection switch is not pressed, scanning for image formation is performed immediately when the copy start switch is pressed. Therefore, scanning for image formation is always started from the state in which the optical scanning device returns to the scanning starting position.

As described in "Effects" 2, according to the present invention, the scanning start position of the optical scanning device for image formation can be kept constant at all times, so the registration of a plurality of copies of a single color can be kept constant. In addition, a color copying apparatus using the overlay transfer IJ method can produce high-quality color copies without color shift.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of an exposure scanning optical system of a variable magnification copying apparatus to which the method of the present invention is applied, and FIG. 2(a) is a main part of the lens and mirror drive system for variable magnification. FIG. 2(b) is a top view showing the optical scanning device, and FIG.
The figure is a front view showing the state of the wire lobe near the scan drive pulley at the end of the scan return, FIG. 4 is a front view showing the state of the wire lobe near the scan drive pulley at the end of the variable magnification operation, and FIG. Flowchart 1 of an embodiment of the image forming method of
, FIG. 6, and FIG. 7 are flowcharts of the following embodiments, respectively. 4...Light source 5.6.7...Mirror 29...Scanning return motor 29-1...Return pulley 60...Scanning drive pulley Fig. 6 Fig. 7

Claims (5)

[Claims] (1) Scanning and returning of the optical scanning device are performed by a wire rope wound around a scanning drive booby driven by a scanning drive motor during scanning and a return pulley driven by a scanning return motor during scanning return, and A variable magnification optical device that performs a variable magnification operation by displacing a part of the optical scanning device to a position according to the magnification using the same wire rope, and which includes a state in which the optical scanning device is returned and a variable magnification operation. In an image forming method for a variable magnification copying device in which an image is formed on a photoreceptor by a variable magnification optical device such that the directions of the tensions acting on the wire rope near the scanning drive boolean are opposite to each other when An image forming method characterized in that scanning for image forming is always started from a state in which the optical scanning device has returned to the scanning start position. (2) As a means of always starting the scanning for image formation from the state where the optical scanning device has returned to the scanning start position, the optical scanning device is moved to the scanning end position during the final scanning cycle of a series of scanning cycles. If you want to change the magnification the next time you create an image, first press the variable magnification selection switch, then press the copy start switch immediately if you do not need to change the magnification, then press the variable magnification selection switch. If the magnification change selection switch is not pressed, the variable magnification device is activated first, and then, if the variable magnification selection switch is not pressed, the optical scanning device is immediately returned to the scanning start position and image forming scanning is started. An image forming method according to claim 1. (3) As a means for always starting the scanning for image formation described in J.2 from the state in which the optical scanning device has returned to the scanning start position, the optical scanning device finishes scanning at the final scanning cycle of a series of scanning cycles. The return motor returns the image to the intermediate position between the position and the scanning start position and holds it there. If magnification is required for the next image creation, press the magnification selection switch, or if magnification is not required, copy immediately. Open (lrI
By pressing the switch, if the variable magnification selection switch is pressed, the variable magnification device operates first, and after that, if the variable magnification selection switch is not pressed, the optical scanning device is moved to the scanning start position. 2. The image forming method according to claim 1, wherein the image forming scan is started after returning to . (4) As a means to always start scanning for image formation from the state where the optical scanning device has returned to the scanning start position, the optical scanning device should be held after the final scanning is completed by turning on the power of the copying device. 7. The image forming method according to claim 2, further comprising moving the optical scanning device to the above-mentioned position if the optical scanning device is not in the above-mentioned position. (5) As a means to always start scanning for image formation as described above from the state in which the optical scanning device has returned to the scanning start position, press the variable magnification selection switch (only when operation 9 is performed). Claim 1, characterized in that the optical scanning device performs one empty scan and returns to the scanning start position, allowing the copy start switch to be pressed.
In item (6) above, the optical scanning device always returns to the scan start position and starts the scanning for image formation while the magnification selection switch is pressed to perform the magnification change operation. In such a case, when the copy open & i switch is pressed, the optical scanning device performs one empty scan and then returns to the original state, and then scans for image formation. Imaging method described.