JPS6038708B2 - variable magnification copying device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a copying device that forms a copied image by projecting an original image onto a photoreceptor in the form of a slit, and more specifically, the present invention relates to a copying apparatus that projects an original image onto a photoreceptor in the form of a slit to form a copied image. The present invention relates to a copying apparatus that forms a copy image using a machine.

2. Description of the Related Art Conventionally, there is a copying apparatus that moves or conveys (hereinafter simply referred to as conveyance) an original document and projects an image of the original onto a photoreceptor in the form of a slit.

When the above-mentioned apparatus has two or more different magnification ratios, the method is generally to transport the copying material and the photoreceptor at the same speed at all times, while transporting the original at a speed corresponding to each magnification. has been adopted. A copying apparatus to which the above method is applied operates only the means for changing the projection magnification of the optical system such as a lens and the conveyance speed of the document conveyance means in accordance with the selection of the magnification, and operates other means for driving the photoreceptor. There is an advantage that the mechanism, conditions, etc. for conveying the copy material do not need to be changed.
On the other hand, for example, in a copying apparatus that conveys a sheet-like original by a driving means such as a roller, and projects an image of the original onto a drum-shaped photoreceptor to obtain a copied image, a photoreceptor image on the photoreceptor is used. The leading edge of the visible image and the leading edge of the copying material are perfectly synchronized so that they can be transferred to a predetermined position on the copying material that is transported to the transfer position, and the two coincide in the transfer position calendar (
(hereinafter simply referred to as tip alignment) is required. The time at which the leading edge of the developed image reaches the transfer position is a certain period of time after the image of the leading edge of the document is projected onto the photoreceptor, regardless of the magnification. However, since the document conveyance speed is changed in accordance with the selected magnification, the time point at which the image of the leading edge of the document is projected onto the photoreceptor differs depending on the selected magnification.
In order to achieve leading edge alignment in such a case, either detect the document to be transported and change the timing at which the copy material starts to be transported using the above-described delay means corresponding to each magnification, or A conceivable method is to arrange a number of document detection sections, selectively use the document detection section according to a set magnification, and determine when to start conveying the copy material based on signals from these document detection sections. However, the method described above requires a large number of delay means and detection members in a copying apparatus capable of copying a large number of types of abnormalities, so it is not preferable because it makes the apparatus complicated and makes adjustment difficult. do not have.

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned inconveniences, and to make it possible to perform edge alignment without complicating the apparatus no matter how many types of variable size copying are performed.
The present invention is characterized by: a first document detection member provided along the document conveyance path; a second document detection member provided at a distance from the document detection member in the document conveyance direction; and a calculation unit related to the detection signal generated from each member,
Based on the time difference between the times when the original passes through the first and second original detecting members, the calculation unit calculates the time when the original starts projecting onto the photoreceptor, and the leading edge position is determined in advance at a predetermined position. Some apparatuses include a copying material conveyance means that waits and then starts conveying the copying material toward the transfer position at the same speed as the photoreceptor.

As the document detection member, a microswitch, a switch using ultrasonic waves, or a switch in which a light source and a light receiving element are combined can also be used. When the document is a sheet material conveyed by rollers or the like, it is preferable to dispose these detection members so as to avoid the document illumination section that forms the slit. However, the first and second document detection members and the calculation section make it possible to determine the point in time when the leading edge of the document passes through the document illumination section for projecting the document. That is, the combination of the first and second document detection members and the calculation section makes it possible to detect the point in time when the leading edge of the document passes through the document illumination section without providing the document detection member in the document illumination section. Of course, since there is no document detecting member in the document illumination section, there is also the effect that the detecting member does not appear in the copied image. Further, according to the present invention, there is no need to increase the number of detection members even if the variable magnification increases, so the configuration and control can be simplified. In the present invention, the photoreceptor is drum-shaped or web-shaped, and moves together with a copying material such as plain paper at a constant speed regardless of changes in magnification.

The (movement) speed of the photoreceptor means the circumferential speed due to rotation when the photoreceptor is drum-shaped, and the moving speed of the photoreceptor when it is web-shaped. Further, the document is in the form of a sheet, and the present invention is particularly effective when the document is conveyed with a slit portion for projecting the document image onto a photoreceptor, which is supported by a roller or a belt. Further, the present invention can also be applied to a movable document table that moves a sheet or three-dimensional document through the slit portion. DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a copying apparatus to which the present invention is applied will be explained with reference to the drawings, and embodiments and application examples of the present invention will be explained in detail. FIG. 1 shows a cross section of a copying apparatus. In the apparatus shown in FIG. 1, there is a first exposure section 1 having a fixed document table for three-dimensional originals, and a second exposure section 1 having an original conveying means for sheet originals. It has part 2.

The present invention is applied to the second exposure side of the exposure units 1 and 2, and variable magnification copying can be performed only on sheet originals. The photoreceptor of the device is constructed in the form of a drum, and the photoreceptor drum 4 rotates in the direction of the arrow. An electrophotographic photoreceptor having a layer and a surface insulating layer is used. Next, the operation of the above device will be briefly explained. When using the first exposure section 1, place the original on the original bridge layer glass plate 5 of the exposure section and press the copy start button (not shown), the photosensitive drum 4 will rotate in the direction of the arrow. start.

Next, the original illumination lamp 6 and the first movable mirror 7 of the optical system move in the direction of the arrow at the same speed as the circumferential speed of the drum 4. Then, in synchronization with the first mirror 7, a second movable mirror 8 moves in the same direction at half the speed of the mirror to scan the original. The original image is projected onto the projection section 11 of the drum 4 via the first mirror, the second mirror 7, 8, the fixed in-lens mirror 9 which includes an aperture and a mirror inside, and the rotatable third mirror 10. be guided. The first and second mirrors 7 and 8, which have reached the two-dot chain line position, reverse their moving directions and return to the starting position. The following case will be described in which the second exposure section 2 is used.

In this case, when the original 13 is placed on the original guide 12 that allows the originals to be overlapped and a copy start button (not shown) is pressed, the original 13 is moved to the guide 12 by the action of the feed roller 14 and the reverse roller 16. They are sent out one by one. Then, the sent document 13 is transported by a pair of transport rollers 6
, 17, the paper passes through a slit portion having a glass plate 18, and is further conveyed onto a paper discharge tray 21 by rollers 9, 2. Note that when the second exposure section 2 is used, the third mirror 10 is located at the position indicated by the two-dot chain line, and the reflected image of the document illuminated by the illumination lamp 22 through the glass plate 18 of the slit section is The unit 23 is configured to be movable in order to change the optical path length, and the lens 2 is also configured to be movable in order to change the imaging magnification of the document image.
4 to the projection section of the photoreceptor. On the other hand, members and means for image formation are arranged around the photosensitive drum 4, and in the figure, 25 is a first corona discharger, 26 is an AC corona discharger, and the photosensitive drum 4 is connected to the photosensitive drum. Reference numeral 27 denotes a lamp for full-surface exposure, which performs static elimination and image projection at the same time.

An electrostatic image corresponding to the original image is formed on the surface of the photosensitive drum 4 by each of these members 25 to 27. Thereafter, the electrostatic image on the photosensitive drum is developed by a developing device 28 and reaches a transfer section. In the figure, a liquid developer is used as the developer 28, and the developer pumped up by a pump is applied to the photosensitive drum by a dish-shaped electrode to develop an electrostatic image. Also,
An appropriate amount of excess developer is squeezed out with a roller or blade, and may be further squeezed out with a corona discharger or the like. In the transfer section, the copying material is conveyed to the visible image on the photosensitive drum, and the copying material that is in close contact with the photosensitive drum 4 in the transfer section receives the electric field of the transfer discharger 29 and is transferred to the visible image on the drum 4. The image is transferred.

The copy material that has been transferred is separated from the drum 4 by the separating means 301, and conveyed 8E onto the scarlet paper tray 33 by the conveyance loaf 32 via the fixing means 31. On the other hand, when the photosensitive drum 4 completes the transfer process, it is uniformly irradiated by the lamp 34, and the remaining developer on the surface is removed by a cleaning roller 35 and a cleaning blade 36, and the photosensitive drum 4 is ready for the next process. In the above figure, reference numerals 37 and 38 are cassettes for storing copy materials, which can store copy materials 39 of different sizes. Further, reference numerals 40 and 41 denote feed-out rollers for sending out the copy material, and the copy material 39 sent out by the roller 41 is synchronized by the register roller 42 and conveyed to the transfer section of the photosensitive drum 4. here,
In the case of variable-magnification copying of a sheet original using the second exposure section 2, if the copying magnification ratio is 1:1/n, and if the conveyance speed of the document is Vo during isometric copying, then during variable-magnification copying The conveyance speed Vn of the document has the relationship Vo:Vn=1:n.

Further, the mifunite 23 and the lens 24 move to the position indicated by the two-dot chain line to form an optical path for variable magnification projection. Next, the relationship between the projection of the original image from the second exposure section 2, the projected image on the photoreceptor, and the synchronization of conveying the copying material with respect to the image on the photoreceptor will be described.

Note that the numbers in FIG. 2 and the following figures are the same as those of the corresponding materials in the apparatus 1 in FIG. be. Second
In the figure, the center position of the projection part on the photosensitive drum 4 is designated as point B, the leading edge position of the copying material 39 loaded in the cassette 37 is designated as point D, and the visible image on the drum 4 is transferred to the copying material 39. The center position of the transfer position to be transferred is defined as point C.

And the length along the circumferential direction on the circumferential surface of the drum,
Let LBc be the distance between point B and point C, and let Loc be the distance between point C and copy material leading edge position D, which is the length along the conveyance path between cassette 37 and drum 4. Figure 2 is LBc L
In the case of configuration Dc, if the conveyance of the copy material 39 is started at the same time when the leading edge image of the document starts being projected onto the point B, the circumferential speed of the drum 4 and the conveyance speed of the copy material will change as described above. Since they are equal, the original image and the leading edge of the copy material can be reliably aligned at the transfer position C. In addition, although the conveyance speed of the above-mentioned original is changed in accordance with variable-magnification copying, since the drum side always rotates at a fixed distance, general feeding of the copying material starts when the image of the leading edge of the original starts to be projected onto the drum 4. In this way, the edges of the copying materials can be aligned reliably in the same way as when copying at full size. Figure 3 shows L8c<Loc in Figure 2 above.
This shows a case where the configuration is as follows.

In this case, before the original image starts to be projected at position B, the leading edge of the copy material 34 is conveyed in advance to a predetermined position E point and kept on standby. Examples of methods for transporting the copy material to point E include driving the roller 40 by a timer by the distance LoB between point 'a' and point E;
The position of the copy material being transported is detected using detection means such as microswitches, ultrasonic elements, light and light receiving elements, etc. The controller 40 may also be stopped. Here, LBc=LEc
Set it to . By keeping the leading edge of the copy material on standby with the leading edge aligned with the point E' as described above, when the leading edge image of the document starts to be projected at the projection position B, as in the configuration shown in FIG. If the conveyance of the copy material 39 is restarted from position E, it becomes possible to perfectly align the leading edges of the copy material for full size and other irregular copies. FIG. 4 shows a case where the configuration in FIG. 2 is such that LBc>Loc.

In this case, the copy material 39 is moved along a path corresponding to the difference between LBc and Loc for the time required for the copy material 39 to be conveyed at a constant speed from the time when the leading edge image of the document starts to be projected at point B. Delay the start of transport using a timer, etc. This makes it possible to align the leading edge of the copy material at the transfer position C point. As described above, even if the distance between the projection position of the original image and the transfer position and the distance between the feeding position and the dotting position of the copy material are different, the photoconductor side and the copy material side are moved at the same speed, and the tip of the copy material is moved at the same speed. It becomes possible to match.

Furthermore, by determining the start time of projection of the document onto the photoreceptor, perfect alignment of the leading edges can always be performed regardless of the magnification being the same or varying the magnification. Therefore, the means for determining the projection start time point will be explained below using an example.

FIG. 5 shows the second exposure section of the apparatus shown in FIG. 1.

In the figure, the width a is the slit width for document illumination;
is the center position of the width a. The sheet-like original is conveyed in the direction of the arrow at a predetermined speed depending on the magnification ratio. In the above configuration, the time when the leading edge of the original passes through point A indicates the point in time when the image of the leading edge of the original is projected onto point B in FIGS. 2 to 4. That is, it is sufficient to detect the point in time when the leading edge of the document passes through point A, and use the detected signal to command the conveyance of the copying material whose leading edge is pre-arranged at the same position for any magnification. By the way, as a method for detecting copy material passing through point A, a microswitch is provided at the point A and the presence of the document is detected based on the thickness of the document when it passes.
Alternatively, a method can be considered in which a light source and a light receiving element are provided at point A, and the presence of the document is detected by blocking the light from the light source when the document passes.

However, since point A is the exposure position of the document, if these position detection members are provided in the slit portion, these detection portions will be projected onto the photoreceptor along with the document image. Therefore, it is preferable to provide the position detection section in an area outside the slit section. The embodiment described below has a set of two document detectors, G and G, and in the case of FIG. There is.

Let b be the distance between the position A and the position of the first document detecting member G, and C be the distance between the position of the detecting member G and the second document detecting member. In the above configuration, when a magnification ratio of n is set, the document is conveyed in the direction of the arrow at a speed of Vn. If the time point at which the leading edge of the document passes at point H is TH, and the time point at which the leading edge of the document passes by point G is TG, then the time point when the leading edge of the document passes at point A (at this point, the image of the leading edge of the document is projected onto point B). T^ is calculated as T^: TG party = TG+ (TG-TH).

By arranging two document detection members at positions other than the slit portion and detecting that the leading edge of the document passes through these two points, the distance between the two points and the document speed are known. The point in time when the leading edge of the document actually passes point A can be calculated. Then, the leading edge alignment is performed by applying the signal resulting from the above calculation to the copying material feeding means as a feeding signal. FIG. 7 shows a case where the first document detecting member G and the second document detecting member are provided on both sides of the center position A of the slit portion.

In this case, the time point T^ when the leading edge of the document passes is T^=TG-
is determined by = TG-No. (TG-TH).

FIG. 8 shows a case in which the document detecting member G is provided behind the center position of the slit in the document conveyance direction.

In this case, the time point T^ when the leading edge of the document passes is T^:TG-
Floor = TG-No. (TG-TH).

Also, when aligning the tips with higher precision, use the first method above.
The register roller 42 described in FIG. 4 can be used.

That is, the registration roller 42, which is closer to the transfer section, is temporarily stopped rotating just before the copy material 39 arrives to prevent the copy material 39 from advancing, thereby causing the copy material to sag. Thereafter, when the roller 42 is rotated again, the unstable conveyance movement of the copy material that occurred during conveyance is absorbed, and good leading edge alignment is achieved. The signal for controlling the roller 42 may be obtained separately from the copying material conveyance start signal, that is, the signal for starting projection of the original image, and the signal may be delayed by a delay means such as a timer and used. Further, in this case as well, since the same delay means can control various types of variable size copying, the apparatus and control method are extremely simple. According to the above-mentioned invention, it is possible to align the leading edges during variable-magnification copying in the same way as aligning the leading edges during full-size copying.

Further, in the present invention, since the calculation unit detects the point in time when the leading edge of the document passes the point A, it is possible to align the leading edge during continuous variable magnification copying. It should be noted that the present invention is applicable not only to an apparatus that transports only a sheet-like original, but also to an apparatus that uses an original table for feeding an original.

In other words, in an apparatus that performs two types of document movement with respect to the same slit section, one for conveying only the document and the other for moving the document table, the movement of the document table is the same as in each embodiment. The following control methods are possible. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of a copying apparatus to which the present invention is applied, FIGS. 2 to 4 are cross-sectional views of a conveyance section showing a standby state of copy material, and FIG. 5 is a slit explaining a slit section. 6 to 8 show cross-sectional views of a slit portion to which the present invention is applied.

In the figure, 2...second exposure section, 4...photosensitive drum, 13...original document, 16-20...transport roller,
18...Glass plate, 22...Lamp, 24...
Lens, 39... Copying material, 42... Registration roller, G, Date... Detection unit position, a.
...Slit width.

Figure 2 Figure 5 Figure 1 Figure 8 Figure 3 Figure 4 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A document conveying means for conveying the document at a speed corresponding to a selected magnification, and an optical system for projecting an image of the document at the selected magnification onto a photoreceptor that moves at the same speed regardless of the magnification. In a variable magnification copying apparatus having a transfer means for transferring an original image formed on the photoreceptor to a copying material that moves at the same speed as the photoreceptor, the first original is provided along the original transport path. It has a detection member, a second document detection member provided at a distance from the member in the document conveyance direction, and a calculation unit related to the detection signals generated from each of the members, and the document detects the first document. Due to the time difference between the passing points of the second document detecting member,
The time point at which the image of the original document starts to be projected onto the photoconductor is calculated by the calculation unit, and the copying material whose leading edge is set in advance at a predetermined position and is kept on standby is directed toward the transfer position and is aligned with the photoconductor. A variable magnification copying apparatus comprising a copy material conveyance means that starts conveyance at a speed. 2. The variable magnification copying apparatus according to claim 1, wherein the first and second document detection members are provided by removing a slit portion through which the document passes in order to be projected onto the photoreceptor.