JPH0350270B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a color variable magnification electrophotographic copying machine using a three-color separation image overlapping transfer method.

Prior Art In a color electrophotographic copying machine using a three-color separation and overlapping transfer method, for example, as shown in FIG. The light beam is irradiated through the slit, passes through the first mirror 5, the second mirror 6, the third mirror 7, the imaging lens 8, and the fourth mirror 9, and forms an image at a certain position on the photosensitive drum 10 for exposure. In the same-magnification slit exposure using the above 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 V of the photoreceptor drum 10, and the second mirror 6 and This is done by moving the three mirrors 7 as one unit at a speed of 1/2·V in the same direction.

Between the fourth mirror 9 and the photosensitive drum 10,
Three color separation filters 11 of blue, green, and red are provided so as to be switchable and insertable into the optical path. Around the photosensitive drum 10, following the exposure position, there are three developing units 12, 13, and 14 each containing a developer containing toner of three colors: yellow, magenta, and cyan.
are arranged, and the latent images formed by being exposed to light passing through blue, green, and red color filters are transferred to yellow, magenta, and cyan color developers 12, 13, respectively.
14 to sequentially form three-color toner images. A transfer drum 15 having the same outer diameter as the circumferential surface of the photoreceptor drum 10 is provided at a position after the three developing units, and is in contact with the circumferential surface of the photoreceptor drum 10 .
It is designed to be rotated at the same circumferential speed in synchronization with the rotation of point 0, and at a linear speed in the same direction at the contact position. A transfer paper 17 is fed to the transfer drum 15 by a paper feeder 16, and its leading end is clamped to a predetermined length by a mechanical clamper 18 and wound around the drum 15, and toner of each color is applied to the transfer drum 15 with each rotation. The image is transferred by a transfer charger 19 provided therein, and by rotating three times, toner images of three colors of yellow, magenta, and cyan are superimposed and transferred. Thereafter, the transfer paper 17 is peeled off from the transfer drum 15, fixed by a fixing device 20, and discharged onto a paper discharge tray 21 to complete a full-size color copy.

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 necessary to change the document scanning speed.

To explain this in more detail, in an optical device with a fixed document table and a moving scanner, the variable magnification function adjusts the vertical direction (perpendicular to the scanning direction) and horizontal direction (scanning direction) of the document to the required magnification. This is very important. When changing the magnification in the vertical direction using an exposure optical system that has the same lens and mirror arrangement as the optical system of the color copying machine shown in FIG. While fixed in position, the second mirror 6, third mirror 7, and lens 8 are displaced from the same magnification position shown by the solid line to the position shown by the chain line in the figure, for example, depending on the magnification ratio. In that case, the second mirror 6 and the third mirror 7 are displaced to positions farther away from the first mirror 5 (for example, positions indicated by 6' and 7') than at the same magnification, both during reduction and enlargement. Lens 8 is the fourth lens during reduction.
It is displaced to a position closer to the mirror 9, for example, 8', and at the time of magnification, to a position closer to the third mirror 7, for example, 8''.

FIG. 3 shows an example of a lens and mirror moving device that moves the second and third mirrors 6, 7 and lens 8 in relation to each other in accordance with the magnification ratio as described above, and scans a document. FIG. 3a shows a lens/mirror displacement mechanism for varying magnification, in which a stepping motor 22 for driving the lens rotates a screw shaft 24 via a gear train 23, and a lens bracket 25 fixes the lens 8. When the lens is moved to the left in the drawing when it is being reduced, and to the right when it is being enlarged by an amount corresponding to the magnification ratio, the cam plate 26 that is integrally attached to the lens bracket 25 is also moved 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. ing. The engagement position of the cam 26a when the cam 26a is at the same magnification is located at the most downwardly protruding position in the figure, and the amount of protrusion decreases from there toward the left and right. Therefore, when 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 the variable power drive lever 28 is accordingly rotated counterclockwise. Its upper end is displaced to the left from its position when the image is at the same magnification. This allows the third
When the light source 4 and the first mirror 5 are fixed by the arrangement of the rope and pulley shown in Figure b, the second and third
Mirrors 6, 7 are displaced to the left in the figure. (Note that the arrangement of lenses and mirrors in Fig. 3b is reversed from Fig. 2.) In this state, by stopping the lens drive stepping motor 22 and rotating the scan drive pulley 30, The light source 4 and the first mirror 5 are displaced at a certain speed, and the second and third mirrors 6 and 7 are synchronously displaced in the same direction at half the speed, thereby performing exposure scanning.

Since the circumferential speed of the photosensitive drum cannot be changed by the process speed, it is necessary to always maintain it at a constant speed V regardless of the copying magnification. Therefore, the scanning speed of the light source 4 and the first mirror 5 is set to V/m, By setting the speed of the second and third mirrors to V/2 m, the magnification in the lateral direction of the document is adjusted to m. For that reason, the third
It is necessary to drive the scan drive pulley 30 shown in FIG. b at a rotational speed inversely proportional to the copying magnification. Note that the reference numeral 29 in FIG. 3b is a scan return servo motor.

The present invention relates to control of the rotational speed of the scan drive pulley 30 and the timing of its start/stop.

Conventionally, the method of driving the scanner drive pulley according to the copying magnification of the variable magnification optical device of a variable magnification copying machine is as follows: (a) Gear trains as many as the number of variable magnifications are provided between the drive source and the scanner drive pulley. , is switched and driven via an electromagnetic clutch, etc.

(b) A servo motor or pulse motor is used as a drive source, and the speed is switched and driven by electrical control means.

Such methods are known.

However, both of these methods require a switching step of an electromagnetic clutch or electrical control means, which inevitably results in a shift in the scan start position from imaging cycle to imaging cycle.

In a color electrophotographic copying machine using a three-color separation image overlapping transfer method, the most important thing is the alignment of the transferred images, so the variable magnification drive method described above is inappropriate for a color copying machine, and this is the reason. For this reason, the reality is that a color electrophotographic copying machine using a superimposed transfer method and equipped with a variable magnification mechanism has not yet been realized.

Although this is not a variable magnification copying machine, there is one that uses a fixed point engagement clutch as an optical scanning drive means that does not cause positional deviation. By employing this constant-point engagement clutch, it is possible to perfectly align the scanning start positions for each image forming cycle, thereby realizing a color variable magnification copying machine using a color separation image overlapping transfer system. That is, as will be explained in detail later, a number of gear trains corresponding to the number of variable-magnification copies are provided between the scanning drive power source and the above-mentioned scanning drive pulley, and each of these gear trains and the above-mentioned drive source are connected to each other. By providing a fixed-point engagement clutch for disengagement and selectively connecting the corresponding clutch depending on the magnification, it is possible to drive the optical scanner at a speed inversely proportional to the magnification, and to adjust the scan start point at each time. It can be set at a predetermined position depending on the magnification ratio. For example, it is possible to align the image formation start reference position on the photoreceptor to a constant position regardless of the magnification ratio.

However, as described above, in the case of a color copying machine using the overlapping transfer method, the leading edge of the transfer paper is held by the mechanical clamper 18 at a fixed width and wrapped around the transfer drum 15, as explained with reference to FIG. but,
Generally, the reference position of the leading edge of the image on the photoreceptor and the leading edge position of the transfer paper wound on the transfer drum are made to match, so that the area of a certain width held in the clamper at the leading edge of the transfer paper is The image is not transferred.

Normally, there is some margin around the leading edge of the original, so when making a full size copy or an enlarged copy, there is almost no chance that part of the original image will be missing due to this, but when making a reduced copy, the transfer paper Since the leading edge is held in the clamper by the same width, the possibility that the original image will be chipped due to this is increased compared to when the original size is the same.

Purpose of the Invention In view of the fact that conventional overlapping transfer type color copying machines have not been capable of variable-magnification copying, the present invention enables variable-magnification copying, and even in the case of reduced copying, it is possible to reproduce the entire original image. It is an object of the present invention to provide a color variable magnification copying apparatus of this type which can make copies without missing parts.

Configuration The present invention will be described in detail below based on embodiments shown in the drawings.

FIG. 4 is a perspective view showing a scanning speed switching unit that enables variable magnification copying in the color electrophotographic copying machine of the type previously explained with reference to FIG. In the embodiment shown in the figure, as an example, the copying magnification m is 1, 1·143,
It is possible to switch between three types of 0.7647.

In the scanning speed switching device section, three shafts, an input shaft 31, a clutch shaft 32, and a drive shaft 33, are provided parallel to the axis of the photosensitive drum 10 and supported by a side plate (not shown).

The input shaft 31 is provided with an input pulley 35 and two gears 36 and 37, which are driven by a main motor of the copying machine via a timing belt (toothed belt) 34.

The clutch shaft 32 includes a gear 38 that meshes with the gear 36 described above to obtain a double speed ratio, and three constant-point mesh pawl clutches 39, 40, and 41, and when these clutches are engaged, the clutch shaft Gears 42, 43, and 44 that rotate integrally with 32 are provided.

A gear 46 fixed to the shaft 45 of the photosensitive drum 10 meshes with the other gear 37 provided on the input shaft 31 at a double speed ratio. Gear photosensitive drum 10 provided at one end of the photosensitive drum 10
A gear provided at one end of the transfer drum 15 having the same diameter as the photoreceptor drum 10 and the transfer drum 15 are in mesh with each other, so that the photosensitive drum 10 and the transfer drum 15 are rotated by the main motor at the same rotational speed in synchronization with the clutch shaft 32.

The structure of the fixed point engaging pawl clutches 39, 40, 41 will be explained with reference to FIGS. 5 and 6.

This clutch has a wheel 101 fixed to the clutch shaft 32 and having a meshing groove 101a around the periphery.
and gears 42, 4 pivotally supported on the clutch shaft 32.
A claw portion 10 is swingably pointed at one point on each side surface of 3 and 44 and can be engaged with the groove 101a at one end.
2a and the hook 10
A claw roller 102b provided near the second claw 102a
A claw release blade 103 that has a circular shape that can make point contact with the circumferential surface and whose outer diameter is expandable and retractable, a blade drive lever 104 that switches the outer diameter of the claw release blade 103 between an enlarged state and a reduced state, and an engaging groove 101a. It is comprised of a relay pin 105 that releases the engagement of the catch pawl 102 rotated together with the gear at a predetermined position when the pawl 102a engages with the hook 102a.

The pawl relay blade 103 includes a unit blade 103a having a rotation center 103c at one end and a blade roller 103d at the other end as shown in FIG. 6e.
A disc 10 that is immovable relative to the machine frame as shown in Fig. 6c.
Two rotational centers 103c are rotatably attached to each side of the rotation center 3b using pins. The mounting pin and blade roller 103d of the unit blade 103a provided on the side opposite to the blade drive lever 104 are connected to the oblong escape hole 103 provided in the unit blade 103a on the blade drive lever side.
e and protrudes toward the blade drive lever 104.

As shown in FIG.
Two grooves 104a and one arm 104b protruding in the radial direction are provided.
A plunger of a solenoid 106 and a spring 107 are connected to the tip of b.

Therefore, when the solenoid 106 is energized, the arm 104d of the blade drive lever 104
is pulled, the blade drive lever 104 rotates by a certain angle, and as a result, the blade roller 103d that engages with the groove 104a is displaced around the clutch shaft 32, and the pawl release blade 10 is rotated as shown in FIG. 6d.
The outer circumference of No. 3 changes from the position shown by the chain line to the position shown by the solid line, and the outer diameter decreases. Claw release blade 1
03 is in the swollen state, the claw roller 102b is in the claw release blade 103 as shown in FIG. 6a.
The toe 102a is pushed out by the outer periphery of the wheel 1
Even when the wheel 101 rotates, the hooking pawl 102 remains stationary together with the gear that supports it. However, when the outside diameter of the pawl release blade 103 is reduced, as shown in FIG. 6b, The claw roller 102b of the hooking claw 102 approaches the wheel 101, the claw tip 102a slides on the outer peripheral surface of the wheel 101, and engages with the groove 101a when it rotates,
Hook claw 102 and gears 42, 43 to which it is attached
Or 44 rotates integrally with the wheel 101.
In other words, the clutch engages.

When the gear and the hook 102 rotate by a predetermined angle, the end of the hook 102 opposite to the hook is pushed down by the release pin 105, and the engagement between the hook 102a and the groove 101a of the wheel 101 is released. This causes the clutch to break.

As shown in FIG.
Gears 47, 48, and 49 are provided to rotate integrally with gears 42, 43, and 44, which are connected to the same. The gear ratios of the gears 42 and 47, 43 and 48, and 44 and 49 are set as follows.

Gear Copying magnification (m) Gear ratio 41, 47 1 1 43, 48 1.143 1/1.143 44, 49 0.7647 1/0.7647 In other words, the gear ratio of each gear train is inversely proportional to the copying magnification m.

A scanning drive pulley 30 is fixedly attached to the drive shaft 33, and the mirror drive wire shown previously in FIG. 3b is wound around it. This drive wire is also wound around a pulley provided on the shaft of the scan return servo motor 29.

Therefore, when the copying machine is turned on and a desired copying magnification is selected using a push button switch or the like, the solenoid 106 corresponding to the selected magnification is turned on, and the fixed point engaging pawl corresponding to that magnification is turned on by the aforementioned action. Clutch 39, 40 or 41 is engaged and gear 4
2, 43 or 44 rotate integrally with the clutch shaft. As a result, the drive shaft 33 rotates at a rotation speed inversely proportional to the copying magnification m, and the wire rope wound around the scanning drive pulley 30 moves the first mirror and the light source lamp to 1/m of the scanning speed V at the same magnification. The second and third mirrors are driven at half that speed. In this way, scaling of the document in the lateral direction (scanning direction) is achieved.

Generally, when the scanner starts scanning, it is unavoidable that the scanner vibrates, so as shown in Figure 8a, the reference edge position of the document 3 is moved to the starting position by a length L _s where the vibration of the scanner does not affect the image. As shown in Figure b, the starting position of the photosensitive drum 10 is shifted by L _Dn from the image forming reference position.

In this example, L _s = 15 mm,
When copying at the same size, L _Dn = L _s = 15 mm.

Now, suppose copy magnification m=1, m=0.7647, m=
10 clutch wheels corresponding to each of 1.143
The deviation angle θm from the reference position of the position of the engaging groove 101a provided on 1 is made proportional to the copying magnification m, and as shown in FIG. Assume that θm=10.953° m=1.143 〃 θm=16.372°. Further, the diameter of the photosensitive drum 10 and the diameter of the scanning drive pulley 30 are both set to 120 mm. Photosensitive drum 10 and clutch shaft 3
2 rotates at the same rotational speed in synchronization with the photoreceptor drum, so the circumferential length L _Dn from the start position of the photosensitive drum to the image leading edge reference position is as follows with respect to the angular magnification.

L _Dn = 15 mm x (θm/14.324°) Copy magnification (m) L _Dn 1 15 mm 0.7647 11.47 mm 1.143 17.154 mm That is, L _Dn is proportional to the magnification m.

However, since the scanning drive pulley 30 rotates at a speed inversely proportional to the magnification m, L _s = L _Dn /m, and L _s
is always kept at a constant value of 15mm. Therefore, the distance between the scanner start position and the document reference edge position
_Ls does not need to be changed depending on the magnification, and the image leading edge position (reference position) on the photosensitive drum remains the same regardless of the magnification.

However, as described above, the photosensitive drum 10 and the transfer drum 15 are rotated synchronously at the same speed by meshing gears provided at one end of each, and as shown in FIG. The image leading edge reference position on the photosensitive drum 10 (the position indicated by "base" in the figure),
The leading edge position of the transfer paper gripped by the clamper on the transfer drum 15 is designed to perfectly match the transfer position, so even in the case of reduced copying, the leading edge position of the image on the photoreceptor drum will be at the same position when the size is the same. In this case, as described above, there is an increased possibility that part of the original image will be missing on the copy due to the clamper.

In order to prevent this, in the variable magnification optical device of the present invention, in the case of reduction copying, the leading edge position of the image formed on the photoreceptor is shifted rearward by an appropriate amount from the position when the image is at full magnification.

To achieve this, it is sufficient to rotate the photoreceptor drum in advance by the amount necessary to shift the image leading edge position, and then to engage the engagement pawl 102 of the clutch with the groove of the wheel 101. That is, the seventh
For reducing the position of the meshing groove of the fixed point meshing clutch wheel explained in the figure, set the deviation angle θm from the reference position by an appropriate amount from the value proportional to the magnification m (10.953° in the example in the figure). Just make it bigger. This is shown in FIG. FIG. 9 is a side view of the wheel 101 of the fixed-point engagement clutch 41 for reduction copying, and the engagement groove shown by the broken line in the figure is located at such a position that the leading edge of the image on the photoreceptor coincides with that at the same magnification. , the position of the groove according to the present invention is provided at a position shifted in such a way that θm becomes larger than this.

In the present invention, a constant-point engaging pawl clutch is used as the variable magnification clutch, so the timing at which the clutch engages is extremely accurate for the selected magnification, and the position of the leading edge of the image on the photoreceptor drum shifts with each image forming process. Never. Therefore, not only monochrome copying but also color copying using the three-color separation image superimposition method can be made at variable magnification, and the leading edge of the image will not be cut off during reduction copying as described above.

Now, when the clutch corresponding to the selected magnification is engaged and the gear corresponding to the clutch rotates by a predetermined angle, the tail of the hook 102 is pressed by the release pin 105, and the wheel 101
is disengaged from the groove 101a, and the rotation of the drive shaft 33 and scanning drive pulley 30 is stopped. At this time, the hook 102 turns on a micro switch (not shown) to turn on the scan return servo motor 29, and drives the mirror drive wire rope in the opposite direction to the scanning direction to return the scanner to the scan start position.

Effects As described above, according to the present invention, the leading edge position of the image on the photoconductor does not shift during each image forming process even during variable-magnification copying, which eliminates the color separation image overlay method in which image position shift is the most problematic. It is now possible to perform variable-magnification copying even with color electrophotographic copying machines, and it is also possible to obtain full-scale copies without missing the original image even when making reduced copies, achieving excellent effects that were previously unachievable. be able to.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the schematic configuration of a known color separation image superimposition type color electrophotographic copying machine, and FIG. A schematic diagram illustrating the variable magnification system, FIG. 3a is a side view showing the main parts of the lens and mirror drive system of the variable magnification system shown in FIG. 2, and b schematically shows the entire mirror drive wire system. FIG. 4 is a perspective view showing the structure of the variable magnification scanning drive unit of the present invention; FIG. 5 is an exploded perspective view showing an example of a constant-point engagement pawl clutch used in the device of the present invention; FIG. is an exploded view showing its constituent parts, No. 7
The figure is a schematic diagram showing an example of the position of the pawl engaging groove of the clutch so that the position of the leading edge of the image on the photoreceptor remains constant regardless of the magnification. Fig. 9 is a schematic diagram showing the relationship with the placement reference position, b is a schematic diagram showing the relationship between the image forming reference position of the photosensitive drum and the transfer paper leading edge reference position of the transfer drum in that case, and Fig. FIG. 3 is a side view showing the position of the meshing grooves of the wheels of the fixed point meshing clutch for reduction copying of the optical magnification device. 2... Original table, 4-9... Exposure system, 1
0... Photosensitive drum, 15... Transfer drum, 17
... Transfer paper, 18 ... Clamper, 30 ... Main scanning pulley, 39, 40, 41 ... Fixed point engagement clutch.

Claims (1)

[Scope of Claims] 1. An original placing table; a photosensitive drum; an image of the original placed on the original placing table is color-separated, and the original image is the same size as that of the original or the image of the original is reduced. means for forming an electrostatic latent image on the photoreceptor drum; means for developing the electrostatic latent image; rotating in synchronization with the photoreceptor drum;
A transfer drum is provided with a clamper that grips a predetermined length of the leading edge of the transfer paper in the rotational direction, and the developed image formed on the photoreceptor drum is gripped by the clamper and formed on the transfer paper wound on the transfer drum. a transfer means for overlapping transfer, and a reference position on the photosensitive drum corresponding to a reference position of the leading edge of the document on the document mounting table and a leading edge position of the transfer paper wound around the transfer drum at the time of starting the transfer, etc. It is characterized by comprising means for making the doubling time coincide with the time, and for reducing the time so that the leading edge position of the transfer paper has a positional relationship corresponding to the downstream side of the reference position on the photosensitive drum with respect to the rotational direction of the transfer drum. A color variable-magnification copying device.