JPH047564A - Copying machine - Google Patents

Abstract

PURPOSE:To stabilize picture quality by controlling the driving of a conveying means for refixation so that a recording form passes through a fixing means plural times when an overhead projector (OHP) mode is selected. CONSTITUTION:A conveyance control means (CPU) controls the driving of the conveying means 58 for refixation so that the recording form passes through the fixing means several times when the OHP mode is selected and the size of the recording form is larger than a specific value or when the OHP mode is selected and the image of an original has a color other than black. Then a fixing speed control means (CPU) make the conveying speed of the recording form to the fixing means 51 slower than usual when the OHP mode is selected and the original image has a color other than black, and holds the conveying speed of the recording form to the fixing means 15 as usual regardless of the selection of the OHP mode when the original image includes only black. Consequently, the picture quality is stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a copying machine that copies an image of an original by an electrophotographic process using at least one developing means that uses a color as a developing color.

[Conventional technology]

The electrophotographic process consists of a charging process in which the surface of a photoreceptor is uniformly charged, an exposure process in which the photoreceptor is irradiated with light to partially eliminate charge in the charging direction and a latent image is formed according to image information, and a latent image is formed in accordance with the image information. A development process in which toner in a developer is attached to the image to form a toner image, a transfer process in which the toner image is transferred to recording paper (hereinafter referred to as "paper"), and the transferred toner image is fixed on the paper by heating. It consists of a fixing process and is widely used as a method of forming hard copy images.

In general, copying machines using an electrophotographic process use plain paper (opaque) as well as overhead projector (OHP) paper.
Transparent sheets can be used as paper.

Now, when forming an OHP copy image containing colors such as red or blue, in order to improve hue reproducibility, the colored toner image is completely melted on a transparent sheet and its surface is flattened. It is necessary to ensure transparency by doing so.

A common method for ensuring transparency is to make the fixing time in the fixing process relatively longer than when copying with plain paper. This method is advantageous in terms of safety compared to a method in which the heating temperature by the fixing means is raised higher than usual.

Therefore, when the OHP mode that ensures transparency is selected using an operation key, conventional copying machines only perform the fixing process of the electrophotographic process described above on the fed transparent sheet. It is composed of That is, it is possible to perform the fixing process multiple times on one transparent resin sheet.

In other words, when obtaining a copy image for OHP using a conventional copying machine, the operator first selects the normal copy mode (the fixing time is the same as for plain paper), and the colored toner image corresponding to the original is semi-fused. The fixed transparent resin sheet is then discharged.

Subsequently, after selecting the OHP mode, the previously ejected transparent resin sheet is manually fed. As a result, the colored toner image is completely melted in the second fixing process, and translucency is ensured.

In addition, conventionally, OHP mode is automatically selected when it detects that the paper is transparent, and in OHP mode,
A copying machine is known in which the fixing time is extended by making the rotational speed of a heating roller serving as a fixing unit slower than usual (Japanese Patent Application Laid-Open No. 188673/1983).

[Problem to be solved by the invention]

As mentioned above, in conventional copying machines that perform the fusing process multiple times, the operator has to manually feed the paper once it has been ejected, making the work cumbersome for the operator and inconvenient to use. There was a problem.

Furthermore, in the electrophotographic process, in order to prevent toner image disturbance (image deterioration) due to expansion and contraction of the paper in the transport direction, the transport speed must be made uniform over the entire surface of the paper.

Therefore, when slowing down the rotation speed of the fixing roller, the rotation speed of the photoreceptor or transfer belt should be slowed down as well as the rotation speed of the fixing roller, or the distance between the transfer position and the fixing position should be at least the length of the paper. Must be.

However, when the rotational speed of the transfer belt or the like is slowed down, it is necessary to slow down the exposure and development speeds as well. In other words, the image forming speed of the entire electrophotographic process is different between the normal copy mode and the OHP mode. For this reason, image formation control becomes complicated, and especially immediately after mode switching,
There is a problem in that it is difficult to obtain the best electrophotographic process conditions (physical property values) suitable for each image forming speed, and the stability of image quality is impaired.

Also, if you want to lengthen the distance between the transfer position and the fixing position to match the size of the paper, you can change the paper size range, for example B.
If an attempt was made to increase the size from 4 to A3, there was a problem in that the copying machine would become larger and the cost would increase accordingly.

Furthermore, when OHP mode is selected, low-speed fixing is performed even though a black-only copy image that does not require transparency is formed, which increases the time required for copying. .

In view of the above-mentioned problems, the present invention provides a copying machine that is easy to use for an operator, allows easy control of electrophotographic process conditions, and has stable image quality when obtaining a transparent copy image of an OHP image. It is intended to.

Another object of the invention is to expand the scope of application regarding the size of recording paper without increasing the size of the copying machine.

Furthermore, the object of the invention of claims 3 and 4 is to
The object of the present invention is to shorten the time required to form a copy image as much as possible.

[Means to solve the problem]

In order to solve the above-mentioned problem, a copying machine according to the invention of claim 1 includes a developing means for forming a colored toner image corresponding to an image of a document, and a fixing means for fixing the colored toner image on a recording sheet. , in a copying machine that copies an image of the document by an electrophotographic process, a re-fixing conveying means for conveying the recording paper sent out from the fixing means to an entrance of the fixing means, and an OHP mode are selected. In some cases, the apparatus further includes a conveyance control means for controlling the drive of the re-fixing conveyance means so that the recording paper passes through the fixing means a plurality of times.

The copying machine according to the invention of claim 2 further comprises: a re-fixing transport means for transporting the recording paper sent out from the fixing means to an entrance of the fixing means; and a paper size detection means for detecting the size of the recording paper. , when an OHP mode is selected and the size of the recording paper is larger than a predetermined value, conveyance control that controls the drive of the re-fixing conveyance means so that the recording paper passes through the fixing means a plurality of times; and means.

The copying machine according to the third aspect of the present invention includes a re-fixing conveyance means for conveying the recording paper sent out from the fixing means to an entrance of the fixing means, a document reading means for reading an image of a document, and the document reading means. color discrimination means for discriminating the color of the image of the document from the document information read by O;
Conveyance control means for controlling drive of the re-fixing conveyance means so that the recording paper passes through the fixing means a plurality of times when the HP mode is selected and the image of the document includes a color other than black; It has the following.

The copying machine according to the invention of claim 4 includes a document reading means for reading an image of a document, a color discrimination means for determining the color of the image of the document from document information read by the document reading means, and an OHP mode is selected. and when the original image includes a color other than black, the conveyance speed of the recording paper to the fixing means is made slower than usual, and when the original image consists only of black, regardless of the OHP mode selection. and fixing speed control means for maintaining the conveyance speed of the recording paper relative to the fixing means at a normal speed.

[For production]

The paper size detection means detects the size of recording paper.

The document reading means reads an image of the document.

The color determining means determines the color of the image of the document from the document information read by the document reading device.

The developing means forms a colored toner image corresponding to the image of the document.

The fixing means fixes the colored toner image onto the recording paper.

The re-fixing conveying means conveys the recording paper sent out from the fixing means to the entrance of the fixing means.

The conveyance control means controls the recording paper when the OHP mode is selected and the size of the recording paper is larger than a predetermined value, or when the OHP mode is selected and the image of the document includes a color other than black. The re-fixing conveyance means is drive-controlled so that it passes through the fixing means a plurality of times.

The fixing speed control means makes the conveyance speed of the recording paper relative to the fixing means slower than usual when the OHP mode is selected and the image on the original includes a color other than black, and when the image on the original consists of only black. , the conveyance speed of the recording paper relative to the fixing means is maintained at a normal level regardless of the selection of the OHP mode.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional front view showing the general structure of the copying machine 1. As shown in FIG.

A photoreceptor drum 3 is placed slightly to the upper left of the center of the copying machine 1 so as to be rotatable in a clockwise direction (direction of arrow M1).
, an editing eraser 5, developing devices 6 to 9, a transfer belt 11 as an intermediate transfer medium, a cleaning device 22, and a main eraser 23 are provided.

The photosensitive drum 3 is provided with a photosensitive layer on its surface, and the surface is uniformly charged by passing through the main eraser 23 and the charger 4, and the optical system 27 described later
is exposed to light to form a latent image.

The editing eraser 5 is an LED in which a large number of LEDs are arranged in a row in a holder arranged along the axial direction of the photoreceptor drum 3.
The latent image on the photosensitive drum 3 can be partially erased.

The timing of turning on and turning off each LED is individually controlled by an erase controller in the image processing section 100 (see FIG. 3).

Each developing device 6, 7, 8.9 has yellow (Y
), magenta (M), cyan (C), black (B
Toner density sensors (ATDC sensors) 717, 71m, 71c and 71k are provided to control the density of the toners of these colors. Further, above the developing device 6, a humidity sensor 70 is provided to detect the humidity inside the copying machine 1.

Note that the developing units 6 to 9 are not limited to a type in which they are fixedly arranged around the photoreceptor drum 3, but may be in a type in which the developing units 6 to 9 are integrated and movable in the vertical direction, for example. Any type of toner may be used as long as it can selectively supply toner of different colors to the photoreceptor drum 3.

The transfer belt 11 is used to temporarily hold the toner image developed on the photoreceptor drum 3 by the developing devices 6 to 9 to transfer (secondary transfer) onto the paper P.
2 to 16 are extended, and are supported so as to be rotatable in the counterclockwise direction (in the direction of arrow M4) while always being in contact with the photoreceptor drum 3.

A transfer charger 17 for primary transfer of the toner image from the photosensitive drum 3 onto the transfer belt 11 is disposed inside the transfer heald 11, and a transfer charger 17 for secondary transfer is disposed outside the transfer heald 17. A belt cleaner 19 having a charger 20, a separation charger 21 for separating the paper P from the transfer belt 11, and a fur brush 19a for cleaning the outer surface of the transfer heald 11 is provided. The fur brush 19a can be pressed into contact with the transfer heald 11 (during cleaning) or separated from the transfer heald 11.

Further, between the rollers 15 and 16 and between the rollers 12 and 13, there are hert mark sensors 72 for detecting the rotational angular positions of the transfer bells 1 to 11, respectively.
72s are fixedly arranged.

A document platen glass 28 is arranged on the top surface of the copying machine 1, and a document size detection device that moves to the rear side directly below the document platen glass 28 and detects the size of the document plate without interfering with scanning. A device 101 is installed.

Further, an optical system 27 is arranged at the top of the copying machine 1. The optical system 27 is located below the document platen glass 28 by an arrow M5.
A scanner 30 capable of reciprocating in the direction (forward direction) and arrow M6 direction (backward direction), a main lens 35 whose position is adjusted according to the copying magnification, a filter selection device 36 that performs color separation exposure, and a filter. A fixed mirror 37 that guides the scanning light reflected by the mirror attached to the selection device 36 to the photosensitive drum 3, and a color image sensor 3 that receives the scanning light that has passed through the mirror of the filter selection device 36.
When the scanner 30 moves forward, it scans the document tray and exposes the photosensitive drum 3.

The scanner 30 includes a first slider 31 having an exposure lamp 33 and a mirror 34, and a second slider 32 having mirrors 35a and 35b. The second slider 32 is driven by a scan motor (not shown) to move forward at a speed of v/2n (n is the copying magnification). scanner 30
The end of the backward movement of the scanner 30, that is, the return of the scanner 30 to the reference position (home position), is detected by a scanner home switch 74 consisting of a photo sensor.

The filter selection device 36 includes a half mirror 36ND (the ratio of transmission and reflection is 6:4) and three filter mirrors 36YB centered on the axis 36a.

36MG and 36CR are provided radially at an angle of 90 degrees to each other, and one of these mirrors is selectively switched by rotating.

Filter mirrors 36YB, 36MG, and 36CR are integrated mirrors and filters by depositing blue (B), green (G), and red (R) color separation filters on the mirror surface, respectively. ,M
, C are used corresponding to the toners of each color.

In exposure scanning for image formation, the reflective surface of the selected mirror is positioned so as to be inclined clockwise by approximately 10 degrees with respect to the vertical plane, so that the scanning light is directed toward the photoreceptor drum 2.
is guided to the exposure point.

In addition, in the preliminary scan to read the image of the document sheet prior to the exposure scan, the half mirror 36ND is used.
is selected, and the MTF (
In order to improve the imaging power), it is positioned perpendicular to the direction of incidence of the scanning light. 77 is a filter selection device 3
This is a rotational position detection sensor for determining the home position of the filter mirror 36CR, and FIG. 1 shows a state in which the filter mirror 36CR is selected and positioned.

In addition, in the following description, half mirror 36ND is used.

Filter mirrors 36YB, 36MG, and 36CR are used as ND filters, B filters, and G filters, respectively, based on their color separation characteristics.
Filter, sometimes called R filter.

The color image sensor 38 is provided with three element rows consisting of a large number of light receiving elements arranged in the main scanning direction, and the first to third element rows are provided with an R filter and a G filter, respectively.
A filter and a B filter are provided. One light receiving element corresponds to one pixel of the original image, and each light receiving element generates a photoelectric conversion signal SO corresponding to the intensity of reflected light for one color of the pixel.
is sent to the image processing section 100 as document information (see FIG. 3).

On the other hand, an upper paper cassette 42 and a lower paper cassette 43 containing paper P are installed in the lower part of the copying machine 1, and the left side of the copying machine 1 is equipped with a paper cassette 42 for storing paper P and a lower paper cassette 43 for manually feeding the paper P. A manual paper feed port 41 is provided which is opened by opening the door 41a, and these paper cassettes 42, 43, and manual paper feed port 41 are used selectively when feeding paper.

The paper cassettes) 42, 43 each have pickup rollers 44, 45 that feed out the paper P one by one, and paper size sensors 81, 8 that detect the size of the paper P.
2. Paper empty sensors 83 and 84 are installed to detect the lack of paper P, and the manual paper feed slot 4
1 is provided with a manual feed sensor 87 for detecting insertion of paper P.

The paper P fed out from the paper cassette 42 is conveyed to the timing roller 46 by a paper feed roller 47, and the paper P fed out from the paper cassette 42 is conveyed to the timing roller 46 by paper feed rollers 4B and 47, where it is placed on standby. do.

Further, the paper P inserted into the manual paper feed port 41 is conveyed to the timing roller 46 by the manual feed roller 49 .

A paper detection sensor 85 is provided near the paper feed roller 47 to detect the presence or absence of paper P in the paper feed path R1 between the paper feed roller 47 and the timing roller 46. A timing sensor 86 for detecting the position of the leading edge of the paper P is provided.

The waiting paper P is conveyed in synchronization with the transfer belt 11 by the rotation of the timing roller 46, and the toner image is secondarily transferred from the transfer belt 11 to the paper P at the transfer position. Thereafter, the paper P is sent to the fixing unit 51 by the transport heald 50 having a linear distance corresponding to an A4 size paper.

The fixing unit 51 includes an upper roller 52 having heater lamps 54 and 55 and a lower roller 53 having a heater lamp 56, and fuses the toner image to fix it on the paper P. Each day - near La 52 and 53,
Temperature sensors 91,92 each consisting of a thermistor are provided.

The paper P on which a desired copy image has been formed by fixing the toner image is transferred to the ejection roller 5 with an ejection sensor 88 disposed nearby.
7 to the sorter 2 and discharged to the storage tray 61 of the sorter 2 or the sorting pen (shelf) 62.

Further, the copying machine 1 of this embodiment is equipped with a return device 60 for re-fixing, which is used when copying in OHP mode, which will be described later. The return device 60 returns the paper P that has passed through the fixing unit 51 to the entrance of the fixing unit 51 (transport belt 50
The conveyance mechanism 58 has a return path R2 leading from the discharge side (exit) of the fixing unit 51 to the above-mentioned timing roller 46, and It is comprised of a switching claw 59 for switching the conveying direction of P to the discharge roller 57 side or the return path R2 side. The switching pawl 59 is driven by a supination solenoid. The transport mechanism 58 includes a guide plate and transport means such as belts or rollers provided at appropriate locations. A detection sensor 89 is arranged.

This return device W60 makes it possible to perform the fixing process on the paper P multiple times without manually refeeding the paper as in the conventional method.

In FIG. 1, 24 is a main motor that mainly drives various parts related to feeding and transporting paper P, and 25
26 is a PC motor that drives the photosensitive drum 3, transfer heald 11, etc., and 26 is a cooling fan.

In the copying machine 1 configured as above, the above-mentioned Y, M,
Monochrome copy image of each single toner color of C and BK, Y
R (Y and M), G (Y and C), and B obtained by superimposing toner images of two of the three primary colors of , M, and C.
The color obtained by superimposing the composite monochrome copy image of (M and C) and the three primary color toner images (
It is possible to create full-color (full color) copied images.

In forming single toner color and composite monochrome copy images, a half mirror 36ND is used to expose and scan the original, and the latent image formed on the photoreceptor drum 2 is developed according to the specified color. The toner image is developed using any one of the containers 6 to 9 and transferred onto the transfer belt II. Furthermore, in the case of a composite monochrome copy image, the same original document is exposed and scanned again by the half mirror 36ND, and the toner image developed using the developing devices 6 to 9 different from the previous one is transferred to the transfer belt 11. The two color toner images are superimposed on a transfer bell (11).

In addition, in forming a color copy image, the copying machine 1:
Y, M to improve the reproducibility of black parts.

Four color toners, including C and BK, are sequentially used. That is, a total of four exposure scans are performed on the same document, and for each scan, the B, G, R, and ND filters and the developing device 6 are
9 to 9 are selectively switched to form and develop a color-separated latent image on the document sheet, toner images are sequentially transferred to a transfer belt 11, and the toner images of each color are superimposed on the transfer belt 11.

When overlapping toner images (hereinafter referred to as "multiple transfer"), it is necessary to transfer each toner image to the same position on the transfer belt 11. Therefore, in the copying machine 1 of this embodiment, the above-mentioned Helt mark The start timing of movement of the scanner 30, that is, the start timing of forming a latent image on the photoreceptor drum 3, is controlled based on the timing of generation of the belt mark signal 310 from the sensor 72 or 72s.

When forming a color copy image, a preliminary scan is performed to distinguish the original image into a color image area containing colored images and a monochrome image area consisting only of achromatic colors.
When creating an image using each of the C toners, the editing eraser 5 erases the latent image corresponding to the monochrome image area prior to development, and conversely, when creating an image using BK toner, the latent image corresponding to the color image area is erased prior to development. do. That is, the color image area is reproduced by multiple transfer of Y, M, and C toners, and the monochrome image area is reproduced only by BK toner. As a result, it is possible to obtain clear reproduced images without subtle color shifts for images with small line widths such as characters and line drawings that are generally expressed in black, and it is also possible to obtain clear reproduced images without subtle color shifts for images with small line widths such as characters and line drawings that are generally expressed in black. A natural-looking copy image with good reproducibility can be obtained.

FIG. 2 is a plan view of the operation panel OP provided on the top surface of the copying machine 1.

On the right side of the operation panel OP, there are a key 250 for specifying automatic paper selection mode and its display LED 252, a key 251 for specifying automatic magnification selection mode and its display LED 253.
, a print key 200 for starting the copying operation.
, an LED 200a that lights up when copying is possible, a numeric keypad 202 for setting copying conditions such as the number of copies,
7-segment LED 201 to display the number of copies, clear/stop key 203, interrupt key 204, magnification up and down keys 205 to set the copy magnification
, 206, 3-digit 7-segment 1-L displaying copy magnification
ED20? , up and down keys 210 and 208 for manually setting the density of the copied image step by step, an LED 211 for displaying the density level of the copied image, an auto density setting key 209, and an auto density display LED 222 for normal copying operations. Keys and display L used in
ED is placed.

Also, on the left side of the operation panel OP are Y and M.

LED 223 that indicates the shortage of toner for each color of C and BK
Y, 223M, 223C, 223BK, LED 224a that indicates whether the waste toner storage container is full, interrupt display LED 224b, paper P jam display LED 224
c.) Rubble display LED 224d, each color (Y, M, C, R, G, B,
Color keys 225 to 231 corresponding to BK), full color key 232.0HP (,
The OHP key 233 is used to select the OHP mode used when the paper P is a transparent sheet for use with a T-Bahend projector. A book key 234 used for copying, LEDs 235 to 244 for display corresponding to each of the keys 225 to 234, and a paper cassette 42.
Paper selection keys 245, 246 for selecting paper cassette 43, LED 24 for displaying the selected paper cassette 42, 43
7.248, Paper empty LED 2 indicating the lack of paper P in the selected paper cassette 42, 43
49 are arranged.

In addition, in the following explanation, color keys 225, 226.2
27, 228, 229, 230, and 231 are sometimes referred to as the Y key, M key, C key, R key, C key, B key, and BK primary key, respectively.

FIG. 3 is a block diagram of the control section 400 of the copying machine 1.

The control unit 400 controls the entire operation of the copying machine I.
U (centering on the central processing bag 401, the scanner 30
a scan motor controller 402 that controls the drive of
A lens motor controller 403 controls the movement of the main lens 35 according to the copying magnification, and a filter mirror motor controller 404 controls the drive of the filter selection device 36.
, a charger controller 405, an exposure lamp controller 406, and the like.

In addition to each controller, the CPU 401 includes a switch matrix 451 and a display matrix 452 in which each operation key on the operation panel OP and various display LEDs are arranged vertically and horizontally, 7-segment LEDs 201 to 207, a decoder 453 corresponding to the switch matrix 451, and each display. Driver 45 that supplies lighting power to LED
4,455 are connected.

The CPU 401 also includes an image processing unit 100 that discriminates the color of each minute area of the document and controls the editing eraser 5 based on the discrimination results, and a combination of outputs from a plurality of reflective photosensors. A document size detection device 101 is connected thereto, which uses a known detection method to determine the size and placement direction (vertical or horizontal) of the document tray.

Furthermore, output signals from sensors arranged in various parts of the copying machine 1 are input to the analog input port and digital input port of the CPU 401, and signals from each of these sensors and the switch matrix 451, as well as the image processing section 100.
Based on the data from the document size detecting device 101 and the document size detecting device 101, on/off or operation level control of various parts such as the motors 24 and 25, various clutches such as a developing clutch, and each charger connected to the output port is performed.

Note that the CPU 401 has a built-in nonvolatile memory for storing management data such as the cumulative number of copies and the number of jam occurrences.

Next, the operation of the copying machine 1 will be explained with reference to a flowchart.

FIG. 4 is a main flowchart schematically showing the operation of the CPU 401.

When the power is turned on and the program starts, first,
Initial settings are made for registers and peripheral ink faces (step #1), and an internal timer is set to specify the length of one routine of the CPU 401 (step #2).
.

In step #3, image forming processing related to the electrophotographic process is performed, and in step #4, scanning processing for scanning the original document is performed.

In step #5, belt mark detection processing is performed to determine the timing of multiple transfer, and in step #6, paper feeding processing is performed to control the feeding and conveyance of paper P. Further, in step #7, a manual paper reception process is executed to determine the timing of manual paper feeding by the manual paper feed port 41.

Next, a temperature adjustment process for adjusting the temperature of the fixing unit 51 (
Step #8), Heald cleaning processing for cleaning the transfer heald 11 (Step #9), Lens processing for controlling the movement of the main lens 35 according to the copying magnification (Step #10), and Operation keys on the operation panel OP Other processing such as input processing for receiving and receiving signals from
A series of copy sequence processes consisting of 1) are executed.

After executing these processes, an internal timer is waited in step #12, and the process returns to step #2. As a result, the length of one routine is kept constant, and each process from step #2 to step #12 is repeated while the power is turned on.

5(a) to 5(c) are flowcharts of the paper feeding process of FIG. 4.

In this routine, first the paper feeding state indicated by the count value of the state counter is checked (step #300), and the following processing is executed in each state.

In the initial state immediately after the power is turned on and in the standby state after the copying operation is completed, the state is "0".

In state "0", first, the paper feed permission flag is checked (step #301).

The paper feed permission flag is used when the main motor 2
4 and the PC motor 25 are turned on, the motor start-up timer is set to wait for the rotation of each motor to become stable, and is set when the timer finishes counting, and is reset when the ejection of the paper P is completed.

When the paper feed permission flag is set, the manual feed tray ( ) flag is subsequently checked (step #302).The manual feed reception flag is set according to the status of each part in the manual feed paper reception process as described later. and reset.

When the manual feed acceptance flag is in the reset state, the pickup roller 44 or 45 and the necessary The paper feed roller 47.4B is turned on. That is, the driving force of the main motor 24 is transmitted to each roller via the clutch (step #303).

Also, if the manual feed reception flag is set,
The manual feed roller 49 is turned on (step #304).

After starting to feed paper from the paper cassettes 42, 43 or the manual paper feed port 41 in this way, the stay 1 is updated to rl (step #305).

In state "1", an on-check is performed to determine whether or not the timing sensor 86 is in the on state, that is, whether or not the paper P is detected.

When the leading edge of the moving paper P reaches the position where the timing sensor 86 is provided and the timing sensor 86 is turned on, the timing roller 46 and the rotating pickup roller 44 or 45 are turned off (step #
312, step #313). Note that the paper feed rollers 47 and 48 that were previously turned on continue to rotate. As a result, the paper P is curved at the entrance of the timing roller 46, and a so-called paper loop is formed for correcting the inclination of the paper P with respect to the transport direction.

Then, set the paper loop timer to time the time it takes to obtain a suitable paper loop. Step #3
14), update the state to "2" (step #31
5).

In state "2", first, the paper loop timer is counted up, that is, the count value is updated (step #321). Thereby, the time measurement by the paper loop timer progresses each time one routine of the main flowchart is executed.

Next, a check is made as to whether the count number of the paper loop timer has reached a predetermined value, that is, a check is made as to whether or not time counting has ended (step #322).

If the timer has finished counting, continue to check the manual feed roller 49 for manual paper feeding (step #3).
23).

If the manual feed roller 49 is in the off state, the rotation of the paper feed rollers 47 and 48 for automatic paper feed is stopped (step #3
24). Moreover, if the manual feed roller 49 is in the ON state,
Stop the rotation of the manual paper feed roller 49 (step #
325).

After completing these processes, the state is updated to "3".

In state "3", it is checked whether it is the registration timing that defines the alignment of the toner image on the transfer heald 11 and the paper P (step #331).

If it is the registration timing, the timing roller 46 is turned on to start transporting the paper P to the transfer position (step #332).

Next, it is checked whether the OHP mode is selected by the OHP key 233 (step #333).

Here, the OHP mode means that the rotational speed of each roller 52, 53 of the fixing unit 51 is made slower than normal, or the paper P is transported so as to pass through the fixing unit 51 multiple times using the return device 60. This is an operation mode in which the heating time for fixing a toner image on one sheet of paper P is made longer than usual. When a copy image is formed in the OHP mode, the toner is completely melted on the paper P, and the surface of the toner image becomes flat, so that the translucency of the colored portions of the copy image is ensured.

First, if the OHP mode is not selected, a series of processes for normal conveyance and discharge are executed. That is, when continuously conveying a plurality of sheets P, a paper feed interval timer is set to keep the interval between each sheet P constant (step #334), and the state is updated to "4" (step #335). ). Then, in state "4", update the paper feed interval timer (Step #341)
, by repeating state "4", step #341 is executed a number of times corresponding to the time set in the paper feed interval timer, and when the time measurement of the paper feed interval timer ends (step #342), the next paper P is fed. The state is returned to the initial state "0" so as to move to paper operation (step #343).

On the other hand, if the OHP mode is selected in the above-mentioned state r3J, it is checked whether the copy image to be formed needs to be translucent (step #336). here,
When it is determined that translucency is unnecessary, full-color reproduction is specified, but when the image processing unit 100 determines that the original image is a black monochrome image,
In some cases, black (BK) is designated as the development color for a monochrome copy using the BK primary key 31. If it is not necessary to ensure such transparency, the above-mentioned series of processes corresponding to normal conveyance and discharge are executed.

On the other hand, if it is necessary to ensure the translucency of the photographed image,
The following processing specific to OHP mode is executed.

That is, a speed change determination timer is set (step #337L state is advanced to "5".
This is for detecting the size of the paper P, which is a criterion for determining whether or not it is possible to reduce the rotation speed of the toner image in order to prevent disturbance of the toner image.

In state "5", the speed switching judgment timer is updated (step #351), and then the current value of the speed switching judgment timer is defined by the distance between the secondary transfer position and the fixing position and the transport speed of the paper P. It is determined whether the value is smaller than the value (step #352).

If the value of the speed switching judgment timer exceeds the specified value,
The size of the paper P is large enough to straddle the secondary transfer position and the fixing unit 51 (for example, A3 size). Therefore, in this case, since the rotational speed of each roller 52, 53 of the fixing unit 51 cannot be lowered, the switching claw 59 is operated in step #353 so that the paper P passes through the return path R2 of the return device 60. ), advance the state to "8".

If the value of the speed switching determination timer is less than the specified value, the timing sensor 86 is checked (step #355).

If the timing sensor 86 is in the OFF state, the trailing edge of the paper P has already passed the timing sensor 86 and the size of the paper P is small, so each roller 52, 5
A reduction in rotational speed of 3 is possible. Therefore, next step #356) is to set a speed switching start timer to wait for the trailing edge of the paper P to pass the secondary transfer position.
Update the state to "6".

In state "6", the speed switching start timer is updated and step #361L checks for completion of timing (
Step #362).

When the speed switching start timer finishes counting, the rotational speed of the main motor 24 is left unchanged, and the rotational speed of each roller 52, 53 of the fixing unit 51 is slowed down using a clutch or the like (step #363).

In addition, in order to prevent damage to the paper P, the fixing unit 51
The drive speed of the discharge roller 57 and the sorter 2 is made slower than usual to match the speed at which the paper P is sent out from the
Step #364).

Then, update the state to “7” (step #36
5).

In state "7", step # is performed to confirm the completion of ejection of the paper P based on the detection state of the ejection sensor 88.
Step #372: Return the driving speed of the 371L fixing unit 51, sorter, etc. to normal speed. Step #
373), returns the state to "0".

In state "8", the return paper detection sensor 89 is checked (step #381), and after waiting for the paper P to be sent to the return path R2, the state is changed to "8".
9” (step #365).

In state "9", the return paper detection sensor 89 is checked again (step #385).
After confirming that the trailing edge of the paper P has passed the return paper detection sensor 89, the switching claw 59 is switched to close the return path R2 (step #386). Then update the state.

In state "10", step #391L stay 1 is returned to "0" to confirm completion of ejection of paper P (
Step #392).

FIG. 6 is a flowchart of the manual paper reception process shown in FIG. 4.

First, the manual feed sensor 87 is checked (step #401L) When the paper P is inserted into the manual paper feed slot 41, the next step is to check whether the copying machine 1 is in a standby state (step #401L). #402).

If it is in the standby state, the above-mentioned manual feeding acceptance flag is set (step #403).

If the state is other than the standby state, based on the value of the counter that counts the number of copies, the paper P being fed at that time, that is, the paper P that has not been ejected, reaches the number of copies specified by the numeric keypad 202. It is checked whether it corresponds to the last sheet in the list (step #404).

If you are dealing with a sheet other than the last one, the next sheet P will be fed from the paper feeder) 42.43, so
In this case, the manual feed reception flag is reset to prevent double feeding of paper P (step #407).

In addition, when corresponding to the last sheet, the transport state of paper P, that is, the state in the paper feeding process described above, is "8".
～Determine whether it is other than “10” (Step #4
05).

If the answer is NO in step #405, the return device 60 will carry out the transfer, so the manual feed acceptance flag is reset in this case as well.

If YES in step #405, then on-check the paper detection sensor 85 (step #4
06).

When the paper detection sensor 85 is in the ON state, exposure scanning is repeated for multiple transfer, etc., and in this case, the paper P in the paper feed path R1 and the paper from the manual paper feed port 41 are In order to prevent overlap with P, the manual feed reception flag is reset.

If the paper detection sensor 85 is in the OFF state, there is no fear that the paper conveyance will be hindered, so step #403 described above is performed.
Set the manual feed reception flag in .

According to the above-described embodiment, the conveyance speed of the path from the fixing unit 51 to the storage tray 61 is reduced in accordance with the speed reduction in the fixing unit 51 to obtain translucency of the copied image. Damage to P can be prevented.

According to the embodiment described above, it is possible to form a translucent copy image on a transparent paper P having a length at least twice the linear distance of the conveyor belt 50.

According to the embodiment described above, even when paper P is inserted into the manual paper feed port 41, the presence or absence of paper feed from the paper cassettes 42 and 43 is detected by the paper detection sensor 85, etc., and the manual feed roller 49 Since the drive control is performed, double conveyance of the paper P can be prevented.

According to the above-described embodiment, the processing speed of the other processes in the electrophotographic process except for the fixing process is constant regardless of the copying mode, so the overall electrophotographic process can be easily controlled and the image quality can be improved. stability is improved.

In the above embodiment, Y to reproduce any color
, M, and C toners, the present invention can also be applied to monochrome copying machines as long as images can be formed using colored toners.

〔Effect of the invention〕

According to the invention of claim 1, it is possible to save the operator's effort in obtaining a translucent copy image of an OHP image, and also to facilitate control of electrophotographic process conditions and stabilize image quality. can be achieved.

According to the invention of claim 2, in addition to the above-mentioned effects, it is possible to form a translucent copy image on a large size recording paper without increasing the size of the copying machine, and it is possible to form a translucent copy image on a large recording paper. The scope of application related to this can be expanded.

According to the inventions of claims 3 and 4, even when the OHP mode is selected, for a copied image that does not require ensuring translucency, an image forming process is performed to ensure translucency. This can speed up copying.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional front view showing the general configuration of the copying machine, Fig. 2 is a plan view of the operation panel provided on the top of the copying machine, Fig. 3 is a block diagram of the control section of the copying machine, and Fig. 4 -FIG. 6 is a flowchart showing the operation of the copying machine. ■...Copy machine, 6,7. Death: Developing device (developing means),
38...Color image sensor (manuscript reading means)
, 51...Fixing unit (fixing means), 58...Returning device (transfer means for re-fixing), 100...Image processing section (color discrimination means), 101...Document size detection bag holder (paper size detection means), 401...CPU (conveyance control means, fixing speed control means), D...original, P...paper (recording paper), SO...reading signal (manuscript information). Applicant Minolta Camera Co., Ltd.

Claims (4)

[Claims] (1) A copying machine that has a developing means for forming a colored toner image corresponding to an image on a document and a fixing means for fixing the colored toner image on recording paper, and that copies the image on the document by an electrophotographic process, a re-fixing transport means for transporting the recording paper sent out from the fixing means to an entrance of the fixing means; and a re-fixing transport means for transporting the recording paper sent out from the fixing means to an entrance of the fixing means, and a transport means for causing the recording paper to pass through the fixing means a plurality of times when an OHP mode is selected. and a conveyance control means for controlling the drive of the re-fixing conveyance means. (2) A copying machine that has a developing means for forming a colored toner image corresponding to an image on a document and a fixing means for fixing the colored toner image on recording paper, and copies the image on the document by an electrophotographic process, a re-fixing transport means for transporting the recording paper sent out from the fixing means to an entrance of the fixing means; a paper size detection means for detecting the size of the recording paper; and an OHP mode is selected; and transport control means for controlling the drive of the re-fixing transport means so that the recording paper passes through the fixing means a plurality of times when the size of the recording paper is larger than a predetermined value. Characteristic copying machine. (3) A copying machine that has a developing means for forming a colored toner image corresponding to an image on a document and a fixing means for fixing the colored toner image on recording paper, and that copies the image on the document by an electrophotographic process, a re-fixing conveyance means for conveying the recording paper sent out from the fixing means to an entrance of the fixing means; a document reading means for reading an image of the document; and a document information read by the document reading means. a color discrimination means for discriminating the color of an image on a document; 1. A copying machine comprising a conveyance control means for controlling the drive of a re-fixing conveyance means. (4) A copying machine that has a developing means for forming a colored toner image corresponding to an image on a document and a fixing means for fixing the colored toner image on recording paper, and copies the image on the document by an electrophotographic process, a document reading device that reads an image of the document; a color determining device that determines the color of the document image from the document information read by the document reading device; and an OHP mode is selected and the document image is black. When the image of the document contains only black, the conveyance speed of the recording paper relative to the fixing means is slower than normal, and regardless of the selection of the OHP mode, the conveyance speed of the recording paper relative to the fixing means is set to be slower than normal. 1. A copying machine comprising: a fixing speed control means for maintaining the fixing speed at a normal level.