JPH01179184A - Electrophotographic copying machine - Google Patents

Abstract

PURPOSE:To prevent the imperfection of an image from occurring at the time of fixing and separating by changing the passing speed of copying paper in case of passing a fixing device on a 2nd and subsequent times lower than the passing speed on a 1st time in an electrophotographic copying machine having a double-sided or synthesized copying function. CONSTITUTION:A built-in microcomputer executes a usual copying action at the time of executing a 1st copying action in a double-sided or synthesized copying mode. When it is decided that it is a 2nd and subsequent copying actions, it inputs a system speed changing signal in a driver 3 to reduce the speed of revolution of a main motor 2. Thus, the imperfection of the image can be prevented, which is caused by making the copying paper strongly abut on a fixing and separation pawl at the time of performing the 2nd and subsequent copying actions.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an electrophotographic copying machine, and more particularly to an electrophotographic copying machine having a duplex or composite copying function in which a copy sheet passes through a fixing device multiple times.

<Prior Art> Conventionally, electrophotographic copying machines (hereinafter referred to as copying machines) have a double-sided copying function that copies original images on both sides of a supplied sheet of copy paper to form images. It is known to have a synthetic copying function that overlaps and forms a plurality of images on one side of a copy sheet. In a copying machine that has these functions, for each copying operation of double-sided copying or composite copying, the required paper surface of the copying paper is faced to the photosensitive drum, and the copying paper on which the image has been transferred is The toner is passed through a fixing device twice, for example twice, and heated, thereby fixing the toner and forming an image.

<Problems to be Solved by the Invention> However, in double-sided copying and composite copying by the copying machine, several parts of the image formed on the copy paper by the second and subsequent copying operations are missing in a straight line. This resulted in the problem of image loss.

The present invention was devised in view of such conventional problems, and an object of the present invention is to provide an electrophotographic copying machine capable of preventing image defects caused by second and subsequent copying operations in double-sided copying and composite copying. The purpose is

Means for Solving the Problems> By the way, the inventors of the present invention have studied the above problems and found that the following facts are considered to be the cause of the above-mentioned image defects. In other words, in the second and subsequent copying operations, the toner adheres to and is fixed on the surface of the copy paper on which the image has already been formed in the first copying operation, so that the paper is Since the toner strongly contacts the fixing separation pawl that constitutes the fixing device and an excessive contact force is applied, a portion of the toner is scraped off by the fixing separation pawl.

The present invention was devised based on the above study results, and provides an electrophotographic copying machine having a double-sided or composite copying function in which copy paper passes through a fixing device multiple times. The present invention is characterized in that it includes means for making the passing speed of the copy sheet slower than the first passing speed.

<Function> According to the above configuration, the speed of the copy paper when it passes through the fixing device in the second and subsequent copying operations is slower than the speed at which it passes the first time, so the copy paper does not pass through the fixing separation claw. The abutting force that is applied by abutting on the surface is reduced, and image defects are prevented from occurring.

<Example> Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 is a cross-sectional view showing a schematic configuration of a copying machine, and FIG. 2 is a front view showing a schematic configuration of an operation panel thereof.

A main motor 2, which serves as a common drive source for various devices that make up this copying machine as a system, is disposed inside the copying machine body l. The rotation speed is controlled via the driver 3 by voltage control from a motor (not shown). Further, a photosensitive drum 4, which is rotationally driven in a counterclockwise direction by a main motor 2, is pivotally supported at a substantially central position within the main body 1 of the copying machine. Around the photosensitive drum 4, a charging charger 5, an inter-image eraser 6, a developing device 7, a transfer charger 8, a separation charger 9, and a cleaner device are arranged at fixed positions spaced apart from each other along the rotation direction of the photosensitive drum 4. Peripheral equipment including a main motor 11 and a main motor 11 are provided.

Further, a paper feed system O is provided to the left of the photosensitive drum 4 and its peripheral devices 5 to 11, and a paper discharge system P is provided to the right of these. Further, above these, equipment constituting the optical system Q is provided, while below these is provided a duplex/composite system R configured to realize a duplex or composite copying function in a copying machine. .

The paper feed system 0 includes a paper feed cassette 13 containing copy sheets on which images are to be formed. The copy paper in this paper feed cassette 13 is taken out by a paper feed roller 14 and then conveyed to a timing roller 16 via an intermediate roller 15, and is transferred to the photoreceptor drum 4 by the rotation of this timing roller 16. It is now being supplied. Note that these rollers 14 to 16 are detachably connected to a drive system connected to the main motor 2 via clutches (not shown), respectively. .

Further, the optical system Q is disposed below the original glass 18 provided on the top surface of the copying machine main body l, and is connected to a scanner 22 formed by integrating an exposure lamp 20 and a first mirror 21, and a common holder. 23, a projection lens 26 that moves as the copying magnification changes, and a fourth mirror 27 that similarly moves and swings as the copying magnification changes. has been done. In addition,
The scanning speeds of the scanner 22 and the holder 23 are synchronized with the rotational speed of the main motor 2.

Therefore, in this copying machine, an area on the surface of the photosensitive drum 4 corresponding to an original (not shown) placed between the original glass 18 and the original holder 19 is charged to the charger 5.
After charging the original to a positive polarity, the scanner 22 with the exposure pump 20 turned on is moved toward the left in the figure in synchronization with the rotation of the photoreceptor drum 2 to scan the original. An electrostatic latent image corresponding to the original image is formed on the surface of body drum 4. At this time, the charges in the areas between images on the surface of the photoreceptor drum 4, that is, the areas corresponding to before the front edge and after the rear edge of the document in the scanning direction, are removed by the image-to-image eraser 6.

Then, the electrostatic latent image is visualized (developed) by toner having a negative polarity supplied from the developing device 5, thereby forming a toner image on the surface of the photoreceptor drum 40.

Subsequently, a copy sheet is supplied to the photosensitive drum 4 from a timing roller 16 of a sheet feeding system 0 operating in synchronization with the photosensitive drum 4, and the toner image is transferred onto this sheet by a transfer charger 8. Note that even after the transfer, the toner remaining on the surface of the photosensitive drum 4 is removed and collected by the cleaner device WIO, and the remaining charge is removed by the main motor 11.

On the other hand, the copy paper on which the toner image has been transferred is separated from the photoreceptor drum 4 by a separation charger 9, and is transported to a fixing roller 31 serving as a fixing device via a transport heald 30 that constitutes a paper ejection system P. The fixing roller 31 heats the toner image on the paper surface of the paper, thereby forming an image. Thereafter, the copy paper on which the image has been formed is peeled off from the fixing roller 31 by the fixing separation claw 32 arranged at an appropriate interval, and then the copying paper in the copying machine is set to the normal standard (single-sided) copy mode. ) When the copy mode is set, the paper is ejected onto the paper ejection tray 36 via the intermediate roller 33, the first switching claw 34 that switches the paper conveyance direction, and the ejection roller 35.

Next, in the duplex/combining system R, the copy mode in the copying machine is a duplex copy mode in which images are formed on both sides of a single sheet of copy paper, or a duplex copy mode in which multiple images are superimposed on one side of copy paper. It is used when a composite copying mode is set, and includes a paper refeed cassette 37 that temporarily stores copy paper on which an image has been formed. The paper refeed cassette 37 is provided with a pickup roller 38 which is used not only for storing paper but also for refeeding the paper.

Therefore, when the copy mode is set to double-sided copy mode, the paper discharged from the fixing roller 31 of the paper discharge system P passes through the intermediate roller 33, and after the conveyance direction is switched by the first switching claw 34, the paper is discharged from the fixing roller 31 of the paper discharge system P. , conveyance roller 40
The paper is conveyed through a paper supply path 39 made up of a guide plate. Then, the conveying direction is again changed to the second switching claw 41.
After being switched to the pink-up roller 38 side by the roller 3B, the paper is stored in the cassette 37 by the roller 3B. Further, the paper stored in this cassette 37 is taken out by a pickup roller 38, and this roller 3
The paper is sequentially conveyed by the first to 611th feed rollers 43 to 47 through the paper refeed path 42, which is made up of a guide plate disposed between the paper feed system 0 and the timing roller 16 of the paper feed system 0. The paper is re-fed to the timing roller 16 in an inverted state.

Furthermore, when the copy mode of the copying machine is set to composite copy mode, the paper that has passed through the paper supply path 39 is
After the conveyance direction of the paper is switched to the paper re-supply passage 42 side by the second switching claw 41, the paper passes through this passage 42 and is re-fed to the timing roller 16 with the paper surface of the paper not being reversed. .

In addition, these rollers 33.35.38.40.43~
47 are also detachably connected to a drive system connected to the main motor 2 via a clutch (not shown).

On the other hand, this copying machine is provided with an operation panel 50 as shown in FIG. The operation panel 50 includes a print key 51 . to instruct the start of copying operation. A group of numeric keys 52 for setting the number of copies, a copy number display section 53 consisting of a group of LEDs such as 7-segment elements, a copying operation after the start of the copying operation or during multi-copying (continuous copying of multiple sheets based on the same original) a clear/stop key 54 for instructing to stop and clear the set number of copies;
An interrupt key 55 is provided for instructing an interrupt copying operation. Furthermore, a duplex/composite mode selection key 5 is used to rotate and select either duplex copy mode or composite copy mode as the copy mode of the copying machine.
6. LED 57 that displays that the double-sided copy mode has been selected and set; LED 58 that displays that the composite copy mode has been selected and set; paper size selection key 60 that rotates and selects the copy paper size; , an LED group 61 for displaying the selected paper size, an image density up key 62 and a down key 63 for selecting and setting the image density in steps, and an LED group 64 for displaying the selected image density. It is set up. In addition to the above-mentioned keys and LEDs, the operation panel 50 is also provided with necessary keys such as a copy magnification change key and a display section, but these are not shown.

Furthermore, this copying machine has a built-in microcomputer (not shown), and this microcomputer operates the copying machine based on settings and instructions by operating various keys provided on the operation panel 50. Various main body equipment and optical system QJl such as the main motor 2, etc.
Next, based on the flowchart of FIG. 3 showing the control program when setting the duplex copying mode and composite copying mode in the copying machine according to this embodiment, The following describes the control details.

(1) When the power is turned on and the program starts,
In step 3101, it is determined whether the double-sided/combining mode selection key 56 has been pressed (ON edge) and how many times this key 56 has been pressed. And this key 56 is
For example, if it is pressed once (odd number of times), 8103
Then, the process moves to 3107, selects and sets the double-sided copy mode as the copy mode of the copying machine, turns on the LED 57 to indicate this, and then moves to 3107. If the key 56 is pressed twice (an even number of times) in 5101, the process moves to 5105, where the composite copy mode is selected and set, and an LED is displayed to indicate this.
After turning on (ON) 58, the process moves to 5107.

Furthermore, as a result of the above judgment, the double-sided/combining mode selection key 5
If 6 is not pressed, that is, if neither duplex nor composite copy mode is selected as the copier's copy mode, the copier returns to the normal main routine. Since the contents of the main routine control program for a copying machine are well known, a description thereof will be omitted.

(2) In step S107, it is determined whether or not the print key 51 instructing the start of copying operation has been pressed (ON edge).
Move to 9. Further, as a result of the determination, if the print key 51 is not pressed, the following steps 3109 to 115 are performed.
Skip and return to the main routine.

(3) In step 3109, it is determined whether or not this is the first copy operation after the print key 51 is pressed. If it is the first copy operation, a known copy operation subroutine is called in step S111. After the normal copying operation of forming an image on one side of the copy paper is executed, the process returns to 5109. In addition, the copying operation at this time is as follows.
This is done at normal system speeds on this copier. Also, in 5109, it is not the first copy operation, that is,
If it is determined that this is the second or subsequent copying operation, step S11
Skip 1 and move to 3113.

(4) In step 5113, the system speed change signal outputted from the microcomputer based on the determination result in step 5109 that it is not the first copy operation is transmitted to the driver 3 via the D/A converter (not shown). main motor 2 connected to this driver 3.
rotation speed is reduced. As a result, the speed at which the copy sheet passes through the fixing roller 31 is set to a low speed that is slower than the speed at which the copy sheet passes through the fixing roller 31 during normal operation, that is, during the first copying operation. In other words, the system speed of the copying machine is set to a lower speed than during the first copying operation. After that, it moves to 5115 and the above 5111
A copy operation subroutine similar to that is called and executed, and an image is formed on the other side of the copy paper in duplex copy mode, or on the same sheet in composite copy mode, after which the main routine is returned. .

By the way, according to experiments conducted by the inventors of the present invention, 1
Fixing roller 31 during the first and second copying operations
When the peripheral speed of rotation was kept constant at 250 W/sec, the image loss caused by the fixing separation claw 32 as described above occurred, but when the peripheral speed during the second copying operation was changed to 150 W/sec.
When the speed is set as slow as 0 ms/sec, the fixing separation claw 3
It has been confirmed that image loss due to 2 does not occur.

In addition, the fixing conditions in this experiment were as follows.
The upper (heating) roller 31a constituting the fixing roller 31 is a CCR Teflon (trade name) roll with a diameter of 40 fins, and the lower (
The pressure roller 31b is also a silicone rubber roll with a diameter of 40 mm, the heating temperature is 195° C., and the fixing pressure is 60 kg/−.

In addition, in the above description, the present invention is explained using a single developing unit 5.
Although the present invention has been described as being applied to a copying machine equipped with a cassette 13 and a paper feed cassette 13, the present invention is not limited to such a copying machine. It goes without saying that a plurality of devices may be installed and these may be used selectively.

<Effects of the Invention> As explained above, according to the present invention, in double-sided copying and composite copying of a copying machine, the passing speed of the copy paper when passing through the fixing device for the second time and thereafter is changed from the first time. Since the speed is slower than the passing speed, the copying paper does not come into strong contact with the fixing/separating claw during the second and subsequent copying operations, thereby preventing excessive contact force from being applied. Therefore, unlike the conventional example, image defects due to excessive contact force do not occur, and
This has the effect of being able to prevent image defects from occurring.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the schematic configuration of a copying machine, and FIG.
FIG. 3 is a front view showing a schematic configuration of the operation panel. FIG. 3 is a flowchart showing a control program when setting the duplex/composite copying mode in the copying machine. In the figure, numeral 1 is the main body of the copying machine, 2 is the main motor, 3 is the driver, 31 is the fixing roller (fixing device), 3
2 is a fixing separation claw (fixing device), 51 is a print key, 5
6 is a duplex/combining mode selection key. Applicant Minolta Camera Co., Ltd. Agent Patent Attorney Oka 1) Kazuhide Figure 3

Claims (1)

[Claims] (1) In an electrophotographic copying machine having a double-sided or composite copying function in which copy paper passes through a fixing device multiple times, the passing speed of the copy paper when passing through the fixing device from the second time onward is calculated as follows: An electrophotographic copying machine characterized by comprising means for slowing down the passing speed of the machine.