JPH04308871A - Image transfer positioning control method for cut paper - Google Patents

Abstract

PURPOSE:To prevent positioning deviation at the time of transfer by making the timing of an image transfer position being reached by the cut paper coincide with the timing the image transfer position is reached by an image written on a photosensitive body. CONSTITUTION:With this printing method, the cut paper is carried inside a carrying path from a paper feeding means and an image written on the photosensitive body at the image transfer position is transferred onto the cut paper. The leading tip of the cut paper carried at a fixed speed by the before mentioned paper feeding means is detected inside the carrying path before the image transfer position and the writing of the image to the photosensitive body 13 can be started based on this detected signal.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for controlling image transfer positioning on cut paper, and in particular, image transfer positioning control in an electrophotographic printer using a light emitting element such as an LED or a laser beam as an exposure means. Regarding the method.

0002

[Prior Art] Conventionally, light emitting elements such as LEDs, lasers, etc.
Among electrophotographic printers using beams, there is one that uses so-called cut paper as a means for outputting information. In this type of printer, the cut sheets stacked in the paper feed tray are conveyed one by one using a paper feeding means.
The toner image formed on the photosensitive drum is transferred onto the cut paper at an image transfer position where the cut paper comes into contact with the photosensitive drum, and the toner image on the cut paper is fixed by a flash fixing device such as a xenon lamp and then ejected. The paper is ejected into a paper tray.

By the way, in the above-mentioned type of printer, the timing at which the cut paper conveyed by the paper feeding means reaches the image transfer position and the image written on the photosensitive drum by the exposure means are adjusted to the image transfer position by the rotation of the photosensitive drum. The timing of arrival must be well-coordinated,
If this timing is not correct, the image writing position will be shifted on the cut paper. Therefore, in this type of printer, control is performed to match the timing of conveying the cut paper and the timing of writing the image on the photosensitive drum, and generally, the timing of writing the image on the photosensitive drum is controlled. The start signal is used as a timing signal to control the conveyance of cut paper by the paper feed means.

0004

[Problems to be Solved by the Invention] However, in the cut paper conveyance path, the cut paper sent out from the paper feed tray is temporarily held at a pair of paper feed rollers called registration rollers, where the leading edge of the cut paper is The paper is straightened to prevent the cut paper from being conveyed at an angle. Then, image writing on the photosensitive drum starts, and the timing signal rotates the registration rollers to feed out the cut paper, so the difference in the amount of biting into the registration rollers due to the difference in paper thickness, and the cut Due to instability in the rise of the registration rollers when feeding the paper and slip phenomena that occur between the registration rollers and the cut paper, variations occur in the time it takes for the cut paper to reach the image transfer position from the registration rollers. There was a possibility that this would appear as a positional shift in the transferred image.

Therefore, the technical problem to be solved by the present invention is to ensure that the timing at which the cut paper reaches the image transfer position matches the timing at which the image written on the photoreceptor reaches the image transfer position. The point is to make it.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned technical problem, the present invention conveys cut paper within a conveying path by a paper feeding means, and transfers an image written on a photoreceptor at an image transfer position. In a printing method for transferring onto cut paper, the leading edge of the cut paper transported at a constant speed by the paper feeding means is detected within the transport path in front of the image transfer position, and the image is transferred to the photoreceptor based on this detection signal. This method uses a cut paper image transfer position alignment control method in which writing is started.

[0007]

[Operation] According to the above-mentioned means, since the leading edge of the cut paper whose conveyance speed has become constant is detected, the time required for the cut paper to reach the image transfer position from the detection of this leading edge is constant. . Then, using this detection signal as a reference, the toner image is transferred to a predetermined location on the cut paper by starting writing the image on the photoconductor in time with the timing when the cut paper reaches the image transfer position on the photoconductor. be able to.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the main parts of a printer for implementing the image transfer positioning control method according to the present invention. This printer is of an electrophotographic type using an LED, a laser beam, or the like as an exposure means, and feeds cut sheets 2 one by one into a conveyance path from a paper feed tray (not shown). The leading edge of the cut paper 2 that has been sent out hits the joint roller surface of the pair of registration rollers 4, and in this state, the cut paper 2 is once curved by the registration guide section 5, so that the leading edge of the cut paper 2 is straightened. A so-called resist correction is performed to match. The cut paper 2 is sent out by the rotation of the registration rollers 4 after correction, and after the passage of the leading edge is detected by the leading edge detection sensor 40 installed near the rear of the registration rollers 4, the cut sheet 2 is conveyed by rotating at the same speed as the registration rollers 4. It is conveyed by roller 6 to the transfer process. Note that the position of the tip detection sensor 40 is the same as that of the registration roller 4.
It is sufficient that the position is behind the point where the rotation of the cut paper 2 is stable and the conveyance speed of the cut paper 2 is constant.

In the transfer process, the photosensitive drum 13, which is rotated by the same drive motor as the transport roller 6 for the cut paper 2, is first uniformly charged in the charging section 14, and then the exposure section is made up of an LED array in which LEDs are arranged in a line. 15, the image information from the host computer is exposed, and further the developing section 16
to form a toner image. The start timing of image writing in the exposure section 15 is controlled based on the leading edge detection signal from the leading edge detection sensor 40. A transfer section 17 is arranged near the lower end of the photosensitive drum 13 in correspondence with the image transfer position P, and due to the charging in the transfer section 17, paper that is conveyed stuck to the photosensitive drum 13 is ,
The toner image formed on the photosensitive drum 13 is transferred at an image transfer position P. A guide for guiding the cut sheet 2 to the image transfer position P is provided by a guide portion 18 disposed close to the photosensitive drum 13 at a position immediately before the cut sheet 2 . The guide section 18 is composed of an upper guide plate 18a and a lower guide plate 18b, and forcibly guides the cut paper 2 conveyed therebetween to the image transfer position P of the photosensitive drum 13. The cut paper 2 on which the image has been transferred is conveyed on a conveyor belt 19 that is set on a horizontal plane that is almost the same as the transfer position.A flash fixing device 20 that uses radiant heat is installed above the rear part of this conveyor belt 19. It is arranged. This flash fixing device 20 has a halogen lamp 21 for preheating and a xenon lamp 22 for fixing that are arranged in the paper width direction and are arranged adjacent to each other in a reflective case. It emits light based on the radiant heat, melts the toner, and fixes it on the paper. Further, the conveyor belt 19 is provided with a large number of small holes (not shown) over the entire surface.
A suction device 23 disposed on the back side of the conveyor belt 19 conveys the cut paper 2 while sucking it onto the belt. Further, around the photosensitive drum 13, there is a static eliminator 24 that applies an alternating voltage to remove static electricity from the charged cut paper 2 in order to separate the cut paper 2 from the photosensitive drum 13 after transfer.
A peeling claw 25 that prevents the cut paper 2 from wrapping around the photosensitive drum 13 and a cleaner unit 26 that scrapes off adhering toner are provided. In addition, the conveyor belt 19
On the rear side of the conveyor belt 19, there are provided a scuff roller rotated by the same drive motor as the conveyor belt 19 and a paper discharge section for discharging the cut paper after the fixing process (both not shown).

Next, a control method for adjusting the image transfer position in the cut paper printing mode using the printer configured as described above will be described with reference to FIGS. 1 and 2. First, the conveyance system of the printer in this embodiment is as follows.
The distance relationship is set as shown in FIG. That is, the conveyance distance between the registration roller 4 and the image transfer position P is L.
1. The transport distance between the leading edge detection sensor 40 and the image transfer position P is L2, and the photosensitive drum 13 written by the exposure section 15
If the moving distance between the image writing position Q and the image transfer position P above is L3, then the relationship between them is L1>L2≧L
3, and the distance L1-L2 is determined by the conveyance speed of the cut paper 2 sent out from the registration rollers 4.
This is at least the distance required to maintain a constant speed. The distance relationship between L1 and L2 is such that, as described above, when the registration rollers 4 are started, the transport speed of the cut paper 2 is not constant, so the present invention uses the leading edge detection signal from the leading edge detection sensor 40 as a control signal for image writing. This is to minimize the influence from the registration rollers 4 in this case. Further, the distance relationship between L2 and L3 is that the conveying speed of the conveying roller 6 for feeding the cut paper 2 to the image transfer position P and the rotation speed of the photosensitive drum 13 are the same, and that the leading edge detection sensor 40 detects the leading edge. From the point that image writing to the photosensitive drum 13 is started based on the signal, L2
must be greater than or at least the same as L3.

In the transfer positioning control, first, based on a control signal from the host computer, a pair of conveyance rollers 6 rotated by the same drive motor and a pair of conveyance rollers 6 rotated by the same drive motor, and a pair of conveyance rollers 6 rotated by different drive motors, respectively, are adjusted to the rotation speed of the photosensitive drum 13 based on a control signal from the host computer. The registration rollers 4 and the conveyor belt 19 are controlled to rotate at the same speed. And paper feed tray 1
When the first cut paper 21 is fed into the transport path, the cut paper 21 is temporarily stopped by the registration rollers 4, the registration is corrected so that the leading edge is aligned straight, and then the cut paper 21 is sent out by the rotation of the registration rollers 4. . After the cut paper 21 run up by the registration rollers 4 reaches a constant speed, the leading edge detection sensor 40 detects the leading edge of the paper. Then, after a time T1 based on the rise of this leading edge detection signal, image writing is started onto the photosensitive drum 13 from the exposure section 15 constituted by an LED array. Furthermore, the charging timing in the transfer unit 17, the charging timing in the static eliminating unit 24, and the lighting start timing of the halogen lamp 21 of the flash fixing device 20 are counted based on the rise of the leading edge detection signal from the leading edge detection sensor 40, and The race will also start after T2 hours. Furthermore, the timing at which the xenon lamp 22 of the flash fixing device 20 starts emitting light is counted based on the rise of the leading edge detection signal from the leading edge detection sensor 40, and the flash flashing starts T3 hours after the cut sheet 21 approaches the xenon lamp 22. do. In this way, in this embodiment, the cut paper 21
The leading edge detection signal is used as a timing signal to control image writing and the start time of the transfer section 17, xenon lamp 22, etc. In addition, T1 time is L2-L3
For example, L2
=L3, T1 also becomes zero.

Even after the cut sheet 21 is detected by the leading edge detection sensor 40, it is transported at a constant speed by the registration rollers 4 for a while, and is then held between a pair of transport rollers 6 that rotate at the same speed and guided at a constant speed. 18. Then, the upper guide plate 18a and the lower guide plate 1
8b, the photosensitive drum 13 is forcibly guided through a distance L2 to the image transfer position P of the photosensitive drum 13. On the other hand, the toner image written on the photosensitive drum 13 in response to the signal from the leading edge detection sensor 40 is transferred at the same time as the first written image at the writing position Q moves a distance L3 and reaches the image transfer position P. Due to the charging in the transfer section 17 described above, the cut paper 2
1 Transferred on top. Since the two have a relationship of L2≧L3, by appropriately setting T1, the timing with the cut paper 21 at the image transfer position P can be very easily matched, and the leading edge of the cut paper 21 reaches. There is no possibility that the image written earlier reaches the image transfer position P first.

Immediately after the transfer, the charge is removed by the charge removal section 24 which is charged in the opposite direction to that of the transfer section 17, and furthermore, after T4 hours from the rising signal from the tip detection sensor 40, the stripping claw 25
The leading edge of the cut paper contacts the photosensitive drum 13 for a predetermined period of time to prevent the leading edge of the cut paper from being caught in the photosensitive drum 13. The cut paper 21 that has come off the conveyor roller 6 is transferred to the conveyor belt 1.
9 and is conveyed at the same speed as above by suction force from below. In the fixing process of the cut paper 21, the toner is preheated by the halogen lamp 21 of the flash fixing device 20, which is turned on at the same time as the transfer section 17, and then melted by the radiant heat of the xenon lamp 22, which emits light at predetermined time intervals. The toner image is then fixed onto the cut paper 21. As described above, in this embodiment, the timing of the start of light emission of the xenon lamp 22 is controlled based on the detection signal from the tip detection sensor 40, but from the tip detection sensor 40 to the installation position of the xenon lamp 22, Since the xenon lamps 21 and 21 are transported at the same speed and the transport time t during that time is constant, by appropriately setting the time T1+T3 from the detection of the tip to the start of light emission, the xenon lamps 2
The start of light emission of the xenon lamp 22 can be appropriately controlled, the occurrence of unfixed toner images can be reliably prevented, and the lamp life can be extended by preventing the xenon lamp 22 from emitting light unnecessarily. The cut paper 21 that has completed the fixing process is sent to the paper ejection section by a scuff roller rotated by the same drive motor as the conveyor belt 19.
Complete the entire printing process.

In the timing control described above, as shown in FIG. 2, the detection signal from the leading edge detection sensor 40 falls when the trailing edge of the cut paper 21 is detected. In this way, the detection signal repeats rising and falling by detecting the leading edge and trailing edge of the cut sheets 22 . . . 2n that are conveyed one after another. The image writing signal on the LED by the exposure unit 15 falls when the writing information from the host computer is interrupted. Furthermore, the charging in the transfer section 17 and the static elimination section 24 and the light emission of the halogen lamp 21 and xenon lamp 22 of the flash fixing device 20 are limited to the initially set cut paper 22.
...The state remains as it is until the number of printed sheets of 2n is completed, but the falling signal of the image writing of the last cut sheet 2n is used as a stop timing signal, and after T5 time, the transfer unit 17 and the static eliminator 24 electrification stops, and T6
After an hour, the halogen lamp 21 stops emitting light, and after a very similar time T7, the xenon lamp 22 stops emitting light.

[0015]

As explained above, according to the image transfer position alignment control method for cut paper according to the present invention, the leading edge of the cut paper whose conveyance speed has reached a constant speed is detected, and this detection signal is used as a reference. Since the control method starts image writing on the photoconductor as a control method, the time from the detection of the leading edge of the cut paper until it reaches the image transfer position is constant, and the image writing on the photoconductor is timed to the timing of this arrival. This makes it easier to control the transfer positioning, and it also makes it possible to reliably transfer the toner image to the predetermined location on the cut paper, eliminating the need for the transfer start position to shift as in the past. do not have.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the main parts of a printer for implementing a cut paper image transfer position alignment control method according to the present invention.

FIG. 2 is a time chart diagram in cut paper printing mode.

[Explanation of symbols]

P Image transfer position Q Image writing position 2 Cut paper 4 Registration roller 13 Photosensitive drum (photosensitive member) 17 Transfer section 18 Guide part 40 Tip detection sensor

Claims (3)

[Claims] 1. A printing method in which a cut sheet is conveyed within a conveyance path by a paper feeder, and an image written on a photoreceptor is transferred onto the cut sheet at an image transfer position, wherein the cut sheet is conveyed at a constant speed by the paper feeder. Image transfer positioning for cut paper, characterized in that the leading edge of the cut paper to be transferred is detected within the conveyance path before the image transfer position, and writing of the image on the photoreceptor is started based on this detection signal. Control method. 2. Conveyance distance L1 between the paper feeding means and the image transfer position, conveyance distance L2 between the leading edge detection position of the cut paper and the image transfer position, and the image writing position and the image transfer position of the photoreceptor. The relationship between the moving distance L3 and the L1>L
2. The cut paper image transfer position alignment control method according to claim 1, wherein 2≧L3. 3. The image transfer positioning of cut paper according to claim 1, wherein the distance L1-L2 is a distance necessary for the conveyance speed of the cut paper sent out from the paper feeding means to be at least a constant speed. Control method.