JPS63257769A - Transfer paper carrying device - Google Patents

Abstract

PURPOSE:To prevent an image misalignment on transfer paper by stopping temporarily the transfer paper at a prescribed position in a carrying path immediately before a photoconductive member, bringing it to holding for a prescribed time after the stop, and driving again a carrying means by synchronizing with a rotation of the photoconductive member. CONSTITUTION:A printer control circuit 31 which has received a detecting signal from a resist pre-sensor 6 carries paper by driving resist rollers 4, 4' by a driving means 301, and the paper tip reaches a position of a paper tip detecting sensor 32. When a paper tip detecting signal is obtained, the paper tip passes through a position of the sensor 32, and after a prescribed time, the rollers 4, 4' are stopped by a temporary stop means 302 and carrying of the paper is stopped. The rollers 4, 4' wait for the time when a latent image moves and comes to a prescribed position where it is developed by a developing device, by following up a rotation of a photosensitive drum 8, and driven again by a redriving means 303 by allowing the timing to match it and carry the paper, therefore, the transfer is executed. In such a way, the image printing accuracy in the paper feeding direction can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a transfer paper conveying device such as a laser beam printer or a copying machine that prints on transfer paper using an electrophotographic process.

[Conventional technology]

Conventionally, in devices that print images on transfer paper, such as laser beam printers and copying machines, the image position on the paper surface has been controlled using control means such as timing rollers.

Here, the control situation will be explained based on the drawings, taking a laser beam printer as an example.

In FIG. 2 showing the internal structure of the printer, 1 is a cassette, 2 is a paper feed roller, 3.3' is a conveyance roller, and 4.4 is a paper feed roller.
' is a registration roller, 5 is a sensor lever, 6 is a resist f11 sensor, 7 is a developer, 8 is a photosensitive tram, 9 is a primary high-voltage charger, 10 is a transfer charger, 11 is a cleaner, 12
13 is a conveyor belt, 13 is a fixing roller, 14 is a heater that heats the fixing roller, 15 is a fixing roller cleaner, 16° 16' is a carry-out roller, 17 is a semiconductor laser, 18 is a rotating polygon mirror, 19 is a reflecting mirror, 20 is a beam detector.

In addition, in FIG. 3 showing the interface signals, 2
1 is a printer control circuit; 22 is a host computer that exchanges necessary signals with the control circuit 21;

Next, the printing operation will be explained with reference to FIGS. 2 and 3.

When the laser beam printer enters the standby state by turning on the power, the printer control circuit 21 (not shown in A) outputs the hereday signal RDY to the host computer 22.
The computer 22 sends a print signal PRINT to the printer:&IN circuit 21 to notify that printing is possible, and the navigation printer starts operating.

That is, by the rotation of the paper feed roller 2, the transfer paper (hereinafter referred to as "paper") in the cassette 1 is sent out from the cassette 1, and is conveyed between the conveyance rollers 3 and 3', where the image to be printed and the paper are conveyed. It advances to registration rollers 4, 4' which have the role of directional alignment.

At this time, the sensor lever 5 disposed immediately in front of the registration rollers 4, 4' is pushed by the leading edge of the paper and rotates in the upward direction, operating the registration sensor 6. It is detected that the tip has reached the registration roller 4.4'. The paper stops temporarily with its leading edge hitting the registration rollers 4 and 4' forming a loop, but the printer control circuit 21, which has received the signal from the above detection, sends a vertical synchronization request signal VSREQ to the postcomputer 22. The computer 22 sends back a vertical synchronization signal VSYNC, thus beginning a sequence of print operations.

On the other hand, the host computer 22 uses the beam detector 2
Horizontal synchronization signal BD from 0 to printer;-control circuit 21
Since the image signal VDO synchronized with the synchronization signal BD and the vertical synchronization signal VSYNC is sent to the printer control circuit 21, the semiconductor laser 17 is driven by the signal VDO.

Therefore, the laser beam irradiated from the semiconductor laser 17 is scanned by a rotating polygon mirror 18 and guided to the rotating photosensitive drum 8 via a reflecting mirror 19.
Forms a latent image on the surface.

The latent image on the photosensitive drum 8 is visualized by a known electrophotographic process, and the registration rollers 4, 4, which have started rotating,
' is transferred onto the paper surface being conveyed.

The transferred paper is transported by a transport belt 12, and after the toner on the paper is fixed by a fixing roller 13 heated by a heater 14, it is ejected from the printer by delivery rollers 16, 16'.

In other words, in a laser beam printer that operates as described above, the image position on the transfer paper is determined by the vertical synchronization signal VSY.
This is controlled by the latent image formation by the semiconductor laser 17 synchronized with the NC and the rotation start timing of the registration rollers 4, 4'.

Since both the latent image formation and the timing of the registration rollers 4.4' are controlled by electrical signals, they are highly accurate and have little variation. Therefore, the leading edge of the paper is on the registration rollers 4, 4'.
As long as it always coincides with the tangent line, it can be printed on the transfer paper with good positional accuracy.

[Problem that the invention seeks to solve]

However, in image forming apparatuses, it is extremely difficult to always keep the leading edge of the paper in contact with the tangent line of both registration rollers, and the position of the leading edge changes depending on the thickness of the paper and the condition of the leading edge, such as curling or waving. This makes it difficult to print on transfer paper with good positional accuracy.
Conventional image forming apparatuses have had a problem in that images are often misaligned.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to obtain a transfer paper conveying device that improves the granularity of image position on transfer paper, and particularly to increase the positioning density in the paper feeding direction.

[Means for solving problems]

The transfer paper conveyance device according to the present invention includes a conveyance means for conveying paper to a transfer area, a stop means for temporarily stopping the paper so as to stop at a predetermined position on a conveyance path between the conveyance means and the transfer area, and a photoconductive The apparatus further includes a driving means for driving the conveying means so as to convey the paper again in synchronization with the development of the member.

[Effect]

In the transfer paper conveying device of the present invention, a detection signal of the leading edge of the transfer paper is obtained by the transfer paper leading edge detection means provided on the conveyance path, and the conveying means is temporarily stopped after a predetermined time A or immediately; If no detection signal is obtained, the conveying means is temporarily stopped based on a predetermined time from the first start of driving of the conveying means, and after waiting for a time synchronized with the development on the photoconductive member, Perform control to re-drive. To obtain an image without positional deviation on transfer paper.

〔Example〕

Hereinafter, a first embodiment of the present invention will be described based on FIG. Note that the same members and corresponding parts as in the conventional example are designated by the same reference numerals, and their explanations will be omitted.

FIG. 1 is a configuration diagram of the main parts of the transfer paper conveyance device. In the figure, 31 is a printer control circuit that is combined with the host computer 22, registration rollers as conveyance means, 4.4
', a driving means 301 for driving, a stopping means 302 for temporarily stopping, and a re-driving means 303 are controlled. Reference numeral 32 denotes a paper leading edge detection sensor as a means for detecting the leading edge of a transfer paper, which is located on the light emitting side and is installed immediately after the registration rollers 4 and 4' across a conveyance path 35 located just in front of the photosensitive drum 8, which is a photoconductive member. It consists of a sensor 33 and a light-receiving sensor 34, which detects the paper leading edge position when the light is blocked and sends a detection signal to the printer control circuit 31.

Since the present invention is characterized by the configuration described above, the paper conveyance control operation is performed according to the flowchart shown in Fig. 4.

Note that S1 to S13 in the figure indicate each step.

Print signal PRINT from host computer 22
The printer control circuit 31 that receives the information drives the paper feed roller 2 and the transport rollers 3, 3' to transport the paper (Sl).

Then, the leading end of the paper presses down the sensor lever 5 and passes, and then hits the tangent to the stopped registration rollers 4, 4', so that the paper forms a loop. By operating the sensor lever 5, the pre-registration sensor 6 detects that the leading edge of the paper has reached just before the registration rollers 4, 4' (Sl).
.

By the way, when the registration sensor 6 detects the leading edge of the paper and the vertical synchronization request signal VSREQ is issued from the printer control circuit 31, the host computer 22 transmits the vertical synchronization signal VSYNC and synchronizes with this. A latent image is formed on the surface of the drum 8 (
S3).

The printer control circuit 31 that receives the detection signal from the registration pre-registration sensor 6 drives the registration rollers 4, 4' by the driving means 301 to transport the paper (S4), so that the leading edge of the paper is detected by the paper leading edge detection sensor. Reach position 32.

At this time, if a paper leading edge detection signal is obtained (S5), a predetermined time t1 seconds elapses after the paper leading edge passes the position of the detection sensor 32, as shown in the time chart of FIG. After that (S6), the registration rollers 4, 4' are stopped by the temporary stop means 302 to stop conveying the paper (S7).
. Note that the operation of returning to S6 is repeated until 1 second has elapsed.

The registration rollers 4, 4' wait for the latent image to be developed by the developing device 7 and moved to a predetermined position as the photosensitive drum 8 rotates (Sa), and then adjust the tanning to the re-driving means. 303 (the waiting time until re-driving is set to t2) (S9), and the paper is conveyed, so that transfer is performed (StO). In addition, registration roller 4
It is assumed that the time from when 4' starts driving for the first time to when a paper leading edge detection signal is obtained is 70 hours.

Note that the time t until a paper leading edge detection signal is obtained is determined by the state of contact between the leading edge of the paper and the tangent of the registration roller 4.4', the slip between the paper and the registration roller 4.4', etc.

is not constant. However, in this embodiment, the printer control circuit 31 detects the leading edge of the paper near the transfer position, controls the paper conveyance means, stops the paper at a certain position, and starts conveying the paper again in time with the development timing. By doing so, it is possible to significantly improve image printing accuracy in the paper feeding direction.

Further, the resist surface sensor 6 is a photo sensor,
Since it is a mechanical detection configuration that is operated by being pushed by the sensor lever 5 which is rotated by being pushed by the leading edge of the paper, the detection timing changes depending on the state in which the leading edge of the paper hits the sensor lever 5. Therefore, an optical sensor with high detection accuracy is used as the transfer paper leading edge detection sensor 32.

However, OHP (Over HeadP) is used as transfer paper.
rojetor) If the leading edge of paper or second base paper cannot be detected, or if paper with poor detection accuracy is used, the leading edge of the paper will not be detected in S5, and the OHP paper will not be detected without a paper leading edge detection signal. etc., passes through the position of the paper leading edge detection sensor 32. Therefore, as shown in the time chart in Figure 6, the estimated time of passing is
Registration rollers 4, 4: first drive start jtxt.

seconds, and the printer control circuit 31 outputs 1o+1. If the paper leading edge detection signal is not obtained until seconds have passed (Sll),
Paper transport is temporarily stopped (S12). This timing is
This is the same as when the paper leading edge detection signal is obtained, and it is considered that the OHPm paper or the like is stopped at almost the same position as when normal paper is used.

Therefore, after the waiting time t2 seconds has elapsed since the registration rollers 4.4' were temporarily stopped (S13), the registration rollers 4, 4' are driven again (S9) to perform transfer (S1).
0). This allows the sequence to be simplified.

Next, a second embodiment will be explained based on FIG. 7 and subsequent figures.

In this second embodiment, as shown in FIG. 7, which is a diagram equivalent to FIG. 1,
The configuration is almost the same as that of the first embodiment, but the driving means 401
．． The control operation of the printer control circuit 41, which has a temporary stop means 402 and a re-drive means 403, is performed as shown in the flowchart of FIG. 8 and the time charts of FIGS. 9 and 10. Note that S1 to S13 indicate each slap in the flowchart.

In FIG. 8, 81 to S4 represent the first embodiment (FIG. 4)
Since this is almost the same as in the case of , the explanation will be omitted.

When the paper leading edge detection sensor 32 detects the leading edge of the paper and outputs a detection signal in S5, the printer control circuit 41 immediately stops the registration rollers 4.4' using the temporary stop means 402 to stop conveying the paper (S6). . Superposition synchronization signal VSY
1. until the latent image formed on the photosensitive drum 8 is developed in synchronization with the NC and reaches a predetermined position. After waiting for a second (S7), when the registration roller 4.4' is reached at the predetermined position (S8), the re-driving means 403 drives the registration roller 4.4' again (S9), and the paper is conveyed, so that transfer is performed (StO).

In addition, if OHPm paper or the like is used and the leading edge of the paper cannot be detected in S5, as described in the first embodiment, from the first start of conveyance by the registration rollers 4, 4' until the leading edge of the paper is detected. Since the value of time to is not constant, the estimated time of tip detection is t. +Δα. However, to+
Δα<1. It is.

For commonly used paper, the leading edge can be reliably detected between to±Δα, but for OHPm paper, etc., it cannot be detected, so the VSYNC signal is Sent registration roller 4, 4
t after ' starts the first drive. +Δα seconds later (sti
), the rollers 4, 4' are temporarily stopped to stop conveying the paper (S12). At this time, assuming that the paper transport speed is V, it is estimated that the leading edge of the paper is at a position that is further advanced toward the photosensitive drum 8 by V×Δα than the position where the leading edge should be detected, that is, the predetermined paper stop position. be done. So, we delayed the re-drive time to t, +Δα seconds? & (S13), the registration rollers 4°4' are driven again (S9) to transport the paper and perform transfer (SIO).

In other words, even when the leading edge of OHP paper is difficult to detect with an optical sensor, printing can be performed with high positional accuracy in the paper feeding direction by the above-mentioned control operation.

(Effects of the Invention) As explained above, according to the present invention, the transfer paper is temporarily stopped on the conveyance path immediately in front of the photoconductive member, and is sent to the transfer area in synchronization with the image of the leading trL member. Since the configuration is configured to control, it is possible to prevent image positional shift on the transfer paper and print with high precision in two positions.

Furthermore, even for paper such as OHP paper whose leading edge is difficult to detect with an optical sensor, it is possible to control the conveyance operation at the same timing as for normal paper using the appropriate means.

[Brief explanation of drawings]

FIG. 1 is a sectional view of essential parts of a transfer paper conveying device according to a first embodiment of the present invention, the second leap is a schematic internal configuration diagram of a conventional laser beam printer, and FIG. 3 is a diagram showing a conventional host computer and A configuration diagram of an interface signal with the printer control circuit, FIG. 4 is a flowchart showing the control operation of transfer paper conveyance in the first embodiment, and FIG. 5 is a time chart of transfer paper conveyance when the leading edge of the paper can be detected. , FIG. 6 is a time chart of transfer paper conveyance when the leading edge of the paper cannot be detected, FIG. 7 is a diagram corresponding to FIG. 1 of the second embodiment, and FIG. 8 is a diagram of the transfer paper of the second embodiment. FIG. 9 is a flowchart showing the transport control operation, and FIG. 9 is a diagram corresponding to FIG. 5, and FIG. 10 is a diagram corresponding to FIG. 6. 4.4'...Registration roller 8...Photosensitive drum 22--Host computer 31--Printer control circuit 32--Paper leading edge detection sensor 35 −・・・Conveyance path

Claims (4)

[Claims] (1) A means for transporting transfer paper; a temporary stop means for stopping the transport means so that the leading edge of the transfer paper stops at a predetermined position in the transport path immediately in front of the photoconductive member; 1. A transfer paper conveying device comprising: a re-driving means for re-driving the conveying means in synchronization with rotation of the transfer member. (2) The temporary stop means temporarily stops the conveyance means after a predetermined period of time has elapsed based on a detection signal of the leading edge of the transfer paper by a transfer paper leading edge detection means provided in the conveyance path. The transfer paper conveyance device according to scope 1. (3) The temporary stop means temporarily stops the conveyance means immediately when a detection signal of the leading edge of the transfer paper is obtained by a transfer paper leading edge detection means provided in the conveyance path. The transfer paper conveyance device described in Section 1. (4) The transfer paper conveyance device according to claim 1, wherein the temporary stop means temporarily stops the conveyance means after a predetermined period of time has elapsed from the start of driving of the conveyance means.