JPS62208065A - Recording device - Google Patents

Abstract

PURPOSE:To improve the position accuracy of an image by reducing the conveyance speed when the tip of a sheet arrives in front of a sensor arranged on a sheet conveyance path, and matching the sheet with resist rollers at an image forming means by the detection of the sensor. CONSTITUTION:When the sensor 17 detects the front end of a conveyed sheet 10, the rotation of a roller 15 is reduced to one quarter and when a sensor 19 detects the front end next, the rotation of the resist rollers 15 is stopped. At the same time, an image output permission signal and an image signal are outputted and a latent image on a photosensitive body is visualized by a developing device 67; and the sheet beings to be conveyed again by the roller 15 a certain time later and the image is transferred to the sheet by a transfer device 9. Thus, the position accuracy of the image can be improved by performing accurate resist matching.

Description

DETAILED DESCRIPTION OF THE INVENTION U) Industrial Application Field The present invention relates to a recording apparatus such as a laser beam printer or an inkjet printer, and more particularly to a resist structure that adjusts the timing of feeding to an image forming means.

(b) Conventional technology In general, laser beam printers that form images by scanning a laser beam onto a photosensitive drum using a rotating polygonal mirror to form a latent image, which is then transferred onto a sheet after development, are well known. This is where I am.

As shown in FIG. 4, this conventional laser beam printer has a photosensitive drum 1 driven by a drive motor 2, and a latent image is formed on the photosensitive drum 1 by an exposure beam 6. The latent image is developed by a developing device 7. On the other hand, a feeding roller 12 is provided in contact with the upper part of the downstream side of the sheet 10 placed on the sheet stacking table 11, and the feeding roller 12 is operated by a drive motor (not shown) and a one-way clutch. Only one of the sheets is separated and the leading edge of the sheet 10 is fed in the direction of the conveying roller 23. When the leading edge of the sheet 10 is further inserted into the conveying roller 23, the feeding roller 12 stops its driving. 10 obtains a conveying force by a conveying roller 23, and the feeding roller 12 idles due to the force received by conveying the sheet 10. Then, the sheet 10 is moved through the conveyance guide 22 by the conveyance roller 23, and its leading edge is pressed against the gap of the registration roller 15, and after aligning the leading edge, the registration roller 15 is moved by the registration roller drive motor 16. Rotationally driven. At this time, conveyance of the sheet 10 is started in synchronization with the formation of the latent image on the photosensitive drum 1 described above.

The sheet 10 conveyed by the registration roller 15 is conveyed downstream by the conveyance guides 20 and 21. On the way, the image visualized by the developing device 7 is transferred onto the sheet 10 by the transfer 41f electric device 9, and then, A printed image is obtained on the sheet 10 by being fixed by a fixing device (not shown). After the transfer, the developer remaining on the photosensitive drum 1 is removed by a cleaning device! 3, and the photosensitive drum 1 is further removed by a charger 5.
The static electricity is removed and the image is prepared for new image formation.

&→ Problems to be Solved by the Invention However, in the case of the above-mentioned conventional registration method, the leading edge of the sheet pressed against the registration rollers 15 by the conveyance roller 23 is not necessarily pressed into the gap between the registration rollers 15; The registration roller 15 may be pressed against the upper or lower position of the register roller 15.
This causes variations in the position of the leading edge of the sheet during registration feeding, which causes variations in the print position of the image printed on the sheet surface. Furthermore, in high-speed laser beam printers, the conveying roller 23 does not stop immediately due to its inertia, and variations in the stopping time also deteriorate registration accuracy and print position accuracy. In particular, in multicolor laser beam printers that print on the same sheet surface by changing toner colors multiple times, improving the accuracy of printing positions is a major issue.

Furthermore, in the case of the conventional registration method, when attempting to feed a sheet after outputting an image signal transmitted from an external controller, the distance from the transfer charger 9 to the registration roller 15 is shorter than the distance from the transfer charger 9 to the photosensitive drum 1. There is a restriction that the distance must be shorter than the distance to the position exposed by the exposure beam 6. This restriction has been a major obstacle since many members such as a developing device are arranged around the photosensitive drum 1.

On the other hand, in order to solve this problem, a method has been considered in which resist feeding is started before image signals start being output from an external controller. This method does not have the above-mentioned restrictions and allows the registration rollers to be placed at a sufficient distance from the transfer position, but on the other hand, there is another restriction that the external controller must start image output in synchronization with the movement of the sheet. However, this is a serious problem for external controllers that must prioritize image output while processing images.
Problems arise in terms of design and cost, such as the need to have two CPUs, a PU and a CPU for image output.

(b) Means for Solving the Problems The present invention aims to solve the above-mentioned problems.The present invention is aimed at solving the above-mentioned problems. A sheet detection means is disposed on the sheet conveyance path between the registration means and the image forming means, and the sheet conveyance speed by the registration means is decelerated at a timing before the sheet detection means, and the sheet conveyance speed by the sheet detection means is reduced. Based on the detection, the registration means is driven to register the image forming means.

(e) Operation Based on the above-described configuration, when the sheet being conveyed by the registration means comes in front of the sheet detection means, the sheet conveyance speed is decelerated and the sheet is slowly conveyed toward the sheet detection means. Thereafter, when the sheet reaches the sheet detection means, the conveyance of the sheet is stopped, and at this point, the registration means is driven at a predetermined timing in accordance with the input of an image forming signal to the image forming means, and registration is performed.

(F) Example Hereinafter, an example in which the present invention is applied to a laser beam printer will be described with reference to the drawings. During the explanation, the fourth
Components that are the same as those shown in the drawings are designated by the same reference numerals.

As shown in FIG. 1, the laser beam printer has a photosensitive drum 1 driven by a drive motor 2, and a latent image is formed on the photosensitive drum 1 by an exposure beam 6.

The latent image is developed in development Wj7. On the other hand, a feed roller 12 is provided in contact with the upper part of the downstream side of the sheet 10 placed on the sheet stacking table 11.
is configured to separate only one of the sheets 10 using a drive motor and one-way clutch (not shown), and feed the leading end of the sheet 10 in the direction of the registration rollers 15 via the conveyance guide 22. In the sheet conveying path 20 between the registration roller 15 and the transfer charger 9, two reflective photosensors 19 and 17, which are sheet insect inspection means, are arranged spaced apart in the sheet conveying direction. Each of the reflective photosensors 19 and 17 detects the presence or absence of the sheet 10 when it is conveyed. The reflective photosensors 19 and 17 are connected to a CPU 25, and the CPU 25 controls the feeding roller 12, the register 1-roller 15, and the like. The registration roller 15 is driven by a registration roller drive motor 16, and the rotation of the registration roller drive motor 16 is controlled by a motor control circuit 1s26, the rotation speed of which is selectable by a switching means 27. #! X.

x2. The number of revolutions caused by the starting circuit Set it to match the transport speed. On the other hand, the rotation speed when switched to the oscillation circuit X2 is the same as that of the starting circuit
, for example, to a speed of about 174, and the front end of the sheet 10 is a reflective photosensor 1 serving as a second sheet detecting means.
7 is detected, the speed of the registration roller 15 is reduced. Therefore, when the paper feed roller 12 rotates and separates one sheet 10, the oscillation circuit . Here, if the leading edge of the sheet 10 is detected by the reflective photosensor 17 which is the second sheet detecting means (FIG. 3(A)), the CPU
25 drives the switching means 27 to change the oscillation circuit from xl to x2.
Switch to As a result, the rotational speed of the registration roller 15 is reduced to about 174, for example. Next, when the leading edge of the sheet 10 is detected by the sheet detection means 19 (FIG. 3(B)), the CPU 25 stops driving the registration rollers 15. At this point, a latent image is formed on the photosensitive drum 1, and the latent image is developed by the developing device 7. After a certain period of time, the registration rollers 15 restart conveyance of the sheet 10, and the transfer charger 9 transfers the toner image on the photosensitive drum 1 onto the surface of the sheet 10. Thereafter, the sheet 10 passes through a conveyance guide 21 and is fixed by a fixing device (not shown) to obtain a printed image. On the other hand, after the transfer, the developer remaining on the photosensitive drum 1 is removed by a cleaning device 3, and the photosensitive drum 1 is further neutralized by a charger 5 in preparation for forming a new image.

Note that in the embodiment of the present invention, the registration roller 15
The deceleration timing is obtained by the reflective photosensor 17, which is the second sheet detection means, but this deceleration timing may also be obtained by a fixed time timer that starts from the feeding timing of the feeding roller 12. . Also,
The registration roller drive motor 16 that drives the registration rollers 15 may be a servo motor or a pulse motor.

Since this embodiment has the above configuration, the CPU 25
When C receives a print signal from an external controller, C
The PU2S drives the drive motor (not shown) of the feeding roller 12 for a certain period of time as shown in FIG.
Select I to start driving the registration drive motor 16,
The registration roller 15 starts rotating. As a result, only one sheet 10 on the sheet stacking table 11 is separated, and is pressed into the gap of the registration rollers 15 via the conveyance guide 22, and is conveyed while being held by the registration rollers 15. Thereafter, the leading edge of the sheet 10 reaches the reflective photosensor 17, which is the second sheet detection means (FIG. 3(A)).

The timing position at this time is shown at position A in FIG.

When the leading edge of the sheet 10 is detected by the reflective photosensor 17, the CPU 25 drives the switching means 27 to switch the oscillation circuit from X to x2. As a result, the rotational speed of the registration roller 15 is reduced to, for example, approximately 174 degrees (FIG. 2).

Next, when the leading edge of the sheet 10 is detected by the reflective photosensor 19 (FIG. 3(B)), the timing position at this time is shown at position B in FIG.

At this timing, the CPU 25 stops the drive motor 16 of the registration roller 15 and outputs an image output permission signal VSREQ signal to the external controller. On the other hand, when the image output standard is completed, the external controller outputs the image to the printer with the sub signal VSYN.
In addition to outputting the C signal, output of the image signal V i D E O signal is started after a certain period of time T0. Through this series of processes, a latent image is formed on the photosensitive drum 1, and the latent image is developed by the developing device 7. Further, upon receiving the VSYNC signal from the external controller, the CPU 25 selects the oscillation circuit x1 by the switching means 27 after a certain period of time TR consisting of the registration alignment timing, drives the registration roller drive unit 16, and causes the registration roller 15 to transport the sheet. The transfer charger 9 transfers the toner image on the photosensitive drum 1 onto the surface of the sheet 10, and a fixing device (not shown) forms a printed image.

On the other hand, after the transfer, the developer remaining on the photosensitive drum 1 is removed by a cleaning device 3, and the photosensitive drum 1 is further neutralized by a charger 5 in preparation for forming a new image.

In an embodiment of the invention, the conveyance of the sheet 10 is carried out in a second
Since the speed is sufficiently decelerated between the reflective photosensor 17 and the reflective photosensor 19, which are the sheet detection means of Reliable registration accuracy can be achieved without making problems with the inertia of the drive motor, the response speed of the drive motor, the response speed of the photosensor 17, 19, etc.

Furthermore, the distance between the photosensors 17 and 19, that is, the deceleration period, takes into consideration the response of the drive motor and the inertia of the registration roller 15, and during this period the rotation speed can be reliably stabilized at a low speed by the oscillation circuit X2. By making the deceleration period as short as possible, the conveyance efficiency of the sheet 10 can be improved.

Furthermore, even if the distance between the transfer charger 9 and the photosensor 19 is made shorter than the distance between the transfer band m-meter 9 and the position of the exposure beam 6, and the registration roller 15 is placed at a position longer than the latter distance, Since a structure can be created in which the timing of image output from the external controller can be performed earlier than the timing of feeding the resist, design constraints can be eliminated and the apparatus can be made smaller.

(g) As described in detail, according to the present invention, the sheet detection means is disposed on the sheet conveyance path between the registration means and the transfer means, and the registration means is activated at a timing before the sheet detection means. The sheet conveyance speed is reduced by the sheet detection means, and based on the sheet detection by the sheet detection means, the registration means is driven to align the registration with the image forming means. This can contribute to improving the positional accuracy of the device, and can also reduce the size of the device.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing a laser beam printer which is an embodiment of the apparatus of the present invention, FIG. 2 is an explanatory diagram of the operation of FIG. 1, and FIGS. 3 (A) and (B) are FIG. 4 is a vertical cross-sectional view of a conventional laser beam printer. DESCRIPTION OF SYMBOLS 1... Photosensitive drum, 9... Transfer means (transfer charger), 10... Sheet, 15... Registration means (registration roller), 17... Sheet detection means (reflection photosensor), 19 ...Second
Sheet detection means (reflective power photosensor), 20...
・Sheet transport! ! ml (sheet a feeding guide).

Claims (2)

[Claims] (1) A recording apparatus that records image information at a rate, comprising an image forming means for forming an image on a sheet and a registration means for conveying the sheet to the image forming means at a predetermined timing, the registration means and the image forming means A sheet detection means is disposed on the sheet conveyance path between the sheets, the sheet conveyance speed by the registration means is decelerated at a timing before the sheet detection means, and the sheet conveyance speed by the registration means is reduced based on the sheet detection by the sheet detection means. A recording apparatus characterized in that the registration means is driven so as to register the registration means with the forming means. (2) The recording apparatus according to claim 1, wherein the timing for starting deceleration of the sheet conveying speed is obtained by a second sheet detecting means disposed before the sheet detecting means.