JPH0594060A - Printing device - Google Patents

Abstract

(57) [Summary] [Purpose] In a printer using an electrophotographic system, the purpose is to control the timing of the electrophotographic process regardless of the paper length, and to eliminate the need for a paper feed cassette corresponding to each paper. To do. [Arrangement] Paper edge detection devices 2 and 9 for detecting the leading edge and the trailing edge of the sheet are provided on the sheet conveying path before transfer and after fixing,
Based on the detection result of each detection device 2, 9, the charging device 4,
The stop control of the developing device 6 and the transfer device 7 is controlled without depending on the paper length by the configuration that controls the operation and stop of the developing device 6 and the transfer device 7 and the timing of the electrophotographic process such as writing on the photoconductor. it can.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a laser printer, LE
More specifically, the present invention relates to a printer such as a D printer, which uses an electrophotographic method for forming a latent image on a photoconductor and flying toner on the latent image to form a toner image.

[0002]

2. Description of the Related Art Generally, in a printing apparatus using an electrophotographic system such as a laser printer and an LED printer, a photoconductor is charged by a charging device (charging step), and then a laser optical system, an LED array, or the like. The optical writing device is used as a recording unit to perform writing (exposure step) on the photosensitive member, and then to perform a developing step, a transferring step, and a fixing step for printing.

A conventional printer using the electrophotographic method will be described below. In FIG. 3, 1 is a paper feed roller for feeding paper into the printing device, 3 is a photoconductor drum, 4 is a charging device for charging the photoconductor drum 3, 5 is an LSU,
An optical writing device such as an LED array, 6 is a developing device that develops the latent image on the photoconductor drum 3 into a toner image, 7 is a transfer device that transfers the toner image on the photoconductor drum 3 onto paper, 8
Is a fixing device for fixing the toner to the sheet, 10 is a registration roller, and 11 is a registration clutch for controlling the operation of the registration roller. A straight line A indicated by a chain double-dashed line indicates a sheet conveyance path.

With respect to the printing apparatus including the above-described respective constituent elements, the relationship and operation between the respective constituent elements will be described below.

The paper feed roller 1 conveys the print paper fed into the printer to the registration roller 10 which is not rotating. Here, after stopping the paper, the registration clutch 11 is activated, the rotation of the main motor (not shown) is transmitted to the registration roller 10, the registration roller 10 is rotated, and the paper is conveyed again to perform printing. ing.

Charging device 4 and developing device 6 in the charging process
The operation control is performed based on the start of rotation of the main motor, and the stop control of the charging device 4, the stop control of the developing device 6 used in the developing process, and the operation of the transfer device 7 used in the transferring process are performed. The stop control and the control of the start and end of writing on the photosensitive drum 3 during the exposure process are performed based on the operation of the registration clutch 11, that is, the rotation start of the registration roller 10.

However, in the conventional method as described above, the rotation start of the registration roller 10 can be used without depending on the paper with reference to the operation start of the transfer device 7 or the like. Since the stop timing of the developing device 6 and the transfer device 7 varies depending on the paper length, in order to control the stop timing of the charging device 4, the developing device 6, and the transfer device 7, a paper feed cassette unique to the paper size is used.
A device for detecting the type of the paper is operated to detect the paper size, and the stop control of the charging device 4, the developing device 6, and the transfer device 7 is performed using the timetable corresponding to the detected paper size. ..

[0008]

However, in the above-mentioned conventional structure, the mechanical members such as the registration clutch 11 and the registration roller 10 are required, and further, the developing device 6 is used.
Since the control of the stop timing of the transfer device 7 and the transfer device 7 differs depending on the paper length, it is necessary to prepare a means for detecting the paper size in the printing device, and a paper feed cassette for each paper size, and to cope with each paper size. There is a problem that it is necessary to set the timing of stop control of the charging device 4, the developing device 6, and the transfer device 7.

The present invention solves the above-mentioned problems of the prior art, and the timing of the electrophotographic process can be controlled independently of the paper length, and a paper feed cassette corresponding to each paper is unnecessary. The purpose is to provide.

[0010]

In order to achieve this object, a printing apparatus of the present invention is provided with respective detecting devices for detecting the leading edge and the trailing edge of a sheet on a sheet conveying path before transfer and after fixing, and each detecting apparatus. The timing of the electrophotographic process such as the operation and stop of the charging device, the developing device, and the transfer device and the writing on the photosensitive member is controlled based on the detection result.

[0011]

With this configuration, the stop control of the developing device, the transfer device and the like can be controlled without depending on the paper length.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1 showing an embodiment of the present invention, the same parts as those of the conventional example are given the same reference numerals and the description thereof will be omitted.

In FIG. 1, reference numeral 2 is a pre-transfer sheet edge detecting device,
Reference numeral 9 denotes a post-fixing sheet edge detecting device. With respect to the printing apparatus having the above-described respective components, the relationship and operation of the respective components will be described below.

In FIG. 2, which shows a timing chart of the printing apparatus according to the embodiment of the present invention, (a) the sheet edge detecting device before transfer and (b) the sheet edge detecting device after fixing are fallen by each sheet edge detecting device. The leading edge of the sheet enters the sheet, the rising edge indicates the trailing edge of the sheet, and (d) the write control signal indicates write prohibition in the high state and write permission in the low state. Other (c) main motor, (e) paper feed roller,
Regarding the charging device (f), the developing device (g) and the transfer device (h), the operation of each device is shown in a high state, and the operation of each device is shown in a low state.

As shown in FIG. 2, first, the charging device 4 is operated at the same time when the main motor starts rotating (A in FIG. 2).
point). When the point where the charging of the photosensitive drum 3 starts reaches the developing device 6 (at the distance indicated by L1 in FIG. 1)
Then, the developing device 6 is operated (point B in FIG. 2). In addition, where the entire photosensitive drum 3 is sufficiently charged, that is,
When the charging device 4 operates and the photosensitive drum 3 makes one rotation or more, the paper feed roller 1 is operated (point C in FIG. 2). The time until the charging device 4 is in the operating state until the developing device 6 is in the operating state, that is, the time T1 from the point A to the point B, and the main motor starts rotating,
Timing until the paper feed roller 1 operates, that is, A
The time T2 from the point to the point C is the rotational speed of the photosensitive drum 3 is PS (mm / Sec), the diameter of the photosensitive drum 3 is φa,
Assuming that the pi is π, T1 is given by (Equation 1) and T2 is given by (Equation 2).

[0017]

[Equation 1]

[0018]

[Equation 2]

The front end of the paper fed by the paper feed roller 1 passes through the pre-transfer paper edge detection device 2 (point D in FIG. 2).

After that, the paper further advances on the paper conveyance path, but the front end of the paper is a contact point P between the photosensitive drum 3 and the transfer device 7.
In order to start printing the print data on the paper when it arrives at the position, the distance from the leading edge of the paper to the contact point P of the photosensitive drum 3 and the transfer device 7 is the distance from the writing device 5 to the transfer device 7 (see FIG. (Indicated by L2 in FIG. 2), the write control signal is set to the write enable state (point E in FIG. 2). Further, when the leading edge of the paper reaches the point P, the transfer device 7 must be in the operating state (point F in FIG. 2).

Therefore, the timing until the leading edge of the sheet passes through the pre-transfer sheet edge detection device 2 and the write control signal is set to the write enable state, that is, the time T3 from point D to point E, and the transfer device 7 is operated. When the distance from the pre-transfer sheet edge detection device 2 to the point P is L3, the timing until the state is set, that is, the time T4 from the point D to the point E is expressed by T3 in (Equation 3) and T4 in (Equation 4). ).

[0022]

[Equation 3]

[0023]

[Equation 4]

Then, the leading edge of the sheet passes through the fixing device 8,
After fixing, the sheet enters the sheet edge detection device 9 (point G in FIG. 2). Further, the sheet edge passes through the pre-transfer sheet edge detection device 2 (see FIG. 2).
Point H).

Similarly to the case where the write control signal is set to the write enable state and then the transfer device 7 is set to the operating state, when the end of the sheet reaches the point P, the transfer device 7 is set to the stop state and the printing is ended. Therefore, when the distance between the end of the paper and the point P becomes equal to L2 on the paper transport path, the write control signal is changed from the write-enabled state to the write-disabled state, and the end of the sheet reaches the point P. Then, the transfer device 7 is stopped. At this time, the trailing edge of the sheet passes through the pre-transfer sheet edge detecting means 2 and the write control means is set to the write-protected state, that is, H
The time T5 from the point to the point I and the timing T6 at which the transfer device is stopped are as shown in (Equation 5) for T5 and (Equation 6) for T6, respectively, similarly to T3 and T4.

[0026]

[Equation 5]

[0027]

[Equation 6]

After that, the sheet end passes through the sheet end detecting device 9 after fixing (point J in FIG. 2). Since the printing process is completed at this point, the charging device 4 is stopped at an appropriate timing T7 based on this point J, and the developing device 6 is stopped at the same timing as from point A to point B. Put in a state. Therefore, the charging device 2 is stopped and the developing device 6
The timing at which the is stopped, that is, the time T8 from the point K to the point L is as shown in (Equation 7).

[0029]

[Equation 7]

Finally, the main motor is stopped at an appropriate timing T9. As described above, according to the present embodiment, means for detecting the leading edge and the trailing edge of the sheet are provided in the sheet conveying path before transfer and after fixing, and the detection result of the sheet edge detecting means is used without depending on the sheet size. The process timing can be determined only by the positional relationship among the charging device, the developing device, the transfer device, and the peripheral length of the photosensitive drum. Therefore, the mechanical members such as the registration clutch and the registration roller can be eliminated, and the paper feed cassette corresponding to each paper is unnecessary.

[0031]

As is apparent from the above description of the embodiments, the present invention is provided with the respective detecting devices for detecting the leading edge and the trailing edge of the paper in the paper conveying path before the transfer and after the fixing, and the detection by the respective detecting devices. Based on the results, the operation and stop of the charging device, the developing device, the transfer device, and the timing of the electrophotographic process such as writing on the photoconductor are controlled, so that the control can be performed regardless of the paper length. It is possible to realize an excellent printing device that does not require a paper feed cassette corresponding to each paper.

[Brief description of drawings]

FIG. 1 is a schematic front view showing the concept of a printing apparatus according to an embodiment of the present invention.

FIG. 2 is a timing chart of the operation of each device of the printing apparatus.

FIG. 3 is a schematic front view showing the concept of a conventional printing device.

[Explanation of symbols]

 2 Pre-transfer paper edge detection device 3 Photosensitive drum 4 Charging device 5 Optical writing device 6 Developing device 7 Transfer device 9 Post-fixing paper edge detection device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location B41J 29/38 Z 8804-2C G03G 15/00 110 7369-2H 15/04 116 9122-2H // B65H 7/02 7456-3F

Claims (1)

[Claims] 1. A printer comprising a paper feeding means, an optical writing means, a developing device, and a fixing device, and each detecting device for detecting the leading edge and the trailing edge of the paper in a paper transport path before transfer and after fixing. A printing device configured to control the timing of an electrophotographic process such as operation and stop of a charging device, a developing device, a transfer device, and writing on a photoconductor, based on the detection result of each detection device. ..