JPH0777913A - Front end resist controller - Google Patents

Abstract

PURPOSE:To enable the exact adjustment of front end resist timing even with paper of an arbitrary length. CONSTITUTION:The time for the paper P past a resist sensor to arrive at the transfer position to a photosensitive drum increases with the increase in the length of the cut paper P. The front end resist timing at two points [paper length points (P) 0, 1] of the paper length is theoretically or empirically set for each of three pieces of rolled paper and between these two points is linearly approximated. The front end resist timing at the arbitrary paper length is determined by the straight line.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a leading edge registration control apparatus for adjusting the image forming position of the leading edge of a sheet fed from a sheet feeding section, that is, adjusting the exposure start timing (leading edge registration timing) in the image forming section. In particular, the invention is applied to an image forming apparatus having a configuration in which a plurality of types of sheets having different sheet lengths are fed toward an image forming unit and the arrival time from the sheet feeding unit to the image forming unit is different depending on the sheet length. The present invention relates to a leading edge resist control device.

[0002]

2. Description of the Related Art In recent years, image forming apparatuses such as large-sized copying machines and plotters for large-sized drawings have a predetermined length before a sheet of paper wound in a roll shape is supplied to an image forming section. A sheet feeding device configured to be cut and used is often used.

By the way, in this type of image forming apparatus, the conveying speed of the conveying roller is increased as it goes downstream. Further, the number of conveyance rollers that nips the paper sheet differs depending on the paper length, and the arrival time of the paper sheet at the image forming unit differs depending on the paper length. Therefore, if you start exposure on the paper of all lengths at the same timing,
The position of the image formed on the leading edge of the sheet differs depending on the sheet length. Therefore, it is necessary to adjust the image forming position of the leading edge of the sheet, that is, the exposure timing (leading edge registration timing) in the image forming unit according to the sheet length.

Conventionally, the leading edge registration timing due to such a difference in sheet length is performed as shown in FIGS. 6 and 7. Here, FIG. 6 shows the relationship between the paper length and the arrival time of the paper to the photosensitive drum when the number of roll papers as the paper feed unit is two. Further, FIG. 7 shows the relationship between the paper length and the leading edge registration timing. In FIG. 6, for each of the two roll papers 1 and 2, when the paper length is between 210 mm (A4 width) and 390 mm, the longer the paper length, the later the arrival time to the photosensitive drum is delayed. . Therefore, the paper length is 2
In the range of 10 to 390 mm, it is necessary to adjust the leading edge registration timing according to an arbitrary paper length. In addition,
For a paper having a maximum paper length (390 mm) or more, the arrival time to the photosensitive drum is constant regardless of the paper length.

[0005]

However, in the conventional adjustment of the leading edge registration timing, as shown in FIG. 7, the paper length is 210 mm and the paper length is 39 mm.
It could only be performed on paper of two types of paper length, that is, 0 mm or more. That is, for the paper having a length exceeding 210 mm, the control was performed at the same timing as the leading edge registration timing for the paper having a length of 390 mm. Therefore, in the conventional control method, 21
There is a problem that accurate control is not performed for a paper having an arbitrary length in the range of 0 to 390 mm.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a leading edge registration control device capable of accurately adjusting the leading edge registration timing even for a sheet having an arbitrary length. is there.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a plurality of types of sheets having different lengths are supplied to an image forming section, and the arrival time from the sheet feeding section to the image forming section is different depending on the sheet length. And a registration sensor for detecting arrival of a sheet fed at a predetermined position between the image forming section and the sheet feeding section, Based on the relationship between the paper length detecting means for detecting the detected paper length and the preset paper length and the leading edge registration timing, the image according to the length of the paper detected by the paper length detecting means. Front-end resist timing determining means for determining the front-end resist timing in the forming unit, and exposure is started in accordance with the timing determined by the front-end resist timing determining means. Those provided with the exposure unit.

With such a structure, in the leading edge registration control device of the present invention, when the arrival of the fed sheet is detected by the registration sensor and the length of the sheet is detected by the sheet length detecting means, the leading edge registration control device is detected. The timing determining means determines the leading edge registration timing (exposure timing) according to the sheet length based on the preset relationship between the sheet length and the leading edge registration timing. The exposure by the exposure unit is started in accordance with the timing determined by the leading edge resist timing determination unit. The "relationship between the paper length and the leading edge registration timing" is theoretically or experimentally calculated from the relationship between the paper length and the arrival time of the paper to the photosensitive drum.

[0009]

Embodiments of the present invention will be specifically described below with reference to the drawings.

FIG. 1 shows a schematic configuration of an image forming apparatus to which a leading edge registration control device according to an embodiment of the present invention is applied. This image forming apparatus includes a photosensitive drum 10 as an image forming unit at the upper position. A paper feeding device 20 is arranged below the photosensitive drum 10. The paper feeding device 20 is provided with a plurality of, for example, three roll papers 21, 22, and 23 arranged in the vertical direction.

Corresponding to each of the roll papers 21 to 23, a conveying roller pair 31 including a driving roller 31a and a pinch roller 31b, a driving roller 32a and a pinch roller 32.
a pair of conveying rollers 32 and a driving roller 33a
And a pair of transport rollers 33 including a pinch roller 33b are arranged in the vicinity of each. These transport roller pairs 3
The sheets P are sent out from the roll sheets 21 to 23 by the sheets 1 to 33, respectively. Conveyor roller pair 31, 3
Sheet sensors 45 to 46 are arranged in the vicinity of the downstream sides of the sheets 2 and 33, respectively. On the downstream side of the conveying roller pairs 31 to 33, a cutter 34 including a fixed blade 34a and a rotary blade 34b, a cutter 35 including a fixed blade 35a and a rotary blade 35b, a fixed blade 36a and a rotary blade 36b are provided. The cutters 36 are arranged so as to cut the paper P sent out from each of the roll papers 21 to 23 into a desired length. The cut sheet P is respectively conveyed by a conveying roller pair 37 including a driving roller 37a and a pinch roller 37b, a conveying roller pair 38 including a driving roller 38a and a pinch roller 38b, and a conveying roller pair 39 including a driving roller 39a and a pinch roller 39b. The direction is changed in the vertical direction, and the sheet is conveyed toward the photoconductor drum 10.

A registration sensor 40 is arranged in the vicinity of the downstream side of the conveying roller pair 37. With reference to the time when the registration sensor 40 detects the leading edge of each sheet P,
The exposure timing (leading edge resist timing) by the exposure unit 57, which will be described later, is determined. Further, paper sensors 41 and 42 are arranged near the downstream sides of the conveying roller pairs 38 and 39, respectively, so that the passage of the paper P can be confirmed. A registration roller pair 43 including a drive roller 43a and a pinch roller 43b is arranged between the uppermost conveyance roller pair 37 and the photoconductor drum 10, and the paper P is located near the downstream side of the registration roller pair 43. A paper sensor 44 for detecting the arrival is arranged.

In this embodiment, the distance between the transfer position A of the photosensitive drum 10 and the registration sensor 40 is 26, for example.
1.4 cm, the distance between the transfer position A and the cutting position by the cutter 34 is, for example, 373.1 cm, and the distance between the transfer position A and the cutting position by the cutter 35 is, for example, 56.
The distance between the transfer position A and the cutting position by the cutter 36 is set to 5.1 cm, for example, 757.1 cm. Further, the conveyance speeds of the respective rollers with respect to the photosensitive drum 10 are 1.2% for the conveyance roller pairs 31 to 33, 2.0% for the conveyance roller pairs 37 to 39, and 2.8% for the registration rollers 43. As described above, the speed is controlled so as to increase toward the downstream side.

FIG. 2 shows the length of the paper P and the registration sensor 4
This shows the relationship with the arrival time of the paper P that has passed 0 to the transfer position A of the photosensitive drum 10, and the arrival time becomes longer as the paper length becomes longer. It should be noted that the arrival time at the photoconductor drum 10 of the paper P having a length longer than the distance between each of the cutters 34 to 36 and the transfer position A of the photoconductor drum 10 is constant regardless of the paper length.

FIG. 3 shows each of the roll papers 21 to 23.
The relationship between the paper length and the leading edge registration timing is shown. In this embodiment, for each roll paper 21-23,
As shown in an example in Table 1 below, the leading edge registration timing at two points of the sheet length [sheet length point (P) 0, 1] is theoretically set, and the two points are linearly approximated. The straight line determines the leading edge registration timing for an arbitrary paper length.

[0016]

[Table 1]

FIG. 4 shows the structure of the control unit in the image forming apparatus of this embodiment. This control unit includes a CPU (central processing unit) 50. The CPU 50 is connected to each unit of the device via a bus. Of these, a ROM (Read Only Memory) 51 stores a program for controlling the operation of each part of the apparatus and a program for leading edge registration control as shown in a flowchart (FIG. 5) described later. The RAM (random access memory) 58 is adapted to temporarily store read data, various calculation results, and the like. NOVRAM The (non-volatile random access memory) 52 so that the variable point data and the gradient data U _N described later is stored. The I / O port 53 is an interface between the registration sensor 40 and the size sensors 54a to 54c and the CPU 50. The operation unit 56 is adapted to input variable point data according to an arbitrary sheet length between the points 1 and 2. The variable point data is 10 m between −70 and +70 msec for each of the paper length points 1 and 2 for each roll paper 21 to 23.
It can be set in 0 to 14 steps every sec. Normally, this variable point data is 0
It is set to the 7th stage of 14 stages (this is set as the reference value (X)), and can be changed by the input data from the operation unit 56. In the CPU 50, this operation unit 56
Variable point data input from the registration sensor 4
The exposure timing (tip registration timing) is determined based on the detection signal from 0 and the output signals from the size sensors 54a to 54c, and a control signal is sent to the exposure unit 57. The timer 55 starts elapse of time after each of the registration sensors 40 is turned on, and elapses a predetermined time according to the determined exposure timing.

Next, the operation of the leading edge registration control apparatus of this embodiment will be described with reference to the flow chart shown in FIG.
First, the CPU 50 reads variable point data and gradient data _UN (N = 1 to 3) set through the operation unit 56 with reference to the reference value (X) (step S50).
0). Incidentally gradient data U _N is the distance between the photosensitive drum 10 and the cutter 34 to 36, respectively, which are calculated by the variable point data, the roll paper 21 is U _1, the roll paper 22 is U ₂ , U ₃ for the roll paper 23. These variable point data and the gradient data U _N are stored in each NOVRAM52,
It is updated whenever data changes.

Variable point data and slope data U _N
Is read, the CPU 50 causes the transport rollers 31 to 33, 3
7 to 39 are driven to selectively feed the paper P from the roll papers 21 to 23 (step S501). When any of the registration sensors 40 detects the leading edge of the paper P (step S502), the CPU 50 causes the registration sensor 4
Based on the detection signal of 0, it is determined from which roll paper 21 to 23 the paper has been supplied (step S50).
3). Further, the timer 55 starts elapse at the same time when the registration sensor 40 is turned on. Subsequently, the CPU 50 obtains the paper length based on the detection signals from the size sensors 54a to 54c (step S504), and the paper length and the roll papers 21 to 21.
The maximum paper length set for each 23 is compared (step S505). Here, the maximum paper length is, for example, 373 mm for the roll paper 21 and 5 for the roll paper 22.
The length is set to 65 mm and the roll paper 23 is set to 757 mm as the distance from the photosensitive drum 10 becomes longer. It should be noted that these maximum sheet lengths are the transfer position A on the photoconductor drum 10 and the cutters 34, 3
It is set in accordance with the distance between the cutting positions 5 and 36.

When the paper length obtained by the size sensors 54a to 54c is less than the maximum paper length set for each roll paper (step S505; Y), the CPU 50 causes the point data PD for the paper being conveyed. Then, the time t until exposure is calculated (step S506). here,
The point data PD is calculated from the gradient data for each of the roll papers 21 to 23 and the length of the paper in the range of 210 mm to the maximum paper length, and is determined by the following equation 1. The time t until exposure is calculated based on the point data PD, and is determined by the following equation 2.

[0021]

[Number 1] PD = P0 + (paper length -210) / U _N

[0022]

## EQU2 ## t = {X + (10 × PD-70)} / 10

When the calculated time t has elapsed, the CPU 50 starts the exposure by the exposure unit 57 (steps S507-509). As a result, the image at the leading edge of the sheet P is formed at an appropriate position according to the sheet length. On the other hand, when the paper length obtained by the size sensors 54a to 54c is equal to or larger than the maximum paper length set for each roll paper (step S5).
05; N), the time t until the exposure corresponding to each of the roll papers 21 to 22 is set to a fixed value as shown in the following Expression 3 (step S510), and the CPU 50, when the time t has elapsed, the exposure unit 57. To start exposure (step S5)
07-508).

[0024]

## EQU3 ## t = {X + (10 * P1-70)} / 10

As described above, in this embodiment, the exposure timing (leading edge registration timing) is determined according to an arbitrary sheet length between the sheet length points 1 and 2, so that the leading edge image is positioned at the proper position regardless of the sheet length. It is possible to accurately control the leading edge resist.

The present invention has been described above with reference to the examples.
The present invention is not limited to the above embodiments, but can be variously modified without changing the gist thereof. For example, in the above-described embodiment, the image forming apparatus having the configuration in which the speed of the transport roller is increased toward the downstream side has been described. However, even if the speed of the transport roller is all constant and the speed is constant, Slippage, back tension of transport rollers,
In consideration of the load and the like, it is necessary to change and adjust the leading edge registration timing depending on the paper length, and it goes without saying that the present invention can be applied to this case as well.

Further, in the above embodiment, the roll paper 2
Although the sheet P supplied from 1 to 23 is cut to a desired length by the cutters 34 to 36 and conveyed to the image forming unit, the lengths are different without using the cutters 34 to 36. The present invention can also be applied to a configuration in which cut sheets are fed. Further, in the above embodiment, a plurality of paper feed units (roll papers 21 to 2) are used as the paper P.
Although the sheet is conveyed from 3) through different conveying paths, the present invention can be applied to an image forming apparatus configured to feed sheets of different lengths for one roll sheet. Further, in the above-described embodiment, the operator inputs point data from the operation unit 57 and adjusts the leading edge resist based on the input data.
Instead of inputting from the, read the paper size output, the output roll, and the leading edge resist position of the image experimentally with another image reading device, and obtain the difference between the data and the value of the regular leading edge resist. Alternatively, the tip resist may be automatically adjusted by converting the variable point data value.

[0028]

As described above, according to the leading edge registration control apparatus of the present invention, the leading edge registration timing is automatically set according to the sheet length based on the preset relationship between the sheet length and the leading edge registration timing. Since the setting is made, there is an effect that the leading edge image is formed at an appropriate position regardless of the paper length, and accurate leading edge registration control can be performed.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a paper length and a paper speed.

FIG. 3 is a diagram showing a relationship between a sheet length and leading edge registration control timing in the present invention.

4 is a block diagram illustrating a configuration of a control unit in the image forming apparatus in FIG.

5 is a flowchart for explaining the operation of the image forming apparatus in FIG.

FIG. 6 is a diagram illustrating a relationship between a conventional paper length and paper speed.

FIG. 7 is a diagram showing a relationship between conventional paper length and leading edge registration control timing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Photosensitive drum, 20 ... Paper feeding part, 21-23 ... Roll paper, 31-33, 37-39 ... Conveying roller, 34-3
6 ... Cutter, 40 ... Registration Sensor, 43 ... Registration Roller, 50 ... CPU (Central Processing Unit), 51 ... ROM
(Read-only memory), 52 ... NOVRAM (random access memory), 54a to 54c ... Size sensor, 55 ... Timer, 56 ... Operation section, 57 ... Exposure section

Claims (1)

[Claims] 1. An image forming apparatus configured to supply a plurality of types of sheets having different lengths toward an image forming section and to have a different arrival time from the sheet feeding section to the image forming section depending on the sheet length. A registration sensor that detects arrival of the fed paper at a predetermined position between the forming unit and the paper feeding unit, and a paper length detection unit that detects the length of the paper detected by the registration sensor, and a preset sensor. Leading edge registration timing determining means for determining leading edge registration timing in the image forming section according to the length of the sheet detected by the sheet length detecting means based on the relationship between the sheet length and leading edge registration timing, and the leading edge registration timing determining means. Leading edge resist control, comprising: exposure means for starting exposure according to the timing determined by the resist timing determination means. Location.