JPH0517059A - Paper feed speed control method and apparatus - Google Patents

Abstract

(57) [Abstract] [Purpose] Even if the conveyance is interrupted in the paper conveyance mechanism that controls the driving means so that the paper conveyance speed is detected and the paper conveyance is performed at a constant speed, Provided is a method and device for controlling the paper feed speed, which allows the paper to be conveyed at a constant speed when the conveyance is restarted regardless of the length. A transporting means for transporting a sheet, a driving means for sending a drive signal to the transporting means, a detecting means for detecting a transporting speed of the sheet, and correcting the drive signal according to the transporting speed. And a driving means for outputting a driving signal corrected by the correction value, in the sheet feeding mechanism for outputting the driving signal corrected by the correction value. When the interruption time exceeds a predetermined value, the correction value at the time of restarting the paper conveyance is set to 0, and when the interruption time is less than the predetermined value, the correction at the time when the paper conveyance is stopped The value is used as the correction value when the paper conveyance is restarted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for controlling a paper feed speed of an image forming apparatus that prints on continuous paper, and more specifically, an error of a carry speed that occurs when a paper is carried. The present invention relates to a paper feed speed control method and apparatus capable of solving the above problem.

[0002]

2. Description of the Related Art Conventionally, laser beam printers,
2. Description of the Related Art An electrophotographic printer that forms an image using an electrophotographic method is known. In the electrophotographic method, first, a uniformly charged surface of a photosensitive drum is exposed based on image information to form an electrostatic latent image, and toner is attached to the latent image to form a toner image. (developing). Next, the toner image is transferred onto the recording paper, and the toner image transferred onto the recording paper is fixed by the fixing device. As a fixing device for a laser beam printer, a recording paper carrying an unfixed toner image is passed through a fixing roller pair consisting of a heat roller heated to a high temperature and a backup roller contacting the heat roller at a predetermined pressure. Therefore, so-called heat roll fixing, in which the toner is fused on the recording paper by heating and pressurizing, is generally adopted.

[0003]

Generally, when recording paper is conveyed in the printer, the conveying system operates so as to convey the recording paper at a predetermined speed due to an error in the diameter of the conveying roller, expansion and contraction of the recording paper, and the like. Even if it does, an error may occur in the conveyance speed of the recording paper.

In particular, in the case where the fixing roller pair also acts as a recording paper conveyance roller, the diameter of the heat roller / backup roller increases or decreases due to temperature change or wear, and the influence of expansion or contraction of the recording paper due to temperature change. Therefore, there is a problem that an error occurs in the conveyance speed of the recording paper.

FIG. 6 shows an example of a fixing roller pair 10 which functions as a recording paper conveying roller. In the figure, a drive source 13 for rotating the heat roller 11 at a predetermined peripheral speed is connected to the heat roller 11. The backup roller 12 is rotatably rotatable with a predetermined pressure.
Is abutted against. The surface of the heat roller 11 is coated with a fluorine resin or silicone oil in order to prevent toner sticking and offset phenomenon. Therefore, the surface of the heat roller 11 has a very low friction coefficient, and when the recording paper is actually conveyed by the fixing roller pair 10, the backup roller 12 is driven by the heat roller 11 which is rotationally driven, and the backup roller 12 is driven by the backup roller 12. The recording paper 20 is driven to be conveyed.

Here, when the recording paper is conveyed in the state as shown in FIG. 6, the area 12B of the backup roller 12 that contacts the recording paper and the heat roller 11 directly outside the recording paper.
A temperature difference occurs in a region 12A that is in contact with. Since the temperature of the area 12A of the backup roller 12 becomes higher than the temperature of the area 12B, the diameter of the area 12A becomes larger than the diameter of the area 12B due to expansion. Therefore, the peripheral speed in the area 12A of the backup roller 12 matches the peripheral speed of the heat roller 11, but the peripheral speed in the area 12B having a smaller diameter is lower than the peripheral speed of the heat roller 11. Therefore, the recording paper 20 conveyed and driven in the area 12B having a small diameter
The transport speed of will be slower. This phenomenon is particularly remarkable when the width of the recording paper is small. In the electrophotographic printer, it is necessary to synchronize the conveyance of the recording paper with the exposure of the optical system and the rotation of the photosensitive drum. Therefore, if the conveyance speed of the recording paper changes as described above, the image formation may not be performed normally. There was a problem.

To solve this problem, a method is known in which the speed of the recording paper is detected, the rotational speed of the heat roll 11 is corrected, and the recording paper transport speed is maintained at a normal value. However, with the method of correcting the rotation speed of the heat roller 11 after detecting the conveyance speed of the recording paper as described above, the correction value cannot be obtained from the time from the start of conveyance of the recording paper to the speed detection. The following problems occur when recording paper is once stopped while the recording paper is being conveyed with the rotational speed of the heat roll 11 being corrected, and the recording paper is conveyed again. At this time, in the case where the number of rotations of the heat roller 11 at the time of restarting the conveyance of the recording paper is set to the number of rotations at the time of stopping the conveyance, the conveyance interruption time is long, the temperature of the backup roller 12 is lowered, and the regions 12A and 1
When the difference between the diameters of 2B is small, the peripheral speed of the region 12B becomes too fast because the rotational speed is corrected.

Further, in the structure in which the number of rotations of the heat roller 11 is returned to the initial value when the recording paper conveyance is restarted, the diameter of the area 12A is larger than the diameter of the area 12B as described above when the conveyance interruption time is relatively short. Since the recording paper conveyance is restarted in the state where
Since 1 is rotationally driven, there is a problem that the peripheral speed of the area 12B, that is, the conveying speed of the recording paper 20 becomes slow.

[0009]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a continuous paper printer which detects the conveying speed of recording paper and controls the conveying means so that the recording paper is conveyed at a constant speed. It is an object of the present invention to provide a paper feed speed control method and device that allows paper to be fed at a prescribed speed regardless of the length of the interruption time even when the conveyance is resumed after the conveyance is interrupted.

Therefore, in the paper feed speed control method and apparatus according to the present invention, a carrying means for carrying the paper, and a driving means for sending a drive signal to the carrying means,
It has a detection means for detecting the conveyance speed of the sheet and a correction means for obtaining a correction value for correcting the drive signal according to the conveyance speed, and the drive means outputs the drive signal corrected by the correction value. In the paper transporting mechanism for outputting, the transport suspending time from when the transport of the paper is stopped until it is restarted is measured, and the correction value at the time of restarting the transport of the paper is determined according to the suspending time. .

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a paper feed control unit of a laser beam printer to which the paper feed speed control method and apparatus of the present invention are applied.

The CPU 1 is connected to a speed detecting means 2 for detecting the conveying speed of the recording paper, and a timer 3 for starting the recording paper conveyance and starting the recording paper, and for measuring the time during which the conveyance is interrupted. ing. In addition, the CPU 1
The pulse number determining means 4 for determining the number of pulses applied to the pulse motor 6 for conveying the recording paper is connected, and the drive pulse is output from the pulse generating means 5 to the motor 6 based on the number of pulses determined here. Further, 7 is a driving means for driving the scanning optical system of the laser beam printer, which is controlled independently of the motor 6.

When the recording paper is being conveyed, the speed detecting means 2 detects the conveying speed of the recording paper, and the CPU
Sent to 1. The correction value A of the drive pulse is determined by the correction means 4 based on this transport speed, and the pulse generation means 5
Thus, the drive pulse corrected based on the correction value A is output to the motor 6.

FIG. 2 is a flowchart showing the outline of the operation of the laser beam printer. When the power is turned on,
In step S1 (hereinafter abbreviated as S1), a self-test / initialization process is performed, and a print signal waiting state is set (S
2). When a print signal comes in, the print process of S3 is performed. In the initialization process, the print restart flag PFR and the drive pulse correction value A, which will be described later, are set to PF.
R = 0 and A = 0 are set, and the drive pulse number N applied to the motor 6 is the reference pulse number N0 which is an initial value.
Is set. When printing is interrupted, the timer 3 is reset (S5). After that, when printing is restarted, S
In step 7, the print restart flag PFR = 1 is set, and the process returns to the print process (S3).

FIG. 3 shows the number N of drive pulses applied to the motor 6.
9 shows a correction value determination interrupt process for calculating the correction value A. This process is executed as an interrupt process each time the recording paper is conveyed by a predetermined amount. First, the current transport speed of the recording paper is detected (S8), then the correction value A of the drive pulse is obtained based on this current transport speed (S9), and the interrupt processing is exited.

FIG. 4 is a flowchart showing the motor drive interrupt processing. This motor drive interrupt processing,
An interrupt process is executed at predetermined time intervals during the print process of S3 in FIG.

When this process is executed for the first time after the power is turned on, the print restart flag PFR is 0, which is the initial value. Therefore, it is determined as No in S11, and the drive pulse N = N0 + A is obtained in S14. Here, since the initial value 0 is set in A, the initial drive pulse number applied to the motor 6 is the reference pulse number N0. The drive pulse N is output to the motor 6 in S15.

As described above, this motor drive interrupt processing is performed at predetermined time intervals until printing is interrupted, S11 and S1.
4 and S15 are executed in this order. In this case, the correction value A is updated by the correction value determination interrupt process of FIG.
The number of drive pulses output to the motor 6 is also updated with time. When the printing is once suspended and then restarted, the printing restart flag PFR = 1 is set in S7 of FIG. Therefore, when the motor drive interrupt process of FIG. 4 is executed, it is determined Yes in S11. Then, the process branches based on the elapsed time T until the printing is restarted, which is measured by the timer 3 which is reset and started when the printing is interrupted.

If the time T from the interruption of printing to the restart is within 30 seconds, the motor is driven with the driving pulse number N = N0 + A using the correction value A immediately before the interruption of printing (S1).
4, S15). When the time T from the interruption of printing to the restart exceeds 30 seconds, the correction value A = 0 (S13), the driving pulse N = N0, and the motor is driven with the reference pulse number N0 (S14, S15). .

FIG. 5 shows a motor drive interrupt process as a second embodiment. In the first embodiment, the value of the correction value A is changed depending on whether the time interval from the interruption of printing to the restart is 30 seconds or less, but in the second embodiment, this time interval T
The value of the correction value A is further corrected depending on whether or not is 10 seconds, 20 seconds, 30 seconds or less or exceeds 30 seconds.

In FIG. 5, the same processes as those in FIG. 4 are indicated by the same step numbers, and the description will be omitted. In this example,
The time interval T is divided into the above-mentioned four steps, and the correction value A is corrected stepwise according to the size of the time interval T.

In S22, it is determined whether the time interval T from the interruption of printing to the restart is 10 seconds or less. In the case of 10 seconds or less, it is considered that the environment before the interruption is almost maintained, so the correction value A is used as the correction value at the time of restart. When the time interval T exceeds 10 seconds and is 20 seconds or less, the correction value ΔA is subtracted from the correction value A. Where ΔA is
If the time interval T is divided into n stages and the correction value = A in the first stage and the correction value = 0 in the n stage, Δ
It is represented by A = A / (n-1). Therefore, in the case of this embodiment, ΔA = A / 3. When the time interval T exceeds 20 seconds and is 30 seconds or less, the correction value A = A-2 · ΔA is corrected as shown in S26. When T exceeds 30 seconds, the correction value A is set to 0 (A-3 · ΔA
= 0).

In the above correction, the correction value A is corrected step by step. For example, when T is 30 seconds or less, A =
If (30−T) A / 30, the decrease of the correction value A during the print interruption time can be approximated by a straight line. Further, if an approximate expression based on experiments is used, more accurate correction becomes possible.

In this embodiment, the correction value at the time of restarting printing is set with reference to the correction value immediately before the interruption of printing.
The interruption time and the correction value corresponding to the interruption time are stored in advance in a memory as an internal table, and when the printing is restarted, the correction value corresponding to the interruption time is read from the internal table to control the rotation speed of the heat roller 11. It is also possible to do so.

In the above embodiment, the border line of the print interruption time interval for returning the number of drive pulses to the initial value is set to 30 seconds, but this may be changed appropriately depending on the configuration of the printer, the material of the backup roller and the like. It goes without saying that it should be done.

[0026]

According to the paper feed speed control and apparatus of the present invention, even if printing is interrupted and then restarted in a printer in which the conveyance speed is controlled to be constant during the conveyance of the recording paper, the printing is interrupted. The speed can be controlled so that the recording paper is conveyed at a predetermined speed in response to the change in the environment depending on the size of time.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a paper feed control system.

FIG. 2 is a flowchart illustrating the operation of a laser beam printer.

FIG. 3 is a flowchart of interrupt processing for determining a drive pulse correction value.

FIG. 4 is a flowchart of motor drive interrupt processing.

FIG. 5 is a flowchart of motor drive interrupt processing as a second embodiment.

FIG. 6 is a schematic perspective view of a fixing roller pair that functions as a recording paper conveyance roller pair.

[Explanation of symbols]

11 fixing roller 12 heat roller 20 recording paper

Claims (6)

[Claims] 1. A transporting means for transporting a sheet, a driving means for sending a drive signal to the transporting means, a detecting means for detecting a transporting speed of the sheet, and a drive signal for outputting the drive signal according to the transporting speed. A sheet conveying mechanism that outputs a drive signal corrected by the correction value, and has a correction unit that obtains a correction value for correction, from when the sheet is stopped to when it is restarted. A method for controlling a paper feed speed, characterized in that a conveyance interruption time is measured and a correction value at the time of resumption of paper conveyance is determined according to the interruption time. 2. The paper feed speed control method according to claim 1, wherein when the interruption time exceeds a predetermined value, the correction value at the time of restarting the paper conveyance is set to 0. 3. The correction value at the time when the conveyance of the sheet is stopped is set as the correction value when the sheet conveyance is restarted when the interruption time is less than a predetermined value. Paper feed speed control method. 4. The correction value at the time of restarting the sheet transportation is determined so as to gradually approach 0 from the correction value at the time of stopping the sheet transportation as the interruption time becomes longer. Paper feed speed control method. 5. The paper feed speed control method according to claim 4, wherein the correction value at the time of restarting the paper conveyance is determined so as to change stepwise according to the interruption time. 6. A transporting means for transporting a sheet, a driving means for sending a drive signal to the transporting means, a detecting means for detecting a transporting speed of the sheet, and a drive signal for outputting the drive signal according to the transporting speed. A sheet conveying mechanism that outputs a drive signal corrected by the correction value, and has a correction unit that obtains a correction value for correction, from when the sheet is stopped to when it is restarted. An interruption time measuring means for measuring the conveyance interruption time, a correction value determining means for deciding a correction value when the paper conveyance is restarted according to the conveyance interruption time measured by the interruption time measuring means, and the driving means. A paper feed speed control device, comprising: a control unit configured to control a drive signal corrected based on the correction value determined by the correction value determination unit to be output to the conveyance unit when the conveyance is restarted.