JPH05155472A - Image forming device - Google Patents

Abstract

PURPOSE:To perform accurate sequential control without exercising an influence on conveyance of sheets even when an output signal from the sheet detecting sensor of an image forming device effects malfunction. CONSTITUTION:An output signal is outputted from a sheet detecting sensor 13 arranged on a conveyance passage for recording sheet for an image forming device and serving to detect the presence of the recording sheets. A signal holding circuit 14 by which the output signal therefrom is held for a preset time is provided between a control part (CPU) 15 by which whole operation of the image forming device is controlled and the sheet detecting sensor 13. A normal output signal for the presence of recording sheets is outputted to the control part 15 in disregard of the signal, for the absence of sheets at a time when the sheets are present, of erroneous output signals from the sheet detecting sensor 13 generated when rigidity of the sheets is high and quality of the sheets is adverse.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention does not affect the conveyance of recording paper even when the output signal of the paper detection sensor malfunctions.
The present invention relates to an image forming apparatus that enables accurate sequential control.

[0002]

2. Description of the Related Art A laser printer shown in FIG. 4 will be described as an example of an image forming apparatus. FIG. 4 is a schematic diagram showing the overall configuration, and a paper feed cassette 1 for containing recording paper.
An optical system 2 that emits a laser beam corresponding to image information, and a photoconductor 3 that forms an electrostatic latent image corresponding to image information on its surface upon receiving image exposure by the laser beam from this optical system. A developing device 4 that develops the electrostatic latent image formed on the surface of the photoconductor with toner to make it visible, and a registration roller 5 that conveys the recording paper fed from a paper feed cassette to a transfer portion at a specific timing. A transfer charger 6 for transferring the exposed image on the photoconductor onto the conveyed recording paper, a fixing device 7 for fixing the image transferred on the recording paper, and the like.

In the above structure, the recording paper fed from the paper feed cassette 1 is conveyed to the transfer portion such as the photoconductor 3 via the registration roller 5 at a constant timing. On the other hand, the electrostatic latent image corresponding to the image information is made visible by the laser beam from the optical system 2 on the surface of the photoconductor uniformly charged in advance. After that, the image on the photoconductor is transferred by the transfer charger 6 to the recording paper conveyed to the transfer portion such as the transfer charger 6. The recording paper after the transfer is fixed by the fixing device 7, and the printing is completed. The recording paper after printing is discharged to the paper discharge tray 8.

FIG. 5 shows an example of a paper detection sensor used in the image forming apparatus. When the recording paper 9 is conveyed in the direction of arrow a and the recording paper is applied to the filler 10, the filler is pushed up in the direction of arrow b. , The signal output of the photo sensor 11 outputs the presence of paper from the output terminal 12. At this time, as the recording paper 9 is being conveyed, the output signal of the photosensor 11 changes to no paper, paper present, or paper none as shown in the timing chart of FIG. However, when the rigidity of the recording paper being conveyed is high or the quality of the paper is poor, the movement of the filler 10 will be so strong that the output signal of the photo sensor will momentarily disappear even when there is paper as shown in the timing chart of. Sometimes it becomes.

[0005]

In the above-mentioned image forming apparatus, when the recording paper is conveyed, the entrance of the recording paper is detected, or the operation of ejecting the recording paper is detected by the paper detection sensor, and then the recording paper is detected. Since the control unit (CPU) performs sequential control such as stopping the motor, the paper detection sensor for detecting the presence / absence of the recording paper needs to output an accurate signal.

However, as described above, when the rigidity of the recording paper to be conveyed is high or the quality of the recording paper is poor, the filler type paper detection sensor or the like has a large movement of the filler and the output of the paper detection sensor. The signal may be wrong.

It is an object of the present invention to carry out accurate sequential control without affecting paper conveyance even when the output signal of the paper detection sensor malfunctions.

[0008]

SUMMARY OF THE INVENTION The present invention is a means for holding an output signal of a paper detection sensor for detecting the presence or absence of recording paper, which is installed on a recording paper conveyance path of an image forming apparatus, for a preset time. Is provided between the control unit that controls the overall operation of the image forming apparatus and the paper detection sensor.

The holding time of the output signal of the paper detection sensor can be changed according to the paper size detected by the paper detection sensor.

[0010]

According to the present invention, since the output signal of the paper feed detection sensor is held for a certain period of time, the paper generated when the rigidity of the recording paper is high or the quality of the recording paper is poor. Among the error output signals of the detection sensor, the signal indicating that there is no paper during the paper is ignored, and a normal output signal indicating that the paper is present can be output to the control unit.

[0011]

1 is a block diagram showing the configuration of an embodiment of the present invention. In FIG. 1, 13 is a paper detection sensor,
The photo sensor 11 shown in FIG. 5 and the paper switch shown in FIG. Reference numeral 14 is a signal holding circuit that holds the output signal of the paper detection sensor 13 for a certain period of time, and 15 is a control unit that controls the entire image forming apparatus, which is composed of a CPU. Reference numeral 16 is a driven part whose operation is controlled by the CPU, and is a motor for paper conveyance, a clutch,
Such as a solenoid. Reference numeral 17 is a ROM in which an operation program for the CPU is stored, and 18 is a RAM for performing image formation under the control of the CPU.

Next, the operation will be described. The paper detection sensor 13
The output signal from is input to the signal holding circuit 14 so that the output signal is held for a certain period of time. When the time for holding the output signal is set as shown in, for example, FIG. 2, the signal indicating the absence of paper while the presence of paper is ignored, and a normal output signal of can be obtained.

As shown in FIG. 2, the area 19 for holding the output signal starts holding from the time when the paper detection sensor 13 changes from the absence of paper to the presence of paper, and releases the holding after a certain period of time. Also, when the next recording paper is conveyed and the signal output of the paper detection sensor changes from no paper to paper present, it is set to start holding again.

Two types of output signal holding time can be set. (1) When the paper size of the image forming apparatus can be carried and the length in the carrying direction is determined by the smallest paper, and (2) when the paper is carried. It may correspond to the length of the paper size in the transport direction.

In the case of (1), the transport speed at the position of the paper detection sensor of the image forming apparatus is x (mm / sec), and the transportable length of the paper size in the transport direction is A.
(mm), the output hold time t (sec) is

[0016]

## EQU1 ## It is given by the equation (1) of t = A ÷ x-B. Here, B is a certain fixed value.

In this case, if the conveying speed is constant by the image forming apparatus, the output holding time t (sec) is a constant value C (se).
given in c).

In the case of (2) If the conveyance speed at the paper detection sensor position of the image forming apparatus is x (mm / sec) and the length of the paper in the conveyance direction is y (mm), the output holding time t (sec) Is

[0019]

## EQU2 ## It is given by the equation (2) of t = y ÷ x-B. Here, B is a certain fixed value.

In the case of (1), the effect is reduced for a paper size long in the carrying direction, but in the case of (2), as shown in FIG. By incorporating the time, the signal output becomes reliable regardless of the paper size.

[0021]

As described above, in the image forming apparatus of the present invention, the output signal of the paper feed detection sensor is held for a certain period of time. When the quality of the paper is poor, it is possible to ignore the no-paper signal during the existence of the paper in the error output signal of the paper detection sensor that occurs and output the normal output signal of the existence of the paper to the control unit.

Therefore, the sequential control such as the conveyance of the recording paper after that becomes reliable.

Further, by incorporating the holding time corresponding to the paper size, the subsequent control becomes reliable regardless of the paper size.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a timing chart showing respective states of output signals of the present invention and a conventional paper detection sensor.

FIG. 3 is a timing chart showing a holding area of an output signal of a paper detection sensor corresponding to a paper size of the present invention.

FIG. 4 is a schematic diagram showing an overall configuration of a laser printer.

FIG. 5 is a diagram showing an example of a paper detection sensor.

[Explanation of symbols]

9 ... Recording paper, 10 ... Filler, 11 ... Photo sensor,
12 ... Output terminal, 13 ... Paper detection sensor, 14 ... Signal holding circuit, 15 ... Control unit (CPU), 16 ... Driven unit, 17
... ROM, 18 ... RAM, 19 ... Output signal holding area.

Claims (2)

[Claims] 1. An overall operation of the image forming apparatus, comprising means for holding an output signal of a paper detection sensor for detecting the presence or absence of the recording paper, which is installed on a recording paper conveyance path of the image forming apparatus for a preset time. An image forming apparatus having a control unit for controlling a sheet and a paper detection sensor. 2. The image forming apparatus according to claim 1, wherein the holding time of the output signal of the paper detection sensor is changed according to the paper size detected by the paper detection sensor.