JPH06218979A - Image forming apparatus - Google Patents

Abstract

PURPOSE:To enable printing to be carried out without any disadvantages even in the case where the size of recording paper is smaller than that of the image. CONSTITUTION:If the size of recording paper supplied from a transportation controller 25 is smaller than that of an image that is sent from a host computer 21, print is conducted by erasing a data on the image in the area which is protruded from the recording paper. In this manner, work such as cleaning are restrained at minimum, so that a printing treatment can be done effectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus for forming an image by, for example, transferring a toner image formed on a photoconductor onto a recording medium.

[0002]

2. Description of the Related Art In recent years, a laser printer has been widely used as an image forming apparatus for printing character information and image information. In this laser printer, an image is formed as an electrostatic latent image on a charged photosensitive member, and this latent image is developed with toner to form a visualized toner image, which is transferred onto a recording paper and subjected to a heat fixing process. It is an image completed through the steps. There are various methods for transferring the toner image onto the recording paper, one of which is by a transfer roller.

The transfer by the transfer roller is applied to the toner image when the transfer roller is arranged in pressure contact with the photoconductor and the recording medium is passed between the photoconductor on which the toner image is formed and the transfer roller. This is performed by applying a transfer bias potential having a polarity opposite to the electric charge to the transfer roller and adsorbing and transferring the toner image on the photoconductor onto the recording paper.

[0004]

In such a laser printer, it is a principle to supply recording paper of a size suitable for the size of the image to be formed, but in the laser printer, the size of the image to be formed is large. However, there are cases in which it is not always possible to supply recording paper suitable for the size of the image. When the size of the formed image is smaller than the recording paper, no particular trouble occurs, but in the opposite case, that is, when the toner image formed on the photoconductor is larger than the recording paper to be transferred, Of the toner image on the photoconductor, the toner of the portion protruding from the recording paper is transferred onto the transfer roller, and the recording paper to be fed next is soiled, or the transfer bias potential applied to the transfer roller is substantially reduced. Result in poor transfer, resulting in defective transfer. This is often a problem when printing foreign documents with different recording paper standards. For example, this corresponds to the case of printing a letter size image on recording paper of A4 standard size in Japan. This is because, in this case, this image must be forcibly printed on A4 recording paper.

Therefore, before and after the printing process of one image, a potential having a polarity opposite to that at the time of transfer is applied to the transfer roller to transfer the toner adhering to the transfer roller to the photoconductor and clean the transfer roller. A method has been proposed (see, for example, JP-A-1-292385). Also, when specifying the size of the image to be formed using the keys on the operation panel, the specified image size is compared with the size of the recording paper to be fed, and if they do not match, it is considered that a jam has occurred and It has been proposed to stop recording and prevent contamination due to toner transfer (Japanese Patent Laid-Open No. 4-8327).
No. 2).

However, in the former method of cleaning the transfer roller before and after the image printing process, the device driving time other than the image formation becomes long and the life of the device is shortened. Furthermore, if cleaning is performed between image prints, even if the time required for one print is the same, extra time is required for multiple image prints, and as a result, much time is required. become.

On the other hand, in the latter method, when the designated image size and the size of the recording paper do not match, it is considered that a jam has occurred and the image recording is stopped. Therefore, it takes time to restore the recordable state. There is an inconvenience that it takes time.

Therefore, in the present invention, in order to solve such a conventional problem, even if the designated image size and the recording paper size do not match, the print processing can be performed without any inconvenience. An object is to provide an image forming apparatus.

[0009]

SUMMARY OF THE INVENTION To achieve the above object, the present invention is an image forming apparatus for transferring a toner image formed on a photoconductor onto a recording paper to form an image, the toner image being transferred. Recording paper size detecting means for detecting the size of the recording paper, image size detecting means for detecting the size of the image formed on the recording paper, and recording paper size detected by the recording paper size detecting means. When the size of the recording paper is smaller than the size of the image as a result of the comparison by the comparing unit that compares the size of the image detected by the image size detecting unit and the size of the image, the toner formed on the photoconductor And an image forming area setting means for storing the image area within the size of the recording paper.

[0010]

According to this structure, the comparing means compares the size of the recording paper detected by the recording paper size detecting means with the size of the image detected by the image size detecting means, and as a result of this comparison, the recording is performed. When the size of the paper is smaller than the size of the image, the image forming area setting unit sets the area of the toner image formed on the photoconductor so as to be within the size of the recording paper.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing the configuration of a laser printer to which the present invention is applied. The surface of the photosensitive drum 1 is charged with a predetermined charge by the charging brush 5. The laser light modulated by the image signal emitted from the semiconductor laser oscillator 2 is scanned in the main scanning direction by the polygon mirror 3 rotating by the polygon mirror drive motor 3a, reflected by the reflection mirror 4 and incident on the photosensitive drum 1. To do. The photoconductor drum 1 is rotated in the direction a in the figure to perform sub-scanning, and an electrostatic latent image is formed on the surface of the photoconductor drum 1 by the above operation. This electrostatic latent image is developed by the developing device 6 and converted into a toner image.

The paper feed roller 9 causes the recording paper C to be fed by a paper feed command.
The feeding of P is started. The paper feed state of the recording paper CP is detected by the paper feed sensor 10, and the recording paper CP is conveyed on the conveyance path and temporarily stopped by a timing roller (not shown).
The toner image on the photosensitive drum 1 is conveyed to the transfer position at the timing when the toner image reaches the transfer position. At this time, a bias having a polarity opposite to the charge of the toner on the photoconductor drum 1 is applied to the transfer roller 7, so that the toner image on the photoconductor drum 1 is transferred to the recording paper CP. The toner image transferred to the recording paper CP is fixed by the fixing roller 11 and then discharged by the paper discharge roller 13. The ejection of the recording paper CP is detected by the paper ejection sensor 12. The toner remaining on the photosensitive drum 1 after the image transfer is removed by the cleaning blade 8. The recording paper CP may be fed from the paper feed cassette or the manual paper feed port.

FIG. 2 is a block diagram showing the configuration of the control system of the laser printer to which the present invention is applied.

The host computer 21 outputs a print request signal for requesting printing of an image read from an image reading device (not shown), outputs the size of the image, and further reads the read image. Is converted into an image signal and output. The printer controller 22 receives a print request signal from the host computer 21 and outputs a command for printing to the engine control unit 24. Operation panel 2
Reference numeral 3 is for giving the recording paper size and other printer control information to the printer controller 22. The engine control unit 24 controls each unit of the printer based on a command from the printer controller 22.

The transport controller 25 controls the feeding of the recording paper CP, and the scanner controller 28 controls the operation by the polygon mirror 3. High voltage controller 29
Is for performing high voltage control such as charging of the photosensitive drum 1, development bias, and application of transfer bias potential to the transfer roller 7. The laser control unit 30 is for performing modulation control of laser light. is there. The paper feed sensor 10 is used as a sensor for recognizing the size of the recording paper CP conveyed, and details of the recognition will be described later.

1 and 2, the paper feed sensor 10 and the engine controller 24 function as recording paper size detecting means, the host computer 21 or the operation panel 23 function as image size detecting means, and the printer The controller 22 functions as a comparing means and an image forming area setting means, respectively.

When the printer controller 22 receives the print request signal from the host computer 21, it outputs a command for printing to the engine controller 24. In response to this command, the engine control unit 24 outputs a paper feed command signal to the transport control unit 25 to command the start of paper feeding, and at the same time commands the scanner control unit 28 to perform scanning preparation, and also to expose the light via the high voltage control unit 29. Preparation for printing is performed by setting the charging of the body drum 1 and the developing bias. In addition, a vertical synchronization request signal is output to the printer controller 22, waiting for reception of the vertical synchronization signal, and when the vertical synchronization signal is output, it is input from the host computer 21 to the laser control unit 30 via the printer controller 22. The laser light is modulated based on the image signal, whereby an electrostatic latent image is formed on the photosensitive drum 1.

In the above-described operation, the recording paper CP is fed from the paper feed cassette in sequence based on the paper feed command signal output from the engine controller 24. As described above, the example laser printer can recognize the size of the fed recording paper CP. The size of the recording paper CP is recognized as follows.

The size of the fed recording paper CP is recognized from the length of the recording paper CP in the conveyance direction detected by the paper feed sensor 10. Since this length cannot be measured directly, as shown in FIG. 1, the paper feed sensor 10 is disposed on the conveyance path of the recording paper CP close to the paper feed roller 9, and the recording paper C
It is recognized from the time when the leading edge and the trailing edge of P pass through the paper feed sensor 10. That is, the leading edge of the recording paper CP is the paper feed sensor 1.
0 is detected, and the trailing end is detected by the paper feed sensor 10.
The size of the recording paper CP is recognized based on the time until it is detected by. Therefore, as for the size of the recording paper CP, the trailing edge of the recording paper CP that is first fed is the paper feed sensor 1.
It will be recognized when it is detected by 0. Then, if the length of the recording paper CP in the transport direction is recognized, the length in the width direction can also be recognized from the standard size of the recording paper CP.

In the above operation, if the size of the recording paper CP matches the size of the image to be printed, or if the size of the recording paper CP is larger than the size of the image to be printed, one of the images Although the problem of part loss does not occur, when the size of the recording paper CP is smaller than the image size to be printed, the toner forming a part of the image directly adheres to the transfer roller 7 and is supplied later. This may stain the recorded recording paper CP.

FIG. 3 is a diagram mainly showing the internal configuration of the printer controller 22 shown in FIG. Host I /
The F35 or the engine I / F 36 is an interface that controls the exchange of information with the host computer 21 or the exchange of information with the engine control unit 24. The program storing ROM 37 stores a program for playing a control role of the printer controller 22 in cooperation with the CPU 38.

The work memory 39 has a function of temporarily storing work information as the printer controller 22 as needed. Received data storage memory 40
Serves as a buffer for receiving and storing data from the host computer 21, and the read image data is stored here. The intermediate data storage memory 41 is the received data storage memory 40.
It is a memory that analyzes the received data in it, converts it into intermediate code, and saves it as intermediate data. Therefore, in this memory, the image data is stored as an intermediate code. The bit image memory 42 is
This is a memory for storing a bit image obtained by expanding the intermediate data in the intermediate data storage memory 41 into a bit image. The DMA circuit 43 is a circuit having a function of outputting the bit data of the bit image memory 42 to the engine control unit 24 via the engine I / F 36.

With the configuration shown in FIG. 3, when the size of the recording paper CP is smaller than the size of the read image, the detailed operation will be described in the flow chart described later under the condition of the compulsory printing command. The image clip shown will be made.

Next, before describing the detailed operation of the image forming apparatus of the present invention, the general operation of the apparatus will be described.
From the host computer 21, image data read by an image scanner (not shown), data regarding the size of the image, and the like are sent to the printer controller 22. The host computer 21
Alternatively, when a print request signal is output from the operation panel 23, the conveyance control unit 25 operates and the recording paper CP is sent out from the designated paper feed port. The size of the recording paper CP is recognized when the trailing edge is detected by the paper feed sensor 10 as described above, and the recognized size of the recording paper CP and the size of the image are compared in the printer controller 22. . When the size of the recording paper CP is smaller than the size of the image sent from the host computer 21, there is a problem that the toner in the peripheral portion which is outside the size of the recording paper CP is transferred to the transfer roller. However, if there is a compulsory printing command to continue the printing process, the bit data of the image corresponding to the protruding portion is changed so that the image of the protruding peripheral portion is not formed as a latent image on the photosensitive drum. to erase. This processing is performed by the CPU 3 in the printer controller 22.
8, bit image storage memory, DMA circuit 43.

Next, the above operation will be described in more detail with reference to the flowcharts of FIGS. Note that this flowchart relates to the printer controller 22. Image data is sent from the host computer 21 before this flowchart is processed, and the image data is stored in the intermediate data storage memory 41 as intermediate data or in the bit image storage memory 42 as bit data. I shall.
It is also assumed that the data regarding the size of the image is sent from the host computer 21.

First, the printer controller 22 sends a signal to the transport controller 25 in accordance with a signal relating to the setting of the sheet feed port from the operation panel 23 or from the host computer 21. Is output. The transport controller 25 switches to a predetermined paper feed port based on this signal (S1). At this time, if the printer controller 22 cannot recognize the size of the recording paper CP to be fed, after the print request signal is output from the operation panel 23 or the host computer 21, A command for printing is output from the printer controller 22 to the engine control unit 24, and the engine control unit 24 receives the command and actuates the conveyance control unit 25, whereby the paper feed roller 9 rotates and paper feeding starts. (S2, S3).

When the paper is fed, the process waits until the size of the fed recording paper CP is recognized. That is, it waits until the paper feed sensor 10 detects the trailing edge of the recording paper CP. The detected size of the recording paper CP may be treated as the maximum size (S4). Next, the printer controller 22 compares the detected size of the recording paper CP with the size of the known image stored as data, and if the size of the image and the size of the recording paper CP are equal, If there is a print, S
Returning to step 1, if there is no print of the same image, the above print processing ends (S5, S6).

As described above, when printing is performed in a state in which the size of the recording paper CP is unknown, the size is recognized, and if the size of the image and the size of the recording paper CP match, the image of the image is recorded. Printing is performed on the recording paper CP.

On the other hand, if it is determined in step S5 that the image size and the recording paper CP size do not match, the printer controller 22 determines that the image size is larger than the recording paper CP size. Under the condition, the engine controller 24 is instructed to perform cleaning for removing the toner adhering to the transfer roller 7. The reason for this cleaning is that if the size of the recording paper fed is smaller than the size of the image, not only incomplete prints with part of the image missing on the recording paper, but also part of the image will be lost. This is because the formed toner directly adheres to the transfer roller 7 and stains the recording paper that is fed later. Therefore, when the size of the fed recording paper is larger than the size of the image, such a problem does not occur and the above cleaning is not performed (S
7, S8).

After this processing is completed, the printer controller 22 displays a message indicating that the size of the image does not match the size of the recording paper CP, that is, displays a size error, and calls the operator's attention. Wait for the forced print command.
This forced printing command is output from the operation panel 23 or the host computer 21 (S9,
S10).

As described above, when the size of the image does not match the size of the recording paper CP, the cleaning process and the error display are performed on condition that the size of the image is larger than the size of the recording paper CP. Done. Further, if the size of the image is smaller than the size of the recording paper CP, only an error display will be performed.

Returning to step S2, when the size of the recording paper CP is recognized, the printer controller 22 determines the size of the detected recording paper CP and the size of the known image stored as data. If the size of the image and the size of the recording paper CP are equal, the process returns to step S3 to perform the above print processing. If the size of the image and the size of the recording paper CP are not equal, the size of the image is A display indicating that the size does not match the size of the recording paper CP, that is, a size error is displayed to call the operator's attention and wait for a command for forced printing (S11).
~ S13).

When a compulsory printing command is issued from the host computer 21 or the operation panel 23, the printer controller 22 returns to the step S3 to perform the above-mentioned printing process if the size of the image is smaller than the size of the recording paper CP. If the size of the image is larger than the size of the recording paper CP, the image clip processing for deleting the image data of the peripheral portion protruding from the recording paper CP is performed.
After that, the process returns to step S3, and the above-mentioned print processing is performed (S14, S15).

FIG. 5 is a subroutine flow chart showing the concrete processing of the above-mentioned image clip. This flowchart is also processed by the printer controller 22.

First, in the case where the image data sent from the host computer 21 is held as intermediate data, the image data is stored in the intermediate data storage memory 41 shown in FIG. Therefore, the intermediate data is converted into a bit image by the CPU 38 and stored in the bit image storage memory 42. It should be noted that such conversion is not necessary for those having a bit image from the beginning (S21). Then C
The PU 38 calculates the address of the address located in the upper left corner of the image. That is, the origin position of the image data is calculated (S22). Then, the address pointer is set to the origin position at the upper left corner and the line counter is set to 0 (S23, S24). Next, the bit data stored in the bit image storage memory 42 is sequentially read according to the set address pointer and line counter. At the time of this reading, the position of the address pointer is the peripheral portion, that is, Chart paper CP
If it is a portion that is out of the area, it is unnecessary data, and therefore a process of erasing the memory contents indicated by the address pointer is performed (S25, S26). Next, it is judged whether the position of the line counter is the last line. If it is on the last line, it is judged whether the position of the address counter is on the right end. If it is on the right end, the process is executed. finish. This is because when the last line and the address counter are located at the right end, the reading of bit data for all image data has been completed (S27, S28). On the other hand, if the position of the line counter is not the final line, it is determined whether the position of the address pointer is the right end. If it is the right end, the line counter is incremented and the address pointer is increased. If it is not at the right end, the line counter is left unchanged and only the address pointer is incremented. The above-described processing sequentially scans the image data bit by bit for each line (S29 to S31). By the above processing, the data of the image located in the portion outside the size of the recording paper is deleted.

As described in the above embodiment, in the image forming apparatus of the present invention, when the size of the image is larger than the size of the recording paper CP, the image data of the portion which is printed out of the recording paper is printed. Since all of them are erased, the number of times of cleaning can be minimized even when forcing a large image on a small recording paper to be printed. Along with this, it is possible to improve the life of each part, shorten the printing time, and reduce the waste toner. Such a process is particularly effective when printing a print that increases the size of the image for each page.

[0037]

As described above, according to the present invention, when the size of the recording paper is smaller than the size of the image, the area of the toner image formed on the photoconductor is within the size of the recording paper. Since it is accommodated, the work such as cleaning can be suppressed to the minimum and efficient print processing can be performed.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a control system of the image forming apparatus according to the present invention.

FIG. 3 is a block diagram showing a schematic configuration of a printer controller in the image forming apparatus of the present invention.

FIG. 4 is an operation flowchart of the image forming apparatus of the present invention.

FIG. 5 is a subroutine flowchart showing an image clip process in the operation flowchart of the image forming apparatus of the present invention.

[Explanation of symbols]

10 ... Paper feed sensor (recording paper size detecting means) 21 ... Host computer (image size detecting means) 22 ... Printer controller (image forming area setting means,
Comparing means 23 ... Operation panel (image size detecting means) 24 ... Engine control unit (recording paper size detecting means)

Claims (1)

[Claims] 1. An image forming apparatus for forming an image by transferring a toner image formed on a photoconductor onto a recording paper, and a recording paper size detecting means for detecting a size of the recording paper on which the toner image is transferred. Comparing the size of the recording paper detected by the recording paper size detecting means with the size of the image detected by the image size detecting means When the size of the recording paper is smaller than the size of the image as a result of the comparison by the comparison unit, the toner image area formed on the photoconductor is within the size of the recording paper. An image forming apparatus comprising: a setting unit.