JPS6240480A - Image recording device - Google Patents

Abstract

PURPOSE:To prevent occurrence of defective cleaning an image carrier due to unfinished transfer by providing a detecting device that detects at least the rear end of recording paper in a recording paper feeding device and stopping developing of a face which is not transferable due to the recording paper by the detecting device of the recording paper when the recording paper is shorter than the developing area developed by a developing device on the image carrier. CONSTITUTION:A charge electrode 1, an exposing section 2, a developing and cleaning device 3, a transfer electrode 5 and a separation pole 6 are arranged around a photosensitive body 8, and further, a feeding device of recording paper 9, a carrying guide 18 and a fixing device 7 are provided, and a sensor 12 is provided in the carrying guide 18. While the sensor 12 is detecting the recording paper, the device 3 acts as a developing device, and the sensor is not detecting, the device 3 works as a cleaning device. On the other hand, when the recording paper is shorter than the developing area developed by the developing device on the image carrier, developing of a face which is not transferable by the recording paper is stopped by the sensor 12.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to improvements in developing means of image recording apparatuses, ie, copying machines, printers, electrostatic recording apparatuses, etc. using electrophotography.

[Conventional technology]

In an image recording device using a general electrophotographic method, a latent image formed by exposing a band 71 on an image carrier becomes a visible image as toner is adhered to it by a developing device such as a magnetic brush, and the image is transferred. , the recording paper is transferred onto the recording paper supplied one by one from the paper feeder by the separation vc unit and separated from the image carrier.The recording paper passes through a thermal fixing device to be fixed and collected. On the other hand, the image carrier is cleaned by a cleaning device, and then charged, exposed, developed, and
The steps of transfer, separation and fixing are repeated. And the cleaning device has 8 blades, brushes, etc.! There are methods that mechanically scrape off dirt, methods that use the same magnetic brush device used for development and remove toner by selecting its bias voltage, or methods that use a combination of mechanical means and magnetism and have a separate magnetic brush. is used.

[Problems to be solved by the invention]

As mentioned above, the magnetic brush cleaning has almost the same structure as the magnetic brush developing means, so it can be used independently, but it is also convenient because it can be used in conjunction with the developing means by changing the bias voltage. However, magnetic brush cleaning is affected by how much toner is deposited per unit area of the image carrier. Usually, 60 to 90% of the toner image formed on the image carrier is transferred to the recording paper, so cleaning is good. However, if the recording paper is shorter than the image to be recorded, a portion of the toner image will reach the cleaning section without being transferred at all, resulting in poor cleaning. Furthermore, since the untransferred toner image is charged by the transfer electrode, cleaning performance becomes even worse. Furthermore, in manual paper feeding, it is difficult to cut the paper size M at the paper feeding unit, and the above-mentioned problem is particularly likely to occur. The purpose of the present invention is to prevent the occurrence of defective cleaning of the image carrier due to non-transfer even when the paper size is shorter than the length of the image to be recorded, or when there is a paper feeding failure and the leading edge of the recording paper does not reach the detection means position. The goal is to establish an image recording device that does not.

[Means to solve the problem]

This objective is achieved by the following technical means. In an image recording apparatus having a developing means by a developing device for an image carrier and at least a recording paper feeding means, the recording paper feeding means is provided with a detection means for detecting at least a trailing edge of the recording paper, and the developing means An image recording apparatus characterized in that when the recording paper is shorter than the development area developed on the image carrier by the recording paper, development of the non-transferable surface by the recording paper is stopped by means of a detection means of the recording paper.

[Example and action]

FIG. 1 shows an embodiment of the present invention, which is applied to an image recording apparatus in which one magnetic brush serves both for development and cleaning, and one image is obtained by two rotations of a photoreceptor that acts as an image carrier. Around the photoconductor 8 are a charging electrode 1, an exposure section 2, and a developing device.
A dual cleaning device 3, a transfer pole 5, and a separation pole 6 are arranged, and a recording paper supply device 9, its conveyance guide 18, and a fixing device 7 are also provided. A sensor 12 is also installed on the transport id 18. While the sensor 12 is detecting the recording paper, the device 3 functions as a developing device, and when the sensor 12 does not detect the recording paper, the device 3 functions as a developing device.
The c-station 3 functions as a cleaning device. In this case, as shown in FIG. 1, the speed at which the transfer paper is conveyed between the sensor 12 and the transfer position, which has a length L, of the open paper path is vl, and the peripheral surface of the photoreceptor between the development position and the transfer position is When the length of is L2 and the circumferential speed of the photoreceptor is v2, the sensor 12 is installed so that L, L2 □n □ vl V2. The sensor is turned ON while passing through 12fIS, and turned OFF again after passing through, and a micro switch is used.The recording paper is kept at the circumferential speed of the photoreceptor v2 until its leading edge reaches the transfer position. The recording paper is transported at an equal but slightly faster speed V, but the transport belt 4 transports the recording paper so that at least after the leading edge passes the transfer position, the speed of the recording paper is exactly equal to the circumferential speed v2 of the photoreceptor. Now, when the leading edge of the recording paper reaches the position of the sensor 12, the sensor 12 is turned on and development begins on the photoconductor, but the development position at that time is an unexposed area, and the actual writing of the image begins. The front side is on the upstream side of the development position on the photoconductor, that is, the distance from the transfer position to the circumferential surface of the photoconductor, and the distance is set to satisfy the following relationship.Therefore, the recording paper reaches the sensor 12 and development is started, and even when the recording paper reaches the transfer position, the unexposed photoconductor part has already reached the transfer position, but the toner-developed part at the actual writing start point has not yet been transferred. A portion of the untransferred toner that does not reach the position remains on the photoreceptor and is not transported to a cleaning device, etc.The developing device continues to operate while the sensor 12 is ON, but if the trailing edge of the recording paper At the same time as passing the sensor 12, the sensor IZ is turned off and the developing device stops functioning, and in this embodiment, the bias voltage is immediately switched to the magnetic brush cleaning voltage.At this time, since the following relationship holds, the developing device stops functioning. Since all of the toner images that have been transferred are transferred to the recording paper, the untransferred portions will not be brought into the cleaning device.The margin of the recording paper from the leading edge of the recording paper to the start of writing is... ', ), and the margin from the trailing edge of the recording paper O to the development end position at the trailing edge of the recording paper N is (L I' - L 2). Also, if the writing ends 0 seconds before the end of the development process, , and then if it is unexposed, the margin at the trailing edge of the recording paper is LI
It becomes LZ+V2α. Furthermore, according to the embodiment of the half-image recording v device, if the recording paper causes trouble during transportation and a paper feed failure occurs, the recording paper does not reach sensor A and remains OFF, so the developing vcfff does not operate and the unused The transferred toner image is not transported to the cleaning device, and cleaning defects in this case can be prevented in advance. Here, as shown in FIG. 1, the leading edge of the transfer paper fed by the #S1 paper feed roller 14 is temporarily stopped by a sensor 13 located at the second paper feed roller 9. Next, the leading edge of the transfer paper is fed to the transfer position by the second paper feeding roller 9, but the rotation start timing of the second paper feeding roller is the timing at which the leading edge of the transfer paper and the start of image writing on the image carrier (the margin of the leading edge (including) so that the position is dotted in the transcription area. It is desirable that the sensor 12 be provided midway between the second paper feed roller 9 and the transfer position. If the distance between the sensor 12 and the sensor 13 is large enough, and the sensor 12 is not ONL when the second paper feed roller starts rotating, it is determined that the feeding is defective. It is possible to issue a warning, display the details of the defect, and keep the developing function OFF, thereby allowing recovery processing of paper feeding defects to be performed without any untransferred images appearing. In this embodiment, the sensors 12 and 13 are microswitches, but photoelectric switches or other non-contact switches may also be used. The photoreceptor is not limited to a drum type, but may also be a belt type. In this embodiment, the magnetic brush is used as a device that serves both the developing and cleaning functions. In order to prevent this, the operation of the developing machine itself may be stopped, the bias voltage may be set to a voltage that makes development impossible, or the bias voltage may be set as a cleaning voltage. A timing chart of an embodiment in which a magnetic brush is used for both development and cleaning is shown in FIG. However, it is not limited to this chart. By applying the above-mentioned measures, highly reliable magnetic brush cleaning without occurrence of cleaning defects becomes possible.

【Effect of the invention】

According to the present invention, development is stopped and magnetic brush cleaning is performed even when recording paper that is insufficient to the specified length is supplied or when the leading edge of the recording paper does not reach the detection means position at the time of starting development due to a paper feeding problem. Because of this, cleaning defects will not occur. Therefore, a VC system has been established that can constantly maintain a clean photoreceptor and produce high quality electrophotography.

[Brief explanation of the drawing]

PIS1 diagram is a block diagram of an embodiment of an image recording apparatus equipped with the functions of the present invention. FIG. 2 is a timing chart of this embodiment. 1... Charger 2... Exposure section 3... Developing device/cleaning device 4... Conveyor belt 5... Transfer pole 6... Minute jFl pole 7... Fixing device 8... Photoreceptor 9...Second paper feed roller 1.2.13...Sensor 14...First paper feed roller 18...Conveyance guide

Claims (1)

[Scope of Claims] 1. In an image recording apparatus having a developing means using a developing device for an image carrier and at least a recording paper feeding means, the recording paper feeding means detects at least the trailing edge of the recording paper. An image recording apparatus comprising a detection means, and when the recording paper is shorter than the development area developed on the image carrier by the developing means, the detection means of the recording paper stops development of the non-transferable surface of the recording paper. . 2. The image recording apparatus according to claim 1, wherein the means for stopping the developing means is to stop the rotation of the developing device. 3. The image recording apparatus according to claim 1, wherein the means for stopping the developing means is to set the bias voltage of the developing device to a voltage that makes development impossible with respect to the image carrier. 4. The image recording apparatus according to claim 1, wherein the bias voltage of the developing device is set as a cleaning voltage with respect to the image carrier as means for stopping the developing means.