JP2759649B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an image forming apparatus, and more particularly to an electrophotographic image forming apparatus, and more particularly, to an image forming medium such as a plurality of electrophotographic photosensitive members. These photosensitive members are subjected to an electrophotographic image forming process to obtain a developed image of each color, and the developed images are sequentially transferred to a transfer material which is a recording material carried and conveyed by a transfer material conveying device to obtain a color image. And a multicolor electrophotographic image forming apparatus. 2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as an electrophotographic copying apparatus, in addition to plain paper, an overhead project called OHP paper, which is thicker than plain paper, is used as a transfer material. Transparent films for Ektor are also frequently used. However, since the OHP paper is thicker and has a higher heat capacity than plain paper as described above, when the image forming apparatus is set to the fixing condition for fixing the plain paper, the OHP paper is fixed under the fixing condition. Then, fixation becomes incomplete. For this reason, conventionally, when a thick transfer material such as OHP paper is used, fixing is performed by another fixing device provided, or in an image forming apparatus having a roller fixing device, such a configuration is used. To fix a transfer material with poor fixability, a method of changing the fixing conditions by increasing the nipping pressure of the fixing roller has been proposed, but the former requires a lot of operation and requires a large operating cost, and On the other hand, the latter has a drawback that the image is crushed due to an increase in the fixing pressure, the resolution is reduced, and the quality of the image is deteriorated. Further, in the conventional apparatus, fixing is generally performed at a fixing speed (second speed) lower than the fixing speed (first speed) of plain paper. When the fixing speed becomes slow as in this type of apparatus, it is preferable to delay the supply timing of the next recording material in order to prevent overlapping with the next recording material. However, if the next recording material is supplied after the unfixed image is fixed on the recording material, the interval between the recording materials cannot be reduced more than between the supply unit and the fixing unit. This causes a problem that it takes time from the completion of the recording to the start of fixing of the next recording material. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problem. When fixing a recording material at the second speed of the fixing unit, the supply unit supplies the next recording material by the end of fixing of the recording material. By doing so, an image forming apparatus capable of forming an image on various types of transfer materials by a very simple operation without deteriorating the image quality without overlapping on the conveying device and with good fixability. To provide. Another object of the present invention is to provide an image forming apparatus capable of forming a good image on a transfer material having a large thickness, such as OHP paper. Another object of the present invention is to provide a multicolor image forming apparatus capable of forming a multicolor image on various types of transfer materials without deteriorating the image quality. Means for Solving the Problems The above object is achieved by an image forming apparatus according to the present invention. In summary, the present invention provides an image forming means for forming an unfixed image, a fixing means for fixing the unfixed image formed by the image forming means to a recording material, and a method for supplying a recording material to the image forming means. The fixing unit is capable of fixing at a first speed and a second speed lower than the first speed, and the recording is fixed by the supplying unit at the second speed of the fixing unit. The time between the supply of the recording material and the supply of the next recording material after the recording material fixed at the second speed is the time between the supply of the recording material fixed at the first speed and the first speed. In an image forming apparatus that is longer than the time required to supply the next recording material after the recording material is fixed, when the recording material is fixed at the second speed of the fixing unit,
The image forming apparatus is characterized in that the supply unit supplies the next recording material until the fixing of the recording material is completed. Next, an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. FIG. 1 shows an embodiment of the image forming apparatus according to the present invention. In this embodiment, a laser beam printer for multicolor copying by an electrophotographic system is shown. The full-color laser beam printer of this embodiment is
Four image forming units Pa, Pb, Pc, and Pd are provided, and each image forming unit is a dedicated electrophotographic photosensitive drum 1a, 1b, 1c, 1d.
Around, each dedicated image forming process means, such as charging units 2a, 2b, 2c, 2d, laser beam exposure means 4a, 4b, 4c, 4d, developing units 6a, 6b, 6c, 6d, transfer unit 8
a, 8b, 8c, 8d, cleaning units 10a, 10b, 10c, 10d, etc. are provided. The photoreceptor drums 1a, 1b, 1c, 1d are driven by a drive motor (not shown), and penetrate the image forming units Pa, Pb, Pc, Pd below the photoreceptor drums 1a, 1b, 1c, 1d. In this manner, a transfer member 30 having an endless belt 32, that is, a moving body that rotates in the direction of the arrow is disposed. The transfer material P, which is a recording material, is fed to the transfer material transport device 30 by the paper feeding device 20, and further transferred to the transfer units 8a, 8c of the image forming units Pa, Pb, Pc, Pc.
It is configured to convey in the direction of the arrow through b, 8c, 8d. In such a configuration, first, the first image forming unit Pa
To form a visible image of yellow toner, and the yellow toner image is transferred to the transfer material P conveyed by the transfer material conveying device 30 at the transfer portion, that is, the transfer position 8a. On the other hand, while the yellow image is being transferred to the transfer material 9, the second image forming means Pb obtains an image with magenta toner, and
When the transfer material P that has been transferred by the image forming means Pa is carried into the transfer position 8b of the second image forming means Pb, the magenta toner image is transferred to a predetermined position on the transfer material P. Hereinafter, the third and fourth image forming units Pc and Pd use cyan,
An image is formed for the black color, and four color toner images are superimposed on the transfer material P. When the transfer process is completed, the transfer material P is fixed by the fixing device 40, and a multi-color (full color) image is obtained on the transfer material P. After the transfer, each of the photosensitive drums removes the residual toner by the cleaning units 10a, 10b, 10c, and 10d, and prepares for the subsequent latent image formation. As described above, the transfer material P after the transfer is transferred to the fixing device 40.
And the transfer image is fixed, but the transfer speed of the endless belt 32 of the transfer material transfer device 30 is slightly faster than the transfer speed of the pair of fixing rollers 42a and 42b, so that wrinkling of the transfer material P during fixing is prevented. Also, the conveying speed of the endless belt 32 depends on each photosensitive drum.
The peripheral velocities 1a, 1b, 1c, and 1d are matched to prevent the occurrence of expansion and contraction of the image when the visible image is transferred to the transfer material. The transfer material P is transferred from the sheet feeding device 20 as a supply unit to the transfer position.
Is provided on the path for feeding the transfer material P. According to the present embodiment, the detecting means are two types of sensors 22 and 24, and an example of the configuration is shown in FIGS. In FIG. 2, the first sensor 22 has a lever 22a extending into the transfer material conveying path, and a photo-interrupter 22b arranged at one end of the lever 22a. When the transfer material is moved, one end of the lever 22a interrupts the sensor surface of the interrupter 22b. The second sensor 24 is a phototransistor 24
a and the LED 24b are arranged so as to sandwich the conveyance path, and the paper quality of the transfer material is detected by detecting a change in the voltage level of the phototransistor 24a caused by the transfer material blocking light from the LED 24b to the phototransistor 24a. Make a judgment. For example, if the transfer material P is a thick paper and is a transparent paper such as an OHP paper, the light level is not blocked and the voltage level of the phototransistor 24a does not change. Therefore, when the levels of the sensors 22 and 24 both change as shown in FIG.
If only the level changes, it is determined that the paper is transparent. Also, even for opaque paper, the light quantity from the LED 24b to the phototransistor 24a varies depending on the thickness of the paper, and the difference in paper quality between the opaque papers can be determined. Needless to say, the paper thickness and paper quality detecting means are not limited to the detecting means having the above configuration, and any suitable means can be selected. In addition, especially when the thickness characteristic of the paper quality alone is a problem, if the accurate determination is insufficient or impossible by the detecting means of the above configuration, the detecting means of the above configuration is used as the detecting means. Instead of the means or as a supplementary means, it is also possible to configure so that the operator can manually input such a signal to the control device of each device. In the present embodiment, the transfer material feeding speed of the fixing device 40 is controlled according to the paper quality (paper thickness) of the transfer material P. For example, when the transfer material P is a transparent paper such as an OHP paper having a large thickness as described above, the above-described transparent paper determination signal by the detection unit is transmitted to a drive control device (not shown) of the fixing device 40. The control device controls a fixing roller driving device (not shown), and the peripheral speed of the pair of fixing rollers 42a and 42b is adjusted to, for example, a second speed that is approximately half the first speed of plain paper. In the case of continuously obtaining a plurality of copies in the image forming apparatus having the configuration shown in the above embodiment, a plurality of transfer materials P are placed on the endless belt 32 of the transport device 30, and each transfer material is Although the interval is reduced to about several mm, in such a state, if the transfer speed of the transfer material in the fixing device is reduced as described above, the transfer materials may overlap. In order to prevent this, in the present embodiment, as described above,
For example, when the sensors 22 and 24 detect that the speed of the fixing device is set to be low, for example, OHP transparent transfer paper is used as the transfer material, the timing of feeding the transfer material is adjusted. FIG. 5 is a flow chart showing one embodiment of a control method for adjusting the feed timing of the transfer material. In this embodiment, when a continuous feed command comes from the operation unit,
First, the first transfer material is fed from the sheet feeding device 20 to the transport device. The first and second sensors 22 and 24 determine whether or not the sheet is an OHP transfer sheet. If the sheet is not an OHP transfer sheet, an image forming sequence for plain paper is started (step 1). If the fed transfer material is an OHP transfer sheet, a timer (not shown) is set, and the current speed of the fixing device is detected in order to reduce the conveying speed of the fixing device. In the case of the normal speed (first speed), the speed of the fixing device is reduced to the speed (second speed) for fixing the OHP transfer paper (step 2). Then, the second sheet feeding is made to wait until a preset time t elapses. In other words, in the case of OHP paper, the amount of time to wait until the time t when the second sheet is fed is set by the timer elapses.
The time from feeding the first sheet to feeding the second sheet is
It is longer than the image forming sequence for plain paper. By setting the time t arbitrarily, for example, a sheet interval can be ensured, or a sheet feeding interval can be set in accordance with the fixing ability of the fixing device (Step 3). After the elapse of the time t, the initially set number of sheets is checked. If the image formation of the set number of sheets has not been completed, the next transfer material is fed. The image forming sequence is stopped (Step 4). In step 3, the time t is set arbitrarily and the next transfer material is supplied until the fixing of the previous transfer material is completed, so that a delay in image formation of the next transfer material can be suppressed. Next, a method of setting the time t will be briefly described with reference to FIG. FIG. 6A shows a state in which transfer materials P1 and P2 are placed at a distance Lmm on the transport device 30, that is, the transport belt 32. FIG. At this time, it is assumed that the speeds of the transport belt 32 and the transfer materials P1 and P2 are the same V1 mm / sec. V2 with constant fixing device speed
Assuming that the transfer material P1 is driven at a speed of mm / sec, the distance between the transfer material P1 loaded in the fixing device and the transfer material P2 still mounted and transported on the transport belt 32 gradually becomes L ′ mm. . L 'may be 0 or more when the transfer material P1 leaves the fixing device. Assuming that the length of the transfer material P1 is 1 mm, the time required for the transfer material to pass through the fixing device is 1 / V2 sec. l / V2 = (l + L) / V1 L = 1 / (V1-V2) / V2 Accordingly, the timing t of the transfer material to be taken at the time of paper feeding is t = L / V1 = l · (V1-V2) / ( V1 and V2). Thus, the time t obtained by the above equation may be determined according to the fixing ability of the fixing device. The present invention is not limited to the multicolor image forming apparatus as described above, but can be embodied in a general electrophotographic copying apparatus as shown in FIG. In this embodiment, the image forming medium 1 is an electrophotographic photosensitive drum. Around the photosensitive drum 1, a primary charger 2, an exposure unit 4 such as a laser beam exposure device, a developing unit 6 and the like are used. Means are provided. Since the configuration and operation of these image forming means are well known to those skilled in the art, further description will be omitted. The image formed on the photosensitive drum 1 is transferred to the transfer material P fed from the paper feed device 20 under the action of the transfer discharger 8. The transfer material P after the transfer is conveyed to the fixing device 40 by the endless belt 32 of the transfer material conveyance device 30, and the transfer image is fixed on the transfer material. At this time, the conveying speed of the endless belt 32 is slightly higher than the conveying speed of the pair of fixing rollers 42a and 42b of the fixing device, and the transfer material P forms a loop to prevent wrinkles during fixing. In addition, the conveying speed of the endless belt 32 is usually set to be equal to the peripheral speed of the photosensitive drum 1 to prevent the expansion and contraction of the image when the image is transferred to the transfer material. The residual developer is removed from the photosensitive drum 1 after the transfer by the cleaner 10 and the next image forming process is performed. A detection unit for detecting the type of the transfer material P is provided on a path for feeding the transfer material P from the paper feeding device 20 to the transfer position.
According to this embodiment, the detecting means comprises two types of sensors 22 and 24.
The sensor 2 described with reference to FIGS.
It has the same configuration and operation as 2 and 24. Also in the present embodiment, the transfer material feeding speed of the fixing device is controlled according to the paper quality (paper thickness) of the transfer material P. For example, when the transfer material P is a transparent paper such as an OHP paper having a large thickness as described above, the above-described transparent paper determination signal by the detection unit is transmitted to a drive control device (not shown) of the fixing device 40. And
The control device controls a fixing roller driving device, for example, a driving motor 45, and adjusts the peripheral speed of the fixing roller pair to, for example, about half, and at the same time, appropriately adjusts the feeding timing of the transfer material. As a method of setting the timing, the method described with reference to FIGS. 5 and 6 can be adopted. According to the image forming apparatus of the present invention configured as described above, the feeding timing of the transfer material and the transfer material feeding speed of the fixing device are controlled by the paper quality, particularly the paper thickness, and the second fixing device
When fixing the recording material at a high speed, the supply unit supplies the next recording material until the fixing of the recording material is completed, so that a delay in image formation of the next recording material can be suppressed.
It is possible to sufficiently fix various transfer materials, for example, a thick OHP transparent transfer material, etc., by a simple operation without overlapping the transfer materials on the transporting device. It has the feature that quality images can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view of an embodiment of an image forming apparatus according to the present invention. 2 and 3 are front views showing one embodiment of the paper quality detecting means. FIG. 4 is a diagram showing an operation sequence of the paper quality detecting means. FIG. 5 is a flow chart showing one embodiment of transfer material feed timing adjustment in the image forming apparatus according to the present invention. FIGS. 6A and 6B are diagrams for explaining the transfer material feeding timing. FIG. 7 is a schematic sectional view of another embodiment of the image forming apparatus according to the present invention. 1, 1a to 1d: image forming medium 20: paper feeding devices 22, 24: detecting means 30: transfer material transport device 40: fixing device

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kazuyoshi Chihisa               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Hirose ▲ Yoshi ▼ hiko               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Yasushi Murayama               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Kunihiko Matsuzawa               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc. (72) Inventor Kazuki Kanekura               3-30-2 Shimomaruko, Ota-ku, Tokyo               Inside Canon Inc.                (56) References JP-A-49-73141 (JP, A)                 Japanese Patent Application Laid-Open No. 55-133303 (JP, A)                 JP-A-62-32471 (JP, A)                 JP-A-61-18983 (JP, A)                 Japanese Patent Laid-Open No. Sho 55-134867 (JP, A)                 JP-A-59-188673 (JP, A)                 JP-A-60-121479 (JP, A)                 JP-A-56-16168 (JP, A)                 JP-A-60-175069 (JP, A)                 JP-A-61-59368 (JP, A)                 JP-A-56-47075 (JP, A)                 Showa 60-39037 (JP, U)                 62-68152 (JP, U)                 Shokai 61-86747 (JP, U)

Claims (1)

(57) [Claims] Image forming means for forming an unfixed image, fixing means for fixing the unfixed image formed by the image forming means to a recording material, and supply means for supplying a recording material to the image forming means. The fixing unit is capable of fixing at a first speed and a second speed lower than the first speed, and after supplying the recording material fixed at the second speed of the fixing unit by the supplying unit, The time required to supply the next recording material after the recording material fixed at the second speed is the time between the supply of the recording material fixed at the first speed and the recording material fixed at the first speed. In an image forming apparatus that is longer than the time required to supply the next recording material, when the recording material is fixed at the second speed of the fixing unit, the supply unit supplies the next recording material by the end of fixing of the recording material. An image forming apparatus for supplying an image.