JP3420578B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrostatic copying machine and a printer, and more particularly to a transfer material carrier for supporting a transfer material. The present invention relates to an image forming apparatus in which transfer is performed a plurality of times on one or both sides of a transfer material. 2. Description of the Related Art In an image forming apparatus as described above, 1
A device that performs multiple printing on a sheet of transfer material and a device that performs printing on both front and back sides have already been proposed. When printing is performed using such an apparatus, the following problems occur. One of the problems in an apparatus in which transfer is performed between an image carrier that carries a toner image on its surface and a transfer material carrier that is disposed opposite to the image carrier will be described below. I do. In the above-described apparatus, when the printing on the first surface of the transfer material is completed and the transfer on the second surface is performed, a toner image is formed on the first surface on the transfer material carrier side.
Further, silicon oil used for preventing offset in the fixing process adheres to the surface of the surface toner image. [0005] A transfer bias is applied by a transfer charger arranged at the transfer site, and the toner image on the image carrier side is transferred to the back surface of the transfer material by the action of the electric field formed thereby. At this time, since the transfer material surface is in contact with the transfer material carrier,
The oil that has adhered to the fixed toner image adheres to the surface of the transfer material carrier. In an image forming apparatus which carries a transfer material by a transfer material carrier and performs multiplex and double-sided printing on the transfer material, usually, a rotating cylindrical transfer drum on which a transfer sheet made of a dielectric material is spread on the surface is transferred. A material carrier is widely used. As means for holding the transfer material on such a transfer material carrier (transfer drum), a transfer drum provided with a gripper for gripping the leading end of the transfer material supplied thereto,
There is a type in which a transfer material is electrostatically attracted to a transfer sheet.
In the former case, the transfer material is firmly gripped, but because of the mechanical mechanism, it is inevitable that a certain space is required in the circumferential and radial directions of the transfer drum, so that transfer to a part of the transfer material is impossible. May cause areas. In the case of the latter, small-sized transfer materials can be placed on multiple transfer sheets, so work efficiency can be improved. However, in the case of multiplex or double-sided printing, the suction force to the transfer sheet is insufficient. Or the curl amount becomes large, or there is a lot of oil,
There has been a problem that the image quality becomes unstable and causes deterioration of image quality and occurrence of jam. In the case of multiple printing, the amount of toner to be used naturally increases. Particularly in the case of color printing, resin-based toner is frequently used. In this case, the contraction ratio between the toner and the transfer material is different. Therefore, the transfer material curls toward the image side where the contraction is large, and the holding of the transfer material on the transfer sheet becomes unstable. The relationship between the amount of toner and the curl of the transfer material, and the amount of curl and the attraction force of the transfer material to the transfer sheet are shown in FIGS. 2 and 3, respectively. Furthermore, in the case of color printing, a large amount of silicone oil is used for the roller in order to improve the releasability between the fixing roller and the toner at the fixing portion. This may cause a decrease in the attraction force of the transfer sheet to the transfer sheet. FIG. 4 shows the relationship between the amount of oil and the attraction force of the transfer material to the transfer sheet. As described above, when performing multiplex or double-sided printing using a transfer material carrier, it is possible to avoid problems such as the occurrence of a jam by using a gripper. It becomes difficult to use the advantage of the holding means utilizing the electrostatic attraction force, such as placing a plurality of transfer materials of a size on the carrier. The present invention has been made in order to cope with such a situation. In an image forming apparatus provided with a transfer member carrier and having a gripper and an electrostatic attraction unit as a transfer material holding unit, the present invention is applied to the same image forming apparatus. When forming an image on the transfer material a plurality of times, a good image is always obtained by selectively using the gripper and the electrostatic suction means depending on the image information amount, image mode, transfer material type, etc. at that time. It is an object of the present invention to provide such an image forming apparatus. [0012] In order to achieve the above object, the present invention provides an image carrier and a transfer material carrier disposed in close proximity to the image carrier and carrying a transfer material. Image forming apparatus, comprising: a transfer member for transferring an image on the image carrier to a surface of a transfer material carried on the transfer material carrier; A gripper for gripping a transfer material on the transfer material carrier, electrostatic attraction means for electrostatically attracting the transfer material to the transfer material carrier, and detection for detecting image information, an image forming mode, and a transfer material type, respectively. Means for determining which of the gripper and the electrostatic attraction means to use in accordance with the detection result of each of the detection means. DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrostatic attraction acting on a transfer material carried on a transfer material carrier changes under the following conditions. (1) Transfer material type: Difference due to transfer material buckling strength (paper thickness, which is the strength of the waist), components, and the like. This state is shown in FIG. (2) Copy mode: In each of the single-color, two-color, three-color and four-color modes, the number of times of receiving the transfer charge is different, so that a difference occurs in the attraction force. See FIG. (3) Image information amount: The attraction force changes as shown in FIG. 7 depending on the amount of toner used. (4) Environmental conditions: Corona discharge efficiency changes due to differences in temperature and humidity, and the adsorption power changes. (5) Reuse: In the case of multiplex printing and color printing, since the paper passes through the fixing means a plurality of times, the suction force changes according to the curl of the transfer material generated in the previous process and the change in the amount of oil adhering to the surface. . FIG. 3 shows the change in the attraction force corresponding to the change in the curl amount, and FIG. 4 shows the change in the attraction force corresponding to the change in the oil amount. The amount of curl varies depending on the type of transfer material and the amount of toner (see FIGS. 8 and 2), and the amount of oil varies according to the amount of toner as shown in FIG. [0015] These factors, the paper thickness which affects the attraction force,
Taking into account the toner amount, oil amount, and other factors, the adsorption force of the transfer material to the transfer material carrier in the case of the multiplexed or double-sided mode is based on the image information amount, that is, the toner amount, the image forming mode, It can be seen that it depends on the type of transfer material. In view of the above, the present invention provides an apparatus capable of constantly holding a transfer material on a transfer material carrier under favorable conditions, which will be described with reference to FIG. When using this apparatus, one or several originals are placed on an original circulation device arranged on the top of the image forming apparatus, and a mode such as the number of copies is set.
It is determined whether the set mode is only one side (S1),
In the case of only one side, the process proceeds to (S2) and thereafter, image formation is performed as usual. In the case of a transfer material of a small size in the multiplex or double-sided mode, whether or not the transfer material has a problem in electrostatic attraction in this mode is stored based on data at the time of previous use.
Determined by comparing with this. At this time, when the cassette is opened and exchanged for a different type of transfer material, it is reset each time and stored for each cassette. If there is no data immediately after the transfer material is replaced with the cassette, the set image forming mode is set as new data. If there is a problem with the electrostatic attraction force, (S
Proceeding to 4), the transfer material is held by the gripper, and thereafter, the image forming operation is performed in a predetermined manner. Next, the same determination is made for the transfer material type (S5). If there is a problem with the curl amount or the like, (S5)
Returning to 4), image formation is performed in a normal manner thereafter. Regarding the image information amount (toner amount),
In step (S7), the amount of image information is determined. If there is no problem on the first and second surfaces, the process proceeds to (S9) and (S11) to form an image. One method when there is a problem on the second side is to proceed to (S6) and (S4) to form an image. In the case where the amount of image information on the first side is larger than that on the second side and the curl becomes larger,
In this case, the order of the first side and the second side is changed using a document circulating device because a problem occurs in the suction of the second side. As a result, there is no problem with the suction of the second surface, and thereafter, the process proceeds to (S8), (S10), and (S9) to perform image formation. When the order is changed, the transfer material is reversed at the reversal portion of the image forming apparatus, or the order of the transfer material is adjusted to the order of the original in each bin at the sorter portion. As described above, according to the present invention, an image carrier, a transfer material carrier, a transfer material on the transfer material carrier, an image formed on the transfer material by multiplexing images on both sides, In the forming apparatus, depending on the image information amount, the image forming mode, and the transfer material type,
Since the transfer material on the transfer material carrier can be selectively held by the electrostatic attraction action and the gripper, a good image can always be obtained regardless of the change in the state of the transfer material surface due to the initial image forming operation. In addition, there is a remarkable effect on the improvement of work efficiency when a small-size transfer material is used.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow chart for explaining the operation of the present invention. FIG. 2 is a graph showing a change in curl of a transfer material depending on an amount of image information (amount of toner). Fig. 4 is a graph showing the relationship between the force and Fig. 4 is a graph showing the relationship between the amount of oil for preventing offset and the suction force. Fig. 5 is a graph showing the relationship between the transfer material type and the suction force. 7) A graph showing the relationship between the amount of image information (toner amount) and the attraction force [FIG. 8] A graph showing the relationship between the transfer material type and the curl amount [FIG. 9] Graph showing the relationship between image information amount (toner amount) and required oil amount

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeo Tsunemi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroshi Kimura 3-30, Shimomaruko, Ota-ku, Tokyo No. 2 Canon Inc. (56) References JP-A-2-16878 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/00 518

Claims (1)

(57) An image carrier, a transfer material carrier disposed in proximity to the image carrier and carrying a transfer material, and an image on the image carrier is transferred to the image carrier. An image forming apparatus comprising: a transfer unit configured to transfer a transfer material onto a surface of a transfer material carried on a material carrier; and a gripper gripping the transfer material on the transfer material carrier. And an electrostatic attraction means for electrostatically attracting the transfer material to the transfer material carrier, and a detection means for respectively detecting image information, an image forming mode, and a transfer material type, and a detection result of each of the detection means. Depending on the gripper,
An image forming apparatus that determines which of the electrostatic suction units is used.