JP2003345101A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the image forming speed by switching the operation of a development separation plate without stopping printing operation in a consecutive printing operation in which color mode and a monochrome mode are both used, and also to improve the image forming speed by switching transport speed without stopping printing operation by taking the time required for transport speed convergence into consideration even in a consecutive printing operation in which the alteration of the carrying speed becomes necessary. <P>SOLUTION: A color image forming device of a tandem type which has a development separation mechanism by which photoreceptor drums of four distinct colors are abutted on and separated from developing rollers which transport developers from image writing devices, has a means for controlling the development separation mechanism according to a print mode. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem type color image forming apparatus having a developing / separating mechanism for controlling the developing / separating mechanism according to a print mode to improve an image forming speed.

[0002]

2. Description of the Related Art In an electrophotographic color image forming apparatus, a multicolor image is obtained by sequentially superposing toner images of a plurality of colors on a photosensitive member. For example, toner images of respective colors are formed on one photosensitive member. There is one that is transferred onto a recording sheet each time it is sequentially formed on the recording sheet, and a toner image is superimposed on the recording sheet. In order to form a full-color image in the color image forming apparatus as described above, a scanning optical system for performing image exposure for three or four colors and a developing device for each color are used, and a transfer device is formed every time a toner image is formed. Therefore, it is necessary to transfer onto a single transfer material. For this reason, a medium carrying and conveying device (hereinafter abbreviated as a conveyor belt) that moves around while carrying the transfer material is used to convey the transfer material a plurality of times to a position facing the transfer device,
The toner images of the respective colors are sequentially superimposed and transferred.

In order to reduce the time required to form a multicolor image, a so-called color image forming unit having a plurality of scanning optical systems for image exposure and developing devices for respective colors forms a so-called multicolor toner image. A tandem type color image forming apparatus has already been proposed. This color image forming apparatus is
For example, a conveyor belt that electrostatically adsorbs and conveys a transfer material and a plurality of photoconductors are arranged around the conveyor belt, and are formed by a charger, a scanning optical system, and a developing device that are provided to face each photoconductor. The toner images of a plurality of colors are sequentially transferred onto a transfer material. Further, in this tandem type color image forming apparatus, it is also possible to form a mono image by separating the photosensitive drum from the developing roller that conveys toner as a developing material. FIG. 7 shows the contacting operation and the separating operation of the developing device. First, in FIG. 7A, since the photosensitive drum 101 in the developing device and the developing roller 103 for supplying the toner as the developer are in contact with each other, the photosensitive drum exposed by the image writing laser light is An image can be formed by conveying the toner. In FIG. 7B, image formation is not performed because the photosensitive drum in the developing device and the developing roller that supplies toner serving as the developer are separated from each other.

FIG. 8 is a schematic view of a tandem type color image forming apparatus having a developing / separating mechanism.
1C, 101Y, 101M, and 101Bk and developing rollers 103C and 103 that convey the developer from the image writing device.
Y, 103M and 103Bk, and the conveyor belt 11 are shown. First, in the case of forming a color image as shown in FIG. 8A, the photosensitive drums 101C and 101C for four colors are formed.
A color image can be formed by bringing Y, 101M, and 101Bk into contact with the developing rollers 103C, 103Y, 103M, and 103Bk that convey the developer from the image writing device. On the other hand, in the case of forming a mono image as shown in FIG. 8B, image formation is performed using only the Bk image writing device in order to reduce performance deterioration of the image writing device. Therefore, as described above, the contact of the image writing device,
Photosensitive drums 101C, 101Y, 1 using the separating operation
01M and developing rollers 103C, 103Y, 103M
Are separated from each other, and the photosensitive drum 101Bk and the developing roller 1
A color image can be formed by contacting only 03Bk. Further, FIG. 8C shows the photosensitive drum 101C,
101Y, 101M and 101Bk and developing roller 103
C, 103Y, 103M, and 103Bk are all in a separated state (hereinafter, home position), and basically this home position is maintained except for the image forming state.

FIG. 9 shows an image forming flowchart of a color mode for forming a color image and a mono mode for forming a mono image by a tandem type color image forming apparatus having a developing and spacing mechanism. First, in response to a print start instruction, the pre-rotation S100 prepares for a printing operation, and then in the development separation mode selection S101, a developing device to be brought into contact is selected according to the print mode. In the case of the color mode, the developing rollers for four colors and the photosensitive drum are brought into contact with each other (S102). In the case of the mono mode, the developing roller of only Bk and the photosensitive drum are brought into contact with each other (S103). When the contact of the developing device is completed, the carrying process S104 is performed in that state.
Then, the transfer material is started to be conveyed, and image formation S105 is performed.
When continuous printing is required in the print continuation determination S106, the next transfer material is conveyed again in the conveyance processing S104, and when the last transfer material is conveyed and the continuous printing is finished, the image is formed in the post-rotation processing S107. The process is performed and the printing operation is completed.

[0006]

When a mono image is continuously formed according to FIG. 9 and then a color image is formed, only the developing roller 103Bk and the photosensitive drum 101Bk are in contact with each other, so that the color image is continuously formed. Can not do it. Further, in the case of forming a mono image after continuously forming color images according to FIG.
Since C, 103Y, 103M and 103Bk and all of the photoconductor drums 101C, 101Y, 101M and 101Bk are in contact with each other, it is possible to continuously form a mono image, but the image writing devices 106C and 106 are excessively necessary.
Since Y and 106M are used, the performance is deteriorated. Therefore, when the color mode and the mono mode are mixed, it is necessary to end the printing operation once, so that the image forming speed is remarkably reduced in the mixed mode, which is large in the tandem type image forming apparatus for increasing the speed. It becomes a problem. Also, if there are print modes that require different control from plain paper such as OHT and thick paper, the print speed needs to be changed. The speed will drop significantly.

[0007]

An image forming apparatus according to claim 1, wherein at least one image carrier is rotatably driven, and latent image means for forming an electrostatic latent image on the image carrier. A developing device that has a developing roller that supplies toner that is a developer to the electrostatic latent image and that forms a toner image by adhering the supplied toner, a transfer unit that transfers the toner image to a transfer material, and a print mode The developing and spacing means for controlling the spacing device for spacing and contacting the developing roller with the image carrier, the sheet feeding means for starting the transport of the transfer material at a predetermined timing, and the transporting material for transporting the transfer material by the sheet feeding means. Transporting means, a transfer material adsorbing means for adsorbing the recording sheet carried on the transfer material onto the transport belt, and the toner transferred by the transfer means to the transfer material transported by the transporting means. In an image forming apparatus having a fixing unit and a discharge detecting unit that determines that the transfer material thermally fixed by the fixing unit is discharged outside the apparatus, when continuous printing in which color mode and mono mode are mixed is reserved. When the print mode for the next image formation is different, the feeding operation of the transfer material is once stopped, and when the discharge detection means detects that the transfer material is discharged to the outside of the apparatus, the development separation control means A print mode switching means for contacting or separating the developing device and the image carrier to perform an image carrier contacting operation in the next print mode, and carrying the transfer material again when the switching process is completed. To do.

In the image forming apparatus according to the second aspect, when continuous printing in which print modes having different conveying speeds of the conveying means are reserved, and the conveying speed of the next image forming is different, the transfer material is fed. The present invention is characterized by having a conveyance speed switching means for switching the conveyance speed and continuing the image forming operation when the operation is temporarily stopped and the discharge detection means detects that the transfer material is discharged to the outside of the apparatus.

In the image forming apparatus according to the third aspect of the present invention, when continuous printing in which print modes in which the transporting speeds of the transporting means are mixed is reserved, the convergence time for switching the transporting speed is temporarily stopped. If it is shorter than the start of image formation again, the image forming operation is continued by switching the transport speed as it is, and if it is longer, the image forming operation is temporarily stopped and image formation is restarted in a new print mode. To do.

In the image forming apparatus according to the present invention, while the speed switching means waits for the conveyance speed to converge, the development / separation control means controls the development / separation apparatus so that all the development device and the image carrier are controlled. It is characterized by being separated.

In the image forming apparatus according to the present invention, when the continuous printing in which the print modes having different transport speeds are mixed and the continuous printing in which the color mode and the mono mode are mixed is reserved, the feeding operation of the transfer material is temporarily stopped. Then, when it is detected by the discharge detecting means that the transfer material is discharged outside the apparatus, the image forming operation is continued by the print mode switching means and the speed switching means.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an image forming apparatus for switching the operation of a developing spacer according to a print mode according to the present invention will be described below with reference to the drawings.

(Embodiment 1) In this embodiment, in a color image forming apparatus having a developing / separating mechanism, in a print operation in which a color mode and a mono mode are mixed, a method for improving the image forming speed without stopping the print operation is described. suggest. It should be noted that the functions described in the above-mentioned conventional example are denoted by the same reference numerals and detailed description thereof will be omitted.

The overall structure of the tandem type color image forming apparatus will be described with reference to FIG. In the tandem type color image forming apparatus, four color photosensitive drums 101C and 10C are used.
1Y, 101M and 101Bk, transfer devices 102C, 102Y, 102M and 10 for transferring a visible image onto a recording sheet
2Bk, image writing device 106C, 106Y, 106M
And 106Bk, and developing rollers 103C, 103Y, 103M, and 103B that convey the developer from the image writing device.
k, the photosensitive drum 101 is irradiated with an image writing laser beam.
Scanner units 108C, 108Y, 108M and 108Bk for forming latent images on C, 101Y, 101M and 101Bk are provided.

Now, the procedure for forming a color image will be described. In the color mode, the transfer material is stored in the paper feed unit 150 and guided to the conveyance path by the pickup roller 151,
The registration roller 140 detects the leading edge of the transfer material, and the media sensor 141 determines the transfer material. Then, electrostatic attraction is performed on the conveyor belt 11 by the attraction roller 153,
The conveyance is started, and in the color mode, the photosensitive drums 101C, 101Y, 101M for four colors are started by the developing separation plate 16.
101Bk and developing rollers 103C, 103Y, 10
The photoconductor drums 101C, 101Y, 101M, 1
On the image formed on 01Bk, the developing roller 103C,
The transfer device 102 forms a visual image using the developer conveyed from the image writing devices 106C, 106Y, 106M, and 106Bk by 103Y, 103M, and 103Bk.
C, 102Y, 102M, and 102Bk are transferred onto the transfer material, and the fixing unit 152 fixes the color images of four colors. When the sheet passes through 160, it is determined that the sheet has been discharged to the outside of the apparatus.

Next, a procedure for forming a mono image will be described. In the mono mode, the image writing devices 106C and 106C
In order to reduce the performance deterioration of Y and 106M, image formation is performed using only the image writing device 106Bk. Therefore, in the mono mode, as shown in FIG. 2, when the conveyance is started, the developing device spacing plate 16 moves the Bk-only photosensitive drum 101Bk so that only the developing roller 103Bk comes into contact with the photosensitive drum 101Bk. A visual image is formed on the image formed above by the developing roller 103Bk using the developer conveyed from the image writing device 106Bk, and is transferred onto the transfer material by the transfer device 102Bk and is transferred to the fixing unit 152 by the fixing unit 152. The image is fixed, and the heat-fixed transfer material is judged to have been discharged to the outside of the apparatus by passing through the discharge sensor 160 composed of an optical photointerrupter.

Next, an image forming procedure when the color mode and the mono mode are mixed will be described. FIG. 3 is a flowchart showing the printing operation when the color mode and the mono mode are mixed. First, according to the print instruction, the pre-rotation S500 prepares for the printing operation, and then in the developing / separating mode selection S101, the contact direction of the developing / separating plate is determined according to the print mode. In the case of the color mode, the developing spacer plate is moved to the color side to move the developing roller 1
03C, 103Y, 103M and 103Bk and the four photosensitive drums 101C, 101Y, 101M and 101Bk
The developing roller for the color and the photosensitive drum are brought into contact with each other (S50
2). In the mono mode, the developing separation plate is moved to the mono side, and the developing roller 103Bk and the developing roller of Bk of the photosensitive drum 101Bk are brought into contact with the photosensitive drum (S5).
03). When the contact direction of the developing spacer is determined, the transfer material is started to be conveyed in the conveying process S504 in that state, and the image formation S505 is performed. If continuous printing is required in the print continuation determination S506, the current development separation mode is compared with the next print reserved mode in S508, and if the print mode needs to be switched, the transfer material is the discharge sensor. Development separation mode selection S5 at the timing when 160 is passed
At 09, the contact direction of the developing spacer is determined according to the print mode. If it is necessary to switch to the color mode here, the developing separation plate is moved to the color side and the developing roller 10 is moved.
3C, 103Y, 103M and 103Bk and the photosensitive drums 101C, 101Y, 101M and 101Bk are brought into contact with the developing rollers and the photosensitive drums for four colors (S510),
Further, a high voltage bias necessary for forming a color image is applied (S512). In the mono mode, the developing spacer plate is moved to the mono side to move the developing roller 103Bk and the photosensitive drum 1 to each other.
The developing roller of only Bk of 01Bk is brought into contact with the photosensitive drum (S511), and the high-voltage bias unnecessary for mono image formation is stopped (S513). Then, the carrying process S5 is performed again.
At 04, the next transfer material is conveyed, and when the last transfer material is conveyed and continuous printing is completed, post-processing of image formation is performed at post-rotation processing S507, and the printing operation is completed.

As described above, in the first embodiment, in the tandem type image forming apparatus having the developing spacer, in the printing operation in which the color mode and the mono mode are mixed, the operation of the developing spacer is switched without stopping the printing operation. It is possible to improve the image formation speed,
Furthermore, image writing devices 106C, 106Y, and
Since 106M is not used, it is possible to reduce performance deterioration of the image writing device.

(Embodiment 2) As a transfer material used in an image forming apparatus of an electrophotographic electrostatic recording method, in addition to plain paper generally used, special materials such as OHT (overhead transparency), glossy paper, and thick paper are used. Transfer materials are also used. Particularly, in the fixing device of the color image forming apparatus, since the toner of each color is melted to develop a color, the heat capacity of the transfer material greatly affects the image quality after fixing. In particular, the heat capacities of paper and special transfer material are significantly different.For example, when the transfer material is OHT, the heat capacity is several times larger, and in order to obtain permeability that can be used as OHT, the paper thickness is several times that of the same paper. It requires heat. Therefore, when the transfer material is a special transfer material such as OHT, in the color image forming apparatus, the conveyance speed of the special transfer material to the fixing device by the conveying means and the fixing speed of the fixing device (specifically, the fixing device The rotation time of the fixing roller and the like) is slowed to lengthen the fixing time of the special transfer material to obtain the amount of heat required for fixing. Therefore,
In this embodiment, in the tandem type image forming apparatus having the developing / separating mechanism, the OH
We propose a method to improve the image forming speed by switching the operation of the development spacer even when print modes such as T and thick paper that require different control from plain paper are mixed. The functions described in the above-mentioned embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

FIG. 4 shows the flow of the printing operation when the print mode of special paper other than plain paper is designated during continuous printing and the transport speed needs to be changed. The flow required when a print mode different from the current transport speed is reserved is from S600 to S604. S500
Since S506 to S506 are the same as those described in the first embodiment, the description thereof will be omitted. When a print mode in which the transfer speed needs to be switched from the current print mode is reserved in S600, the transfer speed is determined to be switched in S601 at the timing when the transfer material passes through the discharge sensor 160. here,
When the conveyance speed is changed, it is necessary to allow for the convergence time of the drive system such as the conveyor belt and the fixing motor.If the transfer material is conveyed without sufficient convergence, color misregistration and paper wrinkles will occur. , Problems such as improper fixing occur. But,
Depending on the mode to be switched, it is determined whether or not the speed mode switching is permitted or disallowed in S602 in consideration of the case where the convergence time of the drive system is longer than necessary. The judgment criteria are shown in Fig. 5. FIG. 5A shows the printing time required when the two images are formed by intermittent printing. Figure 5
(B) shows the print time in the case where the drive convergence time is short when the transport speed in the print mode needs to be switched during continuous printing. FIG. 5C shows a case where it is necessary to switch the print mode conveyance speed during continuous printing.
The print time is shown when the drive convergence time is long. From these relationships, it can be determined that the print speed is shortened as a whole by directly performing the speed switching sequence in FIG. 5B because the convergence time of the conveyance speed is short. On the other hand, FIG. Therefore, it can be determined that the entire print time is shortened if the image formation is performed again from the previous rotation sequence after shifting to the post-rotation sequence. By the above means, it is determined in S602 whether the speed mode switching is permitted or not, and when the speed mode switching is determined not to be permitted, the process proceeds to the post-rotation S507, the printing operation is ended, and the new printing mode is resumed. Start the printing operation. When it is determined in S602 that the speed mode switching is permitted, the photosensitive drums 101C, 101Y, 101M, and 101Bk for four colors are used to prevent the deterioration of the developing device while the speed is being converged.
And developing rollers 103C, 103Y, 103M and 103
It moves to the home position as shown in FIG. 8C so that all Bk are separated. In step S604, the conveyance speed of the drive system such as the conveyance belt 11 and the fixing unit 152 is awaited. Then, if the conveyance speed is converged, the conveyance of the next transfer material is started again in the conveyance process S504 in the new print mode, and the image formation is continued.

In the above, the flow of the printing operation when the print mode of special paper other than plain paper is designated during continuous printing and the transport speed needs to be changed has been described, but naturally the transport speed needs to be changed. Further, it is possible to switch from the color mode to the mono mode or from the mono mode to the color mode. FIG. 6 shows a flow of a printing operation in which the conveyance speed and the development separation mode are switched during continuous printing to form an image. S50
0 to S506 are as described in the first embodiment, and S6
The flow from 00 to S604 is a flow required when a print mode different from the current transport speed is reserved, and is the same as described above. According to this print operation flow, after the transport speed of the drive system such as the transport belt 11 and the fixing unit 152 converges in S604, S50
By comparing the current development separation mode with the next print reserved mode in 8 and executing the processing from S509 as described in the first conventional example at the timing when the transfer material passes through the paper discharge sensor 160. It is possible to switch the carrying speed and the developing separation.

As described above, in the second embodiment, when the print mode of the special paper other than the plain paper is designated during the continuous printing in the tandem type image forming apparatus having the developing spacer, it is necessary to change the transport speed. It is possible to improve the image forming speed, and it is also possible to support the printing operation in which the color mode and the mono mode are mixed.

[0023]

According to the first embodiment, in the continuous printing operation in which the color mode and the mono mode are mixed, it is possible to improve the image forming speed by switching the operation of the developing spacer plate without stopping the printing operation.
Further, since the image writing device is not used more than necessary, it is possible to reduce the performance deterioration of the image writing device.

In the second embodiment, in the continuous printing operation in which the transport speed needs to be changed, the transport speed is switched in consideration of the time required to converge the transport speed, so that the image forming speed can be improved. Furthermore, it is possible to deal with the case where the color mode and the mono mode are mixed. Further, since the image writing device is moved to the home position while waiting for the conveyance speed to converge, it is possible to reduce the performance deterioration of the image writing device.

[Brief description of drawings]

[Figure 1] Overall configuration

[Fig. 2] Mono-mode contact for development separation

FIG. 3 Color mode / mono mode switching flowchart

[Fig. 4] Speed switching flowchart

[Figure 5] Speed switching judgment

[Fig. 6] Color mode, mono mode, speed switching flowchart

FIG. 7: Development separation operation

FIG. 8 is a schematic diagram of development separation.

FIG. 9: Print flowchart

[Explanation of symbols]

11 Transfer belt 16 Development spacer 101 photoconductor drum 102 transfer device 103 developing roller 106 image writing device 108 Scanner unit 150 paper feeder 151 Pickup roller 152 fixing unit 153 Adsorption roller 160 Paper ejection sensor

Continued front page    F term (reference) 2H027 ED08 ED16 ED17 EE03 EE07                       EF09 FA28 FA30 FA35                 2H300 EB04 EB07 EB12 ED02 ED05                       ED07 ED12 ED13 EF02 EF06                       EF08 EF13 EH16 EJ09 EJ25                       EK03 FF02 FF05 FF08 FF12                       FF15 GG31 GG37 QQ13 QQ16                       QQ32 RR12

Claims (5)

[Claims] 1. At least one image carrier that is rotationally driven, a latent image unit that forms an electrostatic latent image on the image carrier, and a toner that is a developer is supplied to the electrostatic latent image. A developing device having a developing roller for adhering the supplied toner to form a toner image, a transfer means for transferring the toner image to a transfer material, and a separation and contact between the developing roller and the image carrier according to a print mode. The developing and spacing means for controlling the spacing device for carrying out the above, the paper feeding means for starting the transportation of the transfer material at a predetermined timing, the transportation means for transporting the transfer material by the paper feeding means, and the recording carried on the transfer material. A transfer material adsorbing means for adsorbing a sheet on a conveying belt, a fixing means for thermally fixing the toner transferred by the transferring means to the transfer material conveyed by the conveying means, and a transfer material thermally fixed by the fixing means. But In an image forming apparatus having discharge detection means for determining discharge to the outside of the apparatus, when continuous print in which color mode and mono mode are mixed is reserved and the print mode of the next image formation is different, the transfer material When the discharge detecting means detects that the transfer material has been discharged to the outside of the apparatus, the developing gap control means brings the developing device into contact with or separates from the image carrier. An image forming apparatus comprising: a print mode switching unit that performs an abutting operation of an image carrier in the next print mode and conveys the transfer material again when the switching process is completed. 2. The image forming apparatus according to claim 1,
When continuous printing in which print modes in which the transporting speed of the transporting unit is different is mixed is reserved, and the transporting speed of the next image formation is different, the feeding operation of the transfer material is temporarily stopped and the discharge detecting unit detects the transfer material. When it is detected that the sheet has been discharged to the outside of the apparatus, the image forming apparatus has a conveying speed switching unit that switches the conveying speed and continues the image forming operation. 3. The image forming apparatus according to claim 1, wherein when a continuous print in which print modes having different transport speeds of the transporting means are reserved, a convergence time for switching the transport speed is formed. If it is shorter than once to stop and start image formation again, the image forming operation is continued by switching the transport speed as it is, and if it is longer, the image forming operation is temporarily stopped and image formation is restarted in a new print mode. An image forming apparatus characterized by the above. 4. The image forming apparatus according to claim 1, wherein while the speed switching unit waits for the conveyance speed to converge, the development separation control unit controls the development separation unit to control the development unit and the image. An image forming apparatus characterized in that all of the carriers are separated. 5. The image forming apparatus according to claim 1, wherein print modes having different conveyance speeds are mixed, and
When continuous printing in which the color mode and the mono mode are mixed is reserved, the feeding operation of the transfer material is temporarily stopped, and when the discharge detecting means detects that the transfer material is discharged to the outside of the apparatus, An image forming apparatus, wherein an image forming operation is continued by a switching unit and the speed switching unit.