JP2004109231A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which ensures productivity and image quality which meet the needs for respective jobs. <P>SOLUTION: The image forming apparatus has paper feed trays (1a to 1d) and obtains an image in such a manner that a toner image formed of toner of a single color or toner of distinct colors is transferred and fixed onto paper conveyed. In the image forming apparatus, a standard paper-conveyance speed and a standard paper-interval are set. The apparatus has the function of setting or canceling a conveyance speed alteration mode for making a conveyance speed lower than the standard conveyance speed and a paper interval alteration mode for making a paper interval longer than the normal paper-interval, which is applied to the respective trays (1a to 1d). <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus using an electrophotographic process, and more particularly, to an image forming apparatus that forms a color image on various paper types.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus, in particular, an image forming apparatus that outputs a full-color image, in order to improve the glossiness of an image, the fixing condition for fixing a toner image on paper is switched. For example, this is due to a change in the temperature of the fixing device, a change in the paper conveyance speed (linear speed of the fixing device), a change in the paper interval, and the like.
The image forming apparatus described in Patent Literature 1 controls fixing conditions in accordance with the length, paper thickness, and surface properties of long paper to prevent image quality deterioration. Further, the fixing device described in Patent Document 2 stops heating of the fixing roller for a certain time during continuous paper passing, and determines the type of paper conveyed to the fixing device from a change in the surface temperature of the fixing roller during that time. The fixing condition is changed according to the result of the determination to improve the fixing property.
[0003]
However, in the above-described switching of the fixing conditions, when the transport speed of the paper is switched, it is necessary to wait for the image forming paper at the previous transport speed remaining in the apparatus to be discharged out of the apparatus. Therefore, an image forming operation including a sheet, particularly a thick sheet, in a job takes a long time to finish the job.
Conversely, if thick paper is handled without switching the transport speed, fixing may be performed but glossiness or the like may be low, or the fixing device may lose heat due to paper passing and may not be able to maintain the set temperature. In order to maintain the set temperature of the fixing device, measures are taken to increase the paper interval. This is easy to execute because there is no switching of the transport speed, and there is no time lag of setting change. On the other hand, in order to maintain the gloss, a measure is taken by switching (rising) the set temperature of the fixing device. In this case, there is a problem that it takes a considerable amount of time to switch from or return to the set temperature of the fixing device when passing plain paper.
[0004]
By the way, the image quality required by the user varies depending on whether the image is a monochrome image, a color image, or a difference in paper type. That is, there is a case where good glossiness or the like of thick paper is required even if the job end is late, or a case where a quick job end is required even for thick paper because the glossiness or the like is not considered.
In the conventional image forming apparatus, since the fixing conditions are controlled uniformly depending on the difference between a single-color image / color image and a paper type, it is difficult to perform the control corresponding to the user's respective needs as described above.
[0005]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 8-220929 [Patent Document 2]
JP-A-11-65362
[Problems to be solved by the invention]
In order to solve the above problems, an object of the present invention is to provide an image forming apparatus that can secure productivity and image quality that meet the needs of each job.
[0007]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 has a plurality of paper feed trays, and transfers a toner image formed of a single color or a plurality of color toners on a sheet to be conveyed. An image forming apparatus that obtains an image by fixing, wherein the image forming apparatus has a standard paper conveying speed and a standard paper interval set therein, and has a conveying speed change mode and a standard paper speed lower than the standard conveying speed. The image forming apparatus is provided with a function of setting or canceling a paper interval change mode that is longer than the interval for each of the paper feed trays.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming apparatus sets a paper interval change mode for a specific sheet of the paper feed tray when forming an image of a single color toner. This is an image forming apparatus that displays so as to allow a user to select a conveyance speed change mode when forming an image with a plurality of color toners.
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the image forming apparatus has a plurality of levels of the paper interval change mode and the transport speed change mode.
According to a fourth aspect of the present invention, in the image forming apparatus according to any one of the first to third aspects, the image forming apparatus has a mode for changing a temperature condition of a fixing device for fixing a toner image on a sheet. The fixing device temperature condition change mode is executed simultaneously with the mode executed before the change to the paper interval change mode and the conveyance speed change mode, and simultaneously with the change to the paper interval change mode and the conveyance speed change mode. And an image forming apparatus.
According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the toner used in the image forming apparatus includes wax.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention. A scanner (2) for reading an original is provided above the image forming apparatus, and an optical writing device (3) for performing optical writing according to the read image data is provided below the scanner (2). The photoconductor (4), which is an image carrier on which a latent image is formed by the optical writing device (3), corresponds to four different colors of toner, and four are arranged in parallel. Each photoconductor (4) includes a charger (6), a developing device (7), and a cleaning device (5) around the photoconductor. Since the photoconductor (4) and its peripheral devices have different driving conditions and timings, they have independent motors (M1 to M4) and are driven to rotate. Below the photoconductors (4), an intermediate transfer body (10) that transfers and carries the toner images formed on the respective photoconductors (4) is provided, and is driven to rotate by a motor (M5).
A plurality of paper feed trays (1a to 1d) are arranged below the image forming apparatus.
The sheet is conveyed from any one of the sheet feeding trays (1), and the toner image on the intermediate transfer body (10) is transferred to the sheet by the transfer device (11). Further, a fixing device (8) including a conveying belt (20) for conveying the sheet after the transfer and a fixing roller pair (81, 82) for fixing the toner image on the sheet is disposed, and both are driven by a shared motor (M8). Being driven. In addition, a double-sided unit (9) is provided in preparation for double-sided image formation, and is driven by a motor (M9). Although the fixing device (8) is shown in FIG. 1 as including a pair of fixing rollers (81, 82), a fixing belt may be used.
[0009]
The image forming operation is as follows. Image data read from the original by the scanner (2) is distributed to each of four colors and sent to the optical writing device (3). The surface of each photoconductor (4) is uniformly charged by a charger (6), and a latent image of each color is written by an optical writing device (3) based on image data. The latent image on each photoreceptor (4) is supplied with toner by each developing device (7) and is visualized. The toner images formed on the respective photoconductors (4) are transferred onto the intermediate transfer body (10) by primary transfer means (not shown), and are sequentially superimposed to form a color image. After the transfer of the toner image, each photoconductor (4) has its surface cleaned by a cleaning device (5), and is prepared for the next image formation.
The paper stacked on the paper feed tray (1) is separated and conveyed one by one by a paper feed roller pair (13) driven by an independent motor (M6), and a registration roller pair for performing timing adjustment and skew adjustment. (12) After being sent to the (independent motor (M7) or paper feed motor (M6) drive transmission clutch), it is sent to the transfer device (11). Here, the color image on the intermediate transfer member (10) is transferred onto paper. Thereafter, the sheet is sent to the fixing device (8) by the transport belt (20), where heat and pressure are applied to fix the toner image, and the sheet is discharged out of the apparatus. When forming a two-sided image, the sheet after one-sided fixing is conveyed to the two-sided unit (9), turned over, and sent again to the pair of registration rollers (12) to transfer the image on the other side to the transfer device (11). Is transferred. The subsequent fixing operation is the same as described above.
[0010]
In this image forming apparatus, the values of the standard paper transport speed and the standard paper interval when plain paper is passed are set in advance. When plain paper is passed, the respective motors are driven in accordance with the set values, and an image is formed.
Here, FIG. 2 is a diagram showing a time transition of the fixing temperature of the fixing device (8). When plain paper is passed, the fixing temperature is set to the set temperature 1, and the plain paper passes through the fixing device at a preset standard transport speed. On the other hand, when thick paper is passed, more heat energy is required to achieve glossiness equivalent to that of plain paper. However, if the standard transport speed is set in advance, the heat supply to the thick paper cannot keep up, and the fixing temperature may decrease. A decrease in the fixing temperature leads to a decrease in the fixability of the toner image.
Therefore, in order to solve such a fixing problem, the sheet conveying speed or the sheet interval is controlled so as to increase the fixing thermal energy applied to the thick paper. FIG. 3 schematically shows the transport speed change mode and the paper interval change mode. In the normal transport mode applied when plain paper is passed, the paper is transported at a standard transport speed set in advance, with the paper passing time of the fixing unit being A1, and the inter-paper time being B2.
In order to obtain glossiness equivalent to that of plain paper when thick paper is passed, the conveyance speed change mode is applied. In the transport speed change mode, the transport speed is set lower than the standard transport speed to set the paper passage time A2, and the paper is transported at B2, which is slightly longer than the normal transport mode. By lowering the transport speed, the toner image on the thick paper can obtain more heat energy from the pair of fixing rollers (81, 82), and good fixability and gloss can be obtained. Further, since the inter-sheet time is also longer than that in the normal transport mode, the decrease in the fixing temperature after the thick paper is passed is recovered, and the next fixing operation is not hindered.
In the transport speed change mode, the transport speed must be switched after the paper being transported at the speed before the switch has been discharged to the outside of the apparatus, so that the productivity is reduced. Depending on the use situation, it is sufficient that the image is fixed on the cardboard, and glossiness may not be required. In this case, the paper interval change mode is applied. In the paper interval change mode, the paper passing time of the fixing unit is A1 at the same standard transport speed as that of plain paper, and the paper interval is longer than the standard paper interval, and the paper is transported as the paper interval B3. Since the paper passes through the fixing section at the standard transport speed, the heat energy given to the toner image on the thick paper from the pair of fixing rollers (81, 82) is smaller than that of plain paper, and glossiness cannot be obtained. The fixing temperature is recovered by the long sheet interval, and the temperature can be maintained, so that the fixing property can be secured. As described above, the paper interval changing mode is a mode in which the glossiness of an image is slightly sacrificed, but the decrease in productivity is suppressed.
[0011]
The image forming apparatus of the present invention has a function of setting or canceling the above-described mode for each paper feed tray. FIG. 4 is a diagram illustrating an operation panel provided on the upper surface of the image forming apparatus main body. The setting of the mode for each paper feed tray can be performed on the operation panel (14). “Productivity thick paper” indicates paper passing in the paper interval change mode, “image thick paper” indicates paper passing in the transport speed change mode, and “none” indicates the normal transport mode. Depending on the use condition, the optimum paper passing mode for securing the fixability and glossiness of the toner image can be freely set or canceled for each paper feed tray. As a result, it is possible to obtain the output of the fixing property and the image quality (glossiness) that meet the needs at that time.
[0012]
Next, a description will be given of mode selection when forming an image with a single color toner and when forming an image with a plurality of color toners. FIG. 5 is a diagram schematically showing a single-color toner image and a multi-color toner image. The single-color toner image does not carry the toner of each color as compared with the multi-color toner image, so that less heat energy is applied to the sheet in the fixing unit. In particular, for a monochrome black image, it is preferable that the glossiness is low. In the case of a single-color toner image, even if the paper is thick paper, the fixing property of the image can be secured at the same fixing temperature as that of plain paper. Therefore, when forming a monochromatic toner image on thick paper, a paper interval change mode in which the fixing interval is not switched and the paper interval is longer than the standard paper interval at the standard transport speed is suitable. Conversely, since it is preferable that the image of the multi-color toner has higher gloss, a transport speed changing mode in which the transport speed is lower than the standard transport speed is suitable.
The image forming apparatus of the present invention displays on the operation panel (14) so that the paper interval change mode can be selected when forming an image with a single color toner, and the conveyance speed changing mode can be selected when forming an image with a plurality of colors. As a result, it is possible to provide image fixability and image quality (gloss) that meet the needs at that time.
[0013]
Next, the setting of the mode according to the type of the thick paper will be described. Even for thick paper, there is a difference in thermal energy required for fixing a toner image depending on the basis weight. For this reason, even in the above-described paper interval change mode and transport speed change mode, there may be cases where the fixing property and the gloss cannot be ensured. FIG. 6 is a diagram schematically illustrating the types of thick paper, the set fixing temperature required for each, and the nip passage time. Paper having a slightly larger basis weight than plain paper is referred to as thick paper 1, and paper having a considerably larger basis weight than plain paper is referred to as thick paper 2. It is assumed that the heat energy required for fixing the plain paper is one block, the thick paper 1 needs two blocks, and the thick paper 2 needs four blocks. Since the effect of increasing the paper interval is an increase in the set temperature and the effect of reducing the transport speed is an increase in the nip time, the example of applying the above-described paper interval change mode and transport speed change mode for the thick paper 1 is as follows. , In the form of two blocks as shown in FIG. In order to secure four blocks of the thick paper 2, a mode in which the paper interval is changed and a mode in which the transport speed is changed can be set in addition to a mode in which the paper interval is further increased and a mode in which the transport speed is further reduced. Therefore, each of the paper interval change mode and the conveyance speed change mode has a plurality of modes, and a combination of the modes can be selected. As a result, it is possible to obtain the toner image fixability and image quality (glossiness) that meet the needs at that time according to the type of paper.
[0014]
Although the paper interval change mode and the conveyance speed change mode have been described above, the present image forming apparatus can provide an image with more excellent glossiness by further having a fixing temperature change mode. The mode control in the case where the fixing temperature change mode is provided will be described. FIG. 7 is a diagram showing the time transition of the fixing temperature of the fixing device (8) in the fixing temperature change mode. For example, as shown in FIG. 7, it takes a long time to change from the plain paper set temperature to the thick paper set temperature as indicated by A and B in FIG. However, when glossiness is not so required as a required image forming condition and the fixing start temperature of the thick paper used is equal to or lower than the plain paper set temperature, the fixability of the toner image can be ensured even at the plain paper set temperature. . Therefore, after appropriately selecting the paper interval change mode and the conveyance speed change mode, the set temperature is switched while passing the paper. As a result, it is possible to pass the time required for the part A and the part B required for switching the set temperature, thereby increasing the productivity.
On the other hand, in the case of image formation requiring glossiness, the image forming apparatus stands by without switching the paper between the set temperature switching times A and B. In this case, in the part A, the fixing rollers (81, 82) are rotated and the internal heater (83) is turned on to raise the temperature while adjusting the temperature. In the part B, the heater (83) is turned off to fix the image. The roller pair (81, 82) is rotated to facilitate heat radiation. When the fixing temperature reaches the set temperature, the paper interval change mode or the conveyance speed change mode is appropriately executed, and the paper passing is started.
As described above, when switching between the paper interval change mode and the conveyance speed change mode, it is possible to select whether or not to feed the paper at the switching time of the fixing set temperature (A section, B section), thereby meeting the needs at that time. The fixing property and the image quality (glossiness) of the toner image can be obtained.
[0015]
The image forming apparatus of the present invention is capable of performing effective image fixing especially when the toner to be used for development contains wax. The wax-containing toner is used in a device that employs a so-called oilless fixing method in which silicone oil is not applied to the fixing roller pair (81, 82) of the fixing device (8). The wax component contained in the toner oozes to the surface at the nip portion of the pair of fixing rollers (81, 82), and the sheet is separated after fixing. However, the toner containing wax tends to have a lower color developing property due to the change of the toner composition in order to separate the paper. Therefore, more heat energy is required in the fixing unit in order to improve the color developing property, and the combination with the paper interval changing mode, the conveyance speed changing mode, and the fixing temperature changing mode as described above is effectively used. Can be used. According to the image forming apparatus of the present invention, even when a wax-containing toner is used, it is possible to obtain the toner image fixing property and color developing property that meet the needs at that time.
[0016]
【The invention's effect】
As described above, according to the present invention, the mode for changing the conveyance speed and the paper interval at the time of paper passing is provided, and the configuration can be set or canceled, so that the fixing property, glossiness, and productivity of the image at each time are improved. An image forming apparatus capable of forming an image according to the needs of the present invention can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.
FIG. 2 is a diagram illustrating a change over time of a fixing temperature of a fixing device.
FIG. 3 schematically shows a transport speed change mode and a paper interval change mode.
FIG. 4 is a diagram illustrating an operation panel provided on an upper surface of the image forming apparatus main body.
FIG. 5 is a diagram schematically illustrating a single-color toner image and a multi-color toner image.
FIG. 6 is a diagram schematically illustrating types of thick paper, a set fixing temperature required for each, and a nip passage time.
FIG. 7 is a diagram illustrating a change over time of the fixing temperature of the fixing device in the fixing temperature change mode.
[Explanation of symbols]
1a to 1d Paper feed tray 4 Photoconductor (image carrier)
6 Charger 7 Developing device 8 Fixing device 10 Intermediate transfer body 11 Transfer device 14 Operation panel

Claims (5)

An image forming apparatus that has a plurality of paper feed trays and obtains an image by transferring and fixing a toner image formed of a single color or a plurality of color toners on a conveyed sheet,
The image forming apparatus is provided with a standard transport speed and a standard paper interval for paper, and a transport speed change mode for decreasing the standard transport speed and a paper interval change mode for increasing the standard paper interval. An image forming apparatus having a function of setting or canceling an image. The image forming apparatus according to claim 1,
The image forming apparatus is configured to display a specific paper in the paper feed tray so that a paper interval change mode can be selected when a single color toner image is formed and a transport speed change mode can be selected when a multicolor toner image is formed. Characteristic image forming apparatus. The image forming apparatus according to claim 1, wherein
The image forming apparatus has a plurality of stages of the paper interval change mode and the transport speed change mode. The image forming apparatus according to claim 1, wherein
The image forming apparatus has a mode for changing a temperature condition of a fixing device for fixing a toner image on a sheet, and the fixing device temperature condition changing mode includes a mode for changing to the paper interval changing mode and a conveyance speed changing mode. An image forming apparatus comprising: a mode that is executed in advance; and a mode that is executed simultaneously with the change to the paper interval change mode and the conveyance speed change mode. The image forming apparatus according to claim 1, wherein
An image forming apparatus, wherein the toner used in the image forming apparatus contains wax.

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