JP2002006579A - Tandem-type full color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tandem-type full color image forming device, capable of effectively suppressing deterioration of color toner which is used less frequently. SOLUTION: In this tandem-type full color image forming device, both a photoreceptor drum and a developing roller in a developing device are driven, to be rotated both in a monochrome image-forming area and a color image forming area at forming of a full color image. At the formation of a monochrome image, both the photoreceptor drum and the developing roller in the developing device are driven to rotate in the monochrome image-forming area, and the photoreceptor drum is driven to rotate but the developing roller in the developing device is not driven to rotate or is driven to rotate at a speed lower than that at the formation of the full color image in the color image forming area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus for forming a full-color image by electrophotography, and more particularly, to a monochrome image forming area for forming a monochrome image and a color image forming apparatus. At least one color image forming area is arranged side by side on a transfer belt that conveys transfer paper, and a developing roller that supplies a toner of a predetermined color onto a developing area is provided for each image forming area. The present invention relates to a tandem type full-color image forming apparatus in which a developing unit provided and a photosensitive drum are arranged.

[0002]

2. Description of the Related Art At present, as an apparatus for forming an image by an electrophotographic method, such as a copying machine, a facsimile, and a printer, a full-color image forming apparatus capable of forming a full-color image as well as a monochrome image is commercially available. As such a full-color image forming apparatus, a monochrome image forming region, and a color image forming region such as a yellow image forming region, a magenta image forming region, and a cyan image forming region,
2. Description of the Related Art A tandem-type full-color image forming apparatus is known which is arranged side by side on a transfer belt that conveys transfer paper. In such an image forming apparatus, a photoconductive drum and a developing device are provided for each image forming area, and a transfer roller is arranged below the transfer belt so as to face each photoconductive drum. For example, in a monochrome image forming area, a monochrome developing device filled with black toner is provided,
Color developing such as a developing device filled with yellow toner in the yellow image forming region, a developing device filled with magenta toner in the magenta image forming region, and a developing device filled with cyan toner in the cyan image forming region. Units are arranged around photoreceptor drums provided in each image forming area. That is, when forming a monochrome image,
The electrostatic latent image formed on the photosensitive drum is developed with black toner in a monochrome developing device to form a monochrome toner image, which is transferred to a transfer material such as paper, thereby forming a monochrome image. The formation takes place. When a full-color image is formed, the electrostatic latent image formed on the photosensitive drum is divided into a black toner in a monochrome developing device and a color toner in a color developing device for each color. Development and transfer of the transferred toner image are performed, and a black toner image and a color toner image of each color are superimposed on a transfer material to form a full-color image. The developing device filled with the black toner and the color toner of each color has a built-in developing roller for holding and transporting the developer containing the toner by magnetic force or the like, and the developing device is filled with the developing roller. By transporting the toner to a developing area, that is, onto the surface of the photosensitive drum on which the electrostatic latent image is formed, the electrostatic latent image is developed with the toner.

In a tandem-type color image forming apparatus, since each image forming area is arranged side by side on a transfer belt that conveys a transfer sheet, the image forming area is used for both monochrome image formation and full color image formation. Also, the photosensitive drum of each image forming area is provided so as to be driven and rotated, but conventionally known ones are configured such that the developing roller in each developing unit is also driven and rotated at the time of any image formation. ing. That is, since a full-color image is formed by superimposing a monochrome toner image using black toner and a toner image of each color using color toner, inevitably the developing rollers in all the developing units are used during full-color image formation. Although the monochrome image is formed by only the black toner, the developing roller in the color developing device for each color is driven and rotated even when such a monochrome image is formed. This is because a single driving source drives the developing rollers in all the developing units.

[0004]

Generally, the toner charged in the developing device is used in the form of a one-component magnetic developer or a two-component magnetic developer, and the charged toner is developed in the form of a magnetic brush. The toner is held and conveyed by the roller, but as the toner is conveyed by the developing roller, the surface characteristics of the toner deteriorate and the amount of charge fluctuates. For example, in the case of color toners such as yellow, magenta, and cyan, the charge amount increases as the toner is transported by the developing roller, and as a result, a problem occurs in that the density of these colors decreases. On the other hand, in the case of the black toner, the charge amount is reduced, which also causes a problem that the density is reduced. Further, when a black toner or a color toner is used in the form of a two-component magnetic developer composed of a toner and a magnetic carrier, the charge amount fluctuates, the coating layer on the carrier surface peels off, and the like. Also, the problem of fusing of the toner occurs.

However, in the conventional tandem type full-color image forming apparatus described above, the color toner is
Degradation proceeds to the same extent as black toner used for forming both monochrome and full-color images, although it is used only for forming full-color images and is not used for forming monochrome images at all. There is a problem of doing. That is, in a conventionally known full-color image forming apparatus, in both cases of forming a monochrome image and a full-color image, since the developing rollers in all the developing units are driven, a monochrome image is frequently formed, and a full-color image is formed. Even when the formation of the color toner is hardly performed, the deterioration of the color toner proceeds at the same rate as that of the black toner.

Accordingly, it is an object of the present invention to provide a tandem-type full-color image forming apparatus in which deterioration of a color toner which is not frequently used is effectively suppressed.

[0007]

According to the present invention, a monochrome image forming area for forming a monochrome image and at least one color image forming area for forming a color image are provided.
A developing device, which is arranged side by side on a transfer belt that conveys transfer paper and has a developing roller for supplying a toner of a predetermined color onto a developing area for each image forming area, and a photosensitive drum are arranged. In the tandem type full-color image forming apparatus described above, when forming a full-color image, in both the monochrome image forming area and the color image forming area, both the photosensitive drum and the developing roller in the developing device are driven and rotated. When a monochrome image is formed, both the photosensitive drum and the developing roller in the developing device are driven and rotated in the monochrome image forming region, and the photosensitive drum is driven and rotated in the color image forming region. A tandem type full-color developing roller, which does not rotate or rotates at a lower speed than at the time of full-color image formation. Color image forming apparatus is provided.

That is, in the tandem type full-color image forming apparatus of the present invention, the developing roller of the developing device (color developing device) provided in the color image forming area is stopped or full-color when forming a monochrome image. It is set so as to drive and rotate at a lower speed than during image formation. Therefore, in the present invention, the holding of the developing roller is compared with a conventionally known apparatus in which the developing roller of the color developing device is driven to rotate in both the case of forming a monochrome image and the case of forming a full-color image. In addition, the deterioration of the color toner due to the conveyance is effectively suppressed.

In the present invention, the drive control of the developing roller as described above is performed in the case where the developing rollers in each of the developing units provided in each image forming area are driven by independent driving sources, respectively. At the time of formation, it can be performed very easily by stopping only the driving source for driving the developing roller in the color developing device or by performing software control so as to reduce the driving rotation speed of the driving source. When each developing roller is driven using one drive source, the driving mechanism may be configured as follows.

For example, when a developing roller in a color developing unit is stopped at the time of forming a monochrome image, a driving mechanism for driving and rotating the developing roller of each developing unit is provided with a developing device (provided in a monochrome image forming area). Monochrome developing device)
A first drive transmission gear for transmitting the drive to the developing roller, a second drive transmission gear for transmitting the drive to the developing roller of the color developing device, and a drive gear provided on a drive shaft connected to a drive source. And a drive control gear movably arranged, wherein the first drive transmission gear is always arranged to mesh with the drive gear, and the second drive transmission gear is driven via the drive control gear. It is preferable to arrange the transmission so that the driving rotation of the gear is transmitted. That is, when a full-color image is formed, the drive control gear is positioned so as to mesh with the drive gear and the second gear, so that the drive roller of the monochrome developing device is driven to rotate at the same time as the drive rotation of the drive gear is driven. The power is transmitted to the second drive transmission gear via the control gear to drive and rotate the developing roller of the color developing device. On the other hand, at the time of forming a monochrome image, the drive control gear is moved to a position where the engagement between the drive gear and the second drive transmission gear is released, so that the developing roller of the color developing device is not driven to rotate, so that the monochrome developing is not performed. Only the developing roller of the container is driven and rotated.

When a developing roller in a color developing device is driven at a low speed during the formation of a monochrome image, a first drive transmission for transmitting a driving mechanism of the developing roller of each developing device to the developing roller of the monochrome developing device. A second drive transmission gear for transmitting a drive to the developing roller of the color developing device;
A first drive gear provided on a drive shaft connected to a drive source; a second drive gear provided on the drive shaft and having a smaller diameter than the first drive gear; a drive control shaft movably provided; A first drive control gear provided on the drive control shaft;
And a second drive control gear provided on the drive control shaft and having a larger diameter than the first drive control gear and capable of rotating integrally with the first drive transmission gear. That is,
The first drive transmission gear is disposed so as to always mesh with the first drive gear. Further, at the time of forming a full-color image, the first drive control gear is positioned so as to mesh with both the first drive gear and the second drive transmission gear, and the second drive control gear is connected to another drive control gear. Place it in a position that does not mesh with the gear. Thereby, at the same time when the developing roller of the monochrome developing device is driven to rotate, the driving rotation of the first driving gear is transmitted to the second driving transmission gear via the first driving control gear, and the developing roller of the color developing device is driven. Drive and rotate. On the other hand, when a monochrome image is formed, the drive control shaft is moved to move the first drive control gear to a position where the first drive control gear meshes with the second drive transmission gear but is disengaged from the first drive gear. . Further, the second drive control gear is moved to a position where it meshes with the second drive gear. Accordingly, the driving rotation of the second driving gear is transmitted to the second driving transmission gear via the second driving control gear and the first driving control gear at the same time when the developing roller of the monochrome developing device is driven and rotated. Then, the developing roller of the color developing device is driven and rotated. In this case, the second
Is smaller in diameter than the first drive gear, and the second drive control gear meshing with the second drive gear is
The diameter of the first drive control gear is larger than that of the first drive control gear, and the second drive transmission gear and the first drive transmission gear rotate integrally. The roller is driven and rotated at a lower speed than during full-color image formation.

In the present invention, three color image forming areas of a yellow image forming area, a magenta image forming area, and a cyan image forming area are usually arranged as the color image forming areas arranged on the transfer belt. As with the previously known tandem-type full-color image forming apparatus described above, a yellow developing unit for developing with a yellow toner is used as a color developing unit in a yellow image forming area, and a developing unit using a magenta toner is used for a magenta image forming area. In the magenta developing device and the cyan image forming area, a cyan developing device for developing with cyan toner is used.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific examples shown in the accompanying drawings. FIG. 1 is a diagram illustrating a schematic structure of a tandem-type full-color image forming apparatus of the present invention, and FIG. 2 is a diagram illustrating an example of a driving mechanism of a developing roller used in the image forming apparatus illustrated in FIG. FIG. 3 is a schematic top view showing another example of the drive mechanism of the developing roller used in the image forming apparatus shown in FIG. 1, and FIG. 4 is a schematic front view of the drive mechanism of FIG.

FIG. 1 shows a schematic structure of a tandem-type full-color image forming apparatus according to the present invention. The apparatus includes a transfer belt 1 stretched between a pair of rollers. The paper 2 is transported in the direction of the arrow in the figure. On the transfer belt 1, a monochrome image forming area B, a cyan image forming area C, a magenta image forming area M, and a yellow image forming area Y are provided in this order from the right. ,
A photoconductor drum 5 is arranged, and a transfer roller 6 is arranged below the transfer belt 1 so as to face each photoconductor drum. (Note that the arrangement order of the image forming areas is not particularly limited, and this arrangement can be appropriately changed.)

In each image forming area, around the photosensitive drum 5, a main charger 7, an optical system 8 for image exposure, and a developing device specific to each image forming area are arranged in this order. I have. That is, in the monochrome image forming region B, the monochrome developing device 9B filled with black toner, in the cyan image forming region C, the cyan developing device 9C filled with cyan toner, and in the magenta image forming region M, magenta toner is filled. Magenta developing device 9M, in yellow image forming area Y, yellow developing device 9 filled with yellow toner.
Y is provided. Further, a static eliminator (not shown) is provided between the area where the transfer roller 6 is provided and the main charger 7.
And a cleaning device 10.

The image forming cycle in each image forming area is
A description will be given taking the monochrome image forming area B as an example. First,
The photosensitive drum 5 is uniformly charged to a predetermined polarity by the main charger 7 including a corona charger or a contact charging roller. Next, image exposure is performed by light irradiation from an optical system 7 such as an LED, and an electrostatic latent image is formed on the surface of the photosensitive drum 5. This electrostatic latent image is developed by the monochrome developing device 9B filled with black toner, and a toner image is formed on the surface of the photosensitive drum 5. The charge polarity of this toner image is
When development is performed by so-called reversal development, the charge polarity of the photoconductor drum 5 charged by the main charger 7 is the same polarity. When development is performed by so-called regular development, the charge polarity of the photoconductor drum 5 is And reverse polarity. The toner image thus formed on the surface of the photosensitive drum 5 is transferred to the transfer belt 1 in an area (transfer area) facing the transfer roller 6.
The image is transferred onto the transfer paper 2 conveyed above. This transfer is performed by applying a bias voltage having a polarity opposite to that of the toner image to the transfer roller 6. Also, the transfer roller 6
Alternatively, transfer can be performed by using a corona charger and charging the back surface of the transfer paper 2 to a polarity opposite to that of the toner image. After the transfer is completed, the photosensitive drum 5 is moved by a static eliminator and a cleaning device 10 (not shown).
And the toner remaining on the surface of the drum 5 is cleaned, and the next image forming cycle is performed.

As described above, in the monochrome image forming area B, a monochrome image composed of black toner is formed on the transfer paper 2, and similarly, in the cyan image forming area C, the cyan toner is formed on the transfer paper 2. In the magenta image forming region M, a red image formed of magenta toner is formed, and in the yellow image forming region Y, a yellow image formed of yellow toner is formed. That is, when forming a monochrome image, the above-described image forming cycle is executed only in the monochrome image forming area B, and a monochrome image is formed on the transfer paper 2. When a full-color image is formed, the above-described image forming cycle is executed in each of the image forming areas B, C, M, and Y.
The toner images of the respective colors are superimposed to form a full-color image on the transfer paper 2. The transfer paper 2 on which the above-described image is formed is discharged from the transfer belt 1 and introduced into a fixing device (not shown), where the image is fixed and discharged.

In the above-described tandem type full-color image forming apparatus, the developing units 9B, 9C, 9M, 9Y are provided with developing rollers 10B, 10C, 10M, 10Y so as to face the photosensitive drum 5, respectively. By the rotation of the developing roller, the toner (indicated by reference numeral 15 in FIG. 1) filled in each of the developing devices is developed (in a portion where each developing roller faces the photosensitive drum 5).
The electrostatic latent image is developed by the toner 15. These developing rollers 10B, 10C, 10M,
10Y has a built-in magnet having many magnetic poles, and holds and transports the charged toner 15 in the form of a magnetic brush by rotating the roller. In this case, the rotation direction of the roller may be the same direction as the photosensitive drum 5 in the area (developing area) facing the photosensitive drum 5 or may be the opposite direction to the photosensitive drum 5. Generally, as shown in FIG. 1, it is preferable that the photosensitive drum 5 is set to rotate in the same direction as the photosensitive drum 5 in the developing area.

The toner 15 is used in the form of a so-called one-component magnetic developer or a two-component magnetic developer. The one-component magnetic developer uses the toner 15 alone as a developer. The toner 15 contains a magnetic material together with a colorant and a charge control agent of each color. A brush is formed. The two-component developer is composed of a toner 15 (which is basically non-magnetic) and a magnetic carrier, and holds the charged toner 15 on a magnetic brush formed by the magnetic carrier. still,
Each of the developing devices 9B, 9C, 9M, and 9Y is provided with an agitating device 16 such as an agitating paddle together with the developing roller described above. The agitating device frictionally charges the toner 15 to a predetermined polarity, and the charged toner 15 is charged. In the form of a magnetic brush, it is conveyed to a development zone by a development roller. The magnetic brush introduced into the developing area is adjusted to a predetermined spike length by the cutting blade 17. In the development area, the magnetic brush of the toner 15 may be in contact with the photosensitive drum 5,
It may be non-contact. Further, when developing the electrostatic latent image with the toner 15, a developing bias voltage can be applied between the photosensitive drum 5 and the developing roller.

In the full-color image forming apparatus having the above-described structure, since the photosensitive drums 5 arranged in each image forming area are arranged side by side along the transfer direction of the transfer belt 1, a full-color image and a monochrome image are formed. In the case of forming any one of the above, it is set so as to be always driven to rotate. However, according to the present invention, when forming a full-color image, each of the developing units 9B, 9C,
9M, 9Y developing rollers 10B, 10C, 10M, 10
In the case of forming a monochrome image, the developing roller 10B of the monochrome developing device 9B filled with black toner is driven and rotated in the same manner as in full-color image formation. The developing rollers 10C, 10M, and 10Y of the containers 9C, 9M, and 9Y do not rotate or rotate.
Alternatively, it is set so as to drive and rotate at a lower speed than during full-color image formation. Therefore, the color developing units 9C, 9
The deterioration of the color toner (cyan toner, magenta toner, and yellow toner) filled in the M and 9Y due to the driving of the developing roller is effectively suppressed as compared with the black toner filled in the monochrome developing device 9B. The lower the frequency of color image formation, the more effectively the deterioration of the color toner is suppressed.

The developing rollers 10B, 10C,
The drive control of 10M and 10Y can be extremely easily performed by software control when a dedicated drive source (drive motor) is provided for each of these developing rollers and each developing roller is driven independently. . However, providing a drive source for each developing roller is not desirable because it increases the size and cost of the apparatus. Therefore, in the present invention, it is desirable to drive each developing roller using one drive source and to perform the above-described drive control.

In the present invention, using one drive source,
When forming a monochrome image, the color developing devices 9C and 9
When the driving of the M and 9Y developing rollers 10C, 10M and 10Y is stopped, it is preferable to use a driving mechanism having a structure as shown in FIG.

In FIG. 2, the drive mechanism includes a drive gear 21 provided on a drive shaft 20 which is driven and rotated by the operation of a drive motor (not shown), and the above-described monochrome developing device 9.
A first drive transmission gear 22 for transmitting drive to the B developing roller 10B, and a second drive transmission gear for transmitting drive to each of the developing rollers 10C, 10M, 10Y of the color developing units 9C, 9M, 9Y. 23, and a drive control gear 24 for performing the above-described drive control. The drive control gear 24 is supported by an arm 27 rotatably held on a shaft 26.
It is provided so as to be able to turn integrally with.

In the drive mechanism shown in FIG. 2, the drive gear 21 and the first drive transmission gear 22 are always in mesh with each other. Therefore, in both cases of monochrome image formation and full-color image formation, the monochrome developing device is used. 9B developing roller 10B
Is designed to rotate.

On the other hand, the drive control gear 24 is arranged at a position where it meshes with both the drive gear 21 and the second drive transmission gear 23 when forming a full-color image, as shown in FIG. Therefore, when forming a full-color image, the driving gear 2
Through the first and second drive transmission gears 23, the developing rollers 10C, 10M, 10Y of the color developing devices 9C, 9M, 9Y
Are driven to rotate.

When forming a monochrome image, the arm 2
7, the drive control gear 24 also turns in the direction indicated by the arrow X in FIG. 2, and as a result, the engagement between the drive control gear 24, the drive gear 21 and the second drive transmission gear 23 is released. Is done. Therefore, when forming a monochrome image, the driving gear 21
Is not transmitted to the second drive transmission gear 23, and the developing rollers 10C, 10Y of the color developing units 9C, 9M, 9Y are not transmitted.
M and 10Y are not driven to rotate. When the formation of a monochrome image is completed or the formation of a full-color image is started, the arm 27 turns in the opposite direction, and the drive control gear 24 returns to the position shown in FIG.

In the drive mechanism shown in FIG. 2, the turning of the arm 27 for changing the position of the drive control gear 24 is performed as follows.
For example, it can be performed by rotating the support shaft 26 of the arm 27 by a forward / reverse rotation motor or the like. Further, the arm 27 itself is energized by a solenoid, and the position of the drive control gear 24 can be changed by turning the arm 27 as described above by turning the solenoid on and off.

As described above, according to the driving mechanism shown in FIG. 2, when forming a full-color image, the developing rollers 10B, 10C,
When the monochrome image is formed, only the developing roller 10B of the monochrome developing device 9B is driven to rotate, and the developing rollers 10C, 10M, and 10Y of the color developing devices 9C, 9M, and 9Y are not driven to rotate. .

In order to drive and rotate the developing rollers 10C, 10M, and 10Y of the color developing units 9C, 9M, and 9Y at a lower speed in forming a monochrome image than in forming a full-color image, FIGS. The drive mechanism shown in FIG. (FIG. 3 is a schematic top view, and FIG. 4 is a schematic front view.)

The drive mechanism shown in FIGS. 3 and 4 includes a first drive transmission gear 30 for transmitting a drive to a developing roller 10B of a monochrome developing device 9B; and a developing roller 10C, 10M of a color developing device 9C, 9M, 9Y. A second drive transmission gear 31 for transmitting drive to each of 10Y; a first drive gear 33 provided on a drive shaft 32 connected to a drive source;
A drive control shaft 35; a first drive control gear 36 and a second drive control gear 37 provided on the drive control shaft 35;

The drive shaft 32 is provided with the first drive gear 33 and the second drive gear 34 as described above, and the first drive transmission gear 3 is provided via these gears 33 and 34.
The drive rotation of the drive motor is transmitted to the 0 and second drive transmission gears 31, and the developing rollers 10B, 10C, 10M, 1
The driving of 0Y is performed. Here, as is apparent from FIG. 3, the diameter (a) of the first drive gear 33 is larger than the diameter (b) of the second drive gear 34. That is, a> b.

The first drive control gear 36 and the second drive control gear 37 provided on the drive control shaft 35 are
It rotates integrally via the drive control shaft 35, and performs the above-described drive control. As is apparent from FIG. 3, the diameter (c) of the first drive control gear 36 is
Is smaller than the diameter (d) of the drive control gear 37 of FIG. That is, c
<D.

Further, the drive control shaft 35 has a pair of arms 4 slidably and pivotably supported by a shaft 40.
1, 41. Therefore, the drive control shaft 3
As shown in FIG. 4, the arm 5 pivots about the shaft 40 integrally with the arm 41, and can slide up and down in parallel with the shaft 40 in FIG. That is, by turning or sliding the drive control shaft 35 via the arm 41, the first drive control gear 36 and the second drive control gear 37 are provided so that their positions can be adjusted.

In the driving mechanism of FIGS. 3 and 4 described above,
The first drive transmission gear 30 always has the first drive gear 33
It is arranged to mesh with. Therefore, by the drive transmission via the first drive gear 33 and the first drive transmission gear 30, the developing roller 10B of the monochrome developing device 9B is driven in both the case of monochrome image formation and the case of full color image formation. It is designed to rotate.

In particular, as shown in FIG. 3, when forming a full-color image, the first drive control gear 3
6 is positioned so as to mesh with both the first drive gear 33 and the second drive transmission gear 31. In this state, the second drive control gear 37 is arranged at a position where it does not mesh with another gear. Therefore, at the time of full-color image formation, the driving rotation of the first driving gear 33 is simultaneously performed with the driving rotation of the developing roller 10B of the monochrome developing device 9B.
Is transmitted to the second drive transmission gear 37 via the drive control gear 36, and the developing rollers 10C, 10M, 10Y of the color developing devices 9C, 9M, 9Y are driven to rotate.

As can be understood from the above description, when the peripheral speed of the first drive gear 33 is represented by N, the peripheral speed of the first drive transmission gear 30 that defines the rotation speed of the developing roller 10B of the monochrome developing device. Speed and developing roller 10C of the color developing device,
The peripheral speed of the second drive transmission gear 31 that defines the rotation speeds of 10M and 10Y satisfies the condition represented by the following equation (1) during full-color image formation. N = peripheral speed of first drive transmission gear 30 = peripheral speed of second drive transmission gear 31 / (1)

On the other hand, when a monochrome image is formed, the drive control shaft 35 is moved by turning and sliding the above-described arm 41 to control the position of the first drive control gear 36 and the second drive control gear 37. Do. That is, by this position control, the first drive control gear 36 moves to the position indicated by the dotted line in FIG. 3 and meshes with the second drive transmission gear 31 but meshes with the first drive gear 33. Is canceled.
At the same time, the second drive control gear 37 moves to the position shown by the dotted line in FIG. 3, and meshes with the second drive gear 34. Therefore, during monochrome image formation, the second drive gear 3
4 is transmitted to the drive control shaft 35 via the second drive control gear 37, and the drive rotation of the drive control shaft 35 is
The power is transmitted from the first drive control gear 36 to the second drive transmission gear 31, and as a result, the developing roller 10 of the color developing device is
C, 10M, and 10Y are driven and rotated.

By the way, also at the time of monochrome image formation, the first drive gear 33 is driven and rotated at the peripheral speed N as in the case of full color image formation. Therefore, the peripheral speed of the second drive gear 34 and the peripheral speed of the second drive control gear 37 are represented by the following equations. Peripheral speed of second drive gear 34 = Peripheral speed of second drive control gear 37 = N x (b / a)） (2) where a = gear diameter of first drive gear 33, b = second gear Gear diameter of the drive gear 34 of FIG.

The peripheral speeds of the first and second drive control gears 36 and 37 at the time of monochrome image formation satisfy the relationship of the following equation (3). Circumferential speed of first drive control gear 36 = Circumferential speed of second drive control gear 37 × (c / d) ‥ (3) where c = gear diameter of first drive control gear 36, d = second gear Gear diameter of the drive control gear 37 of FIG.

Further, the peripheral speed of the second drive transmission gear 31 is:
Since the peripheral speed is equal to the peripheral speed of the first drive control gear 36, this peripheral speed is obtained from the above-described formulas (2) and (3) by using the following formula (4).
It is represented by Peripheral speed of second drive transmission gear 31 = Peripheral speed of first drive control gear 36 = Peripheral speed of second drive control gear 37 x (c / d) = N x (b / a) x (c / d) ‥ (4)

In Expression (4), since a> b and c <d, from Expression (4), the peripheral speed of the second drive transmission gear 31 at the time of forming a monochrome image is equal to that at the time of forming a full-color image. Is smaller than the peripheral speed N of the gear 31 at That is, in the drive mechanism of FIGS. 3 and 4,
At the time of monochrome image formation, the developing rollers 10C, 10M, and 10Y of the color developing device are driven to rotate at a lower speed than at the time of full color image formation. Therefore, the degree of deterioration of the color toner in the color developing devices 9C, 9M, and 9Y is suppressed to be lower than that of the black toner in the monochrome developing device 9B.

In the drive mechanism shown in FIGS. 3 and 4, the position control of the first and second drive control gears 36 and 37 by turning and sliding the arm 41 can be performed, for example, as follows. it can. That is, for example, the shaft 40 is rotated by a drive source such as a forward / reverse rotation motor and the arm 41 is turned in the direction of the arrow J as shown in FIG. The engagement between the first drive gear 33 and the second drive transmission gear 31 is released. In this state, the arm 41 is slid upward as shown in FIG. 3 so that the first drive control gear 36 does not mesh with the first drive gear 33 and the second drive transmission gear 31 And the second drive control gear 37 is
The arm 41 may be turned in the direction opposite to the arrow J at the time when the arm 41 comes to a position where it can mesh with the drive gear 34. The sliding of the arm 41 can be easily performed by, for example, ON-OFF control of a solenoid.

[0043]

As described above, according to the present invention, the deterioration of the color toner in the color developing device is effectively suppressed by stopping or reducing the driving rotation of the developing roller of the color developing device when forming a monochrome image. can do. In addition, when a monochrome image is formed, the driving rotation of the developing roller of the color developing unit is stopped or decelerated, so that the vibration noise of the apparatus is reduced and the life of the apparatus can be shortened.

[Brief description of the drawings]

FIG. 1 is a view showing a schematic structure of a tandem type full-color image forming apparatus of the present invention.

FIG. 2 is a diagram illustrating an example of a driving mechanism of a developing roller used in the image forming apparatus illustrated in FIG.

FIG. 3 is a schematic top view showing another example of a driving mechanism of a developing roller used in the image forming apparatus shown in FIG.

FIG. 4 is a schematic front view of the drive mechanism of FIG.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shokane Dobashi 1-2-28 Tamazo, Chuo-ku, Osaka-shi F-term in Kyocera Mita Corporation (reference) 2H030 AB02 AD08 AD17 BB02 BB33 2H077 BA01 BA03 DB11 DB14 GA03 GA13 GA15

Claims (3)

[Claims] 1. A monochrome image forming area for forming a monochrome image and at least one color image forming area for forming a color image are juxtaposed side by side on a transfer belt that conveys transfer paper. In a tandem-type full-color image forming apparatus in which a developing device having a developing roller for supplying a toner of a predetermined color onto a developing area and a photosensitive drum for each forming area, when forming a full-color image, In both the image forming area and the color image forming area, both the photosensitive drum and the developing roller in the developing device are driven and rotated. When a monochrome image is formed, the photosensitive drum and the developing roller in the monochrome image forming area are rotated. Both the developing roller in the developing device is driven to rotate, and in the color image forming area, the photosensitive drum is driven to rotate. Developing roller in the vessel is a tandem type full-color image forming apparatus characterized by rotationally driving at a low speed than at or full-color image formation is not rotated. 2. A driving mechanism for driving and rotating a developing roller of a developing device provided in each image forming area includes a first drive transmitting gear for transmitting power to a developing roller of the developing device in a monochrome image forming area. A second drive transmission gear for transmitting a drive to a developing roller of a developing device in a color image forming area, a drive gear provided on a drive shaft connected to a drive source, and a drive control gear movably disposed The first drive transmission gear is arranged so as to always mesh with the drive gear, and the second drive transmission gear transmits the drive rotation of the drive gear via the drive control gear. When a full-color image is formed, the drive control gear is positioned so as to mesh with the drive gear and the second drive transmission gear. At the same time as the developing roller of the developing device is driven to rotate, the driving rotation of the driving gear is transmitted to the second drive transmission gear via the driving control gear, so that the developing roller of the developing device in the color developing area is driven to rotate, and a monochrome image is formed. The drive control gear is moved to a position where the engagement between the drive gear and the second drive transmission gear is released during the formation, whereby only the developing roller of the developing device in the monochrome image forming area is driven to rotate. 5. A tandem-type full-color image forming apparatus according to item 1. 3. A driving mechanism for driving and rotating a developing roller of a developing device in each image forming area includes: a first drive transmitting gear for transmitting driving to a developing roller of the developing device in a monochrome image forming area; A second drive transmission gear for transmitting the drive to the developing roller of the developing device, a first drive gear provided on a drive shaft connected to a drive source, and a first drive gear provided on the drive shaft. A second drive gear having a small diameter; a drive control shaft movably provided; a first drive control gear provided on the drive control shaft; and a first drive control gear provided on the drive control shaft. A second drive control gear having a large diameter and capable of rotating integrally with the first drive transmission gear; the first drive transmission gear is arranged to always mesh with the first drive transmission gear. And full color painting During image formation, the first drive control gear
The second drive control gear is located so as to mesh with both the first drive gear and the second drive transmission gear, and the second drive control gear is not meshed with other gears. At the same time as the developing roller of the developing device in the area is driven to rotate, the driving rotation of the first driving gear is transmitted to the second driving transmission gear via the first driving control gear, and the developing device in the color image forming area is developed. The roller is driven and rotated, and when forming a monochrome image, the movement of the drive control shaft
The first drive control gear moves to a position where it meshes with the second drive transmission gear but is disengaged from the first drive gear, and the second drive control gear is a second drive gear. At the same time as the developing roller of the developing device in the monochrome image forming area is driven and rotated.
The drive rotation of the second drive gear is controlled by the second drive control gear,
2. The color image according to claim 1, wherein the color image is transmitted to the second drive transmission gear via the drive control gear, and the developing roller of the developing device in the color image forming area is driven to rotate at a lower speed than at the time of full color image formation. Forming equipment.