JP3508804B2 - Image forming device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer, a facsimile, and other image forming apparatuses that form an image using toner. In particular, it relates to a transfer technique for transferring a toner image formed on the surface of an image carrier to the surface of an intermediate transfer belt.

[0002]

2. Description of the Related Art In an image forming apparatus for forming an image using toner, a toner image formed on the surface of an image bearing member such as a photosensitive drum is once transferred onto an intermediate transfer belt, and then the intermediate transfer belt is used. A type is known in which a toner image is further transferred onto a recording material such as paper.

In the image forming apparatus of this type,
In order to faithfully reproduce the toner image formed on the surface of the image carrier on the recording material, it is necessary to at least first faithfully transfer the toner image formed on the surface of the image carrier to the intermediate transfer belt. is important. For that purpose, it is important to drive the image carrier and the intermediate transfer belt in synchronism with each other, and one of the methods is to engage the gear that drives the image carrier with the gear that drives the intermediate transfer belt. A driving method may be used. However, in this way,
Due to backlash between the driving gears, speed fluctuation occurs, and in particular, when color toners of a plurality of colors are sequentially superposed on the intermediate transfer belt to form a color image, there is a problem that color misregistration or color unevenness occurs. .

As a technique for preventing speed fluctuations due to backlash between driving gears, for example, Japanese Patent Laid-Open No. 5-28 is known.
No. 9536 is cited. JP-A-5-289536
Japanese Patent Laid-Open Publication No. 2003-242242 discloses a structure in which the gear speed driving the intermediate transfer belt is transmitted to the gear wheel driving the photoconductor belt, and the peripheral speed of the photoconductor belt is slightly higher than the peripheral speed of the intermediate transfer belt. The frictional force generated between the photoconductor belt and the intermediate transfer belt acts as a load so that the gear that drives the photoconductor and the gear that drives the intermediate transfer belt always mesh with each other in a fixed direction to ensure stable operation. It is intended to transmit the driving force.

Further, in the above-mentioned conventional technique, the drive roller for driving the intermediate transfer belt is the primary transfer position for transferring the toner image on the photoconductor belt to the intermediate transfer belt when viewed from the conveying direction of the intermediate transfer belt. Is disposed on the upstream side of the intermediate transfer belt, and the intermediate transfer belt is wound around the photosensitive member in an arc shape at the primary transfer position.

[0006]

However, in the configuration of the above-mentioned conventional technique, the amount of toner adhered on the photosensitive belt and the intermediate transfer belt, the fluctuation of the surface potential of the photosensitive belt and the intermediate transfer belt, etc. The frictional force at the primary transfer position is not stable. Moreover, since the primary transfer position is located on the side where the intermediate transfer belt is pushed out from the drive roller (so-called slack side), the speed of the intermediate transfer belt varies only with the frictional force variation at the primary transfer position. However, there is a problem that the contact angle of the intermediate transfer belt before and after the primary transfer position varies, and image deterioration such as toner image scattering occurs during the primary transfer.

Further, the above-mentioned structure has a problem that when the frictional force at the primary transfer position is largely changed, the intermediate transfer belt is in a slackened state, the transfer belt is vibrated, and the image is disturbed.

Further, in the above-mentioned structure, when sufficient frictional force cannot be obtained at the primary transfer portion, the backlash between the drive gears also causes speed fluctuations, resulting in color misregistration and color unevenness. There was a problem.

An object of the present invention is to solve the above-mentioned problems and to synchronously drive the photosensitive member and the intermediate transfer belt with a simple structure, thus forming an image with good reproducibility. To provide a device.

[0010]

In order to achieve the above object, an image forming apparatus according to claim 1 comprises a latent image forming means for forming a latent image on a drum-shaped photosensitive member , and A developing means for developing the latent image on the photoconductor with toner, a primary transfer means for sequentially transferring the toner image on the photoconductor onto the intermediate transfer belt, and a toner image superposed on the intermediate transfer belt at the same time. an image forming apparatus that includes a secondary transfer unit that transfers onto the recording material Te, a driving source for driving the photosensitive member, before
Photoconductor teeth provided on the photoconductor and rotating integrally with the photoconductor
A car, a drive roller for driving the intermediate transfer belt,
Rotates integrally with the drive roller and meshes with the photoconductor gear
Has a drive roller gear, and the driving force of the driving source is transmitted to the photosensitive member, wherein the transmitting the driving force of the photosensitive member to the intermediate transfer belt, synchronous drive and the intermediate transfer belt and the photoreceptor The drive roller gear is arranged on the downstream side of the primary transfer means with respect to the conveying direction of the intermediate transfer belt, and the pitch circle diameter of the photoconductor gear is smaller than the pitch circle diameter of the drive roller gear. Is also set to be large.

An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect.
In the image forming apparatus described above, the peripheral speed of the intermediate transfer belt is set to be higher than the peripheral speed of the photoconductor .

The image forming apparatus according to claim 3 is the image forming apparatus according to claim 1.
The image forming apparatus, wherein said primary transfer means is characterized by being urged through the intermediate transfer belt to the photosensitive member side.

The image forming apparatus according to claim 4 is the image forming apparatus according to claim 3.
In the image forming apparatus described, the intermediate transfer belt,
At the primary transfer position where the primary transfer means is arranged,
It is characterized in that the photosensitive member is stretched in a substantially tangential direction.

An image forming apparatus according to a fifth aspect is the image forming apparatus according to the first aspect.
The image forming apparatus described above is characterized in that a wrinkle prevention unit is arranged upstream of the primary transfer unit to extend wrinkles generated on the intermediate transfer belt before being conveyed to the primary transfer position.

The image forming apparatus according to claim 6 is the image forming apparatus according to claim 1.
In the image forming apparatus described above, the number of teeth of the photoconductor gear from the latent image forming position on the photoconductor to the primary transfer position is an integer, and the photoconductor gear receives a driving force from a driving source. It is characterized in that the number of teeth of the photoconductor gear from the drive position to the drive transmission position for transmitting the drive force to the drive roller gear is an integer.

[0016]

[0017]

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings by taking an apparatus for forming a color image as an example.

FIG. 1 is a sectional view of an image forming apparatus of the present invention, which is a color image forming apparatus using a belt-shaped intermediate transfer member.

The overall structure and operation of this apparatus will be described with reference to FIG.

In FIG. 1, a drum-shaped photosensitive member 1 (image bearing member) is rotationally driven in the direction of arrow D by a drive source such as a motor (not shown). A charging means 2 such as a charging roller is arranged on the outer periphery of the photoconductor 1 so that the surface of the photoconductor 1 is uniformly charged while rotating in contact with the photoconductor 1.

The photosensitive member 1 whose surface is uniformly charged is selectively scanned and exposed by the latent image forming means 3 such as a laser scanning optical system according to the image information of the first color, for example, yellow, and the photosensitive member 1 for yellow is used. An electrostatic latent image is formed.

On the downstream side in the rotation direction of the photoconductor 1 on which the electrostatic latent image is recorded, yellow, magenta, cyan, and black toners are stored as developers, respectively, so that the development can be freely performed with respect to the photoconductor 1. Means 4, 5, 6, 7 are arranged, and the formed yellow electrostatic latent image is developed by contacting only the yellow developing means 4 with the photoconductor 1 to develop a yellow toner image.

An intermediate transfer belt 8 is arranged adjacent to the photoconductor 1 on the downstream side in the rotation direction of the photoconductor 1 on which the toner image is formed. The intermediate transfer belt 8 is wound around a drive roller 9, a backup roller 10, a tension roller 11, and a wrinkle removing roller 12, and is driven at the same speed as the peripheral speed of the photoconductor 1. Further, by transmitting the driving force of the photoconductor 1 to the drive roller 9, the photoconductor 1 and the intermediate transfer belt 8 are synchronously driven.

The primary transfer roller 13 is biased toward the photoconductor 1 via the intermediate transfer belt 8, and at the primary transfer position where the intermediate transfer belt 8 is sandwiched between the photoconductor 1 and the primary transfer roller 13, By supplying a voltage to the primary transfer roller 13 from a high voltage power source (not shown), the yellow toner image formed by the above-described procedure is transferred to the surface of the intermediate transfer belt 8.

The photosensitive member 1 on which the yellow toner image has been transferred onto the intermediate transfer belt 8 is further rotated in the direction of arrow D, and the toner remaining on the surface of the photosensitive member 1 is scratched by the photosensitive member cleaner 14 composed of a cleaner blade or the like. Then, the image can be formed again.

By repeating the same procedure for the second to fourth color images (magenta, cyan, black), four color toner images are sequentially superposed and recorded on the intermediate transfer belt 8.

When the four color toner images have been superposed on the intermediate transfer belt 8, the recording sheet 17 is fed by the paper feed roller 20 and the pair of paper transport rollers 15 and 16, and a clutch mechanism (not shown) is synchronized with this. And the cam mechanism causes the secondary transfer roller 18 to rotate in the direction of arrow E about the secondary transfer fulcrum shaft 19 and contact the backup roller 10 via the intermediate transfer belt 8, and a voltage is transferred from a high voltage power source (not shown) to the secondary transfer roller 10. By being applied to the roller 18, the four color toner images on the intermediate transfer belt 8 are collectively transferred to the recording sheet 17. On the intermediate transfer belt 8 that has completed the secondary transfer, a cleaner 21 composed of a cleaner blade or the like rotates in the direction of arrow F by a clutch mechanism and a cam mechanism (not shown) to come into contact with the intermediate transfer belt 8 and remains on the surface of the intermediate transfer belt 8. When the toner is scraped off and the scraping is completed, the cleaner 21 rotates in the direction opposite to the arrow F and retracts.

Recording sheet 1 onto which toner images of four colors have been transferred
A fixing unit 22 having a heating roller including a heating unit such as a halogen lamp is nipped and conveyed while being heated and pressed to fix the toner image. The recording sheet 17 on which the toner image is fixed is discharged to the outside of the apparatus by the pair of discharging rollers 23 and 24, and the color image recording is completed.

FIG. 2 is a side sectional view showing the drive transmission system and the positional relationship between the photosensitive member and the intermediate transfer member of the present invention.

The photoreceptor 1 and the intermediate transfer belt 8 will be described with reference to FIG.
The driving operation of will be briefly described.

In FIG. 2, when the driving gear 25 is rotated by the driving force of a driving source (not shown), the driving gear 25 becomes
The driving force is transmitted to the photoconductor gear 26 (first drive transmission means) provided on the side surface of the photoconductor 1 and rotating integrally with the photoconductor 1, and the photoconductor 1 is rotated. Subsequently, the photoconductor gear 26 is driven by the drive roller gear 27 that rotates integrally with the drive roller 9.
The (second drive transmission means) is rotationally driven to drive and convey the intermediate transfer belt 8 in the arrow direction.

The peripheral speed of the intermediate transfer belt 8 is set to be higher than the peripheral speed of the photosensitive member 1. In particular,
When the outer diameter of the driving roller 9 is the smallest within a tolerance range of a predetermined dimension, and the outer diameter of the drum-shaped photoreceptor 1 is a maximum within a tolerance range of the predetermined dimension, the intermediate transfer belt 8 is formed.
The peripheral speed of is equal to or slightly higher than the peripheral speed of the photoconductor 1.

The intermediate transfer belt 8 is primarily driven by a driving roller 9 disposed upstream of the primary transfer position C and a wrinkle removing roller 12 disposed downstream of the primary transfer position C when viewed from the conveying direction of the intermediate transfer belt 8. At the transfer position C, the photosensitive member 1 is stretched in a substantially tangential direction.

Further, the wrinkle removing roller 1 of the intermediate transfer belt 8
The length from the winding end to the winding end to the drive roller 9 to the driving roller 9 is set to 60 mm or less. Further, the length from the winding end of the wrinkle removing roller 12 of the intermediate transfer belt 8 to the primary transfer position C is set to be 30 mm or less.

The pitch circle diameter of the photoconductor gear 25 is
The diameter is set larger than the pitch circle diameter of the drive roller gear 27, and the drive transmission system from the photoconductor gear 25 to the drive roller gear 27 is configured to be a speed increasing system.

From the latent image forming position G of the latent image forming means 3 on the photosensitive member 1 to the primary transfer position C where the primary transfer roller 13 is pressed against the photosensitive member 1 via the intermediate transfer belt 8, the photosensitive member 1 , The photosensitive member gear 26 rotates by the number of teeth Z2. The meshing position A between the drive gear 25 and the photoconductor gear 26
To the meshing position B between the photoconductor gear 26 and the drive roller gear 27, the photoconductor gear 26 moves while the photoconductor 1 moves.
Rotates the number of teeth Z1. Then, the number of teeth Z of the photoconductor gear 26
1 and Z2 are set to be integers.

Next, the speed fluctuations of the photoconductor 1 and the intermediate transfer belt 8 due to the drive gear 25, the photoconductor gear 26, and the drive roller gear 27 will be briefly described with reference to FIG.

FIG. 3 is a diagram showing speed fluctuations of the photosensitive member and the intermediate transfer member of the present invention.

When the driving force is transmitted from the driving gear 25 to the photoconductor gear 26, the speed of one gear cycle of the gear varies, but the teeth of the photoconductor gear from the latent image forming position G to the primary transfer position C are changed. By setting the number Z1 to an integer, the photoconductor 1
When the latent image forming position G (time T1) is rotated to the primary transfer position C (time T2), the phase of the speed fluctuation is the same at both positions.

That is, in the speed fluctuation, the portion where the latent image is formed at a high speed at the latent image forming position G, that is, the portion where the image density is narrowed in the rotation direction of the photoconductor is at a high speed at the primary transfer position C. Becomes On the contrary, the portion where the latent image is formed at the slow speed at the latent image forming position G, that is, the portion where the image density is wide in the photoconductor rotation direction becomes slow at the primary transfer position C.

At this time, the drive gear 25 and the photoconductor gear 26
By setting the photoconductor gear 26 from the meshing position A to the meshing position B of the photoconductor gear 26 and the drive roller gear 27 to be an integer, the speed fluctuation of the photoconductor 1 and the speed fluctuation of the intermediate transfer belt 8 are in opposite phases. Becomes

Therefore, when the photoconductor 1 advances fast, the intermediate transfer belt 8 advances slowly, and when the photoconductor 1 advances slowly, the intermediate transfer belt 8 advances fast. Therefore, the toner image on the photoconductor 1 is relatively enlarged on the intermediate transfer belt 8 in the part where the image density is narrow in the photoconductor rotation direction, and on the intermediate transfer belt 8 in the part where the image density is wide in the photoconductor rotation direction. By being relatively reduced by, the unevenness of the image due to the period of one tooth of the photoconductor gear 26 can be reduced.

As described above, the drum-shaped photosensitive member 1 is used as the image bearing member.
However, it is also possible to use a belt.

The wrinkle removing roller 12 may have a shape other than the roller, for example, a blade. Furthermore, it is possible to serve also as a guide means for preventing the meandering of the intermediate transfer belt.

Although the transfer roller has been described as the primary transfer means, it is also possible to use a transfer brush or a transfer blade.

[0047]

As described above, according to the image forming apparatus of the present invention, with the structure of claim 1, the primary transfer position is on the side where the intermediate transfer belt is pulled by the drive roller (so-called tension side). Since it is located, the intermediate transfer belt can be driven more stably than on the slack side. Therefore, the speed fluctuation of the intermediate transfer belt due to the fluctuation of the frictional force between the photoconductor and the intermediate transfer belt at the primary transfer position, the slack of the intermediate transfer belt, and the contact angle of the intermediate transfer belt before and after the primary transfer position. Can be prevented, and image deterioration such as color misregistration, color unevenness, and toner image scattering that occur during primary transfer can be prevented with a simple configuration.

Further, by disposing a driving roller having a strong frictional force with respect to the intermediate transfer belt downstream and in the vicinity of the primary transfer position, for example, on the upstream side of the primary transfer position when seen from the conveyance direction of the intermediate transfer belt, Even if the intermediate transfer belt shakes in the lateral direction due to the cleaner of the intermediate transfer belt or the separation / contact of the secondary transfer roller, the lateral shake of the intermediate transfer belt is suppressed at the primary transfer position, and color misregistration or color unevenness is suppressed. Can be prevented. Further, by making the pitch circle diameter of the gear that drives the photoconductor larger than the pitch circle diameter of the gear that drives the intermediate transfer belt, the drive transmission system becomes the speed-up system, so that the photoconductor from the drive source to the photoconductor
In the drive transmission system where the drive is transmitted from the body to the intermediate transfer belt
At this time, the play between the gears is absorbed and the intermediate transfer with the photoconductor
The belt can be driven stably without speed fluctuation,
Therefore, color misregistration and color unevenness can be prevented. It
In addition, color misregistration and color unevenness are more visible in the long cycle.
Since it is difficult, the pitch circle diameter of the gear that drives the photoconductor is
Larger than the pitch circle diameter of the gear that drives the transfer belt
Comb and drive transmission from the photoconductor to the intermediate transfer belt
Therefore, the speed of one gear cycle is caused by the eccentricity of the gear.
Even if a color shift or color unevenness occurs due to fluctuation,
It is possible to obtain an image in which no color shift or uneven color is felt.

Further, according to the image forming apparatus of the present invention, according to the structure of claim 2, the drive transmission from the drive transmission means of the photoconductor to the drive transmission means of the intermediate transfer belt is performed by the photoconductor or the intermediate transfer belt. It can be stably performed regardless of the dimensional variation of the driving roller to be driven.

Further, according to the image forming apparatus of the present invention, the frictional force between the photoconductor and the intermediate transfer belt at the primary transfer position can be prevented by the toner between the photoconductor and the intermediate transfer belt. It can be stably obtained regardless of fluctuations in quantity or electrostatic force. Therefore, it is possible to prevent fluctuations in the speed of the intermediate transfer belt and fluctuations in the contact angle of the intermediate transfer belt before and after the primary transfer position, and image deterioration such as color misregistration, color unevenness, and toner image scattering that occurs during primary transfer. Can be prevented with a simple configuration.

Further, the contact width between the photoconductor and the intermediate transfer belt at the primary transfer position can be made narrower than that of the structure in which the intermediary transfer belt is wound around the photoconductor. Therefore, since the portion occupied by the primary transfer position in the entire outer circumference of the photoconductor is reduced, the degree of freedom in arranging other process means such as developing means on the outer circumference of the photoconductor is increased and the outer diameter is increased. A smaller photosensitive member can be used, and a smaller image forming apparatus can be configured.

According to the image forming apparatus of the present invention, the tension of the intermediate transfer belt is increased at the primary transfer position, for example, the cleaner of the intermediate transfer belt or the secondary transfer roller acts as the intermediate transfer belt. Even if it fluctuates when it comes into contact with or separates from the contact surface, the pressure for biasing the primary transfer roller to the photoconductor via the intermediate transfer belt does not fluctuate, and the pressure on the intermediate transfer belt before and after the primary transfer position does not change. The contact angle does not change. Therefore, it is possible to form a good image with no image distortion with a simple configuration.

Further, according to the image forming apparatus of the present invention, with the structure described in claim 5, it is possible to straighten the wrinkles generated on the intermediate transfer belt before being conveyed to the primary transfer position. In particular, the surface of the intermediate transfer belt on the tension side with respect to the drive roller is strongly pulled by the drive roller, so wrinkles are likely to occur in a direction substantially parallel to the conveyance direction of the intermediate transfer belt. Since voids are formed in the contact portion between the transfer roller and the intermediate transfer belt and between the intermediate transfer belt and the photosensitive member, image deterioration such as hollowness and scattering of the toner image in the primary transfer and reduction in transfer efficiency occur. However, in the present invention, by disposing the wrinkle removing roller upstream and in the vicinity of the primary transfer position,
In particular, even when the primary transfer position is arranged upstream and in the vicinity of the driving roller of the intermediate transfer belt, the wrinkles generated on the intermediate transfer belt can be stretched before being conveyed to the primary transfer position, so that the configuration is simple. A good result can be obtained without color unevenness or image deterioration.

In the image forming apparatus of the present invention,
With the structure according to the sixth aspect, it is possible to prevent the color shift and the color unevenness due to the gear driving the photoconductor and the gear driving the intermediate transfer member with a simple structure.

[0055]

[0056]

[0057]

[Brief description of drawings]

FIG. 1 is an apparatus cross-sectional view showing an overall configuration of an image forming apparatus of the present invention.

FIG. 2 is a side sectional view showing a drive transmission system and an arrangement relationship between the image carrier and the intermediate transfer member of the present invention.

FIG. 3 is a diagram showing speed fluctuations of the photosensitive member and the intermediate transfer member of the present invention.

[Explanation of symbols]

1 ... Photoreceptor 8 ... Intermediate transfer belt 9 ... Drive roller 12 ... Wrinkle removing roller 13 ... Primary transfer roller 25 ... Drive gear 26 ... Photosensitive gear 27 ... Drive roller gear

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Claims (6)

(57) [Claims] 1. A latent image forming means for forming a latent image on a photosensitive drum, a developing unit for developing a latent image on said photosensitive member by the toner, the intermediate transfer belt the toner image on the photoreceptor An image forming apparatus comprising: a primary transfer unit that sequentially transfers toner images on the intermediate transfer belt; and a secondary transfer unit that collectively transfers the toner images stacked on the intermediate transfer belt onto a recording material.
A driving source for driving the photosensitive member, provided in the photoreceptor photosensitive
The photoconductor gear that rotates integrally with the body and the intermediate transfer belt
Drive roller that drives the
Rolling to have a driving roller gear meshing with the photoconductor gear, the driving force of the driving source is transmitted to the photosensitive member, it transmits a driving force of the photosensitive member to the intermediate transfer belt, the photosensitive
The body and the intermediate transfer belt are driven synchronously to drive the drive roller.
The roller gear is arranged downstream of the primary transfer means with respect to the conveyance direction of the intermediate transfer belt, and the pitch circle diameter of the photoconductor gear is set larger than the pitch circle diameter of the drive roller gear. An image forming apparatus characterized by being provided. 2. The image forming apparatus according to claim 1, wherein the peripheral speed of the intermediate transfer belt is set to be higher than the peripheral speed of the photoconductor . Wherein the primary transfer unit, an image forming apparatus according to claim 1, characterized in that it is urged through the intermediate transfer belt to the photosensitive member side. 4. The image forming apparatus according to claim 3, wherein the intermediate transfer belt is stretched in a substantially tangential direction of the photoconductor at a primary transfer position where the primary transfer means is arranged. . 5. A wrinkle prevention means for extending wrinkles generated on the intermediate transfer belt before being conveyed to the primary transfer position is arranged upstream of the primary transfer means. The image forming apparatus described. 6. The number of teeth of the photoconductor gear from the latent image forming position on the photoconductor to the primary transfer position is an integer, and
Claim 1, wherein the number of teeth of the photoconductor gears to the drive transmitting position where the photosensitive member gear for transmitting a driving force from the driving position to receive a driving force to the driving roller gear from the driving source is an integer Image forming device.