JP2003316177A - Transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transfer device free from disorder of printing, voids of characters, or the like by approximately equalizing the peripheral speed of an image carrying roll and that of a photoreceptor roller in the case of the existence of a transfer material between the image carrying roll and the photoreceptor roller to prevent peeling discharge caused by a difference between the carrying speed on the image carrying roll side and the photoreceptor roller side of the transfer material. <P>SOLUTION: A transfer roll transmission gear 54 for transmitting a power to a transfer roll 25 is engaged with a photoreceptor roller transmission gear 53 for transmitting a power to a photoreceptor roller 21. When a form doesn't exist between the photoreceptor roller 21 and the transfer roll 25, a gear ratio of the photoreceptor roller transmission gear 53 and the transfer roll transmission gear 54 is so set that the transfer roll 25 is rotated at a peripheral speed obtained by adding an extent of reduction of the peripheral speed of the transfer roll 25 for the existence of the form to the peripheral speed of the photoreceptor roller 21. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transfer device of an image forming apparatus for printing on a transfer material image information read by a document reading device or image information received by a receiving device from each information terminal connected to a network. Regarding

[0002]

2. Description of the Related Art In a transfer device of a conventional image forming apparatus, a transfer roller is brought into rolling contact with a roller-shaped electrostatic latent image bearing member (hereinafter referred to as a photosensitive member roller), and the outer peripheral surface of the photosensitive member roller is provided. When the formed toner image reaches the contact portion (nip portion) between the photoconductor roller and the transfer roller, the toner image is transferred to the transfer material (paper) supplied to the nip portion. The conventional transfer roller is driven independently or is driven by the photoconductor roller in common with the photoconductor roller. In this transfer roller driving method, the peripheral speed of the transfer roller is set to be substantially the same as the peripheral speed of the photoconductor roller.

In such a transfer device, when a sheet is present between the photoconductor roller and the transfer roller, a rotational load is generated, and the peripheral speed of the transfer roller is reduced, and the peripheral speed of the photoconductor roller and the transfer speed are reduced. The peripheral speed of the roller becomes different. Such a difference in peripheral speed causes disturbance of the leading edge or the trailing edge of the image when the leading edge or the trailing edge of the sheet plunges into or separates from the nip portion.

FIG. 9 is a schematic view showing a photoconductor roller, a sheet and a transfer roller. When the sheet 1 charged by the transfer roller 25 leaves the nip portion, the transfer roller 25
Since the peripheral speed is lower than the peripheral speed of the photoconductor roller 21, the conveyance speed Vβ of the back surface of the sheet 1 becomes lower than the conveyance speed Vα of the front surface of the sheet 1, and the sheet 1 is peeled off faster on the side of the photoreceptor roller 21 and on the transfer roller 25 side. The peeling is delayed and the curl is conveyed to the transfer roller 25 side. At this time, peeling discharge occurs between the paper 1, the photoconductor roller 21, and the transfer roller 25 due to the applied voltage of the transfer roller 25, the surface potential of the photoconductor roller 21, and the charging voltage of the paper 1. The peeling discharge occurs because the transfer electric field is received by the paper 1 and the unfixed developer is overcharged on the paper. When the peeling discharge occurs, problems such as disorder of printing and hollow characters in characters occur.

As a transfer device for solving the above-mentioned problems,
In Japanese Patent Laid-Open No. 3-194575, a transfer roller is slid on a photosensitive member roller when no paper is present in the nip portion, and when a paper is present, the transfer roller is driven by a separate drive source. A device invention is disclosed. In this transfer device, when a sheet is present in the nip portion, the transfer roller is driven to rotate at a constant speed with respect to the photoconductor roller to solve the above-mentioned problem.

[0006]

However, in the above-mentioned transfer device, a complicated mechanism for controlling the switching between the driven rotation and the driving rotation is required. Furthermore, a slight delay occurs at the time of switching the rotation before and after the sheet enters the nip portion, and the peripheral speeds are different, so that not only the problem cannot be solved but also the transfer blur of the image information occurs. There was a fear.

The present invention has been made in view of the above circumstances. When the transfer roller is driven by the image bearing roller and no transfer material is present between the image bearing roller and the transfer roller, the transfer is performed. If the transfer roller is configured to rotate at a peripheral speed obtained by adding the amount of decrease in the peripheral speed of the transfer roller when the transfer material is present, to the transfer roller when the transfer material is present, Since the peripheral velocities of the image bearing rollers are substantially equal, the transport speed of the transfer material becomes substantially constant on the image bearing roller side and the transfer roller side, and the peeling discharge caused by the difference in the transport speed of the image bearing roller side and the transfer roller side. SUMMARY OF THE INVENTION An object of the present invention is to provide a transfer device capable of preventing the above-mentioned problems, causing no disturbance in printing, missing characters, etc., and causing no transfer blur of image information.

Further, according to the present invention, when the transfer material is not present between the image carrying roller and the transfer roller, the peripheral speed of the transfer roller is higher than that of the transfer material conveying roller. The transfer material is prevented from sagging at the sandwiched portion, overcharge of the transfer material can be prevented, and the peripheral speed of the transfer roller is substantially equal to the peripheral speed of the fixing roller. The transfer material is not pulled out, and the transfer can be performed in the state where the printing magnification is accurate, and the overcharging caused by the contact of the trailing edge of the transfer material with the transfer roller is prevented to prevent the peeling discharge. It is an object of the present invention to provide a transfer device capable of performing the above.

According to the present invention, the image bearing roller transmitting gear for transmitting the power of the driving source to the image bearing roller and the transfer roller transmitting for transmitting the power to the transfer roller are meshed with the image bearing roller transmitting gear. By including the gear for
When the transfer material is not present between the image carrying roller and the transfer roller, the transfer roller is moved at a peripheral speed obtained by adding the amount of decrease in the peripheral speed of the transfer roller when the transfer material is present to the peripheral speed of the image carrying roller. By setting the gear ratio of the image carrier roller transmission gear and the transfer roller transmission gear so as to rotate, the peripheral speed of the carrier roller and the transfer roller is surely equalized in the presence of the transfer material. The purpose is to provide.

Further, according to the present invention, by forming the transfer roller from an elastic member, when the transfer material exists between the image bearing roller and the transfer roller, the radius of the transfer roller contacts the transfer material. It is an object of the present invention to provide a transfer device in which the peripheral velocities of the image carrying roller and the transfer roller are apparently constant velocities with a simple configuration because the transfer material is reduced by the thickness of the transfer material.

[0011]

SUMMARY OF THE INVENTION A transfer device according to the present invention comprises an image bearing roller having a photosensitive layer on which an electrostatic latent image is formed and a toner image is formed by developing the electrostatic latent image, and a transfer roller. And a transfer device configured to transfer the toner image to the transfer material, the transfer roller being driven by the image bearing roller, and the image bearing roller and the transfer roller. If the transfer material is not present between
The transfer roller is configured to rotate at a peripheral speed obtained by adding a reduction amount of the peripheral speed of the transfer roller when the transfer material exists to the peripheral speed of the image bearing roller.

In the present invention, the peripheral speed of the transfer roller is set higher than the peripheral speed of the image bearing roller when the transfer material is not present, and the peripheral speeds of the transfer roller and the image bearing roller are set when the transfer material is present. Since the speeds are substantially equal, the transfer material conveyance speed is substantially constant on the image carrying roller side and the transfer roller side, and peeling discharge due to the difference in the conveying speed between the image carrying roller side and the transfer roller side can be prevented. It is possible to prevent disorder of printing and omission of characters. Further, the peripheral speed of the transfer roller decreases in accordance with the timing when the transfer material is inserted between the image carrying roller and the transfer roller, and becomes equal to the peripheral speed of the image carrying roller, so that transfer blurring of image information occurs. Nothing. Further, in the present invention, the transfer roller is driven by the image carrying roller in common with the image carrying roller, and a separate drive source and driving force for adjusting the peripheral speed of the transfer roller are provided. A peeling discharge can be prevented with a simple structure without requiring a transmission mechanism.

According to the present invention, a transfer material carrying roller for carrying the transfer material between the image carrying roller and the transfer roller, and the toner image is thermally fixed after the toner image is transferred to the transfer material. If the transfer material does not exist between the image bearing roller and the transfer roller, the peripheral speed of the transfer roller is higher than the peripheral speed of the transfer material conveying roller, It is characterized in that it is configured to be substantially constant in speed with the peripheral speed of.

In the present invention, when the transfer material is sandwiched between the image carrying roller and the transfer roller, and between the transfer material carrying roller, the transfer roller and the image carrying roller pull the transfer material, and the transfer material is It is possible to prevent the transfer material from being overcharged without sagging at the nip portion. Also,
By setting the peripheral speed of the transfer roller to be substantially equal to the peripheral speed of the fixing roller, the transfer material is not pulled out at the time of transfer, and it is possible to transfer the transfer material to the transfer material with an accurate printing magnification. Further, slack does not occur at the rear end of the transfer material, and overcharge that occurs when the rear end of the transfer material comes into contact with the transfer roller is prevented, and peeling discharge can be prevented.

In the transfer device of the present invention, the image carrier roller transmission gear for transmitting the power of the drive source to the image carrier roller and the image carrier roller transmission gear are meshed with each other, and the power is transmitted to the transfer roller. And a transmission gear for the transfer roller.

In the present invention, when the transfer material is present between the image carrying roller and the transfer roller, the gap between the image carrying roller transmitting gear and the transfer roller transmitting gear is determined by the thickness of the transfer material. It gets a little bigger. As a result, the rotational speed of the transfer roller transmitting gear that receives the driving force from the image bearing roller transmitting gear is slightly reduced, and the peripheral speed of the transfer roller is reduced. Therefore, when the transfer material does not exist, the image carrying roller is rotated so that the transfer roller rotates at a peripheral speed obtained by adding the amount of decrease in the peripheral speed of the transfer roller when the transfer material exists to the peripheral speed of the image carrying roller. By setting the gear ratio between the transmission gear and the transfer roller transmission gear, the peripheral velocities of the transfer roller and the image carrying roller can be reliably equalized when the transfer material is present.

In the transfer device of the present invention, the transfer roller is composed of an elastic member, and when the transfer material is present between the image carrying roller and the transfer roller, the peripheral speed of the image carrying roller is The peripheral speed of the transfer roller is apparently constant.

In the present invention, the transfer roller is made of an elastic member, so that the diameter of the transfer roller changes depending on the presence or absence of the transfer material. In other words, when the transfer material is present between the image carrying roller and the transfer roller, the pressure between the image carrying roller and the transfer roller increases due to the thickness of the transfer material, and compared with the case where the transfer material does not exist. The diameter of the transfer roller becomes smaller. When the transfer material is present between the image bearing roller and the transfer roller, the radius of the transfer roller is reduced by the thickness of the transfer material at the portion in contact with the transfer material. When there is no transfer material between the image carrying roller and the transfer roller, the peripheral speed of the transfer roller is V = r (radius) .omega. (Angular speed), and the peripheral speed of the transfer roller is the peripheral speed of the image carrying roller. Faster than speed. The radius of the transfer roller is r ′ due to the presence of the transfer material.
(<R), the peripheral velocity V ′ of the transfer roller is V ′.
= R ′ · ω, the peripheral velocities of the image bearing roller and the transfer roller are apparently constant velocities (only in the contact portion with the transfer material,
The peripheral speed is equal to the peripheral speed of the image bearing roller, so it is expressed as apparent). In the present invention, the peripheral velocities of the image bearing roller and the transfer roller can be made apparently constant with a simple configuration, and peeling discharge can be reliably prevented.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 is a side view showing an image forming apparatus according to this embodiment. The image reading unit 10 of the image forming apparatus includes an original table 11 made of transparent glass or the like provided on the upper surface of the image forming apparatus, and an optical system reading mechanism provided below the original table 11. The exposure light source 12 of the optical system reading mechanism irradiates the document placed on the document table 11 with light, and the light reflected by irradiating the document passes through the plurality of reflecting mirrors 13, 13, 13 and the coupling lens 14. It is led to the photoelectric conversion element (hereinafter referred to as CCD) 15 as original image data via the light source.

The image forming section 20 includes a laser scanning unit (not shown) (hereinafter referred to as LSU), a photosensitive roller 21 which is rotationally driven in the direction of the arrow in the figure, and a main charging section 2.
2, a developing unit 23, a transfer roller 25, a cleaning unit 26, a registration roller 27, and a fixing roller 28. The document image data read by the CCD 15 is subjected to image processing, and the image-processed document image data is transmitted to the LSU. The photosensitive layer on the outer peripheral surface of the photoconductor roller 21 is charged to a predetermined potential by the main charging unit 22, and the LSU irradiates the outer peripheral surface of the photoconductor roller 21 with a laser beam to attenuate the potential, Photoconductor roller 21
An electrostatic latent image is formed on the outer peripheral surface of the. The electrostatic latent image formed on the outer peripheral surface of the photoconductor roller 21 is supplied with toner in the developing unit 23, and the toner is attracted to be developed into a visible (toner) image. When the toner image on the photoconductor roller 21 reaches the contact portion (nip portion) between the photoconductor roller 21 and the transfer roller 25, the paper 1 is supplied, and a transfer bias is applied to the transfer roller 25 to transfer it to the paper 1. To be done. Then, the toner remaining on the outer peripheral surface of the photoconductor roller 21 is removed by the cleaning unit 26.

The paper 1 is stored in the paper feed cassette 31. A half-moon roller 32 is arranged at the end of the paper feed cassette 31, and the paper 1 is picked up by the half-moon roller 32 and sent out to the conveyance path 41 by the paper feed roller 33. Before the registration, the pre-registration detection switch (not shown) detects the passage of the sheet 1, and the pre-registration detection switch detects the passage of the sheet 1 and based on the signal transmitted, the registration roller 27 causes the photoconductor roller 21 to move. The upper toner image and the sheet 1 are aligned with each other, and the sheet 1 is conveyed with the conveying path 42 toward the nip portion. Then, the toner image is transferred onto the sheet 1 as described above.

On the sheet 1 having the toner image transferred at the nip portion, the toner image is fixed by heat by the fixing roller 28,
By the fixing paper detection switch (not shown), the fixing roller 2
It is detected that the paper 1 has passed through 8, and a paper discharge detection switch (not shown) has detected that the paper 1 has passed a predetermined position of the transport path 43. A side of the unit 20 and a paper cassette 31
Is discharged to the paper discharge unit 46 corresponding to the upper part of the image reading unit 10 and the lower part of the image reading unit 10.

Paper 1 placed in manual cassette 35
Are picked up by the half-moon roller 36 and sent out to the conveyance path 44 by the paper feed roller 37. After that, similarly to the paper 1 stored in the paper feed cassette 31, the registration roller 27 aligns the toner image on the photoconductor roller 21, the paper is conveyed toward the nip portion of the conveyance path 42, and the transfer roller 25 conveys it. The toner image is transferred and discharged to the paper discharge unit 46.

In the case of double-sided copying, the sheet conveyed to the discharge roller 34 is conveyed by the discharge roller 34 to the conveying path 43.
Is conveyed in the opposite direction, and is conveyed along the conveying path 40 by the conveying rollers 38, 3
8 and 38, the registration roller 27 again aligns the toner image on the photoconductor roller 21, the conveyance path 42 conveys the toner image, and the transfer roller 25 transfers the toner image to the paper discharge unit 46. Is discharged.

FIG. 2 is an enlarged view showing the image forming section 20. Each component of the image forming unit 20 rotates in the arrow direction shown in the figure. The paper 1 is guided by the paper guide 29 a from the registration roller 27, and the toner image is transferred onto the paper 1 at the nip portion between the photoconductor roller 21 and the transfer roller 25 in the transfer roller unit 24. After the transfer, the paper 1 is guided by the paper guide 29b, and the heat source 28
a is conveyed to the fixing roller 28 having a
Thus, the toner image is thermally fixed on the sheet 1.

FIG. 3 is a side view showing the photoconductor roller 21 and the transfer roller 25. A motor coupling gear 52 is integrally rotatably provided at an end of an output shaft 51a of a motor 51 attached to the apparatus frame 50, and a photoconductor roller transmission gear 53 is meshed with the motor coupling gear 52. ing. A transfer roller transmission gear 54 is meshed with the photoconductor roller transmission gear 53. Motor coupling gear 52
Are driven by the motor 51. The rotation speed of the transfer roller 25 is determined by the gear ratio of the motor coupling gear 52, the photoconductor roller transmission gear 53, and the transfer roller transmission gear 54.

Next, the operation of the photoconductor roller 21 and the transfer roller 25 in this embodiment will be described. FIG. 4 is a schematic diagram showing a state in which the sheet 1 exists between the photoconductor roller 21 and the transfer roller 25. Photoconductor roller 2
1 is not present between the transfer roller 25 and the transfer roller 25, the peripheral speed V ₂ of the transfer roller 25 is set to the photosensitive member by setting the gear ratio of the photosensitive roller transmission gear 53 and the transfer roller transmission gear 54. It is set to be higher than the peripheral speed V ₁ of the roller 21.

When the paper 1 is present, the transfer roller 2
The peripheral speed of 5 will be slower than V ₂ V ₂ '. Transfer roller 2
The lowering of the peripheral speed of No. 5 is that the paper 1 enters the nip portion between the transfer roller 25 and the photoconductor roller 21, and depending on the thickness of the paper 1, the photoconductor roller transmission gear 53 and the transfer roller transmission gear 54. And the rotational speed of the transfer roller transmission gear 54, which receives the driving force from the photoconductor roller transmission gear 54, slightly decreases. At this time, by setting the gear ratio such that V ₂ ′ = V ₁ , the sheet 1 is conveyed at a constant speed from both the photoconductor roller 21 and the transfer roller 25 (see FIG. 4). As shown, the transport speed Vα on the front surface side of the sheet 1 and the transport speed Vβ on the back surface side become equal to each other, and peeling discharge due to the difference in the transport speed can be prevented. Therefore,
Distortion of printing and omission of characters do not occur. In the present embodiment, the transfer roller 25 is driven by the photoconductor roller 21 by the same motor 51 as the photoconductor roller 21, and a separate drive source and drive force transmission for adjusting the peripheral speed of the transfer roller 21. A mechanism is not required, and the peripheral speeds of the photoconductor roller 21 and the transfer roller 25 can be surely made equal to each other in the presence of the paper 1 with a simple configuration, and peeling discharge can be prevented.

In the above structure, the transfer roller 25
It is conceivable that the amount of decrease in the peripheral speed of the sheet changes depending on the thickness of the sheet 1. However, in the present embodiment, it is assumed that the thickness of the sheet 1 is about 80 μm, which is most frequently used, and the peripheral speeds of the photosensitive roller 21 and the transfer roller 25 when the sheet 1 is conveyed are set to be equal. By doing so, suitable results can be obtained.

FIG. 5 is a schematic diagram showing the registration roller (paper conveying roller) 27, the photosensitive roller 21, the transfer roller 25, and the fixing roller 28 when the paper 1 is not present. When the sheet 1 does not exist, the peripheral speeds V ₁ , V ₂ , V ₃ and V ₄ of the photoconductor roller 21, the transfer roller 25, the registration roller 27 and the fixing roller 28 shown in FIG. 5 are V ₁ (= V ₃ ) It is set to satisfy the relationship of <V ₂ = V ₄ .

FIG. 6 is a schematic diagram showing the registration roller 27, the photoconductor roller 21, the transfer roller 25, and the fixing roller 28 when the sheet 1 is present. In this case, as described above, by setting the peripheral velocity V ₂ ′ of the transfer roller 25 to be equal to V ₁ , the relational expression of V ₁ (= V ₃ ) = V ₂ ′ <V ₄ is established.

In the present embodiment, by satisfying the above relational expression, when the paper 1 is sandwiched between the photoconductor roller 21 and the transfer roller 25 and also between the registration rollers 27, the transfer roller 25. Since the photosensitive member roller 21 pulls the sheet 1 and the sheet 1 does not sag in the nip portion, it is possible to prevent the sheet 1 from being overcharged. Further, by setting the peripheral speed V ₂ of the transfer roller 25 when the paper 1 is not present to be substantially equal to the peripheral speed V ₄ of the fixing roller 28, the paper 1 is not pulled out at the time of transfer, and the printing magnification is made accurate. In this state, the toner image can be transferred onto the sheet 1. Further, the slack of the sheet 1 does not occur at the trailing edge of the sheet 1, and overcharging that occurs when the trailing edge of the sheet 1 contacts the transfer roller 25 can be prevented to prevent peeling discharge.

In this embodiment, the case where the transfer roller transmission gear 54 meshes with the photoconductor roller transmission gear 53 has been described, but the present invention is not limited to this. A coupling gear may be interposed between the transmission gear 53 and the transfer roller transmission gear 54, and the peripheral speed of the transfer roller 25 may be set by the gear ratio of each coupled gear.

Embodiment 2. The configuration of the image forming apparatus according to the second embodiment is similar to that of the image forming apparatus according to the first embodiment. Unlike the image forming unit according to the first exemplary embodiment, the image forming unit according to the second exemplary embodiment does not include the transfer roller transmission gear 54, and the transfer roller 25 slides and follows the photoconductor roller 21 driven by the motor 51. It is configured to be done. Further, the transfer roller 25 is a foamable EPD.
A conductive member such as carbon black is mixed with M, hydrin rubber or the like to form a roller, which has elasticity.

7 and 8 are schematic views showing the photoconductor roller 21 and the transfer roller 25 according to the present embodiment,
7 shows the case where the sheet 1 does not exist, and FIG. 8 shows the case where the sheet 1 exists. 7 and 8, the photoconductor roller 2
The radius of ₁ is r ₁ , the radius of the transfer roller 25 is r ₂ (r ₂ ′ when the paper is nipped), and the angular velocity of the photoconductor roller 21 is ω.
₁ and the angular velocity of the transfer roller 25 is ω ₂ . When the sheet 1 is present, the radius r ₂ of the transfer roller 25 at the nip portion is reduced by the thickness of the sheet to r ₂ ′ as compared with the case where the sheet 1 is not present. The peripheral speed V ₁ of the photoconductor roller 21 is
V ₁ = r ₁ × ω ₁ , and the peripheral velocity V _{2 of the} transfer roller 25.
Is V ₂ = r ₂ × ω ₂ , but V ₂ ′ = r ₂ ′ at the contact portion of the paper 1 with the photosensitive roller 21 and the transfer roller 25.
× ω ₂ . That is, the peripheral speed V of the photoconductor roller 21
₁ and the peripheral velocity V ₂ ′ of the transfer roller 25 are apparently constant velocity, and the sheet 1 is conveyed at a constant velocity from both the photoconductor roller 21 and the transfer roller 25, and peels due to the difference in the conveyance speed. Discharge can be prevented, and problems such as disorder of printing and character dropout phenomenon do not occur. In the present embodiment, the peripheral velocities of the photoconductor roller 21 and the transfer roller 25 at the time of transfer can be made equal by a simple configuration.

In the present embodiment, the case where the transfer roller 25 is formed into a roller shape by mixing a conductive member such as carbon black with foamable EPDM, hydrin rubber or the like has been described, but the present invention is not limited to this. However, the transfer roller 25 may be made of another material.

Further, in the first and second embodiments, the case where the transfer device of the present invention is used as a device for transferring the image information read by the document reading portion 10 of the image forming apparatus onto the sheet 1 will be described. However, the present invention is not limited to this, and the receiving device of the image forming apparatus may be used as a device for transferring the image information received from the information terminal connected to the network onto the sheet 1.

[0038]

According to the present invention, the transfer roller is driven by the image bearing roller, and when the transfer material does not exist between the image bearing roller and the transfer roller, the transfer roller when the transfer material exists. Since the transfer roller is configured to rotate at the peripheral speed obtained by adding the amount of decrease in the peripheral speed of the transfer roller to the peripheral speed of the image bearing roller, when the transfer material is present, the peripheral speeds of the transfer roller and the image bearing roller are The transfer material conveyance speeds are substantially equal on the image carrying roller side and the transfer roller side,
It is possible to prevent peeling discharge caused by a difference in transport speed between the image bearing roller side and the transfer roller side, and print disturbance and character dropout do not occur. Then, the peripheral speed of the transfer roller decreases corresponding to the timing when the transfer material is inserted between the image carrying roller and the transfer roller, and becomes equal to the peripheral speed of the image carrying roller, so that transfer blurring of image information occurs. Nothing. Further, in the present invention, the transfer roller is driven by the image carrying roller in common with the image carrying roller, and a separate drive source and driving force for adjusting the peripheral speed of the transfer roller are provided. A peeling discharge can be prevented with a simple structure without requiring a transmission mechanism.

According to the present invention, the peripheral speed of the transfer roller is higher than the peripheral speed of the transfer material conveying roller when the transfer material is not present between the image bearing roller and the transfer roller. Therefore, the transfer material does not sag in the sandwiched portion, and the transfer material can be prevented from being overcharged. Further, since the peripheral speed of the transfer roller is substantially equal to the peripheral speed of the fixing roller when there is no transfer material, the transfer material is not pulled out at the time of transfer, and the printing magnification is made accurate. In this state, the transfer can be performed, and it is possible to prevent over-charging that occurs when the rear end of the transfer material comes into contact with the transfer roller and prevent peeling discharge.

Further, according to the present invention, an image carrier roller transmission gear for transmitting the power of the drive source to the image carrier roller,
When the transfer material is not present between the image carrying roller and the transfer roller, the transfer material is provided between the image carrying roller and the transfer roller because the transfer roller transmitting gear is provided for meshing with the image carrying roller transmitting gear and transmitting power to the transfer roller. When there is a gear ratio between the image-bearing-roller transmission gear and the transfer-roller transmission gear, the transfer roller rotates at a peripheral speed obtained by adding the amount of decrease in the peripheral speed of the transfer roller to the peripheral speed of the image-bearing roller. By setting, when the transfer material is present, the peripheral speeds of the carrier roller and the transfer roller are surely equalized.

Further, according to the present invention, since the transfer roller is made of an elastic member, when the transfer material is present between the image carrying roller and the transfer roller, the radius of the transfer roller contacts the transfer material. The thickness of the transfer material is reduced by a portion, and the peripheral velocities of the image carrying roller and the transfer roller are apparently constant with a simple structure, and peeling discharge is prevented.

[Brief description of drawings]

FIG. 1 is a side view showing an image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged view showing an image forming unit according to the first embodiment.

FIG. 3 is a side view showing a photoconductor roller and a transfer roller.

FIG. 4 is a schematic view showing a state in which a sheet exists between a photoconductor roller and a transfer roller.

FIG. 5 is a schematic diagram showing a registration roller, a photoconductor roller, a transfer roller, and a fixing roller when paper is not present.

FIG. 6 is a schematic diagram showing a registration roller, a photoconductor roller, a transfer roller, and a fixing roller when paper is present.

FIG. 7 is a schematic diagram showing a photoconductor roller and a transfer roller according to the second embodiment when there is no sheet.

FIG. 8 is a schematic diagram showing a photoconductor roller and a transfer roller according to the second embodiment when paper is present.

FIG. 9 is a schematic view showing a photoconductor roller, a sheet, and a transfer roller.

[Explanation of symbols]

1 sheet 21 photoconductor roller 25 Transfer roller 27 Registration roller 28 fixing roller 51 motor 52 Connection Gear 53 Photosensitive roller transmission gear 54 Transfer roller transmission gear

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yoshie Iwakura             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company (72) Inventor Minoru Minoru             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F-term (reference) 2H072 CA01 JA02                 2H200 FA04 FA20 GA23 GB25 HA03                       HB12 HB22 HB45 HB47 JA02                       JA25 JA27 JB10 JB17 LA29                       MA03 MA14 MC01 PA11 PB12                 3F049 DA12 EA10 LA01 LB03

Claims (4)

[Claims] 1. A transfer material is supplied between an image bearing roller having a photosensitive layer on which an electrostatic latent image is formed and a toner image is formed by developing the electrostatic latent image, and a transfer material. In a transfer device configured to transfer a toner image to the transfer material, the transfer roller follows the image bearing roller, and when the transfer material does not exist between the image bearing roller and the transfer roller. Is configured to rotate the transfer roller at a peripheral speed obtained by adding a reduction amount of the peripheral speed of the transfer roller when the transfer material is present to the peripheral speed of the image bearing roller. apparatus. 2. A transfer material transport roller for transporting the transfer material between the image bearing roller and the transfer roller, and for thermally fixing the toner image after transferring the toner image to the transfer material. If the transfer material is not present between the image bearing roller and the transfer roller, the peripheral speed of the transfer roller is higher than the peripheral speed of the transfer material conveying roller, and the peripheral speed of the fixing roller is The transfer device according to claim 1, wherein the transfer device is configured to be substantially constant in speed. 3. A transfer roller transmission gear for transmitting the power of a driving source to the image bearing roller, and an image bearing roller transmission gear meshing with the image bearing roller transmission gear for transmitting power to the transfer roller. The transfer device according to claim 1, further comprising a gear. 4. The transfer roller is composed of an elastic member, and when the transfer material is present between the image carrying roller and the transfer roller, the peripheral speed of the image carrying roller and the peripheral speed of the transfer roller. The transfer device according to claim 1 or 2, wherein and have an apparently constant speed.