JP2002123148A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device capable of eliminating both trouble such as the elongation and irregularity of a toner image and trouble such as the soiling of an image caused by deposits on the surface of a pressuring roller. SOLUTION: This image forming device A is provided with an image forming part for forming the toner image on a sheet S, a fixing part 11 for fixing the toner image formed on the sheet S on the sheet S, a 1st motor 16 for driving the image forming part, and a 2nd motor 17 for driving the fixing part 11. When the sheet S is held and carried by both the image forming part and the fixing part 11, the fixing and driving speed of the fixing part 11 is controlled by the 2nd motor 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an image forming apparatus capable of preventing disturbance and image contamination.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus having a plurality of driving sources, an electrophotographic printer as shown in FIG. 8 has been proposed. As shown in FIG. 8, the image forming apparatus B sends a laser L based on the obtained image information to a laser scanner.
The laser beam is emitted by the laser beam 101 onto the photosensitive drum 103 built in the process cartridge 102. Then, a latent image is formed on the photosensitive drum 103, and the latent image is developed with toner by the process cartridge 102.

On the other hand, sheets S stacked on a recording sheet stacking plate 105 are fed while being separated one by one by a feed roller 106 and a separation pad 107, and an intermediate roller 108
And transported by the transport roller 109 to the downstream side,
On the conveyed sheet, the toner image formed by the toner formed on the photosensitive drum 103 is transferred by the transfer roller 104.

The sheet S on which the unfixed toner image is formed is conveyed further downstream through a conveyance guide 113, where the toner image is fixed by a fixing unit 110 having a heat source therein. Is discharged to the outside of the apparatus by the discharge roller 112.

Further, the process cartridge 102 can be taken out of the apparatus through the apparatus opening K.
Since the photosensitive drum 103 is built in the movable area of the process cartridge 102, a space larger than the sheet conveyance area is required as an operation space.

Here, the configuration of the fixing unit will be described in detail. FIG. 9 shows an enlarged view of a section of the fixing unit. As shown in FIG. 9, the fixing unit 110 is a tension-less type film heating type heating device driven by a pressure member (Japanese Patent Laid-Open Nos. 4-44075 to 44083 and 4-204980 to 204484).
No.).

A stay 110a made of a heat-resistant resin serves as an inner surface guide member of an endless heat-resistant film (fixing film) 110b and has a heater 110c as a heating element. In the fixing film 110b, the outer peripheral length of the stay 110a including the heater 110c is larger than that of the fixing film 110b. Therefore, the fixing film 110b is loosely in contact with the stay 110a with a margin in the perimeter.

The fixing pressure roller 110d forms a pressure contact nip with the heater sandwiching the fixing film 110b, and drives the fixing film 110b. The fixing pressure roller 110d is composed of a metal shaft and a silicone rubber sheathed on the metal shaft.

Here, the temperature of the fixing pressure roller 110d rises as time passes with the heating of the heater 110c. At this time, the outer diameter increases due to thermal expansion of the rubber portion.
Since the fixing pressure roller 110d is normally driven to rotate at a constant rotational speed, when the fixing pressure roller 110d is at a high temperature, the thermal expansion is greater than at a low temperature, and the rotational peripheral speed is increased. It will be faster.

As shown in FIG. 9, the distance l from the transfer roller 104 to the fixing unit 110 is set short in order to further reduce the size of the apparatus. In such an apparatus, the transfer roller 104
Since the slack of the sheet S from the transfer roller to the fixing unit 110 is small, the tension of the sheet S from the transfer roller 104 to the fixing unit 110 is more likely to fluctuate due to the change in the fixing driving speed between the transfer and the fixing. If there is a toner image in the forming section, a problem such as expansion and disturbance of the toner image may occur due to a shock due to tension.

As means for solving such a problem, a heating apparatus and an image forming apparatus disclosed in JP-A-7-261584 have been proposed. In this method, the motor 114 (image forming system motor) for driving the image forming unit and the motor 115 (fixing system motor) for driving the fixing unit 110 are separate motors.
By controlling the driving speed of the fixing system motor 115, the tension of the sheet S from the transfer roller to the fixing unit does not fluctuate, and the above problem can be solved. Therefore, as shown in FIG. 8, in the image forming apparatus B, the tension of the sheet S from the transfer roller 104 to the fixing unit 110 is not increased, and thus, there is no problem such as expansion and disturbance of the toner image.

On the other hand, when a sheet containing a large amount of calcium carbonate, which has been increasing in recent years, is conveyed, the fixing pressure roller
Since the toner and paper dust are deposited on the surface of the sheet 110d, a problem arises in that the toner and paper dust later become large lumps and adhere to the sheet to stain the image.

Due to the tension of the sheet S from the transfer roller 104 to the fixing unit 110, the fixing pressure roller 110d is rubbed against the sheet S by using the speed difference between the fixing pressure roller 110d and the sheet S, and the toner fixed on the surface is removed. Paper dust deposits (hereinafter referred to as deposits) can be isolated and discharged in an invisible size on a sheet.

[0014]

However, in the above-described conventional image forming apparatus, in order to solve the problem of elongation and turbulence of the toner image, dirt on the image is deteriorated by deposits on the surface of the pressure roller. Attempts to solve the contamination of the image due to the deposits on the roller surface have a problem in that the elongation and disturbance of the toner image are exacerbated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus which can solve both the problem of toner image elongation and disturbance and the problem of image contamination due to deposits on the surface of a pressure roller.

[0016]

In order to solve the above-mentioned problems, a typical configuration of an image forming apparatus according to the present invention includes an image forming section for forming a toner image on a sheet, and a toner image formed on the sheet. An image forming apparatus having a fixing unit that fixes the sheet, a first drive source that drives the image forming unit, and a second drive source that drives the fixing unit, wherein the image forming unit and the fixing unit The fixing drive speed of the fixing unit is controlled by the second drive source when the sheet is nipped and conveyed by both.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment, FIG. 2 is a top view of a driving mechanism, FIG. 3 is a diagram illustrating driving of an image forming unit, and FIG.
FIG. 5 is a view for explaining the driving of the fixing unit, and FIG.
FIG. 6 is a control flowchart of the image forming apparatus, and FIG. 7 is a detailed view of a fixing unit of the image forming apparatus.

As shown in FIG. 1, in an image forming apparatus (laser beam printer) A for forming an image by an electrophotographic image forming process, a charging means 5 charges a drum-shaped electrophotographic photosensitive drum (hereinafter referred to as a photosensitive drum) of a process cartridge 2. Then, the photosensitive drum 3 is irradiated with a laser beam L corresponding to image information from the exposure means 1 to form a latent image. Then, the latent image is developed by the developing means 6 to form a toner image.

On the other hand, the sheet S stacked on the feed tray 7 is conveyed to an image forming section so as to be synchronized with the toner image on the photosensitive drum 3, and the toner image on the photosensitive drum 3 is transferred to the sheet S. Transcribed above.

The sheet S on which the unfixed toner image is formed is conveyed further downstream to the fixing unit 11 through the conveyance guide 53, and the toner image is fixed by the fixing unit 11 having a heat source therein. The sheet is discharged outside the apparatus by the discharge roller 15 via the intermediate discharge roller 14.

The fixing unit 11 is a tension-less type film heating type heating means driven by a pressure member.
(JP-A-4-44075-44083, JP-A-4-204980-204484)
᏷ It comprises a stay 12a, a fixing film 12b, a heater 12c, and a fixing pressure roller 13.

The stay 12a made of a heat-resistant resin serves as an inner surface guide member of an endless heat-resistant film (fixing film) 12b and has a heater 12c as a heating element. The fixing film 12b includes a stay 12a including a heater 12c.
The outer peripheral length of the fixing film 12b is made larger,
Therefore, the circumference of the fixing film 12b is loosely in contact with the stay 12a with a margin.

The fixing pressure roller 13 is composed of a metal shaft and a silicone rubber sheathed on the metal shaft, forms a pressure nip between the heater and the heater with the fixing film 12b interposed therebetween, and drives the fixing film 12b.

Here, transfer and fixing will be described in detail. The image forming section for transferring (forming) the toner image onto the sheet S is driven mainly by a first motor 16 which is a first driving source. The first motor 16 is a DC motor, and drives the photosensitive drum 3, the transfer roller 4, the feed roller 8, the intermediate roller 9, and the transport roller 10.

The toner image formed on the sheet S is
The fixing unit 11 for fixing the image mainly to the second driving source
Driven by the motor 17. The second motor 17 is a stepping motor, drives the fixing pressure roller 13, the discharge roller 15, and the intermediate discharge roller 14, and can control the speed.

As shown in FIG. 2, the first motor 16 and the second motor 17 are arranged to face each other with the sheet conveying path therebetween.

The first motor 16 is mounted on a frame 30 and has a gear shaft for transmitting power from the first motor 16 to the photosensitive drum 3, the transfer roller 4, the feed roller 8, the intermediate roller 9, and the transport roller 10. Rotatable gear train (drive transmission means)
Each gear shaft G1 is attached to the drive side plate 31.

The motor 17 is mounted on the frame 30, and is provided with a fixing pressure roller 13, a discharge roller
15. Each gear shaft of a gear train (drive transmission means) G2 rotatable around a gear shaft for transmitting drive to the intermediate discharge roller 14 is attached to the drive side plate 32.

As shown in FIG. 3, the drive transmission means G1 is
Motor gear 16a, drum drive gear 33, intermediate roller gear 9
a, conveying roller gear 10a, toothless feeding roller gear 8
a, a two-stage gear 18, in which two gears are integrally formed,
20, composed of idler gears 19 and 21 to 29.

The motor gear 16a is attached to the motor shaft of the first motor 16, and transfers the driving force of the first motor 16 to the two-stage gear 18.
To communicate. The driving force transmitted to the second gear 18 is transmitted to the drum drive gear 33 and the idler gear 22 via the idler gear 19, the second gear 20, and the idler gear 21. The drum drive gear 33 meshes with the photosensitive drum 3 and drives the photosensitive drum 3.

The driving force transmitted to the idler gear 22 is transmitted to the transport roller gear 10a via idler gears 23 to 25. The transport roller gear 10a is attached to the transport roller 10, and drives the transport roller 10. Also, the transport roller gear
The driving force transmitted to 10a is transmitted to the intermediate roller gear 9a via the idler gear 26. Intermediate roller gear 9a
Is attached to the intermediate roller 9 and drives the intermediate roller 9. The driving force transmitted to the intermediate roller gear 9a is intermittently transmitted to the feed roller gear 8a via the idler gears 27 to 29. The feed roller gear 8a is attached to the feed roller 8, and drives the feed roller 8.

As shown in FIG. 4, the drive transmission means G2 comprises:
The motor gear 17a, the pressure roller gear 13a, the intermediate discharge roller gear 14a, the discharge roller gear 15a, the two-stage gears 34, 38, 44 formed of two gears, and the idler gear 35 to
37, 39 to 43, and 45.

The motor gear 17a is attached to the motor shaft of the second motor 17, and transmits the driving force of the second motor 17 to the second gear 3.
4, idler gear 36 and two-stage gear 4 via idler gear 35
Communicate to 4.

The driving force transmitted to the idler gear 36 is transmitted to the intermediate discharge roller gear 14a and the idler gear 42 via the idler gear 37, the two-stage gear 38, and the idler gears 39 to 41. The intermediate discharge roller gear 14a is attached to the intermediate discharge roller 14, and drives the intermediate discharge roller 14. The driving force transmitted to the idler gear 42 is transmitted to the pressure roller gear 13a via the idler gear 43. Pressure roller gear 13a
Is attached to the fixing pressure roller 13, and the fixing pressure roller
Drive 13

The driving force transmitted to the second gear 44 is transmitted to the discharge roller gear 15a via the idler gear 45. The discharge roller gear 15a is attached to the discharge roller 15, and drives the discharge roller 15.

As shown in FIG. 5, the control system of the image forming apparatus A includes a CPU 46 for accumulating and processing the entire control information.
A host computer 47 for supplying image information, a controller 48 for controlling laser emission and a scanner motor, a controller 49 for the first motor 16, a controller 50 for the second motor 17, and other control system circuits such as monitoring of a sheet position and a speed.
Consists of 51.

When the conveyance of the sheet S is started (S1: see FIG. 6), the control system of the image forming apparatus A determines from the image information of the host computer 47 (wider than the image forming section nip).
The margin information (information that does not transfer the toner image)
(S2: see FIG. 6). Then, the sheet S reaches the fixing unit 11, and the sheet S is nipped and conveyed by both the image forming unit and the fixing unit 11 (S3: see FIG. 6), and the controller 50 controls the second motor 17 to control the fixing drive speed. Control is started (S4:
(See FIG. 6).

The control of the fixing driving speed is performed by judging whether or not there is a margin larger than the nip of the image forming portion on the photosensitive drum.
(S5: see FIG. 6), if there is no margin (when transferring a toner image), the fixing drive speed is reduced (S6: see FIG. 6), and if there is such a margin (the toner image is not transferred). Is performed by increasing the fixing drive speed (S7: see FIG. 6).

As shown in FIG. 7, increasing the fixing driving speed causes a difference between the fixing pressing roller driving speed Vp and the sheet conveying speed Vs (the driving speed Vd of the photosensitive drum 3), and the tension on the sheet S is increased. Occur (pull) (Vp
> Vs = Vd). As a result, the fixing pressure roller 13 slip-conveys the sheet S, and the fixing pressure roller 13
Is rubbed against the sheet S, separated into the sheet portion Sa after the fixing unit is discharged, and discharged as an invisible size deposit Ts.

Then, the rear end of the sheet S is conveyed from the image forming section (S8: see FIG. 6), and the control of the fixing drive speed is ended (S9: see FIG. 6). Thereafter, the sheet S on which the toner image has been transferred and fixed is discharged to the discharge tray 52 by the discharge roller 15 (S10: see FIG. 6).

With the above configuration, when a toner image is present in the image forming unit nip based on the image information of the host computer 47, control is performed so that the tension of the sheet portion Sb from the transfer roller 4 to the fixing unit 11 does not change. Therefore, problems such as expansion and disturbance of the toner image do not occur.

Also, when a margin larger than the image forming portion nib on the photosensitive drum reaches the image forming portion nip from the image information of the host computer 47, the fixing pressure roller is rubbed against the sheet in order to increase the fixing driving speed. Since the deposits on the fixing and pressing roller are discharged, there is no problem that the image is stained. Further, the tension of the sheet portion Sb from the transfer roller 4 to the fixing unit 11 increases due to an increase in the fixing driving speed. However, since the toner image is not present in the image forming unit, the toner image is elongated and disturbed by the shock due to the tension. Can be prevented.

Therefore, according to the present embodiment, it is possible to achieve both a solution to the problem of elongation and disturbance of the toner image and a problem of soiling the image due to the accumulation of toner and paper dust on the surface of the pressure roller, thereby achieving a high quality image. A forming device can be provided.

[0044]

As described above, a high quality image can be achieved by solving both the problems of toner image elongation and disturbance and the problem of image contamination due to accumulation of toner and paper dust on the surface of the pressure roller. A forming device can be provided.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an image forming apparatus according to an embodiment.

FIG. 2 is a top view of a driving mechanism.

FIG. 3 is a diagram illustrating driving of an image forming unit.

FIG. 4 is a diagram illustrating driving of a fixing unit.

FIG. 5 is a diagram illustrating transfer and fixing of a toner image.

FIG. 6 is a control flowchart of the image forming apparatus.

FIG. 7 is a detailed view of a fixing unit of the image forming apparatus.

FIG. 8 is a configuration diagram of a conventional image forming apparatus.

FIG. 9 is a detailed view of a fixing unit according to a conventional image forming apparatus.

[Explanation of symbols]

 A: Image forming apparatus G1, G2: Drive transmission means K: Device opening L: Laser S: Sheet S0: Whole sheet Sa, Sb: Sheet part Tp, Ts: Deposits Vd, Vp: Drive speed Vs: Transport speed l ... Distance 1 ... Exposure means 2 ... Process cartridge 3 ... Photosensitive drum 4 ... Transfer roller 5 ... Charging means 6 ... Developing means 7 ... Supply tray 8 ... Supply roller 8a ... Supply roller gear 9 ... Intermediate roller 9a ... Intermediate roller gear 10 ... conveying roller 10a ... conveying roller gear 11 ... fixing section 12a ... stay 12b ... fixing film 12c ... heater 13 ... fixing pressure roller 13a ... pressure roller gear 14 ... intermediate discharge roller 14a ... intermediate discharge roller gear 15 ... discharge roller 15a ... discharge roller gear 16 First motor 16a Motor gear 17 Second motor 18, 20, 34, 38, 44 Two-stage gear 19, 21 to 29, 35 to 37 39～43,45 ... idler gear 30 ... Frame 31, 32 ... driving plate 33 ... drum drive gear 46 ... CPU 47 ... host computer 48 to 50 ... controller 51 ... control system circuit 52 ... discharge tray 53 ... conveying guide

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Miya ▲ Saki ▼ Yoshiyuki 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2H027 DA17 DA20 ED02 ED16 ED24 ED25 EE03 EE04 EF09 2H033 AA15 AA20 BB01 BB37 CA36 CA40 2H071 CA07 DA12 DA23

Claims (5)

[Claims] An image forming unit for forming a toner image on a sheet; a fixing unit for fixing the toner image formed on the sheet to the sheet; a first drive source for driving the image forming unit; An image forming apparatus having a second driving source for driving the fixing unit, wherein when the sheet is nipped and conveyed in both the image forming unit and the fixing unit, the fixing driving speed of the fixing unit is controlled by the second driving source. An image forming apparatus. 2. The image forming apparatus according to claim 1, wherein when a transfer of the toner image is not performed in the image forming unit, a fixing driving speed of a fixing unit is increased by a second driving source. 3. When the fixing drive speed of the fixing unit is increased by the second drive source, tension is generated on the sheet due to a difference between the sheet conveyance speed of the image forming unit and the fixing drive speed of the fixing unit. The image forming apparatus according to claim 1. 4. The image forming section has a photosensitive drum and a transfer roller that rotates while being in pressure contact with the photosensitive drum, wherein the photosensitive drum is driven by a first drive source. Item 4. The image forming apparatus according to any one of Items 1 to 3. 5. The fixing device according to claim 1, wherein the fixing unit includes a heating body and a rotating body that rotates while being pressed against the heating body, and the rotating body is driven by a second driving source. Item 5. The image forming apparatus according to any one of Items 1 to 4.