JPH08241008A - Image forming device - Google Patents

Abstract

PURPOSE: To provide an image forming device constituted so that a high-quality image is always and stably obtained by suppressing transfer deviation occurring at a transfer part accompanying the impact when a transfer material rushes in a fixing means. CONSTITUTION: The copying machine (image forming device) is constituted including a photoreceptor drum (image carrier) 1, a transfer electrostatic charger (transfer means) 4 transferring an unfixed toner image formed on the drum 1 on the transfer material P and a fixing device (fixing means) 18 fixing the unfixed toner image transferred on the transfer material P by the charger 4. Then, it is constituted by arranging the charger 4 and the fixing device 18 so that a distance L1 between them becomes shorter than the length L of the transfer material P in a carrying direction. Besides, it is provided with a flywheel (control member) 33 for keeping the circumferential speed of the fixing roller 18a of the fixing device 18 constant. By the flywheel 33, the circumferential speed of the roller 18a is kept constant.

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 such as an electrophotographic copying machine or an electrophotographic printer which utilizes an electrostatic transfer process.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, as shown in FIG. 5, an unfixed developer image carried on a photosensitive drum 101 which is an image carrier is supplied by a registration roller 115 at an appropriate timing. The image is transferred onto the transferred transfer material P by the action of the transfer charger 104. Then, the transfer material P that has received the transfer of the unfixed developer image is separated by the separation charger 105.
After being separated from the photosensitive drum 101 by the action of, the belt conveying device 116 feeds it to the fixing device 118 along the pre-fixing guide 117, and passes between the fixing roller 118a and the pressure roller 118b of the fixing device 118. The unfixed developer image is fixed by heat and pressure.

By the way, since the image forming apparatus has been downsized in recent years, the distance L ₁ between the transfer charger 104 and the fixing device 118 is a length L in the conveying direction of the transfer material P as shown in FIG. May be shorter (L ₁ <L).

[0004]

In such a case, when the transfer material P enters the fixing device 118, the trailing edge of the transfer material P does not pass over the transfer charger 104, so that the transfer material P is not transferred. When P rushes into the fixing device 118, the transfer material P vibrates due to the impact, and transfer deviation occurs at the rear end portion of the transfer material P.

As a measure against the above problem, several kinds of proposals as shown in FIG. 6 have been made. As an example thereof, the pre-fixing guide 217 continuing from the belt conveying device 216 to the fixing device 218 is bent in an inverted shape so that the transfer material P has a slack, so that the shock is absorbed and vibration is not transmitted to the transfer portion. There is something like this.

Although the above method is effective, the pre-transfer guide 2
The portion E in the figure of E must be arranged at a position lowered downward as compared with the conventional one, and it is applicable when there is a space in the downward direction, but it can be applied to the lower side of the belt conveying device 216. For example, when a double-sided multi-passage is provided, there is no room in space and the device must be upsized. This conflicts with the recent miniaturization of devices.

As another example, the pressure roller 218b of the fixing roller 218a and the pressure roller 218b of the fixing device 218 is moved to the position shown by the broken line in FIG.
There is one in which the vector direction of the impact when the sheet rushes into the fixing device 218 is directed in the direction of the arrow A so that the vibration is not transmitted to the transfer portion. This method is also effective,
Since the position of the pressure roller 218b is moved in the direction of the broken line in FIG. 6, the curl of the transfer material P (in particular, the downward curl) becomes large, and the rear end of the transfer material P bounces. Then, in order to solve these problems, a major change in the device is required.

Further, as another example, the belt conveying device 21
It is also proposed that a suction fan 235 is provided in the unit 6 to increase the suction force between the transfer material P and the conveyor belt 216a so that the vibration is not transmitted to the transfer unit.

However, in the above method, the suction fan 235
It is unavoidable that the cost for adding the driving means itself and the driving means is increased, and it cannot be said to be the best means for implementing.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress the occurrence of a transfer deviation in a transfer portion due to an impact at the time when a transfer material is rushed into a fixing means, and to achieve high quality. An object of the present invention is to provide an image forming apparatus that can always stably obtain an image.

[0011]

In order to achieve the above object, the invention according to claim 1 provides an image carrier and a transfer means for transferring an unfixed developer image formed on the image carrier onto a transfer material. And a fixing means for fixing the unfixed developer image transferred to the transfer material by the transfer means, wherein the distance between the transfer means and the fixing means is longer than the length of the transfer material in the conveyance direction. In the image forming apparatus arranged so as to be shortened, a control member for keeping the peripheral speed of the fixing roller of the fixing means constant is provided.

According to a second aspect of the present invention, in the first aspect of the invention, the control member is a flywheel for increasing the inertial force of the fixing roller.

According to a third aspect of the present invention, in the second aspect of the invention, the rotation of the fixing roller is transmitted to the flywheel via a speed increasing gear.

According to a fourth aspect of the present invention, in the second aspect of the invention, the flywheel is provided in the middle of a driving force transmission system to the fixing means.

[0015]

[Function] Distortion of an image when the transfer material enters the fixing means
It is considered to occur based on the following phenomenon.

That is, when the front end of the transfer material plunges between the fixing roller of the fixing means and the pressure roller which is an elastic member, the peripheral speed of the roller is once reduced by the resistance due to the thickness of the transfer material, and then the pressure is applied. Due to the elastic force of the roller, the peripheral speed of the roller sharply increases and the roller draws in the transfer material, which causes an impact, and the impact is propagated to the transfer material to move the transfer material, causing a transfer deviation in the transfer area. To do. Therefore, by suppressing the peripheral speed fluctuation of the fixing roller when the transfer material plunges into the fixing means, it is possible to suppress the occurrence of image disturbance due to the transfer deviation.

According to the first aspect of the invention, since the peripheral speed of the fixing roller of the fixing unit is kept constant by the control member, the occurrence of image disturbance due to transfer deviation is suppressed, and the image disturbance is suppressed. It is possible to always obtain a high-quality image free of noise.

According to the second aspect of the invention, the inertial force of the fixing roller is increased by the flywheel, and the peripheral speed of the fixing roller is kept constant by this, so that the occurrence of image disturbance due to transfer deviation occurs. Suppressed.

According to the third aspect of the present invention, the rotation of the fixing roller is speeded up by the speed increasing gear and transmitted to the flywheel, so that the diameter of the flywheel can be reduced and the apparatus can be made compact. be able to.

According to the fourth aspect of the present invention, the inertial force of the fixing roller is also increased by the flywheel provided in the middle of the driving force transmission system to the fixing means, whereby the peripheral speed of the fixing roller is constant. Therefore, the occurrence of image distortion due to transfer deviation is suppressed.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

<First Embodiment> FIG. 1 is a fragmentary side view of an essential part of an image forming apparatus according to the present invention, FIG. 2 is a plan view of a fixing device of the image forming apparatus, and FIG. 3 is a vertical sectional view of the image forming apparatus. Is.

First, a schematic structure of an electrophotographic copying machine which is an image forming apparatus according to the present invention will be described with reference to FIG.

A photosensitive drum 1 as an image carrier is rotatably accommodated in a main body 10 of the copying machine, and a primary charger 2, a developing device 3, a transfer charger 4 are provided around the photosensitive drum 1. Process devices such as a separation charger 5 and a cleaner 6 are arranged. A toner hopper 7 for replenishing the toner as a developer is installed above the developing device 3.

Further, on one side of the apparatus main body 10 (on the right side in FIG. 3), sheet feeding cassettes 11, 12, and 13 formed by stacking and accommodating a plurality of transfer materials P are provided in upper and lower three stages. Cage,
A paper feed tray 14 for manual feeding is provided above the paper feed cassette 11.
Is provided.

Thus, the paper feed cassettes 11, 12, 13
Alternatively, the transfer material P supplied from the paper feed tray 14 for manual feeding
3 is conveyed from the right side to the left side in FIG. 3 in the apparatus main body 10, and the registration roller 15, the belt conveyance device 16, the pre-fixing guide 17, the fixing device 18, the discharge roller 19 and the like are provided on the conveyance path. It is arranged.

The fixing device 18 is composed of a fixing roller 18a and a pressure roller 18b which come into contact with each other and rotate. The pressure roller 18b has a surface layer made of an elastic material.

On the other hand, the lamp 20, the reflecting mirrors 21 to 24, the optical lens 25, and the like, which constitute an optical system, are arranged in the upper portion of the apparatus main body 10.

Then, an original (not shown) set on the original placing table 26 provided on the upper surface of the apparatus main body 10 is read by an optical system, and an optical image corresponding to the original is exposed on the photosensitive drum 1. Then, an electrostatic latent image is formed on the photosensitive drum 1 whose surface is charged by the primary charger 2, and the electrostatic latent image is developed by the developing device 3 and visualized as a toner image. To be done.

On the other hand, the transfer material P is supplied from, for example, the paper feed cassette 11, and the transfer material P is transferred to the registration roller 15 described above.
The toner image formed on the photosensitive drum 1 is transferred to the transfer portion between the photosensitive drum 1 and the transfer charger 4 at a timing adjusted by the photosensitive drum 1 and then the photosensitive drum 1 is operated by the separating charger 5. Separated from 1.

Then, the transfer material P separated from the photosensitive drum 1 is sent to the fixing device 18 by the belt conveying device 16, and is nipped by the fixing roller 18a and the pressure roller 18b of the fixing device 18 to hold them. After passing, the toner image is fixed by heat and pressure, and then discharged by the discharging roller 19 to the outside of the apparatus main body 10.

By the way, since the copying machine according to the present embodiment is downsized, the distance L ₁ between the transfer charger 4 and the fixing device 18 is the transfer direction of the transfer material P as shown in FIG. It may be shorter than the length L (L ₁ <L).

The structure of the drive system of the fixing device 18 will now be described with reference to FIGS. 1 and 2.

The fixing roller 18a of the fixing device 18 is rotationally driven by the electric motor 27 shown in FIG. 1, and the pulley 28 connected to the output shaft end of the electric motor 27 and the pulley 30 connected to one end of the rotation shaft 29. An endless drive belt 31 is wound between the two. A gear G1 is attached to the other end of the rotary shaft 29, and the rotary shaft 1 of the fixing roller 18a is connected to the gear G1.
A gear G5 is attached to one end of 8a-1. The gear G1 meshes with the gear G5 via the gears G2 to G4.

On the other hand, the rotating shaft 18a-of the fixing roller 18a
A large-diameter gear G6 is attached to the other end of the gear 1, and the gear G6 meshes with a small-diameter gear G7 attached to the rotary shaft 32. A flywheel 33 is attached to the free end of the rotary shaft 32.

When the image forming operation is started, the electric motor 27 is driven, and the rotation of the electric motor 27 is transmitted to the rotary shaft 29 via the pulley 28, the drive belt 31 and the pulley 30, and the rotary shaft 29 is rotated. The rotation of 29 is transmitted to the fixing roller 18a via the gears G1 to G5, and the fixing roller 18a is rotated.
A is rotationally driven at a predetermined speed and is used for fixing the toner image described above.

The rotation of the fixing roller 18a is accelerated by gears (accelerating gears) G6 and G7, and the rotation shaft 3 is rotated.
The rotary shaft 32 and the flywheel 33 attached to the rotary shaft 32 are driven to rotate at a speed faster than that of the fixing roller 18a.

By the way, in the conventional image forming apparatus shown in FIG. 5, the distance L ₁ between the transfer charger 104 and the fixing device 118 is shorter than the length L of the transfer material P in the conveying direction as shown in FIG. When L ₁ <L, the transfer material P fixing device 118
Disturbance of the image occurred at the time of entry into, but it is considered that this disturbance of the image occurs based on the following phenomenon.

That is, the leading end of the transfer material P and the fixing roller 108a of the fixing device 118 and the pressure roller 180b which is an elastic body.
When it rushes into the gap between the rollers 108a and 108b, the peripheral speed of the rollers 108a and 108b is once reduced by the resistance due to the thickness of the transfer material P, and then the elastic force of the pressure roller 108b causes the roller 108 to rotate.
The peripheral speeds of a and 108b are rapidly increased,
An impact is generated because a and 108b pull in the transfer material P, and the impact is propagated to the transfer material P and the transfer material P moves, so that a transfer deviation occurs in the transfer area. Therefore, when the transfer material P enters the fixing device 118, the fixing roller 1
By suppressing the fluctuation of the peripheral speed of 08a to be small, it is possible to suppress the occurrence of image disturbance due to the transfer deviation.

Thus, according to the present embodiment, the flywheel 33 increases the inertial force of the fixing roller 18a and keeps the peripheral speed constant, so that the occurrence of image distortion due to transfer deviation is suppressed. , A high-quality image without image distortion can always be obtained stably.

Further, according to this embodiment, the fixing roller 18a
Since the rotation of is increased by the speed increasing gears G6 and G7 and transmitted to the flywheel 33, the diameter of the flywheel 33 can be reduced, and the device can be made compact.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a plan view of the fixing device of the image forming apparatus according to this embodiment. In this figure, the same elements as those shown in FIG.
Hereinafter, the description of them will be omitted.

In this embodiment, the flywheel 33 is in the middle of the driving force transmission system to the fixing device 18, specifically, the gear G4.
In this case, the flywheel 33 also increases the inertial force of the fixing roller 18a and keeps the peripheral speed constant, so that the occurrence of image distortion due to transfer deviation is suppressed. High-quality images without image distortion can always be obtained stably.

Although the flywheel 33 is arranged coaxially with the gear G4 in this embodiment, the flywheel 33 can be arranged at any position in the middle of the driving force transmission system.

[0045]

As is apparent from the above description, claim 1
According to the invention described above, since the peripheral speed of the fixing roller of the fixing unit is kept constant by the control member, the occurrence of image distortion due to the transfer deviation is suppressed, and a high-quality image without image distortion is always stable. Obtainable.

According to the second aspect of the present invention, the inertial force of the fixing roller is increased by the flywheel, and the peripheral speed of the fixing roller is kept constant by this, so that the occurrence of image distortion due to transfer deviation occurs. The effect of being suppressed is obtained.

According to the third aspect of the present invention, the rotation of the fixing roller is speeded up by the speed increasing gear and transmitted to the flywheel. Therefore, the diameter of the flywheel can be reduced and the apparatus can be made compact. The effect that can be obtained is obtained.

According to the fourth aspect of the invention, the inertial force of the fixing roller is also increased by the flywheel provided in the middle of the driving force transmission system to the fixing means, whereby the peripheral speed of the fixing roller is constant. Therefore, it is possible to obtain the effect of suppressing the occurrence of image distortion due to transfer deviation.

[Brief description of drawings]

FIG. 1 is a cutaway side view of an essential part of an image forming apparatus according to the present invention.

FIG. 2 is a plan view of a fixing device of the image forming apparatus according to the present invention.

FIG. 3 is a vertical cross-sectional view of the image forming apparatus.

FIG. 4 is a plan view of a fixing device of an image forming apparatus according to a second exemplary embodiment of the present invention.

FIG. 5 is a side sectional view of a main part of a conventional image forming apparatus.

FIG. 6 is a sectional view of a main part of the image forming apparatus for explaining a conventional transfer deviation countermeasure.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 4 Transfer charging device (transfer means) 18 Fixing device (fixing means) 18a Fixing roller 33 Flywheel (control member) G6, G7 Accelerating gear L Transfer material conveyance direction length L ₁ Transfer Distance between charger and fixing device P Transfer material

Claims (4)

[Claims] 1. An image carrier, transfer means for transferring the unfixed developer image formed on the image carrier to a transfer material, and fixing the unfixed developer image transferred to the transfer material by the transfer means. In the image forming apparatus, the image forming apparatus is configured to include a fixing unit that allows the transfer unit and the fixing unit to be arranged such that the distance between them is shorter than the length of the transfer material in the conveyance direction.
An image forming apparatus comprising a control member for keeping a peripheral speed of a fixing roller of the fixing unit constant. 2. The image forming apparatus according to claim 1, wherein the control member is a flywheel for increasing an inertial force of the fixing roller. 3. The image forming apparatus according to claim 2, wherein the rotation of the fixing roller is transmitted to the flywheel via a speed increasing gear. 4. The image forming apparatus according to claim 2, wherein the flywheel is provided in the middle of a driving force transmission system to the fixing unit.