JP3090559B2 - 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 an image forming apparatus such as a copying machine or a laser beam printer, and more particularly, to a recording material carrying a toner image formed on the surface of an image carrier. The present invention relates to an image forming apparatus for transferring images to an image forming apparatus.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional color image forming apparatus for forming a full-color image. In this image forming apparatus, a photosensitive drum 1 as an image carrier is rotatably supported in the direction of an arrow R1, and a primary charger 2, an optical system 3, a developing device 5, a transfer device 6 are provided around the photosensitive drum 1. , A cleaning device 7 is disposed.

The primary charger 2 has a shield member disposed just above the photosensitive drum 1 such that an opening faces the surface of the photosensitive drum 1, and a discharge wire disposed inside the shield member. The surface of the photosensitive drum 1 is uniformly charged by corona discharge generated by applying a high voltage to the discharge wire.

The optical system 3 is a laser beam exposure device that includes a document scanning section and a color separation filter, and irradiates the photosensitive drum 1 with a color-separated light image or a light image E corresponding thereto. The photosensitive drum 1 charged by the primary charger 2 is image-scan-irradiated with a light image E for each separation color to form an electrostatic latent image. The developing device 5 is a rotary developing device, and four developing devices, that is, a yellow developing device 5Y and a magenta developing device 5
M, a cyan developing unit 5C, and a black developing unit 5BK are mounted, and a predetermined developing unit is rotationally moved to a developing position opposed to the photosensitive drum 1 to reversely develop the electrostatic latent image on the photosensitive drum 1 to perform reverse development. 1, a toner image is formed with a resin-based toner.

[0005] Further, the toner image on the photosensitive drum 1 is transferred to the recording material P by the transfer device 6. Transfer device 6
Has a transfer charger 6b, a suction roller 6g opposed to a suction corona charger 6c for electrostatically attracting the recording material P, an inner corona charger 6d, and an outer corona charger 6e, and is driven to rotate. A recording material carrying sheet 6f made of a dielectric is integrally stretched in a cylindrical shape in a peripheral opening area of the transfer drum 6a pivotally supported by the recording drum 6a. The recording material P is supplied to the transfer device 6 from a recording material cassette 9 via a transport system. As the transfer drum 6a rotates in the direction of the arrow R6, the toner image on the photosensitive drum 1 is charged uniformly on the recording material P carried on the recording material carrying sheet 6f by the transfer charger 6b. The electrostatic transfer is performed with the opposite polarity to that of the above.

[0006] A desired number of color images are transferred to the recording material P sucked and conveyed on the recording material carrying sheet 6f to form a full color image.

When the transfer of the desired number of toner images is completed, the recording material P is separated from the transfer drum 6a by the separating charger 6h and the separating means 10, and the toner image is fixed by the fixing device 11 having a heat roller. Then, the paper is discharged onto the paper discharge tray 12.

On the other hand, the photosensitive drum 1 after the transfer of the toner image
After the residual toner on the surface is cleaned and removed by the cleaning device 7, the toner is again subjected to the image forming process.

[0009]

However, according to the image forming apparatus shown in the above-mentioned prior art, when the recording material P is jammed (paper is clogged), the recording material P on the transfer drum 6a is lost.
Removal work was complicated. That is, in general, when the apparatus main body is stopped including a jam, the photosensitive drum 1 and the transfer drum 6a stop in a state in which their surfaces are brought into contact with each other to form a transfer nip portion, as in the transfer. . Therefore, in order to remove the recording material held between the transfer nip portions, the photosensitive drum 1 and the transfer drum 6a are temporarily
Separate. The separation between the two drums 1 and 6a is performed by a dedicated release lever. When removing the jammed paper, the operator manually swings the release lever to separate the photosensitive drum 1 and the transfer drum 6a from each other, to release the nipping state of the recording material, and then to pull out the recording material. Take out.
Incidentally, it is not preferable that the release lever is too large in terms of space efficiency, and the release lever is formed in a minimum necessary size. Therefore, it is difficult for the operator to find the release lever, and even if the release lever is found promptly, thereafter, the separating operation by manually operating the above-described release lever, and further, after the recording material is removed, the separated state is returned to the original contact state. A complicated operation such as a return operation to return to the normal state is forced. In addition, there is a problem of durability due to the repeated operation of the release lever.

In view of the above, the present invention provides, for example, an interval changing means for changing a relative position between an image carrier (photosensitive drum) and a recording material carrier (transfer drum) at a predetermined timing. When stopped, the image carrier and the recording material carrier take a standby position in which they are separated from each other, so that the release lever is actively omitted, thereby eliminating complicated lever operation during a jam. It is an object to provide a forming apparatus.

[0011]

In order to achieve the above object,
According to the first aspect of the present invention, there is provided an image carrier for carrying an image.
Image carrier having a first gear for rotating the image carrier
Means, a recording material carrier for supporting the recording material, and the recording material carrier.
A second engageable with the first gear to rotate the carrier;
And a recording material carrying means having a second gear.
The image on the carrier is transferred to the recording material carried by the recording material carrier.
In an image forming apparatus that performs transfer at a transfer position, image formation is performed.
At a predetermined time after the image carrier starts rotating to start
After a lapse of time, the first gear and the second gear mesh with each other.
Move the recording material holding means so that the engagement position is different from the last time.
Move from the position farther than the transfer position to the transfer position
Characterized by the following. The present invention according to claim 2 provides:
2. The image forming apparatus according to claim 1, wherein the predetermined time is the time.
The image carrier is longer than one rotation time.
You. The present invention according to claim 3 provides the image form according to claim 1 or 2
In the forming apparatus, from the image carrier to the recording material carrier
Images of multiple colors can be sequentially transferred and superimposed on the carried recording material.
The number of teeth of the first gear and the second gear is one
Is an integral multiple of the other.

According to a fourth aspect of the present invention, a recording material is supported.
Recording material carrier and a first member for rotating the recording material carrier
Recording material carrying means having a gear, and image carrying carrying an image
Engageable with a body and a first gear for rotating the image carrier
And an image bearing means having a second gear.
The image on the carrier is transferred to the recording material carried by the recording material carrier.
In an image forming apparatus that transfers images at the
A predetermined time after the recording material carrier starts rotating
After a lapse of time, the first gear and the second gear
Move the image carrier forward so that the meshing position is different from the previous
From the position farther from the transfer position to the transfer position.
To be characterized. The present invention according to claim 5 is a contract
5. The image forming apparatus according to claim 4, wherein the predetermined time is equal to the above-mentioned time.
The recording material carrier is longer than one rotation time.
I do. The invention according to claim 6 is the image according to claim 4 or 5.
In the forming apparatus, the recording material carrier may be separated from the image carrier.
Images of multiple colors can be sequentially transferred and superimposed on the recording material carried by
And the number of teeth of the first gear and the second gear is one.
Is an integral multiple of the other.

According to the present invention, there is provided an image bearing image.
It has a carrier and a first gear for rotating the image carrier.
Image carrying means, a recording material carrier for carrying a recording material, and
Engage with the first gear to rotate the recording material carrier
Recording material carrying means having a possible second gear;
The image on the image carrier is carried on the recording material carrier.
In an image forming apparatus for transferring to a recording material,
Each time an image is formed on a number of recording materials, the first gear
So that the image carrier does not mesh with the second gear.
While moving the step or the recording material carrying means,
The meshing position between the first gear and the second gear is
Performing a change operation for changing the state differently.
You.

According to the present invention, a recording material is supported.
Recording material carrier and a first member for rotating the recording material carrier
Recording material carrying means having a gear, and image carrying carrying an image
Engageable with a body and a first gear for rotating the image carrier
And an image bearing means having a second gear.
The image on the carrier is transferred to the recording material carried by the recording material carrier.
In an image forming apparatus that transfers images at a shooting position,
Each time an image is formed on a number of recording materials, the first gear
The image bearing means so as not to mesh with the second gear;
Or, while moving the recording material holding means,
The meshing position between the first gear and the second gear is different from the last time.
Performing a change operation to change the
You.

[0015]

According to the above construction, the image carrier and the recording material carrier are separated from each other by the interval changing means when the apparatus main body is stopped, for example, when a jam occurs. Therefore, the operator can easily remove the jammed paper without performing a complicated operation such as separating the two by the operation lever when removing the jammed paper.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. <Embodiment 1> An outline of the structure and operation of an image forming apparatus according to the present invention will be described with reference to FIG. This image forming apparatus is a digital four-color full-color image forming apparatus, and comprises a reader unit I disposed above and a printer unit II disposed below, forming an apparatus main body.

The reader unit I reads the image information of the document 30 and sends the image information to the printer unit II. A transparent platen glass 31 is disposed on the upper surface of the reader unit I, and the document 30 to be read is placed with its image surface facing downward. Below the platen glass 31, an exposure lamp 32 that can reciprocate freely is arranged.
The exposure lamp 32 irradiates the right and left width (the front and back direction in FIG. 1) of the document 30 and moves in the front and rear direction (the left and right direction in FIG. 1) to scan the entire image surface of the document 30. Light that has been exposed and scanned on the image surface is once reflected by the image surface, and further condensed on a full-color sensor 35 via a mirror, a lens 33 and the like, whereby a color-separated image signal is obtained. The color-separated image signal is processed by a video processing unit via an amplifier circuit (not shown) and sent to the printer unit II.

The printer unit II is provided with a photosensitive drum 1 as an image carrier. The photosensitive drum 1 is a photosensitive member made of an organic photoconductor as described later, and is rotatably supported by the printer main body in the direction of arrow R1. Around the photosensitive drum 1, a corona charger 2, a laser exposure optical system 3, a potential sensor 15, and four developing devices 5 Y, 5 C, 5 M each containing a toner of a different color are sequentially arranged along the rotation direction. 5BK, a light amount detecting means 16 on the photosensitive drum 1, a transfer device 6, a cleaning device 7, and a pre-exposure lamp 13 are arranged.

The laser exposure optical system 3 converts an image signal from the reader unit I into an optical signal for image scan exposure at a laser output unit (not shown), and reflects the converted laser light on a polygon mirror 3a. Lens 3b and mirror 3c
Is projected on the surface of the photosensitive drum 1 via the.

At the time of image formation in the printer section II, the photosensitive drum 1 is rotated in the direction of the arrow R1 and the pre-exposure lamp 1 is rotated.
The photosensitive drum 1 after the static elimination in step 3 is uniformly charged negatively (negative polarity) by the charger 2 and irradiates a light image E for each separation color to form an electrostatic latent image. On the surface of the photosensitive drum 1 that has been negatively charged, the charge of the portion irradiated with the light image E is removed (substantially zero potential), and this portion becomes an electrostatic latent image corresponding to the document image.

Next, a predetermined developing device corresponding to each color is operated to reversely develop the electrostatic latent image on the photosensitive drum 1, and a toner image (developer Image). The yellow, cyan, magenta, and black developing units 5Y, 5C, 5M, and 5BK are
The operation of the eccentric cams 17Y, 17C, 17M, and 17BK is configured to selectively approach the photosensitive drum 1 according to each separation color.

Further, the toner image on the photosensitive drum 1 is transferred from a recording material cassette 9 to a recording material P supplied to a transfer nip portion facing the photosensitive drum 1 via a transport system and a transfer device 6. In this example, the transfer device 6 has a cylindrical transfer drum 6a having a peripheral length corresponding to the maximum recording material length, a transfer charger 6b, and an attraction charger 6c for electrostatically attracting the recording material P, and faces the same. Suction roller 6g, inner charger 6
d, a recording material supporting sheet 6f made of a dielectric material is integrally stretched into a cylindrical shape in an opening area of a peripheral surface of the transfer drum 6a which has an outer charger 6e and is rotatably supported so as to be rotatably driven. ing. The recording material supporting sheet 6f uses a dielectric sheet such as a polycarbonate film. The transfer device 6 transfers the toner image on the photosensitive drum 1 onto the recording material P carried by the recording material carrying sheet 6f by the operation of the transfer charger 6b as the transfer drum 6a rotates.

On the other hand, the photosensitive drum 1 after the transfer of the toner image
The residual toner on the surface is cleaned and removed by the cleaning device 7, the electricity is removed by the pre-exposure lamp 13, and then the image forming process is performed again.

The above-described series of image forming processes such as primary charging, exposure, development, transfer, and cleaning are performed by yellow,
By repeating the process for the four colors of cyan, magenta, and black, toner images of four colors are transferred to the recording material P of the recording material carrying sheet 6f in a stacked state. In the case of full-color image formation, when the transfer of the four color toner images is completed in this way, the recording material P is separated from the separation charger 6h,
The sheet is separated from the transfer drum 6a by the action of the separation claw 10a and the separation push-up roller 10b, and is conveyed to the fixing device 11.

The fixing device 11 includes a fixing roller 11a, a pressure roller 11b, a release agent applying roller 11c, and a cleaning roller 11d. The toner image is heated and pressed to be fixed on the recording material P. The recording material P to which the toner image is fixed is
Thereafter, the paper is discharged onto the paper discharge tray 12.

When an image is formed on both sides of the recording material P, the recording material P is not discharged onto the paper discharge tray 12 after the image formation on one surface (first surface) is completed, and is fixed to the fixing device 11. Is immediately led to the transport path switching guide 19, and the transport vertical path 2
0, and once guided to the reversing path 2la, by reversing the reversing roller 2lb, retreats in a direction opposite to the direction of feeding, with the trailing end at the time of feeding in, and is stored in the intermediate tray 22. You. Thereafter, the recording material P is again supplied to the transfer nip portion via the transport system and the transfer device 6, and the above-described image forming process is repeated to form an image on the other surface (second surface). You.

The transfer drum 6a of the transfer device 6 is provided with a recording material supporting sheet 6f for preventing scattering of powder on the recording material supporting sheet 6f, adhesion of oil on the recording material P, and the like. Fur brush 23 and backup brush 25, which face each other, and recording material carrying sheet 6f
The cleaning is performed by the action of the oil removal roller 26 and the backup brush 27 which face each other via the. Such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.

Next, with reference to FIG. 2, the structure and operation of the interval changing means 52 for changing the interval between the photosensitive drum 1 and the transfer drum 6a, which is a feature of the present invention, will be described. The diameter d1 of the photosensitive drum 1 and the transfer drum 6
The following description proceeds assuming that the diameter d6 of a is the same size (d1 = d6).

Gears having the same shape and the same number of teeth, that is, a photosensitive drum gear 1G and a transfer drum gear 6G are fixed to one side of the photosensitive drum 1 and the side of the transfer drum 6a on the same side. The two gears mesh with each other (however, FIG. 2 shows these gears 1G, 6G
Shows only a part located near the transfer nip portion N. ). Of these gears 1G and 6G, the photosensitive drum gear 1G is connected via a necessary idle gear or the like (not shown).
The driving means 50 is connected to a driving means 50 such as a motor. The driving means 50 is further connected to a rotation control means 51 for controlling the rotation speed and the rotation angle of the photosensitive drum 1 via the driving means 50 and the photosensitive drum gear 1G. Have been. on the other hand,
The transfer drum 6a has no driving means, and the transfer drum gear 6G is rotated by rotation of the photosensitive drum gear 1G in the direction of arrow R1.
Via G, it is driven to rotate in the direction of arrow R6.

An interval changing means 52 for changing the interval between the transfer drum 6a and the photosensitive drum 1 is provided obliquely below the transfer drum 6a. The interval changing means 52 includes an eccentric cam 53 that rotates about a shaft 53a and a cam follower 5 that swings about a shaft 55a following the eccentric cam 53.
5 is provided. It is assumed that the eccentric cam 53 has its operation timing, operation amount, and the like controlled by drive means and control means (not shown). The cam follower 55 is connected to an axis 6A of the transfer drum 6a via an interlocking mechanism (not shown). The position of the axis 6A is changed by the swing of the cam follower 55, and the axis of the photosensitive drum 1 is changed. 1A
The distance from is increased or decreased. That is, the transfer drum 6a is configured such that the distance from the photosensitive drum 1 can be arbitrarily changed by changing the position of the shaft center 6A. As a result, for example, the transfer drum 6a is in proximity to the photosensitive drum 1 and has a transfer position M1 (shown by a solid line in FIG. 2) where the surface contacts the surface of the photosensitive drum 1, and a standby position M2 that is separated from the photosensitive drum 1. (Shown by a dotted line in FIG. 2). Due to such separation of the transfer drum 6a from the photosensitive drum 1, the transfer drum gear 6G naturally also moves the photosensitive drum gear 1G.
And the gears 6G, 1G are disengaged from each other. For example, if the standby position M2 is set at a position where the transfer drum 6a is separated by a distance longer than the tooth length of these gears 6G, 1G, the engagement of both gears 6G, 1G is completely released. The rotation of the photosensitive drum gear 1G is not transmitted to the transfer drum gear 6G, and the transfer drum 6a stops. By adopting such a configuration, the transfer drum 6a is moved to the standby position M2 which is separated from the photosensitive drum 1 by a predetermined distance during standby when the power of the apparatus main body is turned on or when the power is turned off, and furthermore, at the time of jam. It is located. In this separated state,
The engagement between the photosensitive drum gear 1G and the transfer drum gear 6G is completely released. Then, while rotating the photosensitive drum 1 in response to an image formation signal (copy start signal), the interval changing means 52 is operated to bring the transfer drum 6a at the standby position into contact with the photosensitive drum 1, and at the same time, the photosensitive drum gear 1 is engaged with the transfer drum gear 6G. This makes it possible to transfer the toner image from the photosensitive drum 1 to the recording material P carried by the transfer drum 6a.

FIG. 3 is a schematic timing chart when a single small-size image is printed by the image forming apparatus of this embodiment.

One rotation of the transfer drum 6a is divided into an A surface and a B surface, and the transfer drum 1 is indicated by A and B in FIG.
It corresponds to the time for the rotation. As shown in FIG. 3, after a lapse of a predetermined time T shorter than one rotation of the photosensitive drum from the start of rotation of the photosensitive drum 1, the eccentric cam 53 is moved to the gears 1G, 6G.
G is driven in the direction in which the gears mesh with each other, so that the two gears 1G and 6G mesh with each other, and at the same time, the transfer drum 6a is moved to the transfer position M2 and brought into contact with the photosensitive drum 1. On the other hand, during standby or the like, the eccentric cam 53 is driven in a direction in which the gears 1G and 6G are disengaged from each other, and is retracted to the standby position M2.

[0033] In the above embodiment, the photosensitive drum gear 1
The rotation of the drive before engagement of the G and the transfer drum gear 6G and the photosensitive drum 1, but this is not essential. When the transfer drum 6a has a rotary drive unit, the present invention also includes a case where both the photosensitive drum 1 and the transfer drum 6a have a rotary drive unit, and the same effect can be obtained.

In the above embodiment, the distance changing means 52 is provided as means for connecting and disconnecting the drive between the photosensitive drum 1 and the transfer drum 6a, thereby separating the transfer drum 6a from the photosensitive drum 1. At the same time, the engagement of the transfer drum gear 6G with the photosensitive drum gear 1G has been released, but the present invention is not limited to this. For example, the position of the transfer drum 6a may be immovable, and an interval changing unit for separating the photosensitive drum 1 may be provided, so that the engagement between the photosensitive drum gear 1G and the transfer drum gear 6G may be released. Further, a connection / disconnection mechanism such as a clutch is provided between the transfer drum gear 6G and the transfer drum 6a, and the transfer drum gear 6G and the transfer drum 6a are connected via this connection / disconnection mechanism.
And the gears 1G and 6G may be engaged with each other at a predetermined timing.

According to the present invention, during standby or when the power is turned off,
Therefore, this includes the moment when the photosensitive drum 1 starts up and the time of a jam. At these times, the following effects are obtained based on the fact that the transfer drum 6a is separated from the photosensitive drum 1. (1) The transfer drum 6a can be pulled out by one action. Further, jammed paper sandwiched between the photosensitive drum 1 and the transfer drum 6a can be easily removed. (2) The load at the time of starting the photosensitive drum 1 is reduced. FIG.
(A) shows that the transfer drum 6 is
This indicates the torque of the photosensitive drum 1 when the photosensitive drum 1 starts rotating in the state where it is in contact with a, and a torque of Tmax (a) is required at startup. On the other hand, FIG. 4B shows that when the photosensitive drum 1 is rotationally driven in the separated state with the torque in the case of the configuration of the present invention, the load is light, and the maximum value of the torque is suppressed low. Since the transfer drum 6a is brought into contact with the photosensitive drum 1 while rotating the photosensitive drum 1, the maximum value of the torque is Tmax (b) (<Tma
x (a)). Gear wear and the like due to the large maximum torque can be prevented. (3) Since the photosensitive drum 1 is rotated when the transfer drum 6a is moved from the standby position M2 to the transfer position M1, the transfer drum gear 6G smoothly meshes without climbing up to the photosensitive drum gear 1G, and the gears 1G, 6G are worn. In addition, it is possible to prevent vibration pitch unevenness or the like caused by the gear 6G climbing up. In addition, it is possible to adopt a configuration of the gears 1G and 6G such as a sharp tooth to prevent the gear 6G from rising, but this is not necessarily a good measure because it leads to an increase in cost. . (4) This configuration, which is a configuration for preventing wear and pitch unevenness of the gears 1G and 6G, is particularly effective when applied to an image forming apparatus using a laser scanning optical system as in this embodiment. Also,
When applied to a color image forming apparatus, it is particularly effective in preventing color misregistration and color unevenness. (5) Damage to the recording material supporting sheet 6f and the photosensitive drum 1 due to the stationary contact thereof can be eliminated. The damage of the photosensitive drum 1 is, for example, the photosensitive drum 1
When the polarity of the uniform charge on the recording material carrying sheet 6f and the polarity of the charge remaining on the recording material carrying sheet 6f are opposite to each other, there is particularly significant electrostatic damage. The damage of the recording material supporting sheet 6f is as follows.
For example, mechanical damage such as thermal permanent deformation of the recording material carrying sheet 6f, which is particularly remarkable when the photosensitive drum 1 has a drum heater (not shown) for improving the photoreceptor characteristics, and electrostatic damage.

According to the structure of the present invention, the engagement positional relationship between the photosensitive drum 1 and the transfer drum 6a can be easily changed. That is, when the transfer drum 6a is brought into contact with the photosensitive drum 1 that has started rotating, if the operation timing of the interval changing means 52 is slightly shifted, the engagement between the photosensitive drum gear 1G and the transfer drum gear 6G is slightly shifted. The effect of this is as follows. (1) When the photosensitive drum 1 stops, a specific portion of the surface is prevented from always being located immediately below the primary charger 2, and deterioration of the surface of the photosensitive drum 1 due to NOx generated by corona discharge is specified. It is possible to prevent the photosensitive drum 1 from dispersing over the entirety of the photosensitive drum 1 without concentrating on the portion, thereby extending the durability life of the photosensitive drum 1. (2) This is particularly effective when images are formed on both sides of the recording material P as in the first embodiment. One surface (first surface) of the recording material P
When an image is formed on the recording material P, the silicone oil impregnated on the recording material P is transferred from the release agent (silicone oil) application roller 11c to the fixing roller 11a and the pressure roller 11b of the fixing device 11. At the time of image formation on the surface (second surface), it adheres to the photosensitive drum 1 and the recording material carrying sheet 6f of the transfer drum 6a via the recording material P. If the adhered silicon oil is not sufficiently removed and accumulates on the photosensitive drum 1 for a certain degree or more, a cleaning failure occurs in the cleaning device 7, and a band-like or linear streak may appear on the final image. In addition, since the attachment region of the silicone oil is localized on the recording material carrying sheet 6f, when the positional relationship between the recording material carrying sheet 6f and the photosensitive drum 1 does not change, the transfer drum is transferred via the transfer nip N. 6a
Similarly, the oil adhering area is also localized on the photosensitive drum 1 in contact with. For this reason, the cleaning failure of the cleaning device 7 is further promoted.

When the present invention is applied to such a case, it is possible to eliminate the localization of the oil adhering area on the photosensitive drum 1 and to prevent defective cleaning. (3) In the present embodiment, the photosensitive drum 1 and the transfer drum 6a are engaged with gears having an integer multiple of the number of teeth of both gears, for example, one to one.

In this way, the angular velocity of the photosensitive drum 1 and the angular velocity of the transfer drum 6a are set to an integral multiple relationship, that is, one to one in FIG. 2, so that the angular velocity is multiplied on the recording material P held on the transfer drum 6a. Photosensitive drum 1 of each color toner image to be transferred
The upper position can be common. For this reason, even if the photosensitive drum 1 has eccentricity, sensitivity unevenness, and the like as effects of the present embodiment, it is possible to prevent color shift and color unevenness of a color image. The configuration of the present embodiment is configured to take advantage of the above-described integer multiple ratio and eliminate the disadvantage described in the conventional example in which the engagement of the integer multiple ratio is the same.

In the present embodiment, the ratio between the number of gear teeth of the photosensitive drum 1 and the number of gear teeth of the transfer drum 6a is set to 1: 1, but one is the other, such as 1: 1, 2: 1, etc. The case of an integer is also included in the present embodiment, and has an effect of preventing color shift and color unevenness of a color image. In the one-to-one case, the position on the photosensitive drum 1 corresponding to the case where the recording material P is used for substantially one round of the transfer drum 6a is the same for each of the separated colors, so that the color misregistration of the color image and the color Although the effect of the present embodiment for preventing the unevenness is remarkable, the damage on the photosensitive drum 1 described in the above-mentioned problem of the related art may easily appear on an image. In this case, by applying the present invention, the problem could be cleared while utilizing the effects of the embodiment.

The rotation time in a state where the engagement of the photosensitive drum 1 is released, that is, the time T (upper left in FIG. 3) of FIG.
May be changed, or the meshing may be made random to make the meshing random, and the damage of the conventional example may be randomly dispersed. Further, the fact that the time T is within the rotation time of the transfer drum 1 means that it is the minimum time necessary for the purpose of shifting the engagement. However, in some cases, it is better to set T to be longer than one rotation time because of the necessity of the rotation stabilization time of the photosensitive drum 1 or the like.

Since the mechanical structure for shifting the engagement is the rotation of the photosensitive drum 1 and there is no special means for shifting, the structure of the entire apparatus can be simplified.

Further, the present invention is similarly applied to a so-called tandem type image forming apparatus having a plurality of photosensitive drums.

In addition, the timing of shifting the engagement is immediately before image formation, but the present invention is not limited to this. A counter may be provided to shift the engagement after a predetermined job (after a predetermined number of copies). If the number of shifts of the meshing is large, gear wear may occur in rare cases. To prevent this, it is optimal to set the number of jobs that can prevent accumulation of damage and have no gear wear. <Embodiment 2> FIG. 5 shows an example of another image forming apparatus to which the present invention is applied.

In this embodiment, a photosensitive belt 70 is employed as an image carrier instead of the photosensitive drum 1 which is an image carrier of the image forming apparatus shown in FIG.

Around the photosensitive drum 70, substantially the same members and devices as those around the photosensitive drum 1 of the image forming apparatus of the first embodiment described with reference to FIG. The same reference numerals are used).

In this embodiment, the ratio between the circumference of the photosensitive belt 70 and the circumference of the recording material carrying sheet 6f is set, for example, to 1: 1. , 72, 73, 74. Then, of the four rotating rollers 71, 72, 73, 74, the rotating roller 71, 72 on the side closer to the transfer drum 6a is moved by an interval changing means (not shown).
, And the photosensitive belt 70 and the transfer drum 6a are shifted. According to the present embodiment, a tensioner commonly used when attaching and detaching the photosensitive belt 70 to and from the rotating rollers 71, 72, 73, 74 can be used as the interval changing means. No need to do. Therefore, the first embodiment has a simple configuration.
The same effect can be obtained.

Finally, the specific effects of the present invention are raised.
In the color image forming apparatus shown in FIG.
Stopping for 0 second, repeating this for 8 hours continuously, and then standing for 16 hours ", the durability was promoted. When the conventional method was used, a band-like pattern appeared on the image in about 3000 sheets, and the life was extended. Whereas, according to the present invention, about 2
Good images were output even when the number of sheets exceeded 0000.

[0048]

According to the first aspect of the present invention, the image form
At a predetermined time after the image carrier starts rotating to start
After a lapse of time, the meshing position between the first gear and the second gear
Move the recording material carrying means from the transfer position so that the
To move to the transfer position from a distant position.
To prevent the occurrence of image defects and start rotating the image carrier.
Gear wear, etc.
Can be controlled. Further, according to the present invention according to claim 4,
Then, the recording material carrier rotates and opens to start image formation.
After a lapse of a predetermined time from the start, the first gear and the second gear
Image holding means so that the meshing position with
A mechanism for moving from a position farther from the transfer position to the transfer position
To prevent the occurrence of image defects, and
By reducing the load when starting to rotate the body,
Wear and the like can be suppressed.

According to the present invention according to claims 7 and 8,
Each time an image is formed on a fixed number of recording materials, the first gear
The image bearing means or the recording medium is so set as not to mesh with the second gear.
While moving the material carrying means, the first gear and the second gear
Change the gear meshing position so that it differs from the previous time.
Gears, so that gear wear can be suppressed.
Can be.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a schematic diagram illustrating a configuration of an interval changing unit according to the first embodiment.

FIG. 3 is a timing chart of the first embodiment.

FIG. 4A is a diagram illustrating a starting torque of a conventional photosensitive drum. FIG. 3B is a diagram illustrating a starting torque of the photosensitive drum according to the first exemplary embodiment.

FIG. 5 is a longitudinal sectional view schematically illustrating an image forming apparatus according to a second embodiment of the present invention.

FIG. 6 is a longitudinal sectional view schematically showing a conventional image forming apparatus.

[Explanation of symbols]

 Reference Signs List 1 image carrier (photosensitive drum) 3 laser scanning optical system (optical system) 6a recording material carrier (transfer drum) 11 fixing device 11a fixing roller 52 interval changing means 53 eccentric cam 55 cam follower M1 transfer position M2 standby position P recording material

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-192273 (JP, A) JP-A-60-33575 (JP, A) JP-A-61-100770 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) G03G 15/16 G03G 21/00 350 G03G 21/14

Claims (8)

(57) [Claims] (1)An image carrier for carrying an image and the image carrier
Image bearing means having a first gear for rotating, and a recording material
Rotating the recording material carrier and the recording material carrier
And a second gear engageable with the first gear.
Recording material carrying means, and an image on the image carrier is provided.
Transferring to a recording material carried on the recording material carrier at a transfer position
Image forming apparatus, The image carrier starts rotating to start image formation.
After a predetermined time has elapsed from the first gear and the second gear
The recording material so that the meshing position with the gear is different from the previous time.
The transfer unit is moved from a position farther than the transfer position.
Move to position, An image forming apparatus comprising: 2. The apparatus according to claim 1, wherein said image carrier rotates once during said predetermined time.
2. The method of claim 1 , wherein the time is longer than
Image forming device. (3)The image carrier bears on the recording material carrier.
It is possible to transfer multiple color images sequentially on the held recording material.
The first gear and the second gear have one of the number of teeth.
An integer multiple of the other, The image forming apparatus according to claim 1, wherein:
Place. (4)A recording material support for supporting a recording material and
A recording material carrier having a first gear for rotating the recording material carrier;
Holding means, an image carrier for carrying an image, and rotating the image carrier
Image having a first gear engageable with a second gear
Carrying means, wherein the image on the image carrier is recorded on the recording material.
Image type that is transferred to the recording material carried on the carrier at the transfer position
In the production equipment, The recording material carrier starts rotating to start image formation
After a lapse of a predetermined time, the first gear and the second gear
So that the meshing position with the second gear is different from the previous time.
The transfer unit is moved from a position farther than the transfer position.
Move to position, An image forming apparatus comprising: 5. The apparatus according to claim 1, wherein the recording material carrier is used once for the predetermined time.
5. The image forming apparatus according to claim 4, wherein the time is longer than the rotation time . 6.The image carrier bears on the recording material carrier.
It is possible to transfer multiple color images sequentially on the held recording material.
The first gear and the second gear have one of the number of teeth.
An integer multiple of the other, The image forming apparatus according to claim 4 or 5, wherein
Place. 7.An image carrier for carrying an image and the image carrier
Image bearing means having a first gear for rotating, and a recording material
Rotating the recording material carrier and the recording material carrier
And a second gear engageable with the first gear.
Recording material carrying means, and an image on the image carrier is provided.
Image type to be transferred to a recording material carried on the recording material carrier
In the production equipment, Each time an image is formed on a predetermined number of recording materials,
So that the first gear and the second gear do not mesh with each other.
When moving the image bearing means or the recording material bearing means,
In addition, the meshing position between the first gear and the second gear
Perform a change operation to change the location so that it is different from the previous An image forming apparatus comprising: Claim 8. A recording material support for supporting a recording material and
A recording material carrier having a first gear for rotating the recording material carrier;
Holding means, an image carrier for carrying an image, and rotating the image carrier
Image having a first gear engageable with a second gear
Carrying means, wherein the image on the image carrier is recorded on the recording material.
Image type that is transferred to the recording material carried on the carrier at the transfer position
In the production equipment, Each time an image is formed on a predetermined number of recording materials,
So that the first gear and the second gear do not mesh with each other.
When moving the image bearing means or the recording material bearing means,
In addition, the meshing position between the first gear and the second gear
Perform a change action to change the location so that it is different from the last time, An image forming apparatus comprising: