JP3293755B2 - Positioning structure and positioning method of developing roller with respect to photosensitive drum, and image forming apparatus employing them - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning structure and a positioning method for a developing roller with respect to a photosensitive drum.
And an image forming apparatus employing the same.

[0002]

2. Description of the Related Art Conventionally, an electrostatic image forming apparatus using a non-magnetic one-component toner as a developer has been known. In such an apparatus, a developing roller is generally used to develop the electrostatic latent image formed on the surface of the photoconductor drum,
A contact developing method in which a developing roller is brought into contact with a photosensitive drum is employed.

In an image forming apparatus employing this contact developing system, an elastic member (for example, an elastic member) for urging the developing roller toward the photosensitive drum so that the developing roller contacts the photosensitive drum at a predetermined pressure. Coil spring). Further, since the developing roller is configured to contact the photosensitive drum, the developing roller is made of an elastic material such as rubber, for example, in order to prevent the photosensitive layer from being damaged by friction between the developing roller and the photosensitive drum. Rubber rollers are often used.

However, when a rubber roller is used as the developing roller, when the ambient temperature of the developing roller changes, the hardness of the rubber changes, and the amount of the developing roller biting into the photosensitive drum varies. For example, when the ambient temperature rises, the rubber softens, and the amount of the developing roller biting into the photosensitive drum increases. If the amount of biting of the developing roller with respect to the photoconductor drum fluctuates, the amount of toner supplied to the photoconductor drum becomes unstable, and a problem such as uneven density may occur in a formed image.

Therefore, the conventional device is provided with a regulating roller for regulating the amount of the developing roller biting into the photosensitive drum. The regulating rollers are attached to both ends of the rotation shaft of the developing roller, and come into contact with tube portions (portions where the photosensitive layer is not formed) provided at both ends of the photosensitive drum. This restricts the developing roller from being pressed against the photosensitive drum more than necessary, so that the amount of the developing roller biting into the photosensitive drum is kept constant.

[0006]

However, since the photosensitive drum is formed by forming a photosensitive layer on the surface of a thin-walled tube made of, for example, aluminum, the regulating roller is moved by the elastic force of the elastic member. If the photosensitive drum is strongly pressed, the tube portion of the photosensitive drum is deformed or scraped, and the amount of the developing roller biting into the photosensitive drum fluctuates.

Maintaining a constant positional relationship between the photosensitive drum and the developing roller is not limited to the case of using a one-component developer. That is, even in an image forming apparatus using a two-component developer composed of a toner and a carrier and forming a spike of the developer on the peripheral surface of the developing roller, the gap between the photosensitive drum and the developing roller is kept constant. Need to keep. As described above, maintaining a constant positional relationship between the photosensitive drum and the developing roller is a common problem for an image forming apparatus including the photosensitive drum and the developing roller.

SUMMARY OF THE INVENTION An object of the present invention is to provide a structure for positioning a developing roller with respect to a photosensitive drum, which can maintain a constant positional relationship between the photosensitive drum and the developing roller. Another object of the present invention is to provide a positioning method capable of accurately positioning a developing roller with respect to a photosensitive drum.

Another object of the present invention is to provide an image forming apparatus which does not cause a problem such as uneven density in a formed image.

[0010]

Means for Solving the Problems The invention according to claim 1 for achieving the above object, a positioning structure for positioning the developing roller to the photosensitive drum, the upper
Serial engaged with the peripheral surface of both ends of the photosensitive drum, and a holding member for rotatably holding the photosensitive drum, is provided on the developing roller, abuts on the holding member, the sense <br /> includes a regulating member for regulating the approaching distance of the developing roller with respect to the optical drum, and a biasing means for the regulating member to urge the developing roller in a direction to be pressed into the holding member,
The urging means are provided at both ends of the photosensitive drum.
Driven gears provided at both ends of the developing roller from the drive gear
When the rotational force is transmitted to the rotating shaft of the developing roller
Utilizing the acting force to bias the developing roller
It is a positioning structure characterized by the following.

[0011] According to a second aspect of the invention, the holding member is fitted on the bare <br/> ring on the peripheral surface of both ends of the photoreceptor drum, the developing roller, the rotation shaft from both ends There projects, the regulating member is mounted for each rotation to the rotary shaft at both ends of the developing roller, according to claim 1, characterized in that a regulating roller that is brought into contact with the outer peripheral surface of the bearing This is the positioning structure.

According to the first aspect of the present invention, the urging means urges the developing roller in a direction in which the regulating member is pressed against the holding member. On the other hand, when the regulating member is in contact with the holding member, the displacement of the developing roller in the direction approaching the photosensitive drum is regulated. As a result, the developing roller is accurately positioned with respect to the photosensitive drum.

Further, according to the above configuration, since the regulating member is in contact with the holding member, the regulating member is strongly pressed against the photosensitive drum, as in the prior art, so that the tube portion of the photosensitive drum is formed. Is not deformed or scraped. Therefore, the position of the developing roller with respect to the photosensitive drum can be kept constant. Specifically, as described in claim 2, the holding member is formed of a bearing to which both ends of the photosensitive drum are fitted, and the regulating member is
The developing roller is constituted by regulating rollers provided rotatably at both ends of a rotating shaft of the developing roller.

Therefore, even when the photosensitive drum and the developing roller are rotated, the outer ring of the bearing and the regulating roller do not rotate, so that the bearing or the regulating roller is not scraped by the friction between the bearing and the regulating roller, and the photosensitive drum is not rotated. There is no change in the position of the developing roller. Further, even if the developing roller is strongly pressed by the urging means, if the outer peripheral portion of the bearing and the regulating roller are strong, the bearing and the regulating roller do not deform, so that the position of the developing roller with respect to the photosensitive drum does not change. .

Further, since the bearing is manufactured with high accuracy due to its nature, the developing roller can be accurately positioned with respect to the photosensitive drum. Furthermore, drive
When the rotational force is transmitted from the moving gear to the driven gear,
The developing roller uses the force acting on the rotating shaft of the
Is pressed against the drum, which causes the developing roller to
Claim 1 or 2 since the position is fixed relative to the drum.
In the device that adopts the positioning structure of
Bullets, such as coil springs, which elastically bias toward the body drum
No elastic member is required, compared to devices using this elastic member.
The number of component parts is reduced, and it is necessary to assemble the device.
The labor is reduced. According to a third aspect of the invention, there is provided a positioning method for positioning a developing roller to the photosensitive drum, holding member a predetermined portion of the developing roller, rotatably holding the peripheral surface of the photosensitive drum Abut
And drive gears provided at both ends of the photosensitive drum.
A to the driven gears provided at both ends of the developing roller.
Acts on the rotating shaft of the developing roller when the rolling force is transmitted.
Utilizing a part of the force, the regulating member
By urging the developing roller in the pressing direction,
Ri is a positioning method which is characterized in that the positioning of the developing roller against the photosensitive drum is performed.

In the method of positioning by contacting a predetermined portion of the developing roller with the peripheral surface of the photosensitive drum, when the photosensitive drum is deformed or when the mounting accuracy of the photosensitive drum is not good, the developing is performed. The roller cannot be positioned accurately. However, according to the method of the third aspect, since the positioning of the developing roller is performed by bringing a predetermined portion of the developing roller into contact with the holding member, if the holding member is manufactured with high accuracy, the photosensitive drum can be used. On the other hand, the developing roller can be accurately positioned. Also drive gear
When the rotational force is transmitted from the
The developing roller uses the force acting on the rotating shaft to turn the photosensitive drum
, Which causes the developing roller to
The position is fixed with respect to
With the developing device, the developing roller is elastically
There is no need for an elastic member such as a coil spring
The number of component parts is smaller than that of a device using
Dullness and labor required for assembling the device are reduced.

According to a fourth aspect of the present invention , drive gears are provided at both ends.
A photosensitive drum for forming an electrostatic latent image on the surface thereof ; and a photosensitive drum arranged in parallel with the photosensitive drum.
At the end, a driven gear meshing with the drive gear is provided.
It is a developing roller for supplying the developer to the surface of the photosensitive drum, the developing low relative to the photosensitive drum
And a positioning structure for positioning the
An image, wherein the positioning structure according to claim 1 or 2, or a positioning structure for positioning the developing roller with respect to the photosensitive drum by the positioning method according to claim 3 is applied. It is a forming device.

According to the fourth aspect, the developing roller is accurately positioned with respect to the photosensitive drum.
The supply amount of the developer to the photosensitive drum can be made appropriate. Therefore, a problem such as uneven density due to uneven supply of the developer does not occur in the formed image. Also,
Coil spring that elastically urges the roller toward the photosensitive drum
No elastic member such as
The number of component parts is reduced compared to the conventional image forming apparatus.
The time required for assembling the equipment can be reduced.
You.

[0019]

An embodiment of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view schematically showing the internal configuration of a digital full-color printer according to an embodiment of the present invention. With reference to FIG. 1, this digital full-color printer
Transport mechanism 43 for transporting the toner in a straight line, and transport mechanism 4
4 for black, magenta, cyan and yellow arranged in a line along the paper transport path formed by
Image forming units 10B, 10M, 10C, 10Y
(Hereinafter, when collectively referred to as “image forming unit 10”
That. ), Black, magenta, cyan, and cyan formed on the photosensitive drums 11B, 11M, 11C, and 11Y (hereinafter, collectively referred to as “photosensitive drums 11”) included in each image forming unit. This is a so-called tandem-type full-color printer that obtains a full-color image by sequentially superimposing and transferring a yellow toner image onto one sheet of paper P.

More specifically, the transport mechanism 43 includes:
Drive roller 4 arranged downstream with respect to the paper transport direction
4, a driven roller 45 disposed on the upstream side, an endless transport belt 46 wound around the drive roller 44 and the driven roller 45, and auxiliary rollers 47 to 49 for suppressing the deflection of the transport belt 46. It is included. When the driving roller 44 is driven to rotate, the paper P on which the toner image is transferred
Indicates that the arrow 9 is set on the upper surface of the conveyor belt 46.
It is conveyed linearly in eight directions.

Below the upper conveyor belt 46, a black transfer roller 50B, a magenta transfer roller 50M, a cyan transfer roller 50C, and a yellow transfer roller 50Y are provided at positions facing the photosensitive drums 11B, 11M, 11C, and 11Y, respectively. Are located. These transfer rollers 50B, 50M, 50C, and 50Y are transport belts 46.
Is pressed from below onto the photosensitive drums 11B, 11M, 11C and 11Y.

A belt cleaner 17 is provided below the driving roller 44 for removing dirt such as toner and paper powder attached to the surface of the conveyor belt 46. In this embodiment, the transport mechanism 43, the transfer rollers 50B, 50
M, 50C, 50Y and the belt cleaner 17 are held by a unit case 41 to form a transfer belt unit 40. The transfer belt unit 40 can be moved back and forth with respect to the printer main body 2 by slide mechanisms 42 provided on both right and left sides of the unit case 41 in FIG.

On the other hand, below the transfer belt unit 40, a sheet feed tray 3 capable of storing a plurality of sheets P is provided. In connection with the paper feed tray 3, a paper feed roller 5 for feeding out the paper P one by one from the paper feed tray 3 onto the transport path 4 is provided. The paper P sent out onto the transport path 4 by the rotation of the paper feed roller 5 is transported by the transport roller 6 toward the registration roller 7. The registration roller 7 is disposed on the upstream side of the transfer belt unit 40 with respect to the transport direction of the paper P, and once stops the transported paper P, forms a toner image in the black image forming unit 10B (described later). The sheet P is sent out onto the conveyor belt 46 at the same timing as the sheet P.

Above the image forming unit 10, a black laser scanning unit 2 for irradiating the photosensitive drums 11B, 11M, 11C and 11Y with laser beams, respectively.
0B, a magenta laser scanning unit 20M, a cyan laser scanning unit 20C, and a yellow laser scanning unit 20Y. The printer body 2 is connected to an external device (not shown) such as a microcomputer. Image data input from an external device is separated into digital color image data representing the density of each color component of black, magenta, cyan, and yellow, and then laser scanning units 20B, 20M, and 20 corresponding to the respective colors.
C, 20Y.

When the black image data is supplied to the black laser scanning unit 20B, a laser beam corresponding to the supplied black image data is generated from a laser light source (not shown). This laser beam is reflected by a polygon mirror 21 rotating at a predetermined high speed, and guided to a first reflecting mirror 23 via a lens 22. The light path of the light guided to the first reflecting mirror 23 is turned back by the first reflecting mirror 23 and the second reflecting mirror 24 and guided to the third reflecting mirror 25. Then, the optical path is bent downward by the third reflecting mirror 25 and is incident on the black image forming unit 10B.

In the black image forming unit 10B,
A photosensitive drum 11B is provided which rotates at a constant speed in the direction of an arrow (clockwise in FIG. 1) during image formation.
Around the photosensitive drum 11B, a main charger 12B, a black developing unit 13B, and a cleaner 14B are arranged in this order along the rotation direction. The laser beam incident from the black laser scanning unit is
Main charger 12B and black developing unit 13B
Is irradiated on the surface of the photosensitive drum 11B.

After the surface of the photosensitive drum 11B is charged to a uniform predetermined potential by the discharge of the main charger 12B, it is exposed to a laser beam incident from the black laser scanning unit 20B. Then, the charged charge in the exposed portion escapes, and a high potential portion and a low potential portion are generated on the surface of the photosensitive drum 11B, so that a so-called electrostatic latent image is formed.

Photosensitive drum 11B on which an electrostatic latent image is formed
Next, the black toner is attached to a portion having a low potential, facing the black developing unit 13B. More specifically, the black developing unit 13B includes a developing roller 15, a sub-roller 16,
6 and a stirrer 87 are provided. Stirrer 87
Is for agitating the toner in the black developing unit 13B to uniformly apply the toner to the developing roller 15 and the sub-roller 16.

In the black developing unit 13B, a non-magnetic one-component black toner is stored. When the developing roller 15 and the sub-roller 16 are respectively rotated in predetermined directions, the toner is transferred to the developing roller 15 and the sub-roller 16. The toner is charged by friction with the sub-roller 16 and mainly adheres to the surface of the developing roller 15. At this time, the rotation of the sub roller 16 helps the toner to adhere to the surface of the developing roller 15. The toner adhering to the surface of the developing roller 15 forms a thin layer regulated to a certain thickness by the thin layer blade 86.

The developing roller 15 having the toner layer formed thereon is
The toner layer is rotated at a speed higher than the peripheral speed of the photoconductor drum 11B to bring the toner layer into contact with the surface of the photoconductor drum 11B. A predetermined voltage is applied to the developing roller 15, and the potential of the developing roller 15 is lower than the potential of the unexposed portion of the photosensitive drum 11B and higher than the potential of the exposed portion. . Therefore, when the photosensitive drum 11B comes into contact with the toner layer on the developing roller 15, the charged toner on the developing roller 15 is transferred to the photosensitive drum 11B.
The process moves to the exposure portion B (low potential portion), and the electrostatic latent image on the photosensitive drum 11B is visualized as a toner image.

When the photosensitive drum 11B is further rotated, the black toner image formed on the surface of the photosensitive drum 11B faces the transfer belt unit 40. On the other hand, the registration roller 7 is driven to rotate at a timing synchronized with the opposition of the toner image to the transfer belt unit 40, and the paper P is sent by the transport belt 46.
A predetermined voltage is applied to the black transfer roller 50B disposed below the transport belt 46, and the black toner on the surface of the photoconductor drum 11B is attracted to the black transfer roller 50B and the upper surface of the paper P Move on to
As a result, the black toner image is transferred onto the paper P. The toner remaining on the surface of the photosensitive drum 11B after the transfer is collected by the cleaner 14B.

Paper P on which a black toner image has been transferred
Is transported by the transport belt 46 toward the magenta image forming unit 10M. When all the black image data is input to the black laser scanning unit 20B,
Next, the magenta image data is transferred to the magenta laser scanning unit 2.
0M is input. Then, a laser beam corresponding to the magenta image data is generated from a laser light source (not shown). The laser beam is reflected by the polygon mirror 26, passes through the lens 27, and the optical path is bent downward by the fourth reflecting mirror 28, and is incident on the magenta image forming unit 10M.

In the magenta image forming unit 10M,
The photosensitive drum 11M, the main charger 12M, the magenta developing unit 13M, and the cleaner 14M are provided, and a magenta toner image is formed on the surface of the photosensitive drum 11M through the same process as in the case of black. The magenta toner image is transferred to a magenta transfer roller 50 facing the photosensitive drum 11M with the conveyance belt 46 interposed therebetween.
By the action of M, the black toner image is transferred onto the sheet P on which the black toner image has been transferred.

When the input of the image data to the magenta laser scanning unit 20M is completed, the cyan image data is input to the cyan laser scanning unit 20C. Then, a laser beam generated from a laser light source (not shown) based on cyan image data is reflected by the polygon mirror 29 and passes through the lens 30, after which the fifth reflecting mirror 31, the sixth reflecting mirror 32, and the seventh The reflection mirror 33 guides the image to the cyan image forming unit 10C.

The cyan image forming unit 10C includes a photosensitive drum 11C, a main charger 12C, a cyan developing unit 13C, and a cleaner 14C. The cyan image formed on the surface of the photosensitive drum 11C in the same manner as described above. Is transferred to the sheet P on which the magenta toner image is transferred by the action of the cyan transfer roller 50C facing the photosensitive drum 11C with the transport belt 46 interposed therebetween.
It is transcribed on top of it.

When the input of the image data to the cyan laser scanning unit 10C is completed, the yellow image data is input to the yellow laser scanning unit 20Y. A laser beam generated from a laser light source (not shown) based on yellow image data is
After being reflected at 4 and passing through the lens 35, the light is guided to the yellow image forming unit 10Y by the eighth reflecting mirror 36, the ninth reflecting mirror 37, and the tenth reflecting mirror 38.

In the yellow image forming unit 10Y,
The photosensitive drum 11Y, the main charger 12Y, the yellow developing unit 13Y, and the cleaner 14Y are provided. The yellow toner image formed on the surface of the photosensitive drum 11Y in the same manner as described above By the function of the yellow transfer roller 50Y facing the body drum 11Y, the cyan toner image is transferred onto the sheet P on which the cyan toner image has been transferred.

As described above, the tandem type full-color image forming apparatus has a configuration in which the toner images of the respective colors are superimposedly transferred onto the sheet P while the sheet P is conveyed substantially linearly by the conveying belt 46. When transfer misregistration occurs in each color toner image, color misregistration occurs in a formed image. Therefore, in the digital full-color printer according to the present embodiment, various measures are taken to prevent transfer deviation.

For example, by making the interval between the photosensitive drums adjacent to each other (the interval between transfer positions) substantially equal to the outer diameter of the photosensitive drums, color misregistration hardly occurs. Further, by making the outer diameter of the drive roller for running the transport belt 46 substantially equal to the outer diameter of the photosensitive drum, it is possible to prevent a synchronous deviation between the paper transport speed and the peripheral speed of the photosensitive drum. .

As described above, the paper P on which the toner images of the respective colors are transferred in an overlapping manner is separated from the conveyor belt 46 by the discharge of the separation charger 19, and the fixing unit 80
It is led to. The fixing unit 80 includes two rollers 8
The heat fixing belt 83 includes a heat fixing belt 83, a heat roller 84 for heating the heat fixing belt 83, and a lower roller 85 provided below the heat fixing belt 83.

The heat fixing belt 83 is pressed against the lower roller 85 at an appropriate pressure near the downstream end in the sheet conveying direction, and is arranged so as to extend toward the upstream side. As a result, the toner of each color on the sheet P conveyed toward the fixing unit 80 is pre-heated by the heat of the heat fixing belt 83 before reaching the nip position between the heat fixing belt 83 and the lower roller 85. After being heated, it is heated and pressed by the heat fixing belt 83 and the lower roller 85 and is fixed on the paper P. Therefore, the toner on the sheet P is sufficiently melted, and the surface of the toner image after the fixing process becomes flat, and the color developability of the color image is improved. The paper P after the fixing process is discharged by discharge rollers 8 and 9 to a discharge section 18 formed on the upper surface of the printer main body 2.

The above is one cycle of the image forming operation when the full-color image is formed on the paper P. As a means for fixing the toner to the paper, a heat roller and a pressure roller, which have been widely used, may be adopted. However, in order to obtain the same effect as described above, the diameter of the heat roller is increased. Therefore, the above-described configuration using the thermal transfer belt 83 is more preferable from the viewpoint of miniaturization.

FIG. 2 is a plan sectional view schematically showing the structure of the photosensitive drum 11 and the developing unit. FIG. 3 is an exploded perspective view showing the configuration of the photoconductor drum 11, and shows only one side of the photoconductor drum 11 (the rear side when provided in the printer main body). Further, FIG.
FIG. 3 is a diagram when the image forming unit 10 is viewed from the front side of the printer main body 2, and a driving mechanism is omitted for simplicity.

In the following description, the black developing unit 13B, the magenta developing unit 13M, the cyan developing unit 13C, and the yellow developing unit 13Y
Are simply referred to as “developing unit 13”. Referring to FIGS. 2 and 3, photoconductor drum 11 has a cylindrical element tube 111 made of, for example, aluminum. A photosensitive layer 112 having a predetermined width is formed on the peripheral surface of the raw tube 111 by applying a photosensitive material. Raw tube 11
1 is exposed at both ends of the photosensitive drum 11,
The photoreceptor drum 11 is rotatably held by receiving the exposed tube portion by the pair of drum unit side plates 124 and 125.

Openings 113 and 114 at both ends of the photosensitive drum 11 (base tube 111) have drum flanges 1 respectively.
15, 116 are press-fitted and fixed. An input gear 117 to which the driving force from the motor 120 is input and a driving force from the developing roller 15 are provided on the drum flange 115 located on the right side (the rear side when the printer body 2 is provided) in FIG.
And a press-fit portion 119 (see FIG. 3) that is press-fitted into the photosensitive drum 11.
These are integrally formed.

An output gear 121 attached to an output shaft of a motor 120 is meshed with the input gear 117.
When the motor 120 is driven, the driving force of the motor 120 is given to the input gear 117 via the output gear 121,
The photosensitive drum 11 is driven to rotate. The other drum flange 116 includes a drum gear 122 for transmitting a driving force to the developing roller 15 and a press-fit portion (not shown) for press-fitting the photosensitive drum 11, both of which are integrally formed. Have been.

On the other hand, referring to FIG. 2, developing roller 15 and sub-roller 16 are rotatably held with a pair of side plates of developing unit housing 130 receiving developing roller shaft 128 and sub-roller shaft 129, respectively. ing. Developing roller gears 133 and 134 are attached to both end portions of the developing roller shaft 128 via one-way clutches 131 and 132, respectively. The developing roller gears 133 and 134 are respectively connected to the drum gear 11
The developing roller 15 is rotated when the photosensitive drum 11 rotates.

The developing roller gears 133 and 134 are
The developing roller 15 is formed to have a smaller diameter than the drum gears 118 and 122, so that the developing roller 15 is faster than the photosensitive drum 11. Specifically, the peripheral speed ratio S / D between the developing roller 15 and the photosensitive drum 11 is set to be, for example, S / D = 1.2 to 2.5. Thereby, the developing roller 1
5, the necessary and sufficient amount of toner is supplied to the photosensitive drum 11.

Inside the developing roller gears 133 and 134, regulating rollers 135 and 136 are provided rotatably with respect to the developing roller shaft 128, respectively. The regulating rollers 135 and 136 are respectively in contact with the outer peripheral surfaces of bearings 126 and 127 (described later) that hold both ends of the photosensitive drum 11, and when the amount of biting of the developing roller 15 into the photosensitive drum 11 is equal to or greater than a certain value. It is to regulate so that it does not become.

The developing roller shaft 128 is provided with a regulating roller 135 located at the back side when it is provided in the printer main body 2.
, A driving force transmission gear 137 is attached. The driving force transmission gear 137 is connected to the sub roller shaft 129.
The sub-roller 16 is engaged with the sub-roller gear 138 attached to the sub-roller 16 when the developing roller 15 rotates.

As described above, when the photosensitive drum 11 is rotationally driven, the rotational force is transmitted from the drum gears 118 and 122 to the developing roller gears 133 and 134, and a rotational force is applied to the developing roller 15 from both ends. . That is,
Since both ends of the developing roller 15 receive substantially equal rotational force, one end of the developing roller 15 does not rotate first. Therefore, the developing roller 15
Of the photosensitive drum 11
There is no such thing as leaning against. Therefore, the amount of the developing roller 15 biting into the photosensitive drum 11 can be kept uniform in the axial direction of the photosensitive drum 11 and the developing roller 15.

As described above, the developing roller gear 1
33, 134 are one-way clutch 131,
132 is attached to the developing roller shaft 128. When the developing roller gear 133 or the developing roller gear 134 and the developing roller shaft 128 rotate in opposite directions, the one-way clutches 131 and 132 allow relative rotation between the developing roller gear 133 or the developing roller gear 134 and the developing roller gear 133 or the developing roller gear 134. When the roller shaft 128 and the roller shaft 128 rotate in the same direction, relative rotation between the two is prevented. Developing roller shaft 128 and developing roller gear 13
Between the one-way clutch 131,
The presence of each of the 132 has the following advantages.

FIG. 5 shows one-way clutches 131 and 13.
FIG. 3 is an illustrative view for explaining a second function; In the case of applying a rotational force to the developing roller 15 from both sides, it is assumed that the developing roller shaft 128 and the developing roller gears 133 and 134 are engaged with each other as shown in FIG. That is, the drum gears 118 and 122 and the developing roller gear 13
As long as there is a backlash with the gears 3, 134, for example, the tooth surface 122a of the drum gear 122 on the near side in FIG.
Is in contact with the tooth surface 134 a of the developing roller gear 134, it is assumed that the tooth of the developing roller gear 133 that has entered the tooth groove of the drum gear 118 on the rear side does not contact the tooth surface of the drum gear 118. If the developing roller 15 continues to rotate in this state, as a result, the rotational force is input only from one side of the developing roller 15, and the merit of applying the rotational force to the developing roller 15 from both sides is obtained. May not be able to be withdrawn.

In this embodiment, one-way clutches 131 and 132 are interposed between the developing roller shaft 128 and the developing roller gears 133 and 134, respectively. Accordingly, under the above assumption, when the rotational force is transmitted from the drum gear 122 on the near side to the developing roller gear 134 and the developing roller shaft 128 is rotated, the developing roller gear 133 on the far side It becomes a free rotation state with respect to the rotation. That is, the developing roller shaft 1
Even if 28 is rotated, the developing roller gear 133 on the rear side does not rotate and remains stopped.

Then, the tooth surface 1 of the rear drum gear 118
When the rotational force is transmitted from the drum gear 118 to the developing roller gear 133, the developing roller gear 133 is rotated in the same direction as the developing roller shaft 128. Rotation is prevented, and the rotational force transmitted to the developing roller gear 133 is transmitted to the developing roller shaft 128.

Thus, by interposing the one-way clutches 131 and 132 between the developing roller shaft 128 and the developing roller gears 133 and 134, the driving force is transmitted to the developing roller 15 from only one side. Is prevented. However, when the drum gears 118 and 122 and the developing roller gears 133 and 134 are mounted with high precision so as not to be in the above-mentioned assumed state, the intervention of the one-way clutches 131 and 132 can be omitted. .

Referring to FIGS. 2 and 4, a pair of drum unit side plates 124 and 125 facing each other at a predetermined interval are provided.
Are formed with openings 139 and 140 at positions facing each other. Bearings 12 for rotatably holding the photosensitive drum 11 are provided in the openings 139 and 140.
6, 127 are fitted respectively, and the outer peripheral portion thereof is fixed. In the photosensitive drum 11, the raw tubes 111 exposed at both end portions are connected to the drum unit side plates 124, 1 respectively.
25 is rotatably held by being received by bearings 126, 127 provided in 25.

Thus, as compared with a configuration in which a drum shaft serving as a rotation center is passed through the photosensitive drum 11 and both ends of the drum shaft are held by bearings,
Runout can be reduced. Therefore, it is possible to reduce the possibility that a problem such as color shift occurs in the formed image. Further, as shown in FIG. 4, the drum unit side plates 124 and 125 are cut vertically downward from the upper end edges, and are further opened obliquely downward.
By cutting to 9,140, regulation roller 1
Guide portions 141 for guiding 35 and 136 are formed, respectively.

The developing unit 13 is connected to the drum unit side plate 1
When attaching to the control rollers 135, 1
36 is fitted from the upper end of the guide portion 141 and brought into contact with the outer peripheral surfaces of the bearings 126 and 127. Thus, the position of the developing roller 15 with respect to the photosensitive drum 11 is determined. As described above, the developing roller shaft 128 is attached to the bearings 126 and 127 that rotatably hold the photosensitive drum 11.
The developing roller 15 is contacted with the regulating rollers 135 and 136 provided on the
Is one of the features of this embodiment. According to this configuration, the following effects can be obtained.

The positional relationship between the developing roller 15 and the photosensitive drum 11 is determined by the bearings 126 and 127 and the regulating roller 1.
It is determined by the outer diameter of 35,136. Bearing 126,
127 and the regulating rollers 135 and 136 are manufactured with high accuracy due to their properties.
Can be accurately positioned with respect to the photosensitive drum 11.

Since the regulating rollers 135 and 136 are in contact with the bearings 126 and 127, respectively, the bearings 126 and 127 are deformed even if they are strongly pressed, so that the developing roller 15 bites into the photosensitive drum 11. The amount does not fluctuate. In addition, bearing 1
Since the outer rings 26 and 127 do not rotate, the bearing 12
6,127 and the friction between the control rollers 135,136,
Bearings 126, 127 or regulating rollers 135, 13
6 is removed, and the developing roller 15 with respect to the photosensitive drum 11 is
There is no fluctuation in the amount of bite. Therefore, the variation in the amount of the developing roller 15 biting into the photosensitive drum 11 does not change the supply amount of the developer to the photosensitive drum 11, and a defect such as density unevenness occurs in the formed image. The fear can be eliminated.

In addition to the developing roller 15, the main charger 12, the cleaner 14, and the transfer rollers 50B, 50
M, 50C, 50Y, etc. may be positioned with respect to the photosensitive drum 11 by bringing predetermined portions into contact with bearings 126, 127, respectively. Since the bearings 126 and 127 are manufactured with high accuracy,
Each of the above members can be accurately positioned with respect to the photosensitive drum 11.

In order to fix the position of the developing roller 15 with respect to the photosensitive drum 11, means for urging the developing roller 15 toward the photosensitive drum 11, in other words, the regulating rollers 135 and 136 127 is required. As the urging means, in the conventional apparatus, an elastic member (for example, a coil spring) for elastically urging the developing roller 15 toward the photosensitive drum 11 is provided.

However, in this embodiment, an elastic member for elastically urging the developing roller 15 toward the photosensitive drum 11 is not provided.
The developing roller 15 is moved to the photosensitive drum 11 by utilizing the forces received by the
Pressing toward. This eliminates the need for a conventionally used elastic member, and can simplify the structure of the developing unit 13.

The mechanism by which the developing roller 15 is pressed toward the photosensitive drum 11 will be described below. FIG.
FIG. 5 is a diagram for describing the force that the developing roller gears 133 and 134 receive from the drum gears 118 and 122, respectively. FIG. 7 is a diagram for describing the force that the developing roller 15 receives from the photosensitive drum 11.
Further, FIG. 8 is a diagram for describing the force that the developing roller shaft 128 receives.

Referring to FIG. 6, when drum gears 118 and 122 are rotated clockwise by the driving force of motor 120 (see FIG. 2), developing roller gears 133 and 134 meshing with drum gears 118 and 122, respectively. Is rotated counterclockwise. At this time, the developing roller gear 13
The teeth 3134 receive a force fg in the direction of the arrow from the teeth of the drum gears 118 and 122.

When a driving force is transmitted from the drum gears 118 and 122 (see FIG. 6) to the developing roller gears 133 and 134, the developing roller 15 rotates counterclockwise in FIG. Then, the developing roller 15 and the photosensitive drum 11
And the developing roller 15 receives a frictional force f _D1 from the photosensitive drum 11. Further, at this time, since the developing roller 15 is pressed against the photosensitive drum 11, the developing roller 15 receives a drag f _D2 from the photosensitive drum 11 toward the center of the developing roller 15. Therefore, the developing roller 15
Receives a resultant force f _D of the frictional force f _D1 and drag f _D2 from the photosensitive drum 11.

As described above, the developing roller gears 133, 13
4 receives the force fg from the drum gears 118 and 122,
Developing roller 15 is subjected to the force f _D from the photosensitive drum 11. As a result, the developing roller shaft 128, as shown in FIG. 8, the resultant force F of the force fg and the force f _D acts. FIG.
Indicates that the force F received by the developing roller shaft 128 is
FIG. 5 is a diagram for explaining a mechanism for converting a force into a direction approaching the photosensitive drum 11.

Referring to FIGS. 4 and 9, regulating rollers 135 and 136 attached to developing roller shaft 128 are in contact with bearings 126 and 127, respectively, while guiding rollers formed on drum unit side plates 124 and 125. Part 1
41 is supported by the lower surface 142 (support surface 142) of the inclined portion. As a result, the force F acting on the developing roller shaft 128 is divided into a force f _{1 in a} direction perpendicular to the support surface 142 and a force f _{2 in a} direction parallel to the support surface 142. The force f ₂ in the direction parallel to the support surface 142 is
Since 5,136 is the direction of the force closer to the bearing 126 and 127, by the force f _2, the regulating rotatable member 13
5,136 are pressed against bearings 126,127, respectively.

As described above, the developing roller gears 133, 13
4, when the driving force is transmitted from the drum gears 118 and 122 to the developing roller shaft 128,
Since the regulating rollers 135 and 136 are pressed against the bearings 126 and 127, the urging means required for the conventional device is not required, and the number of parts can be reduced. Therefore, the labor required for assembling the device can be reduced.

The angle Q of the support surface 142 is determined by the fact that the force F acting on the developing roller shaft 128 is
May be converted into a force acting in a direction of pressing the bearing against the bearings 126 and 127, and a line connecting the developing roller shaft 128 and the rotation center 143 of the photosensitive drum 11 and the support surface 142 are parallel to each other. It is preferable that the angle be an appropriate angle.

[0072] Although as described above the description of an embodiment of the present invention, the present invention is not name limited to the embodiments described above.

For example , in the above embodiment, a digital full-color printer is described as an example. However, the present invention is not limited to a digital full-color printer, but may be an analog full-color printer, a digital or analog full-color copying machine. The present invention can be applied to a full-color image forming apparatus such as a printer, a mono-color image forming apparatus that forms only a single-color image, and the like.

In addition, various changes can be made within the scope described in the claims.

[0075]

According to the first to third aspects of the present invention, the developing roller can be accurately positioned with respect to the photosensitive drum. According to the fourth aspect of the invention, since the developing roller is accurately positioned with respect to the photosensitive drum, the supply amount of the developer to the photosensitive drum can be made appropriate. Therefore, a problem such as uneven density due to uneven supply of the developer does not occur in the formed image.

[Brief description of the drawings]

FIG. 1 is a simplified cross-sectional view showing the internal configuration of a digital full-color printer according to an embodiment of the present invention.

FIG. 2 is a plan cross-sectional view schematically showing a configuration of a photosensitive drum and a developing unit.

FIG. 3 is an exploded perspective view illustrating a configuration of a photosensitive drum.

FIG. 4 is a diagram when the image forming unit is viewed from the front side of the printer body.

FIG. 5 is an illustrative view for explaining a function of a one-way clutch;

FIG. 6 is an illustrative view for explaining a force that a developing roller gear receives from a drum gear;

FIG. 7 is an illustrative view for explaining a force that a developing roller receives from a photosensitive drum;

FIG. 8 is an illustrative view for explaining a force applied to a developing roller shaft;

FIG. 9 is an illustrative view for explaining a mechanism for converting a force applied to a developing roller shaft into a force in a direction in which the developing roller approaches a photosensitive drum;

[Explanation of symbols]

 2 Printer body 10B, 10M, 10C, 10Y Image forming unit 11B, 11M, 11C, 11Y Photoconductor drum 15 Developing rollers 126, 127 Bearing 128 Developing roller shaft 135, 136 Control roller

────────────────────────────────────────────────── ─── Continuing on the front page (72) Kazuya Uehira, 1-2-28 Tamazo, Chuo-ku, Osaka-shi, Osaka Prefecture Inside Mita Kogyo Co., Ltd. No. 28 of Mita Kogyo Co., Ltd. (72) Inventor Noriaki Miyamoto 1-2-28 Tamatsukuri, Chuo-ku, Osaka City, Osaka Prefecture Mita Kogyo Co., Ltd. (56) References JP-A-55-98773 A) JP-A-2-29763 (JP, A) JP-A-7-160095 (JP, A) JP-A-63-188664 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) ) G03G 15/08-15/095

Claims (4)

(57) [Claims] 1. A positioning structure for positioning the developing roller to the photosensitive drum, are engaged with the peripheral surface of both ends of the photosensitive drum, the holding member for rotatably holding the photosensitive drum If the direction is provided on the developing roller, abuts on the holding member, a regulating member for regulating the approaching distance of the developing roller against the photosensitive drum, that the regulating member is pressed by the holding member a and a biasing means for biasing the current <br/> image roller, the biasing means is provided at both ends of the photosensitive drum
Driven gears provided at both ends of the developing roller from the drive gear
When the rotational force is transmitted to the rotating shaft of the developing roller
Utilizing the acting force to bias the developing roller
Positioning structure, characterized in that it. Wherein said retaining member is fitted over the bearing on the peripheral surface of both ends of the photoreceptor drum, the developing roller is rotating shaft projects from both ends, the regulating member, the developing roller 2. The positioning structure according to claim 1, wherein the control rollers are rotatably provided on the rotation shafts at both ends of the bearing and are in contact with the outer peripheral surface of the bearing. 3. A positioning method for positioning a developing roller to the photosensitive drum, the predetermined portion of the developing roller, abutting the holding member for rotatably holding the peripheral surface of the photosensitive drum Let me know
Drive gears provided at both ends of the photosensitive drum
The rotational force is transmitted to driven gears provided at both ends of the image roller.
Part of the force acting on the rotating shaft of the developing roller when
Utilizing the restriction member pressed by the holding member
Positioning method characterized by Ri especially good for urging the developing roller to the direction, the positioning of the developing roller against the photosensitive drum is performed. 4. A drive gear provided at both ends, a photosensitive drum for forming an electrostatic latent image on a surface thereof, and a drive gear disposed in parallel with the photosensitive drum, and the drive gear provided at both ends thereof.
A driven gear for meshing with the moving gear ; a developing roller for supplying a developer to the surface of the photosensitive drum; and a developing roller for positioning the developing roller with respect to the photosensitive drum.
And a because of the positioning structure, as the positioning structure, a positioning structure for positioning the claim 1 or the positioning structure 2 described or the developing roller against the photosensitive drum by a positioning method according to claim 3, applied an image forming apparatus characterized in that it is.