JPH11143160A - Unit positioning mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a unit positioning mechanism which ensures unit positioning accuracy for a long period of time without a cost increase and also reduces workload in maintenance. SOLUTION: When a photoreceptive drum (first unit) 1 and a developing device (second unit) 4, which moves close/apart to/from the photoreceptive drum 1, are close to each other, the photoreceptive drum 1 and developing device 4 are positioned in relation to each other. Also, the unit positioning mechanism is composed of positioning means (butting block 103 and butting roller 105) which take several positions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning mechanism for a unit such as a developing device which moves toward and away from an image carrier in an image forming apparatus such as a copying machine, a facsimile, and a printer.

[0002]

2. Description of the Related Art A developing unit of an image forming apparatus is an example of a unit which can be brought into contact with and separated from another unit and is positioned under pressure with respect to the other unit. explain.

In a developing device of an image forming apparatus, a developing roller as a developer carrier is disposed with a predetermined gap formed between the developing roller and a photosensitive drum as an image carrier, and toner on the developing roller is transferred onto the photosensitive drum. A non-contact developing method of flying an electrostatic latent image as a toner image by flying onto the electrostatic latent image is often used.

In a developing device adopting such a non-contact developing method, an abutting member provided on a developing roller side abuts against an abutted member provided on a photosensitive drum side, and the developing device itself is connected to the photosensitive drum side. To maintain the gap between the developing roller and the photosensitive drum with high accuracy.

For example, in a multicolor image forming apparatus having a plurality of developing devices around a photosensitive drum, only a developing device having a desired toner is moved from the standby position to the developing position toward the photosensitive drum. The positioning of the photosensitive drum and the developing position is performed by abutting the abutting members provided at the front and rear two places on the developing roller side against the abutted members provided at the front and rear two places on the photosensitive drum side opposed thereto. This is performed by pressing the photosensitive drum.

[0006]

However, in the developing device in which the gap between the photosensitive drum and the developing roller is kept constant via the abutting member and the abutted member as described above, the developing device is The abutting portion of the abutted member is worn by long-term use due to the pressing force when the abutting member is abutted against the side, so that the gap between the photosensitive drum and the developing roller changes, and the image quality is degraded.

As a specific example of the deterioration of the image quality, when the gap between the photosensitive drum and the developing roller becomes smaller than a predetermined value due to wear of the contact portion, it appears as a change in the entire image density, or the contact portion before and after the contact portion. In the case where the wear amounts are different, there is a phenomenon that appears as image density unevenness.

In order to solve such a problem, there is a method of increasing the surface hardness of the abutting member and the abutted member to improve their wear resistance. However, such a method is disadvantageous in cost. Not effective for long-term use. Therefore, the amount of wear of the abutting member and the abutted member is checked at the time of maintenance, and a member having a large amount of abrasion is replaced with a new member, so that the maintenance burden is very large.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its object is to guarantee the positioning accuracy of a unit for a long period of time without increasing the cost and to reduce the burden of maintenance. It is an object of the present invention to provide a unit positioning mechanism capable of performing such operations.

[0010]

In order to achieve the above object, the invention according to claim 1 is characterized in that a first unit and a second unit that moves close to and away from the first unit are close to each other. In addition, the unit positioning mechanism is configured to perform positioning between the two units and to provide a positioning unit capable of taking a plurality of positions with respect to the unit in at least one of the first unit and the second unit.

According to a second aspect of the present invention, in the first aspect of the invention, when the second unit moves close to the first unit, the two units come into contact with each other, and the positions of the two units are determined. And a second contact surface at a position slightly retreated from the contact surface.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the first unit is a unit having an image carrier, and the second unit is a developing unit. I do.

According to a fourth aspect of the present invention, in the first, second or third aspect, the first unit is a drum unit having a photosensitive drum, and the second unit is a developing unit. And

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the positioning means is fixed coaxially with a rotation axis of a drum unit having a photosensitive drum.
It has first and second positioning surfaces coaxial with the rotation axis.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the positioning means is rotatably fixed coaxially with a rotating shaft of a drum unit having a photosensitive drum, and has a plurality of positions in a rotating direction. It is characterized by being fixable to.

[0016]

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

FIG. 1 is a schematic sectional view of a full-color image forming apparatus. The full-color image forming apparatus has a digital image reader section at an upper portion and a digital color image printer section at a lower portion.

In the digital image reader, the original 30 is placed on an original platen glass 31 and is exposed and scanned by an exposure lamp 32 so that a reflected light image from the original 30 is condensed on a full-color CCD sensor 34 by a lens 33. To obtain a color separation image signal. Then, this color separation image signal is processed by a video processing unit (not shown) through an amplification circuit (not shown) and sent to a digital color image printer unit.

In the digital color image printer section, a photosensitive drum 1 as an image carrier is rotatably supported in the direction of the arrow shown in the figure. Around the photosensitive drum 1, a pre-exposure lamp 11, a corona charger 2, A laser exposure optical system 3, a potential sensor 12, four developing units 4y having different colors,
4c, 4m, 4bk, on-drum light amount detecting means 13, transfer device 5, and cleaning device 6 are arranged.

In the laser exposure optical system 3, the image signal from the reader unit is converted into an optical signal by a laser output unit (not shown), and the laser light converted into the optical signal is reflected by the polygon mirror 3a, and the lens 3b And is projected on the surface of the photosensitive drum 1 through the mirror 3c.

At the time of image formation in the printer section, the photosensitive drum 1 is rotated in the direction of the arrow shown in the figure, and the photosensitive drum 1 whose charge has been removed by the pre-exposure lamp 11 is uniformly charged by the corona charger 2. Light image E for each separation color
Is irradiated to form a latent image on the photosensitive drum 1.

Next, predetermined developing units (4y, 4c, 4m,
4b) is operated, the latent image on the photosensitive drum 1 is developed, and a toner image based on a resin and a pigment is formed on the photosensitive drum 1. The developing units 4y, 4c, 4m, 4
bk is configured to selectively approach the photosensitive drum 1 according to each separation color by the operation of the eccentric cams 24y, 24c, 24m, and 24bk.

On the other hand, the recording material is supplied from the recording material cassette 7 to a position (transfer position) corresponding to the photosensitive drum 1 via the transport system and the transfer device 5, and is placed on the recording material.
The upper toner image is transferred.

The transfer device 5 includes a transfer drum 5a, a transfer charger 5b, and an adsorption charger 5 for electrostatically adsorbing a recording material.
c, a transfer roller 5g having an attraction roller 5g, an inner charger 5d, and an outer charger 5e facing the attraction charger 5c, and is rotatably driven so that the transfer drum 5a has a circumferential opening area formed of a dielectric material. The recording material carrying sheet 5f is integrally stretched in a cylindrical shape. Here, a dielectric sheet such as a polycarbonate film is used as the recording material supporting sheet 5f.

In the transfer device 5, the transfer drum 5
As a is rotated, the toner image on the photosensitive drum 1 is transferred by the transfer charger 5b onto the recording material carried on the recording material carrying sheet 5f. As described above, a desired number of color images are transferred to the recording material conveyed while being electrostatically attracted to the recording material carrying sheet 5f, thereby forming a full-color image.

In the case of full-color image formation, when the transfer of the four color toner images to the recording material is completed as described above,
Separation claw 8a, separation push-up roller 8b and separation charger 5h
The recording material is separated from the transfer drum 5a by the action of
The toner image is sent to the heat roller fixing device 9 and is fixed.
The recording material on which the toner image has been fixed is discharged out of the apparatus and stacked on the discharge tray 10. In addition, the photosensitive drum 1 after the transfer
After the residual toner on the surface is cleaned by the cleaning device 6,
The image is again subjected to the image forming process.

When an image is formed on both sides of the recording material, the conveyance path switching guide 19 is driven immediately after the recording material passes through the heat roller fixing device 9, and the recording material is reversed through the conveyance vertical path 20. After the recording material is once guided to the path 21a, the reversing roller 21b is rotated in the reverse direction, and the recording material is retracted in a direction opposite to the direction in which the recording material is fed, with the rear end leading, and stored in the intermediate tray 22. Thereafter, an image is formed on the other surface of the recording material through the above-described image forming step again.

The recording material supporting sheet 5 of the transfer drum 5a
f, a backup brush 15 and an oil facing the fur brush 14 via the fur brush 14 and the recording material supporting sheet 5f in order to prevent scattering and adhesion of powder such as toner on the recording medium f. The recording material carrying sheet 5f is cleaned by the action of the backup brush 17 facing the oil removing roller 16 via the removing roller 16 and the recording material carrying sheet 5f. Such cleaning is performed before or after image formation, and is performed at any time when a jam (paper jam) occurs.

In this embodiment, the eccentric cam 25 is operated at a desired timing, and the cam follower 5i integrated with the transfer drum 5a is operated.
The gap between the recording material carrying sheet 5f and the photosensitive drum 1 can be arbitrarily set. For example, during standby or when the power is off, the interval between the transfer drum 5a and the photosensitive drum 1 is increased.

FIGS. 2 and 3 show the developing units 4 (4y, 4c, 4).
m, 4bk) and a sectional view of the photosensitive drum 1. FIG. 2 shows a state in which the developing device 4 is in a non-operating position (a state in which the developing device 4 and the photosensitive drum 1 are separated), and FIG. Indicates a state in which the developing unit 4 and the photosensitive drum 1 are in the contact pressing position.

The positioning between the developing device 4 and the photosensitive drum 1 is performed by bringing a contact roller 105 provided coaxially with the developing sleeve 104 into contact with a contact block 103 fixed coaxially with the rotating shaft 101 of the photosensitive drum 1. It is done by things. The abutting block 103 and the abutting roller 105 have the same configuration before and after the apparatus. The butting block 103 rotatably supports the photosensitive drum 1 via a bearing 102. The abutment block 013 is formed in an arcuate curved shape with the rotation shaft 101 as a center, and the color developing units 4y, 4y,
Abutment portions corresponding to 4c, 4m, and 4bk are provided on the periphery.

In the above configuration, when the developing device 4 operates, the eccentric cams 24 (24y, 24c, 24m, 24b)
k), the developing device 4 is moved and pressurized in the direction of arrow A in the drawing to be in the contact pressurized state shown in FIG.

Here, the radius of the abutting block 103 and the abutting roller 15 is determined by the photosensitive drum 1 and the developing sleeve 104.
Is set larger than the sum of the radii by a predetermined gap,
As a result, the gap between the photosensitive drum 1 and the developing sleeve 104 is maintained with high accuracy.

The abutting block 103 has an abutting portion 103a for abutting rollers 105 and an abutting portion 103a.
The abutting confirming unit 10 in which only L shown in FIG.
3b is formed.

The abutting portion 103a is abutted and pressed by the abutting roller 105 during operation of the developing device 4, so that the abutting portion wears out due to long-term use. By confirming the amount, it is possible to accurately grasp the replacement time of the butting block 103. Specifically, when the abutment section 103a has been worn down to the check section 103b, it is determined that the abutment block 103 is to be replaced. In order to prevent the deterioration of the image quality, the step L should be 30 to 50 μm.
It is desirable to set to about.

The abutting roller 105 is used for the developing sleeve 10.
4, so that the abutment block 10
Wear does not concentrate on one point of the contact part as in 3,
Therefore, the abrasion of the butting roller 105 does not matter.

As described above, according to the present embodiment, not only can the timing of component replacement be accurately grasped only by visually checking the abrasion state of the abutting portion, but also the deterioration of image quality can be prevented beforehand. Therefore, the burden of maintenance can be greatly reduced.

Next, a method of fixing the butting block 103 will be described with reference to FIG. FIG. 4 shows the developing device 4 (4
(y, 4c, 4m, 4bk) and a sectional view around the photosensitive drum 1.

Photosensitive drum unit 2 including photosensitive drum 1
Reference numeral 00 is fixed to the apparatus main body around the rotation shaft 101 by a unit front plate 201 and a rear plate (not shown). The abutment block 103 is fixed to the unit front side plate 201 with the bearing 102 as a center. The abutment block 103 is formed with positioning holes 202a, 202b, and 202c concentrically around the bearing 102. The unit front side plate 201 is integrally provided with positioning pins 201a that fit into one of the positioning holes 202a to 202c.

When the abutment block 103 is fixed to the unit side plate (the unit front side plate 201 and the unit rear side plate not shown), the abutment block 103 is formed by a plurality (three in this embodiment) formed on the unit. The positioning hole 2
In this configuration, the abutment block 103 can be fixed at a position indicated by a two-dot chain line shown in FIG. The same configuration is adopted for a unit rear side plate and a rear abutment block (not shown).

Here, as described above, when the abutment portion 103a of the abutment roller 105 (see FIGS. 2 and 3) of the abutment block 103 is worn due to long-term use, the abutment block 103 is removed. By changing the fixing position without replacement, a gap between the photosensitive drum 1 and the developing sleeve 104 can be guaranteed, and high image quality can be maintained without increasing costs. Therefore, the maintenance burden can be reduced. The abutting portion 103a of the abutting block 103 is attached to the checking portion 103 shown in FIGS.
If b is provided, it is more effective.

[0042]

As is apparent from the above description, according to the present invention, when the first unit and the second unit that moves close to and away from the first unit come close to each other, And a unit positioning mechanism is provided in at least one of the first unit and the second unit for positioning the unit at a plurality of positions with respect to the unit. Is ensured over a long period of time, and the effect of reducing the burden on maintenance can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a full-color image forming apparatus.

FIG. 2 is a cross-sectional view of a developing device and a photosensitive drum (a state in which the developing device is at a non-operating position).

FIG. 3 is a cross-sectional view of the developing device and the photosensitive drum (a state where the developing device and the photosensitive drum are at a contact pressing position).

FIG. 4 is a cross-sectional view around a developing device and a photosensitive drum.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum (image carrier: first unit) 4 developing unit (second unit) 101 rotating shaft of drum unit 103 butting block (positioning means) 103a butting part (first abutting surface) 103b checking part (Second contact surface) 105 Butting roller (positioning means)

Claims (6)

[Claims] When a first unit and a second unit that moves close to and away from the first unit approach each other, positioning between the two units is performed, and a plurality of positions can be taken with respect to the unit. A unit positioning mechanism, wherein positioning means is provided in at least one of the first unit and the second unit. 2. The positioning means has a first contact surface on which the two units come into contact when the second unit moves close to each other, and the positions of the two units are determined. 2. The unit positioning mechanism according to claim 1, further comprising a second contact surface at a position where the unit is retracted. 3. The unit positioning mechanism according to claim 1, wherein the first unit is a unit having an image carrier, and the second unit is a developing unit. 4. The unit positioning mechanism according to claim 1, wherein said first unit is a drum unit having a photosensitive drum, and said second unit is a developing device. 5. The positioning unit according to claim 4, wherein the positioning unit is fixed coaxially with a rotation axis of the drum unit having the photosensitive drum, and has first and second positioning surfaces coaxial with the rotation axis. Unit positioning mechanism. 6. The apparatus according to claim 5, wherein said positioning means is rotatably fixed coaxially with a rotation axis of a drum unit having a photosensitive drum, and is capable of being fixed at a plurality of positions in a rotation direction. Unit positioning mechanism.