JP3315451B2 - Image forming apparatus and process cartridge - 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 (LBP) and a process cartridge detachably mountable thereto.

[0002]

2. Description of the Related Art A plurality of photosensitive drums (electrophotographic photosensitive members) are provided, images of different colors are formed for each of the photosensitive drums, and the images are transferred onto a single recording medium in a superimposed manner. Image forming apparatuses capable of forming multicolor images are widely known (for example, Japanese Patent Application Laid-Open No. 59-62879).

[0003] In this method, a laser scanning system, a developing device, a cleaner and a transfer device of different colors are provided for a plurality of photosensitive drums, and in each laser scanning system, a beam from a laser light source is scanned by a polarizer such as a polygon mirror. While the direction is polarized, the polarized beam is image-irradiated to each photosensitive drum via an imaging lens, while the latent image formed on each photosensitive drum is visualized by each developing device, and each photosensitive drum is visualized. The upper toner image is sequentially transferred onto one recording sheet by each transfer device. The toner remaining on the photosensitive drum after the transfer is removed by a cleaner.

The following proposals have been made to further develop such an image forming apparatus. That is, the photosensitive drum and the process means (developing unit, cleaner, etc.) acting on the drum are integrally integrated into a plurality of process cartridges, and each process cartridge is supported by one cartridge support. The cartridge support is detachable from the apparatus main body.

As shown in FIG. 5, this apparatus has a process cartridge 54 in which a photosensitive drum 51, a developing unit 52, and a cleaner 53 are integrally assembled. A rotatable drum shaft 56 is provided, and the drum shaft 56 is provided on the process cartridge 54 side.
Are provided. The bearings 57 are provided on both side walls 54a and 54b of the process cartridge 54 which correspond to both side portions of the photosensitive drum 51, and one of the bearings 57a is a sliding bearing 57a.
And the other is a bearing 57b. Therefore, when the process cartridge 54 set on the cartridge support 58 is slidably mounted on the apparatus main body 55, the drum shaft 56 on the apparatus main body 55 side and the sliding bearing 57a on the process cartridge 54 side. And the bearing 57b is fitted and positioned. At this time, the projection 56a provided on the drum shaft 56 and the photosensitive drum
The photosensitive drum 51 rotates integrally with the drum shaft 56 by engaging with the concave portion 51a provided in the 51.
As shown in FIG. 6 (a sectional view taken along the line YY in FIG. 5), when the process cartridge 54 is mounted, the sliding bearing 57a moves while sliding on the drum shaft 56.
A notch is provided so that the convex portion 56a provided on the slide bearing 57a does not catch on the slide bearing 57a. 59a and 59b are members for holding the photosensitive drum 51.

[0006]

However, in the above conventional example, of the bearings 57 that support the drum shaft 56,
The sliding bearing 57a is shaved due to durability and the process cartridge
Accurate positioning of the 54 could be lost.
Further, when the accurate positioning of the process cartridge 54 is not performed, the photosensitive drum 51 of the blade in the cleaner 53 is
There is a risk that the amount of intrusion into the device may deviate from the set value.

The shaving of the sliding bearing 57a is particularly caused by the sliding bearing 57a.
It is more facilitated when force is applied to 57a. In general, the drive input of the rollers and the like in the process cartridge 54 is often taken on the side where the sliding bearing 57a is provided, and in such a case, a large force is applied to the sliding bearing 57a, and the scraping is promoted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to stabilize image quality by facilitating mounting of a process cartridge and constantly maintaining its position accurately. And to improve the durable life of functional components such as the photosensitive drum.

[0009]

A typical configuration according to the present invention for achieving the above object is that a process cartridge having an image bearing member is detachable, and a process cartridge is provided with respect to a rotating shaft provided in an apparatus main body. In the image forming apparatus in which the image carrier of the process cartridge is fitted and the process cartridge is mounted on the apparatus main body, the rotation shaft has a connecting portion for rotating integrally with the image carrier. A portion provided on one end side of the rotating shaft and projecting in a radial direction of the rotating body and engaging with an engaging portion provided on the image carrier; and a diameter of the other end side of the rotating shaft is The process cartridge has side plates that are respectively provided on the sides of the image carrier, and is larger than the rotation locus of the protrusion with respect to one side plate. other A first rolling bearing that side and fitted,
A second rolling bearing having an inner diameter smaller than that of the first rolling bearing and being fitted to the one end of the rotary shaft is provided with respect to the other side plate, and the one end of the rotary shaft from the first rolling bearing is provided. It is characterized by being mounted in the thrust direction.

[0010]

In the image forming apparatus having the above-mentioned structure, since the rolling bearing is used as the bearing for positioning the process cartridge with respect to the rotating shaft and as a bearing member, it is possible to reduce wear of the bearing due to durability. In addition, a projection is provided at one end of the rotation shaft, and the diameter of the other end of the rotation shaft is made larger than the rotation locus of the projection. A large and small rolling bearing is provided on each of the provided side plates, and a process cartridge is mounted in the thrust direction from the first rolling bearing fitted to the other end having a large diameter to one end having a small diameter of the rotating shaft in the thrust direction. Easy to attach to.

[0011]

[First Embodiment] A first embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. In the present embodiment, a multicolor image forming apparatus provided with a plurality of image forming units for forming an image on a recording medium by acting on a photosensitive drum will be described as the image forming apparatus. FIG. 1 is an explanatory sectional view showing a schematic configuration of the multicolor image forming apparatus.

First, the schematic structure of a multi-color image forming apparatus will be described with reference to FIG. 1. The multi-color image forming apparatus in this embodiment is a four-drum type color image forming apparatus. In order to achieve this, there are provided four image forming units each having a photosensitive drum and process means arranged around the photosensitive drum, and a conveying unit in which an image on the photosensitive drum formed by each of the image forming units moves adjacent to the photosensitive drum. Is configured to be sequentially transferred onto a recording medium carried / transported.

More specifically, the image forming units Pa, Pb, and P having process means are built in the apparatus main body 1.
c, Pd are arranged in the horizontal direction, and each image forming unit P
a, Pb, Pc, Pd, a belt driving roller 2
An endless transfer belt 3 is stretched around a and 2b.
The transfer belt 3 is rotated in the direction of arrow C by rotating the belt drive rollers 2a and 2b in the direction of arrow B by a drive motor (not shown).

Reference numeral 4 denotes a cassette in which recording sheets 5, which are recording media, are stacked and stored. The recording sheets 5 stored in the cassette 4 are separated and fed one by one from a top by a pickup roller 6. Sent. The skew is corrected by a pair of registration rollers (not shown), and the sheet is conveyed onto the transfer belt 3 in synchronization with the image forming units Pa, Pb, Pc, and Pd.

The configuration of the image forming units Pa, Pb, Pc, and Pd will be described. Each of the four photosensitive drums 8 (specifically, 8a to 8d) is arranged independently. Has a laser scanning system 9 (specifically, 9a
9d), a primary charger 10 (specifically, 10a to 10d) for charging the surface of the photosensitive drum 8 in advance, and toner of each color of magenta, cyan, yellow, and black are provided around each photosensitive drum 8. Developing device 11 (specifically, 11a to 11
d), a transfer charger 12 (specifically, 12a to 12d) for transferring a toner image on each photosensitive drum 8 to a recording sheet 5 as a recording medium, and cleaning for removing residual toner on each photosensitive drum 8 A device 13 (specifically, 13a to 13d) and a static eliminator 14 (specifically, 14a to 14d) for removing residual charges on each photosensitive drum 8 are provided.

In FIG. 1, reference numeral 15 denotes a fixing device for fixing a transferred image transferred to the recording sheet 5, and a fixing roller 15a having a heating means such as a heater therein and a pressurizing roller 15a pressed against the fixing roller 15a. It has a roller 15b. Reference numeral 16 denotes a discharge roller pair for discharging the recording sheet 5 after the fixing process to the outside of the apparatus.

Next, an image forming operation will be described. When an image forming operation start signal is input to the apparatus main body 1, the photosensitive drum 8a starts rotating in the direction of arrow A, and the primary charger 10a is started.
The drum surface is irradiated with laser light modulated by an image signal corresponding to the magenta component of the original image by the laser scanning system 9 to form an electrostatic latent image (exposure). Next, a magenta toner is supplied by the developing device 11a to form a toner image in which the latent image is visualized.

On the other hand, the recording sheet 5 stored in the cassette 4 is fed by a pickup roller 6, and after skew is corrected by a pair of registration rollers (not shown), the toner image formed on the photosensitive drum 9a is removed. Is conveyed onto the transfer belt 3 at the timing shown in FIG. The recording sheet 5 sent to the transfer belt 3 is transferred and charged by the transfer charger 12a at the transfer position of the image forming unit Pa, and the toner image is transferred to the recording sheet 5. The above steps are similarly performed in the image forming units Pb, Pc, and Pd, and a cyan toner image, a yellow toner image, and a black toner image are sequentially transferred to the recording sheet 5.

The recording sheet 5 on which the image transfer has been completed is separated from the transfer belt 3 by a separation charger (not shown), and is conveyed to the fixing device 15. The recording sheet 5 on which the image has been fixed by the fixing device 15 is discharged out of the apparatus by a discharge roller pair 16.

In this embodiment, the photosensitive drum, the developing device, and the cleaning device are integrated into a cartridge for each of the image forming units, and are formed into a cartridge. Is configured to be attachable to and detachable from a cartridge support provided in the printer.

Hereinafter, the process unit and its unit support will be described with reference to the drawings. FIG. 2 is a sectional explanatory view schematically showing a state in which the process unit is mounted on the apparatus main body.

As shown in FIG. 2, each of the process cartridges U (specifically, Ua to Ud) includes a photosensitive drum 8, a developing device 11, and a cleaning device 13 from both sides of a front plate 17a.
And the rear side plate 17b to be integrally formed.
The photosensitive drum 8 is provided with holding members 19a, 18a, 18a, 18b having flanges 18a, 18b at both ends provided on inner walls of the side plates 17a, 17b, respectively.
19b. A drum shaft serving as a rotation drive shaft of the photosensitive drum 8 is provided at a predetermined position on the side plates 17a and 17b.
Rolling bearings 21a and 21b are provided as 20 bearing members. In this embodiment, the rolling bearings 21a, 21b
Are used as bearings. Also, the drum shaft 20
Is provided on the apparatus main body 1 side. When the process cartridge U is mounted, the projection 20a provided on the drum shaft 20 and the groove 18a1 provided on the flange 18a of the photosensitive drum 8 are engaged with each other, so that the photosensitive drum 8 and the drum shaft 20 are configured to rotate integrally. Further, the drum shaft
20 has a step, the bearing of the process unit U
The diameter R1 on the side supported by 21b is configured to be larger than the rotation locus R2 of the projection 20a (R1> R
2).

Next, a unit support of the process unit U and a method of mounting the process unit U will be described with reference to the drawings. FIG. 3 is an explanatory view showing a state where the unit support is pulled out from the apparatus main body, and FIG. 4 is an explanatory view showing a state where the process unit supported by the unit support is mounted on the apparatus main body.

In FIG. 3, reference numeral 22a denotes a support front plate, 22b denotes a support rear plate, 22c denotes a stay connecting the support front plate 22a and the support rear plate 22b, and these three members 22a, 22b, 22
A frame of the cartridge support 22 is formed by c.
The cartridge supporting member 22 is a rail member that can be extended and contracted with respect to the apparatus main body 1, for example, Accuride rails 23 a and 23 b.
(See FIG. 1). In FIG. 3, the cartridge support 22 is drawn out of the front side plate 1a of the apparatus main body 1 along the accelerating rail 23a, and at this time, the front end of the drum shaft 20 is connected to the rear plate of the cartridge support 22.
22b is engaged with the bearing 22b1. In this state, the process cartridge U is set in the cartridge support 22 by dropping it in the direction of arrow D.

After the four color process cartridges U are mounted on the cartridge support 22, the cartridge support plate
When the cartridge 22 is slid in the direction of the arrow E (inside the apparatus main body), the bearing 22 on the rear plate 22b of the cartridge support 22 moves on the drum shaft 20.
While the b1 slides, the drum shaft 20 is guided into the photosensitive drum 8 via the bearing 21b in the process cartridge U. When the cartridge support 22 is further pushed into the apparatus main body 1, the drum shaft 20 is moved forward by the front plate 22a of the cartridge support 22.
Of the bearing 22a1. Then, the pins 22a2 of the front plate 22a of the cartridge support 22 are connected to the front side plate 1a of the apparatus main body 1.
The pin 24 of the process cartridge U fits into the hole 1b1 of the rear plate 1b of the apparatus main body 1 (see FIG. 4).

By the above operation, the process cartridges U of each color are transferred to the drum shaft 20 of each cartridge and the main assembly 1 of the apparatus.
Is completed. After that, the knob 25 is mounted on the front side of each drum shaft 20 and the front plate of the unit support 22 is
22a (centering plate) is fixed.

The position of the process cartridge U is determined by fitting the bearings 21a and 21b to the drum shaft 20 so that the process cartridge U can be positioned relative to the drum shaft 20.
Position is determined. This is because, in the process cartridge U, the developing sleeve of the developing device 11 and the photosensitive drum 8 of the cleaning blade of the cleaning device 13 are used.
This is because it is extremely important to accurately assure relative distances (SD gap and blade penetration amount) with respect to maintaining image quality and durability of functional components such as photosensitive drums.

Accordingly, in this embodiment, since the bearings 21a and 21b, which are rolling bearings, are used as the positioning and bearing members of the process cartridge U with respect to the drum shaft 20, it is possible to reduce wear of the bearing due to durability. Also, the drum shaft 20 has a step, and the diameter R1 of a portion fitted with the bearing 21b is set to be larger than the diameter R2 of the rotation locus of the projection 20a of the drum shaft 20, so that when the process cartridge is attached / detached. The bearing 21
b does not interfere with the projection 20a of the drum shaft 20.

[Other Embodiments] The above-described process cartridge includes an electrophotographic photosensitive member and at least one of processing means. Accordingly, as a mode of the process cartridge, in addition to the above-described embodiment, for example, the photosensitive drum and the charging unit are integrally formed as a cartridge and can be attached to and detached from the apparatus main body. The photosensitive drum and the developing means are integrally formed into a cartridge and can be attached to and detached from the apparatus main body. A photosensitive drum and a cleaning means are integrally formed into a cartridge so that the photosensitive drum and the cleaning means can be attached to and detached from the apparatus main body. Further, there is a type in which a photosensitive drum and two or more of the above-mentioned process means are combined into a cartridge to be detachable from the apparatus main body.

That is, the above-mentioned process cartridge is one in which the charging means, the developing means or the cleaning means and the electrophotographic photosensitive member are integrally formed into a cartridge, and this cartridge is made detachable from the main body of the image forming apparatus. . In addition, at least one of the charging unit, the developing unit, and the cleaning unit and the electrophotographic photosensitive member are integrally formed into a cartridge so that the cartridge can be attached to and detached from the image forming apparatus main body. Further, it means that at least the developing means and the electrophotographic photosensitive member are integrally formed into a cartridge so as to be detachable from the apparatus main body.

Also, a potential sensor for measuring the potential of the primary charger and the surface of the photosensitive drum, a density sensor for detecting a toner image on the photosensitive drum after development, or a charge on the surface of the photosensitive drum after cleaning is removed. Process means such as a pre-exposure lamp may be included in the cartridge.

If the photosensitive drum is not included in the process cartridge, the holding members 19a and 19b shown in FIG. 2 may be removed from the process cartridge, and a member holding the photosensitive drum may be attached to the cartridge support instead (see FIG. 2). Not shown).

In the above embodiment, an example in which the present invention is applied to a multi-color image forming apparatus has been described. However, the present invention is not limited to this, and may be applied to a single-color image forming apparatus.

In the above-described embodiment, a laser beam printer is exemplified as an image forming apparatus. However, the present invention is not limited to this. For example, an electrophotographic copying machine, a facsimile apparatus, or another image forming apparatus such as a word processor. Of course, it is also possible to use.

[0035]

As described above, by using the rolling bearing as the bearing member and the positioning of the process cartridge with respect to the rotating shaft, it is possible to reduce the wear of the bearing due to durability. In addition, a projection is provided at one end of the rotation shaft, and the diameter of the other end of the rotation shaft is made larger than the rotation locus of the projection. A large and small rolling bearing is provided on each of the provided side plates, and a process cartridge is mounted in the thrust direction from the first rolling bearing fitted to the other end having a large diameter to one end having a small diameter of the rotating shaft in the thrust direction. It became easy to attach to.

[Brief description of the drawings]

FIG. 1 is an explanatory cross-sectional view illustrating a schematic configuration of a multicolor image forming apparatus.

FIG. 2 is a plan view schematically showing a process cartridge according to the present invention.

FIG. 3 is an explanatory diagram showing a state where a process cartridge is pulled out from a cartridge support.

FIG. 4 is an explanatory diagram illustrating a state where a process cartridge is mounted on an apparatus main body.

FIG. 5 is an explanatory diagram of a conventional technique.

FIG. 6 is an explanatory diagram of a conventional technique.

[Explanation of symbols]

 Pa, Pb, Pc, Pd: Image forming unit Ua, Ub, Uc, Ud: Process cartridge 1: Apparatus main body 1a: Front side plate 1a1, Hole 1b: Rear side plate 1b2: Hole 2a, 2b: Belt drive roller 3: Transfer belt 4 cassette 5 recording sheet 6 pickup roller 8a, 8b, 8c, 8d photosensitive drum 9a, 9b, 9c, 9c laser scanning system 910a, 10b, 10c, 10d primary charger 11a, 11b, 11c, 11d: Developing devices 12a, 12b, 12c, 12d: Transfer chargers 13a, 13b, 13c, 13d: Cleaning devices 14a, 14b, 14c, 14d: Static eliminator 15: Fixing device 15a: Fixing roller 15b: Pressure roller 16: Discharge roller pair 17a Front plate 17b Rear plate 18a, 18b Flange 18a1 Groove 19a, 19b Holding member 20 Drum shaft 20a Projection 21a, 21b Bearing 22 Cartridge support 22a Front plate 22a1 Bearing 22a2 Pin 22b Rear plate 22c Stay 22b1 Bearing 23a, 23b Accuride rail 24 Pin 25 Knob

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Claims (2)

(57) [Claims] A process cartridge having an image carrier is detachable, and the image carrier of the process cartridge is fitted to a rotation shaft provided on the apparatus main body, and the process cartridge is mounted on the apparatus main body. In the image forming apparatus, the rotating shaft has a connecting portion for rotating integrally with the image carrier, and the connecting portion is provided at one end of the rotating shaft and projects in a radial direction of the rotating body. A projecting portion that engages with an engaging portion provided on the image carrier; a diameter of the other end of the rotating shaft is larger than a rotation locus of the projecting portion; A first rolling bearing that is larger than the rotation locus of the protruding portion with respect to one side plate and is fitted to the other end side of the rotating shaft, with respect to the other side plate. The first roll A second rolling bearing having an inner diameter smaller than that of the bearing and being fitted to the one end of the rotating shaft, and being mounted in the thrust direction from the first rolling bearing to the one end of the rotating shaft. Image forming apparatus. 2. A process cartridge having an image carrier, wherein the image carrier is engaged with a rotation shaft provided in an image forming apparatus main body, wherein the image carrier protrudes radially to one end side. The image bearing member further includes an engaging portion that has a protruding portion and has a diameter at the other end that is larger than a rotation locus of the protruding portion and that engages with the protruding portion to rotate integrally with the rotation shaft. A first rolling bearing that is larger than the rotation trajectory of the protruding portion with respect to one side plate and is fitted to the other end of the rotary shaft, with respect to the other side plate. A second rolling bearing having an inner diameter smaller than that of the first rolling bearing and fitted to the one end of the rotating shaft, and mounted in the thrust direction from the first rolling bearing to the one end of the rotating shaft. A process cartridge characterized by being performed.