JPH08137156A - Process cartridge and image forming device - Google Patents

Abstract

PURPOSE: To prevent influences of irregular rotation on an image caused by the pitch error of gears which can not be formed into a small module because strength should be considered. CONSTITUTION: In a process cartridge or a laser printer which is driven by engaging a drum gear 31 fixed to a photosensitive drum 21 and a gear 32 fixed to a developing roller 23a, a polyacetal resin or polycarbonate resin is used for the gears 31, 32. To prevent problems relating to strength even when the module is made in a small size, a polyacetal resin containing a potassium titanate whisker or polyamide MXD containing a potassium titanate whisker is used. By this method, about 0.3 module degree as the lowest limit can be obtd. although the limit of the module degree for a conventional one is about 1. Practically, irregular rotation can be suppressed with about 0.7 module degree. The diameter of the photosensitive drum 21 is 24 to 35mm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a photosensitive drum of a process cartridge which is detachably mountable to an image forming apparatus such as a laser beam printer or a copying machine, and an image forming for a laser beam printer or a copying machine using this cartridge. It relates to the device.

[0002]

2. Description of the Related Art For example, in a laser beam printer, a charging roller for uniformly charging the photosensitive drum and a developing roller for developing a latent image formed on the photosensitive drum are arranged around the photosensitive drum. , The drive receiving gear fixed to the photosensitive drum (hereinafter referred to as the drum gear) meshes with the gear fixed to the developing roller, and the drive gear on the image forming apparatus main body side receives the power transmitted from the drive source of the image forming apparatus. The drive gear and the drum gear pair mesh with the drum gear, and the rotation resistance of the charging roller driven by the photosensitive drum,
The rotation resistance of the developing roller and the rotation resistance of the photosensitive drum are applied, and an inertial load is applied to these at the time of startup.

The photosensitive drum, the charging roller and the developing roller are directly assembled in the main body of the image forming apparatus, and a process cartridge in which each of these members and the like is detachably attached to the image forming apparatus. There is something to prepare for.

In a process cartridge detachably mountable to a main body of an image forming apparatus used in a conventional laser beam printer or the like, an involute gear of about module 1 is used as a gear for receiving a photosensitive drum, a developing roller and a photosensitive drum. There is. The involute gear is theoretically supposed to rotate at a uniform angular rotation ratio. However, a pitch error occurs due to manufacturing, and the tooth distortion due to the load is not uniform due to the change of the meshing ratio during rotation in the usage state, and it becomes a dynamic pitch unevenness together with the pitch error, which corresponds to the pitch unevenness. Rotational unevenness occurs. For example, when the diameter of the photosensitive drum in the module 1 is 24 to 35 mm, the engagement rate is about 2.5 when the diameter is 24 mm. Due to such uneven rotation mainly due to uneven pitch,
Sometimes good quality images could not be obtained. The material of these gears is, for example, polyacetal resin or polycarbonate resin. The same applies to an image forming apparatus in which each process device is incorporated in the apparatus main body without using the process cartridge.

[0005]

The process cartridge and the image forming apparatus have the following problems. 1. When using the process cartridge to obtain a halftone image or the like, uneven rotation occurs due to pitch error of the drum gear or the like, and therefore uneven rotation corresponding to the gear pitch appears in the image to obtain a high-quality image. There was something I couldn't do. 2. When the teeth of the drum gear etc. are made of polyacetal resin or polycarbonate resin to a small module of about 0.6, uneven rotation of the photosensitive drum is reduced, but it is strong in terms of chipping and safety factor of one tooth of the gear. Is inferior to
It lacked durability and suffered damage such as chipping of teeth, which caused quality problems. 3. Therefore, if metals such as brass and steel with high bending strength (high hardness) are used for the drive gear, drum gear, and gear fixed to the developing roller, durability is obtained but vibration occurs when the teeth are engaged. Rotational unevenness increases.

According to the present invention, there is provided an image including a process cartridge having a drum gear having a small rotational unevenness and a smooth meshing and a gear pair fixed to a developing roller, and a drive gear which is detachably provided with the process cartridge and meshes with the drum gear. It is an object of the present invention to provide an image forming apparatus in which the process device with the gear is directly incorporated without including the forming device and the process cartridge.

[0007]

According to a first aspect of the present invention, a photosensitive drum and a developing roller having a diameter at least smaller than that of the photosensitive drum in the image forming process and performing a developing process are provided around the photosensitive drum. A driven helical gear that receives an external force is fixed to the drum, a helical gear that meshes with a helical gear that is fixed to the photosensitive drum is fixed to the developing roller, and a helical gear that is fixed to the photosensitive drum. And the helical gear fixed to the developing roller has an involute tooth profile of module 0.3 to 0.7, and the material of each gear is potassium titanate whisker-containing polyamide MXD or potassium titanate whisker-containing polyacetal resin. It is a process cartridge characterized by the fact that it is present.

In a second aspect of the present invention, the photosensitive drum has a diameter of 24 to 35 mm, a helical gear pair module has a diameter of 0.3 to 0.7, and the material of each helical gear has a bending strength. 1
The process cartridge according to the first invention, which is a polyamide MXD containing potassium titanate whisker of 50 MPa to 200 MPa.

According to a third aspect of the present invention, the photosensitive drum has a diameter of 24 to 35 mm, the helical gear pair module has a diameter of 0.3 to 0.7, and the material of each helical gear has a bending strength. 1
The process cartridge according to the first invention, which is a polyacetal resin containing potassium titanate whisker of 30 MPa to 180 MPa.

According to a fourth aspect of the present invention, a photosensitive drum and a developing roller having a diameter at least smaller than that of the inner photosensitive drum in the image forming process and performing a developing process are provided around the photosensitive drum, and the photosensitive drum receives an external force. The driven helical gear is fixed, the developing roller is engaged with the helical gear fixed to the photosensitive drum, the helical gear is fixed, and the helical gear fixed to the photosensitive drum is fixed to the developing roller. The helical gear has an involute tooth profile of module 0.3 to 0.7, and the material of each of these gears is a detachable process cartridge that is a polyamide MXD containing potassium titanate whiskers or a polyacetal resin containing potassium titanate whiskers. In preparation for the above, a drive gear that meshes with a helical gear fixed to the photosensitive drum is provided, and the material of the drive gear is potassium titanate whisker. An image forming apparatus, characterized in that Ri is a polyamide MXD or potassium whisker-containing polyacetal resin titanate.

In a fifth aspect of the present invention, the driving gear has a module of 0.3 to 0.7 and a bending strength of 150MP.
The image forming apparatus according to the fourth invention is a polyamide MXD resin material containing potassium titanate whiskers of a to 200 MPa.

According to a sixth aspect of the present invention, the driving gear has a module of 0.3 to 0.7 and a bending strength of 130MP.
An image forming apparatus according to a fourth invention, which is a polyacetal resin material containing potassium titanate whisker of a to 180 MPa.

A seventh aspect of the present invention is provided with a photosensitive drum and a developing roller for performing a developing process, wherein a gear fixed to the photosensitive drum meshes with a driving gear for transmitting a driving force from a driving source and is fixed to the developing roller. In the image forming apparatus that meshes with the gears, each gear is a module 0.3 to
It has an involute tooth profile of 0.7 and the material of each gear is polyamide MXD containing potassium titanate whiskers.
Alternatively, the image forming apparatus is a polyacetal resin containing potassium titanate whiskers.

[0014]

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

[First Embodiment] FIG. 1 schematically shows an image forming apparatus using a process cartridge according to the present invention. This image forming apparatus is a laser beam printer using an electrophotographic process in which a process cartridge including a charging device and the like is detachably mounted.

The image forming apparatus includes a lower housing 1 and a lower housing 1.
And an upper housing 2 that can be opened and closed. Upper housing 2
Is the hinge support shaft 3 on the rear side (left side in FIG. 1) of the lower housing 1.
Is rotatably supported in the direction of arrow a around the center, and has an open position (two-dot chain line in the figure) and a closed position (solid line in the figure),
Process cartridge 5 in open position (detailed below)
It becomes possible to attach and detach in the direction of arrow B.

On the front side (right side in the figure) of the process cartridge 5 arranged at a predetermined position with the upper housing 2 closed, a laser scanner unit 6 which is a main part of the exposure apparatus.
And a sheet cassette 7 containing a sheet material P as an image forming target is disposed below the sheet cassette. On the downstream side of the sheet cassette 7, a sheet feeding roller 9, a pair of registration rollers 10, a transfer guide 11, a transfer charger 12, a transfer member 13, and a fixing device 1 are arranged along the sheet P conveyance direction.
5 etc. are arranged. Note that all of these members are arranged on the side of the lower housing 1.

On the other hand, the fixing device 1 is provided on the upper housing 2 side.
5, a paper discharge roller 16, a paper discharge tray 17, a reflection mirror 19 and a process cartridge 5 are disposed downstream of the process cartridge 5.

As shown in FIG. 2, the process cartridge 5 includes a rotatable photosensitive drum 21 as a member to be charged, a charging device 22 having a charging roller 30 rotatably mounted in a cartridge frame 20, and a rotation. Freely developing roller 23a
The developing device 23 that supports the photosensitive drum 21 and the cleaning device 25 are integrally accommodated in the process device. An exposure window 20a is formed on the upper surface of the cartridge frame 20 and the photosensitive drum 21 is formed on the lower surface. A closing cover 20c that closes the transfer opening 20b is opened and closed. The open / close cover 20c moves to the closed position when the process cartridge 5 is taken out from the printer main body of the image forming apparatus or when the upper housing 2 is opened, and the photosensitive surface of the photosensitive drum 21 is covered. Conceal protection. The process cartridge 5 may include at least the photosensitive drum 21 and the developing device 23.

Next, an outline of image formation will be described. Based on the print start signal, the photosensitive drum 21 is rotationally driven in the direction of arrow K1 at a predetermined peripheral speed (process speed). The charging roller 30 of the charging device 22 to which a bias voltage is applied is in contact with the outer peripheral surface of the photosensitive drum 21, and the outer peripheral surface of the photosensitive drum 21 is uniformly and uniformly charged by the charging device 22.

The laser scanner unit 6 outputs laser light L which is modulated in accordance with the time-series electric digital pixel signals of the target image information, which is reflected by the reflection mirror 19 and further the upper surface of the cartridge frame 20. The light enters into the cartridge frame 20 through the exposure window portion 20a, and the charged surface of the photosensitive drum 21 is scanned and exposed. This allows
An electrostatic latent image corresponding to the target image information is formed on the outer peripheral surface of the photosensitive drum 21. This electrostatic latent image is transferred to the developing device 2
The developing blade 23b of No. 3 regulates the layer thickness and develops with the developer (toner) applied on the developing roller 23a.

On the other hand, from the sheet cassette 7 to the sheet feeding roller 9
Then, only one sheet material P is fed by the registration roller pair 10 and is supplied to the transfer position between the photosensitive drum 21 and the transfer charger 12 through the transfer guide 11 in synchronization with the laser output timing. As a result, the toner images on the photosensitive drum 21 side are sequentially transferred to the sheet material P.

The sheet material P to which the toner image has been transferred is separated from the photosensitive drum 21 and is conveyed to the fixing device 15 by the conveying member 13, where the fixing roller 15a and the pressure roller 15b are provided.
The toner image is fixed by passing through the nip part with
The paper is discharged to the paper discharge tray 17 by the paper discharge roller 16.
The residual toner on the outer peripheral surface of the photosensitive drum 21 after the transfer is removed by the cleaning blade 25a of the cleaning device 25, and the photosensitive drum 21 is again subjected to image formation starting from charging.

FIG. 3 is a development view including the photosensitive drum, the developing roller and the axis of the driving gear of the laser beam printer of the present invention. The photosensitive drum 21 has a photosensitive member on the outer periphery of an aluminum hollow cylinder, has a diameter of 30 mm, and has one end of a polyamide MXD containing potassium titanate whiskers.
The drum gear 31 which is a helical gear of the module 0.5 manufactured in 1. is fixed. The drum gear 31 meshes with a gear 32 fixed to the developing roller 23a, and rotationally drives it. The drum positioning pin 34 attached to the cartridge frame 20 is fitted in the center hole of the drum gear 31 to rotatably support the photosensitive drum 21. Rotation is transmitted from a motor (not shown) of the main body to a drum driving gear 33, which is a helical gear provided in the main body of the laser beam printer, to drive the drum gear 31.

The driving gear 33 and the gear 32 fixed to the developing roller 23a are made of polyamide MXD containing potassium titanate whiskers, like the drum gear 31. The bending strength of the material of each gear 31, 32, 33 is 150 MPa.
~ 200MPa range, the gear is module 0.5
Is a helical gear with a twist angle of 20 °.

Two gears 31, 32, and 33 were produced and tested, and as a result, uneven rotation of the photosensitive drum 21 due to pitch error of each gear was reduced, and the gears 31, 32 and 32 of the module 0.5 were reduced. In No. 33, the standard deviation of the rotation unevenness due to the pitch error of the halftone image of 2 dots and 3 spaces was reduced by about 10% compared with the gear of module 0.7 made of polyamide MXD containing potassium titanate whiskers.
It was also confirmed from the human eye's point of view that the gears of the module 0.5 had less uneven rotation due to the pitch unevenness than the gears of the module 0.7. Further, the helical gears used here are machined to have substantially the same gear precision (meshing error JGMA (Gear Accuracy Standard established by the Japan Gear Manufacturers Association) grade 3, tooth line error JIS4).
Class).

By using the gear of module 0.5 with the material having the bending strength described above, one tooth of the gear has an appropriate toughness, and vibration such as when the teeth are meshed with each other is absorbed to cause pitch unevenness. It is possible to reduce.

By changing the pitch of the gear using the above material,
Moreover, the diameter of the photosensitive drum 21 is 24 mm and the gear of the module 0.7 is necessary to reduce the rotation unevenness of the photosensitive drum 21 clearly with respect to the gear of the conventional module 1 by changing the diameter of the photosensitive drum 21 variously. It was found that the smaller the module, the smoother the photosensitive drum 21 rotates. When the diameter of the photosensitive drum 21 is about 24 mm, the diameter of the developing roller 23a is about 12 mm, and the gear of the module 0.7 is calculated as a spur gear, the standard gear with a pressure angle of 20 ° has a meshing ratio of 3.4. In the conventional example of No. 1, the meshing ratio is 2.5. In practice, for example, the gear having a bevel angle of about 20 ° is slightly larger than the meshing ratio.

The smaller the module, the larger the meshing ratio, and the smoother the rotation of the photosensitive drum 21 due to a pitch error or the like, but the strength of the teeth and the durability due to the wear of the teeth decrease. Therefore, if the diameter of the photosensitive drum 21 is set to 24 mm, the theoretical minimum value of the module is 0.3 in view of durability. It has been found that when the photosensitive drum 21 having a large diameter is driven by this module 0.3, the inertial load increases, and therefore there is a limit, and it is desirable in calculation that the diameter of the photosensitive drum 21 be 35 mm or less.

Example 2 Similar results were obtained when only the gear material in Example was used a polyacetal resin containing potassium titanate whiskers having a bending strength of 130 MPa to 180 MPa. In this example, the bending strength is lower than that of the first embodiment, but nevertheless, the same result is obtained. In the laser beam printer, the impact due to the inertial load generated corresponding to the starting torque of the motor of the driving source is caused by the material. It is considered that durability is obtained because the vibration state does not occur due to the damping ability due to the appropriate toughness.

Although the laser beam printer is exemplified as the image forming apparatus in the above-mentioned embodiments, the present invention is not limited to this, and may be used in other image forming apparatuses such as a copying machine or a facsimile machine. This is naturally possible, and need not be limited to the developing device for the process cartridge illustrated in the embodiment, and naturally is applicable to, for example, a conventional image forming apparatus that does not use the process cartridge system.

[0032]

According to the first aspect of the present invention, a photosensitive drum and a developing roller having a diameter at least smaller than that of the photosensitive drum in the image forming process and performing a developing process are provided around the photosensitive drum, and an external force is applied to the photosensitive drum. The driven helical gear is fixed to the developing roller, the helical gear that meshes with the helical gear fixed to the photosensitive drum is fixed to the developing roller, and the helical gear fixed to the photosensitive drum and the developing roller are fixed to the developing roller. The fixed helical gear has an involute tooth profile of module 0.3 to 0.7, and the material of each gear is potassium titanate whisker-containing polyamide MXD or potassium titanate whisker-containing polyacetal resin. Gear grinding is performed to make the dimensional control extremely strict, to reduce pitch error and gear error extremely, to reduce the back gap and also to eliminate the back gap. Nor has adopted a configuration, the photosensitive drum becomes uniformly rotatable, it can provide a process cartridge is not reduced the quality of the halftone.

In a second aspect of the present invention, the photosensitive drum has a diameter of 24 to 35 mm, a helical gear pair module is 0.3 to 0.7, and the material of each helical gear has a bending strength of 15
With the polyamide MXD containing potassium titanate Isca of 0 MPa to 200 MPa, the effect of the first invention can be preferably realized.

According to a third aspect of the present invention, the photosensitive drum has a diameter of 24 to 35 mm, the helical gear pair module has a diameter of 0.3 to 0.7, and the material of each helical gear has a bending strength. 1
By using a polyacetal resin containing potassium titanate whisker of 30 MPa to 180 MPa, the effect of the first invention can be suitably realized.

According to a fourth aspect of the present invention, a photosensitive drum and a developing roller having a diameter at least smaller than that of the inner photosensitive drum in the image forming process and performing a developing process are provided around the photosensitive drum, and the photosensitive drum receives an external force. The driven helical gear is fixed, the developing roller is engaged with the helical gear fixed to the photosensitive drum, the helical gear is fixed, and the helical gear fixed to the photosensitive drum is fixed to the developing roller. The helical gear has an involute tooth profile of module 0.3 to 0.7, and the material of each of these gears is a detachable process cartridge that is a polyamide MXD containing potassium titanate whiskers or a polyacetal resin containing potassium titanate whiskers. In preparation for this, there is a drive gear that meshes with a helical gear fixed to the photosensitive drum, and the material of the drive gear is potassium titanate isca Polyamide MXD or polyacetal resin containing potassium titanate whiskers makes gear grinding extremely strict in dimensional control, pitch error and gear error to be extremely small, and the back gap can be made small, and furthermore there is no back. It is possible to provide an image forming apparatus in which the photosensitive drum can be rotated uniformly without adopting a mechanism for forming a gap and which does not deteriorate halftone image quality.

According to a fifth aspect of the present invention, the driving gear has a module of 0.3 to 0.7 and a bending strength of 150 MPa or more.
With the polyamide MXD resin material containing 200 MPa of potassium titanate whiskers, the effect of the fourth invention can be preferably realized.

According to a sixth aspect of the present invention, the driving gear has a module of 0.3 to 0.7 and a bending strength of 130MP.
By using the polyacetal resin material containing potassium titanate whisker of a to 180 MPa, the effect of the fourth invention can be preferably realized.

A seventh aspect of the present invention comprises a photosensitive drum and a developing roller for performing a developing process, wherein a gear fixed to the photosensitive drum meshes with a driving gear to which a driving force is transmitted from a driving source and is fixed to the developing roller. In the image forming apparatus that meshes with the gears,
It has an involute tooth profile of 0.7 and the material of each gear is polyamide MXD containing potassium titanate whiskers.
Or, it is made of polyacetal resin containing potassium titanate whiskers, so that the grinding of the gears makes the dimensional control extremely strict, the pitch error and the gear error are extremely small, and the back gap is made small and there is no back gap. It is possible to provide an image forming apparatus in which the photosensitive drum can be rotated uniformly without adopting a mechanism for changing, and the image quality of halftone is not deteriorated.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view schematically showing a laser beam printer equipped with a process cartridge.

FIG. 2 is an enlarged vertical sectional view of a process cartridge.

FIG. 3 is a development view including the drive gear, the photosensitive drum, and the axis of the developing roller of the embodiment.

[Explanation of symbols]

 1 Lower Housing 2 Upper Housing 3 Hinge Support Shaft 5 Process Cartridge 6 Scanner Unit 7 Sheet Cassette 9 Paper Feed Roller 10 Registration Roller Pair 11 Transfer Guide 12 Transfer Charger 13 Conveying Member 15 Fixing Device 15a Fixing Roller 15b Pressure Roller 16 Ejection Paper roller 17 Paper discharge tray 19 Reflection mirror 20 Cartridge frame 20a Exposure window 20c Open / close cover 21 Photosensitive drum 22 Charging device 23 Developing device 23a Developing roller 23b Developing blade 25 Cleaning device, 25a Cleaning blade 29b Transfer opening 30 Charging member ( Charging roller) 31 Drum gear 32 Development roller gear 33 Drive gear 34 Drum positioning pin L Laser light P Sheet material

Claims (7)

[Claims] 1. A photosensitive drum and a developing roller having a diameter at least smaller than that of the inner photosensitive drum in the image forming process and performing a developing process are provided around the photosensitive drum, and the photosensitive drum is driven to receive an external force. The gear is fixed, the developing roller is engaged with the helical gear fixed to the photosensitive drum, the helical gear is fixed, the helical gear fixed to the photosensitive drum and the helical gear fixed to the developing roller are Module 0.
It has an involute tooth profile of 3 to 0.7, and the material of each gear is polyamide M containing potassium titanate whiskers.
A process cartridge characterized by being a polyacetal resin containing XD or potassium titanate whiskers. 2. The photosensitive drum has a diameter of 24 to 35 mm.
The helical gear pair module is 0.3 to 0.7, and the material of each helical gear has a bending strength of 150 MPa to 200M.
Polyamide MXD with Pa potassium titanate whiskers
The process cartridge according to claim 1, wherein 3. The photosensitive drum has a diameter of 24-35 mm.
The helical gear pair module is 0.3 to 0.7, and the material of each helical gear has a bending strength of 130 MPa to 180M.
The process cartridge according to claim 1, wherein the process cartridge is a polyacetal resin containing Pa potassium titanate whiskers. 4. A photosensitive drum and at least a developing roller having a diameter smaller than that of the inner photosensitive drum of the image forming process and performing a developing process are provided around the photosensitive drum, and the photosensitive drum is driven by a driven spacer that receives an external force. The gear is fixed, the developing roller is engaged with the helical gear fixed to the photosensitive drum, the helical gear is fixed, the helical gear fixed to the photosensitive drum and the helical gear fixed to the developing roller are Module 0.
It has an involute tooth profile of 3 to 0.7, and the material of each gear is polyamide M containing potassium titanate whiskers.
A process cartridge made of XD or polyacetal resin containing potassium titanate whiskers is detachably provided and has a drive gear that meshes with a helical gear fixed to a photosensitive drum. The material of the drive gear is polyamide MXD containing potassium titanate whiskers. Alternatively, the image forming apparatus is a polyacetal resin containing potassium titanate whiskers. 5. The drive gear has a module of 0.3 to
When the material is 0.7, the bending strength is 150 MPa to 200 MPa.
5. The image forming apparatus according to claim 4, which is the polyamide MXD resin material containing potassium titanate whiskers. 6. The drive gear has a module of 0.3 to
At 0.7, the material has a bending strength of 130 MPa to 180 MPa
5. The image forming apparatus according to claim 4, which is the polyacetal resin material containing potassium titanate whiskers. 7. An image in which a photosensitive drum and a developing roller for performing a developing process are provided, and a gear fixed to the photosensitive drum meshes with a driving gear to which a driving force is transmitted from a driving source and meshes with a gear fixed to the developing roller. In the forming apparatus, each gear has an involute tooth profile of module 0.3 to 0.7, and the material of each gear is potassium titanate whisker-containing polyamide MXD or potassium titanate whisker-containing polyacetal resin. Image forming apparatus.