JP2014115349A - Process unit and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process unit having a gear train which satisfies an arbitrary drive condition between an image carrier and a developer carrier, and preventing an abnormal image, such as banding or blur, while improving layout flexibility.SOLUTION: A photoreceptor drum 2 is fixed axially on an image carrier holding side plate 209. A developing roller 103 is fixed axially on a developer carrier holding side plate 210. The developer carrier holding side plate 210 is supported at a rotation fulcrum 211 so as to be vertically turned with respect to the image carrier holding side plate 209. The developing roller 103 is driven in contact with the photoreceptor drum 2 with predetermined pressure. The rotation fulcrum 211 is located on a straight line 219 which indicates a direction of force to be applied in a reference circle contact of idler gears 207, 208.

Description

  The present invention relates to a copying machine, a printer, a facsimile machine, a plotter, an image forming apparatus such as a multifunction machine provided with at least one of them, and a process unit mounted on the image forming apparatus.

2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, various types of developing devices are used to develop an electrostatic latent image formed on an image carrier (photosensitive drum).
As such a developing device, in addition to a two-component developing type developing device using a developer containing toner and a carrier, a one-component developing type developing device using only toner as a developer without using a carrier. It has been known.
In a one-component developing type developing device, a contact-type developing device that performs development by bringing a developer held on the surface of a developer carrier (developing roller) into contact with the surface of an image carrier on which an electrostatic latent image is formed. A developing device is known.
In addition, there is also known a non-contact type developing device in which a developer carrying member is provided so as to face an image carrying member with a predetermined interval.
In the non-contact type, an alternating voltage is applied to the developer carrying member to cause an alternating electric field to act between the developer carrying member and the image carrying member, so that the developer held on the surface of the developer carrying member is electrostatically charged. Development is performed by supplying the image carrier to which the latent image is formed.

As the developer carrying member, generally, a roller in which an elastic layer is formed of rubber or the like, or a roller in which a metal surface is blasted to be roughened is used.
In the one-component development, the requirements for driving conditions of the image carrier and the developer carrier vary depending on the development method employed, the material, the developer, the size of both the carriers, and the like.
When trying to obtain the required drive conditions, the rotation speed of the image carrier and the developer carrier is too different, and the layout breaks down if only one drive motor and one drive gear train are used. Sometimes.
As a countermeasure, a plurality of motors can be arranged to drive the image carrier and developer carrier separately, or the drive gear train can be branched before transmitting the drive to the process unit so that a long gear train can be provided on the main body side. There is a method of driving in combination.

However, if a large number of motors are arranged, it is easy to directly increase the cost.
The method of branching the drive gear train in front of the process unit has a problem that the number of gears increases and energy transmission loss tends to increase.
Although it is best if the axial gear of the developer carrier can be directly driven by the axial gear of the image carrier, the above-mentioned target driving condition is not always satisfied.
In order to use this direct drive configuration, there is only means for correcting by tuning other parts such as the developer and the material of the developer carrier, and it may take a lot of time and cost to search for optimum conditions. .
Further, the contact condition between the image carrier and the developer carrier may change due to shrinkage or the like of the frame of the process unit or the developer carrier due to environmental changes.
If the contact condition changes, abnormal images such as banding and blurring are generated.
For this reason, it may be necessary to avoid the above-described problem by adopting a configuration in which a constant load is applied to the image carrier by applying a constant load such as a spring bias.
However, in this case, the position or orientation of the developing device changes depending on the environment, and the environmental variation of the inter-axis distance is taken into account in the portion where the drive from the image carrier to the developer carrier is performed in the process unit. Design is required.

  The present invention was devised in view of such a current situation, and realizes a gear train that can satisfy an arbitrary driving condition between an image carrier and a developer carrier, and an abnormal image such as banding or blurring. Its main purpose is to provide a process unit that can suppress the occurrence of the occurrence and contribute to the improvement of the flexibility of layout.

  In order to achieve the above object, the present invention includes an image carrier and a developing device that visualizes an electrostatic latent image formed on the image carrier with a developer. In a process unit having a developer carrier that is arranged at a position facing the image carrier and rotates while carrying the developer, the image carrier is rotated. A first support member that can be supported; a second support member that rotatably supports the developing device; and that is rotatably provided around one rotation fulcrum; and the development with respect to the image carrier. An urging means for applying an urging force to the second support member so as to pressurize the agent carrier with a constant pressure, a first gear provided on the rotation shaft of the image carrier, and the development A second gear provided on the rotation shaft of the agent carrier, and a drive from the image carrier. One or more idler gears provided between a first gear and a second gear so that force can be transmitted to the developer carrier, wherein at least one of the idler gears is the image carrier. An idler gear whose axial position is fixed with respect to the image carrier, and a gear adjacent to the idler gear on the downstream side in the driving force transmission direction, the developer carrier The idler gear or the second gear whose axial position is fixed with respect to the distance between the image carrier and the developer carrier when the distance between the shafts is pressurized with the constant pressure. The rotational fulcrum is an idler gear whose axial position is fixed with respect to the image carrier and a gear adjacent to the idler gear. The developer Wherein the tooth surface of the shaft position is fixed idler or the second gear is positioned in the force vector collinear to receive each other with respect to lifting member.

  The present invention further includes an image carrier and a developing device that visualizes the electrostatic latent image formed on the image carrier with a developer, and the developing device includes the image carrier. In an image forming apparatus having a developer carrier that is disposed at a position opposite to the substrate and conveys the developer to the image carrier by rotating while carrying the developer, the image carrier is rotatably supported. A first support member, a second support member that rotatably supports the developing device, and that is rotatably provided around one rotation fulcrum; and the developer carrier relative to the image carrier. An urging means for applying an urging force to the second support member so as to pressurize with a constant pressing force, a first gear provided on the rotation shaft of the image carrier, and a developer carrier A second gear provided on the rotating shaft and the driving force from the image carrier to carry the developer One or more idler gears provided between the first gear and the second gear so as to be able to transmit to the at least one of the idler gears, and at least one of the idler gears has a fixed axial position with respect to the image carrier. An idler gear whose axial position is fixed with respect to the image carrier, and a gear adjacent to the idler gear on the downstream side in the driving force transmission direction, the axial position being fixed with respect to the developer carrier. The idler gear or the second gear, when the distance between the axes is the positional relationship between the image carrier and the developer carrier when the constant pressure is applied. The rotation support point is an idler gear whose axial position is fixed with respect to the image carrier, and a gear adjacent to the idler gear, the developer carrier. Axis position with respect to Wherein the tooth surface of the fixed idler gear or the second gear is positioned in the receiving power of the vector collinear with each other.

  According to the present invention, in a process unit or an image forming apparatus having a mechanism for driving an image carrier and a developer carrier, an abnormal image such as banding or blurring is realized while realizing a gear train that can satisfy an arbitrary driving condition. Generation can be suppressed, and the layout can be improved.

1 is a configuration diagram illustrating a main part of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view around a developing device. It is a general | schematic longitudinal cross-sectional view in the axial direction of a developing device. 2A and 2B are diagrams illustrating a driving configuration between the photosensitive drum and the developing roller, in which FIG. 1A illustrates a contact state, and FIG. 2B illustrates a gear configuration that transmits driving force on the photosensitive drum side to the developing roller. It is. 2A and 2B are diagrams illustrating a displacement configuration of the developing device with respect to the photosensitive drum, in which FIG. 1A illustrates a state before the developing roller is pressed against the photosensitive drum, and FIG. It is. It is a figure which shows that the distance from a rotation fulcrum to the reference | standard circle contact of an idler gear is shorter than the distance from a rotation fulcrum to the contact point of a photosensitive drum and a developing roller. FIG. 6 is a diagram for explaining a disadvantage of holding an idler gear that receives a driving force directly from the photosensitive drum side on a developer carrier holding side plate. FIG. 6 is a diagram for explaining the reason why an abnormal image such as banding can be suppressed even if the position of the contact point between the photosensitive drum and the developing roller is deviated due to environmental fluctuations or variations in manufacturing accuracy of parts.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a main part of a printer 100 as an image forming apparatus according to the present embodiment.
The printer 100 includes four process cartridges 1 as process units, an intermediate transfer belt 7 as an intermediate transfer member that is wound around a plurality of support rollers and moves in the direction of arrow A, an exposure device 6 as exposure means, and a fixing device 12. Etc.
Each process cartridge 1 is detachably attached to a printer main body (hereinafter also referred to as “image forming apparatus main body”).
Here, the “process unit” refers to a unit in which a developing device and a photoconductor are assembled together.

FIG. 2 is an enlarged cross-sectional view of one of the four process cartridges 1.
Each process cartridge 1 includes a photosensitive drum 2 as an image carrier, a charging member 3, a developing device 4 that visualizes an electrostatic latent image formed on the photosensitive drum 2 with a developer, and an image carrier. The body cleaning member 5 is integrally supported to form a unit.
Each process cartridge 1 can be attached to and detached from the image forming apparatus main body by releasing a stopper (not shown).

The photosensitive drum 2 rotates in the clockwise direction as indicated by the arrow in the drawing.
The charging member 3 is a roller-shaped charging roller, is pressed against the surface of the photosensitive drum 2, and is rotated by the rotation of the photosensitive drum 2.
At the time of image formation, a predetermined bias is applied to the charging member 3 by a high voltage power source (not shown) to charge the surface of the photosensitive drum 2.
Here, a roller-shaped member that contacts the surface of the photosensitive drum 2 is used as the charging member 3, but the charging means is not limited to this, and a non-contact charging method such as corona charging may be used. good.

The exposure device 6 exposes the surface of the photosensitive drum 2 based on image information, and forms an electrostatic latent image on the surface of the photosensitive drum 2.
In the present embodiment, a laser beam scanner system using a laser diode is used as the exposure device, but other configurations such as an LED array may be used as the exposure means.
The image carrier cleaning member 5 cleans the developer remaining after transfer onto the surface of the photosensitive drum 2 that has passed the position facing the intermediate transfer belt 7.
The four process cartridges 1 form toner images for the respective colors of yellow, cyan, magenta, and black on the photosensitive drum 2.

The four process cartridges 1 are arranged in parallel in the surface movement direction of the intermediate transfer belt 7, and the toner images formed on the respective photosensitive drums 2 are transferred so as to be superimposed on the intermediate transfer belt 7 in order.
As shown in FIG. 1, a primary transfer roller 8 is disposed at a position facing each photosensitive drum 2 with the intermediate transfer belt 7 interposed therebetween.
A primary transfer bias is applied to the primary transfer roller 8 by a high voltage power supply (not shown), and a primary transfer electric field is formed between the primary transfer roller 8 and the photosensitive drum 2.
By forming a primary transfer electric field between the photosensitive drum 2 and the primary transfer roller 8, the toner image formed on the surface of the photosensitive drum 2 is transferred to the surface of the intermediate transfer belt 7.

One of the plurality of support rollers that support the intermediate transfer belt 7 is rotated by a drive motor (not shown), so that the intermediate transfer belt 7 moves in the direction of arrow A.
A toner image of each color is sequentially superimposed and transferred onto the surface of the intermediate transfer belt 7, thereby forming a full color image on the surface of the intermediate transfer belt 7.
With respect to the position where the four process cartridges 1 face the intermediate transfer belt 7, the intermediate transfer belt 7 is located on the downstream side in the movement direction of the intermediate transfer belt 7 with respect to the secondary transfer facing roller 9 a that is one of the support rollers. The secondary transfer roller 9 is disposed at a position facing each other with the image interposed therebetween.
The secondary transfer roller 9 forms a secondary transfer nip with the intermediate transfer belt 7.
A predetermined voltage is applied between the secondary transfer roller 9 and the secondary transfer counter roller 9a to form a secondary transfer electric field.
Thereby, when the transfer paper P as a recording medium conveyed in the direction of arrow B passes through the secondary transfer nip, the full-color image formed on the surface of the intermediate transfer belt 7 is transferred to the transfer paper P.

A fixing device 12 is disposed on the downstream side of the transfer direction of the transfer paper P with respect to the secondary transfer nip.
The transfer paper P that has passed through the secondary transfer nip reaches the fixing device 12, and the full-color image transferred onto the transfer paper P is fixed by heating and pressurization in the fixing device 12.
The transfer paper P on which the image is fixed is discharged to a discharge tray (not shown).
On the other hand, the developer remaining on the surface of the intermediate transfer belt 7 without being transferred to the transfer paper P at the secondary transfer nip is collected by the transfer belt cleaning device 11.

Next, the developing device 4 included in the process cartridge 1 will be described with reference to FIGS. 2 and 3.
FIG. 2 is a schematic cross-sectional view of the developing device 4 in the vicinity of the rotation axes of the developer conveying member 106, the developer agitating member 108, and the developer supplying roller 105, which are linearly arranged in the vertical direction.
The developing device 4 includes a developer storage chamber 101 that stores a developer, and a developer supply chamber 102 that is provided below the developer storage chamber 101.
A partition member 110 is provided so as to partition the developer storage chamber 101 and the developer supply chamber 102.

As shown in FIG. 3, the partition member 110 is provided with a plurality of openings.
The plurality of openings of the partition member 110 return the developer in the developer accommodating chamber 101 to the developer supplying chamber 102 and the developer in the developer supplying chamber 102 to the developer accommodating chamber 101. And a return port 107.
As shown in FIG. 2, a developing roller 103, which is a developer carrier, is provided below the developer supply chamber 102.

In the developer supply chamber 102, a developer supply roller 105, which is a developer supply member that supplies developer to the surface of the developing roller 103, is provided in contact with the surface of the developing roller 103.
In the developer supply chamber 102, a developer layer regulating member 104 is provided in contact with the surface of the developing roller 103.
The developer layer restricting member 104 is supplied onto the surface of the developing roller 103 by the developer supplying roller 105, and restricts the layer thickness of the developer toward the facing portion between the photosensitive drum 2 and the developer carrying roller 103.
A predetermined bias is applied to the developing roller 103 from a high voltage power source (not shown).

In the developer accommodating chamber 101, a developer conveying member 106 that conveys the developer in the developer accommodating chamber 101 in a direction parallel to the rotation axis of the photosensitive drum 2 (a direction orthogonal to the paper surface in FIG. 2). Is provided.
As the developer stored in the developer storage chamber 101, a developer prepared by a polymerization method is used.
This developer has an average particle diameter of 6.5 [μm], a circularity of 0.98, an angle of repose of 33 [°], and strontium titanate as an external additive.
However, the developer is not limited to this.

As shown in FIG. 3, the developer transport member 106 provided in the developer storage chamber 101 is a member having a rotating shaft in which a transport screw 106 a and a transport plate 106 b are combined.
The developer transport member 106 can transport the developer in the developer storage chamber 101 in a substantially horizontal direction (in the direction of arrow C in FIG. 3) parallel to the rotation axis of the developer transport member 106 by rotating the transport screw 106a. It has a configuration.
Here, the conveyance screw 106a is provided, but the developer conveyance member is not limited to this, and a developer having a conveyance function such as a conveyance belt or a coiled rotating body can be used.
Furthermore, what has these conveyance functions and what has a loosening function, such as a paddle formed by bending a plate member such as a blade or a wire, may be combined.

In the present embodiment, the developer is conveyed from the developer accommodating chamber 101 toward the developer supply roller 105 in a direction substantially perpendicular to the rotation axis of the developer conveying member 106 and substantially vertically downward.
The developer transport direction may be configured to be transported in a substantially horizontal direction perpendicular to the rotation axis of the developer transport member 106.
A developer stirring member 108 is disposed in the developer supply chamber 102 vertically below the partition member 110.
The developer stirring member 108 is a member having a rotating shaft in which a stirring screw 108a and a stirring plate 108b are combined.
The developer stirring member 108 rotates the stirring screw 108a to move the developer in the developer supply chamber 102 in a substantially horizontal direction (in the direction of arrow D or E in FIG. 3) parallel to the rotation axis of the developer stirring member 108. It can be transported.

The agitating screw 108a of the developer agitating member 108 is provided with a spiral wing portion so as to convey the developer in the direction toward the outside (in the direction of arrow D in FIG. 3) across the supply port 111 in the axial direction. Yes.
Furthermore, the agitating screw 108a has spiral wings that are wound in reverse directions on the outside and inside of the two return ports 107 in the axial direction.
For this reason, the developer supplied from the supply port 111 to the developer supply chamber 102 is conveyed outward in the axial direction (in the direction of arrow D) by the rotation of the stirring screw 108a of the developer stirring member 108.
The developer that has reached the outside of the return port 107 is conveyed inward (in the direction of arrow E) in the axial direction toward the return port 107 by a stirring screw 108a whose wings are reversely wound.
The developer conveying direction by the stirring screw 108 a is opposite between the outside and the inside in the axial direction across the return port 107, and a transport force is applied to the developer toward the return port 107. Below, the developer is collected from both sides in the axial direction and pushed up in a mountain shape.

As a result, when the developer supplied from the developer storage chamber 101 to the developer supply chamber 102 through the supply port 111 or the return port 107 is excessive, the developer storage chamber 101 is returned to the developer storage chamber 101.
That is, the developer pushed up in a mountain shape at the return port 107 is returned from the developer supply chamber 102 to the developer storage chamber 101 through the return port 107.
Further, the developer agitating member 108 has a role of agitating the developer in the developer supply chamber 102 and further supplying the developer to the developing roller 103 and the developer supplying roller 105 in the lower part.
The surface of the developer supply roller 105 is covered with a foam material having a structure having pores (cells), and the developer supplied into the developer supply chamber 102 is efficiently attached and taken in, and the development roller The deterioration of the developer due to the pressure concentration at the contact portion with 103 is prevented.
In addition, this foaming material is set to an electrical resistance value of 10 ³ to 10 ¹⁴ [Ω].

A supply bias is applied to the developer supply roller 105 to assist the action of pressing the precharged developer against the development roller 103 at the contact portion with the development roller 103.
As shown by the arrow in FIG. 2, the developer supply roller 105 rotates counterclockwise and supplies the developer attached to the surface so that the developer is applied to the surface of the developing roller 103.
The developer layer regulating member 104 is arranged so as to come into contact with the surface of the developing roller 103 on the downstream side in the surface movement direction of the developing roller 103 from the position where the developer supplying roller 105 abuts.
The developer supplied from the developer supply roller 105 to the surface of the developing roller 103 is conveyed to a position where the developer layer regulating member 104 comes into contact with the rotation of the developing roller 103.

The developer layer regulating member 104 abuts the free end side against the surface of the developing roller 103 with a pressing force of 10 to 100 [N / m].
As a result, the developer layer regulating member 104 allows the developer on the developing roller 103 to pass under the pressing force, thereby thinning the developer layer and applying charge to the developer by frictional charging. To do.

The photosensitive drum 2 rotates in the clockwise direction in FIG.
For this reason, in the developing region where the developing roller 103 and the photosensitive drum 2 face each other, the surface moving direction of the developing roller 103 and the surface moving direction of the photosensitive drum 2 are the same direction.
The thinned developer layer on the developing roller 103 is conveyed to the developing region by the rotation of the developing roller 103.
The developer layer moves to the surface of the photosensitive drum 2 according to the bias applied to the developing roller 103 and the latent image electric field formed by the electrostatic latent image on the photosensitive drum 2, and The electrostatic latent image on the surface is developed.
At a location where the developer that is not used for development in the development region and remains on the development roller 103 returns to the developer supply chamber 102 again, a static elimination seal 109 that is a developer static elimination member contacts the development roller 103. Is provided.
Thus, the developer is sealed so as not to leak out of the developing device 4. A bias may be applied to the static elimination seal 109 in order to assist the static elimination capability.

FIG. 4A shows a case where the target driving condition can be achieved only with the gears having the reference circle diameters denoted by reference numerals 203 and 204 due to the rotation directions of the photosensitive drum 2 and the developing roller 103 and layout constraints. .
In this example, the photosensitive drum 2 rotates in the clockwise direction, and the developing roller 103 rotates in the counterclockwise direction.
By arranging idler gears 207 and 208 having a reference circle diameter indicated by a broken line as shown in FIG. 4B, the driving torque of the photosensitive drum 2 can be transmitted to the developing roller 103 at a desired rotational speed. it can.
In the case of a driving condition that further requires an increase / decrease ratio, the idler gears 207 and 208 may be multistage gears.

The gear 203 is a first gear that is provided on the rotating shaft of the photosensitive drum 2 and rotates synchronously with the photosensitive drum 2.
In other words, the gear 203 is an image carrier driving gear that meshes with a main body side gear as a driving gear when the process cartridge 1 is mounted on the main body of the image forming apparatus.
The gear 204 is a second gear that is provided on the rotation shaft of the developing roller 103 and rotates in synchronization with the developing roller 103.
In other words, the gear 204 is a developer carrier driving gear.
The idler gear 207 and the idler gear 208 are idler gears provided between the first gear and the second gear so that the driving force from the photosensitive drum 2 side can be transmitted to the developing roller 103.

As shown in FIG. 5A, the photosensitive drum 2 is rotatably supported with its axial position fixed to an image carrier holding side plate 209 as a first support member.
The developing roller 103 is axially fixed to a developer carrier holding side plate 210 as a second support member and is rotatably supported.
Although not shown, the developing device 4 itself is held on the developer carrier holding side plate 210.
The developer carrier holding side plate 210 is supported by the rotation fulcrum 211 so as to be rotatable in the vertical direction with respect to the image carrier holding side plate 209.

The idler gear 207 is supported by the image carrier holding side plate 209 and is an idler gear whose axial position is fixed with respect to the photosensitive drum 2.
The idler gear 208 is an idler gear supported on the developer carrier holding side plate 210 and having an axial position fixed to the developing roller 103.
The idler gear 208 is a gear adjacent to the idler gear 207 on the downstream side in the driving force transmission direction.

The developer carrier holding side plate 210 is biased in the direction of the photosensitive drum by a pressure spring 212 as a biasing means whose base end is fixed to the image carrier holding side plate 209.
As a result, as shown in FIG. 5B, the developing roller 103 is pressed against the photosensitive drum 2 with a constant pressing force (biasing force) and is in contact with the photosensitive drum 2 via the developer. Driven.
At this time, that is, when the positional relationship between the photosensitive drum 2 and the developing roller 103 is being applied with a constant pressure, the idler gear 207 and the idler gear 208 are arranged so as to have a target inter-axis distance. Has been.
At the contact point between the reference circles of the idler gear 207 and the idler gear 208, the tooth surface of the idler gear 208 receives an acting force in the direction of the illustrated pressure angle θ (pressure angle 20 deg).
The rotation fulcrum 211 is provided so as to be positioned on a straight line 219 indicating a vector of action / reaction force received by the tooth surfaces of the idler gear 207 and the idler gear 208.
That is, it is located on the same straight line as the vector.

As shown in FIG. 6, the distance L1 between the reference circular contact 216 of the idler gears 207 and 208 and the rotation fulcrum 211 is larger than the distance L2 between the contact point 215 of the photosensitive drum 2 and the developing roller 103 and the rotation fulcrum 211. It is set to be shorter.
By adopting such a configuration, it is possible to configure a gear train that realizes a desired rotational speed only by adding a relatively small idler gear train instead of adding motors and gear trains on the apparatus body side.
Further, in the configuration in which the developing device is biased by a spring, the distance between the gear shafts can be kept appropriate, and abnormal image generation such as banding due to abnormal vibration during gear driving can be prevented.

Since the rotation fulcrum 211 of the developing device is arranged on the reaction force vector received by the idler gear 208 in the developing device, the reaction force does not rotate the entire developing device.
Therefore, the developing roller 103 can be continuously pressed against the photosensitive drum 2 with an appropriate pressure.
In this embodiment, the idler gear 207 is fixed to the image carrier holding side plate 209 and the idler gear 208 is fixed to the developer carrier holding side plate 210.
In this way, the rotation fulcrum 211 of the developing device can be placed at a position where the developing roller 103 is pressed toward the axial center of the photosensitive drum 2.

If the idler gear 207 is configured to be fixed to the developer carrier holding side plate 210, the position of the rotation fulcrum indicated by reference numeral 211-2 in FIG. 7 is taken, and the size of the developing device is increased.
Further, when the developer carrier holding side plate 210 is rotated to press the developing roller 103, the pressing direction is greatly deviated from the axis center of the photosensitive drum 2.
In FIG. 7, reference numeral 210a denotes a developer carrier holding side plate.

Even if the position of the contact point 215 between the photosensitive drum 2 and the developing roller 103 deviates by d1 due to environmental fluctuations and variations in the manufacturing accuracy of parts, θ1 = θ2 does not change.
For this reason, the deviation in the inter-axis distance of the idler gears 207 and 208 can be suppressed by the lever principle by making the distance L1 shorter than L2, and the abnormal image such as banding caused by the vibration due to the deviation in the distance between the gear axes is suppressed. Can do.
The deviation d2 in the distance between the gear shafts is obtained from θ1 = θ2 in a similar relationship from d1, and d1 × (L1 / L2) = d2.
Therefore, for example, if L1 is halved to L2, the deviation in the inter-axis distance can be suppressed to half.

DESCRIPTION OF SYMBOLS 1 Process cartridge as a process unit 2 Photosensitive drum as an image carrier 4 Developing device 103 Developing roller 103 as a developer carrier
Reference Signs List 203 First gear 204 Second gear 207, 208 Idler gear 209 Image carrier holding side plate 210 as a first support member 210 Developer carrier holding side plate as a second support member 211 Rotation fulcrum 212 As an urging means Pressure spring

Japanese Patent No. 4440372 JP 04-219550 A Japanese Patent No. 3599632

Claims (5)

An image carrier;
A developing device that visualizes the electrostatic latent image formed on the image carrier with a developer;
Have
In the process unit having a developer carrier that is disposed at a position facing the image carrier and rotates the developer carrying the developer to the image carrier by rotating the developer device.
A first support member that rotatably supports the image carrier;
A second support member that rotatably supports the developing device and is provided to be rotatable about one rotation fulcrum;
An urging means for applying an urging force to the second support member so as to pressurize the developer carrier with a constant pressure against the image carrier;
A first gear provided on the rotation shaft of the image carrier;
A second gear provided on the rotation shaft of the developer carrier;
One or more idler gears provided between the first gear and the second gear so that the driving force from the image carrier can be transmitted to the developer carrier;
With
At least one of the idler gears has an axial position fixed with respect to the image carrier,
An idler gear whose axial position is fixed with respect to the image carrier and a gear adjacent to the idler gear on the downstream side in the driving force transmission direction, the idler gear whose axial position is fixed with respect to the developer carrier; The second gear refers to the distance between the axes when the distance between the axes is the positional relationship between the image carrier and the developer carrier when the constant pressure is applied. It is arranged to be a distance,
The rotation fulcrum is an idler gear whose axial position is fixed with respect to the image carrier and a gear adjacent to the idler gear, and an idler gear whose axial position is fixed with respect to the developer carrier or a second gear. A process unit characterized in that a tooth surface with a gear is positioned on the same straight line as a vector of forces received by each other. The process unit according to claim 1, wherein
An idler gear whose axial position is fixed with respect to the image carrier, and a gear adjacent to the idler gear, the idler gear or the second gear whose axial position is fixed with respect to the developer carrier are tooth surfaces. The point of contact with the image carrier is disposed closer to the rotation fulcrum than the point of contact between the developer carrier and the image carrier in a cross section perpendicular to the rotation axis of the image carrier. A process unit characterized by   An image forming apparatus comprising the process unit according to claim 1 detachably. An image carrier;
A developing device that visualizes the electrostatic latent image formed on the image carrier with a developer;
Have
In the image forming apparatus, the developing device is disposed at a position facing the image carrier, and has a developer carrier that conveys the developer to the image carrier by rotating in a state of carrying the developer.
A first support member that rotatably supports the image carrier;
A second support member that rotatably supports the developing device and is provided to be rotatable about one rotation fulcrum;
An urging means for applying an urging force to the second support member so as to pressurize the developer carrier with a constant pressure against the image carrier;
A first gear provided on the rotation shaft of the image carrier;
A second gear provided on the rotation shaft of the developer carrier;
One or more idler gears provided between the first gear and the second gear so that the driving force from the image carrier can be transmitted to the developer carrier;
With
At least one of the idler gears has an axial position fixed with respect to the image carrier,
An idler gear whose axial position is fixed with respect to the image carrier and a gear adjacent to the idler gear on the downstream side in the driving force transmission direction, the idler gear whose axial position is fixed with respect to the developer carrier; The second gear refers to the distance between the axes when the distance between the axes is the positional relationship between the image carrier and the developer carrier when the constant pressure is applied. It is arranged to be a distance,
The rotation fulcrum is an idler gear whose axial position is fixed with respect to the image carrier and a gear adjacent to the idler gear, and an idler gear whose axial position is fixed with respect to the developer carrier or a second gear. An image forming apparatus, wherein tooth surfaces of gears are positioned on the same straight line as a vector of forces received by each other. The image forming apparatus according to claim 4.
An idler gear whose axial position is fixed with respect to the image carrier, and a gear adjacent to the idler gear, the idler gear or the second gear whose axial position is fixed with respect to the developer carrier are tooth surfaces. The point of contact with the image carrier is disposed closer to the rotation fulcrum than the point of contact between the developer carrier and the image carrier in a cross section perpendicular to the rotation axis of the image carrier. An image forming apparatus.

Images