JP6494319B2 - Image forming apparatus - Google Patents

Description

The present invention, a latent image formed on the sensitive light drum is developed with toner, the driving on the recording medium relates to an image forming apparatus of an electrophotographic system performing transfer and fixing to record the toner images, especially sensitive light drum It is related with the meshing structure of the gear which transmits force.

In the image forming apparatus applying the electrophotographic process, if a gear for driving the downstream to the developing sleeve and the charging roller of the drum coupling to rotate integrally with the sensitive light drum are engaged, the load of each of the gears And unevenness in rotation due to backlash or the like. In the image forming apparatus to continue to form an image at a right angle to the scanning direction while scanning the laser beam on the sensitive light drum, the image formed by the rotation unevenness of the sensitive light drums, so-called banding occurs. In an image forming apparatus that forms a color image, color unevenness due to banding is caused.

As a countermeasure against banding, conventionally, as shown in the block diagram of FIG. 6, a branching means for dividing the driving force is provided on the path for transmitting the driving force from the driving source to the drum driving gear. (For example, see Patent Document 1). That is, independently by the driving force divided by the branching means to drive the like developing sleeve and a charging roller, thereby eliminating the influence of the load and backlash of the downstream gear sensitive light drum.

JP-A-8-334934

However, in this way be configured not to affect the downstream side of the gear to the rotation of the sensitive light drum, the load fluctuation of the sensitive light drum is caused by disturbance such as paper behavior is a recording medium, sensitive optical de There was a problem that uneven rotation of the ram was likely to deteriorate. That is, roller nip intrusion and departure of sensitive light drum surface abuts with the recording medium being conveyed at the time of image formation, changes in the sudden conveying speed in such abutment against the conveying guide occurs. This change is spread into sensitive light drums, resulting uneven rotation by the load on the sensitive light drum is changed, the banding level of the image formed is deteriorated.

The present invention has been made to solve the problems of the prior art described above, it is an object to provide an image forming apparatus capable of suppressing a rotational fluctuation of the sensitive light drum due to the behavior of the recording medium There is.

In order to achieve the above object, the present invention provides:
A photosensitive drum on which a latent image is formed, a developing device for developing said latent image as a toner image by toner supplied by the developing sleeve abuts against the photosensitive drum, a process cartridge Ru provided with,
An apparatus main body to which the process cartridge is detachably mounted , and a drum driving gear for transmitting a driving force from a driving source to the photosensitive drum via a drum coupling, and a developing sleeve via a sleeve coupling An apparatus body having a sleeve drive gear that transmits to
In an image forming apparatus comprising:
In the apparatus main body, the sleeve driving gear is disposed downstream of the drum driving gear with respect to the driving source, and a driving force is transmitted through the drum driving gear through a path that does not pass through the drum coupling. age,
In the process cartridge, the photosensitive drum and the developing sleeve are in contact with each other at least during image formation, and the developing sleeve rotates in a reverse direction with respect to the photosensitive drum at a higher peripheral speed than the photosensitive drum. Thus, the driving force is transmitted from the sleeve driving gear.

According to the present invention, it is possible to suppress the rotational fluctuation of the sensitive light drum due to the behavior of the recording medium.

FIG. 3 is a cross-sectional explanatory diagram illustrating a transmission path of a driving force from a driving source of the image forming apparatus according to the first embodiment of the present invention. FIG. 2 is a cross-sectional explanatory view of the image forming apparatus in FIG. 1. The block diagram which shows the transmission path | route of the driving force from the drive source of FIG. FIG. 2 is an explanatory diagram showing a meshing state between the drum driving gear of FIG. 1 and upstream and downstream idler gears. FIG. 2 is a cross-sectional explanatory view of the process cartridge of FIG. 1. FIG. 6 is a block diagram illustrating a driving force transmission path from a driving source of a conventional image forming apparatus. The figure which shows the relationship of the force which acts on a drum drive gear from an upstream idler gear and a downstream idler gear.

The present invention will be described below based on the illustrated embodiments.
First, the overall configuration of the image forming apparatus 28 to which the present invention is applied will be described with reference to FIG.
The image forming apparatus 28 shown is a so-called laser beam printer, a sensitive optical drum 1 on which a latent image is formed, toner images the latent image by toner supplied by the developing sleeve 5 abuts against the sensitive light drum 1 A developing device 50.
A paper feed tray 9 on which a recording medium P such as recording paper is set is provided on the lower side of the apparatus. The recording medium P is disposed on the middle plate 21 in the paper feed tray 9, and the middle plate 21 is urged in the arrow z direction by the middle plate spring 22. Further, the intermediate plate 21 is provided with a paper feed cam contact portion 23, and the paper feed cam contact portion 23 is stationary at a position in contact with the paper feed cam 11.

When the drive is transmitted from the motor 33 which is a drive source and the paper feed roller 10 rotates, the paper feed cam 11 coaxial with the paper feed roller 10 also starts to rotate. As the sheet feeding cam 11 rotates, the radius of the surface in contact with the sheet feeding cam contact portion 23 changes, so that the intermediate plate 21 moves up and down with respect to the arrow z direction. When the intermediate plate 21 moves in the arrow z direction, the recording media P stacked on the paper feed tray 9 are fed one by one in order from the one stacked on the top surface.
The recording medium P sent out by the paper feeding roller 10 enters the nip formed by the pressure contact between the transport driving roller 12 and the transport driven roller 13, and is further moved by the transport driving roller 12 and the transport driven roller 13. It is conveyed downstream.

Sensitive light drum 1 and the developing device 50 is incorporated into the process cartridge 4, the process cartridge 4, it is freely mounted Configurations detachable from the image forming apparatus main body 28A. The process cartridge 4, is sensitive light drum 1 and the developing sleeve 5 is rotatably supported, and supplies the developing sleeve 5, the toner in the sensitive light drum 1 in contact with the sensitive light drum 1 at least the image forming It is like that. The process cartridge 4 is provided with a developer roller 6 (charger) that is rotatably supported and a developer container 6 that stores toner.
Image formed is sensitive light drum 1 surface is uniformly charged by the charging roller 2, the laser beam 3 emitted from the laser scanner unit 8, a latent image is drawn on the surface of the sensitive light drum 1, the latent image The toner is supplied to the developing sleeve 5 to form a toner image. If there recording medium P is conveyed, a sensitive optical drum 1, the transfer roller 14 at the transfer nip formed of a toner image is transferred onto the recording medium P as an unfixed image.

  In order to heat and fix the transferred toner image, the recording medium P further passes through a nip composed of a fixing pressure roller 15 and a fixing heater 16, and the unfixed image is heat-fixed. The recording medium P after image fixing is directed along the conveyance guide 24 toward a paper discharge nip formed by the paper discharge driving roller 17 and the paper discharge driven roller 18. The paper discharge driving roller 17 and the paper discharge driven roller 18 discharge the recording medium P to the outside of the image forming apparatus 28, and the recording medium P is stacked above the paper discharge tray 19 and the paper discharge extension tray 25.

(Description of driving force transmission path)
Next, the configuration of the driving force transmission path of the image forming apparatus 28 according to the present embodiment will be described with reference to FIG.
The drive force transmission path is constituted by a gear train, and the drive force of the motor 33 as a drive source is transmitted to the downstream gear train by the motor pinion 27 that rotates together with the motor drive shaft. The driving force transmitted from the motor pinion 27 is transmitted to the drum driving gear 29 via a reduction gear 34 that is a reduction mechanism and a plurality of idler gears, in the illustrated example, four idler gears 35c, 35d, 35e, and 35a. Driving force is transmitted from the drum driving gear 29 further downstream to the sleeve driving gear 30 via the downstream idler gear 35b. The sleeve drive gear 30 is not a gear that is coaxial with the developing sleeve 5, but three idler gears are connected between the sleeve driving gear 30 and a gear (not shown) provided coaxially with the developing sleeve 5 to transmit the drive. It is. In short, as shown in FIG. 5, the gear train is determined so that the rotation direction of the developing sleeve 5 and the rotation direction of the photosensitive drum 1 are opposite.
The upstream idler gear 35a and the downstream idler gear 35b that mesh with the drum drive gear 29 in the upstream and downstream positions are at positions where the resultant force is reduced.
That is, the gear is arranged at a position where the resultant force (vector) of the following two forces applied to the drum drive gear 29 becomes small.
1) Driving force Fa received from the upstream idler gear 35a upstream of the drum driving gear 29
2) Reaction force Fb received from the downstream idler gear 35b on the downstream side of the drum drive gear 29
For example, FIG. 7A shows the gear configuration of FIG. 1, and FIG. 7B shows the downstream idler gear 35b.
It is the gear structure which changed arrangement | positioning.
In FIG. 7A, the upstream idler gear 35a and the sleeve drive gear 30 are located on the opposite side of the straight line connecting the center of the drum drive gear 29 and the downstream idler gear 35b . In FIG. 7B, the upstream idler gear 35a and the sleeve drive gear 30 are arranged on the same side with respect to the straight line connecting the center of the drum drive gear 29 and the downstream idler gear 35b .
In the arrangement relationship of FIG. 7B, the upstream idler gear 35a, the drum drive gear 29, and the downstream idler gear 35b are arranged close to a straight line, and the driving force Fa and reaction force Fb acting on the drum driving gear 29 are: It becomes almost parallel and the resultant force F is large.
On the other hand, in FIG. 7A, the angle between the driving force Fa and the reaction force Fb acting on the drum driving gear 29 is 90 ° or more, and the resultant force F is small.
The rotating shafts 29a and 30a of the drum driving gear 29 and the sleeve driving gear 30 are supported at both ends with respect to the image forming apparatus main body 28A, and the supporting strength is increased. Although not particularly illustrated, it is preferable that the image forming apparatus is supported by a sheet metal.

  Further, the image forming apparatus 28 has a branching unit that divides the driving force via an idler gear 35 in a driving force transmission path from the motor pinion 27 to the drum driving gear 29. By the branching unit, a sheet feeding unit and a fixing unit are provided. The driving force is transmitted to other systems. Although not particularly illustrated, the branching unit may employ various configurations such as a configuration in which an unillustrated gear is engaged with the idler gear 35 and a configuration in which another gear is fixed to the rotation shaft and the transmission path is branched.

  In this embodiment, the reduction gear 34 and the plurality of idler gears 35 are used as means for transmitting the driving force. However, the motor pinion 27 and the drum driving gear 29, and the drum driving gear 29 and the sleeve driving gear are not used. The driving force may be transmitted by directly engaging 30. The driving force transmission means from the driving source other than the upstream idler gear 35a and the downstream idler gear 35b that mesh with the drum driving gear 29 is not limited to a gear, and for example, the driving force is transmitted by a belt. Also good.

FIG. 3 is a block diagram showing how the driving force is transmitted in this embodiment.
Drum drive gear 29 which is supported on the image forming apparatus main body 28A performs the transmission of the driving force to the sensitive light drum 1 supported by the process cartridge 4 through the drum coupling 61. Similarly, the sleeve drive gear 30 supported in the image forming apparatus 28 transmits power to the developing sleeve 5 supported in the process cartridge 4 via the sleeve coupling 62. Further, power is transmitted from the sleeve coupling 62 to other systems such as the charging roller 2.
In the drawing, each component of the image forming apparatus main body 28A to which the driving force is transmitted is expressed as an abstract functional expression as a speed reduction unit, a paper feeding unit, a paper conveying unit, a fixing unit, and a paper discharging unit. 2, the drive source is the motor 33, the speed reduction means is the speed reduction gear 34, the paper feed means is the paper feed roller 10, the paper transport means is the transport drive roller 12, and the fixing means is fixing. The pressure roller 15 and the paper discharge means are a paper discharge drive roller 17. In FIG. 3, reference numerals of corresponding members are given to the blocks in which each function is expressed.

(Technical explanation for suppressing uneven rotation of the drum)
The upper part of FIG. 4 shows a meshing portion between the drum driving gear 29 and the upstream idler gear 35a that is adjacent to the drum driving gear 29 and rotates in the direction of the arrow K ′ to transmit the driving force to the drum driving gear 29 It is. If the sensitive light drum 1 has an ideal rotated without causing rotation variation, the drum drive gear 29 receives the driving force that rotates the upstream idler gear 35a in the arrow K direction, always in the same direction The backlash is offset.
But was such a conventional art shown in FIG. 6, when the sudden load on the sensitive light drum 1 is applied, the drum drive gear 29, not fixed more direction of backlash between the upstream idler gear 35a, sensitive It occurs the rotation unevenness in the light drum 1. The sudden load is, for example, a change in the conveyance speed that occurs when the recording medium P enters the nip between the fixing pressure roller 15 and the fixing heater 16 or contacts the conveyance guide 24 during image formation.

In the present embodiment, in addition to the meshing of the upper gear in FIG. 4 described above, the drum drive gear 29 and the downstream idler gear 35b are meshed as shown in the lower part of FIG. The downstream idler gear 35b receives a driving force that rotates from the drum driving gear 29 in the direction of the arrow K ′. Furthermore, as shown in FIG. 6 is a cross-sectional view of the process cartridge 4, the developing sleeve 5, while in contact with the sensitive light drum 1 equivalent, opposite direction to the sensitive light drum 1, rotated in the arrow K 'direction To do. The peripheral speed of the developing sleeve 5 is set so as to increase pivot relative peripheral speed of the sensitive light drum 1, to turn early sensitive light drum 1 in the arrow K direction.
By the above configuration, even sudden load change relative sensitive light drum 1 has occurred, and biasing the backlash at all times as shown in the lower part of FIG. 4, the rotation unevenness of the sensitive light drum 1 Can be suppressed.
Thus, the present invention is, on the downstream side of the drum drive gear 29 for transmitting the driving force to the photosensitive light drum 1 that the sleeve driving gear 30 for transmitting the driving force to the developing sleeve 5, sensitive light drum 1 the developing sleeve 5 abuts to turn quickly than sensitive light drum 1. By this way rotation, can always be biased in one direction backlash of the drum drive gear 29, it is possible to suppress the load fluctuation of the sensitive light drum 1.
In particular, the present invention is effective in constituting sliding friction and rotation impact against sensitive light drum 1 is small. For example, as in the process cartridge of this embodiment, no cleaning means for removing the developer sensitive light drum 1 surface while in contact with the surface against sensitive light drum 1, a so-called cleanerless Valid for configuration. However, the present invention is not limited to cleanerless, and the effect is also exhibited in the process cartridge 4 having cleaning means.

<Other embodiments>
In the above embodiment has been described with respect to a monochrome image forming apparatus of the rotary type having one sensitive light drum 1. However, the present invention is not limited thereto, it can also be applied in a tandem color image forming apparatus having a plurality of sensitive light drum 1. The present invention can also be applied to an image forming apparatus 28 that uses a transfer material carrying belt that carries and conveys a transfer material.
Furthermore, in the above-described embodiment, the image forming apparatus including the process cartridge that is detachable from the image forming apparatus main body has been described. However, the present invention can also be applied to an image forming apparatus that does not have a process cartridge.

Further, in the above embodiment has been described as an example a laser beam printer as an image forming apparatus, using a sensitive light drum as an image bearing member, forming an electrostatic latent image which in applying the electrophotographic image forming process However, the present invention can be applied to various apparatuses that form images on a recording medium. For example, electrophotographic printers other than laser beam printers (for example, LED printers), electrophotographic copying machines, electrophotographic facsimile machines, and electrophotographic word processors are included. Furthermore, a mono-color or full-color image forming apparatus that is used as an output device such as a multifunction peripheral or a workstation having these functions is included. The recording medium is an image on which an electrophotographic image forming apparatus forms an image, and includes, for example, paper, an OHP sheet, and the like.

P recording medium 1 sense light drum 4 process cartridges 5 developing sleeve 27 motor pinion 28 the image forming apparatus 28A image forming apparatus main body 29 drum drive gear 30 sleeve drive gear 33 motor (drive source)
35a Upstream idler gear 35b Downstream idler gear

Claims (5)

A photosensitive drum on which a latent image is formed, a developing device for developing said latent image as a toner image by toner supplied by the developing sleeve abuts against the photosensitive drum, a process cartridge Ru provided with,
An apparatus main body to which the process cartridge is detachably mounted , and a drum driving gear for transmitting a driving force from a driving source to the photosensitive drum via a drum coupling, and a developing sleeve via a sleeve coupling An apparatus body having a sleeve drive gear that transmits to
In an image forming apparatus comprising:
In the apparatus main body, the sleeve driving gear is disposed downstream of the drum driving gear with respect to the driving source, and a driving force is transmitted through the drum driving gear through a path that does not pass through the drum coupling. age,
In the process cartridge, the photosensitive drum and the developing sleeve are in contact with each other at least during image formation, and the developing sleeve rotates in a reverse direction with respect to the photosensitive drum at a higher peripheral speed than the photosensitive drum. Thus, the image forming apparatus is configured to transmit a driving force from the sleeve driving gear.   The image forming apparatus according to claim 1, wherein a speed transmission ratio of a gear train is set so that the developing sleeve rotates at a higher peripheral speed than the photosensitive drum. The drum drive gear and the sleeve driving gear, an image forming apparatus according to claim 1 or 2 at both ends of the pivot shaft with respect to the image forming apparatus body is characterized in that it is supported.   The image forming apparatus according to claim 1, wherein the gear that meshes with the drum driving gear upstream and downstream is disposed at a position where a resultant force of the force applied to the drum driving gear becomes small.   The image forming apparatus according to claim 1, wherein the photosensitive drum does not have a cleaning unit that removes the developer on the surface of the photosensitive drum while being in contact with the surface of the photosensitive drum.

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