JP4049736B2 - Image forming apparatus - Google Patents

Description

The present invention comprises an apparatus main body provided with a main body drive gear for obtaining rotational driving from a drive motor, and an image forming unit provided with a developing roller,
When the image forming unit is mounted on the apparatus main body, a passive gear that receives rotational driving from the main body driving gear can be meshed with the main body driving gear by, for example, a proximity operation in the radial direction of the main body driving gear. Relates to the device.

  An electrophotographic image forming apparatus includes an image forming unit that can be separated and assembled to the apparatus main body. As shown in FIG. 1, the image forming unit includes an image forming drum 2 and an image forming drum 2. In some cases, a developing roller 3 is provided, and a rotational drive transmission system is configured so that a predetermined relative rotational state is realized between the image forming drum 2 and the developing roller 3.

  A driving motor M as a driving source for rotational driving in these rotating bodies is provided on the driving side (specifically, on the main body side of the image forming apparatus), and the developing roller 3 is positioned below the driving conduction. Here, the drive motor M is capable of normal rotation and reverse rotation, and the drive motor M rotates forward in a state where image formation is normally performed.

  For example, a paper jam (hereinafter referred to as a jam) or the like occurs in the image forming apparatus, and when the jammed paper is pulled out to the bypass side or the cassette side, the drive motor is linked with these actions. May rotate in reverse.

  Now, with regard to the configuration of the drive transmission system to the developing roller having the above-described configuration, a one-way clutch is interposed in a timing pulley connected to a motor for the purpose of smoothly mounting the image forming unit. There is a thing (for example, patent document 1).

  In this structure, a one-way clutch is provided between the drive motor on the main body side and the developing roller on the unit side, so that relative rotation between the gears to be meshed is allowed when the unit is mounted, and smooth. Can be embedded.

In this prior art, the one-way clutch performs drive transmission during forward rotation and does not perform drive transmission with the lower side free during reverse rotation.
Further, as the clutch, a generally used toothed wheel type is adopted, and the occupied space occupied by the drive transmission system is relatively large.

On the other hand, in order to prevent the occurrence of jitter on a printed image and the deterioration of print quality, there is a drive transmission system with a one-way clutch (for example, Patent Document 2).
In this prior art, the one-way clutch is provided with first and second transmission gears that are supported by the one-way clutch. In contrast, both transmission gears are locked.
As a result, backlash between the photoconductor gear and the second transmission gear and between the first transmission gear and the second reduction gear can be prevented by this one-way clutch.

JP-A-6-118784 (Claims, FIGS. 1, 2 and 3)

Japanese Unexamined Patent Publication No. 64-25159 (Claims, FIG. 1)

  Now, in the rotational drive transmission system from the drive motor to the developing roller, when the drive transmission always occurs regardless of forward rotation or reverse rotation, the developing roller reverses with the reverse rotation of the drive motor, and the toner forming layer on the surface of the developing roller The trouble which disturbs will occur. In addition, there is a possibility that problems (abnormal images, drum scratches, etc.) due to agent ejection in the two-component development may occur due to the relationship with the image forming drum.

  For the purpose of preventing this problem, it is necessary to provide a one-way clutch between the input shaft of the developing roller, which is the lowermost side of the rotation drive transmission system referred to in the present application, and the developing roller driving gear attached to the shaft. Although it is preferable, the developing roller is usually made of a relatively soft material such as an aluminum material, so that the problem of wear on the shaft side is likely to occur. When SUS or the like is used as a constituent material of the developing roller, the problem of wear is solved, but the cost of the image forming unit as a replacement is increased.

  On the other hand, in the technique disclosed in the above-described prior art 1, the rotational drive transmission system is relatively large in the axial direction of the developing roller, and the one-way clutch is a claw-tooth type. It is easy to enlarge in the radial direction, and the cost is high.

  Regarding the above-described prior art 2, the one-way clutch itself is different.

  The object of the present invention is that even if a reverse rotation occurs in the drive motor, the reverse rotation is not transmitted to the developing roller, and it is possible to avoid the occurrence of various problems. It is an object of the present invention to obtain an image forming apparatus having a rotational drive transmission system that can exhibit one-way conductivity with a simple configuration and a small number of parts.

The characteristic configuration of the image forming apparatus according to the present application, which can achieve the above object,
A developing roller driving gear that rotates integrally with the developing roller;
In the rotational drive transmission system from the passive gear to the developing roller drive gear, an idle gear mechanism configured to include a pair of input gear and output gear is provided,
In the idle gear mechanism, in the forward rotation operation in which the forward rotation is transmitted to the input gear, the reverse rotation is transmitted to the input gear in the conduction state in which the output gear rotates integrally with the input gear. In a rotational operation, comprising a latch mechanism for selectively determining the relative rotational relationship between the input gear and the output gear in a non-conductive state where the rotational conduction to the output gear is blocked,
The rotational drive can be transmitted from the passive gear to the input gear, and the rotational drive can be transmitted from the output gear to the developing roller drive gear .
The latch mechanism is configured by including a coil spring interposed between the input gear and the output gear, and an intermediate body biased toward one of the gears by the coil spring.
A latch action portion constituting the latch mechanism is provided on an inner surface of the gear and an inner surface of the gear that intersects with a thrust direction on the side where the intermediate body is biased .

In this image forming apparatus, by providing the developing roller with the developing roller driving gear integrally with the developing roller, problems such as wear on the supporting shaft of the developing roller do not occur.
By providing an idle gear mechanism just above the developing roller drive gear, the one-way transmission function is exhibited, and, for example, the occurrence of problems such as rotation of the developing roller when the drive motor is reversed is avoided. it can. In addition, since the idle gear mechanism having this configuration is actually composed of the input / output gear and the latch mechanism interposed therebetween, it should be simple and perform the desired function with a small number of parts. Can do. Therefore, the cost can be reduced as compared with the case where a commercially available so-called one-way clutch is employed.

Furthermore, by providing this one-way function unit at a position closest to the developing roller, it is possible to eliminate problems such as play that may occur in gear conduction as much as possible.
Furthermore, the intermediate body is urged to one gear side by the coil spring, and the engagement or sliding state can be realized with a simple configuration in the biased state due to the relationship between the intermediate body and the gear inner surface of the urging side. .

The idle gear mechanism is preferably configured as a multistage gear mechanism having an idle gear on the input side of the input gear.
In this way, by configuring the idle gear mechanism in multiple stages, the speed ratio of the gear train can be adjusted well, and the rotation direction required for the developing roller can be appropriately set as necessary.

  In this way, in order to configure the rotational drive transmission system composed of the gear train according to the present application, rotational drive is transmitted from the drum drive gear that rotationally drives the imaging drum provided in the imaging unit to the input gear. It is preferable that a developing idle gear is provided, and the developing idle gear is supported on a rotating shaft of the developing roller so as to be freely rotatable.

  In this configuration, the relative rotation drive is ensured at a predetermined speed ratio by setting the gear ratio between the drum drive gear for rotating the image forming drum and the developing roller drive gear for rotating the developing roller. Can be realized. That is, the synchronization of the driving relationship between the image forming drum and the developing roller can be ensured, and a stable image characteristic can be obtained.

  Further, in the gear train of this configuration, it is only necessary to have a development idle gear and a development roller drive gear with respect to the support shaft of the development roller, and further to provide a pair of input gear and output gear in idle form. As shown in FIG. 1, a pair of gears can be configured to be combined in a conductive manner around two axes, and a very compact, efficient, and highly reliable rotary drive transmission system is constructed. it can.

Now, when this kind of configuration is realized, a convex claw portion as the latch action portion is provided corresponding to the intermediate body and the inner surface of the gear, and the intermediate convex shape that engages in a transmission state of rotational drive. It is preferable that either one or both of the engaging surface of the claw portion and the engaging surface of the corresponding gear convex claw portion have a reverse gradient with respect to the mold opening direction.
When this configuration is employed, the engagement state between the intermediate body and the biasing gear can be reliably realized, and the latch operation can be ensured.

Furthermore, it is preferable that the coil spring is a bamboo child spring whose diameter is increased or decreased in the coil axial direction.
With this configuration, the occupied space required for the idle gear mechanism can be made as small as possible.

In the image forming apparatus having this configuration, even when the main motor is reversely rotated during bypass jam processing, the developing roller does not reversely rotate, and no abnormal image is generated.
By preventing reverse rotation of the developing roller, which occurs when the image forming unit is inserted into and removed from the main body, abnormal images do not occur.
The above two measures can be taken at low cost without using a one-way clutch or the like.

An image forming apparatus (not shown) according to the present application will be described below with reference to the drawings.
The image forming apparatus includes an image forming unit 4 including an image forming drum 2 and a developing roller 3, and an apparatus main body 5 to which the image forming unit 4 is mounted. A drive motor M as a drive source 3 is provided on the apparatus main body 5 side.

[Rotation drive transmission system of image forming unit]
FIG. 1 is a diagram showing a rotational drive transmission system A mainly on the image forming unit 4 side in an electrophotographic image forming apparatus.
The image forming unit 4 provided in the image forming apparatus is configured to be detachable with respect to the apparatus main body 5, and after the operation of inserting the image forming unit 4, as shown in FIG. 2. The developing roller 3 moves in the radial direction (upward direction in the figure) of the drum roller, so that the apparatus main body 5 is connected to the driving motor M and connected to the driving motor M. The drum drive gear 7 as a passive gear is configured to be meshed and connectable.

  In the meshing state, the main body drive gear 6 that is rotationally driven by the drive motor M rotationally drives the drum drive gear 7 provided in the image forming unit 4 so that the drive rotation is transmitted to the image forming unit 4 side. The

Now, the rotational drive transmission system A on the image forming unit 4 side will be described below with reference to FIG.
The rotational drive is input to a drum drive gear 7 for the image forming drum, and is further transmitted to a development idle gear 8 that is rotatably mounted on the support shaft 3a of the development roller 3, from which an idle drive pin is transmitted. 9 is transmitted to an input gear Gi that can rotate freely around 9, and is output via an output gear Go when the rotation is forward rotation, and is transmitted to a developing roller driving gear 10 that rotates integrally with the support shaft 3a of the developing roller 3. Then, the developing roller 3 is driven to rotate.

  In the present application, the conduction system from the passive gear 7 to the developing roller drive gear 10 is referred to as an idle gear mechanism. Further, the input and output gears Gi and Go and the devices interposed therein are referred to as the rotational drive transmission mechanism 1.

  The role of the rotation drive transmission mechanism 1 is so-called unidirectional conduction. For rotation in the positive rotation direction indicated by N in FIG. 1, the input gear Gi and the output gear Go are rotated together as a single unit. Rotation drive is transmitted to the side. On the other hand, for the rotation in the reverse rotation direction indicated by R in the figure, the conduction state between the input gear Gi and the output gear Go is cut off, and the rotational drive is not conducted to the lower conduction side regardless of the rotation on the input side. .

  That is, in the forward rotation state, the image forming drum 2 and the developing roller 3 are both driven to rotate by the rotational drive generated by the drive motor M, but in the reverse rotation state, only the image forming drum 2 rotates. Then, the developing roller 3 remains at the current position.

[Rotary drive transmission mechanism 1]
The rotational drive transmission mechanism 1 employed in the present application has two forms.
1st Embodiment is the most basic form provided with the intermediate body P and the coil spring B between the input gear Gi and the output gear Go, and 2nd Embodiment is the input gear Gi, the intermediate body P, and It has a feature in the engagement structure between.
1 to 5 show the first embodiment, and FIGS. 6 and 7 show the second embodiment.

(1) 1st Embodiment As shown in FIG. 1, the rotational drive transmission mechanism 1 is the diameter of the rotational drive from the drive motor M as a drive source which can be rotated forward / reversely with the gear part g provided in the outer periphery. An input gear Gi that rotates around the idle drive pin 9 when received from the outer side in the direction, and receives the rotation from the input gear Gi and rotates around the idle drive pin 9 so that a gear portion g provided on the outer periphery is provided. And an output gear Go that outputs to the driven side located radially outward.

  Here, the width in the thrust direction (the axial direction width of the rotating shaft) of the rotational drive transmission mechanism 1 is substantially the same as the widths of the gear portions g and g provided at the outer diameter portions of the input gear Gi and the output gear Go. It is just a thing, and downsizing is achieved well.

  Further, an intermediate body P and a coil spring B are interposed between the input gear Gi and the output gear Go in the thrust direction that is the axial direction of the idle drive pin 9. In the rotational drive transmission mechanism 1, in order to realize one-way transmission, the member that is actually deformed is the coil spring B, and the moving member is an intermediate member that is biased toward the input gear Gi by the coil spring B. Body P.

  In the one-way transmission, the intermediate body P that rotates integrally with the output gear Go, the intermediate convex claw portion Pa provided in the intermediate body P, and the intermediate body storage space Gis provided in the input gear Gi are input. It is determined by the contact and sliding relationship with the inclined projection C as the gear convex claw portion.

Substantially, the intermediate body P and the inclined protrusion C constitute a latch mechanism (ratchet) in which the intermediate convex claw Pa moves in the axial direction of the idle drive pin 9 to engage and slide. Will be. As shown in FIG. 4, the inclined protrusions C are equally arranged at two places in the circumferential direction at a pitch of 180 degrees.

1 Input / Output Gear As shown in FIG. 2, the input gear Gi is provided with an intermediate housing space Gis that is bored in the axial direction of the idle drive pin 9 on the radially inner side from the gear portion g. The gear Go includes a spring storage space Gos provided on the radially inner diameter side of the gear portion g with respect to the intermediate storage space Gis (formed at a position corresponding to the radial position).

These spaces Gis and Gos are configured to have opposite side wall surfaces at positions corresponding to each other in the radial direction, and the intermediate housing space Gis provided on the input gear side is shown in FIGS. As described above, a configuration for receiving the intermediate P is adopted.
Then, the inclined protrusion C is formed so as to protrude from the bottom surface thereof, and the inclined protrusion C is formed on the tip t of the intermediate convex claw part Pa provided in the intermediate body P in the forward rotation operation. An abutting surface Ca that abuts and a slidable contact surface Cb on which the outer surface Paw of the intermediate convex claw P is slidably contacted in the reverse rotation operation.

  As a result, the inclined protrusion C as the relative rotation control unit includes the inclined sliding contact surface Cb that sequentially approaches the output gear Go side in the reverse rotation direction from the bottom surface b of the intermediate body storage space Gis. A step surface that rapidly drops from the tip of the contact surface Cb to the bottom surface b of the intermediate body storage space Gis is provided as the contact surface Ca described so far.

As shown in FIGS. 2 and 4, in the output gear Go, the engagement projecting into the space so that the output gear Go and the intermediate body P are rotationally driven integrally in the spring housing space Gos. A convex portion 11 is provided, and an engaging concave portion 12 is provided at a predetermined position on the peripheral portion of the intermediate body P.
Therefore, the output gear Go and the intermediate body P rotate integrally in the assembled state.
2 Coil spring Coil spring B is inserted between output gear Go and intermediate body P as shown in FIG. 2, and is used to urge intermediate body P from output gear Go toward input gear Gi. Is done.
The coil spring B is a so-called bamboo spring, and when the spring is compressed in the axial direction, the thickness of the coil spring B is substantially equal to the thickness of the wire forming the coil.
Further, with respect to the urging force, the input gear Gi rotates in the reverse direction while the intermediate body P is urged toward the input gear Gi side, and the intermediate body P is integrated with the output gear Go. The intermediate body P retracts toward the output gear Go in the axial direction with respect to the gear Gi, and the relative rotation between the intermediate body P and the input gear Gi, in other words, the relative sliding transfer between the input gear Gi and the output gear Go. In this case, a slip between the intermediate body P and the output gear Go is generated.

3 Intermediate P
The configuration of the intermediate body P will be described. As shown in FIGS. 2, 3, and 4, the output gear Go side surface is a contact surface of the coil spring B, and the input gear Gi side surface is with respect to the input gear Gi. It is configured as a contact surface.
The intermediate body P includes a back surface Pb that comes into contact with the coil spring B, and a convex claw portion Pa that comes into contact with an inclined protrusion C provided on the input gear Gi on a surface Pf opposite to the back surface Pb. ing. As shown in FIG. 4, the convex claw Pa is configured in such a manner that the protruding height increases as it proceeds in the reverse rotation direction, and falls to the bottom surface of the rotation control space at the step in the reverse rotation direction. It is configured. This step becomes an engaging surface.
Here, the distribution angle (expansion angle) α of the convex claw Pa is selected to be about 50 degrees.

  By adopting the above configuration, in the forward rotation operation in which the forward rotation (rotation direction indicated by N) is transmitted from the drive motor M to the input gear Gi, the tip t of the convex claw portion Pa provided in the intermediate body P is Abutting against the stepped surface Ca, the rotational drive of the input gear Gi is transmitted to the output gear Go, and these gears Gi and Go rotate together (see FIG. 5 (A)).

  On the other hand, in the reverse rotation operation in which reverse rotation (rotation direction indicated by R) is transmitted to the input gear Gi, the outer surface Paw of the intermediate convex pawl portion Pa of the intermediate P slides on the sliding contact surface Cb. Thus, in a state where a rotational drive with a predetermined torque or more is applied in the reverse rotation direction, the transmission of the rotational drive to the output gear Go is cut off and the rotational drive is not output (see FIG. 5B).

  As a result, in the forward rotation operation and the reverse rotation operation, the imaging drum 2 and the developing roller 3 are driven and rotated in a predetermined direction in the former operation, and only the imaging drum 3 is driven and rotated in the latter operation. The target operation can be realized with a very simple configuration and a small number of parts, using a small occupied space.

(2) Second Embodiment In the first embodiment, the stepped portion of the convex claw portion Pa provided in the intermediate body P is used as an engaging surface, and further, the engaging surface is provided in the input gear Gi. At the time of molding these members, a so-called positive draft is set so that the die-cutting operation can be performed satisfactorily.

However, considering the certainty of the engagement between the intermediate body P and the input gear Gi, the convex claw portion Pa as the latch action portion is provided corresponding to the intermediate body P and the inner surface of the gear, and is driven to rotate. The engagement surface of the intermediate convex claw Pa that engages in the transmission state and the engagement surface of the corresponding gear convex claw C are in the mold opening direction (downward sectional view of FIG. 6, FIG. 6). It is preferable that the slope is reverse to the perspective view of FIG.
Here, the reverse gradient means that the gradient β shown in FIGS. 6 and 7 is within a range of 1 to 5 degrees, for example.

  By doing so, the intermediate body P and the output gear Go can be reliably engaged.

  One-way transmission of rotational drive is performed by a rotational drive transmission mechanism configured with parts with a simple configuration, and an image forming apparatus that does not cause reverse rotation of the developing roller can be obtained.

Diagram showing the rotational drive transmission system from the drive motor to the developing roller 1 is an exploded perspective view of a rotational drive transmission mechanism according to a first embodiment. The longitudinal cross-sectional view of the rotational drive transmission mechanism which concerns on 1st Embodiment Cross-sectional view of the rotary drive transmission mechanism according to the first embodiment Explanatory drawing of the one-way transmission operation | movement of the rotational drive transmission mechanism which concerns on 1st Embodiment. The longitudinal cross-sectional view of the rotational drive transmission mechanism which concerns on 2nd Embodiment, and the perspective view of an intermediate body The longitudinal cross-sectional view of another structure of the rotational drive transmission mechanism which concerns on 2nd Embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotation drive transmission mechanism 2 Image formation drum 3 Developing roller 4 Image formation unit 5 Main body 6 Main body drive gear 7 Drum drive gear 10 Development roller drive gear A Rotation drive transmission system b Bottom surface C Inclination protrusion Ca Contact surface (engagement surface) )
Cb Sliding contact surface Gi Input gear Go Output gear g Gear part P Intermediate body Pa Intermediate body convex claw part

Claims (5)

An apparatus main body provided with a main body drive gear for obtaining rotational drive from a drive motor, and an image forming unit provided with a developing roller;
When the image forming unit is attached to the apparatus main body, an image forming apparatus configured to be able to mesh with the main body drive gear a passive gear that receives the rotational drive from the main body drive gear,
A developing roller driving gear that rotates integrally with the developing roller;
In the rotational drive transmission system from the passive gear to the developing roller drive gear, an idle gear mechanism configured to include a pair of input gear and output gear is provided,
In the idle gear mechanism, in the forward rotation operation in which the forward rotation is transmitted to the input gear, the reverse rotation is transmitted to the input gear in the conduction state in which the output gear rotates integrally with the input gear. In a rotational operation, a latch mechanism that selectively determines the relative rotational relationship between the input gear and the output gear in a non-conductive state in which rotational conduction to the output gear is blocked,
The rotational drive can be transmitted from the passive gear to the input gear, and the rotational drive can be transmitted from the output gear to the developing roller drive gear.
The latch mechanism is configured by including a coil spring interposed between the input gear and the output gear, and an intermediate body biased toward one of the gears by the coil spring.
An image forming apparatus in which a latch action portion constituting the latch mechanism is provided on an inner surface of a gear that intersects the thrust direction on the side to which the intermediate body is urged .   The image forming apparatus according to claim 1, wherein the idle gear mechanism is configured as a multistage gear mechanism including an idle gear on an input side of the input gear. A convex claw portion as the latch action portion is provided corresponding to the intermediate body and the inner surface of the gear, and the engagement surface of the intermediate convex claw portion that engages in the transmission state of the rotational drive and the corresponding gear. one or both of the mating surfaces of the convex claw, relative to the mold opening direction, the image forming apparatus according to claim 1, wherein there is a reverse slope. The image forming apparatus according to claim 1, wherein the coil spring is a bamboo shoot spring having a diameter increased or reduced in a coil axial direction. The rotational drive transmission system includes a development idle gear that transmits rotational drive from the drum drive gear that rotationally drives the imaging drum provided in the imaging unit to the input gear, and the development idle gear includes: The image forming apparatus according to claim 1, wherein the image forming apparatus is supported on a rotating shaft of the developing roller so as to be free to rotate.

Images