Transfer device of image forming apparatus and related image forming apparatus

The transfer device transfers a toner image to a recording medium. The recording medium passes through a nip portion formed by a belt roller which is disposed on a main body of an apparatus and a transfer roller which is disposed on an opening and closing cover. The opening and closing cover opens and closes an opening of a main body of the apparatus. The main body includes a positioning member which positions the transfer roller which moves according to a closing operation of the opening and closing cover, to a predetermined distance with respect to the belt roller. The main body also includes an engaging member which engages with the transfer roller and pushes the transfer roller toward a positioning position of the positioning member, by being urged by a pressurizing spring.

FIELD

Embodiments described herein relate to a pressurizing mechanism of a transfer device which is provided in an image forming apparatus such as a copy machine or a printer.

BACKGROUND

An image forming apparatus such as an electrophotography-type copy machine or a printer includes a transfer device which transfers a toner image which is carried by an image carrier, using a transfer member such as a transfer roller which is disposed at a transfer position, to a member for transferral.

There is a type of a transfer device which allows sheets to pass through between a photoconductive drum as an image carrier and a transfer roller which comes into contact with the photoconductive drum in a pressurizing manner, and transfers a toner image carried on the photoconductive drum to the sheets. In addition, there is a type of a transfer device which primarily transfers the toner image which is carried in the photoconductive drum onto an endless transfer belt, and then transfers the toner image on the transfer belt to the sheet which is allowed to pass through a nip portion between the external transfer roller and the transfer belt, with respect to a pair of transfer rollers which are disposed to face each other in the inside and outside of the transfer belt.

Meanwhile, in the image forming apparatus, an opening and closing cover, which is opened and closed with respect to a main body of the image forming apparatus, is provided at a portion of a sheet conveying path, in order to remove jammed paper in the main body of the image forming apparatus. A configuration in which a transfer member of the transfer device is attached as one such opening and closing cover is proposed.

When the opening and closing cover with the transfer member attached is opened with respect to the image forming apparatus main body, the pinched state of the sheet is released, since the transfer member is separated from the transfer position. In addition, when the opening and closing cover with the transfer member attached is opened, it becomes possible for someone to insert their hands into the sheet conveying path including the periphery of the transfer position, and it is possible to easily treat the jammed paper on which an unfixed toner image is carried.

The transfer member which is attached to the opening and closing cover is held to the opening and closing cover through a pressurizing mechanism which is configured by a spring, or the like. In a state where the opening and closing cover is closed, the transfer member applies a sufficient nip load to the sheet which is passed through for transferring, in order to perform a stable transfer to various sheets.

When the opening and closing cover with the transfer member attached is closed, a reaction force of the nip load is applied to the opening and closing cover with the transfer member attached. For this reason, it is necessary for the opening and closing cover with the transfer member attached to have a high strength and high rigidity and, as a result, the opening and closing cover becomes large and heavy with a complicated structure. In addition, a strong force which resists the pressurizing force of the pressurizing mechanism is necessary when closing the opening and closing cover with the transfer member attached.

Further, the nip load between a transfer member which is attached to the opening and closing cover, for example, a transfer roller on the cover side and a transfer roller (or a photoconductive drum) which is disposed on the main body side of the image forming apparatus which forms a nip portion with the transfer roller on the cover side, is determined, for example, on the basis of the distance between axes of both transfer rollers. The transfer roller on the opening and closing cover side comes into close contact with a positioning member, which is fixed to the main body of the image forming apparatus, and is positioned. For this reason, a predetermined nip load may not be obtained depending on the precision of parts or the precision of attachment, or variation may occur in the nip load in the front and rear of the transfer roller in the axial direction.

DETAILED DESCRIPTION

In general, according to one embodiment of the invention, there is provided a transfer device which transfers a toner image to a member for transferral which passes through a nip portion which is formed by a first transfer member disposed on a main body of an apparatus, and a second transfer member which is disposed on an opening and closing cover which opens and closes an opening portion of the main body of the apparatus.

There is provided a positioning member which positions the second transfer member which moves according to a closing operation of the opening and closing cover, to a predetermined distance with respect to the first transfer member.

There is provided an engaging member which engages with the second transfer member, and pushes the second transfer member toward a position which is positioned by the positioning member, by being urged by an elastic member.

First Embodiment

First, a first embodiment will be described with reference to drawings.

FIG. 1is a front view which illustrates a schematic configuration of an electrophotography-type image forming apparatus.

The image forming apparatus1shown inFIG. 1is a Multi-Function Peripheral (MFP) which has an opening and closing cover3on one side of a main body2of the image forming apparatus, and an image reading unit4on the upper side of the main body2of the image forming apparatus. An endless transfer belt (a primary transfer member)5, which moves in a direction of an arrow a, is disposed in the main body2of the image forming apparatus. The transfer belt5is turned over a roller such as a driving roller5a, a transfer roller11on one side of a transfer device10, or the like. A process cartridge6Y of yellow, a process cartridge6M of magenta, a process cartridge6C of cyan, and a process cartridge6K of black are disposed in the periphery of the transfer belt5. Photoconductive drums7Y,7M,7C, and7K of each process cartridge come into contact with the transfer belt5in a pressurizing manner, through the primary transfer rollers8Y,8M,8C, and8K at a primary transfer position.

A latent image is formed in each of the photoconductive drums7Y,7M,7C, and7K, using exposure light of images from a laser unit9, and each latent image is developed using toner and using the developing unit of each of process cartridges6Y,6M,6C, and6K. The toner image which is formed on each of photoconductive drums7Y,7M,7C, and7K is primarily transferred to the transfer belt5, using the primary transfer rollers8Y,8M,8C, and8K, and moves toward a secondary transfer position on which a transfer device10is disposed.

Regarding the transfer device10, one transfer roller11and the other transfer roller12are disposed in the inside of the transfer roller5, to face each other, with the transfer belt5interposed therebetween. The other transfer roller12is pressurized toward the one transfer roller11. One transfer roller11is attached to a main body2side of an image forming apparatus, and the other transfer roller12is attached to an opening and closing cover3side. A sheet S is conveyed to a nip portion between the other transfer roller12and the transfer roller5, from a sheet feeding cassette13, and the toner image on the transfer belt5is transferred to the sheet S. The sheet S on which an unfixed toner image is secondarily transferred, is conveyed toward a fixing unit14, and the unfixed toner image is fixed to the sheet S by being pressurized and heated. The sheet S on which the image is fixed, is conveyed to a discharge tray16, through a sheet conveying path15.

Here, when a double-sided printing is performed, a flapper17moves in a direction of an arrow b, and the sheet S on which one-sided printing is ended, is guided to a reverse path18. A portion of the reverse path18is attached to the opening and closing cover3. Accordingly, when paper jamming occurs in the transfer device10, if the opening and closing cover3which clogs an opening portion2aof the main body2of the image forming apparatus, is opened, the other transfer roller12is separated from a secondary transfer position. Accordingly, it is possible for someone to insert their hands into the secondary transfer position, and it is possible to easily treat the jamming of the sheet S which is carrying the unfixed toner image.

FIG. 2is a partially-cut front view of the transfer device shown inFIG. 1.FIG. 3is a diagram which illustrates the positioning member shown inFIG. 2.FIG. 4is a diagram which illustrates the roller hook shown inFIG. 2.FIG. 5is a diagram which illustrates the main body of the image forming apparatus when the opening and closing cover shown inFIG. 2is opened.FIG. 6is a front view of the opening and closing cover shown inFIG. 2, which is opened.

As shown inFIGS. 2 and 5, in the one transfer roller11of the transfer device10, a roller axis portion11bprotrudes from each of both ends of the roller main body11ain an axial direction toward the outside in the axial direction, and these roller axis portions11bare rotatably and pivotally supported by the main body2of the image forming apparatus. The positioning member30which performs the positioning of the other transfer roller12is fixed to both sides of the roller main body11ain the axial direction, respectively in the main body2of the image forming apparatus. As shown inFIG. 3, in the positioning member30, an engaging portion32which extends in a horizontal direction from a flat plate-shaped main body31, protrudes to the outside of the main body2of the apparatus, through the opening portion2aof the main body2of the apparatus. The engaging portion32has a fitting recess33whose front end is open. The fitting recess33is formed to be surrounded by an upper arm portion34and a lower arm portion35which vertically face each other, and extends vertically and horizontally, and a deep end surface36which extends in a perpendicular direction.

Both roller axis portions11bof the one side transfer roller11are attached with, for example, an antifriction bearing37, and a roller hook38is mounted in the antifriction bearing37. As shown inFIG. 4, in the roller hook38with a shape of a flat L lever, a hole portion39which fits to an outer periphery portion of the antifriction bearing37is formed in the center portion. A hook portion41is formed in a front end portion of a first lever portion40of the roller hook38, and a spring hole45to which a pressurizing spring44for applying the nip load to a second lever portion42is attached, is formed. One end of the pressurizing spring44is attached to the main body2of the image forming apparatus, and the other end is attached to the spring hole45, and rotates the roller hook38clockwise when a spring force is applied in a direction of an arrow c.

In the hook portion41of the roller hook38, a locking end surface43is positioned in front of the fitting recess33, and an engaging space46for engaging is formed between the hook portion41and a front end of the lower arm portion35.

In the other transfer roller12, a roller axis portion12bprotrudes from each of both ends of the roller main body12ain an axial direction to the outside in the axial direction. For example, an antifriction bearing50is mounted on each of both roller axis portions12b, and a front end portion of each roller axis portion12bis rotatably and pivotally supported by an axis hole portion3bwhich is formed on a side wall portion3aof the opening and closing cover3. The antifriction bearing50engages with the fitting recess33in a vertical direction without backlash.

An internal diameter of the axis hole portion3bis formed to be larger than an external diameter of the roller axis portion12b, and the roller axis portion12bis able to move in the axis hole portion3bin a radial direction. Accordingly, the other transfer roller12is able to move in a plane which is perpendicular to the other transfer roller in an axial direction, with respect to the opening and closing cover3.

On the main body2side of the image forming apparatus, a cover lock axis2bfacing the opening portion2is attached facing the main body2of the image forming apparatus in a front and rear direction, to an upper position of the opening2a. In addition, a bearing member2cfor the opening and closing cover facing the opening portion2ais attached facing the main body2of the image forming apparatus in the front and rear direction, to a lower position of the opening2. An opening and closing axis3cwhich is pivotally supported by each bearing member2c, is attached to the lower portion of the opening and closing cover3, and the opening and closing cover3is opened and closed using the opening and closing axis3cas a fulcrum.

A hook48for the cover lock which is urged in a direction of an arrow d using a locking spring47, is provided to correspond to a cover lock axis2bin the opening and closing cover3. Further, if the opening and closing cover3is closed, the hook48for the cover lock engages with the cover lock axis2b, and the opening and closing cover3is locked at a closing position.

When the opening and closing cover3rotates around the opening and closing axis3cwhich is the fulcrum, the engaging space46for the engaging is positioned in a moving trace of the antifriction bearing50which is provided in the other transfer roller12.

Accordingly, when the opening and closing cover3is rotated to the closing position, the antifriction bearing50rotates the roller hook38counterclockwise against the spring force of the pressurizing spring44, in order to widen the engaging space46. Further, if the antifriction bearing50is pushed into the fitting recess33, the roller hook38rotates clockwise due to the spring force of the pressurizing spring44, and the locking end surface43of the hook portion41pushes the antifriction bearing50toward the deep end surface36.

The distance between axes of the one transfer roller11and the other transfer roller12is set to a predetermined distance under the optimal transfer conditions, at a position where the antifriction bearing50of the other transfer roller12comes into close contact with the deep end surface36of the positioning member30. In addition, the spring force of the pressurizing spring44is applied to the other transfer roller12through the roller hook38which is attached to the main body2side of the image forming apparatus. Accordingly, it is possible to pressurize the other transfer roller12with respect to the one transfer roller11, with a predetermined nip load.

In addition, the locking end surface43is perpendicular to a horizontal axis line L which connects center axes of both transfer rollers11and12, in a state which is shown inFIG. 2, where the roller hook38locks the antifriction bearing50of the other transfer roller12, and the predetermined distance between axes which is determined under the optimal transfer conditions, is set with respect to the one transfer roller11. In addition, the center axis of the other transfer roller12and the center of the opening and closing axis3care deviated by a distance L1.

The spring force of the pressurizing spring44which is applied to the other transfer roller12is not applied to the opening and closing cover3. Therefore, the strength or the like, of the opening and closing cover3may be set without considering the nip load which is applied to the one transfer roller11by the other transfer roller12.

In the embodiment of the invention, as shown inFIG. 5, the spring force of the pressurizing spring44is applied to the one transfer roller11using the roller hook38, in a state where the roller hook38is disposed between the positioning member30and the roller main body11a, and both roller axis portions12bof the other transfer roller12are supported by the positioning member30. In this case, the other transfer roller12is bent toward the one transfer roller11, using both the positioning members30as a fulcrum. For this reason, it is possible for the roller main body12aof the other transfer roller12to apply a substantially uniform nip load along the axial direction to the roller main body11aof the one transfer roller11.

In addition, if the opening and closing cover3is opened, the roller hook30rotates counterclockwise, the locking end surface43is retreated from the front of the fitting recess33of the positioning member30to widen the locking space46, and the locking of the antifriction bearing50of the other transfer roller12is released.

Second Embodiment

FIG. 7illustrates a roller hook according to a second embodiment, andFIG. 8illustrates a transfer device where an opening and closing cover is closed, according to the second embodiment of the invention.FIG. 9is a diagram which illustrates a state where the opening and closing cover is about to be closed inFIG. 8.

Differences between a roller hook60shown inFIG. 7and the roller hook38shown inFIG. 4are that a locking end surface63of a hook portion41is formed to be an inclined surface with an angle θ, and a length of a second lever portion42which is sufficient to come into contact with a stopper axis65, is provided to a front end side of a spring hole45.

In the embodiment, in a state shown inFIG. 8where the roller hook60is locked to an antifriction bearing50of the other transfer roller12, and a predetermined distance between axes is set with respect to the one transfer roller11, the locking end surface63is formed to be an inclined surface with the angle θ, with respect to a horizontal axis line L which connects the center axes of both transfer rollers11and12.

With such a configuration, as shown inFIG. 9, the antifriction bearing50which is provided in the other transfer roller12comes into contact with the locking end surface63immediately before an opening and closing cover3is completely closed. In addition, when the opening and closing cover3is further pushed in a closing direction, the roller hook60rotates clockwise due to a spring force of a pressurizing spring44, the antifriction bearing50is pushed toward the deep end surface36of the fitting recess33using a wedge effect of the locking end surface63, and the roller hook60stops rotating at a stop position where a second lever portion42which is a stopper shown inFIG. 8, comes into close contact with a stopper axis65.

At this stop position, the one transfer roller11and the other transfer roller12are maintained at a predetermined distance between axes which is determined under the optimal transfer conditions, similarly to the first embodiment, and a predetermined nip load is generated.

In the embodiment, the force of the roller hook60which pulls the other transfer roller12to the one transfer roller11is generated due to the wedge effect of the locking end surface63, using a spring force of the pressurizing spring44. For this reason, a return force of the pressurizing spring44is added to the opening and closing cover3, accordingly, it is possible to smoothly close the opening and closing cover3, and the opening and closing cover3is elastically maintained at a closing position, using the spring force of the pressurizing spring44. In addition, it is possible to set a pressing force of the opening and closing cover3to a level that can be easily operated when closing the opening and closing cover3, by changing the spring force of the pressurizing spring44and an inclined angle of the locking end surface63.

Third Embodiment

FIG. 10illustrates a roller hook according to a third embodiment. In the third embodiment, it has a structure in which a distance between axes of the one transfer roller11and the other transfer roller12is changed, and the nip load is adjusted, in a state where an opening and closing cover3is closed. InFIG. 11, the distance between axes of the pair of transfer rollers11and12is short. InFIG. 12, the distance between axes of the pair of transfer rollers11and12is medium. InFIG. 13, the distance between axes of the pair of transfer rollers11and12is widened to be a non-contact state.

Differences between a roller hook60shown inFIG. 7and the roller hook70shown inFIG. 10are that a push back protrusion (a contact portion)71which comes into close contact with an antifriction bearing50provided in the other transfer roller12, is provided, facing a locking end surface63of a hook portion41, and an eccentric cam72is rotatably provided, instead of the stopper axis65shown inFIGS. 8 and 9.

The eccentric cam72has a configuration in which a cam plate74is fixed to a cam axis73, by deviating an axis center of the cam axis73which is rotatably and pivotally supported by the main body2of the image forming apparatus and an axis center of the disc-shaped cam plate74, and a second lever portion42comes into contact with the outer peripheral surface of the cam plate74. If an offset amount at a cam position shown inFIG. 11is 0, the offset amount in the eccentric cam72increases as the cam axis73rotates clockwise.FIG. 12shows a case where the rotation angle of the cam axis73is 90 degrees, andFIG. 13shows a case where the rotation angle of the cam axis73is 180 degrees. The offset amount of the eccentric cam72shown inFIG. 13is the maximum.

The eccentric cams72which are respectively provided to both ends of the one transfer roller11in an axial direction, may rotatably drive the cam axis73, individually, for example, using a motor75.

If the eccentric cam72is adjusted to a reference position which is shown inFIG. 11where the offset amount is 0, the antifriction bearing50which is provided to the other transfer roller12is set to a distance between axes which is determined under the optimal transfer conditions in which the antifriction bearing50comes into close contact with the deep end surface63of the fitting recess33of the positioning member30. In addition, in a state where the distance between axes is set, irrespective of whether the push back protrusion of the roller hook70comes into contact with the antifriction bearing50, or not, a force is not applied in a direction of push back.

Accordingly, the counterclockwise rotation of the roller hook70is suppressed using the eccentric cam72as the stopper, the pair of transfer rollers11and12are set to the distance between axes which is determined under the optimal transfer conditions, and the optimal nip load is applied.

When the eccentric cam72rotates clockwise, the roller hook70rotates counterclockwise against to the spring force of the pressurizing spring44, and the antifriction bearings50which are respectively provided to both ends of the other transfer roller12in an axial direction come into close contact with the push back protrusion71, and are pushed back toward the locking end surface63. For this reason, the distance between axes of the pair of transfer rollers11and12, is adjusted. It is possible to separately adjust the distance between axes in the front and rear direction, by allowing the eccentric cams72which are disposed at both ends of the one transfer roller11in an axial direction (the front and rear direction), to be eccentric, respectively.

The nip load between the transfer rollers in the front and rear direction becomes uneven, when the distance between axes of the other transfer roller12in the front and rear direction is different, due to a variation in precision of a size of the positioning member30which is provided on the main body2side of the image forming apparatus, or a precision of attachment. There is a problem that the uneven nip load between the transfer rollers causes deterioration of images.

However, according to the embodiment, it is possible to adjust the distance between axes of the pair of transfer rollers11and12in the front and rear direction, to be equal, by separately adjusting the eccentric cams72which are respectively disposed at the front and rear of one transfer roller11.

In addition, as shown inFIG. 13, when opening the opening and closing cover3, the roller hook70largely rotates counterclockwise, so as to widen a space46in advance. If the opening and closing cover3rotates in an opening direction in this state, the antifriction bearing50allows the roller hook70to slightly rotate counterclockwise, to further widen the space46. For this reason, the antifriction bearing50is extracted from the space46, thereby opening the opening and closing cover3.

Subsequently, when the opening and closing cover3is closed while maintaining the roller hook70at a state shown inFIG. 13, the antifriction bearing50engages with the roller hook70with almost no load, and comes into close contact with the push back protrusion71. In addition, the nip load is set to the optimal transfer conditions, by rotating the eccentric cams72which are disposed at the front and rear of the one transfer roller11, respectively, to a position which is shown inFIG. 11, due to a driving by a motor M, or a position shown inFIG. 12where the distance between axes in the front and rear is separately adjusted. For this reason, a reaction force of the nip load is not applied to the opening and closing cover3, when closing the opening and closing cover3.

Fourth Embodiment

FIGS. 14 and 15illustrate a transfer device according to a fourth embodiment. In the embodiment, a modified example of the second embodiment shown inFIGS. 7 to 9is illustrated, and in the embodiment, a stop position of a roller hook60can be adjusted.

In the embodiment, a difference from the second embodiment shown inFIGS. 7 to 9is that it is possible to adjust a stop position of the roller hook60using a screw-type adjusting portion80, instead of the stopper axis65. The screw-type adjusting portion80is formed of a nut member81which is fixed to a main body2of the image forming apparatus, and an adjusting screw82which is screw-fitted to the nut member81and whose front end comes into contact with a second lever portion42of the roller hook60.

When the adjusting screw82shown inFIG. 14is rotated to the right, as shown inFIG. 15, the adjusting screw82moves toward the second lever portion42, and the contact position with the second lever portion42of the roller hook60, is changed. In this manner, it is possible to adjust the distance between axes of the pair of transfer rollers11and12to the optimal transfer conditions by rotating the adjusting screw82to the right or to the left, and by adjusting a front end position of the adjusting screw82which is the stopper end. Further, it is possible to adjust a variation of the nip load in the axial direction of the pair of transfer rollers11and12, by separately adjusting screw-type adjusting portions80which are provided to the one transfer roller11in a front and rear direction.

Fifth Embodiment

FIGS. 16 and 17illustrate a transfer device according to a fifth embodiment. In the embodiment, a modified example of the second embodiment shown inFIGS. 7 to 9is illustrated, similarly to the fourth embodiment. Further, it is possible to adjust a stop position of a roller hook60.

In the embodiment, a difference from the second embodiment shown inFIGS. 7 to 9, is that it is possible to adjust the stop position of the roller hook60using the eccentric cam72according to the third embodiment which is shown inFIGS. 11 to 13, instead of the stopper axis65.

If the eccentric cam72is rotated from a position shown inFIG. 16where the offset amount is 0, by driving a cam axis73using a motor, the offset amount increases, and a position where a second lever portion42of the roller hook60comes into close contact with a cam plate74is changed. In this case, it is also possible to adjust a distance between axes of a pair of transfer rollers11and12to the optimal transfer conditions, similarly to the above-described fourth embodiment. Further, it is possible to adjust a variation of a nip load of the pair of transfer rollers11and12, in an axial direction, by separately adjusting screw-type adjusting portions80provided in the one transfer roller11, in the front and rear direction.

Sixth Embodiment

FIG. 18illustrates a sixth embodiment. In the embodiment, in contrast to the first embodiment shown inFIG. 2, a roller hook38, a positioning member30, and a pressurizing spring44are disposed on an opening and closing cover3. In addition, an antifriction bearing37which is provided in the one transfer roller11which is disposed on a main body2side of the image forming apparatus, is fitted to a fitting recess33of a positioning member30. The roller hook38engages with the antifriction bearing37, and draws in the antifriction bearing37towards the other transfer roller12to have the predetermined distance of axes. In this case, a roller axis11bof the one transfer roller11is shaft supported by a shaft hole2dwhich is provided on the main body2side of the image forming apparatus. The inner diameter of the shaft hole2dis larger than the outer diameter of the roller axis11b, and the one transfer roller11can move freely around the shaft.

In the embodiment, in contrast to the first embodiment, the positioning member30and the roller hook38are disposed on the opening and closing cover3side; however, this reverse configuration may be similarly applied to the above-described second embodiment to the fifth embodiment.

In addition, in each embodiment described above, an example was described in which the opening and closing cover3rotated around the opening and closing axis3as the fulcrum; however, the cover may be a translation-type opening and closing cover.