CN112462585B

CN112462585B - Image forming apparatus having a plurality of image forming units

Info

Publication number: CN112462585B
Application number: CN202010927875.1A
Authority: CN
Inventors: 久我透
Original assignee: Ricoh Co Ltd
Current assignee: Ricoh Co Ltd
Priority date: 2019-09-09
Filing date: 2020-09-07
Publication date: 2023-10-13
Anticipated expiration: 2040-09-07
Also published as: CN112462585A; JP2021043281A

Abstract

The present invention relates to an image forming apparatus that appropriately rotates a transfer roller with respect to an image carrier without increasing the number of parts. It comprises the following steps: an image forming apparatus includes an image carrier that carries a toner image and is driven, a transfer rotator that is driven to rotate on the image carrier and transfers the toner image onto a recording medium, and a driven auxiliary member that imparts an auxiliary force that assists the driven rotation of the transfer rotator to the transfer rotator.

Description

Image forming apparatus having a plurality of image forming units

Technical Field

The present invention relates to an image forming apparatus.

Background

Conventionally, in an image forming apparatus of an electrophotographic system, a technique for transferring a toner image formed on an image carrier onto a recording medium using a transfer roller or the like has been known.

Further, a technique is disclosed in which the transfer roller is rotated by the image carrier, so that a variation in the peripheral speed of the transfer roller with respect to the image carrier is suppressed, and image defects such as a magnification error in the conveyance direction in a toner image on a recording medium are prevented (for example, refer to patent documents 1 and 2).

However, in the technique of patent document 1, since the electrostatic cleaning brush that contacts the transfer roller that rotates in the same direction as the rotation direction of the transfer roller is rotated, the friction force of the electrostatic cleaning brush may prevent the rotation of the transfer roller, and thus, an image defect may occur. In the technique of patent document 2, a torque limiter or the like is used to rotate the transfer roller with respect to the image carrier, and thus the number of parts may be increased.

Japanese patent document 1 (Kokai) No. 5038045

Japanese patent document 1 (JP-A) No. 11-52757

Disclosure of Invention

The technology disclosed in the present specification aims to solve the problem of appropriately rotating the transfer roller with respect to the image carrier without increasing the number of parts.

An image forming apparatus according to an embodiment of the disclosed technology includes: an image forming apparatus includes an image carrier that carries a toner image and is driven, a transfer rotator that is driven to rotate on the image carrier and transfers the toner image onto a recording medium, and a driven auxiliary member that imparts an auxiliary force that assists the driven rotation of the transfer rotator to the transfer rotator.

According to the technology disclosed in the present specification, the transfer roller can be appropriately driven to rotate relative to the image carrier without increasing the number of parts.

Drawings

Fig. 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment.

Fig. 2 is an enlarged perspective view of a main portion of the image forming apparatus according to the first embodiment.

Fig. 3 is a configuration diagram of a main portion of the image forming apparatus according to the first comparative example.

Fig. 4 is a configuration diagram of a main portion of an image forming apparatus according to a second comparative example.

Fig. 5 is an explanatory diagram of an assisting force assisting the driven rotation of the secondary transfer roller.

Fig. 6 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

Fig. 7 is an enlarged perspective view of a main portion of an image forming apparatus according to a second embodiment.

Fig. 8 is a configuration diagram of a main part of an image forming apparatus according to a modification.

Detailed Description

Hereinafter, modes for carrying out the present invention will be described with reference to the drawings. In each drawing, the same structural parts are given the same reference numerals, and a repetitive description thereof may be omitted.

In the embodiment, the driven rotation is performed on the image carrier that carries the toner image and is driven, and the transfer rotating body that causes the toner image to be transferred onto the recording medium imparts an assist force that assists the driven rotation.

For example, in the embodiment, the assist force for assisting the driven rotation is given to the transfer rotating body by rotating the cleaning brush or the like that is brought into contact with the transfer rotating body to slide and rub the surface of the transfer rotating body in a direction opposite to the rotation direction of the transfer rotating body.

Thereby, the driven load that hinders the driven rotation of the transfer rotary body is reduced, and the transfer rotary body is driven rotated appropriately with respect to the image carrier. Then, the fluctuation of the peripheral speed of the transfer rotary body with respect to the image carrier is suppressed, and image defects such as magnification errors in the conveying direction and the like in the toner image on the recording medium are prevented.

Here, the driven rotation of the transfer rotary body means that the transfer rotary body itself is not connected to a driving section such as a motor, but the transfer rotary body is rotated in accordance with the image carrier by using, as a driving source, a frictional force or the like of the image carrier driven in contact with the transfer rotary body. Since such driven rotation is referred to as motoring rotation, in the description of the embodiment, driven rotation is referred to as motoring rotation.

Hereinafter, an embodiment will be described by taking a serial image forming apparatus as an example. In the embodiment, the intermediate transfer belt is used as an image carrier, the secondary transfer roller is used as a transfer rotator, and the paper is used as a recording medium.

First embodiment

< construction example of image Forming apparatus 100 >

First, the configuration of an image forming apparatus 100 according to a first embodiment will be described with reference to fig. 1. Fig. 1 is an exemplary diagram illustrating a configuration of an image forming apparatus 100. As shown in fig. 1, an image forming apparatus 100 has an intermediate transfer belt 1 as an endless belt.

The intermediate transfer belt 1 is supported by a driving roller 11 that is rotationally driven by a driving unit such as a motor, driven rollers 12 and 13 that are rotationally driven by the intermediate transfer belt 1, and a secondary transfer opposing roller 41 that is an opposing rotating body. The intermediate transfer belt 1 is driven by rotation of the driving roller 11, and moves around in the A1 direction.

The image forming apparatus 100 includes photosensitive drums 2Y, 2M, 2C, and 2Bk, and is capable of forming images corresponding to colors decomposed into yellow (Y), magenta (M), cyan (C), and black (Bk), respectively. The photosensitive drums 2Y, 2M, 2C, 2Bk (hereinafter referred to as photosensitive drum 2 in the case of no distinction, and also referred to as a generic term in the case of no distinction among other members such as primary transfer rollers) are arranged side by side in this color order from the upstream side toward the downstream side in the A1 direction.

After being charged by a charging device provided around the photosensitive drum 2, optical writing based on image information is performed on the photosensitive drum 2 by an optical writing device, and an electrostatic latent image is formed on the photosensitive drum 2. The electrostatic latent image is visualized as a toner image by a developing device. The toner images formed on the photosensitive drums 2 are superimposed transferred (primary transfer) onto the same position of the intermediate transfer belt 1 during the travel of the intermediate transfer belt 1. In fig. 1, the charging device, the optical writing device, and the developing device are not shown.

The primary transfer is performed by applying a voltage to a primary transfer roller 3 as a transfer rotating body so as to face the photosensitive drums 2 of the respective colors with the intermediate transfer belt 1 interposed therebetween, and shifting the timing from the upstream side to the downstream side in the A1 direction. By the primary transfer, a color toner image is formed on the intermediate transfer belt 1. The intermediate transfer belt 1 carries the formed color toner image and travels.

A secondary transfer roller 40 and a secondary transfer counter roller 41 as transfer rotating bodies are provided downstream of the driving roller 11 in the A1 direction. The secondary transfer roller 40 and the secondary transfer opposing roller 41 are opposed to each other with the intermediate transfer belt 1 interposed therebetween. The secondary transfer roller 40 is pressed against the secondary transfer opposing roller 41 to press-contact the intermediate transfer belt 1, and a press-contact portion 410 is formed between the secondary transfer roller and the intermediate transfer belt 1. Here, the pressure contact portion refers to a contact portion between the intermediate transfer belt 1 and the secondary transfer roller 40 formed by applying pressure, and is a portion surrounded by a broken-line circle in fig. 1. The nip portion 410 is formed by applying pressure to the secondary transfer roller 40 and the secondary transfer opposing roller 41 with the intermediate transfer belt 1 interposed therebetween to form a nip portion.

The secondary transfer roller 40 is configured to be separated from each other for preventing abrasion of the intermediate transfer belt 1 or the like during non-image formation in the image forming apparatus 100, and to be in contact with the intermediate transfer belt 1 only during image formation. However, the components may not necessarily be separable.

The sheet S fed from a sheet feeder (not shown) is fed from the registration roller pair 5 in the direction A2 at a predetermined timing, and enters the pressure-bonding section 410. When the sheet S enters the press-contact portion 410 and passes through, a voltage is applied by the secondary transfer roller 40, and the toner image on the intermediate transfer belt 1 is secondarily transferred onto the sheet S.

The sheet S to which the toner image is transferred is sent to the fixing device 6. Then, by applying heat and pressure in the fixing device 6, the toner image on the sheet S is melted and fixed on the sheet S.

In the case of duplex printing, the front and rear sides of the sheet S after fixing and the front and rear ends in the conveying direction are reversed, and the sheet S is conveyed toward the secondary transfer roller 40 again. Then, the toner image is secondarily transferred and fixed on the surface opposite to the surface on which the toner image is fixed. The sheet S having the toner image fixed on one side or both sides is discharged to the outside of the image forming apparatus 100 after curl is reduced.

Next, the configuration of the secondary transfer roller 40 and its surroundings will be described in more detail with reference to fig. 1.

The secondary transfer roller 40 is not connected to a driving unit such as a motor, but is rotated in the B1 direction (counterclockwise direction) by the urging force of the intermediate transfer belt 1 as the intermediate transfer belt 1 advances in the A1 direction (clockwise direction). By such rotation, the secondary transfer roller 40 can rotate at the same peripheral speed as the traveling speed of the intermediate transfer belt 1.

The secondary transfer opposing roller 41 is also not connected to a driving unit such as a motor, and is rotated by the intermediate transfer belt 1 by the urging force of the intermediate transfer belt 1.

A cleaning brush 42 as a driven auxiliary member, a cleaning blade 43 as a driven load member, and a lubricant application brush 44 as a driven auxiliary member are provided around the secondary transfer roller 40. They are in contact with the surface (surface in contact with the sheet S) of the secondary transfer roller 40 in a rotatable state. In addition, a waste toner screw 45 is provided in contact with the cleaning brush 42. The cleaning brush 42, the lubricant applying brush 44, and the waste toner screw 45 are rotationally driven by a motor 46 via pulleys, gears, or the like, respectively.

The cleaning brush 42 is a brush roller rotated in the B2 direction (clockwise direction) by the motor 46. The cleaning blade 43 is a blade member supported by a cantilever such as a frame of the image forming apparatus 100, and the free end side thereof abuts against the surface of the secondary transfer roller 40 in the opposite direction.

The cleaning brush 42 cleans the surface of the secondary transfer roller 40 by sliding and rubbing the residual toner adhering to the surface of the secondary transfer roller 40. The cleaning blade 43 picks up the residual toner from the secondary transfer roller 40 by the blade edge, and cleans the surface of the secondary transfer roller 40.

The residual toner, which is slidably rubbed by the cleaning brush 42 and scraped off from the secondary transfer roller 40, moves with the rotation of the cleaning brush 42, and is scraped off from the cleaning brush 42 by contact with the waste toner screw 45. The waste toner screw 45 is rotated in the B3 direction (counterclockwise direction) by the motor 46, and the scraped-off residual toner is conveyed in the rotation axis direction of the waste toner screw 45 and stored in a storage portion such as a waste toner tank.

The lubricant applying brush 44 is constituted by a cylindrical rotating shaft member and a plurality of fuzzes provided on the outer peripheral surface of the rotating shaft member, and is rotated in the B4 direction (clockwise direction) by the motor 46. In the lubricant applying brush 44, a solid lubricant 441 biased toward the lubricant applying brush 44 by a coil spring or the like is pressed against.

The lubricant applying brush 44 applies lubricant powder taken from the solid lubricant 441 onto the surface of the secondary transfer roller 40 by rotating. By applying the lubricant to the surface of the secondary transfer roller 40, the surface friction resistance of the secondary transfer roller 40 can be reduced, and the cleaning property, transfer property, and the like can be improved. In addition, in the member for applying the lubricant, a sponge-coated roller having a sponge-made roller portion may be used instead of the lubricant-coated brush 44.

Next, fig. 2 is an enlarged perspective view showing the configuration of the secondary transfer roller 40 and its surroundings, and is a configuration diagram showing the main part of the image forming apparatus 100.

As shown in fig. 2, a pressing spring 411 is connected to both axial ends of the secondary transfer roller 40, and a force in the positive Z direction is applied to the secondary transfer roller 40 by the elastic force of the pressing spring 411. The secondary transfer roller 40 is pressed against the secondary transfer opposing roller 41 by the elastic force of the pressing spring 411 to press-contact the intermediate transfer belt 1, and a press-contact portion 410 is formed between the secondary transfer roller and the intermediate transfer belt 1.

In addition, as shown in fig. 2, the motor 46 transmits a driving force to the waste toner screw 45 via the gear 451, thereby rotating the waste toner screw 45 in the B3 direction. In addition, the motor 46 transmits a driving force to the cleaning brush 42 via the gear 451 and the gear pulley 421 to rotate the cleaning brush 42 in the B2 direction. Further, the motor 46 transmits a driving force to the lubricant brush 44 via the gear 451, the gear pulley 421, the toothed belt 462, and the pulley 442 to rotate the lubricant brush 44 in the B4 direction.

< principal part constitution of image Forming apparatus according to comparative example >

Here, before explaining the operation of the image forming apparatus 100 according to the embodiment, an image forming apparatus according to a comparative example will be described.

In the secondary transfer step, slippage or the like occurs between the intermediate transfer belt and the secondary transfer roller due to the type of paper (paper type), environment, amount of toner to be transferred, and the like, and the peripheral speed of the secondary transfer roller may vary with respect to the intermediate transfer belt. As a result, the speed of the sheet passing through the nip portion formed by the intermediate transfer belt and the secondary transfer roller fluctuates, and image defects such as magnification errors in the conveying direction (passing direction) may occur in the toner image on the sheet.

Such image defects such as magnification errors can be prevented by rotating the secondary transfer roller at the same peripheral speed as the traveling speed of the intermediate transfer belt by rotating the secondary transfer roller with the intermediate transfer belt.

Here, fig. 3 is an explanatory diagram of a first comparative example in which the secondary transfer roller is rotated with the intermediate transfer belt. A schematic diagram showing the main part configuration of the image forming apparatus 100' according to the first comparative example is shown. As shown in fig. 3, the image forming apparatus 100 'has an intermediate transfer belt 1', a secondary transfer roller 40', and a secondary transfer opposing roller 41'.

The secondary transfer roller 40 'is pressed against the secondary transfer opposing roller 41' to press-contact the intermediate transfer belt 1', and forms a press-contact portion with the intermediate transfer belt 1'. Further, electrostatic cleaning brushes 471' and 472' are provided around the secondary transfer roller 40 '. The electrostatic cleaning brushes 471' and 472' are in contact with the surface of the secondary transfer roller 40' in a rotatable state.

The secondary transfer roller 40' is not connected to the driving section, but is rotated in the B1' direction (counterclockwise direction) by the urging force of the intermediate transfer belt 1' as the intermediate transfer belt 1' advances in the A1' direction (clockwise direction). The secondary transfer opposing roller 41 'is similarly rotated by the intermediate transfer belt 1'.

On the other hand, the electrostatic cleaning brush 471 'rotates in the B2' direction (counterclockwise direction), and the electrostatic cleaning brush 472 'rotates in the B3' direction (counterclockwise direction). The B2' and B3' directions are the same direction as the rotation direction of the secondary transfer roller 40 '.

Accordingly, the frictional force generated by the contact of the electrostatic cleaning brushes 471 'and 472' with the surface of the secondary transfer roller 40', respectively, acts as a driven load that resists the driving rotation of the secondary transfer roller 40'.

Therefore, in the case where the frictional force between the intermediate transfer belt 1' and the secondary transfer roller 40' is insufficient, or the like, the driven load due to the electrostatic cleaning brushes 471' and 472' may prevent the secondary transfer roller 40' from rotating, and a fluctuation in the peripheral speed of the secondary transfer roller 40' with respect to the intermediate transfer belt 1' may occur. Then, the speed of the paper passing through the pressure contact portion may vary, and the above-described magnification error may occur.

Fig. 4 is an explanatory diagram of a second comparative example in which the secondary transfer roller is rotated by the intermediate transfer belt. A schematic diagram showing the main part configuration of the image forming apparatus 100″ according to the second comparative example is shown. As shown in fig. 4, the image forming apparatus 100 "has an intermediate transfer belt 1", a secondary transfer roller 40", and a secondary transfer opposing roller 41".

The secondary transfer roller 40 "is pressed against the secondary transfer opposing roller 41" to press against the intermediate transfer belt 1 "rotating in the A1" direction (clockwise direction), and forms a press-contact portion with the intermediate transfer belt 1". The secondary transfer roller 40 "is rotationally driven in the direction B1" (counterclockwise) by a motor 401"B" connected via a torque limiter 402 ".

Further, a cleaning blade 43″ is provided around the secondary transfer roller 40″. The cleaning blade 43 "abuts against the surface of the secondary transfer roller 40" in the opposite direction.

When the rotational load of the secondary transfer roller 40 "increases due to frictional resistance of the intermediate transfer belt 1" or the cleaning blade 43", the image forming apparatus 100" restricts the torque of the secondary transfer roller 40 "by the torque limiter 402". By the torque limitation, the secondary transfer roller 40 "is rotated by the intermediate transfer belt 1", and the secondary transfer roller 40 "can be rotated at a peripheral speed substantially equal to the traveling speed of the intermediate transfer belt.

However, in the image forming apparatus 100", a torque limiter or the like is added to the configuration, so that the number of parts may be increased.

< action of driven auxiliary Member according to the embodiment >

As described above, in the image forming apparatus 100 according to the embodiment, the rotation direction (B2 direction) of the cleaning brush 42 and the rotation direction (B4 direction) of the lubricant applying brush 44 are opposite to each other with respect to the rotation direction (B1 direction) of the secondary transfer roller 40. Accordingly, the frictional force generated by the contact of the cleaning brush 42 and the lubricant applying brush 44 with the surface of the secondary transfer roller 40 acts as an assisting force assisting the rotation of the secondary transfer roller 40.

In other words, the motor 46 can apply an assist force for assisting the rotation to the secondary transfer roller 40 by rotating the cleaning brush 42 and the lubricant applying brush 44 in the direction opposite to the rotation direction of the secondary transfer roller 40.

Here, fig. 5 is an explanatory diagram of an assisting force assisting the rotation of the secondary transfer roller 40. As shown in fig. 5, the secondary transfer roller 40 rotates in the B1 direction, the cleaning brush 42 rotates in the B2 direction, and the lubricant applying brush 44 rotates in the B4 direction.

In a portion where the secondary transfer roller 40 is in contact with the cleaning brush 42, a frictional force generated by the contact of the cleaning brush 42 acts in the C1 direction indicated by an arrow of a broken line and acts in the same direction as the driving direction in the same position of the secondary transfer roller 40. Therefore, the cleaning brush 42 can give an assisting force for assisting the rotation of the secondary transfer roller 40 by rotating as a driven assisting member.

In addition, in the portion where the secondary transfer roller 40 is in contact with the lubricant application brush 44, the frictional force generated by the contact of the lubricant application brush 44 acts in the C2 direction indicated by the arrow of the chain line and acts in the same direction as the driving direction in the same position of the secondary transfer roller 40. Therefore, the lubricant applying brush 44 can give an assisting force for assisting the rotation of the secondary transfer roller 40 by rotating as a driven assisting member.

On the other hand, the frictional force of the cleaning blade 43 in contact with the secondary transfer roller 40 acts in the direction of C3 indicated by the arrow of the two-dot chain line and acts in the opposite direction to the driving direction in the same position as the secondary transfer roller 40. Therefore, as a driven load member, the cleaning blade 43 applies a driven load to the secondary transfer roller 40 that impedes the driving rotation of the secondary transfer roller 40.

Here, the description is continued with reference to fig. 2. The cleaning brush 42 and the lubricant applying brush 44 are examples of the rotating body contact member. The cleaning brush 42 is an example of a rotating body cleaning brush, and the lubricant applying brush 44 is an example of a rotating body applying brush. The motor 46 that rotates them is an example of a rotating body contact member driving member.

In the present embodiment, the motor 46, the cleaning brush 42, the lubricant applying brush 44, the gear 451, the gear pulley 421, the toothed belt 462, and the pulley 442 constitute a driven auxiliary member that imparts an auxiliary force for assisting the rotation of the secondary transfer roller 40.

However, the configuration of the driven auxiliary member is not limited thereto. The driven auxiliary member may be provided with either the cleaning brush 42 or the lubricant application brush 44, and may be provided with other members as long as the auxiliary force is applied. The driven auxiliary member may include only a part of the gear 451, the gear pulley 421, the toothed belt 462, and the pulley 442, or may include other driving force transmission members.

On the other hand, since the cleaning blade 43 is abutted against the surface of the secondary transfer roller 40 in the opposite direction, a driven load that hinders the driving rotation is applied to the secondary transfer roller 40 in the opposite direction to the driving rotation direction of the secondary transfer roller 40. Such a cleaning blade 43 is an example of a driven load member.

However, the driven load is not limited to being applied by the driven load member of the cleaning blade 43 or the like. For example, a conveying load or the like, which is a load for conveying the sheet S, corresponds to a driven load because torque fluctuation of the secondary transfer roller 40 occurs.

The auxiliary force is applied to the secondary transfer roller 40 by the auxiliary member, so that the load of the secondary transfer roller 40 can be reduced. Alternatively, the auxiliary force of the driven load or more applied to the secondary transfer roller 40 is applied to the secondary transfer roller 40 by a driven load member or the like, whereby the driven load of the secondary transfer roller 40 can be eliminated.

< Effect of image Forming apparatus 100 >

As described above, in the present embodiment, the assist force assisting the rotation by the intermediate transfer belt 1 is applied to the secondary transfer roller 40.

Specifically, the image forming apparatus 100 rotates the cleaning brush 42 in contact with the secondary transfer roller 40 in the opposite direction (B2 direction) to the rotation direction (B1 direction) of the secondary transfer roller 40. In addition, the lubricant application brush 44 in contact with the secondary transfer roller 40 is also rotated in the opposite direction (B4 direction) to the rotation direction (B1 direction) of the secondary transfer roller 40. Thereby, an assist force assisting rotation by the intermediate transfer belt 1 is applied to the secondary transfer roller 40.

By applying the assist force, it is possible to suppress the fluctuation of the peripheral speed of the secondary transfer roller 40 caused by the driven load, and to appropriately rotate the secondary transfer roller 40 by the intermediate transfer belt 1.

On the other hand, in order to apply the assist force, since the rotation direction of the motor 46 is set so that the cleaning brush 42 and the lubricant applying brush 44 rotate in the opposite direction to the secondary transfer roller 40, no new parts such as a torque limiter or a one-way clutch may be added to the image forming apparatus 100.

As described above, in the present embodiment, the secondary transfer roller 40 can be appropriately rotated with respect to the intermediate transfer belt 1 without increasing the number of parts. Then, the speed variation of the sheet S passing through the pressure contact portion 410 in the secondary transfer step can be suppressed, and image defects such as magnification errors in the sheet conveying direction in the toner image on the sheet S can be prevented.

Here, the peripheral speed of the cleaning brush 42 and the lubricant application brush 44 is preferably greater than the peripheral speed of the secondary transfer roller 40. For example, the peripheral speeds of the cleaning brush 42 and the lubricant applying brush 44 are set to 1.01 times the peripheral speed of the secondary transfer roller 40, or the like.

In this way, the assisting force by the cleaning brush 42 and the lubricant applying brush 44 can be ensured, and even when the driven load of the driven load member or the like becomes large, the driven load can be reduced, and the secondary transfer roller 40 can be stably rotated by the intermediate transfer belt 1.

Further, since the raised portions are recessed after the contact with the secondary transfer roller 40, the peripheral speeds of the cleaning brush 42 and the lubricant application brush 44 are preferably the peripheral speeds in a state where the rotation radius of the brush roller is slightly shortened.

In addition, it is preferable that the motor 46 starts the rotation driving at an earlier timing than the photosensitive drum 2 primary-transfers the toner image onto the intermediate transfer belt 1, and stops the rotation driving after the secondary transfer to the sheet S is completed. In this way, the auxiliary force can be applied to the secondary transfer roller 40 in all the periods from the end to the end of the secondary transfer, and the secondary transfer roller 40 can be stably rotated by the intermediate transfer belt 1.

When the sheet S enters the pressure contact portion 410, the surface of the secondary transfer roller 40 drops downward by the thickness of the sheet S. When the secondary transfer roller 40 is rotated, the secondary transfer roller is shaped to follow the back surface of the sheet S.

Therefore, when image formation is continuously performed on a plurality of sheets S, torque fluctuation corresponding to the conveyance load of the sheets S may occur during a period from when the subsequent sheet S after the secondary transfer enters the pressure contact portion 410. Therefore, in the period during which the sheet S is conveyed and the period until the subsequent sheet S enters the pressure contact portion 410 (period during which the sheet S is not conveyed), since the conveyance load is different, it is preferable to make the assisting force of the two different. As such, the conveyance load of the sheet S can be reduced, and the secondary transfer roller 40 can be stably rotated by the intermediate transfer belt 1.

In addition, although fig. 2 shows an example in which the secondary transfer roller 40 is brought into contact with the secondary transfer counter roller 41 by the elastic force of the pressing spring 411, the present invention is not limited thereto. The secondary transfer roller 40 may be brought into contact with and separated from the secondary transfer opposing roller 41 by advancing and retreating either the secondary transfer roller 40 or the secondary transfer opposing roller 41 in the Z direction of fig. 2 using a cam.

In addition, a load for rotating the secondary transfer roller 40 and the secondary transfer counter roller 41 and a conveying load of the sheet S are applied to the intermediate transfer belt 1 at the time of image formation. Since the conveyance load of the sheet S varies depending on the sheet type or sheet thickness of the sheet S, it is preferable to design the driving roller 11, the driven rollers 12 to 13, and the like so that the driving torque can be ensured even under the condition that the conveyance load is maximum.

Second embodiment

Next, an image forming apparatus 100a according to a second embodiment will be described with reference to fig. 6 and 7. In addition, components having the same functions and structures as those of the first embodiment are described with the same reference numerals.

< construction example of image Forming apparatus 100a >

Fig. 6 is a schematic diagram of an embodiment of an image forming apparatus 100 a. Fig. 7 is an enlarged perspective view of an exemplary configuration of a main portion of image forming apparatus 100 a.

As shown in fig. 6 and 7, the image forming apparatus 100a includes a secondary transfer belt 47 and two driven rollers 48. The secondary transfer belt 47 is supported by the secondary transfer roller 40 and two driven rollers 48.

As a material, the secondary transfer belt 47 is made of polyimide resin. The secondary transfer belt 47 is pressed against the secondary transfer opposing roller 41 by the secondary transfer roller 40 to press-contact the intermediate transfer belt 1, and forms a press-contact portion 410a shown by a circle of a broken line with the intermediate transfer belt 1. For example, the nip portion is formed by applying pressure to the secondary transfer roller 40 and the secondary transfer opposing roller 41 with the intermediate transfer belt 2 and the secondary transfer belt 47 interposed therebetween, and the pressure contact portion 410a is formed.

In addition, the secondary transfer belt 47 is moved around in the A3 direction (counterclockwise direction) by rotating with the secondary transfer belt 47 being driven with respect to the secondary transfer roller 40 of the intermediate transfer belt 1. Here, the secondary transfer belt 47 is an example of a belt member, and each of the two driven rollers 48 is an example of a suspension member.

A cleaning brush 42a as a driven auxiliary member, a cleaning blade 43a as a driven load member, and a lubricant application brush 44a as a driven auxiliary member are provided around the secondary transfer roller 47. They are in contact with the surface of the secondary transfer belt 47 on the side contacting the sheet S.

In addition, a waste toner screw 45 is provided in contact with the cleaning brush 42 a. The cleaning brush 42a, the lubricant applying brush 44a, and the waste toner screw 45 are all rotationally driven by a motor 46a via pulleys, gears, or the like.

The function of the cleaning brush 42a is the same as that of the cleaning brush 42 in the first embodiment except that the surface against which the secondary transfer belt 47 abuts. The function of the cleaning blade 43a is the same as that of the cleaning blade 43 in the first embodiment except that the surface that abuts is the surface of the secondary transfer belt 47. The function of the lubricant applying brush 44a is the same as that of the lubricant applying brush 44 in the first embodiment except that the surface that abuts against is the surface of the secondary transfer belt 47. Therefore, these duplicate descriptions are omitted herein.

The rotation direction (B2 direction) of the cleaning brush 42a and the rotation direction (B4 direction) of the lubricant applying brush 44a are each opposite to the rotation direction (B1 direction) of the secondary transfer roller 40. Therefore, the frictional force generated by the contact of the cleaning brush 42a and the lubricant applying brush 44a with the belt surface of the secondary transfer belt 47 assists the traveling movement of the secondary transfer belt 47, and the secondary transfer belt 47 serves as a driven auxiliary member to assist the rotation of the secondary transfer roller 40.

In other words, the motor 46a can impart an auxiliary force for assisting the rotation of the secondary transfer roller 40 by the secondary transfer belt 47 by rotating the cleaning brush 42a and the lubricant applying brush 44a in the direction opposite to the rotation direction of the secondary transfer roller 40.

On the other hand, the frictional force of the cleaning blade 43a abutting against the secondary transfer belt 47 acts in the opposite direction to the driving direction of the secondary transfer belt 47. Therefore, as a driven load member, the cleaning blade 47a applies a driven load to the secondary transfer roller 40 via the secondary transfer belt 47, which resists the driving rotation of the secondary transfer roller 40.

Here, the cleaning brush 42a and the lubricant applying brush 44a are examples of the belt contact member. The cleaning brush 42a is an example of a belt cleaning brush, and the lubricant applying brush 44a is an example of a belt applying brush. The motor 46a that rotates them is one example of a belt contact member driving member. The cleaning blade 43a is an example of a driven load member.

In the present embodiment, the motor 46a, the cleaning brush 42a, the lubricant applying brush 44a, the gear 451, the gear pulley 421, the toothed belt 462, and the pulley 442 constitute driven auxiliary members.

However, the configuration of the driven auxiliary member is not limited thereto. The driven auxiliary member may be provided with either the cleaning brush 42a or the lubricant application brush 44a, and may be provided with other members as long as the auxiliary force is applied. The driven auxiliary member may include only a part of the gear 451, the gear pulley 421, the toothed belt 462, and the pulley 442, or may include other driving force transmission members.

The auxiliary force is applied to the secondary transfer roller 40 by the auxiliary member via the secondary transfer belt 47, so that the load of the secondary transfer roller 40 can be reduced. Alternatively, the auxiliary force of the driven load or more given to the secondary transfer roller 40 by the driven load member or the like is applied to the secondary transfer roller 40 by the secondary transfer belt 47, and the driven load of the secondary transfer roller 40 can be eliminated by the secondary transfer belt 47.

< Effect of image Forming apparatus 100a >

As described above, in the present embodiment, the secondary transfer belt 47 supported by the secondary transfer roller 40 and the two driven rollers 48 is provided, and the assist force for assisting the interlocking rotation is applied to the secondary transfer roller 40 via the secondary transfer belt 47.

Specifically, the image forming apparatus 100a rotates the cleaning brush 42a in contact with the secondary transfer belt 47 in a direction (B2 direction) opposite to the rotation direction (B1 direction) of the secondary transfer roller 40. In addition, the lubricant applying brush 44a in contact with the secondary transfer belt 47 is also rotated in the opposite direction (B4 direction) to the rotation direction (B1 direction) of the secondary transfer roller 40. Thereby, the above-described assist force is applied to the secondary transfer roller 40.

As in the first embodiment, in order to apply the assist force, the rotation direction of the motor 46a is set so that the cleaning brush 42a and the lubricant applying brush 44a rotate in the opposite direction to the secondary transfer roller 40, and therefore, no new parts such as a torque limiter and a one-way clutch may be added to the image forming apparatus 100 a.

Further, since the cleaning blade 43a is brought into contact with the secondary transfer belt 47 made of polyimide resin having a small friction coefficient, the driven load on the secondary transfer roller 40 due to friction with the cleaning blade 43a can be further suppressed.

The effects other than the above are the same as those described in the first embodiment.

While the preferred embodiments and examples of the present invention have been described in detail, the present invention is not limited to these embodiments and examples, and various modifications and changes can be made within the gist of the present invention described in the claims.

For example, when an elastic intermediate transfer belt having an elastic layer applied to the surface thereof is used as the intermediate transfer belt 1, the frictional resistance of the elastic layer may be increased, and the secondary transfer roller 40 may be unstable in rotation with respect to the intermediate transfer belt 1. Therefore, when an elastic intermediate transfer belt is used as the intermediate transfer belt 1, the embodiment is preferably applied. In addition, in the elastic intermediate transfer belt, polyimide resin may be used as a base material, and an acrylic rubber or the like may be coated on the surface of the base material.

In addition, when a roller (soft roller) which is an elastically deformable counter roller having a surface layer deformed by a contact pressure is used as the secondary transfer counter roller 41 and a roller (hard roller) which is harder than the counter roller is used as the secondary transfer roller 40 as a transfer rotating body for deforming the surface layer of the secondary transfer counter roller 41, the secondary transfer roller 40 may be unstable against the driving rotation of the intermediate transfer belt 1.

Therefore, when such a soft roller and a hard roller are used, an embodiment is more preferable. In addition, as the soft roll, a roll having a surface layer of foamed polyurethane formed on the axial center of the metal, or the like can be used. As the hard roll, a metal roll such as SUS (stainless steel), SAM, or the like, a surface-treated metal roll, a roll whose surface is coated with a resin such as polytetrafluoroethylene, or the like can be used.

In the above-described embodiment, the example in which the intermediate transfer belt 1 is used for the image carrier has been shown, but the present invention is not limited thereto. The embodiment can be applied even in a configuration in which the toner image formed on the photosensitive drum is directly transferred onto the sheet S without via the intermediate transfer belt. In this case, the photosensitive drum corresponds to the image carrier, and can be appropriately brought into rotation with respect to the photosensitive drum rotationally driven by a driving member such as a motor.

Further, the embodiment can be applied to a configuration in which a photosensitive belt is provided in place of the photosensitive drum 2, and a toner image formed on the photosensitive belt is directly transferred onto the sheet S. In this case, the photosensitive belt corresponds to the image carrier, and the secondary transfer roller 40 can be appropriately brought into rotation with respect to the photosensitive belt driven and traveling by the driving roller.

In the above example of direct transfer, the secondary transfer step is performed using the secondary transfer roller 40, but the same applies to the case of performing the secondary transfer step using the secondary transfer roller 40 and the secondary transfer belt 47.

In the above embodiment, the example was described in which the secondary transfer roller 40 is pressed against the secondary transfer opposing roller 41 to press-contact the intermediate transfer belt 1, and the pressure contact portion 410 is formed between the secondary transfer roller and the intermediate transfer belt 1, but the present invention is not limited to this. As shown in fig. 8, the embodiment can be applied even in the case where the secondary transfer roller 40 is pressed against the intermediate transfer belt 1 by the two rollers 41a and 41b to be in pressure contact therewith, and the pressure contact portion 420 is formed between the secondary transfer roller and the intermediate transfer belt 1.

Claims

1. An image forming apparatus, characterized by comprising:

an image carrier that carries a toner image and is driven;

a transfer rotator which is driven to rotate on the image carrier and transfers the toner image to a recording medium, and

and a driven auxiliary member that imparts an auxiliary force for assisting the driven rotation of the transfer rotating body to the transfer rotating body.

2. The image forming apparatus according to claim 1, wherein:

a driven load member for imparting a driven load to the transfer rotating body, the driven load being a force that resists the driven rotation,

the auxiliary force applied by the auxiliary load member is applied to the transfer rotating body by the auxiliary force applied by the auxiliary load member.

3. The image forming apparatus according to claim 1 or 2, wherein:

the driven auxiliary member includes a rotation body contact member contacting the transfer rotation body and a rotation body contact member driving part rotating the rotation body contact member,

the rotary body contact member driving unit rotates the rotary body contact member in a direction opposite to the rotation direction of the transfer rotary body, and applies the assist force.

4. An image forming apparatus according to claim 3, wherein:

the rotating body contact member includes at least one of a rotating body cleaning brush that slides against a surface of the transfer rotating body, and a rotating body coating brush that coats a lubricant on the surface of the transfer rotating body.

5. An image forming apparatus according to claim 3, wherein:

the peripheral speed of the rotating body contact member is greater than the peripheral speed of the transfer rotating body.

6. The image forming apparatus according to claim 1 or 2, wherein:

has a belt member supported by the transfer rotating body and the suspension member,

the transfer rotator transfers the toner image onto the recording medium through the belt member,

the driven assisting member includes a belt contact member that contacts the belt member, and a belt contact member driving member that rotates the belt contact member,

the belt contact member driving member rotates the belt contact member in a direction opposite to a rotation direction of the transfer rotating body, and imparts the assist force.

7. The image forming apparatus according to claim 6, wherein:

the belt contact member includes at least one of a belt cleaning brush that slides against a surface of the belt member, and a belt coating brush that coats a lubricant on the surface of the belt member.

8. The image forming apparatus according to claim 6, wherein:

the peripheral speed of the belt contact member is greater than the peripheral speed of the transfer rotary body.

9. The image forming apparatus according to claim 1, wherein:

an opposing rotating body having a surface layer deformed by contact pressure and opposing the transfer rotating body with the image carrier interposed therebetween,

the transfer rotator is configured to deform the surface layer.

10. The image forming apparatus according to claim 1, wherein:

the image carrier is an intermediate transfer belt.

11. The image forming apparatus according to claim 10, wherein:

the intermediate transfer belt is an elastic intermediate transfer belt having an elastic layer.