JPH09311522A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the positional deviation of each color toner image caused by speed fluctuation due to load fluctuation by providing a press-contact member for always applying a frictional load to the rotation of a driving shaft and making the influence of the load fluctuation relatively little. SOLUTION: A cleaner cam shaft 53 is rotated at the timing of the arrival of a nonimage part at a part with which a belt cleaner 27 comes into press- contact, so that the belt cleaner 27 comes into press-contact with a belt 22, to remove toner remaining after a secondary transfer is performed. Further, the belt cleaner 27 and a transfer roller are brought into press-contact with each other, while a primary transfer is performed and the belt 22 is stopped at a position where the nonimage part faces an image forming unit. After that, the belt cleaner 27 and the transfer roller are separated from the belt 22. In such a case, a blade 50 comes into press-contact with the driving shaft 23, so that the load of the belt 22 is increase and frictional force for driving the belt 22 by the driving shaft 23 is increased as well. Further, a press-contact blade 60 comes into press-contact with the driving shaft 23 used also for the belt cleaner 27, so that the load fluctuation due to the eccentricity of the driving shaft 23 is offset by a cleaner part and a braking part.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a color printer,
The present invention relates to a color image forming apparatus applied to a color copying machine or a color facsimile.

[0002]

[Prior art]

(Conventional Example 1) As a conventional image forming apparatus, for example, Japanese Patent Laid-Open No.
The one described in Japanese Patent No. 333921 is known, and FIG. 18 is a diagram showing its structure. In the figure, around the photoconductor 101, a charger 102, an exposure device 103,
Four color developing units 104Y, 104M, 104C and 104Bk for yellow, magenta, cyan and black,
Cleaning device 1 including transfer charger 105, cleaning blade 106, and pressure contact blade 107
08 is provided. The cleaning blade 106, which is movable in the direction of the arrow shown in the drawing with respect to the photoconductor 101, moves toward and away from the photoconductor 101 as necessary. on the other hand,
The pressure contact blades 107 are constantly in pressure contact with the peripheral surfaces of the non-image portions at both ends of the photoconductor.

Next, the operation of the above conventional image forming apparatus will be described. First, after the photoconductor 101 is charged by the charging device 102, an electrostatic latent image is formed by the exposure device 103 and developed by the yellow developing device 104Y. Thereafter, an electrostatic latent image formed on the photoconductor 101 holding the yellow toner image in the same process is used as a magenta developing unit 104M.
To develop. This process is sequentially performed for cyan and black, and toner images of four colors are superposed on the photoconductor 101 to form a color image. Then, the transfer charger 10
5, the toner images are collectively transferred onto the recording paper 108 and fixed by a fixing device (not shown) to obtain a color image. During the image formation, the cleaning blade 106 is separated from the photosensitive drum so as not to disturb the toner image. And
The transfer residual toner is removed by contacting the photoconductor 101 at a predetermined timing.

(Prior Art 2) As another conventional image forming apparatus, the one described in Japanese Patent Application Laid-Open No. 5-72912 is also known, and FIG. 19 is a diagram showing the configuration thereof.
In the figure, a charger 122,
Exposure device 123, developing devices 124Y, 124M, and 124C for four colors of yellow, magenta, cyan, and black
And 124 Bk, the intermediate transfer belt 125, and the photoconductor cleaner 126 that is constantly in pressure contact with the photoconductor 121. A belt cleaner 127 and a transfer roller 128 are arranged around the intermediate transfer belt 125.
The belt cleaner 127 and the transfer roller 128 can be brought into contact with and separated from the intermediate transfer belt 125 in the directions of arrows shown in the figure.

The operation of the image forming apparatus of the conventional example 2 will be described. First, after the photoconductor 121 is charged by the charger 122, an electrostatic latent image is formed by the exposure device 123 and developed by the yellow developing device 124Y. The developed yellow toner image is immediately transferred to the intermediate transfer belt 125. Then, in the same process, the electrostatic latent image on the photoconductor 121 is developed by the magenta developing unit 124M, and the magenta toner image is transferred onto the intermediate transfer belt 125 holding the yellow toner image in an overlapping manner. Further, the same steps are sequentially performed for cyan and black, and the toner images of four colors are superimposed on the intermediate transfer belt 125 to form a color image. Then, the intermediate transfer belt 125 does not disturb the toner image.
The transfer roller 128 separated from the recording paper 129 is pressed against the intermediate transfer belt 125 via the recording paper 129 to collectively transfer the toner images to the recording paper 129, and the toner image is fixed by a fixing device (not shown) to obtain a color image. During this image formation, the belt cleaner 127 is separated from the intermediate transfer belt 125 so as not to disturb the toner image. Then, the transfer residual toner is removed by contacting at a predetermined timing.

FIG. 20 is a view showing the structure around the transfer roller 128. The transfer roller 128 is coaxially provided with a roller gear 131 via a one-way clutch 130 as shown in FIG. 20, and when it is separated from the intermediate transfer belt 125, the peripheral speed of the intermediate transfer belt 125 is controlled by a roller drive gear 132 on the main body side. It is configured to be slower than the peripheral speed.

[0007]

However, in the above-mentioned conventional example 1 (FIG. 18), by pressing the cleaning blade 106 in the normal direction of the photoconductor 101, the pressing force is increased in a short time, and the pressing force is rapidly increased. Load fluctuations. For this reason, there is a problem in that the rotational fluctuation cannot be suppressed and the image expands and contracts due to the speed fluctuation, resulting in color misregistration in the toner image of each color. In addition, there is a similar problem in Conventional Example 2 (FIG. 19). Generally, when a blade or the like that is constantly in pressure contact with the peripheral surface of the belt is provided, the effective tension acting on the belt increases, and so-called creep slip occurs between the belt and the drive shaft. For example, “machine design”, 33rd
As described in Vol. 16, No. 16 (pages 93 to 100) and the like, this creep slip always occurs in the state where the drive shaft transmits the drive force to the belt, and the tension of the belt is increased. The cause is the expansion and contraction of the belt due to the effective tension, which is the difference in tension between the loose side and the loose side. When the above-described creep slip occurs in the color image forming apparatus, the drive shaft and the belt are out of phase, and the speed variation pattern of the drive shaft affects the position on the belt. Therefore, as the image forming process is repeated for yellow, magenta, cyan, and black, there arises a problem that expansion and contraction due to speed fluctuations of different patterns cause color misregistration in toner images of respective colors. Conventional example 2
In consideration of this point, the pressure contact structure is not always used, and the belt cleaner 127 and the transfer roller 128 are pressed against the intermediate transfer belt 125 only when necessary. However, the belt cleaner 12 for the intermediate transfer belt 125
Intermediate transfer belt 12 caused by load fluctuation due to pressure contact of 7
It was not possible to sufficiently cope with the fluctuation of the peripheral speed of No. 5. Therefore, the position of the toner image of each color is displaced on the intermediate transfer belt 125, and the image quality is deteriorated.

A high-precision contact / separation operation mechanism can be used to suppress the load fluctuation, but in that case, the so-called bite amount of the cleaning blade 106 and the belt cleaner 127 is kept small for a long time. The cleaning blade 106 or the belt cleaner 1 is rubbed by friction with the photoconductor 101 or the intermediate transfer belt 125.
There is a problem that 27 is turned up and cleaning becomes impossible.

Further, in the structure in which the one-way clutch 130 is provided on the transfer roller 128 as in the second conventional example (FIGS. 19 and 20), the one-way clutch 130 accelerates and rotates the transfer roller 128.
It is necessary to transmit force in the acceleration direction and idle in the deceleration direction. Therefore, in the configuration using the one-way clutch 130, the peripheral speed of the transfer roller 128 is set to be slower than the peripheral speed of the belt, and the transfer roller 128 is accelerated when being pressed against the belt and driven.

The graph of FIG. 21 shows the relationship between the bite amount and the rotational speed when the transfer roller 128, which is an elastic body, is in contact with and driven by the intermediate transfer belt 125. As shown in the figure, the rotation speed is low at the beginning of contact due to sliding, but
After that, the speed rises rapidly, and after the friction is stabilized (speed U), the rotation speed decreases as the bite amount increases. That is, the virtual radius of the transfer roller 128 increases as the biting amount increases. The relationship between the bite amount and the virtual radius can be calculated from the ratio of the deformation volume of the elastic roller due to pressure contact to the deformation region.
Pp. 267-268). Therefore, when the transfer roller 128 rotating slower than the peripheral speed of the intermediate transfer belt 125 is brought into pressure contact with the intermediate transfer belt 125, the transfer roller 128 is once accelerated in the first half of the bite and then decelerated as the bite amount increases. .

Generally, when controlling at a constant speed, when the deceleration load increases, the motor tries to maintain the speed by increasing the acceleration force. However, if an acceleration load is generated after the deceleration load is increased, the acceleration control is combined with the acceleration force of the motor, resulting in excessive acceleration and unstable speed control. Therefore, the configuration in which the deceleration load changes to the acceleration load is not suitable for the purpose of obtaining a constant speed.

The present invention has been made in order to solve the above problems, and provides a color image forming apparatus capable of preventing positional deviation of toner images of respective colors due to speed fluctuations caused by load fluctuations. With the goal.

[0013]

In order to solve the above problems, the present invention comprises a pressure contact member which constantly applies a frictional load to the rotation of the drive shaft, whereby a belt cleaner and a transfer roller are pressed against each other. In this case, a configuration is provided in which the influence of load fluctuations is relatively small.

Further, the present invention comprises a pressing contact / separation mechanism for contacting / separating the press contact member with respect to the drive shaft, and simultaneously presses the belt cleaner or the transfer roller against the intermediate transfer belt and separates the press contact member from the drive shaft. It is equipped with the configuration.

Further, the present invention comprises a friction clutch for disconnecting and connecting the driving force to the roller driving mechanism for driving the transfer roller, and the friction force of the friction clutch is smaller than the friction force of the intermediate transfer belt and the transfer roller. It is equipped with.

Further, in the present invention, the rotational speed V of the transfer roller is equal to or higher than the rotational speed W when the transfer roller is pressed against the intermediate transfer belt and driven by the frictional force, and the pressing of the belt cleaner and the transfer roller are performed. It is equipped with a structure in which the pressure welding is performed almost at the same time.

Further, the present invention has a construction in which the cleaner contact / separation mechanism presses one end of the cleaning blade in the longitudinal direction prior to the other end while primary transfer of the toner image of the last color to the intermediate transfer belt. It is a thing.

According to the present invention, the cleaning blade is pressed against the intermediate transfer belt while the toner image of the last color is primarily transferred onto the intermediate transfer belt, and the tip of the cleaning blade is pressed from the direction substantially tangential to the intermediate transfer belt during this pressing operation. It has a configuration in which it comes into contact and moves to a predetermined pressure contact position.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The color image forming apparatus of the present invention is
A plurality of developing devices having toners of different colors, a photoconductor on which toner images of a plurality of colors are formed by the developing devices, and a supporting shaft including a rotating drive shaft are stretched to face the photoconductor. An intermediate transfer belt that runs on the photoconductor and sequentially primary-transfers the toner images on the photoconductor, and a transfer unit that secondarily transfers the toner images on the intermediate transfer belt to a recording sheet.
A belt cleaner that holds the intermediate transfer belt so that it can be brought into and out of contact with the intermediate transfer belt, and removes toner remaining after secondary transfer on the intermediate transfer belt, and a mechanism that presses and separates the belt cleaner from the intermediate transfer belt. Therefore, during the primary transfer of the toner image of the last color in the primary transfer to the intermediate transfer belt, a cleaner contact / separation mechanism that presses the belt cleaner and a drive shaft is constantly pressed to rotate the drive shaft. And a pressure contact member that applies a frictional load.

Further, another color image forming apparatus of the present invention comprises a plurality of developing devices having toners of different colors,
The developing device runs by being stretched so as to face the photoconductor with a photoconductor on which toner images of multiple colors are formed on the surface and a supporting shaft including a rotating drive shaft, and the toner images on the photoconductor are sequentially superposed. On the intermediate transfer belt, a transfer roller that holds the intermediate transfer belt so that the toner image is secondarily transferred to the recording paper that is sandwiched between the intermediate transfer belt and the intermediate transfer belt that is primarily transferred. Secondary transfer A mechanism that presses and separates the belt cleaner that removes residual toner and the transfer roller from the intermediate transfer belt, and during the primary transfer of the toner image of the last color in the primary transfer to the intermediate transfer belt. A roller contacting / separating mechanism that presses the transfer roller, and a pressing member that constantly presses the drive shaft and applies a frictional load to the rotation of the drive shaft.

The pressing member may be pressed against the cylindrical surface of the drive shaft.

Another color image forming apparatus of the present invention comprises a plurality of developing devices having toners of different colors.
The developing device runs by being stretched so as to face the photoconductor with a photoconductor on which toner images of multiple colors are formed on the surface and a supporting shaft including a rotating drive shaft, and the toner images on the photoconductor are sequentially superposed. Intermediate transfer belt for primary transfer by means of a secondary transfer, transfer means for secondary transfer of the toner image on the intermediate transfer belt to the recording paper, and the intermediate transfer belt are held so that they can come into contact with and separate from each other. A belt cleaner that removes residual toner after the next transfer and a mechanism that presses and separates the belt cleaner from the intermediate transfer belt, and during the primary transfer of the toner image of the last color in the primary transfer to the intermediate transfer belt, A cleaner contact / separation mechanism that presses the belt cleaner, a press contact member that presses the drive shaft to apply a frictional load to the rotation of the drive shaft, and a mechanism that causes the press contact member to contact and separate from the drive shaft. A pressure contact against the intermediate transfer belt of the belt cleaner, is characterized in that it has at the same time performing configuration and spacing relative to the drive shaft of the pressing member.

The intermediate transfer belt, the pressure contact member, and the belt cleaner may be integrally formed as a belt unit that can be attached to and detached from the main body of the color image forming apparatus.

Further, another color image forming apparatus of the present invention includes a plurality of developing devices having toners of different colors,
An intermediate transfer belt that runs on the surface of a photoconductor on which toner images of multiple colors are formed by a developing device and the photoconductor is run, and the toner images on the photoconductor are sequentially superposed and primarily transferred. A transfer roller that is held so that it can be brought into contact with and separated from the belt, and that has elasticity to secondarily transfer the toner image on the intermediate transfer belt to the recording paper that is sandwiched between the intermediate transfer belt and the intermediate transfer belt; A roller contacting / separating mechanism for pressing and separating, a roller driving mechanism for disconnecting and connecting the driving force to the transfer roller by using a friction clutch having a frictional force smaller than the frictional force between the intermediate transfer belt and the transfer roller,
It is provided with.

When the transfer roller is separated from the intermediate transfer belt, the transfer roller is configured to rotate at a peripheral speed substantially equal to the peripheral speed of the surface of the intermediate transfer belt by the driving force of the roller driving mechanism. May be.

Further, a belt cleaner for removing the residual toner after secondary transfer on the intermediate transfer belt is provided, the transfer roller is installed below the belt cleaner, and the clutch of the roller driving mechanism is not coaxial with the transfer roller. A configuration installed in the gear is also possible.

Further, another image forming apparatus of the present invention is rotatable with a plurality of developing devices having toners of different colors and a photoconductor on which toner images of a plurality of colors are sequentially formed by the developing devices. An intermediate transfer belt that is stretched to face the photoconductor by a plurality of support shafts and runs, and the toner images of different colors on the photoconductor are sequentially superposed and primarily transferred. When the toner is held and is in contact with the intermediate transfer belt, the transfer roller having elasticity to secondarily transfer the toner image on the intermediate transfer belt to the recording paper sandwiched between the intermediate transfer belt and the transfer roller is moved to press and separate the intermediate transfer belt. The roller contact / separation mechanism for performing, the roller driving mechanism for driving the transfer roller, and the intermediate transfer belt are held so that they can be contacted and separated from each other. Comprising a belt cleaner for removing the toner, and a cleaner and away mechanism for contacting and separating the belt cleaner to the intermediate transfer belt, the rotational speed V of the transfer roller
Is equal to or higher than the rotational speed W when the transfer roller is pressed against the intermediate transfer belt and driven by a frictional force, and is configured to press the belt cleaner and the transfer roller at substantially the same time. To do.

A drum cleaner that is in constant pressure contact with the photoconductor to remove the toner on the photoconductor after the primary transfer, a photoconductor drive unit that drives the photoconductor, and a belt drive unit that drives the drive shaft are provided. The photosensitive member driving unit and the belt driving unit may be connected and driven by the same driving source.

In the primary transfer, the electrostatic latent image of the last color may be formed on the photosensitive member while the belt cleaner is pressed against it.

The belt cleaner may be provided with a cleaning blade that is in pressure contact with the intermediate transfer belt.

Further, another color image forming apparatus of the present invention comprises a plurality of developing devices having toners of different colors,
A developing device forms a toner image of a plurality of colors on its surface, and a supporting shaft including a rotating drive shaft stretches the photosensitive member so as to face the photosensitive member. The intermediate transfer belt that is primarily transferred, the transfer unit that secondarily transfers the toner image on the intermediate transfer belt to the recording paper, and the secondary transfer that is held in contact with and separated from the intermediate transfer belt. A belt cleaner equipped with a cleaning blade that removes the remaining toner, and a cleaner contact / separation mechanism that contacts and separates the cleaning blade with respect to the intermediate transfer belt.In the primary transfer, the toner image of the last color is transferred to the intermediate transfer belt. It is characterized in that the cleaner contacting / separating mechanism is configured to press one end of the cleaning blade in the longitudinal direction into pressure contact prior to the other end while performing the primary transfer.

Further, another color image forming apparatus of the present invention comprises a plurality of developing devices having toners of different colors,
A developing device forms a toner image of a plurality of colors on its surface, and a supporting shaft including a rotating drive shaft stretches the photosensitive member so as to face the photosensitive member. The intermediate transfer belt that is primarily transferred, the transfer unit that secondarily transfers the toner image on the intermediate transfer belt to the recording paper, and the secondary transfer that is held in contact with and separated from the intermediate transfer belt. A belt cleaner having a cleaning blade for removing the remaining toner and a cleaner contact / separation mechanism for contacting / separating the cleaning blade with respect to the intermediate transfer belt are provided, and in the primary transfer, the toner image of the last color is transferred to the intermediate transfer belt. While the primary transfer is in progress, the cleaning blade is pressed against the intermediate transfer belt, and the tip of the cleaning blade is contacted from the tangential direction of the intermediate transfer belt during this pressing operation. , Characterized in that it is configured to move to a predetermined pressing position.

[0033]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 17. << Embodiment 1 >> The overall configuration and operation of a color image forming apparatus according to Embodiment 1 will be described with reference to FIGS. In FIG. 1, the image forming unit 1 includes yellow, magenta,
A process element is disposed around and integrated with an organic photoconductor (hereinafter simply referred to as a photoconductor) 2 for each color of cyan and black. Since each color has the same configuration, only the black image forming unit 1 will be described here, and description of the image forming units for yellow, magenta, and cyan will be omitted. The photoconductor 2 is mainly composed of a polycarbonate-based binder resin using phthalocyanine as a light-sensitive material. The charger 3 charges the photoconductor 2. The grid 4 controls the charging potential. The laser light enters the image forming unit 1 through the exposure window 5.

The developing device 6 comprises a toner hopper 7, a developing roller 8, a doctor blade 9 and the like. The toner hopper 7 contains negatively charged black toner 10. Photoconductor cleaner 1 for cleaning the toner on the surface of the photoconductor 2
The reference numeral 1 includes a photoconductor blade 12 made of polyurethane rubber, which is constantly in pressure contact with the photoconductor 2 for cleaning, and a waste toner reservoir 13. The photoconductor blade 12 has a rectangular cross section with a thickness of 1.5 mm and a length of 9 mm, is set to a free end length of 5 mm, the press contact angle with the tangent line of the photoconductor 2 is 22 degrees, and the biting amount in the normal direction is It is 1.2 mm. The diameter of the photoconductor 2 is 30
mm, the developing roller 8 has a diameter of 16 mm and is rotatably held.

FIG. 2 shows the belt unit 20. The belt unit 20 includes a unit case 21, an intermediate transfer belt 22, a drive shaft 23, an A driven shaft 24, a B driven shaft 25, a tension roller 26, a belt cleaner 27, a waste toner reservoir 28, a position detector 29, and a brake 30. Equipped with.
The intermediate transfer belt 22 is made of an endless belt-shaped semi-conductive (medium resistance) urethane having a thickness of 100 μm as a base material, and the surface layer is made of a fluororesin such as PFA / PTFE and has a total thickness of 100 to 500 μm. It consists of a film. In the following description of the embodiments, the intermediate transfer belt 22 is simply referred to as the belt 22. The belt 22 is stretched around a drive shaft 23, an A driven shaft 24, a B driven shaft 25, and a tension roller 26, and is configured to be able to run by the rotation of the drive shaft 23.

Since the toner images of the respective colors are transferred on the belt 22 without positional deviation, the belt 22 has a peripheral length satisfying an integer multiple of the outer peripheral length of the drive shaft 23, and the recording paper is It is set longer than the length. Therefore, if the belt circumferential length is not enough to be n times the outer circumference of the drive shaft 23 for some reason, it must be extended to n + 1 times the circumferential length. Here, the length of the non-image portion of the difference between the recording paper and the belt circumference is 9
It is set to 0 mm. The circumference of the contact portion from the A driven shaft 24 to the tension roller 26 is set shorter than that of the non-image portion of the belt 22. Since the belt unit 20 is mounted so that the portion stretched between the A driven shaft 24 and the tension roller 26 abuts on the photoconductor 2, the non-image portion of the belt 22 should be positioned in this range at the time of shipping. It is set. At this time, if the image portion of the belt 22 is in this range, the image portion may be damaged or contaminated when the belt unit 20 is attached or detached. Further, the non-image area is set at a position including the seam of the belt 22.

The position detector 29 is configured to detect passage of a detection hole provided in the belt 22. In the position detector 29, the distance between the detection hole and the position detector 29 when the belt 22 is stopped at the position where the non-image portion faces the photoconductor 2 is such that the drive motor runs stably at a constant speed when the rotation starts. It is set to be longer than the required run-up distance. The drive shaft 23 and the B driven shaft 25 each have a diameter of about 30.
mm, the tension roller 26 and the A driven shaft 24 each have a diameter of about 15 mm. FIG. 3 shows the configuration of the belt gear 31 coaxial with the drive shaft 23 and the drive gear 32 on the main body side that transmits the meshing drive force. The drive gear 32 is a large diameter gear 33.
And coaxial. The belt drive system 34 shares a drive motor 35 with a photoconductor drive system 36 that drives the photoconductor 2 as shown in the drawing, and a gear system is connected thereto. This gear system is composed of gears having an integer number of teeth so that one rotation of the drive shaft 23 coincides with one rotation of the photoconductor 2. The integer ratio may be the number of teeth such that all the gears including the motor rotate an integral number of times in one rotation of the drive shaft 23.

FIG. 4 shows the structure around the drive shaft. The belt cleaner 27 includes a cleaning blade 50 and a toner receiver 5
1 is provided. In the description of the embodiments below, the cleaning blade 50 is simply referred to as the blade 50. The blade 50 is made of polyurethane rubber and has a thickness of 1.5 mm and a length of 9 m.
with a rectangular cross section of m, set to a free end length of 5 mm,
The pressure contact angle with the tangent line of the photoconductor 2 is 22 degrees, and the biting amount in the normal direction is 1.2 mm, and the belt 22 is positioned within the winding range of the drive shaft 23. The cleaner contact / separation mechanism 52 is
A cleaner cam shaft 53 on the apparatus main body side, two cleaner cams 54 installed on the shafts, a cam receiver 55 on the belt unit 20 (FIG. 2) side, a cleaner spring 56, and a positioning pin 57 that regulates the bite amount of the blade 50. With. The blade 50 is held by the cleaner contacting / separating mechanism 52 together with the toner receiver 51 so as to rotate around a cleaner shaft 27C provided in the extending direction of the blade 50 so as to be able to contact and separate from the belt 22. The toner receiver 51 also includes a seal member (not shown) that prevents the toner removed during cleaning from scattering.

The pressure contact portion of the blade 50 is constructed such that the belt 22 is projected from the direction of gravity. This is because when the belt cleaner 27 separates from the belt 22, the blade 5
This is because the toner adhering to the tip of 0 is collected by the toner receiver. If the protrusion is not used, the toner will fall along the belt 22 and the toner will be spilled. The brake 30 includes a press contact blade 60 and a brake holder 61 that holds the press contact blade 60. The press contact blade 60 is made of polyurethane rubber and has a rectangular cross section with a thickness of 1.5 mm and a length of 9 mm, and is set to a free end length of 5 mm. The press contact angle with the tangent line of the photoconductor 2 is 10 degrees and the normal direction. The amount of bite is 1.2 mm, which is disposed in the brake holder 61 in the space inside the belt 22 and is constantly in pressure contact with the cylindrical surface of the drive shaft 23 in a range where it does not contact the belt 22.
Since the pressure contact blade 60 that applies a frictional load to the rotation of the drive shaft 23 is in pressure contact with the drive shaft 23, the load on the belt 22 does not increase. Therefore, it is possible to prevent the shift of the drive phase caused by the creep slip due to the load of the belt 22 while applying a stable load and reducing the influence of the load fluctuation due to the pressure contact of the belt cleaner 27. As a result, it is possible to prevent positional deviation of the toner images of the respective colors superimposed on the belt 22. If the press contact blade 60 is provided on a shaft other than the drive shaft 23, the load on the belt 22 increases, creep slip increases, and the shift of the drive phase increases.

Further, since the brake 30 is constantly in pressure contact with the drive shaft 23, the belt unit 20 also has a rotational load as a single unit when taken out from the main body of the color image forming apparatus. As a result, the belt 22 can be prevented from freely spinning when it is not worn, and thus the non-image portion can be always exposed at the portion stretched between the A driven shaft 24 and the tension roller 26. At this time,
When the blade 50 is constantly pressed against the belt 22 in order to prevent the belt 22 from idling, there is a problem that the belt 22 is deformed by the pressing force of the blade 50 and the image quality is deteriorated.

FIG. 5 shows a main body 40 of a color image forming apparatus using a plurality of image forming units 1 and a belt unit 20, 40A is an alligator, and a hinge shaft 40B on the lower side of the main body 40 is centered. You can open and close it freely. The belt unit 20 is attachable / detachable in the direction of the arrow shown in the figure.
Open 0A. Further, each image forming unit 1 is detachable at a predetermined position by opening the upper plate 40C of the main body. Static elimination needle 4
1 is provided to prevent the toner image from being disturbed when the paper 42 separates from the belt 22. The transfer roller 43 is made of anti-conductive sponge and can be brought into contact with or separated from the belt 22. The laser exposure device 44 outputs a signal light 45 corresponding to image information, and the signal light 45 is reflected by a mirror 46 as shown in the figure.
The photoconductor 2 at the image forming position is scanned and exposed in the generatrix direction to form an electrostatic latent image. The feeding roller 47 is arranged inside the main body alligator 40A, and a recording paper conveyance path is formed so that the recording paper 42 is fed to the nip portion where the belt 22 and the transfer roller 43 are in pressure contact with each other. The fixing device 48 is provided on the upper inside of the main body.

FIGS. 6 and 7 are views showing the details of the structure around the transfer roller 43. As shown in FIG. 6, the transfer roller 43 is held by an arm 65 rotatable about an arm shaft 65C, and a roller contact / separation mechanism 69 including a roller spring 66, a roller cam 67, and a roller cam shaft 68 is used to drive the B driven shaft 2
The belt 22 can be brought into contact with and separated from the belt 22 within the winding range of the belt 22. The transfer roller 43 contacts the belt 22 at a position where the recording paper 42 (FIG. 5) nipped between the transfer roller 43 and the belt 22 is conveyed toward the fixing device 48. The spacer 70 defines the amount of the transfer roller 43 biting into the belt 22. Further, as shown in FIG. 7, the transfer roller 43 is a roller drive gear 7 connected to a motor in the main body.
1a (coaxial with roller drive gear 71b) to roller gear 7
Due to the driving force transmitted to the belt 22, the peripheral speed of the outer diameter in the state of being separated from the belt 22 rotates at a speed that matches the peripheral speed of the belt 22. When the door of the alligator 40A (FIG. 5) is opened, the connection between the roller drive gear 71a and the roller gear 72 is released.

As shown in FIG. 5, the image forming units 1Y, 1M, 1C and 1Bk for the respective colors are arranged in a segment in the holding frame 39 when the main body is mounted. At this time,
Each electrode of the image forming unit 1 is in contact with the corresponding electrode in the holding frame 39. The image forming unit 1 is sequentially rotated by the rotation of the holding frame 39 to be positioned at the image forming position for each color, while the units of other colors are in the retracted position.

FIG. 8 shows the belt 22 and the holding frame 39.
The rotation directions of (FIG. 5) are indicated by solid arrows B and F, respectively. At the image forming position, the electrodes in the frame (not shown) come into contact with the main body electrodes, and it is possible to supply a voltage from the main body 40 (FIG. 5) to the image forming unit 1 at the image forming position. The photoconductor 2 installed at the image forming position is firmly and accurately positioned by the positioning means of the main body 40, and in this state, the photoconductor 2 is rotated in the arrow P direction at a peripheral speed of 100 mm / sec by receiving the driving force from the main body. To do. The image forming operation is performed only in the image forming position, and does not operate in other positions. The belt 22 opposes the photoconductor 2 at the image forming position at a position stretched between the tension roller 26 and the A driven shaft 24, and is brought into pressure contact with a tension of about 3 kg. When the units are switched, the holding frame 39 rotates while rubbing the photoconductor 2 against the stretched belt 22. At this time, based on the position detection signal from the position detector 29 (FIG. 2), the belt 22 is stopped so that its non-image portion is located at the portion facing the photoconductor 2.

As shown in FIG. 3, the drive gear 3 of the photoconductor 2
2 and the belt gear 31 are connected by a gear having an integer number of teeth, so that the photoconductor drive system 36 and the belt drive system 3 are connected.
It is possible to match the phase of the periodic speed fluctuation on the belt 22 due to the eccentricity of the gear with the gear No. 4. Particularly, even if the speed fluctuates due to the load fluctuation, the belt 22 and the photoconductor 2 are completely connected, so that the speed fluctuation is shared and the toner image position deviation in the primary transfer can be prevented. Further, since the photoconductor cleaner 11 (FIG. 1) is constantly in pressure contact with the photoconductor 2, the overall load of the drive system is stably increased.
The rate of load fluctuation due to the pressure contact of the belt cleaner 27 (FIG. 2) and the transfer roller 43 (FIG. 5) with respect to the belt 22 (FIG. 2) is reduced.

Next, the full-color image forming process will be described. First, as shown in FIG. 5, the yellow image forming unit 1Y is set to the image forming position, and the photosensitive member 2 is firmly and accurately positioned by the positioning means of the main body 40 to start the image forming operation. At this time, the belt cleaner 27 (FIG. 4) and the transfer roller 43 are at positions separated from the belt 22 by the cleaner contact / separation mechanism 52 (FIG. 4) and the roller contact / separation mechanism 69 (FIG. 6), respectively. First, the photoconductor 2 is rotated and the surface is charged to −450 V by the charger 3 (FIG. 1). At the same time, the belt 22 is rotated and the position of the belt 22 is detected by a signal generated from the position detector 29 (FIG. 2). An electrostatic latent image having an exposure potential of −50 V is formed on the photoconductor 2 by the signal light 45 based on this signal. This electrostatic latent image is passed through a portion facing the developing roller 8Y, which bears yellow toner by applying a voltage of -250V, and forms a yellow toner image on the photoconductor 2. And + applied to the A driven shaft 24 (Fig. 2)
With the voltage of 1.0 kV, the yellow toner image is transferred onto the belt 22 at the same time as the image formation. The peripheral speed of the belt 22 is
It is set to be 1.5% faster than the peripheral speed of the photoconductor 2 in order to prevent the defective transfer of the toner image.

After the transfer of all the yellow toner images, the photoconductor 2 is stopped, the positioning by the positioning means is released, and the belt 22 is stopped at the position where the non-image portion faces the photoconductor 2. Then, the holding frame 39 is rotated by 90 ° in the direction of arrow F to switch the unit at the image forming position to the unit 1M. At the time of this switching, the photoconductor 2 of the image forming unit 1 is moved while sliding on the non-image portion of the belt 22. After the switching is completed, the formation and transfer of a magenta toner image are performed as in the case of yellow.
The irradiation timing of the signal light 45 for this magenta is also controlled based on the signal from the position detector 29 (FIG. 2),
On the belt 22, the magenta toner image is superposed on the yellow toner image so as to be in position. afterwards,
Similarly, the image forming unit 1 is switched, and the cyan toner image and then the black toner image are also superimposed on the belt 22. During this time, the belt cleaner 27 (FIG. 2) and the transfer roller 43 are retracted to the position where they are not in contact with the belt 22, so that the toner image on the belt 22 is not disturbed.

As a result, the toner images of four colors are superposed on the belt 22 in a positionally aligned manner to form a full-color image. Before the exposure for the final black toner image is completed, the roller cam shaft 68 (FIG. 6) is rotated at the timing when the non-image portion comes to the portion where the transfer roller 43 is pressed,
The transfer roller 43 to which a voltage of 3 kV is applied is attached to the belt 22.
Press against. Then, the paper feed cassette 49 is attached to the pressure contact portion.
The toner images of four colors are secondarily transferred collectively onto the recording paper 42 sent from the printer. Thereafter, fixing is performed by the fixing device 48, and a color image is obtained. At this time, similarly to the transfer roller 43, before the exposure for the final black toner image is completed, the cleaner cam shaft 53 (FIG. 4) is reached at the timing when the non-image portion comes into contact with the belt cleaner 27 (FIG. 4). Is rotated to bring the belt cleaner 27 into pressure contact with the belt 22 to remove the secondary transfer residual toner. Since the primary transfer position is downstream of the exposure position in the rotational direction of the photoconductor 2, the timing before the exposure is completed, that is, the primary transfer is also performed.

By press-contacting the belt cleaner 27 and the transfer roller 43 during the primary transfer, it is possible to improve the image throughput, eliminate the extra idle distance of the belt 22, and realize the miniaturization of the apparatus main body. At this time, if it is attempted to press the belt cleaner 27 after the completion of the primary transfer, it is necessary to secure a running distance longer than the image range between the primary transfer position and the press contact position of the belt cleaner 27 and the transfer roller 43. The non-image part is the image forming unit 1
After stopping the belt 22 at a position opposite to the position, the holding frame 39 is rotated to move the image forming unit 1Y to the image forming position again, and the belt cleaner 27 and the transfer roller 43 are separated from the belt 22. Prepare for the full-color image creation process.

Since the blade 50 (FIG. 4) is in pressure contact with the drive shaft 23, the load on the belt 22 increases and the frictional force for driving the belt 22 by the drive shaft 23 also increases. Therefore, slippage of the belt 22 due to load fluctuation can be reduced.
Further, since the belt cleaner 27 is applied to the belt 22 within the range of winding around the drive shaft 23, the pressure contact state of the belt cleaner 27 is stable, and cleaning failure can be prevented.
Further, since the press contact blade 60 is pressed against the same drive shaft 23 as the belt cleaner 27, the load variation due to the eccentricity of the drive shaft 23 is canceled by the cleaner portion and the brake portion, and the load variation during steady rotation is suppressed.

As described above, according to the first embodiment, as shown in FIG. 4, by providing the pressure contact blade 60 which applies a frictional load to the rotation of the drive shaft 23 in pressure contact with the drive shaft 23, the belt 22 is provided. The load on does not increase. Therefore,
It is possible to prevent a drive phase shift caused by creep slip due to the load of the belt 22. Further, since the load on the belt unit 20 itself increases steadily, the belt cleaner 27
The ratio of the load fluctuation due to the pressure contact of the transfer roller 43 (FIG. 5) to the total load is reduced, and the influence of the load fluctuation is reduced. Therefore, speed fluctuations can be suppressed. Thus
It is possible to prevent displacement of the toner images of the respective colors superposed on the belt 22. Further, since the load ratio of the drive shaft 23 is stably increased as compared with the load of the other shafts, the reaction of the driving force acting on the drive gear is reduced, and the jitter of the belt unit 20 (FIG. 2) can be reduced.

Further, while the toner image of the last color is primarily transferred to the belt 22, the belt cleaner 27 and the transfer roller 43 (FIG. 5) are brought into pressure contact with each other, thereby improving the image throughput and eliminating the extra space of the belt 22. The mileage can be eliminated and the device body can be made smaller. Further, by pressing the pressure contact blade 60 against the cylindrical surface of the drive shaft 23, foreign matter on the friction surface between the drive shaft 23 and the belt 22 can be removed, and the friction between the belt 22 and the drive shaft 23 can be stabilized to stabilize the belt 22. High-speed driving is stable.

Further, since the belt 22, the brake 30, and the belt cleaner 27 can be attached to and detached from the main body as the integrated belt unit 20, it is possible to realize simple maintenance without being contaminated by toner. Furthermore, blade 5
The mutual positional accuracy of 0, the belt 22, the drive shaft 23, and the press contact blade 60 can be easily maintained within a predetermined range. In addition, since the drive shaft 23 is loaded by the press contact blade 60, the belt 22 does not spin spontaneously when the belt unit 20 is not mounted. Therefore, the non-image portion can be surely exposed to the portion stretched between the A driven shaft 24 and the tension roller 26.

The photoconductor 2 and the drive shaft 23 are connected by a gear having an integer number of teeth, and are driven by the same motor, so that the phases of periodic speed fluctuations are made to coincide on the belt 22. be able to. Further, even if the speed fluctuates due to the load fluctuation, the belt 22 and the photoconductor 2 also share the speed fluctuation, so that the positional deviation of the toner image in the primary transfer can be prevented. Further, since the photoconductor cleaner 11 is constantly in pressure contact, the overall load of the drive system is stably increased.
Belt cleaner 27 and transfer roller 4 for belt 22
The rate of load fluctuation due to the pressure contact of No. 3 is reduced. For this reason,
With a simple structure, the belt cleaner 27 and the transfer roller 43 can be pressed against each other during the primary transfer, the throughput of image output can be improved, and the extra idle running distance of the belt 22 can be eliminated to reduce the size of the apparatus main body.

Further, when the belt cleaner 27 is pressed against the photosensitive member 2 while the electrostatic latent image of the last color is formed on the photosensitive member 2, the speed fluctuation for suppressing the exposure of the photosensitive member 2 at a constant speed can be suppressed. Although very important, downsizing can be realized by further improving the throughput of image output and reducing the free running distance. In particular, when the belt cleaner 27 is provided with the blade 50 that comes into pressure contact with the belt 22, the load fluctuation is larger than that of a method such as a fur brush or roller cleaning. Therefore, it is important to suppress the load fluctuation.

In the above description, the pressing blade 60 is pressed against the cylindrical surface of the drive shaft 23.
Instead of the cylindrical surface of No. 3, it may be provided on the side surface of the drive shaft 23 or on the bearing. In addition, the belt cleaner 27 is exposed during the exposure for the black image.
Although the operation of pressing the transfer roller 43 and the transfer roller 43 has been described, the present invention is not limited to the case where the exposure is completed, and a structure where the pressing operation is performed after the exposure and before the primary transfer is also possible. Further, the configuration has been described in which the belt cleaner 27 and the transfer roller 43 are brought into pressure contact with each other at their respective timings. A configuration in which the pressure contact of 27 and the pressure contact of the transfer roller 43 are performed at substantially the same time is also possible.
According to this configuration, the load fluctuation in the acceleration direction to the belt drive system 34 due to the pressure contact of the transfer roller 43 and the load fluctuation in the deceleration direction due to the pressure contact of the belt cleaner 27 are offset, and the speed fluctuation is suppressed and the difference between the colors is reduced. An image without displacement can be obtained.

<< Embodiment 2 >> FIG. 9 is a diagram showing a structure around a drive shaft 23 according to Embodiment 2 including a belt cleaner 27 and a brake 30. The differences from the configuration of FIG. 4 will be mainly described. The brake holder 61 is rotatable around the brake shaft 30C and holds the pressure contact blade 60. The brake spring 75 connects the press contact blade 60 to the drive shaft 2
Press to 3. The brake pin 76 is used for the drive shaft 2 during pressure contact.
Specify the amount of bite into 3. The brake cam 77 is provided on the cleaner cam shaft 53 in an opposite phase to the cleaner cam 54. When the brake cam 77 rotates and comes into contact with the upper end of the brake holder 61 and is further pushed down, the brake cam 61 rotates clockwise to compress the brake spring 75 and separate the press contact blade 60 from the drive shaft. At this time, the belt cleaner 27 follows the cleaner cam 54, rotates clockwise, and comes into pressure contact with the belt 22. That is, when the belt cleaner 27 is pressed, the pressing blade 60 is pressed.
Are configured to be separated from the drive shaft 23.

Further, FIG. 10 shows a drive force transmission system to the transfer roller 43, which has a roller gear 72 and main body side roller drive gears 71a and 71b. The difference from the configuration of FIG. 7 is that the frictional force is smaller than the contact surface between the transfer roller 43 and the belt 22 and larger than the bearing of the transfer roller 43.
This is the point provided between a and 71b. Roller drive gear 71a
And 71b are rotated so that the peripheral speed is equal to the peripheral speed of the surface of the belt 22 with the transfer roller 43 being separated from the belt 22. Other configurations are the same as in the first embodiment.

The operation of the image forming apparatus configured as above will be described. At the start of recording, the transfer roller 4
3 and the belt cleaner 27 are separated from each other, and the pressure contact blade 60 is in pressure contact with the drive shaft 23. Before the exposure of the final black image in the color superimposing step is completed, the cleaner cam shaft 53 is rotated at the timing when the non-image portion comes to the portion where the belt cleaner 27 is in pressure contact, and the belt cleaner 2 is rotated.
Press 7 into contact. At the same time, the rotation of the brake cam 77 causes the brake holder 61 to rotate and the press contact blade 60 to separate from the drive shaft 23. For this reason, the increase and decrease of the load fluctuation are offset and the overall load does not change. At the end of recording, the cleaner cam shaft 53 rotates again to separate the belt cleaner 27 and press the press contact blade 60 against the drive shaft 23.

On the other hand, before the end of the exposure of the final black image in the color superimposing step, the roller cam shaft 68 (FIG. 6) is rotated at the timing when the non-image portion comes to the portion where the transfer roller 43 comes into pressure contact with the transfer roller 43. Is pressed against the belt 22. When the transfer roller 43 is separated from the belt 22, the transfer roller 43 is rotated so that the peripheral speed becomes equal to the peripheral speed of the surface of the belt 22. Therefore, no load fluctuation occurs at the start of the pressing of the transfer roller 43. However, when the transfer roller 43 is pressed against the belt 22, the virtual radius of the transfer roller 43 increases, so that the frictional force between the belt 22 and the transfer roller 43 is reduced.
3 is trying to rotate at a lower rotation speed. By sliding the friction clutch 78 having a smaller frictional force than this frictional force, the transfer roller 43 rotates following the circumferential movement of the belt 22. Therefore, the driving force of the transfer roller 43 does not cause a load variation on the driving system of the belt 22. Therefore, the belt 22 undergoes only a slight load change due to the inertial force when the transfer roller 43 is decelerated, and the influence on the image is reduced. The speed when the transfer roller 43 is separated is not necessarily the same as the peripheral speed of the belt 22, but
The fluctuation increases as the distance from the constant speed increases.

FIG. 11 is a graph showing the relationship of the speed fluctuation with respect to the time after contact (the amount of bite) using the speed at the time of separation as a parameter. W is a rotation speed when pressed and driven by a predetermined amount of biting, and U is a rotation speed in which the peripheral speed is equal to the surface speed of the belt 22 in the separated state. In the process of increasing the bite amount, the rotational speed V of the roller does not depend on the initial rotational speed, but once changes to U, changes to W. When the initial speed is low, the deceleration load is applied to the belt 22, and then the acceleration load is applied immediately.
Therefore, even if the difference between the initial V and W is equal, the problem is greater when the initial V is slower than when it is early.

Since the friction clutch 78 is installed on the main body gear which is not coaxial with the transfer roller 43, the toner is prevented from spilling when the belt cleaner 27 is separated and the paper path toward the fixing device is ensured, while the friction from the belt cleaner 27 is ensured. The toner spill does not enter the friction clutch, and the friction clutch 7
The slip of 8 becomes stable. At this time, the belt cleaner 27
Even if the transfer roller 43 coaxially equipped with the friction clutch 78 is installed at a position other than below, the sliding of the friction clutch 78 is stable, but the recording paper after the secondary transfer cannot be guided to the fixing device. Become. Other operations are the same as in the first embodiment.

As described above, since the press contact blade 60 is separated from the drive shaft 23 at the same time as the press contact of the belt cleaner 27, an image having no speed fluctuation and no positional deviation between colors can be obtained. Further, a transfer roller 43 having elasticity capable of coming into contact with and separating from the belt 22 and a friction clutch 78 having a frictional force smaller than a frictional force between the belt 22 and the transfer roller 43 are transmitted to the transfer roller 43 by a drive gear 71a. , 7
By providing between 1b, it is possible to mitigate the influence of the load fluctuation when the transfer roller 43 is brought into pressure contact with the simple structure without controlling the timing. In particular, the transfer roller 43 is the belt 2
The influence of the peripheral speed when separated from 2 can be minimized by making the peripheral speed equal to the peripheral speed of the surface of the belt 22.

The friction clutch 78 of the roller drive mechanism is also used.
Is installed in the drive gear 71 on the main body side that is not coaxial with the transfer roller 43, so that toner spills from the belt cleaner 27 coming in and out of the transfer roller 43 do not enter the friction clutch 78, and the sliding of the friction clutch 78 is stabilized. Although the structure in which the friction clutch 78 is provided in the main body has been described, the transfer roller 43 has a structure in which the toner does not affect the friction clutch 78.
The friction clutch 78 and the friction clutch 78 may be coaxially provided. Further, although the cleaner has been described as having a configuration using a blade, it may be implemented in other shapes such as a roller shape instead of a blade shape.

<Third Embodiment> FIG. 12 is a diagram showing a detailed structure of a blade contacting / separating mechanism 52 around a drive shaft 23 and a belt cleaner 27 according to a third embodiment. Differences from the configuration of FIG. 9 will be described. First, the belt cleaner 27 is held by the support plates 80 provided at both ends so that the belt cleaner 27 can move in parallel along the guide plate 81, and the belt cleaner 27 can move in parallel with the compression spring 82 that urges the belt cleaner 27 against the belt 22. The cam receiver 55 that moves the cleaner 27 by pressing the support plate 80 with the tapered surface 55C, and the cam receiver 55 to the cleaner cam 54
A pressure spring 83 for applying pressure to a and 54b is provided. Further, as shown in the side view (a) and the plan view (b) of FIG.
5a and 55b are arranged so that the phases of the respective pressing start points are different. Further, the brake holder 61 is held by the support plates 90 provided at both ends so as to be movable in parallel along the guide plate 91, the support plate 90 is brought into contact with the tapered surface 55B of the cam receiver 55, and the brake 30 is brought into contact with the belt 22. A compression spring 92 that biases the compression spring 92 is provided. Further, due to the movement of the cam receiver 55, the abutting of the blade 50 on the a side (the left end side in the plan view (b)) and the a of the pressing blade 60 by a
The separation of the ends, the pressure contact of the b side of the blade 50 (the right end side in the plan view (b)) and the separation of the b end of the pressure contact blade 60 are simultaneously set. Other configurations are similar to those of the second embodiment.

The operation of the image forming apparatus constructed as above will be described below. At the start of recording, the transfer roller 43 (FIG. 5) and the belt cleaner 27 are separated from each other, and the pressure contact blade 60 is in pressure contact with the drive shaft 23. Before the exposure of the final black image in the color superimposing step is completed, the cleaner cam shaft 53 is rotated at the timing when the non-image portion comes into contact with the belt cleaner 27. First, the cleaner cam 54a raises the cam receiver 55a,
As shown by the broken line in the plan view (b) of FIG. 13, only the a side of the belt cleaner 27 is pressed against the belt 22, and at the same time, the brake holder 61a moves to separate only the a side of the pressing blade 60 from the drive shaft. Then the cleaner cam 54
b raises the cam receiver 55b to press the b side of the belt cleaner 27 against the belt 22. At the same time, the brake holder 61b moves so that the b side of the press contact blade 60 moves toward the belt 22.
Separate from.

Therefore, the contact length of the blade 50 gradually increases from the end a to the end b, and the entire blade 50 comes into contact. Therefore, as shown in FIG. 14, the load fluctuation in the present configuration shown by the solid line is gentler than that in the pressure contact by parallel movement in the normal direction shown by the broken line, and the speed fluctuation can be suppressed. Further, the press contact length of the blade 50 is gradually increased and the entire press contact is made, and at the same time, the press contact blade 60 is gradually separated from the end a at the drive shaft 23 and separated from the drive shaft 23 as a whole. Therefore, the pressure contact of the belt cleaner 27 and the opening of the brake 30 are performed over a certain period of time. Therefore, it becomes easy to adjust the pressure contact of the belt cleaner 27 and the opening timing of the brake 30,
The load fluctuation can be surely suppressed. At the end of recording, the cleaner cam shaft rotates again to separate the belt cleaner 27 and press the press contact blade 60 against the drive shaft 23. Other operations are similar to those of the second embodiment.

As described above, the cleaner contact / separation mechanism 52 with respect to the belt 22 presses one end of the blade 50 in the lengthwise direction prior to the other end so that the blade 50 bites slowly even with the cleaner cam 54 of low precision. It can be increased and the influence of load fluctuation can be reduced. Furthermore, by separating the brake 30 simultaneously with the pressure contact of the blade 50, the load fluctuation can be suppressed by easy timing adjustment,
It is possible to prevent the positional deviation between the colors. In the third embodiment, the belt cleaner 27 is moved in parallel. However, as shown in FIG. 15, the blade 50 has a structure in which one end of the blade 50 is contacted prior to the other end. It is also possible to implement a configuration in which the rotary shaft 85 is rotated and moved.

<Fourth Embodiment> FIG. 16 is a view showing a blade contacting / separating mechanism 52 according to a fourth embodiment. The difference from the configuration of FIG. 9 is that a cleaner shaft 27C that is the rotation center of the belt cleaner 27 is provided on a straight line that passes through the center of the drive shaft 23 and the tip of the blade 50. Other configurations are similar to those of the second embodiment. Regarding the image forming apparatus configured as described above,
The operation will be described below. At the start of recording, the transfer roller 4
3 (FIG. 5) and the belt cleaner 27 are separated from each other, and the pressure contact blade 60 is in pressure contact with the drive shaft 23. Before the end of the exposure of the signal light for the final black toner image in the step of sequentially superposing colors, the cleaner cam shaft 53 is rotated at the timing when the non-image portion comes to the portion where the belt cleaner 27 is in pressure contact. The cam receiver 55 is the cleaner cam 54.
Following this, the cleaner 27 rotationally moves around the cleaner shaft 27C, and the tip of the blade 50 moves from the tangential direction of the drive shaft 23 to the pressure contact position of the belt 22. Blade 50
Is pressed against the drive shaft 23 of the belt 22, so that the belt 22 is also approached from the tangential direction and installed at a predetermined pressing position.

In the pressure contact operation of the cleaner contacting / separating mechanism 52, since the moving direction from the contact of the tip of the blade 50 to the belt 22 to the predetermined pressure contact position is the tangential direction of the belt 22, the contact of the blade 50 is predetermined. It takes longer to move to the bite position. For this reason, since the gradient of the increase in the load fluctuation becomes gentle, the bite of the blade 50 can be slowly increased even with the low precision cleaner cam 54, the speed fluctuation can be suppressed, and the positional deviation between the colors can be prevented. Moreover, when the contact between the blade 50 and the belt 22 is started, the angle between them is smaller than the angle at the predetermined cleaning position. Therefore, it is possible to prevent the blade 50 from curling even in a range in which the blade 50 does not bite significantly.

When the blade 50 starts contacting the belt 22, the moving direction of the tip of the blade 50 is the belt 2
The moving component in the tangential direction of 2 is moving in a direction larger than the moving component in the normal direction. As a result, even if the blade 50 is rolled up due to frictional force, the amount of movement of the blade 50 in the tangential direction is large, so that the rollup is corrected and the tip of the blade 50 can be pressed against a predetermined direction, so that the rollup of the blade 50 can be further suppressed. . At the same time, since the relative speed between the belt 22 and the blade 50 at the start of contact becomes small, the load fluctuation at the start of contact can be suppressed. On the other hand, at the time of contact / separation, the toner is adhered to the tip of the blade 50 and the belt 22 because the toner is separated in the tangential direction. Therefore, when the blade 50 is separated, a large amount of toner adheres to the belt 22 on the line, and it is possible to prevent the constituent members such as the transfer roller 43 and the image forming unit 1 from being contaminated and the toner spilling into the main body 40.

Since the blade 50 is always in a uniform pressure contact condition in the longitudinal direction, it does not induce the meandering of the belt 22. If the pressure is unevenly contacted in the longitudinal direction, the frictional force between the belt 22 and the drive shaft 23 will vary from side to side, and the belt 22 will meander or skew. According to experiments conducted by the inventors, if the moving time from the start of contact of the blade 50 to the predetermined biting position is at least twice the biting amount of the blade 50 in the normal direction to the press contact position, the image is significantly affected. There wasn't. Under this condition, the moving time from the start of contact of the blade 50 to the predetermined biting position is twice or more, and the gradient of increase in load fluctuation is 1/2 or less. This is, for example, a rotational movement having a rotation center within a range of 30 degrees (within QOP) from the normal line of the belt 22 at the tip of the blade 50 shown in FIG. 17, or 3 from the tangent line of the belt 22.
This can be achieved by parallel movement in the direction of the 0 degree range (Q'OP 'in the figure). Furthermore, under the condition that the moving direction of the tip of the blade 50 when the blade 50 starts contacting the belt 22 moves in a direction in which the moving component in the tangential direction of the belt 22 is twice or more larger than the moving component in the normal direction. There was no effect. This is, for example, a rotational movement having a rotation center within a range of 26 degrees (within ROP) from the normal line of the belt 22 at the tip of the blade 50 shown in FIG. 17, or a direction within a range of 26 degrees from the tangent line of the belt 22 (R'OP 'shown in the figure). Can be achieved by parallel movement to.

Simultaneously with the pressure contact of the blade 50, the pressure contact blade 60 is separated from the drive shaft 23 by the rotation of the brake cam 77. When the recording ends, the cleaner cam shaft 5
3 rotates to separate the belt cleaner 27 and press the press contact blade 60 against the drive shaft 23. Other operations are similar to those of the second embodiment. As described above, the cleaner contact / separation mechanism 5
When the rotary shaft 27C of the cleaner 27 is provided on the line connecting the center of the drive shaft 23 and the tip of the blade 50 during the pressing operation of No. 2, the moving direction from the contact of the tip of the blade 50 to the belt 22 to the predetermined press contact position is changed. Belt 2 in pressure contact position
2 is almost tangential. As a result, the biting of the blade 50 can be slowly increased and the effect of load fluctuation can be reduced even with a low-precision cam without inducing the meandering of the belt 22. Moreover, since the blade 50 starts contacting from a place where the biting angle is low, it is possible to prevent the blade 50 from curling in a range where the biting is small. Further, the moving direction of the tip of the blade 50 when the blade 50 starts to contact the belt 22 is larger in the tangential direction moving component of the belt 22 than in the normal direction moving component, so that the blade 50 is less likely to bite. The blade 50 can be further prevented from turning. At the same time, since the relative speed between the belt 22 and the blade 50 at the start of contact becomes small, the load fluctuation at the start of contact can be suppressed.

In each of the embodiments described above, the pressure contact member is the pressure contact blade, but the shape is not limited to the blade shape, and a roller shape, felt, rod-shaped resin, or the like may be pressed into contact with the drive shaft 23 to cause a friction load. Can be similarly implemented as long as it gives Further, the example in which the developing device and the photoconductor 2 are configured by the detachable image forming unit has been described, but it is not always necessary to be detachable. Further, the example in which the plurality of photoconductors 2 and the plurality of developing devices are used has been described, but a configuration in which a plurality of developing devices are moved with respect to a single photoconductor 2 to form a color image can be similarly implemented. Is. Further, although the drive system of the photoconductor 2 and the belt 22 are connected by the gears, it is possible to drive them by using different motors.

[0075]

The present invention described above has the following effects. A cleaner contact / separation mechanism that presses the belt cleaner during the primary transfer of the toner image of the last color in the primary transfer to the intermediate transfer belt, and a press contact that constantly presses the drive shaft and applies a friction load to the rotation of the drive shaft. By including the member, it is possible to prevent the shift of the drive phase caused by the sliding of the belt due to the increase of the belt load, and at the same time reduce the influence of the load variation due to the cleaner pressure contact to prevent the position shift of the toner image of each color. It is possible to improve the image throughput, eliminate the extra idle distance of the intermediate transfer belt, and realize the downsizing of the apparatus body. Moreover, the jitter of the belt unit can be reduced.

Further, according to the present invention, a roller contact / separation mechanism for pressing the transfer roller into pressure during the primary transfer of the toner image of the last color in the primary transfer to the intermediate transfer belt, and a drive shaft which is always in pressure contact with the drive shaft. By providing the pressure contact member that applies a frictional load to the rotation, the same effect as described above can be obtained for mitigating the effect of the load fluctuation caused by the transfer roller.

Further, according to the present invention, the friction surface of the drive shaft with respect to the belt can be cleaned by pressing the pressure contact member against the cylindrical surface of the drive shaft, and the friction with the belt is stabilized.
Belt slip can be prevented.

Further, according to the present invention, since the pressure contact member is separated from the drive shaft at the same time as the pressure contact of the cleaner, it is possible to cancel the load fluctuation, and it is possible to obtain an image having no positional deviation between the colors.

Furthermore, according to the present invention, since the intermediate transfer belt, the pressure contact member and the belt cleaner can be attached to and detached from the main body as an integral belt unit, it is possible to realize simple maintenance without being contaminated by toner and to carry out blade and belt cleaning. As it is easy to guarantee the accuracy of each position of the drive shaft and the pressure contact member, and the load is applied to the drive shaft by the pressure contact member, it is possible to prevent the belt from spinning spontaneously when the belt unit is not installed, and prevent the belt from slipping to the specified position. It is possible to reliably expose the image area. Moreover, since it is not necessary to constantly press the cleaner against the belt, it is possible to prevent the blade and the belt from becoming worn.

Further, according to the present invention, a friction clutch for disconnecting and connecting the driving force to the roller driving mechanism for driving the transfer roller for secondarily transferring the toner image on the intermediate transfer belt is provided. Is smaller than the frictional force between the intermediate transfer belt and the transfer roller, it is possible to reduce the influence of load fluctuation when the secondary transfer roller is brought into pressure contact with a simple structure without controlling the timing.

Further, when the transfer roller is separated from the intermediate transfer belt, the outer peripheral speed of the transfer roller is substantially equal to the peripheral speed of the surface of the intermediate transfer belt, so that the load fluctuation can be suppressed to the minimum. it can.

Further, according to the present invention, the secondary transfer roller having elasticity is installed below the belt cleaner of the intermediate transfer belt, and the clutch of the roller driving mechanism is installed on the main body gear which is not coaxial with the secondary transfer roller. This makes it possible to prevent toner from adhering to the belt when the belt cleaner is separated, to convey removed toner to the waste toner reservoir, and to guarantee a paper path toward the fixing device, while preventing toner spillage from the belt cleaner. The clutch does not enter the clutch and the switching of the clutch drive is stable.

Further, according to the present invention, the rotational speed V of the transfer roller is equal to or higher than the rotational speed W when the transfer roller is pressed against the intermediate transfer belt and driven by the frictional force, and the pressing of the belt cleaner and the transfer roller are performed. By performing the pressure contact of the above described substantially simultaneously, the pressure contact of the belt cleaner, which is the deceleration load, and the pressure contact of the secondary transfer roller, which is the acceleration load, cancel out the influence of the load variation with each other, and the speed variation of the entire drive system can be prevented.

Further, according to the present invention, the photoconductor drive means is provided with a drum cleaner which is constantly in pressure contact with the photoconductor and removes the toner on the photoconductor after the primary transfer, a photoconductor drive means, and a belt drive means. And belt drive means are connected and driven by the same drive source, the speed fluctuations of the photoconductor and drive shaft can be matched in phase for each color, and the ratio of load fluctuations to the overall load of the drive system is reduced. To do.
In particular, even if the speed changes due to the load change, if the belt and the photoconductor are completely connected, it is possible to prevent the positional deviation between the colors in the primary transfer. Therefore, the belt cleaner and the transfer roller can be pressed against each other during the primary transfer with a simple structure, the throughput can be improved, and the extra idle running distance of the intermediate transfer belt can be eliminated to reduce the size of the apparatus main body.

When the belt cleaner is pressed against the photosensitive member while the electrostatic latent image of the last color is formed on the photosensitive member, it is very important to suppress the speed fluctuation for exposing the photosensitive member at a constant speed. However, further improvement in throughput and miniaturization can be realized.

Further, according to the present invention, the intermediate transfer belt can be contacted and separated from the intermediate transfer belt, and when contacting, the intermediate transfer belt is pressed against
It is equipped with a cleaning blade that removes the residual toner after secondary transfer on the surface, and a cleaner contact and separation mechanism that contacts and separates the cleaning blade from the intermediate transfer belt. By pressing the blades ahead of the end, the bite of the blade can be slowly increased even with a low-precision cam, and the influence of load fluctuation can be reduced.

Further, according to the present invention, while the toner image of the last color is primarily transferred onto the belt, the cleaning blade is pressed against the belt, and the moving direction of the blade tip when the cleaning blade starts contact with the belt is Since it is in the tangential direction, the bite of the blade can be slowly increased even with a low-precision cam without inducing the meandering of the belt, and the influence of load fluctuation can be reduced. Moreover, since the cleaning blade starts contacting at a low biting angle, it is possible to prevent the blade from curling in a range where the biting is small. At the same time, the relative speed between the belt and the blade at the start of contact becomes small, so that the load fluctuation at the start of contact can be suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an image forming unit according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a belt unit according to the first embodiment of the present invention.

FIG. 3 is a side view showing a belt drive system according to the first embodiment of the present invention.

FIG. 4 is a side view showing the periphery of the drive shaft according to the first embodiment of the present invention.

FIG. 5 is a sectional view showing a color image forming apparatus according to a first embodiment of the present invention.

FIG. 6 is a side view showing a transfer roller contacting / separating mechanism according to the first embodiment of the present invention.

FIG. 7 is a side view showing a roller drive system according to the first embodiment of the present invention.

FIG. 8 is a schematic diagram showing a rotation direction according to the first embodiment of the present invention.

FIG. 9 is a side view showing the periphery of a drive shaft according to a second embodiment of the present invention.

FIG. 10 is a front view showing a roller drive system according to a second embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the time after contact of the transfer roller and the rotation speed.

FIG. 12 is a side view showing the periphery of a drive shaft according to a third embodiment of the present invention.

13A and 13B are a side view and a plan view showing a cam according to a third embodiment of the present invention.

FIG. 14 is a graph showing a load change according to the third embodiment of the present invention.

FIG. 15 is a perspective view showing a blade contacting / separating mechanism according to another embodiment of the present invention.

FIG. 16 is a side view showing the periphery of a drive shaft according to a fourth embodiment of the present invention.

FIG. 17 is a diagram showing a rotation center and a moving direction of the cleaner contact / separation mechanism.

FIG. 18 is a sectional view showing a conventional color image forming apparatus.

FIG. 19 is a sectional view showing a conventional color image forming apparatus.

FIG. 20 is a sectional view showing a transfer roller of a conventional color image forming apparatus.

FIG. 21 is a graph showing the relationship between the biting amount of the elastic roller and the rotation speed.

[Explanation of symbols]

 1 image forming unit 2 photoconductor 20 belt unit 22 intermediate transfer belt 23 drive shaft 27 belt cleaner 30 brake 43 transfer roller 52 cleaner contact / separation mechanism 69 roller contact / separation mechanism 71a, 71b roller drive gear 78 friction clutch

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Aizawa 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (14)

[Claims] 1. A plurality of developing devices having toners of different colors, a photoconductor on which toner images of a plurality of colors are formed by the developing devices, and a photoconductor by a supporting shaft including a rotating drive shaft. An intermediate transfer belt which is stretched so as to face each other and primary-transfers the toner images on the photoconductor in sequence, and a transfer unit which secondarily transfers the toner images on the intermediate transfer belt to a recording sheet. A belt cleaner that is held so that it can come into contact with and separate from the intermediate transfer belt, and that removes residual toner after secondary transfer on the intermediate transfer belt, and the belt cleaner is pressed against and separated from the intermediate transfer belt. A cleaner contacting / separating mechanism that presses the belt cleaner during the primary transfer of the toner image of the last color in the primary transfer onto the intermediate transfer belt; A color image forming apparatus comprising: a pressure contact member that is in constant pressure contact with a shaft and applies a frictional load to the rotation of the drive shaft. 2. A plurality of developing devices having toners of different colors, a photoconductor on which toner images of a plurality of colors are formed by the developing devices, and a photoconductor by a supporting shaft including a rotating drive shaft. An intermediate transfer belt which is stretched to face each other and which is primarily transferred by sequentially superposing the toner images on the photoconductor; and an intermediate transfer belt which is held so as to be able to come into contact with and separate from the intermediate transfer belt. A transfer roller that secondarily transfers the toner image to the recording paper sandwiched therebetween, a belt cleaner that removes the toner remaining after the secondary transfer on the intermediate transfer belt, and the transfer roller that is pressed against the intermediate transfer belt. A mechanism for separating, a roller contact / separation mechanism for pressing the transfer roller into pressure during the primary transfer of the toner image of the last color in the primary transfer to the intermediate transfer belt, A color image forming apparatus comprising: a pressure contact member that is in pressure contact with the drive shaft and applies a frictional load to the rotation of the drive shaft. 3. The color image forming apparatus according to claim 1, wherein the pressing member is pressed against the cylindrical surface of the drive shaft. 4. A plurality of developing units having toners of different colors, a photoconductor on which toner images of a plurality of colors are formed by the developing units, and a photoconductor by a supporting shaft including a rotating drive shaft. An intermediate transfer belt which is stretched so as to face each other and primary-transfers the toner images on the photoconductor in sequence, and a transfer unit which secondarily transfers the toner images on the intermediate transfer belt to a recording sheet. A belt cleaner that is held so that it can come into contact with and separate from the intermediate transfer belt, and that removes residual toner after secondary transfer on the intermediate transfer belt, and the belt cleaner is pressed against and separated from the intermediate transfer belt. A cleaner contacting / separating mechanism that presses the belt cleaner during the primary transfer of the toner image of the last color in the primary transfer onto the intermediate transfer belt; A press contact member that presses against the shaft and applies a frictional load to the rotation of the drive shaft; and a mechanism that moves the press contact member toward and away from the drive shaft, and press contact between the belt cleaner and the intermediate transfer belt. A color image forming apparatus, wherein the pressing member is separated from the drive shaft at the same time. 5. The color according to claim 1, 3 or 4, wherein the intermediate transfer belt, the pressure contact member, and the belt cleaner are detachable from the main body of the color image forming apparatus as an integral belt unit. Image forming apparatus. 6. A plurality of developing devices having toners of different colors, a photoconductor on which toner images of a plurality of colors are formed on the surface by the developing devices, and a photoconductor that runs opposite to the photoconductors and sequentially the photoconductors. An intermediate transfer belt on which the toner image on the body is primarily transferred, and a recording paper held between the intermediate transfer belt and the intermediate transfer belt so that the toner image is sandwiched between the intermediate transfer belt and the intermediate transfer belt. An elastic transfer roller that secondarily transfers the toner image, a roller contact / separation mechanism that presses / separates the transfer roller to / from the intermediate transfer belt, and a friction smaller than a friction force between the intermediate transfer belt and the transfer roller. A color image forming apparatus comprising: a roller driving mechanism that has a friction clutch having a force and that disconnects and connects the driving force to the transfer roller. 7. When the transfer roller is separated from the intermediate transfer belt, the peripheral speed of the transfer roller is substantially equal to the peripheral speed of the surface of the intermediate transfer belt by the driving force of the roller driving mechanism. The color image forming apparatus according to claim 6, wherein the color image forming apparatus rotates. 8. A belt cleaner for removing toner remaining after secondary transfer on the intermediate transfer belt, wherein the transfer roller is installed below the belt cleaner, and a clutch of the roller driving mechanism is coaxial with the transfer roller. 7. The non-main body gear is installed in a non-main body gear.
3. The color image forming apparatus according to 1. 9. A plurality of developing devices having toners of different colors, a photoconductor on which toner images of a plurality of colors are sequentially formed on the surface by the developing device, and a photoconductor by a plurality of rotatable supporting shafts. An intermediate transfer belt that is stretched in opposition to each other and runs, and primary transfer is performed by sequentially superimposing toner images of different colors on the photoconductor; A transfer roller having elasticity for secondarily transferring a toner image on the intermediate transfer belt to a recording paper sandwiched between the intermediate transfer belt, and a roller for moving the transfer roller to press and separate the intermediate transfer belt. A contact / separation mechanism, a roller driving mechanism that drives the transfer roller, and a contact / separation mechanism that is held so as to be capable of contact / separation with respect to the intermediate transfer belt. A belt cleaner for removing the toner remaining on the upper secondary transfer and a cleaner contact / separation mechanism for contacting / separating the belt cleaner with respect to the intermediate transfer belt are provided. The rotational speed is equal to or higher than the rotational speed W when the intermediate transfer belt is pressed to be driven by a frictional force, and the pressure of the belt cleaner and the pressure of the transfer roller are configured to be substantially simultaneously performed. Image forming apparatus. 10. A drum cleaner that is in constant pressure contact with the photoconductor to remove toner on the photoconductor after primary transfer, a photoconductor driving unit that drives the photoconductor, and a belt drive that drives the drive shaft. 10. The color image forming apparatus according to claim 1, further comprising: a means for driving the photosensitive member and the belt driving means, which are connected to each other and driven by the same driving source. 11. The primary transfer comprises a structure in which the belt cleaner is brought into pressure contact with the electrostatic latent image of the last color formed on the photosensitive member.
The color image forming apparatus according to item 0. 12. The color image forming apparatus according to claim 1, wherein the belt cleaner includes a cleaning blade that comes into pressure contact with the intermediate transfer belt. 13. A plurality of developing devices having toners of different colors, a photoconductor on which toner images of a plurality of colors are formed on the surface by the developing devices, and a photoconductor by a supporting shaft including a rotating drive shaft. An intermediate transfer belt that is stretched in opposition to each other and that is primarily transferred by sequentially superimposing the toner images on the photoconductor; and a transfer unit that secondarily transfers the toner images on the intermediate transfer belt to a recording sheet. A belt cleaner that is held so as to be able to come into contact with and separate from the intermediate transfer belt, and that has a cleaning blade that removes toner remaining after secondary transfer on the intermediate transfer belt; and the cleaning blade with respect to the intermediate transfer belt. A cleaner contact / separation mechanism for contacting / separating the cleaner, the cleaner contact / separation mechanism while primary transferring the toner image of the last color to the intermediate transfer belt in the primary transfer. Is configured so that one end in the longitudinal direction of the cleaning blade is pressed against the other end before the other end. 14. A plurality of developing devices having toners of different colors, a photoconductor on which toner images of a plurality of colors are formed by the developing devices, and a photoconductor by a supporting shaft including a rotating drive shaft. An intermediate transfer belt that is stretched in opposition to each other and that is primarily transferred by sequentially superimposing the toner images on the photoconductor; and a transfer unit that secondarily transfers the toner images on the intermediate transfer belt to a recording sheet. A belt cleaner that is held so that it can be brought into contact with and separated from the intermediate transfer belt, and has a cleaning blade that removes residual toner after secondary transfer on the intermediate transfer belt; and the cleaning blade is brought into contact with and separated from the intermediate transfer belt. And a cleaner contacting / separating mechanism that allows the cleaning blade to move while the primary transfer of the toner image of the last color to the intermediate transfer belt is performed in the primary transfer. A color image forming apparatus configured to be in pressure contact with the intermediate transfer belt, and the tip of the cleaning blade is contacted from a substantially tangential direction of the intermediate transfer belt during the pressure contact operation to move to a predetermined pressure contact position. .