JPH1124350A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent meshing vibration from occurring, to stably drive a photoreceptor drum and to eliminate the elongation of a carrying belt by frictionally engaging a driving belt with the photoreceptor drum or a pulley and driving and rotating it by a motor for driving the carrying belt. SOLUTION: A driving roller 220 is formed to be a column of metallic material, and its rotary shaft is rotatably attached to the arm F1 a of a frame body F1 through a bearing. Driven rollers 23 and 83 are formed to be column and the rotary shaft of the roller 23 is rotatably attached to the arm F2a of a frame body F2 through the bearing, and the rotary shaft of the roller 83 is rotatably attached to the arm F2b of the frame body F2 through the bearing. A steel belt having higher Young's modulus than the carrying belt 21 and having no joint is taken as base material in the driving belt 81, which is driven by the same motor 24 driving the belt 21. Backup rollers 86C to 86K are disposed just under the pulleys 42C to 42K of the photoreceptor drum 41 in a state that the belt 81 is put in between and is made bring into press-contact with the pulleys 42C to 42K by spring force, whereby the occurrence of slip is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a color copying machine and a printer, and more particularly to a driven driving technique of a photosensitive drum in a tandem type image forming apparatus.

[0002]

2. Description of the Related Art In recent years, various types of color copying machines have been developed in order to meet the demand for color copying. One of them is to arrange a plurality of photosensitive drums on a conveyor belt. There is a tandem-type copying machine that can perform color copying at a relatively high speed. A conventional example of such a tandem type copying machine is shown in FIG.
-104154.

As shown in FIG. 1, a copying machine 100 comprises:
A timing belt 102 fixed to one end of the conveyor belt 101; and a gear 1 that is axially attached to one end of the photosensitive drums 104C to 104K and meshes with the timing belt 102.
05C to 105K.

[0004] The gears 107 and 108 are
When the photosensitive drum 104K is rotationally driven through the belt, the timing belt 102 meshing with the gear 105K is driven to rotate, and the transport belt 101 is driven to rotate by following the timing belt 102.
The photoreceptor drums 104C to 104Y are driven to rotate at the same peripheral speed as the transport belt 101 by the gears 105C to 105Y meshing with the belt 2.

[0005]

However, in the above-described conventional copying machine, the timing belt 102 and the gear 1 are not provided.
05C to 105K and each photosensitive drum 104
To drive C to 104Y, meshing vibration occurs,
Degradation of image quality cannot be avoided. Therefore,
It is preferable that each photosensitive drum is driven by frictional force.

As a conventional technique of the friction drive, there is a system in which a conveyor belt and a photosensitive drum are brought into contact with each other and each photosensitive drum is driven by frictional force between the conveyor belt and each photosensitive drum. Coulomb force is used. In order to guarantee the transfer performance of reliably transferring the toner image to the recording sheet, the conveyor belt must be made of a soft insulating material such as a resin (for example, PET (polyethylene terephthalate)) and thinly formed. In order to exhibit the drive performance of each photoconductor drum while eliminating elongation, the contradictory performance that the conveyor belt must be thickly shaped is required. Driving is difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and is a driven drive system using a frictional force without meshing vibration. It is an object of the present invention to provide an image forming apparatus having a novel structure that can be used.

[0008]

In order to achieve the above object, an image forming apparatus according to the present invention converts an image formed on a plurality of photosensitive drums arranged in a row on a conveyor belt into the conveyor belt or the photosensitive drum. An image forming apparatus for transferring to a recording sheet conveyed by a belt, comprising a drive belt dedicated to driving a photosensitive drum separated from the transport belt, wherein the drive belt is coaxial with each photosensitive drum or the photosensitive drum. , And is configured to be rotationally driven by the same motor as the motor that drives the transport belt, while being frictionally engaged with a pulley attached to the conveyor belt.

In the image forming apparatus according to the present invention, the driving belt and the transport belt may be wound around the same driving roller driven by a motor.

Further, the image forming apparatus according to the present invention may be configured such that the sum of the thickness of the belt and the radius of the driving roller is equal in the two belt portions.

In the image forming apparatus according to the present invention, the driving belt may be made of a material having a higher Young's modulus than the conveying belt.

Further, the image forming apparatus according to the present invention may be configured to include a frictional force increasing means for increasing a frictional force between each photosensitive drum or pulley and the driving belt. .

Further, in the image forming apparatus according to the present invention, the frictional force enhancing means includes a winding roller or a drive belt for winding the drive belt around a part of the peripheral surface of each photosensitive drum or pulley. A configuration in which the pressure roller is a pressure roller that presses against a drum or a pulley may be employed.

In the image forming apparatus according to the present invention, each of the photosensitive drums can be set in accordance with a color print mode for forming an image on all the photosensitive drums and a subtractive print mode for forming an image on some of the photosensitive drums. Alternatively, a configuration may be provided in which a switching unit that switches between engagement and disengagement between the pulley and the drive belt is provided.

Further, in the image forming apparatus according to the present invention, a tension roller for a transport belt for applying tension to the transport belt and a tension roller for a drive belt for applying tension to the drive belt are separately provided. May be adopted.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A case where an image forming apparatus according to the present invention is applied to a tandem-type digital color copying machine (hereinafter, simply referred to as "copying machine") will be described based on an embodiment.

Embodiment 1 (1) Overall Configuration of Copying Machine FIG. 1 is a diagram showing the overall configuration of a copying machine 1 according to the present invention. The copying machine 1 shown in FIG. 1 includes an image reader section IR for reading a document image, and a printer section PR for printing the read image on a recording sheet S and reproducing it.

The image reader IR is an image sensor such as a CCD, and converts an original image into red (R), green (G), and blue (B).
The image data for each of the red (R), green (G), and blue (B) color components obtained by the image reader unit IR is read by the control unit 10. After undergoing necessary data processing by the image processing unit 12 (see FIG. 7), the image data is further converted into image data of each reproduced color of cyan (C), magenta (M), yellow (Y), and black (K) ( Hereinafter, each of the reproduced colors of cyan, magenta, yellow, and black is simply referred to as “C, M, Y, K”, and “C, M, Y, K” of the components related to each reproduced color is added as a subscript. The image data of C, M, Y, and K is temporarily stored in the image memory 13 of the control unit 10 (see FIG. 7), and then synchronized with the supply of the recording sheet S for each scanning line. And becomes a driving signal of the laser diode.

The printer unit PR is a known type that forms an image by an electrostatic copying method. The printer unit PR has a recording sheet conveying unit 20 on which a conveying belt 21 (see FIG. 2) is stretched and a recording sheet conveying unit 20 on the conveying belt 21. C, M, and C are arranged at predetermined intervals from the upstream side in the recording sheet conveyance direction (hereinafter, simply referred to as “upstream side”) to the downstream side in the conveyance direction (hereinafter, simply referred to as “downstream side”).
Y, K image forming units 30C to 30K, a sheet feeding unit 60 disposed upstream of the recording sheet conveying unit 20, a fixing unit 70 disposed downstream thereof, and a driving belt 81 ( 2) (see FIG. 2).

The image forming units 30C to 30K include an image forming process unit 40C to 40K and an exposure scanning unit 50C to 50K, respectively.
50K.

The exposure scanning units 50C to 50K are rotated by laser diodes 51C to 51K which receive a drive signal output from the control unit 10 and emit laser light, and polygon motors 52C to 52K. A polygon mirror 53 for deflecting light and exposing and scanning the surfaces of the photosensitive drums 41C to 41K in the main scanning direction.
C to 53K.

The image forming process units 40C to 40K are mainly composed of photosensitive drums 41C to 41K. Pulleys 42C to 42K coaxially mounted on the photosensitive drums 41C to 41K, and photosensitive drums 41C to 41K. Cleaners 43C to 43K, charging chargers 44C to 44K, developing units 45C to 45K, and a transfer charger 46C disposed immediately below the photosensitive drums 41C to 41K with the conveyor belt 21 interposed therebetween. 46K or the like.

The paper supply unit 60 includes a paper supply cassette 61 for storing recording sheets of a predetermined size in a stacked state, a paper supply roller 62 for feeding out the recording sheets S from the paper supply cassette 61, and a conveyance belt 21. And a registration roller 63 for setting the timing for feeding the sheet. Immediately before the upstream of the registration roller 63, a sheet detection sensor SE1 for detecting the leading end of the recording sheet S is provided. When the leading end of the recording sheet S reaches the registration roller 63, it is detected by the sheet detection sensor SE1. , Control unit 10
Receives the detection signal and adjusts the timing,
The sheet is fed by the registration roller 63 and the recording sheet S
In the direction of the conveyor belt 21.

The laser diodes 51C to 51K of the exposure scanning units 50C to 50K receive drive signals from the control unit 10 and emit laser light, respectively.
The polygon mirrors 53C to 53K, which are driven to rotate at a constant speed by the polygon motors 52C to 52K, are reflected and deflected by the mirror surfaces, and expose and scan the surfaces of the photosensitive drums 41C to 41K.

Before the photosensitive drums 41C to 41K are subjected to the above-described exposure, the residual toner on the surface is removed by cleaners 43C to 43K, and the photosensitive drums are irradiated with an eraser lamp (not shown) to remove the charge. The photosensitive drums 41C to 41K are electrostatically charged, and when exposed to the laser light in such a state, the electrostatic latent images are formed on the photosensitive drums 41C to 41K.

Each of the electrostatic latent images is developed by receiving CK toners supplied from developing units 45C to 45K, whereby C, M, Y, and C are formed on the surfaces of the photosensitive drums 41C, 41M, 41Y, and 41K. K toner images are respectively formed. On the other hand, in synchronization with the image forming operation of the photosensitive drums 41 </ b> C to 41 </ b> K, the recording sheet S is exposed from the sheet cassette 61 in the sheet feeding unit 60 by the sheet feeding roller 62, the timing roller 63, and the transport belt 21. Paper is fed to a transfer position immediately below the body drums 41C to 41K. At this transfer position, the toner images formed on the photosensitive drums 41C to 41K are sequentially transferred onto the recording sheet S by the electrostatic force of the transfer chargers 46C to 46K installed on the back of the transport belt 21. Thereafter, the recording sheet S on which the toner image has been transferred is conveyed to the fixing device 70 by the conveying belt 21, and the toner particles on the recording sheet surface are melted and adhered to the sheet surface by the fixing device 70 and fixed. Is discharged.

An operation panel 90 provided with a print key for setting various copy modes such as the number of copies and a copy magnification and for instructing the start of copying is arranged at an easily operable position on the front of the image reader section IR. Has been established.

(2) Configuration of Image Forming Process Driving Unit 200 (Configuration of Recording Sheet Transporting Unit 20 and Photosensitive Drum Driving Unit 80) FIG. 2 shows the configuration of the recording sheet transporting unit 20 and photosensitive drum driving unit 80. 3 is a side view as viewed from arrow A in FIG. 2, FIG. 4 is a partially cutaway top view as viewed from arrow B in FIG. 2, and FIG. FIG. 6 is a view showing a structure of the material, and FIG. 6 is a view showing a contact state of the drive belt 81 with the pulleys 42C to 42K and the drive belt drive roller 82.

As shown in these figures, the recording sheet transport unit 20 includes a transport belt 21, a driving roller 220 and a driven roller 23 around which the transport belt 21 is stretched, and a DC motor or the like for driving the driving roller 220. A motor 24;
It comprises a rotary encoder 25 coaxially mounted on the motor 24, a rotation detection sensor SE2 for detecting the rotation position of the rotary encoder 25, and the like.

The photosensitive drum driving section 80 is provided with the driving roller 2
20 is used in common with the recording sheet transport unit 20, and includes a driving roller 220 and a driven roller 83;
3 and a separate drive belt 81 separated from the conveyor belt 21, and the drive belt 81 is connected to pulleys 42C to 42K.
And backup rollers 86C to 86K which are in pressure contact with the lower end of the roller.

The driving roller 220 is formed of a metal material such as aluminum in a cylindrical shape, and the rotating shaft of the driving roller 220 is rotatable on a pair of arms F1a of the frame F1 via bearings (not shown). Attached to. The portion of the drive roller 220 where the transport belt 21 is stretched is referred to as “transport belt drive roller”, and the portion where the drive belt 81 is stretched is referred to as “drive belt drive roller”. The driven rollers 23 and 83 are formed in a cylindrical shape by coating a metal material such as aluminum or the like with a material such as neoprene rubber on the surface thereof. The driven roller 23 has a rotating shaft formed by a pair of arms of the frame F2. The rotary shaft of the driven roller 83 is rotatably mounted on the pair of arms F2b of the frame body F2 via bearings (not shown). .

The transport belt 21 is formed endlessly from an insulating material such as PET. On the other hand, the drive belt 81 has a Young's modulus higher than that of the conveyor belt 21 and is based on a seamless steel belt 81a (see FIG. 5B, Young's modulus: 20000 kgf / mm ² ). For this reason, the drive belt 81 can be made harder to stretch than the transport belt 21 and can be formed thin.

Such a seamless steel belt 8
1a is produced by, for example, an electroforming method in which iron is electrodeposited on a model by applying the principle of electroplating to produce an endless seamless belt. By the way, instead of this electroforming method, as shown in FIG. 5 (a), it is conceivable to join both ends of a steel plate by welding and grind and flatten this joint, but in this case, It is difficult to eliminate uneven thickness at the joint, which causes uneven rotation. Further, since the strength of the seam is weak, if the tension is increased to obtain a large torque, the seam may be broken. On the other hand, in the case of the steel belt 81a, since there is no seam, such a defect does not occur.

The drive belt 81 is formed by applying high μ coat layers 81b and 81c (see FIG. 6) to the inner and outer peripheral surfaces of the steel belt 81a, respectively. The high μ coat layers 81b and 81c are formed by applying and drying, for example, a Si-based resin material on the outer peripheral surface and the inner peripheral surface of the steel belt 81a.
The high μ coat layers 81b and 81c can obtain a friction coefficient of 1.7 or more. For this reason, the high μ
The coating layer 81b enhances the frictional force with the pulleys 42C to 42K, prevents the slip from being generated between the pulleys 42C to 42K, and uses the high μ coating layer 81c on the inner peripheral surface to form the driving belt. The frictional force with the drive roller 82 is increased, and the occurrence of slip with the drive belt drive roller 82 is prevented.

The drive belt drive roller 82 is formed in a columnar shape by forming a high μ coat layer 82 a on a portion of the outer peripheral surface of the base material made of a metal material which is in contact with the drive belt 81, and has a friction with the drive belt 81. The force is increased, and the occurrence of slip with the drive belt 81 is prevented.

The backup rollers 86C to 86K are disposed immediately below the pulleys 42C to 42K with the drive belt 81 interposed therebetween.
It is designed to be pressed against 42K. Thus, even if the drive belt 81 is loosely stretched and stretched, the drive belt 81 can be reliably brought into contact with the lowest point of the pulleys 42C to 42K. Friction with the drive belt 8
1 is prevented from slipping between the pulley 1 and the pulleys 42C to 42K.

The pulleys 42C to 42K are composed of a base made of a metal material such as aluminum and a drive belt 8 on the outer peripheral surface thereof.
1 and a high μ coat layer 42a formed in a contacting part are formed in a columnar shape. Thereby, the frictional force with the drive belt 81 is increased, and the occurrence of slip with the drive belt 81 is prevented.

In this embodiment, the drive belt 81
Inner and outer peripheral surfaces of the drive belt drive roller 82
And a high μ coating layer 8 on the outer peripheral surfaces of the pulleys 42C to 42K.
1b, 81c, 42a and 82a are formed, but in order to prevent slipping on the pulleys 42C to 42K, slipping on one of the high μ coating layers 81b and 42a and the driving belt driving roller 82 is prevented. For this purpose, only one of the high μ coat layers 81c and 82a may be used. In this case, the frictional force of the pulleys 42C to 42K and the driving belt driving roller 82 can be sufficiently increased.

For example, when the pulleys 42C to 42K are set to have the same diameter as the photosensitive drum,
And the drive belt drive roller 82 is D2 + 2 · t2
= D1 + 2 · t1. In this case, if the drive belt 81 is thicker than the transport belt 21 (t1 <t2), the drive belt drive roller 82
(See FIG. 4B), and in the opposite case, the substrate of the transport belt drive roller 22 may be cut.

The pitch between the pulleys 42C to 42K,
That is, the pitch between the photosensitive drums 41C to 41K and the distance L0 between the transfer positions of the photosensitive drums 41C to 41K are equal, and the distance (the diameter D2 of the drive belt drive roller 82 plus the thickness t2 of the drive belt 81) ( D2 + 2 · t2) is set to be an integer (n2) times (n2 · π).
D2 = L0). Therefore, the drive belt drive roller 82
Is eccentric, the peripheral speeds of the photosensitive drums 41C to 41K fluctuate, and the images formed on the surfaces of the photosensitive drums 41C to 41K are distorted in the sub-scanning direction (transport direction). Since the phases of the distortions of the photosensitive drums 41C to 41K coincide with each other and are transferred to the recording sheet S, the color shift of the superposed image can be made inconspicuous.

Further, if the conveying belt driving roller 22 coaxial with the driving belt driving roller 82 is eccentric, the peripheral speed of the conveying belt 21 fluctuates, and the photosensitive drums 41C to 41K
The image is distorted in the sub-scanning direction when the image is transferred to the recording sheet S, but the distance L0 between the transfer positions is equal to the diameter D1 of the conveying belt driving roller 22 and the thickness t1 of the conveying belt 21.
Is set to be an integer (n1) times the distance (D1 + 2 · t1) obtained by adding the following equation (L0 = n1 · π · D1).
= N 2 · π · D 2) and the phase of the distortion at the time of transfer from the photosensitive drums 41C to 41K to the recording sheet S is also transferred in the same manner, so that the color shift of the superposed image can be made inconspicuous. .

(3) Configuration of Control Unit 10 FIG. 7 is a block diagram showing the configuration of the control unit 10. As shown in FIG. 1, the control unit 10 includes a CPU 11, an image processing unit 12, an image memory 13, a laser diode driving unit 14, a RAM 15, a ROM 16, and the like.

The image processing section 12 performs correction such as shading correction and edge emphasis processing on R, G, and B multi-valued image data obtained by scanning the original, and then performs C, M, and
The image memory 13 generates image data of Y and K reproduction colors and
Output to The image memory 13 stores the image data for each reproduction color. The laser diode driving unit 14
Each of the laser diodes 51C to 5C based on the image data
Drive 1K.

The RAM 15 temporarily stores various control flags and copy modes such as the number of copies and the magnification set from the operation panel 90. The ROM 16 stores a program such as a program related to a scanning operation in the image reader unit IR and an image forming operation in the printer unit PR and data related to the image forming operation.

The CPU 11 receives input from various sensors, reads out necessary programs from the ROM 16 and controls the processing contents of image data in the image processing section 12, or operates the image reader section IR and the printer section PR. And a smooth copying operation is performed by taking control of the timing.

More specifically, the CPU 11 drives the motor 24 of the recording sheet transport section 20 so that the transport speed of the recording sheet S reaches the target system speed based on the detection output of the rotation detection sensor SE2. The motor 24 is driven so that the peripheral speed of the photosensitive drums 41C to 41K matches the system speed based on the detection output of SE2. Therefore, in the recording sheet transport section 20, when the drive roller 220 is rotationally driven by the motor 24, the transport belt 21 is driven to rotate, and the recording sheet S is transported immediately below the photosensitive drums 41C to 41K at the system speed. On the other hand, in the photosensitive drum driving unit 80, the drive belt 81 is driven to rotate, and accordingly, the pulleys 42C to 42K and the photosensitive drums 41C to 41K are driven to rotate at the same peripheral speed as the system speed of the recording sheet S. Is done.

Transfer Conveying Function and Photosensitive Drums 41C-41
Since the Y drive function is divided, the transport belt 21 can exhibit optimal performance for transporting and transferring the recording sheet S. In addition, the photosensitive belt can be exposed to the drive belt 81 without imparting meshing vibration as in the related art. Body drum 41C-41
The optimum performance for driving K can be exhibited.

The drive belt 81 is provided with a mark (not shown) indicating a reference position for one round, and the ROM 16 has a drive belt 8 based on the mark.
The speed variation for one round of 1 is stored in advance, and the CPU 1
1 controls the motor 24 so that the peripheral speed of the drive belt 81 becomes constant, based on the information on the speed unevenness of one revolution of the drive belt 81 stored in the ROM 16. For this reason, even if the drive roller 82 is eccentric and the drive belt 81 has uneven thickness, in this case, the circumference L2 of the drive belt 81 becomes smaller when the drive belt drive roller 82 makes one rotation. It is set to an integral multiple of the traveling distance (n2.pi. (D2 + 2t2) = L2
Since the positional relationship between the drive belt drive roller 82 and the drive belt 81 does not deviate, fluctuations in the peripheral speed of the drive belt 81 can be prevented based on the above information.

In the present embodiment, the sum (D1 + 2 · t1) of the diameter D1 of the transport belt driving roller 22 and the thickness t1 of the transport belt 21 and the drive belt driving roller 82
Of the diameter D2 of the drive belt 81 and the thickness t2 of the drive belt 81 (D2
+ 2 · t2), but the sum of the diameter D1 of the transport belt drive roller 22 and the thickness t1 of the transport belt 21 and the diameter D2 of the drive belt drive roller 82 are set.
And the thickness t2 of the drive belt 81 may be different, the diameter D1 of the transport belt drive roller 22, the diameter D2 of the drive belt drive roller 82, the diameter D3 of the pulleys 42C to 42K, and the photosensitive drums 41C to 41K. May be set so that the conveying speed of the recording sheet S and the peripheral speed of the photosensitive drums 41C to 41K match.

When the motor 24 is constituted by a pulse motor, the rotation can be controlled by the number of input pulses, so that the rotary encoder 25 and the rotation detection sensor SE2 can be omitted.

(Embodiment 2) FIG. 8 is a side view showing a main part of a copying machine according to Embodiment 2 of the present invention. In Embodiment 1 described above, backup rollers 86C-86
Although the drive belt 81 is pressed against the pulleys 42C to 42K with K, in the present embodiment, as shown in FIG.
A configuration in which winding rollers 87a to 87e for winding the drive belt 81 around the pulleys 42C to 42K is employed.
Other points in the present embodiment are the same as those in the first embodiment.

Backup roller 86C of the first embodiment
86K, the drive belt 81 is brought into line contact with the pulleys 42C to 42K.
Pulleys 42C to 42 of the drive belt 81 by a to 87e
K, that is, the drive belt 81 is connected to the pulley 42
This is a configuration that makes a surface contact with C to 42K. Therefore, the frictional force between the drive belt 81 and the pulleys 42C to 42K is secured by surface contact.

In this case, the winding angle θ is set to 30 degrees or more and 180 degrees.
The winding rollers 87a, 87
Preferably, c and 87e are provided. Thereby, a sufficient contact area can be secured, and the frictional force can be sufficiently increased.

By the way, a slight amount of eccentricity cannot be avoided from the viewpoint of production processing accuracy with respect to the axes of the rotating shafts of the photosensitive drums 41C to 41K and the pulleys 42C to 42K.
In this case, when the eccentric phases of all the pulleys 42C to 42K match, for example, when the major axis side of each of the pulleys 42C to 42K is simultaneously located at the lowermost end, the amount by which the drive belt 81 is pressed down is one compared to the case where one pulley is pressed. When the short diameter side of each of the pulleys 42C to 42K is located at the lowermost end, the amount by which the drive belt 81 is pressed is reduced to 1/4. Therefore, the tension of the drive belt 81 fluctuates due to the fluctuation of the pressing amount, and the fluctuation may cause uneven rotation of the pulleys 42C to 42K. In the present embodiment, the drive belt 81 is wound around with the eccentric phases of the pulleys 42C to 42K, that is, the eccentric phases of the photosensitive drums 41C to 41K shifted by 180 degrees. Thereby, for example, the pulley 4
When the pushing amount of the drive belt 81 is the maximum at 2K, the pushing amount of the pulleys 42Y and 42C is the minimum, and the pushing amount of the pulley 42M is the maximum,
The amount of depression caused by eccentricity is offset. As a result, almost the same tension is applied to the drive belt 81 as when the pulleys 42C to 42K have no eccentricity. In addition, since the winding angle is large, even if the deviation of the eccentric phase of the pulleys 42C to 42K is slightly different from 180 degrees, the difference can be averaged and the installation deviation can be absorbed.

In order to easily shift the eccentric phase by 180 degrees, pulleys 42C on the side end faces of pulleys 42C to 42K are used.
A triangular phase mark is provided at a reference position of ~ 42K (for example, a position indicating the direction of the longest diameter), and the phase mark can be easily shifted by 180 degrees. This triangular phase mark indicates the pulley 42C
It is preferable that a metal mold be used when creating ~ 42K. Then, pulleys 42C-
The reference position of 42K can be almost completely matched.

(Embodiment 3) FIG. 9 is a side view showing a main part of a copying machine according to Embodiment 3 of the present invention. In the present embodiment, similarly to the above-described second embodiment, the drive belt 81 is pulled by the winding rollers 88a to 88h to pulleys 42C to 42H.
In this embodiment, the winding rollers 88a to 88h are pressed toward the centers of the pulleys 42C to 42K by the elastic restoring force of the pressing springs, and the driving belt is driven by the elastic pressing force. 81 pulleys 4
The pressure contact force to 2C to 42K can be adjusted.
As a result, the drive belt 81 comes into surface contact with the pulleys 42C to 42K with an appropriate pressing force, and the frictional force can be further increased. The winding roller 8
Even if the eccentricities 8a to 88h are eccentric, the eccentricities are absorbed by the pressing springs pressing the wrapping rollers 88a to 88h, so that there is an advantage that the belt speed of the drive belt 81 is not affected.

(Embodiment 4) FIG. 10 is a perspective view of a recording sheet transport section 20 and a photosensitive drum driving section 80 according to Embodiment 4 of the present invention, and FIG. 11 is a main view seen from an arrow C in FIG. It is a side view of a part. In the first to third embodiments, the driven rollers 23 and 83 are connected to the arms F2a and F2 of the frame F2.
In this embodiment, the driven rollers 23 and 83 function as tension rollers, and the other points are the same as those in the first embodiment. is there.

As shown in FIG. 11, an elongated hole F3 into which the shaft of the driven roller 83 is inserted and a pin F4 are provided in the arm F2b on the near side of the frame F2. A spring F5 is stretched between the roller 83 and the shaft. The back side arm F2b has the same configuration. Thus, the driven roller 83 functions as a tension roller. The arms F2a of the frame F2 have the same structure as the arms F2b on the near side, and the driven roller 23 functions as a tension roller. Thereby, the optimal tension for transmitting the driving force to the driving belt 81 and the optimal tension for transporting and transferring the recording sheet S to the transport belt 21 can be independently applied. In this case, the configuration is such that the tension of the drive belt 81 is set larger than that of the transport belt 21. Therefore, the drive belt 81
Thus, it is possible to reliably apply the optimum tension for transmitting the driving force.

(Fifth Embodiment) FIG. 12 is a side view showing a main part of a copying machine according to a fifth embodiment of the present invention. In the fourth embodiment, the function of the tension roller is exerted on the driven rollers 23 and 83. However, in the present embodiment, the tension roller 28 that applies tension to the transport belt 21 and the tension is applied to the drive belt 81. And a tension roller 88 to be separately provided. Also in this case, the configuration is such that the tension of the drive belt 81 is set to be larger than that of the transport belt 21. In this manner, the optimal tension for transmitting the driving force to the drive belt 81 and the optimal tension for transporting and transferring the recording sheet S to the transport belt 21 can be independently applied.

(Embodiment 6) FIG. 13 is a side view showing a main part of a copying machine according to Embodiment 6 of the present invention. In this embodiment, a tension roller 28 for applying tension to the transport belt 21 and a tension roller 88 for applying tension to the drive belt 81 are separately provided.
Roller 87 for winding the roller around pulleys 42C to 42K
b, 87c, and 87d, and the other points are the same as those of the first to fifth embodiments. Note that, in this case as well, the drive belt 81
Is set to be large.

In this manner, the optimum tension for transmitting the driving force to the driving belt 81 and the optimum tension for conveying and transferring the recording sheet S to the conveyor belt 21 can be independently applied. Belt 81 and pulley 42C
~ 42K can be increased.

(Seventh Embodiment) FIG. 14 is a side view showing a main part of a copying machine according to a seventh embodiment of the present invention. In the present embodiment, while the driven roller 83 functions as a tension roller, the winding rollers 87c and 87e
By a displacement mechanism (not shown) in the direction indicated by the arrow in the figure (the winding direction (see FIG. 14A)) and the direction opposite to the direction shown in FIG.
)). Other points in the present embodiment are the same as in Embodiments 1 to 6.

The displacement mechanism may be a known mechanism including a solenoid and a cam mechanism. For example, the winding roller 87
The bearing members c and 87e are slidably held in the vertical direction of a frame (not shown), and are urged toward the drive belt 81 by an elastic member such as a compression spring so as to be connected to each bearing member. When the energized solenoid is energized, the bearing members of the wrapping rollers 87c and 87e are driven by the drive belt 8 against the urging by the elastic member.
What is necessary is just to make it displace in the direction away from 1. Such control is performed by the control unit 10.

In the full color print mode, the CPU
Numeral 11 moves the winding rollers 87c and 87e in the winding direction to make the pulleys 42C to 42K wind and contact the drive belt 81. Therefore, all of the pulleys 42C to 42K are driven and driven in accordance with the movement of the drive belt 81. On the other hand, in the monochrome print mode, the winding rollers 87c and 87e are moved in the non-winding direction, the driving belt 81 is wound around only the pulley 42K, and the driving belt 81 is separated from the pulleys 42C to 42Y. It has become. Therefore, only the pulley 42K is driven and driven in accordance with the movement of the drive belt 81. Accordingly, the transmission of the driving force to the pulleys 42C to 42Y is released, and the consumption of the photosensitive drums 41C, 41M, 41Y and the like is prevented.

(Embodiment 8) FIG. 15 is a perspective view of a recording sheet conveying section 20 and a photosensitive drum driving section 80 according to Embodiment 8 of the present invention. In the first to seventh embodiments, pulleys 42C to 42C are attached to photosensitive drums 41C to 41K.
K is mounted coaxially, and the pulleys 42C to 42K are driven by the frictional force with the drive belt 81. In the present embodiment, the photosensitive drums 41C 'to 41K are longer than the photosensitive drums 41C to 41K. The photosensitive drums 41C 'to 41K' are driven by a frictional force between the photosensitive drums 41C 'and 41K'. Other points in the present embodiment are the same as those in the first embodiment.

This also allows the transport belt 21 to exhibit optimal performance for transporting and transferring the recording sheet S, and furthermore, does not apply any meshing vibration as in the prior art, and applies the photosensitive drum 41C to the drive belt 81. '~ 41
The optimum performance for driving K ′ can be exhibited.

(4) Modifications Although the image forming apparatus according to the present invention has been described based on the embodiment, it goes without saying that the content of the present invention is not limited to the above-described embodiment. The following modified example is conceivable.

(4-1) In the above embodiment, iron is used as the base material of the drive belt 81, but a material having a higher Young's modulus than the transport belt 21, such as aluminum, can be used.

(4-2) In the eighth embodiment, the configurations of the second to seventh embodiments can be applied.

(4-3) In the above embodiment,
Although the toner images formed on the photoconductor drums 41C to 41K are directly transferred to the recording sheet S, the toner images formed on the photoconductor drums 41C to 41K are temporarily transferred to the transport belt 21 and are then transferred to the recording sheet S. It can also be transferred to S.

(4-4) In the above embodiment,
Although monochrome printing is performed in black, monochrome printing may be performed in C to Y, or printing may be performed in a combination of these two colors or three colors.

(4-5) Further, in the above embodiment, the copying machine has been described, but the present invention can be applied to other image forming apparatuses such as a laser printer.

[0073]

As described above, according to the image forming apparatus of the present invention, there is provided a drive belt dedicated to driving the photosensitive drum separated from the transport belt, and the drive belt is provided for each photosensitive drum or photosensitive member. Since it is frictionally engaged with a pulley coaxially attached to the drum and is driven to rotate by the same motor as that for driving the transport belt, a design that satisfies the performance required for each belt is adopted. It is possible to stably drive the photosensitive drum without generating the conventional meshing vibration, and it is not necessary to pull the transport belt more than necessary. Can be simplified.

Further, according to the image forming apparatus of the present invention, since the driving belt and the transport belt are wound around the same driving roller driven by the motor, the driving force of the motor can be easily applied to both belts. Can be distributed.

According to the image forming apparatus of the present invention, since the sum of the thickness of the belt and the radius of the driving roller is equal in the two belt portions, the driving speeds of the two belt portions can be easily matched. .

Further, according to the image forming apparatus of the present invention, since the drive belt is made of a material having a higher Young's modulus than the transport belt, it is possible to realize a thin and hardly stretchable drive belt.

Further, according to the image forming apparatus of the present invention, since the frictional force increasing means for increasing the frictional force between each photosensitive drum or pulley and the driving belt is provided,
Slip between the photosensitive drum or the pulley and the drive belt can be suppressed.

Further, according to the image forming apparatus of the present invention, the frictional force enhancing means includes a winding roller or a drive belt for winding the drive belt around a part of the peripheral surface of each photosensitive drum or pulley. Since the pressure roller is a pressure roller that presses against the body drum or the pulley, by increasing the contact area, it is possible to reduce the occurrence of slip between the photoconductor drum or the pulley and the drive belt.

Further, according to the image forming apparatus of the present invention, each of the photosensitive members can be changed according to a color print mode for forming an image on all photosensitive drums and a subtractive print mode for forming an image on some photosensitive drums. Since the switching means for switching the engagement or disengagement between the drum or the pulley and the drive belt is provided, it is possible to avoid unnecessary consumption of the photosensitive drum or the like which does not contribute to image formation.

Further, according to the image forming apparatus of the present invention, the transport belt tension roller for applying tension to the transport belt and the drive belt tension roller for applying tension to the drive belt are separately provided. Therefore, it is possible to individually apply the optimal tension to exhibit the performance required for both belts, and to easily stretch both rollers with both belts loose, eliminating this slack and exposing The drive belt can be reliably brought into contact with the body drum or the pulley.

[Brief description of the drawings]

FIG. 1 is a diagram showing an entire configuration of a copying machine 1 according to the present invention.

FIG. 2 is a perspective view illustrating a configuration of a recording sheet transport unit 20 and a photosensitive drum driving unit 80 in FIG.

FIG. 3 is a side view as viewed from an arrow A in FIG. 2;

FIG. 4 is a partially cutaway top view as viewed from an arrow B in FIG. 2;

FIG. 5 is a diagram showing a structure of a base material of a drive belt 81.

FIG. 6 is a diagram illustrating a contact state between a driving belt 81, pulleys 42C to 42K, and a driving belt driving roller 82;

FIG. 7 is a block diagram showing a configuration of a control unit 10 of FIG.

FIG. 8 is a side view illustrating a main part of a copying machine according to a second embodiment of the present invention.

FIG. 9 is a side view showing a main part of a copying machine according to a third embodiment of the present invention.

FIG. 10 shows a recording sheet transport unit 2 according to a fourth embodiment of the present invention.
FIG. 2 is a perspective view of a photosensitive drum driving unit 80 of FIG.

FIG. 11 is a side view as viewed from arrow C in FIG. 10;

FIG. 12 is a side view showing a main part of a copying machine according to a fifth embodiment of the present invention.

FIG. 13 is a side view showing a main part of a copying machine according to a sixth embodiment of the present invention.

FIG. 14 is a side view showing a main part of a copying machine according to a seventh embodiment of the present invention.

FIG. 15 shows a recording sheet transport unit 2 according to the eighth embodiment of the present invention.
FIG. 2 is a perspective view of a photosensitive drum driving unit 80 of FIG.

FIG. 16 is a diagram showing a configuration of a conventional copying machine.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 copier 10 control unit 11 CPU 12 image processing unit 13 image memory 14 laser diode drive unit 15 RAM 16 ROM 20 recording sheet transport unit 21 transport belt 22 transport belt drive rollers 23, 83 driven rollers 24 motor 28, 88 tension roller 25 Rotary encoder 30C-30K Image forming unit 40C-40K Image forming process unit 50C-50K Exposure scanning unit 60 Feed unit 70 Fixing unit 80 Photoconductor drum driving unit 81 Drive belt 82 Drive belt drive roller 86C-86K Backup roller 87a-87e , 88a-88h Wrapping roller 220 Drive roller S Recording sheet SE2 Rotation detection sensor

Claims (8)

[Claims] 1. An image forming apparatus for transferring images formed on a plurality of photosensitive drums arranged in a row on a transport belt to the transport belt or a recording sheet transported by the belt. A drive belt dedicated to driving the separated photosensitive drum is provided, the drive belt being frictionally engaged with each photosensitive drum or a pulley coaxially attached to the photosensitive drum, and driving the transport belt. An image forming apparatus, which is configured to be driven to rotate by the same motor as the motor. 2. The image forming apparatus according to claim 1, wherein the drive belt and the transport belt are wound around the same drive roller driven by a motor. 3. The image forming apparatus according to claim 2, wherein the sum of the thickness of the belt and the radius of the driving roller is equal in the two belt portions. 4. The image forming apparatus according to claim 1, wherein the drive belt is made of a material having a higher Young's modulus than a transport belt. 5. The image forming apparatus according to claim 1, further comprising a frictional force increasing unit that increases a frictional force between each of the photosensitive drums or the pulleys and the driving belt. 6. The frictional force enhancing means is a winding roller that winds the drive belt around a part of the peripheral surface of each photoconductor drum or pulley, or a pressure roller that presses the drive belt against the photoconductor drum or pulley. The image forming apparatus according to claim 5, wherein: 7. A method according to claim 1, wherein a plurality of photosensitive drums or pulleys are engaged with a drive belt in accordance with a color print mode for forming an image on all of the photosensitive drums and a subtractive color print mode for forming an image on some of the photosensitive drums. The image forming apparatus according to any one of claims 1 to 6, further comprising a switching unit that switches between non-engagement states. 8. The transport belt tension roller that applies tension to the transport belt, and a drive belt tension roller that applies tension to the drive belt, are separately provided. An image forming apparatus according to any one of the above.