JP3368781B2 - Tandem color image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention
StretchedTransfer and transferWhen the belt is not driven, relax it
ToTandem color image formationRelated to the device. [0002] 2. Description of the Related Art FIG.4(a), (b), (c)
As described above, there are various electrophotographic image forming apparatuses. Same figure
(a), (b), and (c) are the main parts of each image forming apparatus.
Only one is shown. [0003]4(a) Image formation for monochrome printing
Endless belt 1 includes a driving roller 2a and a driven roller
Roller 2b with a predetermined degree of tension. Follower
A suction roller 3 is attached to the roller 2 b via the endless belt 1.
They are pressed against each other.
The paper P is pinched and transported. The endless belt 1 generally has a thickness of about one hundred and several tens μm.
Of a film-like member. For this endless belt 1
The photosensitive drum 4-1 is pressed against the outer peripheral surface of the paper P which is transported.
The endless belt 1 faces the photosensitive drum 4-1.
The transfer brush 4-2 is in sliding contact with the upper inner peripheral surface. Photoconductor
Around the peripheral surface of the ram 4-1, the cleaner 4-
3, initialization charging brush 4-4, recording head 4-5, development
A device 4-6 is provided. [0005] The initialization charging brush 4-4 is connected to a high voltage power supply.
And a negative high voltage is applied to the photosensitive drum 4-1.
Then, the photosensitive layer on the peripheral surface of the photosensitive drum 4-1 is minus.
Charge uniformly to high potential. The recording head 4-5 has a predetermined
And a negative high potential of the photosensitive drum 4-1.
Selective exposure according to image information is performed on the charged peripheral surface
To generate a negative low-potential part with attenuated potential.
And the electrostatic potential composed of the low potential part and the high potential part
A latent image is formed on the peripheral surface of the photosensitive drum 4-1. The developing device 4-6 has a non-magnetic toner inside the housing.
-T is accommodated, and the developing roller 4-7 is supported at the lower opening.
I have. The developing roller 4-7 is operated by a developing bias power supply.
A bias is applied. The developing roller 4-7 is provided with
Toner T charged to a weak negative charge by rubbing on the surface
The toner T is adhered to the photosensitive drum 4-1 to form a pair.
To the opposite part. [0007] The photosensitive drum 4-1 and the developing roller 4-7
In the opposite portion of the developing roller, the low potential portion of the electrostatic latent image and the developing roller
4-7, a potential difference is formed, and a low potential portion of the electrostatic latent image is formed.
Indicates a positive polarity potential relative to the developing roller 4-7.
Form. Negative polarity due to the electric field due to this potential difference
The charged non-magnetic toner T is applied to the photosensitive drum 4-1.
Transfer to the low potential area of the electrostatic latent image with lath polarity to form a toner image
(Reversal development). The photosensitive drum 4-1 rotates
The toner image is conveyed to a portion facing the endless belt 1. Nothing
The end belt 1 circulates in a counterclockwise direction while the paper
Convey P. The transfer brush 4-2 generates a positive current.
Connected to the output transfer bias power supply
A positive charge is applied. This charge is induced by the endless belt 1.
Is applied to the paper P by the electric effect,
As a result, a photoconductor is applied to the sheet P in contact with the photoconductor drum 4-1.
The negative toner image on the drum 4-1 is transferred. An end portion on the downstream side (left side in the figure) of the endless belt 1
A separation claw 5, the tip of which is lightly attached to the endless belt 1.
It is urged to abut. The toner image has been transferred
The leading edge of the paper P is scooped by the separating claw 5 and the fixing device
Guided to 6. The fixing device 6 is a heating roller surrounded by a heat insulating plate.
And a pressure roller, comprising a rotating heat roller and a pressure roller.
Between the endless belt 1 and the paper P
While thermally fixing the toner image on the paper P to the paper surface.
Is discharged outside the machine (to the left in the figure). FIG.4(b) is a tandem for full-color printing.
It is a system-type printer. In this case a slightly longer endless bell
11 between the driving roller 12a and the driven roller 12b.
Is stretched at a predetermined tension. In the driven roller 12b,
The suction roller 13 is brought into pressure contact with the endless belt 11 via
P is adsorbed to the endless belt 11. Endless belt 1
The paper P is circulated in the counterclockwise direction indicated by the arrow B while moving.
Is transported. Four photoconductors are provided on the upper and outer peripheral surfaces of the endless belt 11.
The drum 14-1 comes into pressure contact with the photosensitive drum 14-1.
4 transfer brushes on the upper inner peripheral surface of the endless belt 11
The sheet 14-2 comes into sliding contact. Take each photoconductor drum 14-1
Winding, respectively cleaner 14-3, initialization charging brush 14
-4, recording head 14-5, and developing unit 14-6 are provided
Is done. The developing device 14-6 has a non-magnetic color toner inside the housing.
-Contains Tx and supports developing roller 14-7 in the lower opening
are doing. Each developing unit 14-6 has, for example, an upstream side (see FIG.
From the right) to center, cyan, yellow, and black colors
The toner Tx is sequentially stored. Downstream of the endless belt 1
Although not particularly shown, a separating claw is provided and is further separated further downstream.
Then, the fixing device 16 is provided. The above-mentioned endless belt 11 and drive roller 12
a, driven roller 12b, suction roller 13, photosensitive drum
14-1, transfer brush 14-2, cleaner 14-3, first
Charging brush 14-4, recording head 14-5, developing unit
14-6, developing roller 14-7, toner Tx, separation claw,
And the fixing device 16 includes the endless belt 1 described in FIG.
Driving roller 2a, driven roller 3b, suction roller 3, photosensitive
Body drum 4-1, transfer brush 4-2, cleaner 4-3,
Initializing charging brush 4-4, recording head 4-5, developing unit 4
-6, developing roller 4-7, non-magnetic toner T, separation claw 5,
And has the same function as that of the fixing device 6. for
Do not flip the paper into a U-shape from below, as indicated by the dashed arrow C.
And the four color toners Tx are sequentially transferred to the paper surface.
The full-color image is heat-fixed by the fixing device 16.
And is discharged out of the machine as indicated by a dashed arrow D in the figure. FIG.4(c) is a space-saving space for monochrome printing.
The printer is a vertical (vertical) printer. This printer is on
With a paper feeder inside, diagonally from upper left to lower right
A paper transport path 21 is provided. Upstream of the transport path 21
(Supposedly diagonally to the upper left in the figure)
Transfer of the paper at the transfer / fixing timing
A standby roll pair 22 is arranged. Under standby roll pair 22
The transfer roller 23 and the transfer path 2
A heating roller 24 that is in pressure contact with the heating roller 24 is disposed inside the heating roller 1. Change
A discharge roll pair 25 is disposed downstream of the printer. The heating roller 24 is slightly skewed to the left and below.
An intermediate transfer roller 26 is disposed in the
Between the roller 26 and the heat roller 24 as an intermediate transfer belt.
Endless belt 27 is stretched. Endless belt 27 is surface
Is formed of an adhesive member, and the
The toner image circulates while carrying a toner image described later. An intermediate transfer roller 26 has an endless belt 27
And press-contact to dispose a cylindrical transparent photoreceptor 28 rotatably
Is done. The inside of the transparent photosensitive member 28 has an axis along the inner peripheral surface.
The recording head 29 is independent of the transparent photoreceptor 28 parallel to the direction
The position is fixed. Notes on the outside of the transparent photoconductor 28
The developing roller 31 is transparent at a position facing the recording head 29.
The photoreceptor 28 is arranged with a slight gap from the peripheral surface thereof.
Developing roller 31 is rotatably held in the lower opening.
A vessel 32 is provided. The developing device 32 has a toner replenishment at an upper portion.
The container 33 is detachably mounted, and the toner T is supplied to the developing roller 3.
Feed to 1. The transparent photosensitive member 28 is counterclockwise indicated by an arrow E in the figure.
Rotate in the direction of rotation to the recording head 29 from the back (inside)
Exposure is performed based on image information.
An electrostatic latent image is formed on the surface. At the same time, the transparent photoconductor 2
8 rotates in the same direction as the transparent photoconductor 28 on the surface facing
The developing roller 31 is connected to the toner supplied from the developing device 32.
-T is sequentially transferred to an electrostatic latent image on the transparent photoreceptor 28 and
Develop the toner image. The developed toner image is transparently exposed
Is transported with the rotation of the body 28, and is intermediate with the transparent photosensitive body 28.
At the pressure contact portion with the transfer roller 26, the endless belt 27
Transferred. The endless belt 27 forms a toner image that adheres.
Carrying it and circulates clockwise as shown by arrow F in the figure,
Opposite transfer of toner image between transfer roller 23 and heating roller 24
To the department. The transfer roller 23 is transported in the transport path 21.
The incoming paper is passed through the endless belt 27 to the heating roller 2.
4 and the heat generating roller 22 is
The transferred toner image is transferred and thermally fixed on a sheet. As described above, FIGS. 4 (a), (b) and (c)
As described above, the electrophotographic image forming apparatus has various forms.
Endless belts are used. [0020] By the way, as described above,
As described above, the conventional belt device always stretches between a plurality of rolls.
Have been. Therefore, if the main unit is not
If the endless belt is in a stopped state in use,
Bending habits are formed at both ends. This
When the endless belt has a bending habit like
During circulating movement, the state of tension on the flat surface changes.
The paper, toner image transfer or transfer, etc.
There was a problem that it was not done well. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional circumstances,
Endless beltTransfer conveyor belt asIs in a long-term outage
Even if there is no bending habitTandem color image formation
It is to provide a device. [0022] The present invention is described below.Tande
Color image formationThe configuration of the device will be described. Of the present inventionTan
Dem type color image formationThe equipment isMultiple image carriers arranged side by side
And a predetermined color toner image individually on the plurality of image carriers.
A plurality of toner image forming means for formingBetween multiple rollers
Passed over toThe transfer material is adsorbed on the outer peripheral surface so that the plurality of image
The transfer material is brought into contact with at least one image carrier of the carrier.
Transfer transport circulating to makeBelt and saidTransfer and transfer
Driving means for driving the belt to circulate;Said
A plurality of image carriers are provided on the inner side of the transfer conveyance belt.
Is disposed so as to constitute a transfer portion, and is in contact with the image carrier.
A plurality of transfer means for transferring a toner image to the transfer material.
The tandem type color image forming apparatus,
Driving means for circulating and moving the transfer conveyance belt
At this time, the transfer material is completely transferred to the transfer material via the transfer conveyance belt.
A first posture to be brought into contact with the image carrier;
A second posture for bringing the transfer material into contact only with the holding body,
The first posture and the second posture when the driving of the driving means is stopped.
Of the transfer conveyance belt in order to take a third posture different from the force
Belt posture changing means for changing the posture, and the belt shape
Cooperating with force change means,The driving meansofWhen drivingTranscription
TransportThe belt is stretched at a predetermined tension to drive the belt.No drive
Operation stopAboveTransfer and transferAdjust the belt tension to the specified level.
Belt tension cut to reduce the tension and relax the belt
Replacement means. [0023] [0024] [0025] [0026] Embodiments of the present invention will be described below with reference to the drawings.
This will be described with reference to FIG. FIG. 1 illustrates one embodiment.
FIG. 2 is a side sectional view schematically showing an internal configuration of the image forming apparatus.
FIG. 2 shows only the belt device portion.
It is a perspective view. As shown in FIG. 1 and FIG.
The device (main device) 40 is located at the lower part in front of the device (right
) Is provided with a paper cassette 41 which can be detached from the paper cassette 41. for
A large number of sheets 42 are placed and stored in a paper cassette 41.
You. Further, an upper lid 43 is provided on the upper surface of the main unit 40.
You. The power switch is not visible on the front side of
Switch, liquid crystal display, multiple input keys, etc.
You. The upper lid 43 has a rear portion that is in contact with a rear upper surface of the main device 40.
Both form a paper discharge tray 44. In the main unit 40, the transfer is substantially at the center.
A conveyor belt (hereinafter simply referred to as a belt) 45 is biased forward and backward.
Arranged in a flat loop, the horizontal ends of the loop
Part is held by a driving roller 46 and a driven roller 47.
You. The belt 45 is driven by a driving roller 46.
And circulates counterclockwise as indicated by arrow H in the figure.
In the upper circulation portion of the belt 45, four photosensitive drums 48
(48a, 48b, 48c, 48d) is the paper transport direction
(From right to left in the figure) in a multistage manner. Each of these photosensitive drums 48 is surrounded.
In the manner described below (typically around the photosensitive drum 48a).
Only the device is denoted by a reference numeral), the cleaner 49,
Initializing charging brush 51, recording head 52, developing unit 53
And a transfer brush 54. Transfer brush 54
Is pressed against the photosensitive drum 48 via the belt 45,
The transfer portion is formed here. The developing device 53 is opened at its lower part.
The developing roller 55 rotatably supported at the opening is a photosensitive drum.
And a developing section is formed there. The recording head 52 is disposed on the back of the upper cover 43.
It is lowered with the closing of the upper lid 43, and the initialization zone
Between the electric brush 51 and the developing roller 55 of the developing device 53.
The recording section is formed here. The upstream side of the transfer brushes 54 in the transport direction.
In the vicinity of the photosensitive drum 48 (48a to 48d)
The backup roller 56 (56a, 56b, 56
c, 56d). These backups
The belt 45 electrostatically attracts the paper to the roller 56 and
In response to the charge being injected for transport,
The charge does not flow through the backup roller 56
Is formed of an appropriate insulator as described above. These backups
The roller 56 is supported by a rotating arm 57 (see FIG. 2).
To form a special belt device.
During operation, do not loosen the upper circulation part of the belt 45 downward.
The photosensitive drum 48 and the belt 4 are supported from below.
5 is maintained. On the downstream back surface of the lower circulation portion of the belt 45,
A tension roller 58 is provided so as to be pressed against the back surface.
You. The tension roller 58 is supported by a fulcrum 59.
The key-shaped member 61 is rotatably supported at one end. Key section
The material 61 is biased by the biasing member 62 engaged with the other end.
Rotate clockwise around fulcrum 59 by force
Is being urged. This rotation power makes tension low
The belt 58 indicates the belt 45 by the arrow J in FIGS.
To lower the belt 45 to absorb the deflection.
Drive roller 46 and driven roller with predetermined tension
It is stretched between 47. At the upstream end of the upper circulation portion of the belt 45,
The suction roller 64 is driven by the driven roller 47 via the belt 45.
To form a paper carry-in port. Adsorption low
The paper 64 (transfer material) carried into the paper carry-in entrance
Is pressed against the belt 45 while applying a suction bias to
The sheet is electrostatically attracted to the belt 45. The photosensitive drum 4 at the uppermost stream in the paper transport direction.
8a to the most downstream photosensitive drum 4 from the developing device 53 corresponding to
8d, each developing device 53 has M
(Magenta) toner, C (cyan) toner, Y (yellow)
ー) Dedicated for printing toner and black parts of characters and images
Bk (black) toners are stored respectively.
I have. Further upstream of the belt 45 in the transport direction (see FIG.
On the right), a pair of standby rolls 65, and then a paper feed plan
An inner path 66 is arranged, and at the lower end of the paper feed guide path 66
A feeding roll pair 67 is provided. Feeding roll pair 67
The paper feed end of the paper cassette 41 described above
Is located. Feed paper above the paper feed end of paper cassette 41
A roller 68 is provided. Feed roller 68 is rotated once
The uppermost sheet stored in the sheet cassette 41 is
The sheet is taken out and fed to the feed roll pair 67. On the other hand, downstream of the belt 45 in the sheet transport direction.
(Left side of the figure) include a fixing device 69, a paper discharge roll pair 71,
A switching lever 72 is provided. The fixing device 69 has a heat insulating property.
Pressure roller, fixing roller,
Heat roller, peripheral surface cleaner, oil application member, thermistor, etc.
And transfer the toner image transferred on the paper to the paper surface.
Fix it. As shown in FIG.
When in the lower position, the upper discharge path 73 and the discharge
The paper is guided to the paper output tray 44 via the
When rotating, open / close tray opened outward from the rear
Guide the paper to 75. Between the belt 45 and the paper cassette 41,
An electrical component 76 is provided. The electrical component 76 includes a plurality of
An appropriate number of turns equipped with a control device consisting of electronic components
Road base is installed. The control device communicates with the controller
The controller unit is a CPU (central processing unit).
Management device), ROM (read only memory), EEPROM
(Rewritable read memory), frame memory,
A host computer with an image data transfer circuit
Analyze the print data input from the data and print data
And transfer it to the engine. The engine unit includes a CPU, a ROM, and the like.
On the input side, data and command signals from the controller
The output of the seed sensor, the output of the paper detection sensor, etc.
On the force side, a motor driver that drives a motor and the like described below,
By rotating the rotating arm 57 shown in FIG.
Switch the drive system of the drive device to be set to one to be described later
The clutch driver that can be
Driver that switches the drive system transmitted to the
Mark for driving the recording head 52 based on the print data.
Driver, initialization charging brush 51, developing roller 55,
A predetermined bias voltage is applied to the transfer brush 54, the suction roller 64, and the like.
Connected to a bias power supply driver that supplies
You. The engine unit receives data and command signals from the controller unit.
Control based on the output of the paper detection sensor
I do. FIGS. 3 (a), 3 (b) and 3 (c) show the belt device of FIG.
FIG. 4 is a side view showing the details in detail.
The state is shown. FIG. 3A is referred to together with FIG.
The configuration will be further described with reference to FIG. As shown in FIG. 2 and FIG.
As described above, in the belt device, the rotating arm 57
The downstream end is coaxial with the backup roller 56d.
It is rotatably supported by the frame of the device 40 and has a fixed position.
Have been. The backup roller 56d is a drive roller 4
6, above the photosensitive drum 48d, which is the most downstream,
It is arranged near the flow side. This backup roller 56d
Indicates that the lowermost photosensitive drum 48d is always in contact with the belt 45.
It is arranged in contact with the inner peripheral surface of the belt 45 to make it touch.
You. The pivot arm 57 is connected to the backup row.
The free end side (centering on the same support shaft as
) Rotates up and down. Backup row at its free end
La 56a is supported. Backup roller 56a
Is the photosensitive drum closest to the driven roller 47, that is, the most upstream photosensitive drum.
Of the belt 45 between the ram 48a and the driven rotary roller 47.
The belt 45 is supported in contact with the inner peripheral surface. And
The backup roller 56a and the backup roller 5
Backup rollers 56b and 56c rotate in the middle of 6d.
Supported by the moving arm 57, the photosensitive drums 48b and 48b respectively.
And contact the inner peripheral surface of the belt 45 near the upstream side of the belt 48c.
The belt 45 is supported. The pivot arm 57 has an upstream end.
The upper end of the intermediate connecting rod 77 is connected in the vicinity of the
The lower end of the connecting rod 77 is perpendicular to the shaft from the end of the drive shaft 78.
Is connected to the tip of a rotating arm 79 protruding from the arm. Drive shaft
Reference numeral 78 denotes a clutch gear 82 via an electromagnetic clutch 81.
I agree. The clutch gear 82 is a one-way rotating gear (
Drive gear 84 of the motor 85 via the
Is engaged. FIGS. 1, 2 and 3 (a) will be described in detail later.
The motor 85 is controlled by the control unit from the reference state of FIG.
Driven in the counterclockwise direction indicated by arrow K in FIG.
As a result, the clutch gear 82
Is driven to rotate the drive shaft 78, and the rotation is fixed to the drive shaft 78.
The arm 79 rotates counterclockwise as indicated by the arrow L in FIG.
To rotate the rotating arm 57 upward through the intermediate connecting rod 77.
And the whole is set to full color print mode.
This shows the state of the case. This state is at the tip of the rotating arm 79
The position detecting projection 79-1 integrally formed is
Is detected by the sensor 87 for
Positioning is performed when the motor 85 stops. Subsequently, the operation of the image forming apparatus 40 having the above configuration is described.
1 and 2 and FIGS. 3 (a), (b) and (c) described above.
It will be explained while referring to the figures. First, switch to full-color printing mode.
A description will be given of the processing operation. The apparatus main body 4 shown in FIG.
The power is turned on to 0 and the paper quality, number of sheets, and printing
The mode and other designations can be keyed in or connected to the host
When input as a signal from the
The illustrated electromagnetic clutch 81 operates by energization to drive the drive shaft 78.
And the clutch gear 82, and subsequently the motor 8
5 is driven, and the rotating arm 57 is rotated upward.
As a result, the backup rollers 56a, 56b and 56c
Move up and move belt 45 to all four photoconductor drivers.
Abut on the tape 48 (48a, 48b, 48c, 48d)
You. Subsequently, the paper feed roller 68 is moved to the paper cassette 41.
Take out one sheet of paper 42 placed and stored in
Of the standby roll pair 65 via the paper feed guide path 66.
Feed to The standby roll pair 65 has stopped rotating,
The leading end of the paper 42 is brought into contact with the holding portion to advance the paper 42.
Stop the line and wait for the transport timing. The drive roller 46 rotates counterclockwise.
Then, the driven roller 47 is driven to move in the counterclockwise direction.
Rotate. Thus, the belt 45 has four upper circulating portions.
The whole contacts the photosensitive drum 48 and circulates counterclockwise in its entirety.
Ring moves. Along with this, the developing unit 53 and the photosensitive drum 4
8 are sequentially driven in accordance with the print timing. Photoconductor
The drum 48 rotates clockwise and initializes the charging brush.
51 is a uniform high negative charge on the peripheral surface of the photosensitive drum 48
, And the recording head 52 moves around the photosensitive drum 48
Exposure is performed on the surface according to the image signal to form a low potential portion
You. Thereby, the high negative potential portion due to the above initialization
And an electrostatic latent image consisting of low negative potential
Is done. The developing roller 55 of the developing device 53 has its electrostatic latent
The toner is transferred to the low potential portion of the image and the photosensitive drum
A toner image is formed on the surface (reversal development). The toner on the peripheral surface of the photosensitive drum 48a at the uppermost stream
-The tip of the image is rotated and conveyed to the point facing the belt 45
At the timing of the arrival, the printing start position of the paper 42 is
The standby roll pair 65 starts rotating so that the positions match.
To feed the paper 42 to the paper carry-in section. The driven roller 47 and the suction roller 64 are fed
The transported sheet 42 is nipped and transported together with the belt 45.
The paper 42 is attracted to the belt 45 and the photosensitive drum 48
a and the first transfer portion formed by the transfer brush 54
Transported to The transfer brush 54 includes a transfer via (not shown).
Transfer current output from the power supply
Apply to paper 42. Depending on the applied transfer current, the photoconductor
The toner image on the drum 48a is transferred to the paper 42,
An image is formed on the sheet 42. Subsequently, the photosensitive drum 48b and the transfer brush
54 to the second transfer portion from the upstream formed by
C (cyan) toner image is transferred to the photosensitive drum.
The upstream formed by the transfer brush 54 and the transfer brush 54
Y (yellow) toner image is transferred at the third transfer section
You. Then, the photosensitive drum 48d and the transfer brush 54
Bk (black) at the most downstream transfer section
Toner images are sequentially transferred, and four color toner images are overcoated.
You. In this manner, the four color toner images are transferred.
The separated paper 42 is separated from the belt 45 and the fixing device 69
It is carried in. The fixing device 69 heats the toner image on the paper 42.
Fix it. After the image is fixed, the paper 42 is
1 to make the toner image upward from the rear discharge port 72,
Prints the toner image from the upper discharge port via the discharge roller pair 74.
It is discharged out of the machine with it down. Next, in the monochrome print mode,
The energization of the magnetic clutch 81 is temporarily interrupted and the drive shaft 78 is closed.
The connection with the latch gear 82 is released, and the rotating arm 57 is
Rotates downward by its own weight and contacts the stopper 88 for reference
Stop in position. Thereafter, the electromagnetic clutch 81 is energized again.
Then, the drive shaft 78 and the clutch gear 82 are connected. motor
85 is driven, the drive shaft 78 rotates, and the tip of the rotating arm 79
Of the position detection projection 79-1 by the monochrome sensor 89
And the motor 85 stops in response to this detection.
You. As a result, the rotating arm 57 moves to the position shown in FIG.
To stop. This is compared with FIG. 3A as a result.
The pivot arm 57 pivots downward from the position shown in FIG.
Is set to And in this state,
The backup rollers 56a, 56b and 56c
5 has been moved downward while being pressed against
The upper circulating portion of the belt 45 includes three photosensitive drums on the upstream side.
It is set in a state separated from the rams 48a to 48c. Ma
The lowermost transfer brush 54 is a frame of the main unit 40.
While the other three transfer blocks on the upstream side are fixed.
The brush 54 is fixed to the rotating arm 57.
Downward together with the rotating arm 57 while sliding on the belt 45.
And is formed between the photosensitive drums 48a to 48c.
The transferred portion has been released. The belt 45 is connected to the drive roller 46 and the back
Abuts only on the photosensitive drum 48d between the rollers 56d
As a result, the most downstream photosensitive drum 48d is
The transfer portion of the black toner formed by the transfer brush 54
Is set to work and the monochrome print mode is set.
It is. Note that the subsequent processing is performed in the full-color printing mode described above.
Since the case is the same as that of the case of C, the description is omitted. In the present embodiment operating as described above,
When the printing operation is stopped in the image forming apparatus
Is turned off when the electromagnetic clutch is turned off.
The position is maintained at the reference position shown in FIG. Fig. 3 (a)
Full-color print mode and monochrome print mode
In all cases, all backup rollers 5
6a to 56d are always in pressure contact with the belt 45,
All four transfer brushes 54 are always in sliding contact with the belt 45,
Then, the key-shaped member 61 is urged by the urging member 62 to
The shock roller 58 always tensions the belt 45.
On the other hand, in FIG.
56a to 56c are separated from the belt 45 to the belt 45
Is released, and the three transfer brushes 54 are also
The sliding contact with the belt 45 is released apart from the belt 45. Soshi
Then, the other end of the key-shaped member 61 comes into contact with the stopper 89 and is urged.
The urging by the member 62 is stopped, and the tension roller 58
Is stopped at a certain position. Thus, the tension of the belt 45 is released.
Drive roller 46, backup roller 56d and
Between the driven roller 47 and the driven roller 47 in a substantially natural state.
Only. As described above, the belt 45 is not in operation.
Since tension is released and natural state is created, bending habit occurs
Always restart printing in the best possible condition
Can be. In the above embodiment, the structure of the belt is changed.
Although it is made of a hard material that gives a bending habit,
It may be made of a soft material such as rubber.
To prevent belt slack caused by premature tension
Can be. [0058] [0059] [0060] [0061] [0062] [0063] [0064] [0065] [0066] As described above, according to the present invention,
Further switching mechanism between full color printing and monochrome printing
Used by being stretched by adding a switching function
The belt tension is released when not in use, so operation is prolonged.
Even if the belt was paused during the period,
There is no setback in a short period of time,
Processing can be resumed in a stable state, and
Can always produce good quality images.
You. Further, the belt is tensioned by engaging with a belt drive system.
Operates because the biasing force of the tension roll for installation is controlled.
The belt tension can be automatically released during a stop.
And therefore, driven by the drive train
If the belt is stretched with the
Release the tension to prevent bending habits and sagging
It is very convenient.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side sectional view schematically showing an internal configuration of an image forming apparatus according to a first embodiment. FIG. 2 is a perspective view showing only a belt device portion of the image forming apparatus. FIG. 3 is a side view showing the belt device in detail, and FIG.
FIG. 7B is a diagram illustrating a state when full-color printing, FIG. 7B is a monochrome printing, and FIG. FIGS. 4A, 4B, and 4C are diagrams showing examples of a conventional electrophotographic image forming apparatus. [Description of Signs] 1, 11 Endless belts 2a, 12a Driving rollers 2b, 12b Followed rollers 3, 13 Suction rollers P Paper 4-1, 14-1 Photoconductor drum 4-2, 14-2 Transfer brush 4-3, 14-3 Cleaner 4-4, 14-4 Initializing charging brush 4-5, 14-5 Recording head 4-6, 14-6 Developing unit 4-7, Section 14-7 Image roller T, Tx non-magnetic toner 5 Separation claw 6, 16 Fixing unit 21 Paper transport path 22 Standing roll pair 23 Transfer roller 24 Heating roller 25 Discharge roll pair 26 Intermediate transfer roller 27 Cryogenic belt 28 Transparent photoconductor 29 Recording head 31 Developing roller 32 Developing device 33 Toner Replenishment container 40 Image forming base (main unit) 41 Paper cassette 42 Paper 43 Top lid 44 Paper discharge tray 45 Transfer / transport belt (belt) 46 Drive roller 47 Follower roller 48 (48a, 48b, 48c, 48d) Photosensitive drum 49 Cleaner 51 Initializing charging brush 52 Recording head 53 Developing device 54 Transfer brush 55 Developing roller 56 (56a, 56b, 56c, 56d) Backup roller 57 Rotating arm 58 Tension roller 59 Fulcrum 61 key-shaped member 62 urging member 64 suction roller 65 standby roll pair 66 paper feed guide path 1 67 feed roll pair 68 paper feed roller 69 fuser 71 discharge roll pair 72 switching lever 73 discharge path 74 discharge roll pair 75 Opening / closing tray 76 Electrical part 77 Intermediate connection km 78 Noise shaft 79 Rotating arm 79-1 Position detecting projection 81 Electromagnetic clutch 82 Clutch gear 83 One-way rotating gear (one-way gear) 84 Drive gear 85 Motor 87 Sensor for full color 88 , 89 stopper

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B65H 5/02 G03G 15/01

Claims (1)

(57) [Claim 1] A plurality of image carriers arranged side by side and the plurality of
That individually form a predetermined color toner image on an image carrier
A toner image forming means, outside spanned between a plurality of rollers
The transfer material is adsorbed to the peripheral surface to reduce the number of the plurality of image carriers.
Circulating transfer to bring the transfer material into contact with one image carrier.
A transfer transfer belt that moves, a driving unit that drives the transfer transfer belt to circulate, and the transfer transfer belt.
A transfer unit is configured inside the unit to correspond to the plurality of image carriers.
To the transfer material that is disposed to be in contact with the image carrier.
Tandem type having a plurality of transfer means for transferring a toner image
In the color image forming apparatus, the driving unit is driven to circulate the transfer / conveying belt.
When moving, the transfer material via the transfer conveyance belt
A first posture for contacting the
A second method in which the transfer material is brought into contact only with the color image carrier;
The first attitude and the first attitude when the driving means stops driving.
Transfer transfer so as to take a third position different from the second position
A belt position changing means for changing the attitude of the belt, the belt attitude change means cooperates, when driving stop of the drive means is stretched the transfer conveyance belt at the time of driving of the driving means at a predetermined degree of tension is A tandem-type color image forming apparatus, comprising: belt tension switching means for relaxing the belt by reducing the tension of the transfer / transport belt from the predetermined tension.