JPH05265271A - Color image forming device capable of switching driving speed - Google Patents

Abstract

PURPOSE:To convey recording paper at low speed at the fixing time so as to improve the quality of a color image by allowing the driving speed of a driving means to be switched to two speeds, and performing the switching of two speeds by an electromagnetic clutch, reduction gears and a one-way clutch. CONSTITUTION:The driving speed of a driving means can be switched to two speeds. When the rear end of recording paper P passes a sensor S1, a signal is transmitted to a CPU 61 from a sensor S, and an electromagnetic clutch 51 is operated through an output part 61A. At this time, a gear 48 is spaced from a friction plate 50, so that torque is transmitted only to reduction gears 52, 53, 54, and turning force is transmitted in the speed-reduced state to a belt 57 through a pulley 55 and to a rotary shaft 45 by a one-way clutch through a pulley 56. A color image is thereby transferred onto the recording paper P in the speed-reduced state compared to the developing time of a photoconductor drum 1, and since a fixing device is also speed-reduced simultaneously, the color image on the recording paper P is fixed at low speed by a fixing heat roller pair 31.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus capable of switching the image forming process speed of a color image forming apparatus to the second speed and improving the image quality.

[0002]

2. Description of the Related Art In recent years, a color image forming apparatus has been widely used as an image forming method. However, it is also used in many image forming means to improve the image quality by making a color image on a recording paper clearer, but as the image quality improving means, a color image is formed on the recording paper by the color image forming apparatus. After fixing and discharging the recording paper, there is used a means for allowing the recording paper on which the color image is formed to pass through another fixing device whose speed is reduced again.

[0003]

In the above-mentioned prior art, the means for fixing the color image recorded on the recording paper and fixing it with another fixing device at a low speed to improve the image quality is a measure for improving the color image quality. However, on the other hand, a fixing device must be separately provided in addition to the color image forming apparatus, resulting in a large installation area of the apparatus and therefore an increase in the cost of the apparatus. Further, since the fixing device is separately provided, there is a problem that the efficiency of the recording work until the image formation is completed is deteriorated.

The present invention has been improved in order to solve the above-mentioned problems, and an object of the present invention is to set a drive source of an image forming apparatus to a two-speed drive system, for example, to change the speed during image formation and fixing. The image quality of the color image was improved by changing the quality and feeding the recording paper at low speed during fixing.

[0005]

To achieve the above object, an image forming apparatus according to the present invention comprises at least an image carrier, a developing device, a fixing device, and a single driving means.
In a color image forming apparatus for driving a recording paper conveying device, the driving speed of the driving means can be switched to the second speed and means for switching the second speed by an electromagnetic clutch, a reduction gear and a one-way clutch. By switching the speed of the stepping motor, this is achieved.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a conventional image forming apparatus. Reference numeral 1 denotes a drum-shaped image bearing member, that is, a photosensitive drum, which is a photosensitive member having a diameter of 100 mm and an OPC photosensitive layer applied on the peripheral surface of the drum, and is driven and rotated clockwise. Reference numeral 2 is a band electrode for applying an electric charge to the photoconductor on the peripheral surface of the photoconductor drum 1, and 3 is a laser writing system unit as an exposure optical system.

Color signals output from an image reading apparatus separate from the image forming apparatus are the laser writing system unit 3
In the laser writing system unit 3, the laser beam generated by the semiconductor laser (not shown) is rotationally scanned by the polygon mirror 5 rotated by the drive motor 4 and passed through the fθ lens 6 to 3 The optical path is bent by the mirrors 7, 8 and 9 and the band electrode 2 is previously formed.
The charges are projected onto the peripheral surface of the photoconductor drum 1 to which electric charges are applied.

On the other hand, when the scanning is started, the laser beam is detected by the index sensor, the modulation of the laser beam by the first color signal is started, and the modulated laser beam moves on the peripheral surface of the photosensitive drum 1. To scan. Therefore, a latent image for the first color is formed on the peripheral surface of the photosensitive drum 1 by the main scanning by the laser beam and the sub-scanning by the rotation of the photosensitive drum 1. This latent image is developed by the developing device 10 that contains, for example, yellow toner as the first color, and a yellow toner image is formed on the peripheral surface of the photosensitive drum 1. The obtained toner image passes under the cleaning device 11 that is temporarily separated from the peripheral surface of the photosensitive drum 1 while being held on the peripheral surface of the photosensitive drum 1, and enters the next copy sequel.

That is, the photosensitive drum 1 is recharged by the band electrode 2, and then the second color signal output from the signal processing unit is input to the laser writing system unit 3 and the above-mentioned first color signal is output. Similarly to the case of the signal, writing with the second color signal is performed on the peripheral surface of the photosensitive drum 1 to form a latent image. The latent image is developed as a second color by the developing device 101 that contains, for example, magenta toner.

This magenta toner image is formed so as to overlap the already formed yellow toner image.

The toner image thus obtained passes under the cleaning device 11 which is separated from the peripheral surface of the photosensitive drum 1 while being held on the peripheral surface of the photosensitive drum 1.
Enter the next copy cycle.

Similarly, writing is performed by the third color signal on the photosensitive drum 1 to form a latent image. This latent image is developed by the developing device 102 that contains, for example, cyan toner as the third color. The cyan toner image is formed on the yellow and magenta toner images described above.

As described above, a color toner image is formed on the photoconductor drum 1 by the three color toners. By similarly superposing the black toner image, a high quality color image can be obtained. Become.

Numerals 10 to 103 are developing devices as developing means for accommodating the yellow, magenta, cyan and black toners, respectively, which carry out the above-mentioned development.

As shown in the example of the developing device 10, each of the developing devices has a developing sleeve 10A having magnetic poles fixed to the inner surface of the photoconductor drum 1 with a predetermined gap therebetween.
And a pair of agitating rollers 10B having conveyance forces in opposite directions.
And 10C, the developer is supplied to the peripheral surface of the rotating developing sleeve 10A after the components of the toner and the carrier are made uniform by the mixing action of the stirring rollers 10B and 10C.

A DC or further AC bias is applied to the developing sleeve of each developing device carrying the developer so that non-contact reversal development by the two-component developer is performed.

The charging by the photosensitive drum 1 and the band electrode 2 provided on the peripheral portion thereof, the exposure by the laser writing system unit 3 for each color and the developing process by the developing devices 10 to 103 are performed four times for each color. As a result, a color toner image is formed on the peripheral surface of the photosensitive drum 1 by superposition.

Reference numeral 12 denotes a sheet feeding cassette, 13 denotes a separating roller, and the stacked recording sheets P in the sheet feeding cassette 12 are carried out and fed one by one from the uppermost layer by the action of the separating roller 13.

Reference numerals 14 and 15 respectively denote a first paper feed roller and a second paper feed roller which are in a constantly rotating state, and 16 and 17 denote arcuate and linear paper feed guides, respectively.

The recording paper P carried out from the paper feed cassette 12 is fed along the paper feed guide 16 by the first paper feed roller 14 and is turned U, that is, turned upside down, and then is fed along the paper feed guide 17. It abuts on the rising portion of the paper feed shutter 18 that is blocked, and temporarily stops. In this case, the second paper feed roller 15 slips on the surface of the recording paper in the stopped state and continues to rotate.

When the paper feed shutter 18 retreats downward in synchronism with the rotation of the photoconductor drum 1 having the toner image, the peripheral speed of the photoconductor drum 1 of the recording paper is reduced by the frictional force of the second paper feed roller 15. And is fed to the transfer unit 19 in synchronism with.

A transfer belt 20 is stretched between a drive roller 21 and a transfer roller 22 and is rotated counterclockwise at the same speed as the peripheral speed of the photosensitive drum 1. The transfer belt 20 is adapted to press and release the press contact with the photosensitive drum 1 with the drive roller 21 as the swing center. That is, the transfer roller 22 is a rotatable roller that has been charged with a voltage and is in a charged state. At the time of pressure contact, the transfer roller 22 transfers a toner image to the recording paper side via the transfer belt 20 at the contact point with the peripheral surface of the photosensitive drum 1. Make up nineteen. Therefore, transfer is performed while the recording paper is being conveyed by the transfer belt 20. Reference numeral 23 is a cleaning means for cleaning the surface of the transfer belt 20.

Numeral 24 is a front band electrode, which is located upstream of the cleaning device 11 and is electrified so that the residual toner on the peripheral surface of the photosensitive drum 1 on which the toner image is transferred onto the recording paper can be easily removed.

The cleaning device 11 presses and releases the photoconductor drum 1 around the swing shaft 26 as a swing center. Reference numerals 27 and 28 denote conductive cleaning brushes and conductive recovery rollers that are cleaning means of the cleaning device 11, and 29 is a waste toner recovery unit that stores the toner recovered by the cleaning means.

The photosensitive drum 1 that has passed through the front electrode 24 is
Residual toner is removed by the cleaning brush 27 brought into a sliding contact state by a signal from the control unit, and the residual toner adhering to the brush 27 is adsorbed by the collecting roller 28 and then sent to the waste toner collecting unit 29. Be done.

The photosensitive drum 1 whose peripheral surface has been cleaned in this way is charged again by the charger 2 to start forming a new image, and at the same time, the cleaning brush 27 is released from the sliding state.

On the other hand, the recording paper P having the toner image transferred at the transfer portion is separated from the peripheral surface of the photosensitive drum 1 and is fed to the fixing device 30. Reference numeral 31 is a fixing heat roller pair, and 32 is a paper discharge roller pair. The recording paper P having the toner fused and fixed by the heat roller pair 31 is discharged from the fixing device 30 to the outside of the apparatus by the paper discharge roller pair 32.

There is a toner replenishing section 33 at the upper right of the figure.
The toner replenishing section 33 has a replenishment toner container (not shown) provided outside the toner replenishing section 33 so as to overlap each other in the figure, and accommodates yellow, magenta, cyan, and black toners for replenishment inside. There is. The developing device 10, 101, 1
Toner supply pipes 10D, 101A, 102A, 103 between 02 and 103
They are connected by A respectively. Toner supply tube 10
D, 101A, 102A, 103A has a screw inside, and when power is transmitted by a signal from the control unit to rotate the screw, the toner in the toner container for replenishment passes through the replenishing pipe to a developing device. Will be replenished inside.

The above-mentioned devices are incorporated in the image forming device 34. Reference numeral 35 denotes a fixing device for re-fixing the recording paper P that has passed through the fixing device 30.
36 is provided, the fixing device 35 is provided on the frame 36, and the guide plate 37
Then, the recording paper P for re-fixing is conveyed to the fixing device 35. 38 is a fixing heat roller pair, and 39 is a paper discharge roller pair.
The fixing heat roller pair 38 is provided with a drive motor 40 separately from the drive source of the image forming apparatus 34, and the fixing speed of the fixing device 35 (generally slower) is changed with respect to the fixing device 30 to change the recording paper. Sharpens the P color image. The above is the re-fixing unit used in the color image forming apparatus 34 that has been used conventionally.

FIG. 2 shows a means of the present invention for forming a color image similar to re-fixing to the image forming apparatus 34 without using the fixing device 35 for re-fixing. A driving device for driving the motor is shown in FIGS. 3, 4 and 5.

FIG. 3 shows a driving device 41, and 42 is a driving motor, and a gear 43 is fixed to the shaft of the driving motor 42. Reference numeral 44 is an electromagnetic clutch, and as shown in FIG. 4, an electromagnet 46 provided around a rotating shaft 45, and a spring which is attracted to the electromagnetic force and which is a spring.
When the gear 48 and the gear 48 provided on the rotary shaft 45 are separated from the electromagnet 46 by the spring 47, as shown in FIG.
A rotary plate 49 fixed to the rotating shaft 45 is in contact with the rotary plate 45 via a friction plate 50. Although the electromagnet 46 is provided around the rotating shaft 45, the electromagnet 46 is loosely engaged regardless of the rotation of the rotating shaft 45.
46 is provided so as to be fixed to a part of the image forming apparatus 34 via the frame 51. The drive of the gear 48 is reduced through the reduction gears 52, 53, 54 at a ratio of 1: 0.17 as compared with that at the time of development.
A transmission belt 57 is suspended from a pulley 55 provided on the rotating shaft 45 from a pulley 55 provided coaxially with 54. The belt 57 may be a timing belt. A one-way clutch 58 is provided between the pulley 56 and the rotating shaft 45 as shown in FIG. Reference numeral 59 is a reduction drive gear fixed to the rotating shaft 45, and 60 is a drive gear driven by the reduction drive gear 59. The drive device is configured as described above, and now the image forming apparatus 34
When the recording is started by driving the drive motor 42 via the output unit 61A according to an instruction from the CPU 61 provided in the gear 43
Is transmitted to the gear 48, and the gear 48 is in contact with the rotating plate 49 via the friction plate 50 by the spring 48.
49 is rotated, and at the same time, the reduction drive gear 59
The drive gear 60 is rotated by being directly transmitted to.
At this time, the one-way clutch 58 is free and does not operate. The drive gear 60, for example, is directly connected to the shaft of the photosensitive drum 1 as shown in FIG. 2, and is connected to the developing device 10, 101, 102, 103 and the fixing heat roller of the fixing device 30 via an interlocking gear, a chain, a timing belt and the like. The transfer belt transfers the color image formed on the photoconductor drum 1 to the recording paper P that is fed in conjunction with the pair 31.
Transfer with 20. Final development is performed on the photoconductor drum 1 by the developing device, for example, by the developing device 103, the recording paper P stopped by the paper feed shutter 18 in the transport unit is released, and the recording paper P is transferred to the transfer unit 19. Is conveyed by the second paper feed roller 15. The sensor S1 provided on the paper feed guide 17 detects that the recording paper P has been conveyed.
A signal is sent from the sensor S1 to the CPU 61 that the rear end has passed the sensor S1, and the electromagnetic clutch 51 is operated via the output unit 61A. At this time, the electromagnet 46 is energized and the gear 48 is attracted to the spring 47, and the gear 48 is separated from the friction plate 50, so that the driving force for the rotating plate 49 is lost, and the gear 48 is the reduction gears 52, 53, 54 only. The rotational force is transmitted to the rotating shaft 45 by the one-way clutch 58 via the belt 57 and the pulley 56 via the pulley 55, and the rotational force is transmitted. Therefore, the color image is transferred onto the recording paper P in a state in which the recording paper P is decelerated compared with the time of developing the photosensitive drum 1, and at the same time, the fixing device is also decelerated.
The color image of is fixed by the fixing heat roller pair 31 at a low speed.

Next, the embodiment shown in FIG. 6 will be described. In this embodiment, a stepping motor 62 is used as a drive unit. As described in the embodiment shown in FIG. , 101, 102, 103 are sequentially developed to form a color image. The recording paper is fed from the paper feed cassette 12 via the paper feed guide 17 by the second paper feed roller 15 to the paper feed shutter 18
It has been sent to the department and stopped. When, for example, the final development is performed on the photosensitive drum 1 by the developing device 103, the paper feed shutter 18 is opened and the recording paper P starts feeding, and the trailing edge of the recording paper P has passed the sensor S1. Is transmitted to the CPU 61, and at the same time, the stepping motor 62 is decelerated at a ratio of 1: 0.17 via the output unit 61A, and in the decelerated state, a color image is transferred onto the recording paper P by the transfer belt 20 and the fixing device 30. Is also decelerated and is fixed by the fixing heat roller pair 31.

Although the embodiment of the present invention is configured to decelerate before transfer, the transfer is performed at the same speed as during development, and after image transfer, before the leading edge of the recording paper enters the fixing device 30. It is also possible to change the position of the sensor S1 so as to decelerate or change the program of the CPU 61 of the image forming apparatus to use.

[0034]

Since the present invention is constructed as described above, it has the following effects.

When a color image is developed on the photosensitive drum 1, the color image is formed rapidly at a normal speed.
Before or after the color image is transferred onto the recording paper P, the conveying speed and the fixing speed of the recording paper P are reduced, and the color images are heat-fixed onto the recording paper P at a low speed. A good color image can be obtained by using one fixing device without using it.

Further, since the present invention uses one fixing device, the entire device can be downsized, and the power consumption and the cost can be greatly reduced.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a color image forming apparatus including a conventional fixing device.

FIG. 2 is a vertical cross-sectional view showing a color image forming apparatus of the present invention including a fixing device.

FIG. 3 is a configuration diagram showing a driving device of a color image forming apparatus.

FIG. 4 is a sectional view of an electromagnetic clutch.

FIG. 5 is a sectional view of a one-way clutch.

FIG. 6 is a vertical cross-sectional view showing another embodiment of a color image forming apparatus including a fixing device.

[Explanation of symbols]

 1 photoconductor drum 3 laser writing system unit 10, 101, 102, 103 developing device 11 cleaning device 12 paper feed cassette 20 transfer belt 30, 35 fixing device 31 fixing heat roller pair S sensor 42 drive motor 43 gears 48, 52, 53 , 54, 59 Gears and reduction gears 58 One-way clutch 60 Drive gear 61 CPU 61A Output 62 Stepping motor

Claims (4)

[Claims] 1. In a color image forming apparatus in which at least an image carrier, a developing device, a fixing device, and a recording paper conveying device are driven by one driving means, the driving speed of the driving means is switched to the second speed. A color image forming apparatus capable of switching a driving speed, which is possible. 2. The color image forming apparatus according to claim 1, wherein the driving speed is switched by an electromagnetic clutch, a reduction gear, and a one-way clutch. 3. The color image forming apparatus according to claim 1, wherein the driving speed is switched by switching a speed of a stepping motor. 4. The color image forming apparatus according to claim 1, wherein the image forming apparatus is a color image forming apparatus.