JPH06236103A - Image forming device having developing means - Google Patents

Abstract

PURPOSE:To avoid the influence of a roller by the contact of a photosensitive drum surface with the roller and especially to prevent the generation of irregularities in a pitch on a latent image at the time of forming the latent image on a photosensitive drum by changing the input voltage of a powder clutch and gradually starting the rotation of a developing rotary sleeve. CONSTITUTION:When the power of a power source 4141 is not applied to an exciting coil C16 by a work control means 414, the rotational force of a rotary cylinder C12 does not generate torque on a shaft to be driven C15, because the rotation is not transmitted to the working part C18 of a rotary rotor C14. Then, the voltage of the power source 4141 is gradually elevated by the work control means 414, so that a magnetic flux C19 by the exciting coil C16 is gradually strengthened and in the follow-up movement of powder C17 as well, the extent of the movement is increased according to the strength of the magnetic flux C19, to increase the torque of the rotary rotor C14. The rotation of the developing rotary sleeve 41 by the shaft to be driven 15 is gradually started by that action, at the time of starting operation and reaches a prescribed number of revolution after a specified time lapses, even if a driving motor M is quickly started to rotate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention When the latent image formed on the image bearing member is developed by a plurality of developing devices, the developing sleeve provided in the developing devices does not suddenly start rotation during development. The present invention relates to an apparatus that is controlled as described above and that does not adversely affect the photosensitive drum for image formation.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, an exposure device using at least a charging device and an ordinary light source or laser light centering around a photosensitive drum as an image carrier and a black developing device, or in the case of color copying. A plurality of developing devices are sequentially arranged. In order to form an image on the photoconductor drum, first, the entire surface of the photoconductor drum is charged by a charging device, and exposure is performed by an exposure device according to an input signal from the document or computer. A latent image corresponding to the signal is formed. The latent image is developed by the developing device. Particularly in the case of the color copying, a developing device containing several kinds of color toners is provided, and only the developing device for developing is brought close to the surface of the photoconductor drum to develop. It is carried out. Generally, the developing device is provided with a developing rotary sleeve, and the developing rotary sleeve is rotated at a high speed (for example, 300 to 350 γpm depending on color) by a driving means through an electromagnetic clutch during development so that any image can be dealt with. Color toner is conveyed to the latent image portion so that good development can be performed.

[0003]

When developing the latent image formed on the photosensitive drum as described above, the developing rotary sleeve is started and rotated by the driving means via the electromagnetic clutch as described above. In general, the photosensitive drum cannot be manufactured in a large diameter because there are restrictions on the entire apparatus and cost. Therefore, even with a small document size that is usually used, the latent image formed on the photosensitive drum reaches the developing device, and the exposure device performs exposure even when the developing rotary sleeve starts to start. As for the exposure mode, normally, the exposed portions are sequentially exposed from the charged portion of the photosensitive drum surface. Particularly, when the exposure is performed by using a laser beam, the photosensitive drum rotates and the exposure is performed synchronously by scanning with a fine width to the left and right. In such a situation, when the developing rotary sleeve of the developing device is started as described above, the electromagnetic clutch is turned on, and at the same time, the developing rotary sleeve rapidly starts to rotate. The impact is large, and the impact on the surface of the photoconductor drum naturally occurs. The reason for this is that in the recent developing device, the developer layer conveyed on the developing rotary sleeve becomes thin, and the gap between the surface of the photosensitive drum (hereinafter referred to as DSD).
It is necessary to accurately maintain a very small DSD width of about 0.5 mm, and as a means for forming this DSD width, rollers are provided on both sides of the developing rotary sleeve, and the rollers are projected onto the surface of the photosensitive drum. By applying it, the accurate DSD width is maintained. Since the roller is provided coaxially with the developing rotary sleeve, the impact at the time of starting by the electromagnetic clutch is transmitted to the photosensitive drum via the roller, and temporarily affects the accurate rotation of the photosensitive drum. Therefore, the latent image forming surface during exposure becomes uneven in pitch at the time of starting, and a defective image occurs when developing. Particularly, in the case of forming a color image by superimposing multicolored colors, there is a disadvantage that uneven pitch is generated in each developing device and a good color image cannot be obtained.

[0004]

The present invention for solving the above-mentioned problems provides an image carrier according to claim 1, a charging unit for applying a charge to the image carrier, an exposing unit, and an exposing unit. In an image forming apparatus having a plurality of developing means for developing the formed latent image and a driving means for driving the plurality of developing means, a developing rotary sleeve provided in each of the plurality of developing means, and the developing rotary sleeve. Drive means for rotating the sleeve respectively, the plurality of developing rotary sleeves, an electromagnetic powder clutch provided in each of the driving means, and the rotating rotary sleeve for development via the electromagnetic powder clutch, 3. An image forming apparatus having developing means, characterized in that the input voltage of the powder clutch is changed to gradually start rotation of the developing rotary sleeve. The developing means are each yellow,
A solution is provided by a plurality of developing means for developing with four colors of magenta, cyan and black, and according to claim 3, having a control means for changing an input voltage of the powder clutch for driving the developing rotary sleeve. did.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an image forming apparatus using the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a main part of an embodiment of an image forming apparatus A of the present invention.

In this embodiment, yellow, magenta, cyan,
Color copying machine A equipped with a non-contact development type laser writing device for four colors of black (hereinafter referred to as Y, M, C, Bk)
Is.

First, the basic structure of the color copying machine main body and the basic operation in the normal mode will be described.

Before being exposed by the laser writing unit 2, the photosensitive drum 1, which is an image carrier, is electrically neutralized by the PCL 12 and then charged by the charging device 13 so that the entire surface is uniformly charged to a predetermined potential. The charging device 13 is a scorotron charger, the grit voltage is -550V, and the charging potential of the photoconductor is -600V. This condition is used in the normal mode.

On the photosensitive drum 1 which has been primary charged,
An electrostatic latent image is sequentially formed by the laser writing unit 2, and the latent image is subjected to non-contact reversal development Y, M, C, Bk.
The developing devices 3, 4, 5 and 6 are sequentially developed. In the case of full color, the photosensitive drum 1 rotates once for each color development, and a total of four rotations are performed, so that toner images of a plurality of colors are overlapped and formed on the photosensitive drum 1. A pre-transfer exposure lamp 7 improves the transfer efficiency.

Reference numeral 8 is a transfer belt device which is a belt-shaped transfer / conveyance device, 81 is a transfer belt which holds an electric charge and adsorbs the recording paper P, and 83 and 84 are provided at both ends of a support member 82 to support the transfer belt 81. A holding roller for extending and rotating, 85 is a paper charger that discharges the recording paper P to the transfer belt 81 by electrostatic force by a conductive brush, and 86 is a toner image on the photosensitive drum 1. Is a transfer electrode which is a transfer charger for transferring the image from the recording medium to the recording paper P. With this configuration, the recording paper P can be firmly attached to the transfer belt 81 and reliably transported, and excellent transfer efficiency and separation efficiency can be obtained in the transfer section.

The transfer belt device 8 includes the photosensitive drum 1.
This is a preferable apparatus in a color image forming apparatus in which toner images are formed on top of each other and transferred onto the recording paper P at one time. In the color copying machine A, the photosensitive drum 1
In order to superimpose a toner image on top, a plurality of developing devices are provided in the peripheral portion of the photosensitive drum 1 to increase the drum diameter, and sufficient separation performance cannot be obtained with the conventional electrostatic transfer separation method, so a more reliable separation performance can be obtained. In the method of superposing toner images, the amount of toner adhered is large, and thus a large amount of transfer charge is required. Therefore, a transfer belt device is used because it is necessary to have a large transfer charge holding ability.

The holding rollers 83 and 84 of the transfer belt device 8 are rollers made of a conductive metal material, and the holding roller 83 on the upstream side is grounded or at a predetermined potential close to the grounded state. The supporting member 82 uses the axis of the holding roller 84 as a fixed shaft, and is normally urged by an elastic member (not shown) so that the holding roller 83 is located below the transfer belt 81.
Retreat away from the surface.

At the time of transfer, the support member 82 is rotated clockwise against the force of the elastic member by, for example, a solenoid or the like which operates under the control of the control unit of the apparatus main body, and the transfer belt is rotated.
Reference numeral 81 is adapted to come into pressure contact with the photosensitive drum 1 with a predetermined pressure.

In the transfer belt device 8, the photosensitive member of the transfer belt 81, which is rotatably driven at the same time as the start of the copying operation, at the same time when the second paper feeding roller 9 which is the paper feeding roller upstream of the transfer portion starts to rotate. A bias voltage for attracting the recording paper P before transfer is applied by the pressure contact with the drum 1 and the paper charger 85. The leading end of the recording paper P is sent to the transfer belt 81 by the second paper feed roller 9. The recording paper P is a transfer belt
It is adsorbed by 81 and conveyed to the transfer section. When the leading edge of the recording paper P passes the transfer portion for a certain length (for example, 5 to 7 mm), the constant voltage power source of the transfer electrode 86 is turned on to start the transfer of the toner image. When the transfer is completed, the transfer belt 81 is separated from the photosensitive drum 1 by the elastic member.

The recording paper P set in the paper feed tray 20
As shown in FIG. 1, the sheets are fed one by one by the feeding roller 16 and fed to the second feeding roller 9 via the first feeding roller 17 and the intermediate conveying roller 18. When the leading edge of the recording paper P comes into contact with the second paper feed roller 9, the paper sensor 91 detects the arrival of the recording paper P and issues a detection signal. With this signal,
The first paper feed roller 17 and the intermediate conveyance roller 18 are stopped, and the recording paper P is in contact with the second paper feed roller 9 and stands by for the transfer of the toner image. As a result, the recording paper P is always fed at the same linear velocity and comes into contact with the second paper feed roller 9 and stands by, and the synchronous rotation of the second paper feed roller 9 ensures the synchronization with the toner image on the photosensitive drum 1. However, the sheet is fed to the transfer portion without causing a timing shift.

Reference numeral 21 denotes a manual feeding tray, and the manual feeding recording paper is always fed to the second paper feeding roller 9 at the same linear velocity paper by the feeding roller 16 as described above, and the recording paper is the second paper feeding roller 9 Awaits transfer.

When the recording paper P passes over the transfer electrode 86, the multicolor toner images formed in an overlapping manner are transferred at one time.

The recording paper P on which the multicolor toner images have been transferred is destaticized by the destaticizer 87, and then is fed to the fixing device 14 by the conveying roller 19 to be fixed. The fixing process is performed using the pair of heat rollers 14a and 14b. A heater is built in the heat roller 14a, and the fixing temperature is controlled by switching the operation time of the heater. This temperature control is performed by two types of uniform switching according to the recording paper mode and negative feedback control based on the environmental temperature measurement result by a temperature sensor (not shown).

After the fixing process, the recording paper P is sent to the external copy tray via the paper discharge roller 15 and discharged.

In the exposure and development process, the transfer belt
81 and the cleaning blade 11 of the cleaning device 11
A is retracted and is in a non-contact state, and the photosensitive drum 1
In the fifth rotation, the transfer belt device 8 and the cleaning device 11 are pressed against each other. The reason why the transfer belt and the like are brought into pressure contact after the multicolor toner image is completely formed in this manner is to prevent the multicolor toner image from being disturbed during image formation.

The control section includes a CPU fixing temperature control means, a process speed control means, a transfer / cleaning pressure bonding control means,
It has a transfer current switching means, etc., and controls process speed switching, transfer current switching, and the like as a whole.

Further, as a drive system block, for example, a DC motor is PLL-controlled to control the photosensitive drum 1 and the developing device 3 to.
6, the first paper feed roller 17, the intermediate transport roller 18, the second paper feed roller 9, the transport belt 19, the heat roller pair 14a of the fixing device 14,
14b etc. are driven. This drive is performed by, for example, the second paper feed roller 9
Is an electromagnetic spring clutch, developing devices 3 to 6, first paper feed roller
17, the intermediate conveying roller 18 and the like are operated by turning on an electromagnetic clutch according to a command from the control unit CPU.

The above is the overall configuration of the image forming apparatus for forming a color image.

An embodiment of the present invention is shown in FIG. 2, in which the charging device 13 and the laser writing unit 2 are provided on the photosensitive drum 1 as in the case of FIG. 1, and further the developing devices for Y, M, C and Bk are provided. 3, 4, 5, 6 are sequentially provided along the peripheral surface of the photosensitive drum 1. And the developing devices 3, 4,
The developing rotary sleeves 31, 41, 51, 61 are provided in the openings of 5, 5 respectively. Further, as shown in FIG. 3, for example, a roller 41 for maintaining a DSD gap at both ends of the developing rotary sleeve 41.
1, 412 are rotatably installed.

Another developing rotary sleeve shown in FIG.
Rollers 411 and 412 similar to those in FIG. 3 are rotatably provided at both ends of 31, 51 and 61, respectively.

The present invention relates to the developing rotary sleeves 31, 41,
51 and 61 are connected by connecting means 313, 411, 511 and 611 via electromagnetic powder clutches C ₁ , C ₂ , C ₃ and C ₄ . A gear, a timing belt, a chain or the like is appropriately used as the connecting means. Further, cams 314, 412, 512, 612 are provided on the non-developing portion side of the developing devices 3, 4, 5, 6 and the cams 314, 412, 51 are provided.
Rotation control means 315, 413, 513, 6 for rotating the 2,612
Connected to the control CPU via 13. A small motor or a stepping motor may be used as the rotation control means. The electromagnetic powder clutches C ₁ , C ₂ , C ₃ , C ₄
Also, the drive motor M is connected to the control CPU via the operation control means 316, 414, 514, 614, and the drive motor M is connected to the control CPU via the operation control means M ₁ .

Next, FIG. 4 shows the electromagnetic powder clutch C ₂
The configuration of is shown in detail. A rotary cylinder C12 formed in the shape of a disk bag is fixed to one end of a drive shaft C11 of the connecting means 4111 driven by the drive motor M, and is driven by a bracket C13 fixed to the main body of the image forming apparatus A. A shaft C11 is rotatably provided, while a rotary rotor C14 is built in the rotary cylinder C12 in a non-contact manner, and the rotary rotor C14 is fixed to one end of a driven shaft C15 of the connecting means 4111. The driven shaft C15 is rotatably provided on the bracket C13. C
Reference numeral 16 denotes an exciting coil arranged on the outer circumference of the rotary cylinder C12, which is provided so as to be electrically insulated and sandwiched by the bracket C13, and the exciting coil C16 is connected to the operation control means 414. 4141 is a power source for the operation control means 316. A powder (magnetic iron powder) C17 is filled in a circumferential portion of the rotary cylinder C12, and an operating portion C18 of the rotor C14 is incorporated in the powder C17.

The embodiment of the present invention is configured as described above. First, a recording start switch (not shown) is turned on to start a recording operation, and an image is recorded on the recording paper P in the order described in FIG. However, according to the present invention, as shown in FIG. 2, the surface of the photosensitive drum 1 is sequentially charged by the charging device 13.
The laser writing unit 2 forms a latent image on the surface of the photosensitive drum 1 in response to an original or an input signal. Photoconductor drum 1
Is controlled by the control CPU using a stepping motor or the like, and the latent image forming position is discriminated by the control CPU by a program. When developing with M (magenta) of the developing device 4 in FIG. 2, the cam 412 is rotated by the control CPU via the rotation control means 413, and the developing device 4 is moved toward the photosensitive drum 1. As shown in FIG. 3, the rollers 411 and 412 are brought into contact with the surface of the photosensitive drum 1, and a predetermined D is provided between the surface of the photosensitive drum 1 and the developing rotary sleeve 41.
Set the SD width. Before the latent image position of the photosensitive drum 1 reaches the position of L ₂ , the clutch C ₂ is controlled by the control CPU.
Therefore, the operation control means 414 is released.

Next, when the developing rotary sleeve 41 of the developing device 4 is rotated for development, the control CPU starts rotation of the drive motor M from the control means M ₁ , and the drive shaft C 11 causes the rotary cylinder C 12 to rotate. Although rotation is started, unless the power source 4141 is energized by the operation control means 414 to the exciting coil C16, the rotational force of the rotary cylinder C12 is not transmitted to the operating portion C18 of the rotary rotor C14, and therefore the torque is applied to the driven shaft C15. Does not occur. Next, the operation control means 414 is controlled by the control CPU so as to gradually increase the voltage shown in FIG. 5, and the voltage of the power supply 4141 is gradually increased so that the magnetic flux C19 generated by the exciting coil C16 is changed to the above voltage. The magnetic flux C19 is increased in proportion to its strength, and the electromagnetic powder C17 is magnetized by the magnetic flux C19 to move the powder C17 following the rotation of the rotary cylinder C12. Therefore, the powder C17 acts on the operating portion C18 of the rotary rotor C14, and the rotary rotor C14 starts rotating in response to the rotation of the rotary cylinder C12. At that time, as shown in FIG.
By gradually increasing the voltage of the power supply 4141 by means of 4, the magnetic flux C19 by the exciting coil C16 is gradually strengthened, and the powder C17
In the following movement, the moving amount increases in accordance with the strength of the magnetic flux C19, and the torque of the rotating rotor C14 increases. Due to such an action, the rotation of the developing rotary sleeve 41 by the driven shaft C15 gradually starts at the time of starting even if the drive motor M is rapidly started and reaches a predetermined number of rotations after a fixed time.

As described above, when the clutch C ₂ is engaged, the developing rotary sleeve 41 is stopped or rotated at a low speed at the start of rotation, and the impact due to the start of the photosensitive drum 1 by the rollers 311 and 312 shown in FIG. Is not transmitted. Therefore, L by the laser writing performed on the photosensitive drum 1
Image disturbance does not occur in latent image formation up to ₁ . The other developing devices 3, 5 and 6 are moved by the cams 314, 512 and 612 so as to be separated from the photosensitive drum 1, and the rollers provided at both ends of the developing rotary sleeves 31, 51 and 61 are photosensitive members. It is separated from the surface of the drum 1. When the developing device M3 is developed by the developing rotary sleeve 41 and the developing devices 3, 5, 6 are used, the developing process is performed in the same manner as described above.

[0032]

As described above, according to the present invention, each developing device 3,
When the latent images on the photosensitive drum 1 are sequentially developed with Nos. 4, 5, and 6, the DSD determining rollers provided in the developing device are brought into contact with each other, and the drive motor for rotating the developing rotary sleeve is started. However, due to the action of the clutches C ₁ , C ₂ , C ₃ , and C ₄ , the developing rotary sleeve stops or rotates at low speed at the time of starting, and is influenced by the contact between the surface of the photosensitive drum and the roller. To prevent uneven pitches in the latent image when the latent image is formed on the photosensitive drum,
It can always provide good images.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a main part of an embodiment of a color image forming apparatus of the present invention.

FIG. 2 is a control configuration diagram of a photosensitive drum and a developing device.

FIG. 3 is a configuration diagram showing a relationship between a photosensitive drum, a developing rotary sleeve, and rollers.

FIG. 4 is a cross-sectional view of an electromagnetic powder clutch used in the present invention.

FIG. 5 is a characteristic diagram showing a voltage of an exciting coil and a rotation speed of a developing rotary sleeve.

[Explanation of symbols]

1 image carrier (photosensitive drum) 2 laser writing unit 3, 4, 5, 6 developing device 7 PTL (pre-transfer exposure lamp) 8 transfer belt device 9 second paper feed roller 10 pre-cleaning static eliminator 11 cleaning device 12 PCL 13 Charging device (scorotron charger) 14 Fixing device 16 Sending roller 17 First feeding roller 18 Intermediate feeding roller 20 Paper feeding tray 25 Output means 31, 41, 51, 61 Rotating sleeve for development 81 Transfer belt 86 Transfer electrode 314, 412,512,612 cam _{C 1, C 2, C 3} , C 4 clutch 411 roller C11 drive shaft C12 rotation cylinder C13 bracket C14 rotating rotor C15 driven shaft C16 exciting coil C17 powder C18 actuating portion

Claims (3)

[Claims] 1. An image carrier, a charging unit for applying an electric charge to the image carrier, an exposing unit, a plurality of developing units for developing a latent image formed by the exposing unit, and a plurality of developing units. In an image forming apparatus having a driving unit for driving
Developing rotary sleeves respectively provided in the plurality of developing means, driving means for rotationally driving the developing rotary sleeves, the plurality of developing rotary sleeves, and electromagnetic powder clutches respectively provided in the driving means, When rotating the developing rotary sleeve via the electromagnetic powder clutch,
An image forming apparatus having a developing means, characterized in that an input voltage of the powder clutch is changed to gradually start the rotation of the developing rotary sleeve. 2. The image forming apparatus having a developing unit according to claim 1, wherein the developing unit is a plurality of developing units that develop with four colors of yellow, magenta, cyan, and black, respectively. 3. An image forming apparatus having developing means according to claim 1, further comprising control means for changing an input voltage of the powder clutch for driving the developing rotary sleeve.