JPH0259778A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the contamination of transfer materials, etc., and to obtaining an image of good quality by controlling the rising speed of a developer carrier, which is the developing roller, to be smooth. CONSTITUTION:A drum shaped electrophotographic sensitive body 1, which is an image carrier, is carried freely rotatable, a latent image is formed on the photosensitive body by a latent image forming means, consisting of an electrifying device 2 and an exposing device 3, and the latent image is made to be a visual image at a developing device 4. A developer T, inside the device, is carried by this developing device 4, and it is provided with the developer carrier 9, which carries the developer T onto an image carrier 1. Then the traveling speed of this developer carrier 9 is increased to the desired developing speed continuously, or gradually in stages. Thus the splashing of developer can be prevented, contamination of the inside of the machine can be prevented, contamination, etc., of transferring material, etc., can be evaded, and an image of good condition can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image forming apparatus that forms a latent image on an image carrier and develops the latent image with a developing device to obtain a visible image. The present invention relates to an image forming apparatus characterized by drive control of a developer carrier such as a developing roller that conveys the developer onto the image carrier.

In general, an image forming apparatus having an image bearing member such as an electrophotographic photoreceptor forms a desired electrostatic latent image on the photoreceptor using a latent image forming means consisting of predetermined steps such as a charging process and an exposure process. The latent image is formed into a visible image (toner image) in a developing device.The toner image is transferred to a transfer material, and later the toner image on the transfer paper is fixed by heat etc. to become a permanent image. .

Various types of development wt devices have been proposed, but a configuration having a developer carrier that carries a developer, conveys the developer onto a photoreceptor, and develops a latent image on the photoreceptor is widely used. has been done. At this time, as the developer carrier, a developing roller consisting of a non-magnetic developing sleeve and a magnet provided inside the developing sleeve, or a developing roller consisting of a magnetic roller alone is used. .

In a developing device having such a configuration, whether it is a one-component development method using magnetic toner as a developer or a two-component development method using toner and a magnetic carrier that adsorbs the toner, in either case, The developer is magnetically restrained by the developing roller, and as the developing roller rotates, it is transported from the inside of the developing device to the developing section facing the photoconductor to perform development.The amount of conveyance of the developer on the developing roller teeth,
Transported while being regulated by a doctor blade. The developer that has been developed in the developing section is collected again into the developing device by further rotation of the developing roller.Nowadays, the above-mentioned developing devices are prepared with multiple colors, and only the developing device of the desired color is exposed. A color image forming apparatus that performs development while facing the body has been announced. In such an apparatus, a developing driving force is selectively supplied only to the developing device facing the photoreceptor, so that the developing roller rotates.

However, the above-mentioned developing device operates extremely well and can perform good development, but when the developing roller starts rotating, the developer that has been restrained on the developing roller is released from the magnetic binding force of the developing roller. Get out of it.

There is a problem with scattering. Particularly in the case of a two-component developer, the toner is released from the carrier and scattered due to the centrifugal force generated when the developing roller starts rotating. As a result, problems such as contamination of the inside of the machine, deterioration of the functions of each image forming apparatus section, and image defects such as fog on the transfer material are caused.

The purpose of the present invention is to reduce the centrifugal force generated when a developer carrying member such as a developing roller starts rotating, prevent the developer from scattering, eliminate contamination inside the machine, avoid staining of transfer materials, etc., and improve the quality of the product. An object of the present invention is to provide an image forming apparatus that can obtain a beautiful image.

Meno The above object is achieved by an image forming apparatus according to the present invention.

To summarize, the present invention provides an image carrier, a latent image forming means for forming a latent image on the image carrier, and a developing device for visualizing the latent image formed on the image carrier. In the image forming apparatus having at least The image forming apparatus is characterized in that the moving speed is gradually increased to a desired developing speed continuously or stepwise.

EMBODIMENT OF THE INVENTION Next, one embodiment of the image forming apparatus according to the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an electrophotographic copying apparatus which is an embodiment of an image forming apparatus according to the present invention. In this embodiment, a drum-shaped electrophotographic photoreceptor l serving as an image carrier is In this embodiment, the charger 2 is supported rotatably in the direction.
A latent image is formed on the photoreceptor by a latent image forming means consisting of an exposure means 3 and an exposure means 3. The latent image is made into a visible image (toner image) by the developing device 14. The toner image on the photoreceptor is transferred onto the transfer material P by the transfer charger 5, and is then turned onto the transfer paper P by the fixing device M6. The image is fixed on the machine, becomes a permanent image, and is ejected outside the machine.

On the other hand, the residual toner on the photoreceptor 1 is removed from the cleaning device 2t7.
The photoreceptor is then cleaned and subjected to the next image forming process.

In the present invention, the developing section W4 includes a developing container 8 containing developer and 1. It has a developer carrier 9 rotatably supported within a developer container 8. In this embodiment, there is one developer carrier 9.
The developing roller is made up of a non-magnetic developing sleeve 10 and a magnet 11 provided inside the developing sleeve 10. The developing roller 9 carries the developer T in the developing container 8 on the surface of the developing sleeve 1O, and rotates in the direction of the arrow to move the developer from inside the developing container 8 to a position facing the photoreceptor 1, that is, to the developing section 12. and transport. The amount of developer transported on the developing sleeve IO is regulated by a doctor blade 13. Further, the developer that has been developed in the developing section 12 is collected again into the developing container 8 by further rotation of the developing sleeve 1o.

According to the present invention, the rotation of the developing roller 9 starts at a peripheral speed of 1, for example 80 mm/sec, before developing the latent image on the photoreceptor 1. Then, the circumferential speed Vz1 is, for example, 200 mm/s.
ec to develop the latent image on the photoreceptor.

To explain further, the drive start signal of the developing device, particularly the developing roller, that is, the motor (not shown) that drives the developing sleeve 10, is generated by detecting, for example, that the photoreceptor has rotated by a predetermined rotation angle from the home position. obtained,
The signal can start driving the motor.

Next, a method of driving the developing motor M will be explained.

FIG. 2 shows a method of applying a driving voltage to the developing sleeve drive motor, and FIG. 3 shows the state of the circumferential speed of the developing sleeve at that time.

As will be understood with reference to FIG. 3, tz~t3(t
The time period a) is the time period in which the latent image on the photoconductor is actually developed in the developing device, and at this time, the developing sleeve lO maintains the circumferential speed M2 required for development. According to the voltage application method of the developing drive motor, as shown in FIG. Until now, the rotation of the developing sleeve was gradually started by controlling the pulse width of the applied voltage, for example, 24 V, and the speed of the developing sleeve was set to VZ during the time period ta necessary for development. Since then, an applied voltage of 24 V has been continuously applied.

Therefore, according to such a voltage application method, since the rotation of the developing sleeve can be started smoothly, it is possible to suppress the developer from scattering due to impact from the developing sleeve at the instant when the rotation of the developing sleeve starts.

In the above embodiment, the developing device was explained as having an independent motor for driving the developing sleeve, but the driving force for the developing sleeve is generated from the main motor that drives the photoreceptor etc. via an electromagnetic clutch. If the time period ta required for development is distributed, the time period ta required for development is t
The configuration is such that the electromagnetic clutch is continuously excited by continuously applying an applied voltage of 24 V up to time 4, so that the circumferential speed of the developing sleeve becomes ma 2, and the excitation applied voltage of the electromagnetic clutch is continuously applied until time to-tl. As shown in FIG. 1, the developing sleeve may be configured to gradually start rotating by controlling the pulse width.

In the above embodiment, the driving of the developing sleeve is as shown in FIG.
P W M (Pulse Width Modula
However, it is also possible to perform two-step speed control by switching the frequency of the reference clock using PLL (Phase Lock Loop) control, which is well known to those skilled in the art. Furthermore, when using a stepping motor, the effects of the present invention can be obtained by controlling the drive pulse frequency.

Incidentally, in each of the above embodiments, the image forming apparatus according to the present invention has been described as a normal electrophotographic copying apparatus equipped with one developing device, but as shown in FIG. A rotating support 100 rotatably supported around
a developing device 4 containing a plurality of different color toners;
(4B, 4Y, 4C14M), rotate a desired developing device (developing device 4B in FIG. 4) to a developing position facing the photoreceptor l, and visualize the latent image formed on the photoreceptor. The invention can also be suitably implemented in a color image forming apparatus that obtains a color image by repeating such an image forming process a plurality of times. In FIG. 1, image forming means such as a latent image forming means, a transfer means, and a cleaning means are omitted because they are well known to those skilled in the art.

To explain further, in an image forming apparatus using such a rotary movement type developing device, the required developing device, which is driven to the developing position by the rotation of the rotating support, is moved to a predetermined developing position facing the photoreceptor. While moving (4th point)
In the figure, an arbitrary position I between the developing device 4M and the developing device 4B is shown.
From I), the developing sleeve of the developing device is driven from the outside or by a developing sleeve drive motor provided in the developing device, and the developing *! is performed until the developing device moves to the developing position. Pre-driving can be performed substantially.

The developing device that has been moved to the developing position is raised to a predetermined speed to perform development.Next, when the developing device finishes developing, the rotating support is rotated again in order to move the next developing device to the developing position. As a result, the used developing device located at the developing position escapes from the developing position and moves.

It is preferable that the developing MW is driven for a while after the start of escape movement and movement, so that the developing roller, that is, the developing sleeve escapes from the developing position while remaining in a rotationally driven state, so that it is not in contact with the photoreceptor surface. Unnecessary developer is prevented from adhering.

Thereafter, the transmission of driving force to the developing device is cut off, and as the rotary support continues to rotate, the next developing device is moved to the developing position and is driven and controlled in the same manner as described above.

The above description has been about a color image forming apparatus using a rotational movement type developing device, but the same effect can be obtained with an image forming apparatus having a parallel movement type developing device in which a plurality of developing devices move in parallel. be able to.

According to the image forming apparatus according to the present invention configured as described above, by smoothly controlling the rising speed of the developer carrier such as the developing roller, the developer held on the developing roller is Since the applied impact acceleration and centrifugal force are suppressed, it is possible to prevent scattering when the developing roller rises, prevent staining of the transfer material, etc., and obtain a good image. In addition, especially in a rotary developing device, the developing roller may be rotated even during non-developing time in order to prevent toner from adhering to the image bearing member during the time period when the developing device faces the image bearing member. Even in such a case, according to the present invention, the rotational speed of the developing roller can be lowered, so that scattering of the developer can be suppressed to a minimum.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of an embodiment of an image forming apparatus according to the present invention. FIG. 2 is an explanatory diagram illustrating a method of applying a drive voltage to a developing sleeve drive motor according to the present invention. FIG. 3 is a graph showing the state of the circumferential speed of the developing sleeve. FIG. 4 is a schematic cross-sectional view of a color image forming apparatus according to an embodiment of the present invention, and the latent image forming means and other image forming means arranged around the photoreceptor are omitted. 1: Image carrier 2: Charger 3: Exposure means 4: Developing device 9: Developer carrier (developing roller) lO: Developing sleeve 11: Magnet Figure 1 Figure 2

Claims (1)

[Claims] 1) It had at least an image carrier, a latent image forming means for forming a latent image on the image carrier, and a developing device for visualizing the latent image formed on the image carrier. In the image forming apparatus, the developing device has a developer carrier that supports developer in the device and transports the developer onto the image carrier, and the moving speed of the developer carrier is continuous. An image forming apparatus characterized in that the development speed is gradually increased to a desired development speed.