JPH10161426A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of an abnormal sound at the time of stopping an image carrier by providing a means for supplying toner onto the image carrier with a developing means, during the stopping of the image carrier after an image is formed. SOLUTION: A CPU 23 applies a developing bias voltage having the same polarity and the same level as those at the time of forming the image to a high-voltage power source only for a short time, after an image forming operation is completed. Thus, the toner is stuck to a noncharged part, on a photoreceptor drum 11, to form a toner image in a region short in the rotational direction (peripheral direction) of the drum 11, in the whole area in the width direction on the drum 11. The toner image is moved to a cleaning position between the drum 11 and a cleaning blade, to be supplied to the gap between and the coefficient of friction between is reduced with the toner. Therefore, the sticking and slipping of the cleaning blade with respect to the drum 11 never occur to prevent the generation of the abnormal sound.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art Generally, in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., an image bearing member composed of, for example, a photosensitive drum, this photosensitive drum is driven to rotate at the time of image formation, and is rotated after image formation. Driving means including a main motor for stopping driving, latent image forming means for forming an electrostatic latent image on the photosensitive drum, and developing the electrostatic latent image on the photosensitive drum into a toner image Means, transfer means for transferring the toner image on the photosensitive drum to a transfer material such as transfer paper or an intermediate transfer belt, cleaning means for cleaning a transfer residual toner image on the photosensitive drum, and the photosensitive drum The image forming process by repeating each process of forming, developing, transferring, cleaning, and removing the electrostatic latent image. You have me.

The latent image forming means includes, for example, a charging means for uniformly charging the photosensitive drum, and a writing means for forming an electrostatic latent image by writing an image by exposing the uniformly charged photosensitive drum. Are used. The cleaning means uses a cleaning blade which contacts the photosensitive drum and cleans the photosensitive drum by scraping off the transfer residual toner remaining on the photosensitive drum without being completely transferred to the transfer material.

As the cleaning blade, a flexible blade such as urethane rubber is generally used. Normally, the cleaning blade considers conditions such as rubber hardness, thickness, elastic modulus, and protrusion amount to increase the frictional resistance between the photosensitive drum and the cleaning blade during image formation. A slight squeaking noise is generated between the cleaning drum and the cleaning blade, and this slight squeaking noise is prevented from resonating with the photosensitive drum and amplified to generate abnormal noise.

Further, Japanese Patent Application Laid-Open Nos. 2-118684, 3-44689 and 3-44981 disclose a cleaning blade and a photosensitive drum having a weight inside a photosensitive member, a damping material attached thereto, and the like. A device that prevents a slight squeaking noise generated between the photoconductor and the photoconductor from resonating is described.

[0006]

In the above-described image forming apparatus, when the photosensitive drum is driven or the photosensitive drum is stopped except when the image is formed while the photosensitive drum is rotating at a constant speed, the cleaning blade moves relative to the photosensitive drum. Sticking and sticking may cause stick slips, which may cause abnormal noise. Here, the photosensitive drum is usually directly driven by the main motor from the viewpoint of image quality stability, so that the time from when the main motor is turned on to when the photosensitive drum is rotated at a constant speed is short. There is no state.

However, when the photosensitive drum is stopped, the photosensitive drum is rotating due to inertia even when the main motor is turned off. During this time, a stick slip occurs due to the cleaning blade and abnormal noise occurs. Would. In particular, when the photosensitive drum is stopped, since the driving of the machine main body other than the photosensitive drum is stopped, the abnormal noise can be easily determined. SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus capable of preventing generation of abnormal noise when an image carrier is stopped.

[0008]

According to a first aspect of the present invention, there is provided an image carrier, and the image carrier is rotatably driven during image formation, and the image carrier is rotated after image formation. Driving means for stopping the operation, a latent image forming means for forming an electrostatic latent image on the image carrier, developing means for developing the electrostatic latent image on the image carrier into a toner image, and In an image forming apparatus including a transfer unit for transferring a toner image on a carrier to a transfer material and a cleaning unit for cleaning a transfer residual toner image on the image carrier, the image carrier is stopped during image formation. And a means for supplying the toner onto the image carrier from the developing means, thereby preventing generation of abnormal noise when the image carrier is stopped.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the transfer unit includes a contact transfer unit that contacts the image carrier, and the image carrier is stopped during image formation. Means for applying a transfer bias having the same polarity as the charged polarity of the toner to the contact transfer means when the toner is supplied onto the image carrier from the developing means. Further, it is possible to prevent generation of abnormal noise when the image carrier is stopped.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, the developing potential between the image bearing member and the developing means is changed during stopping of the image bearing member after image formation. When the toner is supplied from the developing means onto the image carrier, the developing potential at the time of image formation is made different from that at the time of image formation so that the amount of toner adhered to the image carrier is smaller than at the time of image formation. It is possible to prevent poor cleaning of the body and generation of abnormal noise when the image carrier is stopped.

[0011]

FIG. 2 shows an embodiment of the first aspect of the present invention. In the image forming apparatus of this embodiment, an image carrier made of a photoconductor, for example, a photoconductor drum 11
Is a driving unit 12 composed of a main motor during image formation.
(See FIG. 1) to rotate at a constant peripheral speed at a constant speed. The photoreceptor drum 11 is uniformly charged negatively by a charging unit having a contact transfer unit 13 formed of a charging roller in a rotating process, and is exposed to writing light 14 by a writing unit including an exposure unit to write an image. This forms an electrostatic latent image. Here, a charging bias is applied to the charging roller 13 from a high-voltage power supply, and the charging unit having the charging roller 13 and the writing unit constitute a latent image forming unit that forms an electrostatic latent image on the photosensitive drum 11. ing.

A developing device 15 as a developing means applies a developing bias voltage to a developing roller 15a from a high voltage power supply.
The electrostatic latent image on the photosensitive drum 11 is reversely developed to form a toner image. On the other hand, transfer paper as a transfer material is fed from a paper tray of a paper feeder (not shown) to the pair of registration rollers 16 and temporarily stopped, and the pair of registration rollers 16 is moved in synchronization with the rotation of the photosensitive drum 11. The transfer paper is conveyed to a transfer section between the photosensitive drum 11 and a transfer corona charger 17 as transfer means in accordance with the toner image on the drum 11.

The transfer paper conveyed from the pair of registration rollers 16 is transferred with a toner image on the photosensitive drum 11 by a transfer corona charger 17 and separated from the photosensitive drum 11 by a separator 18. After being guided and the toner image is fixed by the fixing device 20, the toner image is discharged to the outside. After transfer of the toner image, the transfer residual toner image is scraped off by a cleaning blade 21a as a cleaning means in the cleaning device 21, and the photosensitive drum 11 is cleaned. A residual charge is removed by a charge removing lamp 22 as a charge removing means. You.

Such an image forming operation is started by turning on a print switch as an image forming start instructing unit of the operation unit, and is repeatedly performed continuously by the number of sheets set by the operation unit, and the photosensitive drum 11 is repeatedly operated. Used for image formation. FIG. 1 schematically shows a circuit configuration of the present embodiment. CPU (microcomputer) 23 as control means
Controls the rotation of the photosensitive drum 11 by controlling a motor drive circuit for driving the main motor 12, and also applies a high voltage as a developing bias voltage applying means for applying a developing bias voltage to the developing roller 15a. The developing bias voltage is controlled by controlling the power supply.

FIG. 4 shows a change in the speed of the photosensitive drum 11 rotated and driven by the main motor 12. CPU23
Checks the input signal from the print switch, and when the print switch is turned on at the point P, starts the drive of the main motor 12 with the motor drive circuit and simultaneously activates the predetermined components of the present embodiment at predetermined timing. In operation, the photosensitive drum 11 is driven to rotate by the main motor 12. At this time, the rotation of the photosensitive drum 11 does not reach the constant-speed rotation until the time a has elapsed from the point of P. After the elapse of the time a from the time point P, the photosensitive drum 11 rotates at a constant speed, and the image forming operation for the set number of sheets is performed as described above while the photosensitive drum 11 is rotating at a constant speed.

Further, the CPU 23 outputs a stop signal to the motor drive circuit when the image forming operation for the set number of sheets is completed and the machine is stopped at the time of S, and the motor drive circuit is immediately activated by the stop signal. The driving of the motor 12 is stopped. Here, as with the current copiers and the like, the main motor 12 is provided with a flywheel so as to prevent rotation unevenness due to the torque fluctuation, for the stability of the image, particularly for preventing the jitter. ing. As described above, when the flywheel is provided on the main motor 12, the moment of inertia increases, and inertia occurs.
The time b from the point of S to the stop of the rotation of the photosensitive drum 11 becomes longer.

FIG. 3 shows the operation timing of this embodiment. The CPU 23 checks an input signal from the print switch, and when the print switch is turned on at the time point P, the CPU 23 starts driving the main motor 12 with respect to the motor drive circuit, and the photosensitive drum 11 rotates at a constant speed. After that, the photosensitive drum 11 is charged by applying a charging bias to the charging roller 13 with respect to a high-voltage power supply for applying a charging bias to the charging roller 13.

When the head of the charged portion of the photosensitive drum 11 charged by the charging roller 13 reaches the developing position between the photosensitive drum 11 and the developing device 15, the CPU 23
The developing bias voltage is turned on for the high-voltage power supply for applying the developing bias voltage to the developing roller 15a (the application of the developing bias voltage is started). Otherwise, when the developing unit 15 reversely develops the electrostatic latent image on the photosensitive drum 11, the developing unit 15 develops the developing roller 15a from the high voltage power supply before the charged portion on the photosensitive drum 11 reaches the developing position. When a bias voltage is applied, a black image is formed on the charged portion on the photosensitive drum 11 by reversal development by the developing device 15,
Further, the developing device 15 transfers the electrostatic latent image on the photosensitive drum 11 to the
In the case of reversal development using the component developer, when a developing bias voltage is applied to the developing roller 15a from a high voltage power supply while the charged portion on the photosensitive drum 11 is passing through the developing position, the uncharged portion on the photosensitive drum 11 The carrier adheres from the developing device 15 to the surface.

When the CPU 23 stops driving the main motor 12 with respect to the motor drive circuit at the time point S after the end of the image forming operation, the rear end of the charged portion on the photosensitive drum 11 while the main motor 12 is stopped. By passing a developing bias voltage of the same polarity and the same magnitude as in image formation for a short time to a high voltage power supply for applying a developing bias voltage to the developing roller 15a in a state where has passed the developing position, The toner is caused to adhere to the non-charged portion on the photosensitive drum 11 to form a toner image in a short region in the rotation direction (outer circumferential direction) of the photosensitive drum 11 over the entire width direction on the photosensitive drum 11.

The toner image is transferred to the photosensitive drum 11 and the cleaning blade 21a as the photosensitive drum 11 rotates.
To the cleaning position between
And the cleaning blade 21a, the friction coefficient between the photosensitive drum 11 and the cleaning blade 21a is reduced by the toner. For this reason, the sticking of the cleaning blade 21a with respect to the photosensitive drum 11 does not occur, and the noise does not occur.

As described above, according to one embodiment of the present invention, the photosensitive drum 11 as an image carrier, the image carrier 11 is driven to rotate during image formation, and the image carrier 11 is rotated after image formation. A main motor 12 as a driving unit for stopping the rotation of the image carrier; a latent image forming unit including a charging unit and a writing unit for forming an electrostatic latent image on the image carrier 11; A developing unit 15 as a developing unit that develops the latent image into a toner image;
A transfer corona charger 17 as transfer means for transferring the toner image on the transfer sheet 1 onto transfer paper as a transfer material; and a cleaning blade 21a as cleaning means for cleaning the transfer residual toner image on the image carrier 11. In the image forming apparatus, a CPU serving as a unit for supplying toner from the developing unit 15 onto the image carrier 11 during the stop of the image carrier 11 after image formation
Because of the provision of 23, generation of abnormal noise when the image carrier is stopped can be prevented.

FIG. 6 shows a part of an embodiment according to the second aspect of the present invention. In this embodiment, a transfer unit having a transfer roller 17a as a contact transfer unit instead of the corona charger 17 for transfer is used as the transfer unit in the embodiment of the first aspect of the present invention. Transfer roller 1
Reference numeral 7a denotes a transfer bias from a high-voltage power source as a transfer bias applying unit when an image is formed (at the time of transfer) when the transfer paper is in contact with the photosensitive drum 11 and the transfer paper passes through a nip portion between the photosensitive drum 11 and the transfer roller 17a. Is applied to transfer the toner image on the photosensitive drum 11 to the transfer paper.

FIG. 5 shows the operation timing of the present embodiment, and FIG. 7 shows a schematic circuit configuration of the present embodiment. CPU
A high voltage power supply 23 for applying a transfer bias to the transfer roller 17a applies a transfer bias to the transfer roller 17a at the time of transfer during the image forming operation, and stops the main motor 12 after the image forming operation is completed. By applying a negative transfer bias to the transfer roller 17a for the same time as the time for applying the developing bias voltage to the developing roller 15a, or for a slightly longer time including that time, the photosensitive drum 11 can be used during image formation. Developing unit 15
A transfer bias having the same polarity as the charging polarity of the normal toner attached from the transfer roller 17a is applied to the transfer roller 17a.

Therefore, the toner image on the photosensitive drum 11 does not adhere to the transfer roller 17a, and
And the cleaning blade 21a. For this reason, the transfer roller 17a is prevented from being stained by the toner, so that sticking of the cleaning blade 21a to the photosensitive drum 11 does not occur, and no abnormal noise occurs.

As described above, according to an embodiment of the present invention, in the image forming apparatus according to the first aspect, the transfer unit is a transfer roller 17 a as a contact transfer unit that comes into contact with the image carrier 11. When toner is supplied from the developing unit 15 onto the image carrier 11 during the stop of the image carrier 11 after image formation, transfer of the same polarity as the charged polarity of the toner to the contact transfer unit 17a is performed. Since the CPU 23 is provided as a means for applying a bias, it is possible to prevent contamination of the contact transfer means by toner and generation of abnormal noise when the image carrier is stopped.

FIG. 8 shows the operation timing of one embodiment of the third aspect of the present invention. In this embodiment, in the embodiment of the first aspect of the present invention, the CPU 23 applies the first level developing bias voltage to a high-voltage power supply for applying the developing bias voltage to the developing roller 15a during image formation. The developing roller 15a is applied to the developing roller 15a while the main motor 12 is stopped and the rear end of the charged portion on the photosensitive drum 11 has passed the developing position.
Then, a second level developing bias voltage having the same polarity as that during image formation and different from the first level is applied for a short time to a high voltage power supply for applying the developing bias voltage. here,
The developing bias voltage at the second level has a developing potential (photosensitive drum 11) higher than the developing bias voltage at the first level.
(The difference between the surface potential of the photosensitive drum 11 in the developing region between the developing roller 15a and the developing bias voltage applied to the developing roller 15a) is reduced.

This is for the following reason. That is, at the time of normal image formation, for example, the surface potential of a writing portion (the portion exposed to the writing light 14) on the photosensitive drum 11 is -150 V, and the developing bias voltage applied to the developing roller 15a from the high voltage power supply is When the voltage is −600 V, the developing potential between the photosensitive drum 11 and the developing device 15 becomes 450 V. However, at the point S when the image forming operation is completed, the charging of the photosensitive drum 11 is already turned off and the photosensitive drum 11 is turned off. While the surface potential of the drum 11 is 0 V, when a developing bias voltage of −600 V is applied to the developing roller 15 a from a high-voltage power supply, the developing potential becomes 600 V, which is larger than that during normal image forming. Developing device 15
As a result, the toner adheres too much to the photosensitive drum 11, and the toner cannot be completely removed by the cleaning blade 21a.

Actually, in order to prevent the abnormal noise caused by the stick slip of the cleaning blade 21a to the photosensitive drum 11, it is sufficient to supply a small amount of toner between the cleaning blade 21a and the photosensitive drum 11. The second level developing bias voltage may be set to a value such that the developing potential is smaller than 450 V.
Of the photosensitive drum 11 at the time of image formation
-4 so that it is lower than the toner adhesion amount at the upper writing point
Development bias voltage greater than 50V (absolute value is 450V
(A smaller negative developing bias voltage).

As described above, in one embodiment of the present invention according to the third aspect, in the image forming apparatus according to the first aspect, the developing potential between the image carrier 11 and the developing means 15 is determined by the image forming apparatus. When toner is supplied onto the image carrier 11 by the developing means 15 during the stop of the image carrier 11 later, the image carrier 1 is supplied more than during image formation.
Since the developing potential at the time of image formation is made different so as to reduce the amount of toner adhered on the image carrier 1, defective cleaning of the image carrier and generation of abnormal noise when the image carrier is stopped can be prevented.

As in the above-described embodiment, the toner image is supplied from the developing device 15 to the photosensitive drum 11 just before the stop of the photosensitive drum 11 to reduce the coefficient of friction between the cleaning blade 21a and the photosensitive drum 11. This can also prevent abnormal noise caused by stick slip of the cleaning blade 21a on the photosensitive drum 11 at the start of the next image formation. Further, the invention according to each claim is not limited to the above embodiment, and for example, an image carrier other than the photoconductor drum 11 may be used.
The present invention is also applicable to an image forming apparatus in which a toner image on an image carrier is once transferred to an intermediate transfer member and then transferred to transfer paper.

[0031]

As described above, according to the first aspect of the present invention, an image carrier and a driving means for rotating the image carrier during image formation and stopping the image carrier after image formation. Latent image forming means for forming an electrostatic latent image on the image carrier, developing means for developing the electrostatic latent image on the image carrier into a toner image, and toner on the image carrier In an image forming apparatus having a transfer unit for transferring an image to a transfer material and a cleaning unit for cleaning a transfer residual toner image on the image carrier, the developing unit may stop the image carrier during image formation after the image formation. Since a means for supplying toner onto the image carrier is provided, it is possible to prevent generation of abnormal noise when the image carrier is stopped.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the transfer unit includes a contact transfer unit that comes into contact with the image carrier, and the image carrier after the image is formed. A means for applying a transfer bias having the same polarity as the charging polarity of the toner to the contact transfer means when toner is supplied from the developing means onto the image carrier during the stop is provided. Further, it is possible to prevent generation of abnormal noise when the image carrier is stopped.

According to the third aspect of the present invention, in the image forming apparatus according to the first aspect, the developing potential between the image bearing member and the developing means is adjusted while stopping the image bearing member after image formation. When the toner is supplied from the developing means onto the image carrier, the developing potential at the time of image formation is made different from that at the time of image formation so that the amount of toner adhering on the image carrier is smaller than at the time of image formation. It is possible to prevent poor cleaning of the body and generation of abnormal noise when the image carrier is stopped.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically showing a circuit configuration according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the same embodiment.

FIG. 3 is a timing chart showing operation timings of the embodiment.

FIG. 4 is a diagram illustrating a change in the speed of a photosensitive drum according to the embodiment.

FIG. 5 is a timing chart showing operation timings of the embodiment.

FIG. 6 is a schematic view showing a part of one embodiment of the invention according to claim 2;

FIG. 7 is a block diagram schematically showing a circuit configuration of the embodiment.

FIG. 8 is a timing chart showing the operation timing of one embodiment of the invention according to claim 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Photosensitive drum 12 Main motor 13 Charging roller 14 Writing light 15 Developing device 17 Corona charger for transfer 17a Transfer roller 21a Cleaning blade 23 CPU

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Toshitaka Yamaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Kenzo Tatsumi 1-3-6 Nakamagome, Ota-ku, Tokyo・ In Ricoh Co., Ltd. (72) Inventor Hiroshi Yoshinaga 1-3-6 Nakamagome, Ota-ku, Tokyo ・ Ricoh Co., Ltd. (72) Takeo Suda, 1-3-6 Nakamagome, Ota-ku, Tokyo ・ Stock Inside Ricoh Company (72) Inventor Ken Amamiya 1-3-6 Nakamagome, Ota-ku, Tokyo / Stock Company Ricoh Company (72) Mayumi Ohori 1-3-6 Nakamagome, Ota-ku, Tokyo Company / Ricoh Company Inside

Claims (3)

[Claims] An image carrier, a driving unit for rotating the image carrier during image formation and stopping the rotation of the image carrier after image formation, and forming an electrostatic latent image on the image carrier. Latent image forming means, developing means for developing the electrostatic latent image on the image carrier to form a toner image, transfer means for transferring the toner image on the image carrier to a transfer material, An image forming apparatus having a cleaning unit for cleaning a transfer residual toner image on a body, wherein the developing unit supplies toner onto the image carrier while the image carrier is stopped after image formation. An image forming apparatus comprising: 2. An image forming apparatus according to claim 1, wherein said transfer means has a contact transfer means for contacting said image carrier, and said developing means is provided by said developing means while said image carrier is stopped after image formation. An image forming apparatus comprising: means for applying a transfer bias having the same polarity as the charge polarity of the toner to the contact transfer means when the toner is supplied onto the image carrier. 3. The image forming apparatus according to claim 1, wherein the developing potential between said image bearing member and said developing means is adjusted by said developing means during stopping of said image bearing member after image formation. An image forming apparatus, wherein a developing potential at the time of image formation is made different from that at the time of image formation so that when toner is supplied to the body, the amount of toner adhered to the image carrier becomes smaller than at the time of image formation.