JP3302468B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having a contact charging member in which a charging member for charging a photosensitive member contacts the photosensitive member.

[0002]

2. Description of the Related Art In a general electrophotographic image forming apparatus represented by the Carlson process, a corona discharge method, which is a non-contact charging method, is used to uniformly charge a photosensitive member. However, since the corona discharge device discharges by applying a high voltage to a 30 to 100 μm tungsten wire called a corona wire, air is ionized and a large amount of ozone and nitric oxide is formed. This ozone and the like is not only harmful to the human body, but also damages the photoreceptor and the machine. In addition, ozone is particularly prominent when negative discharge is performed. In recent years, the photoreceptor has become an organic photoreceptor for negative charging, and environmental standards for generated gas discharged from an image forming apparatus have become strict. This is a serious problem. On the other hand, in a contact charging system in which a charging member is brought into contact with a photoconductor to perform charging,
There is an advantage that only a small voltage needs to be applied to the charging member and the amount of generated ozone is very small. Commercialization of an image forming apparatus employing a roller-shaped contact charging member has already begun.

However, in the present contact charging method, in terms of charging uniformity, the current situation is that the corona wire must be displaced. In order to improve the charging uniformity, for example, in Japanese Patent Application Laid-Open No. 63-149668, an AC voltage having a peak-to-peak voltage that is twice or more the charging start voltage when a DC voltage is applied is superimposed on a charging member. To improve the uniformity of charging.

As described above, the charging performance by the contact charging method has been improved, but there are other problems. That is, the contact charging member is always in contact with the photoreceptor, but if the charging member is left in contact with the photoreceptor in a state where the photoreceptor is stopped, the contact portion on the photoreceptor may come from the surface of the charging member or the like. It becomes a polluted state by adhesion of. The contaminants on the photoreceptor can hardly be visually confirmed, but during development, the toner adheres to the contaminated portion less than the surface of the other photoreceptor.
As a result, a white streak (white spot) image corresponding to the contaminated portion appears in the output image, resulting in an image defect. Further, as the image forming operation is continued, toner and paper dust adhere to the charging member, and as a result, the surface properties of the member (mainly, the releasability from the photoreceptor) change, which also causes There is a problem that the occurrence of white streaks changes.

In order to solve such a problem, for example, in JP-A-4-157485 and JP-A-1-207768, when the photosensitive member is stopped, the charging member is separated from the photosensitive member.
There has been proposed a technique for preventing a charging roller from being left in contact with a photoconductor. Also, Japanese Patent Application Laid-Open No. Hei 1-204081 proposes that a surface coating is applied to a charging roller to improve releasability from a photoreceptor.

[0006]

However, if a support mechanism or a drive mechanism for retracting the charging roller is provided, it is difficult to reduce the size of the apparatus, and the cost is unavoidable. Further, even if the releasability is improved, there is a problem that image defects cannot be completely prevented.

[0007] In view of the above problems, in the present invention, in an image forming apparatus using a contact charging device, when a charging member and a photoreceptor are left in contact with each other, an image defect is caused by an adhered substance on the photoreceptor. It is an object to suppress the above.

[0008]

In order to solve the above problems, the present invention provides a photoconductor (1) for forming an image, which is installed so as to be in contact with the image forming surface of the photoconductor and is in contact with the photoconductor. A contact charging unit (2) for charging the photoconductor, and at least one other contact other than the contact charging unit, which contacts the image forming surface of the photoconductor and causes friction with the image forming surface by rotation of the photoconductor. In the image forming apparatus provided with the members (3, 4, 6): a counting means (12) for counting the total number of executions of the image forming process on the photoreceptor; run the pre-rotation operation, starts the image forming process thereafter, the rotation speed of the photosensitive member at the time of the pre-rotation operation
Control means (7) for automatically adjusting the degree in accordance with the count value of said counting means;

Further, in the invention according to claim 2, the control means sets the time of the pre-rotation operation to a count value of the counting means.
It is configured to adjust automatically according to.

According to the third aspect of the present invention, the control means is configured to form a toner pattern on the image forming surface of the photoconductor during the pre-rotation operation (SB) .

[0011] Note that the symbols shown in the parentheses, but illustrates for reference the sign of the corresponding element in the examples described below, the specific elements in each component of the present invention embodiment It is not limited to only.

[0012]

In the present invention, prior to the execution of a normal image forming process, a pre-rotation operation for driving the photoreceptor (1) for forming an image is executed. At this time, since contact members (developing sleeve, transfer belt, transfer roller, cleaning blade, cleaning fur brush, etc.) other than the contact charging means (for example, charging roller 2) are in contact with the photoconductor,
By the friction between the contact member (especially the cleaning blade) and the surface of the photoreceptor, the deposits on the photoreceptor existing at the contact portion between the charging roller and the photoreceptor are removed. If a normal image forming process is started after the attached matter is removed, the occurrence of white stripes can be suppressed.

In order to minimize the time of the pre-rotation operation and to reliably prevent the occurrence of white streaks, the total number of executions of the image forming process of the photosensitive member up to that time is counted, and based on the number of times. The drive speed of the photoconductor during pre-rotation
It is automatically adjusted according to the total number of executions of the image forming process.
Adjust. That is, depending on the driving speed of the photoconductor, the contact member
(Such as a cleaning blade) and the surface of the photoreceptor
Can be adjusted over time
When white streaks are likely to occur on the
Removes extraneous matter efficiently in a relatively short period of time and generates white stripes
Suppress.

In the image forming apparatus according to a second aspect, the image forming apparatus further comprises:
Then, a necessary minimum time is set based on the total number of executions of the image forming process, and the pre-rotation operation is executed for that time. As a result, the removal operation can be performed efficiently, white stripes on the image can be prevented, and the image quality can be maintained.

In the image forming apparatus according to the third aspect , a toner pattern is formed on the photosensitive member during the pre-rotation operation. As a result, the toner (resin particles) is interposed between the contact member (particularly, the cleaning blade) and the photoreceptor during the pre-rotation operation, so that the adhering matter is efficiently removed by the polishing effect .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the structure of a photoreceptor peripheral portion of a copying machine embodying the present invention. This will be described with reference to FIG. The photoreceptor 1, which is an image carrier, is driven to rotate at a predetermined peripheral speed in a clockwise direction in the drawing during the image forming process. The roller-shaped charging roller 2 installed at a position that is always in contact with the photoreceptor 1 uniformly causes the surface of the photoreceptor 1 to a predetermined potential by a DC voltage supplied from a voltage application power supply 8 in an image forming process. Charge. Also, this charging roller 2
The photoreceptor 1 is constantly pressed against the photoreceptor 1 with a predetermined pressure by a pressure spring (not shown), and rotates in accordance with the rotation of the photoreceptor 1.

The image forming process other than charging is the same as in a general copying machine. That is, the surface of the charged photoconductor is exposed to image light, and the potential distribution corresponding to the density of the image,
That is, an electrostatic latent image is formed, the electrostatic latent image is visualized by a toner in the developing device 3, and the visible toner image on the photoreceptor is transferred to a predetermined transfer paper by the operation of the transfer roller 4. After the cleaning, the cleaning device 5 removes foreign matters such as untransferred toner and paper dust from the photoconductor 1, and prepares for the next image forming process.

A predetermined DC voltage is applied as a bias voltage to a developing sleeve in the developing device 3 from a developing bias applying power source. The cleaning device 5 is provided with a cleaning blade 6 that comes into contact with the surface of the photoconductor 1. A photosensitive member driving device 10 including an electric motor is connected to the central axis of the photosensitive member 1, and the photosensitive member driving device 10 drives the photosensitive member 1 to rotate. Photoconductor driving device 10
Is controlled by the photoconductor drive control unit 11.

The central processing unit 7 includes a microcomputer and performs various controls including an image forming process. The central processing unit 7 includes a voltage application power supply 8, a developing bias application power supply 9, and a photoconductor drive control unit 1.
1 is connected. The central processing unit 7 includes:
A copy number counter 12 is connected. The copy number counter 12 is composed of a non-volatile memory, and its contents are rewritten by the central processing unit 7.
The copy number counter 12 holds a copy number integrated value (total number of copies after the photoconductor is replaced) in order to check a change with time of the photoconductor 1. Copy number counter 1
The contents of 2 can be referred to by the central processing unit 7 as needed.

FIG. 2 shows an outline of the processing executed by the central processing unit 7. The operation of the central processing unit 7 will be described with reference to FIG.

When the power is turned on, initialization is performed in step S1, and then a standby process in step S2 is performed. In this standby process, reading of signals output from various sensors,
It reads key inputs to an operation unit (not shown), controls various elements such as heaters, and identifies various states of the apparatus.

In the next step S3, for example, a check is made as to whether or not the fixing temperature has reached the target temperature, and it is determined whether or not the preparation for the copy process has been completed. If the preparation is not completed, the process returns to step S2. When preparation of the copy process is completed, steps S3 to S
Proceed to 4.

In step S4, it is determined whether or not a start instruction has been given, for example, whether or not a start key of the operation unit has been pressed. If there is no start instruction, step S2
Returning to step S5, if the start instruction is detected, the process proceeds to step S5.
Proceed to.

In step S5, the content Nc of the copy number counter 12 for holding the total copy number is read. In step S6, it static sets the time T determined based on Nc read in S5 to the internal timer - DOO be
You.

[0025] The rotational speed of the photosensitive member in the previous rolling operation, to automatically adjust based on the number of copies Nc, before starting the drive of the photoreceptor, at step SF, the driving speed of the photosensitive member Nc Set according to.

In the next step S7, a predetermined drive start signal is output to the photoconductor drive control unit 11, and the photoconductor 1 starts rotating at a predetermined speed. This is a pre-rotation operation performed prior to the image forming process. At this time, no image is formed. However, during this pre-rotation operation, residual toner, paper dust, and the like adhering to the portion of the photoconductor 1 that was in contact with the charging roller 2 during the stationary period are removed by the cleaning blade 6 and the photoconductor 1. It is removed by an action such as friction of a contact portion with the metal .

In step SB, during the pre-rotation operation,
A toner pattern is formed on the surface of the photoconductor. actually,
Given a latent image potential V _P to the photosensitive member by the charging roller, dummy electrostatic latent image on the photosensitive member - pattern - down is formed. And
When applying a developing bias V _BP to the developing device 3, the position of the developing device, the potential difference V _P -V _BP (development potential)
Occurs. Therefore, when the dummy pattern is developed by the developing device, toner adheres to the position of the dummy pattern, and a visible image (toner pattern) is formed on the photosensitive member.

As a result, the toner (resin particles) is interposed between the contact member (especially, the cleaning blade) and the photosensitive member during the pre-rotation operation.
Deposits on the photoreceptor are efficiently removed .

When starting a normal image forming process, in step SG, the drive speed of the photosensitive member is reset to a normal predetermined speed .

The duration of the pre-rotation operation is determined by a timer. That is, when the internal timer times over after the start of the pre-rotation operation, the process proceeds from step S8 to the next step S9, and a normal image forming process (copy process) is started. In this case, the image forming process may be started after the rotation of the photoconductor 1 is stopped, or the process may be shifted to the image forming process while the rotation of the photoconductor 1 is continued.

The basic contents of the image forming process are the same as those of a general copying machine. However, the charging process is performed in such a manner that the charging roller 2 in contact with the photoreceptor 1 is used instead of corona discharge.
Will be implemented.

When the image forming process in step S9 is completed, the process proceeds to the next step SA. In step SA, the contents of the copy number counter 12 are rewritten so that the contents are incremented by one. Thereafter, repeat the operation again returns to the standby processing in step S2.

[0033]

As described above, according to the present invention, the number of executions of the image forming process is counted, and the drive speed of the photosensitive member at the time of the pre-rotation operation is changed based on the number of times.
Deposits are removed well, and image quality can be maintained.

Further, in the image forming apparatus according to the second aspect, a minimum necessary time can be set based on the number of times of execution of the image forming process, and the pre-rotation operation can be executed for that time. Time can be minimized, and the occurrence of white stripes can be reliably prevented.

Further, in the image forming apparatus according to the third aspect , a toner pattern is formed on the photosensitive member during the pre-rotation operation, so that the toner (resin particles) interposed between the contact member (particularly the cleaning blade) and the photosensitive member. ) By the polishing effect
Deposits can be efficiently removed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration around a photoconductor of a copying machine according to an embodiment.

FIG. 2 is a flowchart showing the operation of a CPU 7 of FIG.

[Explanation of symbols]

 1: Photoconductor 2: Charging roller 3: Developing device 4: Transfer roller 5: Cleaning device 6: Cleaning blade 7: Central processing unit 8: Voltage application power supply 9: Development bias power supply 10: Photoconductor driving device 11: Photoconductor Drive controller 12: copy number counter

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kentaro Matsumoto 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Norio Kikuchi 1 Nakamagome, Ota-ku, Tokyo No. 3-6 Ricoh Co., Ltd. (72) Inventor Koichi Yamazaki 1-3-6 Nakamagome, Ota-ku, Tokyo Incorporation Ricoh Co., Ltd. (72) Inventor Sadao Takahashi Naka, Ota-ku, Tokyo 1-3-6 Magome, Ricoh Co., Ltd. (56) References JP-A-4-234066 (JP, A) JP-A-63-192074 (JP, A) JP-A-4-63364 (JP, A) JP-A-63-158572 (JP, A) JP-A-5-313452 (JP, A) JP-A-7-121077 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 15/00 G03G 15/02 G03G 21/00-21/02 G03G 21/10 G03G 21/14

Claims (3)

(57) [Claims] 1. A photoreceptor for forming an image, a contact charging means which is installed so as to be in contact with an image forming surface of the photoreceptor and charges the photoreceptor in a state of being in contact therewith, and an image forming surface of the photoreceptor An image forming apparatus including at least one other contact member other than the contact charging means, which is in contact with the photosensitive member and causes friction with the image forming surface due to rotation of the photosensitive member: counting the total number of executions of the image forming process on the photosensitive member Counting means; and when a start instruction of the image forming process is issued, a pre-rotation operation of the photoconductor is performed, and thereafter, an image forming process is started, and a rotation speed of the photoconductor at the time of the pre-rotation operation is determined. An image forming apparatus, comprising: a control unit that automatically adjusts according to a count value of the counting unit. 2. The method according to claim 1, wherein the control unit controls a time period of the pre-rotation operation.
Is automatically adjusted according to the count value of the counting means ,
The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 1, wherein the control unit forms a toner pattern on the image forming surface of the photoconductor during the pre-rotation operation.