JPH0750347B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as a copying machine, and more particularly to the formation of an image on an image forming body by writing the image a plurality of times on the image forming body. The present invention relates to a color image forming apparatus of a type that can perform.

BACKGROUND OF THE INVENTION Many methods have already been introduced for obtaining, for example, color copies on recording paper. For example, color separation of the original image is performed, the single color toner image corresponding to the separated color is transferred and fixed on the recording paper, the recording paper once copied is fed again, and the next color separated single color toner image is recorded. It is a method of overlapping on paper. The color copy thus obtained suffers from deterioration of copy quality and image misalignment, and the copy speed per sheet is extremely low.

Further, there is a method in which an intermediate body is provided in addition to the image forming body, and color toner images of respective colors are superposed on the intermediate body, and then transferred onto a recording paper and fixed. When this method is used, the apparatus itself becomes large and the mechanism is inevitably a complicated image forming apparatus.

The applicant of the present invention, as an image forming apparatus that eliminates these drawbacks,
Japanese Patent Application Laid-Open No. 59-181362, Japanese Patent Application No. 60-192710, Japanese Patent Application No. 60
-Proposed as described in No.192711. The present invention is also based on this new proposal.

According to this proposal, in a color image forming apparatus for forming a color image by synthesizing a mono-color image, a plurality of developing devices loaded with toners of respective colors are arranged on the periphery of the image forming body to form an image carrier. A latent image corresponding to each color formed for each rotation is developed by a non-contact type developing means, and a toner image of multiple colors is formed by rotating the image forming body a plurality of times.

After this toner image is transferred to a recording sheet as a transfer target, the residual toner is removed and removed by the action of a cleaning device as in a general image forming apparatus, but the cleaning action is well known. As described above, since the blade member or other cleaning member is pressed against (including abutting against) the image forming surface, it cannot be operated during the formation of the toner image or before the transfer. The blade members are kept in a position separated from each other, and the pressure contact of the blade member is started immediately before the front end of the transferred toner image reaches the cleaning device, and the pressure contact is released immediately after the rear end of the toner image passes. Format is adopted.

[Problems to be solved by the invention]

As described above, particularly in the cleaning device used in the color image forming apparatus, since the operation of pressing and releasing the cleaning member such as the blade member is performed during the rotation cycle of the image forming body, the image forming is performed due to the frictional resistance caused by the operation. A certain degree of fluctuation occurs in the rotational speed of the body, and therefore, when the blade member is pressed or released during the time when the latent image is formed on the image forming surface by exposure, the peripheral speed of the image forming surface changes. As a result, image discontinuity may occur due to discontinuity of scanning of the image, resulting in deterioration of image quality. Needless to say, the same problem can be applied to the formation of a single-color image, although there are some differences.

As a result of solving this problem and improving the present invention, during the formation of a latent image by exposure, the rotational speed of the image forming body does not fluctuate, whereby the original image can be copied as a color image without being disturbed. The purpose of the present invention is to provide a color image forming apparatus capable of obtaining a high quality color image.

[Means for solving problems]

The above-mentioned objects are: (a) charging means on the peripheral portion of the image forming body, image writing means for forming a latent image by performing image exposure at an exposure point, and the latent image as a toner image using a monochromatic developer. A plurality of developing means, a transfer means for transferring a multicolor toner image formed by a plurality of rotations of the image forming body onto a recording paper, and a residual toner after the transfer is pressed against the image forming body. (B) The length of the peripheral surface of the image forming body from the exposure point to the pressure contact position of the cleaning unit via the transfer unit can be transferred. (C) The length of the peripheral surface of the image forming body from the pressure contact position of the cleaning means to the exposure point through the charging means from the minimum screen interval is set to be slightly longer than the maximum recording paper length. Configured to be slightly shorter, (d ) First control means for controlling the operation of the writing means; (e) Based on a signal generated by the first control means,
A second control unit for controlling the operation of the cleaning unit so that the cleaning unit does not press and release the image forming unit while the image writing unit is operating. Image forming apparatus.

Achieved by

〔Example〕

An example of the image forming apparatus according to the present invention will be described with reference to FIGS. 1 to 15 using color image formation as an example.

FIG. 1 shows the entire structure of the color image forming apparatus. A is a reading unit for exposing and scanning an image of an original 2 by a moving optical system, and B is an image forming body for transmitting an image signal sent from the reading unit A. A writing unit which is an image writing means for forming a writing latent image on the photosensitive drum 1 which is a barrel, C is a developing means provided for converting the latent image into a toner image, that is, a plurality of developing devices, and D is a transfer of the toner image. It is a paper feed unit that stores recording paper, which is a transfer member.

In the reading unit A, the original 2 is subjected to the exposure scanning of the movable mirror units 3 and 4 of the moving optical system by the scanner driving motor controlled by the optical system driving CPU, and the image thereof is read by the lens reading unit. After being sent to 5, the image is separated into a plurality of wavelength regions and imaged on a CCD image sensor 6 which receives respective color images.

An image signal for each color is output from the image sensor 6 controlled by the optical system drive CPU, signal processing is performed and the signal is sent to the writing unit B, and the laser drive circuit operates according to the printer interface controlled by the main CPU. Then, the laser beam generated by the semiconductor laser (LD) is projected onto the peripheral surface of the photosensitive drum 1 through an optical system including the polygon mirror 7.

When the scanning is started, the beam is detected by the index sensor, the modulation of the beam by the first color signal is started, and the photosensitive drum 1 which is uniformly charged in advance is scanned. A latent image corresponding to the first color is formed on the drum surface 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 a developing device 11 loaded with red toner, for example, which is controlled by the main CPU to form a toner image on the drum surface. The latent image corresponding to this first color is to be developed. 1 developing device 11
Is disposed at a position closest to the photosensitive drum 1 in the moving direction of the photosensitive drum 1.

The toner image thus obtained passes under the blade member 8a of the cleaning device 8 and the cleaning roller 8b provided on the downstream side thereof, which is separated from the surface of the photosensitive drum 1 held on the drum surface, It is recharged to form a latent image by the second color signal in the same manner as in the case of the first color signal described above, and the latent image is developed by the second developing device 12 corresponding to it, for example, blue toner is loaded, Further, the latent image based on the third color signal is also developed by the third developing device 13 loaded with black toner, for example, and a color toner image is formed by synthesizing these monochromatic toner images. The second and third developing devices 12, 13
After the first developing device 11 described above, the developing devices 12 and 13 are arranged in this order in the moving direction of the photosensitive drum 1.

Further, as shown in FIG. 2, in the moving direction of the photoconductor drum 1 following the developing devices 11, 12, and 13, the transfer and separation electrodes 1
4,15 and through the cleaning device 8 described above, the charging pole
16 and the exposure point p from the writing unit B are arranged, and the color toner image formed on the peripheral surface of the photosensitive drum 1 is transferred to the recording paper conveyed from the paper feeding cassette 9, After separating it, the residual toner is peeled off and cleaned by the blade member 8a and the cleaning roller 8b which are switched to the pressure contact state of the cleaning device 8, and then the toner is charged again and the process for forming a new original image is started. It has become.

Regarding the position of the exposure point p by the writing unit B with respect to the peripheral edge of the photosensitive drum 1 and the press contact position of the blade member 8a in the cleaning device 8, in the present invention, from the exposure point p through the transfer electrode 14 to the blade. Element
The length on the peripheral surface until reaching the pressure contact position of 8a is slightly longer than the maximum transferable recording paper length, and
From the charging pole 16 to the exposure point p,
It is configured to be slightly shorter than the minimum screen interval (the length corresponding to the non-image area). Although a blade member and a cleaning roller are mainly used as the cleaning means here, the present invention is not limited to this, and the rotation speed of the photoconductor is affected by the start and end of the cleaning action such as cleaning with a fur brush or a web. Applicable to give.

Here, the pressing and releasing of the cleaning means is performed by the cleaning means pressure release motor controlled by the main CPU. By doing so, the operation of pressing and releasing the blade member 8a and the cleaning roller 8b of the cleaning device 8 during the exposure, Alternatively, each operation of starting and ending exposure during the cleaning operation is avoided, and each image corresponding to each color is projected by uniform exposure scanning by the stable peripheral speed of the photosensitive drum 1. Become.

FIG. 3 is a block diagram showing the control system of the image forming apparatus which performs the above-mentioned operation, centering on the cleaning pressure contact release. The main CPU performs the above-mentioned image formation and cleaning by the drum index for outputting the specific position information of the photosensitive drum 1 and the input from the operation unit. A first for controlling the operation of the image writing means and for generating a signal corresponding to the operating state of said image writing means
While the image writing means is operating based on the control means and the signal generated by the first control means, the cleaning means pressure release motor is operated so as not to press and release the cleaning means against the photosensitive drum 1. The second control means for controlling the both correspond to the main CPU and are controlled.

Next, the control flowchart of the present invention will be described.
FIG. 4 shows the main routine. First, the power is turned on and initialized, and the key data is processed by the input on the operation unit to enter the idling state. Check whether the copy SW is turned on here, and copy
When the SW is turned on, various copy initialization processing such as the number of copies is performed, and then the sequence is different, so that it is selected whether it is the 2-3 color copy processing or the mono color processing. It is checked whether or not the copying is completed, and the process returns.

Since the effect of the present invention is particularly remarkable in the 2-3 copy processing, the above-mentioned 2.3-color copy processing routine is shown in the flowchart of FIG. The flow of the 2-3 color processing routine is such that when the flag is set, the corresponding process is performed, and when the flag is not set, the corresponding process is skipped and the process proceeds to the next step. That is, when the flag A is 1, flag processing is performed, and when the flag B is 1, copy number processing is performed. Next, if the pre-rotation flag is set, the pre-rotation process is performed.If the pre-rotation flag is not set, the pre-rotation process is skipped, and it is checked whether the next blue flag is set. Then, after the cleaning process is completed, the process returns. In this flowchart, transfer process,
The pre-rotation process, the blue (red, black) color sequence process, the VALID signal process, the cleaning process, and the post-rotation process are in the form of a subroutine as shown in FIGS. 6 to 11.

In the transfer processing sequence of FIG. 6, the flow proceeds in a form of timing-controlled second paper feeding, transfer, and separation, and after the transfer flag is reset, the post-rotation flag is set.

In the pre-rotation processing sequence of FIG. 7, after the main motor for rotating the photosensitive drum 1 is turned on at the timing 1, the cleaning means is brought into pressure contact with the photosensitive drum 1 for preliminary cleaning. Laser writing has not started yet at this point. The state of their operation is shown in the time chart of FIG.

FIG. 8 shows the blue sequence processing as the sequence of the development processing. For red and black, there is the same flowchart as the blue sequence processing. However, the above is the same except that the timings are all different from the positional relationship of the developing means with respect to the photosensitive drum 1.

FIG. 9 shows a VALID signal processing sequence. This sequence is the first control signal of the present invention and is controlled by the output from the main CPU. First, when the reading unit A is at the home position, data is transferred to the optical drive CPU, and it is checked whether the reference signal is output from the drum index shown in FIG. When the reference signal is output, the printer mode or the copy mode is selected. When the reference mode is output, the reading unit A is optically started and the counter A is cleared. Then, at counter A = timing 10, writing starts and V-VALID becomes Hi, and at counter A = timing 11, writing ends and V-VALID becomes Low,
Clear counter B. Here, the timing 11 changes depending on the paper size of the recording paper.

FIG. 10 shows a cleaning processing sequence. This sequence is the second control signal of the present invention and is advanced by the output from the main CPU. First, when the pressure contact of the cleaning means or the pressure contact release is selected, and when the pressure contact of the cleaning means is selected, the counter B cleared by the writing end (V-VALID LOW) in the VALID signal processing is the counter B = Pressing the cleaning blade at timing 12, counter B = timing 13
At, the cleaning roller pressure contact is output, and at the counter B = timing 14, the cleaning roller pressure contact release processing signal is output. Further, when the pressing release of the cleaning means is selected and the post-rotation flag is not set, the counter B, which is also cleared by the completion of writing (V-VALID LOW), releases the pressing contact of the cleaning blade at counter B = timing 15. Counter B = Timing 16
The pressure contact of the cleaning roller is performed, the pressure contact of the cleaning roller is released at the counter B = timing 17, and then the cleaning flag is reset.

FIG. 11 shows the post-rotation processing sequence. In the post-rotation after the predetermined copy, the photosensitive drum 1 is controlled to be cleaned, but writing is not performed here. The polygon motor is controlled to a non-writing low speed rotation, and the photosensitive drum 1 is stopped at a predetermined position by turning off the main motor in accordance with a reference signal from the drum index.

FIG. 12 shows the control time table when two copies of the three-color copy process are made by the above sequence, focusing on writing and cleaning.

Each process of the image forming apparatus shown in FIG. 2 which is operated by the above control means will be described with reference to FIGS. 13 and 14. The cleaning means is performed by pressing the cleaning blade and the cleaning roller against the photosensitive drum.The main part of the cleaning is the pressing contact of the blade, and the cleaning roller adheres to the photosensitive member at the time of the pressing contact of the blade and the releasing of the pressing contact. As described above, only the operation of the blade member will be described.

FIG. 13a shows that the front half X of the preceding image on the peripheral surface of the photosensitive drum 1 rotating in the direction of the arrow is cleaned by the blade member 8a to remove the residual toner, and then the rear half X'is cleaned. Indicates the stage at which action begins
FIG. B shows a state in which exposure of an image corresponding to the first color of the next original is started.

When the latent image I corresponding to the first color is formed by the above-mentioned exposure and the front end F reaches the position of the developing sleeve 11a of the developing device 11 (FIG. 13c), the developing process is performed and the toner image I'is formed.
However, even when the exposure corresponding to the trailing edge R of the latent image I is completed, the leading edge F of the toner image I ′ has not yet reached the pressure contact position of the blade member 8a due to the configuration of the present invention, and thus may be slightly. Since it is located on the front side (Fig. 13d), the pressure contact of the blade member 8a is released during that time to remove the toner image I '.
It is designed to pass through (Fig. 13e). Therefore, during the formation of the latent image I corresponding to the first color, the blade member
The photosensitive drum 1 continues to rotate stably at a constant speed without causing any operation in the pressure contact state 8a.

Subsequently, the photosensitive drum 1 is charged and starts forming a latent image II corresponding to the second color, overlapping the toner image I '(first
13f) In the same manner, the leading edge F reaches the developing sleeve 12a of the developing device 12 and is subjected to development processing (FIG. 13g), and is sequentially converted into a toner image II ', and the blade member 8a is released from pressure contact.
Underneath (Fig. 13h) and again through the same process (Fig. 14i) to form a latent image III and then a toner image III 'corresponding to the third color (Figs. 14j, k). ) The toner images I ′, I
A toner image of a multicolored color is formed by synthesizing with I ', and after the transfer electrode 14 starts transferring this to the recording paper, the tip F of the residual toner on the surface of the photoreceptor is changed to the blade member 8a.
The exposure of the trailing edge R of the latent image III is completed before reaching the position corresponding to the pressure contact of (1 in FIG. 14).

Therefore, during the formation of the latent images II and III for the second and third colors, the blade member 8a is released from the pressure contact and the pressure contact operation is not started. Is able to continue stable and constant speed rotation.

Then, before the tip F of the residual toner reaches the blade member 8a, the blade member 8a moves to the pressure contact state (Fig. 14m), and the residual toner is sequentially removed from the first half Y to the second half Y ', and in the case of continuous copying. The charging exposure for the subsequent copy is started without idling the photosensitive drum 1 (FIG. 14n).

When the outer diameter of the outer peripheral portion of the photosensitive drum 1 is 140 mm and the maximum recording paper to be used is B4 size (length 364 mm), the exposure point p and the position of the blade member 8a satisfying the present invention are set. As shown in That is, the distance between the exposure point p and the blade member 8a is shorter than the length of the non-image portion on the peripheral surface.

Under this condition, when the distance to each developing device is set as shown in FIG. 2 and the drum peripheral speed is 58 mm / sec, the time chart of the above-mentioned image forming process is as shown in FIG. That is, the time required from the exposure point p1 to the developing sleeves 11a, 12a, 13a, the transfer electrode 14, and a fixing device (not shown) 150 mm away from the transfer electrode 14 are as follows.

EFFECTS OF THE INVENTION The present invention is
Since the pressure contact action or the pressure contact release of the cleaning device such as the blade member is not started, it is possible to expose the image corresponding to each color over the entire image surface under the condition of the constant rotation speed of the photosensitive drum, thereby causing the distortion or the distortion. It has become possible to provide an image forming apparatus that can obtain a high-quality color transfer image or a single-color transfer image without disturbance.

[Brief description of drawings]

FIG. 1 is a sectional configuration diagram of an image forming apparatus to which the present invention is applied. FIG. 2 is a view of the main part. FIG. 3 is a block diagram of the control system of the present invention. 4 to 11 show a processing sequence of the present invention, FIG. 4 shows a main routine, and FIGS. 5 to 11 show a subroutine. Figure 12 is a time chart of the control system. FIG. 13 and FIG. 14 are principal part diagrams showing each process of image formation according to the present invention. FIG. 15 shows the time chart. 1 ... photosensitive drum, 8 ... cleaning device 8a ... blade member, 8b ... cleaning roller 11,12,13 ... developing device 11a, 12a, 13a ... developing sleeve 14 ... transfer electrode, 15 ... Separation electrode 16: charged pole, p: exposure point I, II, III ... (corresponding to each color) latent image I ', II', III '... (corresponding to each color) toner image

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-176958 (JP, A) JP-A-50-23234 (JP, A) JP-A-56-117256 (JP, A) JP-A-60- 181758 (JP, A) JP-A-50-122268 (JP, A) JP-A-60-48055 (JP, A)

Claims (1)

[Claims] 1. A charging means is provided at a peripheral portion of an image forming body.
Image writing means for performing image exposure at an exposure point to form a latent image, a plurality of developing means for converting the latent image into a toner image by using a monochromatic developer, and a plurality of rotations of the image forming body. An image forming apparatus comprising: a transfer unit that transfers the formed multicolor toner image onto a recording paper; and a cleaning unit that removes the residual toner after the transfer by pressing against the image forming body. The length of the peripheral surface of the image forming body from the exposure point to the pressure contact position of the cleaning means via the transfer means is made slightly longer than the maximum transferable recording paper length. (C) On the other hand, the cleaning means The length of the peripheral surface of the image forming body from the pressure contact position to the exposure point via the charging means is set to be slightly shorter than the minimum screen interval, and (d) the operation of the writing means is performed. First control means for controlling (E) based on the generated signal of the first control means,
A second control unit for controlling the operation of the cleaning unit so that the cleaning unit does not press and release the image forming unit while the image writing unit is operating. Image forming apparatus.