JP2001013841A - Method and device for image formation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate, by a simple means, a transfer roller soiling due to an image elongation, by forming an image by a method in which, according to the advancing directional length of a sheet-like medium to be subjected to transfer, a void area on its rear end in the advancing direction is altered and an image is written on an image carrier. SOLUTION: Ordinarily, for an image data signal, a void area comprising a blank space is provided in the rear end part. However, in an extreme case, blank spaces extends beyond transfer sheets S1 and S2 due to a difference in peripheral speed between a photoreceptor 1 and a transfer roller 6 and a difference between a speed at which the transfer sheet S1 is carried and a speed at which the transfer sheet S2 is carried. Therefore, image data for writing on a writing means 3 is altered, the value of the blank space is set large in advance, and an image is written on the photoreceptor 1. That is, by the input of the image data signal into the conversion means of the writing means 3 provided for a control means 14, the image data signal is converted to an image data signal for actual writing, and the image is written by causing a light emitting part 3a to emit light intermittently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming method and an image forming apparatus in a copying machine, a printer, a facsimile, and the like.

[0002]

2. Description of the Related Art A drum-shaped photoreceptor is used as an image carrier, and a toner image formed on the photoreceptor is transferred between a transfer roller of a bias voltage application which rotates while being opposed to and pressed against the photoreceptor. 2. Description of the Related Art An image forming apparatus is known in which an electrostatic transfer is performed on a sheet-like medium such as a passing transfer sheet to obtain a toner image on the transfer sheet, and then the sheet is fixed and discharged by passing through a fixing device.

In such an image forming apparatus, an image defect called a so-called "hollow-out" phenomenon in which a central portion of a character or a line image of a transferred image is lost without being transferred is likely to occur. Driving a transfer roller at a peripheral speed has been performed. As a result, the hollow phenomenon disappeared, but this time, a new problem that the image was elongated occurred.

For example, assuming that the peripheral speed of the transfer roller is V2 with respect to the peripheral speed V1 of the photosensitive member, the transfer speed V of the transfer paper
Reference numeral 3 denotes a peripheral speed of the photosensitive member V1 and a peripheral speed of the transfer roller V2.
And V1 <V3 <V2. In other words, the speed of the transfer paper is determined by the dynamic friction coefficient μ1 between the photoconductor and the transfer paper and the dynamic friction coefficient μ2 between the transfer paper and the transfer roller. The kinetic friction coefficient μ1 is affected, and the kinetic friction coefficient μ1 decreases as the amount of toner increases, and the transfer speed V3 of the transfer paper approaches the circumferential speed V2 of the transfer roller. It extends in the transfer direction of the transfer paper, that is, in the feed direction.

[0005] When such image expansion occurs, for example, when transferring a toner image that has been written to the full size of the transfer paper, the toner image portion protrudes outside the transfer paper area, and this protrudes to the transfer roller. The adhered toner adheres and stains the back of the next transfer paper.

Therefore, according to the technique disclosed in Japanese Patent Application Laid-Open No. H08-22153, a portion corresponding to the protruding portion is removed by an eraser before development to prevent toner from adhering. Further, in the technique disclosed in Japanese Patent Application Laid-Open No. Hei 7-154556, magnification correction is performed to reduce the magnification in accordance with the image area ratio of a read image, so that even if the image expands by writing, the image can be accommodated in the transfer paper. ing.

[0007]

However, the above technique requires a means and an eraser for accurately detecting the position of a latent image to be systematically erased, and the above technique requires an advanced image correction technique called magnification correction. A controller for performing the correction is required, and the configuration of the system becomes complicated.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming method and an image forming apparatus capable of eliminating dirt on a transfer roller due to image elongation by simple means and eliminating back dirt on a sheet-like sheet. And

[0009]

The present invention has the following configuration to achieve the above object. (1). In an image forming method in which a toner image formed on an image carrier is electrostatically transferred onto a sheet-like medium by using a transfer roller driven at a different peripheral speed from the image carrier, an image forming method includes: An image is formed on the image carrier by changing the blank area on the rear end side in the traveling direction according to the length in the traveling direction to form an image (claim 1). (2). In an image forming apparatus in which a toner image formed on an image carrier is electrostatically transferred onto a sheet-like medium by using a transfer roller driven at a different peripheral speed from the image carrier, the image data is formed as a normal white spot. There is provided control means for changing the width from a predetermined width to a predetermined blank width (claim 2). (3). (2) In the image forming apparatus as described in (2), the control unit uses an elongation amount of an image determined as a function of a length in a traveling direction of the sheet-shaped medium to be transferred and an image area ratio.
A blank area on the rear end side in the traveling direction of the sheet medium to be transferred is set (claim 3). (4). (3) In the image forming apparatus described in (3), the control unit converts the image area ratio based on a writing time of the writing unit on the image carrier. (5). (3) In the image forming apparatus described in (3), the control unit converts the image area ratio by a pixel amount of an image to be written on the sheet-shaped medium (claim 5). (6). In the image forming apparatus described in (3), the control unit converts the image area ratio based on detection information sampled by an image density detection sensor.

[0010]

Embodiments of the present invention will be described below. [1] Configuration of Image Forming Apparatus FIG. 1 shows an outline of the overall configuration of the image forming apparatus 19, and FIG. In FIG.
Located above the image forming apparatus main body 10 is an image reading device 9 constituted by a scanner. The image forming apparatus of the present invention can read an image of a document by using the image reading device 9 and can function as a copier for copying the image of the document in the image forming device main body 10. By connecting to the printer 11, the image data from the host computer 11 can be made to function as a printer for visualizing the image data on the transfer paper by the image forming apparatus main body 10.

It should be noted that the image forming apparatus 19 shown in FIG. 1 except for the image reading apparatus 9 is used, and a printer or facsimile used only by connecting to an external host computer 11 or a telephone line is an image forming apparatus of the present invention. include.

Here, an image forming apparatus 19 having both functions of a copying machine and a printer will be described. Control means 14
Has a function of controlling the entire image forming process in the image forming apparatus 19 and has a function of the present invention, and is mainly constituted by a CPU.

In FIG. 1, a control means 14 is electrically connected to a host computer 11, an image reading apparatus 9, an operation section 20 in which a number of switches for operating the image forming apparatus 19 are arranged, and the like. You can receive input from. As will be described later, detection information from the toner concentration detection sensor 5 and sensors (not shown) for detecting the cassettes 12 and 13 are input. The operation unit 20 includes a mode changeover switch for switching between a print mode and a copy mode for the image forming apparatus 19, and switching of sheets, that is, the cassette 1
It has switches 2 and 13 and a switch for indicating the number of prints. As shown in FIG. 3, an image data signal SG is input from the host computer 11, an image data signal SG2 is input from the image reading device 9, and an image forming condition signal SG3 is input from the operation unit.

The image data signal SG1 contains, in addition to the image data to be written, information such as the size of the transfer paper, the writing direction, and the number of prints. The image data signal SG2 includes image data obtained by replacing the original image read by the image reading device 9 with an electric signal. The image forming condition data signal SG3 includes information such as a paper size, a writing direction, and the number of sheets.

In the print mode, the image data signal S
G1 is input to the control means 14. In the copy mode, the image data signal SG2 and the image forming condition data signal SG
3 is input to the control means 14. In the print mode, the control means 14 selects a sheet only by the signal of the image data signal SG1, sends out the sheet from one of the cassettes 12 and 13, and executes image formation. In the copy mode, the control unit 14 controls the image data signal SG2 from the image reading device 9 and the image forming condition signal SG from the operation unit.
3 to execute image formation.

An image forming process section and an image forming process of the image forming apparatus main body 10 will be described. These operate in common in both the print mode and the copy mode. In FIGS. 1 and 2, the peripheral speed V1 is set in the direction indicated by the arrow.
Drum-shaped photosensitive member 1 as an image carrier driven by
The charging roller 2, a writing unit 3 for irradiating exposure light L, a developing roller 4, a toner density detection sensor 5, a transfer roller 6, a separation claw 7, a cleaning blade 8, and the like are arranged in the rotation direction.

In forming an image, first, the photosensitive member 1 is uniformly charged by the charging roller 2. Next, scanning is performed by exposure light 3 from the writing means 3. As shown in FIG. 1, the writing means 3 comprises a light emitting section 3a composed of a laser oscillator, a rotary polygon mirror 3b for converting laser light from the light emitting section into scanning light, a deflecting mirror 3c, and an optical system (not shown) for imaging. .

Exposure light L generated by the light emitting section 3a is emitted from the writing means 3 as scanning light, and travels toward the photosensitive member 1. The exposure light L causes the photoreceptor 1 to form an electrostatic latent image according to the image data signal SG1 in the print mode, the image data signal SG2 in the copy mode, and the image formation condition signal SG3 in the copy mode.
Is formed. The electrostatic latent image thus formed is visualized by the developing roller 4 while passing through the developing device, and a toner image is formed.

A transfer sheet S is provided below the image forming apparatus main body 10.
1 (A4 size) and S2 (A4
A cassette 13 accommodating 3 sizes).
Based on the image data signal SG2 or the image forming condition signal SG3, for example, the cassette 12
The transfer paper S1 is fed toward the pair of registration rollers 15 at a predetermined timing programmed as an image forming process from the start, and the registration rollers 15 temporarily enter a standby state.

The transfer paper S1 waiting at the registration roller 15 is sent out so as to coincide with the toner image on the photosensitive member 1 at the position of the transfer roller 6. Transferred paper S
The toner image 1 is transferred from the photoconductor 1 by the transfer roller 6. At this time, since the transfer paper S1 is electrostatically attracted to the photoconductor 1, the transfer paper S1 is separated from the photoconductor 1 by the separation claw 7 and passes through the pair of fixing rollers 16 while the transfer paper S1 is on the transfer paper S1. Is fixed on the transfer paper S1, and
It is discharged to 7.

On the other hand, the toner remaining on the photoreceptor 1 without being transferred is scraped off by the cleaning blade 8, and is transferred to the developing unit 16 or a waste toner bottle (not shown) via a discharge screw (not shown). Collected. The photoconductor 1 is initialized by an unillustrated static elimination lamp.

The toner density detection sensor 5 irradiates a density detection pattern based on a toner image formed on the photoreceptor 1 with light at a predetermined timing in accordance with an instruction from the control means 14, and detects the reflected light to detect the reflected light. Output a detection signal to
Based on this signal, the toner concentration in the developing device 16 is detected, and if the toner concentration falls below a predetermined reference value, toner is supplied from the toner supply bottle.

In this embodiment, if the peripheral speed of the photosensitive member is set to V1 = 100%, the transfer speed of the transfer paper V3 = 102%, and the peripheral speed of the transfer roller V2 is set to V2 = 100% in order to prevent characters from dropping out during transfer.
= 107%. As a result, if no countermeasures are taken, the length of the image to be transferred with respect to the original image ratio extends toward the rear end side in the feed direction of the transfer paper, that is, in the direction of the dashed arrow in FIGS. May be stained.
Hereinafter, an example of the countermeasure will be described. [2] Example Corresponding to Claims 1 and 2 In FIG. 4, the length of the A4 size transfer paper S1 in the traveling direction is 297 mm, and the image data signal SG1 is usually
Is provided with a blank area having a margin of Δ1 at the rear end. As described above, since there is a speed difference between the peripheral speed V1 of the photoconductor, the peripheral speed V2 of the transfer roller, and the transport speed V3 of the transfer paper, the area of the actually transferred toner image indicated by hatching is on the rear end side. The margin Δ1 is reduced by extension, and in an extreme case, the margin Δ1 protrudes outside the transfer sheet S1. The present invention solves this problem. By changing the image data for writing to the writing means 3 to set the value of the margin Δ1 to a large value in advance and writing the image on the photoreceptor 1, the toner is moved out of the transfer paper. The image does not protrude.

In FIG. 3, the image data signal SG1 is converted by the conversion means 14 to the writing means 3 provided in the control means 14.
a is converted into a write image data signal for actual writing, and the light emitting unit 3a is intermittently made to emit light via a light emitting control unit 14b for driving and controlling the light emitting unit 3a to write an image. Do.

In the present invention, the image forming condition data signal SG
3, when there is an instruction to change the blank area, the image data for writing is increased through a blank area changing unit 14c provided between the conversion unit 14a and the light emission control unit 14b so that the margin becomes larger by a predetermined amount. Change the signal,
The write data signal is transmitted from the conversion unit 14a to the light emission control unit 4b. In other words, the blank area changing means 14c changes the margin Δ1 so that the margin Δ1 does not protrude out of the transfer sheet even if the image is stretched.

In this example, the image data corresponding to an increase in the margin Δ1 is lost due to the margin change, but the amount is small. For example, the amount of the image data is small. Even if a part of the display part is missing, the image information is not actually affected.

Since the image elongation is caused by the transfer paper slipping on the photoconductor 1, the image elongation rate is
Regarding the above toner amount, as the image area ratio increases, the image elongation ratio also increases. Therefore, the relationship between the image area ratio and the image elongation ratio was examined by experiments.

In the experiment, A3 size transfer paper was used vertically in the traveling direction, and the image area ratio was 1%, 6%, 15%, 30%,
Changes in the writing length at 50% and 100% were measured. Since the vertical dimension of A3 size is 420mm,
If a margin of 5 mm is provided on each of the leading end and the trailing end, the writing length is 410 mm.

At the writing length of 410, when the image area ratio of a general document is 15%, the peripheral speed V1 of the photosensitive member and the transfer speed are set so that the image elongation ratio becomes 0%. Paper transport speed V3, transfer roller peripheral speed V2
V1 = 100%, V3 = 102%, and V2 =
107%, image area ratio 1%, 6%, 30%, 5%
The change in each writing length at 0% and 100% was measured to determine the image elongation. Table 1 shows the results.

[0030]

[Table 1]

Based on the experimental data shown in Table 1, the size of the transfer paper is large and the size of the transfer paper under the most severe conditions is A3.
Assuming that the size of the image is large and the elongation percentage of the image when the image area ratio is 100% is 1%, the white spot width is set as the following fixed value of 1, 2, and 3.

1. 1. The transfer paper having a length of 210 mm or less in the traveling direction has a blank area width of 2 mm. 2. The transfer paper having a length in the traveling direction of 210 mm to 297 mm has a blank area width of 3 mm. The transfer paper having a length of 297 mm or more in the traveling direction has a blank area width of 3 mm. In this example, the blank area changing means 14c in FIG.
When there is an input from the conversion means 14a to the write data, writing is performed by uniformly changing the blank width so as to meet the above conditions 1, 2 and 3.

In the copy mode, even when an image is formed by the image data signal SG2 from the image reading device 9, the white area changing means 14c in FIG.
When there is an input from the conversion means 14a to write data, writing is performed by changing the white spot width so as to meet the above conditions 1, 2 and 3.

Normally, even for the original read by the image reading device 9, even if the white spot width at the rear end in the traveling direction is set as the fixed value of 1, 2, or 3, the image at the rear end in the traveling direction is a page. Since they are displayed or have a frame of a predetermined format, even if some of them are lost by changing the blank area width, it is considered that problems such as lack of image information do not actually occur.

Further, when a document read by the image reading device 9 is larger than the transfer paper size, for example, when a map is drawn on the entire surface of A3 size, only a part of the image is partially printed on a small size paper. For example, when the user wants to copy on an A4-size transfer sheet, as shown in FIG. 5, the map is copied on the entire surface of the A4-size transfer sheet S1 with no blank space, and no blank space is formed, and the transfer roller is soiled. In this case, according to the present invention, a fixed margin is formed at the rear end of the transfer sheet in the traveling direction. However, although the information in the margins is lost, the information on such end portions is not usually used, and the necessary information is aligned and positioned so that it is located at the center of the transfer paper. Since the reading is performed by the device 9, no practical problem occurs.

When it is desired to avoid loss of information due to the formation of margins, use a transfer paper one size larger than A4 size. In that case, there is a sufficient margin and it is not necessary to change the blank area. If there is a sufficient amount of blank space at the original stage from the beginning, the blank area changing means 1
It is necessary to cancel the function of 4c. If the operation unit 20 is provided with a mode changeover switch in advance in order to respond to such a request, the image data is transmitted to the light emission control unit 14b via the blank area changing unit 14c in FIG. Alternatively, the image data can be sent to the light emission control unit 14b via the white area change unit 14c.

As described above, in this example, the image area ratio is set to 10
By setting the blank width of the sheet-like medium in consideration of only the length of the transfer paper, it is assumed to be 0%, so that a simple configuration can be achieved without using a controller or the like as in the related art, and without the need for memory development. Accordingly, the transfer roller can be prevented from being stained due to the image elongation, and the back stain on the sheet-like sheet can be eliminated. [3] Example Corresponding to Claims 3 to 6 FIG. 6 shows the data of the image area ratio and the image elongation ratio of the A3-size transfer paper shown in Table 1 in a chart, and FIG. Can be approximated to a quadratic curve.
It was found from experiments that the elongation rate of the image was a constant rate corresponding to the image area rate, and the contribution of the length of the transfer paper was small.

In this embodiment, the control means 14 shown in FIG. 3 uses the blank area changing means 14a to expand the image of the sheet-like medium to be transferred, that is, the image length determined by the length of the transfer paper in the traveling direction and the image area ratio. The blank area on the rear end side in the traveling direction of the sheet medium to be transferred is set according to the amount. Note that the function of the control means 14 in this example does not set the blank area width as a fixed value according to the length of the transfer sheet as in the example described in [3] above, but follows the following equation. .

The amount of elongation (= white area width) d of the image is d = α ×
L can be approximated. In this equation, L is the length of the transfer sheet in the traveling direction, and the image data signals SG1, SG2,
The control means 14 can recognize the length L from the image forming condition data signal SG3, a signal from a sensor for detecting the setting state of the cassettes 12, 13, and the like. α is a constant, and in the quadratic curve of FIG. 7, α = −9E−7X ² + 0.002X−
Determined at 0.003. Here, X is the image area ratio in the transfer paper.

Here, the image area ratio is the ratio of the image to the area of the transfer paper, and can be obtained from the writing time per page by the writing means 3. Further, the writing time per page is determined by the light emitting unit 3a per page.
Since the light emission time is a value that can be known from the information from the image data signal in the control means 14, the amount of elongation (= white area width) d of the image is calculated by information processing inside the control means 14. You can set the amount of white spots. Since the image of one page of the image data is equivalent to the image to be transferred to the transfer paper, the amount of expansion of the image can be calculated for each page to set the white spot amount.

The image area ratio is the ratio of the image to the area of the transfer paper, and since the image is a set of pixels, the image area ratio can be calculated from the amount of pixels per page. Since the pixel amount per page is also a value that can be known from the information from the image data signal in the control unit 14, the amount of expansion (= white area width) d of the image is calculated by the information processing inside the control unit 14 and white The amount of omission can be set.

Further, since the toner density detection sensor 5 is a sensor capable of detecting the toner density, the toner density detection sensor 5 detects the toner density only by detecting a part of the front end portion of the page. Thus, it is possible to estimate the image area of the toner image of the page to be transferred in the next process.

Therefore, as shown in FIG. 3, the toner density detection information Q obtained by sampling the toner density at the leading end of the page detected by the toner density detection sensor 5 is used as the white area changing means 1.
4c, the input information processing inside the control means 14 calculates the amount of elongation (= blank width) d of the image, and changes the write information at the rear end in the transfer paper advancing direction. Set the amount of white spots.

[0044]

According to the first and second aspects of the present invention, the image area ratio is taken as 100%, and the blank width of the sheet-like medium is set in consideration of only the length of the transfer paper, so that a simple configuration is achieved. Accordingly, the transfer roller can be prevented from being stained due to the image elongation, and the back stain on the sheet-like sheet can be eliminated.

According to the third aspect of the present invention, the white area can be accurately set by setting the white area in consideration of the image area ratio and the length of the sheet medium to be transferred in the traveling direction. The image area that can be written can be increased.

According to the fourth and fifth aspects of the present invention, the white area can be easily set by the internal processing of the control means. According to the sixth aspect of the present invention, the white area can be easily set by the internal processing of the control unit using the existing toner density detection sensor without adding a new component.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an outline of an overall configuration of an image forming apparatus.

FIG. 2 is an enlarged view of an image forming process unit.

FIG. 3 is a block diagram illustrating a configuration of a control unit.

FIG. 4 is a diagram illustrating an image area (hatched portion) and a blank portion on a transfer sheet.

FIG. 5 is a diagram illustrating an image area (hatched portion) and a blank portion on a transfer sheet.

FIG. 6 is a graph showing a relationship among an image area ratio, an image elongation ratio, and a writing length.

FIG. 7 is a graph in which a relationship between an image area ratio, an image elongation ratio, and a writing length is approximated by a quadratic curve.

[Explanation of symbols]

 6 Transfer roller 14 Control means S1, S2 Transfer paper Δ1 (Defines blank area) Margin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Yoshinami 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Co., Ltd. (72) Inventor Noriyuki Usui 1-3-6 Nakamagome, Ota-ku, Tokyo Ricoh Co., Ltd. (72) Mayumi Ohori, inventor 1-3-6 Nakamagome, Ota-ku, Tokyo ・ Ricoh Co., Ltd. (72) Inventor Toshitaka Yamaguchi 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (72) Inventor Ken Amamiya 1-3-6 Nakamagome, Ota-ku, Tokyo, Japan Incorporation Ricoh (72) Kenzo Tatsumi 1-3-6 Nakamagome, Ota-ku, Tokyo, Co., Ltd. Ricoh (72) Inventor Hiroshi Mizusawa 1-3-6 Nakamagome, Ota-ku, Tokyo, Ricoh Company (72) Inventor Shinichi Kamiyama 1-3-6, Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H027 DB01 DE07 ED02 ED04 ED16 ED24 FD04 2H032 AA05 BA30

Claims (6)

[Claims] An image forming method for electrostatically transferring a toner image formed on an image carrier onto a sheet-like medium using a transfer roller driven at a peripheral speed different from that of the image carrier. An image forming method for writing an image on the image carrier by changing a blank area on the rear end side in the traveling direction according to the length of the sheet-shaped medium in the traveling direction. 2. An image forming apparatus for electrostatically transferring a toner image formed on an image carrier onto a sheet-like medium using a transfer roller driven at a different peripheral speed from the image carrier. An image forming apparatus having control means for changing a white blank width from a normal blank blank width to a predetermined blank blank width. 3. The image forming apparatus according to claim 2, wherein the control means determines the length of the image in the advancing direction of the sheet-shaped medium to be transferred and the amount of elongation of the image determined as a function of the image area ratio. An image forming apparatus for setting a blank area on the trailing end side of a sheet-shaped medium to be advanced in a traveling direction. 4. An image forming apparatus according to claim 3, wherein said control means converts said image area ratio by a writing time of said writing means on said image carrier. 5. The image forming apparatus according to claim 3, wherein the control unit converts the image area ratio based on a pixel amount of an image to be written on the sheet medium. . 6. An image forming apparatus according to claim 3, wherein said control means converts said image area ratio based on detection information sampled by an image density detection sensor.