JP3327737B2 - 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 for forming an image on a recording material.

[0002]

2. Description of the Related Art Conventionally, a density control device of an image forming apparatus has
JP-A-56-7230, JP-A-56-7231, JP-A-62-50818, JP-A-63-1
No. 25338, JP-A-62-291265,
As described in detail in JP-A-1-222273, a sample image is formed on a photosensitive drum or a recording material as a latent image carrier, and the surface potential of the photosensitive drum is determined based on the density of the sample image. , Exposure light amount, developing bias voltage,
By controlling the carrier-to-toner ratio in the developing device and correcting the transfer condition, the density characteristics and the gradation characteristics of the output image are kept constant.

[0003]

However, in the above-mentioned conventional example, the toner on the toner carrier as the developer carrier has not been studied. Layer thickness,
An error may occur in the detection of a sample image due to a change in toner density or toner tribo.

As a result, the density of a sample image is different from the density of an actual image, and the color balance may be lost in a color image forming apparatus or the like.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus which does not cause a density difference between a sample image and an actual image.

[0006]

According to the present invention, an object of the present invention is to provide a latent image carrier having a photosensitive layer on its surface, a charging means for uniformly charging the latent image carrier surface, and Exposure means for exposing the surface of the latent image carrier, a developer carrier for carrying and transporting the developer, and developing the electrostatic latent image formed on the surface of the latent image carrier by exposure with the developer, and a latent image carrier In an image forming apparatus including a transfer unit that transfers a developer image formed on a surface onto a recording material and a density detection unit that detects the density of a sample image, the density detection unit may be used.
Image density based on multiple sample images detected
Degree is controlled, the peripheral length of the developer carrier is L, and the ratio of the peripheral speed of the developer carrier to the peripheral speed of the latent image carrier is N,
The traveling direction of the length of the sample image is shorter than L / N, the upper
The distance between the trailing edge of the preceding sample image and the leading edge of the next sample image is longer than L / N.

[0007]

According to the present invention, assuming that the peripheral length of the developer carrier is L and the ratio of the peripheral speed of the developer carrier to the peripheral speed of the latent image carrier is N, one rotation of the developer carrier is achieved. The length of the image formed on the latent image carrier is represented by L / N. Since the length of the sample image in the traveling direction is shorter than this length L / N, a plurality of sample images are developed. The developer carrier is formed before one rotation, and the developer characteristics when forming a single sample image are uniformed. Further, the distance between the trailing edge of the preceding sample image and the leading edge of the next sample image is longer than the above-mentioned length L / N, so that the developer carrier rotates one or more rotations before the next sample image is formed. That is, the characteristics of the developer are stabilized, and no density difference is caused by the influence of the sleeve ghost.

[0008]

An embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a view for explaining one embodiment of the present invention, in which an organic semiconductor, selenium, zinc oxide, amorphous silicone, or the like is applied or deposited as a photosensitive layer on a metal cylinder such as an aluminum cylinder as a conductor. Is a latent image carrier (hereinafter, referred to as a photoconductor) 1,
At the same time as rotating the photoconductor 1 in the direction of the arrow, the photoconductor 1 is uniformly charged by conventionally known contact charging, corona discharge, or the like. In this apparatus, a DC voltage of -700 V is superimposed on an AC voltage of 1500 Vp-p (peak-to-peak voltage; the same applies hereinafter) by a power source (not shown) on the contact charging member 4 as a charging means, and the surface of the photosensitive member is approximately It is uniformly charged to -700V.

Next, an electric signal of the sample image is applied to the laser driver 6 from the pattern generator 5 to emit light from the laser 7, and the polygon mirror 8, the optical lens 9, and the folding mirror 1 rotated at high speed.
Irradiation is performed on the photoconductor 1 through the photoreceptor 0 to form a latent image.

The latent image formed on the photoreceptor 1 by the exposure means is developed by a developing device. The developing device 11Y includes a stirring member 13, a toner application roller 14, A toner carrier 15 as an agent carrier and a toner regulating member 16 are arranged, and when the stirring member 13 rotates in the direction of the arrow, the toner in the toner container 12 is further transferred to the application roller 14 side to the toner carrier 15, A uniform toner thin layer is formed on the toner carrier 15 by the toner regulating member 16.

When the distance between the toner carrier 15 and the photoconductor 1 is 300 μm, the thin toner layer is
Further, a so-called reversal development in which a DC component of -600 V is superimposed on the AC voltage of 2000 Vp-p and toner adheres to the above-described exposed portion (approximately -100 V) is performed.

The first sample image formed on the photoreceptor 1 by the above-described process is transferred by forming conductive urethane foam 20 on a metal cylinder 19 and polychlorinated bifinyl (PVdF) on the outer surface. The image is transferred onto the transfer drum 18 as a means by applying a transfer bias between the photoconductor 1 and the transfer drum 18. Next, by changing the developing conditions, for example, by setting the DC component from the developing bias power supply 17 to -550 V, the second sample image, -5
The Nth sample image is formed with a change of about 50 V like the third sample image at 00V.

The density of these sample images is read by the light emitting element 22 and the light receiving element 23 shown in FIG. 3, and the read output is compared by the reference comparator 24. The compared output determines an appropriate value, and the developing bias power supply 17 is turned on. By controlling, a stable image can always be obtained.

However, as shown in FIG. 2, when a sample image is to be formed, the thickness of the toner layer on the toner carrier 15, the density of the toner, and the tribo of the toner change. An error occurs. This is because, as is conventionally known, an image pattern preceding the next image is left on the toner carrier 15 and a so-called sleeve ghost (on the toner carrier) appears.

Therefore, in the present invention, when forming a sample image within one round of the toner carrier 15 and forming at least the next sample image after forming the preceding sample image, the toner carrier 15 is rotated by one rotation. I will do more.

Hereinafter, a description will be given using specific numerical values.
The linear velocity of the photoconductor 1 was selected to be 100 mm / sec, the diameter D of the toner carrier 15 was 16 mm, and the linear velocity was 150 mm / sec.
When a sample image is formed in seconds (usually 1 to 2 times), the circumference L of the toner carrier 15 is represented by πD = π × 16 mm, and the speed ratio N between the photoconductor 1 and the toner carrier 15 is 1 .5 times.

As described above, the sample image is transferred to the toner carrier 1
5, the length of the sample image in the traveling direction needs to be L / N mm or less.
To make the interval between the preceding sample image and the next sample image equal to or longer than the length when the toner carrier is rotated one or more times, the distance between the trailing end of the preceding sample image in the traveling direction and the leading end of the next sample image is L / N mm or more is required.

In this embodiment, as a result of forming a sample image under such a setting, it was found that the above-mentioned sleeve ghost was canceled.

Normally, when forming an image, the image area of the majority is as low as about 7 to 8%, and the characteristics of the toner are usually developed in a state where the toner has passed through the toner regulating member 16 a plurality of times. Since the image had a large image area and was developed only after passing through the toner regulating member 16 once, the characteristics of the toner were not stable, and the above-mentioned sleeve ghost appeared.

However, according to the present invention, the sample image is developed with toner that has passed through the toner regulating member 16 a plurality of times, so that the density detected in the sample image always matches the image density of the image formed. I found out.

In the above description, only one color has been described. For example, by controlling the yellow color 11Y as the first color, switching development thereafter, and performing the same processing for the magenta color 11M, the cyan color 11C, and the black color 11BK, All development corrections may be performed.

After completion of such correction, the transfer drum 18 may be cleaned by a transfer cleaning means 25 such as a fur brush. Further, the transfer residual toner on the photoconductor 1 is cleaned by a known blade unit 26 or the like.

Further, after the above-described process, the recording material P is fed to the transfer drum 18 and image light of a yellow image pattern is given from the laser 7 in the same manner as in the sample image formation. Transcribe. In this process, the magenta, cyan, and black processes are performed.
7. Peeled off by the action of the separation claw 28 and fixed and fixed by the fixing device 29. This image forming method is disclosed in
The details are described in, for example, Japanese Patent No. 50935.

In the above description, the method of optimizing the maximum density has been described. For example, when controlling the density of the half tone,
After optimizing the maximum density, the development conditions are fixed,
Arbitrarily select a plurality of output signals from the pattern generator,
A method of forming a plurality of sample images and selecting an appropriate characteristic from the density output may be used. These methods are described in detail in JP-A-63-125338.

In the above description, the output of density detection (change of the light receiving element) is fed back. However, the amount of emitted light is changed so that the amount of reflected light is kept constant, and the level of this emitted light is fed back. May be.

When a sample image is formed on the transfer drum 18 as shown in FIG. 4 in addition to FIG. 2, yellow, then magenta, cyan,...

The present invention is also applicable to an intermediate transfer method or a method of performing collective transfer after multiple development.

In the above description, one-component development has been described, but an apparatus for mixing a carrier and a toner, such as two-component development, can be applied.

When the first image sample is formed, the toner carrier is turned at least one rotation before the first image sample is formed, so that the sample image having the same characteristics as the second image sample and thereafter is formed. Is obtained.

Further, in the above embodiment, the case where a sample image is formed on a transfer drum has been described. However, the present invention can be applied to other methods, for example, a case where a sample image is formed on a photosensitive drum or a recording material. It is.

[0031]

As described above, according to the present invention,
Multiple sample images detected by the density detection means
The density of the image is controlled on the basis of the peripheral length of the developer carrier, and the ratio of the peripheral speed of the developer carrier to the peripheral speed of the latent image carrier is N. Is L /
Shorter than N, since the preceding sample images rear and the distance of the next sample image tip among the plurality of sample images have length than L / N, the characteristics of the developer is stabilized, generating a density difference due to the sleeve ghost Therefore, there is no difference in density between the sample image and the actual image, and the color balance is not lost in the color image forming apparatus.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a sample image on a transfer drum according to an embodiment of the present invention.

FIG. 3 is a diagram showing a concentration detecting device according to one embodiment of the present invention.

FIG. 4 is a diagram in which the sample images of FIG. 2 are arranged in all colors.

[Description of Signs] 1 Photoconductor (latent image carrier) 4 Contact antistatic member (charging unit) 7 Laser (exposure unit) 15 Toner carrier (developer carrier) 18 Transfer drum (transfer unit) 22 Light emitting element (density) Detecting means) 23 light receiving element (density detecting means) P recording material

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroshi Sasame 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tetsuya Kobayashi 3-2-2 Shimomaruko, Ota-ku, Tokyo Canon Inside (72) Inventor Yoichiro Maebashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Akihiko Uchiyama 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. ( 72) Inventor Takaaki Tsuruya 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Tatsuya Kobayashi 3-30-2, Shimomaruko 3-chome, Ota-ku, Tokyo Canon Inc. (56) References JP-A-1-221775 (JP, A) Japanese Utility Model Application No. 55-4403 (JP, U) Japanese Utility Model Application No. 62-104256 (JP, U) Japanese Utility Model Application No. Sho 62-27356 (JP, U) (58) Field (Int.Cl. ^7, DB name) G03G 15/08

Claims (3)

(57) [Claims] 1. A latent image carrier having a photosensitive layer on its surface, charging means for uniformly charging the latent image carrier surface, exposure means for exposing the charged latent image carrier surface to light, and developer Carrying the developer and developing the electrostatic latent image formed on the surface of the latent image carrier by exposure with a developer, and transferring the developer image formed on the surface of the latent image carrier to a recording material. In an image forming apparatus including a transfer unit and a density detection unit that detects the density of a sample image, a plurality of sample images detected by the density detection unit
The density of the image is controlled on the basis of the peripheral length of the developer carrier, and the ratio of the peripheral speed of the developer carrier to the peripheral speed of the latent image carrier is N. Is L /
An image forming apparatus, wherein the distance between the trailing end of the preceding sample image and the leading end of the next sample image among the plurality of sample images is longer than L / N. 2. The method according to claim 1, wherein the plurality of sample images have different densities.
The image form according to claim 1, wherein the image form is formed by:
Equipment. 3. The method according to claim 2, wherein the plurality of sample images are the developer
By changing the developing bias applied to the carrier,
Characterized in that they are formed at different concentrations.
3. The image forming apparatus according to 2.