JP2003149911A - Color image forming apparatus and color image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress uneven hues in an image and between images caused by color mixed recycle toner in a tandem color image forming apparatus using the recycle toner in a state of color mixture with new toner for image forming. SOLUTION: Each image forming unit whose transfer order of a toner image to a transfer material is on and after a second color is provided with a recycle toner feed route to feed the color mixed recycle toner recovered with a doctor blade 34 to each developing device, and a new toner feed route to feed new toner to each developing device. The new toner and color mixed recycle toner which have passed through the feed routes are mixed by a mixing means such as a sieve 40, and the mixed toner is fed to the developing device 30. The rate of color mixture of a developer on a developing sleeve 31 is measured by a reflectance measuring apparatus 35, and the ratio of an amount of supply to the developing device of new toner and color mixed recycle toner is set according to the rate of color mixture.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming technique, and more specifically, it is equipped with an image forming unit corresponding to each color and a cleaning device, so that the toner collected from the image carrier by the cleaning device can be reused. The present invention relates to a color image forming apparatus using an electrophotographic process and a color image forming method using the same.

[0002]

2. Description of the Related Art In a color image forming apparatus using an electrophotographic process, four color (or three color) toner images are formed on an image carrier (photoreceptor) and transferred onto an intermediate transfer body or transferred. By superposing it on a transfer material (recording material) conveyed by a belt (transfer material conveying body), a full-color image is finally formed on the transfer material. In this color image forming apparatus, (1) a four-color toner image is sequentially formed by one or two image carriers, and (2) an image carrier for each of the four colors, and an image carrier. There is a device provided with a developing device for forming a toner image thereon and a cleaning device for cleaning (removing / collecting) the toner on the image carrier.
The latter color image forming apparatus is usually of a so-called tandem type in which the respective colors are arranged in a straight line along the running direction of the intermediate transfer body or transfer belt.

The tandem system is excellent in high speed because it can simultaneously form toner images of four colors. Further, since the image carrier cleaning device is provided for each color, the collected toner cleaned from the image carrier can be easily recycled for reuse for image formation.

By the way, in a color image forming apparatus, the number of colors of toner used is large, and a document having a large image area ratio such as a photographic document is often output as compared with black and white. It is important to recycle toner from the viewpoint of cost reduction.

However, in reality, there are some problems. One is the problem of color mixing that occurs when the upstream color mixes into the downstream color process. Therefore, several patent applications have been filed regarding the invention for preventing this color mixture.

For example, in the color image forming apparatus disclosed in Japanese Unexamined Patent Publication No. 2000-242152, one of the toner particles transferred onto the intermediate transfer member is discharged by the electric discharge when transferring from the image carrier on the upstream side to the intermediate transfer member. The part has a charging polarity opposite to the normal charging polarity, and the toner having the opposite charging polarity is
When the toner of the color on the downstream side is transferred, it is considered that the toner is transferred to the image carrier in reverse, and by providing a recovery means for recovering the reversely transferred toner by utilizing the fact that the charging polarity is opposite, Color mixture on the image carrier is prevented.

However, this image forming apparatus is disadvantageous in terms of space and cost because it is necessary to provide a collecting means, which is not necessary in the past, near the image carrier (photoconductor).
In addition, the toner charged with the opposite polarity is originally stable in the normal charge polarity, and the charge amount of the opposite polarity toner is not stable,
Since there are many toners that have a charge that is almost "0", it is difficult to completely collect them by the collecting means, and the problem of color mixing cannot be fundamentally solved.

On the other hand, in the image forming apparatus described in Japanese Unexamined Patent Publication No. 10-293432, a method of eliminating the background potential before transfer in order to prevent the reverse charging of toner which causes reverse transfer although it is not a tandem system. Has been taken. The level of charge removal is adjusted so that the toner image before transfer does not scatter, but in reality, the charge is rapidly reduced by light removal, so the toner in the image area moves to the periphery and the image blurs. I will end up. If the charge is removed less, discharge will occur and color mixture due to reverse transfer cannot be prevented. Thus, it is very difficult to completely prevent color mixing.

Further, in Japanese Patent Laid-Open No. 8-63067 and Japanese Patent Laid-Open No. 2000-267366, as problems associated with toner collected by cleaning, toner aggregation and deterioration of toner charging characteristics are mentioned, and recycled toner is An invention that optimizes process conditions by determining the supply ratio is disclosed. However, these inventions are not intended to properly use the recycled toner by paying attention to the color mixing state of the toner and detecting or predicting this.

As described above, in the electrophotographic color image forming apparatus, the toner images corresponding to the respective colors on the image carrier are directly or indirectly transferred to the transfer material to form a color image. However, in each image carrier, it is inevitable that part of the toner (toner image) carried on the image carrier is not transferred to the transfer material and remains on the image carrier. The remaining toner is removed and collected by the cleaning means provided in each image carrier. In the case of the tandem system in which the image carrier is provided in the number corresponding to the number of colors, each cleaning means cleans the toner of the color corresponding to the image carrier, and thus the collected toner is recycled to the developing means of that color and re-formed for image formation. It is easy to use. However, in the case of the tandem system, since the image forming systems for the respective colors are independent of each other, there should ideally be no color mixing, but in reality, color mixing is inevitable. This color mixture occurs in the process of transferring the toner images of the respective colors from the image carrier to the transfer material.

Now, consider a case where a toner image is overlapped and transferred from an image carrier of each color on a transfer material conveyed by a transfer belt in a tandem system to form a color image on the transfer material. When the toners (toner images) of the second and subsequent colors (including the second color) on the image carrier are transferred to the transfer material, it goes without saying that the color of the color transferred on the upstream side in the transfer material moving direction is transferred onto the transfer material. Toner is on. The upstream color toner on the transfer material is reversely transferred from the transfer material to the image carrier at the time of transferring the downstream color, and the reversely transferred toner is collected by the downstream color cleaning (for example, the first color toner is the second color toner). The toner of the first color is reversely transferred to the image carrier and is collected by the cleaning means of the second color.) The upstream color is mixed with the toner collected by the cleaning means of the downstream color, so that color mixing occurs.

In the prior art, in the case of a toner having a color mixture, the toner is mixed with the black toner and reused,
It was discarded as waste toner. However, if all the mixed color toners are mixed with the black toner, it becomes difficult to balance the amount of toner actually consumed and the amount of toner supply to the developing means. Depending on the type of image to be formed, an image forming apparatus often uses a document such as a photographic image having a small black ratio, and the amount of recycled toner mixed (cleaning and recovery toner) that is mixed is the consumed toner. A reversal phenomenon that is larger than the quantity may occur.

As described above, in the conventional color image forming apparatus, the toner is collected from the image carrier of each color and the collected toner is directly recycled to the developing means corresponding to the image carrier from which the toner is collected (for example, magenta toner). The toner collected from the image carrier using the toner is supplied to the developing means using magenta toner.), And the hue of the toner in the developing means is
There is a problem that the state where there is no color mixture gradually changes greatly with the lapse of image forming time.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems of the prior art, and its object is to use a tandem type color image in which a recycled toner in a mixed color state is used together with a new toner for image formation. It is an object of the present invention to provide a color image forming apparatus and a color image forming method capable of suppressing hue unevenness in an image and between images due to the mixed color recycled toner and stably obtaining an image having a uniform hue.

[0015]

According to a first aspect of the present invention, a plurality of image forming units each including at least an image carrier and a developing unit and a toner image formed on the image carrier are used as a transfer material. A toner image is transferred to a transfer material in an electrophotographic color image forming apparatus including a transfer unit that transfers and a cleaning unit that removes and collects toner remaining on the image carrier after passing through the transfer unit. For each image forming unit of the second and subsequent colors, a recycled toner supply path for supplying the mixed color recycled toner collected by the cleaning means (hereinafter, mixed color recycled toner) to each developing means, and a new toner (unused toner) And a new toner supply path for supplying to each developing means.

The invention according to claim 2 is the color image forming apparatus according to claim 1, characterized in that the new toner and the mixed color recycled toner are separately supplied to the developing means.

According to a third aspect of the present invention, the new toner and the mixed color recycled toner are mixed by the mixing means, and then the mixed toner is supplied to the developing means.
And the color image forming apparatus.

The invention according to claim 4 is the color image forming apparatus according to claim 3, characterized in that the mixing means is a sieve.

According to a fifth aspect of the invention, there is provided a first color mixing ratio detecting means for detecting the color mixing ratio of the color mixing recycled toner, and the supply of the color mixing recycled toner and the new toner to the developing means based on the signal from the detecting means. A toner supply amount determining unit that determines the amount, a recycled toner supply device that can vary the supply amount of the mixed color recycled toner according to the determination of the toner supply amount determining unit, and a new toner supply amount according to the determination of the toner supply amount determining unit. 5. A color image forming apparatus according to claim 1, further comprising a variable new toner supply device.

According to a sixth aspect of the present invention, the first color mixing ratio detecting means is a reflectance measuring device for measuring the light reflectance of the mixed color recycled toner, and the color image according to the fifth aspect. It is a forming device.

In the invention according to claim 7, the first color mixing ratio detecting means includes a calculation section for calculating the color mixing ratio based on the image signal, and the color image according to claim 5 It is a forming device.

The invention according to claim 8 is the color image forming apparatus according to claim 2, wherein the ratio of the supply amount of the new toner and the recycled toner of mixed color to the developing means is made constant. .

According to a ninth aspect of the present invention, there is provided a second color mixing ratio detecting means for detecting the color mixing ratio of the toner in the developing means, and a developing means for the color mixing recycled toner and the new toner based on a signal from the detecting means. Toner supply amount determining unit that determines the supply amount of the toner, a recycled toner supply device that can vary the supply amount of the mixed color recycled toner according to the determination of the toner supply amount determining unit, and the supply of new toner according to the determination of the toner supply amount determining unit. The color image forming apparatus according to any one of claims 1 to 4, further comprising a new toner supply device whose amount can be changed.

According to a tenth aspect of the present invention, the second color mixing ratio detecting means is a reflectance measuring device for measuring the light reflectance of the toner on the developing sleeve constituting the developing means. Item 9. The color image forming apparatus according to Item 9.

According to the eleventh aspect of the present invention, the first color mixing rate detecting means or the second color mixing rate detecting means is configured to mix the color A and the color A.
6. A light source for irradiating a detected part with light having a wavelength having a large spectral reflectance difference from + B, and a light receiving part for measuring the intensity of reflected light from the detected part. , 6, 9 or 10 is the color image forming apparatus.

According to a twelfth aspect of the present invention, a plurality of image forming units including at least an image carrier and a developing unit, a transfer unit for transferring a toner image formed on the image carrier to a transfer material, In an image forming method using an electrophotographic color image forming apparatus having a cleaning unit that removes and collects toner remaining on the image carrier after the transfer unit has passed, the order in which toner images are transferred to a transfer material is For each of the image forming units of the second and subsequent colors, the color-mixed recycled toner collected by the cleaning unit (hereinafter, color-mixed recycled toner) is supplied to the image carrier that constitutes each image forming unit via each developing unit. At the same time, new toner (unused toner) is supplied to the image carrier that constitutes each image forming unit through each developing means. A color image forming method characterized by.

The thirteenth aspect of the present invention is the color image forming method according to the twelfth aspect, wherein the new toner and the mixed color recycled toner are separately supplied to the developing means.

The invention according to claim 14 is the color image forming method according to claim 12, characterized in that the new toner and the mixed color recycled toner are mixed and then this mixed toner is supplied to the developing means. .

According to a fifteenth aspect of the present invention, the color mixture ratio of the color mixture recycled toner is detected, and the amount of the color mixture recycled toner supplied to the developing device and the amount of the new toner supplied to the developing device are detected based on the detection result of the color mixture ratio. 15. The color image forming method according to any one of claims 12 to 14, characterized in that

According to a sixteenth aspect of the present invention, when it is necessary to supply toner to the developing means, the new toner and the mixed color recycled toner are supplied to the developing means at a constant ratio. Item 13. The color image forming method according to Item 13 or 14.

According to the seventeenth aspect of the present invention, the color mixture ratio of the toner in the developing means is detected, and based on the result of the color mixture ratio detection, the supply amount of the color mixture recycled toner to the developing means and the new toner of the developing means. 13. The color image forming method according to claim 12, wherein the supply amount is determined.

In the eighteenth aspect of the present invention, when detecting the color mixture ratio of the color mixture recycled toner, the toner of the color mixture A + B is irradiated with light having a large difference in spectral reflectance between the color A and the color mixture A + B. The color mixing ratio is determined by obtaining the reflectance by measuring the reflected light intensity and comparing the reflectance data of the color A + B having a known color mixing ratio with the measured reflectance. 17 is a color image forming method.

[0033]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. First Embodiment (Claims 1, 2, 12 and 13) A color image forming apparatus according to the present embodiment includes an image carrier for each color, and charging, exposure, development and transfer corresponding thereto. A so-called tandem system in which each of the cleaning means is provided and after the toner image is formed on the image carrier, the toner images are transferred to a transfer material (for example, recording paper) conveyed by a transfer belt in an overlapping manner to obtain the image. Color image forming apparatus.

The inventor studied the influence of the toner color mixing ratio on the hue of the finally obtained color image.
As a result, an image forming unit (photoreceptor,
(Provided with a developing device, etc.) and a route for supplying the mixed-color recycled toner collected from the developing device of the image forming unit of the collecting source and a route for supplying new toner of each color to the developing device of the image forming unit of the corresponding color. The color image forming apparatus is configured to adjust the ratio of the supply amount of the mixed color recycled toner and the new toner to the developing device, that is, the usage rate of the photoconductor within an appropriate range, thereby changing the hue of the color image. It has been confirmed that the toner can be controlled within an allowable range, and thus the toner can be reused. The present embodiment is a specific example of such a color image forming apparatus.

An experiment was conducted in the color image forming apparatus (full color copying machine) shown in FIG. First, the configuration of the image forming apparatus and its operation will be described. Reference numerals 1a, 1b, 1
Both c and 1d are photoconductors. Reference numeral 2 is a developing device,
3 is a cleaning device, 4 is a charging device, 5 is a writing device, 6 is a transfer conveyance belt, and 7 is a fixing unit. Since an image forming unit having the same configuration is provided around each of the photoconductors, the photoconductor 1a will be mainly described below. The photoconductor 1a rotates counterclockwise.

The toner image developed on the photoconductor 1a is transferred onto the transfer material on the transfer / transport belt 6 at the transfer portion of the photoconductor 1a. Then, on the transfer material, the photoconductors 1b, 1
The toner images are transferred at the transfer portions c and 1d to form a full-color image. This full-color image is the fixing unit 7
Is heat fixed in. On the other hand, the toner not transferred from the photoconductor 1 a to the transfer material remains on the photoconductor 1 a and is collected by the cleaning device 3. The above is the description of the image formation by the photoconductor 1a located on the leftmost side in FIG.

The image formation by the other photoconductors 1b to 1d is almost the same as that by the photoconductor 1a, but is different in the following points. At the time of transferring the toner image from the photoconductors 1b to 1d to the transfer material, the toner image transferred on the upstream side in the transport direction of the transfer material already exists on the transfer material, and the toner image is located on the downstream side of the photoconductor 1b. Reverse transfer to ~ 1d. For example, the photoconductor 1a
Part of the transferred toner image on the transfer material from the
A part of the transferred toner image on the transfer material from the photoconductor 1b is reversely transferred to the photoconductor 1c.

Now, let us consider the photoconductor 1b of the second color, counting from the left in FIG. When the toner is transferred from the photoconductor 1b to the transfer material on the transfer conveyance belt 6, the toner transferred from the photoconductor 1a is already on the transfer material. When the toner is transferred from the photoconductor 1b to the transfer material, the transfer material and the photoconductor 1b come into close contact with each other, and a part of the toner already on the transfer material is reversely transferred to the photoconductor 1b.

If the photoconductor 1a is a yellow (Y) image forming part and the photoconductor 1b is a magenta (M) image forming part, after transfer of the toner image on the photoconductor 1b, it is the transfer residual toner. The magenta toner of No. 2 and the yellow toner of the upstream color which is the reverse transfer toner are present on the photoconductor 1b, and both are removed by the cleaning device. The recycled toner collected by this cleaning device is a mixed color toner in which yellow and magenta are mixed. Therefore, when this mixed color recycled toner is supplied to the magenta developing device and is used again for development, the yellow toner is mixed in the toner of this developing device.

FIG. 2 is a plan view showing an image forming structure of each color constituting the two-component developing type color image forming apparatus according to the present invention. The right side of the drawing is the front side of the apparatus main body and the left side is the back side. is there. In this image forming apparatus, a recycle toner supply path for supplying a mixed color recycle toner (and a carrier) to each developing means and a new toner for each image forming section in which a toner image is transferred to a transfer material in the second color and thereafter. And a new toner supply path for supplying each developing means to each developing means, and the new toner and the mixed color recycled toner are separately supplied to the developing means.

The reference numerals shown in FIG. 2 will be explained.
20 is a developing device, 21 is a cylindrical photosensitive member, 22a and 22b are stirring screws, and 23 is a developing device for recycling toner 20.
To the first recycled toner supply path, 24 is also the second recycled toner supply path, 25 is a developing sleeve, 26 is a toner bottle filled with new toner, 27
Is a new toner supply path for supplying new toner to the developing device 20, and 28 is a reflectance measuring device for measuring the reflection density (light reflectance) of the toner. Toner conveying means (auger, mohno pump, etc.) is provided in the first recycled toner supply path 23.
However, the second recycled toner supply path 24 is provided with measuring / conveying means such as a conveying roller and a screw conveyor, respectively. The new toner supply path 27 is also provided with a measuring / conveying means such as a conveying roller and a screw conveyor. The first recycled toner supply path 23 may be formed from the cleaning device side (not shown) to the stirring screw 22b side with a downwardly sloping bottom surface, and the recycled toner may be conveyed by its own weight.

In the image forming process (image forming process) by this image forming apparatus, the photoconductor 21 rotates clockwise as viewed from the front side of the apparatus main body, and the developing sleeve rotates counterclockwise. The toner in the toner bottle 26 is measured by the measuring / conveying means provided in the new toner supply path 27, and is supplied to the right end portion of the stirring screw 22a in FIG. The recycled toner (and the carrier) collected by the cleaning device (not shown) passes through the first recycled toner supply path 23, and then is measured by the measuring / conveying means provided in the second recycled toner supply path 24, and the stirring screw is used. It is supplied to the left end of 22a. The recycled toner is conveyed in the direction of the arrow by the stirring screw 22a and merges with the new toner at the right end portion thereof. Next, the combined toner is conveyed in the direction of the arrow by a stirring screw 22b on the lower side of the drawing, and the stirring screw 2 is provided at the left end portion thereof.
Flows into 2a. Thus toner (and carrier)
Is partially supplied to the developing sleeve 25 while being circulated and conveyed through the stirring screws 22a and 22b.

In the present embodiment, it is possible to prevent the color mixture from becoming excessive by appropriately controlling the supply amount ratio of the recycled toner and the new toner to the developing sleeve 25.

Example 1 The degree of color mixing is determined from the relationship between the color mixture rate and the color difference, and the degree of color mixing is determined by the target color difference. In Example 1 according to the present embodiment, control was performed with a target color mixing ratio within 10%. The ratio of the supply amount of the recycled toner and the new toner to the developing device was set to 1:10. Originals of landscapes, people, and catalogs were copied by an image forming apparatus provided with image forming units (photoreceptors, etc.) in the order of yellow, magenta, cyan, and black in the running direction of the transfer material.
Therefore, the degree of color mixing of yellow with respect to magenta was evaluated. Make 1000 copies of each original, 1
As a result of measuring the color difference every 00 sheets, all were within the target color difference.

As described above, in the image forming apparatus according to the first embodiment, the new toner and the mixed color recycled toner are separately supplied to the developing means, so that the adjustment of the mixed color amount becomes easy. Further, it becomes possible to supply the required amount of the new toner and the recycled toner of the mixed color to the developing means, and the holding state of each toner in the developing means can be adjusted with a small time delay.

Second Embodiment (Claims 3 and 14) The color image forming apparatus according to the present embodiment is provided with a means for mixing the color-mixed recycled toner and the new toner before feeding them to the developing device. There is a feature in having it. According to such an image forming apparatus, the mixed color toner becomes evenly distributed in the mixed toner of the recycled toner and the new toner, which causes a problem that the mixed color is conspicuous on the image (due to the concentration of the mixed color toner). Can be resolved.

FIG. 3 is a front sectional view showing the structure of the main part of such an image forming apparatus, which corresponds to a part of the right side sectional view of FIG. The reference numerals in the figure will be described.
Reference numeral 0 is a developing device, 31 is a developing sleeve, and 32 is a mixer including two screws 32a and 32b. A pre-stirring unit 33 mixes recycled toner and new toner before being supplied to the developing device. Reference numeral 34 is a doctor blade (cleaning blade), and 35 is a color mixing ratio measuring device (reflectance measuring device). 36 and 37 are toner supply parts, 38 is a fin (stirring blade), 39 is a toner supply roller whose surface layer is made of sponge (more accurately, a developer supply roller).
Is.

During image formation, the developing sleeve 31 rotates counterclockwise in FIG. The mixer 32 is for mixing the carrier and the toner, and the screws 32a and 32b rotate in mutually opposite directions. Toner supply unit 3
The recycled toner from No. 6 and the new toner from the toner supply unit 37 are introduced into the pre-stirring unit 33, these are stirred and mixed by the rotation of the fin 38, and the obtained mixed toner is developed by the rotation of the toner supply roller 39. Supply to the device 30. The mixed toner in the developing device 30 is screw 32
While being circulated and conveyed while being mixed in a and 32b, a part of the mixed toner is supplied to a photoconductor (not shown) through the developing sleeve 31 during this period.

Example 2 Using this image forming apparatus, a performance evaluation experiment was conducted. Magenta toner is supplied from the recycled toner supply unit.
Cyan toner was supplied from the new toner supply unit, and these mixed toners were supplied to the developing device. The developing device (screws 32a, 32b) already contains cyan toner. For easy evaluation, solid images were formed while supplying recycled toner in the same amount as new toner. 10
When 0 images were formed, initially it was a cyan monochromatic image, but as the number of images formed increased, the hue of the image gradually shifted to the magenta side, and finally a uniform blue image was obtained. It was

On the other hand, as a comparative example, when the pre-stirring portion 33 was not provided and the recycled toner and the new toner were directly supplied to the developing device, magenta was partially mixed from around 10 prints, and within one print. The uneven color (uneven hue in the image) started to stand out. While printing 100 sheets, the color gradually became closer to blue, and the uneven color became less noticeable. From the results of this experiment,
(1) When the ratio of the mixed color recycled toner is small, unevenness of hue becomes noticeable due to uneven mixing of the recycled toner and the new toner. It is important to sufficiently mix and disperse the recycled toner, and (3) according to the image forming apparatus of FIG. 3, it is possible to sufficiently mix the color-mixed recycled toner and the new toner, and the hue in the image and between the images is improved. It is the above (1) to (3) that unevenness can be suppressed accurately.

Third Embodiment (Claim 4) FIG. 4 is a front sectional view showing a main structure of a color image forming apparatus according to the present embodiment, which is a right side surface of FIG. It corresponds to a part of the cross-sectional view. This image forming apparatus is characterized in that the mixed color recycled toner and the new toner are mixed by the sieve 40 before being introduced into the developing device. Other configurations are the same as those in FIG. In such an image forming apparatus, the respective color toners are dispersed by the sieve 40 and mixed, so that the mixed color toner is uniformly distributed in the mixed toner of the recycled toner and the new toner,
Good mixing is possible without giving strong stress to the toner, and the problem that color mixing is conspicuous on the image (due to concentration of mixed color toner) can be solved. That is, by supplying the mixed color recycled toner and the new toner onto the sieve 40 and mixing them through the sieve 40, both toners can be finely dispersed and mixed, and the mechanical stress is small. As compared with the case of using No. 38, the toner deterioration preventing effect is improved.

Example 3 Using the image forming apparatus shown in FIG. 4, the same performance evaluation experiment as in Example 2 was carried out. As a result, good hue uniformity was obtained on the image.

Fourth Embodiment (Claim 5) FIG. 5 is a block diagram showing a main configuration of an image forming apparatus according to the present embodiment. Numerals in the drawing will be described. Reference numeral 51 is a color mixing ratio detection means including a sensor and its controller, 52 is a toner supply amount determination unit, 53 is a recycled toner supply device, and 54 is a new toner supply device.
Each of these components can be provided in any of the image forming apparatuses shown in FIGS.

In this image forming apparatus, the color mixing ratio detecting means 51 detects the color mixing ratio of the color-mixed recycled toner, classifies the color mixing degree of the recycled toner based on the detection signal of the sensor, and outputs the signal D indicating the level. To the toner supply amount determination unit 52. The toner supply amount determination unit 52 sends a signal S1 corresponding to the supply amount of recycled toner to the recycled toner supply device 53 based on the signal D, and sends a signal S2 corresponding to the supply amount of new toner to the new toner supply device 54. . Then, the signals S1 and S2
The amount of toner is supplied to the developing means. As described above, in the image forming apparatus according to the present embodiment, the supply amount of each toner to the developing unit is controlled according to the color mixing ratio of the recycled toner, so that excessive color mixing does not occur and Above, good hue uniformity is obtained.

Next, an example of processing in the toner supply amount determining section 52 will be shown. As described above, the data D indicating the color mixture ratio is input to the toner supply amount determination unit. For the input data D, a combination of the signal A1 corresponding to the recycled toner supply amount and the signal A2 corresponding to the new toner supply amount is selected. Selection of this combination follows [Table 1] below.

[0056]

[Table 1]

The above combinations are set so that the sum of the value of the signal A1 and the value of the signal A2 becomes a constant value 16, and from Table 1 an appropriate combination (D is any of 0 to 7).
By selecting, the ratio of each supply amount of recycled toner and new toner is determined.

On the other hand, the total amount of toner supplied to the developing means, that is, the total amount of recycled toner supply and new toner supply is determined by a total toner supply amount determination device (not shown).
Therefore, the supply amount setting data S1 and S sent to the recycled toner supply device 53 and the new toner supply device 54.
2 is calculated as S1 = A1 × N S2 = A2 × N, where N is the value corresponding to the total amount of supplied toner, and S1 = A1 × N S2 = A2 × N
S2 is sent to each new toner supply device.

As described above, the distribution ratios A1 and A2 are the same as N.
By multiplying by S1 and S2, the supply amount ratio of the recycled toner and the new toner becomes A1: A2. Specifically, the values of S1 and S2 correspond, for example, to the rotation time of the screw conveyor provided in the toner supply device.

Example 4 In the example according to the present embodiment, as the data D indicating the color mixture ratio, the data indicating the reflection density (light reflectance) of the recycled toner was used. This reflection density is measured by the reflectance measuring device 28 (FIG. 2), and as shown in FIG.
To the toner supply amount determination unit 52. The reflectance measuring device 28 includes a light source and a sensor that detects the intensity of light emitted from the light source and the intensity of reflected light.

As described above, by obtaining the color mixture ratio of the recycled toner by measuring the reflection density thereof, the color mixture ratio can be directly known, and the ratio of the supply amount of the recycled toner and the new toner to the developing means can be accurately determined. You can control it well. Further, since the color mixture ratio is directly measured, calculation based on assumptions and algorithms do not intervene, and thus highly accurate information can be obtained.

Fifth Embodiment (according to claim 7) Considering the color mixture ratio Pc of recycled toner for the image forming portion of the second color, the reverse transfer rate of the toner of the first color is G, and the image area of the first color is In the following description, Sa is the image area of the second color and Sb is the transfer rate, and R is the transfer rate. The amount of toner reversely transferred to the second-color photoconductor in the second-color image forming unit is Sa × R × G, which is collected in the second-color cleaning unit. Further, for the image formation of the second color, the amount of toner collected by cleaning is area Sb × (1−R). At this time, the color mixture ratio Pc of the recycled toner is Pc = Sa * R * G / ((Sb * (1-R)) + Sa * R * G) (1). After n times of image formation, Sa × R × G of the denominator and numerator in the formula (1) becomes n × Sa × R × G, and the color mixture ratio after n times image formation can be estimated in the same manner. it can. In this case, the reverse transfer rate and the transfer rate of the toner need to be input in advance, but these values are changed depending on environmental data such as temperature and humidity or temporal data such as the number of operating photosensitive members and transfer belts. It is also possible, and the accuracy of the estimation is further improved by doing so.

Example 5 The color mixing ratio estimation method described above was applied to the color mixing ratio detecting means shown in FIG. 5, and an image was formed by the image forming apparatus shown in FIG. The transfer of the toner image to the transfer material on the transfer belt is performed in the order of yellow, magenta, cyan, and black in the running direction of the transfer belt. The resulting color mixture is a color mixture of yellow in magenta, a color mixture of magenta in cyan, and a color mixture of cyan in black. As a result, the color change was not noticeable even after printing 1000 sheets.

Sixth embodiment (according to claim 8) In the image forming apparatus according to claim 4, recycling is performed by maintaining a constant supply ratio of recycled toner and new toner to the developing means. The toner and the new toner can be easily used, and a good image can be obtained. In order to keep the supply ratio constant and prevent the concentration of the mixed color toner in the developing unit from becoming excessive, the supply ratio should be set to a constant value assuming that the recycled toner has a very high color mixture ratio. Good. If the apparatus is configured so that the density of the color-mixed toner in the developing means does not become excessive even if the color-mixing rate of the recycled toner is 100%, the possibility of the excessive density disappears.
In this case, although the amount of recycled toner consumed is very small, it is still consumed at a constant rate.

Seventh Embodiment (according to Claim 9) In the image forming apparatus according to any one of Claims 1 to 4, a second color mixing ratio detecting unit for detecting a color mixing ratio of the toner in the developing unit, A toner supply amount determination unit that determines the supply amounts of the mixed color recycled toner and the new toner to the developing unit based on the signal from the detection unit, and the recycling that can change the supply amount of the mixed color recycled toner according to the determination of the toner supply amount determination unit By including the toner supply device and the new toner supply device that can change the supply amount of the new toner according to the determination of the toner supply amount determination unit, the supply amount of the recycled toner and the supply amount of the new toner can be changed according to the color mixture ratio of the recycled toner. It is possible to control the ratio with the supply amount, and it is possible to accurately prevent excessive color mixing.

In this case, the same processing as the processing shown in the block diagram of FIG. 5 is performed. However, the color mixing ratio detected by the color mixing ratio detecting unit in the block diagram is the color mixing ratio of the toner in the developing unit in the present embodiment. Further, the color mixing rate detecting means for detecting the color mixing rate is a reflectance measuring device for measuring the reflection density of the toner on the developing sleeve which constitutes the developing means. Since the total amount of carrier and toner is conveyed on the developing sleeve while being kept constant, accurate measurement can be performed.

Eighth Embodiment (Claim 10) FIG. 3 is a sectional view showing the structure of the developing device 30. The developing sleeve 31 rotates counterclockwise. For the reasons described below,
The surface of this developing sleeve is sandblasted. A color mixing ratio measuring device (reflectance measuring device) 35, that is, a density sensor for measuring the color mixing ratio of the toner in the developing device is provided in the vicinity of the surface of the developing sleeve 31, and the doctor blade 3 is used.
4 is provided on the downstream side in the rotation direction of the developing sleeve 31. Therefore, the color mixing ratio measuring device 35 is for measuring the toner concentration of the portion of the surface of the developing sleeve 31 immediately after coming into contact with the doctor blade 34. In this case, the degree of color mixing is estimated by irradiating the above-mentioned portion of the developing sleeve 31 with light from the light emitting portion of the color mixing ratio measuring device 35 and measuring the reflected light intensity thereof by the light receiving portion. It should be noted that the toner concentration measurement location is not limited to the above as long as it is within the developing device.

The developing device 30 is a two-component developing device in which a mixture of carrier and toner (two-component developer) is formed into a brush shape by the magnetic force inside the sleeve to form a toner image on a photoconductor (not shown). . In this two-component developing device, the distribution of magnetic force lines is formed by the arrangement of a plurality of magnets provided in the sleeve that constitutes the developing sleeve 31, and the carriers are arranged along these magnetic force lines. Therefore, in the developer, there are a part where the ears stand and a part where the nap is lying. The measurement of the color mixing rate is performed on this lying part. When the color mixing ratio measuring device 35 is provided inside the developing device (as shown in FIG. 3, the position closer to the photoconductor than the doctor blade 34), the measuring device 35 is easily soiled with the developer. When the color mixing ratio is measured for the surface of the developing sleeve where the ears are lying immediately after the contact with the doctor blade, the carrier and the toner are bound by the sleeve, so that the measuring device 35 due to the scattering of the developer is used. Stain is less likely to occur.

In the color mixing ratio measuring device 35, a method of measuring specular reflection light or diffuse reflection light from the developer can be applied, but in the present embodiment, the former is used. However, in the case of the method of measuring the regular reflection light, noise may increase when the reflectance of the sleeve surface is high. Therefore, the surface of the sleeve is subjected to sandblasting in advance, and the carrier is concentrated to measure the portion because the ears are sleeping. Therefore, highly accurate color mixture rate measurement can be performed.

Example 6 In the example according to the present embodiment, the color mixing rate data D obtained by the color mixing rate measuring device 35 is input to the toner supply amount determining unit 52 of the toner supply amount control device shown in FIG. However, when 1000 sheets were continuously printed, all the images were of good quality with little variation in tint.

Ninth Embodiment (Claims 17 and 18) The toner color mixture ratio detecting means provided in the image forming apparatus of the present embodiment is a difference in spectral reflectance between color A and color mixture A + B. Is provided with a light source that emits light of a large wavelength and a light receiving unit that measures the intensity of reflected light when the light of the wavelength is emitted to the detection site. It is possible to easily detect the color mixture ratio of. According to this color mixing ratio detection means, a change in hue due to color mixing is detected as a difference in spectral reflectance. Examples 7 and 8 according to the present embodiment will be described below.

Example 7 The reflectance was measured while changing the wavelength of the light source using the above-mentioned color mixing ratio detecting means. The results are shown in FIGS. 6 and 7.
FIG. 6 shows a case where magenta is mixed with cyan, and FIG. 7 shows a case where magenta is mixed with yellow. The curve a is a result when there is no color mixture, and the curve b is a result when color is mixed. From these curves, it can be seen that the wavelengths at which changes occur due to color mixing are limited. Therefore, if a light source having a wavelength that changes depending on color mixing is used, the color mixing rate can be measured from the reflectance. As a method of selecting the wavelength, there are a method of using a single wavelength light source such as a laser and a method of limiting the wavelength by filtering a white light source.

Example 8 A filter which passes a wavelength shorter than 500 nm was inserted into a white light source, and the reflectance when yellow was mixed with magenta was measured. The results are shown in Fig. 8. The horizontal axis represents the color mixing rate of yellow, and the vertical axis represents the value standardized with the value being 1 when the color mixing rate is 0%. The reflectance is almost saturated at a color mixing rate of about 50%, but a color mixing rate of 50% or less is used for control in the process. Based on this graph, the color mixing ratio was calculated from the reflectance, and this was used as the color mixing ratio data D shown in FIG. 5 to conduct an experiment. In the above [Table 1], D is divided into 8 steps from 0 to 7, so this is simply linearly distributed, and the value of this measurement is set as T, and the value of D = T × 8-1 is input. did. As a result of continuous printing in the same manner as in Example 5, good quality images were obtained. Similarly, FIG. 9 was obtained as a result showing the reflectance of magenta mixed color with respect to cyan. When similar control was performed using this, an image with good quality was obtained. It is also possible to use a short-wavelength LD or LED as the light source of the color mixing ratio measuring device 35 of the apparatus of FIG. 3, and when the color mixing ratio is detected using the LD, the color mixing ratio is detected accurately. I was able to.

The above-described embodiment and example are
Although a component developer is used, the image forming apparatus and the image forming method of the present invention may be a one component developing method using a one component developer.

[0075]

As is apparent from the above description, according to the present invention, the following effects can be obtained. (1) The invention according to claims 1, 2, 12, 13 Since the supply amounts of the new toner and the mixed color recycled toner to the developing means can be adjusted, the mixed color recycled toner is reused regardless of the degree of color mixing. This makes it possible to suppress the hue change of the formed image.

(2) Inventions of Claims 3 and 14 Since the novel toner and the color-mixed recycled toner are mixed in advance, it is possible to form an image with the toner having no partial color-mixing unevenness.

(3) The invention of claim 4 The novel toner and the mixed color recycled toner are mixed with a sieve in advance, so that more reliable mixing can be performed.
It is possible to form an image with a toner with less partial color mixture unevenness.

(4) The invention according to claims 5 and 15, since the supply amount of the new toner and the mixed color recycled toner to the developing means is adjusted on the basis of the color mixture ratio of the mixed color recycled toner, uneven color mixing is small. The toner can be stably supplied to the developing means.

(5) Invention of Claim 6 Since the color mixing ratio of the color-mixed recycled toner is directly measured, the adjustment accuracy of the supply amount of the new toner and the color-mixed recycled toner to the developing means is improved. As a result, it is possible to stably supply the toner having less color mixture unevenness to the developing unit.

(6) The invention according to claim 7, the color mixing ratio detecting means of the color mixing recycled toner is provided with a calculating part for calculating the color mixing ratio from the image signal, so that the measuring means etc. for detecting the color mixing ratio can be omitted. It becomes unnecessary to secure a special space for the configuration of the image forming apparatus.

(7) The invention of claims 8 and 16, the ratio of the supply amount of the mixed color recycled toner and the new toner to the developing means is made constant, so that these toners can be used with a simple structure. it can.

(8) According to the inventions of claims 9 and 17, since the supply amount of the new toner and the mixed color recycled toner to the developing means is adjusted based on the color mixture ratio of the toner in the developing means, uneven color mixture is caused. It is possible to stably supply the toner having a small amount to the developing means.

(9) According to the invention of claim 10, the color mixture ratio of the toner in the developing means is obtained by measuring the reflection density of the toner on the developing sleeve, so that the measurement accuracy of the color mixture ratio is improved, and as a result, the new toner is obtained. The accuracy of adjusting the supply amount of the mixed color recycled toner to the developing means is improved, and the toner having less color mixture unevenness can be stably supplied to the developing means.

(10) Invention of Claim 11 The color mixture ratio of the toner in which the toner of color A and the toner of color B are mixed can be easily detected.

(11) Invention of Claim 18 In the invention of Claim 15 or 17, when detecting the color mixture ratio of toner, light of a wavelength having a large difference in spectral reflectance between color A and color mixture A + B is detected. The toner of color A + B is irradiated, the intensity of the reflected light is measured by the light receiving unit, and the color mixture is judged by comparing it with the reflectance of color A + B whose color mixture is known. The degree of color mixture with the B toner can be easily detected.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part structure of a color image forming apparatus in which an experiment was conducted on the influence of a toner color mixture ratio on a hue of a color image.

FIG. 2 is a plan view showing a structure of an image forming unit for each color which constitutes the two-component developing type color image forming apparatus according to the first embodiment of the invention.

FIG. 3 is a sectional view showing a main structure of a color image forming apparatus according to a second embodiment of the invention.

FIG. 4 is a sectional view showing a main part structure of a color image forming apparatus according to a third embodiment of the invention.

FIG. 5 is a block diagram showing a main configuration of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a graph showing a first result obtained in Example 7 of the present invention.

FIG. 7 is a graph showing a second result obtained in Example 7 of the present invention.

FIG. 8 is a graph showing a first result obtained in Example 8 of the present invention.

FIG. 9 is a graph showing a second result obtained in Example 8 of the present invention.

[Explanation of symbols]

1a to 1d photoconductor 2 Development device 3 cleaning device 4 Charging device 5 writing device 6 Transfer conveyor belt 7 fixing section 20 Developer 21 photoconductor 22a, 22b stirring screw 23 First recycled toner supply route 24 Second recycled toner supply route 25 Development sleeve 26 Toner Bottle 27 New toner supply route 28 Reflectance measuring instrument 30 developing device 31 Development sleeve 32 mixer 32a screw 32b screw 33 Pre-stirring section 34 Doctor Blade 35 Color mixing ratio measuring device (reflectance measuring device) 36, 37 Toner supply unit 38 fins (stirring blade) 39 Toner supply roller 40 sieve 51 Color mixing ratio detection means 52 Toner supply amount determination unit 53 Recycled toner supply device 54 New toner supply device

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 21/10 G03G 21/00 326 F term (reference) 2H030 AA04 AB02 AD01 AD03 BB02 BB23 BB36 BB38 2H077 AA02 AA05 AA37 AB02 AB14 AB15 AB18 AC02 AD02 AD06 AE06 DA10 DA31 DA63 DB02 EA03 GA04 GA13 2H134 GA01 GB02 JA02 JA11 KG07 KH17 KJ02

Claims (18)

[Claims] 1. A plurality of image forming units including at least an image carrier and a developing unit, a transfer unit for transferring a toner image formed on the image carrier to a transfer material, and an image after the transfer unit has passed. In an electrophotographic color image forming apparatus including a cleaning unit that removes and collects toner remaining on a carrier, cleaning is performed on each image forming unit in which a toner image is transferred to a transfer material after the second color. A recycle toner supply path for supplying the mixed color recycled toner collected by the means (hereinafter, referred to as a mixed color recycle toner) to each developing means, and a new toner supply path for supplying the new toner to each developing means. And a color image forming apparatus. 2. The color image forming apparatus according to claim 1, wherein the new toner and the mixed color recycled toner are separately supplied to the developing means. 3. The color image forming apparatus according to claim 1, wherein after the new toner and the mixed color recycled toner are mixed by the mixing means, the mixed toner is supplied to the developing means. 4. The color image forming apparatus according to claim 3, wherein the mixing means is a sieve. 5. A first color mixing ratio detecting unit for detecting a color mixing ratio of the color mixing recycled toner, and a toner supply amount for determining a supply amount of the color mixing recycled toner and the new toner to the developing unit based on a signal from the detection unit. A determination unit, a recycled toner supply device capable of varying the supply amount of mixed color recycled toner according to the determination of the toner supply amount determination unit, and a new toner supply device capable of varying the supply amount of new toner according to the determination of the toner supply amount determination unit. The color image forming apparatus according to any one of claims 1 to 4, further comprising: 6. The color image forming apparatus according to claim 5, wherein the first color mixing ratio detecting means is a reflectance measuring device for measuring the light reflectance of the color mixing recycled toner. 7. The color image forming apparatus according to claim 5, wherein the first color mixing ratio detection unit includes a calculation unit that calculates a color mixing ratio based on the image signal. 8. The color image forming apparatus according to claim 2, wherein the ratio of the supply amount of the new toner and the recycled toner of the mixed color to the developing unit is made constant. 9. A second color mixing ratio detecting unit for detecting a color mixing ratio of toner in the developing unit, and a toner for determining a supply amount of the color mixing recycled toner and the new toner to the developing unit based on a signal from the detecting unit. A supply amount determination unit, a recycled toner supply device capable of varying the supply amount of mixed color recycled toner according to the determination of the toner supply amount determination unit, and a new toner supply capable of varying the supply amount of new toner according to the determination of the toner supply amount determination unit A color image forming apparatus according to any one of claims 1 to 4, further comprising a device. 10. The color image according to claim 9, wherein the second color mixing ratio detecting means is a reflectance measuring device for measuring the light reflectance of the toner on the developing sleeve which constitutes the developing means. Forming equipment. 11. The first color mixing ratio detecting means or the second color mixing ratio detecting means includes a light source for irradiating a detection site with light having a wavelength having a large difference in spectral reflectance between the color A and the color mixing A + B, and 11. The color image forming apparatus according to claim 5, further comprising a light receiving unit that measures the intensity of reflected light from the detection site. 12. A plurality of image forming units including at least an image carrier and a developing unit, a transfer unit for transferring a toner image formed on the image carrier to a transfer material, and an image after the transfer unit has passed. In an image forming method using an electrophotographic color image forming apparatus equipped with a cleaning unit that removes and collects toner remaining on a carrier, each toner image is transferred to a transfer material in the second and subsequent colors. With respect to the units, the mixed color recycled toner collected by the cleaning unit (hereinafter, referred to as mixed color recycled toner) is supplied to the image carrier constituting each image forming unit through each developing unit, and new toner is supplied to each unit. A color image forming method characterized in that the image is supplied to an image carrier constituting each image forming unit via a developing means. . 13. The new toner and the mixed color recycled toner are separately supplied to the developing means.
2. The color image forming method as described in 2. 14. The color image forming method according to claim 12, wherein after the new toner and the mixed color recycled toner are mixed, the mixed toner is supplied to the developing means. 15. The color mixing ratio of the color mixing recycled toner is detected, and the supply amount of the color mixing recycled toner to the developing device and the supply amount of the new toner to the developing device are determined based on the detection result of the color mixing ratio. The color image forming method according to any one of claims 12 to 14. 16. The toner according to claim 13, wherein the new toner and the mixed color recycled toner are supplied to the developing means at a constant ratio when the need to supply the toner to the developing means arises. Color image forming method. 17. A color mixing ratio of toner in a developing device is detected, and a supply amount of a color mixing recycled toner to the developing device and a supply amount of new toner to the developing device are determined based on the detection result of the color mixing ratio. The color image forming method according to claim 12. 18. When detecting the color mixture ratio of a color mixture recycled toner, a color A and a color mixture A are added to a color mixture A + B toner.
By irradiating light with a wavelength having a large difference in spectral reflectance from + B, obtaining the reflectance by measuring the reflected light intensity, and comparing the reflectance data for the color A + B with a known color mixture with the measured reflectance. 18. The color image forming method according to claim 15, wherein the color mixture ratio is determined according to.