JP2009223062A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus which does not hinder color development and color reproducibility of an output image while recycling toner as much as possible. <P>SOLUTION: The tandem type color image forming apparatus includes: collected color toner conveyance paths Y6, C6 and M6 conveying collected toner from cleaning means Y3, C3 and M3 for respective colors other than black to a developing means K2 for black; a collected black toner conveyance path K6 conveying collected toner from a cleaning means K3 for black to the developing means K2 for black; and second new toner conveyance paths Y7, C7 and M7 conveying new toner of respective colors from new toner storing parts Y5, C5 and M5 for respective colors other than black to the developing means K2 for black. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus using an electrophotographic process, and more specifically, a plurality of image forming units are provided for each toner of a predetermined color to form a single color toner image of each color substantially simultaneously and sequentially form them. The present invention relates to a technique for recycling (reusing) toner in a so-called tandem type color image forming apparatus that forms a color image by transferring and superimposing.

  Currently, electrophotographic image forming apparatuses such as copiers, facsimiles, printers, and multi-functional machines have high image forming speeds and are provided with an image forming unit for each toner color. A single-color toner image is formed for each predetermined toner color along the direction of movement of an endless belt such as an intermediate transfer belt of an intermediate transfer method and a transfer conveyance belt of a direct transfer method, which will be described later. A so-called tandem color image forming apparatus in which a plurality of possible image forming units are arranged in series has become the mainstream.

  Such a tandem type color image forming apparatus uses a transfer method to develop each color by a developing unit on a latent image carrier such as a photosensitive drum or a photosensitive belt in each image forming unit provided for each predetermined toner color. A single-color toner image formed by developing with this toner is directly transferred from the latent image carrier onto a transfer material such as copy paper adsorbed on the endless belt, and is sequentially superimposed on the transfer material to form a full-color image. An intermediate transfer member such as an intermediate transfer belt using a primary transfer unit for a single-color toner image formed on a latent image carrier as described above in an image forming unit of a direct transfer method (transfer conveyance method) to be formed and an image forming unit of each color To form a full-color image by sequentially superimposing single-color toner images on the intermediate transfer member, and then transferring them from the intermediate transfer member to the transfer material in a batch using a secondary transfer unit. And an indirect transfer method is roughly classified into.

  In recent years, color image forming apparatuses have more opportunities to output originals with a large image area, such as photographic originals, compared to black and white only image forming apparatuses, which saves resources, reduces environmental burden, and reduces running costs. For the purpose of reduction or the like, there is an increasing demand for toner recycling (reuse) for collecting and reusing transfer residual toner remaining on the latent image carrier after transfer.

  However, in such a tandem type color image forming apparatus, if the transfer residual toner on the latent image carrier is simply recycled (reused) for each color image forming unit, an image on the upstream side in the moving direction of the endless belt is used. There is a problem that the toner of the forming unit is mixed with the recycled toner of the image forming unit provided on the downstream side. That is, in both the direct transfer method and the indirect transfer method, the toner adhering to the transferred image portion is reversely transferred to the latent image carrier of the downstream image forming unit. Hereinafter, this problem is referred to as “mixed color”. Further, there has been a problem of “aggregation” in which properties such as charging characteristics of the toner change in the recycling (reuse) process, and the recycled toner partially aggregates in some places. That is, when the recycled toner aggregates into aggregates, the aggregates form “black spots” when they adhere to the transfer paper. Further, there is a problem that toner having a low charge amount is likely to be scattered. Recycled toner has a problem of causing various abnormal images. This “aggregation” problem is generally considered to occur due to mechanical stress (compression force) applied to the toner when the transfer residual toner is scraped off with a cleaning blade or the like. Since the suppression of mechanical stress is in a trade-off relationship, it has been difficult to solve.

  In order to solve these problems, various image forming apparatuses that recycle toner in a tandem type color image forming apparatus have been proposed. For example, in Patent Document 1, in an intermediate transfer type or direct transfer type tandem type color image forming apparatus, charging means 5 for charging a transfer residual toner on an intermediate transfer belt or a transfer conveyance belt, and transfer after this charging A recovery means 18 is provided for electrostatically recovering the residual toner, and the transfer residual toner remaining on the photosensitive drums 11a to 11d (latent image carrier) after the primary transfer is recovered by the cleaning devices 16a to 16d. An image forming apparatus is disclosed in which the collected toner is returned to the developing units 14a to 14d (developing means) in the image forming units A to D and used again for development (in particular, FIGS. 1 and 6 of Patent Document 1). 7). According to the image forming apparatus described in Patent Document 1, it is said that cleaning failure, negative ghost, and color mixing can be prevented. However, the image forming apparatus disclosed in Patent Document 1 has an intermediate state after secondary transfer or direct transfer. The transfer residual toner remaining on the endless belt such as the transfer belt 1 or the transfer conveyance belt 7b is electrostatically collected, and the secondary transfer residual toner on the endless belt can be removed satisfactorily. In this case, the cleaning residual toner after the primary transfer on the photosensitive drum, which is a latent image carrier, is scraped with a cleaning blade to develop the same color. It is only disclosed to return to the vessel. Therefore, it cannot be said that the above-mentioned “color mixing” problem has been solved at all. In particular, when yellow toner is collected by the second image forming unit B from the upstream side and returned to the developing device 14b of the same color, image formation is performed. It is presumed that magenta toner upstream of the unit B is mixed and color deterioration becomes remarkable and normal image quality cannot be maintained.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses that in an intermediate transfer type or direct transfer type tandem color image forming apparatus, at least the second and subsequent image forming units as viewed from the upstream side in the moving direction of the recording carrier 5 (endless belt). 4 (4b to 4d) of the image carrier 1 (latent image carrier) on the downstream side of the transfer portion (transfer nip), a reversely charged toner that removes toner having a different charge polarity from the toner used in the image forming unit 4 An image forming apparatus provided with removing means 7 (7b to 7d) is disclosed (see FIG. 1 of Patent Document 2). In the image forming apparatus described in Patent Document 2, the recording / conveying member 5 (endless shape) is discharged by a discharge when transferring from the upstream image bearing member 1 (latent image bearing member) to the recording / conveying member 5 (endless belt). A portion of the toner transferred onto the belt) has a charge polarity opposite to the normal charge polarity, and when the toner having this reverse charge polarity is transferred by the image forming unit 4 on the downstream side, the recording carrier 5 ( It is considered that the toner is transferred from the endless belt to the image carrier 1 (latent image carrier), and the reversely transferred toner removing means 7 (the reversely charged toner is utilized by utilizing the reverse charging polarity). 7b to 7d) to prevent color mixing. However, in the image forming apparatus disclosed in Patent Document 2, as described in Paragraph 0021 of the specification of Patent Document 2, the charged polarity of the main body is not removed by the reversely charged toner removing means 7 and the image is carried. There is no particular recovery means for recovering transfer residual toner remaining on the body 1 (latent image carrier), and such transfer residual toner is only recovered by the developing means 3. In other words, when the transfer residual toner is recovered from the image carrier 1 (latent image carrier) by the developing means 3, the transfer residual toner recovery capability and the development performance must be made compatible. In the developer contact developing method, the developing sleeve (developing roller) has a high magnetic force to attract the magnetic carrier of the developer, that is, the magnetic brush ears are hardened to collect the residual transfer toner. On the contrary, the electrostatic latent image is developed during development and the toner image carried on the latent image carrier is scraped off, and the output image is swept with a brush called “sweeper” or “ear mark”. There is a problem that an abnormal image with fine white spots is generated, and it is difficult to achieve both the transfer residual toner collecting ability and the developing performance.

In Patent Document 3, in an indirect transfer type or direct transfer type tandem color image forming apparatus, the arrangement of image forming units is arranged along the moving direction of an endless belt (transfer material conveying belt 10 and intermediate belt 11). An image forming apparatus arranged in the order of yellow (P _Y ) → magenta (P _M ) → cyan (P _C ) → black (P _K ) from the upstream is disclosed (see FIGS. 1 and 5 of Patent Document 3). . The image forming apparatus described in Patent Document 3 has an effect of minimizing a change in color of an output image due to color mixture by arranging the image forming unit as described above. The problem of “color mixing” is not conspicuous in the output image even when color mixing occurs, and is not a fundamental solution.

  In Patent Document 4, in a direct transfer tandem type color image forming apparatus, yellow → magenta → cyan → black from the upstream side in the transfer material transport direction A (the moving direction of the transfer belt 8 (endless belt)). The process cartridge (image forming unit) is disposed, and the toner recycling means 47 is provided in the most upstream process cartridge 18A (image forming unit) to collect the transfer residual toner on the image carrier 2A. The toner recycling means 47 is also provided in the process cartridges 18B to 18D (image forming units) other than the process cartridge 18A arranged in the uppermost stream after returning to the developing device 22A (developing means) of the cartridge 18A, and the respective image carriers 2B to 2B. The transfer residual toner on 2D is collected and each process cartridge 18B-1 is collected. In addition to returning to the developing devices 22B to 22D (developing means) of D (image forming unit), a predetermined amount of toner in the developing devices 22B to 22D, where color mixing is expected, is executed at appropriate times other than during image formation. In addition, an image forming apparatus is disclosed in which the cleaning roller 42 of the transfer belt 8 (endless belt) is periodically discarded into a waste toner bottle 46 via each image carrier (latent image carrier) (see Patent Document 4). (See FIGS. 1 and 2). Although the image forming apparatus described in Patent Document 4 can effectively suppress the deterioration of the color reproducibility of the image due to the color mixture of the toners, the mixed color toners are discarded in principle. The purpose such as reduction of environmental load and running cost has not been achieved.

  Patent Document 5 discloses a photosensitive drum cleaning device 14 (cleaning unit) that cleans a photosensitive drum 11 (latent image carrier) in an indirect transfer type or direct transfer type tandem color image forming apparatus, and intermediate transfer. An intermediate transfer member cleaning device 30 for cleaning the belt 19 (endless belt) is provided, and the recycled toner mixed with a plurality of colors collected by the photosensitive drum cleaning device 14 (cleaning means) or the intermediate transfer member cleaning device 30 is black. Is returned to the developing device 12Bk (developing unit), mixed with black new toner and reused, and the black toner ratio and the toner ratio detecting unit 111 in the black developing device 12Bk (developing unit) are detected. Recycled toner calculated from the ratio of each color toner Depending on the black toner ratio, an image forming apparatus capable of varying the mixing ratio is disclosed (see in particular FIGS. 1, 9 and 10 of Patent Document 5). In the image forming apparatus described in Patent Document 5, the ratio of the collected recycled toner is calculated by indirect calculation means such as image data and replenishment data. In addition, since complicated determination means are used, the cost is high, and since there is no means for supplying new toner of each color to the recycled toner, the image to be output is shifted to a certain color or toner of a certain color When no toner is used, it is presumed that the change in color of the recycled toner cannot be suppressed.

  In Patent Document 6, a tandem color image forming apparatus of an indirect transfer method or a direct transfer method is provided with a color sensor for forming a color patch for each color and measuring the color of the color patch. An image forming apparatus that monitors toner color deterioration based on sensor information is disclosed (in particular, refer to FIGS. 1 and 5 of Patent Document 6). In the image forming apparatus described in Patent Document 6, when the color of the toner to be used is deteriorated, the warning is displayed, and the toner remaining in the developing unit for the target color toner is displayed. It merely urges the user to discard and replace with new toner, or to replenish an appropriate amount of new toner, and does not suppress color change while recycling the toner.

  As described above, in a color image forming apparatus such as a tandem type instead of a black and white image forming apparatus, an image forming apparatus that does not have a problem in image quality while recycling toner is not currently provided.

JP 2000-227727 A JP 2000-242152 A JP-A-8-137174 JP 2002-116593 A JP 2006-18050 A JP 2007-127951 A

  Accordingly, the present invention is to solve the problems of the conventional image forming apparatus, in an electrophotographic color image forming apparatus using a plurality of colors of toner, saving resources, reducing environmental burden, running cost, etc. Therefore, an object of the present invention is to provide a color image forming apparatus that recycles toner as much as possible and that does not hinder color development or color reproduction of an output image.

  In order to solve the above problems, the invention of the transfer device according to claim 1 includes a plurality of image forming units that independently form toner images for each predetermined color including at least a black color, and each of these image forming units. The unit has a latent image carrier that carries an electrostatic latent image on its surface, developing means for developing the electrostatic latent image into a toner image with toner of a predetermined color, and remains attached to the latent image carrier after transfer. A cleaning unit that cleans and collects the transfer residual toner, and further includes a plurality of new toner storage units that store, for each of the predetermined colors, a new toner that is a toner that is not used for development, and for each of these colors. In the color image forming apparatus provided with a first new toner transport path for transporting new toner from the new toner storage unit to the corresponding developing unit of each color for each toner color, the cleaner One or a plurality of recovered color toner transport paths for transporting recovered toner from the cleaning means for each color other than black to the black developing means, and from the black cleaning means to the black developing means A recovered black toner transport path for transporting the recovered toner, and a plurality of second new toner transport paths for transporting the new toner of each color from the new toner accommodating portion of each color other than black to the black developing means, Is provided.

  According to a second aspect of the present invention, the color image forming apparatus according to the first aspect is a tandem type intermediate transfer system in which a plurality of image forming units are arranged in series along the moving direction of the intermediate transfer body. It is characterized by being.

  According to a third aspect of the present invention, in the color image forming apparatus according to the second aspect, the black image forming unit is disposed on the most downstream side when viewed from the moving direction of the intermediate transfer member. The other color image forming units are arranged from the upstream side in the moving direction of the intermediate transfer member in order of poor transfer efficiency when transferring in a single color, and when transferring from the image forming unit arranged at the most upstream to the intermediate transfer member. The applied primary transfer voltage is set to a transfer voltage value at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit, and the image forming unit arranged second from the upstream to the intermediate transfer member. The primary transfer voltage applied at the time of transfer is set to a value obtained by multiplying the transfer voltage at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit by a predetermined ratio smaller than 1, and Or later The primary transfer voltage applied at the time of transfer from the arranged image forming unit to the intermediate transfer member is arranged one upstream upstream to the transfer voltage at which the transfer efficiency is optimum when transferring with the toner single color of the image forming unit. The image forming unit is set to a value multiplied by a value smaller than the predetermined ratio set.

  According to a fourth aspect of the present invention, in the color image forming apparatus according to the first aspect, the black toner image formed by the black image forming unit is transferred from the black latent image carrier to the transfer material. In addition to direct transfer, a single color toner image of each color other than black formed by an image forming unit other than black is temporarily transferred from each latent image carrier to an intermediate transfer member and then transferred to a transfer material. .

  According to a fifth aspect of the present invention, in the color image forming apparatus according to the fourth aspect, the image forming units other than black are arranged upstream in the moving direction of the intermediate transfer member in the order of poor transfer efficiency. The primary transfer voltage applied at the time of transfer from the most upstream image forming unit to the intermediate transfer member is optimal in transfer efficiency when transferring with a single color toner of the image forming unit. The primary transfer voltage applied at the time of transfer from the image forming unit arranged second from the upstream to the intermediate transfer member is set to the toner color of the image forming unit. A primary transfer voltage applied at the time of transfer from the second image forming unit to the intermediate transfer member is set to a value obtained by multiplying the transfer voltage at which transfer efficiency is optimal by a predetermined ratio smaller than 1. The image forming unit is set to a value obtained by multiplying the transfer voltage at which transfer efficiency is optimal when transferring with a single color toner by the image forming unit by a value smaller than the predetermined ratio set in the image forming unit arranged one upstream. It is characterized by.

  According to a sixth aspect of the present invention, in the color image forming apparatus according to any one of the first to fifth aspects, the toner conveying means provided in the collected color toner conveying path mixes the collected toner of each color. The toner conveyance amount is set so that the color of the recovered color toner is close to the color of black with the ratio being a predetermined ratio.

  According to a seventh aspect of the present invention, in the color image forming apparatus according to the sixth aspect, the plurality of toner conveying means provided in the recovered color toner conveying path are rotated at the same rotational speed by the same driving means. The conveying screw is driven, and the toner conveying amount is set by changing means other than the rotational speed such as the fin size of the conveying screw and the angle of the fin of the screw.

  An image forming apparatus according to an eighth aspect of the present invention is the color image forming apparatus according to any one of the first to seventh aspects, wherein each cleaning means abuts on each latent image carrier and collects transfer residual toner. A cleaning toner and a recovery toner storage hopper that is a space for storing transfer residual toner recovered from each latent image carrier are respectively provided. The recovery color toner transport path and the second new toner transport path are used to recover the respective colors. The collected toner of each color communicates with the toner storage hopper, and is temporarily stored in the collected toner storage hopper via the collected color toner transport path for each color and then transported toward the black developing means. The new toner of each color other than is supplied to the black developing means via the second new toner transport path and the collected toner storage hopper of each color. Is the fact characterized.

  According to a ninth aspect of the present invention, in the color image forming apparatus according to the eighth aspect of the present invention, the collected toner storage hopper has a storage residue of a predetermined amount of collected toner that does not hinder the transport of the collected toner. A remaining amount detection sensor for detecting whether or not there is an amount is provided.

  According to a tenth aspect of the present invention, in the color image forming apparatus according to the ninth aspect, the remaining amount of collected toner stored in a remaining amount detection sensor other than black is not more than a predetermined amount. Is detected, the new toner is supplied to the collected toner storage hopper provided with the remaining amount detection sensor through the second new toner transport path.

  An image forming apparatus according to an eleventh aspect is the color image forming apparatus according to the tenth aspect, wherein the remaining amount of the collected toner stored in the remaining amount detection sensor other than the black color is less than a predetermined amount. Is detected, the conveyance of the collected toner from the collected toner storage hopper provided with the remaining amount detection sensor is stopped and the new toner is supplied to the collected toner storage hopper through the second new toner conveyance path. After that, when the remaining amount detection sensor detects that the amount of remaining toner is equal to or greater than a predetermined amount, conveyance of the collected toner from the collected toner storage hopper is started through the collected color toner conveyance path. It is characterized by that.

  According to a twelfth aspect of the present invention, in the color image forming apparatus according to any one of the eighth to eleventh aspects, a full toner detection sensor for detecting the fullness of the collected toner is provided in the collected toner storage hopper. It is characterized by that.

  According to a thirteenth aspect of the present invention, in the color image forming apparatus according to the twelfth aspect, when the fullness is detected by any one of the fullness detection sensors other than the black color, the black color is detected. It is characterized in that the transport of the collected toner is started from all the collected toner storage hoppers other than the above.

  According to a fourteenth aspect of the present invention, there is provided the color image forming apparatus according to the twelfth or thirteenth aspect, wherein the remaining amount of the collected toner is stored by any one of the remaining amount detection sensors other than the black color. The remaining amount of collected toner stored is less than or equal to the predetermined amount when it is detected that the amount is less than or equal to the predetermined amount and full is detected by any of the full detection sensors other than black. If the new toner is supplied to the collected toner storage hopper provided with the remaining amount detection sensor for detecting the remaining amount, and then the remaining amount detection sensor does not detect that the amount of remaining toner is greater than or equal to the predetermined amount, other than black It is characterized in that the transport of the collected toner is not started from all the collected toner storage hoppers.

  An image forming apparatus according to a fifteenth aspect of the present invention is the color image forming apparatus according to any one of the eighth to fourteenth aspects, further comprising stirring means for stirring the recovered toner, and the recovered color toner transport path and the recovered black toner. A collection toner supply unit that communicates with the conveyance path and stirs the collected toner conveyed from the collected toner storage hopper for each color and supplies it to the black developing unit is provided near the black developing unit. And

  According to a sixteenth aspect of the present invention, in the color image forming apparatus according to the fifteenth aspect, a color sensor for detecting the color of the collected toner stored in the collected toner supply unit is provided, and the collected color toner is provided. A toner conveying means that can be independently driven for each toner color is provided in the conveying path, and each toner conveying amount of the collected color toner can be adjusted according to the detection result of the color sensor.

  According to a seventeenth aspect of the present invention, in the color image forming apparatus according to the sixteenth aspect, the tint sensor is a black image forming unit that converts the tint pattern from the collected toner in the collected toner supply unit to a black color. An image is formed on the latent image carrier, and the color of the recovered toner is detected by optically measuring the color pattern.

  The image forming apparatus according to an eighteenth aspect is the color image forming apparatus according to the sixteenth or seventeenth aspect, wherein the recovered toner in the recovered toner supply unit is shifted to a hue based on detection information from the color sensor. If it is determined that the collected color toner is newly conveyed, the collected toner is conveyed to the collected toner supply unit by adjusting the toner conveyance amount so that the newly collected color toner is complementary to the hue.

  In the image forming apparatus according to claim 19, in the color image forming apparatus according to claim 16 or 17, when fullness is detected by any fullness detection sensor other than the black color among the fullness detection sensors, The transport of the collected toner is forcibly started from all the collected toner storage hoppers other than the black color, and then the collected toner in the collected toner supply unit is shifted to a certain hue based on the information from the color sensor. When the determination is made, the collected toner is conveyed to the collected toner supply unit by adjusting the toner conveyance amount so that the newly collected color toner to be conveyed contains a relatively large amount of complementary colors of the hue.

  According to the first aspect of the present invention, in the color image forming apparatus including a plurality of image forming units for each toner of a predetermined color, each color other than the black color in the cleaning unit. One or a plurality of collected color toner conveying paths for conveying the collected toner from the cleaning means to the black developing means, and the collected black toner for conveying the collected toner from the black cleaning means to the black developing means Since a transport path and a plurality of second new toner transport paths for transporting the new toner of each color from the new toner accommodating portion of each color other than black to the black developing means are provided, that is, a latent image The transfer residual toner on the carrier is collected, and the black that is least affected by the color tone according to a predetermined amount (or a fixed ratio) is collected. Since it is supplied to the developing means of the image forming unit, even if the amount of untransferred toner collected for each color varies greatly depending on the frequency of use of the image forming unit for each color, By supplying new toner from the second new toner transport path, the collected toner can be transported to the black color developing means at a predetermined ratio. For this reason, it is possible to recycle the toner as much as possible without causing any trouble in color development or color reproduction of the output image. Thus, resource saving, environmental load reduction, and running cost reduction can be achieved, and environmental conservation can be achieved.

  According to the second aspect of the present invention, the color image forming apparatus according to the first aspect is a tandem type intermediate transfer system in which a plurality of image forming units are arranged in series along the moving direction of the intermediate transfer body. In the intermediate transfer type tandem color image forming apparatus, the above-described effects can be obtained.

  According to a third aspect of the present invention, in the color image forming apparatus according to the second aspect, the black image forming unit is disposed on the most downstream side when viewed from the moving direction of the intermediate transfer member. The color image forming unit is arranged from the upstream side in the moving direction of the intermediate transfer member in the order of poor transfer efficiency when transferring in a single color, and is applied at the time of transfer from the image forming unit arranged at the most upstream to the intermediate transfer member. The primary transfer voltage is set to a transfer voltage value at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit, and is transferred from the image forming unit arranged second to the intermediate transfer body. The primary transfer voltage applied at this time is set to a value obtained by multiplying the transfer voltage at which the transfer efficiency is optimal when transferring with a single color toner of the image forming unit by a predetermined ratio smaller than 1, and the second and later. Arranged The primary transfer voltage applied at the time of transfer from the image forming unit to the intermediate transfer member is arranged one upstream to the transfer voltage at which the transfer efficiency is optimal when transferring with a single color toner of the image forming unit. This value is set to a value smaller than the predetermined ratio set in the image forming unit, so that the toner is difficult to reversely transfer during transfer, and the problem of “color mixing” is reduced. Even when colors are mixed, the change in color of the output image can be made inconspicuous.

  According to the fourth aspect of the present invention, in the color image forming apparatus according to the first aspect, the black toner image formed by the black image forming unit is directly transferred from the black latent image carrier to the transfer material. At the same time, the single-color toner image of each color other than black formed by the image forming unit other than black is temporarily transferred from each latent image carrier to the intermediate transfer member and then transferred to the transfer material. Since the direct transfer system is formed independently of the forming units and the remaining image forming units are the tandem intermediate transfer system, in addition to the above effects, the “color mixing” problem does not occur in the black image forming unit.

  According to a fifth aspect of the present invention, in the color image forming apparatus according to the fourth aspect, the image forming units other than the black color are arranged in series from the upstream side along the moving direction of the intermediate transfer member in the order of poor transfer efficiency. The primary transfer voltage applied at the time of transfer from the most upstream image forming unit to the intermediate transfer member is a transfer that optimizes transfer efficiency when transferring with a single color toner of the image forming unit. The primary transfer voltage, which is set to the voltage value and applied at the time of transfer from the image forming unit arranged second from the upstream to the intermediate transfer member, is the transfer efficiency when transferring with a single color toner of the image forming unit. Is set to a value obtained by multiplying the transfer voltage that is optimal by a predetermined ratio smaller than 1, and the primary transfer voltage applied at the time of transfer from the second image forming unit to the intermediate transfer member is It is set to a value obtained by multiplying a transfer voltage at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit by a value smaller than the predetermined ratio set in the image forming unit arranged one upstream. Therefore, not only the “color mixing” problem does not occur in the black image forming unit, but also the remaining image forming unit is difficult to reversely transfer the toner during the transfer, and the “color mixing” problem is reduced. Even when colors are mixed, the change in the color of the output image can be made inconspicuous.

  According to a sixth aspect of the present invention, in the color image forming apparatus according to any one of the first to fifth aspects, the toner conveying means provided in the collected color toner conveying path has a mixing ratio of the collected toner of each color. Since the toner conveyance amount is set so that the color of the recovered color toner is close to the color of black as the predetermined ratio, in addition to the above effects, the ratio is always determined with a simple and inexpensive structure Thus, the collected toner of each color can be conveyed to the black color developing means.

  According to the seventh aspect of the present invention, in the color image forming apparatus according to the sixth aspect, the plurality of toner conveying units provided in the collected color toner conveying path are driven at the same rotational speed by the same driving unit. Since the toner conveying amount is set by changing means other than the rotational speed such as the size of the conveying screw fins and the angle of the screw fins, the toner conveying amount is set in addition to the above-described effect and at a predetermined ratio. Thus, the collected toner of each color can be conveyed to the black color developing means at the same time, and only one driving means is required, thereby reducing the cost.

  According to an eighth aspect of the present invention, in the color image forming apparatus according to any one of the first to seventh aspects, each cleaning means is a cleaning member that abuts against each latent image carrier and collects transfer residual toner. And a collected toner storage hopper that is a space for storing the transfer residual toner collected from each latent image carrier, and the collected color toner transport path and the second new toner transport path respectively store the collected toner of each color. The collected toner of each color communicates with the hopper unit, is temporarily stored in the collected toner storage hopper unit via the collected color toner conveying path of each color, and then conveyed toward the black developing unit, and other than the black color. The new toner for each color is supplied toward the black developing means via the second new toner transport path and the collected toner storage hopper for each color. In other words, since a certain amount of collected toner is once stored in the collected toner storage hopper and then transported, more accurate amount of toner can be transported and the color of the collected toner is not changed. Can be.

  According to the ninth aspect of the present invention, in the color image forming apparatus according to the eighth aspect, the collected toner storage hopper has a storage amount of the collected toner of a predetermined amount that does not hinder the transport of the collected toner. Since the remaining amount detection sensor for detecting whether or not there is provided, the color of the recovered toner is known.

  According to the tenth aspect of the present invention, in the color image forming apparatus according to the ninth aspect, when it is detected by the remaining amount detection sensor other than the black color that the remaining amount of the collected toner is less than the predetermined amount. Since the new toner is supplied to the collected toner storage hopper provided with the remaining amount detection sensor through the second new toner transport path, that is, even if there is a color where the collected toner does not reach the predetermined amount, Replenishing and adjusting the collected toner of all colors to a predetermined amount and transporting it to the black developing means, it is possible to correct variations in the collected toner amount due to the frequency of use of the toner color, and to balance the supply ratio of the collected toner The color of the recycled toner does not change without breaking.

  According to the eleventh aspect of the present invention, in the color image forming apparatus according to the tenth aspect, when it is detected by the remaining amount detection sensor other than the black color that the stored remaining amount of the collected toner is equal to or less than a predetermined amount. In addition, the transport of the collected toner from the collected toner storage hopper provided with the remaining amount detection sensor is stopped and the new toner is supplied to the collected toner storage hopper through the second new toner transport path. When the amount detection sensor detects that the amount of remaining toner is greater than or equal to a predetermined amount, the recovered toner storage hopper starts transporting the recovered toner from the recovered toner storage hopper through the recovered color toner transfer path. In addition to the above effects, the collected toner does not continue to be transported in a state where there is little recovered toner in the section and there is a problem in transport. In all more accurately predetermined ratio recovered toner colors outside can be conveyed to the black color developing means.

  According to the twelfth aspect of the present invention, in the color image forming apparatus according to any one of the eighth to eleventh aspects, the full toner detection sensor for detecting the fullness of the collected toner is provided in the collected toner storage hopper. Since it can be seen that the amount of collected toner in the collected toner storage hopper has increased, it can be supplied to the black image forming unit before the collected toner in the collected toner storage hopper overflows.

  According to a thirteenth aspect of the present invention, in the color image forming apparatus according to the twelfth or thirteenth aspect, when fullness is detected by any fullness detection sensor other than the black color, all the colors other than the black color are collected. Since the transport of the collected toner is started from the toner storage hopper, that is, the collected toners of all colors other than the black color are simultaneously supplied to the black developing means, so that the color variation of the collected toner can be efficiently balanced and balanced. Can be suppressed. Further, the control can be realized only by turning on / off one driving means of the collected toner conveyance path.

  According to the fourteenth aspect of the present invention, in the color image forming apparatus according to the twelfth or thirteenth aspect, the remaining amount of the collected toner stored by the remaining amount detection sensor other than the black color is equal to or less than a predetermined amount. Recovered toner provided with a remaining amount detection sensor that detects that the remaining amount of collected toner is less than a predetermined amount when full is detected by any fullness detection sensor other than black If the new toner is supplied to the storage hopper, and then the remaining amount detection sensor does not detect that the amount of remaining toner is equal to or greater than the predetermined amount, the recovered toner is transported from all the collected toner storage hoppers other than black. In other words, the timing for supplying the non-black color collected toner from the collected toner storage hopper to the black image forming unit at the same time is defined. As a result, it is possible to store the collected toner in each collected toner storage hopper, and as a result, the collected toner amount is easily supplied at regular intervals. , Color variation can be efficiently controlled in a balanced manner.

  According to the fifteenth aspect of the invention, in the color image forming apparatus according to any one of the eighth to fourteenth aspects, the agitation means for agitating the collected toner is provided, and the collected color toner conveying path and the collected black toner conveying path. And a recovery toner supply unit that stirs the recovery toner conveyed from the recovery toner storage hopper for each color and supplies it to the black development unit in the vicinity of the black development unit. Since the toner is supplied after being accumulated, there is no fluctuation in the supply amount due to driving of the conveying means, and the collected toner is stirred and supplied to the black developing means, so that the fluctuation in the color of the collected toner can be further eliminated. it can.

  According to the sixteenth aspect of the present invention, in the color image forming apparatus according to the fifteenth aspect, the color sensor for detecting the color of the collected toner stored in the collected toner supply unit is provided, and the collected color toner conveyance path is provided. Is provided with toner conveying means that can be independently driven for each toner color, and each toner conveyance amount of the collected color toner can be adjusted according to the detection result of the color sensor, so that the color (color balance) is not lost. Toner recycling of the collected color toner can be performed accurately.

  According to the seventeenth aspect of the present invention, in the color image forming apparatus according to the sixteenth aspect, the color sensor converts the color pattern from the collected toner in the collected toner supply unit to a black color in the black image forming unit. Since the color of the collected toner is detected by optically measuring the color pattern of the latent image on the latent image carrier, in addition to the above effects, the color at the time of image formation is directly adjusted. Therefore, it is possible to recycle the toner with good color balance.

  According to the eighteenth aspect of the present invention, in the color image forming apparatus according to the sixteenth or seventeenth aspect, the collected toner in the collected toner supply unit is shifted to a certain hue based on detection information from the color sensor. If it is determined that the collected color toner is newly conveyed, the collected toner is conveyed to the collected toner supply unit by adjusting the toner conveyance amount so that the complementary color of the collected color toner is complementary to the hue. Based on this, the color of the collected toner in the collected toner supply unit actually used can be surely made black.

  According to the nineteenth aspect of the present invention, in the color image forming apparatus according to the sixteenth or seventeenth aspect, when the fullness is detected by any fullness detection sensor other than the black color, all the recoveries other than the black color are collected. When it is forcibly started to convey the collected toner from the toner storage hopper, and then it is determined that the collected toner in the collected toner supply unit is shifted to a certain hue based on the information from the color sensor, The collected toner is transported to the collected toner supply unit by adjusting the toner conveyance amount so that the collected color toner to be conveyed contains a predetermined amount of complementary color of the hue, so that the collected toner storage hopper overflows with the collected toner. Therefore, the machine can be stopped without reducing productivity, and the toner can be recycled without degrading the color balance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[Embodiment 1]
FIG. 1 is a configuration explanatory diagram showing an outline of the overall configuration of a color image forming apparatus according to a first embodiment of the present invention. Reference numeral 1 in the drawing is a four-tandem type intermediate transfer type color printer exemplified as an embodiment of the present invention, and this color printer 1 is mainly made up of a substantially concave portion near the center. An apparatus main body 10 having a letter-shaped vertical cross section, writing means 2 disposed on the substantially uppermost inner side of the apparatus main body 10, and image formation disposed below the writing means 2 and above the apparatus main body 10. A transfer unit 4 disposed below the image forming unit 3, a sheet feeding unit 5 disposed further below the transfer unit 4 and substantially at the bottom of the inside of the apparatus main body 10, and a transfer unit. Of the apparatus main body 10 provided between the transfer section 4 and the paper feeding section 5 on the side of the fixing section 6. The paper discharge section 7 is formed on the outer surface.

  The writing means 2 scans while irradiating laser light modulated on the basis of image information inputted from a personal computer or the like, and selectively exposes an outer peripheral surface of a uniformly charged later-described photosensitive drum, It functions as an exposure device that lowers the surface potential of the irradiated portion and forms an electrostatic latent image on the photosensitive drum.

The image forming unit 3 is mainly composed of four image forming units 3Y, 3C, 3M, and 3K corresponding to toners of four colors of yellow, cyan, magenta, and black. Are arranged in series in the order of yellow, cyan, magenta, and black from the upstream side. The image forming units 3Y, 3C, 3M, and 3K are provided with photosensitive drums Y, C, M, and K, which are latent image carriers, and around the photosensitive drums Y, C, M, and K, respectively. The electrostatic latent images formed by the writing means 2 on the respective charging drums Y1, C1, M1, and K, and the photosensitive drums Y1, C1, M1, and K, which are charged uniformly by charging the outer peripheral surface, respectively. The developing residuals Y2, C2, M2, and K2 that visualize the toner image with a single color toner are cleaned on the outer peripheral surface of the photosensitive drums Y, C, M, and K after the transfer. Cleaning means Y3, C3, M3, K3, etc. are provided for recovery.
The configuration and arrangement of the image forming unit will be described in detail later.

  The transfer unit 4 includes an intermediate transfer belt 40 as an intermediate transfer member made of an elastic resin endless belt, four support rollers 41, 42, 43, 44 that support and stretch the intermediate transfer belt 40, and four It is mainly composed of four primary transfer rollers 45Y, 45C, 45M, and 45K that face the photosensitive drums Y, C, M, and K across the intermediate transfer belt 40, respectively. The support roller 43 is a drive roller connected to a drive means (not shown), and a secondary transfer roller 46 is provided at a position facing the support roller 43 with the intermediate transfer belt 40 interposed therebetween. The support roller 44 is a cleaning roller to which a voltage having a polarity opposite to the charged polarity of the transferred toner can be applied. A cleaning unit 47 serving as a cleaning unit for the intermediate transfer belt 40 is provided around the cleaning roller 44. It has been.

  These primary transfer rollers 45Y, 45C, 45M, and 45K take image degradation due to gap discharge into consideration, from the directly facing positions where the respective photosensitive drums Y, C, M, and K are in contact with the intermediate transfer belt 40 therebetween. Contact-type transfer bias (transfer voltage) applying means disposed at a position slightly shifted downstream in the transport direction of the intermediate transfer belt 40 (in the direction of the arrow in the figure), and is connected to a bias power source (not shown) to perform primary transfer. The bias is applied from the back surface (inner peripheral surface) of the intermediate transfer belt 40.

  The secondary transfer roller 46 is configured to be pressed against the intermediate transfer belt 40 on the outer periphery of the drive roller 43 by an urging means (not shown) to form a secondary transfer nip. The drive roller 43 is connected to a bias power source (not shown). It is a connected contact-type transfer bias applying means. Further, the secondary transfer roller 46 may be a transfer bias applying unit, and in this case, a transfer bias having a polarity opposite to that of the toner image to be transferred is applied.

  The cleaning unit 47 includes a cleaning roller 44, a cleaning blade 47a, an accommodating portion 47b, a conveying screw 47c, and the like. The cleaning roller 44 electrostatically transfers the transfer residual toner on the intermediate transfer belt 40 with the cleaning roller 44. The cleaning blade 47a is brought into contact with the outer peripheral surface of the scraper 44 to scrape off the transfer residual toner, temporarily stored in the storage portion 47b, and transported to a waste toner storage portion (not shown) by the transport screw 47c.

  The paper supply unit 5 accommodates and stocks a transfer material (not limited to paper) of a predetermined size such as copy paper, resin sheet (OHP sheet, etc.), and two upper and lower supply cassettes 50, 51. And the supply rollers 52 and 53 for feeding the transfer materials one by one to the conveying path on the basis of a control signal from a control means (not shown), and an overlap made of an elastomer. A friction pad (not shown) as a separating member for separating the fed transfer material into one sheet, a registration roller pair 54 for adjusting the timing of conveying the transfer material to the secondary transfer nip, and the like are provided.

  The fixing unit 6 includes a fixing roller 60, a pressure roller 61, and the like. The pressure roller 61 is urged and pressed against the fixing roller 60 by an urging means (not shown) to form a fixing nip. Then, in this fixing nip, the transfer unit 4 applies heat to the transferred transfer material by a heating means (not shown) provided in the fixing roller 60 and the pressure of the pressure roller 61 by the urging means. The toner image transferred to the transfer material is fixed to the transfer material.

  The paper discharge unit 7 is provided with a paper discharge tray 70 provided on the outer surface of the U-shaped notch near the center of the apparatus main body 10 and a transfer material that has passed through the fixing unit 6 to the paper discharge tray 70. A paper discharge roller pair 71 and the like discharged from the main body 10 are provided, and transfer materials discharged from the paper discharge roller pair 71 are stacked on the paper discharge tray 70.

(Image forming unit arrangement and transfer conditions)
Next, the arrangement of image forming units and the primary transfer voltage to be applied will be described.
As described above, the image forming units of the color printer 1 according to this embodiment are arranged in the order of yellow, cyan, magenta, and black from the upstream side along the moving direction A of the intermediate transfer belt 40 (FIG. 1). Is not particularly limited to this arrangement, but is determined by various conditions such as transfer conditions and arrangements that reduce the problem of color mixing. However, when transferring the toner image from the image forming unit provided on the upstream side of the movement direction of the intermediate transfer belt to the intermediate transfer belt, it is difficult to reversely transfer the toner to the photosensitive drum of the image forming unit arranged on the downstream side. It is desirable to select transfer conditions.

The transfer bias (transfer voltage) applied by the primary transfer unit when transferring from the image forming unit to the intermediate transfer belt (intermediate transfer member) is higher as the transfer bias (transfer energy) goes downstream in the moving direction of the intermediate transfer belt. The present inventors have clarified that it is necessary. However, it has also been found that when the transfer bias is increased, the problem that the toner is reversely transferred when transferring from the intermediate transfer belt (intermediate transfer member) to the photosensitive drum (latent image carrier) is likely to occur.
Therefore, the present inventors, when performing toner recycling in a full-color printer, have various transfer voltages using a test machine or the like in order to find the arrangement and conditions of image forming units that are difficult to reversely transfer even at the expense of transfer efficiency. The transfer efficiency at that time and the ratio of the reversely transferred toner were investigated.

  FIG. 2 is a graph showing the relationship between the primary transfer voltage and transfer efficiency for each toner color. As shown in FIG. 2, when the transfer voltage is gradually increased from the bottom when transferring a single color toner, the transfer voltage reaches the maximum level (the peak of the upwardly convex curve). The most requiring (transfer energy) is black, followed by yellow, cyan, and magenta. It can also be seen that there is a slight difference in the difference in transfer voltage (transfer energy) between black and yellow, and between cyan and magenta. That is, the transfer voltage (hereinafter referred to as the optimum transfer voltage) at which the transfer efficiency is optimal when transferring with a black toner single color is around 700 V (about 600 V to 800 V), and the optimum transfer voltage for yellow is 640 V. It can be said that the optimum transfer voltage for cyan is around 620 V (about 550 V to 700 V), and the optimum transfer voltage for magenta color is around 580 V (about 500 V to 650 V). . In consideration of these knowledge and the fact that the reverse transfer is facilitated when the transfer voltage is increased, in this embodiment, the image forming units are arranged as described above (see FIG. 1), and the optimum transfer efficiency is as follows. Was set so as to gradually decrease from the transfer voltage indicating.

  In other words, in order to prevent the image forming unit from being noticeable in the output image even when the toner is mixed in color, black, which is assumed to be most difficult to be visually recognized, is arranged on the most downstream side. For other yellow, cyan and magenta, the transfer efficiency is the same for the same applied voltage, and the transfer belts are arranged in order from the upstream in the transfer belt moving direction, and the yellow, cyan, magenta and black from the upstream side. Arranged in the order of Furthermore, the primary transfer voltage applied by the primary transfer roller 45Y is the highest in the transfer efficiency in order to compensate for the low transfer efficiency when transferring from the yellow image forming unit 3Y arranged at the most upstream to the intermediate transfer belt 40. The voltage, that is, the optimum transfer voltage of yellow color is set to about 640 V, and the primary transfer voltage applied by the next cyan primary transfer roller 45C is 5% lower than the highest transfer efficiency voltage, that is, The optimum transfer voltage for cyan is set to about 620 V × 0.95 (predetermined ratio smaller than 1) = 589 V, and the primary transfer voltage applied by the next magenta primary transfer roller 45M is set to the transfer efficiency. 10% lower than the highest voltage, that is, the optimum transfer voltage of magenta 580V × 0.90 (a predetermined value set in the cyan image forming unit arranged one upstream) (The ratio is smaller than 0.95) = about 589 V, and the primary transfer voltage applied by the black primary transfer roller 45K arranged at the most downstream is 15% lower than the highest transfer efficiency voltage, that is, The optimum transfer voltage for black color is set to 700V × 0.85 (a value smaller than a predetermined ratio of 0.90 set in the magenta image forming unit arranged one upstream) = about 595V.

When the amount of toner reversely transferred under this arrangement and transfer conditions was measured, the amount of reverse transfer toner to which yellow toner was reversely transferred was intermediate from that of yellow image forming unit 3Y in cyan image forming unit 3C. Less than 2% of the amount of toner transferred to the transfer belt 40, less than 1% of the toner amount in the magenta image forming unit 3M, and less than 1% of the toner amount in the black image forming unit 3K. It was only. Further, the amount of reverse transfer toner to which cyan toner is reversely transferred is less than 2% of the amount of toner transferred from the image forming unit 3C to the intermediate transfer belt 40 in the magenta image forming unit 3M. In the image forming unit 3K, it was less than 1% of the toner amount. By selecting such an arrangement and transfer conditions, although the transfer efficiency is somewhat lowered, it is possible to hardly cause toner color mixing, and even if the toner color is mixed, the color of the output image can be changed. It can be made inconspicuous.
Note that the numerical values given in the above description of the primary transfer voltage are affected by the characteristics of the toner used in the experiment, the product error of the intermediate transfer belt, and the like. It is not limited to these numerical values.

(Image forming unit)
Next, the image forming unit according to the present embodiment will be described in more detail.
FIG. 3 is an explanatory diagram illustrating the configuration of the yellow image forming unit according to the present embodiment. First, a yellow image forming unit 3Y will be described as an example of a representative image forming unit. The image forming unit 3Y shown in FIG. 3 is mainly composed of the photosensitive drum Y, the charging unit Y1, the developing unit Y2, and the cleaning unit Y3 as described above, and is contained in a unit case (not shown) that is a housing of the entire image forming unit. It is housed and integrated as a process cartridge. The photosensitive drum Y is pivotally supported by the unit case and can be driven to rotate in the direction of the arrow in the figure.

  The charging unit Y1 mainly includes a charging roller Y10. The charging roller Y10 is rotatably supported by a unit case and rotates around the photosensitive drum Y (in a direction opposite to the rotation direction of the photosensitive drum Y). The surface of the photosensitive drum Y is in contact with the photosensitive drum Y while being rotated, and the surface thereof can be charged to a predetermined polarity of either minus or plus.

  The developing means Y2 includes a developing case Y20 that constitutes a part of the unit case, a developing roller Y21 that is pivotally supported in the developing case Y20 and can apply a developing bias, and rotates in the developing case Y20. It is composed of agitation rollers Y22 and Y23 that are rotatably supported and a doctor blade Y24 that protrudes from the developing case Y20 at a predetermined distance from the developing roller Y21. The developing case Y20 contains a powdery two-component developer composed of yellow toner and a carrier. The developer is stirred by the stirring rollers Y22 and Y23, and the toner is charged to the predetermined polarity. And the carrier is charged to the opposite polarity. Then, the charged yellow toner is carried on the developing roller Y21, the amount of toner is regulated at the tip of the doctor blade Y24, and the developing roller Y21 is rotated so that the developing region is close to the outer peripheral surface of the photosensitive drum Y. Carried to. Therefore, the yellow toner carried on the developing roller Y21 is electrostatically transferred to the electrostatic latent image formed on the outer peripheral surface of the photosensitive drum Y, whereby the electrostatic latent image on the photosensitive drum Y is changed. The toner image is visualized.

The cleaning unit Y3 includes a cleaning blade Y30, which is a cleaning member that contacts the photosensitive drum Y and scrapes and collects the transfer residual toner that remains on the photosensitive drum Y even after the transfer, and the cleaning drum Y30. This is mainly composed of a collected toner storage hopper Y31 which is a space for storing transfer residual toner collected from Y (hereinafter referred to as collected toner). Further, the collected toner storage hopper Y31 is provided with a remaining amount detection sensor Y32 for detecting whether or not there is a stored remaining amount of the collected toner of a predetermined amount that does not hinder the conveyance of the collected toner at the bottom. A fullness detection sensor Y33 for detecting the fullness of the collected toner is provided at the top. The remaining amount detection sensor Y32 and the fullness detection sensor Y33 are general piezoelectric sensors, which are provided at a predetermined height calculated from the capacity of the collected toner storage hopper Y31, and whether there is toner at the height. Is detected and a predetermined signal is transmitted. Specifically, the remaining amount detection sensor Y32 is disposed at a height where a toner conveyance screw, which will be described later, is buried and a constant amount of toner conveyance can be secured, and the fullness detection sensor Y33 is a black image forming unit. The toner is disposed at a height determined by taking into account the amount of toner consumed that contributes to 3K image formation, the timing of replenishment (replenishment timing), and the prevention of overflow of collected toner from the collected toner storage hopper Y31. . For example, when it is desired to supply the collected toner frequently, the fullness detection sensor Y33 is arranged near the remaining amount detection sensor Y32, and if it is not necessary to supply the toner frequently, the overflow of the collected toner storage hopper Y31 is prevented. What is necessary is just to arrange | position in position. Further, instead of the piezoelectric sensor, a light reflection type photosensor may be disposed in the collected toner storage hopper Y31 via a transparent body such as a glass plate to detect a reflected light output value corresponding to the collected toner amount. At this time, it can be detected with high sensitivity that the wavelength emitted from the photosensor varies depending on the color toner. However, the piezoelectric sensor has higher reliability than the photo sensor and has a wider detection range of the collected toner amount, so that it can set the detection level during operation (described later) in a wide range (increased flexibility). Sometimes, it is convenient.
In the present embodiment, the cleaning blade has been described as an example of the cleaning member. However, other known cleaning members such as a brush roller may be used.

Further, one end of a new toner supply path Y4 (first new toner transport path) is connected to the developing case Y20 of the developing means Y2, and the other end of the new toner supply path Y4 is a new toner containing portion. When the toner density in the developing case Y20 is reduced by information from a toner density sensor (not shown) that is connected to the bottle Y5 (see FIG. 1) and is provided in the developing case Y20, yellow new toner is generated from the new toner bottle Y5. It is a mechanism to be replenished.
The “new toner” used in the present invention means a toner that has not yet been developed for image formation, and is distinguished from the toner that has been transferred onto the latent image carrier and collected by the cleaning means. .

  Further, one end of the recovered color toner transport path Y6 is connected to the lower part of the recovered toner storage hopper Y31 of the cleaning unit Y3, and one end of a new toner transport path Y7 that is the second new toner transport path is connected to the upper part. A discharge screw S1 (see FIG. 4), which is a conveying means, is provided from the collected toner storage hopper Y31 to the inlet of the collected color toner conveying path Y6. The other end of the collected color toner transport path Y6 is connected to a later-described recovered toner supply unit 30 so that the collected toner can be transported toward the black developing means K2, and the other end of the new toner transport path Y7. Is connected to the new toner bottle Y5 so that new toner can be supplied to the collected toner storage hopper Y31 (see also FIG. 1).

  As described above, the image forming unit 3Y has been described, but the other color image forming units 3C and 3M (see FIG. 1) have the same configuration. The black image forming unit 3K has substantially the same configuration, but in addition to the above configuration, the black image forming unit 3K has a collected toner supply unit 30 described later above the developing case (K20). Is provided, and the second new toner transport path is not provided. The collected toner supply unit 30 has a stirring means (not shown) for stirring the collected toner, and communicates with the collected color toner transport paths Y6, C6, and M6 for each color and a collected black toner transport path K6 described later, and collects each color. The collected toner conveyed from the toner storage hopper (Y31, C31, M31) is agitated and supplied to the black developing means K2 (see FIG. 1). The collected toner supply unit 30 can be provided in another image forming unit. In the present embodiment, since the respective toners are supplied from the three paths as described above, the collected toner supply unit 30 is agitated by the agitating means. As a temporary buffer function, one is provided near the upper portion of the black color developing means K2 so that it can be made uniform (dispersed) and supplied according to the amount of toner consumed during development.

Next, the collected color toner conveyance path, the second new toner conveyance path, and the collected black toner conveyance path, which are characteristic features of the present invention, will be described in detail with reference to FIGS. 1, 3, and 4. FIG.
(Collected color toner transport path)
FIG. 4 is a perspective view showing three color image forming units and a collected color toner conveyance path according to the present embodiment.
The collected color toner conveyance paths Y6, C6, and M6 shown in FIG. 4 communicate with the cleaning units Y3, C3, and M3 for each color other than the black color and the black development unit K2, and respectively carry toner within a predetermined time. A conveying screw S2, which is a toner conveying means capable of setting the amount, is provided. A plurality of the collected color toner transport paths Y6, C6, and M6 may be provided for each toner color, but as shown in FIG. 4, they are merged from the middle to form one and communicate with the black color developing means K2. Also good.

  Further, in this embodiment, since a predetermined amount of collected toner can be conveyed with a simple structure, a predetermined amount of collected toner can be conveyed for each toner color by adjusting the pitch and size of the fins of the discharge screw S1. It was set as follows. The amount of collected toner in each image forming unit is changed by adjusting the fin angle of the discharge screw S1. Similarly, the fin angle is adjusted when changing the conveyance ratio of the collected toner from each image forming unit. With this configuration, the rotational speed can be made the same for all color image forming units, and the same driving means can be used for ON / OFF control at the same time. The collected toner of each image forming unit is sent to the collected color toner conveyance path by a constant rotation of the discharge screw S1, and rotates in synchronization with the discharge screw S1, but the most upstream when the discharge screw S1 is OFF. The drive timing is set to be long so that the collected toner of the yellow image forming unit 3Y is turned off after the time required for the collected toner supply unit 30 to be supplied. For this reason, it is better to divide the discharge screw S1 and the conveyance screw S2 by using a clutch or the like. Further, the transport speed of the collected toner in the collected color toner transport path may be changed for each color. At this time, the fin angle until reaching the cyan image forming unit 3C should be set so that the transport speed of the collected toner of the yellow image forming unit 3Y is the fastest.

  In addition, a screw-type toner conveying unit has been described as an example. However, a powder pump such as a uniaxial eccentric screw pump or a diaphragm pump proposed by the applicant in Japanese Patent Laid-Open No. 10-333412 was used. You may use as a conveyance means of the system which mixes and conveys airflow and a toner. If this mechanism is used, the operation time of the powder pump can be easily controlled, so that a predetermined recovered toner amount can be supplied more easily. Furthermore, there is an advantage that a free conveyance path can be laid out, and a simple structure can be achieved. As described above, by setting the transport amount of the collected toner from each image forming unit, the mixing ratio of the collected toner from each image forming unit can be set to a predetermined ratio regardless of the simple structure.

(New toner transport path)
As shown in FIGS. 1 and 3, the new toner transport paths Y7, C7, and M7, which are the second new toner transport paths, are the new toner bottles Y5, C5, and M5 for each color and the cleaning means Y3, C3 for each color. Each of the toner collection hoppers Y31 (C31, M31) of M3 communicates with the unillustrated conveying means similar to the discharge screw S1 and the conveying screw S2 and has the same color from each of the new toner bottles Y5, C5, M5. A predetermined amount of new toner can be supplied to the collected toner storage hopper Y31 (C31, M31).

(Recovered black toner transport path)
As shown in FIG. 1, the collected black toner conveyance path K6 includes a collected toner storage hopper (K31) of the black cleaning means K3, and a collected toner supply section 30 provided above the black developing means K2. , And a discharge means (not shown) similar to the above-described discharge screw S1 and transfer screw S2, and the black color recovered by the black cleaning means K3 using the transfer means (not shown) and the discharge screw S1. The collected toner can be supplied to the collected toner supply unit 30.

(Toner transport operation)
Next, toner recovery operations such as the collected color toner transfer path, the second new toner transfer path, the recovered black toner transfer path, the discharge screw S1, and the transfer screw S2 will be described. As described above, the image forming units for the respective colors are provided independently. However, the operation may be controlled so as to be interlocked.
For example, when a signal for starting the supply of the collected toner is transmitted from the black image forming unit 3K, the discharge screws S1 of the yellow, cyan, and magenta color image forming units 3Y, 3C, and 3M rotate all at once. As the transport screw S2 in the recovered color toner transport path operates, the recovered toner is supplied to the recovered toner supply unit 30 of the black image forming unit 3K. Further, when a signal for turning off the supply of the collected toner is transmitted from the black image forming unit 3K, the rotation of all the discharge screws S1 and the conveying screw S2 is stopped, and the supply of the collected toner is stopped. Good.

  At this time, the supply start signal of the collected toner may be transmitted from the black image forming unit 3K or may be transmitted from a control unit (not shown) of the printer 1. Further, it may be transmitted from each color image forming unit. For example, when only the full detection sensor (C33) of the cyan image forming unit 3C detects that the collected toner exceeds the capacity (a predetermined amount or more), a supply start signal is set to be transmitted, and the cyan collected toner is set. May be prevented from overflowing from the collected toner storage hopper (C31).

  Also, the supply stop signal of the collected toner may be transmitted from any of the supply start signals. For example, any one of the collected toner storage hoppers (Y31, C31, M31) for color toners other than black is used. When the remaining amount detection sensor (Y32, C32, M32) detects that the stored amount of the collected toner is less than a predetermined amount, it controls to ignore the supply start signals and stop the supply. As described above, the remaining amount detection sensors (Y32, C32, M32) are disposed at a height at which the discharge screw S1 is buried and a steady amount of toner conveyance can be ensured. This is because it becomes difficult to maintain the conveyance ratio of the collected toners of yellow, cyan, and magenta colors at a predetermined ratio. However, if it is accepted that such a transport ratio of the collected toner cannot be maintained at a predetermined ratio, for example, it is possible to control the supply start ON / OFF at regular time intervals.

  Next, the collected toner supply operation to the collected toner supply unit 30 of the black image forming unit 3K will be described in detail. However, the operation is not limited to the operation described below, and yellow, cyan, and magenta color images are described. Any operation may be used as long as the collected toner of the forming unit can be supplied at a predetermined ratio (a constant amount) at substantially the same time. The same applies to the supply to the collected toner supply unit 30 as long as the collected color toner of each color can be supplied to the developing unit K2 of the black image forming unit 3K and contribute to image formation.

  For example, if the full toner detection sensor (Y33, C33, M33) of the color image forming unit of yellow, cyan, or magenta color detects that the collected toner storage amount is a predetermined amount or more (over capacity), The conveying screw S2 of the collected color toner conveying path (Y6, C6, M6) is rotated so as to forcibly supply the toner to the collected toner supply unit 30. Therefore, the collected toner is not overflowed in any collected toner storage hopper (Y31, C31, M31), and the toner conveying operation and the toner collecting operation are guaranteed.

  If it demonstrates referring FIG. 4, the discharge screw S1 carries out regular rotation operation | movement with rotation start operation | movement of conveyance screw S2. The discharge screw S1 may be turned off after a predetermined time has elapsed, but in this embodiment, the discharge screw S1 is turned off when any remaining amount detection sensor (Y32, C32, M32) of each color detects a certain amount or less. . In addition, a remaining amount detection sensor may be provided in the black collected toner supply unit 30 to transmit an OFF signal when a certain amount or less is detected, or an OFF signal may be transmitted by combining these. It may be.

  As described above, the example in which the toner is supplied to the recovered toner supply unit 30 in accordance with the detection value of any of the fullness detection sensors (Y33, C33, M33) has been described. The supply operation may be turned ON / OFF depending on the amount of toner (replenishment toner). Further, the supply operation may be turned ON / OFF by a combination of the sensor output value and the toner amount in the collected toner supply unit 30. In any case, the remaining amount detection sensor (Y32, C32, M32) of the color image forming unit (3Y, 3C, 3M) of yellow, cyan, or magenta has a storage amount of the collected toner equal to or less than a predetermined amount. If it is detected, supply is prohibited. In the present embodiment, the supply of collected toner to the developing means K2 of the black image forming unit 3K is prohibited until the fullness detection sensors (Y33, C33, M33) detect a predetermined amount or more (over capacity). To control. Therefore, it is preferable to use a vibration capacitive sensor with a wide detection range. By doing so, the rotation operation of the conveying screw S2 can be started by looking at the change in the amount of collected toner stored in each of the color image forming units of yellow, cyan, and magenta before reaching the predetermined amount. Of course, the rotation operation may be started by the state of the image forming unit of each color or a signal from the control means of the image forming apparatus main body, or the rotation operation may be started by a combination thereof.

(Image forming operation)
Next, an image forming operation of the printer 1 will be described with reference to FIG.
In the case of forming a color image, first, when an image forming operation is started in the color printer 1, the photosensitive drums Y, C, M, and K are moved in the directions indicated by the arrows (from the front door side of the color printer 1). In this case, the outer peripheral surfaces of the photosensitive drums Y, C, M, and K are set to a predetermined polarity (for example, minus) by the charging units Y1, M1, C1, and K1. It is charged like this. Next, the charging surface is irradiated with laser light that is light-modulated based on the image information separated into predetermined colors from the writing means 2, whereby the outer circumference of each photosensitive drum Y, C, M, K is irradiated. An electrostatic latent image is formed on the surface. The electrostatic latent image is visualized as a single color toner image by the developing units Y2, C2, M2, and K2, and the toner images of the respective colors are respectively transferred to the corresponding primary transfer rollers 45Y, 45C, 45M, and 45K. As a result, a primary transfer bias is applied and sequentially transferred onto the intermediate transfer belt 40 to form a color toner image. When a single color image is formed, the above operation is performed only with a predetermined single color photosensitive drum such as the black photosensitive drum K.

  On the other hand, the transfer material stocked in the supply tray 50 of the paper supply unit 5 is separated one by one by the pressure contact / drive of the supply rollers 52 and 53 and the friction pad, and is sent toward the registration roller pair 54. Then, the leading edge of the transfer material abuts against the stopped registration roller pair 54. As a result, after the transfer materials are aligned, the intermediate transfer belt 40 is rotated by driving the drive roller 43, and the color toner image formed on the intermediate transfer belt 40 is aligned with the timing at which it reaches the secondary transfer nip. The roller pair 54 is rotated to feed the transfer material toward the secondary transfer nip.

  Next, the transfer material on which the toner image is transferred at the secondary transfer nip of the transfer unit 4 is sent to the fixing nip of the fixing unit 6. Therefore, heat and pressure are applied between the fixing roller 60 and the pressure roller 61, and the unfixed toner image carried on the transfer material is fixed on the transfer material. As described above, after the toner image is fixed on the transfer material, the discharge roller pair 71 rotates and is discharged onto the discharge tray 70 of the discharge unit 7. Further, the transfer residual toner adhering to the surface of the intermediate transfer belt 40 after the secondary transfer is removed by the cleaning unit 47 and prepared for another image forming operation.

  As described above, according to the color printer of the first embodiment (Embodiment 1), the collected toner collected by the color image forming units (3Y, 3C, 3M) of yellow, cyan, and magenta is used. When returning to the black developing means K2 and recycling, the ratio of the transport amount of the recovered toner is determined in advance with a simple and inexpensive configuration from each recovered toner storage hopper (Y31, C31, M31) of each color image forming unit. Thus, the fixed amount of yellow, cyan, and magenta collected toner is supplied to the developing means K2 of the black image forming unit 3K at a predetermined time, so that the color printer 1 according to the present embodiment. Even in such a color image forming apparatus, it is possible to provide an environment-friendly machine without deteriorating the color and color reproducibility of the output image. In addition, the collected toner supply unit 30 is provided in the black image forming unit 3K, and all of the collected toner from the black image forming unit 3K and the replenished new toner from the black new toner bottle K5 are also supplied with this collected toner. Since it is supplied to the unit 30, it is possible to improve the output image so that a substantial black color change hardly occurs.

[Embodiment 2]
Next, a second embodiment of the present invention will be described with reference to FIGS. The difference from the first embodiment is mainly the difference in the arrangement and transfer system of the image forming units in the image forming unit, and each component has the same configuration. Therefore, the same components are denoted by the same reference numerals and description thereof is omitted, and only differences from the first embodiment will be described.
FIG. 5 is an explanatory diagram showing the outline of the overall configuration of the color image forming apparatus according to the second embodiment of the present invention. Reference numeral 1 ′ in the figure denotes a triple tandem black independent type direct / intermediate transfer hybrid type color copy multifunction peripheral 1 ′ exemplified as a second embodiment of the present invention. As shown in FIG. 5, the color copy multifunction peripheral 1 ′ is mainly arranged in an apparatus main body 10 ′, writing means 2 provided near the center of the apparatus main body 10 ′, and above the writing means 2. Image forming unit 3 ′, a transfer unit 4 ′ provided between the image forming unit 3 ′ and the writing unit 2, a paper feeding unit 5 provided at the bottom of the apparatus main body 10 ′, and a transfer unit. The fixing unit 6 is provided above the unit 4 ′, the paper discharge unit 7, and the like. In addition to the configuration similar to that of the color printer 1 according to the first embodiment, the scanner unit 8 for scanning a document, the conveyance path D for duplex conveyance, the manual feed tray E, the intermediate transfer belt cleaning unit 47 ′, A waste toner collecting unit 9 and the like are further provided. However, since these are not the main part of the present invention and are known, detailed description will be omitted.

  As in the first embodiment, the image forming unit 3 ′ mainly includes four image forming units 3Y ′, 3C ′, 3M ′, and 3K ′ that correspond to toners of four colors of yellow, cyan, magenta, and black. The image forming units 3Y ′, 3C ′, 3M ′, and 3K ′ are configured in substantially the same manner. However, the major difference is that the black toner image formed by the black image forming unit 3K ′ is directly transferred from the photosensitive drum K ′, which is a black latent image carrier, to the transfer material, and other than the black color. A single color toner image of each color other than black formed by the color image forming unit is temporarily transferred from the photosensitive drums Y ′, C ′, M ′ to the intermediate transfer belt 40 ′, which is an intermediate transfer member, and then transferred to a transfer material. It is the point which is comprised so that it may transcribe | transfer. That is, the black image forming unit 3K ′ is a single direct transfer system, and is disposed upstream in the transfer paper conveyance direction, and the remaining color image forming units 3Y ′, 3C ′, 3M ′ are intermediate. This is a triple tandem type intermediate transfer system in which yellow, cyan, and magenta are arranged in series from the upstream side along the movement direction B of the lower surface of the transfer belt 40 ′.

  Next, transfer conditions of each image forming unit will be described. In the color copy multifunction peripheral 1 ′, which is an image forming apparatus according to the second embodiment, the image is applied by the black transfer roller 48K arranged alone based on the knowledge described in the first embodiment. When the transfer voltage is set to a voltage with the highest transfer efficiency and the image is transferred from the yellow image forming unit 3Y ′ arranged at the most upstream in the moving direction of the intermediate transfer belt 40 ′ to the intermediate transfer belt 40 ′, the primary transfer roller The primary transfer voltage applied at 45Y ′ is set to a voltage having the highest transfer efficiency, that is, about 640 V, which is the optimum transfer voltage for yellow, and the primary transfer applied by the next cyan primary transfer roller 45C ′. The voltage is set to a value 5% lower than the highest transfer efficiency voltage, that is, about 620 V × 0.95 (a predetermined ratio smaller than 1) = 589 V, which is the optimum transfer voltage of cyan, and the most downstream The primary transfer voltage applied by the primary transfer roller 45M ′ for the magenta color is 10% lower than the highest transfer efficiency voltage, that is, the optimum transfer voltage for magenta color is 580V × 0.90 (located one upstream). The value is smaller than a predetermined ratio of 0.95 set in the cyan image forming unit) = 589V. When the reverse transfer toner amount when the transfer conditions are set in this way is measured, less than 3% of the toner transferred to the intermediate transfer belt 40 ′ by the yellow image forming unit 3Y ′ is cyan image forming unit 3C ′. In the magenta image forming unit 3M ′, less than 1% was measured as the reverse transfer toner amount. Less than 2% of the toner transferred to the intermediate transfer belt 40 ′ by the cyan image forming unit 3 </ b> C ′ was only measured as a reverse transfer toner amount to the magenta unit. In this way, by setting the transfer conditions, in the first embodiment, it is possible to prevent the color mixing problem as much as possible while improving the transfer efficiency of the black image forming unit 3K ′ which is slightly sacrificed. .

  FIG. 6 is an explanatory diagram illustrating a configuration of a yellow image forming unit according to the second embodiment. As shown in FIG. 6, a yellow image forming unit 3Y ′ will be described as an example as a representative of the image forming unit according to the second embodiment. Similar to the color printer 1, the image forming unit 3Y ′ includes a photosensitive drum Y ′, a charging unit Y1 ′, a developing unit Y2 ′, and a cleaning unit Y3 ′, and each configuration is substantially the same. Since the image forming unit 3Y ′ is disposed on the lower surface side of the intermediate transfer belt 40 ′, the image forming unit 3Y ′ has a configuration that is just upside down with respect to the image forming unit 3Y of the first embodiment. However, since the direction in which gravity acts is the same, the collected toner storage hopper Y31 'is provided with a remaining amount detection sensor Y32' at the lower part and a fullness detection sensor Y33 'at the upper part. The collected toner storage hopper Y31 ′ has a lower end connected to one end of a recovered color toner transfer path Y6 ′ and an upper end connected to one end of a new toner transfer path Y7 ′ that is a second new toner transfer path. Yes. Further, the new toner supply path Y4 'has the same configuration as the new toner supply path Y4 (first new toner transport path) of the color printer 1.

  According to the color copy multifunction peripheral 1 ′ of the second embodiment (second embodiment), the transfer efficiency of the black color image forming unit, which has been a concern, in the color printer of the first embodiment 1 is high. The problem of not being able to fully demonstrate can be solved. In particular, when an image is formed under high humidity, the black image density tends to decrease. Therefore, the black color development amount during development must be controlled higher than usual. For example, since the black image forming unit 3K ′ is a single unit, it is not necessary to substantially consider the change in color of the black image as well as the transfer efficiency. Such an arrangement is an example and does not limit the order of arrangement of the image forming units. For example, the cyan image forming unit 3 </ b> C ′ and the magenta image forming unit 3 </ b> M ′ may be determined based on the apparent color tone at the time of color mixing if the transfer energy when transferring in a single color is approximately the same.

[Embodiment 3]
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 7 is an explanatory diagram showing the outline of the overall configuration of the color image forming apparatus according to the third embodiment of the present invention. The difference between the color printer 1 "and the first embodiment is limited to a configuration in which a total of three collection color toner conveyance paths (Y6", C6 ", M6") are provided for each toner color. And the point that the color sensor S3 is newly provided. Therefore, other explanations are omitted.

  The collected color toner conveyance paths (Y6 ″, C6 ″, M6 ″) are similar to the first embodiment in the collected toner storage hoppers Y31, C31, C3, C3, M3 of the cleaning units Y3, C3, M3 other than black. There are three conveying screws S2 ″ that are toner conveying means that communicate with M31 and the toner supply unit 30 provided near the upper side of the black color developing means K2 and that can each set a toner conveying amount per predetermined time. Is provided. Unlike the conveying screw S2 of the first embodiment, the conveying screw S2 ″ can be independently driven for each toner color, and is greatly different in that its rotation speed can be changed and adjusted.

  As shown in FIG. 7, the color sensor S3 detects the color of the collected toner stored in the collected toner supply unit 30, and is provided on the outer peripheral surface of the black photosensitive drum K that is a latent image carrier. It is provided at a position facing and close to. The color sensor S3 is a sensor having sensitivity of three primary colors such as R (red), G (green), B (blue), Y (yellow), M (magenta), and C (cyan). A specific detection method will be described. First, a color pattern is formed on the black photosensitive drum K using the collected toner stored in the collected toner supply unit 30. At this time, a highlight density such as a halftone is set so that the color can be distinguished. Then, the color pattern is optically measured by the color sensor S3, and the color deviation from the black single color stored by the control means (not shown) of the color printer 1 "is calculated.

  Next, the operation for preventing the color change of the collected toner will be described. First, as described above, the color of the collected toner stored in the collected toner supply unit 30 is detected by the color sensor S3. If it is determined that the collected toner is shifted to a certain hue based on the detection information from the color sensor S3, the conveying screw S2 for each color is set so that the newly collected collected color toner is complementary to the hue. By controlling the number of rotations, the toner transport amount is adjusted to transport the collected toner. For example, when a complementary color can be created with one color toner, only one color toner is transported, but in most cases The two color toners are mixed to adjust to a predetermined complementary color, and the collected toner of the necessary color is replenished in this way, and the collected toner storage hopper for the collected toner of the complementary color that needs to be replenished When the remaining amount detection sensor detects a certain amount (the minimum amount that can secure the amount of collected toner transported) or less, the new toner of that color is supplied from the new toner transport path and the remaining amount detection sensor is detected. New toner continues to be supplied until it is detected again that the toner amount exceeds a certain amount, so that the toner can be recycled without losing the balance of the tint. When the full toner detection sensor for the collected toner of colors that should not be replenished detects a certain amount or more, the collected toner is forcibly conveyed to the collected toner replenishment unit 30. At this time, the collected toner of complementary colors that need replenishment is replenished Therefore, the image forming operation is guaranteed without overflowing any of the collected toner storage hoppers.

  As described above, according to the color printer 1 ″ of the third embodiment (Embodiment 3), the color of the collected toner stored in the collected toner storage hopper is directly detected, and the collected toner has a hue. If it is determined that it is offset, the collected toner that is complementary color is adjusted and conveyed, so that the color of the black image forming unit 3K ″ can be the original black color. In addition, when fullness is detected by any fullness detection sensor other than the black color, the transport of the collected toner is forcibly started from all the collected toner storage hoppers other than the black color, and further from the color sensor. If it is determined that the collected toner in the collected toner supply unit is shifted to a certain hue based on the information of the toner, the amount of toner transported so that the newly collected collected color toner contains a relatively large amount of complementary colors of the hue Therefore, the collected toner is conveyed to the collected toner supply unit 30, so that there is no fear that the collected toner overflows from the collected toner supply unit 30.

As described above, as the image forming apparatus according to the embodiment of the present invention, a quadruple tandem type indirect transfer system (Embodiments 1 and 3), a triple tandem black single type direct / indirect hybrid system ( The embodiment 2) has been described as an example. However, the present invention is not necessarily limited to this, and for example, a quadruple tandem direct transfer system may be used. In short, any color image forming apparatus including a plurality of image forming units that independently form toner images for each predetermined color including at least a black color may be used.
In addition, the writing unit, the image forming unit, the transfer unit, the paper feeding unit, the fixing unit, the paper discharge unit, and the like are merely examples, and configurations of other known devices and units may be adopted. it can. Even in such a case, it is clear that the same effect can be obtained with respect to the above-mentioned problem.
In addition, the shape, structure, etc. of each structural member shown by drawing show a preferable example to the last.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory diagram illustrating a schematic configuration of an entire image forming apparatus according to a first embodiment of the present invention. 6 is a graph showing the relationship between primary transfer voltage and transfer efficiency for each toner color. 2 is a configuration explanatory diagram illustrating a configuration of a yellow image forming unit according to Embodiment 1. FIG. FIG. 3 is a perspective view showing three color image forming units according to Embodiment 1 and a collected color toner conveyance path. FIG. 6 is a configuration explanatory diagram illustrating a schematic configuration of an entire image forming apparatus according to a second embodiment of the present invention. FIG. 6 is a configuration explanatory diagram illustrating a configuration of a yellow image forming unit according to a second embodiment. FIG. 6 is a configuration explanatory diagram illustrating a schematic configuration of an entire image forming apparatus according to a third embodiment of the present invention.

Explanation of symbols

1 Color printer (color image forming device)
3Y, 3C, 3M Color image forming unit 3K Black image forming unit S3 Tint sensor Y, C, M, K Photosensitive drum (latent image carrier)
Y2, C2, M2, K2 Developing means Y3, C3, M3, K3 Cleaning means Y31, C31, M31 Recovered toner storage hopper K31 Recovered toner storage hopper Y32, C32, M32 Remaining amount detection sensors Y33, C33, M33 Fullness detection Sensors Y4, C4, M4, K4 New toner supply path (first new toner transport path)
Y5, C5, M5, K5 New toner bottle (new toner container)
Y6, C6, M6 Collection color toner conveyance path K6 Collection black toner conveyance path S1 Discharge screw (conveyance means)
S2 Conveying screw (conveying means)
Y7, C7, M7 New toner transport path (second new toner transport path)
30 Collected toner supply unit 40 Intermediate transfer belt (intermediate transfer member)

Claims (19)

The image forming unit includes a plurality of image forming units that independently form toner images for each predetermined color including at least a black color. Each of these image forming units includes a latent image carrier that carries an electrostatic latent image on its surface, and a static image carrier. A developing unit that develops the electrostatic latent image into a toner image with toner of a predetermined color; and a cleaning unit that cleans and collects the transfer residual toner that remains attached to the latent image carrier after transfer,
Further, a plurality of new toner storage units that store new toner that is not used for development for each of the predetermined colors, and the new toner is transported from the new toner storage unit for each color to the corresponding developing unit for each color. In a color image forming apparatus provided with a first new toner conveying path for each toner color,
Among the cleaning means, one or a plurality of recovered color toner transport paths for transporting the recovered toner from the cleaning means for each color other than black to the black developing means, and from the black cleaning means to the black developing means A recovery black toner transport path for transporting the recovered toner toward the black side, and a plurality of second new toner transport paths for transporting the new toner of each color from the new toner storage section for each color other than black to the black developing means. And a color image forming apparatus.   2. The color image forming apparatus according to claim 1, which is a tandem type intermediate transfer system in which the plurality of image forming units are arranged in series along the moving direction of the intermediate transfer member. The black image forming unit is disposed on the most downstream side when viewed from the moving direction of the intermediate transfer member,
The image forming units of other colors are arranged from the upstream side in the moving direction of the intermediate transfer member in order of poor transfer efficiency when transferring in a single color.
The primary transfer voltage applied at the time of transfer from the image forming unit arranged at the most upstream to the intermediate transfer member is set to a transfer voltage value at which the transfer efficiency is optimal when transferring with a single color toner of the image forming unit. And
The primary transfer voltage applied at the time of transfer from the image forming unit arranged second from the upstream to the intermediate transfer member is a transfer voltage at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit. Set to a value multiplied by a predetermined percentage less than 1,
The primary transfer voltage applied at the time of transfer from the second image forming unit to the intermediate transfer member is 1 to the transfer voltage at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit. 3. The color image forming apparatus according to claim 2, wherein the color image forming apparatus is set to a value obtained by multiplying a value smaller than the predetermined ratio set in the image forming unit arranged upstream.   The black toner image formed by the black image forming unit is directly transferred from the black latent image carrier to the transfer material, and the single color toner image of each color other than black formed by the image forming unit other than black is 2. The color image forming apparatus according to claim 1, wherein each latent image carrier is temporarily transferred to an intermediate transfer member and then transferred to a transfer material. The image forming units other than the black color are tandem types arranged in series from the upstream side along the moving direction of the intermediate transfer member in order of poor transfer efficiency.
The primary transfer voltage applied at the time of transfer from the most upstream image forming unit to the intermediate transfer member is set to a transfer voltage value at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit.
The primary transfer voltage applied at the time of transfer from the image forming unit arranged second from the upstream to the intermediate transfer member is a transfer voltage at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit. Set to a value multiplied by a predetermined percentage less than 1,
The primary transfer voltage applied at the time of transfer from the second image forming unit to the intermediate transfer member is 1 to the transfer voltage at which transfer efficiency is optimal when transferring with a single color toner of the image forming unit. The color image forming apparatus according to claim 4, wherein the color image forming apparatus is set to a value obtained by multiplying a value smaller than the predetermined ratio set in an image forming unit arranged upstream.   The toner conveying means provided in the collected color toner conveying path has a toner conveying amount set so that the color of the collected color toner is close to the color of black with the mixing ratio of the collected toner of each color as a predetermined ratio. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is a color image forming apparatus.   The plurality of toner conveying means provided in the collected color toner conveying path are conveying screws driven at the same rotational speed by the same driving means, and the rotational speed such as the size of the fin of the conveying screw and the angle of the fin of the screw. The color image forming apparatus according to claim 6, wherein the toner conveyance amount is set by changing a means other than the above. Each cleaning means has a cleaning member that contacts each latent image carrier and collects the transfer residual toner, and a collected toner storage hopper that is a space for storing the transfer residual toner collected from each latent image carrier. And
The collected color toner conveyance path and the second new toner conveyance path communicate with the collected toner storage hopper for each color, and the collected toner for each color passes through the collected color toner conveyance path for each color. The toner is stored in the first section and then transported toward the black developing means, and the new toner of each color other than black passes through the second new toner transport path and the collected toner storage hopper section of each color. The color image forming apparatus according to claim 1, wherein the color image forming apparatus is supplied toward a black developing unit.   9. The remaining toner detection hopper is provided with a remaining amount detection sensor for detecting whether or not there is a stored remaining amount of recovered toner that does not hinder the transport of the recovered toner. A color image forming apparatus described in 1.   When the remaining amount detection sensor other than black color among the remaining amount detection sensors detects that the remaining amount of collected toner is less than a predetermined amount, the collected toner storage hopper provided with the remaining amount detection sensor The color image forming apparatus according to claim 9, wherein new toner is supplied through the second new toner conveyance path.   When the remaining amount detection sensor other than the black color among the remaining amount detection sensors detects that the remaining amount of collected toner is less than a predetermined amount, the collected toner storage hopper provided with the remaining amount detection sensor The collected toner is stopped and the new toner is supplied to the collected toner storage hopper through the second new toner conveying path, and then the remaining amount detection sensor has a stored toner remaining amount equal to or larger than a predetermined amount. 11. The color image forming apparatus according to claim 10, wherein when the toner is detected, transport of the recovered toner is started from the recovered toner storage hopper through the recovered color toner transport path.   12. The color image forming apparatus according to claim 8, wherein a fullness detection sensor for detecting a fullness of the collected toner is provided in the collected toner storage hopper.   The transport of recovered toner is started from all of the recovered toner storage hoppers other than black when full is detected by any of the full detection sensors other than black. The color image forming apparatus according to 12.   One of the remaining amount detection sensors other than black is used to detect that the remaining amount of collected toner is less than a predetermined amount, and one of the fullness detection sensors other than black is used. New toner is supplied to the collected toner storage hopper provided with a remaining amount detection sensor that detects that the remaining amount of collected toner is less than or equal to a predetermined amount when the full detection sensor detects fullness, 13. The transport of the collected toner from all the collected toner storage hoppers other than the black color is not started unless the remaining amount detection sensor detects that the remaining amount of the stored toner is not less than a predetermined amount. 14. A color image forming apparatus according to item 13.   A black color developer having stirring means for stirring the collected toner, communicating with the collected color toner conveying path and the collected black toner conveying path, and stirring the collected toner conveyed from the collected toner storage hopper for each color; 15. The color image forming apparatus according to claim 8, further comprising a collected toner supply unit that is provided in the vicinity of the black color developing unit.   A color sensor for detecting the color of the collected toner stored in the collected toner supply unit is provided, and a toner conveying means capable of being independently driven for each toner color is provided in the collected color toner conveying path, and the color sensor detects The color image forming apparatus according to claim 15, wherein each toner conveyance amount of the collected color toner can be adjusted according to a result.   The color sensor forms a color pattern on the black latent image carrier from the collected toner in the collected toner supply unit by a black image forming unit, and optically measures the color pattern. The color image forming apparatus according to claim 16, wherein a color of the collected toner is detected by the method.   When it is determined that the collected toner in the collected toner supply unit is shifted to a certain hue based on the detection information from the color sensor, the newly collected conveyed color toner is complemented with the hue. 18. The color image forming apparatus according to claim 16, wherein the collected toner is conveyed to the collected toner supply unit by adjusting a conveyance amount.   When full detection is detected by any of the full detection sensors other than black among the full detection sensors, the transport of recovered toner is forcibly started from all of the recovered toner storage hoppers other than black, and thereafter When it is determined that the collected toner in the collected toner supply unit is shifted to a certain hue based on the information from the color sensor, the newly collected collected color toner includes a relatively large amount of a complementary color of the hue. 18. The color image forming apparatus according to claim 16, wherein the toner transport amount is adjusted to transport the recovered toner to the recovered toner supply unit.

Images