JP2006215319A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus where the overflow of a toner recovery container provided in each image forming unit is prevented even when a detection sensor is not provided, and an intermediate transfer body is hardly damaged, and which realizes the miniaturization of the toner recovery container and the maintenance of image quality by toner forced consuming operation. <P>SOLUTION: A controller 12 calculates an amount of toner used in the image forming unit 50 and an amount of waste toner recovered in a 1st waste toner recovery tank based on data used to form an image. In the case of consecutively forming a low-density image, a predetermined toner image is formed by the toner forced consuming operation, and toner unsuitable for image forming is transferred to a photoreceptor drum and recovered only by the 1st waste toner recovery tank. When the predetermined amount of waste toner is stored in the 1st waste toner recovery tank, the toner image formed by the toner forced consuming operation is transferred from the photoreceptor drum 51 to the intermediate transfer belt 42, and the toner is recovered also to a 2nd waste toner recovery tank 48. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus including a plurality of image forming units and an intermediate transfer member.

  2. Description of the Related Art Conventionally, in an image forming apparatus such as a printer, a copying machine, or a composite machine including a plurality of image forming units and an intermediate transfer member, each image forming unit is not transferred to the intermediate transfer member in an image forming operation. A toner collection container for collecting the toner remaining on the photosensitive drum is provided. In the toner collection container of the image forming unit arranged along the transfer medium, a large amount of toner is collected in the downstream portion of the transfer medium in the transport direction, so in Patent Document 1, the transfer medium is transported. An image forming apparatus has been proposed in which the capacity of the toner collection container is increased toward the downstream side in the direction so that all the toner collection containers are almost full when all the toner is used up. According to this, since the toner collection container can be made the minimum size, the image forming apparatus can be downsized.

In recent years, image forming apparatuses have been digitized, and image data to be formed is transferred to an image forming unit by a control device, and an electrostatic latent image is formed on the photosensitive drum based on the data. Thus, the amount of toner consumed by each image forming unit can be calculated.
Japanese Patent Application Laid-Open No. 2004-101592 (pages 4 to 6, FIGS. 1 and 2)

  By the way, in the image forming unit, the toner stirred and charged in the developing device is supplied to the photosensitive drum, and the electrostatic latent image is visualized. In the case of forming a low density image, the amount of charge of the toner is increased because the time for stirring until the toner is supplied to the photosensitive drum becomes longer than in the case of forming a high density image. Therefore, when low density images are continuously formed, the toner charge amount becomes excessive, and the formed image density is lower than the desired density.

  Therefore, when image formation of a predetermined density or lower is continued, a toner image having a predetermined size and density is formed on the photosensitive drum in each image forming unit, and toner with an excessive charge amount is forcibly applied. An operation for keeping the charge amount of the toner used for image formation appropriately (hereinafter referred to as toner forced consumption operation) is performed.

  Since most of the toner image formed on the photosensitive drum in the normal image forming operation is transferred to the intermediate transfer member, the toner recovered in the toner recovery container provided in each image forming unit is the photosensitive drum. It is a part of the toner image formed on the top. However, it is desirable not to transfer the toner image formed on the photosensitive drum by the forced toner consumption operation to the intermediate transfer member so that the intermediate transfer member is not damaged, and all the toner images provided in each image forming unit It is collected in a collection container.

  For this reason, the more frequently the forced toner consumption operation is performed, the faster the toner collection containers provided in the respective image forming units are filled. Therefore, in the image forming apparatus proposed in Patent Document 1, the toner collection containers overflow. there is a possibility. In order to prevent this, it is necessary to provide a detection sensor for detecting that the toner collecting container is full of toner. However, providing a detection sensor is not recommended because it leads to an increase in cost and a decrease in the capacity of the toner collection container.

  Therefore, in the present invention, the toner collection container provided in each image forming unit does not overflow without providing a detection sensor, and the intermediate transfer member is not easily damaged. An object of the present invention is to provide an image forming apparatus capable of maintaining image quality according to the above.

  (1) In order to achieve the above object, the present invention provides a photosensitive drum, a toner container that supplies toner to the surface of the photosensitive drum, and a first container that accommodates toner collected from the photosensitive drum. A plurality of image forming units each having a waste toner recovery tank; an intermediate transfer member to which the toner image is transferred from the photosensitive drum; and a second waste toner recovery member for storing toner recovered from the intermediate transfer member An image forming apparatus comprising a tank and a control device, and performing a forced toner consumption operation for forming a predetermined toner image on the circumferential surface of the photosensitive drum after a predetermined image forming operation. Based on data used to control the toner forced consumption operation and to form a toner image in the image forming operation and the toner forced consumption operation. Calculating the amount of toner p consumed from the start of use of the toner container of the image forming unit, and the amount of toner of the toner image transferred when transferring the toner image from the photosensitive drum to the intermediate transfer member; The amount q of waste toner collected in the first waste toner collection tank of each image forming unit can be calculated based on the ratio x to the amount of toner before transfer and the p. In the forced toner consumption operation, the predetermined toner image formed on the peripheral surface of the photosensitive drum has an initial toner amount P stored in the toner container and a capacity of the first waste toner recovery tank Q. If the calculation result by the control device is (Qq)> (1-x) · (Pp), the first waste toner recovery tank is not transferred to the intermediate transfer member. When it is collected and the calculation result by the controller is (Qq) = (1−x) · (P−p), it is transferred from the photosensitive drum to the intermediate transfer member and transferred to the intermediate transfer member. The toner thus collected is collected in the second waste toner collection tank, and the toner remaining on the photosensitive drum is collected in the first waste toner collection tank.

  According to this configuration, the calculated value (Pp) of the amount of toner stored in the toner container and the calculated value (Qq) of the remaining capacity of the first waste toner tank decrease as the image is formed. When the toner (Pp) contained in the toner container is all transferred to the photosensitive drum and the intermediate transfer member, the calculated value (1-x) · (P -P) is less than (Qq), the predetermined toner image formed by the toner forced consumption operation is not transferred to the intermediate transfer member, but is all collected in the first waste toner tank, and the intermediate transfer member Do not transfer to. When (1-x) · (Pp) reaches (Qq), the predetermined toner image formed by the forced toner consumption operation is also transferred to the intermediate transfer member, and the first waste toner tank and the second waste toner tank Collected in both waste toner tanks. Therefore, if the first waste toner tank has a capacity equal to or greater than the minimum capacity (1-x) · P assuming that the toner forced consumption operation is not performed, the image quality is maintained by the toner forced consumption operation. However, it is possible to prevent the waste toner from overflowing without maximizing the use of the intermediate transfer belt so as not to be damaged and without providing a sensor for detecting the waste toner amount.

  (2) According to the present invention, in the image forming apparatus having the above-described configuration, the control device transfers the image when the toner images on the intermediate transfer body and p and q of the image forming units are transferred to a sheet. Based on the ratio of the toner amount of the toner image to the toner amount before transfer, the amount r of waste toner recovered in the second waste toner recovery tank is calculated, and the second waste toner recovery tank When the calculation result of the control device reaches r = R, the operation is suspended until the second waste toner recovery tank is replaced.

  According to this configuration, when the calculated value r of the amount of waste toner collected in the second waste toner collection tank reaches the capacity R of the waste toner collection tank, the image is displayed until the second waste toner collection tank is replaced. The forming device interrupts operation. Therefore, the second waste toner collection tank can prevent the waste toner from overflowing without providing a sensor for detecting the amount of waste toner.

  (3) Further, according to the present invention, in the image forming apparatus having the above-described configuration, a waste toner detection sensor for detecting that the amount of toner collected in the second waste toner collection tank has reached a predetermined amount is provided. It is characterized by.

  According to this configuration, the waste toner detection sensor detects that the amount of waste toner in the second waste toner collection tank has reached a predetermined amount, so that it is possible to prevent the waste toner from overflowing.

  (4) Further, in the image forming apparatus having the above-described configuration, the predetermined image forming operation is to continuously form images having an average density of 10% or less on a predetermined number of sheets. To do.

  According to this configuration, when the image formation on a certain sheet is completed and the average density of the image formed on the predetermined number of sheets before that is 10% or less, the forced toner consumption operation is started. It is possible to ensure that toner whose charge amount has increased and is no longer suitable for image formation is not used for image formation.

  (5) According to the present invention, in the image forming apparatus having the above-described configuration, the predetermined toner image has a maximum width that can be formed by the image forming unit, and corresponds to a toner image having an area of 10% or less of A4 paper. It is characterized by comprising an amount of toner.

  According to this configuration, a toner image made up of an amount of toner corresponding to a toner image having an area of 10% or less of A4 paper of the maximum width that can be formed by the image forming unit is not suitable for image formation due to an increase in charge amount. Since the toner is formed in each image forming unit by a toner forced consumption operation and is consumed evenly in the width direction of the image forming unit, an image can be formed on a sheet with toner suitable for image formation. Further, since toner suitable for image formation is not used, toner is not wasted.

  (6) According to the present invention, in the image forming apparatus configured as described above, the toner container and the first waste toner recovery tank are integrated.

  According to this configuration, the empty toner container and the first waste toner recovery tank that is almost full without waste toner overflowing due to the above control can be replaced at the same time.

  According to the present invention, the control device calculates the amount of toner used for forming the image based on the image data, so that the first toner provided in each image forming unit without providing the detection sensor. It is possible to obtain an image forming apparatus in which the waste toner does not overflow from the collection container and the container can be miniaturized. Further, in this image forming apparatus, the image quality formed on the paper by the forced toner consumption operation can be maintained, and further, the toner image formed by the forced toner consumption operation is not transferred as much as possible, so that the intermediate transfer member is damaged. Hateful.

  An embodiment of the present invention will be described with reference to FIGS. 1 is a schematic configuration diagram of a printer according to an embodiment of an image forming apparatus of the present invention, FIG. 2 is a partially enlarged view in the vicinity of an image forming unit, and FIG. 3 is a perspective view of a toner container and a first waste toner collecting container. .

  First, each part of the printer 10 will be described. Inside the printer 10, a control device 12, a paper feeding unit 30, an image forming unit 40, and a fixing unit 60 are provided. The control device 12 controls operations of the printer 10 such as a sheet conveying operation and an image forming operation.

  The paper feeding unit 30 will be described. The paper feed unit 30 includes a paper feed cassette 31, a paper feed roller 32, a transport roller pair 33 and a registration roller pair 34. The paper feed cassette 31 accommodates paper 37 and is disposed at the lower part of the printer 10. From here, the paper 37 is fed one by one to the paper transport path 36 by the paper feed roller 32 and transported by the transport roller pair 33 and the registration roller pair 34.

  Next, the image forming unit 40 will be described. The image forming unit 40 includes yellow, cyan, magenta and black image forming units 50 a, 50 b, 50 c and 50 d, a primary transfer roller 41, an intermediate transfer belt 42 and a belt cleaner 47.

  The image forming units 50a, 50b, 50c and 50d are arranged in tandem, and the arrangement order can be changed. One primary transfer roller 41 is disposed at a position facing each of the image forming units 50a, 50b, 50c and 50d with the intermediate transfer belt 42 therebetween.

  The intermediate transfer belt 42 is stretched and supported by a driving roller 45 and driven rollers 46a and 46b. All the image forming units 50 a, 50 b, 50 c and 50 d are in contact with the outer surface on the upper side of the intermediate transfer belt 42. The support roller 55a drives the intermediate transfer belt 42, and the intermediate transfer belt 42 rotates clockwise (in the direction of the arrow) in FIG. In this embodiment, the number of driven rollers is 46a and 46b. However, as long as the image forming units 50a, 50b, 50c, and 50d are in contact with the intermediate transfer belt 42, the number of driven rollers may be one or more. The intermediate transfer belt 42 functions as an intermediate transfer body to which the toner images formed by the image forming units 50a, 50b, 50c, and 50d are transferred and further transferred onto the sheet from here. Instead, it may be in the form of a drum.

  The belt cleaner 47 removes toner that has not been transferred to the sheet 37 from the intermediate transfer belt 42, and includes a blade that contacts the intermediate transfer belt 42.

  The image forming units 50a, 50b, 50c, and 50d all have the same structure, and as shown in FIG. 2, around the photosensitive drum 51 that rotates in accordance with the rotation of the intermediate transfer belt 42, According to the rotation direction (arrow direction) from above the photosensitive drum 51, the cleaning device 55 and the static eliminator 56 are arranged around the charging device 52, the LED print head 53, the developing device 54, and the contact portion with the intermediate transfer belt 42. It is arranged as an element. A toner container 57 is attached to the developing device 54, from which toner is supplied. As shown in FIG. 3, the toner container 57 is formed integrally with a first waste toner recovery tank 58 provided at the top.

  Finally, the fixing unit 60 will be described. In the fixing unit 60, the fixing roller 61 and the pressure roller 62 are pressed against each other, and the toner image transferred onto the paper 37 is heated and pressed to be fixed on the paper 37.

  Next, an image forming operation will be described. When a user issues an image formation instruction from an external computer (not shown) connected to the main body 10 directly or via a network, the control device 12 receives the instruction and operates each unit. 1 and 2, the intermediate transfer belt 42 is rotated clockwise (in the direction of the arrow) by the driving roller 45, and the photosensitive drums 51 of the image forming units 50a, 50b, 50c, and 50d that are in contact therewith correspond to each other. Rotate counterclockwise (arrow direction). When the photosensitive drum 51 rotates, the surface of the photosensitive drum 51 is first uniformly charged by the charger 52. Next, based on the electrical signal of the original image sent from the external computer, the light emitted from the LED print head 53 composed of a large number of LEDs is applied to a portion of the image formed on the paper 37 or a portion other than the image. Corresponding charges are erased, and an electrostatic latent image is formed on the surface of the photosensitive drum 51. Then, the toner stirred and charged by the developing roller 54a provided in the developing device 54 is supplied onto the photosensitive drum 51, and the electrostatic latent image is visualized as a toner image.

  When the photosensitive drum 51 further rotates and the toner image comes to a position facing the primary transfer roller 41 with the intermediate transfer belt 42 interposed therebetween, a bias voltage having a polarity opposite to the toner charging polarity is applied to the primary transfer roller 41. The toner image is applied to the intermediate transfer belt 42 from the photosensitive drum 51. Residual toner that has not been transferred is removed by a cleaning device 55 and is transported to the first waste toner collection tank 58 by a waste toner transport pipe 59 having a built-in coil spring provided on the front side of the cleaning device 55 in FIG. The toner is collected from a waste toner collecting port 58a provided on the upper surface. Further, the charge remaining on the surface of the photosensitive drum 51 is removed by the static eliminator 56.

  Toner images are stacked on the intermediate transfer belt 42 in the order of the image forming units 50a to 50b, 50c, and 50d, and the intermediate transfer belt 42 is further rotated. The stacked toner images face the secondary transfer roller 43. When the position reaches the position, the sheet 37 is conveyed along the sheet conveying path 36 between the intermediate transfer belt 42 and the secondary transfer roller 43 accordingly. At this time, a bias voltage having a polarity opposite to the charging polarity of the toner is applied to the secondary transfer roller 43, and the stacked toner images are transferred from the intermediate transfer belt 42 to the paper 37. Residual toner that has not been transferred onto the intermediate transfer belt 42 is removed from the intermediate transfer belt 42 by the belt cleaner 47 and collected in the second waste toner collection tank 48. The sheet 37 on which the toner image has been transferred is conveyed to the fixing unit 60 and heated and pressurized as described above to fix the toner image, and a discharge tray 65 provided on the upper portion of the printer 10 by a discharge roller pair 64. To be discharged.

  In the embodiment of the present invention, all the toner images are formed using the image data that has passed through the control device 12. Therefore, the control device 12 uses the image data to sensitize each of the image forming units 50a, 50b, 50c, and 50d. The toner amount s of the toner image formed on the body drum 51 can be calculated.

  Further, as described above, the toner image formed on the photosensitive drum 51 is transferred to the intermediate transfer belt 42 by the primary transfer roller 41, and remains on the photosensitive drum 51 without being transferred. There is. The ratio of the toner amount of the toner image transferred to the intermediate transfer belt 42 to the toner amount before transfer is defined as a primary transfer efficiency x. Similarly, in the toner image on the intermediate transfer belt 42, the ratio of the amount of toner transferred to the paper 37 by the secondary transfer roller 43 to the amount of toner before transfer is defined as a secondary transfer efficiency y. These primary transfer efficiency x and secondary transfer efficiency y can be obtained by a prior experiment. Here, the toner amount may be weight or volume. In general, when calculated by weight, the primary transfer efficiency x is about 90% and the secondary transfer efficiency y is about 95%.

  For the toner image having the toner amount s, the amount transferred to the intermediate transfer belt 42 is x · s, and the amount recovered by the first waste toner recovery tank 58 is (1−x) · s. Of the x · s toner transferred to the intermediate transfer belt 42, the amount transferred to the paper 37 is y · x · s, and the amount recovered in the second waste toner recovery tank 48 is (1− y) · x · s.

  By summing up all the toner amounts s of the respective images formed from the replacement time of the toner container 57 to a certain time t, the toner amount p used so far can be calculated. By setting the initial toner amount in the toner container 57 as P in the control device 12, the remaining amount of toner in the toner container 57 at time t can be calculated as (P−p).

  Similarly, the amount of waste toner q collected in the first waste toner tank 58 counted from the time of replacement of the toner container 57, that is, from the time of replacement of the first waste toner tank 58 to the time t, From the waste toner capacity Q, the remaining capacity of the first waste toner tank 58 at time t can be calculated as (Q−q).

  Therefore, even if a sensor for detecting the amount of waste toner is not provided in the first waste toner tank 58, it is possible to control that the toner container 57 has become empty and the remaining capacity of the first waste toner tank 58 has been exhausted. 12 can be calculated.

  Further, when all the toner images formed on the photosensitive drum 51 are transferred to the intermediate transfer belt 42, (1-x) · P waste toner is collected in the first waste toner tank. Therefore, if the capacity Q of the first waste toner tank 58 is set to (1−x) · P or more, the control device 12 does not have to calculate the remaining capacity of the first waste toner tank 58, so that the first All the toner in the toner container 57 can be used up without overflowing the waste toner from the waste toner tank 58. That is, even when the toner container 57 and the first waste toner tank 58 are integrally formed as in the embodiment of the present invention, the toner is wasted while the first waste toner tank is made as small as possible. There is nothing.

  Next, the forced toner consumption operation will be described. The developing device 54 stirs and charges an amount of toner that can form a high-density image. When a low-density image is formed, only a part of the charged toner is used. For this reason, when low density images are continuously formed, the toner that is agitated inside the developing device 54 but is not used becomes too charged. An image formed using toner with an excessive charge amount has a lower density than the desired density, so when a certain image forming operation reaches a certain condition at a certain point in time, the image formed on the paper A predetermined toner image different from the above is formed on the photosensitive drum 51, and this toner is forcibly consumed. Here, this operation is called a toner forced consumption operation.

  In the embodiment of the present invention, the toner forcible consumption operation is performed when the average density of images formed on a predetermined number of consecutive sheets (for example, 100 sheets in this case) at the time when image formation is completed on a certain sheet is completed. Performed when 10% or less.

  Here, the density of the toner image in the embodiment of the present invention will be described. The toner image is composed of square grids having a side of 0.04 mm, for example, and each grid is in a state where toner is present or absent. It is assumed that the toner image has a density of 100% when all of the cells constituting a toner image are present, and the toner image has a density of 50% when toner is present in half of the cells. The grid is not limited to a square but may be a rectangle, a hexagon, or the like.

  A toner image formed by the forced toner consumption operation (hereinafter referred to as image A) has a maximum width formed by the image forming units 50a, 50b, 50c and 50d, and has a toner image having an area of 10% or less of A4 paper, That is, the toner consists of an amount of toner corresponding to the toner present in a grid having an area of 10% or less of A4 paper. However, the toner amount of the image A is not zero. As a result, toner that is not suitable for image formation can be consumed evenly in the width direction of the image forming unit, and even toner that is suitable for image formation can be avoided from being wasted as image A. The conditions of the image forming operation for starting the toner forced consumption operation, the size and density of the image A, and the toner amount may be appropriately changed for each image forming apparatus to be used.

  From the viewpoint of protecting the intermediate transfer belt 42, it is preferable that the image A is not transferred to the intermediate transfer belt 42 but is recovered from the photosensitive drum 51 to the first waste toner recovery tank 58. When the toner amount of the image A is a, the toner amount recovered in the first waste toner recovery tank 58 is (1-x) · a when transferred to the intermediate transfer belt 42, and In the case of no transfer, it is a. If x is 90%, there is a 10-fold difference. Accordingly, when control is performed so that the image A is not transferred to the intermediate transfer belt 42, if a large number of low density images are formed by the printer 10, the first waste toner recovery tank 58 is compared with a case where only high density images are formed. A lot of waste toner is collected. When the first waste toner collection tank is small because it is provided in a limited space, the waste toner overflows when the forced toner consumption operation is performed more times than expected.

  However, based on the remaining amount of toner (P−p) in the toner container 57 at the time t calculated by the control device 12 and the remaining capacity (Q−q) of the first waste toner recovery tank 58, as described above. If the image A is transferred to the intermediate transfer belt 42 and is also collected in the second waste toner collection tank 48, the toner is removed from the first waste toner collection tank 58 without providing a waste toner amount detection sensor. It can prevent overflowing.

  The relationship between the initial toner amount P of the toner container 57 and the capacity Q of the first waste toner collection tank 58 is that the toner in the toner container 57 that has not been transferred to the intermediate transfer belt 42 by the first waste toner collection tank 58 is shown. Q> (1-x) · P is set so that the image A can be collected and several images A can be collected.

  As the image forming operation and the forced toner consumption operation are performed, (Qq) and (Pp) decrease, and the calculation result in the control device 12 is the original (Qq)> (1-x) · ( From (Pp), at a certain point, (Qq) = (1-x) · (Pp) is reached. At this time, when all the toner in the toner container 57 is transferred from the photosensitive drum 51 to the intermediate transfer belt 42, the toner remaining on the photosensitive drum 51 without being transferred is recovered in the first waste toner recovery tank 58. Will be. That is, if all the images A are collected by the first waste toner collecting tank 58 after this time, the toner overflows.

  Therefore, if the image A is transferred to the intermediate transfer belt 42 after this time and is collected by the first waste toner collection tank 58 and the second waste toner collection tank 48, the toner in the toner container 57 is used up at the same time. The waste toner in the first waste toner collection tank 58 becomes full.

  With the above-described configuration, the use of the intermediate transfer belt 42 is minimized, and even if the first waste toner collection tank 58 is not provided with a waste toner amount detection sensor, the waste toner does not overflow and the toner is forced. The image quality can be maintained by the consumption operation. Further, the first waste toner collecting tank 58 can be reduced in size, and can be disposed in a limited space in the image forming apparatus.

  Next, the toner collected in the second waste toner collection tank 48 will be described. All the toner containers 57 and the second waste toner collection tank 48 are not always replaced at the same time. However, the amount of toner used from each toner container 57 from an arbitrary time point to another arbitrary time point can be calculated by the control device 12 in consideration of whether or not the image A has been transferred to the intermediate transfer belt. If the toner amounts used in all the image forming units 50a, 50b, 50c and 50d are totaled based on this, the amount of waste toner collected in the second waste toner collection tank 48 during this period is also calculated by the control device 12. be able to. The amount of waste toner collected in the second waste toner collection tank 48 from the time when the second waste toner collection tank 48 is replaced to a certain time is represented by r, and the capacity of the second waste toner collection tank 48 is represented by R. For example, when the calculation result of the control device 12 becomes r = R, the image forming operation is interrupted, and a message that the second waste toner collection tank 48 is to be replaced is displayed on the display unit (not shown). The waste toner does not overflow from the waste toner collection tank. At this time, if the display unit (not shown) displays a message prompting the user to replace the second waste toner collection tank 48, the user is not troubled because the image forming operation is interrupted.

  The second waste toner collection tank 48 may be provided with a sensor (not shown) for detecting the amount of waste toner, such as a reflective sensor. In this case, the waste toner does not overflow from the second waste toner collection tank 48 without performing the complicated calculation as described above in the control device 12.

  The present invention can be generally used for an image forming apparatus using an intermediate transfer member such as a color copying machine and a printer.

1 is a schematic configuration diagram of a printer according to an embodiment of an image forming apparatus of the present invention. Partial enlarged view near the image forming unit Perspective view of toner container and first waste toner collecting container

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Printer 12 Control apparatus 42 Intermediate transfer belt 48 Second waste toner recovery tank 51 Photosensitive drum 57 Toner container 58 First waste toner recovery tank

Claims (6)

A plurality of image forming units each having a photosensitive drum, a toner container for supplying toner to the surface of the photosensitive drum, and a first waste toner recovery tank for storing toner recovered from the photosensitive drum; An intermediate transfer member to which the toner image is transferred from the photosensitive drum, a second waste toner recovery tank for storing toner recovered from the intermediate transfer member, and a control device, and after a predetermined image forming operation In the image forming apparatus for performing a forced toner consumption operation for forming a predetermined toner image on the peripheral surface of the photosensitive drum,
The control device controls the image forming operation and the toner forced consumption operation, and the toner of each of the image forming units based on data used to form a toner image in the image forming operation and the toner forced consumption operation Calculating the amount p of toner consumed from the start of use of the container, and transferring the toner amount of the toner image transferred when the toner image is transferred from the photosensitive drum to the intermediate transfer body before being transferred. The amount q of waste toner collected in the first waste toner collection tank of each image forming unit can be calculated based on the ratio x to the toner amount and p.
In the forced toner consumption operation, the predetermined toner image formed on the peripheral surface of the photosensitive drum has an initial toner amount P stored in the toner container and a capacity Q of the first waste toner recovery tank. When the calculation result by the control device is (Qq)> (1-x) · (Pp), all are collected in the first waste toner collection tank without being transferred to the intermediate transfer member. When the calculation result by the control device is (Q−q) = (1−x) · (P−p), the image is transferred from the photosensitive drum to the intermediate transfer member and transferred to the intermediate transfer member. An image forming apparatus, wherein toner is collected in the second waste toner collection tank, and toner remaining on the photosensitive drum is collected in the first waste toner collection tank.   The control device includes p and q of each of the image forming units, and a ratio of a toner amount of a toner image transferred when the toner image on the intermediate transfer member is transferred to a sheet to a toner amount before transfer. The amount r of waste toner collected in the second waste toner collection tank is calculated based on the above, and the capacity of the second waste toner collection tank is R, and the calculation result by the control device is r = R 2. The image forming apparatus according to claim 1, wherein the operation is interrupted until the second waste toner collecting tank is replaced.   The image forming apparatus according to claim 1, further comprising a waste toner detection sensor configured to detect that the amount of toner collected in the second waste toner collection tank has reached a predetermined amount.   The image forming apparatus according to claim 1, wherein the predetermined image forming operation is to continuously form images having an average density of 10% or less on a predetermined number of sheets. .   The predetermined toner image has a maximum width that can be formed by the image forming unit, and is composed of an amount of toner corresponding to a toner image having an area of 10% or less of A4 paper. The image forming apparatus according to any one of the above.   6. The image forming apparatus according to claim 1, wherein the toner container and the first waste toner collection tank are integrated.

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