JP2015082080A - Image forming apparatus - Google Patents

Abstract

Means for improving the accuracy of toner remaining amount detection is provided. A developing device for containing a developer and supplying the developer from a developer carrying member carrying the developer to form a developer image on the surface of the image carrier, and development in the developing device A developer remaining amount detecting unit for detecting the remaining amount of the developer; a transfer member for transferring and holding the developer image; a detection image forming unit for forming an image for detecting the remaining amount of developer on the transfer member; A determination unit that detects the density of the developer remaining amount detection image and determines the replacement timing of the developing device based on the density, and the developer remaining amount detection image includes a reference density detection image, The reference density detection image is composed of at least one comparison density detection image having an interval corresponding to the length of one circumference of the developer carrier relative to the reference density detection image, and the determination unit includes the reference density detection image and the reference density detection image. The developing device is based on the detected density difference with the comparative density detection image. To determine the replacement timing of, to notify the result of the determination. [Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as an electrophotographic printer or a copying machine.

  A conventional image forming apparatus includes an image forming unit in which a toner container is integrated, and the toner stored in the toner container is supplied to a developing roller via a supply roller and consumed together with image formation. If the toner remaining in the printer becomes too low, the print quality cannot be maintained. Therefore, if the toner consumption exceeds the predetermined consumption, the toner remaining amount detection unit detects toner empty and an alarm is displayed on the display unit. It is displayed to prompt the user to replace the image forming unit.

  Even when there is a sufficient amount of toner, image quality deteriorates when the toner is significantly deteriorated. Therefore, the degree of toner deterioration is calculated from the relationship between the amount of remaining toner and the number of development operations. Based on the degree of deterioration of the toner, it is determined whether or not it has reached the end of its life, and if it is determined that it has reached the end of its life, the printing operation is prohibited and the replacement of the image forming unit is encouraged (for example, , See Patent Document 1).

JP 2010-156792 A

However, in the conventional technology, the degree of toner deterioration is integrated with the number of development operations according to the remaining amount of toner in the image forming unit, so that a low image with a small amount of toner consumption per development operation. When the area ratio printing is repeated, the degree of toner deterioration relative to the remaining amount of toner becomes larger than when printing with a high image area ratio is continuously performed, and the remaining amount of toner is still sufficient. There is a problem that the printing operation is prohibited because it is determined that the image forming unit has reached the end of its life regardless of the state.
An object of the present invention is to solve such a problem and to improve the accuracy of toner remaining amount detection.

  Therefore, the present invention provides a developing device that contains a developer and supplies the developer from a developer carrying member carrying the developer to form a developer image on the surface of the image carrier, and the inside of the developing device. A developer remaining amount detecting unit that detects the remaining amount of developer, a transfer member that transfers and holds the developer image, and a detection image forming unit that forms a developer remaining amount detecting image on the transfer member; A determination unit that detects a density of the developer remaining amount detection image and determines a replacement timing of the developing device based on the density, and the developer remaining amount detection image includes a reference density detection image The reference density detection image includes at least one comparison density detection image having an interval corresponding to the length of one round of the developer carrier, and the determination unit includes the reference density detection image. Based on the detected density difference between the image and the comparative density detection image. Determines the replacement timing of the developing device, and wherein the notifying the determination result.

  According to the present invention as described above, it is possible to improve the accuracy of toner remaining amount detection.

1 is a block diagram illustrating a configuration of a control system of an image forming apparatus according to an embodiment. Schematic side sectional view showing the structure of the image forming apparatus in the embodiment Explanatory drawing of the toner remaining amount detection test pattern in the embodiment The graph which showed the relationship between the residual amount of toner and a density detection value in an Example Explanatory drawing of the contact state of the developing roller and the supply roller in the embodiment The graph which shows the fluctuation | variation of the toner charge amount with respect to the supply roller pushing amount in an Example The flowchart which shows the flow of the lifetime determination process in an Example. Explanatory drawing of the toner remaining amount determination table in the embodiment Explanatory drawing of the modification of the test pattern for toner remaining amount detection in an Example. Timing chart of voltage applied to process cartridge in embodiment Graph showing variation of density detection value with respect to remaining amount of toner in modification

  Embodiments of an image forming apparatus according to the present invention will be described below with reference to the drawings.

FIG. 2 is a schematic cross-sectional side view showing the configuration of the image forming apparatus in the embodiment.
In FIG. 2, an image forming apparatus 10 is a color printer, for example, and includes process cartridges 11a, 11b, 11c, and 11d as four developing devices that respectively form black, yellow, magenta, and cyan images. These are the process cartridge (black) 11a, the process cartridge (yellow) 11b, the process cartridge (magenta) 11c, and the process cartridge (cyan) from the upstream side in the medium conveyance direction indicated by the arrow A in the drawing of the conveyance path 30 of the recording medium P. The image forming apparatus 10 is detachably arranged in the order of 11d.

LED (Light Emitting Diode) print heads 13a, 13b, 13c, and 13d are disposed at positions facing the process cartridges 11a, 11b, 11c, and 11d, respectively.
The process cartridges 11a, 11b, 11c, and 11d have the same internal configuration. Around the photosensitive drum 15 as an image carrier, a charging roller 16 as a charging member, a developing roller 17 as a developer carrier, and a cleaning member A cleaning unit 14 is disposed and integrated with a toner storage unit 20 that stores toner as a developer.
The photosensitive drum 15 has a toner image as a developer image formed on the surface thereof, a photosensitive layer is applied to a conductor such as aluminum, and a shaft coupling is provided rotatably with a drive coupling. ing.

The charging roller 16 is formed by coating a conductive elastic body such as epichlorohydrin with a metal such as stainless steel as an axis. The charging roller 16 is rotated by the rotation of the photosensitive drum 15 and is applied with a high voltage. The surface of the photosensitive drum 15 is charged.
The developing roller 17 is a developer carrier that carries toner. The developing roller 17 is formed by coating a conductive elastic body such as urethane with a metal such as stainless steel as an axis. The developing roller 17 is provided with a drive coupling at the end of the axis and is rotated by drive transmission from the image forming apparatus 10. Then, a high voltage is applied to form an electric field between the surface of the photosensitive drum 15 and toner is supplied to the electrostatic latent image formed on the surface of the photosensitive drum 15 charged by the exposure of the LED head 13. Develop the toner image. A supply roller 18 and a regulating blade 19 are disposed around the developing roller 17.

The supply roller 18 is formed by coating a foaming elastic body such as silicon with a metal such as stainless steel as an axis. The supply roller 18 is provided with a gear at an end of the axis and rotated by drive transmission from the developing roller 17. The toner is frictionally charged by friction with the toner 17 and is supplied to the developing roller 17.
The regulating blade 19 is made of, for example, a stainless steel thin plate, and is an elastic blade having one end fixed to a holder. The other end is pressed against the developing roller 17 and disposed on the developing roller 17 while frictionally charging the toner. The toner layer thickness is regulated to form a thin layer of charged toner.

The cleaning blade 14 scrapes off and collects the toner remaining on the photosensitive drum 15 after the transfer.
The toner storage units 20 of the process cartridges 11 a to 11 d store toner of each color, and the toner is supplied to the developing roller 17 via the supply roller 18.
The configurations of the LED print heads 13a, 13b, 13c, and 13d are the same, and a printed wiring board on which a plurality of LED array chips are arranged and the light emitted from the LED array is formed on the surface of the photosensitive drum 15 at an equal magnification. The LED print heads 13a to 13d are arranged so as to face the process cartridges 11a to 11d.

  Under the image forming apparatus 10, a paper feed cassette 31 for storing the recording medium P and a hopping roller 32 for separating and feeding the stacked recording media P one by one are disposed. After the recording medium P is fed by the hopping roller 32, the recording medium P is conveyed along the conveyance path 30 by a pair of registration rollers 33 and 34 for performing skew feeding (skew) and the like, and is further transferred by a transfer unit (transfer belt unit) 35. It is conveyed sequentially through the process cartridges 11a to 11d.

  An electric field is formed on the photosensitive drum 15 at a position facing the process cartridges 11a to 11d of the transfer portion (transfer belt unit) 35 via a transfer belt 36 as a transfer member that transfers and holds the toner image. A transfer roller 37 to which a voltage is applied is disposed, and an electric field is formed from the back surface of the recording medium P conveyed via the transfer belt 36, and the toner image on the photosensitive drum 15 is electrically attracted and recorded. Transfer is sequentially performed on the medium P.

The density sensor 21 is a reflection type optical sensor composed of a pair of a light emitting part and a light receiving part, and is further downstream than the process cartridge 11d disposed on the most downstream side in the conveying direction of the transfer belt 36 indicated by an arrow A in the drawing. It is disposed at a position facing the transfer belt 36 in the region.
The fixing unit (fixing device) 41 is disposed in contact with the heating roller and the backup roller, and the toner transferred onto the recording medium P is fixed to the recording medium P by pressurization and heating of the heating roller and the backup roller. Is done.
The recording medium P discharged from the fixing unit (fixing device) 41 is discharged to the stacker 43 by the discharge roller 42 along the conveyance path 30.

FIG. 1 is a block diagram showing the configuration of the control system of the image forming apparatus in the embodiment. Based on FIG. 1, the configuration of the control system of the image forming apparatus will be described with reference to FIG.
1, the image forming apparatus 10 includes a process cartridge 11 (11a to 11d), an LED head 13 (13a to 13d), a transfer unit 35, a fixing unit 41, a paper feeding unit 50, and a display unit 51. , Density sensor 21, control unit 60, image forming voltage control unit 65, LED head control unit 66, transfer control unit 67, fixing control unit 68, paper feed control unit 69, and display control unit 70. The concentration measurement control unit 71 and an I / F (InterFace) 81 are included.

The control unit 60 includes a CPU (Central Processing Unit) 61 and controls the operation of the entire image forming apparatus 10. When image data is transmitted from an external host device to the I / F 81, the I / F 81 outputs the image data to the control unit 60. When receiving the image data, the control unit 60 outputs drive signals for various motors of the paper feed control unit 69 that controls the operation of the paper feed unit 50 in accordance with the print timing generated by the CPU 61. Thereby, the feeding of the recording medium P is started by the hopping roller 32 or the like.
The control unit 60 transmits image data to the LED head control unit 66 that controls the light emission operation of the LED head 13 along with the start of paper feeding, and the image forming voltage control unit 65 is notified when the recording medium P reaches the process cartridge 11. Output a control signal.

The image forming voltage control unit 65 controls a high voltage applied to the charging roller 16, the developing roller 17, and the supply roller 18 of each process cartridge 11, and the LED head control unit 66 lights the LED head 13 according to the image data. As a result, a toner image is formed on the surface of the photosensitive drum 15.
Further, the control unit 60 outputs a control signal to the transfer control unit 67, and the transfer control unit 67 controls the transfer unit 35 to apply a high voltage in synchronization with the conveyance of the recording medium P, so that the toner image is recorded on the recording medium. Transfer on P.
The control unit 60 outputs a control signal to the fixing control unit 68, and the fixing control unit 68 controls the fixing speed and fixing temperature of the fixing unit 41 to fix the toner image on the recording medium P passing through the fixing unit 41.

The display control unit 70 controls the display unit 51 in accordance with the control signal input from the control unit 60 and displays various information and the like on the display unit 51. This display unit 51 is arranged on the front part of the image forming apparatus 10 together with input keys for selecting menu items and changing setting contents.
The control unit 60 also includes a toner remaining amount detecting unit 62 as a developer remaining amount detecting unit that detects the remaining amount of toner in the process cartridge 11 and density detection as an image for detecting the remaining amount of developer on the transfer belt 36. The replacement timing according to the life of the process cartridge 11 is determined based on the density value of the density detection pattern measured and detected by the density measurement control unit 71 and the density sensor 21. A life determination unit 64 as a determination unit.

  The toner remaining amount detecting unit 62 converts (measures) the integrated value of the dot count of the toner image formed by the process cartridge 11 during the image forming process into a toner consumption amount, and calculates the internal value of the process cartridge 11 from the difference from the initial toner amount. The remaining amount of toner is calculated and detected. The toner consumption amount per dot count is experimentally determined, and a conversion coefficient for converting the unit amount of the dot count into the toner consumption amount is stored in the storage unit in advance, and the initial toner amount filled in the process cartridge 11 Is also stored in the storage unit.

  When the image forming operation is executed, the toner remaining amount detecting unit 62 counts the dot count value for each operation, and then adds the dot count value to the dot count integrated value measured from the start of use of the process cartridge 11. The toner remaining amount detection unit 62 calculates the toner consumption amount using the dot count integrated value and the toner consumption amount conversion coefficient, and calculates the toner remaining amount by obtaining a difference between the calculated toner consumption amount and the initial toner amount. To do.

The toner remaining amount detection unit 62 compares the calculated toner remaining amount with a toner low threshold value that is set in advance and stored in the storage unit, and the toner remaining amount is low when the toner remaining amount reaches the toner low threshold value. And the display unit 51 displays the toner low state. For example, the toner low threshold is set so that the toner low state is determined when the remaining amount of toner becomes 20% with respect to the initial toner filling amount.
Such a toner remaining amount detection method does not require a toner remaining amount detection mechanism such as an optical sensor, and is suitable for the image forming apparatus 10 of a small-sized machine or a low-priced machine. An error may occur in the detected value of the remaining amount of toner due to a difference in use state of the forming apparatus 10.

  In the image forming apparatus 10, even when the image quality is maintained, a small amount of toner, such as fog toner, that is not counted in the dot count during image formation occurs. Therefore, for example, when a so-called low duty image having a low image area ratio is continuously printed, an error is likely to occur between the toner consumption calculated from the dot count value and the actual toner consumption. Further, the amount of fog toner varies depending on the temperature and humidity around the image forming apparatus 10, and the error in toner consumption is not always constant. Further, when the low duty image is continuously printed, the toner consumption is small, so the number of prints of the process cartridge 11 is increased. For example, the photosensitive drum 15 and the supply roller 18 are worn, the toner is deteriorated, etc. Fluctuation is likely to occur, which causes an error in toner consumption.

  In this embodiment, the toner remaining amount detecting unit 62 detects the toner low state and then measures the density of the test pattern formed on the transfer belt 36 to detect a decrease in image density caused by a decrease in the remaining amount of toner. As a result, it is determined whether the remaining amount of toner in the process cartridge 11 has reached the empty state, or whether the remaining amount is still sufficient, and the life of the process cartridge 11 is determined.

FIG. 3 is an explanatory diagram of a remaining toner amount detection test pattern in the embodiment. The remaining toner amount detection test pattern in the present embodiment will be described with reference to FIGS. 1 and 2 based on FIG.
In FIG. 3, a toner remaining amount detection test pattern 631 is an example formed on the transfer belt 36 by the detection image forming unit 63. In this embodiment, a toner remaining amount detection test pattern 631 formed by a process cartridge 11a having only a single color, for example, a black color will be described.

The toner remaining amount detection test pattern 631 is formed on the transfer belt 36 and includes two rectangular reference density measurement patches 631a and a comparative density measurement patch 631b.
The formation position of the toner remaining amount detection test pattern 631 is a position where the density sensor 21 faces, and the direction indicated by the arrow D in the figure is the transport direction of the transfer belt 36 (hereinafter referred to as “transport direction D”). At this time, the remaining toner amount detecting test pattern 631 is set so that the center position M of the reference density measuring patch 631a and the comparative density measuring patch 631b in the direction orthogonal to the transport direction D coincides with the arrangement position of the density sensor 21. Form.

The comparative density measurement patch 631b holds a distance P1 that is the length of one rotation (one rotation period) of the developing roller 17 on the downstream side in the conveyance direction D of the transfer belt 36 with respect to the reference density measurement patch 631a. And at least one is formed.
The interval P1 which is the length of one circumference of the developing roller 17 corresponds to the outer circumference of the developing roller 17 when the transfer belt 36, the photosensitive drum 15, and the developing roller 17 have the same surface speed. Further, when the surface speeds of the transfer belt 36 and the photosensitive drum 15 are the same and the developing roller 17 rotates at a surface speed 1.2 times that of the photosensitive drum 15, The interval P <b> 1 that is the length of one round is a length that is 1/2 of the outer circumference of the developing roller 17.

It should be noted that the density measurement patch is located at a position (region) that is separated from the reference density measurement patch 631a by an interval P1 that is the length of one rotation of the developing roller 17 on the upstream side in the conveyance direction D of the transfer belt 36. Is not formed.
The image area ratio of the reference density measurement patch 631a and the comparative density measurement patch 631b is arbitrary, but an image having a high image area ratio such as a so-called solid pattern (100% duty image) having an image area ratio of 100% is desirable. .
The lengths W11, W12, W21, and W22 of each side of the reference density measurement patch 631a and the comparative density measurement patch 631b may be dimensions that completely cover the measurement range of the density sensor 21.

  Further, although the reference density measurement patch 631a and the comparative density measurement patch 631b are described as being formed separately, this is to reduce the toner consumption as much as possible, and the reference density measurement patch. 631a and the comparative density measurement patch 631b may be formed in one image pattern. At least the image density of the measurement patch formed at the interval P1 that is the length of one circumference of the developing roller 17 is measured by the density sensor 21 and the respective density values can be compared with the image area ratio. .

As described above, the reference density measuring patch 631a is in a state in which image formation is not performed at least before one rotation of the developing roller 17, and for example, on the developing roller 17 during warm-up. This corresponds to a state where an image pattern is formed from a state where toner supply and charging are stable.
On the other hand, the comparative density measurement patch 631b is in a state where an image is formed before one rotation of the developing roller 17, and the toner is supplied from the supply roller 18 to the developing roller 17 and charged only once. This corresponds to a state in which an image pattern is formed from a state in which the amount of toner supplied to the developing roller 17 is easily affected by the amount of toner accommodated around the supply roller 18.

  Normally, when the remaining amount of toner in the process cartridge 11 is sufficient, the amount of toner around the supply roller 18 is also large, and the amount of toner supplied to the developing roller 17 is large. Even if image formation has been performed previously, the toner density does not decrease. This is because, for example, even when a high-duty image such as a solid pattern is printed, there is no reduction in toner density after the second turn of the developing roller 17 or blur printing due to insufficient toner, and a good solid pattern image can be formed. It can be determined that high image quality can be maintained.

However, if the remaining amount of toner in the process cartridge 11 decreases and the amount of toner around the supply roller 18 decreases, the amount of toner supplied to the developing roller 17 decreases, so that an image is formed before one cycle of the developing roller 17. Is performed, the thickness of the toner layer formed on the developing roller 17 becomes thin, and the toner density of the image tends to decrease.
Further, when the remaining amount of toner decreases, the number of contact times of individual toners with respect to the supply roller 18 and the like increases, and the charge amount of the toner tends to increase, and the toner is transferred from the developing roller 17 to the electrostatic latent image on the photosensitive drum 15. It becomes difficult to move. Accordingly, the toner density of the image is likely to decrease. At this time, for example, when a high-duty image such as a solid pattern is printed, the toner density decreases after the second turn of the developing roller 17 and printing defects called so-called blur and ghost are likely to occur, which is good. It can be determined that the image quality cannot be maintained.

The life determination unit 64 determines the reference density of the reference density measurement patch 631a of the toner remaining amount detection test pattern 631 formed by the detection image forming unit 63 and the comparison density of the comparison density measurement patch 631b as the density sensor 21. And the difference between the comparative density and the reference density is detected as a density detection value, and the process cartridge 11 compares the density detection value with the toner empty threshold value (replacement time determination threshold value) stored in the storage unit. It is determined whether or not good image quality cannot be maintained due to a decrease in the remaining amount of toner and the life has been reached, that is, whether or not it is time to replace the process cartridge 11.
Next, the life determination method of the process cartridge 11 performed by the life determination unit 64 will be described with reference to FIGS. 1 and 2 using a graph showing the relationship between the remaining amount of toner and the detected density value in the embodiment of FIG. To do.

FIG. 4 is a graph showing the relationship between the remaining amount of toner in the process cartridge 11 and the density detection value, where the horizontal axis represents the toner remaining amount [g], the vertical axis represents the density detection value [OD], and the solid line C1 represents the solid line C1. For example, the number of printed sheets of the process cartridge 11 is about 1000 sheets, and the broken line C2 is a state in which the printing operation of the process cartridge 11 is repeated more than the solid line C1, for example, about 5000 sheets are printed. The later state is shown.
The density detection value is a value obtained by subtracting the reference density from the comparison density measured by the density sensor 21, and is a value obtained by converting the detection value of the reflectance of the detected light into an OD (Optical Density) value that is an index as an image density. Represents. For example, when the comparative concentration is measured as 1.4 [OD] and the reference concentration is 1.5 [OD], the detected concentration value is −0.10 [OD], indicating that the concentration is decreasing.

As shown in FIG. 4, the remaining amount of toner in the process cartridge 11 decreases as the toner is consumed by the image forming operation. However, if a certain amount of toner remains, the comparative density is equal to the reference density, and the density reference The value does not decrease. In FIG. 4, the density detection value does not decrease even when the remaining amount of toner is reduced to about 15 [g].
However, when the remaining amount of toner further decreases, the amount of decrease in the density detection value increases as the remaining amount of toner decreases. As described above, when the density detection value decreases, a good image quality cannot be maintained, so that a predetermined value of the density detection value is set in the storage unit as a toner empty threshold indicating that the remaining amount of toner is exhausted. When the density detection value reaches the toner empty threshold, it is determined that the process cartridge 11 has reached the end of its life.

The toner empty threshold as the replacement time determination threshold may be appropriately determined in consideration of various factors such as the specifications of the image forming apparatus 10 and user requirements based on an objective evaluation value of the image quality with respect to the density detection value. The determined toner empty threshold is stored in the storage unit in advance. In FIG. 4, the decrease amount of the density detection value is set to −0.10 as the toner empty threshold, and the toner empty threshold is represented by a broken line T.
Further, the variation of the density detection value with respect to the remaining amount of toner is not uniform, and may vary depending on the operating conditions of the process cartridge 11 such as the number of printed sheets and the image duty, or the operating environment conditions of the image forming apparatus 10 such as temperature and humidity. is there.

In FIG. 4, as an example, a state where the number of printed sheets of the process cartridge 11 is about 5000, for example, is indicated by a broken line C2. In the broken line C2, compared to the solid line C1, the density detection value starts to decrease from the state where the toner remaining amount is large, and the toner remaining amount when the toner empty threshold is reached is also large.
This is due to fluctuations in the characteristics of the process cartridge 11 over time, and is considered to be mainly caused by a decrease in the toner transportability due to wear of the supply roller 18 and a decrease in the amount of toner supplied to the developing roller 17. It is done.

  Another factor that may cause a change in the characteristics of the process cartridge 11 with time is toner deterioration. The condition for increasing the number of printed sheets is a state in which a so-called low duty image is continuously printed with a small amount of toner consumption in printing on one recording medium P. If the circulation is repeated and the number of friction increases and damage occurs, the fluidity may decrease and the amount of toner supplied to the developing roller 17 may decrease. In addition, the chargeability is also lowered due to the deterioration of the toner, and the image quality is sometimes lowered due to the fogging caused by the low-charge toner.

In this embodiment, the toner deterioration is minimized by defining the amount of pressing of the supply roller 18 with respect to the developing roller 17 with respect to the toner deterioration.
Next, the contact state between the developing roller and the supply roller will be described with reference to FIG. 2 using the explanatory diagram of the contact state between the development roller and the supply roller in the embodiment of FIG.
The developing roller 17 in the process cartridge 11 is disposed so as to contact the photosensitive drum 15.

Further, the supply roller 18 has a configuration in which a sponge layer 18 b as a foaming elastic member is coated around the metal shaft 18 a, and scraping operation of the toner layer formed on the developing roller 17 and the developing roller 17. In order to perform the toner supplying operation and the toner triboelectric charging operation, the toner is pressed against the developing roller 17 so as to obtain a constant pressing amount N.
In this embodiment, the outer diameter of the developing roller 17 is 16 mm. Further, a sponge layer 18b having a thickness of 4.3 mm is formed around a metal shaft 18a having an outer diameter of 14.6 mm and an outer diameter of 6 mm so that the pushing amount N into the developing roller 17 is 0.6 mm. It is arranged and configured.

At this time, the ratio of the pushing amount N to the sponge layer 18b and the sponge thickness S, that is, the ratio of the pushing amount N to the developing roller 17 with respect to the thickness S of the sponge layer 18b, is 0. .6 / 4.3≈0.14.
There is a correlation between the pushing amount N and the toner damage, and as the pushing amount N increases, the frictional force to the toner in the contact area between the supply roller 18 and the developing roller 17 increases, and thus the toner damage increases.
On the other hand, when the pushing amount N into the supply roller 18 becomes small, the frictional force against the toner becomes small and the toner charge amount tends to decrease.

  FIG. 6 is a graph showing the variation of the toner charge amount with respect to the supply roller push-in amount in the example, and it can be seen that when the supply roller push-in amount N is less than 0.5 mm, the toner charge amount decreases as the push-in amount decreases. . The supply roller push-in amount N is preferably 1.0 mm or less in order to suppress damage to the toner. In this embodiment, the supply roller push-in amount is maintained in order to maintain the toner charge amount while suppressing damage to the toner. The amount N is set to 0.6 mm.

In addition, the larger the sponge compression ratio, the faster the deterioration progress due to wear of the sponge. However, it has been experimentally confirmed that sufficient durability can be secured if the sponge compression ratio is 0.20 or less.
Since the process cartridge 11 of this embodiment is configured to minimize toner deterioration in this way, it is possible to suppress the occurrence of fogging, and to leave the toner remaining in a state where printing defects such as blurring and ghosting do not occur. Can be used up to quantity.

In this embodiment using the process cartridge 11 configured as described above, the remaining toner amount detection unit 62 shown in FIG. 1 sets the remaining toner amount 20 g as a toner low threshold, and the toner consumption state is calculated by calculating the toner consumption amount. After the determination, the remaining toner amount detection pattern is formed by the detection image forming unit 63, the density detection value is obtained by the life determination unit 64, and is compared with the toner empty threshold value. Accordingly, the life determination unit 64 determines that the toner cartridge is in the empty state when the remaining amount of toner is 8 g at the solid line C1 shown in FIG. 4 where the number of printed sheets of the process cartridge 11 is small, and the number of printed sheets of the process cartridge 11 is large. In the broken line C2 shown in FIG. 5, it is determined that the toner is empty when the remaining amount of toner is 10 g.
As described above, when the life determination unit 64 determines that the remaining amount of toner has decreased to a toner empty state in which good print quality cannot be maintained regardless of the use state of the process cartridge 11, the process cartridge 11 reaches the end of its life. The display unit 51 displays that the process cartridge 11 needs to be replaced.

The operation of the above configuration will be described.
The process cartridge life determination process performed by the image forming apparatus will be described with reference to FIGS. 1 and 2 in accordance with a step represented by S in the flowchart showing the flow of the life determination process in the embodiment of FIG.
S1: When the image forming apparatus 10 performs the image forming operation and the image formation on the recording medium P is completed, the control unit 60 starts the life determination process of the process cartridge 11.
S2: The toner remaining amount detection unit 62 of the control unit 60 calculates the toner consumption based on a value obtained by integrating the dot counts from the initial stage of the process cartridge 11 by the image forming operation.

S3: The toner remaining amount detecting unit 62 compares the calculated toner consumption amount with the toner low threshold value stored in the storage unit in advance, and ends the process when determining that the toner consumption amount has not reached the toner low threshold value. Then, the next image forming operation is waited, and if it is determined that the toner consumption amount has reached the toner low threshold, the process proceeds to S4.
S4: When the toner remaining amount detection unit 62 determines that the toner consumption amount has reached the toner low threshold value, the detection image forming unit 63 and the life determination unit 64 perform processing for measuring the density reduction amount of the developing roller cycle.

Here, the detection image forming unit 63 forms a test pattern for detecting the remaining amount of toner on the transfer belt 36, and the life determination unit 64 is a test pattern for detecting the remaining amount of toner based on the control by the density measurement control unit 71. The density of the image patch is measured by the density sensor 21, and the amount of density decrease in the developing roller cycle is detected as the density detection value.
S5: The life determination unit 64 compares the detected density detection value with the toner empty threshold value stored in the storage unit in advance. If it is determined that the density detection value has not reached the toner empty threshold value, the process proceeds to S7. If it is determined that the density detection value has reached the toner empty threshold, the process proceeds to S6.

S6: When the life determination unit 64 determines that the density detection value has reached the toner empty threshold, the life determination unit 64 determines that the toner remaining state has decreased to a state where the remaining amount of toner cannot maintain good image quality, and the display unit The fact that the toner is empty is displayed and informed at 51, prompting the user to replace the process cartridge 11, and the process is terminated.
S7: On the other hand, the life determination unit 64 that has determined that the density detection value has not reached the toner empty threshold value indicates that the remaining amount of toner is low but the toner is in a low toner state that can maintain good image quality. The determination is made, the fact that the toner is low is displayed on the display unit 51 and notified, the user is prompted to prepare for the replacement of the process cartridge 11, and the present process is terminated.

As described above, after the toner remaining amount detection unit 62 determines the toner low state based on the calculated toner consumption, the detection image forming unit 63 forms a toner remaining amount detection pattern on the transfer belt 36 to determine the life. The unit 64 reads the toner remaining amount detection pattern with the density sensor 21 to obtain a density detection value, and determines that the process cartridge 11 has reached the end of its life when it is determined that the toner empty state is compared with the toner empty threshold. Then, the display unit 51 displays that the process cartridge 11 needs to be replaced.
Therefore, the accuracy of toner remaining amount detection can be improved without using a toner remaining amount sensor.

In addition, regardless of the use state of the process cartridge 11, it is possible to consume the toner to the maximum while maintaining good print quality until the life of the process cartridge 11 due to toner empty is reached, thereby reducing the printing cost. it can.
The start timing of the process for determining the life of the process cartridge 11 is arbitrary, and may be executed, for example, at the timing when the job of the printing operation is completed. However, in the above-described processing for measuring the density decrease in the developing roller cycle in S4, the toner is consumed due to the formation of the test pattern for detecting the remaining amount of toner, and therefore the processing is frequently executed and the amount of toner consumption is excessive. For example, the processing may be executed every time a predetermined number of printed sheets is exceeded.

  Further, as another means for reducing the number of times the test pattern for detecting the remaining amount of toner is formed, a difference between the detected density value and the toner empty threshold value is calculated in the process of comparing the detected density value with the toner empty threshold value in S5. The remaining amount of toner that can be used until the lifetime of the process cartridge 11 based on the value of the difference (the remaining amount of usable developer), for example, can be used until the lifetime of the process cartridge determined by the toner remaining amount determination table shown in FIG. When the toner consumption calculated by the toner remaining amount detection unit 62 reaches the set toner remaining amount after displaying the toner low in S7 and finishing the processing, the toner empty state is set. It may be determined that there is a toner empty message on the display unit 51.

FIG. 8 is an explanatory diagram of a toner remaining amount determination table in the embodiment. The relationship between the range of difference between the density detection value and the toner empty threshold and the remaining amount of toner that can be used until the lifetime of the process cartridge 11 is used as a table. Is.
For example, as shown in FIG. 4, when the detected density value is −0.05, the toner empty threshold is set to −0.10. Therefore, the difference between the detected density value and the toner empty threshold is 0.05. Is calculated as Then, with reference to the table shown in FIG. 8, the remaining toner amount 3g that can be used until the lifetime of the process cartridge 11 is extracted and set, and the image forming operation is continued. By doing so, the number of times of formation of the test pattern for detecting the remaining amount of toner in S4 shown in FIG. 7 can be set to 1, and the toner empty state can be detected.

FIG. 9 is an explanatory diagram of a modified example of the remaining toner amount detection test pattern in the embodiment.
In FIG. 9, the toner remaining amount detection test pattern 632 forms an image patch 632b by holding the interval P1 of the developing roller cycle on the downstream side in the transport direction D of the transfer belt 36 of the reference density measurement patch 632a. Further, the comparative density measurement patch 632c is formed by holding the interval P1 of the period of the developing roller on the downstream side in the transport direction D of the transfer belt 36 of the image patch 632b.

In the density detection value detection process by the life determination unit 64 shown in FIG. 1, the difference between the density of the comparative density measurement patch 632c and the density of the reference density measurement patch 632a is calculated as the density detection value. As a result, the density detection value detects a density decrease for two rotations of the developing roller when forming a high-duty image such as a solid pattern. Since the density detection is performed under a condition where the density decrease tends to occur, the remaining toner amount It is possible to more reliably detect that the print quality is degraded such as blur printing or afterimage printing due to the degradation.
The timing of the voltage applied to the process cartridge will be described with reference to FIGS. 1 and 2 based on the timing chart of the voltage applied to the process cartridge in the embodiment of FIG.

  FIG. 10 shows a sequence of bias voltage applied to the process cartridge 11 controlled by the image forming voltage control unit 65 when the detection image forming unit 63 forms a test pattern for detecting the remaining amount of toner. For the charging bias voltage CB to be applied, the developing bias voltage DB to be applied to the developing roller 17, and the supply bias voltage SB to be applied to the supply roller 18, a sequence T1 of the applied bias voltage during normal image formation and a toner remaining amount detection, respectively. A sequence T2 of the applied bias voltage at the time of test pattern formation is shown.

In the embodiment described above, the sequence of the applied bias voltage when forming the test pattern for detecting the remaining amount of toner is the same as the sequence of the applied bias voltage during normal image formation. FIG. An example is shown in which the applied bias voltage at the time of detection test pattern formation is controlled to be different from the applied bias voltage at the time of normal image formation.
In FIG. 10, the supply bias voltage SB in the sequence T1 of the applied bias voltage during normal image formation is Vsb1, whereas the supply bias voltage SB in the sequence T2 of the applied bias voltage in forming the remaining toner amount detection test pattern. The absolute value of Vsb2 is reduced. For example, Vsb1 is −350V, Vsb2 is −250V, and the absolute value is reduced.

The charging bias voltage CB is Vch, the development bias voltage DB is Vdb, and the applied bias voltage sequence T1 during normal image formation is the same as the applied bias voltage sequence T2 during toner remaining amount detection test pattern formation. Yes, for example, Vcb is set to -1000V, and Vdb is set to -200V.
At this time, the absolute value of the difference between the supply bias voltage SB and the development bias voltage DB is reduced from 150 V at the time of normal image formation to 50 V at the time of forming the remaining toner amount detection test pattern. The difference between the supply bias voltage SB and the development bias voltage DB is the magnitude of the electric field when toner is supplied from the supply roller 18 to the development roller 17. When the electric field is small, the electrostatic force applied to the charged toner is reduced and the development roller 17. The amount of toner supplied to the toner is reduced. Accordingly, the density of the remaining toner amount detection test pattern is lower than that of a normal image.

FIG. 11 is a graph showing the variation of the density detection value with respect to the remaining amount of toner in the modified example. The solid line C1 is the same as that in FIG. 4, and the broken line C3 is shown in FIG. 6 shows the variation of the density detection value calculated by measuring the density of the toner remaining amount detection test pattern formed by the sequence T2 of the applied bias voltage when forming the remaining toner amount detecting test pattern with respect to the remaining amount of toner. .
As shown in FIG. 11, the broken line C3 has a decrease in density detection value from a state where the remaining amount of toner is larger than the solid line C1. Then, by changing the toner empty threshold from −0.10 indicated by the broken line T1 to −0.25 indicated by the broken line T2, it is possible to compare the detected density values when the toner amount is the same with a large absolute value. Therefore, the determination of the toner empty state can be performed more accurately.

  As described above, in this embodiment, after the toner remaining amount detection unit determines the toner low state based on the toner consumption, the detection image forming unit forms a toner remaining amount detection pattern on the transfer belt, and the life The determination unit obtains the density detection value of the toner remaining amount detection pattern and detects the toner empty state of the process cartridge in comparison with the toner empty threshold value, thereby improving the accuracy of toner remaining amount detection. The effect that it can be obtained.

Regardless of the state of use of the process cartridge, such as when low-duty images are continuously printed, it is possible to consume the maximum amount of toner while maintaining good print quality until the end of the process cartridge life due to toner empty. As a result, the printing cost can be reduced.
In this embodiment, the image forming apparatus is described as a color printer. However, the image forming apparatus is not limited thereto, and may be a multifunction machine, a facsimile machine, a monochrome printer, or the like.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 (11a, 11b, 11c, 11d) Process cartridge 13 LED print head 14 Cleaning part 15 Photoconductor drum 16 Charging roller 17 Developing roller 18 Supply roller 19 Restriction blade 20 Toner accommodating part 21 Density sensor 35 Transfer part ( Transfer belt unit)
36 Transfer Belt 41 Fixing Unit 50 Paper Feeding Unit 51 Display Unit 60 Control Unit 62 Remaining Toner Detection Unit 63 Detection Image Forming Unit 64 Life Determination Unit 65 Image Formation Voltage Control Unit 66 LED Head Control Unit 67 Transfer Control Unit 68 Fixing Control Unit 69 Paper feed control unit 70 Display control unit 71 Density measurement control unit

Claims (9)

A developing device that contains a developer and forms the developer image on the surface of the image carrier by supplying the developer from a developer carrier that carries the developer;
A developer remaining amount detecting unit for detecting the remaining amount of developer in the developing device;
A transfer member for transferring and holding the developer image;
An image forming unit for detection that forms an image for detecting the remaining amount of developer on the transfer member;
A determination unit that detects a density of the developer remaining amount detection image and determines a replacement timing of the developing device based on the density;
The developer remaining amount detection image includes a reference density detection image and at least one comparison density detection having an interval corresponding to the length of one round of the developer carrier relative to the reference density detection image. Image and
The image forming apparatus, wherein the determination unit determines a replacement time of the developing device based on a detected density difference between the reference density detection image and the comparative density detection image, and notifies the determination result. The image forming apparatus according to claim 1.
At least one of the comparative density detection images is formed downstream of the reference density detection image in the transport direction of the transfer member while maintaining an interval corresponding to the rotation period of the developer carrier.
An image is not formed in a region spaced from the reference density detection image by an interval corresponding to the length of one circumference of the developer carrier on the upstream side in the conveyance direction of the transfer member. Image forming apparatus. The image forming apparatus according to claim 1, wherein:
The determination unit determines that it is a replacement time of the developing device when the detected density difference reaches a replacement time determination threshold stored in a storage unit. The image forming apparatus according to any one of claims 1 to 3,
The determination unit detects a remaining amount of usable developer based on a difference between the detected density difference and a replacement time determination threshold value stored in a storage unit, and calculates a consumption amount of the developer from the remaining usable developer amount. An image forming apparatus that measures and determines that it is time to replace the developing device when the remaining amount of usable developer runs out. 5. The image forming apparatus according to claim 1, wherein:
The image forming apparatus, wherein the developer remaining amount detecting unit measures a developer consumption amount based on a dot count value in an image forming process of the developer image, and detects the developer remaining amount. The image forming apparatus according to claim 1, wherein:
An image forming voltage control unit that controls a voltage applied to the developing device during normal image formation and image formation of the developer remaining amount detection image;
The image forming voltage control unit controls the voltage value at the time of image formation of the developer remaining amount detection image so as to be different from the voltage value at the time of the normal image formation. The image forming apparatus according to claim 6.
The image forming voltage control unit is configured such that a voltage value at the time of image formation of the developer remaining amount detection image is equal to a voltage value at the time of normal image formation, and the density of the developer remaining amount detection image is the normal value. The image forming apparatus is controlled so as to be lower than the image density. The image forming apparatus according to any one of claims 1 to 7,
The developing device further includes a developer supply member that supplies the developer to the developer carrier,
An image forming apparatus, wherein an amount of pressing of the developer supply member into the developer carrying member is in a range of 0.5 mm or more and 1.0 mm or less. The image forming apparatus according to claim 8.
The developer supply member has a configuration in which a foaming elastic member is coated around a metal shaft,
An image forming apparatus, wherein a ratio of an amount of pressing into the developer carrying member with respect to a thickness of the foamable elastic member is 0.20 or less.

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