Device and method of managing life of toner cartridge, and image forming apparatus using the same

It is managed a life of at least one toner cartridge loaded in an apparatus for forming an image on a recording medium with toner stored in the toner cartridge. A counter counts a remaining amount of each of a plurality of predetermined parameters. A replacement determinant determines that the toner cartridge should be replaced with another one when the remaining amount of any one of the parameters is a predetermined amount or less. A display is operable to display the remaining amount of each of the parameters as a percentage relative to a full remaining amount thereof. A selector selects one of the parameters indicating the lowest remaining amount as the remaining amount displayed on the display.

BACKGROUND OF THE INVENTION

The present invention relates to a device and method of managing the life of a toner cartridge as well as an image-forming apparatus using the same.

An image forming apparatus which forms an image through use of toner must manage the life of a toner cartridge by ascertaining the amount of toner consumption or the amount of remaining toner in order to facilitate maintenance, such as toner replenishment, or preservation of image quality. Japanese Patent Publication No. 2002-174929A discloses a method for calculating toner consumption with simple configuration which enable accurate determination of toner consumption.

A relationship between the number of a printed dot and the amount of toner consumption is nonlinear, and the relationship also changes depending on the state of another printed dot adjacent to that printed dot. In light of this relationship, the method classifies a train of printed dots into three patterns; that is, an isolated dot, two consecutive dots, and an dot of intermediate value. The number of dots formed is counted on a per-pattern basis. The amount of toner consumption is determined on the basis of the counted values.

In such an image forming apparatus, the toner filled in the toner cartridge is gradually consumed and decreased as a result of repeated formation of an image. When the amount of toner filled in the cartridge has decreased to a certain level or less, a message “Please replace the toner cartridge” appears on a display of the image forming apparatus, thereby alerting the user.

Even in view of effective utilization of resources, the user desires to accurately recognize the amount of toner consumption and replace a toner cartridge at an appropriate time. This publication teaches a pattern into which a train of printed dots is arranged is classified into three categories. There is disclosed determination of the amount of toner consumed per page during a certain job period on the basis of the pattern in which a train of printed dots is arranged. However, there is no description on the configuration for knowing the residual amount of toner contained in the toner cartridge and judging the point of time for the interchange of the toner cartridge.

Japanese Patent Publication No. 2001-83846A discloses a technique for individually displaying the residual amounts of toner for a large-capacity cartridge and a small-capacity cartridge. Specifically, there are provided a gauge used for displaying the residual amount of toner corresponding to the large-capacity cartridge and a gauge used for displaying the residual amount of toner corresponding to the small-capacity cartridge. In this case, the residual amounts of toner are displayed as absolute values (analog values). For this reason, the user can judge the current values of the residual amounts of toner visually.

However, there is a problem that the cost of the mechanism for individually displaying the residual amounts of toner increases. Moreover, the residual amount of toner in the small-capacity cartridge is displayed at a reduced ratio compared with the residual amount of toner in the large-capacity cartridge or displayed with a color different from the color used for displaying the residual amount of toner in the large-capacity cartridge. Or the two display forms are different, for example, in the width of change of each gauge. There is a problem that the user has a difficulty in reading the displayed residual amounts of toner.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to provide a device and method for managing the life of a toner cartridge in which the residual amount of a count value easy for a user to view can be displayed inexpensively. It is also an object of the invention to provide an image forming apparatus using such device and method.

In order to achieve the above objects, according to the invention, there is provided a device for managing a life of at least one toner cartridge loaded in an apparatus for forming an image on a recording medium with toner stored in the toner cartridge, the device comprising:

a counter, which counts a remaining amount of each of a plurality of predetermined parameters;

a replacement determinant, which determines that the toner cartridge should be replaced with another one when the remaining amount of any one of the parameters is a predetermined amount or less;

a display, operable to display the remaining amount of each of the parameters as a percentage relative to a full remaining amount thereof; and

a selector, which selects one of the parameters indicating the lowest remaining amount as the remaining amount displayed on the display.

With such a configuration, a user can certainly recognize a time that the toner cartridge should be replaced with another one.

Preferably, the toner cartridge is provided with a development roller which supplies the toner to the outside of the toner cartridge. The parameters includes an amount of the toner remaining in the toner cartridge, and a remained operable time of the development roller.

Here, it is preferable that a plurality of toner cartridges having different capacities are provided for the same color. The display is provided with a scale which is common to the parameters and the toner cartridges, so that a predetermined percentage is associated with a threshold value regarding the remaining amount for each of the parameters and the toner cartridges.

With such a configuration, the display can be inexpensively provided. Further, the user can recognize the remaining amount of the toner irrespective of the size of the toner cartridges without confusion.

The threshold value may be the same as or different from the predetermined value. In accordance with the preset configuration, the replacement time of the toner cartridge can be ascertained as the user requires.

It is also preferable that the device further comprises a storage, which stores an initial amount of the toner remaining in the toner cartridge as the full remaining amount. The counter subtracts a consumed amount of the toner to determine the amount of toner remaining in the toner cartridge.

It is also preferable that the device further comprises a storage, which stores an initial amount of the operable time of the development roller as the full remaining amount. The counter subtracts an operated time of the development roller to determine the remained operable time of the development roller.

For both cases, it is further preferable that the storage is provided with the toner cartridge. With such a configuration, the life management can be secured even if the toner cartridge is temporarily unloaded from the image forming apparatus.

It is also preferable that a plurality of colors of toner including black toner are used to form the image. The threshold value associated with the black toner is less than the threshold value associated with any one of the colors of toner. In general, the black toner is consumed more than any other colors of toner. Therefore, the opportunity for replacing the cartridge for the black toner can be decreased.

It is also preferable that the remaining amount for one of the toner cartridges which is associated with the predetermined amount is different from the remaining amount for another one of the toner cartridges which is associated with the predetermined amount.

Preferably, the predetermined amount is changed in accordance with an image occupation ratio which is an area ratio of the image formed with the toner relative to the recording medium.

According to the invention, there is also provided a method for managing a life of at least one toner cartridge loaded in an apparatus for forming an image on a recording medium with toner stored in the toner cartridge, the method comprising steps of:

counting a remaining amount of each of a plurality of predetermined parameters;

determining that the toner cartridge should be replaced with another one when the remaining amount of any one of the parameters is a predetermined amount or less;

selecting one of the parameters indicating the lowest remaining amount; and

displaying the lowest remaining amount of the selected one of the parameters on a display as a percentage relative to a full remaining amount thereof.

With such a configuration, the internal processing performed in the display can be simplified.

According to the invention, there is also provided an image forming apparatus, comprising the above device, wherein the toner supplied from the toner cartridge is transferred onto an image supporting member to form a toner image for visualizing an electrostatic latent image formed on the image supporting member in advance.

Preferably, the toner image is transferred onto an intermediate transferring member before the toner image is transferred onto the recording medium.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will be described hereinbelow in detail with reference to the accompanying drawings. An image forming apparatus shown inFIG. 8is for forming a full-color image by superposing four-color images; that is, a yellow (Y) toner image, a cyan (C) toner image, a magenta (M) toner image, and a black (K) toner image, and a monochrome image through use of only the black (K) toner image. In the image forming apparatus of the present invention, an image signal is inputted to a main controller11from an external apparatus such as a host computer in accordance with a user's request for forming an image. At this time, an instruction signal is transmitted from the main controller11to an engine controller10. In accordance with the instruction signal, the engine controller10controls individual sections of an engine section EG, thereby forming on a sheet S (recording medium) an image corresponding to the image signal.

This engine section EG is provided with a photosensitive member2serving as an image carrier, such that the photosensitive member is rotatable in the direction of an arrow D1shown inFIG. 7. A charger3, a rotary developer4, and a cleaner5are provided around the photosensitive member2along the rotating direction D1thereof. A charging bias output from a charging controller103is applied to the charger3, thereby uniformly charging an outer peripheral surface of the photosensitive member2to a predetermined surface potential. A light beam L is emitted from an exposer6toward the outer peripheral surface of the photosensitive member2charged by the charger3. In accordance with a control instruction issued by an exposure controller102, the exposer6irradiates the photosensitive member2with the light beam L, thereby forming an electrostatic latent image corresponding to an image signal. The exposer6is provided with optical elements, such as a lens, a mirror, or the like, as required.

When an image signal is delivered from an external apparatus, such as a host computer, to a CPU111of the main controller11by way of an interlace112, a CPU101of the engine controller10outputs, to the exposure controller102and at a predetermined timing, a control signal corresponding to the image signal. The light beam L is radiated from the exposer6on the photosensitive member2in accordance with this control signal, whereupon an electrostatic latent image corresponding to the image signal is formed on the photosensitive member2.

The thus-formed electrostatic latent image is subjected to toner development by the rotary developer4. Specifically, in the present embodiment, the rotary developer4is equipped with a support frame40which is provided so as to be rotatable about the axial center; and another member, such as a rotary driver omitted from the drawing.

The rotary developer4is further provided with an yellow developing section4Y, a cyan developing section4C, a magenta developing section4M, and a black developing section4K, which are detachably installed in the support frame40and accommodate colors of toner (the color developing sections4Y,4C,4M, and4K are herein sometimes called “toner cartridges”).

As shown inFIG. 9, the rotary developer4is controlled by a development controller104. In accordance with a control instruction output from the development controller104, the rotary developer4is rotated. The developing sections4Y,4C,4M, and4K are selectively placed at predetermined development positions opposing to the photosensitive member2, thereby imparting a selected color of toner to the surface of the photosensitive member2. As a result, the electrostatic latent image on the photosensitive member2is rendered visible in the selected color of toner.

A development roller44provided on the developing section is placed at the development position (i.e., the yellow developing section4Y in the embodiment shown inFIG. 8) and comes into contact with the photosensitive member2or is arranged so as to oppose the photosensitive member2with a predetermined gap therebetween. The development roller44serves as a toner carrier for carrying the frictionally-charged toner to the surface of the photosensitive member2. As the development roller44rotates, the toner is sequentially transported to the position where the development roller44opposes the photosensitive member2having an electrostatic latent image formed thereon.

Here, the developing section controller104applies, to the development roller44, a development bias on which a DC voltage and an AC voltage are superposed. By such a development bias, the toner carried by the development roller44partially adheres to individual sections of the surface of the photosensitive member2in accordance with the surface potentials of the sections, whereby the electrostatic latent image formed on the photosensitive member2is rendered visible as a toner image of the toner color.

The toner image developed by the developer4in the manner mentioned above is transferred to an intermediate transfer belt (an intermediate transfer member)71of a transferor7in a primary transfer area TR1through primary transfer. The transferor7comprises the intermediate transfer belt71suspended by a plurality of rollers72to75; and a drive section (not shown) for circulating the intermediate transfer belt71in a predetermined rotating direction D2by rotating the roller73.

Moreover, a secondary transfer roller78, which is retractably brought into contact with the surface of the belt71by an unillustrated electromagnetic clutch, is disposed at a position which opposes the roller73with the intermediate transfer belt71interposed therebetween. When a color image is transferred to a sheet S (recording medium), the toner images of respective colors formed on the photosensitive member2are superposed on the intermediate transfer belt71, to thereby form a color image.

A color image is transferred onto the sheet S which is taken out of a cassette8and conveyed to a secondary transfer area TR2between the intermediate transfer belt71and a secondary transfer roller78. Moreover, the sheet having the color image formed thereon is transported to an output tray section provided on a top section of a main body of the apparatus by way of a fixer9.

The surface potential of the photosensitive member2that has transferred the toner image on the intermediate transfer belt71through primary transfer operation is reset by a discharger omitted from the drawing. After the toner remaining on the surface of the photosensitive member2has been removed by the cleaner5, the photosensitive member2is subjected to the next charging by the charger3. The toner removed by the cleaner5is recovered by an unillustrated toner tank.

A cleaner76, a density sensor60, and a vertical synchronization sensor77are arranged in the vicinity of the roller75. Of these elements, the cleaner76can be retractably brought into close contact with the roller75by an unillustrated electromagnetic clutch. A blade of the cleaner76comes into contact with the surface of the intermediate transfer belt71passed around the roller75with the cleaner76having moved to the roller75, thereby removing the toner still remaining on and adhering to the outer peripheral surface of the intermediate transfer belt71after secondary transfer operation. The toner removed by the blade of the cleaner76is recovered by a waste toner tank (not shown).

The vertical synchronization sensor77is a sensor for detecting the reference position of the intermediate transfer belt71. The vertical synchronization sensor77is a sensor for acquiring a synchronization signal output in association with circulation of the intermediate transfer belt71; that is, a vertical synchronization signal Vsync. In this apparatus, operations of the individual sections of the apparatus are controlled in accordance with the vertical synchronization signal Vsync in order to make operation timings of the individual sections coincide with each other and accurately superpose the toner images formed in respective colors on each other. The density sensor60is disposed so as to oppose to the surface of the intermediate transfer belt71. In the density control operation, the optical density of the patch image formed on the outer peripheral surface of the intermediate transfer belt71is measured.

As shown inFIG. 9, the respective developing sections (toner cartridges)4Y,4C,4M, and4K are equipped with memory devices91to94for storing data pertaining to a manufacturing lot of the developing sections, the history of use of the developing sections, and the amount of toner remaining in the developing sections. The respective developing sections4Y,4C,4M, and4K are provided with connectors49Y,49C,49M, and49K.

The connectors49Y,49C,49M, and49K are selectively connected to a connector108provided on the main body, as required. Therefore, data are exchanged between the CPU101of the engine controller10and the memory devices91to94by way of an interface105, thereby managing various information items such as consumable item management of the developing sections (i.e., the cartridges). In this embodiment, the connector108of the main body and the connector49K of the developing section are mechanically fitted together, thereby mutually exchanging data. However, data may be exchanged in a non-contact manner through use of, e.g., electromagnetic means such as radio communication.

The memory devices91to94for storing data unique to the respective developing sections4Y,4C,4M, and4K are preferably nonvolatile memory devices capable of storing data even while the memory devices remain in a powered off state or even while the developing sections are removed from the main body. For instance, a flash memory, a ferroelectric memory (FRAM, Ferroelectric Random Access Memory), or an EEPROM (Electronically Erasable and Programmable Read Only Memory) can be used as such nonvolatile memory.

Although omitted fromFIG. 8, the image forming apparatus is provided with a display12(FIG. 9). A predetermined message is displayed in accordance with a control instruction issued by the CPU111, as required, thereby informing the user of required information. For instance, in the event that an anomaly, such as a failure in the apparatus or a paper jam, has arisen, a message for informing the user of occurrence of the anomaly is displayed. Alternatively, when the amount of toner remaining in any of the developing sections has decreased to a predetermined level or less; e.g., a near-end level to be described later, a message for announcing the approach of a time for replacement of the developing sections is displayed.

A display device; e.g., a liquid-crystal display or the like, can be used as the display12. In place of the display device, a warning lamp which is illuminated or caused to blink may also be employed when necessary. Moreover, a warning device, which issues sound, such as a previously-recorded voice message or beep sound, other than visual information of a message to the user through display of the message may be employed, or the warning lamp and the warning device may be used in combination, if necessary.

The controller11is provided with image memory113for storing an image output from an external apparatus such as a host computer, by way of the interface112. Reference numeral106designates a ROM for storing a calculating program to be executed by the CPU101and control data to be used for controlling the engine section EG. Reference numeral107designates a RAM for temporarily storing results of calculating operation performed by the CPU101and other data. As mentioned previously, a nonvolatile FRAM may be employed for the RAM107.

There will now be describe the manner of determining the amount of remaining toner in the respective developing sections (i.e., toner cartridges)4Y,4M,4C, and4K in the image forming apparatus having the foregoing configuration. In relation to the image forming apparatus of this type there has already been developed a single image forming apparatus which enables replacement and loading of toner cartridges having two different volumes; that is, a toner cartridge accommodating a large amount of toner and another cartridge accommodating a small amount of toner. In such a case, the life of the toner cartridge varies according to the amount of toner accommodated in the large toner cartridge or the amount of toner accommodated in the small toner cartridge.

InFIG. 4, a count of the toner counter is set on the horizontal axis, and an operated time of the development roller (a cumulative time [sec]) is set on the vertical axis. In connection with the count of the toner counter, a maximum of 130,000,000 is set as an example count in the case of a large toner cartridge which enables formation of images on 6000 sheets of A4-size paper.

Moreover, in the case of a small toner cartridge which is to be loaded in the same image forming apparatus and enables formation of images on 2000 sheets of A4-sized paper, the count of the toner counter is set to a maximum of 5,000,000. According to the present invention, regardless of the toner cartridge used, the large toner cartridge or the small toner cartridge, the life of the toner cartridge can be managed appropriately.

In the case of the large toner cartridge, the operated time of the development roller set on the vertical axis is set to a maximum of, e.g., 12,000 sec. Moreover, in the case of the small toner cartridge, the operated time of the development roller is set to a maximum time of, e.g., 4,000 sec. The life of the toner cartridge is determined on the basis of whether or not any of parameters; that is, whether or not the count of the toner counter set on the horizontal axis and the operated time of the development roller set on the vertical axis, has reached a preset value. Specifically, the life of the toner cartridge is determined on the basis of a logical OR value in relation to which of the count of the toner counter and the operated time of the development roller has reached the preset value.

In the embodiment shown inFIG. 4, three levels are set according to the amount of remaining toner at the time of determination of the life of such a toner cartridge. Specifically, the levels are set in decreasing sequence of the amount of remaining toner; that is, (1) a near-end level, (2) an end level, and (3) an end-end level, from the largest amount to smaller amounts. When the amount of remaining toner has decreased from the initial value and reached the (1) near-end level, a warning message “Only a small amount of toner remains” or “The toner cartridge must be replaced soon” is displayed on the display12.

When the amount of remaining toner has further decreased from (1) near-end level and reached (2) end level, an operation call “Please replace the toner cartridge” is displayed on the display12. The image forming apparatus may be imparted with the function of displaying the operation call every time an image is formed on one sheet, to thus hinder consecutive formation of images.

When the amount of remaining toner has reached (3) end-end level as a result of a further decrease in the amount of remaining toner, control operation is performed such that no image can be formed on the sheet. Therefore, the user can ascertain the time for replacement of a toner cartridge stepwise, and hence superior convenience is achieved, whereby the user's convenience can be enhanced.

InFIG. 4, a dashed line R designates a near-end level; a chain line S designates an end level; and a solid line T designates an end—end level. The count of the toner counter set on the horizontal axis is set to the maximum value A3, the near-end value A2, and the end value A1. Further, the operated time of the development roller set on the vertical axis is set to the maximum (end—end) level B3, the end level B2, and the near-end level B1.

The count of the toner counter is set by the number of pieces (sheets) of recording paper on which images are to be formed and the size of an image formation area on a sheet (i.e., an image occupation ratio). Specifically, the count of the toner counter varies according to the total amount of images formed on a sheet. InFIG. 4, U designates a characteristic achieved at an image occupation ratio of 1%; V designates a characteristic achieved at an image occupation ratio of 5%; and W designates a characteristic achieved at an image occupation ratio of 20%. The characteristic U is assumed to form images on four A4-sized sheets per job; and the other characteristics V, W are assumed to form images for one A4-sized sheet per job. As can be seen fromFIG. 4, there is a tendency toward the higher the image occupation ratio, the higher the count of the toner counter and the smaller the amount of remaining toner.

In the embodiment, the near-end value A2 is achieved at 6400 (Ua) sheets in the case of the characteristic U achieved at the image occupation ratio of 1%; 4800 sheets (Va) in the case of the characteristic V achieved at the image occupation ratio of 5%; and 1200 sheets (Wa) in the case of the characteristic W achieved at the image occupation ratio of 20%. The end value A1 is achieved at 8000 (Ub) sheets in the case of the characteristic U achieved at the image occupation ratio of 1%; 6000 sheets (Vb) in the case of the characteristic V achieved at the image occupation ratio of 5%; and 1500 sheets (Wb) in the case of the characteristic W achieved at the image occupation ratio of 20%. Moreover, the end—end level is achieved at 9090 (Uc) sheets in the case of the characteristic U; 6800 sheets (Vc) in the case of the characteristic V; and 1700 sheets (Wc) in the case of the characteristic W.

As mentioned above, in the case of the characteristic U achieved at the image occupation ratio of 1% in the embodiment shown inFIG. 4, a 20% difference exists between 6400 sheets (Ua) and 8000 sheets(Ub). Further, a difference of 1090 between 8000 sheets (Ub) and the 9090 sheets (Uc) exists between the near-end A1 and the end. Moreover, in the case of the characteristic V having an image occupation ratio of 5%, a difference of 20% between 4,800 sheets (Va) and 6,000 sheets (Vb) exists between the near-end A2 and the end A1. Moreover, a difference of 800 sheets between 6000 sheets (Vb) and 6,800 sheets (Vc) is present between the end A1 and the end—end.

In relation to the operated time of the development roller set on the vertical axis, the maximum (end—end) level B3, the end level B2, and the near-end level B1 are set for each of the characteristics U, V, and W. For instance, the end—end level B3 of the characteristic U assumes a value of 12,000 sec. An appropriate near-end level and an appropriate end level are set in correspondence with the end—end level for each of the characteristics U, V, and W. In connection with determination of the life of the toner cartridge depending on the operated time of the development roller, it can be seen that the life of the toner cartridge tends to become shorter as the image occupation ratio becomes smaller.

Specifically, at a given image occupation ratio the count of the toner counter and the operated time of the development roller are contrary in characteristic to each other in terms of the life of the toner cartridge. What is meant by this is that even in the case where the image occupation rate is low, the life viewed from the operated time of the development roller is shortened though the amount of consumed toner is small because deterioration of toner packed in the toner cartridge is accelerated by the rotation of the development roller.

As mentioned previously, the life of the toner cartridge can be determined in terms of whether the count of the toner counter or the operated time of the development roller has reached a predetermined level.

FIG. 5is a characteristic drawing showing the relationship between the count of the toner counter and the amount of remaining toner. The count of the toner counter is set on the horizontal axis, and the amount of remaining toner (g) is set on the vertical axis. Even in this case, a characteristic achieved by the large cartridge changes from that achieved by the small cartridge.FIG. 5shows the characteristic of, e.g., the large toner cartridge, which is intended for a case where an image is formed on an A4-sized sheet at an image occupation ratio of 5%.

In the embodiment shown inFIG. 5, a standard value and a numerical value which falls within ±12.5% of the standard value are set as a toner-end level. The characteristic Y designates a standard amount of remaining toner; the characteristic X designates +12.5% of the standard amount; and the characteristic Z designates −12.5% of the standard amount. InFIG. 5, an initial value C4 of the amount of toner is set to, e.g., 225 g. Moreover, the standard end value C2 of the amount of remaining toner is set to 54 g; an end value C3 achieved by the characteristic X is set to 79 g; and an end value C1 achieved at the characteristic Z is set to 30 g.

The maximum value A3, the near-end value A2, and the end value A1, which are the same as those shown inFIG. 4, are set on the horizontal axis. A near-end value Ya of a standard characteristic Y assumes a value of 83 g in this embodiment. In the present invention, the count of the toner counter used at the time of determination of the amount of remaining toner at a near-end position is set in conformity with realities of formation of images in respective colors.

FIG. 6is an explanatory view showing an example of a table of toner counter count values for defining the near-end value of the remaining amount of toner. For example, this table is stored in the FRAM107shown inFIG. 9. InFIG. 6, the “type” represents the capacity of each toner cartridge. For example, Pa shows the large-capacity toner cartridge, and Pb shows the small-capacity toner cartridge. The near-end value of the remaining amount of toner is set as “count value” for each “color”, that is, yellow (Y), cyan (C), magenta (M) and black (K).

In the example shown inFIG. 6, the near-end values of the remaining amount of toner for colors Y, C and M in the toner cartridge Pa are set to be a1 equally while the near-end value of the remaining amount of toner for K is a2. The near-end values of the remaining amount of toner for colors Y, C and M in the toner cartridge Pb are set to be a3 equally. Incidentally, a2 is set as a numerical value smaller than a1, and a3 is set as a numerical value smaller than a2.

In this embodiment, the near-end value of the remaining amount of toner is determined in consideration of characteristic of each color, when the image formation is performed with respect to the recording medium. Specifically, the characteristic includes the size of a print region, the amount (offset) of toner deposited on a non-image region, and so on.

In consideration of the aforementioned characteristic, the amount of consumed toner for black (K) becomes larger when image formation is performed on a predetermined number of sheets. Accordingly, the remaining amounts of toner for the respective colors are not equal. Therefore, in the example shown inFIG. 6, the near-end value of the remaining amount of toner for black (K) is set to be a numerical value smaller than those for the other colors, that is, the life count value for black (K) is set to be larger than those for the other colors to meet the actual situation of the amount of consumed toner.

Accordingly, accurate toner cartridge life management can be performed in conformity with the actual situation of toner consumption.

Next, there will be described how to manage the remaining amount of toner in the toner cartridge with reference toFIGS. 1A and 1B.FIG. 1Ashows a case for the large-capacity cartridge, andFIG. 1Bshows a case for the small-capacity cartridge. In these figures, the horizontal axis expresses toner count value, and the vertical axis expresses the displayed remaining amount (%) of the toner.

InFIG. 1A, D4 is the maximum value (initial value) of the toner count value. The displayed remaining amount of toner in this case is 100%. D3 is the near-end value of the toner count value. D2 is the end value of the toner count value. D1 is the end—end value of the toner count value. In the example shown inFIG. 1A, the near-end value D3 corresponds to 20% in terms of the displayed remaining amount of toner. That is, in this embodiment, the displayed remaining amount of toner in accordance with the consumption of toner is expressed not in absolute value (analog number) but in the rate (%) relative to the initial value (100%).

InFIG. 1B, E4 is the initial value of the toner count value, E3 is the near-end value of the toner count value, E2 is the end value of the toner count value, and E1 is the end—end value of the toner count value. Also in this case, the near-end value E3 of the toner count value is set at 20% in terms of the displayed remaining amount of toner. That is, in this embodiment, the divisions of a scale for displaying the remaining amount of toner are used in common to the case where the large-capacity toner cartridge is used and the case where the small-capacity toner cartridge is used.

For this reason, it is possible to simplify the configuration of a toner remaining amount display mechanism in the image forming apparatus using toner cartridges different in capacity of toner. Moreover, arithmetic processing can be performed easily because it is unnecessary to perform separate arithmetic operations for displaying the remaining amounts of toner according to the toner cartridges different in capacity of toner. Moreover, user's convenience is improved because there is no possibility that the user will misread the remaining amounts of toner when the toner cartridges different in capacity of toner are used.

Incidentally, as will be described later, when the toner cartridges different in capacity of toner are used, the remaining amounts of toner are displayed in use of the divisions of the same scale while the near-end values in the toner cartridges are displayed at the same rate and the end values of the remaining amount of toner in the toner cartridges are displayed at the same numerical value. For this reason, it is unnecessary to change the arithmetic processing whenever a toner cartridge different in capacity of toner is used. Accordingly, internal processing can be performed quickly.

FIGS. 2A and 2Bshows an alternative way to manage the remaining amount of toner in the toner cartridge.FIG. 2Ashows a case for the large-capacity cartridge, andFIG. 2Bshows a case for the small-capacity cartridge. In these figures, the horizontal axis expresses the accumulated operation time of the development roller (sec), and the vertical axis expresses the displayed remaining amount (%) of the toner (the operable time of the development roller).

InFIG. 2A, F4 is the initial value (0) of the operated time of the development roller, F3 is the near-end value thereof, F2 is the end value thereof, and F1 is the end—end value thereof. Also in the case shown inFIG. 2A, the near-end value F3 corresponds to 20 (%) in terms of the displayed remaining amount of the toner (the operable time of the development roller).

InFIG. 2B, G4 is the initial value (0) of the operated time of the development roller, G3 is the near-end value thereof, G2 is the end value thereof, and G1 is the end—end value thereof. Also in the example shown inFIG. 2B, the near-end value G3 is set at 20 (%) in terms of the displayed remaining amount of toner (the operable time of the development roller). Accordingly, even in the case where the operated time of the development roller is used as a parameter for displaying the remaining amount of toner (the operable time of the development roller), the remaining amounts can be displayed by using the divisions of the same scale when toner cartridges different in capacity of toner are used.

That is, in this embodiment, the near-end value of the remaining amount of toner (the operable time of the development roller) is displayed as the same rate of 20% even in the case where either of the toner count value and the operated time of the development roller is used as a parameter. For this reason, user's confusion caused by change in the rate of the displayed remaining amount of toner (the operable time of the development roller) in accordance with the near-end value can be avoided even in the case where the parameter is changed.

As shown inFIG. 3, an external computer (host computer)20sends image data to the main controller11. The display12is connected to the main controller11and provided for displaying various kinds of messages and the remaining amount of toner as a rate (%) relative to the initial value described above with reference toFIGS. 1A through 2B.

The CPU101and the FRAM107are provided in the engine controller10. Each of the toner cartridges4is provided with a memory device (91to94inFIG. 9) regardless of whether the toner cartridge4is of a large-capacity type or of a small-capacity type. The initial values of the toner counter count value and the operated time of the development roller and current values of the remaining amount of toner and the remaining operable time of the development roller are stored in each memory device.

After a large-capacity cartridge used for performing image formation on a recording medium is interchanged with a small-capacity cartridge for performing image formation by use of the small-capacity cartridge, the small-capacity cartridge may be interchanged with the large-capacity cartridge again by the user for performing image formation again by use of the large-capacity cartridge. Even in this case, the values of the remaining amount of toner corresponding to the large-capacity cartridge before the interchange of the large-capacity cartridge with the small-capacity cartridge have been already stored in the memory devices. Accordingly, even in the case where a toner cartridge is exchanged with another toner cartridge different in capacity before the life end of the toner cartridge, the remaining amount of toner in each of the toner cartridges can be recognized accurately. Accordingly, the life of each toner cartridge can be managed accurately.

Incidentally, when, for example, the initial value of the toner counter count value of the large-capacity toner cartridge is 130,000,000, the value of 130,000,000 is not directly stored in each memory in the toner cartridge. For example, a numerical value 150 obtained by suitably rounding a result (208) of calculation in which the value of 130,000,000 is divided by 216is set as the initial value of the toner counter count value for the sake of saving memory resources.

As will be described later in detail, the CPU101of the engine controller10calculates the amount of consumed toner and subtracts the amount of consumed toner from the initial value to thereby update information concerning the current remaining amount of toner. Alternatively, the CPU101adds the accumulated operation time of the development roller to the initial value to thereby update information concerning the current remaining amount of the operable time of the development roller. The updated information concerning the remaining amount of toner or the operable time of the development roller is stored not only in the FRAM107but also in each memory device in the toner cartridge4. The process of updating the remaining amount information is performed in accordance with every color, so that the latest information concerning the remaining amount of the toner or the operable time of the development roller is always stored in the FRAM107and each memory device in the toner cartridge4.

As described above with reference toFIG. 9, the CPU111is provided in the main controller11. A dot counter and an image processor are provided in the CPU111. As will be described later with reference toFIG. 10, each toner counter for counting the amount of consumed toner is formed as a software or hardware in the CPU101of the engine controller10.

When image data given from the external computer20is input into the image processor of the main controller11, the image processor generates an exposure signal and inputs the exposure signal into the dot counter. The dot counter counts the number of pixels by color by page on the basis of the exposure signal and sends the count value to the CPU101. The CPU101of the engine controller10reads the initial value and coefficient of the amount of toner packed in the toner cartridge from the FRAM107for every color.

For example, the coefficient is a weighting coefficient used for image formation. The coefficient will be described later in detail. The CPU101calculates a result of an arithmetic operation in which the count value is weighted by the coefficient, that is, the CPU101calculates the amount of consumed toner. In this manner, the CPU101of the engine controller10calculates the dot count value, that is, the toner counter count value (the amount of consumed toner) on the basis of the count value received from the dot counter for every color and every page and the coefficient read from the FRAM107.

The CPU101calculates a new remaining amount of toner by subtracting the amount of consumed toner from the old remaining amount of toner and stores the result in the FRAM107. The information concerning the remaining amount of toner is also sent to the main controller11. Though not shown, a signal of a timer concerning the operated time of the development roller is input into the CPU101of the engine controller10when the development roller is operating. The operated time is accumulated in accordance with every job, so that the accumulated operation time is stored in the FRAM107.

The initial value (0) of the operated time and the maximum value of the remaining operable time of the development roller are stored in the FRAM107. The CPU101sends the toner cartridge drive time measured by the timer or program timer as described above to a counter210(FIG. 10) for counting the accumulated operation time of the development roller. An calculator206acquires the accumulated value of the operated time of the development roller of the toner cartridge counted by the counter210. The accumulated value of the operated time of the development roller is sent to the CPU101. The CPU101adds the accumulated value to the initial value of the operated time of the development roller read from the FRAM107. The CPU101subtracts the accumulated total value from the maximum value read from the FRAM107to thereby calculate the remaining amount of the operable time of the development roller.

Accordingly, the operated time of the development roller is accumulated from the initial value successively, so that the accumulated value of the operated time of the development roller is stored in the FRAM107. The CPU101calculates the remaining amount of the operable time of the development roller on the basis of the current accumulated operation time and judges the life of the toner cartridge from the remaining amount of the operable time of the development roller. When the drive time reaches the near-end value, a message of “The time for interchange of cartridge is approaching” is displayed on the display.

Next, a specific example of display of the remaining amount of toner (the remaining amount of the operable time of the development roller, hereinafter simply referred to as “remaining amount of operable time”) will be described. The CPU101of the engine controller10calculates the remaining amount of toner or the remaining amount of operable time on the basis of the toner counter count value or the accumulated operable time of the development roller. Accordingly, the CPU101has information concerning the remaining amount of toner (the remaining amount of operable time) in a range of from the end—end value (0%) to the initial value (100%). As described above with reference toFIGS. 1A through 2B, the near-end value is set, for example, as the rate of 20%.

As shown inFIG. 3, an end value H is set between the near-end value and the end—end value. The engine controller10sends information concerning the remaining amount of toner (the remaining amount of operable time) to the main controller11. The remaining amount of toner (the remaining amount of operable time) is displayed on the display12on the basis of the information. On this occasion, the remaining amount of toner (the remaining amount of operable time) displayed on the display is expressed as the rate (%) relative to the initial value 100% in the condition that the end value corresponds to 0%.

That is, information (v) of the remaining amount of toner (the remaining amount of operable time) in the engine controller10is provided so that the end—end value is set at 0% with respect to the initial value. On the other hand, information (u) of the remaining amount of toner (the remaining amount of operable time) in the main controller11is provided so that the end value is set at 0%. Although a message of “Interchange the toner cartridge” is displayed on the display when the remaining amount of toner (the remaining amount of operable time) reaches the end value, the message does not change even in the case where the remaining amount of toner (the remaining amount of operable time) reaches the end—end value. Incidentally, in each information (u) or (v), only an example of display of the remaining amount of toner is shown for the sake of simplification.

If the user is notified of the fact that the remaining amount of toner (the remaining amount of operable time) reaches the end value, the user can understand that the toner cartridge must be interchanged with a another one. Accordingly, it can be said that this display meets the actual situation because it is particularly unnecessary to display the end—end value smaller in the remaining amount of toner (the remaining amount of operable time) than the end value.

The display of the end value of the remaining amount of toner (the remaining amount of operable time) will be described further specifically. The remaining amount of toner (the remaining amount of operable time) is displayed on the display12by the divisions of the same scale regardless of the toner capacity of the toner cartridge while the near-end value of the remaining amount of toner (the remaining amount of operable time) is displayed, for example, at the same rate of 20%. In this manner, the remaining amount of toner (the remaining amount of operable time) is displayed at the same rate regardless of the toner capacity (the maximum value of the operable time of the development roller) of the toner cartridge in the period of from the point of time when the toner cartridge is attached newly to the point of time when the remaining amount of toner (the remaining amount of operable time) reaches the near-end value. Accordingly, the user can recognize the remaining amount of toner (the remaining amount of operable time) without confusion.

The end value is displayed as the rate of 0% on the assumption that the maximum value of the toner capacity or development roller drive time is regarded as 100%. In the engine controller, the end—end value is however set as the rate of 0% in the aforementioned manner. Accordingly, the end value H between the near-end value and the end—end value is formed so that the rate of the end value H managed by the engine controller10has a certain value (e.g. 10%) with respect to the maximum value.

In this embodiment, the end value of the remaining amount of toner (the remaining amount of operable time) is sent to the main controller11so that the end value is expressed as a numerical value common to the plurality of toner cartridges. That is, the end value H is set as a significant numerical value regardless of the capacity of the toner cartridge, and the end value H is sent to the main controller11when the engine controller10judges the end value H. For example, the end value H of the remaining amount of toner is set as a numerical value of about 500,000 which is about 10% as large as the initial value 5,000,000 in the small-capacity toner cartridge.

In this manner, the near-end value of the remaining amount of toner (the remaining amount of operable time) is displayed at the rate common to the plurality of toner cartridges. Accordingly, the user can recognize the remaining amount of toner without confusion. Moreover, the end value of the remaining amount of toner (the remaining amount of operable time of the development roller) is displayed as a numerical value common to the plurality of toner cartridges. Accordingly, the user can recognize the toner cartridge's arrival at the end value clearly regardless of the toner capacity of the toner cartridge. For this reason, it is possible to prevent image deterioration such as image caused by shortage of the remaining amount of toner (the operable time of the development roller) in continuous image formation.

InFIG. 3, when the remaining amount of toner (the remaining amount of operable time) is newly stored in the FRAM107in the aforementioned manner, the CPU101compares the updated remaining amount of toner (the updated remaining amount of operable time) with the near-end value. When the remaining amount of toner (the remaining amount of operable time) reaches the near-end value, the CPU101outputs a signal for notifying the user of the fact that the life of the toner cartridge is running out.

Incidentally, there may be configured such that the rate of the remaining amount of toner and the rate of the remaining amount of the operable time of the development roller are compared with each other, and that a lower one is selected by the CPU101and displayed. In this case, the user can recognize the shortage of the life of the toner cartridge more clearly because smaller one of the rate of the remaining amount of toner and the rate of the remaining amount of the operable time of the development roller is displayed. The user can make preparation for interchange of the toner cartridge. In addition, internal processing for displaying the remaining amount can be performed easily compared with the case where both the remaining amounts are displayed because only smaller one in terms of the rate of the remaining amount is displayed.

FIG. 7is a flow chart showing a process of judging the life of the toner cartridge on the basis of the remaining amount of toner or the remaining amount of the operable time of the development roller is performed. The life is managed in accordance with every capacity of the toner cartridge and every color. When the apparatus is activated (step S1), the state of the remaining amount of toner is judged (step S2). When the judgment in step S2results in the end—end state, the state is transited to the end—end state (step S3). The term “transition of state” means transition from a certain state to another certain state.

When the judgment in step S2results in the near-end state, the state is transited to the near-end state (step S4). When the judgment in step S2results in a normal state in which toner more than the near-end level is remaining in the toner cartridge, the state is transited to the normal state (step S5). In the normal state, generation of a signal for displaying a message of “The time interchange of the toner cartridge is approaching” is inhibited in the case where a toner near-end (warning) signal is generated by a malfunction. Further, generation of a signal as an operation call for urging the user to interchange the toner cartridge in the toner end state is also inhibited.

Incidentally, in the normal state, the amount of consumed toner and the operated time of the development roller are counted and stored in the FRAM107. When the state is transited from the normal state to the near-end state, an operation for the near-end state is performed. The transition of state in this case is expressed by the bold arrow so as to be distinguished from the transition of state at the time of apparatus activation. In the operation for the near-end state, a message of “The time for interchange of the toner cartridge is approaching” is displayed but notification of an operation call for urging the user to interchange the toner cartridge is inhibited.

In the near-end state, the amount of consumed toner and the operated time of the development roller are counted and stored in the FRAM107. When the state is transited from the near-end state to the end—end state, an operation for the toner end—end state is performed. In this case, generation of a message signal based on the toner near-end state stops and generation of a signal for the interchange of the toner cartridge is performed. In this manner, inFIG. 7, when the remaining amount of toner in the toner cartridge is in the normal state, the near-end state or the end—end state, a flag is set for indicating each state. Accordingly, only generation of a signal corresponding to the flagged state is validated. Processing is made so that instructions valid in the other states are not accepted.

In the case where the toner cartridge is interchanged with a another one in each of the normal state, the near-end state and the end—end state, a life expectancy value obtained by subtracting the remaining amount of toner from the initial value of the toner cartridge is reset and necessary processing such as updating the initial value is performed with the interchange of the toner cartridge. Then, the life judgment of the toner cartridge in S1is performed.

There will now be described the configuration and operation of the toner counter with reference toFIG. 10.

In this device, the CPU101performs predetermined processing operation on the basis of the program stored in the ROM106shown inFIG. 9, thereby determining the amount of toner consumed by the image formation area. Specifically, all the configuration of the toner counter is implemented by software but may also be implemented by hardware.

Here, the principle of operation of the toner counter according to the invention will be described while a toner counter200having the hardware configuration shown inFIG. 10is taken as an example. Even when the circuit shown inFIG. 10is implemented by software, the amount of toner consumption can be determined on the basis of the same principle as that employed in the case of the hardware.

On the basis of a control signal identical with that delivered from the CPU101to the exposure controller102; that is, an image signal input from the external apparatus, a signal converted into a gradation value for each color of toner is input to the toner counter200. On the basis of the control signal, the comparator201permits passage of a signal corresponding to a print dot whose gradation value is equal to or larger than a predetermined threshold value, and the signal is input to a discriminator202. The discriminator202determines the arrangement of print dots on the basis of the signal output from the comparator201.

Specifically, the discriminator202detects the number of dots constituting the train of print dots, classifies the dots into three categories; that is, a pattern of dots which are larger than a threshold value; a pattern of four continuous dots; and a pattern of isolated dots, and outputs “1” to any of counters203to205according to the category. Here, the isolated dots are dots in which adjacent pixels on both sides of a pixel of certain threshold value or more are less than the threshold value. The counters203,204, and205are provided so as to correspond to the pattern of dots which are larger than a threshold value, the pattern of four continuous dots, and the pattern of isolated dots, respectively. The counters203to205count the number of times a train of print dots is formed into a pattern of interest, by counting a signal output from the discriminator202at any times.

For instance, when the control signal input to the comparator201corresponds to the pattern of isolated dots, the discriminator202determines the print dots as isolated dots in accordance with the signal output from the comparator201. The discriminator202outputs “1” to the counter205but “0” to the other counters203,204. By such processing, only the count of the counter205, which shows the number of times the pattern of isolated dots is formed is incremented by one.

However, at this time, the counts of the other counters203,204remain unchanged. Similarly, when the control signal input to the comparator201corresponds to the pattern of four continuous dots, the count of the corresponding counter204is incremented by one. Thus, the number of times the print dots are formed is individually counted on a per-pattern basis.

The counts C1, C2, and C3 are input to a calculator206. In addition to the count values C1, C2, and C3, offset values “No” for respective colors output from the CPU101and an output from a coefficient table207are input to the calculator206. An output from the calculator206is input to the CPU101and the coefficient table207. The coefficient table207stores a plurality of sets of numerals, which would be candidates for “weighting coefficients” Kx, K1, K2, and K3 (see Equation 1 provided below), beforehand, and any one is selected from the sets in accordance with an output from the calculator206.

The calculator206multiplies the counts C1, C2, and C3 output from the respective counters203to205by the weighting coefficients K1, K2, and K3 selectively output from the coefficient table207, as well as summating them. Further, the offset value No output from the CPU101is added to a product of the sum and the coefficient Kx. Through the foregoing calculations defined by Equation (1), the amount of toner consumption Ct (first amount of toner consumption) is determined. Here, Kx designates a color dependence coefficient which changes from color to color.
Ct=Kx(K1−C1+K2·C2+K3·C3)+No

As mentioned previously, in the embodiment, all the functions of the toner counter200are implemented as software. Such a configuration obviates a necessity for adding special hardware for addition of the amount of toner consumption and renders the configuration of the image forming apparatus simple, thereby curtailing costs of the apparatus.

As has been described above, according to the present invention, in an image forming apparatus which forms an image on a recording medium in a plurality of colors of toner through use of a rotary developer, the amount of toner consumption can be calculated with high accuracy in keeping with the realities of image forming operation. Even in the image forming apparatus using the intermediate transfer member, the quantity of toner consumption can be calculated with high accuracy.

The foregoing embodiment is directed toward the image forming apparatus configured so as to be able to form a full-color image through use of four colors of toner; that is, yellow toner, cyan toner, magenta toner, and black toner. In terms of the colors of toner to be employed and the number of colors of toner to be employed, the present invention is not limited to the embodiments, and arbitrary colors of toner and numbers of colors can be employed. For instance, the present invention can also be applied to an apparatus which forms a monochrome image through use of, e.g., only black toner. Moreover, the amount of toner consumed by a plurality of developers can be determined individually by a single hardware configuration.

Further, according to the embodiments, the present invention is applied to a printer which performs image forming operation on the basis of an image signal output from an external apparatus. The present invention is not limited solely to such a printer. Needless to say, the present invention can be applied to a copier which prepares an image signal in an apparatus in response to an image forming request from the user; e.g., a user's action of pressing a copy button, and performs an image forming operation in accordance with the image signal or a facsimile apparatus which performs an image forming operation in accordance with an image signal received by way of a communications line.

Incidentally, in the above description, the remaining amount of the toner counter count value and the remaining amount of the operable time of the development roller are used as parameters for managing the life of each toner cartridge. The invention can be also applied to the case where the remaining amounts of count values in other parameters are expressed as rates to thereby manage the life of each toner cartridge. In this case, the user can judge the time for interchange of the toner cartridge more clearly when the lowest one of the remaining amounts of count values in the parameters is displayed as the rate.