EP4621491A1

EP4621491A1 - Method of recycling toner cartridge

Info

Publication number: EP4621491A1
Application number: EP25164021.5A
Authority: EP
Inventors: Daisuke MAETA
Original assignee: Brother Industries Ltd
Current assignee: Brother Industries Ltd
Priority date: 2024-03-19
Filing date: 2025-03-17
Publication date: 2025-09-24
Also published as: JP2025143989A

Abstract

Provided is a method of recycling a toner cartridge including a casing and a memory. The method includes: a first toner determining step of determining, when genuine product information stored in the memory indicates that the toner cartridge is a genuine product, whether a difference between a first charge amount stored in the memory and a second charge amount is less than a first threshold value, the first charge amount being an amount of electric charge of toner remaining in the casing, the second charge amount being an amount of electric charge of new toner with which the casing is to be refilled; and a first refilling step of refilling, when determining that the difference between the first charge amount and the second charge amount is less than the first threshold value, the casing with the new toner without discharging the toner remaining in the casing.

Description

The present disclosure relates to a method of recycling a toner cartridge.
A conventional method of recycling toner cartridges is known in the art (see Japanese Patent Application Publication No. H05-210304 ). In this recycling method, an amount of electric charge of toner remaining in a used toner cartridge is compared to that of new toner to be used for replenishing the toner cartridge. If the amounts of electric charge are the same, the toner cartridge is refilled with the new toner, without cleaning the toner cartridge.
However, this conventional method of recycling toner cartridges is not efficient since a toner cartridge cannot be recycled when the amount of electric charge of toner remaining in the toner cartridge differs from the amount of electric charge of new toner as a result of comparison. Moreover, there is concern that the recycled product may contain a mixture of genuine toner and non-genuine toner since the conventional method does not distinguish between genuine toner cartridges and non-genuine toner cartridges.
In view of the foregoing, it is an object of the present disclosure to provide a method of recycling a toner cartridge efficiently while restraining non-genuine toner from being mixed with genuine toner in a recycled product.
(1) In order to attain the above and other object, according to aspect (1), the present disclosure provides a method of recycling a toner cartridge. The method includes: a first toner determining step of determining, when genuine product information stored in a memory of the toner cartridge indicates that the toner cartridge is a genuine product, whether a difference between a first charge amount and a second charge amount is less than a first threshold value, the first charge amount being stored in the memory, the first charge amount being an amount of electric charge of toner remaining in a casing of the toner cartridge, the second charge amount being an amount of electric charge of new toner with which the casing is to be refilled; and a first refilling step of refilling, when determining in the first toner determining step that the difference between the first charge amount and the second charge amount is less than the first threshold value, the casing with the new toner without discharging the toner remaining in the casing.
In the above method, the casing is refilled with the new toner without discharging the toner remaining in the casing even if the first charge amount and the second charge amount are not the same as each other, provided that the difference between the first charge amount and the second charge amount is less than the first threshold value. Accordingly, the toner cartridge can be recycled efficiently. Further, since the first toner determining step is executed only when the toner cartridge is a genuine product, this method can suppress non-genuine toner from being mixed with genuine toner in a recycled product.
(2) According to aspect (2), preferably, the method of aspect (1) further includes: a reading step of reading the genuine product information and the first charge amount from the memory.
(3) According to aspect (3), preferably, the method of aspect (2) further includes: a genuine product determining step of determining whether the genuine product information read in the reading step indicates that the toner cartridge is a genuine product.
(4) According to aspect (4), in the method of aspect (1), it is preferable that: in the first refilling step, the casing is refilled with the new toner without cleaning an interior of the casing.
The interior of the casing is not cleaned in the first refilling step, whereby a process of recycling can be simplified.
(5) According to aspect (5), preferably, the method of aspect (1) further includes: a second refilling step of refilling, when the genuine product information stored in the memory indicates that the toner cartridge is not a genuine product, the casing with the new toner after discharging the toner remaining in the casing.
When the genuine product information stored in the memory indicates that the toner cartridge is not a genuine product, the remaining toner in the casing is discharged before the casing is refilled with the new toner. This operation can suppress toner of a non-genuine product from becoming mixed with new toner in the recycled product.
(6) According to aspect (6), in the method of aspect (5), it is preferable that: in the second refilling step, the casing is refilled with the new toner after cleaning an interior of the casing.
The interior of the casing is cleaned in the second refilling step. This method suppresses toner from a non-genuine product from becoming mixed with new toner in the recycled product.
(7) According to aspect (7), preferably, the method of aspect (1) further includes: a second toner determining step of determining, when determining in the first toner determining step that the difference between the first charge amount and the second charge amount is not less than the first threshold value, whether a remaining toner quantity stored in the memory is less than a second threshold value, the remaining toner quantity being a quantity of the toner remaining in the casing. It is also preferable that the first refilling step is performed when determining in the second toner determining step that the remaining toner quantity is less than the second threshold value.
The casing is refilled with the new toner without discharging the toner remaining in the casing even when the difference between the first charge amount and the second charge amount is not less than the first threshold value, provided that the remaining toner quantity is less than the second threshold value. Thus, the toner cartridge can be recycled efficiently.
(8) According to aspect (8), preferably, the method of aspect (1) further includes: a second toner determining step of determining, when determining in the first toner determining step that the difference between the first charge amount and the second charge amount is not less than the first threshold value, whether a remaining toner quantity stored in the memory is less than a second threshold value, the remaining toner quantity being a quantity of the toner remaining in the casing; and a second refilling step of refilling, when determining in the second toner determining step that the remaining toner quantity is not less than the second threshold value, the casing with the new toner after discharging the toner remaining in the casing.
When the difference between the first charge amount and the second charge amount is not less than the first threshold value and the remaining toner quantity is determined not to be less than the second threshold value, the toner remaining in the casing is first discharged from the casing before the casing is refilled with the new toner. This operation can restrain a certain amount of the remaining toner with the first charge amount different from the second charge amount of the new toner from becoming mixed with the new toner and effecting on the quality of the toner.
(9) According to aspect (9), in the method of aspect (1), it is preferable that: the memory stores therein an initial charge amount and usage history information, the initial charge amount being an amount of electric charge of toner initially filled in the casing, the usage history information indicating a usage history of the toner cartridge.
The first charge amount of the toner can be calculated when the memory stores therein the initial charge amount and the usage history information.
(10) According to aspect (10), in the method of aspect (9), it is preferable that: the toner cartridge includes a developing roller, and the usage history information includes at least one of: a cumulative number of rotations of the developing roller; a cumulative dot count for pixels formed using the toner cartridge; and a cumulative number of sheets printed using the toner cartridge.
(11) According to aspect (11), in the method of aspect (10), it is preferable that: the first charge amount is calculated based on at least one of the initial charge amount, the cumulative number of rotations of the developing roller, the cumulative dot count for pixels formed using the toner cartridge, and the cumulative number of sheets printed using the toner cartridge.
(12) According to aspect (12), the present disclosure also provides a method of recycling a toner cartridge. The method includes: a selecting step of selecting, when genuine product information stored in a memory of the toner cartridge indicates that the toner cartridge is a genuine product, a type of toner from among a plurality of types of toners that has an amount of electric charge closest to a first charge amount, the first charge amount being stored in the memory, the first charge amount being an amount of electric charge of toner remaining in a casing of the toner cartridge; and a first refilling step of refilling the casing with the type of toner selected in the selecting step without discharging the toner remaining in the casing.
In the above method, the toner cartridge can be recycled efficiently by performing the selecting step to select toner having an amount of electric charge closest to the first charge amount from among a plurality of types of toner. Moreover, since the selecting step is performed only when the toner cartridge is a genuine product, the above method can suppress toner in a non-genuine product from being mixed with new toner in the recycled product.
(13) According to aspect (13), preferably, the method of aspect (12) further includes: a toner determining step of determining, after performing the selecting step, whether a difference between the first charge amount and the amount of electric charge of the type of toner selected in the selecting step is less than a first threshold value. It is also preferable that: the first refilling step is performed when determining in the toner determining step that the difference between the first charge amount and the amount of electric charge of the type of toner is less than the first threshold value.
In the above method, the casing is refilled with the type of toner selected in the selecting step without discharging the toner remaining in the casing even if the first charge amount and the amount of electric charge of the type of toner selected in the selecting step are not the same as each other, provided that the difference between the first charge amount and the amount of electric charge of the selected type of toner is less than the first threshold value. Accordingly, the toner cartridge can be recycled efficiently.

Fig. 1 is a cross-sectional view of a toner cartridge.
Fig. 2 is a perspective view of the toner cartridge.
Fig. 3 is a diagram illustrating information stored in a memory.
Fig. 4 is a flowchart illustrating steps in a method of recycling the toner cartridge according to a first embodiment.
Fig. 5 is a flowchart illustrating steps in a method of recycling the toner cartridge according to a second embodiment.

Hereinafter, a first embodiment of the present disclosure will be described while referring to the accompanying drawings. A toner cartridge 60 is for use in an image forming apparatus such as a printer. The toner cartridge 60 is, for example, attachable to and detachable from a main housing of the image forming apparatus.
As illustrated in Fig. 1, the toner cartridge 60 includes a casing 61, an agitator 62, a developing roller 63, a supply roller 64, and a memory 65.
The casing 61 is configured to accommodate toner therein. The agitator 62 is configured to agitate toner in the casing 61. The developing roller 63 and the supply roller 64 are rotatably supported by the casing 61. The supply roller 64 is configured to supply toner in the casing 61 to the developing roller 63.
As illustrated in Fig. 2, the memory 65 is positioned at an outer surface of the casing 65. The memory 65 is, for example, an IC chip. The memory 65 is configured to store therein information related to the toner cartridge 60.
As illustrated in Fig. 3, the information related to the toner cartridge 60 includes product information 65A, usage history information 65B, and toner information 65C for the toner cartridge 60.
The product information 65A includes a serial number, genuine product information, an initial toner volume, and an initial charge amount. The serial number is a number unique to the toner cartridge 60. The genuine product information indicates whether or not the toner cartridge 60 is a genuine product. The initial toner volume is an initial volume of toner with which the toner cartridge 60 is filled. The initial charge amount denotes an amount of electric charge of toner initially filled in the casing 61. The initial charge amount is measured in advance for all toner used to fill the casing 61. Note that the product information 65A need not include the genuine product information, the initial toner volume, and the initial charge amount if these pieces of information can be determined from the serial number.
The usage history information 65B indicates a usage history of the toner cartridge 60. The usage history information 65B includes at least one of: a cumulative rotation number which is the cumulative number of rotations of the developing roller 63, a cumulative dot count which is the cumulative dot count for pixels formed using the toner cartridge 60, and a cumulative printed sheet number which is the cumulative number of sheets printed using the toner cartridge 60.
The toner information 65C includes a remaining toner quantity, and a first charge amount.
The remaining toner quantity is a quantity of toner currently remaining in the casing 61. The current remaining toner quantity can be calculated from the initial toner volume and the usage history information 65B. Therefore, the remaining toner quantity may be stored in the memory 65 after each image formation has been performed, or may be calculated when necessary, without being stored in the memory 65. In other words, the remaining toner quantity may be a value calculated from at least one of: the initial toner volume, the cumulative number of rotations of the developing roller 63, the cumulative dot count for pixels formed using the toner cartridge 60, and the cumulative number of sheets printed using the toner cartridge 60.
The first charge amount is a current amount of electric charge of the toner remaining in the casing 61. The first charge amount can be calculated from the initial charge amount and the usage history information 65B. Therefore, the first charge amount may be calculated and stored in the memory 65 after each image formation has been performed, or may be calculated as needed without being stored in the memory 65. In other words, the first charge amount may be a value calculated based on at least one of: the initial charge amount, the cumulative number of rotations of the developing roller 63, the cumulative dot count for pixels formed using the toner cartridge 60, and the cumulative number of sheets printed using the toner cartridge 60.
Next, a method of recycling the toner cartridges 60 will be described. The toner cartridges 60 are collected for recycling at a recycling factory where recycling takes place.
The following method is for recycling used toner cartridges 60. The method of recycling the toner cartridges 60 includes a reading step, a genuine product determining step, a first toner determining step, a second toner determining step, a first refilling step, a second refilling step, and a writing step.
In the reading step, the genuine product information and the first charge amount are read from the memory 65. The reading step is performed using a reading device exclusive for reading information from the memories 65 of the collected toner cartridges 60.
The genuine product determining step is performed to determine whether or not the genuine product information stored in the memory 65 indicates that the toner cartridge 60 is a genuine product. The determination of whether or not the toner cartridge 60 is a genuine product can be achieved by determining whether or not the serial number and the genuine product information correspond to information in the shipment record in a factory, for example.
When the genuine product information stored in the memory 65 indicates that the toner cartridge 60 is not a genuine product, the second refilling step is performed. In the second refilling step, the casing 61 is refilled with new toner after all toner remaining in the casing 61 is discharged from the casing 61. In the present embodiment, an interior of the casing 61 is also cleaned in the second refilling step before refilling the casing 61 with new toner. While not particularly limited, a method of cleaning the interior of the casing 61 may be a method of blowing toner out of the casing 61 with compressed air or flushing the toner from the casing 61 with a liquid and then drying the interior of the casing 61.
When the genuine product information stored in the memory 65 indicates that the toner cartridge 60 is a genuine product, the first toner determining step is executed. The first toner determining step is performed to determine whether or not a difference between the first charge amount stored in the memory 65 and a second charge amount is less than a first threshold value. The second charge amount is an amount of electric charge of new toner with which the casing 61 is to be refilled. As an example, the first threshold value may be 5 µC. In a case where the first charge amount is 36 µC and the second charge amount is 40 µC, for example, the difference between the first charge amount and the second charge amount is 4 µC. In this case, the difference between the first charge amount and the second charge amount is determined to be smaller than the first threshold value.
When the difference between the first charge amount and the second charge amount is determined to be less than the first threshold value in the first toner determining step, the first refilling step is executed. In the first refilling step, the casing 61 is refilled with new toner without discharging the toner remaining in the casing 61. In other words, the casing 61 is refilled with new toner without cleaning the interior of the casing 61 in the first refilling step. Hence, after executing the first refilling step, the remaining toner remaining in the casing 61 is mixed with new toner added to the casing 61.
When the difference between the first charge amount and the second charge amount is determined not to be less than the first threshold value in the first toner determining step, the second toner determining step is executed. The second toner determining step is performed to determine whether or not the remaining toner quantity is less than a second threshold value. In other words, the second toner determining step is not executed when determining that the difference between the first charge amount and the second charge amount is less than the first threshold value.
When the remaining toner quantity is determined to be less than the second threshold value in the second toner determining step, the first refilling step is executed. When the remaining toner quantity is determined not to be less than the second threshold value, on the other hand, the second refilling step is executed.
The writing step is executed after completing the first refilling step or the second refilling step. In the writing step, information indicating that the casing 61 was replenished with new toner is written in the memory 65. Specifically, the serial number, the initial toner volume, and the first charge amount which are illustrated in Fig. 3 are overwritten with a new serial number, a new initial toner volume, and a new first charge amount, respectively. The usage history information 65B is reset.
Next, a method of recycling the toner cartridge 60 according to the first embodiment will be described with reference to the flowchart in Fig. 4.
When recycling a used toner cartridge 60, first in S11 of Fig. 4 the reading step is performed to read the genuine product information and the first charge amount from the memory 65.
Following the reading step of S11, in S12 the genuine product determining step is executed to determine whether or not the toner cartridge 60 is a genuine product.
When the toner cartridge 60 is determined not to be a genuine product in S12 (S12: NO), in S16 the second refilling step is performed. In the second refilling step, toner remaining in the casing 61 is discharged, after which the interior of the casing 61 is cleaned and the casing 61 is refilled with new toner.
On the other hand, when the toner cartridge 60 is determined to be a genuine product in S12 (S12: YES), in S13 the first toner determining step is performed to determine whether or not the difference between the first charge amount of the toner remaining in the used toner cartridge 60 and the second charge amount of new toner to be used for refilling the casing 61 is less than the first threshold value.
When the difference between the first charge amount and the second charge amount is determined to be less than the first threshold value in S13 (S13: YES), in S15 the first refilling step is performed to refill the casing 61 with new toner, without discharging the remaining toner from the casing 61.
On the other hand, when the difference between the first charge amount and the second charge amount is determined not to be less than the first threshold value in S13 (S13: NO), in S14 the second toner determining step is performed to determine whether or not the remaining toner quantity is less than the second threshold value.
When the remaining toner quantity is determined not to be less than the second threshold value in S14 (S14: NO), in S16 the second refilling step is performed to discharge toner from the casing 61, clean the interior of the casing 61, and refill the casing 61 with new toner.
On the other hand, when the remaining toner quantity is determined to be less than the second threshold value in S14 (S14: YES), in S15 the first refilling step is performed to refill the casing 61 with new toner without discharging the remaining toner in the casing 60.
After refilling the casing 61 with new toner in the process of S15 or S16, in S17 the writing step is performed to write information in the memory 65 indicating that the casing 61 has been refilled with new toner.
The first embodiment described above can obtain the following technical advantages. According to the method in the first embodiment of recycling toner cartridges 60, the casing 61 is refilled with new toner without discharging toner remaining in the casing 61 even if the first charge amount and the second charge amount are not the same as each other, provided that the difference between the first charge amount and the second charge amount is less than the first threshold value. Hence, if the amount of electric charge of the used toner falls within a certain range, the toner cartridge 60 can be recycled efficiently even if this amount of electric charge is not equivalent to the amount of electric charge of the new toner. This method is also environmentally friendly since the remaining toner in the casing 61 need not be discarded.
Further, since the first toner determining step is executed only when the toner cartridge 60 is a genuine product, this method can suppress non-genuine toner from being mixed with genuine toner in a recycled product. If toner in a non-genuine toner cartridge 60 were to become mixed with toner for a genuine toner cartridge 60, the quality of toner could not be guaranteed. Conversely, the quality of toner can be guaranteed if the toner in the non-genuine toner cartridge 60 is not mixed with toner for the genuine toner cartridge 60.
The interior of the casing 61 is not cleaned in the first refilling step. This method not only simplifies a process of recycling but is also environmentally friendly.
When the genuine product information stored in the memory 65 indicates that the toner cartridge 60 is not a genuine product, the remaining toner in the casing 61 is discharged before the casing 61 is refilled with new toner. This operation can suppress toner of a non-genuine product from becoming mixed with new toner in the recycled product.
The interior of the casing 61 is cleaned in the second refilling step. This method suppresses toner from a non-genuine product from becoming mixed with new toner in the recycled product.
The casing 61 is refilled with new toner without discharging the remaining toner in the casing 61 even when the difference between the first charge amount and the second charge amount is not less than the first threshold value, provided that the remaining toner quantity is less than the second threshold value. In other words, a small amount of remaining toner in the casing 61 has little effect on the overall quality of the toner, even when the difference between the first charge amount and the second charge amount is greater than or equal to the first threshold value. Accordingly, the casing 61 can be refilled with new toner without discharging the remaining toner in the casing 61. Thus, the toner cartridge 60 can be recycled efficiently. Moreover, the process is environmentally friendly since the remaining toner in the casing 61 need not be discarded.
When the difference between the first charge amount and the second charge amount is not less than the first threshold value and the remaining toner quantity is determined not to be less than the second threshold value, the toner remaining in the casing 61 is first discharged from the casing 61 before the casing 61 is refilled with new toner. This operation can restrain a certain amount of remaining toner with the first charge amount different from the second charge amount of new toner from becoming mixed with the new toner and effecting on the quality of the toner.
The first charge amount of the toner can be calculated when the memory 65 stores therein the initial charge amount and the usage history information 65B. In this case, the first charge amount need not be written to the memory 65 each time image formation is performed.
Next, a second embodiment of the present disclosure will be described. The second embodiment differs from the first embodiment in that multiple toners with amounts of electric charge different from one another are prepared for refilling the casing 61.
Specifically, the method according to the second embodiment for recycling toner cartridges 60 includes a reading step, a genuine product determining step, a selecting step, a toner determining step, a first refilling step, a second refilling step, and a writing step. The reading step, the genuine product determining step, the second refilling step, and the writing step are identical to those in the first embodiment, and a description of these steps will be omitted.
The selecting step is executed when the genuine product information stored in the memory 65 indicates that the toner cartridge 60 is a genuine product. The selecting step is a process of selecting a type of toner that has an amount of electric charge that is closest to the first charge amount from among a plurality of types of toner. As an example, assume that the recycling factory has three types of toner available with the amounts of electric charge of 35 µC, 38 µC, and 41 µC, respectively, and that the amount of electric charge (i.e., the first charge amount) of the remaining toner in the used toner cartridge 60 is 37 µC. In this case, the toner with the amount of electric charge of 38 µC has the closest amount of electric charge to the amount of electric charge of the remaining toner, and is selected in the selecting step.
The toner determining step is executed to determine whether or not the difference between the first charge amount and the amount of electric charge of the toner selected in the selecting step is less than the first threshold value.
In the first refilling step, the casing 61 is refilled with the new toner selected in the selecting step without discharging the remaining toner from the casing 61.
Next, a method according to the second embodiment of recycling the toner cartridge 60 will be described with reference to the flowchart in Fig. 5. Here, only steps that differ from those in the first embodiment will be described, while a description of the common steps will be omitted.
When the toner cartridge 60 is determined to be a genuine product in S12 (S12: YES), in S23 the selecting step is executed to select toner having an amount of electric charge closest to the first charge amount.
After toner is selected in S23, in S24 the toner determining step is performed to determine whether or not the difference between the first charge amount and the amount of electric charge of the selected toner is less than the first threshold value.
When the difference between the first charge amount and the second charge amount (i.e., the amount of electric charge of the toner selected in S23) is determined to be less than the first threshold value in S24 (S24: YES), in S15 the first refilling step is performed to refill the casing 61 with new toner without discharging the remaining toner in the casing 61.
On the other hand, when the difference between the first charge amount and the second charge amount is determined not to be less than the first threshold value in S24 (S24: NO), in S16 the second refilling step is performed to discharge the remaining toner from the casing 61 and clean the interior of the casing 61 before refilling the casing 61 with new toner.
According to the method in the second embodiment described above for recycling toner cartridges 60, even if there is variation among amounts of electric charge of toner in used toner cartridges 60, the toner cartridges 60 can be recycled efficiently by performing the selecting step to select toner having the closest amount of electric charge to the first charge amount from among a plurality of types of toner. Moreover, since the selecting step is executed only when the toner cartridge 60 is a genuine product, this method can suppress toner in a non-genuine product from being mixed with new toner in the recycled product.
While the description has been made with reference to the specific embodiments, the detailed configurations in the toner cartridge 60 and/or the detailed steps in the method of recycling may be modified as needed.
Although the toner cartridge 60 in the embodiments described above includes the developing roller 63, the toner cartridge 60 need not include a developing roller. In this case, the memory 65 stores therein at least one of the following as the usage history information 65B: the cumulative dot count for pixels formed using the toner cartridge 60; and the cumulative number of sheets printed using the toner cartridge 60.
In the second refilling step of the embodiments described above, the interior of the casing 61 is cleaned before the casing 61 is refilled with new toner, but the cleaning process may be omitted.
While the memory 65 is an IC chip in the embodiments described above, the memory 65 may be any medium as long as the medium can store information therein.
The above embodiments illustrate examples in which the toner cartridge 60 is attachable to a printer or other image forming apparatus, but the toner cartridge 60 may be attachable to a copying machine, a multifunction peripheral, or the like.
The elements appearing in the embodiments and modifications described above may be implemented in any suitable combination.

Claims

A method of recycling a toner cartridge (60),
the method comprising:
a first toner determining step (S13) of determining, when genuine product information stored in a memory (65) of the toner cartridge (60) indicates that the toner cartridge (60) is a genuine product, whether a difference between a first charge amount and a second charge amount is less than a first threshold value, the first charge amount being stored in the memory (65), the first charge amount being an amount of electric charge of toner remaining in a casing (61) of the toner cartridge (60), the second charge amount being an amount of electric charge of new toner with which the casing (61) is to be refilled; and

a first refilling step (S15) of refilling, when determining in the first toner determining step (S13) that the difference between the first charge amount and the second charge amount is less than the first threshold value, the casing (61) with the new toner without discharging the toner remaining in the casing (61).
The method according to claim 1, further comprising:
a reading step (S11) of reading the genuine product information and the first charge amount from the memory (65).
The method according to claim 2, further comprising:
a genuine product determining step (S12) of determining whether the genuine product information read in the reading step (S11) indicates that the toner cartridge (60) is a genuine product.
The method according to claim 1,
wherein, in the first refilling step (S15), the casing (61) is refilled with the new toner without cleaning an interior of the casing (61).
The method according to claim 1, further comprising:
a second refilling step (S16) of refilling, when the genuine product information stored in the memory (65) indicates that the toner cartridge (60) is not a genuine product, the casing (61) with the new toner after discharging the toner remaining in the casing (61).
The method according to claim 5,
wherein, in the second refilling step (S16), the casing (61) is refilled with the new toner after cleaning an interior of the casing (61).
The method according to claim 1, further comprising:
a second toner determining step (S14) of determining, when determining in the first toner determining step (S13) that the difference between the first charge amount and the second charge amount is not less than the first threshold value, whether a remaining toner quantity stored in the memory (65) is less than a second threshold value, the remaining toner quantity being a quantity of the toner remaining in the casing (61),
wherein the first refilling step (S15) is performed when determining in the second toner determining step (S14) that the remaining toner quantity is less than the second threshold value.
The method according to claim 1, further comprising:
a second toner determining step (S14) of determining, when determining in the first toner determining step (S13) that the difference between the first charge amount and the second charge amount is not less than the first threshold value, whether a remaining toner quantity stored in the memory (65) is less than a second threshold value, the remaining toner quantity being a quantity of the toner remaining in the casing (61); and

a second refilling step (S16) of refilling, when determining in the second toner determining step (S14) that the remaining toner quantity is not less than the second threshold value, the casing (61) with the new toner after discharging the toner remaining in the casing (61).
The method according to claim 1,
wherein the memory (65) stores therein an initial charge amount and usage history information (65B), the initial charge amount being an amount of electric charge of toner initially filled in the casing (61), the usage history information (65B) indicating a usage history of the toner cartridge (60).
The method according to claim 9,
wherein the toner cartridge (60) includes a developing roller (63), and

wherein the usage history information (65B) includes at least one of:
a cumulative number of rotations of the developing roller (63);

a cumulative dot count for pixels formed using the toner cartridge (60); and

a cumulative number of sheets printed using the toner cartridge (60).
The method according to claim 10,
wherein the first charge amount is calculated based on at least one of the initial charge amount, the cumulative number of rotations of the developing roller (63), the cumulative dot count for pixels formed using the toner cartridge (60), and the cumulative number of sheets printed using the toner cartridge (60).