Patent Application
20180275598
The entire disclosure of Japanese patent Application No. 2017-054886, filed on Mar. 21, 2017, is incorporated herein by reference in its entirety.
The present invention relates to an image forming apparatus that uses toner to form an image. More specifically, the present invention relates to an image forming apparatus in Which a photosensitive member and a developing device are unitized to be separately replaceable. In addition, a program that controls such an image forming apparatus is also targeted,
Conventionally, there is an image forming apparatus that uses toner and in which a developing device is unitized to be replaceable. In such an image forming apparatus, the end of the lifetime of the developing device is reached due to execution of image formation. For that reason, there is a device that performs lifetime management of the developing device based on an index value such as the number of images to be formed. Meanwhile, in a recent image forming apparatus, not only the developing device but also a photosensitive member is unitized, and the photosensitive member is replaceable separately from replacement of the developing unit in some cases.
An example of such an image forming apparatus is disclosed in JP 2012-008539 A. In the image forgoing apparatus disclosed in JP 2012-008539 A, notice of being near the end of the lifetime of a latent image unit (photosensitive member unit) is performed only in a case where both the latent image unit and the developing unit are near the end of the lifetime. That is, even if the latent image unit has reached a state of being near the end of the lifetime, the notice is not performed only by that (see [0017] and
However, in the above-described conventional techniques, there have been the following problems. In the apparatus of JP-A-2012-008539, the lifetime itself of the latent image unit or the developing unit is basically determined by rotation time of the photosensitive member and rotation time of the developing roller ([0016] of JP 2012-008539 A). That is, the lifetime of each of the latent image unit and the developing unit is independently set. For that reason, it has been necessary to set the lifetime attic developing unit so that image quality is maintained regardless of the state of the latent image unit. For this reason, depending on the situation, there have been cases where it is forced to replace the developing unit even though image formation is possible with sufficiently high image quality. This is a case where the developing unit reaches the end of the set lifetime in a state in which the latent image unit is still close to a new one. There has been a similar problem with respect to the lifetime of the latent image unit.
The present invention has been made to solve the problems of the above-described conventional techniques. That is, an object of the present invention is to provide an image forming apparatus and a program for the image forming apparatus in which replacement determination is efficiently made for the developing unit and the photosensitive member unit in accordance with the situations of the both units.
To achieve the abovementioned object, according to an aspect of the present invention, an image forming apparatus reflecting one aspect of the present invention comprises: a photosensitive member that rotates; a charger that charges a surface of the photosensitive member; an exposure device that forms a latent image on a position of the surface of the photosensitive member charged by the charger; and a developing device that applies toner to the latent image to form a toner image, wherein the photosensitive member is incorporated in a detachable photosensitive member unit, and the developing device is incorporated in a detachable developing unit, the image forming apparatus including: an optimization controller that performs optimization of a charging bias of the charger and a developing bias of the developing device at time of non-image formation; and a replacement determiner that determines which of the photosensitive member unit and the developing unit is to be replaced when an optimized developing bias that is the developing bias at time of optimization by the optimization controller is out of a predetermined allowable range, wherein the replacement determiner determines that the developing unit is to he replaced in a case where a usage situation until then corresponds to a predetermined developing device replacement matter, and determines that the photosensitive member unit is to he replaced in a case where it is not determined that the developing unit is to be replaced.
The advantages and features provided by one or more embodiments of the invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which are given by way of illustration only; and thus are not intended as a definition of the limits of the present invention:
Hereinafter, one or more embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the disclosed embodiments. In the present embodiment, the present invention is applied to an image forming apparatus 1 illustrated in
In more detail, each of the image forming devices 10 includes a photosensitive member 21 and a developing device 30. The image forming apparatus 1 further includes an exposure device 11 that writes a latent image on each photosensitive member 21, a transfer roller 60 that transfers a toner image from the intermediate transfer belt 50 to the printing paper P, a fixing device 80 that fixes the toner image on the printing paper P, and a toner image sensor 40 that detects the toner image on the intermediate transfer belt 50. The image forming apparatus 1 is also includes a controller 76. The controller 76 incorporates a control program and control data for executing various types of operation of the image forming apparatus 1. The control program includes a lifetime determination program to be described later. In addition, because of the lifetime determination program, rotation time of the photosensitive member 21 due to image formation and the number of printed sheets are counted up.
The image forming device 10 will be further described with reference to the cross-sectional view of
As further illustrated in
In addition, the photosensitive member unit 20 and the developing unit 32 are arranged such that writing light 1, from the exposure device 11 is emitted to the photosensitive member 21 through a gap between the photosensitive member unit 20 and the developing unit 32. Further, a transfer roller 12 is provided on a back side of the intermediate transfer belt 50 as viewed from the photosensitive member 21. As a result, in the image forming apparatus 1, a latent image is written with the writing light L at a position that is on a surface of the photosensitive member 21 and charged by the charger 22, and a toner image is formed on the latent image by the developing device 30. Such a toner image is superimposed on the intermediate transfer belt 50 and is transferred onto the printing paper P.
In the image forming apparatus 1 of the present embodiment, image stabilization control is performed in addition to normal image forming operation. The image stabilization control is a control that adjusts various process conditions to optimize image quality of the toner image formed in the normal image forming operation, and is performed at times other than the time of image formation. The image stabilization control is executed immediately after turning on the power or at timing for each predetermined number of printed sheets. The image stabilization control is also performed when there is a change in environmental conditions. Adhesion amount adjustment control is included as part of the image stabilization control. The adhesion amount adjustment control is a control that adjusts a developing bias of the developing device 30 to optimize a toner adhesion amount of the toner image to be formed.
Details of the adhesion amount adjustment control will be described with reference to
In the image forming apparatus of the present embodiment, following the adhesion amount adjustment control, the lifetime determination program is executed for the developing unit 32 and the photosensitive member unit 20. This is because the developing bias Vdc0 determined as described above includes information on a remaining lifetime of the developing unit 32. By executing this lifetime determination program, a user is prompted to replace the developing unit 32 or the photosensitive member unit 20 with a new one appropriately as necessary. When replacement is actually performed, a history of the replacement is recorded in the memory 79 of the controller 76. In the present embodiment, since the developing unit 32 is more expensive than the photosensitive member unit 20, replacement of the developing unit 32 is suppressed to a minimum necessary. The lifetime determination program is executed for each color.
In a flow of
In the lifetime determination, first in S1, it is determined whether or not the developing bias Vdc0 is out of its appropriate range (S2). The appropriate range of the developing bias Vdc0 is determined for each color in advance as illustrated in
In a case where the developing bias Vdc0 determined in S1 is out of the appropriate range (S2: Yes), it is determined whether or not the developing bias Vdc0 is less than a lower limit (for example, 270 [V]) of the appropriate range (S4). If it is not less than the lower limit (S4: No), an upper limit of the appropriate range (for example, 550 [V]) is exceeded. In this case, if image formation is performed as it is, there is a high possibility that fogging occurs and only low image quality can be obtained. Therefore, in this case, it is determined that the end of the lifetime has arrived of the developing unit 32 (S5). This is because, this phenomenon of a rise of the developing bias Vdc0 is basically caused by deterioration of the developing roller 31 or deterioration of the developer, and it is not caused by the photosensitive member unit 20. For this reason, the developing unit 32 has to be replaced. Therefore, the image formation is stopped and a message is issued to the user prompting to replace the developing unit 32 with a new one. Alternatively, a message to the user is issued to the effect that the end of the lifetime is approaching of the developing unit 32.
In a case where the developing bias Vdc0 is less than the lower limit of the appropriate range (S4: Yes), if the image formation is performed as it is, there is a high possibility that only images with low image density can be obtained. In this case, however, there is a possibility that the image quality can be restored by replacement of the photosensitive member unit 20 instead of replacement of the developing unit 32. Therefore, the number of times of replacement of the photosensitive member unit 20 is checked. That is, the number of times of replacement of the photosensitive member unit 20 is compared with a reference number of times determined in advance, and it is determined Whether or not the number of times of replacement is equal to or greater than the reference number of times (S6). Here, the number of times of replacement of the photosensitive member unit 20 to be compared is the number of times of replacement of the photosensitive member unit 20 after the developing unit S2 becomes the present one. The number of times of replacement is grasped from the replacement history to new ones of the photosensitive member unit 20 and the developing unit 32 recorded in the memory 79 of the controller 76. The reference number of times is stored in the memory 79 of the controller 76.
In a case where the number of times of replacement of the photosensitive member unit 20 is equal to or greater than the reference number of times (S6: Yes), the developing unit 32 at present has already become considerably old. For that reason, in this case, it is determined that the end of the lifetime has arrived of the developing unit 32 (S5). On the other hand, in a case where the number of times of replacement has not reached the reference number of times (S6: No), the developing unit 32 at present has not become so old yet. For this reason, further determination is trade. This is because there is a possibility that the image quality can be restored by replacing the photosensitive member unit 20.
The next determination is determination on magnitude of variation in the developing bias Vdc0 determined in the past. For this reason, the history is referred to of the developing bias Vdc0 stored in the memory 79 of the controller 76. Then, the variation is calculated in a most recent predetermined number of times of developing biases Vdc0 including the latest value. The predetermined number of times is determined in advance. This variation is compared with a predetermined upper limit variation, and it is determined whether or not the calculated variation is equal to or less than the upper limit variation (S7).
In a case where the variation exceeds the upper limit variation (S7: No), the developing unit 32 at present has already considerably deteriorated. For that reason, in this case, it is determined that the end of the lifetime has arrived of the developing unit 32 (S5). On the other hand, in a case where the variation is equal to or less than the upper limit variation (S7: Yes), the developing unit 32 at present has not deteriorated so much yet. For this reason, further determination is made.
The next determination is based on a comparison of predicted costs between a case where the developing unit 32 is replaced and a case where the photosensitive member unit 20 is replaced. In short, it is which one of the developing unit 32 and the photosensitive member unit 20 currently in use has a higher remaining value. For this reason, first, an extension amount is estimated of the lifetime of the developing unit 32 that can he expected in a case where the photosensitive member unit 20 is replaced (S8). This estimation is performed as follows.
First, referring to the history of the developing bias Vdc0 stored in the memory 79 of the controller 76, a table is created as illustrated in
The column of “first” of “number of photosensitive members” in the table indicates the transition of the developing bias Vdc0 when the first photosensitive member unit 20 was mounted and operating as the developing unit 32 at present. In the same column, it can be seen that the developing bias Vdc0 started from 480 [V] at the beginning, and gradually decreased. Incidentally, in the same column in
The “third” column in the same table indicates transition prediction of the future developing bias Vdc0 by estimation instead of the past history. That is, the developing bias value of the first row in the same column is a predicted value based on a developing bias difference between the developing biases of the “first” column and the “second” column in the first row, and the developing bias Vdc0 of the first row in the “second” column. Similarly, predicted values of the “3rd” column are also entered for the second and subsequent rows. From the predicted values, it can be estimated that the developing bias Vdc0 falls below 270 [V] at about 5000 minutes of the rotation time of the photosensitive member 21 in a case where the image formation is continued by replacing the photosensitive member unit 20 with the third one.
The contents of
The third graph can be drawn as follows. That is, a start point G3 is placed at an equal interval with respect to start points G1 and G2 of the “first” and “second” graphs (intersection points between a vertical line of the zero point and the “first” and “second” graphs). Then, the “third” graph can be drawn to pass through the start point G3 and to be parallel to the “first” and “second” graphs. If slopes do not completely coincide with each other between the “first” and “second” graphs, the average of the slopes can be used. Incidentally, in the case where S8 in the flow of
After estimating the extension amount of the lifetime of the developing unit 32, cost calculation is performed in a case of replacement of the developing unit 32 and in a case of replacement of the photosensitive member unit 20 (S9).
A symbol “H” in the second row is the number of printed sheets for image formation that has been made from when the developing unit is replaced to the developing unit 32 at present to the present. The value of the “H” is counted for each execution of the image formation and is stored in the memory 79 of the controller 76. A symbol “R” in the third row is a value obtained by converting the extension amount of the lifetime calculated in S8 into the number of printed sheets. Since a proportional coefficient between the rotation time of the photosensitive member 21 and the number of printed sheets is known, this conversion is easy. A symbol “Udev” in the fourth row and a symbol “Upc” in the fifth row are purchase prices of the developing unit 32 and the photosensitive member unit 20, respectively. These purchase prices are stored in the memory 79 of the controller 76 in advance.
A symbol “α” in the sixth row is a wear rate of the photosensitive member unit 20 at present. The “α” is a ratio occupied by the current rotation time in the photosensitive member unit 20 at present with respect to the original rotatable time of the photosensitive member unit 20. In the example of
A symbol “β” in the seventh row in
The cost calculation is performed on the basis of the parameters of
1. The cost per image formation for the developing unit 32 at present to be replaced, in a case where the developing unit 32 is replaced immediately (see
2. The cost per image formation for the developing unit 32 at present, in a case where the photosensitive member unit 20 is replaced immediately, and the developing unit 32 is replaced when the developing bias Vdc0 reaches the lower limit next time (see
In the cost calculation of the above “1.”, the denominator is “H” itself in
(1) Cost of the photosensitive member unit 20 already used for the developing unit 32 at present and discarded
(2) Cost of an already consumed part of the total lifetime of the photosensitive member unit 20 currently in use
(3) Cost of the developing unit 32 at present
The cost of the above (1) is a product of the “N” and the “Upc” in
Cost (1.)=[{N+(a/100)}×Upc×Udev]/H [Expression 1]
The denominator in the cost calculation of the above “2,” is a sum of the “H” and the “R” in
(4) Cost of the photosensitive member unit 20 already used for the developing unit 32 at present
(5) Cost to be consumed before the time of replacement of the developing unit 32, out of the total lifetime of the photosensitive member unit 20 to be newly mounted
(6) Cost of the developing unit 32 at present
Since the photosensitive member unit 20 currently in use is added, the cost of the above (4) is a greater value by an amount for the one unit than the cost of the (1) above. Therefore, the cost of the (4) is a product of “N+1” and the “Upc”. The cost of the (5) is the former of costs obtained by proportionally dividing the cost of the photosensitive member unit 20 to be newly mounted, between the number of sheets that can be printed again before the developing bias Vdc0 reaches the lower limit after mounting, and the number of sheets that can be printed further after replacing the developing unit 32. The cost of the (5) is given by a product of the “Upc” and the “β” (%) in
Cost (2.)=[{N+1+(β/100)}×Upc+Udev]/(H+R) [Expression 2]
In this way, the cost calculation of S9 in
On the other hand, if there is a cost merit in the cost of the “1.” (S10: No), it is determined that the developing unit 32 is to be replaced (S5). Therefore, as described above, the image formation is stopped and a message is issued to the user prompting to replace the developing unit 32 with a new one. Alternatively, a message to the user is issued to the effect that the end of the lifetime is approaching of the developing unit 32.
Incidentally, the cost calculation and comparison in S9 and S10 compare the cost per image formation throughout the lifetime of the developing unit 32 at present. However, cost comparison, by another method may be used.
As the other method of cost comparison, for example, the following method is available. That is, it is a. method of comparing parts to be wasted by being replaced, out of the developing unit 32 and the photosensitive member unit 20. In a case where the developing unit 32 is replaced in the situation as in the above example (
Cost(X)=Udev×{R/(H+R)}
Cost(Z)=Upc×{1−(αa/100)}[Expression 3]
As yet another method, there may he a method of simply setting a threshold value for the remaining value of the developing unit 32 in advance. It is a method of selecting replacement of the photosensitive member unit 20 when the remaining value of the developing unit 32 is greater than the threshold value, and selecting replacement of the developing unit 32 when the remaining value of the developing unit 32 falls below the threshold value. That is, when the remaining value of the developing unit 32 is large to some extent, the photosensitive member unit 20 is replaced, and when the remaining value of the developing unit 32 becomes small, the developing unit 32 is replaced. As the remaining value of the developing unit 32, the value of the above-described “X” or the aforementioned “R” can be used.
As described above in detail, according to the present embodiment, the adhesion amount adjustment: control is performed at appropriate intervals in the image forming apparatus 1 in which the photosensitive member unit 20 and the developing unit 32 are detachable independently of each other. On the basis of the developing bias Vdc0 determined at that time, it is determined whether or not to replace the photosensitive member unit 20 or the developing unit 32, and which one is to he replaced when replacing the photosensitive member unit 20 or the developing unit 32. Here, basically, the photosensitive member unit 20 is replaced, and in a case where a predetermined developing device replacement matter occurs, the developing unit 32 is replaced. As a result, the inexpensive photosensitive member unit 20 is replaced, as far as it is possible. Thus, the image forming apparatus 1 is provided capable of executing the image formation while minimizing cost burden.
Incidentally, the present embodiment is merely an example and does not limit the present invention at all. Therefore, various improvements and modifications can be made within the scope not departing from the gist of the present invention. For example, the targeted image forming apparatus 1 may be a monochrome type, or may have both a scanner function and an external transmission/reception function of a print job. In addition, various developing device replacement matters are illustrated in
Although embodiments of the present invention have been described and illustrated in detail, the disclosed embodiments are made for purposes of illustration and example only and not limitation. The scope of the present invention should be interpreted by terms of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2017-054886 | Mar 2017 | JP | national |
