Patent Application
20240402627
This patent application is based on and claims priority pursuant to 35 U.S.C. § 119 (a) to Japanese Patent Application No. 2023-088509, filed on May 30, 2023, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
Embodiments of the present disclosure relate to an image forming apparatus.
An image forming apparatus (as an image forming apparatus and method capable of controlling a transfer bias applied to a transferor) is known that detects a voltage value of a transfer bias to be applied to the transferor such as a transfer roller when a recording medium is not positioned at a transfer section and determines a control target value of the transfer bias when the recording medium passes the transfer section based on a detection result of the voltage value of the transfer bias.
In an embodiment of the present disclosure, an image forming apparatus includes a plurality of image bearers, a movable intermediate transferor, a plurality of primary transferors, a primary transfer power source, a primary transfer current detector, and processing circuitry. The plurality of image bearers carry toner images of a plurality of colors. The intermediate transferor secondarily transfers the toner images, which have been primarily transferred from the plurality of image bearers, onto a transfer medium. The plurality of primary transferors primarily transfer the toner images from the plurality of image bearers onto the intermediate transferor at primary transfer sections at which the plurality of image bearers contact an outer circumferential surface of the intermediate transferor. The primary transfer power source applies voltage to the plurality of primary transferors. The primary transfer current detector detects a current flowing through the plurality of primary transferors when a specified voltage is applied to the plurality of primary transferors and is connected to only one primary transferor corresponding to an image bearer of one color among the plurality of image bearers of all of the plurality of colors. The processing circuitry determines a primary transfer voltage based on a current value detected by the primary transfer current detector and determines a primary transfer voltage value of the plurality of primary transferors corresponding to all of the plurality of colors based on the detected current value.
A more complete appreciation of embodiments of the present disclosure and many of the attendant advantages and features thereof can be readily obtained and understood from the following detailed description with reference to the accompanying drawings, wherein:
The accompanying drawings are intended to depict embodiments of the present disclosure and should not be interpreted to limit the scope thereof. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. Also, identical or similar reference numerals designate identical or similar components throughout the several views.
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this specification is not intended to be limited to the specific terminology so selected and it is to be understood that each specific element includes all technical equivalents that have a similar function, operate in a similar manner, and achieve a similar result.
Referring now to the drawings, embodiments of the present disclosure are described below. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
An intermediate transfer belt 3 as an intermediate transfer member is disposed facing the first to fourth photoconductors 1a, 1b, 1c, and 1d. The photoconductors 1a, 1b, 1c, and 1d contact the surface of the intermediate transfer belt 3. The intermediate transfer belt 3 secondarily transfers toner images, which have been primarily transferred to the intermediate transfer belt 3 from the photoconductors 1a, 1b, 1c, and 1d, onto a transfer medium. The intermediate transfer belt 3 illustrated in
The configuration for forming toner images on the photoconductors 1a, 1b, 1c, and 1d and the configuration for transferring the toner images onto the intermediate transfer belt 3 are all substantially the same, except the colors of the respective toner images formed on the photoconductors 1a, 1b, 1c, and 1d. Accordingly, a description is given of only the configuration and operation for forming a black toner image on the first photoconductor 1a and transferring the black toner image onto the intermediate transfer belt 3. The photoconductor 1a is rotated in a counterclockwise direction as indicated by the arrow A in
The electrostatic latent image formed on the photoconductor 1a is visualized as a visible black toner image when the electrostatic latent image passes a developing device 10. On the other hand, inside the intermediate transfer belt 3, primary transfer rollers 11a, 11b, 11c, and 11d (hereinafter, referred to as a “primary transfer roller 11” as appropriate when colors are not distinguished) as primary transferors positioned substantially opposite to the photoconductors 1a, 1b, 1c, and 1d via the intermediate transfer belt 3 are arranged. The primary transfer roller 11 contacts the back surface of the intermediate transfer belt 3, so that an appropriate transfer nip between the photoconductor 1 and the intermediate transfer belt 3 is ensured. The primary transfer roller 11 is made of metal and is arranged with slight offset relative to the photoconductor 1 (an indirect transfer method). In the present embodiment, a belt distance (offset amount) between the photoconductor 1 and the primary transfer roller 11 in which the intermediate transfer belt 3 does not contact any of the photoconductor 1 and the primary transfer roller 11 is 4 to 5 mm.
A transfer voltage having a polarity (e.g., a positive polarity in this example) opposite to the toner charge polarity of the toner image formed on the photoconductor 1a is applied to the primary transfer roller 11a. Accordingly, a transfer electric field is formed between the photoconductor 1a and the intermediate transfer belt 3, and in the primary transfer section where the photoconductor 1a and the outer circumferential surface of the intermediate transfer belt 3 contact with each other, the toner image on the photoconductor 1a is electrostatically transferred onto the intermediate transfer belt 3 which is rotated in synchronization with the photoconductor 1a (primary transfer process). Untransferred toner adhering to the surface of the photoconductor 1a after the toner image is transferred to the intermediate transfer belt 3 is removed by a cleaning device, and the surface of the photoconductor 1a is cleaned.
In the same manner, a magenta toner image, a cyan toner image, and a yellow toner image are formed on the second to fourth photoconductors 1b, 1c, and 1d, respectively. The toner images of the respective colors are sequentially superimposed and electrostatically transferred onto the intermediate transfer belt 3 on which the black toner image is transferred.
The image forming apparatus 100 has two types of modes, which are a full-color mode in which four color toner images are used and a black monochrome mode in which a black toner image alone is used. In the full-color mode, the intermediate transfer belt 3 and the photoconductors 1 of four colors contact with each other, and toner of all four colors is transferred onto the intermediate transfer belt 3. On the other hand, in the black monochrome mode, only the black photoconductor 1a contacts the intermediate transfer belt 3 and only the black toner is transferred onto the intermediate transfer belt 3. At this time, the intermediate transfer belt 3 and the magenta, cyan, and yellow photoconductors 1b, 1c, and 1d are not in contact with each other, and the primary transfer rollers 11b, 11c, and 11d are separated from the photoconductors 1b, 1c, and 1d by a contact-and-separation mechanism included in the image forming apparatus 100.
In the image forming apparatus 100 according to the present embodiment, the primary transfer roller 11 contacts the inner circumferential surface of the intermediate transfer belt 3 such that a contact region between the photoconductor 1 and the intermediate transfer belt 3 and a contact region between the primary transfer roller 11 and the intermediate transfer belt 3 do not overlap each other in the moving direction of the intermediate transfer belt 3.
On the other hand, as illustrated in
The recording medium P on which the composite toner image is secondarily transferred is further conveyed upward and passes a fixing device 18. At this time, the toner image on the recording medium P is fixed by the action of heat and pressure. The recording medium P that has passed the fixing device 18 is ejected to the outside of the image forming apparatus 100 via a sheet ejection roller pair 19 disposed in a sheet ejection section.
The untransferred toner adhering to the intermediate transfer belt 3 after transfer of the toner image is removed by a belt cleaner. The belt cleaner according to the present embodiment includes a cleaning blade 21 having a blade shape made of, for example, urethane. The cleaning blade 21 contacts the outer circumferential surface of the intermediate transfer belt 3 in a counter direction with respect to the moving direction of the intermediate transfer belt 3. As is clear to the person skilled in the art, various kinds of components can be used as the belt cleaner as appropriate, and for example, the belt cleaner may be a capacitance type.
The untransferred toner removed from the intermediate transfer belt 3 by the cleaning blade 21 is sent to the rear side in the longitudinal direction by a waste-toner coil in a cleaning case of the cleaning device, and is conveyed to a waste-toner container via a waste-toner passage disposed in the apparatus body.
When the output of the primary-transfer-bias power source 27BK is under constant-voltage control, the detector 28 is a primary-transfer-current detector that detects the amount of current flowing through the primary transfer roller 11a when a bias is applied to the primary transfer roller 11a. When the output of the primary-transfer-bias power source 27BK is under constant-current control, the detector 28 detects an output bias of the primary-transfer-bias power source 27BK.
Voltages are applied to the other primary transfer rollers 11b, 11c, and 11d by another primary-transfer-bias power source 29FC. Accordingly, the image forming apparatus 100 includes a plurality of primary-transfer-bias power sources 27BK and 29FC, one of which is connected to the primary transfer roller 11a corresponding to the photoconductor 1a for the black toner image, and the detector 28 is also coupled only with the primary transfer roller 11a corresponding to the photoconductor 1a for the black toner image. As a result, the image forming apparatus 100 need only include one detector 28, which reduces the costs of the configuration of the intermediate transfer unit and the resistance detection configuration. Control for changing the target value of the transfer bias over time and every time the environment changes is unnecessary. Driving the intermediate transfer device and the image bearer each time is not necessary, so that the life of the intermediate transfer member and the image bearer can be extended.
The controller 30 is connected to the primary-transfer-bias power source 27BK, the primary-transfer-bias power source 29FC, and the detector 28, and determines the primary transfer voltage of the primary transfer roller 11a corresponding to all colors on the basis of a detection result by the detector 28, that is, the detection current value X detected by the detector 28.
Details of the embodiment of the present disclosure are described below with an example of the case where the primary-transfer-bias power source 27BK is under constant-voltage control. When the primary-transfer-bias power source 27BK is under constant-voltage control, the transfer ratio changes due to the resistance of the intermediate transfer belt 3, so that the optimum transfer voltage changes (see
An intermediate-transfer-belt resistance value is estimated on the basis of an average current value detected by the detector 28 when a specified bias (2000V) is applied to the primary transfer roller 11a from the primary-transfer-bias power source 27BK for black over about one turn of the intermediate transfer belt 3, and then a voltage value to be applied to the primary transfer roller 11a is determined.
At this time, the intermediate-transfer-belt resistance value is estimated by the primary-transfer-bias power source 27BK for black and the detector 28. The value of the primary-transfer-bias power source 29FC to be applied to the other three colors are also determined on the basis of the result by the detector 28. From the data of the intermediate-transfer-belt resistance value and the transfer ratio in
A plurality of methods for correcting the primary transfer bias by the detected current value are possible depending on the apparatus. First, as illustrated in
As illustrated in
The present inventor has verified conversion formulae and has found that the best fit is obtained by using a quadratic function as the conversion formula. It is conceivable that the optimum conversion formula changes depending on conditions around the primary transfer section, for example, the distance between the photoconductor 1 and the primary transfer roller 11, the resistance value of the intermediate transfer belt 3 to be used, and the type of toner.
One example of the conversion formula for the detection current value X [uA] and the primary transfer bias Y [V] is Y=A1× X2+B1× X+C1 (A1≠0). In other words, the conversion formula for the primary transfer bias Y is a quadratic function with the detection current value X as independent variable. Here, it is assumed that A1=0.5, B1=77, and C=3700. When X=50 [μA], Y=1100 [V] is satisfied. According to this method, the controller 30 can more finely determine the optimum primary transfer bias Y corresponding to the variation of the resistance value of the intermediate transfer belt.
As illustrated in
Another example of the conversion formula for the detection current value X [uA] and the primary transfer bias Y [V] is as below;
In other words, the conversion formula for the primary transfer bias Y is determined by a plurality of conversion formulae according to the magnitude of the detection current value X and using the detection current value X as a variable. Here, it is assumed that A2=0.5, B2=−77, C2=3700, D2=−22, and E2=2200. As a result, when X=60 [μA], Y=880 [V] is satisfied. According to this method, the controller 30 can more finely determine the optimum primary transfer bias value corresponding to the variation of the resistance value of the intermediate transfer belt 3.
In a case where the intermediate-transfer-belt resistance value hardly changes over time, the above-described correction control of the primary transfer bias may be performed only when the intermediate transfer belt unit is started to use. In this case, a minimum travel amount is required without unnecessarily moving the intermediate transferor and the image bearer, and thus the life of other components can be extended.
In the above-described embodiment, the standard primary transfer bias Y is calculated using the above-described conversion formula. However, the primary transfer bias Y to be actually applied is determined by further multiplying the detection current value X by a correction coefficient of the use environment and the belt linear speed depending on the use environment and the belt linear speed (paper type or mode).
As described above, in the image forming apparatus 100 according to an embodiment of the present disclosure, the transferor is formed by the indirect transfer method with less increase of resistance, and only one detector 28 is disposed to detect the value of the current flowing through the primary transfer roller 11 when a constant voltage is applied to the primary transfer roller 11 from the primary-transfer-bias power source 27BK. The primary transfer bias Y corresponding to all colors is determined based on the detection current result, so that cost reduction of the configuration of the intermediate transfer unit and the configuration of resistance detection can be achieved.
Aspects of the present disclosure are, for example, as follows.
An image forming apparatus (e.g., the image forming apparatus 100) includes a plurality of image bearers (e.g., the photoconductors 1a, 1b, 1c, and 1d), a movable intermediate transferor (e.g., the intermediate transfer belt 3), a plurality of primary transferors (e.g., the primary transfer rollers 11a, 11b, 11c, and 11d), a primary transfer power source (e.g., the primary-transfer-bias power source 27BK, the primary-transfer-bias power source 29FC), a primary transfer current detector (e.g., the detector 28), and a controller (e.g., the controller 30). The plurality of image bearers carry toner images of a plurality of colors. The intermediate transferor secondarily transfers the toner images, which have been primarily transferred from the plurality of image bearers, onto a transfer medium. The plurality of primary transferors primarily transfer the toner images from the plurality of image bearers onto the intermediate transferor at primary transfer sections at which the plurality of image bearers contact an outer circumferential surface of the intermediate transferor. The primary transfer power source applies voltage to the plurality of primary transferors. The primary transfer current detector detects a current flowing through the plurality of primary transferors when a specified voltage is applied to the plurality of primary transferors. The controller determines a primary transfer voltage based on a current value detected by the primary transfer current detector. The primary transfer current detector is connected to only one primary transferor corresponding to an image bearer of one color among the plurality of image bearers of all of the plurality of colors. The controller determines a primary transfer voltage value (e.g., the primary transfer voltage value Y) of the plurality of primary transferors corresponding to all of the plurality of colors based on the detected current value.
In the image forming apparatus (e.g., the image forming apparatus 100) according to the first aspect, one of a plurality of primary transfer power sources including the primary transfer power source (e.g., the primary-transfer-bias power source 27BK, the primary-transfer-bias power source 29FC) is connected to one of the plurality of primary transferors (e.g., the primary transfer rollers 11a, 11b, 11c, and 11d) corresponding to one of the plurality of image bearers (e.g., the photoconductors 1a, 1b, 1c, and 1d) for a black toner image, and the primary transfer current detector (e.g., the detector 28) is also connected to the one of the plurality of primary transferors (e.g., the primary transfer rollers 11a, 11b, 11c, and 11d) corresponding to the one of the plurality of image bearers for the black toner image.
In the image forming apparatus (e.g., the image forming apparatus 100) according to the first or second aspect, the primary transfer voltage value (e.g., the primary transfer voltage value Y) is determined from a plurality of fixed values corresponding to magnitudes of the detected current value.
In the image forming apparatus (e.g., the image forming apparatus 100) according to the first or second aspect, the primary transfer voltage value (e.g., the primary transfer voltage value Y) is determined by a conversion formula using the detected current value as a variable.
In the image forming apparatus (e.g., the image forming apparatus 100) according to the fourth aspect, the conversion formula for the primary transfer voltage value (e.g., the primary transfer voltage value Y) is a quadratic function with the detected current value as an independent variable.
In the image forming apparatus (e.g., the image forming apparatus 100) according to the fifth aspect, the quadratic function is represented by Y=A1×X2+B1×X+C1 (A1≠0), where the primary transfer voltage value is Y [V] and the detected current value is X [μA].
In the image forming apparatus (e.g., the image forming apparatus 100) according to any one of the first to sixth aspects, the primary transfer voltage value (e.g., the primary transfer voltage value Y) is determined by a plurality of conversion formulae corresponding to magnitudes of the detected current value and using the detected current value as a variable.
In the image forming apparatus (e.g., the image forming apparatus 100) according to the seventh aspect, the plurality of conversion formulae are represented by Y=A2×X2+B2×X+C2 when X<α, and Y=D2×X+E2 when X≥α, where the primary transfer voltage value (e.g., the primary transfer voltage value Y) is Y [V], the detected current value is X [μA], α>0, A2≠0, and D2≠0.
In the image forming apparatus (e.g., the image forming apparatus 100) according to any one of the first to eighth aspects, the plurality of primary transferors (e.g., the primary transfer rollers 11a, 11b, 11c, and 11d) contact an inner circumferential surface of the intermediate transferor (e.g., the intermediate transfer belt 3) such that a contact region between the intermediate transferor and each of the plurality of image bearers (e.g., the photoconductors 1a, 1b, 1c, and 1d) and a contact region between the intermediate transferor and each of the plurality of primary transferors do not overlap each other in a moving direction of the intermediate transferor.
The above-described embodiments are illustrative and do not limit the present invention. Thus, numerous additional modifications and variations are possible in light of the above teachings. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of the present invention. Any one of the above-described operations may be performed in various other ways, for example, in an order different from the one described above.
The functionality of the elements disclosed herein may be implemented using circuitry or processing circuitry which includes general purpose processors, special purpose processors, integrated circuits, application specific integrated circuits (ASICs), digital signal processors (DSPs), field programmable gate arrays (FPGAs), conventional circuitry and/or combinations thereof which are configured or programmed to perform the disclosed functionality. Processors are considered processing circuitry or circuitry as they include transistors and other circuitry therein. In the disclosure, the circuitry, units, or means are hardware that carry out or are programmed to perform the recited functionality. The hardware may be any hardware disclosed herein or otherwise known which is programmed or configured to carry out the recited functionality. When the hardware is a processor which may be considered a type of circuitry, the circuitry, means, or units are a combination of hardware and software, the software being used to configure the hardware and/or processor.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-088509 | May 2023 | JP | national |
