Patent Application
20210033997
This patent application is based on and claims priority pursuant to 35 U.S.C. § 119(a) to Japanese Patent Application No. 2019-141155, filed on Jul. 31, 2019, in the Japan Patent Office, the entire disclosure of which is hereby incorporated by reference herein.
Embodiments of the present disclosure generally relate to a powder amount detector, a powder supply device, and an image forming apparatus.
There is known a powder amount detector, which includes a pair of electrodes, configured to detect an amount of powder in a powder container based on capacitance between the pair of electrodes.
Embodiments of the present disclosure describe an improved powder amount detector that detects an amount of powder in a powder container of a cylindrical shape arranged horizontally. The powder amount detector includes a pair of measuring electrodes configured to detect capacitance between the pair of measuring electrodes to detect the amount of powder. The pair of measuring electrodes is disposed around the powder container. One of the pair of measuring electrodes has a flat shape, and the other of the pair of measuring electrodes has an arc shape following a shape of the powder container.
A more complete appreciation of the disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with 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. In addition, identical or similar reference numerals designate identical or similar components throughout the several views, and redundant descriptions are omitted or simplified below as required.
Descriptions are given of embodiments of the present disclosure with reference to the drawings.
In describing embodiments illustrated in the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent 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 the same function, operate in a similar manner, and achieve a similar result.
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.
It is to be noted that the suffixes Y, M, C, and K attached to each reference numeral indicate only that components indicated thereby are used for forming yellow, magenta, cyan, and black images, respectively, and hereinafter may be omitted when color discrimination is not necessary.
The four toner containers 32Y, 32M, 32C, and 32K, the four image forming units 6Y, 6M, 6C, and 6K, and the four toner supply devices 60Y, 60M, 60C, and 60K have similar configurations except for the color of toner used therein. Accordingly, in the description and drawings below, the suffixes Y, M, C, and K, each representing the color of toner, are omitted unless color discrimination is necessary.
The photoconductor 1 rotates clockwise in
After the primary transfer process, a certain amount of untransferred toner remains on the surface of the photoconductor 1. When the surface of the photoconductor 1 reaches a position opposite the cleaning device 2, a cleaning blade 2a of the cleaning device 2 mechanically collects the untransferred toner remaining on the photoconductor 1 (cleaning process). Subsequently, the surface of the photoconductor 1 reaches a position opposite the discharge device, and the discharge device removes any residual potential on the photoconductor 1.
The intermediate transfer unit 15 includes the intermediate transfer belt 8, four primary transfer rollers 9Y, 9M, 9C, and 9K, a secondary transfer backup roller 12, multiple 20 tension rollers, and a belt cleaning device. The intermediate transfer belt 8 is stretched around and supported by the above-described multiple rollers and is rotated counterclockwise in
A transfer bias opposite in polarity to toner is applied to each of the primary transfer rollers 9Y, 9M, 9C, and 9K. The intermediate transfer belt 8 rotates in the direction indicated by arrow A1 in
The intermediate transfer belt 8 carrying the multicolor toner image reaches a position opposite a secondary transfer roller 19. The secondary transfer backup roller 12 and the secondary transfer roller 19 press against each other via the intermediate transfer belt 8, and the contact portion therebetween is hereinafter referred to as a secondary transfer nip. The multicolor toner image on the intermediate transfer belt 8 is transferred onto a recording medium P such as a transfer sheet conveyed to the secondary transfer nip (secondary transfer process). After the secondary transfer process, a certain amount of untransferred toner, which is not transferred to the recording medium P, remains on the intermediate transfer belt 8. When the intermediate transfer belt 8 reaches a position opposite the belt cleaning device, the untransferred toner is collected from the intermediate transfer belt 8 by the belt cleaning device to complete a series of transfer processes performed on the intermediate transfer belt 8.
The recording medium P is conveyed from a sheet feeding tray 26 disposed in a lower portion of the printer 100 to the secondary transfer nip via a sheet feeding roller 27 and a registration roller pair 28. More specifically, the sheet feeding tray 26 contains multiple recording media P piled one on another. As the sheet feeding roller 27 rotates counterclockwise in
The recording medium P onto which the multicolor toner image is transferred at the secondary transfer nip is conveyed to a fixing device 20. In the fixing device 20, a fixing belt and a pressure roller apply heat and pressure to the recording medium P to fix the multicolor toner image on the recording medium P. Subsequently, the recording medium P is ejected by an output roller pair 29 to the exterior of the printer 100. The ejected recording media P are sequentially stacked as output images on a stack tray 30 to complete a sequence of image forming processes performed in the printer 100.
Next, the configuration and operation of the developing device 5 of the image forming unit 6 are described in further detail below. As illustrated in
The sleeve of the developing roller 51 rotates counterclockwise as indicated by arrow A2 in
The two conveying screws 55 stir and mix the developer G with the toner supplied to the second developer containing compartment 54 while circulating the developer G in the first and second developer containing compartments 53 and 54. The toner in the developer G is triboelectrically charged by friction with the carrier and electrostatically attracted to the carrier. Then, the toner is carried on the developing roller 51 together with the carrier by magnetic force generated on the developing roller 51. The developer G on the developing roller 51 is carried in the direction indicated by arrow A2 in
An amount of developer G on the developing roller 51 is adjusted by the doctor blade 52. Then, the developer G is carried to a development range opposite the photoconductor 1, and toner in the developer G is attracted to the latent image on the photoconductor 1 by an electric field generated in the development range. Subsequently, as the sleeve rotates, the developer G remaining on the developing roller 51 reaches an upper portion of the first developer containing compartment 53 and separates from the developing roller 51.
Next, the toner supply device 60 and the toner container 32 are described in further detail.
The toner containers 32 are inserted into the toner container mount 70 of the printer 100 in the direction indicated by arrow Q in
The container body 33 includes a helical rib 331 protruding inward from an inner circumference face of the container body 33. As the container body 33 rotates, the helical rib 331 conveys toner in the container body 33 from the container rear end to the container front end (from the left to the right in
As illustrated in
A controller 150 (see
The toner end sensor is disposed on a side wall of the hopper 61 and detects that the amount of toner stored in the hopper 61 has fallen below a predetermined amount. For example, a piezoelectric sensor can be used as the toner end sensor. As the toner end sensor detects that the amount of toner stored in the hopper 61 has fallen below the predetermined amount, the drive motor 91 is driven. As a result, the container body 33 of the toner container 32 is rotated in the predetermined period, thereby supplying toner to the hopper 61. In the present embodiment, the hopper 61 stores toner discharged from the toner container 32, but alternatively, toner discharged from the toner container 32 may be directly supplied to the developing device 5.
In certain image forming apparatuses, an amount of toner remaining in a toner container is estimated and reported to a user. A method to estimate the amount of toner remaining in the toner container is based on cumulative drive duration of a toner conveying screw. Since an amount of toner conveyed by the toner conveying screw is approximately proportional to a rotation angle (a rotation duration), an amount of toner usage can be calculated based on a record of the total rotation duration of the toner conveying screw. Therefore, the amount of toner remaining in the toner container can be calculated by subtracting the amount of toner usage from an initial amount of toner filling the toner container. However, since the amount of toner conveyed by the toner conveying screw varies depending on the environment, drive duration, supply frequency (supply interval), and the like, the estimated value of the amount of toner remaining in the toner container also varies.
Another method to estimate the amount of toner remaining in the toner container is based on an output image pattern. An amount of toner usage to output a printed image can be calculated because an amount of toner adhering to a photoconductor per image area is approximately constant. Therefore, the amount of toner usage can be calculated based on a cumulative image area. However, with this method, it is difficult to accurately estimate the amount of toner remaining in the toner container because the amount of toner adhering to the photoconductor varies due to various errors.
In a comparative example of a toner amount detector, electrodes are disposed on an upper and a lower inner walls of a box-shaped toner container, and the amount of toner remaining in the toner container is estimated by measuring capacitance corresponding to an amount of toner. However, toner may adhere to the electrodes because the electrodes are disposed on the inner walls of the toner container, and the toner is not removed by light force such as vibration and remains on the electrodes. If a lot of toner adheres to the electrodes under certain environmental conditions, for example, a false detection may occur that toner still remains in the toner container even though, in fact, the toner in the toner container is depleted.
In another comparative example, a cylindrical ink container to store ink that is liquid rather than powder is arranged such that a discharge port disposed on one end of the ink container in the longitudinal direction faces vertically downward. An amount of the ink is detected based on change of capacitance between two electrodes. The two electrodes have a curved shape along the side face of the ink container. However, if this structure is directly applied to a powder amount detector, toner as powder may clog the discharge port under gravity, thereby preventing the toner from being discharged.
In the present embodiment, as illustrated in
In the present embodiment, one of the pair of measuring electrodes 65 and 66, that is, the upper measuring electrode 65 has an arc shape following the shape of the toner container 32. The other measuring electrode 66, which is the lower measuring electrode 66, has a flat shape. In another embodiment, the shapes of the measuring electrodes 65 and 66 may be inverted. That is, the upper measuring electrode 65 may have the flat shape, and the lower measuring electrode 66 may have the arc shape following the shape of the toner container 32. The measuring electrodes 65 and 66 are secured to the walls 67 and 68 of the printer 100 with double-sided tape or the like, respectively. The measuring electrodes 65 and 66 are made of any conductive material, for example, iron plate. The projected areas of the upper and lower measuring electrodes 65 and 66 projected onto the horizontal plane by projection light L1 directed in the vertical direction have the same size, but are not limited thereto.
Since only one of the measuring electrodes 65 and 66 is arranged along the toner container 32, the distance between both ends of the upper and lower measuring electrodes 65 and 66 can be increased as compared with the case in which both of the measuring electrodes 65 and 66 are arranged along the toner container 32. In the case in which both of the measuring electrodes 65 and 66 are arranged along the toner container 32, as illustrated in
Therefore, in the present embodiment, only one of the measuring electrode 65 and 66 is arranged along the toner container 32. As a result, the distance between both ends of the upper and lower measuring electrodes 65 and 66 can be increased, and the difference of the lines of electric force between the end and the center portion can be reduced. With this configuration, the difference of the capacitance is decreased between when the toner in the toner container 32 is unevenly distributed to the left or right and when the toner in the toner container 32 is evenly distributed, thereby improving the measurement accuracy.
For example, in the case of flat upper and lower electrodes, the calculated amount of toner varies as follows.
Capacitance:
Toner sensitivity of capacitance : 2.0 counts/g
If the voltage variation is ±0.5%, the amount of toner varies from ±7.8 g to 9.5 g.
On the other hand, in the case of a flat lower electrode and an arc-shaped upper electrode, the calculated amount of toner varies as follows.
Capacitance:
Toner sensitivity of capacitance: 3.0 counts/g
If the voltage variation is ±0.5%, the amount of toner varies from ±6.1 g to 7.8 g.
With the arc-shaped upper measuring electrode 65, the space between the upper and lower measuring electrodes 65 and 66 can be narrowed. Accordingly, the sensitivity of measuring capacitance is increased, so that the toner sensitivity is increased. Further, although the capacitance of only air increases, the ratio of the capacitance of air to the capacitance including the toner container 32 and toner decreases. As a result, the variation of the amount of toner can be reduced by ±1.7 g.
When the amount of toner in the toner container 32 is large, the difference of the variation of the capacitance between the flat electrode and the arc-shaped electrode is not large, but when the amount of toner is small, the difference of the variation is large. Therefore, the arc-shaped measuring electrode 65 is useful for detecting amount of toner because high detection accuracy is required when the amount of toner is small.
As illustrated in
The detection result obtained by the capacitance detection circuit 111 is transmitted to a toner amount calculation circuit 112, and a toner amount calculation circuit 112 calculates the amount of toner remaining in the toner container 32 based on the detected capacitance. The detected capacitance varies depending on a dielectric constant between the measuring electrodes 65 and 66. Toner has a higher dielectric constant than air. Therefore, the dielectric constant varies according to the amount of toner in an electric field between the measuring electrodes 65 and 66. As a result, the capacitance varies according to the amount of toner in the toner container 32 sandwiched by the pair of measuring electrodes 65 and 66. Thus, the amount of toner in the toner container 32 can be calculated by detecting the capacitance.
In the present embodiment, the toner amount calculation circuit 112 calculates the amount of toner remaining in the toner container 32 based on a calibration curve stored in a 35 memory 113 and the capacitance obtained by the capacitance detection circuit 111. The calibration curve preliminarily acquired indicates the relation between the capacitance and the amount of toner in the toner container 32. A temperature and humidity sensor 114 is provided to detect temperature and humidity around the toner container 32, and the amount of toner remaining in the toner container 32 is corrected based on a detection result obtained by the temperature and humidity sensor 114. The amount of toner obtained by the toner amount calculation circuit 112 is displayed on a display 115 (e.g., a control panel).
As described above, in the present embodiment, a powder amount detector (a toner amount detector) includes the measuring electrodes 65 and 66 and the powder amount detection unit 110 including the capacitance detection circuit 111, the toner amount calculation circuit 112, the memory 113, the temperature and humidity sensor 114, and the display 115. In the present embodiment, the measuring electrodes 65 and 66 are disposed outboard of the toner container 32, thereby preventing toner from adhering to the measuring electrodes 65 and 66. Therefore, the amount of toner can be detected accurately. The number of components and the cost of the toner container 32 can be reduced. Under high temperature environment, the amount of toner remaining in the toner container 32 can be accurately detected without being affected by thermal expansion of the toner container 32.
With such a configuration in which the pair of measuring electrodes 65 and 66 sandwiches the toner container 32, the capacitance does not vary due to the shape error or rotational eccentricity of the toner container 32. Therefore, the amount of toner remaining in the toner container 32 can be detected accurately. In the present embodiment, the pair of measuring electrodes 65 and 66 covers almost the entire toner container 32. Specifically, the projection areas of the measuring electrodes 65 and 66 projected on the horizontal plane by the projection light L1 directed in the vertical direction include the projection area of the toner container 32. With this configuration, since almost all toner in the toner container 32 is included in the lines of electric force between the pair of measuring electrodes 65 and 66 (i.e., electric field), the amount of toner remaining in the toner container 32 can be detected accurately even if the toner is unevenly distributed in the toner container 32, and the accurate amount of toner remaining in the toner container 32 can be reported to a user.
As the calibration curve calculation starts, the controller 150 causes the display 115 to display an instruction to install an empty toner container 32 in the toner container mount 70. After setting the empty toner container 32 in the toner container mount 70, an operator operates the display 115, for example, pushes a start button, thereby measuring capacitance. After measuring the capacitance of the empty toner container 32, the controller 150 causes the display 115 to display an instruction to install a full toner container 32 in the toner container mount 70. After setting the full toner container 32 in the toner container mount 70, the operator operates the display 115, thereby measuring capacitance. After measuring the capacitance of the full toner container 32, the controller 150 acquires a calibration curve based on the capacitances of the empty and full toner containers 32 and stores the calibration curve in the memory 113. The calibration curve calculation is performed for each color of Y, M, C, and K.
Alternatively, the controller 150 may acquire a calibration curve based on capacitance of a toner container 32 containing a small amount of toner instead of the empty toner container 32 or capacitance without the toner container 32, and the capacitance of the full toner container 32. That is, the capacitance between the pair of measuring electrodes 65 and 66 is measured in at least two states in which the amount of toner between the pair of measuring electrodes 65 and 66 is different from each other to acquire the calibration curve. Further, the calibration curve may be acquired by an imitation of the toner container 32 in which an amount of material, such as an acrylonitrile-butadiene-styrene (ABS) resin, is adjusted so as to have the capacitance identical to that of the toner container 32. As described above, the controller 150 performs the calibration curve calculation.
In the present embodiment, the temperature and humidity sensor 114 is provided to detect temperature and humidity around the toner container 32, and the amount of toner is corrected based on a detection result obtained by the temperature and humidity sensor 114. This is because the distance between the measuring electrodes 65 and 66 varies due to the thermal expansion of components to which the measuring electrodes 65 and 66 are secured (i.e., components constructing the upper and lower walls 67 and 68). Further, moisture between the measuring electrodes 65 and 66 varies. As a result, the capacitance between the measuring electrodes 65 and 66 varies.
The temperature and humidity at the time of measuring the above-described calibration curve are stored in the memory 113, and the amount of toner is corrected according to the difference of temperature and humidity between at the time of measuring the capacitance of the toner container 32 actually used and at the time of measuring the calibration curve in consideration of a predetermined temperature and humidity correction factor. As a result, the calculation error of the amount of toner due to ambient temperature and humidity is minimized, thereby acquiring the amount of toner accurately.
For example, a correction factor a at high temperature and high humidity and a correction factor β at low temperature and low humidity are stored in the memory 113. If temperature and humidity detected by the temperature and humidity sensor 114 are equal to or higher than a predetermined first threshold, the amount of toner is corrected by multiplying the calculated amount of toner by the correction factor a at high temperature and high humidity. If temperature and humidity detected by the temperature and humidity sensor 114 are equal to or less than a second threshold which is lower than the first threshold, the amount of toner is corrected by multiplying the calculated amount of toner by the correction factor 13 at low temperature and low humidity. As a result, the calculation error of the amount of toner due to ambient temperature and humidity is minimized, thereby acquiring the amount of toner accurately. As described above, the calculated amount of toner is corrected according to temperature and humidity, but alternatively, the detected capacitance can be corrected according to temperature and humidity.
However, as illustrated in
In addition to the ground electrodes 120 on the left and right side in
In the example in
In the above-described embodiments, the measuring electrodes 65 and 66, one of which has the flat shape and the other of which has the arc shape following the shape of the powder container 32, are arranged vertically, but, alternatively, measuring electrodes may be arranged horizontally.
As described above, according to the present disclosure, a powder amount detector can accurately detect an amount of powder.
The above-described embodiments are illustrative and do not limit the present disclosure. 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 disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-141155 | Jul 2019 | JP | national |
