Patent Grant
8811833
This application is a National Stage filing of PCT application No. PCT/JP2010/068772, filed Oct. 18, 2010, which claims priority from Japanese Patent Application No. 2009-243768, filed Oct. 22, 2009, Japanese Patent Application No. 2009-283456, filed Dec. 14, 2009, Japanese Patent Application No. 2009-292839, filed Dec. 24, 2009, and Japanese Patent Application No. 2010-003027, filed Jan. 8, 2010, all of which are hereby incorporated by reference herein in their entirety.
The present invention relates to an image forming apparatus including a developing device having a toner bearing member and a toner supply member that supplies the toner bearing member with a toner, and more particularly to an image forming apparatus including a detection mechanism that detects a capacitance between an electrode member provided in the toner bearing member and an electrode member provided in the toner supply member.
A method for detecting a remaining toner amount in a developing device used in an image forming apparatus, such as an electrophotographic apparatus, may be a capacitance detection method that provides information relating to the remaining toner amount by detecting a capacitance between two electrodes provided in the developing device.
In particular, if a developing device including a development roller serving as a toner bearing member, and a supply roller having a foam layer serving as a toner supply member is used, the capacitance detection method may be a method that provides information relating to the remaining toner amount by detecting a capacitance between a shaft of the development roller and a shaft of the supply roller. The method is, for example, disclosed in Patent Literature 1. In this method, since the remaining toner amount of the developing device is correlated with the capacitance between the shafts, the remaining toner amount can be measured by detecting the capacitance.
When the image forming apparatus that measures the remaining toner amount by detecting the capacitance in the developing device is used, if temperature and humidity environment is changed, the capacitance may be changed. The measurement accuracy for the remaining toner amount may be degraded, and the image forming apparatus may not notify a user that the remaining toner amount is smaller than a predetermined amount or that a cartridge has to be replaced. To reduce the influence by the change in environment, for example, Patent Literature 2 discloses a technique that corrects timing of a notice by using a temperature sensor and a humidity sensor.
In the image forming apparatus configured to detect the capacitance between the electrode member provided in the toner bearing member and the electrode member provided in the toner supply member as described in Patent Literature 1, the capacitance is changed if the temperature and humidity environment is changed. Hence, the measurement accuracy for the remaining toner amount may be degraded, and the image forming apparatus may not notify a user that the remaining toner amount is smaller than the predetermined amount or that the cartridge has to be replaced. To reduce the influence by the change in environment, if the temperature sensor and the humidity sensor are provided as described in Patent Literature 2, the degree of freedom for design may be reduced because the arrangement may be limited by these sensors, and the cost may be increased.
Thus, the present invention provides an image forming apparatus that can notify a user with high accuracy that a remaining toner amount is smaller than a predetermined amount or that a cartridge has to be replaced, without a temperature sensor or a humidity sensor even if the temperature and humidity environment is changed.
An image forming apparatus according to a first aspect of the present invention includes a developing device including a container that has an opening and contains a toner, a toner bearing member arranged at the opening of the container, having a first electrode member, and supplying an electrostatic latent image with the toner by bearing and conveying the toner, and a toner supply member arranged in the container and having a second electrode member and a foam layer, the foam layer being provided around the second electrode member and sucking and discharging the toner, the developing device supplying the toner bearing member with the toner in the container by rotating the toner supply member in a contact manner with the toner bearing member; a detection mode execution unit configured to execute a detection mode in which a predetermined period for changing a toner amount in the foam layer by rotating the toner supply member is provided, a capacitance C1 between the first and second electrode members is detected before the period, and a capacitance C2 between the first and second electrode members is detected after the period; and a notice signal generating unit configured to generate a notice signal if an absolute value |C1−C2| of a difference between the capacitances C1 and C2 is smaller than a predetermined threshold, the notice signal being indicative of that a toner amount in the container is smaller than a predetermined amount.
An image forming apparatus according to a second aspect of the present invention includes a developing device including a container that has an opening and contains a toner, a toner bearing member arranged at the opening of the container, having a first electrode member, and supplying an electrostatic latent image with the toner by bearing and conveying the toner, and a toner supply member arranged in the container and having a second electrode member and a foam layer, the foam layer being provided around the second electrode member and sucking and discharging the toner, the developing device supplying the toner bearing member with the toner in the container by rotating the toner supply member in a contact manner with the toner bearing member; a mount portion on which the developing device is mounted in a replaceable manner; a detection mode execution unit configured to execute a detection mode in which a predetermined period for changing a toner amount in the foam layer by rotating the toner supply member is provided, a capacitance C1 between the first and second electrode members is detected before the period, and a capacitance C2 between the first and second electrode members is detected after the period; and a notice signal generating unit configured to generate a notice signal if an absolute value |C1−C2| of a difference between the capacitances C1 and C2 is smaller than a predetermined threshold, the notice signal promoting replacement of the developing device.
The image forming apparatus can be provided, the apparatus which can notify a user with high accuracy that the remaining toner amount is smaller than the predetermined amount or that the cartridge has to be replaced, without the temperature sensor or the humidity sensor even if the temperature and humidity environment is changed.
A first embodiment of the present invention will be described below with reference to the drawings. However, dimensions, materials, shapes, and relative arrangements of components described in the embodiment may be properly changed in accordance with a configuration to which the present invention is applied or various conditions. The embodiment does not intend to limit the scope of the present invention.
Image formation by the image forming apparatus will be described. A controller 70 collectively controls the image formation in accordance with a predetermined control program and a reference table as follows. First, the charging roller 2 causes the surface of the photosensitive drum 1 to be charged by a predetermined potential while the photosensitive drum 1 is rotated at 100 mm/sec in the direction R1. An electrostatic latent image is formed on the photosensitive drum 1 at the exposure position A by a laser beam emitted by the exposure devise 3 and reflected by the reflection mirror 4 in accordance with an image signal for each color. The formed electrostatic latent image is developed by the developing device 5 at a development position C. Thus, a toner image is formed. The toner image formed on the photosensitive drum 1 is transferred on the transfer material P at a transfer position B. The transfer material P with the toner image transferred thereon is conveyed to the fixing unit 15. The fixing unit 15 applies pressure and heat to the toner image on the transfer material P to fix the toner image to the transfer material P. Thus, a final image is obtained.
The developing device 5 will be described in detail below with reference to
The development roller 25 rotates while being in contact with the photosensitive drum 1 during developing. A driving force is transmitted from a drive-P 60 serving as a first drive and provided in the apparatus body of the image forming apparatus, to the development roller 25 and the supply roller 24. Hence, the development roller 25 and the supply roller 24 are synchronously rotated and stopped. After developing, a cam 20 provided in the apparatus body of the image forming apparatus rotates and pushes an upper portion of the cartridge 21. The cartridge 21 rotates around a swing center axis 30, and the development roller 25 is separated from the photosensitive drum 1. After the separation, the drive-P 60 stops the rotation.
The development roller 25 includes a conductive shaft 25a and a conductive elastic layer 25b. The conductive shaft 25a serves as a first electrode member made of, for example, stainless steel or an aluminum alloy, and has a diameter of φ8 mm. The conductive elastic layer 25b is formed around the shaft 25a and has a base layer made of silicone rubber. The development roller 25 has a surface layer coated with an acrylic urethane rubber layer. The development roller 25 has an outer diameter of φ13 mm, and a volume resistivity of about 10E5 Ω·cm. During developing, the development roller 25 is supported by the cartridge 21 such that the development roller 25 contacts the photosensitive drum 1 at the development position C and is rotated in a direction R4 in
The supply roller 24 includes a conductive shaft 24a and a urethane spongy layer 24b. The conductive shaft 24a serves as a second electrode member made of, for example, stainless steel or an aluminum alloy, and has a diameter of φ6 mm. The urethane spongy layer 24b is formed around the shaft 24a, and is a foam layer made of a soft open-cell foam material. The supply roller 24 has an outer diameter of φ15 mm, and a volume resistivity of about 10E8 Ω·cm. In this embodiment, a distance between the center of the shaft 25a of the development roller 25 and the center of the shaft 24a of the supply roller 24 (hereinafter, referred to as a center distance) is 13 mm. The development roller 25 and the supply roller 24 are arranged such that the surface of the development roller 25 pushes the urethane spongy layer 24b of the supply roller 24 by an entering distance of about 1.0 mm. The entering distance is a distance obtained by dividing the sum of the outer diameter of the supply roller 24 and the outer diameter of the development roller 25 by two and then subtracting the center distance from the obtained value.
The supply roller 24 is supported by the cartridge 21 such that the supply roller 24 can be rotated in a direction R5 in
The restriction blade 27 is formed of a flexible phosphor bronze sheet. The restriction blade 27 has an end fixed to the cartridge 21 and the other end that is a free end. The restriction blade 27 contacts the development roller 25. The restriction blade 27 is arranged such that a flat smooth surface located near the free end slides on the surface of the development roller 25 in an opposite direction to a rotating direction of the development roller 25.
Also, a leakage prevention seal 26 is provided to seal a gap between the development roller 25 and the cartridge 21. Further, referring to
Described next are the behavior of the urethane spongy layer 24b of the supply roller 24 and the behavior of the toner around the urethane spongy layer 24b when the supply roller 24 and the development roller 25 are rotated at predetermined speeds. The urethane spongy layer 24b of the supply roller 24 is compressed in a region (portion X in
In contrast, since the supply roller 24 is released from the compressed state and is restored to the original shape in the portion Y, the toner dispersed into the air is sucked into the supply roller 24. The toner can be smoothly sucked into and discharged from the urethane spongy layer 24b. Thus, the pressure of the toner as powder accumulated in the portion near the supply roller 24 and the pressure of the toner as powder in the supply roller 24 are balanced. The toner amount held in the supply roller 24 is correlated with the total toner amount in the cartridge 21. Hence, the capacitance between the shaft 24a of the supply roller 24 and the shaft 25a of the development roller 25 indicates the toner amount held in the supply roller 24 and also expects the total toner amount in the cartridge 21 (see Patent Literature 1). The toner is sucked and discharged mainly when the supply roller 24 is rotated. The supply roller 24 after the rotation is stopped holds the toner amount obtained by the rotation. Even if the developing device 5 is moved or the posture thereof is changed in this state, the toner amount held in the supply roller 24 is not substantially changed, and the change is negligible.
Next, a method for measuring the remaining toner amount of the developing device 5 according to this embodiment will be described. In this embodiment, if the remaining toner amount is large, a pixel counting unit (pixel counter) that can count the number of pixels (pixel count) of light emitted by the exposure device 3 is used to roughly estimate a toner use amount (hereinafter, this method is referred to as a pixel count method). The toner amount required for developing a certain image is substantially proportional to the number of pixels (pixel count) of light emitted by the exposure device 3. Hence, in the pixel count method, a toner use amount per pixel count is stored in a memory in the apparatus body, and a total toner use amount is estimated by using an integrated value of the stored value and the number of pixels (pixel count) counted by the pixel counter. The integrated value is stored in a memory provided in the developing device 5.
If the remaining toner amount becomes relatively small, a high accuracy detection mode (described later) using a capacitance is executed to accurately detect the run out timing of the toner, and the replacement timing of the developing device 5. The “run out of toner” does not indicates a state in which the toner does not remain in the developing device 5 at all, but indicates a state in which the toner remains by an amount having a difficulty in maintaining the desired level of an image quality. Hereinafter, it is assumed that the wordings “run out of toner” have the meaning as described above.
A flow for measuring the remaining toner amount will be described in detail below with reference to
In a standby state (S000), when image formation is started (S001), the number of pixels is counted (measurement for the pixel count is performed) (S002). When the image formation is ended, the counted numbers of pixels (measured pixel counts) are integrated, and hence a pixel count integrated value Pcount is calculated (S003). Then, it is determined whether the integrated value Pcount reaches a predetermined value Pth (S004). If the integrated value Pcount reaches the predetermined value Pth, a remaining toner amount measurement sequence (high accuracy detection mode) using the capacitance is started (S005). If the integrated value Pcount does not reach the predetermined value Pth, the normal image formation is continued until Pcount becomes equal to or larger than Pth (S006).
In this embodiment, when the predetermined value Pth is an integrated value that is 20% smaller than a pixel count integrated value P0% expected to be obtained when the toner is run out (see Expression 1), the first execution timing for the high accuracy detection mode is determined as follows:
Pth=P0%×0.8 (1).
The first execution timing for the high accuracy detection mode is determined when the remaining toner amount is larger than the remaining toner amount when the toner is run out by the following reason. The remaining toner amount estimated by the pixel counts may be fluctuated due to variation of the toner use amount. The high accuracy detection mode has to be reliably executed by taking into account the variation so that an image with a low density or an image with an unprinted portion is not generated. Therefore, the high accuracy detection mode is executed at timing slightly earlier than the run out timing of the toner estimated by using the pixel counts.
After the first high accuracy detection mode is executed, Pth is calculated again by a calculating method (described later), and when the integrated value Pcount reaches the predetermined value Pth that is newly set, the next high accuracy detection mode is executed. Accordingly, the run out of the toner can be detected by executing the high accuracy detection mode a few number of times.
In this embodiment, the pixel count method is used in order to roughly estimate the remaining toner amount in a short time when the remaining toner amount is large. To accurately detect the run out timing of the toner and the replacement timing of the developing device, required herein is that the high accuracy detection mode is executed. The pixel count method may not be used. For example, the high accuracy detection mode may be executed every time when the image formation is performed for a predetermined number of sheets. Alternatively, the start timing of the high accuracy detection mode may be determined by another method for measuring the remaining toner amount.
A method for measuring a capacitance, the method which is required for executing the high accuracy detection mode, will be described below. Referring to
(Alternatively, an AC voltage may be applied to the shaft 25a and the remaining toner amount may be measured by using a voltage induced at the shaft 24a. However, since the development roller 25 faces the photosensitive drum 1, if the AC voltage is applied to the shaft 25a, the toner may adhere to the photosensitive drum 1. In contrast, since the supply roller 24 does not face the photosensitive drum 1, it is desirable to apply the AC voltage to the supply roller 24 because the toner hardly adheres to the photosensitive drum 1.) The capacitance is detected when the development roller 25 is separated from the photosensitive drum 1 and the rotation of the development roller 25 is stopped.
Accordingly, the influence of the photosensitive drum 1 to the capacitance to be detected can be reduced. Also, a stable output can be obtained as long as the capacitance is detected after the development roller 25 is stopped. However, to obtain the advantage of reducing the influence by the temperature and humidity environment, the development roller 25 does not have to be separated, or the development roller 25 does not have to be stopped when the capacitance is detected. Referring to
It is to be noted that the capacitance between the shafts 25a and 24a is correlated with the toner amount in the supply roller 24 as shown in
The high accuracy detection mode that is a feature of the present invention will be described below with reference to
If the pixel count integrated value Pcount of the developing device 5 reaches the predetermined value Pth, after developing, the high accuracy detection mode is started (S005, S100). The development roller 25 and the supply roller 24 are brought into a drive transmission enabled state, in which the drive-P 60 can transmit driving forces to the development roller 25 and the supply roller 24 (S101). Then, while a first DC voltage is applied between the shafts 25a and 24a from the DC power supply 90 serving as the voltage applying unit, the supply roller 24 is rotated for a first predetermined time (S102). When the first DC voltage is applied, a potential Va for the shaft 24a is −500 V and a potential Vb for the shaft 25a is −300 V. Hence, the potential difference between the shafts 24a and 25a is ΔV1=Va−Vb=−200 V.
The first predetermined time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the first predetermined time is 60 seconds. After the rotation for the first predetermined time, to measure the remaining toner amount, the development roller 25 is separated from the photosensitive drum 1, and the rotation of the development roller 25 and the supply roller 24 is stopped (S103). Then, a first capacitance C1 is measured (S104).
Then, the state is brought into the drive transmission enabled state (S105). While a second DC voltage is applied between the shafts 25a and 24a from the DC power supply 90 serving as the voltage applying unit, the development roller 25 and the supply roller 24 are rotated for a second predetermined time. With the rotation, the toner amount in the foam layer of the supply roller 24 increases (S106). When the second DC voltage is applied, a potential Vc for the shaft 24a is −100 V and a potential Vd for the shaft 25a is −300 V. Hence, the potential difference between the shafts 24a and 25a is ΔV2=Vc−Vd=+200 V.
The second predetermined time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the second predetermined time is 60 seconds. After the rotation for the second predetermined time, to measure the remaining toner amount, the development roller 25 is separated from the photosensitive drum 1, and the rotation of the development roller 25 and the supply roller 24 is stopped (S107). Then, a second capacitance C2 is measured (S108).
When an absolute value |C1−C2| of the difference between the detected capacitances C1 and C2 is ΔC, the relationship between ΔC and the remaining toner amount in the developing device 5 becomes one illustrated in
In contrast, if ΔC is not equal to or smaller than ΔCth (NO in S202), a difference ΔD between ΔC and ΔCth is calculated (S204), and Pth is reset (S205). The image formation is continued until the pixel count integrated value Pcount reaches the newly set predetermined value Pth (S206). (The process goes back to S000 or S001 in
Next, a method for resetting Pth by using ΔD will be described. The relationship between the remaining toner amount and ΔC is illustrated in
Here, the physical meaning of the correlation between the capacitance difference (difference between capacitances) and the toner amount in the cartridge 21 will be discussed on the basis of the observed result of the developing device 5.
The inventors of the present invention found that the relationship between the remaining toner amount and the toner amount in the supply roller 24 was changed by the potential difference ΔV of the DC voltage that was applied between the shaft 24a of the supply roller 24 and the shaft 25a of the development roller 25.
From the observed result by the inventors of the present invention, it was found that the discharge amount of the toner to the portion X (
In contrast, when the toner remains in the cartridge 21 by a very small amount (point B), the toner in the portion Y (
Consequently, the relationship between the toner amount in the cartridge 21 and the toner amount in the supply roller 24 becomes one shown in
With regard to the above-described points, the advantage according to this embodiment of the present invention will be described in detail.
Accordingly, if the capacitance differences with the various potential differences are used as parameters for detecting the remaining toner amount, the influence by the change in environment to the capacitance can be canceled. By measuring the remaining toner amount with the high accuracy detection mode according to this embodiment, even if the temperature and humidity environment is changed, the remaining toner amount can be highly accurately measured without the temperature sensor or the humidity sensor. Thus, a user can be notified with high accuracy that the remaining toner amount is smaller than a predetermined amount or that the cartridge 21 has to be replaced, without the temperature sensor or the humidity sensor even if the temperature and humidity environment is changed.
In this embodiment, the potential difference is ΔV1=−200 V when the first DC voltage is applied and the potential difference is ΔV2=+200 V when the second DC voltage is applied in the high accuracy detection mode. If the high accuracy detection mode is ended after the rotation with the potential difference of ΔV2=+200 V, as compared with the case in which the high accuracy detection mode is ended after the rotation with the potential difference of ΔV1=−200 V, the development can be started with the more toner contained in the supply roller 24 for the next image formation.
That is, by applying the first and second DC voltages such that the value of ΔV1−ΔV2, i.e., the value of (Va−Vb)−(Vc−Vd) is homopolar with the normal charge polarity of the toner, an image with a low density or an image with an unprinted portion is less frequently generated even if an image with a high coverage rate is output after the high accuracy detection mode, as compared with the antipolar case. However, to obtain the advantage according to the present invention of highly accurately measuring the remaining toner amount even if the temperature and humidity environment is changed, the relationship between ΔV1−ΔV2 and the normal charge polarity of the toner does not have to be satisfied.
Also, the values used for the first and second DC voltages are not limited thereto, and may be desirably selected. However, since the relationship between the remaining toner amount and the toner amount in the supply roller 24 is changed by using the voltages with different values ΔV as described above, this embodiment does not include a configuration using the same voltage. Further, the supply roller rotation time required so that the toner amount in the supply roller 24 becomes stable depends on, for example, the rotation speed of the supply roller 24. Hence, the first and second predetermined times are not limited to the values according to this embodiment, and do not have to be the same.
Further, in this embodiment, the potential of the shaft 25a of the development roller 25 is fixed whereas the potential of the shaft 24a of the supply roller 24 is changed by the plurality of steps when the first DC voltage is applied and when the second DC voltage is applied. However, required herein is that the potential difference between the shafts 25a and 24a is changed. Hence, the potential of the shaft 25a may be changed.
A second embodiment of the present invention will be described below with reference to the drawings. However, dimensions, materials, shapes, and relative arrangements of components described in the embodiment may be properly changed in accordance with a configuration to which the present invention is applied or various conditions. The embodiment does not intend to limit the scope of the present invention.
Developing devices 5a, 5b, 5c, and 5d respectively contain a yellow toner, a magenta toner, a cyan toner, and a black toner each having a negative normal charge polarity. The developing devices 5a to 5d have the same configuration, and hence, if the contained toners do not have to be distinguished from each other, the developing devices 5a to 5d are collectively described as developing devices 5. The developing devices 5 are cartridges that are mounted on mount portions of a rotary drum 50 in a replaceable manner. The rotary drum 50 is rotatably supported with the developing devices 5 attached thereto. The rotary drum 50 can rotate to bring a desirable one of the developing devices 5 (for example, the developing device 5a) to a development position C at which the developing device 5 (5a) faces and contacts the photosensitive drum 1.
A transfer belt 16 serving as an intermediate transfer member is provided below the photosensitive drum 1 and supported by a plurality of rollers. The transfer belt 16 is rotatable in a direction R3 in
The roller 16b is named a secondary transfer opposite roller 16b for the secondary transfer roller 18. The position, at which the secondary transfer roller 18 contacts and is separated from the transfer belt 16, is named a secondary transfer position D. Although described later, an image is transferred on a conveyed transfer material P at the secondary transfer position D. The transfer material P after the transferring is conveyed to a fixing unit 15.
A transfer cleaning device 19 is provided downstream the secondary transfer position D in a moving direction of the transfer belt 16. The cleaning device 19 includes a blade being in contact with the transfer belt 16 so that the blade scrapes a toner on the transfer belt 16. Also, a photosensitive member cleaning device 9 is provided downstream the primary transfer position B in a moving direction of the photosensitive drum 1. The cleaning device 9 includes a blade being in contact with the photosensitive drum 1 so that the blade scrapes a toner on the photosensitive drum 1.
Image formation by the image forming apparatus will be described. The charging roller 2 causes the surface of the photosensitive drum 1 to be charged by a predetermined potential while the photosensitive drum 1 is rotated at 100 mm/sec in the direction R1. An electrostatic latent image is formed on the photosensitive drum 1 at the exposure position A by a laser beam emitted by the exposure device 3 and reflected by the reflection mirror 4 in accordance with an image signal for each color. The formed electrostatic latent image is developed by the developing device 5 at the development position C. Thus, a toner image is formed. The developing device 5 that is provided at the development position C is determined in accordance with the image signal for each color. The rotary drum 50 is rotated in a direction R2 in advance, so that the developing device 5 of a desirable color is provided at the development position C. The order of toner images to be developed is also determined. In this embodiment, toner images are formed in order of yellow, magenta, cyan, and black.
The toner images formed on the photosensitive drum 1 are transferred on the transfer belt 16 at the primary transfer position B. By superposing the toner images successively on one another, a full-color toner image is formed on the transfer belt 16.
The secondary transfer roller 18 is separated from the transfer belt 16 until the full-color toner image is formed. After the full-color image is formed, the secondary transfer roller 18 contacts the transfer belt 16. The transfer material P is conveyed to the secondary transfer position D at the timing when the formed full-color toner image reaches the secondary transfer position D. The secondary transfer roller 18 and the secondary transfer opposite roller 16b pinch the transfer material P together with the transfer belt 16, so that the full-color toner image is transferred on the transfer material P. The transfer material P with the full-color toner image transferred thereon is conveyed to the fixing unit 15. The fixing unit 15 applies pressure and heat to the full-color toner image on the transfer material P to fix the full-color toner image to the transfer material P. Thus, a final image is obtained.
The developing device 5 used in the second embodiment has a configuration similar to the configuration of the developing device 5 used in the first embodiment. The developing device 5 of the second embodiment has a development roller 25 and a supply roller 24 similar to those of the first embodiment. The peripheral speed of the development roller 25 is 160 mm/sec, and the peripheral speed of the supply roller 24 is 140 mm/sec during image formation. In this embodiment, a DC voltage that is applied from a DC power supply 90 to the supply roller 24 can be changed by a plurality of steps like the first embodiment.
Next, a method for measuring a remaining toner amount of the developing device 5 according to this embodiment will be described. The method for measuring the remaining toner amount is basically similar to that of the first embodiment, and hence, only feature part of this embodiment will be described. In this embodiment, the developing device 5 as the subject of detection for the remaining toner amount is provided on a rotary support member, i.e., the rotary drum 30. A drive-Q 60 (second drive) rotates the rotary drum 50, so that the developing device 5 is moved to a detection position E for measurement. The detection position E is the position of the developing device 5c in
At the detection position E, since a toner around the supply roller 24 is dropped by own weight, the influence of the toner near the supply roller 24 can be reduced. Accordingly, the toner near the supply roller 24 hardly disturbs the detection. The toner amount in the supply roller 24 can be correctly measured.
Also, in this embodiment, a pixel counting unit (pixel counter) is provided to calculate a light-emitting rate of the exposure device 3 like the first embodiment. A pixel count integrated value for each developing device 5 is calculated, and a toner use amount is roughly estimated. The pixel count integrated value is stored in a memory provided in each developing device 5. The execution timing for the high accuracy detection mode is determined by using the pixel count integrated value as a trigger like the first embodiment. However, to accurately detect the run out timing of the toner and the replacement timing of the developing device 5, required herein is that the high accuracy detection mode is executed. Hence, the pixel count method may not be used.
The operation in the high accuracy detection mode according to this embodiment will be described.
After the rotation for the predetermined time, the developing device 5 is moved to the detection position E (S303), and a first capacitance C1 is measured (S304). Then, the developing device 5 is moved to the development position C again (S305). To change the toner amount in the foam layer of the supply roller 24 again, a second DC voltage is applied between the first and second electrode members at that position, and the supply roller 24 is rotated for a second predetermined time (S306). Similarly to the first embodiment, when the second DC voltage is applied, a potential Vc for the shaft 24a is −100 V and a potential Vd for the shaft 25a is −300 V. Hence, the potential difference between the shafts 24a and 25a is ΔV2=Vc−Vd=+200 V.
The second predetermined time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the second predetermined time is 60 seconds. Then, the developing device 5 is moved to the detection position E (S307), and a second capacitance C2 is measured (S308).
An absolute value |C1−C2| of the difference between the detected capacitances C1 and C2 is ΔC. After ΔC is calculated, it is determined whether ΔC exceeds a threshold through the flow shown in
This embodiment provides an advantage on account of the use of the rotary drum 50, in addition to the advantage attained in the first embodiment. The advantage will be described. The capacitance difference ΔC in this embodiment has a tendency as shown in
The phenomenon that the inclination of the capacitance difference ΔC to the toner amount in the cartridge 21 is increased by the configuration of this embodiment will be described below.
This phenomenon will be discussed.
The supply roller 24 is supplied with the toner mainly through suction from the portion Y. Hence, by conveying the toner to the portion Y by the rotation of the rotary drum 50, the toner in the supply roller 24 can be increased. When the supply roller 24 is rotated with the potential difference ΔV of −200 V, the toner is likely discharged from the supply roller 24 due to the electric field, and hence the discharged amount of the toner to the portion X becomes larger than the sucked amount of the toner from the portion Y. The toner amount in the foam layer hardly varies depending on whether the rotary drum 50 is rotated or not. In contrast, when the supply roller 24 is rotated with the potential difference ΔV of +200 V, the toner is attracted to the supply roller 24 due to the electric field. The suction of the toner from the portion Y is predominant over the discharge of the toner to the portion X. Accordingly, the supply roller 24 easily sucks the toner.
The capacitance does not markedly change after the rotation with the potential difference ΔV of −200 V, whereas the capacitance increases after the rotation with the potential difference ΔV of +200 V. The capacitance difference is larger as compared with a configuration without the rotary drum 50. If the toner amount is very small, the toner in the portion Y is used up. The toner amount in the supply roller 24 becomes small after the rotation with the potential difference ΔV of +200 V. The case with the rotation of the rotary drum 50 is no longer different from the first embodiment.
Hence, it is considered that the inclination of the capacitance difference ΔC with respect to the toner amount in the cartridge 21 is larger than that of the first embodiment. The variation in remaining toner amount is smaller than the variation appearing during the detection for the capacitance difference ΔC. The remaining toner amount can be highly accurately detected.
The rotary drum 50 attains another advantage such that the toner is hardly affected even if the toner is left for a long period because the toner is stirred by the rotation of the rotary drum 50. Thus, the toner amount in the supply roller 24 becomes stable after the rotation of the supply roller 24. The variation in toner amount when the capacitance is measured can be reduced.
In this embodiment, the potential difference is ΔV1=−200 V when the first DC voltage is applied and the Potential difference is ΔV2=+200 V when the second DC voltage is applied in the high accuracy detection mode. If the high accuracy detection mode is ended after the rotation with the potential difference of ΔV2=+200 V, as compared with the case in which the high accuracy detection mode is ended after the rotation with the potential difference of ΔV1=−200 V, the supply roller 24 can contain the toner by a large amount for the next image formation.
That is, by applying the first and second DC voltages such that the value of ΔV1−ΔV2, i.e., the value of (Va−Vb)−(Vc−Vd) is homopolar with the normal charge polarity of the toner, an image with a low density or an image with an unprinted portion is less frequently generated even if an image with a high coverage rate is output after the high accuracy detection mode, as compared with the antipolar case. However, to obtain the advantage according to the present invention of highly accurately measuring the remaining toner amount even if the temperature and humidity environment is changed, the relationship between ΔV1−ΔV2 and the normal charge polarity of the toner does not have to be satisfied.
Also, the values used for the first and second DC voltages are not limited thereto, and may be desirably selected. However, since the relationship between the remaining toner amount and the toner amount in the supply roller 24 is changed by using the voltages with different values ΔV as described above, this embodiment does not include a configuration using the same voltage.
Further, the supply roller rotation time required so that the toner amount in the supply roller 24 becomes stable depends on, for example, the rotation speed of the supply roller 24. Hence, the first and second predetermined times are not limited to the values according to this embodiment, and do not have to be the same. Further, in this embodiment, the potential of the shaft 25a of the development roller 25 is fixed whereas the potential of the shaft 24a of the supply roller 24 is changed by the plurality of steps when the first DC voltage is applied and when the second DC voltage is applied. However, required herein is that the potential difference between the shafts 25a and 24a is changed. Hence, the potential of the shaft 25a may be changed.
An image forming apparatus according to a third embodiment of the present invention has a basic configuration similar to the image forming apparatus in
The same reference signs refer the members having the same configurations and functions as those of the first embodiment. Also, redundant description will be omitted except for the high accuracy detection mode.
Only feature part of the embodiment will be described.
As mentioned above, the image forming apparatus of this embodiment includes the drive-P 60 (
The high accuracy detection mode that is a feature of this embodiment will be described with reference to FIG. 18. If a pixel count integrated value Pcount of a certain developing device reaches the predetermined value Pth, after developing, the high accuracy detection mode is started (S005, S400). First, the state is brought into the drive transmission enabled state (S401). To change the toner amount in the foam layer of the supply roller 24, the supply roller 24 is rotated at a first rotation speed for a first predetermined time (S402). The first rotation speed is a rotation speed during normal image formation. This rotation speed is defined as 100%. The rotation time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the rotation time is 15 seconds. After the rotation for 15 seconds, to measure the remaining toner amount, the development roller 25 is separated from the photosensitive drum 1, and the rotation of the development roller 25 and the supply roller 24 is stopped (S403). Then, a first capacitance C1 is measured (S404).
Then, the state is brought into the drive transmission enabled state again (S405). To change the toner amount in the foam layer of the supply roller 24, the supply roller 24 is rotated at a second rotation speed for a second predetermined time (S406). When the rotation speed during the normal image formation is 100%, the second rotation speed is 40%. The rotation time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the rotation time is 40 seconds.
After the rotation for 40 seconds, to measure the remaining toner amount, the development roller 25 is separated from the photosensitive drum 1, and the rotation of the development roller 25 and the supply roller 24 is stopped (S407). Then, a second capacitance C2 is measured (S408). (Since the toner amount in the supply roller 24 becomes stable faster if the rotation speed is a higher rotation speed of the first and second rotation speeds, the rotation time at the higher rotation speed is shorter than the rotation time at a lower rotation speed. Accordingly, the time required for the high accuracy detection mode can be reduced as compared with the case in which the rotation time at the higher rotation speed is longer than the rotation time at the lower rotation speed.)
When an absolute value |C1−C2| of the difference between the detected capacitances C1 and C2 is ΔC, the relationship between ΔC and the remaining toner amount in the developing device 5 provides the result similar to one illustrated in
Here, the physical meaning in this embodiment of the correlation between the capacitance difference and the toner amount in the cartridge 21 will be discussed on the basis of the observed result of the developing device 5.
The inventors of the present invention found that the relationship between the remaining toner amount and the toner amount in the supply roller 24 was changed by the rotation speed of the supply roller 24.
From the observed result by the inventors of the present invention, it was found that the discharged amount of the toner to the portion X (
In contrast, when the toner remains in the cartridge 21 by a very small amount (point B), the toner in the portion Y (
Consequently, the relationship between the toner amount in the cartridge 21 and the toner amount in the supply roller 24 becomes one shown in
With regard to the above-described points, the advantage according to this embodiment of the present invention will be described in detail.
In this embodiment, the first rotation speed of the supply roller 24 is high, and the subsequent second rotation speed is low in the high accuracy detection mode. This is because if the high accuracy detection mode is ended after the rotation at the low speed, the supply roller 24 can contain the toner by a large amount for the next image formation. Accordingly, an image with a low density or an image with an unprinted portion is less frequently generated even if an image with a high coverage rate is output after the high accuracy detection mode. However, to obtain the advantage according to the present invention of highly accurately measuring the remaining toner amount even if the temperature and humidity environment is changed, the rotation speeds do not have to be set in that order.
An image forming apparatus according to a fourth embodiment of the present invention has a basic configuration similar to the image forming apparatus in
The same reference signs refer the members having the same configurations and functions as those of the second embodiment. Also, redundant description will be omitted except for the high accuracy detection mode.
Only feature part of the embodiment will be described.
As mentioned above, the image forming apparatus of this embodiment includes the drive-P 60 (
The high accuracy detection mode that is a feature of this embodiment will be described with reference to
After the rotation for 15 seconds, the developing device 5 is moved to the detection position E (S503), and a first capacitance C1 is measured (S504). Then, the developing device 5 is moved to the development position C again (S505). To change the toner amount in the foam layer of the supply roller 24, the supply roller 24 is rotated at this position at a second rotation speed that is lower than the first rotation speed, for a second predetermined time (S506). The second rotation speed is 40% of the rotation speed during normal image formation. The second rotation time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the second rotation time is 30 seconds. Then, the developing device 5 is moved to the detection position E (S507), and a second capacitance C2 is measured (S508).
An absolute value |C1−C2| of the difference between the detected capacitances C1 and C2 is ΔC. In this embodiment, by using the calculated value ΔC, it is determined whether ΔC exceeds a threshold through the flow shown in
This embodiment uses the drive-P 60 functioning as the changing unit like the third embodiment. This embodiment provides an advantage on account of the use of the rotary drum 50, in addition to the advantage attained in the third embodiment. The advantage will be described. The capacitance difference ΔC in this embodiment has a tendency as shown in
The supply roller 24 is supplied with the toner mainly through suction from the portion Y. Hence, by conveying the toner to the portion Y by the rotation of the rotary drum 50, the toner in the supply roller 24 can be increased. When the supply roller 24 is rotated at the high speed, the amount of the toner discharged to the portion X is larger than the amount of the toner supplied from the portion Y. Hence, the toner amount hardly varies depending on whether the rotary drum 50 is rotated or not. However, if the supply roller 24 is rotated at the low speed, since the discharge amount of the toner to the portion X is small, the supply roller 24 is supplied with the toner mainly through the suction from the portion Y. Accordingly, the supply roller 24 easily sucks the toner. The capacitance does not markedly change after the rotation at the high speed, whereas the capacitance increases after the rotation at the low speed. The capacitance difference is larger as compared with a configuration without the rotary drum 50. If the toner amount is very small, the toner in the portion Y is used up. The toner amount in the supply roller 24 becomes small after the rotation at the low speed. The case with the rotation of the rotary drum 50 is no longer different from the third embodiment.
Hence, the inclination of the capacitance difference ΔC with respect to the toner amount in the cartridge 21 is larger than that of the third embodiment. That is, the variation in remaining toner amount is smaller than the variation appearing during the detection for the capacitance difference ΔC in the third embodiment. The remaining toner amount and the replacement of the developing device 5 can be highly accurately notified.
For another advantage of the rotary drum 50, since the toner is conveyed to the portion Y through the rotation of the rotary drum 50, the supply roller 24 can easily suck the toner. Thus, the toner amount in the supply roller 24 can become stable faster during the rotation at the low speed. Accordingly the rotation time at the low speed can be reduced. The rotary drum 50 attains another advantage such that the toner is hardly affected even if the toner is left for a long period because the toner is stirred by the rotation of the rotary drum 50. Thus, the toner amount in the supply roller 24 becomes stable after the rotation of the supply roller 24. The variation in capacitance can be reduced.
An image forming apparatus according to a fifth embodiment of the present invention has a basic configuration similar to the image forming apparatus in
The same reference signs refer the members having the same configurations and functions as those of the first embodiment. Also, redundant description will be partly omitted except for the high accuracy detection mode.
Only feature part of the embodiment will be described.
The developing device 5 will be described in detail below with reference to
A separation distance between the development roller 25 and the photosensitive drum 1 is determined by a rotation phase of the cam 20. At the same time, the posture of the developing device 5 is determined. A swing center 30 shown in
Although described later, required herein is that the developing device 5 allows the supply roller 24 to be rotatable at a plurality of different posture steps in order to measure capacitances after the supply roller 24 is rotated to the plurality of different posture steps. For example, a plurality of drives may be provided to transmit driving forces to the supply roller 24 so that the supply roller 24 can be rotated to the different posture steps.
During image formation, while the development roller 25 is in contact with the photosensitive drum 1, the developing device 5 has a posture of Δy=4.5 mm where Δy is a difference y1−y2 between a top position y1 of the supply roller 24 and a top position y2 of the development roller 25 in the y-axis direction, which is directed upward in the vertical direction, as shown in
The high accuracy detection mode that is a feature of the present invention will be described with reference to
At the first posture, referring to
The cam 20 is rotated, and the posture of the developing device 5 is changed by the drive-P 60 to the second posture that is in the drive transmission enabled state (S605). To change the toner amount in the foam layer of the supply roller 24 again, the supply roller 24 is rotated at a predetermined rotation speed for a second predetermined time (S606). At the second posture, referring to
The rotation time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the rotation time is 25 seconds. After the rotation for the second predetermined time, to measure the remaining toner amount, the rotation of the development roller 25 and the supply roller 24 is stopped. The posture of the developing device 5 is changed again to the first posture for the measurement of the first capacitance C1 by the rotation of the cam 20 (S607). However, the developing device 5 does not have to be brought into the first posture in S607 if electric contact is provided for the developing device 5 so that the capacitance can be detected even at the second posture. Then, a second capacitance C2 is measured (S608).
In this embodiment, the development roller 25 is separated from the photosensitive drum 1 at both the first and second postures when the supply roller 24 is rotated, in order to prevent the photosensitive drum 1 from being scratched by the development roller 25. However, to attain the advantage of the present invention, the supply roller 24 may be rotated while the development roller 25 is in contact with the photosensitive drum 1 as long as the first and second postures provides the different heights of the top of the toner supply member with respect to the top of the toner bearing member.
When an absolute value |C1−C2| of the difference between the detected capacitances C1 and C2 is ΔC, the relationship between ΔC and the remaining toner amount in the developing device 5 becomes similar to one illustrated in
In this embodiment, by using the calculated value ΔC, it is determined whether ΔC exceeds a threshold through the flow shown in
Here, the physical meaning of the correlation between the capacitance difference and the remaining toner amount in the cartridge 21 will be discussed on the basis of the observed result of the developing device 5.
The inventors of the present invention found that the relationship between the remaining toner amount and the toner amount in the supply roller 24 was changed by the posture of the developing device 5 when the supply roller 24 was rotated.
From the observed result by the inventors of the present invention, it was found that the toner could not move across the top of the supply roller 24 from the portion X to the portion Y in a direction opposite to the rotating direction of the supply roller 24 around the supply roller 24 as shown in
Also, when the remaining toner amount in the cartridge 21 is very small (point B in
Consequently, the relationship between the remaining toner amount in the cartridge 21 and the toner amount in the supply roller 24 becomes one shown in
With regard to the above-described points, the advantage according to this embodiment of the present invention will be described in detail.
With these results, the influence by the temperature and humidity to the capacitance is substantially equivalent even if the posture of the developing device 5 is changed. Accordingly, if the capacitance differences at the respective postures are used as parameters for detecting the remaining toner amount, the influence by the change in environment to the capacitance can be canceled. By measuring the remaining toner amount with the difference detection method according to this embodiment, even if the temperature and humidity environment is changed, the remaining toner amount can be highly accurately measured without the temperature sensor or the humidity sensor. Thus, a user can be notified with high accuracy that the remaining toner amount is smaller than a predetermined amount or that a cartridge 21 has to be replaced, without a temperature sensor or a humidity sensor even if the temperature and humidity environment is changed.
In this embodiment, the difference Δy″=y1″−y2″ between the top position of the supply roller 24 and the top position of the development roller 25 at the second posture is smaller than the difference Δy′=y1′−y2′ between the top position of the supply roller 24 and the top position of the development roller 25 at the first posture, for the rotation of the supply roller 24 in the high accuracy detection mode. The differences Δy′ and Δy″ include negative values, and Δy′>Δy″ is established.
Hence, if the high accuracy detection mode is ended after the rotation at the posture with the small value of Δy″, the development can be started for the following image formation when the supply roller 24 contains a large amount of toner. Accordingly, an image with a low density or an image with an unprinted portion is less frequently generated even if an image with a high coverage rate is output after the high accuracy detection mode. However, to obtain the advantage according to the present invention of highly accurately measuring the remaining toner amount even if the temperature and humidity environment is changed, the postures of the developing device 5 during the rotation of the supply roller 24 do not have to be set in that order.
Also, in this embodiment, the rotation speed of the supply roller 24 in the high accuracy detection mode is lower than the rotation speed during the image formation. Accordingly, the remaining toner amount can be further highly accurately measured. The resulting advantage will be described below with reference to
In contrast, if the toner amount in the cartridge 21 is very small, the toner amount in the portion Y is small. The capacitance difference ΔC is not substantially changed by the change in rotation speed. If the low-speed rotation is selected, the inclination of the capacitance difference ΔC becomes large with respect to the remaining toner amount in the cartridge 21. If the inclination of the capacitance difference ΔC becomes large, the variation in remaining toner amount becomes smaller than the variation appearing during the detection for the capacitance difference ΔC. The remaining toner amount can be highly accurately detected. As described above, by changing the rotation speed of the supply roller 24 to the lower rotation speed as compared with the speed during the image formation like this embodiment, the remaining toner amount can be highly accurately measured.
The supply roller rotation time required so that the toner amount in the supply roller 24 becomes stable depends on, for example, the rotation speed of the supply roller 24. Hence, the first and second predetermined times are not limited to the values according to this embodiment, and may be the same or different.
An image forming apparatus according to a sixth embodiment of the present invention has a basic configuration similar to the image forming apparatus in
Only feature part of the embodiment will be described.
The developing device 5 used in the sixth embodiment has a configuration similar to the configuration of the developing device used in the fifth embodiment shown in
In this embodiment, the posture of the developing device 5 can be changed to a plurality of postures at which the supply roller 24 is rotatable like the fifth embodiment. The posture of the developing device 5 is changed when the drive-Q 60 (second drive) provided in the apparatus body of the image forming apparatus rotates the rotary drum 50 that supports the developing device 5. In other words, the posture of the developing device 5 is changed to a desirable posture when the position of the developing device 5 relative to the center of the rotary drum 50 is changed, the position which is determined by a rotation phase of the rotary drum 50.
In this embodiment, an Oldham coupling is used. Hence, driving forces are transmitted from the drive-P 60 (first drive) provided in the apparatus body of the image forming apparatus to the development roller 25 and the supply roller 24 through the Oldham coupling while the developing device 5 is located at any of different development positions. In this embodiment, though described later, the supply roller 24 can be rotated when the developing device 5 is located at two separation positions F (part (a) in
Next, a method for measuring a remaining toner amount of the developing device 5 according to this embodiment will be described. The method for measuring the remaining toner amount is basically similar to that of the first embodiment, and hence, only feature part of this embodiment will be described. In this embodiment, the developing device 5 as the subject of detection for the remaining toner amount is provided on a rotary support member, i.e., the rotary drum 50. The drive-Q 60 (second drive) rotates the rotary drum 50, so that the developing device 5 is moved to a detection position E for measurement. The detection position E is the position of the developing device 5c in
At the detection position E, since a toner around the supply roller 24 is dropped by own weight, the influence of the toner near the supply roller 24 can be reduced. Accordingly, the toner near the supply roller 24 hardly disturbs the detection. The toner amount in the supply roller 24 can be correctly measured.
The operation during the high accuracy detection mode after the flow shown in
To change the toner amount in the foam layer of the supply roller 24, the supply roller 24 is rotated at this position at a predetermined rotation speed for a first predetermined rotation time (S702). The rotation speed of the supply roller 24 used herein is 40% of the rotation speed of the supply roller 24 during the normal image formation. The rotation time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the rotation time is 40 seconds. After the rotation for the predetermined time, the developing device 5 is moved to a capacitance measurement position E (S703), and a first capacitance C1 is measured (S704). Then, the developing device 5 is moved to a supply roller rotation position G serving as a second posture by the rotation of the rotary drum 50 (S705). At the second posture, referring to
The rotation time is determined so that the toner amount in the supply roller 24 becomes stable. In this embodiment, the rotation time is 20 seconds. Then, the developing device 5 is moved to the capacitance measurement position E (S707), and a second capacitance C2 is measured (S708). Similarly to the first embodiment, at the first and second postures when the supply roller 24 is rotated, the development roller 25 does not have to be separated from the photosensitive drum 1.
An absolute value |C1−C2| of the difference between the detected capacitances C1 and C2 is ΔC. In this embodiment, ΔC in accordance with the remaining toner amount is shown in
In this embodiment, the influence by the temperature and humidity to the capacitance is substantially equivalent even if the posture of the developing device 5 is changed. Accordingly, if the capacitance differences at the respective postures are used as parameters for detecting the remaining toner amount, the influence by the change in environment to the capacitance can be canceled. By measuring the remaining toner amount with the difference detection method according to this embodiment, even if the temperature and humidity environment is changed, the remaining toner amount can be highly accurately measured without the temperature sensor or the humidity sensor. Thus, a user can be notified with high accuracy that the remaining toner amount is smaller than a predetermined amount or that the cartridge 21 has to be replaced, without the temperature sensor or the humidity sensor even if the temperature and humidity environment is changed.
This embodiment provides an advantage on account of the use of the rotary drum 50. The advantage will be described.
Since the rotary drum 50 is used as the posture changing device in this embodiment, the advantage of this embodiment can be attained while a cam member or the like does not have to be newly added for changing the posture unlike the fifth embodiment.
Since the supply roller 24 is supplied with the toner mainly through the suction from the portion Y, if the toner is conveyed to the portion Y by the rotation of the rotary drum 50, the toner is easily sucked to the supply roller 24 when the supply roller 24 is rotated. The toner amount in the supply roller 24 can become stable quickly. In particular, when the supply roller 24 is rotated at the low speed, the discharge amount of the toner to the portion X is small. The suction of the toner to the supply roller 24 from the portion Y is predominant over the discharge of the toner to the portion X. As the result, the supply roller 24 sucks the toner more quickly, and the rotation time can be reduced. Accordingly, in this embodiment, by sending the toner to the portion Y by the rotation of the rotary drum 50, the toner amount in the supply roller 24 can become stable with a reduced supply roller rotation time as compared with the fifth embodiment. The supply roller rotation time can be reduced.
With the configuration of this embodiment, the toner is moved as described above before the supply roller 24 is rotated. However, referring to
The rotary drum 50 attains another advantage such that the toner is hardly affected even if the toner is left for a long period because the toner is stirred by the rotation of the rotary drum 50. Thus, the toner amount in the supply roller 24 becomes stable after the rotation of the supply roller 24. The variation in capacitance can be reduced.
The supply roller rotation time required so that the toner amount in the supply roller 24 becomes stable depends on, for example, the rotation speed of the supply roller 24. Hence, the first and second predetermined times are not limited to the values according to this embodiment, and may be the same or different.
An image forming apparatus according to a seventh embodiment of the present invention has a basic configuration similar to the image forming apparatus in
The flow of the high accuracy detection mode that is a feature of this embodiment and the movement of the rotary drum 50 will be described with reference to
Then, the developing device 5 is moved to the supply roller rotation position again (S805). To change the toner amount contained in the foam layer of the supply roller 24 again, the supply roller 24 is rotated at this position for 3 seconds as a second predetermined time t2, so that the toner amount in the foam layer becomes larger than the toner amount in the foam layer at the detection of C1 (S806). Hereinafter, the rotation operation of the supply roller 24 here is called suction mode. Then, the developing device 5 is moved to the toner remaining amount detection position (S807), and a second capacitance C2 is measured (S808).
Although the rotary drum 50 is rotated, unless the rotation causes the toner to be moved toward the portion Y as shown in
When an absolute value |C1−C2| of the difference between the detected capacitances C1 and C2 is ΔC, the relationship between ΔC and the remaining toner amount in the developing device 5 becomes similar to one illustrated in
Here, the physical meaning of the correlation between the capacitance difference and the toner amount in the cartridge 21 will be discussed on the basis of the observed result of the developing device 5.
The inventors of the present invention found that the relationship between the rotation time of the supply toner 24 and the toner amount in the supply roller 24 was changed by the remaining toner amount.
From the observed result by the inventors of the present invention, it was found that the balance between the discharge and the suction was changed in accordance with the rotation time. This phenomenon will be discussed.
Hence, the toner is sucked by a large amount in the portion Y at the moment of the decompression. Since the toner is mainly sucked into the supply roller 24 from the portion Y, the state of the toner in the portion Y affects the toner amount in the supply roller 24. If the toner amount in the portion Y is small, it may be difficult to supply the supply roller 24 with the toner. The toner amount in the supply roller 24 decreases. Accordingly, when the toner is conveyed to the portion Y by the rotation of the rotary drum 50, the toner in the supply roller 24 can be increased. Since the supply roller 24 is supplied with the toner for a while even after the rotation of the rotary drum 50, the toner in the supply roller 24 increases. If the toner in the portion Y is used up, the toner is no longer provided from the portion Y, and the influence by the discharge from the portion X becomes large. Thus, the toner amount in the supply roller 24 may decrease.
When the toner amount in the cartridge 21 is very small (point B), the toner amount in the portion X shown in
Consequently, the relationship between the toner amount in the cartridge 21 and the toner amount in the supply roller 24 becomes one shown in
With regard to the above-described points, the advantage according to this embodiment of the present invention will be described in detail.
Accordingly, if the capacitance differences for the suction mode and the discharge mode are used as parameters for detecting the remaining toner amount, the influence by the change in environment to the capacitance can be canceled. By measuring the remaining toner amount with the difference detection method according to this embodiment, even if the temperature and humidity environment is changed, the remaining toner amount can be highly accurately measured without the temperature sensor or the humidity sensor. Thus, a user can be notified with high accuracy that the remaining toner amount is smaller than a predetermined amount or that the cartridge 21 has to be replaced, without the temperature sensor or the humidity sensor even if the temperature and humidity environment is changed.
In this embodiment, the first rotation time of the supply roller 24 is the discharge mode and the second rotation time of the next rotation is the suction mode. This is because if the high accuracy detection mode is ended after the suction mode, the supply roller 24 can contain the toner by a large amount for the next image formation. Accordingly, an image with a low density or an image with an unprinted portion is less frequently generated even if an image with a high coverage rate is output after the high accuracy detection mode.
An image forming apparatus according to an eighth embodiment of the present invention has a basic configuration similar to the image forming apparatus in
In this embodiment, the developing device 5 as the subject of detection for the remaining toner amount is provided on a rotary support member, i.e., a rotary drum 50. A drive-Q 60 (second drive) rotates the rotary drum 50, so that the developing device 5 is moved, the toner is stirred, and the developing device 5 is moved to a toner remaining amount detection position F. The detection position F is the position of a developing device 5a in
The time t1 is 3 seconds in this embodiment because this time causes the toner amount in the supply roller 24 to exceed a maximum value once like the first embodiment. Then, a first capacitance C1 is measured (S903). The capacitance is measured while the supply roller 24 is rotated by the drive-P 60. After C1 is measured, to change the toner amount in the foam layer of the supply roller 24, the supply roller 24 is rotated for a second predetermined time t2 (10 seconds) that causes the toner in the supply roller 24 to be sufficiently discharged (S904). Then, a second capacitance C2 is measured (S905). When an absolute value |C1−C2| of the difference between the detected capacitances C1 and C2 is ΔC, the relationship between ΔC and the remaining toner amount in the developing device 5 becomes similar to one illustrated in
As described above, in this embodiment, the rotary drum 50 is rotated first, and then the capacitance is measured at the position, at which developing can be performed, while the supply roller 24 is rotated. Accordingly, the capacitance can be continuously measured without the rotary drum 50 is rotated between the measurement of C1 and the measurement of C2 unlike the seventh embodiment. The measurement time can be reduced as compared with the seventh embodiment.
Also, in the seventh embodiment, the toner is not moved to the portion Y in the cartridge 21 by the rotation of the rotary drum 50 before the supply roller 24 is rotated for the first predetermined time, and the start point of the toner amount in the curve shown in
In this embodiment, the toner is moved to the portion Y by the rotation of the rotary drum 50 and then the capacitance is detected two times while the supply roller 24 is rotated. Alternatively, the capacitance may be detected three times or more until the reduction ratio of the capacitance with respect to the rotation time of the supply roller 24 becomes below a predetermined value. The details are described below.
Thus obtained ΔC is used for notifying a user about the remaining toner amount and the replacement of the cartridge 21 through the flow in
As described above, since the toner is moved to the portion Y by the rotation of the rotary drum 50 and then the capacitance is detected three times or more while the supply roller 24 is rotated, the change in capacitance can be monitored. By using the highest capacitance and the lowest capacitance, a large value can be obtained as the absolute value of the capacitance difference. The change in absolute value of the capacitance difference becomes large as compared with the change in remaining toner amount. Accordingly, the remaining toner amount and the replacement timing of the cartridge 21 can be highly accurately notified.
According to the present invention, like the high accuracy detection mode described in any of the first to eighth embodiments, the remaining toner amount can be detected by using |C1−C2| as long as a predetermined period for changing the toner amount in the foam layer by rotating the supply roller is provided between the measurement of the capacitance C1 and the measurement of the capacitance C2. Thus, a user can be notified with high accuracy that the remaining toner amount is smaller than a predetermined amount or that the cartridge has to be replaced, without the temperature sensor or the humidity sensor even if the temperature and humidity environment is changed. Also, since the supply roller is rotated for the predetermined period even before the measurement of the capacitance C1, the change in toner amount in the foam layer resulted from image formation before the high accuracy detection mode is executed can be reduced. The value that is more stable than the capacitance C1 can be measured. Accordingly, the notification can be performed highly accurately.
In addition, with the high accuracy detection mode described in any of the first to eighth embodiments, the operation from the measurement of the capacitance C1 to the measurement of the capacitance C2 is continuously performed. The operation is desirably performed continuously. However, it is not limited thereto unless the environment and the toner amount in the cartridge are not markedly changed between the measurement of C1 and the measurement of C2. For example, if an image has a low coverage ratio, the image may be printed for several sheets between the measurement of C1 and the measurement of C2.
Also, in the high accuracy detection mode described in any of the first to eighth embodiments, the supply roller and the development roller are rotated for the predetermined period for changing the toner amount in the foam layer. However, only the supply roller may be rotated to allow the toner to be sucked into and discharged from the foam layer.
Further, in any of the first to eighth embodiments, only the developing device is the cartridge that can be mounted on the apparatus body of the image forming apparatus in a replaceable manner. However, a combined cartridge in which the developing device and the photosensitive drum are integrally formed can be mounted on the apparatus body of the image forming apparatus in a replaceable manner.
Further, the notice content by the notice signal generating unit according to the present invention may be a notice that notifies the user about the toner amount being smaller than the predetermined amount and promotes the user to replace the developing device. For example, a display of the apparatus body of the image forming apparatus, or a display of a PC that is connected with the image forming apparatus through a network may display notices such as “remaining toner amount is small,” “toner is run out,” and “replace cartridge.” That is, it is obvious that the notification can be made even if the apparatus body of the image forming apparatus does not have a display. Further, by setting a plurality of thresholds, the toner amount can be detected stepwise. Accordingly, the remaining toner amount can be notified stepwise for the user.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2009-243768 | Oct 2009 | JP | national |
| 2009-283456 | Dec 2009 | JP | national |
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| 2010-003027 | Jan 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2010/068772 | 10/18/2010 | WO | 00 | 3/13/2012 |
| Publishing Document | Publishing Date | Country | Kind |
|---|---|---|---|
| WO2011/049219 | 4/28/2011 | WO | A |
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| Number | Date | Country | |
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| 20120195611 A1 | Aug 2012 | US |
