Patent Application
20140186062
1. Field of the Invention
The present invention relates to a developer container unit used for an image forming apparatus.
2. Description of the Related Art
Some existing developer container units used for image forming apparatuses, such as electrophotographic printers, include a detection mechanism that uses a piezoelectric element to detect the remaining amount of developer.
Japanese Patent Laid-Open No. 3-271785 describes an image forming apparatus that detects the amount of developer in a developer container unit on the basis of a pressure that the developer applies to a polymer piezoelectric plate that is attached to an agitation plate of an agitation member for agitating the developer. This agitation plate is a substantially rigid plate that does not deform. The polymer piezoelectric plate detects the amount of developer on the basis of a pressure applied thereto in the thickness direction.
It is difficult for the existing image forming apparatus described above to detect the amount of developer with high accuracy because the output from the polymer piezoelectric plate is limited to an output caused by strain of the piezoelectric plate in the thickness direction. The present invention provides an improved developer container unit that can detect the amount of developer with high accuracy.
According to an aspect of the present disclosure, a developer container unit includes a container containing developer and a piezoelectric film for detecting an amount of developer in the container. A sensitivity of the piezoelectric film to a stress in a direction parallel to a film surface is greater than a sensitivity of the piezoelectric film to a stress in a direction perpendicular to the film surface, and the piezoelectric film is deformable with a movement thereof relative to the developer.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
First, the overall structure of an electrophotographic image forming apparatus will be described.
The image forming apparatus 100 includes first, second, third, and fourth image forming units SY, SM, SC, and SK, which respectively form yellow (Y), magenta (M), cyan (C), and black (K) images. In the first embodiment, the first to fourth image forming units SY, SM, SC, and SK are arranged along a line that intersects the vertical direction.
In the first embodiment, the first to fourth image forming units have substantially the same structure and are operated in substantially the same way, except that they form images of different colors. Therefore, hereinafter, the characters Y, M, C, and K for denoting the colors will be omitted unless it is necessary to discriminate between the colors.
The image forming apparatus 100 includes four photoconductor drums 1 (electrophotographic photoconductors) that are arranged along a line that intersects the vertical direction. Each of the photoconductor drums 1 corresponds to an image carrier. The photoconductor drum 1 is rotated by a driving unit (not shown) in the direction of arrow A (clockwise direction) in
The developing unit 4 uses a non-magnetic single component toner as a developer. In the first embodiment, the developing unit 4 performs reversal development by making the developing roller (described below), which is a developer carrying member, contact the photoconductor drum 1. To be specific, in the first embodiment, the developing unit 4 develops an electrostatic image by making toner, which has been charged so as to have a polarity the same as that of the photoconductor drum 1 (in the first embodiment, a negative polarity), adhere to a portion (image portion, exposed portion) of the photoconductor drum 1 at which the charge has been weakened by irradiation of a laser beam.
The photoconductor drum 1, the charge roller 2 (a process unit acting on the photoconductor drum 1), the developing unit 4, and the cleaning member 6 are integrated with each other and constitute a process cartridge 7. The process cartridge 7 is attachable to and removable from the image forming apparatus 100 by means of attachment members, such as a guide member and a positioning member, which are disposed in the image forming apparatus body. In the first embodiment, all of the process cartridges 7 have the same shape and respectively contain yellow (Y), magenta (M), cyan (C), and black (K) toners.
The intermediate transfer belt 5 (intermediate transfer body) is an endless belt that is in contact with all of the photoconductor drums 1. The intermediate transfer belt 5 moves around (rotates) in the direction of arrow B (counterclockwise direction) in
Four primary transfer rollers 8 (primary transfer units) are arranged along an inner peripheral surface of the intermediate transfer belt 5 so as to respectively face the four photoconductor drums 1. Each of the primary transfer rollers 8 presses the intermediate transfer belt 5 toward a corresponding one of the photoconductor drums 1 and forms a primary transfer region N1 at which the intermediate transfer belt 5 and the photoconductor drum 1 contact each other. To each of the primary transfer rollers 8, a bias voltage having a polarity opposite to a regular polarity of the charge of toner is applied by a primary transfer bias power source (high-voltage power supply, not shown), which is a primary transfer bias application unit. Thus, toner images on the photoconductor drums 1 are transferred (primarily transferred) to the intermediate transfer belt 5.
A secondary transfer roller 9 (second transfer unit) is disposed outside of the intermediate transfer belt 5 at a position facing the secondary transfer opposing roller 52. The secondary transfer roller 9 is in pressed against the secondary transfer opposing roller 52 with the intermediate transfer belt 5 therebetween so as to form a secondary transfer region N2 at which the intermediate transfer belt 5 and the secondary transfer roller 9 contact each other. To the secondary transfer roller 9, a bias voltage having a polarity opposite to the regular polarity of the charge of toner is applied by a secondary transfer bias power source (high-voltage power supply, not shown), which is a secondary transfer bias application unit. Thus, toner images on the intermediate transfer belt 5 are transferred (secondarily transferred) to the recording medium 12.
When the image forming apparatus 100 forms an image, first, the charge roller 2 uniformly charges the surface of the photoconductor drum 1. Next, the scanner unit 3 emits a laser beam on the basis of image information, the charged surface of the photoconductor drum 1 is scanned by the laser beam, and thereby an electrostatic image based on the image information is formed on the photoconductor drum 1. Next, the developing unit 4 develops the electrostatic image formed on the photoconductor drum 1 into a toner image. The primary transfer roller 8 transfers (primarily transfers) the toner image formed on the photoconductor drum 1 to the intermediate transfer belt 5.
When forming a full-color image, the first to fourth image forming units SY, SM, SC, and SK successively perform the operation described above, and thereby color toner images are primarily transferred to the intermediate transfer belt 5 in an overlapping manner.
Subsequently, the recording medium 12 is transported to the secondary transfer region N2 in synchronism with the movement of the intermediate transfer belt 5. Then, the secondary transfer roller 9, which is pressed against the intermediate transfer belt 5 with the recording medium 12 therebetween, simultaneously secondarily-transfers the four-color toner images on the intermediate transfer belt 5 to the recording medium 12.
The recording medium 12, to which the toner images have been transferred, is transported to a fixing device 10 (fixing unit). The fixing device 10 applies heat and pressure to the recording medium 12, and thereby the toner images are fixed to the recording medium 12.
The cleaning member 6 removes and recovers toner remaining on the photoconductor drum 1 after the primary transfer operation has been finished. An intermediate transfer belt cleaning device 11 removes toner remaining on the intermediate transfer belt 5 after the secondary transfer operation has been finished.
The image forming apparatus 100 may form a monochrome or a multi-color image by using one or more (but not all of the) image forming units.
The overall structure of the process cartridge 7 mounted in the image forming apparatus 100 according to the first embodiment will be described.
The process cartridge 7 includes a photoconductor unit 13, which includes the photoconductor drum 1 and other components, and the developing unit 4, which includes a developing roller 17 and other components.
The photoconductor unit 13 includes a cleaning frame body 14 for supporting various components of the photoconductor unit 13. The photoconductor drum 1 is rotatably mounted on the cleaning frame body 14 through bearings (not shown). A driving force of a driving motor (not shown) is transmitted to the photoconductor unit 13, and the photoconductor drum 1 is rotated in the direction of arrow A (clockwise direction) in accordance with an image formation operation. The photoconductor drum 1 is a main component for performing an image formation process. The photoconductor drum 1 is an organic photoconductor drum including an aluminum cylinder whose peripheral surface is coated with functional layers, including an undercoat layer, a carrier generating layer, and a carrier transport layer in this order.
The photoconductor unit 13 includes the cleaning member 6 and the charge roller 2, which are in contact with the peripheral surface of the photoconductor drum 1. The cleaning member 6 removes residual toner on the surface of the photoconductor drum 1. The residual toner drops into and is contained in the cleaning frame body 14.
The developing unit 4 includes the developing roller 17, a developing blade 21, a toner supply roller 20, a toner 80 used for development, and a toner container 18.
An agitation member 25 for agitating toner is disposed in the toner container 18. The agitation member 25 includes a rotary shaft 22, an agitation sheet 23 (flexible sheet) one end of which is fixed to the rotary shaft 22, and a piezoelectric film 24 (see
The developing blade 21 is in contact with the developing roller 17 in a counter direction to the developing roller 17. The developing blade 21 regulates the amount of toner with which the surface of the developing roller 17 is coated. The developing blade 21 also charges the toner. The developing blade 21 is a thin plate-shaped member that generates an elastic force with which the developing blade 21 is pressed against the developing roller 17. The surface of the developing blade 21 is in contact with the toner and the developing roller 17. The developing roller 17 rotates in the direction of an arrow D, and the toner is charged with triboelectricity generated by friction between the developing blade 21 and the developing roller 17. At the same time, the developing roller 17 regulates the thickness of the toner. A blade bias power source (not shown) applies a predetermined voltage to the developing blade 21, so that coating with toner can be stably performed.
In a region (contact region) in which the developing roller 17 and the photoconductor drum 1 face each other, the surfaces of the developing roller 17 and the photoconductor drum 1 move in the same direction (in the first embodiment, upward). In the first embodiment, the developing roller 17 is in contact with the photoconductor drum 1. Alternatively, the developing roller 17 may be disposed at a predetermined small distance from the photoconductor drum 1.
In the first embodiment, the toner is negatively charged with triboelectricity. Because a predetermined DC bias is applied to the developing roller 17, an electrostatic latent image is developed into a visible image as the toner is transferred to only exposed portions of the photoconductor drum 1 that have been irradiated with a laser beam.
The toner supply roller 20 and the developing roller 17 are disposed so as to form a nip therebetween. The toner supply roller 20 rotates in the direction of an arrow E in
The developing roller 17 and the toner supply roller 20 each have an outer diameter of φ20, and the developing roller 17 is pressed against the toner supply roller 20 so that the surface of the toner supply roller 20 is recessed by the amount of 1.5 mm.
The sensitivity (piezoelectricity) of the piezoelectric film 24 to a stress in a direction parallel to a film surface is greater than the sensitivity (piezoelectricity) of the piezoelectric film 24 to a stress in a direction perpendicular to the film surface. The sensitivity of the piezoelectric film 24 to a compressive stress is greater than the sensitivity of the piezoelectric film 24 to a tensile stress. In particular, the sensitivity to a tensile stress in a rolling direction, in which the piezoelectric film 24 was rolled in a manufacturing process, is the highest. The piezoelectric film 24 is bonded to the agitation sheet 23 so that the rolling direction is perpendicular to the axial direction of the agitation member 25. The agitation sheet 23 is electrically insulating. As illustrated in
By disposing the piezoelectric film 24 on the agitation sheet 23 as described above, a slight change in toner-powder pressure can be detected by using a piezoelectric film having a relatively small area.
The operational effects of the structure of the first embodiment will be described below in comparison with the structure an agitation member of a related-art example, which is described in Japanese Patent Laid-Open No. 3-271785.
The piezoelectric film is thin and flexible. Because the film is thin and has a very small cross-sectional area, a greater stress is generated by a small tension in a direction parallel to the film surface. In particular, the piezoelectric film has the highest sensitivity to a tension in the rolling direction. The ratio of the standard effective sensitivity in the rolling direction to that in the thickness direction is about 1000:1. With the first embodiment, the toner-powder pressure can be detected with a high sensitivity by effectively utilizing such characteristics of the piezoelectric film 24.
In contrast, with the structure of the first embodiment illustrated in
As illustrated in
In the first embodiment, the agitation sheet 23 has a free end. Therefore, a very small toner-powder pressure can cause a large deformation of the agitation sheet 23 and a large change in voltage.
In the first embodiment, the piezoelectric film 24 is disposed so that the amount of deformation of the piezoelectric film 24 in the rolling direction, in which the piezoelectric film 24 has the highest sensitivity, is greater than the amount of deformation of the piezoelectric film 24 in a direction perpendicular to the rolling direction. However, even if the piezoelectric film 24 is disposed so that the amount of deformation of the piezoelectric film 24 in the width direction perpendicular to the rolling direction is larger, an advantage of a sensitivity greater than that of the related-art example can be obtained in principle. For example, the piezoelectric film 24 may be disposed so that the rolling direction of the piezoelectric film 24 coincides with the axial direction of the rotary shaft 22.
In the first embodiment, the piezoelectric film 24 is affixed to a portion of the agitation sheet 23 that is in the middle in the longitudinal direction and that extends from one end to the other end of the agitation sheet 23 in the transversal direction (radial direction from the rotary shaft). However, this is not a limitation. For example, the piezoelectric film 24 may be affixed only to a portion of the agitation sheet 23 near the free end or to any appropriate portion of the agitation sheet 23 in accordance with the structure of the agitation member and the structure of the developer container.
The relationship between the amount of deformation of the agitation sheet 23 illustrated in
As illustrated in
In the profile illustrated in
Parameters that change in accordance with Remaining Amount of Toner
(i) negative peak voltage occurrence timing Ta, negative peak voltage Va
(ii) toner surface entry timing Tb
(iii) positive peak voltage Vf
(iv) integral value of profile for one cycle of agitation member
examples: integral value α=sum of absolute value of output voltage
integral value β=sum of positive output voltage
integral value γ=sum of negative output voltage
Referring to the profile shown in
When the amount of toner (developer) decreases, the surface of the toner becomes lower (in
Because the surface of the toner becomes lower and the amount of toner agitated by the agitation sheet 23 decreases, the timing at which the amount of deformation of the agitation sheet 23 starts decreasing is advanced, and therefore the negative peak voltage occurrence timing Ta ((i)) is advanced in one rotation cycle of agitation. For the same reason, the maximum amount of deformation of the agitation sheet decreases, the amount of recovery of the agitation sheet 23 decreases, and therefore the negative peak voltage Va decreases.
Because the toner surface becomes lower, the toner surface entry timing Tb ((ii)) is delayed. Because the total amount of toner agitated by the agitation sheet 23 decreases, the maximum amount of deformation of the agitation sheet 23 decreases, and therefore the positive peak voltage Vf ((iii)) decreases.
The integral value of the profile ((iv)) decreases as the surface of the toner become lower decreases and the amount of toner agitated by the agitation sheet 23 decreases.
As illustrated in
The agitation sheet 23 is disposed so that the free end of the agitation sheet 23 does not contact the inner wall of the container at a timing at which the agitation sheet 23 enters through the toner surface (when the agitation sheet 23 is near the positions shown in
In the first embodiment, as illustrated in
The structure and the advantage of the first embodiment are mainly as follows.
The developing unit 4 according to the first embodiment includes the toner container 18 containing toner and the piezoelectric film 24 for detecting the amount of toner in the developer container. The sensitivity of the piezoelectric film 24 to a stress in a direction parallel to a film surface is greater than the sensitivity of the piezoelectric film 24 to a stress in a direction perpendicular to the film surface. Thus, the amount of toner can be detected with high accuracy.
The piezoelectric film 24 is rotatable in the developer container, and the sensitivity of the piezoelectric film 24 to a stress in a direction parallel to the film surface and perpendicular to the rotation axis of the piezoelectric film 24 is greater than the sensitivity of the piezoelectric film to a stress in a direction of the rotation axis. Thus, when the piezoelectric film 24 rotates, a force that the piezoelectric film 24 receives from the toner is efficiently converted into a voltage, and thereby the accuracy of detection of the amount of toner can be further increased. The sensitivity of the piezoelectric film 24 to a stress in the direction parallel to the film surface and perpendicular to the rotation axis of the piezoelectric film 24 is greater than the sensitivity of the piezoelectric film 24 to a stress in any other directions parallel to the film surface. Thus, the accuracy of detection of the amount of toner can be further increased.
The piezoelectric film 24 is integrated with the agitation sheet 23 having an elastic resilience greater than that of the piezoelectric film 24, and the piezoelectric film 24 and the agitation sheet 23 constitute the agitation member 25 that agitates the toner. Thus, high accuracy of detection of the amount of toner and high agitation performance of the agitation member can be both obtained. The piezoelectric film 24 is located at a position separated from a neutral axis of the agitation member 25 in a cross section of the agitation member 25 along a plane perpendicular to the film surface. Thus, the accuracy of detection of the amount of toner can be further increased. The piezoelectric film 24 is disposed on a surface of the agitation member 25 on a downstream side in a rotation direction of the agitation member 25 (see
The length L of the piezoelectric film 24 in a direction perpendicular to the rotary axis of the piezoelectric film 24 is greater than the length W of the piezoelectric film 24 in the direction of the rotation axis. Accordingly, the piezoelectric film 24 can efficiently deform and the accuracy of detection of the amount of toner can be further increased.
The piezoelectric film 24 is disposed close to or in contact with the rotary shaft. Accordingly, the piezoelectric film 24 can be electrically connected to the image forming apparatus body easily.
In the first embodiment, the flexible piezoelectric film 24 is affixed to the flexible agitation sheet 23 so as to be integrated with the flexible agitation sheet 23. Alternatively, the agitation sheet 23 and the piezoelectric film 24 may be disposed so as to be rotatable independently, and the piezoelectric film 24 may be only used to detect the amount of toner.
For example, an advantage the same as that of the first embodiment can be obtained by using an agitation member illustrated in
In the first embodiment, the piezoelectric film 24 is disposed on the surface of the agitation member on the downstream side in the rotation direction of the agitation member. Alternatively, the piezoelectric film 24 may be disposed on the surface of the agitation sheet on the upstream side. Further alternatively, the piezoelectric film 24 may be sandwiched between a plurality of agitation sheets. As long as the piezoelectric film 24 is deformable as described above, an output voltage obtained with the first embodiment is greater than that of existing structures, which is dependent on deformation in the thickness direction. Therefore, the amount of toner can be detected with high accuracy.
In the first embodiment, the piezoelectric film 24 is disposed on the agitation sheet 23. In the second embodiment, the piezoelectric film 24 is independent from the agitation sheet 23, and the piezoelectric film 24 is disposed on the inner wall of the developer container. Components of the second embodiment the same as those of the first embodiment will not be described.
The toner-amount detection member 32 is affixed to a middle portion of the inner wall of the developer container in the longitudinal direction. The width of the toner-amount detection member 32 in the longitudinal direction of the developer container is 10 mm. The length of the toner-amount detection member 32 from a free end to a fixed end that is fixed to the inner wall of the developer container is 20 mm. With such a structure, the accuracy of detection of the amount of toner can be increased while suppressing the influence of decrease in the agitation performance due to the presence of the toner-amount detection member.
As in the first embodiment, electrodes are formed on both surfaces of the piezoelectric film 24, and the electrodes are connected to a voltage detection circuit of the image forming apparatus body. As compared with the first embodiment, the second embodiment can be manufactured easily because the electrodes for detecting the voltage generated in the piezoelectric film have a simpler structure. With the first embodiment, it is necessary to electrically connect the piezoelectric film 24, which is affixed to the agitation sheet 23, to the output voltage detector of the image forming apparatus through sliding electrodes. In contrast, with the second embodiment, it is not necessary to use the sliding electrodes. Instead, it is only necessary to electrically connect the piezoelectric film 24 to the outside of the container through the inner wall of the container.
In the second embodiment, the toner-amount detection member 32 is disposed on the bottom surface of the toner container 18. Thus, after the amount of toner has decreased to a certain level, the amount of deformation of the toner-amount detection member 32 changes for every rotation cycles of the agitation member. The amount of toner can be detected with high accuracy from the profile of voltage generated in the piezoelectric film 24 at this time.
The structure and the advantage of the second embodiment are mainly as follows.
The developing unit 4 according to the second embodiment includes the toner container 18 containing toner and the piezoelectric film 24 for detecting the amount of toner in the developer container. The sensitivity of the piezoelectric film 24 to a stress in a direction parallel to a film surface is greater than the sensitivity of the piezoelectric film 24 to a stress in a direction perpendicular to the film surface. Thus, as in the first embodiment, the amount of toner can be detected with high accuracy.
The piezoelectric film 24 is integrated with the flexible sheet 35 having an elastic resilience greater than that of the piezoelectric film 24, and the piezoelectric film 24 and the flexible sheet 35 constitute the toner-amount detection member 32. The toner-amount detection member 32 is attached to the inner wall of the toner container 18, and the toner-amount detection member 32 deforms when the agitation member 33 agitates the toner. Thus, the piezoelectric film 24 easily returns to its original shape after deforming as the agitation member 33 agitates the toner. Therefore, the accuracy of detection of the amount of toner can be increased. As compared with the first embodiment, the structure of electrical contacts connected to the piezoelectric film 24 can be simplified.
The piezoelectric film 24 is located at a position separated from the neutral axis of the toner-amount detection member 32. Thus, the accuracy of detection of the amount of toner can be further increased. The piezoelectric film 24 is disposed on the surface of the toner-amount detection member 32 on the upstream side in the rotation direction of the agitation member 33. Thus, when the agitation member 33 rotates, the piezoelectric film 24 can efficiently deform, and the accuracy of detection of the amount of toner can be further increased.
In the second embodiment, the agitation member 33 is disposed so that the agitation member 33 contacts the toner-amount detection member 32 while the agitation member 33 agitates the toner. By doing so, it is possible to detect an output voltage that is specifically generated at the instant at which the agitation member 33 contacts the toner-amount detection member 32. Therefore, as compared with the first embodiment, the rotation phase of the agitation member can be easily detected in principle. Accordingly, the accuracy of analysis the output voltage is increased and the accuracy of detection is increased.
In the second embodiment, the toner-amount detection member 32 is disposed on the inner wall of the developer container so as to have a free end. Alternatively, the toner-amount detection member 32 may be rolled up and disposed as illustrated in
In the second embodiment, the piezoelectric film 24 and the flexible sheet 35 are integrated with each other. Alternatively, only the piezoelectric film 24 may be attached to the inner wall of the developer container. By doing so, as compared with the first embodiment, the structure of electrical contacts connected to the piezoelectric film can be simplified. In this case, in order to facilitate detection of the rotation phase of the agitation member 33, the agitation member 33 may be disposed so as to contact the piezoelectric film when agitating the toner.
In the second embodiment, the piezoelectric film 24 is disposed on the surface of the toner-amount detection member 32 on the upstream side in the rotation direction of the agitation member 33. Alternatively, the piezoelectric film 24 may be disposed on the surface of the toner-amount detection member 32 on the downstream side. Further alternatively, the piezoelectric film 24 may be sandwiched between a plurality of flexible sheets. As long as the piezoelectric film 24 is deformable as described above, an output voltage obtained with the second embodiment is higher than that of existing structures, which is dependent on deformation in the thickness direction. Therefore, the amount of toner can be detected with high accuracy.
With the present invention, a developer container unit that can detect the remaining amount of developer with higher accuracy can be provided.
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.
This application claims the benefit of Japanese Patent Application No. 2012-285802, filed Dec. 27, 2012, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-285802 | Dec 2012 | JP | national |
