Patent Application
20210364975
The present invention relates to an image forming apparatus that performs static elimination on a photosensitive drum using light.
It is conventional to eliminate static from a photosensitive drum by irradiating the photosensitive drum with light from a static elimination lamp in image forming apparatuses such as copiers, facsimile machines, printers, and multifunction peripherals. An image forming apparatus includes, for example, an image forming unit (image former), a transfer device, and a fixing device as an image forming mechanism. The image forming unit forms a toner image. The toner image formed is transferred onto paper. The fixing device fixes the transferred toner image to the paper. The paper having the image formed thereon is ejected out of the image forming apparatus.
The image forming unit has a photosensitive drum, a development device, and the like. An electrostatic latent image is formed on the photosensitive drum and developed into a toner image, and the toner image is transferred from the photosensitive drum onto paper. After the toner image has been transferred onto the paper, the photosensitive drum is irradiated with light (static elimination light) from a static elimination lamp to reduce the potential of the photosensitive drum. Thus, static is eliminated from the photosensitive drum, so that a next electrostatic latent image can be formed thereon.
Preferably, a static elimination device including the static elimination lamp performs the static elimination using light having a uniform dose distribution by uniformly irradiating static elimination light onto the photosensitive drum, so that image degradation can be prevented or reduced. Various techniques have been disclosed regarding such a static elimination device.
For example, Japanese Unexamined Patent Application Publication No. 2001-042715 discloses an image forming apparatus including a light path restriction member that restricts static elimination light emitted by a static elimination lamp from being irradiated onto ends of a photosensitive drum.
For another example, Japanese Unexamined Patent Application Publication No. 2017-181878 discloses a static elimination device including: a light source; a light guide member having an end surface (one end surface) that receives incoming light from the light source and an end surface (opposite end surface) opposite to the one end surface; a reflective member that causes the light emitted from the opposite end surface of the light guide member to re-enter the light guide member; and a holding member that holds an opposite end surface-ward end of the light guide member. The light guide member includes, on a surface thereof located away from an image bearing member, a reflective portion that extends in an axial direction and reflects the light incoming through the one end surface. The light guide member also includes a light emission surface which faces the image bearing member and from which the light reflected by the reflective portion is emitted toward the image bearing member. The light guide member has a static elimination region where the light emitted from the light emission surface is irradiated onto the image bearing member and a light-blocking region where the holding member blocks the light emitted from the light emission surface. The static elimination region and the light-blocking region are adjacent to each other in the axial direction. The reflective portion continuously spans across the static elimination region and at least a portion of the light-blocking region.
The image forming apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2001-042715 and the static elimination device disclosed in Japanese Unexamined Patent Application Publication No. 2017-181878 are aimed at uniform static elimination on the photosensitive drum (image bearing member) and reduction of image degradation. Other than the inventions disclosed in Japanese Unexamined Patent Application Publication No. 2001-042715 and Japanese Unexamined Patent Application Publication No. 2017-181878, inventions aimed at uniform static elimination on photosensitive drums have been proposed.
However, the conventional image forming apparatus and the conventional static elimination device described above are not sufficient in terms of uniform static elimination, and an image forming apparatus that achieves higher performance has been desired. In the case of a recent less-expensive model of image forming apparatus including a charging roller, in particular, a light guide plate having a Fresnel pitch is used with a single light source provided at one end thereof, in terms of cost reduction. However, it is difficult to apply such a light guide plate having a Fresnel pitch to the invention disclosed in Japanese Unexamined Patent Application Publication No. 2001-042715. It is possible to apply a light guide plate having a Fresnel pitch to the invention disclosed in Japanese Unexamined Patent Application Publication No. 2017-181878. However, it is difficult to achieve a uniform dose distribution on the image bearing member, and therefore chargeability of the image bearing member tends to be non-uniform in portions around ends thereof.
The present invention has been made in view of the circumstances described above, and an object thereof is to provide an image forming apparatus that achieves cost reduction, static elimination on a photosensitive drum with light having a uniform dose distribution, and prevention or reduction of image degradation.
An image forming apparatus according to an embodiment of the present invention includes: a photosensitive drum; a light guide plate that is disposed with a longitudinal direction thereof being substantially parallel to an axial direction of the photosensitive drum and that irradiates, onto the photosensitive drum, static elimination light incoming through an end thereof by emitting the static elimination light from an irradiation end surface thereof, the irradiation end surface of the light guide plate being a surface facing the photosensitive drum; a light source that emits the static elimination light into the light guide plate, the light source being disposed in the vicinity of the end of the light guide plate; and a blocking member that restricts the static elimination light emitted from the irradiation end surface in a non-uniform manner in the longitudinal direction of the light guide plate, the blocking member being disposed between the light guide plate and the photosensitive drum, and covering the irradiation end surface, wherein the static elimination light emitted from the irradiation end surface includes static elimination light emitted from end regions located around ends of the light guide plate and static elimination light emitted to a central region being a region other than the end regions of the light guide plate, and the static elimination light emitted from the end regions is less restricted by the blocking member than the static elimination light emitted from the central region.
According to this configuration, the static elimination light emitted from the irradiation end surface is irradiated onto the photosensitive drum after being restricted by the blocking member. Portions of the static elimination light emitted from end regions located around ends of the light guide plate are less restricted by the blocking member than a portion emitted to a central region being a region other than the end regions of the light guide plate. According to this configuration, the static elimination light irradiated onto the photosensitive drum achieves a more uniform dose distribution throughout a length of the photosensitive drum in the axial direction (longitudinal direction) of the photosensitive drum. This reduces non-uniformity in chargeability of the photosensitive drum and image unevenness that can occur during image formation.
In the image forming apparatus described above, the blocking member may be a blocking wall having a height that varies according to locations in the longitudinal direction, and being disposed substantially parallel to the axial direction of the photosensitive drum between the light source and the photosensitive drum, and the blocking wall may restrict the static elimination light emitted from the irradiation end surface by blocking the static elimination light.
According to this configuration, the blocking wall restricts the static elimination light emitted from the irradiation end surface. Thus, it is possible to restrict the static elimination light more reliably with a simple configuration.
In the image forming apparatus described above, the height of the blocking wall may be higher in a portion corresponding to the central region than in portions corresponding to the end regions.
According to this configuration, the degree of the restriction on the static elimination light emitted from the irradiation end surface is higher in the central region than in the end regions. Thus, the static elimination light irradiated onto the photosensitive drum achieves a more uniform dose distribution throughout the length of the photosensitive drum in the axial direction (longitudinal direction) of the photosensitive drum. This reduces non-uniformity in chargeability of the photosensitive drum and image unevenness that can occur during image formation.
In the image forming apparatus described above, the blocking wall may be stair-like and have a plurality of levels of height, and boundaries between the different levels of height may be vertical.
This configuration makes it possible to accurately set the restriction on the static elimination light to a desired degree for each of the regions that are different in the height of the blocking wall. It is therefore possible to achieve a desired dose distribution throughout the length of the photosensitive drum in the axial direction (longitudinal direction) of the photosensitive drum.
In the image forming apparatus described above, the end regions may not be provided with the blocking wall.
The structure according to this configuration that eliminates the need for the blocking wall in the end regions allows for a reduction in cost for manufacturing the blocking wall. Since the end regions are not provided with the blocking wall, the static elimination light in these regions can be efficiently used, avoiding a waste of the static elimination light, and thus reducing power consumption.
The image forming apparatus described above may further include a housing that accommodates the light guide plate therein, the housing having an opening in a side thereof facing the photosensitive drum. In this configuration, the blocking wall may be provided on an edge of the opening of the housing, the blocking wall may not be provided around ends of the housing, and the edge of the opening may have grooves around the ends of the housing to widen the opening.
According to this configuration, the opening is widened at ends of the edge, thereby reducing the restriction on the static elimination light. It is therefore possible to use the static elimination light efficiently. Since the opening is widened by forming the grooves in the housing, a common housing may be used for different models by forming grooves as necessary. The use of the common housing for different models allows for mass production of the housing, achieving cost reduction.
In the image forming apparatus described above, the blocking wall may be provided with a reflective member on a surface thereof facing the irradiation end surface, and the reflective member diffusely reflects light.
According to this configuration, a portion of the static elimination light emitted from the irradiation end surface is diffusely reflected by the reflective member, and the resulting scattered light is reflected off the irradiation end surface and re-emitted from the irradiation end surface. Repetition of such light emission from the irradiation end surface reduces non-uniformity in light emitted from the irradiation end surface that can occur in a light guide plate having a Fresnel pitch. Thus, it is possible to reduce occurrence of a defect such as a fringe pattern in an image formed.
In the image forming apparatus described above, the height of the blocking wall may be at a highest level in a location corresponding to a dose peak in a dose distribution of the static elimination light irradiated onto the photosensitive drum from the light source without the blocking wall, and the height of the blocking wall may be determined according to the dose distribution.
According to this configuration, it is possible to achieve an optimal height of the blocking wall. Thus, the static elimination light irradiated onto the photosensitive drum achieves a more uniform dose distribution throughout the length of the photosensitive drum in the axial direction (longitudinal direction) of the photosensitive drum. This reduces non-uniformity in chargeability of the photosensitive drum and image unevenness that can occur during image formation.
According to the present invention, it is possible to provide an image forming apparatus that achieves cost reduction, static elimination on a photosensitive drum with light having a uniform dose distribution, and prevention or reduction of image degradation.
The following describes Embodiment 1 of the present invention in detail with reference to the accompanying drawings.
The image forming apparatus 100 according to Embodiment 1 is an electrophotographic image forming apparatus, and includes an image reader 1, an image former 3 disposed under the image reader 1, and a paper feeder 2 disposed under the image former 3 as illustrated in
The image reader 1 includes a document table 11 including transparent glass, an automatic document feeder (ADF) 12 that automatically feeds a document onto the document table 11, and a document image reader 13 that scans and reads an image of the document placed on the document table 11. The image former 3 is provided in an image forming apparatus main body 110. The image former 3 includes a photosensitive drum 30 (image bearing member) and various constituent elements disposed around the photosensitive drum 30 for performing an electrophotographic process.
The image former 3 includes the photosensitive drum 30, a charger 31, an exposure device 32, a developing device 33, a transfer device 50, a static eliminator 34, and a cleaner 55.
The charger 31, the exposure device 32, the developing device 33, the transfer device 50, the static eliminator 34, and the cleaner 55 are provided around the photosensitive drum 30 in the stated order.
The charger 31 uniformly charges a surface of the photosensitive drum 30 to a predetermined potential through application of a direct-current (DC) voltage. The charger 31 includes a charging roller 31a and a charger cleaning roller 31b. Only a direct-current voltage component excluding an alternating-current voltage component is applied to the charging roller 31a. The charging roller 31a passively rotates in accompaniment to rotation (surface movement) of the photosensitive drum 30 while in contact with the surface of the photosensitive drum 30. The charger cleaning roller 31b cleans a surface of the charging roller 31a. The charger cleaning roller 31b passively rotates in accompaniment to rotation (surface movement) of the charging roller 31a while in contact with the surface of the charging roller 31a.
The exposure device 32 emits image writing light modulated based on image data from a laser light source 32a toward the photosensitive drum 30. More specifically, the exposure device 32 (laser light source 32a) irradiates the surface of the photosensitive drum 30 rotating and being uniformly charged to the predetermined potential with the image writing light while scanning the image writing light in a main scanning direction. Thus, the exposure device 32 can write a latent image (electrostatic latent image) on the photosensitive drum 30.
The developing device 33 makes visible the latent image formed on the photosensitive drum 30 with a toner. The developing device 33 causes a charged toner to adhere to the latent image formed on the photosensitive drum 30 by the exposure device 32. By thus making visible the latent image on the photosensitive drum 30, the developing device 33 can develop the latent image into a toner image.
The transfer device 50 electrostatically transfers the toner image formed on the photosensitive drum 30 onto paper P such as image transfer paper. The transfer device 50 includes a transfer roller 51 (transfer member). The transfer roller 51 passively rotates in accompaniment to the rotation (surface movement) of the photosensitive drum 30 while in contact with the surface of the photosensitive drum 30. A transfer bias (voltage) is applied to the transfer roller 51.
The static eliminator 34 eliminates residual potential remaining on the photosensitive drum 30 after the image transfer. The static eliminator 34 is located downstream of the transfer device 50 and upstream of the charger 31 in a rotation direction of the photosensitive drum 30. In the present example, the static eliminator 34 is disposed between the transfer device 50 and the cleaner 55. The static eliminator 34 eliminates residual potential remaining on the photosensitive drum 30 by irradiating the surface of the photosensitive drum 30 with light (static elimination light), as described in detail below.
The cleaner 55 removes residual toner remaining on the photosensitive drum 30 after the image transfer without being transferred by the transfer device 50. The residual toner removed by the cleaner 55 is collected in a waste toner collection container (not shown) disposed between a front cabinet of the image forming apparatus 100 and the image former 3.
As illustrated in
The image forming apparatus 100 further includes the paper feeder 2 and a transporter 4. The paper feeder 2 includes a paper feed cassette 21 and a manual paper feed tray 22 as a plurality of paper feed devices. The image forming apparatus 100 selects one paper feed device from the paper feed cassette 21 and the manual paper feed tray 22. Furthermore, the image forming apparatus 100 separately transports the paper P to the transporter 4 one sheet at a time using a pickup roller 23 for the selected paper feed device. The transporter 4 includes a registration roller 20, an ejection roller 25, and a transport roller 26. The registration roller 20 transports, in a transport direction Y, the paper P sent thereto from the paper feeder 2 toward a transfer nip N. The registration roller 20 stays at rest before the paper P is sent thereto. The registration roller 20 is driven to start rotating such that the electrostatic latent image on the photosensitive drum 30 and an image formation area (area other than a void (margin) area) of the paper P coincide when the paper P abuts the transfer nip N.
The image forming apparatus 100 includes transport paths S1 and S2, an inverting transport path S3, and a catch tray 24. Through the transport paths S1 and S2, the paper P is transported from the paper feeder 2 to the image former 3, and the paper P having the toner image fixed thereto is transported to the catch tray 24. The inverting transport path S3 is used for duplex printing. After the paper P having the toner image printed on a front side thereof has turned around at the ejection roller 25, the inverting transport path S3 guides the paper P back to the registration roller 20 with the front and back sides of the paper P inverted. Thus, the image forming apparatus 100 can form a toner image on the back side of the paper P as well as on the front side in duplex printing. Transport rollers for transporting the paper P are disposed in appropriate positions in the vicinity of the transport paths S1 and S2, and the inverting transport path S3.
The image forming apparatus 100 according to Embodiment 1 has pre-transfer paper guides 60 and 61 between the registration roller 20 and the transfer nip N. The pre-transfer paper guide 60, which guides a printing side of the paper P, is held by the developing device 33. Note here that “the pre-transfer paper guide 60 being held by the developing device 33” encompasses both a configuration in which a housing of the developing device 33 itself is used as the pre-transfer paper guide 60 and a configuration in which the pre-transfer paper guide 60 being a separate member is supported on the housing of the developing device 33. As a result of the pre-transfer paper guide 60 being held by the developing device 33, the positional accuracy between the photosensitive drum 30 and a tip of the pre-transfer paper guide 60 increases, reducing streaks and banding that can occur due to impact. The pre-transfer paper guide 60 being held by the developing device 33 also contributes to a reduction in size of the image forming apparatus 100.
In the case where the housing of the developing device 33 itself is used as the pre-transfer paper guide 60, the pre-transfer paper guide 60 is made from a resin (for example, polycarbonate/acrylonitrile-butadiene-styrene (PC/ABS) resin), which is the same material as the housing of the developing device 33. Likewise, in the case where the pre-transfer paper guide being a separate member is supported on the housing of the developing device 33, the pre-transfer paper guide 60 is preferably made from a resin. In the present embodiment, the pre-transfer paper guide 60 is made from a resin.
The following describes the static eliminator 34 in detail with reference to the drawings.
As illustrated in
As in the case of the light guide plate 34b, a longitudinal direction of the housing 34c is substantially parallel to the rotation axis 30a (axial direction) of the photosensitive drum 30 since the housing 34c accommodates the light guide plate 34b. The static elimination light source 34a is disposed in the vicinity of one end of the light guide plate 34b. As described above, the housing 34c has the opening 34d in the side thereof facing the photosensitive drum 30. Note that a blocking wall 36 is provided on an edge 35 of the opening 34d. The blocking wall 36 has a height that varies according to locations in the longitudinal direction of the photosensitive drum 30. That is, the blocking wall 36 is disposed between the light guide plate 34b and the photosensitive drum 30. Thus, as described in detail below, the blocking wall 36 closes the opening 34d, and light L emitted from the light guide plate 34b is irradiated onto the photosensitive drum 30 after being restricted in a non-uniform manner in the longitudinal direction of the light guide plate 34b. Since the photosensitive drum 30 rotates in the rotation direction D, the entirety of the outer circumferential surface of the photosensitive drum 30 is irradiated with the light L.
The static elimination light source 34a emits the light L toward the light guide plate 34b. The static elimination light source 34a is, for example, a light-emitting element such as a light-emitting diode (LED). The light L, which is static elimination light emitted from the static elimination light source 34a, enters the light guide plate 34b through an end surface of the light guide plate 34b. The light L that has entered the light guide plate 34b is then emitted toward the photosensitive drum 30 from an irradiation end surface 34e facing the opening 34d of the housing 34c. The light L emitted from the irradiation end surface 34e passes through the opening 34d to reach the photosensitive drum 30. The blocking wall 36 herein is disposed between the light guide plate 34b and the photosensitive drum 30 so as to cover the irradiation end surface 34e, and thus the light L emitted from the irradiation end surface 34e is irradiated onto the photosensitive drum 30 after being restricted by the blocking wall 36.
Note that in order to irradiate the photosensitive drum 30 throughout a length thereof in the longitudinal direction with the light emitted from the light guide plate 34b, the light guide plate 34b (irradiation end surface 34e) has a length in the longitudinal direction on par with (substantially equal to) the longitudinal length of the photosensitive drum 30, the light guide plate 34b and the photosensitive drum 30 are opposed to each other, and the light L is emitted toward the photosensitive drum 30 from the entirety of the irradiation end surface 34e. Since the light L is emitted toward the photosensitive drum 30 from the irradiation end surface 34e of the light guide plate 34b as described above, the light L in
As a result of the light L emitted by the static elimination light source 34a being irradiated onto the photosensitive drum 30 through the light guide plate 34b, residual potential remaining on the photosensitive drum 30 is eliminated. Note that it is preferable that the static elimination on the photosensitive drum 30 be uniform. Non-uniform static elimination can adversely affect image formation and degrade the resulting image. It is therefore preferable that the dose distribution of the light L (static elimination light) on the photosensitive drum 30 be uniform.
As illustrated in
That is, the blocking wall 36 has a plurality of levels of height, and is therefore stair-like. Boundaries between the regions that are different in the height of the blocking wall 36 are vertical. Specifically, the boundary between the regions R1 and R31, the boundary between the regions R31 and R32, the boundary between the regions R32 and R33, and the boundary between the regions R33 and R2 each extend in a vertical direction. Note here that the regions R1 and R2 are end regions located around ends of the light guide plate 34b. Since the photosensitive drum 30 and the light guide plate 34b have substantially the same length and are opposed to each other as described above, the photosensitive drum 30 has equivalent regions corresponding to those of the light guide plate 34b. That is, the regions R1 and the R2 can be described as end regions located at ends of the photosensitive drum 30. Likewise, the region R3 (regions R31, R32, and R33) can be described as a central region, which is a region other than the end regions at the ends of the photosensitive drum 30.
As described above, the light L emitted from the irradiation end surface 34e to be irradiated onto the photosensitive drum 30 is restricted by the blocking wall 36 while passing through the opening 34d. The degree of the restriction has a proportionate relationship to the height of the blocking wall 36. Specifically, the degree of the restriction is lower in the regions R1 and R2 where the height of the blocking wall 36 is “0” than in the regions R31 and R33 where the height of the blocking wall 36 is h1. The degree of the restriction is lower in the regions R1 and R2 than in the region R32 where the height of the blocking wall 36 is h2. The degree of the restriction is lower in the regions R31 and R33 where the height of the blocking wall 36 is h1 than in the region R32 where the height of the blocking wall 36 is h2.
Reducing the degree of the restriction on the light L to be emitted from the irradiation end surface 34e by setting the height of the blocking wall 36 in the regions R1 and R2 to a lower level than in the region R3 (regions R31, R32, and R33) as described above allows for irradiation of the photosensitive drum 30 with the light L achieving a more uniform dose distribution throughout the length of the photosensitive drum 30 in the longitudinal direction of the photosensitive drum 30. The region R32 where the height of the blocking wall 36 is at the highest level is a region including a portion of the photosensitive drum 30 to be irradiated with the largest dose of light if the light L is irradiated without the blocking wall 36. Setting the height of the blocking wall 36 in the region R32 to a highest level allows for irradiation of the photosensitive drum 30 with the light L achieving a more uniform dose distribution throughout the length of the photosensitive drum 30 in the longitudinal direction of the photosensitive drum 30. Generally, the dose peak in dose distribution is located toward the end facing the static elimination light source 34a away from a center of the photosensitive drum 30 in the longitudinal direction.
In Embodiment 1, as described above, setting the degree of the restriction on the light L to be emitted from the irradiation end surface 34e to a lower level in the regions R1 and R2, which are the end regions located around the ends of the light guide plate 34b, than in the other region, which is the region R3, allows for irradiation of the photosensitive drum 30 with the light L achieving a more uniform dose distribution throughout the length of the photosensitive drum 30 in the longitudinal direction of the photosensitive drum 30. This reduces non-uniformity in chargeability of the photosensitive drum 30 and image unevenness that can occur during the image formation on the paper P. As described above, it is preferable to set the height of the blocking wall 36 to a highest level to increase the degree of the restriction in the region R32, which is a region including a portion of the photosensitive drum 30 to be irradiated with the largest dose of light if the light L is irradiated without the blocking wall 36. This configuration allows for irradiation of the photosensitive drum 30 with the light L achieving a more uniform dose distribution throughout the length of the photosensitive drum 30 in the longitudinal direction of the photosensitive drum 30, and thus reduces non-uniformity in chargeability of the photosensitive drum 30 and image unevenness that can occur during the image formation on the paper P.
In some cases, a common component is applied to different models of image forming apparatuses, because mass production of components and the like results in cost reduction. In a case where common components (for example, the static elimination light source 34a, the light guide plate 34b, and the housing 34c) are applied to different models of image forming apparatuses, the dose distribution of the light L to be irradiated onto the photosensitive drum 30 can be different between the different models. However, non-uniformity in the dose distribution in each model can be reduced by employing the blocking wall 36 specific to the model. That is, the blocking wall 36 for each model is given a configuration specific to the model by changing the height, the regions different in height, and the like, while common components are used as the static elimination light source 34a, the light guide plate 34b, the housing 34c, and the like, allowing for cost reduction through mass production of such components.
The following describes the static eliminator 34 of the image forming apparatus 100 according to Embodiment 1 using Example 1. Note that the following particularly describes the blocking wall 36.
As illustrated in
In
A graph in a dashed line in
As shown in
Through the above, Example 1 has been described. However, the image forming apparatus 100 according to Embodiment 1 may have a configuration other than as described above. For example, the dose distribution also changes depending on the dose of the light L at the time when the light L is emitted from the static elimination light source 34a and the angle of the light L emitted from the static elimination light source 34a. It is therefore preferable to determine the configuration of the blocking wall 36 according to the dose distribution.
In a case where the longitudinal location of the peak of the dose distribution in the configuration including no blocking wall 36 is toward the end facing the static elimination light source 34a away from the longitudinal center of the light guide plate 34b, for example, the blocking wall 36 may take any of the following first to third forms.
In the first form, the height of the blocking wall 36 is set to a highest level in a region corresponding to the peak and to a lower level in two regions having the region corresponding to the peak therebetween, and one of the two regions that is closer to the static elimination light source 34a has a smaller range than the other of the two regions that is farther from the static elimination light source 34a.
In the second form, the height of the blocking wall 36 is set to a highest level in a region corresponding to the peak and to a lower level in two regions having the region corresponding to the peak therebetween, and each of the two regions is divided into a plurality of regions having a plurality of levels of height of the blocking wall 36. Furthermore, the number of levels of height of the blocking wall 36 (the number of regions different in height) is smaller in one of the two regions that is closer to the static elimination light source 34a than in the other of the two regions that is farther from the static elimination light source 34a.
In the third form, the height of the blocking wall 36 is set to a highest level in a region corresponding to the peak and to a lower level in two regions having the region corresponding to the peak therebetween, and each of the two regions is divided into a plurality of regions having a plurality of levels of height of the blocking wall 36. Furthermore, the range of each of the regions in the two regions is set so that the farther from the static elimination light source 34a the region is, the larger the range thereof is. In this case, the two regions are other than regions respectively including the ends of the light guide plate 34b. That is, the two regions are regions located inward of the regions (outermost regions) respectively including the ends of the light guide plate 34b.
In a case where the longitudinal location of the peak of the dose distribution in the configuration including no blocking wall 36 is toward the end opposite to the static elimination light source 34a away from the longitudinal center of the light guide plate 34b, for example, the blocking wall 36 may take any of forms respectively achieved through inversion of the first to third forms described above at the longitudinal center.
In a case where the longitudinal location of the peak of the dose distribution in the configuration including no blocking wall 36 is at the longitudinal center of the light guide plate 34b, for example, the blocking wall 36 may take a form in which the height of the blocking wall 36 is set to a highest level in a region corresponding to the peak, the region corresponding to the peak is located at the longitudinal center, and the height of the blocking wall 36 in each of the other regions is set so that the farther from the longitudinal center the region is, the lower the height of the blocking wall 36 in the region is, and thus the blocking wall 36 has a symmetrical shape with respect to the longitudinal center.
The image forming apparatus 100 according to Embodiment 1 has been described above. However, the present invention is not limited to the configuration described above. For example, as described with reference to
Preferably, the inside of the housing 34c is white in order for the light L that has entered the light guide plate 34b from the static elimination light source 34a to be diffusely reflected. However, the inside of the housing 34c is not limited to being white, and may alternatively be black. Alternatively, the inside of the housing 34c may be black and a portion thereof may be white. For example, at least portions of the inside of the housing 34c that are located around the ends of the light guide plate 34b may be white. This configuration promotes reflection of the light L, and thus improves uniformity of the light L to be irradiated onto the photosensitive drum 30 in the longitudinal direction.
The following describes an image forming apparatus according to Embodiment 2 of the present invention with reference to the drawings. Note that components that have the same function and operation as the components that have already been described are labelled using the same reference signs, and detailed description thereof is omitted.
The edge 35 of the housing 34c further includes the grooves 37 in the portions thereof corresponding to the ends of the light guide plate 34b as illustrated in
Furthermore, a blocking wall 36 is provided in a region R203 being a central region located between the regions R201 and R202. The region R203 is divided into regions R231, R232, and R233, where the blocking wall 36 has a height that varies from region to region.
Generally, the dose of the light L emitted from regions around the ends of the light guide plate 34b is lower than the dose of the light L emitted from the other regions. The dose of the light L to be emitted can therefore be increased by forming the grooves 37 as described above, and thus widening the opening 34d in the portions around the ends of the light guide plate 34b.
For example, the opening 34d may be widened by forming the grooves 37 in the edge 35 as described above to ensure a sufficient dose of the light L around the ends of the light guide plate 34b in a case where the dose distribution of the light L on the photosensitive drum 30 obtained by providing the blocking wall 36 on the edge 35 is not sufficiently uniform throughout a length of the photosensitive drum 30 in a longitudinal direction of the photosensitive drum 30. The thus widened opening 34d allows for irradiation of the photosensitive drum 30 with the light L achieving a more uniform dose distribution throughout the length of the photosensitive drum 30 in the longitudinal direction of the photosensitive drum 30, reducing non-uniformity in chargeability of the photosensitive drum 30 and image unevenness that can occur during image formation on paper P.
This configuration may also be applied to a case where common components are used in different models of image forming apparatuses. That is, in a case where the dose distribution of the light L obtained by employing a different blocking wall 36 for each of the models is not sufficiently uniform throughout the length of the photosensitive drum 30 in the longitudinal direction of the photosensitive drum 30, the grooves 37 may be formed to ensure a sufficient dose of the light L at the ends, and thus to achieve a more uniform dose distribution throughout the length of the photosensitive drum 30 in the longitudinal direction of the photosensitive drum 30. This eliminates the need for producing a different housing 34c for each model. That is, a common housing 34c can be used for different models by forming the grooves 37, achieving cost reduction.
The following describes the static eliminator 34 of the image forming apparatus 100 according to Embodiment 2 using Example 2. Note that the following particularly describes a portion of a blocking wall 36 around an end of a light guide plate 34b facing a static elimination light source 34a.
In
A graph in a dashed line in
The following next describes a method for determining the height of the blocking wall 36 in each region and the depth of the grooves 37 with reference to the drawings.
Note that in
Preferably, the height of the blocking wall 36 in each region and the depth of the grooves 37 are determined in consideration of reducing deterioration of the photosensitive drum 30 due to light fatigue as well as achieving a more uniform dose distribution of the light L to be irradiated onto the photosensitive drum 30. Note here that charging and static elimination on the photosensitive drum 30 are performed by causing charge transfer in an organic film in the photosensitive drum 30 through irradiation of the photosensitive drum 30 with light, and thus controlling the potential of the photosensitive drum 30. The chargeability of the photosensitive drum 30 decreases as charging and static elimination are repeated on the photosensitive drum 30. In particular, the higher the dose of the light L irradiated onto the photosensitive drum 30 is, the more the chargeability of the photosensitive drum 30 decreases. It is therefore preferable to irradiate the light L onto the photosensitive drum 30 in a dose that allows sufficient static elimination on the photosensitive drum 30 and that reduces the decrease in the chargeability to a greater extent.
That is, it is preferable to set the height of the blocking wall 36 in each region and the depth of the grooves 37 so as to obtain a more uniform dose distribution of the light L on the photosensitive drum 30 for sufficient static elimination and reduce deterioration of the photosensitive drum 30 due to light fatigue.
In order to determine the height of the blocking wall 36 in each region and the depth of the grooves 37, the dose distribution of the light L is obtained first by irradiating the light L onto the photosensitive drum 30 without the blocking wall 36 and the grooves 37 in the edge 35 as illustrated in
A range where the dose is substantially equal to the reference dose in
Specifically, in the housing 34c, regions RO1 and RO2, which are end regions located at the ends of the light guide plate 34b, are to be provided with the grooves 37 in the edge 35, and a region RC of a central region, which is a region other than the end regions, is to be provided with the blocking wall 36 and a region RS of the central region is to only have the edge 35, as illustrated in
The light L that is irradiated onto the photosensitive drum 30 after forming the blocking wall 36 and the grooves 37 having configurations illustrated in
The following describes an image forming apparatus according to Embodiment 3 of the present invention with reference to the drawings. Note that components that have the same function and operation as the components that have already been described are labelled using the same reference signs, and detailed description thereof is omitted.
The blocking wall 36 is provided with the reflective member 36a for diffusely reflecting light on the side thereof facing an irradiation end surface 34e as illustrated in
The bright spot unevenness as used herein refers to light being distributed in a non-uniform manner in the longitudinal direction after having been emitted from the light guide plate 34b with a Fresnel pitch due to distribution on a Fresnel surface. The bright spot unevenness can make the chargeability of the photosensitive drum 30 non-uniform and cause occurrence of a fringe pattern in an image formed on paper P. However, as a result of providing the reflective member 36a, it is possible to reduce the bright spot unevenness and to reduce occurrence of such a defect.
Note that the reflective member 36a may have the same shape as the blocking wall 36 and may be a white member. Since it is preferable that the light L be diffusely reflected by the reflective member 36a, the reflective member 36a preferably has a rough surface rather than a glossy and smooth surface.
The reflective member 36a may be provided also on portions of the edge 35 that do not have the blocking wall 36. In this case, the edge 35 may be provided with the reflective member 36a directly on a side thereof facing the light guide plate 34b. The reflective member 36a may extend over the entire length of an opening 34d and may be provided on either the side of the edge 35 or the side of the blocking wall 36 facing the light guide plate 34b. Alternatively or additionally, the reflective member 36a may be provided on an inner surface of the housing 34c where the light guide plate 34b is disposed. This configuration allows the light L to be further reflected, thereby reducing bright spot unevenness, reducing non-uniform charging on the photosensitive drum 30, and reducing occurrence of a defect in an image to be formed.
The present invention is not limited to the embodiments described above and may be embodied in other specific forms. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting the invention described herein. Scope of the present invention is indicated by the appended claims rather than by the foregoing description. All modifications and changes that come within the meaning and range of equivalency of the claims are intended to be embraced within their scope.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-088201 | May 2020 | JP | national |
