Patent ID: 12210297

DESCRIPTION OF THE EMBODIMENTS

Exemplary embodiments for carrying out the present disclosure will be described below with reference to the drawings. The scope of the disclosure is not limited only to the dimensions, materials, shapes, relative arrangements, and the like of components described in the following exemplary embodiments, unless otherwise specified.

(Image Forming Apparatus)

A schematic configuration of an image forming apparatus1will now be described.FIG.1Ais a schematic sectional view of the image forming apparatus1. The image forming apparatus1illustrated inFIG.1Ais a color printer (single function printer (SFP)) including no scanning device, but instead may be a copying machine including a scanning device. In exemplary embodiments of the present disclosure, not only a color image forming apparatus including a plurality of photosensitive drums103as illustrated inFIG.1A, but also a color image forming apparatus including a single photosensitive drum103, or an image forming apparatus that forms a monochrome image may be used.

The image forming apparatus1illustrated inFIG.1Aincludes four image forming units102Y,102M,102C, and102K (hereinafter collectively referred to simply as an image forming unit102). The image forming units102Y,102M,102C, and102K form toner images of yellow, magenta, cyan, and black, respectively. The image forming units102Y,102M,102C, and102K include photosensitive drums103Y,103M,103C, and103K (hereinafter collectively referred to simply as a photosensitive drum103), respectively. The image forming units102Y,102M,102C, and102K also include chargers104Y,104M,104C, and104K (hereinafter collectively referred to simply as a charger104) that charge the photosensitive drums103Y,103M,103C, and103K, respectively. The image forming units102Y,102M,102C, and102K also include light-emitting diode (LED) exposure units520Y,520M,520C, and520K (hereinafter collectively referred to simply as an exposure unit520), respectively. The LED exposure units520Y,520M,520C, and520K are exposure light sources that emit light to expose surfaces of the photosensitive drums103Y,103M,103C, and103K, respectively. The image forming units102Y,102M,102C, and102K also include developing units106Y,106M,106C, and106K (hereinafter collectively referred to simply as a developing device106), respectively. The developing device106is a developing unit that develops, with toner, an electrostatic latent image formed on the photosensitive drum103into a toner image, so that toner images of respective colors is developed on the respective photosensitive drums103. Characters Y, M, C, and K added to each reference numeral represent yellow, magenta, cyan, and black colors of toner, respectively.

The image forming apparatus1illustrated inFIG.1Ais an image forming apparatus that adopts what is called a lower surface exposure method for exposing the surface of the photosensitive drum103to light from below. The following description is provided on the premise that the image forming apparatus1adopts the lower surface exposure method. However, the image forming apparatus1may adopt an upper surface exposure method for exposing the surface of the photosensitive drum103to light from above, as with an image forming apparatus2illustrated inFIG.1B. InFIG.1B, portions that represent the same components as those inFIG.1Aare denoted by the same reference symbols.

The image forming apparatus1also includes an intermediate transfer belt107and primary transfer rollers108(108Y,108M,108C, and108K). Toner images formed on the photosensitive drums103are transferred to the intermediate transfer belt107. The primary transfer rollers108(108Y,108M,108C, and108K) sequentially transfer the toner images formed on the photosensitive drums103to the intermediate transfer belt107. The image forming apparatus1also includes a secondary transfer roller109and a fixing unit100. The secondary transfer roller109is a transfer unit that transfers the toner images formed on the intermediate transfer belt107to recording paper P that is conveyed from a sheet feeding unit101. The fixing unit100fixes the secondarily transferred images to the recording paper P.

(Image Forming Process)

The exposure unit520Y exposes the surface of the photosensitive drum103Y, which has been charged by the charger104Y, to light. As a result, an electrostatic latent image is formed on the surface of the photosensitive drum103Y. Next, the developing device106Y develops the electrostatic latent image formed on the surface of the photosensitive drum103Y with yellow toner. The yellow toner image developed on the surface of the photosensitive drum103Y is transferred to the intermediate transfer belt107by the primary transfer roller108Y. Magenta, cyan, and black toner images are transferred to the intermediate transfer belt107through a similar image forming process.

The toner images of the respective colors transferred to the intermediate transfer belt107are conveyed to a secondary transfer portion T2by the intermediate transfer belt107. A transfer bias for transferring the toner images to the recording paper P is applied to the secondary transfer roller109disposed on the secondary transfer portion T2. The toner images conveyed to the secondary transfer portion T2are transferred to the recording paper P which has been conveyed from the sheet feeding unit101by the transfer bias of the secondary transfer roller109. The recording paper P to which the toner images are transferred is conveyed to the fixing unit100. The fixing unit100fixes the toner images to the recording paper P with heat and pressure. The recording paper P on which the fixation process has been performed by the fixing unit100is discharged to a sheet discharge portion111.

(Drum Units and Developing Units)

Drum units518Y,518M,518C, and518K (hereinafter collectively referred to simply as a drum unit518) including the photosensitive drums103are attached to the image forming apparatus1. In the present exemplary embodiment, the drum unit518is also referred to as a photosensitive member unit. The drum unit518is a cartridge that is replaced by an operator, such as a user or maintenance engineer. The drum unit518rotatably supports the photosensitive drum103. In this case, the drum unit518also functions as a drum support member that rotatably supports the photosensitive drum103. In the present exemplary embodiment, a drum unit including the drum support member is referred to as the drum unit518. Specifically, the photosensitive drum103is rotatably supported by a frame member of the drum unit518. The drum unit518need not necessarily include the charger104and a cleaning device.

Developing units641Y,641M,641C, and641K (hereinafter collectively referred to simply as a developing unit641), which are provided separately from the drum units518, are attached to the image forming apparatus1according to the present exemplary embodiment. The developing unit641according to the present exemplary embodiment is a cartridge having a configuration in which the developing device106illustrated inFIG.1Aand a toner storage portion are integrated. The developing device106includes a developing sleeve (not illustrated) that carries developer. The developing unit641is provided with a plurality of gears for rotating a screw to mix toner and carrier. For example, when the gears have degraded with time, the operator detaches the developing unit641from an apparatus body of the image forming apparatus1and replaces the developing unit641. The drum unit518and the developing unit641according to the present exemplary embodiment may be a process cartridge having a configuration in which the drum unit518and the developing unit641described above are integrated.

FIG.2Ais a perspective view schematically illustrating a structure in the vicinity of the drum units518(518Y,518M,518C, and518K) and the developing units641(641Y,641M,641C, and641K) included in the image forming apparatus1.FIG.2Billustrates a state where the drum units518are inserted into the image forming apparatus1from the outside of the apparatus body.

As illustrated inFIG.2A, the image forming apparatus1includes a front side plate642that is formed of a metal sheet, and a back side plate643that is also formed of a metal sheet. The front side plate642is a side wall provided on the front side of the image forming apparatus1. The front side plate642constitutes part of a housing of the apparatus body on the front side of the apparatus body of the image forming apparatus1. The back side plate643is a side wall provided on the back side of the image forming apparatus1. The back side plate643constitutes part of the housing of the apparatus body on the back side of the apparatus body of the image forming apparatus1. As illustrated inFIG.2A, the front side plate642and the back side plate643are arranged to be facing each other, and a metal sheet (not illustrated) serving as a beam is bridged over the front side plate642and the back side plate643. The front side plate642, the back side plate643, and the beam (not illustrated) constitute part of a frame member of the image forming apparatus1. The term front surface side or front side of the image forming apparatus1or the components thereof according to the present exemplary embodiment refers to a side where the drum unit518is inserted into or removed from the apparatus body.

The front side plate642is provided with an opening for inserting or removing the drum unit518and the developing unit641into or from the apparatus body on the front side of the image forming apparatus1. The drum unit518and the developing unit641are each mounted at a predetermined position in the apparatus body of the image forming apparatus1through the opening. The image forming apparatus1also includes covers558Y,558M,558C, and558K (hereinafter also collectively referred to simply as a cover558) that cover the front side of the respective drum units518and the respective developing units641. One end of the cover558is fixed to the apparatus body of the image forming apparatus1with a hinge. The hinge enables the cover558to pivot relative to the apparatus body of the image forming apparatus1. The operator opens the cover558, takes out the drum unit518or the developing unit641from the apparatus body, and then inserts a new drum unit518or a new developing unit641and closes the cover558, to thereby complete a replacement operation.

As illustrated inFIGS.2A and2B, a side where the front side plate642is located is hereinafter defined as the front side (or the front surface side) of the apparatus body, and a side where the back side plate643is located is hereinafter defined as the back side (or the back surface side) of the apparatus body. With respect to the photosensitive drum103K on which the electrostatic latent image for the black toner image is formed, a side where the photosensitive drum103Y on which the electrostatic latent image for the yellow toner image is formed is disposed is defined as the right side. With respect to the photosensitive drum103Y on which the electrostatic latent image for the yellow toner image is formed, a side where the photosensitive drum103K on which the electrostatic latent image for the black toner image is formed is disposed is defined as the left side. A direction that is perpendicular to the front-back direction and left-right direction defined herein and that is a vertically upward direction is defined as an up direction, and a direction that is perpendicular to the front-back direction and left-right direction defined herein and that is a vertically downward direction is defined as a down direction. The front direction, the back direction, the right direction, the left direction, the up direction, and the down direction, which are defined above, are illustrated inFIG.2B. The term rotational axis direction of the photosensitive drum103used herein refers to a direction that coincides with the front-back direction illustrated inFIG.2B. The term longitudinal direction of an optical printhead105also refers to the direction that coincides with the front-back direction illustrated inFIG.2B. In other words, the rotational axis direction of the photosensitive drum103and the longitudinal direction of the optical printhead105coincide with each other.

(Exposure Unit)

Next, the exposure unit520including the optical printhead105will be described. The optical printhead105has a longitudinal shape extending in the rotational axis direction of the photosensitive drum103. The optical printhead105includes a holding member505, a lens array506, and a substrate502. The lens array506and the substrate502are held by the holding member505. In the present exemplary embodiment, the holding member505is a member that is made of metal and is formed by bending a plate material obtained by performing a plating process on a galvanized steel plate or cold-rolled steel plate. The use of a metal plate material makes it possible to achieve strength by performing a bending process, while reducing costs. However, the configuration of the holding member505is not limited to the configuration obtained by performing the bending process on the metal plate material. The holding member505can also be, for example, what is called a die-cast product. The die-cast product refers to a product manufactured by die-casting, i.e., cooling and solidifying molten metal injected into a mold (cavity). In a case where the die-casting is adopted as the manufacturing method, a product having a complex shape can be manufactured depending on a shape of the mold serving as a basis for the product's shape. Meanwhile, since fabrication of the mold is costly, there is a disadvantage in that there is no cost advantage when there is no need to manufacture a large amount of identical products. In the present exemplary embodiment, the holding member505may be manufactured by bending a metal sheet or may be manufactured by die-casting. The use of the holding member505which is made of metal for the optical printhead105makes it possible to increase the strength of the optical printhead105. The holding member505which is made of metal has higher thermal conductivity than that of a holding member made of resin. Accordingly, the possibility that the holding member505may be deformed can be reduced even when the temperature of each electronic component mounted on the substrate502increases and the temperature in the space near the substrate increases.

An example of the exposure method to be used for an electrophotographic image forming apparatus is a laser beam scanning exposure method. In this method, the surface of the photosensitive drum103is scanned with an irradiation beam which is emitted from a semiconductor laser, is reflected by a rotating polygon mirror or the like, and goes through an f-O lens or the like. The optical printhead105described in the present exemplary embodiment is used in an LED exposure method for exposing the surface of the photosensitive drum103using light-emitting elements such as LEDs arrayed in the rotational axis direction of the photosensitive drum103, and is not used in the above-described laser beam scanning exposure method.

The exposure unit520described in the present exemplary embodiment is provided on the lower side in the vertical direction relative to the rotational axis of the photosensitive drum103. The substrate (not illustrated) included in the holding member505is provided with LEDs as the light-emitting elements, and the light-emitting elements emit light to which the surface of the photosensitive drum103is exposed from below. However, the exposure unit520may be provided on the upper side in the vertical direction relative to the rotational axis of the photosensitive drum103, and the surface of the photosensitive drum103may be exposed to light from above (seeFIG.1B).

FIG.3is a schematic perspective view of the exposure unit520included in the image forming apparatus1according to the present exemplary embodiment.

As illustrated inFIG.3, the exposure unit520includes the optical printhead105, a support member526, a first link mechanism530, and a second link mechanism540. The holding member505is provided with a contact pin514and a contact pin515. The contact pin514and the contact pin515are straight pins made of metal. For example, the contact pin515is provided on the holding member505on one side (back side) of the lens array506in the rotational axis direction of the photosensitive drum103, and projects from both sides of the holding member505in an optical axis direction of the lens array506. The contact pin514has a configuration similar to that of the contact pin515. When the contact pin514and the contact pin515are brought into contact with the drum unit518, a gap is formed between the photosensitive drum103and a light-emitting surface of the lens array506. Thus, the position of the optical printhead105with respect to the photosensitive drum103is determined.

The contact pin514and the contact pin515are fixed to the holding member505, which is made of metal, by welding. Thus, in the present exemplary embodiment, the contact pin514and the contact pin515are integrated with the holding member505. The method for fixing the contact pin514and the contact pin515to the holding member505is not limited to welding, but instead may be fixation with an adhesive. The contact pin514and the contact pin515may be threaded and screwed into the holding member505to be fastened to the holding member505.

The first link mechanism530includes a link member535and a link member536. The second link mechanism540includes a link member537and a link member538. As described in detail below, the link member535is attached to the back side relative to the center of the holding member505in the rotational axis direction of the photosensitive drum103, and the link member537is attached to the front side relative to the center of the holding member505in the rotational axis direction of the photosensitive drum103.

A slide member (slider)525to be described below slides in the front-back direction along with an opening and closing operation of the cover558provided on the front side of the image forming apparatus1. The link members535to538rotate along with the slide movement of the slide member525, thereby enabling the optical printhead105to move in the up-down direction.

In the present exemplary embodiment, the optical printhead105is provided on the lower side in the vertical direction relative to the photosensitive drum103. Specifically, in the image forming apparatus1according to the present exemplary embodiment, the surface of the photosensitive drum103is exposed to light emitted by the optical printhead105from below in the vertical direction.

As illustrated inFIG.3, the exposure unit520includes the support member526. The support member526supports the optical printhead105via the first link mechanism530and the second link mechanism540. Specifically, the link member535of the first link mechanism530supports the holding member505, and the link member537of the second link mechanism540supports the holding member505.

In this manner, the link member535and the link member537support the holding member505directly or indirectly. Since the link member535and the link member537are made of resin, the holding member505is not grounded, or is in an electrically floating state.

The support member526is formed by bending a metal sheet into a U-shape. The support member526is a longitudinal member extending in the rotational axis direction of the photosensitive drum103. One end (front side) of the support member526in the longitudinal direction of the support member526is fixed to the front side plate642, and the other end (back side) of the support member526in the longitudinal direction of the support member526is fixed to the back side plate643. Thus, the position of the support member526is fixed with respect to the photosensitive drum103on the side opposite to the side where the photosensitive drum103is disposed with respect to the holding member505in the optical axis direction of the lens array506. The support member526is grounded via one or both of the front side plate642and the back side plate643.

The support member526includes the slide member525that is movable in the longitudinal direction of the support member526. The link members535to538rotate along with the movement of the slide member525relative to the support member526, thereby enabling the optical printhead105to move relative to the support member526.

(Configurations of Substrate and Lens Array)

Next, the substrate502and the lens array506will be described with reference toFIGS.4A,4B1,4B2,4C1, and4C2. First, the substrate502will be described.FIG.4Ais a schematic perspective view of the substrate502. FIG.4B1illustrates an array of a plurality of LEDs503provided on the substrate502, and FIG.4B2illustrates an enlarged view of FIG.4B1.

LED chips639are mounted on the substrate502. As illustrated inFIG.4A, the LED chips639are provided on one surface of the substrate502, and a connector504is provided on the back surface of the substrate502. The substrate502is provided with a wiring pattern for supplying a signal to each of the LED chips639. To the connector504, one end of a flexible flat cable (FFC) (not illustrated) is connected. The main body of the image forming apparatus1is provided with a substrate that is different from the substrate502. This substrate is provided with a central processing unit (CPU) for controlling a light-emitting timing of each of the LEDs503. The other end of the FFC is connected to a connector mounted on the substrate provided on the image forming apparatus1. The FFC transmits a drive signal for driving each of the LEDs503to the substrate502from the substrate provided on the image forming apparatus1.

The LED chips639mounted on the substrate502will be described in more detail. As illustrated in FIGS.4B1and4B2, a plurality of (29) LED chips639-1to639-29each including the plurality of LEDs503arranged thereon is arrayed on one surface of the substrate502.

On each of the LED chips639-1to639-29, 516 LEDs503(light-emitting elements) are arrayed in a row in the longitudinal direction of the LED chips639. A center-to-center distance k2between the adjacent LEDs503in the longitudinal direction of the LED chips639corresponds to the resolution of the image forming apparatus1. The image forming apparatus1according to the present exemplary embodiment has a resolution of 1200 dpi. Accordingly, the array of the LEDs503is formed such that the center-to-center distance k2between the adjacent LEDs503is 21.16 μm in the longitudinal direction of the LED chips639-1to639-29. Therefore, the optical printhead105according to the present exemplary embodiment has an exposure range of about 316 mm. A photosensitive layer of the photosensitive drum103is formed to have a width greater than or equal to 316 mm. Since the length of a long side of an A4-size recording sheet and the length of a short side of an A3-size recording sheet are 297 mm, the optical printhead105according to the present exemplary embodiment has the exposure range capable of forming images on an A4-size recording sheet and an A3-size recording sheet.

The LED chips639-1to639-29are alternately arranged in two rows in the rotational axis direction of the photosensitive drum103. Specifically, as illustrated in FIG.4B1, the odd-numbered LED chips639-1,639-3, . . . , and639-29counted from the left side are mounted in one row in the longitudinal direction of the substrate502. The even-numbered LED chips639-2,639-4, . . . , and639-28counted from the left side are mounted in one row in the longitudinal direction of the substrate502. By arranging the LED chips639in this manner, as illustrated in FIG.4B2, a center-to-center distance k1between an LED503disposed on one end of one of the adjacent different LED chips639and an LED503disposed on the other end of the other of the adjacent different LED chips639can be made equal to the center-to-center distance k2between the adjacent LEDs503on a single LED chip639in the longitudinal direction of the LED chip639.

In the present exemplary embodiment, each light-emitting element is a semiconductor LED, but instead may be, for example, an organic light-emitting diode (OLED). The OLED is also referred to as an organic electro-luminescence (EL) and is a current-driven light-emitting element. For example, OLEDs are arranged on a line in a main scanning direction (rotational axis direction of the photosensitive drum103) on a substrate of a thin film transistor (TFT) and are electrically connected in parallel by a power supply line that is also provided in the main scanning direction.

Next, the lens array506will be described. FIG.4C1is a schematic view of the lens array506as viewed from the photosensitive drum103. FIG.4C2is a schematic perspective view of the lens array506. The lens array506functions to collect light emitted from the LEDs503on the surface of the photosensitive drum103. As illustrated in FIG.4C1, a plurality of lenses of the lens array506is arranged in two rows in the array direction of the plurality of LEDs503. The lenses are alternately arranged such that one of the lenses in one of the rows of lenses is disposed to contact both of adjacent lenses in the array direction of the other of the rows of lenses. Each of the lenses is a cylindrical rod lens made of glass. Each of the lenses includes an incidence surface on which light emitted from each of the LEDs503is incident, and an emitting surface from which light incident from the incidence surface is emitted. The material of each lens is not limited to glass, but instead may be plastic. The shape of each lens is not limited to a cylindrical shape, but instead may be, for example, a polygonal column such as a hexagonal column.

A dashed line Z illustrated in FIG.4C2indicates a lens optical axis. The above-described movement mechanism enables the optical printhead105to move in a direction that is substantially in the lens optical axis indicated by the dashed line Z. The term lens optical axis used herein refers to a line that connects a focal point of a certain lens selected from among the plurality of lenses constituting the lens array506and the center of the light-emitting surface of the lens. To be exact, the optical axis of each lens may slightly vary from lens to lens. Even if an angle formed between the optical axis of a certain lens and the optical axis of another lens is not 0 degrees, the angle may be only a small angle. When the term lens optical axis is used, such a slight difference is not taken into consideration, and it is assumed that the term lens optical axis indicates the optical axis of any one of the plurality of lenses constituting the lens array506. In addition, it is assumed that the direction of the optical axis of one lens coincides with the direction of the optical axis of another lens.

Next, a wiring pattern552formed on the substrate502will be described.FIG.5illustrates the back surface of the substrate502. The LED chips639including the LEDs503are mounted on the front surface of the substrate502, and electronic components such as one or more driver integrated circuits (ICs)551aand551bfor driving the LEDs503are mounted on the back surface of the substrate502. In other words, the back surface of the substrate502refers to a surface of the substrate502that is opposite to the surface on which the light-emitting elements are mounted.

The term wiring pattern552used herein refers to a plurality of electric wires formed on the substrate502. Typical examples of the electric wires include an electric wire552a(power line) for driving the driver IC551a(551b), and a ground wire552bhaving a reference potential. The ground wire552balso functions as an electric wire for grounding the driver ICs551aand551b. While the electric wire552ais described as being a power line, the electric wire552amay also be a signal line for transmitting a control signal to drive each of the LEDs503.

The connector504is mounted in the vicinity of the center of the back surface of the substrate502. An FFC510is attached to the connector504. The FFC510is a cable formed of a plurality of electric wires.

Examples of the electric wires include an electric wire for transmitting a control signal (drive signal) to control the light-emitting timing of each of the LEDs503, a supply line (also referred to as a power line) for supplying power, and a ground wire for grounding the wiring pattern552.

The back surface of the substrate502is also provided with ground pads550aand550beach having the same potential as that of the ground wire552b. A conductive member701to be described below contacts the ground pad550a(550b) and the holding member505, thereby electrically connecting the ground pad550a(550b) and the holding member505.

(Conductive Member)

FIG.6Ais a sectional view of the optical printhead105taken along a section perpendicular to the longitudinal direction of the optical printhead105. As illustrated inFIG.6A, the substrate502and the lens array506are held by the holding member505such that the substrate502and the lens array506face each other.

As seen from the sectional views of the image forming apparatus1illustrated inFIGS.1A and1B, the charger104is disposed in the vicinity of the optical printhead105. A high voltage is applied to a charging roller included in the charger104, and an intense electric field is formed in the vicinity of the charging roller. Accordingly, the optical printhead105is also located in the intense electric field, and thus the holding member505is gradually charged. In this case, if there is a difference between the potential of the holding member505and the potential of the wiring pattern552of the substrate502, an electric current may be discharged from the holding member505and the wiring pattern552. Even when the holding member505is grounded, the holding member505cannot be fully grounded in some cases due to a contact failure between components constituting a ground path. Thus, it is difficult to completely eliminate the difference between the potential of the holding member505and the potential of the wiring pattern552of the substrate502. Therefore, it is desirable to provide a configuration for making the difference between the potential of the holding member505and the potential of the wiring pattern552of the substrate502as close to zero as possible.

In recent years, there has been a demand for a further increase in speed of the image forming apparatus1. Along with the recent demand, there has been an increasing demand for the higher transmission accuracy of a signal for driving light-emitting elements. One of main factors for deterioration in signal transmission accuracy is noise emitted from the wiring pattern552of the substrate502. The noise emitted from the wiring pattern552may have an effect on a signal transmitted through another part in the wiring pattern552. To reduce the intensity of the noise emitted from the wiring pattern552, it is desirable to fully ground the ground wire for the wiring pattern552. In general, the ground wire for the wiring pattern552is grounded via the ground wire for the FFC510. However, since the ground wire for the FFC510is extremely thin, it cannot be said that the ground wire for the wiring pattern552is fully grounded.

Accordingly, in the optical printhead105according to the present exemplary embodiment, the ground wire552bfor the wiring pattern552of the substrate502and the holding member505are electrically connected to thereby ground the wiring pattern552of the substrate502.

As illustrated inFIG.6A, the holding member505includes a fixed portion505athat is provided with an opening708into which the lens array506is inserted, and a pair of wall portions505bextending from both ends of the fixed portion505ain a direction perpendicular to the rotational axis direction of the photosensitive drum103. In the present exemplary embodiment, the holding member505is formed by bending a metal sheet. The holding member505is bent at both end portions of the fixed portion505aso that the pair of wall portions505bprojects toward the side opposite to the side where the photosensitive drum103is disposed.

In this case, the pair of wall portions505bis each provided with an opening703. Protrusions formed on the conductive member701to be described below are fitted into respective openings703. The conductive member701is a conductive component and electrically connects the holding member505with the ground wire552bfor the wiring pattern552formed on the substrate502. The configuration makes the potential of the holding member505equal to the potential of the ground wire552bfor the wiring pattern552.

FIG.6Bis a bottom view of the holding member505, andFIG.6Cis a view illustrating a method for attaching the conductive member701to the holding member505.

As seen fromFIG.6B, the conductive member701is a metal component formed in a U-shape, and plate-like portions corresponding to both leg portions of the conductive member701are elastically deformable. As illustrated inFIG.6C, when the conductive member701is inserted from below the holding member505, the portions corresponding to the both leg portions of the conductive member701are fitted to the holding member505while being deformed inside.

(Movement Mechanism)

Next, a mechanism that enables the optical printhead105to move along with the slide movement of the slide member525will be described with reference toFIGS.7A and7B.FIGS.7A and7Billustrate the exposure unit520as viewed from the left side. For ease of description, the support member526is not illustrated.FIG.7Aillustrates a state where the optical printhead105is located at an exposure position (first position) corresponding to a position where the photosensitive drum103is exposed to light.FIG.7Billustrates a state where the optical printhead105is located at a retracted position (second position) farther from the photosensitive drum103than the exposure position. In the present exemplary embodiment, a distance between the photosensitive drum103and the light-emitting surface of the lens array506when the optical printhead105is located at the exposure position is about 3 mm.

As illustrated inFIGS.7A and7B, the link member535is rotatably connected to one end of the slide member525in the longitudinal direction of the slide member525, and the link member537is rotatably connected to the other end of the slide member525in the longitudinal direction of the slide member525.

The slide member525slides to the back side from the front side when the cover558(not illustrated) is rotated to an open state from a closed state. When the slide member525slides from the front side to the back side, the link member535and the link member537rotate counterclockwise inFIGS.7A and7B. The link member535and the link member536are rotatably connected to each other. The link member537and the link member538are also rotatably connected to each other.

One end of the link member536is rotatably connected to the support member526(not illustrated). Accordingly, the link member536also rotates about the support member526along with the rotation of the link member535. One end of the link member538is rotatably connected to the support member526(not illustrated). Accordingly, the link member538also rotates about the support member526along with the rotation of the link member537. When the slide member525moves to the back side from the front side, the link member536and the link member538rotate clockwise about the support member526. In this case, the other end of the link member535is rotatably connected to the holding member505, and the other end of the link member537is rotatably connected to the holding member505.

Accordingly, the link member535and the link member537rotate counterclockwise when the slide member525slide to the back side from the front side, so that the other end of the link member535and the other end of the link member537move in a direction away from the photosensitive drum103. Thus, the optical printhead105moves to the retracted position from the exposure position.

Next, a procedure where the optical printhead105moves from the state illustrated inFIG.7Bto the state illustrated inFIG.7A, i.e., from the retracted position to the exposure position, along with the slide movement of the slide member525will be described.

The slide member525moves to the front side from the back side along with the rotation of the cover558(not illustrated) to the closed state from the open state. When the slide member525slides to the front side from the back side, the link member535and the link member537rotate clockwise inFIGS.7A and7B. At the same time, the link member536and the link member538rotate counterclockwise. When the link member535and the link member537rotate clockwise along with the slide movement of the slide member525from the back side to the front side, the other end of the link member535and the other end of the link member537move in a direction approaching the photosensitive drum103. Thus, the optical printhead105moves to the exposure position from the retracted position. In the present exemplary embodiment, the movement direction of the optical printhead105that moves to the retracted position and to the exposure position substantially coincides with the optical axis direction of the lens array506.

When the holding member505of the optical printhead105gradually moves to the exposure position from the retracted position along with the slide movement of the slide member525, the contact pin514provided at one end of the holding member505in the longitudinal direction of the holding member505and the contact pin515provided at the other end of the holding member505contact the drum unit518. In other words, when the optical printhead105is located at the exposure position, the contact pin514and the contact pin515contact the frame of the drum unit518. The term frame used herein refers to a part of the frame member of the drum unit518. In the manner as described above, the position of the holding member505with respect to the drum unit518, i.e., the position of the optical printhead105, is determined.

When the position of the holding member505with respect to the drum unit518is determined as described above, the distance between the light-emitting surface of the lens array506and the photosensitive drum103is also determined, and thus the movement of the optical printhead105to the exposure position is completed.

The configurations of the first link mechanism530and the second link mechanism540will be described in more detail with reference toFIGS.8A and8BandFIGS.9A and9B.FIG.8Ais a schematic perspective view of the front side of the support member526as viewed from the left side.FIG.8Bis a schematic perspective view of the front side of the support member526as viewed from the right side. The first link mechanism530provided on the front side of the support member526will be described below. The configuration of the second link mechanism540is substantially the same as the configuration of the first link mechanism530, and thus the description thereof is omitted.

As illustrated inFIGS.8A and8B, the support member526includes a support shaft531and an E-shaped retaining ring533. A right side wall surface and a left side wall surface of the support member526processed into a U-shape are respectively provided with holes into which the support shaft531is inserted. In a state where the support shaft531is inserted into the holes, the support shaft531is fixed to the support member526with the E-shaped retaining ring533.

The slide member525is a plate-shaped member made of metal. As illustrated inFIG.8A, the slide member525is provided with a long hole691extending in the front-back direction. The support shaft531is inserted into the long hole691. In the present exemplary embodiment, the support shaft531is loosely fitted into the long hole691with a gap of about 0.1 to 0.5 mm in the vertical direction. The diameter of the long hole691in the longitudinal direction is about 350 mm. The configuration enables the slide member525to slide in the front-back direction by about 350 mm with respect to the support member526.

An assist member539is attached to one end of the slide member525(front side of the slide member525) in the longitudinal direction of the slide member525. The assist member539is provided with an accommodation space562. The accommodation space562accommodates a protrusion formed on the cover558. When the cover558rotates, the protrusion that moves with the rotating cover558is brought into contact with a side wall on the front side or a side wall on the back side of the accommodation space562. The protrusion pushes the side wall on the front side of the accommodation space562, thereby enabling the slide member525to move to the front side. In contrast, the protrusion pushes the side wall on the back side of the accommodation space562, thereby enabling the slide member525to move to the back side. With this configuration, the slide member525moves in the front-back direction along with the rotation of the cover558.

The first link mechanism530includes the link member535and the link member536. The link member535and the link member536are longitudinal resin plate materials. In the longitudinal direction of the link member535, a protrusion655is formed at one end (upper side inFIG.8A) of the link member535. In contrast, in the longitudinal direction of the link member535, a tube portion610is formed at the other end (lower side inFIG.8A) of the link member535. The protrusion655is fitted into an opening formed on the front side of the holding member505. This configuration enables the link member536to rotate about the protrusion655with respect to the holding member505. The tube portion610is a hollow cylinder. As illustrated inFIGS.8A and8B, a protrusion projecting from the slide member525is fitted into the tube portion610. This configuration enables the link member536to rotate also with respect to the slide member525.

One end (upper side inFIG.8B) of the link member536in the longitudinal direction is rotatably attached to the link member535. In other words, the link member535and the link member536are rotatably connected to each other. In contrast, the other end (lower side inFIG.8B) of the link member536in the longitudinal direction of the link member536is rotatably attached to the support member526. Specifically, a lower side wall surface of the link member536and a left side wall surface of the support member526are provided with holes, respectively, and an insertion pin532is inserted into the holes. With this configuration, the link member536is rotatably fixed to the support member526.

FIGS.9A and9Beach illustrate a state where the link member535and the link member536included in the first link mechanism530rotate. As described above, the tube portion610formed on the link member535is fitted to a protrusion534formed on the support member526. Accordingly, when the slide member525slides from the front side to the back side, the link member535rotates about the protrusion534clockwise inFIGS.9A and9B. Since the link member535and the link member536are rotatably connected to each other, the link member536rotates counterclockwise with respect to the slide member525along with the clockwise rotation of the link member535. In this case, the link member536rotates about the insertion pin532with respect to the support member526. When the link member535rotates while being rotatably supported by the link member536, the protrusion655of the link member535moves to the lower side.

Herein, where L1is a distance between the rotational center axis of the link member535with respect to the slide member525and the center axis of connection between the link member535and the link member536, L2is a distance between the rotational center axis of the link member536with respect to the support member526and the center axis of connection between the link member535and the link member536, and L3is a distance between the rotational center axis of the link member535with respect to the holding member505and the center axis of connection between the link member535and the link member536, the distances L1, L2, and L3are equal to each other. In general, such a link mechanism is referred to as a Scott-Russell mechanism. When the distances L1to L3are equal to each other, the movement direction of the protrusion655along with the slide movement of the slide member525coincides with the vertical direction. Specifically, the protrusion655moves along a dashed line A illustrated inFIG.9B. This configuration enables the holding member505to move in the vertical direction along with the slide movement of the slide member525.

(Grounding Mechanism)

As described above, since the holding member505is made of metal, the holding member505can be charged due to the effect of an electric field formed by the charger104. Since the holding member505is a longitudinal member, the holding member505behaves like an antenna when the holding member505acquires an electric charge. When the holding member505behaves like an antenna, noise may be superimposed on a signal to be transmitted through the wiring pattern552of the substrate502, which may cause a defective image. For this reason, it is desirable to ground the holding member505.

FIG.10is a diagram illustrating a grounding mechanism according to the present exemplary embodiment. The support member526made of metal is supported by the front side plate642provided on the front side of the image forming apparatus1and by the back side plate643provided on the back side of the image forming apparatus1. Accordingly, the support member526is grounded through one or both of the front side plate642and the back side plate643.

A plate spring711that is made of metal is attached to the back side of the support member526with a screw710. As illustrated inFIG.10, a leading end of the plate spring711contacts the contact pin515. The plate spring711is elastically deformed. The contact pin515is pressed in the rotational axis direction of the photosensitive drum103by a restoring force of the plate spring711. Specifically, the plate spring711presses the contact pin515in a direction from the front side to the back side of the image forming apparatus1. Since the plate spring711is constantly pressed against the contact pin515by an elastic force, the holding member505can be reliably grounded via the contact pin515. In the present exemplary embodiment, the plate spring711is used as a member via which the holding member505is grounded, but instead a wire spring or the like can be used as such a member. Instead of using a plate spring or a wire spring, the contact pin515and the support member526may be directly connected with a conductor wire to obtain an effect that the holding member505is grounded. However, since the optical printhead105according to the present exemplary embodiment moves to the exposure position and to the retracted position, if the contact pin515and the support member526are connected with a conductor wire, the conductor wire can be deformed when the optical printhead105is located at the retracted position. If the deformed conductor wire is caught on, for example, the link member535(536), the conductor wire can be damaged. Accordingly, it may be desirable to separately perform a process for routing the conductor wire. Therefore, it is desirable to use the plate spring711, as in the present exemplary embodiment, to obtain the effect that the holding member505is grounded.

FIG.11Aillustrates a positional relationship between the contact pin515and the plate spring711when the holding member505is located at the exposure position.FIG.11Billustrates a positional relationship between the contact pin515and the plate spring711when the holding member505is located at the retracted position. To simplify the illustration inFIGS.11A and11B, the holding member505is not illustrated. As seen fromFIGS.11A and11B, even when the contact pin515moves together with the holding member505that moves to the exposure position and to the retracted position, the plate spring711is constantly in contact with the contact pin515. In other words, the contact pin515moves together with the holding member505while being in contact with the plate spring711. Accordingly, the holding member505is constantly grounded via the contact pin515.

The shape of the conductive member701and the portion where the conductive member701is attached according to another exemplary embodiment will be described.

FIG.12illustrates an example where a conductive member704is used in place of the conductive member701. As illustrated inFIG.12, portions corresponding to both leg portions of the conductive member704are each bent at a middle portion thereof. Each of the pair of wall portions505bof the holding member505is provided with a dent705in place of the opening703. The bent portion of each of the portions corresponding to the both leg portions of the conductive member704is fitted into the dent705. Thus, the conductive member704is fixed to the holding member505.

FIG.13illustrates an example where the conductive member701is attached to the substrate502such that the conductive member701is brought into contact with the surface of the substrate502. In this case, before the substrate502is attached to the holding member505, the conductive member701is first fixed to the inside of the holding member505by bonding or the like. After that, the substrate502is inserted into the holding member505from below, and then the substrate502is fixed to the holding member505in a state where the substrate502is pressed against the conductive member701. It is desirable to form the ground pads550aand550bof the substrate502on the surface of the substrate502. The use of the configuration according to the present exemplary embodiment makes it possible to effectively use a space formed between the substrate502and the fixed portion505aof the holding member505. Consequently, the size of the optical printhead105in the vertical direction can be reduced.

As described above, according to the configuration of the present exemplary embodiment, the potential of the ground wire552bfor the wiring pattern552of the substrate502can be made equal to the potential of the holding member505with a simple configuration. Further, since the holding member505is grounded, the ground wire552bfor the wiring pattern552of the substrate502can be reliably grounded. Consequently, the intensity of noise emitted from the substrate502can be reduced.

The ground wire552bfor the wiring pattern552of the substrate502can be grounded with a simple configuration.

While the present disclosure has been described with reference to exemplary embodiments, it is to be understood that the disclosure 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.