Image forming apparatus

Abstract

To solve the problem in which: in a configuration that holds a substrate with a resin holder, a ground line of a wiring pattern on the substrate cannot be grounded through the holder.SOLUTION: In a configuration that holds a substrate with a metal holder, a ground line of a wiring pattern on the substrate and the holder are connected with a conductive member. By grounding the holder, the ground line of the wiring pattern is grounded through the holder.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an image forming apparatus having an exposure head.

Background Art

[0002] In image forming apparatuses such as printers and copiers, there are some that use an exposure head including a plurality of light emitting elements for exposing a photoreceptor. As examples of the light emitting elements, some use LEDs (Light Emitting Diodes), organic ELs (Electro Luminescence), etc. The exposure head has a resin holder that holds a substrate on which the light emitting elements are arranged and a lens array for condensing the light emitted from the light emitting elements onto the photoreceptor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to achieve further higher image quality of the image forming apparatus, it is necessary to reduce the intensity of noise radiated from the wiring pattern on the substrate. For this purpose, it is effective to ground the ground wire of the wiring pattern formed on the substrate. Here, since the substrate is held by a resin holder, the ground of the ground wire formed on the substrate cannot be taken through the holder.

[0005] Therefore, an object of the present invention is to provide a configuration capable of grounding the ground wire of the wiring pattern on the substrate with a simple configuration.

Means for Solving the Problems

[0006] The image forming apparatus according to the present invention includes a rotatable photoreceptor, a plurality of light emitting units arranged along the rotational axis direction of the photoreceptor and emitting light for exposing the photoreceptor, a driving unit for driving the plurality of light emitting units, and the driving unit A pad electrically connected thereto, and a substrate having the same, a lens array that condenses the light emitted from the plurality of light emitting Part units onto the photoreceptor, a holder made of metal that holds the substrate and the lens array, Connected to the reference potential and a conductive member that electrically connects them. An image forming apparatus characterized by comprising the same. A holder that extends in the optical axis direction of the lens array and has a pair of wall portions facing each other in the short side direction orthogonal to the rotation axis direction and the optical axis direction, and holds the substrate between the pair of wall portions in the short side direction; and contacts the pad and the inside of the wall portion, and connects the pad and the holder

Advantages of the Invention

[0007] The ground of the ground wire of the wiring pattern on the substrate can be taken with a simple configuration.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 6

Figure 7

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Figure 12

Figure 13

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. Note that dimensions, materials, shapes, relative arrangements, etc. of the components described below are not intended to limit the scope of the present invention only to these, unless otherwise specifically described.

[0010] (Image forming apparatus) First, the schematic configuration of the image forming apparatus 1 will be described. Fig. 1(a) is a schematic cross-sectional view of the image forming apparatus 1. The image forming apparatus 1 shown in Fig. 1(a) is a color printer (SFP: Single Function Printer) without a reading device, but the embodiment may be a copying machine with a reading device. Further, the embodiment is not limited to a color image forming apparatus including a plurality of photosensitive drums 103 as shown in Fig. 1(a), and may also be a color image forming apparatus including one photosensitive drum 103 or an image forming apparatus that forms a monochrome image.

[0011] The image forming apparatus 1 shown in Fig. 1(a) includes four image forming units 102Y, 102M, 102C, and 102K (hereinafter collectively referred to simply as "image forming unit 102") that form toner images of yellow, magenta, cyan, and black colors. Further, the image forming units 102Y, 102M, 102C, and 102K each include photosensitive drums 103Y, 103M, 103C, and 103K (hereinafter collectively referred to simply as "photosensitive drum 103"). Also, the image forming units 102Y, 102M, 102C, and 102K each include chargers 104Y, 104M, 104C, and 104K (hereinafter collectively referred to simply as "charger 104") that charge the photosensitive drums 103Y, 103M, 103C, and 103K, respectively. Moreover, the image forming units 102Y, 102M, 102C, and 102K include LED (Light Emitting Diode, hereinafter referred to as LED) exposure units 520Y, 520M, 520C, and 520K (hereinafter collectively referred to simply as "exposure unit 520") as exposure light sources that emit light for exposing the photosensitive drums 103Y, 103M, 103C, and 103K. Further, the image forming units 102Y, 102M, 102C, and 102K include developing devices 106Y, 106M, 106C, and 106K (hereinafter collectively referred to simply as "developing device 106") as developing means that develop the electrostatic latent images on the photosensitive drum 103 with toner and develop toner images of each color on the photosensitive drum 103. Note that Y, M, C, and K attached to the reference signs indicate the colors of the toner.

[0012] The image forming apparatus 1 shown in Fig. 1(a) is an image forming apparatus that adopts a so-called "bottom surface exposure method" in which the photosensitive drum 103 is exposed from below. Hereinafter, the description will proceed on the premise of an image forming apparatus that adopts the bottom surface exposure method, but as an embodiment, an image forming apparatus that adopts an "upper surface exposure method" in which the photosensitive drum 103 is exposed from above, such as the image forming apparatus 2 shown in Fig. 1(b), may also be used. In Fig. 1(b), the same reference numerals are used for the portions showing the same configuration as in Fig. 1(a).

[0013] The image forming apparatus 1 includes an intermediate transfer belt 107 onto which the toner image formed on the photosensitive drum 103 is transferred, and a primary transfer roller 108 (Y, M, C, K) that sequentially transfers the toner image formed on the photosensitive drum 103 onto the intermediate transfer belt. Further, the image forming apparatus 1 includes a secondary transfer roller 109 as a transfer means for transferring the toner image on the intermediate transfer belt 107 onto the recording paper P conveyed from the paper feed unit 101, and a fixing device 100 for fixing the secondarily transferred image onto the recording paper P.

[0014] (Image forming process) The exposure unit 520Y exposes the surface of the photosensitive drum 103Y charged by the charger 104Y. Thereby, an electrostatic latent image is formed on the photosensitive drum 103Y. Next, the developing device 106Y develops the electrostatic latent image formed on the photosensitive drum 103Y with yellow toner. The yellow toner image developed on the surface of the photosensitive drum 103Y is transferred onto the intermediate transfer belt 107 by the primary transfer roller 108Y. The magenta, cyan, and black toner images are also transferred onto the intermediate transfer belt 107 by the same image forming process.

[0015] The toner images of respective colors transferred onto the intermediate transfer belt 107 are conveyed to the secondary transfer unit T2 by the intermediate transfer belt 107. A transfer bias for transferring the toner image onto the recording paper P is applied to the secondary transfer roller 109 disposed in the secondary transfer unit T2. The toner image conveyed to the secondary transfer unit T2 is transferred onto the recording paper P conveyed from the paper feed unit 101 by the transfer bias of the secondary transfer roller 109. The recording paper P onto which the toner image is transferred is conveyed to the fixing device 100. The fixing device 100 fixes the toner image onto the recording paper P by heat and pressure. The recording paper P on which the fixing process has been performed by the fixing device 100 is discharged to the paper discharge unit 111.

[0016] (Drum unit and developing unit) The image forming apparatus 1 is attached with drum units 518Y, 518M, 518C, and 518K (hereinafter collectively referred to simply as "drum unit 518") each including a photosensitive drum 103. In this embodiment, the drum unit 518 is also referred to as a photoreceptor unit. The drum unit 518 is a cartridge that is replaced by an operator such as a user or a maintenance person. The drum unit 518 rotatably supports the photosensitive drum 103. Here, the drum unit 518 also functions as a drum support member that rotatably supports the photosensitive drum 103. In this embodiment, the drum unit 518 includes the drum support member. Specifically, the photosensitive drum 103 is rotatably supported by the frame of the drum unit 518. Note that the drum unit 518 may be configured not to include a charger 104 or a cleaning device.

[0017] Further, developing units 641Y, 641M, 641C, and 641K (hereinafter collectively referred to simply as "developing unit 641"), which are separate from the drum unit 518, are attached to the image forming apparatus 1 of this embodiment. The developing unit 641 of this embodiment is a cartridge in which a developing device 106 shown in Fig. 1(a) and a toner storage section are integrated. The developing device 106 includes a developing sleeve (not shown) that carries a developer. A plurality of gears for rotating a screw for stirring toner and a carrier are provided in the developing unit 641. When these gears deteriorate over time or the like, an operator removes the developing unit 641 from the apparatus main body of the image forming apparatus 1 and replaces it. Note that the embodiments of the drum unit 518 and the developing unit 641 may be a process cartridge in which the drum unit 518 and the developing unit 641 are integrated.

[0018] Fig. 2(a) is a perspective view showing a schematic structure around the drum unit 518 (Y, M, C, K) and around the developing unit 641 (Y, M, C, K) included in the image forming apparatus 1. Fig. 2(b) is a view showing a state in which the drum unit 518 is inserted into the image forming apparatus 1 from the outside of the apparatus main body.

[0019] As shown in FIG. 2(a), the image forming apparatus 1 includes a front plate 642 formed of sheet metal and a rear plate 643 also formed of sheet metal. The front plate 642 is a side wall provided on the front side of the image forming apparatus 1. The front plate 642 forms a part of the housing of the apparatus main body on the front side of the image forming apparatus 1 main body. The rear plate 643 is a side wall provided on the rear side of the image forming apparatus 1. The rear plate 643 forms a part of the housing of the apparatus main body on the back side of the image forming apparatus 1 main body. As shown in FIG. 2(a), the front plate 642 and the rear plate 643 are arranged facing each other, and a sheet metal (not shown) as a beam is bridged between the two. The front plate 642, the rear plate 643, and the beam (not shown) each constitute a part of the frame of the image forming apparatus 1. Here, with respect to the image forming apparatus 1 or its constituent members of the present embodiment, the front side or the front side means the side where the drum unit 518 is inserted into and removed from (inserted and removed) the apparatus main body.

[0020] An opening is formed in the front plate 642 so that the drum unit 518 and the developing unit 641 can be inserted into and removed from the front side of the image forming apparatus 1. The drum unit 518 and the developing unit 641 are mounted at predetermined positions in the image forming apparatus 1 main body through the opening. Further, the image forming apparatus 1 includes covers 558Y, 558M, 558C, 558K (hereinafter, collectively referred to simply as "cover 558") that cover the front sides of both the drum unit 518 and the developing unit 641. One end of the cover 558 is fixed to the image forming apparatus 1 main body by a hinge, and is rotatable with respect to the image forming apparatus 1 main body by the hinge. The replacement work is completed when the operator opens the cover 558, takes out the drum unit 518 or the developing unit 641 inside the main body, inserts a new drum unit 518 or developing unit 641, and closes the cover 558.

[0021] Here, as shown in FIGS. 2(a) and 2(b), in the following description, the side of the front plate 642 with respect to the apparatus main body is defined as the front side (front or front face side), and the side of the rear plate 643 is defined as the rear side (rear or back side). Further, when the photosensitive drum 103K on which an electrostatic latent image regarding the black toner image is formed is taken as a reference, the side on which the photosensitive drum 103Y on which an electrostatic latent image regarding the yellow toner image is formed is arranged is defined as the right side. When the photosensitive drum 103Y on which an electrostatic latent image regarding the yellow toner image is formed is taken as a reference, the side on which the photosensitive drum 103K on which an electrostatic latent image regarding the black toner image is formed is arranged is defined as the left side. Furthermore, the direction perpendicular to the front-rear direction and the left-right direction defined here and vertically upward is defined as the upward direction, and the direction perpendicular to the front-rear direction and the left-right direction defined here and vertically downward is defined as the downward direction. The defined front direction, rear direction, right direction, left direction, upward direction, and downward direction are shown in FIG. 2. Also, the direction of the rotation axis of the photosensitive drum 103 described in the following text coincides with the front-rear direction shown in FIG. 2. Also, the longitudinal direction of the optical print head 105 also coincides with the front-rear direction shown in FIG. 2. That is, the direction of the rotation axis of the photosensitive drum 103 and the longitudinal direction of the optical print head 105 coincide with each other.

[0022] (Exposure unit) Next, the exposure unit 520 including the optical print head 105 will be described. The optical print head 105 has an elongated shape extending in the rotational axis direction of the photosensitive drum 103. The optical print head 105 includes a holding member 505, a lens array 506, and a substrate 502. The lens array 506 and the substrate 502 are held by the holding member 505. In the present embodiment, the holding member 505 is a metal member formed by bending a plate material obtained by plating a galvanized steel sheet or a cold-rolled steel sheet. By using a metal plate material, the cost can be suppressed, and the strength can be obtained by performing bending processing. However, the configuration of the holding member 505 is not limited to the configuration of bending a metal plate material, and for example, so-called die casting may be used. Die casting refers to a product manufactured by cooling and solidifying molten metal injected into a mold (cavity) or its manufacturing method. When die casting is adopted as the manufacturing method, it can correspond to a complex shape depending on the original mold. On the other hand, since the cost of mold production is high, there is also a demerit that there is no cost merit when it is not necessary to manufacture the same product in large quantities. In the present embodiment, the holding member 505 may be manufactured by bending sheet metal or may be manufactured by adopting die casting. By adopting the metal holding member 505 for the optical print head 105, the strength of the optical print head 105 itself can be increased. In addition, the metal holding member 505 has higher thermal conductivity than a resin holding member. Therefore, even when the electronic components mounted on the substrate 502 are heated and the temperature of the space near the substrate rises, the possibility of deformation of the holding member 505 itself can be reduced.

[0023] By the way, as an example of an exposure method adopted in an electrophotographic image forming apparatus, there is a laser beam scanning exposure method in which an irradiation beam of a semiconductor laser is scanned by a polygon mirror or the like that rotates, and the photosensitive drum is exposed through an f-θ lens or the like. The "optical print head 105" described in this embodiment is used for an LED exposure method in which the photosensitive drum 103 is exposed using light emitting elements such as LEDs arranged along the rotation axis direction of the photosensitive drum 103, and is not used for the laser beam scanning exposure method described above.

[0024] The exposure unit 520 described in this embodiment is provided below the photosensitive drum 103 in the vertical direction with respect to the rotation axis of the photosensitive drum 103. LEDs as light emitting elements are provided on a substrate (not shown) of the holding member 505, and these light emitting elements expose the photosensitive drum 103 from below. However, the exposure unit 520 may be provided above the photosensitive drum 103 in the vertical direction with respect to the rotation axis of the photosensitive drum 103 to expose the photosensitive drum 103 from above (see Fig. 1(b)).

[0025] Fig. 3 is a schematic perspective view of the exposure unit 520 included in the image forming apparatus 1 of this embodiment. As shown in Fig. 3, the exposure unit 520 includes an optical print head 105, a support member 526, a first link mechanism 530, and a second link mechanism 540. In addition, a contact pin 514 and a contact pin 515 are provided on the holding member 505. Both the contact pin 514 and the contact pin 515 are straight pins made of metal. For example, the contact pin 515 is provided on the holding member 505 on one side (the back side) of the lens array 506 in the rotation axis direction of the photosensitive drum 103, and protrudes from both sides of the holding member 505 in the optical axis direction of the lens array 506. The same applies to the contact pin 514. When the contact pin 514 and the contact pin 515 abut against the drum unit 518, a gap is formed between the light emitting surface of the lens array 506 and the photosensitive drum 103. In this way, the position of the optical print head 105 with respect to the photosensitive drum 103 is determined.

[0026] Also, the contact pins 514 and 515 are fixed to the metal holding member 505 by welding. Thus, in this embodiment, the contact pins 514 and 515 are integrated with the holding member 505. Note that the fixing of the contact pins 514 and 515 to the holding member 505 is not limited to welding and may be fixed by an adhesive. Also, threads may be cut on the contact pins 514 and 515 and they may be fastened by screwing into the holding member 505.

[0027] The first link mechanism 530 includes a link member 535 and a link member 536. The second link mechanism 540 includes a link member 537 and a link member 538. Although details will be described later, the link member 535 is attached on the back side of the center of the holding member 505 in the rotational axis direction of the photosensitive drum 103, and the link member 537 is attached on the front side of the center of the holding member 505 in the rotational axis direction of the photosensitive drum 103.

[0028] As the cover 558 provided on the front side of the image forming apparatus 1 is opened and closed, a slide member (slider) 525 described later slides in the front - rear direction. In conjunction with the sliding movement of the slide member 525, the link members 535 to 538 rotate, and the optical print head 105 moves up and down.

[0029] In this embodiment, the optical print head 105 is provided below the photosensitive drum 103 in the vertical direction. That is, in the image forming apparatus 1 of this embodiment, the optical print head 105 exposes the photosensitive drum 103 from below in the vertical direction.

[0030] Further, as shown in FIG. 3, the exposure unit 520 includes a support member 526. The support member 526 supports the optical print head 105 via the first link mechanism 530 and the second link mechanism 540. Specifically, the link member 535 of the first link mechanism 530 supports the holding member 505, and the link member 537 of the second link mechanism 540 supports the holding member 505. In this way, the link member 535 and the link member 537 support the holding member 505 directly or indirectly. Since the link member 535 and the link member 537 are made of resin, the holding member 505 is in a state where it is not grounded, that is, in an electrically floating state.

[0031] The support member 526 is formed by bending a sheet metal into a U-shape. The support member 526 is a longitudinally shaped member extending in the direction of the rotation axis of the photosensitive drum 103. One end side (front side) of the support member 526 in the longitudinal direction is fixed to the front side plate 642, and the other end side (rear side) of the support member 526 in the longitudinal direction is fixed to the rear side plate 643. In this way, the position of the support member 526 with respect to the photosensitive drum 103 is fixed on the side opposite to the side where the photosensitive drum 103 is arranged with respect to the holding member 505 in the optical axis direction of the lens array 506. The support member 526 is grounded via one or both of the front side plate 642 and the rear side plate 643.

[0032] The support member 526 includes a slide member 525 that is movable in the longitudinal direction of the support member 526. As the slide member 525 moves with respect to the support member 526, the link members 535 to 538 rotate and the optical print head 105 moves with respect to the support member 526.

[0033] (Configuration of the substrate and the lens array) Next, the substrate 502 and the lens array 506 will be described with reference to FIG. 4. First, the substrate 502 will be described. FIG. 4(a) is a schematic perspective view of the substrate 502. FIG. 4(b1) shows the arrangement of a plurality of LEDs 503 provided on the substrate 502, and FIG. 4(b2) shows an enlarged view of FIG. 4(b1).

[0034] An LED chip 639 is mounted on the substrate 502. As shown in FIG. 4(a), the LED chip 639 is provided on one surface of the substrate 502, and the connector 504 is provided on the back surface. A wiring pattern for supplying signals to each LED chip 639 is formed on the substrate 502. One end of a flexible flat cable (FFC) (not shown) is connected to the connector 504. A substrate different from the substrate 502 is provided in the main body of the image forming apparatus 1. A CPU for controlling the light emission timing of the LED 503 and the like is mounted on this substrate. The other end of the FFC is connected to a connector mounted on a substrate provided in the image forming apparatus 1. The FFC transmits a drive signal for driving the LED 503 from the substrate provided in the image forming apparatus 1 to the substrate 502.

[0035] The LED chip 639 mounted on the substrate 502 will be described in more detail. As shown in FIGS. 4(b1) and 4(b2), a plurality of LED chips 639-1 to 639-29 (29 in total) in which a plurality of LEDs 503 are arranged are arrayed on one surface of the substrate 502. In each of the LED chips 639-1 to 639-29, 516 LEDs (light emitting elements) are arranged in a row in the longitudinal direction thereof. The center-to-center distance k2 between adjacent LEDs in the longitudinal direction of the LED chip 639 corresponds to the resolution of the image forming apparatus 1. Since the resolution of the image forming apparatus 1 in this embodiment is 1200 dpi, in the longitudinal direction of the LED chips 639-1 to 639-29, the LEDs are arranged in a row such that the center-to-center distance between adjacent LEDs is 21.16 μm. Therefore, the exposure range of the optical print head 105 in this embodiment is approximately 316 mm. The photosensitive layer of the photosensitive drum 103 is formed with a width of 316 mm or more. Since the length of the long side of the A4 size recording paper and the length of the short side of the A3 size recording paper are 297 mm, the optical print head 105 in this embodiment has an exposure range capable of forming an image on the A4 size recording paper and the A3 size recording paper.

[0036] LED chips 639-1 to 639-29 are alternately arranged in two rows along the rotation axis direction of the photosensitive drum 103. That is, as shown in Fig. 4(b1), the odd-numbered LED chips 639-1, 639-3, ··· 639-29 counted from the left are mounted in a row in the longitudinal direction of the substrate 502, and the even-numbered LED chips 639-2, 639-4, ··· 639-28 are mounted in a row in the longitudinal direction of the substrate 502. By arranging the LED chips 639 in this way, as shown in Fig. 4(b2), in the longitudinal direction of the LED chip 639, the center-to-center distance k1 between the centers of the LEDs arranged at one end of one LED chip 639 and the other end of the other adjacent LED chip 639 among different adjacent LED chips 639 can be made equal to the center-to-center distance k2 between adjacent LEDs on one LED chip 639.

[0037] In addition, in this embodiment, the light-emitting element is a semiconductor LED which is a light-emitting diode, but for example, it may also be an OLED (Organic Light Emitting Diode). This OLED is also called organic EL (Organic Electro-Luminescence) and is a current-driven light-emitting element. The OLEDs are arranged in a line along the main scanning direction (the rotation axis direction of the photosensitive drum 103) on, for example, a TFT (Thin Film Transistor) substrate, and are electrically connected in parallel by a power supply wiring provided along the same main scanning direction.

[0038] Next, the lens array 506 will be described. FIG. 4(c1) is a schematic view of the lens array 506 as seen from the photosensitive drum 103 side. Further, FIG. 4(c2) is a schematic perspective view of the lens array 506. The lens array 506 has the role of condensing the light emitted from the LED 503 onto the surface of the photosensitive drum 103. As shown in FIG. 4(c1), these plurality of lenses are arranged in two rows along the arrangement direction of the plurality of LEDs 503. Each lens is alternately arranged such that one lens of the other row is arranged so as to be in contact with both of the adjacent lenses in the arrangement direction of the lenses in one row. Each lens is a cylindrical glass rod lens and has an incident surface on which the light emitted from the LED 503 is incident and an exit surface from which the light incident from the incident surface exits. Note that the material of the lens is not limited to glass and may be plastic. The shape of the lens is not limited to a cylindrical shape and may be a polygonal prism such as a hexagonal prism, for example.

[0039] The dotted line Z shown in FIG. 4(c2) indicates the optical axis of the lens. The optical print head 105 is moved in a direction generally along the optical axis of the lens indicated by the dotted line Z by the above-described moving mechanism 640. The optical axis of the lens referred to here means a line connecting the center of the light exit surface of the lens and the focal point of the lens when any one lens is selected from the plurality of lenses constituting the lens array 506. Strictly speaking, the optical axes of the respective lenses may be slightly different from each other. Even if the angle formed by the optical axis of a certain lens and the optical axis of another lens is not 0 degrees, that angle is a small one. When referring to the "optical axis of the lens", such a slight error is not considered, and it is considered to mean the optical axis of any one lens selected from the plurality of lenses constituting the lens array 506. And it is considered that the direction of the optical axis is the same as the direction of the optical axes of the other lenses.

[0040] Next, the wiring pattern 552 on the substrate 502 will be described. FIG. 5 shows the back surface of the substrate 502. An LED chip 639 having an LED 503 is mounted on the front surface of the substrate 502, and electronic components such as driver ICs 551a and 551b for driving the LED 503 are mounted on the back surface of the substrate 502. That is, the back surface of the substrate means the surface of the substrate 502 that is opposite to the surface on which the light-emitting element is mounted.

[0041] The wiring pattern 552 mentioned here refers to a plurality of electric wires formed on the substrate 502. Typical types of electric wires include an electric wire 552a (power line) for driving the driver IC 551a (551b) and a ground wire 552b having a reference potential. The ground wire 552b also functions as an electric wire for grounding the driver ICs 551a and 551b. Here, the electric wire 552a is described as a power line, but examples of the type of the electric wire 552a include a signal line through which a control signal for driving the LED 503 is transmitted.

[0042] A connector 504 is mounted near the center of the back surface of the substrate 502. An FFC 510 is attached to the connector 504. The FFC 510 is a cable composed of a plurality of electric wires. Examples of the types of electric wires include an electric wire through which a control signal (driving signal) for controlling the light emission timing of the LED 503 is transmitted, a supply line (also referred to as a power line) for supplying power, and a ground wire for grounding the wiring pattern 552.

[0043] Also, ground pads 550a and 550b having the same potential as the ground wire 552b are provided on the back surface of the substrate. The conduction member 701 described later contacts the ground pads 550a (550b) and the holding member 505 to electrically connect the two.

[0044] (Conduction member) FIG. 6(a) is a cross-sectional view when the optical print head 105 is cut along a plane perpendicular to the longitudinal direction of the optical print head 105. As shown in FIG. 6(a), the substrate 502 and the lens array 506 are held by the holding member 505 so as to face each other.

[0045] Here, as is clear from the cross-sectional view of the image forming apparatus 1 in FIG. 1, a charger 104 is disposed near the optical print head 105. A high voltage is applied to the charging roller of the charger 104, and a strong electric field is formed near the charging roller. Therefore, since the optical print head 105 is also located in the strong electric field, the holding member 505 will also become charged. Thus, when a difference occurs between the potential of the holding member 505 and the potential of the wiring pattern 552 of the substrate 502, there is a risk of discharge occurring between the holding member 505 and the wiring pattern 552. Even when the holding member 505 is grounded, depending on poor contact between components constituting the grounding path, it may not be possible to sufficiently ground. In this way, it is difficult to completely eliminate the potential difference between the holding member 505 and the wiring pattern 552 of the substrate 502. Therefore, a configuration is required that brings the potential difference between the holding member 505 and the wiring pattern 552 of the substrate 502 as close to zero as possible.

[0046] In recent years, the image forming apparatus 1 has been required to operate at even higher speeds. Along with this, the requirements for the transmission accuracy of signals for driving the light emitting elements have also increased. A main cause of reducing the signal transmission accuracy is noise radiated from the wiring pattern 552 of the substrate 502. The noise radiated from the wiring pattern 552 may affect signals being transmitted in other parts of the wiring pattern 552. To reduce the intensity of the noise radiated from the wiring pattern 552, it is desirable to sufficiently ground the ground wire of the wiring pattern 552. Generally, the ground of the ground wire of the wiring pattern 552 is taken through the ground wire of the FFC 510. However, the ground wire of the FFC 510 is very thin, and it is difficult to say that it is sufficient for grounding the ground wire of the wiring pattern 552.

[0047] Therefore, in the optical print head 105 in the present embodiment, the ground of the wiring pattern 552 of the substrate 502 is taken by electrically connecting the ground wire 552b of the wiring pattern 552 of the substrate 502 and the holding member 505.

[0048] As shown in FIG. 5, the holding member 505 has a fixing portion 505a in which an opening 708 into which the lens array 506 is inserted is formed, and a pair of wall portions 505b extending from both ends of the fixing portion 505a in a direction perpendicular to the rotation axis direction of the photosensitive drum 103. In the present embodiment, the holding member 505 is formed by bending a single sheet of sheet metal. The pair of wall portions 505b are bent at both end portions of the fixing portion 505a so as to protrude toward the side opposite to the side where the photosensitive drum 103 is disposed.

[0049] Here, openings 703 are formed in the pair of wall portions 505b. Protrusions formed on the conduction member 701 described later are fitted into the openings 703. The conduction member 701 is a conductive component and electrically connects the ground wire 552b of the wiring pattern 552 formed on the substrate 502 and the holding member 505. As a result, the ground wire 552b of the wiring pattern 552 and the holding member 505 are at the same potential.

[0050] FIG. 6(b) is a view of the holding member 505 seen from below, and FIG. 6(c) is a view for explaining a method of attaching the conduction member 701 to the holding member 505.

[0051] As can be seen from FIG. 6(b), the conduction member 701 is a U-shaped metal component, and the plate-like portions corresponding to both legs are elastically deformable. As shown in FIG. 6(c), when the conduction member 701 is inserted from below the holding member 505, the portions corresponding to both legs of the conduction member 701 are bent inward and fitted into the holding member 505.

[0052] (Moving mechanism) Next, with reference to FIG. 7, a mechanism will be described in which the optical print head 105 moves in conjunction with the sliding movement of the slide member 525. FIG. 7 is a view of the exposure unit 520 as seen from the left side. For simplicity of explanation, the support member 526 is not shown. Note that FIG. 7(a) shows a state in which the optical print head 105 is located at the exposure position (the first position), which is the position when the optical print head 105 exposes the photosensitive drum 103. On the other hand, FIG. 7(b) shows a state in which the optical print head 105 is located at the retracted position (the second position) retracted from the photosensitive drum 103 compared to the exposure position. Here, in the present embodiment, the distance between the photosensitive drum 103 and the light emission surface of the lens array 506 when the optical print head 105 is located at the exposure position is approximately 3 mm.

[0053] As shown in FIG. 7, a link member 535 is rotatably connected to one end side of the slide member 525 in the longitudinal direction of the slide member 525, and a link member 537 is rotatably connected to the other end side of the slide member 525 in the longitudinal direction of the slide member 525. As the cover 558 (not shown) is rotated from the closed state to the open state, the slide member 525 slides from the front side to the back side. When the slide member 525 slides from the front side to the back side, the link member 535 and the link member 537 rotate counterclockwise as referred to in FIG. 7. Also, the link member 535 and the link member 536 are rotatably connected to each other. The link member 537 and the link member 538 are also rotatably connected to each other.

[0054] Since one end of the link member 536 is rotatably connected to a support member 526 (not shown), the link member 536 also rotates with respect to the support member 526 in conjunction with the rotation of the link member 535. Also, since one end of the link member 538 is rotatably connected to a support member 526 (not shown), the link member 538 also rotates with respect to the support member 526 in conjunction with the rotation of the link member 537. When the slide member 525 moves from the front side toward the back side, both the link member 536 and the link member 538 rotate clockwise with respect to the support member 526. Here, the other end of the link member 535 is rotatably connected to the holding member 505, and the other end of the link member 537 is rotatably connected to the holding member 505. Therefore, in conjunction with the slide member 525 slidingly moving from the front side toward the back side, the link member 535 and the link member 537 rotate counterclockwise, and the other end of the link member 535 and the other end of the link member 537 move away from the photosensitive drum 103, respectively. Thus, the optical print head 105 moves from the exposure position toward the retracted position.

[0055] Next, the manner in which the optical print head 105 moves from the state shown in FIG. 7(b) to the state shown in FIG. 7(a), that is, from the retracted position toward the exposure position, in conjunction with the sliding movement of the slide member 525 will be described.

[0056] The slide member 525 moves from the back side toward the front side in conjunction with the rotation of a cover 558 (not shown) from an open state to a closed state. When the slide member slides from the back side toward the front side, the link member 535 and the link member 537 rotate clockwise as shown in FIG. 7. At the same time, the link member 536 and the link member 538 rotate counterclockwise. In conjunction with the slide movement of the slide member 525 from the back side toward the front side, as the link member 535 and the link member 537 rotate clockwise, the other end sides of the link member 535 and the link member 537 move in directions approaching the photosensitive drum 103. Thus, the optical print head 105 moves from the retracted position toward the exposure position. In the present embodiment, the moving direction of the optical print head 105 that moves between the retracted position and the exposure position substantially coincides with the optical axis direction of the lens array 506.

[0057] As the holding member 505 of the optical print head 105 moves from the retracted position toward the exposure position in conjunction with the slide movement of the slide member 525, a contact pin 514 provided at one end side of the holding member 505 in the longitudinal direction of the holding member 505 and a contact pin 515 provided at the other end side of the holding member 505 abut against the drum unit 518. In other words, when the optical print head 105 is positioned at the exposure position, the contact pin 514 and the contact pin 515 are in contact with the frame of the drum unit 518. Here, the frame refers to a part of the frame of the drum unit 518. Thus, the position of the holding member 505 with respect to the drum unit 518, that is, the position of the optical print head 105 is determined.

[0058] When the position of the holding member 505 with respect to the drum unit 518 is determined as described above, the distance between the photosensitive drum 103 and the light emitting surface of the lens array 506 is also determined, and the movement of the optical print head 105 to the exposure position is completed.

[0059] Using FIGS. 8 and 9, the mechanism of link mechanism 530 and link mechanism 540 will be described in more detail. FIG. 8(a) is a schematic perspective view of the front side of support member 526 as viewed from the left side. Also, FIG. 8(b) is a schematic perspective view of the front side of support member 526 as viewed from the right side. Hereinafter, link mechanism 530 provided on the front side of support member 526 will be described. Since the configuration of link mechanism 540 is substantially the same as that of link mechanism 530, its description will be omitted.

[0060] As shown in FIG. 8, support member 526 includes a support shaft 531 and an E-ring 533. Holes through which support shaft 531 is inserted are formed in the right side wall surface and the left side wall surface of support member 526 processed in a U-shape. With support shaft 531 inserted through these holes, support shaft 531 is fixed to support member 526 by E-ring 533.

[0061] Slide member 525 is a plate-shaped member made of metal. As shown in FIG. 8(a), a long hole 691 extending in the front-rear direction is formed in slide member 525. Support shaft 531 is inserted through this long hole 691. In the present embodiment, support shaft 531 is loosely fitted in long hole 691 with a gap of about 0.1 to 0.5 mm in the vertical direction. Also, the diameter in the longitudinal direction of long hole 691 is about 350 mm. Thereby, slide member 525 can slide in the front-rear direction by about 350 mm with respect to support member 526.

[0062] Also, an auxiliary member 539 is attached to one end side (the front side of the slide member 525) of the slide member 525 in the longitudinal direction. A housing space 562 is formed in the auxiliary member 539. Protrusions provided on the cover 558 are housed in the housing space 562. When the cover 558 rotates, the protrusions that move together with the rotating cover 558 abut against the front side wall or the back side wall of the housing space 562. By the protrusions pushing in the front side wall of the housing space 562, the slide member 525 moves forward. On the other hand, by the protrusions pushing in the back side wall of the housing space 562, the slide member 525 moves backward. In this way, the slide member 525 also moves back and forth in conjunction with the rotation of the cover 558.

[0063] The link mechanism 530 includes a link member 535 and a link member 536. Both the link member 535 and the link member 536 are plate members made of resin in a longitudinal shape. A protrusion 655 is formed at one end side (the upper side in FIG. 8(a)) of the link member 535 in the longitudinal direction. On the other hand, a cylindrical portion 610 is formed at the other end side (the lower side in FIG. 8(a)) of the link member 535 in the longitudinal direction. The protrusion 655 fits into an opening formed on the front side of the holding member 505. Thereby, the link member 536 can rotate with respect to the holding member 505 with the protrusion 655 as the rotation center. The cylindrical portion 610 is a hollow cylinder. In FIG. 8, a protrusion protruding from the slide member 525 is fitted into the cylindrical portion 610. Thereby, the link member 536 can also rotate with respect to the slide member 525.

[0064] Also, one end side in the longitudinal direction of the link member 536 (the upper side in FIG. 8(b)) is rotatably attached to the link member 535. That is, the link member 535 and the link member 536 are rotatable relative to each other. On the other hand, the other end side of the link member 536 in the longitudinal direction of the link member 536 (the lower side in FIG. 8(b)) is rotatably attached to the support member 526. Specifically, holes are formed in the lower side of the link member 536 and the left side wall surface of the support member 526, and the insertion pin 532 is inserted through these holes. Thus, the link member 536 is rotatably fixed to the support member 526.

[0065] FIG. 9 is a diagram for explaining the rotation states of the link member 535 and the link member 536 included in the link mechanism 530. As described above, the cylindrical portion 610 formed in the link member 535 is fitted to the protrusion 534 formed in the support member 526. Therefore, when the slide member 525 slides from the front side toward the back side, the link member 535 rotates clockwise (in the sense of FIG. 9) with the protrusion 534 as the rotation center. Since the link member 535 and the link member 536 are rotatably connected to each other, the link member 536 rotates counterclockwise relative to the slide member 525 in conjunction with the clockwise rotation of the link member 535. At this time, the link member 536 rotates relative to the support member 526 with the insertion pin 532 as the rotation center. The link member 535 rotates while being rotatably supported by the link member 536, so that the protrusion 655 of the link member 535 moves downward.

[0066] Here, let the distance between the rotation center axis of the link member 535 with respect to the slide member 525 and the connection center axis of the link member 535 and the link member 536 be L1, the distance between the rotation center axis of the link member 536 with respect to the support member 526 and the connection center axis of the link member 535 and the link member 536 be L2, and the distance between the rotation center axis of the link member 535 with respect to the holding member 505 and the connection center axis of the link member 535 and the link member 536 be L3. Then, L1 to L3 are equal to each other. Generally, such a link mechanism is also called a Scott Russell mechanism. By making the distances L1 to L3 equal, the moving direction of the protrusion 655 linked to the sliding movement of the slide member 525 becomes the vertical direction. Specifically, the protrusion 655 moves on the dotted line A shown in FIG. 9(b). Thereby, the holding member 505 can be moved in the vertical direction in conjunction with the sliding movement of the slide member 525.

[0067] (Grounding mechanism) As described above, since the holding member 505 is made of metal, it may be charged under the influence of the electric field formed by the charger 104. Since the holding member 505 is a longitudinally shaped member, when it has an electric charge, it behaves like an antenna. When the holding member 505 behaves like an antenna, noise may be added to the signal transmitted through the wiring pattern 552 of the substrate 502, which may cause image defects. Therefore, it is necessary to ground the holding member 505.

[0068] FIG. 10 is a diagram for explaining the grounding mechanism in the present embodiment. The metal support member 526 is supported by the front side plate 642 provided on the front side of the image forming apparatus 1 and the rear side plate 643 provided on the back side of the image forming apparatus 1. Therefore, the support member 526 is grounded by either one or both of the front side plate 642 and the rear side plate 643.

[0069] A leaf spring 711 made of metal is attached by screws 710 to the back side of the support member 526. As shown in FIG. 10, the tip of the leaf spring 711 is in contact with the pin 515. The leaf spring 711 is elastically deformed, and its restoring force presses the pin 515 in the rotational axis direction of the photosensitive drum 103. Specifically, the leaf spring 711 presses the pin 515 in the direction from the front side to the back side of the image forming apparatus 1. Since the leaf spring 711 is constantly pressed toward the pin 515 by the elastic force, the ground of the holding member 505 can be surely taken through the pin 515. In the present embodiment, the spring 711 that was used as the member for taking the ground of the holding member 505 is used, but a coil spring or the like may also be used. Further, if the purpose is to achieve the effect of taking the ground, instead of a leaf spring or a coil spring, the pin 515 and the support member 526 may be directly connected by a conducting wire. However, since the optical print head 105 of the present embodiment moves between the exposure position and the retracted position, if the pin 515 and the support member 526 are connected by a conducting wire, when the optical print head 105 is in the retracted position, the conducting wire will bend. If the bent conducting wire gets caught on, for example, the link member 535(536), there is a risk of damage to the conducting wire. Therefore, separate processing is required for the routing of the conducting wire. Thus, if the only purpose is to take the ground of the holding member 505, it is preferable to use the leaf spring 711 as in the present embodiment.

[0070] FIG. 11 is a diagram for explaining the positional relationship between the pin 515 and the leaf spring 711 when the holding member 505 is in the exposure position and the positional relationship between the pin 515 and the leaf spring 711 when the holding member 505 is in the retracted position. FIG. 11(a) is a diagram for explaining the positional relationship between the pin 515 and the leaf spring 711 when the holding member 505 is in the exposure position, and FIG. 11(b) is a diagram for explaining the positional relationship between the pin 515 and the leaf spring 711 when the holding member 505 is in the retracted position. In both figures, for the sake of simplicity of explanation, the holding member 505 is not shown. As can be seen from these figures, even when the pin 515 moves together with the holding member 505 that moves between the exposure position and the retracted position, the leaf spring 711 always contacts the pin 515. In other words, the pin 515 moves together with the holding member 505 while contacting the leaf spring 711. Therefore, the ground of the holding member 505 is always taken through the pin 515.

[0071] (Other embodiments) Another embodiment regarding the shape of the conductive member 701 and the attachment location of the conductive member 701 will be described.

[0072] FIG. 12 shows an example in which the conductive member 704 is used instead of the conductive member 701. As shown in FIG. 12, the portions corresponding to both legs of the conductive member 704 are bent in the middle. Further, instead of the opening 703, a recess 705 is formed in a pair of wall portions 505b of the holding member 505. The bent portion in the middle of the portions corresponding to both legs of the conductive member 704 fits into the recess 705. In this way, the conductive member 704 is fixed to the holding member 505.

[0073] FIG. 13 shows an example of attaching the conductive member 709 in contact with the surface of the substrate 502. In this case, before attaching the substrate 502 to the holding member 505, first, the conductive member 709 is fixed by adhering it inside the holding member 505 or the like. Then, the substrate 502 is inserted from below the holding member 505, and the substrate 502 is fixed to the holding member 505 in a state where the substrate 502 is pressed against the conductive member 709. Although it is necessary to provide the ground pads 550a and 550b of the substrate 502 on the surface of the substrate 502, by adopting this configuration, the space formed between the substrate 502 and the fixing portion 505a of the holding member 505 can be effectively utilized, so that the optical print head 105 can be miniaturized in the vertical direction.

[0074] As described above, according to the configuration of the present embodiment, the potential of the ground wire 552b of the wiring pattern 552 of the substrate 502 and the potential of the holding member 505 can be made the same with a simple configuration. Further, since the holding member 505 is grounded, the ground of the ground wire 552b of the wiring pattern 552 of the substrate 502 can be surely taken. Thereby, the intensity of the noise radiated from the wiring pattern 552 of the substrate 502 can be reduced.

Description of Reference Numerals

[0075] 1 Image forming apparatus 105 Optical print head 502 Substrate 504 Connector 505 Holding member 510 Flexible flat cable 552 Wiring pattern 552a Electric wire 552b Ground wire 550a, 550b Ground pads 701 Conductive member 703 Opening

Claims

1. A rotatable photoreceptor; a plurality of light-emitting units arranged along the rotation axis direction of the photoreceptor and emitting light for exposing the photoreceptor; a driving unit for driving the plurality of light-emitting units; and a pad electrically connected to the driving unit, a substrate having the same; a lens array that condenses the light emitted from the plurality of light-emitting units onto the photoreceptor; a holder made of metal that holds the substrate and the lens array and is grounded, extending in the optical axis direction of the lens array, having a pair of wall portions facing each other in the short side direction orthogonal to the rotation axis direction and the optical axis direction, and holding the substrate between the pair of wall portions in the short side direction; a conductive member that contacts the pad and the inside of the pair of wall portions and conducts the pad and the holder; An image forming apparatus comprising the above.

2. The image forming apparatus according to claim 1, wherein the pad and the driving unit are electrically connected.

3. The image forming apparatus according to claim 1, wherein the conductive member is provided on the holder.

4. The image forming apparatus according to claim 1, wherein the pad is provided on the substrate on the side opposite to the side where the light-emitting unit is mounted.

5. The conductive member is a leaf spring formed with protrusions, holes into which the protrusions are fitted are formed in the pair of wall portions, The image forming apparatus according to claim 1, wherein the conductive member is fixed to the pair of wall portions by fitting the protrusions into the holes in a state where the conductive member is bent.

6. The image forming apparatus according to any one of claims 1 to 5, further comprising a moving mechanism that moves the holder to a first position that is a position for exposing the photoreceptor and a second position that is farther from the photoreceptor than the first position.

7. A flexible flat cable connected to the substrate and transmitting a driving signal for driving the driving unit is provided, The image forming apparatus according to any one of claims 1 to 6, wherein the flexible flat cable has an electric wire for grounding the driving unit.

8. A rotatable photoreceptor; A substrate having a plurality of light-emitting units that are arranged along the rotation axis direction of the photoreceptor and emit light for exposing the photoreceptor, a driving unit for driving the plurality of light-emitting units, and a wiring pattern including a ground wire for grounding the driving unit. A lens array that condenses the light emitted from the plurality of light-emitting units onto the photoreceptor. A metal holder that holds the substrate and the lens array and is grounded. A conductive member that electrically connects the holder and the ground wire. The holder further has an opening into which the lens array is inserted, a fixing portion for fixing the lens array, and a pair of wall portions that protrude from both ends of the fixing portion in a direction perpendicular to the rotation axis direction, on the side opposite to the side where the photoreceptor is disposed. The substrate is fixed to the pair of wall portions between the pair of wall portions. The conductive member is fixed to the ground wire and the pair of wall portions. An image forming apparatus characterized by the above.

Images