JP2020086035A - Image formation device with optical printing head - Google Patents

Abstract

To remove the possibility that the static electricity which has flown from a finger tip of an operator to a conductive member will flow to a substrate or a control substrate of an optical print head when the earth route from a conductive member to the ground circuit of a power source substrate partially exists in a part of the earth route from the substrate of the optical print head to the ground circuit.SOLUTION: The earth route from a conductive member to the ground circuit of a power source substrate extends away from the substrate of the optical print head and the control substrate.SELECTED DRAWING: Figure 6

Description

The present invention relates to an image forming apparatus including a cover that opens and closes an opening formed in a main body of an apparatus, and the cover is provided with an optical print head.

An image forming apparatus such as a printer or a copying machine has an optical print head including a plurality of light emitting elements for exposing a photosensitive drum. As an optical print head, there is one using an LED (Light Emitting Diode), an organic EL (Electro Luminescence), or the like as an example of a light emitting element. The optical print head includes a substrate in which a plurality of these light emitting elements are arranged in, for example, one row or two rows in a staggered pattern along the rotation axis direction of the photosensitive drum. Further, the optical print head includes a plurality of lenses for condensing light emitted from the plurality of light emitting elements on the photosensitive drum. The plurality of lenses are arranged between the plurality of light emitting elements and the photosensitive drum so as to face the surface of the photosensitive drum along the arrangement direction of the light emitting elements. The light emitted from the plurality of light emitting elements is condensed on the surface of the photosensitive drum via the lens, and an electrostatic latent image is formed on the photosensitive drum.

Further, as an image forming apparatus including an optical print head, there is one in which an optical print head is provided on an upper cover that is rotatable with respect to a main body housing. An opening is formed in the upper part of the main body housing, and the upper cover covers this opening. The upper cover rotates with the back side of the main body housing as a rotation axis. The optical print head moves to an exposure position for exposing the photosensitive drum and a retracted position retracted from the photosensitive drum with respect to the exposure position in association with the rotation of the upper cover. The optical print head is located at the retracted position when the upper cover is opened to open the opening. On the other hand, when the upper cover is closed to close the opening, the optical print head is located at the exposure position.

In the configuration in which the optical print head is provided on the upper cover as described above, the cable for transmitting a signal to the optical print head may be exposed to the user side when the upper cover is opened. When the user's finger approaches the cable with the upper cover open, static electricity may be discharged from the finger to the cable, and the semiconductor element or the like on the substrate connected to the cable may be damaged. Therefore, a configuration has been proposed in which a conductive member (conductive portion) is provided on the user side of the cable to prevent static electricity from being scattered from the user's finger to the cable (see, for example, Patent Document 1). In the image forming apparatus disclosed in Patent Document 1, the conductive member is formed by cutting and raising a sheet metal supported by an upper cover (top cover). Since the sheet metal is grounded, the conductive member is also grounded.

JP, 2014-044333, A

The LED substrate included in the optical print head and the control substrate included in the main body housing are electrically connected by a cable. The cable has a signal line for transmitting a signal from the control board to the LED board and a GND line. Further, the control board is grounded via a ground electrode for commercial power input which the power supply board has. Therefore, the LED board is grounded via the ground paths (1) to (3), which are (1) the GND line of the cable, (2) the control board, and (3) the power supply board.

Here, the grounding of the conductive member and the grounding of the LED substrate may be provided on the sheet metal of the upper cover. In this case, the ground path of the conductive member is (1) LED board, (2) cable GND line, (3) control board, and (4) power board, which are the paths (1) to (4). There will be a ground path for the LED substrate in a part of. In such a configuration, there is a possibility that static electricity, which has flown from the user's fingertip to the conductive member, flows through a part of the LED board or a part of the control board and damages the LED board or the control board.

To solve the above problems, the image forming apparatus of the present invention has an opening formed therein, a main body housing to which a drum unit having a photosensitive drum is detachable, a position where the opening through which the detachable drum unit passes is opened, and the opening. A cover provided on the main body housing to be rotatable to a closed position; a light emitting element for emitting light for exposing the photosensitive drum; and a first substrate having the light emitting element. A long optical print head provided on the cover, and a metal provided along the longitudinal direction of the optical print head and in a direction perpendicular to the longitudinal direction with a gap from the first substrate. Made of a conductive member, a second substrate provided in the main body housing and generating a drive signal for driving the light emitting element, a cable for transmitting the drive signal from the second substrate to the first substrate, and grounded. A power supply board which has a ground circuit and which receives a power supply from a commercial power supply to generate a drive voltage for driving the image forming apparatus, the first board via the cable and the second board. The grounding circuit is grounded, and the conductive member is grounded to the grounding circuit without interposing the first substrate and the second substrate.

Further, in the image forming apparatus of the present invention, an opening is formed, a main body housing in which a drum unit having a photosensitive drum is detachable, a position where the opening through which the detachable drum unit passes is opened, and a position where the opening is closed. , A cover provided on the main body housing so as to be movable, a sheet metal provided on the cover, a light emitting element for emitting light for exposing the photosensitive drum, and a first substrate having the light emitting element. And a long optical print head provided on the cover, and with a gap from the first substrate along a longitudinal direction of the optical print head and in a direction perpendicular to the longitudinal direction. A conductive member, a part of which is in contact with the sheet metal, a second substrate which is provided in the main body housing and which generates a drive signal for driving the light emitting element, and the drive signal from the second substrate. A cable for transmitting to the first substrate; and a power supply substrate that has a grounded ground circuit and that receives a supply of power from a commercial power supply to generate a drive voltage for driving the image forming apparatus. The grounding circuit is grounded through the cable and the second substrate, and the conductive member is through the sheet metal grounded to the grounding circuit without the first substrate and the second substrate. It is characterized by being grounded.

According to the present invention, the ground path from the conductive member to the ground circuit of the power board is provided electrically independent of the ground path from the board of the optical print head to the ground circuit of the power board. It is possible to reduce the possibility that static electricity that has flown from the fingertips of the worker to the conductive member will flow to the board or control board of the optical print head.

FIG. 3 is a schematic cross-sectional view of the image forming apparatus with the cover closed. FIG. 3 is a schematic cross-sectional view of the image forming apparatus with the cover opened. FIG. 3 is a schematic view showing an optical print head and a photosensitive drum. FIG. 6 is a diagram for explaining a substrate and an LED chip of the optical print head. FIG. 3 is a diagram showing a configuration of an image forming apparatus for explaining a ground path of a substrate and a conductive member included in an optical print head. FIG. 6 is a simplified circuit diagram for explaining a ground path of a substrate and a conductive member included in the optical print head. FIG. 6 is a diagram showing a configuration of an image forming apparatus according to a second embodiment for explaining a ground path of a substrate and a conductive member included in an optical print head. 6 is a simplified circuit diagram for explaining a ground path of a substrate and a conductive member included in a print head in the image forming apparatus of Embodiment 2. FIG. FIG. 6 is a simplified circuit diagram for explaining a ground path of a substrate and a conductive member included in a print head in the image forming apparatus according to the third embodiment. FIG. 6 is a simplified circuit diagram for explaining a ground path of a substrate and a conductive member included in a print head in an image forming apparatus of a conventional example.

Preferred embodiments for carrying out the present invention will be described below with reference to the accompanying drawings. However, the components described in this description are merely examples, and the present invention is not limited to the embodiments described in this description.

<<Example 1>>
(Overall structure of image forming apparatus)
First, the schematic configuration of the image forming apparatus 1 will be described. FIG. 1 is a schematic sectional view of the image forming apparatus 1. The image forming apparatus 1 illustrated in FIG. 1 is a color printer (SFP: Single Function Printer) that does not include a reading device, but the embodiment may be a multifunction machine including a reading device. Further, the embodiment is not limited to the so-called tandem type color image forming apparatus including a plurality of photosensitive drums 102 as shown in FIG. For example, a color image forming apparatus including one photosensitive drum 102 or an image forming apparatus that forms a monochrome image may be used.

The image forming apparatus 1 shown in FIG. 1 includes photosensitive drums 102Y, 102M, 102C, and 102K (hereinafter collectively referred to simply as "photosensitive drum 102") corresponding to each color of yellow, magenta, cyan, and black. These photosensitive drums are arranged separately from each other.

As shown in FIG. 1, in the following description, the side where the photosensitive drum 102K corresponding to black is arranged with respect to the photosensitive drum 102Y corresponding to yellow is defined as the front side. Further, the side on which the photosensitive drum 102Y corresponding to yellow is arranged with respect to the photosensitive drum 102K corresponding to black is defined as the back side. Further, as shown in FIG. 1, the upper side in the drawing is defined as the upper side in the vertical direction, and the lower side is defined as the lower side in the vertical direction.

The image forming apparatus 1 includes chargers 402Y, 402M, 402C, and 402K (hereinafter collectively referred to simply as “charger 402”) that charge the photosensitive drums 102Y, 102M, 102C, and 102K, respectively. The image forming apparatus 1 also includes optical print heads 106Y, 106M, 106C, and 106K (hereinafter collectively referred to simply as “optical print head 106”) as exposure light sources that emit light that exposes the photosensitive drums 102Y, 102M, 102C, and 102K. "Also referred to as"). The optical print head 106 has an elongated shape extending in the rotation axis direction of the photosensitive drum 102. The image forming apparatus 1 shown in FIG. 1 is a so-called “upper surface exposure type” image forming apparatus that exposes the photosensitive drum 102 from above in the vertical direction.

Here, as an example of an exposure method adopted in an electrophotographic image forming apparatus, a laser beam scanning method in which an outgoing beam of a semiconductor laser is scanned by a rotating polygon mirror or the like and a photosensitive drum is exposed through an f-θ lens or the like. There is an exposure method. The “optical print head 106” described in the present embodiment is used in an LED exposure system that exposes the photosensitive drum 102 using light emitting elements such as LEDs arranged along the rotation axis direction of the photosensitive drum 102. Therefore, it is not used in the laser beam scanning exposure method described above.

Further, the image forming apparatus 1 develops the electrostatic latent image on the photosensitive drum 102 with toner, and develops the toner images of the respective colors on the photosensitive drum 102 by developing units 403Y, 403M, 403C, 403K (hereinafter collectively referred to as "developers"). (Also simply referred to as "developing device 403"). It should be noted that Y, M, C, and K attached to the reference numerals indicate toner colors.

The image forming apparatus 1 includes an intermediate transfer belt 406 to which the toner image formed on the photosensitive drum 102 is transferred. The toner image formed on the photosensitive drum 102 is sequentially transferred to the intermediate transfer belt 406. The image forming apparatus 1 also has a secondary transfer roller 407 that transfers the toner image on the intermediate transfer belt 406 onto the recording paper P conveyed from the paper supply unit 408, and the secondary transferred image onto the recording paper P. And a fixing device 404 for fixing.

Next, the image forming process will be briefly described by taking the process of transferring the yellow toner image on the intermediate transfer belt 406 as an example. The optical print head 106Y exposes the surface of the photosensitive drum 102Y charged by the charger 402Y. As a result, an electrostatic latent image is formed on the photosensitive drum 102Y. Next, the developing device 403Y develops the electrostatic latent image formed on the photosensitive drum 102Y with yellow toner. After that, the yellow toner image developed on the surface of the photosensitive drum 102Y is transferred onto the intermediate transfer belt 406. The magenta, cyan, and black toner images are also transferred to the intermediate transfer belt 406 in the same image forming process.

The toner images of the respective colors transferred onto the intermediate transfer belt 406 are transferred onto the recording paper P conveyed from the paper supply unit 408 by the transfer bias of the secondary transfer roller 407.

The fixing device 404 fixes the toner image on the recording paper P by heat and pressure. The recording paper P that has been subjected to the fixing processing by the fixing device 404 is ejected to the paper ejection unit 409.

The image forming apparatus 1 includes a main body housing 100 and a cover 410. The main body housing 100 is a housing that houses the intermediate transfer belt 406, the paper feeding unit 408, the fixing device 404, and the like. Here, the exterior cover is also referred to as the main body housing 100. The cover 410 partially has a metal frame in order to increase its strength. Note that the cover 410 may be made of a single metal plate to enhance strength. The cover 410 is provided on the upper part of the main body housing 100 and rotates with respect to the main body housing 100.

The main body housing 100 is provided with a power supply board 550 that generates electric power for driving the image forming apparatus 1. As shown in FIG. 1, the power supply substrate 550 is arranged on the back side of the main body housing 100 with respect to the paper feeding unit 408. The power supply board 550 has a function of converting the power supply voltage supplied from the commercial power supply input 120, which is a so-called outlet, into a voltage value desired by each unit of the image forming apparatus 1, and driving the image forming apparatus 1. The commercial power input 120 and the power board 550 are connected by, for example, a power cord (not shown). Although not shown in FIG. 1, the power supply board 550 has a ground circuit, and in this embodiment, the ground of each part of the image forming apparatus 1 is connected to this ground circuit.

Further, as will be described later in detail, the main body housing 100 includes a control board 500. The control board 500 generates a drive signal for driving the light emitting element 126 included in the optical print head 106. The control board 500 controls the drive signal to adjust the light emission timing and the light amount of the light emitting element 126. The drive signal generated by the control board 500 is transmitted to the relay board 510 via the signal line 530 of the cable. As shown in FIG. 1, the relay substrate 510 is provided on the cover 410. The drive signal transmitted to the relay board 510 is transmitted to each optical print head 106 via the cable 505.

FIG. 2 shows the image forming apparatus 1 with the cover 410 opened. As shown in FIG. 2, an opening 121 is formed on the upper side in the vertical direction of the main body housing 100. The cover 410 rotates about a rotation shaft 110 provided in the main body housing 100 and can move to a position where the opening 121 is closed and a position where the opening 121 is opened. As shown in FIG. 2, the drum unit 128 is attached to and detached from the main body housing 100 with the cover 410 opened. When the drum unit 128 is attached to and detached from the main body housing 100, it is attached and detached via the opening 121. That is, the drum unit 128 passes through the opening 121 both when the operator removes the drum unit 128 from the main body housing 100 and when the drum unit 128 is attached to the main body housing 100. When the cover 410 is in the closed state, the cover 410 blocks the passage path of the opening 121 of the drum unit 128. On the other hand, when the cover 410 is open, the passage of the opening 121 of the drum unit 128 is open. When the cover 410 is in the closed state, the opening 121 does not need to be completely closed, and the passage of the opening 121 of the drum unit 128 described above may be blocked.

The drum unit 128 is a replaceable cartridge in which the photosensitive drum 102, the charging device 402, and the developing device 403 are integrated. The drum unit 128 is regularly replaced by an operator such as a user or a service person. As described above, the “drum unit 128” referred to here may include at least the photosensitive drum 102. The photosensitive drum 102 is rotatably supported by the frame of the drum unit 128.

Further, only the photosensitive drum 102 may be configured to be detachable from the drum unit 128. With such a configuration, the operator can remove the photosensitive drum 102 from the drum unit 128 after removing the drum unit 128 from the main body housing 100 and replace it with a new photosensitive drum 102. As a result, only the photosensitive drum 102 can be replaced without replacing the developing device 403 and the charging device 402.

Here, the cover 410 shown in FIGS. 1 and 2 rotates about a rotation shaft 110 extending in the direction of the rotation axis of the photosensitive drum 102. In other words, the direction of the rotation axis of the cover 410 and the direction of the rotation axis of the photosensitive drum 102 match. That is, the optical print heads 106Y to 106K are arranged in a direction perpendicular to the direction of the rotation center axis of the cover 410. However, the rotation direction of the cover 410 is not limited to the direction shown in FIG. 1, and the rotation shaft 110 may extend in a direction orthogonal to the direction of the rotation axis of the photosensitive drum 102. As a result, the cover 410 can be moved around the rotation shaft 110 as a rotation center between a position opened to open the opening 121 and a position closed to close the opening 121.

The rotation shaft 110 is a rod-shaped member provided on the main body housing 100 and extending from one end side to the other end side of the main body housing 100 in the rotation axis direction of the photosensitive drum 102. In other words, the rotating shaft 110 extends from the right side to the left side of the main body housing 100 on the back side of the main body housing 100. In the present embodiment, the rotary shaft 110 is a metal support pole that is grounded. By making the rotating shaft 110 of metal, the rigidity of the main body housing 100 can be increased. However, the rotating shaft 110 does not have to be made of metal, but may be made of resin.

Further, the rotating shaft 110 does not have to be a rod-shaped member extending from the right side to the left side of the main body housing 100 as in the present embodiment, and is provided at two positions on the right side and the left side of the main body housing 100, respectively. It doesn't matter if it has been. In this case, the right side and the left side of the cover 410 are rotatably attached to the rotating shafts 110 provided at the two positions of the right side and the left side of the main body housing 100, respectively. The rotation center axis lines of the rotation shafts 110 at the two locations coincide with each other. As a matter of course, the number of places where the rotary shaft 110 is provided is not limited to two, and may be three or more.

(Structure of optical print head)
Next, the positional relationship between the photosensitive drum 102 and the optical print head 106 will be described.

FIG. 3A is a diagram for explaining how the optical print head 106 is arranged with respect to the photosensitive drum 102 when the cover 410 is closed. As shown in FIG. 3A, when the cover 410 is closed, the optical print head 106 faces the photosensitive drum 102. Then, the photosensitive drum 102 is exposed from above in the vertical direction of the photosensitive drum 102.

Further, FIG. 3B is a diagram for explaining the path of the light emitted from the optical print head 106. The optical print head 106 includes a housing 204, a substrate 202, and a lens array 203. The housing 204 holds the substrate 202 and the lens array 203. In the present embodiment, the housing 204 is a resin molded product that is injection molded. However, the housing 204 may be a metal frame to which a resin-molded member is attached. The housing 204 is an elongated molded product that extends in the rotation axis direction of the photosensitive drum 102.

Here, the structure of the mounting portion of the optical print head 106 and the cover 410 will be described. In the present embodiment, the housing 204 is rotatably attached to the cover 410. For example, both ends of the housing 204 in the longitudinal direction of the optical print head 106 are rotatably attached to the cover 410 with screws or the like. As another configuration, the housing 204 may be rotatably attached to the cover 410 by a support member (not shown). That is, the optical print head 106 may not be directly attached to the cover 410, but may be attached to the cover 410 via another member. The conductive member 307 may be provided on a support member as another member. The conductive member 307 does not necessarily have to be provided in the housing 204, and may be provided in other members when the housing 204 is attached to the cover 410 via some other member. Of course, the other members and the housing 204 may be collectively referred to as the optical print head 106.

As will be described in detail later, a plurality of LED chips 201 are mounted on the substrate 202. The LED chip 201 includes a plurality of LEDs (Light Emitting Diodes) as light emitting elements 126 described later. The light emitted from these light emitting elements 126 is condensed on the surface of the photosensitive drum 102 via the lens array 203.

As shown in FIGS. 3A and 3B, a connector 301 is provided on the side of the substrate 202 opposite to the side on which the LED chip 201 is mounted. In the present embodiment, the cable 505 extending from the relay board 510 is connected to this connector 301. As a result, the relay substrate 510 and the substrate 202 are electrically connected. Although details will be described later, the image forming apparatus 1 does not necessarily have to include the relay substrate 510. The connector 301 and the control board 500 provided on the main body housing 100 may be connected by a cable 505.

When an operator such as a user or a service person performs the opening/closing operation of the cover 410, the fingertip of the operator may approach the optical print head 106, for example. In addition, if foreign matter such as dust or dirt adheres to the surface of the lens array 203, the foreign matter may partially block the light emitted from the lens array 203, resulting in defective image formation. Therefore, an operator may clean the surface of the lens array 203 by wiping the surface of the lens array 203 with a cloth or the like. Even when such cleaning is performed, the fingertip of the operator approaches the optical print head 106. When the operator's fingertip approaches the optical print head 106 as in the above example, static electricity may fly from the fingertip toward the substrate 202. A semiconductor element such as the light emitting element 126 mounted on the substrate 202 has a low withstand voltage and cannot be said to have sufficient withstand voltage against electrostatic discharge. Therefore, when the electric charge charged to the worker flows into the circuit pattern of the substrate 202 by electrostatic discharge, elements such as the light emitting element 126 provided on the substrate 202 may be damaged.

Therefore, as shown in FIG. 3, the optical print head 106 is provided with a conductive member 307 with a gap from the substrate 202. That is, the substrate 202 and the conductive member 307 are in a relationship of being insulated from each other. The conductive member 307 is a metal member that extends in the longitudinal direction of the optical print head 106, and is, for example, a sheet metal, a wire, or a wire spring. Conductive member 307 in the present embodiment is a rectangular aluminum sheet metal having a size of 80 mm×350 mm, and its resistivity is 3.00×10 ⁻⁸ Ωm. The material of the member used for the conductive member 307 has conductivity, and the lower the resistivity, the better. The conductive member 307 is fixed to the housing 204 with, for example, an adhesive or an aluminum tape. It should be noted that the “longitudinal direction of the optical print head 106” referred to here is a direction that substantially coincides with the rotational axis direction of the cover 410. Further, this direction is a direction that substantially coincides with the rotation axis direction of the photosensitive drum 102.

In this embodiment mode, the conductive member 307 and the substrate 202 are provided with a space of 5 mm. If this distance is a small gap of less than 1 mm, when static electricity is discharged from the fingertip of the worker to the conductive member 307, the conductive member 307 may be further discharged to the substrate 202. In order to prevent this, it is preferable to leave a gap of at least 1 mm between the conductive member 307 and the substrate 202, or to attach an insulating sheet or the like between the conductive member 307 and the substrate 202.

The conductive member 307 is provided on one side and the other side of the substrate 202 in the direction perpendicular to both the normal direction of the substrate 202 and the longitudinal direction of the optical print head 106. That is, since the conductive member 307 is disposed on the front side and the back side of the substrate 202, when the fingertip of the worker approaches the optical print head 106, the conductive member 307 is attached to the conductive member 307 before the substrate 202. Static electricity flies from your fingertips. As a result, it is possible to reduce the possibility that static electricity may fly from the operator's fingertip to the substrate 202.

A ground wire 308 is attached to the conductive member 307, and the ground wire 308 is electrically connected to the ground circuit of the power supply board 550. That is, when the static electricity charged on the worker flies from the fingertip of the worker to the conductive member 307, the current flows through the ground wire 308 to the ground circuit of the power supply board 550. As described above, the ground path of the conductive member 307 is electrically independent of the ground paths of the substrate 202 and the control board 500 included in the optical print head 106. Therefore, the current flowing from the fingertip of the worker to the conductive member 307 does not pass through the ground path of the substrate 202 and the control substrate 500 included in the optical print head 106.

The ground wire 308, like the conductive member 307, is a metal member such as a metal plate, a wire, and a wire spring. The ground wire 308 in the present embodiment is a copper conductor wire and its resistivity is 1.6×10 ⁻⁸ Ωm. The surroundings may be covered with an insulating film or the like. By being covered, the insulation between the substrate 202 of the optical print head 106 and the ground path of the control substrate 500 is surely ensured, and the conductive member 307 and the ground circuit of the power supply substrate 550 are electrically connected. You can Although the conductive member 307 and the ground wire 308 are referred to separately here, these two members may be collectively referred to as the conductive member 307 or the ground wire 308. ..

Next, the configuration of the substrate 202 will be described in detail. FIG. 4 shows an enlarged view of the substrate 202. FIG. 4A shows a surface on which the LED chip 201 is mounted (hereinafter referred to as a mounting surface). On the other hand, FIG. 4B shows a surface opposite to the surface on which the LED chip 201 is mounted (hereinafter referred to as a non-mounting surface). As shown in FIG. 4A, 29 LED chips 201 are arranged in a zigzag pattern on the mounting surface. In each LED chip, 512 light emitting elements 126 (LEDs) are arranged at a predetermined resolution pitch in the longitudinal direction of the chip. The resolution of the image forming apparatus 1 of this embodiment is 1200 dpi. Therefore, the respective light emitting elements 126 are arranged in a line in the longitudinal direction of the LED chip 201 such that the center-to-center distance between the adjacent light emitting elements 126 is 21.16 μm. In one LED chip 201, the distance from one end to another of the light emitting elements 126 arranged is about 10.8 mm. By arranging 29 LED chips 201, the number of light-emitting elements 126 that can be exposed is 14,848. This enables image formation corresponding to an image width of about 314 mm.

FIG. 4C shows a state of a boundary portion between the LED chips 201. A wire bonding pad 125 for inputting a drive signal is arranged at the end of the LED chip 201. A drive signal for controlling the light emission timing of the light emitting element 126 to drive the light emitting element 126 is input from the wire bonding pad 125 to the LED chip 201. Also in the boundary portion between the chips, the pitch in the longitudinal direction of the light emitting element 126 is 21.16 μm. The intervals between the light emitting points of the two rows of LED chips 201 (S in the figure) are about 84 μm (4 pixels for 1200 dpi, 8 pixels for 2400 dpi). A drive voltage control element 302 that controls a voltage for driving the LED chip 201, a connector 301, and a storage element 303 are arranged on the non-mounting surface of the substrate. The storage element 303 temporarily stores information on a signal for driving the LED chip 201.

A signal line for controlling the drive voltage control element 302 and the storage element 303, a power supply, and a ground line are connected to the connector 301 from the control board 500. The wiring extending from the drive voltage control element 302 for driving the LED chips 201 passes through the inner layer of the substrate 202 and is connected to each LED chip 201.

(Ground path)
FIG. 5 is a diagram for explaining the ground path of the substrate 202 and the ground path of the conductive member 307 of the optical print head 106.

As shown in FIG. 5, the cover 410 is provided with a metal frame 410a and a metal frame 410b in order to increase its rigidity. Each of these metal frames 410a and 410b is an example of a sheet metal provided on the cover 410. The metal frames 410a and 410b have the purpose of not only increasing the rigidity of the cover 410 but also forming part of the earth path. The frame 410a and the frame 410b are electrically independent members. A ground wire 308 connected to the conductive member 307 is attached to the frame 410a or 410b. Of course, the conductive member 307 may be directly attached to the frame 410a. It does not matter whether the ground wire 308 is interposed or not, as long as the conduction between the conductive member 307 and the frame 410a is ensured. Therefore, a configuration in which a part of the conductive member 307 is in contact with the frame 410a is sufficient. Further, the frame 410a is connected to the ground circuit of the power supply board 550 via a ground wire 521. The ground wire 521 is also a member similar to the ground wire 308 described above. As a result, the conductive member 307 is grounded via the ground line 308, the frame 410a, the ground line 521, and the ground circuit of the power supply board 550. As a matter of course, the ground path from the conductive member 307 to the ground circuit of the power supply board 550 may be via the separate members such as the ground wire 308, the frame 410a, and the ground wire 521 as described above, or these. May be formed as an integral member. Further, the cover 410 may have a configuration in which the frame 410a and the ground circuit of the power supply substrate 550 are directly connected without the ground wire 521.

Next, the ground path of the substrate 202 included in the optical print head 106 will be described. As described above, the board 202 and the relay board 510 are electrically connected by the cable 505. Further, the relay board 510 and the control board 500 are connected by a cable 620.

Here, the control board 500 is a board that controls each part of the main body during image formation. The control board 500 includes a main CPU (not shown), and the main CPU controls each unit of the main body. For example, the control board 500 generates a drive signal for driving each light emitting element 126. The main CPU of the control board 500 controls the timing and amount of light emitted by the light emitting element 126. In addition to this, the control board 500 directly or other controls the rotation speed of the drive roller that drives the photosensitive drum 102 and the transport belt for transporting the paper P, the transport speed of the paper P in the fixing device 404, and the like. It is indirectly controlled via a substrate (for example, the relay substrate 510). That is, in FIG. 5, the relay board 510 is not essential, and the control board 500 and each of the boards 202Y to 202K included in the optical print heads 106 are electrically connected using the cable 505 and the cable 620 to connect the relay board 510. It may be controlled without intervention.

Further, in the present embodiment, each of the cables 505Y to 505K and the cable 620 is a flexible flat cable (FFC) in which a plurality of conductor wires covered with a resin coating are bundled into one band. The plurality of conducting wires include a signal line through which a control signal for driving the light emitting element 126 such as the timing of light emission and the amount of light is transmitted, and a GND line for grounding. Here, the cables 505Y to 505K and the cable 620 do not necessarily have to be flexible flat cables, and other cables may be used as long as they have the above-described signal line and GND line.

The number of signal lines included in each of the cables 505Y to 505K is smaller than the number of signal lines included in the cable 620.

The control board 500 includes an image control unit (not shown) that performs image processing, and when receiving an image formation instruction from the main CPU, outputs image data to be formed to the relay board 510. The image data includes a plurality of unit image data so as to correspond to the plurality of light emitting elements 126 included in the LED chip 201. An image control unit (not shown) provided on the control board 500 outputs image data to the relay board 510 in a predetermined order. The relay board 510 generates irradiation data using the image data output from the control board 500. The image data from the main board includes color information indicating which color it is. The relay substrate 510 transmits the irradiation data corresponding to each color to the substrates 202Y, 202M, 202C, 202K corresponding to each color based on this color information. The light emitting element 126 is turned on based on the irradiation data transmitted to the substrate 202, and the photosensitive drum 102 is irradiated with light. As described above, the control board 500 controls each part of the image forming apparatus 1 at the time of image formation by a known method.

Although the details will be described later, the cable 505 and the cable 620 have a signal line through which a control signal for controlling the driving of the light emitting element 126 is transmitted and a GND line for grounding. The substrate 202 of the optical print head 106 is grounded through the GND line of the cable 505, the ground circuit of the relay substrate 510, the GND line of the cable 620, and the ground circuit of the control substrate 500. This ground path is electrically independent from the ground path of the conductive member 307 described above.

To summarize the above, the conductive member 307 is grounded to the ground circuit of the power supply substrate 550 through the ground paths of (1) ground wire 308, (2) frame 410a, and (3) ground wire 521. On the other hand, the substrate 202 of the optical print head 106 passes through ground paths of (1) the GND line of the cable 505, (2) the relay substrate 510, (3) the GND line of the cable 620, and (4) the control substrate 500, and the power source. It is grounded to the ground circuit of the substrate 550. In this way, the ground path from the conductive member 307 to the ground circuit of the power supply board 550 and the ground path from the board 202 to the ground circuit of the power supply board 550 are electrically independent from each other. With such a configuration, static electricity that has flown from the operator's fingertip to the conductive member 307 flows into the ground path from the substrate 202 to the ground circuit of the power supply substrate 550, and thus the substrate 202, the relay substrate 510, and the control substrate 500 can be connected. It is possible to reduce the risk that the mounted semiconductor components will be damaged.

FIG. 6 is a simplified circuit diagram for explaining the ground path of the substrate 202 and the conductive member 307 included in the optical print head 106. The ground path of the substrate 202 and the ground path of the conductive member 307 will be described with reference to this simplified circuit diagram.

As shown in FIG. 6, the conductive member 307 and the cover 410 a are electrically connected by the ground wire 308. Further, the cover 410a and the ground circuit of the power supply substrate 550 are electrically connected by a ground wire 521. Here, 550a to 550e correspond to the ground circuit of the power supply board 550. As shown in FIG. 6, the ground wire 521 passes through the ground circuit 550d, the ground circuit 550e, and the ground circuit 550c, and is grounded via the ground electrode of the commercial power input 120 which is a so-called outlet.

On the other hand, the substrate 202 of the optical print head 106 is electrically connected to the ground circuits 510a, 510c, 510d of the relay substrate 510 via the GND line (not shown) of the cable 505. The ground circuit 510a is electrically connected to the ground circuit 500a of the control board 500 via the GND line 520a of the cable 620. The ground circuits 500a to 500c of the control board 500 are electrically connected to the ground circuits 550a to 550e of the power supply board 550 via the ground circuits 500c and 550a.

That the ground path from the conductive member 307 to the ground circuits 550a to 550e of the power board 550 and the ground path from the board 202 to the ground circuits 550a to 550e of the power board 550 are electrically independent ground paths, For example, it can be confirmed as follows.

First, the grounding circuits 500a to 500c of the control board 500 and the grounding circuits 550a to 550e of the power supply board 550 are electrically connected to each other by, for example, disconnecting the parts.

Next, the test leads of the tester are brought into contact with a part of the conductive member 307 and a part of the GND pattern of the substrate 202 to confirm the continuity between the two. When the conductive member 307 and the GND pattern of the substrate 202 are not electrically connected by this checking method, the ground path from the conductive member 307 to the ground circuits 550a to 550e of the power supply substrate 550, and the substrate 202 to the power supply substrate 550. It can be said that the ground paths to the ground circuits 550a to 550e are electrically independent.

Here, in order to easily understand the effects of the present invention, a simplified circuit diagram of the conventional configuration shown in FIG. 10 will be described. In the conventional configuration shown in FIG. 10, unlike the configuration of the present invention described above, the ground circuits 510a to 510c of the relay board 510 and the ground wire 308 are connected to the frame 410a of the cover 410. That is, the grounding of the conductive member 307 is performed by grounding the power supply board 550 through the ground wire 308→the frame 410a→the ground circuits 510a to 510c of the relay board 510→the GND wire 520a of the cable 620→the ground circuits 500a to 500c of the control board 500. It is taken by the ground circuit 550a.

On the other hand, the optical print head 106 is grounded by connecting the cable 505 to the ground circuit 510a to 510c of the relay board 510 to the GND line 520a of the cable 620 to the ground circuit 500a to 500c of the control board 500 to the ground circuit 550a of the power board 550. Has been taken by.

In this way, the ground of the conductive member 307 is grounded via a part of the ground path of the substrate 202 of the optical print head 106. Therefore, when static electricity is blown from the fingertip of the worker to the conductive member 307, the current also flows into a part of the ground path of the substrate 202 of the optical print head 106, and as a result, the relay substrate 510 and the control substrate 500 are There is a risk of damaging a semiconductor element or the like that the semiconductor device has.

As in the configuration of the present invention shown in FIG. 6, even when static electricity is discharged from the fingertip of the worker to the conductive member 307, the current does not flow to the ground path of the substrate 202, so that the relay substrate 510 is formed. It is possible to reduce damage caused by damage to the control board 500.

<<Example 2>>
FIG. 7 is a schematic circuit diagram of a configuration in which the conductive member 307 and the ground circuits 550a to 550e of the power supply board 550 are connected by the ground wire 308. In FIG. 7, members having substantially the same function corresponding to the members included in the image forming apparatus 1 according to the first embodiment will be described with the same reference numerals, and redundant description may be omitted. The ground wire 308 is fixed to the cover 410 with an adhesive or a fastener. The static electricity that has flown from the fingertip of the worker to the conductive member 307 flows to the ground circuit of the power supply board 550 via the ground wire 308 fixed to the cover 410. As described above, unlike the configuration shown in FIG. 6, the configuration shown in FIG. 7 does not include the frame 410a and the ground wire 521 in the ground path of the conductive member 307. The electrically conductive member 307 may be grounded in the configuration shown in FIG. 7 as long as it is electrically independent of the ground path of the substrate 202. Naturally, the conductive member 307 and the ground wire 521 may be formed as one member.

FIG. 8 is a schematic circuit diagram for explaining the ground paths of the substrate 202 and the conductive member 307 of the optical print head 106 in the image forming apparatus according to the second embodiment. The ground path of the substrate 202 and the ground path of the conductive member 307 will be described with reference to this simplified circuit diagram.

As shown in FIG. 8, the conductive member 307 and the ground circuit of the power supply substrate 550 are electrically connected by the ground wire 308. Here, 550a to 550e correspond to the ground circuit of the power supply board 550. As shown in FIG. 8, the ground wire 308 passes through the ground circuit 550d, the ground circuit 550e, and the ground circuit 550c, and is grounded via the ground electrode of the commercial power input 120 which is a so-called outlet.

On the other hand, the substrate 202 included in the optical print head 106 is electrically connected to the ground circuits 510a to 510c of the relay substrate 510 via the GND line (not shown) of the cable 505. The ground circuit 510a is electrically connected to the ground circuit 500a of the control board 500 via the GND line 520a of the cable 620. The ground circuits 500a to 500c of the control board 500 are electrically connected to the ground circuits 550a to 550e of the power supply board 550 via the ground circuits 500c and 550a.

<<Example 3>>
FIG. 9 is a simplified circuit diagram for explaining a case where the image forming apparatus 1 according to the first exemplary embodiment does not include the relay board 510. When the relay board 510 is not provided, each of the optical print heads 106Y to 106K is electrically connected to the control board 500 by cables 620Y to 620K. Although not shown, the optical print head 106Y has a substrate 202Y, the optical print head 106M has a substrate 202M, the optical print head 106C has a substrate 202C, and the optical print head 106K has a substrate 202K. The substrates 202Y to 202K have the same configuration as the substrate 202 in the first and second embodiments.

The substrate 202Y included in the optical print head 106Y is electrically connected to the control substrate 500 by the cable 620Y, and the substrate 202M included in the optical print head 106M is electrically connected to the control substrate 500 by the cable 620M and included in the optical print head 106C. The board 202C is electrically connected to the control board 500 by a cable 620C, and the board 202K included in the optical print head 106K is electrically connected to the control board 500 by a cable 620K. In FIG. 9, the cables 620Y to 620K appear to overlap, but they are independent cables. The cable 620Y has a signal line 530Y and a GND line 520Y, the cable 620M has a signal line 530M and a GND line 520M, the cable 620C has a signal line 530C and a GND line 520C, and the cable 620K has a It has a signal line 530K and a GND line 520K. All the GND lines 520Y to 520K are grounded to the ground circuit 500a of the control board 500.

106 Optical Print Head 110 Rotating Axis 120 Commercial Power Input 307 Conductive Member 308 Ground Wire 410 Cover 410a Frame 410b Frame 500 Control Board 505 Cable 510 Relay Board 550 Power Board

Claims (10)

A main body housing in which an opening is formed and a drum unit having a photosensitive drum is detachable;
A cover provided on the main body housing so as to be rotatable between a position where an opening through which the drum unit to be detached and attached passes is opened and a position where the opening is closed;
A long optical print head provided on the cover, having a light emitting element that emits light for exposing the photosensitive drum, and a first substrate having the light emitting element,
A metal conductive member provided along the longitudinal direction of the optical print head and in a direction perpendicular to the longitudinal direction with a gap from the first substrate;
A second substrate which is provided in the main body housing and generates a drive signal for driving the light emitting element;
A cable for transmitting the drive signal from the second board to the first board;
A power supply board that has a grounding circuit that is grounded and that receives a supply of power from a commercial power supply and that generates a drive voltage that drives the image forming apparatus;
The first board is grounded to the ground circuit via the cable and the second board, and the conductive member is grounded to the ground circuit without passing through the first board and the second board. An image forming apparatus characterized in that The cover has a third substrate that relays the drive signal generated by the second substrate and transmits the drive signal to the first substrate.
The cable electrically connects the second substrate and the third substrate and electrically connects the third substrate and the first substrate, and outputs the control signal generated by the second substrate. The image forming apparatus according to claim 1, wherein the control signal is transmitted to a third substrate and further the control signal is transmitted from the third substrate to the first substrate. The image forming apparatus according to claim 2, wherein the cable is a flexible flat cable. The number of signal lines included in the cable that electrically connects the second substrate and the third substrate is larger than the number of signal lines of the cable that connects the first substrate and the third substrate. The image forming apparatus according to claim 3. A main body housing in which an opening is formed and a drum unit having a photosensitive drum is detachable;
A cover provided on the main body housing so as to be movable between a position where an opening through which the drum unit to be detached and attached passes is opened and a position where the opening is closed;
A sheet metal provided on the cover,
A long optical print head provided on the cover, having a light emitting element that emits light for exposing the photosensitive drum, and a first substrate having the light emitting element,
A conductive member that is provided along the longitudinal direction of the optical print head and in a direction perpendicular to the longitudinal direction with a gap from the first substrate, and a part of which is in contact with the sheet metal;
A second substrate which is provided in the main body housing and generates a drive signal for driving the light emitting element;
A cable for transmitting the drive signal from the second board to the first board;
A power supply board that has a grounding circuit that is grounded and that receives a supply of power from a commercial power supply and that generates a drive voltage that drives the image forming apparatus;
The first board is grounded to the ground circuit via the cable and the second board, and the conductive member is grounded to the ground circuit without passing through the first board and the second board. An image forming apparatus, which is grounded through the sheet metal. The cover has a third substrate that relays a driving signal generated by the second substrate and transmits the driving signal to the first substrate.
The cable electrically connects the second substrate and the third substrate and electrically connects the third substrate and the first substrate, and outputs the drive signal generated by the second substrate. The image forming apparatus according to claim 5, wherein the drive signal is transmitted to the third substrate and further the drive signal is transmitted from the third substrate to the first substrate. The image forming apparatus according to claim 6, wherein the cable is a flexible flat cable. The number of signal lines included in the cable that electrically connects the second substrate and the third substrate is larger than the number of signal lines of the cable that connects the first substrate and the third substrate. The image forming apparatus according to claim 7. The image forming apparatus according to any one of claims 5 to 8, wherein the conductive member is fixed to a metal plate. The image forming apparatus according to any one of claims 1 to 9, wherein the conductive member is provided in the optical print head.

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