JP2021045919A - Optical scanner and image formation apparatus having the same - Google Patents

Abstract

To solve such a problem that the number of components is increased since a configuration in which the GND of two substrates is commonized while reducing the electromagnetic wave noise emitted from a drive IC and leaking to the outside of an image formation apparatus becomes complex.SOLUTION: An optical scanner comprises a sheet metal which is electrically connected to a first ground pattern of a first substrate and a second ground pattern of a second substrate, covers a first drive IC on the side opposite to the side on which an optical box is arranged with respect to the first drive IC in the direction vertical to the mounting surface of the first substrate and covers a second drive IC on the side opposite to the side on which the optical box is arranged with respect to the second drive IC in the direction vertical to the mounting surface of the second substrate.SELECTED DRAWING: Figure 8

Description

The present invention relates to an image forming apparatus such as a copier or a printer that forms an image on recording paper by using an electrophotographic method.

In recent years, with the miniaturization and weight reduction of electronic devices, the density and integration of electronic components such as CPUs, LSIs, and peripheral semiconductors mounted inside have been increased, and the density of electronic components such as electronic components mounted on printed wiring boards has been increased. It is becoming more and more popular. In addition, the frequencies handled are increasing in order to improve the performance of electronic devices. Along with this, the influence of electromagnetic noise emitted from electronic components or conduction noise transmitted through the wiring circuit of the printed wiring board on electronic devices has become a problem. There is also a standard: EMC (Electromagnetic Compatibility) that attempts to suppress the electromagnetic energy radiated from electronic devices below a certain level. The above-mentioned problem is the same in the image forming apparatus.

Some electrophotographic image forming devices include an optical scanning device that irradiates the surface of a charged photosensitive drum with a laser beam to form an electrostatic latent image. The optical scanning device includes an optical system component such as a light source, a rotating multifaceted mirror, a mirror, and a lens that deflects a laser beam emitted from the light source, and an optical box that is a housing that covers the optical system component. The optical box is provided with a laser substrate for controlling the light emission timing and the amount of light of the light source. It is known that this laser substrate is the main source of noise.

Reference 1 discloses a configuration in which two laser substrates are provided in an optical box. One laser substrate drives a semiconductor laser corresponding to yellow and a semiconductor laser corresponding to magenta, and the other laser substrate drives a semiconductor laser corresponding to cyan and a semiconductor laser corresponding to black. Drive ICs are provided on the substrate corresponding to each semiconductor laser, and each drive IC drives each semiconductor laser in response to a drive signal from the controller of the image forming apparatus main body.

Japanese Unexamined Patent Publication No. 2015-163949

In a configuration in which two laser substrates are provided in one optical box as in Cited Document 1, a method is known in which the GNDs of the respective substrates are connected to each other by, for example, bundled wires to share the ground.

Further, in order to realize high speed and high image quality of the image forming apparatus, electromagnetic noise radiated from the drive IC of the laser substrate tends to increase. In order to comply with standards such as VCSI and MEC, there is a need for a configuration that reduces electromagnetic noise radiated from the drive IC to the outside of the image forming apparatus as much as possible. In particular, the rear side of the optical scanning device is close to the rear side plate of the image forming device, and electromagnetic noise radiated from the optical scanning device toward the rear side of the image forming device often leaks to the outside of the image forming device.

As described above, it is complicated to realize both configurations of (1) sharing the GND of the two substrates and (2) reducing the electromagnetic noise leaking from the rear of the image forming apparatus to the outside. There was a problem that it was necessary to take a configuration and the number of parts increased.

The optical scanning apparatus according to the present invention includes a first light source that emits a light beam for exposing the first photosensitive drum, a second light source that emits a light beam for exposing the second photosensitive drum, and the first light source. A deflector that deflects the light beam emitted from the light source to guide it to the first photosensitive drum and deflects the light beam emitted from the second light source to guide it to the second photosensitive drum, and the deflector. A first substrate having an optical box to be accommodated, a first light source, a first drive IC for driving the first light source, and a first ground pattern, and attached to the outside of the optical box, and the second light source. A second substrate having a second drive IC for driving the second light source and a second ground pattern, and attached to the outside of the optical box, and the first ground pattern and the second ground pattern are electrically charged. The first drive IC is covered and the first drive IC is covered on the side opposite to the side where the optical box is arranged with respect to the first drive IC in a direction perpendicular to the mounting surface of the first substrate. 2. A sheet metal covering the second drive IC on the side opposite to the side on which the optical box is arranged with respect to the second drive IC in a direction perpendicular to the mounting surface of the substrate is provided. ..

The optical scanning apparatus according to the present invention has a first light source that emits a light beam for exposing the first photosensitive drum, a second light source that emits a light beam for exposing the second photosensitive drum, and a third light source. A third light source that emits a light beam for exposing a drum, a fourth light source that emits a light beam for exposing a fourth photosensitive drum, and a light beam emitted from the first light source are subjected to the first exposure. To deflect the light beam emitted from the second light source to guide it to the drum, to direct the light beam emitted from the second light source to the second photosensitive drum, and to guide the light beam emitted from the third light source to the third photosensitive drum. A deflector that deflects the light beam emitted from the fourth light source to guide it to the fourth photosensitive drum, an optical box that houses the deflector, the first light source, and the first light source. A first substrate having a first drive IC for driving, the second light source, a second drive IC for driving the second light source, and a first ground pattern, and mounted on the outside of the optical box. A third light source, a third drive IC for driving the third light source, a fourth light source, a fourth drive IC for driving the fourth light source, and a second ground pattern. The first drive IC and the first drive IC are electrically connected to the second substrate mounted on the outside of the box, the first ground pattern, and the second ground pattern, and in a direction perpendicular to the mounting surface of the first substrate. Both the first drive IC and the second drive IC are covered on the side opposite to the side where the optical box is arranged with respect to both the second drive IC, and the second substrate is mounted. The third drive IC and the fourth drive IC are on the side opposite to the side where the optical box is arranged with respect to both the third drive IC and the fourth drive IC in a direction perpendicular to the surface. It is characterized by including a sheet metal that covers both sides.

By providing a sheet metal connected to the GND of each of the two laser substrates so as to cover the drive IC of each laser substrate, the GND of the two laser substrates can be shared from the drive IC with a simple configuration. Of the radiated electromagnetic wave noise, the electromagnetic wave noise radiated from the rear of the image forming apparatus to the outside is reduced.

The schematic block diagram explaining the general structure of the image forming apparatus. The figure for demonstrating the structure of an optical scanning apparatus. The figure for demonstrating the attachment / detachment configuration of an optical scanning apparatus with respect to an image forming apparatus. The figure for demonstrating the conventional structure of an optical scanning apparatus. The figure for demonstrating the control block of an optical scanning apparatus. The figure for demonstrating the internal structure of the optical scanning apparatus of the opposed scanning system. The figure for demonstrating the observation result of the noise radiated from the image forming apparatus. The figure for demonstrating the structure of the electromagnetic wave noise measures applied to the optical scanning apparatus. The figure for demonstrating the modification about the earth composition of a sheet metal. The figure for demonstrating the electromagnetic wave noise countermeasure configuration of Example 2. The figure for demonstrating the electromagnetic wave noise countermeasure configuration of Example 3.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. The dimensions, materials, shapes, relative arrangements, and the like of the components described below are not intended to limit the scope of the present invention to those, unless otherwise specified.

<Example 1>
(Image forming device)
FIG. 1 is a schematic cross-sectional view showing the overall configuration of the image forming apparatus 1 according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 in the present embodiment corresponds to yellow (Y), magenta (M), cyan (C), and black (Bk), and is compatible with four colors of photosensitive drums 5Y ( 5M (an example of a second photosensitive drum), 5C (an example of a third photosensitive drum), and 5Bk (an example of a fourth photosensitive drum) are provided. Hereinafter, it is also collectively referred to as a photosensitive drum 5. The image forming apparatus 1 is a tandem type color laser beam printer including four image forming units 10Y, 10M, 10C, and 10Bk that form a toner image for each color.

The image forming apparatus 1 is an intermediate transfer belt 20 (an example of transfer means) on which a toner image imaged by each image forming unit 10Y, 10M, 10C, 10Bk (hereinafter, also simply referred to as an image forming unit 10) is transferred. To be equipped. The intermediate transfer belt 20 transfers the toner image transferred from each image forming unit 10 to the recording paper P. The image forming units 10Y, 10M, 10C, and 10Bk are configured to be substantially the same except that the color of the toner used in each image forming unit 10 is different. Hereinafter, the image forming unit 10Y of each image forming unit 10 will be described as an example. Since the image forming units 10M, 10C, and 10Bk have the same configuration as the image forming unit 10Y, the description thereof will be omitted.

The image forming unit 10Y develops the photosensitive drum 5Y, the charging roller 12Y that uniformly charges the photosensitive drum 5Y, and the electrostatic latent image formed on the photosensitive drum 5Y by an optical scanning device described later with toner, and then toner. A developer 13Y (an example of developing means) for forming an image and a primary transfer roller 15Y for transferring the formed toner image to the intermediate transfer belt 20 are provided. The primary transfer roller 15Y forms a primary transfer portion with the photosensitive drum 5Y via the intermediate transfer belt 20. The toner image formed on the photosensitive drum 5Y is transferred to the intermediate transfer belt 20 by applying a predetermined transfer voltage to the primary transfer roller 15Y.

The intermediate transfer belt 20 is an endless belt laid around the first belt transfer roller 21 and the second belt transfer roller 22, and rotates in the direction of arrow H. The toner images formed by the image forming portions 10Y, 10M, 10C, and 10Bk are transferred to the rotating intermediate transfer belt 20. Here, the four image forming portions 10 are arranged in parallel on the lower side in the vertical direction of the intermediate transfer belt 20. As a result, the toner image formed on the photosensitive drum 5 is transferred to the intermediate transfer belt 20 according to the image information of each color.

Further, the first belt transfer roller 21 and the secondary transfer roller 60 are in pressure contact with each other with the intermediate transfer belt 20 interposed therebetween. As a result, the first belt transfer roller 21 forms a secondary transfer portion with the secondary transfer roller 60 via the intermediate transfer belt 20. The recording paper P is inserted through the secondary transfer unit, and the toner image is transferred from the intermediate transfer belt 20. The transfer residual toner remaining on the surface of the intermediate transfer belt 20 is collected by a cleaning device (not shown).

Here, each image forming unit 10 forms a yellow toner image from the upstream side with respect to the secondary transfer unit in the rotation direction (arrow H direction) of the intermediate transfer belt 20, and the toner image of the image forming unit 10Y and magenta. The image forming unit 10M forming the black toner image, the image forming unit 10C forming the cyan toner image, and the image forming unit 10Bk forming the black toner image are arranged in this order.

Further, below each image forming unit 10 in the vertical direction, light that scans a laser beam (light beam) on each of the photosensitive drums 5 corresponding to each color to form an electrostatic latent image on the surface of each photosensitive drum 5. A scanning device is provided.

Further, the optical scanning device 40 accommodates optical members such as a rotating multi-sided mirror 46a (an example of a deflector) and a reflection mirror 62. Further, the optical scanning apparatus 40 according to the present embodiment has four semiconductor lasers (not shown) that emit laser beams modulated according to the image information of each color. The plurality of semiconductor lasers are light sources for exposing each of the corresponding photosensitive drums 5. The rotary multifaceted mirror 42 is rotated at high speed by a polygon motor (not shown). As a result, each laser beam emitted from each semiconductor laser is reflected so as to scan the photosensitive drum 5 along the rotation axis direction (main scanning direction) of each photosensitive drum 5. Each laser beam emitted from the semiconductor laser and reflected by the rotating multifaceted mirror 42 is guided by an optical system component such as a lens arranged inside the optical scanning device 40, and each emission port provided on the upper portion of the optical scanning device 40. The light is emitted from the inside of the optical scanning device 40 to the outside through a transparent window covering each of them. The laser light emitted from the optical scanning device 40 exposes each photosensitive drum 5.

In the present embodiment, a light beam is emitted from one optical scanning device 40 to each of the four photosensitive drums 5, but the embodiment is not limited to this.

On the other hand, the recording paper P is housed in the paper feed cassette 2 arranged in the lower part of the image forming apparatus 1. Then, the recording paper P is fed by the pickup roller 24 to the separation nip portion formed by the feeding roller 25 and the retard roller 26. Here, the drive of the retard roller 26 is transmitted so as to rotate in the reverse direction when a plurality of recording sheets P are fed by the pickup roller 24. As a result, the recording paper P is conveyed one by one to prevent double feeding of the recording paper P. The recording paper P, which has been conveyed one by one by the feeding roller 25 and the retard roller 26, is conveyed to a conveying path 27 extending substantially vertically along the right side surface of the image forming apparatus 1.

Then, the recording paper P is conveyed from the lower side in the vertical direction to the upper side of the image forming apparatus 1 through the transfer path 27, and is conveyed to the registration roller 29. The registration roller 29 temporarily stops the conveyed recording paper P and corrects the skew of the recording paper P. After that, the registration roller 29 conveys the recording paper P to the secondary transfer unit at the timing when the toner image formed on the intermediate transfer belt 20 is transferred to the secondary transfer unit. After that, the recording paper P on which the toner image is transferred in the secondary transfer unit is conveyed to the fixing device 3, and is heated and pressurized by the fixing device 3 to fix the toner image on the recording paper P. Then, the recording paper P on which the toner image is fixed is discharged by the discharge roller 28 to the discharge tray 420 provided on the outer side of the image forming device 1 and on the upper part of the main body of the image forming device 1.

(Optical scanning device)
The optical scanning device 40 exposes the photosensitive drums 5Y, 5M, 5C, and 5Bk of the image forming unit 10 at their respective predetermined timings according to the image information of each color. As a result, toner images of each color corresponding to the image information of each color are formed on each photosensitive drum 5.

FIG. 2 is a diagram for explaining an outline of the configuration of the optical scanning device 40. The optical scanning device 40 includes a laser substrate 42, a semiconductor laser element (hereinafter referred to as a light source) 43, a collimating lens 44, a cylindrical lens 45, a motor 46, an fθ lens 47, and a reflection mirror 48. The laser substrate 42 in FIG. 2 is a substrate corresponding to the first laser substrate 42a and the second laser substrate 42b, which will be described later. Further, the light source 43 corresponds to the light source 43Y, the light source 43M, the light source 43C, and the light source 43Bk, which will be described later. The motor 46 has a rotor 46b. The rotating multi-sided mirror 46a rotates integrally with the rotor 46b. In this embodiment, the controller 17 is provided on the main body of the image forming apparatus 1 outside the optical scanning apparatus 40. The controller 17 and the optical scanning device 40 are electrically connected. The laser beam (light beam L) emitted from the light source 43 reaches the rotating multifaceted mirror 46a via the collimating lens 44 and the cylindrical lens 45. The light beam L is deflected by the rotating multi-sided mirror 46a and scans on the photosensitive drum 5 via the fθ lens 47 and the reflection mirror 48 in the main scanning direction indicated by the arrow X to form an electrostatic latent image. The number of light sources 43 is the same as the number of reference colors used in the image forming apparatus 1 (four of Y, M, C, and Bk in this embodiment). These light sources 43 are mounted on the laser substrate 42.

3 (a) and 3 (b) are schematic views of the image forming apparatus 1 of FIG. 1 in the present embodiment. Hereinafter, the configuration of attaching / detaching the optical scanning device 40 to / from the image forming apparatus 1 will be described with reference to FIGS. 3 (a) and 3 (b).

FIG. 3A is a diagram for explaining a state when the optical box 80 of the optical scanning apparatus 40 is attached to the image forming apparatus 1. As shown in FIG. 3A, the image forming apparatus 1 in the present embodiment includes an apparatus main body 100 and a pressure plate portion 421 provided on the upper portion of the apparatus main body 100. A discharge tray 420 is provided in the middle of the front side (right side of FIG. 3A) of the apparatus main body 100. An opening 419 is formed on the side surface 441 of the apparatus main body 100. The optical box 80 is detachably mounted on the mounting portion 440 provided inside the device main body 100 of the image forming apparatus 1 through the opening 419. The opening 419 is closed by a lid member (not shown). In other words, the opening 419 is an example of an opening formed on the side surface of the device main body 100 so that the optical box 80 inserted from the outside to the inside of the device main body 100 and attached to the device main body 100 passes through.

FIG. 3B is a schematic view of the image forming apparatus 1 in which the optical box 80 is positioned with respect to the apparatus main body 100. As shown in FIG. 3B, the optical box 80 is attached to the mounting portion 440 inside the device main body 100 from the outside of the device main body 100 through the opening 419, and is positioned with respect to the device main body 100.

Further, a rear side plate 103 is provided on the back side of the apparatus main body 100. The optical box 80 mounted on the mounting portion 440 via the opening 419 is arranged at a position facing the rear plate 103.

(Ground of laser substrate)
FIG. 4 is a perspective view of the optical scanning device 600 having a conventional configuration. As shown in FIG. 4, the optical scanning apparatus 600 includes an optical box 300, a first laser substrate 42a, and a second laser substrate 42b. The optical scanning device 600 includes light sources 43Y (an example of a first light source), 43M (an example of a second light source), and 43C (an example of a third light source) that emit light beams that expose each of the photosensitive drums 5Y, 5M, 5C, and 5Bk. ), 43Bk (an example of a fourth light source). The light beam emitted from the light source 43Y is deflected by a rotating multifaceted mirror (not shown), passes through the transparent window 41Y, and reaches the photosensitive drum 5Y. Further, the light beam emitted from the light source 43M is deflected by a rotating multifaceted mirror (not shown), passes through the transparent window 41M, and reaches the photosensitive drum 5M. Further, the light beam emitted from the light source 43C is deflected by a rotating multifaceted mirror (not shown), passes through the transparent window 41C, and reaches the photosensitive drum 5C. Further, the light beam emitted from the light source 43Bk is deflected by a rotating multifaceted mirror (not shown), passes through the transparent window 43Bk, and reaches the photosensitive drum 5Bk.

Both the first laser substrate 42a and the second laser substrate 42b are attached to the outside of the optical box 300 so as to face the optical box 300. The first laser substrate 42a includes a light source 43Y, a driver IC 50Y that controls the light source 43Y, a light source 43M, a driver IC 50M that controls the light source 43M, and a connector 100. The light source 43Y and the light source 43M are provided on the mounting surface of the first laser substrate 42a. Specifically, the legs of the light source 43Y and the legs of the light source 43M are inserted and fixed from the mounting surface side of the first laser substrate 42a. Here, the light source 43Y and the light source 43M are, for example, semiconductor laser diode elements, and their legs are extended. The legs are attached by being soldered to the circuit pattern of the first laser substrate 42a. Electric power is supplied to the light source 43Y and the light source 43M from the circuit pattern via the legs. As shown in FIG. 4, the legs of the light source 43Y and the legs of the light source 43M are fixed in a state of being partially exposed from the surface opposite to the mounting surface of the first laser substrate 42a. In this way, the light source 43Y and the light source 43M are mounted on the mounting surface of the first laser substrate 42a. The driver IC 50Y, the driver IC 50M, and the connector 58a are all mounted on a surface opposite to the mounting surface of the first laser substrate 42a.

Similar to the first laser substrate 42a, the light source 43C, the light source 43Bk, the driver IC 50C for driving the light source 43C, the driver IC 50Bk for driving the light source 43Bk, and the connector 58b are mounted on the second laser substrate 42b. Since the mounting configuration of each element is the same as that of the first laser substrate 42a described above, the description thereof will be omitted.

In the present embodiment, the flexible flat cable 101 is connected to the connector 100. Drive signals for controlling the drive of the light sources 43Y to Bk generated by the controller 17 provided in the apparatus main body 100 are input to the connector 100 via the flexible flat cable 101. As shown in FIG. 4, the driver IC 50Y and the light source 43Y are electrically connected by a circuit pattern 505Y formed on the first laser substrate 42a. Further, the driver IC 50M and the light source 43M are electrically connected by a circuit pattern 505M formed on the first laser substrate 42a. Further, the driver IC 50C and the light source 43C are electrically connected by a circuit pattern 505C formed on the second laser substrate 42b. Further, the driver IC 50Bk and the light source 43Bk are electrically connected by a circuit pattern 505Bk formed on the second laser substrate 42b.

The driver IC 50Y and the driver IC 50M control the driving of the light source 43Y and the light source 43M based on the sent drive signal. The drive signal sent via the cable 100 includes a signal for controlling the drive of the light source 43Y and the light source 43M, and a signal for controlling the drive of the light source 43C and the light source 43Bk. The first laser substrate 42a is provided with the connector 58a, and the second laser substrate 42b is provided with the connector 58b. The connector 58a and the connector 58b are connected by a flexible flat cable (not shown). The signal for controlling the drive of the light source 43C and the light source 43Bk sent via the cable 100 is sent to the second laser substrate 42b via the flexible flat cable connecting the connector 58a and the connector 58b described above. The driver IC 50C and the driver IC 50Bk control the light source 43C and the light source 43Bk based on the drive signal sent to the second laser substrate 42b.

The flexible flat cable 101 in the present embodiment is a cable formed into a tape by sandwiching a plurality of thin wire conductors arranged in parallel from both sides with an insulator such as a resin sheet. A part of the thin wire conductor is a GND line for grounding, and is electrically connected to the ground of the power supply on the device main body 100 side. That is, the grounds of the first laser substrate 42a and the second laser substrate 42b also fall to the ground of the power supply of the apparatus main body 100 via the flexible flat cable 101. In this way, the first laser substrate 42a and the second laser substrate 42b are grounded.

FIG. 5 is a control block diagram of the optical scanning device 600. This control block diagram is the same as the control block diagram of the optical scanning device 40 in the present embodiment. The controller 17 is provided in the apparatus main body 100 as a separate body from the optical scanning apparatus 600. The controller 17 generates drive signals for driving the light sources 43Y, 43M, 43C, and 43Bk in the driver IC 50Y, the driver IC 50M, the driver IC 50C, and the driver IC 50Bk, respectively, based on the input image data. The drive signal generated by the controller 17 is transmitted to each driver IC 50Y to Bk via the flexible flat cable 101.

The drive signal generated by the controller 17 in this embodiment is a PWM signal. The driver IC 50Y controls the drive of the light source 43Y based on the PWM-Y signal transmitted from the controller 17. Further, the driver IC 50M controls the driving of the light source 43M based on the PWM-M signal transmitted from the controller 17. Further, the driver IC 50C controls the driving of the light source 43C based on the PWM-C signal transmitted from the controller 17. Further, the driver IC 50Bk controls the driving of the light source 43Bk based on the PWM-Bk signal transmitted from the controller 17.

FIG. 6 is a diagram for explaining the internal structure of the optical box 300 included in the optical scanning device 600. The light beam 430Y emitted from the light source 43Y, the light beam 430M emitted from the light source 43M, the light beam 430C emitted from the light source 43C, and the light beam 430Bk emitted from the light source 43Bk are deflected by the deflector 46a and are respectively deflected. It advances toward the photosensitive drum 5 corresponding to the light beam (43Y to 43Bk). The optical scanning device 40 in the present embodiment is a so-called opposed scanning type, and the optical beam 430Y and the optical beam 430M and the optical beam 430C and the optical beam 430Bk are reflected on opposite sides by the deflector 46a, respectively. That is, the light beam 430Y and the light beam 430M are incident on one side of the deflector 46a (the left side as shown in FIG. 6), and the light beam 430C and the light beam 430Bk are incident on the other side of the deflector 46a (as shown in FIG. 6). It is incident on the right side). The light beam 430Y and the light beam 430M are reflected to the left by the deflector 46a, and the light beam 430C and the light beam 430Bk are reflected to the right by the deflector 46a.

Here, the left-right direction shown in FIG. 6 is a direction that coincides with the arrangement direction of the photosensitive drums 5Y, 5M, 5C, and 5Bk. The front-rear direction in FIG. 6 coincides with the rotation axis direction of each photosensitive drum 5.

The configuration of the conventional optical scanning device 600 described above is the same as that of the optical scanning device 80 in the present embodiment.

Here, unlike the optical scanning device 80 in the present embodiment, the conventional optical scanning device 600 includes a common ground cable 201. The common ground cable 201 is electrically connected to a GND pad 200a (an example of a first ground pattern) having one end formed on the first laser substrate 42a and the other end having the GND pad 200b formed on the second laser substrate 42b. It is electrically connected to (an example of the second ground pattern). A plurality of circuit patterns are formed on a circuit board such as the first laser board 42a and the second laser board 42b. The circuit pattern has a ground pattern having a ground potential, and a ground terminal is formed on the ground pattern. This ground terminal corresponds to the GND pad 200a and the GND pad 200b referred to here. In the GND pad 200a and the GND pad 200b, the plating is exposed from the circuit board, and for example, one side has a square shape of 10 mm square. A through hole penetrating the substrate itself is formed near the center, and the common ground cable 201 is fastened to the first laser substrate 42a and the second laser substrate 42b through the through hole, for example, by a screw. In this way, the ground of the first laser substrate 42a and the ground of the second laser substrate 42b are shared.

Here, as the GND line, there is also a flexible flat cable (not shown) that connects the first laser substrate 42a and the second laser substrate 42b. However, in general, the GND line of a flexible flat cable has a thin wiring thickness. By using the GND pad 200a, the GND pad 200b, and the common ground cable 201, the impedance of the GND line can be suppressed. This makes it possible to reduce the effects of voltage drop and electromagnetic induction when a current flows. Further, by ensuring a stable GND as a return path of a signal radiating noise, it is an object of preventing impedance mismatch and resonance of a transmission line due to an unintended return path. By taking noise countermeasures on the first laser substrate 42a and the second laser substrate 42b in this way, the influence of electromagnetic wave noise due to the speeding up and high image quality of the image forming apparatus 1 is reduced.

(Countermeasures against electromagnetic noise leaking to the outside of the image forming device)
In recent years, with the miniaturization and weight reduction of electronic devices, the density and integration of electronic components such as CPUs, LSIs, and peripheral semiconductors mounted inside have been increased, and the high-density mounting of electronic components on printed wiring boards. It is becoming more and more popular. In addition, the frequencies handled are increasing in order to improve the performance of electronic devices. Along with this, the influence of electromagnetic noise emitted from electronic components or conduction noise transmitted through the wiring circuit of the printed wiring board on electronic devices has become a problem. There are also standards that try to keep the electromagnetic energy radiated from electronic devices below a certain level. Standards include, for example, VCSI (Voluntary Control Council for Interference by Information Technology) and EMC (Electromagnetic Compatibility). Such reduction of noise radiated from equipment is also required for copiers and printers.

FIG. 7A is a frequency spectrum of the electromagnetic wave noise radiated to the outside of the image forming apparatus 1 among the electromagnetic wave noise radiated from the optical scanning device 800 of the conventional configuration. The electromagnetic noise level was observed for the electromagnetic noise having a frequency of 0 to 500 MHz. For reference, the reference value of electromagnetic noise leaking to the outside from an electronic device defined by the VCSI standard (ClassB) is shown in accordance with FIG. 7 (a). FIG. 7B is a frequency spectrum of the electromagnetic wave noise radiated to the outside of the image forming apparatus 1 among the electromagnetic wave noise radiated from the optical scanning device 80 in the present embodiment. Details of FIG. 7B will be described later.

The VCCI standard is established by the VCCI Association (Voluntary Control Council for Radio Interference such as Information Processing Devices). The VCCI Association is an association established for the purpose of self-regulating electromagnetic noise emitted from electronic devices in order to reduce the influence of electromagnetic noise leaking from electronic devices on other electronic devices and the like. Members of the VCCI Association will conduct a conformity confirmation test to the interference wave standard for their MME (multimedia equipment) prior to shipping to Japan to confirm conformity with the standard. Conformity verification tests need to use measuring equipment registered with the VCSI Association. The measurement results shown in FIG. 7 are the measurement results of experiments performed based on the VCSI standard. Confirmation of conformity is carried out according to the classification of MME. The classification of MME is divided into "class A" and "class B" according to the environment in which the target device is used. The VCSI standard standard shown in FIG. 7 (a) is a class B standard.

The peak waveform 57 appears in the spectrum 56 of the electromagnetic noise level measurement result shown in FIG. 7A. When impedance mismatch or reflection from the termination occurs in the path from transmission to reception of wiring signals within or between boards, resonance of the transmission line occurs due to the length of the signal path and the wavelength of the signal frequency. It may appear as electromagnetic noise.

In the example of FIG. 7A, since the period of the image signal that causes the light source 43 to emit light is 72 MHz, the peak waveform 57 that resonates at the multiplication factor of 72 MHz is observed. There are three locations near 216 MHz (57a), which is three times the image signal period of 72 MHz, 360 MHz (57b), which is five times, and 432 MHz (57c), which is six times, and 216 MHz (57a) exceeds the standard. I understand.

As a factor of exceeding the standard of electromagnetic noise, for example, the first laser substrate 42a and the controller 17 may be connected by a flexible flat cable 101. This is because the GND line is thin with a flexible flat cable and the GND state is not stable.

Therefore, a noise countermeasure method for the optical scanning apparatus 80 according to the present embodiment will be described with reference to FIG. FIG. 8A is a perspective view of the optical box 40 of the optical scanning device 80 according to the present embodiment. Further, FIG. 8B is a view of the optical scanning device 80 as viewed from above.

As shown in FIGS. 8A and 8B, the sheet metal 60 is arranged so as to face at least a part of the first laser substrate 42a and at least a part of the second laser substrate 42b. Of the front and back surfaces of the first laser substrate 42a, when the side on which the light source 43Y and the light source 43M are mounted is the mounting surface and the side on which the driver IC 50Y and the driver IC 50M are provided is the opposite surface, the sheet metal 60 is opposite. It is arranged so as to face at least a part of the surface. In other words, the sheet metal 60 overlaps at least a part of the opposite surface of the first laser substrate 42a in the direction perpendicular to the opposite surface of the first laser substrate 42a (or the direction perpendicular to the mounting surface). Similarly, of the front and back surfaces of the second laser substrate 42b, when the side on which the light source 43C and the light source 43Bk are mounted is the mounting surface and the side on which the driver IC 50C and the driver IC 50Bk are provided is the opposite surface, the sheet metal 60 is arranged so as to face at least a part of the opposite surface. In other words, the sheet metal 60 overlaps at least a part of the opposite surface of the first laser substrate 42b in the direction perpendicular to the opposite surface of the first laser substrate 42b (or the direction perpendicular to the mounting surface).

The main sources of electromagnetic noise are driver ICs 50Y, 50M, 50C, and 50Bk. Therefore, the sheet metal 60 covers both the driver IC 50Y and the driver IC 50M on the side opposite to the side where the optical box 40 is arranged with respect to the driver IC 50Y in the direction perpendicular to the mounting surface of the first laser substrate 42a. It is provided in.

Further, the sheet metal 60 covers both the driver IC 50C and the driver IC 50Bk on the side opposite to the side where the optical box 40 is arranged with respect to the driver IC 50C in the direction perpendicular to the mounting surface of the second laser substrate 42b. It is provided in. Further, as can be seen from FIGS. 8A and 8B, the sheet metal 60 is arranged to face the drivers ICs 50Y, 50M, 50C, and 50Bk. That is, when the sheet metal 60 is viewed from the outside of the optical scanning device 80 in the direction perpendicular to the mounting surface of the first laser substrate 42a, the driver ICs 50Y, 50M, 50C, and 50Bk all overlap the sheet metal 60. By doing so, it is possible to effectively reduce the electromagnetic wave noise radiated from the image forming apparatus 1 to the outside.

Here, the sheet metal 60 does not have to be arranged so as to completely cover all of the drivers ICs 50Y, 50M, 50C, and 50Bk. For example, when the sheet metal 60 is viewed from the outside of the optical scanning device 80 in a direction perpendicular to the mounting surface of the first laser substrate 42a due to the arrangement with surrounding parts, a part of the drivers IC 50Y, 50M, 50C, and 50Bk. It doesn't matter if you can see. Even in that case, it is preferable that 90% or more of the area of the driver ICs 50Y, 50M, 50C, and 50Bk is covered by the sheet metal 60. In other words, the sheet metal 60 may be arranged so as to cover an area of 90% or more of the driver ICs 50Y, 50M, 50C, and 50Bk.

Here, as can be seen from FIGS. 8A and 8B, there is a gap between the sheet metal 60 and the first laser substrate 42a and the second laser substrate 42b in the vertical direction (vertical direction). is there. That is, when the optical box 40 is viewed from above or below, the drivers ICs 50Y to BK are not in a positional relationship so as to overlap the sheet metal 60. Electromagnetic noise is radiated radially from each of the driver ICs 50Y to Bk. Therefore, most of the electromagnetic noise radiated from the driver ICs 50Y and 50M is reflected and attenuated by the sheet metal 60 in the direction perpendicular to the mounting surface of the first laser substrate 42a. On the other hand, electromagnetic noise radiated upward or downward from the driver ICs 50Y and 50M proceeds without being reflected or attenuated by the sheet metal 60. However, the image forming apparatus 1 has other members such as an intermediate transfer belt 20 above the optical scanning apparatus 80, and a member such as a paper feed cassette 2 below the optical scanning apparatus 80. Therefore, among the electromagnetic wave noise radiated in the vertical direction from the driver ICs 50Y to Bk, the electromagnetic wave noise radiated to the outside of the image forming apparatus 1 is not large. Of the electromagnetic noise radiated to the outside of the image forming apparatus 1, the dominant electromagnetic noise is the electromagnetic wave noise radiated from the driver ICs 50Y to Bk toward the rear side of the image forming apparatus 1, that is, the rear side plate 103 shown in FIG. 8 (b). .. Therefore, as shown in FIGS. 8A and 8B, the sheet metal 60 faces the driver ICs 50Y and 50M in the direction perpendicular to the mounting surface of the first laser substrate 42a and is placed on the mounting surface of the second laser substrate 42b. By arranging the driver ICs 50C and 50Bk at positions facing each other in the vertical direction, it is possible to reduce the electromagnetic wave noise radiated from the image forming apparatus 1 to the outside.

The sheet metal 60 may have a structure in which an opening, for example, a minute hole is formed in a part thereof. When image formation is started, the drivers ICs 50Y, 50M, 50C, and 50Bk generate heat and the temperature rises. As a result, the temperature around the first laser substrate 42a and the second laser substrate 42b may rise. An increase in the temperature around the first laser substrate 42a and the second laser substrate 42b may cause fluctuations in the characteristics of the light sources 43Y, 43M, 43C, and 43Bk. Since the opening is formed in the sheet metal 60, it is possible to reduce the possibility that the heat released from the driver ICs 50Y, 50M, 50C, and 50Bk stays between the optical box 40 and the sheet metal 60. Even if the sheet metal 60 has an opening formed, the noise emitted to the outside of the image forming apparatus 1 can be reduced by arranging the sheet metal 60 so as to cover the drivers ICs 50Y to Bk.

As shown in FIG. 8A, the sheet metal 60 is provided with a leg portion 600a and a leg portion 600b. The legs 600a and the legs 600b form a gap of about 15 mm between the sheet metal 60 and the first laser substrate 42a and between the sheet metal 60 and the second laser substrate 42b. In addition to the drivers IC50Y to Bk, the first laser substrate 42a and the second laser substrate 42b are provided with mounting components such as an electrolytic capacitor and a resistor. Since the legs 600a and the legs 600b float the sheet metal 60 with respect to the optical box 40, it is possible to prevent these mounting components and the sheet metal 60 from buffering each other.

The first laser substrate 42a is attached to the optical box 40 by two screws 55a and 65a. Further, the second laser substrate 42b is attached to the optical box 40 by two screws 55b and 65b. A hole through which the screw 55a is passed is formed in the leg portion 600a. A GND pad 61a, which is a part of the ground wire of the circuit pattern, is formed on the first laser substrate 42a, and the leg portion 600a and the GND pad 61a are fastened by the screw 55a to be electrically conductive. Similarly, the leg portion 600b is also fastened to the GND pad 61b formed on the second laser substrate 42b by the screw 55b. In this way, the sheet metal 60 is connected to the GND pad 61a and the GND pad 61b. Therefore, the ground of the first laser substrate 42a and the ground of the second laser substrate 42b are shared.

As described above, in the optical scanning apparatus 80 of the present embodiment, the ground of the first laser substrate 42a and the ground of the second laser substrate 42b are shared, and the electromagnetic noise level leaking from the image forming apparatus 1 is reduced. , Is realized with a simple configuration.

FIG. 7B shows a measurement result of noise radiated from the image forming apparatus 1 including the optical scanning apparatus 80 in the present embodiment. From FIG. 7B, the peak waveform 57'is observed in the spectrum 56'of the measurement result, and there are three places near 216 MHz (57a'), 360 MHz (57b'), and 432 MHz (57c'). It can be seen that 216 MHz (57a') is within the standard. By taking the noise countermeasures of the configuration of the present embodiment described above as described above, the noise radiated from the image forming apparatus 1 can be reduced.

As described above, the GND pad 61a of the first laser substrate 42a and the GND pad 61b of the second laser substrate 42b are electrically connected to the ground of the power supply of the apparatus main body 100 via the GND line of the flexible flat cable 101. Has been done. FIG. 9 is a diagram illustrating a modified example of how to ground the GND pad 61a of the first laser substrate 42a and the GND pad 61b of the second laser substrate 42b.

As shown in FIG. 9, the sheet metal 60 is provided with a leaf spring 102 protruding toward the rear side plate 103. The rear side plate 103 is made of metal, and an opening 104 is formed in a part thereof. When the optical scanning device 80 is attached to the apparatus main body 100 of the image forming apparatus 1, the leaf spring 102 flexes and fits into the opening 104. In this way, the electrical contacts between the GND pad 61a, the GND pad 61b, and the rear side plate 103 are secured. Since the rear side plate 103 is grounded, the GND pad 61a and the GND pad 61b are grounded. The ground of the GND pad 61a and the GND pad 61b may be configured to be secured as in this modification.

<Example 2>
In FIG. 10, a metal connecting member 62a is provided between the leg portion 600a of the sheet metal 60 and the GND pad 61a, and a metal connecting member 62b is provided between the leg portion 600b of the sheet metal 60 and the GND pad 61b. It is a figure which shows the structure. Here, the connecting member 62a and the connecting member 62b are, for example, plate-shaped metal pieces. As described above, the member that serves to shield the electromagnetic wave noise radiated from the first laser substrate 42a and the second laser substrate 42b needs to be composed of one member like the sheet metal 60 in the first embodiment. There is no. However, in the configuration of the second embodiment, since the GND line is composed of the connecting member 62a, the sheet metal 60, and the connecting member 62b, the impedance becomes high at the boundary portion of each member, and the electromagnetic wave propagating inside is reflected. Sometimes. Therefore, from the viewpoint of sharing the ground between the first laser substrate 42a and the second laser substrate 42b, Example 1 is preferable to Example 2.

<Example 3>
In the first and second embodiments, the first laser substrate 42a includes a light source 43Y that emits a light beam for exposing the photosensitive drum 5Y and a light source 43M that emits a light beam for exposing the photosensitive drum 5M. The second laser substrate 42b includes a light source 43C that emits a light beam for exposing the photosensitive drum 5C and a light source 43Bk that emits a light beam for exposing the photosensitive drum 5Bk. On the other hand, in the third embodiment, the image forming apparatus 1 includes two optical scanning devices and a total of four laser substrates.

As shown in FIG. 11, the image forming apparatus 1 in the third embodiment includes a counter-scanning type optical scanning device 85YM and a counter-scanning type optical scanning device 85CBk. The optical scanning apparatus 85YM includes a first laser substrate 86Y and a second laser substrate 86M. Light emitted from a light source (not shown) provided on the first laser substrate 86Y passes through the transparent window 85Y and exposes the photosensitive drum 5Y. Further, the light emitted from a light source (not shown) provided on the second laser substrate 86M passes through the transparent window 85M and exposes the photosensitive drum 5M. Then, in order to reduce the noise radiated from the image forming apparatus, the sheet metal 87 is provided on the drive IC 89Y provided on the first laser substrate 86Y to drive the light source and on the second laser substrate 86M to drive the light source. It is arranged so as to cover both the driven IC 89M and the drive IC 89M. Further, the sheet metal 87 is connected to the GND pad of the first laser substrate 86Y and the GND pad of the second laser substrate 86M, and the ground of the first laser substrate 86Y and the second laser substrate 86M is shared.

Similarly, the optical scanning apparatus 85CBk includes a third laser substrate 86C and a fourth laser substrate 86Bk. Light emitted from a light source (not shown) provided on the third laser substrate 86C passes through the transparent window 85C and exposes the photosensitive drum 5C. Further, the light emitted from a light source (not shown) provided on the fourth laser substrate 86Bk passes through the transparent window 85Bk and exposes the photosensitive drum 5Bk. Then, in order to reduce the electromagnetic wave noise radiated from the image forming apparatus, the sheet metal 88 is attached to the drive IC 89C provided on the third laser substrate 86C to drive the light source and to the fourth laser substrate 86Bk to drive the light source. It is arranged so as to cover the provided drive IC 89Bk. Further, the sheet metal 88 is connected to the GND pad of the third laser substrate 86C and the GND pad of the fourth laser substrate 86Bk, and the ground of the third laser substrate 86C and the fourth laser substrate 86Bk is shared.

40 Optical scanning device 41Y Transparent window 41M Transparent window 41C Transparent window 41Bk Transparent window 42a 1st laser substrate 42b 2nd laser substrate 43Y Light source 43M Light source 43C Light source 43Bk Light source 50Y Driver IC
50M driver IC
50C driver IC
50Bk driver IC
55a screw 55b screw 58a connector 58b connector 60 sheet metal 61a GND pad 61b GND pad 80 optical box 600a leg 600b leg

Claims (10)

A first light source that emits a light beam for exposing the first photosensitive drum,
A second light source that emits a light beam for exposing the second photosensitive drum,
A deflector that deflects the light beam emitted from the first light source to guide it to the first photosensitive drum, and deflects the light beam emitted from the second light source to guide it to the second photosensitive drum.
An optical box containing the deflector and
A first substrate having a first light source, a first drive IC for driving the first light source, and a first ground pattern, and attached to the outside of the optical box.
A second substrate having the second light source, the second drive IC for driving the second light source, and the second ground pattern, and attached to the outside of the optical box,
The side that is electrically connected to the first ground pattern and the second ground pattern and in which the optical box is arranged with respect to the first drive IC in a direction perpendicular to the mounting surface of the first substrate is The second drive covers the first drive IC on the opposite side and is opposite to the side on which the optical box is arranged with respect to the second drive IC in a direction perpendicular to the mounting surface of the second substrate. An optical scanning device including a sheet metal covering an IC. The first light source and the first driver IC are connected by a first circuit pattern formed on the first substrate.
The second light source and the second driver IC are connected by a second circuit pattern formed on the second substrate.
The sheet metal is
Arranged so as to overlap at least a part of the first circuit pattern in the vertical direction.
The optical scanning apparatus according to claim 1, wherein the optical scanning apparatus is arranged so as to overlap at least a part of the second circuit pattern in the vertical direction. The optical scanning apparatus according to claim 1 or 2, wherein the sheet metal is fastened to the first ground pattern and the second ground pattern by screws. The light beam emitted from the first light source is incident on the deflector from one side of the deflector in the arrangement direction of the first photosensitive drum and the second photosensitive drum.
The method according to any one of claims 1 to 3, wherein the light beam emitted from the second light source is incident on the deflector from the other side of the deflector in the arrangement direction. Optical scanning device. It has the first photosensitive drum and the second photosensitive drum.
The optical scanning apparatus according to any one of claims 1 to 4, wherein the first photosensitive drum and the second photosensitive drum are irradiated with a light beam to form an electrostatic latent image.
A developing means for developing an electrostatic latent image formed by the optical scanning device using toner, and
An image forming apparatus comprising: a transfer means for transferring a toner image formed by the developing means onto a recording paper. A first light source that emits a light beam for exposing the first photosensitive drum,
A second light source that emits a light beam for exposing the second photosensitive drum,
A third light source that emits a light beam for exposing the third photosensitive drum,
A fourth light source that emits a light beam for exposing the fourth photosensitive drum,
The light beam emitted from the first light source is deflected to be guided to the first photosensitive drum, the light beam emitted from the second light source is deflected to be guided to the second photosensitive drum, and the third light source is deflected. A deflector that deflects the light beam emitted from the light beam to guide it to the third photosensitive drum and deflects the light beam emitted from the fourth light source to guide it to the fourth photosensitive drum.
An optical box containing the deflector and
The optical box having the first light source, the first drive IC for driving the first light source, the second light source, the second drive IC for driving the second light source, and the first ground pattern. The first board attached to the outside of
The optical box having the third light source, the third drive IC for driving the third light source, the fourth light source, the fourth drive IC for driving the fourth light source, and the second ground pattern. The second board attached to the outside of the
Electrically connected to the first ground pattern and the second ground pattern,
The first drive IC and the first drive IC and the second drive IC are on the side opposite to the side where the optical box is arranged with respect to both the first drive IC and the second drive IC in a direction perpendicular to the mounting surface of the first substrate. Covers both with the second drive IC and
The third drive IC and the third drive IC and the fourth drive IC are on the side opposite to the side where the optical box is arranged with respect to both the third drive IC and the fourth drive IC in a direction perpendicular to the mounting surface of the second substrate. An optical scanning device including a sheet metal that covers both the fourth drive IC and the fourth drive IC. The first light source and the first driver IC are connected by a first circuit pattern formed on the first substrate.
The second light source and the second driver IC are connected by a second circuit pattern formed on the first substrate.
The third light source and the third driver IC are connected by a third circuit pattern formed on the second substrate.
The fourth light source and the fourth driver IC are connected by a fourth circuit pattern formed on the second substrate.
The sheet metal is
It is arranged so as to overlap at least a part of the first circuit pattern and at least a part of the second circuit pattern in the vertical direction.
The optical scanning apparatus according to claim 6, wherein the optical scanning apparatus is arranged so as to overlap at least a part of the third circuit pattern and at least a part of the fourth circuit pattern in the vertical direction. The optical scanning apparatus according to claim 6, wherein the sheet metal is fastened to the first ground pattern and the second ground pattern by screws. The light beam emitted from the first light source and the light beam emitted from the second light source are the arrangement directions of the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum. From one side of the deflector toward the deflector,
A claim that the light beam emitted from the third light source and the light beam emitted from the fourth light source travel toward the deflector from the other side of the deflector in the arrangement direction. The optical scanning apparatus according to any one of claims 6 to 8. It has the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum.
Any one of claims 6 to 9 for forming an electrostatic latent image by irradiating the first photosensitive drum, the second photosensitive drum, the third photosensitive drum, and the fourth photosensitive drum with a light beam. The optical scanning device described in
A developing means for developing an electrostatic latent image formed by the optical scanning device using toner, and
An image forming apparatus comprising: a transfer means for transferring a toner image formed by the developing means onto a recording paper.

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