JP7532215B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming device equipped with a flat cable.

Conventionally, image forming devices use flexible flat cables (hereinafter referred to as FFCs) to connect an image data generating unit with a driving unit for driving a device based on image data. Since FFCs have a linearly configured metallic body for transmitting signals, they function as antennas and tend to be a source of unwanted radiation noise. Therefore, when a signal is driven into the FFC, a magnetic field is generated around it, and the magnetic fields of other FFCs placed nearby interact with each other, causing cross-coupling between the signal lines. This phenomenon is called crosstalk. Patent Document 1 describes a method of shielding signal lines by adhering a thin metal film to the FFC in order to suppress radiation noise and crosstalk emitted from the FFC.

JP 2015-139946 A

In an image forming apparatus that forms a color image, a driving unit is provided for each color. The multiple driving units are arranged relatively close to each other, but may be separated due to arrangement constraints. Therefore, it is difficult to connect all the driving units with a single FFC. Therefore, multiple FFCs are used to connect the image data generating unit to each driving unit. In recent years, with the miniaturization and multi-function of image forming apparatuses, there is a design demand to run multiple FFCs in parallel to share part of the wiring path. In this case, since other FFCs are arranged near one FFC, crosstalk occurs as described above, and there is a risk of malfunction due to the unintended electrical signal. In contrast, if an FFC with a full-length shielding process is used as described in Patent Document 1, there is a problem that the impedance of the signal line decreases and the signal waveform deteriorates.

The present invention aims to suppress crosstalk between flat cables while maintaining signal quality when multiple flat cables are used in parallel, ensuring stable device operation.

The image forming apparatus of the present invention is an image forming apparatus comprising an image forming unit that forms an image, a controller that controls the image forming unit, a first flat cable and a second flat cable that each transmit signals between the controller and the image forming unit, and a shielding portion that covers the first flat cable, wherein the first flat cable includes a first portion and a second portion, the first portion of the first flat cable overlaps with the second flat cable when viewed in a direction intersecting a plane of the first flat cable, and At least a portion of the second portion of the first flat cable is covered by the shielding portion, and the second portion of the first flat cable is located at a different position from the second flat cable when viewed in the direction, or is located at a position farther away from the second flat cable in the direction than the first portion, and at least a portion of the second portion of the first flat cable is exposed to the shielding portion, the first and second portions of the first flat cable are continuous, and the second portion is covered by the shielding portion within a predetermined distance from the boundary with the first portion.

According to the present invention, when multiple flat cables are used in parallel, crosstalk between the flat cables can be suppressed while maintaining signal quality, enabling stable operation of the device.

FIG. 1 is a diagram illustrating an example of the overall configuration of an image forming apparatus. FIG. 2 is a diagram showing a transmission line of a video signal. FIG. 2 is a perspective view showing the arrangement of an FFC according to the first embodiment. FIG. 2 is a plan view showing the arrangement of the FFC according to the first embodiment. FIG. 2 is a plan view showing the FFC according to the first embodiment. FIG. 11 is a perspective view showing the arrangement of an FFC according to a second embodiment. FIG. 11 is a plan view showing the arrangement of an FFC according to a second embodiment. FIG. 11 is a plan view showing an FFC according to a second embodiment. FIG. 11 is a perspective view showing the arrangement of an FFC according to a third embodiment. A diagram showing the signal waveform of FFC-YM121. A diagram showing the signal waveform of FFC-CBk122.

The following describes an embodiment of the present invention with reference to the attached drawings.

First Embodiment
In this embodiment, an image forming apparatus is described that is provided with a plurality of FFCs (flexible flat cables) for transmitting signals (for example, image signals).

[Overall Configuration of Image Forming Apparatus]
1 is a schematic cross-sectional view of an image forming apparatus. The image forming apparatus 100 of this embodiment is a digital full-color printer that forms an image using toner of multiple colors. In this embodiment, a digital full-color printer will be described as an example of the image forming apparatus, but the image forming apparatus is not limited to a digital full-color printer and may be a multifunction machine having a copy function, a facsimile function, or a combination of these functions.

The image forming apparatus 100 has four image forming units 101Y, 101M, 101C, and 101Bk that form images for each color. Here, Y, M, C, and Bk represent yellow, magenta, cyan, and black, respectively. The image forming units 101Y, 101M, 101C, and 101Bk form images using yellow, magenta, cyan, and black toner, respectively. Note that in this embodiment, the image forming units 101Y, 101M, 101C, and 101Bk form images using an electrophotographic method, but they may also form images using other printing methods, such as an inkjet method.

The image forming units 101Y, 101M, 101C, and 101Bk each include a photosensitive drum 102Y, 102M, 102C, and 102Bk as a photosensitive member. Around the photosensitive drums 102Y, 102M, 102C, and 102Bk, charging devices 103Y, 103M, 103C, and 103Bk, optical scanning devices 104Y, 104M, 104C, and 104Bk, and developing devices 105Y, 105M, 105C, and 105Bk are provided, respectively. In addition, around the photosensitive drums 102Y, 102M, 102C, and 102Bk, drum cleaning devices 106Y, 106M, 106C, and 106Bk are provided.

An endless belt-like intermediate transfer belt 107 (intermediate transfer body) is disposed below the photosensitive drums 102Y, 102M, 102C, and 102Bk. The intermediate transfer belt 107 is stretched around a drive roller 108 and driven rollers 109 and 110, and rotates in the direction of arrow B in the figure during image formation. Primary transfer devices 111Y, 111M, 111C, and 111Bk are provided at positions facing the photosensitive drums 102Y, 102M, 102C, and 102Bk via the intermediate transfer belt 107. The image forming apparatus 100 of this embodiment also includes a secondary transfer device 112 for transferring the toner image on the intermediate transfer belt 107 to the recording material P, and a fixing device 113 for fixing the toner image on the recording material P.

Here, we will explain the image formation process from the charging process to the developing process of the image forming apparatus 100 having such a configuration. Since the image formation process in each image forming unit is the same, we will explain it using the image forming unit 101Y as an example, and omit the explanation of the image formation process in the image forming units 101M, 101C, and 101Bk.

First, the photosensitive drum 102Y, which is rotated, is charged by the charging device 103Y of the image forming unit 101Y. The charged photosensitive drum 102Y (on the image carrier) is exposed to laser light emitted from the optical scanning device 104Y. The optical scanning device 104Y is electrically connected to the controller 120 by the FFC-YM121 (Figure 2). The details of the FFC connection and arrangement will be described later. The optical scanning device 104Y controls the turning on of the laser light based on the video signal VDO-YZ (Figure 2) generated by the controller 120. As a result, an electrostatic latent image is formed on the rotating photosensitive body. The electrostatic latent image is then developed into a yellow toner image by the developing device 105Y.

The image formation process after the transfer step will be described below. Primary transfer devices 111Y, 111M, 111C, and 111Bk apply a transfer bias to the transfer belt. As a result, the yellow, magenta, cyan, and black toner images formed on the photosensitive drums 102Y, 102M, 102C, and 102Bk of each image forming unit are transferred to the intermediate transfer belt 107. This causes the toner images of each color to be superimposed on the intermediate transfer belt 107.

When the four-color toner image is transferred onto the intermediate transfer belt 107, the four-color toner image transferred onto the intermediate transfer belt 107 is transferred again (secondary transfer) by a secondary transfer device 112 onto a recording material P conveyed from a manual feed cassette 114 or a paper feed cassette 115. The toner image on the recording material P is then heated and fixed by a fixing device 113 and discharged to a paper discharge section 116, whereby a full-color image is obtained on the recording material P.
After the transfer is completed, the photosensitive drums 102Y, 102M, 102C, and 102Bk are cleaned of residual toner by the drum cleaning devices 106Y, 106M, 106C, and 106Bk, after which the above-mentioned image forming process is continued.

[Video signal transmission line]
Next, a video signal used when the optical scanning devices 104Y, 104M, 104C, and 104Bk control the lighting of the laser light will be described. The video signal is an example of an image signal. FIG. 2 is a diagram showing a transmission line through which the video signals of each color generated by the controller 120 are input to the optical scanning devices 104Y, 104M, 104C, and 104Bk. The controller 120 is composed of an IC 150 and an IC-Y 151. The IC 150 is an example of an image data generating section, and generates and outputs image data (hereinafter, referred to as video signals VDO-Y, VDO-M, VDO-C, and VDO-Bk) separated into yellow, magenta, cyan, and black based on image information to be formed on the recording material P.

IC-Y151 is an example of an image processing unit, and performs special image processing on image data of some colors among the image data of each color output from IC150. An example of special image processing is embedding the individual number of the image forming device 100 in the video signal. In this embodiment, IC-Y151 performs special image processing on VDO-Y. Therefore, the video signal VDO-YZ output from IC-Y151 has a higher frequency than the video signal output from IC150. In addition, IC-Y151 has a higher driving ability than IC150. Therefore, VDO-YZ has a larger amplitude than the video signal output from IC150. Therefore, VDO-YZ is more likely to be a noise generating factor than VDO-M, VDO-C, and VDO-Bk.

The FFC-YM121 is connected to the controller 120 and the laser driver board-YM131. The laser driver board-YM131 and the laser driver board-CBk132, which will be described next, are examples of a drive unit, and have a laser driver IC mounted on them. VDO-YZ and VDO-M output from the controller 120 are input to the laser driver board-YM131 via the FFC-YM121. The laser driver board-YM131 outputs VDO-YZ and VDO-M to the optical scanning device 104Y and the optical scanning device 104M.

Similarly, FFC-CBk122 is connected to the controller 120 and the laser driver board-CBk132. VDO-C and VDO-Bk output from the controller 120 are input to the laser driver board-CBk132 via FFC-CBk122. The laser driver board-CBk132 outputs VDO-C and VDO-Bk to the optical scanning device 104C and the optical scanning device 104Bk.

As described above, the image forming apparatus 100 is provided with separate drive units for driving the image forming units 101Y and 101M and drive units for driving the image forming units 101C and 101Bk, and image data from the controller 120 is transmitted to the corresponding drive units. In this embodiment, since the drive units are arranged separately, the controller 120 and each drive unit are connected using multiple FFCs (FFC-YM121 and FFC-CBk122).

FFC-YM121 and FFC-CBk122 are examples of flat cables, and are made by integrating multiple conductors arranged in parallel at a predetermined interval in a plane along the longitudinal direction and covered with an insulating film. The number of conductors is, for example, 20 to 50. In this embodiment, FFC-YM121 and FFC-CBk122 are thin sheets and have flexibility in the direction of bending along the longitudinal direction.

[Location of FFC]
Next, the positional relationship between the FFC-YM121 and the FFC-CBk122 and the peripheral units will be described. Fig. 3 is a perspective view showing the arrangement of the FFC-YM121 and the FFC-CBk122. Fig. 4 is an xy plan view of the configuration in Fig. 3, seen from the positive direction of the z axis shown in Fig. 3.
The controller 120 is provided with a connector 123 for connecting the FFC-YM121 and a connector 124 for connecting the FFC-CBk122. The laser driver board-YM131 is provided with a connector 125 for connecting the FFC-YM121. The laser driver board-CBk132 is provided with a connector 126 for connecting the FFC-CBk122.

The controller 120 and laser driver board-YM131 are connected by connecting each end of the FFC-YM121 to connectors 123 and 125, respectively. Similarly, the controller 120 and laser driver board-CBk132 are connected by connecting each end of the FFC-CBk122 to connectors 124 and 126, respectively. The laser driver board-YM131 is connected to the optical scanning devices 104Y and 104M, and the laser driver board-CBk132 is connected to the optical scanning devices 104C and 104Bk.

3, connector 124 is provided near connector 123. Connector 126 is provided near connector 125. Therefore, there is a portion in the middle of the wiring paths of the multiple FFCs (FFC-YM121 and FFC-CBk122) where the paths are shared. In this embodiment, the multiple FFCs are arranged side by side so as to overlap each other in this shared portion. This reduces the number of parts for fixing the positions of the FFCs and eliminates the need to secure individual paths, thereby realizing cost reduction and space saving.
In the image forming apparatus 100 of the present embodiment, two overlapping FFCs are used, but the number of overlapping FFCs is not limited to two, and may be three or more.

Six FFC guides 140 to 145 are attached to a metal plate 170, which is a part of the metal plate constituting the housing of the image forming apparatus 100, as fixing members for fixing the arrangement of the FFC-YM 121 and the FFC-CBk 122. The FFC guides 140 to 145 are plate-like members made of a non-conductive resin material.
The FFC guides 140 to 143 have a width equal to the width of the FFC, and one end in the vertical direction is attached to the metal plate 170. In addition, a slit slightly wider than the thickness of the FFC is formed near the other end in the vertical direction. The FFC-YM121 is inserted into each slit of the FFC guides 140 to 143. As a result, the FFC-YM121 is bent midway along the wiring path and fixed at a predetermined distance from the metal plate 170 in the section including d1 and b4 in FIG. 3.

FFC guides 144 and 145 each have a substantially L-shape, one end of which is attached to sheet metal 170, extends from the attachment position in the negative direction of the x-axis, and bends at a position a predetermined distance away from sheet metal 170. FFC guide 144 extends from the bent position in the positive direction of the z-axis by a length equal to the width of the FFC. FFC guide 145 extends from the bent position in the positive direction of the y-axis by a length equal to the width of the FFC. The distance from the attachment position to the bent position is slightly longer than the thickness of the FFC. As a result, gaps are formed between FFC guides 144 and 145 and sheet metal 170, and FFC-CBk 122 is inserted into these gaps. As a result, FFC-CBk 122 is fixed in contact with or in close proximity to sheet metal 170 in sections b1, b2, and b3 in FIG. 3.

FFC guides 142 and 143 are used to insert and fix only FFC-YM121. FFC guides 144 and 145 are used to insert and fix only FFC-CBk122. On the other hand, FFC guides 140 and 141 are used to insert and fix FFC-YM121 and FFC-CBk122 in an overlapping manner. Therefore, in the sections d1, d2, and d3 in FIG. 3, FFC-YM121 and FFC-CBk122 are arranged side by side so as to overlap. The sections d1, d2, and d3 correspond to the sections where multiple flat cables are arranged side by side. In this embodiment, overlapping means that the flat surfaces of the flat cables are in contact or close to each other along the longitudinal direction.

In the sections d1, d2, and d3, the FFC-YM121 and the FFC-CBk122 run parallel to each other, so their magnetic fields interact with each other, causing crosstalk between the signal lines. In particular, the VDO-YZ is prone to become a noise source as described above, so it interferes with the signal line of the FFC-CBk122, causing unintended electrical signals to be generated.
Furthermore, in sections b1, b2, and b3, since the FFC-CBk 122 is in contact with the metal plate 170, the electrical signal generated by the interference propagates to the metal plate 170 (metal member), causing the metal plate 170 to act as an antenna, generating unnecessary radiated noise.

Therefore, the FFC-YM121 is covered with a shielding material in the sections d1, d2, and d3 (hatched areas in Figure 3). This suppresses the occurrence of crosstalk and the emission of unnecessary radiated noise. On the other hand, if the section covered with the shielding material becomes long, the impedance of the signal line decreases, and the signal waveform inside the FFC-YM121 tends to deteriorate. Therefore, in sections other than d1, d2, and d3, the FFC-YM121 is not covered with a shielding material. That is, the FFC-YM121 has a shielded section covered with a shielding material and a non-shielded section not covered with a shielding material. This maintains the quality of the transmitted signal. The FFC-YM121 is an example of a first flat cable. On the other hand, the FFC-CBk122 is not covered with a shielding material in the entire section. The FFC-CBk122 is an example of a second flat cable.

Figure 5 is a diagram showing the state of FFC-YM121 when placed on a flat surface without folding. Figure 5(a) shows the front side of FFC-YM121, and Figure 5(b) shows the back side of FFC-YM121. In Figures 5(a) and 5(b), solid lines indicate folds, and shaded areas indicate parts covered with shielding material. In this embodiment, a thin metal film is used as the shielding material, but this is not limited to this and it may be shielded with other materials as long as they have an electromagnetic wave shielding effect. The thin metal films on the front and back sides are electrically conductive.

In the first embodiment described above, shielding is performed at locations where the FFCs run parallel to one another. This prevents signals from interfering with other FFCs. Furthermore, no shielding is performed at locations where the FFCs do not run parallel to one another. In other words, shielding is performed only at locations where signals are likely to interfere. Therefore, crosstalk between the FFCs is suppressed while maintaining signal quality, enabling stable operation of the image forming device 100.

In the above-mentioned first embodiment, an example was described in which FFC-YM121 was shielded, but the FFC-CBk122 side or both FFC-YM121 and FFC-CBk122 may also be shielded.

In addition, in the first embodiment described above, both sides of the FFC-YM121 are covered with shielding material, but if the signal level of the crosstalk to be suppressed is small, only the side closest to other FFCs may be covered with shielding material.

Furthermore, the shielding material covered by the FFC-YM121 in the first embodiment described above may be configured to be connected to the ground of the image forming apparatus 100. One method for connecting the shielding to the ground is to use at least one of the signal lines of the FFC-YM121 as a ground line, partially remove the insulating film to expose part of the metal part of the ground line, and then adhere the shielding material from above. Another method is to use at least one of the signal lines of the FFC as a ground line and connect it to a terminal part whose metal part is originally exposed. However, if the latter method is used, the terminal part needs to be located near the end of the shielding material covered by the FFC-YM121.

In the first embodiment described above, the frequency and amplitude of the video signal VDO-YZ are configured to be greater than those of the other video signals (VDO-M, VDO-C, VDO-Bk), but the present invention is not limited to this configuration and may be equivalent to the other video signals. In this configuration, IC-Y151 is not required.
Furthermore, in the above-described first embodiment, a video signal is transmitted using FFC, but the transmitted signal is not limited to a video signal and may be a control signal.

In addition, in the first embodiment described above, the FFC-CBk122 is configured to contact the metal plate 170, but this is not limited thereto, and the FFC-YM121 side or both the FFC-YM121 and the FFC-CBk122 may be configured to contact the metal plate 170.

Second Embodiment
Next, an image forming apparatus 100 according to a second embodiment will be described with reference to Figures 6 to 8. Below, differences from the first embodiment will be described, and descriptions of configurations similar to those of the first embodiment will be omitted.

Figure 6 is a perspective view showing the arrangement of FFC-YM121 and FFC-CBk122. Also, Figure 7 is an xy plan view of the configuration of Figure 6, seen from the positive direction of the z axis shown in Figure 6. Figure 8 is a diagram showing the state when FFC-YM121 is placed on a flat surface without folding. Figure 8(a) shows the front side of FFC-YM121, and Figure 8(b) shows the back side of FFC-YM121.

In the second embodiment, the length of the portion covered with the shielding material (shield length) is different from that of the first embodiment. Specifically, compared to the first embodiment, the shield length is extended by a distance a in the direction of the laser driver board -YM131, and by a distance b in the direction of the controller 120. That is, in the first embodiment, only the parallel running parts were shielded, but in the second embodiment, non-parallel running parts within a predetermined distance from the boundary between the parallel running parts and non-parallel running parts are also shielded.

The reason for this is that when the spatial distance between the FFCs is short, crosstalk between signal lines occurs even when the FFCs are not in contact with each other. In the second embodiment, the FFC-YM121 is shielded in sections a and b in addition to sections d1, d2, and d3. This can further suppress crosstalk. Note that in the second embodiment, the section within 2 mm from the boundary is shielded, but this may be increased or decreased as appropriate depending on the specifications of the receiving circuit that receives the signal.

Third Embodiment
Next, an image forming apparatus 100 according to a third embodiment will be described with reference to Figures 9 to 11. Below, differences from the first embodiment will be described, and descriptions of configurations similar to those of the first embodiment will be omitted.
FIG. 9 is a perspective view showing the arrangement of the FFC-YM121 and the FFC-CBk122.
In the third embodiment, the FFC-YM121 is covered with a shielding material in sections d4, d2, and d5. d4 is shorter than d1, and d5 is shorter than d3. That is, in the first embodiment, the entire parallel running portion is shielded, but in the third embodiment, only a part of the parallel running portion is shielded.

Figure 10 shows the signal waveform of FFC-YM121. Figure 10(a) shows the waveform of a specified signal. Figure 10(b) shows the waveform when the signal of Figure 10(a) is input to FFC-YM121 of the first embodiment. Figure 10(c) shows the waveform when the signal of Figure 10(a) is input to FFC-YM121 of the third embodiment.

Comparing FIG. 10(b) and FIG. 10(c), the rise time Tb in FIG. 10(b) is longer than the rise time Tc in FIG. 10(c). This shows that the larger the shielded area, the slower the rise time of the signal. In the third embodiment, the shield lengths d4 and d5 of the FFC-YM121 can be adjusted according to the required specifications of the receiving devices of the optical scanning devices 104Y and 104M. For example, if the required specification for the rise time is equal to or less than Tc, it is necessary to make the shield lengths d4 and d5 even shorter than in the state of FIG. 10(c).

Figure 11 shows the signal waveform of FFC-CBk122. Figure 11(a) shows the waveform of a specified signal. Figure 11(b) shows the waveform when the signal of Figure 11(a) is input to FFC-CBk122 in a conventional configuration, that is, a configuration in which FFC-YM121 is not shielded. Figure 11(c) shows the waveform when the signal of Figure 11(a) is input to FFC-CBk122 of the third embodiment. In Figures 11(b) and 11(c), a specified signal is input to FFC-YM121 when the signal shown in Figure 11(a) is input to FFC-CBk122.

The waveform in FIG. 11(b) is heavily influenced by crosstalk from FFC-YM121, with high-frequency, large-amplitude noise superimposed. Due to the superimposed noise, the metal plate 170 and the like act as antennas, emitting high levels of unnecessary radiation noise. For this reason, shielding is required for FFC-YM121. The longer the shield length, the greater the effect of suppressing crosstalk. However, as described above, if the shield length is too long, the required specifications of the receiving devices of the optical scanning devices 104Y and 104M may not be met. Therefore, by adjusting the shield lengths d4 and d6, it is possible to reduce the level of radiation noise caused by crosstalk as much as possible while ensuring the required specifications of the receiving devices of the optical scanning devices 104Y and 104M.

In the third embodiment described above, some of the locations where the FFCs run parallel to each other are shielded. This makes it possible to reduce the level of unnecessary radiation noise caused by crosstalk between the FFCs while ensuring the required specifications of the device receiving the signal. In other words, stable operation of the image forming apparatus 100 becomes possible.

The present invention has been described above with reference to embodiments, but the above embodiments are merely examples of concrete ways of implementing the present invention, and the technical scope of the present invention should not be interpreted in a limiting manner based on these. In other words, the present invention can be implemented in various forms without departing from its technical concept or main features.

100: Image forming device, 101Y, 101M, 101C, 101Bk: Image forming unit, 120: Controller, 121: FFC-YM, 122: FFC-CBk, 131: Laser driver board-YM, 132: Laser driver board-CBk

Claims (11)

an image forming unit that forms an image;
A controller for controlling the image forming unit;
a first flat cable and a second flat cable, each of which transmits signals between the controller and the image forming unit;
a shield portion that covers the first flat cable;
An image forming apparatus comprising:
the first flat cable includes a first portion and a second portion;
the first portion of the first flat cable overlaps the second flat cable when viewed in a direction transverse to a plane of the first flat cable;
At least a part of the first portion of the first flat cable is covered by the shield portion,
the second portion of the first flat cable is disposed at a position different from that of the second flat cable when viewed in the direction, or is disposed at a position spaced apart from the second flat cable in the direction compared to the first portion,
At least a part of the second portion of the first flat cable is exposed to the shield portion ,
the first portion and the second portion of the first flat cable are continuous,
The second portion is covered by the shield portion within a predetermined distance from a boundary with the first portion.
1. An image forming apparatus comprising: a part of the first portion of the first flat cable is exposed to the shield portion;
2. The image forming apparatus according to claim 1, The cable further includes a plurality of fixing members for fixing the first flat cable and the second flat cable,
The plurality of fixing members include
a first fixing member that fixes only the first flat cable out of the first flat cable and the second flat cable;
a second fixing member that fixes only the second flat cable out of the first flat cable and the second flat cable; and
a third fixing member that fixes both the first flat cable and the second flat cable,
2. The image forming apparatus according to claim 1, the image forming unit includes a first image forming unit that forms an image of a first color, and a second image forming unit that forms an image of a second color different from the first color;
the first flat cable is connected to the first image forming unit,
the second flat cable is connected to the second image forming unit;
2. The image forming apparatus according to claim 1, an image processing unit that performs additional processing on the signal output to the first flat cable in addition to the processing performed on both the signal output to the first flat cable and the signal output to the second flat cable;
5. The image forming apparatus according to claim 4 . The additional processing includes embedding a device serial number into the video signal.
6. The image forming apparatus according to claim 5 , The frequency of the signal transmitted by the first flat cable is higher than the frequency of the signal transmitted by the second flat cable.
2. The image forming apparatus according to claim 1, the amplitude of a signal transmitted through the first flat cable is greater than the amplitude of a signal transmitted through the second flat cable;
2. The image forming apparatus according to claim 1, the shield portion covers a first surface of the first portion of the first flat cable that faces the second flat cable, and does not cover a second surface of the first portion that is opposite to the first surface.
2. The image forming apparatus according to claim 1, the shield portion covers both a first surface of the first portion of the first flat cable, the first surface facing the second flat cable, and a second surface opposite to the first surface.
2. The image forming apparatus according to claim 1, The shield portion is formed of a metal thin film and is connected to ground.
2. The image forming apparatus according to claim 1,

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