JP2010124105A - Image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To set a frequency of radiation noise generated owing to a structure of an image reading apparatus, at 230 MHz or more, and to reduce a countermeasure load by putting the frequency into a 7 dB relaxation zone. <P>SOLUTION: To solve the problem by the image reading apparatus which is provided with: an image sensor board 106 which mounts an image sensor reading an original document; a first cable 103 which is connected to the image sensor board at the end, and transmits an image signal created in the image sensor; a relay board 120 which is connected to another end of the first cable through a connector, is connected to an end of a second cable through a connector, and relays the image signal transmitted by the first cable to the second cable; and a control board 201 which is connected to the other end of the second cable 121 or a following end, and has an image processing circuit mounted thereon which processes the image signal transmitted by the second cable. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image reading apparatus used for a copying machine or the like, and more particularly to suppression of radiation noise.

  Conventionally, in an image reading apparatus used for a facsimile or a copying machine, for example, a light source means for linearly illuminating in the main scanning direction, an image forming means for forming an image of reflected light of a document illuminated by the light source means, Photoelectric conversion means for converting the image information of the document into a read image signal by making the reflected light imaged by the imaging means incident; and image signal transmission means for transmitting the image signal created by the photoelectric conversion; There has been proposed an image reading apparatus that reads a book document by moving and scanning a reading unit including a carriage member that supports an image sensor including the image sensor (Patent Document 1).

The reading unit is connected to the image signal receiving unit via a flexible flexible cable or the like which is an image signal transmitting unit. Since the image reading apparatus having such a structure has an advantage that the thickness of the apparatus can be suppressed, it is suitable for a small apparatus.
In such an image reading apparatus, a strip unit having a plurality of cable conductors and a covering member covering each cable conductor is connected to the reading unit that reciprocates within the scanning range and a control circuit provided in the apparatus body. A flat flexible cable (hereinafter referred to as FFC) which is a multipolar cable is used. The FFC is applied to various image reading apparatuses because a plurality of cables can be wired between the reading unit and the control circuit in a state where the space occupied in the apparatus main body is small.

  However, since the FFC generates an electromagnetic wave by transmitting a signal through the cable, it may be a source of EMI (Electro Magnetic Interference) noise (hereinafter referred to as noise).

  As a noise suppression means, a structure has been proposed in which an adhesive member is attached to the laying surface of the FFC to reliably lay and stick the adhesive inside the apparatus body to reduce the generation of noise from the FFC (Patent Document 2). .

Further, in the case of a configuration in which the thickness of the apparatus, which is an advantage of such an image reading apparatus, is minimized, a configuration in which a control board for controlling the reading unit is arranged outside the scanning range of the reading unit can be considered.
The configuration example will be described with reference to FIG. FIG. 9A is a top view of the image reading apparatus, and FIG. 9B is a cross-sectional view in the sub-scanning direction.
When the reading unit 702 reads a document placed on the platen glass 710 with a sensor substrate 706 mounted with an image sensor such as a CCD, the reading unit 702 follows the drive shaft 704 and the guide rail 705 along the left side to the right side of FIG. Move in a predetermined range toward
Image data read by the reading unit 702 is transmitted to the control board 711 via the cable 703.

The housing of the image reading apparatus includes an upper frame 701 and a lower frame 709, and the drive shaft 704, guide rail 705, and control board 711 are fixed to the lower frame 709.
The cable 703 can follow the movement of the reading unit 702 by using FFC. Further, as shown in FIG. 9A, outside the movable range of the cable 703 according to the movement of the reading unit 702, the control unit 711 is connected to the control board 711 with a single cable by bending the reading unit 702 at a right angle with respect to the moving direction. Connectable.
However, as the speed of the image reading apparatus increases, the sensor substrate 706 and the cable 703 may become radiation sources, and a means for suppressing radiation noise by dividing the plane of the power supply layer of the substrate into a plurality of planes has been proposed. (Patent Document 3).
JP-A-8-195860 Japanese Patent Laid-Open No. 2003-100156 JP 2007-158243 A

In the case of the image reading apparatus having the above-described configuration, it has been confirmed by the inventors that radiation noise having a frequency corresponding to the size of the sensor substrate and the length of the cable is generated.
FIG. 10 shows only the sensor substrate 706 and the cable 703 of the image reading apparatus shown in FIG. 9 modeled for electromagnetic field simulation. As a result, the intensity of the electromagnetic field radiated when propagating the clock signal at the time of image reading to the sensor substrate 706 and the cable 703 was simulated. FIG. 11 shows the simulation result.

The graph of FIG. 11 represents the intensity of the electromagnetic field radiated from the model of FIG. 10 along the frequency.
The intensity peaks shown in (1) to (5) in the graph are resonance points generated according to the length of the sensor substrate 706 and the cable 703 and the wavelength of the electric signal propagating therethrough. If the wavelength of the electrical signal is λ,
(1) to (5) are: (1) Resonance with (sensor substrate length) + (cable length) λ / 2 (2) Resonance with (cable length) λ / 2 (3) (sensor substrate length) Resonance in which + (cable length) is λ (4) Resonance in which (cable length) is λ (5) Resonance in which (cable length) is 3λ / 2. In such a case, the lowest resonance frequency is (1), and the highest resonance frequency is (5).
Radiation noise that occurs mainly due to the structure, shape, etc. of the device as in the above case is difficult to suppress unless the device itself is changed.

FIG. 12 shows the regulation value of the electromagnetic wave intensity radiated from the electronic device defined by VCCI and CISPR. There are two types of standards, “Class A” and “Class B”, depending on the target device. In both cases, the standard value is changed at a frequency of 230 MHz, and when it exceeds 230 MHz, 7 [dBuV / m] is relaxed.
From these, even when radiation noise that occurs mainly due to the structure, shape, etc. of the device is generated, if the generated frequency is larger than 230 MHz, a margin for measures can be secured.

  The present invention has been made under such circumstances, and an object of the present invention is to provide an image reading apparatus that can easily cope with a predetermined limit value of electromagnetic wave intensity.

  In order to solve the above-described problem, in the present invention, an image reading apparatus is configured as described in (1) below.

(1) an image sensor board on which an image sensor for reading a document is mounted;
A first cable having one end connected to the image sensor substrate and transmitting an image signal generated by the image sensor;
The other end of the first cable is connected via a connector, the other end of the second cable is connected via a connector, and the image signal transmitted by the first cable is relayed to the second cable. Relay board to
A control board connected to the other end of the second cable and mounted with an image processing circuit for processing an image signal transmitted by the second cable;
With
An image reading apparatus configured to have a length of the first cable such that a minimum resonance frequency of an electric signal by the image sensor substrate and the first cable is 230 MHz or more.

  According to the present invention, it is possible to reduce the countermeasure load by bringing the frequency of the radiation noise generated due to the structure of the apparatus to 230 MHz or more and entering the 7 dB relaxation region.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

  An “image reading apparatus” that is Embodiment 1 will be described.

  1 and 2 show the configuration of the image reading apparatus. FIG. 1 is a top view and FIG. 2 is a functional block diagram.

In this image reading apparatus, an outer shape of the apparatus is formed by a casing upper frame 101 and a casing lower frame 109 which are conductive members. The opening 100 places a document via the document table glass 110, and reads the image while moving the document reading unit 102 from the left side to the right side in FIG. 1 by the reading unit drive motor 202 shown in FIG.
The document reading unit 102 includes an image sensor substrate 106, document illumination 107a and 107b, reflection plates 108a and 108b, and optical components (not shown).

During the image reading operation, the originals 107a and 107b irradiate the original placed on the original platen glass, and the reflected light is imaged on the image sensor 111 mounted on the image sensor substrate 106 by the optical component. . Further, it is connected to a control board 201 shown in FIG. 2 to be described later via a cable <also referred to as a harness> 103, a relay board 120, and a cable (harness) 121.
The original illuminations 107a and 107b are obtained by collecting point light sources such as LEDs in a line on the printed wiring board in the main scanning direction, and have a length approximately equal to the length of the image reading area in the main scanning direction. The reflectors 108a and 108b are formed by depositing metal on a base material so as to have a predetermined reflectance so as to reflect and collect the light emitted from the original illumination 107a and 107b, and the original illumination 107a and 107b. Have a length equal to or greater than

  The drive shaft 104 and the guide rail 105 maintain the orientation of the document reading unit 102 when the document reading unit 102 moves in the sub-scanning direction during the image reading operation. The relay board 120 and the control board 201 are fixed to the lower frame 109 of the housing.

FIG. 2 is a block diagram illustrating functions of the image reading apparatus.
The image sensor 111 mounted on the image sensor substrate 106 mounted on the document reading unit 102 receives reflected light from the document irradiated by the document illumination 107 through the optical component, and generates an electrical signal as image data 115. Converted to output. The output image data 115 is converted into a digital signal 209 by the AD converter 113 via the amplifier 112 and transmitted to the image processing circuit 204 on the control board 201 via the cable 103, the relay board 120, and the cable 121. In the image processing circuit 204, the input digital signal 209 is subjected to predetermined image processing such as γ correction and then transmitted to an image forming apparatus (not shown) via the interface circuit 213. In this embodiment, the cable 121 is directly connected to the image processing circuit 204, but the image processing circuit may be connected after another cable or circuit is inserted after the cable 121. Therefore, in the claims, it is defined as “an image processing circuit connected to the other end of the second cable and processing an image signal transmitted by the second cable”.

  The control circuit 205 on the control board 201 generates a reference signal 207 for driving the image sensor 111 and transmits the reference signal 207 to the image sensor driving circuit 114 on the image sensor board 106 via the cable 121, the relay board 120, and the cable 103. The image sensor driving circuit 114 generates an image sensor driving signal 117 from the reference signal 207 generated by the control circuit 205 and drives the image sensor 111.

  The control circuit 205 generates a reference clock signal 208 of the AD converter 113 on the image sensor substrate 106 and a control signal 211 of the document illumination 107, and similarly, the AD converter 113 and document illumination drive via the cable 103. Input to the circuit 118. The document illumination drive circuit 118 generates a document illumination drive signal 119 and drives the document illumination 107.

  Further, the control circuit 205 generates a reference signal 214 for controlling the reading unit driving motor 202 that moves the document reading unit 102 and inputs the reference signal 214 to the motor driving circuit 212. The motor drive circuit 212 converts the reference signal 214 generated by the control circuit 205 into a motor drive signal and controls the reading unit drive motor 202.

  As shown in FIG. 3, the distances from the position where the signal line of the reference signal 207 of the cable 103 is connected to the image sensor substrate 106 to the substrate end in the main scanning direction are L1102 and L1103, respectively. The length of the cable 103 is L1101. The cable 103 corresponds to a first cable in the claims, and the cable 121 corresponds to a second cable. Further, the end portion of the cable 103 on the image sensor substrate 106 side corresponds to one end of the first cable in the claims, and the end portion on the relay substrate side corresponds to the other end of the first cable.

  FIG. 4 and FIG. 5 show the effect obtained by configuring the cable connecting the image sensor board 106 and the control board 201 with two cables (cable 103 and cable 121) and the relay board 120 instead of one cable. explain.

  FIG. 4 is a model of the configuration of FIG. 3 for electromagnetic field simulation. That is, the case where the cable 103 and the cable 121 are formed by one cable, and two cables having a predetermined length as in the present embodiment, and both are connected at the connection position of the two cables. This is a comparison with the case of being composed of another member corresponding to 120.

FIG. 5 is an example of the simulation result of FIG.
L1101: 250mm, L1102: 200mm, L1201: 200mm
Is set.
In FIG. 5, reference numeral 1301 denotes the radiation noise intensity when the number of cables is one, and reference numeral 1302 denotes the radiation noise intensity when the number of cables is two. When the number of cables is one, the lowest resonance frequency of 1301 has a peak 1303 around 230 MHz, but when two cables are used, the peak 1304 moves to a region exceeding 300 MHz. Can be confirmed.
From the above, the frequency having a wavelength that matches twice the total length of the length L1101 of the cable 103 and the length L1102 in the longitudinal direction of the image sensor substrate 106 has the smallest resonance frequency. Ie

  Therefore, by setting the lengths L1101 and L1102 such that F is greater than 230 MHz, all the resonance frequencies generated due to this structure can be greater than 230 MHz. The lengths L1101 and L1102 are set in the claims as follows: “The length of the first cable is set so that the minimum resonance frequency of an electric signal by the image sensor board and the first cable is 230 MHz or more. Corresponds to “constituted in length”.

FIG. 6 is an external view illustrating the details of the relay board 120, and is a diagram showing the “location of the relay board” in the claims.
In the relay board 120, the cable 103 is connected to the connector 301 and the cable 121 is connected to the connector 302. The signal lines between the cable 103 and the cable 121 are connected one-to-one with the pattern group 304 between the connectors 301 and 302. .
The pattern group 304 is formed on a surface different from the surface on which the connectors 301 and 302 are mounted, and the pattern forming the pattern group 304 is applied so that the impedance is equal to that of the cable 103 and the cable 121, respectively. A ground pattern 303 is provided around the periphery.
A ground pattern 313 is formed on the mounting surfaces of the connectors 301 and 302, and is connected to the ground pattern 303 by a plurality of VIAs (through holes) not shown. The cable 103 is connected to the ground pattern 313 via the shielded connector 301. In addition, holes that can be fixed with conductive screws 305 to 308 are provided in the vicinity of the connectors 301 and 302.

FIG. 6B is a side view in which the relay substrate 120 is mounted on the lower frame 109 of the image reading apparatus. The lower frame 109 is provided with bases 309 to 312 having a predetermined height to be fixed with screws 305 to 308, and the lower frame 109 and the ground pattern 313 are electrically connected therewith.
By electrically connecting the lower frame 109, which is a conductive member, and the ground pattern 313 of the relay board 120, the length of the cable related to the resonance phenomenon generated by the length of the image sensor board 106 and the length of the cable is reduced. The above conditions can be satisfied. As a result, the resonance frequency in this portion can be made higher than 230 MHz.

FIG. 7 shows the positional relationship between the cable 103 and the relay board 120 in the range of movement during the reading operation of the document reading unit 102.
FIG. 7A is a diagram illustrating a case where the document reading unit 102 is at the rightmost end during the reading operation of the image reading apparatus, and FIG. 7B is a position at the leftmost end.
In the case of FIG. 7A, the cable 103 is immediately away from the lower frame 109 from the portion connected to the relay board 120, but in FIG. In this state, the lower frame 109 is in contact.

  During the reading operation, the cable 103 repeats the states shown in FIGS. 7A and 7B, and the impedance is not stable and also causes generation of radiation noise. For this reason, it is desirable that the cable 103 is composed of a shielded cable or a thin coaxial cable.

FIG. 8 is a diagram for explaining a mounting state of the cable 121 that connects the relay board 120 and the control board 201.
The cable 121 can be fixed at a fixed position regardless of the operation of the document reading unit 102.
Since the cable 121 is brought into close contact with the lower frame 109 immediately after being pulled out from the relay board 120, the cable 121 is fixed at a plurality of locations by the holding member 502, and is connected to the control board 201 through the opening 501 provided in a part of the lower frame 109. Connected to.
Since the cable 121 is fixed to the lower frame 109, the impedance is stable, and an effect equivalent to that of a shielded cable can be obtained by configuring the lower frame 109 with a conductive member. Is possible.

  As described above, according to the present embodiment, it is possible to reduce the countermeasure load by bringing the frequency of generated radiated noise to 230 MHz or higher due to the structure of the apparatus and entering the 7 dB relaxation region.

The top view which shows the structure of Example 1 Functional block diagram showing the configuration of the first embodiment The figure which shows the principal part structure of Example 1. FIG. FIG. 3 is a diagram illustrating the configuration of FIG. 3 modeled for electromagnetic field simulation. The figure which shows an example of the simulation result of the structure of FIG. Diagram showing details of relay board The figure which shows the positional relationship of the cable 103 and the relay board | substrate 120 in reading operation. Diagram showing the mounting state of the cable connecting the relay board and the control board Diagram showing the configuration of a conventional example FIG. 9 is a diagram showing only the sensor board and the cable in FIG. 9 modeled for electromagnetic field simulation. The figure which shows the simulation result of FIG. The figure which shows the regulation value of the electromagnetic wave intensity radiated | emitted from the electronic device prescribed | regulated by VCCI and CISPR

Explanation of symbols

103 Cable 106 Image sensor board 120 Relay board 121 Cable 201 Control board 301 Connector 302 Connector

Claims (2)

An image sensor board on which an image sensor for reading a document is mounted;
A first cable having one end connected to the image sensor substrate and transmitting an image signal generated by the image sensor;
The other end of the first cable is connected via a connector, the other end of the second cable is connected via a connector, and the image signal transmitted by the first cable is relayed to the second cable. Relay board to
A control board connected to the other end of the second cable and mounted with an image processing circuit for processing an image signal transmitted by the second cable;
With
An image reading apparatus characterized in that the length of the first cable is configured such that a minimum resonance frequency of an electric signal by the image sensor substrate and the first cable is 230 MHz or more. The image reading apparatus according to claim 1,
An image reading apparatus, wherein a ground of a connector connected to the other end of the first cable is connected to a ground of the image reading apparatus at a place where the relay board is installed.