JP4646800B2 - Image reading device - Google Patents

Description

  The present invention relates to an image reading apparatus that is used in a digital copying machine, an image scanner, or the like to scan and read a document.

  2. Description of the Related Art Conventionally, in a mirror scanning type copying machine, an original is placed on a contact glass of an original reading unit, and a scanning optical system such as a light source or a traveling mirror provided below the contact glass is used to drive an original with a predetermined driving device. A mechanism that reads a document image by moving it parallel to the surface is widely used.

  FIG. 5 is a schematic plan view showing an example of a conventional image reading apparatus. In the figure, reference numeral 100 denotes an image reading device, and a pair of guide rails 2 are installed in parallel with contact glass (not shown) on the upper surface of the device frame 1 between the left and right side surfaces 1a and 1b. . An illumination unit 3 and a mirror unit 4 are placed on the pair of guide rails 2. In the vicinity of the right side surface 1a, a drive shaft 5 that can be rotated forward and reversely by a motor (not shown) is disposed so as to be orthogonal to the guide rail 2, and is located outside the guide rail 2. A drive pulley 6 having a large diameter portion and a small diameter portion is attached to both ends of the shaft 5. Further, a support shaft 8 provided with a driven pulley 7 having the same diameter as the drive pulley 6 at both ends is disposed in the vicinity of the left side surface 1b.

  A driving wire 9 a is stretched over the large diameter portions of the driving pulley 6 and the driven pulley 7. Similarly, a driving wire 9 b is stretched over the small diameter portion of the driving pulley 6 and the driven pulley 7. Yes. A part of the illumination unit 3 is fixed to the drive wire 9a, and a part of the mirror unit 4 is fixed to the drive wire 9b. Two contactors 10 are provided at the portions where the illumination unit 3 and the mirror unit 4 are in contact with the upper surface of the guide rail 2, and the contact surface of each contactor 10 with the guide rail 2 is a spherical surface. .

  When the drive shaft 5 is rotated by the motor and the drive wires 9a and 9b are rotated, the illumination unit 3 and the mirror unit 4 are moved along the guide rail 2 in the scanning direction (left and right direction in the figure). Here, since the diameter ratio of the large diameter portion and the small diameter portion of the drive pulley 6 and the driven pulley 7 is 2: 1, the ratio of the moving distance between the illumination unit 3 and the mirror unit 4 is also 2: 1.

  A plate-like support member (hereinafter referred to as ISU base) 11 is attached between the frames in the front-rear direction of the apparatus frame 1, and a condensing lens 12 and a photoelectric as reading means are mounted on the upper surface of the ISU base 11. A conversion element (hereinafter referred to as CCD) 13 is mounted. The image reading apparatus 100 includes control clock means (not shown) that generates a control clock based on the reference clock input from the oscillating means, and controls the driving of the CCD 13 by this control clock.

  The condenser lens 12 is installed on a lens support 14, and the lens support 14 is fixed to the ISU base 11. Reference numeral 15 denotes a guide member that is movably supported by the lens support base 14. A CCD substrate 16 that controls the driving of the CCD 13 is fixed to the back surface of the guide member 15. Further, an opening window 15 a through which the image light condensed by the condenser lens 12 passes is provided near the center of the guide member 15. The CCD 13 is mounted on the CCD substrate 16 and the optical axis incident on the CCD 13 can be corrected by finely adjusting the position of the guide member 15.

  When reading a document image, the illumination unit 3 illuminates the document with the light source of the illumination unit 3, the illumination unit 3 moves in the direction of arrow A at a predetermined speed, and the mirror unit 4 has the same speed at half the illumination unit 3. Move in the direction. As a result, the image light formed by the illumination of the illumination unit 3 is guided to the condenser lens 12 by the mirror unit 4, and after being condensed, passes through the opening window 15 a of the guide member 15 and forms an image on the CCD 13. The The imaged image light is separated into pixels by the CCD 13 and converted into an electrical signal corresponding to the density of each pixel, and the image is read.

  6 is a view of the image reading apparatus of FIG. 5 as viewed from the front side (lower side of FIG. 5). For convenience of explanation, the guide rail 2, the driving pulley 6, the driven pulley 7, and the driving wires 9a and 9b are not shown. In the figure, a contact glass 17 is installed on the upper surface of the apparatus frame 1, and a document scanned by the illumination unit 3 and the mirror unit 4 is placed on the contact glass 17 facing down. When scanning a document, the illumination unit 3 is first moved from the scanner home side (left side in FIG. 6) to the scanner return side (right side in FIG. 6). At the same time, the document is irradiated with light from the light source 3a of the illumination unit 3.

  The light reflected from the original is changed in its optical path by the mirror 3b and the mirrors 4a and 4b of the mirror unit 4, and then passes through the condenser lens 12 and the aperture window 15a to form an image on the CCD 13 (dashed line in the figure). . The moving distance of the mirror unit 4 in this scanning is ½ of the moving distance of the illumination unit 3 as described above, and the optical path length from the document surface to the CCD 13 is kept constant.

  Next, another driving mechanism of the conventional image reading apparatus will be described. FIG. 7A is a perspective view showing a drive mechanism of the image reading apparatus, and FIG. 7B is a schematic view of the drive mechanism as viewed from the front side of the apparatus (left side of FIG. 7A). For convenience of explanation, the device frame 1, the guide rail 2, the condenser lens 12, the CCD 13, and the like are not shown. In this configuration, the wire drum 18 is fixed to both ends of the drive shaft 5, and the drive wire 9 a is wound around the wire drum 18 by a predetermined amount. One end of the drive wire 9a extending from the wire drum 18 in the scanning direction (arrow A direction) is stretched over the pulley 19a to change the direction, and over the pulley 19b to change the direction again. It is locked to.

  On the other hand, the other end extending in the opposite direction is stretched over the pulley 19c to change the direction, and then spanned over the pulley 19b to change the direction again. Fixed. The illumination unit 3 is fixed to the driving wire 9a between the pulley 19a and the pulley 19b, and the mirror unit 4 is fixed to the pulley 19b. The pulleys 19 a and 19 c are fixed to the apparatus main body, but the pulley 19 b can reciprocate together with the mirror unit 4.

  When the drive shaft 5 and the wire drum 18 are rotationally driven in the direction of arrow B during document reading, the drive wire 9a moves in the direction of arrow A, and the illumination unit 3 and the mirror unit 4 follow the same direction. Move to. At this time, since the pulley 19b serves as a moving pulley, the mirror unit 4 moves in the same direction with respect to the illumination unit 3 at 1/2 speed. Further, after the reading is completed, the wire drum 18 is reversely rotated to return the illumination unit 3 and the mirror unit 4 to their original positions.

  In such an image reading apparatus, it is conventionally known that the periphery of the CCD 13 is an electromagnetic noise source. The cause is that the CCD 13 can be easily adjusted by reducing the number of screwing points so that the image light can be received at an optimum position, and the grounding (grounding) of the CCD substrate 16 is not sufficient. Conceivable. Further, the drive shaft 5 that crosses the apparatus frame 1 is disposed in the vicinity of the CCD substrate 16, and the drive shaft 5 itself is floating without being grounded, or is grounded via the bearing of the bearing portion even if it is grounded. Therefore, the ground contact was not stable.

  Therefore, induced noise is generated in the drive shaft 5 due to the current flowing through the CCD substrate 16, and the drive shaft 5 is turned into an antenna to generate secondary radiation noise. The secondary radiation noise causes radio wave interference in other electronic devices such as a radio and a television receiver around the device. In conventional image reading apparatuses, as disclosed in Patent Documents 1 and 2, a countermeasure is taken to prevent leakage of electromagnetic noise by covering a circuit board such as a CCD board with a grounded conductive shield member. It was done.

  However, in addition to high cost by providing a shield member, the position of the CCD substrate may be changed for optical axis adjustment, and the shield member needs to be sized and shaped in consideration of it, so the shield member In addition, it is difficult to design the device, and also hinders space saving of the apparatus. Further, there is a concern about heat buildup in the shield, and if the temperature rises too much, the CCD substrate may be damaged. Furthermore, if cooling measures are taken for that purpose, it will lead to a significant cost increase.

  Therefore, various methods for preventing secondary radiation noise from the drive shaft without directly shielding the CCD substrate that becomes a noise source have been proposed. For example, Patent Document 3 discloses an intermediate portion of a rail or a guide shaft and a frame. A method of reducing the generation of noise by grounding the frame side with a conductive member interposed therebetween is disclosed. Patent Document 4 discloses an image reading apparatus in which a conductive metal plate is disposed between a CCD substrate and a drive shaft so as to be bonded to a cover member that covers an image reading unit on which a CCD is mounted.

However, the method of Patent Document 3 is effective for grounding a rail and a shaft fixed to the frame, but when applied to a drive shaft that is driven to rotate, uneven rotation of the drive shaft due to friction with the conductive member. And wear and heat generation become problems. Further, in the method of Patent Document 4, since the CCD substrate is isolated by the cover member and the metal plate, the position adjustment of the CCD substrate becomes complicated. Further, when the cover member that covers the CCD substrate is removed, the CCD substrate and the drive shaft are not completely separated, and thus there is a problem that the generation of induction noise cannot be sufficiently suppressed.
JP 2002-237924 A JP 2002-344893 A Japanese Patent Laid-Open No. 8-23419 Japanese Patent Application Laid-Open No. 2002-36895

  In view of the above problems, an object of the present invention is to provide an image reading apparatus that can reliably prevent the generation of secondary radiation noise from a drive shaft and can smoothly perform an optical axis correction operation.

  To achieve the above object, the present invention provides a scanning optical system that illuminates a document and forms an image using reflected light from the document as image light, and a photoelectric conversion element that reads image light imaged by the scanning optical system. A control board that controls driving of the photoelectric conversion element; and a drive shaft that transmits a driving force to the scanning optical system via a driving wire, and reciprocates the scanning optical system at a constant scanning speed. In the image reading apparatus for reading a document image, a metal device frame and a grounded conductive member are provided between the drive shaft and the control board, and at least in the longitudinal direction of the drive shaft. A part of the conductive member is surrounded by the conductive member or the conductive member and the device frame.

  According to the present invention, in the image reading apparatus configured as described above, the conductive member is provided so as to cover at least the entire portion facing the control board in the longitudinal direction of the drive shaft.

  According to the present invention, in the image reading apparatus having the above-described configuration, the conductive member has a substantially U-shaped cross section having an opening end in a part thereof, and the apparatus frame body or the apparatus so that the opening end faces downward. It is characterized by being fixed to a metal member grounded to the frame.

  According to the first configuration of the present invention, since the drive shaft is entirely surrounded by the conductive material and shielded from the CCD substrate, induction noise caused by the influence of the current flowing through the CCD substrate near the drive shaft is reduced. Generation | occurrence | production can be suppressed effectively. Further, since the CCD substrate is not covered with the cover or the shield member, the position adjustment of the CCD substrate is facilitated, and there is no possibility that the CCD substrate is damaged due to the temperature rise.

  According to the second configuration of the present invention, in the image reading apparatus having the first configuration, the conductive member shields at least the entire portion of the drive shaft facing the CCD substrate, so that the current flowing through the CCD substrate is The generation of induction noise can be more effectively suppressed by reducing the action on the drive shaft.

  Further, according to the third configuration of the present invention, in the image reading apparatus having the first or second configuration, the conductive member having a substantially U-shaped cross section is fixed with the opening end facing downward. The shape of the member becomes simple, and attachment work is also facilitated.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing the internal structure of the image reading apparatus according to the first embodiment of the present invention. FIG. 2 is a front view of the image reading apparatus of the first embodiment (downward direction in FIG. 1). FIG. Portions common to FIGS. 5 and 6 of the conventional example are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, a conductive member 22 having a U-shaped cross section is fixed to the bottom surface 1c of the metal device frame 1 so as to cover the drive shaft 5 from above.

  With this configuration, the drive shaft 5 is shielded entirely by the conductive member 22 and the bottom surface 1c in the circumferential direction, and the conductive member 22 is grounded to the bottom surface 1c, so that the drive shaft 5 is separated from the CCD substrate 16 near the drive shaft. Generation of inductive noise due to the influence of current flowing through the CCD substrate 16 can be effectively prevented. Further, since the conductive member 22 has a U-shaped cross section and is fixed to the bottom surface 1c with the opening end facing downward, the shape of the conductive member 22 becomes simple, and the mounting work is facilitated, so that the manufacturing cost can be reduced. . Further, since the CCD substrate 16 is not covered with a cover or a shield member, the position of the CCD substrate 16 can be easily adjusted, and damage to the CCD substrate 16 due to temperature rise is suppressed.

  The material of the conductive member 22 is not particularly limited as long as it is a conductive material such as a metal or a conductive resin, but is preferably made of a metal having high conductivity and excellent durability. Is bent into a predetermined shape to form the conductive member 22. As the metal plate, an electrogalvanized steel plate (SECC) that is inexpensive and easy to process is particularly preferable. As a method for fixing the conductive member 22, various fixing methods such as a fixing method using screws, eyelets, rivets or the like, or a fixing method using caulking or adhesive tape can be used. When the conductive member 22 is made of metal, it can be fixed by welding.

  Here, in the longitudinal direction of the drive shaft 5, the entire portion facing the CCD substrate 16 is shielded by the conductive member 22. For example, even if the shield portion by the conductive member 22 is made smaller than the CCD substrate, Some effect can be expected. However, in order to reduce the action of the current flowing through the CCD substrate 16 on the drive shaft 5 and to effectively suppress the generation of induction noise, at least the entire portion facing the CCD substrate 16 is covered as shown in FIG. It is preferable to dispose the conductive member 22 on the surface.

  FIG. 3 is a front view showing the internal structure of the image reading apparatus according to the second embodiment of the present invention. Portions common to FIG. 2 are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, a conductive member 22 having an L-shaped cross section is fixed to the bottom surface 1c and the side surface 1a of the apparatus frame 1 so as to cover the drive shaft 5 from above. Since the material and fixing method of the conductive member 22 are the same as those in the first embodiment, the description thereof is omitted.

  With this configuration, as in the first embodiment, the entire drive shaft 5 is shielded by the conductive member 22, the bottom surface 1c, and the side surface 1a in the entire circumferential direction, and the conductive member 22 is grounded to the apparatus frame 1. Generation of induction noise can be effectively prevented without impairing workability when adjusting the position of the substrate 16, and temperature rise of the CCD substrate 16 is also suppressed.

  FIG. 4 is a front view showing the internal structure of the image reading apparatus according to the third embodiment of the present invention. Portions common to FIGS. 2 and 3 are denoted by the same reference numerals and description thereof is omitted. In the present embodiment, a cylindrical conductive member 22 having a rectangular cross section is extrapolated to the drive shaft 5 at a predetermined interval. In this case, both ends of the conductive member 22 in the longitudinal direction do not interfere with driving of the illumination unit 3 and the mirror unit 4, for example, in the front-rear direction of the apparatus frame 1 (paper surface direction in FIG. 4) It is being fixed to the rib (not shown) integrally formed with the bottom face 1c so that it may become inner side from the drive wires 9a and 9b (all refer FIG. 1).

  With this configuration, as in the first and second embodiments, the entire drive shaft 5 is shielded by the conductive member 22 and the conductive member 22 is grounded to the apparatus frame 1. Generation of induction noise can be effectively prevented without impairing workability during position adjustment, and temperature rise of the CCD substrate 16 is also suppressed. Further, even when the drive shaft 5 is located away from the bottom surface 1c and the side surface 1a, the conductive member 22 can be reduced in size, and the arrangement space for the conductive member as compared with the first and second embodiments. This is advantageous in terms of cost.

  In addition, this invention is not limited to the said embodiment, A various change is possible in the range which does not deviate from the meaning of this invention. For example, the conductive member 22 having a U-shaped cross section in the first embodiment, an L-shaped cross section in the second embodiment, and a rectangular cross-sectional shape in the third embodiment is used. Other shapes such as a circular cross section may be used.

  In the first and second embodiments, the conductive member 22 is directly fixed to the bottom surface or the side surface of the apparatus frame 1 and the conductive member 22 and the apparatus frame 1 are grounded. For example, the ISU base 11 It can also be fixed to another metal member that is grounded to the apparatus frame 1, such as the lens support 14 or the lens support base 14. The present invention can be applied to an image forming apparatus having a drive mechanism that uses the principle of a moving pulley as shown in FIG.

The shielding effect of secondary radiation noise by the image reading apparatus of the present invention was investigated. As the test method, as shown in FIGS. 1 and 2, the image reading apparatus of the first embodiment (the present invention) in which the drive shaft is shielded using a conductive member having a U-shaped cross section, and the drive shaft is shielded. The secondary radiation noise is measured for each noise frequency generated from the CCD substrate using an image reading device (comparative example) that is not, and the margin from the noise standard value (standard value-measured value) and the present invention and the comparative example The noise difference was calculated. As the noise standard value, the standard value of EMI (Electro Magnetic Interference) based on the class B classification of the radio wave interference voluntary regulation council (VCCI) such as information processing apparatus was used. The results are shown in Table 1.

  As is apparent from Table 1, the image reading apparatus of the comparative example in which the drive shaft was not shielded was 4.1 dB lower than the noise of the frequency 766.74 MHz generated from the CCD substrate, but at other frequencies the standard value Secondary radiation noise equivalent to or exceeding the specified value was measured. On the other hand, in the image reading apparatus of the present invention in which the drive shaft is shielded, only secondary radiation noise that is 5.0 to 10.5 dB lower than the EMI standard value is generated with respect to the noise of each frequency, which is approximately compared with the comparative example. 4-10 dB lower. From this result, it was confirmed that the image reading apparatus of the present invention can effectively reduce the generation of secondary radiation noise due to the influence of noise of each frequency generated from the CCD substrate.

  Although not shown here, it has been confirmed that the image reading apparatuses of the second and third embodiments having different conductive member shapes can obtain the same results as in the present example.

  The present invention relates to a scanning optical system that illuminates a document and forms reflected light from the document as image light, a photoelectric conversion element that reads the image light imaged by the scanning optical system, and driving of the photoelectric conversion element In an image reading apparatus that includes a control board that controls a scanning optical system and a drive shaft that transmits a driving force to the scanning optical system via a driving wire, and reads the document image by reciprocating the scanning optical system at a constant scanning speed In addition, a metal device frame and a grounded conductive member are provided between the drive shaft and the control board, and at least part of the longitudinal direction of the drive shaft is a conductive member, or a conductive member. And the device frame.

  As a result, it is possible to provide an image reading apparatus that can effectively prevent the generation of inductive noise due to the influence of the current flowing through the CCD substrate and the emission of secondary radiation noise from the antenna-driven drive shaft at a low cost. This contributes to the realization of an image forming apparatus and an image scanner having little influence on peripheral electronic devices. In addition, the ease of optical axis correction work by adjusting the position of the CCD substrate can be ensured, and the temperature rise of the CCD substrate can also be suppressed, resulting in excellent productivity and durability.

  In addition, since at least the entire portion of the drive shaft facing the CCD substrate is shielded by the conductive member, the generation of induction noise can be more effectively suppressed. In addition, the conductive member has a substantially U-shaped cross section, and is fixed to the apparatus frame body or the metal member grounded to the apparatus frame body so that the opening end faces downward, so that the shape of the conductive member becomes simple, In addition, the installation work is facilitated.

These are the schematic plan views which show the internal structure of the image reading apparatus which concerns on 1st Embodiment of this invention. FIG. 2 is a front view showing an internal structure of the image forming apparatus according to the first embodiment. These are the front views which show the internal structure of the image reading apparatus which concerns on 2nd Embodiment of this invention. These are the front views which show the internal structure of the image reading apparatus which concerns on 3rd Embodiment of this invention. These are schematic plan views showing the internal structure of a conventional image reading apparatus. These are front views showing the internal structure of a conventional image reading apparatus. These are the perspective view and schematic front view which show the other drive mechanism of the conventional image reading apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus frame 1a, 1b Side surface 1c Bottom surface 2 Guide rail 3 Illumination unit (scanning optical system)
4 Mirror unit (scanning optical system)
5 Drive shaft 6 Drive pulley 9a, 9b Drive wire 11 ISU base 12 Condensing lens 13 CCD (photoelectric conversion element)
16 CCD board (control board)
18 Wire drum 19a to 19c Pulley 22 Conductive member 100 Image reading device

Claims (2)

A scanning optical system that illuminates an original and forms an image using reflected light from the original as image light, a photoelectric conversion element that reads image light imaged by the scanning optical system, and a control that controls driving of the photoelectric conversion element In an image reading apparatus that includes a substrate and a drive shaft that transmits a driving force to the scanning optical system via a driving wire, and reads the document image by reciprocating the scanning optical system at a constant scanning speed.
A metal device frame and a grounded conductive member are provided between the drive shaft and the control board, and at least the entire portion of the longitudinal direction of the drive shaft facing the control board. Is surrounded by only the conductive member, or is surrounded by the conductive member and the apparatus frame. The conductive member has a substantially U-shaped cross section with an opening end in part, and is fixed to the device frame body or a metal member grounded to the device frame body so that the opening end faces downward. The image reading apparatus according to claim 1.

Images