JP2002368956A - Image reader - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reader which is hardly affected by variations in optical adjustment and can obtain stable noise reduction effect. SOLUTION: This image reader has a scanning optical system 104 which irradiates a document with light and reads its read surface, an image read part 109 which is unitized by mounting on a substrate a photodetection sensor photodetecting the light from the scanning optical system 104, and a driving part including a driving shaft which drives the scanning optical system 104. A conductive plate which is so arranged and constituted as to secure conduction to a device frame body is stood between the substrate and driving shaft 108 and a cover member 901 which is bonded covering the image read part 109 is joined with the metal plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image reading apparatus, and more particularly to a configuration for reducing radiation noise generated when an image reading section is driven.

[0002]

2. Description of the Related Art In a conventional image forming apparatus, as a measure against radiation noise, a cover is mounted on a substrate on which a CCD is mounted.
A configuration for shielding direct radiation from a substrate is known. Alternatively, a radiation noise reduction method has been adopted in which a plurality of braided wires are output from a substrate to change the conductor length and shift the resonance frequency.

[0003] In this type of apparatus, the periphery of a CCD corresponding to an image reading unit is conventionally known as a portion where radiation noise is likely to occur. This is considered to be due in part to the fact that the substrate on which the CCD is mounted is mounted with an adjustable configuration so that the reflected light of the original emitted from the light source can be received at an efficient position. That is, although the GND is installed, it is conceivable that the number of screw fixing portions with respect to the substrate size is small relative to other substrates, the substrate length becomes long, and the substrate functions as a radiation source in a relatively low frequency range.

FIG. 5 shows an external configuration of a conventional general image reading apparatus. Reference numeral 101 denotes a frame of the image reading apparatus, which is a leader frame. Reference numeral 102 denotes a lens hood, the main purpose of which is a conductive cover for covering the CCD unit (not shown) so that light other than the document irradiation light does not enter the CCD unit. By the way, Figure 2
The CCD unit 109 shown in FIG.
Is a unit configured by a substrate, a mechanical member (sheet metal), a lens, and the like on which is mounted, and adjusted by using an adjustment jig (not shown) to combine the relative distance and relative angle between the CCD and the lens. Then, when a unit failure occurs, another unit is replaced, so that there is no need to perform optical adjustment again.

An optical motor 103 scans the mirror base 104 in the sub-scanning direction via a drive shaft. Also, 105
Is a rail for scanning the mirror base 104. 106
Reference numeral 107 denotes a light receiving window of a lens hood provided to focus the original irradiation light on a CCD (not shown). Reference numeral 107 denotes an opening window for a reflection type original size detection sensor.

FIG. 6 is a sectional view for clarifying the difference from the configuration of the present invention. In FIG. 6, when scanning a document (not shown), the mirror table 104 and the reflection mirror 110 sequentially scan the document from left to right in the figure, and the document passes through the optical path indicated by the dotted line in the figure. Irradiation light is CC
An image is formed on the CCD light receiving surface of the D unit 109. 108
Indicates a drive shaft. Here, the lens hood 102
Has a notch in a portion passing through the drive shaft 108, and in this configuration, there is no barrier between the CCD mounting substrate and the drive shaft.

FIG. 7 is an enlarged view of this state. In the figure, reference numeral 301 denotes a CCD mounting substrate, and 10
Reference numeral 8 denotes a drive shaft, 302 denotes a current flowing in the substrate and an induced current, and 303 denotes a model imagining secondary radiation noise generated by the induced current.

FIG. 8 shows a mounting mode of the CCD unit when the lens hood is removed. Here, the CCD unit 109 is grounded to the leader frame 101 by a leaf spring 401. As long as the three-point height adjustment on the side of the leader frame 101 is not deviated, the recovery in the event of a failure is enabled by replacing the CCD unit 109.

FIG. 9 shows an example of conventional measures against radiation noise. In other words, the configuration is such that the substrate is covered with the cover 501 so that an induced current is not directly generated from the substrate on which the CCD is mounted to the drive shaft. This cross section is shown in FIG.
0. As is clear from the drawing, the CCD unit 109 is provided with a cover so as to cover the entire substrate. In this configuration, the cost increases due to the increase in the number of cover members, and the CCD unit 10 that has been optically adjusted.
9 requires an increase in assembly time, which means that a cover must be put on later, increases the cost, and varies the noise level due to the assembly accuracy when assembling the countermeasure parts.

If the radiation noise level cannot be reduced only by the above-described board cover, as shown in FIG.
It is soldered to the GND land of the D mounting board 301.
A configuration may be adopted in which grounding is provided to the leader frame 101 through a braided wire hole (not shown) provided in the substrate cover 501. In such a configuration, the mounting cost is further increased, and the effect is accordingly increased. On the other hand, since the level change occurs in the state in which the braided wire 701 is moved, the support at the time of mounting increases, and the image reading unit becomes difficult to assemble. .

Further, in a system covered with the conventional lens hood 102 as shown in FIG. 12, when the mirror base 140 approaches the vicinity of the drive shaft, the radiation noise level of a specific frequency tends to increase. This is the CCD unit 109
, An induced current is generated in the drive shaft 108 indicated by the arrow 1201 from the CCD mounting substrate 301, and secondary radiation indicated by the arrow 1202 is emitted from the floating metal portion of the mirror base 104 to the antenna. Figure 1 shows how noise works
As shown in FIG. 3, the mirror 301 acts on the drive shaft 108 from the substrate 301 as shown by an arrow 1301, and the portion of the drive shaft 108 that comes out of the cover as shown by an arrow 1302.
Working on 4.

[0012]

As described above, measures for the CCD substrate, which is a radiation source, are sequentially incorporated.
However, a direct countermeasure for a unit having an adjustment mechanism cannot always provide a stable countermeasure result due to variations in optical adjustment and the like. For this reason, a countermeasure is often required after the countermeasure, and in fact, the radiation noise countermeasure is repeated many times.

In view of such circumstances, an object of the present invention is to provide an image reading apparatus which is hardly affected by variations in optical adjustment and which can obtain a stable noise reduction effect.

[0014]

An image reading apparatus according to the present invention has a scanning optical system for irradiating a document with light and scanning a reading surface, and a light receiving sensor for receiving light from the scanning optical system on a substrate. An image reading apparatus comprising: an image reading unit configured as a unit and a drive unit including a drive shaft for driving the scanning optical system, wherein conduction between the substrate and the drive shaft is ensured with an apparatus frame. A conductive metal plate arranged so as to be erected, and a cover member to be attached so as to cover the image reading unit and the metal plate are joined.

Further, in the image reading apparatus of the present invention, the image reading section is unitized by a three-point supporting sheet metal having reproducibility with respect to the apparatus frame, and is set on the apparatus frame by a leaf spring. It is characterized by being performed.

Further, in the image reading apparatus of the present invention, the image reading section is set on the basis of a surface on which three-point height adjustment has been performed on the apparatus frame.

Further, in the image reading apparatus according to the present invention, the metal plate is vertically provided on a back side of a substrate of the image reading section.

Here, in this type of apparatus, the substrate on which the CCD is mounted is generally a substrate having a short length and a long width. That is, most of them have a configuration in which both ends of the CCD are grounded via screws at both ends. Therefore, there is a strong tendency that a low-frequency antenna is configured for a current flowing in the substrate, and a peak frequency is generated in a frequency band in which measures must be taken against general radiation noise standards. Also,
In an image reading apparatus that scans a document, particularly in an image forming apparatus that has a configuration in which a mirror base on which a light source is mounted is scanned in a sub-scanning direction, the drive shaft generally crosses the apparatus frame.
Even if the drive shaft itself is a floating metal or has a grounding configuration, the driving shaft is grounded through a bearing at the support portion, and a stable grounding state cannot be expected.

According to the present invention, the current flowing through the substrate on which the CCD is mounted induces induction noise on the drive shaft that is not sufficiently spaced from the substrate, and the drive shaft becomes a secondary radiation source. The study was based on the measured data. Based on the result, by adopting a configuration that does not generate secondary radiation of the drive shaft, it is possible to realize reduction of radiation noise and simplification of the device configuration of the image forming apparatus.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings, members that are substantially the same as or correspond to those of the prior art will be denoted by the same reference numerals.
A preferred embodiment of the image reading apparatus according to the present invention will be described. FIG. 1 shows an external configuration of an image reading apparatus according to the present invention. Reference numeral 101 denotes a frame of the image reading apparatus, which is a leader frame. Reference numeral 102 denotes a lens hood, the main purpose of which is a conductive cover for covering the CCD unit (not shown) so that light other than the document irradiation light does not enter the CCD unit. By the way, the CCD shown in FIG.
The unit 109 is a CCD, a substrate on which the CCD is mounted,
This unit is configured by a mechanical member (sheet metal), a lens, and the like, and is adjusted by using an adjustment jig (not shown) to combine the relative distance and the relative angle between the CCD and the lens. Then, when a unit failure occurs, another unit is replaced, so that there is no need to perform optical adjustment again.

An optical motor 103 scans the mirror table 104 in the sub-scanning direction via a drive shaft. Also, 105
Is a rail for scanning the mirror base 104. 106
Reference numeral 107 denotes a light receiving window of a lens hood provided to focus the original irradiation light on a CCD (not shown). Reference numeral 107 denotes an opening window for a reflection type original size detection sensor.

Although not shown, the CCD unit 10
On the back surface of the sheet metal portion (CCD stay) colored 9, planar accuracy is obtained by two points in the vicinity of the leaf spring 401 and one point from the CCD in total. As described above, the CCD unit 109 constituting the image reading unit of the present invention is unitized by the three-point support sheet metal having reproducibility with respect to the apparatus frame, and is set on the apparatus frame by the leaf spring 401. You. In this case, the image reading unit is set on the basis of the surface on which the three-point height adjustment has been performed on the apparatus frame.

Here, the image reading section according to the present invention generates a clock having a frequency higher than a reference frequency based on the clock input from the oscillating means, and uses the high frequency clock and a plurality of counter means to perform various control operations. It has clock generation means for generating a clock, and is equipped with a CCD sensor driven by the generated clock.

FIG. 2 is a view showing the configuration of a main part of this embodiment,
That is, it shows the leader frame of the drive shaft separation type. In the figure, reference numeral 108 denotes a drive shaft, and reference numeral 801 denotes a shielding plate that blocks the drive shaft 108 from a CCD mounting substrate (not shown).
Reference numeral 802 denotes a screw hole for fixing the shielding plate 801 and a lens hood (not shown) with screws. In this example, the shielding plate 801 is formed by erecting a conductive metal plate disposed between the substrate and the drive shaft 108 so as to ensure conduction with the device frame.

FIG. 3 is a sectional view of FIG. As is apparent from comparison with FIG. 10, in the configuration of FIG.
Is completely separated from the CCD unit by a shielding plate 801, a lens hood 901, and a screw fixing portion (screw hole 802).

As shown in FIG. 12 or FIG. 13, with respect to the phenomenon that the mirror table 104 acts on the radiation, the drive shaft 108 is completely separated as shown in FIG. The effect can be prevented. In addition, since the drive shaft 108 is not a secondary radiation source, the radiation noise level does not change even when the mirror base 104 approaches.

As described above, the present invention relates to a CCD for an image reading apparatus.
Realized a configuration that hardly emits radiation noise caused by driving,
Minimize level fluctuations due to assembly variations. Then, a configuration is realized in which the radiation noise level is kept low without increasing the accumulation cost and the manufacturing cost.

[0028]

As described above, according to the present invention, C
It is possible to realize a configuration of an image reading apparatus capable of suppressing radiation noise due to CD driving to a low level, simplifying noise countermeasures for a CCD mounting substrate, and obtaining a stable noise suppression effect without increasing costs. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an external configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration in which a drive shaft shielding plate according to an embodiment of the present invention is set up from a leader frame.

FIG. 3 is a longitudinal sectional view of FIG.

FIG. 4 is a diagram illustrating a radiation noise suppression effect in the embodiment of the present invention.

FIG. 5 is an external view of a conventional image reading apparatus.

6 is a longitudinal sectional view of FIG.

FIG. 7 is a diagram showing a correlation between a CCD mounting substrate and a drive shaft in a conventional device.

FIG. 8 is a diagram showing a positional relationship between a CCD unit and a drive shaft in a conventional device.

FIG. 9 is a diagram showing a state in which a substrate cover of a CCD unit in a conventional device is covered.

FIG. 10 is a longitudinal sectional view of FIG. 9;

FIG. 11 is a diagram showing an example of a noise countermeasure in which a braided wire is added to a substrate cover in a conventional device.

FIG. 12 is a diagram showing a radiation noise generation image in the conventional device.

FIG. 13 is an orthographic view of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Device frame 102 Lens hood 103 Optical motor 104 Mirror stand 105 Rail 106 Light receiving window 107 Opening window 108 Drive shaft 109 CCD unit 301 CCD mounting board 401 Leaf spring 801 Shielding plate 802 Screw hole

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 5B047 AA01 BA02 BB02 BC05 BC09 BC11 BC14 BC20 5C062 AA05 AB02 AB17 AB33 AD06 BA00 5C072 AA01 BA13 BA20 DA30 EA05 LA02 MA01 MB01

Claims (4)

[Claims] A scanning optical system that irradiates a document with light and scans a reading surface; an image reading unit configured as a unit with a light receiving sensor that receives light from the scanning optical system mounted on a substrate; An image reading apparatus having a drive unit including a drive shaft for driving a scanning optical system, comprising: a conductive metal plate disposed between the substrate and the drive shaft so as to ensure conduction with an apparatus frame. An image reading apparatus, wherein a cover member to be attached so as to cover the image reading section and the metal plate are joined. 2. The image reading section is unitized by a three-point support sheet metal having repositioning reproducibility with respect to the apparatus frame, and is set on the apparatus frame by a leaf spring. Item 2. The image reading device according to Item 1. 3. The image reading apparatus according to claim 2, wherein the image reading section is set based on a surface on which three-point height adjustment has been performed on the apparatus frame. 4. The image reading apparatus according to claim 1, wherein the metal plate is provided vertically on a rear surface side of a substrate of the image reading unit.