JP2009288393A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus that prevents leakage of electromagnetic wave noise regardless of variance in manufacture of each apparatus. <P>SOLUTION: A noise detector 1702 detects wavelength of electromagnetic wave noise under control of a circuit board 1703. The circuit board 1703 is a generating source of the electromagnetic wave noise. A metallic plate 1704 slides in a direction shown by an arrow A along an inner wall surface of a housing 1701 by bend of artificial muscles 1705 and displacement of a rack 1709, and reflects the electromagnetic wave noise generated by the circuit board 1703. Assuming that a distance L between the metallic plate 1704 and the circuit board 1703 is (n/2)times as large as the wavelength λ of the electromagnetic wave noise (provided that n is an odd number), a phase of the electromagnetic wave noise incident on the metallic plate 1704 and a phase of the electromagnetic wave noise reflected on the metallic plate 1704 are shifted by half wavelength, whereby the electromagnetic wave noise is attenuated by their mutual interference. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to a technique for preventing leakage of electromagnetic noise generated from a circuit board regardless of manufacturing variations of the image forming apparatus.

As a result of the widespread use of various electronic devices in recent years, electromagnetic interference (EMI: Electromagnetic interference (EMI) that interferes with the operation of other electronic devices or affects the human body due to electromagnetic noise generated by electronic devices.
Magnetic Interference) is a problem.
The problem of electromagnetic interference becomes even more pronounced because electronic devices are more susceptible to electromagnetic noise due to the miniaturization and power saving of semiconductor chips, and the electromagnetic susceptibility (EMS) tends to decrease. ing.

Image forming apparatuses such as multifunction peripherals and copiers also incorporate circuit boards of various sizes and generate electromagnetic noise. In order to prevent such electromagnetic noise from causing electromagnetic interference, measures have been taken to shield the circuit board with a metal casing, but there is a concern that electromagnetic noise leaks from the end or gap of the metal casing. .
In response to such problems, for example, by providing a groove structure at the end of the shield structure that shields the electromagnetic noise source, a reflected wave having a phase opposite to that of the electromagnetic noise leaking from the shield structure is generated, A technique for canceling out is disclosed (Patent Document 1).
JP 2005-11975 A

However, in order to cancel out electromagnetic wave noise using this groove structure, the depth of the groove and the wavelength of the electromagnetic wave noise must have a strictly constant relationship in size.
On the other hand, in general, any apparatus has variations at the time of manufacture, and the image forming apparatus cannot avoid these variations. For this reason, the frequency of electromagnetic noise generated by the image forming apparatus and the depth of the groove structure vary from apparatus to apparatus. In addition, the shield structure also has variations due to loose screws and ground variations in the housing.

For this reason, even if a groove structure is added to the shield structure, leakage of electromagnetic noise cannot always be prevented.
SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that prevents leakage of electromagnetic noise regardless of manufacturing variations among apparatuses.

  In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus including a shield structure storing a control board that controls the operation of the apparatus, and the shield structure includes electromagnetic noise generated by the control board. And an adjusting means for adjusting the distance between the control board and the reflecting plate, and the adjusting means reflects the electromagnetic wave noise incident on the reflecting plate and the reflecting plate. The electromagnetic wave noise is adjusted so as to have an opposite phase.

By doing so, the frequency of the electromagnetic wave applied to the radio wave absorber is regulated by changing the opening diameter by the regulating means, and the electromagnetic wave noise is detected by detecting the temperature rise of the radio wave absorber by the temperature sensor. Can be specified (= aperture diameter). Therefore, the wavelength and frequency of electromagnetic noise can be specified by a small and inexpensive detection device.
The adjusting means includes first driving means for sliding the reflecting plate, and second driving means for sliding the first driving means, and the first driving means is higher than the second driving means. It is desirable that the distance that the second driving means can slide the first driving means is larger than the distance that the first driving means can slide the reflecting plate with accuracy.

In this case, it is more preferable that the first driving means slides the reflecting plate by the ion conduction actuator, and the second driving means slides the first driving means by the rack and pinion mechanism.
In addition, a noise detector for detecting the wavelength or frequency of electromagnetic noise is provided, and if the adjusting means slides the reflector according to the wavelength or frequency of the electromagnetic noise detected by the noise detector, the size of the apparatus can be increased. The object of the present invention can be achieved without inviting.

Hereinafter, an embodiment of an electromagnetic wave noise detection apparatus according to the present invention will be described with an image forming apparatus as an example with reference to the drawings.
[1] Configuration of Image Forming Apparatus First, the configuration of the image forming apparatus according to the present embodiment will be described.
FIG. 1 is a cross-sectional view showing the configuration of the image forming apparatus according to the present embodiment. As shown in FIG. 1, the image forming apparatus 1 includes a noise detector 100, a control unit 110, an intermediate transfer belt 120, a secondary transfer roller 121, a driving roller 122, a driven roller 123, and primary transfer rollers 124Y to 124K. The image units 130Y to 130K, a paper feed cassette 140, a paper feed roller 141, a fixing device 150, and a paper discharge roller 160 are provided.

The intermediate transfer belt 120 is disposed almost at the center inside the image forming apparatus 1. The intermediate transfer belt 120 is stretched around the outer periphery of the drive roller 122 and the driven roller 123 and is driven to rotate in the direction of arrow A. The driving roller 122 is rotationally driven by a driving motor (not shown), and the driven roller 123 is driven to rotate by friction with the intermediate transfer belt 120.
The image forming units 130 </ b> Y to 130 </ b> K create toner images of respective colors of yellow (Y), magenta (M), cyan (C), and black (K). The image forming units 130 </ b> Y to 130 </ b> K are disposed below the intermediate transfer belt 120 along the intermediate transfer belt 120.

The primary transfer rollers 124Y to 124K are arranged to face the image forming units 130Y to 130K with the intermediate transfer belt 120 interposed therebetween. Further, around the photosensitive drum 131, a charger 132, a print head unit 133, a developing device 134, and a cleaner (not shown) are arranged along the rotation direction.
A secondary transfer roller 121 is pressed against the driving roller 122 with the intermediate transfer belt 120 interposed therebetween, and the NIP portion between the secondary transfer roller 121 and the intermediate transfer belt 120 is a secondary transfer region 170.

The fixing device 150 includes a fixing roller 101, a pressure roller 102, and a magnetic flux generation unit 103. A pressure contact portion between the fixing roller 101 and the pressure roller 102 is a fixing NIP region 171.
The paper feed cassette 140 is detachably disposed at the lower part of the image forming apparatus 1. The recording sheets P stacked and housed in the paper feed cassette 140 are sent out one by one from the uppermost one to the transport path 160 by the rotation of the paper feed roller 141.

The control unit 110 controls the operation of each unit of the image forming apparatus 1. The noise detector 100 detects electromagnetic noise that leaks from the control unit 110.
[2] Configuration of Noise Detector 100 Next, the noise detector 100 will be described.
FIG. 2 is a cross-sectional view showing the positional relationship between the noise detector 100 and the control unit 110. As shown in FIG. 2, the noise detector 100 includes noise detection units 200 to 203. Each of the noise detection units 200 to 203 has a box shape having an opening on one surface, and the opening faces the control unit 110 side.

  While any of the noise detection units 200 to 203 can adjust the opening diameter, the opening diameters do not overlap between the noise detection units 200 to 203 even if the opening diameter is adjusted. For example, even if the opening diameter of the noise detection unit 200 is adjusted to be the smallest and the opening diameter of the noise detection unit 201 is adjusted to be the largest, the size of the opening diameter between the noise detection units 200 and 201 is small. The relationship does not change.

In this way, the wavelength of electromagnetic noise having the highest intensity can be searched and specified over a wider wavelength range.
Now, since the noise detection units 200 to 203 have the same configuration except that the opening diameters are different, the noise detection unit 200 will be described below, and thus will be replaced with another description.
FIG. 3 is an external perspective view of the noise detection unit 200. As shown in FIG. 3, the noise detection unit 200 includes an artificial muscle 301, a housing 302, a radio wave absorbing sheet 303, and a temperature sensor 304.

All of the artificial muscles 301 are plate-like members, and twelve pieces are arranged along the inner edge of the opening 305 of the noise detection unit 200. The artificial muscle 301 is supported by a support wall (not shown) provided at the inner edge of the opening 305. When a voltage is applied by an electrode (not shown), the artificial muscle 301 bends toward the center of the opening 305 and opens. To change.
The housing 302 is a metal rectangular parallelepiped container, and the artificial muscle 301 is disposed in the opening 305 as described above. An opening is also provided at a position facing the opening 305, and the opening is covered with a radio wave absorbing sheet 303. The electromagnetic wave noise incident from the opening 305 is absorbed by the radio wave absorbing sheet 303 and raises the temperature of the radio wave absorbing sheet 303.

The temperature sensor 304 is a contact type thermistor and measures the temperature of the radio wave absorbing sheet 303.
4A and 4B are views showing the shape of the housing 302, where FIG. 4A is a view seen from the opening 305 side, and FIG. 4B is a cross-sectional perspective view. As shown in FIG. 4, a support wall 302 a is provided on the inner edge of the opening 305 to support the artificial muscle 301.

  5A and 5B are diagrams showing the structure of the noise detection unit 200, where FIG. 5A is a view seen from the opening 305 side, and FIG. 5B is a cross-sectional perspective view. As shown in FIG. 5, all the artificial muscles 301 are bonded and held via the electrode foil 501 at the end of the support wall 302a. An electrode foil 502 is attached to a position facing the electrode foil 501 across the artificial muscle 301.

The variable voltage source 503 applies a voltage to the artificial muscle 301 under the control of the control unit 110. The artificial muscle 301 does not flex in a state where no voltage is applied, and is almost flat. Further, the temperature sensor 304 inputs a temperature signal to the control unit 110.
FIG. 6 is a diagram illustrating the structure of the noise detection unit 200 in a state where a voltage (0.85 V) is applied to the artificial muscle 301, and (a) is a diagram viewed from the opening 305 side. b) is a cross-sectional perspective view. As shown in FIG. 6, the artificial muscle 301 bends toward the center of the opening 305 when a voltage is applied from the variable voltage source 503 through the electrode foils 501 and 502 under the control of the control unit 110. As a result, the opening diameter of the opening 305 changes.

In FIG. 6, the opening diameter of the opening 305 when the artificial muscle 301 is not bent is r1 (50 mm in the present embodiment), whereas the opening when the artificial muscle 301 is bent by c. The opening diameter of the part 305 is r2 (for example, 33 mm).
7A and 7B are diagrams illustrating voltage bending characteristics of the artificial muscle 301, where FIG. 7A is a diagram illustrating the curl amount of the artificial muscle 301, and FIG. 7B is a voltage applied to the artificial muscle 301 and the curl amount. It is a graph which shows the relationship.

As shown in FIG. 7A, the amount of bending of the artificial muscle 301 in a state where a voltage is applied to the artificial muscle 301 in comparison with a state where no voltage is applied to the artificial muscle 301, The amount of displacement at the other end when fixed is evaluated, and this amount of displacement is called a curl amount.
As shown in FIG. 7B, the curl amount of the artificial muscle 301 is proportional to the applied voltage. Therefore, since the curl amount of the artificial muscle 301 can be easily and accurately controlled by controlling the applied voltage, the opening diameter of the opening 305 can be controlled.

  Here, the artificial muscle 301 is an ion conduction actuator in which a gold electrode film is bonded to both surfaces of a perfluorocarboxylic acid film. The perfluorocarboxylic acid film, which is an ion exchange resin, swells as the water content increases, just like a general polymer gel. Therefore, the cation in the film moves to the cathode side with water in the electric field generated by the application of voltage. However, it is considered that the water content is uneven and bent.

Now, an electromagnetic wave having a wavelength larger than the opening diameter of the opening 305 cannot pass through the opening 305 and enter the radio wave absorbing sheet 303. Conversely, an electromagnetic wave having a wavelength equal to or smaller than the opening diameter of the opening 305 passes through the opening 305 and is incident on the radio wave absorbing sheet 303, so that the temperature can be raised.
Therefore, the intensity of electromagnetic noise having a wavelength between the two opening diameters is detected by making the opening 305 have two different opening diameters and comparing the temperature of the radio wave absorbing sheet 303 between the two opening diameters. Can do.

Moreover, since the noise detection units 200 to 203 have different opening diameters, the intensity of the electromagnetic wave noise for each wavelength band can also be detected by comparing the temperature of the radio wave absorption sheet between the noise detection units 200 to 203. .
[2] Configuration of Control Unit 110 Next, the configuration of the control unit 110 will be described.

FIG. 8 is a cross-sectional view showing the main structure of the control unit 110. As shown in FIG. 8, the control unit 110 is formed by fixing a lid 803 with a bolt to a housing 802 that houses a circuit board 801.
A hollow waveguide portion is formed at the edge of the housing 802 and constitutes a noise attenuator 800. The noise attenuator 800 will be described later.

Various semiconductor elements are mounted on the circuit board 801 and generate electromagnetic wave noise. The electromagnetic wave noise enters the noise attenuator 800 through the gap between the housing 802 and the lid 803 and is attenuated.
The circuit board 801 receives a temperature signal from the noise detector 100 and inputs a control signal to the noise detector 100. The circuit board 801 controls the noise attenuator 800 based on the temperature signal.

[3] Configuration of Noise Attenuator 800 Next, the configuration of the noise attenuator 800 will be described.
FIG. 9 is a cross-sectional view showing the configuration of the noise attenuator 800. As shown in FIG. 9, the noise attenuator 800 includes a waveguide portion 901, a reflection plate 902, an artificial muscle 903, a support plate 904, a rack 905 and a pinion 906.

The pinion 906 is rotationally driven by a motor (not shown) controlled by the circuit board 801 and moves the rack 905 up and down. As a result, the tube length L from the reflector 902 to the lid 803 is adjusted.
The rack 905 is supported by a guide rail (not shown) so as to be slidable up and down. The rack 905 forms a piston together with the reflection plate 902, the artificial muscle 903, and the support plate 904, and reflects electromagnetic wave noise that has entered the waveguide portion 901.

The support plate 904 is fixed to one end of the rack 905.
The artificial muscle 903 is fixed to the support plate 904 and supports the reflection plate 902.
FIG. 10 is an external perspective view showing the artificial muscle 903. As shown in FIG. 10, four artificial muscles 903 are alternately fixed to the support plate 404 via the electrode foil 1000. The control unit 110 controls the voltage that the variable voltage source 1001 applies to the artificial muscle 903, whereby the curl amount of the artificial muscle 903 is controlled.

In this way, under the control of the control unit 110, the tube length L from the reflector 902 to the lid 803 is adjusted by the rack and pinion mechanism and the bending of the artificial muscle 903.
If the tube length L is (n / 2) times the wavelength λ of electromagnetic wave noise (where n is an odd number), the phase of the electromagnetic wave noise entering the waveguide section 901 and the electromagnetic wave noise reflected by the reflector 902 Since the phases are shifted from each other by half a wavelength and are opposite to each other, the electromagnetic noise is attenuated by the interference between the phases.

Further, by using the artificial muscle 903 in addition to the rack and pinion mechanism, the tube length L can be adjusted more precisely than in the case where only the rack and pinion mechanism is used.
[4] Hardware Configuration of Control Unit 110 Next, the hardware configuration of the control unit 110 will be described.
FIG. 11 is a block diagram illustrating a hardware configuration of the control unit 110. As shown in FIG. 11, the control unit 110 includes a CPU (Central Processing Unit) 1101, a ROM (Read Only Memory) 1102, a RAM (Random Access Memory) 1103, and an A / D converter (ADC: Analogue to Digital Converter) 1104. A D / A converter (DAC: Digital to Analogue Converter) 1105 is connected via an internal bus 1106.

The CPU 1101 reads a control program stored in the ROM 1102 and executes the control program using the RAM 1103 as a work area.
The A / D converter 1104 compares the temperature signals output from the noise detection units 200 to 203 with the temperature signals output from the in-machine temperature sensor 1107. If the difference is equal to or greater than a predetermined value, the A / D converter 1104 indicates that a temperature increase has occurred. Is sent to the CPU 1101.

FIG. 12 is a diagram showing a configuration of the A / D converter 1104. As shown in FIG. 12, the A / D converter 1104 compares the temperature signals output from the noise detection units 200 to 203 with the temperature signals output from the in-machine temperature sensor 1107, and amplifies the difference signal. The first stage comparator 1201 for output is provided.
The difference signal output from the first-stage comparator 1201 is compared with the reference signal by the second-stage comparator 1202, and a digital signal indicating whether or not the temperature has risen is output. FIG. 13A is a diagram illustrating the bit assignment of the digital signal output from the A / D converter 1104. In 32 bits of 1 word, the presence or absence of temperature rise for each noise detection unit is shown in the lower 4 bits.

The in-machine temperature sensor 1107 measures the temperature around the noise detector 100 (atmosphere temperature) and outputs a temperature signal indicating the ambient temperature. Further, the CPU 1101 sets the amplification factor of the differential signal and the voltage level of the reference signal. Thereby, the detection accuracy of the temperature rise is determined.
The D / A converter 1105 converts the digital signal input by the CPU 1101 into a control signal and inputs the control signal to the noise detector 100. FIG. 13B is a diagram illustrating a bit assignment of a digital signal that the CPU 1101 inputs to the D / A converter 1105 in order to control the noise detector 100.

As shown in FIG. 13B, 8 bits from the least significant bit are used for designating the degree of bending of the artificial muscle (256 levels) for each noise detection unit.
For example, the integer value 0x0000 is input to the D / A converter 1105 when the artificial muscles of the detection units 200 to 203 are not bent at all. The integer value 0x0f00 is input to the D / A converter 1105 in order to bend only the artificial muscle of the detection unit 202 to the maximum degree of the 256 steps.

The D / A converter 1105 converts the digital signal input by the CPU 1101 into a control signal and inputs the control signal to the noise attenuator 800. FIG. 13C is a diagram illustrating the bit assignment of a digital signal that the CPU 1101 inputs to the D / A converter 1105 in order to control the noise attenuator 800.
As shown in FIG. 13 (c), the least significant 8 bits are used to specify the degree of bending (256 steps) of the artificial muscle 903, and the subsequent 8 bits are used to control the rack and pinion mechanism (256 steps). Used for.

For example, the integer value 0x0000 is input to the D / A converter 1105 when the artificial muscle 903 is not bent at all and the rack is lowered to the lowest position to maximize the tube length L. On the other hand, the integer value 0x00ff is input to the D / A converter 1105 when the artificial muscle 903 is bent to the maximum of the 256 steps, the rack is raised to the highest position, and the tube length L is set to zero.
It should be noted that even if the artificial muscle 903 is bent to the maximum degree of the 256 steps, the tube length L can be changed by a distance smaller than that of raising and lowering the rack by one step in the 256 steps. The converter 1105 outputs a control signal.

The CPU 1101 has a built-in timer and counts elapsed time by counting clocks. Further, the CPU 1101 outputs all the digital signals by a memory mapped I / O (memory mapped input / output) method.
[5] Operation of Control Unit 110 Next, the operation of the control unit 110 will be described.

FIG. 14 is a flowchart showing the operation of the control unit 110. As shown in FIG. 14, the control unit 110 first controls the noise detector 100 to execute a noise wavelength specifying process for specifying the frequency of electromagnetic noise having the highest intensity (S1401).
Next, the control unit 110 executes noise attenuation processing (S1402). The noise attenuation process attenuates the intensity of electromagnetic noise having the frequency specified by the noise wavelength specifying process.

Thereafter, the control unit 110 sets the timer to a predetermined time and starts (S1403). If a timeout occurs in the timer (S1404: Yes), the above process is repeated. As a result, even if the frequency of the electromagnetic wave noise having the highest intensity varies, the intensity can be attenuated.
(A) Noise wavelength specifying process Next, the noise wavelength specifying process (S1401) will be described in more detail.

  FIG. 15 is a flowchart showing details of the noise wavelength specifying process (S1401). As shown in FIG. 15, the control unit 110 first initializes the aperture diameters of the noise detection units 200 to 203 constituting the noise detector 100 (S1501). In this case, the noise detection unit 200 maximizes the aperture diameter, and the noise detection unit 203 minimizes the aperture diameter.

Next, the control unit 110 sets a timer (S1502), and when a timeout occurs (S1503: Yes), receives a temperature signal from the noise detector 100 (S1504).
The control unit 110 refers to the temperature signal from the noise detector 100, and if any noise detection unit has not detected an increase in temperature (S1505: Yes), and if any noise detection unit has been detected ( S1506: Yes), it is determined that the electromagnetic wave noise is not generated, or it cannot be attenuated by the noise attenuator 800 because the wavelength of the electromagnetic wave noise is too large, and the process is terminated.

When the noise detection unit that has detected the temperature rise and the noise detection unit that has not been detected coexist (S1506: No), it is determined whether or not to increase the detection accuracy of the electromagnetic wave noise wavelength.
The control unit 110 cannot further reduce the aperture diameter of the noise detection unit having the smallest aperture diameter among the noise detection units that have detected the temperature rise, and is open among the noise detection units that have not detected the temperature rise. When the aperture diameter of the noise detection unit having the largest aperture cannot be further increased (case A), it is determined that the detection accuracy cannot be increased.

Further, the control unit 110 further reduces the opening diameter of the noise detection unit having the smallest opening diameter among the noise detection units that have detected the temperature increase, and as a result, the noise detection unit does not detect the temperature increase (Case B). ) Also determines that the detection accuracy cannot be increased.
Furthermore, the control unit 110 further increases the aperture diameter of the noise detection unit having the largest aperture diameter among the noise detection units that have not detected the temperature increase, and as a result, the noise detection unit detects a temperature increase (Case C). ) Also determines that the detection accuracy cannot be increased.

If it is determined that the detection accuracy can be increased (S1507: No), the noise wavelength is specified as follows (S1508), and then the process returns to the upper routine.
In case A, the control unit has the smallest opening diameter of the noise detection unit that has the smallest opening diameter among the noise detection units that have detected the temperature rise, and the largest opening diameter among the noise detection units that have not detected the temperature rise. The intermediate value with the aperture diameter of the noise detection unit is the wavelength of electromagnetic noise having the highest intensity.

In Case B, the intermediate value of the aperture diameter of the noise detection unit before and after the aperture diameter of the noise detection unit is made smaller is the wavelength of electromagnetic noise having the highest intensity.
In case C, the intermediate value of the aperture diameter of the noise detection unit before and after reducing the aperture diameter of the noise detection unit is the wavelength of electromagnetic wave noise having the highest intensity.
If it is determined that the detection accuracy can be increased (S1507: Yes), after changing the opening diameter of the noise detection units 200 to 203 as described below (S1509), the process proceeds to step S1502 and described above. Repeat the process.

Since Steps S1505 and S1506 are both determined No, when proceeding to Step S1509, one of the noise detection units detects a temperature rise, and the other noise detection unit detects a temperature rise. Absent.
That is, referring to the noise detection unit from the larger opening diameter, first, the noise detection unit that detects the temperature rise appears, and then the noise detection unit that does not detect the temperature rise appears.

Therefore, noise detection units that are adjacent to each other in order of opening diameter, one of which detects a temperature rise and the other of which does not detect a temperature rise, The opening diameter is reduced by one step, and the opening diameter of the noise detection unit that did not detect the temperature rise is increased by one step.
As a result, when the wavelength of the electromagnetic wave noise becomes larger than the larger opening diameter, both the two noise detection units do not detect the temperature rise, so that it corresponds to the case B and the wavelength of the electromagnetic wave noise can be specified. .

Further, when the wavelength of the electromagnetic wave noise becomes smaller than the smaller opening diameter, the two noise detection units both detect the temperature rise, so that it corresponds to the case C and the wavelength of the electromagnetic wave noise can be specified. it can.
In addition, even if the opening diameter is continuously changed, if one of the noise detection units continues to detect a temperature rise and the other noise detection unit does not detect a temperature rise, this corresponds to the case A, and the electromagnetic noise is also detected. The wavelength can be specified.

Note that after proceeding to step S1509, the processing from steps S1504 to S1508 may be performed only for the noise detection unit whose opening diameter has been changed.
(B) Noise Attenuation Process Next, the noise attenuation process (S1402) will be described.
FIG. 16 is a flowchart showing details of the noise attenuation process. As shown in FIG. 16, first, the displacement amount of the rack and pinion mechanism is determined (S1601), and then the curl amount for compensating the remaining displacement amount to the artificial muscle 903 by bending is determined (S1602). . Then, the control unit 110 transmits a control signal to the noise attenuator 800 (S1603), and returns to the upper routine.

  Here, as described above, the rack and pinion mechanism can be displaced by 256 steps. However, the displacement amount for one step of the rack and pinion mechanism is drp, and the reciprocal of the wavelength of the electromagnetic wave noise specified by the noise wavelength specifying process. If λ is λ, the required displacement of the rack and pinion mechanism is [λ / 2drp]. However, [·] is a Gaussian symbol and represents the integer part of the numerical value in the symbol.

Further, if the artificial muscle 903 bends by 256 steps, and the amount of curl for one step is c, the necessary amount of curl of the artificial muscle 903 is [((λ / 2) − [λ / 2drp]) / c]. It is. That is, the curl amount necessary to cover the half-wavelength excluding the length covered by the displacement of the rack and pinion mechanism by the bending of the artificial muscle 903 is given by the above equation.
[6] Another Example of Noise Attenuator Next, another example of the noise attenuator will be described.

In the above description, the case where the noise attenuator 800 attenuates the electromagnetic wave noise has been described, but instead of this, or in addition to this, the electromagnetic wave noise may be attenuated as follows.
FIG. 17 is a diagram illustrating a main configuration of the control unit according to the present embodiment. As shown in FIG. 17, the control unit 1700 includes a housing 1701, a noise detector 1702, a circuit board 1703, a metal plate 1704, an artificial muscle 1705, rollers 1706, 1707, 1710, a pinion 1708, a rack 1709, and a guide rail 1711. It has.

The noise detector 1702 is disposed inside the housing 1701, and detects the wavelength of electromagnetic noise under the control of the circuit board 1703 by the same mechanism as in the above embodiment. The circuit board 1703 is the same as the circuit board 801 according to the above embodiment and is a source of electromagnetic noise.
The metal plate 1704 reflects electromagnetic noise generated by the circuit board 1703. A guide rail 1711 is attached to the metal plate 1704. The guide rail 1711 is sandwiched between the roller 1710 and the wall surface of the control unit 1700 and slides along the inner wall surface of the housing 1701.

One end of the artificial muscle 1705 is fixed to the metal plate 1704 and bends in the direction of arrow A. The pinion 1708 and the rack 1709 constitute a rack and pinion mechanism. The rack 1709 is supported by a pinion 1708 and rollers 1706 and 1707, and the pinion 1708 is displaced in the arrow A direction by rotating in the arrow B direction.
One end of the rack 1709 is fixed to the artificial muscle 1705, and the metal plate 1704 slides in the direction of arrow A due to the bending of the artificial muscle 1705 and the displacement of the rack 1709. When the metal plate 1704 slides, the distance L between the metal plate 1704 and the circuit board 1703 changes. When this distance L is (n / 2) times the wavelength λ of electromagnetic wave noise (where n is an odd number), the phase of electromagnetic wave noise incident on the metal plate 1704 and the phase of electromagnetic wave noise reflected by the metal plate 1704 Are shifted by a half wavelength, so that they interfere with each other to attenuate electromagnetic noise.

[7] Modifications Although the present invention has been described based on the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and the following modifications can be implemented. .
(1) Although the case where the four noise detection units are arranged in a straight line has been described in the above embodiment, it goes without saying that the present invention is not limited to this, and the arrangement may be other than a straight line such as a square arrangement. good. The number of noise detection units is not limited to four as long as it is two or more.

(2) Although the case where a contact type thermistor is used as the temperature sensor 304 has been described in the above embodiment, it goes without saying that the present invention is not limited to this, and a temperature sensor other than a contact type thermistor such as a non-contact type thermistor. May be used. However, a temperature sensor that does not cause a temperature drop of the radio wave absorbing sheet 303 during temperature measurement is desirable.
(3) Although not particularly mentioned in the above embodiment, it is desirable that the maximum value of the opening diameter of the noise detection units 200 to 203 is twice the tube length L in the noise attenuator 800. This is because the noise attenuator 800 cannot attenuate electromagnetic waves having a wavelength greater than 2L.

In this sense, the noise detector 100 includes a noise detection unit that can change the opening diameter from L to 2L and noise that can change the opening diameter from L to 0 as long as the strength of the artificial muscle allows. A detection unit may be provided.
When C is the upper limit of the range in which the opening diameter can be changed due to the performance of the artificial muscle, it is sufficient to provide (N + 1) noise detection units as long as N = [2L / C]. That is, a noise detection unit capable of changing the opening diameter from (2L-NC) to 0 by reducing the opening diameter by C from the noise detection unit capable of changing the opening diameter from 2L to (2L-C). You may prepare until.

(4) In the above embodiment, the case where the aperture diameters of the noise detection units constituting the noise detector 100 are not overlapped with each other has been described. Needless to say, the present invention is not limited to this. You may do as follows.
That is, you may provide three or more noise detection units with which the range of the aperture diameter which can be changed overlaps. For example, with respect to the tube length L of the noise attenuator, the number N of noise detection units, and the maximum curl amount C of the artificial muscle, the opening diameter of the first noise detection unit is changed from 0 to (C + ((2L−C) / N)), and the aperture diameter of the i-th noise detection unit is sequentially from ((2L−C) / N) × (i−1) to (C + ((2L−C) i / N)). Just do it. In this way, the difference between the upper and lower limits of the opening diameter of the noise detection unit is C, and the lower limit of the opening diameter of the noise detection unit is increased in order from the smallest ((2-LC) / N). A combination can be obtained.

FIG. 18 is a diagram for explaining the operation of the noise detector according to this modification. In FIG. 18, an arrow represents a noise detection unit in which the temperature rise is recognized. In addition, a broken line is applied to the noise detection unit with the smallest opening diameter among the noise detection units in which the temperature increase is recognized and the noise detection unit with the largest opening diameter among the noise detection units in which the temperature increase is not recognized. .
As shown in FIG. 18, the opening diameter of the noise detection unit 1801 is maximized, the opening diameter of the noise detection unit 1804 is minimized, and the opening diameters of the noise detection units 1802 and 1803 are set to an intermediate opening diameter between them. Is done. Accordingly, the range from the minimum wavelength to the maximum wavelength that can be detected by the noise detection units 1801 to 1804 is monitored.

As a result, for example, when the temperature rise is recognized in the noise detection units 1801 and 1802 and the temperature rise is not recognized in the noise detection units 1803 and 1804, the wavelength of the electromagnetic wave noise having the highest intensity is the aperture diameter of the noise detection unit 1803. It can be seen that (S1) is equal to or larger than the opening diameter (L1) of the noise detection unit 1802 (FIG. 18A).
Next, in order to improve the detection accuracy of electromagnetic noise, the opening diameter of the noise detection unit 1801 is set to L1, the opening diameter of the noise detection unit 1804 is set to S1, and the opening diameters of the noise detection units 1802 and 1803 are set to these. As an intermediate opening diameter, the temperature rise of the noise detection units 1801 to 1804 is monitored.

As a result, for example, when the temperature rise is recognized only in the noise detection unit 1801 and the temperature rise is not recognized in the noise detection units 1802 to 1804, the wavelength of the electromagnetic wave noise having the highest intensity is the aperture diameter of the noise detection unit 1802 ( It can be seen that it is equal to or larger than S2) and equal to or smaller than the opening diameter (L1) of the noise detection unit 1801 (FIG. 18B).
Next, while keeping the opening diameter of the noise detection unit 1801 at L1, the opening diameter of the noise detection unit 1804 is set to S2, and the opening diameters of the noise detection units 1802 and 1803 are set to an intermediate opening diameter between these, the temperature rise is increased. Monitor.

As a result, for example, when the temperature rise is recognized in the noise detection units 1801 to 1803 and the temperature rise is not recognized only in the noise detection unit 180, the wavelength of the electromagnetic wave noise having the highest intensity is the aperture diameter of the noise detection unit 1804 ( It can be seen that it is not less than S2) and not more than the opening diameter (L2) of the noise detection unit 1803 (FIG. 18C).
Furthermore, as a result of setting the opening diameter of the noise detection unit 1801 to L2 and the opening diameters of the noise detection units 1802 and 1803 between L2 and S2, for example, temperature rise is recognized in the noise detection units 1801 and 1802, and noise detection is performed. When no temperature rise is observed in the units 1803 and 1804, the wavelength of the electromagnetic wave noise having the highest intensity is not less than the opening diameter (S3) of the noise detection unit 1803 and not more than the opening diameter (L3) of the noise detection unit 1802. It turns out that there exists (FIG.18 (d)).

As described above, the wavelength of electromagnetic noise having the highest intensity can be specified by adjusting the opening diameter while referring to the presence or absence of the temperature rise of the noise detection units 1801 to 1804.
(5) In the above embodiment, the case of using an ion conduction actuator using a perfluorocarboxylic acid film as an artificial muscle has been described, but it goes without saying that the present invention is not limited to this. Instead, other materials such as perfluorosulfonic acid may be used.

In addition, even if an artificial muscle other than an ion conduction actuator or an actuator other than an artificial muscle, such as a piezoelectric element, the effect of the present invention can be obtained by using a plate-like member that bends according to the magnitude of an applied voltage. Can do.
(6) In the above embodiment, the case where the electromagnetic wave noise having the highest intensity is attenuated has been described. However, it goes without saying that the present invention is not limited to this, and the following may be used instead.

The control unit according to the present modification has substantially the same configuration as the control unit 110 according to the above embodiment, but differs in that a plurality of noise attenuators are individually controlled. Hereinafter, the description will be given focusing on the differences.
FIG. 19 is a cross-sectional view showing the main configuration of a control unit according to this modification. As shown in FIG. 19, the control unit 1900 includes a noise attenuator 1901 having a tube length La and a noise attenuator 1902 having a tube length Lb.

FIG. 20 is a graph illustrating the relationship between the wavelength of electromagnetic noise and the electric field strength. In FIG. 20 (a), both electromagnetic noises Na and Nb have a higher electric field strength than background noise, and more than a predetermined threshold value (threshold value necessary for satisfying standards related to EMC (electro-magnetic compatibility)). Also, the electric field strength is high.
The control unit 1900 uses a noise detector (not shown) to specify the wavelength of the electromagnetic wave noise Na, which is the electromagnetic wave noise having the highest electric field strength, according to the procedure shown in the above embodiment. Since the electromagnetic wave noise Na has the highest electric field strength, the wavelength of the electromagnetic wave noise Na can be specified by detecting the aperture diameter with the highest temperature rise by the noise detector.

In this way, the electromagnetic wave noise Na can be attenuated by adjusting the tube length La of the noise attenuator 1901 using the specified wavelength of the electromagnetic wave noise Na. As shown in FIG. 20B, when the electromagnetic wave noise Na is attenuated, only the electromagnetic wave noise Nb has an electric field strength higher than the threshold value.
Next, the control unit 1900 uses the noise detector again to identify the wavelength of electromagnetic wave noise having the highest electric field strength. Thereby, the wavelength of the electromagnetic wave noise Nb is specified. If the tube length Lb of the noise attenuator 1902 is adjusted using the specified wavelength of the electromagnetic wave noise Nb, the electromagnetic wave noise Nb can also be attenuated.

As described above, if the procedure of detecting the electromagnetic wave noise wavelength having the highest wavelength with the highest electric field intensity and attenuating it with one of two or more noise attenuators, the individual quality of the image forming apparatus is improved. The standard regarding EMC can be satisfied irrespective of the variation of the wavelength of the electromagnetic noise generated by the variation.
(7) In the above embodiment, twelve plate-like artificial muscles 301 are arranged along the inner edge of the opening 305 of the noise detection unit 200, and the four artificial muscles 903 are alternately arranged in the electrode foil. Although the case where it fixes to the support plate 404 via 1000 was demonstrated, it cannot be overemphasized that this invention is not limited to this, You may comprise these by another number.

Needless to say, the shape of the artificial muscle 301 is not limited to a strip shape, and other shapes may be used. For example, a trapezoidal shape that widens from one end in the longitudinal direction toward the other end may be used.In such a case, an electrode is attached to the widened end, and the opening diameter is set at the other end that is narrowed. Adjustment is preferred.
(8) In the above embodiment, the case where the waveguide portion 901 is formed at the edge of the housing 802 has been described. However, it goes without saying that the present invention is not limited to this, and a lid is used instead of the housing 802. A waveguide portion 901 may be formed in the portion 803.

  (9) In the above embodiment, the case where the noise attenuator 800 is controlled according to the wavelength of the electromagnetic wave noise detected by the noise detector 100 using the artificial muscle 903 has been described, but the present invention is limited to this. Needless to say, the noise attenuator 800 may be controlled in accordance with the wavelength of electromagnetic noise detected by another device or the frequency of electromagnetic noise instead of the noise detector 100.

  Similarly, the control unit 1700 may control the metal plate 1704 according to the wavelength or frequency of electromagnetic wave noise detected by another device instead of the noise detector 1702 using artificial muscle.

  The electromagnetic wave noise detection apparatus according to the present invention is useful as an apparatus that is built in an image forming apparatus and identifies the wavelength and frequency of electromagnetic noise.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a cross-sectional view showing a positional relationship between a noise detector 100 and a control unit 110. FIG. 2 is an external perspective view of a noise detection unit 200. FIG. It is a figure showing the shape of the housing | casing 302, Comprising: (a) is the figure seen from the opening part 305 side, (b) is a cross-sectional perspective view. It is a figure showing the structure of the noise detection unit 200, Comprising: (a) is the figure seen from the opening part 305 side, (b) is a cross-sectional perspective view. It is a figure which illustrates the structure of the noise detection unit 200 in the state by which the voltage (0.85V) was applied to the artificial muscle 301, (a) is the figure seen from the opening part 305 side, (b) is a cross section. It is a perspective view. It is a figure which illustrates the voltage bending characteristic of the artificial muscle 301, (a) is a figure explaining the curl amount of the artificial muscle 301, (b) shows the relationship between the voltage applied to the artificial muscle 301 and the curl amount. It is a graph to show. 2 is a cross-sectional view showing a main structure of a control unit 110. FIG. 3 is a cross-sectional view showing a configuration of a noise attenuator 800. FIG. 1 is an external perspective view showing an artificial muscle 903. FIG. 2 is a block diagram illustrating a hardware configuration of a control unit 110. FIG. 2 is a diagram showing a configuration of an A / D converter 1104. FIG. (A) is a figure which illustrates the bit assignment of the digital signal which A / D converter 1104 outputs. FIG. 6B is a diagram illustrating a bit assignment of a digital signal that the CPU 1101 inputs to the D / A converter 1105 in order to control the noise detector 100. FIG. 13C is a diagram illustrating the bit assignment of a digital signal that the CPU 1101 inputs to the D / A converter 1105 in order to control the noise attenuator 800. 4 is a flowchart showing the operation of the control unit 110. It is a flowchart which shows the detail of a noise wavelength specific process (S1401). It is a flowchart which shows the detail of a noise attenuation process (S1402). It is a figure which shows the main structures of the control unit which concerns on the other Example of a noise attenuator. It is a figure explaining operation | movement of the noise detector which concerns on the modification (4) of this invention. It is sectional drawing which shows the main structures of the control unit which concerns on the modification (6) of this invention. It is a graph which illustrates the relationship between the wavelength of electromagnetic wave noise, and electric field strength.

Explanation of symbols

1 ………………………………………… Image forming apparatus 100, 1702 ………………………… Noise detector 110, 1700, 1900 ………… Control unit 200 -203, 1801-1804 ... Noise detection units 301, 903, 1705 ..... Artificial muscle 303 ........ …………………………………………………………………………………………………………………………………………………… ……………… Temperature sensors 503, 1001 …………………… Variable voltage sources 800, 1901, 1902 …………… Noise attenuators 801, 1703 …………………… …… Circuit board 1107 …………………………………… In-machine temperature sensor

Claims (4)

An image forming apparatus including a shield structure that stores a control board that controls the operation of the apparatus,
The shield structure
A reflector that reflects electromagnetic noise generated by the control board toward the control board;
Adjusting means for adjusting the distance between the control board and the reflector,
The adjustment unit adjusts the electromagnetic wave noise incident on the reflecting plate and the electromagnetic wave noise reflected by the reflecting plate to have opposite phases. Adjustment means
First drive means for sliding the reflector;
Second driving means for sliding the first driving means,
The first driving means slides the reflector with higher accuracy than the second driving means,
2. The image forming apparatus according to claim 1, wherein a distance by which the second driving unit can slide the first driving unit is larger than a distance by which the first driving unit can slide the reflecting plate. . The first driving means slides the reflecting plate with an ion conduction actuator,
The image forming apparatus according to claim 2, wherein the second driving unit slides the first driving unit with a rack and pinion mechanism. It has a noise detector that detects the wavelength or frequency of electromagnetic noise,
The image forming apparatus according to claim 1, wherein the adjusting unit slides the reflecting plate in accordance with the wavelength or frequency of the electromagnetic wave noise detected by the noise detector.

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