JP6814413B2 - Sound absorbing device, electronic device and image forming device - Google Patents

Description

The present invention relates to a sound absorbing device using a Helmholtz resonator, and an electronic device and an image forming device using the sound absorbing device.

In the electrophotographic image forming apparatus, driving sounds of various driving units and sounds of rotating polygon mirrors are generated at the time of image formation. Patent Documents 1 and 2 describe an image forming apparatus including a sound absorbing device using a Helmholtz resonator as a configuration capable of absorbing sound generated during image formation.

The Helmholtz resonator is formed by a cavity having a certain volume and a communication portion that communicates the cavity with the outside. Then, assuming that the volume of the cavity is "V", the opening area of the communication part is "S", the length of the communication part in the communication direction is "H", and the sound velocity is "c", the sound absorption using the Helmholtz resonator is used. The frequency "f" of the sound absorbed by the device is obtained by the following equation (1).

（Δｒ：開口端補正）

(Δr: end correction)

As a result of diligent studies by the present inventors on a sound absorbing device equipped with a Helmholtz resonator, the following problems have been found.
That is, when a sound absorbing device equipped with a Helmholtz resonator that absorbs sound of a certain frequency is arranged, the volume of the sound of the frequency to be absorbed by the Helmholtz resonator included in the sound absorbing device is reduced. However, there is a problem that the volume of sound having a frequency different from the frequency to be absorbed is louder than that before the sound absorbing device is installed.
Such a problem is a problem that can occur not only when the sound absorbing portion of the sound absorbing device is a Helmholtz resonator.

The present invention has been made in view of the above problems, and an object of the present invention is a sound absorbing device provided with a sound absorbing unit, which can suppress loudness of sound at a frequency other than the target frequency to be absorbed by the sound absorbing unit. The present invention provides an apparatus, and an electronic device and an image forming apparatus equipped with the apparatus.

In order to achieve the above object, the invention of claim 1 is a sound absorbing device including at least a first sound absorbing unit and a second sound absorbing unit, wherein the first sound absorbing unit has a Helmholtz resonator configuration. With respect to the sound generated by the sound source, the second sound absorbing portion has a region of a first sound absorbing frequency in which the volume decreases and a region of a first volume increasing frequency in which the volume increases, and the second sound absorbing portion has Helmholtz resonance. It has the configuration of a device, and has a second sound absorption frequency region in which the volume decreases and a second volume increase frequency region in which the volume increases with respect to the sound generated by the sound source. The region of the sound absorbing frequency is larger than the region of the first volume increasing frequency, and the region of the first volume increasing frequency and the region of the second sound absorbing frequency are at least in the region of the first volume increasing frequency. It is characterized in that the frequencies having the highest volume are partially overlapped so as to be included in the region of the second sound absorbing frequency .

According to the present invention, in a sound absorbing device provided with a sound absorbing portion, there is an excellent effect that it is possible to suppress an increase in sound at a frequency other than the target frequency to be absorbed by the sound absorbing portion.

The schematic sectional view of the sound absorbing apparatus of Example 1. FIG. The schematic block diagram of the copying machine which concerns on embodiment. Schematic diagram of the vicinity of the photoconductor in the copying machine. Explanatory view of a perspective view of the copier with the front opening / closing cover open. A perspective view of a copying machine in which the exterior cover on the left side is removed from the state shown in FIG. FIG. 5 is a perspective explanatory view of the copying machine in the state of FIG. 5 when the inner surface of the front housing forming plate to which the front inner cover is fixed is viewed from a visible angle. Explanatory drawing of the mounting position of the sound absorbing device in the front inner cover. Schematic diagram of a sound absorbing device using a Helmholtz resonator. An enlarged perspective view of the sound absorbing device of the first embodiment. The graph which shows the experimental result which confirmed the sound absorption effect with and without the sound absorption apparatus made only of a resin material. The graph which added the experimental result which confirmed the sound absorption effect in the state which made the Helmholtz resonator set to 900 [Hz] and 850 [Hz] the sound absorption frequency to the graph shown in FIG. The perspective explanatory view of the sound absorbing apparatus of Example 2. FIG. FIG. 3 is a schematic cross-sectional view of the sound absorbing device of the second embodiment. The graph which shows the experimental result which confirmed the sound absorption effect by the presence or absence of a sound absorption apparatus containing a metal material. A schematic perspective view of the sound absorbing device of the first modification, (a) is an explanatory view of a state in which the sound absorbing cover member and the sound absorbing main body member are assembled, and (b) is an exploded view. A graph plotting the calculation results of the sound absorption frequencies of the seven Helmholtz resonators for each of the states of pattern 1 and pattern 2. Schematic diagram of a sound absorbing device that can automatically change the sound absorbing frequency. FIG. 6 is a block diagram showing a control system of a sound absorbing main body member rotating motor of the sound absorbing device shown in FIG. A schematic perspective view of the sound absorbing device of the second modification, (a) is an explanatory view of a state in which the sound absorbing cover member and the sound absorbing main body member are assembled, and (b) is an exploded view. A graph schematically showing the sound absorption effect of two Helmholtz resonators having different sound absorption frequencies, (a) is a graph in which the sound absorption frequency is set to 930 [Hz], and (b) is a graph in which the sound absorption frequency is set to 770 [Hz]. The set graph.

Hereinafter, an embodiment of an electrophotographic copying machine (hereinafter, simply referred to as “copying machine 500”) as an image forming apparatus to which the present invention is applied will be described. In the present embodiment, the monochrome image forming apparatus will be described as an example of the copying machine 500, but the same can be applied to a known color image forming apparatus.

First, the configuration of the copying machine 500 will be described.
FIG. 2 is a schematic configuration diagram of the entire copying machine 500 according to the present embodiment. In FIG. 2, the image reading device 200 is mounted on the copying machine main body 100 of the copying machine 500, and the copying machine main body 100 is placed on the recording paper bank 300. An automatic document transfer device 400 that is rotatably configured with the back side (the back side of the paper in the drawing) as a fulcrum is mounted on the image reading device 200.

Inside the copying machine main body 100, a drum-shaped photoconductor 10 is provided as a latent image carrier. FIG. 3 is a schematic configuration diagram in which the vicinity of the photoconductor 10 is enlarged. As shown in FIG. 3, a static elimination lamp 9, a charging device 11 using a charging roller, a developing device 12, a transfer unit 13, and a cleaning device 14 having a photoconductor cleaning blade 8 are arranged around the photoconductor 10. There is. The developing apparatus 12 uses a polymerized toner produced by a polymerization method as a toner, and attaches the polymerized toner to an electrostatic latent image on the photoconductor 10 by using a developing roller 121 as a developing agent carrier, and attaches the polymerized toner to the electrostatic latent image. Make a visible image.

The transfer unit 13 includes a transfer belt 17 that is hung around two roller members, a first belt tension roller 15 and a second belt tension roller 16, and the transfer belt 17 is photosensitive at the transfer position B. It is pressed against the peripheral surface of the body 10.

Foreign matter such as residual toner and paper dust remaining on the transfer belt 17 after the recording paper P is separated is provided in the transfer belt cleaning section C and comes into contact with the first belt tension roller 15 via the transfer belt 17. It is scraped off by the belt cleaning blade 18.

Further, the copying machine main body 100 is provided with a toner replenishing device 20 for replenishing the developing device 12 with new toner on the left side of the drawing of the charging device 11 and the cleaning device 14.

Further, the copying machine main body 100 is provided with a recording paper conveying device 60 that conveys the recording paper P sent out from the recording paper cassette 61 of the recording paper bank 300 to the discharge stack portion 39 via the transfer position B. The recording paper transport device 60 transports the recording paper P along the supply path R1, the manual feed supply path R2, and the recording paper transport path R. A resist roller pair 21 is provided on the recording paper transport path R on the upstream side in the recording paper transport direction with respect to the transfer position B.

On the other hand, a heat fixing device 22 is provided on the downstream side of the recording paper transport path R in the recording paper transport direction with respect to the transfer position B. In the heat fixing device 22, the recording paper P is sandwiched between the heating roller 30 which is a heating member and the pressure roller 32 which is a pressure member, and heat pressure fixing is performed.

A discharge branch claw 34, a discharge roller 35, a first pressure roller 36, a second pressure roller 37, and a stiff roller 38 are provided further downstream of the heat fixing device 22 in the recording paper transport direction. Further, a discharge stack portion 39 for stacking the image-formed recording paper P that has passed through the heat fixing device 22 is also provided.

Further, the copying machine main body 100 is provided with a switchback device 42 on the right side in the drawing. In this switchback device 42, the reversing path R3 branched from the position where the discharge branch claw 34 of the recording paper transport path R is arranged and the recording paper P passing through the reversing path R3 are resisted again on the recording paper transport path R. The recording paper P is conveyed along the reconveying path R4 that leads to the position of the roller pair 21. The reversing path R3 is provided with a switchback roller pair 43, and the reconveying path R4 is provided with a plurality of recording paper transport roller pairs 66.

As shown in FIG. 2, the copying machine main body 100 is provided with a laser writing device 47 on the left side of the drawing of the developing device 12. The laser writing device 47 includes a scanning optical system such as a laser light source, a polygon mirror 48 which is a rotating multifaceted mirror for scanning, a polygon motor 49, and an fθ lens.

Further, the image reading device 200 includes a light source 53, a plurality of mirrors 54, an optical lens 55 for imaging, an image sensor 56 such as a CCD image sensor, and the like, and a contact glass 57 is provided on the upper surface thereof.
Further, the automatic document transfer device 400 is provided with a document set table, and a document stack table is provided at a document ejection position. The automatic document transfer device 400 includes a plurality of document transfer rollers, and the document is transferred from the document set table to the document stack table via the scanning position on the contact glass 57 of the image reading device 200. To.

The recording paper bank 300 is provided with a plurality of recording paper cassettes 61 for accommodating recording paper P such as paper as a recording material and an OHP film. Each recording paper cassette 61 is provided with a calling roller 62, a supply roller 63, and a separation roller 64, respectively. On the right side of the chart of the recording paper cassette 61, the above-mentioned supply path R1 leading to the recording paper transport path R of the copying machine main body 100 is formed. The supply path R1 is also provided with several recording paper transport roller pairs 66 for transporting the recording paper P.

The copying machine main body 100 is provided with a manual paper feed unit 68 on the right side in FIG. A manual feed tray 67 is provided in the manual feed feed section 68 so as to be openable and closable, and the above-mentioned manual feed supply path R2 for guiding the recording paper P set on the manual feed tray 67 to the recording paper transport path R is formed. ing. Similar to the recording paper cassette 61, the manual paper feed unit 68 is also provided with a calling roller 62, a supply roller 63, and a separation roller 64.

Next, the operation of the copying machine 500 will be described.
When making a copy using the copier 500, first, the main switch is turned on and the original is set on the original set table of the automatic original transfer device 400. In the case of a book document, the automatic document transfer device 400 is opened, the document is set directly on the contact glass 57 of the image reading device 200, the automatic document transfer device 400 is closed, and the document is pressed by the contact glass 57.

After that, when the start switch is pressed, when a document is set in the automatic document transfer device 400, the document is moved to the contact glass 57 through the document transfer path by the document transfer roller, and then the image reading device 200 is driven. Then, the contents of the original are read and ejected onto the original stack table.
On the other hand, when the original is set directly on the contact glass 57, the image reading device 200 is immediately driven to read the original contents.
When reading the contents of the document, the image reading device 200 irradiates the document surface on the contact glass 57 with the light from the light source 53 while moving the light source 53 along the contact glass 57. Then, the reflected light is guided to the imaging optical lens 55 by a plurality of mirrors 54 and put into the image sensor 56, and the content of the document is read by the image sensor 56.

In the copying machine 500, the photoconductor 10 is rotated by the photoconductor drive motor at the same time as reading the contents of the document. Then, first, the surface of the photoconductor 10 is uniformly charged, for example, around −1000 [V] by the charging device 11. Next, the photoconductor 10 is irradiated with laser light from the laser writing device 47 according to the content of the document read by the above-mentioned image reading device 200 to perform laser writing, and an electrostatic latent image is formed on the surface of the photoconductor 10. The surface potential of the portion irradiated with the laser beam (latent image portion) is, for example, 0 [V] to −200 [V]. After that, toner is adhered to the electrostatic latent image by the developing device 12, and this is visualized.

At the same time as the start switch is pressed, the copying machine 500 sends out the recording paper P from the plurality of recording paper cassettes 61 included in the recording paper bank 300 corresponding to the selected size by the calling roller 62. Then, the sent out recording paper P is separated one by one by the supply roller 63 and the separation roller 64, and the one sheet is guided to the supply path R1 and guided to the recording paper transfer path R by the recording paper transfer roller pair 66. .. The recording paper P conveyed to the recording paper transport path R abuts on the resist roller pair 21 and is stopped.

When using the manual feed feed unit 68, the manual feed tray 67 is opened and the recording paper P is set therein. Also in this case, only one sheet of the recording paper P set on the bypass tray 67 is conveyed to the bypass supply path R2 by the calling roller 62, the supply roller 63, and the separation roller 64, and the recording paper is conveyed by the recording paper transfer roller vs. 66. You will be led to Road R. The recording paper P guided to the recording paper transport path R abuts on the resist roller pair 21 and is stopped.
In this way, the recording paper P stopped by the resist roller pair 21 starts rotating at the timing when the tip of the visible toner image of the photoconductor 10 enters the transfer position B. By pair 21, it is sent to the transfer position B.

The toner image on the photoconductor 10 is transferred by the transfer unit 13 on the recording paper P fed to the transfer position B, and the toner image is supported on the surface thereof. The residual toner remaining on the surface of the photoconductor 10 after transfer is removed by the cleaning device 14, and the residual potential on the photoconductor 10 is also removed by the static elimination lamp 9. By removing the residual potential, the surface potential is averaged to a reference potential of 0 [V] to −150 [V] to prepare for the next image formation starting from the charging device 11.

On the other hand, the recording paper P carrying the toner image is conveyed by the transfer belt 17 and enters the heat fixing device 22. Then, heat and pressure are applied while being conveyed between the heating roller 30 and the pressure roller 32, and the toner image on the recording paper P is fixed. After that, the recording paper P is stiffened by the discharge roller 35, the first pressure roller 36, the second pressure roller 37, and the stiff roller 38, is discharged onto the discharge stack portion 39, and is stacked there. ..

When forming an image on both sides of the recording paper P, the discharge branch claw 34 is switched, the toner image is transferred to one side of the recording paper P and fixed, and then the recording paper P is reversed from the recording paper transport path R. Put in R3. The recording paper P put in the reversing path R3 is conveyed by the recording paper conveying roller pair 66 and put into the switchback position 44, then switched back by the switchback roller pair 43, and this time put in the re-conveying path R4 for recording. The paper transport roller pair 66 guides the recording paper transport path R again. Then, the toner image is transferred to the opposite surface of the recording paper P that has passed through the reconveying path R4 in the same manner as described above.

FIG. 4 is a perspective explanatory view of the copying machine 500 in a state where the front opening / closing cover 101 is opened.
The copying machine 500 shown in FIG. 4 is in a state in which the automatic document transporting device 400 and the optical system inside the image reading device 200 are removed. Further, by opening the front opening / closing cover 101 which is the exterior cover, the front inner cover 102 which is the interior cover is exposed. Further, in the copying machine 500 shown in FIG. 4, the toner bottle provided in the toner replenishing device 20 is removed, and the bottle set hole 20a, which is a portion of the front inner cover 102 into which the toner bottle is inserted, is opened. ing. Further, below the front opening / closing cover 101 of the copying machine 500, a recording paper cassette exterior cover 61a provided with a handle for pulling out the recording paper cassette 61 is arranged.

FIG. 5 is a perspective view of the copying machine 500 in which the left side exterior cover 103 is removed from the state shown in FIG. 4 and the left side housing 520 is exposed. FIG. 6 is a perspective description of the copying machine 500 in the state of FIG. 5 when the inner surface of the front housing 510 provided inside the front inner cover 102 and to which the front inner cover 102 is fixed is viewed from a visible angle. It is a figure.
As shown in FIG. 6, the copying machine 500 is provided with a sound absorbing device 600 using a Helmholtz resonator, which will be described in detail later, at a position facing the laser writing device 47 inside the front surface.

FIG. 7 is an explanatory view of the mounting position of the sound absorbing device 600 on the front inner cover 102. As shown in FIG. 7, the front inner cover 102 includes a sound absorbing device installation portion 160 on the inner surface thereof. Then, as shown by the arrow in FIG. 7, the sound absorbing device 600 is attached to and fixed to the sound absorbing device installation portion 160, and the front inner cover 102 is fixed to the front housing 510. As a result, as shown in FIG. 6, the sound absorbing device 600 protrudes inward from the opening 510a for installing the sound absorbing device, which is an opening formed in the front housing 510. The sound absorbing device 600 is a sound absorbing device using a Helmholtz resonator.

FIG. 8 is a schematic view of a sound absorbing device 600 using a Helmholtz resonator.
As shown in FIG. 8, the Helmholtz resonator is shaped like a container with a narrow inlet, and is composed of a cavity portion 601 having a certain volume and a communication portion 603 smaller than the cavity portion 603, and the communication portion 603 has a communication portion 603. Absorbs incoming sound of a specific frequency.
The volume of the cavity 601 is "V", the opening area of the opening 602 in the communication portion 603 is "S", the length of the communication portion 603 is "H", the sound velocity is "c", and the sound absorption frequency in the sound absorbing device 600. If is "f", the following equation (1) holds.

（Δｒ：開口端補正）

(Δr: end correction)

“Δr” in the equation (1) is an end correction, and generally, “Δr = 0.6r” is used when the radius of the communication portion 603 is circular and the radius is “r”.
As shown in the equation (1), the frequency of the sound absorbed by the sound absorbing device 600 can be obtained from the volume V of the cavity portion 601, the length H of the communicating portion 603, and the opening area S of the communicating portion 603.

In the copying machine 500, various sounds such as a driving sound of a drive motor that transmits rotational driving to various rollers, a moving sound of moving members such as various rollers, and a rotating sound of a polygon mirror 48 of a laser writing device 47 are generated. .. Such a sound may be transmitted to the outside of the copying machine 500 and become a noise that causes discomfort to people in the vicinity. By forming the sound absorbing device 600 in accordance with the frequency of the sound whose transmission to the outside is desired to be suppressed among such sounds that can be noise, the sound that can be noise can be absorbed by the sound absorbing device 600.

Since the copying machine 500 is provided with an exterior cover, sound leakage to some extent can be prevented. As a result of diligent studies by the present inventors, the following was found. That is, for sounds having a frequency higher than 1500 [Hz] to some extent, sound leakage to the outside can be sufficiently suppressed by the exterior cover. However, for sounds with a low frequency of 1500 [Hz] or less, sound leakage to the outside cannot be sufficiently suppressed by the exterior cover alone.
Therefore, by setting the frequency (sound absorption frequency) of the sound absorbed by the sound absorbing device 600 using the Hertz Holtz resonator to 1500 [Hz] or less, the sound leakage of the sound having a frequency that cannot be sufficiently suppressed by the exterior cover Can be suppressed.
In addition, it is difficult for the human ear to hear low-frequency sounds, and in most cases, noise above 200 [Hz] is a problem with ordinary image forming devices, and sound absorbing devices that absorb sound below 100 [Hz] are set. Since it is difficult, the sound absorbing frequency of the sound absorbing device 600 is set to 100 [Hz] or more.

[Example 1]
Hereinafter, the first embodiment of the sound absorbing device 600 of the present embodiment (hereinafter referred to as “Example 1”) will be described.
FIG. 9 is an enlarged perspective view of the sound absorbing device 600 of the first embodiment, and FIG. 1 is a schematic cross-sectional view of the sound absorbing device 600 of the first embodiment attached to the front inner cover 102. The sound absorbing device 600 of the first embodiment is obtained by applying the characteristic configuration of the present embodiment to the sound absorbing device 600 shown in FIGS. 6 and 7. As shown in FIGS. 9 and 1, the sound absorbing device 600 is a three-body sound absorbing device including a sound absorbing main body member 610, a sound absorbing cover member 620, and a sound absorbing cap member 630. The sound absorbing cover member 620 is fixed to the sound absorbing main body member 610 by the cover fixing screw 640, and the sound absorbing main body member 610 is fixed to the front inner cover 102 by the main body fixing screw 650.

As shown in FIG. 1, the sound absorbing device 600 includes three Helmholtz resonators 670 (first resonator 670a, second resonator 670b, third resonator) by a set of sound absorbing cover member 620 and sound absorbing main body member 610. 670c) is formed.
The sound absorbing main body member 610 includes a main body side wall portion 611 (611a to 611c) forming a side surface of the hollow portion 601 (601a to 601c) of each Helmholtz resonator 670. On the other hand, the sound absorbing cover member 620 includes a cavity upper surface portion 623 (623a to 623c) forming the upper surface of the cavity portion 601 (601a to 601c) of each Helmholtz resonator 670. Further, the sound absorbing cap member 630 (630a to 630c) is attached to each of the three openings formed in the sound absorbing cover member 620.

The sound absorbing device 600 shown in FIG. 1 is a separate member of the sound absorbing cover member 620 forming the wall surface provided with the communicating portion 603 (603a to 603c) and the sound absorbing cap member 630 (630a to 630c) forming the communicating portion 603. It is supposed to be. As a result, by replacing the sound absorbing cap member 630 with a different shape, the values of the length H of the communication portion 603 and the opening area S of the communication portion 603 in the above equation (1) can be easily changed, which is inexpensive and easy. The sound absorption frequency can be changed.

The sound absorbing device 600 using the Helmholtz resonator silences sound of a specific frequency as a noise countermeasure for electronic devices. In an image forming apparatus having a plurality of printing speeds, the frequency of sound that can be noise differs depending on the printing speed. The sound absorbing device 600 has a configuration in which the sound absorbing cap member 630 is a separate member from the sound absorbing main body member 610 and the sound absorbing cover member 620 forming the wall surface of the cavity portion 601. In such a sound absorbing device 600, by exchanging the sound absorbing cap member 630, the sound absorbing frequency can be easily changed to the sound absorbing frequency according to each printing speed at low cost.

Further, in the configuration in which the wall surface of the cavity portion 601 is formed of two members, the sound absorbing main body member 610 and the sound absorbing cover member 620, as in the sound absorbing device 600 shown in FIG. 1, the joint portion is formed due to a manufacturing error or an assembly error of the members. There may be a gap. If a gap is formed in the joint portion, the airtightness of the cavity portion 601 cannot be ensured, and a desired sound absorption effect cannot be obtained.

To solve such a problem, it is conceivable to provide a concave portion in the joint portion of the sound absorbing cover member 620 with the sound absorbing main body member 610, and to provide a sealing member made of an elastic material in the concave portion. By providing the sealing member in the concave portion, when the sound absorbing cover member 620 and the sound absorbing main body member 610 are joined, the sealing member is sandwiched between the two members and pressed, so that the sound absorbing cover member 620 and the sound absorbing cover member 620 and It can be deformed along the surface of the sound absorbing main body member 610 to close the gap.

However, if only the sealing member is provided in the concave portion, when the sound absorbing cover member 620 vibrates with respect to the sound absorbing main body member 610, the shape of the cavity portion 601 may change or a gap may be generated in the joint portion. , There is a risk that the desired sound absorption effect cannot be obtained.
In the sound absorbing device 600 shown in FIG. 1, the sound absorbing cover member 620 and the sound absorbing main body member 610 sandwich the sealing member, and the sound absorbing cover member 620 and the sound absorbing main body member 610 are held in a state in which the sealing member is deformed as compared with that before pressurization. A cover fixing screw 640 for fixing is provided.
By fixing the sound absorbing cover member 620 and the sound absorbing main body member 610 with the cover fixing screw 640, pressure is applied to the joint portion between the sound absorbing cover member 620 and the sound absorbing main body member 610. Then, the sealing member arranged in the concave portion, which is the joint portion, is crushed to close the gap between the joint portion between the sound absorbing cover member 620 and the sound absorbing main body member 610, and the sealing portion of the cavity portion 601 can be improved, so that the sound absorbing effect can be improved. Will increase.
Further, since the sealing member made of the elastic material is crushed and the sound absorbing cover member 620 and the sound absorbing main body member 610 are fixed, the vibration of the sound absorbing cover member 620 with respect to the sound absorbing main body member 610 can be reduced, so that a higher sound absorbing effect is expected. become able to.

If a fixing member such as the cover fixing screw 640 is inside the cavity portion 601, the function as a Helmholtz resonator is deteriorated. In the sound absorbing device 600 shown in FIG. 1, since the cover fixing screw 640, which is a fixing member, is installed outside the cavity portion 601, the function as a Helmholtz resonator is deteriorated due to the provision of the fixing member. Can be prevented.

In the sound absorbing device 600 shown in FIG. 1, the sealing member is pushed by the tip of the main body side wall portion 611, which is a portion forming the cavity portion 601 of the sound absorbing main body member 610, and is deformed along the surface of the main body side wall portion 611. It even touches the sides. As a result, the sealing member closes the gap between the main body side wall portion 611 of the sound absorbing main body member 610 and the concave portion of the sound absorbing cover member 620.
As the material of the sound absorbing cover member 620, the sound absorbing main body member 610, and the sound absorbing cap member 630, resin materials such as polycarbonate and ABS resin can be used, but the material is not limited thereto.

Next, the feature portion of the sound absorbing device 600 of the first embodiment will be described.
In the sound absorbing device 600, the sound absorbing frequency of the second resonator 670b out of the three Helmholtz resonators 670 is set to the frequency of the sound whose volume is increased by providing the first resonator 670a. Further, the sound absorption frequency of the third resonator 670c is set to the frequency of the sound whose volume is increased by providing the second resonator 670b. Specifically, the sound absorption frequency of the first resonator 670a is set to 900 [Hz], the sound absorption frequency of the second resonator 670b is set to 850 [Hz], and the sound absorption frequency of the third resonator 670c is set to 800 [Hz]. There is.

FIG. 10 is a graph showing the experimental results of confirming the sound absorbing effect with and without the sound absorbing device 600 made of only the resin material whose sound absorbing frequency is set to 900 [Hz]. In the graph shown in FIG. 10, a sound absorbing device 600 in front of a speaker that emits sound over a wide area is arranged, and a microphone as a measuring device is arranged on the opposite side of the speaker with the sound absorbing device 600 in between for measurement. The horizontal axis in FIG. 10 indicates the frequency, and the vertical axis indicates the measurement result of the volume (sound pressure) of each frequency. The graph shown by the solid line in bold in FIG. 10 is a measurement result when the communication portion 603 of the sound absorbing device 600 is covered so as not to function as a Helmholtz resonator. The graph shown by the broken line in FIG. 10 is a measurement result when the lid is removed from the communication portion 603 of the sound absorbing device 600 to function as a Helmholtz resonator having a sound absorbing frequency of 900 [Hz].

In the graph shown in FIG. 10, the volume of the sound near 900 [Hz], which is the sound absorption frequency, is reduced by using the Helmholtz resonator, but the sound having a frequency of about 830 [Hz] to 870 [Hz] is reduced. , The volume is higher than when the Helmholtz resonator is not used. That is, it can be seen that by providing the sound absorbing device 600 using the Helmholtz resonator, the sound absorbing effect is deteriorated for sounds having a certain frequency range.

As a result of diligent studies by the present inventors, the Helmholtz resonator deteriorates the sound absorption effect for a sound having a frequency as low as 50 [Hz] to 200 [Hz] with respect to the sound absorption frequency, that is, the volume becomes louder. It turns out that it can get bigger. Furthermore, as a result of diligent studies by the present inventions, it has been found that the frequency of sound at which the sound absorption effect deteriorates tends to depend on the material of the member forming the Helmholtz resonator. Specifically, in the sound absorbing device 600 made of only a resin material like the sound absorbing device 600 of the first embodiment, the sound absorbing effect deteriorates in the sound having a frequency about 30 [Hz] to 70 [Hz] lower than the sound absorbing frequency. .. Further, in the sound absorbing device 600 containing a metal material such as the sound absorbing device 600 of the second embodiment described later, the sound absorbing effect is deteriorated in the sound having a frequency about 70 [Hz] to 200 [Hz] lower than the sound absorbing frequency.

FIG. 11 shows the sound absorption effect in the state in which the Helmholtz resonator whose sound absorption frequency is set to 900 [Hz] and the Helmholtz resonator whose sound absorption frequency is set to 850 [Hz] are functioning in the graph shown in FIG. It is a graph in which the confirmed experimental results are added with fine solid lines. The graph shown by the solid line in bold and the graph shown by the broken line in FIG. 11 are the same as the graph shown in FIG.
As shown in FIG. 11, by adding a Helmholtz resonator whose sound absorption frequency is set to 850 [Hz], the sound absorption effect is deteriorated only by the Helmholtz resonator whose sound absorption frequency is set to 900 [Hz]. The increase in volume can be suppressed.

The sound absorbing device 600 of the first embodiment includes three Helmholtz resonators 670, and the sound absorbing frequencies of the Helmholtz resonators 670 are set at specific intervals (50 [Hz]). As a result, the sound of the frequency at which the sound absorption effect deteriorates by providing the first resonator 670a having the highest sound absorption frequency is absorbed by the second resonator 670b, and the sound absorption effect deteriorates by providing the second resonator 670b. The sound of frequency can be absorbed by the third resonator 670c. Therefore, in the sound absorbing device 600 of the first embodiment, the Helmholtz resonator 670 is provided, and one Helmholtz resonator 670 absorbs sound so as to compensate for the frequency at which the sound absorbing effect deteriorates, and the sound of a frequency other than the sound absorbing frequency becomes loud. It becomes possible to suppress the occurrence.

If there is only one sound absorption frequency, the effect of sound absorption over a wide range of frequencies will be diminished as a whole. By providing a plurality of Helmholtz resonators having different sound absorption frequencies, the sound absorbing device 600 of the first embodiment can obtain a sound absorbing effect not only for a specific frequency but also for a sound having a frequency over a wide range. The sound absorbing device 600 of the first embodiment includes three Helmholtz resonators 670, but if one Helmholtz resonator 670 absorbs sound at a frequency at which the sound absorbing effect deteriorates with the other Helmholtz resonator 670, two Helmholtz resonators 670 are provided. However, it may be four or more.

[Example 2]
Hereinafter, a second embodiment of the sound absorbing device 600 of the present embodiment (hereinafter referred to as “Example 2”) will be described.
FIG. 12 is a perspective explanatory view of the sound absorbing device 600 of the second embodiment, and FIG. 13 is a schematic cross-sectional view of the sound absorbing device 600 of the second embodiment in the dd cross section in FIG. The sound absorbing device 600 of the second embodiment is composed of two members, a sound absorbing main body member 610 made of a resin material and a sound absorbing cover member 620 made of a metal material (sheet metal). Further, a plurality of Helmholtz resonators 670 (four in the cross section shown in FIG. 13) are formed by a set of the sound absorbing cover member 620 and the sound absorbing main body member 610.

As shown in FIG. 13, the sound absorbing cover member 620 made of sheet metal is provided with flange portions 625 forming a plurality of communicating portions 603. The sound absorbing device 600 of the second embodiment is provided with a flange portion 625 which is an upright portion so as to stand up in the communication direction with respect to the plate-shaped portion of the sound absorbing cover member 620, and is provided inside the hollow portion 601. The flange portion 625 stands upright toward it.
The sound absorbing main body member 610 made of a resin material is provided with a main body side wall portion 611 which is a partition for forming a plurality of hollow portions 601. One Helmholtz resonator 670 is formed by each communication portion 603 and the cavity portion 601, and the frequency (sound absorption frequency) of the sound to be absorbed is determined by the shape.

In the sound absorbing device 600 of the second embodiment, the sound absorbing frequency of the second resonator 670b out of the four Helmholtz resonators 670 is set to the frequency of the sound whose volume is increased by providing the first resonator 670a. Further, the sound absorption frequency of the third resonator 670c is set to the frequency of the sound whose volume is increased by providing the second resonator 670b. Further, the sound absorption frequency of the fourth resonator 670d is set to the frequency of the sound whose volume is increased by providing the third resonator 670c. Specifically, the sound absorption frequency of the first resonator 670a is 800 [Hz], the sound absorption frequency of the second resonator 670b is 700 [Hz], the sound absorption frequency of the third resonator 670c is 600 [Hz], and the fourth resonance. The sound absorption frequency of the device 670d is set to 500 [Hz].

The sound absorbing cover member 620 has a flange portion 625 formed by burring, and the inside of the flange portion 625 serves as a communication portion 603 having an opening area S and a length H. The sound absorbing cover member 620 and the sound absorbing main body member 610 are brought into close contact with each other by screwing, insert molding, or the like, and the cavity portion 601 having a volume V is formed by this close contact.
Here, burring is to make a hole called a pilot hole in the plate material, push a punch with a diameter larger than the pilot hole into the pilot hole, stand while widening the edge of the pilot hole, and form a flange around the opening. It is a processing method. By forming the communication portion 603 by burring, the opening 602 without separately providing a member for forming the communication portion 603 with respect to the sound absorbing cover member 620 forming a part of the wall surface forming the cavity portion 601. It is possible to form a communication portion 603 having the above.

Further, in the sound absorbing device 600 of the second embodiment, the sound absorbing frequencies of the four Helmholtz resonators 670 are made different by making the values of the burring heights (t1, t2, t3 and t4 in FIG. 13) different. ing. Since the sound absorption frequencies can be made different without changing the shape of the cavity portion 601, a plurality of Helmholtz resonators 670 can be efficiently arranged at equal intervals.

FIG. 14 shows the experimental results confirming the sound absorbing effect with and without the sound absorbing device 600 in which the sound absorbing cover member 620 uses sheet metal and the sound absorbing main body member 610 uses a resin material and the sound absorbing frequency is set to 930 [Hz]. It is a graph which shows. In the graph shown in FIG. 14, similarly to the graph shown in FIG. 10, a sound absorbing device 600 is arranged in front of the speaker that emits a wide range of sound, and a microphone as a measuring device is arranged on the opposite side of the speaker with the sound absorbing device 600 in between. And measured.
The horizontal axis in FIG. 14 indicates the frequency, and the vertical axis indicates the measurement result of the volume (sound pressure) of each frequency. The graph shown by the solid line in bold in FIG. 14 is a measurement result when the communication portion 603 of the sound absorbing device 600 is covered so as not to function as a Helmholtz resonator. The graph shown by the broken line in FIG. 14 is a measurement result when the lid is removed from the communication portion 603 of the sound absorbing device 600 to function as a Helmholtz resonator having a sound absorbing frequency of 930 [Hz].

In the graph shown in FIG. 14, the volume of the sound near 930 [Hz], which is the sound absorption frequency, is reduced by using the Helmholtz resonator, but the sound having a frequency of about 700 [Hz] to 830 [Hz] is reduced. , The volume is higher than when the Helmholtz resonator is not used. That is, it can be seen that by providing the sound absorbing device 600 using the Helmholtz resonator, the sound absorbing effect is deteriorated for sounds having a certain frequency range.

In the sound absorbing device 600 using a metal material for the sound absorbing cover member 620 as in the second embodiment, as shown in FIG. 14, the sound absorbing effect is obtained at a frequency about 70 [Hz] to 200 [Hz] lower than the sound absorbing frequency. Getting worse. In order to absorb sound having a frequency in a range in which the sound absorbing effect is deteriorated, the four Helmholtz resonators 670 having the cross section shown in FIG. 13 of the sound absorbing device 600 of the second embodiment set the sound absorbing frequency at a specific interval (100 [Hz]). ]) Is set.

As a result, the sound of the frequency at which the sound absorption effect deteriorates by providing the first resonator 670a having the highest sound absorption frequency is absorbed by the second resonator 670b, and the sound absorption effect deteriorates by providing the second resonator 670b. The sound of frequency can be absorbed by the third resonator 670c. Further, by providing the third resonator 670c, the sound of the frequency at which the sound absorption effect is deteriorated can be absorbed by the fourth resonator 670d. Therefore, in the sound absorbing device 600 of the second embodiment, the Helmholtz resonator 670 is provided, and one Helmholtz resonator 670 absorbs sound so as to supplement the sound having a frequency at which the sound absorbing effect deteriorates, and the sound has a frequency other than the sound absorbing frequency. Can be suppressed from becoming large.

Polycarbonate and ABS resin can be used as the resin material used for the sound absorbing main body member 610 of the sound absorbing device 600 of the second embodiment, but the resin material is not limited thereto. Further, as the sheet metal used for the sound absorbing cover member 620 of the sound absorbing device 600 of the second embodiment, an iron plate such as a galvanized steel plate can be used, but one made of other metals such as aluminum may also be used.

The sound absorbing device 600 of the second embodiment can be attached to an exterior cover such as the front opening / closing cover 101 of the copying machine 500. In this case, the sound absorbing body member 610 formed of the resin material is integrally formed on the inner surface of the exterior cover made of the resin material, and the sound absorbing cover member 620 is fixed to the sound absorbing body member 610 formed on the exterior cover. May be. By providing the sound absorbing device 600 on the outer cover, it is possible to absorb the sound that is about to leak to the outside through the outer cover. Further, the number of parts can be reduced by integrally forming at least a part of the sound absorbing device 600 as a part of the exterior cover.

In the sound absorbing device 600 of the first embodiment and the second embodiment, the second resonator 670b that absorbs sound at a frequency at which the sound absorbing effect deteriorates by arranging the first resonator 670a is placed next to the first resonator 670a. A resonator 670b is arranged. The same applies to the arrangement of the third resonator 670c and the fourth resonator 670d. This makes it easier for another Helmholtz resonator to absorb sound at a frequency at which the sound absorption effect has deteriorated in one Helmholtz resonator.

In the first and second embodiments, the specific interval of the sound absorption frequency between the plurality of Helmholtz resonators is determined by the material of the member forming the Helmholtz resonator. Specifically, in the sound absorbing device 600 of Example 1 made of only a resin material, a specific interval of the sound absorbing frequency is set to 50 [Hz], and in the sound absorbing device 600 of Example 2 including a metal material, the sound absorbing frequency is set. A specific interval is set to 100 [Hz]. The specific interval between the sound absorption frequencies of the Helmholtz resonators is not limited to that determined by the material of the member forming the Helmholtz resonator.

For example, it may be determined as follows. First, when a Helmholtz resonator created so that the frequency of the sound most desired to be absorbed in the sound generated from the sound source is the sound absorption frequency, the frequency of the sound whose volume becomes louder is measured experimentally. Another Helmholtz resonator is created so that the frequency of the sound whose volume increases by this measurement becomes the sound absorption frequency, and when this Helmholtz resonator is used, the frequency of the sound whose volume increases is further measured by experiments. In this way, the frequency at which the volume actually increases with the Helmholtz resonator is measured experimentally, and a Helmholtz resonator whose sound absorption frequency is the frequency is created and combined.

As shown in FIG. 6, the sound absorbing device 600 of the first embodiment is arranged at a position facing the laser writing device 47, and can hear the rotation sound of the polygon mirror 48 of the laser writing device 47 and the driving sound of the polygon motor 49. Sound can be absorbed efficiently. As the sound absorbing device having the characteristic configuration of the present embodiment, it may be appropriately arranged at another position of the image forming device as in the exterior cover of the second embodiment.

[Modification 1]
Next, as a sound absorbing device to which the characteristic configuration of the present embodiment can be applied, a first modification of the sound absorbing device 600 (hereinafter referred to as “modification example 1”) will be described.
FIG. 15 is a schematic perspective view of the sound absorbing device 600 of the first modification, FIG. 15 (a) is an explanatory view of a state in which the sound absorbing cover member 620 and the sound absorbing main body member 610 are assembled, and FIG. 15 (b) is an explanatory view. It is explanatory drawing of the state which disassembled the sound absorption cover member 620 and the sound absorption main body member 610.
As shown in FIG. 15, the sound absorbing device 600 of the first modification is a cylindrical sound absorbing device using a Helmholtz resonator.

The sound absorbing cover member 620 forms a wall surface provided with a communication portion 603 communicating with the outside among the wall surfaces forming the cavity portion 601 of the Helmholtz resonator, and the neck portion 1603 (1603a) forming a hole portion to be the communication portion 603. ~ 1603d) is provided in plurality (four).
The sound absorbing main body member 610 forms a wall surface other than the wall surface provided with the communication portion 603 among the wall surfaces forming the hollow portion 601 by the main body side wall portion 611. Further, the sound absorbing main body member 610 has a plurality of opening space portions 1601 (1601a to 1601d) which are surrounded by the wall surface of the main body side wall portion 611 and become a hollow portion 601 by closing the opening with the sound absorbing cover member 620. One) is formed.

In the sound absorbing device 600 of the first modification, one Helmholtz resonator 670 is formed by assembling the sound absorbing cover member 620 and the sound absorbing main body member 610 so that one neck portion 1603 and one opening space portion 1601 face each other. .. In the first modification, the four Helmholtz resonators 670 are formed by assembling the four neck portions 1603 (1603a to 1603d) so as to face the four opening space portions 1601 (1601a to 1601d).

The opening area of the hole formed by the neck portion 1603 becomes the opening area of the communication portion 603 at the time of assembly, and becomes "S" of the above formula (1). Further, the length of the hole formed by the neck portion 1603 is the length of the communication portion 603 at the time of assembly, which is "H" in the above equation (1). Further, the volume of the opening space portion 1601 becomes the volume of the cavity portion 601 at the time of assembly, which is the “V” of the above equation (1).
Then, from the above equation (1), the sound absorption frequency (resonance frequency) in one Helmholtz resonator 670 is determined by these three parameters excluding the sound velocity "c".

In the first modification, either or both of the parameters of the neck portion 1603 (the above-mentioned "S" or "H") and the parameters of the opening space portion 1601 (the above-mentioned "V") are set to be different. The different parameters of the neck 1603 mean that one of the four neck 1603s has at least one of the other three neck 1603s and the opening area (“S”) or length (“H” above) of the hole. ) At least one of the parameters is different. Further, when the parameters of the opening space 1601 are different, one of the four opening spaces 1601 has a different volume (“V”) parameter from at least one of the other three opening spaces 1601. It is in a state.

As shown by the arrow α in FIG. 15 (a), a certain neck portion is formed by rotating the sound absorbing main body member 610 in which the opening space portion 1601 is formed with respect to the sound absorbing cover member 620 provided with the neck portion 1603. The combination of the opening space 1601 facing the 1603 changes. This makes it possible to change the sound absorption frequency of a Holmholtz resonator formed by a neck 1603.
In FIG. 15, the sound absorbing main body member 610 is rotated with respect to the sound absorbing cover member 620, but the sound absorbing main body member 620 may be rotated with respect to the sound absorbing main body member 610.

An example in which the sound absorbing device 600 similar to the first modification is provided with seven neck portions 1603 and seven opening space portions 1601, and the sound absorbing frequency changes when the combination of the neck portion 1603 and the opening space portion 1601 is changed. Is shown in Table 1.

In Table 1, the opening space 1601 is indicated by (1) to (7), and the neck 1603 is indicated by (a) to (g). The sound absorbing main body member 610 of the example shown in Table 1 includes four opening spaces 1601 having a volume of 8000 [mm ³ ] and ^three opening spaces 1601 having a volume of 16000 [mm ³ ], and has seven opening spaces. The portions 1601 are arranged in a circumferential shape. Further, the sound absorbing cover member 620 shown in Table 1 is provided with seven necks 1603 having hole lengths of 2 [mm] and different hole diameters, which are arranged on the circumference. ..

In the state of pattern 1, the opening space 1601 of (1) faces the neck 1603 of (a), and similarly, the opening space 1601 of (2) to (7) is of (b) to (g). It faces the neck 1603 respectively. Then, the sound absorbing main body member 610 or the sound absorbing cover member 620 is rotated from the state of the pattern 1 so that the opening space 1601 of (1) faces the neck 1603 of (g) in the pattern 2.

FIG. 16 is a graph plotting the calculation results of the sound absorption frequencies of the seven Helmholtz resonators 670 formed by the opening space 1601 of (1) to (7) for each of the states of pattern 1 and pattern 2. Is.
As shown in FIG. 16, pattern 1 and pattern 2 have different frequency ranges including more sound absorbing frequencies of the Helmholtz resonator 670. A large sound absorbing effect can be expected in the range of 1500 [Hz] to 2600 [Hz] for pattern 1 and in the range of 2300 [Hz] to 3400 [Hz] for pattern 2.

A conventional Helmholtz resonator can absorb only a single frequency. Therefore, for a Helmholtz resonator, when changing the frequency of the sound to be absorbed (sound absorption frequency), either the opening area of the communication portion 603, the length of the communication portion 603, or the volume of the cavity portion 601 that determines the sound absorption frequency is determined. Need to change. In order to change these, it was necessary to change the shape of the member forming the Helmholtz resonator, and there was no choice but to change it by replacing the member forming the Helmholtz resonator.

In the sound absorbing device 600 of the first modification, a plurality of opening space portions 1601 and a neck portion 1603 capable of forming the Helmholtz resonator 670 are prepared, and a plurality of parameters are prepared for each. Then, by switching the combination of the opening space portion 1601 and the neck portion 1603, the sound absorbing frequency of the Helmholtz resonator 670 formed in the sound absorbing device 600 can be changed without replacing the members constituting the Helmholtz resonator 670.
Further, in the sound absorbing device 600 of the first modification, the sound absorbing frequencies of the plurality of Helmholtz resonators 670 can be changed at once.

In FIG. 17, a microphone 1607, which is a sound detecting means, and a sound absorbing main body member rotating motor 1606, which is a cavity forming member moving means for moving the sound absorbing main body member 610, are added to the sound absorbing device 600 of the first modification, and the sound absorbing frequency is automatically set. It is a schematic explanatory diagram of the configuration which can be changed by. The sound absorbing main body member rotating motor 1606 is a drive source that moves the sound absorbing main body member 610 relative to the sound absorbing cover member 620 by moving the sound absorbing main body member 610 in the circumferential direction around the rotating shaft 1606a.

FIG. 18 is a block diagram showing a control system of the sound absorbing main body member rotating motor 1606 of the sound absorbing device 600 shown in FIG.
The control unit 1650, which is a cavity forming member movement control means, controls the sound absorbing main body member rotating motor 1606 based on the detection result of the microphone 1607, and changes the relative position of the sound absorbing main body member 610 with respect to the sound absorbing cover member 620.

Further, the sound absorbing device 600 shown in FIG. 17 includes a rotation position detection sensor 1670 that detects the position of the sound absorbing main body member 610 in the rotation direction with respect to the sound absorbing cover member 620. In the sound absorbing device 600 shown in FIG. 17, four Helmholtz resonators 670 are formed by the four opening space 1601 and the four neck 1603. The positional relationship between the sound absorbing cover member 620 and the sound absorbing main body member 610, in which the opening space 1601 and the neck 1603 face each other, can be set to four different positional relationships. The sound absorption frequencies of the four Helmholtz resonators 670 are stored in the storage unit 1680 in advance for each of the four positional relationships. Then, the positional relationship between the sound absorbing cover member 620 and the sound absorbing main body member 610 that can form four Helmholtz resonators 670 having a high sound absorbing effect with respect to the sound detected by the microphone 1607 is calculated. Then, the calculated positional relationship is compared with the positional relationship detected by the rotation position detection sensor 1670, and the sound absorbing main body member rotating motor 1606 is driven so as to have the calculated positional relationship, so that the sound absorbing main body member 610 is rotated in the circumferential direction. Move to.

In such a configuration, the microphone 1607 collects the sound generated near the sound absorbing device 600, and detects the frequency having a particularly high volume among the frequencies to be absorbed included in the collected sound. Then, the sound absorbing main body member rotating motor 1606 rotates the sound absorbing main body member 610 according to the detection result, and the Helmholtz resonator can be automatically optimized so as to be closest to the frequency to be absorbed.
In the case of the configuration in which the sound absorbing main body member 610 is rotated, it is assumed that the sound absorbing cover member 620 including the neck portion 1603 is fixed to another member (in the case of an image forming apparatus, a stay in the device or the like). What is moved by the cavity forming member moving means is not limited to the sound absorbing main body member 610 forming the opening space 1601, and may be moving the sound absorbing cover member 620 including the neck 1603. In this case, the sound absorbing main body member 610 is fixed to the device main body.

[Modification 2]
Next, as a sound absorbing device to which the characteristic configuration of the present embodiment can be applied, a second modification of the sound absorbing device 600 (hereinafter referred to as “modification example 2”) will be described.
FIG. 19 is a schematic perspective view of the sound absorbing device 600 of the modified example 2, FIG. 19 (a) is an explanatory view of a state in which the sound absorbing cover member 620 and the sound absorbing main body member 610 are assembled, and FIG. 19 (b) is an explanatory view. It is explanatory drawing of the state which disassembled the sound absorption cover member 620 and the sound absorption main body member 610.
As shown in FIG. 19, the sound absorbing device 600 of the second modification is a sound absorbing device in which a plurality of Helmholtz resonators are linearly arranged. The sound absorbing device 600 of the second modification is configured to change the sound absorbing frequency of the Helmholtz resonator 670 formed by sliding one of the sound absorbing cover member 620 and the sound absorbing main body member 610 with respect to the other.

The sound absorbing cover member 620 forms a wall surface provided with a communication portion 603 communicating with the outside among the wall surfaces forming the cavity portion 601 of the Helmholtz resonator, and the neck portion 1603 (1603a) forming a hole portion to be the communication portion 603. ~ 1603f) is provided in plurality (six).
The sound absorbing main body member 610 forms a wall surface other than the wall surface provided with the communication portion 603 among the wall surfaces forming the hollow portion 601 by the main body side wall portion 611. Further, the sound absorbing main body member 610 has a plurality of opening space portions 1601 (1601a to 1601f) (6) which are surrounded by the wall surface of the main body side wall portion 611 and become a hollow portion 601 by closing the opening with the sound absorbing cover member 620. One) is formed.

In the sound absorbing device 600 of the modified example 2, the sound absorbing cover member 620 and the sound absorbing main body member 610 are assembled so that the one neck portion 1603 and the one opening space 1601 face each other, as in the modified example 1. The Helmholtz resonator 670 is formed. Further, in the second modification, as shown in FIG. 19A, the six Helmholtz are assembled by assembling the six neck portions 1603 (1603a to 1603f) so as to face the six opening space portions 1601 (1601a to 1601f). It forms a resonator 670.

In variant 2, one of the six necks 1603 is at least one of the other five necks 1603 and at least one of the opening area (“S”) or length (“H”) of the hole. Parameters are different. Further, in the second modification, one of the six opening space 1601 has a volume (“V”) parameter different from that of at least one of the other five opening space 1601.
Then, in the sound absorbing device 600 of the second modification, one of the sound absorbing cover member 620 including the neck portion 1603 and the sound absorbing main body member 610 forming the opening space 1601 is shown by an arrow β in FIG. 19 with respect to the other. Slide it. Thereby, similarly to the sound absorbing device 600 of the first modification, the sound absorbing frequency of one Holmholtz resonator formed by one neck 1603 can be changed.
In the second modification, the sound absorbing frequency formed by the sound absorbing device 600 can be changed by sliding the sound absorbing cover member 620 or the sound absorbing main body member 610 and changing the combination of the neck portion 1603 and the opening space portion 1601.

Further, as in the second modification, the sound absorbing cover member 620 or the sound absorbing main body member 610 may be slid, or a drive source capable of linearly reciprocating any of the members may be provided. As a result, the Helmholtz resonator can be automatically optimized so as to be closest to the frequency to be absorbed, similar to the sound absorbing device 600 shown in FIG.

In the sound absorbing device 600 of the first modification and the second modification, one of the sound absorbing cover member 620 and the sound absorbing main body member 610 may be a magnet and the other may be a ferromagnetic material. In the sound absorbing device 600 of the modified example 1 and the modified example 2, since one of the sound absorbing cover member 620 and the sound absorbing main body member 610 is moved with respect to the other, the sound absorbing cover member 620 and the sound absorbing main body member 610 are screwed or the like. Cannot be fixed by. There may be a gap at the joint between the sound absorbing cover member 620 and the sound absorbing main body member 610 that do not fix them, and the desired sound absorbing effect may not be obtained. On the other hand, by using one of the sound absorbing cover member 620 and the sound absorbing body member 610 as a magnet and the other as a ferromagnet, the two members attract each other even if they are relatively movable. Therefore, the airtightness at the joint can be improved.

In the Helmholtz resonator 670, the sound absorption frequency changes if the length of the communication portion 603 or the opening area is different. Further, if the volume of the cavity portion 601 is also different, the sound absorption frequency can be further changed. By making the combination of the neck portion 1603 forming the hole portion to be the communication portion 603 and the opening space portion 1601 to be the cavity portion 601 switchable, sound absorption is performed without changing the shape of the member forming the Helmholtz resonator 670. The frequency can be changed.

Further, also in the sound absorbing device 600 of the modified example 1 and the modified example 2, the sound absorbing frequency of at least one Helmholtz resonator among the plurality of Helmholtz resonators is increased by providing another Helmholtz resonator. It may be configured to be set to a frequency. As a result, the sound absorption frequency can be easily changed, and it is possible to suppress that the sound of a frequency other than the target frequency to be absorbed by a certain Helmholtz resonator becomes loud.

FIG. 20 is a graph schematically showing the sound absorption effect of two Helmholtz resonators having different sound absorption frequencies. FIG. 20 (a) is a graph of an example of a Helmholtz resonator whose sound absorption frequency is set to 930 [Hz], and FIG. 20 (b) is an example of a Helmholtz resonator whose sound absorption frequency is set to 770 [Hz]. It is a graph.

In FIG. 20, the sound when the opening of the sound absorbing portion (communication portion 603) is covered to prevent the Helmholtz resonator from functioning is used as the standard sound, and is shown by a straight broken line for convenience. As shown in FIG. 10 and the like, the standard sound of is different in sound pressure depending on the frequency.
Further, in FIG. 20, the measured sound in a state where the lid of the opening of the sound absorbing portion is removed to function as a Helmholtz resonator is shown by a curved solid line. As shown in FIG. 10 and the like, the sound pressure measured in the state of functioning as a Helmholtz resonator also differs depending on the frequency. In FIG. 20, the difference in volume (sound pressure) between the measured sound and the standard sound in the state of functioning as a Helmholtz resonator is schematically shown for easy understanding. The shaded area in FIG. 20 is the area where the volume was reduced when the Helmholtz resonator was functioning, and the area shown by the grid in FIG. 20 was the volume when the Helmholtz resonator was functioning. Is a region where the sound reduction has deteriorated.

The sound absorbing part using the Helmholtz resonator can be designed to absorb sound having a frequency of 930 [Hz] by determining the values of "S", "V" and "H" in the above equation (1). it can. However, in the example shown in FIG. 20A, a sound having a frequency near 930 [Hz] with respect to a standard sound (sound without a sound absorbing portion) has a sound absorbing effect, but has a frequency of 700 to 830 [Hz]. ], The volume of the sound increases.
Therefore, like the sound absorbing device 600 of the above-described embodiment, it is provided with a sound absorbing unit using a plurality of Helmholtz resonators, and is installed next to the sound absorbing unit (not adjacent to it) where the sound absorbing effect shown in FIG. 20A can be obtained. A sound absorbing portion that can obtain the sound absorbing effect shown in FIG. 20 (b) is arranged. By providing the sound absorbing portion having a sound absorbing frequency of 770 [Hz] shown in FIG. 20 (b), the sound increased by providing the sound absorbing portion having a sound absorbing frequency of 930 [Hz] shown in FIG. 20 (a) can be absorbed. Can be done.

As shown in FIG. 20 (b), the sound whose volume is increased by providing the sound absorbing portion using the Hertzholtz resonator having a sound absorbing frequency of 770 [Hz] (sound having a frequency of 500 to 600 [Hz]) is A sound absorbing unit that absorbs sound in this frequency band may be provided separately.
Further, if the sound source does not generate a sound having a frequency of 500 to 600 [Hz], it is not necessary to provide a new sound absorbing unit.

Next, a procedure for confirming whether or not a sound absorbing device having a plurality of sound absorbing parts using a Helmholtz resonator includes a characteristic part of the sound absorbing device 600 according to the present embodiment will be described.

(1) Sounds of various frequencies (white noise) are generated from speakers and the like.
(2) "Data 1" is obtained by measuring the sound with the lids on all the openings of the plurality of sound absorbing portions provided in the sound absorbing device.
(3) With the lid of the opening of one of the plurality of sound absorbing portions provided in the sound absorbing device removed, the sound is measured and "data 2" is obtained.
(4) Information on the sound absorbing effect as shown in the graph of FIG. 20 is acquired for the sound absorbing portion whose lid is removed from the difference between "data 1" and "data 2".

Information on each sound absorbing effect is acquired for a plurality of sound absorbing parts using the Helmholtz resonator provided in the sound absorbing device. Then, if the frequencies of the "deterioration region" of one sound absorbing portion and the "reducing effect region" of the other sound absorbing portion overlap, the sound absorbing device has the sound absorbing region according to the present embodiment. It corresponds to a sound absorbing device including a feature portion of the device 600.

In the present embodiment, the case where the electronic device provided with the sound absorbing device is an image forming device has been described, but the configuration includes a sound source unit that generates sound during operation and a sound absorbing device that absorbs sound emitted from the sound source unit. For example, the characteristic configuration of this embodiment can be applied to electronic devices other than the image forming apparatus.

The above description is an example, and the present invention exerts a unique effect for each of the following aspects.

(Aspect A)
In a sound absorbing device such as a sound absorbing device 600 in which a plurality of sound absorbing parts such as the first resonator 670a, the second resonator 670b and the third resonator 670c are arranged, at least the second resonator 670b or the like among the plurality of sound absorbing parts is used. One sound absorbing part has at least the frequency of the sound whose volume is reduced by providing the sound absorbing part and the frequency of the sound whose volume is increased by providing the other sound absorbing part such as the first resonator 670a. It is a configuration in which some frequencies overlap.
According to this, as described in the above-described embodiment, by providing a certain sound absorbing unit, it is possible to absorb sound having a frequency at which the volume becomes louder by another sound absorbing unit. As a result, it is possible to suppress that the sound of a frequency other than the target frequency to be absorbed by a certain sound absorbing unit becomes loud.

(Aspect B)
In aspect A, the sound absorbing section comprises the configuration of a Helmholtz resonator such as the Helmholtz resonator 670.
According to this, as described in the above-described embodiment, by providing one Helmholtz resonator, a sound having a frequency at which the volume becomes louder can be absorbed by another Helmholtz resonator. This makes it possible to suppress loud sounds at frequencies other than the target frequency that a certain Helmholtz resonator absorbs.

(Aspect C)
In the B aspect, the member forming the Helmholtz resonator such as the Helmholtz resonator 670 is made of a resin material, and the frequency of the sound absorbed by one Helmholtz resonator such as the first resonator 670a and the second resonator 670b and the like. The interval from the frequency of the sound absorbed by other Helmholtz resonators is 30 [Hz] to 70 [Hz].
According to this, as described in the first embodiment, in a sound absorbing device made of only a resin material, a sound having a frequency at which a certain Helmholtz resonator is provided can be absorbed by another Helmholtz resonator. it can.

(Aspect D)
In the B aspect, the member forming the Helmholtz resonator such as the Helmholtz resonator 670 includes a member made of a metal material such as a sheet metal, and the frequency of the sound absorbed by one Helmholtz resonator such as the first resonator 670a and the first The interval from the frequency of the sound absorbed by another Helmholtz resonator such as the two resonators 670b is 70 [Hz] to 200 [Hz].
According to this, as described in the second embodiment, in a sound absorbing device containing a metal material, by providing a certain Helmholtz resonator, a sound having a frequency at which the volume becomes loud can be absorbed by another Helmholtz resonator. ..

(Aspect E)
In the first aspect D, among the walls forming the cavity portion 601 such as the Helmholtz resonator 670, the sound absorbing cover member 620 and the like forming the wall provided with the communication portion such as the communication portion 603 communicating with the outside. It is provided with a member and a second member such as a sound absorbing main body member 610 that forms another wall surface of the cavity, the first member is made of a metal material such as sheet metal, and the communicating portion is burring processed on a plate-shaped metal material. Is formed by applying.
According to this, as described in the above embodiment, the communication portion is provided without separately providing a member for forming the communication portion with respect to the first member forming a part of the wall surface forming the cavity portion. Can be formed.

(Aspect F)
In any of aspects B to E, one Helmholtz resonator such as the first resonator 670a and another Helmholtz resonator such as the second resonator 670b are arranged adjacent to each other.
According to this, as described in the above-described embodiment, it becomes easy for another Helmholtz resonator to absorb sound at a frequency at which the sound absorption effect is deteriorated by one Helmholtz resonator.

(Aspect G)
In any of aspects B to F, if the length of the communicating portion such as the communicating portion 603 communicating with the outside is different among the walls forming the hollow portion 601 of the Helmholtz resonator such as the Helmholtz resonator 670. By making them different, the frequencies of the sound absorbed by the plurality of Helmholtz resonators such as the first resonator 670a, the second resonator 670b, and the third resonator 670c are made different.
According to this, as described in the above embodiment, since the sound absorption frequencies can be made different without changing the shape of the cavity, a plurality of Helmholtz resonators can be efficiently arranged at equal intervals.

(Aspect H)
In any of aspects B to G, the frequency of sound absorbed by at least one of a plurality of Helmholtz resonators such as the first resonator 670a, the second resonator 670b, and the third resonator 670c is 100 [. It is in the range of [Hz] or more and 1500 [Hz] or less.
According to this, as described in the above-described embodiment, it is possible to suppress sound leakage of a sound having a frequency that cannot be sufficiently suppressed only by a shielding member such as an exterior cover.

(Aspect I)
In any of aspects B to H, the first member such as the sound absorbing cover member 620 forming the wall surface having the communication portion communicating with the outside among the wall surfaces forming the cavity portion of the Helmholtz resonator, and the cavity portion. It is provided with a second member such as a sound absorbing main body member 610 that forms another wall surface, and the first member is provided with a plurality of holes such as a hole of a neck portion 1603 that serves as a communication portion, and the second member is provided by another wall surface. A plurality of opening spaces such as the opening space 1601 which is surrounded and closed by the first member to form a cavity are formed so that the plurality of holes and the plurality of opening spaces face each other. A plurality of Helmholtz resonators are formed by assembling the first member and the second member, and at least one of the plurality of holes has a different length and diameter from the other holes. At least one of the plurality of opening spaces has a different volume from the other opening spaces, and the combination of the holes facing each other and the opening space can be switched.
According to this, as described in the first modification and the second modification, by switching the combination of the holes facing each other and the opening space, the sound absorbing device can be used without replacing the members constituting the Helmholtz resonator. The sound absorption frequency of the Helmholtz resonator formed can be changed.

(Aspect J)
In the aspect I, by changing the relative position of the second member such as the sound absorbing main body member 610 with respect to the first member such as the sound absorbing cover member 620, the hole portion and the opening space portion such as the hole portion of the neck portion 1603 facing each other are changed. The combination with the opening space such as 1601 is switched.
According to this, as described in the first modification and the second modification, the Helmholtz resonator formed in the sound absorbing device by moving one of the first member and the second member relative to the other. It is possible to realize a configuration in which the sound absorption frequency of the above can be changed.

(Aspect K)
In aspect J, one of the sound detecting means such as a microphone 1607 arranged on the first member such as the sound absorbing cover member 620 and detecting sound and the second member such as the first member or the sound absorbing main body member 610 are relative to the other. The cavity forming member moving means such as the sound absorbing main body member rotating motor 1606 and the cavity forming member moving means are controlled based on the detection result of the sound detecting means, and the relative position of the second member with respect to the first member is determined. It is provided with a cavity forming member movement control means such as a control unit 1650 to be changed.
According to this, as described in the first modification and the second modification, the Helmholtz resonator can be automatically optimized so that the sound absorption frequency is closest to the frequency to be absorbed.

(Aspect L)
In any of the aspects J or K, the holes such as the holes of the plurality of necks 1603 and the opening spaces such as the opening space 1601 are arranged in a circumferential shape.
According to this, as described in the first modification, one of the first member such as the sound absorbing cover member 620 and the second member such as the sound absorbing main body member 610 is rotated with respect to the other to form the sound absorbing device. The sound absorption frequency of the Helmholtz resonator can be changed. Further, since the sound absorbing frequency can be changed by rotating, the volume of the entire sound absorbing device including the Helmholtz sound absorbing device does not change, so that the Helmholtz resonator can be arranged by making maximum use in a predetermined space.

(Aspect M)
In any of the aspects J or K, the holes such as the holes of the plurality of necks 1603 and the opening spaces such as the opening space 1601 are arranged linearly.
According to this, as described in the second modification, one of the first member such as the sound absorbing cover member 620 and the second member such as the sound absorbing main body member 610 is slid linearly with respect to the other to absorb sound. The sound absorption frequency of the Helmholtz resonator formed in the device can be changed. Further, since the sound absorbing frequency can be changed by sliding, a sound absorbing device capable of changing the sound absorbing frequency can be installed even when there is only an elongated space.

(Aspect N)
In any of aspects I to M, one of the first member such as the sound absorbing cover member 620 and the second member such as the sound absorbing body member 610 is a magnet and the other is a ferromagnet.
According to this, as described in the first modification and the second modification, the first member and the second member can be brought into close contact with each other by a magnetic force. As a result, it is possible to change the combination of the hole portion such as the hole portion of the neck portion 1603 and the opening space portion such as the opening space portion 1601 while ensuring the airtightness of the cavity portion of the Helmholtz resonator.

(Aspect O)
In an electronic device such as a copying machine 500 provided with a sound absorbing means for absorbing sound during operation, a sound absorbing device such as a sound absorbing device 600 according to any one of aspects A to N is used as the sound absorbing means.
According to this, as described in the above embodiment, while the sound generated during the operation of the electronic device is absorbed by the sound absorbing portion of the Helmholtz resonator 670 or the like, the sound having a frequency other than the target frequency absorbed by the sound absorbing portion is loud. It becomes possible to suppress the occurrence. As a result, the sound absorbing effect of the sound generated during the operation of the electronic device can be enhanced.

(Aspect P)
An electrophotographic image forming apparatus such as a copying machine 500 includes the configuration of the electronic device according to the aspect O.
According to this, as described in the above embodiment, while the sound generated during the operation of the image forming apparatus is absorbed by the sound absorbing unit such as the Helmholtz resonator, the sound having a frequency other than the target frequency absorbed by the sound absorbing unit is large. It becomes possible to suppress the occurrence. This makes it possible to enhance the sound absorbing effect of the sound generated when the image forming apparatus is operated.

8 Photoreceptor cleaning blade 9 Static elimination lamp 10 Photoreceptor 11 Charging device 12 Developing device 13 Transfer unit 14 Cleaning device 15 First belt tension roller 16 Second belt tension roller 17 Transfer belt 18 Belt cleaning blade 20 Toner replenishment device 20a Bottle Set hole 21 Resist roller vs. 22 Thermal fixing device 30 Heating roller 32 Pressurized roller 34 Discharge branch claw 35 Discharge roller 36 First pressurized roller 37 Second pressurized roller 38 Stiff roller 39 Discharge stack 42 Switchback device 43 Switch Back roller vs. 44 Switchback position 47 Laser writing device 48 Polygon mirror 49 Polygon motor 53 Light source 54 Mirror 55 Optical lens for imaging 56 Image sensor 57 Contact glass 60 Recording paper carrier 61 Recording paper cassette 61a Recording paper cassette exterior cover 62 Calling roller 63 Supply roller 64 Separation roller 66 Recording paper transport roller vs. 67 Manual feed tray 68 Manual paper feed unit 100 Copier body 101 Front opening / closing cover 102 Front inner cover 103 Left side exterior cover 121 Development roller 160 Sound absorbing device installation unit 200 Image reading Device 300 Recording paper bank 400 Automatic document transfer device 500 Copier 510 Front housing 510a Opening for sound absorbing device installation 520 Left side housing 600 Sound absorbing device 601 Cavity 602 Opening 603 Communication part 610 Sound absorbing body member 611 Main body side wall 620 Sound absorption cover member 623 Cavity upper surface part 625 Flange part 630 Sound absorption cap member 670 Helmholtz resonator 670a First resonator 670b Second resonator 670c Third resonator 670d Fourth resonator 1601 Open space 1603 Neck part 1606 Sound absorption body member Rotating motor 1606a Rotating axis 1607 Microphone 1650 Control unit 1670 Rotation position detection sensor 1680 Storage unit B Transfer position C Transfer belt cleaning unit P Recording paper R Recording paper Transport path R1 Supply path R2 Manual feed supply path R3 Reverse path R4 Re-transport path

Japanese Unexamined Patent Publication No. 2000-235396 Japanese Unexamined Patent Publication No. 2000-112306 Japanese Patent No. 3816678 JP-A-2007-146852

Claims (15)

In a sound absorbing device having at least a first sound absorbing part and a second sound absorbing part ,
The first sound absorbing unit has a Helmholtz resonator configuration, and has a region of a first sound absorbing frequency in which the volume decreases and a region of a first volume increasing frequency in which the volume increases with respect to the sound generated by the sound source. And have
The second sound absorbing unit has a Helmholtz resonator configuration, and has a second sound absorbing frequency region in which the volume decreases and a second volume increasing frequency region in which the volume increases with respect to the sound generated by the sound source. And have
The region of the second sound absorbing frequency is larger than the region of the first volume increasing frequency.
The region of the first volume increasing frequency and the region of the second sound absorbing frequency include at least the frequency having the highest volume in the region of the first volume increasing frequency in the region of the second sound absorbing frequency. A sound absorbing device characterized in that it partially overlaps with each other. In the sound absorbing device請Motomeko 1,
The member forming the Helmholtz resonator is made of a resin material, and the distance between the first sound absorbing frequency and the second sound absorbing frequency is 30 [Hz] to 70 [Hz]. apparatus. In the sound absorbing device of claim 1 ,
The member forming the Helmholtz resonator includes a member made of a metal material, and the distance between the first sound absorbing frequency and the second sound absorbing frequency is 70 [Hz] to 200 [Hz]. Sound absorbing device. In the sound absorbing device of claim 3 ,
The Helmholtz resonator of the first sound absorbing portion and the second sound absorbing portion includes a first member forming a wall surface having a communicating portion communicating with the outside among the wall surfaces forming the cavity portion of the Helmholtz resonator. A second member that forms another wall surface of the cavity is provided.
A sound absorbing device characterized in that the first member is made of a metal material, and the communicating portion is formed by subjecting a plate-shaped metal material to a burring process. In the sound absorbing device according to any one of claims 1 to 4 .
Absorbing device, characterized in that said Helmholtz resonator and the Helmholtz resonator of the first sound absorbing part the second intake clef are arranged adjacent. In the sound absorbing device according to any one of claims 1 to 5 ,
Among the walls forming the cavity of the Helmholtz resonator, the length of the communicating portion communicating with the outside is made different, so that the frequencies of the sound absorbed by the plurality of Helmholtz resonators are made different. Sound absorbing device. In the sound absorbing device according to any one of claims 1 to 6 .
A sound absorbing device characterized in that the frequency of sound absorbed by at least one of the plurality of Helmholtz resonators is in the range of 100 [Hz] or more and 1500 [Hz] or less. In the sound absorbing device according to any one of claims 1 to 7 .
Among the wall surfaces forming the cavity portion of the Helmholtz resonator, a first member forming a wall surface having a communicating portion communicating with the outside and a second member forming another wall surface of the cavity portion are provided.
The first member is provided with a plurality of holes that serve as communication portions, the second member is surrounded by the other wall surface, and the opening is closed by the first member to form an opening space that becomes the cavity. Multiple parts are formed,
The plurality of Helmholtz resonators are formed by assembling the first member and the second member so that the plurality of holes and the plurality of opening spaces face each other.
At least one of the plurality of holes has a different length and diameter from the other holes, and at least one of the plurality of opening spaces has a different volume from the other opening spaces.
A sound absorbing device having a configuration in which a combination of the holes and the opening space facing each other can be switched. In the sound absorbing device of claim 8 ,
A sound absorbing device characterized in that the combination of the hole portion and the opening space portion facing each other is switched by changing the relative position of the second member with respect to the first member. In the sound absorbing device according to claim 9 ,
A sound detecting means for detecting the sound arranged on the first member, and
A cavity-forming member moving means for moving one of the first member or the second member relative to the other.
It is characterized by comprising a cavity forming member moving control means for controlling the cavity forming member moving means based on the detection result of the sound detecting means and changing the relative position of the second member with respect to the first member. Sound absorbing device. In the sound absorbing device according to claim 9 or 10 .
A sound absorbing device characterized in that a plurality of the holes and the opening space are arranged in a cylindrical shape. In the sound absorbing device according to claim 9 or 10 .
A sound absorbing device characterized in that a plurality of the holes and the opening space are arranged in a straight line. In the sound absorbing device according to any one of claims 8 to 12 ,
A sound absorbing device characterized in that one of the first member and the second member is a magnet and the other is a ferromagnetic material. In an electronic device equipped with a sound absorbing means that absorbs the sound during operation
An electronic device characterized in that the sound absorbing device according to any one of claims 1 to 13 is used as the sound absorbing means. In an electrophotographic image forming apparatus
An image forming apparatus comprising the configuration of the electronic device according to claim 14 .

Images