JP2021043387A - Silencer and image forming device - Google Patents

Abstract

To be able to improve muffling effect while suppressing increase in size.SOLUTION: In a silencer 10 provided with an expansion chamber 14, an inner cylinder 15 having a tubular shape extending from a first opening 11 toward the inside of the expansion chamber 14 is provided, and a tip of the inner cylinder 15 has a third opening 13. A cross-sectional area of the expansion chamber 14 between the third opening 13 and the second opening 12 with respect to a direction of the center line 15c of the inner cylinder 15 is provided larger than the cross-sectional area of the inner cylinder 15 between the third opening 13 and the first opening 11, and the second opening 12, respectively. With respect to the direction of the center line 15c of the inner cylinder 15, when a distance between the third opening 13 and the second opening 12 is a first distance L1, and a distance between the third opening 13 and the first opening 11 is a second distance L2, n-0.1<L1/L2<n+0.1 (n=1,2,3,...) is satisfied.SELECTED DRAWING: Figure 1

Description

The present invention relates to an expansion chamber type sound deadening device, a sheet transport device having a sound deadening device, and an image forming device such as a copying machine, a printer, a facsimile, and a multifunction device having a plurality of these functions.

As a configuration for reducing the operating noise of the image forming apparatus, a silencer that reduces the sound of a plurality of peaks and a wide frequency band is used (see Patent Document 1). As the sound deadening device in this case, an expansion chamber type silencer configured by providing an expansion chamber having a cross-sectional area S1 wider than the cross-sectional area S2 in the middle of the pipe having the cross-sectional area S2 is applied. In the expansion chamber type silencer, the sound waves propagating from the sound source are reflected inside (inner surface) of the expansion chamber, so that the sound waves of a specific frequency corresponding to the length L along the propagation path of the expansion chamber overlap and cancel each other. The principle is used. It is known that the larger the ratio of the cross-sectional area S1 of the expansion chamber to the cross-sectional area S2 of the pipe, the greater the sound deadening effect.

JP-A-2009-67015

However, the muffling device of Patent Document 1 described above exerts a muffling effect at a peak of a specific frequency, but in order to realize a higher muffling effect, the cross-sectional area ratio S1 / S2 is increased, that is, the cross-sectional area of the expansion chamber. It is necessary to increase S1. However, if the cross-sectional area S1 of the expansion chamber is increased, the muffling device becomes large. On the other hand, it is also conceivable to provide an outer cylinder for discharging sound to the outside of the expansion chamber of the expansion chamber type silencer to improve the sound deadening effect. However, in this case as well, the muffling device becomes large, and even if some member is to be arranged around the outer cylinder, a dead space may be generated due to design restrictions.

An object of the present invention is to provide a muffling device and an image forming device capable of improving a muffling effect while suppressing an increase in size.

The muffling device according to one aspect of the present invention has a first opening and a second opening, and the sound emitted from the sound source is incident from one of the first opening and the second opening to reduce the sound. In a muffling device provided with a muffling chamber that is emitted from the other of the first opening and the second opening, the muffling device has a tubular shape extending from the first opening toward the inside of the muffling chamber. An inner cylinder provided with a gap between the wall portion of the muffling chamber and the wall portion of the sound deadening chamber is provided in a direction orthogonal to the center line of the tubular shape, and the inner tip portion of the inner cylinder has a third opening. Then, with respect to the direction of the center line of the inner cylinder, the cross-sectional area of the sound deadening chamber between the third opening and the second opening is the cross-sectional area between the third opening and the first opening. The cross-sectional area of the inner cylinder and the distance between the third opening and the second opening are defined as the first distance L1 with respect to the direction of the center line of the inner cylinder. When the distance between the third opening and the first opening is the second distance L2,
n-0.1 <L1 / L2 <n + 0.1 (n = 1, 2, 3, ...)
It is characterized by satisfying.

An image forming apparatus according to another aspect of the present invention is characterized by including an image forming unit for forming an image on a sheet and the muffling device described above.

According to the present invention, it is possible to improve the muffling effect while suppressing the increase in size.

The schematic block sectional view of the image forming apparatus which concerns on 1st Embodiment. The exploded perspective view which shows the muffling device of the image forming apparatus which concerns on 1st Embodiment. The graph which shows the relationship between the frequency by the muffling device of the image forming apparatus which concerns on 1st Embodiment, and a muffling effect. The cross-sectional view which shows the muffling device of the image forming apparatus which concerns on 2nd Embodiment. The graph which shows the relationship between the frequency by the muffling device of the image forming apparatus which concerns on 2nd Embodiment, and the muffling effect. FIG. 6 is a schematic configuration sectional view of an image forming apparatus according to a third embodiment. The exploded perspective view which shows the muffling device of the image forming apparatus which concerns on 3rd Embodiment. It is a schematic diagram for demonstrating the principle of muffling of a conventional muffler, (a) is an expansion chamber type muffler, and (b) is a side branch type muffler.

<First Embodiment>
The first embodiment will be described with reference to FIGS. 1 to 3. First, the schematic configuration of the image forming apparatus 1 of the present embodiment will be described with reference to FIG.

[Image forming device]
The image forming apparatus 1 shown in FIG. 1 includes an apparatus main body 2 and a document reading unit 3. The document reading unit 3 is provided on the upper part of the apparatus main body 2 and can read the document. The document reading unit 3 has an image sensor or the like that irradiates a document placed on a platen glass as a document mounting table with light and converts the reflected light into a digital signal. The device main body 2 has an image forming unit 4 that forms an image on the sheet S, a sheet feeding device 5 that feeds the sheet S to the image forming unit 4, and the sheet S is inverted and conveyed to the image forming unit 4. A sheet reversing portion 6 is provided. An internal space 7 is formed between the apparatus main body 2 and the document reading unit 3.

The image forming unit 4 has four color (yellow, magenta, cyan, black) process cartridges PY, PM, PC, and PK. That is, the image forming apparatus 1 is an electrophotographic full-color printer. In the present embodiment, the process cartridges PY, PM, PC, and PK are arranged along the rotation direction of the intermediate transfer belt 25, which will be described later, in an intermediate transfer tandem system. The image forming apparatus 1 records a toner image (image) in response to an image signal from a host device such as a personal computer that is communicably connected to the document reading unit 3 connected to the apparatus main body 2 or the apparatus main body 2. It is formed on the sheet S as. Examples of the recording material include sheet materials such as paper, plastic film, and cloth.

The process cartridge PY includes a photosensitive drum cartridge 43y and a developing cartridge 44y for forming a toner image, and the process cartridge PM includes a photosensitive drum cartridge 43m and a developing cartridge 44m. Similarly, the process cartridge PC includes a photosensitive drum cartridge 43c and a developing cartridge 44c for forming a toner image, and the process cartridge PK includes a photosensitive drum cartridge 43k and a developing cartridge 44k. Further, the image forming unit 4 includes an exposure unit 42, an intermediate transfer unit 45, a secondary transfer unit 56, and a fixing unit 57.

The four photosensitive drum cartridges 43y, 43m, 43c, 43k and the four developing cartridges 44y, 44m, 44c, 44k have the same configuration except for their different colors. explain. The photosensitive drum cartridge 43y includes a photosensitive drum 21y, a charging roller 22y, and a drum cleaning blade 23y. The developing cartridge 44y includes a developing roller 24y.

The intermediate transfer unit 45 includes an intermediate transfer belt 25 stretched on a belt drive roller 26, a secondary transfer inner roller 56a, and the like, and a primary transfer roller 27y that abuts on the intermediate transfer belt 25 at a position facing the photosensitive drum 21y. , Is equipped. The secondary transfer unit 56 is composed of a secondary transfer inner roller 56a and a secondary transfer outer roller 56b that is in contact with the secondary transfer inner roller 56a via an intermediate transfer belt 25. The fixing portion 57 includes a fixing inner roller 57a and a fixing outer roller 57b. Since the fixing portion 57 becomes hot during use, a fixing fan 57c for air-cooling the fixing portion 57 is provided.

The sheet feeding device 5 includes a cassette 51 for storing the sheet S. A plurality of cassettes 51 may be provided. Further, the sheet separation feeding unit 52 having a function of feeding the sheets S housed in the cassette 51 one by one while separating them by frictional force is provided.

Next, the image forming operation by the image forming apparatus 1 will be described. When the image forming operation is started, the exposure unit 42 first irradiates the surface of the photosensitive drum 21y with a laser beam based on image information from a personal computer or the like (not shown). At this time, the surface of the photosensitive drum 21y is uniformly charged to a predetermined polarity and potential by the charging roller 22y, and when the laser beam is irradiated, the charge of the portion irradiated with the laser beam is attenuated, so that the photosensitive drum is charged. An electrostatic latent image is formed on the surface of 21y.

After that, a predetermined potential is applied to the developing roller 24y, and yellow toner is supplied from the developing roller 24y to develop the electrostatic latent image as a toner image. Then, the electrostatic latent image is also developed as a toner image for magenta, cyan, and black. A full-color toner image is formed on the intermediate transfer belt 25 by sequentially transferring each color toner image to the intermediate transfer belt 25 by the primary transfer bias applied to the primary transfer roller. On the other hand, in parallel with this toner image forming operation, the sheet feeding device 5 separates and feeds only one sheet S from the cassette 51 by the sheet separating feeding unit 52. After that, the sheet S is brought into contact with the stopped resist roller pairs 62a and 62b, so that the position of the tip end is adjusted.

Next, in the secondary transfer unit 56, the resist rollers 62a and 62b are driven at the timing when the full-color toner image on the intermediate transfer belt 25 and the position of the sheet S are matched. As a result, the sheet S is conveyed to the secondary transfer unit 56, and the full-color toner image is collectively transferred onto the sheet S by the secondary transfer bias applied to the secondary transfer outer roller 56b at the secondary transfer unit 56. Will be done. The sheet S to which the full-color toner image is transferred is conveyed to the fixing portion 57, and the sheet S is sandwiched and conveyed between the fixing inner roller 57a and the fixing outer roller 57b, so that the toner image on the sheet S is heated and conveyed. It is pressurized and fixed on the sheet S as a full-color image. After that, the sheet S on which the image is fixed is discharged by the discharge unit 58 provided downstream of the fixing unit 57.

The sheet S discharged by the discharge unit 58 is loaded on the discharge tray 59 as an example of the discharge sheet loading unit formed in the muffling device 10 described later. The discharge tray 59 is arranged in the body space 7, and the sheet S on which the image is formed by the image forming unit 4 is discharged. When forming an image on both sides of the sheet S, the transport direction of the sheet S is reversed by the sheet reversing section 6, and the sheet S is transported to the image forming section 4 again.

Here, in the present embodiment, the vent 2a is provided on the bottom surface 7a of the body space 7. A fixing fan is arranged inside the vicinity of the ventilation port 2a, and air is sucked from the ventilation port 2a by driving the fixing fan 57c. On the other hand, the discharge tray 59 is placed on the bottom surface 7a of the body space 7, and the vent 2a is communicated with the side of the body space 7 at the lower part of the discharge tray 59. If a simple ventilation duct communicating with the ventilation port 2a is provided in the lower part of the discharge tray 59, the aerodynamic sound of the fixing fan 57c may leak from the ventilation duct and generate noise to the outside. Further, from the image forming unit 4, in addition to the aerodynamic sound generated by the fan, various sounds such as the sound from the conveyed seat S and the driving sound by the electric motor are generated. These sounds may leak out from the vent 2a, for example, and become noise. Therefore, in the present embodiment, a muffling device 10 is provided at the lower part of the discharge tray 59 so that air can be sucked into the vent 2a from the outside and noise is reduced.

Next, the configuration of the muffling device 10 included in the image forming device 1 of the present embodiment will be described with reference to FIGS. 1 and 2. In the present embodiment, an expansion chamber type silencer made of synthetic resin is applied as the silencer 10. The muffling device 10 includes an expansion chamber 14 and an inner cylinder 15 as an example of the muffling chamber. The expansion chamber 14 has a first opening 11 and a second opening 12, and the sound emitted from the sound source is incident from the second opening 12, is reduced, and is emitted from the first opening 11. That is, the sound source is a fixing fan 57c for flowing air inside and outside the apparatus main body 2, and air flows between the first opening 11 and the second opening 12 by driving the fixing fan 57c. In the present embodiment, since there is a sound source in the vicinity of the second opening 12, the sound is muted from the second opening 12 toward the first opening 11, but the sound is not limited to this, and the same muting device 10 is used. However, the sound is also muted from the first opening 11 to the second opening 12. That is, in the muffling device 10, the sound emitted from the sound source is incident from one of the first opening 11 and the second opening 12, is reduced, and is emitted from the other of the first opening 11 and the second opening 12. To do.

In the present embodiment, the expansion chamber 14 has a substantially flat box shape, and has a bottom wall 14a, a back wall 14b, an upper wall 14c, a front wall 14d inclined with the back wall 14b side raised, and an apparatus main body at the time of installation. It has a side wall 14e on the front side and a side wall 14f on the back side of 2. The silencer 10 is mounted on the bottom surface 7a of the body space 7, the bottom wall 14a is mounted on the bottom surface 7a, the back wall 14b faces the side of the device body 2, and the front wall 14d is the discharge portion 58. It is provided facing. The upper surfaces of the upper wall 14c and the front wall 14d form a discharge tray 59. That is, the muffling device 10 has a discharge tray 59 on the upper surface. The first opening 11 is rectangular and is formed on the back wall 14b, and the second opening 12 is rectangular and is formed on the bottom wall 14a. The second opening 12 is provided so as to overlap and communicate with the vent 2a on the bottom surface 7a of the body space 7.

The inner cylinder 15 has a tubular shape extending from the first opening 11 of the back wall 14b toward the inside of the expansion chamber 14. The inner cylinder 15 has a rectangular tubular shape with a rectangular cross section, and one end thereof is integrated with the edge portion of the first opening 11. Therefore, the opening area of the first opening 11 and the cross-sectional area of the inner cylinder 15 match. The inner cylinder 15 is provided between the bottom wall 14a, the upper wall 14c, and the side walls 14e and 14f with gaps G for all of them in a direction orthogonal to the center line 15c of the cylinder shape. ing. However, it is not limited to having a gap G for all of the bottom wall 14a, the upper wall 14c, and the side walls 14e and 14f, and it is sufficient that the gap G is provided for at least a part of the side walls 14e and 14f. The bottom wall 14a, the upper wall 14c, and the side walls 14e and 14f form a wall portion. The inner tip of the expansion chamber 14 of the inner cylinder 15 has a third opening 13.

In the present embodiment, the opening areas of the first opening 11 and the second opening 12 are both S2. For the inner cylinder 15, the cross-sectional area between the third opening 13 and the first opening 11 is S2 with respect to the direction (center line direction) of the center line 15c of the inner cylinder 15. On the other hand, with respect to the direction of the center line 15c of the inner cylinder 15, the cross-sectional area of the expansion chamber 14 between the center of the third opening 13 and the center of the second opening 12 is set to S1 between the upper wall 14c and the bottom wall 14a. , It becomes smaller than S1 with the inclination of the front wall 14d between the front wall 14d and the bottom wall 14a. In the present embodiment, with respect to the direction of the center line 15c of the inner cylinder 15, the cross-sectional area of the expansion chamber 14 between the third opening 13 and the second opening 12 is the third opening 13 and the first opening 11. It is provided larger than the cross-sectional area S2 of the inner cylinder 15 and the second opening 12 between the two. It is known that in the expansion chamber type silencer, the larger the ratio of the cross-sectional area S1 of the expansion chamber 14 to the cross-sectional area S2 of the inner cylinder 15, the greater the muffling effect. Therefore, in the present embodiment, since S1> S2, a high muffling effect can be obtained.

Further, with respect to the direction of the center line 15c of the inner cylinder 15, the distance between the center of the third opening 13 and the center of the second opening 12 is defined as the first distance L1. The distance between the third opening 13 and the first opening 11 with respect to the direction of the center line 15c of the inner cylinder 15 is defined as the second distance L2. That is, the inner cylinder 15 has a cross-sectional area S2 and extends from the first opening 11 to the inside of the expansion chamber 14 by a second distance L2. In the present embodiment, the distance between the center of the third opening 13 and the center of the second opening 12 is set to the first distance L1 with respect to the direction of the center line 15c of the inner cylinder 15, but the distance is not limited to this. For example, the first distance L1 may be the distance between the third opening 13 and the second opening 12 on a straight line directly connecting the center of the third opening 13 and the center of the second opening 12.

Here, the principle of sound deadening of the expansion chamber type silencer and the side branch type silencer will be described with reference to FIGS. 8 (a) and 8 (b). As shown in FIG. 8A, in the expansion chamber type silencer 200, an expansion chamber 201 having a cross-sectional area S1 larger than S2 is provided in the middle of the pipe 202 having a cross-sectional area S2. In the expansion chamber type silencer 200, sound waves propagating from a sound source (not shown) are reflected inside (inner surface) of the expansion chamber 201, so that sound waves of a specific frequency corresponding to the length L of the expansion chamber 201 overlap. The principle of canceling each other is used.

Further, the relationship between the specific frequency f (Hz) muted by the expansion chamber type silencer 200 and the length L of the expansion chamber 201 is as shown in Equation 1 below. Here, c is the speed of sound (about 340 m / s).
f = c / (4 × L)… (1)

When the frequency of the noise is the specific frequency f of the expansion chamber type silencer 200, the maximum noise reduction effect (sound pressure decrease) can be obtained for the noise of the specific frequency f and the noise of an odd multiple of the frequency (FIG. 3). See comparative example). It is known that the larger the cross-sectional area ratio S1 / S2 of the cross-sectional area S1 of the expansion chamber 201 and the cross-sectional area S2 of the pipe 202, the greater the muffling effect.

Further, as shown in FIG. 8B, also in the side branch type silencer 210, as in the expansion chamber type silencer 200, sound waves of a specific frequency corresponding to the length of the cylinder may overlap and cancel each other. Are known. In the side branch type silencer 210, a bottomed cylinder 211 having a cross-sectional area S1 having a length L and a surface perpendicular to the length L is provided in the middle of the pipe 212 having a cross-sectional area S2 so as to extend perpendicular to the sound traveling direction. Has been done. The sound propagating from the sound source is incident on the cylinder 211 from the tube 212, and then is reflected by the bottom or the side wall so that the sound waves having a specific frequency corresponding to the length L and an odd multiple of the frequency overlap and cancel each other. In the side branch type silencer 210 as well, as in the expansion chamber type silencer 200, the larger the cross-sectional area ratio S1 / S2 between the cross-sectional area S1 of the cylinder 211 and the cross-sectional area S2 of the pipe 212, the greater the muffling effect.

In the present embodiment, the aerodynamic sound generated by the fixing fan 57c that cools the fixing portion 57 leaks to the outside via the inner cylinder 15. The aerodynamic noise generated by the fan includes a peak noise determined by the number of revolutions x the number of blades and a broadband noise generated by air vortices and turbulence. Since the noise generated by the fan is about 600 Hz and a frequency that is an integral multiple, the first distance L1 of the expansion chamber 14 of the silencer 10 of the present embodiment is determined, and the noise is silenced for the specific frequency f and the odd multiple frequency thereof. To do.

In the present embodiment, similarly to the expansion chamber type silencer 200 shown in FIG. 8A, the sound wave propagating from the sound source is reflected inside (inner surface) of the expansion chamber 14 to be the length of the expansion chamber 14. The principle that sound waves of a specific frequency corresponding to the first distance L1 overlap and cancel each other is used. That is, for example, the sound incident from the second opening 12 hits the bottom wall 14a, the upper wall 14c, the side walls 14e, 14f, or the edge of the third opening 13 at the first distance L1 from the second opening 12. The hit sound is reflected concentrically, and a part of the reflected sound returns to the second opening 12, and the sound waves overlap and cancel each other.

Also in this embodiment, the specific frequency f to be silenced by the expansion chamber 14 is expressed by the following mathematical formula 2 as in the general expansion chamber type silencer 200 shown in FIG. 8 (a). Here, c is the speed of sound (about 340 m / s). When the frequency of the noise is the specific frequency f of the silencer, the maximum noise reduction effect (sound pressure decrease) can be obtained for the noise of the specific frequency f and the noise of an odd multiple of the frequency. Therefore, in the present embodiment, since the fixing fan 57c is particularly targeted for muffling, the first distance L1 is determined so that the generated frequency and the specific frequency f of the equation 2 match. From Equation 2, it is calculated as L1 = c / 4f.
f = c / (4 × L1)… (2)

Further, similarly to the general side-branch type silencer 210 shown in FIG. 8B, the principle that sound waves of specific frequencies overlap and cancel each other is also applied by the second distance L2 of the inner cylinder 15. That is, for example, the sound that spreads from the portion of the first distance L1 of the expansion chamber 14 toward the back wall 14b along the outer peripheral wall of the inner cylinder 15 is reflected by the back wall 14b, and a part of the reflected sound is reflected by the expansion chamber 14. Returning to the part of the first distance L1, the sound waves overlap and cancel each other out.

In the present embodiment, in order to improve the sound deadening performance at the specific frequency f, the inner cylinder 15 is extended inside the expansion chamber 14, and the second distance L2 is set so as to satisfy the mathematical formula 3 with respect to the first distance L1. ing. By determining the first distance L1 and the second distance L2 so as to satisfy the equation 3, the muffling frequency can be tuned and a higher effect can be obtained.
1-0.1 <L1 / L2 <1 + 0.1 ... (3)

Here, the permissible range of the ratio in the formula 3 will be described. In general, it is known that the muffling effect of the expansion chamber type silencer and the inner cylinder is greatly attenuated when the muffling effect deviates from the muffling peak. In the case of the present embodiment, the range in which the muffling effect is 50% or more with respect to the maximum value is the range in which the ratio of L1 / L2 is within 1 ± 0.1. Therefore, as a configuration aiming at improving the muffling effect in the present embodiment, it is defined as in Equation 3.

Next, the operation of the muffling device 10 described above will be described with reference to FIG. When the image forming apparatus 1 starts operating, the fixing fan 57c is driven. As a result, the outside air of the image forming apparatus 1 is sucked from the first opening 11, flows into the expansion chamber 14 through the inner cylinder 15, and enters the apparatus main body 2 through the second opening 12. The air that has entered is used by the fixing fan 57c to cool the fixing portion 57. That is, the muffling device 10 has a function of taking in outside air from the first opening 11 through the inner cylinder 15 and the second opening 12, passing it to the fixing fan 57c, and cooling the heated fixing portion 57.

A part of the sound generated by the fixing fan 57c enters the muffling device 10 through the second opening 12. The muffler 10 is effective as an expansion chamber type silencer in the portion (L1 region) of the first distance L1 of the expansion chamber 14 for a specific frequency f corresponding to the first distance L1 and an odd multiple frequency thereof. Mute the sound. Further, in the silencer 10, the sound silencer has a specific frequency f corresponding to the second distance L2 as a side branch type silencer in the peripheral portion (L2 region) of the inner cylinder 15, and is effective for sounds having an odd multiple of the frequency f. Mute the sound. Further, in the present embodiment, since the first distance L1 and the second distance L2 are set so as to satisfy the mathematical formula 3, the muffling frequency can be tuned and a higher effect can be obtained.

On the other hand, the sheet S on which the image is formed is discharged by the discharge unit 58 and loaded on the discharge tray 59 formed on the upper surface of the muffling device 10. Therefore, the muffling device 10 and the discharge tray 59 can be used in combination.

As described above, according to the image forming apparatus 1 of the present embodiment, the relationship between the first distance L1 of the expansion chamber 14 and the second distance L2 of the inner cylinder 15 is set as in Equation 3. Therefore, the effect of the L1 region of the expansion chamber 14 as an expansion chamber type silencer and the effect of the expansion chamber 14 as a side branch type silencer can be superposed, so that the muffling effect is improved. be able to. Here, in order to enhance the sound deadening effect, it is conceivable to increase the cross-sectional area S1 of the expansion chamber 14 or to provide an outer cylinder outside the expansion chamber 14, but this would cause the sound deadening device 10 to become large or dead space. May occur. On the other hand, in the present embodiment, since the inner cylinder 15 is provided inside the expansion chamber 14, it is possible to suppress the increase in size and the occurrence of dead space. That is, it is possible to improve the muffling effect while suppressing the increase in size.

Further, according to the image forming apparatus 1 of the present embodiment, the intake air to the fixing fan 57c is distributed inside the muffling apparatus 10. Therefore, it is possible to suppress the sound leakage of the fan noise, which is one of the causes of the noise in the image forming apparatus 1, to the outside, and to secure the flow path of the outside air for cooling.

Further, according to the image forming apparatus 1 of the present embodiment, since the discharge tray 59 is formed on the upper surface of the sound deadening device 10, the sound deadening device 10 and the discharge tray 59 can be used in combination. As a result, it is possible to suppress an increase in the number of parts due to the provision of the muffling device 10.

[Example]
Here, as an example of the present embodiment, the relationship between the sound frequency and the muffling effect was confirmed. Here, using the image forming apparatus 1 of the present embodiment, sound is emitted from a sound source whose target frequency for muffling is a specific frequency f, and the muffling effect (dB) of the muffling device 10 is measured. The result is shown in FIG. As shown in FIG. 3, the muffling effect was improved at a specific frequency f and an odd multiple of the specific frequency f.

[Comparison example]
On the other hand, as a comparative example, in the case where the muffling device does not have an inner cylinder, the relationship between the sound frequency and the muffling effect was confirmed as in the embodiment. The result is shown in FIG. As shown in FIG. 3, at a specific frequency f and an odd multiple of the specific frequency f, both were inferior to the examples. Therefore, according to the muffling device 10 having the inner cylinder 15 of the present embodiment, it was confirmed that the muffling effect is improved as compared with the comparative example having no inner cylinder.

In the above-described embodiment, the fan sound of the fixing fan 57c is applied as the target frequency for muffling the sound deadening device 10, but the sound is not limited to this. The target frequency for muffling can be appropriately selected by the setter in consideration of, for example, the overall configuration of the image forming apparatus 1. Therefore, in addition to the fan sound of the fixing fan 57c, the motor sound of the fixing fan 57c, the fan sound or motor sound of another fan, or the sound from another sound source can be widely applied to the expansion chamber of the muffling device 10. The first distance L1 of 14 can be determined.

Further, in the above-described embodiment, in Equation 3, the same frequency is muted in the L1 region and the L2 region of the expansion chamber 14 based on the fact that L1 / L2 is about 1. Is not limited. For example, it may be set as in the following mathematical formula 4 so that the ratio of L1 / L2 is an odd multiple (n = 3, 5, ...) With different ratios.
n-0.1 <L1 / L2 <n + 0.1 ... (4)

In this case, for example, if n = 3, the muffling by the L2 region of the expansion chamber 14 is 3f, 6f, 9f, ... It is effective at the frequency of. Therefore, by selecting n as an odd number such as 1, 3, 5, ... According to the frequency for muffling, a large muffling effect can be obtained at the selected frequency.

Further, in the above-described embodiment, the first opening 11, the second opening 12, and the inner cylinder 15 all have a rectangular cross section, but the cross section is not limited to this, and for example, a perfect circular cross section, an elliptical cross section, or the like. , Other shapes may be used. Further, the inner cylinder 15 may be provided in the second opening 12 instead of the first opening 11. In this case, the outside air flows into the expansion chamber 14 from the first opening 11 having no inner cylinder, flows from the third opening 13 of the inner cylinder 15 through the inner cylinder 15, and flows into the device main body 2 from the second opening 12. Will be done. In this way, the same muffling effect can be obtained even if the direction of air circulation changes. Alternatively, inner cylinders may be provided in both the first opening 11 and the second opening 12.

Further, in the above-described embodiment, the second opening 12 is formed in the bottom wall 14a, but the present invention is not limited to this, and depending on the position of the vent 2a, for example, the second opening 12 is provided in the front wall 14d or another wall portion. You may do so. Also in this case, the muffling effect can be obtained by appropriately setting the first distance L1.

<Second embodiment>
Next, a second embodiment of the present invention will be described in detail with reference to FIGS. 4 and 5. The present embodiment is different from the first embodiment in that the ratio L1 / L2 of the first distance L1 and the second distance L2 of the silencer 10A is set to an even multiple. However, since the other configurations are the same as those in the first embodiment, the same reference numerals are given and detailed description thereof will be omitted.

As shown in FIG. 4, the sound of the fixing fan 57c leaks from the inner cylinder 15A of the muffling device 10A as in the first embodiment. In the first embodiment, the frequencies to be silenced are the specific frequency f and an odd multiple of the specific frequency f, so L1 / L2 is set to 1. On the other hand, depending on the fixing fan 57c, the frequency for which muffling is desired may be the specific frequency f and the entire integral multiple of the specific frequency f. In this case, in order to mute the entire frequency more effectively, it is desired to mute an even multiple of the specific frequency f in addition to the odd multiple frequency of the specific frequency f targeted in the first embodiment. .. Therefore, in the present embodiment, the muffling device 10A sets the first distance L1 to about twice the second distance L2 so as to satisfy the following formula 5. The first distance L1 is set using the above-mentioned mathematical formula 2.
2-0.1 <L1 / L2 <2 + 0.1 ... (5)

As described above, according to the image forming apparatus 1 of the present embodiment, the relationship between the first distance L1 of the expansion chamber 14 and the second distance L2 of the inner cylinder 15 is set as in Equation 5. Therefore, the effect of the L1 region of the expansion chamber 14 as an expansion chamber type silencer and the effect of the expansion chamber 14 as a side branch type silencer can be superposed, so that the muffling effect is improved. be able to. Here, the muffling effect of the L1 region of the expansion chamber 14 is an odd multiple of the specific frequency f, whereas the muffling effect of the L2 region of the expansion chamber 14 is an even multiple of the specific frequency f. Therefore, since the portion where the muffling effect by the L1 region of the expansion chamber 14 is small can be supplemented by the muffling effect by the L2 region of the expansion chamber 14, the muffling effect can be obtained over the entire frequency band. That is, it is possible to improve the muffling effect while suppressing the increase in size.

Further, according to the image forming apparatus 1 of the present embodiment, the length of the inner cylinder 15 can be shortened as compared with the first embodiment. Therefore, the configuration can be simplified and the muffling device 10A can be downsized.

[Example]
Here, as an example of the present embodiment, the relationship between the sound frequency and the muffling effect was confirmed. Here, using the image forming apparatus 1 of the present embodiment, sound is emitted from a sound source whose target frequency for muffling is a specific frequency f, and the muffling effect (dB) of the muffling device 10A is measured. The result is shown in FIG. As shown in FIG. 5, a similar muffling effect was observed at a specific frequency f and an even multiple of the specific frequency f. Therefore, it was confirmed that the muffling effect can be obtained over the entire frequency band.

In the above-described embodiment, in Equation 5, the sound is muted even at an even multiple of the specific frequency f based on the fact that L1 / L2 is about 2, but the present invention is not limited to this. For example, it may be set as in the following mathematical formula 6 so that the ratio of L1 / L2 is an even multiple (n = 4, 6, ...) With different ratios.
n-0.1 <L1 / L2 <n + 0.1 ... (6)

In this case, for example, if n = 4, the muffling by the L2 region of the expansion chamber 14 is 4f, 8f, 12f, ... It is effective at the frequency of. Therefore, by selecting n as an even number such as 2, 4, 6, ... Depending on the frequency for muffling, the muffling effect can be obtained over the entire frequency band.

<Third embodiment>
Next, a third embodiment of the present invention will be described in detail with reference to FIGS. 6 and 7. The present embodiment is different from the first embodiment in that the sheet S is horizontally transported.

The image forming apparatus 101 shown in FIG. 6 is provided with an image forming unit 104 that forms an image on the sheet S and a sheet feeding device 105 that feeds the sheet S to the image forming unit 104 in the apparatus main body 102. .. The image forming unit 104 has four color (yellow, magenta, cyan, black) process cartridges PY, PM, PC, and PK. The image forming apparatus 101 is an electrophotographic full-color printer and employs an intermediate transfer tandem system.

The process cartridge PY includes a photosensitive drum cartridge 143y and a developing cartridge 144y for forming a toner image, and the process cartridge PM includes a photosensitive drum cartridge 143m and a developing cartridge 144m. Similarly, the process cartridge PC includes a photosensitive drum cartridge 143c and a developing cartridge 144c for forming a toner image, and the process cartridge PK includes a photosensitive drum cartridge 143k and a developing cartridge 144k. Further, the image forming unit 104 includes an exposure unit 142, an intermediate transfer unit 145, a secondary transfer unit 156, and a fixing unit 157.

The four photosensitive drum cartridges 143y, 143m, 143c, and 143k and the four developing cartridges 144y, 144m, 144c, and 144k have the same configuration except for their different colors. explain. The photosensitive drum cartridge 143y includes a photosensitive drum 121y, a charging roller 122y, and a drum cleaning blade 123y. The developing cartridge 144y includes a developing roller 124y.

The intermediate transfer unit 145 includes an intermediate transfer belt 125 stretched on a belt drive roller 126, a secondary transfer inner roller 156a, and the like, and a primary transfer roller 127y that abuts on the intermediate transfer belt 125 at a position facing the photosensitive drum 121y. , Is equipped. The secondary transfer unit 156 is composed of a secondary transfer inner roller 156a and a secondary transfer outer roller 156b which is in contact with the secondary transfer inner roller 156a via an intermediate transfer belt 125. The fixing portion 157 includes a fixing inner roller 157a and an outer fixing roller 157b, which are examples of driving members. The fixing inner roller 157a and the fixing outer roller 157b are driven by an electric motor M arranged in the vicinity. The sheet feeding device 105 includes a cassette 151 for accommodating the sheet S. Further, the sheet separation feeding unit 152 having a function of feeding the sheets S housed in the cassette 151 one by one while separating them by frictional force is provided.

Next, the image forming operation by the image forming apparatus 101 will be described. When the image forming operation is started, the exposure unit 142 irradiates the surface of the photosensitive drum 121y with a laser beam based on the image information. An electrostatic latent image is formed on the surface of the photosensitive drum 121y by attenuating the electric charge of the portion irradiated with the laser beam. After that, the electrostatic latent image is developed as a toner image by supplying yellow toner from the developing roller 124y. Then, the electrostatic latent image is also developed as a toner image for magenta, cyan, and black. A full-color toner image is formed on the intermediate transfer belt 125 by sequentially transferring each color toner image to the intermediate transfer belt 125 by the primary transfer bias applied to the primary transfer roller. On the other hand, in parallel with this toner image forming operation, the sheet feeding device 105 separately feeds only one sheet S from the cassette 151.

Then, in the secondary transfer unit 156, the resist roller pairs 162a and 162b are driven at the timing when the full-color toner image on the intermediate transfer belt 125 and the position of the sheet S are matched. As a result, the sheet S is conveyed to the secondary transfer unit 156, and the full-color toner image is collectively transferred onto the sheet S at the secondary transfer unit 156. The sheet S on which the full-color toner image is transferred is conveyed to the fixing portion 157, and the sheet S is sandwiched and conveyed between the inner roller 157a and the outer roller 157b, so that the toner image on the sheet S is heated and conveyed. It is pressurized and fixed on the sheet S as a full-color image. After that, the sheet S on which the image is fixed is discharged by the discharge unit 158 provided downstream of the fixing unit 157.

Next, the configuration of the muffling device 110 included in the image forming apparatus 101 of the present embodiment will be described with reference to FIGS. 6 and 7. In the present embodiment, an expansion chamber type silencer made of synthetic resin is applied as the silencer 110. The muffling device 110 includes an expansion chamber 114 as an example of a muffling chamber and an inner cylinder 115. The expansion chamber 114 has a first opening 111 and a second opening 112, and the sound emitted from the sound source is incident from the second opening 112, reduced in sound, and emitted from the first opening 111. The sound source is an electric motor M for driving the fixing inner roller 157a and the fixing outer roller 157b, and the muffling device 110 is arranged with the second opening 112 facing the electric motor M. In the present embodiment, the muffling device 110 arranges the second opening 112 toward the electric motor M, but is not limited to this, and arranges the first opening 111 toward the electric motor M. You may do so. In this case as well, the muffling device 110 silences the sound from the first opening 111 toward the second opening 112. That is, in the muffling device 110, the sound emitted from the sound source is incident from one of the first opening 111 and the second opening 112, is reduced, and is emitted from the other of the first opening 111 and the second opening 112. To do.

In the present embodiment, the expansion chamber 114 has a substantially rectangular parallelepiped shape, and has a bottom wall 114a, a back wall 114b, an upper wall 114c, a front wall 114d, a side wall 114e on the front side of the apparatus main body 2 at the time of installation, and a back side. It has a side wall 114f of the above. The muffling device 110 is installed inside the device main body 2, the front wall 114d faces the electric motor M, and the back wall 114b faces the outside of the device main body 2. The first opening 111 is substantially square and is formed on the back wall 114b, and the second opening 112 is substantially square and is formed on the front wall 114d. The first opening 11 is provided, for example, so as to face a vent (not shown) formed in the housing of the device main body 2.

The inner cylinder 115 has a tubular shape extending from the first opening 111 of the back wall 114b toward the inside of the expansion chamber 114. The inner cylinder 115 has a square tubular shape with a square cross section, and one end thereof is integrated with the edge portion of the first opening 111. Therefore, the opening area of the first opening 111 and the cross-sectional area of the inner cylinder 115 match. The inner cylinder 115 is provided between the bottom wall 114a, the upper wall 114c, and each of the side walls 114e and 114f with a gap G in the direction orthogonal to the center line 115c of the tubular shape. ing. However, it is not limited to having a gap G for all of the bottom wall 114a, the upper wall 114c, and the side walls 114e and 14f, and it is sufficient that the gap G is provided for at least a part of the side walls 114e and 14f. The bottom wall 114a, the upper wall 114c, and the side walls 114e and 114f form a wall portion. The inner tip of the expansion chamber 114 of the inner cylinder 115 has a third opening 113.

In the present embodiment, the opening areas of the first opening 111 and the second opening 112 are both S2. For the inner cylinder 115, the cross-sectional area between the third opening 113 and the first opening 111 is S2 with respect to the direction of the center line 115c of the inner cylinder 115. On the other hand, with respect to the direction of the center line 115c of the inner cylinder 115, the cross-sectional area of the expansion chamber 114 between the third opening 113 and the second opening 112 is S1. In the present embodiment, with respect to the direction of the center line 115c of the inner cylinder 115, the cross-sectional area S1 of the expansion chamber 114 between the third opening 113 and the second opening 112 is the third opening 113 and the first opening. It is provided larger than the cross-sectional area S2 of the inner cylinder 115 between the inner cylinder and the 111. Similarly, with respect to the direction of the center line 115c of the inner cylinder 115, the cross-sectional area S1 of the expansion chamber 114 between the third opening 113 and the second opening 112 is provided larger than that of the second opening 112. It is known that in the expansion chamber type silencer, the larger the ratio of the cross-sectional area S1 of the expansion chamber 114 to the cross-sectional area S2 of the inner cylinder 115, the greater the muffling effect. Therefore, in the present embodiment, since S1> S2, a high muffling effect can be obtained.

Further, the distance between the third opening 113 and the second opening 112 with respect to the direction of the center line 115c of the inner cylinder 115 is defined as the first distance L1. The distance between the third opening 113 and the first opening 111 with respect to the direction of the center line 115c of the inner cylinder 115 is defined as the second distance L2. That is, the inner cylinder 115 has a cross-sectional area S2 and extends from the first opening 111 to the inside of the expansion chamber 114 by a second distance L2.

Here, various sounds such as aerodynamic sounds from the fan, sounds from the sheet S being conveyed, and driving sounds from various motors are generated from the inside of the image forming unit 104. In order to reduce the noise, it is necessary to reduce not only the aerodynamic noise generated by the fan but also the noise generated by the electric motor M, for example. In the present embodiment, the first distance L1 which is the length of the expansion chamber 114 is determined so that the specific frequency f of the electric motor M is set to f in the equation 2. The cross-sectional area of the surface perpendicular to the first distance L1 is S1, and the cross-sectional area of the surface perpendicular to the normal direction of the second opening 112 and the inner cylinder 115 is S2. Further, the second distance L2 of the inner cylinder 115 is determined by the mathematical formula 5 so that the peak sound which is an even multiple of the specific frequency f of the electric motor M can be reduced.

The drive sound generated by the electric motor M flows into the second opening 112 and is reflected inside (inner surface) of the silencer 110. As a result, sound waves of specific frequencies corresponding to the first distance L1 of the expansion chamber 114 and the second distance L2 of the inner cylinder 115 overlap and cancel each other, and are discharged from the inner cylinder 115.

As described above, according to the image forming apparatus 101 of the present embodiment, the relationship between the first distance L1 of the expansion chamber 114 of the silencer 110 and the second distance L2 of the inner cylinder 115 is set as in Equation 5. There is. Therefore, the effect of the expansion chamber 114 as an expansion chamber type silencer by the L1 region and the effect of the expansion chamber 114 as a side branch type silencer by the L2 region can be superimposed, so that the sound deadening effect is improved. be able to. That is, it is possible to improve the muffling effect while suppressing the increase in size.

Further, according to the image forming apparatus 101 of the present embodiment, since the sound deadening device 110 is arranged toward the electric motor M for driving the fixing inner roller 157a and the fixing outer roller 157b, it is generated by the electric motor M. You can mute the sound. As described above, the muffling device according to the present invention can mute the sound of each sound source by arranging the muffling device toward various sound sources arranged inside the image forming device.

In each of the above-described embodiments, the case where L1 / L2 is an odd number or an even number has been described, but the present invention is not limited to this. For example, as in Equation 7 below, the ratio of L1 / L2 may be a natural number multiple (n = 1, 2, 3, ...).
n-0.1 <L1 / L2 <n + 0.1 ... (7)

In this case, the effect of particularly improving the muffling effect at an odd multiple of the specific frequency f (see FIG. 3) and the effect of obtaining the muffling effect even at an even multiple of the specific frequency f (see FIG. 5) can be appropriately selected depending on the sound source. it can. Therefore, a suitable muffling effect can be obtained by selecting n as an odd number or an even number according to the frequency for muffling.

Further, in each of the above-described embodiments, the case where the fixing fan 57c or the electric motor M is applied as the sound source has been described, but the present invention is not limited to this. For example, the sound source may be an electric component such as a power transformer arranged on an electrical board, and in that case, the sound source frequency has a switching interval period of about 10 kHz. Alternatively, the sound source may be an electric component such as a stepping motor arranged in the drive unit, in which case the sound source frequency has a PPS period of about 1 kHz.

Further, in each of the above-described embodiments, the case where the muffling devices 10 and 110 are applied to the image forming devices 1, 101 has been described, but the present invention is not limited to this. The target of the muffling device may be, for example, a device that conveys a sheet, and can be applied to all devices such as a scanner, a post-processing device, and a sheet loading device, and is also applied to all devices that do not convey a sheet. be able to.

1 ... Image forming device, 2 ... Device main body, 3 ... Original reading unit, 4 ... Image forming unit, 7 ... Internal space, 10, 10A, 110 ... Mute device, 11, 111 ... First opening, 12, 112 ... 2nd opening, 13,113 ... 3rd opening, 14,114 ... Anechoic chamber (expansion chamber), 14a, 114a ... Bottom wall (wall part), 14c, 114c ... Upper wall (wall part), 14e, 114e ... Side wall (wall part), 14f, 114f ... Side wall (wall part), 15,115 ... Inner cylinder, 15c, 115c ... Center line, 57c ... Fixing fan (sound source, fan), 59 ... Discharge tray (discharge sheet loading) Part) 157a ... Roller inside fixing (driving member), 157b ... Roller outside fixing (driving member), G ... Gap, M ... Electric motor (sound source).

Claims (9)

It has a first opening and a second opening, and the sound emitted from the sound source is incident from one of the first opening and the second opening and is reduced to reduce the sound of the first opening and the second opening. In a muffling device with a muffling chamber emitted from the other side of the opening
It has a tubular shape extending from the first opening toward the inside of the muffling chamber, and is provided with a gap between it and the wall portion of the muffling chamber in a direction orthogonal to the center line of the tubular shape. Equipped with an inner cylinder
The inner tip of the inner cylinder has a third opening.
With respect to the center line direction of the inner cylinder, the cross-sectional area of the sound deadening chamber between the third opening and the second opening is the inner cylinder between the third opening and the first opening. The cross-sectional area of the above and the second opening are larger than each of the above.
With respect to the center line direction of the inner cylinder, the distance between the third opening and the second opening is defined as the first distance L1, and the distance between the third opening and the first opening is defined as the second distance L2. If you do
n-0.1 <L1 / L2 <n + 0.1 (n = 1, 2, 3, ...)
Meet,
A silencer characterized by that. The n is an odd number,
The muffling device according to claim 1. The n is an even number,
The muffling device according to claim 1. The first distance L1 is L1 = c / 4f when c is the speed of sound and f is the specific frequency of the sound source.
The muffling device according to any one of claims 1 to 3, wherein the muffling device. An image forming part that forms an image on the sheet,
The silencer according to any one of claims 1 to 4.
An image forming apparatus characterized in that. The sound source is a fan for flowing air inside and outside the main body of the device.
By driving the fan, air flows between the first opening and the second opening.
The image forming apparatus according to claim 5. The muffling device has a discharge sheet loading portion on the upper surface from which the sheet on which the image is formed by the image forming portion is discharged.
The image forming apparatus according to claim 5 or 6. A document reader that can read documents is provided at the top of the device body.
The discharge sheet loading unit is arranged in a body space formed between the apparatus main body and the document reading unit.
The image forming apparatus according to claim 7. The sound source is an electric motor for driving a driving member, and is
The silencer is arranged with the first opening or the second opening facing the electric motor.
The image forming apparatus according to claim 5.

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