JP2019040060A - Exterior member and image formation device and image projection device - Google Patents

Abstract

To provide an exterior member capable of reducing the noise(leakage sound) having a plurality of frequency component peaks from image formation device etc. without preventing the exhaust heat of the image formation device etc. by setting the hollow tube length of the silencer structure(hollow tube) provided at the outer cover and the protrusion length of the hollow tube length outside of the outer cover.SOLUTION: An exterior cover 100 has a plurality of hollow tubes 101 to 103 protruding from an outer side surface 100a, and the hollow tubes 101 to 103 form a silencer structure. A protrusion length L2 of the hollow tube 102 is set to about half a protrusion length L1 of the hollow tube 101, and a protrusion length L3 of the hollow tube 103 is set to about half the protrusion length L2 of the hollow tube 102.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an exterior member, an image forming apparatus, and an image projection apparatus, and more particularly, to a silencing structure in an exterior member having a silencing structure.

  Conventionally, in image forming apparatuses such as copiers and printers and image projection apparatuses such as liquid crystal projectors, heat generated by a heat source in the apparatus is exhausted outside the apparatus in order to maintain the normal operation of these apparatuses. The opening for this is provided in the exterior member of the apparatus. In many cases, in order to effectively exhaust the heat in the apparatus, air blown by a fan or the like is used, and a heated air stream is exhausted from the opening to the outside of the apparatus. However, in the apparatus having such a configuration, there is a problem that the operation sound of the fan leaks from the opening and the operation sound of each part in the apparatus accompanying the image formation, and the surrounding environment where the apparatus is installed is lowered. Arise.

  In order to solve such a problem, Patent Documents 1 and 2 propose to reduce the leakage of operation sound by configuring the opening with a hollow tube. According to Patent Documents 1 and 2, a plurality of hollow circular tubes having the same protruding length protruding from the exterior member into the apparatus or out of the apparatus are arranged.

  FIG. 17: Soundproof plate that does not inhibit airflow (the soundproof plate 420 includes a plurality of cylindrical members 412).

  In Patent Document 3, a silencer composed of a plurality of hollow tubes is used in order to reduce outdoor noise propagated indoors through a ventilation fan, and the hollow tube is changed by changing the material and shape of the hollow tube. It is described that it is possible to cope with the reduction of the peaks of a plurality of frequency components in the frequency spectrum of noise by changing the resonance frequency.

  FIG. 18: A breathable cover having a noise reduction effect of the ventilation fan suction port (the breathable cover 500 includes a silencing element 501 made of an elastic material between the holding panels 502).

JP2015-152794A WO2012-0866680 JP 63-143440 A

  However, each of the openings formed by the above-described conventional hollow tubes has the following problems.

  Problems to Patent Documents 1 and 2: In the proposal in this prior art document, since the protruding length of the hollow tube from the panel portion is constant, the frequency band of the leaking sound that is silenced by the interference of the reflected sound from the mounting wall However, the noise (leakage noise) of an image forming apparatus or the like is generally a noise having a plurality of frequency component peaks, and is therefore proposed in this prior art document. It can be said that the soundproofing plate is insufficient for reducing the leakage sound from the image forming apparatus or the like.

  Problem to Patent Document 3: In the proposal in this prior art document, there is a description that it can cope with noise having a plurality of frequency component peaks, and the elastic material or inner diameter of the hollow tube is changed to correspond to the frequency to be silenced. It is supposed to be possible. However, the method proposed in this prior art document complicates the structure of the breathable cover. That is, in general, the configuration of the present proposal in which the use of an elastic material is indispensable for an exterior cover of an image forming apparatus or the like that is integrally molded with a resin material is not preferable in terms of manufacturing, and it can be said that the cost is increased. In addition, in order to change the corresponding frequency, it is necessary to select an elastic material. For this reason, there is a problem that the number of frequencies that can be handled may be limited. In particular, this point becomes a further problem in noise (leakage sound) from an image forming apparatus or the like generally having a plurality of frequency component peaks.

  Therefore, the present invention has been made in view of such a fact, and generally reduces noise (leakage sound) from an image forming apparatus having peaks of a plurality of frequency components, and the hollow tube. An exterior member provided with a sound deadening structure that can suppress noise generated by interference of reflected sound from the exterior surface due to protrusion from the exterior surface, and can be molded integrally with a resin material, and an image forming apparatus provided with the exterior member Alternatively, an object is to provide an image projection apparatus.

In order to achieve the above object, the exterior member according to the present invention is:
In the exterior member provided with a silencer in the opening provided in the exterior member of the image forming apparatus and the image projection apparatus,
The silencer is composed of at least two hollow tubes protruding from the exterior member to the outside of the image forming apparatus and the image projection apparatus,
The hollow tube has at least two projecting lengths, and at least one of the projecting lengths is 1/4 to 3/4 times any of the projecting lengths. It is characterized by a protruding length.

  In the exterior member according to the present invention, a plurality of hollow tubes having at least one length are arranged with different projecting lengths to the exterior of the exterior member. Here, the protrusion length to the inside of the exterior member is uniquely determined by the hollow tube length and the protrusion length to the outside. With such a configuration, in general, noise (leakage sound) from an image forming apparatus having a plurality of frequency component peaks can be reduced. Moreover, the increase of the noise (leakage sound) and the noise which generate | occur | produce by the protrusion of a hollow tube can be suppressed by the device of the setting of several different protrusion length of a hollow tube. In addition, the exterior member can be integrally formed with a resin material, which is advantageous in terms of reducing manufacturing steps or reducing costs.

  As described above, in the present invention, by setting the projection length of the hollow tube provided on the exterior member to the outside of the exterior member, noise (leakage noise) having a plurality of frequency component peaks from the image forming apparatus or the like can be reduced. It is possible to provide an exterior member that can be achieved without hindering the exhaust heat inside the image forming apparatus or the like. Moreover, an image forming apparatus or an image projection apparatus provided with such an exterior member can be provided.

The figure (perspective view) which shows the exterior member which concerns on the 1st Embodiment of this invention The figure which shows schematic structure of the image forming apparatus provided with the exterior member which concerns on the 1st Embodiment of this invention The figure (perspective view) which shows the exterior member which concerns on the 1st Embodiment of this invention The figure which shows the exterior member which concerns on the 1st Embodiment of this invention (a) Side view: Supplementary figure (b) Sectional drawing: Supplementary figure The figure which shows the principal part structure which concerns on the 1st Embodiment of this invention (sectional drawing) Schematic configuration diagram showing an example of the first embodiment of the present invention The figure which shows the effect which concerns on the 1st Embodiment of this invention (a) Reduction frequency 1 (b) Reduction frequency 2 The figure (perspective view) which shows the exterior member which concerns on the 2nd Embodiment of this invention The figure (sectional drawing) which shows the principal part structure which concerns on the 2nd Embodiment of this invention. The figure (perspective view) which shows the exterior member which concerns on the 3rd Embodiment of this invention The figure (sectional drawing) which shows the principal part structure which concerns on the 3rd Embodiment of this invention. The figure which shows the principal part structure which concerns on the 3rd Embodiment of this invention (supplementary figure). The figure (perspective view) which shows the exterior member which concerns on the 4th Embodiment of this invention The figure (sectional drawing) which shows the principal part structure which concerns on the 4th Embodiment of this invention. The figure which shows schematic structure of the image projection apparatus provided with the exterior member which concerns on the 5th Embodiment of this invention. The figure (sectional drawing) which shows the principal part structure which concerns on the 5th Embodiment of this invention. The figure which shows the soundproof board of the conventional example The figure which shows the breathable cover of a prior art example (perspective view)

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings. Note that the following embodiments do not limit the invention according to the claims, and only an image forming apparatus described later has an electrophotographic process as an example. The same applies to the image projection apparatus described later.

  FIG. 1 is a perspective view showing an exterior cover of an image forming apparatus which is an example of a mechanical apparatus including a silencing structure according to the first embodiment of the present invention. FIG. 2 includes such an exterior cover. FIG. 2 is a schematic configuration diagram (cross-sectional view) of a four-drum full-color image forming apparatus using an intermediate transfer belt among the image forming apparatuses. FIGS. 3 to 5 are a perspective view, a side view, a cross-sectional view, and an enlarged cross-sectional view of the main part for explaining the exterior cover. FIG. 6 is a diagram showing the noise reduction effect in the present invention.

[Configuration and operation of image forming apparatus]
First, the overall configuration of the image forming apparatus will be described with reference to FIG.

  In FIG. 2, reference numeral 1 denotes a 4-drum full-color image forming apparatus. The image forming apparatus 1 has an image forming apparatus main body 2. Reference numerals PY, PM, PC, and PBk are process cartridges of four colors of yellow, magenta, cyan, and black, which are detachably provided in the image forming apparatus main body 2. The image forming apparatus 1 includes an intermediate transfer belt unit 31 and a fixing device 25. The intermediate transfer belt unit 31 includes an intermediate transfer belt 30 that is an intermediate transfer member.

  The process cartridges PY, PM, PC, and PBk are arranged in parallel along the intermediate transfer belt 30. Each process cartridge PY, PM, PC, PBk has a photosensitive drum 26Y, 26M, 26C, 26Bk, which is an image carrier. The photosensitive drums 26Y, 26M, 26C, and 26Bk are collectively referred to as the photosensitive drum 26.

  Each process cartridge PY, PM, PC, PBk is disposed on the outer peripheral surface of the photosensitive drum 26 and has a primary charger 50 that uniformly charges the surface of the photosensitive drum 26. Further, each process cartridge PY, PM, PC, and PBk converts the electrostatic latent image of each color on the surface of the photosensitive drum 26 formed by exposure by the laser exposure devices 28Y, 28M, 28C, and 28Bk to the corresponding color. A developing unit 51 that develops using yellow, magenta, cyan, and black toners is provided. The developing roller 54 in the developing device 51 is configured to be separated from the photosensitive drum 26 together with the developing device 51 and to stop the rotation, thereby preventing the deterioration of the developer. At a position where the intermediate transfer belt 30 is sandwiched with the photosensitive drum 26, a primary transfer roller 52 that forms a primary transfer portion together with the photosensitive drum 26 is disposed oppositely.

  On the other hand, the intermediate transfer belt unit 31 includes an intermediate transfer belt 30, a driving roller 80 that stretches the intermediate transfer belt 30, a tension roller 85, and a secondary transfer counter roller 88. The intermediate transfer belt 30 is rotated and conveyed by rotating the driving roller 80 by a belt driving motor (not shown).

  The tension roller 85 is configured to be movable in the horizontal direction in FIG. 2 according to the length of the intermediate transfer belt 30. Further, in the vicinity of the tension roller 85, two registration detection sensors 90 for detecting toner patches on the intermediate transfer belt 30 are installed at both ends in the roller longitudinal direction (thrust direction). A secondary transfer roller 27 is provided at a position between the secondary transfer counter roller 88 and the intermediate transfer belt 30. A transfer conveyance unit 33 holding the secondary transfer roller 27 is provided below the secondary transfer roller 27.

  Under the image forming apparatus 1, a recording material is transferred to a secondary transfer portion (transfer portion) constituted by a contact portion between the secondary transfer roller 27 and the secondary transfer counter roller 88 sandwiching the intermediate transfer belt 30. A feeding unit 3 for feeding P is provided. The feeding unit 3 includes a cassette 20 containing a plurality of recording materials P, a feeding roller 21, a retard roller pair 22 for preventing double feeding, a pair of conveying rollers 23a and 23b, a pair of registration rollers 24, and the like. Discharge roller pairs 61, 62, and 63 are provided in the downstream conveyance path of the fixing device 25.

  A belt drive motor (not shown) is a drive unit for driving the intermediate transfer belt 30 to rotate at a predetermined speed in response to an instruction from an image formation control unit (not shown). A drum drive motor (not shown) is a drive means for driving all the photosensitive drums 26 to rotate at a predetermined speed in response to an instruction from an image formation control unit (not shown).

  Next, the image forming operation of the image forming apparatus 1 configured as described above will be described with reference to FIG. 2 again.

  When the image forming operation is started, the recording material P in the cassette 20 is first fed by the feeding roller 21, and then separated one by one by the retard roller pair 22, and then the conveying roller pair 23a, 23b. And the like are conveyed to the registration roller pair 24. At this time, the registration roller pair 24 has stopped rotating, and the recording material P is abutted against the nip of the registration roller pair 24, whereby the skew of the recording material P is corrected.

  On the other hand, in parallel with the conveying operation of the recording material P, for example, in the yellow process cartridge PY, the surface of the photosensitive drum 26Y is first uniformly negatively charged by the primary charger 50, and then the laser exposure device. Image exposure is performed by 28Y. As a result, an electrostatic latent image corresponding to the yellow image component of the image signal is formed on the surface of the photosensitive drum 26Y. While the developing roller 54 in the developing device 51 is rotationally driven, the developing roller 54 comes into contact with the photosensitive drum 26Y, and the electrostatic latent image is developed with the negatively charged yellow toner by the developing device 51 and visualized as a yellow toner image. The The yellow toner image thus obtained is primarily transferred onto the intermediate transfer belt 30 by the primary transfer roller 52 supplied with the primary transfer bias. After the toner image is transferred, the transfer residual toner adhering to the surface of the photosensitive drum 26Y is removed by the cleaner 53.

  Such a series of toner image forming operations are sequentially performed at a predetermined timing in the other process cartridges PM, PC, and PBk, and the respective color toner images formed on the respective photosensitive drums 26 are intermediated by the respective primary transfer portions. Primary transfer is performed by sequentially overlapping the transfer belt 30. When the developing operation is finished, the developing roller 54 is sequentially separated from the photosensitive drum and stops rotating in order to prevent the deterioration of the developer even if the downstream process cartridge is in the primary transfer.

  Next, the four-color toner images superimposed and transferred on the intermediate transfer belt 30 in this way are moved to the secondary transfer portion as the intermediate transfer belt 30 rotates. Further, the recording material P whose skew has been corrected by the registration roller pair 24 is sent to the secondary transfer portion in time with the image on the intermediate transfer belt 30. Thereafter, the four-color toner images on the intermediate transfer belt 30 are secondarily transferred onto the recording material P by the secondary transfer roller 27 in contact with the intermediate transfer belt 30 with the recording material P interposed therebetween. Then, the recording material P onto which the toner image has been transferred in this manner is conveyed to the fixing device 25, where the toner image is fixed by heating and pressurization, and then the discharge roller pairs 61, 62, 63. Thus, it is discharged and loaded on the upper surface of the apparatus main body. The intermediate transfer belt 30 that has finished the secondary transfer has the transfer residual toner remaining on the surface removed by a belt cleaner (not shown) installed in the vicinity of the drive roller 80.

[Silent structure]
Next, with reference to FIG. 1 and FIGS. 3 to 6, a first embodiment of a muffler structure that is a main part of the present invention will be described.

  FIG. 1 is a perspective view (outside view of the apparatus) showing an exterior cover 100 provided on the outer surface of an image forming apparatus 1 having a silencing structure according to the present invention. Here, the exterior cover 100 indicates one of the exterior covers of the image forming apparatus 1 that are attached.

  The present invention is not limited to a specific exterior cover among the exterior covers provided in the image forming apparatus 1, and the description of the exterior cover 100 in this figure is also applied to other exterior covers having a similar sound deadening structure. It holds. Therefore, only the description of the exterior cover 100 will be given below.

  As shown in the figure, the exterior cover 100 is provided with a plurality of hollow tubes 101 to 103 protruding from the outer surface 100a of the exterior cover 100, and the hollow tubes 101 to 103 form a silencing structure. (Here, reference numerals 101 to 103 do not indicate a specific one of a plurality of hollow tubes as shown in the figure, but are attached to one hollow tube as a representative. ) The hollow tube 101 to 103 communicates the inside and the outside of the image forming apparatus 1 and functions as a heat exhaust path for exhausting heat generated during image formation. Here, the hollow tubes 101 to 103 have different projecting lengths from the outer surface 100a. In this embodiment, the protruding length is set to hollow tube 101> hollow tube 102> hollow tube 103.

  FIG. 3 shows the opposite surface (surface inside the image forming apparatus 1) of the exterior cover 100 shown in FIG.

  In the present embodiment, the lengths of the hollow tubes 101 to 103 themselves are all set to be the same, and only the protruding length from the outer surface 100a is different as described above. Therefore, as shown in this figure, the protruding length of the hollow tubes 101 to 103 inside the apparatus is hollow tube 101 <hollow tube 102 <hollow tube 103. In the hollow tubes 101 to 103, the side shown in the figure is an inlet as an exhaust heat path, and the side shown in FIG. 1 is an outlet. Noise generated during image formation in the image forming apparatus 1 is reflected and attenuated due to a sudden change in the cross section of the propagation region at the entrance, thereby reducing noise propagating in the hollow tubes 101 to 103. Further, the same phenomenon occurs at the outlet, and noise transmitted to the outside of the image forming apparatus 1 is reduced. Further, noise reduction due to fluid resistance on the inner peripheral surfaces of the hollow tubes 101 to 103 also occurs. That is, since the sound deadening structure by the hollow tube is provided on the exterior cover, noise (leakage sound) can be reduced while maintaining the exhaust heat in the image forming apparatus.

  FIG. 4A is a side view of the exterior cover 100 as viewed from the outer side surface 100a (supplementary view). FIG.4 (b) is sectional drawing which shows the cross section AA in Fig.4 (a) (supplementary figure). FIG. 5 is an enlarged cross-sectional view of a main part showing the inside of an enclosure B in 4 (b) in the drawing. Details of the hollow tubes 101 to 103 will be described with reference to FIG.

  Reference symbol L indicates the length of the hollow tubes 101 to 103 themselves. In the present embodiment, the hollow tube length L is fixed, and the hollow tube 101 to 103 has a common length. Reference symbol L <b> 1 is a protruding length from the outer surface 100 a of the hollow tube 101. Reference symbol L <b> 2 is a protruding length from the outer surface 100 a of the hollow tube 102. Reference numeral L <b> 3 is a protruding length from the outer surface 100 a of the hollow tube 103. As shown in the figure and as described above, the protruding lengths are formed such that L1> L2> L3. Here, the hollow tube length L and the protruding length L1 are set so as to correspond to the reduction of noise such as frequency components that become peaks in the frequency spectrum of noise (leakage sound) generated when the image forming apparatus 1 forms an image. (The frequencies corresponding to the protrusion lengths L2 and L3 will be described later).

  In the present embodiment, the above-described protrusion lengths are determined by shifting the position of the hollow tube in the direction perpendicular to the same plane portion of the exterior. However, the configuration is not limited to a flat exterior. For example, as shown in FIG. 6, the hollow tube mounting surface of the exterior is different for each hollow tube, and has a stepped shape such as 100a, 100b, and 100c. It does not matter.

The calculation formula of the frequency FL of the noise reduced by the setting of the hollow tube length L is shown. From the theory of the expansion silencer using the rapid change in the cross section of the inlet and outlet of the hollow tube, the frequency FL is
FL = ((2n−1) · c) / (4 · L)
Is calculated by Here, c: sound velocity [m / s], L: hollow tube length [m], n: positive integer (1, 2, 3,...).

  The calculation formulas of the frequency FL1 at which the noise is reduced most by the setting of the protrusion length L1 and the frequency FL1 'at which the noise is amplified most are shown. Note that the corresponding reduction frequency is not the frequency of noise (leakage sound) generated by the image forming apparatus 1 during image formation, unlike FL1, and the calculation formulas of FL2 and FL3 are the same. The calculation formulas of FL2 'and FL3' are the same as those of FL1 '.

  The difference ΔL in the propagation path length between the sound wave (direct wave) directly propagating from the hollow tubes 101 to 103 to the observation point of noise (leakage sound) and the sound wave (reflected wave) reflected and propagated by the outer surface 100a is 2Li (here, i = 1, 2, 3). When the direct wave and the reflected wave are encountered with their phases shifted by a half wavelength, the amplitude becomes zero (or greatly reduced) due to the principle of wave overlap. That is, the noise (leakage sound) is most reduced at a frequency at which the propagation path length difference ΔL = 2Li is an odd multiple of a half wavelength. On the other hand, when the direct wave and the reflected wave are encountered with their phases shifted by an integer wavelength, the amplitude is amplified most. That is, noise (leakage sound) is amplified at a frequency such that ΔL = 2Li is an integer wavelength.

From this, the reduced frequency FLi and the amplified frequency FLi ′ (in this embodiment, i = 1, 2, 3) are
FLi = ((2n−1) · c) / (4 · Li)
FLi ′ = (2 m · c) / (4 · Li)
Is calculated by Here, c: sound velocity [m / s], Li: protrusion length [m], n: positive integer (1, 2, 3,...), M: positive integer (1, 2, 3,.・ ・）.

  Next, the frequencies FL2 and FL3 corresponding to the protrusion lengths L2 and L3 will be described.

  The protrusion length L2 is set so as to reduce the noise (frequency FL1 ') amplified by the protrusion length L1 of the hollow tube 101. The protrusion length L3 is set so as to reduce noise (frequency FL1 ', FL2') amplified by the protrusion length L1 of the hollow tube 101 and the protrusion length L2 of the hollow tube 102. Specifically, the protrusion length L2 = L1 / 2 and the protrusion length L3 = L2 / 2 are set so that the frequencies FL2 = FL1 ′ and FL3 = FL2 ′. By setting in this way, the amplification frequency FL1 '(m: odd number) of the hollow tube 101 and the reduction frequency FL2 of the hollow tube 102 coincide with each other from the aforementioned FLi and FLi' equations. Thereby, the noise of the amplification frequency FL1 '(m: odd number) of the hollow tube 101 can be suppressed.

  Further, the amplification frequency FL1 '(m: even number) of the hollow tube 101, the amplification frequency FL2' (m: odd number) of the hollow tube 102, and the reduction frequency FL3 of the hollow tube 103 coincide. Thereby, the noise of the amplification frequency FL1 '(m: even number) of the hollow tube 101 and the amplification frequency FL2' (m: odd number) of the hollow tube 102 can be suppressed. In general, noise (leakage) propagating to the outside of the image forming apparatus 1 is a noise having a wide frequency band, and noise amplification due to interference between a direct wave and a reflected wave from the hollow tube may be a problem. The above-described amplification can be reduced by setting the protruding lengths L2 and L3.

  In this embodiment, the protruding length L2 of the hollow tube 102 is set to be half of the protruding length L1 of the hollow tube 101. However, the protrusion length L2 of the hollow tube 102 is not limited to this, and the maximum is about the above half time, and the noise reduction effect decreases as the distance from the half value increases, but the protrusion length L1 of the hollow tube 101 decreases. It may be set to an arbitrary length within a range larger than 1/4 times and smaller than 3/4 times. Similarly, the hollow tube 103 may have any length within a range that is larger than 1/4 of the protruding length L2 of the hollow tube 102 and smaller than 3/4 times. In this embodiment, the protrusion length L3 is set on the assumption that noise amplification at the frequency FL2 ′ is a problem. However, when noise amplification at the frequency FL2 ′ is not a problem, the protrusion length L3 is displayed as an image. You may set to arbitrary length according to the frequency spectrum etc. of the noise (leakage sound) which generate | occur | produces in the case of the image formation of the forming apparatus 1. FIG.

  Subsequently, the number of the hollow tubes 101 to 103 will be described.

  As described above, in this embodiment, the frequency of noise that can be reduced is four, FL, FL1, FL2, and FL3 (reduction of noise (leakage sound) generated during image formation of the image forming apparatus 1). Are two frequencies, FL and FL1). Since the noise reduction at the frequency FL is effective in all the hollow tubes 101 to 103, the noise of the maximum peak frequency component of noise (leakage sound) (or the frequency component that is most desired to be reduced in consideration of audibility) is reduced. Therefore, the number of the hollow tubes 101 to 103 may be set in consideration of the exhaust heat capacity. Noise reduction at the frequencies FL1 to FL3 uses a reflected wave on the outer surface 100a. In general, the sound pressure of the reflected wave decreases (distance attenuation with respect to the direct wave and attenuation when reflected on the reflection wall), and the sound pressure of the direct wave cannot be reduced to zero when superimposed on the direct wave. From this, the number of arrangement of the hollow tubes 101 (frequency FL1 at which noise can be reduced) is the frequency component of noise (leakage sound) that becomes the second and subsequent peaks (or frequency components that are desired to be reduced in consideration of audibility). An appropriate number of arrangements may be set in accordance with each noise frequency component so that reduction can be achieved.

  Further, the number of the hollow tubes 102 (frequency FL2 at which noise can be reduced) is set such that the noise noise (frequency FL1 ′) due to the reflected wave from the exterior surface of the hollow tube 101 can be reduced. An appropriate number of arrangements may be set according to the components. Further, the number of hollow tubes 103 (frequency FL3 at which noise can be reduced) is the same as that of the hollow tubes 102, and the amplified noise (frequency FL1 ′) due to the reflected waves from the hollow tube 101 and the outer surface of the hollow tube 102 is also measured. , FL2 ′), an appropriate number of arrangements may be set in accordance with each noise frequency component. In general, the exterior member of the image forming apparatus is manufactured by integral molding using a resin material. In the present embodiment, even if the hollow tubes 101 to 103 have different projecting lengths L1 to L3, it is easy to integrally form them in the outer cover 100, and therefore, the viewpoint of suppressing the manufacturing man-hours or the cost increase. It can be said that it is an advantageous form.

  As described above, in the exterior cover 100 of the present embodiment, the image forming apparatus is configured by setting the hollow tube length L of the hollow tubes 101 to 103 provided in the exterior cover 100 and the projecting lengths L1 to L3 to the outside of the exterior cover. It is possible to reduce a plurality of frequency components of noise (leakage sound) generated from the image forming apparatus 1 without hindering the exhaust heat inside. Therefore, by providing such an exterior cover 100, it is possible to provide an image forming apparatus that achieves both exhaust heat inside the image forming apparatus 1 during image formation and reduction of noise (leakage noise).

  In addition, in this Embodiment, although the protrusion length of a hollow tube is made into three types of protrusion length L1-L3, this is set as an example to the last and this invention is not limited to this form. The required number of protrusion lengths can be arbitrarily set according to the number of peak frequency components of noise (leakage sound) to be reduced or the number of frequency bands to be reduced. For example, when amplification becomes a problem with respect to the amplification frequencies FL2 ′ (m: even number) and FL3 ′ that cannot be reduced by the hollow tube 102 and the hollow tube 103, the protrusion length becomes half of L3. It is good to suppress the amplification which becomes a problem by arrange | positioning an empty tube. By adding hollow tubes with a short protruding length in this way, the noise amplification frequency due to the protruding length of the additional hollow tube shifts to a high frequency band where the ear sensitivity is low, and does not become a problem.

  FIGS. 7A and 7B are diagrams showing the noise reduction effect in the basic configuration of the present embodiment verified by acoustic analysis using the boundary element method.

In this experiment, the hollow tubes 101 to 103 are set as follows as an example. This is because it is assumed that the setting is made to reduce noise (leakage sound) in the vicinity of 3 kHz where human hearing sensitivity is high.
Common to hollow tubes 101 to 103:
Hollow tube length L 0.03 (m)
Frequency FL 2833 (Hz), 8500 (Hz): Noise reduction by hollow tube Frequency hollow tube 101:
Protrusion length L1 0.03 (m)
Frequency FL1 2833 (Hz), 8500 (Hz): Cancellation frequency by reflected wave Frequency FL1 '5667 (Hz), 11333 (Hz): Amplified frequency hollow tube 102 by reflected wave:
Protrusion length L2 0.015 (m)
Frequency FL2 5667 (Hz): Cancellation frequency by reflected wave Frequency FL2 ′ 11333 (Hz): Amplified frequency hollow tube 103 by reflected wave:
Protrusion length L3 0.0075 (m)
Frequency FL3 11333 (Hz): Cancellation frequency due to reflected waves In this figure, the effects of frequency FL2 and frequency FL3 are particularly shown. Fig.7 (a) is the figure which compared the noise reduction effect in frequency FL2 (5667 (Hz)).

  Configuration 1 in the drawing is an opening having three round hole shapes (the same inner diameter and an inner diameter of 10 mm) that are comparison objects 1. Configuration 2 in the figure is a comparison target (No. 2), and is an opening in which all three hollow tubes 101 are projected to the outside of the exterior cover. Configuration 3 in the figure is the configuration of the present invention, and is an opening that is projected to the outside of the exterior cover using the hollow tubes 101 to 103. That is, in the configurations 2 and 3, the hollow tubes have the same length, the protruding lengths from the outer cover are different from the three, and the protruding length of the hollow tube 102 is the protruding length of the hollow tube 101. Half, the protruding length of the hollow tube 103 is half of the protruding length of the hollow tube 102.

  As shown in the figure, in the configuration 2, the observation point sound pressure is increased by 0.9 (dB) compared to the configuration 1, and the noise amplification effect of the direct wave and the reflected wave by the protrusion length L1 of the hollow tube 101 is increased. Can be confirmed. Further, in the configuration 3, the observation point sound pressure is reduced by 5 (dB) compared with the configuration 2, and the above-described noise is generated by canceling the sound wave using the reflected wave by the protruding length L2 of the hollow tube 102 of the configuration 3. It can be confirmed that the amplification effect is reduced.

  FIG. 7B is a diagram comparing noise reduction effects at the frequency FL3 (11333 (Hz)).

  Configurations 1 to 3 in the figure are the same as described above. In the configuration 2, the observation point sound pressure is increased by 0.6 (dB) compared to the configuration 1, and the noise amplification effect of the direct wave and the reflected wave by the protruding length L1 of the hollow tube 101 can be confirmed. Further, in the configuration 3, the observation point sound pressure is reduced by 3.5 (dB) compared to the configuration 2, and the above-mentioned is achieved by canceling the sound wave using the reflected wave by the protruding length L3 of the hollow tube 103 of the configuration 3. It can be confirmed that the noise amplification effect is reduced.

  Next, a second embodiment of the present invention will be described. In the description of the second embodiment, only differences from the first embodiment described above will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. Here, the difference between the exterior cover 200 in the present embodiment and the exterior cover 100 in the first embodiment is that the exterior cover 200 is provided with hollow tubes having a hollow tube length L and a hollow tube length L ′. It is a point.

  The present embodiment will be described with reference to FIGS.

  FIG. 8 is a perspective view showing an exterior cover of an image forming apparatus including a muffler structure according to the second embodiment of the present invention.

  As illustrated, the hollow tube 201 and the hollow tube 202 are formed so as to protrude from the outer surface 200a of the exterior cover 200 (here, a plurality of reference numerals 201 and 202 are provided as illustrated. It does not indicate a specific one of the hollow tubes, but is representatively attached to one hollow tube). Here, the hollow tube 201 is formed to have a hollow tube length L. Further, the hollow tube 202 and the hollow tube 203 are formed to have a hollow tube length L ′.

FIG. 9 is an enlarged cross-sectional view of a main part passing through the centers of the hollow tubes 201 to 203 (corresponding to FIG. 5 in the description of the first embodiment). Here, the hollow tubes 201 to 203 in the present embodiment are set as follows.
Hollow tube 201:
Hollow tube length L 0.0325 (m)
Frequency FL 2615 (Hz), 7845 (Hz): Noise reduction frequency by hollow tube Protrusion length L1 0.03 (m)
Frequency FL1 2833 (Hz), 8500 (Hz): Cancellation frequency by reflected wave Frequency FL1 ′ 5667 (Hz), 11333 (Hz): Amplified frequency hollow tube 202 by reflected wave 202:
Hollow tube length L '0.0295 (m)
Frequency FL '2786 (Hz): Noise reduction frequency by hollow tube Protrusion length L2 0.015 (m)
Frequency FL2 5667 (Hz): Cancellation frequency by reflected wave Frequency FL2 ′ 11333 (Hz): Amplified frequency hollow tube 203 by reflected wave:
Hollow tube length L '0.0295 (m)
Frequency FL '2786 (Hz): Noise reduction frequency by hollow tube Protrusion length L3 0.0075 (m)
Frequency FL3 11333 (Hz): Cancellation frequency due to reflected waves Here, in general, noise is not only reduced by a single frequency component (here FL, FL ′), but in practice the frequencies FL and FL The peripheral band of 'is also reduced. That is, the frequencies FL and FL ′ are the center frequencies at which noise is reduced, noise is reduced in the frequency bands before and after that, and the amount of noise reduction is reduced as the frequency is separated from the frequencies FL and FL ′ that are the center frequencies. It is common for this phenomenon to occur. For this reason, noise can be reduced in the frequency band of about 2600 (Hz) to about 2800 (Hz) by setting the hollow tubes 201 and 202 as described above.

  In this embodiment, the hollow tube length is set to be different, and the noise reduction effect that occurs when passing through these hollow tubes is obtained, so it is more effective than the silencing using the reflected wave on the outer surface of the exterior cover Is big. Therefore, this embodiment has an effective configuration for reducing noise having a large peak in a certain frequency band (frequency band from about 2600 (Hz) to about 2800 (Hz) in the setting example described above). come. Further, when the frequency spectrum of noise (leakage sound) has a frequency component having two major peaks, for example, the present embodiment can be selected as a configuration for reducing each frequency component.

  In this embodiment, two different lengths of the hollow tube are set. However, the length is not limited to this, and more different lengths are set depending on the number of noise (leakage sound) frequency spectrum to be reduced. You can set it. The protruding length L2 of the hollow tube 202 is set to be half of the protruding length L1 of the hollow tube 201, and the protruding length L3 of the hollow tube 203 is set to be half of the protruding length L2 of the hollow tube 202. The point which has an effect which reduces the amplification noise by the reflected wave from the exterior surface by each protrusion length of the hollow tubes 201 and 202 is the same as that of 1st Embodiment.

  Next, a third embodiment of the present invention will be described. In the description of the third embodiment, only differences from the first and second embodiments described above will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. Here, the difference between the exterior cover 300 in the present embodiment and the exterior covers 100 and 200 in the first and second embodiments described above is that the outer surface 300a of the exterior cover 300 has a curved surface. The sound deadening structure is provided in the curved surface area.

  The present embodiment will be described with reference to FIG. FIG. 10 is a perspective view of the exterior cover 300 in the present embodiment. As shown in the figure, the outer surface 300a is formed with a curved surface 300b that is formed in a convex shape from the outer surface 300a. A hollow tube 301 that is a silencing structure is provided near the inner end of the curved surface 300b, and a hollow tube 302 is provided near the center of the curved surface 300b (here, reference numerals 301 and 302 denote It does not indicate a specific one of a plurality of hollow tubes provided as shown in the figure, but is attached to one hollow tube as a representative).

  FIG. 11 is an enlarged cross-sectional view of the main part showing the exterior cover 300 as seen from the reference c in FIG. As shown in the figure, in this embodiment, the hollow tube lengths L of the hollow tube 301 and the hollow tube 302 are all the same. However, since the hollow tube 301 is provided near the inner end of the curved surface 300b, the protruding length L1 of the hollow tube 301 from the curved surface 300b is provided near the center of the curved surface 300b. The protrusion length L2 from the curved surface 300b of the hollow tube 302 and the other hollow tubes are different.

  FIG. 12 is a view in which the hollow tube 301 is not shown in FIG. Symbol e indicates the distance (curved surface height) between the outer surface 300a and the apex 300c of the curved surface 300b. Here, in order to suppress the amplified noise due to the reflected wave from the exterior surface due to the projection length L1 of the hollow tube 301, the projection length L2 of the hollow tube 302 with respect to the curved surface 300b is the projection length of the hollow tube 301 with respect to the curved surface 300b. The curved surface height e is set to be about half that of L1.

  As described above, in the present embodiment, the protruding length of the hollow tube 301 from the curved surface 300b is continuously shortened from the vicinity of the inner end of the region to the vicinity of the center of the region. The frequency component of noise reduced by the reflected wave (corresponding to the frequency FLi in the first embodiment) is also continuous. Therefore, when the noise (leakage sound) to be reduced is not the noise (leakage sound) that peaks at a specific frequency component, but the noise (leakage sound) that peaks in a certain frequency band In addition, it is preferable to take this embodiment, and noise (leakage sound) can be reduced in the frequency band.

  The hollow tube length L, the protruding length, and the curved surface height e may be appropriately set in view of the frequency band of noise to be reduced. For example, in this embodiment, the projecting length of the hollow tube near the center in the region is half of the projecting length of the hollow tube near the inner end of the region. May be set to be a quarter of the protruding length of the hollow tube near the inner end of the region. Further, in the present embodiment, the curved surface 300b is formed to be more convex than the outer surface 300a. However, the present embodiment is not limited to this configuration, and the curved surface is concave from the outer surface 300a (= device). It may be formed in a convex shape on the inside, and has the same effect.

  Next, a fourth embodiment of the present invention will be described. In the description of the fourth embodiment, only differences from the first to third embodiments described above will be described, and the same components will be denoted by the same reference numerals and description thereof will be omitted. Here, the difference between the exterior cover 400 in the present embodiment and the exterior covers 100, 200, and 300 in the first to third embodiments described above is that the sound deadening structure is formed in the recessed area formed in the exterior cover 400. Is provided such that the tip is located on the inner side of the apparatus with respect to the outer surface 400 a of the outer cover 400.

  The present embodiment will be described with reference to FIG. FIG. 13 is a perspective view of the exterior cover 400 in the present embodiment. As shown in the figure, the exterior cover 400 is formed with a recess from the outer surface 400a. In the region of the concave surface 400b, there are provided hollow tubes 401 to 403 that are sound deadening structures (here, reference numerals 401, 402, and 403 are a plurality of hollow tubes provided as shown in the figure). It is attached to one hollow tube as a representative.

  FIG. 14 is an enlarged cross-sectional view of the main part showing the exterior cover 400 as seen from the reference c in FIG. As shown in the figure, in this embodiment, the hollow tube lengths L of the hollow tubes 401 to 403 are all the same. The projecting length from the recessed surface 400b of the hollow tube 401 toward the outside of the apparatus is L1, and the projecting length L2 of the hollow tube 402 and the projecting length L3 of the hollow tube 403 are L2 = L1 / 2 and L3, respectively. = L2 / 2. Further, the recess surface depth f, which is the depth of the recess surface 400b from the outer surface 400a, is set to be larger than the maximum protrusion length L1 from the recess surface 400b of the hollow tube.

  As described above, in the present embodiment, since the recess surface depth f is larger than the maximum protrusion length L1 of the hollow tube, the tip of the hollow tube does not protrude outward from the outer surface 400a. For this reason, the possibility that an object or a person collides with the hollow tube and breaks down, and the durability is improved.

  Next, a fifth embodiment of the present invention will be described. In the present embodiment, the silencing structure described in the above-described embodiment is applied to an image projection apparatus (hereinafter referred to as a liquid crystal projector). Therefore, the silencing structure that is the main part is the same as the silencing structure in the above-described embodiment and has the same effect. Therefore, the detailed description thereof is omitted in the present embodiment, and the silencing structure is provided. An outline of a main body configuration of a liquid crystal projector and a silencing structure in the present embodiment will be described with reference to the drawings.

  FIG. 15 is an overall schematic configuration of a liquid crystal projector 600 according to the present embodiment. Here, the reference numerals are given only to the components directly related to the proposal. Each part will be described in the order of the symbols.

  Reference numeral 601 denotes a light source lamp, reference numeral 602 denotes a PFC power supply board that generates DC power from a commercial 100V power supply to each board, and reference numeral 603 operates together with the PFC power supply board 602 to drive the light source lamp 601 to light. This is a ballast power supply board. Reference numeral 604 denotes a lamp cooling fan that sends blowing air to the light source lamp 601 to cool the light source lamp 601. Reference numeral 605 denotes a lower exterior case that houses the light source lamp 601, the power system boards 602 and 603, and the like.

  Reference numeral 606 denotes a power supply cooling fan, which sucks air from the intake ports 605a and 605b provided in the lower exterior case 605 and cools them by circulating cooling air through the PFC power supply board 602 and the ballast power supply board 603. To do. Reference numeral 607 denotes an exhaust fan, which is sent from the lamp cooling fan 604 to the light source lamp 601 and discharges hot air after cooling the light source lamp 601 from an exhaust port formed in the right cover 608 described later. Reference numeral 608 denotes a right cover. The right cover 608 is the sound deadening structure described so far, but is provided with the hollow tubes 609 and 610. As described above, the exhaust path for hot air from the exhaust fan 607 is provided. Function as. Here, the silencing structure is composed of one hollow tube length as shown in the figure, and is configured to have two types of protrusion lengths to the outside of the right cover 608.

  FIG. 16 is an enlarged cross-sectional view of a main part for explaining the outline of the hollow tubes 609 and 610 provided in the right cover 608.

  The hollow tubes 609 and 610 are both formed to have a hollow tube length L51, and the noise (leakage sound) of the frequency component calculated at the frequency FL described in the first embodiment using the hollow tube length L51. Reduce (noise reduction by hollow tube). Further, the hollow tube 609 protrudes from the outer surface 608a of the right cover 608 by the protruding length L52, and the frequency component calculated by the frequency FLi described in the first embodiment using the protruding length L52 is used. Reduce noise (leakage noise) (noise reduction by canceling sound waves using reflected waves). Further, the hollow tube 610 protrudes from the outer surface 608a of the right cover 608 by a protrusion length L53. The protruding length L53 of the hollow tube 610 is about half the protruding length L52 of the hollow tube 609, and the noise of the frequency component calculated by the frequency FLi ′ described in the first embodiment. Suppression of noise (noise reduction by canceling sound waves using reflected waves).

[Supplementary items in the embodiment]
The present invention is not limited to the sound deadening structure configuration (hollow tube length, protrusion length, number of each hollow tube, etc.) described in the first to fifth embodiments. The sound deadening structure configuration can be individually set in consideration of a frequency problem of noise (leakage sound) generated in the image forming apparatus and the image projection apparatus, that is, a frequency component or a frequency band to be reduced. Moreover, although the silencing structure (hollow tube) described in the first to fifth embodiments has been described in the case of using a cylindrical hollow tube, the present invention provides a cylindrical hollow tube. It is not limited to a tube, and may be a hollow tube having another cross-sectional shape, and the same effect is obtained. Furthermore, the silencing structure (hollow tube) described in the first to fifth embodiments is illustrated in a state of being integrally formed with the exterior cover in each embodiment. The sound deadening structure portion may be a separate structure for convenience in manufacturing the outer cover or in assembling the apparatus, and the same effect can be obtained.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus, 100 exterior cover (1st Embodiment),
101 hollow tube 1 (first embodiment), 102 hollow tube 2 (first embodiment),
103 hollow tube 3 (first embodiment), L hollow tube length, L ′ hollow tube length,
L1 Projection length 1, L2 Projection length 2, L3 Projection length 3,
200 exterior cover (second embodiment), 201 hollow tube 1 (second embodiment),
202 hollow tube 2 (second embodiment), 203 hollow tube 3 (second embodiment),
300 exterior cover (third embodiment), 301 hollow tube 1 (third embodiment),
302 hollow tube 2 (third embodiment), 303 hollow tube 3 (third embodiment),
400 exterior cover (fourth embodiment), 401 hollow tube 1 (fourth embodiment),
402 hollow tube 2 (fourth embodiment), 403 hollow tube 3 (fourth embodiment),
600 image projection device, 608 right cover (fifth embodiment),
420 Soundproof plate (conventional form), 500 Breathable cover (conventional form)

Claims (10)

In the exterior member provided with a silencer in the opening provided in the exterior member of the image forming apparatus and the image projection apparatus,
The silencer is composed of at least two hollow tubes protruding from the exterior member to the outside of the image forming apparatus and the image projection apparatus,
The hollow tube has at least two projecting lengths, and at least one of the projecting lengths is 1/4 to 3/4 times any of the projecting lengths. An exterior member having a protruding length. 2. The exterior according to claim 1, wherein the exterior has two or more projecting lengths that are ¼ to ¾ times of any one of the projecting lengths. Element. The exterior member according to claim 2, wherein at least one of the projecting lengths is any half of the projecting lengths. The hollow tube length of the hollow tube, which is the length of the hollow tube, is set so as to correspond to a frequency component that becomes a maximum frequency peak of noise passing through the opening. 3. The exterior member according to 3. 5. The exterior member according to claim 4, wherein the protrusion length is set so as to correspond to a frequency component that is a second or subsequent frequency peak of noise passing through the opening. The number of arrangement | positioning of the said hollow tube length and each said protrusion length is set according to the magnitude | size of the peak of the frequency component which set this hollow tube length and this protrusion length, It is characterized by the above-mentioned. Exterior member. The exterior member according to claim 6, wherein the hollow tube length includes a plurality of the hollow tube lengths. The exterior member according to claim 6, wherein the hollow tube is disposed in a curved region provided in the exterior member. The concave portion is provided in the exterior member, the hollow tube is disposed in the concave portion, and the depth of the concave portion is equal to or longer than a protruding length of the hollow tube. Exterior member. An image forming apparatus and an image projection apparatus provided with the exterior member according to claim 1.