Patent Publication Number: US-2016230719-A1

Title: Intake noise reducing apparatus for internal combustion engine

Description:
TECHNICAL FIELD 
     The present invention relates to an intake noise reducing apparatus that reduces intake noise of an internal combustion engine, and more particularly to an intake noise reducing apparatus formed with a bellows-shaped chamber that can elastically deform. 
     BACKGROUND ART 
     Patent Literature 1 discloses an intake noise reducing apparatus for an internal combustion engine, which was previously proposed by an applicant of the present application. This intake noise reducing apparatus separately forms a chamber by use of a bellows-shaped elastic member which can elastically deform. This chamber is connected to an intake passage of the internal combustion engine through a connecting tube which constitutes a neck tube of a Helmholtz-type resonator element. The elastic member is accommodated in an inner space of a cylindrical case which is exposed to ambient air. 
     CITATION LIST 
     Patent Literature 
     [Patent Literature 1] Japanese Patent Application Publication No. 2013-124599 
     SUMMARY OF THE INVENTION 
     Problem to Be Solved 
     In the case of the above-mentioned intake noise reducing apparatus, an intake noise in a specific frequency range is reduced as an effect of the Helmholtz-type resonator element constructed by connecting the chamber through the neck tube to the intake passage. In addition, an intake noise in a second specific frequency range is also reduced because the bellows-shaped elastic member expands and contracts to reduce sound pressure energy in response to an intake-air pulsation. 
     Conventionally, as the bellows-shaped elastic member, a mountain portion and a valley portion each of which is in a simple V-shape in cross section have been used. However, according to further research by the applicant of the present application, such a general bellows-shaped elastic member having the V-shape in cross section is displaced slightly in a radial direction in addition to its displacement in an axial direction, in response to the intake-air pulsation. Accordingly, it was found that an axial amplitude of the bellows-shaped elastic member is reduced so that an intake-noise reducing effect of the expansion-and-contraction deformation is not obtained to a maximum extent. That is, there is room for improvement on the intake-noise reducing effect. 
     Solution to Problem 
     According to the present invention, there is provided an intake noise reducing apparatus for an internal combustion engine, comprising: an elastic member being in a substantially cylindrical shape and including a base end which is open, a tip which is closed, and a peripheral wall which is bent in a bellows shape; a base plate holding the base end of the elastic member; and a communicating tube including one end connected with the base plate such that a chamber formed in the elastic member communicates with an intake passage of the internal combustion engine, wherein the bellows-shaped peripheral wall of the elastic member includes a plurality of high rigidity portions whose radial rigidities are locally strengthened, and the plurality of high rigidity portions are located axially away from each other. 
     For example, each of the high rigidity portions is formed by providing a straight-line portion parallel to an axial direction of the elastic member, at a crest portion of at least one of a mountain portion and a valley portion of the bellows-shaped peripheral wall. 
     Thus, the plurality of high rigidity portions are provided away from each other in the axial direction. Hence, a radial displacement of the elastic member which is caused by the intake-air pulsation introduced into the chamber of the elastic member is suppressed. Hence, an axial amplitude of the elastic member which is caused by the intake-air pulsation is increased so that sound pressure energy is converted into kinetic energy of the elastic member more effectively. Therefore, the intake-noise reducing effect of the expansion-and-contraction deformation of the elastic member can be obtained more effectively. 
     EFFECTS OF INVENTION 
     According to the present invention, intake noise in a specific frequency range is reduced as the Helmholtz-type resonator element. Moreover, the intake-noise reducing effect in a second specific frequency range can also be obtained by the expansion-and-contraction deformation of the bellows-shaped elastic member. In particular, the intake-noise reducing effect in the second specific frequency range is more effective because the radial displacement of the bellows-shaped elastic member is suppressed. 
    
    
     
       BRIEF EXPLANATION OF DRAWINGS 
         FIG. 1  An oblique perspective view illustrating an intake system for an internal combustion engine, which includes an intake noise reducing apparatus according to the present invention. 
         FIG. 2  An oblique perspective view illustrating the intake noise reducing apparatus in the state where a part of a case is cut. 
         FIG. 3  An oblique perspective view of an elastic member. 
         FIG. 4  A half sectional view of the elastic member. 
         FIG. 5  An enlarged sectional view of main part of the elastic member. 
         FIG. 6  A characteristic view illustrating an axial amplitude of the elastic member associated with intake-air pulsation in an embodiment, as compared with that in a comparative example. 
         FIG. 7  An enlarged sectional view illustrating a main part of an elastic member in the comparative example. 
         FIG. 8  A characteristic view illustrating an intake-noise reducing effect of the intake noise reducing apparatus in the embodiment. 
         FIG. 9  A characteristic view illustrating an intake-noise reducing effect of the intake noise reducing apparatus in the embodiment in another frequency range. 
         FIG. 10  An enlarged sectional view illustrating a main part of an elastic member in a second embodiment. 
         FIG. 11  An enlarged sectional view illustrating a main part of an elastic member in a third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Hereinafter, an embodiment according to the present invention will be explained in detail referring to the drawings. 
       FIG. 1  shows an intake system of an internal combustion engine for a vehicle (automobile), which includes an intake noise reducing apparatus  1  according to the present invention. An air cleaner  2  includes an air cleaner element therein. A downstream side of the air cleaner element, i.e. a so-called clean side of the air cleaner  2  is connected through a flexible intake duct  3  to the internal combustion engine (not shown). An upstream side of the air cleaner element, i.e. a so-called dust side of the air cleaner  2  is connected with an air introduction duct  4 . The air introduction duct  4  is formed by rigid synthetic-resin mold products. A tip of the air introduction duct  4  is open as an air introducing port  4   a.  An outside air taken from the air introducing port  4   a  passes through the air cleaner  2 , and then is introduced through the intake duct  3  into the internal combustion engine. 
     The air introduction duct  4  constitutes a part of an intake passage ranging from the air introducing port  4   a  to the internal combustion engine. In this embodiment, the intake noise reducing apparatus  1  is connected with a lateral surface of the air introduction duct  4 . The intake noise reducing apparatus  1  is provided for reducing an intake noise (such as a pulsation noise associated with pulsation of intake air and a flow noise associated with flow of intake air) which leaks from the air introducing port  4   a  to an outside. More specifically, a branch pipe  5  is formed such that the branch pipe  5  branches off from (i.e. arises from) the air introduction duct  4  formed of synthetic resin. The branch pipe  5  extends in a direction substantially perpendicular to a mainstream of intake air. The intake noise reducing apparatus  1  is connected with the branch pipe  5 . 
     Also as shown in  FIG. 2 , the intake noise reducing apparatus  1  mainly includes a base plate  12 , a case  13  and an elastic member  14 . The base plate  12  is formed in a circular shape (more specifically, in an annular shape). The base plate  12  includes a communicating tube  11  located at a center portion of the base plate  12 . The communicating tube  11  is fitted into the branch pipe  5  and thereby connected with the branch pipe  5 . The case  13  is formed in a cylindrical shape. One end  13   a  of the case  13  is fitted into the base plate  12 . The elastic member  14  is formed in a bellows shape (accordion shape), and is accommodated in the case  13 . 
     For example, the base plate  12  is formed integrally with the communicating tube  11  by means of molding of rigid synthetic resin. The base plate  12  includes an outer circumferential edge portion  12   a  that protrudes in an axial direction. The one end  13   a  of the case  13  is fitted into a radially inner surface of the outer circumferential edge portion  12   a.  The communicating tube  11  cooperates with the branch pipe  5  to define a neck tube of a so-called Helmholtz-type resonator element. A tube length and a bore diameter of a combination of the communicating tube  11  and the branch pipe  5  are set so as to correspond to a desired resonance frequency. 
     For example, the case  13  is a rigid synthetic-resin mold product. The case  13  includes a flange portion  16  and an end-portion wall  17 . The flange portion  16  is formed in an annular shape at a location near the one end  13   a  which is fitted into the outer circumferential edge portion  12   a  of the base plate  12 . The flange portion  16  conducts a positioning by becoming axially in contact with the outer circumferential edge portion  12   a.  The end-portion wall  17  is located at another end  13   b  of the case  13 . The end-portion wall  17  extends along a plane perpendicular to the axial direction of the case  13 , and is located at an outer circumferential portion of the case  13 . A center portion of the another end  13   b  is open as a circular communicating hole  18 . Hence, an inside of the case  13  is exposed through the communicating hole  18  to ambient air. The communicating hole  18  is surrounded by a cylindrical portion (tubular portion)  19 . The cylindrical portion  19  is formed continuously with the end-portion wall  17 , and has a relatively short length. Basically, the case  13  is provided in order to protect the elastic member  14  from touching external objects. However, the case  13  does not necessarily need to be provided in the intake noise reducing apparatus according to the present invention. 
     Also as shown in  FIGS. 3 and 4 , the elastic member  14  is substantially in a cylindrical shape, and includes a base end  14   a  (see  FIG. 4 ), a tip  14   b  and a peripheral wall  14   c . The base end  14   a  is open whereas the tip  14   b  is closed and sealed. The peripheral wall  14   c  is formed such that the peripheral wall  14   c  is bent in a bellows shape. The elastic member  14  is formed of an elastomer having a proper elasticity (such as a thermoplastic elastomer), and is integrally molded. At the tip  14   b  which functions as a sealing end, a circular end plate  21  which is a rigid synthetic-resin mold product is placed in order to avoid an undesired deformation of a tip-surface portion. The end plate  21  is attached integrally to the elastic member  14  by means of so-called insert molding when molding the elastic member  14 . 
     At the base end  14   a  which functions as an opening end, an annular mounting flange  22  is formed to be relatively thick. The mounting flange  22  has an outer diameter which enables the mounting flange  22  to be fitted closely into an inside of the outer circumferential edge portion  12   a  of the base plate  12 . The mounting flange  22  is sandwiched and held between the base plate  12  and the one end  13   a  of the case  13 , and thereby the elastic member  14  is held and fixed to the base plate  12 . A sealing protrusion  23  is formed on a contact surface of the mounting flange  22  on which the base plate  12  abuts. 
     In the state where the elastic member  14  has been attached to the base plate  12 , a chamber  24  formed in the elastic member  14  is a space enclosed and separated from a space formed in the case  13 . In this state, the chamber  24  communicates with an intake passage of the air introduction duct  4  through the communicating tube  11  of the base plate  12 . 
     An outer diameter of the peripheral wall  14   c  of the elastic member  14  is set to be slightly smaller than an inner diameter of the case  13 . The tip  14   b  of the elastic member  14  is located properly away from the end-portion wall  17  of the case  13 . Therefore, in the state where the base end  14   a  has been fixed to the base plate  12 , the elastic member  14  can freely expand and contract in the case  13  by causing the tip  14   b  to function as a free end. 
     As a basic operation of the intake noise reducing apparatus  1  as constructed above, the so-called Helmholtz-type resonator element is realized. The chamber  24  set to have a proper volume is connected (communicated) with the intake passage of the internal combustion engine through the communicating tube  11  and the branch pipe  5  which function as the neck tube of the Helmholtz-type resonator element. Therefore, the intake noise is reduced in a specific frequency range. It is noted that the volume of the chamber  24  or the like is adjusted such that a reducing effect of the intake noise can be obtained in a desired frequency band. 
     At the same time, the intake-air pulsation is introduced into the chamber  24 . As a result, the shape of the elastic member  14  is changed such that the elastic member  14  expands and contracts in the axial direction. Thus, a sound pressure energy is converted into a kinetic energy of the elastic member  14 . Hence, the reducing effect of the intake noise can be obtained in a second specific frequency range. This second specific frequency range can be set at a desired frequency range by setting a spring constant of the elastic member  14  and a weight of the elastic member  14  or the like. It is noted that, although the frequency range of the Helmholtz-type resonator element may overlap with the second frequency range, the intake noise can be reduced over a wider range by suitably setting the frequency range of the Helmholtz-type resonator element and the second frequency range. 
     Next, a structure of the peripheral wall  14   c  of the elastic member  14  which is a major part according to the present invention will now be explained in more detail. 
     As shown in  FIG. 4 , in this embodiment, the peripheral wall  14   c  is formed in a bellows shape such that mountain portions (hill portions)  31  and valley portions (trough portions)  32  are alternately formed between the mounting flange  22  and the end plate  21 . The number of the mountain portions  31  is “n” (for example, 10) whereas the number of the valley portions  32  is “n−1” (for example, 9). The n mountain portions  31  have longitudinally-cross-sectional shapes identical with one another. The (n−1) valley portions  32  have longitudinally-cross-sectional shapes identical with one another. As shown in an enlarged view of  FIG. 5 , the mountain portion  31  and the valley portion  32  which are adjacent to each other are connected to each other through a taper wall  33 . The taper wall  33  is inclined relative to an axis (center line) of the elastic member  14 . As shown in  FIG. 5 , each taper wall  33  extends in a straight-line shape in longitudinally-cross section. The elastic member  14  has a rotator shape as obtained by rotating a longitudinally-cross-sectional shape shown in  FIGS. 4 and 5  about the axis. Hence, in detail, the taper wall  33  is an annular conical surface which is small in width. Each mountain portion  31  is connected with one pair of taper walls  33  which exist on upper and lower sides of the mountain portion  31 . These two taper walls  33  have shapes symmetrical to each other with respect to the mountain portion  31 . 
     A crest portion of each mountain portion  31  is formed as a straight-line portion  35  parallel to the axis (center line) of the elastic member  14 . In the same manner, a crest portion of each valley portion  32  is formed as a straight-line portion  36  parallel to the axis (center line) of the elastic member  14 . That is, as shown in  FIG. 5 , each mountain portion  31  is bent at two points of a point A 1  and a point A 2  in longitudinally-cross section. Each mountain portion  31  cooperates with both the adjacent taper walls  33  to construct a trapezoidal shape in longitudinally-cross section. In the same manner, each valley portion  32  is bent at two points of a point A 3  and a point A 4  in longitudinally-cross section. Each valley portion  32  cooperates with both the adjacent taper walls  33  to construct a trapezoidal shape in longitudinally-cross section. As viewed in longitudinally-cross section, the trapezoidal shape of the mountain portion  31  is the same as the trapezoidal shape of the valley portion  32 . It is noted that a thickness is basically constant over all portions except the mounting flange  22 . 
     It is favorable that an inclination angle α (i.e. angle with respect to a plane perpendicular to the axis of the elastic member  14 ) of each taper wall  33  is relatively small in order to facilitate axial deformation and vibration of the elastic member  14 . For example, it is favorable that the inclination angle α is smaller than or equal to 25 degrees. 
     In this embodiment, each of the straight-line portion  35  of the mountain portion  31  and the straight-line portion  36  of the valley portion  32  is short in length, but forms a cylindrical shape as viewed in three dimensions. Hence, each of the straight-line portion  35  and the straight-line portion  36  is difficult to change in shape in a radial direction. That is, the straight-line portions  35  and the straight-line portions  36  are high rigidity portions each of which has a high rigidity in the radial direction. When an internal pressure of the chamber  24  changes, the taper walls  33  each of which connects the straight-line portion  35  of the mountain portion  31  with the straight-line portion  36  of the valley portion  32  swing about the bending points A 1  to A 4 . Hence, basically, the elastic member  14  expands and contracts only in the axial direction. As a result, an amplitude in the axial direction can be largely secured for the intake-air pulsation, so that a more effective reducing effect of the intake noise can be obtained. In other words, the plurality of high rigidity portions exist annularly and are away from one another in the axial direction such that the taper walls  33  which are capable of swing deformation connect these high rigidity portions with each other. Accordingly, a free deformation (i.e. change in shape) in the axial direction is permitted while suppressing a displacement in the radial direction. Therefore, a larger amplitude can be obtained against a change of sound pressure. 
       FIG. 6  is a view showing a vibration amplitude (a displacement of the end plate  21 ) relative to the intake-air pulsation of the elastic member  14 , as compared with a comparative example. As shown in  FIG. 7 , an elastic member in the comparative example includes mountain portions  131  and valley portions  132  each of which is formed in a simple V-shape in longitudinally-cross section. The number of mountain portions  131 , the number of valley portions  132  and a thickness of a peripheral wall, etc. in the comparative example are basically the same as those in this embodiment according to the present invention. 
     As shown in  FIG. 6 , the amplitude in this embodiment is approximately three times as large as that in the comparative example. It is noted that a frequency value having a peak of silencing effect in  FIG. 6  is somewhat different between in this embodiment and in the comparative example because the shapes of the mountain portions  131  and the valley portions  132  are respectively different from the shapes of the mountain portions  31  and the valley portions  32 . However, the silencing-effect result shown in  FIG. 6  is basically the same as in the case that the structure has been adjusted such that the frequency value having the peak of silencing effect is constant between in this embodiment and in the comparative example. 
       FIG. 8  is a characteristic view showing a characteristic of the intake-noise reducing effect produced by the intake noise reducing apparatus  1  which includes the elastic member  14  formed in a bellows shape and in a trapezoidal shape in longitudinally-cross section as mentioned above. In  FIG. 8 , the characteristic is compared with an intake noise characteristic produced in the case where the intake noise reducing apparatus  1  has been removed from the intake system shown in  FIG. 1  as a “second comparative example”. As shown in  FIG. 8 , the intake-noise reducing effect was obtained in a frequency range shown by a region “a”. This is because the elastic member  14  conducts the axial expansion-and-contraction deformation as explained above. In particular, in this embodiment, the amplitude in the axial direction can be largely secured as shown in  FIG. 6 . Hence, sound pressure energy is effectively converted into kinetic energy so that a larger intake-noise reducing effect can be produced. 
     On the other hand,  FIG. 9  shows the intake-noise reducing effect in a frequency range in which the intake-noise reducing effect as the Helmholtz-type resonator element can be obtained (i.e. in a relatively high frequency region as compared with  FIG. 8 ). The “second comparative example” of  FIG. 9  is the case where the intake noise reducing apparatus  1  has been removed from the intake system of  FIG. 1  in the same manner as  FIG. 8 . As shown in  FIG. 9 , the intake-noise reducing effect as the Helmholtz-type resonator element is not impaired although each of the mountain portions  31  and the valley portions  32  is formed in a trapezoidal shape in cross section. Accordingly, favorable intake-noise reducing effect can be realized over a relatively wide frequency range. 
     In the above embodiment, both of the mountain portions  31  and the valley portions  32  include the straight-line portions  35  and  36 , i.e. the high rigidity portions. However, according to the present invention, only one side of the mountain portions  31  and the valley portions  32  may include the straight-line portions  35  or  36 . Moreover, according to the present invention, the trapezoidal shape of each mountain portion  31  may be designed to differ from the trapezoidal shape of each valley portion  32 . Furthermore, according to the present invention, each of the plurality of mountain portions  31  (or each of the plurality of valley portions  32 ) does not necessarily need to be formed in an identical shape. Instead, the plurality of mountain portions  31  or the plurality of valley portions  32  may include different cross-sectional shapes. 
     Next,  FIG. 10  is a view showing an elastic member  14  in a second embodiment according to the present invention. In this second embodiment, the elastic member  14  includes a plurality of main valley portions  32 A (for example, three to five main valley portions  32 A) which have not-strengthened radial rigidities. Between adjacent two of the plurality of main valley portions  32 A in the axial direction, two sub-mountain portions  31 B and one sub-valley portion  32 B are provided such that a pitch (i.e. an axial length) of each of the two sub-mountain portions  31 B and the one sub-valley portion  32 B is narrowed locally. Each of the main valley portions  32 A, the sub-mountain portions  31 A and the sub-valley portions  32 B is formed in a simple V-shape in longitudinally-cross section. 
     That is, a peripheral wall  14   c  of the elastic member  14  is bent at five bending points B 1  to B 5  shown in  FIG. 10 . A pitch between the bending point B 1  which is a crest portion of the sub-mountain portion  31 A and the bending point B 3  which is a crest portion of the next sub-mountain portion  31 A is narrower than a pitch between the bending point B 3  and the bending portion B 5  which sandwich the main valley portion  32 A. In other words, three bending points (B 1 , B 2 , B 3 ) at which a bending direction is changed with short pitches (lengths) are provided between adjacent two main valley portions  32 A. These bending points B 1 , B 2  and B 3 , i.e. the two sub-mountain portions  31 A and the sub-valley portion  32 B sandwiched therebetween constitute a high rigidity portion which has a radial rigidity strengthened locally. It is noted that an inner diameter of the sub-valley portion  32 B is larger than an inner diameter of the main valley portion  32 A as shown in  FIG. 10 . 
     Next,  FIG. 11  is a view showing an elastic member  14  in a third embodiment according to the present invention. In this third embodiment, a straight-line portion  41  which substantially extends along a plane perpendicular to an axis of the elastic member  14  is provided between a mountain portion  31  and a valley portion  32  which are adjacent to each other. Each mountain portion  31  is constituted by a pair of taper walls  42  combined in a substantially V-shape. Each valley portion  32  is constituted by a pair of taper walls  43  combined in a substantially V-shape. The taper wall  42  of the mountain portion  31  is connected through the straight-line portion  41  to the taper wall  43  of the valley portion  32 . 
     In other words, the combination of one mountain portion  31  and one valley portion  32  is given by six bending points C 1  to C 6  shown in longitudinally-cross section. Thus, this part bends multiple times. Hence, in particular, the straight-line portion  41  which includes the bending points C 3  and C 4  has a rigidity locally strengthened in the radial direction, so that a radial displacement of the elastic member  14  in response to change in sound pressure is suppressed. 
     Although certain embodiments according to the present invention have been explained in detail, the invention is not limited to the embodiments described above. Various modifications of the embodiments described above will occur. For example, in the above embodiments, the intake noise reducing apparatus  1  which uses the elastic member  14  is connected with the air introduction duct  4  of the intake system. However, the intake noise reducing apparatus  1  may be connected with the other part of the intake system. 
     EXPLANATION OF REFERENCE SIGNS 
     
         
           1  Intake noise reducing apparatus 
           11  Communicating tube 
           12  Base plate 
           13  Case 
           14  Elastic member 
           21  End plate 
           24  Chamber 
           31  Mountain portion 
           32  Valley portion 
           33  Taper wall 
           35 ,  36  Straight-line portion