Abstract:
A noise insulation structure of a synthetic resin made conduit includes a synthetic resin made chamber and a rubber made noise insulation member. Since the chamber is closely covered around with the noise insulation member through projections and grooves formed on the contact surface of the chamber with the noise insulation member. Further, cylindrical blind-end bores are provided on the inner surface of the noise insulation member so as to form air columns when the noise insulation member is installed on the chamber. The air columns serve as resonators to muffle noise.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a synthetic resin made chamber of a conduit system for an internal combustion engine and more particularly to a noise insulation structure of the synthetic resin made chamber including an intake manifold and an intake chamber.  
           [0003]    2. Discussion of Prior Art  
           [0004]    In recent years, intake manifolds made of synthetic resin attract an interest in view of weight reduction, cost reduction and recycleability of automobile components. However, synthetic resin intake manifolds have a defect that noise is penetrable because of light weight. In order to effectively insulate and eliminate a noise propagated from air stream in the intake manifold (hereinafter, referred to as intake noise), the synthetic resin intake manifolds are inferior to aluminum alloy made intake manifolds.  
           [0005]    The synthetic resin intake manifold with a larger wall thickness has a greater effect of noise insulation but has a disadvantage in productivity due to more elongated time for curing resin, therefore there is a limit in increasing the wall thickness of the synthetic resin intake manifold.  
           [0006]    This problem is not limited to synthetic resin intake manifolds and also occurs in fabricating miscellaneous synthetic resin chambers including synthetic resin intake chambers.  
         SUMMARY OF THE INVENTION  
         [0007]    It is an object of the present invention to provide a synthetic resin chamber having a high noise insulation ability and capable of being manufactured at low cost.  
           [0008]    In order to achieve the object, a noise insulation structure of a conduit system of an internal combustion engine comprises a synthetic resin made chamber and a noise insulation member installed on the chamber in such a manner as covering the chamber. Specifically, the synthetic resin made chamber has a plurality of ribs and a plurality of first grooves formed between two adjacent ribs on the outer surface thereof, the noise insulation member has a plurality of projections extending along the ribs and a plurality of second grooves formed between two adjacent projections, the ribs fit to the second grooves and the projections fit to the first grooves so that the chamber has a close contact with the noise insulation member.  
           [0009]    Further, the projection has a plurality of cylindrical blind-end bores provided along an extending direction of the projection on a top portion of the projection. These cylindrical blind-end bores make air columns when the chamber is covered with the noise insulation member and the air columns serves as muffling noise due to the resonance effect. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    [0010]FIG. 1 is atop view of a synthetic resin intake manifold according to the present invention;  
         [0011]    [0011]FIG. 2 is a front view of a synthetic resin intake manifold according to the present invention;  
         [0012]    [0012]FIG. 3 is a sectional view taken along a line A-A of FIG. 2;  
         [0013]    [0013]FIGS. 4 a  and  4   b  are explanatory views showing how to mount a noise insulation member;  
         [0014]    [0014]FIG. 5 is a sectional view taken along a line B-B of FIG. 1;  
         [0015]    [0015]FIGS. 6 a  and  6   b  are enlarged views of fitting portions; and  
         [0016]    [0016]FIGS. 7 a  and  7   b  are enlarged views of fitting portions. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]    Referring now to FIGS. 1 and 2, reference numeral  1  denotes an intake manifold made of synthetic resin for a horizontally opposed four cylinders engine. Intake passages  2   a ,  2   b ,  2   c  and  2   d  and a chamber section  3  are integrally formed with the intake manifold  1 . The chamber section  3  has an air intake inlet  4  for introducing air through a throttle valve (not shown) on the rear side thereof. Intake passages  2   a  and  2   c  extend from one side of the chamber section  3  to supply air to two cylinders on the left bank side and intake passages  2   b  and  2   d  extend from the other side of the chamber section  3  to supply air to two cylinders on the right bank side. The adjacent paired intake passages  2   a  and  2   c  (or  2   b  and  2   d ) gradually go apart from each other as they extend toward the left (or right) bank of the engine. There is provided a flange section  5   a  at the left end of the paired intake passages  2   a ,  2   c  and there is a provided a flange section  5   b  at the right end of the paired intake passages  2   b ,  2   d . Further, there is provided each opening of the intake passages  2   a ,  2   c  on the under surface of the flange section  5   a  and there is provided each opening of the intake passages  2   b ,  2   d  on the under surface of the flange section  5   b . The intake manifold  1  is mounted on a cylinder head (not shown) of the engine. Air introduced from the air intake inlet  4  to the chamber section  3  is guided to respective intake ports of the cylinder head through the bifurcated intake passages  2   a ,  2   b ,  2   c  and  2   d.    
         [0018]    Installation sections  6   a ,  6   b ,  6   c  and  6   d  on which sensors, wires, pipes and the like are installed are formed integrally with the chamber section  3  in such a manner as projecting from the exterior surface of the chamber section  3 . Further, there are provided injector installation sections  7   a ,  7   b ,  7   c  and  7   d  in the vicinity of the flange sections  5   a ,  5   b . When fuel injectors (not shown) are mounted on the injector installation sections  7   a ,  7   b ,  7   c  and  7   d , fuel injection nozzles of the fuel injectors is opposite to the intake passages  2   a ,  2   b ,  2   c  and  2   d  so as to inject fuel towards the intake ports of the engine. Further, a plurality of ribs  8  is integrally formed with the intake manifold  1  in such a manner as projecting from the exterior surface of the intake manifold  1 . These ribs  8  are disposed in appropriate positions of the exterior surface of the intake manifold  1 , such as the outer wall of the intake passages  2   a ,  2   b ,  2   c  and  2   d , the connecting portion of the intake passages  2   a ,  2   b ,  2   c  and  2   d  with the chamber  3  and others. These ribs  8  serves as enhancing the strength of the intake manifold  1  and damping vibrations so as to raise the noise insulation performance of the intake manifold  1  itself.  
         [0019]    The chamber section  3  is closely covered around with a noise insulation member  9 . The noise insulation member  9  is made of rubber sheet molded on the configuration of the chamber section  3 . In this embodiment, the noise insulation member  9  has a thickness of  6  millimeters and is made of ethylene propylene rubber (EPDM), synthetic rubber which is inexpensive and durable, or made of butyl rubber which is thermoplastic elastic body. Further, the noise insulation member  9  has relief holes for avoiding the ribs  8  and installation sections  6   a ,  6   b ,  6   c  and  6   d.    
         [0020]    A plurality of protrusions  10  are integrally molded on the exterior surface of the chamber section  3 . The noise insulation member  9  is secured to the chamber section  3  by deforming a top section of the protrusions  10  by applying heat thereto. The protrusions  10   a  and  10   b  are shaped such that the top sections of the protrusions  10   a  and  10   b  are projected from the exterior surface of the noise insulation member  9  when the noise insulation member  9  is fitted to the chamber section  3 . On the other hand, the noise insulation member  9  has through holes  11   a  and  11   b  for allowing the protrusions  10   a  and  10   b  to pass through the interior and exterior surfaces of the noise insulation member  9  in a right position corresponding to the protrusions  10   a  and  10   b , respectively.  
         [0021]    When the noise insulation member  9  is installed, first the through hole  11   a  of the noise insulation member  9  is fitted over the protrusion  10   a  of the chamber section  3  to locate the noise insulation member  9  in a proper position, as shown in FIG. 4 a . Then, the top section of the protrusion  10   a  is heated to be deformed (heat caulking). Thus, one side of the noise insulation member  9  is secured to the chamber section  3  (see FIG. 4 b ). Then, the noise insulation member  9  is closely fitted on the chamber section  3  in an arrow direction of FIG. 3. The tight fitting of the noise insulation member  9  on the chamber section  3  is accomplished by inlaying convex portions formed on the surface of the chamber section  3  into concave portions formed on the surface of the noise insulation member  9  or vise versa. Then, the protrusion  10   b  passes through the through hole  11   b  and the chamber section  3  is covered around with the noise insulation member  9 . Finally, the aforesaid heat caulking is applied to the protrusion  10   b . Thus, the noise insulation member  9  can be secured to the chamber section  3  with a relatively easy work.  
         [0022]    Referring to FIG. 5, a plurality of engagement ribs  12  are integrally formed on the exterior surface of the chamber section  3  in order to secure strength of the chamber section  3  and tightness of the noise insulation member  9 . These engagement ribs  12  have a specified height, for example,  2  millimeters high, are arranged at a specified interval and each of the engagement ribs  12  extend straight along the configuration of the chamber section  3 . Further, a plurality of engagement projections  13  having approximately the same height as the engagement ribs  12  are formed on the contact surface with the chamber section  3  of the noise insulation member  9 . The engagement projections  13  have approximately the same width as a groove formed between two adjacent engagement ribs  12 ,  12  and extend straight in an extending direction of the engagement ribs  12 . The engagement projections  13  are fitted to the groove formed between two adjacent engagement ribs  12 ,  12 . Further, the engagement ribs  12  are fitted to a groove formed between two adjacent engagement projections  13 ,  13 . Thus, in addition to the heat caulking applied, since the projections and grooves formed on the both surfaces of the chamber section  3  and noise insulation member  9  are fitted to or over each other, the noise insulation member  9  is secured to the chamber section  3 .  
         [0023]    Referring to FIGS. 6 a  and  6   b , cylindrical blind-end bores  14  are formed along a straight line on the top surface of the engagement projections  13 . When the engagement ribs  12  and the engagement projections  13  are fitted to the grooves respectively, air is sealed in the cylindrical blind-end bores  14  and an air column is formed. The air column has a resonance effect, in which a noise having a specific frequency is suppressed or muffled according to the diameter or length of the air column. The diameter and the length of the cylindrical bores  14  are properly established in consideration of frequency of the intake noise to be muffled. The cylindrical bores  14  are not limited to have a cylindrical configuration but may have an appropriate configuration including polygonal pole.  
         [0024]    In this embodiment, the chamber section  3  which is a primary source of intake noise is covered around with the noise insulation member  9  having an excellent noise insulation effect. Particularly, since the engagement ribs  12  integrally formed with the chamber section  3  are engaged with the engagement projections  13  integrally formed with the noise insulation member  9 , the noise insulation member  9  can have a close contact with the chamber section  3 . As a result, the chamber section  3  is furnished with an excellent damping effect against noise. Further, since air is sealed in the cylindrical blind-end bores  14  formed on the top portions of the engagement projections  13 , the cylindrical blind-end bores  14  serves as a resonator and as a result the noise insulation performance enhances. Thus, intake noise whose main source is the chamber section  3  can be reduced to almost the same level as an intake manifold made of aluminum alloy.  
         [0025]    Further, the location of the noise insulation member  9  can be easily determined by fitting the protrusion  10  of the chamber section  3  to the through hole  11  of the noise insulation member  9 . Further, the noise insulation member  9  can be easily secured to the chamber section  3  by heat caulking without using additional equipments for installation. Accordingly, the installation work of the noise insulation member  9  can be accomplished easily and efficiently. Further, since the number of components can be reduced, the manufacturing cost can be reduced.  
         [0026]    In the aforesaid embodiment, the cylindrical bores  14  are provided on the noise insulation member  9  but these cylindrical bores  14  may be provided on the chamber section  3 , as shown in FIGS. 7 a  and  7   b . Further, in the aforesaid embodiment, the chamber section of the intake manifold has been exemplified but the chamber does not belong only to the intake manifold. The chamber structure may be applied to other miscellaneous synthetic resin chambers used in an engine.  
         [0027]    While the presently preferred embodiments of the present invention have been shown and described, it is to be understood that these disclosures are for the purpose of illustration and that various changes and modifications may be made without departing from the scope of the invention as set forth in the appended claims.