Assembly structure for synthetic-resin component

Abstract

 An assembly structure includes a duct (11) including a protruding portion (31) provided in an outer circumference of the duct (11); a first component (13) including a first tubular fitting portion (34) configured to be fitted to a tip portion of the duct (11) by an insertion of the duct (11); and a second component (14) configured to be tip side of the second tubular fitting portion (35) and configured to be fitted to an outer circumferential surface of the first tubular fitting portion (34), a small diameter portion (37) located at a root side of the second tubular fitting portion (35) and configured to be fitted to the duct, and a step surface (38) located between the large diameter portion (30) and the small diameter portion (37). The step surface (38) faces a tip surface (41) of the first tubular fitting portion (34) to provide a concave portion (42) between the step surface (38) and the tip surface (41), and the protruding portion (31) is fitted to the concave portion (42), under a state where the duct (11) and the first and second components (13,14) have been attached to one another.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a synthetic-resin component which is suitable for, e.g., a component for air-intake system such as a resonator and an air-intake duct in an internal combustion engine of vehicle, and more particularly, relates to the improvement of an assembly structure using elasticity of synthetic-resin material itself.

[0002] Japanese Patent Application Publication No. 2002-106437 discloses a previously proposed apparatus. As disclosed in this document, there is a tendency to employ a following technique. That is, each of components constituting an air-intake system such as a resonator for reducing intake noise and an air-intake duct attached to the resonator in an internal combustion engine of vehicle is formed of synthetic-resin material having a proper flexibility by a blow molding or an injection molding. These components are fitted and attached to each other under a sealed state by using an elasticity of components themselves.

SUMMARY OF THE INVENTION

[0003] FIGS. 6 and 7 are views showing one comparative example of components of an air-intake system. In this comparative example, a body 63 formed of synthetic resin is connected with a cover 64 formed of synthetic resin at opening edge portions of the body 63 and cover 64 so as to form a volume chamber 62 around an air-intake duct 61 formed of synthetic resin. The volume chamber 62 functions as a resonance chamber of resonator. The air-intake duct 61 is inserted into a tubular fitting portion 65 of the body 63, by press fitting. Thereby, a positioning protruding portion 66 provided in an outer circumference of the air-intake duct 61 is fitted to a concave portion 67 of the tubular fitting portion 65, so that the air-intake duct 61 is attached to the body 63 under the sealed state. On the other hand, the opening edge portion of cover 64 is connected and fixed to a connecting portion 68 of the body 63 by means of vibration welding or the like.

[0004] In such an example, the connecting portion 68 of body 63 to which the cover 64 is connected needs to be provided away from the tubular fitting portion 65 of body 63 to which the air-intake duct 61 is fitted. Hence, an interval (distance) D1 between an inner space of the air-intake duct 61 and the volume chamber 62 provided around the air-intake duct 61 is large. As a result, a dead space which is not available as the volume chamber becomes large to reduce a capacity (volume) of the volume chamber 62. If trying to secure a necessary capacity of the volume chamber 62, whole of the air-intake system grows in size. Moreover, if trying to bend and/or elongate the air-intake duct by making a detour to avoid the volume chamber, an increase of airflow resistance and a reduction of engine output due to this airflow-resistance increase and the like are incurred.

[0005] It is an object of the present invention to provide an assembly structure for synthetic-resin components, devised to secure a sufficient capacity of volume chamber without incurring the size growth of system in a layout in which the volume chamber is provided around the duct.

[0006] According to one aspect of the present invention, there is provided an assembly structure comprising: a duct formed of synthetic resin, the duct including a protruding portion provided in an outer circumference of the duct; a first component formed of synthetic resin, the first component including a first tubular fitting portion configured to be fitted to a tip portion of the duct by an insertion of the duct; and a second component formed of synthetic resin and configured to be fitted to the first component to define a volume chamber around the duct, the second component including a second tubular fitting portion having a large diameter portion located at a tip side of the second tubular fitting portion relative to an insertion direction of the duct and configured to be fitted to an outer circumferential surface of the first tubular fitting portion, a small diameter portion located at a root side of the second tubular fitting portion relative to the insertion direction and configured to be fitted to the duct, and a step surface located between the large diameter portion and the small diameter portion, wherein the step surface faces a tip surface of the first tubular fitting portion to provide a concave portion between the step surface and the tip surface, and the protruding portion is fitted to the concave portion, under a state where the duct and the first and second components have been attached to one another.

[0007] According to another aspect of the present invention, there is provided an assembly method for synthetic-resin components, the synthetic-resin components including a duct formed of synthetic resin, the duct including a protruding portion provided in an outer circumference of the duct; a first component formed of synthetic resin, the first component including a first tubular fitting portion; and a second component formed of synthetic resin, the second component including a second tubular fitting portion having a large diameter portion located at a tip side of the second tubular fitting portion, a small diameter portion located at a root side of the second tubular fitting portion, and a step surface located between the large diameter portion and the small diameter portion, the assembly method comprising: fitting the large diameter portion to an outer circumferential surface of the first tubular fitting portion to define a volume chamber; causing the step surface to face a tip surface of the first tubular fitting portion so as to provide a concave portion between the step surface and the tip surface; fitting a tip portion of the duct to the first tubular fitting portion by an insertion of the duct; fitting the small diameter portion to the duct; and fitting the protruding portion to the concave portion, so that the duct and the first and second components are attached to one another to form the volume chamber around the duct.

[0008] The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG. 1 is a cross sectional view showing components of air-intake system under an assembled state, in an embodiment according to the present invention.

[0010] FIG. 2 is a cross sectional view showing the components of air-intake system under an exploded state, in the embodiment.

[0011] FIG. 3 is an exploded perspective view of the components of air-intake system.

[0012] FIG. 4 is a perspective view showing the components of air-intake system.

[0013] FIG. 5 is a cross sectional view showing the components of air-intake system.

[0014] FIG. 6 is a cross sectional view showing an assembled state of components of air-intake system, in a comparative example.

[0015] FIG. 7 is a cross sectional view showing an exploded state of the components of air-intake system, in the comparative example.

DETAILED DESCRIPTION OF THE INVENTION

[0016] Reference will hereinafter be made to the drawings in order to facilitate better understandings of the present invention.

[0017] An embodiment according to the present invention will be now explained in detail. FIGS. 3 to 5 show components formed of synthetic-resin in the embodiment according to the present invention. These components function as components of air-intake system (induction system) for an internal combustion engine of vehicle. A structure of air-intake system is given by connecting (assembling) a plurality of components with one another. The plurality of components are formed by an injection molding of synthetic-resin material. The components of intake-air system include an air intake duct 11, a body 13, a cover 14, and a housing 15. The air intake duct 11 is formed in a cylindrically tubular shape. The body 13 cooperates with the cover 14 to define a volume chamber 12, by causing one opening edge portion of the body 13 to be fitted to (engaged with) an opening edge portion of the cover 14. The volume chamber 12 is formed by the body 13 and the cover 14 around the air intake duct 11, as a resonant chamber of resonator. The housing 15 is engaged with (or fitted to) another opening edge portion of the body 13. Thereby, the housing 15 holds the body 13 and supports a filter element 16 by sandwiching the filter element 16 between the housing 15 and the body 13. It is noted that the body 13 corresponds to a first component according to the present invention, and the cover 14 corresponds to a second component according to the present invention.

[0018] The air intake duct 11 includes a pair of duct division members 17 and 18 which are fitted to each other. That is, the air intake duct 11 can be divided in half, i.e., into the duct division members 17 and 18 along a passage-length direction of the air intake duct 11. A plurality of locking nails (hooks) 19 are provided to an opening edge portion of one of the duct division members 17 and 18. On the other hand, a plurality of locking grooves (engaging grooves) 20 are provided to an opening edge portion of another of the duct division members 17 and 18. The both duct division members 17 and 18 are combined integrally with each other, by causing the plurality of locking nails 19 to be engaged with the plurality of locking grooves 20. Thereby, the both opening edge portions of duct division members 17 and 18 are fitted to each other. One end portion 21 of air intake duct 11 which is attached to the body 13 and the cover 14 is not dividable, i.e., is formed by one (18 in FIG. 3) of the duct division members 17 and 18 in a cylindrical tube shape. That is, the one end portion 21 is formed by one member in order to secure an assembling performance and its accuracy. This one end portion 21 includes an after-mentioned protruding portion 31 and a duct-side diameter-enlarged portion 32.

[0019] A plurality of hooks 22 are provided to the opening edge portion of one (14 in FIG. 3) of the body 13 and cover 14. On the other hand, a plurality of locking protrusions 23 are provided to the opening edge portion of another (13 in FIG. 3) of the body 13 and cover 14. The plurality of hooks 22 are engaged (locked) with the plurality of locking protrusions 23 so that the cover 14 is attached integrally to the body 13. Moreover, a plurality of metal pieces 24 are provided to the opening edge portion of one (13 in FIG. 3) of the body 13 and the housing 15, and on the other hand, a plurality of locking portions 25 are provided to an opening edge portion of another (15 in FIG. 3) of the body 13 and the housing 15. The plurality of metal pieces 24 are engaged with the plurality of locking portions 25, so that the body 13 is attached integrally to the housing 15 so as to sandwich the filter element 16 between the body 13 and the housing 15.

[0020] An intake air which has been introduced from the air intake duct 11 into the body 13 is partly supplied through a return pipe passage 26 to the volume chamber 12. The return pipe passage 26 functions as a neck portion (throttle portion). Also, (the other part of) the intake air inside the body 13 is supplied through the filter element 16 to the side of a combustion chamber of the internal combustion engine. An opening portion 27 is formed in an outer wall of the body 13 to pass through the outer wall, in order to prevent an undercut of the return pipe passage 26 at the time of injection molding of the body 13. This opening portion 27 is covered by a cover portion (lid) 28, afterwards.

[0021] FIGS. 1 and 2 are cross sectional views showing an assembly structure among the air intake duct 11, the body 13 and the cover 14, which constitutes a main part according to this embodiment. FIGS. 1 and 2 are simplified views for clearly showing a part surrounded by an alternate long-and-short dash line α of FIG. 5. FIG. 1 shows an assembled state of the air intake duct 11, the body 13 and the cover 14. FIG. 2 shows a not-yet-assembled state (pre-assembly state) of the air intake duct 11, the body 13 and the cover 14.

[0022] A duct outer circumferential surface 30 of the air intake duct 11 is formed in a cylindrical surface which is tapering gradually toward a tip side of air intake duct 11 (in a lower direction of FIGS. 1 and 2). That is, the duct outer circumferential surface 30 is a gentle tapered surface whose diameter becomes smaller as a location for measuring the diameter is more shifted in an insertion direction S1. This duct outer circumferential surface 30 is formed with the protruding portion 31 which bulges outwardly in a radial direction of air intake duct 11. That is, the protruding portion 31 is formed to protrude in an expanded state from the duct outer circumferential surface 30. In this embodiment, this protruding portion 31 is provided to extend along an entire circumference of the duct outer circumferential surface 30, i.e., is formed over the entire circumferential range of the duct outer circumferential surface 30 in a strip shape (belt shape). However, according to this embodiment, a plurality of protruding portions each of which is formed in an embossed shape may be provided on the duct outer circumferential surface 30 intermittently in a circumferential direction of air intake duct 11, instead of the strip-shaped protruding portion 31.

[0023] Moreover, a duct-side diameter-enlarged portion 32 is provided in an outer circumference of the air intake duct 11, i.e., on the duct outer circumferential surface 30 of air intake duct 11. This duct-side diameter-enlarged portion 32 is formed at a root side (counter-tip side of air intake duct 11) beyond the protruding portion 31 (at an upper location of FIGS. 1 and 2 beyond the protruding portion 31), and bulges outwardly in the radial direction so as to increase thickness and outer diameter of the air intake duct 11. Thereby, a duct-side tapered-surface portion 33 which has a relatively steeply-inclined surface is provided between an outer circumferential surface of the duct-side diameter-enlarged portion 32 and the duct outer circumferential surface 30. The duct-side tapered-surface portion 33 reduces its outer diameter more as a location for measuring this outer diameter is more shifted in a tip direction (insertion direction S1) of air intake duct 11. The duct-side tapered-surface portion 33 is continuous with the duct outer circumferential surface 30.

[0024] The body 13 includes a first tubular fitting portion (joint portion) 34 into which the tip of air intake duct 11 is fitted. The cover 14 includes a second tubular fitting portion 35. (An inner circumference of) This second tubular fitting portion 35 includes a large diameter portion 36 located at a tip side of second tubular fitting portion 35 in the insertion direction S1 and a small diameter portion 37 located at a root portion of the second tubular fitting portion 35, and thereby, is formed in a step shape. That is, at a boundary portion between the large diameter portion 36 and the small diameter portion 37, the inner circumference of second tubular fitting portion 35 includes a step surface 38 which is an annular flat surface perpendicular to the insertion direction S1. The large diameter portion 36 is fitted over an outer circumferential surface of the first tubular fitting portion 34 by press fitting. The air intake duct 11 is fitted into the small diameter portion 37 by press fitting.

[0025] Moreover, the inner circumference of second tubular fitting portion 35 includes a cover-side diameter-enlarged portion 39 provided at a root side beyond the small diameter portion 37, and a cover-side tapered-surface portion 40 provided between the cover-side diameter-enlarged portion 39 and the small diameter portion 37. The cover-side diameter-enlarged portion 39 has an inner diameter larger than that of the small diameter portion 37. The cover-side tapered-surface portion 40 has a steeply tapered surface, i.e., reduces its inner diameter in the tip direction continuously from the cover-side diameter-enlarged portion 39 to the small diameter portion 37. Under the assembled state, the duct-side diameter-enlarged portion 32 and duct-side tapered-surface portion 33 of the air intake duct 11 are respectively in contact with the cover-side diameter-enlarged portion 39 and the cover-side tapered-surface portion 40 by surface contact. At this state, a sealing is attained between the duct-side diameter-enlarged portion 32 and the cover-side diameter-enlarged portion 39 and also between the duct-side tapered-surface portion 33 and the cover-side tapered-surface portion 40.

[0026] When the cover 14 has been attached to the body 13 by locking the hooks 22 of cover 14 onto the locking protrusions 23 of body 13, a tip portion of the second tubular fitting portion 35 is fitted on and fixed to the outer circumferential surface of first tubular fitting portion 34 under a surface contact by press fitting, as shown in FIG. 1. When the cover 14 has been attached to the body 13, a concave portion 42 is secured between the step surface 38 of second tubular fitting portion 35 and a tip surface 41 of first tubular fitting portion 34 which faces the step surface 38. This tip surface 41 is an annular flat surface perpendicular to an axial direction of the first tubular fitting portion 34 (insertion direction S1). The concave portion 42 is a space which opens in a radially inner direction, and is formed in a channel shape, i.e., in an angular-U shape in cross section taken parallel to the insertion direction S1. That is, sizes of the first and second tubular fitting portions 34 and 35 and the like are determined and set so as to obtain the concave portion 42.

[0027] Then, when the air intake duct 11 is inserted into the assembled first and second tubular fitting portions 34 and 35 in the insertion direction S1 by press insertion, the protruding portion 31 formed in the outer circumference of air intake duct 11 can smoothly ride over (move through) the small diameter portion 37 by use of the cover-side tapered-surface portion 40 of second tubular fitting portion 35. Thereby, the protruding portion 31 moves into (i.e., is fitted into) the concave portion 42, so that a positioning of the air intake duct 11 relative to the first and second tubular fitting portions 34 and 35 is conducted in the insertion direction S1. Thus, the air intake duct 11 and the first and second tubular fitting portions 34 and 35 are integrally assembled, i.e., are attached to one another.

[0028] As explained above, in this embodiment, the body 13, the cover 14 and the air intake duct 11 are attached to one another without a connecting process using vibration welding or the like. Hence, the sealing among these three members is attained by means of elasticity of synthetic resin itself. Particularly, the body 13, the cover 14 and the air intake duct 11 can be assembled by only inserting the air intake duct 11 into the first and second tubular fitting portions 34 and 35, i.e., can be assembled by a so-called simple snap-fit fixing structure. Therefore, an assembly operation for these three members is very easy.

[0029] As mentioned above, the air intake duct 11 is fitted integrally to the first and second tubular fitting portions 34 and 35 defining a part of an inner wall surface of the volume chamber 12. Hence, an interval (or distance) D2 between an air-flow space of the air intake duct 11 and the volume chamber 12 arranged around the air intake duct 11 can be suppressed to the minimum. Specifically, this interval D2 corresponds to a width of the air intake duct 11 and the first and second tubular fitting portions 34 and 35 (sum of a duct thickness of air intake duct 11 and a tube thickness of first and second tubular fitting portions 34 and 35) under the assembled state. As a result, a dead space which is not available as the volume chamber 12 is suppressed to the minimum, so that a space efficiency is improved. Therefore, a sufficient capacity (volume) of the volume chamber 12 can be secured while downsizing whole of the system including the volume chamber 12. In this embodiment, these two of the securement of sufficient capacity and the downsizing of system can be achieved at a high level.

[0030] Moreover, under the assembled state, a tip portion of the first tubular fitting portion 34 of body 13 is sandwiched between the air intake duct 11 and the tip portion of second tubular fitting portion 35 of cover 14. Hence, there are provided a surface-contact portion between an inner circumferential surface of the first tubular fitting portion 34 and the outer circumferential surface 30 of air intake duct 11, and a surface-contact portion between the outer circumferential surface of the first tubular fitting portion 34 and an inner circumferential surface of second tubular fitting portion 35. Therefore, a double sealing is constructed so that a high sealing performance can be obtained.

[0031] Moreover, the protruding portion 31 is fitted into the concave portion 42. Also, the duct-side diameter-enlarged portion 32 and the duct-side tapered-surface portion 33 of the air intake duct 11 are mutually in surface-contact with the cover-side diameter-enlarged portion 39 and the cover-side tapered-surface portion 40 of the second tubular fitting portion 35. Accordingly, the air intake duct 11 is held reliably and stably without fluctuating in the insertion direction S1. Therefore, a stable assembling performance can be attained.

[0032] Moreover, the outer circumferential surface 30 of air intake duct 11 and the inner circumferential surface of first tubular fitting portion 34 which are in surface-contact with each other form complementary tapered-surfaces whose diameters become smaller as the points for measuring the diameters moves in the insertion direction S1. Hence, an appropriate sealing surface-pressure is applied to the air intake duct 11 and the first tubular fitting portion 34, by the insertion of air intake duct 11. Also, at this time, the first tubular fitting portion 34 is bent (or deformed) in the radially outer direction (diameter-enlarging direction). Thereby, an appropriate sealing surface-pressure is applied also to the surface-contact portion between the first tubular fitting portion 34 and the second tubular fitting portion 35. Therefore, a sufficient sealing performance in the air intake duct 11 and also in the volume chamber 12 which causes an air pulsation can be ensured.

[0033] Although the invention has been described above with reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art in light of the above teachings.

[0034] In the above embodiment, after the cover 14 was attached to the body 13, the air intake duct 11 is attached to an assembled member of the cover 14 and the body 13. However, the structure according to the present invention is not limited to this. For example, the cover 14 may be attached to an assembled member of the air intake duct 11 and the body 13 after the air intake duct 11 was attached to the first tubular fitting portion 34 of body 13. In this case, the duct-side diameter-enlarged portion 32 and the cover-side diameter-enlarged portion 39 are not provided in order for the cover 14 to be attached to the assembled member of air intake duct 11 and body 13.

[0035] In the above embodiment, the volume chamber 12 is provided over an entire circumference around the air intake duct 11 as shown in FIGS. 1 and 2. However, the structure according to the present invention is not limited to this. For example, the volume chamber 12 may be provided over a part of the entire circumference around the air intake duct 11.

[0036] In the above embodiment, the assembly structure according to the present invention is applied to the components for air-intake system of an internal combustion engine. However, the structure according to the present invention is not limited to this. For example, the assembly structure according to the present invention is widely applicable to various synthetic-resin components such as a component having a duct shape and a component having a box shape. Moreover, in the above embodiment, the respective components are formed by the injection molding. However, the assembly structure according to the present invention is applicable also to components formed by the other molding methods such as a blow molding.

[0037] This application is based on a prior Japanese Patent Application No. 2009-291633 filed on December 24, 2009. The entire contents of this Japanese Patent Application are hereby incorporated by reference.

[0038] The scope of the invention is defined with reference to the following claims.

Claims

1. An assembly structure comprising:

a duct (11) formed of synthetic resin, the duct (11) including a protruding portion (31) provided in an outer circumference of the duct (11);

a first component (13) formed of synthetic resin, the first component (13) including
a first tubular fitting portion (34) configured to be fitted to a tip portion of the duct (11) by an insertion of the duct (11); and

a second component (14) formed of synthetic resin and configured to be fitted to the first component (13) to define a volume chamber (12) around the duct (11), the second component (14) including
a second tubular fitting portion (35) having
a large diameter portion (36) located at a tip side of the second tubular fitting portion (35) relative to an insertion direction (S1) of the duct (11) and configured to be fitted to an outer circumferential surface of the first tubular fitting portion (34),
a small diameter portion (37) located at a root side of the second tubular fitting portion (35) relative to the insertion direction (S1) and configured to be fitted to the duct (11), and
a step surface (38) located between the large diameter portion (36) and the small diameter portion (37),

wherein the step surface (38) faces a tip surface (41) of the first tubular fitting portion (34) to provide a concave portion (42) between the step surface (38) and the tip surface (41), and the protruding portion (31) is fitted to the concave portion (42), under a state where the duct (11) and the first and second components (13, 14) have been attached to one another.

2. The assembly structure as claimed in Claim 1, wherein
an inner circumferential surface of the first tubular fitting portion (34) is in contact with an outer circumferential surface of the duct (11) by surface contact, under the state where the duct (11) and the first and second components (13, 14) have been attached to one another.

3. The assembly structure as claimed in Claim 2, wherein
the inner circumferential surface of the first tubular fitting portion (34) and the outer circumferential surface of the duct (11) are tapered surfaces whose diameters are reduced toward the insertion direction (S1) of the duct (11).

4. The assembly structure as claimed in one of Claims 1 to 3, wherein
the first tubular fitting portion (34) cooperates with the second tubular fitting portion (35) to define a part of inner wall surface of the volume chamber (12).

5. The assembly structure as claimed in one of Claims 1 to 4, wherein
the duct (11), the first component (13) and the second component (14) are components for an air-intake system of internal combustion engine, and
the duct (11) is an air-intake duct, and the volume chamber (12) is a resonant chamber of a resonator.

6. An assembly method for synthetic-resin components, the synthetic-resin components including
a duct (11) formed of synthetic resin, the duct (11) including a protruding portion (31) provided in an outer circumference of the duct (11);
a first component (13) formed of synthetic resin, the first component (13) including
a first tubular fitting portion (34); and
a second component (14) formed of synthetic resin, the second component (14) including
a second tubular fitting portion (35) having
a large diameter portion (36) located at a tip side of the second tubular fitting portion (35),
a small diameter portion (37) located at a root side of the second tubular fitting portion (35), and
a step surface (38) located between the large diameter portion (36) and the small diameter portion (37),
the assembly method comprising:
fitting the large diameter portion (36) to an outer circumferential surface of the first tubular fitting portion (34) to define a volume chamber (12);
causing the step surface (38) to face a tip surface (41) of the first tubular fitting portion (34) so as to provide a concave portion (42) between the step surface (38) and the tip surface (41);
fitting a tip portion of the duct (11) to the first tubular fitting portion (34) by an insertion of the duct (11);
fitting the small diameter portion (37) to the duct (11); and
fitting the protruding portion (31) to the concave portion (42), so that the duct (11) and the first and second components (13, 14) are attached to one another to form the volume chamber (12) around the duct (11).

Drawing