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Title:
INTAKE MANIFOLD
Document Type and Number:
WIPO Patent Application WO/2014/068381
Kind Code:
A1
Abstract:
In an intake manifold, a distance between an extending lower end portion of a first joining surface and an extending lower end portion of a second joining surface that faces the extending lower end portion of the first joining surface is formed shorter than a distance between a region of the first joining surface excluding the extending lower end portion and a region of the second joining surface excluding the extending lower end portion that faces this region.

Inventors:
YAMANARI KENJI (JP)
Application Number:
IB2013/002371
Publication Date:
May 08, 2014
Filing Date:
October 24, 2013
Export Citation:
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Assignee:
TOYOTA MOTOR CO LTD (JP)
YAMANARI KENJI (JP)
International Classes:
F02M35/10; B60K5/02; F02M35/112
Foreign References:
US20090241886A12009-10-01
EP0732495A11996-09-18
DE102005036104A12006-02-23
US20030226535A12003-12-11
DE102004002641A12005-08-11
JP2009066819A2009-04-02
JP2012158994A2012-08-23
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Claims:
CLAIMS

1. An intake manifold that is connected to an internal combustion engine so as to be positioned below a fuel system component, and that introduces intake air into cylinders of the internal combustion engine, comprising:

a plurality of split bodies that are joined via joining surfaces, the plurality of split bodies including

a first split body provided farthest away, of the plurality of split bodies, from a side surface of the internal combustion engine,

a second split body provided on the internal combustion engine side of the first split body, the second split body being joined to the first split body via a first joining surface, and

a third split body provided on the internal combustion engine side of the second split body, the third split body being joined to the second split body via a second joining surface,

wherein a distance between the first joining surface and the second joining surface is smallest at a lower end portion of the first joining surface.

2. The intake manifold according to claim 1, wherein the plurality of split bodies further includes a fourth split body provided on the internal combustion engine side of the third split body, the fourth split body being joined to the third split body via a third joining surface,

wherein a distance between the second joining surface and the third joining surface is smallest at an upper end portion of the second joining surface.

3. The intake manifold according to claim 1 or 2, wherein a joint strength of the first joining surface, the second joining surface, and the third joining surface is set higher from the first joining surface toward the third joining surface. 4. The intake manifold according to any one of claims 1 to 3, wherein the second joining surface and the third joining surface are parallel to the first joining surface.

5. The intake manifold according to any one of claims 1 to 4, wherein the internal combustion engine is arranged longitudinal mounted such that a crankshaft axis extends in a longitudinal direction of a vehicle, and the intake manifold is mounted to a side surface of the internal combustion engine so as to be positioned on one side with respect to the longitudinal direction of the vehicle.

Description:
INTAKE MANIFOLD

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to an intake manifold, and more particularly, to an intake manifold that is connected to an internal combustion engine and introduces intake air into cylinders of the internal combustion engine. 2. Description of Related Art

[0002] An intake manifold that includes a surge tank and intake branch pipes that distribute intake air to each cylinder of an internal combustion engine mounted in a vehicle is attached to the internal combustion engine. This intake manifold is a complex shape and is thus formed by a plurality of split bodies joined via joining surfaces.

[0003] Fuel system components such as fuel injection valves and a delivery pipe that supplies fuel to the fuel injection valves are mounted to the internal combustion engine, and it is necessary to inhibit the intake manifold from colliding with the fuel system components in the event of a vehicle collision.

[0004] Japanese Patent Application Publication No. 2012-158994 (JP

2012-158994 A) describes one such known intake manifold that is inhibited from colliding with fuel system components. The intake manifold is formed divided into a side near the internal combustion engine and a side away from the internal combustion engine, and includes a plurality of split bodies that are joined together. The strength of a base split body on the side near the internal combustion engine is greater than the strength of another split body on the side away from the internal combustion engine. Therefore, when a vehicle collision occurs, the other split body that is on the side farther away from the internal combustion engine will deform earlier and absorb the impact.

[0005] In this kind of related intake manifold, the impact is able to be absorbed by having the other split body on the side farther away from the internal combustion engine deform earlier. However, no consideration is given to having a plurality of split bodies regularly separate so as to be able to distribute the impact. Therefore, it may not be possible to inhibit impact from the deformation of the intake manifold from being transferred to the fuel system components. SUMMARY OF THE INVENTION

[0006] The invention provides an intake manifold capable of distributing impact force when a vehicle collision occurs, and thus inhibiting impact from deformation of the intake manifold from being transferred to a fuel system component.

[0007] A first aspect of the invention relates to an intake manifold that is connected to an internal combustion engine so as to be positioned below a fuel system component, and that introduces intake air into cylinders of the internal combustion engine. This intake manifold includes a plurality of split bodies that are joined via joining surfaces, the plurality of split bodies including a first split body provided farthest away, of the plurality of split bodies, from a side surface of the internal combustion engine, a second split body provided on the internal combustion engine side of the first split body, the second split body being joined to the first split body via a first joining surface, and a third split body provided on the internal combustion engine side of the second split body, the third split body being joined to the second split body via a second joining surface. A distance between an extending lower end portion of the first joining surface and an extending lower end portion of the second joining surface that faces the extending lower end portion is formed shorter than a distance between a region excluding the extending lower end portion of the first joining surface and a region of the second joining surface that faces the region excluding the extending lower end portion of the first joining surface. That is, a distance between the first joining surface and the second joining surface is smallest at a lower end portion of the first joining surface.

[0008] With this intake manifold, the distance between the extending lower end portion of the first joining surface and the extending lower end portion of the second joining surface that faces this extending lower end portion is formed shorter than the distance between the region excluding the extending lower end portion of the first joining surface and the region of the second joining surface that faces the extending lower end portion of the first joining surface, so when impact force is applied to a first split body that is farthest from the internal combustion engine when a vehicle collision occurs, e.g., when a bumper reinforcement collides with the intake manifold and impact force is applied to the first split body, the second split body will separate from the third split body after the first split body has separated from the second split body from the extending lower end portion of the first joining surface.

[0009] Having the plurality of split bodies regularly separate in this way enables impact when a vehicle collision occurs to be distributed by the intake manifold, such that impact transferred from the intake manifold to the internal combustion engine and fuel system components is able to be reduced.

[0010] In the intake manifold described above, the plurality of split bodies may also include a fourth split body that is provided on the internal combustion engine side of the third split body, and joined to the third split body via a third joining surface. A distance between an extending upper end portion of the second joining surface and the third joining surface that faces the extending upper end portion may be formed shorter than a distance between a region excluding the extending upper end portion of the second joining surface and a region of the third joining surface that faces the region excluding the extending upper end portion of the second joining surface. That is, a distance between the second joining surface and the third joining surface may be smallest at an upper end portion of the second joining surface.

[0011] With this intake manifold, the distance between the extending upper end portion of the second joining surface and the third joining surface that faces this extending upper end portion is formed shorter than the distance between the region excluding the upper end portion of the second joining surface and the region of the third joining surface that faces the region excluding the upper end portion of the second joining surface, so the second split body will separate from the third split body from the extending upper end portion of the second joining surface after the first split body has separated from the second split body from the extending lower end portion of the first joining surface.

[0012] Therefore, the plurality of split bodies regularly efficiently separates from the first split body to the third split body in this order, so impact when a vehicle collision occurs is more efficiently distributed by the intake manifold, and thus the impact that is transferred from the intake manifold to the internal combustion engine and the fuel system components is able to be reduced even more.

[0013] In the intake manifold described above, a joint strength of the first joining surface, the second joining surface, and the third joining surface may be set higher from the first joining surface toward the third joining surface.

[0014] With this intake manifold, the joint strength of the first joining surface, the second joining surface, and the third joining surface is set higher from the first joining surface toward the third joining surface, so the intake manifold is able to regularly separate in order from the first split body arranged farthest from the side surface of the internal combustion engine to the split body near the internal combustion engine when a vehicle collision occurs. Therefore, the impact when a vehicle collision occurs is able to be even further impeded from being transferred from the intake manifold to the internal combustion engine and fuel system components.

[0015] In the intake manifold described above, the second joining surface and the third joining surface may be parallel to the first joining surface.

[0016] With this intake manifold, the second joining surface and the third joining surface are parallel to the first joining surface, so when an impact is applied to the split bodies from one direction, the directions in which the split bodies separate are able to be the same direction, which facilitates separation of the split bodies.

[0017] In the intake manifold described above, the internal combustion engine may be arranged longitudinal mounted such that a crankshaft axis extends in a longitudinal direction of a vehicle, and the intake manifold may be mounted to a side surface of the internal combustion engine so as to be positioned on one side with respect to the longitudinal direction of the vehicle.

[0018] With this intake manifold, the intake manifold is mounted to a side surface of the internal combustion engine so as to be positioned on one side with respect to the longitudinal direction of the vehicle, so when the vehicle is involved in an offset collision in which one of the left or the right front portion of the vehicle collides with an object, and a bumper reinforcement deforms and collides with the first split body that is farthest from the side surface of the internal combustion engine, the split bodies are able to regularly separate in order from the first split body to the split body near the internal combustion engine. Therefore, impact when a vehicle collision occurs is able to be efficiently distributed by the intake manifold, so impact that is transferred from the intake manifold to the internal combustion engine and fuel system components is able to be reduced.

[0019] The intake manifold according to the aspect of the invention described above enables impact force when a vehicle collision occurs to be distributed, such that impact from deformation of the intake manifold is able to be inhibited from being transferred to a fuel system component. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a block diagram schematically showing an internal combustion engine provided with an intake manifold according to one example embodiment of the invention;

FIG. 2 is a side view of the intake manifold mounted to a cylinder head;

FIG. 3 is a rear view of the intake manifold mounted to the cylinder head;

FIG. 4 is a view showing the arrangement of an engine and the intake manifold in a vehicle;

FIG. 5A is a front view of the intake manifold, and FIG. 5B is a side view of the intake manifold viewed from the direction of arrow 5B in FIG. 5A;

FIG. 6A is a rear view of the intake manifold, and FIG. 6B is a side view of the intake manifold viewed from the direction of arrow 6B in FIG. 6A;

FIG. 7A is a rear view of a fourth split body of the intake manifold, and FIG. 7B is a side view of the fourth split body viewed from the direction of arrow 7B in FIG. 7A;

FIG. 8 is a rear view of the fourth split body;

FIG. 9A is a front view of a third split body of the intake manifold, and FIG. 9B is a side view of the third split body viewed from the direction of arrow 9B in FIG. 9A;

FIG. 10 is a rear view of the third split body;

FIG. 11A is a front view of a second split body of the intake manifold, and FIG. 11B is a side view of the second split body viewed from the direction of arrow 11B in FIG. 11 A;

FIG. 12 is a rear view of the second split body;

FIG. 13A is a front view of a first split body of the intake manifold, and FIG. 13B is a side view of the first split body viewed from the direction of arrow 13B in FIG. 13A;

FIG. 14 is a rear view of the first split body; and

FIG. 15 is a view illustrating the relationship between the amount of displacement of the intake manifold when a vehicle collision occurs, and the reaction force of impact applied to the intake manifold.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021] Hereinafter, example embodiments of the intake manifold of the invention will be described with reference to the accompanying drawings. FIGS. 1 to 15 are views of an intake manifold according to one example embodiment of the invention. First the structure will be described. In FIG. 1, an engine 1 that is an internal combustion engine includes a cylinder head la and a cylinder block lb. An intake manifold 2 is connected to the cylinder head la.

[0022] The intake manifold 2 distributes and introduces outside air that has been introduced from an air duct, not shown, via an intake pipe 3 to a combustion chamber 4 of each cylinder formed in the cylinder block lb via an intake port formed in the cylinder head la.

[0023] An exhaust manifold 5 is connected to the cylinder head la. The exhaust manifold 5 collects exhaust gas discharged from the combustion chamber 4 of each cylinder in the engine 1, and discharges the exhaust gas to an exhaust pipe 6.

[0024] A throttle valve 7 is provided in the intake pipe 3. The throttle valve 7 regulates the amount of intake air introduced into the combustion chamber 4. The intake manifold 2 includes a surge tank 8 that is connected to the intake pipe 3, and intake branch pipes 9 that branch off from the surge tank 8 and have distribution passages that are communicated with the combustion chambers of the engine 1.

[0025] The number of intake branch pipes 9 that are provided is the same as the number of cylinders in the engine 1. The intake manifold 2 in this example embodiment is applied to a four-cylinder engine, so four intake branch pipes 9 are provided. However, the number of cylinders of the engine 1 is not particularly limited to four.

[0026] A fuel injection valve 10 is mounted to an upper portion of the cylinder head la above the intake branch pipe 9. This fuel injection valve 10 injects fuel into the combustion chamber 4 through an intake port formed in the cylinder head la.

[0027] When fuel is injected into the combustion chamber 4 from the fuel injection valve 10, a mixture of air and fuel introduced from the distribution passage of the intake branch pipe 9 is charged into the combustion chamber 4. This air-fuel mixture is combusted by being ignited by a spark plug 11 provided in each cylinder.

[0028] Combustion energy at this time causes a piston 12 to move in a reciprocating manner. This reciprocating motion of the piston 12 is converted into rotary motion of a crankshaft 13 of the engine 1. An EGR mechanism 14 for reducing the amount of oxides of nitrogen (NOx) in the exhaust gas is provided in the engine 1. This EGR mechanism 14 returns some of the exhaust gas discharged to the exhaust pipe 6 to the intake manifold 2.

[0029] The EGR mechanism 14 includes an EGR pipe 15 that connects the exhaust pipe 6 to the intake manifold 2, and an EGR valve 16 that regulates the flow rate of EGR gas circulated from the exhaust pipe 6 to the intake manifold 2 by varying an opening amount in the EGR pipe 15.

[0030] This EGR mechanism 14 circulates some of the exhaust gas of the engine 1 to the intake manifold 2. As a result, the combustion temperature of the air-fuel mixture in the combustion chamber 4 is reduced, which lowers the production of NOx, thereby enabling the amount of NOx in the exhaust gas of the engine 1 to be reduced.

[0031] As shown in FIGS. 2 and 3, a metal delivery pipe 17 is provided on the cylinder head la. This delivery pipe 17 extends in the axial direction of the crankshaft 13, i.e., the direction of the crankshaft. The fuel injection valve 10 provided for each cylinder is connected to the delivery pipe 17, and fuel is supplied from the delivery pipe 17 to the fuel injection valve 10. The fuel injection valve 10 and the delivery pipe 17 of the engine 1 in this example embodiment form fuel system components.

[0032] As shown in FIG. 4, the engine 1 in this example embodiment is arranged longitudinal mounted such that the axis of the crankshaft 13, i.e., the crankshaft axis extends in the longitudinal direction of a vehicle 50. The intake manifold 2 is arranged on a side surface of the engine 1 so as to be positioned on one side with respect to the longitudinal direction of the vehicle 50.

[0033] Next, the specific structure of the intake manifold 2 will be described with reference to FIGS. 2, 3, and 5A to 14.

[0034] As shown in FIGS. 2, 3, 5A, 5B, 6A, and 6B, the intake manifold 2 includes a plurality of split bodies. The plurality of split bodies are arranged on a side near the side surface of the engine 1 and a side away from the side surface of the engine 1, and are joined via joining surfaces.

[0035] More specifically, the intake manifold 2 is formed by a first split body 21, a second split body 22, a third split body 23, and a fourth split body 24, all of which are made of resin, arranged from the side away from the side surface of the engine 1 toward the side near the side surface of the engine 1, respectively.

[0036] The first split body 21 and the second split body 22 are joined via a first joining surface 25. The second split body 22 and the third split body 23 are joined via a second joining surface 26. The third split body 23 and the fourth split body 24 are joined via a third joining surface 27. The first split body 21, the second split body 22, the third split body 23, and the fourth split body 24 are joined by adhesion or welding or the like.

[0037] In the intake manifold 2 of this example embodiment, the surge tank 8 is formed by the first split body 21 and the second split body 22, and four intake branch pipes 9A to 9D are formed by the third split body 23 and the fourth split body 24.

[0038] As shown in FIGS. 7A, 7B, and 8, the fourth split body 24 forms one of the intake branch pipes 9 A to 9D. A flange portion 31 that is connected to the cylinder head la is formed on an upper portion of the fourth split body 24. Openings 31a to 31d that are communicated with intake ports of the cylinder head la are formed in this flange portion 31.

[0039] A plurality of bolt insertion holes 31 A are formed in the flange portion 31. The flange portion 31 is fastened to the cylinder head la by bolts, not shown, being inserted through these bolt insertion holes 31A and screwed to the cylinder head la. Also, a mating surface 32 is formed on one surface of the fourth split body 24 (see FIG. 8).

[0040] As shown in FIGS. 9A, 9B, and 10, the third split body 23 forms the other intake branch pipes 9A to 9D. A mating surface 33 is formed on one surface of the third split body 23 (see FIG. 9A). This mating surface 33 is joined to the mating surface 32 of the fourth split body 24. The third joining surface 27 is formed by the mating surface 32 and the mating surface 33.

[0041] A plurality of openings 34a to 34d are formed in a lower portion of the third split body 23. These openings 34a to 34d are communicated with an inner peripheral portion of the intake branch pipes 9A to 9D formed by the third split body 23 and the fourth split body 24, i.e., with distribution passages 35a to 35d of the intake branch pipes 9A to 9D.

[0042] More specifically, as shown in FIGS. 8, 9A, and 9B, the distribution passages 35a to 35d are formed by one surface of the third split body 23 and one surface of the fourth split body 24. The openings 34a to 34d are communicated with these distribution passages 35a to 35d.

[0043] As shown in FIG. 10, an EGR gas introducing portion 36 is provided on the other surface of the third split body 23. This EGR gas introducing portion 36 is connected to the EGR pipe 15, and EGR gas is introduced from this EGR pipe 15.

[0044] Communication holes 37a to 37d are formed in the third split body 23. These communication holes 37a to 37d are communicated with the distribution passages 35a to 35d, respectively. A main passage portion 38a that is communicated with the EGR gas introducing portion 36, and distribution passage portions 38b to 38e that branch off from this main passage portion 38a and are communicatively connected to the communication holes 37a to 37d, are formed on the other surface of the third split body 23.

[0045] A mating surface 39 is formed on the other surface of the third split body 23 (see FIG. 10). This mating surface 39 is formed at a portion of the third split body 23 that surrounds the main passage portion 38a, the distribution passage portions 38b to 38e, and the openings 34a to 34d.

[0046] As shown in FIGS. 11 A and 11B, a mating surface 41 is formed on one surface of the second split body 22. This mating surface 41 is joined to the mating surface 39 of the third split body 23. The second joining surface 26 is formed by the mating surface 39 and the mating surface 41.

[0047] A main passage portion 40a that is communicated with the EGR gas introducing portion 36, and distribution passage portions 40b to 40e that branch off from this main passage portion 40a, are formed on one surface of the second split body 22.

[0048] A main passage 42a is defined by the main passage portion 38a and the main passage portion 40a, and distribution passages 42b to 42e are defined by the distribution passage portions 38b to 38e and the distribution passage portions 40b to 40e, by the mating surface 41 of the second split body 22 and the mating surface 39 of the third split body 23 being overlapped and the second split body 22 and the third split body 23 being joined together. The reference characters of the main passage 42a and the distribution passages 42b to 42e are only shown in FIG. 11 A.

[0049] As shown in FIG. 12, a mating surface 43 is formed on the other surface of the second split body 22. This mating surface 43 is formed along the circumference of the other surface of the second split body 22.

[0050] A plurality of ribs 44 are formed below the distribution passage portions 40b to 40e of the second split body 22. These ribs 44 are positioned between adjacent openings 31a to 3 Id of the third split body 23 of the second split body 22, and serve to guide the intake air introduced into the openings 31a to 31d.

[0051] As shown in FIGS. 13A and 13B, a mating surface 45 is formed on one surface of the first split body 21. This mating surface 45 is formed along the circumference of the first split body 21. This mating surface 45 is joined to the mating surface 43 of the second split body 22, and the first joining surface 25 is formed by the mating surface 43 and the mating surface 45.

[0052] As shown in FIGS. 13A, 13B, and 14, an intake air introducing portion 46 is provided on the first split body 21. This intake air introducing portion 46 is connected to the intake pipe 3. Intake air is introduced through the intake pipe 3.

[0053] This first split body 21 is such that an intake passage 47 into which intake air is introduced from the intake air introducing portion 46 is defined between one surface of the first split body 21 and the other surface of the second split body 22. When intake air is introduced from the intake air introducing portion 46 into the intake passage 47, this intake air is guided by the ribs 44 of the second split body 22 and introduced into the openings 31a to 3 Id of the third split body 23. The intake air introduced into the openings 31a to 31d is led to the combustion chambers 4 of the engine 1 through the distribution passages 35a to 35d of the intake branch pipes 9A to 9D formed by the third split body 23 and the fourth split body 24.

[0054] A purge gas introducing portion 51 is provided on the first split body 21. Fuel vapor from fuel vaporized from a fuel tank, not shown, is introduced into the intake passage 47 through the purge gas introducing portion 51. This fuel vapor is introduced, together with intake air, into the combustion chambers 4 of the engine 1 from the intake passage 47 through the distribution passages 35a to 35d.

[0055] The mating surfaces 32, 33, 39, and 41 are formed parallel to the mating surfaces 43 and 45. Therefore, the second joining surface 26 and the third joining surface 27 are parallel to the first joining surface 25.

[0056] As shown in FIG. 5B, a distance A between an extending lower end portion 25a (i.e., a lower end portion 25a in the extending direction) of the first joining surface 25 and an extending lower end portion 26a (i.e., a lower end portion 26a in the extending direction) of the second joining surface 26 that faces the extending lower end portion 25a, is formed shorter than a distance B between a region 25b of the first joining surface 25 excluding the extending lower end portion 25a and a region 26b of the second joining surface 26 excluding the extending lower end portion 26a that faces this region 25b.

[0057] The extending lower end portion 25a of the first joining surface 25 and the extending lower end portion 26a of the second joining surface 26 are provided nearest, of the first joining surface 25 and the second joining surface 26 that faces the first joining surface 25.

[0058] The portion of the second joining surface 26 that faces the first joining surface 25 is a portion positioned on an axis L that intersects the intake manifold 2 with respect to the first joining surface 25, as shown in FIG. 5B, for example.

[0059] A distance C between an extending upper end portion 26c (i.e., an upper end portion 26c in the extending direction) of the second joining surface 26 and a portion 27a of the third joining surface 27 that faces the extending upper end portion 26c, is formed shorter than a distance D between a region 26b of the second joining surface 26 excluding the extending upper end portion 26c of the second joining surface 26 and a region 27b of the third joining surface 27 that faces this region 26b.

[0060] The extending upper end portion 26c of the second joining surface 26 and a portion 27a of the third joining surface 27 that faces the extending upper end portion 26c are the nearest, of the second joining surface 26 and the third joining surface 27 that faces the second joining surface 26.

[0061] The portion of the third joining surface 27 that faces the second joining surface 26 is a portion positioned on an axis L that intersects the intake manifold 2 with respect to the second joining surface 26, as shown in FIG. 5B, for example.

[0062] The joint strength of the first joining surface 25 to the third joining surface 27 is set higher from the first joining surface 25 toward the third joining surface 27. That is, the joint strength is set higher in order from the first joining surface 25 to the second joining surface 26 to the third joining surface 27, i.e., the joint strength of the second joining surface 26 is set higher than the joint strength of the first joining surface 25, and the joint strength of the third joining surface 27 is set higher than the joint strength of the second joining surface 26.

[0063] To simplify the description, the area of the first joining surface 25 to the third joining surface 27 is indicated by bold lines in FIG. 5B.

[0064] Next, the operation will be described. As shown in FIG. 4, the engine 1 is arranged longitudinal mounted such that the axis of the crankshaft 13 extends in the longitudinal direction of the vehicle 50. The intake manifold 2 is arranged on a side surface of the engine 1 so as to be positioned on one side with respect to the longitudinal direction of the vehicle 50.

[0065] A bumper reinforcement 48 that forms a portion of a chassis is provided toward the front of the vehicle 50. If one of the left front surface and the right front surface of the vehicle 50 collides with an object X, i.e., if an offset collision occurs, the bumper reinforcement 48 will deform in the manner shown by the broken line and collide with the intake manifold 2. At this time, the end portion of the bumper reinforcement 48 will first collide with the first split body 21 of the intake manifold 2, and the intake manifold 2 will be crushed toward the engine 1 side.

[0066] With the intake manifold 2 in this example embodiment, the distance A between the extending lower end portion 25a of the first joining surface 25 and the extending lower end portion 26a of the second joining surface 26 that faces the extending lower end portion 25a is formed shorter than the distance B between the region 25b of the first joining surface 25 excluding the extending lower end portion 25a and the region 26b of the second joining surface 26 excluding the extending lower end portion 26a that faces this region 25b. Therefore, the first split body 21 will separate from the second split body 22 from the extending lower end portion 25a. [0067] More specifically, if an impact is applied to the first split body 21, first the first split body 21 will deform. The distance A between the extending lower end portion 25a of the first joining surface 25 and the extending lower end portion 26a of the second joining surface 26 is formed the shortest in the extending direction of the first joining surface 25 and the second joining surface 26. Therefore, when the first split body 21 deforms, the extending lower end portion 25a of the first joining surface 25 and the extending lower end portion 26a of the second joining surface 26 will be collided with first.

[0068] The distance B between the regions 25b and 26b of the first joining surface 25 and the second joining surface 26 excluding the extending lower end portions 25a and the 26a is greater than the distance A. Therefore, the first split body 21 of the portion where the distance between the first joining surface 25 and the second joining surface 26 is the distance B will continue to deform.

[0069] Therefore, reaction force from the deformation of the first split body 21 will concentrate at the extending lower end portion 25a of the first joining surface 25 and the extending lower end portion 26a of the second joining surface 26. As a result, at the first joining surface 25, the extending lower end portion 25a of the first split body 21 will separate from the second split body 22 first.

[0070] When the first split body 21 separates from the second split body 22, the second split body 22 deforms. The distance C between the extending upper end portion 26c of the second joining surface 26 and the portion 27a of the third joining surface 27 that faces the extending upper end portion 26c is formed shorter than the distance D between the region 26b excluding the extending upper end portion 26c of the second joining surface 26 and the region 27b of the third joining surface 27 that faces this region 26b. Therefore, at the second joining surface 26, the second split body 22 will separate from the third split body 23 from the extending upper end portion 26c.

[0071] More specifically, the distance C between the extending upper end portion 26c of the second joining surface 26 and the third joining surface 27 that faces the extending upper end portion 26c is formed the shortest in the extending direction of the second joining surface 26 and the third joining surface 27. Therefore, when the second split body 22 deforms, the extending upper end portion 26c of the second joining surface 26 will first collide with the portion 27a of the third joining surface 27 that faces the extending upper end portion 26c.

[0072] The distance D is greater than the distance C. Therefore, the second split body 22 of the portion where the distance between the second joining surface 26 and the third joining surface 27 is the distance D will continue to deform. Therefore, reaction force from the deformation of the second split body 22 will concentrate at the extending upper end portion 26c of the second joining surface 26 and the portion 27a of the third joining surface 27 that faces the extending upper end portion 26c. As a result, at the second joining surface 26, the extending upper end portion 26c of the second split body 22 will separate from the third split body 23 first. Then the third split body 23 will separate from the fourth split body 24.

[0073] In this way, the intake manifold 2 will regularly separate from the first split body 21 that is farthest from the side surface of the engine 1, to the second split body 22, to the third split body 23 in this order. In this way, the impact when a collision of the vehicle 50 occurs is distributed by the intake manifold 2.

[0074] Therefore, the impact when a collision of the vehicle 50 occurs is inhibited from concentrating at the flange portion 31. As a result, impact that is transferred from the intake manifold 2 to the engine 1 and fuel system components including the fuel injection valves 10 and the delivery pipe 17 is able to be reduced. As a result, impact transferred from the intake manifold 2 to the engine 1 and the fuel injection valves 10 is able to be suppressed.

[0075] FIG. 15 is a view showing the amount of displacement of the intake manifold 2 at the time of a vehicle collision and the reaction force of the impact applied to the intake manifold 2 obtained through testing. It has become apparent through testing that the intake manifold 2 in this example embodiment distributes the impact when the first split body 21 to the third split body 23 separates from the first joining surface 25 to the third joining surface 27, as is evident from FIG. 15.

[0076] With the intake manifold 2 in this example embodiment, the joint strength of the first joining surface 25, the second joining surface 26, and the third joining surface 27 is set higher from the first joining surface 25 toward the third joining surface 27. As a result, when the vehicle 50 is involved in a collision, the intake manifold 2 regularly separates in order from the first split body 21 arranged farthest from the side surface of the engine 1 to the third split body 23 nearest to the engine 1. Therefore, impact at the time of the collision of the vehicle 50 is more efficiently distributed in the intake manifold 2, so impact that is transferred from the intake manifold 2 to the engine 1 and the fuel system components is reduced even more.

[0077] With the intake manifold 2, the second joining surface 26 and the third joining surface 27 are parallel to the first joining surface 25. Therefore, the directions in which the first split body 21 to the third split body 23 separate when impact is applied from one direction to the first split body 21 to the third split body 23 are the same direction, so the first split body 21 to the third split body 23 separate more easily.

[0078] In this example embodiment, the split bodies are formed from the four split bodies that include the first split body 21 to the fourth split body 24, but the split bodies may also be formed of three split bodies or five or more split bodies.

[0079] As described above, the intake manifold according to the example embodiment of the invention is able to distribute the impact force when a vehicle collision occurs, thereby making it possible to inhibit impact from deformation of the intake manifold from being transferred to fuel system components. The intake manifold according to the example embodiment of the invention is useful as an intake manifold or the like that is connected to an internal combustion engine and introduces intake air into cylinders of the internal combustion engine.