Intake manifold

An intake manifold includes a surge tank and a plurality of inlet pipes extending from the surge tank. Of the inlet pipes, proximal portions of an adjacent pair of inlet pipes are integrated, for example, by being connected with a plate-like connecting portion. The proximal portions of the two adjacent inlet pipes are integrated with a side wall of the surge tank by a reinforcing rib. The reinforcing rib extends, for example, from the connecting portion to the side wall of the surge tank. The intake manifold may be formed by a lower half body and an upper half body, which are welded to each other by using welding margins provided in the half bodies. In this case, it is preferable that parts of each welding margin that are located to correspond to the proximal portions of the inlet pipes be wider than the remainder of the same welding margin.

BACKGROUND OF THE INVENTION

The present invention relates to an intake manifold for an engine.

Japanese Laid-Open Patent Publication No. 2008-184939 discloses an intake manifold that includes a manifold body. The manifold body is a synthetic resin single component that includes a surge tank and a plurality of inlet pipes. Synthetic resin internal pipes are provided inside the manifold body. Each internal pipe protrudes into the surge tank from the proximal portion of one of the inlet pipes, or from a portion of the inlet pipe that is coupled to the surge tank.

Because of the internal pipes provided separately from the manifold body, the conventional intake manifold has a large number of components and a complicated structure. Omission of the internal pipes would simplify the structure. However, such omission would lower the pressure capacity of portions of the intake manifold including the proximal portions of the inlet pipes. The internal pipes have a function for correcting molding strains, which often occur in the vicinity of the proximal portions of the inlet pipes when a surge tank and inlet pipes are integrally molded with synthetic resin. The omission of the internal pipes would therefore make drawbacks due to molding strains conspicuous.

SUMMARY OF THE INVENTION

Accordingly, it is an objective of the present invention to provide an intake manifold of a simple structure with a small number of components, in which the pressure capacity of portions of the intake manifold including the proximal portions of the inlet pipes is high, and molding strains do not easily occur in the vicinity of the proximal portions of the inlet pipes.

To achieve the foregoing objective and in accordance with one aspect of the present invention, an intake manifold is provided that includes a surge tank having an opening; and a plurality of inlet pipes extending from the surge tank. Each inlet pipe has an inlet connected to the surge tank. The inlet of each inlet pipe is located side by side with the inlet of another inlet pipe in a direction along which air supplied into the surge tank through the opening flows within the surge tank. Of the inlet pipes, proximal portions of an adjacent pair of inlet pipes are integrated, and the proximal portions of the pair are integrated with a side wall of the surge tank by a reinforcing rib.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, one embodiment of the present invention will now be described with reference toFIGS. 1 to 5. In the following description, left and right refer to the left and right sides as viewed inFIG. 2, respectively, and front and rear refer to the lower and upper sides as viewed inFIG. 2, respectively.

An intake manifold11according to the present embodiment is mounted in a horizontally-opposed four-cylinder engine. The intake manifold is formed, as a single component, of heat-resistant synthetic resin such as a polyamide resin. As shown inFIGS. 1 and 2, the intake manifold11includes a surge tank12and a plurality of inlet pipes13. The surge tank12is located at a center of the intake manifold11. The inlet pipes13extend from the left and right sides of the surge tank12. The inlet pipes13are substantially at left-right symmetrical positions.

As shown inFIGS. 1 and 3, an opening14is formed at the front side of the surge tank12. The opening14is connected to an air duct (not shown), which directs air that has been filtered by an air cleaner (not shown) to the surge tank12. The directed air is introduced into the surge tank12through the opening14. Each of the inlet pipes13, which are arranged in a pair on each of the left and right sides, corresponds to one of the combustion chambers of the horizontally opposed four cylinder engine. Air that has been drawn into the surge tank12is supplied to each combustion chamber through one of the inlet pipes13.

A clearance S is formed between each pair of inlet pipes13that are adjacent to each other in the front-rear direction. Each clearance S extends from between the proximal portions to between the distal ends of one of the front-rear adjacent pairs of inlet pipes13. That is, a pipe wall13b, which constructs each of the inlet pipes13, is independent from the pipe walls13bof any other inlet pipes13. Each inlet pipe13has an inlet13aconnected to the surge tank12. Each inlet13ais substantially at a position opposed to the inlet13aof another inlet pipe13. The inlet13aof each inlet pipe13is oriented in a direction that intersects the direction of the flow of air that has been supplied to the surge tank12through the opening14. Along the direction of the flow of air, or along the front-rear direction, each inlet13ais side by side with the inlet13aof another inlet pipe13a.

As shown inFIG. 1, the intake manifold11as a whole is formed by a lower half body15A and an upper half body15B. As shown inFIGS. 4 and 5, the lower half body15A has an open upper end, and the upper half body15B has an open lower end. The opening14of the surge tank12is located at a front face of the lower half body15A. The surge tank12and the inlet pipes13are formed integrally by placing and joining the upper half body15B onto the lower half body15A.

As shown inFIGS. 4 and 5, a flange16is formed at the open edge of the lower half body15A. The flange16has a protrusion16aon the upper surface. A flange17is formed at the open edge of the upper half body15B. The flange17has a protrusion17aon the lower surface. The flange16of the lower half body15A and the flange17of the upper half body15B have shapes that correspond to each other. A rib17band a rib17care formed on the lower surface of the flange17of the upper half body15B. The rib17band the rib17care located inside and outside of and away from the protrusion17a, respectively.

The lower half body15A and the upper half body15B are joined to each other by placing the upper half body15B on the lower half body15A such that the protrusion16aof the lower half body15A and the protrusion17aof the upper half body15B face each other, and then vibrating the half bodies15A,15B. The vibration applied to the half bodies15A,15B generates frictional heat between the protrusion16aand the protrusion17a, so that the protrusions16a,17afunction as welding margins. That is, the half bodies15A,15B of the intake manifold11are vibration welded to each other using the protrusions16a,17aas welding margins.

As shown inFIG. 3, portions of each protrusion16a,17athat are located to correspond to the proximal portions of the inlet pipes13are wider than the remainders of the same protrusion16a,17a. Further, portions of each protrusion16a,17athat are close to the left and right side walls of the surge tank12are gradually widened toward the proximal portions of the respective inlet pipes13. Therefore, the joint between the lower half body15A and the upper half body15B is firmer at the left and right side walls of the surge tank12and at the proximal portions of the inlet pipes13than at other parts.

The lower half body15A has plate-like connecting portions18, each located between the proximal portions of one of the front-rear adjacent pairs of inlet pipes13. Each connecting portion18is continuous to the flange16. Each connecting portion18fills the clearance S between one of the front-rear adjacent pairs of inlet pipes13, and is formed integrally with the lower half body15A. A reinforcing rib19extends downward from a center in the front-rear direction of each connecting portion18. Each reinforcing ribs19are continuous to one of the left and right side walls of the surge tank12and formed integrally with the lower half body15A. The upper half body15B has connecting portions20that correspond to the connecting portions18of the lower half body15A. Each connecting portion20of the upper half body15B is located between the proximal portions of one of the front-rear adjacent pairs of inlet pipes13, and is continuous to the flange17. Each connecting portion20fills the clearance S between one of the front-rear adjacent pairs of inlet pipes13, and is formed integrally with the upper half body15B.

As illustrated inFIGS. 2 and 3, the lower half body15A has attachment seats21, which are formed integrally with the lower half body15A. Each attachment seat21is provided at the distal ends of one of the front-rear adjacent pairs of inlet pipes13. Each attachment seat21has a plurality of attachment holes22, which are used for securing the entire intake manifold11to a cylinder block (not shown) of the engine with bolts (not shown).

As described above, the lower half body15A has the connecting portions18, and the upper half body15B has the connecting portions20. Thus, when molding the lower half body15A and the upper half body15B, it is possible to prevent deformation and displacement from being caused at the proximal portions of the inlet pipes13due to molding strains. Particularly, unlike the lower half body15A having the attachment seats21, the upper half body15B of the intake manifold11, which is indicated by lines formed by a long dash alternating with two short dashes inFIG. 1, has the inlet pipes13the distal ends of which are free ends. Therefore, molding strains are likely to be generated in the inlet pipes13of the upper half body15B. In this regard, according to the present embodiment, since the connecting portions20are each provided between the proximal portions of one of the front-rear adjacent pairs of inlet pipes13, the generation of molding strains in the inlet pipes13of the upper half body15B is suppressed.

In an engine having the intake manifold11of the present embodiment, air that is taken into the surge tank12through the opening14is drawn into each inlet pipe13through one of the inlets13a, and then supplied to the intake system of the engine. In this case, when negative pressure is produced in the surge tank12and the inlet pipes13, stress is concentrated on the left and right side walls of the surge tank12and the proximal portions of the inlet pipes13. Also, when a back-fire occurs in the intake manifold11and the interior pressure of the intake manifold11increases, stress is concentrated on the same locations. In this regard, each of the protrusion16aof the lower half body15A and the protrusion17aof the upper half body15B, which are used as welding margins, includes parts that are close to the left and right side walls of the surge tank12. These parts of each protrusion16a,17aare wider than the remainder of the same protrusion16a,17a. Therefore, the proximal portions of the inlet pipes13have relatively high pressure capacity. This prevents abnormal deformation of the surge tank12and the inlet pipes13, and detachment of the welded portions.

Further, the connecting portions18,20are each provided between the proximal portions of one of the front-rear adjacent pairs of inlet pipes13, and each reinforcing rib19, which is continuous to one of the left and right side walls of the surge tank12, extends downward from one of the connecting portions18of the lower half body15A. This further reliably prevents abnormal deformation of the surge tank12and the inlet pipes13, and detachment of the welded portions.

Accordingly, the present embodiment has the following advantages.

In the intake manifold11of the present embodiment, the proximal portions of each pair of inlet pipes13that are adjacent to each other in the front-rear direction are connected to each other by one of the connecting portions18and one of the connecting portions20, so that the proximal portions are integrated with each other. Each connecting portion18of the lower half body15A is connected to one of the left and right side walls of the surge tank12by corresponding one of the reinforcing ribs19, so that the proximal portions of each pair of inlet pipes13that are adjacent to each other in the front-rear direction are integrated with one of the left and right side walls of the surge tank12. Therefore, the left and right side walls of the surge tank12and the proximal portions of the inlet pipes13have relatively high pressure capacity, so that abnormal deformation of the surge tank12and the inlet pipes13or detachment of the welded portions is unlikely to occur. Also, molding strains are unlikely to be generated in the vicinity of the proximal portions of the inlet pipes13.

Further, since the left and right side walls of the surge tank12and the proximal portions of the inlet pipes13have a relatively high pressure capacity, the configuration requires no additional members such as internal pipes to increase the pressure capacity, unlike the intake manifold of Japanese Laid-Open Patent Publication No. 2008-184939. This reduces the number of components of the intake manifold11and thus simplifies the structure of the intake manifold11.

Each of the protrusion16aof the lower half body15A and the protrusion17aof the upper half body15B, which are used as welding margins, includes parts that are located to correspond to the proximal portions of the inlet pipes13. These parts of each protrusion16a,17aare wider than the remainder of the same protrusion16a,17a. This reinforces the joint between the half bodies15A and15B at the left and right side walls of the surge tank12and the inlet pipes13, thereby increasing the pressure capacity of the same locations.

The above embodiment may be modified as follows.

The number of the inlet pipes13may be changed as necessary in accordance with the number of cylinders in an engine. For example, three inlet pipes13may be provided on either of the left and right side of the surge tank12, so that the intake manifold11is used in a horizontally-opposed six-cylinder engine.

In the above embodiment, a clearance S is located between each pair of inlet pipes13that are adjacent to each other in the front-rear direction, and each front-rear adjacent pair of inlet pipes13are connected to each other by one of the connecting portions18and one of the connecting portions20. However, the pipe walls13bof each front-rear adjacent pair of inlet pipes13may be joined to each other without providing a clearance S between the pair of inlet pipes13. In this case, each reinforcing rib19is provided to extend from the joint between the pipe walls13bof one of the front-rear adjacent pairs of inlet pipes13to corresponding one of the left and right side walls of the surge tank12.