Internal-combustion engines – Intake manifold – Manifold having plenum
Reexamination Certificate
2002-08-08
2003-06-03
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Intake manifold
Manifold having plenum
C123S184210, C123S184530
Reexamination Certificate
active
06571760
ABSTRACT:
TECHNICAL FIELD
The present invention refers to an air inlet manifold for an internal combustion engine, which air inlet manifold has pipes for distribution of air to cylinders of the engine.
BACKGROUND OF THE INVENTION
A combustion engine comprises combustion chambers, cylinders, a fuel supply, and an air inlet manifold to supply and distribute air to the combustion chambers of the engine. The air is supplied to the air inlet manifold via a throttle, which controls the amount of air. The manifold comprises at least one distribution chamber and a number of pipes mounted to the combustion chambers, normally one pipe per combustion chamber.
The features of the distribution chamber and the pipes are important for many reasons. When a driver increases or decreases pressure on the gas pedal, thereby demanding a change in throttle and airflow, it is desirable to have the engine respond as quickly as possible. One way to achieve this is to have a small volume in the air inlet manifold, since such a small volume gives a smaller air volume within the air inlet manifold, and the smaller air volume responds more quickly to changes of airflow/pressure dependent on the changes of the throttle. To get a small volume, it is desirable to place the pipes as close together as possible.
The features of the pipes are important for providing the best air supply to the combustion chambers. Between the combustion chambers and the pipes there are valves that open and close, typically, synchronized with the movement of the pistons in the combustion chambers. The valves are mounted in the cylinder head, which cylinder head is mounted to the pipe. Each valve opens with a movement away from the cylinder head, i.e., in the direction of the airflow, and closes with a movement in the opposite direction. When the valve opens, a pressure pulse propagates in the pipe into the distribution chamber of the air inlet manifold, where the pulse changes direction and returns back into the pipe. This phenomena is well known, and it is desirable to design the pipes in such a way that when the engine rotates with a predetermined rotation per minute, rpm, the pulse returns to the valve when the valve opens, thereby pushing en extra amount of air into the combustion chamber. When designing a combustion engine, this phenomenon is normally designed to occur when the torque curve is reaching its maximum, giving an extra amount of air into the cylinder. In fact, the design of the pipes normally decides the torque maximum.
A typical air inlet manifold extends in a longitudinal direction from a first end to a second end, and the air inlet manifold has an air inlet at the first end, a distribution chamber for air extending in the longitudinal direction restricted by at least a first internal wall, and an end wall at the second end. At least one air pipe for each cylinder is distributed along the longitudinal direction and protrudes essentially perpendicular to the first wall. The pipes each have an pipe inlet, a pipe channel restricted by at least a second internal wall, and a pipe outlet. The upper part of the pipes, the part of the pipe closest to the distribution chamber, extends essentially perpendicular to the first internal wall of the distribution chamber, with the pipe inlet towards the distribution chamber. The pipe inlet of each pipe has a phased edge that is rounded by a convex radius from the second internal wall to first internal wall, which edge is uniform around the pipe inlet.
In view of the above, it is important that the volume in the distribution chamber is small enough to give good engine response, and the features of the pipes are important to gain a good pressure pulse charging. One important feature for gaining good pressure pulse charging is that the edges in the pipes are phased with a small convex radius. However, when the engine is running at high engine speed, the airflow is high. If the edges are phased with too small a radius, undesirable turbulent phenomena can occur which limits the air flow in the pipe channels. Thus, to supply maximum air to the combustion chambers at high engine speeds, it is important that the edges have a radius large enough to avoid turbulent phenomena around the pipe inlet. Thus, there is a problem in designing the air inlet manifold since the design of the edge at the pipe inlet has to be a trade off between good pressure pulse charging and avoiding turbulent phenomena to supply enough air to the combustion chambers at high engine speed.
Pipes with different geometric features are known, for example, circular cross-sections, oval cross-sections, rectangular cross-sections, and D-shaped pipes. However, the trade off problem mentioned above applies to all.
In a multi-cylinder engine, it is desirable to have similar conditions in each combustion chamber. This implies that the air for the different combustion chambers shall be as similar as possible, i.e., the air inlet manifold must distribute the air equally over the pipes. This in turn implies that each pipe in the air inlet manifold have similar properties regarding the shape of the pipe inlet, pipe channel, and a pipe outlet. In the case where the pipes are mounted to the distribution chamber in a row, the shape of the pipe farthest from the air inlet of the air inlet manifold differs from the other pipes.
The second internal wall of the last pipe differs from the corresponding parts in the other pipes in that the second internal wall of the last pipe transitions into the end wall of the distribution chamber, i.e., the second internal wall of the last pipe does not have a phased edge on this part, but the second internal wall continues in a straight line and then follows the curvature of the end wall. Thus, the last pipe does not have the same geometry around the pipe inlet as the other pipes, thereby supplying air to the corresponding combustion chamber differently than the other pipes supplying air to their corresponding combustion chambers, thereby giving rise to different conditions for the different combustion chambers. As mentioned before, it is desirable to have as similar conditions as possible in the respective combustion chambers. The different features of the last pipe give rise to the problem of non-similar properties in the different combustion chambers. It is important to have similar properties regarding the air supply to the combustion chamber for good emissions.
SUMMARY OF THE INVENTION
The present invention aims to solve the above-mentioned problems by introducing a new shape of the edges of the pipe inlets in the air inlet manifold. The pipes can be fitted closer to each other, giving a smaller volume and thereby an engine with quick response. The invention also solves the problem of good pressure pulse charging. The invention also solves the problem with an air inlet manifold distributing the air equally over the pipes.
The identified problems are solved, according to the invention, by using an air inlet manifold for a multi-cylinder internal combustion engine. The air inlet manifold has a first end, an opposing second end with an end wall, and at least a first internal wall, if the body of the air inlet manifold has a circular cross-section. Alternatively, the air inlet manifold body has a rectangular cross-section, with several internal walls.
The air inlet manifold extends in a longitudinal direction from the first end to the second end. The air inlet manifold has an air inlet at the first end and at least one distribution chamber for air extending along the longitudinal direction and restricted by at least the first internal wall. The air inlet manifold also has at least one air pipe for each cylinder. The pipes are distributed along the longitudinal direction. The pipes each have an inlet towards the distribution chamber, and an opposing outlet, an upper part defined by a first length, L
1
from the inlet to a first point. The upper part protrudes essentially perpendicular to the first internal wall.
Each pipe has a pipe channel between the inlet and the outlet, which is restricted by at least a
Argenbright Tony M.
Brehob Diana D.
Volvo Car Corporation
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