Internal-combustion engines – Valve – Valve head cooperates with manifold
Patent
1987-04-20
1989-05-30
Wolfe, Willis R.
Internal-combustion engines
Valve
Valve head cooperates with manifold
123308, F02B 3100, F02M 3510
Patent
active
048340359
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a variable swirl intake apparatus for an engine, for controlling a swirl of intake air in a cylinder chamber of, e.g., a direct injection type diesel engine.
BACKGROUND ART
An intake port for guiding air to a cylinder chamber is formed in a cylinder head of a direct injection type diesel engine, and an intake valve arranged in the intake port is opened or closed in response to each stroke of the engine.
Air guided from the intake port to the cylinder chamber is compressed, is mixed with fuel injected from an injection nozzle, and is then combusted. As is well known in this case, as air and fuel are mixed better, a combustion efficiency is improved.
Various means for improving the mixing state of air and fuel have been conventionally used. For example, a technique using a high swirl port (forcible swirl intake hole), a so-called HSP structure, is known.
The HSP structure is as shown in FIGS. 1, 2A, and 2B. Reference numeral 1 denotes a cylinder liner; 2, a cylinder chamber; 3, a cylinder head; and 4, an intake apparatus. Intake apparatus 4 is constituted by intake port 5 and intake valve 6. Reference numeral 7 denotes an exhaust port. A fuel injection nozzle (not shown) is arranged on cylinder head 3 to face cylinder chamber 2.
Intake port 5 is slightly eccentric to the center of intake valve 6. Upon intake stroke wherein intake valve 6 is moved downward and intake port 5 is opened, intake air which receives "eccentricity" due to intake port 5 is guided to cylinder chamber 2, and a swirl is focibly formed along the circumferential direction of chamber 2. Therefore, the intake air is mixed well with fuel injected from an injection nozzle, and hence, a combustion efficiency can be improved.
Note that a ratio of a swirl speed of intake air in the cylinder chamber to a rotational frequency of an engine is called a "swirl ratio". The swirl ratio is preferably variable for the various reasons, as will be described later.
For example, when intake ports having different swirl ratios are alternately set on an identical cylinder chamber to compare engine performances, the experimental results shown in FIG. 3 are obtained. In FIG. 3, a curve indicated by a corresponds to the intake port having a high swirl ratio, a curve indicated by b corresponds to the intake port having a middle swirl ratio, and a curve indicated by c corresponds to the intake port having a low swirl ratio. As shown in FIG. 3, in the case of high swirl ratio a, when the engine speed is at low speed a1, the best engine performance can be obtained. In the case of middle swirl ratio b, when the engine speed is at middle speed b1, the best engine performance can be obtained. In the case of low swirl ratio c, when the engine speed is at high speed c1, the best engine performance can be obtained. Therefore, when the swirl ratio is constant, the performance is inevitably degraded in some engine speed range.
The reason why the engine performance varies in accordance with a change in engine speed while the swirl ratio is constant is as follows. More specifically, as shown in FIG. 4, when angle .theta. of spray flowing together with a swirl during fuel injection period .theta.inj [degree: crank angle] in unit time coincides with angle .theta.0 between two adjacent sprays, the best engine performance can be obtained. If .theta. does not reach .theta.1, this means air between adjacent sprays is not satisfactorily utilized. Therefore, if .theta. exceeds .theta.0, the immediately preceding spray overlaps the next spray, and fuel is "baked" due to air shortage in this overlapping portion. (Ns/Nc): swirl ratio, B: cylinder bore diameter [mm], D: combustion chamber diameter [mm]]
In the relationship between injection period .theta.inj and engine speed Ne, as engine speed Ne increases, .theta.inj is prolonged, as shown in FIG. 5. Furthermore, as shown in FIG. 6, as engine speed Ne increases, the rotating speed of an injection pump is increased, and the injection pressure is increased, thereby shortening a time (in
REFERENCES:
patent: 4256062 (1981-03-01), Schafer
patent: 4438741 (1984-03-01), Okumura
patent: 4491102 (1985-01-01), Nakasima
patent: 4499868 (1985-02-01), Kanda et al.
Komuro Shuichi
Miyata Osamu
Mizote Eiji
Nakagawa Tomomi
Shimada Taizo
Macy M.
Mitsubishi Jidosha Kogyo Kabushiki Kaisha
Wolfe Willis R.
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