JPH0313428B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides two intake valves for each cylinder and two intake passages connected to the intake valves, one of which is closed during low load. The present invention relates to a multi-cylinder engine that is designed to keep the intake flow velocity in the remaining intake passage as high as possible.

[Conventional technology]

This type of engine is already known, but due to the structure of the cylinder head, there are two parts connected to the intake valve.
Preferably, the intake ports are horizontally juxtaposed. Therefore, in multi-cylinder engines adopting this intake configuration, the valve stem of the butterfly valve provided in the high-load passage passes through the other passage.

[Problem to be solved by the invention]

However, in this structure in which the valve stem passes through the intake passage, the intake resistance increases due to the valve stem. Conventionally, attempts have been made to make the valve shaft thinner in the intake passage where no valve is required, as seen in Japanese Patent Publication No. 55-51920, in order to eliminate this problem, but this is still not sufficient.

[Means to solve the problem]

This invention was made in view of the above-mentioned circumstances, and the two intake passages are vertically offset from each other when viewed in the crankshaft direction on the upstream side of the cylinder head, and the mutually offset upstream ends are connected to the intake expansion chamber. A butterfly-shaped blockage valve is provided in one of the biased intake passages and is closed during low load operation of the engine, and the intake passage row in the intake passages connected to the same plane of the intake expansion chamber is connected to the same side of the intake expansion chamber. The overall width of the valve is set to be narrower on the intake expansion chamber side than on the cylinder head side, and the valve shafts of each cylinder of the closing valve are arranged concentrically and connected to each other.

[Effect]

The valve stem of the closure valve provided in one intake passage no longer passes through the other intake passage.

〔Example〕

The present invention will be explained below with reference to illustrated embodiments. In the figure, reference numeral 1 denotes a two-intake valve type in-line four-cylinder four-stroke engine, whose combustion chamber 2 is formed by a cylinder head 3, a cylinder 4, and a piston 4a. ports 5, 6 and two intake valves 7 that open and close them;
8 are provided, and each intake port 5, 6 opens in a horizontal direction on the side surface of the cylinder head 3.
9 is an exhaust port connected to the combustion chamber 2 via an exhaust valve 10, and 11 is an ignition plug. 12 is a long intake pipe, which is attached to the side of the cylinder head 3;
A high-load passage 5 connected to the intake ports 5 and 6
a and a passageway 6a for the entire area, and is gently bent upward on the side of the cylinder head 3. The upstream portions of the high-load passage 5a and the wide-area passage 6a are arranged such that the relationship between the two passages is twisted approximately 90 degrees upstream from the bent portion to position the high-load passage 5a above the wide-area passage 6a. In particular, they are offset vertically relative to each other when viewed in the direction of the crankshaft. The upstream side of the intake pipe 12 is connected to the intake expansion chamber 14 via the valve member 13, and forms an intake branch pipe together with the intake expansion chamber 14. As shown in FIG. The width is set to be narrower on the intake expansion chamber side than on the side. The intake expansion chamber 14 is a large-capacity chamber extending in the direction in which the cylinders 4 are arranged, and the upstream side thereof communicates with the atmosphere through an intake pipe 14a shared by each cylinder and an air cleaner (not shown). 15 is a throttle valve that is manually operated to control the engine output. The valve member 13 is
It has a high-load passage 5b and a wide-area passage 6b that are vertically offset from each other, and the high-load passage 5b
is equipped with a butterfly-shaped shutoff valve 16 that is closed during low-load operation.
is supported by a valve shaft 17 rotatably supported by the valve member 13 so as to be openable and closable. Note that the high-load passage 5b and the wide-area passage 6b of this valve member 13
are communicated with the high-load passage 5a and the wide-area passage 6a of the intake pipe 12, respectively. Reference numeral 18 denotes a shaft coupling that connects the valve shafts 17 of adjacent cylinders to each other. There are various methods for closing the blockage valve 16 during low loads, such as a method using negative intake pressure and a method that is related to the opening degree of the throttle valve 15, but these methods are already well known to those skilled in the art, so they will not be particularly explained. do not.

Next, the operation of this embodiment will be explained. First, when the engine is operated at a low load, the blockage valve 16 closes the high-load passage 5b, so that the entire amount of intake air measured by the throttle valve 15 is distributed to each cylinder within the intake expansion chamber 14. The whole area passageway 6 is relatively fast.
b, 6a and the intake port 6 into the combustion chamber 2. At this time, since the valve shaft 17 for the blockage valve 16 does not exist in the wide area passage 6b, the intake passage area is not narrowed by the valve shaft 17 and the vortex is not generated. It is possible to prevent the occurrence of a so-called "torque valley", which is a phenomenon in which the increase in torque tends to reach a plateau. When the engine load further increases, the blockage valve 16 opens and the entire amount of intake air is guided into the combustion chamber 2 via the intake pipe 12 and the intake ports 5 and 6. At this time, as well, the valve shaft of the blockage valve 16 17 can be avoided, and the maximum output can be improved.

〔Effect of the invention〕

As described above, the present invention has two intake passages that are vertically offset from each other as viewed in the crankshaft direction on the upstream side of the cylinder head, and the mutually offset upstream ends are connected to the same surface of the intake expansion chamber. A butterfly-shaped blocking valve that is closed during low-load operation of the engine is provided in one of the biased intake passages, and the entire width of the intake passage row in the intake passage connected to the same side of the intake expansion chamber is extended to the cylinder head side. The width is narrower on the side of the intake expansion chamber, and the valve stems of the blockage valves for each cylinder are arranged concentrically and connected to each other, so that the valve stems of the blockage valves are narrower than the valves of other cylinders. When connected to the shaft, it is not necessary to pass through the other intake passage, so it is possible to prevent a decrease in output due to an increase in intake resistance. Also,
The two intake passages are vertically offset from each other as viewed in the crankshaft direction on the upstream side of the cylinder head, and the mutually offset upstream ends are connected to the same surface of the intake expansion chamber, so that each intake port in the cylinder head The shape can be substantially the same or symmetrical, and an intake port shape with low intake resistance can be obtained. Furthermore, since the overall width of the intake passage row is narrower at the intake expansion chamber side connection section than at the cylinder head side connection section, the longitudinal dimension of the intake expansion chamber can be shortened and its size can be reduced. Another effect is that the degree of freedom in design, such as the installation position of the expansion chamber, can be increased.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a system diagram showing an intake passage of an engine, FIG. 2 is a sectional view thereof, and FIG. 3 is a sectional view thereof. 2... Combustion chamber, 5a, 5b... High load passage,
6a, 6b... wide area passage, 15... throttle valve, 1
6...Occupation valve, 17...Valve stem.

Claims (1)

[Claims] 1 In a multi-cylinder engine with two intake valves for each cylinder and two intake passages of different lengths, the two intake passages are viewed from the upstream side of the cylinder head in the direction of the crankshaft. The upper and lower ends of the intake passages, which are offset from each other, are connected to the same surface of the intake expansion chamber, and one of the offset intake passages is provided with a butterfly-shaped shutoff valve that closes during low-load operation of the engine. , the total width of the intake passage rows in the intake passages connected to the same surface of the intake expansion chamber is set to be narrower on the intake expansion chamber side than on the cylinder head side, and the valve shafts of the blockage valves for each cylinder are set to be the same. An intake system for a multi-cylinder engine characterized by being arranged on a core and connected to each other.