JPH04116258A - Intake structure for engine - Google Patents

Abstract

PURPOSE:To compactly arrange independent intake passages with their data such as the passage lengths unified for individual cylinders by forming them so that the radius of curvature of the curve section for the independent intake passage of a cylinder near to the connection face of a collection section is made larger than that for the independent intake passage of a cylinder apart from the connection face. CONSTITUTION:Independent intake passages 5a-5d communicated to individual cylinders respectively are extended to one side in the cylinder train direction above an engine 1 and curved and collected on the connection face 11 of an intake collection section 6. The independent intake passage of a cylinder near to the connection face 11 of the intake collection section 6 is shorter than the independent intake passage of a cylinder apart from the connection face 11 of the intake collection section 6, i.e., in the order of the independent intake passages 5d, 5c, 5b, 5a, e.g. the independent intake passage 5b is shorter than the independent intake passage 5, thus the radius of curvature of the second curve section 22 is made larger than that of the first curve section 21 to extend the passage length, and the independent intake passages 5a-5d are connected to the connection face 11 of the intake collection section 6 respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an intake structure for an engine, and particularly to one in which intake air is supercharged by utilizing a dynamic effect (intake inertia effect).

(Prior art) In recent years, in order to improve the output torque of an engine, the filling efficiency of the intake air has been improved by supercharging the intake air supplied to the engine cylinders using dynamic effects such as the intake inertia effect. Efforts are being made to increase the

In other words, in supercharging based on the intake inertia effect, when a negative pressure wave of intake air is generated at the intake port as the intake valve opens at the beginning of the intake stroke of each cylinder in a predetermined engine rotation range (tuned rotation range), This intake negative pressure wave is propagated at the speed of sound toward the upstream side within an independent intake passage connected to the intake port, and this negative pressure wave is reversed into a positive pressure wave in a predetermined volume portion (volume chamber). Furthermore, this positive pressure wave is propagated downstream along the same path at the speed of sound, reaching the intake port of the same cylinder at the end of the intake stroke just before the intake valve closes, and this positive pressure wave pushes the intake air into the combustion chamber. The filling efficiency is increased.

Generally, a surge tank is used as a gathering part to reverse the intake pressure waves.In this surge tank, the length from the upstream passage to each independent intake passage is different for each cylinder. There are problems such as uneven distribution of intake air to the cylinders and uneven intake inertia effect.

Therefore, conventionally, Utility Model Application Publication No. 60-88062 has
The upstream ends of the independent intake passages that communicate with each cylinder from one side of the engine are formed into a substantially truncated conical space, with the downstream end of the main intake passage at the small diameter end of the space, and the plurality of independent intake passages at the large diameter end. It has been proposed to connect the independent intake passages, respectively, and arrange the upstream end openings of the independent intake passages symmetrically with respect to an axis passing through the axis of the lower IN end opening of the main intake passage. According to this, the distance from the downstream end opening of the main intake passage to the upstream end opening of each independent intake passage in the gathering part located in the center of the cylinder row direction of the engine is approximately equal for each independent intake passage, and each cylinder The distribution of intake air is uniform, and the intake flow path from the main intake passage to each cylinder is no longer sharply curved, reducing intake resistance.Furthermore, the upstream end openings of each independent intake passage are arranged close to each other. , each independent intake passage or another independent intake passage can be used as a volume chamber for the intake inertia effect, so that the size of the gathering part itself can be made compact.

(Problem to be Solved by the Invention) By the way, in an in-line engine, if the independent intake passages are gathered at the center in the direction of the cylinder rows, space is required in the width direction and the width of the engine in the lateral direction increases. become.

Therefore, in order to avoid this problem, each independent intake passage is curved, and then its upstream end is extended above the engine and to one side in the direction of the cylinder row, so that a set of air passages that are approximately perpendicular to the direction of the cylinder row of the engine are formed. The structure may be such that it connects to the connection surface of the section.

However, if all the independent intake passages are above the engine and extend to one side in the cylinder row direction, the passage length of the independent intake passages themselves will be different for each cylinder, and the intake air between the independent intake passages will be different. Differences occur in the distribution performance and intake inertia effect.

Also, among the independent intake passages, the independent intake passage of the cylinder located near the connection surface of the gathering section is the same as the independent intake passage of the cylinder located far from the connection surface of the gathering section. The cylinder itself is required to make a sharp curvature, which increases intake resistance and causes variations in charging efficiency between cylinders.

The present invention has been made in view of these points, and its purpose is to adjust the length of the independent intake passage for each cylinder by appropriately setting the radius of curvature of the curved portion of each independent intake passage. The objective is to arrange the cylinder compactly with uniform specifications, eliminate sharp curvatures in the passage itself, reduce intake resistance, and eliminate variations in filling efficiency between cylinders.

Another object of the present invention is to improve the maneuverability of each independent intake passage by specifying the connection position of each independent intake passage with respect to the connection surface of the above-mentioned gathering portion.

(Means for Solving the Problem) In order to achieve the above object, the solving means taken by the invention according to claim (1) is to provide an engine having a plurality of cylinders with independent communication with each cylinder from one side of the engine. The present invention is based on an engine intake structure in which an intake passage is provided, and each of the independent intake passages is curved and then their upstream ends are gathered at one place. Each of the independent intake passages is connected to the gathering portion at the upstream end thereof through a connecting surface substantially orthogonal to the direction of the cylinder row of the engine, and the gathering portion is connected above the engine and on one side in the direction of the cylinder row. position. Furthermore, among the independent intake passages, the independent intake passage of the cylinder located closer to the connecting surface of the collecting part is curved more than the independent intake passage of the cylinder located farther from the connecting face of the collecting part. The structure is such that the radius of curvature of the portion is formed to be large.

Furthermore, the solution taken by the invention according to claim (2) is to move the independent intake passages of the cylinders that are located close to the connection surface of the gathering section among the independent intake passages to the upper side of the connection surface of the gathering section. On the other hand, the independent intake passages of the cylinders located far from the connecting surface of the collecting section are connected to the lower side of the connecting surface of the collecting section.

Furthermore, the solution taken by the invention according to claim (3) is:
It has three or more cylinders, and among the independent intake passages, the independent intake passages of the cylinders located on both sides are connected to the engine side of the connection surface of the gathering part, while the independent intake passages of the cylinders located in the center are connected. The structure is such that it is connected to the side opposite to the engine on the connection surface of the section.

(Function) With the above configuration, in the invention according to claim (1), the independent intake passages that communicate with each cylinder are curved and converge with each other so as to extend above the engine and toward one side in the cylinder row direction. The parts are gathered together at the connecting surface, and are arranged compactly without increasing the width in the lateral direction of the engine. In that case, among the independent intake passages, the independent intake passage of the cylinder located closer to the connecting surface of the gathering part is larger than the independent intake passage of the cylinder located far from the connecting surface of the collecting part. The passage length is increased by increasing the radius of curvature of the curved part as it becomes shorter.It is connected to the connecting surface of the gathering section by a thread path, while the independent intake passage of the cylinder is located far away from the connecting surface of the gathering section. However, the radius of curvature of the curved part is made smaller by the length of the independent intake passage of the cylinder located near the connecting surface of the collecting part, so that the passage length is shortened. It is connected. Therefore, the length of the independent intake passages themselves is the same for each cylinder, the distribution of intake air between the independent intake passages is uniform, and there is no difference in the intake inertia effect.

In addition, as mentioned above, the independent intake passages of the cylinders near the collecting part are connected to the connection surface of the collecting part by a thread that increases the radius of curvature of the curved part and lengthens the passage length. In the independent intake passages of the cylinders that are close to each other, the steep curvature of the passage itself is relaxed, and intake resistance is reduced.

Furthermore, in the invention according to claim (2), among the independent intake passages, the independent intake passage of the cylinder farthest from the connection surface of the gathering part is different from the independent intake passage of the cylinder that is closer to the connection surface of the gathering part. In order to bypass the curved part with a large radius of curvature, it extends upward with a curved part with a small radius of curvature by the length of the independent intake passage in the cylinder row direction compared to the independent intake passage of the nearby cylinder, and is placed above the connection surface of the gathering part. On the other hand, the independent intake passages of the cylinders that are close to the connecting surface of the collecting section are not obstructed by the independent intake passages of the cylinders that are far from the connecting surface of the collecting section, compared to the independent intake passages. A curved portion whose radius of curvature is increased by an amount corresponding to the shortening in the cylinder row direction is easily routed below the independent intake passage of a distant cylinder and connected to the lower side of the connection surface of the gathering portion. For this reason, the independent intake passage of a cylinder that is far from the gathering section is connected to the lower side of the connecting surface of the gathering section, and the independent intake passage of a cylinder that is close to the gathering section is connected to the cylinder that is far from the gathering section. This makes it easy to route the intake passages without making the passage length unnecessarily long or reducing the radius of curvature of the curved portion.

Further, in the invention according to claim (3), among the independent intake passages that have three or more cylinders and communicate with each cylinder, the independent intake passage of the cylinder located in the center in the cylinder row direction is In order to avoid disturbing the curved parts of the independent intake passages located on both sides between each cylinder (engine) and the collecting part, the collecting part is curved on a plane perpendicular to the direction of the cylinder row and moves away from the engine. While connected to the opposite side of the connection surface, the independent intake passages located on both sides are
It is curved with a margin in the direction of the cylinder row, which is the side where no cylinders are present, and is connected to the engine side of the connection surface of the gathering part. Therefore, in order to achieve compactness, even if the gathering part is placed close to each cylinder, the independent intake passage of each cylinder can be curved and easily routed without being constrained by the radius of curvature of the curved part. Become.

(Example) Embodiments of the present invention will be described below based on the drawings.

1 to 3 show a first embodiment in which the present invention is applied to an in-line four-cylinder engine. In the figure, 1 is the first to fourth
This is an in-line four-cylinder engine having four cylinders 2a to 2d, and these first to fourth cylinders 2a to 2d are formed in series at equal intervals. These cylinders 2a to 2d are, for example, first cylinder 2a→third cylinder 2C→
The intake stroke progresses in the order of second cylinder 2b=fourth cylinder 2d.

Reference numeral 4 denotes an intake passage that supplies intake air to each of the cylinders 2a to 2d.
Four independent intake passages 5a, 5b, 5c5d connected to the intake ports 3 of C and 2d, respectively, and a substantially truncated conical intake assembly connected to the upstream end of each independent intake passage 5a, 5b, 5c, 5d. The main air intake passage 7 is connected to the upstream end of the air intake collecting portion 6. These are arranged on one side of the engine 1 (on the right side in FIG. 2), and their upstream ends are connected to an air cleaner (not shown). An air flow meter (not shown) for detecting the amount of intake air is provided in the main intake passage 7 on the downstream side of the air cleaner. In addition, each of the independent intake passages 5a, 5b, 5c, 5
The upstream ends of the pipes d are made of aluminum pipe material, and the upstream ends of the pipes are gathered in the intake collecting section 6 in close proximity to each other, and communicated with the main intake passage 7.

The intake collecting section 6 has an upstream end 6a that opens at the downstream end of the main intake passage 7, and a cross-sectional area larger than the upstream end, and has a cross-sectional area larger than that of the upstream end, and has an upstream end 6a that opens at the downstream end of the main intake passage 7. The upstream end has a downstream end 6b that is arranged in a substantially square shape and opens so as to surround the central axis ρ of the downstream end opening of the main intake passage 7, and has a cross-sectional area from the upstream end 6a to the downstream end 6b. Or it is increasing smoothly. The downstream end 6b of the intake collecting portion 6 is formed in a connecting surface 11 that is substantially orthogonal to the cylinder row direction of the engine 1, and the upstream ends of the independent intake passages 5a, 5b, 5c, and 5d are connected to each other. It is now possible to do so. Further, the intake air collecting portion 6 is located above the engine 1 and on one side in the direction of the cylinder row (on the left side in FIGS. 1 and 2).

Furthermore, among the independent intake passages 5a, 5b, and 5c5d, the first cylinder 2a and the second cylinder 2b are located far from the connection surface 11 (downstream end 6b) of the intake collecting section 6.
Each independent intake passage 5a, 5b has these intake pipes 20.
(pipe material) is horizontally extended in a direction away from the engine 1 side, then curved by bending and extended upward, and the first curved portion 21 has its upstream end directed toward one side in the cylinder row direction.
and a second curved portion 22 are provided. On the other hand, the independent intake passages 5c of the third cylinder 2c and the fourth cylinder 2d are located close to the intake collecting portion 6.

5d, a third curved portion 23 and a fourth curved portion 2 are formed in which these intake pipes 20 draw an arc from below to above in a direction away from the engine 1 side, and whose upstream ends are directed toward one side in the cylinder row direction.
4 are provided.

Each of the independent intake passages 5c and 5d of the third cylinder 2C and the fourth cylinder 2d has a fourth curved portion of the independent intake passage 5d of the fourth cylinder 2a, which is closer to the connecting surface 11 of the intake collecting portion 6. The radius of curvature R4 of the third curved portion 23 of the independent intake passage 5C of the third cylinder 2C which is far from the connection surface 11 of the intake collecting portion 6 is set to 70 m++, respectively, and the radius of curvature R4 of the The radius of curvature R4 of the fourth curved portion 24 is larger than the radius of curvature R3 of the third curved portion 23. On the other hand, in the first cylinder 2a and the second cylinder 2b, the radius of curvature R2 of the second curved part 22 of the second cylinder 2b, which is closer to the connection surface 11 of the intake collecting part 6, is 50 mm. The radius of curvature R1 of the first curved portion 21 of the first cylinder 2a, which is far from the connection surface 11 of It is designed to be larger than the In this case, each of the independent intake passages 2a~
The first to fourth curved portions 21 to 24 of 2d are arranged in the order of the independent intake passages of the cylinders closest to the connection surface 11 of the intake collecting portion 6, that is, the radius of curvature R4 (70++++s) of the fourth curved portion 24.
, the radius of curvature R3 (60 m+s) of the third curved part 23, the radius of curvature R2 (50 mm) of the second curved part 22, and the radius of curvature R1 (40 mm) of the first curved part 21. .

Further, each of the independent intake passages 5a, 5b of the first cylinder 2a and the second cylinder 2b is connected to the connecting surface 11 of the intake collecting part 6, and the intake collecting part 6 is common to the central axis g of the main intake passage 7. It is connected above the horizontal line m passing through the central axis g of. On the other hand, each of the independent intake passages 5c and 5d of the third cylinder 2C and the fourth cylinder 2d is located below a horizontal line m passing through the central axis g of the intake collecting part 6 with respect to the connecting surface 11 of the intake collecting part 6. connected to the side. Also, the second cylinder 2
Each independent intake passage 5b, 5c of the third cylinder 2c and the third cylinder 2c is
With respect to the connecting surface 11 of the intake air collecting section 6, the side opposite to the engine 1 (
In Fig. 3, it is connected to the right side). On the other hand, each independent intake passage 5a, 5d of the first cylinder 2a and the fourth cylinder 2d
is connected to the connecting surface 11 of the intake air collecting portion 6 on the side closer to the engine 1 (on the left side in FIG. 3) than the vertical line p passing through the central axis g of the air intake collecting portion 6.

Therefore, in the above embodiment, each cylinder 2a, 2b, 2c
, 2d, independent intake passages 5a, 5b, respectively communicating with
.
The connecting surfaces 11 are gathered together to provide a compact arrangement without increasing the width of the engine 1 in the lateral direction. In that case, among the independent intake passages 5a, 5b, 5c, 5d,
The order of the independent intake passages of the cylinders located close to the connection surface 11 of the intake collecting part 6, that is, the independent intake passage 5d of the fourth cylinder 2d, the independent intake passage 5c of the third cylinder 2C, the second cylinder 2
b, independent intake passage 5b, first cylinder 2a independent intake passage 5
The independent intake passage 5b of the second cylinder 2b is shorter than the independent intake passage 5a of the first cylinder 2a, which is located farthest from the connection surface 11 of the intake collecting section 6 in the order of adjacent parts a. The radius of curvature R2 (50 mm) of the second curved part 22 is 10 times smaller than the radius of curvature R1 (40 mm) of the first curved part 21.
Intake gathering part 6 with yarn path that increases +om and lengthens the passage length.
The radius of curvature R3 (60°) of the third curved portion 23 is curved into a second curve on the connection surface 11 of 10 mm larger than the radius of curvature R2 (5011111) of part 22
By increasing the length of the thread to lengthen the passage length, a fourth line is formed on the connection surface 11 of the intake collecting portion 6 to compensate for the length of the independent intake passage 5d of the fourth cylinder 2d being shorter than that of the independent intake passage 5C of the third cylinder 2C. The radius of curvature R4 (70 mm) of the curved portion 24 is the third curved portion 23.
The connecting surface 11 of the suction gathering portion 6 is made by increasing the curvature radius R3 (60 mm+) by 10+am to lengthen the passage length.
are connected to each.

For this reason, the intake pipes 21. of the independent intake passages 5a, 5b, 5c, 5d. ...The length of each cylinder 2a, 2b, 2c,
Equal length every 2d, independent intake passages 5g, 5b, 5c,
In addition to making the distribution of intake air uniform between 5d, it is also possible to effectively perform supercharging due to the intake inertia effect.

In addition, as described above, each independent intake passage 5a, 5b5c, 5d
Or, the independent intake passages 5d and 5c of the fourth cylinder 2d to the first cylinder 2a, which are close to the intake collecting part 6.

In the order of 5b and 5a, the radius of curvature of each curved part is 10
Since it is connected to the connecting surface 11 of the intake collecting section 6 by a thread that lengthens the passage length by increasing the length of the passage, each independent intake of the fourth cylinder 2d and the third cylinder 2C, which are close to the intake collecting section 6, Passage 5d.

5C intake pipe 21. ...The sharp curvature of the body itself is alleviated, and intake resistance can be reduced. Moreover, each independent intake passage 5
a, 5b, 5c, and 5d are the independent intake passages 5d to 5a of the fourth cylinder 2d to the first cylinder 2a, which are closer to the intake collecting portion 6, in that order, and are the intake pipes 21. ...Since the curvature of the cylinder itself is relaxed, the independent intake passages 5a, 5b, 5c of each cylinder 2a to 2d
, 5d becomes uniform, and each cylinder 2a to 2
It is possible to eliminate variations in filling efficiency between d.

Furthermore, among the independent intake passages 5a, 5b, 5c, and 5d, the first cylinder 2a that is farthest from the connection surface 11 of the intake collecting section 6
And the radius of curvature R3, R4 of each independent intake passage 5c, 5d of the third cylinder 2c and fourth cylinder 2d, where each independent intake passage 5a, 5b of the second cylinder 2b is close to the connection surface 11 of the intake collecting part 6. Large first curved portion 21 and second curved portion 2
2, extending upward with a third curved portion 23 and a fourth curved portion 24 having small curvature radii R3 and R4,
It is connected to the connection surface 11 above the horizontal line m passing through the central axis g of the intake air collection section 6 . On the other hand, the third cylinder 2c and the fourth cylinder 2d which are close to the connection surface 11 of the intake collecting part 6
The independent intake passages 5a of the first cylinder 2a and the second cylinder 2b are far from the connection surface 11 of the intake collecting portion 6.

Each independent intake passage 5a without being obstructed by 5b.

5b, the first curved part 21 and the second curved part 22 with large curvature radii R3 and R4 are easily routed and pass through the central axis p of the intake collecting part 6 with respect to the connection surface 11 of the intake collecting part 6. It is connected below the horizontal line m. For this reason, the independent intake passages of the first and second cylinders, which are far from the intake collecting part, are connected to the lower side of the connection surface of the intake collecting part, and the independent intake passages of the third and fourth cylinders, which are far from the intake collecting part, are connected to the lower side of the connection surface of the intake collecting part. The independent intake passages of the cylinders are connected while avoiding the independent intake passages of the first and second cylinders that are far away from the intake gathering part, thereby making the passage length unnecessarily long or reducing the radius of curvature of the curved part. Each independent intake passage 5a,
5b, 5c, and 5d can be easily handled.

Moreover, among the independent intake passages 5a, 5b, 5c, and 5d, the independent intake passages 5b and 5C of the second cylinder 2b and the third cylinder 2C, which are located in the center in the cylinder row direction, ) and the gathering portion, the independent intake passages 5a of the first cylinder 2a and the fourth cylinder 2d are located on both sides.

Be careful not to get in the way of the curved parts 21 and 24 of 5d.

It is curved on a plane perpendicular to the direction of the cylinder row, and is connected to the connection surface 11 of the intake collecting section 6 on the side opposite to the engine 1 from the vertical line p passing through the central axis g of the intake collecting section 6. on the other hand,
The independent intake passages 5a and 5d of the first cylinder 2a and the fourth cylinder 2d located on both sides are curved with a margin in the direction of the cylinder row on the side where no cylinder exists, so that the connecting surface 11 of the intake collecting portion 6 In contrast, it is connected to the engine 1 side with respect to a vertical line m passing through the central axis g of the intake air gathering portion 6. Therefore, in order to make the intake collecting section 6 more compact, each cylinder 2a,
2b, 2c, 2d (! engine 1), the independent intake passages 5 of each cylinder 2a to 2d
8 to 5d are curved and easily routed without being restricted by the curvature radii R1, R2, R3, and R4 of the curved portions 21, 22, 23°24, and the independent intake passages 5a, 5b, 5
c, 5d can be more easily handled.

It should be noted that the present invention is not limited to the above embodiments, but includes various other modifications.

For example, in the above embodiment, the independent intake passages 5a and 5b of the first cylinder 2a and the second cylinder 2b are connected to the connecting surface 11 above the horizontal line m passing through the central axis g of the intake collecting section 6, while the Although the independent intake passages 5c and 5d of the third cylinder 2c and the fourth cylinder 2d are connected to the connecting surface 11 below the horizontal line m passing through the central axis g of the intake collecting section 6, Each independent intake passage is connected to a connecting surface below a horizontal line passing through the central axis of the intake collecting section, while each independent intake passage of the third and fourth cylinders is connected to a connecting surface below a horizontal line passing through the central axis of the intake collecting part. may also be connected to the upper connection surface. Moreover, each independent intake passage 5b of the second cylinder 2b and the third cylinder 2C.

5c is connected to the connection surface 11 on the side opposite to the engine 1 from the vertical line p passing through the center axis Ω of the intake collecting section 6, while the independent intake passages 5a and 5d of the first cylinder 2a and the fourth cylinder 2d are connected to the intake collecting part 6. Although it was connected to the connection surface 11 on the engine 1 side with respect to the vertical line m passing through the central axis g of the section 6, the second cylinder and the third cylinder
Each independent intake passage of the cylinder is connected to a connecting surface on the engine side from a vertical line passing through the central axis of the intake collecting section, while the first
Each independent intake passage of the cylinder and the fourth cylinder may be connected to a connecting surface on the side opposite to the engine from a vertical line passing through the central axis of the intake collecting section. In these cases, the length of the intake pipe itself of the independent intake passages is made equal for each cylinder, and the distribution of intake air between the independent intake passages is made uniform, thereby achieving supercharging due to the intake inertia effect. In addition, it is possible to reduce the intake resistance by alleviating the sharp curvature of the intake pipes themselves in the independent intake passages of the fourth and third cylinders, which are close to the intake collecting part, and By making the intake resistance of the intake passage uniform, variations in filling efficiency between cylinders can be eliminated.

Further, although the above embodiment is an example applied to an in-line four-cylinder engine 1, the present invention can be applied to an in-line engine having a plurality of cylinders. For example, in the case of an in-line six-cylinder engine, the cylinders located far away from the intake collecting section and the cylinders located close to it are divided into three cylinders each.
In addition to communicating the independent intake passages of each cylinder with the upper and lower sides of the intake collecting part, two cylinders each are connected to each cylinder located far away from the intake collecting part, two cylinders are located close to the intake part, and two cylinders are located in the middle. Separate the independent intake passages for each of these two cylinders into the upper part of the intake collecting section.

It is also possible to communicate with the lower side and the center.

(Effects of the Invention) As explained above, according to the invention according to claim (1), among the independent intake passages of each cylinder, the independent intake passages of the cylinders that are closer to the connection surface of the collecting part are connected to the connecting face of the collecting part. Compared to the independent intake passages of cylinders that are far from the connection surface, the radius of curvature of the curved part is increased by the length of the passage, which is shorter in the direction of the cylinder row. The intake passage itself can be arranged compactly by making the length of each cylinder equal, ensuring uniform distribution of intake air between independent intake passages, and effectively performing supercharging through dynamic effects. I can do it. Moreover, the sharp curvature of the independent intake passages of the cylinders near the gathering part can be alleviated to reduce intake resistance, and the intake resistance of the independent intake passages of each cylinder can be made uniform, so that the air flow between each cylinder can be reduced. Can eliminate variations in filling efficiency.

Further, according to the invention according to claim (2), among the independent intake passages, the independent intake passage of a cylinder far from the connection surface of the gathering portion is replaced with the independent intake passage of a cylinder close to the connection surface of the gathering portion. The curved part has a smaller radius of curvature due to its length compared to the above, and is extended upward to bypass the curved part of the independent intake passage of the nearby cylinder and connect to the upper side of the connecting surface of the collecting part. The independent intake passage of the cylinder close to the surface,
A curved portion with a radius of curvature that is shorter than the independent intake passage of a cylinder far from the connection surface of the gathering portion is curved below the independent intake passage and connected to the lower side of the connection surface of the gathering portion. has been done. Therefore, each independent intake passage can be easily routed without unnecessarily lengthening the passage length or reducing the radius of curvature of the curved portion, thereby improving the maneuverability of each independent intake passage.

Further, according to the invention according to claim (3), among the independent intake passages, the independent intake passage of the central cylinder is arranged on a plane perpendicular to the cylinder row direction between each cylinder and the gathering part, which is difficult in terms of layout. At the same time, each independent intake passage on both sides was curved with a margin in the direction of the cylinder row and connected to the engine side of the connecting surface of the gathering section, so that the connecting section of the gathering section Even if each independent intake passage is arranged between each cylinder and the gathering part, which is close to each cylinder in order to make it more compact, the layout is difficult. It can be curved without any restrictions and can be routed more easily, making it possible to improve the maneuverability of each independent intake passage.

[Brief explanation of drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is a plan view of the engine and intake system, FIG. 2 is a side view related to FIG. 1, and FIG. 3 is a front view related to FIG. 1. It is a diagram. 1... Engine 2a to 2d... Cylinder 5a to 5d... Independent intake passage 6... Intake gathering part (gathering part) 11... Connection surface 21 to 24... Curved part and 1 other person

Claims (3)

[Claims] (1) An engine having a plurality of cylinders is provided with independent intake passages that communicate with each cylinder from one side of the engine, and each independent intake passage is curved and then its upstream ends are gathered in one place. In the intake structure of the engine, each of the independent intake passages is connected to a gathering portion at the upstream end thereof at a connecting surface substantially orthogonal to the cylinder row direction of the engine, and the gathering portion is above the engine and connected to the cylinders. It is located on one side in the column direction, and among the above independent intake passages,
The independent intake passages of cylinders located close to the connection surface of the gathering section are formed so that the radius of curvature of the curved section is larger than that of the independent intake passages of cylinders located far from the connection surface of the gathering section. An engine intake structure characterized by: (2) Among the independent intake passages, the independent intake passage of the cylinder located close to the connecting surface of the collecting section is connected to the upper side of the connecting surface of the collecting section, while the independent intake passage of the cylinder located near the connecting surface of the collecting section 2. The engine intake structure according to claim 1, wherein the independent intake passages of the cylinders located far away from each other are connected to the lower side of the connection surface of the gathering portion. (3) It has three or more cylinders, and among the independent intake passages, the independent intake passages of the cylinders located on both sides are connected to the engine side of the connecting surface of the gathering part, while the independent intake passages of the cylinders located in the center are 2. The engine intake structure according to claim 1, wherein the independent intake passage is connected to a side opposite to the engine of a connection surface of the gathering portion.