JP2525001B2 - Engine intake system - Google Patents

Description

TECHNICAL FIELD The present invention relates to an intake device for an engine equipped with a surge tank.

[Prior Art] A negative pressure wave generated in an intake port near the intake valve when it is opened is inverted into a positive pressure wave and propagated to a combustion chamber, so that pressure wave supercharging by an inertial effect is performed. The engine air intake system is well known. In such an intake device, a surge tank having a sufficient volume for inverting the negative pressure wave to the positive pressure wave is provided at a predetermined position in the intake passage, and the intake air from the surge tank to the combustion chamber is The length of the system is set to be relatively large so that pressure wave supercharging is most effectively performed in a predetermined operating region, and has a slightly bulky configuration.

By the way, in order to effectively use the limited space,
There are various restrictions on the layout of the equipment in the engine room. For the surge tank and the intake system downstream thereof, it is possible to attach / detach the brake master back 15 as shown in FIG. 1, for example. However, their shapes are set while ensuring a predetermined surge tank volume and a predetermined intake passage length under the constraint that there is no interference with the inclined bonnet.

Under such restrictions, in order to make the surge tank and the intake system downstream thereof as compact as possible, for example, the surge tank is arranged above the engine body and Independent intake pipe has a curved shape that bulges to the side of the engine (see Japanese Utility Model Laid-Open No. Sho 59-175666). Furthermore, by improving this, the surge tank becomes longer in the output shaft direction above the engine body. like,
Further, the cylinders are arranged so as to be inclined in the output shaft direction, and the independent intake passages of the respective cylinders downstream of the surge tank are connected closer to the high-side end of the surge tank, and are arranged closer to the engine body. (See Japanese Patent Application No. 61-50991 (JP-A No. 62-210254)) and the like have been proposed.

However, in such a conventional one, the cross-sectional area of the opening of each independent intake passage to the surge tank becomes larger as the one connected closer to the end of the surge tank on the installation side,
As a result, the amount of intake air supplied to each cylinder or the charging efficiency becomes uneven, and there is a problem that idle stability and EGR deteriorate.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and is effective in an intake system for an engine provided with a surge tank for performing pressure wave supercharging due to an inertial effect. In addition, it is possible to provide an engine intake device that has a compact structure, does not hinder the handling of other equipment, and evenly supplies the intake air to each cylinder to improve idle stability and EGR. To aim.

In order to achieve the above object, the present invention has an opening area of the independent intake passage to the surge tank as the radius of curvature of the curved inner peripheral side wall surface of the curved connection portion of the independent intake passage to the surge tank becomes smaller. Focusing on the fact that the power consumption is reduced, the surge tank is arranged above the engine body so as to be long in the output shaft direction, and is bent from the side wall of the surge tank extending in the output shaft direction into a substantially C-shape. In a cylinder engine that is formed by extension and has an independent intake passage that connects a surge tank and an intake port of each cylinder, one end of the surge tank is positioned higher than the other end in the output axis direction. Inclination so that the independent intake passage near the end on the high position side is closer to the engine body than the independent intake passage near the end on the low position side. The curvature of the air passage is set, and the radius of curvature of the curved inner peripheral side wall surface of the curved connection portion of the independent intake passage to the surge tank is set to be smaller as it is located closer to the high-side end of the surge tank. An intake system for an engine, characterized by being set to.

[Advantages of the Invention] In the conventional one, the opening area to the surge tank becomes larger as the independent intake passage arranged closer to the original engine (closer to the end on the high position side of the surge tank) becomes larger. The area of opening to the surge tank is reduced by decreasing the radius of curvature of the curved center side wall surface of the connection part to the surge tank for the independent intake passage located closer to the engine body, so that the area increase by the former And the area reduction due to the latter are offset, the area of the opening to the surge tank of all independent intake passages becomes the same, the intake air supply to each cylinder can be made uniform, and idle stability, EGR, etc. are improved. To do.

[Examples] Examples of the present invention will be specifically described below.

As shown in FIG. 1, the intake system of the four-cylinder reciprocating engine E is, for example, in the case of the first cylinder 1a, when the intake valve (not shown) is opened, each of the combustion chamber 2a The basic structure is such that intake air is supplied to the combustion chamber 2a through the first and second intake ports 3a and 4a opening on the upper surface, and these first and second intake ports 3a and 4a are branched parts 5a. On the upstream side, they are collected in one common intake port 6a. In order to guide the intake air to the common intake port 6a, an independent intake passage 7a communicating with this is provided. Further, the intake system of the second to fourth cylinders has the same structure as the first cylinder. It should be noted that members having the same function provided in the first to fourth cylinders are respectively given the same reference numerals, and subscripts a, b, c, d are added in order of the first to fourth cylinders to distinguish them. . First of these
The upstream side ends of the independent intake passages 7a, 7b, 7c, 7d of the fourth cylinder are connected to the side surfaces of the surge tank 8 arranged above the engine E, which will be described in detail later. And
The first to fourth independent intake passages 7a, 7b, 7c, 7d are connected from the surge tank 8 to the common intake ports 6a, 6b, 6c, 6d when viewed from the front side of the engine E (lower side in FIG. 1). It is formed in a substantially C-shape that is curved and bulges in the direction opposite to the engine E direction (left side in FIG. 1). The first to fourth independent intake air passages 7a, 7b, 7c, 7d are respectively provided at the predetermined positions of the bulging portions at the upstream independent intake pipes 9a, 9b, 9c, 9 in order to simplify the manufacturing method.
d and the independent intake pipes 11a, 11b, 11c, 11d on the downstream side,
These are connected to all the independent intake passages 7a, 7b, 7c, 7d by upper and lower two flanges 12p, 12q integrally formed.

For example, for the first cylinder 1a, the surge tank 8 is generated in the first and second intake ports 3a, 4a near the intake valve when the intake valve is opened at the beginning of the intake stroke, and the sonic velocity is increased. The negative pressure wave propagating upstream through the common intake port 6a and the independent intake passage 7a is inverted to a positive pressure wave in order, and this is sequentially reversed to the independent intake passage 7a, the common intake port 6a, and the
1. Propagate toward the downstream through the first and second intake ports 3a and 4a so as to reach the combustion chamber 2a at the end of the intake stroke,
The intake air is pushed into the combustion chamber 2a to have a sufficient volume so that supercharging can be performed effectively. Also, the first to fourth cylinders
The intake system of 1a, 1b, 1c, 1d is set to a length such that the pressure wave reaches the combustion chamber 2a at the above timing and the pressure wave supercharging can be effectively performed in a predetermined operating region. Therefore, the lengths of the intake systems of the cylinders 1a, 1b, 1c, 1d are set to be the same.

Such a surge tank 8 and the first to fourth independent intake passages
In order to make the structure of 7a, 7b, 7c, 7d more compact, their shape and layout have been devised,
Hereinafter, this will be described.

2 and 3 and 4 respectively show the surge tank 8
FIG. 4A is a plan view, a front view, and a side view of an intake system including first to fourth upstream independent intake pipes 9a, 9b, 9c, 9d.

As shown in these figures, the surge tank 8 avoids interference with a bonnet (not shown) that inclines downward toward the front of the vehicle, while effectively utilizing the space in the engine room, The area of the cross section in the direction perpendicular to the output shaft is arranged such that the output shaft (not shown) is inclined so as to descend toward the front (rightward in FIGS. 2 and 3). It is formed so as to be uniform.

Therefore, as shown in FIG. 3, the upstream independent intake pipe closer to the lowest end of the surge tank 8 has a smaller height from the upper flange 12p, that is, the first to the first 4 The upstream independent intake pipes 9a, 9b, 9c, 9d are configured so that the height increases in this order. On the other hand, since the lengths of the first to fourth upstream independent intake pipes 9a, 9b, 9c, 9d need to be the same as described above (the intake system of each cylinder downstream of the lower flange 12q is also respectively They have the same length.),
As shown in FIG. 2, in the horizontal direction, the upstream side independent intake pipe having a low height projects in the direction opposite to the engine E direction (downward in FIG. 2), that is, the first to fourth parts. The upstream independent intake pipes 9a, 9b, 9c, 9d are configured so that the horizontal length becomes shorter in this order.

Therefore, as shown in FIG. 4, the connecting portions of the first to fourth upstream intake pipes 9a, 9b, 9c, 9d to the surge tank 8 have curved shapes, respectively, and are located at the outermost side of the curve. The angle between the wall surface of the upstream independent intake pipe and the side surface of the surge tank 8 is determined by the first to fourth upstream independent intake pipes 9a, 9b, 9c, 9d.
It becomes smaller in order. Therefore, like the conventional one, the radius of curvature of the wall surface of each of the first to fourth upstream independent intake pipes 9a, 9b, 9c, 9d located on the innermost side (bentness center side) of the curve of the connecting portion is almost the same. If set to the same, as described above, the opening area of the first to fourth upstream independent intake pipes 9a, 9b, 9c, 9d to the surge tank 8 increases in this order,
The intake air supply amount or the charging efficiency for each cylinder becomes uneven.

Therefore, in the present invention, the radius of curvature is set to be smaller in the order of the first to fourth upstream independent intake pipes 9a, 9b, 9c, 9d so that each opening has the same area.

For example, in the fourth upstream independent intake pipe 9d, as shown in FIG. 5, the radius of curvature of the curved inner peripheral surface of the connecting portion is set to a predetermined relatively small value Rd. As a result, the wall surface S located on the innermost side of the curve is connected to the side surface of the surge tank 8 at a position higher than the conventional one by a predetermined height.
The opening area is smaller than the conventional one by a predetermined amount.

On the other hand, in the first upstream independent intake pipe 9a, as shown in FIG. 6, the radius of curvature of the curved inner peripheral surface of the connection portion is set to a predetermined relatively large value Ra. In this case, the wall surface T located on the innermost side of the curve is connected to the side surface of the surge tank 8 at a lower position than in the case of the fourth upstream independent intake pipe 9d, and the opening area thereof is the fourth upstream independent intake air. It is almost equal to the case of tube 9d.

In this way, the first to fourth upstream independent intake pipes 9a, 9b,
The areas of the openings of the 9c and 9d to the surge tank 8 are substantially equal to each other, and the intake supply amount or the charging efficiency to the first to fourth cylinders 1a, 1b, 1c and 1d becomes uniform, idle stability, EGR, etc. Is improved.

[Brief description of drawings]

FIG. 1 is a plan layout view of an intake system for an engine equipped with a surge tank showing an embodiment of the present invention. FIG. 2, FIG. 3, and FIG. 4 are a plan view, a front view, and a side view of an intake system including a surge tank and an independent intake passage, respectively. FIG. 5 and FIG. 6 are side cross-sectional explanatory views of the connection portions of the fourth independent intake passage and the first independent intake passage to the surge tank, respectively. E ... Engine, 3a, 3b, 3c, 3d ... First intake port, 4a,
4b, 4c, 4d …… Second intake port, 6a, 6b, 6c, 6d …… Common intake port, 7a, 7b, 7c, 7d …… Independent intake passage, 8 …… Surge tank.

Claims (1)

(57) [Claims] 1. A surge tank which is arranged above an engine body so as to be long in the output shaft direction, and a surge tank which extends from the side wall of the surge tank extending in the output shaft direction while bending in a substantially C shape. In a multi-cylinder engine equipped with a surge tank and an independent intake passage communicating with the intake port of each cylinder, one end of the surge tank is positioned higher than the other end in the output axis direction. Inclination is set, and the curvature of each independent intake passage is set so that the independent intake passage near the end on the high position side is arranged closer to the engine body than the independent intake passage near the end on the lower position side, and The curvature radius of the curved inner peripheral side wall surface of the curved connection portion of the independent intake passage to the surge tank is set to be smaller as it is closer to the end portion on the high position side of the surge tank. Intake device for the engine.