JPH06100089B2 - Combustion chamber of internal combustion engine - Google Patents

Description

The present invention relates to a combustion chamber of an internal combustion engine, in particular, a squish zone is formed between a piston top and a lower surface of a cylinder head facing the top, and a swirl is generated. For a combustion chamber of an internal combustion engine having an intake passage for a vehicle.

(Prior Art) For example, Japanese Patent Application Laid-Open No. 57-193717 discloses a so-called single-pentroof type combustion chamber structure. In this combustion chamber, as shown in FIG. 5, the lower surface 2a (the ceiling surface of the combustion chamber) of the cylinder head 2 facing the top of the piston 1 is formed into a roof shape by two inclined surfaces, and A ridge 1a is provided on one side of the top so that a squish zone 3 is formed between the piston 1 and one inclined surface of the lower surface 2a of the cylinder head when the piston 1 is at the top dead center position. A combustion space 4 is defined between the other side upper surface 1b of the piston top and the other inclined surface of the cylinder head lower surface 2a. During the compression stroke of the piston 1, the squish flowing into the combustion space 4 from the squish zone 3 promotes mixing of air and fuel and propagation of flame after ignition, thereby improving combustibility. .

On the other hand, in order to improve the combustibility of the internal combustion engine, in addition to providing the squish zone as described above, an intake passage for swirl generation is provided to swirl the intake air flowing into the combustion chamber, thereby generating or not producing a mixture. There is a method of using a so-called swirl that accelerates the propagation of flame.

By the way, in a one-pento-roof type combustion chamber provided with a ridge to form the squish zone as described above, if it is attempted to further use the swirl,
As shown in the figure, a swirl is generated in the combustion space 12 provided on the side of the piston top opposite to the raised portion 11a. In this case, when the combustion space is provided on the intake passage side and the ridge is provided on the exhaust passage side, the intake air flowing from the swirl generation passage provided as the intake passage collides with the side surface of the ridge on the combustion space side. As a result, a good swirl cannot be obtained.
Is usually provided on the intake passage 13 side and the combustion space 12 on the exhaust passage 14 side. However, in this case, the intake air flowing in the direction A from the swirl generation passage 13a that is oriented substantially tangentially to the combustion chamber for generating the swirl has an inclined upper surface for forming the squish zone in the raised portion 11a. The ridge 11b between the side surface on the side of the combustion space 12 and the side surface on the side of the combustion space 12 disturbs the turbulence, which causes a problem that a strong swirl cannot be obtained.

(Object of the Invention) The present invention has been made in view of the above situation in a combustion chamber of an internal combustion engine, and a squish zone is formed on the intake passage side of the combustion chamber by forming a protrusion on one side of the piston top. And a structure in which a combustion space is provided on the exhaust passage side of the combustion chamber, a combustion chamber in which a strong swirl is generated despite the presence of the above-mentioned ridge is realized, which enables effective squish and swirl. The purpose is to obtain good flammability by utilizing.

(Structure of the Invention) The combustion chamber of the internal combustion engine according to the present invention is characterized by having the following structure in order to achieve the above object.

That is, a ridge is provided on the side of the intake passage side of the top of the piston so that a squish zone is formed between the piston and the lower surface of the cylinder head when the piston is at the top dead center position.
Further, in a combustion chamber of an internal combustion engine in which a combustion space is formed between an upper surface of a side of the piston top on the exhaust passage side and a lower surface of the cylinder head, a swirl generating passage is provided as the intake passage, and the piston top is provided. A cutout is provided at least at the opening-oriented position of the swirl generating passage in the raised portion of the.

(Effect of the Invention) According to the above configuration, squish that flows into the combustion space from between the upper surface of the raised portion and the lower surface of the cylinder head occurs at the end of the compression stroke, and swirl occurs in the combustion space during the intake stroke. However, since the notch is provided at the opening direction position of the swirl generation passage in the ridge of the piston top, the intake air flowing in from the swirl generation passage is not blocked by the ridge of the piston top. The flow passes through the cutout portion and is vigorously flown into the combustion space, and the intake air passes through the cutout portion, so that the flow is positively directional. As a result, a strong swirl is generated, and the effect of this swirl and the effect of the squish are combined to promote the mixing of air and fuel and the propagation of the flame after ignition, so that combustion takes place in a short time. In addition, the fuel is completely burned and the combustibility is improved.

(Example) Hereinafter, the Example of this invention is described.

As shown in FIG. 1, the engine 20 includes a cylinder block.
21 and a cylinder head 23 installed on the upper surface of the block 21 via a gasket 22.
A combustion chamber 26 is defined by a cylinder bore 24 provided in the cylinder 24, an upper surface of a piston 25 fitted in the bore 24, and a lower surface of the cylinder head 23.

The ceiling surface (lower surface of the cylinder head) of the combustion chamber 26 is formed by two inclined surfaces 23a and 23b which are inclined in opposite directions, and is recessed like a roof. In addition, the high-load port 2 is provided on the roof-like inclined surfaces 23a and 23b of the cylinder head 23.
7a and a port 27b for low load, and an intake port 27 that communicates with the combustion chamber 26 from one side surface, and an exhaust port 28 that communicates with the combustion chamber 26 from the other side surface, and these An intake valve 29 and an exhaust valve 30 that open and close the openings of the ports 27 and 28 to the combustion chamber 26 are provided. Here, the low-load port 27b is branched from the high-load port 27a on the upstream side of the intake port 27, and is substantially in contact with the cylinder bore 24 at a position immediately upstream of the opening of the intake port 27. Is opened in the direction a (see FIG. 2), so that a swirl is formed by the airflow flowing into the combustion chamber 26 from the low load port 27b. Although not shown, a shutter valve is provided upstream of the high load port 27a, and when the engine 20 has a low load, the shutter valve is closed and intake air is burned only from the low load port 27b. The shutter valve is opened when the load is high and the intake air is supplied to the combustion chamber 26 from both the high load port 27a and the low load port 27b.

On the other hand, the intake port 27 at the top 25a of the piston 25
A ridge 25b is formed on one side of the cylinder head along one inclined surface 23a on the lower surface of the cylinder head.
When 25 reaches the top dead center position, a squish zone X is formed between the inclined upper surface 25b 'of the raised portion 25b and the inclined surface 23a of the cylinder head 23. Further, the side of the top 25a of the piston 25 on the side of the exhaust boat 28 is flat, and a combustion space Y having a required volume is formed between the upper surface 25c and the other inclined surface 23b of the lower surface of the cylinder head. There is.

In addition, in this embodiment, the top portion 25 of the piston 25 is
A concave groove 25d extending from a side surface 25b ″ of the raised portion 25b on the combustion space Y side to an upper surface 25c on the combustion space Y side is provided along the side surface 25b ″. As shown in FIG. 3, the recessed groove 25d has the raised portion 25b with the cross-sectional shape centering on an upper point O.
The side surface 25b ″ on the side of the combustion space Y and the upper surface 25c on the side of the combustion space Y are notched in a circular arc shape with a circle having a relatively small radius of curvature Ra. Is set so as to be located on a locus O '(see FIG. 2) which is an arc with a relatively large radius of curvature Rb centered on a point P located obliquely above. The central portion of the top portion 25a of the piston 25 is deepest at the center portion, and is gradually shallowed toward both ends, and the point P is closer to the exhaust port 28 side. Has a shape curved toward the raised portion 25b.

In addition to the above configuration, the piston 25 is provided with a cutout portion 25f on a ridge portion 25e between the upper surface 25b 'and the side surface 25b "of the raised portion 25b, which is a feature of the present invention. The cutout portion 25f is formed in the ridge portion 25e at the directivity (direction a) of the low load port 27b.

According to the above configuration, the piston can be operated with the intake valve 29 opened.
During the intake stroke when 25 moves downward, from intake port 27 to combustion chamber 26
Intake air (air mixture) is sucked into the inside, but when the engine 20 has a high load, a large amount of intake air is mainly sucked from the high load port 27a, and when the engine 20 has a low load, the intake air is sucked from only the low load port 27b. Since the low load port 27b has a small cross-sectional area and is opened substantially tangentially to the cylinder bore 24, swirl is generated in the combustion chamber 26 at a low load despite a small intake amount. become.

Next, the piston 25 moves upward from the bottom dead center and the intake valve 29
Is closed and transitions to the compression stroke.In the latter half of the stroke, the upper surface 25b 'of the raised portion 25b at one side of the piston 25 and the cylinder facing it in the latter half of the stroke. Intake is pushed out from the squish zone X between the one inclined surface 23a on the lower surface of the head to the combustion space Y formed on the other side, and squish is generated. The swirl and squish promote the propagation of the flame after the mixture of air and fuel or the ignition of the air-fuel mixture, the combustion in the combustion chamber 26, and the complete combustion of the fuel.

Incidentally, in the so-called one-pento-roof type combustion chamber structure in which the squish zone is formed on one side of the piston top in this manner, the combustion space is narrowed, so that the swirl generated in the space is easily attenuated. However, in this embodiment, the ridge 2 on one side of the piston top 25a
A concave groove 25d having an arc-shaped cross section is provided on the side surface 25b ″ of the 5b so as to extend over the upper surface 25c on the combustion space Y side, and the volume of the swirl generation space in the combustion space Y is increased.
Since 25d is formed so as to bend toward the raised portion 25b side in a plan view, the concave groove 25d and the inner peripheral surface of the combustion chamber 26 on the exhaust port 28 side are smoothly continuous, and these Swirl attenuation will be suppressed.

However, when the above-mentioned ridge is provided at the top of the piston, the intake air that flows in tangentially to the combustion chamber to generate swirl during the intake stroke collides with the ridge of the ridge and is disturbed, which is strong. There is a problem that you can not get such swirl. However, as a characteristic part of the present invention, the low load port 27 in the raised portion 25b of the piston top portion 25a.
The cutout portion 2 is located at the opening orientation position of b, that is, the orientation (a direction) of the low load port 27b at the ridge portion 25e between the upper surface 25b ′ and the side surface 25b ″ of the raised portion 25b of the piston top portion 25a.
5f is provided. Therefore, the flow of the intake air flowing into the combustion chamber 26 from the port 27b flows into the combustion space Y through the notch 25f without being blocked by the raised portion 25b. Furthermore, since the cutout portion 25f is provided in the opening directing direction of the low load port 27b, when the intake air passes through the cutout portion 25f, the flow direction is positively given. . As a result, a strong swirl is generated during the intake stroke, and the effect of this swirl and the effect of the squish are combined to promote the mixing of air and fuel and the propagation of flame after ignition, resulting in a better combustibility. Will be obtained.

Here, as described above, the ridge portion 25e of the raised portion 25b of the piston top portion 25a may be entirely cut off without cutting out a part thereof, and according to this, the shape of the piston top portion 25a is simplified. There is an advantage that the cost is reduced.

In this embodiment, both ends of the ridge portion 25e of the piston top portion 25a are cut off to form cut portions 25g, 25g, and the distance between the cut portions 25g, 25g and the lower surface of the cylinder head 23 is reduced. It is large. Therefore, squish (see FIG. 2) in the direction b indicated by the chain line from both ends (cutoffs 25g, 25g) of the raised portion 25b does not occur, which causes the combustion space Y from the center of the raised portion 25b. The problem that the squish in the c direction flowing to the center is attenuated by the squish in the b direction is prevented.

Further, in the piston 25, since the raised portion 25b is provided only on one side of the top portion 25a, the weight of one side portion becomes heavier than the other side portion by the amount of this raised portion 25b, but in this embodiment. Is a piston 25 connected to a connecting rod 31 via a piston pin 32 as shown in FIG.
Reinforcing ribs 25i, 25i for reinforcing the boss 25h of the
It is provided so as to be inclined to the side portion on the opposite side of 25b, whereby the weight balance of the entire piston 25 is maintained.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 to 4 show an embodiment of the present invention. FIG. 1 is a vertical sectional view of a combustion chamber and its periphery, and FIGS. 2 to 4 are plan views of pistons and vertical cross sections, respectively. It is a front view and a principal part perspective view. Also,
FIG. 5 is a vertical sectional front view showing a conventional example, and FIGS. 6 and 7 are a plan view and a vertical sectional front view of a piston showing conventional problems. 20 …… Internal combustion engine (engine), 23 …… Cylinder head,
25 ... Piston, 25a ... Piston top, 25b ... Rise, 25f ... Notch, 26 ... Combustion chamber, 27 ... Intake passage (intake port), 27b ... Swirl generation passage (for low load) Port), 28 ... exhaust passage, X ... squish zone, Y ... combustion space.

Claims (1)

[Claims] 1. A ridge is provided on a side of an intake passage side of a top of a piston so that a squish zone is formed between the piston and a lower surface of a cylinder head when the piston is at a top dead center position. A combustion chamber of an internal combustion engine having a combustion space between an upper surface of a side portion on the exhaust passage side of the top portion and a lower surface of the cylinder head, and a swirl generating passage is provided as the intake passage, and A combustion chamber of an internal combustion engine, wherein a notch is provided at least at a position at which the swirl generation passage is directed toward the opening in the protrusion of the piston top.