JP2820946B2 - Engine combustion chamber structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a combustion chamber structure of a reciprocating piston engine ignited by a spark plug, and in particular, a hollow portion on an inner surface of a cylinder head constituting an upper part of the combustion chamber. The present invention relates to a combustion chamber structure formed in a roof shape (pent roof shape).

<< Conventional Technology >> The combustion chambers of general four-stroke gasoline engines are classified into hemispherical, polyspherical, funnel-shaped, wedge-shaped, bathtub-shaped, roof-shaped, etc. according to their shapes. Of these, one roof-type combustion chamber
Widely used in four-valve engines in which two intake and exhaust valves are provided for each cylinder (for example, “Guide to Automobile Mechanisms” published by Grand Prix Co., Ltd., 30-32)
Page).

As is well known, in the roof-type combustion chamber, the inner surface of the cylinder head is hollow-shaped, and two intake ports are formed on one inclined surface of the roof-shaped concave portion, and two intake ports are formed on the other inclined surface. An exhaust port is formed (for four valves).
The spark plug is attached to the top of the roof-shaped recess, and is located at the center of each intake / exhaust port.

In the case of a conventional roof-type combustion chamber, the piston head that defines the lower part of the combustion chamber is generally a flat head or a spherical convex head. In order to prevent the piston head from coming into contact with the valve, a valve recess (recess) is formed. ) Is also provided.

FIG. 4 shows an example of a roof combustion chamber. In FIG. 4, 41 is a cylinder block, 42 is a cylinder head,
43 is a piston, 44 is a spark plug, 45 is an intake port,
46 is an intake valve, 37 is an exhaust port, 48 is an exhaust valve, 49
Is a combustion chamber. The two inclined surfaces defining the upper shape of the roof-shaped combustion chamber 49 have asymmetric inclinations, and the intake port 45
The angle of the inclined surface where the
The angle of the inclined surface on which is formed is large. Therefore, the inclination of the intake valve 46 with respect to the center line of the cylinder is relatively small, and the inclination angle of the exhaust valve 48 is relatively large. That is,
The difference between the angles of the two inclined surfaces of the roof-shaped recess formed in the cylinder head 42 is the same as the difference between the inclination angles of the intake valve 46 and the exhaust valve 48 attached to the respective inclined surfaces. .

<< Problems to be Solved by the Invention >> As shown in FIG. 4, when the angles of the two upper inclined surfaces of the roof-shaped combustion chamber are different, the upper surface and the lower surface (piston
43 is relatively large on the intake port 45 side and small on the exhaust port 47 side. When viewed from the spark plug 44 arranged at the center of the combustion chamber 49, the combustion chamber space on the intake port 45 side is large, and the combustion chamber space on the exhaust port 47 side is very small. Thus, due to the asymmetry of the combustion chamber space,
There is a problem that the flame does not propagate uniformly from the spark plug 44 to the entire combustion chamber 49, resulting in poor combustion characteristics.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and its purpose is to uniformly propagate a flame from a spark plug into a combustion chamber even if the inclination angles of the left and right roof-shaped recesses on the inner surface of the cylinder head are different. Another object of the present invention is to provide a combustion chamber structure of an engine with improved combustion characteristics.

<< Means for Solving the Problems >> In the combustion chamber structure of the engine according to the present invention, the hollow portion on the inner surface of the cylinder head constituting the upper portion of the combustion chamber is formed in a substantially trapezoidal roof shape having different left and right inclination angles. And
The roof-shaped depression has a combustion chamber structure of a four-cycle engine in which intake and exhaust ports are formed on both inclined surfaces corresponding to the upper side and the oblique side of the trapezoidal shape. A concave portion is formed, and the depth of the concave portion is opposed to a large inclined surface having a large inclination angle corresponding to the oblique side from one side facing a small inclination angle corresponding to the upper side of the roof-shaped concave portion. The other side of the hollow portion of the piston head is formed deeply so that the vertical interval of the entire combustion chamber on the other side approaches the vertical interval of the entire combustion chamber on the one side. It is characterized by having.

Further, a squish zone is formed on the outer periphery of the roof-shaped recess and the recess of the piston, and the recess of the piston head has a curved surface having a center of curvature on the cylinder head side from the one side to the other side. It is characterized by the following.

In addition, the intake port is formed on the side of the roof-shaped depression having a small inclination angle corresponding to the upper side, and the exhaust port is formed on the side of the roof-shaped depression having a large inclination angle corresponding to the hypotenuse. Is formed.

Further, two intake ports are provided, and a squish zone on the intake side is set between the intake ports.

Further, a squish zone on the intake side and a squish zone on the exhaust side are respectively set on the intake port arrangement side and the exhaust port arrangement side outside the roof-shaped recess, and the area of the squish zone is such that the intake side is larger than the exhaust side. It is characterized by being set large.

Further, the engine is a V-type engine,
An inclined surface having a small inclination angle corresponding to the upper side of the roof-shaped depression is disposed between the banks.

<Operation> In the invention of claim 1, a recess is formed in the piston head constituting the lower part of the combustion chamber, and the depth of the recess corresponds to the upper side of the roof-shaped recess. The slope gradually changes from one side facing the small inclined surface to the other side facing the large inclined surface corresponding to the hypotenuse, and the vertical interval of the entire combustion chamber on the other side is the one side. So that it approaches the vertical spacing of the entire combustion chamber
The other side of the recess of the piston head is formed deep, whereby the depth of the recess of the piston head is asymmetrically corresponding to the difference in the inclination angle of the substantially trapezoidal roof-shaped recess of the cylinder head. The vertical interval between the combustion chambers on the other large inclined surface side approaches the vertical interval between the combustion chambers on the small inclined surface side on the other side, and the vertical interval between the combustion chambers is substantially uniform over the entire combustion chamber. .

In the invention of claim 2, a squish zone is formed on the outer periphery of the roof-shaped recess and the recess of the piston head, and the recess of the piston head has a curvature toward the cylinder head from the one side to the other side. It has a curved shape with a center, so that even if the radial dimension of the combustion chamber is reduced, the vertical distance of the entire combustion chamber can be secured within the limited volume of the combustion chamber at the compression top dead center. Since there is no combustion space, flammability is improved. Further, the squish zone further improves the combustibility.

According to the third aspect of the present invention, on the premise of the configuration of the first aspect, the intake port is formed on an inclined surface having a small inclination angle corresponding to the upper side of the roof-shaped depression, and the roof-shaped depression is formed. The exhaust port is formed on the side of the inclined surface having a large inclination angle corresponding to the hypotenuse, whereby a volume on the exhaust side where combustion is fast can be ensured in the same manner as the intake side,
Combustion characteristics are improved.

According to the fourth aspect of the present invention, when a squish zone on the intake side is set between the intake ports in a combustion chamber provided with two intake ports, the squish flow into the combustion chamber is enhanced. .

In the invention according to claim 5, a squish zone on the intake side and a squish zone on the exhaust side are set on the intake port arrangement side and the exhaust port arrangement side, respectively, outside the roof-shaped recess. The area of is set larger on the intake side than on the exhaust side, thereby increasing the squish flow on the intake side with respect to the exhaust side, improving the combustion speed, and improving the combustibility on the intake side. In addition to making the volume close to the volume of the combustion chamber on the side and making the volume substantially uniform, it is possible to make the combustibility of the entire combustion chamber uniform.

<< Embodiment >> FIG. 1 shows an engine employing the combustion chamber structure of the present invention. As shown in the figure, the engine 1 of the present embodiment has V
This is a multi-cylinder engine having a structure arranged in a shape, and a mechanical supercharger 30 is disposed in an intermediate portion of a V-shaped cylinder arrangement.

In this embodiment, basically, the recess 5 on the inner surface of the cylinder head 2 constituting the upper part of the combustion chamber 7 is formed in a substantially trapezoidal roof shape having different left and right inclination angles, and the roof recess is formed. 5 is a combustion chamber structure of a four-stroke engine in which intake and exhaust ports 9 and 13 are formed on both inclined surfaces 5a and 5b corresponding to the upper side and the oblique side of the trapezoidal shape. A concave portion (a concave portion on the upper surface of the piston 4) 6 is formed in the head, and the depth of the concave portion 6 is one side opposite to the inclined surface 5a having a small inclination angle corresponding to the upper side of the roof-shaped concave portion 5. From the other side facing the large inclined surface 5b having a large inclination angle corresponding to the hypotenuse, so that the vertical interval of the entire combustion chamber on the other side approaches the vertical interval of the entire combustion chamber on the one side. The other side of the recess 6 of the piston head Is formed deeply.

A flat portion 40 serving as a squish zone is formed on the outer periphery of the roof-shaped recess 5 and the recess 6 of the piston head, and the recess 6 of the piston head has a center of curvature toward the cylinder head 2 from the one side to the other side. And has a curved surface shape.

In addition, an intake port 9 is formed on the side of the inclined surface 5a having a small inclination angle corresponding to the upper side of the roof-shaped concave portion 5, and the exhaust port is formed on the side of the inclined surface 5b having a large inclined angle corresponding to the inclined side of the roof-shaped concave portion 5. Port 13 is formed.

In addition, two intake ports 9 are provided, and a plane portion 40 serving as a squish zone on the intake side is set between the intake ports 9.

In addition, outside the roof-shaped recess 5, an intake port 9 is provided.
A flat portion 40 serving as a squish zone on the intake side and a flat portion 40 serving as a squish zone on the exhaust side are set on each of the exhaust port 13 on the disposition side, and the flat portion 40
Is set to be larger on the intake side than on the exhaust side.

Further, the engine 1 is a V-type engine, and an inclined surface 5a having a small inclination angle corresponding to the upper side of the roof-shaped concave portion 5 is arranged between the V banks.

Further, the recess 5 on the inner surface of the cylinder head 2 constituting the upper part of the combustion chamber 7 is a combustion chamber structure of a four-stroke engine in which the left and right inclination angles are different from each other. Of the inclined surfaces 5a and 5b, the inclined surface 5a having a smaller inclination angle with respect to the mating surface of the cylinder head 2 and the cylinder block 3 (in the drawing, the angle between the axis orthogonal to the inclined surface 5a and the cylinder axis is smaller). Intake port 9 on the smaller side)
Is formed, and on the inclined surface 5b side having a large inclination angle with respect to the mating surface of the cylinder head 2 and the cylinder block 3 (in the drawing, the side formed by the axis perpendicular to the inclined surface 5b and the cylinder axis has a large angle). ), An exhaust port 13 is formed, and a hollow portion 6 is formed in a piston head constituting a lower portion of the combustion chamber 7. A vertical portion of the entire combustion chamber on the intake side and the exhaust side is formed around the top of the roof-shaped hollow portion 5. The depth of the recess 6 of the piston head is formed so that the depth on the exhaust side is deeper than on the intake side so that the interval changes almost uniformly outward of the recess 5. You.

Each cylinder includes a cylinder head 2 and a cylinder block 3, and a piston 4 is mounted in the cylinder block 3 so as to be vertically slidable. On the inner surface of the cylinder head 2, a roof-shaped recess 5 having an asymmetric inclined surface is formed, and a recess 6 described later is also formed on the upper surface of the piston 4, and the combustion chamber is formed by these recesses 5 and 6. 7 is formed. In this embodiment, a V-type engine is illustrated, and a small-angled inclined surface 5a that forms a roof-shaped recess 5 of the cylinder head 2 is disposed between the V banks, and the inclined surface 5a is provided on the inclined surface 5a. , Two intake ports 9 for connecting the combustion chamber 7 and the intake passage 8 are formed, and an intake valve 10 for opening and closing the intake ports 9 is mounted in the intake ports 9. Similarly, two exhaust ports 13 communicating the combustion chamber 7 and the exhaust passage 12 are formed on the other large inclined surface 5b of the roof-shaped recess 5, and an exhaust valve is formed there.
14 is installed. In addition, a spark plug 31 (FIG. 2) is mounted at the center of the four intake / exhaust ports 9 and 13 in total.

In FIG. 1, reference numeral 15 denotes a fuel injection valve, 16 and 17 denote valve stems, 18 and 19 denote lash adjusters, and 21 and 22 denote valve cams.

FIG. 2 is an enlarged view of a combustion chamber portion in FIG.
FIG. 3 is a detailed view of the shape of the roof-shaped recess 5 of the cylinder head 2.

As shown in FIG. 2 and FIG.
The inclination angles of the two inclined surfaces 5a and 5b forming the roof-shaped recess 5 are different, the angle of the inclined surface 5a on the side where the intake port 9 is formed is small, and the inclined surface on the side where the exhaust port 13 is formed. The inclination angle of 5b is large. Accordingly, the inclination angle of the intake valve system 16 with respect to the piston center line P is small, and the inclination angle of the exhaust valve stem 17 is large. In other words,
Of the inclined surfaces 5a and 5b of the roof-shaped recess 5, these inclined surfaces 5
It can also be said that the intake port 9 is formed on the side where the angle between the axis perpendicular to a and 5b and the cylinder axis (piston center line P) is small, and the exhaust port 13 is formed on the large side. The spark plug 31 has two V-shaped valve stems 16 and 17
It is attached to the center of the top of the roof-shaped depression 5 at an angle so as to be equally divided.

On the other hand, as shown in FIG. 2, the upper surface concave portion 6 of the piston 4 constituting the lower portion of the combustion chamber 7 has a connected curved surface shape, and the depth of the upper surface concave portion 6 is the same as the roof-shaped concave portion 5. In FIG. 5, the depth gradually increases from the side facing the small-angled inclined surface 5a toward the side facing the large-angled inclined surface 5b. As a result, the difference in the angle between the inclined surfaces 5a and 5b is offset (supplemented) by the difference in the depth of the recess 6 on the piston head side, and the upper and lower spaces of the combustion chamber 7 are almost all over the combustion chamber 7. Be uniformed. Accordingly, the volume distribution of the combustion chamber 7 as viewed from the spark plug 31 arranged at the upper center of the combustion chamber 7 is substantially uniform over the entire circumference, and the flame propagates from the spark plug 31 to the periphery thereof almost uniformly, and the combustion characteristics are reduced. improves.

Particularly, in the present embodiment, the intake port 9 is formed on the side of the inclined surface 5a having a small angle, and the exhaust port 13 is formed on the side of the inclined surface 5b having a large angle. In this configuration, when the upper surface of the piston 4 is flat as in the related art, the combustion chamber on the exhaust side where combustion is fast becomes shallower than the intake side where combustion is slow, and the combustion is liable to deteriorate significantly. However, as described above, the depth of the recess 6 is changed.
Is provided on the upper surface of the piston 4, the depth of the combustion chamber on the exhaust side also increases, and a volume on the exhaust side where combustion is fast is secured.
The effect of improving the combustion characteristics becomes very large.

Also, as shown in FIGS.
Roof-shaped recess 5 and upper surface recess 6 of piston 4
Each has a contour shape smaller than the bore of the cylinder block 3, and there is a plane portion 40 surrounding the recess between the recesses 5 and the contour of the recess 6 and the bore 32.
In particular, as is apparent from the drawing, the flat part 40 is expanded so as to enter between two intake ports 9 arranged side by side. The flat portion 40 is formed as a squish zone surrounding the outer periphery of the combustion chamber 7, and a squish flow flows into the combustion chamber 7 from the squish zone at the time of compression, thereby promoting combustion and further improving combustion characteristics.

In the embodiment shown in FIG. 1, since the intake is forcibly performed by the supercharger 30, the diameter of the intake port 9 can be reduced, which is effective in reducing the size of the cylinder head.

In the above embodiment, the opening and closing control is performed so that the valve opening timings of the intake valve and the exhaust valve overlap,
The residual gas in the combustion chamber 7 may be scavenged by the intake air. In this case, the concave portion 6 on the upper surface of the piston 4 whose depth is changed as described above acts so as to enhance the scavenging effect of the residual gas by the intake air.

Further, a recess 6 is provided on the upper surface of the piston 4 so that the combustion chamber 7
As in the conventional case, it is not necessary to form a valve recess on the piston side, and it is possible to avoid excessive interference between the valve and the piston even when the valve timing belt or chain is cut.

<< Effects of the Invention >> As described in detail above, in the combustion chamber structure of the engine according to the present invention, a recess is formed in the piston head constituting the lower portion of the combustion chamber, and the depth of the recess is set to the above-described value. The roof-shaped depression is gradually changed from one side facing the small inclined surface corresponding to the upper side to the other side facing the large inclined surface corresponding to the inclined side. Since the other side of the hollow portion of the piston head is formed deeper so that the vertical interval of the entire combustion chamber approaches the vertical interval of the entire combustion chamber on the one side, the depth of the hollow portion of the piston head is reduced. Asymmetry corresponding to the difference in the inclination angle of the substantially trapezoidal roof-shaped recessed portion of the cylinder head, the vertical spacing of the combustion chamber on the other large inclined surface side, the combustion chamber on the small inclined surface side on one side. It is possible to approach the vertical interval, the vertical interval of the combustion chamber can be made substantially uniform over the entire combustion chamber, and it is possible to improve the combustibility in all directions of the combustion chamber,
Combustion characteristics can be improved.

Further, a squish zone is formed on the outer periphery of the roof-shaped recess and the recess of the piston head, and the recess of the piston head has a curved surface shape having a center of curvature on the cylinder head side from the one side to the other side. Therefore, even if the radial size of the combustion chamber is reduced, there is no small combustion space because there is no space for the entire combustion chamber in the limited volume of the combustion chamber at the time of compression top dead center. can do. Further, the squish zone can further improve the combustibility.

Further, on the premise of the configuration of claim 1, the intake port is formed on the side of the roof having a small inclination angle corresponding to the upper side of the roof-shaped depression, and the inclination angle corresponding to the hypotenuse of the roof-shaped depression. Since the exhaust port is formed on the side of the large inclined surface, the volume on the exhaust side where combustion is fast can be secured in the same manner as on the intake side, and the combustion characteristics can be improved.

In addition, the combustion chamber has two intake ports, and a squish zone on the intake side is set between these intake ports. Therefore, the squish flow into the combustion chamber is further enhanced, and the combustion characteristics are also improved from this aspect. Can be improved.

Further, a squish zone on the intake side and a squish zone on the exhaust side are respectively set on the intake port arrangement side and the exhaust port arrangement side outside the roof-shaped recess, and the area of the squish zone is smaller than that on the exhaust side. Since the intake side is set to be large, the squish flow on the intake side can be increased with respect to the exhaust side, the combustion speed can be improved and the combustion performance on the intake side can be improved, and the exhaust side has a combustion chamber on the intake side. In addition to making the volume close to the volume and making it almost uniform, it is possible to make the combustibility of the entire combustion chamber uniform.

[Brief description of the drawings]

1 is an overall sectional view of an engine according to one embodiment of the present invention, FIG. 2 is a partial sectional view mainly showing a combustion chamber portion in FIG. 1, and FIG. 3 (A) is a sectional view of FIG. FIG. 4 (B) is a bottom view of the cylinder head, FIG. 4 (B) is a sectional view taken along line BB in FIG. 4 (A), FIG. 4 (C) is a sectional view taken along line CC in FIG. It is a schematic sectional drawing of the conventional combustion chamber structure. DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Cylinder head 3 ... Cylinder block 4 ... Piston 5 ... Roof-shaped recessed part, 5a, 5b ... Slope surface 6 ... Piston head recessed part, 7 ... Combustion chamber 8 …… Intake passage, 9 …… Intake port, 10 …… Intake valve 12 …… Exhaust passage, 13 …… Exhaust port, 14 …… Exhaust valve

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-68705 (JP, A) JP-A-63-12818 (JP, A) JP-A-63-201314 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) F02B 1/00-23/10

Claims (6)

(57) [Claims] An indentation on an inner surface of a cylinder head constituting an upper portion of a combustion chamber is formed in a substantially trapezoidal roof shape having different right and left inclination angles, and an upper side of the trapezoidal shape of the roof-shaped indentation portion is provided. This is a combustion chamber structure of a four-stroke engine in which intake and exhaust ports are formed on both inclined surfaces corresponding to the hypotenuses. A recess is formed in a piston head constituting a lower portion of the combustion chamber, and a depth of the recess is formed. Is gradually changed from one side facing the small inclined surface corresponding to the upper side of the roof-shaped depression to the other side facing the large inclined surface corresponding to the inclined side, The combustion chamber structure of an engine, wherein the other side of the hollow portion of the piston head is formed deep so that the vertical interval of the entire combustion chamber on the other side approaches the vertical interval of the entire combustion chamber on the one side. 2. A squish zone is formed on the outer periphery of the roof-shaped recess and the recess of the piston head.
The combustion chamber structure of an engine according to claim 1, wherein the hollow portion of the piston head has a curved surface shape having a center of curvature on the cylinder head side from the one side to the other side. 3. An intake port is formed on an inclined surface having a small inclination angle corresponding to the upper side of the roof-shaped depression, and the intake port is formed on an inclination surface having a large inclination angle corresponding to the inclined side of the roof depression. The combustion chamber structure for an engine according to claim 1, wherein an exhaust port is formed. 4. The engine combustion according to claim 1, wherein two intake ports are provided, and a squish zone on an intake side is set between the intake ports. Room structure. 5. A squish zone on the intake side and a squish zone on the exhaust side on the intake port side and the exhaust port side on the outside of the roof-shaped recess, and the area of the squish zone is on the intake side. The exhaust gas side is set to be larger than the exhaust side.
A combustion chamber structure for an engine according to any one of the above items 4. 6. A combustion chamber structure for an engine according to claim 1, wherein said engine is a V-type engine, and said upper side of said roof-shaped recess is provided between said V banks. A combustion chamber structure for an engine, wherein an inclined surface having a small inclination angle corresponding to the above is disposed.