JPS6172827A - Internal-combustion engine - Google Patents

Abstract

PURPOSE:To shorten a combustion time and improve antiknocking performance, by forming a combustion chamber into a vent roof type, and making it possible to generate a squish flow at two squish areas on both sides with respect to the combustion chamber. CONSTITUTION:A vent roof type combustion chamber 6 is formed at a lower surface of a cylinder head 3 in such a manner as to include inclined inner wall surfaces 9 and 10 extending upwardly obliquely to an axis 8 of a cylinder bore 2 on opposite sides with respect to a longitudinal center line extending in the same direction as an axis of a crank shaft passing through a center point of the cylinder bore 2. The inner wall surfaces 9 and 10 are formed with openings communicating the combustion chamber 6 with suction and exhaust ports 13, 14 and 15, 16. The lower surface of the cylinder head 3 is formed with squish areas 37 and 38 to a top surface of a piston 5 on the outside of the openings. An ignition plug 12 is located in the vicinity of the center point of the cylinder bore 2, and an axis 26 of the plug is inclined at the same angle as an axis 24 of suction valves 20 and 21.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spark ignition internal combustion engine in which each cylinder has two intake valves and two exhaust valves for the combustion chamber of the engine.

[Conventional technology]

Japanese Patent Laid-Open No. 10130/1983 proposes to provide two intake valves and two exhaust valves to the combustion chamber for the purpose of improving engine output and the like.

On the other hand, increasing the compression ratio is effective in improving thermal efficiency in internal combustion engines, but increasing the compression ratio causes knocking in the low rotation range, so there is a certain limit to increasing the compression ratio. There is. To suppress the occurrence of knocking, make the combustion chamber compact and shorten the distance from the ignition plug to every corner of the combustion chamber, that is, the distance of flame propagation.

■ To improve the flame propagation speed and shorten the combustion time by creating a turbulent flow in the air-fuel mixture in the combustion chamber.

is known to be effective, and a second method is known to provide a squish area around the combustion chamber.

[Problem that the invention seeks to solve]

However, in the conventional combustion chamber described in the above publication, the combustion chamber into which two intake ports and two exhaust ports open is formed into a flat spherical shape, so the distance from the ignition plug to each corner of the combustion chamber is is far away, and not only is it not possible to fully satisfy the first means described above, but the influence of the squish flow from the squish area formed around the combustion chamber cannot be sufficiently exerted on the ignition plug, and the second means The means were also inadequate. Furthermore, in the conventional device described in the above-mentioned publication, the ignition plug is arranged approximately in the center between both intake ports and the re-exhaust port, and the axis of the ignition plug is relative to the axis of the cylinder bore. The upper surface of the cylinder head is divided into left and right sides by the spark plug, so a valve mechanism such as a camshaft that opens and closes the two intake valves and a valve mechanism such as a camshaft that opens and closes the two exhaust valves are connected to each other. Since the valve operating mechanism, such as the camshaft, which opens and closes the engine, is constructed separately, the cylinder head becomes significantly larger and weighs more.

The present invention solves the above-mentioned conventional problems in internal combustion engines having two intake valves and two exhaust valves.

[Means to solve the problem]

For this reason, the present invention opens two intake ports and two exhaust ports in a combustion chamber recessed on the lower surface of the cylinder head of an engine, intakes the air-fuel mixture from the two intake ports, and directs the exhaust gas into the two intake ports. In an internal combustion engine configured to exhaust air from an exhaust port, the combustion chamber is provided with inclined inner wall surfaces extending diagonally upward toward the center line of the cylinder bore on both sides of the center line passing through the center point of the cylinder bore in a plan view of the engine. and is formed into a pent roof type in which both the inclined inner wall surfaces intersect at a ridge line parallel to a center line passing through the center point of the cylinder bore, and the both inclined inner wall surfaces are formed on one of the inclined inner wall surfaces of the combustion chamber. The opening of the intake port to the combustion chamber is located on the other inclined inner wall surface, and the opening of the re-exhaust port to the combustion chamber is located on the other inclined inner wall surface. A squish area for the top surface of the piston is formed in a region outside the opening to the combustion chamber, a poppet-type intake valve is provided at the opening to the combustion chamber of both intake ports, and a poppet-type intake valve is provided to the opening to the combustion chamber of the re-exhaust port. A poppet-type exhaust valve is provided in the intake valve and the exhaust valve so that the axes of the intake valve and the exhaust valve are inclined in directions opposite to each other with respect to the axis of the cylinder bore. An ignition plug is arranged approximately at the center of the opening of the exhaust port into the combustion chamber, and the axis of the ignition plug is inclined in the same direction as the axis of the intake valve with respect to the axis of the cylinder bore. It is.

[Effect]

As mentioned above, the combustion chamber in which both the intake ports and the re-exhaust port are open is located on both sides of the center line passing through the center point of the cylinder bore in a plan view of the engine, in an inclined shape extending diagonally upward toward the center line of the cylinder bore. The spark plug is formed into a pent roof type having a wall surface, and both inclined inner wall surfaces intersect at a ridge line parallel to a center line passing through the center point of the cylinder bore, and the ignition plug is located approximately at the center of both intake ports and re-exhaust port. By arranging the piston at the top dead center position, the distance from the ignition plug to every corner of the combustion chamber at the end of the compression stroke when the piston is at top dead center and when spark ignition is performed is as follows: In some cases, the flame propagation distance can be shortened by having a spherical shape, and the distance from the ignition plug to each corner of the combustion chamber can be made approximately equal to each other, so that the shortening of the flame propagation distance according to the first means can be effectively achieved. can.

Furthermore, since both the intake ports and both exhaust ports are provided on the left and right inclined inner wall surfaces forming the pent roof type combustion chamber, the inner diameters, that is, the cross-sectional areas of both the intake ports and both exhaust ports are It can be made larger than in the case of a flat spherical shape.

Next, at the end of the compression stroke, when the top surface of the piston approaches the bottom surface of the cylinder head, the area on the bottom surface of the cylinder head outside the openings of both intake ports and both exhaust ports to the combustion chamber, A squish action occurs between the left and right squish areas formed on the left and right sides of the combustion chamber and the top surface of the piston, and these two squish flows flow along the slanted inner wall surfaces of the pent roof-shaped combustion chamber. After ejecting toward the center of the combustion chamber, the mixture collides at the center of the combustion chamber, resulting in a highly disturbed state of the air-fuel mixture within the combustion chamber, increasing the flame propagation speed. The combustion time of the second means can be effectively shortened.

Furthermore, the axes of the poppet-type intake valves in both intake ports and the poppet-type exhaust valves in both exhaust ports are inclined in opposite directions with respect to the axis of the cylinder bore, while the axis of the spark plug is inclined in the direction opposite to the axis of the cylinder bore. Because the cylinder head is tilted in the same direction as the axis of the intake valve, a space is inevitably formed on the upper surface of the cylinder head in the area between the poppet-type intake valve and the ignition plug and the poppet-type exhaust valve. Therefore, it is possible to install a common camshaft for the intake valve and exhaust valve in this space, and the valve mechanism for the intake valve and exhaust valve can be partially shared, allowing two intake ports and two exhaust ports each. This avoids increasing the size of the upper part of the cylinder head.

C Embodiment] The present invention will be explained below with reference to the drawings of the embodiment. In the drawings, 1 is a cylinder block having a cylinder bore 2;
indicates a cylinder head fastened to the upper surface of the cylinder block 1 with a gasket 4 in between; 5 indicates a piston reciprocating within the cylinder bore 2; a combustion chamber 6 is recessed in the lower surface of the cylinder head 3; This combustion chamber 6
In plan view of the engine, slanted inner wall surfaces 9.10 extend obliquely upward toward the axis 8 of the cylinder bore 3 on both left and right sides of the longitudinal centerline 7 passing through the center point of the cylinder bore 2 in the same direction as the crank axis. The combustion chamber 6 is of a pent roof type in which both oblique inner wall surfaces 9 and 10 intersect at a ridge line 11 parallel to the longitudinal center line 7, and in the combustion chamber 6 there is a center of the cylinder bore 2 in a plan view. An ignition plug 12 screwed onto the cylinder head 3 is visible at a position near the point.

13 and 14 are two intake ports for one combustion chamber 6, 15 and 16 are two exhaust ports for one combustion chamber 6, and both intake ports 13, 14 and both exhaust ports 15, 1. 6 is provided on both left and right sides sandwiching the longitudinal center line 7 in plan view, and 13 and 14 are one side surface 17 of the cylinder head 3 and one inclined inner wall surface of the combustion chamber 6. Both exhaust ports 15 and 16 open separately on the other inclined inner wall surface 1° of the combustion chamber 6, and on the other side surface 18 of the cylinder head 3. The openings of both intake ports 13.14 and both exhaust ports 15.16 to the combustion chamber 6 pass through the center point of the cylinder bore 2 in a plan view of the engine. The spark plugs 12 are located on both sides of the orthogonal center line 19 that is perpendicular to the longitudinal center line 7.
It is located approximately at the center of the openings of both intake bows) 13 and 14 into the combustion chamber 6 and the openings of both exhaust bows) 15 and 16 into the combustion chamber 6.

Both intake ports 1 are provided on the lower surface of the cylinder head 3.
3.14 is located outside the one inclined inner wall surface 9 which opens into the combustion chamber 6, and both exhaust ports 15.16 are located outside the other inclined inner wall surface 10 which opens into the combustion chamber 6, Squish area 3 relative to top surface 36 of piston 2
7.38 shall be provided.

The openings of both intake bows) 13 and 14 to the combustion chamber 6 and the openings of both exhaust bows) 15 and 16 to the combustion chamber 6 include:
Poppet-type intake valves 20 . 21 and exhaust valves 22 . 23 are each provided such that the stems of these valves project onto the upper surface of the cylinder head 3 .

In this case, the axes 24 of the intake valves 20.21 and the axes 25 of the exhaust valves 22.23 are inclined in opposite directions by appropriate angles (θ1) and (θ2) with respect to the axis 8 of the cylinder bore 2. Further, the axis 26 of the spark plug 12 is also inclined in the same direction as the intake valve 20.degree. 21 by an appropriate angle (.theta.3) with respect to the axis 8 of the cylinder bore 2.

In this case, the values of (θ1), (θ2), and (θ3) are such that (θ1) is greater than or equal to 0 degrees and less than or equal to 45 degrees, and (θ2)
is preferably greater than or equal to zero degrees and less than or equal to 40 degrees, and (θ3) is preferably greater than or equal to zero degrees and less than or equal to (θ1).

In this way, the axes 24 of both intake valves 20 and 21, and both exhaust valves 2
By tilting the axis 25 of 2.23 and the axis 26 of the spark plug 12, the upper surface of the cylinder head 3 has a space between both intake valves 20.21 and the spark plug 112 and both exhaust valves 22.23. Since a space 27 is formed in the space 27, a common camshaft 28 for both intake valves 20.21 and both exhaust valves 22.23 and a rocker arm for both intake valves 20.21 are provided in this space 27. The shaft 29 and the rocker arm shaft 30 that opposes both exhaust valves 22 and 23 are arranged parallel to a crankshaft (not shown). Further, on the rocker arm shaft 29 for the intake valve, there is a rocker arm 31, 32 for both the intake valves 20° 21, and on the rocker arm shaft 31 for the re-exhaust valve, there is a common 7-shaped flat rocker arm for both the exhaust valves 22° 23. A rocker arm 33 is provided respectively.

In the figure, reference numeral 34 is a cylinder head cover for the upper surface of the cylinder head 3, and 35 is a cylindrical cover for the ignition plug 12.

In this configuration, both intake valves 20.21 open simultaneously during the intake stroke accompanying the descent of the piston 5, so that both intake ports 13.14 are located in the combustion chamber 6 and the cylinder bore 3.
The air-fuel mixture is sucked in from the intake valve 2 after this intake stroke.
0.21 closes and enters a compression stroke as the piston 5 rises. When the top surface 36 of the piston 5 approaches the lower surface of the cylinder head 3 at the end of the compression stroke, one of the lower surfaces of the cylinder head in the combustion chamber 6 Squish areas 37 and 38 on the outside of the inclined inner wall surface 9 of the piston 2 and on the outer side of the other inclined inner wall surface 10, and the top surface 36 of the piston 2.
A squish action occurs at the two squish areas, and squish flow is ejected inward from both squish areas 25 and 26, resulting in a highly disturbed state of the air-fuel mixture in the combustion chamber 6. After that, the ignition plug The fuel is ignited by a spark caused by 12, and both exhaust valves 22.23 open during the exhaust stroke, so that the exhaust gas is discharged from the re-exhaust port 15.16.

In addition, two intake ports 13.1 for one combustion chamber
4 in a plan view of the engine as shown in FIG.
If the respective axes 39 and 40 are arranged at an angle so that they form a V-shape that widens toward the combustion chamber, both intake ports 13
．． The inflowing air-fuel mixture from 14 is shown by arrow 41 in FIG.
As shown by arrows 41 and 42 in the same figure, the air mixture flows into the cylinder bore 2 while widening the interval, and is then guided inward along the circumferential inner wall surface of the cylinder bore 5. Since two swirl flows rotating in opposite directions as shown in FIG.

〔Effect of the invention〕

The present invention has the following unique effects.

■By forming the combustion chamber into a pent roof shape, the flame propagation distance in the combustion chamber can be shortened, but the squish flow from the two squish areas on both the left and right sides of the combustion chamber creates a severe disturbance state in the combustion chamber. Since the flame propagation speed can be improved and the combustion time can be shortened, the knock resistance can be synergistically improved by both of them, and the compression ratio can be increased by that amount.

■ By locating the openings of both intake ports on one sloping inner wall surface of the pent roof-type combustion chamber and the openings of both exhaust ports on the other sloping inner wall surface, both intake ports and exhaust ports Since the cross-sectional area can be increased, the intake resistance of the air-fuel mixture and the outflow resistance of the exhaust gas are reduced, and therefore the filling efficiency of intake air in the engine can be improved. In addition, the synergistic effect of this improvement in charging efficiency and the ability to increase the compression ratio can significantly improve the output and fuel consumption rate of the engine.

08 The axes of both intake valves and spark plugs and the axes of both exhaust valves are inclined in opposite directions to the cylinder bore axis, so that both intake valves, spark plugs, and both exhaust valves are arranged on the upper surface of the cylinder head. A space is formed in the space between them, and a part of the common valve mechanism for both intake valves and exhaust valves can be provided in this space, so by having two intake valves and two exhaust valves each, This prevents the upper part of the cylinder head from increasing in size and weight, making the engine smaller and more compact.
Weight reduction can be achieved.

■By tilting the axis of the 0 spark plug in the same direction as the axis of both intake valves, the spark plug approaches the intake port where the temperature is low, reducing the thermal load on the spark plug and improving its durability. can.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a longitudinal sectional front view of the main parts of the engine, and FIG. 2 is a sectional view taken along line rI in FIG. 1.
-n bottom view, Figure 3 is a sectional view taken along the mm line in Figure 2, and Figure 4 is a
The figure is a cross-sectional view taken along the line IV-IV in Figure 1, and Figure 5 is a cross-sectional view of
-V sectional view. 1... Cylinder block, 2... Cylinder bore, 3... Cylinder head, 5... Piston, 6
... Combustion chamber, 7... Longitudinal center line, 8... Cylinder bore axis, 9.10... Inclined inner wall surface, 11
...Ridge, 12...Ignition plug, 13.14...
...Intake port, 15.16...Exhaust port, 36
... Piston top surface, 37.38 ... Skin area, 20.21 ... Intake valve, 22.23 ...
・Exhaust valve, 24...Intake valve axis, 25...Exhaust valve axis, 26...Ignition plug axis, 27...Space, 28...Cam shaft, 29°30 ...Rocker arm shaft, 31, 32.33...Rocker arm.

Claims (1)

[Claims] (1) Two intake ports and two exhaust ports are opened in the combustion chamber recessed on the lower surface of the cylinder head of the engine, the air-fuel mixture is taken in from the two intake ports, and the exhaust gas is released from the two exhaust ports. In an internal combustion engine configured to discharge exhaust gas, the combustion chamber is provided with inclined inner wall surfaces extending obliquely upward toward the center line of the cylinder bore on both sides of the center line passing through the center point of the cylinder bore in a plan view of the engine, The combustion chamber is formed into a pent roof type in which both of the inclined inner wall surfaces intersect at a ridge line parallel to a center line passing through the center point of the cylinder bore, and both of the intake ports are formed on one of the inclined inner wall surfaces of the combustion chamber. the opening to the combustion chamber,
The openings of both exhaust ports to the combustion chamber are located on the other inclined inner wall surface, and the piston is located on the lower surface of the cylinder head in an area outside the openings of both intake ports and both exhaust ports to the combustion chamber. Forms a squish area against the top surface,
Further, poppet-type intake valves are provided at openings of both intake ports to the combustion chamber, poppet-type exhaust valves are provided at openings of both exhaust ports to the combustion chamber, and axes of these intake valves and exhaust valves are aligned with the cylinder bore. The spark plugs are provided so as to be inclined in opposite directions with respect to the axes of the intake ports, and an ignition plug is provided approximately at the center of the openings of both intake ports to the combustion chamber and the openings of both exhaust ports to the combustion chamber. An internal combustion engine characterized in that the axis of the spark plug is inclined with respect to the axis of the cylinder bore in the same direction as the axis of the intake valve.