JPS5857613B2 - internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an internal combustion engine for a vehicle such as an automobile, and more particularly to an overhead valve type spark ignition internal combustion engine having a combustion chamber of a new shape.

In spark-ignition internal combustion engines, the shape of the combustion chamber has a large effect on the combustion of the air-fuel mixture, and by modifying the shape of the combustion chamber, good combustion of the air-fuel mixture is achieved, resulting in improved output, fuel efficiency, and quiet operation. It is well known that engine performance such as engine performance can be improved.

The important things in modifying the combustion chamber shape are to shorten the flame propagation distance, to generate moderately strong turbulence of the air-fuel mixture in the combustion chamber in the latter half of the compression stroke, and to increase the combustion speed. This includes reducing the temperature rise of the end gas.

Incidentally, in order to increase the combustion speed within the combustion chamber, many internal combustion engines have conventionally utilized compressed vortex flow, that is, squish.

Squish is a narrow gap between the piston head and the lower surface of the cylinder head, that is, the diameter of the cylinder bore that occurs when the air-fuel mixture that exists in the squish area is forced into the main space of the combustion chamber near the end of the compression stroke. The shape of the combustion chamber determines its size, location, and strength of turbulence within the combustion chamber.

In overhead valve type spark ignition internal combustion engines,
A so-called wedge-shaped combustion chamber, which has a wedge-shaped combustion chamber recess on the lower surface of a cylinder head, is well known as one type of combustion chamber that generates a moderately strong squish.

In an internal combustion engine with a wedge-shaped combustion chamber, the combustion chamber recess in the cylinder head is relatively deep and shaped in order to secure the main space of the combustion chamber necessary at piston top dead center and to obtain the necessary compression ratio. It must be.

However, in a deeply formed combustion chamber, the peripheral wall of the combustion chamber recess becomes a shroud wall that surrounds the intake port opening into the slope of the combustion chamber recess, and the masking effect worsens the intake effect.

This is also a problem in internal combustion engines that have bathtub-shaped combustion chambers in their cylinder heads.

In addition, in conventional wedge-shaped combustion chambers, there may not be enough space in the exhaust valve area of the combustion chamber when the piston is at top dead center, so the air-fuel mixture in this area heats up significantly. and is prone to knocking, which is an obstacle in reducing the required octane number.

An object of the present invention is to provide an internal combustion engine having an improved combustion chamber that can generate squish well, without reducing the intake efficiency, and can reduce the temperature rise of end gas near the exhaust valve. It is an object.

According to the present invention, such an object includes a cylinder block having a cylinder bore, a cylinder head that closes one end of the cylinder bore, and a piston disposed in the cylinder bore, the cylinder head closing an end of the cylinder bore. and a combustion chamber recess; the piston has a flat portion and a piston recess at its top facing the cylinder head; the flat portions of each of the cylinder head and the piston close the cylinder bore; a first plane part and a second plane part located at mutually opposing parts sandwiching the combustion chamber depression and the piston depression, respectively, in a direction along one diameter of the piston, the piston being at a top dead center position; At some point, the first plane part of the cylinder head and the first plane part of the piston are close to each other and overlap with each other by aligning the boundaries between the combustion chamber recess and the piston recess to form a first squish area. and the second flat surface of the cylinder head and the second flat surface of the piston are configured to closely overlap each other to define a second squish area, and the second squish area of the first squish The area of the area is larger than that of the second squish area, and the combustion chamber recess has a relatively gently sloped slope on the side closer to the first flat surface of the cylinder head, and The head is formed in a wedge shape with a relatively steep slope on the side near the second flat surface, and the gentle slope is provided with an intake port, an exhaust port, and an intake valve and an exhaust valve for opening and closing them. an ignition plug is provided on the steep slope portion with its ignition portion located near the same plane as the first and second plane portions of the cylinder head; - and a bottom surface substantially parallel to a plane containing the second plane part.

According to this configuration, when the piston reaches its top dead center, there is a substantially uniform and sufficiently deep gap on both sides of the planar squish flow emitted from the first and second squish areas. As a result, the squish flow flows unhindered across the center of the combustion chamber, which consists of the combustion chamber recess and the piston recess. They form a layer of microturbulence that extends over the ignition area, and then collide with each other near the ignition part of the spark plug, where they create even greater turbulence in the air-fuel mixture, and the flame from this area is directed throughout the combustion chamber. Helps spread the word quickly.

Furthermore, since the boundary between the combustion chamber recess and the piston recess that define at least the first squish area is aligned, the squish flow emitted from the first squish area is disturbed by the Coanda effect. can proceed along the central region of the combustion chamber without any problems.

The combustion chamber depression is formed in a wedge shape including a gentle slope part on the side of the first squish area and a steep slope part on the side of the second squish area, and the squish flow launched from the first squish area Since the amount of squish ejected from the second squish area collides at the part corresponding to the deepest position of this wedge-shaped combustion chamber recess, the squish flow after the collision flows along the gentle slope of the combustion chamber recess. Since the piston can turn to the side of the first squish area, and the piston recess also has a bottom surface with a substantially uniform depth, the squish flow after the collision can be directed to the first squish area along this bottom surface. can be turned to the side of the squish area of the combustion chamber, thereby stirring the air-fuel mixture over the entire area of the combustion chamber and thereby also ensuring rapid flame propagation over the entire area of the combustion chamber.

According to the present invention, the required octane number can be greatly reduced compared to conventional internal combustion engines of this type, and the compression ratio of the internal combustion engine can be correspondingly increased compared to conventional ones, and the output of the internal combustion engine can be reduced. You can make improvements.

In addition, squish reduces fluctuations in combustion from cycle to cycle, resulting in stable combustion, which suppresses increases in HC and NOx in exhaust gas, and allows the use of leaner air-fuel mixtures than before. It is possible to improve fuel efficiency and further improve exhaust emissions.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings.

The attached FIG. 1 is a sectional view showing the main parts of one embodiment of the internal combustion engine according to the present invention, and in particular, the line 1 in FIG.
-I, FIG. 2 is a bottom view of the cylinder head of the internal combustion engine shown in FIG. 1, and FIG. 3 is a bottom view of the piston of the internal combustion engine shown in FIG. FIG.

In the figure, 1 indicates a cylinder block, and this cylinder block 1 has a cylinder bore 2.

A gasket 3 is disposed on the upper surface of the cylinder block 1, and a cylinder head 4 is attached thereon to close the upper end of the cylinder bore 2.

The cylinder head 4 has a wedge-shaped combustion chamber recess 5 at a position offset to one side, that is, to the left in the figure, from an imaginary plane containing the central axis of the cylinder bore 2.

The combustion chamber recess 5 has a relatively gentle slope section 5a on the right side in the figure, and a relatively steep slope section 5b on the left side in the figure.
An intake port 6 and an exhaust port 7 are opened in the gentle slope portion 5a, and these ports are opened and closed by an intake valve 8 and an exhaust valve 9.

Further, an ignition plug hole 10 opens toward the central axis of the cylinder bore 2 in the steep slope portion 5b of the combustion chamber recess 5, and a spark plug 11 is inserted into the ignition plug hole 10.
is screwed in, and its ignition part 11' is located within the combustion chamber recess 5.

In this case, the ignition plug 11 is arranged so that its ignition portion 11' is as close as possible to the boundary between the cylinder head 4 and the piston 12 at the top dead center position within the combustion chamber.

A piston 12 is provided within the cylinder bore 2, and two compression rings 13 and 14 and an oil ring 15 are attached to the side circumference of the piston 12.

The piston 12 has a dish-shaped piston recess 16 with a portion of the top surface remaining.

Similar to the combustion chamber depression 5, this piston depression 16 is provided at a position offset to the left in the figure from a virtual plane containing the central axis of the cylinder bore 2, and its periphery is entirely similar to that of the combustion chamber depression 5. It is adapted to substantially conform to the periphery.

That is, the planar shape of the piston recess 16 and the combustion chamber recess 5
have substantially the same planar shape, and face each other, and when the piston 12 is at the top dead center position, the cylinder bore 2 has a boundary between the joint surface of the cylinder block 1 and the cylinder head 4. The main combustion chamber space is defined on both sides in the axial direction.

The spatial volume of the combustion chamber recess 5 and the spatial volume of the piston recess 16 are made substantially equal to each other.

The bottom of the piston recess 1'6 may have a bottom surface parallel to the top surface of the piston, as shown in FIG.
As shown in FIG. 4, the combustion chamber recess 5 may have an inclined bottom surface parallel to and opposite to the gentle slope portion 5a.

In this case, a larger space is provided below the exhaust valve, and the temperature rise of the air-fuel mixture existing in that area is effectively suppressed.

Further, the side wall 17 of the piston recess 16 is a steep wall surface, as shown in the figure.

Piston 1 left on one side of the piston recess 16
The top surface portion 18 having a relatively large area of the spark plug 2 faces the remaining bottom surface portion 19 of the cylinder head 4, and the top surface portion 18 of the spark plug 1
A main first squish area 20 is defined on the side opposite to the side where the combustion chamber recess 5 is provided, that is, on the side of the gentle slope portion 5a of the combustion chamber recess 5.

Further, the relatively small area top surface 21 of the piston 12 remaining on the other side of the piston recess 16 cooperates with the bottom surface 22 of the cylinder head 4 opposite to the top surface 21 of the piston 12 to form the first squish area. A second squish area 23 smaller than 20 is defined.

The area ratio of the first squish area 20 and the second squish area 23 is set so that the ratio of squish intensities generated by each squish area is about 4:1.

During the compression stroke of the internal combustion engine, when the piston 12 rises from the bottom dead center position toward the top dead center position, the air-fuel mixture in the combustion chamber is compressed accordingly.

When the piston 12 rises to near the top dead center position, the top surface 18 of the piston 12 and the bottom surface 19 of the cylinder head 4
and a first squish area 20 between the top surface 21 of the piston 12 and the bottom surface 22 of the cylinder head 4.
A gap between the second squish area 23 and
The mixture present in this part is compressed more strongly than that present in other parts, so that the mixture in the squish area is pushed into the main combustion chamber space formed by the combustion chamber recess 5 and the piston recess 16. Ru.

That is, a squish flow occurs.

This movement of the mixture causes turbulence of the mixture within the main combustion chamber space.

Since the first squish area 20 is wider than the second squish area 23, the air-fuel mixture blows out from the squish area from the second squish area 23 toward the main combustion chamber space. The squish area 20 toward the main combustion chamber space is stronger than the first squish area 20, and at the ignition timing, the first squish area 20 near the ignition part 11' of the spark plug 11
squish style and the second squish area 23
The squish flow just collides with the ignition part 1.
A fine turbulence of the air-fuel mixture, so-called microturbulence, occurs near the point 1', which results in good ignition and combustion of the air-fuel mixture.

In this case, the ignition timing is 40 to 1 minute before top dead center at crank angle.
0°, especially about 25 to 15° is good.

Since the periphery of the combustion chamber recess 5 and the periphery of the piston recess 16 are substantially aligned with each other at the edges defining the squish area, the air-fuel mixture flows from the squish area into the main combustion chamber space. Since the squish flow is ejected directly into the main combustion chamber space without along the top surface of the piston when being extruded, the squish flow is not attenuated by viscous resistance with the wall surface.

In this case, the microturbulence of the air-fuel mixture caused by squish also diffuses into the area below the exhaust valve, which causes turbulence and flow in the air-fuel mixture in the area below, suppressing the temperature rise of this air-fuel mixture. Also, the flame from the spark plug is easily transmitted to this air-fuel mixture, and knocking is prevented from occurring.

Furthermore, if the side wall 17 of the piston recess 16 is steep at the side defining the squish area as shown, the squish flow will not follow the side wall due to the Coanda effect. The squish flow is injected toward the center of the main combustion chamber space or toward the recess side of the combustion chamber, and generates good air-fuel mixture turbulence within the main combustion chamber space including the region below the exhaust valve.

This results in rapid and stable combustion, and also suppresses the temperature rise of the air-fuel mixture below the exhaust valve.

When the air-fuel mixture is ignited by the spark plug 11 and then the piston 12 descends, the air-fuel mixture or combustion gas in the main combustion chamber space is reversed to when the piston 12 moves up. First and second squish areas 20.2
3 will be sucked into the room.

The movement of the air-fuel mixture at this time also helps in achieving stable and rapid combustion.

The above-mentioned vortices of the air-fuel mixture or combustion gas caused by the rising and falling of the piston improve the combustion of the air-fuel mixture, - significantly shorten the combustion time per cycle, and reduce the combustion time of each cycle. fluctuation becomes smaller.

As a result, stable combustion can be obtained even if a lean mixture is used or exhaust gas is recirculated, and harmful components in the exhaust gas can be effectively reduced.

Furthermore, because of the rapid combustion, abnormal combustion such as knocking is less likely to occur.

As a result, the compression ratio of the engine can be increased,
In addition to improving output performance, it can be expected to have a particularly large effect on reducing fuel consumption.

FIG. 5 is a bottom view of a cylinder head showing another embodiment of the internal combustion engine according to the present invention, and FIG. 6 is a plan view of the piston thereof.

In FIGS. 5 and 6, parts corresponding to those in FIGS. 1 to 3 are designated by the same reference numerals as those in FIGS. 1 to 3.

In this embodiment, the peripheral edges of the combustion chamber recess 5 on the side of the first and second squish areas are defined by straight lines parallel to each other.

Further, the peripheral edge of the piston recess 16 of the piston 12 corresponds to the combustion chamber recess 5, and the sides defining the first and second squish areas are defined by straight lines parallel to each other.

In this embodiment as well, the peripheral edge of the combustion chamber recess 16 and the peripheral edge of the piston recess 16 are substantially aligned with each other at the side defining the squish area, so that it is different from the embodiment described above. It will be understood that similar effects can be obtained.

FIG. 7 is a cross-sectional view showing the main parts of another embodiment of the internal combustion engine according to the present invention, especially the line
8 is a bottom view showing the cylinder head of the internal combustion engine shown in FIG. 7, and FIG. 9 is a plan view of the piston thereof.

In addition, in FIGS. 7 to 9, parts corresponding to FIGS. 1 to 3 are indicated by the same reference numerals as those in FIGS. 1 to 3.

In such an embodiment, the combustion chamber recess 5 is connected to the cylinder bore 2.
It is formed to be biased to the right side in the figure, that is, to the side where the main first squish area 20 is formed, from a virtual plane including the central axis of the squish area.

Further, the piston recess of the piston 12 has a peripheral edge shape as clearly shown in FIG. It is adapted to substantially conform to the periphery of the portion.

Further, the piston recess 16 is enlarged at portions corresponding to the intake valve 8 and the exhaust valve 9, as indicated by reference numerals 16' and 16''.

Further, in this embodiment, the peripheral wall 17 of the piston recess 16 on the first squish area side is steep, but the wall surface 17' on the second squish area side is a relatively gentle slope.

In this case, since the peripheral wall 17' of the piston recess 16 on the side of the second squish area 23 is relatively gently sloped, the squish flow generated in the second squish area 23 is slightly affected by the Coanda effect. The squish flow will flow along the side wall 17' of the piston recess 16, and its substantial strength will be adjusted to the squish flow generated in the first squish area 20.

10 to 12 show other embodiments of the piston used in the present invention.

In FIGS. 10 to 12, parts corresponding to FIGS. 1 to 3 are designated by the same reference numerals as those in FIGS. 1 to 3.

The piston recess 16 of the piston 12 shown in FIG. 10 has a side defining a main squish area by a straight line, and a side defining a second squish area by an arc concentric with its outer periphery. It is given.

The cylinder head of an internal combustion engine using this piston may have a combustion chamber recess with a periphery that substantially matches the periphery of the piston recess 16.

Further, the piston shown in FIGS. 11 and 12 has a piston top section which is divided into upper and lower sections, and has a piston recess 16 with an open peripheral edge.

In an internal combustion engine using this piston, the squish area is defined only on the side where the top surface 18 is provided.

In the above embodiments, an internal combustion engine having a wedge-shaped combustion chamber has been described, but the present invention can also be applied to an internal combustion engine having a bathtub-shaped combustion chamber.

Although the present invention has been described in detail with respect to specific embodiments above, it is understood that the present invention is not limited to these embodiments, and that various modifications can be made within the scope of the present invention. This will be obvious to businesses.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view showing the main parts of one embodiment of the internal combustion engine according to the present invention, and especially the line 1-I in FIG.
FIG. 2 is a bottom view of a cylinder head of the internal combustion engine shown in FIG. 1, FIG. 3 is a plan view of a piston used in the internal combustion engine also shown in FIG. 1, and FIG. 4 is an internal combustion engine according to the present invention. FIG. 3 is a longitudinal cross-sectional view showing the main parts of another embodiment of the present invention, particularly a cross-sectional view taken along line Il in FIG. 2; FIG. 5 is a bottom view showing another embodiment of the cylinder head for an internal combustion engine according to the present invention, FIG. 6 is a plan view of a piston used in the internal combustion engine also shown in FIG. 5, and FIG. FIG. 8 is a longitudinal cross-sectional view showing the main parts of yet another embodiment of the internal combustion engine according to the invention, and in particular is a cross-sectional view taken along the line ■-■ in FIG. 8; 8 is a bottom view of the cylinder head of the internal combustion engine shown in FIG. 7, FIG. 9 is a plan view of the piston of the internal combustion engine also shown in FIG. 7, and FIG. 10 is a bottom view of the cylinder head of the internal combustion engine shown in FIG. Plane y1 11th showing another example of the piston to be used
FIG. 12 is a plan view showing still another example of a piston used in an internal combustion engine according to the present invention, and FIG.
It is a sectional view taken along the line ■-■ in the figure. 1... Cylinder block, 2... Cylinder bore, 3... Gasket, 4...
Cylinder head, 5... Combustion chamber recess, 6...
...Intake port, 7...Exhaust port, 8...
...Intake valve, 9...Exhaust valve, 10...
...Spark plug hole, 11...Spark plug,
11'...Ignition part, 12...Piston, 13.14...Compression ring, 1
5...Oil ring, 16...Piston recess, 17.17'...Side wall of piston recess, 18...Top surface of piston, 19... ...
・Lower surface of cylinder head, 20...first squish area, 21...top of piston,
22...Bottom part of cylinder block, 23...
...Second squish area.

Claims (1)

[Claims] 1 A cylinder block having a cylinder bore, a cylinder head that closes one end of the cylinder bore, and a piston disposed within the cylinder bore, the cylinder head having a flat part that closes the end of the cylinder bore, and a combustion chamber recess. the piston has a flat portion and a piston recess at its top facing the cylinder head, the flat portions of each of the cylinder head and piston each extending in a direction along a diameter of one of the cylinder bores; a first flat part and a second flat part located at mutually opposing portions sandwiching the combustion chamber recess and the piston recess, and when the piston is at the top dead center position, the first flat part of the cylinder head The planar portion and the first planar portion of the piston are close to each other and overlap with the boundaries of the respective combustion chamber recesses and the piston recesses aligned to define a first squish area and to define a first squish area of the cylinder head. The second flat portion and the second flat portion of the piston closely overlap each other to define a second squish area, and the area of the first squish area is larger than the second squish area. is larger than that of
The combustion chamber recess has a relatively gently sloped slope on the side closer to the first flat surface of the cylinder head, and a relatively steep slope on the side closer to the second flat surface of the cylinder head. The ignition plug is formed into a wedge shape having a portion, and the gentle slope portion is provided with an intake port and an exhaust port, as well as an intake valve and an exhaust valve for opening and closing them, and the steep slope portion is provided with an ignition plug that connects its ignition portion to the cylinder. The piston recess is located near the same plane as the first and second plane parts of the head, and the piston recess is located near the same plane as the first and second plane parts of the head.
and a bottom surface substantially parallel to a plane including the second plane portion.