Combustion chamber for side-valve type internal-combustion engine

A side-valve type internal-combustion engine has a cylinder head formed with a recess or recesses each of which forms a combustion chamber with the associated cylinder and which is large enough to permit the alternate flow of suction or exhaust gas between the suction (inlet) or exhaust valve and the cylinder. In plan, the configuration of the recess is generally L-shaped and covers the both valves and part of the cylinder. One leg of the L-shaped recess provides a straight line passage between the suction or inlet valve and the cylinder, while the exhaust valve and the cylinder are connected in series by the one leg of the recess from the cylinder to the suction valve and then by the other leg from the suction valve to the exhaust valve. The height of the recess is reduced in the region directly above the exhaust valve to a level considerably lower than the rest of the recess so that the upper wall surface of the recess is very close to the exhaust valve when it is in its uppermost position.

SUMMARY OF THE INVENTION 
This invention relates to the combustion chambers as typically represented 
in FIGS. 1 and 3. FIG. 1 is a phantom view of such a chamber as seen from 
above the cylinder head, and FIG. 3 is a sectional view taken along the 
line A--A of FIG. 1. 
As shown, the suction valve 2 and the exhaust valve 3 are located offset a 
certain distance from the cylinder 1. The recess 5 formed in the cylinder 
head 4 permits the passage therethrough of the fuel-air mixture from the 
suction valve 2 to the cylinder 1 and of the exhaust gas from the cylinder 
to the exhaust valve 3. The transverse configuration of the recess 5 is 
substantially trapezoidal, covering the suction and exhaust valves and 
part of the cylinder, so that the charge can flow from the suction valve 2 
to the cylinder and, after the combustion, to the exhaust valve 3, in 
either case along a generally straight path. As indicated in FIG. 3, the 
recess 5 is of substantially the same depth, or height, from the openings 
of the suction and exhaust valves. The recess, which together with the 
upper portion of the cylinder 1 forms a combustion chamber, is rather flat 
and has a far less volume per unit surface area of its walls than the 
corresponding recess of the overhead-valve engine. The side-valve type, 
therefore, has had the following disadvantages: 
(1) Requires longer fuel combustion time and involves slower increase in 
cylinder pressure and lower output per stroke volume. Hence greater fuel 
consumption. 
(2) The rate of unburned fuel deposition on the combustion chamber wall is 
higher, with a consequent increase in the hydrocarbon contents of the 
exhaust. 
In an attempt to eliminate these disadvantages and increase the recess 
capacity per unit wall area, a modified agreement as shown in FIG. 2 has 
been proposed. Like FIG. 1, the figure is a phantom plan view of the 
cylinder head, and a section through the line A--A of FIG. 2 is identical 
with FIG. 3 showing the original arrangement. As can be seen from FIG. 2 
in comparison with FIG. 1, this modified arrangement dispenses with the 
straight line passage of the charge from the suction valve 2 to the 
cylinder 1 in FIG. 1, and the horizontal sectional area of the recess 5 is 
accordingly much smaller than that in FIG. 1. However, the modified design 
still has a disadvantage of increased flow passage resistance from the 
suction or inlet valve to the cylinder due to the provision of a corner 
5a, as shown in FIG. 2, which causes the suction gas to adopt a curved 
flow path as indicated by broken-line arrows. 
In another prior art arrangement as shown in U.S. Pat. No. 2,076,593 to 
Ricardo, the recess has a horizontal shape as shown in FIG. 1. Reduced 
head room is provided over the exhaust valve and provides a mounting for 
the spark plug. This arrangement does nothing to reduce the heat loading 
on the exhaust valve, since combustion commences directly over the exhaust 
valve. 
In British Pat. No. 358,908 the recess is in the shape of a free form 
triangle. Flow passes directly to the exhaust valve from the cylinder. In 
this arrangement the spark plug is located above the cylinder. 
In the U.S. Pat. No. 1,875,589 an L-shaped recess is shown, however, the 
intake valve is at the remote end of the L-shaped passage and the spark 
plug is located directly over the exhaust valve. 
An object of the present invention is to provide a side-valve type 
internal-combustion engine which eliminates the afore-mentioned 
disadvantages and achieves improved fuel consumption as well as reduction 
of noxious exhaust emissions while attaining enhanced power output per 
unit stroke volume of the cylinder by increasing the combustion chamber 
volume per unit surface area of the surrounding walls. 
This object of the invention is attained by providing a combustion chamber 
for a side-valve type internal-combustion engine wherein the cylinder head 
is formed with a generally L-shaped recess or recesses each of which is 
large enough to permit the alternate flow therethrough of suction or 
exhaust gas between the suction or exhaust valve and the associated 
cylinder, characterized in that the L-shaped plan configuration of the 
recess covers the suction and exhaust valves and part of the cylinder, and 
the suction valve communicates in a straight line with the cylinder while 
the exhaust valve is communicated with the cylinder by way of the recess 
located above the suction valve. In other words, the L-shaped recess has 
two angularly disposed legs, one extending from the cylinder to the 
suction valve and the other from the suction valve to the exhaust valve. 
As a result, flow from the cylinder first passes through the one leg and 
then through the other flowing an L-shaped path. Further, the height of 
the recess is reduced in the region above the exhaust valve to a level 
much lower than the rest of the recess and adequately close to the exhaust 
valve when it is in the uppermost position. 
The various features of novelty which characterize the invention are 
pointed out with particularity in the claims annexed to and forming a part 
of this disclosure. For a better understanding of the invention, its 
operating advantages and specific objects attained by its use, reference 
should be had to the accompanying drawings and descriptive matter in which 
there are illustrated and described preferred embodiments of the invention 
.

DETAILED DESCRIPTION OF THE INVENTION 
The present invention will now be described in detail with reference to 
FIGS. 4 to 6 showing an embodiment thereof. 
As shown in FIGS. 4(a), 4(b), 5 and 6, the cylinder head 28 has a recess 20 
formed therein to permit the flow of suction gas from the suction or inlet 
valve 22 to the cylinder 21 or the flow of exhaust gas from the cylinder 
21 to the exhaust valve 23. This recess 20 combines with the space 29a 
above the piston 29 to constitute a combustion chamber. As viewed in plan, 
the recess 20 is of a generally L-shaped configuration covering the 
suction valve 22, the exhaust valve 23, and an adjacent part of the 
cylinder 21 and permitting a straight line passage between the suction 
valve 22 and the cylinder 21 along one leg of the L-shaped recess while 
connecting the exhaust valve 23 to the cylinder 21 via the other leg of 
the recess. The junction of the legs of the L-shaped recess being at the 
suction valve 22, as illustrated in FIGS. 4(a) and 4(b). Flow to and from 
the cylinder 29 is shown by the dashed lines and arrows in FIGS. 4(a) and 
4(b). The flow from the suction valve 22 to the cylinder 29 is along a 
straight line, while flow from the cylinder to the exhaust valve 23 moves 
along a somewhat curved line, since first it must traverse the leg running 
from the cylinder to the suction valve before it turns into the other leg 
for passage to the exhaust valve. 
The height of the recess 20, for the most part, is substantially equal to 
that in FIGS. 1 to 3 but, as can be seen from FIG. 6, the height decreases 
directly above the exhaust valve 23 to a much lower height, with the upper 
surface forming the recess 20 being quite close to the exhaust valve 23 at 
the zenith of its upward movement, note FIGS. 5 and 6. An ignition or 
spark plug 30 is positioned in the wall portion of the cylinder head 28 
directly above the suction valve 22, note FIGS. 4(a), 4(b), 5 and 6. 
During the suction stroke of the piston 29, a fuel-air mixture is charged 
from the opening of the suction or inlet valve 22 to the cylinder 21 into 
a space 25, forming part of the recess 20, immediately above the valve, 
then through a suction-exhaust-gas passage 27, into a space 24 directly 
above the cylinder 21. The space 25 is connected through the intermediate 
passage 27 to the space 24 in a straight-line relation, as indicated by 
broken-line arrows in FIG. 4(a). Since the flow passage is straight and 
shorter than in FIG. 2, the charge will meet less resistance through the 
flow passage. 
The remainder of the previous charge, after combustion, is left behind in 
the space 26 directly above the exhaust valve 23 and, scarcely miscible 
with the stream of the fresh charge, it remains in the same space as 
hatched in FIG. 4(a). 
On the compression stroke of the piston 29, the charge in the cylinder 21 
is compressed and forced with an increasing pressure in the direction 
indicated by the curved broken-line arrows in FIG. 4(b) that is, it flows 
through the one leg of the L-shaped recess until it reaches the junction 
in the recess above the suction valve at which location it then flows into 
the other leg over the exhaust valve. As the compression stroke nears its 
completion, the remaining gas is pressed into the space 26 of low height 
above the exhaust valve so that the fuel air mixture mainly fills the 
space above the suction valve 22 and that portion of the space above the 
cylinder 29. At the same time, the residual gas trapped in the space 26 
above the exhaust valve 23 is compressed, too, to a reduced volume and is 
forced to a corner region of the space 26 as hatched in FIG. 4(b). 
Subsequently, when the ignition plug 30 discharges a spark, the mixture in 
the space above the suction valve is the first to be ignited and burned 
while the combustion is transmitted to the fuel-air mixture over the 
cylinder. The remaining gas passed into the space 26 above the exhaust 
valve 23 does not participate in the combustion process. 
With the construction so far described, the combustion chamber according to 
the present invention offers the following advantages: 
(1) The L-shaped plan configuration of the recess formed in the cylinder 
head, which establishes straight-line communication between the suction 
valve and cylinder, reduces the pressure loss in the suction-gas flow 
passage due to the low flow resistance of that passage. 
(2) As stated, the L-shaped plan configuration of the recess is also such 
that the exhaust valve is communicated with the cylinder through the 
suction valve, and the height of the recess is significantly decreased in 
the region directly above the exhaust valve to a level lower than the rest 
of the upper surface of the recess and adequately close to the exhaust 
valve in its uppermost position. This permits retention of residual gas in 
the space above the exhaust valve. Consequently, a very substantial part 
of the combustion chamber volume during the combustion process is 
constituted by the space extending from the suction valve to the cylinder 
via the suction-exhaust-gas passage, and the volume of the combustion 
chamber per unit surface area of the walls surrounding the chamber is by 
far larger than that of a conventional side-valve type engine, thus 
approaching to some degree the so-called spherical conbustion chamber. 
With a combustion chamber of the construction described the period of time 
required for combustion is shorter than in the ordinary side-valve type 
engine, and therefore the pressure in the cylinder rises to a higher 
level. Accordingly, the mean effective pressure increases, thereby 
enhancing the power output per stroke volume and saving the fuel 
consumption. Furthermore, the shortened combustion time reduces the amount 
of fuel left unburned, most of which consists of harmful hydrocarbons. 
Because of the limited wall surface area on which the unburned fuel is 
allowed to deposit, the noxious hydrocarbon contents of the exhaust can be 
decreased. 
While specific embodiments of the invention have been shown and described 
in detail to illustrate the application of the inventive principles, it 
will be understood that the invention may be embodied otherwise without 
departing from such principles.