Two-cycle internal combustion engine

A two-cycle internal combustion engine provided with at least one fuel injection nozzle, wherein the fuel injection nozzle is provided with a heating element for heating the fuel so as to cause the fuel to undergo a phase change before the fuel is injected from the fuel injection nozzle. A fuel control circuit for controlling the heating element is attached to the engine so that an AC electromotive force generated at a generator portion of an ignition device is input therein and, based on such electromotive force, the heating element is controlled. All of the ignition device, the fuel controlling circuit and the generator portion are formed into a single integrated body which functions as an ignition/fuel controlling device.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a two-cycle internal combustion engine of the 
fuel injection type, and in particular to a two-cycle internal combustion 
engine of the fuel injection type which is relatively small in size and 
suited for use in a portable working machine such as a chain saw or a bush 
cutter. 
2. The Prior Art 
Because of the increasing concern in recent years of environmental 
problems, a reduction not only of the toxic substances in the exhaust gas 
but also of the engine noise is strongly demanded even in a small 
two-cycle internal combustion engine. In particular, there are pollution 
problems inherent to a two-cycle internal combustion engine, i.e. a 
problem of how to reduce the quantity of HC in the exhaust gas which is 
brought about due to a phenomenon of blow-by of unburnt air-fuel mixture 
from a combustion chamber, and a problem of how to prevent the discharge 
of unburnt fuel which is brought about due to a phenomenon of spitting of 
fuel toward the air-cleaner. These problems are also desired to be solved. 
On the other hand, a lean burn engine, or a direct injection engine wherein 
fuel is directly injected into a combustion chamber has been recently 
proposed as a four-cycle internal combustion engine. In these types of 
engine, the reduction of toxic substances in the exhaust gas by means of a 
lean-burning technique is taken into consideration. Therefore, it is now 
studied how to apply this technique to a two-cycle internal combustion 
engine. 
For example, a two-cycle internal combustion engine of the direct fuel 
injection type is proposed in U.S. Pat. No. 4,813,391. According to this 
technique, a fuel injection nozzle is disposed at a cylinder head portion 
of the combustion chamber so as to permit the injection of fuel to be 
effected directly into the combustion chamber. In this case, a fuel pump 
is actuated taking advantage of the fluctuation in pressure within a crank 
case, and, through this actuation of the fuel pump, fuel is fed to the 
fuel injection nozzle and then directly injected into the combustion 
chamber. The stroke of fuel injection, i.e. the injection of fuel from the 
injection nozzle, is performed as follows. Namely, as a piston is moved 
downward, the pressure inside a crank-case is proportionally increased, 
and when the piston is brought down to approximately the bottom dead 
center, the fuel pump is actuated by the pressure inside the crank-case, 
thus feeding fuel to the fuel injection nozzle, from which the fuel is 
injected by the pressing force of the fuel pump into the combustion 
chamber. 
There is also known another example of a two-cycle internal combustion 
engine of the direct fuel injection type, wherein a fuel injection nozzle 
is disposed midway of an air passage (scavenging passage) communicating 
with a combustion chamber. Fuel from the injection nozzle is injected 
toward a heat conductive wall constituting a cylinder wall and impinged 
thereon so as to be gasified and mixed with air passing through the air 
passage, the resultant air-fuel mixture being fed to a combustion chamber 
(U.S. Pat. No. 4,876,999). 
However, in the case of the former engine of the direct fuel injection type 
(U.S. Pat. No. 4,813,391), wherein the fuel injection nozzle is mounted on 
a cylinder body and fuel is directly injected from the fuel injection 
nozzle into the combustion chamber, the timing and manner of fuel 
injection are set such that the fuel pump is actuated depending on the 
pressure change inside the crank-case and the fuel is injected by the 
delivery pressure of the fuel pump, so that the timing of fuel injection 
as well as the quantity of fuel to be injected are rather difficult to 
adjust. At the same time, a fuel pump for injection of fuel as well as an 
operation system for actuating the fuel pump are required to be employed. 
Therefore, this fuel injection mechanism is not suited for the combustion 
control (air/fuel ratio control) of the engine and the structure thereof 
is rather complicated, thus raising a problem that the manufacturing cost 
thereof would be increased. 
On the other hand, in the case of the injection system of a fuel injection 
nozzle which is commonly employed in a four-cycle internal combustion 
engine, fuel is compressed by means of a plunger pump and then fed to the 
fuel injection nozzle. An electrically operable member such as an 
electromagnetic solenoid is mounted on the fuel injection nozzle. On the 
occasion of fuel injection, the electrically operable member is magnetized 
to open or close the valve of the fuel injection nozzle. 
In this fuel injection system, the timing of fuel injection is controlled 
electrically, thus making it possible to inject fuel at an appropriate 
timing and to adjust the quantity of fuel. However, it is required 
according to this system to provide the fuel injection nozzle with an 
electrically operable member and a nozzle shut-off valve, and at the same 
time to install a control device for controlling the fuel injection 
nozzle. These devices which are required in the manufacture of the fuel 
injection type engine as mentioned above are rather expensive, so that the 
application of the fuel injection nozzle of this system to a two-cycle 
internal combustion engine for a bush cutter, etc. is not suitable in 
terms of cost. 
SUMMARY OF THE INVENTION 
The present invention has been made under the circumstances mentioned 
above. It is therefore an object of the present invention to provide a 
two-cycle internal combustion engine having a fuel injection nozzle of low 
cost and with a controlling device for controlling the fuel injection 
nozzle, wherein the injection timing of fuel as well as the quantity of 
fuel can be easily adjusted. 
According to the present invention, there is provided a two-cycle internal 
combustion engine of the fuel injection type provided with a plurality of 
fuel injection nozzles, wherein each of said fuel injection nozzles is 
provided with a heating element for heating the fuel so as to cause the 
fuel to undergo a phase change before the fuel is injected from the fuel 
injection nozzle. 
According to the present invention, there is further provided a two-cycle 
internal combustion engine of the fuel injection type, which is provided 
with a fuel controlling circuit as means for controlling the 
aforementioned heating element; the fuel controlling circuit being 
designed such that an AC electromotive force generated at a generator 
portion of an ignition device can be input thereto and, based on this 
electromotive force, the heating element can be controlled; and all of the 
ignition device, the fuel controlling circuit and the generator portion 
being formed into a single integrated body to function as an ignition/fuel 
controlling device. 
When a two-cycle internal combustion engine of the fuel injection type 
constructed as mentioned above according to the invention is assumed to be 
formed of a Schnurle type crank chamber pre-compression and piston valve 
system, the engine will operate as follows. Namely, when the piston moves 
upward to start the discharge of combustion exhaust gas from the 
combustion chamber, the scavenging port is opened to allow the 
pre-compressed intake air in the crank chamber to flow via the scavenging 
passage into the combustion chamber so as to discharge any residual 
combustion exhaust gas from the combustion chamber, thereby scavenging the 
combustion chamber. 
While the cylinder chamber is being scavenged, the piston starts to move 
upward to ultimately close the scavenging port. At a suitable timing 
before the scavenging port is completely closed, a signal is emitted from 
the ignition/fuel controlling device to instantaneously heat the heating 
element of the fuel injection nozzle with a high voltage. When the heating 
element is heated in this manner, the fuel that has been fed to the nozzle 
is instantaneously heated to undergo a phase change so as to generate 
bubbles. Simultaneously with the growth of the bubbles, the inner pressure 
in the end portion of the nozzle is increased so that the fuel is forced 
to be injected from the distal end of the nozzle into the combustion 
chamber and mixed with air. After this injection of fuel, the piston is 
further moved upward to enter into a compression stroke. When the piston 
is further advanced to reach near the top dead center, a signal is emitted 
from the ignition/fuel controlling device to cause the spark plug to 
spark, thereby causing the air-fuel mixture to be explosively burnt. 
In the expansion stoke following the explosion of the air-fuel mixture, the 
piston is moved downward to pre-compress the air that has been sucked in 
the crank chamber, thus making it ready to repeat a sequence of the 
strokes as mentioned above. 
Since the two-cycle internal combustion engine according to this invention 
is designed such that fuel is instantaneously heated by a heating element 
of a fuel injection nozzle before the fuel is injected, there is no need 
to employ a special fuel compression pump or a shut-off valve, so that the 
construction of the fuel injection nozzle can be simplified. Furthermore, 
since the two-cycle internal combustion engine according to this invention 
is provided with a plurality of the fuel injection nozzles, each provided 
with a heating element as mentioned above, the quantity of fuel to be 
injected in a single injection can be easily altered. 
Moreover, since the injection of fuel is performed by a plurality of 
injection nozzles and, at the same time, the quantity of fuel can be 
adjusted by a plurality of injection nozzles, it is possible to accurately 
and easily to control the air/fuel ratio of lean burn combustion, for 
instance. 
Furthermore, since the heat control of the heating element can be effected 
by taking advantage of an AC electromotive force of the generator means of 
the ignition device, it is possible to simplify the structure of the fuel 
injection control device. Additionally, since all of the ignition device, 
the generator means and the fuel controlling circuit are integrated into a 
single body as an ignition/fuel controlling device and are placed near the 
fan rotor for air-cooling, the overall dimension of the ignition/fuel 
controlling device can be made compact.

DETAILED DESCRIPTION OF THE INVENTION 
The invention will be further explained with reference to the drawings 
depicting one embodiment of a two-cycle internal combustion engine 
according to this invention. 
In the embodiment illustrated in FIG. 1, a fuel injection type, two-cycle 
internal combustion engine 1 (hereinafter referred to simply as an 
internal combustion engine) constructed in accordance with the invention 
comprises a so-called Schnurle type crank chamber pre-compression system 
two-cycle internal combustion engine. It includes a cylinder block 2 
having a combustion chamber 3 in which a piston 4 is adapted to be 
slidingly moved up and down, a split type crankcase 5 attached to the 
lower end portion of the cylinder block 2 and provided therein with a 
crank chamber 6, a cylinder head 7 which is formed integrally with the 
upper portion of the cylinder block 2, a plurality of cooling fins 8 for 
air-cooling formed on the outer periphery of the cylinder block 2, and a 
spark plug 9 attached to a suitable portion of the cylinder head 7 and 
connected via a high voltage cable 36a to an ignition device 37 to be 
explained hereinafter. 
The crank chamber 6 is cylindrical in shape, short in height and 
hermetically closed. A crank shaft 30 is axially held at a central portion 
of each of the right and left sides of the crank chamber 6. The piston 4 
is connected via a connecting rod 32 to a crank pin 31 of the crank shaft 
30. A pair of sector shaped crank webs 34 are fixed at the right and left 
ends of the crank pin 31 so that the connecting rod 32 is interposed 
between the pair of sector shaped crank webs 34. Consequently, the crank 
webs 34 are designed to be rotated integral with the crank shaft 30. 
A fan rotor 35 for air-cooling is fixed to one end portion of the crank 
shaft 30. A plurality of magnets 35a are embedded in the outer peripheral 
wall of the fan rotor 35. An ignition/fuel controlling device 36 (to be 
explained in detail hereinafter) is disposed to face the outer peripheral 
wall of the fan rotor 35, thereby allowing the output power of the 
ignition/fuel controlling device 36 to be supplied to the spark plug 9 and 
to a fuel injection nozzle 46 (to be explained in detail hereinafter). 
The cylinder block 2 is provided with an exhaust port 40 which opens at a 
portion of the inner wall of the combustion chamber 3 that is directed to 
intersect at a right angle with the axis of the crank shaft 30. The 
cylinder block 2 is also provided with a suction port 41 which opens at a 
portion of the inner wall of the combustion chamber 3 that approximately 
faces the exhaust port 40 (a portion which is dislocated by an angle of 
180) but is located at somewhat lower level than where the exhaust port 40 
is located. Furthermore, a pair of scavenging ports 42 are formed in the 
cylinder block 2 to face each other at portions of inner wall of the 
cylinder block 2 that are located at an intermediate portion between the 
exhaust port 40 and the suction port 41, i.e. each port 42 is dislocated 
by an angle of 90 from the exhaust port 40 and the suction port 41 (right 
and left sides in FIG. 1). These scavenging ports 42 are formed 
respectively on the top of each of so-called wall type scavenging passages 
43, each of which extends from the scavenging ports 42 toward the lower 
portion of the cylinder block 2 so as to communicate with the crank 
chamber 6. 
In order to facilitate the monoblock casting of the cylinder block 2 and 
cylinder head 7 by means of a high pressure die casting, a pair of 
openings-for-casting 44 are formed respectively along the scavenging 
passages 43, thereby allowing the outer side of each scavenging passage 43 
to communicate with the outer atmosphere. Accordingly, a pair of 
scavenging passage covers 45, each having a smoothly curved inner surface 
in conformity with the scavenging passage 43 and prepared separately from 
the cylinder block 2, is attached to the openings-for-casting 44, 
respectively. When the scavenging passage covers 45 are fixed to the 
openings-for-casting 44 respectively by making use of an adhesive for 
instance, the openings-for-casting 44 are closed, thereby completing 
smoothly curved passages so as to allow scavenging air to pass 
therethrough, thus exhibiting an efficient scavenging. 
One (the one on the left side in FIG. 1) of the scavenging passage covers 
45 is provided with an internally threaded through-hole 45a, in which a 
fuel injection nozzle 46 having an external thread on its outer peripheral 
wall is inserted or screwed. The distal end 46a of the fuel injection 
nozzle 46 is directed toward the top of the combustion chamber 3, so that 
when the fuel is injected, it is fed to a region inside the combustion 
chamber 3 that is optimum for the combustion of the fuel. 
FIG. 2 shows a block diagram illustrating the relationship between the 
ignition/fuel controlling device 36 and the spark plug 9 or the fuel 
injection nozzle 46, which are to be actuated by the ignition/fuel 
controlling device 36. 
The ignition/fuel controlling device 36 comprises an AC generating means 38 
and a fuel control circuit 39 which are integrally incorporated into the 
ignition/fuel controlling device 36 in addition to an ignition device 37 
of an ordinary CDI or TCI system. The AC generating means 38 is adapted to 
generate electricity through the rotation of the fan rotor 35 and to feed 
the electricity thus generated to the ignition device 37 and the fuel 
control circuit 39, so as to actuate the spark plug 9 and the fuel 
injection nozzle 46. 
The ignition device 37 is of the ordinary type and comprises a pick-up coil 
37a for controlling the timing of ignition, an ignition electric source 
circuit 37b for performing a half-wave rectification of AC current 
supplied from the AC generating means 38, an ignition-controlling circuit 
37c and an ignition coil 37d. The fuel control circuit 39 is constituted 
by an injection electric source circuit 39a for performing a half-wave 
rectification (opposite in phase to the ignition electric source circuit 
37b) of AC current, and an injection control circuit 39b. The ignition 
device 37 is connected via the high voltage cable 36a to the spark plug 9, 
while the fuel control circuit 39 is connected via wirings 36b to the fuel 
injection nozzle 46. 
The fuel injection nozzle 46 is connected to a fuel tank 47, so that the 
fuel from the fuel tank 47 is fed to the position of the fuel injection 
nozzle 46 (because the fuel tank 47 is generally disposed lower than the 
fuel injection nozzle 46) by means of a priming pump (at the occasion of 
start-up) or a lift pump (during operation), both of which (not shown) are 
of the ordinary type employed usually in a two-cycle internal combustion 
engine (air-fuel mixture suction). 
The fuel injection nozzle 46 is provided with a heating element 46b formed 
of an electric heater, etc., which is connected to the fuel control 
circuit 39. The heating element 46b is adapted to be instantaneously 
heated by power of high voltage which is supplied from the fuel control 
circuit 39. When the heating element 46b is heated in this manner, the 
fuel which has been fed to the nozzle 46 is instantaneously heated to 
undergo a phase change so as to generate bubbles 46c. Simultaneously with 
the growth of the bubbles 46c, the inner pressure of the nozzle 46 is 
increased, so that the fuel is caused to be injected from the opening of 
the distal end portion 46a of the nozzle 46 into the combustion chamber 3. 
Since the cylinder block 2 is provided with a plurality of the injection 
nozzles 46, each having a heating element 46b, the quantity of fuel to be 
injected can be adjusted by individually controlling the heating elements 
46b. It is also possible to set a porous body such as a ceramic porous 
body in the interior of the nozzle 46 so as to allow the fuel to be soaked 
into the porous body and then be heated by the heating element 46b. 
The ignition action of the ignition device 37 is effected by taking 
advantage of an AC electromotive force which is generated at the AC 
generating means 38. The electromotive force which is actually utilized in 
this ignition action is either a positive half-wave voltage, or a negative 
half-wave voltage so that the other half-wave voltage is not utilized at 
all. In this embodiment, the half-wave voltage that is not utilized in the 
ignition action is utilized for actuating the fuel injection nozzle 46. 
Specifically, the AC generating means 38 is designed to generate an AC 
electromotive force through the rotation of the fan rotor 35. Ignition is 
effected by the voltage of the positive side (or the negative side) at the 
moment when AC voltage is changed from the positive side (or the negative 
side) to the negative side. The fuel injection nozzle 46 is designed to 
utilize a voltage of the opposite side of this AC electromotive force, 
i.e. a voltage of the negative side (or the positive side) as explained 
below. Namely, the output signal of the AC electromotive force is taken 
out of the ignition control circuit 37c and transmitted to the injection 
control circuit 39b, which is then actuated to cause the heating element 
46b of the fuel injection nozzle 46 to be instantaneously heated through 
an application of high voltage by taking advantage of the voltage which is 
opposite to that employed in the ignition device 37, i.e. the voltage of 
negative (or the positive) side, thereby heating and injecting the fuel 
therefrom. Specifically, the AC power generated at the AC generating means 
38 is rectified by the injection electric source circuit 39a into a DC 
power, which is then supplied to the fuel control circuit 39. The 
injection control circuit 39b is designed to receive an output signal 
(timing signal) of the AC electromotive force from the ignition control 
circuit 37c. Based on this output signal, an electric power is transmitted 
through the wiring 36b to the heating elements 46b so as to 
instantaneously heat the heating elements 46b by the application of a high 
voltage. The fuel heated by the heating elements 46b is then injected from 
the end portion 46a of the fuel injection nozzle 46 in conformity with the 
timing of the scavenging stroke of the internal combustion engine 1. The 
adjustment in the quantity of fuel injected can be controlled by suitably 
selecting the heating element 46b attached respectively to each end 
portion 46a of the nozzle 46 by making use of the injection control 
circuit 39b. 
Next, the operation of the aforementioned internal combustion engine 1 
according to this embodiment will be explained as follows. 
The internal combustion engine 1 according to this embodiment is of a 
so-called piston valve system, wherein neither a suction valve nor an 
exhaust valve is provided, and the suction port 41 and the exhaust port 40 
are alternatively allowed to communicate respectively with the crank 
chamber 6 and with the combustion chamber 3 by the reciprocating movement 
(up and down movement) of the piston 4, thereby performing the suction and 
exhaust action of the engine 1 in the same manner as the aforementioned 
suction valve and exhaust valve. 
In the operating condition of the internal combustion engine 1 where the 
piston 4 moves up and down, when the piston 4 moves down to come close to 
the bottom dead center, the exhaust port 40 is opened at first thereby 
allowing the combustion exhaust gas to be discharged from the interior of 
the combustion chamber 3 to the outside of the internal combustion engine 
1. Then, the scavenging ports 42 are opened to allow the air sucked and 
pre-compressed in the crank chamber 6 to flow via the scavenging passages 
43 into the combustion chamber 3, thereby purging any residual combustion 
exhaust gas out of the combustion chamber 3 through the exhaust port 40, 
thus scavenging the combustion chamber 3. A little amount of the sucked 
air is also discharged through the exhaust port 40. 
During this scavenging operation, the piston 4 starts to move upward to 
close the scavenging port 42 again. However, at a suitable timing 
immediately before the scavenging port 42 is closed, the heating element 
46b of the fuel injection nozzle 46 is instantaneously heated in 
accordance with an output signal from the control circuit 39b of the 
ignition/fuel controlling device 36, thereby allowing the fuel to be 
injected directly into the combustion chamber 3 from the distal end 46a of 
the fuel injection nozzle 46 and mixed with the air sucked in the 
combustion chamber 3. After the injection of fuel, the piston 4 is further 
moved upward to close the scavenging ports 42 at first and then to enter 
into the compression stroke while closing the exhaust port 40. When the 
piston 4 is further advanced to reach near the top dead center, a power of 
high voltage is supplied via the high voltage cable 36a to the spark plug 
9 from the ignition device 37 of the ignition/fuel controlling device 36 
thereby to cause the spark plug 9 to spark and the air-fuel mixture to be 
explosively burnt. 
As explained above, when the piston 4 is in the compression stroke, the 
pressure in the crank chamber 6 is gradually decreased with the ascending 
movement of the piston 4, so that when the skirt portion 4a of the piston 
4 moves up past the suction port 41, thus allowing the suction port 41 to 
be communicated with the crank chamber 6, the ambient air is sucked into 
the crank chamber 6 through an air cleaner (not shown). 
In the expansion stoke following the explosion of the air-fuel mixture, 
when the piston 4 moves downward to close the suction port 41, the air 
that has been sucked in the crank chamber 6 is pre-compressed, and then 
the scavenging ports 42 are opened to allow the crank chamber 6 to 
communicate with the combustion chamber 3. As a result, the air that has 
been sucked and pre-compressed in the crank chamber 6 is forced to enter 
via the scavenging passages 43 into the combustion chamber 3 from the 
scavenging ports 42, thus making it ready to repeat a sequence of the 
strokes as mentioned above. 
Since the two-cycle internal combustion engine 1 according to this 
embodiment is designed such that the fuel injection nozzle 46 provided 
with the heating element 46b is disposed in the scavenging passage 43, so 
as to instantaneously heat the fuel by the heating element 46b before the 
fuel is injected, there is no need to employ an expensive special fuel 
compression pump or a shut-off valve, so that the construction of the fuel 
injection nozzle 46 can be simplified. Furthermore, since the two-cycle 
internal combustion engine 1 according to this embodiment is provided with 
a plurality of fuel injection nozzles 46, each provided heating element 
46b as mentioned above, the quantity of fuel to be injected in a single 
injection can be easily controlled. 
Moreover, since the injection of fuel is performed by a plurality of 
injection nozzles 46 and, at the same time, the quantity of fuel can be 
adjusted by a plurality of injection nozzles 46, it is possible to 
accurately and easily to control the air/fuel ratio of lean burn 
combustion for instance. 
Further, since the heat control timing of the heating elements 46b is 
designed to take advantage of the ignition signal from the ignition 
control circuit 37c, the device 39 for controlling the injection of fuel 
can be made simple in structure. 
Furthermore, since all of the ignition device 37, the generator means 38 
and the fuel controlling circuit 39 are integrated into a single body as 
an ignition/fuel controlling device 36 and are placed near the fan rotor 
35 for air-cooling, the overall dimension of the ignition/fuel controlling 
device 36 can be made compact. At the same time, it has become possible to 
control both ignition and fuel injection by making use of only the 
ignition/fuel controlling device 36. 
Since the ignition/fuel controlling device 36 is formed into an integral 
body, the wiring and assembling work can be easily performed in the same 
manner as in the case of the conventional ignition device, and the repair 
of the device can be easily performed. Furthermore, the number of parts 
for the ignition/fuel controlling device 36 can be minimized. 
In the foregoing explanation, the present invention has been explained with 
reference to one embodiment. However, the present invention should not be 
construed to be limited to this embodiment, but may be variously modified 
within the spirit of the invention as set out in the claims. 
As explained above, since the two-cycle internal combustion engine 
according to the invention is constructed such that fuel is injected 
through the heating of the fuel injection nozzle, and since the heating 
timing is determined by making use of the ignition timing signal from the 
existing ignition device, it is possible to provide a two cycle internal 
combustion engine of fuel injection type which is simple in structure. 
Moreover, as all of the ignition control device and the fuel injection 
control device are integrated into a single body, the overall dimension of 
the device can be made compact. Also, the workability, such as assembling 
and repair, of the device can be improved and, at the same time, the 
overall weight and manufacturing cost of the device can be minimized.