Patent Description:
One-stroke internal combustion engines are known in the art. In one-stroke internal combustion engines, one combustion is produced per piston stroke. The intake, compression, power, and exhaust strokes occur in a single turn of an output shaft or crankshaft. Every piston stroke is the power stroke so that only one power stroke is required to rotate the output shaft or crankshaft continuously to complete a full cycle.

One example of a one-stroke internal combustion engine is disclosed in <CIT>. The engine comprises a combustion chamber and a compression chamber. A compression member is provided within the compression chamber for defining first and second combustion sub-chambers. A piston is slidably disposed within the combustion chamber in communication with the compression member for defining the first and second combustion sub-chambers. Motion of the piston toward the first combustion sub-chamber enables a first fuel-air mixture to flow into the second combustion sub-chamber from the second combustion sub-chamber for subsequent combustion therein together with drawing of a second fuel-air mixture into the first compression chamber. Motion of the piston toward the second combustion sub-chamber enables the second fuel-air mixture to flow into the first combustion sub-chamber from the first combustion sub-chamber for subsequent combustion therein together with drawing of a third fuel/air mixture into the second compression chamber.

A further example of a one-stroke internal combustion engine is disclosed in <CIT>. It comprises intake, compression, combustion and exhaust chambers operating with a linear, rotary or opposed piston configuration. A crankshaft is driven as pistons are alternately ignited.

<CIT>, filed by the same applicant as the present application, refers to an opposed piston engine capable of completing the entire cycle in just one time. For this purpose, mutually opposed power cams are connected to respective rotary shafts such that reciprocation of pistons acting on power cams imparts a rotating motion to the rotary shafts to drive the engine.

Axial or barrel engines are known in the art such as the one disclosed in <CIT> having cylinders arranged around and parallel to a central shaft, like the chambers in the cylinder of a revolver. Although such motors have low frontal area with very good balance and great compactness, problems, such as poor access for maintenance, are usually found on the swashplate that is used for converting the piston thrust into rotary motion.

Although known internal combustion engines have been shown to provide a number of significant benefits, such as smaller displacement and lower emissions, there still remains a need for a simpler engine that requires much fewer auxiliary parts and higher specific power and higher power to weight ratio.

A two-stroke axial internal combustion engine is disclosed herein with which at least the above needs are met and with which further advantages and benefits are obtained.

The present two-stroke axial internal combustion engine comprises at least one cylinder, such as two or four. Other suitable number of cylinders are possible. The cylinders may be arranged to work in any desired position, such as horizontal vertical or inclined.

A piston assembly is slidably received within each cylinder. Thus, the present axial internal combustion engine comprises as many piston assemblies as cylinders. The piston assembly defines, within the cylinder, a combustion chamber and a pump chamber. The present engine in referred herein to as axial internal combustion engine since the pump chamber within the cylinder is arranged axially relative to the combustion chamber. An engine mount is provided for supporting the cylinder or cylinders. The engine mount may have an opening for receiving the piston body.

The pump chamber is intended for suction of air to be pumped into the combustion chamber. The combustion chamber is intended for compressing a fuel-air-oil mixture in one stroke of the piston assembly and subsequent explosion of the compressed fuel-air-oil mixture.

The piston assembly comprises a piston head, a piston body, and a piston rod. The piston rod has a first end that is connected to the piston head. A cam follower is attached to the piston body. The cam follower may be, for example, a roller rotatably mounted in the piston body.

The piston head is preferably frusto-conical in shape. The piston rod is connected to the piston head and the piston body so that swinging is limited. Loads are therefore withstood by the piston body and not by the piston head with no side loads being present against the cylinder and therefore with less wear. Fitting of the piston assembly within the cylinder is facilitated and opening and closing of ports are more effective.

A single power cam is provided. The above mentioned cam follower provided at the second end of the piston rod is intended to bear directly, i.e. to roll, on a surface of said single power cam. A roller bearing is preferably provided for rotation of the single power cam.

The piston assembly is configured to move along a first direction inside the cylinder causing a fuel-air-oil mixture to be drawn into the pump chamber through intake ports while transfer and exhaust ports are closed, then to move along a second, opposite direction, for pumping the fuel-air-oil mixture into the combustion chamber through transfer ports, then to move again along the first direction where the fuel-air-oil mixture is compressed by the piston assembly within the combustion chamber, and then to move again along the second direction inside the cylinder due to ignition of the compressed fuel-air-oil mixture, performing the power stroke and opening the exhaust ports such that combustion gases are exhausted out from the combustion chamber. Fresh fuel-air-oil mixture is then pumped again into the pump chamber for subsequent cycle.

Displacement of the piston assembly within the cylinder along the second, opposite direction causes the cam follower to roll onto the surface of the single power cam causing the single power cam to be rotated. This, in turn, causes an output shaft connected to the single power cam to be rotated. This is repeated for subsequent strokes of the piston assembly.

Counter cams may be provided in the output shaft for receiving corresponding counter cam followers that are mounted in the piston body coaxially with the cam followers of the piston assembly. The diameter of the counter cams is smaller than the diameter of the power cams. The counter cams are intended to prevent piston assemblies from losing contact with the single power cam.

With the configuration as described above, no crankshaft is required so that an advantageous compact design is achieved with a high power to weight ratio. Provision of a single power cam results in an efficient, robust engine with improved mass balance and low vibrations.

Within the meaning of the present disclosure, a one-stroke refers to an engine that requires one single power stroke to rotate the power cam <NUM>° completing the cycle.

The cam follower may be provided with at least one channel for the passage of lubricant. Also, the cam follower may preferably be arranged to act close to a central area of the surface of the single power cam. Other configurations are possible.

As stated above, a number of cylinders may be provided each with a corresponding piston assembly slidably received there within. In that case, still a single power cam is associated with all the piston assemblies. Also in that case, a pump chamber and a combustion chamber as stated above are defined by each piston assembly within each cylinder.

The cylinder may include a single crankcase that is part of the pump chamber. Said single crankcase is associated with a piston assembly. A common crankcase for the cylinders may be provided. Said common crankcase may be integrally formed with the engine mount, or it may be a separate part.

Fuel control means are preferably provided for adjusting the amount of fuel and/or air entering the cylinders. The fuel control means may be, for example, at least one carburetor, or a fuel injection system. In any case, it may be advantageous that the fuel control means are arranged in the above mentioned common crankcase, if provided.

At least one intake port may be provided for the intake of the fuel-air-oil mixture into the pump chamber of the cylinder. At least one transfer port may be provided for the flow of the fuel-air-oil mixture from the pump chamber into the combustion chamber of the cylinder. At least one exhaust port may be provided for the exhaust of combustion gases out of the engine. The exhaust port may be preferably arranged to open before the transfer port opens and to close after the transfer port closes.

One or more longitudinal guides may be advantageously provided for guiding the piston body of the piston assembly as it is moved within the cylinder. Optimally, at least one longitudinal guide provided in an outermost part of the engine mount is larger than other longitudinal guides arranged at other locations of the piston assembly.

In the axial internal combustion engine described above, a clearance volume, that is, a part of the cylinder volume that is not swept by the piston, is advantageously very small. This results in a higher compression ratio, volumetric efficiency, and enhanced cooling capacity. In has been found that, for the same power, costs are significantly lower as compared to standard internal combustion engines. The present engine is lightweight, and it easily spins up which is beneficial in flying vehicles such as model airplanes. The present engine also finds advantageous application in cars and many other.

A non-limiting example of the present two-stroke axial internal combustion engine will be described in the following, with reference to the appended drawings.

A non-limiting example of a two-stroke axial internal combustion engine <NUM> for a model airplane is shown in <FIG> of the drawings and described below.

The two-stroke axial internal combustion engine <NUM> comprises four cylinders <NUM> each having a cylinder head <NUM> as shown in <FIG> and <FIG>. The cylinders <NUM> are supported by an engine mount <NUM> as shown in <FIG> of the drawings. A different number of cylinders <NUM> is of course possible depending on the specific application of the engine <NUM>. As shown in <FIG>, the engine mount <NUM> has an opening <NUM> suitable for receiving the piston body <NUM>. The piston body <NUM> can be thus fully received into the engine mount <NUM>. The opening <NUM> is defined by spaced apart walls <NUM> inside the engine mount <NUM>.

Within each cylinder <NUM>, a piston assembly <NUM> is slidably received as shown in <FIG>. The piston assembly <NUM> is shown in detail in <FIG> of the drawings. In use, the piston assembly <NUM> reciprocates along a longitudinal axis L of the cylinder <NUM> depicted in <FIG> of the drawings.

As shown in <FIG>, the piston assembly <NUM> comprises a piston head <NUM>, a piston body <NUM>, and a piston rod <NUM>. A cam follower <NUM> is attached to the piston body <NUM>. In use, the piston rod <NUM> connects the piston head <NUM> with the piston body <NUM> together, as shown in <FIG>. In particular, referring to <FIG> of the drawings, the piston rod <NUM> has one end connected to the piston head <NUM> through a connecting clip <NUM>. The connecting clip <NUM> has two arms, as shown in <FIG>. In use, the arms of the connecting clip <NUM> pass through an opening <NUM> formed in a connecting body <NUM> formed inside the piston head <NUM>. In turn, the arms of the connecting clip <NUM> are received into and press against an annular groove <NUM> formed said end of the piston rod <NUM>, as shown in <FIG>. In this way, the piston rod <NUM> is connected to the piston head <NUM> with a little swinging freedom.

As shown in <FIG>, each piston assembly <NUM> defines, within the corresponding cylinder <NUM>, a combustion chamber <NUM> and a pump chamber <NUM>.

The combustion chamber <NUM> may be also referred herein to as compression chamber since it is configured to receive a fuel-air-oil mixture to be compressed by the piston assembly <NUM> in one stroke of the combustion engine <NUM>.

The pump chamber <NUM> is arranged axially relative to the combustion chamber <NUM> along said longitudinal axis L of the cylinder <NUM>. The pump chamber <NUM> may be also referred to as sweeping chamber since it is configured to draw air there from a common crankcase <NUM> into the combustion chamber <NUM> in the stroke of the combustion engine <NUM>.

Reference is now made to <FIG> of the drawings where the piston assembly <NUM> is shown with the piston head <NUM> connected with the piston body <NUM> through the piston rod <NUM> as described above. The piston rod <NUM> has a first end that is connected to the piston head <NUM> and a second end that is connected to the piston body <NUM>.

A number of parallel channels <NUM>, shown in detail in <FIG>, are provided in the piston body <NUM>. The channels <NUM>, in turn, are provided with ports <NUM> for cooling and delivery of lubricant. The channels <NUM> in the piston body <NUM> are configured for receiving longitudinal guides <NUM> formed in the engine mount <NUM> as shown in <FIG>. In use, the longitudinal guides <NUM> guide the piston body <NUM> as it is moved within the engine mount <NUM>. Longitudinal guides <NUM> located at an outermost part of the engine mount <NUM> are larger than other longitudinal guides <NUM> located at other locations of the engine mount <NUM>.

A single power cam <NUM> is provided as shown in <FIG>. The single power cam <NUM> is attached to an output shaft <NUM>. The output shaft <NUM> is in turn attached to a propeller carrier as shown in the figures.

The above mentioned cam follower <NUM> of each piston assembly <NUM> is intended to bear directly on a surface <NUM> in the single power cam <NUM>. In particular, the cam follower <NUM> is arranged to act close to a central area of the surface of the single power cam <NUM>. In operation, a displacement of the piston assembly <NUM> within the cylinders <NUM> causes the cam follower <NUM> of the piston assembly <NUM> to roll onto said surface <NUM> of the single power cam <NUM> causing the single power cam <NUM> with the output shaft <NUM> to be rotated together. The single power cam <NUM> is supported in rotation by a roller bearing <NUM> as shown in <FIG>.

As a result of the above configuration, no crankshaft is required so a compact design is achieved with a high power to weight ratio and an improved mass balance with low vibrations.

Referring now to <FIG>, counter cams <NUM> are formed in the output shaft <NUM>. Counter cams <NUM> are intended to receive corresponding counter cam followers <NUM>. The opening <NUM> in the engine mount <NUM> is suitable for receiving the counter cams <NUM>. As shown in <FIG>, counter cam followers <NUM> are mounted in the piston body <NUM> coaxially with the cam followers <NUM> of the piston assembly <NUM>. As shown in <FIG>, the diameter of the counter cams <NUM> is smaller than the diameter of the power cam <NUM>. The counter cams <NUM> are intended to prevent piston assemblies <NUM> from losing contact with the single power cam <NUM>.

Each cylinder <NUM> includes a single crankcase that is part of the pump chamber <NUM>. Further, the above mentioned common crankcase <NUM> that is part of the engine mount <NUM> is also provided as shown in <FIG> and <FIG> of the drawings.

For adjusting the amount of fuel and/or air entering the cylinders <NUM>, in particular, entering the pump chamber <NUM> of cylinders <NUM>, fuel control means <NUM> are provided in the above mentioned common crankcase <NUM>. In the non-limiting example shown in the figures, the fuel control means <NUM> comprises one or more carburetors. Other fuel control means <NUM>, for example, based on fuel injection, may be possible.

Intake of a fuel-air-oil mixture into the pump chamber <NUM> is carried out through intake ports <NUM> formed in the engine mount <NUM> as shown in <FIG>. Transfer ports <NUM> are provided for the flow of the fuel-air-oil mixture from the pump chamber <NUM> into the combustion chamber <NUM> within the cylinders <NUM> as shown in <FIG>. Exhaust ports <NUM> shown in <FIG>, <FIG> are also provided for the exhaust of combustion gases out of the engine <NUM> through corresponding exhaust pipes <NUM>. The exhaust ports <NUM> are arranged to open before the transfer ports <NUM> open and to close after the transfer ports <NUM> close.

In operation, the piston assembly <NUM> first moves along a first direction inside the cylinder along said longitudinal axis L of the cylinder <NUM> causing a fuel-air-oil mixture coming from carburettors <NUM> to be drawn into the pump chamber <NUM> through intake ports <NUM> while transfer ports <NUM> and exhaust ports <NUM> are closed. The piston assembly <NUM> then moves along a second, opposite direction along said longitudinal axis L of the cylinder <NUM> pumping the fuel-air-oil mixture through transfer into the combustion chamber <NUM>. The piston assembly <NUM> then moves again along the first direction where the fuel-air-oil mixture is compressed by the piston assembly <NUM> within the combustion chamber <NUM>. Finally, the piston assembly <NUM> moves along the second direction inside the cylinder <NUM> due to ignition of the compressed fuel-air-oil mixture by spark plugs <NUM> performing the power stroke and opening the exhaust ports <NUM> such that combustion gases are exhausted out from the combustion chamber <NUM> through exhaust pipes <NUM>. Fresh fuel-air-oil mixture is then pumped again into the pump chamber <NUM> for subsequent cycle. This is repeated for subsequent strokes of the piston assembly <NUM> causing the cam followers <NUM> to roll onto the surface <NUM> of the single power cam <NUM> so that the single power cam <NUM> is rotated and thus the output shaft <NUM> that is connected thereto.

As the piston assembly <NUM> moves within the cylinder <NUM>, the transfer port <NUM> and the exhaust port <NUM> are opened and closed correspondingly. An intake leaf valve is provided in the intake port <NUM> that is driven as the piston assembly <NUM> moves within the cylinder <NUM>. The intake leaf valve opens and closes under internal pressure on the cylinder <NUM>.

The scope of the present disclosure should not be limited by the particular example disclosed herein but should be determined only by the claims that follow.

Claim 1:
Two stroke axial internal combustion engine (<NUM>) comprising at least one cylinder (<NUM>) supported by an engine mount (<NUM>) and a piston assembly (<NUM>),
characterized in that the piston assembly (<NUM>) is slidably received within the cylinder (<NUM>) defining a combustion chamber (<NUM>) and a pump chamber (<NUM>) arranged axially relative to each other, the piston assembly (<NUM>) being configured to move along a first direction inside the cylinder (<NUM>) causing a fuel-air-oil mixture to be drawn into the pump chamber (<NUM>), then to move along a second, opposite direction, for pumping the fuel-air-oil mixture into the combustion chamber (<NUM>), then to move again along the first direction where the fuel-air-oil mixture is compressed by the piston assembly (<NUM>) within the combustion chamber (<NUM>), and then to move again along the second direction inside the cylinder (<NUM>) due to ignition of the compressed fuel-air-oil mixture,
and wherein the piston assembly (<NUM>) comprises:
- a piston head (<NUM>),
- a piston body (<NUM>), and
- a piston rod (<NUM>) having an end (<NUM>) connected to the piston head (<NUM>);
- a cam follower (<NUM>) attached to the piston body (<NUM>) to bear directly on a surface (<NUM>) of a single power cam (<NUM>), whereby displacement of the piston assembly (<NUM>) within the cylinder (<NUM>) causes the cam follower (<NUM>) to roll onto the surface (<NUM>) of the single power cam (<NUM>) causing the single power cam (<NUM>) to be rotated.