GB2121107A

GB2121107A - Supercharged opposed piston internal combustion engine

Info

Publication number: GB2121107A
Application number: GB08314565A
Authority: GB
Inventors: Brian Carchpole
Original assignee: Commonwealth of Australia
Current assignee: Commonwealth of Australia
Priority date: 1982-05-31
Filing date: 1983-05-26
Publication date: 1983-12-14
Also published as: FR2527687A1; AU1486483A; DE3319720A1; GB8314565D0

Abstract

The engine cylinder (12) has two opposed pistons (13, 14) connected to crankshafts (20, 21) which are coupled for synchronous rotation. Inlet (16) and outlet (17) ports open when the pistons are furthest apart. The supercharging blower (11) comprises a rotor (42) eccentrically mounted in a chamber (40), vanes (43) being pivotally mounted to the rotor so as to engage the chamber walls under centrifugal action. The pivoted inner edges (44) of the vanes lead the trailing outer edges (45) so that back pressure can be relieved around the vane outer edges, e.g. if the engine backfires. The vanes are complementary to the rotor outer surface and can retract onto the rotor. <IMAGE>

Description

SPECIFICATION Power source This invention relates to power sources and is particularly applicable to power sources for remotely controlled aircraft but the invention is not limited to this particular application.

Remotely controlled aircraft requiring relatively small power sources are well known, particularly as a hobby. Such aircraft require a compact and sufficiently powerful power source but many of the engines known in the past are not suitable for powering aircraft having wingspans of several metres. Such aircraft are required for carrying larger loads such as cameras for surveying and reconnaissance purposes.

Accordingly it is an object of the present invention to provide a power source which can be made relatively simple and compact so as to be adapted for use in small aircraft.

According to the present invention there is provided a power source including an internal combustion engine and a feed blower, the engine including: a cylinder, two opposed pistons within the cylinder and defining a combustion chamber between the pistons, an inlet port in the cylinder for admitting a fuel charge to the combustion chamber, and an exhaust port in the cylinder for exhausting combustion products from the combustion chamber, the two pistons being movable towards each other within the cylinder during a compression stroke to compress the fuel charge and being movable away from each other during an expansion stroke upon ignition of the compressed charge, the feed blower being arranged to force the fuel charge through the inlet port into the combustion chamber under pressure, the feed blower including: a pumping chamber having internal chamber walls, a driven rotor eccentrically mounted within the pumping chamber, at least one pumping vane having an inner edge pivotally connected to the rotor and an outer edge operable to engage the pumping chamber walls under centrifugal force during rotation of the rotor and to pivotally retract towards the rotor, an intake port for receiving a fluid used in the fuel charge, the intake port being located in the pumping chamber wall at an expansion side thereof where the outer edge of the or each vane moves outwardly away from the rotor under centrifugal force, an outlet port located in the pumping chamber wall at a compression side thereof where the outer edge of the or each vane retracts inwardly towards the rotor where the chamber side wall approaches the eccentrically mounted rotor, the outlet port being in communication with the inlet port of the cylinder to supply the fluid under pressure to the engine. Preferably the rotor is driven in a direction such that the outer edge of the or each vane trails behind the inner edge thereof whereby any fluid back pressure transmitted through the outlet port can be relieved between the vane outer edge and the chamber walls by pivoting of the vane towards the rotor. This arrangement can be made quite compact and can be of relatively simple construction.

Preferably the or each vane is curved across its radial width to provide opposite concave and convex surfaces, the concave surface facing towards the rotor and being generally complementary to the outer surface of the rotor so that the vane can pivot to a fully retracted position with the concave surface closely overlying the rotor outer surface. In the preferred construction of the feed blower a plurality of pumping vanes are provided, each vane being pivotally connected to the rotor and arranged so that the vanes when fully retracted cover substantially the entire.

circumference of the rotor.

The engine may include two crank-shafts to which the pistons are respectively connected by connecting rods, the crank-shafts being coupled together for synchronous rotation.

The inlet port may be comprised by one or more apertures in the cylinder arranged to be uncovered and thereby opened by one of the pistons as it reaches its outermost extent of movement, the outlet port being comprised by one or more apertures in the cylinder arranged to be uncovered and thereby opened by the other of the pistons as it reaches its outermost extent of movement, the inlet and outlet ports being both open simultaneously whereby admission of the fuel charge under pressure through the inlet port forces at least part of the combustion products out through the exhaust port.

A possible preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a part sectional view of a power source according to the present invention, and Figure 2 is a sectional view along the line Il-Il of Figure 1.

The power source illustrated includes an internal combustion engine 10 and a feed blower 1 The engine 10 includes a cylinder 12 and two opposed pistons 13, 14 within the cylinder 12 and defining a combustion chamber 1 5 between the pistons 13, 14. An inlet port 1 6 in the cylinder 12 is provided for admitting a fuel charge such as an air/fuel mixture to the combustion chamber 1 5. An exhaust port 1 7 is provided in the cylinder 1 2 for exhausting combustion products from the combustion chamber 15.

The two pistons 13, 14 are movable towards each other within the cylinder 1 2 during a compression stroke to compress the fuel charge and are movable away from each other during an expansion or power stroke upon ignition of the compressed charge, e.g. by spark plug 1 9.

The engine 10 includes two crank-shafts 20, 21 to which the pistons 13, 1 4 are respectively connected by connecting rods 22, 23. The crank shafts 20, 21 are coupled together for synchronous rotation. The two crank-shafts 20, 21 are rotatable about respective axes which are parallel to each other. The two crank-shafts 20, 21 are coupled together for synchronous rotation by providing pulley wheels 24, 25 or the like at corresponding ends of the crank-shafts 20, 21 around which a toothed belt 26 or the like runs so that the crank-shafts 20, 21 will rotate in synchronism. It will be appreciated that a chain and sprocket arrangement or an equivalent mechanism could be used as an alternative.

The engine 10 may be arranged to operate as a four stroke engine. However preferably the engine 10 is a two stroke engine so that each relative approach of the pistons 13, 1 4 is a compression stroke and each relative separation constitutes an expansion or power stroke of the engine 10. The two pistons 13, 14 are arranged to approach each other most closely at a central portion of the cylinder 1 2 at which position there is provided the spark plug 1 9 for igniting the compressed air/fuel mixture to initiate the expansion stroke.

The inlet port 1 6 is provided at or towards one end of the cylinder 12 and the exhaust port 17 at the opposite end of the cylinder 12. The inlet and exhaust ports 16, 17 may be opened and closed by means of associated valves which may be operated from a cam-shaft in generally conventional manner. However, in the preferred embodiment illustrated the inlet and exhaust ports 16, 17 are arranged to be opened and closed by the respective pistons 14, 1 3. That is, the inlet port 1 6 is comprised by apertures 28 in the cylinder 1 2 arranged to be uncovered and thereby opened by the piston 14 as it reaches its outermost extent of movement as shown in Figure 1.The outlet port 1 7 is comprised by apertures 29 in the cylinder 12 arranged to be uncovered and thereby opened by the other piston 1 3 as it reaches its outermost extent of movement (Figure 1). The inlet and outlet ports 16, 17 are both open simultaneously whereby admission of the fuel charge under pressure through the inlet port 1 6 forces at least part of the combustion products out through the exhaust port 1 7.

The inlet port 1 6 is in communication with an inlet manifold 30 extending around the inside of the cylinder 1 2. Similarly the exhaust port 1 7 is in communication with an exhaust manifold 31 (Figure 2) extending around at least part of the outside of the cylinder 1 2.

The power source illustrated also includes a feed blower 11 arranged to force the fuel charge through the inlet port 1 6 into the combustion chamber 1 5 under pressure. In the drawings the blower 11 receives an air/fuel mixture from the mixing device 34 which receives fuel through inlet 35 and air through inlet 36. It will be appreciated that other arrangements are possible. For example blower 11 may be arranged to compress air to which fuel is added after the compression process.

The introduction of the air/fuel mixture under pressure is desirable for rapidly introducing the air/fuel charge into the cylinder 12 and in the preferred arrangement of the engine 10 illustrated, introduction of the air/fuel mixture into the cylinder 12 through inlet port 1 6 under pressure forces at least part of the combustion products out of the exhaust port 1 7.

The blower 11 is shown as a centrifugal pump driven by the crank-shaft 20 of the engine 10, through appropriate gearing if necessary.

The centrifugal pump illustrated includes a pumping chamber 40 having internal chamber walls 41 and a driven rotor 42 eccentrically mounted within the pumping chamber 40. The blower 11 includes three pumping vanes 43, each having an inner edge 44 pivotally connected to the rotor 42 and an outer edge 45 operable to engage the pumping chamber walls 41 under centrifugal force during rotation of the rotor 42 and to pivotally retract towards the rotor 42.

The blower 11 includes an intake port 46 for receiving the air/fuel mixture, the intake port 46 being located in the pumping chamber wall 41 at an expansion side (left side in Figure 2) where the outer edge of each vane 43 moves outwardly away from the rotor 42 under centrifugal force.

The blower 11 also includes an outlet port 47 located in the pumping chamber wall 41 at a compression side (right side of chamber 40 in Figure 2) where the outer edge 45 of each vane 43 retracts inwardly towards the rotor 42 where the chamber side wall 41 approaches the eccentrically mounted rotor 42. The output port 47 is in communication through line 48 and inlet manifold 30 with the inlet port 16 of the cylinder 12 to supply the air/fuel mixture under pressure to the engine.

The rotor 42 is driven in the direction of arrow A in Figure 2 such that the outer edge 45 of each vane 43 trails behind the inner edge 44 thereof whereby any fluid back pressure transmitted through the outlet port 47 can be relieved between the vane outer edge 45 and the chamber walls 41 by pivoting of the vane 43 towards the rotor 42.

The blower 11 includes a housing 50 which defines the pumping chamber 40. The pumping chamber 40 may be substantially cylindrical having a pair of opposed end walls (not shown), one of which may be defined by a removable cover plate enabling access to the chamber 40 for assembly and maintenance purposes. The associated crank-shaft 20 may extend through the other end wall.

Preferably the outlet port 47 is located so that the fluid does not expand when entering the outlet port 47 since this would be wasteful of the work input to the rotor 42.

The rotor 42 is substantially cylindrical and preferably has its drive shaft 51 constituted by the associated crank-shaft 20, i.e. the crank-shaft which passes through the chamber end wall remote from the cover plate. The drive shaft 51 may be supported by suitable bearings (not shown).

The vanes 43 are preferably generally rectangular. Also, as can be seen in Figure 2, each vane 43 is curved across its radial width to provide opposite concave and convex broad surfaces 52, 53, the concave surface 52 facing towards the rotor 42 and being generally complementary to the outer surface of the rotor 42 so that the vane 43 can pivot to a fully retracted position with the concave surface 52 closely overlying the rotor outer surface -- see uppermost vane in Figure 2.

With rotation in the direction of arrow A in Figure 2, fluid (air, fuel or the air/fuel mixture) is compressed in front of the convex vane surfaces 53 and fluid is drawn into the pumping chamber 40 from behind the concave vane surfaces 52 as the vanes 43 sweep past the inlet port 46.

The three vanes 43 have radial widths such that the vanes 43 substantially cover the entire rotor curved surface or circumference if all the vanes 43 are fully retracted onto the rotor 42.

That is, with the three vanes 43 provided, each has a concave surface radius of curvature the same as the radius of the outer surface of the rotor 42 and each vane width is approximately equal to one third of the circumference of the rotor 42.

Each vane 43 is provided with an enlarged pivoting head at its inner edge 44, the rotor 42 being provided with a complementary groove 55 having a restricted opening 56 in the radially outer portion of the groove 55, the pivoting head being received within the groove 55 and the restricted opening 56 preventing radial removal of the pivoting head from the groove 55. The pivoting heads extend along the inner edges 44 and the grooves 55 are parallel to the axis of rotation of the rotor 42. Each vane 43 can be assembled with the rotor 42 by sliding the pivoting head into the complementary groove from one end of the cylindrical rotor 42.

The pumping vanes 43 may be made of any suitable material. Preferably a rigid wear-resistant material such as metal is used.

It will be seen that excessive back-pressure in the outlet 47 will not damage the pump described since the vanes 43 can pivot towards the rotor 42 in response to any excessive back-pressure to allow pressure relief between the outer edges 45 of the vanes 43 and the chamber side walls 41.

Thus backfiring in the internal combustion engine 10 will not damage this type of pump.

Claims

1. A power source including an internal combustion engine and a feed blower, the engine including: a cylinder, two opposed pistons within the cylinder and defining a combustion engine between the pistons, an inlet port in the cylinder for admitting a fuel charge to the combustion chamber, and an exhaust port in the cylinder for exhausting combustion products from the combustion chamber, the two pistons being movable towards each other within the.cylinder during a compression stroke to compress the fuel charge and being movable away from each other during an expansion stroke upon ignition of the compressed charge, the feed blower being arranged to force the fuel charge through the inlet port into the combustion chamber under pressure, the feed blower including:: a pumping chamber having internal chamber walls, a driven rotor eccentrically mounted within the pumping chamber, at least one pumping vane having an inner edge pivotally connected to the rotor and an outer edge operable to engage the pumping chamber walls under centrifugal force during rotation of the rotor and to pivotally retract towards the rotor, an intake port for receiving a fluid used in the fuel charge, the intake port being located in the pumping chamber wall at an expansion side thereof where the outer edge of said at least one vane moves outwardly away from the rotor under centrifugal force, an outlet port located in the pumping chamber wall at a compression side thereof where the outer edge of said at least one vane retracts inwardly towards the rotor where the chamber side wall approaches the eccentrically mounted rotor, the outlet port being in communication with the inlet port of the cylinder to supply the fluid under pressure to the engine, the rotor being driven in a direction such that the outer edge of said at least one vane trails behind the inner edge thereof whereby any fluid back pressure transmitted through the outlet port can be relieved between the vane outer edge and the chamber walls by pivoting of the vane towards the rotor.

2. A power source as claimed in Claim 1 wherein said at least one vane is curved across its radial width to provide opposite concave and convex surfaces, the concave surface facing towards the rotor and being generally complementary to the outer surface of the rotor so that the vane can pivot to a fully retracted position with the concave surface closely overlying the rotor outer surface.

3. A power source as claimed in Claim 2 wherein a plurality of pumping vanes are provided, each vane being pivotally connected to the rotor and arranged so that the vanes when fully retracted cover substantially the entire circumference of the rotor.

4. A power source as claimed in Claim 1 wherein said at least one vane is provided with an enlarged pivoting head at its inner edge, the rotor being provided with a complementary groove having a restricted opening in the radially outer portion of the groove, the pivoting head being received within the groove and the restricted opening preventing radial removal of the pivoting head from the groove.

5. A power source as claimed in Claim 1 wherein the engine includes two crank-shafts to which the pistons are respectively connected by connecting rods, the crank-shafts being coupled together for synchronous rotation.

6. A power source as claimed in Claim 1 wherein the inlet port is comprised by an aperture in the cylinder arranged to be uncovered and thereby opened by one of the pistons as it reaches its outermost extent of movement, the outlet port being comprised by an aperture in the cylinder arranged to be uncovered and thereby opened by the other of the pistons as it reaches its outermost extent of movement, the inlet and outlet ports being both open simultaneously whereby admission of the fuel charge under pressure through the inlet port forces at least part of the combustion products out through the exhaust port.

7. A power source constructed and arranged substantially as hereinbefore described and shown in the accompanying drawings.