GB2258013A - Rotary piston internal combustion engine. - Google Patents

Abstract

In a stator 11 of the engine means are provided to admit a fuel 1 air mixture to operate the engine and an external slide surface 12 is provided on the stator 11 which, together with an internal surface 14 of a hollow rotor 13 which surrounds the stator 11 defines a chamber in which successive induction, compression, ignition and exhaust stages can occur during rotation of the rotor. First and second sets of vane type pistons VL and VT are slidably mounted in the wall of the rotor 13 for movement inwardly and outwardly relative to the stator, with one piston VL of the first set cooperating with a corresponding piston VT of the second set so as to form a cooperating pair of pistons which define successive induction, combustion, ignition and exhaust stages as they move around the stator. External guide means in the forms of cams C1 and C2 surround the rotor 13 and have first and second guide surfaces which are engageable respectively with the outer ends of the pistons VL, VT to control the inward and outward movement of the pistons. <IMAGE>

Description

ROTARY PISTON ENGINE This invention relates to a rotary piston type internal combustion engine which comprises a stator, a rotor, a chamber defined between the rotor and the stator, and a set of pistons carried by the rotor and movable through the chamber in order to carry out successive induction. compression, ignition and exhaust stages of operation of the engine.

Throughout the major part of this century, the reciprocating piston type of internal combustion engine has been considered to be the only practical type of engine, and particularly for propelling vehicles, whether in the form of a spark ignition engine or a compression ignition engine. and operating on the two or four stroke cycle.

However. the concept of linear reciprocation of a piston to drive a crank shaft is not a very elegant solution to the problem of providing smooth transmission of the explosive power generated in an internal combustion engine to a rotary shaft. as the mass of the piston undergoes total reversal of movement at the end of each stroke, and the forces generated by this movement must be borne by the connections between the piston and the crankshaft.

As the engine speed increases. these forces increase, and in addition unless turbocharging is provided. the efficiency of the engine tends to decrease by reason of inability to properly charge the cylinders with a proper fuel / air mixture.

Therefore, for many years engineers have striven to provide internal combustion engines in which the power generated by an explosive fuel / air mixture can be transmitted directly into rotary motion which is applied to a driven shaft. Gas turbines come into this category, but while these are satisfactory for use in aircraft (where the driven shaft operates the compressor stage of the turbine), or for use as a prime mover in large units, such as drive units of railway trains, or very large trucks, they are not practical for the smaller power outputs required by cars and most trucks.

A further example which has arisen during the last 20 years, and which appeared initially to have a significant potential. has been the rotary piston or "wankel" type engine in which a rotor in the form of a trochoid is mounted inside a stator and has "lobes" which form piston tips which sweep along the specially shaped inner chamber surface of the stator in order to progress through successive induction. compression, ignition and exhaust stages. whereby the rotor carries out an equivalent function to a linearly reciprocating piston of a standard internal combustion engine.

However, while there was initially great enthusiasm for this new type of internal combusion engine, and apparent technical and commercial potential. in practice the levels of fuel efficiency never reached satisfactory levels and there were also substantial problems of maintaining satisfactory sealing between the tips of the rotor and the inner wall of the stator housing, and also substantial problems of accelerated wear of the surfaces.

Therefore, the planned use of wankel type engines in cars has fallen away, although a small scale design has been used with some success in recent years in racing type motor cycles.

The present invention is concerned with a rotary piston type of internal combustion engine, but approaches the problem of providing satisfactory sealing between the edges of the "pistons" and the walls of the stator along which the piston edges slide from an entirely different aspect, and in a novel and technically advantageous way.

According to the invention there is provided a rotary piston type internal combusion engine which comprises: a stator; means within the stator for admitting a fuel / air mixture to operate the engine; an external slide surface on the stator; a hollow rotor which surrounds the stator and which is rotatable around the stator, the internal surface of the rotor and the external slide surface of the stator together defining a chamber in which successive induction, compression, ignition and exhaust stages can occur during rotation of the rotor; means for admitting a fuel I air mixture from the stator to the chamber to permit the induction stage to take place; means for exhausting gases from the chamber after the ignition stage;; first and second sets of vane type pistons slidably mounted in the wall of the rotor for movement inwardly and outwardly relative to the stator, with one piston of the first set co-operating with a corresponding piston of the second set so as to form a co-operating pair of pistons which define successive induction, combustion, ignition and exhaust stages as they move around the stator; and, an external guide means surrounding the rotor and having first and second guide surfaces which are engageable respectively with the outer ends of the pistons of the first and second sets in order to control the inward and outward movement of the pistons. whereby the co-operating pairs of pistons of the first and second sets carry out consecutive induction, compression, ignition and exhaust stages as each pair moves around the stator.

The external guide means having the first and second guide surfaces to engage respectively with the outer ends of the pistons of the first and second sets provides a simple and yet reliable means for controlling the necessary inward and outward movements of the pistons during rotation of the rotor, and the only essential moving parts, in addition to the rotor, will comprise the vane type pistons themselves, which can slide in and out in suitable mounting slots provided in the wall of the rotor.

The pistons of the first set of pistons will normally form the leading piston in each pair, and the generation of the explosive force from the fuel / air mixture during the ignition stage will apply a force against this leading piston which applies a power input to the rotor.

Preferably, the inner wall of the rotor has a subchamber defined therein, and the fuel / air mixture admitted during the induction stage can then undergo substantial compression into this subchamber during the compression stage prior to initiation of the ignition stage.

Preferably, a suitable pumped lubrication system is provided to apply lubricating oil to lubricate the sliding movement of the vane type pistons. but only very small amounts of lubricating oil will reach the inner ends of the pistons since the oil will tend to be dispelled outwardly under centrifugal action. However, care will be taken to ensure that a minimum necessary amount of lubricating oil in the form of small drops can reach the inner ends of the vane type pistons, to lubricate the movement of the inner ends of the pistons over the surface of the stator.

Alternatively, or in addition, the inner ends of the vane type pistons may be coated with any suitable material which will provide necessary lubrication, while being capable of withstanding the wear forces to which it will be exposed, and also the temperatures which will be generated.

In one preferred embodiment, there will be only the first and second sets of vane type blades, with each set being composed of four vanes, and the engine will then function in generally equivalent manner to a four cylinder engine. However, if it is decided to provide an arrangement which is equivalent to a more, or less than four cylinder linear reciprocating engine, different numbers of sets of vane type pistons may be provided, with suitable redesign of the shape of the external surface of the stator and the internal surface of the rotor. The numbers of sets of vanes therefore can vary from 1 to X, although in certain circumstances a balancing device may be required to balance the particular number of sets of vanes.

One embodiment of rotary piston type internal combustion engine according to the invention will now be described in detail, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a cross sectional view and in schematic form of the engine; Figures 2 and 3 are side views showing the passage of inlet and exhaust gases through the hollow stator of the engine; and, Figure 4 shows successive induction. compression, ignition and exhaust stages in a cycle of operation of the engine.

Referring now to the drawings, a rotary piston type internal combustion engine according to the invention is designated generally by reference 10, and comprises a hollow stator 11, and means within the stator for admitting a fuel / air mixture to operate the engine, and also means to exhaust the gases generated as a result of the combustion in the engine. An external slide surface 12 is provided on the stator 11, along which can sweep the inner ends of a set of vane-type pistons, as will be described in more detail below.

A hollow rotor 13 in the form of a drive ring surrounds the stator 11 and is rotatable around the stator, the internal surface 14 of the rotor and the external slide surface 12 of the stator 11 together defining a chamber in which successive induction, compression, ignition and exhaust stages can occur during rotation of the rotor.

Although not shown, any suitable coupling means will be provided to transmit drive to a rotary power output from the rotor 13.

Means is provided to admit a fuel / air mixture from the interior of the stator 11 to this chamber to permit the induction stage to take place, and to exhaust gases from this chamber after the ignition stage.

First and second sets of vane type pistons VL and VT are slidably mounted in the wall of the rotor 13 for movement inwardly and outwardly relative to the stator, with one piston VL of the first set co-operating with a corresponding piston VT of the second set so as to form a co-operating pair of pistons which define successive induction. combustion, ignition and exhaust stages as they move around the stator. This is shown in Figures 4a to 4d, in respect of a co-operating pair of leading vane type piston VL and trailing vane type piston VT. References VL1 and VT1 refer to the first or induction stage, VL2 and VT2 to the second or compression stage, and Figures 4c and 4d show the ignition and exhaust stages of these pistons.

External guide means surrounds the rotor 13 and has first and second guide surfaces which are engageable respectively with the outer ends of the pistons of the first and second sets in order to control the inward and outward movement of the pistons, whereby the co-operating pairs of pistons of the first and second sets carry out the consecutive stages of an operating cycle as each pair moves around the stator.

The external guide means comprises a pair of outer cams C2, shown in Figures 2 and 3, and a central cam C1.

Cam C1 controls the vane type pistons VL and the cams C2 control the vanes VT.

As the vanes will be rotating with the rotor 13, they will be thrown outward by centrifugal force. However, the radial displacement of the vanes will be controlled by having a suitable bearing (not shown in detail) on the outer end of each of the external parts of the vanes, which will act upon a respective one of the cams. Each bearing may comprise a hydrodynamic "sledge".

It can be seen from Figures 2 and 3 that two cams C2 are provided for a single purpose, such that the two arms on the vanes VT can act without interference from the cam C1.

The shape of the cams is identical, except that one is 1800 out of phase with the other. However, the profile of the cams could be such (along with corresponding profile of the stator) that the length of the explosion stroke could be longer than that of the compression stroke. Alternatively, the vanes VL could be advanced inwards at a greater rate than that of the vanes VT. thereby allowing the operating performance of the engine to be adjusted to suit requirements.

It will also be possible to vary the compression ratio, from cycle to cycle, depending upon the performance of the engine required. or the type of fuel which is being used.

The two different types of vane type pistons VL and VT have two distinct purposes. The purpose of vanes VT is to compress the gas / fuel mixture, and also to assist the induction of the following cycle. The purpose of the vanes VL is that they are pushed by the combusion gases and, in turn, push out the exhaust gases generated by the preceding cycle.

Although not shown, a preferred sealing system employed in the engine will comprise an oil feed, a scraper seal and a further seal. These can be of similar construction to existing designs of piston rings.

As can be seen particularly in Figures 1 and 2, the inner wall surface 14 of rotor 13 is provided with four combustion chambers 15 formed therein, and externally mounted spark plugs (not shown) will be located appropriately to cause ignition at the required times, and means may be provided to cause automatic advance or retard of the ignition to suit operating requirements.

The inward and outward movement of the vane type pistons VL and VT, during each cycle of operations, can be clearly seen from Figures 1 to 4 of the drawings, with the inner ends of the pistons sweeping over the external slide surface 12 of the stator 11 at appropriate stages in the operating cycle, but being moved radially outwardly therefrom at necessary other stages. all of this being under the control of the cam surfaces C1 and C2 engaging the outer ends of the vanes as the rotor rotates around the stator.

Claims (5)

1. A rotary piston type internal combusion engine which comprises: a stator; means within the stator for admitting a fuel / air mixture to operate the engine; an external slide surface on the stator: a hollow rotor which surrounds the stator and which is rotatable around the stator, the internal surface of the rotor and the external slide surface of the stator together defining a chamber in which successive induction, compression, ignition and exhaust stages can occur during rotation of the rotor; means for admitting a fuel / air mixture from the stator to the chamber to permit the induction stage to take place; means for exhausting gases from the chamber after the ignition stage;; first and second sets of vane type pistons slidably mounted in the wall of the rotor for movement inwardly and outwardly relative to the stator, with one piston of the first set co-operating with a corresponding piston of the second set so as to form a co-operating pair of pistons which define successive induction, compression. ignition and exhaust stages as they move around the stator; and, an external guide means surrounding the rotor and having first and second guide surfaces which are engageable respectively with the outer ends of the pistons of the first and second sets in order to control the inward and outward movement of the pistons, whereby the co-operating pairs of pistons of the first and second sets carry out consecutive induction, compression, ignition and exhaust stages as each pair moves around the stator.

2. An engine according to Claim 1, in which the inner wall of the rotor has a sub-chamber defined therein, in which fuel / air mixture admitted during the induction stage can then undergo substantial compression in the sub-chamber during the compression stage prior to initiation of the ignition stage.

3. An engine according to Claim 1 or 2, in which the profile of the external surface of the stator and the internal surface of the rotor, together with the number of vane type pistons are selected such that the engine operates in equivalent manner to a four cylinder reciprocating piston engine.

4. An engine according to any one of Claims 1 to 3, in which the external profile of the stator is generally elliptical, and the vane type pistons are slidable in slots formed in the wall of the rotor having axes which extend substantially through the intersection of the two planes of symmetry of the stator.

5. An engine according to Claim 1 and substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.