WO2013108277A1

WO2013108277A1 - Two-stroke internal combustion engine with a cylinder subdivided along the axis

Info

Publication number: WO2013108277A1
Application number: PCT/IT2012/000403
Authority: WO
Inventors: Roland HOLZNER
Original assignee: Aspa S.R.L.
Priority date: 2012-01-17
Filing date: 2012-12-28
Publication date: 2013-07-25
Also published as: ITMO20120012A1

Abstract

A two-stroke internal combustion engine with axially subdivided cylinder, comprises two parts in which there are suction, transfer and exhaust ports and ducts; and the cylinder is subdivided independently of and separately from the constructive form of the other parts constituting the engine and equipped with a barrel in the reassembled cylinder fixed to the engine casing; namely a barrel (8) is made in one single part and is separable from the parts (2, 3) of the cylinder and from the other parts of the engine; or, a barrel (38) is made separate from the cylinder (31) and in two parts (51, 52) which are housed, when joined, in the reassembled cylinder; finally, a barrel (68) is made by deposit of hard material (69) on the internal cylindrical wall of the two parts (61, 62) of the cylinder (61).

Description

TWO-STROKE INTERNAL COMBUSTION ENGINE WITH A CYLINDER SUBDIVIDED ALONG THE AXIS

Field of the invention

The present invention relates to a two-stroke internal combustion engine with axially subdivided cylinder, namely an internal combustion engine where the piston carries out the reciprocating motion in a cylinder which is subdivided into two parts in the direction of the axis of the same cylinder.

Known art

The background art includes different types of single-cylinder and multi- cylinder internal combustion engines with axially subdivided cylinder in which for constructive reasons and production cost reduction the engine casing and the cylinder and sometimes also the head are made joined, but with a parting plane which coincides with an axial plane containing also the axis of the driving shaft. Indeed, in this way the construction is rendered simpler and less expensive due to the fewer coupling works, which are necessary when engines are constructed in the usual way with head separated from the cylinder and the cylinder separated from the engine casing or engine bed in the four-stroke engines, and also the same is in turn constructed in two parts to house the driving shaft in a more advantageous way, particularly in the two-stroke single-cylinder engines.

In the technique, as previously said, a document DE 1993272 is known in which a two-stroke single-cylinder internal combustion engine is described which is made with the cylinder subdivided into two halves in connection with the engine casing and also, in an embodiment for air-cooled engine, in a single piece with the head. As previously said the purpose of joining the parts and subdividing on an axial plane is to simplify the construction, so the proposed solutions include the execution of the parting of the cylinder always in connection with the engine casing or in connection with the head.

Indeed, the engine casing in the two-stroke engines is intended to work as pump casing and therefore it is an important part of the engine for its volumetric functioning.

Moreover, in the technique the document DE 2718162 is known where a two- stroke cycle single-cylinder engine is described where the head and the liner in the cylinder are made in a single piece; so, in order to house said liner and head in a single piece, also the engine casing and the cylinder are made in two halves subdivided on an axial plane containing the rotation axis of the driving shaft.

Moreover, in said background art a response is not given relatively to the execution versatility of a cylinder for two-stroke internal combustion engine, advantageously of the single-cylinder type, in which intervention may be possible several times for maintenance or for preparation of the same for specific performance in the power curve or torque curve which may be necessary in use. This is particularly important when the engine must be used in sports competitions such as go-kart competitions.

Finally, also in the field of the multi-cylinder engines, modular disassembly of the engine body is often sought, to obtain construction savings seeking modularity, namely to be able to indifferently mount engines with few or many cylinders, as well as to drastically reduce construction costs. This causes quite complex constructions in the need to make an engine-cylinders-heads casing assembly which is made with complex means and tensioned tie rods between the parts, having to be rigid so as to ensure a correct engine functioning during the expected duration of the same.

This background art is susceptible to important improvements relatively to the possibility to produce a two-stroke internal combustion engine with axially subdivided cylinder which overcomes the aforementioned drawbacks and makes the construction, the maintenance and the specific preparation of the engine performance functional to the immediate needs of the user. Therefore, the technical problem which is at the base of the present invention is to produce a two-stroke internal combustion engine with axially subdivided cylinder where the constructor realises the greatest savings in the construction, being then able to allow the user or the maintenance-operator an easier change or replacement of the engine parts as the barrel, the piston and the configuration of the ports, successively to the construction.

A further and not least aim of the present invention is to produce an internal combustion engine with reduced mass and unaltered performance, still maintaining a simple configuration, typical of the two-stroke cycle internal combustion engines, which may also be configured as desired by the user also after the construction and in very short intervention times.

Finally, a further part of the aforesaid technical problem is to make it very fast to construct the engine without altering the final performance also reaching the further purpose to reduce the masses of the engine limiting the thicknesses of the walls or superposition of thicknesses of different parts and to allow the use inside the cylinder of insulating layers for fluids and gases at the entry into and exit from the cylinder. Summary of the invention

This problem is solved, according to the present invention, through a two-stroke internal combustion engine with axially subdivided cylinder, comprising two parts in which there are suction, transfer and exhaust ports and ducts; characterised in that the cylinder is subdivided independently of and separately from the constructive form of the other parts constituting the engine and equipped with a barrel in the reassembled cylinder fixed to the engine casing.

Moreover, in a first specific constructive form: the barrel is made in a single part and is separable from the parts of the cylinder and from the other parts of the engine.

In a second and preferred constructive form: the barrel is made separated from the cylinder and made in two parts which are housed in the reassembled cylinder, when joined.

Still more, in an additional third constructive form: the barrel is made by deposit of hard material on the internal cylindrical wall of the two parts of the cylinder.

Moreover, in an improved constructive form: the parting axial plane intersects one or more intake or exhaust ducts of the fluids from the cylinder.

Still more, a specific embodiment provides one or more of the intersected ducts internally coated by insulating material for the specific fluid which runs through it.

Moreover, in the constructive forms described above also the ports and/or the ducts for the intake or exhaust fluids are made with inserts which can be replaced by similarly constructed inserts which can be housed in the same seat as said replaceable inserts, for determining specific conformations of the ports or ducts involved in the replacement.

Still more, in the constructive form with barrel separable from the cylinder, the transfer ducts are equipped with insulating inserts applied to the outside of the external cylindrical surface of the single-part or two-part barrel when housed in the reassembled two-part cylinder.

Moreover, in a specific and further embodiment each internal cylindrical surface of the two parts of the barrel subdivided into two parts, being covered by deposit of hard material.

Finally, in the aforesaid constructive forms the inlet ports and channels of the fluids into the cylinder and the exhaust or exit ports and channels of the burnt gases from the cylinder are made with precise working. The features and the advantages of the present invention in the execution of a two-stroke internal combustion engine with axially subdivided cylinder are mentioned in the following description of some illustrative and not limiting schematic execution examples, with reference to the eight enclosed sheets of drawings.

Brief description of the drawings

Figures 1 and 2 are perspective schematic views of the two halves of a cylinder for two-stroke internal combustion endothermic engine in which at the coupling of them the barrel of Figure 3 is inserted, which is also in a perspective and schematic view, according to the invention;

- Figure 4 is a schematic view from below with the transfer and stratification channels of the feeding of the assembled cylinder with the parts of previous Figures 1-3;

- Figure 5 is a schematic section V-V of Figure 4 made on the separating plane of the cylinder and with the barrel in one single piece;

- Figure 6 is a schematic section VI-VI of Figure 4 made in normal direction to the section plane of Figure 5 where the transfer ports and channels are visible;

- Figure 7 is a perspective schematic view of the assembled cylinder of Figure 4 where the transfer channels from the pump casing are visible;

- Figures 8 and 9 are perspective schematic views of the two halves of a cylinder for two-stroke internal combustion endothermic engine in which also the barrel is subdivided into two halves on the same parting plane as the cylinder, according to a further constructive form of the invention;

- Figure 10 is a schematic view from below with the transfer and stratification channels of the feeding of the assembled cylinder with the parts of the previous Figures 8-9;

- Figure 11 is a schematic section XI-XI of Figure 10 made on the separating plane of the cylinder and the barrel;

- Figure 12 is a schematic section XII-XII of Figure 10 made in normal direction to the section plane of Figure 11 where the transfer channels and ports are visible;

- Figure 13 is a perspective schematic view of the assembled cylinder of Figure 10 where the transfer channels from the pump casing are visible;

- Figure 14 is a schematic view from below with the transfer and stratification channels of the feeding of the assembled cylinder with the parts of the previous Figures 1-3 in which on the partition wall of the transfer ducts and the barrel an insert is placed made of insulating material, to prevent the fluid from receiving heat from the barrel during the transfer;

- Figure 15 is a schematic section XV-XV of Figure 14 where the transfer channels are visible which are protected by insulating inserts towards the external cylindrical surface of the barrel on which they are applied;

- Figures 16 and 17 are perspective schematic views of the two halves of a cylinder for two-stroke internal combustion endothermic engine in which: the barrel is made by deposit of hard material on the two barrel halves in the cylinder; moreover, insulating inserts are visible which are inserted inside the exhaust duct and the stratification duct, according to further constructive forms of the invention to make a light and versatile construction of internal combustion engine, and to protect the fluids from heat-exchange with the walls of the ducts. Detailed description of a preferred embodiment

Figures 1 to 7 show a first constructive form of two-stroke cycle endothermic engine in which only the cylinder 1 is represented, subdivided into two halves, the right half 2, and the left half 3, almost identical, on an axial plane to the cylinder axis and joined with reference pins 4 and connection screws 5, here schematized in the right half, by means of corresponding threaded holes 6 and reference holes 7 in the other left half, to house and tighten a barrel 8 equipped with upper lip 9 for support in the cylinder 1 and the feeding port 10, transfer ports 11 and 12, stratification port 13 and exhaust port 14. On the external cylindrical surface 15 of the barrel annular seats 16 are present with seal rings to separate the upper end 17 and lower end 18 of the barrel from the intermediate zone 19 where said ports are grouped, so as to avoid fluid leaks in the coupling between the external cylindrical surface 15 and the two internal cylindrical surface halves, the right one 21 , and the left one 22, in the cylinder 1. The transfer ducts 23 are made in the cylinder in correspondence of the transfer ports 11 and 12 and in connection with the pump casing at the base of the cylinder, not represented here because of known type. In the cylinder in correspondence of the ports in the barrel 8 an exhaust duct 24 and a stratification duct 25 are also present, for the connection of the suction duct in the pump casing with the cylinder, as known in the art.

Figures 8 to 13 show a second constructive form of two-stroke cycle endothermic engine in which only the cylinder 31 is represented, which is subdivided into two halves, the right half 32, and the left half 33, almost identical, on an axial plane to the cylinder axis and joined with reference pins 4 and connection screws 5, here schematised in the right half 32, by means of corresponding threaded holes 6 and reference holes 7 in the other left half 33, to house and tighten a barrel 38 equipped with upper lip 39 for support in the cylinder 31 and with the feeding port 40, transfer ports 41 and 42, stratification port 43 and exhaust port 44. The barrel is subdivided into two parts, here two almost identical halves are represented with their parting plane coinciding with the parting plane of the cylinder 31. The two halves of the barrel, the right half 51 , and the left half 52, corresponding to the two halves of the cylinder 31 , are housed in the internal cylindrical surface 45 of the cylinder 31 and make the same arrangement as the transfer and stratification ports and ducts as described in the first constructive form with single-part barrel 8. Also in this second constructive form the transfer ducts 53 are made in the cylinder in correspondence of the transfer ports 41 and 42 and in connection with the pump casing at the base of the cylinder, here not represented because of known type. In the cylinder in correspondence of the ports in the barrel 38 an exhaust duct 54 and a stratification duct 55 are also present, for the connection of the suction duct in the pump casing with the cylinder, as known in the art.

In Figures 14 and 15 a cylinder as represented in the first constructive form is equipped with a single-part barrel 8 which, in the external cylindrical surface 15 corresponding to the internal part of the transfer ducts 23, has insulating inserts 26 added on said cylindrical surface in such a way as to shape the respective transfer ducts and insulate the fluids passing through the transfer ducts from the heat emitted from the barrel 8, during the functioning. Thus, also the parts of barrel 38, in two halves 51 and 52 of Figures 8-13, even though not represented, can receive the application of insulating inserts analogous to the aforementioned inserts 26, in the external cylindrical surface part of the barrel part facing the transfer ducts 53, to insulate the fluids passing through the transfer ducts from the heat emitted from the same barrel part.

Figures 16 and 17 show a third constructive form of two-stroke cycle endothermic engine in which only the cylinder 61 is represented, subdivided into two halves, the right half 62, and the left half 63, almost identical, on an axial plane to the cylinder axis and joined with reference pins 4 and connection screws 5, here schematised in the right half 62, by means of corresponding threaded holes 6 or reference holes 7 in the other left half 63, to form a barrel 68 when joined, said barrel being obtained by deposit 69 of hard and abrasion-resistant material. In the cylinder 61 the usual feeding port 70, transfer port 71 , stratification port 73 and exhaust port 74 are made. The cylinder and therefore the barrel so obtained by deposit of hard material is subdivided into two parts, here two halves are represented coinciding with the parting plane of the cylinder 61. The two parts of cylinder, the right part 62, and the left part 63, may also not be similar or specular as represented, but subdivided with levels intersecting on the cylinder axis and having between each other an angle in a field of the neighbourhood of a straight angle. The transfer ducts 72 are made in the cylinder in correspondence of the transfer ports 71 and in connection with the pump casing at the base of the cylinder, here not represented because of known type. In the cylinder 61 an exhaust duct 75 and a stratification duct 76 are also present, for the connection of the suction duct in the pump casing with the cylinder, as known in the art. Moreover, the exhaust duct 75 is coated by insulating material with deposit 77 of high-temperature resistant material in the two halves of the duct, each in a respective half 62 and 63 of the cylinder; in a similar way, the stratification duct 76 is coated by insulating material with deposit 78 of medium and low temperature resistant material. Thus the burnt gases exiting the cylinder transmit little heat through the wall of the exhaust duct 75 to the cylinder 61 and, the latter, due to the thermal conductivity of the metal it is made of, does not transmit heat to the cool fluids entering the cylinder by means of the stratification duct 76.

The functioning of a two-stroke internal combustion engine with axially subdivided cylinder according to the invention occurs as known in the art for the two-stroke engines, but the steps of construction, assembly preparation and maintenance or modification or elaboration, being final or extemporary, occur as follows.

In the constructive form with single-part barrel, the barrel 8 is housed within the two cylinder parts and seals with construction precision with the seal rings 16 placed to define the intermediate zone 19 of the ports of the cylindrical external surface 15 of the barrel. The so assembled cylinder 1 can be housed on the respective engine casing and realise the two-stroke cycle internal combustion engine of the invention. Moreover, for possibly intervening in the maintenance, or in the preparation of the engine, for specific engine performance requirements, as it generally happens in the single-cylinder engines for go-kart competitions, the user, simply without dismounting the engine casing, can dismount the head and the cylinder from the engine casing and disassemble the cylinder itself getting very quickly to the inlet, transfer, stratification or exhaust ports being able to modify them, in the cylinder or in the barrel itself, or also being able to replace the external parts of the cylinder with others having a more suitable shape of the ducts for the desired results. Moreover, considering the strongly restrictive rules on the re-boring of pistons/barrels used in sports competitions, it is also possible to replace only the barrel and the piston housed therein with the only cost of the barrel and the piston, bringing the so assembled engine back within the limits prescribed by the aforementioned rules. Moreover, the single-part barrel extractable from the cylinder and the cylinder in two halves allow a precise mechanical work of the ports and their further modification, always by means of mechanical work, but with certainty to carry out dimensionings of said ports or ducts of the fluids which have not been possible so far with the known and applied construction methods.

The possibility to intervene on the ports which are on the barrel and on the ducts present in the cylinder parts also allows to pre-order the construction of inserts with standardised contour which can be replaced if necessary, under construction, maintenance or, as said for the competition engines, at any time when any specific preparation occurs which the engine makeready men need to apply. This operation, with the inserts in the ports or in the ducts, makes the engine equipped with them very versatile, being it possible to prepare it for a different performance also between a run and the successive one of the sports competitions including more than one run.

What previously said for the single-part barrel constructive form can be applied, in the same way, to the constructive form with the barrel subdivided into two parts, which do not necessarily coincide with the same parting of the parts of the cylinder, as said in the text. The different parting of the internal cylindrical wall of the barrel does not create any sealing problems in the cut between the two barrel parts: indeed, it has been verified that with a simple precise cut the seal of the burnt gases and fluids inside the cylinder still remains also with the barrel subdivided into two parts in one of the known cutting or fracture ways without significant material removal. The barrel parts when joined again can operate in the same way and function as the single-part barrel as said above. Moreover, the operations of preparation, creation, housing and replacement of inserts in the ports of the barrel, when it is made in two parts, are rendered much faster and more incisive, by not operating from the exterior of the barrel, and being able to house the inserts with the two barrel parts opened. Still more, on the internal cylindrical surface of the barrel in two parts a coating of hard material can be added, as known in the art in an easy way, since it can be applied on each single part from the interior of the barrel. Still more, the seal rings 16, provided in the single-part barrel 8, in the barrel subdivided into two parts are replaced by analogous seal rings, though limited to 180°, namely to a half-circumference, on each of the two external surfaces of the subdivided barrel parts. So the versatility, simplification of the assembly, maintenance and preparation, can be further improved with the barrel subdivided into two parts, in a similar way as the adoption of the inserts added with insulating material in the stratification duct and in the exhaust duct described in Figures 16 and 17 can be matched to the constructive form with single-part barrel or with barrel subdivided into two halves.

Also the internal coating of the transfer ducts, on the external wall of the barrel of Figures 14 and 15, can be applied in combination with the inserts added in the stratification and exhaust ducts described in the Figures 16 and 17, in association also with the particular execution of the barrel with deposit of a hard material layer inside the two parts of the cylinder or the two parts of the barrel if subdivided.

Finally, as described in the text showing the constructive forms represented in the Figures: the parting of the cylinder, of the barrel and all the more the execution of the barrel by deposit of hard material on the internal surface of the cylinder, as described in the constructive form of Figures 16 and 17, render the construction of an internal combustion engine much less expensive, even though the operations following the construction do not allow such a wide possibility for modifications, which are instead possible with the single-part barrel or barrel subdivided into two parts described above.

There are many advantages in the execution and use of a two-stroke internal combustion engine with axially subdivided cylinder and each of them is very advantageous so as to be able to be profitably applied alone; but if said advantages are combined they lead to a very great overall advantage of the two- stroke internal combustion engines made according to the present invention, if compared to the engines known in the technique.

in conclusion, the most evident advantages are made through: a greater constructive simplification for high performance engines and through a significant reduction of the masses, particularly with the constructive forms of barrel obtained by deposit of hard material; easier and faster maintenance, which in the versions for competition engines leads to drastically reduce the preparation and modification costs, as well as costs for overhaul of competition engines; finally, an easier execution of constructive forms of the internal combustion engine which allows the use of operating cycles with greater and higher combustion operating temperatures, still without transmitting great part of the heat generated in the combustion to the fluid going in the suction in the stratification duct or in the transfer from the pump casing into the cylinder.

Obviously, in order to meet specific and contingent needs, a technician of the field may introduce many modifications to the two-stroke internal combustion engine with axially subdivided cylinder described above, all of them by the way falling within the scope of protection of the present invention as defined by the following claims.

Claims

1. Two-stroke internal combustion engine with axially subdivided cylinder, comprising two parts in which there are suction, transfer and exhaust ports and ducts; characterised in that the cylinder is subdivided independently of and separately from the constructive form of the other parts constituting the engine and equipped with a barrel in the reassembled cylinder fixed to the engine casing.

2. Internal combustion engine, according to claim 1 , where the barrel (8) is made in one single part and is separable from the parts (2, 3) of the cylinder and from the other parts of the engine.

3. Internal combustion engine, according to claim 1 , where the barrel (38) is made separate from the cylinder (31) and in two parts (51 , 52) which are housed, when joined, in the reassembled cylinder.

4. Internal combustion engine, according to claim 1 , where the barrel (68) is made by deposit of hard material (69) on the internal cylindrical wall of the two parts (61 , 62) of the cylinder (61).

5. Internal combustion engine, according to one of the claims 1 to 4, where the parting axial plane intersects one or more inlet ducts (25, 55, 76) or exhaust ducts (24, 54, 75) of the fluids from the cylinder.

6. Internal combustion engine, according to claim 5, where one or more of the intersected ducts is internally coated with insulating material (77, 78) for the specific fluid which runs through it.

7. Internal combustion engine, according to one of the claims 1 to 4, where the ports and/or the ducts for the inlet or exhaust fluids are made with inserts which can be replaced by similarly constructed inserts which can be housed in the same seat as said replaceable inserts, for determining specific conformations of the ports or ducts involved in the replacement.

8. Internal combustion engine, according to one of the claims 1 to 3, where the transfer ducts (23) are equipped with insulating inserts (26) applied to the exterior of the external cylindrical surface of the single-part or two-part barrel when housed in the reassembled two-part cylinder.

9. Internal combustion engine, according to claim 3, where each internal cylindrical surface of the two barrel parts (51 , 52) is covered by deposit of hard material.

10. Internal combustion engine, according to one of the claims 1 to 9, where the inlet ports and channels of the fluids into the cylinder and the exhaust or exit ports and channels of the burnt gases from the cylinder are made with precise working.