Injection system for two-stroke engines

Abstract

An electronic injection two-stroke endothermic engine comprising an upper fuel injector (13) and a lower fuel injector (14), both accommodated in an intake duct (12) directly facing the cylinder (1), the latter closed by a head to form a combustion chamber (6) with one or more spark plugs (5) and connected to a pump-crankcase underneath via a plurality of side transfer ports (7, 8) which a central transfer port (15) is added to and crosses said intake duct (12) and allows the fuel sprayed by said lower injector (14) to reach the inside of the cylinder (1).

Claims

1. A controlled ignition two-stroke endothermic engine, comprising at least one cylinder whose interior slidingly houses a piston, wherein the at least one cylinder is connected to a head on its upper side so as to define a combustion chamber, the head comprising at least one spark plug, wherein the at least one cylinder is connected to a pump-crankcase on its lower side, wherein the pump-crankcase is in communication with the at least one cylinder at least via a central transfer port, wherein the at least one cylinder is in direct communication with the external world via an exhaust duct and an intake duct, wherein the intake duct is crossed by the central transfer port, wherein further the intake duct houses on its top side an upper fuel injector and houses on its bottom side a lower fuel injector, wherein the lower fuel injector is oriented so that fuel sprayed from it reaches the inside of the at least one cylinder after first having crossed the intake duct and subsequently running the upper part of the central transfer port which connects the intake duct with said cylinder, wherein air pressure of air introduced into the at least one cylinder from the intake duct does not exceed the pressure of the external world.

2. The engine of claim 1, wherein the at least one cylinder further communicates with the pump-crankcase via at least one side transfer port.

3. The engine of claim 2, wherein the speed of the fuel sprayed by the upper fuel injector comprises a component parallel to the axis of the at least one cylinder directed toward the pump-crankcase and a component orthogonal to the central axis of the at least one cylinder directed toward the inside of the cylinder.

4. The engine according to claim 3, wherein the central transfer port crosses the part of the intake duct between the upper fuel injector and the lower fuel injector and the at least one cylinder.

5. The engine of claim 4, wherein the lower fuel injector is housed in the lower part of the intake duct so that the axis according to which it sprays the fuel crosses the central transfer port up to reaching the inside of the at least one cylinder.

6. The engine of claim 5, wherein the intake duct is subdivided into two or several parts, of which a first part is integral with the at least one cylinder and a second part comprises a separate element, integrally connected to the at least one cylinder through coupling means, wherein the second part forms a stand-alone sub-assembly.

7. The engine of claim 6, wherein the central transfer port intersects the first part of the intake duct and wherein the second part of the intake duct comprises seats for the upper fuel injector, the lower fuel injector and a lamellar pack.

8. The engine of claim 7, wherein the central transfer port is directed toward the electrode of the spark plug.

9. The engine of claim 1, wherein the speed of the fuel sprayed by the upper fuel injector comprises a component parallel to the axis of the at least one cylinder directed toward the pump-crankcase and a component orthogonal to the central axis of the at least one cylinder directed toward the inside of the at least one cylinder.

10. The engine according to claim 9, wherein the central transfer port crosses the part of the intake duct between the upper fuel injector and the lower fuel injector and the at least one cylinder.

11. The engine of claim 10, wherein the lower fuel injector is housed in the lower part of the intake duct so that the axis according to which it sprays the fuel crosses the central transfer port and reaches up to the inside of the at least one cylinder.

12. The engine of claim 11, wherein the intake duct is subdivided into two or several parts, of which a first part is integral with the at least one cylinder and a second part comprises a separate element, integrally connected to the at least one cylinder through coupling means, wherein the second part forms a stand-alone sub-assembly.

13. The engine of claim 12, wherein the central transfer port is directed toward the electrode of the spark plug.

14. The engine of claim 1, wherein the intake duct is subdivided into two or several parts, of which a first part is integral with the at least one cylinder and a second part comprises a separate element, integrally connected to the at least one cylinder through coupling means, wherein the second part forms a stand-alone sub-assembly.

15. The engine of claim 14, wherein the central transfer port intersects the first part of the intake duct and wherein the second part of the intake duct comprises seats for the upper fuel injector, the lower fuel injector and a lamellar pack.

16. The engine of claim 1, wherein the central transfer port is directed toward the electrode of said spark plug.

17. The engine of claim 1, wherein the lower fuel injector is housed in the lower part of the intake duct so that the axis according to which it sprays the fuel crosses the central transfer port and reaches up to the inside of the at least one cylinder.

18. The engine according to claim 1, wherein the central transfer port crosses the part of the intake duct between the upper fuel injector and the lower fuel injector and the at least one cylinder.

19. A method for operating a two-stroke engine realized according to claim 1, wherein whenever the power demand of the engine is low the lower injector is operated in such a way as to end fuel injection before the central transfer port is closed by the piston, by injecting the fuel into the air stream that during the descending stroke of the piston is flowing up along the central transfer port, and in that the upper injector is operated just at the minimum rate necessary to lubricate a crank-gear located in the pump-crankcase.

20. The method of claim 19, wherein as the power demand of the engine increases, the amount of fuel transferred by the lower injector increases up to its maximum capacity, wherein afterwards the upper injector progressively increases its own delivery of fuel which goes down into the pump-crankcase from which, during the next descent of said piston, fuel will enter the combustion chamber through one of the transfer ports.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a rear view of the cylinder of the endothermic engine according to the present patent application in an embodiment wherein the suction channel presents a first part integral with the cylinder (1) and a second part consisting of a stand-alone element, the latter comprising seats for an upper injector (13), a lower injector (14), and for a lamellar pack (9). The view also shows the trace of the cutting plane of the cross-section shown in the following figure.

(2) FIG. 2 shows a cross-section view wherein it is possible to look at inside the cylinder (1), with its respective longitudinal axis (X), connected to the external world via an intake duct (12) and an exhaust duct (11).

(3) FIG. 3 shows a cross-sectional view of an embodiment of the endothermic engine according to the present patent application which allows to look at the peculiar features of the invention; the piston is shown in its lower dead point.

(4) The figure shows the cylinder (1), which presents an exhaust duct (11), side transfer ports (7, 8), and a central transfer port (15). The upper inner part of said cylinder, closed by the head (3) which comprises a seat for a spark plug (5), operates as a combustion chamber (6).

(5) The figure shows an embodiment whereby the intake duct (12) is split into two parts, a former part being integral with the cylinder (1) and comprising an intersection with the central transfer port (15), and a second part, on the right-hand side of the drawing, wherein seats for the accommodation of the upper injector (13) and of the lower injector (14) are obtained, as well as a seat for the lamellar pack (9).

(6) In the side walls of the cylinder (1) the ducts for the engine cooling thermal vector fluid, typically an aqueous mixture, are visible.

(7) A crank-gear (4) is housed inside a pump-crankcase, the latter not being shown.

(8) The figure also shows the longitudinal axis (X) of the cylinder and the longitudinal axis (B) of the lower injector which, in proximity of the lower dead point, reaches the combustion chamber with no intersection at all, by transversally crossing the intake duct (12) and subsequently entering the upper section of the central transfer port (15).

(9) FIG. 4 shows a cross-sectional view of the embodiment shown in FIG. 3, the piston being at the upper dead point. With respect to the references of the previous figure, the drawing shows the longitudinal axis (A) of the upper injector and the lower section of the central transfer port (15) placed between the intake duct (12) and the pump-crankcase.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

(10) The following detailed description, which is made for explanatory not limitative purposes with reference to the attached drawings, highlights the further features and advantages deriving therefrom and which are an integral part of the subject invention.

(11) In a particularly compact and economical embodiment, the controlled ignition two-stroke endothermic engine according to the present patent application comprises at least one cylinder (1), featuring a substantially circular cross-section, which slidingly accommodates internally thereto a substantially cylindrical piston (2), and is connected on the top side to a head (3) in such a way as to define a combustion chamber (6) with at least one spark plug (5).

(12) The cylinder (1) is connected on the bottom side to a pump-crankcase, the latter communicating with said cylinder (1) by way of at least one central transfer port (15) and, usually, also by way of one or several side transfer ports (7, 8); the cylinder (1) also includes an exhaust duct (11) and an intake duct (12), the latter accommodates an upper fuel injector (13) and a lower fuel injector (14).

(13) The two injectors may have different characteristics and their operation is controlled independently by an appropriate drive and control system which, advantageously, is controlled electronically.

(14) Furthermore, in proximity of the wall of the cylinder (1), the intake duct (12) is crossed by a further transfer port (15) called central transfer port.

(15) The upper injector (13) is accommodated in the higher part of the intake duct (12) and the speed of the fuel sprayed by it has both a component parallel to the axis (X) of the cylinder (1) directed toward the pump-crankcase, and a component orthogonal to the central axis of said cylinder (1) directed toward the inside of the cylinder (1).

(16) The lower injector (14) is housed in the lower part or said intake duct (12) so that the fuel sprayed by it reaches the inside of said cylinder (1) after first crossing said intake duct (12) and subsequently going along the upper section of said central transfer port (15).

(17) In a particularly simple and practical embodiment the outer end of said intake duct (12) includes a seat for mounting the lamellar pack (9) thereon.

(18) Advantageously said intake duct (12), in which seats are obtained for housing said upper injector (13) and said lower injector (14), is aligned with the suction port obtained on said cylinder (1) which it is integrally coupled with.

(19) In a convenient embodiment the intake duct (12) is diametrically opposed to the exhaust duct (11).

(20) The intake duct (12) can be completely obtained in a part of the cylinder (1), or be split into two or more parts, a first part of which is integral with the cylinder (1) and a second part consists of a stand-alone element, integrally connected to the cylinder (1) via coupling means of a known type.

(21) In the embodiment illustrated in the drawings attached to the present patent application, the part integral with the cylinder (1) comprises a section wherein the intake duct (12) crosses the central transfer port (15), whereas the part consisting of a stand-alone element comprises the seat for the injectors (13, 14) and the lamellar pack (9), thus forming a stand-alone sub-assembly which can also be used on different cylinders, provided the latter have all presettings necessary for coupling with said sub-assembly.