Two-stroke internal combustion engine

Abstract

The invention relates to a two-stroke internal combustion engine, in particular for a motor vehicle, with direct fuel injection, comprising at least one working cylinder (1) which comprises a bushing and in which a piston (6) can be moved in an oscillating manner; at least one outlet channel (2) which opens into the working cylinder (1) above the upper dead center of the piston (6); at least two inlet openings (5) which are distributed over the circumference of the bushing and which open into the working cylinder (1) above the lower dead center of the piston (6) such that a uniflow scavenging process of the working cylinder (1) is produced during the operation of the two-stroke internal combustion engine; and a slider which releases and closes the inlet openings (5), whereby the slider is designed as a tube slider (4) which surrounds the bushing of the working cylinder (1) and which comprises a closed casing. The slider releases or closes the inlet openings (5) in an oscillating manner in the longitudinal direction of the bushing during the charge cycle.

Claims

1. A two-stroke direct-injection internal combustion engine, comprising: a cylinder with a cylinder liner; a piston movable in an oscillating manner within the cylinder; at least one outlet port arranged in the cylinder above a top dead center position of the piston; at least two inlet openings spatially separated from one another around a circumference of the cylinder liner and arranged above a bottom dead center position of the piston; a slide valve formed by a sleeve around the cylinder liner which oscillates in a longitudinal direction of the cylinder and releases and blocks the at least two inlet openings during a charge cycle of the engine, thereby providing uniflow scavenging of the cylinder during operation of the engine, an annular sealing element arranged in a gap between an inner wall of the sleeve and an outer wall of the cylinder liner; and a swirl ring arranged on and spaced at a distance from an outside of the sleeve.

2. The two-stroke direct-injection internal combustion engine according to claim 1, wherein the oscillating movement of the sleeve along an outer wall of the cylinder liner is affected by a desmodronic control device in form of a cam controller with a lever engaging an outer circumference of the sleeve.

3. The two-stroke direct-injection internal combustion engine according to claim 1, wherein the oscillating movement of the sleeve along an outer wall of the cylinder liner is affected by an electromagnetic control device.

4. The two-stroke direct-injection internal combustion engine according to claim 1, wherein the oscillating movement of the sleeve along an outer wall of the cylinder liner is affected by a hydraulic control device.

5. The two-stroke direct-injection internal combustion engine according to claim 1, wherein the cylinder is formed with a monobloc cylinder head.

6. The two-stroke direct-injection internal combustion engine according to claim 1, wherein the swirl ring has flow channels with different tangential inflow angles.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) An example embodiment will be explained by reference to the following drawings:

(2) FIG. 1 is a schematic representation of the working cylinder of a two-stroke internal combustion engine.

(3) FIG. 2 shows an inlet region with a sleeve.

DETAILED DESCRIPTION

(4) FIG. 1 shows a schematic representation of the working cylinder 1 of a two-stroke internal combustion engine. For ease of understanding, reference will be made below only to one working cylinder and the working cylinder 1 shown as a cylinder liner in blind-hole design.

(5) The two-stroke internal combustion enginehereinafter referred to as two-stroke diesel engineconsists essentially of the crankcase having the crankshaft, a working cylinder 1 having injection nozzle 9 arranged in the region of top dead center and four valve-controlled outlet ports 2, a piston 6 movable in an oscillating manner in the working cylinder 1 and connected to the crankshaft via a connecting rod 3.

(6) The working cylinder 1 having a blind-hole-shaped cylinder liner has inlet openings 5 distributed over the circumference in the region of bottom dead center. A sleeve 4 having a closed shell is arranged on the outer wall of the cylinder liner, which sleeve blocks or releases the inlet openings 5 in an oscillating manner.

(7) The arrangement of the inlet openings 5 in the region of bottom dead center in connection with the sleeve 4 is shown in FIG. 2.

(8) The inlet openings 5 are arranged at a uniform distance from each other distributed over the circumference of the cylinder liner. Sealing rings 7 are held above and below the inlet openings 5 in circumferential grooves on the outer wall of the cylinder liner of the working cylinder 1. These seal the gap between the cylinder liner of the working cylinder 1 and sleeve 4.

(9) The sleeve 4 has a closed shell and thus controls the release or closing of the inlet openings 5 through its oscillating movement by means of the control edge 4 a.

(10) This eliminates the actual control of the inlet openings 5 by the top edge of the piston 6 and the seal in the direction of the crankcase by a substantially longer piston skirt and the corresponding piston ring.

(11) In the present example, the control of the sleeve 4 with the aid of a desmodromic control unit in the form of a cam controller is performed with a rotatably engaging and fork-shaped lever 8 on the outer circumference of the sleeve 4.

(12) The illustrated two-stroke diesel engine operates as follows:

(13) After completion of the compression stroke and the injection of the fuel, the fuel-air mixture ignites. The outlet ports 2 are closed, the inlet openings 5 are also closed by means of the sleeve 4. In the downward movement of the piston 6 (power stroke), the outlet ports 2 partially open at a specified time, and it starts the blow-down. Upon reaching the inlet openings through the upper edge of the piston 6, the sleeve 4 starts by moving in the same direction as the piston 6 to release the inlet slots 5 with its control edge 4 a and the fresh air enters via the inlet slots in the cylinder chamber. The outlet ports 2 are completely open at the same time. The overpressure of the fresh air is generated by an exhaust gas turbocharger (not shown in detail) and an electrically driven compressor.

(14) For proper scavenging, the scavenging air purposefully enters into the cylinder tangentially through flow channels 11 of a swirl ring 10 and forms a swirling column standing on the piston base that increases by helically rising in height, forms a plug and displaces the combustion gases. These combustion gases are driven out through the fully open outlet ports.

(15) The outlet ports 2 and the inlet openings 5 are fully opened in the piston position bottom dead center.

(16) At the same time with the movement of the piston 6, the sleeve 4 is moved via the desmodromic control on the outer wall of the cylinder liner of the working cylinder 1 in the same direction and closes the inlet openings 5.

(17) The fresh air is further compressed in the further course of the upward movement of the piston 6. Shortly before reaching the top dead center, the fuel is injected via the injection nozzle 9 and ignited. The process begins again.

(18) In the case of starting up the two-stroke internal combustion engine, the generation of the overpressure of the fresh air for scavenging is performed by means of a switchable electric compressor which is switched off again after start-up of the exhaust gas turbocharger.

(19) The switchable electric compressor, however, can also work simultaneously with the exhaust gas turbocharger.

LIST OF REFERENCE NUMBERS

(20) 1 working cylinder 2 outlet port 3 connecting rod 4 sleeve 4a control edge 5 inlet openings 6 piston 7 annular sealing element 8 lever 9 injection nozzle