GB2235495A

GB2235495A - I.c. engine with combustion inspection window

Info

Publication number: GB2235495A
Application number: GB9018468A
Authority: GB
Inventors: Erich Schreiber; Reinhard Knoll; Hans Oberth
Original assignee: AVL List GmbH; AVL Gesellschaft fuer Verbrennungskraftmaschinen und Messtechnik mbH
Current assignee: AVL List GmbH
Priority date: 1989-08-30
Filing date: 1990-08-22
Publication date: 1991-03-06
Anticipated expiration: 2010-08-22
Also published as: GB9018468D0; AT392351B; GB2235495B; ATA204489A

Abstract

Oil from a lubricated piston 4 is prevented from collecting in the interior of the rod 7 of a non-lubricated piston 13 with a glass combustion inspection window 14 by the application of fan suction to draw air through apertures 27, 28 in the rod and cylinder 2. An annular chamber 29 subject to suction communicates with the rod interior through the rod apertures 27 when during piston reciprocation the apertures are below the sealing ring 30. <IMAGE>

Description

A RECIPROCATING PISTON INTERNAL COMBUSTION ENGINE FOR OPTICAL INVESTIGATION IN THE COMBUSTION CHAMBER This invention relates to a reciprocating piston internal combustion engine for optical investigations in tfle combustion chamber, with a non-lubricated cylinder housing attached to the engine block, and a tubular piston rod, which is fastened to the oil-lubricated engine piston and carries a non-lubricated piston with a glass window on its upper end, and which is provided with oblong openings permitting the insertion of a tilted mirror from outside and the deflection of an approximately horizontal light beam, e.g., a laser beam, into the combustion chamber.

In this known design the general layout of the additional assembly is similar to that of a dry-running compressor. A major difference to the conventional design of dry-running compressors is the special means provided for protecting the assembly from the oil rising from the oillubricated engine piston.

As is well-known oil-lubricated pistons cannot be made fully oilproof at the piston speeds encountered during operation of the engine, and oil droplets or vapors cannot be prevented from leaking upwards eventually, especially in those instances when there is a partial vacuum above the piston, or insufficient backpressure.

In internal combustion engines for optical inspection of the combustion chamber it is essential that the components of the engine to be inspected can be employed without any major modifications, for instance, without having to reconstruct the piston drive of the engine and convert it into a crosshead design, and that a path be provided for the lightrays which must be able to enter the combustion chamber.

The latter demand reqires the hollow piston rod with large, oblong openings, which cannot be made oiltight by means of the conventional sealing systems of dry-running compressors.

It is an object of the invention to protect the optical paths and deflection devices for the light beam, which are provided in the assembly, from being soiled by dripping oil or oil vapors during investigation, in order to maintain the expensive equipment in perfect condition even during long periods of observation, i.e. to prevent the build-up of any oil film and to avoid complicated cleaning of oil-stained surfaces.

In the invention this object is achieved providing an annular chamber above the oil-lubricated cylinder liner and between the non-lubricated cylinder housing and the tubular piston rod, with the use of a sealing ring, for instance, a radial packing ring or a labyrinth seal, which chamber is supplied with air via one or more oblong openings in the tubular piston rod during at least part of the piston stroke, and by further providing a suction fan evacuating the annular chamber via one or more bores leading into it. In this manner the oil or oil vapor leaking from the oil-lubricated piston is collected upon leaving the piston rod and is carried outside in order to prevent it from reaching the dry-running piston and the combustion chamber under inspection, and to protect the glass window and the light deflection devices from being covered by an oil film.The annular chamber formed by means of the sealing ring is supplied with air through the oblong openings in the tubular piston rod during part of the piston stroke, and is evacuated by means of the suction fan via bores leading into it.

In a preferred variant of the invention four air outlet bores are evenly distributed along the circumference of the annular chamber, and two diametrically opposed openings are provided on the piston rod, with one air outlet bore being situated approximately in the middle of the width of each opening.

It is provided in a further development of the invention that ventilation of the annular chamber be interrupted during parts of the piston stroke, for instance, in the area of the upper dead center. In this way a temporary vacuum is generated in the annular chamber, which will produce very high air velocities in this area upon the opening of the air inlet port or ports. The oil particles entering the annular chamber in the dead center position of the oillubricated piston are particularly critical. In the invention ventilation of the annular chamber is interrupted as the piston approaches its upper dead center, such that a strong vacuum is generated in the annular chamber.As a consequence, when the lower edge of the openings in the piston rod passes the sealing lip of the sealing ring, air will enter the annular chamber with great force, pushing before it any oil residues and vapors into the air outlet bores and glass preventing oil contamination of the assembly with great efficiency.

It is an advantage if the scavenging air is controlled in accordance with the piston movements by means of the air inlet ports formed by the openings, and the air outlet bores.

The invention will now be further described by way of example only with reference to the accompanying drawings, in which Fig. 1 gives an axial section of a single-cylinder internal combustion engine in accordance with the invention, Fig. 2 a section of the same engine according to line II-II in Fig. 1, Fig. 3 a section according to line III-III in Fig. 2, and Fig. 4 a section according to line IV-IV in Fig. 2.

The single-cylinder, reciprocating piston internal combustion engine comprises an engine block 1 to which a dryrunning cylinder housing 2 is fastened by means of bolts 2'.

The engine block 1 contains the cylinder liner 3, which is inserted into it and in which the oil-lubricated piston 4 is moved upwards and downwards by the connecting rod 6 which is held by the piston pin 5. Figures 1 and 2 show the piston in its upper dead center position. The tubular piston rod 7 is connected to the piston 4 by means of four bolts 8 located in the bottom part 7' of the piston rod 7. The bottom part 7' of the piston rod 7 thus forms the top of the piston 4 and as such is provided with a sliding seal 9 consisting of a sliding part 10 made of teflon or similar material, and an O-ring 11.

The piston 4 has a similar sliding seal 12.

On its upper end the piston rod 7 carries a dryrunning piston 13, which is held in a non-lubricated liner 13' and is provided with a glass window 14 held by a threaded tubular part 17 with interposed seals 15 and 16. This tubular part 17 has a flexible ring-shaped part 18 offering a flexible and uniform support to the glass window 14. In the area of the non-lubricated piston 13 the piston rod 7 is provided with a guide ring 19 for oil-free operation, which may be made of teflon.

The cooling water chamber of the dry-running cylinder housing 2 has the reference number 20, the water inlet is 21.

On the dry-running cylinder housing 2 is placed the cylinder head 22 with its intake valve 23 and exhaust valve 24.

exhaust pipe has the reference number 25. The non-lubricated piston 13 contains the combustion chamber 26, which is bounded by the cylinder head 22 on one side and by the glass window 14 on the other side.

The piston rod 7 is provided with two diametrically opposed openings 27 of approximately twice the length of the piston stroke, which correspond to the openings 28 in the lower part of the dry-running cylinder housing 2, such that the lower part is permanently open for the insertion of mirrors, etc.

According to the invention an annular chamber 29 is formed above the oil-lubricated cylinder liner 3 and between the dry-running cylinder housing 2 and the piston rod 7, which chamber 29 is sealed against the outside by the sealing ring 30. If necessary, the sealing lip 31 of this ring made of rubber or similar material, may be supported by a helical spring. The sealing ring 30 may be bonded to a sheet-metal casing 31; in addition, a rubber layer 32 may be provided on the outside of this casing 31.

Via bores 33 and 34 in the dry-running cylinder housing 2 the annular chamber 29 is connected with a suction fan (not shown here) by means of tubes 35 and 36.

In the upper dead center position of the piston 4, which is shown in this drawing, the lower edges of the openings 27 are situated above the annular chamber 29 bounded by the sealing lip 30', such that the suction fan will generate a strong vacuum in the annular chamber 29. When the piston 4 and thus the piston rod 7 are moving downwards, the annular chamber 29 is suddenly connected with the atmosphere via the openings 27, and air from outside will flow in rapidly, all the more so as it is being sucked out through the passages 33 and 34 at the same time. In this way any oil particles in the annular chamber 29 are forced out through the suction bores 33 and 34. By suitable design and arrangement of the openings 27 and proper control of the suction fan it is possible to optimize cleaning of the annular chamber 29.

The advantages described here can also be achieved if the elements of the above assembly are used for optical investigations in multi-cylinder engines.

Claims

1. A reciprocating piston internal combustion engine for optical investigations in the combustion chamber, with a non-lubricated cylinder housing attached to the engine block, and a tubular piston rod, which is fastened to the oil-lubricated engine piston and carries a non-lubricated piston with a glass window on its upper end, and which is provided with oblong openings permitting the insertion of a tilted mirror from outside and the deflection of an approximately horizontal light beam, e.g., a laser beam, into the combustion chamber, wherein there is provided an annular chamber (29) above the oil-lubricated cylinder liner (3) and between the non-lubricated cylinder housing (2) and the tubular piston rod (7), with the use of a sealing ring (30), for instance, a radial packing ring or a labyrinth seal, which chamber (29) is supplied with air via one or more oblong openings (27) in the tubular piston rod (7) during at least part of the piston stroke, and wherein there is further provided a suction fan evacuating the annular chamber (29) through one or more bores (33, 34) leading into it.

2. An internal combustion engine as in claim 1, wherein four air outlet bores (33, 34) are evenly distributed along the circumference o'f the annular chamber (29), and two diametrically opposed openings (27) are provided on the piston rod (7), with one air outlet bore (34) being situated approximately in the middle of the width of each opening (27).

3. An internal combustion engine as in claim 1 or 2, wherein ventilation of the annular chamber (29) is interrupted during parts of the piston stroke, in particular in the area of the upper dead center.

4. An internal combustion engine as in any of claims 1 to wherein the scavenging air is controlled in accordance with the piston movements by means of the air inlet ports formed by the openings (27) afld the air outlet bores (33, 34).