US2939273A

US2939273A - Method and apparatus for starting free-piston engines

Info

Publication number: US2939273A
Application number: US678717A
Authority: US
Inventors: Janicke Hermann
Original assignee: Individual
Current assignee: Individual
Priority date: 1956-08-24
Filing date: 1957-08-16
Publication date: 1960-06-07
Anticipated expiration: 1977-06-07

Description

June 7, 1960 H. JANlcKE ,9

METHOD AND APPARATUS FOR STARTING FREE-PISTON ENGINES Filed Aug. 16, 1957 Inventor:

2,939,273 Patented June 7, 1960 METH D APPA ATUS. ronsmmo FREE-PISTON ENGINES Hermann Jiinicke, Ahornstrass Loc'bhanrnear Munich, German" Filed Aug. 16, 1957, Ser.No. 67,717 A Claims priority, application: Germany Aug. 24, 1956; 3 Claims. CI. 60-13) The present invention relates to a method and apparatus for starting so-calledfree-piston engines to which is connected a turbine which is driven by the exhaust gases of the engine, and in turn drives a compressor supplying the compressed air required for supercharging the engine cylinder.

It is known to start free-piston engines by means of compressed air which is taken from a compressed air reservoir provided for this purpose. This compressed air reservoir which serves only for starting, and the equipment necessary for recharging such reservoir, constitute an important factor of additional expenses which is avoided by the present invention.

According to the invention, the starting of a freepiston engine, the engine cylinder of which is supercharged with compressed air delivered by a compressor driven by an exhaust-driven turbine, is effected in such a manner that the compressed air delivered by the compressor is used for starting the engine.

In a preferred embodiment of the starting method according to the invention the exhaust-driven turbine and the compressor coupled therewith are first accelerated by an auxiliary starter motor to approximately the speed at which the exhaust-driven turbine runs during normal operation of the free-piston engine, whereupon the compressed air delivered by the compressor is admitted to act on the free pistons of the internal combustion engine as soon as the required starting pressure has been attained.

According to a further feature of the invention a portion of the compressed air supplied by the compressor during starting, may be supplied directly to the scavenging ports of the engine cylinder, and through the exhaust ports of the latter to the exhausbdriven turbine.

The invention will now be described in more detail with reference to the accompanying drawing.

The drawing shows in diagrammatic representation, and partly in longitudinal section, a free-piston internal combustion engine to each piston of which there is connected a pair of pump pistons arranged at right angles thereto.

The engine pistons 2, 2 are freely movable in the engine cylinder 1 in a manner known per se. Each of the engine pistons 2, 2 is rigidly connected with a return piston 5, respectively 5' which operates in an associated return cylinder 6, respectively 6'. The return cylinders serve to return the pistons to their inner dead center position. The work required therefor is performed by the compressed air supplied by a compressor 7. The compressor 7 which is driven by an exhaustdziven turbine 13 connected to an exhaust conduit =12,-

supplies on the one hand the compressed air for supercharging the engine through a conduit 9 and scavenging ports 10, and on the other hand the working pressure for the return cylinders 28, 28' through conduits 8, 8.

Each of the engine pistons drives, through a connecting rod 3, respectively 3', a pump pair 4, 4 respectively 4', 4 which supplies pressure fluid to a hydraulic apparatus,

for example to a hydraulic motor. The arrangement and drive of such fluid pumps in connection with free piston engines is known and described for example in my co-pending U-.S.applica' tion Serial No. 666,114.

The exhaust conduit 12 leading to the exhaust-driven turbine 13 is connected to the exhaust ports 11 of the engine cylinder 1 via a pressure-retaining valve 14 which maintains the pressure at a predetermined constant value during operation but valve 14 is inoperative during starting. Thus, the under pressure delivered by the compressor into line 9 during starting can pass without reduction through line 12 to the turbine and assist the operation of compressor 7. I

From conduit 8, a conduit 15 leads to the housing 16 of the starting, valve which comprises a control piston 17 kept in the closed position by a spring ,18 which is set to the desired starting pressure. A conduit 19 contreats the valve housing 16 with the valve housing 20 the piston 21 of which actiiate's, through

links

22, 23 and levers 24, 24' throttle valves 25, 25' provided in the conduits 8, 8 respectively. The throttle valves 25, 25' are brought into their closed position by a spring 26, when the pressure prevailing in conduit 8 drops below a predetermined value after the internal combustion engine has been stopped, so that piston 17 closes conduit 15 under the action of spring 18, and the compressed air contained in housing 20 escapes at the rear of piston 17 through an opening 27.

Reference numeral 29 designates an electric starter motor to which current may be supplied from a battery 37 by closing a switch 36, whereby the shaft of the starter motor is displaced and its pinion 32 is brought into engagement with a gear 31, as is common practice in motor vehicles. Gear 31 is in mesh with a gear 30 mounted on the shaft of unit 7, 13, so that this unit can be accelerated to approximately operational speed by the motor 29.

The starting operation is as follows:

Let it be supposed that the pistons 2 and 2 are in their outer dead center positions. For starting the engine, switch 36 is closed so that unit 7, 13 is accelerated approximately to the speed which corresponds to normal operation of the internal combustion engine. The compressor 7 supplies on the one hand the compressed air required by engine cylinder 1 through 9, 10 a portion of which air is supplied to the exhaust-driven turbine 13 through the exhaust ports 11. The pressure-retaining valve 14 which may be provided is not an essential element of the engine. Valve 14 is inoperative during the starting operation.

Turbine 13 brings about a retarding influence or choking during starting because of the outlet nozzles usually provided in the stationary part of the turbine to direct the air under pressure to the runner blades. This choking effect is assisted by the retarding efiect due to restrictions 10, 11 but not by valve 14 which is inoperative during starting.

After the pressure required for starting the engine has been attained in conduits 8, 9 as well as in engine cylinder 1 and in conduit 12, the valve 16, 17 opens, so that the compressed air acts on piston 21 which begins to move and opens the previously closed

throttle valves

25, 25. Thereby the compressed air acts on the return pistons 5, 5' which are moved inwards so that the internal combustion is started in the known manner. Switch 36 may now be opened so that starter motor 29 comes to a standstill and pinion 32 is disengaged from gear 31.

By the air pressure prevaiing on condut 15, throttle valves 25, 25' are kept open through valves 17 and 21 also during normal operation of the internal combustion engine. After the engine has been stopped, the pistons 2 and 2" are returned to'their'outer dead center position i by any suitable means which are not "an object of the present invention.

. 1: vis, g u v .als i s u e ydraul .Q jot 2a. a

pneumatic star me us instead bfi'theele'etric' :TI claimz j L'The ombination comprising f a free-piston engine including a cylinder and'disposedtherein two' oppositely reciprocating 'ipi'stons defining betwe'enfthem inner combustion space, each'of 'said pistons at its out er'end being providediwith an enlarged retum piston movable in an outer return cylinder, "an exhaust-driven turbine and an air compressor fdriven thereby, 'an'exhaust-con-f duitexte'ndingfrom said combustion 'space to said'tur bine, said compressor supplying compressed airiwhich is delivered through airlines rintothe outer return cylinders for actuatingthe-return' pistons andfallso through scavenging ports into the combustion space; pressure responsive. means responsive'to the'delivery pressure of said compressor andadapted to open said air-linesconne cting said compressor to said returncylinders when said delivery pressure a predetermined value;

and an auxiliary starter motor operatively connected to saidcompressor for starting the free-piston engine.

2. The combination as set forth in claim 1 in which the starter motor is constructed to accelerate the exhaust-dr-iven turbine and the compressor driven thereby to approximate the speed at which said exhaust-driven ator un du n n m ra on O h free piston engine, the pressure responsive f-mean's comprising valve means adapted to be open when pressure of the air delivered by, the compressor reaches the predetermined value.

3. The combination as setforth in claim 1 in which a portion of theairjdeliveredbythe compressor during starting enterstheinner combustion": spacethrough the scavenging and leaves the combustion'i space through the exhaust conduit and is fed to the exhaustdriven turbine. J

p References Cited in the file of this patent UNI TED-TSTATE S PATENTS