US2834329A

US2834329A - Free piston engine

Info

Publication number: US2834329A
Application number: US612617A
Authority: US
Inventors: Carl F Bachle; Earl R Klinge
Original assignee: Continental Aviation and Engineering Corp
Current assignee: Continental Aviation and Engineering Corp
Priority date: 1956-09-28
Filing date: 1956-09-28
Publication date: 1958-05-13
Anticipated expiration: 1975-05-13

Description

y ,5 v c. F. BACHLE ETAL ,834,

FREE PISTON ENGINE Filed Sept. 28, 1956 2 Sheets-Sheet 1 INVEN 0R5 May 13, 1958 Filed Sept. 28, 1956 C. F. BACHLE ETAL FREE PISTON ENGINE I 2 Sheets-Sheet 2 iv R? IV ng/ INVENTORS CARL F. BACH LE BY EARL R. KLINGE ATTo R EYS United States Patentfifice FREE PISTON ENGINE Carl F. Bachle, Grosse Pointe, and Earl R. Klinge, Harper Woods, Mich., assignors to Continental Aviation & Engineering Corporation, Detroit, Mich., a corporation of Virginia Application September 28, 1956, Serial No. 612,617 8 Claims. (Cl. 123.41.35)

The present invention relates to internal combustion engines of the free piston type, and more particularly to a means for altering the free piston reciprocating cycle frequency for various engine operating ranges.

In the development of free piston engines capable of operating at relatively high speeds, the reciprocating cycle frequency of the free piston is determined by a number of factors, including the mass of the piston, its stroke, and the volumes of the combustion chamber cylinder, the air compressor cylinder, and the bounce chamber. A major problem encountered is the relatively high and uneconomical fuel consumption at idling operation, since' the reciprocating cycle frequency remains at the relatively high value determined by the above recited factors.

An object of the present invention is to attain more economical fuel consumption during free piston idling operation by providing a means for increasing the mass of the piston to reduce reciprocating cycle frequency thereof.

Another object of the present invention is to provide a free piston engine with controllable piston reciprocating cycle frequency by constructing a chambered piston having a means for selectively filling same with liquid to increase its mass during engine idling operation.

A further object of the present invention is to provide a free piston engine with a variable mass piston by constructing a chambered piston having liquid coolant passages opening into the piston chamber and providing means for selectively trapping a required amount of coolant in the chamber.

For a more detailed understanding of the invention, reference may be had to the accompanying drawings illustrating a preferred embodiment of the invention in which like characters refer to like parts throughout the several views and in which Fig. 1 is a cutaway longitudinal sectional view of a preferred type of free piston engine utilizing the present invention and including a diagrammatic representation of a source of coolant supply.

Fig. 2 is a sectional view taken substantially on the line 2-2 of Fig. 1, and

Fig. 3 is a sectional view taken substantially on the line 3-3 of Fig. 1.

A preferred type of free piston engine is illustrated as having a three-step cylinder structure comprising a -combustion chamber cylinder 11, an air compressor cylinder 12, and a bounce chamber cylinder 13. The bounce chamber is contained by an engine cylinder head 10a. A free piston structure 14 preferably comprising a power piston portion 15 and a larger air compressor piston portion 16, reciprocates in the combustion chamber cylinder and the air compressor cylinder respectively. A chamber 17 in the piston comprises a power piston compartment 17a and a compressor piston compartment 17b, which are openly connected by ports 18 shown in Figs. 1 and 2. This compartmented chamber 2,834,329 Patented May 13, 1958 17 is adapted to trap liquid coolant for increasing the mass of the piston.

The power piston portion 15 is provided with an annular coolant passage 20 connected to a central axially extending tube 21. Liquid coolant is preferably supplied from a cooler and reservoir structure 22, and is pumped by a pump 23 through a conduit 24 to an intake duct 25 extending axially into the end of the engine 10, and through the center of the compressor piston portion 16, terminating just short of the inner end of the power piston portion 15 when the piston is at the outermost limit of travel. The tube 21'is adapted to slide within the duct 25 as the piston 14 reciprocates, so that the coolant passage 20 will be continuously supplied with liquid coolant.

After circulation through the passage 20, the coolant passes through ports 26 into the chamber 17. Drain tubes 27 are secured to the piston portion 16 and extend into drilled bores 28 in the cylinder head 100. As the piston 14 reciprocates, the tubes 27 slide in the bores 28, maintaining continuous contact therewith. An upper drain conduit 30 is connected by suitable fittings and passages to the upper bore 28 in the cylinder head and lower drain conduit 31 is similarly connected to the lower bore 28. The two conduits 30 and 31 are connected with a T-coupling or union 32 and drained coolant is returned through a conduit 33 to the cooler and reservoir 22. A valve 34 is provided in the lower conduit 31.

During normal engine operation at speeds above idling, the liquid coolant circulating through the passage 20 and passing into the chamber 17 is drained off through the lower conduit 31, the valve 34 being in an open position. The mass of the piston 14 will consequently be at a minimum and the reciprocating cycle frequency will be at a maximum. As the engine is idled, the valve 34 will be closed, either manually orby any suitable automatic means. The liquid will then be trapped, and will fill both the large compartment 17b and the small compartment 17a of the chamber 17. When substantially completely filled to the level of the upper drain tube 27, the coolant will then continue to drain through the conduit 39, providing for continuous circulation through the system. With the piston now filled with liquid, its mass is correspondingly increased and the reciprocating cycle frequency is reduced to a minimum for more economical operation of the engine.

Although but one preferred embodiment of the invention has been described herein, it will be apparent to one skilled in the art to which the invention pertains that various changes and modifications may be made therein without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. In an internal combustion engine of the free piston type and having a cylinder structure, a free piston reciprocating in said cylinder structure, a chamber in said piston, means connecting said chamber with a source of liquid supply, and means selectively operable to trap a desired amount of liquid in said chamber whereby to change the mass of said piston and alter the reciprocating cycle frequency thereof.

2. In an internal combustion engine of the free piston type and having a cylinder structure, a free piston reciprocating in said cylinder structure, a chamber in said piston, means connecting said chamber With a source of liquid supply, and controllable outlets from said chamber for varying the amount of liquid trapped in said chamber whereby to change the mass of said piston and alter the reciprocating cycle frequency thereof.

3. In an internal combustion engine of the free piston type and having a cylinder structure, ,a free piston reciproof liquid trapped in. said. chamber whereby to change the mass of said piston and alter the reciprocating cycle frequency thereof, said last mentioned means comprising a plurality of, outlets from various levels. of said chama her, and valve means selectively closing the lowerlevel outletto, trap a controlled amount ofv liquidinsaidchamber.

4'. Man internal combustionengine of the free piston type and having a cylinder structure, afree piston reciprocating in said cylinder structure, a chamber in said piston,,means connectingsaidchamber with a: source of liquid supply, and. means selectively operable to vary the amount, of. liquid trapped insaid chamber whereby to change the mass of. said piston and alter the reciproeating cycle frequency thereof, said last mentioned means comprisingupper and lowerv outlets from said chamber, and valve means selectively closing saidlower outlet to trap liquid in, said chamber 'to the height of saidupper outlet.

5. In an internal combustion engine of the free piston type and having, a. cylinder structure, a free piston reciprocating in said cylinder structure, a chamber in said piston, means connecting said chamber with a source of liquid supply, and means selectively operable to vary the amount. of liquid trapped insaid chamber whereby to change the mass of said piston and alter the reciprocating cycle frequency thereof, said last mentioned means comprising upper and lower outletsfrom said chamber, and valve means selectively closing said lower outlet to trap liquid in said chamber. to the height of said upper outlet, said pistoncomprising'relatively small and large diameter portions, said outletsbeing in said large diameter portion.

6. In aninternal combustion engine of the freepiston type andhaving; a cylinder structure, a free piston reciprocating in said cylinder. structure, a coolant passage in: said piston, achamber. in said: piston and openly connected with said coolant passage, means conducting coolant under pressure into said coolant passage, and means selectively trapping varying amounts of coolant in said chamber whereby to change the mass of said piston and alter the reciprocating cycle frequency of same.

7. In an internal combustion engine of the free piston type and having a cylinder structure, a free piston reciprocating. in said: cylinder. structure, a chamber in said piston, means connectingsaid chamber witha source of liquid supply, andimeansselectively operable to vary the amount of liquid trapped in said chamber: whereby. to change the mass of said piston and. alter the reciprocating cycle frequency thereof, said coolant trapping means comprising a plurality of' drairrv outlets located at various levels of said chamber, and valve means selectively operable to close one or more of said drain outlets to control. the amountof coolant trapped in said chamber.

8. In, an internal combustionengine of the-free piston type and having a, cylinder structure, a free piston reciprocating in said cylinder. structure, a chamber in said piston, means connecting saidchamber with a source of liquid supply, and controllable outlets from said chamber for varying the amount of liquid trapped in, said chamber whereby to change the mass-of said piston and alter the reciprocating cycle frequency thereof, said valve means normally. open. for engine high speedoperation to maintain substantially aminimum'of coolantin said chamher. and thereby attain a maximum reciprocating. cycle frequency of saidv piston, and. said valve means closing. the lower. level outlet: for engine idle operationltomaintain substantially a maximum of coolant in said chamber andthereby attain aminimum reciprocating cycle frequency of said piston;

References Cited inthe'file of this patent.

UNITED STATES PATENTS 2,645,213. Huber July 14, 1953