DE1945924A1 - Free piston machine - Google Patents

Description

FAIENIANWXUE 1 94592 A

DR. E. WIEGAND DIPL-ING. W. NIEAAANN DR. M. KOHLER DIPL-ING. C GERNHARDT

MDNCHEN HAMBURG

2000 HAMBURG 50, lo. Sept. 1969 TELEGRAMS: KARPATENT KDNIGSTRASSE 28

W. 23922/69 12 / Pa

Karl Werner Lenger Hamburg

Free piston machine.

The invention relates to a free-piston machine, which is used in particular as a free-piston gas generator or free-piston gas compressor can be applied. In conventional free-piston machines of this type, the one is guided in the engine cylinder Motor piston with the compressor piston guided in the compressor cylinder connected to work.

At present, maximum pressures in the range of 12o to 15o atm are used in such free-piston machines. Such pressures naturally lead to relatively high temperatures. Because of this, the cylinders and the usual pistons with piston rings are cooled, wooei for the cylinder external cooling and for the piston internal cooling is usually used. This results in a comparatively complicated and weight-wise structure Heavy design of the free piston machine, which in turn reduces the number of piston clearances and thus the performance of the machine, which also depends on the number of games.

When attempting to increase the maximum pressures and thus the performance of such machines, comparisons emerge heavy loads, especially on the piston rings, because these are the most sensitive components fail first under the high pressure and heat loads. In addition, there is increased wear and tear as well on the cylinder as well as on the piston. Attempts have already been made to use ringless pistons in internal combustion engines

109812/0884 BAD O _R ia, NAL

to use.' Pistons and cylinders were made from the usual. Material produced and the piston guided by means of a special guide on the piston rod. There the material of the piston and cylinder has comparatively large and also different thermal expansion, the execution must be made so that at least in the cold state relatively large clearance between the piston and cylinder is available. This in turn leads to undesirably large gap losses or leakage losses. Another Problem the use of ringless pistons is that both the piston and the cylinder burn through can result, namely due to the hot combustion gases, which in large quantities and with relatively high Speed through the gap between piston and cylinder stream. The said large clearance between the piston and cylinder cannot be reduced even if for The same material is used for the piston and cylinder, especially not because the piston is in the Operation is hotter than the cylinder.

The aim of the invention is to create a free piston machine of the type mentioned in the introduction, in which the above-mentioned Disadvantages are avoided.

According to the invention, a free piston machine of the type mentioned is characterized in that at least the The engine piston and the engine cylinder are made of material with low thermal expansion and that the clearance of the ringless The engine piston downstream or outside of the combustion chamber or the gas exchange slots is smaller than in the combustion chamber is.

According to a preferred embodiment of the invention can also be the compressor cylinder and the one guided in it Pistons can be formed from material of low thermal expansion.

A material is preferably used for the piston and cylinder which has a maximum coefficient of thermal expansion of 30 10 "/ ⁰ C. Such a material can preferably

109812/0884

Quartz glass or a suitable ceramic material or a nickel steel or chromium-nickel steel such as Invar steel or El-Invar steel. The thermal expansion of the steels mentioned is somewhat greater than the thermal expansion of ceramic materials. In general, the ceramic materials are preferred because they allow a lighter design in terms of weight, whereby the piston frequency or the number of piston cycles of the machine and thus also the performance can be increased. Another advantageous property of ceramic materials is their low thermal conductivity, which reduces the heat losses from the machine to the outside. A suitable ceramic material is pyroceram, which / has a coefficient of thermal expansion of about 10 10 χ ~ '° C and can be used at temperatures up to 1200 ⁰ C.

By using material with very low thermal expansion, as suggested here, it is possible to compare the gap between the engine piston and cylinder to keep small, which in particular the gap losses or leakage losses are reduced, but also that mentioned burn-through is essentially avoided.

If the engine cylinder is made of ceramic material, an off is preferably made around the cylinder suitable metal existing shrink jacket is provided, which absorbs the combustion pressure and thus the cylinder protects against damage or destruction.

An engine piston guide device is provided outside the combustion zone, which preferably consists of self-lubricating material with a maximum coefficient of thermal expansion from 4o χ 10 ~ '/ ° C. Preferred materials are carbon such as graphite or synthetic charcoal, with ceramic particles if necessary to increase the wear resistance are stored. The Puhrungseinrichtung can preferably be designed as a socket and in the "cold" Be arranged at the end of the engine cylinder. You can according to

109817 / ΠΒ8 / 4

of the invention, however, also formed on the inner cylinder wall by combustion spraying processes or flame spraying processes be.

According to a preferred embodiment of the invention pressurized gas is introduced in the area of the engine piston guide device, which acts as sliding gas. Will be such a Lubricating gas is used ^ so it is preferred that the guide surface the engine piston guide device by longitudinal webs and circumferential ridges divided into a plurality of fields is, each of which has one or more compressed gas supply openings and one or more Druckgaswegführöffnungen assigned are. In such an embodiment, in order to keep the pressure gas striving to position the piston in the middle, It is important that the Druckgaswegführöffnungen are dimensioned so large that in the area separating the fields If the piston is pressed against the cylinder wall from the side, no pressure build-up can result would lead to the fact that the force pushing the engine piston into the lateral position is greater than the force, which tries to push the engine piston into the central, straight position. In other words, would if sliding gas laterally in the gap below these webs and into the gap in front of and behind an inflow field, you can see the force exerted by it on a larger one Pressure acting on the surface arises, the levitation force, which corresponds only to the area of the fields, exceeding and a lateral Cause the piston to press and thus make smooth sliding impossible. To prevent this from happening, you have to the gas that had crept in was carried away as quickly as possible will.

According to another preferred embodiment of the invention, the compressor piston is also without a piston Rings formed and centered on a pin by means of a Bush made of self-lubricating or lubricant-storing Material led. Furthermore, the compressor

1098 1-2 / 0884

- 5 - ■ ■

piston and the engine piston run separately, and that The corresponding end of the motor piston is arranged with play in or on a corresponding hub of the compressor piston.

The invention is a free piston machine created at the beginning, which makes it possible to achieve comparatively high levels without risking the essential components Apply maximum pressures. In addition, a larger number of piston clearances can be obtained, so that a larger one Performance results. When using ceramic material for the piston and cylinder, the weight of the Machine reduced, which also increases the number of piston play and thus the performance leads.

The invention is explained below with reference to the drawing, for example.

Pig. Fig. 1 is a partial sectional view of the part of an essential part for explaining the invention Free piston machine.

Fig. 2 is a partial sectional view of a piston guide device according to the invention. Fig. 3 is a partial sectional view of a modified one Execution of a piston guide device according to the invention.

4 is a partial sectional view of a further modified embodiment of a piston guide device according to the invention. Fig. 5 is a partial sectional view of another modified embodiment of a piston guide device according to the invention.

FIGS. 6 and 7 are two partial sectional views, on the basis of which the effect of the sliding gas is explained. In Fig. 1, those parts of a with direct current scavenging and in the two-stroke process are essentially schematically working free piston machine shown, which aind necessary to explain the invention. Frelkolbenmasohinen

10 9 8 17/0884

of this general type are known, so a detailed one Description of their overall structure and their basic mode of operation does not appear necessary.

According to the drawing, an engine piston 1 is arranged to be movable back and forth in a cylinder 2. In the engine cylinder 2, the usual charge exchange slots 3 are formed through which the combustion gases and Purge air escape and through the exhaust 4 to a not propellant gas collector shown.

The rear or "cold" end of the engine piston 1 is operatively connected to a compressor piston 5, the can be pushed back and forth in a cylinder 6. When the compressor piston 5 moves to the left as shown in FIG becomes air released during the previous stroke of the piston 5 has been drawn to the right through substantially annular suction valves 7 into the cylinder 6, by a Compressed air outlet 8 pressed into a scavenging air collector 9, from which it in a known manner at the right time enters cylinder 2. The compressor piston 5 performs its pressure stroke in a manner known per se under the Effect of an air cushion formed by air on the right side of the compressor piston according to Pig 5 is enclosed in the cylinder 6.

In the embodiment shown, the engine piston 1 and the engine cylinder 2 are made of a material with very low thermal expansion and a maximum coefficient of thermal expansion of approximately 50 10 ″ ″ / ⁰ C, preferably made of ceramic material that has a thermal expansion coefficient in the range of 10 χ 10 "'/ ° C and can be used at operating temperatures of about 1200 ⁰ C. However, a nickel steel or stainless steel can be as invar or El-invar steel used for the engine piston 1 and the cylinder 2. These steels have a slightly larger Thermal expansion as quartz glass or ceramic materials such as Pyrooeram or the like.

1098I7 / D884

In order to prevent the engine cylinder 2 made of ceramic material from being damaged or destroyed at the high combustion pressures that occur, a shrink jacket 2o in the form of a metal or steel bushing is arranged around the engine cylinder 2, as shown. This jacket 2o absorbs the combustion pressure, so that damage or destruction of the engine cylinder 2 is prevented. The engine piston 1 is guided downstream or outside of the charge exchange slots 3 by a special guide device Io. According to FIG. 1, this guide device has a bushing made of self-lubricating material with a maximum coefficient of thermal expansion of about 40 10 ~ / ° C, ^{such as} carbon, graphite or charcoal, optionally with inclusions of ceramic particles to increase wear resistance. To increase the sliding ability or to reduce the sliding resistance, a device 11 is provided by means of which pressurized gas through the guide device Io against the engine piston! is judged. This compressed gas can either be compressed air supplied by a separate compressor or gas taken from the machine.

As can be seen from Fig. 1, in the engine cylinder 2 at the point where the guide device Io begins, a low level formed so that the game or the gap between piston 1 and cylinder wall in an area 12 in front of the guide device Io is somewhat larger than in the area IJ is within the guidance device Io. The gap in the area IJ of the guide device Io is chosen to be so small that that direct contact between the engine piston 1 and the guide device Io is essentially avoided is. The gap between the engine piston 1 and the cylinder wall in the area 12 is, as stated above, somewhat larger than in the area IJ, but it is also chosen so small that the piston 1 does not come into contact with the inclined position that is possible for it within the guide device Io

109817/0884

1345924

the cylinder wall can occur and that the, gap losses Are within permissible limits * The level is used continues to contribute to the purpose in front of the guide device Io any slight inclined pitch of the engine voltoene 1 is under combustion pressure on its entire circumference ■ to allow gases; in order to prevent unilateral pressure loading of the Motor Coltoens 1 to prevent direct contact between the engine piston 1 and the cylinder wall could lead. Also, if such a stage can not There is * direct contact between the engine pistons 1 and cylinder wall 2 cannot be avoided; if a five-r Jcungselnrlehtung is used, in which no sliding gas or Pressurized gas is used.

In Flg. 2 and j5 there are different execution forms shown by piston guide elements IQa and 10b,

According to FIg. 2, the guide device has a socket IQa "made of self-lubricating material., Such as graphite _Λ charcoal ο.: The like .., which is arranged in the engine cylinder 2 at its" cold "end. The guide surface of the socket 10a is, as in particular from FIGS. 6 and 7 it can be seen ,, by a plurality of!, ängsrlppen 14 and peripheral ribs 15 is divided into a plurality of fields. in each FeIu elin passage 16 opens for compressed gas. in addition, UEs fields are lieg guide by gange 1? associated Die'Wegführdurchgänge are are -ZWlsehen formed adjacent fields, for example in annular grooves "the Ströinungsverlauf of the compressed gas is InFIg, 6 indicated by ITeile sehematiseh ,. There, gait important ;, the passages Γβ dassdureh supplied pressurized gas through the passages 17 ausreichenä quickly weggefuniPt .can ,.% u this purpose and also for the reason _Λ that the emerging compressed gas nat a slightly lower pressure and thus a larger volume than the incoming compressed gas, are the Passages 17 made larger than the passages 16 . It is also important that no more pressurized gas is supplied than can be carried away.

If the lead-away passages 17 are not large enough, a serious disadvantage can arise if the engine piston 1 is disturbed by any external interference tilts something out of its central position. In such a case it will be on part of the circumference of the engine piston 1 the distance to the longitudinal ribs 14 and circumferential ribs 15 is greater than on another part of the piston circumference. Due to this now larger distance or larger gap, the throttling effect is reduced and, if so, the pressurized gas is not led away quickly enough through the passages 17, this results in a certain pressure build-up, so that the compressive force tending to push the piston into the inclined position is greater than the compressive force the opposite side of the piston that tends to return the piston to its central position to press.

In general, the engine piston 1 slides essentially smoothly on the sliding gas tube in the engine cylinder 2, and only in the event of a drop in the sliding gas pressure or the occurrence of other operational, short-term disruptive factors, does a temporary self-lubricating sliding of the piston 1 on the guide bushing Io take place. In this way, wear on the engine piston 1 and the cylinder 2 can be essentially avoided.

The pressure of the gas introduced through the passages 16 should be slightly higher than the pressure of the purge air. The difference in pressure depends on the. respective special design of the piston guide device Io. In general, it has been found that the higher the purge air pressure, the greater the difference to the pressure of the sliding gas should be. _; ,

The embodiment according to FIG. 3 corresponds in terms of its mode of operation to the embodiment according to FIG. 2 or according to FIGS. 6 and 7. The difference is that according to FIG "^ / ⁰ C has, through

1098 12/0884

- Io -

Combustion spray process applied to the cylinder wall surface is. In the embodiment according to FIG. 4, the one described above Step at the beginning of the guide device 10 in part by a guide bushing protruding a little further inward 10c and partly created by a counter shoulder la formed on the outer surface of the piston 1. Even In this embodiment, the piston clearance or the gap between piston 1 and cylinder 2 is in the area 12 in front of the Guide device 10 slightly larger than in the area IJ in the guide device.

In Fig. 5, a simplified embodiment of a guide device is shown, which is only a simple one Made of self-lubricating material according to the above Description formed socket 1Od has. A sliding gas guide is not provided in this version.

It is possible in certain cases for the guide device not to use self-lubricating material. Such an embodiment would be the embodiment according to FIG correspond, but then no self-lubricating material is applied to the cylinder wall, one However, sliding gas guidance is provided.

The compressor piston 5 is guided in the cylinder 6 on an axial pin 18, with the interposition of a bush 19 made of self-lubricating or lubricant absorbent material. If self-lubricating material is used, the same material can be used as used for the engine piston guide bushing Io. If lubricant absorbent material is used, sintered metal with graphite lubrication, oil-soaked sintered metal or oil-soaked ceramic material can be used will. To keep the coefficient of thermal expansion low, nickel - graphite or chromium-nickel-graphite with Invar or El-Invar particles can be used. With the same components can also produce fritted sliding bushes (self-lubricating DEVA metal).

109817/0884.

1345924

- ii -

The Verdishter piston 5 is provided on its side facing the engine piston 1 with a hub 21 which cooperates with the corresponding end 22 of the engine piston 1. As shown, the end 22 of the engine piston is arranged with radial play on the hub 21 of the compressor piston 5, so that this ringless piston 3 can also be adjusted radially independently of the engine piston 1. However, a connection between the twisted piston 5 and the engine piston 1 is through The end face of the piston end 22 engages with an end face formed on the compressor collet 5.

The coupling between the engine piston 1 and the twisting piston 5 is preferably designed as a helical spring Spring 25 achieved at one end on the engine piston 1 and is fixed at the other end on the compressor cylinder 6 » The spring 23 extends see through the hollow Fiaferungszapf en 1B for the twisting piston 5. The guide pin 18 is at one end with the twisting cylinder 6 uniformly formed or connected to it in some other way.

To limit the movement of the twisting piston 5 1 to the right in the twisted cylinder 6 an advantageously annular abutment 24 is formed, as shown in FIG.

It should also be noted that, if necessary, in the combustion chamber water, either separately or injected together with the fuel, in a manner known per se can be achieved if additional cooling of the machine is achieved shall be. Means. With which such a water injection are known and are therefore not in the individually described or illustrated.

In a free piston machine according to the invention can Due to the special design, a number of piston play can be achieved that is about twice the number of piston play currently available Free piston machine is »In other words from

109812/0884

much higher performance is obtained using the invention on a machine of the same size. It is thus possible through the invention to produce free piston machines to build with a comparatively high output per machine unit. Thus, machines according to the invention for motor vehicles and stationary systems as well as ship propulsion systems or the like. be used.

109812/088 / «

Claims (1)

Claims '' Free piston machine, the more movable in the engine cylinder The motor piston is operationally connected to the compressor piston that is movable in the compressor cylinder, characterized by that at least the engine piston (1) and the engine cylinder (2) are made of material with low thermal expansion are and that the game of the ringless engine piston (1) downstream b3w. outside the combustion chamber or the Charge exchange slots (3) are smaller than in the combustion chamber. 2. Machine according to claim 1, characterized in that the compressor cylinder (6) and the compressor piston (5) are made of material with low thermal expansion. 3. Machine according to claim 1 or 2, characterized in that the piston (1, 5) and cylinder (2,6) are made of one material with a maximum coefficient of thermal expansion of about 30 χ 10 "* '/ ° C are. 4. Machine according to one of claims 1 to 3j characterized in that the piston (1, 5) and cylinder (2, 6) made of quartz glass or ceramic material, such as pyroceram or the like., are formed. 5. Machine according to claim 4, characterized in that the motor cylinder (2) is provided for receiving the combustion pressure with a metal jacket (2o) is. 6. Machine according to claim 1 or 2, characterized in that that piston (1, 5) and cylinder (2, 6) are made of Invar steel or El-Invar steel. 7. Machine according to one of claims 1 to 6, characterized in that a piston guide device (Xo) made of material of low thermal expansion is provided in the engine cylinder (2) outside the combustion chamber or the charge exchange socket (3). 109812/088 / » 8. Machine according to claim 7 '» characterized in that the motor piston guide device (Io) is formed from self-lubricating material with a maximum coefficient of thermal expansion of about 4θ χ 10 ~ v ° C. 7 or _rt 9. Machine according to claim / 8, characterized in that that the engine piston guide device (lo) made of carbon, is preferably formed graphite or charcoal, with optionally embedded wear-reducing ceramic particles are. 10. Machine according to one of claims 7 to 9, characterized characterized in that the engine piston guide device (Io) is in the form of a socket which is attached to the "cold" end of the engine cylinder (2) is arranged, 11. Machine according to one of claims 7 to 9, characterized in that the engine piston guide device (lob) is formed in the form of a coating of self-lubricating material applied to the inner wall of the engine cylinder (2) by thermal spraying or flame spraying. 12. Machine according to one of claims 7 to 11, characterized in that the motor piston guide device is provided with means (11, 16) through which from the guide surface of the engine piston guide device Pressurized gas can be let out. 15. Machine according to claim 12, characterized in that that compressed gas is blown out of the cylinder inner wall forming the guide surface. 14. Machine according to claim 12, characterized in that that pressurized gas is blown out of the inner wall of self-lubricating material which forms the guide surface. 15. Machine according to one of claims 7 to 14, characterized characterized in that the guide surface of the engine piston guide unit is divided into a plurality of fields by longitudinal webs (14) and circumferential webs (15) and One or more compressed gas supply openings (I6) for each field 109812/0884 and one or more Druckgaswegführöffnungen (17) are assigned. 16. Machine according to claim 15, characterized in that that the Druckgaswegführöffnungen (17) are formed between adjacent fields. 17. Machine according to claim 15 or l6, characterized in that that the cross section of the compressed gas supply openings (16) smaller than the cross section of the Druckgaswegführöffnungen (17) is. 18. Machine according to one of claims 12 to 17, characterized characterized in that the pressure of the supplied gas is higher than the purge air pressure of the machine. 19. Machine according to one of claims 1 to l8, characterized in that the ringless compressor piston (5) an axial guide pin connected to the compressor housing (18) by means of a bush (I9) made of self-lubricating or lubricant-storing material is. 20. Machine according to claim 19, characterized in that that the socket (19) made of carbon, such as graphite or Artificial carbon, sintered metal impregnated with lubricant or ceramic lubricants
Fabric-soaked / or fritted material is formed. 21. Machine according to one of claims 1 to 2o, characterized in that for keeping the motor piston in contact (1) and the compressor piston (5) when the engine is started, a spring (2J) is provided which at one end is attached in the hollow engine piston (1) and at its other end to the compressor housing. 22. Machine according to claim 21, characterized in that the spring is a helical spring (23) and through the hollow compressor piston support pin (18) passed through is. 23. Machine according to one of claims 1 to 22, characterized in that the compressor piston (5) its side facing the engine piston (1) with a 109812/088 4 Hub (21) is provided on which the corresponding end (22) of the motor cage (1) is arranged with radial play is. . ... - 24. Machine according to one of claims 1 to 2J _3, characterized in that a stop device (24) "is provided in the compressor cylinder (6), which the axial» movement of the motor piston / and compressor piston (5) under the action of the spring (23) limited. 25. Machine according to one of claims 1 to 24 * through an institution; » through which water can be injected into the combustion chamber. 109η ι? / Nee u