EP3622167A1

EP3622167A1 - Hot gas engine having a step piston

Info

Publication number: EP3622167A1
Application number: EP18722503.2A
Authority: EP
Inventors: Josef Frauscher
Original assignee: Frauscher Holding GmbH
Current assignee: Frauscher Holding GmbH
Priority date: 2017-05-09
Filing date: 2018-05-03
Publication date: 2020-03-18
Anticipated expiration: 2038-05-03
Also published as: US11725607B2; PL3622167T3; US20220106926A1; EP3622167B1; DE102017109967B9; CA3096716C; EP4273393A3; DE102017109967B4; JP2020519813A; EP3622167C0; US11215139B2; JP7202365B2; WO2018206412A1; EP4273393A2; US20200408168A1; DE102017109967A1; CA3096716A1; ES2951904T3

Abstract

A Stirling engine is described which, in accordance with a first exemplary embodiment, has a transmission with a connecting rod and a double-acting step piston which is arranged in a cylinder. The step piston has a first section with a greater diameter and a second section with a smaller diameter, and is at least partially hollow. The connecting rod runs on the inside through the second section, and is connected in an articulated manner in the first section of the step piston.

Description

HOT GAS MACHINE WITH LEVEL PISTON

TECHNICAL AREA

[0001] The present description relates to a hot gas engine with at least one double-acting displacer or working piston, for example a Stirling engine.

BACKGROUND

Stirling engines are probably the best known representatives of hot gas engines. If air is used as working gas, the term hot air machine is also used. Some such machines can be operated both as an external combustion engine, as a heat pump or chiller. Other known types of hot gas engines are e.g. the Manson engine, the Ericsson engine, etc. Nowadays, the term "Stirling engine" is used as a generic term for different hot gas engines with a closed gas cycle (ie the working gas circulates exclusively within the engine without contact with the surrounding atmosphere) A distinction is made between types which are referred to as alpha type, beta type and gamma type, whereby in turn different variants of the individual types have become known in some cases under special names (eg rider motor, Siemens motor, etc.) In addition, a distinction is made in the alpha type between single-acting and double-acting machines, of which all types are known for a variety of specific designs , an improved hot gas machine ne which avoids certain disadvantages of Stirling engines with displacement piston (beta and gamma type) or with double-acting working piston (double-acting alpha type) and other types of hot gas engines.

SUMMARY

The above object is achieved by the Stirling engine according to claim 1, 15 or 25. Various embodiments and further developments are the subject of the dependent claims. It is a hot gas engine is described, which has a transmission (engine, crank mechanism) with a connecting rod and arranged in a cylinder double-acting stepped piston according to a first embodiment. The stepped piston has a first portion with a larger diameter and a second portion with a smaller diameter and is at least partially hollow. The connecting rod extends inside through the second section and is articulated in the first section of the stepped piston.

In a general embodiment, the hot gas engine, a transmission with a connecting rod and arranged in a cylinder double-acting piston (differential piston) on. Cylinders and pistons are configured to form an annular cylinder space in the cylinder, the piston being at least partially hollow, and the connecting rod being articulated in the interior of the piston at a position such that the annular cylinder space extends around the connecting rod. The piston may be either a differential piston designed as a stepped piston or a differential piston which is guided on the outside on a tube arranged coaxially to the cylinder, which protrudes into the cylinder interior, whereby the annular cylinder space is formed below the piston.

According to a further embodiment, the hot gas engine, a transmission with a connecting rod, a cylinder and a tube which is at least partially disposed in the interior of the cylinder. One end of an at least partially hollow differential piston is disposed between the tube and the inner wall of the cylinder, so that an annular cylinder space is formed. The connecting rod passes through the tube and is articulated in the interior of the differential piston at this.

According to a further embodiment, the hot gas engine to a transmission which is arranged in a gear compartment, in the ambient pressure prevails. The Stirling engine further includes a double-acting, stepped piston arranged in a cylinder, which has a first portion with a larger diameter and a second portion with a smaller diameter. The stepped piston is at least partially hollow and has inside a piston rod which is mechanically coupled to the transmission. The gearbox facing second portion of the stepped piston opens into a buffer space for the working gas of the Stirling engine, and inside the Stepped piston is at least a part of a sealing device arranged which seals a passage of the piston rod between the buffer space and gear room.

BRIEF DESCRIPTION OF THE FIGURES

The invention will be explained in more detail with reference to the examples shown in the figures. The illustrations are not necessarily to scale and the invention is not limited to the aspects presented. Rather, emphasis is placed on representing the principles underlying the invention. To the pictures:

Figure 1 shows a schematic structure of a Stiiiingmaschine gamma type.

FIG. 2 shows a schematic structure of a double acting alpha type stuffer.

FIG. 3 shows an exemplary embodiment of a Gamma-type Stirling engine with a displacer piston designed as a stepped piston.

Figure 4 shows an embodiment of a piston-cylinder unit of a Stirling engine of the double-acting alpha-type with a stepped piston designed as a working piston.

FIG. 5 shows an exemplary embodiment of a gamma-type Stii ingmaschine similar to FIG. 3, wherein the working piston is designed as (single-acting) stepped piston. ,

Figure 6 shows an embodiment of a gamma-type forming machine similar in function to the example of Figure 5, but having pistons and cylinders arranged in parallel.

Figure 7 shows an embodiment of a Stiiiingmaschine gamma-type, which, as far as the function is similar to the example of FIG. 6, but as a crank mechanism has a so-called Ross-Yoke-Getüebe. FIG. 8 shows an exemplary embodiment of a piston-cylinder unit of a Stirling engine of double-acting alpha type as a stepped piston working piston, which are coupled via a wobble disc gear with a shaft.

Figure 9 shows an embodiment of a Stirling machine of the beta type with a trained as a stepped piston displacer.

Figure 10 shows an embodiment which, in terms of function and kinematics, is practically equivalent to the example of Figure 3; However, instead of a stepped piston, an at least partially hollow differential piston which is arranged between a tube protruding into the cylinder and the cylinder inner wall is used as the displacement piston.

Figure 1 1 shows an embodiment which, as far as the function and the kinematics is concerned, is practically equivalent to the example of Figure 5, being used as a displacer instead of a stepped piston, an at least partially hollow differential piston and a working piston as an annular piston, wherein both the differential piston and the annular piston are each arranged between a tube which projects into the respective cylinder, and the cylinder inner wall.

Figure 12 shows an embodiment of a piston-cylinder unit of a Stirling engine of the double-acting alpha-type (similar to Fig. 4) with a working piston, which is designed as a differential piston which projects between a tube which projects into the cylinder, and the cylinder inner wall is arranged.

Figure 13 illustrates an example of a Manson motor with a stepped piston according to the embodiments described herein.

FIG. 14 shows an alternative coupling between the stepped piston and the crank drive of a Stirling engine according to FIG. 4.

DETAILED DESCRIPTION

The embodiments described herein mainly relate to different types of Stirling engines. The concepts described here (in particular the However, basic shape of the piston and its mechanical coupling with the transmission) are at least partially transferable to other types of hot gas engines. In addition, the designs of cylinder and piston explained with reference to the various exemplary embodiments described here can be combined as desired in multi-cylinder machines. Fig. 1 shows an example of the structure of a Stirling machine of the gamma type. The operation of such a gyro-type Stirling engine is based on the fact that, for example, via a crank drive (eg crankshaft 10 and connecting rod 12) operated displacement piston VK in a positive displacement VZ the working gas alternately via heat exchanger (heater E), regenerator R and radiator K between a "hot" side H and a "cool" side C of the displacer VZ reciprocated. The resulting pressure changes act on a working piston AK (right in FIG. 1), which transmits the resulting forces to the crankshaft 10 and generates a torque there. The piston rod 13 of the displacer VK is led out via a passage from the displacer cylinder VZ (seal 30) and connected via a short connecting rod 12 with the crankshaft 10. The trailing with, for example, 90 degrees behind the displacer VK working piston AK is connected via a line L to the displacer VZ. Not shown are means for guiding the connecting rod to receive the lateral force. Various examples are described in the publications WO 2009/082997 A2 and DE 102 29 442 AI.

A with the arranged in the displacer VZ displacer VK in the gamma type (see Fig. 1) comparable construction is used in a double-acting Stirling machine of the alpha type (also called Siemens type), which is shown in Fig. 2 by way of example , Unlike the gamma type of Fig. 1, however, an alpha-type double-acting Stirling engine does not have a separate displacer or displacer but a plurality of interconnected reciprocating working-cylinder units. Here, as shown in FIG. 2, the hot end H of a working cylinder AZ is connected via heater E, regenerator R and radiator K to the cold end C of the next working cylinder AZ '. In this respect, this type only works on machines with several cylinders. Frequently - as shown in Fig. 2 - four piston-cylinder units are used, each having the same structure and whose pistons are 90 degrees out of phase (based on a full revolution of the crankshaft) working out of phase. The angular positions of the individual working pistons are shown in Fig. 2. It Even machines with more than four piston-cylinder units are possible. Not shown are means for guiding the connecting rod to receive the lateral force. The illustrated double-acting Stirling engine is also referred to as a Siemens hot gas engine. Various other examples are described in the publications US 3,940,934, US 4,069,671 and US 4,195,554

Common to both examples from Figures 1 and 2 is that the piston (displacer VK in the gamma type, see Fig. 1, and the working piston AK in the double-acting alpha type, see Fig. 2) within a gas-tight cylinder filled with working gas (displacement cylinder VZ for gamma type or working cylinder AZ for double-acting type alpha). The piston force is transmitted via a piston rod 13 attached to the piston VK or AK. The piston rod 13 is guided in the illustrated examples at the cool end C of the cylinder VZ or AZ through an opening and sealed (see Fig. 1, seal 30). The outwardly directed end of the piston rod 13 may be connected to a connecting rod of a crank mechanism (e.g., connecting rod 12, crankshaft 10) which provides the oscillating motions. The term piston rod referred to in the embodiments described herein, a rod which is rigidly connected to the respective piston (non-pivoting), so that the piston rod can move only along the piston longitudinal axis S. In contrast, a connecting rod with respect to the piston longitudinal axis S is pivotally mounted.

In the illustrated constructions, the piston rod 13 in the region of the passage from the cylinder VZ (see Fig. 1) or AZ (see Fig. 2) takes those side forces, which are caused by the inclination of the connecting rod 12. These lateral forces may be problematic with respect to the bearing of the piston rod 13. In some constructions, therefore, additional longitudinal guides - such as crosshead guides - mounted to relieve the piston rod 13. However, such machine elements can lead to an increase in the overall height of the entire arrangement, which is why usually relatively short connecting rods 12 are used. These in turn cause an unfavorable ratio of crank radius ΓΚ to Pleuellänge l _p (lambda value, see Fig. 1), which affects both in terms of high lateral forces as well as a high proportion of second order inertial forces. In addition, it may be unfavorable for the thermodynamic process of the Stirling engine, if the piston movement deviates greatly from a sinusoidal course. In oil-lubricated crank mechanism, it may be necessary to take measures along the piston rod 13, so that the oil can not get into the process chamber or in the working gas. Such seals may additionally contribute to lengthening the height of the Stirling engine. It should be noted at this point that a crank drive is generally considered to be a mechanical functional unit designed to convert an oscillating translatory movement of the pistons into a rotation. A crank mechanism does not necessarily have to be configured as in the examples according to FIG. 1 or 2, in which the connecting rods are deflected directly on a crankshaft. In an alternative embodiment, the crank mechanism may have a Ross-Yoke mechanism. In a further alternative embodiment, a swash plate may be connected to the shaft to convert the oscillating motion of the pistons into a rotation.

Fig. 3 shows an example of an improved embodiment of a Stirling machine of the gamma type. The illustrated example is substantially the same as the example of Fig. 1, but the displacer VK has at its lower end (on the "cool" side C) instead of the piston rod 13, a hollow cylinder (tube) having an outer diameter d, the smaller In other words, the piston VK is a differential piston formed as a (double-acting) stepped piston, which has a first portion Si of a larger diameter D and a second portion S _{2 of} a smaller diameter d having.

The designed as a stepped piston displacer VK is at least partially hollow, and the hollow cylinder with diameter d (section S _{2 of} the stepped piston) allows a passage for a sufficiently long connecting rod 12, the upper end in the interior of the stepped piston VK in the region of larger diameter D (section Si of the stepped piston VK) is hinged thereto. The connecting rod 12 is therefore not connected to the lower end of the piston VK with this, but extends far into the piston VK into the section Si inside. Compared to the example of FIG. 1, the connecting rod 12 can thereby be made significantly longer. The area of the larger diameter D (section Si) is clearly delimited in the exemplary embodiments illustrated here and lies (in the axial direction) above the step in the stepped piston, at which the diameter widens from the smaller value d to the larger value D. When the transition from small neren diameter d to the larger diameter D is not in a step, but gradually, the region Si of the larger diameter is that (axial) cylinder portion in which the diameter is larger than the small diameter d.

The pivot axis of the connecting rod 12 is designated A. The connecting rod 12 may be articulated by means of different types of bearings in the piston. For example, a cylindrical plain bearing or rolling bearing can be used. Alternatively, a spherical spherical plain bearing can be used. This may e.g. be arranged at the upper end of the connecting rod 12. The connecting rod is articulated as mentioned in the first section Si (in which the diameter of the piston VK is greater than the small diameter d) of the stepped piston. This means that the pivot axis A of the connecting rod 12 is located in the section Si.

For receiving the piston side force perpendicular to the central axis S of the displacer VZ, it may be useful both in the region of the large diameter D (section Si) of the stepped piston VK and in the region of the small diameter d (section S ₂ ) each one Guide element F (sliding surfaces) provided. Because of the low crank radius / rod length ratio, the piston force perpendicular to the piston center axis S is relatively low. Since this force is distributed to the two guide surfaces F, an extremely low specific surface loading of the sliding surfaces occurs. This arrangement allows the use of oil-free sliding elements as guide elements F, for example, PTFE-graphite compounds with a low coefficient of friction. The two sliding elements F also ensure an exact linear guidance of the piston VK and prevent tilting movements, as they can occur selementen in one-piece or closely spaced guide.

The dimensioning of the diameter of the stepped piston VK can for example be such that the smaller diameter d of the stepped piston (outer diameter hollow cylinder) has about 70% of the larger diameter D of the stepped piston, corresponding to a surface division of the forming annular surface ((D ² - ά ² ) χπ / 4) in relation to the circular surface defined by the hollow cylinder (ά ² χπ / 4) of approximately 1: 1. Between the second section S _{2 of} the stepped piston VK and the cylinder surface there is an annular volume which, during operation, is cooled working gas is filled. The area below the step of the step cylinder is therefore the "cool side" C the stepped piston VK and the positive displacement VZ. The cylinder volume in the displacement cylinder VZ above the stepped piston VK is filled during operation with hot working gas. The area above the first section Si of the stepped piston VK is therefore the "hot side" H.

In the second section S _{2 of} the stepped piston VK, a sealing ring 20 is arranged. Likewise, a further sealing ring 21 is arranged in the first section Si of the stepped piston VK. The sealing ring 21 seals the hot side H against the cool side C of the displacer VZ, whereas the sealing ring 20 seals the cool side C of the displacer VZ against an underlying buffer space P (see also Fig. 4, where there the stepped piston a working piston a double-acting alpha machine and are provided as seals piston rings). In the illustrated case of a gamma machine, the hot side H and the cool side C of the displacer cylinder VZ are connected via heaters E, regenerator R and cooler K, and therefore substantially equal pressure prevails on both sides. The sealing ring 21 thus essentially serves to prevent a flow (leakage) of process gas between the stepped piston VK and the cylinder inner wall. In contrast, the sealing ring 20 must seal the interior of the displacer VZ against the buffer space P out, which is why the sealing ring 20 will usually be formed as a piston ring. Similarly, arranged on the working piston AK seal 22 must seal the working space of the working cylinder AZ against an underlying buffer space P, which is why the seal 22 will usually also be designed as a piston ring.

In the embodiments described here, it is not important whether the piston guides F and piston seals 20, 21 (piston rings) are mounted on or in the piston as moving with the piston elements or on the cylinder inside as fixed, non-moving elements are arranged and slide along the piston shaft. 3, the piston ring 21 and the guide element F are arranged in the region of the large diameter D of the stepped piston and the elements slide accordingly on the inner wall of the cylinder VZ. In contrast, in the area of the small diameter d of the stepped piston, the guide member F and the piston ring 20 are fixedly attached to the cylinder inner side. The above mounting situations no Depending on the function of the Stirling engine, any variant which is most suitable for a particular construction can be chosen. Therefore, the remainder of this discussion will not address this issue.

Fig. 4 shows an example of an improved embodiment of a piston-cylinder unit, a double-acting Stirling machine alpha-type. From this piston-cylinder unit, multiple (e.g., four as in the example of Figure 2) may be coupled to a double-acting alpha machine. The illustrated example is essentially the same as the piston-cylinder units in the example of FIG. 2, but the working piston AK, AK 'at its lower end (on the "cool" side C) instead of the piston rods 13 each have a hollow cylinder (tube By itself, the working pistons AK in the present example may be constructed substantially the same as the displacer VK formed as a stepped piston in the previous example 3 and 4, however, the operation of the two motor types in Figures 3 and 4 is different (see the above description of Figures 1 and 2). The working pistons AK designed as stepped pistons may become However, for example in the seals differ from the displacement piston VK formed as a stepped piston VK from the previous example ge 20 and 21 may be formed in the present case both as (pressure-loaded) piston rings, since they have to withstand the pressure difference between the hot side H (expansion space) and the cool side C (compression space) of the working cylinder AZ, AZ '.

In oil-lubricated crank mechanism, there is the possibility of Ölab streaking elements A (Ölab streifringe) in the field of leadership of the small piston diameter (section S ₂ ) to install, without increasing the overall length of the machine significantly. A low lambda value (Γ _Κ / I _P ) allows an approximately sinusoidal piston movement along with low second-order force forces and a favorable course of the gas mass flow through heater E, regenerator R and radiator K. In the illustration according to FIG. 4, the working piston is located AK approximately in the middle position, which is why no cranking is visible on the crankshaft 10. Fig. 5 shows another embodiment of a Stirling engine from

Gamma type, which has a similar structure and as the example of FIG. 3. Unlike in FIG. 3, however, the working piston AK is designed as a single-acting stepped piston. The stepped piston has a first section Si 'with a larger outer diameter D' and a second section S ₂ 'with a smaller outer diameter d'. The working space AR of the working cylinder AZ is the annular space which is formed between the cylinder inner wall and the second portion S ₂ 'of the stepped piston. The connecting line L hiss the cool side C of the displacer VZ and the working cylinder thus flows into said annulus (cylinder space AR).

The working piston AK has along its longitudinal axis on a continuous opening, so that between the buffer space P and the cylinder space P 'on the end face of the working piston AK pressure equalization can take place. The arrows shown in Fig. 5, which extend through the working piston, indicate that through the opening in the working piston AK through a gas flow is possible, which allows the mentioned pressure equalization. Coupled with the working piston AK connecting rod 12 is - similar to the displacer VK - articulated in the interior of the working piston AK in the area Si 'of the larger diameter D'. The sealing ring 23 seals the cylinder space AR (working space / annular space) of the working cylinder AZ from the buffer space P out. Similarly seals the sealing ring 22 working space AR to the frontal cylinder chamber P ', in which the same pressure prevails as in the buffer space P. Both seals 22, 23 may be formed as piston rings. Otherwise (in particular with regard to the displacement cylinder VZ and the crank drive), reference is made to the description of FIG. 3. Compared to the example of FIG. 3, the variant of FIG. 5 enables a shorter line L between the displacement cylinder VZ and the working cylinder AZ and consequently a smaller dead space, with a comparatively long connecting rod 11.

Fig. 6 shows another embodiment of a Stirling engine from

Gamma type, which - as regards the function and design of the piston - is very similar to the previous example of FIG. The essential difference between the examples of FIGS. 5 and 6 is the position of the cylinders relative to each other. According to FIG. 6, the longitudinal axes S and S 'of the displacement cylinder VZ and the working cylinder AZ are parallel, whereas in the previous example the longitudinal axes S and S' are essentially parallel. a right angle and thus form a V-engine. The parallel arrangement of the cylinders allows, in comparison to the previous example, an even shorter line connection L between the displacement cylinder VZ and the working cylinder AZ and consequently an even smaller dead space. Incidentally, reference is made to the description of FIGS. 3 and 5.

Fig. 7 shows a variant of the example of Fig. 6. The essential difference between the examples of Figs. 6 and 7 is in the crank mechanism, which has a so-called Ross-Yoke-Mechamsmus according to FIG. In the Ross-Yoke, the connecting rods 11 and 12 do not directly connect the pistons with the crankshaft 10, but the ends of the connecting rods 11 and 12 facing away from the pistons are articulated on a rocker 14 (yoke, yoke) which controls the oscillating motion of the pistons on the crankshaft Crankshaft 10 transmits. The rocker 14 is additionally mounted on a further connecting rod 13 to the transmission housing. Such a Ross-Yoke-Mechamsmus is known per se and is therefore not explained in detail. Apart from the crank mechanism, the example of FIG. 7 is practically the same as the example of FIG. 6 and reference is made to the above explanations.

Fig. 8 shows a variant of the example of Fig. 4, wherein four or more cylinder units (working cylinder AZ, working cylinder AZ ') via a swash plate gear drive an output shaft 10. In the sectional view shown in Fig. 8, two (with respect to the transmission) opposite arranged cylinder units are shown. In this case, the "crank" of the shaft 10 is formed by the inclined swash plate on which the connecting rods 11 and 12 are hinged (e.g., by means of spherical bearings).) Swash plate gears are known per se and therefore will not be further explained here.

Similar to the example of Fig. 2, at least four cylinder units are necessary to form an alpha-type double-acting Stirling machine. The box at the bottom right in FIG. 8 shows a schematic plan view, in which it is shown how such a motor can be constructed. In each case two cylinders AZ and AZ 'are arranged in the planes Ei and E ₂ , wherein the cylinder longitudinal axes lie in the planes Ei and E ₂ , which are each perpendicular to each other (which does not necessarily have to be the case). A cylinder AZ in the first level Ei is connected (via heater E, regenerator R and radiator K) to a corresponding cylinder AZ in the second plane E ₂ . This in turn is connected to the second cylinder AZ 'in the first plane, etc. In this way, a Four-cylinder engine formed. As mentioned, however, constructions with more than four cylinders are possible.

A stepped piston as described in the above examples of a gamma-type and (double-acting) alpha-type Stirling machine can also be used in a beta-type Stirling machine. An example of a beta machine is shown in FIG. Similar to a gamma machine (see Fig. 3), a beta machine has a displacer VK and a working piston AK. However, unlike in the example according to Fig. 3, displacement piston VK and working piston AK move in the same cylinder Z. The displacement piston VK is designed as a stepped piston, as in the gamma machine (see Fig. 3), wherein the connecting rod 12, which the stepped piston VK connects to the crankshaft 10, passes through the second portion S _{2 of} the (at least partially hollow) stepped piston VK and is articulated in the first portion Si of the stepped piston VK. The illustrated embodiment of the displacer VK allows the use of a comparatively long connecting rod 12 and an improvement in the lambda value. For receiving the piston lateral force perpendicular to the central axis S of the cylinder Z, a guide element F (sliding surfaces) can be provided in the region of the large diameter D (section Si) of the stepped piston VK. With regard to the displacer VK embodied as a stepped piston, reference is otherwise made to the description of FIG. 3.

The working piston AK is designed as an annular piston (ring piston) and moves coaxially to the displacer VK. The outer diameter of the annular piston AK is denoted by D _A and the inner diameter of the annular piston corresponds (apart from the piston clearance) to the small diameter d of the stepped piston VK. The section S _{2 of} the stepped piston VK with the smaller diameter d is passed through the annular piston AK. The sealing rings (piston rings) can be arranged on the annular piston AK, once outside sealing (seal 22a) once inside sealing (seal 22b). Similarly, the guide sliding surfaces F can be arranged on the annular piston AK (inside and outside). However, other designs are also possible in this regard, eg the arrangement of the piston ring 22b on the stepped piston VK in the section S ₂ or the arrangement of the guide sliding surfaces F on the cylinder Z. As shown in Fig. 9, designed as an annular piston piston AK is coupled via two symmetrically to the central axis S arranged connecting rod I Ia, 1 lb to the crankshaft 10. In order to obtain more space for the articulation of the upper ends of the connecting rods I Ia, 1 Ib, the cylinder Z is stepped, which allows a larger outer diameter D _{A of} the annular piston AK compared to the outer diameter D of the portion Si of the stepped piston VK. The piston surface obtained by the larger outer diameter D _A (annular surface (Ü _A ² -d ² ) x ^ 4) can be used to correspondingly reduce the piston stroke of the working piston. This can be at the connecting rods 1 la, 1 lb, which are necessarily shorter than the connecting rod 12, a similar favorable lambda reach as the connecting rod 12 of the displacer VK. The piston surfaces (annular surfaces) of stepped pistons (displacer piston VK) and annular piston (working piston AK) and the associated piston strokes can be selected so that the ratio of the stroke volumes is approximately 1: 1. In the illustration according to FIG. 6, the displacement piston VK is located approximately at half the stroke, for which reason no cranking is visible on the crankshaft 10. As with gamma machines too, the displacer VK advances the working piston AK about 90 degrees (in relation to the angular position of the crankshaft 10). The crankshaft 10 is arranged in the buffer space P as in the example according to FIG. 3.

Fig. 10 shows a variant of the embodiment of Fig. 3. The examples of Figs. 3 and 10 are functionally and kinematically equivalent. The two examples differ only in the construction of the displacement cylinder VZ and the displacer VK arranged therein, wherein the piston stroke and cylinder volume can be the same in both variants. 10, a slightly differently designed differential piston is used instead of a stepped piston. In the present example, the differential piston is guided coaxially to a tube R, which projects into the interior of the displacement cylinder VZ (and in the differential piston). The differential piston is (at least partially) hollow and disposed between the tube R and the cylinder inner wall, so that below the differential piston between the lateral surface of the tube R and the inner surface of the cylinder, an annular cylinder space (annulus) is formed, as is the case with the use of a stepped piston Case would be. The guide not shown in FIG. 10 may be arranged on the differential piston outside or on the cylinder inner wall. The tube R is rigidly connected to the motor housing (eg screwed) and the seal 20 seals the annulus (ie the cool side C of the displacer VZ) to the inside of the differential piston, where the same pressure prevails as in the buffer space P. The through the Pipe R extending arrows in Fig. 10 indicate again the possibility of gas flow and a pressure equalization (analogous to Fig. 5). The seal 21 only has to prevent leakage, as already explained with reference to FIG. 3. The connecting rod 12 is passed through the tube R and hinged inside the differential piston VK. Thus, the same favorable ratio of crank radius ΓΚ to Pleuellänge l _p (lambda value, see Fig. 1) can be achieved as in the example of Fig. 3. Incidentally, reference is made to the explanations to Fig. 3.

The example of Fig. 11 is a modification of the example of Fig. 5. Both examples are functionally and kinematically equivalent. According to FIG. 11, displacement cylinders VZ and displacement pistons VK have the same structure as in the previous example from FIG. 10. This construction replaces the stepped piston from FIG. 5. The working piston AK is designed as an annular piston according to FIG. 11, which is likewise located between a pipe R '. , which projects into the working piston AK, arranged and sealed to the lateral surface of a tube R '(see, for example piston ring 23). The pipe R 'is - analogous to the pipe R in the displacement cylinder VZ - rigidly connected to the motor housing and protrudes as mentioned in the working cylinder AZ inside. As in FIG. 5, the working piston AK is hollow and allows pressure equalization between the buffer space P and the cylinder space P 'on the end face of the working piston AK. The sealing ring 22 is substantially the same as in Fig. 5. The sealing ring 23 seals between the working piston AK and pipe R '.

The example of Fig. 12 is a modification of the example of Fig. 4, wherein the stepped piston of Fig. 4 has been replaced by a differential piston. Working cylinder AZ and working piston AK (differential piston) are essentially constructed as displacement piston VK and displacement cylinder in Fig. 11 and reference is made to the above explanations. As already explained with reference to Fig. 4, similar to the example of Fig. 2, a plurality (e.g., four) of cylinder units may be combined to form an alpha-type double acting Stirling engine.

Fig. 13 shows an example of a hot gas engine, which has become known under the name Manson engine. Since the working gas does not circulate in a closed circuit (but via a valve is a connection to the buffer space or to the atmosphere), the Manson engine shown is actually not a Stirling engine. Of the Stepped piston acts equally as positive displacement and working piston and is referred to in the present example with AK. At the top and bottom dead centers of the piston movement, for example via a mechanical valve control, a valve V is opened for a short time, which connects the annular cylinder space (between the narrower portion of the stepped piston and the inner wall of the cylinder AZ) with the ambient pressure in the buffer space P. The mechanical valve control may, for example, comprise a lever 41 which is mounted pivotably about a pivot point 40 and which is tilted by means of cams 44a and 44b arranged on the shaft 10. The lever 41 transmits this tilting movement to the valve stem of the valve V against the restoring force of a spring 42. At the lower end of the lever 41, a roller 43 may be attached, which rolls on the shaft 10. Structure and function of a Manson motor are known per se (eg from the publications DE 199 04 269 AI and GB 2554458 A) and are therefore not further explained here. The advantages explained in relation to the other exemplary embodiments of the articulation of the connecting rod 12 in the region of the large diameter D of the stepped piston also apply to the Manson motor.

In some constructions of Stirling engines, the transmission (see Fig. 14, gear compartment G) is not used as a buffer space, but operates under atmospheric pressure. In such cases, the buffer space (which is under the pressure of the working gas) must be sealed against the gear housing, which is done with a piston rod, for example by means of special sealing elements. The so-called "Leningrad seal", in which sealing elements are preloaded with a spring, has proven to be useful Two conically shaped discs press the sealing element against the piston rod in order to initiate the sealing function Such a sealing element is known per se.

Such an example is shown in FIG. Fig. 14 shows a piston-cylinder unit of an alpha-type double acting Stirling engine. Several of these piston-cylinder units (eg four as in the example of Figure 2) may be coupled to a double-acting alpha machine. To save height, a double-acting stepped piston is provided as a working piston AK according to the illustrated example. The stepped piston AK has, as in the previous examples, a first section Si with a larger diameter D and a second section S ₂ with a smaller diameter d, wherein the stepped piston AK at least partially (at least in the region of the second section S ₂ with diameter d) is hollow. Unlike in the example 4, however, the stepped piston AK is not directly connected to a connecting rod of a crank mechanism, but has (as in the example of FIG. 2) a piston rod 13. Unlike in the example of FIG. 2, however, the guiding and sealing elements of the piston rod 13 can be arranged within the piston stem of the stepped piston facing the crank drive (section S ₂ with external diameter d). In this embodiment, the piston rod 13, for example via a connecting rod with a crankshaft in the same or similar manner be connected as in the example of FIG. 2 (with the associated disadvantages). It may therefore be better to couple the piston rod 13 with a Ross yoke, a Schiefscheibentriebwerk or a swashplate engine, as these types of transmissions design-related smaller Pleuelauslenkungen or need no connecting rod. Such transmissions are known, for example, from the publications GB 2174457 A or WO 2010/093666 A2.

The second portion S _{2 of} the stepped piston AK which faces the crank mechanism (eg crankshaft 10, cf., for example, FIG. 2) opens into a buffer space P for the working gas of the Stirling engine. A partition wall 33 separates the crankcase between buffer space P and gear space G, in which the transmission is arranged (not shown in FIG. 14, cf. FIGS. 7 and 8). The piston rod 13 connected to the stepped piston AK is passed through an opening in the partition wall 33. The seal comprises a sleeve 31 rigidly connected to the partition wall 33, through which the piston rod 13 passes. Within the sleeve 31, an annular sealing member 35 is disposed around the piston rod 13 around. The sealing element 35 is clamped along the longitudinal axis S of the piston rod 13 (cylinder axis S) between two conically shaped discs 34. The necessary biasing force is generated by a spring 32, which may be disposed within the sleeve 31 around the piston rod 13 around (eg in the case of a coil spring) and on the discs 34 a force along the longitudinal axis S of the piston rod 13 exerts. In the examples according to FIGS. 2 and 4, there is no separation between buffer space P and gear space G, and the crank drive is arranged in the buffer space. The present example, however, allows a separation of buffer space P and gear room G, so that the transmission can operate under ambient pressure. A construction according to FIG. 2 would theoretically not require any buffer space. In the present example according to FIG. 5, a separate buffer space P may be advantageous since otherwise the lower piston section S ₂ would generate too high pressure oscillations and consequently too high forces on the housing and the partition 33 due to its displaced volume.

Claims

CLAIMS:

1. A hot gas engine comprising:

a transmission (10) with a connecting rod (12);

a double-acting step piston (VK; AK) arranged in a cylinder (VZ; AZ; Z), which has a first section with a larger diameter (D) and a second section with a smaller diameter (d),

wherein the stepped piston (VK; AK) is at least partially hollow, and the connecting rod (12) extends inside through the second section (S ₂ ) and is articulated in the first section (Si) of the stepped piston (VK; AK).

2. The hot gas machine according to claim 1,

wherein the stepped piston (VK; AK) has sliding surfaces which slide on the cylinder surface both in the first section (Si) and in the second section (S2).

3. The hot gas machine according to claim 1 or 2,

wherein the cylinder (VZ; AZ; Z) has guide elements (F) which slide in the first section (Si) and in the second section (S ₂ ) of the stepped piston (VK; AK) on the piston surface.

4. The hot gas machine according to one of claims 1 to 3,

wherein the stepped piston (VK; AK) has sealing rings (20, 21) both in the first section (Si) and in the second section (S ₂ ).

5. The hot gas machine according to one of claims 1 to 4,

wherein the connecting rod (12) in the stepped piston (VK, AK) is articulated by means of a sliding bearing or a roller bearing or by means of a spherical hinge bearing.

6. The hot gas machine according to one of claims 1 to 5,

wherein the transmission facing the second portion (S ₂ ) of the stepped piston (VK, AK) opens in a buffer space (P) for the working gas of the Stirling engine.

7. The hot gas engine according to claim 6,

wherein the transmission (10) is arranged in the buffer space (P).

8. The hot gas machine according to one of claims 1 to 7,

wherein the Stirling engine is a double-acting Alpha-type Stirling engine or a beta or gamma-type Stirling engine, and

wherein the ring volume between cylinder (VZ; AZ) and the second portion (S ₂ ) is filled in operation with cooled working gas.

9. The hot gas machine according to one of claims 1 to 7,

wherein the Stirling engine is a Beta-type Stirling engine and has an annular piston (AK) disposed in the cylinder (Z) through which the second portion (S2) of the stepped piston (VK) passes.

10. The hot gas machine according to claim 9,

wherein the transmission (10) has two further connecting rods (I Ia, I Ib), which are articulated on the annular piston (AK) symmetrically to the piston longitudinal axis (S).

11. The hot gas machine according to claim 9 or 10,

wherein the cylinder (Z) is formed as a stepped cylinder having a first portion of smaller diameter (D) and a second portion of larger diameter D _A ), and

wherein the annular piston (AK) in the second portion of the cylinder (Z) is arranged.

12. The hot gas engine according to one of claims 1 to 7, further comprising;

a in another cylinder (AZ) arranged further piston (AK), which is coupled by means of another connecting rod (11) with the transmission.

13. The hot gas engine according to claim 12,

wherein the stepped piston is a displacement piston (VK) and the other piston is a working piston (AK), which is also designed as a stepped piston or as an annular piston.

14. The hot gas machine according to claim 12 or 13,

wherein in each of the cylinder (VZ) and in the further cylinder (AZ) in each case an annular cylinder space is formed, and

wherein the annular cylinder space of the cylinder (VZ) and annular cylinder space of the further cylinder (AZ) are connected via a line.

15. A hot gas engine comprising:

a transmission (10) with a connecting rod (12);

a cylinder (VZ; AZ; Z); and

a differential piston (VK; AK) arranged in the cylinder (VZ; AZ; Z), wherein cylinders (VZ; AZ; Z) and differential pistons (VK; AK) are designed such that an annular cylinder space is formed in the cylinder,

wherein the differential piston (VK; AK) is at least partially hollow, and the connecting rod (12) in the interior of the differential piston (VK; AK) is articulated at a position such that the annular cylinder space extends around the connecting rod (12).

16. The hot gas engine according to claim 15,

wherein the differential piston (VK; AK) is a stepped piston having a first portion (Si) with a larger diameter (D) and a second portion (S ₂ ) with a smaller diameter (d), and

wherein the annular cylinder space between the second portion (S ₂ ) of the stepped piston and an inner wall of the cylinder (VZ, AZ) is formed.

17. The hot gas engine according to claim 16,

wherein the connecting rod (12) extends inside through the second portion (S ₂ ) of the stepped piston and in the first portion (Si) of the stepped piston (VK; AK) is articulated.

18. The hot gas engine according to claim 15, further comprising:

a pipe (R, R ') protruding into the cylinder (VZ; AZ), one end of the differential piston (VK; AK) being interposed between the pipe (R, R') and an inner wall of the cylinder (VZ; AZ) is.

19. The hot gas engine according to claim 18, wherein the tube (R, R ') extends so far into the cylinder (VZ, AZ) that it also projects into the interior of the differential piston (VK, AK) when it is at its top dead center.

20. The hot gas machine according to claim 18 or 19,

wherein tube (R, R '), differential piston (VK; AK) and cylinder (VZ; AZ) are arranged coaxially with each other.

21. The hot gas engine according to any one of claims 18 to 20,

wherein the tube (R, R ') is immovable relative to the cylinder (VZ; AZ).

22. The hot gas engine according to any one of claims 18 to 21,

wherein between the tube (R, R ') and an inner wall of the differential piston (VK; AK), a sealing ring (20) is arranged.

23. The hot gas machine according to claim 15, further comprising:

24. The hot gas engine according to claim 23,

wherein the annular cylinder space of the cylinder (VZ) and annular cylinder space of the further cylinder (AZ) via a line (L) are connected.

25. A hot gas engine comprising:

a transmission (10) disposed in a gear room (G) in which ambient pressure prevails;

a double-acting step piston (AK) arranged in a cylinder (AZ), which has a first section with a larger diameter (D) and a second section with a smaller diameter (d),

wherein the stepped piston (AK) is at least partially hollow and in the interior has a piston rod (13) which is mechanically coupled to the transmission; wherein the transmission facing the second portion (S ₂ ) of the stepped piston (AK) opens into a buffer space (P) for the working gas of the Stirling engine;

and

wherein inside the stepped piston (AK) at least a part of a sealing device is arranged, which seals a passage of the piston rod (13) between the buffer space (P) and gear chamber (G).

26. The hot gas machine according to claim 26,

wherein the seal comprises a sleeve (31) in which a spring (3) is arranged which presses on a between the sleeve (31) and the piston rod (13) arranged sealing element (35).