U.S. patent application number 10/193967 was filed with the patent office on 2003-01-16 for piston engine.
Invention is credited to Reithofer, Klaus.
Application Number | 20030010200 10/193967 |
Document ID | / |
Family ID | 7691038 |
Filed Date | 2003-01-16 |
United States Patent
Application |
20030010200 |
Kind Code |
A1 |
Reithofer, Klaus |
January 16, 2003 |
Piston engine
Abstract
A piston engine has at least one piston which is mounted to be
movable in a cylinder in a linear manner towards a cylinder head
and a deformable element extends around the piston between the
piston and the cylinder.
Inventors: |
Reithofer, Klaus;
(Rorschacherberg, CH) |
Correspondence
Address: |
Gregory P. LaPointe
BACHMAN & LaPOINTE, P.C.
Suite 1201
900 Chapel Street
New Haven
CT
06510-2802
US
|
Family ID: |
7691038 |
Appl. No.: |
10/193967 |
Filed: |
July 10, 2002 |
Current U.S.
Class: |
92/130R |
Current CPC
Class: |
F02B 75/36 20130101 |
Class at
Publication: |
92/130.00R |
International
Class: |
F01B 031/00 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 11, 2001 |
DE |
101 33 102.9 |
Claims
1. A piston engine comprising: a piston; a cylinder having a
cylinder head; drive means for moving the piston in the cylinder in
a linear manner toward and away from the cylinder head; and a
deformable element extending around the piston between the piston
and the cylinder wherein the deformable element forms (1) a sealed
working space for the piston and (2) a linear guide for the
piston.
2. A piston engine according to claim 1, wherein the cylinder
further includes a cylinder wall and the piston moves in the sealed
working space without contacting the cylinder wall.
3. A piston engine according to claim 1, wherein the drive means is
mounted in a crank case wherein the working space is hermetically
sealed off from the crankcase by the deformable element.
4. The piston engine according to claim 1, wherein the elastic
element encompasses the piston coaxially and is connected in a
hermetically sealed manner to a portion of the cylinder.
5. The piston engine according to claim 1, wherein the cylinder
head has a shape and the end face of the piston has a shape
substantially the same as the shape of the cylinder head.
6. The piston engine according to claim 4, wherein the piston has a
top dead center proximate to the cylinder head such that a dead
volume of working space is created which is virtually zero.
7. The piston engine according to claim 5, wherein, at the top dead
center, a dead volume of the deformable element is virtually
zero.
8. The piston engine according to claim 1, wherein the deformable
element is formed from a plurality of spring elements.
9. The piston engine according to claim 1, wherein the deformable
element is fixedly connected at one end to the cylinder and at the
other end to the piston.
10. The piston engine according to claim 1, wherein the piston
comprises an outward-projecting flange and the deformable element
is connected to the flange at one end and to the cylinder at the
other end.
11. The piston engine according to claim 7, wherein the deformable
element is composed of a plurality of stacked rings each having an
internal radius and an external radius wherein the stacked rings
are connected to one another alternately at the external radius and
internal radius.
12. The piston engine according to claim 7, wherein means are
provided to reduce the dead volume of the piston and the cylinder
and the dead volume of the deformable element.
13. The piston engine according to claim 11, wherein a stroke of
the piston can be influenced by the number of stacked rings.
14. The piston engine according to claim 1, wherein a shape of the
piston is approximately matched to a shape of the cylinder head and
the piston is movable without contact toward the cylinder head by
the deformable element encompassing the piston coaxially.
15. The piston engine according to claim 11, wherein the stacked
rings rest one upon the other when the piston is at top dead center
without a dead volume being formed between the individual
rings.
16. The piston engine according to claim 3, wherein the crankcase
is of pressure-free form.
17. The piston engine according to claim 1, wherein the deformable
element comprises a radial bearing for the piston.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a piston engine, especially
a compressor or Stirling engine, having at least one piston which
is mounted to be movable in a cylinder in a linear manner toward a
cylinder head, the piston being connected to at least one drive
element, especially a crankshaft.
[0002] Such piston engines are known and obtainable in the market
in very different shapes and designs. They are known as
conventional Stirling engines, compressors that are driven by means
of a medium or that compress any desired medium.
[0003] A disadvantage of such piston engines that they usually do
not operate without oil and are subject to severe wear. In
addition, sealing problems frequently arise with excessive energy
consumption.
[0004] Frequently, such piston engines exhibit large dead volumes,
which is likewise undesirable, as these impair the efficiency. In
addition, these are subject to a high degree of wear, caused by
friction, which is likewise undesirable.
[0005] A further disadvantage is that these piston engines exhibit
low efficiencies as a result of sealing problems and have only a
limited pressure resistance.
[0006] Furthermore, combustion engines and compressors are known in
which pistons are reciprocally movable in cylinders in a
conventional manner with oil lubrication. In the food industry,
however, oil lubrication of the piston in piston engines is
undesirable, as it also is in equipment used in medical technology.
In Stirling engines, also, oil-lubricated pistons are highly
disadvantageous, as their regenerators, like many small heat
exchangers, would be rendered useless by coking or oil mist after a
short service life.
[0007] In the oil-free, conventional piston engines, especially
coated cylinder and piston running surfaces and piston rings made
from Teflon alloys are generally used, but these are subject to
severe wear and then have only a short service life. In addition,
they are also suitable and usable only within limited temperature
ranges.
[0008] A further problem with conventional piston engines is that
the sealing of the cylinder relative to the crankcase, especially
for the compression of noble gases such as, for example, helium and
other gases requires an enormous expenditure of energy,
particularly in the case of Stirling engines and in the case of
compressors. It is therefore frequently necessary either for gas
losses arising to be continuously replaced or for the crankcase
additionally to be hermetically sealed and of pressure-resistant
design, which is again undesirable.
[0009] In order to prevent gas loss in coolant compressors, it is
conventionally customary to install the motor and compressor units
in a sealed housing, which requires elaborate and costly
apparatus.
[0010] It is an object of the present invention to provide a piston
engine of the type referred to initially which eliminates the
above-mentioned disadvantages and by means of which efficiencies
can be improved, the dead volumes reduced, friction eliminated and
the use of lubricant avoided.
SUMMARY OF THE INVENTION
[0011] The foregoing object is achieved wherein an elastic,
deformable element extending around the piston is inserted between
piston and cylinder or cylinder head.
[0012] In the present invention, the elastically deformable
elements which guarantee a contact-free movement of a piston in a
cylinder are inserted between piston and cylinder or cylinder wall
and form a hermetically sealed pressure-resistant and leaktight
working space. At the same time, the elastically deformable element
forms a linear guide for the piston, which is reciprocally movable
without contact in the cylinder or along the cylinder wall. The
element preferably consists of spring elements, which are formed
from a stack of rings in the form of spring washers, or the like.
These spring elements are reciprocally connected, preferably welded
or connected in a pressure-resistant manner by means of hard solder
or even adhesively bonded, to one another, alternately at the
internal and external radius. The piston is preferably coaxially
fixed on the cylinder via the spring elements in such a way that
the gas volume between the spring elements is likewise expelled
during the compression movement of the piston. As a result, there
now remains a very small dead volume in the cylinder which
approximately corresponds to the minimum play between piston and
cylinder wall, as a result of which a high sealing ratio can be
achieved. Since, with this arrangement of the spring elements, no
dead volume or unused stroke space arises, the number of stacked
spring elements or spring washers can be adapted to the desired
piston stroke as required.
[0013] In the shaping of the spring washers, it is likewise
possible for these to achieve a large spring travel for each
element, to guarantee high pressure resistance and also to
withstand long-term loading with high stroke frequencies.
[0014] When the individual spring elements, especially the spring
washers, are compressed, the internal radius becomes smaller and
the external radius larger, as a result of which the material is
primarily compressively stressed in the radial direction, which
results in very high rigidity. The effect of this is to ensure that
the piston can be reciprocally moved in the cylinder or within the
cylinder wall in a linearly centered manner and without
contact.
[0015] In order to connect spring washers fixedly to one another,
they have to be so shaped that they possess a flat connecting
surface at the internal and at the external radius, as a result of
which the rigidity can be further increased and/or a spring travel
can then be restricted. This is also intended to come within the
scope of the present invention.
[0016] However, in order to obtain a large spring travel, spring
elements of cross-sectionally sinusoidal form may be used, so that
a resilience in the radial direction is obtained which withstands
enormous tensile and/or compressive stresses and permits a stroke
movement by means of low bending forces.
[0017] In the case of the present invention, a piston engine is
provided which permits a large number of embodiments and possible
applications. As an amount of play is provided between piston and
cylinder wall, it is unnecessary for any costly close tolerances to
be observed during manufacture, which significantly minimizes the
production costs. Cylinder and piston can therefore be produced
particularly cost-effectively from, for example, deep-drawn steel
sheets. In addition to cylindrical shapes, other shapes, such as
for example conical shapes, are also possible. The corresponding
piston bases and cylinder heads can then be adapted in accordance
with that shape and, to minimize the moved masses, especially of
stable shapes, be formed as cones or shapes of hemispherical form.
This is also intended to be included within the concept of the
present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Further advantages, features and details of the invention
will be apparent from the description of preferred examples of
embodiment that follows and by reference to the drawings, in
which:
[0019] FIG. 1 shows a diagrammatically illustrated cross section
through a component of the piston engine;
[0020] FIGS. 2a to 2d show diagrammatically illustrated examples of
embodiment of components of the piston engine in accordance with
FIG. 1;
[0021] FIGS. 3a to 3d show diagrammatically illustrated cross
sections through possible examples of embodiment of elastic
elements, especially spring elements;
[0022] FIG. 4 shows a diagrammatically illustrated partial cross
section through a further example of embodiment of a piston engine,
especially a Stirling engine.
DETAILED DESCRIPTION
[0023] According to FIG. 1, a piston engine R.sub.1 according to
the invention comprises a crankcase 1 in which two pistons 2,
arranged opposite one another, are reciprocally movable along a
cylinder 3, especially along a cylinder wall without contact and
kept apart from one another by a spacer 4. At least one piston 2 is
connected via a connecting rod 5 to a working element, preferably
to a crankshaft 6.
[0024] At its end faces, the cylinder wall 3 is adjoined at each
end by a cylinder head 7. In a preferred example of embodiment,
inlet lines 8 and outlet lines 9 open into the cylinder head 7, but
these may also be designed as inlet valves or outlet valves.
[0025] It is important in the present invention that the at least
one piston 2 is reciprocally movable in a linear manner in the
cylinder wall 3, as represented by the double-arrow direction X.
For this purpose, according to the invention, an elastically
deformable element 10 is inserted between the cylinder head 7 and
the piston 2, this being fixedly connected, preferably welded, at
one end to the cylinder head 7 and fixedly connected, especially
welded, at the other end to a flange 11 or shoulder 12.
[0026] It is important in the present invention that the elastic
element 10 coaxially encompasses a piston wall 13 and completely
and hermetically seals off a working space 14. The working space 14
is defined by the cylinder head 7, the piston 2 and the elastic
element 10. The crankcase 1, by contrast, is free of pressure and
may or may not be open to the environment.
[0027] The elastic element 10 additionally has the function of
providing a bearing for, or centering, the piston 2, without
contact to be linearly movable in the X direction shown so that the
piston 2 is mounted to be movable in the double-arrow direction X
shown in a manner completely sealed off from the cylinder head 7.
Preferably, the elastic element 10 is welded fixedly to the
cylinder head 7 or the cylinder wall 3 at one end and to the flange
11 or shoulder 12 of the piston 2 at the other end.
[0028] If, as shown in FIG. 1, the upper piston 2 moves toward the
upper cylinder head 7, a dead volume of the working space 14 at top
dead center 15 can be reduced, or is virtually zero.
[0029] At the same time, the elastic element 10 is compressed by
the movement of the piston 10 toward the cylinder head 7, so that a
dead volume of the element 10 is likewise reduced, or is virtually
zero.
[0030] Preferably, the element 10 is formed from individual spring
elements 16, which can be compressed.
[0031] When the individual spring elements 16 lie one upon the
other in the compressed state, they can simultaneously form a stop,
especially a damper of the top dead center 15, for the piston
2.
[0032] It is important, however, that the individual spring
elements 16 are welded or soldered fixedly to one another and
circumferentially, or adhesively bonded to one another. These are
connected to one another in a manner resistant to high temperatures
and pressure.
[0033] As a result, the piston 2 can be reciprocally moved relative
to the cylinder head 7 in the cylinder 3 with complete freedom from
friction, absence of contact and freedom from play.
[0034] As a result, a high pressure can be built up in the working
space 14, the piston 2 being capable of creating an oil-free
compression in the working space 14.
[0035] A further advantage of the present invention is that an
absolute seal is formed between the piston 2 and the elastic
element 10 and the cylinder head 7, the piston 2 being
simultaneously linearly movable, radially centered and mounted
within the elastic element 10.
[0036] In a further example of embodiment of the present invention,
as shown in FIGS. 2a to 2d, individual pistons 2 are guided within
cylinder walls 3 with adjoining cylinder head 7, the shape of the
piston 2 approximately corresponding to the shape of the cylinder
head 7.
[0037] In this case, as is shown in particular in FIG. 2a, the
piston 2 may be flat and may be moved onto a flat cylinder head 7
in the double-arrow direction X shown, in order, for example, to
compress the volume in the working space 14 or, in the event of
superatmospheric pressure in the working space 14, to drive the
piston 2. The present invention is not confined hereto.
[0038] FIGS. 3a to 3d each show examples of embodiment of the
elastically deformable element 10, the elastic element 10 being
composed in each case of individual spring elements 16. Preferably,
spring elements 16 in the form of spring washers are laid
alternately one upon the other and circumferentially and fixedly
welded to one another alternately at their external radius 17 and
internal radius 18 so that they are connected to one another in a
pressure-resistant and hermetically sealed manner.
[0039] In this case, the individual spring elements 16 can also be
adhesively bonded or hard-soldered to one another. The invention is
not confined hereto.
[0040] The spring elements 16 may also be provided in the form of
flat spring washers and spring elements 16 of curved form. The
invention is not confined hereto. Preferably, however, spring
elements 16 are used which are of the same form and consistency, so
that when subjected to pressure they rest one upon the other and no
volume is formed between them. As a result, the dead volume in the
compressed state or at top dead center 15 of the piston 2 close to
the cylinder head 7 can likewise be substantially reduced.
[0041] In the last example of embodiment of the present invention,
as shown in FIG. 4, the piston engine R.sub.2 is illustrated as a
Stirling engine having two pistons, the crankcase 1 being formed
without pressure and the pistons 2 being reciprocally movable
toward the latter in the cylinder walls 3 in an oil-free
manner.
[0042] If the elastically deformable element 10 is compressed, no
dead volume is formed, which substantially increases the efficiency
of the piston engine R.sub.1, R.sub.2 and, in addition, the piston
2 is guided to be reciprocally movable with complete freedom from
friction in the cylinder 3 toward the cylinder head 7 and is
radially mounted by the element 10.
[0043] The upper cylinder head 7 is adjoined by a heater 19, which
is adjoined by a regenerator 20 and then by a cooler 21, which is
in connection with the second cylinder head 7.
[0044] The more detailed manner of operation of the Stirling engine
will not be dealt with here; this is described and known in the
prior art in many different forms and embodiments.
[0045] It is important, however, in the present invention that, as
a result of the mode of operation of the piston 2, especially as a
result of its mounting by means of the element 10 and its guidance,
a dead volume is minimized. The piston 2 can be moved toward the
cylinder head 7 without play or contact. The piston engine of this
type can be used, for example, as a compressor, as a Stirling
engine or as a heat pump, and especially as an oil-free compressor.
It also serves to compress gases in, for example, the chemical
industry, where no oil-containing components need be present in the
engine.
[0046] It may also serve as a cooling unit, in which case any
coolant can be processed or compressed here. This is likewise
intended to be included in the scope of the present invention.
* * * * *