U.S. patent application number 13/515583 was filed with the patent office on 2013-02-07 for refrigerant compressor having linear drive.
This patent application is currently assigned to ACC Austria GmbH. The applicant listed for this patent is Hans Peter Schoegler. Invention is credited to Hans Peter Schoegler.
Application Number | 20130034456 13/515583 |
Document ID | / |
Family ID | 44246906 |
Filed Date | 2013-02-07 |
United States Patent
Application |
20130034456 |
Kind Code |
A1 |
Schoegler; Hans Peter |
February 7, 2013 |
REFRIGERANT COMPRESSOR HAVING LINEAR DRIVE
Abstract
A coolant compressor has a hermetically sealed compressor
housing, in the interior of which lies a piston cylinder unit that
compresses a coolant. The cylinder housing of the piston cylinder
unit is closed at the front end thereof by a cylinder head. A
linear drive is provided, comprising at least one oscillating body
which is surrounded by an excitation winding and which is connected
to the piston to move same along a longitudinal axis in an
oscillating manner. The piston cylinder unit has at least one first
permanent magnet that lies on the piston, and at least one second
permanent magnet that lies on the cylinder housing. Both magnets
face each other and are oriented in the same magnetic pole
direction in order to generate a repelling effect between both
magnets to limit the path of the piston in the region of the top or
bottom dead center.
Inventors: |
Schoegler; Hans Peter;
(Fehring, AT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Schoegler; Hans Peter |
Fehring |
|
AT |
|
|
Assignee: |
ACC Austria GmbH
Fuerstenfeld
AT
|
Family ID: |
44246906 |
Appl. No.: |
13/515583 |
Filed: |
December 14, 2010 |
PCT Filed: |
December 14, 2010 |
PCT NO: |
PCT/AT2010/000478 |
371 Date: |
June 27, 2012 |
Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04B 2201/0206 20130101;
F04B 17/04 20130101; F04B 49/12 20130101; F04B 35/045 20130101;
F04B 2201/02 20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04B 35/00 20060101
F04B035/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 14, 2009 |
AT |
GM 790/2009 |
Claims
1-23. (canceled)
24. A refrigerant compressor having a hermetically sealed
compressor housing, in whose interior a piston-cylinder unit (21),
which compresses a refrigerant, is arranged, whose cylinder housing
(1) is frontally closed by means of a cylinder head (4), in which a
suction opening (17) and a pressure opening (18) are provided, via
which refrigerant is suctioned in via a suction valve (15) through
the suction opening and compressed via a pressure valve (16) to the
pressure opening, the piston-cylinder unit (21) having at least one
piston (3) guided in a piston bore (2) of the cylinder housing (1),
a working space (14) for compressing a refrigerant being formed
between the cylinder head (4) and a first front side (3a) of the
piston (3), a linear drive (6) being provided, comprising at least
one oscillating body (7) enclosed by an exciter winding (8), which
is connected to the piston (3), in order to move it along a piston
longitudinal axis (9) in oscillating manner, the piston-cylinder
unit (21) being equipped with at least one permanent magnet
arrangement, comprising respectively at least one first permanent
magnet (11) arranged on the piston (3) or on a component connected
to the piston (3), wherein the at least one permanent magnet
arrangement comprises at least one second permanent magnet (12)
arranged on the cylinder housing (1) or on a component connected to
the cylinder housing (1), the first permanent magnet (11) and the
second permanent magnet (12) pointing toward one another with the
same magnetic pole direction in each case, to generate a repelling
effect between the two permanent magnets (11, 12) to delimit the
piston travel in the region of the top dead center and/or in the
region of the bottom dead center upon approach of the first
permanent magnet (11) to the second permanent magnet (12), the
component connected to the cylinder housing (1), on or in which the
at least one second permanent magnet (12) is arranged, is the
cylinder head (4), a valve plate (5) is arranged in the cylinder
head (4) and the at least one second permanent magnet (12) is
arranged on the valve plate (5), preferably at least sectionally
countersunk in the valve plate (5), in order to delimit the piston
travel in the region of the top dead center, the permanent magnets
(11, 12) are countersunk into the front side (3a, 3b) of the piston
(3) and/or the valve plate (5) so that at least one free space (13)
is provided between permanent magnet and piston or valve plate,
which communicates with the working space (14), and this free space
(13) extends along the entire periphery of the permanent magnets
(11, 12).
25. The refrigerant compressor according to claim 24, wherein the
component connected to the piston (3), on which the at least one
first permanent magnet (11) is arranged, is the oscillating body
(7) or a piston shaft (22) connecting the piston (3) to the
oscillating body (7).
26. The refrigerant compressor according to claim 24, wherein the
at least one second permanent magnet (12) is arranged inside the
piston bore (2) of the cylinder housing (1).
27. The refrigerant compressor according to claim 24, wherein the
at least one second permanent magnet (12) is arranged inside the
working space (14) or to delimit the working space (14).
28. The refrigerant compressor according to claim 24, wherein the
at least one first permanent magnet (11) is arranged in the region
of the first front side (3a) of the piston (3) facing toward the
cylinder head (4).
29. The refrigerant compressor according to claim 28, wherein the
at least one first permanent magnet (11) is sectionally or entirely
countersunk in the front side (3a) and/or in the piston shaft
(22).
30. The refrigerant compressor according to claim 24, wherein the
free space (13) is implemented as a gap, whose clear opening width
widens in the direction of the working space (14).
31. The refrigerant compressor according to claim 29, wherein the
free space (13) is filled using a non-ferromagnetic material.
32. The refrigerant compressor according to claim 24, wherein the
at least one first permanent magnet (11) is arranged opposite to
the at least one second permanent magnet (12).
33. The refrigerant compressor according to claim 24, wherein the
permanent magnets (11, 12) are implemented as essentially
ring-shaped, the ring shape preferably extending
rotationally-symmetric to the piston longitudinal axis (9) and/or
the free space preferably being implemented as a ring gap.
34. The refrigerant compressor according to claim 24, wherein one
front side (11a) of the at least one first permanent magnet (11)
extends substantially parallel to one front side (12a) of the at
least one second permanent magnet (12).
35. The refrigerant compressor according to claim 29, wherein the
at least one first permanent magnet (11) has an essentially equal
field strength, preferably an essentially equal mass, as the at
least one second permanent magnet (12).
36. The refrigerant compressor according to claim 29, wherein
multiple permanent magnets (11, 12) are arranged on a circle
extending concentrically to the piston longitudinal axis (9), the
angle spacing of adjacent permanent magnets (11, 12) being
essentially equal.
37. The refrigerant compressor according to claim 24, wherein the
piston (3) is implemented as a double piston, comprising two piston
sections (19, 20), arranged on opposing end regions of the double
piston (3) and each forming one front side (3a, 3b) of the double
piston, a first working space (14) being formed between the first
front side (3a) of the double piston (3) and a first cylinder head
(4) comprising a first valve plate (5) and a second working space
(14') being formed between the second front side (3b) of the double
piston (3) and a second cylinder head (4') comprising a second
valve plate (5'), and the oscillating body (7) being arranged
between the two front side (3a, 3b) of the double piston (3),
preferably enclosed by the double piston (3), and one permanent
magnet arrangement according to one of the preceding claims being
provided for each cylinder head-piston section pair (4/19, 4'/20).
Description
[0001] The invention relates to a refrigerant compressor having a
hermetically sealed compressor housing, in whose interior a
piston-cylinder unit which compresses a refrigerant is arranged,
whose cylinder housing is frontally closed by means of a cylinder
head, in which a suction opening and a pressure opening are
provided, via which refrigerant is suctioned in via a suction valve
through the suction opening and compressed via a pressure valve
through the pressure opening, the piston-cylinder unit having at
least one piston guided in a piston bore of the cylinder housing, a
workspace for compressing a refrigerant being formed between the
cylinder head and a first front side of the piston, a linear drive
being provided, comprising at least one oscillating body enclosed
by an exciter coil, which is connected to the piston in order to
move it in an oscillating manner along a piston longitudinal axis,
according to the preamble of claim 1.
[0002] The refrigerating machine process using azeotropic gases has
been known per se for some time. The refrigerant is heated and
finally superheated by absorbing energy from the space to be cooled
in a vaporizer, which results in vaporization, and is compressed to
a higher pressure level by means of a piston-cylinder unit of the
refrigerant compressor, where it releases heat via a condenser and
is conveyed back into the vaporizer again via a throttle, in which
pressure reduction and cooling of the refrigerant occur. Such
refrigerant compressors are used in the domestic and industrial
fields, where they are typically arranged on the back side of a
refrigerator or refrigerated shelf.
[0003] The piston-cylinder unit comprises a cylinder housing
provided with a piston bore, in which an oscillating piston is
guided.
[0004] The piston bore of the cylinder housing is closed in a first
axial end area by a cylinder head or by a valve plate, while the
piston bore is open in a second axial end area for accommodating
the piston or is penetrated by a connecting rod in the installed
state of the refrigerant compressor.
[0005] The cylinder head can be implemented in general, on the one
hand, as a solid, cap-shaped component, for example, having a
pressure chamber and a suction chamber, which carries a valve plate
on its inner side. It can be implemented as a ring-shaped
component, which holds the valve plate on the cylinder housing,
however, it can also be implemented solely as a valve plate, which
is clamped by means of a clamping device on the cylindrical part of
the cylinder housing. The suction opening for suctioning the
refrigerant out of the refrigerant circuit is then arranged in the
valve plate, as well as the pressure opening, through which the
compressed refrigerant is expelled by the piston after the
compression procedure in the refrigerant circuit.
[0006] The valve plate is screwed together with the front side of
the cylinder housing in the most widespread refrigerant piston
compressors. For this purpose, bores are arranged both on the
cylinder housing and also in the valve plate, the bores in the
cylinder housing each being provided with a thread, via which the
screw connection is performed. On the side of the valve plate
opposite to the cylinder housing, in this most widespread type of
refrigerant compressors, a cylinder cover is provided, which has a
pressure chamber, in which compressed refrigerant expelled from the
cylinder is briefly buffered in order to overflow into the
refrigerant circuit thereafter. Exemplary embodiments are also
known in which a suction chamber corresponding to the pressure
chamber is provided, via which the refrigerant is suctioned through
the suction opening into the cylinder. Pressure chamber and suction
chamber are separated from one another by appropriate structural
measures in the cylinder cover in such cases.
[0007] A refrigerant compressor of conventional construction
comprises an electric motor, which drives the piston oscillating in
the piston bore via a crankshaft.
[0008] To make the provision of a crankshaft superfluous, diverse
linear compressor solutions exist, in which the piston is driven
directly by an electric linear drive. In this case, the piston is
connected to an oscillating body, which, enclosed by an exciter
winding (also referred to as a stator) is set into movement in an
oscillating manner along a piston longitudinal axis. The piston
stroke (=piston travel) can be determined by a variably induced
voltage on the linear drive.
[0009] The exact delimitation of the piston travel during
oscillation of the piston is problematic in such solutions. On the
one hand, the piston is to be prevented from striking in the region
of the top dead center on the cylinder head or on the valve plate
arranged in the cylinder head. On the other hand, however, the top
dead center of the piston is also to be prevented from being
displaced too far downward, or the piston approaching the cylinder
head or the valve plate is to be prevented from executing a
reversal movement excessively early, thus resulting in a
performance-reducing dead space.
[0010] Mechanical spring elements for buffering the piston and
therefore for delimiting the piston travel are proposed for this
purpose in publications CN 101240793 A and DE 10 2006 009 270 A.
Changing the piston travel by means of adjustable spring elements
is known from DE 10 2006 009 256 A.
[0011] The disadvantage of such systems is mechanical wear in the
spring elements and the piston components. The spring elements
occupy valuable space and have proven to be inflexible if the
refrigerating capacity of the refrigerant compressor or the piston
stroke are to be changed.
[0012] Linear compressors also exist in which the piston is
exclusively held in position during its oscillation by an
electronic controller of the linear drive. Such solutions for
delimiting the piston travel, which are known, e.g., from WO
01/48379 A and WO 2009/103138 A2, are only implementable with
provision of complex sensor and analysis technology, however. In
particular, sensors are provided which ascertain the duration of a
piston movement, which is compared thereafter by a microprocessor
to a reference duration stored on a storage medium and the current
position of the piston is calculated therefrom. Such systems are
costly and are therefore hardly used in standard compressor
manufacturing.
[0013] The present invention is therefore based on the problem of
proposing a simple and reliable possibility for delimiting the
piston travel in refrigerant compressors having linear drive, which
makes both provision of mechanical spring elements and also
provision of complex sensor and control electronics for delimiting
the piston travel superfluous. Dead space occurring in the cylinder
housing is to be reduced as much as possible.
[0014] These problems are solved according to the invention by a
device having the characterizing features of claim 1.
[0015] It is provided that the piston-cylinder unit is equipped
with at least one permanent magnet arrangement, comprising
respectively at least one first permanent magnet arranged on the
piston or on a component connected to the piston and at least one
second permanent magnet arranged on the cylinder housing or on a
component connected to the cylinder housing, the first permanent
magnet and the second permanent magnet respectively having the same
magnetic pole direction to one another, in order to generate a
repelling action between the two permanent magnets to delimit the
piston travel in the region of the top dead center and/or in the
region of the bottom dead center upon approach of the first
permanent magnet to the second permanent magnet.
[0016] The piston travel of the piston can be limited simply and
reliably in this manner. Striking of the piston on elements of the
cylinder housing, in particular on the valve plate, is also
prevented without electronic sensor and control elements.
[0017] Fundamentally, an arbitrary number of first and second
permanent magnets can be arranged in arbitrary position and
configuration.
[0018] The component connected to the piston, on which the at least
one first--movable--permanent magnet is arranged, can be the
oscillating body or a piston shaft connecting the piston to the
oscillating body in a special embodiment variant of the
invention.
[0019] The component connected to the cylinder housing, on or in
which the at least one second--fixed--permanent magnet is arranged,
is the cylinder head in a preferred embodiment variant of the
invention.
[0020] A valve plate can be arranged in the cylinder head, the at
least one second permanent magnet being arranged on the valve
plate, preferably being at least sectionally countersunk in the
valve plate. In this way, the piston travel is delimited in the
region of the top dead center. The second permanent magnet can be
arranged both externally and also internally on or even entirely or
partially in the valve plate. The delimitation of the piston travel
in the bottom dead center can also be performed using permanent
magnets, however, it can also be performed conventionally, for
example, by means of spring elements.
[0021] According to an alternative embodiment variant of the
invention, the component connected to the cylinder housing, on or
in which the at least one second permanent magnet is arranged, is a
housing enclosing the oscillating body. This housing preferably is
a support for the exciter winding (the stator) or the exciter
winding itself.
[0022] According to a particularly preferred embodiment variant of
the invention, the at least one second permanent magnet is arranged
inside the piston bore of the cylinder housing, in particular
inside the working space or delimiting the working space. Thus, for
example, one of the permanent magnets could be countersunk into the
cylinder housing so that it delimits the working space using its
front side. The working space is formed by the cylinder housing and
designates the space within the cylinder housing which the piston
passes through during its oscillation.
[0023] As already mentioned, it would also be possible according to
a further embodiment variant of the invention to arrange the second
permanent magnet outside the piston bore or the working space.
[0024] Of course, the at least one first permanent magnet can also
be arranged outside the piston bore or the working space, e.g., as
already proposed above, on the oscillating body or on the piston
shaft.
[0025] There can be provided a different or further permanent
magnet arrangement, in order to delimit the piston travel
alternatively or additionally in the region of the bottom dead
center, the at least one second permanent magnet being arranged in
an end region of the cylinder housing, the end region facing the
cylinder head. It is sensible if the at least one first permanent
magnet is arranged on a second front side of the piston facing away
from the cylinder head or on a piston shaft.
[0026] A particularly simple embodiment provides that the at least
one first permanent magnet is arranged in the region of the first
front side of the piston facing toward the cylinder head.
[0027] To avoid dead space losses, it can be provided that--as
already in the case of the second permanent magnets--the at least
one first permanent magnet is sectionally or entirely countersunk
in the front side and/or in the piston shaft. In particular, it is
possible that the countersunk first and/or second permanent magnet
is sheathed, preferably sheathed on all sides, by the material of
the piston or the cylinder head or the valve plate.
[0028] According to a refinement of the invention, it is provided
that the permanent magnet is countersunk into the front side of the
piston and/or the valve plate so that at least one free space,
which communicates with the working space, is provided between
permanent magnet and piston or permanent magnet and valve plate.
This free space preferably extends along the entire periphery of
the permanent magnet. The gap-shaped recess promotes free unfolding
of the magnetic action of the permanent magnet or expansion of the
magnetic field lines originating from the permanent magnet.
[0029] Expansion of the magnetic field lines originating from the
permanent magnet is promoted further in that the free space is
implemented as a gap according to a preferred embodiment variant of
the invention, whose clear opening width widens in the direction of
the working space.
[0030] The free space can be filled using a non-ferromagnetic
material, such as plastic. Through such filling of the recess,
undesired dead space (remaining space between piston and cylinder
head or valve plate in the top dead center of the piston), which
would decrease the performance of the refrigerant compressor, can
be avoided.
[0031] According to another preferred embodiment variant of the
invention, the first permanent magnet arranged on the piston side
is arranged opposite to the second permanent magnet arranged on the
cylinder housing. For example, both permanent magnets can be
arranged congruently in the piston longitudinal axis.
[0032] For optimal pairing of the first permanent magnet arranged
on the piston side and the second permanent magnet arranged on the
cylinder housing side, measures according to the invention are
proposed hereafter. In each case a focused action of the permanent
magnets on one another and a stable location of the piston, in
particular during its reversal movement at the dead centers, are to
be ensured.
[0033] The permanent magnets can be implemented as substantially
cylindrical.
[0034] In particular, the permanent magnets can be implemented as
substantially ring-shaped, the ring shape preferably extending
rotationally-symmetric to the piston longitudinal axis. The
permanent magnets preferably have a ring-cylindrical shape in this
case, so that countersunk permanent magnets can be enclosed by a
free space in the form of a ring gap.
[0035] The permanent magnets can also be arranged
rotationally-symmetric to an axis which is parallel to the piston
longitudinal axis.
[0036] Arbitrary modifications to the ring shape are also possible,
e.g., oval or elliptical shapes. Alternative embodiment variants
would be, e.g., spiral-shaped or lattice-shaped permanent magnets.
In a special embodiment variant, multiple permanent magnets are
arranged concentrically around the piston longitudinal axis.
[0037] If the front side of the at least one first permanent magnet
arranged on the piston side extends substantially parallel to the
front side of the at least one second permanent magnet arranged on
the cylinder housing side, uniform implementation of the magnetic
field is ensured.
[0038] According to a further preferred embodiment variant of the
invention, the first permanent magnet arranged on the piston side
substantially has an equal field strength, therefore, in the case
of identical material preferably a substantially equal mass, as the
second permanent magnet arranged on the cylinder housing side. A
symmetrical magnetic field is thus generated.
[0039] A uniform magnetic field is also achieved if multiple
permanent magnets are arranged on a circle extending concentrically
to the piston longitudinal axis, the angle spacing of adjacent
permanent magnets being substantially equal. The piston-side
permanent magnets and the cylinder-housing-side permanent magnets
are expediently respectively arranged on a circle, piston-side
permanent magnets and cylinder-housing-side permanent magnets being
diametrically opposite (i.e., being congruent viewed in the piston
longitudinal axis).
[0040] In a special type of construction, the piston can be
implemented as a double piston, comprising two piston sections
arranged on opposing end regions of the double piston, each forming
one front side of the double piston. A first working space is
formed between the first front side of the double piston and a
first cylinder head comprising a first valve plate and a second
working space is formed between the second front side of the double
piston and a second cylinder head comprising a second valve plate.
The oscillating body is arranged between the two front sides of the
double piston, preferably enclosed by the double piston, an
arrangement according to the invention of permanent magnets being
provided for each cylinder head-piston section pair.
[0041] In a method according to the invention for establishing the
piston travel of a linear compressor in a refrigerant compressor
according to the preamble of claim 1, it is provided that the
piston-cylinder unit is implemented according to one of claims 1 to
20 and in the case of predefined permanent magnets, the drive
strength of the linear drive is set so that the piston changes its
movement direction in a predefined top dead center and/or bottom
dead center without using a mechanical spring element.
[0042] It can be provided, e.g., that the piston only changes its
movement direction because of a permanent magnet arrangement in
each case both at the top dead center and also at the bottom dead
center. However, it can also be provided that the piston only
changes its movement direction because of a permanent magnet
arrangement in one dead center, while a known spring element is
used for the change of the movement direction in the other dead
center.
[0043] With the permanent magnets, the piston forms a nonlinear
mass-spring system jointly with the oscillating body and optionally
the piston shaft. Different resonance frequencies are therefore
possible in this mass-spring system if the full travel of the
mass-spring system is not utilized, while in a linear mass-spring
system, for example, in the case of exclusive use of spring
elements, only one resonance frequency occurs, at which the piston
is normally operated.
[0044] Therefore, different piston frequencies and therefore
different refrigerating capacities are possible according to the
invention.
[0045] Correspondingly, it can therefore be provided that--to
achieve different refrigerating capacities--a specific frequency of
the linear drive is additionally predefined.
[0046] As an additional safety measure, so that the piston does not
strike on the valve plate, it can be provided that the drive
strength and/or frequency of the linear drive are set based on
measured position data of the piston or magnetic field strengths.
For this purpose, for example, Hall sensors as in inductive
encoders or current-voltage measurements of the exciter winding can
be used.
[0047] The invention will be explained in greater detail on the
basis of an exemplary embodiment. In the figures:
[0048] FIG. 1 shows a schematic view of a linear compressor
according to the invention
[0049] FIG. 2 shows a longitudinal section through a
piston-cylinder unit according to the invention
[0050] FIG. 3 shows a piston-cylinder unit according to the
invention having a spring element
[0051] FIG. 4 shows a piston-cylinder unit according to the
invention having permanent magnets on the oscillating body of the
linear drive
[0052] FIG. 5 shows the embodiment variant according to FIG. 4, the
piston being located in its bottom dead center
[0053] FIG. 6 shows a detail "B" from FIG. 4
[0054] FIG. 7 shows a modification of the embodiment variant
according to FIG. 4 with spring element
[0055] FIG. 8 shows a schematic view of the magnetic fields
developed in the region of the permanent magnets in the form of
field lines (piston in bottom dead center)
[0056] FIG. 9 shows a view as in FIG. 8 (piston on the path in the
direction of top dead center)
[0057] FIG. 10 shows a view as in FIG. 8 (piston reaches top dead
center)
[0058] FIG. 11 shows a force-distance diagram to illustrate the
increase of the magnetic force upon approach of the first permanent
magnet to the second permanent magnet
[0059] FIG. 12 shows a piston-cylinder unit according to the
invention having double piston
[0060] FIG. 13 shows a schematic view of a linear compressor
according to the invention arranged in a compressor housing.
[0061] FIG. 1 schematically shows the construction of a linear
compressor 23 according to the invention, which is arranged by
means of a suspension device 28 within a hermetically sealed
compressor housing 29 (shown in FIG. 13) of a small refrigerant
compressor. The linear compressor 23 comprises a piston-cylinder
unit 21 having at least one piston 3 guided in a piston bore 2 of a
cylinder housing 1. The cylinder housing 1 is frontally closed
using a cylinder head 4, more specifically using a valve plate 5
held in the cylinder head 4.
[0062] The piston 3 is movable in an oscillating manner by a linear
drive 6 along a piston longitudinal axis 9. In a known manner, the
linear drive 6 comprises an oscillating body 7, which is rigidly
connected or articulated with the piston 3, enclosed by an exciter
winding (a stator) 8. In the present exemplary embodiment, the
oscillating body 7 is connected by means of a piston rod or a
piston shaft 22 to the piston 3.
[0063] According to the invention, the piston-cylinder unit 21 is
equipped with at least one permanent magnet arrangement (namely two
here: 11a and 12a; 11b and 12b), respectively comprising at least
one first permanent magnet 11a, 11b arranged on the piston 3 or on
a component connected to the piston 3--in particular, this could be
the oscillating body 7 or the piston shaft 22 in this case--and
comprising at least one second permanent magnet 12a, 12b arranged
on the cylinder housing 1 or on a component connected to the
cylinder housing 1. The at least one first permanent magnet 11a,
11b and the at least one second permanent magnet 12a, 12b
respectively point in the same magnetic pole direction to one
another, so that upon approach of the at least one first permanent
magnet 11 to the at least one second permanent magnet 12, a
repelling effect arises between the two permanent magnets 11 and 12
and therefore an action which delimits the piston travel in the
region of the top dead center and/or in the region of the bottom
dead center of the piston 3.
[0064] In the case of FIG. 1, a first permanent magnet 11a is
attached to the front side of the piston 3 and a further first
permanent magnet 11b, namely a ring-shaped permanent magnet, is
attached to the opposing side. A second permanent magnet 12a is
attached to the cylinder head 4 or to its valve plate, and a
further permanent magnet 12b is attached to the opposing side of
the cylinder housing 1, where the piston shaft 22 passes through
the cylinder housing 1. The latter permanent magnet is implemented
as ring-shaped. The permanent magnets 11a and 12a cooperate and
determine on the basis of their field strength the force increase
in the direction of the top dead center of the piston 3, while the
permanent magnets 11b and 12b cooperate and establish on the basis
of their field strength the force increase in the direction of the
bottom dead center of the piston 3. Depending on load, the points
at which the piston 3 actually reverses can vary.
[0065] An embodiment similar to that in FIG. 1 is shown in FIG. 2,
except that in FIG. 2 a ring-shaped permanent magnet 11 is
countersunk in the first front side 3a of the piston 3 and a
ring-shaped second permanent magnet 12 is countersunk corresponding
thereto in the valve plate 5 of the piston 4. The surface of the
first permanent magnet 11 facing toward the working space 14 is in
a plane with the first front side 3a of the piston 3. The surface
of the second permanent magnet 12 facing toward the working space
14 is in a plane with the level inner surface of the valve plate
5.
[0066] The valve plate 5 has a suction opening 17, which is
closable on the inner side of the valve plate 5 using a suction
valve 15. Furthermore, it has a pressure opening 18, which can be
closed on the outer side of the valve plate 5 using a pressure
valve 16.
[0067] During the intake stroke shown here (the piston 3 moves to
the right), the refrigerant flows via the suction opening 17 past
the open suction valve 15 into a working space 14 formed between
the valve plate 5 and a first front side 3a of the piston 3 facing
toward it. During the compression stroke (the piston 3 moves to the
left), refrigerant is conveyed back out of the interior of the
cylinder housing 1 via the pressure opening 18. The piston shaft 22
is not shown in FIG. 2.
[0068] The two permanent magnets 11, 12 have identical dimensions
and are manufactured from the same ferromagnetic material, so that
they have equal magnetic field strength. They are implemented as
ring cylinders, the inner and the outer surfaces therefore have the
shape of a cylindrical sheath, the contact surface on the piston 3
has the shape of a circular ring, as does the surface of the
permanent magnets 11, 12 facing toward the working space 14.
[0069] Both permanent magnets 11, 12 are countersunk in ring-shaped
depressions of the piston 3 or the valve plate 5, respectively, so
that the surface of the permanent magnet 11, 12 facing toward the
working space 14 terminates level with the first front side 3a of
the piston or with the inner side of the valve plate 5,
respectively. The permanent magnets 11, 12 each rest on the base of
the ring-shaped depression, between the outer surface of the
permanent magnets 11, 12, which is implemented as a cylindrical
sheath, and the wall of the depression, however, a free space 13 is
provided, so that the magnetic field lines--undisturbed by the
metallic material of the piston 3 or the valve plate 5--can exit
through the outer surface in the form of a cylindrical sheath of
the permanent magnets 11, 12. The free space 13 can also, as shown
in the case of the piston 3, be filled using a non-ferromagnetic
material, for example, using plastic. The dead space is thus
decreased, i.e., the space between the piston in the dead center
and the valve plate which can be filled with refrigerant.
[0070] The piston travel is delimited at the top dead center by the
permanent magnets 11, 12 using the embodiment according to FIG. 2.
To delimit the piston travel at the bottom dead center, either a
further first permanent magnet, like permanent magnet 11b in FIG.
1, can also be arranged on the second front side 3b of the piston
3, with a corresponding permanent magnet 12b on the cylinder
housing.
[0071] Or, as shown in FIG. 3, a spring element 27 can be provided,
which establishes the bottom dead center of the piston 3. The
embodiment of the piston-cylinder unit is equivalent to that of
FIG. 2. In addition, the exciter winding 8 is also shown in FIG.
3.
[0072] In the embodiment variant according to FIGS. 4-6, the first
permanent magnets 11a, 11b are not arranged on the piston 3, but
rather on the cylindrical oscillating body 7 of the linear drive 6.
The corresponding second permanent magnets 12a, 12b are arranged on
the inner side of the housing 24 of the linear drive 6, so that
they align in the direction of the piston longitudinal axis 9 with
the permanent magnets 11a, 11b.
[0073] The permanent magnets 11a, 11b, 12a, 12b are also
implemented as ring cylinders here, but are not countersunk in the
oscillating body 7 or the housing 24, respectively, but rather are
fastened on the circular surfaces of the oscillating body 7 or on
opposing inner walls of the housing 24, respectively. The ring
cylinders are arranged concentrically to the piston longitudinal
axis 9.
[0074] When the piston 3 is located in the top dead center, see
FIG. 4, the permanent magnets 11a and 12a--viewed in the direction
of the piston longitudinal axis 9--have the least possible distance
from one another because of the force of the linear drive 6 acting
on the oscillating body 7. However, the permanent magnets 11b and
12b have the greatest possible distance from one another, which
essentially corresponds to the piston stroke of the piston 3.
[0075] If the piston 3 is located in the bottom dead center, see
FIG. 5, the permanent magnets 11b and 12b--viewed in the direction
of the piston longitudinal axis 9--have the least possible distance
from one another because of the force of the linear drive 6 acting
on the oscillating body 7.
[0076] However, the permanent magnets 11a and 12a have the greatest
possible distance from one another, which essentially corresponds
to the piston stroke of the piston 3.
[0077] FIG. 6 shows detail B from FIG. 4 in enlarged form. The
permanent magnets 11a and 12a are visible of the one permanent
magnet arrangement (a), only permanent magnet 11b is visible of the
second permanent magnet arrangement (b). The radial external
diameter of the permanent magnets 11a and 11b almost corresponds to
the radial diameter of the cylindrical oscillating body 7, the
diameter of the permanent magnets 11a, 11b, 12a, 12b is only
approximately 1-5% smaller than that of the oscillating body 7.
[0078] FIG. 7 shows a modification of the embodiment variant
according to FIG. 4, in that the permanent magnet arrangement for
establishing the bottom dead center from FIG. 4 is replaced by a
spring element 27. The permanent magnets 11a and 12a from FIG. 4
are maintained, the permanent magnets 11b and 12b are replaced by
the spring element 27.
[0079] FIG. 8 shows a schematic view of the magnetic fields
developed in the region of the permanent magnets 11, 12 of FIGS. 2
and 3 in the form of field lines 25 or 26, respectively, the piston
3 being located in the region of its bottom dead center. Magnetic
field lines are closed, they each exit at the so-called "north
pole" from the permanent magnets and enter therein at the so-called
"south pole". When the south pole of a permanent magnet approaches
the north pole of another permanent magnet, the permanent magnets
attract and adhere to one another. If the north pole of one
permanent magnet approaches the north pole of another permanent
magnet (or the south pole approaches the south pole of another
permanent magnet), the two permanent magnets repel, it is not
possible or it is only possible using a specific force for the
permanent magnets to approach close enough to one another so that
their south poles touch. This principle is utilized in this
invention. Since the repelling force between the magnetic poles of
the same name is inversely proportional to the distance of the
magnetic poles, the force for the approach of the piston 3 to the
valve plate 5 is not linear to the distance between piston 3 and
valve plate 5. This is a substantial difference from a spring
element arranged between valve plate 5 and piston 3, in which the
force is linearly dependent on the distance between valve plate 5
and piston 3.
[0080] Both valve plate 5 and also piston 3 are manufactured in
this exemplary embodiment from steel, i.e., they are ferromagnetic
themselves, therefore the magnetic field lines 25, 26 can penetrate
into the valve plate 5 and the piston 3. The distance between
piston 3 and piston bore 2 is shown exaggeratedly large here.
[0081] FIG. 9 shows the piston-cylinder arrangement 21 during the
progressing compression stroke, the piston is on the path in the
direction of top dead center. The first permanent magnet 11
arranged on the first front side 3a of the piston 3 approaches the
fixed second permanent magnet 12 countersunk in the valve plate 5.
The magnetic fields of the two permanent magnets 11, 12 influence
one another significantly more than in FIG. 8. In the working
region 14, the distance between the separate field lines 25, 26 of
the permanent magnets decreases, the magnetic field strength
becomes greater, the field lines are "tensioned" similarly to a
spring.
[0082] According to FIG. 10, the piston 3 has reached its top dead
center. Striking of the first front side 3a of the piston 3 on the
valve plate 5 is prevented, since the two permanent magnets 11 and
12 each point toward one another with identical magnetic pole
direction (with the "north pole") and therefore repel one another.
If the exciter field of the exciter winding 8 was now turned off,
the piston 3 would be displaced to the right by the repelling force
of the permanent magnets 11, 12.
[0083] The piston travel in the region of the bottom dead center
can also be delimited in the same fundamental way as the piston
travel was delimited according to FIGS. 8-10 in the region of the
top dead center.
[0084] FIG. 11 shows a force-distance graph to illustrate the
increase of the magnetic force during the approach of the first
permanent magnet 11 to the second permanent magnet 12. The distance
between first permanent magnet 11 and second permanent magnet 12 in
centimeters is plotted on the horizontal axis, the magnetic force F
in % is plotted on the vertical axis, 100% representing the
repelling magnetic force in the top dead center. This force must be
applied by the linear drive 6 and the mass inertia of the piston 3
having oscillating body 7 to hold the piston 3 for a short time in
the top dead center. In this example, the top dead center is given
at a distance of 0.05-0.5 mm between first permanent magnet 11 and
second permanent magnet 12. Both the rhomboid measuring points and
also the measuring curve interpolated based on the measuring points
are shown.
[0085] FIG. 12 shows a piston-cylinder unit according to the
invention having a double piston. The piston 3 is implemented as a
double piston and comprises two piston sections 19, 20, arranged on
opposing end regions and each forming one front side 3a, 3b of the
double piston. A first working space 14 is formed between the first
front side 3a of the double piston and a first cylinder head 4
comprising a first valve plate 5, and a second working space 14' is
formed between the second front side 3b of the double piston and a
second cylinder head 4' comprising a second valve plate 5'. The
oscillating body 7 is arranged between the two front sides 3a, 3b
of the double piston, preferably enclosed by the double piston 3.
One permanent magnet arrangement 11a, 12a or 11b, 12b according to
the invention is provided for each cylinder head-piston section
pair 4/19 or 4'/20.
LIST OF REFERENCE NUMERALS
[0086] 1 cylinder housing
[0087] 2 piston bore
[0088] 3 piston
[0089] 3a first front side of the piston
[0090] 3b second front side of the piston
[0091] 4 cylinder head
[0092] 4' second cylinder head
[0093] 5 valve plate
[0094] 5' second valve plate
[0095] 6 linear drive
[0096] 7 oscillating body
[0097] 8 exciter winding (stator)
[0098] 9 piston longitudinal axis
[0099] 11, 11a, 11b first permanent magnet
[0100] 12, 12a, 12b second permanent magnet
[0101] 13 free space
[0102] 14 working space of the piston 3
[0103] 14' second working space of the piston 3
[0104] 15 suction valve
[0105] 15' second suction valve
[0106] 16 pressure valve
[0107] 16' second pressure valve
[0108] 17 suction opening
[0109] 17' second section opening
[0110] 18 pressure opening
[0111] 18' second pressure opening
[0112] 19 first piston section of the double piston
[0113] 20 second piston section of the double piston
[0114] 21 piston-cylinder unit
[0115] 22 piston shaft
[0116] 23 linear compressor
[0117] 24 housing of the linear drive
[0118] 25 field lines of the first permanent magnet
[0119] 26 field lines of the second permanent magnet
[0120] 27 spring element
* * * * *