U.S. patent application number 12/224510 was filed with the patent office on 2009-12-10 for linear drive and linear compressor with adaptive output.
This patent application is currently assigned to BSH Bosch und Siemens Hausgerate GmbH. Invention is credited to Johannes Reinschke.
Application Number | 20090304525 12/224510 |
Document ID | / |
Family ID | 37951877 |
Filed Date | 2009-12-10 |
United States Patent
Application |
20090304525 |
Kind Code |
A1 |
Reinschke; Johannes |
December 10, 2009 |
Linear Drive and Linear Compressor with Adaptive Output
Abstract
An apparatus having at least one of a linear drive having a
stator and a rotor configured for reciprocating movement therein
along a drive axis between a first and a second rotor reversal
point about a rotor zero position, and a linear compressor, having
a piston housing and a compressor piston configured for
reciprocating movement therein along a piston axis between a first
and a second piston reversal point about a piston zero position and
configured to be driven by the linear drive, wherein at least one
of the rotor zero position and the piston zero position is
adjustable.
Inventors: |
Reinschke; Johannes;
(Nurnberg, DE) |
Correspondence
Address: |
BSH HOME APPLIANCES CORPORATION;INTELLECTUAL PROPERTY DEPARTMENT
100 BOSCH BOULEVARD
NEW BERN
NC
28562
US
|
Assignee: |
BSH Bosch und Siemens Hausgerate
GmbH
Munchen
DE
|
Family ID: |
37951877 |
Appl. No.: |
12/224510 |
Filed: |
January 22, 2007 |
PCT Filed: |
January 22, 2007 |
PCT NO: |
PCT/EP2007/050597 |
371 Date: |
November 19, 2008 |
Current U.S.
Class: |
417/53 ;
417/416 |
Current CPC
Class: |
F04B 2201/0201 20130101;
F04B 2201/0206 20130101; F04B 35/045 20130101 |
Class at
Publication: |
417/53 ;
417/416 |
International
Class: |
F04B 35/04 20060101
F04B035/04 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 28, 2006 |
DE |
10 2006 009 256.2 |
Claims
1-14. (canceled)
15. An apparatus comprising at least one of a linear drive having a
stator and a rotor configured for reciprocating movement therein
along a drive axis between a first and a second rotor reversal
point about a rotor zero position, and a linear compressor having a
piston housing and a compressor piston configured for reciprocating
movement therein along a piston axis between a first and a second
piston reversal point about a piston zero position and configured
to be driven by the linear drive, wherein at least one of the rotor
zero position and the piston zero position is adjustable.
16. An apparatus comprising at least one of a linear drive having a
stator and a rotor movable in a reciprocating manner therein along
a drive axis between a first and a second rotor reversal point
about a rotor zero position, and a linear compressor having a
piston housing and a compressor piston configured for reciprocating
movement therein along a piston axis between a first and a second
piston reversal point about a piston zero position and configured
for being driven by the linear drive, the apparatus comprising at
least one spring element configured for action on at least one of
the rotor and the compressor piston, wherein at least one of the
length the spring element can be varied, in particular shortened,
and the spring constant of the spring element can be varied, in
particular increased.
17. An apparatus comprising at least one of a linear drive having a
stator and a rotor configured for reciprocating movement therein
along a drive axis between a first and a second rotor reversal
point about a rotor zero position, and a linear reciprocating
movement therein along a piston axis between a first and a second
piston reversal point about a piston zero position and configured
for being driven by the linear drive, the apparatus comprising
means for reducing the mechanical power that can be delivered by at
least one of the linear compressor and the linear drive, in
particular from a normalized nominal power value of about 1 to
about 0.6, preferably from a normalized nominal power value of
about 1 to about 0.5, whereby at least one of electromechanical
efficiency in the event of a change in the mechanical power is
always greater than about 60%, in particular greater than about
70%, preferably greater than about 80%, and the electromechanical
efficiency falls in the event of a reduction in the mechanical
power from a normalized nominal power value of about 1 to about 0.6
on average with a gradient less than about 0.8, in particular with
a gradient less than about 0.5, preferably with a gradient less
than about 0.2, by particular preference with a gradient less than
about 0.1.
18. The apparatus according to claim 15 and further comprising a
drive coil configured for acting with an electromagnetic force on
at least one of the rotor and the compressor piston, and means for
controlling the drive coil, whereby the means for controlling the
drive coil includes means for adjusting at least one of the first
rotor reversal point and the first piston reversal point.
19. The apparatus according to claim 15 wherein at least one of the
rotor zero position is adjustable relative to the first rotor
reversal point and the piston zero position is adjustable relative
to the first piston reversal point in a manner wherein at least one
of the rotor and the compressor piston is capable of executing a
substantially symmetrical oscillation about the adjusted zero
position when the reversal point is changed.
20. The apparatus according claim 15 wherein at least one of the
rotor and the compressor piston are mounted between a spring
element on the working side and a spring element disposed
oppositely from the working side.
21. The apparatus according to claim 20 wherein the spring elements
are configured with at least one of different spring constants and
different spring lengths.
22. The apparatus according to claim 20 wherein for any position of
at least one of the rotor and the compressor piston, the spring
elements have a length which is less than about 95% of the
uncompressed spring element length, in particular less than about
90% of the uncompressed spring element length.
23. The apparatus according to claim 20 wherein for any position of
at least one of the rotor and the compressor piston, the spring
elements have a length which is greater than about 40% of the
uncompressed spring element length, in particular greater than
about 50% of the uncompressed spring element length.
24. The apparatus according to claim 20, wherein at least one of:
the working-side spring element has a spring constant in the range
of about 1 N/mm to about 5 N/mm, in particular in the range from
about 1.8 N/mm to about 3.6 N/mm, preferably in the range from
about 2.3 N/mm to about 2.9 N/mm; and the opposite spring element
has a spring constant in the range from about 4 N/mm to about 12
N/mm, in particular in the range from about 6.5 N/mm to about 9.5
N/mm, preferably in the range from about 7.5 N/mm to about 8.5
N/mm; the working-side spring element has an uncompressed spring
length in the range from about 40 mm to about 60 mm, in particular
in the range from about 48 mm to about 62 mm; and the opposite
spring element has an uncompressed spring length in the range from
about 25 mm to about 40 mm, in particular in the range from about
30 mm to about 36 mm; and the stroke of at least one of the rotor
and the compressor piston is between about 10 mm and about 30 mm,
in particular between about 12 mm and about 20 mm; and at least one
of the first rotor reversal point and the first piston reversal
point can be shifted by at least about 5 mm, in particular by at
least about 10 mm, preferably by about 20 mm.
25. The apparatus according to claim 15 wherein at least one of the
second rotor reversal point and the second piston reversal point is
fixed.
26. The apparatus according to claim 15 wherein the apparatus is at
least one of an air conditioning system and a refrigeration device,
in particular as at least one of a refrigerator and a freezer.
27. The apparatus according to claim 15 and further comprising at
least one of at least one spring element configured for action on
at least one of the rotor and the compressor piston, wherein at
least one of the length of the spring element can be varied, in
particular shortened, and the spring constant of the spring element
can be varied, in particular increased; and means for reducing the
mechanical power that can be delivered by at least one of the
linear compressor and the linear drive, in particular from a
normalized nominal power value of about 1 to about 0.6, preferably
from a normalized nominal power value of about 1 to about 0.5,
whereby at least one of electromechanical efficiency in the event
of a change in the mechanical power is always greater than about
60%, in particular greater than about 70%, preferably greater than
about 80%, and the electromechanical efficiency falls in the event
of a reduction in the mechanical power from a normalized nominal
power value of about 1 to about 0.6 on average with a gradient less
than about 0.8, in particular with a gradient less than about 0.5,
preferably with a gradient less than about 0.2, by particular
preference with a gradient less than about 0.1.
28. A method for at least one of cooling a commodity and
compressing a fluid wherein the method comprises the steps of
providing and operating an apparatus including at least one of a
linear drive having a stator and a rotor configured for
reciprocating movement therein along a drive axis between a first
and a second rotor reversal point about a rotor zero position, and
a linear compressor having a piston housing and a compressor piston
configured for reciprocating movement therein along a piston axis
between a first and a second piston reversal point about a piston
zero position and configured to be driven by the linear drive,
wherein at least one of the rotor zero position and the piston zero
position is adjustable.
Description
[0001] The invention relates to an apparatus comprising a linear
drive, which has a stator and a rotor which is movable in a
reciprocating manner therein along a drive axis between a first and
a second rotor reversal point about a rotor zero position, and/or
comprising a linear compressor which has a piston housing and a
compressor piston which is movable in a reciprocating manner
therein along a piston axis between a first and a second piston
reversal point about a piston zero position and can be driven by
the linear drive, and a method for cooling a commodity and/or for
compressing a fluid.
[0002] Linear compressors are currently being developed for
domestic refrigeration equipment, such as refrigerators and/or
freezers or air conditioning systems for example. Such compressors
are required in different output classes, for example with 7
cooling capacities of 40 W, 70 W, 80 W, 100 W, 120 W, 140 W and 160
W. In this connection the compressors for the different output
classes are designed in such a manner that they achieve an optimum
efficiency for the respective cooling capacity. With regard to
known linear compressors, a special design of linear compressor is
required for the individual cooling capacities. Such a design is
complex, cost-intensive and considerably increases the spectrum of
components and spare parts required.
[0003] The object of the present invention is therefore to set down
a linear drive and a linear compressor which are comparatively
simple to mass produce and which operate reliably and in an
energy-saving manner. The object of the invention is also to set
down a method for cooling commodities or for compressing a fluid,
which can be employed for different cooling capacities and which
operates reliably and in an energy-saving manner.
[0004] The object is achieved according to the invention by the
apparatus and by the method as set down in the independent claims.
Further advantageous embodiments and developments, which can each
be applied individually or can be combined with one another as
desired, are the subject of the respective dependent claims.
[0005] The apparatus according to the invention comprising a linear
drive, which has a stator and a rotor which is movable in a
reciprocating manner therein along a drive axis between a first and
a second rotor reversal point about a rotor zero position, and/or
comprising a linear compressor which has a piston housing and a
compressor piston which is movable in a reciprocating manner
therein along a piston axis between a first and a second piston
reversal point about a piston zero position and can be driven by
the linear drive, makes provision in a first variant such that the
rotor zero position or the piston zero position can be
adjusted.
[0006] The apparatus according to the invention comprising a linear
drive, which has a stator and a rotor which is movable in a
reciprocating manner therein along a drive axis between a first and
a second rotor reversal point about a rotor zero position, and/or
comprising a linear compressor which has a piston housing and a
compressor piston which is movable in a reciprocating manner
therein along a piston axis between a first and a second piston
reversal point about a piston zero position and can be driven by
the linear drive, makes provision in a second variant such that at
least one spring element acts on the rotor or on the compressor
piston, the length of which can be varied, in particular
shortened.
[0007] The apparatus according to the invention comprising a linear
drive, which has a stator and a rotor which is movable in a
reciprocating manner therein along a drive axis between a first and
a second rotor reversal point about a rotor zero position, and/or
comprising a linear compressor which has a piston housing and a
compressor piston which is movable in a reciprocating manner
therein along a piston axis between a first and a second piston
reversal point about a piston zero position and can be driven by
the linear drive, makes provision in a third variant such that at
least one spring element acts on the rotor or on the compressor
piston, the spring constant of which can be varied or
increased.
[0008] The apparatus according to the invention comprising a linear
drive, which has a stator and a rotor which is movable in a
reciprocating manner therein along a drive axis between a first and
a second rotor reversal point about a rotor zero position, and/or
comprising a linear compressor which has a piston housing and a
compressor piston which is movable in a reciprocating manner
therein along a piston axis between a first and a second piston
reversal point about a piston zero position and can be driven by
the linear drive, makes provision in a fourth variant such that the
mechanical power which can be delivered by the linear compressor or
by the linear drive can be reduced, in particular from a normalized
nominal power value of 1 to 0.6, preferably from a normalized
nominal power value of 1 to 0.5, whereby the electromechanical
efficiency in the event of a change in the mechanical power is
always greater than 60%, in particular greater than 70%, preferably
greater than 80%.
[0009] The apparatus according to the invention comprising a linear
drive, which has a stator and a rotor which is movable in a
reciprocating manner therein along a drive axis between a first and
a second rotor reversal point about a rotor zero position, and/or
comprising a linear compressor which has a piston housing and a
compressor piston which is movable in a reciprocating manner
therein along a piston axis between a first and a second piston
reversal point about a piston zero position and can be driven by
the linear drive, makes provision in a fifth variant of the
invention such that the electromechanical efficiency falls in the
event of a reduction in the mechanical power for a normalized
nominal power value of 1 to 0.6 on average with a gradient <0.8,
in particular with a gradient <0.5, preferably with a gradient
<0.2, by particular preference with a gradient <0.1.
[0010] The five variants of the invention exist in parallel, but
can also be combined with one another in any manner. With the
apparatus according to the invention in the different variants it
is possible to build one or two construction types, different in
terms of design engineering, of linear drives or of linear
compressors which are adjustable in terms of hardware and software
such that all output classes above a factor 4 can hereby be covered
in the power, for example between 40 W and 160 W. The spectrum of
the equipment parts required for coverage of all output classes is
considerably reduced in total, as a result of which the costs of a
linear compressor are reduced for an individual output class.
[0011] The linear drive according to the invention is suited and
intended in particular for a linear compressor.
[0012] Whereas in the case of known linear drives or linear
compressors a varied activation of the linear drive or of the
linear compressor required in order to change a cooling capacity
would result in a considerable reduction in the electromechanical
efficiency, the apparatus according to the invention operates in
the specified variants with a high degree of efficiency even in the
event of a variation or adaptation of the cooling capacity.
[0013] The rotor or the compressor piston executes a reciprocating
motion between two respective reversal points, at which the
direction of motion changes. In this connection, the rotor or the
compressor piston oscillates about a respective zero position. The
respective zero positions are predefined by the mechanical
oscillation system of the linear drive or of the linear compressor.
In the case of a symmetrical design of the linear drive or of the
linear compressor, the zero position is situated centrally between
the two reversal points.
[0014] If a cooling capacity level is changed, the rotor or the
compressor piston generally executes a different stroke.
[0015] On reducing the cooling capacity of a linear compressor, the
amplitude of a piston stroke is reduced for example. In order to
operate the linear compressor particularly efficiently, it is
advantageous to reduce a dead volume situated in the piston
housing. If the linear compressor operates with a smaller piston
stroke, then its efficiency is reduced, either as a result of the
fact that the dead volume is increased or that the
electromechanical motor efficiency is degraded.
[0016] It has been recognized that a degradation of the
electromechanical motor efficiency on changing the piston stroke
and whilst retaining as small a dead volume as possible occurring
in the case of known apparatuses has its origin in the fact that at
the changed second reversal point a spring is less strongly
pretensioned, contains less energy in other words, with the result
that any missing spring (energy) needs additionally to be delivered
electrically in the compression half-wave. An unequal delivery of
electrical energy between compression half-wave and expansion
half-wave degrades the electromagnetic efficiency. In addition,
further disadvantageous effects can occur: If the second reversal
point is increased to the extent that the spring energy at the
second reversal point is less than the sum of the spring energy at
the first reversal point and the residual gas energy (by virtue of
the non-disappearing dead volume at the first reversal point), it
is necessary to perform electrical braking during the expansion
half-wave. The electrical braking results in a further energy loss
and a reduction in the efficiency of the linear compressor or of
the linear drive.
[0017] As a result of the adaptation of the rotor zero position and
as a result of the adaptation of the piston zero position, the
mechanical system is adapted to the changed conditions and the
linear drive or the linear compressor can continue to operate close
to its maximum efficiency in spite of the change in the output
class.
[0018] The change in the rotor zero position or the piston zero
position can be effected by changing the length of a spring element
used. Spring elements are understood to include all springs such as
for example diaphragm springs or coil springs and also
corresponding compound spring packages. By changing the length of
the spring element it is possible to shift the piston zero position
such that the linear drive or the linear compressor can operate at
high efficiency.
[0019] By changing the length of the spring element or of the
spring constant of the spring element it is however also possible,
without changing the rotor zero position or the piston zero
position, to shift the natural frequency of the mechanical system
in such a marked manner that the linear drive or the linear
compressor operates at a correspondingly altered frequency, as a
result of which the power of the linear drive or of the linear
compressor can likewise be influenced.
[0020] Depending on the type of construction of the linear
compressor or of the linear drive it can be more advantageous to
change the length of the spring element or the spring tension of
the spring element. To this end, the spring as such can on the one
hand be shortened, in other words the length of the spring in its
detensioned state is changed by for example changing the mounting
of the spring, but the spring can also be more strongly compressed,
as a result of which the length of the spring element changes when
installed in the linear compressor or in the linear drive. A change
to the spring constant can for example be effected by adding
reinforcing elements to the spring. The shortening of the spring
can be irreversible, for example by clipping off a part of the
spring.
[0021] As a result of changing the rotor zero position or the
piston zero position and/or as a result of changing the length of
the spring element and/or as a result of changing the spring
constant of the spring element the linear drive or linear
compressor can be operated at its optimum point of sale. By this
means it is possible to ensure that the electromechanical
efficiency is always greater than 80% in the event of a change in
the mechanical power from a normalized nominal power value of 1 to
0.6. The nominal power value for a linear compressor or a linear
drive corresponds to the maximum power output provided during
continuous operation of the linear compressor or of the linear
drive. The mechanical power which can be delivered is based on this
nominal power value.
[0022] If a linear compressor is designed for example for 32 W, a
normalized nominal power value of 0.6 means that the linear
compressor is operated at 0.6.times.32=19.2 W. The
electromechanical efficiency is defined by
.eta. el / mech = P mech P mech + P ohm ##EQU00001##
where P.sub.mech is the mechanical power delivered at the linear
compressor and P.sub.ohm is the ohmic power loss. The
electromechanical efficiency thus represented merely approximately
reflects the actual electromechanical efficiency because it does
not take into consideration the electronics losses for position
measurement, processor and drive coil current regulator (MOSFET
bridge).
[0023] The electromechanical efficiency advantageously falls on
reduction of the mechanical power from a normalized nominal power
value of 1 to 0.6 on average with a gradient <0.1. Given
suitable dimensioning of the spring elements, of the moving masses
and the reversal points or zero positions, the electromechanical
efficiency can be essentially maintained in spite of the change in
the mechanical power delivered by the linear drive or the linear
compressor. This stands in contrast to known solutions in which a
considerably reduced electromechanical efficiency needed to be
accepted if the mechanical power yielded was reduced by more than
10%.
[0024] Energy-saving, efficient and reliable operation of the
linear drive or of the linear compressor is made possible by means
of the invention even in the situation when the power level of the
linear drive or of the linear compressor is changed. Through this,
the manufacture of a set of different linear compressors or linear
drives for different power levels becomes simpler and more
cost-effective. With the specified linear compressor or linear
drive it is possible to cover all power levels, in particular all
cooling capacity classes of linear compressors from 40 W to 160 W,
with only two structurally different linear compressors or linear
drives. To this end, a linear compressor or a linear drive is
designed for a maximum power level, for example a maximum cooling
capacity of 160 W, and can be lowered to a half, for example to
approx. 80 W cooling capacity, without requiring structural changes
to the linear compressor. A second linear compressor or a second
linear drive is designed for the maximum cooling capacity of 80 W
and can be lowered down to approx. 40 W cooling capacity. Even if
such a linear compressor operated beneath the maximum power level
is somewhat overdimensioned in respect of its electrical design
(for example the drive coils or the drive coil current circuit),
the savings effects are advantageous as a result of the drastically
reduced diversity and associated with this the increase in product
quantities.
[0025] In addition, the capability to adapt the zero positions, the
spring constants or the spring lengths can also be used in order to
fine tune the mechanical oscillation system with regard to the
normal manufacturing tolerances, in particular to precisely set the
natural frequency. A method for tuning the natural frequency of a
linear drive, and/or with a linear compressor, is particularly
advantageous.
[0026] In one embodiment of the invention a drive coil, which acts
with an electromagnetic force on the rotor or on the compressor
piston, and a means for controlling the drive coil are provided,
whereby the means allows the location of the first rotor reversal
point or of the first piston reversal point to be adjusted.
[0027] With the aid of this means it is possible on the control
side, on the software side for example, to adjust the location of
the first rotor reversal point or of the first piston reversal
point.
[0028] The activation of the drive coil can also take place within
the framework of a regulation system in which sensors are provided
which sense the position of the rotor or the position of the
compressor piston and an appropriate activation of the drive coil
is effected on the basis of the position information. The
reciprocating motion of the rotor or of the compressor piston can
thus be both controlled and also regulated.
[0029] In a particularly advantageous embodiment the rotor zero
position is adjustable relative to the first rotor reversal point
or the piston zero position is adjustable relative to the first
piston reversal point in such a manner that the rotor or the
compressor piston is able to execute an essentially symmetrical
oscillation about the adjusted zero position when the reversal
point is changed.
[0030] As a result of the adaptation of the zero positions to the
respective changed reversal points, the required technical control
or regulation motion can be brought into coincidence with the
natural motion of the physical oscillation system. A high degree of
efficiency of the linear compressor or of the linear drive can be
achieved by this means.
[0031] As a result of the adaptation of the natural frequency of
the mechanical oscillation system, the power delivered can be
influenced and the efficiency can be optimized.
[0032] In a particularly advantageous embodiment of the invention
the rotor and/or the compressor piston are mounted between a spring
element on the working side and a spring element situated opposite
the latter.
[0033] On the working side here means the side on which the work is
to be done. In the case of a piston rod, which connects the linear
drive to the linear compressor, the working side is the side facing
the compressor piston. The opposite side is that facing the rotor.
A particularly stable reciprocating motion is brought about by this
form of mounting.
[0034] In a special embodiment of the invention the spring elements
have different spring constants and/or different spring
lengths.
[0035] The spring elements are advantageously under tension for any
position of the rotor or of the compressor piston and in their
mounted state have a length which is less than 95% of the
uncompressed spring element length, in particular less than 90% of
the uncompressed spring element length. This ensures that both
spring elements have a tensioning state for each rotor or
compressor piston position, which likewise serves to enable a
stable reciprocating motion.
[0036] In order to avoid any striking it is advantageous for the
spring elements to have a length for each position of the rotor or
of the compressor piston which is greater than 40% of the
uncompressed spring element length, in particular greater than 50%
of the uncompressed spring element length. This prevents the spring
elements from ever being pressed together to the extent that the
individual spring connections come into contact with one another.
Any hard striking is effectively avoided by this means.
[0037] In a special embodiment of the invention at least one of the
following criteria (.alpha.1) to (.alpha.6) is achieved. [0038]
(.alpha.1) the working-side spring element (14) has a spring
constant in the range from 1 N/mm to 5 N/mm, in particular in the
range from 1.8 N/mm to 3.6 N/mm, preferably in the range from 2.3
N/mm to 2.9 N/mm; [0039] (.alpha.2) the opposite spring element
(15) has a spring constant in the range from 4 N/mm to 12 N/mm, in
particular in the range from 6.5 N/mm to 9.5 N/mm, preferably in
the range from 7.5 N/mm to 8.5 N/mm; [0040] (.alpha.3) the
working-side spring element (14) has an uncompressed spring length
in the range from 40 mm to 60 mm, in particular in the range from
48 mm to 62 mm; [0041] (.alpha.4) the opposite spring element (15)
has an uncompressed spring length in the range from 25 mm to 40 mm,
in particular in the range from 30 mm to 36 mm; [0042] (.alpha.5)
the stroke of the rotor (5) or of the compressor piston (6) is
between 10 mm and 30 mm, in particular between 12 mm and 20 mm;
[0043] (.alpha.6) the first rotor reversal point (11) or the first
piston reversal point (21) can be shifted by at least 5 mm, in
particular by at least 10 mm, preferably by 20 mm.
[0044] A combination of the criteria (.alpha.1) to (.alpha.6) is
particularly advantageous, whereby however the individual criteria
can each be applied individually or can be combined with one
another as desired.
[0045] It is furthermore advantageous if the second rotor reversal
point and/or the second piston reversal point are fixed. By this
means it is possible for example with regard to linear compressors
to ensure that the dead volume present in the piston housing is
kept as small as possible, which improves the efficiency of the
linear compressor.
[0046] The apparatus according to the invention can be embodied as
a refrigeration device, in particular as a refrigerator and/or
freezer or as an air conditioning system.
[0047] Although the different variants of the invention have been
described separately above, the variants can however also be
combined with one another as desired. The variants stand partially
overlapping, partially non-overlapping alongside one another.
[0048] The method according to the invention for cooling a
commodity and/or for compressing a fluid uses the apparatus
according to the invention. Commodities can be cooled speedily,
reliably and in an energy efficient manner or a fluid can be
compressed reliably and efficiently on account of the high
efficiency of the linear drive or of the linear compressor, the
high reliability and energy economy, even if it is necessary to
operate with different power levels.
[0049] Further advantageous details and special features will be
described in detail with reference to the following drawing which
should not restrict the present invention but is intended merely as
an illustration by way of example.
[0050] In the schematic drawings:
[0051] FIG. 1 shows a sectional view of an apparatus according to
the invention;
[0052] FIG. 2 shows a refrigeration device with an apparatus
according to FIG. 1;
[0053] FIG. 3 shows a graph in which the electromechanical
efficiency of an apparatus according to the invention and also of a
known apparatus is plotted against a power output generated
therewith.
[0054] FIG. 1 shows an apparatus 1 according to the invention in a
sectional view with a linear drive 2 and a linear compressor 3. The
linear drive 2 has a stator 4, in which a rotor 5 moves in a
reciprocating manner along a drive axis 9. The rotor 5 is driven
with the aid of a drive coil 16 which is supplied with a drive coil
current by a means 17 for actuating the drive coil 16. The rotor 5
oscillates between a first rotor reversal point 11 and a second
rotor reversal point 12 and in doing so passes through a rotor zero
position 13. The motion of the rotor 5 is sensed with the aid of a
position sensor 25 which passes on the position information to the
means 17 for actuating the drive coil 16, with the result that in
total a control system is implemented for the motion of the rotor
5.
[0055] The linear compressor 3 has a piston housing 7, in which a
compressor piston 6 oscillates in a reciprocating manner along a
piston axis 8 between a first piston reversal point 21 and a second
piston reversal point. During its reciprocating motion the
compressor piston 6 compresses a fluid 18 which is drawn in by way
of a suction connection 18 and is discharged by way of a pressure
connection 29. The intake and discharge of the fluid 18 is switched
with the aid of a valve plate 30. The compressor piston is mounted
in contact-free fashion in the piston housing 7 by means of a
housing wall 20 having openings 19. Fluid 18 is forced through the
openings 19 by means of a feed system 31 in such a manner that a
gas cushion is built up between the housing wall 20 and the
compressor piston 6, as a result of which a gas pressure bearing is
produced.
[0056] The rotor 5 is connected to the compressor piston 6 by way
of a piston rod 24 which has two couplings 26 in order to absorb
bending forces. The zero positions 13, 23 are defined by the
arrangement of spring elements 14, 15. The compressor piston 6 is
mounted between a working-side spring element 14 and a spring
element 15 situated opposite the latter. The working-side spring
element has a length L1 and the opposite spring element 15 has a
length L2. The uncompressed spring length of the working-side
spring element is 59 mm. The uncompressed spring length of the
opposite spring element 15 is 33 mm. The zero positions 13, 23 can
be adjusted by means of an adjustment aid 34. The linear compressor
operates at a nominal power value of 80 W. If the nominal power
value is to be reduced to 40 W, the spring elements 14, 15 are
compressed by the adjustment aid 34 and the activation of the drive
coils is adapted using the means 17 such that the drive oscillation
at the coil 16 coincides approximately with the natural physical
motion. By this means, a braking of the linear drive 2 is avoided
and a particularly high efficiency is achieved even if the linear
compressor 3 is operated at 40 W.
[0057] FIG. 2 shows a refrigeration device 10 with an apparatus 1
according to the invention, with which commodities 27 can be cooled
speedily, efficiently and in an energy efficient manner. For a
product range comprising 7 refrigerators having different power
levels from 40 W to 160 W only two different linear compressor
designs are required, as a result of which the manufacturing costs
of an individual refrigerator are reduced. Thanks to the high
efficiency, efficient and energy saving cooling of the commodities
27 is possible.
[0058] FIG. 3 shows the electromechanical efficiency of the linear
compressor according to the invention (see curve 33) and also the
efficiency for a known linear compressor (see curve 32), depending
on the respective power delivered by the linear compressors. The
electromagnetic efficiency is defined as
.eta. el / mech = P mech p mech + P ohm ##EQU00002##
[0059] The power delivered is normalized to the nominal power, in
other words the maximum power achievable during continuous
operation of the refrigeration device. It can be seen that with
regard to known linear compressors the efficiency essentially
depends linearly on the power delivered whereas with regard to the
linear compressor according to the invention the electromagnetic
efficiency essentially remains constant for delivered power levels
of 100% to 50%.
[0060] The invention relates to an apparatus 1 comprising a linear
drive 2, which has a stator 4 and a rotor 5 which is movable in a
reciprocating manner therein along a drive axis 9 between a first
11 and a second 12 rotor reversal point about a rotor zero position
13, and/or comprising a linear compressor 3 which has a piston
housing 7 and a compressor piston 6 which is movable in a
reciprocating manner therein along a piston axis 8 between a first
21 and a second 22 piston reversal point about a piston zero
position 23 and can be driven by the linear drive 2, whereby either
the rotor zero position 13 or the piston zero position 23 is
adjustable and/or at least one spring element 14, 15 acts on the
rotor 5 or on the compressor piston 6, the length of which can be
varied, in particular shortened, and/or the spring constant of
which can be varied, in particular increased; and a method for
cooling commodities 27 and/or for compressing a fluid 18.
[0061] The invention is distinguished by the fact that adaptation
of the power delivered by the apparatus has no substantial effect
on the electromechanical efficiency of the apparatus, as a result
of which a linear drive 2 and a linear compressor 3 can be
constructed in an especially cost-effective manner since the
diversity of the component parts can be considerably reduced.
LIST OF REFERENCE CHARACTERS
[0062] 1 Apparatus [0063] 2 Linear drive [0064] 3 Linear compressor
[0065] 4 Stator [0066] 5 Rotor [0067] 6 Compressor piston [0068] 7
Piston housing [0069] 8 Piston axis [0070] 9 Drive axis [0071] 10
Refrigeration device [0072] 11 First rotor reversal point [0073] 12
Second rotor reversal point [0074] 13 Rotor zero position [0075] 14
Working-side spring element [0076] 15 Opposite spring element
[0077] 16 Drive coil [0078] 17 Means for actuating the drive coil
16 [0079] 18 Fluid [0080] 19 Openings [0081] 20 Housing wall [0082]
21 First piston reversal point [0083] 22 Second piston reversal
point [0084] 23 Piston zero position [0085] 24 Piston rod [0086] 25
Position sensor [0087] 26 Coupling [0088] 27 Commodity [0089] 28
Suction connection [0090] 29 Pressure connection [0091] 30 Valve
plate [0092] 31 Feed system [0093] 32 Efficiency without zero
position adaptation [0094] 33 Efficiency with zero position
adaptation [0095] 34 Adjustment aid [0096] L1 Length of
working-side spring element 14 [0097] L2 Length of opposite spring
element 15
* * * * *