U.S. patent application number 16/376430 was filed with the patent office on 2019-08-01 for semi-hermetic refrigerant compressor.
The applicant listed for this patent is BITZER Kuehlmaschinenbau GmbH. Invention is credited to Rainer Grosse-Kracht, Jens Mannewitz, Eduardo Martin, Hermann Renz.
Application Number | 20190234392 16/376430 |
Document ID | / |
Family ID | 57104046 |
Filed Date | 2019-08-01 |
View All Diagrams
United States Patent
Application |
20190234392 |
Kind Code |
A1 |
Grosse-Kracht; Rainer ; et
al. |
August 1, 2019 |
Semi-Hermetic Refrigerant Compressor
Abstract
In order to improve a semi-hermetic refrigerant compressor,
comprising a reciprocating piston compressor, an electric motor, an
overall housing which has a motor housing portion for the electric
motor and a compressor housing portion for the reciprocating piston
compressor, a suction-side refrigerant path which leads from a
suction connection on the overall housing to an inlet chamber of
the reciprocating piston compressor, and a pressure-side
refrigerant path which leads from an outlet chamber of the
reciprocating piston compressor to a pressure connection on the
overall housing, such that the refrigerant compressor functions
more efficiently, it is proposed that the electric motor is
configured as a synchronous motor, in the rotor of which there are
arranged permanent magnets for the synchronous operation of the
electric motor and a squirrel cage for starting up the electric
motor in asynchronous operation.
Inventors: |
Grosse-Kracht; Rainer;
(Sindelfingen, DE) ; Renz; Hermann; (Egenhausen,
DE) ; Martin; Eduardo; (Leipzig, DE) ;
Mannewitz; Jens; (Schkeuditz, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BITZER Kuehlmaschinenbau GmbH |
Sindelfingen |
|
DE |
|
|
Family ID: |
57104046 |
Appl. No.: |
16/376430 |
Filed: |
April 5, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/EP2016/074063 |
Oct 7, 2016 |
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16376430 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 39/121 20130101;
F04B 49/24 20130101; F04B 35/01 20130101; F04B 27/053 20130101;
F04B 7/0076 20130101; F04B 35/04 20130101; F04B 39/123 20130101;
F04B 39/125 20130101; F04B 49/06 20130101 |
International
Class: |
F04B 39/12 20060101
F04B039/12; F04B 35/04 20060101 F04B035/04; F04B 7/00 20060101
F04B007/00 |
Claims
1. A semi-hermetic refrigerant compressor, comprising a
reciprocating piston compressor and an electric motor, an overall
housing which has a motor housing portion for the electric motor
and a compressor housing portion for the reciprocating piston
compressor, a suction-side refrigerant path which leads from a
suction connection on the overall housing to an inlet chamber of
the reciprocating piston compressor, and a pressure-side
refrigerant path which leads from an outlet chamber of the
reciprocating piston compressor to a pressure connection on the
overall housing, wherein at least one cylinder of the reciprocating
piston compressor is provided in the compressor housing portion and
has a piston movable in a cylinder bore formed in the compressor
housing portion, a valve plate closing the cylinder bore, and a
cylinder head extending over the valve plate and forming part of
the compressor housing portion, the electric motor is configured as
a synchronous motor, in the rotor of which there are arranged
permanent magnets for the synchronous operation of the electric
motor and a squirrel cage for the start-up of the electric motor in
asynchronous operation.
2. A refrigerant compressor according to claim 1, wherein the
permanent magnets extend parallel to a rotor axis of the rotor.
3. A refrigerant compressor according to claim 2, wherein the
permanent magnets are formed as planar bodies, the flat sides of
which extend in a longitudinal direction and in a transverse
direction running transversely to the longitudinal direction.
4. A refrigerant compressor according to claim 1, wherein the
permanent magnets each extend with their longitudinal direction
parallel to the rotor axis.
5. A refrigerant compressor according to claim 1, wherein the
permanent magnets extend with their transverse directions along
outer edges of a geometric rectangle that is symmetrical with
respect to the rotor axis.
6. A refrigerant compressor according to claim 1, wherein the
permanent magnets formed as planar bodies have a different magnetic
polarity (N, S) on their mutually opposite flat sides, one of which
faces towards the rotor axis and the other of which faces away from
the rotor axis.
7. A refrigerant compressor according to claim 1, wherein the
suction-side refrigerant path passes through the motor housing for
cooling of the electric motor.
8. A semi-hermetic refrigerant compressor, comprising a
reciprocating piston compressor and an electric motor, an overall
housing which has a motor housing portion for the electric motor
and a compressor housing portion for the reciprocating piston
compressor, a suction-side refrigerant path which leads from a
suction connection on the overall housing to an inlet chamber of
the reciprocating piston compressor, and a pressure-side
refrigerant path which leads from an outlet chamber of the
reciprocating piston compressor to a pressure connection on the
overall housing, wherein at least one cylinder of the reciprocating
piston compressor is provided in the compressor housing portion and
has a piston movable in a cylinder bore formed in the compressor
housing portion, a valve plate closing the cylinder bore, and a
cylinder head extending over the valve plate and forming part of
the compressor housing portion, the refrigerant compressor is
provided with an externally controlled mechanical capacity control
unit.
9. A semi-hermetic refrigerant compressor, comprising a
reciprocating piston compressor and an electric motor, an overall
housing which has a motor housing portion for the electric motor
and a compressor housing portion for the reciprocating piston
compressor, a suction-side refrigerant path which leads from a
suction connection on the overall housing to an inlet chamber of
the reciprocating piston compressor, and a pressure-side
refrigerant path which leads from an outlet chamber of the
reciprocating piston compressor to a pressure connection on the
overall housing, wherein at least one cylinder of the reciprocating
piston compressor is provided in the compressor housing portion and
has a piston movable in a cylinder bore formed in the compressor
housing portion, a valve plate closing the cylinder bore, and a
cylinder head extending over the valve plate and forming part of
the compressor housing portion, the mechanical capacity control
unit for capacity reduction in at least one cylinder connects the
outlet-side refrigerant path to the inlet-side refrigerant
path.
10. A refrigerant compressor according to claim 9, wherein the
mechanical capacity control unit is arranged on the at least one
cylinder head.
11. A refrigerant compressor according to claim 10, wherein the
mechanical capacity control unit is at least partially integrated
in the at least one cylinder head.
12. A refrigerant compressor according to claim 9, wherein the
mechanical capacity control unit, for capacity reduction, connects
an outlet chamber in the cylinder head to an inlet chamber in the
cylinder head by means of a connection channel.
13. A refrigerant compressor according to claim 12, wherein the
connection channel is arranged integrated in the cylinder head.
14. A refrigerant compressor according to claim 1, wherein the
outlet chamber is arranged in the cylinder head directly adjacently
to at least one outlet opening for the corresponding cylinder in
the valve plate.
15. A refrigerant compressor according to claim 1, wherein the
inlet chamber is arranged in the cylinder head directly adjacently
to an inlet opening for the corresponding cylinder in the valve
plate.
16. A refrigerant compressor according to claim 9, wherein the
mechanical capacity control unit has a sealing piston for closing
the connection channel.
17. A refrigerant compressor according to claim 16, wherein the
sealing piston, in order to close the connection channel, is
placeable against a seal seat, which runs around the connection
channel peripherally.
18. A refrigerant compressor according to claim 16, wherein a seal
region of the sealing piston is made of a metal having a lower
hardness than a metal from which the seal seat is made.
19. A refrigerant compressor according to claim 17, wherein the
seal seat is arranged in a wall portion of the cylinder head
separating the inlet chamber from the outlet chamber.
20. A refrigerant compressor according to claim 17, wherein the
seal seat is arranged in a wall portion running above the valve
plate and above the inlet chamber.
21. A refrigerant compressor according to claim 17, wherein the
seal seat is arranged on the side of the inlet chamber opposite the
valve plate.
22. A refrigerant compressor according to claim 17, wherein
starting from the seal seat, the stroke of the sealing piston
ranges from a quarter to half of the mean diameter of the
connection channel.
23. A refrigerant compressor according to claim 1, wherein a
cylinder head has an inlet chamber and an outlet chamber for a
cylinder bank comprising at least two cylinders.
24. A refrigerant compressor according to claim 1, wherein the
mechanical capacity control unit is associated with a cylinder
bank.
25. A refrigerant compressor according to claim 23, wherein in the
case of N cylinder banks of the refrigerant compressor a mechanical
capacity control unit is associated with at least N-1 cylinder
bank(s).
26. A refrigerant compressor according to claim 23, wherein a
mechanical capacity control unit is associated with each cylinder
bank.
27. A refrigerant compressor according to claim 1, wherein a check
valve is provided in the compressor housing portion following on
from the refrigerant paths that can be influenced by the mechanical
capacity control unit.
28. A refrigerant compressor according to claim 27, wherein the
check valve has an outlet opening provided in the valve plate and a
valve element cooperating with the valve plate.
29. A refrigerant compressor according to claim 28, wherein the
valve element is held on the valve plate.
30. A refrigerant compressor according to claim 16, wherein the
sealing piston in the direction of its position cooperating with
the seal seat is acted on by a compression spring.
31. A refrigerant compressor according to claim 16, wherein the
sealing piston is actuable by a pressure chamber, which is actable
on either by suction pressure or by high pressure depending on the
external control of the capacity control unit.
32. A refrigerant compressor according to claim 31, wherein the
pressure chamber in the open position of the sealing piston has a
volume that is less than a third, better still less than a quarter
of the maximum volume of the pressure chamber in the closed
position.
33. A refrigerant compressor according to claim 8, wherein a
control unit comprised by the capacity control unit is provided and
is usable to control the pressure applied to the sealing
piston.
34. A refrigerant compressor according to claim 8, wherein a
capacity controller is provided and controls the at least one
mechanical capacity control unit in accordance with a required
compressor delivery capacity.
35. A refrigerant compressor according to claim 1, wherein a
start-up control unit is provided and controls the start-up of the
electric motor.
36. A refrigerant compressor according to claim 35, wherein the
start-up control unit operates the electric motor to start up with
the windings connected in a manner reducing the start-up
current.
37. A refrigerant compressor according to claim 35, wherein the
start-up control unit in order to start up the electric motor
initially energizes a first part-winding and then energizes a
second part-winding in a stator of the electric motor.
38. A refrigerant compressor according to claim 35, wherein the
start-up control unit controls the capacity controller at the
start-up of the electric motor such that the reciprocating piston
compressor operates only with reduced compressor delivery capacity
at the start-up of the electric motor.
39. A refrigerant compressor according to claim 38, wherein the
start-up control unit controls the capacity controller in such a
way that the reciprocating piston compressor works with the
smallest possible compressor delivery capacity at the start-up of
the electric motor.
40. A refrigerant compressor according to claim 1, wherein the
reciprocating piston compressor works with a suction pressure
ranging from 10 bar to 50 bar.
41. A refrigerant compressor according to claim 1, wherein the
reciprocating piston compressor works with a high pressure ranging
from 40 to 160 bar.
42. A refrigerant compressor according to claim 1, wherein the
reciprocating piston compressor works with carbon dioxide as
refrigerant and in particular is configured for operation with
carbon dioxide as refrigerant.
Description
CROSS-REFERENCE TO RELATED PATENT APPLICATION
[0001] This application is a continuation of International
application number PCT/EP2016/074063 filed on Oct. 7, 2016.
[0002] This patent application claims the benefit of International
application No. PCT/EP2016/074063 of Oct. 7, 2016 the teachings and
disclosure of which are hereby incorporated in their entirety by
reference thereto.
BACKGROUND OF THE INVENTION
[0003] The invention relates to a semi-hermetic refrigerant
compressor, comprising a reciprocating piston compressor and an
electric motor, an overall housing which has a motor housing
portion for the electric motor and a compressor housing portion for
the reciprocating piston compressor, a suction-side refrigerant
path which leads from a suction connection on the overall housing
to an inlet chamber of the reciprocating piston compressor, and a
pressure-side refrigerant path which leads from an outlet chamber
of the reciprocating piston compressor to a pressure connection on
the overall housing, wherein at least one cylinder of the
reciprocating piston compressor is provided in the compressor
housing portion and has a piston movable in a cylinder bore formed
in the compressor housing portion, a valve plate closing the
cylinder bore, and a cylinder head extending over the valve plate
and forming part of the compressor housing portion.
[0004] Semi-hermetic refrigerant compressors of this kind are known
from the prior art.
[0005] A semi-hermetic refrigerant compressor comprises the overall
housing as outer housing, wherein in particular the electric motor
is arranged in a refrigerant atmosphere. A semi-hermetic
refrigerant compressor is not provided with an outer encapsulation
fully enclosing the reciprocating piston compressor and the
electric motor jointly, but instead the compressor housing forming
the at least one cylinder housing constitutes the outer
housing.
[0006] The problem exists of operating these compressors
energy-efficiently.
SUMMARY OF THE INVENTION
[0007] In accordance with the invention this problem is solved in a
semi-hermetic refrigerant compressor of the kind described in the
introduction in that the electric motor is designed as a
synchronous motor, in the rotor of which there are arranged
permanent magnets for the synchronous operation of the electric
motor and a squirrel cage for start-up of the electric motor in
asynchronous operation.
[0008] The advantage of the solution according to the invention can
be considered the fact that an electric motor of this kind for
driving a semi-hermetic refrigerant compressor has a higher energy
efficiency, in particular under full load and also under partial
load. A further advantage of an electric motor of this kind can be
considered the fact that the delivery volume is constant by means
of the synchronous operation, even in the high-load range.
[0009] No further details have yet been provided in respect of the
configuration of the permanent magnets.
[0010] An advantageous solution provides that the permanent magnets
extend parallel to a rotor axis of the rotor.
[0011] It is also preferably provided that the permanent magnets
are formed as planar bodies, the flat sides of which extend in a
longitudinal direction and in a transverse direction running
transversely to the longitudinal direction.
[0012] The permanent magnets in this case are expediently arranged
in the rotor such that they each extend with their longitudinal
direction parallel to the rotor axis.
[0013] The permanent magnets are also preferably arranged in the
rotor such that they extend with their transverse directions along
outer edges of a geometric rectangle that is symmetrical with
respect to the rotor axis.
[0014] Also, no further details have yet been provided in respect
of the magnetization of the permanent magnets.
[0015] An advantageous solution provides that the permanent magnets
configured as planar bodies have a different magnetic polarity on
their mutually opposite flat sides, one of which faces towards the
rotor axis and the other of which faces away from the rotor axis,
such that planar magnetic poles are thus available in the rotor in
a simple way for the synchronous operation of the electric
motor.
[0016] In principle, the electric motor can be cooled in a wide
range of ways.
[0017] An advantageous solution provides that the suction-side
refrigerant path passes through the motor housing for cooling of
the electric motor.
[0018] Furthermore, alternatively or additionally to the previously
described features of the semi-hermetic refrigerant compressor, a
further solution according to the invention provides that the
refrigerant compressor is provided with a mechanical externally
controllable or controlled capacity control unit.
[0019] An externally controlled capacity control unit of this kind
creates the possibility of controlling the compressor delivery
capacity of the semi-hermetic refrigerant compressor without a
frequency converter for the electric motor by means of the
mechanical capacity control unit, which is cost-effective and
efficient, and additionally in particular opens up the possibility
of reducing the mechanical loads on the reciprocating piston
compressor.
[0020] In particular, it is provided here that the mechanical
capacity control unit for capacity reduction in at least one
cylinder connects the outlet-side refrigerant path to the
inlet-side refrigerant path. This creates the possibility of
operating the at least one cylinder such that it does not
contribute to the compressor delivery capacity.
[0021] This solution has the advantage that, when implementing a
capacity reduction, the mechanical load on the components of the
reciprocating piston compressor is thus low, since the refrigerant
is at a pressure level close to the inlet side and flows back from
the outlet side to the inlet side, wherein this is not accompanied
by any great pressure fluctuations or even pressure peaks or
temperature peaks in the reciprocating piston compressor, which in
particular also reduce the efficiency in the event of capacity
reduction.
[0022] A wide range of different possible solutions are conceivable
in respect of the arrangement of the mechanical capacity control
unit.
[0023] In accordance with an advantageous solution, the mechanical
capacity control unit is arranged on the cylinder head, thus
resulting in the advantage that the mechanical capacity control
unit can thus cooperate easily with at least one of the
cylinders.
[0024] It is particularly favorable if the mechanical capacity
control unit is at least partially integrated in the at least one
cylinder head.
[0025] In order to be able to cooperate as optimally as possible
with at least one cylinder, it is preferably provided that the
mechanical capacity control unit, for capacity reduction, connects
an outlet chamber in the cylinder head to an inlet chamber in the
cylinder head by means of a connection channel.
[0026] A direct cooperation of the capacity control unit with the
at least one cylinder associated with the cylinder head is thus
possible, such that a compact design of the refrigerant compressor
thus can be realized in the case of a capacity control unit
incorporated in this way.
[0027] It is particularly expedient if the connection channel is
arranged integrated in the cylinder head, such that likewise the
spatial requirement for the cooperation of the capacity control
unit with the inlet chamber and the outlet chamber thus can be
optimized.
[0028] In particular is provided that the outlet chamber is
arranged in the cylinder head directly adjacently to at least one
outlet opening for the corresponding cylinder in the valve plate,
and therefore in particular the outlet chamber is also directly
adjacently to the valve plate and the outlet opening, in particular
with the outlet valve.
[0029] It is also preferably provided that the inlet chamber in the
cylinder head is arranged directly adjacently to an inlet opening
for the corresponding cylinder in the valve plate, such that the
inlet chamber is also directly adjacently to the valve plate and
the inlet opening.
[0030] A wide range of possibilities are conceivable with regard to
the way in which the mechanical capacity control unit opens or
closes the connection channel between the outlet chamber and the
inlet chamber.
[0031] For example, it would be conceivable to use conventional
gate designs.
[0032] A particularly advantageous solution provides that the
mechanical capacity control unit has a sealing piston for closing
the connection channel.
[0033] A sealing piston of this kind creates the possibility of
opening or closing the connection channel in particular with the
shortest response time possible.
[0034] In order to provide a reliable seal the sealing piston is
preferably guided in a guide bore, in particular in the cylinder
head, in a manner sealed by means of a piston ring.
[0035] In particular, it is provided that the sealing piston, in
order to close the connection channel, is placeable against a seal
seat, which runs around the connection channel peripherally, such
that the connection channel is interrupted when the sealing piston
is placed against the seal seat, whereas the connection channel is
opened again when the sealing piston is lifted from the seal
seat.
[0036] In order to achieve reliable closure durably, it is
preferably provided that a seal region of the sealing piston, which
seal region can be placed against the seal seat, is made of a metal
having a lower hardness than a metal from which the seal seat is
made, or vice versa.
[0037] The seal seat can be arranged in a wide range of different
ways.
[0038] A particularly advantageous and compact solution provides
that the seal seat is arranged on a wall portion of the cylinder
head separating the inlet chamber from the outlet chamber.
[0039] Here, either the seal seat can be formed as part of the wall
portion or the seal seat is formed by a component inserted into the
wall portion of the cylinder head.
[0040] The seal seat is preferably arranged such that it is
arranged in a wall portion running above the valve plate and above
the inlet chamber, and therefore in particular the seal seat at the
same time constitutes an inlet opening, opposite the valve plate,
for the inlet chamber.
[0041] It is also furthermore preferably provided that the seal
seat at the same time constitutes an outlet opening for the outlet
chamber, such that a direct transition from the outlet chamber into
the inlet chamber is realized by the seal seat.
[0042] For a spatial compact assembly, it has proven to be
particularly favorable if the seal seat is arranged on a side of
the inlet chamber opposite the valve plate.
[0043] A rapid change of the sealing piston between the closed
position and the open position is possible preferably if, starting
from the seal seat, the stroke of the sealing piston ranges from a
quarter to half of the mean diameter of the connection channel.
[0044] No further details have been provided with the explanation
of the individual embodiments provided thus far in respect of the
association of the mechanical capacity control unit with individual
cylinders.
[0045] One solution provides that the mechanical capacity control
unit is associated with one cylinder and if a plurality of
cylinders is provided then a plurality of mechanical capacity
control units is provided, wherein it is not absolutely necessary
for a mechanical capacity control unit to be associated with each
cylinder.
[0046] A favorable solution provides that a cylinder head has an
inlet chamber and an outlet chamber for a cylinder bank comprising
at least two cylinders.
[0047] In this case, a plurality of cylinders is therefore combined
to form a cylinder bank.
[0048] In a solution of this kind it is advantageously provided
that the mechanical capacity control unit is associated with a
cylinder bank, in particular comprising at least two cylinders.
[0049] In the case of a refrigerant compressor comprising a
plurality of cylinder banks, for example N cylinder banks, it is
preferably provided that a mechanical capacity control unit is
associated with at least N-1 cylinder bank(s).
[0050] However, in order to reduce the capacity of the refrigerant
compressor optimally, it is preferably provided that a mechanical
capacity control unit is associated with each cylinder bank.
[0051] In order to avoid a backflow of highly pressurized
refrigerant and therefore a pressure drop at the outlet connection
element during a capacity reduction, a check valve is provided in
the compressor housing portion following on from the refrigerant
paths that can be influenced by the mechanical capacity control
unit.
[0052] It is also preferably provided that the check valve has an
outlet opening provided in the valve plate and a valve element
cooperating with the valve plate, such that the valve plate can be
used also for the arrangement and forming of the check valve.
[0053] In particular it is provided that the valve element is held
on the valve plate such that the valve plate is used not only to
form the inlet and outlet valves, but also to hold the valve
element of the check valve.
[0054] No further details have been provided in conjunction with
the explanation of the individual exemplary embodiments provided
thus far in respect of the control of the sealing piston.
[0055] An advantageous solution thus provides that the sealing
piston, in the direction of its position cooperating with the seal
seat, is acted on by a compression spring such that the compression
spring ensures that the sealing piston in the non-working state of
the refrigerant compressor closes the connection channel on account
of the effect of the compression spring.
[0056] It is also preferably provided that the sealing piston can
be controlled by a pressure chamber, which can be acted on either
by suction pressure or by high pressure depending on the external
control of the capacity control unit, wherein, in the event that
the pressure chamber is acted on by suction pressure, the sealing
piston transitions into its open position, and, in the event that
the pressure chamber is acted on by high pressure, the sealing
piston is acted on in the direction of its closed position,
additionally to the effect of the compression spring.
[0057] The volume of the pressure chamber is in particular so low
that, in the open position of the sealing piston, it is less than a
third, better still less than a quarter, even better still less
than a fifth, more advantageously less than a sixth, and
particularly advantageously less than a seventh, and even more
advantageously less than an eighth of the maximum volume of the
pressure chamber in the closed position of the sealing piston.
[0058] This dimension of the pressure chamber makes it possible to
change quickly between the closed position and the open position,
since the pressure must be changed between suction pressure and
high pressure only in a small volume.
[0059] A control unit comprised by the capacity control unit is
preferably provided in order to act on the pressure chamber with
high pressure or suction pressure and can be used to control the
pressure applied to the sealing piston.
[0060] In order to execute this capacity control of the refrigerant
compressor, a capacity controller is preferably provided which
controls the at least one capacity control unit in accordance with
a required compressor delivery capacity.
[0061] The capacity controller is in particular connected to a
higher level system controller and receives information from the
system controller regarding the required compressor delivery
capacity.
[0062] The capacity controller then controls the at least one or
more capacity control units on the basis of this information
regarding the required compressor delivery capacity, such that the
refrigerant compressor provides the required compressor delivery
capacity but does not provide an unnecessarily high compressor
delivery capacity.
[0063] To this end, the refrigerant compressor is designed such
that the maximum compressor delivery capacity thereof is sufficient
for the maximum compressor delivery capacity required by the system
controller, and lower compressor delivery capacities are achieved
by capacity reduction by means of the at least one capacity control
unit.
[0064] In addition, a start-up control unit is preferably provided
for the refrigerant compressor, in particular the refrigerant
compressor is provided with a start-up control unit which controls
the start-up of the electric motor, which in the solution according
to the invention starts up as an asynchronous motor until it has
reached the synchronous speed, and then runs as a synchronous
motor.
[0065] The start-up control unit can control the operation of the
refrigerant compressor differently so as to allow the electric
motor to start up suitably.
[0066] In particular, the start-up control unit works such that it
operates the electric motor to start up with the windings connected
in a manner reducing the start-up current.
[0067] This could be realized for example by a switchover from a
star connection for start-up into a delta connection after
start-up.
[0068] An advantageous solution provides that the start-up control
unit, to start up the electric motor, firstly energizes a first
part-winding and then energizes a second part-winding in a stator
of the electric motor.
[0069] The start-up of the electric motor with a first part-winding
has the advantage that it is thus possible to reduce the start-up
current and therefore for example to avoid a heavy loading of the
electrical supply network caused by an excessively high start-up
current.
[0070] Alternatively or additionally the start-up control unit is
configured such that it controls the capacity controller during the
start-up of the electric motor such that the reciprocating piston
compressor works only with reduced compressor delivery capacity at
the time of start-up of the electric motor.
[0071] It is particularly favorable for the start-up of the
electric motor if the start-up controller controls the capacity
controller in such a way that the reciprocating piston compressor
works with the smallest possible compressor delivery capacity at
the time of start-up of the electric motor.
[0072] The smallest possible compressor delivery capacity may be a
compressor delivery capacity at which one or more cylinders are
still operating.
[0073] A particularly favorable embodiment provides that the
capacity of the reciprocating piston compressor can be controlled
in such a way that at the smallest possible compressor delivery
capacity none of the cylinders compress refrigerant, such that the
torque necessary to start up the reciprocating piston compressor is
thus minimal.
[0074] In addition, an advantageous solution provides that the
start-up controller controls the capacity controller in such a way
that, once synchronous operation of the electric motor has been
reached, the compressor delivery capacity is increased in steps,
for example with the additional connection of a further cylinder or
a further cylinder bank or optionally successive additional
connection of further cylinders or further cylinder banks.
[0075] No further details have been provided in conjunction with
the solution according to the invention in respect of the operating
states of the reciprocating piston compressor.
[0076] In principle, the reciprocating piston compressor according
to the invention can operate with all refrigerants usual for
semi-hermetic refrigerant compressors.
[0077] However, the solution according to the invention creates
particular advantages for the operation of the reciprocating piston
compressor, in particular for damage-free operation of the
reciprocating piston compressor when the reciprocating piston
compressor works with a suction pressure ranging from 10 bar to 50
bar.
[0078] The solution according to the invention is also particularly
advantageous in respect of the mechanical loading of the
reciprocating piston compressor if the reciprocating piston
compressor works with a high pressure ranging from 40 bar to
16.sub.0 bar.
[0079] In particular, the refrigerant compressor according to the
invention can be used particularly advantageously if the
reciprocating piston compressor works with carbon dioxide as
refrigerant and in particular is configured for operation with
carbon dioxide as refrigerant.
[0080] Further features and advantages of the invention are the
subject of the following description and the drawings of several
exemplary embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0081] FIG. 1 shows a side view of an exemplary embodiment of a
refrigerant compressor according to the invention;
[0082] FIG. 2 shows a plan view in the direction of the arrow A in
FIG. 1 of the refrigerant compressor according to the
invention;
[0083] FIG. 3 shows a front view of the exemplary embodiment of the
refrigerant compressor according to the invention;
[0084] FIG. 4 shows a section, offset to one side, along line 4-4
in FIG. 2;
[0085] FIG. 5 shows a longitudinal section through the refrigerant
compressor according to the invention;
[0086] FIG. 6 shows a section along line 6-6 in FIG. 7;
[0087] FIG. 7 shows a section along line 7-7 in FIG. 6 with a
closed connection channel between inlet chamber and outlet
chamber;
[0088] FIG. 8 shows a section similar to FIG. 7 with open
connection channel between the outlet chamber and the inlet
chamber;
[0089] FIG. 9 shows a section along line 9-9 in FIG. 5 through a
rotor of the electric motor;
[0090] FIG. 10 shows a schematic depiction of the start-up of the
electric motor; and
[0091] FIG. 11 shows a section similar to FIG. 7 through a second
exemplary embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0092] An exemplary embodiment of a semi-hermetic refrigerant
compressor according to the invention, shown in FIGS. 1 to 5,
comprises an overall housing 10, in which there are arranged a
reciprocating piston compressor 12 and an electric motor 14.
[0093] The overall housing 10 is formed preferably by a one-piece
housing body 26, which extends in the direction parallel to a
central axis 28 explained in greater detail hereinafter and is
closed at the end on the side of the compressor housing portion 22
by means of a bearing cap 32 and is closed at the end in the region
of the motor portion 24 by an end cap 34.
[0094] A compressor shaft denoted as a whole by 42 extends in the
compressor housing portion 22 coaxially with the central axis 28
between a first shaft bearing 44 arranged on the bearing cap 32 to
a second shaft bearing 46 arranged between the reciprocating piston
compressor 12 and the electric motor 14, wherein the second shaft
bearing 46 is held on a middle wall 48, which is molded into the
housing body 26 and which delimits a drive chamber 52, which is
situated between the bearing cap 32 and the middle wall 48 and
through which the compressor shaft 42 extends and in which cams 54
and 56 of the compressor shaft 42 are arranged, wherein two
connecting rods 62.sub.1 and 62.sub.2, or 64.sub.1 and 64.sub.2 are
arranged on the cams 54 and 56 respectively, wherein the connecting
rods 62.sub.1 and 62.sub.2 drive the pistons 66.sub.1 and 68.sub.1
and the connecting rods 64.sub.1 and 64.sub.2 drive the pistons
66.sub.2 and 68.sub.2.
[0095] The pistons 66 and 68 are guided in cylinder bores 72 and
74, which are formed by cylinder housings 76, 78 molded into the
compressor housing portion 22, in particular molded in
integrally.
[0096] Each cylinder housing 76, 78 with the cylinder bore 72, 74
and the piston 66, 68 guided therein forms a cylinder 82, 84.
[0097] The two first cylinders 82.sub.1 and 84.sub.1 molded into
the compressor housing portion 22 form a first cylinder bank
86.sub.1, whereas the two cylinders 82.sub.2 and 84.sub.2 molded
into the compressor housing portion 22 form a second cylinder bank
86.sub.2.
[0098] In each of the cylinder banks 86.sub.1 and 86.sub.2, the
respective cylinder bores 72.sub.1, 74.sub.1 and 72.sub.2, 74.sub.2
are closed by a common valve plate 88.sub.1 and 88.sub.2, which
abuts on the corresponding cylinder housings 76.sub.1 and 78.sub.1,
or 76.sub.2 and 78.sub.2 in a tightly sealing manner, with a
compression chamber being enclosed by each valve plate 88.sub.1 or
88.sub.2 and the respective pistons 66.sub.1 and 68.sub.1 or
66.sub.2 and 68.sub.2, and the cylinder bores 72.sub.1 and 74.sub.1
or 72.sub.2 and 74.sub.2.
[0099] The valve plates 88.sub.1 and 88.sub.2 for their part are
covered in turn by a cylinder head 92.sub.1 or 92.sub.2.
[0100] As shown in FIGS. 6 to 8, an inlet chamber 94 and an outlet
chamber 96 are arranged in each of the cylinder heads 92.sub.1 and
92.sub.2 and are associated with the two cylinders 82 and 84 of the
corresponding cylinder bank 86.
[0101] In particular, the inlet chamber 94 is arranged above inlet
openings 10.sub.2 and 10.sub.4 of the cylinder 82 and inlet
openings 10.sub.6 and 10.sub.8 of the cylinder 84.
[0102] Furthermore, the outlet chamber 96 is arranged above outlet
openings 112 and 114 of the cylinder 82 which are arranged in the
valve plate 88, and above outlet openings 116 and 118 of the
cylinder 84, the outlet openings being provided with outlet valves
113, 115, 117, 119 sitting on the valve plate 88, and the outlet
chamber is arranged in particular directly adjacently to said
outlet openings.
[0103] As shown in FIGS. 6 to 8, each cylinder head 92 comprises an
outer body 122, which passes over the corresponding valve plate 88
and surrounds the inlet chamber 94 and the outlet chamber 96, which
for their part are in turn separated from one another by a
partition body 124 running within the outer body 122, wherein the
partition body 124 rises starting from the respective valve plate
88 and extends in a manner spanning above the inlet chamber 94.
[0104] The outlet chamber 96 is thus arranged in the region of the
valve plate 88 laterally next to the inlet chamber 94, but between
the outer body 122 and the partition body 124 extends over the
inlet chamber 94 at least in some regions.
[0105] In order to control the capacity of the refrigerant
compressor, that is to say in order to control the compressor
delivery capacity, a mechanical capacity control unit 142 actively
controlled by a capacity controller 138 is associated with each
cylinder head 92 and can be used to close or open a connection
channel 144 between the outlet chamber 96 and the inlet chamber 94,
wherein the cylinders 82, 84 associated with the cylinder head 92
compress refrigerant at full capacity when the connection channel
144 is closed (FIG. 7) and do not compress any refrigerant when the
connection channel is open, since the refrigerant flows back from
the outlet chamber 96 into the inlet chamber 94.
[0106] The connection channel 144 runs here through an insert part
146, which is inserted into the partition body 124 and forms a seal
seat 148, which faces the outlet chamber 96 and borders a part of
the outlet chamber 96 surrounding the seal seat 148 and arranged
adjacently thereto.
[0107] Furthermore, the seal seat 148 faces a sealing piston 152,
which for example can be placed with a metallic seal region 154
against the seal seat 148 in order to close the connection channel
144 in a tightly sealed manner and which can be raised from the
seal seat 148 to such an extent that the seal region 154 is at a
spacing from the seal seat 148 and therefore refrigerant can flow
from the outlet chamber 96 into the inlet chamber 94.
[0108] The sealing piston 152 is preferably guided in a guide bore
156 coaxially with the insert part 146 towards the seal seat 148
and sealed by means of a piston ring 153, the guide bore being
formed by a guide sleeve body 158 of the cylinder head 92
integrally formed on the outer body 122.
[0109] The sealing piston 152 itself or at least the seal region
154 is preferably made of a metal, for example a non-ferrous metal,
which has a lower hardness than the metal of the seal seat 148,
which for example is made of steel, in particular hardened
steel.
[0110] In order to enable rapid movement of the sealing piston 152,
the stroke of the sealing piston 152 between a closed position and
an open position lies in particular between a quarter and half of
the mean diameter of the connection channel 144.
[0111] The sealing piston 152 delimits a pressure chamber 162,
which is arranged on the side of the sealing piston 152 remote from
the seal region 154 and is closed on the side opposite the sealing
piston 152 by a terminating body 164.
[0112] In the open position of the sealing piston, the volume of
the pressure chamber 162 is in particular so small that it is less
than a third, better still less than a quarter, even better still
less than a fifth, advantageously less than a sixth, and even more
advantageously less than an eighth of the maximum volume of the
pressure chamber 162 in the closed position of the sealing piston
152.
[0113] Furthermore, a compression spring 166 is also arranged in
the pressure chamber 162 and at one end is supported on the
terminating body 164 and at the other end acts on the sealing
piston 152 in the direction of the closed position of said piston,
sitting on the seal seat 148.
[0114] Depending on the pressure application of the pressure
chamber 162, the sealing piston 158 can be moved into its open
position shown in FIG. 8 or into its closed position shown in FIG.
7.
[0115] To this end, the sealing piston 152 is penetrated by a
throttle channel 172, which extends from the pressure chamber 162,
through the sealing piston 152, to an opening which is arranged
radially outside the seal region 154 on a side facing the seal seat
148, however, since the opening is arranged radially outside the
seal element 154, when the sealing piston 152 is in the closed
position the opening allows an entry of refrigerant that is under
pressure in the outlet chamber 96 and flows around the seal seat
and feeds this refrigerant in a throttled manner to the pressure
chamber 162.
[0116] In addition, a relief channel 176, which can be connected by
means of a solenoid valve denoted as a whole by 182 to a pressure
relief channel 184 which is connected to the inlet chamber 94,
leads into the pressure chamber 162, more specifically for example
through the terminating body 164.
[0117] For example, the solenoid valve 182 is formed in such a way
that it has a valve body 186 by means of which the connection
between the pressure relief channel 184 and the relief channel 176
can be interrupted or established.
[0118] If the connection is established between the relief channel
176 and the pressure relief channel 184, the suction pressure thus
prevails in the pressure chamber 162, whereas the sealing piston
152 is acted on by the pressure in the outlet chamber 96 on its
side facing towards the outlet chamber 96 is therefore moved into
its open position.
[0119] If, however, the connection between the pressure relief
channel 184 and the relief channel 176 is interrupted by the valve
body 186, the compression spring 166 presses the sealing piston 152
against the seal seat 148 and in addition high pressure flows
through the throttle channel 172 into the pressure chamber 162,
such that high pressure builds up in the pressure chamber 162 and
presses the sealing piston 152 with the seal element 154 against
the seal seat 148, additionally to the effect of the compression
spring 166.
[0120] In particular, the sealing piston 152 is formed such that it
extends radially beyond the seal seat 148, such that even when the
sealing piston 152 is in the closed position the piston area
situated radially outside the seal seat 148 and acted on by high
pressure causes the sealing piston 152 to be moved against the
force of the compression spring 166 into the open position, shown
in FIG. 5, provided the valve body 186 of the solenoid valve 182
establishes the connection between the relief channel 176 and the
pressure relief channel 184, which causes a suction pressure to be
set in the pressure chamber 162.
[0121] Refrigerant under suction pressure is fed via a feed channel
202, which is molded into the compressor housing portion 22 and
which leads to an inlet opening 204 leading to the valve plate 88,
through which inlet opening refrigerant under suction pressure
flows to a passage opening 206 in the valve plate 88 and passes
therethrough into the inlet chamber 93.
[0122] In addition, as shown in FIGS. 7 and 8, the outlet chamber
96 leads to an outlet opening 212 arranged in the valve plate 88,
through which outlet opening the refrigerant under pressure in the
outlet chamber 96 passes into an outlet channel 214 provided in the
compressor housing portion 22 and can flow to an outlet connection
element 216.
[0123] In particular, the outlet opening 212 of the valve plate 88
is associated with a check valve 222, which is held on the valve
plate 88, and a valve element 224 is arranged on the side of the
valve plate 88 facing the outlet channel 214 and, in the case that
the sealing piston 152 is in the open position and therefore in the
case that the refrigerant flows from the outlet chamber 96 into the
inlet chamber 94, ensures that the pressure in the outlet channel
214 does not drop, but instead is maintained by the closing check
valve 222.
[0124] The check valve 222, together with a catch element 226
associated with the check valve, is preferably held on the valve
plate 88 by means of a holding element 228 and provides a seal with
respect to the valve plate 88.
[0125] The refrigerant compressor according to the invention is
formed as a semi-hermetic compressor, such that refrigerant under
suction pressure is fed by means of an inlet connection element 232
arranged on the end cap 34 to a motor compartment 234, and flows
through the electric motor 14 in the direction of the middle wall
48, and passes from the motor compartment 234 into the feed channel
202, such that the electric motor 14 in the motor compartment 234
is cooled by the fed suction-side refrigerant.
[0126] The electric motor 14 in turn comprises a stator 252 which
is held securely in the motor housing portion 24 and has a stator
winding 254 which for example has two part-windings 256 and 258
which are used to magnetize a stator laminated core 262.
[0127] The stator 252 surrounds a rotor, denoted as a whole by 272,
with a squirrel cage 276 being arranged in the rotor laminated core
274 of said rotor, as shown in FIG. 9, said squirrel cage
comprising bars 278 which run parallel to a rotor axis 282 and are
electrically conductively connected to one another at the ends in
the peripheral direction.
[0128] Furthermore, planar permanent magnets 292 are inserted into
the laminated core 274, with the flat sides 294 of said magnets
extending with a longitudinal direction 296 parallel to the rotor
axis 282 and with a transverse direction 298 transverse to the
rotor axis 282, more specifically in such a way that the transverse
directions 292 form a geometric rectangle extending around the
rotor axis 282 as axis of symmetry.
[0129] The permanent magnets 292 are also formed such that, in a
peripheral direction 302 about the rotor axis 282, successive
permanent magnets 292 have an alternating polarity on their side
facing the rotor axis 282, such that, by means of the permanent
magnets 292, the rotor 272 as a whole has alternating magnetic
poles in the peripheral direction.
[0130] An electric motor 14 provided with a rotor 272 of this kind
operates, on account of the permanent magnets 292 provided in the
rotor 272, as a synchronous motor in the normal operation, wherein
on account of the permanent magnets 292 a synchronous motor of this
kind has an advantageous energy efficiency and higher refrigerant
delivery capacity.
[0131] The rotary field generated by the stator 252 revolves with a
defined frequency on account of an energization of the stator
winding 254, said frequency being caused for example in that the
stator winding 254 is fed by an AC system.
[0132] In order to enable the stator 252 to be started up with a
rotary field circulating at constant frequency, the rotor 272 is
provided with the squirrel cage 276, which makes it possible for
the electric motor 14 to start up initially as an asynchronous
motor, until it has reached the rotational speed corresponding to
the revolving rotary field of the stator winding, and then to
operate as a synchronous motor on account of the magnetic poles
caused by the permanent magnets 292.
[0133] A refrigerant compressor with an electric motor of this kind
thus can be operated fed by a conventional AC system, since this
motor starts up like an asynchronous motor.
[0134] It is also possible, however, to operate a refrigerant
compressor of this kind with a frequency converter.
[0135] In order to facilitate the start-up of the electric motor 14
it is also possible to initially energize only one of the
part-windings 256 or 258 by means of a start-up controller 310
associated with the refrigerant compressor--as shown in FIG. 10--so
as to reduce the start-up current, and then to connect the other
part-windings 258, 256 after a short start-up phase of the electric
motor 114 as asynchronous motor.
[0136] In the event of use of the refrigerant compressor according
to the invention for large pressure differences, for example as a
compressor for CO.sub.2, the start-up controller 312 intervenes in
the provided capacity controller 138 for the active control of the
capacity control units 142 and causes at least one cylinder bank
86, preferably both cylinder banks 86.sub.1 and 86.sub.2, to be
deactivated, such that in the event of deactivation of at least one
cylinder bank 86 the torque required by the reciprocating piston
compressor 12 is reduced, and in the event of deactivation of both
cylinder banks 86.sub.1 and 86.sub.2 the torque required by the
reciprocating piston compressor 12 is low, since there is no
compression of refrigerant, and therefore on the one hand the
start-up current of the electric motor 14 is kept low and on the
other hand the electric motor then transitions very quickly from
its operation as asynchronous motor into the operation as
synchronous motor in which the full torque is available, such that
the cylinder banks 86.sub.1 and 86.sub.2 can be activated either
simultaneously or in succession (FIG. 10).
[0137] In a second exemplary embodiment, shown in FIG. 11, the
parts identical to those in the first exemplary embodiment are
provided with the same reference signs, and therefore reference can
be made fully to the descriptions of the first exemplary
embodiment.
[0138] In contrast to the first exemplary embodiment, the catch
element 226' of the check valve 222' is formed in the compressor
housing portion 22, for example by a recess laterally of the outlet
channel 214, which recess delimits the possible path of the valve
element 224' between its closed position abutting against the valve
plate 88 and the maximum open position.
[0139] A catch element 226' of this kind may be provided generally
in all compressor housing portions 22 of all refrigerant
compressors of the same assembly, regardless of whether or not they
are provided with a check valve 222', and therefore there is
possible a simple retrofitting of the refrigerant compressors with
a check valve 222' and in particular also with at least one
mechanical capacity control unit 142 according to the invention
together with a check valve 222' of this kind.
* * * * *