U.S. patent application number 14/785910 was filed with the patent office on 2016-09-22 for method and device for cooling a motor.
The applicant listed for this patent is ROBERT BOSCH GmbH. Invention is credited to Simon KLINK, Max MEISE.
Application Number | 20160273812 14/785910 |
Document ID | / |
Family ID | 50434195 |
Filed Date | 2016-09-22 |
United States Patent
Application |
20160273812 |
Kind Code |
A1 |
KLINK; Simon ; et
al. |
September 22, 2016 |
method and device for cooling a motor
Abstract
The invention relates to a method and to a device for cooling a
motor, the motor driving at least one, at least two-stage
compressor (2) of a coolant circuit (1), which includes at least
one first compression stage and a second compression stage (4), and
a coolant is conducted through the coolant circuit (1), which is
brought from a low pressure level to a medium pressure level in the
first compression stage (3), and from the medium pressure level to
a high pressure level in the second compression stage (4), and
which is then expanded to the medium pressure level following the
second compression stage (4) while outputting heat.
Inventors: |
KLINK; Simon; (Pohlheim,
DE) ; MEISE; Max; (Giessen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROBERT BOSCH GmbH |
Stuttgart |
|
DE |
|
|
Family ID: |
50434195 |
Appl. No.: |
14/785910 |
Filed: |
April 2, 2014 |
PCT Filed: |
April 2, 2014 |
PCT NO: |
PCT/EP2014/056567 |
371 Date: |
June 15, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F25B 31/006 20130101;
F25B 2400/23 20130101; F25B 2400/13 20130101; F25B 1/10 20130101;
F25B 2341/0662 20130101; F25B 31/026 20130101; F25B 49/025
20130101 |
International
Class: |
F25B 31/02 20060101
F25B031/02; F25B 49/02 20060101 F25B049/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 23, 2013 |
DE |
10 2013 207 344.5 |
Claims
1. A method for cooling a motor which drives at least one, at least
two-stage compressor (2) of a coolant circuit (1), which includes
at least one first compression stage (3) and a second compression
stage (4), a coolant being routed through the coolant circuit (1),
which is brought from a low pressure level to a medium pressure
level in the first compression stage (3), and from the medium
pressure level to a high pressure level in the second compression
stage (4), and then is expanded to the medium pressure level
following the second compression stage (4) while outputting heat,
wherein the motor (5) is cooled by a two-phase coolant main flow,
which has the medium pressure level.
2. The method as recited in claim 1, wherein the coolant main flow
is split into a liquid coolant component and a gaseous coolant
component after cooling of the motor (5), the gaseous coolant
component being supplied to the second compression stage (4), and
the liquid fluid component being supplied to the first compression
stage (3) of the two-stage compressor (2).
3. The method as recited in claim 1 or 2, wherein the coolant is
evaporated prior to the first compression stage (3) while absorbing
heat, and is condensed following the second compression stage (4)
while outputting heat.
4. The method as recited in one of claims 1 through 3, wherein
following the first compression stage (3), the coolant component is
combined with the coolant component coming from the second
compression stage (4) after outputting heat, prior to being
utilized for cooling the motor (5).
5. The method as recited in one of claims 1 through 3, wherein
following the first compression stage (3), the coolant component is
supplied directly to the second compression stage (4), the coolant
component, which is gaseous after cooling of the motor (5), being
combined with the coolant component coming from the first
compression stage (3) and conveyed to the second compression stage
(4), and the coolant that forms the coolant main flow and comes
from the second compression stage (4) is used for cooling the motor
(4) after outputting heat.
6. A device, in particular a two-stage heat pump, climate-control
device or cooling system, for implementing a method as recited in
claims 1 through 5, wherein the device has a motor (5) and a
coolant circuit (1), in which a two-stage compressor (2) having a
first compression stage (3) and a second compression stage (4) is
situated, which compressor is able to be driven by the motor (5),
and a motor cooling system is integrated into the coolant circuit
(1) in such a way that a coolant main flow is able to flow through
it, a phase separation element (12) being disposed downstream from
the motor cooling system in the direction of the flow, which is
connected via a suction gas line (17) for a gaseous coolant
component to the second compression stage (4), and via a first line
(16) for a fluid coolant component to the first compression stage
(3) of the two-stage coolant compressor (2).
7. The device as recited in claim 6, wherein an evaporator (14) and
possibly a throttle element (13) and possibly further components
are situated in the first line (16) upstream from the first
compression stage (3).
8. The device as recited in claim 6 or 7, wherein a capacitor (9)
and possibly a throttle element (11) as well as possibly further
components are situated in a second line (8) of the coolant circuit
(1) downstream from the second compression stage (4).
9. The device as recited in one of claims 6 through 8, wherein a
mixing device is situated in the coolant circuit (1) upstream from
the motor cooling system, which is connected to a pressurized gas
line (6) coming from the first compression stage (3), and to the
second line (8).
10. The device as recited in one of claims 6 through 8, wherein the
second line (8) is connected to the motor cooling system, and a
pressurized gas line (6) coming from the first compression stage
(3) discharges into the suction gas line (17) leading to the second
compression stage (4).
11. The device as recited in one of claims 6 through 8, wherein
additional components are situated in a coolant line between the
motor cooling system (5) and the phase separation element (12).
12. The device as recited in one of claims 6 through 11, wherein
the coolant compressor (2) has more than two compression stages (3,
4), and the method as recited in one of claims 1 through 5 is used
between two of the compression stages.
13. The device as recited in one of claims 6 through 11, wherein it
has at least two coolant compressors, and the method as recited in
one of claims 1 through 5 is used between the coolant compressors
or between compression stages of the coolant compressor, possibly
more than one motor being cooled.
Description
[0001] The present invention relates to a method for cooling a
motor according to the definition of the species of claim 1, and to
a device for implementing the method.
[0002] Such a coolant circuit equipped with a two-stage compressor
is used in connection with heat pumps, for instance. The two
compression stages of the compressor are driven via a motor, to
which it is connected for this purpose. With the aid of the first
compression stage of the compressor, the coolant gas is compressed
from a low level to a medium level. In the second compression
stage, the pressure level is then increased further until the
coolant has attained a high pressure level. Via a capacitor
connected downstream from the second compression stage heat can
then be output by the coolant, which is subsequently expanded and
can once again absorb heat in an evaporator in order to be supplied
in gaseous form to the first compression stage of the
compressor.
[0003] Depending on the operating mode, for example, such a coolant
circuit makes it possible to achieve heating or cooling of a space.
The coolant is simultaneously used for cooling the motor, which is
able to be operated at an optimal operating temperature in this
way. In coolant circuits the motor of the compressor is usually
cooled either by the coolant aspirated by the compressor or by the
already compressed gaseous coolant. The waste heat of the motor is
conveyed to the gaseous coolant either directly prior to or
directly following the compression. In coolant circuits having
two-stage compressors, which include a first compression stage and
a second compression stage, it is known to cool the motor with the
aid of the coolant that is at the medium pressure level. As a
result, this will happen either by the aspirated gas prior to the
second or second compression stage or by the pressurized gas of the
first or first compression stage [sic]. Only gaseous coolant is
normally used for cooling the motor in order to prevent a dilution
of the lubricant oil provided for lubrication in the motor bearings
inside the motor. This could lead to insufficient lubrication in
the bearings and therefore cause damage to the motor. However, the
cooling by aspirated gas prior to the compression in the second
compression stage of the compressor reduces the efficiency of the
coolant circuit because of the heating of the aspirated gas, in as
much as it causes a decrease in the density of the aspirated gas
and thus of the supplied mass flow. The cooling of the motor by
pressurized gas after the compression in the first compression
stage results in losses and increases the temperature of the
pressurized gas of the first compression stage. This also increases
the demands on the temperature stability of the motor.
[0004] To cool a motor of a two-stage compressor, it is known to
divert from the main coolant flow of the coolant circuit a subflow
flow after a capacitor connected downstream from the second
compression stage, and to guide it to a motor cooling system via a
type of bypass link. A separate expansion takes place in the bypass
line, for which, depending on the operating mode, one or two
expansion valves are required, which necessitate a separate
control.
[0005] The known methods for cooling the motor therefore cause
either a reduced efficiency of the overall system or they are
relatively complex and able to be realized only by providing
additional lines and expansion valves for which a separate control
is required in addition.
[0006] The present invention is based on the objective of
overcoming the disadvantages of the related art and, in particular,
of providing a method and a device for cooling a motor in which the
waste heat of the motor is returned into the cooling circuit
without any negative effect on the efficiency of the overall
system. The production expense and the control outlay should be as
low as possible and the fewest components possible should
suffice.
[0007] In the present invention, this objective is achieved by a
method having the features of claim 1 and by a device having the
features of claim 6. Advantageous developments are indicated in the
dependent claims.
[0008] In a method for cooling at least one motor driving at least
one compressor, having at least two stages, of a coolant circuit
which includes at least one first compression stage and a second
compression stage, and a coolant is conveyed through the coolant
circuit, which is brought from a low pressure level to a medium
pressure level in the first compression stage, and from a medium
pressure level to a high pressure level in the second compression
stage, and which is then expanded to the medium pressure level
while dissipating heat following the second compression stage, the
present invention provides for cooling of the motor by a two-phase
coolant main flow that exhibits the medium pressure level.
[0009] The two-phase coolant main flow contains both gaseous and
fluid coolant. Since the coolant main flow, that is to say, usually
the entire coolant flow, is utilized for cooling the motor, no
additional expansion valves are required. Accordingly, no
corresponding control is necessary. The waste heat dissipated by
the motor has no negative influence on the efficiency, since no
negative effect arises either on the individual pressure side or
the individual suction side of the compression stages.
[0010] In the case of coolant compressors that are provided with
more than two compression stages, the method is used between two of
the compression stages. In case of more than one coolant
compressor, the method may be used between two coolant compressors.
It is also possible to cool more than one motor, in which case each
motor may possibly be allocated its own coolant circuit.
[0011] In one preferred further development, the coolant main flow
is split into a fluid coolant component and a gaseous coolant
component after cooling of the motor, the gaseous coolant component
being supplied to the second compression stage and the fluid
coolant component to the first compression stage of the two-stage
compressor. After the motor has been cooled, the two-phase coolant
main flow is therefore split up into the two phases, the gaseous
component being compressed further in the second compression stage.
In this way a very efficient compression of the gaseous coolant to
a high pressure at a high temperature may take place directly in
the second compression stage. A medium pressure accumulator, for
example, may be used for separating the phases of the coolant from
the coolant main flow, this being a collection container in which
the coolant is separated into a gaseous component and a fluid
component.
[0012] The coolant is preferably evaporated while absorbing heat
before the first compression stage, and condensed while outputting
heat following the second compression stage. Following the
subdivision of the coolant main flow into the liquid and the
gaseous coolant component, an expansion of the fluid coolant
component therefore takes place, with a subsequent evaporation in
an evaporator, in which heat from the environment is able to be
absorbed, for example. This induces the previously fluid coolant
component to transition to the gaseous phase as well, whereupon it
is supplied, in gaseous form, to the first compression stage of the
two-stage compressor, to be compressed and heated there. A
capacitor may be provided, for instance following the second
compression stage, in which the previously gaseous coolant is
condensed and, for example, heat is output to the environment in
the process. From there, the coolant is conducted further under
high pressure and in partially liquid form and subsequently
expanded to the medium pressure level.
[0013] In one preferred specific embodiments following the first
compression stage, the coolant component is combined with the
coolant component that has come from the second compression stage
after emitting heat, before being used for cooling the motor. A
combination of the two coolant components thus takes place, so that
the entire coolant flow is available for cooling the motor.
[0014] In one alternative development, the coolant component is
supplied directly to the second compression stage following the
first compression stage; the center portion, which is gaseous once
the motor has been cooled, is supplied to the second compression
stage and combined with the coolant component coming from the first
compression stage; the coolant that forms the coolant main flow and
comes from the second compression stage after outputting heat is
used for cooling the motor. This results in a relatively simple
structure, and the entire coolant flow is used for cooling the
motor even then.
[0015] In a device for implementing the aforementioned method,
which is developed as a two-stage heat pump, climate control device
or cooling system, in particular, it is provided according to the
present invention that the device has a motor and a coolant circuit
in which a two-stage compressor is situated, which has a first
compression stage and a second compression stage able to be driven
by the motor; and that a motor cooling system is integrated into
the coolant circuit in such a way that a coolant main flow is able
to be flow through it, and a phase separation element is situated
downstream from the motor cooling system in the direction of flow,
which is connected to the second compression stage via a suction
gas line for a gaseous coolant component and to the first
compression stage of the two-stage coolant compressor via a first
line for a fluid coolant component.
[0016] This makes it possible to use the entire coolant that is at
a medium pressure level for cooling the motor, and the waste heat
to be recirculated into the coolant circuit. A negative effect on
the efficiency therefore does not arise since a separation into a
gaseous and a fluid coolant component takes place with the aid of
the phase separation element once the waste heat of the motor has
been absorbed or once the motor has been cooled, and only the
gaseous coolant component is supplied to the second compression
stage and condensed further thereby. It can therefore be operated
with high efficiency.
[0017] An additional bypass link including additional expansion
valves for supplying the motor cooling system can be dispensed
with. Instead, the motor cooling system is simply traversed by the
coolant main flow, which is able to absorb the corresponding heat.
No additional control is required, for this purpose, so that the
production and control expense is kept low.
[0018] In one preferred further refinement, an evaporator and
possibly a throttle element as well additional components are
disposed in the first line, upstream from the first compression
stage. This makes it possible for the previously fluid coolant
component to expand and to evaporate, so that it is able to be
supplied to the first compression stage in gaseous form. Heat
absorption from an environment, which is cooled as a result, takes
place in the evaporator. The further components include filters or
similar items, for example.
[0019] It is especially preferred that a capacitor and possibly a
throttle element as well as possibly additional components are
disposed in a second line of the coolant circuit, downstream from
the second compression stage. Following the second compression
stage, heat can be dissipated to the environment from the gaseous
coolant component in the capacitor, which at least partially
liquefies this coolant component. Because of the throttle element
that follows, which may be developed as a simple throttle or as an
expansion valve, for example, this coolant component is expanded,
so that it is able to be utilized for cooling the motor at a medium
pressure level in liquid and/or gaseous form. The further
components, for example, may be developed as cooling elements for a
power electronics system or a similar device.
[0020] In one preferred specific development, a mixing device,
which is connected to a pressurized gas line coming from the first
compression stage, and to the second line, is situated in the
coolant circuit upstream from the motor cooling system. That is to
say, the coolant component coming from the first compression stage
and the coolant component coming from the second compression stage
meet each other and can jointly be conducted from there to the
motor cooling system. The entire coolant flow is therefore used for
cooling the motor.
[0021] In one alternative development, the second line is connected
to the motor cooling system, a pressurized gas line coming from the
first compression stage discharging into the suction gas line
leading to the second compression stage. The gaseous coolant
component downstream from the phase separation element is able to
be combined with the coolant component conveyed from the first to
the second compression stage, upstream from the second compression
stage. Even in this simplified design the entire coolant flow is
routed to the motor cooling system where it is used for absorbing
waste heat. However, the coolant component coming from the first
compression stage is not combined with the coolant component coming
from the second compression stage directly upstream from the motor
cooling system, but first also travels through the second
compression stage.
[0022] It is possible to place further components in a coolant line
between the motor cooling system and the phase separation element.
For example, these are throttle elements and/or additional cooling
elements, which are used for cooling elements of a power
electronics system, for instance.
[0023] The coolant compressor preferably has more than two
compression stages, the method as recited in one of claims 1
through 5 being used between two of the compression stages. In this
way even extensive cooling is achievable.
[0024] In one preferred further development, the device has two
coolant compressors, and the method as recited in one of claims 1
through 5 is applied between the coolant compressors or between
compression stages of the coolant compressors, it being possible to
cool more than a single motor. In this way the device can be used
in a very universal manner.
[0025] In the following text the present invention is described in
greater detail based on preferred exemplary embodiments in
conjunction with the drawing.
[0026] The figures show:
[0027] FIG. 1 a first specific development of a coolant circuit
having a two-stage compressor; and
[0028] FIG. 2 a second specific development of a coolant circuit
having a two-stage compressor.
[0029] FIG. 1 schematically shows a coolant circuit 1 of a heat
pump, which has a two-stage compressor 2 equipped with a first
compression stage 3 and a second compression stage 4. Two-stage
compressor 2 is operated by a motor 5; a mechanical link between
motor 5 and compression stages 3, 4 of two-stage compressor 2 is
not shown for reasons of clarity.
[0030] With the aid of compression stages 3, 4 of two-stage
compressor 2, the pressure level of a coolant is initially raised
from a first pressure level to a medium pressure level, and then to
a high pressure level. A liquid fluid under overpressure, which
becomes gaseous following a pressure removal and the absorption of
heat, is used as coolant. The coolant is conveyed in gaseous form,
for instance, and at a low pressure to first compression stage 3 of
compressor 2, where it is brought to a medium pressure level and
heated at the same time.
[0031] Via a pressurized gas line 6, a gaseous coolant component in
the coolant circuit according to the present invention then arrives
at a mixing device 7 and is combined there with a coolant component
that comes from second compression stage 4. This cooling component
was supplied to the second compression stage of compressor 2 in
gaseous form at a medium pressure level and was brought to a high
pressure level in second compression stage 4 while being heated at
the same time.
[0032] Following second compression stage 4, the gaseous coolant
component is subsequently conveyed to a capacitor 9 via a second
line 8. There, heat is output from the cooling component to an
environment or a heat sink 10. The resulting condensed coolant
component, which may include both liquid and gaseous phases, is
subsequently expanded to the medium pressure level with the aid of
a throttle element 11, which is developed as an expansion valve,
for instance; coolant component arrives at mixing device 7 at this
medium pressure and is combined with the coolant component coming
from first compression stage 3.
[0033] The combined coolant components, i.e., the coolant main
flow, which includes the entire volumetric flow, travels from
mixing device 7 to a motor cooling system of motor 5 and absorbs
heat from motor 5 there. Then, the coolant main flow is separated
into the gaseous coolant component and the liquid cooling component
in a phase separation element 12. The gaseous coolant component is
subsequently conveyed to second compression stage 4 again.
[0034] The liquid cooling component is expanded with the aid of a
throttle element 13, which may once again be developed as an
expansion valve, and conveyed at a low pressure and low temperature
to an evaporator 14 in which the liquid coolant component is
transferred into a gaseous phase. In so doing, evaporator 14
absorbs heat from the environment or a heat sink 15, which is
absorbed by the coolant component. Throttle element 13 and
evaporator 14 are situated in a first line 16, which connects phase
separation element 12 to first compression stage 3 of two-stage
compressor 2. The pressure of the coolant component evaporated in
evaporator 14 is then increased in first compression stage 3, so
that it is able to be conveyed to mixing device 7 again at a medium
pressure level and at an increased temperature.
[0035] FIG. 2 shows an alternative preferred exemplary embodiment,
in which corresponding elements have been provided with matching
reference numerals. In contrast to the exemplary embodiment
according to FIG. 1, the coolant component is not conveyed to a
mixing device upstream from the motor cooling system following
first compression stage 3, but directly to second compression stage
4. Since the gaseous coolant component coming from phase separation
element 12 is conveyed to second compression stage 4 as well, the
coolant main flow is brought to the high pressure level in second
compression stage 4 and heated in the process. Following the heat
dissipation and condensation in condenser 9 and the subsequent
expansion via throttle element 11, the coolant main flow, which has
gaseous and liquid components, arrives at the cooling system of
motor 5 and can the absorb heat there. The fluid coolant component
separated from the coolant main flow by phase separation element 12
is conveyed via first line 16 and initially expanded to a low
pressure level with the aid of throttle element 13. This is
followed by an evaporation in evaporator 14, so that it is
ultimately supplied to first compression stage 3 of compressor 3 in
gaseous form, where it is brought to a medium pressure level while
being heated at the same time, in order to then reach second
compression stage 4.
[0036] In the method according to the present invention, or in the
devices according to the present invention, which involve a heat
pump system in particular, cooling of the motor that is required
for driving the two-stage compressor takes place with the aid of
the coolant main flow, i.e., by the entire coolant. An additional
bypass link in order to divert a portion of the coolant for cooling
the motor is not required. This results in a simplified design,
especially on account of the reduced number of required expansion
valves, and thus in a less complex control.
[0037] The waste heat from the motor is supplied to the coolant
circuit again without reducing the efficiency of the overall system
because of the phase separation that takes place after the waste
heat has been absorbed.
[0038] With relatively little outlay, the procedure according to
the present invention is adaptable to a coolant circuit having a
single-stage compressor, an intermediate injection and an internal
heat transmitter being able to be used or also an intermediate
injection and a phase separation in a phase separation element.
[0039] Because of the design of the coolant circuit, a reversal of
the cooling circuit for a defrosting and/or for the cooling
operation is able to tabs place, although the flow must always
traverse the phase separation element in the same direction.
* * * * *