U.S. patent application number 11/637976 was filed with the patent office on 2007-08-09 for ejector refrigerant cycle device and control method thereof.
This patent application is currently assigned to DENSO Corporation. Invention is credited to Takayuki Sugiura, Hirotsugu Takeuchi.
Application Number | 20070180852 11/637976 |
Document ID | / |
Family ID | 38190191 |
Filed Date | 2007-08-09 |
United States Patent
Application |
20070180852 |
Kind Code |
A1 |
Sugiura; Takayuki ; et
al. |
August 9, 2007 |
Ejector refrigerant cycle device and control method thereof
Abstract
An ejector refrigerant cycle device includes an ejector that has
a nozzle portion for reducing pressure of refrigerant on a
downstream side of a radiator to expand the refrigerant, and a
refrigerant suction port from which refrigerant is drawn by a
high-velocity refrigerant flow jetted from the nozzle portion, an
evaporator that evaporates refrigerant and flows out the evaporated
refrigerant to the refrigerant suction port, a flow amount changing
unit that changes a refrigerant flow amount flowing into the
evaporator, and a pressure abnormality detecting portion for
detecting a pressure abnormality of a high-pressure refrigerant on
an upstream side of the nozzle portion. In the ejector refrigerant
cycle device, when the pressure abnormality detecting portion
detects the pressure abnormality, the flow amount changing unit
makes the refrigerant flow amount flowing into the evaporator
larger than that in a normal pressure state of the high-pressure
refrigerant.
Inventors: |
Sugiura; Takayuki;
(Anjo-city, JP) ; Takeuchi; Hirotsugu;
(Nagoya-city, JP) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Assignee: |
DENSO Corporation
Kariya-city
JP
|
Family ID: |
38190191 |
Appl. No.: |
11/637976 |
Filed: |
December 13, 2006 |
Current U.S.
Class: |
62/500 ;
62/170 |
Current CPC
Class: |
F25B 2400/23 20130101;
F25B 41/00 20130101; F25B 9/008 20130101; F25B 2341/0012 20130101;
B60H 2001/3298 20130101; F25B 2309/061 20130101; F25B 2600/2515
20130101 |
Class at
Publication: |
062/500 ;
062/170 |
International
Class: |
F25B 19/02 20060101
F25B019/02; F25B 1/06 20060101 F25B001/06 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2005 |
JP |
2005-359093 |
Claims
1. An ejector refrigerant cycle device comprising: a compressor
that draws, compresses and discharges refrigerant; a radiator that
radiates heat of refrigerant discharged from the compressor; an
ejector that has a nozzle portion for reducing pressure of
refrigerant on a downstream side of the radiator to expand the
refrigerant, and a refrigerant suction port from which refrigerant
is drawn by a high-velocity refrigerant flow jetted from the nozzle
portion, wherein the ejector mixes refrigerant drawn from the
refrigerant suction port and refrigerant jetted from the nozzle
portion, and reduces the velocity of the mixed refrigerant so as to
increase its pressure; an evaporator that evaporates refrigerant
and flows out the evaporated refrigerant to the refrigerant suction
port; a flow amount changing unit that changes a refrigerant flow
amount flowing into the evaporator; and a pressure abnormality
detecting means that detects a pressure abnormality of a
high-pressure refrigerant on an upstream side of the nozzle
portion, wherein the compressor draws refrigerant on a downstream
side of the ejector, and wherein when the pressure abnormality
detecting means detects the pressure abnormality, the flow amount
changing unit makes the refrigerant flow amount flowing into the
evaporator larger than that in a normal pressure state of the
high-pressure refrigerant.
2. The ejector refrigerant cycle device as in claim 1, further
comprising: an accumulator that separates refrigerant flowing out
of the ejector into vapor refrigerant and liquid refrigerant; and a
liquid refrigerant passage through which the liquid refrigerant
flows from the accumulator into the evaporator, wherein the flow
amount changing unit is arranged in the liquid refrigerant
passage.
3. The ejector refrigerant cycle device as in claim 1, further
comprising: a branch passage branched from a point between a
downstream side of the radiator and an upstream side of the nozzle
portion, and is joined to the refrigerant suction port of the
ejector, wherein the flow amount changing unit is arranged in the
branch passage.
4. The ejector refrigerant cycle device as in claim 1, wherein when
a high-pressure refrigerant pressure on the upstream side of the
nozzle portion becomes not less than a predetermined value, the
pressure abnormality detecting means detects the pressure
abnormality.
5. The ejector refrigerant cycle device as in claim 1, wherein when
a pressure-increase amount per unit time of the high-pressure
refrigerant on the upstream side of the nozzle portion becomes not
less than a predetermined amount, the pressure abnormality
detecting means detects the pressure abnormality.
6. The ejector refrigerant cycle device as in claim 1, wherein the
flow amount changing unit is a variable throttle mechanism that is
constructed to change an area of a refrigerant passage.
7. The ejector refrigerant cycle device as in claim 1, further
comprising: a drive member that drives the flow amount changing
unit to change a refrigerant passage area in the flow amount
changing unit; and a control unit that controls operation of the
drive member, wherein the pressure abnormality detecting means
includes a pressure sensor for detecting a pressure of
high-pressure refrigerant on the upstream side of the nozzle
portion, and determination means that determines whether or not a
detection value of the pressure sensor corresponds to the pressure
abnormality, and wherein when the determination means determines
that the detection value of the pressure sensor corresponds to the
pressure abnormality, the control unit controls the drive member so
as to expand the refrigerant passage area.
8. The ejector refrigerant cycle device as in claim 1, wherein the
ejector further includes a mixing portion in which the refrigerant
jetted from the nozzle portion and the refrigerant drawn from the
refrigerant suction port are mixed, and a diffuser portion which
increases pressure of the mixed refrigerant from the mixing
portion, the device further comprising reducing means for reducing
a pressure increasing amount of the mixed refrigerant in the
diffuser portion, wherein when the pressure abnormality detecting
means detects the pressure abnormality, the reducing means reduces
the pressure increasing amount of the mixed refrigerant in the
diffuser portion than that in the normal pressure state of the
high-pressure refrigerant.
9. The ejector refrigerant cycle device as in claim 8, wherein the
flow amount changing unit is used as the reducing means.
10. The ejector refrigerant cycle device according to claim 3,
further comprising an another evaporator for evaporating
refrigerant flowing out of an outlet port of the ejector.
11. An ejector refrigerant cycle device comprising: a compressor
that draws, compresses and discharges refrigerant; a radiator that
radiates heat of refrigerant discharged from the compressor; an
ejector that has a nozzle portion for reducing pressure of
refrigerant on a downstream side of the radiator to expand the
refrigerant, a refrigerant suction port from which refrigerant is
drawn by a high-velocity refrigerant flow jetted from the nozzle
portion, a mixing portion in which the refrigerant jetted from the
nozzle portion and the refrigerant drawn from the refrigerant
suction port are mixed, and a diffuser portion which increases
pressure of the mixed refrigerant from the mixing portion; an
evaporator that evaporates refrigerant and flows out the evaporated
refrigerant to the refrigerant suction port; a pressure abnormality
detecting means that detects a pressure abnormality of a
high-pressure refrigerant on an upstream side of the nozzle
portion; and reducing means for reducing a pressure increasing
amount of the mixed refrigerant in the diffuser portion of the
ejector, wherein the compressor draws refrigerant on a downstream
side of the ejector, and wherein when the pressure abnormality
detecting means detects the pressure abnormality, the reducing
means reduces a pressure increasing amount of the mixed refrigerant
in the diffuser portion than that in a normal pressure state of the
high-pressure refrigerant.
12. The ejector refrigerant cycle device according to claim 11,
wherein the pressure abnormality detecting means detects the
pressure abnormality when the pressure of refrigerant at the
upstream side of the nozzle portion is higher than a predetermined
amount.
13. A control method of an ejector refrigerant cycle device having
an ejector that includes a nozzle portion for reducing pressure of
a high-pressure refrigerant, a refrigerant suction port from which
refrigerant from an evaporator is drawn by a high-velocity
refrigerant flow jetted from the nozzle portion, a mixing portion
in which the refrigerant jetted from the nozzle portion and the
refrigerant drawn from the refrigerant suction port are mixed, and
a diffuser portion which increases pressure of the mixed
refrigerant from the mixing portion, the control method comprising:
detecting a pressure abnormality of the high-pressure refrigerant
on an upstream side of the nozzle portion; and reducing a pressure
increasing amount of the mixed refrigerant in the diffuser portion
than that in a normal pressure state of the high-pressure
refrigerant.
14. The control method according to claim 13, wherein the reducing
is performed by increasing a refrigerant amount flowing into the
evaporator, which has a refrigerant outlet coupled to the
refrigerant suction port of the ejector, to be larger than that in
the normal pressure state of the high-pressure refrigerant.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application is based on Japanese Patent Application No.
2005-359093 filed on Dec. 13, 2005, the contents of which are
incorporated herein by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention relates to an ejector refrigerant
cycle device having an ejector, and a control method of an ejector
refrigerant cycle device.
BACKGROUND OF THE INVENTION
[0003] U.S. Pat. No. 6,837,069 (corresponding to JP-A-2004-53028)
describes an ejector refrigerant cycle device that is so
constructed as to avoid an abnormal increase in a high-pressure
side refrigerant pressure in order to secure the reliability of
refrigerant piping and functional parts which receive the
high-pressure side refrigerant pressure of the cycle.
[0004] In the ejector refrigerant cycle device of U.S. Pat. No.
6,837,069 (corresponding to JP-A-2004-53028), a branch point for
branching a high-pressure refrigerant flow is provided on an
upstream side of a nozzle portion of an ejector, a bypass passage
for relieving high-pressure refrigerant to a portion between a
downstream side of an evaporator and a refrigerant suction port of
the ejector from this branch point is provided, and a mechanical
control valve that is opened when the high-pressure side
refrigerant pressure on the upstream side of the nozzle portion
satisfies a specified pressure condition (for example, not less
than about 10 MPa at a refrigerant temperature of 40.degree. C.) is
arranged in this bypass passage.
[0005] According to the above-mentioned construction, when the
high-pressure side refrigerant pressure satisfies the specified
condition, the control valve is opened to relieve the high-pressure
refrigerant on the upstream side of the nozzle portion to the
position between the downstream side of an evaporator and the
refrigerant suction port via the bypass passage, thereby an
abnormal increase in the high-pressure side refrigerant pressure of
the cycle can be avoided.
[0006] However, in the ejector refrigerant cycle device described
in U.S. Pat. No. 6,837,069 (corresponding to JP-A-2004-53028),
because the high-pressure refrigerant is relieved to the downstream
side of the evaporator when the high-pressure side refrigerant
pressure satisfies the specified pressure condition, the pressure
of the high-pressure side refrigerant is applied to the evaporator.
For this reason, the evaporator is required to have resistance to
the pressure of the high-pressure refrigerant, which results in
enlarging the size of the evaporator and increasing cost.
Accordingly, the size and cost of the whole ejector refrigerant
cycle device are increased.
SUMMARY OF THE INVENTION
[0007] In view of the above-mentioned problems, an object of the
present invention is to provide an ejector refrigerant cycle device
which can prevent the pressure of high-pressure side refrigerant
from being applied to an evaporator, and avoid an abnormal increase
in the pressure of the high-pressure side refrigerant.
[0008] It is another object of the present invention to provide a
control method of an ejector refrigerant cycle device.
[0009] According to an aspect of the present invention, an ejector
refrigerant cycle device includes a compressor that draws,
compresses and discharges refrigerant, a radiator that radiates
heat of refrigerant discharged from the compressor, and an ejector
that has a nozzle portion for reducing pressure of refrigerant on a
downstream side of the radiator to expand the refrigerant, and a
refrigerant suction port from which refrigerant is drawn by a
high-velocity refrigerant flow jetted from the nozzle portion.
Here, the ejector mixes refrigerant drawn from the refrigerant
suction port and refrigerant jetted from the nozzle portion, and
reduces the velocity of the mixed refrigerant so as to increase its
pressure. The ejector refrigerant cycle device further includes an
evaporator that evaporates refrigerant and flows out the evaporated
refrigerant to the refrigerant suction port, a flow amount changing
unit that changes a refrigerant flow amount flowing into the
evaporator, and a pressure abnormality detecting means that detects
a pressure abnormality of a high-pressure side refrigerant on an
upstream side of the nozzle portion. In the ejector refrigerant
cycle device, the compressor draws refrigerant on a downstream side
of the ejector, and the flow amount changing unit makes the
refrigerant flow amount flowing into the evaporator larger than
that in a normal pressure state of the high-pressure side
refrigerant when the pressure abnormality detecting means detects
the pressure abnormality.
[0010] Because the flow amount changing unit makes the refrigerant
flow amount flowing into the evaporator larger than that in the
normal pressure state of the high-pressure side refrigerant when
the pressure abnormality detecting means detects the pressure
abnormality, the flow amount of suction refrigerant drawn into the
refrigerant port is increased. Here, the normal pressure state of
the high-pressure refrigerant is a state where the pressure
abnormality detecting means does not detect a pressure
abnormality.
[0011] When the flow rate of suction refrigerant drawn into the
refrigerant suction port of the ejector increases, in the velocity
energy of the high-velocity refrigerant flow jetted from the nozzle
portion, the amount of energy consumed to suck refrigerant
increases, thereby the velocity of the high-velocity refrigerant
flow decreases.
[0012] Further, because the flow rate of suction refrigerant which
is slow in the velocity of flow with respect to the high-velocity
refrigerant flow increases, the velocity of the flow of the mixed
refrigerant flowing into the diffuser portion decreases.
[0013] The diffuser portion converts the kinetic energy of the
mixed refrigerant flow to pressure energy to increase the pressure
of refrigerant. Thus, when the velocity of the mixed refrigerant
flowing into the diffuser portion decreases, the amount of pressure
increase of refrigerant in the diffuser portion also decreases.
With this, the pressure of refrigerant flowing out of the ejector
decreases.
[0014] For this reason, the pressure of refrigerant flowing out of
the ejector and drawn by the compressor decreases, and the pressure
of the high-pressure side refrigerant can be decreased in the
ejector refrigerant cycle device. As a result, the pressure of
high-pressure side refrigerant is not applied to the evaporator,
and an abnormal increase in the high-pressure side refrigerant
pressure can be avoided.
[0015] Further, even when the evaporator refrigerant flow amount
increases, a predetermined amount of refrigerant evaporates in the
evaporator to exert a heat absorbing action. Thus, the ejector
refrigerant cycle device can perform a cooling operation even at
the time of avoiding an abnormal increase in the high-pressure side
refrigerant pressure. Here, the refrigerant flow amount in the
present invention may be a mass flow rate.
[0016] For example, an accumulator for separating refrigerant
flowing out of the ejector into vapor refrigerant and liquid
refrigerant may be arranged in a liquid refrigerant passage such
that the liquid refrigerant flows from the accumulator into the
evaporator. In this case, the flow amount changing unit is arranged
in the liquid refrigerant passage.
[0017] Alternatively, a branch passage may be provided to be
branched from a point between a downstream side of the radiator and
an upstream side of the nozzle portion, and to be joined to the
refrigerant suction port of the ejector. In this case, the flow
amount changing unit is arranged in the branch passage.
[0018] The pressure abnormality detecting means may be provided
such that, when a high-pressure refrigerant pressure on the
upstream side of the nozzle portion becomes not less than a
predetermined value, the pressure abnormality detecting means
detects the pressure abnormality. Alternatively, the pressure
abnormality detecting means may be provided such that, when the
pressure-increase amount per unit time of the high-pressure
refrigerant on the upstream side of the nozzle portion becomes not
less than a predetermined amount, the pressure abnormality
detecting means detects the pressure abnormality.
[0019] Furthermore, the flow amount changing unit may be a variable
throttle mechanism that is constructed to change an area of a
refrigerant passage. In this case, the flow amount changing unit
can decompress refrigerant flowing into the evaporator.
[0020] According to another aspect of the present invention, a
control method of an ejector refrigerant cycle device having an
ejector includes a step of detecting a pressure abnormality of a
high-pressure side refrigerant on an upstream side of a nozzle
portion of the ejector, and a step of reducing a pressure
increasing amount in a diffuser portion of the ejector than that in
a normal pressure state of the high-pressure refrigerant.
Therefore, when the pressure abnormality is detected, the pressure
of high-pressure side refrigerant can be reduced, thereby
preventing the pressure of high-pressure side refrigerant from
being applied to the evaporator, and avoiding an abnormal increase
in the pressure of the high-pressure side refrigerant.
[0021] For example, the reducing can be performed by increasing a
refrigerant amount flowing into the evaporator, which has a
refrigerant outlet coupled to the refrigerant suction port of the
ejector, to be larger than that in the normal pressure state of the
high-pressure refrigerant.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] Additional objects and advantages of the present invention
will be more readily apparent from the following detailed
description of preferred embodiments when taken together with the
accompanying drawings.
[0023] FIG. 1 is a general construction diagram of an ejector
refrigerant cycle device of a first embodiment of the present
invention.
[0024] FIG. 2 is a flow chart to show the control of a variable
throttle mechanism of an air-conditioning control unit of the first
embodiment.
[0025] FIG. 3 is a general construction diagram of an ejector
refrigerant cycle device of a second embodiment of the second
embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
[0026] In this embodiment, refrigerant (e.g., carbon dioxide) in
which a high-pressure side refrigerant pressure is higher than a
supercritical pressure is used as the refrigerant of an ejector
refrigerant cycle device. Thus, the ejector refrigerant cycle
device of this embodiment constructs a supercritical refrigerant
cycle.
[0027] First, in an ejector refrigerant cycle device 10, a
compressor 11 draws, compresses and discharges refrigerant, and
increases the pressure of refrigerant to a supercritical pressure
in this embodiment. This compressor 11 has a driving force
transmitted thereto from a vehicle running engine (not shown) via a
pulley and a belt, thereby being rotated and driven. Moreover, in
this embodiment, a well-known swash-plate type variable
displacement compressor capable of controlling a discharge volume
variably and continuously by a control signal from the outside is
used as the compressor 11.
[0028] Here, the discharge volume means the geometric volume of an
operating space in which refrigerant is drawn and compressed and,
specifically, means the cylinder volume between the top dead center
and the bottom dead center of the stroke of a piston in the
compressor 11. By changing the discharge volume, the discharge
capacity of the compressor 11 can be adjusted. The changing of the
discharge volume of the compressor 11 is performed by controlling
the pressure Pc of a swash plate chamber (not shown) constructed in
the compressor 11 so as to change the slant angle of a swash plate
and change the stroke of the piston.
[0029] The pressure Pc of the swash plate chamber is controlled
by-changing a ratio of a discharge refrigerant pressure Pd to a
suction refrigerant pressure Ps by using an electromagnetic volume
control valve 11a, in the compressor 11. The electromagnetic volume
control valve 11a is driven by the output signal of an
air-conditioning control unit 20 to be described later. With this,
the compressor 11 can change the discharge volume (displacement)
continuously within a range of from nearly 0% to 100%.
[0030] Moreover, because the compressor 11 can change the discharge
volume continuously within a range of nearly from 0% to 100%, the
compressor 11 can be brought to an operating stop state by
decreasing the discharge volume to nearly 0%. Thus, this embodiment
adopts a clutch-less construction in which the rotary shaft of the
compressor 11 is always coupled to the vehicle running engine via
the pulley and the belt.
[0031] The variable displacement compressor 11 may be provided such
that power is transmitted from the vehicle running engine to the
compressor 11 via an electromagnetic clutch. Moreover, when a fixed
displacement compressor is used as the compressor 11, it is also
recommend that an on-off control of operating the compressor
intermittently by an electromagnetic clutch is performed to control
the ratio of the on operation to the off operation of the
compressor. Even in this case, the discharge volume of refrigerant
of the compressor can be effectively controlled.
[0032] A radiator 12 is connected to a downstream side of the
refrigerant flow of the compressor 11. The radiator 12 is a heat
exchanger that exchanges heat between high-pressure refrigerant
discharged from the compressor 11 and outside air (i.e., air
outside a vehicle compartment) blown by a blower fan 12a, so as to
cool the high-pressure refrigerant. The blower fan 12a is an
electrically operated fan driven by a motor 12b. Moreover, the
motor 12b is rotated and driven by control voltage outputted from
the air-conditioning control unit 20 (A/C control unit) to be
described later.
[0033] This embodiment constructs a supercritical refrigerant
cycle, so refrigerant is not condensed in the radiator 12 and
radiates heat as it is held in a supercritical pressure state.
[0034] An ejector 13 is connected to the downstream side of the
refrigerant flow of the radiator 12. The ejector 13 includes: a
nozzle portion 13a that throttles refrigerant flowing from the
radiator 12 so as to reduce the pressure of refrigerant and to
expand refrigerant in an isentropic manner; and a refrigerant
suction port 13b that is arranged so as to communicate with the jet
port of the nozzle portion 13a and draws refrigerant on the
downstream side of an evaporator 17 to be described later.
[0035] Further, the ejector 13 further includes: a mixing portion
13c that is arranged on the downstream side of the nozzle portion
13a and the refrigerant suction port 13b and mixes a high-velocity
refrigerant flow from the nozzle portion 13a with suction
refrigerant drawn from the refrigerant suction port 13b; and a
diffuser portion 13d that is arranged on the downstream side of the
mixing portion 13c and reduces the velocity of the refrigerant flow
so as to increase the pressure of refrigerant.
[0036] This diffuser portion 13d is formed in a shape to gradually
increase the area of passage of refrigerant and has a function of
reducing the velocity of the refrigerant flow so as to increase the
pressure of refrigerant, that is, a function of converting the
velocity energy of refrigerant to pressure energy thereof.
[0037] An accumulator 14 is connected to the downstream side of the
refrigerant flow of the diffuser portion 13d of the ejector 13. The
accumulator 14 is formed in the shape of a tank and is a
vapor/liquid separating unit. The accumulator 14 separates
refrigerant in a vapor/liquid mixed state, flowed from the diffuser
portion 13d of the ejector 13, into vapor-phase refrigerant and
liquid-phase refrigerant by a difference in density. Thus, the
vapor-phase refrigerant is collected on the upper side in the
vertical direction of the inner space of a tank part of the
accumulator 14 and the liquid-phase refrigerant is collected in the
lower side on the vertical direction.
[0038] Further, a vapor-phase refrigerant outlet 14a is provided in
the top of tank-shaped accumulator 14. The vapor-phase refrigerant
outlet 14a is connected to the refrigerant suction side of the
compressor 11. On the other hand, a liquid-phase refrigerant outlet
14b is provided in the bottom of the tank part of the accumulator
14. The liquid-phase refrigerant outlet 14b is connected to a
liquid-phase refrigerant passage 15.
[0039] This liquid-phase refrigerant passage 15 is refrigerant
piping for connecting the liquid-phase refrigerant outlet 14b of
the accumulator 14 to the refrigerant suction port 13b of the
ejector 13. In the liquid-phase refrigerant passage 15 are arranged
a variable throttle mechanism 16 and an evaporator 17. The variable
throttle mechanism 16 reduces the pressure of liquid-phase
refrigerant flowing out of the accumulator 14 to adjust the
evaporation pressure of refrigerant in the evaporator 17. In this
embodiment, the variable throttle mechanism 16 is an electric
variable throttle mechanism controlled by the control signal of the
air-conditioning control unit 20.
[0040] For example, the variable throttle mechanism 16 is a flow
rate adjusting valve that includes a valve mechanism 16a
constructed so as to change the area of passage of refrigerant and
a stepping motor 16b rotated and driven by a control signal (pulse
signal) outputted from the air-conditioning control unit 20. When
the stepping motor 16 is rotated, the valve body of the valve
mechanism 16a is displaced to adjust the area of passage of
refrigerant continuously.
[0041] Thus, the valve mechanism 16a of the variable throttle
mechanism 16 constructs flow amount changing unit for changing an
evaporator refrigerant flow amount Ge flowing into the evaporator
17, and the stepping motor 16b constructs drive means for changing
the area of passage of refrigerant of the valve mechanism 16a.
[0042] The evaporator 17 is a heat exchanger that is arranged on
the downstream side of the refrigerant flow of the variable
throttle mechanism 16 in the liquid-phase refrigerant passage 15
and exchanges heat between low-pressure refrigerant having pressure
reduced by the variable throttle mechanism 16 and air blown by the
blower fan 17a. The low-pressure refrigerant in the evaporator 17
absorbs heat from air so as to cool air in a compartment to be
cooled.
[0043] Moreover, the blower fan 17a is an electrically operated fan
driven by a motor 17b. The motor 17b is rotated and driven by
control voltage outputted from the air-conditioning control unit 20
to be described later. Further, as described above, the downstream
side of the evaporator 17 is connected to the refrigerant suction
port 13b of the ejector 13, such that the refrigerant from the
evaporator 17 is drawn into the refrigerant suction port 13b of the
ejector 13.
[0044] Next, an electric control operation of this embodiment will
be described. The air-conditioning control unit 20 is constructed
of a well-known microcomputer including a CPU, a ROM, a RAM and the
like and its peripheral circuit, and performs various kinds of
computations and processing on the basis of control programs stored
in the ROM to control the operations of the above-mentioned various
kinds of devices 11a, 12b, 16b, 17b, for example.
[0045] Moreover, to the air-conditioning control unit 20, detection
signals from a group of various kinds of sensors and various
operating signals from operating panel (not shown) are inputted.
Specifically, the group of sensors include a temperature sensor 21
for detecting a refrigerant temperature Tev on the downstream side
of the evaporator 17, a pressure sensor 22 for detecting a
refrigerant pressure Pev on the downstream side of the evaporator
17, and a pressure sensor 23 for detecting a refrigerant pressure
Pnoz on the upstream side of the nozzle portion 13a. Moreover, the
operating panel is provided with an operating switch for operating
a refrigerating unit and a temperature setting switch for setting
temperature in the compartment to be cooled (e.g., refrigeration
compartment).
[0046] Next, operation of the ejector refrigerant cycle device in
the above-mentioned construction will be described. First, when the
vehicle running engine is operated, a rotational drive force is
transmitted from the vehicle running engine to the compressor 11.
Further, when the operating signal of the operating switch is
inputted to the air-conditioning control unit 20 from the operating
panel, an output signal is outputted from the air-conditioning
control unit 20 to the electromagnetic volume control valve 11a on
the basis of the previously stored control program.
[0047] The discharge volume (displacement) of the compressor 11 is
determined by this output signal, and the compressor 11 draws
vapor-phase refrigerant from the vapor-phase refrigerant outlet 14a
of the accumulator 14 and compresses the vapor-phase refrigerant to
a supercritical state and then discharges the vapor-phase
refrigerant. The refrigerant in the supercritical state, discharged
from the compressor 11, flows into the radiator 12 and is cooled by
outside air. Further, refrigerant flowing out of the radiator 12
flows into the nozzle portion 13a of the ejector 13.
[0048] The refrigerant flowing into the nozzle portion 13a of the
ejector 13 has its pressure reduced in the nozzle portion 13a,
thereby being brought to a two-phase state of vapor and liquid. The
pressure energy of high-pressure refrigerant is converted to
velocity energy by the nozzle portion 13a, thereby refrigerant is
brought to a high-velocity refrigerant flow and is jetted from the
jet port of the nozzle portion 13a. Refrigerant on the downstream
side of the evaporator 17 is drawn from the refrigerant suction
port 13b by a pressure drop produced near the jet port of the
nozzle portion 13a at this time.
[0049] The refrigerant jetted from the nozzle portion 13a and the
refrigerant drawn from the refrigerant suction port 13b are mixed
with each other in the mixing portion 13c on the downstream side of
the nozzle portion 13a, and flows into the diffuser portion 13d. In
this diffuser portion 13d, the velocity energy of the refrigerant
is converted to pressure energy by the area of passage being
enlarged, so the pressure of the refrigerant on the downstream side
of the ejector 13 is increased according to the velocity of the
flow of the refrigerant flowing into the diffuser portion 13d.
[0050] The refrigerant flowing out of the diffuser portion 13d of
the ejector 13 flows into the accumulator 14, and is separated into
vapor-phase refrigerant and liquid-phase refrigerant. The
vapor-phase refrigerant in the accumulator 14 is again drawn into
and compressed by the compressor 11.
[0051] On the other hand, the liquid-phase refrigerant in the
accumulator 14 flows into the liquid-phase refrigerant passage 15
by the suction function of the ejector 13. This liquid-phase
refrigerant has flow-rate adjusted and pressure-reduced by the
variable throttle mechanism 16, and flows into the evaporator 17.
When the liquid-phase refrigerant is evaporated in the evaporator
17, the liquid-phase refrigerant absorbs heat from air in the
refrigeration compartment (i.e., the compartment to be cooled)
blown by the blower fan 17a, thereby air in the refrigeration
compartment is cooled.
[0052] The refrigerant flowing out of the evaporator 17 is drawn
into the refrigerant suction port 13b and is mixed with a
high-velocity refrigerant flow jetted from the nozzle portion
13a.
[0053] The air-conditioning control unit 20 in this embodiment
controls the stepping motor 16b of the variable throttle mechanism
16 so as to change the area of passage of refrigerant of the valve
mechanism 16a. The operation of the air-conditioning control unit
20 will be described on the basis of a flow chart shown in FIG. 2.
First, at step S1, the control signals of a refrigerant temperature
Tev on the downstream side of the evaporator 17, a refrigerant
pressure Pev on the downstream side of the evaporator 17, and a
refrigerant pressure Pnoz on the upstream side of the nozzle
portion 13a are read.
[0054] Next, at step 82, it is determined on the basis of Pnoz read
at step S1 whether or not the high-pressure side refrigerant
pressure of the cycle is abnormal. Specifically, it is determined
whether or not the detected refrigerant pressure Pnoz is not higher
than a reference high-pressure refrigerant pressure KPnoz.
[0055] Here, the reference high-pressure refrigerant pressure KPnoz
is a value previously set to determine that a high-pressure side
refrigerant pressure on the upstream side of the nozzle portion 13a
becomes abnormally high within a range not exceeding the pressure
resistance value of the refrigerant piping and the functional parts
(for example, radiator 12), which receive the high-pressure side
refrigerant pressure on the upstream side of the nozzle portion
13a.
[0056] Thus, when it is determined that Pnoz.ltoreq.Kpnoz at step
S2, it is determined that the high-pressure side refrigerant
pressure of the cycle is not in the state of abnormal pressure and
the control routine proceeds to step S3. When it is not determined
that Pnoz.ltoreq.KPnoz, it is determined that the high-pressure
side refrigerant pressure of the cycle is in the state of abnormal
pressure and the control routine proceeds to step S5. For this
reason, in this embodiment, step S2 is a determination means for
determining whether or not the high-pressure side refrigerant
pressure of the cycle is in the state of abnormal pressure on the
basis of the detection value of the pressure sensor 23.
[0057] At step S3, a normal operation control is performed because
the high-pressure side refrigerant pressure is not in the state of
abnormal pressure. In this normal operation control, the
refrigerant passage area of the valve mechanism 16a is controlled
in such a way that refrigerant on the downstream side of the
evaporator 17 has a set degree of superheat.
[0058] For example, the degree of superheat of refrigerant on the
downstream side of the evaporator 17 is computed on the basis of
the refrigerant temperature Tev and the refrigerant pressure Pev
which are read at step S1 by the air-conditioning control unit 20,
and a control signal (pulse signal) is outputted to the stepping
motor 16b so that this degree of superheat approaches to a
previously set value.
[0059] By controlling the degree of superheat of refrigerant on the
downstream side of the evaporator 17 to a predetermined degree of
superheat, when liquid-phase refrigerant flowing into the
evaporator 17 is evaporated, the liquid-phase refrigerant absorbs
heat from air blown by the blower fan 17 to cool the air blown.
Therefore, it can prevent the evaporator refrigerant flow amount Ge
flowing into the evaporator 17 from being increased
unnecessarily.
[0060] For this reason, the flow rate of suction refrigerant drawn
into the refrigerant suction port 13b of the ejector 13 is not
increased unnecessarily either, thereby the velocity of flow of a
mixed flow produced by mixing the suction refrigerant with the
high-velocity refrigerant flow jetted from the nozzle portion 13a
is not reduced. The velocity energy of the mixed flow is converted
to pressure energy in the diffuser portion 13d to increase the
pressure of refrigerant on the downstream side of the ejector
13.
[0061] Thus, the refrigerant evaporation pressure of the evaporator
17 connected to the refrigerant suction port 13b becomes lower than
the refrigerant pressure on the downstream side of the ejector 13.
Even when the refrigerant evaporation temperature in the evaporator
17 is set to a cooling temperature (for example, from -5.degree. C.
to 5.degree. C.) suitable for refrigeration, the pressure of
refrigerant drawn by the compressor 11 can be made higher than the
refrigerant evaporation pressure in the evaporator 17. As a result,
the drive power of the compressor 11 can be reduced and the
operation efficiency of the cycle can be improved.
[0062] When the normal operation control at step S3 is performed,
the control routine proceeds to step S4 and then after a set time T
(e.g., a unit time) elapses, the control routine returns again to
step S1.
[0063] Next, when it is not determined at step S2 that
Pnoz.ltoreq.KPnoz, it is determined that the high-pressure side
refrigerant pressure of the cycle is in the state of abnormal
pressure and the control routine proceeds to step S5. At step S5,
the air-conditioning control unit 20 outputs a control signal
(pulse signal) to the stepping motor 16b so as to expand the
refrigerant passage area of the valve mechanism 16a by a specified
value and then routine proceeds to step S6.
[0064] Next, Pnoz is read again at step S6 and the control routine
proceeds to step S7. At step S7, it is determined whether or not
Pnoz is not less than the previously set reference high-pressure
refrigerant pressure KPnoz--.alpha.. Here, .alpha. is a
predetermined value for setting a hysteresis width so as to prevent
the refrigerant passage area control of the valve mechanism 16a
from hunting.
[0065] Specifically, it is determined at step S7 whether or not
Pnoz.ltoreq.KPnoz--.alpha.. When it is determined that
Pnoz.ltoreq.KPnoz--.alpha., it is determined that the high-pressure
side refrigerant pressure becomes out of the state of abnormal
pressure and the control routine proceeds to step S4. That is, when
Pnoz.ltoreq.KPnoz--.alpha. at step S7, it is determined that the
high-pressure side refrigerant pressure becomes the normal state.
On the other hand, when it is not determined that
Pnoz.ltoreq.KPnoz--.alpha., it is determined that the high-pressure
side 10 refrigerant pressure continues to be in the state of
abnormal pressure, that is, is abnormally high pressure, and the
control routine returns to step S5. Thus, the air-conditioning
control unit 20 outputs a control signal (pulse signal) to the
stepping motor 16b so as to expand the refrigerant passage area of
the valve mechanism 16a.
[0066] In this manner, when it is determined that the high-pressure
side refrigerant pressure is in the state of abnormal pressure, the
air-conditioning control unit 20 controls the stepping motor 16b so
as to expand the refrigerant passage area of the valve mechanism
16a. In this case, the evaporator refrigerant flow amount Ge
flowing into the evaporator 17 is increased. For this reason, the
flow rate of suction refrigerant drawn into the refrigerant suction
port 13b of the ejector 13 is also increased.
[0067] Thus, the velocity of flow of the mixed refrigerant produced
by the mix of the suction refrigerant flow with the high-velocity
refrigerant flow is also decreased so as to reduce also the
velocity energy of the mixed refrigerant flow to be converted to
the pressure energy in the diffuser portion 13d of the ejector 13.
In this case, the amount of increase in the refrigerant pressure in
the diffuser portion of the ejector 13 is reduced. As a result, the
pressure of refrigerant drawn by the compressor 11 is reduced as
compared with pressure at the time of a normal operation and the
pressure of refrigerant discharged from the compressor 11 is also
reduced, thereby an abnormal increase in the high-pressure side
refrigerant pressure of the cycle can be avoided.
[0068] Further, even when the evaporator refrigerant flow amount Ge
(refrigerant flow rate) is increased, because a part of
liquid-phase refrigerant flowing into the evaporator 17 from the
accumulator 14 is evaporated, this part absorbs heat from air blown
from the blower fan 17a and hence can cool the air blown from the
air blower fan 17a. That is, the cycle can perform a cooling
operation even in this abnormal operation control.
[0069] In this embodiment, in the normal operation control in which
a pressure abnormality in the high-pressure side refrigerant
pressure of the cycle is not detected, it is possible to reduce the
drive force of the compressor 11 and to improve the operation
efficiency of the cycle by increasing the pressure of refrigerant
to be drawn by the compressor 11 using the pressure increasing
function of the diffuser portion 13d.
[0070] Further, when a pressure abnormality on the high-pressure
side refrigerant pressure of the cycle is detected, the evaporator
refrigerant flow amount Ge (refrigerant flow rate) is increased and
the abnormal operation control is performed. Accordingly, in the
abnormal operation control, it is possible to suppress the
refrigerant pressure increase in the diffuser portion 13d while
performing the cooling operation of the cycle, and to avoid the
abnormally high pressure of the cycle. Therefore, in the ejector
refrigerant cycle device of this embodiment, the cooling operation
can be performed without applying the pressure of high-pressure
side refrigerant to the evaporator 12.
Second Embodiment
[0071] In the above-described first embodiment, refrigerant cycle
is provided with the liquid-phase refrigerant passage 15 for
connecting the liquid-phase refrigerant outlet 14b of the
accumulator 14 to the refrigerant suction port 13b of the ejector
13, and the variable throttle mechanism 16 and the evaporator 17
are arranged in this liquid-phase refrigerant passage 15. In the
second embodiment, however, as shown in FIG. 3, the liquid-phase
refrigerant passage 15 is not provided but there is provided a
branch passage 25 for branching the refrigerant flow at a branch
point Z that is positioned between the downstream side of the
radiator 12 and the upstream side of the nozzle portion 13a of the
ejector 13.
[0072] This branch passage 25 is a refrigerant passage for
connecting the branch point Z to the refrigerant suction port 13b
of the ejector 13. In this embodiment, the variable throttle
mechanism 16 is arranged in the branch passage 25, and the
evaporator 17 is arranged on the downstream side of the refrigerant
flow of the variable throttle mechanism 16 in the branch passage
25. The variable throttle mechanism 16 and the evaporator 17 have
structures, respectively, similar to those described in the first
embodiment. Here, in this embodiment, in order to avoid confusion
with a second evaporator 26 to be described later, the evaporator
17 is referred to as a first evaporator in the following
description.
[0073] Moreover, in this embodiment, the second evaporator 26 is
arranged between the downstream side of the ejector 13 and the
accumulator 14. The second evaporator 26 is a heat exchanger that
exchanges heat between low-pressure refrigerant on the downstream
side of the ejector 13 and air in the refrigeration compartment
(compartment to be cooled), blown from the blower fan 17a, to make
the low-pressure refrigerant absorb heat to cool air in the
refrigeration compartment.
[0074] Further, in this embodiment, the pressure sensor 23 for
detecting the refrigerant pressure Pnoz on the upstream side of the
nozzle portion 13a is arranged on the upstream side of the branch
point Z. Of course, the position of the pressure sensor 23 is not
limited to this position, but for example, may be arranged between
the branch point Z and the nozzle portion 13a. In the second
embodiment, the other structures of the ejector refrigerant cycle
device can be made similar to those of the above-described first
embodiment.
[0075] Next, the operation of the ejector refrigerant cycle device
according to this embodiment will be described. First, when the
vehicle running engine is operated, just as in the first
embodiment, refrigerant in a supercritical state flows from the
compressor 11 into the condenser 12, thereby being cooled by the
outside air.
[0076] Further, refrigerant flowing out from the radiator 12 is
branched at the branch point Z into a refrigerant flow flowing into
the nozzle portion 13a of the ejector 13 and a refrigerant flow
flowing into the branch passage 25. Thus, in this embodiment, the
flow rate of the refrigerant flowing into the branch passage 25
becomes the evaporator refrigerant flow amount Ge.
[0077] The refrigerant flowing into the nozzle portion 13, just as
in the first embodiment, is pressure-reduced in the nozzle portion
13a and draws refrigerant on the downstream side of the first
evaporator 17 from the refrigerant suction port 13b. Further,
refrigerant jetted from the nozzle portion 13a and refrigerant
drawn from the refrigerant suction port 13b are mixed with each
other in the mixing portion 13c and is pressure-increased in the
diffuser portion 13d according to the velocity energy of the mixed
refrigerant flow.
[0078] Refrigerant flowing out from the diffuser portion 13d flows
into the second evaporator 26. In the second evaporator 26, the
low-pressure refrigerant having pressure-reduced in the nozzle
portion 13a absorbs heat from air blown from the blower fan 17a and
evaporates. The refrigerant after having passed through the second
evaporator 26 flows into the accumulator 14 and is separated into
vapor-phase refrigerant and liquid-phase refrigerant. The
vapor-phase refrigerant in the accumulator 14 is drawn and
compressed again by the compressor 11.
[0079] On the other hand, the refrigerant flowing into the branch
passage 25 is flow-rate adjusted and pressure-reduced by the
variable throttle mechanism 16 and flows into the first evaporator
17. In the first evaporator 17, the low-pressure refrigerant
flowing therein absorbs heat from air flowing from the second
evaporator 26 and evaporates. With this, air blown by the blower
fan 17a and cooled by the second evaporator 26 is further cooled in
the first evaporator 17. The refrigerant on the downstream side of
the first evaporator 17 is drawn into the refrigerant suction port
13b and is mixed with high-velocity refrigerant flow from the
nozzle portion 13a.
[0080] Also in the above-mentioned construction, the degree of
throttle opening of the variable throttle mechanism 16 can be
controlled as shown by the flow chart in FIG. 2, just as in the
first embodiment. That is, in the normal operation control in which
a pressure abnormality in the high-pressure side refrigerant
pressure of the cycle is not detected, it is possible to reduce the
drive force of the compressor 11 and to improve the operation
efficiency of the cycle by increasing the pressure of refrigerant
to be drawn by the compressor 11, by using the pressure increase of
refrigerant in the diffuser portion 13d.
[0081] Further, when a pressure abnormality in the high-pressure
side refrigerant pressure of the cycle is detected, the evaporator
refrigerant flow amount Ge is increased. Accordingly, it is
possible to suppress the pressure increase of refrigerant in the
diffuser portion 13d, thereby preventing an abnormal high pressure
of the cycle while performing the cooling operation of the cycle.
Therefore, a high pressure is not applied to the first evaporator
17.
[0082] Still further, in this embodiment, because the refrigerant
flow is branched at the branch point Z on the upstream side of the
nozzle portion 13a, the variable throttle mechanism 16 increases
the evaporation refrigerant flow amount Ge and at the same time
reduces the flow rate of the refrigerant flowing into the nozzle
portion 13a. As a result, the velocity of the mixed refrigerant
flowing into the diffuser portion 13d is reduced, thereby reducing
the amount of pressure increase in the refrigerant in the diffuser
portion 13d.
Other Embodiment
[0083] The present invention is not limited to the above-mentioned
embodiments but can be modified variously as described below.
[0084] (1) In the above-mentioned embodiments, the electric
variable throttle mechanism is used as the variable throttle
mechanism 16 that has the flow rate adjustment function, but a
mechanical variable throttle mechanism also can be employed as the
variable throttle mechanism 16 having the flow rate adjustment
function.
[0085] For example, a pressure responding means displaced in
response to the high-pressure side refrigerant on the upstream side
of the nozzle portion 13a may be provided. In this case, the
pressure responding means is constructed of a diaphragm or a
bellows. Furthermore, a load is applied to the pressure responding
means by elastic means such as a coil spring from a direction
opposite to the force that the pressure responding means receives
from the high-pressure refrigerant pressure. With this, pressure
abnormality detecting means can be constructed such that, when the
high-pressure refrigerant pressure becomes not less than a
predetermined value determined by the elastic means, the pressure
responding means is displaced.
[0086] Further, a valve mechanism of the flow amount changing unit
for changing the evaporator refrigerant flow amount Ge can be
combined with the variable throttle mechanism so as to expand the
refrigerant passage area according to the amount of displacement of
this pressure responding means. This construction can mechanically
construct the variable throttle mechanism (flow amount changing
unit) that increases the evaporator refrigerant flow amount Ge when
the high-pressure side refrigerant pressure increases.
[0087] (2) In the above-mentioned embodiment, at step S2 of the
control program executed by the air-conditioning control unit 20, a
pressure abnormality is detected when the refrigerant pressure Pnoz
on the upstream side of the nozzle 13a is larger than the reference
high-pressure refrigerant pressure KNnoz. However, a pressure
abnormality may be detected on the basis of the amount of increase
per unit time in the refrigerant pressure Pnoz on the upstream side
of the nozzle portion 13a.
[0088] For example, the discharge side refrigerant pressure of the
compressor 12 may be abruptly increased by an abrupt increase in
the number of revolutions of the compressor 11, even if the actual
refrigerant pressure on the upstream side of the nozzle portion 13a
is not increased to the reference high-pressure refrigerant
pressure Kpnoz. Even in this case, a pressure abnormality can be
actually detected on the basis of the amount of increase per unit
time in Pnoz. With this, it is possible to more surely ensure the
reliability of the refrigerant piping and the functional parts.
[0089] (3) In the above-mentioned second embodiment, the first and
second evaporators 17, 26 cool the same compartment to be cooled
(e.g., air in the refrigeration compartment). However, the first
and second evaporators 17, 26 may cool different objects or spaces
to be cooled.
[0090] For example, it is possible to use the first evaporator 17
for cooling air in the compartment of a refrigerator for a vehicle
and to use the second evaporator 26 for cooling air in a passenger
compartment of the vehicle. In this case, since the outlet side of
the first evaporator 17 is connected to the refrigerant suction
port 13b of the ejector 13, it is possible to apply the lowest
pressure immediately after reducing pressure in the nozzle portion
13a to the outlet side of the first evaporator 17 and to apply
pressure after being increased in the diffuser portion 14b as the
refrigerant pressure of the second evaporator 26.
[0091] With this, the refrigerant evaporation pressure (refrigerant
evaporation temperature) of the first evaporator 17 can be made
lower than the refrigerant evaporation pressure (refrigerant
evaporation temperature) of the second evaporator 26. Thus, it is
possible to perform a cooling operation in a relatively high
temperature range suitable for cooling the passenger compartment by
the second evaporator 26, and at the same time to perform a cooling
operation in a further lower temperature range suitable for cooling
the refrigerator by the first evaporator 17.
[0092] Even when the second evaporator 26 is arranged on the
downstream side of the diffuser portion 13d of the ejector 13 in
the first embodiment, it is possible to produce the effect
described in the first embodiment.
[0093] (4) In the above-mentioned embodiments, the first evaporator
17 and the second evaporator 26 are used as use-side heat
exchangers for cooling air in the refrigeration compartment, which
is the compartment to be cooled, while the radiator 12 is as a heat
exchanger for radiating heat to the atmosphere. On the contrary to
this, the present invention may be applied to a construction (heat
pump cycle) having the first evaporator 17 and the second
evaporator 26 as heat exchangers for absorbing heat from a heat
source such as the atmosphere, and having the radiator 12 as a
use-side heat exchanger for heating air or water which is an object
to be heated.
[0094] In other words, the refrigeration cycle according to the
embodiments may be used as a heat pump cycle that constructs the
radiator 12 as a use-side heat exchanger (e.g., heater).
[0095] (5) In the above-mentioned embodiments, there may be
provided an inner heat exchanger for exchanging heat between
high-pressure refrigerant on the downstream side of the radiator 12
and low-pressure refrigerant on the suction side of the compressor
11. According to this construction, refrigerant on the downstream
side of the radiator 12 is cooled, so it is possible to increase a
difference in enthalpy (cooling capacity) of refrigerant between
the refrigerant inlet and outlet in each of the first evaporator 17
and the second evaporator 26.
[0096] (6) In the above-mentioned embodiments has been described an
example of using carbon dioxide as refrigerant and constructing a
supercritical refrigerant cycle in which high-pressure side
refrigerant pressure exceeds a supercritical pressure. However,
fron-based or HC-based refrigerant may be used as the refrigerant.
Further, the present invention may be applied also to a case of
constructing a vapor compression type subcritical refrigerant cycle
in which high pressure does not exceed a supercritical
pressure.
[0097] (7) In the above-mentioned embodiments, a fixed nozzle
having a constant refrigerant passage area has been shown as an
example of the nozzle portion 13a. However, a variable ejector
having a variable nozzle portion capable of adjusting the
refrigerant passage area may be used as the ejector 13. As an
example, the variable nozzle portion can be employed, for example,
a mechanism in which the position of a needle inserted into the
passage of the variable nozzle portion is controlled by an electric
actuator to adjust the refrigerant passage area.
[0098] Such changes and modifications are to be understood as being
within the scope of the present invention as defined by the
appended claims.
* * * * *