U.S. patent application number 15/449533 was filed with the patent office on 2017-09-21 for multistage compressor.
The applicant listed for this patent is Hitachi Industrial Equipment Systems Co., Ltd.. Invention is credited to Masayuki KASAHARA.
Application Number | 20170268498 15/449533 |
Document ID | / |
Family ID | 59847696 |
Filed Date | 2017-09-21 |
United States Patent
Application |
20170268498 |
Kind Code |
A1 |
KASAHARA; Masayuki |
September 21, 2017 |
Multistage Compressor
Abstract
A multistage compressor including: at least a first compressor
main body and a second compressor main body configured to suck
compressed gas discharged from the first compressor main body to
discharge the compressed gas with higher pressure; a first driving
source configured to drive the first compressor main body; a second
driving source configured to drive the second compressor main body;
an intermediate pipe configured to connect a discharge side of the
first compressor main body and a suction side of the second
compressor main body; a low-pressure side discharge piping system
branched from the intermediate pipe; an on-off valve disposed in
the low-pressure side discharge piping system and configured to
switch permission and prohibition of a flow of compressed gas
discharged from the first compressor main body; and a control unit
configured to control driving of the first driving source and the
second driving source.
Inventors: |
KASAHARA; Masayuki; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hitachi Industrial Equipment Systems Co., Ltd. |
Tokyo |
|
JP |
|
|
Family ID: |
59847696 |
Appl. No.: |
15/449533 |
Filed: |
March 3, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04B 49/22 20130101;
F04B 2205/05 20130101; F04B 49/24 20130101; F04B 39/06 20130101;
F04B 41/06 20130101; F04B 49/08 20130101; F04B 49/007 20130101;
F04B 35/04 20130101 |
International
Class: |
F04B 49/00 20060101
F04B049/00; F04B 49/24 20060101 F04B049/24; F04B 49/08 20060101
F04B049/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 16, 2016 |
JP |
2016-051854 |
Claims
1. A multistage compressor comprising: at least a first compressor
main body and a second compressor main body configured to suck
compressed gas discharged from the first compressor main body to
discharge the compressed gas with higher pressure; a first driving
source configured to drive the first compressor main body; a second
driving source configured to drive the second compressor main body;
an intermediate pipe configured to connect a discharge side of the
first compressor main body and a suction side of the second
compressor main body; a low-pressure side discharge piping system
branched from the intermediate pipe; an on-off valve disposed in
the low-pressure side discharge piping system and configured to
switch permission and prohibition of a flow of compressed gas
discharged from the first compressor main body; and a control unit
configured to control driving of the first driving source and the
second driving source, wherein the control unit is configured to
drive the first driving source alone when the on-off valve is
opened.
2. The multistage compressor according to claim 1, wherein the
intermediate pipe includes a suction side on-off valve configured
to switch permission and prohibition of the flow of compressed gas
discharged from the first compressor main body to the suction side
of the second compressor main body and, the control unit is
configured to drive the first driving source alone when the on-off
valve is opened, and the suction side on-off valve is closed.
3. The multistage compressor according to claim 1, wherein the
control unit is configured to further drive the second driving
source, when the on-off valve is opened.
4. The multistage compressor according to claim 1, comprising: a
by-pass pipe configured to connect a discharge pipe of the second
compressor main body and a downstream side of the on-off valve
disposed at the low-pressure side discharge pipe, and a by-pass
valve configured to switch permission and prohibition of a flow of
compressed gas into the by-pass pipe, the compressed gas flowing
through the discharge pipe, wherein the control unit is configured
to drive the first driving source alone when the by-pass valve is
opened, and the suction side on-off valve is closed.
5. The multistage compressor according to claim 1, wherein at least
one of the on-off valve, the suction side on-off valve, and the
by-pass valve is an electromagnetic valve, and the control unit is
configured to control the electromagnetic valve.
6. A multistage compressor comprising: at least a first compressor
main body and a second compressor main body configured to suck
compressed gas discharged from the first compressor main body to
discharge the compressed gas with higher pressure; a first driving
source configured to drive the first compressor main body; a second
driving source configured to drive the second compressor main body;
an intermediate pipe which connects a discharge side of the first
compressor main body, and a suction side of the second compressor
main body; a low-pressure side discharge piping system branched
from the intermediate pipe; an on-off valve disposed in the
low-pressure side discharge piping system and configured to switch
permission and prohibition of a flow of compressed gas discharged
from the first compressor main body; a by-pass pipe configured to
connect a discharge pipe of the second compressor main body and a
downstream side of the on-off valve of the low-pressure side
discharge pipe; a by-pass valve configured to switch permission and
prohibition of a flow of compressed gas into the by-pass pipe, the
compressed gas flowing through the discharge pipe; a suction pipe
connected to the intermediate pipe or a suction side of the second
compression main body and in which gas flows without passing
through the first compressor main body; a valve body disposed at
the suction pipe, and configured to permit or prohibit a flow of
the gas; and a control unit configured to control driving of the
first driving source and the second driving source, wherein the
control unit configured to drive the second driving source alone
when the on-off valve, the by-pass valve, and the valve body are
opened.
7. The multistage compressor according to claim 6, wherein the
control unit is configured to drive the first driving source alone
in place of the second driving source when the valve body is closed
and the on-off valve and the by-pass valve are opened.
8. The multistage compressor according to claim 6, where in the
control unit is configured to drive the first driving source also
when the by-pass valve and the valve body is closed, and the on-off
valve is opened.
9. The multistage compressor according to claim 6, wherein at least
one of the on-off valve, the by-pass valve, and the valve body is
an electromagnetic valve, and the control unit is configured to
control the electromagnetic valve.
10. The multistage compressor according to claim 2, wherein at
least one of the on-off valve, the suction side on-off valve, and
the by-pass valve is an electromagnetic valve, and the control unit
is configured to control the electromagnetic valve.
11. The multistage compressor according to claim 3, wherein at
least one of the on-off valve, the suction side on-off valve, and
the by-pass valve is an electromagnetic valve, and the control unit
is configured to control the electromagnetic valve.
12. The multistage compressor according to claim 4, wherein at
least one of the on-off valve, the suction side on-off valve, and
the by-pass valve is an electromagnetic valve, and the control unit
is configured to control the electromagnetic valve.
13. The multistage compressor according to claim 7, wherein at
least one of the on-off valve, the by-pass valve, and the valve
body is an electromagnetic valve, and the control unit is
configured to control the electromagnetic valve.
14. The multistage compressor according to claim 8, wherein at
least one of the on-off valve, the by-pass valve, and the valve
body is an electromagnetic valve, and the control unit is
configured to control the electromagnetic valve.
Description
INCORPORATION BY REFERENCE
[0001] The present application claims priority from Japanese
application JP-2016-051854 filed on Mar. 16, 2016, the content of
which is hereby incorporated by reference into this
application.
TECHNICAL FIELD
[0002] The present invention relates to a multistage compressor and
relates to a multistage compressor including a plurality of
compressor main bodies.
BACKGROUND OF THE INVENTION
[0003] A known gas compressor configured to suck gas (for example,
air) to generate compressed gas (for example, compressed air)
includes a multistage compressor that connects gas passages of a
plurality of compressor bodies in series (hereinafter referred to
as "multistage compressor"). In some multistage compressors, a gas
discharge side of a low-pressure stage compressor main body and a
gas suction side of a high-pressure stage compressor main body are
connected through an inter cooler (intercooler), and gas is
compressed in two-stages.
[0004] In a so-called single stage compressor having one stage
compressor, there is no intercooler, and accordingly there are few
piping parts, so it can be said that this configuration is
advantageous mainly in terms of cost.
[0005] Meanwhile, it can be said that a two-stage compressor has a
compression process close to isothermal compression as compared
with the single stage compressor, so the compression efficiency can
be increased and the temperature of each component such as a rotor
and a casing becomes lower, and thus there is also little
constraint on a heat resistance about materials and the like.
[0006] For the two-stage compressor, it is known that when the
compression ratio of a first stage side compressor (low-pressure
stage compressor) and the compression ratio of a second stage side
compressor (high-pressure stage compressor) are made equal, the
highest efficiency is achieved. In the general design of a
two-stage compressor, the speed of each stage is thus decided such
that the compression ratio of a low-pressure stage compressor and
the compression ratio of a high-pressure stage compressor become
equal at a rated point.
[0007] Meanwhile, a lot of adjustable-speed apparatus are used in
recent years which control a gas flow by changing the operating
speed of a compressor when necessary quantity of gas varies from a
viewpoint of energy saving. In this case, since an intermediate
pressure loss changes with a change of quantity of gas, if the
quantity of gas decreases, for example and an intermediate pressure
loss falls, the suction pressure of a high-pressure stage
compressor will become high. Operations are performed under
pressure conditions different from the rated point. As a result,
the optimal speed ratio of the low-pressure stage compressor and
the high-pressure stage compressor differs from the rated point.
Generally, in a two-stage compressor, the number of driving sources
(for example, motor) is one, and since transmitting power to a
low-pressure stage compressor and a high-pressure stage compressor
is performed by the gear having a constant speed increasing ratio
with respect to each stage compressor, the speed ratio of a
low-pressure stage compressor and a high-pressure stage compressor
cannot be changed. Therefore, there is a case that the operation at
the optimum speed ratio is not performed at the time of using the
partial load.
[0008] As a measure, which optimizes the operation speed ratio of
the low-pressure stage compressor and the high-pressure stage
compressor, there is a configuration in which the compressor main
body of each stage is independently driven. JP 3352187 B2 discloses
an operation method in which each of a low-pressure stage
compressor main body and a high-pressure stage compressor main body
is provided with a motor, which allows an independent drive, the
intermediate pressure is detected, and the rotational speed is
adjusted based on the detection pressure. For example, when the
amount of air used decreases and the rotation speed decreases, the
intermediate pressure becomes high. Therefore, when the pressure
exceeds a certain set pressure, a control signal is outputted to an
inverter from a controller so as to decrease the rotational speed
of a low-pressure stage compressor main body or increase the
rotational speed of a high-pressure stage compressor main body.
According to JP 3352187 B2, the compression ratio of each stage can
be made equal at the time of partial load also, and efficient
operation will be achieved.
SUMMARY OF THE INVENTION
[0009] JP 3352187 B2 requires two motors, which are main parts of
the compressor system. In addition, when increasing the speed by
gears or belts, the number of these parts also increases. Thus,
independent control of the rotational speed of each stage only for
optimization of intermediate pressure increases the number of
parts, and various problems such as the increase in material cost,
required space, and also maintenance cost remain.
[0010] Meanwhile, some compressor users selectively use
high-pressure gas and low-pressure gas depending on the
application. In this case, compressors for high pressure and low
pressure may be provided separately, but there are problems of
increase in installation area or mounting area and increase in
cost.
[0011] In this regard, one compressor can allow the selective use
of both compressors. For example, high-pressure compressed gas is
generated from a compressor, and this gas is stored in a reservoir
tank, and when a low-pressure compressed gas is required, the
pressure is reduced to a desired pressure before use. Reduced
pressure in this manner results in loss of the high-pressure
compressed gas energy.
[0012] A technique of obtaining compressed gas having different
pressures more conveniently and efficiently is desired.
[0013] In order to solve the above problem, for example, the
configuration described in the claims is applied. That is, the
configuration is a multistage compressor including: at least a
first compressor main body 1 and a second compressor main body 2
configured to suck compressed gas discharged from the first
compressor main body 1 to discharge the compressed gas with higher
pressure; a first driving source 3 configured to drive the first
compressor main body 1; a second driving source 4 configured to
drive the second compressor main body 2; an intermediate pipe
configured to connect a discharge side of the first compressor main
body 1 and a suction side of the second compressor main body 2; a
low-pressure side discharge piping system branched from the
intermediate pipe; an on-off valve 13 disposed in the low-pressure
side discharge piping system and configured to switch permission
and prohibition of a flow of compressed gas discharged from the
first compressor main body 1; and a control unit 10 configured to
control driving of the first driving source 3 and the second
driving source 4, wherein the control unit 10 is configured to
drive the first driving source 3 alone when the on-off valve 13 is
opened.
[0014] Additionally, for example, another configuration is a
multistage compressor including: at least a first compressor main
body 1 and a second compressor main body 2 configured to suck
compressed gas discharged from the first compressor main body 1 to
discharge the compressed gas with higher pressure; a first driving
source 3 configured to drive the first compressor main body 1; a
second driving source 4 configured to drive the second compressor
main body 2; an intermediate pipe which connects a discharge side
of the first compressor main body 1, and a suction side of the
second compressor main body 2; a low-pressure side discharge piping
system branched from the intermediate pipe; an on-off valve 13
disposed in the low-pressure side discharge piping system and
configured to switch permission and prohibition of a flow of
compressed gas discharged from the first compressor main body 1; a
by-pass pipe 25 configured to a discharge pipe of the second
compressor main body 2 and a downstream side of the on-off valve 13
of the low-pressure side discharge pipe; a by-pass valve 26
configured to switch permission and prohibition of a flow of
compressed gas into the by-pass pipe 25, the compressed gas flowing
through the discharge pipe; a suction pipe connected to the
intermediate pipe or a suction side of the second compression main
body and in which gas flows without passing through the first
compressor main body 1; a valve body 36 disposed at the suction
pipe, and configured to permit or prohibit a flow of the gas; and a
control unit 10 configured to control driving of the first driving
source 3 and the second driving source 4, wherein the control unit
10 configured to drive the second driving source 4 alone when the
on-off valve 13, the by-pass valve 26, and the valve body 36 are
opened.
[0015] According to the present invention, high-pressure and
low-pressure compressed gases can be efficiently generated. Other
problems, configurations, and effects of the present invention will
become clear from the description below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a block diagram schematically showing a
configuration of an oilless screw compressor according to
Embodiment 1 to which the present invention is applied;
[0017] FIG. 2 is a cross-sectional view showing a compressor body
configuration of an oilless screw compressor in detail, and a
schematic view of its control system diagram according to
Embodiment 1;
[0018] FIG. 3 is a block diagram schematically showing a
configuration of an oilless screw compressor according to
Embodiment 2 to which the present invention is applied; and
[0019] FIG. 4 is a block diagram schematically showing a
configuration of an oilless screw compressor according to
Embodiment 3 to which the present invention is applied.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Hereinafter, embodiments of the present invention will be
described with reference to the drawings.
Embodiment 1
[0021] FIG. 1 is a schematic view of a two-stage screw air
compressor (hereinafter simply referred to as "compressor") 20A,
and a configuration of a compressor system (including a
high-pressure/low-pressure air lines, a reservoir tank 8 and the
like), and a gas flow according to Embodiment 1 to which the
present invention is applied. Although an oilless screw air
compressor is applied in this embodiment, the present invention is
not limited thereto, and a liquid supply (oil, water, etc.) type
compressor may be applied. Compression mechanism such as scroll,
reciprocation, vane or the like may be applied, and multistage
configurations from a combination of various types and the like may
be applied. Various configurations are applicable within a scope
not deviating from the spirit thereof.
[0022] The compressor 20A includes a low-pressure stage compressor
main body 1, a driving source (for example, motor 3) configured to
drive the low-pressure stage compressor main body 1, a
high-pressure stage compressor main body 2, a driving source (motor
4) that is configured to drive the high-pressure stage compressor
main body 2, an intercooler 6, and aftercooler 7. A piping system
of the discharge side of the low-pressure stage compressor main
body 1 is connected with a piping system of the suction side of the
high-pressure stage compressor main body 2 in series. The
low-pressure stage compressor main body 1 compresses the suction
atmosphere from the outside, and the discharged compressed air is
intercooled by the intercooler 6. Then, the high-pressure stage
compressor main body 2 sucks this cooled air, and further
pressurizes it, discharges more high-pressure compressed air, and
the resultant compressed air is cooled by the aftercooler 7 to a
predetermined temperature.
[0023] The intermediate piping system connected to the
high-pressure stage compressor main body 2 from the intercooler 6
branches from its midway. One branch pipe is provided with a
low-pressure stage discharge check valve 19 and a low-pressure line
discharge valve (on-off valve) 13, and is connected to one or more
low-pressure air lines 100 to supply low-pressure compressed air to
customers. The low-pressure line discharge valve 13 and the
low-pressure stage discharge check valve 19 permit or prohibit flow
in the low-pressure air line 100 from an intermediate pipe.
[0024] The other branch pipe is connected to the suction side of
the high-pressure stage compressor main body 2 through a
high-pressure stage suction valve 14. The discharge side piping
system of the high-pressure stage compressor main body 2 is
provided with a high-pressure stage discharge check valve 18 and
the aftercooler 7 where the high-pressure stage discharge check
valve 18 is disposed upstream of the aftercooler 7, and the
discharge side piping system is connected with the reservoir tank 8
disposed outside of the compressor 20A. The reservoir tank 8 is
connected with one or more high-pressure air lines 200 to supply
high-pressure compressed air to customers.
[0025] The compressor 20A includes a pressure sensor 21 that
detects the discharge pressure of the low-pressure stage compressor
main body 1 and which is disposed between the downstream side of
the intercooler 6 and the branch point of the intermediate pipe.
The reservoir tank 8 is provided with a pressure sensor 22 which
detects the internal pressure of the reservoir tank 8. The pressure
sensor 22 may be disposed in a piping system downstream from the
high-pressure stage discharge check valve 18 in the compressor 20A.
The detection pressure of each pressure sensor 21 and 22 is
inputted into a control unit 10 which is communicably connected
with each pressure sensor 21 and 22, and the control unit 10
controls the drive rotation of the motors 3 and 4 according to
these pressure values. In this embodiment, inverters 11A and 11B
are provided for the motors 3 and 4, respectively, and the control
unit 10 performs variable speed control through the inverters.
[0026] FIG. 2 shows a specific configuration of each of compressor
main bodies, motors and the like on the low-pressure stage side and
the high-pressure stage side. The low-pressure stage compressor
main body 1 includes a pair of male and female screw rotors 51a and
51b in a compression chamber formed in a compressor main body
casing 50. The respective screw rotors mesh with each other in a
non-contact manner through a predetermined gap, and the rotors and
the inner wall of the compression chamber serve as a compression
operating chamber. The shaft of the male rotor is formed in series
with a main shaft 52 of the motor 3 in the coaxial direction, and a
timing gear 53 which meshes with the gear installed at the end
portion of the female rotor to transmit power is disposed at the
opposite side end portion of the motor 3 in the axial direction.
The compressor main body casing 50 and a motor casing 55 are
integrally connected along the shaft. Although the rotor 51a and a
main shaft 52 of the motor are directly connected in this
embodiment, gear connection or belt drive may be applied. Further,
although the motor 3 and the like are a radial motor as an example,
other types of motors such as an axial motor and the like may be
used.
[0027] The high-pressure stage compressor main body 2 has
substantially similar configuration as the low-pressure stage
compressor main body 1 except that the high-pressure stage
compressor main body 1 has a smaller compression volume and a
higher number of revolutions.
[0028] As mentioned above, the motors 3 and 4 disposed in each
compressor main body receive power supply from the inverters 11a
and 11b, respectively. Each of the inverters 11a and 11b is
configured so that the control unit 10 can independently transmit
rotational frequency command values. Accordingly, the low-pressure
stage compressor main body 1 and the high-pressure stage compressor
main body 2 can be independently controlled.
[0029] In this regard, for example, in the case of a multistage
compressor having one drive source and configured to simultaneously
drive the low-pressure side and the high-pressure side via a gear
or belt, the rotational drive ratio of each compressor body is
fixed, and it is impossible to perform drive control of either one
alone. However, the compressor 20A of the present embodiment is
characterized in that the drive control of either one alone is
possible.
[0030] The control unit 10 is a function part in which cooperation
of an arithmetic unit and a program is performed. It has an
external input/output interface (not shown), receives various
inputs relating to setting values, switching of operation modes and
the like, and can appropriately outputs driving conditions and
various control information.
[0031] The control unit 10 is communicatively connected with the
pressure sensors 21 and 22 (dot-and-dash line in the figure), and
performs control according to the detection pressure. Further, it
is connected to a solenoid valve such as a low-pressure line
discharge valve 13 and a high-pressure stage suction valve 14
(dotted line in the figure) to control opening and closing
operations of these valves.
[0032] One feature of the compressor 20A having such a
configuration is that it can use separately both of low-pressure
compressed air generated by the low-pressure stage compressor main
body 1 alone, and high-pressure compressed air generated from the
low-pressure stage compressor main body 1 and the high-pressure
stage compressor main body 2 to supply each air to customers.
Specifically, (1) when using low-pressure compressed air generated
by the low-pressure stage compressor main body 1 alone, the
low-pressure line discharge valve 13 is "opened", the high-pressure
stage suction valve 14 is "closed", and the operation of the
high-pressure stage compressor main body 2 is stopped. (2) When
using high-pressure compressed air, the low-pressure line discharge
valve 13 is "closed" and the high-pressure stage suction valve 14
is "opened", and both of the low-pressure stage compressor main
body and the high-pressure stage compressor main body are operated.
(3) When using the compressed air of both of the low-pressure stage
compressor main body 1 and the high-pressure stage compressor main
body 2, both of the low-pressure line discharge valve 13 and the
high-pressure stage suction valve 14 are "opened", and both of
low-pressure stage compressor main bodies 1 and high-pressure stage
compressor main bodies 2 are operated.
[0033] Hereinafter, each operation mode is specifically
described.
[0034] When used as an ordinary two-stage compressor, operation is
performed such that the low-pressure line discharge valve 13 is
"closed" and the high-pressure stage suction valve 14 is "opened".
All the compressed air discharged from the low-pressure stage
compressor main body 1 is sucked by the high-pressure stage
compressor main body 2, is further compressed into high pressure,
and is discharged by the reservoir tank 8. In this case, the
operating speed of the low-pressure stage compressor main body 1
and the high-pressure stage compressor main body 2 is changed
according to used air flow rate. For example, when the amount of
used air is small, since the intermediate pressure becomes higher
than that of the rated operation, if the ratio (n1/n2) of speed n1
of the low-pressure stage compressor main body 1 to speed n2 of the
high-pressure stage compressor main body is made small relative to
the rating, intermediate pressure can be lowered appropriately.
[0035] Next, when using the compressed air alone which the
low-pressure stage compressor main body 1 generates, the
low-pressure line discharge valve 13 is "opened", the high-pressure
stage suction valve 14 is "closed", and operation of the
high-pressure stage compressor main body 2 stops. Accordingly,
high-pressure stage compressor main body 2 is separated from the
operation system, and the compressed air can be supplied only to
the low-pressure air line 100.
[0036] Finally, when compressed air of the low-pressure stage
compressor main body 1 and compressed air generated by the
high-pressure stage compressor main body 2 are used at the same
time, both the low-pressure line discharge valve 13 and the
high-pressure stage suction valve 14 are opened".
[0037] Here, when supplied to the low-pressure air line from the
low-pressure stage compressor main body 1, intermediate pressure
will lower according to the supplied amount of air. The fall in the
intermediate pressure does not allow proper suction pressure of the
high-pressure stage compressor main body 2 to be achieved.
Accordingly, the two-stage compressor lost an efficient pressure
balance, leading to an inefficient operation. In addition, the
pressure ratio in the high-pressure stage compressor main body 2
becomes large, and if accordingly, the power becomes excessive, the
pressure required on the high-pressure stage side may be difficult
to obtain or the operation may be impossible as rise in temperature
becomes large.
[0038] In this embodiment, therefore, the ratio (n1/n2) of speed n1
of the low-pressure stage compressor main body 1 to speed n2 of the
high-pressure stage compressor main body 2 is increased relative to
the rating so as to raise the intermediate pressure. Specifically,
based on the output of pressure sensors 21 and 22, the control unit
10 determines a rotational speed ratio so that the compression
ratio in the low-pressure stage compressor main body 1 and the
compression ratio in the high-pressure stage compressor main body 2
are made to be equal.
[0039] In Embodiment 1 described above, the compressor 20A can
achieve three kinds of air supply modes, which are a supply of
compressed air generated by driving the low-pressure stage
compressor main body 1 alone, a supply of compressed air generated
by driving the two-stage compressor main bodies 1 and 2, which is
an ordinal supply, and a supply of compressed air generated by
driving the two-stage compressor main bodies 1 and 2, and
compressed air generated by driving the low-pressure stage
compressor main body 1 alone.
[0040] In cases where the compressor 20A generates low-pressure
compressed air, there is the advantage that energy loss is
prevented by driving the low-pressure stage compressor main body 1
alone as compared with the case where high-pressure air is
decompressed before use.
[0041] In addition, it is possible to simultaneously produce
high-pressure compressed air as a two-stage compressor and
low-pressure compressed air as a single stage machine.
[0042] Furthermore, one two-stage compressor has a configuration
such that it can be used as a single stage compressor, a two-stage
compressor, and a single-stage/two-stage simultaneously driven
compressor, and achieves users' advantage relating to installation
location and cost aspect, and also manufacturers' merits such as a
reduction in the number of parts.
Embodiment 2
[0043] A compressor 20B according to Embodiment 2 of the present
invention will be described. The main difference from Embodiment 1
is that the high-pressure stage suction valve 14 of Embodiment 1 is
not provided and a by-pass pipe 25 is connected between a pipe
between the low-pressure stage discharge check valve 19 in the
low-pressure air line 100 side piping system and the low-pressure
line discharge valve 13, and a pipe from the discharge side of the
high-pressure stage compressor main body 1, a discharge side
by-pass valve 26 is provided midway of this by-pass pipe 25, and in
addition, in the discharge side pipe of the high-pressure stage
compressor main body 2, a pressure regulating check valve 27 is
provided downstream of the branch point with the by-pass pipe
25.
[0044] Further, the compressor 20B of Embodiment 2 is capable of
supplying the compressed air generated by the low-pressure stage
compressor main body 1 alone to the low-pressure air line and can
perform the normal operation of the two-stage compressor. It does
not operate to supply compressed air to both the high-pressure air
line and the low-pressure air line by driving both compressor main
bodies. The other configuration is similar to that of Embodiment 1.
The same reference numerals are used for the same members and
elements. Detailed description will be omitted.
[0045] Although the high-pressure stage suction valve 14 of
Embodiment 1 invites a slight pressure loss of the compressed air
which passes through it, in cases of the configuration of
Embodiment 2, there is the advantage that such pressure loss does
not occur at the time of the normal operation of the two-stage
compressor.
[0046] The pressure regulating check valve 27 is a check valve
which restricts flow of compressed air when the pressure is lower
than a predetermined pressure. In this embodiment, in the pressure
environment in which only the low-pressure stage compressor main
body 1 is driven, the pressure regulating check valve 27 serves as
"closed", and it serves as "opened" in the high-pressure discharge
environment during the normal operation of the two-stage
compressor.
[0047] The discharge side by-pass valve 26 is an electromagnetic
valve, and is controlled by the control unit 10. The discharge side
by-pass valve 26 drives the low-pressure stage compressor main body
1 alone, and in cases where it supplies compressed air to the
low-pressure air line, it serves as "opened", and serves as "close"
at the time of the normal operation of the two-stage
compressor.
Embodiment 3
[0048] A compressor 20C according to Embodiment 3 of the present
invention will be described. The main differences between
Embodiment 3 and other embodiments is that when compressed air is
supplied to the low-pressure air line alone, either one of the
low-pressure stage compressor main body 1 or the high-pressure
stage compressor main body 2 is selectively operated so that
compressed air can be supplied.
[0049] When compressor air is supplied only to the low-pressure air
line, in cases where the amount of air used is small, it is
generally more efficient to operate the high-pressure stage
compressor with a smaller volume at a higher speed than operating
the low-pressure stage compressor at a low speed.
[0050] FIG. 4 shows a schematic configuration of the compressor 20C
according to Embodiment 3. In the following description, the same
reference numerals are used for the same members and elements, and
a detailed description will be omitted.
[0051] The suction side piping system of the low-pressure stage
compressor main body 1 branches. One pipe serves as a suction
system of the low-pressure stage compressor main body 1, and
another pipe 40 serves as a suction pipe connected so that it may
communicate with the intermediate pipe. The pipe 40 may be
connected to the suction side of the high-pressure stage compressor
main body 2 without being connected to the intermediate pipe. The
pipe 40 is provided with a solenoid valve (valve body) 36, and the
opening and closing of the pipe 40 is controlled by the control
unit 10 so that the flow of gas in the pipe 40 is permitted or
prohibited.
[0052] As with Embodiment 2, Embodiment 3 has a by-pass pipe 25
branched from the discharge side piping system of the high-pressure
stage compressor main body 2 to extend to the low-pressure air line
100. This embodiment has a configuration such that the by-pass pipe
25 branches from the outlet or the middle of aftercooler 7 to
extend to the low-pressure air line 100.
[0053] In the compressor 20C having the above configuration, when
supplying the compressed air only to the low-pressure air line, in
cases where the amount of air is large, the low-pressure stage
compressor main body 1 alone is operated whit the low-pressure line
discharge valve 13 "opened", and the electromagnetic valve 36 and
the by-pass valve 26 "opened". On the other hand, when the amount
of air is small, in the compressor 20, the high-pressure stage
compressor main body 2 alone is operated with the low-pressure line
discharge valve 13, the electromagnetic valve 36 and the by-pass
valve 26 "closed".
[0054] Namely, the high-pressure stage compressor main body 2 sucks
the outside air which does not pass through the discharge port of
the low-pressure stage compressor main body 1, and generates the
compressor air supplied to the low-pressure air line 100.
[0055] When high-pressure compressed air is supplied to the
high-pressure air line alone by the normal operation of the
two-stage compressor, the compressor 20C makes all the low-pressure
line discharge valve 13, the electromagnetic valve 36, and the
by-pass valve 26 "closed". Further, when air is supplied to both
air lines, the low-pressure line discharge valve 13 is "opened",
the electromagnetic valve 36 and the by-pass valve 26 are "closed",
and operation is performed by changing the operation speed ratio of
the low-pressure stage compressor main body 1 and the high-pressure
stage compressor main body 2 according to the amount of used
air.
[0056] Thus, according to the compressor 20C of Embodiment 3, when
compressed air is supplied to the low-pressure air line alone,
either the low-pressure stage compressor main body 1 or the
high-pressure stage compressor main body 2 is selected according to
the amount of compressed air to supply, and the compressed air can
be supplied more efficiently.
[0057] Although examples for carrying out the present invention
have been described above, the present invention is not limited to
the above-described various configurations and the like, and
various modifications are possible without departing from the
spirit thereof. It is also possible to replace the configuration of
a specific embodiment with other embodiments. For example, in the
above embodiment, the low-pressure line discharge valve 13 and the
like are controlled by the control unit 10, but instead, a part or
the whole of the electromagnetic valve may be a manual valve body,
the operation may be such that compressed air is supplied to the
low-pressure air line by the switching operation by the user.
* * * * *