DESCRIPTION
AIR COMPRESSING DEVICE
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to an air compressing device that generates
compressed air.
Description of Related Art
[0002] As an air compressing device that generates compressed air, for example, an
air compressing device that is installed in a railway vehicle and generates compressed
air that is used in the railway vehicle is disclosed in JP 2006-226245A. Also, the air
compressing device disclosed in JP 2006-226245Ais configured as a device that
generates compressed air by compressing air that is accompanied by oil, and then
separating the oil from the compressed air. Accordingly, this air compressing device is
configured such that sealing and lubrication functions can be fulfilled with an oil film.
[0003] When an air compressing device that generates compressed air using oil such
as described above is used under humid environment, excess moisture is easily
incorporated into the oil. If the oil temperature decreases in a state in which excess
moisture is incorporated into the oil of the air compressing device, emulsification of the
oil is likely to occur. Also, if excess moisture is incorporated into the oil of the air
compressing device and remains in the oil for a long time period, degradation of the oil
serving as lubricant oil is caused, and, furthermore, corrosion of devices made from
metal is also likely to be caused.
[0004] In view of this, the air compressing device disclosed in JP 2006-226245A is

provided with a bypass line that constantly extracts and returns part of compressed
air that was dried by drying means to an intake of a compressor, in order to suppress
degradation in oil performance even under humid environment and ensure reliable
operation of the air compressing device.
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
[0005] As disclosed in JP 2006-226245A, an air compressing device that generates
compressed air using oil desirably has a configuration for suppressing degradation of
oil, in order to enable reliable operation even under humid environment.
[0006] However, since the air compressing device disclosed in JP 2006-226245A is
configured to constantly extract and return part of compressed air that was dried by
drying means to an intake of the compressor, there is a problem that efficiency when
generating compressed air is reduced. That is, the air compressing device disclosed in
JP 2006-226245Ahas reduced capability to accumulate compressed air in an air
reservoir compared with an air compressing device having the same capacity
specifications and a configuration in which dried air is not returned to the intake of the
compressor. More specifically, an increase in the time that is required for
accumulating compressed air in the air reservoir or a reduction in the maximum
pressure of compressed air that can be accumulated in the air reservoir is caused.
[0007] In view of the above-described circumstances, it is an object of the present
invention to provide an air compressing device that can suppress degradation of oil,
realize reliable operation even under humid environment, and also prevent a reduction
in efficiency when generating compressed air.

Means for Solving the Problem
[0008] An air compressing device according to one aspect of the present invention for
achieving the above-described object is an air compressing device that generates
compressed air, including: a compressor that compresses air suctioned from the
outside; an oil supply path that supplies oil to the compressor; an oil recovery unit that
has an oil tank, is configured to have guided thereto compressed air that was
compressed along with oil in the compressor, separate the oil from the compressed air,
and recover the oil in the oil tank, and is in communication with the oil supply path; a
dehumidifier that dehumidifies the compressed air from which oil has been separated;
a compressed air delivery unit that delivers the dehumidified compressed air to an air
reservoir for accumulating compressed air; a changeover valve that is provided on a
path that communicates the dehumidifier with the compressed air delivery unit; and a
communication path that communicates the changeover valve with a suction side of
the compressor; the changeover valve being switched so as to enable all of the
dehumidified compressed air to be supplied to one of the compressed air delivery unit
and the communication path.
[0009] According to this configuration, the air compressing device is such that when
the changeover valve is in a state of having been switched so as to communicate the
downstream side of the dehumidifier and the communication path, all of the
dehumidified compressed air is supplied to the suction side of the compressor via the
communication path. Accordingly, the state in which dehumidified compressed air
expands in the communication path, and a large part thereof is then suctioned and
compressed by the compressor and again dehumidified occurs repeatedly. Therefore,
by simply operating the air compressing device while appropriately switching the
changeover valve, it is possible to easily remove moisture that was incorporated into oil

in the air compressing device. This makes it possible, even if the air compressing
device is used under humid environment, to easily avoid the situation in which
ernulsification of oil occurs. It is also possible to prevent excess moisture from being
incorporated into oil in the air compressing device and remaining for a long time
period. This makes it possible to suppress degradation of oil serving as lubricant oil
even when the air compressing device is used under humid environment, and,
furthermore, also suppress corrosion of devices made from metal. Therefore, it is
possible to realize reliable operation even under humid environment.
[0010] On the other hand, the air compressing device is such that when the
changeover valve is in a state of having been switched so as to communicate the
downstream side of the dehumidifier and the compressed air delivery unit, all of the
dehumidified compressed air is delivered to the air reservoir via the compressed air
delivery unit. Accordingly, in the operation state of accumulating compressed air in
the air reservoir, a reduction in efficiency when generating compressed air can be
prevented. In other words, there is neither an increase in the time that is required for
accumulating compressed air in the air reservoir nor a decrease in the maximum
pressure of compressed air that can be accumulated in the air reservoir. Therefore, it
is possible to provide an air compressing device whose capability to accumulate
compressed air in an air reservoir is not reduced.
[0011] Therefore, according to the above configuration, it is possible to provide an air
compressing device that can suppress degradation of oil, realize reliable operation even
under humid environment, and, furthermore, prevent a reduction in efficiency when
generating compressed air.
[0012] Moreover, the air compressing device according to one aspect of the present
invention preferably further includes: a control unit configured to set the operation

mode to a normal operation mode or a warm air moisture removal operation mode,
and control an operation state on the basis of either one of the operation modes.
When the operation mode is set to the normal operation mode, the control unit
preferably performs control to switch the changeover valve so as to supply all of the
dehumidified compressed air to the compressed air delivery unit, and when the
operation mode is set to the warm air moisture removal operation mode, the control
unit preferably performs control to switch the changeover valve so as to supply all of
the dehumidified compressed air to the communication path. Even if a condition for
setting the operation mode to the warm air moisture removal operation mode is
satisfied, the control unit preferably sets the operation mode to the normal operation
mode in a case where a condition for accumulating compressed air in the air reservoir
is satisfied.
[0013] According to this configuration, even in a case where the condition for setting
the operation mode to the warm air moisture removal operation mode is satisfied, the
operation mode is set to the normal operation mode if the condition for accumulating
compressed air in the air reservoir is satisfied. Therefore, when it is necessary to
increase or maintain the pressure of compressed air in the air reservoir, the
compressed air is reliably delivered to the air reservoir. On the other hand, even if
the above-described operation causes moisture to temporarily enter the inside of the
air compressing device, the operation in the warm air moisture removal operation
mode is immediately performed at the point in time at which the condition for
accumulating compressed air in the air reservoir is no longer satisfied, if the condition
for setting the operation mode to the warm air moisture removal operation mode is
satisfied. Accordingly, the moisture that has temporarily entered the inside of the air
compressing device is immediately removed. Therefore, in the air compressing device

that can realize reliable operation even under humid environment and prevent a
reduction in efficiency when generating compressed air, a reduction in the pressure of
the compressed air in the air reservoir can, furthermore, reliably be prevented when
the pressure of the compressed air in the air reservoir needs to be increased or
maintained.
[0014] The air compressing device according to one aspect of the present invention
preferably includes a plurality of types of detection units that detect the condition for
setting the operation mode to the warm air moisture removal operation mode.
[0015] According to this configuration, since the plurality of types of detection units
that detect the condition for setting the operation mode to the warm air moisture
removal operation mode are provided, it is possible to determine a timing for switching
the operation mode to the warm air moisture removal operation mode on the basis of a
plurality of types of conditions. Therefore, it is possible to improve flexibility with
respect to the determination of the timing for switching the operation mode to the
warm air moisture removal operation mode. For example, if the operation mode is
set to be shifted to the warm air moisture removal operation mode in the case where
any of the plurality of types of conditions is satisfied, it is easy to ensure opportunities
for setting the operation mode to the warm air moisture removal operation mode.
This makes it possible to more efficiently suppress degradation of oil from occurring,
enabling a further improvement in reliability. Also, if the operation mode is set to be
shifted to the warm air moisture removal operation mode in the case where all of the
plurality of types of conditions are satisfied, it is possible to rigorously select
opportunities for setting the operation mode to the warm air moisture removal
operation mode. Accordingly, it is possible to prevent the operation mode from being
set to the warm air moisture removal operation mode when the necessity to switch the

operation mode to the warm air moisture removal operation mode is low, enabling
energy consumption to be suppressed.
[0016] Moreover, the air compressing device according to one aspect of the present
invention preferably includes, as a detection unit that detects the condition for setting
the operation mode to the warm air moisture removal operation mode, at least one of
an oil temperature sensor that detects the oil temperature in the. oil recovery unit, a
discharged air temperature sensor that detects the temperature of compressed air
discharged from the oil recovery unit, a compressor temperature sensor that detects
the temperature of the compressor, a tank temperature sensor that detects the
temperature of the oil tank, an outside air temperature sensor that detects the
temperature of the outside air, a humidity sensor that detects the outside humidity, a
timer that detects time, an operation time detection unit that detects the operation
time of the compressor in a predetermined time period, and an operation frequency
detection unit that detects the number of times that the compressor operates in a
predetermined time period.
[0017] According to this configuration, the condition for setting the operation mode to
the warm air moisture removal operation mode can be determined based on the
temperature of oil in the oil recovery unit, the temperature of compressed air
discharged from the oil recovery unit, the temperature of the compressor, the
temperature of the oil tank, the temperature of the outside air, the outside humidity,
the time, the operation time of the compressor, or the operation frequency of the
compressor.
Effects of the Invention
[0018] According to the present invention, it is possible to provide an air compressing

device that can suppress degradation of oil, realize reliable operation even under
humid environment, and, furthermore, also prevent a reduction in efficiency when
generating compressed air.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram schematically illustrating a configuration of an air
compressing device according to an embodiment of the present invention.
FIG. 2 is a block diagram that relates to the air compressing device shown in
FIG. 1 and also schematically illustrates an installation configuration of sensors.
FIG. 3 is an example of a flowchart illustrating operation of the air
compressing device shown in FIG. 1.
FIG. 4 is a block diagram schematically illustrating a configuration of an air
compressing device according to a modification.
FIG. 5 is an example of a flowchart illustrating operation of the air
compressing device shown in FIG. 4.
DETAILED DESCRIPTION OF THE INVENTION
[0020] Hereinafter, an embodiment for carrying out the present invention will be
described with reference to the drawings. Note that the present embodiment is
widely applicable in air compressing devices that generate compressed air by
compressing air along with oil and then separating the oil from the compressed air.
Also, the air compressing device of the present embodiment is installed in a railway
vehicle and is used as a railway vehicle air compressing device for generating
compressed air that is used in the railway vehicle.
[0021] FIG. 1 is a block diagram schematically illustrating a configuration of an air

compressing device 1 according to an embodiment of the present invention. FIG. 2 is
a block diagram that relates to the configuration of the air compressing device 1 and
also schematically illustrates an installation configuration of sensors. The air
compressing device 1 shown in FIGS. 1 and 2 is installed in a railway vehicle (not
shown), for example. Compressed air generated in the air compressing device 1 is
used in order to operate a pneumatic device such as a braking device in a railway
vehicle. Note that the air compressing device 1 is disposed in each carriage of the
railway vehicle, for example.
[0022] The air compressing device 1 shown in FIGS. 1 and 2 is configured so as to
include a housing case 11, a suction filter 12, a suction valve 13, a compressor 14, a
motor 15, a fan 16, an oil recovery unit 17, an oil separating filter 18, an air cooler 19, a
dehumidifier 20, a changeover valve 21, a compressed air delivery unit 22, an air
reservoir 23, an oil filter 24, an oil cooler 25, a control unit 26, an oil temperature
sensor 27, a tank temperature sensor 28, a compressor temperature sensor 29, a
discharged air temperature sensor 30, an outside air temperature sensor 31, a
humidity sensor 32, a pressure sensor 33, an oil supply path 34, a communication path
35, and the like.
[0023] The air compressing device 1 is configured as an apparatus in which air
suctioned from the suction valve 13 via the suction filter 12 is first compressed by the
compressor 14 and cooled by the air cooler 19, and then delivered from the compressed
air delivery unit 22 and accumulated in the air reservoir 23 as compressed air.
Moreover, due to including the oil supply path 34, the oil recovery unit 17, the oil
separating filter 18, the oil filter 24, the oil cooler 25, and the like, the air compressing
device 1 is configured as an apparatus that generates compressed air by first
compressing air along with oil and then separating the oil from the compressed air.

Accordingly, the air compressing device 1 has a configuration in which compression
heat can be removed, and sealing and lubrication functions can be fulfilled with an oil
film. The following is a detailed description of the constituent elements of the air
compressing device 1.
[0024] The housing case 11 is provided as a box-shaped casing for housing the
compressor 14, the motor 15, the fan 16, the oil recovery unit 17, the oil separating
filter 18, the air cooler 19, the dehumidifier 20, the changeover valve 21, the oil filter 24,
the oil cooler 25, the control unit 26, and the like. The suction filter 12, the suction
valve 13, and the compressed air delivery unit 22 are disposed on or near a wall
portion of this housing case 11, for example.
[0025] Air (outside air) that is to be compressed by the compressor 14 is suctioned via
the suction filter 12 and the suction valve 13 that are disposed on the housing case 11.
The suction filter 12 and the suction valve 13 are disposed so as to be in
communication with the suction side of the compressor 14. Note that in FIGS. 1 and
2, the flow of suctioned outside air, the flow of dried air, the flow of air that contains oil
droplets, water droplets, or water vapor, and the flow of oil are shown by solid-line
arrows.
[0026] The suction filter 12 is provided as a filter that suppresses the passage of dust
such as sand-dust as suctioned air passes through. The suction valve 13 is provided
as a valve that is formed so as to be integrated with the body of the compressor 14.
The suction valve 13 is configured so as to include a valve body, a valve seat to/from
which the valve body can be attach/detach, and a spring that biases the valve body in
the direction of attaching to the valve seat. When the compressor 14 operates and the
compressor 14 side becomes negatively pressurized, the valve body is caused by
outside air pressure to detach from the valve seat against the spring force of the spring,

and air is suctioned into the compressor 14.
[0027] Also, the air reservoir 23 is disposed outside the housing case 11. The air
reservoir 23 is configured so as to include an air tank for accumulating compressed air
that, after being compressed by the compressor 14, has had oil separated therefrom by
being passed through the oil recovery unit 17, and has furthermore been cooled by the
air cooler 19. The pressure sensor 33 is installed in this air reservoir 23. The
pressure sensor 33 is provided as a sensor that detects the air pressure in the air
reservoir 23 (that is, the pressure of the compressed air accumulated in the air
reservoir 23). Also, the pressure sensor 33 is connected to the control unit 26 so as to
be able to output signals thereto. That is, a signal having the pressure value detected
by the pressure sensor 33 is input to the control unit 26.
[0028] Also, the compressed air delivery unit 22 delivers compressed air to the air
reservoir 23. The compressed air delivery unit 22 is provided as a mechanism that
delivers compressed air that has been dehumidified by the later-described
dehumidifier 20 to the air reservoir 23. The compressed air delivery unit 22 is
provided by way of a piping system that includes a check valve 22a. The compressed
air that passes through the dehumidifier 20 and flows into the compressed air delivery
unit 22 is allowed to flow only in the direction toward the air reservoir 23 by the check
valve 22a, and is delivered to the air reservoir 23. Also, the check valve 22a restricts
return of compressed air that was delivered to the air reservoir 23 to the dehumidifier
20 side via the compressed air delivery unit 22. Note that the check valve 22a is
configured to permit the passage of compressed air that has pressure of a
predetermined value or greater toward to the air reservoir 23 side.
[0029] The compressor 14 is configured so as to compress air suctioned from the
outside via the suction filter 12 and the suction valve 13. The compressor 14 is

provided by way of a screw-type air compressor, which has a pair of screws that rotate
in mutually opposite directions so as to compress air, for example. Inside the
compressor body in which the screws are disposed, the air pressure rises from the
portion in communication with the suction valve 13 to the portion in communication
with the oil recovery unit 17.
[0030] Note that although the present embodiment describes an example where the
compressor 14 is provided by way of a screw-type air compressor, another
configuration may be used. The compressor 14 may be provided by way of a
scroll-type air compressor, a reciprocating air compressor that is driven upon
transmission of a reciprocating driving force obtained by the conversion of rotational
driving force from the motor 15 via a crankshaft, or the like.
[0031] The motor 15 is configured as an electric motor and provided by way of a
driving mechanism that drives the compressor 14 so as to rotate. The motor 15 is
configured to operate in accordance with a command signal from the control unit 26,
for example, with its rotating speed and supply current controlled by a driver (not
shown). Also, the rotation shaft of the motor 15 is coupled with the rotation shaft of
the compressor 14 via a coupling.
[0032] Note that although the present embodiment describes an example of an
embodiment in which no speed reducer is provided between the motor 15 and the
compressor 14 and the motor 15 is directly connected to the compressor 14, another
configuration may be used. That is, an embodiment may be implemented in which a
speed reducer that decelerates the rotational driving force of the motor 15 and
transfers the decelerated rotational driving force is provided between the motor 15 and
the compressor 14. Also, the motor 15 may be configured as a motor that includes a
speed reducer.

[0033] The fan 16 is provided by way of a cooling fan that generates cooled air for
cooling compressed air and oil via the air cooler 19 and the oil cooler 25. The fan 16 is
attached to the motor 15, on the end portion thereof that is on the side opposite to the
side to which the compressor 14 is coupled. The cooling fan 16 is provided by way of
an axial flow fan, which is configured so as to include a propeller unit (not shown).
The cooling fan 16 is also disposed such that the driving force from the rotation shaft of
the motor 15 is transmitted to the propeller unit on the side opposite to the compressor
14 side.
[0034] In this way, the cooling fan 16 is configured so as to be driven by the driving
force from the motor 15 so as to rotate, and thus generate a flow of cooled air. Also, a
filter (not shown) is provided on a wall portion of the housing case 11 that is located on
the upstream side of the flow of cooled air generated by the fan 16. This filter is
provided by way of a metallic mesh that is attached to the housing case 11. The
cooled air obtained by the fan 16 rotating the outside air will be suctioned via the filter.
Note that although the present embodiment describes the example in which the
cooling fan 16 is an axial flow fan, another configuration may be used, and it is possible
to use another type of cooling fan such as a sirocco fan.
[0035] The air cooler 19 is provided by way of a heat exchanger that cools compressed
air in which compression heat remains due to being compressed by the compressor 14.
This air cooler 19 is disposed on the upstream side or the downstream side of the fan
16 with respect to the flow of cooled air generated by the fan 16 (note that FIGS. 1 and
2 are schematic diagrams and do not specify the layout of the air cooler 19 in the
housing case 11). Accordingly, the air cooler 19 is cooled from the outside by cooled air
generated by the fan 16, and thus compressed air passing through the inside of the air
cooler 19 is cooled. Note that the air cooler 19 is, for example, formed so as to be

integrally joined with the later-described oil cooler 25.
[0036] The oil recovery unit 17 is configured so as to include an oil tank 17a. An
oil-containing compressed air discharge path 36 that communicates the compressor 14
with the oil tank 17a is provided between the oil tank 17a and the compressor 14.
Compressed air that has been compressed along with oil in the compressor 14 is
guided to the oil tank 17a via the oil-containing compressed air discharge path 36.
Then, oil discharged into the oil tank 17a from the on-containing compressed air
discharge path 36 along with the compressed air is recovered in the oil tank 17a.
[0037] Although not shown in FIGS. 1 and 2, a separator for separating large oil
droplets is disposed in a discharge portion of the on-containing compressed air
discharge path 36 that is inside the oil tank 17a. When the compressed air along
with oil that is guided through the oil-containing compressed air discharge path 36 is
discharged from the discharge portion, oil is separated from the compressed air by the
separator. This separated oil falls due to gravity while dispersing inside the oil tank
17a, and thus is recovered in the oil tank 17a. Thereafter, recovered oil is stored in
the oil tank 17a.
[0038] The oil supply path 34 is disposed so as to be in communication with the oil
tank 17a of the oil recovery unit 17 and the compressor 14, and is provided by way of a
path through which oil is supplied to the compressor 14 from the oil tank 17a. The oil
supply path 34 is in communication with the compressor body of the compressor 14 on
a low-pressure side which is a suction side that is in communication with the suction
valve 13 and on which the pressure is low. Also, the oil supply path 34 is configured
so as to be in communication with the oil tank 17a at a position lower than the oil level
of the oil in the oil tank 17a. Since the oil supply path 34 is in communication with
the compressor 14 and the oil tank 17a in this way, compressed air discharged from

the oil-containing compressed air discharge path 36 pushes the oil level of the oil in the
oil tank 17a downward, and thus the oil is supplied to the compressor 14 via the oil
supply path 34.
[0039] The oil separating filter 18 is disposed on a path that communicates the oil
tank 17a of the oil recovery unit 17 with the air cooler 19. Also, the oil separating
filter 18 is configured so as to include a filter that further separates oil from the
compressed air that was compressed along with oil in the compressor 14 and has
passed through the oil recovery unit 17. The oil separating filter 18 separates, from
the compressed air, small oil droplets that were not recovered in the oil recovery unit
17.
[0040] Also, the oil separating filter 18 is in communication with the compressor 14
or the suction valve 13 via, for example, a communication path (not shown) that is
provided with a throttle unit for suppressing the amount of compressed air passing
therethrough. This communication path is disposed so as to communicate a lower
portion inside a housing portion of the oil separating filter 18 with the compressor 14.
Then, oil separated by the oil separating filter 18 is pushed upward by the compressed
air and supplied to the compressor 14.
[0041] Also, a pressure-retaining check valve (not shown) and a safety valve (not
shown) may be provided on a path that communicates the oil separating filter 18 with
the air cooler 19. In this case, the above-described pressure-retaining check valve is
provided as a valve that permits the passage of compressed air toward the air cooler 19
when the pressure is greater than or equal to a predetermined pressure. Also, the
safety valve is provided as a valve that allows compressed air to escape to the outside
when the pressure of the compressed air is greater than or equal to a predetermined
excessive pressure.

[0042] The oil cooler 25 is provided by way of a heat exchanger by which oil in the oil
tank 17a can be cooled and supplied to the oil supply path 34. Although part of the
communication is not shown in FIGS. 1 and 2, the oil cooler 25 is provided so as to be
in communication with the oil supply path 34, on the oil tank 17a side via an oil path
37 and on the compressor 14 side via an oil path 38.
[0043] As described above, the oil cooler 25 is configured such that part of oil flowing
from the oil tank 17a into the oil supply path 34 is taken in via the oil path 37 and then
cooled, and then the cooled oil is returned to the oil supply path 34 via the oil path 38.
That is, oil that has a high temperature due to heat generated due to the compression
of air by the compressor 14 flows into the oil cooler 25 via the oil path 37, and oil
having a low temperature that was cooled by the oil cooler 25 is returned to the oil
supply path 34 via the oil path 38. Note that the oil is caused to flow between the oil
tank 17a and the oil cooler 25 due to the oil level of the oil in the oil tank 17a being
pushed downward by the compressed air discharged from the oflxontaining
compressed air discharge path 36.
[0044] Note that, although not shown in FIGS. 1 and 2, an oil temperature adjusting
valve is provided at a location where the oil supply path 34 and the oil path 37
communicate, the oil temperature adjusting valve being capable of switching between
a communication position in which oil is in communication with an inlet of the oil path
37 and a blocking position in which oil is blocked from flowing into the inlet of oil path
37. This oil temperature adjusting valve is configured as, for example, a self-standing
valve that operates by a wax or bimetal mechanism whose volume changes according
to temperature. Also, with this configuration, this oil temperature adjusting valve is
configured so as to operate independently according to the oil temperature in the oil
tank 17a, instead of the later described control by the control unit 26. That is, this oil

temperature adjusting valve is configured to be switched independently to either of the
communication position and the blocking position according to the oil temperature in
the oil tank 17a.
[0045] With this, the oil temperature adjusting valve is configured so as to adjust the
oil temperature in the oil tank 17a by switching to either a state of circulating oil to the
oil cooler 25 or a state of restricting the circulation of oil, according to the oil
temperature in the oil tank 17a. Note that with the operation of this oil temperature
adjusting valve, the oil temperature in the oil tank 17a is controlled so as to be in a
range that does not exceed a predetermined temperature, and thus oxidation of the oil
due to the oil temperature being too high is prevented.
[0046] As previously mentioned, the oil cooler 25 is formed so as to be integrally
joined with the air cooler 19. Also, the oil cooler 25 is disposed on the upstream side
or the downstream side of the fan 16 in terms of the flow of cooled air (note that FIGS.
1 and 2 are schematic diagrams and do not specify the layout of the oil cooler 25 in the
housing case 11). As a result of the oil cooler 25 being cooled from the outside by the
cooled air generated by the fen 16, oil passing through the inside of the oil cooler 25 is
cooled.
[0047] Also, an oil filter 24 is disposed partway along the oil path 38. The oil filter
24 is provided as a filter that prevents foreign substances generated in or incorporated
into the oil from being supplied to the inside of the compressor 14. Note that
examples of the above-described foreign substances include scum-like substances
resulting from the aggregation of degraded oil.
[0048] The dehumidifier 20 is disposed on a path that communicates the air cooler 19
with the later-described changeover valve 21, and is provided by way of a mechanism
that dehumidifi.es compressed air from which oil has been separated by the oil

separating filter 18. That is, compressed air that is to be delivered to the air reservoir
23 is subjected to dehumidification by the dehumidifier 20. This dehumidifier 20 is
provided with a niter that contains a desiccant or a filter that performs
dehumidification using hollow fiber membranes.
[0049] Note that the dehumidifier 20 may further be provided with, in addition to the
filter that contains a desiccant or the hollow fiber membrane type filter, an
upstream-side filter for separating water and the minute amounts of oil that were not
separated by the oil separating filter 18 from compressed air on the upstream side of
the dehumidifier 20, which is the air cooler 19 side opposing the filter that contains a
desiccant or the hollow fiber membrane type filter. Note that water and oil that are
separated by the above-described upstream-side filter are discharged from, for
example, a drain valve attached to the dehumidifier 20. Also, the dehumidifier 20
may be provided with an exhaust valve that can exhaust compressed air that has
passed through the air cooler 19 to the outside. This exhaust valve is provided by
way of an electromagnetic valve that operates in accordance with a command signal
from the control unit 26, for example.
[0050] The changeover valve 21 is provided on a path that communicates the
dehumidifier 20 with the compressed air delivery unit 22, and is configured so as to
operate in accordance with a command signal from the later-described control unit 26.
For example, the changeover valve 21 is configured as an electromagnetic valve that is
subjected to a switching operation according to displacement of a spool that is driven in
accordance with the command signal from the control unit 26. The communication
path 35 is provided by way of a path that communicates the changeover valve 21 with
the suction side of the compressor 14. According to the present embodiment, the
communication path 35 is provided by way of a piping path that communicates the

changeover valve 21 with the suction valve 13.
[0051] Also, the changeover valve 21 is switched so as to be able to supply all of the
compressed air that was dehumidified by the dehumidifier 20 to either the compressed
air delivery unit 22 or the communication path 35. That is, the changeover valve 21
is switched, in accordance with a command signal from the control unit 26, from a
state in which all of the dehumidified compressed air is supplied to the compressed air
delivery unit 22 to a state in which all of the dehumidified compressed air is supplied
to the communication path 35. Also, the changeover valve 21 is switched, in
accordance with a command signal from the control unit 26, from the state in which all
of the dehumidified compressed air is supplied to the communication path 35 to the
state in which all of the dehumidified compressed air is supplied to the compressed air
delivery unit 22.
[0052] In the state in which all of the dehumidified compressed air is supplied to the
compressed air delivery unit 22, the changeover valve 21 communicates the
dehumidifier 20 and the compressed air delivery unit 22, and blocks the path from the
dehumidifier 20 to the communication path 35 as well as the path from the
compressed air delivery unit 22 to the communication path 35. On the other hand, in
the state in which all of the dehumidified compressed air is supplied to the
communication path 35, the changeover valve 21 communicates the dehumidifier 20
and the communication path 35, and blocks a path from the dehumidifier 20 to the
compressed air delivery unit 22 as well as the path from the communication path 35 to
the compressed air delivery unit 22.
[0053] The control unit 26 is provided by way of a control unit that controls the
operation state of the air compressing device 1. Also, this control unit 26 is configured
so as to include, for example, a processor (not shown) such as a Central Processing

Unit (CPU), a memory, an interface circuit, and the like, and to be able to transmit and
receive signals to and from a superordinate control unit (not shown).
[0054] Also, the control unit 26 is configured so as to be able to receive signals from
the pressure sensor 33 that detects the air pressure in the air reservoir 23, and signals
from each of the oil temperature sensor 27, the tank temperature sensor 28, the
compressor temperature sensor 29, the discharged air temperature sensor 30, the
outside air temperature sensor 31, and the humidity sensor 32 that are described later.
Also, the control unit 26 is configured so as to control operation of the compressor 14 by
controlling operation of the motor 15. The control unit 26 is also configured so as to
control operation of the changeover valve 21.
[0055] Also, the control unit 26 can set the operation mode to a normal operation
mode and a warm air moisture removal operation mode that are described later, and is
configured so as to control the operation state of the air compressing device 1 on the
basis of either of the operation modes. The operation mode is set so as to be
switchable by the control unit 26 mutually changing between one of a flag that
corresponds to the normal operation mode and a flag that corresponds to the warm air
moisture removal operation mode. Note that switching of the setting of the operation
mode, that is to say, switching of setting of the flag is performed by the control unit 26
on the basis of signals from the sensors (27, 28, 29, 30, 31, 32, and 33). Configurations
for switching of the setting of the operation mode include at least switching of the
setting of the operation mode from the normal operation mode to the warm air
moisture removal operation mode, and switching of setting of the operation mode from
the warm air moisture removal operation mode to the normal operation mode.
[0056] Also, when the operation mode is set to the normal operation mode, the
control unit 26 performs control to switch the changeover valve 21 so as to supply all of

the compressed air dehumidified by the dehumidifier 20 to the compressed air delivery
unit 22. That is, when the operation mode is set to the normal operation mode, the
control unit 26 controls the changeover valve 21, which is an electromagnetic valve, so
as to be in a spool position in which the dehumidifier 20 and the compressed air
delivery unit 22 communicate, and the communication path 35 is blocked with respect
to both the dehumidifier 20 and the compressed air delivery unit 22 sides.
[0057] On the other hand, when the operation mode is set to the warm air moisture
removal operation mode, the control unit 26 performs control to switch the changeover
valve 21 so as to supply all of the compressed air dehumidified by the dehumidifier 20
to the communication path 35. That is, when the operation mode is set to the warm
air moisture removal operation mode, the control unit 26 controls the changeover valve
21, which is an electromagnetic valve, so as to be in a spool position in which the
dehumidifier 20 and the communication path 35 communicate, and compressed air
delivery unit 22 sides is blocked with respect to both the dehumidifier 20 and the
communication path 35.
[0058] The normal operation mode is configured as an operation mode in which when
compressed air is required to be accumulated in the air reservoir 23, the motor 15 is
driven so as to operate the compressor 14, and compressed air is accumulated in the
air reservoir 23. More specifically, when a later-described pressure accumulation
condition is satisfied in the case where the operation mode is set to the normal
operation mode, the changeover valve 21 is switched, by control of the control unit 26,
so as to communicate the dehumidifier 20 and the compressed air delivery unit 22, and
also the motor 15 is driven so as to operate the compressor 14 and compressed air is
accumulated in the air reservoir 23.
[0059] The above-described pressure accumulation condition is configured as a

condition for accumulating the pressure of compressed air in the air reservoir 23 by
accumulating the compressed air in the air reservoir 23. Also, in the control unit 26,
it is determined whether or not the pressure accumulation condition is satisfied, based
on the pressure value (pressure value of the air pressure in the air reservoir 23)
detected by the pressure sensor 33.
[0060] Also, when it is not necessary to accumulate compressed air in the air
reservoir 23 in the case where the operation mode is set to the normal operation mode,
that is, when the pressure accumulation condition is not satisfied, the driving of the
motor 15 is stopped and thus the compressor 14 stops operating. Accordingly, when
the operation mode is set to the normal operation mode and the pressure accumulation
condition is not satisfied, compressed air is not delivered to the air reservoir 23.
[0061] Note that the above-described pressure accumulation condition may be
configured as, for example, a condition that is satisfied when the pressure value
detected by the pressure sensor 33 (that is, the air pressure of the air reservoir 23)
becomes less than a predetermined first pressure value, and is no longer satisfied
when the pressure value detected by the pressure sensor 33 subsequently becomes
greater than or equal to a predetermined second pressure value that is greater than
the first pressure value. In this case, when the operation mode is set to the normal
operation mode and the pressure value detected by the pressure sensor 33 becomes
less than the predetermined first pressure value, operation of the motor 15 is started
so as to operate the compressor 14 and compressed air is generated in accordance with
a command signal from the control unit 26. At that time, the changeover valve 21
communicates only the dehumidifier 20 and the compressed air delivery unit 22, and.
thus the generated compressed air is delivered to the air reservoir 23 and accumulated
therein. Also, when the pressure value detected by the pressure sensor 33 increases

so as to be greater than or equal to the predetermined second pressure value, the
operation of the motor 15 is stopped and thus the operation of the compressor 14 is
stopped, and accumulation of compressed air in the air reservoir 23 is stopped in
accordance with a command signal from the control unit 26.
[0062] When the compressed air accumulated in the air reservoir 23 is consumed by
operation of a pneumatic device such as a braking device in a railway vehicle, and the
air pressure in the air reservoir 23 decreases, the air compressing device 1 operates in
the normal operation mode and the compressor 14 operates, as described above.
Accordingly, compressed air is accumulated in the air reservoir 23. Also, in the state
in which the operation mode is set to the normal operation mode, the compressor 14
repeatedly operates intermittently in response to the situation of a reduction in the air
pressure in the air reservoir 23, and the air pressure in the air reservoir 23 is thus
recovered as needed.
[0063] On the other hand, the warm air moisture removal operation mode is
configured as an operation mode in which when it is necessary to remove moisture
from oil in the air compressing device 1 while heating air, the motor 15 is driven so as
to operate the compressor 14, and compressed air subjected to dehumidification is
supplied to the compressor 14 via the communication path 35 and the suction valve 13.
More specifically, when a warm air moisture removal operation condition, which is a
condition for setting the operation mode to the warm air moisture removal operation
mode, is satisfied and the above-described pressure accumulation condition is not
satisfied, the operation mode is maintained in a state of being set to the warm air
moisture removal operation mode. Also, in the state in which the operation mode is
set to the warm air moisture removal operation mode, the changeover valve 21 is
switched, by control of the control unit 26, so as to communicate the dehumidifier 20

and the communication path 35, the motor 15 is driven so as to operate the compressor
14, and all of the dehumidified compressed air is supplied to the communication path
35.
[0064] As described above, when operation is performed in the warm air moisture
removal operation mode, all of the dehumidified compressed air is supplied to the
suction side of the compressor 14 via the communication path 35. Accordingly, the
state in which dehumidified compressed air expands in the communication path 35,
and a large part thereof is then suctioned and compressed by the compressor 14 and
again dehumidified occurs repeatedly. Therefore, in the warm air moisture removal
operation mode, moisture that was incorporated into oil in the air compressing device
1 is removed.
[0065] Note that in the state in which air that has been dehumidified and dried
returns to the suction side of the compressor 14 via the changeover valve 21 and the
communication path 35, the pressure of this air corresponds to the pressure of the
outside air (atmospheric pressure). Also, this state does not change even when
operation is performed in the warm air moisture removal operation mode. Therefore,
during operation of the air compressing device 1 in the warm air moisture removal
operation mode, a problem of noise is not caused.
[0066] Also, the air compressing device that is installed in a railway vehicle and used
in the railway vehicle is in generally likely to have a low rate of operation and a short
operation time, and thus moisture is easily incorporated into oil in the air compressing
device. However, even when the oil temperature in the tank 17a is low, the oil
temperature increases due to heat generated by air being compressed by the
compressor 14 when the air compressing device operates in the warm air moisture
removal operation mode, thus preventing emulsification of oil from occurring.

Further, by the air compressing device 1 operating in the warm air moisture removal
operation mode, moisture that was incorporated into oil in the air compressing device
1 is immediately removed.
[0067] Also, even when the above-described warm air moisture removal operation
condition is satisfied, the control unit 26 sets the operation mode to the normal
operation mode if the pressure accumulation condition is satisfied. For example,
when the pressure accumulation condition is satisfied in the state in which the
operation mode is set to the warm air moisture removal operation mode, the operation
mode is switched from the warm air moisture removal operation mode to the normal
operation mode and set thereto. Also, even when the warm air moisture removal
operation condition is satisfied in the state in which the operation mode is set to the
normal operation mode and the pressure accumulation condition is satisfied, the
operation mode remains as being set to the normal operation mode.
[0068] Also, the air compressing device 1 is provided with a plurality of types of
detection units that detect the warm air moisture removal operation condition, which
is a condition for setting the operation mode to the warm air moisture removal
operation mode. In the present embodiment, the air compressing device 1 including,
as the above-described detection unit, the oil temperature sensor 27, the tank
temperature sensor 28, the compressor temperature sensor 29, the discharged air
temperature sensor 30, the outside air temperature sensor 31, and the humidity
sensor 32 is taken as an example.
[0069] The oil temperature sensor 27 is provided by way of a detection unit that is
disposed in the oil tankl7a of the oil recovery unit 17, and detects the oil temperature
in the oil tank 17a. The tank temperature sensor 28 is provided by way of a detection
unit that detects the temperature of the oil tank 17a. The tank temperature sensor

28 is disposed, for example, on the wall portion of the oil tank 17a. The compressor
temperature sensor 29 is provided by way of a detection unit that detects the
temperature of the compressor 14. The compressor temperature sensor 29 is
disposed, for example, on the wall portion of the compressor body of the compressor 14.
[0070] The discharged air temperature sensor 30 is provided by way of a detection
unit that detects the temperature of compressed air discharged from the oil recovery
unit 17. Also, the discharged air temperature sensor 30 is disposed so as to detect the
temperature of the compressed air from which oil has been separated. For example,
the discharged air temperature sensor 30 is disposed so as to be able to detect the
temperature of compressed air flowing through a path that communicates the oil
separating filter 18 with the air cooler 19. The outside air temperature sensor 31 is
provided by way of a detection unit that detects the temperature of outside air. The
outside air temperature sensor 31 is disposed, for example, on the outer wall portion of
the housing case 11. The humidity sensor 32 is provided by way of a detection unit
that detects the outside humidity. The humidity sensor 32 is disposed, for example,
on the outer wall portion of the housing case 11.
[0071] Note that the oil temperature sensor 27, the tank temperature sensor 28, the
compressor temperature sensor 29, the discharged air temperature sensor 30, and the
outside air temperature sensor 31 are each configured as a temperature switch that
outputs on/off signals to the control unit 26 when a detection temperature detected as
a target temperature is a predetermined temperature or less and when a detection
temperature detected as a target temperature exceeds the predetermined temperature.
Also, since the above-described sensors (27,28, 29, 30, and 31) suppress chattering in
the vicinity of a predetermined temperature from orcurring, a differential in output
temperature between the on-signal and the off-signal may be suitably set.

[0072] Also, as the above-described sensors (27, 28, 29, 30, and 31), a temperature
sensor that is configured to be of a type other than a temperature switch may be used.
For example, a configuration is possible in which, as the above-described sensors (27,
28, 29, 30, and 31), temperature sensors that are each configured to output a signal of
the detection temperature to the control unit 26, and the control unit 26 determines,
on the basis of this signal of the detected temperature, whether or not the detected
temperature is a predetermined temperature or less.
[0073] The warm air moisture removal operation condition is detected as a detection
result of each of the sensors (27,28, 29, 30, 31, 32) serving as detection units. The
control unit 26 determines whether or not the warm air moisture removal operation
condition is satisfied on the basis of at least one of the detection results of the
above-described sensors (27 to 32), and performs setting of an operation mode.
[0074] Examples of the warm air moisture removal operation condition whose
satisfaction is determined based on the detection result of the above-described sensor
(27 to 32) include a condition of low temperature and high humidity. Specifically, the
warm air moisture removal operation condition may be a condition in which the
detection temperature detected by the oil temperature sensor 27 is a predetermined
temperature or less. Also, the warm air moisture removal operation condition may be
a condition in which the detection temperature by the tank temperature sensor 28 is a
predetermined temperature or less. Also, the warm air moisture removal operation
condition may be a condition in which the detection temperature by the compressor
temperature sensor 29 is a predetermined temperature or less. Also, the warm air
moisture removal operation condition may be a condition in which the detection
temperature by the discharged air temperature sensor 30 is a predetermined
temperature or less. Also, the warm air moisture removal operation condition may be

a condition in which the detection temperature by the outside air temperature sensor
31 is a predetermined temperature or less. Also, the warm air moisture removal
operation condition may be a condition in which the outside humidity detected by the
humidity sensor 32 is a predetermined humidity or more.
[0075] Note that the warm air moisture removal operation condition may be
configured as at least one of the above-described conditions. Alternatively, the warm
air moisture removal operation condition may be configured as an arbitrary
combination of any of the above-described conditions. When the warm air moisture
removal operation condition is configured as an arbitrary combination of any of the
above-described conditions, the warm air moisture removal operation condition may
further be configured as an arbitrary combination of AND conditions or OR conditions
thereof.
[0076] Next, operation of the above-described air compressing device 1 is described.
First, the state of the air compressing device 1 in which the operation mode is set to
the normal operation mode and compressed air is generated will be described. In this
state, air (outside air) is first suctioned through the suction filter 12 and the suction
valve 13 due to negative pressure produced by the operation of the compressor 14.
The suctioned air then passes through the suction valve 32, which is in the open state
due to the pressure of the suctioned air, and flows into the compressor 14. At this
time, oil is being supplied from the oil supply path 34 to the compressor 14 as
described above, and the suctioned air is compressed along with oil in the compressor
14.
[0077] The compressed air that was compressed along with oil passes through the
on-containing compressed air discharge path 36, further passes through the
above-described separator (not shown) that separates large oil droplets, and is

discharged into the oil tank 17a. Also, the oil separated from the compressed air by
the separator is recovered in the oil tank 17a. This recovered oil is supplied to the
compressor 14 via the oil supply path 34. That is, oil circulates between the oil
recovery unit 17 and the compressor 14. Also, if the oil temperature in the oil tank
17a rises and reaches a predetermined high temperature, the above-described oil
temperature adjusting valve (not shown) is switched from the blocking position to the
communication position, and the oil cooler 25 cools the oil.
[0078] The compressed air that was discharged into the oil tank 17a passes through
the oil separating filter 18, and oil is further separated from the compressed air. The
compressed air that passes through the oil separating filter 18 is then guided to the air
cooler 19 and cooled in the air cooler 19. The compressed air that was cooled by the
air cooler 19 is then subjected to dehumidification by the dehumidifier 20. Since in
the state in which the operation mode is set to the normal operation mode, the
changeover valve 21 is switched to the compressed air delivery unit 22 side, only the
dehumidifier 20 and the compressed air delivery unit 22 communicate, and the
communication path 35 is blocked. Accordingly, all of the dehumidified compressed
air is delivered to the air reservoir 23 via the compressed air delivery unit 22 and
accumulated in the air reservoir 23.
[0079] On the other hand, in the state in which the operation mode is set to the warm
air moisture removal operation mode, a similar configuration to the above-described
configuration is achieved in which air is suctioned from the suction valve 13, then
passes through the compressor 14 and the like, and reaches the changeover valve 21
as compressed air. However, during the operation in the warm air moisture removal
operation mode, since the changeover valve 21 is switched to the communication path
35 side, only the dehumidifier 20 and the communication path 35 are in

communication, and the compressed air delivery unit 22 side is blocked. Accordingly,
all of the dehumidified compressed air is supplied to the suction side of the compressor
14 via the communication path 35. The state in which air expands in the
communication path 35 while flowing therein, and then suctioned and compressed by
the compressor 14 and again dehumidified occurs repeatedly. With this, moisture
that was incorporated into oil of the air compressing device 1 is removed.
[0080] Next, the flow of operation mode switching of the air compressing device 1
whose operation state is controlled by the control unit 26 will be described with
reference to the flowchart shown in FIG. 3. Note that FIG. 3 is an exemplary
flowchart illustrating operation of the air compressing device 1. When the air
compressing device 1 starts operating in accordance with a command signal to start
the operation that was received from a superordinate control unit, the operation mode
is first set by the control unit 26 to the normal operation mode (step S101).
[0081] When the operation mode is first set to the normal operation mode (step S101),
it is then determined whether or not the above-described warm air moisture removal
operation condition is satisfied (step S102). If it is determined that the warm air
moisture removal operation condition is satisfied (YES in step S102), the operation
mode is switched from the normal operation mode to the warm air moisture removal
operation mode and set thereto (step S103).
[0082] As described above, when the operation mode is set to the warm air moisture
removal operation mode, it is then determined whether or not the above-described
pressure accumulation condition is satisfied (step S104). If it is determined that the
pressure accumulation condition is not satisfied (NO in step S104), the changeover
valve 21 is switched in accordance with the setting of the operation mode. That is,
since the operation mode is the warm air moisture removal operation mode, the

changeover valve 21 is switched to the communication path 35 side (step S105). Note
that if the changeover valve 21 has already been switched to the communication path
35 side, this state is maintained.
[0083] In contrast, if it is determined that the pressure accumulation condition is
satisfied (YES in step S104), the operation mode is switched from the warm air
moisture removal operation mode to the normal operation mode and set thereto (step
S106). Then, the changeover valve 21 is switched in accordance with the setting of
the operation mode. That is, since the operation mode is the normal operation mode,
the changeover valve 21 is switched to the compressed air delivery unit 22 side (step
S107). Note that if the changeover valve 21 has already been switched to the
compressed air delivery unit 22 side, this state is maintained.
[0084] If the changeover valve 21 is switched to the communication path 35 side or
the compressed air delivery unit 22 side (steps S105 and 107), then, driving of the
motor 15 is started (step S108). Accordingly, the compressor 14 starts operating and
generates compressed air, and the compressed air is delivered to the air reservoir 23 or
to the suction side of the compressor 14.
[0085] Once driving of the motor 15 has started, it is then determined whether or not
a command signal to stop the operation of the air compressing device 1 has been
received from the superordinate control unit (step S109). If the command signal to
stop the operation of the air compressing device 1 has not been received (NO in step
S109), the processing in step S102 onward is repeated. In the state in which the
above-described stop signal has not been received, if the warm air moisture removal
operation condition is satisfied but the pressure accumulation condition is not satisfied,
driving of the motor 15 is continued and the generated compressed air is continuously
delivered to the suction side of the compressor 14. Also, in the state in which the

above-described stop signal has not been received, if the warm air moisture removal
operation condition is satisfied and the pressure accumulation condition is satisfied,
driving of the motorl5 is continued and the generated compressed air is continuously
delivered to the air reservoir 23.
[0086] If it is determined in step S109 that the command signal to stop the operation
of the air compressing device 1 has been received (YES in step S109), driving of the
motor 15 is stopped. Then, the air compressing device 1 stops operating and the
processing ends.
[0087] On the other hand, if, after the operation mode has been set to the normal
operation mode in step S101, it is determined that the warm air moisture removal
operation condition is not satisfied (NO in step S102), the changeover valve 21 is
switched according to the setting of the operation mode. That is, since the operation
mode is the normal operation mode, the changeover valve 21 is switched to the
compressed air delivery unit 22 side (step Sill). Note that if the changeover valve 21
has already been switched to the compressed air delivery unit 22 side, this state is
maintained.
[0088] If the changeover valve 21 is switched (step Sill), it is then determined
whether or not the pressure accumulation condition is satisfied (step S112). Kit is
determined that the pressure accumulation condition is satisfied (YES in step S112),
driving of the motor 15 is started (step S108). Accordingly, the compressor 14 starts
operating and generates compressed air, and the compressed air is delivered to the air
reservoir 23. Note that the processing in steps S108 onward is similar to the
above-described processing.
[0089] In contrast, if it is determined that the pressure accumulation condition is not
satisfied (NO in step S112), the driving of the motor 15 is stopped (step S113). If the

driving of the motor 15 has already stopped, this state is maintained. Then, it is
determined whether or not a command signal to stop the operation of the air
compressing device 1 has been received from the superordinate control unit (step
S109). Note that the processing in steps S109 onward is similar to the
above-described processing.
[0090] As described above, according to the present embodiment, when the air
compressing device 1 is in the state in which the changeover valve 21 is switched so as
to communicate the downstream side of the dehumidifier 20 with the communication
path 35, all of the dehumidified compressed air is supplied to the suction side of the
compressor 14 via the communication path 35. Accordingly, the state in which the
dehumidified compressed air expands in the communication path 35, and a large part
thereof is then suctioned and compressed by the compressor 14 and again
dehumidified occurs repeatedly. With this, simply by operating the air compressing
device 1 while suitably switching the changeover valve 21, it is easily possible to
remove moisture that was incorporated into oil of the air compressing device 1.
Therefore, even when the air compressing device 1 is used under humid environment,
it is easily possible to prevent emulsification of oil from occurring. It is also possible to
prevent excess moisture from being incorporated into oil in the air compressing device
1 and remaining in the oil for a long time period. With this, even when the air
compressing device 1 is used under humid environment, it is possible to suppress
degradation of oil that serves as lubricant oil, and corrosion of the device made from
metal from occurring. It is therefore possible to realize reliable operation even under
humid environment.
[0091] On the other hand, when the air compressing device 1 is in the state in which
the changeover valve 21 is switched so as to communicates the downstream side of the

dehumidifier 20 and the compressed air delivery unit 22, all of the dehumidified
compressed air is delivered to the air reservoir 23 via the compressed air delivery unit
22. Accordingly, in the case of the operation state of accumulating compressed air in
the air reservoir 23, it is possible to prevent a reduction in efficiency when generating
compressed air. That is, it is possible to prevent an increase in the time that is
required for accumulating compressed air in the air reservoir 23 and a reduction in the
maximum pressure of compressed air that can be accumulated in the air reservoir. It
is therefore possible to provide the air compressing device 1 whose capacity to
accumulate compressed air in the air reservoir 23 is not reduced.
[0092] Therefore, according to the present embodiment, it is possible to provide the
air compressing device 1 that can suppress degradation of oil, realize reliable operation
even under humid environment, and, furthermore, also prevent a reduction in
efficiency when generating compressed air.
[0093] Also, according to the air compressing device 1, even when the condition for
setting the operation mode to the warm air moisture removal operation mode is
satisfied, the operation mode is set to the normal operation mode if the condition for
accumulating compressed air in the air reservoir is satisfied. Therefore, when it is
necessary to increase or maintain the pressure of compressed air in the air reservoir 23,
compressed air is reliably delivered to the air reservoir 23. On the other hand, even if
moisture has temporarily entered the air compressing device 1, by performing the
above-described operation, the operation in the warm air moisture removal operation
mode is immediately performed if the condition for setting to the warm air moisture
removal operation mode is satisfied at the point in time at which the condition for
accumulating compressed air into the air reservoir 23 is cancelled. Accordingly,
moisture that has temporarily entered the air compressing device 1 will also

immediately be removed. Therefore, in the air compressing device 1 that can realize
reliable operation even under humid environment and prevent a reduction in
efficiency when generating compressed air, it is possible to reliably prevent the
pressure of compressed air in the air reservoir 23 from being reduced when the
pressure of compressed air in the air reservoir 23 needs to be increased or maintained.
[00941 Also, according to the air compressing device 1, since a plurality of types of
detection units (27,28, 29, 30, 31, and 32) are provided that detects a condition for
setting the operation mode to the warm air moisture removal operation mode, it is
possible to determine, based on the plurality of types of conditions, a timing at which
the operation mode is switched to the warm air moisture removal operation mode.
Therefore, it is possible to improve flexibility with respect to the determination of the
timing at which the operation mode is switched to the warm air moisture removal
operation mode. For example, if it is set that the operation mode is shifted to the
warm air moisture removal operation mode when any of the plurality of types of
conditions is satisfied, the opportunity for setting of the operation mode to the warm
air moisture removal operation mode can easily be obtained. Accordingly, it is
possible to suppress degradation of oil from being caused more efficiently, further
improving the reliability. Also, if it is set that the operation mode is shifted to the
warm air moisture removal operation mode if all of the types of conditions are satisfied,
the opportunity for setting the operation mode to the warm air moisture removal
operation mode can be selected more rigorously. Accordingly, it is possible to suppress
the phenomenon that the operation mode is set to the warm air moisture removal
operation mode when the necessity to switch the operation mode to the warm air
moisture removal operation mode is low, enabling energy consumption to be
suppressed.

[0095] Also, according to the air compressing device 1, the condition for setting the
operation mode to the warm air moisture removal operation mode can be determined
based on the temperature of oil in the oil recovery unit 17, the temperature of
compressed air discharged from the oil recovery unit 17, the temperature of the
compressor 14, the temperature of the oil tank 17a, the temperature of the outside air,
or the outside humidity.
[0096] Although an embodiment of the present invention has been described above,
the present invention is not limited to the above-described embodiment, and can be
carried out with various modifications to the extent set forth in the claims. For
example, the present invention can be carried out with the following modifications.
[0097] (l) Although the above-described embodiment was described by taking as the
example of the configuration in which an air cooler and an oil cooler are provided,
these constituent elements may not necessarily be provided. Also, although the
above-described embodiment was described by taking as an example the embodiment
in which devices such as a compressor, a motor, an oil recovery unit, and the like are
accommodated in a housing case, the present invention is not necessarily be limited to
this embodiment.
[0098] (2)The detection unit that detects the condition for setting the operation mode
to the warm air moisture removal operation mode need not be limited to the detection
unit exemplified in the above-described embodiment. That is, an air compressing
device that includes a detection unit other than the detection unit exemplified in the
above-described embodiment may be implemented.
[0099] FIG. 4 is a block diagram schematically illustrating a configuration of an air
compressing device 2 according to a modification. The air compressing device 2
shown in FIG. 4 is configured similarly to the air compressing device 1 of the

above-described embodiment. However, the air compressing device 2 differs from the
air compressing device 1 in the configuration of the detection unit. In the following
description of the air compressing device 2, a different configuration from that of the
air compressing device 1 of the above-described embodiment will be described. Also,
by giving the same reference numerals to those of the above-described embodiment to
the diagram, or referring to the same terms or reference numerals as those of the
above-described embodiment, description of elements that have a similar configuration
to those of the above-described embodiment is omitted.
[0100] The air compressing device 2 shown in FIG. 4 includes, as a detection unit, the
oil temperature sensor 27, the tank temperature sensor 28, the compressor
temperature sensor 29, the discharged air temperature sensor 30, the outside air
temperature sensor 31, and the humidity sensor 32, as with the air compressing device
1. The air compressing device 2 further includes, as a detection unit that detects the
warm air moisture removal operation condition, a timer 40, an operation time
detection unit 41, and an operation frequency detection unit 42.
[0101] In the air compressing device 2, the timer 40, the operation time detection unit
41, and the operation frequency detection unit 42 are provided in a control unit 39.
The control unit 39 is configured similarly to the control unit 26 of the above-described
embodiment. That is, the control unit 39 is configured so as to include a processor
such as a Central Processing Unit (CPU) (not shown), a memory, an interface circuit,
and the like, and to be capable of transmitting and receiving signals to and from a
superordinate control unit (not shown). The control unit 39 is also configured so as to
be able to receive signals from the sensors (27 to 33). The control unit 39 is further
configured to be able to set the operation mode to the normal operation mode or the
warm air moisture removal operation mode, and control the operation state of the air

compressing device 2 based on either one of the operation modes.
[0102] The timer 40 is provided by way of a clock for detecting time that is
incorporated into the control unit 39. Examples of the warm air moisture removal
operation condition whose satisfaction is determined based on the detection results by
the timer 40 include a condition of a predetermined time. For example, a
configuration may be possible in which the warm air moisture removal operation
condition is detected when the predetermined time arrives every day, and the
operation mode is set to the warm air moisture removal operation mode.
[0103] The operation time detection unit 41 and the operation frequency detection
unit 42 are configured by the processor in the control unit 39. The operation time
detection unit 41 and the operation frequency detection unit 42 are realized by the
processor reading out programs stored in the memory of the control unit 39 and
executing the read out programs.
[0104] Also, the operation time detection unit 41 is configured so as to detect an
operation time of the compressor 14 for a predetermined time period on the basis of the
time measured by the timer 40. For example, the operation time detection unit 41 is
configured so as to detect an operation time of the compressor 14 for a most recent
predetermined time period (e.g., 24 hours) as the above-described predetermined time
period. Examples of the warm air moisture removal operation condition whose
satisfaction is determined based on the detection result by the operation time detection
unit 41 include a condition that the operation time of the compressor 14 in the most
recent predetermined time period is 0 hours.
[0105] Also, the operation frequency detection unit 42 is configured so as to detect the
operation frequency of the compressor 14 during a predetermined time period on the
basis.of the time measured by the timer 40. For example, the operation frequency

detection unit 42 is configured to detect the operation frequency of the compressor 14
during a most recent predetermined time period (e.g., 24 hours) as the predetermined
time period. Examples of the warm air moisture removal operation condition whose
satisfaction is determined based on the detection result by the operation frequency
detection unit 42 include a condition that the operation frequency of the compressor 14
during the most recent predetermined time period is 0 times.
[0106] According to the above-described air compressing device 2, the determination
can be made using, as the condition for setting the operation mode to the warm air
moisture removal operation mode, not only the oil temperature in the oil recovery unit,
the temperature of compressed air discharged from the oil recovery unit, the
temperature of the compressor, the temperature of the oil tank, the temperature of the
outside air, the outside humidity, but also the time, the operation time of the
compressor, and the operation frequency of the compressor.
[0107] Also, the air compressing device 2 operates according to a flowchart similar to
the flowchart of operation of the air compressing device 1 shown in FIG. 3. When the
air compressing device 2 operates according to the flowchart shown in FIG. 3, it is also
determined in step S102 whether or not the warm air moisture removal operation
condition is satisfied on the basis of the detection results by the timer 40, the operation
time detection unit 41, and the operation frequency detection unit 42.
[0108] Also, the air compressing device 2 can operate according to a flowchart other
than the flowchart shown in FIG. 3. FIG. 5 is an exemplary flowchart illustrating the
operation of the air compressing device 2. The flowchart shown in FIG. 5 differs from
the flowchart shown in FIG. 3 in that steps S201 and S202 are included. Hereinafter,
the flowchart shown in FIG. 5 is described only with respect to the steps that are
different from those of the flowchart shown in FIG. 3.

[0109] In the case where the air compressing device 2 operates in line with the
flowchart shown in FIG. 5, when the operation mode is set to the warm air moisture
removal operation mode in step S103, it is then determined by the control unit 39
whether or not a predetermined length of time has elapsed from satisfaction of the
warm air moisture removal operation condition on the basis of the time measured by
the timer 40 (step S201).
[0110] If it is determined that the predetermined length of time has elapsed (YES in
step S201), the operation mode is switched from the warm air moisture removal
operation mode to the normal operation mode and set thereto (step S202). After the
operation mode has been set to the normal operation mode (step S202), the processing
in steps Sill onward is repeated. On the other hand, if it is determined that the
predetermined length of time has not elapsed (NO in step S201), the processing in
steps S104 onward is repeated with the operation mode set to the warm air moisture
removal operation mode.
[0111] As described above, since the operation mode is switched to the normal
operation mode when the predetermined length of time has elapsed from satisfaction
of the warm air moisture removal operation condition in a state where the operation
mode is set to the warm air moisture removal operation mode, it is possible to prevent
operation in the warm air moisture removal operation mode from being continued for
an excessive long time period.
Industrial Applicability
[0112] The present invention is widely applicable to air compressing devices that
generate compressed air.

Descriptions of Reference Numerals
[0113]
1 Air compressing device
14 Compressor
17 Oil recovery unit
17a OH tank
20 Dehumidifier
21 Changeover valve
22 Compressed air delivery unit
23 Air reservoir

34 Oil supply path
35 Communication path

WHAT IS CLAIMED IS:
1. An air compressing device that generates compressed air, comprising:
a compressor that compresses air suctioned from the outside>'
an oil supply path that supplies oil to the compressor;
an oil recovery unit that has an oil tank, is configured to have guided thereto
compressed air that was compressed along with oil in the compressor, separate the oil
from the compressed air, and recover the oil in the oil tank, and is in communication
with the oil supply path;
a dehumidifier that dehumidifies the compressed air from which oil has been
separated!
a compressed air delivery unit that delivers the dehumidified compressed air
to an air reservoir for accumulating compressed air;
a changeover valve that is provided on a path that communicates the
dehumidifier with the compressed air delivery unit; and
a communication path that communicates the changeover valve with a
suction side of the compressor,'
wherein the changeover valve is switched so as to enable all of the
dehumidified compressed air to be supplied to one of the compressed air delivery unit
and the communication path.
2. The air compressing device according to claim 1, further comprising:
a control unit configured to set the operation mode to a normal operation
mode or a warm air moisture removal operation mode, and control an operation state
on the basis of either one of the operation modes,

wherein when the operation mode is set to the normal operation mode, the
control unit performs control to switch the changeover valve so as to supply all of the
dehumidified compressed air to the compressed air delivery unit,
when the operation mode is set to the warm air moisture removal operation
mode, the control unit performs control to switch the changeover valve so as to supply
all of the dehumidified compressed air to the communication path, and
even if a condition for setting the operation mode to the warm air moisture
removal operation mode is satisfied, the control unit sets the operation mode to the
normal operation mode in a case where a condition for accumulating compressed air in
the air reservoir is satisfied.
3. The air compressing device according to claim 2,
wherein a plurality of types of detection units that detect the condition for
setting the operation mode to the warm air moisture removal operation mode are
provided.
4. The air compressing device according to claim 2 or 3,
wherein the air compressing device includes, as a detection unit that detects
the condition for setting the operation mode to the warm air moisture removal
operation mode, at least one of an oil temperature sensor that detects the oil
temperature in the oil recovery unit, a discharged air temperature sensor that detects
the temperature of compressed air discharged from the oil recovery unit, a compressor
temperature sensor that detects the temperature of the compressor, a tank
temperature sensor that detects the temperature of the oil tank, an outside air
temperature sensor that detects the temperature of the outside air, a humidity sensor

thai detects the outside humidity, a timer that detects time, an operation time
detection unit that detects the operation time of the compressor in a predetermined
time period, and an operation frequency detection unit that detects the number of
times that the compressor operates in a predetermined time period.

ABSTRACT

Provided is an air compressing device that can suppress degradation of oil,
realize reliable operation even under humid environment, and further prevent
efficiency when generating compressed air from being reduced. An oil recovery unit
17 is configured to have guided thereto compressed air that was compressed along
with oil in a compressor 14, separate the oil from the compressed air, and recover the
oil in an oil tank 17a. A dehumidifier 20 subjects the compressed air from which oil
has been separated to dehumidification. A compressed air delivery unit 22 delivers
the dehumidified compressed air to an air reservoir 23 for accumulating compressed
air. A changeover valve 21 is provided on a path that communicates the dehumidifier
20 with the compressed air delivery unit 22. A communication path 35 communicates
the changeover valve 21 and the suction side of the compressor 14. The changeover
valve 21 is switched so that all of the dehumidified compressed air is supplied to either
the compressed air delivery unit 22 or the communication path 35.