Abstract:
A compressed air supply apparatus includes an air compressor for compressing air to at least atmospheric pressure, a tank for storing the compressed air and supplying the compressed air, via a supply port, to various devices that use the compressed air as a working fluid, a first pipe that connects the air compressor to the tank, a heat pump including an evaporator for cooling at least a part of the first pipe, a selection device for selecting whether a cool air cooled by the evaporator, which is fluidly distinct from the compressed air, is introduced into a vehicle interior or discharged outside of the vehicle interior, and a control device configured to control the selection device so that the cool air is introduced into the vehicle interior when an air conditioner switch is turned ON and discharged outside of the vehicle interior when the air conditioner switch is turned OFF.

Description:
This application is a continuation application of PCT/JP2010/070810, filed on Nov. 22, 2010. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a compressed air supply apparatus for supplying a compressed air as a working fluid. 
     2. Description of Related Art 
     In various apparatuses that are actuated by a compressed air as a working fluid, when a compressed air containing a large amount of oil and water is supplied, for example, a valve and the like may be corroded. To deal with this problem, as described in Japanese Laid-Open (Kokai) Patent Application Publication No. H5(1993)-201329, compressed air supply apparatus employ oil mist separators and air dryers to remove the oil and the water contained in a compressed air discharged from an air compressor. 
     However, although such oil mist separators and dryers can remove an oil content and a water content having certain particle sizes, it is difficult to remove all of fine particles of an oil content and a water content having smaller particle sizes. When a compressed air containing fine particles of oil content and water content is supplied to various devices, corrosion of, for example, a valve, may still be of concern. 
     SUMMARY OF THE INVENTION 
     Under these circumstances, considering the above problem in the art, it is an object of the present invention to provide a compressed air supply apparatus which can remove fine particles of oil content and water content in compressed air. 
     To solve the above problem, the compressed air supply apparatus includes: an air compressor that compresses an air to at least atmospheric pressure; and a tank that stores a compressed air produced by the air compressor and has a supply port for supplying the compressed air to various devices that use the compressed air as a working fluid. Furthermore, at least a part of a first pipe through which the air compressor communicates with the tank is cooled by an evaporator constituting a heat pump of an air conditioner. 
     According to the compressed air supply apparatus, a compressed air produced by an air compressor and thereby having a high temperature is cooled by an evaporator constituting a heat pump to a temperature at which an oil content and a water content are condensed or a lower temperature. Accordingly, when the compressed air is supplied to the tank, the oil content and the water content are condensed and adhere to the inner wall of the tank. The oil content and the water content adhered to the inner wall of the tank are accumulated by gravity at a lower portion of the tank and are removed. Here, since the oil content and the water content are removed by using condensation, they can be removed even if they have fine particle sizes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic view of a vehicle on which a compressed air supply apparatus according to a first embodiment is mounted. 
         FIG. 2  is a schematic view of a vehicle on which a compressed air supply apparatus according to a second embodiment is mounted. 
         FIG. 3  is a flow chart illustrating a control program of the second embodiment. 
         FIG. 4  is a schematic view of a vehicle on which an air conditioning system according to a third embodiment is mounted. 
         FIG. 5  is a flow chart illustrating a control program of the third embodiment. 
         FIG. 6  is a perspective view illustrating a construction for supplementing shortage of cooling capacity of an evaporator. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereunder embodiments for carrying out the invention will be described in detail with reference to accompanying drawings. 
       FIG. 1  schematically illustrates a vehicle on which a compressed air supply apparatus is mounted. 
     A compressed air supply apparatus  10  has an air compressor  12 , a tank  14  having a predetermined capacity, an oil mist separator  16  for removing an oil content contained in a compressed air, and an air dryer  18  for removing a water content contained in the compressed air. 
     The air compressor  12 , for example, compresses an air from which foreign objects have been filtered out by an air filter, to at least atmospheric pressure. The compressed air produced by the air compressor  12  is supplied through a first pipe  20  to the tank  14  and temporarily stored in the tank  14 . On a peripheral wall of the tank  14 , a delivery port  14 A is provided, which supplies a compressed air to various apparatuses such as air cylinders using the compressed air as a working fluid. Furthermore, on a bottom portion of the tank  14 , an auto drain valve  14 B is provided, which discharges a liquid such as an oil content and a water content periodically (for example, at predetermined time intervals). In a second pipe  22  connected to the delivery port  14 A of the tank  14 , an oil mist separator  16  and an air dryer  18  are disposed in this order along a supply direction of the compressed air. 
     Further, a heat pump  30  of an air conditioner is constituted by at least a compressor  34 , a condenser  36 , an expansion valve  38  and an evaporator  40 , which are provided in a pipe  32  constituting a closed circuit through which a refrigerant is circulated. As the refrigerant, HFC-134a (R134a) that does not damage the ozone layer is employed. 
     The compressor  34  compresses a refrigerant in a form of low pressure-low temperature gas into a high pressure-high temperature gas. The condenser  36  cools the refrigerant that has changed into the high pressure-high temperature gas by the compressor  34 , to a condensation point to change the refrigerant into a high pressure-normal temperature liquid. The expansion valve  38  rapidly expands the refrigerant that has changed into the high pressure-normal temperature liquid by the condenser  36 , to change the refrigerant into a low pressure-low temperature gas. The evaporator  40  makes the refrigerant that has changed into the low pressure-low temperature gas by the expansion valve  38 , absorb heat from the surround air. Since the refrigerant absorbs heat from the surround air in the evaporator  40 , an air present around the evaporator is cooled to produce a cooling effect. 
     The expansion valve  38  and the evaporator  40  are integrated into a cooling unit  42  attached so as to face a vehicle interior. On one end of the cooling unit  42 , an air intake port  42 A opens so as to allow an air to be forcefully supplied thereto by, for example, a centrifugal blower  44 . 
     In the compressed air supply apparatus  10 , at least a part of a first pipe  20  through which the air compressor  12  communicates with the tank  14 , is disposed so as to be cooled by the evaporator  40  constituting the heat pump  30 . Specifically, at least a part of the first pipe  20  is disposed in the vicinity of an air exit side of the evaporator  40 , or disposed so that it contacts with a cooling fin of the evaporator  40 . 
     According to such a compressed air supply apparatus  10 , a compressed air produced by the air compressor  12  and thereby having a high temperature, is cooled by the evaporator  40  constituting the heat pump  30  to a temperature at which an oil content and a water content are condensed or to a lower temperature. Accordingly, when the compressed air is supplied to the tank  14 , the oil content and the water content are condensed and adhere to its inner wall. The oil content and the water content adhered to the inner wall of the tank  14  are accumulated by gravity into a lower portion of the tank  14  and removed. Here, since the oil content and the water content are removed by using condensation, they can be removed even if they have fine particle sizes. Further, since the oil content and the water content accumulated in the lower portion of the tank  14  are periodically removed by the auto drain valve  14 B, maintenance of the tank  14  is unnecessary or reduced. 
     The compressed air temporarily stored in the tank  14  passes through the oil mist separator  16  and the air dryer  18  before it is supplied to various devices, thus enabling to further remove the oil content and the water content that have not been removed by condensation. Accordingly, it is possible to address various devices requiring cleaner compressed air. 
     Here, since a certain degree of the oil content and the water content are removed by condensation in the tank  14 , it is possible to reduce the size of the oil mist separator  16  and the air dryer  18 . Further, if no problem occurs in devices using a compressed air as a working fluid, it is possible to omit at least one of the oil mist separator  16  and the air dryer  18 . In short, it is sufficient that at least one of the oil mist separator  16  and the air dryer  18  be disposed in a second pipe  22  to be connected to the delivery port  14 A of the tank  14 , as the situation requires. 
     In the above-described embodiment, in order to efficiently cool the compressed air by the evaporator  40 , the following construction may be added. Here, with respect to constructions common to those of the embodiment illustrated in  FIG. 1 , the same reference signs are applied and their explanations are omitted. 
     That is, as illustrated in  FIG. 2 , in the first pipe  20  disposed between the air compressor  12  and the evaporator  40 , a humidity sensor  50  for detecting the humidity of a compressed air discharged from the air compressor  12  is attached. Furthermore, to the evaporator  40 , a temperature sensor  52  for detecting the temperature of the evaporator  40  is attached. Signals of the humidity sensor  50  and the temperature sensor  52  are input to a control unit  54  having a computer. The control unit  54  executes a control program stored in, for example, a ROM (Read Only Memory) to electronically control the opening degree of the expansion valve  38 . Here, the control unit  54  may, for example, be integrated into a control unit for electronically controlling an air conditioner. 
       FIG. 3  illustrates a control of the expansion valve  38  repeatedly executed by the control unit  54  at first predetermined time intervals after start of an engine. 
     In Step  1  (which is abbreviated as “S 1 ” in the drawings; the same rule is applied hereinafter), the control unit  54  reads a humidity of a compressed air from the humidity sensor  50  and reads a temperature of the evaporator  40  from the temperature sensor  52 . 
     In Step  2 , the control unit  54  refers to a map that defines the opening degree of the expansion valve  38  in relation to the humidity of the compressed air and the temperature of the evaporator  40 , and computes an opening degree corresponding to the humidity and the temperature read in Step  1 . Here, the map defines, for example, an opening degree at which a compressed air flowing through the first pipe  20  is cooled to a temperature below the dew points of an oil content and a water content, that is obtained by, for example, experiment, that is, an opening degree at which a compressed air flowing through the first pipe  20  is cooled to a temperature at which the oil content and the water content are condensed or to a lower temperature. 
     In Step  3 , the control unit  54  controls the expansion valve  38  so that its opening degree becomes one computed in Step  2 . 
     Thus, the opening degree of the expansion valve  38  is dynamically controlled to cool the compressed air to a temperature at which the oil content and the water content are condensed or a lower temperature based on the humidity of the compressed air discharged from the air compressor  12  and the temperature of the evaporator  40 . Accordingly, it is not necessary to operate the heat pump  30  always at a high load in order to remove the oil content and the water content from the compressed air, and it is possible to save energy for operating the compressor  34 . Here, when an opening degree for maintaining a vehicle interior temperature set by, for example, a vehicle driver is greater than the opening degree for removing the oil content and the water content from the compressed air, it is sufficient that the temperature setting be prioritized. 
     Here, even when, for example, a vehicle driver does not desire operation of the air conditioner, specifically, even when the driver turns OFF an air conditioner switch, the heat pump  30  continues to run to cool the compressed air. In this case, a cool air, which has passed through the evaporator  40  to be cooled, is introduced into the vehicle interior, and such a state is against the intention of, for example, the vehicle driver. To solve this problem, the following construction may be further added. 
     As illustrated in  FIG. 4 , to the other end portion of the cooling unit  42 , that is, to a cool air exit side of the evaporator  40 , for example, a door  60  including a plate-shaped member is rotatably attached, which is configured to selectively switch between introduction of the cool air into the vehicle interior and discharge of the cool air to the outside of the vehicle interior. To the rotation axis  60 A of the door  60 , for example, an actuator  62  such as an electric motor is connected. 
     To the control unit  54 , an output signal of an air conditioner switch operated by, for example, a vehicle driver, is input. The air conditioner switch outputs an ON signal when operation of the air conditioner is desired, and outputs an OFF signal when operation of the air conditioner is not desired. The control unit  54  controls electronically the actuator  62  for rotating the door  60  according to the signal of the air conditioner switch. 
     Here, the door  60  and the actuator  62  are mentioned as an example of the selection device, and the control unit  54  is mentioned as an example of the control device. 
       FIG. 5  illustrates a control of the actuator  62  repeatedly executed by the control unit  54  at second predetermined time intervals after start of an engine. Here, the second predetermined time interval may be the same as the first predetermined time interval. 
     In Step  11 , the control unit  54  reads the signal of the air conditioner switch. 
     In Step  12 , the control unit  54  judges whether or not the air conditioner switch is ON. When the control unit  54  judges that the air conditioner switch is ON (Yes), it proceeds with the process to Step  13 . On the other hand, when the control unit  54  judges that the air conditioner switch is OFF (No), it proceeds with the process to Step  14 . 
     In Step  13 , the control unit  54  controls the actuator  62  for rotating the door  60  so as to rotate the door  60  to the position indicated by the solid line in order to allow a cool air be introduced into the vehicle interior. 
     In Step  14 , the control unit  54  controls the actuator  62  for rotating the door  60  so as to rotate the door  60  to the position indicated by the broken line in order to discharge the cool air to the outside of the vehicle interior. 
     By such a configuration, since the cool air is discharged to the outside of the vehicle interior when the air conditioner switch is OFF, it is possible to eliminate discomfort felt by, for example, a vehicle driver due to introduction of the cool air into the vehicle interior. Here, the actuator  62  for rotating the door  60  is not limited to one electronically controlled by the control unit  54 , and it may be one controlled by a relay actuated by the signal of the air conditioner switch. In this case, the relay is mentioned as another example of the control device. 
     Since the evaporator  40  is used not only for providing a cooling function of the air conditioner but also for cooling the compressed air, its capacity may become insufficient. In such a case, as illustrated in  FIG. 6 , a pair of evaporators  40  may be provided to sandwich a part of the first piping  20  therebetween.