Abstract:
Disclosed is a vehicle compressed air supply device, comprising pressure maintenance valves for service brakes, which are positioned between a junction chamber and compressed air channels for primary brakes; a pressure maintenance valve for the parking brake, which is positioned between the junction chamber and a compressed air channel for the parking brake; and a pressure maintenance valve, positioned on a supply path that connects the pressure maintenance valve for the parking, brake with the junction chamber, and which is closed until the pressure of the compressed air that is supplied to the compressed air channels for the primary brakes reaches a prescribed pressure value. The pressure maintenance valve has the same structure as the pressure maintenance valves for service brakes and the pressure maintenance valve for the parking brake.

Description:
TECHNICAL FIELD 
     The present invention relates to a vehicle compressed air supply device which supplies compressed air to a brake of a vehicle. 
     BACKGROUND ART 
     In the related art, a large vehicle such as a truck or a bus employs pneumatic brake device using compressed air as an operating fluid which operates a brake chamber. In the type of brake device, a vehicle compressed air supply device supplying compressed air to each brake chamber is mounted. 
     The vehicle compressed air supply device includes an air compressor and retains the compressed air discharged from the air compressor in an air tank, and supplies the compressed air inside the air tank to each brake circuit if required. In addition, the vehicle compressed air supply device includes pressure protection valves corresponding to each of brake circuits respectively. When one of the brake circuits is failed, the pressure protection valve corresponding to the brake circuit, which is failed, is closed and thereby the pressure protection valve has a function to protect the other brake circuits which are not failed. 
     In addition, recently, from the viewpoint of further safety, when a pressure of the compressed air supplied to a service brake circuit does not reaches a predetermined pressure value, the pressure protection valve corresponding to a parking brake circuit is closed and thereby the pressure supply to the parking brake is stopped. Usually, the service brake actuates a braking force with the pressure of the supplied compressed air. Meanwhile, the parking brake is a spring brake using a bias force of a spring and is configured such that a braking force is released by the pressure of the supplied, compressed air. Thus, a control valve is provided upstream the pressure protection valve corresponding to the parking brake circuit and in a case where the service brake is not actuated because the pressure of the compressed air supplied to the service brake circuit is not enough, the control valve is closed and thereby the pressure supply to the parking brake circuit is stopped and the parking brake cannot be released (for example, PTL 1). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] JP-A-2009-23627 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, since the control valve of the related art is controlled to be opened and closed by a command pressure of a solenoid valve which is controlled by a detected pressure of the service brake circuit, it is necessary that a solenoid valve or a line which outputs the command pressure from the solenoid valve to the control valve is provided in the device, and it is a problem that a configuration of the device becomes complicated. 
     An object of the invention is to provide a vehicle compressed air supply device in which a simplification of the device configuration is realized. 
     Solution to Problem 
     In order to accomplish the object described above, a vehicle compressed air supply device of the invention which includes an air compressor mounted on a vehicle and supplies compressed air discharged from the air compressor to each of a plurality of loads of the vehicle, includes: a junction chamber which is provided at a discharge line of the air compressor and distributes the compressed air to each of the loads; a service brake pressure protection valve which is disposed between the junction chamber and a service brake circuit provided as the loads; a parking brake pressure protection valve which is disposed between the junction chamber and a parking brake circuit provided as the loads; and a valve unit which is disposed in a flow path connecting the parking brake pressure protection valve and the junction chamber, and is closed until pressure of the compressed air supplied to the service brake circuit reaches a predetermined pressure value, wherein the valve unit is formed of a pressure protection valve having the same structure as each of the pressure protection valves. 
     In the configuration described above, the valve unit, the service brake pressure protection valve and the parking brake pressure protection valve may have structure including a partition wall which divides an inner space and an outer space inside a main body; a valve seat which is provided at the partition wall; and valve body which abuts the valve seat with an elastic force respectively, the service brake pressure protection valve and the parking brake pressure protection valve introduce an air into the inner space and discharge the air from the outer space and on the other hand, the valve unit is connected to an air supply path so as to introduce the air into the outer space and discharge the air from the inner space. 
     In addition, the valve unit may be set to open at a pressure value higher than the service brake pressure protection valve and the parking brake pressure protection valve, and set to be closed in a pressure value lower than the service brake pressure protection valve and the parking brake pressure protection valve. 
     In addition, an air communication pipe, which connects downstream of the parking brake pressure protection valve and the discharge line, may be provided and a check valve, which operates when an air pressure of the parking brake circuit increases higher than an air pressure of the discharge line, may be provided at the air communication pipe. 
     Advantageous Effects of Invention 
     According to the invention, since the valve unit, which is closed until the pressure of the compressed air supplied to the service brake circuit reaches a predetermined pressure value, is formed of the pressure protection valve having the same structure as each of the pressure protection valves, parts can be produced in common; the solenoid valve which is controlled by the detected pressure of the service brake circuit or a line which outputs the command pressure from the solenoid valve is not required and thereby the simplification of the device configuration can be realized. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a view illustrating a configuration of a compressed air supply system according to an embodiment. 
         FIG. 2  is a schematic side cross-sectional view of a pressure protection valve, 
         FIG. 2A  illustrates a valve closed state and  FIG. 2B  illustrates a valve opened state. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the invention is described with reference to the drawings. 
       FIG. 1  is a view illustrating a configuration of a compressed air supply system  1  according to the embodiment in which the invention is applied. 
     The compressed air supply system  1  (a vehicle compressed air supply device) illustrated  FIG. 1  is a device which supplies a compressed air for driving to pneumatic brake device mounted on for example, a large vehicle such as a truck or a bus, and is configured to include a compressor  4  (an air compressor), an ECU  2  controlling the compressor  4 , and an air dryer module  10  removing moisture of compressed air discharged from the compressor  4  and supplying dried compressed air to a load (for example, a brake device) of the vehicle. 
     The ECU  2  controls an engine of the vehicle based on a vehicle speed or the like of the vehicle on which the compressed air supply system  1  is mounted and controls operation of the compressor  4  and the air dryer module  10 . In addition, in the ECU  2 , information relating to a running situation of the vehicle such as information relating to the vehicle speed of the vehicle and information relating to a running distance of the vehicle is input and information relating to a operation situation of the air dryer  32 . 
     The air dryer module  10  includes an output port  21  where a load  51  is connected, an output port  22  where a load  52  is connected, an output port  23  where a load  53  is connected, an output port  24  where a load  54  is connected and an output port  25  where a load  55  is connected. 
     The loads  51  to  53  configure the brake device described above, and in the embodiment, the load  51  is a main brake (a service brake) of a front wheel, the load  52  is a main brake (a service brake) of a rear wheel and the load  53  is a parking brake. In addition, the loads  54  and  55  are accessories such as a horn and a clutch driving mechanism which are driven by the compressed air. 
     In addition, the loads  51  to  55  include compressed air circuits (a service brake circuit and a parking brake circuit)  51   a  to  55   a  in which compressed air flows. In the compressed air circuits  51   a  to  55   a , air tanks  51   b  to  55   b  are connected respectively. 
     The air dryer module  10  includes electromagnetic valves  101  and  102  which are opened and closed by the control of the ECU  2 , and pressure sensors  121 ,  122  and  123  which detect an air pressure in each portion of the air dryer module  10  and thereby outputs the detected value to the ECU  2 . The ECU  2  opens and closes the electromagnetic valves  101  and  102 , based on the detected value of the pressure sensors  121  to  123 . 
     The compressor  4  is connected to the engine via an auxiliary belt (not shown) and compresses the air with a driving force of the engine. The compressor  4  is controlled by the air pressure and the electromagnetic valve  101  is connected to a control line  26  thereof. A load state where the compressor  4  compresses the air and an unload state where the compression is not performed are switched by the opening and closing of the electromagnetic valve  101 . 
     A discharge pipe (a discharge line)  11  of the compressor  4  is connected to a flow-in pipe  31  of the air dryer module  10  and the air dryer  32  is connected to the flow-in pipe  31 . The air dryer  32  accommodates desiccant inside a case and foreign material such as moisture included in the compressed air, which is discharged from the compressor  4 , is removed by desiccant. 
     A junction pipe  31 A branched from the flow-in pipe  31  is connected between the compressor  4  and the air dryer  32 . In the junction pipe  31 A, an exhaust valve  33  and an exhaust opening  34  are connected in series. When the exhaust valve  33  is opened, the compressed air inside the main body of the air dryer  32  is discharged from the exhaust opening  34  to the outside directly. The exhaust valve  33  is controlled by the air pressure and the electromagnetic valve  102  is connected to the control line  39 . The electromagnetic valve  102  is opened and closed by the control of the ECU  2  and provide the air pressure of downstream of the air dryer  32  to the exhaust valve  33  in an opened state of the valve. The exhaust valve  33  is usually closed and only when the air pressure is applied from the electromagnetic valve  102 , the exhaust valve  33  is opened and thereby the compressed air is discharged from the exhaust opening  34 . 
     Here, in a state where the air pressure inside the air dryer module  10  is high enough, when the exhaust valve  33  is opened, the compressed air, which is accumulated downstream side (for example, a supply path  35  or inside the air tank  55   a ) than the air dryer  32 , is made to flow backward inside the case of the air dryer  32  and discharged from the exhaust opening  34 . At this time, since the air passing through the case becomes a super-dried state by rapid decompression and moisture from desiccant inside the case is captured and thereby desiccant is regenerated. Desiccant after regeneration is configured such that adsorption ability adsorbing the moisture is recovered and the moisture of the compressed air can be removed. The regeneration operation is performed every time which is set beforehand due to the opening of electromagnetic valve  102  by the ECU  2  or a predetermined regeneration timing (a predetermined timing) such as a case where the air pressure or the like inside the air dryer module  10  satisfies conditions which are set beforehand. 
     In addition, another junction pipe  31 B, which is branched from the flow-in pipe  31 , is connected between the compressor  4  and the air dryer  32 , and the junction pipe  31 B is connected to a supply port  28  via an air pressure supply valve  36 . The air supply valve  36  includes an operation switch  36 A which is manually operated to open and close. When the operation switch  36 A is pushed, the air supply valve  36  is opened and then the compressed air is discharged from the supply port  28 . The supply port  28  is configured for example, to connect to a valve (an opening in which the air enters) of a tire of the vehicle and the air can be supplied in the tire by operating the operation switch  36 A. In addition, a safety valve  37  is provided at the junction pipe  35 A branched from the supply path  35  downstream of the air dryer  32 . The safety valve  37  is a valve that is opened when the air pressure inside the supply path  35  or inside the air tanks  51   b  to  55   b  is abnormally increased, and thereby the pressure is escaped to the outside. 
     A junction chamber  38  is connected to the supply path  35  downstream than the air dryer  32  and three supply paths  40 ,  41  and  42  are connected to the junction chamber  38 . A reducing valve  43  is provided at the supply path  40  and the supply path  40  is branched to two supply paths  40 A and  40 B downstream the reducing valve  43 . Each of the supply paths  40 A and  40 B is connected to each of the output ports  21  and  22  via the service brake pressure protection valves  44  and  45  respectively. In addition, the reducing valve  46  and the pressure protection valve (the valve unit)  47  are provided at another supply path (a flow path)  41  connected to the junction chamber  38 . The supply path  41  is branched to two supply paths  41 A and  41 B at downstream of the pressure protection valve  47 . Each of the supply paths  41 A and  41 B is connected to each of the output ports  23  and  24  via the parking brake pressure protection valve  48  and the accessory pressure protection valve  49  respectively. Furthermore, another supply path  42  connected to the junction chamber  38  is connected to the output port  25 . 
     The service brake pressure protection valves  44  and  45  are arranged with a throttle valve and a check valve in parallel. The service brake pressure protection valves  44  and  45 , the parking brake pressure protection valve  48  and the accessory pressure protection valve  49  are closed at the loads  51  to  54  connected to the corresponding output ports  21  to  24  respectively when the compressed air circuits  51   a  to  54   a , where the compressed air flows, are failed, in other words, the air pressure is lower than a predetermined closing pressure value at the circuit. In addition, the service brake pressure protection valves  44  and  45 , the parking brake pressure valve protection valve  48  and the accessory pressure protection valve  49  are configured to open when the air pressure inside the supply path, where each of pressure protection valves is provided, is higher than a predetermined opening valve pressure value. 
     In addition, a bleed-back path (an air communication pipe)  60 , which communicates each of supply paths  42  and  41 A, is provided between the supply path  42  where the junction chamber  38  is connected and the supply path  41 A downstream of the parking brake pressure protection valve  48 . The feedback path  60  includes a reflex valve (a check valve  61 ) which blocks the flow of the air from the supply path  42  (in other words, the junction chamber  38 ) to the output port  23 . The check valve  61  is opened when the air pressure inside the supply path  41 A is higher than the air pressure inside the supply path  42  and has a function to escape the pressure inside (for example, the parking brake air tank  53   b ) the supply path  41 A. 
     The pressure sensor  123  detects the air pressure of the supply path  35 , the pressure sensor  121  detects the air pressure downstream of the service brake pressure protection valve  44  of one side in other words, the air pressure of the output port  21  and the pressure sensor  122  detects the air pressure of the output port  22  which is downstream of the service brake pressure protection valve  45  of the other side. The detection values are output from each of pressure sensors  121  to  123  to the ECU  2  at any time. 
     The braking force of the parking brake device of the vehicle corresponding to the load  53  is released by the air pressure and thereby the vehicle can be run. Specifically, the parking brake opens a brake shoe with the force of the spring and exerts the braking force during the parking, and the brake shoe is closed against the force of the spring by the air pressure supplied from the air dryer module  10  during releasing. 
     Thus, the parking brake device can release the parking brake by the air pressure in a case where the compressed air inside the air tank  53   b  is filled enough. Meanwhile, in a case where the compressed air circuit  53   a  corresponding to the parking brake is failed, since the parking brake pressure protection valve  48  is closed and thereby the supply of the compressed air to the compressed air circuit  53   a  is cut, the parking brake cannot be released. 
     Here, it is a premise that the parking brake device can be released during the main brake device is able to use in view of safety, and in a case where the air pressure of air tanks  51   b  and  52   b  corresponding to the main brake device is not enough, it is desirable that the parking brake be not released. 
     Thus, in an initial state (for example, in a case where the pressure inside the air tanks  51   b  and  52   b  is not enough) time of a new vehicle or time of chicking the vehicle, it is necessary that the supply of the compressed air to the compressed air circuit  53   a  corresponding to the parking brake is closed until the air pressure inside the air tanks  51   b  and  52   b  becomes enough. In the configuration, the pressure protection valve  47  is provided at the supply path  41  connected to the junction chamber  38  and opening valve pressure set value of the pressure protection valve  47  is set higher than the opening valve pressure set value of the service brake pressure protection valves  44  and  45 . Accordingly, the compressed air is prevented from supplying to the air tank  53   b  of the parking brake device before the air pressure is enough inside the air tanks  51   b  and  52   b  of the main brake device. 
     Furthermore, in the configuration, the bleed-back path  60  is provided and thereby the parking brake cannot be released when the compressed air circuits  51   a  and  52   a  corresponding to the main brake device are failed. Specifically, when the compressed air circuits  51   a  and  52   a  are failed, since the air pressure inside the supply path  42  decreases, the check valve  61  of the feedback path  60  is opened and the air inside the air tank  53   b  is discharged via the feedback path  60 . Furthermore, the parking brake pressure protection valve  48  is closed according to the decrease of the air pressure inside the air tank  53   b . Thus, the supply of the compressed air to the compressed air circuit  53   a  is cut and the parking brake cannot be released. 
     In addition, the pressure protection valve  47  is configured having the same structure as the service brake pressure protection valves  44  and  45 , the parking brake pressure protection valve  48  and the accessory pressure protection valve  49 . Accordingly, since each of pressure protection valves can be produced in common and the solenoid valve which is controlled by the detected pressure of the service brake circuit or a line which outputs the command pressure from the solenoid valve is not required as the control valve of the related art thereby the simplification of the device configuration can be realized. 
     Next, the pressure protection valve  47  is described. 
       FIG. 2  is a schematic side cross-sectional view of the pressure protection valve  47 ,  FIG. 2A  illustrates the closed state of the valve and  FIG. 2B  illustrates the opened state of the valve. 
     As shown in  FIG. 2A , the pressure protection valve  47  includes a valve main body (a main body)  70  and a cover body  71  provided at the upper side of the valve main body  70 . In the inside of the cover body  71 , a coil spring  80 , a first spring receiving member  81  which receives an upper end of the coil spring  80 , and a second spring receiving member  82  which receives a lower end of the coil spring  80 , and at the upper end portion of the cover body  71 , an adjustment spring  83  is attached. A tip of the adjustment spring  83  is tapered and abuts to an inner bottom portion of the second spring receiving member  82 . The tip thereof can be descended while pushing the coil spring  80  according to the depth of a screw. 
     In addition, at the lower surface of the second spring receiving member  82 , a valve body  84 , which is formed substantially in the same size as an inner diameter of the valve main body  70 , is attached and moves along an axial direction of the coil spring  80  with the second spring receiving member  82 . 
     Meanwhile, a partition wall  90 , which is vertically and cylindrically arranged inside the valve main body  70  and a cylindrical inner space  91  and a donut-shaped outer space  92  are divided by the partition wall  90 . The partition wall  90  is provided at a position of a substantially half of the inner diameter of the valve main body  70  and a circular valve seat  93  is formed at the upper end portion of the partition wall  90 . For example, when the air pressure of the compressed air made to flow in from the inner space  91  is higher than a spring force F of the coil spring  80 , the valve body  84  moves in a direction away from the valve seat  93  due to the air pressure and the pressure protection valve  47  is opened. 
     A port (not shown) is formed at a position where the inner space  91  and the outer space  92  are communicated at the valve main body  70 , and supply paths shown in  FIG. 1  are disposed to communicate the via the port. 
     Here, the pressure protection valve  47  is described, however in the embodiment, the service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48  are also configured to have the same structure as the pressure protection valve  47 . Thus, in a case where the opening valve pressure set value of the pressure protection valve  47  is set higher than the opening valve pressure set value of the service brake pressure protection valves  44  and  45 , the height of the coil spring  80  may be adjusted by adjusting the adjustment spring  83 . 
     Meanwhile, in a case where the opening valve pressure set value of the pressure protection valve  47  is set higher than the opening pressure set value of the service brake pressure protection valves  44  and  45 , it is general that the closing pressure set value of the pressure protection valve  47  is also higher than the closing pressure set value of the service brake pressure protection valves  44  and  45 . 
     In this case, when the air pressure inside the supply path decreases lower than a predetermined closing pressure set value, initially, the pressure protection valve  47  is closed and inconvenience occurs. Thus, in the configuration, service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48  are connected to each of supply paths  40 A,  40 B and  41 A wherein a port communicating with the outer space  92  is an air flow-in port and a port communicating with the inner space  91  is an air flow-out port. In contrast, the pressure protection valve  47  is connected to the supply path  41  wherein a port communicating with the inner space  91  is the air flow-in port and a port communicating with the outer space  92  is the air flow-out port contrary to the service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48 . 
     In the pressure protection valve of this type, it is recognized that a differential pressure between the opening pressure set value and the closing pressure set value becomes large in a case where the port communicating with the inner space  91  is used as the air flow-in port and the port communicating with the outer space  92  is used as the air flow-out port compared to the case where the port communicating with the outer space  92  is used as the air flow-in port and the port communicating with the inner space  91  is used as the air flow-out port. 
     Next, description is given where a connection position of the port with respect to the supply path is changed and thereby the differential pressure between the opening pressure set value and the closing pressure set value is changed. Here, a diameter of the partition wall corresponding to the inner space  91  is referred to as A, a inner diameter of the valve main body  70  corresponding to the inner space  91  and the outer space  92  is referred to as B, the spring force is referred to as F, the opening pressure set value is referred to as P, the closing pressure set value is referred to as P′. In addition, for the convenience of the description, the pressure is present at a side where the air flows in, however, the atmosphere pressure (0 Pa) is present at a side where the air flows out. 
     (1) In a case where the port communicating with the outer space  92  is used as the air flow-in port and the portion communicating with the inner space  91  is used as the air flow-out port, the balance of the force during opening of the valve become below.
 
 P= 4 F/π× 1/( B   2   −A   2 )  (1)
 
     Meanwhile, the balance of the force during closing of the valve become below.
 
 P′= 4 F /π×(1 /B   2 )  (2)
 
     The differential pressure ΔP 1  becomes below from expressions (1) and (2) described above.
 
Δ P 1 =P−P′= 4 F/π×[A   2   /B   2 ( B   2   −A   2 )]  (3)
 
(2) In a case where the port communicating with the inner space  91  is used as the air flow-in port and the portion communicating with the outer space  92  is used as the air flow-out port, the balance of the force during opening of the valve become below.
 
 P= 4 F /π×(1 /A   2 )  (4)
 
     Meanwhile, the balance of the force during closing of the valve become below.
 
 P′= 4 F /π×(1 /B   2 )  (5)
 
     The differential pressure ΔP 2  becomes below from expressions (4) and (5) described above.
 
Δ P 2= P−P′= 4 F /π×( B   2   −A   2 )/ A   2   B   2   (6)
 
     In the embodiment, since a ranges B=(1.5 to 2.5)×A are set, when the ranges substitute the expressions (3) and (6), the differential pressures become below.
 
Δ P 1 &lt;ΔP 2  (7)
 
     The differential pressure between the opening pressure set value and the closing pressure set value becomes large in a case where the port communicating with the inner space  91  is used as the air flow-in port and the port communicating with the outer space  92  is used as the air flow-out port compared to the case where the port communicating with the outer space  92  is used as the air flow-in port and the port communicating with the inner space  91  is used as the air flow-out port. 
     In addition, the reason why B&gt;1.5A is because the partition wall  90  is difficult to produce inside the valve main body  70  on the production process, in a case of the same or below conditions. In addition, the reason why B&lt;2.5A is because the valve main body  70  is increased in size in a case of the same or above conditions. It is recognized that B=(1.8 to 1.9)×A is the optimized in the conditions. 
     Thus, the closing pressure set value of the pressure protection valve  47  can be decreased lower than the closing pressure set value of the service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48 , and the inconvenience that the pressure protection valve  47  is closed earlier than the service brake pressure protection valves  44  and  45  can be avoid, with a simple configuration in which the connection position of the port with respect to the supply path is changed. 
     As described above, according to the embodiment, the invention includes the service brake pressure protection valves  44  and  45  which are arranged between the junction chamber  38  and the main brake compressed air circuits  51   a  and  52   a , the parking brake pressure protection valve  48  which is arranged between the junction chamber  38  and the parking brake compressed air circuit  53   a , the pressure protection valve  47  which is arranged at the supply path  41  connecting the parking brake pressure protection valve  48  and the junction chamber  38 , and opens the valve until the pressure of compressed air supplied to the main brake compressed air circuit  51   a  and  52   a . In addition, since the pressure protection valve  47  has the same structure as the service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48 , each of pressure protection valves can be produced in common and the solenoid valve which is controlled by the detected pressure of the service brake circuit or a line which outputs the command pressure from the solenoid valve is not required as the control valve of the related art and thereby the simplification of the device configuration can be realized. 
     In addition, according to the embodiment, since service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48  are connected to the air supply path wherein the air is made to flow into the inner space  91  and the air is discharged from the outer space  92 , in contrast, the pressure protection valve  47  is connected to the air supply path wherein the air is made to flow into the outer space  92  and the air is discharged from the inner space  91  contrary to the service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48 , the closing pressure set value of the pressure protection valve  47  can be decreased lower than the closing pressure set value of the service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48 , and the inconvenience that the pressure protection valve  47  is closed earlier than the service brake pressure protection valves  44  and  45  can be avoid, with a simple configuration in which the positions of the flowing in and the discharging of the air are changed with respect to the air supply path. 
     In addition, according to the embodiment, since the pressure protection valve  47  is set to open at a pressure value higher than the service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48 , and is set to be closed in a pressure value lower than the service brake pressure protection valves  44  and  45 , and the parking brake pressure protection valve  48 , advantages can be realized simultaneously in which the compressed air is prevented from supplying to the air tank  53   b  of the parking brake device before the air pressure is enough inside the air tanks  51   b  and  52   b  of the main brake device and the inconvenience that the parking brake pressure protection valve  48  is closed earlier than the service brake pressure protection valves  44  and  45  can be avoid with the simple configuration. 
     In addition, according to the embodiment, since the bleed-back path  60  is provided which connects the supply path  41 A downstream of the parking brake pressure protection valve  48  and the supply path  42  extending from the junction chamber  38 , and the check valve  61 , which is operated when the air pressure of the parking brake compressed air circuit  53   a  increases higher than the air pressure of the supply path  42 , is provided at the bleed-back path  60 , in a case where the compressed air circuits  51   a  and  52   a  of the main brake device is failed, the parking brake cannot be released because the compressed air inside the compressed air circuit  53   a  of the parking brake device can be opened, even with a simple configuration in which the pressure protection valve  47  is provided. 
     In addition, the embodiment described above illustrates an embodiment that applies the invention and the invention is not limited to the embodiment. For example, the vehicle as the applying object of the vehicle compressed air supply device of the invention is not limited specifically. The vehicle may be any of a large vehicle, a small vehicle, a special vehicle, a wrecker vehicle, a two-wheeled vehicle or a three-wheeled vehicle, and the scale and form thereof are arbitrary. 
     REFERENCE SIGNS LIST 
     
         
           1 : compressed air supply system (compressed air supply device) 
           4 : compressor 
           31 : flow-in pipe (discharge line) 
           38 : junction chamber 
           40 A,  40 B,  41 A,  41 B,  42 : supply path 
           41 : supply path (path) 
           44 ,  45 : service brake pressure protection valve 
           47 : pressure protection valve (valve unit) 
           48 : perking brake pressure protection valve 
           49 : accessory pressure protection valve 
           51  to  55 : load 
           51   a ,  52   a : compressed air path (service brake circuit) 
           53   a : compressed air path (perking brake circuit) 
           51   b  to  55   b : air tank 
           60 : bleed-back path (air communication pipe) 
           61 : check valve 
           70 : valve main body (main body) 
           84 : valve body 
           90 : partition wall 
           91 : inner space 
           92 : outer space 
           93 : valve seat