Abstract:
A vehicle compressed air supply system includes a supply part with compressor, an air drying part and a consumer part including consumer circuits with brake circuits supplied with compressed air via a multi-circuit safety valve. The brake circuits, and optionally at least one other consumer circuit, include compressed air tanks. Pressure in the circuits is monitored by sensors and evaluated by an electronic control device. To determine system parameters in terms of tank size and compressor output, when filling circuits, the rate of pressure increase in a circuit is determined as a function of compressor speed, and air-drying regeneration is effected. The period of a pre-defined pressure drop or pre-defined pressure gradient is determined and air volume for completing regeneration is calculated from the magnitude of the pressure drop, regeneration time and throttle diameter. Tank volume is determined therefrom. Compressor output is calculated from tank volume and rate of pressure increase.

Description:
FIELD OF THE INVENTION 
     The present invention generally relates to a compressed air supply system for motor vehicles and a method for determining the parameters of the system. 
     BACKGROUND OF THE INVENTION 
     WO 09847751 A1 describes a pneumatic vehicle brake system, which is provided with a compressor, at least one air-consuming circuit, such as a service brake circuit, a parking brake circuit, a low-pressure auxiliary circuit and a high-pressure circuit, wherein the circuits contain compressed air tanks and demand valves. A first electrically actuatable valve, which is closed in home position, is disposed between the compressor and each consuming circuit. A second electrically actuatable valve, which is open in home position, is disposed between the compressor and the auxiliary circuit. The valves are actuated by an electronic control unit. The output ports of the first valves of the air-consuming circuits are in communication via check valves with the output port of the second normally open valve. Should a pressure demand be present in one of the circuits, for example because of insufficient tank pressure, the corresponding valve is opened by the control unit and, simultaneously, the second valve of the auxiliary circuit is closed. Failure of the compressor leads to a pressure drop, which is recognized by the control unit, which closes the valves or keeps them closed, thus maintaining the pressure in the circuits. A pressure regulating valve determines the pressure level. In the event of failure of the pressure regulating valve, overpressure is discharged via an overpressure valve. Pressure sensors monitor the circuits. The circuits are supplied with air via the second normally open valve and via the check valves connected upstream from the circuits. If the electrical system fails, all valves switch to home position. Nevertheless, the compressor continues to run and to supply the circuits with air via the second normally open valve of the auxiliary circuit, in which case the system pressure is determined by a low-pressure discharge valve of the auxiliary circuit. If a valve fails, the associated circuit can be supplied with air via the valve of the auxiliary circuit and the check valve. The known system is complex, since each consuming circuit is equipped with a compressed air tank. 
     DE 10004091 C2 describes a compressed air supply device for vehicle compressed air systems having a multi-circuit protective valve, a pressure regulator, a supply line for supplying the circuits of the multi-circuit protective valve with compressed air, and a compressor, which can be switched by means of a pneumatic switching mechanism, a pilot valve being provided to control the pressure regulator and the switching mechanism and a throttle being provided between the pilot valve and the switching mechanism. Each circuit contains a compressed air tank. The pilot valve is controlled and/or regulated by an electronic control and/or regulating unit. Pressure sensors monitor the pressure in the circuits and in the supply line. 
     The known air supply systems have the disadvantage that either they must be adjusted mechanically by the manufacturer or they must be parameterized by software. 
     SUMMARY OF THE INVENTION 
     Generally speaking, it is an object of the present invention to optimize the type of regeneration step described above for an air supply system to the point that the air dryer is universally usable. 
     The present invention provides embodiments of a multi-circuit protective valve having valves for the individual consuming circuits and an electronic pressure conditioning system having adaptive behavior for determining the pneumatic layout of the vehicle, such as compressor output capacity, tank configuration, etc. The tank size and compressor output capacity are estimated by determining parameters. For this purpose, an adjustment can be made such that over-regeneration of the air dryer cartridge takes place at least in the first regeneration step. The drying behavior of the air dryer is optimized, and, in this way, reduced energy consumption for compressed air generation is achieved. It is no longer necessary to parameterize the air supply system in a manner corresponding to the pneumatic layout of the vehicle. The embodiments of the present invention therefore provide a universal air dryer, which can be installed without adaptation in different vehicles. The valves of the multi-circuit protective valve may be of mechanical or electromagnetic type. 
     Still other objects and advantages of the present invention will in part be obvious and will in part be apparent from the specification. 
     The present invention accordingly comprises the features of construction, combination of elements, arrangement of parts, and the various steps and the relation of one or more of such steps with respect to each of the others, all as exemplified in the constructions herein set forth, and the scope of the invention will be indicated in the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be discussed in greater detail hereinafter on the basis of the accompanying drawings, wherein: 
         FIG. 1  is a basic circuit diagram of a compressed air supply system having a mechanical multi-circuit protective valve in accordance with an embodiment of the present invention; 
         FIG. 2  is a basic circuit diagram of a compressed air supply system having an electromagnetic multi-circuit protective valve in accordance with an embodiment of the present invention; and 
         FIG. 3  is a graphical representation of the determination of tank volume and compressor output during a first filling of the systems depicted in  FIGS. 1 and 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Like and corresponding parts in the drawing figures are represented by like reference numerals. 
     In the drawings, pressurized fluid lines are represented as solid lines and electrical lines are represented as dashed lines. 
       FIG. 1  of the drawings shows a compressed air supply system  2  having a compressed air supply part  4  and a consuming part  6 . Compressed air supply part  4  comprises a compressor  7 , a compressor control device  8  and an air dryer part  10 . 
     Consuming part  6  is provided with a compressed air distributor line  14 , which branches out to a plurality of valves  16 ,  18 ,  20 ,  22 ,  24  and to a plurality of consuming circuits  26 ,  28 ,  30 ,  32 ,  34  supplied with compressed air via the valves. 
     From compressor  7 , a compressed air supply line  40  leads via an air dryer cartridge  44 , upstream of which there may be connected a filter (not illustrated), and via a check valve  46  to distributor line  14 , from which lines  48 ,  50 ,  52 ,  54  branch off and lead to the valves. From the valves, compressed air lines  58 ,  60 ,  62 ,  64  lead to the consuming circuits. Line  64  branches out to lines  64 ′,  64 ″ leading to circuits  32  and  34 . Line  64 ′ branches off to lines  65 ,  66  leading to consuming circuits  30 ,  32 . A check valve  68  and a throttle  69  are also disposed in line  65 . A pressure limiter  70  is disposed in supply line  54 . Valve  24  is disposed in line  64 ″. 
     Pressure sensors  72 ,  74 ,  76 ,  78 ,  80  monitor the pressure in the consuming circuits and transmit the respective pressure as a pressure signal to an electronic control unit  84 , which controls compressed air supply part  4 . The pressure in distributor line  14  may be monitored by a pressure sensor (not illustrated). 
     In addition to the pressure or instead of the pressure, other variables of state such as air flow, air mass, energy, etc., can also be monitored or determined in the consuming circuits and in the connecting lines. 
     As an example, consuming circuits  28 ,  30  may be service brake circuits; consuming circuit  32  may be a trailer brake circuit and/or a parking brake circuit; consuming circuit  34  may be a secondary consuming circuit, such as, for example, driver&#39;s cab suspension, door controller, etc. (i.e., nothing that involves the service brake circuits); and consuming circuit  26  may be a high-pressure circuit for an air-suspension system. An air-suspension system normally needs high pressure because the air-suspension bellows have large volume and relatively high pressures. 
     Service brake circuits  28 ,  30  are desirably provided with compressed air tanks (not illustrated) in conformity with the 98/12/EU Directives. High-pressure circuit  26  can also have a compressed air tank. 
     Compressor  7  is controlled mechanically (pneumatically) via compressor controller  8 . Compressor controller  8  comprises a solenoid valve  94  (having small nominal width), which can be switched by electronic control unit  84  and which in de-energized home condition, as illustrated, is vented. In this condition, compressor  7  is turned on and at least one consuming circuit is filled with compressed air. When a set pressure threshold is reached, control unit  84  reverses solenoid valve  94  so that compressed air turns off pneumatically actuatable compressor  7  via a line  40 ′. If solenoid valve  94  is switched to de-energized condition for refilling in response to air consumption, valve  94  is switched back to the home condition illustrated in the drawing and line  40 ′ is vented via a line  40 ″, thus turning on compressor  7 . As an alternative to the described exemplary embodiment, a pneumatically switchable valve, which in the unactuated home position is vented, can be connected downstream from solenoid valve  94  to relieve compressor  7  in the actuated condition. 
     Air dryer part  10  comprises a regeneration solenoid valve  100  (with small nominal width), the input  102  of which is in communication with distributor line  14  and via the output  104  of which there is pneumatically switched a shutoff valve  106 , which is in communication with supply line  40  of compressor  7  and serves to relieve the compressor. Regeneration of air dryer cartridge  44  also takes place via regeneration valve  100 . Line  40  is then open to atmosphere. 
     When regeneration solenoid valve  100  is in passing condition, compressor  7  no longer supplies the consuming circuits but, instead, discharges via valve  106 . Simultaneously, dry air flows out of consuming circuits  26 ,  28 ,  30  via distributor line  14 , solenoid valve  100 , throttle  108  and check valve  110  through air dryer cartridge  44  for regeneration of its desiccant and continues via valve  106 . 
     Reference numeral  112  denotes an overpressure valve. 
     Valves  16 ,  18 ,  20 ,  22 ,  24  are mechanical overflow valves, the opening pressures and closing pressures of which are set to correspond to the respective circuits. The pressure in the circuits is monitored directly at the valves by pressure sensors  72 ,  74 ,  76 ,  78 ,  80 . 
     The embodiment depicted in  FIG. 2  shows compressed air supply system  2  having compressed air supply part  4  and consuming part  6 . Compressed air supply part  4  comprises compressor  7 , compressor control device  8  and air dryer part  10 . 
     Consuming part  6  is provided with compressed air distributor line  14 . In contrast to the embodiment of  FIG. 1 , consuming part  6  includes a plurality of electrically actuatable solenoid valves  116 ,  118 ,  120 ,  122 ,  124  having restoring springs. The consuming circuits  26 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38  are supplied with compressed air via the solenoid valves. 
     From compressor  7 , compressed air supply line  40  leads via a filter  42 , air dryer cartridge  44  and check valve  46  to distributor line  14 , from which lines  48 ,  50 ,  52 ,  54 ,  56  branch off and lead to the solenoid valves. From the solenoid valves, compressed air lines  58 ,  60 ,  62 ,  64 ,  66  lead to the consuming circuits. Line  62  branches out to lines  62 ′,  62 ″ leading to circuits  32  and  34 , and check valve  68  is also disposed in line  62 ″. A pressure limiter  70  is disposed in supply line  52 . Line  54  leading to solenoid valve  122  branches off downstream from pressure limiter  70 . Line  64  branches out to lines  64 ′,  64 ″ leading to circuits  36  and  38 . 
     Pressure sensors  72 ,  74 ,  76 ,  78 ,  80  monitor the pressure in the consuming circuits (and, if necessary, in distributor line  14 ) and transmit the respective pressure as a pressure signal to electronic control unit  84 , which controls compressed air supply part  4 . 
     In addition to the pressure or instead of the pressure, other variables of state such as air flow, air mass, energy, etc. can also be monitored or determined in the consuming circuits and in the connecting lines. 
     As an example, consuming circuits  28 ,  30  may be service brake circuits; consuming circuit  34  may be a trailer brake circuit, in which case normally two lines lead to the trailer; consuming circuit  32  may be a parking brake circuit having spring actuators; consuming circuits  36  and  38  may be secondary consuming circuits, such as, for example, driver&#39;s cab suspension, door controller, etc. (i.e., nothing that involves the service brake circuits); and consuming circuit  26  may be a high-pressure circuit for an air-suspension system. 
     Service brake circuits  28 ,  30  are desirably provided with compressed air tanks  90 ,  92  in conformity with the 98/12/EU Directives. High-pressure circuit  26  contains a compressed air tank  39 . Secondary consuming circuits  36 ,  38  may also contain compressed air tanks  36 ′,  38 ′. 
     Compressor  7  is controlled mechanically (pneumatically) via compressor controller  8 . Compressor controller  8  comprises solenoid valve  94  (having small nominal width), which can be switched by electronic control unit  84  and which in de-energized home position, as illustrated, is vented, and a valve  96 , which can be switched pneumatically via solenoid valve  94  and which, as illustrated, is vented in unactuated home position. If compressor  7  is to be turned on (for example, because a consuming circuit needs compressed air), control unit  84  reverses solenoid valve  94  so that pressure acts on control input  98  of the valve, whereby valve  96  switches back (or is switched) to home condition and turns on the pneumatically actuatable compressor via a line  40 ′. If solenoid valve  94  is switched to de-energized condition after the circuit has been filled, control input  98  is vented via the solenoid valve, whereby valve  96  switches to its other position and air is admitted to line  40 ′ so that compressor  7  is turned off. As an alternative, valve  96  can be dispensed with, as in the exemplary embodiment according to  FIG. 1 . 
     Air dryer part  10  comprises solenoid valve  100  (with small nominal width), the input  102  of which is in communication with distributor line  14  and via the output  104  of which there is pneumatically switched a shutoff valve  106 , which is in communication with supply line  40  of compressor  7  and serves to relieve the compressor. 
     When solenoid valve  100  is in passing condition, compressor  7  no longer supplies the consuming circuits but, instead, discharges via valve  106 . Simultaneously, dry air flows out of distributor line  14  (from tanks  90 ,  92  of the service brake circuits), via solenoid valve  100 , throttle  108  and check valve  110  through air dryer cartridge  44  for regeneration of the desiccant and continues via filter  42  and valve  106 . 
     Reference numeral  112  denotes an overpressure valve. 
     In the compressed air supply system according to embodiments of the present invention, the compressed air tank volume and compressor output capacity are determined during a first filling by determining the rate of rise of the air pressure in the service brake circuit, for example, or the time for filling this circuit, for which purpose the time of the pressure rise in the associated tank is measured in control device  84 , as a function of the compressor speed, which depends on the engine speed, from the start of supply until a defined upper pressure value p 1  is reached (see curve part a in  FIG. 3 ). 
     After the upper pre-definable pressure value p 1  monitored by pressure sensor  74  is reached, compressor  7  is turned off via valve  94 , while solenoid valve  100  of air dryer part  10  is switched to passing condition, so that the compressor discharges no longer into line  40  but, instead, via valve  106 . Simultaneously, dry air flows from the tank of circuit  28  filled to p 1  via distributor line  14 , solenoid valve  100 , throttle  108  and check valve  110  through air dryer cartridge  44  for regeneration of the desiccant and continues via valve  106 . 
     Regeneration takes place over a time (see curve part b in  FIG. 3 ) in which adequate regeneration can be achieved, for example until the pressure in the tank has dropped to a pre-definable value p 2 . Since the throttle orifice diameter is known and is stored in control device  84 , the amount of compressed air used for regeneration can be determined from the pressure drop p 1 -p 2 , the regeneration time and the orifice diameter. From the amount of compressed air, the orifice diameter and the regeneration time, control device  84  calculates the tank volume of circuit  28 . From the rate of pressure rise, determined as a function of compressor speed, or from the measured filling time in circuit  28 , as well as the determined compressor speed and the determined volume of circuit  28 , control device  84  then calculates the compressor output capacity. 
     After regeneration of air dryer cartridge  44  by dry air from circuit  28 , filling of circuit  28  continues from time t 2  (curve part c) until a defined pressure p 3  is reached at instant t 3 . Thereafter, filling of circuit  30  additionally takes place while filling of circuit  28  continues (curve parts d and e), and, from instant t 4  on, filling of circuits  32 ,  34  (curve part f) also takes place so that simultaneous filling of circuits  28 ,  30 ,  32 ,  34  takes place from instant t 4  on. 
     As soon as the same pressure p 5  is present in circuits  28 ,  30 ,  32  and  34  (see instant t 5 ), the rate of pressure rise in circuits  28 ,  30 ,  32  and  34  is determined as a function of compressor speed until instant t 6 . Thereafter, as soon as pressure p 6  is reached at instant t 6 , circuits  32 ,  34  are shut off, so that the pressure p 6  in circuits  32 ,  34  remains constant (see straight curve part g). The pressure in circuits  28 ,  30  is further raised (curve part h) until it reaches a pre-definable pressure p 7  (instant t 7 ). The rate of pressure rise as a function of the compressor speed is determined in circuits  28  and  30  from the pressure difference p 7 -p 6  and the time t 7 -t 6 . Thereafter, air dryer cartridge  44  is regenerated by dry air from circuits  28  and  30  (curve part i) and then filling of both circuits continues until they are shut off at a pre-defined pressure p 8  in these circuits at instant t 8 . 
     From the already calculated compressor output capacity and the determined rate of pressure rise in circuits  28  and  30 , the tank volume of circuits  28  and  30  can then be calculated in the control device. 
     The tank volume of circuits  28  and  30  can be verified from the amount of compressed air needed for regeneration, the known orifice diameter and the regeneration time. 
     The above-described method can be carried out not only for individual tanks or groups of tanks but also for the total volume of all tanks. 
     The data determined in the above-described manner for compressor capacity and tank volumes are saved in the control device. The saved values are used to monitor the compressor output capacity during driving operation, so that, in the event of declining output capacity, the regeneration process can be adapted to the poorer output capacity and a warning signal can be generated if necessary. Moreover, the inventive method makes it possible to monitor the regeneration orifice for fouling that could reduce the orifice diameter, in turn, making it possible for such fouling to be signaled if necessary. 
     In case of change or replacement of components of the compressed air supply system, such as the compressor or a tank, etc., the parameters of the compressed air system are re-determined. 
     Re-determination of the parameters is initiated via a diagnostic unit by programmed or manual action. 
     Instead of, or in addition to, the air dryer part and its orifice, it is possible to use another pneumatic component having definite and known orifice size for determining the parameters of the compressed air supply system. 
     It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween.