Patent Document

BACKGROUND/SUMMARY 
     Vacuum is a medium for providing actuating force in some vehicles. For example, vacuum may be used to assist a driver to apply vehicle brakes. Vacuum may be sourced to actuators via an engine intake manifold, vacuum pump, or an ejector. Engine intake manifold vacuum may be a suitable vacuum source for naturally aspirated engines; however, there may be insufficient engine intake manifold vacuum for operating vacuum actuators when the engine is turbocharged. Therefore, vacuum may be provided for turbocharged engines via an ejector or a vacuum pump. 
     An ejector provides vacuum by way of providing a low pressure region in a flow path of a motive fluid. In some examples, the motive fluid may contain fuel vapors, untreated engine emissions, and/or engine crankcase vapors. If the ejector develops a leak, it may be possible for gases to enter the atmosphere. For example, an ejector leak may be manifested in a converging section, a diverging section, or a vacuum or suction section. Since pressure within the converging, diverging, and suction sections may vary significantly, it may require three or more sensors (e.g., a sensor in each section) to determine which, if any, ejector section is leaking. Consequently, it may be expensive and challenging to determine whether or not an ejector is leaking so that the engine control system can detect degradation and alert the driver and potentially take mitigating action. Further, it may be expensive or difficult to meet requirements of regulating agencies for determining if tubes that connect to an ejector have been disconnected. 
     The inventors herein have recognized the above-mentioned disadvantages and have developed a system for providing vacuum for a vehicle, comprising: an engine including an air intake passage; and a vacuum generating device including a motive fluid inlet section, a diverging discharge section positioned within the air intake passage, and a suction inlet. 
     By placing a diverging section of an ejector or a venturi within an engine air intake passage, it may be possible to avoid making measurements of the ejector diverging section to detect leaks in the diverging section since any leaks in the diverging section will be released into the closed boundary of the engine. Consequently, hydrocarbons or untreated exhaust gases entrained in the motive fluid, which provides vacuum via the ejector, are directed to engine cylinders where they may be combusted and then treated in the engine exhaust system. Additionally, a particular benefit of arranging an ejector within an engine air intake is that a disconnect or leak in the diverging section outlet may be unnecessary to detect because it is within the engine air intake. A connection at the diverging section is expensive to detect due to a requirement of additional pressure sensors within the diverging section. 
     The present description may provide several advantages. Specifically, the approach may reduce the need to monitor all sections of an ejector to diagnose the ejector for leaks. Further, the approach may reduce a number of sensors required to monitor an ejector for leaks. Further still, ejector leaks may be determined without adding any additional sensors to the vehicle system. 
     The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings. 
     It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  shows a schematic depiction of an engine; 
         FIG. 2  shows a schematic depiction of a prior art air passage; 
         FIGS. 3-4  show example configurations of a vacuum providing device such that it may not be necessary to monitor a diverging section of the ejector or venturi; 
         FIG. 5  shows an example venturi or ejector; and 
         FIG. 6  shows an example method for leak testing a vacuum providing device. 
     
    
    
     DETAILED DESCRIPTION 
     The present description is related to providing vacuum to assists in actuator operation.  FIG. 1  shows one example system for providing vacuum for a vehicle.  FIG. 2  shows a prior art ejector system that may develop leaks to atmosphere.  FIGS. 3 and 4  show example ejector or venturi systems whereby leaks to atmosphere via a diverging section of the ejector or venturi may be avoided. An example ejector and an example venturi are shown in  FIGS. 5A and 5B . Finally, a method for diagnosing an ejector or venturi is shown in  FIG. 6 . 
     Referring to  FIG. 1 , internal combustion engine  10 , comprising a plurality of cylinders, one cylinder of which is shown in  FIG. 1 , is controlled by electronic engine controller  12 . Engine  10  includes combustion chamber  30  and cylinder walls  32  with piston  36  positioned therein and connected to crankshaft  40 . Combustion chamber  30  is shown communicating with intake manifold  44  and exhaust manifold  48  via respective intake valve  52  and exhaust valve  54 . Each intake and exhaust valve may be operated by an intake cam  51  and an exhaust cam  53 . The position of intake cam  51  may be determined by intake cam sensor  55 . The position of exhaust cam  53  may be determined by exhaust cam sensor  57 . 
     Fuel injector  66  is shown positioned to inject fuel directly into cylinder  30 , which is known to those skilled in the art as direct injection. Alternatively, fuel may be injected to an intake port, which is known to those skilled in the art as port injection. Fuel injector  66  delivers liquid fuel in proportion to the pulse width of signal FPW from controller  12 . Fuel is delivered to fuel injector  66  by a fuel system (not shown) including a fuel tank, fuel pump, and fuel rail (not shown). Fuel injector  66  is supplied operating current from driver  68  which responds to controller  12 . In addition, intake manifold  44  is shown communicating with optional electronic throttle  62  which adjusts a position of throttle plate  64  to control air flow from intake boost chamber  46 . 
     Compressor  162  draws air from air intake passage  42  to supply boost chamber  46 . Exhaust gases spin turbine  164  which is coupled to compressor  162  via shaft  161 . Compressor bypass valve  158  may be electrically operated via a signal from controller  12 . Compressor bypass valve  158  allows pressurized air to be circulated back to the compressor inlet to limit boost pressure. Similarly, waste gate actuator  72  allows exhaust gases to bypass turbine  164  so that boost pressure can be controlled under varying operating conditions. 
     Vacuum is supplied to vehicle systems via vacuum providing device  24 . Compressor  162  provides compressed air as a motive fluid via converging section duct  31  to operate vacuum providing device  24 . The motive fluid is combined with air from vacuum reservoir  138  via vacuum port duct  37  and check valve  60 . Check valve  60  allows flow when the pressure produced via the ejector within vacuum port duct  37  is lower than the pressure within reservoir  138 . Mixed air exits at diverging section  33 . In some examples, vacuum reservoir  138  may be referred to as a vacuum system reservoir since it can supply vacuum throughout the vacuum system and since brake booster  140  may contain a vacuum reservoir too. Pressure in reservoir  138  may be monitored via vacuum reservoir pressure sensor  193 . Vacuum system reservoir  138  provides vacuum to brake booster  140  via check valve  65 . Check valve  65  allows air to enter vacuum system reservoir  138  from brake booster  140  and substantially prevents air from entering brake booster  140  from vacuum system reservoir  138 . Vacuum system reservoir  138  may also provide vacuum to other vacuum consumers such as turbocharger waste gate actuators, heating and ventilation actuators, driveline actuators (e.g., four wheel drive actuators), fuel vapor purging systems, engine crankcase ventilation, and fuel system leak testing systems. Check valve  61  limits air flow from secondary vacuum consumers (e.g., vacuum consumers other than the vehicle braking system) to vacuum system reservoir  138 . Brake booster  140  may include an internal vacuum reservoir, and it may amplify force provided by foot  152  via brake pedal  150  to master cylinder  148  for applying vehicle brakes (not shown). 
     Distributorless ignition system  88  provides an ignition spark to combustion chamber  30  via spark plug  92  in response to controller  12 . Universal Exhaust Gas Oxygen (UEGO) sensor  126  is shown coupled to exhaust manifold  48  upstream of catalytic converter  70 . Alternatively, a two-state exhaust gas oxygen sensor may be substituted for UEGO sensor  126 . 
     Converter  70  can include multiple catalyst bricks, in one example. In another example, multiple emission control devices, each with multiple bricks, can be used. Converter  70  can be a three-way type catalyst in one example. 
     Controller  12  is shown in  FIG. 1  as a conventional microcomputer including: microprocessor unit  102 , input/output ports  104 , read-only memory  106 , random access memory  108 , keep alive memory  110 , and a conventional data bus. Controller  12  is shown receiving various signals from sensors coupled to engine  10 , in addition to those signals previously discussed, including: engine coolant temperature (ECT) from temperature sensor  112  coupled to cooling sleeve  114 ; a position sensor  134  coupled to an accelerator pedal  130  for sensing accelerator position adjusted by foot  132 ; a position sensor  154  coupled to brake pedal  150  for sensing brake pedal position; a knock sensor for determining ignition of end gases (not shown); a measurement of engine manifold pressure (MAP) from pressure sensor  121  coupled to intake manifold  44 ; a measurement of boost pressure from pressure sensor  122  coupled to boost chamber  46 ; an engine position sensor from a Hall effect sensor  118  sensing crankshaft  40  position; a measurement of air mass entering the engine from sensor  120  (e.g., a hot wire air flow meter); and a measurement of throttle position from sensor  58 . Barometric pressure may also be sensed (sensor not shown) for processing by controller  12 . Engine position sensor  118  produces a predetermined number of equally spaced pulses every revolution of the crankshaft from which engine speed (RPM) can be determined. 
     In some examples, the engine may be coupled to an electric motor/battery system in a hybrid vehicle. The hybrid vehicle may have a parallel configuration, series configuration, or variation or combinations thereof. Further, in some examples, other engine configurations may be employed, for example a diesel engine. 
     During operation, each cylinder within engine  10  typically undergoes a four stroke cycle: the cycle includes the intake stroke, compression stroke, expansion stroke, and exhaust stroke. During the intake stroke, generally, the exhaust valve  54  closes and intake valve  52  opens. Air is introduced into combustion chamber  30  via intake manifold  44 , and piston  36  moves to the bottom of the cylinder so as to increase the volume within combustion chamber  30 . The position at which piston  36  is near the bottom of the cylinder and at the end of its stroke (e.g. when combustion chamber  30  is at its largest volume) is typically referred to by those of skill in the art as bottom dead center (BDC). During the compression stroke, intake valve  52  and exhaust valve  54  are closed. Piston  36  moves toward the cylinder head so as to compress the air within combustion chamber  30 . The point at which piston  36  is at the end of its stroke and closest to the cylinder head (e.g. when combustion chamber  30  is at its smallest volume) is typically referred to by those of skill in the art as top dead center (TDC). In a process hereinafter referred to as injection, fuel is introduced into the combustion chamber. In a process hereinafter referred to as ignition, the injected fuel is ignited by known ignition means such as spark plug  92 , resulting in combustion. During the expansion stroke, the expanding gases push piston  36  back to BDC. Crankshaft  40  converts piston movement into a rotational torque of the rotary shaft. Finally, during the exhaust stroke, the exhaust valve  54  opens to release the combusted air-fuel mixture to exhaust manifold  48  and the piston returns to TDC. Note that the above is described merely as an example, and that intake and exhaust valve opening and/or closing timings may vary, such as to provide positive or negative valve overlap, late intake valve closing, or various other examples. 
     Referring now to  FIG. 2 , a schematic depiction of a prior art engine air inlet passage is shown. Engine air inlet passage  42  includes compressor  162  and boost chamber  46 . Vacuum providing device  24  includes a converging section  35 , a throat  201 , a diverging section  33 , and a vacuum port  214 . A converging section duct or conduit  31  connects boost chamber  46  to converging section  35  of vacuum providing device  24  and provides for fluidic communication between boost chamber  46  and vacuum producing device  24 . Vacuum port duct  37  begins at the vacuum port  214  in throat  37  and is connected to vacuum reservoir  138  via check valve  60 . Diverging section  33  is in communication with engine air inlet passage  42  via diverging section duct or conduit  210 . Diverging section duct  210  provides fluidic communication between diverging section  33  and engine air inlet  42 . 
     The system of  FIG. 2  operates as follows. Air flows through compressor  162  in the direction of the arrows. Boost chamber  46  holds air that is at a higher pressure than locations upstream of compressor  162 . Air exits boost chamber  46  and proceeds to engine  10  or enters converging section duct  31  leading to vacuum providing device  24 . Air that enters converging section duct  31  accelerates through throat  201  where air pressure drops to provide a vacuum that draws air from vacuum port duct  37  via vacuum port  214 . Air flows from vacuum reservoir  138  to throat  201  of vacuum providing device  24  via check valve  60 . Next, air flows through diverging section  33  and returns to engine air intake  42 . Converging section  35  and diverging section  33  are surrounded by atmosphere. A leak may occur in converging section  35  or diverging section  33  such that air and gases within vacuum providing device  24  escape to atmosphere. 
     In this system, if diverging section  33  is disconnected from engine air intake  42 , it creates an engine intake leak. This engine intake leak may be detected using a compressor inlet pressure (CIP) sensor, crankcase pressure sensor, or a crankcase vent tube pressure sensor. For example, at high engine air flows, an air leak around the air filter results in failure to detect an air pressure drop across the air cleaner, and some undesirable gases may be emitted to atmosphere. However, if a small diameter tube is used to couple diverging section  33  to engine air intake  42 , a disconnect at either end of the duct  210  remains undetectable. The use of a large diameter (e.g. 12 mm) duct  210  at  42  would solve diagnose-ability at the connection neat the engine air intake  42 . On the other hand, use of a large diameter tube from  33  to  42  solves the detection issue. However, the large diameter connectors and tubes create a detectable problem instead of a non-detectable one (e.g., false positive leaks). 
     Regarding leaks of vacuum, if a disconnected duct or leak occurs between check valve  60  and vacuum reservoir  138 , the leak may be determined at this location via a vacuum check at the vacuum user end. For example, a pressure that is higher than is expected in vacuum reservoir  138  may be determined to be a leak. 
     Regarding leaks of motive fluid supplied to the vacuum producing device  24 , if a disconnected duct or leak occurs between boost chamber  46  and converging section  35  along duct  212 , such a leak may be determined from an inability to build expected compressor outlet pressure. 
     Finally, if the disconnect occurs between throat  201  and vacuum inlet  37 , it can be diagnosed as failure to increase vacuum in the item in which vacuum is to be created. 
     Referring now to  FIG. 3 , a first example configuration of a vacuum providing device such that it may not be necessary to monitor a diverging section for leaks is shown. Engine air inlet passage  42  includes compressor  162  and boost chamber  46  along its length. Vacuum providing device  24  includes a converging section  35 , a throat  201 , a diverging section  33 , and a vacuum port  201 . A converging section duct or conduit  31  connects boost chamber  46  to converging section  35  of vacuum providing device  24 , and the converging section duct  31  provides for fluidic communication between boost chamber  46  and vacuum producing device  24 . Vacuum port  214  begins at a low pressure region of throat  37  and vacuum port duct  37  connects vacuum port  214  to vacuum reservoir  138  via check valve  60 . Vacuum port duct or conduit  214  provides connectivity and fluidic communication between vacuum port  214  and check valve  60 . Diverging section  33  is positioned within engine air inlet passage  42  so that via diverging section duct or conduit  210  is eliminated. 
     The system of  FIG. 3  operates as follows. Air flows in engine air inlet passage  42  in the direction of the arrows. Compressor  162  receives air at compressor inlet  399  and compresses air in boost chamber  46 . Air may exit boost chamber  46  to engine  10  or vacuum providing device  24 . Boost chamber  46  includes outlet port  342  where air leaves boost chamber  46  to enter converging section duct  31  leading to vacuum providing device  24 . Valve  362  is positioned within boost chamber  46  and it controls air flow through vacuum providing device  24 . Alternatively, valve  362  may be located within engine air inlet passage  42  as indicated by the dashed lines. Valve  362  may be variably adjusted to a plurality of positions between full open and full close to adjust air flow through vacuum providing device  24 . Converging section  35  directs compressed air to throat  201 . In some examples, converging section  35  may also be described as a motive fluid inlet. Air reenters engine air inlet passage  42  via inlet port  340 . Air accelerates through throat  201  causing a pressure drop, thereby providing a vacuum source. Vacuum port  214  opens up to a low pressure region in throat  201 . Air may be drawn from vacuum reservoir  138  via check valve  60  to throat  210 . Air from reservoir  138  and air from boost chamber  46  combine in diverging section  33 . In this example, diverging section  33  and engine air inlet passage  42  share wall  320 . Atmosphere surrounds engine air inlet passage  42  and converging section  35 . Diverging section releases motive fluid (e.g., air) and air from vacuum reservoir  138  directly into engine intake passage  42 . Air must pass through wall  320  of engine air inlet passage  42  to exit diverging section  33 . Thus, the engine air inlet passage  42  may provide a barrier between diverging section  33  and atmosphere. Consequently, if diverging section  33  develops a leak on the interior side of engine air inlet passage  42 , the leak may be constrained by engine air inlet passage  42 . However, if a leak develops in wall  320  diverging section  33 , undesirable gases may be released to atmosphere from diverging section  33 . 
     Referring now to  FIG. 4 , an alternative example vacuum providing device is shown. Engine air inlet passage  42  includes compressor  162  and boost chamber  46  along its length. Air flows in engine air inlet passage  42  in the direction of the arrows. Compressor  162  receives air at compressor inlet  399  and compresses air in boost chamber  46 . Air may exit boost chamber  46  to engine  10  or vacuum providing device  24 . Boost chamber  46  includes outlet port  342  where air leaves boost chamber  46  to enter converging section duct  31 . Valve  362  controls air flow through vacuum providing device  24  and it is located within boost chamber  46  so as to provide a seal between boost chamber  46  and converging section duct  31 . Thus, valve  362  may be closed to prevent air from leaks in converging section duct  31  from escaping to atmosphere. Alternatively, valve  362  may be located within engine air inlet  42 . Valve  362  may be variably adjusted to a plurality of positions between full open and full close to adjust air flow through vacuum providing device  24 . Converging section  35  directs compressed air to throat  201 . In some examples, converging section  35  may also be described as a motive fluid inlet. Air reenters engine air inlet passage  42  via inlet port  340 . Air accelerates through throat  201  causing a pressure drop, thereby providing a vacuum source at vacuum port  214 . Vacuum port  214  opens up to a low pressure region in throat  210 . Air may be drawn from vacuum reservoir  138  via check valve  60  to throat  210 . Air from reservoir  138  and air from boost chamber  46  combine in diverging section  33 . In this example, diverging section  33  and engine air inlet passage  42  do not share a common wall. Rather, wall  402  surrounds at least a portion of diverging section  33  and the diverging section  33  of the vacuum providing device  24  is completely enclosed within the engine air inlet passage  42 . Atmosphere surrounds engine air inlet passage  42  and converging section  35 . Diverging section releases motive fluid (e.g., air) and air from vacuum reservoir  138  directly into engine air inlet passage  42 . Air may exit all portions of diverging section  33  and still be retained in engine air inlet passage  42 . Thus, the engine air inlet passage  42  completely surrounds diverging section  33  to isolate it form atmosphere. In other words, diverging section  33  is completely within air intake passage  42 . Consequently, if diverging section  33  develops a leak, the leak may be constrained from exiting to atmosphere by engine air inlet passage  42 . 
     Referring now to  FIG. 5 , a first example of a vacuum providing device  24  is shown. In this example, vacuum providing device  24  takes the form of a venturi. Vacuum providing device  24  includes converging section  35  (e.g., a motive fluid inlet) where motive fluid arrives at a higher first pressure and is accelerated into throat  201 . A second pressure region at a lower pressure than the higher first pressure forms in throat  210  so that air may be drawn into vacuum providing device  24  via vacuum port  214 . Motive fluid and air combine and exit vacuum providing device  24  via diverging section  33 . In diverging section  33 , pressure recovers to a higher third pressure which is a higher pressure than the pressure in the second pressure region. 
     It should be noted that the presence of valve  362  presents opportunities to improve diagnoses of a disconnected duct as compared to locating valve  362  external to boost chamber  46  or engine air inlet  42 . For example, if valve  362  is housed in boost chamber  46 , valve  362  may be opened or closed during boost conditions. If a disconnected duct is present at converging section  35 , a compressor loss may occur when the valve  362  is open, but not when it is closed. If valve  362  is housed within engine air inlet  42 , a lack of CIP vacuum at high air flow may occur if valve  362  is open, but not when valve  362  is closed. 
     Thus, the system of FIGS.  1  and  3 - 5 B provides for a system that provides vacuum for a vehicle, comprising: an engine including an air intake passage; and a vacuum generating device including a motive fluid inlet section, a diverging discharge section positioned within the air intake passage, and a suction inlet. The system includes where the vacuum generating device is an ejector. The system includes where the vacuum generating device is a venturi. 
     In some examples, the system further comprises an air compressor positioned along the air intake passage and providing air to the motive fluid inlet. The system includes where the diverging discharge section is positioned upstream of an air inlet of the air compressor. The system includes where the suction inlet is in pneumatic communication with a vacuum reservoir that supplies vacuum to vacuum consumers of the vehicle. The system further comprises a controller, the controller including non-transitory executable instructions to diagnose leaks of the vacuum generating device. The system includes where the discharge section form a portion of a wall of the air intake passage. 
     The system of FIGS.  1  and  3 - 5 B provides for a system that provides vacuum for a vehicle, comprising: an engine including an air intake passage; a vacuum generating device including a motive fluid inlet section, a diverging discharge section completely positioned within the air intake passage, a throat section completely positioned within the air intake passage, and a suction inlet; and a controller including non-transitory executable instructions to diagnose leaks of the vacuum generating device. The system includes where the controller includes instructions for determining leaks in the motive fluid inlet section and suction, the controller not including instructions for determining leaks in the discharge section. The system includes where the controller includes additional instructions for determining leaks in the air intake passage instead of the discharge section. 
     In some examples, the system further comprises a compressor positioned along the air intake passage, and where the motive fluid inlet section extends from upstream of the compressor to downstream of the compressor. The system further comprises a valve positioned along a length of the motive fluid inlet section. The system includes where the vacuum generating device is an ejector or a venture. 
     Referring now to  FIG. 6 , a method for leak testing a vacuum providing device is shown. The method of  FIG. 6  may be stored in non-transitory memory as executable instructions of controller  12  in  FIG. 1 . The method of  FIG. 6  may be applied to a system as described in  FIGS. 1 ,  3 ,  4 ,  5 A, and  5 B. 
     At  602 , method  600  judges whether or not to diagnose a vacuum providing device for leaks. The vacuum providing device may be an ejector or a venturi. The vacuum providing device may be diagnosed for leaks when selected conditions are met. For example, method  600  may judge to perform a diagnostic leak test after a threshold amount of time between vacuum device leak tests has been exceeded. In another example, a diagnostic leak test of the vacuum device may be performed when vacuum is not being produced at a desired rate. If method  600  judges that a diagnostic vacuum device leak test is to be performed, the answer is yes and method  600  proceeds to  604 . Otherwise, the answer is no and method  600  proceeds to exit. 
     At  604 , method  600  determines leakage at a suction inlet of the vacuum providing device and at a vacuum line between the vacuum providing device and a vacuum reservoir. In one example, a valve is opened to start flow of a motive fluid through the vacuum providing device. The motive fluid may be air and the air may be compressed via a turbocharger. All vacuum consumers are commanded to a closed state and pressure within the vacuum reservoir is sensed by a pressure sensor. Air is drawn from the vacuum reservoir to the vacuum providing device, provided limited leakage is present. The motive fluid is returned to the engine with air from the vacuum reservoir at a location upstream of the compressor via a diverging discharge section of a vacuum generating device positioned within an engine air inlet. If less than a threshold amount of vacuum develops in the vacuum reservoir, it may be determined that there is a leak at the suction port of the vacuum providing device. Method  600  proceeds to  606  after leak testing of the suction port is performed. 
     At  606 , method  600  determines leakage of a converging section of a vacuum providing device. In one example, a compressor is operated at a steady speed while throttle position is constant and when engine speed is constant. If less than a desired pressure develops downstream of the compressor, it may be determined that there is a leak in the converging section of the vacuum providing device. Further, in some examples, two conditions including pressure less than a threshold downstream of the compressor and vacuum being provided at less than a threshold rate may be conditions for determining leakage of a converging section of a vacuum providing device. Note that for some systems which include an ejector, the converging section may include a chest area of the ejector. Method  600  proceeds to  608 . 
     Note that the suction inlet and converging section may be outside of the engine air inlet so that any leaks in the suction inlet and converging section are exposed to atmosphere. 
     At  608 , method  600  may determine leakage of a diverging section of a vacuum providing device. Alternatively, in some examples method  600  may not provide instructions for determining leakage of the diverging section of the vacuum providing device because the vacuum providing device is positioned within the engine air intake inlet as shown in  FIGS. 3 and 4 . Since the vacuum providing device diverging section is within the engine air inlet passage, leaks are directed from the vacuum providing device diverging discharge section to the engine air inlet passage. If method  600  includes instructions for determining leakage in the vacuum providing device diverging section, a pressure or flow rate in the engine intake inlet upstream of the compressor may be compared to a threshold engine intake pressure or flow rate at constant engine speed, constant boost pressure chamber pressure, constant throttle position, and constant compressor flow. If the engine intake pressure is less than a threshold pressure or if the engine intake flow rate is greater than a threshold flow rate, method  600  may judge that a leak in the vacuum providing device diverging section is present. In this way, method  600  determines leaks in an air intake passage for determining leaks from the discharge section to atmosphere. 
     If a leak is determined at  604 ,  606 , or  608 , method  600  provides an indication to the driver to service the engine. Further, method  600  may store leak information in memory. Method  600  exits after performing the leak tests. 
     Thus, the method of  FIG. 6  provides a method for providing vacuum for a vehicle, comprising: drawing an amount of air from a vacuum reservoir via a low pressure region of a vacuum generating device; and supplying the amount of air to an engine air intake passage via a diverging discharge section of the vacuum generating device positioned within the engine air intake passage. The method further comprises diagnosing leaks from the vacuum generating device that are outside of the engine air intake passage. The method further comprises providing motive fluid to the vacuum generating device via a compressor. The method includes where the amount of air is provided at a location upstream of an inlet of the compressor. The method further comprises directing leaks from the diverging discharge section to the engine air intake passage. The method includes where the amount of air is combined with air originating from the engine air intake system before being expelled from the diverging discharge section. 
     As will be appreciated by one of ordinary skill in the art, the methods described in  FIG. 6  may represent one or more of any number of processing strategies such as event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various steps or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Likewise, the order of processing is not necessarily required to achieve the objects, features, and advantages described herein, but is provided for ease of illustration and description. Although not explicitly illustrated, one of ordinary skill in the art will recognize that one or more of the illustrated steps or functions may be repeatedly performed depending on the particular strategy being used. In addition, the terms aspirator or venturi may be substituted for ejector since the devices may perform in a similar manner. 
     This concludes the description. The reading of it by those skilled in the art would bring to mind many alterations and modifications without departing from the spirit and the scope of the description. For example, single cylinder, I2, I3, I4, I5, V6, V8, V10, V12 and V16 engines operating in natural gas, gasoline, diesel, or alternative fuel configurations could use the present description to advantage.

Technology Category: y