Abstract:
An aspirator for a brake system is provided having integrated functions of a flow bypass and a check valve for automotive applications to achieve various suction flow openings in response to different engine operating conditions to enhance brake boost performance. The brake system includes a brake vacuum booster, an engine having an intake manifold, an aspirator having a movable convergence nozzle, the aspirator being connected to the manifold, and a vacuum line connecting the booster to the aspirator. The aspirator includes a body having an interior end wall. A biasing element such as a spring is provided between the movable convergence nozzle and the interior end wall of the aspirator body. The body of the aspirator has an air flow path having an upstream area and a downstream area. The movable convergence nozzle is positioned in the upstream area of the flow path.

Description:
TECHNICAL FIELD 
     The disclosed inventive concept relates generally to intake manifolds for internal combustion engines. More particularly, the disclosed inventive concept relates to an aspirator having integrated functions of a flow bypass and a check valve to enhance brake boost performance. 
     BACKGROUND OF THE INVENTION 
     Brake systems for vehicles rely on a vacuum brake booster connected to the vehicle&#39;s intake manifold. The total air flow rate into the intake manifold at engine idle and low load conditions can be difficult to control. A typical response to this situation is to provide a control valve having an expensive electric actuator. The control valve and control system is needed to shut down motive flow during engine low load and idle conditions. 
     Another response to this situation is to position an aspirator between the vacuum brake booster and the manifold. The aspirator provides a narrow flow introduction gap from the air suction flow to the main flow (the motive flow) that functions at a low vacuum pressure all the way to negative 60 kPa. 
     Under some engine operation conditions (such as during engine idle), pressure inside the brake boost tank may be higher than intake manifold. The narrow gap of the aspirator prevents a high flow rate from the boost tank to the intake manifold. Accordingly, a separate flow bypass is required to quickly flow air out of brake boost tank to achieve desired performance. 
     The separate flow bypass required by known brake arrangements introduces an additional component that adds cost to the arrangement. In addition, the requirement for the separate flow bypass introduces another element into the vehicle braking system that is subject to failure. Furthermore, the addition of a separate flow bypass adds an additional challenge to engine compartment packaging. 
     Thus, known brake systems that include aspirators are subject to improvement. Accordingly, a brake system for use with a vehicle that provides an advantage over known systems remains wanting. 
     SUMMARY OF THE INVENTION 
     The disclosed inventive concept overcomes the problems associated with known brake boost systems. In general, the disclosed inventive concept provides an aspirator for a brake system having integrated functions of a flow bypass and a control valve for automotive applications to achieve various suction flow openings in response to different engine operating condition to enhance brake boost performance. 
     The disclosed inventive concept provides a brake system for a vehicle that includes a brake vacuum booster, an engine having an intake manifold, an aspirator having a movable convergence nozzle, the aspirator being connected to the manifold, and a vacuum line connecting the booster to the aspirator. The aspirator includes a body having an interior end wall. A biasing element such as a spring is provided between the movable convergence nozzle and the internal end wall of the aspirator body. 
     The body of the aspirator has an air flow path having an upstream area and a downstream area. The movable convergence nozzle is positioned in the upstream area of the flow path. The aspirator is connected to the intake manifold at an inlet boss. 
     The disclosed inventive concept achieves a reduction in production costs by eliminating the bypass flow passage and the associated check valve by providing a sufficient suction flow rate under low vacuum pressure conditions. 
     The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
         FIG. 1  is a diagrammatic illustration of an existing arrangement of an aspirator in relation to a brake booster and the intake manifold of a vehicle engine; 
         FIG. 2  is a diagrammatic illustration of an arrangement of an aspirator according to the disclosed inventive concept in relation to a brake booster and the intake manifold of a vehicle engine 
         FIG. 3  illustrates a sectional view of an integrated multi-function aspirator according to the disclosed inventive concept under normal operating conditions; and 
         FIG. 4  illustrates a sectional view of the integrated multi-function aspirator according to the disclosed inventive concept under a deep vacuum condition. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     As those of ordinary skill in the art will understand, various features of the embodiments illustrated and described with reference to any one of the Figures may be combined with features illustrated in one or more other Figures to produce alternative embodiments that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present disclosure may be desired for particular applications or implementations. 
       FIG. 1  illustrates a traditional and known brake boost system layout while  FIGS. 2 through 4  illustrate the brake boost and aspirator according to the disclosed inventive concept. It is to be understood that the arrangement and illustrated shapes of the components of the disclosed inventive concept are suggestive and are not intended as being limiting as other variations of the disclosed inventive concept may be possible without deviating from the spirit and scope of the concept as illustrated, described and claimed. 
     Referring to  FIG. 1 , a diagrammatic illustration of an existing arrangement of a brake boost system is illustrated. The system, generally illustrated as  10 , includes a vacuum booster assembly  12  and an engine  14  having an intake manifold  16 . The engine  14  includes an exhaust manifold  18  associated with a three-way catalytic converter  20  and a muffler  22 . The intake manifold  16  is associated with a throttle body  24  and a charge air cooler  26 . Ambient air  28  enters the charge air cooler  26  for delivery to the throttle body  24 . 
     Between the vacuum booster assembly  12  and the intake manifold  16  is a flow line  30  having a check valve  32 . The flow line  30  includes a booster-to-aspirator portion  34  and an aspirator-to-intake manifold portion  36 . Also between the vacuum booster assembly  12  and the intake manifold  16  is a flow bypass line  38  having a check valve  40 . 
     The flow line  30  further includes an aspirator  42 . The aspirator  42  includes an aspirator intake end  44  into which ambient, motive flow air enters and an aspirator output end  46 . A suction flow introduction gap  48  is formed within the aspirator  42 . The suction flow introduction gap  48  is fluidly associated with the booster-to-aspirator portion  34  of the flow line  30 . The suction flow introduction gap  48  is also fluidly disposed between the aspirator intake end  44  and the aspirator output end  46 . 
     Referring to  FIG. 2 , a diagrammatic illustration of a brake boost system incorporating the aspirator design according to the disclosed inventive concept is illustrated. The system, generally illustrated as  50 , includes an engine  54  having an intake manifold  56 . The engine  54  includes an exhaust manifold  58  associated with a three-way catalytic converter  60  and a muffler  62 . The intake manifold  56  is associated with a throttle body  64  and a charge air cooler  66 . Ambient air  68  enters the charge air cooler  66  for delivery to the throttle body  64 . 
     Between the vacuum booster assembly  52  and the intake manifold  56  is a vacuum booster flow line  70  having a flow line split  72 . The flow line split  72  divides the flow line into two flow paths, a primary vacuum booster flow path  74  having a primary vacuum booster flow path check valve  76  and a secondary vacuum booster flow path  78  having a secondary vacuum booster flow path check valve  80 . 
     Both the primary vacuum booster flow path  74  and the secondary vacuum booster flow path  78  are fluidly connected to an aspirator  82  having integrated flow bypass and control valve functions according to the disclosed inventive concept. The aspirator  82  is attached to the intake manifold  56  by a mounting boss  84  attached to the intake manifold  56  by, for example, welding. The aspirator  82  according to the disclosed inventive concept avoids the need for a separate flow bypass line as is known in the art and as is discussed above in relation to the prior art illustrated in  FIG. 1 . 
       FIGS. 3 and 4  illustrate in section views the aspirator  82  under different operating conditions. Particularly, the aspirator  82  illustrated in  FIG. 3  is shown under normal operating conditions in which P vacuum &lt;P manifold . In  FIG. 4 , on the other hand, the aspirator  82  illustrated in  FIG. 4  is shown under engine low load and idle conditions in which P vacuum &gt;P manifold . 
     Referring to  FIG. 3 , the aspirator  82  includes an aspirator body  84  having a primary vacuum inlet  86  attached to the primary vacuum booster flow path  74  and a secondary vacuum inlet  88  attached to the secondary vacuum booster flow path  78 . The aspirator body  84  includes a divergence nozzle  89 . The primary vacuum inlet  86  and the secondary vacuum inlet  88  provide the vacuum suction flow (p vacuum ) to the aspirator  82 . 
     The secondary vacuum booster flow path  78  terminates in a cavity  90 . The cavity  90  is in fluid relation to a central bore  92  centrally formed within the divergence nozzle  89  having a narrow inlet  94  and a conical outlet  96  via a pathway  97 . 
     The aspirator body  84  further includes a pair of opposed atmosphere inlets  98  and  98 ′ into which streams of ambient air  100  and  100 ′ flow. An air filter (not shown) is attached to the opposed atmosphere inlets  98  and  98 ′. The opposed atmosphere inlets  98  and  98 ′ are located in the upstream area of the central bore  92 . 
     Formed within the upstream end of the aspirator body  84  is an axial bore  102  having a downstream wall  104  and an opposed upstream wall  105 . A movable convergence nozzle  106  is fluidly associated with the primary vacuum inlet  86 . The movable convergence nozzle  106  includes a wide inlet end  108  and a narrow, conical outlet end  110 . Extending from the movable convergence nozzle  106  are stoppers  112  and  112 ′. The stoppers  112  and  112 ′ may be of any configuration, such as a ring. 
     Disposed between the end wall  104  of the axial bore  102  and the stoppers  112  and  112 ′ is a pair of pre-loaded biasing elements  114  and  114 ′. The pre-loaded biasing elements  114  and  114 ′ are illustrated as being in the form of springs, although other biasing elements would be suitable as well. The movable convergence nozzle  106  is located in the upstream area of the aspirator body  84  while the pre-loaded biasing elements  114  and  114 ′ urge the movable convergence nozzle  106  in the upstream direction. 
     Under normal operating conditions as illustrated in  FIG. 3  where P vacuum &lt;P manifold , the movable convergence nozzle  106  is urged away from the downstream divergence nozzle  89  and upstream by the pre-loaded biasing pre-loaded elements  114  and  114 ′ until the stoppers  112  and  112 ′ abut the upstream wall  105 . In this position, the movable convergence nozzle  106  is spaced apart from the narrow inlet  94  of the central bore  92  of the divergence nozzle  89 . Because of this spacing, an incoming flow of air from both of the opposed atmosphere inlets  98  and  98 ′ is permitted that joins the flow of brake vacuum reservoir air from the primary path  74  entering the primary vacuum inlet  86  as well as from the secondary path  78  entering the secondary vacuum inlet  88 . The comingled air enters the intake manifold  56 . 
     As illustrated in  FIG. 3 , the position of the convergence nozzle  108  results in a pressure difference between the atmosphere and the intake manifold  56  that drives motive flow and creates a low static pressure at the narrow, conical outlet end  110 . As the static pressure at the narrow, conical outlet end  110  is lower than the pressure inside of the vacuum booster assembly  52 , air inside of the brake reservoir starts to flow through the primary vacuum booster flow path  74  and the secondary vacuum booster flow path  78  towards the intake manifold  56 . Accordingly, a vacuum is generated inside of the vacuum booster assembly  52 . 
     However, during other engine operating conditions such as under conditions of very low pressure in the intake manifold  56  where P vacuum &gt;P manifold , intake manifold pressure is lower than vacuum pressure inside of the vacuum booster assembly  52 . Higher pressure in the movable converge nozzle  106  overcomes the resistive force of the pre-loaded biasing elements  114  and  114 ′ and pushes the movable converge nozzle  106  downstream toward the divergence nozzle  89  until the conical outlet end  110  comes into contact with the narrow inlet  94  of the central bore  92  of the divergence nozzle  89 , thus closing shut the motive flow path. As a result of the change of flow path created by movement of the movable convergence nozzle  106  in the downstream direction, air inside of the vacuum booster assembly  52  flows through the primary vacuum booster flow path  74  and the secondary vacuum booster flow path  78  to the intake manifold  56 . Force balance can be optimized through resizing of the pre-loaded biasing elements  114  based on engine operation condition and applications. 
     The disclosed invention as set forth above overcomes the challenges faced by known brake boost systems by eliminating the need for an additional bypass line and by eliminating an expensive control valve and an associated actuator. However, one skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.