Abstract:
An integral vacuum generator system for an internal combustion engine includes a throttle body and intake manifold defining a bypass passage which is connected with a vacuum manifold by both a venturi and a direct vacuum supply passage. Vacuum flow through the venturi and the direct vacuum supply passage are controlled by check valves.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an integral vacuum generator system for an internal combustion engine in which the vacuum generator is integrated with an air induction throttle body and intake manifold. 
     2. Disclosure Information 
     Vehicles having vacuum operated brake boosters require a significant vacuum signal to provide the desired pedal assist. Under some operating conditions, and with certain engines, engine vacuum may be insufficient to meet the required level of brake boost without a vacuum enhancer or external vacuum source. US Patent Publication 2006/0016477 A1, which is assigned to the assignee of the present invention, discloses a vacuum enhancing check valve which is intended to provide additional vacuum with a unit which is mounted externally of a brake booster. The system shown in the &#39;477 publication presents a potential issue, concerning packaging space, in crowded engine compartments. Other known types of vacuum intensifiers are positioned between an automotive brake booster and an internal combustion engine intake. Such intensifiers are connected with hoses to the brake booster and intake. Such devices however, suffer from increased vacuum leak paths, which are troublesome to diagnose and correct. 
     It would be desirable to provide an integral vacuum generator for a vehicular engine which is packaged efficiently upon the engine by integrating the vacuum generator with existing engine hardware, while simultaneously minimizing the number of potential vacuum leak paths. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the present invention, an internal combustion engine includes an intake manifold and a throttle body having a main passage connected with the intake manifold. The throttle body has a throttle plate for controlling airflow through the main passage and the intake manifold. A bypass passage has a first portion formed in the throttle body, and a second portion formed integrally with the intake manifold. A venturi formed in the second portion of the bypass passage has a vacuum passage extending into a vacuum manifold. A direct vacuum supply passage extends from the second portion of the bypass passage into the vacuum manifold. According to another aspect of the present invention, a first check valve is positioned in a valve chamber formed in the venturi vacuum passage between the venturi and the vacuum manifold, and a second check valve is positioned in a valve chamber formed in the direct vacuum supply passage between the second portion of the bypass passage and the vacuum manifold. 
     According to another aspect of the present invention, the intake manifold and the bypass passage are preferably molded integrally into a first assembly, and the vacuum manifold, the venturi vacuum passage, and the direct vacuum supply passage are molded integrally as a second assembly, with the first and second assemblies being joined after molding. 
     It is an advantage of a system according to the present invention that the potential for vacuum leaks is greatly mitigated, as compared with known vacuum intensifier devices. 
     It is another advantage of a system according to the present invention that the present integral vacuum generator requires very little package space within the underhood environment of a vehicle. 
     Other advantages, as well as features of the present invention, will become apparent to the reader of this specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic representation of a vehicular internal combustion engine having an integral vacuum generator system according to the present invention. 
         FIG. 2  is a cutaway of the present integral vacuum generator, shown in a closed throttle operating mode. 
         FIG. 3  is similar to  FIG. 2 , but shows the present integral vacuum generator system operating in an open throttle mode. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in  FIG. 1 , according to an aspect of the present invention, engine  10  has an integral vacuum generator system,  12 , which is mounted to intake manifold  14  and throttle body  18 . Throttle body  18  is also connected with airflow meter  24  and air cleaner,  16 .  FIG. 1  also shows integral vacuum generator system  12  as being connected with brake booster  32  by hose  51 . 
       FIGS. 2 and 3  illustrate various component parts and passages of integral vacuum generator  12 . Throttle body  18  has a main passage,  20 ; airflow through passage  20  is controlled by rotatable throttle plate  22 . Throttle body  18  is bolted or otherwise attached to intake manifold  14 . Note from  FIG. 1  that mass air meter  24  is interposed between air cleaner  16  and throttle body  18  such that all of the air flowing into engine  10  passes through the mass air meter  24 , so as to allow precise control of the air-fuel ratio of engine  10 , regardless of the division of airflow between the various passages defining the current vacuum generator system. 
     As further shown in  FIGS. 2 and 3 , throttle body  18  has a bypass passage, with a first portion including a radially extending passage,  26   a , which transforms into an axial segment,  26   b , which is itself in communication with a second portion,  26   c , formed integrally with intake manifold  14 . Venturi  30  is formed in second portion  26   c  of bypass passage  26 . Venturi  30  has a throat,  30   a , with a vacuum passage,  34 , extending radially therefrom. Passage  34  communicates the vacuum generated by venturi  30  with a valve chamber,  38 , which allows the vacuum to be communicated to a vacuum manifold,  50 . Check valve disc  36  is positioned within valve chamber  38 . The function of valve disc  36  will be explained below. 
     Direct vacuum supply passage  42  extends radially into valve chamber  46 , which is occupied in part by check valve disc  44 , which controls flow from vacuum manifold  50  into passage  42 . 
     Valve discs  36  and  44  are not spring loaded. Rather, the discs float in their respective valve chambers and when not adhering to the portions of the chambers adjoining vacuum manifold  50 , remain poised upon serrated pedestals  54  and  58 . These pedestals allow airflow past valve discs  36  and  44 , respectively, when the discs are positioned upon their individual pedestals. 
     When the present integral vacuum generator is being operated with throttle plate  22  in the closed position of  FIG. 2 , the vacuum within intake manifold  14  is at a higher level, which is communicated through direct passage  42  to valve chamber  46 . Thus, valve disc  44  will be open, allowing airflow from a brake booster or other vacuum-consuming device, such as booster  32  of  FIG. 1 , to enter engine  10 . In other words, a high level of vacuum will be present within vacuum manifold  50 . This vacuum signal will cause valve discs  36  and  44  to be in the locations shown in  FIG. 2 , and vacuum will be furnished to booster  32 . In the operational mode of  FIG. 2 , disc  36  is seated against port  37 , which prevents vacuum flow into valve chamber  38 . 
     In the configuration of  FIG. 3 , throttle plate  22  is open, and vacuum within intake manifold  14  is accordingly less. However, airflow through engine  10  is higher when the throttle plate  22  is open and engine  10  has accelerated, and air flowing through venturi  30  produces a usable vacuum signal at throat  30   a  which is communicated by means of vacuum passage  34  and valve chamber  38  to vacuum manifold  50 . The vacuum signal which opens valve disc  36  will be communicated by manifold  50  to valve disc  44  by means of port  47 , thereby causing valve disc  44  to be positioned in a sealing position with respect to port  47 . Taken together, these check valve positions allow vacuum to build within booster  32 . 
     In a preferred embodiment, intake manifold  14 , including bypass passages  26   c  and  26   d  are molded integrally from resin. This allows valve chambers  38  and  46 , which may be formed integrally with vacuum manifold  50 , to be friction or solvent welded to intake manifold  14 . Those skilled in the art will appreciate however, that the present vacuum generator system could be configured as a single casting combining the vacuum generator with the throttle body and intake manifold. 
     Although the present invention has been described in connection with particular embodiments thereof, it is to be understood that various modifications, alterations, and adaptations may be made by those skilled in the art without departing from the spirit and scope of the invention set forth in the following claims.