Abstract:
A sensor for an engine manifold is provided that includes a sensing component positioned within the engine manifold and responsive to a condition, such as temperature or pressure, within the engine manifold. The sensor includes a shield partially surrounding the sensing component upstream of the sensing component in flow within the manifold, which includes exhaust gases and manifold intake air. The shield does not surround a downstream side of the sensing component. The shield minimizes contamination of the sensing component by contaminants within the exhaust gases or manifold intake air, without compromising responsiveness of the sensing component to changes in the sensed condition, as the sensing component is still directly open to the manifold air (i.e., the exhaust gases and intake air).

Description:
TECHNICAL FIELD 
     The invention relates to a sensor for an engine manifold having a sensing component positioned in the manifold with a shield partially surrounding the sensing component upstream of the component. 
     BACKGROUND OF THE INVENTION 
     Exhaust gas recirculation is used to allow a controlled amount of oxygen depleted exhaust gas to be mixed with intake air flowing to an engine for combustion in the cylinders of the engine. The engine manifold also typically includes sensors for sensing manifold pressure, manifold air temperature, or both, or for sensing other manifold conditions. Particulate and other contaminants in the recirculated air tend to buildup on the sensors, reducing their efficiency and accuracy. The sensing elements of some sensors have been encased to address this problem; however, encasing the sensing element may reduce its responsiveness to changing manifold conditions. 
     SUMMARY OF THE INVENTION 
     A sensor for an engine manifold is provided that includes a sensing component positioned within the engine manifold and responsive to a condition within the engine manifold, such as temperature or pressure. For example, the sensor may be a manifold air pressure (MAP) sensor and the sensing component may be a pressure port. Alternatively, the sensor may be a temperature manifold air pressure sensor (TMAP), and the sensing component may be a temperature sensing element. Still alternatively, the sensor may be simply be a temperature sensor, with the sensing component being a temperature sensing element. 
     The sensor also includes a shield partially surrounding the sensing component upstream of the sensing component in flow within the manifold. The shield does not surround a downstream side of the sensing component. The shield minimizes contamination of the sensing component by contaminants within the exhaust gas and intake air, without compromising responsiveness of the sensing component to changes in the sensed condition, as the sensing component is still directly open to the manifold air. 
     The sensor may include a sensor body from which the sensing component and the shield extend in a common direction. A gap is defined between the sensing component and the shield. The gap allows manifold air to surround the sensing component, thereby increasing responsiveness of the sensing component to the sensed condition. 
     The sensor may be part of an engine assembly, such as a diesel engine assembly, in which the intake manifold is operatively connected to an engine block for providing air for combustion within an engine cylinder defined by the engine block. The engine assembly also includes an exhaust gas recirculation system that routes engine exhaust from the engine cylinder to the intake manifold. The sensing component may be configured to sense and generate a sensor signal that is correlated with the sensed condition within the intake manifold. The sensor signal is sent to an electronic controller which controls the engine assembly based at least in part on the sensed condition. 
     Thus, by shielding the upstream side of the sensing component, contaminants in the exhaust gases and intake manifold air are blocked from direct impingement on the sensor component. Furthermore, because the shield does not surround the downstream side of the sensor component, the sensor component is exposed to the manifold air (i.e., the intake manifold air and the exhaust gases) and can respond in an efficient and timely manner to changing sensed conditions. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an engine assembly including a manifold sensor; 
         FIG. 2A  is a schematic perspective illustration of the manifold sensor of  FIG. 1 ; 
         FIG. 2B  is a schematic cross-sectional illustration of the manifold sensor and shield of  FIG. 2A  taken at the arrows  2 B in  FIG. 2A ; 
         FIG. 3  is a schematic side view illustration of a shield of the manifold sensor of  FIG. 2A , with the shield rotated with respect to  FIG. 2A ; 
         FIG. 4  is a schematic perspective illustration of an alternative embodiment of a manifold sensor for use in the engine assembly of  FIG. 1 ; and 
         FIG. 5  is a schematic side view illustration of a shield of the manifold sensor of  FIG. 4 , with the shield rotated with respect to  FIG. 4 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, wherein like reference numbers refer to like components, an engine assembly  10  is illustrated that includes an engine, represented in part by an engine block  12 . Air (represented by arrow A) is drawn into an intake manifold  14  through a throttle  16 . The intake manifold  14  is connected with the engine block  12 . The throttle  16  regulates mass air flow into the intake manifold  14 . Air within the intake manifold  14  is distributed into cylinders  18  (only one shown) that are formed or machined in the cylinder block  12 . 
     The engine assembly  10  includes an intake valve  22  that selectively opens and closes to enable the air/fuel mixture to enter the cylinder  18 . The intake valve position is regulated by an intake camshaft  24 . A piston (not shown) compresses the air/fuel mixture within the cylinder  18 . The piston drives the crank shaft (not shown) to produce drive torque. Combustion exhaust within the cylinder  18  is forced out of an exhaust port when an exhaust valve  28  is in an opened position. The exhaust valve position is regulated by an exhaust camshaft  30 . Although only a single intake and exhaust valve  22 ,  28 , respectively, are illustrated connected with the cylinder  18 , multiple intake and exhaust valves may be used per cylinder. 
     The engine assembly  10  may include an intake cam phaser  32  and exhaust cam phaser  34  that respectively regulate the rotational timing of the intake and exhaust camshafts  24 ,  30 . 
     The engine assembly  10  also includes an exhaust gas recirculation EGR system  36 . The remainder of exhaust flow, labeled B, is exhausted from the engine. The EGR system  36  includes an EGR valve  38  that regulates a portion of exhaust flow back into the intake manifold  14 . The EGR system is generally implemented to regulate emissions. 
     Functioning of the engine assembly  10 , such as opening and closing of the intake and exhaust valves  22 ,  28  and positioning of the throttle  16 , is at least partly controlled by the electronic controller  43 , also referred to as a control module. The electronic controller  43  responds to a sensor signal  41  received from a manifold sensor  40 . The electronic controller  43  also responds to sensor signals received from a throttle position sensor  42 , an intake air temperature sensor  44 , an engine coolant temperature sensor  50 , and an engine speed sensor  52 . The intake air temperature sensor  44  is responsive to a temperature of the intake air (indicated flowing in the direction of the arrow under the mass airflow sensor  46  in  FIG. 1 ) and generates an intake air temperature signal. The mass airflow sensor  46  is responsive to the mass of the intake airflow and generates a mass airflow signal. The engine coolant temperature sensor  50  is responsive to a coolant temperature and generates an engine temperature signal. An engine speed sensor  52  is responsive to a rotational speed of the engine and generates an engine speed signal. Each of the signals generated by the sensors  40 ,  42 ,  44 ,  46 ,  50 ,  52  is received by the control module  43 . The control module  43  also regulates a fuel injection system  20 , the camshaft phasers  32 ,  34 , and the EGR system  36 . 
     The manifold sensor  40  is responsive to a condition within the intake manifold  14  associated at least in part with manifold airflow  48 , and generates the sensor signal  41 . The recirculated exhaust gas in the EGR system enters the manifold  14  and flows in a direction indicated by arrows representing airflow  48  toward the manifold sensor  40 . 
     It should be appreciated that the manifold sensor  40  may be a manifold air pressure MAP sensor, a temperature and manifold air pressure TMAP sensor, a manifold temperature sensor, or any other type of sensor sensing a condition within the manifold  14 . 
     Contaminates  54  enter into the intake manifold  14  with the intake air and the recirculated exhaust gases and are carried toward the manifold sensor  40  in the direction of flow  48  within the manifold. The contaminants  54  may be, for example, exhaust gas particulate, oil pullover, water/ice or other impurities. To prevent the build up of contaminates  54  on an operative sensing component of the sensor  40 , the sensor  40  is configured with a shield  56  in an upstream position with respect to the sensing element, as shown and described in detail with respect to  FIG. 2A . 
     Referring to  FIG. 2A , one embodiment of the manifold sensor  40  is shown that is a TMAP sensor. The manifold sensor  40  has a sensor body  60  from which both the shield  56  and a sensing component  62  extend. The sensor body  60  has a flange  64  configured to abut a wall  66  (see  FIG. 1 ) of the manifold  14 , with the sensing element  62  and shield  56  extending through an opening in the wall  66  in a common direction, generally perpendicular to the flow  48  shown in  FIG. 1 . Electronics within an upper portion  68  of the body  60  relay the signal  41  (see  FIG. 1 ) to the electronic controller  43 , as is known. In this embodiment, the sensing element  62  senses a temperature of the manifold cavity  61  of  FIG. 1 . 
     The sensing component  62  is supported by support structure  70 . The shield  56  partially surrounds the sensing component  62  on an upstream side  72  thereof. A downstream side  74  of the sensing component  62  is not surrounded by the shield  56 . As shown in  FIG. 3 , the shield  56  is a generally concave component defining a partial cavity  76  which opens toward the sensing component  62  and has a back surface  78  that faces the flow  48 . An end  79  protects the sensing component  62  from a direction perpendicular to the flow  48 . There is a gap  80  between the shield  56  and the downstream side  74  of the sensing component  62 . The gap  80  extends along the length of the sensing component  62  within the concave shield  56 , as best illustrated in  FIG. 2B , in which the support structure  70  and body  60  are removed for clarity. Thus, the entire sensing component  62  is open to the manifold cavity  61  of  FIG. 1 , and is not encased within (i.e., is not completely surrounded by) the shield  56 . 
     Referring to  FIG. 4 , another embodiment of a sensor  140  that may be used in place of sensor  40  of  FIGS. 1 and 2A  is illustrated. The sensor  140  is a TMAP sensor. The sensor  140  has a sensor body  160  from which both the shield  156  and a sensing component  162  extend. The sensor body  160  has a flange  164  configured to abut the wall  66  of  FIG. 1  with the sensing component  162  and shield  156  extending in a common direction through an opening of the wall  66  (see  FIG. 1 ) of the manifold  14 , generally perpendicular to the flow  48  shown in  FIG. 1 . Electronics within an upper portion  168  of the body  160  relay the signal  41  (see  FIG. 1 ) to the control module  43 . In this embodiment, the sensing component  162  senses a temperature of the manifold cavity  61  of  FIG. 1 . The sensor  140  also has a pressure sensing component  163  within a pressure port  165  located above the temperature sensing component  162  and in communication with a larger port area  166 . 
     The shield  156  partially surrounds the sensing component  162  on an upstream side  172  thereof. A downstream side  174  of the sensing component  162  is not surrounded by the shield  156 . Referring to  FIG. 5 , the shield  156  is a generally concave component defining a partial cavity  176  which opens toward the sensing component  162  of  FIG. 4  and has a back surface  178  that faces the flow  48  of  FIG. 1 . An end  179  protects the sensing component  162  from a direction perpendicular to the flow  48 . As illustrated in  FIG. 4 , there is a gap  180  between the shield  156  and the downstream side  174  of the sensing element  162 . The gap  180  extends along the length of the sensing element  162  within the concave shield  156  (i.e., gap  180  is substantially similar to gap  80  of  FIG. 2B ). Thus, the entire sensing component  162  is open to the manifold cavity  61  of  FIG. 1 , and is not encased within the shield  156 . The pressure port  165  is also open to the manifold cavity  61  of  FIG. 1  via the larger port area  166 , and is not encased by the shield  156 . 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.