Patent Publication Number: US-2021190555-A1

Title: Air physical quantity sensor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation application of U.S. patent application Ser. No. 16/267,421 filed Feb. 5, 2019 which is a continuation of International Patent Application No. PCT/JP2017/030232 filed on Aug. 24, 2017, which designated the U.S. and claims the benefits of priority of Japanese Patent Application No. 2016-212114 on Oct. 28, 2016. The entire disclosure of all of the above applications are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an air physical quantity sensor for detecting a specific physical quantity of air flowing through a flow passage. 
     BACKGROUND 
     In an air physical quantity sensor, a sensor filter is fixed to a sensor cap having a cap window portion penetrating between the flow passage and the body opening portion. As a result, the sensor filter can suppress the deterioration of the sensor element in the body concave portion due to foreign matter in the air by filtering the air flowing into the body concave portion through the cap window portion and the body opening portion from the flow passage. 
     SUMMARY 
     An object of the present disclosure is to provide an air physical quantity sensor that suppresses separation of a sensor filter. 
     In aspects of the present disclosure, 
     an air physical quantity sensor for detecting a specific physical quantity related to air flowing in a flow passage, includes: 
     a sensor element configured to output a detection signal in accordance with the specific physical quantity, 
     a sensor body having a body recess in which the sensor element is houses, the body recess opening at a body opening portion, 
     a sensor substrate having a mounting surface on which a circuit element for processing a detection signal is mounted and being configured to hold the sensor body by the mounting surface, 
     a sensor cover having a cover window configured to communicate between the flow passage and the body opening portion, the sensor covering the sensor body, 
     a sensor filter which is interposed between the sensor body and the sensor cover and filters air flowing from the flow passage into the body recess through the cover window and the body opening portion, and 
     a potting resin body which is hardened in a state where the circuit element is sealed on the mounting surface and in which the sensor cover is embedded on an outer peripheral side of the sensor body. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a partial cross-sectional view, showing an air physical quantity sensor attached to an air flow detection unit in an internal combustion engine; 
         FIG. 2  is a perspective view, showing the air flow detection unit provided with the air physical quantity sensor in a first embodiment; 
         FIG. 3  is a perspective and partial cross-sectional view showing the air flow detection unit in the first embodiment; 
         FIG. 4  is a plan view showing an air physical quantity sensor according to a first embodiment. 
         FIG. 5  is a cross-sectional view showing the air physical quantity sensor in the first embodiment; 
         FIG. 6  is a cross-sectional view showing the sensor unit in the first embodiment; 
         FIG. 7  is a plan view showing the sensor unit in the first embodiment; 
         FIG. 8  is a schematic diagram showing a method for manufacturing the sensor unit in the first embodiment; 
         FIG. 9  is a schematic diagram showing a detailed configuration of the sensor unit in the first embodiment; 
         FIG. 10  is a schematic diagram showing a detailed configuration of the sensor unit in the first embodiment; 
         FIG. 11  is a schematic diagram showing a detailed configuration of a sensor filter in the first embodiment; 
         FIG. 12  is a cross-sectional view showing a sensor unit in a second embodiment; 
         FIG. 13  is a perspective view showing the sensor unit in the second embodiment; 
         FIG. 14  is a schematic view for explaining a method of manufacturing a sensor unit according to a second embodiment; 
         FIG. 15  is a cross-sectional view showing a sensor unit in a third embodiment; 
         FIG. 16  is a plan view showing the sensor unit in the third embodiment; 
         FIG. 17  is a schematic view for explaining a method of manufacturing the sensor unit in the third embodiment; 
         FIG. 18  is a cross-sectional view showing a sensor unit in a fourth embodiment; 
         FIG. 19  is a perspective view showing the sensor unit in the fourth embodiment; 
         FIG. 20  is a cross-sectional view showing a sensor unit in a fifth embodiment; 
         FIG. 21  is a plan view showing the sensor unit in the fifth embodiment; 
         FIG. 22  is a cross-sectional view showing a sensor unit in a sixth embodiment; 
         FIG. 23  is a plan view showing the sensor unit in the sixth embodiment; 
         FIG. 24  is a schematic diagram showing a detailed configuration of the sensor unit in the sixth embodiment; 
         FIG. 25  is a schematic diagram showing a detailed configuration of the sensor unit in the sixth embodiment; 
         FIG. 26  is a cross-sectional view showing a sensor unit in a seventh embodiment; 
         FIG. 27  is a plan view showing a sensor unit in the seventh embodiment; 
         FIG. 28  is a schematic diagram showing a detailed configuration of the sensor unit in the seventh embodiment; 
         FIG. 29  is a schematic diagram showing a detailed configuration of the sensor unit in the seventh embodiment; 
         FIG. 30  is a cross-sectional view showing a sensor unit in a eighth embodiment; 
         FIG. 31  is a schematic diagram showing a detailed configuration of the sensor unit in the eighth embodiment; 
         FIG. 32  is a schematic diagram showing a modified example of  FIG. 9 ; 
         FIG. 33  is a schematic diagram showing a modified example of  FIG. 10 ; 
         FIG. 34  is a schematic diagram showing a modified example of  FIG. 31 ; 
         FIG. 35  is a schematic diagram showing a modified example of  FIG. 24 ; 
         FIG. 36  is a schematic diagram showing a modified example of  FIG. 25 ; 
         FIG. 37  is a plan view showing a modified example of  FIG. 23 ; 
         FIG. 38  is a plan view showing a modified example of  FIG. 27 ; 
         FIG. 39  is a plan view showing a modified example of  FIG. 23 ; 
         FIG. 40  is a plan view showing a modified example of  FIG. 27 ; 
         FIG. 41  is a plan view showing a modified example of  FIG. 7 ; 
         FIG. 42  is a plan view showing a modified example of  FIG. 7 ; 
         FIG. 43  is a cross-sectional view showing a modified example of  FIG. 6 ; 
         FIG. 44  is a cross-sectional view showing a modified example of  FIG. 5 ; 
         FIG. 45  is a cross-sectional view showing a modified example of  FIG. 18 ; 
         FIG. 46  is a plan view showing a modified example of  FIG. 21 ; 
         FIG. 47  is a plan view showing a modified example of  FIG. 21 ; 
         FIG. 48  is a partial cross-sectional perspective view showing a modified example of  FIG. 3 ; 
         FIG. 49  is a cross-sectional view for explaining a modified example of  FIG. 48 ; 
         FIG. 50  is a cross-sectional view showing a modified example of  FIG. 6 ; and 
         FIG. 51  is a cross-sectional view showing a modified example of  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     In the following, embodiments of the present disclosure are described with reference to the accompanying drawings. In the description and in the drawings, identical or similar components bear the same reference numerals or characters. If a part of the features in each embodiment is explained, the remaining part of the features may apply to the remaining part of the features in other embodiments. In each embodiment, a combination of the features is disclosed in the specification, and in addition to the combination, the features in the embodiments may be combined, even if such combinations are not apparently disclosed in the specification. 
     First Embodiment 
     As shown in  FIG. 1 , an air physical quantity sensor  10  is applied to an air flow detection unit  2  in an internal combustion engine  1 .   tection unit  2  in an internal combustion engine  1 . 
     The air flow detection unit  2  is attached to an attachment opening  4   a  of an intake air duct  4  formed as an intake passage  3  in the internal combustion engine  1 . The air flow detection unit  2  is provided with a flow detection body  5  located in the intake passage  3 . As shown in  FIGS. 2 and 3 , the flow detection body  5  has a bypass passage  6  in a detection portion  5   a.  Along an arrow of the broken line shown in  FIGS. 1 and 3 , a part of the intake air flowing into a cylinder of the internal combustion engine  1  through the intake passage  3  is distributed in the bypass passage  6  from the intake passage  3 . 
     As shown in  FIG. 3 , the bypass passage  6  comprises a first passage portion  7  and a second passage portion  8 . The straight first passage portion  7  includes an inlet  7   a  and an outlet  7   b,  both of which open the intake passage  3 . In a direction of an arrow of the dashed line shown in  FIG. 3 , the first passage portion  7  introduces the intake air in a substantially same direction along the intake passage  3  from the inlet  7   a  to the outlet  7   b.  The curved second passage portion  8  comprises an inlet  8   a  facing a middle part of the first passage portion  7 , and an outlet  8   b  facing the intake passage  3 , such that the second passage portion  8  is branched from the first passage portion  7 . In the direction of the arrow of the dashed line shown in  FIG. 3 , the second passage portion  8  turns the intake air in an opposite direction with respect to the intake passage  3  and then flows the intake air in a same direction along the intake passage  3  between the inlet  8   a  and the outlet  8   b.    
     The flow detection body  5  further includes a flow sensor  9  and the above mentioned bypass passage  6 . A sensor element  9   a  of the flow sensor  9  is exposed to the second passage portion  8 . The sensor element  9   a  outputs a flow signal depending on an amount of intake air flowing in the second passage portion  8 . The flow sensor  9  includes a circuit module  9   b,  which calculates the amount of the intake air in the intake passage  3  based on the flow signal outputted from the sensor element  9   a.  The amount of intake air calculated by the circuit module  9   b  is transmitted to an engine control unit provided outside of the intake passage  3  via a signal transmission through a plurality of terminals  5   b  in the flow detection body  5 . The flow detection body  5  detects the amount of the intake air flowing in the intake passage  3  by means of the sensor element  9   a.    
     As shown in  FIGS. 1 and 2 , the air physical quantity sensor  10  is integrally provided with the air flow detection unit  2 . The air physical quantity sensor  10  is arranged outside of the bypass passage  6  such that the sensor  10  is exposed to the intake passage  3  referred to as flow passage. The air physical quantity sensor  10  is configured to have a predetermined width extending in the intake air flow direction in the intake passage  3  in the direction of the arrow of the dashed line shown in  FIG. 1 , and the air physical quantity sensor  10  is configured to be formed as thick belt shape extending in a vertical direction with respect to the intake air flow direction as a whole. X direction is defined as the intake air flow direction in the intake passage  3 . Z direction is defined as a longitudinal direction in which the air physical quantity sensor  10  extends in the vertical direction with respect to the flow direction. Y direction is defined as a vertical direction with respect to both X direction and Z direction. 
     As shown in  FIGS. 4 and 5 , the air physical quantity sensor  10  includes a sensor case  20 , a reinforced plate  30 , a sensor substrate  40 , a sensor unit  50 , a terminal  60 , a circuit module  70 , and a potting resin body  80 . For ease of understanding of the explanation, in  FIG. 4 , the potting resin body  80  is shown in a state in which most of the potting resin body  80  is cut. 
     The sensor case  20  is made of a hard resin, such as polyphenylene sulfide (PPS). The sensor case  20  is formed as thick belt shape, corresponding to a whole contour of the air physical quantity sensor  10 . The sensor case  20  has a connector portion  22  and a recess portion  24 . The connector portion  22  is provided at one end in Z direction as the longitudinal direction of the sensor case  20 . The recess portion  24  is provided on the other end side with respect to one end portion in the Z direction provided with the connector portion  22  in the sensor case  20 . The recess portion  24  faces in Y direction toward the flow detection body  5 , and the recess portion  24  has a bottomed rectangular shape in planar view in Y direction. After other components  30 ,  40 ,  50  and  60  of the air physical quantity sensor  10  are housed in the recess portion  24 , the potting resin body  80  is filled into the recess portion  24 . 
     The reinforced plate  30  is made of a metal, such as stainless steel. The reinforced plate  30  is formed as a narrow-width and short thin belt shape in comparison with the sensor case  20 . The reinforced plate  30  is positioned and fixed on a bottom surface  24   a  of the recess portion  24  in a surface contact state. The reinforced plate  30  is embedded by the potting resin body  80  in the recess portion  24 . 
     The sensor substrate  40  is made of a soft resin, such as polyimide, and is called as flexible printed board. The sensor substrate  40  is formed as a narrow-width and short shape in comparison with the sensor case  20 , and the sensor substrate  40  is formed as a narrow-width and long thin belt shape in comparison with the reinforced plate  30 . The sensor substrate  40  is positioned and fixed on a reinforced surface  30   a  of the reinforced plate  30  on the opposite side of the bottom surface  24   a  of the recess portion  24  in a surface contact state. The sensor substrate  40  is embedded by the potting resin body  80  in the recess portion  24 , and a part  40   a  of the sensor substrate  40  in Z direction as a longitudinal direction is reinforced by the reinforced plate  30 . The sensor substrate  40  is provided with a mounting surface  40   b  in a reinforced part  40   a,  which is formed as a planar surface positioned on the opposite side of the reinforced plate  30 . 
     The sensor unit  50  has a sensor element  54  which detects humidity representing a ratio of water vapor in the intake air. Humidity is referred to as specified physical quantity relating to the intake air flowing in the intake passage  3 . The sensor element  54  of the sensor unit  50  outputs a humidity signal, referred to as a detection signal in accordance with the humidity of the intake air as a detecting target. The sensor unit  50  is formed as a rectangular shape as a whole. The sensor unit  50  is mounted on the mounting surface  40   b  in the reinforced part  40   a  on the sensor substrate  40 . A part of the sensor unit  50  in Y direction is embedded by the potting resin body  80  in the recess portion  24 , and a remaining part of the sensor unit  50  in Y direction is exposed to the intake passage  3  positioned outside of the sensor case  20 . 
     A plurality of terminals  60  are provided. Each of the terminals  60  is made of a metal, such as phosphor bronze. Each of the terminals  60  is formed as a narrow-width and short thin belt shape in comparison with the sensor case  20 . Each of the terminals  60  is disposed substantially in parallel in X direction each other. A part  60   a  of each of the terminals  60  in Z direction is embedded in the sensor case  20  toward the connector portion  22  from the bottom wall  24   b  formed as the bottom surface  24   a  of the recess portion  24 . Other part  60   b  of each of the terminals  60  in Z direction is protruded toward outside of the sensor case  20  from the connector portion  22 . The other part  60   b  of each of the terminals  60  is electrically connected to the engine control unit via any one of the terminals  5   b  in the air flow detection unit  2 . It is preferable that each of the terminals  60  is formed as thin having a thickness of 0.2 mm (for example), and is functioned as a low thermal conductivity. So, a heat insulating function is obtained between an outside including the engine control unit, and the circuit module  70  and the sensor element  54  such that a detection error due to increasing of a temperature of the sensor element  54  can be suppressed. 
     The circuit module  70  is electrically connected to the sensor element  54  and each of the terminals  60  through a metal conductor provided on the sensor substrate  40 . The circuit module  70  includes a plurality of circuit elements  72  for processing a humidity signal outputted from the sensor element  54 . Each of the circuit elements  72  is mounted on the mounting surface  40   b  in the reinforced part  40   a  on the sensor substrate  40 . A control circuit  72   a  in the circuit elements  72  calculates the humidity of the intake air in the intake passage  3  based on the humidity signal. The humidity calculated by the control circuit  72   a  is transmitted to the engine control unit by means of the signal through each of the terminals  60 . 
     The potting resin body  80  is made of a hard thermoset resin, such as an epoxy resin or a polyurethane, etc. The potting resin body  80  covers almost of the recess portion  24 . So, the potting resin body  80  covers the mounting surface  40   b  such that all circuit elements  72  on the mounting surface  40   b  are sealed. An electrical short between the circuit elements  72  and a damage of the circuit elements  72  are suppressed because the circuit elements  72  are sealed. 
     Sensor Unit 
     The sensor unit  50  is explained in detail below. 
     As shown in  FIGS. 6 and 7 , the sensor unit  50  has a sensor body  52 , a sensor element  54 , a sensor cover  56 , and a sensor filter  58 . 
     The sensor body  52  according to  FIG. 6  is formed of a thermoset resin, such as an epoxy resin, etc. The sensor body  52  is formed as a rectangular shape having 6 (six) surfaces along each direction of X, Y and Z directions. One surface  52   b  of the sensor body  52  is positioned and fixed on the mounting surface  40   b  of the sensor substrate  40  in a surface contact state such that the sensor body  52  is held on the mounting surface  40   b.    
     The sensor body  52  has a body recess  53 . As shown in  FIGS. 6 and 7 , the body recess  53  is provided at a central portion in X and Z directions in the sensor body  52 . The body recess  53  opens in the opposite side of the sensor substrate  40  in Y direction, and is formed as a circle bottomed hole in planar view in Y direction. The body recess  53  is formed in the opposite surface  52   a  of the sensor body  52  with respect to the mounting surface  40   b,  and opens at a body opening portion  53   a.  The body recess  53  according to the first embodiment is formed as a truncated cone hole shape such that a diameter becomes gradually larger toward the body opening portion  53   a  from a bottom surface  53   b.    
     As shown in  FIG. 6 , the sensor element  54  senses the humidity of the intake air based on a change of a dielectric constant in a polymer film due to a predetermined correlation with respect to the humidity change of the intake air flowing in the intake passage  3 . The sensor element  54  is positioned and fixed on the bottom surface  53   b  separated from the body opening portion  53   a,  and the sensor element  54  is housed in the body recess  53 . The sensor element  54  is electrically connected to a metal conductor on the sensor substrate  40  through a metal conductor (not shown) which is embedded on a bottom wall  53   c  forming as the bottom surface  53   b  of the body recess  53  in the sensor body  52 . So, the sensor element  54  is configured to output a humidity signal, which varies electrically based on the sensed humidity to the circuit module  70  according to  FIGS. 4 and 5 . 
     As shown in  FIG. 6 , the sensor cover  56  is made of a hard resin, such as PPS or polybutylene terephthalate (PBT), in order to minimize a difference in thermal expansion coefficients with respect to at least the sensor case  20  and the potting resin body  80 . As shown in  FIGS. 6 and 7 , the sensor cover  56  opens in a side of the sensor substrate  40  in Y direction, and is formed as a bottomed rectangular shape in planar view in Y direction. The sensor cover  56  includes a cover peripheral wall portion  56   b  formed as a rectangular tube shape opening at an body opening portion  56   a,  and a bottom wall portion  56   c  formed as a rectangular plate shape closing the cover peripheral wall portion  56   b  in an opposite side of the body opening portion  56   a  in Y direction. The cover peripheral wall portion  56   b  and the bottom wall portion  56   c  are integrally formed. 
     An inner surface of the cover peripheral wall portion  56   b  is fitted to the sensor body  52  along Y direction. The cover peripheral wall portion  56   b  surrounds total outer surface of the sensor body  52 . As shown in  FIG. 6 , the cover peripheral wall portion  56   b  has the body opening portion  56   a  in an opposite side of the bottom wall portion  56   c  in Y direction. A part  56   d  of the cover peripheral wall portion  56   b  extending from the body opening portion  56   a  to the bottom wall portion  56   c  is positioned and fixed in the potting resin body  80 . The cover peripheral wall portion  56   b  is provided with an embedded portion  56   d , which is embedded outside of the sensor body  52  from the body opening portion  56   a  by the potting resin body  80 . 
     In order to manufacture the sensor unit  50 , as shown in  FIG. 8 , when the sensor cover  56  is embedded and fixed in the potting resin body  80 , a thermosetting resin  80   a  as a forming material of the potting resin body  80  fills into the recess portion  24  in a melting state and is cooled thereafter. At this time, in order to suppress the floating of the sensor cover  56  caused by the internal pressure of the injected thermosetting resin  80   a  and to continue to immerse the entire area of the embedded portion  56   d  in the thermosetting resin  80   a,  the load directed toward the bottom surface  24   a  side of the recess portion  24  is continuously acted on the sensor cover  56  as indicated by outlined arrows in  FIG. 8 . The thermosetting resin  80   a  is cured on the mounting surface  40   b  of the sensor substrate  40 , and the embedded portion  56   d  of the cover peripheral wall portion  56   b  is embedded and fixed in the potting resin body  80 . 
     Since the thermosetting resin  80   a  heat-shrinks by cooling and curing, a fixing strength of the cover peripheral wall portion  56   b  by the potting resin body  80  can be enhanced. Since the thermosetting resin  80   a  is entered into a fitting clearance  56   i  between the sensor body  52  and the cover peripheral wall portion  56   b  from the body opening portion  56   a,  and is cooled and cued thereafter, the fixing strength of the cover peripheral wall portion  56   b  by the potting resin body  80  can be further enhanced. The embedded portion  56   d  is embedded and fixed in the potting resin body  80  by cooling and curing of the thermosetting resin  80   a,  and a filter peripheral portion  58   a  of the sensor filter  58  (later explained) is held between the sensor body  52  and the bottom wall portion  56   c.    
     As shown in  FIGS. 6 and 7 , the bottom wall portion  56   c  is continuously formed substantially vertical to the cover peripheral wall portion  56   b  at an opposite side of the body opening portion  56   a  in Y direction. The cover peripheral wall portion  56   b  fits outside of the sensor body  52 , and the bottom wall portion  56   c  is embedded in the potting resin body  80 . The bottom wall portion  56   c  covers the sensor body  52  from the opposite side of the sensor substrate  40  in Y direction. A part of the intake passage  3  is formed between an outer surface  56   g  in the opposite side of the bottom wall portion  56   c  with respect to the sensor body  52  and the detection portion  5   a  of the flow detection body  5  according to  FIG. 2 . As shown in  FIG. 6 , the outer surface  56   g  of the bottom wall portion  56   c  exposes the intake passage  3 . An inner surface  56   e  of the bottom wall portion  56   c  in the opposite side of the outer surface  56   g  is separated in Y direction from an opposite surface  52   a  opposite to the mounting surface  40   b  with respect to the sensor body  52 . 
     As shown in  FIGS. 6 and 7 , a cover window  56   f  is formed as penetrating the bottom wall portion  56   c  at a central portion in X and Z directions. The cover window  56   f  faces the intake passage  3  and is separated from the body opening portion  53   a.  The cover window  56   f  is provided between the intake passage  3  and the body opening portion  53   a,  and penetrates the bottom wall portion  56   c  in Y direction. The cover window  56   f  is formed as a circle penetrating hole shape (cylindrical hole shape) in planar view in Y direction. 
     As shown in  FIG. 6 , the sensor filter  58  is made of a soft resin, such as Polytetrafluoroethylene (PTFE) and is formed as a porous shape. The sensor filter  58  made of PTFE is excellent in a chemical resistance and a heat resistance such that the sensor filter in a hot intake passage  3 , in which the intake air including oil flows, hardly deteriorates. Furthermore, a deterioration of a filtering performance is minimized, because a water drop and an oil in the intake air hardly spread in an inside of the sensor filter  58 . 
     As shown in  FIGS. 6 and 7 , the sensor filter  58  is formed as a flat membrane shape, which is spread along a virtual plane S extending virtually in X and Y directions, and is provided with the filter peripheral portion  58   a.  The filter peripheral portion  58   a  has a rectangular contour  58   ae  in planar view in Y direction such that the filter peripheral portion  58   a  is surrounded by the cover peripheral wall portion  56   b  from outside of the filter peripheral portion  58   a.  In the embodiment according to  FIGS. 6 and 7 , a size of the contour  58   ae  of the filter peripheral portion  58   a  is substantially equal to that of an outer contour  52   c  of the sensor body  52 . Within a range satisfied with a formula 1 (later explained), the size of the contour  58   ae  of the filter peripheral portion  58   a  may be smaller than that of an outer contour  52   c  of the sensor body  52 . 
     As shown in  FIG. 6 , one surface  58   b  of the filter peripheral portion  58   a  in Y direction comes into surface contact to the opposite surface  52   a  of the sensor body  52  with respect to the mounting surface  40   b  in a non-joining state. An opposite side surface  58   c  in the Y direction in the filter peripheral portion  58   a  is in surface contact with the inner surface  56   e  of the cover bottom wall portion  56   c  in a non-joining state. The filter peripheral portion  58   a  comes into surface contact to both the sensor body  52  and the bottom wall portion  56   c  such that the filter peripheral portion  58   a  is held between the sensor body  52  and the bottom wall portion  56   c.  In an inner peripheral side positioned inwardly with respect to a holding portion in the sensor filter  58 , one surface  58   b  faces the intake passage  3  through the cover window  56   f,  and the opposite surface  58   c  faces the body opening portion  53   a  in Y direction. 
     A slight deformation of the sensor filter  58  held between the sensor body  52  and the bottom wall portion  56   c  may be occurred due to a microscopically roughness of each of the sensor body  52  and the bottom wall portion  56   c  contacting the filter peripheral portion  58   a.  A specification (for example, dimension and material) for the sensor filter  58 , the sensor body  52 , and the bottom wall portion  56   c,  is determined in such a manner that the slight deformation is targeted within a permissible range, not hindering a filtering performance of the sensor filter  58 . 
     An area in an inner peripheral side positioned inwardly with respect to the contour  58   ae  of the filter peripheral portion  58   a  in the projection view in Y direction with respect to the virtual plane S is defined as a filtering area R partitioned by dots hatching area in  FIG. 9 . Under such definition, in the projection view (namely, a projection view in  FIG. 9 ) in Y direction with respect to the virtual plane S, the cover window  56   f  and the body opening portion  53   a  are positioned in the filtering area R. In the projection view in Y direction with respect to the virtual plane S, the opening portion  53   a  is positioned in the contour of the cover window  56   f  within the filtering area R. 
     According to the first embodiment, in which an arrangement of each component is explained by utilizing the projection view, the body opening portion  53   a  as a circle contour shape, the cover window  56   f , and a rectangular contour  58   ae  as the filtering area R are arranged in such a manner that each center of the body opening portion  53   a,  the cover window  56   f,  and the rectangular contour  58   ae  is substantially aligned, as shown in  FIG. 10 . In the first embodiment, the diameter A of the circle contour of the body opening portion  53   a,  the diameter B of the circle contour of the cover window  56   f,  and the minimum distance C (minimum distance in the radial direction) of the rectangular contour  58   ae  of the filter peripheral portion  58   a  in the filtering area R satisfy the following formula 1, as shown in  FIG. 10 . 
       A&lt;B&lt;C  (Formula 1)
 
     The sensor filter  58  filters the intake air flowing into the body recess  53  through the cover window  56   f  and the body opening portion  53   a  from the intake passage  3 . A filtering performance of the sensor filter  58  can be achieved. When the filtering performance is determined, a presumption in which a carbon  1000 , which is a foreign particle in the intake air and has a minimum diameter among the foreign particles, is adhered on the sensor filter  58  and arranged to contact each other on the sensor filter  58  only with a gap  1001 , is considered, as shown in  FIG. 11 . In such presumption, if for example the minimum diameter (pc of each carbon  1000  is about 0.03 μm, in the gap  1001  the maximum diameter of an inscribed circle  1002  inside three carbons  1000  is about 0.0046 μm. This FIG. 0.0046 μm is larger than 0.0004 μm, which designates a minimum diameter of a gap for passing the water vapor in the intake air for the humidity detection. A mesh (namely, gap size for passing the water vapor) of the sensor filter  58  for determining the filter performance is set to between for example 0.001-0.003 μm such that the water vapor in the intake air can be passed through the gap  1001  and through the sensor filter  58 . In consideration with the mesh, the thickness between both of the surfaces  58   b,    58   c  of the sensor filter  58  is set to for example, about 0.1 mm. 
     Effects 
     The effects of the first embodiment explained so far will be described below. 
     According to the first embodiment, the sensor filter  58  is interposed between the sensor body  52  and the sensor cover  56 . According to this configuration, it is possible to suppress a situation in which the sensor filter  58  is separated from the regular position between the sensor body  52  and the sensor cover  56 . Furthermore, the sensor cover  56  is embedded in the potting resin body  80  for sealing the circuit element  72  on the mounting surface  40   b  of the sensor substrate  40  holding the sensor body  52 , on the outer peripheral side of the sensor body  52 . As a result, the sensor cover  56  can be fixed in position relative to the sensor substrate  40  with a large embedded surface area that can be secured by hardening the potting resin body  80  and secured on the outer peripheral side of the sensor body  52 . It is possible to suppress a situation in which the sensor filter  58  is separated from the regular position to the intake passage  3  by the sensor cover  56  fixed in position. Since the sensor cover  56  is fixed in position by using the potting resin body  80  for sealing the circuit element  72 , a special process such as adhesion or welding for fixing the sensor cover  56  to the sensor substrate  40  or the sensor case  20  can be omitted. 
     Furthermore, according to the first embodiment, the sensor cover  56  having the bottomed cup shape is configured such that the sensor filter  58  held between the bottom wall portion  56   c  of the sensor cover  56  and the sensor body  52  is surrounded from the outer peripheral side by the cover peripheral wall portion  56   b  of the sensor cover  58 . It is possible to prevent the sensor filter  58  from being separated from the regular position between the sensor body  52  and the cover bottom wall portion  56   c  into the intake passage  3 , in a state where the sensor filter  58  is held and surrounded by the sensor cover  56 . Further, in the sensor cover  56  having the bottomed cup shape, since the cover peripheral wall portion  56   b  surrounding the sensor body  52  from the outer peripheral side is embedded in the potting resin body  80 , the embedded surface area secured on the outer peripheral side can be extended to the range of the axial direction length of the cover peripheral wall portion  56   b.  Therefore, it is possible to reliably suppress the detachment of the sensor filter  58  from the regular position to the intake passage  3  by means of the cover peripheral wall portion  56   b  of the sensor cover  56  fixed in position with respect to the sensor substrate  40 . 
     According to the first embodiment, in the sensor cover  56  having a bottomed cup shape, the entire outer peripheral side of the sensor body  52  is covered with the cover peripheral wall portion  56   b.  According to this configuration, it is possible to reliably prevent foreign matter passing from between the sensor body  52  and the cover peripheral wall portion  56   b  to between the sensor body  52  and the cover bottom wall portion  56   c  from entering into the body recess  53 , so that the deterioration of the sensor element  54  due to the foreign matter can be suppressed. 
     In the first embodiment, the sensor body  52  having the body recess  53  opened at the body opening portion  53   a  is covered by the sensor cover  56  having the cover window  56   f  communicating between the intake passage  3  and the body opening portion  53   a.  With such a configuration, in the projection view with respect to the virtual plane S, the body opening portion  53   a  and the cover window  56   f  are formed in the filter region R on the inner peripheral side of the contour  58   ae  of the filter peripheral portion  58   a  formed by the sensor filter  58  spreading along the virtual plane S. As a result, the sensor filter  58  is interposed between the sensor body  52  and the sensor cover  56  at the filter outer peripheral portion  58  in such projection view, so that the separation of the sensor filter  58  from between the sensor body  52  and the sensor cover  56  can be reliably suppressed. 
     According to the first embodiment, in the projection view with respect to the virtual plane S, the body opening portion  53   a  is contained within the cover window  56   f  in the filter region R. The air passing through the cover window  56   f  and the sensor filter  58  from the intake passage  3  is not blocked by the sensor body  52  around the body opening portion  53   a  but flows from the body opening portion  53   a  into the body recess  53 . Therefore, the air from the intake passage  3  easily reaches the sensor element  54  in the body recess  53 . Here, the sensor filter  58  along the virtual plane S between the sensor body  52  and the sensor cover  56  comes as close as possible to the sensor element  54  in the body recess  53 . As a result, the internal volume of the body recess  53  decreases, so that the arrival time of air from the intake passage  3  to the sensor element  54  can be shortened. Therefore, according to these reachability and shortening of arrival time, the detection response by the sensor element  54  can be enhanced. 
     According to the first embodiment, the air containing the foreign matter in the intake passage  3  of the internal combustion engine  1  is filtered by the sensor filter  58 , which is prevented from being separated, before entering into the body recess  53 . This makes it possible to prevent the sensor element  54  in the body recess  53  from being deteriorated by foreign matter and to prevent the detached sensor filter  58  from being sucked into the cylinder on the downstream side from the intake passage  3 . 
     Second Embodiment 
     The second embodiment is a modified example of the first embodiment. 
     As shown in  FIGS. 12 and 13 , the sensor cover  2056  having a bottomed cup shape according to the second embodiment has a through hole portion  2056   h  in the cover peripheral wall portion  56   b.  One through hole portion  2056   h  is provided in each of the two opposed walls of the rectangular tubular four walls in the cover peripheral wall portion  56   b.  Each through hole portion  2056   h  penetrates the embedded portion  56   d  of the cover peripheral wall portion  56   b  embedded in the potting resin body  80  in the Z direction. Here, in particular, each through hole portion  2056   h  in the second embodiment opens an end portion of the cover opening portion  56   a  side constituting the embedded portion  56   d  of the cover peripheral wall portion  56   b,  and communicates with the cover opening portion  56   a.    
     As shown in  FIG. 14 , in the second embodiment, the thermosetting resin  80   a,  which is a material for forming the potting resin body  80 , is filled in each through hole portion  2056   h  in a hot melted state, and then it enters into a fitting clearance  56   i  between the sensor body  52  and the cover peripheral wall portion  56   b  and is cooled and hardened. As a result, as shown in  FIG. 12 , the potting resin body  80  fills the inside of each through hole portion  2056   h  and is provided along the fitting clearance  56   i  between the sensor body  52  and the cover peripheral wall portion  56   b  from each of the through hole portion  2056   h.    
     As described above, in the sensor cover  2056  having a bottomed cup shape according to the second embodiment, the potting resin body  80  is provided from the through hole portion  2056   h  penetrating the cover peripheral wall portion  56   b  along the clearance between the sensor body  52  and the cover peripheral wall portion  56   b.  As a result, in the sensor cover  2056 , the surface area between the sensor body  52  and the cover peripheral wall portion  56   b  can be added to the embedded surface area that can be secured on the outer peripheral side of the sensor body  52 . Therefore, the effect of suppressing the separation of the sensor filter  58  from the regular position to the intake passage  3  can be enhanced by effectively utilizing the cover peripheral wall portion  56   b  of the sensor cover  2056  fixed in position with respect to the sensor substrate  40 . 
     Third Embodiment 
     The third embodiment is a modified example of the second embodiment. As shown in  FIGS. 15 and 16 , a sensor cover  3056  having a bottomed cup shape according to the third embodiment has a through hole portion  3056   h  different from that of the second embodiment in the cover peripheral wall portion  56   b.  The through hole portion  3056   h  is provided on each of the four walls of the rectangular tubular shape in the cover peripheral wall portion  56   b.  Each through hole portion  3056   h  penetrates the embedded portion  56   d  of the cover peripheral wall portion  56   b  embedded in the potting resin body  80  in the X direction or the Z direction. Here, in particular, each through hole portion  3056   h  of the third embodiment penetrates the embedded portion  56   d  between an end portion on the cover opening portion  56   a  side and an end portion on the cover bottom wall portion  56   c  side of the cover peripheral wall portion  56   b.    
     As shown in  FIG. 17 , in the third embodiment, the thermosetting resin  80   a  is filled in each through hole portion  3056   h  in a hot melted state, and then it enters into a fitting clearance  56   i  between the sensor body  52  and the cover peripheral wall portions  56   b  and is cooled and hardened. As a result, as shown in  FIG. 15 , the potting resin body  80  fills the inside of each through hole portion  3056   h  and is provided along the fitting clearance  56   i  between the sensor body  52  and the cover peripheral wall portion  56   b  from each of the through hole portions  3056   h.    
     As described above, in the sensor cover  3056  having a bottomed cup shape according to the third embodiment, the through hole portion  3056   h  penetrates the cover peripheral wall portion  56   b  between the end portion on the cover opening portion  56   a  side and the end portion on the cover bottom wall portion  56   c  side. According to this configuration, the thermosetting resin  80   a,  which is the potting resin body  80  before curing, is injected into the through hole portion  3056   h , whereby the internal pressure of the injected resin is utilized and the lifting of the sensor cover  3056  with respect to the sensor substrate  40  can be suppressed. Therefore, since the sensor cover  3056  is fixed at the intended position with respect to the sensor substrate  40 , it is possible to prevent the sensor filter  58  between the sensor cover  3056  and the sensor body  52  from deviating from the regular position. In the third embodiment exhibiting such effects, the load according to the first embodiment may be continuously applied in the immersed state of the embedded portion  56   d  in the thermosetting resin  80   a,  and as shown in  FIG. 27 , it is unnecessary to use continuously the above mentioned load by using the own weight of the sensor cover  3056 . 
     Fourth Embodiment 
     The fourth embodiment is a modified example of the first embodiment. 
     As shown in  FIGS. 18 and 19 , the sensor cover  4056  having a bottomed cup shape according to the fourth embodiment has a plurality of anchor portions  4056   j.  The anchor portions  4056   j  protrudes one by one from two opposing walls of the rectangular tubular four walls at the cover peripheral wall portion  56   b.  Each anchor portion  4056   j  protrudes from the embedded portion  56   d  in the potting resin body  80  of the cover peripheral wall portion  56   b  in a direction opposite to the sensor body  52  along the Z direction. Here, in particular, each anchor portion  4056   j  of the fourth embodiment protrudes from the embedded portion  56   d  toward the opposite side with a substantially constant thickness. Due to such protrusion configuration, each of the anchor portions  4056   j  is entirely embedded in the potting resin body  80 . Any of the configurations of the second and third embodiments may be adopted as the configuration of the sensor body  50  other than the one described above, in place of the configuration described in the first embodiment. 
     In the bottomed cup-shaped sensor cover  4056  according to the fourth embodiment, the anchor portions  4056   j  projecting from the cover peripheral wall portion  56   b  are embedded at the outer peripheral side of the sensor body  52 . As a result, in the sensor cover  4056 , the anchor portions  4056   j  are caught in the hardened potting resin body  80 , so that it is difficult for the sensor cover  4056  to come off from the potting resin body  80 . The surface area of the anchor portions  4056   j  can be added to the embedded surface area that can be secured on the outer peripheral side of the sensor body  52 . Therefore, the cover peripheral wall portion  56   b  and the anchor portions  4056   j  of the sensor cover  4056  fixed in position with respect to the sensor substrate  40  can enhance the effect of suppressing the sensor filter  58  from being separated from the regular position into the flow passage. 
     Fifth Embodiment 
     The fifth embodiment is a modified example of the first embodiment. 
     As shown in  FIGS. 20 and 21 , the bottomed cup-shaped sensor cover  5056  according to the fifth embodiment has a overhanging portion  5056   k.  The overhanging portion  5056   k  protrudes toward the inner peripheral side of the cover window  56   f  at the cover bottom wall portion  56   c  of the sensor cover  5056 . Here, in particular, the overhanging portion  5056   k  of the fifth embodiment protrudes from two positions opposed to each other in the radial direction at the cover window  56   f  having a circular contour and connects the two portions. In particular, the overhanging portion  5056   k  of the fifth embodiment is in surface contact with the side surface  58   c  opposite to the sensor body  52  of the sensor filter  58  and on the inner surface  56   e  side of the cover bottom wall portion  56   c.  Any of the configurations of the second to fourth embodiments may be adopted as the configuration of the sensor body  50  other than the one described above, in place of the configuration described in the first embodiment. 
     When the sensor filter  58  is deformed due to vibration, cold heat change or the like and enters the inner circumferential side of the cover window  56   f,  the sensor filter  58  may be detached from the regular position. However, in the sensor cover  5056  according to the fifth embodiment, it is possible to reliably suppress that the deformed sensor filter  58  enters into the inner peripheral side of the cover window  56   f  and is separated from the cover window  56   f  by the overhanging portion  5056   k  projecting toward the inner peripheral side. 
     Sixth Embodiment 
     The sixth embodiment is a modified example of the first embodiment. 
     As shown in  FIG. 22 , in the sensor filter  6058  according to the sixth embodiment, one surface  58   b  of the filter peripheral portion  58   a  is bonded to the side surface  52   a  opposite to the mounting surface  40   b  of the sensor body  52  in a surface contact state by, for example, welding or bonding. As a result, as shown in  FIGS. 22 and 23 , the filter peripheral portion  58   a  is provided with a body side connecting portion  6058   d  on the side of the sensor body  52 , and the body side connecting portion  6058   d  is formed as a continuous circle belt shape with a substantially constant width in a plan view in the Y direction. The filter peripheral portion  58   a  in the sensor filter  6058  is in surface contact with the inner surface  56   e  of the bottom wall portion  56   c  of the sensor cover  56  shown in  FIG. 22  at the side surface  58   c  opposite to the sensor body  52  so that the filter peripheral portion  58   a  is interposed between the sensor body  52  and the bottom wall portion  56   c.  In the sensor filter  6058  joined to the sensor body  52  in the interposed state, a slight deformation of the filter peripheral portion  58   a  may be occurred due to a microscopically roughness of each of the sensor body  52  and the bottom wall portion  56   c  contacting the filter peripheral portion  58   a.  A specification (for example, dimension and material) for the sensor filter  6058 , the sensor body  52 , and the bottom wall portion  56   c  is determined in such a manner that the slight deformation is targeted within a permissible range not hindering a filtering performance of the sensor filter  6058 . 
     As shown in  FIG. 24 , under the same definition of the filtering area R in the first embodiment, in the projection view in Y direction with respect to the virtual plane S, the cover window  56   f,  the body opening portion  53   a,  and the body side connecting portion  6058   d  are positioned in the filtering area R. In the projection view in Y direction with respect to the virtual plane S, the body side connecting portion  6058   d  is positioned outside of the contour of the body opening portion  53   a  and outside of the contour of the cover window  56   f  within the filtering area R. Namely, in the projection view in Y direction with respect to the virtual plane S, the body side connecting portion  6058   d  is positioned between the rectangular contour  58   ae  of the filter peripheral portion  58   a  and the contour of the cover window  56   f.    
     According to the sixth embodiment, the body side connecting portion  6058   d  having a circle belt shape, the body opening portion  53   a  having a circle contour shape, the cover window  56   f,  and a rectangular contour  58   ae  as the filtering area R are arranged in such a manner that each center of the body side connecting portion  6058   d,  the body opening portion  53   a,  the cover window  56   f,  and a rectangular contour  58   ae  is substantially aligned, as shown in  FIG. 25 . In the second embodiment, the diameter D of the inner side of the body side connecting portion  6058   d,  the diameter E of the outer side of the body side connecting portion  6058   d,  the diameter A of the circle contour of the body opening portion  53   a,  the diameter B of the circle contour of the cover window  56   f,  and the minimum distance C (minimum distance in the radial direction) of the rectangular contour  58   ae  of the filter peripheral portion  58   a  in the filtering area R satisfy the following formula 2, as shown in  FIG. 25 . Any of the configurations of the second to fifth embodiments may be adopted as the configuration of the sensor body  50  other than the one described above, in place of the configuration described in the first embodiment. 
       A&lt;B&lt;D&lt;E&lt;C  (Formula 2)
 
     As described above, since the sensor filter  6058  according to the sixth embodiment is joined to the sensor body  52  in a state of being held between the sensor body  52  and the sensor cover  56 , it is possible to reliably suppress the detachment of the sensor filter  6058  from the regular position. 
     Seventh Embodiment 
     The seventh embodiment is a modified example of the first embodiment. 
     As shown in  FIG. 26 , in a sensor filter  7058  according to the seventh embodiment, one surface  58   c  of the filter peripheral portion  58   a  opposite to the sensor body  52  is connected to the inner surface  56   e  of the bottom wall portion  56   c  in the sensor cover  56  in a surface contacting state by welded or bonded, etc. The filter peripheral portion  58   a,  as shown in  FIGS. 26 and 27 , is provided with a cover side connecting portion  7058   e  on the side of the sensor cover  56 , and the cover side connecting portion  7058   e  is formed as a circle belt shape having a substantially same width in a plan view in Y direction. 
     The filter peripheral portion  58   a  in the sensor filter  7058  makes one surface  58   b  into surface-contact with the side surface  52   a  opposite to the mounting surface  40   b  of the sensor body  52  shown in  FIG. 26  such that the filter peripheral portion  58   a  is interposed between the sensor body  52  and the bottom wall portion  56   c.  In the sensor filter  7058  joined to the sensor cover  56  in the interposed state, a slight deformation of the filter peripheral portion  58   a  may be occurred due to a microscopically roughness of each of the sensor body  52  and the bottom wall portion  56   c  contacting the filter peripheral portion  58   a.  A specification (for example, dimension and material) for the sensor filter  7058 , the sensor body  52 , and the bottom wall portion  56   c  is determined in such a manner that the slight deformation is targeted within a permissible range not hindering a filtering performance of the sensor filter  7058 . 
     As shown in  FIG. 28 , under the same definition of the filtering area R in the first embodiment, in the projection view in Y direction with respect to the virtual plane S, the cover window  56   f,  the body opening portion  53   a,  and the cover side connecting portion  7058   e  are positioned in the filtering area R. In the projection view in Y direction with respect to the virtual plane S, the cover side connecting portion  7058   e  is positioned outside of the contour of the body opening portion  53   a  and outside of the contour of the cover window  56   f  within the filtering area R. Namely, in the projection view in Y direction with respect to the virtual plane S, the cover side connecting portion  7058   e  is positioned between the rectangular contour  58   ae  of the filter peripheral portion  58   a  and the contour of the cover window  56   f.    
     According to the seventh embodiment, the cover side connecting portion  7058   e  having a circle belt shape, the body opening portion  53   a  having a circle contour shape, the cover window  56   f,  and a rectangular contour  58   ae  as the filtering area R are arranged in such a manner that each center of the body side connecting portion  6058   d,  the body opening portion  53   a,  the cover window  56   f,  and a rectangular contour  58   ae  is substantially aligned, as shown in  FIG. 29 . In the seventh embodiment, the diameter F of the inner side of the cover side connecting portion  7058   e,  the diameter E of the outer side of the cover side connecting portion  7058   e,  the diameter A of the circle contour of the body opening portion  53   a,  the diameter B of the circle contour of the cover window  56   f,  and the minimum distance C (minimum distance in the radial direction) of the rectangular contour  58   ae  of the filter peripheral portion  58   a  in the filtering area R satisfy the following formula 3, as shown in  FIG. 29 . Any of the configurations of the second to fifth embodiments may be adopted as the configuration of the sensor body  50  other than the one described above, in place of the configuration described in the first embodiment. 
       A&lt;B&lt;F&lt;G&lt;C  (Formula 3)
 
     As described above, since the sensor filter  7058  according to the seventh embodiment is joined to the sensor cover  56  in a state of being held between the sensor body  52  and the sensor cover  56 , it is possible to reliably suppress the detachment of the sensor filter  6058  from the regular position. 
     Eighth Embodiment 
     The eighth embodiment is a modified example combining the sixth and seventh embodiments. 
     As shown in  FIG. 30 , the sensor filter  8058  according to the eighth embodiment is joined to the sensor body  52  and the sensor cover  56  that interpose the sensor filter  8058  in a surface contacting state by welded or bonded, etc. As a result, the sensor filter  8058  forms a body side connecting portion  6058   d  similar to that of the sixth embodiment and a cover side connecting portion  7058   e  similar to the seventh embodiment. 
     Here, under the definition of the filter region R similar to the first embodiment, both the projection view similar to the seventh embodiment and the projection view similar to the eighth embodiment are realized. In addition, in the seventh embodiment in which such a projection view is established, as shown in  FIG. 31 , the diameter D on the inner peripheral side of the body side connecting portion  6058   d  and the inner diameter side F of the cover side connecting portion  7058   e  substantially coincide. In addition, in the seventh embodiment, the peripheral side diameter E of the body side connecting portion  6058   d  and the peripheral side diameter G of the cover side connecting portion  7058   e  substantially coincide. Any of the configurations of the second to fifth embodiments may be adopted as the configuration of the sensor body  50  other than the one described above, in place of the configuration described in the first embodiment. 
     As described above, since the sensor filter  8058  according to the eighth embodiment is joined to the sensor body  52  and the sensor cover  56  in a state of being held between the sensor body  52  and the sensor cover  56 , it is possible to reliably suppress the detachment of the sensor filter  7058  from the regular position. 
     Other Embodiments 
     Although a plurality of embodiments of the present disclosure have been described above, the present disclosure is not construed as being limited to these embodiments, and can be applied to various embodiments and combinations within a scope that does not deviate from the gist of the present disclosure. 
     In the modification 1 relating to the first to the eighth embodiments, in the projection view in Y direction with respect to the virtual plane S, the cover window  56   f  is positioned in an inner side with respect to the contour of the body opening portion  53   a  within the filtering area R as shown in  FIG. 32 . In the modification 1 relating to the first to fifth embodiments, as shown in  FIG. 33 , the following formula 4 is satisfied. In the modification 1 relating to the sixth and the eighth embodiments, as shown in  FIG. 34 , the following formula 5 is satisfied. In the modification 1 relating to the seventh and the eighth embodiments, as shown in  FIG. 34 , the following formula 6 is satisfied.  FIGS. 32 and 33  show the modification 1 relating to the first embodiment,  FIG. 34  shows the modification 1 relating to the eighth embodiment. 
       B&lt;A&lt;C  (Formula 4)
 
       B&lt;A&lt;D&lt;E&lt;C  (Formula 5)
 
       B&lt;A&lt;F&lt;G&lt;C  (Formula 6)
 
     In the modification 2 relating to the sixth and the eighth embodiments, in the projection view in Y direction with respect to the virtual plane S, the body side connecting portion  6058   d  may be positioned within the outline of the cover window  56   f  and outside the contour of the body opening portion  53   a  within the filtering area R, as shown in  FIG. 35 . In the projection view in Y direction with respect to the virtual plane S, the body side connecting portion  6058   d  may be positioned between the contour of the body opening portion  53   a  and the contour of the cover window  56   f.  In the modification 2, as shown in  FIG. 36 , the following formula 7 is satisfied.  FIGS. 35 and 36  show the modification 2 relating to the sixth embodiment. 
       A&lt;D&lt;E&lt;B&lt;C  (Formula 7)
 
     In a modification 3 relating to the eighth embodiment, the inner diameter D of the body side connecting portion  6058   d  may be different from the inner diameter F of the cover side connecting portion  7058   e . In a modification 4 relating to the eighth embodiment, the outer diameter E of the body side connecting portion  6058   d  may be different from the outer diameter G of the cover side connecting portion  7058   e . 
     In a modification 5 relating to the sixth and the eighth embodiments, in planar view in Y direction, the body side connecting portion  6058   d  may be formed as, for example, a rectangular belt shape as shown in  FIG. 37  instead of a circle belt shape. In a modification 6 relating to the seventh and eighth embodiments, in planar view in Y direction, the cover side connecting portion  7058   e  may be formed as, for example, a rectangular belt shape shown in  FIG. 38  instead of a circle belt shape.  FIG. 37  shows the modification 5 relating to the sixth embodiment.  FIG. 38  shows the modification 6 relating to the seventh embodiment. 
     In a modification 7 relating to the sixth and the eighth embodiments, as shown in  FIG. 39 , a plurality of the body side connecting portions  6058   d  may be provided at a predetermined gap in a circumferential direction on the filter peripheral portion  58   a.  In a modification 8 relating to the seventh and the eighth embodiments, as shown in  FIG. 40 , a plurality of the cover side connecting portions  7058   e  may be provided at a predetermined gap in a circumferential direction on the filter peripheral portion  58   a.    FIG. 39  shows the modification 7 relating to the sixth embodiment.  FIG. 40  shows the modification 8 relating to the seventh embodiment. 
     In a modification 9 relating to the first to the eighth embodiments, in planar view in Y direction, as shown in  FIG. 41 , the body opening portion  53   a  may be formed as, for example, a rectangular shape instead of a circle shape. In a modification 10 relating to the first to the eighth embodiments, in planar view in Y direction, as shown in  FIG. 41 , the cover window  56   f  may be formed as, for example, a rectangular shape instead of a circle shape. In a modification 11 relating to the first to the eighth embodiments, in planar view in Y direction, as shown in  FIG. 42 , the filter peripheral portion  58   a  may be provided with the contour  58   ae  having, for example, a circle shape instead of a rectangular shape.  FIG. 41  shows the modifications 9, 10 relating to the first embodiment, and  FIG. 42  shows the modification 11 relating to the first embodiment. 
     In a modification 12 relating to the first to the eighth embodiments, the sensor filters  58 ,  6058 ,  7058 , and  8058  are not only a porous filter made of PTFE but also, for example, a waterproof filter or an air-permeable filter. The filter used in the sixth to the eighth embodiments may be a fibrous filter made of other material by considering a bonding property. In a modification 13 relating to the first to the eighth embodiments, as shown in  FIG. 43 , the sensor filters  58 ,  6058 ,  7058 , and  8058  are made from a plurality of filter elements  58   f , each of which is different from each other as for a material, a roughness, and/or a thickness. In a modification 14 relating to the first to the eighth embodiments, as shown in  FIG. 44 , a reinforced plate  30  may be omitted, because the sensor substrate  40  is made from a hard substrate, such as a glass epoxy substrate instead of the soft flexible substrate.  FIGS. 43 and 44  show respectively the modifications 13, 14 relating to the first embodiment. 
     The anchor portion  4056   j  of the fourth embodiment protrudes with a constant thickness, the anchor portion  4056   j  of the modification 15 related to the fourth embodiment may be made thinner toward the protruding side as shown in  FIG. 45 , for example. The overhanging portion  5056   k  of the modification 16 relating to the fifth embodiment is not limited to the overhanging configuration in which the two portions of the cover window  56   f  are connected, for example, the overhanging portion  5056   k  may be formed in an overhanging manner as shown in  FIGS. 46 and 47 . In the cover window  56   f  of the modification 15 shown in  FIG. 46 , an overhanging portion  5056   k  connecting two positions facing each other in the radial direction and an overhanging portion  5056   k  connecting the other positions facing each other in the radial direction protrude toward the inner peripheral side. On the other hand, in the cover window  56   f  of the modification 16 shown in  FIG. 47 , the overhanging portion  5056   k  protrudes from two positions opposed to each other in the radial direction to the inner peripheral side with a length not reaching the center of the circular contour. 
     As a modification 17 relating to the first to eighth embodiments, as shown in  FIG. 48 , the air physical quantity sensor  10  is integrally formed with the air flow detection unit  2 . The sensor unit  50  may be exposed to a second passage portion  8  of the bypass passage  6 . In the modification 17 shown in  FIG. 48 , the sensor case  20  is shared with the detection body  5   a  of the flow detection body  5 , and the terminal  60  is shared with the terminal  5   b  of the flow detection body  5 . In the modification 17 shown in  FIG. 48 , the sensor body  50  and the circuit module  70  are mounted together with the sensor element  9   a  and the circuit module  9   b  on the sensor substrate  40 . As a result, the sensor filter  58  of the sensor body  50  filters a part of the intake air flowing from the bypass passage  6  as the “flow passage” into the body recess  53  through the cover window  56   f  and the body opening  53   a.  In  FIG. 48 , illustration of each constituent element constituting the sensor body  50  of the embodiment to be applied is omitted. 
     In further modification 18 of the modification 17 relating to the first to the eighth embodiments, as shown in  FIG. 49 , another bypass passage  1006  is configured to separate from the bypass passage  6 , and the bypass passage  1006  has an inlet  1006   a  and an outlet  1006   b,  both of which expose the intake passage  3 . The bypass passage  1006  is referred to as the flow passage. The sensor unit  50  may be exposed to the bypass passage  1006 . In the modification 18, a sensor substrate  40 , on which the sensor element  9   a  and the circuit module  9   b  are not mounted, is applied as described in the first embodiment. In  FIG. 49 , illustration of each constituent element constituting the sensor body  50  of the embodiment to be applied is omitted. 
     In a modification 19 relating to the first to the eighth embodiments, as shown in  FIG. 50 , a hole portion  53   d  penetrates in Y direction through the sensor body  52 , and the hole portion  53   d  is covered by the sensor substrate  40 , on which the sensor element  54  is mounted. The body recess  53  may be formed as being surrounded by the hole portion  53   d  and the sensor substrate  40 . In a modification 20 relating to the first to the eighth embodiments, the sensor element  54  may detect a specified physical quantity, such as temperature, pressure, thermal conductivity, density, or flow amount for air except for the air humidity. In a modification 21 relating to the first to the eighth embodiments, as shown in  FIG. 51 , a plurality of the sensor elements  54  which detect the different physical quantity or detect same physical quantity may be housed in the body recess  53 .  FIGS. 50 and 51  show respectively the modification 19, 21 relating to the first embodiment. 
     In our disclosure, the sensor filter is interposed between the sensor cover and the sensor body which covers the sensor cover. According to this configuration, it is possible to suppress a situation in which the sensor filter is separated from the regular position between the sensor body and the sensor cover. Furthermore, the sensor cover is embedded in the potting resin body for sealing the circuit element on the mounting surface of the sensor substrate holding the sensor body, on the outer peripheral side of the sensor body. As a result, the sensor cover can be fixed in position relative to the sensor substrate with a large embedded surface area that can be secured by hardening the potting resin body and secured on the outer peripheral side of the sensor body. It is possible to suppress a situation in which the sensor filter is separated from the regular position to the flow passage by the sensor cover fixed in position.