Patent Publication Number: US-10775215-B2

Title: Flow meter

Description:
TECHNICAL FIELD 
     The invention relates to a flowmeter. 
     BACKGROUND ART 
     As a flowmeter for measuring the mass flow rate of a measurement target gas flowing in a main path, there is a thermal type flowmeter. Such a flowmeter is configured such that a portion of a measurement target gas flowing in a pipe, which is a main path, is taken into a sub path and is guided to a flow rate measurement unit. In the flow rate measurement unit, a hot wire, a silicon element, or the like is disposed and the mass flow rate in the pipe is measured by using a fact that the hot wire, the silicon element, or the like is cooled by an air stream and the electrical resistivity changes. 
     In PTL 1, a technique of an thermal type flowmeter, in which a static electricity dissipation region is provided in a bypass path and electric charge of the corrupting substance is eliminated in viewpoint of a countermeasure against corruption for preventing a corrupting substance from adhering to the flow rate measurement unit, is proposed (PTL 1). 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: US2013/061684 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     Meanwhile, in recent years, there is proposed a structure of a thermal type flowmeter having a structure in which a circuit package is installed in a housing, the circuit package being formed by molding a lead frame and a circuit component with resin. 
     In the case of the circuit package, since the lead frame and the circuit component are embedded in a resin material, it is difficult to establish electrical connection with a conductor exposed in a place through which the measurement target gas passes. 
     The invention has been made in consideration of the above-described point and an object thereof is to obtain a flowmeter with which it is possible to easily establish electrical connection with a conductor exposed in a place through which a measurement target gas passes. 
     Solution to Problem 
     A flowmeter according to the invention for solving the above-described problem includes a package that includes a lead and a circuit component installed on the lead, a portion of the lead being molded with resin. The package is provided with an exposure portion which is electrically connected to a conductor constituting a portion of a sub path with a portion of the lead exposed out of the resin material. 
     Advantageous Effects of Invention 
     According to the invention, since the package is provided with the exposure portion, it is possible to easily connect the conductor to the package. Note that, a problem, a configuration, and an effect other than those described above will be apparent in description of an embodiment below. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a system diagram illustrating an example where a thermal type flowmeter according to the invention is used in an internal combustion engine control system. 
         FIG. 2A  is a front view illustrating the external appearance of the thermal type flowmeter according to the invention. 
         FIG. 2B  is a left side view illustrating the external appearance of the thermal type flowmeter according to the invention. 
         FIG. 2C  is a rear view illustrating the external appearance of the thermal type flowmeter according to the invention. 
         FIG. 2D  is a right side view illustrating the external appearance of the thermal type flowmeter according to the invention. 
         FIG. 3A  is a front view illustrating the state of a housing with a front cover and a rear cover removed from the thermal type flowmeter according to the invention. 
         FIG. 3B  is a rear view illustrating the state of the housing with the front cover and the rear cover removed from the thermal type flowmeter according to the invention. 
         FIG. 4A  is a view illustrating a facing surface of the front cover. 
         FIG. 4B  is a sectional view taken along line IVB-IVB in  FIG. 4A . 
         FIG. 5A  is a view illustrating a facing surface of the rear cover. 
         FIG. 5B  is a sectional view taken along line VB-VB in  FIG. 5A . 
         FIG. 6A  is a sectional view taken along line VIA-VIA in  FIG. 2A . 
         FIG. 6B  is an enlarged view of VIB in  FIG. 6A . 
         FIG. 6C  is a sectional view taken along line VIC-VIC in  FIG. 2A . 
         FIG. 6D  is a sectional view taken along line VID-VID in  FIG. 2A . 
         FIG. 7  is a view for describing a method of connecting a lead frame and a conductor. 
         FIG. 8  is a view illustrating a front surface of a circuit package. 
         FIG. 9  is a view illustrating a specific configuration example of the lead frame. 
         FIG. 10A  is a schematic view illustrating another configuration example in which an exposure portion and the conductor are connected to each other. 
         FIG. 10B  is a schematic view illustrating another configuration example in which the exposure portion and the conductor are connected to each other. 
         FIG. 10C  is a schematic view illustrating another configuration example in which the exposure portion and the conductor are connected to each other. 
         FIG. 10D  is a schematic view illustrating another configuration example in which the exposure portion and the conductor are connected to each other. 
         FIG. 10E  is a schematic view illustrating another configuration example in which the exposure portion and the conductor are connected to each other. 
         FIG. 10F  is a schematic view illustrating another configuration example in which the exposure portion and the conductor are connected to each other. 
         FIG. 11  is a diagram conceptually illustrating a configuration of a thermal type flowmeter of Example 1. 
         FIG. 12  is a view for describing another configuration example in which the conductor is connected and fixed. 
         FIG. 13A  is a front view illustrating a main portion of the thermal type flowmeter in an enlarged manner. 
         FIG. 13B  is a view schematically illustrating a specific example of a configuration for holding an intermediate member. 
         FIG. 13C  is a view schematically illustrating a specific example of the configuration for holding the intermediate member. 
         FIG. 13D  is a view schematically illustrating a specific example of the configuration for holding the intermediate member. 
         FIG. 13E  is a view schematically illustrating a specific example of the configuration for holding the intermediate member. 
         FIG. 14A  is a view for describing a configuration example of a method of connecting the exposure portion and the conductor. 
         FIG. 14B  is a view for describing a configuration example of a method of connecting the exposure portion and the conductor. 
         FIG. 14C  is a view for describing a configuration example of a method of connecting the exposure portion and the conductor. 
         FIG. 14D  is a view for describing a configuration example of a method of connecting the exposure portion and the conductor. 
         FIG. 14E  is a view for describing a configuration example of a method of connecting the exposure portion and the conductor. 
         FIG. 14F  is a view for describing a configuration example of a method of connecting the exposure portion and the conductor. 
         FIG. 15  is a view for describing another configuration example of the conductor. 
         FIG. 16A  is a view for describing a configuration of a conductor in Example 2. 
         FIG. 16B  is a view for describing the configuration of the conductor in Example 2. 
         FIG. 17  is a view for describing a configuration of a conductive circuit in Example 2. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Next, an embodiment of the invention will be described by using drawings. 
       FIG. 1  is a system diagram illustrating an example where a thermal type flowmeter according to the invention is used in an electronic fuel injection type internal combustion engine control system. Based on the motion of an internal combustion engine  110  provided with an engine cylinder  112  and an engine piston  114 , an inhaled air as a measurement target gas  30  is inhaled from an air cleaner  122  and the inhaled air is guided to a combustion chamber of the engine cylinder  112  via, for example, an intake pipe which is a main path  124 , a throttle body  126 , and an intake manifold  128 . The flow rate of the measurement target gas  30 , which is the inhaled air guided to the combustion chamber, is measured by a thermal type flowmeter  300  according to the invention, fuel is supplied from a fuel injection valve  152  based on the measured flow rate, and the fuel is guided to the combustion chamber in a state of being an air-fuel mixture together with the measurement target gas  30 , which is the inhaled air. Note that, in the present example, the fuel injection valve  152  is provided in an intake port of the internal combustion engine and fuel injected into the intake port forms the air-fuel mixture together with the measurement target gas  30 , which is the inhaled air, is guided to the combustion chamber via an intake valve  116 , and is burned such that mechanical energy is generated. 
     The fuel and air guided to the combustion chamber are in an air-fuel mixed state and are subject to explosive combustion due to spark-ignition of an ignition plug  154  such that mechanical energy is generated. Gas after the combustion is guided to an exhaust pipe from an exhaust valve  118  and is discharged as an exhaust gas  24 , to the outside of a vehicle from the exhaust pipe. The flow rate of the measurement target gas  30 , which is the inhaled air guided to the combustion chamber, is controlled by a throttle valve  132  of which the openness changes based on an operation on an accelerator pedal. The amount of fuel supply is controlled based on the flow rate of the inhaled air guided to the combustion chamber and a driver can control mechanical energy generated by the internal combustion engine by controlling the flow rate of the inhaled air guided to the combustion chamber by controlling the openness of the throttle valve  132 . 
     The flow rate and the temperature of the measurement target gas  30 , which is the inhaled air that is taken in via the air cleaner  122  and flows in the main path  124 , are measured by the thermal type flowmeter  300  and an electric signal indicating the flow rate and the temperature of the inhaled air from the thermal type flowmeter  300  is input to a control device  200 . In addition, output from a throttle angle sensor  144  that measures the openness of the throttle valve  132  is input to the control device  200 , and output from a rotation angle sensor  146  is input to the control device  200  in order to measure the position and the state of the engine piston  114 , the intake valve  116 , or the exhaust valve  118  of the internal combustion engine and the rotation speed of the internal combustion engine. In order to measure the state of a mixture ratio between the amount of fuel and the amount of air from the state of the exhaust gas  24 , output from an oxygen sensor  148  is input to the control device  200 . 
     The control device  200  calculates the amount of fuel injection and the timing of ignition based on the flow rate of the inhaled air, which is output from the thermal type flowmeter  300 , and the rotation speed of the internal combustion engine measured based on the output from the rotation angle sensor  146 . Based on the result of the calculation, the amount of fuel supplied from the fuel injection valve  152  and the timing of ignition at which ignition is performed by the ignition plug  154  are controlled. Actually, the amount of fuel supply and the timing of ignition are finely controlled based on the state of change in intake temperature measured by the thermal type flowmeter  300  or throttle angle, the state of change in engine rotation speed, and the state of an air-fuel ratio measured by the oxygen sensor  148  in addition to the above-described factors. Furthermore, the control device  200  controls the amount of air bypassing the throttle valve  132  by using an idle air control valve  156  in an idle operation state of the internal combustion engine and controls the rotation speed of the internal combustion engine in the idle operation state. 
       FIG. 2  illustrates the external appearance of the thermal type flowmeter  300 .  FIG. 2A  is a front view of the thermal type flowmeter  300 ,  FIG. 2B  is a left side view,  FIG. 2C  is a rear view, and  FIG. 2D  is a right side view. The thermal type flowmeter  300  is provided with a housing  302 . The housing  302  is inserted into the intake pipe and is disposed in the main path  124  (refer to  FIG. 1 ). Abase end portion of the housing  302  is provided with a flange  305  for fixation to the intake pipe and a connector (external connection portion)  306  which is exposed to the outside of the intake pipe. 
     The housing  302  is supported in a cantilever manner with the flange  305  being fixed to the intake pipe and is disposed along a direction perpendicular to a main flowing direction of the measurement target gas flowing in the main path  124 . The housing  302  is provided with a sub path for taking in the measurement target gas  30  flowing in the main path  124  and a flow rate measurement unit  451  for measuring the flow rate of the measurement target gas  30  is disposed in the sub path. 
     At a position that is close to a tip end of the housing  302  and is on an upstream side in the main flowing direction, an inlet  311  for taking a portion of the measurement target gas  30  such as the inhaled air into the sub path is provided. Furthermore, at positions that are close to the tip end and are on a downstream side in the main flowing direction, a first outlet  312  and a second outlet  313  for returning the measurement target gas  30  from the sub path to the main path  124  are provided. The first outlet  312  and the second outlet  313  are disposed to be laterally arranged in a thickness direction of the housing  302  as illustrated in  FIG. 2D . 
     Since the inlet  311  is provided close to the tip end of the housing  302 , a gas in a portion close to the central portion, which is separated from an inner wall surface of the main path, can be taken into the sub path. Accordingly, influence of the temperature of the inner wall surface of the main path is suppressed and thus it is possible to suppress a decrease in measurement accuracy of the flow rate or the temperature of a gas. 
     In the vicinity of the inner wall surface of the main path, fluid resistance is great and the flow speed is lower than an average flow speed in the main path. However, in the thermal type flowmeter  300  in the present example, since the inlet  311  is provided close to the tip end of the thin and long housing  302  which extends toward the center of the main path from the flange  305 , it is possible to take a gas in the central portion of the main path, of which the flow speed is high, into the sub path. In addition, since the first outlet  312  and the second outlet  313  of the sub path are also provided close to the tip end of the housing  302 , it is possible to return a gas flowing in the sub path to the central portion of the main path, in which the flow speed is high. 
     The housing  302  has a shape of which side surfaces are narrow (a thin shape) although a front surface thereof is an approximately rectangular wide surface. Front and rear surfaces of the housing  302  are disposed along the main flowing direction of the measurement target gas flowing in the main path and side surfaces are disposed to face each other in the main flowing direction. Accordingly, the thermal type flowmeter  300  can be provided with a sub path having a sufficient length while reducing fluid resistance with respect to the measurement target gas  30 . 
     That is, regarding the thermal type flowmeter in the present example, the shape of the housing projected onto an orthogonal plane orthogonal to a flowing direction of the measurement target gas  30  flowing in the main path  124  has a length dimension that is defined on the orthogonal plane in a first direction  50  and a thickness dimension that is defined on the orthogonal plane in a second direction  51  that is perpendicular to the first direction  50  (refer to  FIG. 2B ), the thickness dimension being smaller than the length dimension. 
     The housing  302  is provided with a temperature measurement unit  452  for measuring the temperature of the measurement target gas  30 . The housing  302  has a shape that is recessed toward the downstream side at a position that is in the central portion in a longitudinal direction and is on the upstream side in the main flowing direction of the measurement target gas and the temperature measurement unit  452  is provided in the recessed position. The temperature measurement unit  452  has a shape that protrudes toward the upstream side in the main flowing direction from an upstream side outer wall of the housing  302 . 
       FIG. 3  illustrates the state of the housing  302  with a front cover  303  and a rear cover  304  being removed from the thermal type flowmeter  300 .  FIG. 3A  is a front view of the housing  302  and  FIG. 3B  is a rear view. 
     In the housing  302 , a circuit package  400  provided with the flow rate measurement unit  451  for measuring the flow rate of the measurement target gas  30  flowing in the main path  124  or the temperature measurement unit  452  for measuring the temperature of the measurement target gas  30  flowing in the main path  124  is integrally formed through molding (refer to  FIG. 3A ). 
     Furthermore, in the housing  302 , sub path grooves constituting a sub path  307  are formed. In the present example, the sub path grooves are provided on both of front and rear surfaces of the housing  302  and the sub path  307  is completed when the front and rear surfaces of the housing  302  are covered with the front cover  303  and the rear cover  304 . According to this configuration, it is possible to mold the entire housing  302  with both of a front side sub path groove  321  and a rear side sub path groove  331  being molded as a portion of the housing  302  by using molds provided on opposite surfaces of the housing  302  at the time of molding of the housing  302  (resin molding process). 
     The sub path groove is configured with the rear side sub path groove  331  formed on the rear surface of the housing  302  and the front side sub path groove  321  formed on the front surface of the housing  302 . The rear side sub path groove  331  is provided with a first groove portion  332  and a second groove portion  333  that branches off from an intermediate portion of the first groove portion  332 . 
     The first groove portion  332  linearly extends along the main flowing direction of the measurement target gas  30  at a tip end portion of the housing  302 , one end of the first groove portion  332  communicates with the inlet  311  of the housing  302 , and the other end of the first groove portion  332  communicates with the outlet  312  of the housing  302 . The first groove portion  332  is provided with a linear portion  332 A that has an approximately constant sectional shape and extends from the inlet  311  and a throttle portion  332 B of which the groove width becomes gradually narrower toward the outlet  312  from the linear portion  332 A. 
     The linear portion  332 A of the first groove portion  332  is provided with a plurality of linear projection portions  335 . The linear projection portions  335  are provided on a bottom wall surface  332   b  of the linear portion  332 A such that the plurality of linear projection portions  335  are arranged at predetermined intervals in a groove width direction of the first groove portion  332  and the linear projection portions  335  extend along the linear portion  332 A over an area from the inlet  311  to the throttle portion  332 B. Each linear projection portion  335  has a trapezoid-shaped section and opposite side surfaces thereof are obliquely inclined. Therefore, in a case where a water droplet adheres, it is possible to lower the height of the water droplet by increasing a contact angle with respect to the water droplet and it is possible to cause the water droplet to quickly flow toward the downstream side from the upstream side by increasing a wettability. Accordingly, in a case where a water droplet adheres to the first groove portion  332 , it is possible to effectively prevent the water droplet from flowing into the second groove portion  333  from the first groove portion  332  and it is possible to quickly discharge the water droplet to the outside. 
     The second groove portion  333  branches off from the linear portion  332 A of the first groove portion  332 , extends toward the base end of the housing  302  while being curved, and communicates with a measurement flow path  341  provided in the central portion of the housing  302  in the longitudinal direction. An upstream end of the second groove portion  333  communicates with a side wall surface  332   a , which is positioned close to the base end of the housing  302  and is one of a pair of side wall surfaces constituting the first groove portion  332 , and a bottom wall surface  333   a  is connected to the bottom wall surface  332   b  of the linear portion  332 A of the first groove portion  332  such that the bottom wall surface  333   a  becomes flush with the bottom wall surface  332   b.    
     A level difference portion  334  is provided along a boundary portion between the bottom wall surface  332   b  of the first groove portion  332  of the housing  302  and the bottom wall surface  333   a  of the second groove portion  333 . The level difference portion  334  is formed on a line that linearly connects an intersection point between the side wall surface  332   a  of the first groove portion  332  and a side wall surface  333   b  of the second groove portion  333 , which is on an inner circumferential side, to an intersection point between the side wall surface  332   a  of the first groove portion  332  and a side wall surface  333   c  of the second groove portion  333 , which is on an outer circumferential side. 
     In a case where a water droplet adhering to the bottom wall surface  332   b  of the linear portion  332 A of the first groove portion  332  flows by being pressed by the measurement target gas  30  and moves toward the second groove portion  333 , the level difference portion  334  can hold back the water droplet by means of the level difference portion  334  and can prevent the water droplet from flowing to the bottom wall surface  333   a  of the second groove portion  333  from the bottom wall surface  332   b  of the first groove portion  332 . Accordingly, it is possible to prevent the water droplet from infiltrating into the second groove portion  333  from the first groove portion  332  via a path wall surface and it is possible to protect the flow rate measurement unit  451  from water. 
     As with the linear projection portions  335 , the level difference portion  334  has a trapezoid-shaped section and opposite side surfaces thereof are obliquely inclined. Therefore, in a case where a water droplet adheres, it is possible to lower the height of the water droplet by increasing a contact angle with respect to the water droplet and it is possible to cause the water droplet to quickly flow toward the downstream side from the upstream side by increasing a wettability. Accordingly, in a case where a water droplet adheres to the level difference portion  334 , it is possible to effectively prevent the water droplet from flowing into the second groove portion  333  from the first groove portion  332  and it is possible to quickly discharge the water droplet to the outside from the first groove portion  332 . 
     The side wall surface  333   b  of the second groove portion  333 , which is on the inner side of a curve, is provided with a recess Portion  333   e  and thus water infiltrating into the second groove portion  333  can be drawn into the recess portion  333   e  and can be discharged to the outside via a drain hole  376  (refer to  FIG. 2C ) that is drilled in the rear cover  304  while being positioned to face the recess portion  333   e.    
     The measurement flow path  341  is formed to penetrate the housing  302  from a front side to a rear side in the thickness direction and a flow path exposure portion  430  of the circuit package  400  is disposed to protrude. The second groove portion  333  communicates with the measurement flow path  341  at a position on an upstream side of the flow path exposure portion  430  of the circuit package  400  in the sub path. 
     The second groove portion  333  has a shape such that the groove depth thereof becomes greater toward the measurement flow path  341  and particularly, the second groove portion  333  is provided with a steep inclined portion  333   d  of which the depth suddenly increases in front of the measurement flow path  341 . The steep inclined portion  333   d  allows a gas in the measurement target gas  30  to proceed to a front surface  431  side, which is one of the front surface  431  and a rear surface  432  of the flow path exposure portion  430  of the circuit package  400  in the measurement flow path  341  and on which the flow rate measurement unit  451  is provided, and allows a foreign substance such as dust included in the measurement target gas  30  to proceed to the rear surface  432  side. 
     The measurement target gas  30  gradually moves in a direction toward a front side (back side of  FIG. 3B ) of the housing  302  as the measurement target gas  30  flows inside the rear side sub path Groove  331 . Furthermore, a portion of air, which is small in mass, moves along the steep inclined portion  333   d  and flows toward the front surface  431  (refer to  FIG. 3A ) of the flow path exposure portion  430  in the measurement flow path  341 . Meanwhile, since it is difficult for the foreign substance, which is large in mass, to suddenly change the course due to a centrifugal force, the foreign substance cannot flow along the steep inclined portion  333   d  and flows to the rear surface  432  (refer to  FIG. 3B ) of the flow path exposure portion  430  in the measurement flow path  341 . 
     The flow rate measurement unit  451  is provided on the front surface  431  of the flow path exposure portion  430  of the circuit package  400 . In the flow rate measurement unit  451 , heat is transmitted from the measurement target gas  30  flowing to the front surface  431  of the flow path exposure portion  430  via a heat transmission surface and the flow rate is measured. 
     When the measurement target gas  30  passes by the front surface  431  side and the rear surface  432  side of the flow path exposure portion  430  of the circuit package  400 , the measurement target gas  30  flows into the front side sub path groove  321  from a sub path downstream side portion of the measurement flow path  341 , and flows inside the front side sub path groove  321 , and is discharged to the main path  124  from the second outlet  313 . 
     As illustrated in  FIG. 3A , one end of the front side sub path groove  321  communicates with the sub path downstream side portion of the measurement flow path  341  and the other end of the front side sub path groove  321  communicates with the outlet  313  formed close to the tip end of the housing  302 . The front side sub path groove  321  has a shape that is curved such that the front side sub path groove  321  gradually becomes closer to the downstream side in the main flowing direction toward the tip end of the housing  302 , linearly extends toward the downstream side in the main flowing direction of the measurement target gas  30  at the tip end portion of the housing  302 , and the groove width thereof gradually becomes smaller toward the second outlet  313 . 
     In this example, a flow path configured with the rear side sub path groove  331  extends from the tip end of the housing  302  to the base end side, which is the flange  305  side, while describing a curve, the measurement target gas  30  flowing in the sub path  307  flows in a direction opposite to the main flowing direction in the main path  124  at a position closest to the flange  305 , and the rear side sub path, which is provided on the rear surface side of the housing  302 , is connected to the front side sub path, which is provided on the front surface side, at a portion in which the measurement target gas flows in the direction opposite to the main flowing direction. 
     The measurement flow path  341  is divided into a space on the front surface  431  side and a space on the rear surface  432  side by the flow path exposure portion  430  of the circuit package  400  and is not divided by the housing  302 . That is, the measurement flow path  341  is formed to penetrate the front and rear surfaces of the housing  302  and the circuit package  400  is disposed in the one space to protrude in a cantilever manner. According to this configuration, it is possible to mold the sub path grooves on both of front and rear surfaces of the housing  302  through one resin molding process and it is possible to mold a structure that connecting the sub path grooves on both surfaces at the same time. Note that, the circuit package  400  is fixed while being embedded in fixation portions  351 ,  352 , and  353  of the housing  302  through resin molding. 
     In addition, according to the above-described configuration, it is possible to insert and mount the circuit package  400  in the housing  302  at the same time as when forming the housing  302  through resin molding. Note that, it is also possible to form the shape of a sub path connecting the rear side sub path groove  331  and the front side sub path groove  321  to each other through one resin molding process by configuring any one of a path upstream side, which is on the upstream side of the circuit package  400 , and a path downstream side, which is on the downstream side, to be penetrated in a width direction of the housing  302 . 
     When the front side sub path groove  321  is closed by the front cover  303 , the front side sub path of the housing  302  is formed and a side wall upper end portion of each of a pair of side wall surfaces constituting the front side sub path groove  321 , which is on the upper side in a groove height direction, comes into close contact with a facing surface of the front cover  303 . Furthermore, when the rear side sub path groove  331  closed by the rear cover  304 , the rear side sub path of the housing  302  is formed and a side wall upper end portion of each of a pair of side wall surfaces constituting the rear side sub path groove  331 , which is on the upper side in the groove height direction, comes into close contact with a facing surface of the rear cover  304 . 
     As illustrated in  FIGS. 3A and 3B , in the housing  302 , a cavity portion  342 , which becomes a circuit chamber, is formed between the flange  305  and a portion in which the sub path grooves are formed. The cavity portion  342  is formed by penetrating the housing  302  in the thickness direction and in the present example, the cavity portion  342  is divided into two parts of a cavity portion  342 A on the flange side and a cavity portion  342 B on the sub path side by the fixation portion  352  of the housing  302 . 
     In the cavity portion  342 A, outer leads (connection terminal)  412  of the circuit package  400  and an inner end  306   a  of an external terminal of a connector  306  are electrically connected to each other via spot welding, laser welding, or the like. The cavity portion  342 B is provided with a conductive intermediate member  551 . When the front cover  303  is attached to the housing  302 , the intermediate member  551  is interposed between a conductor  501  of the front cover  303  and a lead frame  401  of the circuit package  400  and electrically connects the conductor  501  and the lead frame  401  to each other. The cavity portion  342  is closed when the front cover  303  and the rear cover  304  are attached to the housing  302  and the vicinity of the cavity portion  342  is sealed by being laser-welded to the front cover  303  and the rear cover  304 . 
       FIG. 4  is a view for describing a configuration of the front cover and  FIG. 5  is a view for describing a configuration of the rear cover.  FIG. 4A  is a view illustrating a facing surface of the front cover and  FIG. 4B  is a sectional view taken along line B-B in  FIG. 4A .  FIG. 5A  is a view illustrating a facing surface of the rear cover and  FIG. 5B  is a view illustrating a side surface of the rear cover. 
     The front cover  303  or the rear cover  304  has a thin plate-like shape and has a shape provided with a wide cooling surface. Therefore, the thermal type flowmeter  300  has an effect that air resistance is reduced and the thermal type flowmeter  300  is likely to be cooled by the measurement target gas flowing in the main path  124 . 
     The front cover  303  has a size such that the front cover  303  covers the front surface of the housing  302 . On the facing surface of the front cover  303 , a fifth region  361  that closes the front side sub path groove  321  of the housing  302 , a sixth region  362  that closes a front side of the measurement flow path  341  of the housing  302 , and a seventh region  363  that closes a front side of the cavity portion  342  are formed. The seventh region  363  is provided with a region  363 A that closes the cavity portion  342 A, which is a portion of the cavity portion  342  and is close to the flange  305  of the housing  302 , and a region  363 B that closes the cavity portion  342 B which is on the sub path side. 
     Furthermore, a recess portion  361   a  into which side wall upper end portions of the front side sub path groove  321  of the housing  302  are inserted is provided around the peripheral portions of the fifth region  361  and the sixth region  362 . In addition, a recess portion  363   a  into which a front side outer circumferential end portion of the cavity portion  342  is inserted provided around the peripheral portion of the seventh region  363 . Furthermore, on the facing surface of the front cover  303 , a projection portion  362   a  which is inserted into a gap between a tip end of the flow path exposure portion  430  of the circuit package  400  and the measurement flow path  341  of the housing  302  is provided. 
     The front cover  303  is laser-welded to the side wall upper end portions of the front side sub path groove  321  of the housing  302  inserted into the recess portion  361   a  with the facing surface of the front cover  303  facing the front surface of the housing  302  and the front cover  303  is laser-welded to the peripheral portion of the cavity portion  342  of the housing  302  inserted into the recess portion  363   a  such that the front cover  303  is tightly fixed to the housing  302 . 
     The front cover  303  is provided with the conductor  501 . The conductor  501  is provided to remove electricity such that the foreign substance such as dust included in the measurement target gas is prevented from adhering the flow rate measurement unit  451  or the vicinity thereof while being electrically charged and is formed of, for example, a conductive metal plate or conductive metal foil formed of iron, aluminum alloy, copper, copper alloy, stainless steel, or nickel. In the present example, the conductor  501  is insert-molded into the front cover  303 . 
     The conductor  501  is provided with a flat plate portion  502  that is disposed in the sixth region  362  of the front cover  303  and an arm portion  503  which protrudes from the flat plate portion  502  and of which a tip end is disposed in the seventh region  363 . The flat plate portion  502  is disposed on the facing surface of the front cover  303  with at least a portion thereof exposed and is positioned to face at least the flow rate measurement unit  451  on the front surface  431  of the flow path exposure portion  430  of the circuit package  400  in the measurement flow path  341  of the housing  302 . The flat plate portion  502  has a projecting shape, of which the central portion in the flowing direction of the measurement target gas  30  protrudes like a mountain, such that the flow speed of the measurement target gas  30  passing through a space between the flat plate portion  502  and the flow rate measurement unit  451  is increased. The arm portion  503  is provided with a claw portion  504  that protrudes with a tip end thereof folded. The claw portion  504  abuts onto a tip end of the intermediate member  551  in a state where the front cover  303  is attached to the housing  302 . 
     The rear cover  304  has a size such that the rear cover  304  covers the rear surface of the housing  302 . On the facing surface of the rear cover  304 , a first region  371 A that closes the first groove portion  332  of the rear side sub path groove  331  of the housing  302 , a second region  371 B that closes the second groove portion  333 , a third region  372  that closes a rear side of the measurement flow path  341  of the housing  302 , and a fourth region  373  that closes a rear side of the cavity portion  342  are formed. The fourth region  373  is provided with a region  373 A that closes the cavity portion  342 A of the cavity portion  342  which is close to the flange  305  of the housing  302  and a region  373 B that closes the cavity portion  342 B of the cavity portion  342  which is on the sub path side. Furthermore, a recess portion  371   a  into which side wall upper end portions of the rear side sub path groove  331  of the housing  302  are inserted is provided around the peripheral portions of the first region  371 A, the second region  371 B, and the third region  372 . In addition, a recess portion  373   a  into which a rear side outer circumferential end portion of the cavity portion  342  is inserted is provided around the peripheral portion of the fourth region  373 . 
     The first region  371 A of the rear cover  304  is provided with a plurality of linear projection portions  377 . The linear projection portions  377  extend along a longitudinal direction of the first region  371 A and are provided such that the plurality of linear projection portions  377  are arranged at predetermined intervals in a transverse direction. Each linear projection portion  377  has the same section as a level difference portion  375 , which is a trapezoid-shaped section, and opposite side surfaces thereof are obliquely inclined. Therefore, in a case where a water droplet adheres, it is possible to lower the height of the water droplet by increasing a contact angle with respect to the water droplet and it is possible to cause the adhering water droplet to quickly flow toward the downstream side from the upstream side by increasing a wettability. Accordingly, it is possible to effectively prevent the water droplet from flowing into the second region  371 B from the first region  371 A and it is possible to quickly discharge the water droplet to the outside. 
     The drain hole  376  that communicates with the sub path  307  is drilled in the rear cover  304 . The drain hole  376  is formed to penetrate at a position that closes the recess portion  333   e  of the housing  302  in a state where the rear cover  304  is attached to the housing  302  and thus water drawn into the recess portion  333   e  of the second groove portion  333  can be discharged to the outside of the housing  302 . 
     On the facing surface of the rear cover  304 , a projection portion  372   a  which is inserted into the gap between the tip end of the flow path exposure portion  430  of the circuit package  400  and the measurement flow path  341  of the housing  302  is provided. The projection portion  372   a  fills the gap between the tip end of the flow path exposure portion  430  of the circuit package  400  and the measurement flow path  341  of the housing  302  in cooperation with the projection portion  362   a  of the front cover  303 . 
     The front cover  303  and the rear cover  304  are respectively attached to the front surface and the rear surface of the housing  302  and form the sub path  307  in cooperation with the front side sub path groove  321  and the rear side sub path groove  331 . The sub path  307  is provided with a first path that linearly extends from the inlet  311  to the first outlet  312  and a second path that branches off from an intermediate portion of the first path and extends toward the flow rate measurement unit  451  while being curved. The conductor  501  provided on the front cover  303  is conductively connected to the lead frame  401  of the circuit package  400  via the intermediate member  551  when the front cover  303  is attached to the housing  302 . Accordingly, it is possible to configure a conductive circuit in which the conductor  501  is connected to the ground and it is possible to remove electricity of the flow rate measurement unit  451  in the sub path  307  which is a place where the conductor  501  is disposed and through which the measurement target gas  30  passes or a component in the vicinity of the flow rate measurement unit  451 . Accordingly, it is possible to prevent a foreign substance such as fine particles included in the measurement target gas  30  from firmly adhering to the flow rate measurement unit  451  or the like while being electrically charged and to prevent deterioration in measurement performance due to corruption. 
       FIG. 6A  is a sectional view taken along line VIA-VIA in  FIG. 2A ,  FIG. 6B  is an enlarged view of VIB in  FIG. 6A ,  FIG. 6C  is a sectional view taken along line VIC-VIC in  FIG. 2A , and  FIG. 6D  is a sectional view taken along line VID-VID in  FIG. 2A . 
     The circuit package  400  is configured by integrally molding the lead frame  401  and circuit components installed into the lead frame  401  by using a thermosetting resin material  403 . In the present example, as the circuit components, as illustrated in FIG.  9 , an LSI  453 , a capacitor chip  454 , and a sensor element of the flow rate measurement unit  451  or the temperature measurement unit  452  are installed in the lead frame  401 . 
     As illustrated in  FIG. 8 , the circuit package  400  has a vertically long flat plate-like shape and when the circuit package  400  is molded into the housing  302 , the flow path exposure portion  430  protrudes inside the sub path  307  and the front surface  431  and the rear surface  432  of the flow path exposure portion  430  are disposed to be parallel with each other along the flowing direction of the measurement target gas  30  in the sub path  307 . One long side portion of the circuit package  400  is provided with a protrusion portion  433  and a tip end of the protrusion portion  433  is provided with the temperature measurement unit  452 . The protrusion portion  433  protrudes along a flat surface of the circuit package  400 , penetrates an upstream side outer wall  317  of the housing  302 , and is disposed at a position such that the temperature measurement unit  452  is exposed to the outside of the housing  302 . 
     The other long side portion of the circuit package  400  is provided with an exposure portion  405  at which a portion of the lead frame  401  is exposed out of the resin material  403 . The exposure portion  405  is configured by cutting the resin material  403  of an end portion of the circuit package  400  and is provided on front and rear surfaces of the lead frame  401 . In the present example, the exposure portion  405  is formed by causing the lead frame  401  to be interposed between molds respectively abutting onto the front and rear surfaces of the lead frame  401  and preventing resin from flowing into the exposure portion  405  at the time of molding the circuit package  400  with the resin material  403 . 
     The exposure portion  405  of the lead frame  401  is pressed by the conductor  501  via the intermediate member  551 . The intermediate member  551  is formed of a conductive elastic member such as electroconductive rubber and abuts onto the exposure portion  405  of the lead frame  401 . The intermediate member  551  is disposed in the cavity portion  342 B of the housing  302  and electrically connects the exposure portion  405  of the lead frame  401  and the conductor  501  of the front cover  303  to each other. The intermediate member  551  is formed of an elastic body that can be elastically deformed in accordance with a change in distance between the conductor  501  and the exposure portion  405 . 
     As illustrated in  FIG. 6D , a base end of the intermediate member  551  is supported by a supporting portion  343  of the housing  302  and a tip end thereof is interposed between the exposure portion  405  of the lead frame  401  and the claw portion  504  of the conductor  501 . Regarding the intermediate member  551 , when the front cover  303  is attached to the housing  302 , the tip end of the intermediate member  551  is interposed between the exposure portion  405  of the lead frame  401  and the claw portion  504  of the conductor  501  and is elastically deformed to press the exposure portion  405  of the lead frame  401  with a predetermined pressing force. 
       FIG. 7  is a view for describing a method of connecting the lead frame and the conductor. The supporting portion  343  of the housing  302  which supports the intermediate member  551  is provided to protrude in the cavity portion  342 B of the housing  302  (refer to  FIG. 7 ( 1 )). The supporting portion  343  is provided with a plurality of rod-shaped members that are erected toward the front surface side of the housing  302 . The intermediate member  551  is pressed from the front surface side of the housing  302  to the supporting portion  343  along the axial direction of the rod-shaped members, the base end is inserted between the plurality of rod-shaped members, and the central rod-shaped member is fitted into a circular hole of the base end of the intermediate member  551  such that the intermediate member  551  is supported by the supporting portion  343  (refer to  FIG. 7 ( 2 )). 
     Then, the front cover  303  is attached to the housing  302 . In  FIG. 7 ( 3 ), the front cover  303  is not illustrated and only the conductor  501  provided on the front cover  303  is illustrated. Since the front cover  303  is attached, the intermediate member  551  abuts onto the claw portion  504  of the conductor  501 , is pressed in the thickness direction of the housing  302 , interposed between the claw portion  504  of the conductor  501  and the exposure portion  405  of the circuit package  400 , and is held in a state of being elastically deformed in a pressing direction. Since the intermediate member  551  is formed of electroconductive rubber, the conductor  501  and the exposure portion  405  of the circuit package  400  can be electrically connected to each other. 
     It is possible to cause the intermediate member  551  to electrically connect the conductor  501  of the front cover  303  and the exposure portion  405  of the lead frame  401  to each other only by attaching the front cover  303  to the housing  302 . Accordingly, it is possible to easily establish electric connection between the conductor  501  of the front cover  303  and the exposure portion  405  of the circuit package  400  and it is possible to prevent a foreign substance included in the measurement target gas  30  from adhering to the flow rate measurement unit  451  or the like while being electrically charged by removing electricity of the flow rate measurement unit  451  in the sub path  307  or a component in the vicinity of the flow rate measurement unit  451 . 
       FIG. 9  is a view illustrating a specific configuration example of the lead frame. 
     The lead frame  401  is provided with a mounting portion  404  on which a circuit component such as the LSI  453  is mounted and the exposure portion  405  of which at least a portion is exposed out of the resin material  403  and which is pressed by the conductor  501  via the intermediate member  551 . The exposure portion  405  is disposed to be adjacent to the mounting portion  404 . The mounting portion  404  and the exposure portion  405  are connected to GND of the lead frame  401  and are connected to the inner end  306   a  of the external terminal of the connector  306  via the outer leads  412  from inner leads  411 . 
     The lead frame  401  is configured such that the mounting portion  404  and the exposure portion  405  are separated from each other at least partially. In the present example, a slit  406  is provided between the mounting portion  404  and a pressed region  405   a  of the exposure portion  405  that is pressed via the intermediate member  551 . 
     According to the present example, since the lead frame  401  is provided with the slit  406  and the mounting portion  404  of the lead frame  401  and the exposure portion  405  are separated from each other, it is possible to prevent a stress at a time when the pressed region  405   a  of the exposure portion  405  is pressed via the intermediate member  551  from acting on a mounting region of the mounting portion  404 . 
     Regarding the circuit package  400 , circuit wires are packaged and it is necessary that the circuit package  400  is provided with the exposure portion  405  at which the lead frame  401  is exposed in order to establish electric connection with the conductor  501 . Since the exposure portion  405  of the lead frame  401  is formed by causing a portion of the lead frame  401  to be interposed between molds on upper and lower sides when forming the circuit package  400  through molding, the resin material  403  is not present on front and rear surfaces of the portion and the hardness of the portion is particularly lower than a nearby portion. 
     Accordingly, if there is no slit  406 , there is a possibility that a stress acting on the exposure portion  405  is transmitted to the mounting portion  404  and characteristics of the LSI  453  installed in the mounting portion  404  or an element of the flow rate measurement unit  451  are changed in a case where the pressed region  405   a  of the exposure portion  405  of the lead frame  401  is pressed by the conductor  501  via the intermediate member  551 . 
     However, in the present invention, the lead frame  401  is provided with the slit  406  and the mounting portion  404  of the lead frame  401  and the exposure portion  405  are separated from each other. Accordingly, it is possible to isolate a stress that acts on the exposure portion  405  in a case where the pressed region  405   a  of the exposure portion  405  of the lead frame  401  is pressed via the intermediate member  551  by using the slit  406  and to prevent the stress from being transmitted to the mounting portion  404  from the exposure portion  405  and thus it is possible to prevent characteristics of the circuit components such as the LSI  453  mounted on the mounting portion  404  from being influenced. 
     According to the present example, since the circuit package  400  is provided with the exposure portion  405  and the exposure portion  405  is electrically connected to the conductor  501  of the front cover  303 , it is possible to easily connect the conductor  501  to the lead frame  401  in the circuit package  400 . Accordingly, it is possible to remove electricity of the flow rate measurement unit  451  in the sub path  307  which is a place where the conductor is disposed and through which the measurement target gas passes or a component in the vicinity of the flow rate measurement unit  451  and thus it is possible to prevent a foreign substance such as fine particles included in the measurement target gas  30  from firmly adhering to the flow rate measurement unit  451  or the like while being electrically charged and to prevent deterioration in measurement performance due to corruption. 
     In the present example, an end portion of the circuit package  400  is provided with a U-shaped notch such that the exposure portion  405  is formed. Therefore, a wrinkle is not likely formed on a film that is interposed between the molds at the time of molding and it is easy to perform molding in comparison with a case where the circuit Package  400  is formed such that a surface thereof is provided with a circular hole-shaped recess. In addition, since it is possible to support the intermediate member  551 , which abuts onto the exposure portion  405 , at a position on a lateral side of the circuit package  400 , it is not necessary that the circuit package  400  is provided with a side wall for protecting the intermediate member  551  and it is possible to prevent an increase in stress on the LSI  453  which is caused by the side wall. 
       FIGS. 10A to 10F  are schematic views illustrating other configuration examples in which the exposure portion  405  and the conductor  501  are connected to each other. In a configuration example illustrated in  FIG. 10A , a portion of an outer lead  413  that protrudes from an end portion of the circuit package  400  is folded into a bellows-like shape and is connected to the conductor  501 . A folded portion  413   a  that is folded into a bellows-like shape abuts onto the arm portion  503  of the conductor  501  with a predetermined pressing force due to elastic deformation and is electrically connected to the arm portion  503 . According to this configuration example, it is possible to omit the intermediate member  551  and thus it is possible to decrease the number of components and to simplify an assembly operation. In addition, it is possible to decrease the number of contact points and to decrease a possibility of poor contact. 
     In a configuration example illustrated in  FIG. 10B , the intermediate member  551  is held while being stuck into the exposure portion  405  of the lead frame  401 . A fitting hole, into which the intermediate member  551  is fitted such that the intermediate member  551  is held, is formed in the exposure portion  405  in advance. According to this configuration example, it is not necessary that the housing  302  is provided with the supporting portion  343  and it is possible to simplify the configuration of the housing  302 . 
     In a configuration example illustrated in  FIGS. 10C and 10D , a flat spring  552  is used as the intermediate member  551 . The flat spring  552  is formed by folding a metal plate into a U-shape, a base end portion  552   a  is fixed to the supporting portion  343  of the housing  302 , one end portion  552   b  abuts onto the exposure portion  405  with a predetermined pressing force due to elastic deformation, and the other end portion  552   c  abuts onto the arm portion  503  of the conductor  501  such that both components are electrically connected to each other. According to this configuration example, a pressing force on the exposure portion  405  and a pressing force on the conductor  501  can be set to be different from each other, each of the exposure Portion  405  and the conductor  501  can come into contact with the flat spring while being pressed with an appropriate pressing force, and it is possible to prevent an excessive force from acting on the LSI  453  or the like. 
       FIGS. 10E and 10F  illustrate other configuration examples of the intermediate member. In the above-described example, the description has been made by using a case where the intermediate member  551  has a rectangular block-like shape as an example. However, the intermediate member  551  may have an O-like shape as illustrated in  FIG. 10E  or may have a shape in which a squashing projection portion is installed on an abutting surface as illustrated in  FIG. 10F . An intermediate member  553  illustrated in  FIG. 10E  is provided with a space portion  553   c  between an upper surface  553   a  that abuts onto the arm portion  503  of the conductor  501  and a lower surface  553   b  that abuts onto the exposure portion  405  and the elastic force thereof can be adjusted by changing geometric settings of the space chamber  553   c . The elastic force of an intermediate member  554  illustrated in  FIG. 10F  can be adjusted by changing the sizes or the shapes of a projection portion  554   a  that abuts onto the arm portion  503  of the conductor  501  and a projection portion  554   b  that abuts onto the exposure portion  405 . 
       FIG. 11  is a diagram conceptually illustrating a configuration of the thermal type flowmeter of Example 1, and  FIG. 12  is a view for describing another configuration example in which the conductor is connected and fixed. In the present example, the conductor  501  is configured through component bonding with respect to the sub path  307 , is configured through contact connection with respect to the circuit component such as the LSI  453  of the circuit package  400 , and is configured separately from the sub path  30  and the circuit component. For example, as another configuration example, the conductor may be connected to the exposure portion  405  of the circuit package  400  as illustrated in  FIG. 12  such that an ASSY is obtained or, although not shown in the drawings, a conductive material may be over-molded with respect to the circuit package  400  such that an ASSY is obtained. Even in this case, the conductor  501  is configured separately from the sub path  307  and the circuit component. 
       FIGS. 13A to 13E  are views for describing other configuration examples of the thermal type flowmeter, where  FIG. 13A  is a front view illustrating a main portion of the thermal type flowmeter in an enlarged manner and  FIGS. 13B to 13E  are views schematically illustrating specific examples of configurations for holding an intermediate member  555 . 
     In this configuration example, an exposure portion  407  is formed by providing a circular hole-shaped recess on the front surface of the circuit package  400 . The recess is provided on front and rear surfaces of the circuit package  400  and a portion of the lead frame  401  is exposed on a front surface side and a rear surface side. In addition, the intermediate member  555  is formed of electroconductive rubber as with the intermediate member  551  and has a columnar shape. 
     As illustrated in  FIG. 13B , the front cover  303  is provided with a guide  365  for holding the intermediate member  551 . The guide  365  is formed on the facing surface of the front cover  303  such that the guide  365  protrudes and is provided with a fitting hole  365   a  into which the base end of the intermediate member  551  can be fitted. The base end of the intermediate member  551  abuts onto the arm portion  503  of the conductor  501 , the tip end of the intermediate member  551  abuts onto the exposure portion  407  of the circuit package  400 , and the conductor  501  and the lead frame  401  of the circuit package  400  are electrically connected to each other. According to the above-described configuration, for example, it is possible to prevent the intermediate member  551  from falling off the fitting hole  365   a  while the front cover  303  is being attached to the housing  302  and to improve assembly workability. 
     In addition, as illustrated in  FIG. 13C , the claw portion  504  provided on the tip end of the arm portion  503  of the conductor  501  may be stuck into the base end of the intermediate member  551  to hold the intermediate member  551  such that the intermediate member  551  becomes less likely to fall off. 
     As illustrated in  FIG. 13D , the circuit package  400  may be provided with a guide  421  for installing the intermediate member  555  onto an exposed portion of the exposure portion  405 . The guide  421  may be integrally provided with the circuit package  400  and may be provided separately from the circuit package  400 . 
     In addition, as illustrated in  FIG. 135 , a recess formed on the rear surface of the circuit package  400  may be filled with a resin  422  such that the recess is hidden. Since the exposure portion  407  is formed by causing a portion of the lead frame  401  to be interposed between forming dies on the front surface side and the rear surface side, the recess is formed on the rear surface of the circuit package  400  as well. Therefore, the recess may be filled with the resin  422  for protection from gas and the like as well. 
       FIGS. 14A to 14F  are views for describing configuration examples of a method of connecting the exposure portion  407  and the conductor  501 . 
     Although an intermediate member  556  is formed of electroconductive rubber as with the intermediate member  551 , the intermediate member  556  may have a shape other than a columnar shape or a prismatic columnar shape. For example, as illustrated in  FIG. 14A , the intermediate member  556  may have a shape corresponding to the shape of a portion of the circuit package  400  in the vicinity of the exposure portion  407 . According to this configuration, a tip end of the intermediate member  556  is fitted into the exposure portion  407  of the circuit package  400  and thus it is possible to prevent positional deviation of the intermediate member  556 . In the present example, the circuit package  400  is provided with the guide  421  such that the positional deviation of the intermediate member  556  is further prevented. 
     Furthermore, an intermediate member  557  may be formed of a metal coil spring as illustrated in  FIG. 14B . The intermediate member  557  is interposed between the exposure portion  407  of the circuit package  400  and the conductor  501  of the front cover  303  in a compressed state and electrically connects the lead frame  401  of the circuit package  400  and the conductor  501  to each other. 
     In an example illustrated in  FIG. 14C , an outer guide  365  that covers an outer side of the intermediate member  557  at a position close to the base end of the intermediate member  557  and an inner guide  366  that is disposed inside the intermediate member  557  are provided on the front cover  303 . Accordingly, it is possible to prevent the intermediate member  557  from falling off the front cover  303 . 
     In an example illustrated in  FIG. 14D , a second arm portion  505  is provided to continuously extend from the tip of the arm portion  503  of the conductor  501  and a tip end of the second arm portion  505  is in direct contact with the exposure portion  407  of the circuit package  400 . According to this configuration, it is not necessary to separately provide the intermediate member and thus it is possible to decrease the number of components and to simplify an assembly operation. 
     In an example illustrated in  FIG. 14E , the tip end of the second arm portion  505  is connected via a connecting method other than contact connection and for example, a bonding portion  506  that is bonded through welding, a conductive adhesive agent, or a paste is provided. Since the tip end is bonded to the exposure portion  407  via such a bonding portion  506 , it is possible to more reliably establish electrical connection. 
     In a configuration example illustrated in  FIG. 14F , the second arm portion  505  that protrudes from the arm portion  503  of the conductor  501  is formed to be folded into a bellows-like shape and the tip end is bonded to the conductor  501  via the bonding portion  506 . The second arm portion  505  that is folded into a bellows-like shape abuts onto the exposure portion  405  of the circuit package  400  with a predetermined pressing force due to elastic deformation and is electrically connected to the exposure portion  405 . According to this configuration example, it is possible to omit the intermediate member  551  and thus it is possible to decrease the number of components and to simplify an assembly operation. In addition, it is possible to decrease the number of contact points and to decrease a possibility of poor contact. 
       FIG. 15  is a view for describing another configuration example of the conductor. In  FIG. 15 , the conductor  501  provided on the front cover  303  is also illustrated. 
     A characteristic point in this configuration example is that the conductor  501  is provided with a shield portion  507  that faces and covers a region of the circuit package  400  in which the LSI  453  and a measuring element are provided. The shield portion  507  is formed to continuously extend from the arm portion  503  of the conductor  501 , planarly extends in the cavity portion  342 B of the housing  302 , and is disposed to face the region of the circuit package  400  in which the LSI  453  and the measuring element are provided. 
     Since the thermal type flowmeter  300  is provided with a conductive circuit including the conductor  501 , a shield effect with respect to an electric wave is improved and output error is improved. Particularly, since the electrical conductivity of a metal plate used for the conductor  501  is extremely great and the metal plate has a low intrinsic impedance. Energy of an electric wave cannot infiltrate into the metal plate since the intrinsic impedance of a space is tens of thousands of times the intrinsic impedance of the metal plate in terms of order. Therefore, it is possible to improve a shield effect with respect to an electric wave of the LSI  453  or the measuring element of the circuit package  400  by installing the conductive circuit which uses the metal plate. The electrical resistivity of the conductor  501  in an unprocessed state is very low and the conductor  501  has a merit that the conductor  501  is inexpensive, is distributed globally, and can be obtained easily. Surface treatment can be performed on the metal plate of the conductor  501  in order to improve corrosion performance. 
     In this configuration example, the conductor  501  is installed such that the shield portion  507  covers the entire LSI  453  and the entire measuring element. It is possible to further improve the shield effect by covering the entire LSI  453  and the entire measuring element with the shield portion  507  in this manner. 
     In the above-described configuration example, the description has been made by using a case where the conductor  501  is connected to the exposure portion  405  of the circuit package  400  as an example. However, the conductor  501  may be connected to, for example, the inner lead of the outer lead of the circuit package  400  as long as the conductor  501  can be connected to the ground. 
     Example 2 
     Next, Example 2 of the invention will be described.  FIGS. 16A and 16B  are views for describing a configuration of a conductor in Example 2 and  FIG. 17  is a view for describing a configuration of a conductive circuit in Example 2. 
     A characteristic point in this example is that the conductor  501  is directly connected to an inner end  306   b  of the external terminal of the connector  306  instead of the lead frame  401  of the circuit package  400 . The conductor  501  is configured such that the arm portion  503  extends up to the cavity portion  342 A of the housing  302 . As illustrated in  FIG. 16B , the inner end  306   b  of the external terminal is folded into a crank-like shape in the cavity portion  342 A. Specifically, the inner end  306   b  protrudes toward the tip end of the housing  302  from the flange  305  side of the cavity portion  342 A at the central position in the thickness direction and the width direction of the housing  302 , is folded toward the front cover  303  side at an intermediate position, is folded again at an end portion of the housing  302  in the thickness direction and the width direction, and a tip end portion thereof protrudes toward the tip end of the housing  302 . Furthermore, when the front cover  303  is attached to the housing  302 , the arm portion  503  of the conductor  501  abuts onto the tip end portion of the inner end  306   b  while overlapping the tip end portion in the cavity portion  342 A such that the arm portion  503  is electrically connected to the tip end portion. 
     As illustrated in  FIG. 17 , the thermal type flowmeter  300  is provided with an AFS drive circuit  601  and a conductive circuit  602  on an AFS side. In addition, the connector  306  is connected with a connector coupler (not shown) on an ECU  603  side such that the connector  306  is electrically connected and thus the connector  306  can communicate with the ECU  603  by an electric signal. 
     The conductive circuit  602  is electrically connected when the connector coupler is connected to the connector  306 . In the present example, the AFS drive circuit  601  and the conductive circuit  602  are configured separately from each other. Accordingly, for example, even when a surge is applied to the conductive circuit at the time of an assembly operation, since the circuit is in an electrically floating state, it is possible to prevent the AFS drive circuit  601  from being damaged. 
     Note that, connection with the conductive circuit  602  may be established by directly integrating the conductive circuit  602  with a connector terminal and may be established through welding or by using a conductive indirect member. 
     Hereinbefore, embodiments of the invention have been described in detail, but the invention is not limited to the embodiments, and various design changes can be made in a range not departing from the spirit of the invention described in claims. For example, the embodiments have been described in detail for easy explanation of the invention, but it is not limited to include all of the above-described configurations. In addition, a part of configurations of one embodiment can be substituted with configurations of another embodiment, and configurations of another embodiment may be added to configurations of one embodiment. In addition, addition, deletion, substitution of other configurations can be made with respect to parts of configurations of each embodiment. 
     REFERENCE SIGNS LIST 
     
         
           300  thermal type flowmeter 
           302  housing 
           303  front cover (cover) 
           400  circuit package 
           401  lead frame 
           403  resin material 
           404  mounting portion 
           405  exposure portion 
           406  slit 
           408  gold wire 
           451  flow rate measurement unit (sensor element) 
           452  temperature measurement unit (sensor element) 
           453  LSI (circuit component) 
           501  conductor 
           551  intermediate member (elastic member)