Thermal flow meter with less turbulence in fluid flow

A thermal flow meter comprising:

• a cylindrical body forming a main passage through which a fluid passes and an opening on a wall thereof;
• a central member insertable through said opening and positioned approximately at a radial center of said main passage;
• a rib connected to one part of said central member at one end thereof, said rib having an upstream end in line with an upstream end of said central member;
• and
• a mounting section connected to an other end of said rib and mounted on said cylindrical body to close said opening,
• wherein said central member has a profile which provides a cross section of flow passage relative to said cylindrical body, said cross section decreasing gradually toward a downstream of said main passage;
• and
• wherein said central member includes:
• an introduction inlet introducing thereinto a part of a fluid flowing in said main passage;
• a bypass passage the through which the fluid introduced through said introduction inlet flows;
• a sensor disposed in said bypass passage for measuring a flow amount of the fluid in said bypass passage;
• and
• an exit opened in a shape of a letter C on an outermost wall of said central member except for said one part to which said rib is connected for reverting the fluid flowing in said bypass passage to said main passage;
• wherein said bypass passage includes a first passage communicated with said introduction inlet, and a second passage communicated with a downstream portion of said first passage and said exit and generally surrounding said first passage so that fluid flows in opposite directions in said first passage and said second passage, and
• wherein said exit is formed at a position between upstream and downstream ends of said rib,
• wherein said exit has two circumferential ends which cover said one part of said central member therebetween and generally correspond to said opening of said cylindrical body.

A thermal flow meter for use with a cylindrical body having a predetermined opening on a cylindrical wall thereof, said meter comprising:

• a central member having an outer wall constructed to be inserted into said cylindrical body radially through said opening;
• a rib connected to one part of said outer wall of said central member and having a length adapted to locate said central member radially centrally in said cylindrical body when inserted with said central member through said opening, said rib having an upstream end in line with an upstream end of said central member;
• and
• a mounting section connected to said rib and having a shape to close said opening and fixedly support said central member in said cylindrical body,
• wherein said central member includes:
• an inlet for introducing therethrough a part of a fluid flowing in said cylindrical body;
• a bypass passage communicated with said inlet to flow said a part of fluid therethrough;
• a sensing element disposed in said bypass passage to sense an amount of air flow of said fluid;
• an outlet communicated with said bypass passage to discharge therethrough said a part of fluid into said cylindrical body, said outlet being formed circumferentially in a C-shape on said outer wall except for said one part,
• wherein said outlet has two circumferential ends which cover said one part of said central member therebetween and generally correspond to said opening of said cylindrical body.

A thermal flow meter for use with a cylindrical body having a predetermined opening on a cylindrical wall thereof, said meter comprising:

• a central member having an outer wall constructed to be inserted into said cylindrical body radially through said opening;
• a rib connected to one part of said outer wall of said central member and having a length adapted to locate said central member radially centrally in said cylindrical body when inserted with said central member through said opening, said rib having an upstream end in line with an upstream end of said central member;
• and
• a mounting section connected to said rib and having a shape to close said opening and fixedly support said central member in said cylindrical body,
• wherein said central member includes:
• an inlet for introducing therethrough a part of a fluid flowing in said cylindrical body;
• a bypass passage communicated with said inlet to flow said a part of fluid therethrough;
• a sensing element disposed in said bypass passage to sense an amount of air flow of said fluid;
• an outlet communicated with said bypass passage to discharge therethrough said a part of fluid into said cylindrical body, said outlet being formed circumferentially in a C-shape on said outer wall except for said one part,
• wherein said outlet is located between upstream and downstream ends of said rib,
• wherein said passage includes:
• a central passage extending from said inlet centrally in a direction of fluid flow;
• and
• an outer passage generally surrounding said central passage and communicated with said central passage and said outlet,
• wherein said outlet has two circumferential ends which cover said one part of said central member therebetween and generally correspond to said opening of said cylindrical body,
• wherein said outlet is located between upstream and downstream ends of said rib.

A thermal flow meter comprising:

• a cylindrical body forming a main passage through which a fluid passes and an opening on a wall thereof;
• a central member insertable through said opening and positioned approximately at a radial center of said main passage;
• a single rib connected to one part of said central member at one end thereof, said rib having an upstream end in axial alignment with an upstream end of said central member and wherein an electronic circuit is provided within said rib;
• and
• a mounting section connected to an other end of said rib and mounted on said cylindrical body to close said opening,
• wherein said central member includes:
• an introduction inlet introducing thereinto a part of a fluid flowing in said main passage;
• a bypass passage through which the fluid introduced through said introduction inlet flows;
• a sensor disposed in said bypass passage for measuring a flow amount of the fluid in said bypass passage;
• and
• an exit opened in a shape of a letter C on an outermost wall of said central member except for said one part to which said rib is connected for reverting the fluid flowing in said bypass passage to said main passage;
• and
• wherein said exit is formed at a position between upstream and downstream ends of said rib.