Thermal flow rate measuring device

Abstract

A thermal type flow rate measuring device can certainly prevent adhesion of water droplet onto a sensor element and thus achieve high reliability. The thermal type flow rate measuring device includes an auxiliary passage defined within a main passage for introducing a part of fluid flowing through the main passage, a sensor disposed within the auxiliary passage for detecting flow rate of the fluid and capturing means formed on an inner periphery of the auxiliary passage for capturing liquid contained in the fluid and transferring the captured liquid.

1. A thermal type flow rate measuring device comprising:
 an auxiliary passage defined within a main passage for introducing a part of fluid flowing through said main passage; 
 a thermal type flow rate measuring sensor disposed within said auxiliary passage for detecting flow rate of the fluid; and 
 capturing means including one of at least one groove and at least one protrusion formed on an inner periphery of said auxiliary passage for capturing liquid contained in said fluid and transferring the captured liquid from said capturing means. 
 
     
     
       2. A thermal type flow rate measuring device as set forth in  claim 1 , which further comprises means for discharging the liquid captured by said capturing means to an outside portion of said auxiliary passage. 
     
     
       3. A thermal type flow rate measuring device as set forth in  claim 2 , wherein at least one of said capturing means and said discharging means is formed with one of a plurality of grooves and a plurality of beam-like ridges, said captured liquid being is transferred along said one of said plurality of grooves said plurality of beam-like ridges said one of at least one groove and at least one protrusion. 
     
     
       4. A thermal type flow rate measuring device as set forth in  claim 3 , wherein one of a plurality of grooves and a plurality of beam-like ridges said one of at least one groove and at least one protrusion extends from upstream side to downstream side in said auxiliary passage in a manner directed from portions on said inner periphery of said auxiliary passage where liquid passing through said auxiliary passage is hardly concentrated to portions on said inner periphery of said auxiliary passage where said liquid passing through said auxiliary passage is easily concentrated at said portions on said inner periphery of said auxiliary passage. 
     
     
       5. A thermal type flow rate measuring device as set forth in  claim 3 , wherein one of a plurality of grooves and a plurality of beam-like ridges said one of at least one groove and at least one protrusion extends from an upstream side to downstream side in said auxiliary passage in a manner directed from portions of said inner periphery of said auxiliary passage where centrifugal force to be applied is small to portions of said inner periphery of said auxiliary passage where centrifugal force to be applied is large at said portions of said inner periphery of said auxiliary passage. 
     
     
       6. A thermal type flow rate measuring device as set forth in  claim 3 , wherein one of a plurality of grooves and a plurality of beam-like ridges said one of at least one groove and at least one protrusion extends obliquely relative to flow direction of the fluid. 
     
     
       7. A thermal type flow rate measuring device as set forth in  claim 2 , wherein at least one of said capturing means and said discharge means has hydrophilic characteristics on said inner periphery of said auxiliary passage so that when the liquid adheres on said inner periphery of said auxiliary passage, a contact angle being is less than or equal to 30°. 
     
     
       8. A thermal type flow rate measuring device as set forth in  claim 2 , wherein at least one of said capturing means and said discharging means is one of a plurality of grooves and a plurality of beam-like ridges, and another a separate groove is coupled with one of a plurality of grooves and a plurality of beam-like ridges said one of at least one groove and at least one protrusion and extends from a portion of said inner periphery of said auxiliary passage in a vicinity of an inlet portion of said auxiliary passage and a portion of said inner periphery of said auxiliary passage in a vicinity of an outlet portion of said auxiliary passage. 
     
     
       9. A thermal type flow rate measuring device as set forth in  claim 2 , said capturing means is a plurality of grooves formed on said inner periphery of said auxiliary passage, and said inner periphery of said auxiliary passage of portions other than those formed by said plurality of grooves are provided with water repellent characteristics so that when the liquid adheres on said inner periphery of said auxiliary passage, a contact angle thereof being greater than or equal to about 90°. 
     
     
       10. A thermal type flow rate measuring device as set forth in  claim 2 , wherein said capturing means is a plurality of grooves formed in said inner periphery of said auxiliary passage, and said discharging means comprises through-holes formed on at a downstream side of said plurality of grooves in communication with said plurality of grooves. 
     
     
       11. A thermal type flow rate measuring device comprising:
 a thermal type flow rate measuring sensor provided within a main passage through which fluid flows for measuring flow rate of the fluid in said main passage; 
 said main passage being curved in a vicinity of an upstream side of said flow rate measuring sensor; and 
 capturing means including one of at least one groove and at least one protrusion formed on an inner periphery of said main passage for capturing liquid carried by the fluid. 
 
     
     
       12. A thermal type flow rate measuring device in a vehicle control system including a thermal type flow rate control device, a control unit for controlling a vehicle on the basis of a condition of the vehicle detected by said thermal type flow rate measuring sensor, the thermal type flow rate measuring device including an auxiliary passage introducing a part of fluid flowing through a main passage, and a thermal type flow rate measuring sensor for detecting flow rate of the fluid, for detecting flow rate of the liquid,
 at least one of a liquid capturing means and discharging means being including one of at least one groove and at least one protrusion provided on an inner periphery of said auxiliary passage. 
 
     
     
       13. A flow rate measuring device incorporated in a first passage, for measuring a flow rate of fluid flowing through the first passage, comprising,
 a first opening for introducing a part of the fluid flowing through the first passage,   a second opening for discharging at least a part of the introduced fluid into the first passage;   a second passage through which the fluid introduced through the first opening and discharged from the second opening flows;   a thermal type sensor arranged in the second passage between the first opening and the second opening, for measuring a flow rate of the fluid;   a third opening arranged at a position where at least another part of the fluid introduced from the first opening can reach without said at least another part of the fluid passing by a position of the sensor, and communicated with the first passage, and   a groove formed on an inner periphery between the first opening and the third opening.   
     
     
       14. A flow rate measuring device incorporated in a first passage, for measuring a flow rate of fluid flowing through the first passage, comprising,
 a first opening for introducing a part of the fluid flowing through the first passage,   a second opening for discharging at least a part of the introduced fluid into the first passage;   a second passage through which the fluid introduced through the first opening and discharged from the second opening flows;   a thermal type sensor arranged in the second passage between the first opening and the second opening, for measuring a flow rate of the fluid;   a third opening arranged at a position where at least another part of the fluid introduced from the first opening can reach without said at least another part of the fluid passing by a position of the sensor, and communicated with the first passage, and   a protrusion provided on an inner periphery between the first opening and the third opening.   
     
     
       15. A fluid flow rate measuring device, comprising:
 a first opening for receiving fluid;   a second opening for discharging at least a part of said fluid;   a thermal flow rate sensor arranged between said first opening and said second opening;   at least one third opening; and   a capturing structure including at least one of at least one groove and at least one protrusion formed between said first opening and respective ones of said at least one third opening, wherein said capturing structure removes liquid contained in said fluid and discharges said liquid through said at least one third opening.   
     
     
       16. A thermal type flow rate measuring device comprising:
 a passage for receiving fluid;   a thermal type flow rate measuring sensor disposed within said passage for detecting flow rate of the fluid; and   a capturing structure including at least one of at least one groove and at least one protrusion formed on an inner periphery of said passage for capturing liquid contained in said fluid and for transferring the captured liquid away from said capturing structure.   
     
     
       17. A thermal type flow rate measuring device as set forth in claim 16, which further comprises a discharging structure for discharging the liquid captured by said capturing structure to outside of said passage. 
     
     
       18. A thermal type flow rate measuring device as set forth in claim 17, wherein said captured liquid is transferred along said at least one of at least one groove and at least one protrusion. 
     
     
       19. A thermal type flow rate measuring device as set forth in claim 18, wherein said at least one of at least one groove and at least one protrusion extends from upstream side to downstream side in said passage in a manner directed from portions on an inner periphery of said passage where liquid passing through said passage is hardly concentrated to portions on said inner periphery of said passage where said liquid passing through said auxiliary passage is easily concentrated at said portions on said inner periphery of said passage. 
     
     
       20. A thermal type flow rate measuring device as set forth in claim 18, wherein extends from an upstream side to downstream side in said passage in a manner directed from portions of said inner periphery of said passage where centrifugal force to be applied is small to portions of said inner periphery of said passage where centrifugal force to be applied is large at said portions of said inner periphery of said passage. 
     
     
       21. A thermal type flow rate measuring device as set forth in claim 18, wherein said at least one of at least one groove and at least one protrusion extends obliquely relative to flow direction of the fluid. 
     
     
       22. A thermal type flow rate measuring device as set forth in claim 17, wherein at least one of said capturing structure and said discharge structure has hydrophilic characteristics on an inner periphery of said passage so that when the liquid adheres on said inner periphery of said passage, a contact angle is less than or equal to 30 degrees. 
     
     
       23. A thermal type flow rate measuring device as set forth in claim 17, wherein a separate groove is coupled with said at least one of at least one groove and at least one protrusion and extends from a portion of an inner periphery of said passage in a vicinity of an inlet portion of said passage and a portion of said inner periphery of said passage in a vicinity of an outlet portion of said passage. 
     
     
       24. A thermal type flow rate measuring device as set forth in claim 17, wherein said capturing structure is a plurality of grooves formed on an inner periphery of said passage, and said inner periphery of said passage of portions other than those formed by said plurality of grooves are provided with water repellent characteristics so that when the liquid adheres on said inner periphery of said passage, a contact angle thereof being greater than or equal to about 90°. 
     
     
       25. A thermal type flow rate measuring device as set forth in claim 17, wherein said capturing structure is a plurality of grooves formed in an inner periphery of said passage, and said discharging structure comprises through-holes formed on at a downstream side of said plurality of grooves in communication with said plurality of grooves. 
     
     
       26. A thermal type flow rate measuring device comprising:
 a thermal type flow rate measuring sensor provided within a main passage through which fluid flows for measuring flow rate of the fluid in said main passage;   said main passage being curved in a vicinity of an upstream side of said flow rate measuring sensor; and   a capturing device including at least one of at least one groove and at least one protrusion formed on an inner periphery of said main passage for capturing liquid carried by the fluid.   
     
     
       27. A thermal type flow rate measuring device in a vehicle control system including a thermal type flow rate control device, a control unit for controlling a vehicle on the basis of a condition of the vehicle detected by said thermal type flow rate measuring sensor, the thermal type flow rate measuring device including a passage introducing a part of fluid flowing in the vicinity of said measuring device, and a thermal type flow rate measuring sensor for detecting flow rate of the fluid,
 a liquid capturing structure including at least one of at least one groove and at least one protrusion provided on an inner periphery of said passage.   
     
     
       28. A vehicle engine control system including a control unit for controlling a vehicle on the basis of a condition of the vehicle detected by a thermal type flow rate measuring device, the thermal type flow rate measuring device including a passage introducing a part of fluid flowing through a portion of said vehicle engine, and a liquid capturing means including at least one of at least one groove and at least one protrusion provided on an inner periphery of said passage.