Measuring and testing – Volume or rate of flow – Proportional
Reexamination Certificate
2001-09-14
2003-06-03
Williams, Hezron (Department: 2855)
Measuring and testing
Volume or rate of flow
Proportional
C073S204220
Reexamination Certificate
active
06571621
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a flow rate measuring device for detecting a flow rate of a fluid. More particularly, the invention relates to a thermal type flow rate measuring device which defines an auxiliary passage within a main passage flowing a fluid and measuring a flow rate of the fluid flowing through the auxiliary passage.
As prior art of a thermal type flow rate measuring device, there is a thermal type flow meter disclosed in Japanese Patent Application Laid-Open No. Heisei 9(1997)-304140. The disclosed thermal type flow meter is formed with an L-shaped auxiliary passage in a flow passage, and a sensor element for detecting flow rate is arranged within the auxiliary passage.
On the other hand, an air flow meter disclosed in Japanese Patent Application Laid-Open No. Heisei 9(1997)-287991 includes a reversed U-shaped auxiliary passage formed within an air passage. A sensor element for detecting flow rate is arranged in the vicinity of the outlet portion of the auxiliary passage.
In case of the air flow rate measuring device for measuring an intake air of an automotive vehicle, while traveling behind a vehicle splashing a large amount of water under rainy condition, while traveling in heavy rain, rain water may easily pass through an air cleaner to penetrate into an air intake passage in a form of fine mist.
It has been known to artisan in the art that the thermal type air flow rate measuring device inherently cause output error as adhering water droplet on the flow rate detecting sensor element and keeps output error until the adhered water droplet is evaporated completely. When error is output in out put of the air flow rate detecting sensor for automotive vehicle, it becomes difficult to obtain appropriate air/fuel ratio to cause difficulty in maintaining normal engine revolution.
In case of the technology disclosed in the foregoing Japanese Patent Application Laid-Open No. Heisei 9-304140, when moisture penetrates into the air intake passage, it may directly collide on the flow rate detecting sensor element to adhere thereon to cause difficulty in obtaining accurate output.
On the other hand, in case of the technology disclosed in Japanese Patent Application Laid-Open No. Heisei 9-287991, since the flow rate detecting sensor element is disposed in the reversed U-shaped passage. Therefore, possibility that the water droplet directly contact with the flow rate detecting sensor element to adhere thereon, is quite low.
However, even with the U-shaped auxiliary passage structure, it is not possible to completely avoid adhesion of water droplet on the sensor element. Namely, when moisture penetrates into the auxiliary passage, a part of mixture may adhere on the peripheral wall of the auxiliary passage initially in a form of small water droplet. Then, small water droplets are coupled to form large water droplet.
Since large water droplet may be easily brown by air flow, the water droplet thus blown may adhere on the sensor element.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a thermal type flow rate measuring device which can certainly prevent adhesion of water droplet onto a sensor element and thus achieve high reliability.
According to the first aspect of the present invention, a thermal type flow rate measuring device comprises:
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.
In the preferred construction, a thermal type flow rate measuring device further comprises discharging means for discharging the liquid captured by the capturing means out of the auxiliary passage.
The capturing means or the capturing means and the discharge means may be formed with one of a plurality of grooves, a plurality of beam-like ridges and a combination of a plurality of grooves and a plurality of beam-like ridges, the captured liquid may be transferred along the one of a plurality of grooves, a plurality of beam-like ridges and a combination of a plurality of grooves and a plurality of beam-like ridges,
A plurality of grooves, a plurality of beam-like ridges and a combination of a plurality of grooves and a plurality of beam-like ridges may extend from upstream side to downstream side in the auxiliary passage in a manner directed from portions on the inner periphery of the auxiliary passage where liquid passing through the auxiliary passage is hardly concentrated to portions on the inner periphery of the auxiliary passage where liquid passing through the auxiliary passage is easily concentrated.
In the alternative, a plurality of grooves, a plurality of beam-like ridges and a combination of a plurality of grooves and a plurality of beam-like ridges extends from upstream side to downstream side in the auxiliary passage in a manner directed from portions of the inner periphery of the auxiliary passage where centrifugal to be applied may be small to portions of the inner periphery of the auxiliary passage where centrifugal force to be applied is large.
A plurality of grooves, a plurality of beam-like ridges and a combination of a plurality of grooves and a plurality of beam-like ridges may extend oblique relative to flow direction of the fluid.
The capturing means and/or the discharge means may have hydrophilic film formed on the inner periphery of the auxiliary passage so that when the liquid adheres on the inner periphery of the auxiliary passage, a contact angle is less than or equal to 30°.
The capturing means and the discharge means may be a plurality of grooves, a plurality of beam-like ridges and a combination of a plurality of grooves and a plurality of beam-like ridges, and another groove coupled with a plurality of grooves, a plurality of beam-like ridges and a combination of a plurality of grooves and a plurality of beam-like ridges, extends from a portion of the inner periphery of the auxiliary passage in the vicinity of an inlet portion of the auxiliary passage and a portion of the inner periphery of the auxiliary passage in the vicinity of an outlet portion of the auxiliary passage,
The capturing means may be a plurality of grooves formed on the inner periphery of the auxiliary passage, and the inner periphery of the auxiliary passage of the portions other than those formed the plurality of grooves are provided water repellent characteristics so that when the liquid adheres on the inner periphery of the auxiliary passage, its contact angle thereof becomes greater than or equal to about 90°.
The capturing means may be a plurality of grooves formed in the inner periphery of the auxiliary passage, and the discharge means is through holes formed on at downstream side of the plurality of grooves in communication with the grooves.
According to the second aspect of the present invention, a thermal type flow rate measuring device comprises:
a sensor provided within a main passage through which a fluid flows, for measuring flow rate of the fluid in the main passage;
the main passage being curved in the vicinity of an upstream side of the sensor; and
capturing means formed on an inner periphery of the main passage for capturing a liquid carried by the fluid.
According to the third aspect of the invention, 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 the condition of vehicle detected by the 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 sensor for detecting flow rate of the fluid, for detecting flow rate of the liquid,
a liquid capturing means and/or discharging means being provided on an inner periphery of the auxiliary passage.
As se
Horie Junichi
Nakada Keiichi
Ueyama Kei
Watanabe Izumi
Hitachi , Ltd.
Miller Takisha S
Williams Hezron
LandOfFree
Thermal flow rate measuring device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermal flow rate measuring device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal flow rate measuring device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3112181