Measuring and testing – Volume or rate of flow – Proportional
Reexamination Certificate
2001-01-05
2002-11-05
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Volume or rate of flow
Proportional
Reexamination Certificate
active
06474154
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a device for measuring various quantities concerning a flow, among others, relates to a flow rate and flow velocity measurement device using a detection element integrally formed on a support body and/or a temperature sensitive semiconductor chip, and relates to a measurement device suitably applied, for example, as a combustion controlling mass flow rate sensor of an engine for a vehicle or industry, or a mass flow rate sensor for an industrial air conditioning system and compressor pressurized air supply system and, furthermore, an air/fuel ratio controlling flow rate sensor of a domestic gas hotplate.
2. Description of the Related Art Japanese patent application laid-open No. 9-503311 proposes “A sensor support body for a device measuring an intake of internal combustion engine, provided with a sensor support body and a sensor element on a plate inserted into a flow rate medium, wherein the sensor element has at least one measurement resistor concerned with temperature, and the sensor element is accommodated in a notch of the sensor support body while forming approximately the same face as the sensor support body”. Further, in an embodiment of the same gazette “The sensor element has a plate-like shape, and its largest surface is lined up parallel to an inflowing medium”.
The same Japanese patent application laid-open No. 9-503311 recites that “When manufacturing the device, it is important to bond a surface of the sensor element into the notch such that it becomes, as far as possible, the same face as a surface of the sensor support body. This is because even if a smallest displacement owing, for example, to a bonding layer unevenly applied exists, it follows that a vortex flow and exfoliation region is generated, and the vortex flow and exfoliation region exerts an adverse effect on a heat extraction of the measurement resistor especially at the surface of the sensor element, so that a measurement result becomes erroneous”.
However, in order to “bond a surface of the sensor element into the notch such that it becomes, as far as possible, the same face as a surface of the sensor support body” as proposed in Japanese patent application laid-open No. 9-503311, there is a problem in that a high and precise manufacturing technique is required and manufacturing efficiency is thereby decreased.
Further, in order to assure that the surface of the sensor element is the same face as the surface of the sensor support body, a further problem arises in that a precise inspection is necessary.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a flow measurement device, which is easy to manufacture and has excellent detection accuracy.
A flow measurement device of a first aspect of the invention has means, provided so as to act on a flow in a divided flow pipe, for forming such a flow as to obliquely impinge against a detection face of a flow-detection element, as schematically shown in FIG.
1
(A) wherein a flow
12
is shown by a upper arrow slanting against the detection element face. In order to obliquely impinge the flow against the detection element, a flow passage or inner diameter of the divided flow pipe is reduced so as to form a passage-narrowest portion and in addition the pipe is bent at the passage-narrowest portion so as to form a inverted arc whereat the detection element is placed. In this structure, a flow speed maximizes at the passage-narrowest portion and a flow of an object such as a gas impinges obliquely on the element. A better performance of the flow measurement device is attained when an upstream flow passage and a downstream passage along the inverted arc wherein the detection element is placed in a middle is shaped in symmetry along the inverted arc, according to one of the aspects of the invention.
It is considered that, by this flow control means, a flow to be detected is constantly supplied to the detection face of the detection element and it follows that the flow to be detected surely flows on the detection face. In addition, it is considered as an advantage that generation of a vortex flow and exfoliation in the vicinity of the detection face are suppressed so that flow detection accuracy and flow detection reproducibility are improved.
Further, since it is considered that, in this measurement device, the flow on the detection face is stabilized, the detection face is not necessarily positioned on the same face as a flow passage face on both sides of the detection portion. In other words, this measurement device allows a step between the detection face and the flow passage face in the vicinity of the detection portion and, further, enlarges an allowable width in relative positional accuracy of the detection- element detection face with respect to the flow passage face.
Therefore, according to the measurement device of the first preferred aspect of the invention, it becomes unnecessary to bond the detection element into a notch of its support body with a lot of care, as required in Japanese patent application laid-open No. 9-503311 wherein the detection element surface and the support body surface is strictly on the same face without a step therebetween. That is, this measurement device allows forming such a step between the detection face and the flow passage face on both sides of the detection portion, which step is easily generated as an error. As a result, manufacture of the device is easy, and accuracy in dimensional and/or positional inspection of the element in the flow measurement device can be lowered without lowering the performance of the flow measurement device.
In this manner, since the flow measurement device of the first preferred aspect of the invention allows such a step mentioned above, it becomes possible to attach the detection element so as to be detachable from the divided flow pipe fixed to a main flow pipe by constituting the detection element and its support body as separate bodies or by constituting the detection element and its support body as bodies separate from the divided flow pipe. As a result, it is possible to exchange the detection element if the element has been deteriorated or contaminated by long term use.
Here, effects derived from the flow measurement device of the first important aspect of the invention are exemplified below.
(1) By forming a flow (or rather a down flow) obliquely impinging toward the detection face of the detection element according to the invention, generation of a vortex flow and exfoliation are suppressed in the vicinity of the detection face and, as a result, it is possible to obtain a stable detection property and reproducibility.
(2) Even if the detection face is not at the same level as the detection element support body surface, detection is possible. As a result, assembly of the detection element becomes easy.
(3) Because a down flow is formed, an accurate and stable detection of quantities concerning the flow, e.g., flow rate and flow velocity, becomes possible at a flow passage wall. In this case, it suffices if only a detection element surface or the detection face is exposed inside the flow passage.
(4) Since the detection of the flow rate and flow velocity at the flow passage wall is possible with a rough positional accuracy of the detection element, the detection element and the divided flow pipe can be made separate bodies, so that structures of the detection element and the divided flow pipe are respectively simplified and become easy to manufacture.
(5) It is possible to constitute a flow passage shape of the divided flow pipe in compliance with a requirement for measuring both a normal flow and a reverse flow, or either the normal flow and the reverse flow is selectively measured so as not to be influenced by the other flow, by forming the flow passage in symmetry between upstream and downstream sides with the detection element placed therebetween.
(6) Since another divided flow passage can be formed in the divided flow pipe, improvements in contamination resista
Kohmura Yoshihiko
Kojima Takio
Kuzuya Yasuhisa
Maeda Shunsuke
Oshima Takafumi
NGK Spark Plug Co. Ltd.
Thompson Jewel V.
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