JPH09329473A - Gas flow measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas flow rate measuring device capable of working in good correspondence to individual engines by using as common component an element support fitted at the tip with a flow rate detecting element, and mounting it on each pipe having different diameter. SOLUTION: Element supports 13 are equipped with interchangeability so that installation can be made both on a pipe 1 of a suction air flow measuring device A in small size and the pipe 1' of another suction air flow measuring device B having a large diameter. Even when element support 13 is mounted on the pipe 1 of the device A of smaller structure, it is possible to mount a plate-form flow rate detecting element 15 in the first passage 7 of a bypass 5. Even in the case where element support is mounted on the pipe 1' of the device B having greater size, it is also practicable to install the same type of flow rate detecting element 15 in the first passage 7' of a bypass 5'. Thereby influence of the pulsation and counter-flow of the suction air can be reduced, thus enabling high precision detection of the flow rate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas flow rate measuring device suitable for detecting an intake air flow rate of, for example, an automobile engine.

[0002]

2. Description of the Related Art Generally, in an engine for an automobile or the like, a mixture of fuel and intake air is burned in a combustion chamber of an engine body, and a rotational output of the engine is taken out from the combustion pressure. It is required to accurately detect the intake air flow rate in order to calculate the above values with high accuracy.

Therefore, as a conventional technique, for example, Japanese Patent Laid-Open No.
A gas flow rate measuring device as disclosed in Japanese Patent Laid-Open No. 1-65053 is known. In this gas flow rate measuring device, a pipe body whose inside is a ventilation passage through which a measured gas (intake air) flows,
A housing provided so as to extend in the diametrical direction inside the pipe body, and a part of the gas to be measured which is formed in a substantially O-shape in the housing and bypasses the ventilation passage from the inlet to the outlet. And a flow rate detecting element that is provided in the middle of the bypass channel and that detects the flow rate of the measured gas flowing through the bypass channel. Further, a passage throttle portion is formed in the middle of the bypass passage, and a bobbin type heat ray probe and a temperature probe are provided as flow rate detecting elements at the position of the passage throttle portion. It is cooled by the flow of the intake air that flows, and the intake air flow rate is detected based on the change in the resistance value of the heat ray probe.

Further, by making the passage length of the bypass passage longer than the length of the ventilation passage to cause a pressure difference in the bypass passage, intake air increases in accordance with opening and closing of the intake valve. Even when the pulsation is reduced and the pulsation occurs, the pulsation is attenuated.

Moreover, in this gas flow rate measuring device, since the bypass passage is lengthened and the flow rate detecting element is arranged at the position of the minimum passage area, the turbulence of the air flow due to the pulsation in the bypass passage is reduced. It is possible to measure the intake air flow rate while eliminating variations in the detection signal output from the flow rate detection element.

[0006]

By the way, in recent automobile engines, due to the diversification thereof, the pipe dimensions of the intake pipe, the air cleaner, etc. are 70
There are various ranges up to 90 mm, and accordingly, there are also various outer diameter dimensions of the tube body that constitutes the gas flow rate measuring device (air flow meter).

Further, in the conventional gas flow rate measuring device,
The tubular body, the housing, and the flow rate detecting element are integrally formed. Therefore, in order to manufacture gas flow rate measuring devices corresponding to individual intake pipe and air cleaner pipe line dimensions, it is necessary to prepare other types of gas flow rate measuring devices, which results in production of other products in small numbers. However, there is a drawback that the cost is increased.

The present invention has been made in view of the above-mentioned problems of the prior art. The present invention provides a gas flow rate that can be attached to a tube having various outer diameter dimensions by making the element supports compatible with each other. It is intended to provide a measuring device.

[0009]

In order to solve the above-mentioned problems, the gas flow rate measuring device adopted by the invention of claim 1 is a pipe body having an inside as a ventilation passage through which a measured gas flows. A mounting opening provided on the tube wall of the tubular body, and a housing provided at a position facing the mounting opening so as to radially project from the tubular wall toward the axial center position in the tubular body;
A bypass passage formed in the housing, which bypasses the ventilation passage and circulates a part of the gas to be measured, and the bypass on the axial center side of the ventilation passage and at a position facing the attachment port of the pipe body. An element insertion opening formed in the housing by opening in the passage, and detachably attached from the attachment opening of the tubular body toward the element insertion opening, and located in the bypass passage at the tip end side of the bypass passage. It is composed of an element support provided with a flow rate detection element for detecting the flow rate of the gas to be measured flowing through.

With the above structure, when the element support is inserted and attached to the attachment port of the pipe body, the flow rate detecting element on the tip side is positioned in the bypass passage through the element insertion port at the axial center position of the ventilation passage. The flow rate of the bypass passage, which branches off a part of the measured gas flowing through the ventilation passage, can be detected by the flow rate detecting element. Further, since the element support can be attached to and detached from the attachment port of the tube, the element support can be made compatible and can be attached to tubes having various outer diameter dimensions.

According to the second aspect of the invention, the flow rate detecting element is formed as a plate type flow rate detecting element in which the flow rate detecting body is arranged on the insulating substrate.

With the above structure, when the gas to be measured flows through the bypass passage, the flow rate detector is cooled and the flow rate is detected by this cooling action. At this time, since the plate-type flow rate detection element has a small heat capacity, it is possible to detect with good responsiveness.

According to the third aspect of the present invention, the element support contains a circuit for exchanging an electric signal with the flow rate detecting element.

With the above construction, it is not necessary to provide a circuit component for signal transmission / reception separately from the element support body, and the element support body can be attached as a common component to various pipes having different radial directions, and the standards differ. A gas flow measuring device can be manufactured.

In the invention of claim 4, the bypass passage is located in the vicinity of the axial center of the ventilation passage, extends in the axial direction from the upstream side to the downstream side, and has a first passage having an element insertion opening, and the first passage. From a second passage extending radially outward from the first passage toward the pipe wall of the pipe body, and a third passage located radially outside the housing and extending from the second passage toward the upstream side in parallel to the axial direction. And the passage restrictor is the second passage or the third passage.
The flow rate detecting element is provided on either side of the passage, and the flow rate detecting element is the first
It was installed in the passage.

With the above structure, by making the bypass passage sufficiently long with respect to the length of the ventilation passage, a pressure difference is generated, and the influence on the inside of the bypass passage when pulsation or backflow occurs can be reduced. .

According to the invention of claim 5, the inflow port side of the bypass passage is formed in a tapered shape in which the passage area gradually decreases.

With the above structure, the gas to be measured flowing in the bypass passage can be gradually advanced and rectified, and the rectified gas to be measured can be applied to the flow rate detecting element.

According to the sixth aspect of the invention, the element insertion port is closed by the wall portion of the element support with the flow rate detection element inserted.

As described above, by closing the element insertion port with the wall portion of the element support, the seal of the first passage of the bypass passage can be formed.

[0021] In the invention of claim 7, the length of the tubular body upstream of the housing is L, and the diameter D of the tubular body is 0.5 to 0.5.
It is set to 2.0 times.

With the above structure, the rectifying property of the gas to be measured can be improved.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
Shows an embodiment according to the present invention. In the present embodiment, an intake air flow rate measuring device will be described as an example of the gas flow rate measuring device.

In the figure, reference numeral 1 denotes a tubular body which constitutes the main body of the intake air flow rate measuring device, and the tubular body 1 is formed of a resin material or a metal material into a cylindrical shape having an outer diameter R1. Is formed on the pipe wall 1A which is the ventilation passage 2 through which the intake air as the gas to be measured flows, the flange portion 1B which is formed on one side which is the upstream side, and the other side which is the downstream side. It is composed of a cylindrical connecting portion 1C.

Here, the pipe body 1 is connected in the middle of the intake pipe of the engine, an air cleaner is connected to the flange portion 1B side, and an intake passage communicating with the cylinder of the engine via a pipe is connected to the connection portion 1C side. A throttle valve (neither is shown) is connected. And the tubular body 1
Causes the air cleaned by the air cleaner to be sucked into the cylinder in response to the reciprocating movement of the piston (not shown).

Reference numeral 3 designates a mounting port, which is formed in a small-diameter cylindrical shape which is opened substantially at an intermediate portion of the tube wall 1A of the tubular body 1 and which projects radially outward from the tube wall 1A. , The mounting port 3
An element support 13, which will be described later, is inserted into and attached to this.

Reference numeral 4 denotes a housing, and the housing 4
At a position facing the mounting opening 3, is projected radially inward from the pipe wall 1A of the pipe body 1 to a position in the vicinity of the axial center O-O of the air passage 2, and is integrally formed with the pipe body 1. It is formed in a vertically elongated rectangular shape. The housing 4 has a front surface 4A on the upstream side and a rear surface 4 on the downstream side with respect to the flow of intake air.
B, including left side surface 4C, right side surface 4D and upper surface 4E 5
It is a face piece.

Reference numeral 5 denotes a bypass passage provided in the housing 4. The bypass passage 5 is formed in a substantially U-shape in the housing 4 as shown in FIGS. Here, the bypass passage 5 includes an inflow port 6 located on the front surface 4A side of the housing 4 near the axial center O-O of the air passage 2 and opened to the upstream side of the air passage 2, and the inflow port 6. A first passage 7 located in the vicinity of the axis center O-O and extending in the axial direction from the upstream side to the downstream side, and communicates with the first passage 7, and the vicinity of the axis center OO on the rear surface 4B side. From the second passage 8 extending radially outward from the above to the pipe wall 1A of the pipe body 1 and communicating with the second passage 8 and located radially outside of the housing 4 from the second passage 8 to the upstream side. A third passage 9 extending in parallel with the axial direction toward the third passage 9 and a side surface 4C of the housing 4 located outside the housing 4 in the radial direction, communicating with the third passage 9;
It is composed of the outlets 10 and 10 that open to 4D.

As shown in FIG. 6, the first passage 7 communicating with the inflow port 6 is formed by inclined surfaces 7A, 7A having a substantially V shape or a taper shape in which the passage area gradually decreases. Also, the upper surface 4E has an element insertion port 12 described later.
Are formed.

Reference numeral 11 denotes a passage narrowing portion formed in the housing 4 for narrowing the middle of the bypass passage 5. The passage narrowing portion 11 is formed in the middle of the second passage 8 and is formed in the second passage 8.
The rear surface 4B side of the passage 8 has the inclined surfaces 7 of the first passage 7.
Since it is throttled by A, the axial center O- of the second passage 8 is
From the O position to the passage narrowing portion 11, as shown in FIG. 6, the front surface 4 is changed from a trapezoidal passage to a rectangular passage.
The passage area is narrowed down by reducing the bottom of the A side.

Here, the passage area S0 formed by the passage throttle portion 11 is a plate type flow rate detecting element 15 which will be described later.
Is smaller than the passage area S1 of the first passage 7 in which the air passage 2 is disposed, and the ratio of the flow rate of the bypass passage 5 to the flow rate of the bypass passage 2 (hereinafter, referred to as a shunt ratio) is determined so that The flow rate at which the ratio of the flow rate of the intake air to the flow rate is constant is controlled so as to flow in the bypass passage 5.

Further, in the bypass passage 5 thus constructed, the relationship between the passage area S from the inlet 6 to each outlet 10 is as shown in FIG. That is, the passage area S is the largest at the position of the inflow port 6, the passage area is S1 at the element mounting position, and gradually narrows from the element mounting position to the passage narrowing portion 11.
Has a passage area S0, the passage area S rapidly increases from the downstream side of the passage narrowing portion 11, and the passage area 10 is narrowed again.

Further, 12 is an element insertion port, which is formed by opening the upper surface 4E of the housing 4 in a rectangular shape, and the element type insertion port 12 has a plate type flow rate detection element 15 described later. Is inserted.

Reference numeral 13 designates an element support which is a compatible and common component. The element support 13 is formed in a stepped columnar shape, and the connector 1 is provided on the base end side with a flange-shaped mounting portion 13A.
3B is formed, and the rectangular circuit accommodating portion 13 is closed by the cover 13C1 from the mounting portion 13A toward the tip side.
C is formed, and the front end side of the circuit housing portion 13C is the wall portion 13
The flow rate detecting element 15 is provided so as to project from the position of the wall portion 13D. Further, the first passage 7 is sealed by bringing the wall portion 13D of the element support 13 into contact with the upper surface 4E of the housing 4.

Reference numeral 14 is a circuit accommodating portion 13C of the element support 13.
The circuit component 14 is housed and provided inside, and the circuit component 14 transmits and receives an electrical signal to and from the flow rate detecting element 15. Therefore, the circuit component 14 is configured to include a heater control circuit that controls the heater 18 of the flow rate detection element 15, an amplification circuit that amplifies a detection signal from the resistance temperature detectors 19 and 20, a backflow detection circuit, and the like. In addition, the circuit housing portion 1
The circuit component 14 in 3C is cooled by intake air through a resin cover 13C1 and the like.

Numeral 15 is provided at the tip of the element support 13.
A plate type flow rate detecting element is shown, and the plate type flow rate detecting element is shown.
The element 15 is, as shown in FIGS. 9 and 10,
Silicon substrate with a trapezoidal processing hole 16A formed in the middle
16 and an oxide film (S
iO₂  ) Or nitride film (SiN)
The edge film 17 and the silicon substrate 1 through the insulating film 17
Example of depositing platinum at the position corresponding to the processed hole 16A on 6
For example, the heater 18 having a film thickness of about 0.2 μm,
Located on the left and right of the heater 18, in the same manner as the heater 18.
Temperature measuring resistors 19 and 20 which are flow rate detectors formed by
It consists of In addition, it was formed on the silicon substrate 16
The processed hole 16A is an anisotropic etch of silicon from the lower surface side.
It is formed in a trapezoidal shape by applying a groove.

Here, in the flow rate detecting element 15, when the air flows as indicated by the arrow A, the change in the resistance value of the resistance temperature detectors 19 and 20 cooled by the air flow is utilized to
Detect the flow rate. In addition, since the flow rate detecting element 15 has the resistance temperature detectors 19 and 20 arranged on the left and right of the heater 18, it can be used both in the direction of arrow A and in the opposite direction. It is an element for forward and reverse flow detection that can be similarly detected.

The intake air flow rate measuring device according to this embodiment is
With the above-mentioned configuration, and to describe its operation next, a part of the intake air flowing through the air passage 2 in the pipe body 1 is branched and flows into the bypass passage 5, and the inside of the bypass passage 5 is The flow rate of the flowing air is detected by the flow rate detecting element 15 to detect the flow rate of the intake air sucked into the engine.

Further, the passage area S0 due to the passage throttle portion 11 formed in the middle of the bypass passage 5 is determined by the flow rate detecting element 1
Since the first passage 7 is formed so as to be smaller than the passage area S1 of the first passage 7, the passage area S0 can control the diversion ratio flowing through the bypass passage 5 and always flow through the ventilation passage 2. A flow rate of a constant ratio with respect to the flow rate of intake air can be made to flow in the bypass passage 5. As a result, the flow rate of air flowing through the bypass passage 5 is detected by the flow rate detecting element 15, so that the flow rate of air flowing through the air passage 2 can be accurately detected.

Further, the length L of the tube body 1 on the upstream side of the housing 4 is set to 0.5 to 2.0 times (preferably 1 time) the diameter D of the tube body 1 to rectify the flow. The flow characteristics can be improved by the action.

Here, the bypass passage 5 according to the present embodiment.
Is formed in a substantially U shape by the first passage 7, the second passage 8 and the third passage 9, so that the passage length of the bypass passage 5 is set sufficiently longer than the length of the ventilation passage 2. A pressure difference can be provided between the inflow port 6 and the outflow port 10, and the influence of pulsation generated in the pipe body 1 can be mitigated.

The first passage 7 is located in the vicinity of the axial center O--O of the ventilation passage 2 and communicates with the inflow port 6 opening upstream of the intake air, and the third passage 9 has a diameter of the housing 4. It is located outside in the direction and communicates with the outlets 10, 10 that open to the side surfaces 4C, 4D of the housing 4. As shown in FIG. 2, the flow velocity V of the air flow flowing in the pipe body 1 is fast in the vicinity of the axial center O-O and slow in the vicinity of the pipe wall 1A. Therefore, a pressure difference is generated between the inflow port 6 and the outflow port 10, and the air flowing into the bypass passage 5 satisfactorily flows into the bypass passage 5 when the engine is in the forward flow for sucking air. be able to.

Further, the element support 13 has the mounting portion 1 thereof.
By attaching 3A to the attachment opening 3 of the tubular body 1, the plate-type flow rate detection element 15 located on the tip side is attached to the element insertion opening 1
2 is disposed in the first passage 7 of the bypass passage 5 via the flow passage 2, and the flow rate detecting element 15 is disposed on the upstream side of the passage throttle portion 11, so that it is possible to prevent air from flowing in the forward direction. As a result, the rectified air can be made to flow through the flow rate detection element 15, and the flow rate detection sensitivity of the element 15 can be increased. On the other hand, the flow in the reverse direction is buffered by the passage throttle portion 11 to reduce the reverse flow of the intake air flowing into the flow rate detecting element 15.

Further, the element insertion port 12 in which the flow rate detecting element 15 is arranged is formed in a substantially V shape or a tapered shape by the inclined surfaces 7A and 7A so that the passage area gradually decreases. Therefore, the flow velocity of the air flowing through the flow rate detecting element 15 can be accelerated and the rectification can be promoted together with the action of the passage throttle portion 11 provided in the middle of the bypass passage 5.
The flow rate detection sensitivity can be further increased.

In addition, the plate type flow rate detecting element 15 according to the present embodiment has a resistance temperature detector 19 on the left and right of the heater 18,
Since this is an element for detecting the forward and reverse flows having 20, when the reverse flow flows through the bypass passage 5, the air flow rate in the reverse direction can be detected.

Further, in the element support 13, the circuit component 14 for exchanging electric signals with the plate type flow rate detection element 15 is accommodated in the circuit accommodating portion 13C, and the circuit accommodating portion 13C is accommodated in the element supporting member. In the state where 13 is attached to the pipe body 1, it is exposed to the inside of the ventilation passage 2, so that the circuit component 1
4 can be cooled by the intake air flowing through the ventilation path 2, the temperature rise of the circuit component 14 can be suppressed, and the superimposition of temperature drift or the like on the electric signal output from the circuit component 14 can be reduced.

Thus, in the present embodiment, the influence of pulsation can be greatly reduced by the length and shape of the bypass passage 5 formed in the housing 4, and the detection accuracy of the intake air flow rate can be increased.

Further, the plate type flow rate detecting element 15
Is composed of a thin-film heater 18 and resistance temperature detectors 19 and 20 on a silicon substrate 16 with an insulating film 17 interposed therebetween, so that the heat capacity can be made smaller than that of the bobbin type heat ray probe used in the prior art. The responsiveness to the detection of the flow rate of the intake air can be improved.

Further, the element support 13 according to the present embodiment.
Is detachably attached to the element insertion opening 12 from the attachment opening 3 of the tubular body 1 as a compatible common part. Therefore, the element support 13 is a small intake air flow rate measurement device shown in FIG. In addition to the case of the device A, the tube body 1 ′ of the large intake air flow rate measuring device B as shown in FIGS. 12 and 13 is used.
It can also be attached to. In the large intake air flow rate measuring device B, the same components as those in the small intake air flow rate measuring device A are denoted by reference numerals with a dash (') and the description thereof is omitted.

That is, the pipe body 1'of the large intake air flow rate measuring device B shown in FIG. 13 has a larger diameter than the outer diameter dimension R1 of the pipe body 1 of the small intake air flow rate measuring device A shown in FIG. The outer diameter is R2. Therefore, the tube wall 1 of the tube body 1 '
The shapes of the housing 4'and the bypass passage 5'formed in A'are the same as the housing 4 of the tubular body 1 and the bypass passage 5 '.
Although it is formed almost the same as
The housing 4'is formed in a vertically long rectangular shape having a height height so as to be -O.

By attaching the element support 13 to the attachment port 3'of the tube body 1'of the large intake air flow rate measuring device B constructed as described above, for example, intake air suitable for an engine with a large displacement can be obtained. A flow rate measuring device can be realized.

Thus, in this embodiment, the element support 13
Since they are compatible with each other, they can be attached to various types of intake air flow rate measuring devices composed of various pipe bodies having different outer diameter dimensions. Therefore, even if there are many types of pipes and housings of the intake air flow rate measuring device, various intake pipes and air cleaners can be obtained by simply attaching the element support 13 which is a common component to the pipes and the housing. It is possible to manufacture an intake air flow rate measuring device that matches the dimensions of the conduits such as. Therefore, as compared with the case of manufacturing the intake air flow rate measuring device for each engine as in the conventional technique, the element support 13 can be manufactured as a common component,
The manufacturing cost can be significantly reduced.

Since the element mounting port 12 to which the flow rate detecting element 15 is attached is located at the position of the first passage 7 on the inflow port 6 side, the flow rate detecting element 15 is arranged when the element support 13 is attached. The bypass passage 5 has a rectangular shape. Therefore, the element support 1 can be applied to various pipes.
Even when 3 is attached, the installation error can be reduced and the flow rate of the intake air can always be accurately detected by arranging it in the rectangular passage.

Further, in the tubular body 1 ', the length L'of the tubular body 1'upstream of the housing 4'is 0.5 to 2.0 times the diameter D'of the tubular body 1' ( (Preferably 1 time)
By setting to, it is possible to improve the flow rate detection accuracy by the rectification function and to reduce the size.

In the above embodiment, the outlet 10 of the bypass passage 5 is connected to the left and right side surfaces 4C and 4D of the housing 4.
However, the present invention is not limited to this.
The outlet may be formed so as to open on one side surface.

In the above embodiment, the passage throttle portion 11 is formed in the second passage 8 of the bypass passage 5 and the flow rate detecting element 15 is arranged in the first passage 7. However, the present invention is not limited to this. Alternatively, the flow passage detecting portion may be formed in the third passage 9 and the flow rate detecting element 15 may be arranged in the first passage 7 or the second passage 8. In short, the flow detecting element 15 is arranged on the upstream side of the passage narrowing portion. Anything can be used.

On the other hand, the plate type flow rate detecting element 15 is positive,
The element is not limited to the element for detecting the backflow, but may be an element for detecting the flow rate in only one direction.

[0058]

As described in detail above, according to the first aspect of the invention, when the element support is inserted and attached to the attachment port of the pipe,
The flow rate detection element on the tip side is located in the bypass passage via the element insertion port located at the axial center of the ventilation passage, and the flow rate in the bypass passage obtained by branching a part of the measured gas flowing in the ventilation passage is described above. It can be detected by the flow rate detection element. At this time, since the element support is removably attached to the attachment opening of the tubular body,
By making the element supports compatible, they can be attached to pipes having different outer diameter dimensions, and a gas flow rate measuring device suitable for various intake pipes, air cleaners, etc. can be manufactured at low cost. it can. Further, the element support and the bypass passage can be separated, and a sufficiently long bypass passage can be formed.

According to the second aspect of the invention, since the flow rate detecting element is a plate type, the heat capacity can be made small and the flow rate when the gas to be measured flows in the bypass passage can be detected with good responsiveness.

According to the third aspect of the present invention, since the circuit component is stored in the element support body, it is not necessary to provide the circuit component separately from the element support body, and the element support body can be used as a common component in the outer diameter dimension. It is possible to easily manufacture gas flow rate measuring devices having different standards simply by mounting them on various different pipes. Further, the circuit components can be cooled by the intake air.

According to the invention of claim 4, the bypass passage has the first passage.
It is formed by a passage, a second passage, and a third passage, and the inlet of the bypass passage is located near the axial center of the ventilation passage and the outlet is located near the pipe wall of the pipe body. A pressure difference can be created between the outlet and the measured gas that flows from the upstream side to the front surface of the housing, and can flow from the axial center to the outlet located near the pipe wall. The flow rate of the gas to be measured flowing inside can be accurately measured by the flow rate detecting element.

According to the fifth aspect of the present invention, the measured gas flowing from the inlet side to the bypass passage is rectified by forming the inlet side of the bypass passage in a tapered shape in which the passage area gradually decreases. Therefore, the rectified gas to be measured can be detected with high accuracy by the flow rate detection element.

According to the sixth aspect of the invention, the element insertion port is closed by the wall portion of the element supporting member, whereby the first bypass passage is formed.
The passage can be sealed.

In the invention of claim 7, the length L of the tubular body upstream of the housing is set to 0.5 to 0.5 of the diameter D of the tubular body.
Since it is set to 2.0 times, the rectifying property of the gas to be measured can be enhanced and the detection accuracy can be enhanced.

[Brief description of drawings]

FIG. 1 is a front view showing an intake air flow rate measuring device according to an embodiment.

FIG. 2 is a cross-sectional view showing the intake air flow rate measuring device according to the present embodiment as seen from the direction of arrows II-II in FIG.

FIG. 3 is an exploded cross-sectional view showing a tubular body and an element support body in a disassembled state.

FIG. 4 is a vertical cross-sectional view of the housing as seen obliquely.

FIG. 5 is a vertical sectional view of a housing.

FIG. 6 is a transverse sectional view as seen from the direction of arrows VI-VI in FIG. 5;

FIG. 7 is a vertical cross-sectional view taken along the line VII-VII in FIG.

8 is a vertical cross-sectional view as seen from the direction of arrows VIII-VIII in FIG.

FIG. 9 is a perspective view showing a plate type flow rate detecting element.

FIG. 10 is a vertical cross-sectional view as seen from the direction of arrow XX in FIG.

FIG. 11 is a characteristic diagram showing a passage area with respect to a passage length of a bypass passage.

FIG. 12 is an exploded view showing a state before the compatible element support body according to the present embodiment is attached to two types of tube bodies having different outer diameter dimensions.

FIG. 13 is an exploded cross-sectional view showing a state where the tube body and the element support body are disassembled in the large-diameter intake air flow rate measuring device.

[Explanation of symbols]

 1,1 'Tube 2,2' Ventilation path 3,3 'Mounting port 4,4' Housing 5,5 'Bypass passage 6,6' Inlet 7,7 'First passage 8,8' Second passage 9 , 9'Third passage 10, 10 'Outlet 11, 11' Passage restrictor 12, 12 'Element insertion port 13 Element support 14 Circuit component 15 Plate type flow rate detection element 16 Silicon substrate 18 Heater 19, 20 Temperature measurement resistance Body (Flow rate detector) A Small intake air flow rate measuring device B Large diameter intake air flow rate measuring device

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Atsushi Arai 1370 Onna, Atsugi-shi, Kanagawa Prefecture

Claims (7)

[Claims] 1. A pipe body having an air passage inside which a gas to be measured flows, an attachment opening provided in a pipe wall of the pipe body, and the inside of the pipe body at a position facing the attachment opening. A housing that is provided so as to project radially from the pipe wall toward the axial center position, a bypass passage that is formed in the housing and that bypasses the ventilation passage and circulates a part of the measured gas, and the ventilation passage. An element insertion opening formed in the housing by opening to the bypass passage at a position that is on the axial center side of the passage and faces the mounting opening of the tubular body, and from the mounting opening of the tubular body to the element insertion opening. A gas flow rate measurement device, which is detachably mounted on the tip side of the bypass passage and is provided with a flow rate detecting element for detecting the flow rate of the gas to be measured flowing through the bypass passage. apparatus. 2. The gas flow measuring device according to claim 1, wherein the flow rate detecting element is formed as a plate type flow rate detecting element in which a flow rate detecting body is arranged on an insulating substrate. 3. The element supporting member stores a circuit for transmitting and receiving an electric signal to and from the flow rate detecting element.
Or the gas flow rate measuring device according to 2. 4. The first passage, wherein the bypass passage is located in the vicinity of the axial center of the ventilation passage, extends in the axial direction from the upstream side to the downstream side, and the element insertion port is opened, and the first passage. From the second passage extending radially outward toward the pipe wall of the pipe body, and a third passage located radially outside the housing extending from the second passage toward the upstream side in parallel to the axial direction.
4. The gas flow rate according to claim 1, wherein the flow rate detection element is provided in the first passage, and the passage throttle portion is provided on either side of the second passage or the third passage. Measuring device. 5. The inflow port side of the bypass passage is formed in a tapered shape in which the passage area gradually decreases.
The gas flow rate measuring device according to 2, 3, or 4. 6. The gas flow rate measurement device according to claim 1, wherein the element insertion port is configured to be closed by a wall portion of the element support in a state where the flow rate detection element is inserted. . 7. The pipe body is configured such that the length L of the pipe body upstream of the housing is set to 0.5 to 2.0 times the diameter D of the pipe body. 4. The gas flow rate measuring device according to 4 or 5.