JPH0618300A - Flowmeter - Google Patents

Abstract

PURPOSE:To reduce the pressure loss due to collision of the stream in a main passage and the stream from a branch passage. CONSTITUTION:An air meter 1 for measuring a suction air quantity into an automobile engine has an opening 3 on the upper stream side and an opening 5 on the downstream side, and forms a part of an inlet passage. In the about central part in the inlet passage within the meter 1, a cannonball-shaped central member is supported by four ribs 140, 150 (only two are illustrated). A part of sucked air is led from an inlet opening 410 into a branch pipe 420, flows in the outside of the pipe 420 after it flows in a measuring pipe 430, and flows out from an outlet openings 440, 450. Then, the flow is measured with sensors 570, 580. The air from the openings 440, 450 smoothly joins the flow of air in the inlet passage, because the outlet openings 440, 450 are inclined toward the downstream on the upper stream side of the central member and opened, and the inlet passage areas on the downstream sides of the openings 440, 450 are gradually increased. Accordingly the pressure loss can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluid flow meter for detecting the flow rate of a fluid, and more particularly to a fluid flow meter for forming a branch passage in a main passage through which the fluid flows and measuring the flow rate of the fluid flowing in the branch passage. Regarding

[0002]

2. Description of the Related Art Conventionally, as this type of fluid flow meter, an air flow meter for detecting the amount of intake air drawn into an automobile engine has been known.

For example, an "air flow meter" disclosed in Japanese Patent Laid-Open No. 60-185118 is known. This air flow meter supports a cylindrical member in a substantially central portion of an intake passage through which intake air to the engine flows, and forms a branch passage in the member to measure the amount of air flowing in the branch passage by a thermal method. It is measured by a flow meter.

[0004]

In the case where the branch passage is formed substantially in the center of the main passage like the above air flow meter,
Since air is introduced into the branch passage from approximately the center of the main passage, it is possible to introduce a flow rate that corresponds well to the flow rate of the main passage into the branch passage. You can know exactly. Also, since the temperature of the branch passage changes in response to the temperature of the air flowing through the main passage with good responsiveness, when installing a thermal type flow meter in the branch passage, outside the main passage, for example, from the engine room, It is possible to measure the flow rate accurately without being easily affected by the temperature disturbance.

By the way, in the air flow meter disclosed in the above publication, the flow from the outlet of the branch passage collides with the flow in the main passage substantially perpendicularly, so that the flow in the main passage is throttled and the pressure in the main passage is reduced. This may lead to increased loss. When the pressure loss increases, the resistance of the air taken into the internal combustion engine becomes a resistance, and the engine output may be reduced.

In view of the problems of the prior art as described above, the present invention provides a flowmeter for forming and supporting a branch passage in the main passage, and in particular, by improving the position and shape of the outlet of the branch passage, the branch passage is improved. The purpose is to prevent the flow from the outlet from restricting the flow in the main passage.

[0007]

In order to solve the above-mentioned problems, the present invention forms a main passage through which a fluid passes, and a housing in which a gradually increasing portion whose inner diameter gradually increases is formed, and a shell-like shape. A central member that is formed in a substantially central portion of the main passage with an outer peripheral diameter of which is gradually increased toward the downstream at a rate smaller than the rate of increase of the gradually increasing portion of the housing and is located at the gradually increasing portion. An inlet opening to the central member for introducing a part of the fluid flowing through the main passage, a branch passage formed in the central member for flowing the fluid introduced from the inlet, and provided in the branch passage And a sensor for measuring the flow rate in the branch passage, and the enlarged portion of the central member, which is opened at an inclination toward the downstream side,
The flow rate meter is provided with an outlet for returning the fluid flowing through the distribution passage to the main passage again.

[0008]

According to the above-described structure of the present invention, the shell-shaped central member is provided at the substantially central portion of the main passage inside the housing. An inlet, a branch passage, and an outlet are formed in the central member, and a sensor is provided in the branch passage to measure the flow rate of the fluid. Moreover, this outlet is opened at the enlarged portion where the outer diameter of the central member gradually increases toward the downstream side, and is further inclined and opened downstream.
Further, the enlarged portion is located at the gradually increasing portion formed on the housing, and is formed so as to gradually increase at a rate smaller than the gradually increasing rate of the gradually increasing portion.

Here, the flow of the main passage flows along an enlarged portion in which the outer diameter of the central member gradually increases as it goes downstream. Therefore, the flow in the main passage is a flow inclined from the axial direction toward the outer diameter direction. Then, the gradually increasing portion of the housing causes the flow of the main passage inclined along the central member to be further inclined toward the outer diameter direction.

On the other hand, the flow from the outlet formed in the enlarged portion merges at a small angle with the flow of the main passage inclined toward the outer diameter direction because the outlet is inclined toward the downstream side. Is discharged to the main passage.

Therefore, the above two flows can be smoothly merged, and the collision between the flow in the main passage and the flow in the branch passage can be reduced. Therefore, the flow from the outlet of the branch passage is prevented from restricting the flow in the main passage.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a thermal air flow meter for measuring the amount of intake air drawn into an automobile engine will be described below with reference to FIGS. 1, 2 and 3.

FIG. 1 is a sectional view of a thermal type air flow meter, and FIG.
2 is a view as seen from the direction of arrow A in FIG. Note that FIG. 1 shows the I-I cross section of FIG. Intake air is introduced into the air flow meter 1 from the left side in the figure and flows out to the right side in the figure. The upstream opening 3 of the air flow meter 1 is inserted and attached to an air cleaner (not shown). On the other hand, the downstream opening 5 is inserted into an intake duct (not shown) having a diameter larger than that of the air flow meter 1, and is tightened from the outer periphery by a belt (not shown).

The air flow meter 1 includes a central cylindrical portion 100, an upstream cylindrical portion 200 and a downstream cylindrical portion 300 which form an intake passage.
It has and. A circuit container 110 accommodating a control circuit is integrally formed on the outside of the central cylindrical portion 100 made of resin, and a lid is put on the circuit container 110. A control circuit for a thermal sensor, which will be described later, is housed in the circuit container 110. Further, on the outside of the central cylindrical portion 100, fixing nuts 111 and 11 are provided.
Support portions 115 and 117, in which 3 is insert-molded, are molded. The inner side of the central cylindrical portion 100 is formed into a cylindrical shape, and four ribs 120, 130, 140, and
150 is integrally molded. Furthermore, the rib 120,
A cylindrical central housing 160 is integrally formed at the tips of 130, 140 and 150. Central housing 1
60 has a partition wall 163 in the center thereof.
A hole 165 is opened in the center of 3.

The resin-made upstream cylindrical portion 200 is formed in such a shape that the inner cross-sectional area gradually expands toward the downstream side, the bell mouth portion 210 is formed at the upstream end portion, and the bell cleaner portion 210 is attached to the air cleaner on the outer periphery. There is a step for use. And
The upstream side cylindrical portion 200 is inserted inside the central cylindrical portion 100 and fixed to the central cylindrical portion 100.

The resin-made downstream cylindrical portion 300 is formed with a straight pipe portion 310 which is inserted into an intake duct (not shown), and is fixed to the downstream end portion of the central cylindrical portion 100. The inner side of the downstream side cylindrical portion 300 is formed into a cylindrical shape, and four ribs 320, 330, 340 and 350 are integrally formed toward the inside. Further, ribs 320, 330, 340, 350
A bowl-shaped downstream housing 360 is integrally formed at the tip of the.

Then, the four ribs 320, 330, 34
0 and 350 are ribs 12 extending from the central cylindrical portion 100.
It is located on the downstream side of 0, 130, 140, 150 and assembled in a sectional shape as shown in FIG. Further, the bowl-shaped downstream housing 360 closes the downstream side of the central housing 160 supported by the central cylindrical portion 100, and is assembled into a smooth shell shape.

A shell-shaped resin upstream housing 400 is inserted and fixed on the upstream side of the central housing 160 supported by the central cylindrical portion 100. Upstream housing 40
An inlet opening 410 is opened at the center of the upstream side of 0, and a branch pipe 420 linearly extending from the inlet opening 410 toward the downstream is integrally formed inside the upstream housing 400. A measuring pipe 430 is inserted at the downstream end of the branch pipe 420. The measuring pipe 430 includes an inner pipe 433 made of stainless steel and an outer pipe 435 made of resin.
A bell mouth is formed on the upstream side of 3, and its inner diameter is smaller than that of the branch pipe 420. Further, outlet openings 440 and 450 are provided outside the shell-shaped upstream housing 400 along the circumferential direction. A plurality of outlet openings 440 and 450 are formed as slit-shaped openings extending in the circumferential direction over substantially the entire circumference. Further, the outlet openings 440 and 450 are opened so as to be inclined toward the downstream side from the inside to the outside of the upstream housing 400. Moreover, the wall surface on the downstream side from the upstream side is more inclined toward the downstream side, so that air can be smoothly discharged.

The upstream housing 400 is the central housing 1.
It is inserted and fixed on the upstream side of 60. At this time, the downstream end of the branch pipe 420 contacts the upstream end faces of the plate-shaped ribs 167 and 169 radially formed inside the central housing 160. It should be noted that FIG. 1 illustrates two of the four plate-shaped ribs radially provided, 167 and 169. As a result, a predetermined gap is formed between the downstream end of the measuring pipe 430 and the partition wall 163 of the central housing 160, and an air passage from the downstream end of the measuring pipe 430 to the outer peripheral side of the measuring pipe 430 and the branch pipe 420. Is secured. The central member formed by the upstream housing 400, the central housing 160, and the downstream housing 360 is assembled in a cocoon shape with a smooth outer shape.

Here, between the upstream side of the outlet openings 440 and 450 of the upstream housing 400 and the upstream side cylindrical portion 200, there is formed a throttle portion in which the cross-sectional area of the intake passage is most narrowed. The flow path cross-sectional area at the position indicated by the medium-dot chain line B is the smallest. As a result, the airflow that has flowed in from the upstream side opening 3 is throttled by the throttle portion and is rectified so as to have a uniform flow along the outer circumference of the upstream housing 400.

Further, in the hole 165 of the partition wall 163,
The sensor unit 500 is inserted from the downstream side,
Is fixed to the partition wall 163. The sensor unit 500 includes a cylindrical resin unit 510, four support pins 520, 530,
It is formed by insert-molding 540 and 550 and fixing a fixing flange 560 to one end side. The support pins projecting upstream consist of two types, long and short, and two long 520, 53
One sensor 570 is supported between 0 and two short 5
One sensor 580 is supported between 40 and 550. The sensors 570 and 580 are made by winding a platinum wire around the outer circumference of a ceramic bobbin and connecting the lead wires at both ends of the bobbin, and those having the same characteristics are used.

Further, the space formed between the central housing 160 and the downstream housing 360, and the circuit container 11
0, a conductive member is disposed through the inside of the rib 140, and this conductive member is connected to a support pin projecting to the downstream side of the sensor unit 500 via a flexible wiring board (not shown). Therefore, the control circuit housed in the circuit container 110 is connected to the sensor via the conductive member, the flexible wiring board, and the support pin.

In the embodiment described above, the intake passage is formed inside the upstream cylinder portion 200, the central cylinder portion 100 and the downstream cylinder portion 300. And the upstream housing 4
00, the central housing 160, and the downstream housing 360 form a cocoon-shaped central member, which is supported at the center of the intake passage by four ribs. Then, the intake air mainly flows outside the central member.

Further, a branch pipe 420, a measuring pipe 430, a measuring pipe 430 and a partition wall 163 are provided between the upstream housing 400 and the central housing 160 from the inlet opening 410.
A branch passage is formed through the gap between and to reach the outlet openings 440 and 450. Therefore, a part of the air flowing in the intake passage passes through the branch pipe 420 from the inlet opening 410 and is introduced into the measurement pipe 430. And the partition wall 16
3 to change the direction of the flow in the radial direction, and further flow through the outside of the branch pipe 420 toward the outlet openings 440, 450. Then, it again flows into the intake passage from the outlet openings 440 and 450. At this time, the outlet openings 440 and 450
Since the cross-sectional area of the intake passage in the vicinity is narrowed, the flow velocity of the intake passage increases, and the pressure in the vicinity of the outlet openings 440 and 450 becomes negative pressure, so that the air in the upstream housing 400 is sucked out.

Then, the flow rate of the air flowing through the branch passage is measured by the sensors 570 and 580 located inside the measuring pipe 430. Here, one sensor is used for temperature measurement, the other sensor is heated to a predetermined temperature, and its heat radiation amount changes according to the air flow rate. Then, the control circuit housed in the circuit container 110 detects the electric power required to heat the sensor to a predetermined temperature, and outputs this electric power as an output signal indicating the measured flow rate. The output signal output from the control circuit is supplied to the fuel injection amount control device or the like and used for calculating the fuel injection amount.

In the above embodiment, the outlet openings 440, 45.
Since the throttle portion B is formed on the upstream side of 0, the negative pressure that acts on the outlet openings 440 and 450 acts evenly over the entire circumference in the circumferential direction. Therefore, even if there is a deviation in the air flow that flows in from the upstream opening 3, the deviation can be rectified and acted on the outlet openings 440 and 450.

Further, although the separation of the airflow generated on the surface of the central member also affects the outlet openings 440 and 450, since the outlet openings 440 and 450 are opened at a position near the upstream of the central member where the separation is relatively small. It is possible to obtain stable operation in a wide range from low flow rate to high flow rate.

Further, the outlet openings 440 and 450 have ribs 12 respectively.
0, 130, 140, 150 open upstream from the branch passages without being affected by the turbulence generated by the separation of the airflow generated on the rib surface and the turbulence generated at the downstream end of the rib. Can be drained.

Further, since the outlet openings 440 and 450 are opened on the outer circumference of the upstream housing 400 over substantially the entire circumference, they are affected by the flow of the entire intake passage. Therefore, it is possible to prevent the flow rate in the branch passage from fluctuating due to a part of the turbulent flow.

As described above, in this embodiment, the flow of air at the outlet openings 440 and 450 can be maintained in a state where there is little turbulence, and the ratio between the total flow rate of the intake passage and the flow rate of the branch passage can be accurately determined. It is possible to maintain the above ratio, and it is possible to accurately detect the flow in the entire intake passage by measuring the flow rate in the branch passage.

Further, the outlet openings 440 and 450 are opened from the inside of the shell-shaped upstream housing 400 toward the downstream side so as to be inclined, and the wall surface on the downstream side from the upstream side is larger toward the downstream side. It is inclined. And
The openings 440 and 450 are formed on the upstream side of the upstream housing 400, that is, in the enlarged portion where the outer diameter of the central member gradually increases toward the downstream side. The upstream cylindrical portion 200 located near the outer circumference of the enlarged portion is formed with a gradually increasing portion whose inner diameter gradually increases toward the downstream side. Here, the enlarged portion of the central member is formed such that the gradual increase rate of the outer peripheral diameter thereof is smaller than the gradual increase rate of the inner peripheral diameter of the gradual increase portion.

With such a construction, the flow in the intake passage first flows along the enlarged portion of the central member, and therefore is inclined toward the outer radial direction with respect to the axial direction. Further, due to the gradually increasing portion of the upstream side cylindrical portion 200, the flow of the main passage inclined along the central member is inclined further outward.

On the other hand, the flow flowing out from the outlet openings 440 and 450 is inclined toward the downstream side because the openings are inclined toward the downstream side.
It is possible to join the flow of the intake passage inclined toward the outer diameter direction at a small angle. Therefore, the two flows can be smoothly merged, and the collision between the two flows is significantly reduced. Therefore, it is possible to prevent the flow in the intake passage from being throttled due to the collision of the flows and to increase the pressure loss, and it is possible to reduce the intake resistance in the air flow meter 1. Therefore, the intake air can be smoothly drawn into the internal combustion engine, and the engine output can be improved.

Further, the gradually increasing portion of the upstream side cylindrical portion 200 is formed so that the gradually increasing rate thereof is larger than that of the enlarged portion of the central member, so that the area of the intake passage on the downstream side of the outlet openings 440 and 450 is increased. The rate of increase of
It is larger than that on the upstream side. Therefore, the outlet opening 44
Even when the air flowing out from 0, 450 merges with the air flowing in the intake passage, the increase in the air flow rate prevents the flow in the intake passage from being throttled. For this reason,
It is possible to prevent the flow from being narrowed due to the increase in the flow rate and the pressure loss from increasing. Therefore, air can be smoothly drawn into the internal combustion engine, and the engine output can be improved.

Further, the ribs 120, 130, 140, 1
Ribs 320, 330, 340, 350 downstream of 50
Are formed between the downstream housing 360 and the downstream cylindrical portion 300. The rib acts to prevent the straight pipe portion 310 from being deformed. That is, the rib prevents the straight pipe portion 310 from being deformed when the belt is fastened to the straight pipe portion 310 of the downstream side cylindrical portion 300 via the intake duct. Further, when the temperature is high, the straight pipe portion 310 is deformed by the tightening force of the belt, and a gap is formed between the intake duct and the downstream side cylinder portion 300, and air flows in through this gap, which causes excess air into the engine. It is possible to prevent the reduction of the output of the engine due to the intake of air and the reduction of the air-fuel ratio.

Further, since the inside and outside of the branch pipe are used as the branch passages in this embodiment, a long branch passage can be made compact, and the sensor response when the intake air amount changes or the intake pulsation of the engine. The passage shape can be used to adjust the response to backflow.

Also, in this embodiment, the outlet openings 440, 4
Fifty is open upstream. Therefore, the rib can be formed up to the upstream side and high strength can be obtained.
Further, in this embodiment, the housing of the air flow meter that constitutes a part of the intake passage is divided into a plurality of parts in the flow direction of the intake passage and assembled. Moreover, the sensor portion is inserted axially from the wall surface on the downstream side of the branch passage. Therefore, when assembling the air flow meter, it suffices to assemble the parts each having a substantially cylindrical outer shape in the axial direction, and the assembling work can be facilitated.

In this embodiment, the air passing through the sensors 570 and 580 in the branch passage passes through the gap between the measuring pipe 430 and the partition wall 163 and then flows toward the upstream side again, and the outlet opening It flows out from 440 and 450 to the intake passage. However, the invention is not limited to such an embodiment, and for example, the partition wall 163 can be provided without bypassing the branch passage.
May be extended in the radial direction along the line to be joined obliquely toward the intake passage. Also in this case, the outer wall of the central member at the confluence portion with the intake passage is shaped to gradually expand toward the downstream side, and the inner wall of the cylindrical portion is also gradually shaped toward the downstream side.

[0039]

According to the above-described structure and operation of the present invention, the outlet of the branch passage is formed in the enlarged portion in which the outer diameter of the shell-shaped central member gradually increases toward the downstream side. , Is inclined and opened downstream. Furthermore, the inner circumference of the housing is provided with a gradually increasing portion formed so that the inner diameter thereof is gradually larger than the gradually increasing ratio of the gradually increasing portion, and the enlarged portion is located in the gradually increasing portion.

Therefore, the flow of the main passage and the flow of the branch passage are smoothly joined, and the collision of these two flows is alleviated. Therefore, increase in pressure loss can be suppressed, and engine output can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment to which the present invention is applied.

FIG. 2 is a view on arrow A in FIG.

3 is a sectional view taken along line III-III in FIG.

[Explanation of symbols]

 1 Air Flowmeter 3 Upstream Side Opening 5 Downstream Side Opening 100 Central Cylindrical Section 160 Central Housing 140 Rib 150 Rib 200 Upstream Cylindrical Section 300 Downstream Cylindrical Section 340 Rib 350 Rib 360 Downstream Housing 400 Upstream Housing 410 Inlet Opening 420 Branch Pipe 430 Measuring tube 440 Outlet opening 450 Outlet opening 500 Sensor section

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Takao Ban 1-1, Showa-cho, Kariya city, Aichi Prefecture Nihon Denso Co., Ltd. (72) Inventor Rei Nagasaka 1-1-chome, Showa town, Kariya city, Aichi prefecture Nidec Co., Ltd. (72) Inventor Yukio Sawada 1-1, Showa-cho, Kariya city, Aichi prefecture Nihon Denso Co., Ltd.

Claims (1)

[Claims] 1. A housing having a main passage through which a fluid passes, and a gradually increasing portion whose inner peripheral diameter gradually increases, and a housing formed in a shell shape, the outer peripheral diameter of which gradually increases at the gradually increasing portion of the housing. A central member that is provided in an approximately central portion of the main passage with an enlarged portion that gradually increases toward the downstream at a rate smaller than the proportion, and a fluid that flows through the main passage and opens in the central member. An inlet for introducing a portion, a branch passage formed in the central member for flowing the fluid introduced from the inlet, a sensor provided in the branch passage for measuring a flow rate in the branch passage, the center A flowmeter, wherein the enlarged portion of the member is provided with an outlet that is inclinedly opened downstream and returns the fluid flowing through the distribution passage to the main passage again.