JPH0618301A - Flowmeter - Google Patents

Abstract

PURPOSE:To prevent the deformation of a cylindrical part on the downstream side. CONSTITUTION:An air flowmeter 1 for measuring the amount of suction air into an automobile engine has an opening 3 on the upstream side and an opening 5 on the downstream side, constituting a part of a passage for the suction air. A cocoon-shaped central member is supported by four side 120, 130, 140, 150 approximately at the center of the suction air passage in the air flowmeter 1. A branch passage is formed at the central member to guide part of the suction air, where the flow rate is measured. Moreover, ribs 320, 330, 340, 350 are formed between a downstream cylindrical part 300 and a downstream housing 360 on the downstream side of the ribs. The ribs prevent the deformation of the cylindrical part 300 made of a resin when the cylindrical part is fitted to a suction duct and securely fastened by a belt.

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, a "gas flow measuring device" disclosed in Japanese Patent Laid-Open No. 62-235525 is known. This air flow meter is provided with a shell-shaped member supported movably in the axial direction in a substantially central portion of a resin housing that forms an intake passage therein, and measures the air amount by the moving amount of this member. ing.

[0004]

The resin housing of the above-mentioned prior art air flow meter is inserted and connected to an intake pipe connected to a throttle body for adjusting the amount of air taken into the engine. Here, in order to secure the sealing property between the housing and the intake pipe, it may be fastened and fixed by a belt or the like. At this time, if the inside of the engine room is in a high temperature environment, the resin housing is deformed by the tightening force applied to the tightening portion, and a gap may be formed between the intake pipe and the flow meter. When air flows in through this gap, an excess of the amount of air that has passed through the air flow meter is sucked into the engine, and the air-fuel ratio becomes thin, which may cause the engine to malfunction.

SUMMARY OF THE INVENTION The present invention has been made in view of the problems of the prior art as described above, and an object thereof is to prevent deformation of a resin housing.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a flowmeter connected to a fluid pipe through which a fluid flows, by fixing the outer periphery with a fastening portion which is fixed to the fluid pipe. A resin housing having a fluid passage formed therein, a central member provided substantially in the center of the passage, and a sensor portion provided in the central member for measuring the flow rate of the fluid flowing through the passage. And a support member which is provided between the housing and the central member and which supports the central member near the center of the passage and is located inside the tightening portion so as to withstand a load acting on the tightening portion. A technical means called a flow meter characterized by being provided is adopted.

[0007]

According to the structure of the present invention described above, the housing is clamped and fixed to the fluid pipe through which the fluid flows.
A central member having a sensor unit is provided inside the housing, and the sensor unit measures the flow rate in the passage. Further, a support member is provided between the central member and the housing, and is located inside the tightening portion of the housing that is connected to the fluid pipe. By this support member, the central member is supported near the center of the passage, and it is possible to withstand the load acting on the tightening portion. For this reason,
Even when a load is applied to the resin housing from the outside, the supporting member resists the load, so that the housing is prevented from being deformed.

[0008]

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. A step is formed for attaching the grommets for use. Then, 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 cylinder 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 cylinder 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.

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 type 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.

Furthermore, 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, the outlet openings 440 and 450 are affected by the separation of the air flow generated on the surface of the central member, but 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
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 to 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 by measuring the flow rate in the branch passage, the flow in the entire intake passage can be accurately detected.

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 shell-shaped upstream housing 400, 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.

According to this structure, the flow of the intake passage first flows along the enlarged portion of the central member, so that it 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 of the outlet openings 440 and 450 is 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 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.

Next, another embodiment to which the present invention is applied will be described with reference to FIG. Here, differences from the embodiment shown in FIG. 1 will be described. Also in this embodiment, four ribs are formed toward the inside of the intake passage, as in the above-described embodiments, and the central member is supported at the center of the intake passage. Then, the outlet openings of the branch passages are ribs 121, 131, 14
1, 151 (121 and 131 are not shown). Furthermore, the ribs 121, 131, 141,
Ribs 321, 331, 34 are provided at the downstream end of 151.
1, 351 (321 and 331 are not shown) are formed. In this embodiment, the central housing 161 comprises a cylindrical portion 162 and a wall portion 164 having a diameter smaller than that of the cylindrical portion 162, and the wall portion 164 has ribs 121, 131, 141 and 15 respectively.
Supported by 1. Therefore, four thin arc-shaped passages are formed between the cylindrical portion 162 and the wall portion 164. In FIG. 4, two of the four passages 166 and 16 are shown.
8 are shown. Then, these passages are directly connected to the outlet openings 441 and 451.

Further, an upstream housing 401 having an inlet opening 411 is fixed on the upstream side of the cylindrical portion 162,
Inside the cylindrical portion 162, a metal measuring pipe member 431 having a pipe formed in the center of the disc is fixed. The branch pipe member 4 is provided between the inlet opening 411 and the measurement pipe member 431.
21 is provided to connect the inlet opening 411 and the conduit of the measuring pipe member 431.

Therefore, in this embodiment, a part of the air in the intake passage is introduced into the branch passage from the inlet opening 411, passes through the branch pipe member 421 and the measuring pipe member 431, and then the wall portion 164.
Colliding with and changing the flow direction in the radial direction, the passages 166, 1
Through 68 to outlet openings 441, 451. Moreover, at the position indicated by the one-dot chain line C in the figure, the air flow meter 2
Of the intake passage, the narrowed portion C having the smallest passage cross-sectional area is formed, and the narrowed portion C is formed at the position indicated by the alternate long and short dash line D in the figure.
Next to this, a narrowed portion D having a narrow passage cross-sectional area is formed. Therefore, the airflow flowing from the upstream opening 3 is rectified by the narrowest narrowed portion C in the circumferential direction into a substantially uniform flow, and then flows to the narrowed narrowed portion D. Then, a negative pressure is generated in the throttle portion D due to the increase of the flow velocity, and the outlet openings 441 and 45 are formed.
The air in the branch passage is sucked out from 1.

Therefore, according to this embodiment, since the outlet openings 441 and 451 are provided downstream of the throttle portion C,
The flow deviation in the vicinity of the outlet openings 441 and 451 can be reduced, and the flow rate in the branch passage can stably correspond to the flow rate in the entire intake passage. Also, the outlet opening 441,
Since 451 is opened over almost the entire circumference except for the ribs, an average negative pressure according to the flow rate of the entire intake passage can be made to act on the outlet opening, and the flow rate flowing out from the branch passage can be adjusted to the entire intake passage. It can be maintained at a desired ratio to the flow rate. Also, in this embodiment, the outlet opening 44
Since the openings 1 and 451 are provided between the ribs, the air can be discharged from the branch passage without being affected by the turbulent flow generated downstream of the ribs. Therefore, problems such as turbulent flow occurring in the branch passage and the flow rate in the branch passage not corresponding to the flow rate in the entire intake passage are prevented, and accurate flow rate measurement is possible.

Also in the case of this embodiment, the rib 12
The ribs 321, 331, 341, and 351 formed on the downstream side of 1, 131, 141, and 151 prevent deformation of the downstream side cylindrical portion 300, and prevent deformation when connected to the intake duct and tightened with a belt. it can.

In the embodiment shown in FIG. 1, the inside and outside of the branch pipe are used as branch passages, so that a longer branch passage can be made compact as compared with the embodiment shown in FIG. 4, and when the intake air amount changes. The sensor responsiveness, or the responsiveness to the engine intake pulsation and backflow can be adjusted by the passage shape.

Further, in the case where the outlet opening is formed between the ribs as shown in FIG. 4, the length of the rib on the upstream side of the outlet opening in the flow direction is shortened so that the upstream end face of the rib and the rib surface are separated from each other. It can be expected to suppress the influence of turbulent flow generated at. Therefore, in the embodiment of FIG. 4, the length of the rib along the flow direction is shorter than that of the embodiment of FIG. Further, in the embodiment of FIG. 1, the outlet openings 440 and 450 are opened on the upstream side of the outlet openings 441 and 451 of the embodiment of FIG. Therefore, in the embodiment of FIG. 1, the ribs can be formed up to the upstream side as compared with the embodiment of FIG. 4, and high strength can be obtained.

Further, in the above-described embodiments, the housing of the air flow meter constituting 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, a thermal type flow meter to which the present invention is applied is described. However, JP-A-62
The present invention may be applied to a flow meter as disclosed in Japanese Patent Publication No. 235525, which measures a flow rate by an axial movement amount of a shell-shaped member provided in the intake passage.

[0041]

According to the structure and operation of the present invention described above, the support member is formed so as to support the central member in the center of the passage and to be located inside the housing tightening portion, so that the load is applied to the housing from the outside. This load can be resisted even when is applied, and the deformation of the housing can be prevented.

[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.

FIG. 4 is a sectional view of another embodiment to which the present invention is applied.

[Explanation of symbols]

 1 Air Flowmeter 3 Upstream Side Opening 5 Downstream Side Opening 100 Central Cylindrical Section 160 Central Housing 120 Rib 130 Rib 140 Rib 150 Rib 200 Upstream Cylindrical Section 300 Downstream Cylindrical Section 320 Rib 330 Rib 340 Rib 350 Rib 360 Downstream Housing 400 Upstream Housing 410 Inlet opening 420 Branch pipe 430 Measuring pipe 440 Outlet opening 450 Outlet opening 500 Sensor part

Front Page Continuation (72) Inventor Yukio Sawada 1-1 Showa-cho, Kariya, Aichi Prefecture, Nihon Denso Co., Ltd. (72) Inventor Yukio Mori 1-1-chome Showa-cho, Kariya, Aichi Nihondenso Co., Ltd. (72) Inventor Takao, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd. (72) Inventor, Kunihiro Umezu, 1-1, Showa-cho, Kariya city, Aichi prefecture, Nihon Denso Co., Ltd.

Claims (1)

[Claims] 1. A flowmeter connected to a fluid pipe through which a fluid flows, the housing being made of resin, the outer periphery of which is fastened and fixed, and has a fastening portion which is coupled to the fluid pipe, and in which a fluid passage is formed. A central member provided in substantially the central portion of the passage, a sensor portion provided in the central member for measuring the flow rate of the fluid flowing in the passage, and provided between the housing and the central member, A flowmeter, comprising: a support member that supports a central member in the vicinity of the center of the passage and is located inside the tightening portion so as to withstand a load acting on the tightening portion.