JPH063172A - Heat generation resistance type air flowmeter - Google Patents

Abstract

(57) [Summary] [Structure] The measurement sub-passage 7 is provided inside the stay 10 penetrating the main passage 3 toward the circuit unit 2 and eccentrically from the axial center of the main passage 3. The groove formed at the upstream end 10a of the stay is partially covered with the plate-like member 11 so that the four sub-passage entrances 4
A, 4b, 4c and 4d are formed around the axial center of the main passage 3. A radial collecting passage 6 that joins the four flows is provided upstream of the measurement sub passage 7 in the axial direction. A mountain-shaped flow guide 31 is provided at the inlet of the collecting passage 6, and a notch groove 32 is provided at the outer corner of the connection portion with the measurement sub passage 7. [Effect] Multiple uneven flows (dynamic pressure, static pressure) can be captured for various flow velocity distributions, and sufficient merging allows
Flow velocity information proportional to the average flow velocity can be obtained in the measurement sub-passage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistance type air flow meter, and more particularly, to a heat generating device which constitutes an intake system of an automobile engine, detects an intake air amount thereof, and controls a fuel injection amount. The present invention relates to a resistance type air flow meter.

[0002]

2. Description of the Related Art A conventional heating device has a structure in which a heat generating resistor is arranged in an eccentric passage which is eccentric to the center of the main passage, and which aims to reduce a measurement error even when the flow of the flow meter flow is largely deflected. As a technique, there is a technique in which a plurality of sub-passages are provided and a heating resistor is arranged in each of the sub-passages as in Japanese Utility Model Laid-Open No. 61-195418. With this configuration, output information proportional to the average flow velocity of a plurality of flows upstream of the sub-passage is obtained, and the measurement accuracy is higher in the case where there is a drift in the upstream than in the case where there is one sub-passage. improves. But,
In this disclosed example in which the inlet openings of all sub-passages are provided in the outer peripheral portion of the main passage, it is impossible to obtain an output corresponding to the overall average flow velocity of the upstream flow, and a plurality of intakes of various types of non-uniform flow Significant output changes occur between duct systems.
In addition, there are drawbacks that a plurality of heating resistors are used and the electric circuit becomes complicated, the body structure becomes complicated and the cost becomes high.

On the other hand, as disclosed in JP-A-63-281016,
Although there is one measurement sub-passage for arranging the heating resistor, a configuration is disclosed in which a plurality of sub-passage inlets are provided to take in a plurality of upstream flows and merge these flows in the measurement sub-passage (aggregate passage). ing. With such a configuration and ideally achieving merging, output information proportional to the average flow velocity of a plurality of upstream flows can be obtained, and in the case where there is a drift in the upstream, there is one auxiliary passage inlet. Compared with, the measurement accuracy is improved.
However, in a configuration such as this disclosure in which the measurement sub-passages are merged (consolidated) passages, if the length of the passage from the inlet of the collection passages to the heating resistor is not long, "ideal confluence = average velocity Is not achieved. Further, in the configuration like the disclosed example, the inlet of the sub-passage can be formed only in the outer peripheral portion of the main passage as in the previous example, and it is impossible to take in the overall average flow velocity of the upstream flow velocity. Further, in this disclosed example, no consideration is given to the shape of the confluent portion,
It is said that low noise can be obtained by the two-dimensional air flow simulation, but from a fluid engineering point of view, a vortex is always generated at the downstream of the corner of the passage junction, and a vortex is generated upstream of the main flow at the junction. A dead water region (a part where the flow collides and the flow becomes unstable) occurs on the wall surface, and the flow after merging is unstable, and it is unlikely that it is low noise. Further, in these disclosed examples, since the entire sub passage is formed inside the flowmeter body forming the outer peripheral wall of the main passage, and the air in the main passage does not flow around the sub passage, the air in the sub passage is not formed. The temperature is easily influenced by the body temperature, and there is a drawback that a measurement error due to a change in the body temperature is large.

[0004]

In the prior art, the difference in the drift pattern (flow velocity distribution) of the flow meter flow due to the difference in the shape of the intake pipe system arranged in the flow meter flow such as the air cleaner or the duct, or these shapes. Although certain considerations have been made to reduce the output change with respect to changes in the drift pattern due to variations in mounting and mounting, there are still a number of problems. The object of the present invention is not only to minimize the output fluctuation under the various drifts of the flowmeter flow as described above, but also to eliminate the output error due to the body temperature, the output error under the pulsating flow, and the secular change due to pollution. Another object of the present invention is to provide a heat resistance type air flow meter that is strong against backfire of engines and can be produced at low cost. This allows the electronically controlled fuel injection system to be provided with accurate intake air amount information, achieves low fuel consumption of the engine and purification of exhaust gas, and also enables common use of flowmeters in various vehicles, air cleaner and duct shapes and mounting. It is possible to allow for variations and eliminate the need for readjustment of the flowmeter output when the design of the intake pipe system is changed.

[0005]

In order to achieve the above-mentioned object, a heating resistance type air flow meter of the present invention has a main passage through which most of the metered air flows, and the air in the main passage entirely surrounds the main passage. Measurement in which a sub-passage through which a part of the metered air is circulated is formed inside the member disposed in the main passage so that the sub-passage has a plurality of inlet openings and a heating resistor is arranged. In a heat resistance type air flow meter configured so that the central axis of the auxiliary passage is parallel and eccentric to the central axis of the main passage, a plurality of auxiliary passage inlet openings are arranged around the center of the main passage and taken in from the plurality of inlet openings. A collecting sub-passage formed in the radial direction that joins the air flow is provided upstream of the measurement sub-passage.

[0006]

[Function] By arranging a plurality of sub-passage inlet openings around the center of the main passage, the flow velocity distribution is different from the flow velocity with various flow velocity distributions generated by the flow meter It is possible to capture a plurality of flows having a flow velocity representative of the above. By providing the aggregation passage upstream of the measurement sub-passage, the merging of the flows with different flow velocities taken in from the multiple inlet openings can be sufficiently achieved, and at the position of the heating resistance element arranged in the measurement sub-passage, the multiple intake A flow having a flow velocity proportional to the average value of the dynamic pressure and static pressure of the flow is obtained. As a result, a heat resistance type air flow meter with a small output change can be realized even if it is applied to various intake pipe systems having various flow velocity distributions (differential flow patterns).

The sub passage is configured to be longer than the main passage having some bends so that the flow resistance of the sub passage is increased and backfire from the engine and the invasion of blowback to the sub passage are reduced. This is to reduce the intrusion of dust into the sub passage and reduce the pulsation amplitude of the pulsating flow. Further, by disposing the member in which the entire sub passage is formed inside in the main passage so that the air in the main passage flows around the main passage, heat exchange between the main flow air and the sub passage forming member becomes good. As a result, the temperature of the air flowing through the auxiliary passage is always kept close to the temperature of the mainstream air, and the change in the output of the heating resistor due to the change in the body temperature can be reduced. By these actions, the basic requirements for the flowmeter, that is, the stability over time, the assurance of measurement accuracy, etc. are achieved.

[0008]

1 and 2 show a first embodiment of the present invention. The flow meter body 1 constitutes a part of the intake pipe of the engine, and forms the main passage 3 therein. The intake air flows in from the left side of FIG. 1, and the engine is connected to the downstream side of the right side. A projecting member (stay) 10 formed integrally with the body 1 penetrates the main passage 3 in a stay shape connecting the body wall 1a facing the body wall 1a on the side where the circuit unit 2 for outputting a flow rate signal is mounted. Is formed. Therefore, the main airflow flowing through the main passage 3 contacts the stay 10 and flows on both sides thereof. Inside the stay 10, a measurement sub passage 7 is formed with its central axis parallel to the central axis of the main passage 3 and eccentric to the circuit unit side. Stay 1
In the body wall 1a connected to 0, the measurement sub-passage 7
There is a hole penetrating to the circuit unit 2
Insert the molded part 2c integrated with the heating resistor 2a
And the temperature compensation element 2b is arranged in the measurement sub-passage 7. The circuit unit 2 is fixed to the body 1 with screw members 21 and 22. The signal of the circuit is output from the connector 2d to a control unit (not shown) of the engine.

At the upstream end 10a of the stay 10, the entrances 4 of four auxiliary passages arranged around the center of the main passage 3 are provided.
a, 4b, 4c and 4d are formed. The sub passage entrances 4a to 4d, the integration sub passage 6, and the introduction sub passages 5a, 5b, 5c, 5d are covered by the plate-like member 11 while leaving a groove formed in one surface of the stay upstream end 10a. It is formed by doing. The portions of the introduction sub-passages 5a, 5b, 5c, 5d and the integration sub-passages 6 covered by the plate-like member 11 are shown by broken lines in FIG. The plate member 11 is fixed to the stay upstream end 10a by a screw member 23 or the like.

The sub-air streams taken in from the sub-passage entrances 4a to 4d are introduced into the sub-passages 5a, 5b, 5c and 5d, respectively.
And merges before the aggregate passage 6 formed in the radial direction of the main passage and completes the merge in the aggregate passage 6, that is, the dynamic pressure and static pressure possessed by each of the captured flows are averaged. As a result, the measured flow flows into the auxiliary measurement passage 7. In addition, in order to ideally achieve the merging, the aggregate passage 6
A mountain-shaped flow guide 31 is provided at the entrance of the.
Further, a cutout groove 32 for confining a vortex generated therein is provided at an outer corner of the bend-shaped passage at the joint portion of the concentrating passage 6 and the measurement sub-passage 7, and the vortex flows into the measurement sub-passage. To prevent the generation of unnecessary noise.
The flow is further rectified in the measurement sub-passage 7, and as a result, a flow having a flow velocity proportional to the state quantities of the plurality of flows taken in is obtained at the position of the heating resistor. Therefore, a flow meter with a small output change can be realized even for various flow velocity distributions of the flow meter flow.

However, when there are several tens of types of intake pipe systems to which the flow meter is applied, as shown in this embodiment, the honeycomb rectifying member 13 is used as the auxiliary passage. It is also important to provide it upstream of the entrances 4A to 4d.
Further, if the cost permits, it is effective to provide another rectifying member such as a mesh member at a certain distance upstream of the honeycomb 13.

A downstream sub-passage 8 formed again in the radial direction is provided downstream of the measurement sub-passage 7, and the final end thereof is the outlet 9 of the entire sub-passage. The downstream sub-passage 8 and the sub-passage outlet 9 are formed by covering the groove formed at the downstream end 10b of the stay 10 with the plate-shaped member 12 except the outlet portion 9. The plate member 12 is a screw member 24.
Etc., and is fixed to the stay downstream end 10b. The connecting portion between the measurement sub-passage 7 and the downstream sub-passage 8 is a bend-type passage again. With such a configuration, the fluid resistance of the sub-passage increases even against backflow, and Reduces the intrusion of backfire and blowback flow into the secondary passage,
Damage to the measuring elements 2a and 2b is prevented.

A thin rib 10c is provided below the upstream end 10a of the stay 10. The reason why it is formed in this way is to reduce the pressure loss of the mainstream as much as possible.
This is to improve the flow of molten metal when molding is performed by die casting.

FIG. 3 and FIG. 4 show a second embodiment of the present invention. The axial sectional view of this embodiment is almost the same as that of the first embodiment shown in FIG. 1 and therefore omitted, and FIG. 3 corresponds to the II sectional view of FIG. The flowmeter body 41 has a main passage 43 formed therein. A stay 50 formed integrally with the body 41 is formed so as to penetrate the main passage 43,
A measurement sub-passage 47 is formed in the interior of 0 with the same configuration as in the first embodiment. Further, the circuit unit 2 is mounted by the same method.

At the upstream end 50a of the stay 50, two sub passage entrances 4 are arranged around the center of the main passage 43.
4a and 44b are provided. These sub passage entrances 4
4a, 44b, the integration sub-passage 46, and the introduction sub-passage 4
5a and 45b are formed by covering the groove formed at the stay upstream end 50a with the plate-shaped member 51, leaving the inlet portions 44a and 44b. The sub-air flows taken in from the sub-passage inlets 44a and 44b pass through the introduction sub-passages 45a and 45b, respectively, and the mountain-shaped flow guide 6
1 completes merging in the integrated sub-passage 46 provided in front of it, and flows into the measurement sub-passage 47. Introduction passage 45a,
The bottom surfaces 65a and 65b of the 45b are formed to be inclined as shown in the figure, and this is to slightly reduce the pressure loss in this passage portion. Aggregation sub-passage 46 and measurement sub-passage 47
A cutout groove 62 is formed at the outer corner of the bend-shaped passage of the connection portion with and, and a downstream sub-passage 48 is formed downstream of the measurement sub-passage 47. From the rear surface of the auxiliary passage entrance forming portion of the stay upstream end 50a to the downstream end 50b
Toward, thin ribs 50a and 50b are provided to improve the flow of molten metal during molding.

FIGS. 5 and 6 show a third embodiment of the present invention. The flowmeter body 71 formed of a resin material has a main passage 73 formed therein. A stay 80 formed integrally with the body 71 is formed so as to penetrate the main passage 73, and a measurement auxiliary passage 77 is formed inside the stay 80 with the same configuration as that of the first embodiment. Wearing 2 is done in the same way.

At the upstream end 80a of the stay 80, three sub-passage entrances 7 are arranged around the center of the main passage 73.
4a, 74b, 74c are provided. The sub passage entrances 74, 74b, 74c, the consolidating sub passage 76, and the introduction sub passages 75a, 75b, 75c have the grooves formed at the stay upstream end 80a, the entrance portions 74a, 74b,
It is formed by covering with a plate member 81 made of a resin material while leaving 74c. The plate member 81 is fixed to the portion of the stay upstream end 80a by welding. The sub-airflows taken in from the sub-passage entrances 74a, 74b, 74c pass through the introduction sub-passages 75a, 75b, 75c, respectively, and merge before the aggregate sub-passage 76, and the merge is completed in the aggregate sub-passage 76. , Into the measurement sub-passage 77. The bottom surface 93 of the collecting sub-passage 76 is formed to be inclined as shown in the drawing, and slightly reduces the pressure loss of the entire sub-passage. A cutout groove 92 is provided at the outer corner of the bend-shaped passage at the joint between the integration sub-passage 76 and the measurement sub-passage 77, and downstream of the measurement sub-passage 77, as in the first embodiment. A sub passage 78 is formed. The downstream auxiliary passage 78 is the downstream end 8 of the stay 80.
The groove provided in 0b is formed by covering the plate member 82 made of a resin material. The plate member 82 is also fixed by welding.

FIG. 7 shows a fourth embodiment of the present invention. The flowmeter body 101 has a main passage 103 formed therein. The stay 110 formed integrally with the body 101 has a main passage.
A measurement sub-passage 107 is formed in the stay 110 so as to penetrate through the stay 110, and has the same structure as that of the first embodiment. The circuit unit 2 is also mounted by a similar method.

At the upstream end of the stay 110 having a constant width, two sub passage entrances 104 arranged around the center of the main passage.
a and 104b are provided. These sub passage entrances 1
Reference numerals 04a and 104b are holes provided in the plate member 111. The plate-shaped member 111 covers the groove formed at the upstream end of the stay 110 and also forms the introduction sub-passages 105a and 105b and the aggregation sub-passages 106a and 106b. Stay 1
By forming 10 with a constant width, there is a restriction on the distance from the center of the main passage 103 to the sub passage entrances 104a and 104b, but since the area occupied by the stay 110 in the main passage 103 can be reduced, the first to third Main passage 1 compared to the embodiment
The pressure loss of 03 can be reduced.

The sub-air streams flowing in from the sub-passage inlets 104a and 104b merge through the introduction passages 105a and 105b, and are re-branched into the integrated sub-passages 105a and 106b.
After that, the flow merges again before the measurement sub-passage 107. In this configuration, merging occurs at the entrance of the measurement sub-passage 107, but since the merging has already been performed once in the front concentrating passages 105a and 105b, a short distance of the measurement sub-passage 107 is required to achieve ideal merging. It is possible with. The configuration of the downstream auxiliary passage and the like is almost the same as that of the first embodiment.

FIG. 8 shows a fifth embodiment of the present invention. The flowmeter body 121 has a main passage 123 formed therein. The stay 130 formed integrally with the body 121 is a main passage.
A sub-passage 127 for measurement is formed inside the stay 130 in the same configuration as that of the first embodiment, and the circuit unit 2 is mounted by the same method.

At the upstream end of the stay 130 having a constant width, there are four auxiliary passage entrances 124 arranged around the center of the main passage.
a, 124b, 124c, and 124d are provided.
The entrances of these sub passages and the introduction sub passages 125a, 12a
5b, 125c, 125d and the aggregation sub passage 126,
The groove provided at the upstream end of the stay 130 is connected to the entrance 124a-
The plate-shaped member 131 is formed by cutting out a portion corresponding to 124d. Therefore, the sub-passage entrances 124a to 124d in this embodiment are formed slightly parallel to the main airflow, unlike the previous embodiments. That is, the sub air flow is in the form of being sucked from the upstream end side surface of the stay 130. Since the stay 130 has a constant width, it is advantageous for reducing the pressure loss of the main air flow, as in the previous embodiment.

Sub passage entrances 124a, 124b, 124
The sub-airflows flowing in from c and 124d pass through the respective introduction sub-passages 125a, 125b, 125c and 125d, merge at the entrance of the introduction sub-passage 126 having the chevron-shaped flow guide member 132, and in the central sub-passage 126. After the merging is completed, the flow enters the measurement auxiliary passage 127. The configuration of the downstream auxiliary passage and the like is almost the same as that of the first embodiment.

9 and 10 show a sixth embodiment of the present invention. A flowmeter body 141 formed of a resin material has a main passage 143 formed therein, and a stay 150 having a constant width formed integrally with the body 141 is formed through the main passage 143. The measurement auxiliary passage 147 of the stay 150 is
It is formed with the same configuration as that of the first embodiment, and the circuit unit 2 is mounted by the same method.

At the upstream end 150a of the stay 150, an auxiliary passage entrance piece 151, which is also made of a resin material, is fixed by welding. In the entrance piece 151,
Two auxiliary passage inlets 144a and 144b and introduction auxiliary passages 145a and 145b are provided. The two sub passage entrances 144a and 144b are arranged at positions upstream of the stay 150 sandwiching the center of the main passage. The introduction sub passages 145a and 145b are formed to be inclined toward the center of the main passage 143, respectively, and the sub air flow taken in from the inlets 144a and 144b is
They meet at the center of the main passage 143. The confluence hole 161 is
It is configured to connect at the central position of the main sub-passage 143 and the central sub-passage 146, which is a radial groove formed at the stay upstream end 150a.

An arc-shaped flow guide 162 is formed as a part of the inlet piece 151 at the outer corner of the bend-shaped passage which is the junction of the collecting sub-passage 146 and the measurement sub-passage 147. As a result, the flow flows from the collecting sub passage 146 into the measurement sub passage 147 without being disturbed. This embodiment is different from the previous embodiments in that the introduction sub passage 145a,
That is, 145b and the aggregate sub-passage 146 are not in the same plane in the radial direction. The structure of the downstream auxiliary passage 148 and the like is almost the same as that of the first embodiment.

11 and 12 show a seventh embodiment of the present invention. The flow meter body 171 constitutes a part of the intake pipe of the engine, and forms the main passage 173 therein. Circuit board 201 and measurement sub passage 177, downstream sub passage 178,
The entire sub passage such as the sub passage outlet 179 and the heating resistance element 1
The circuit unit 172, which accommodates 72a, the temperature compensating element 172b, etc., leaves only the connector portion 172d for outputting a signal to the control unit outside the body 171, and the main passage 1
It is attached through 73. The insertion portion of the circuit unit 172 into the main passage 173 is formed in a stay shape having a substantially constant width as in the fourth, fifth, and sixth embodiments. Seam line 20
It is made by joining at the 2 position.

Entrances 174a, 174 for the four sub-passages
b, 174c, 174d are circuit unit upstream ends 172c
In addition, it is formed so as to be arranged around the center of the main passage 173. In addition, the introduction sub-passages 175a, 175b, 17
5c, 175d and the sub-aggregate passage 176 are similar to those in the fifth embodiment (FIG. 8) and have inlets 174a, 174.
It is formed in the same plane as b, 174c, 174d.
However, the difference from the fifth embodiment is that the grooves corresponding to the respective passages are internally molded without the addition of a plate-like member and the measuring sub-passage 177 is connected to the body 171 by a connector 172.
This is a point formed at a position opposite to d. This is because the heating resistor 172a and the temperature compensation element 172b arranged in the measurement sub passage 177, the circuit board 201, and the connector 1 are arranged.
It depends on the connection with 72d.

The sub-air flow and the main air flow are basically the same as those in the previous embodiments.

[0030]

According to the present invention, even when applied to various intake duct systems having various flow velocity distributions (differential flow patterns) generated in a flow meter flow, a heat resistance type air flow meter with a small output change can be provided. Will be realized. In addition, the basic requirements for a flow meter, such as measuring the average flow rate of pulsating flow and ensuring measurement accuracy with respect to environmental temperature changes, ensuring the accuracy of aged measurement that prevents contamination such as dust adhesion, and measuring against engine backfire and blowback At the same time, damage prevention of the device is achieved. Therefore,
By using the heating resistance type air flow meter of the present invention, accurate intake air amount information is given to the electronic fuel injection system for controlling the engine, the fuel efficiency of the engine and the exhaust gas purification are obtained, and the intake duct system It can be applied to different types of engines without adjusting the circuit unit for each engine.

[Brief description of drawings]

FIG. 1 is an axial sectional view of a first embodiment of the present invention.

FIG. 2 is a sectional view taken along the line II of FIG.

FIG. 3 is a sectional view of a portion corresponding to FIG. 2 of the second embodiment of the present invention.

FIG. 4 is a sectional view taken along the line IV-IV of FIG.

FIG. 5 is an axial sectional view of a third embodiment of the present invention.

6 is a cross-sectional view taken along the line VV of FIG.

FIG. 7 is a sectional view of a portion corresponding to FIG. 2 of the fourth embodiment of the present invention.

FIG. 8 is a sectional view of a portion corresponding to FIG. 2 of a fifth embodiment of the present invention.

FIG. 9 is an axial sectional view of a sixth embodiment of the present invention.

10 is a cross-sectional view taken along the line VI-VI of FIG.

FIG. 11 is an axial sectional view of a seventh embodiment of the present invention.

12 is a cross-sectional view taken along the line XX of FIG.

[Explanation of symbols]

1 ... Flowmeter body, 2 ... Circuit unit, 3 ... Main passage, 4
... Sub-passage entrance, 6 ... Aggregation sub-passage, 7 ... Measurement sub-passage, 8
... Downstream auxiliary passage, 10 ... Stay (projecting member), 11, 12
... plate-like member, 31 ... chevron-shaped flow guide, 32 ... notch groove.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Shinya Igarashi 2477 Kashima Yatsu, Takaba, Katsuta-shi, Ibaraki 3 Hitachi Automotive Engineering Co., Ltd. (72) Hiroshi Hirayama Kashima Yatsu Kashima, Katsuta, Ibaraki 2477 Address 3 Hitachi Automotive Engineering Co., Ltd.

Claims (1)

[Claims] 1. A main passage through which most of the metered air flows,
The auxiliary passage is formed inside the member disposed in the main passage and allows a part of the metered air to flow therethrough, and the auxiliary passage has a plurality of inlet openings and a center eccentric in parallel with the central axis of the main passage. In a heating resistance type air flow meter having a measurement sub-passage in which a heating resistance element is arranged inside a shaft, the plurality of inlet openings are arranged around the axis center of the main passage, and upstream of the measurement sub-passage. An exothermic resistance type air flow meter, characterized in that a collective sub-passage formed in the radial direction is provided.