JPH0610261Y2 - Intake air flow rate detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an intake air flow rate detection device that is preferably used for detecting the intake air flow rate of, for example, an automobile engine, and more particularly, to an intake passage The present invention relates to an intake air flow rate detection device capable of preventing erroneous detection of the intake air flow rate due to blowback of exhaust gas, pulsating flow in an intake passage, or the like.

[Conventional technology]

 FIG. 6 shows a prior art intake air flow rate detecting device.

In the figure, reference numeral 1 denotes a casing constituting the main body of the intake air flow rate detecting device, the casing 1 is formed by a cylindrical pipe or the like, and both ends of the casing 1 are connected to cylindrical pipe members 2 and 3. . Here, the casing 1 forms an intake passage that communicates with the cylinders (not shown) of the engine together with the pipe members 2 and 3, and an air cleaner (not shown) or the like is provided at one end of the pipe member 2. . Then, the casing 1 and the pipe members 2 and 3 suck air (outside air) cleaned by an air cleaner into a cylinder connected to the other end of the pipe member 3 in response to reciprocating movement of a piston (not shown). It seems to be.

Reference numeral 4 denotes a heat-ray element mounted in the casing 1 via a slender rod-shaped bracket 5. The heat-ray element 4 is formed of a heat-sensitive resistor made of a platinum wire or the like whose resistance value changes in response to a temperature change. A heat wire flow meter (hot wire air flow meter) is configured by being heated from the outside through the lead wires 6, 6 and the like. Here, the heating element 4 is disposed on the central axis of the casing 1 via the bracket 5, and the flow velocity V ₁ or V _{2 of the} air passing through the central axis is detected to detect a control unit (not shown) or the like. The average air flow rate is calculated by the following equation, and the intake air flow rate is detected from the following equation for obtaining the flow rate Q from the average flow rate V ₀ and the cross-sectional area A: Q = A × V ₀ (1)

That is, since the intake passage including the casing 1 and the pipe members 2 and 3 extends linearly, the intake air flow passing through the inside is symmetrical with respect to the central axis of the intake passage, and its flow velocity distribution is shown in the figure. As illustrated by the chain double-dashed line, the flow velocity distribution F ₁ is obtained when the flow velocity is low, and the flow velocity distribution F ₂ is obtained when the flow velocity is increased. The heat ray element 4 is cooled as the flow velocity V ₁ , V ₂ of the intake air becomes faster, and the resistance value changes. Therefore, for example, the flow velocity V of the flow velocity distributions F ₁ , F ₂ passing on the central axis V ₁ ,
V ₂ is detected as a change in the resistance value, and this flow velocity V ₁ ,
By calculating the average flow velocity of the flow velocity distribution F _1, F ₂ from V _2, so as to detect the intake air flow rate.

The prior art intake air flow rate detecting device has the above-mentioned structure, and the heat ray element 4 which is disposed on the central axis of the casing 1 and which is electrically energized and heated from the outside through the respective lead wires 6 is the casing. It is cooled by intake air flowing in the 1, by detecting the intake air passing over the center axis of the flow velocity V _1, V _2, etc. as a change in resistance, so that it point by point detecting an intake air flow rate.

[Problems to be solved by the device]

By the way, in the above-mentioned conventional technique, since the intake air flow rate is detected by the change in the resistance value when the heating wire element 4 is cooled based on the flow velocity V ₁ , V _{2 of the} intake air, etc., the heating wire element 4 is As shown in FIG. 7, it is cooled by the intake air flow that flows forward to the cylinder side of the engine, and is also cooled by the air flow that flows in the reverse direction as shown in FIG. There is an unsolved problem of erroneously detecting the intake air flow rate.

That is, the intake air flowing through the intake passage is sucked into each cylinder when each intake valve (not shown) opens in response to each piston reciprocating in the cylinder of multiple cylinders. The intake air becomes pulsating in the intake passage. For example, as shown in FIG. 9, the flow velocity V at the position of the heat ray element 4 changes like the characteristic 7 in the low speed region of the engine, and in the medium speed region. Like the characteristic 8, it changes like the characteristic 9 in the high speed range.

In this case, since the engine intake and exhaust amounts are both small in the low speed range, the pulsation state of characteristic 7 is relatively small, but when the intake and exhaust amounts increase in the medium speed range, the exhaust valve (not shown) is shown. Of the exhaust valve may open before the exhaust valve opens, and a part of the exhaust gas may be blown back from the intake valve into the intake passage. Part 8
A, 8B, ... Temporarily becomes negative, and the intake air flows in the opposite direction in the intake passage as illustrated in FIG. Further, in the high speed range, the overlap time becomes short due to the high speed rotation of the engine, and the blowback of exhaust gas is canceled out among a plurality of cylinders, so that the flow velocity V becomes negative as in the characteristic 9. Things will disappear.

Therefore, in the prior art, the intake air flow rate Q in the low and high speed regions of the engine can be detected by the heat wire element 4 as characteristics 10 and 12 as illustrated in FIG. 10 in correspondence with the characteristics 7 and 9 of the flow velocity V. However, in the medium speed range, part 8 of characteristic 8
The flow velocity V in the opposite direction is detected by the A, 8B, ... And the erroneous extra detection is made as the intake air flow rate Q sucked into each cylinder like the portions 11A, 11B ,. I will end up.

As a result, the relationship between the detected intake air flow rate Q actually by the actual flow rate Q _a and thermo-elements 4 of the suction intake air not the corresponding relationship as expressed by the line 13 shown in FIG. 11,
There is a problem in that the detection accuracy is reduced due to the extra detection of the curved portion 13A.

The present invention has been made in view of the above-mentioned drawbacks of the prior art.The present invention is designed so that even if a backward air flow or the like occurs in the intake passage due to blowback or pulsation of exhaust gas, the heat ray element reverses the flow velocity. It is intended to provide an intake air flow rate detection device capable of preventing the detection of the above and reliably improving the detection accuracy.

[Means for Solving the Problems]

In order to solve the above-mentioned problems, the present invention is provided with an intake passage provided on an intake side of an engine, a throttle member provided to form a throttle part in the middle of the intake passage, and the throttle member. An upstream passage opening upstream of the intake passage,
A downstream passage that communicates with the upstream passage and opens downstream of the intake passage; and a bypass passage that includes a suction passage that opens from a branch portion between the upstream passage and the downstream passage to the position of the throttle portion. , And a heat ray element for detecting the intake air flow rate, which is provided in the throttle member and located in the upstream side passage of the bypass passage.

[Action]

Since the suction passage opening to the position of the throttle portion is provided between the upstream passage and the downstream passage of the bypass passage, an air flow in the reverse direction flowing from the downstream side to the upstream side is generated in the intake passage,
Even if it flows into the downstream side passage of the bypass passage, the air flow in the opposite direction can be made to flow out from the suction passage into the intake passage through the throttle portion, and the air flow in the opposite direction can flow in the upstream passage. It can be prevented from flowing toward the heat wire element.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. In the embodiment, the same components as those of the prior art shown in FIG. 6 described above are designated by the same reference numerals, and the description thereof will be omitted.

1 and 2 show a first embodiment of the present invention.

In the figure, reference numeral 21 denotes a tubular casing that forms an intake passage together with the pipe members 2 and 3, and the casing 21 constitutes the main body of the intake air flow rate detection device as in the case of the casing 1 described in the prior art. A projecting portion 21B having a substantially semicircular cross section is formed on the peripheral wall 21A of the casing 21 so as to form a downstream passage 24C of a bypass passage 24 described later.

Reference numeral 22 denotes a throttle member that is located on the protruding portion 21B side of the casing 21 and is fixed to the inner circumference of the casing 21. The throttle member 22 is located on the upstream side of the intake passage and extends in the axial direction in a semi-cylindrical shape. From an elongated portion 22A and a semi-oval curved portion 22B that protrudes inward in the radial direction of the casing 21 in a semi-elliptical shape from the downstream end of the elongated portion 22A and extends to the vicinity of the downstream end of the protruding portion 21B. Has become. Here, the throttle passage 22 defines an intake passage in the casing 21 into a main passage 23 and a bypass passage 24.
A curved portion 22B of the throttle member 22 forms a throttle portion 23A for reducing the passage area thereof in the middle of 3.

Reference numeral 24 denotes a bypass passage formed in the throttle member 22 by branching from the main passage 23.
An upstream side passage 24A that opens to the upstream side of the main passage 23 and extends axially with the peripheral wall 21A of the casing 21.
And the upstream end face 21B ₁ of the protruding portion 21B, communicates with the upstream passage 24A through a branch portion 24B that is bent in a substantially L shape, and extends axially between the protruding portion 21B. The downstream passage 24C communicates with the branch portion 24B of the downstream passage 24C and the upstream passage 24A, and the throttle portion 23A.
Suction passage 24D that opens substantially vertically to the position
The suction passage 24D is configured to constantly suck the air in the bypass passage 24 by utilizing the throttling action of the main passage 23 by the throttle portion 23A. Further, the downstream passage 24C is provided on the downstream end surface 21 of the protruding portion 21B.
It opens so as to face B _2, and communicates with the downstream side of the main passage 23 in a substantially vertical direction.

Reference numeral 25 denotes a heat ray element for detecting the intake air flow rate, which is provided between the throttle member 22 and the casing 21 and is located in the upstream passage 24A of the bypass passage 24.
Numeral 5 designates, for example, the peripheral wall 21A of the casing 21 via the bracket 26 and the like, almost the same as the heat ray element 4 described in the prior art.
It is attached to the air conditioner and is heated to a predetermined temperature by the energization from the external lead wires 27, 27 to detect the flow velocity V _{3 of the} intake air. Here, the heat wire element 25 calculates the average flow velocity V ₀ in the control unit based on the flow velocity V _{3 and the} like as in the prior art, but in the control unit, the overall cross-sectional area A and the average of the bypass passage 24 and the main passage 23 are averaged. From the flow velocity V ₀ , the intake air flow rate is obtained by the above equation (1).

The intake air flow rate detecting device according to the present embodiment has the above-mentioned configuration, and its detecting operation will be described below.

First, the intake air sucked into the intake passage due to the operation of the engine passes through the main passage 23 and the bypass passage 24 to the first position.
It flows in the forward direction indicated by the solid arrow in the figure and flows into each cylinder of the engine. Here, the intake air flowing through the bypass passage 24 flows from the upstream passage 24A to the branch portion 24.
It branches in two directions on the B side, and from the suction passage 24D to the throttle portion 24.
The air is sucked to the A side and merges with the intake air flow in the main passage 23, and also merges into the main passage 23 from the downstream passage 24C. In this case, the flow velocity of the intake air in the main passage 23 is increased by the throttle portion 23A, and the throttle portion 23A
Since a negative pressure is generated on the A side, the air in the upstream passage 24A is sucked into the suction passage 24D by this negative pressure and flows out into the main passage 23.

The thermo-elements 25 arranged on the upstream side passage 24A of the bypass passage 24 is cooled by the air flow flowing through the upstream passage 24A in the forward direction, by detecting the flow velocity V ₃ and the like, controls this Output to the unit,
The average flow velocity V _{0 and the} like are calculated to detect the entire intake air flow rate sucked into the intake passage one by one.

Thus, according to this embodiment, the throttle member 22 is provided on the peripheral wall 21A of the casing 21 in order to form the throttle portion 23A in the middle of the main passage 23 in the casing 21, and the upstream side is provided in the throttle member 22. Since the bypass passage 24 including the passage 24A, the downstream passage 24C, and the suction passage 24D is formed and the suction passage 24C is opened at the position of the throttle portion 23A, the exhaust air is blown back into the intake passage, pulsation, etc. The air flow in the opposite direction shown by the dotted arrow in FIG. 2 is generated in the intake passage, which is the downstream passage 24C of the bypass passage 24.
Even if the air flows in, the air flow in the opposite direction is applied to the suction passage 24D.
It can be sucked inward by utilizing the negative pressure on the side of the throttle portion 23A, and can be made to flow out into the main passage 23, so that the air flow in the opposite direction can effectively flow into the upstream passage 24A. It can be prevented.

Therefore, it is possible to prevent the heat ray element 25 in the upstream passage 24A from being exposed to the air flow in the opposite direction and cooled, and only the forward air flow shown by the solid line in FIG. 11
Can be detected intake air flow rate Q corresponding to the actual flow rate Q _a of intake air as a straight line 13 shown in the figure, it is possible to reliably improve the detection accuracy. Although the casing 21 and the throttle member 22 are separately formed in the first embodiment, it goes without saying that they may be integrally formed in advance.

Next, FIGS. 3 to 5 show a second embodiment of the present invention. The feature of this embodiment is that the throttle member 32 is arranged on the central axis of the casing 31 as shown in FIG. , ……
It was installed through. Where the casing 31
Constitutes a main body of the detection device similarly to the casing 1 described in the prior art, and forms an intake passage together with the pipe members 2 and 3. The throttle member 32 includes, for example, a spherical portion 32A formed in an oval shape and a small-diameter cylindrical portion 32B extending axially from the downstream end of the spherical portion 32A, and is formed in a streamlined shape as a whole. There is. The throttle member 32 defines an intake passage in the casing 31 into a main passage 34 and a bypass passage 35, which will be described later, and the passage area is reduced in the middle of the main passage 34 by the spherical portion 32A of the throttle member 32. A narrowed portion 34A is formed.

In the figure, reference numeral 35 denotes a bypass passage formed in the throttle member 32. The bypass passage 35 opens upstream of the main passage 34 and extends axially in the upstream passage 35A, and the upstream passage 35A. And a downstream passage 35C axially extending into the cylindrical portion 32B of the throttle member 32 and a branch portion 35B extending in the spherical portion 32A in the left and right radial directions. , The suction passages 35D and 35D opening to the position of the throttle portion 34A, and the downstream passage 3
5C is an opening portion 3 which is bent in an L shape on the downstream end side of the columnar portion 32B and which is vertically opened to the downstream side of the main passage 34.
It has 5C ₁ .

Reference numeral 36 denotes a heat ray element disposed in the middle of the upstream passage 35A of the bypass passage 35, and the heat ray element 36 is the throttle member 32.
As shown in FIG. 5, it is mounted inside via a bracket 37, and is heated to a predetermined temperature by being energized by external lead wires 38. Then, the heat ray element 36 is cooled by the forward airflow (shown by the solid arrow in FIG. 3) similarly to the heat ray element 25 described in the first embodiment, and the flow velocity V _{4 and the} like are detected. It is like this.

Thus, also in the present embodiment configured as described above, when the intake air flows through the intake passage in the forward direction shown by the solid line arrow in FIG. 3, the hot wire element 36 detects the flow velocity V _4, etc. Thus, the intake air flow rate can be detected corresponding to the actual flow rate, and the detection accuracy can be improved. That is, even if an air flow in the opposite direction shown by the dotted arrow in FIG. 4 is generated in the intake passage and this flows into the downstream passage 35C of the bypass passage 35 through the opening 35C ₁ , this reverse The airflow in the directional direction can be sucked into each suction passage 35D by using the negative pressure on the throttle portion 34A side and can be discharged toward the main passage 34, and the airflow in the opposite direction can flow into the upstream passage 35A. It is possible to prevent the inflow, and it is possible to obtain substantially the same effect as that of the first embodiment.

[Effect of device]

As described in detail above, according to the present invention, a bypass passage including an upstream passage, a downstream passage, and a suction passage is provided in a throttle member that forms a throttle portion in the middle of an intake passage, and a heat ray is provided in the middle of the upstream passage. Since the element is arranged, even if an air flow in the opposite direction is generated in the intake passage and flows into the bypass passage from the downstream passage, it is caused to flow out from the suction passage and into the upstream passage. It is possible to prevent the inflow, detect the forward airflow by the heat ray element, and reliably improve the detection accuracy.

[Brief description of drawings]

1 and 2 show a first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a flow rate detecting device showing a forward direction of an air flow, and FIG. 2 is a reverse direction of the air flow. 1 is a vertical sectional view similar to FIG. 1, and FIGS. 3 to 5 show a second embodiment,
3 is a longitudinal sectional view of the flow rate detecting device showing the forward direction of the air flow, FIG. 4 is a vertical sectional view similar to FIG. 3 showing the reverse direction of the air flow, and FIG. 5 is in FIG. 6 and 11 show a prior art, FIG. 6 is a vertical sectional view of an intake passage provided with a flow rate detecting device, and FIG. 7 is a forward flow velocity distribution. 8 is a vertical cross-sectional view of the intake passage, FIG. 8 is a vertical cross-sectional view of the intake passage showing a reverse flow velocity distribution, FIG. 9 is a characteristic diagram showing the flow velocity of intake air, and FIG. 10 is the detected intake air. FIG. 11 is a characteristic diagram of the flow rate, and FIG. 11 is a characteristic diagram showing the relationship between the actual intake air flow rate and the detected intake air flow rate. 2, 3 ... Pipe members 21, 31 ... Casing, 22,
32 ... throttle member, 23, 34 ... main passage, 23
A, 34A ... throttle part, 24, 35 ... bypass passage,
24A, 35A ... upstream passage, 24B, 35B ... branching portion, 24C, 35C ... downstream passage, 24D, 35D
...... Suction passage, 25, 36 ...... Heat ray element.

Claims (1)

[Scope of utility model registration request] 1. An intake passage provided on an intake side of an engine, a throttle member provided to form a throttle portion in the middle of the intake passage, and an throttle passage formed on the throttle member at an upstream side of the intake passage. An upstream passage that opens, a downstream passage that communicates with the upstream passage and opens downstream of the intake passage, and a suction that opens from the branch portion between the upstream passage and the downstream passage to the position of the throttle portion. An intake air flow rate detection device comprising: a bypass passage formed of a passage; and a heat ray element for detecting an intake air flow rate provided in the throttle member, located in the upstream side passage of the bypass passage.