JPS5965217A - Device for detecting air flow rate - Google Patents

Abstract

PURPOSE:To obtain approximately the same output under the same conditions, by providing the inlet opening part of a bent pipe in the direction, which does not receive the dynamic pressure of an intake air flow with respect to the axial line of a Venturi part, and guiding a static pressure to the inlet opening part of the bent pipe. CONSTITUTION:An inlet opening part 18 of a bent pipe 12 is opened at a clearance angle theta as shown by a cutting line D with respect to an axial direction line C of a Venturi part 3. The intake air flows along the axial direction line of the Venturi part 3, but the inlet opening part 18 of the bent pipe 12 does not receive the dynamic pressure of the intake air flow. Therefore, the output of a heat sensitive resistor, which is arranged in a bypass air path 8 of an air flow rate detecting device, becomes approximately the same under the same conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a hot wire type air amount detection device, and particularly to an air film detection device used in a fuel supply device for an internal combustion engine.

[Prior art]

Conventionally, various air detection devices for internal combustion engines have been proposed. It passes through the venturi section of the 'Rti passage and is supplied to the engine via the throttle valve.

A bypass air passage 1117 is further provided in parallel with this intake passage, and a heat resistance (hot wire) 11 and is provided within this bypass passage. The output signal appearing on the heat-sensitive resistor provided in this bypass passage is the air passage (i
The number 18 indicates the total air flow supplied to the engine, for example, and is used for calculating the optimum required fuel flow tI'L by manual input to the control unit. Then, the injector is controlled based on the trt appropriate fuel flow calculated by this control unit, and fuel is supplied to the engine.

In the air amount detection device as described above, the air that enters the air passage from the air cleaner creates, for example, a vortex and draws complicated streamlines. Such turbulence in the airflow also affects the airflow in the bypass air passage.
It has the disadvantage of disturbing the output of the thermal resistor and giving a false indication of air flow rate.

In internal combustion engines, carbon and oil layers enter the air passages and further into the bypass passages due to phenomena such as blowback. There is also a drawback that the carbon and oil droplets form f=J on the surface of the heat-sensitive resistor, that is, the heat wire provided in the bypass passage, and as a result, the detection output is disturbed.

Therefore, in order to solve the above-mentioned problems, the present applicant has proposed a 14-structure air pressure detection device as shown in FIGS. 1 and 2.

First, based on FIGS. 1 and 2, an explanation will be given of the air deposit detection candy proposed by Mizude To.

In FIG. 1, an air cleaner 1 is disposed above an air passage 2 having a venturi portion 3 at the center of its inner surface. Below this air passage 2, a throttle pulp 4
, and a fuel injector 6 are attached. The air that has passed through the filter 5 of the factory cleaner 1 passes through the venturi section 3 of the air passage 2, is mixed with fuel injected from the injector 6, and is guided to the cylinders of the engine (not shown).

As is commonly known, the fuel supplied to the engine is
The air flow rate Qm supplied to the engine is detected, and this 4?
It is set to the optimum value calculated by the control unit 7 based on the immediate result. Then, the fuel injection time of the injector 6 is controlled according to this optimum fuel.

A throttle body including an air passage 2 having a venturi portion 3 is formed, for example, by aluminum die casting, and a bypass air passage 8 is further formed in the venturi portion 2 within the throttle body. The entrance of this bypass escape route is opened to a land part 10 formed on one side of the airbone part 9 at the upper part of the air passage 2, and the exit thereof is opened through a land part 11 formed at the narrowest part of the venturi part 6. , are led to the air passage 11.

Furthermore, a pipe 12 made of gold FA, for example, is attached to the upper part of the bypass air passage 8.

Inside the bypass air passage 8, there is a heat-sensitive resistor, that is, a heat wire 13, whose resistance value changes depending on the air flow rate.
is provided.

The hot wire 13 arranged in the bypass air path 8 usually consists of two hot wires. These hot wires form the second leg of the bridge circuit.

The air flow rate QA flowing through the air passage 2 of the throttle body is
Generally, an air flow defined by the venturi section 3 and proportional to this air flow rate, ie, the air flow rate supplied to the engine, flows into the bypass air passage 8. The hot wire whose resistance value changes according to the air flow rate flowing through the bypass passage 8 is
Therefore, it will generate an output signal that is proportional to the air flow rate supplied to the engine.

Generally, in an air flow rate detection device having an air passage and a bypass air passage provided in parallel with the air passage, the air flow particularly at the upstream portion of the bypass passage is easily disturbed by, for example, swirls. The air flow rate detection device proposed by the applicant is based on the following experimentally discovered facts. That is, the length t of the upstream portion of the hot wire 13 of the bypass passage 8 is at least 2 times the diameter of the bypass passage 8.
This is the fact that by more than doubling the amount, it is possible to reduce the negative effects of turbulence in the surrounding airflow. On the other hand, the length of the bypass passage is 11. The length of the second flow section is determined by the size or structure of the throttle body, so if it is set to a desired length, = ti
tmuj “It’s strange.

In order to reduce the length of the hot wire upstream portion of this bypass passage to a desired length, a pipe 12 bent at a predetermined angle is attached to the upstream entrance of the airflow curve 8. . This pipe 12 is, for example, a metal pipe, and has a flange capital 14 cut off by welding or the like. This bent pipe 12 with a 7 rank section 14? Yo, screw 1
5, it is firmly fixed to the land n1NO where the throttle is not rested. Further, a support member 16 made of metal, for example, is attached to this land portion with a screw 17, and the support portion 1fA'l6rJl and the bent pipe 12t are further firmly supported.

As is clear from the figure, the bent pipe 12 is inserted into the upper projection part of the venturi part 3 and along the outer surface at a substantially right angle to the axial direction of the venturi part 3. The outlet opening 111 is opened to a bypass passage upstream of the hot wire 13.

By providing such a bent pipe 12, air with low inertia is guided into the bypass 3LIJ path 8 through the pipe 12, but on the other hand, carbon and oil droplets with large inertia compared to air are guided into the pipe 12. It becomes difficult to invade. Therefore, heat rays of carbon and oil droplets due to phenomena such as blowback1
It is possible to prevent adhesion to 3.

In the air amount detection device proposed by the applicant as described above, the length upstream of the hot wire in the bypass passage can be made sufficiently long, so air turbulence does not occur in the bypass passage, and carbon and oil droplets are removed in the axial direction of the venturi. It is difficult to enter the bypass passage by using a bent pipe that opens at right angles to the line.

By the way, after actually manufacturing the air amount detecting device proposed by the present applicant as a product, a problem arose that when the output of the air amount detecting device was determined, the output varied between individual devices. Therefore, when considering why this problem occurs, we found that the artificial opening of the bent pipe 12 is
It was found that this was caused by the fact that the opening was not exactly perpendicular to the axial direction of the shaft.

As described above, the reason why the artificial opening of the bent pipe 12 does not open at right angles to the axial line of the venturi 8 is that the opening angle of the bent pipe 120 cannot be made constant over the individual pipes (normally There is an error of ±5°.

), secondly, it is considered that the installation error when fixing the bent pipe 12 to the land 7τl 510 is not constant.

In particular, when the inlet opening of the bent pipe 12 opens in the air flow direction and receives the dynamic pressure of the intake air flow, the air flow h1 detection device generates an extremely large output. The output will vary greatly depending on the degree.

[Purpose of the invention]

The object of the present invention is to
The purpose of the present invention is to ensure that the output representing , , does not vary from one air quantity detection device to another, and that each air quantity detection device can obtain substantially the same output under the same conditions.

[Summary of the invention]

A feature of the present invention is that the inlet opening of the bent pipe is opened in a direction that does not receive the dynamic pressure of the intake air flow with respect to the axis of the venturi part, so that the bending pipe introduces static pressure to the inlet opening of the shivive. This is how it was done.

[Embodiments of the invention]

Examples of the present invention will be described in detail below.

In FIG. 3, the inlet opening 18 of the bent pipe 12 has a clearance angle θ with respect to the axial direction C of the venturi portion 3 (translated parallel to the central axis of the venturi portion 3). It has an opening. That is, the distance t from the central axis M of the bypass passage 8 to the lowest end 18d of the inlet opening 18 is shorter than the distance P79L from the central axis M of the bypass passage 8 to the uppermost end 18u of the inlet opening 18. Therefore, the flow of intake air flows along the axial line of the venturi section 3, but the bent pipe 120 entry and opening section 18 has a relief angle of 0 in any air flow M detection device, so that the intake air flows along the axial direction line of the venturi section 3. It is designed not to receive the dynamic pressure of the flow. Therefore, both airflow (i) detection devices can obtain approximately the same output under the same conditions.

In FIG. 4, the relationship between the clearance angle θ and the rate of change in the output of the air amount detection device is explained. The horizontal axis represents the value of the relief angle θ, and Qdeg is the opening part 1 of the bent pipe 120.
8 and the axial line of the venturi part 3 are at right angles,
The + side indicates when the inlet opening 18 is open to receive dynamic pressure, and the - side indicates when the inlet opening 18 is υ110 so as not to receive dynamic pressure as shown in Figure 3. It shows. The vertical axis represents the amount of air taken into the internal combustion engine at a constant rate (2 ol
(y/h) and shows how much the output fluctuates based on the output value when the clearance angle θ is □ deg.

As can be understood from Fig. 4, the clearance angle θ is on the + side,
In other words, when the music is being played, when the opening part 18 of the Shivibe 120 receives the pressure of the intake air flow, the output fluctuates sharply, and when the music is being played, the artificial opening 18 of the Shivibe 12 has a relief angle θ on the negative side. When doing so, we can see that individual skies and their outputs also vary widely. On the other hand, when the relief angle θ of the bent pipe 12 is not affected by the dynamic pressure of the suction airflow when one lifting platform, that is, the artificial opening 18 of the bent pipe 12, is not subjected to the dynamic pressure of the suction airflow, the output may fluctuate slightly. It remains almost constant even when the song is Shivibe 12
It can be seen that if the inlet opening 18 has a clearance angle θ on one side, the output will be kept almost constant even if the clearance angle θ varies among individual air canopy detection devices.

In this way, if the clearance angle of the opening part 18 of the bent pipe 120 is set to one side in any air quantity detection device, the inlet opening of the bent pipe 12 of each air quantity detection device can be adjusted. As long as the clearance angle of the part varies on one side,
As explained in FIG. 4, the output of the air amount detection device is kept substantially constant.

The above was proposed by taking into account the influence of dynamic pressure on the intake airflow, but when considering the output of the air amount detection device, the accuracy of the output can be improved by considering the following: becomes.

In other words, if the clearance angle θ of the artificial opening 18 of the bent pipe 12 is unnecessarily increased to one side, airflow turbulence will occur at the clearance angle θ, and this turbulence will adversely affect the pipe waste passage 8. Conceivable.

In FIG. 5, the horizontal axis shows the relief angle θ of the inlet opening 18 of the curved pipe 12, and the vertical axis shows the constant intake air amount (20Ky/
b) It shows the median output value and the rate of change in the output deviation width under the conditions of (b). As can be understood from FIG. 5, when the clearance angle θ is set to -1j'+deg or more, there is a problem in that the rate of fluctuation of the Ill force suddenly becomes thick f3.

This is considered to be due to the fact that when the relief angle θ becomes -15 degrees or more, air turbulence suddenly occurs in this part.

Therefore, it is desirable that the clearance angle θ is approximately -15'deg at maximum.

FIG. 6 shows how to determine the clearance angle θ of the bent pipe 12.

Now, the error range of the bending angle of the Shivibe 12 is ±5 degrees. Therefore, Magarinoku Eve 12
When attaching the to the land 10 of the air horn part 9 (=
If the J error is +2 degrees, the overall error in the clearance angle θ is +7 degrees. Conventionally, the inlet opening 18 of the bent pipe 12 is within this range of ±7 deg.
This means that there was variation with respect to the axial direction line C. In the present invention, the inlet opening 18 of the curved pipe 12 is cut at a cutting angle θl so that the tip of the curved pipe 12 becomes the inlet opening 18. This cutting angle θl is g deg
is set to . Then, when the overall error is +7 degrees at the maximum on the + side, the relief angle θ is θ=
+7 deg -8deg=-1deg, and on the other hand, when the overall error is -7deg at the maximum on one side, the relief angle θ is θ=-7deg-s deg=-15deg,
Limit range Kf shown in the experimental results of Figures 4 and 5
l'It is a whole thing.

As described above, in the example shown in FIG. 6, the operation is extremely simple because only the tip of the bent pipe is simply cut at a predetermined cutting angle θl.

Next, another embodiment of the present invention will be described based on FIG.

FIG. 7 shows another embodiment of the present invention, which differs from FIG. 6 in that the inlet opening 1 at the tip of the bent pipe 12
8 is not cut with the cutting angle θl, and the bending angle θ2 is a predetermined value corresponding to the cutting angle θ1.

That is, the inlet opening 18 of the bent pipe 12 opens at right angles to the axis of the bent pipe 12, which is similar to the embodiment shown in FIG. However, the bending angle θ2 of the bent pipe 12 is 90' or less and is bent by 82 degrees. Therefore, the curved pipe 12 is connected to the land IO [the established 11 fox-entering opening part] 8 has a relief angle σ as shown in FIG. Therefore, the dynamic pressure of the air flow no longer acts on the artificial opening 18 as shown in FIG.

The reason why the bending angle θ2 of the bent pipe 12 is set to 82 degrees is as follows.

As mentioned above, the overall installation error of the bent pipe 12 is as follows.
It is +7 degrees. Therefore, when the mounting error on the + side is large and becomes +7 degrees, the clearance angle θ is θ=+7d.
eg+82deg=89deg (=-1deg). On the other hand, when the installation error is -7deg at the maximum on one side,
Relief angle θ is 0=-7deg+82deg=75deg (=-15d
eg), which falls within the limit range shown in the experimental results of FIGS. 4 and 5.

In this manner, in the example shown in FIG. 7, the work is extremely simple because the bending angle θ2 of the bent pipe is simply bent to a predetermined distance.

What is common to the embodiments shown in FIGS. 6 and 7 is that the clearance angle θ is on one side and its maximum is in the range of −15 degrees, so that the dynamic pressure of the air flow is not applied to the artificial opening 18. This means that no significant air turbulence occurs in the area of the artificial opening 18.

〔Effect of the invention〕

As described above, according to the present invention, the artificial openings of the bent pipes are opened in the direction in which the individual air m and all of the detection devices do not receive dynamic pressure, so that the individual air h1. The output of the detection device can be kept almost constant under the same conditions.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view of the nitrogen amount detection device proposed by the present applicant, Fig. 2 is a view from the ■-■ arrow of No. 1 L'21, and Fig. 3 is an embodiment of the present invention. Figures 4 and 5 are diagrams showing the relief angle of the bent pipe and changes in the output of the air h1 detection device, and Figure 6 is a sectional view of the bent pipe. The figure shows air J which is another embodiment of the present invention.
i1 is a sectional view of main parts of the detection device. 2... Air passage, 3... Venturi part, 4... Throttle heartz, 8... Bypass passage, 9... Air horn part, lO... Land part, 11... Slit,
12... bent pipe, 13... hot wire, 18...
Artificial opening, θ...Escape 1 2nd mouth/7 10 3rd blunder 40 boiling cup (de'A) 'f5'f' 74 (d-e3) cod 6 kaku8

Claims (1)

[Scope of Claims] 1. A venturi section formed in the middle of an air passage that supplies air to the internal combustion barrier, and a bypass that opens upstream of the venturi section and bypasses the soaking passage and opens into the venturi section. In an air TFI detection device comprising a passageway and an air h1-detecting means provided in the middle of the air passageway, an artificial opening opens into the air passageway, and an air h1-detecting means is provided in the middle of the air passageway.
A curved tube opening into the bypass passage upstream of the air flow detection means is provided, and the inlet opening fS11 of the curved tube is configured to: 1) move the air flow flowing through the air passageway; An air amount detecting device (1a) characterized in that it is opened in a direction that does not receive pressure. 2, 11!1', -1'l' In claim 1, the opening part of the FiiJ recorder of the shivibu is located on the air flow direction side with respect to the axial direction line of the venturi part. An air detection instrument characterized by being opened in an I-building enclosure with a maximum of 15 deg. 3. In claim 2, the distance from the upper end of the OiJ entry opening of the bent pipe to the center 1 drawing line of the bypass passage, and the +i of the bent pipe.
The distance t from the lowermost end of the opening part to the central axis of the bypass passage has a relationship of L>t, and the line connecting the uppermost end and the lowermost end is connected to the uppermost end. The angle formed with the axial line of the venturi portion through which it passes is at most 15 de
An air film detection device characterized in that g. 4. Particularly, 5/[In claim 3, the air amount detection device is an air amount detection device in which the air amount detection means is a hot wire type air amount detection device.