JPH04203937A - Air flowmeter - Google Patents

Abstract

PURPOSE:To prevent influences of a divagation by controlling the ventilation resistance of a rectifier grating, and making constant the flow velocity of a measuring part in accordance with the pattern of the sneaking divagation. CONSTITUTION:A rectifier grating 12 bordered by a holding frame is rigidly held by a grating fixing member at an entrance where a suction air enters the body of the flowmeter. The grating is fine over an entrance 15 of a bypass, so that the ventilation resistance becomes large and the flow velocity is decreased. On the other hand, the grating 12 becomes coarse at the opposite side of the entrance 15, and therefore the ventilation resistance is small and the flow velocity is consequently increased. When a divagation pattern 17 which flows fast over the entrance 15 and slowly at the opposite side enters the body through a suction air duct 13, the flow velocity of the air entering the entrance 15 becomes generally uniform. Accordingly, even if the distribution of the flow rate after the air passes thought the grating 12 is not uniform, since the ventilation resistance over the entrance 15 is controlled so as to achieve the same flow velocity at the same flow rate, the influences of the divagation can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an air flow meter for measuring the intake air flow rate in an internal combustion engine for an automobile, and more particularly to a hot wire air flow meter.

[Conventional technology]

In the prior art, Japanese Patent Application Laid-Open No. 64-2
As described in No. 6112, in the fluid regulating structure, ventilation resistances approximately proportional to the flow velocity of the fluid are provided at matching positions, thereby making the flow velocity within the conduit uniform.

[Problem to be solved by the invention]

, 2. The prior art described in section 2 has a structure in which ventilation resistance is approximately proportional to the flow velocity so as to make the cross-sectional flow velocity within the air passage uniform. However, in reality, there are various drift patterns when considering when the engine is installed.

There was a problem in that it was very difficult to maintain a uniform flow velocity across the cross section of the intake pipe.

An object of the present invention is to provide a rectifier grid with ventilation resistance so that the flow velocity at a point near the intake air detection part is always constant at the same flow rate even in various drift patterns in the intake pipe, and to prevent the influence of drift. Our goal is to provide a hot wire air flow meter.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a rectifying grid structure provided on the upstream side of a hot wire air flow meter that is disposed within an air passage and detects the flow velocity of air to measure the flow rate. The rectifying grid is provided with ventilation resistance so that the flow velocity near the flow velocity measuring section is always constant even when various drifts occur in the same flow rate.

[Effect]

According to the above structure, even if a biased flow occurs on the upstream side of the rectifier grid, the same flow velocity can always be measured at the same flow rate, and the flow velocity distribution is not affected, making it possible to accurately measure the flow rate. I can do it.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 to 10. In FIG. 1, a body 1 constituting an air passage of a hot wire air flow meter has a bypass passage 6 integrated into a main air passage 5 disposed outside the center of the main air passage 5. Further, in the bypass passage 6, a hot wire 3 for detecting the amount of intake air and a temperature sensitive resistor 4 for detecting the temperature of the intake air are arranged. Furthermore, an electronic control module 2 is arranged that converts the amount of intake air detected by the hot wire 3 into an electrical signal. The air 7 sucked into the main air passage 5 and the bypass passage 6 are divided into a main air passage 5 and a bypass passage 6. The amount of air flowing through the bypass passage 6 passes through the hot wire 3 and the temperature-sensitive resistor 4 and merges into the main air passage 5 from the bypass passage outlet 15. A rectifying grid 12 framed by a holding frame 10 is fixedly held at the intake air inlet portion of the body 1 by a rectifying grid fixing member 11. Moreover, the coarseness of the rectifying grating 12 is the third
As shown in the figure, the bypass passage population 15 is denser on the upper side and coarser on the opposite side.

In FIG. 4, the flow velocity is high through the intake air duct 1-13 and on the bypass inlet part 15 like the drift pattern 17.
On the other side, if a slow drift enters body 1, then on the bypass population 15.

Since the roughness of the rectifier grid is dense, the ventilation resistance is large and the flow velocity is slow. On the opposite side of the bypass inlet 150, the roughness of the rectifier grid is coarse, so the ventilation resistance is small and the bypass population is low. The diversion method that was slow on 15 becomes faster. As a result, the flow velocity distribution after passing through the rectifying grid 12 is not uniform within the main air passage, but takes the form of a distribution 24 in which the flow velocity is fast at the center of the main air passage 5 and slow at both ends.
The flow velocity vector of the air entering the bypass passageway 15 is as shown in 16b. On the other hand, in FIG. 5, the rectifier grid 12 above the bypass passage inlet has a coarse mesh, and the opposite grid has a dense mesh. Now, suppose that a biased flow 18 having the same flow rate as the biased flow 17 which is slow on the bypass population 15 and faster on the opposite side as shown in FIG. 6 enters the body 1 through the intake air duct 13, then the side opposite to the bypass population 15 In this case, since the rectifying grid 12 has a coarse mesh, the ventilation resistance is large, and the incoming flow rate is slow.

On the contrary, since the ventilation resistance is small above the bypass port 15, the flow rate becomes faster. As a result, the flow velocity distribution after passing through the rectifying grid 12 is not uniform within the main air passage 5;
The shape of the distribution 25 is such that the center is fast and the ends are slow, and the flow velocity vector of the air entering the bypass population 15 is 16d.
It will look like this. 4 and 6, the flow velocity distribution after passing through the rectifying grid 12 is not uniform within the cross section of the main air passage, but the flow velocity vector 1 of the air entering the bypass population 15
6b and 16d show almost the same value. As a result, even if different drifts occur, or even if the flow velocity distribution after passing through the rectifier grid is different, the ventilation resistance at the entrance of the bypass passage can be controlled, and the flow velocity remains the same at the same flow rate. It is possible to prevent the influence of drifting by providing ventilation resistance such that

In the hot wire air flow meter, there are various drift patterns depending on the shape of the intake air duct 13, the shape of the air cleaner, and the like. Figure 7 shows an example of measures to be taken when a particularly high flow velocity occurs only on the bypass passage population 15, and Figures 8 and 9
The figure shows an example of countermeasures when there is a change in the flow velocity distribution only on the bridge that constitutes the bypass passage 6, and Fig. 10 shows an example of countermeasures when there is a change in the flow velocity distribution diagonally with respect to the bridge that constitutes the bypass passage 6. This is an example of countermeasures.

〔Effect of the invention〕

According to the present invention, there is an effect of providing a hot-wire type air flow meter in which even when a drift occurs from the upstream side, the influence of the drift is reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hot wire air flow meter showing an embodiment of the present invention, FIG. 2 is a side view of FIG. 1 viewed from the upstream side of the air flow, and FIG. 3 is a rectifier grid of the present invention. Figure 4 is an explanatory diagram showing the flow velocity distribution at the air inlet of a hot wire air flow meter using the rectifying grid shown in Figure 3.
Figure 6 shows the flow velocity distribution at the air inlet of a hot-wire air flowmeter using the rectifier grid shown in Figure 5, with the coarseness of the rectifier grid reversed for the air inlet of a hot-wire air flowmeter. The explanatory drawings, FIGS. 7 to 10, are diagrams showing application examples for making the flow velocity at the air inlet of a hot wire air flow meter constant in response to various drifting flows. 1...Body, 2...Electronic control module, 3...
・Hot wire, 4... Temperature sensitive resistor, 5... Main air passage, 6
...Bypass air passage, 7...Intake air amount, 8...
- Amount of air flowing through the main air passage, 9... Amount of air flowing through the bypass air passage, 10... Rectifying grid holding frame, 11.
... Rectifier grid fixing member, 12... Rectifier, grid (1), 1
3... Intake air duct, 14... Seal member, 15
... Bypass passage entrance, 16... Flow velocity entering the bypass passage, 17... Unbalanced flow pattern (1), 18...
Straight flow pattern (2), 19... rectifier grating (2), 20...
- Rectifier grid (3), 21... Rectifier grid (4), 22...
- Rectifier grid (5), 23... bypass passage outlet, 24
...Normal flow after passing through the rectifying grid 12 (1), 25-4
The polarized flow after passing through the I flow grid 12 (2), 26 bypass passage. Fig. 9 7O polishing

Claims (1)

[Scope of Claims] 1. In a fluid regulating structure provided in the upstream side of the passage of an air flow meter that is disposed in a fluid passage and measures the flow rate by detecting the flow velocity of the fluid, An air flowmeter characterized in that ventilation resistances are provided at positions that match each other so that the flow velocity of the fluid near the flow velocity detection section is approximately constant regardless of the degree of drift that occurs on the upstream side of the fluid regulator. 2. In claim 1, the flow regulator has the following functions for various drifting currents:
An air flow meter characterized by matching and setting ventilation resistance for each.