JPH0385416A - Hot-wire type airometer - Google Patents

Abstract

PURPOSE:To enable reduction of the effect of engine pulsation at the time when the title meter is fitted to an actual vehicle by doubling the structure of a bypass passage provided in a flow rate measuring element. CONSTITUTION:It is assemed that engine pulsation 11 caused by the opening and closing of a valve of an engine comes into a body 1. When this pulsation 11 comes near the entrance of a bypass passage, it is sucked into the bypass passage wherein a flow velocity is large. While the flow velocity is almost the same both in an inside bypass passage 6 and in an outside bypass passage 7, the wall 2 of the inside bypass passage is so shaped as to project toward the wall 3 of the outside bypass passage. Therefore, it is hard for the pulsation 11 to enter the passage 6 and the pulsation passes through the passage 7 and gets out into a main air passage 8 through a bypass passage 14 traversing the passage 8 at a right angle. Accordingly, the entry of the pulsation 11 into the passage 6 from the vicinity of the entrance is reduced. At the same time, the pulsation 11 getting in from the passage 8 is hindered also virtually from advancing into the passage 6 by a passage wall 2. According to this constitution, a hot wire 12 for measuring the quantity of sucked air is hardly affected by the pulsa tion 11 and thus a two-value phenomenon and a leap phenomenon can be reduced.

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]

The bypass passage structure of an air flowmeter using a flow rate measuring tube is described in Japanese Patent Publication No. 51-65053.

However, the above does not particularly discuss the structure of the bypass air passage for suppressing the binary phenomenon and jump phenomenon of the hot wire air flow meter due to engine pulsation. Therefore, when mounted on an actual vehicle, there is a drawback that problems occur due to binary values and jumps.

[Problem to be solved by the invention]

The above conventional technology does not take into consideration the influence of pulsation from the engine when installed in an actual vehicle, and the problem is that engine pulsation easily enters from the air inlet and outlet in the bypass passage, and binary phenomena and jump phenomena are likely to occur. was there.

An object of the present invention is to provide a hot-wire air flowmeter that reduces the influence of engine pulsation when mounted on an actual vehicle.

[Means to solve the problem]

The above object is achieved by doubling the structure of the bypass passage provided in the flow rate measuring section.

[Effect]

The influence of engine pulsation when installed on an actual vehicle can be countered by the structure of the bypass passage. That is, the structure is such that pulsation from the engine is difficult to enter into the bypass passage where the flow rate detection section is located. Engine pulsations not only come from the air outlet of the bypass passage, but also enter the air intake.

According to the present invention, engine pulsations entering from the air inlet of the bypass passage enter the outer bypass passage without passing through the inner bypass passage. This is because the flow velocity through the bypass passage is faster than the flow velocity in the main passage. The engine pulsation that goes around and enters is sucked into the bypass passage, but since the engine pulsation goes around from the outermost part of the whole bypass passage, it is easy to enter the outer bypass passage, and it is difficult to enter the inner bypass passage where the flow rate detection part is located. This is because In addition, engine pulsation entering from the air outlet of the bypass passage hits the inner bypass passage wall and is prevented from entering the inner bypass.

As a result of the above, the influence of pulsation from the engine on the detection unit is reduced.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. A double bypass air passage in which an inner bypass passage 6 and an outer bypass passage 7 are integrated is arranged in the center of a main air passage 8 in an aluminum die-cast body. The double bypass passage structure has only a portion parallel to the main air passage 8, and a bypass passage 14 that crosses the main air passage 8 at right angles is shared. Further, a hot wire 12 and a heat-sensitive resistor 13 for measuring intake air supplied to the engine are installed in the inner bypass passage 6. Furthermore, the relationship between the flow velocity 10 of air flowing through the main air passage 8 and the flow velocity 9 of air flowing through the bypass passage is always (flow velocity 9 of air flowing through the bypass passage)>(flow velocity of air flowing through the main air passage). . This is because the magnitude of the flow velocity is determined by the pressure difference between upstream and downstream of the flow path.

Here, engine pulsation 1 due to engine valve opening and closing, etc.
Suppose that 1 enters body l.

When the engine pulsation 11 comes near the bypass passage entrance,
The engine pulse tIJIL is sucked into the bypass passage where the flow velocity is high. Although the flow speeds of the inner bypass passage 6 and the outer bypass passage 7 are almost the same, the inner bypass passage wall 2 has a convex shape with respect to the outer bypass passage wall 3, so that the engine pulsation 11 is difficult to enter the inner bypass passage 6. It passes through the outer bypass passage 7 and exits to the main air passage 8 via a bypass passageway 4 that crosses the main air passage 8 at right angles. Therefore, the entrance of engine pulsation 11 from the vicinity of the entrance to inner bypass passage 6 is reduced. Further, engine pulsation 11 entering from the main air passage 8 is similarly prevented from entering the inner bypass passage 6 by the inner bypass passage wall 2.

As described above, according to this embodiment, the hot wire 12 for measuring the amount of intake air is less susceptible to the influence of the engine pulsation 11.
Binary phenomena and jump phenomena can be reduced.

〔Effect of the invention〕

According to the present invention, since it is possible to prevent binary values and jumps when installed in an actual vehicle, there is an effect of providing a hot wire type air flow meter that is less affected by engine pulsation.

[Brief explanation of drawings]

FIG. 1 is a view of a hot wire type air flow meter showing one embodiment of the present invention, viewed from the upstream side through which air flows, and FIG. 2 is a sectional view thereof. 1...Body, 2...Inner bypass passage wall, 3...
・Outer bypass passage wall, 4... passage cover, 5...
Module, 6... Inner bypass passage, 7... Outer bypass passage, 8... Main air passage, 9... Air flow velocity flowing through the bus pass passage, 10... Air flow velocity flowing through the main air passage. , 11...Engine pulsation, 12...Heating wire, 13...Heat-sensitive resistor, 14...Bye crossing the main air passage at right angles.

Claims (1)

[Scope of Claims] 1. A flow measuring section having a bypass passage is provided in a direction substantially perpendicular to the main air passage, and a heat wire for detecting the intake air amount and a sensor for detecting the air temperature are provided in the bypass passage. In a hot wire air flow meter that measures the air flow rate flowing through a main air passage using a temperature resistance element, a bypass passage parallel to the main air passage is made double, and the hot wire and temperature sensitive resistance element are provided in the inner bypass air passage. A hot wire air flow meter characterized by: 2. The hot wire air flow meter according to claim 1, wherein each bypass passage has a bypass passage that crosses the shared main air passage at a substantially right angle. 3. The hot wire air flowmeter according to claim 1, wherein each bypass passage wall is provided with a step so that the inner bypass passage wall is lengthened.