JPS6253060B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air flow rate detection device for an electronic fuel supply system, and more particularly to an air flow rate detection device using a hot wire.

First, a conventional air flow rate detection device will be explained based on FIG.

In FIG. 1, reference numeral 1 denotes an air valve body with an intake passage 2 formed inside. A throttle valve 3 is rotatably arranged in the intake passage 2, and the intake passage 2 above the throttle valve 3
A bench lily portion 4 is formed, and an airphone portion 5 is further formed above the bench lily portion 4. A land portion 5A is formed on one side of the airphone portion 5, and an entrance portion 6A of the bypass passage 6 is opened in this land portion 5A. On the other hand, the bypass passage 6 opens at the narrowest part of the bench lily part 4 via an outlet 6B, as shown in FIG. A hot wire 7 is provided in the middle of the bypass passage 6, and the output of the hot wire 7 is sent to a detection circuit 8 fixed to the air valve body and electrically processed. That is, by detecting the amount of air flowing through the bypass passage 6, the amount of air flowing through the intake passage 2 is determined, thereby determining the amount of fuel supplied to the internal combustion engine.

The above devices are already well known. Incidentally, it is known that this type of internal combustion engine causes blowback, and this blowback causes carbon and oil droplets to enter the airphone section 5 and further flow into the bypass passage 6. Therefore,
This carbon and oil droplets adhere to the hot wire 7 provided in the bypass passage 6, causing a problem in that the output changes, making it impossible to accurately detect the amount of air.

SUMMARY OF THE INVENTION An object of the present invention is to provide an air flow rate detection device having a structure that prevents carbon and oil droplets from entering the bypass passage.

A feature of the present invention is that a pipe is provided at the inlet of the bypass passage, and the inlet of this pipe is substantially aligned with the axis of the bench lily and is opened substantially perpendicular to the axis of the bench lily.

An embodiment of the present invention will be described above with reference to FIGS. 2 and 3, where the same reference numerals as in FIG. 1 indicate the same parts.

In FIGS. 2 and 3, a pipe 9 is inserted into the entrance 6A of the bypass passage 6, and this pipe 9 is connected to the bench lily part 4 upstream of the bench lily part 4.
The opening is substantially perpendicular to the axis of the bench lily part 4 in the projection part 4A, and opens through the inlet 9A at a substantially right angle to the axis of the bench lily part 4. The pipe 9 is fixed to the air valve body 1 by a fixing member 10 provided on the land portion 5A and a support member 11 provided on the airphone portion 5. Therefore, air is supplied to the bypass passage 6 only through the inlet 9A of the pipe 9. Note that the pipe 9A is bent with a predetermined curvature.

In the above, when blowback occurs, the intake air due to the blowback flows through the bench lily section 4 to the airphone section 5, and then flows reversely from the airphone section 5 into the bench lily section 4. Therefore, the flow of intake air within the projection portion 4A of the bench lily portion 4 is approximately perpendicular to the inlet 9A of the pipe 9. Therefore, air with low inertia is sent into the bypass passage 6 through the inlet 9A of the pipe 9, but carbon and oil droplets with high inertia have a vector in the axial direction of the bench lily portion 4, so the inlet of the pipe 9 This eliminates the problem of carbon or oil droplets entering the bypass passage 6 because it becomes difficult to enter the bypass passage 6.

The reason why the inlet 9A of the pipe 9 is opened almost in line with the axis of the bench lily part 4 as shown in Figs. 2 and 3 is that the flow velocity is fastest on the axis of the bench lily part 4. This is to provide inertial force to the droplets. Further, the reason why the pipe 9 is given a predetermined curvature so that the inlet 9A and the inlet 6A of the bypass passage 6 are communicated is to not disturb the air flowing inside the pipe 9.

In this way, the pipe 9 is inserted into the inlet 6A of the bypass passage 6, and the inlet 9A of the pipe 9 is aligned approximately with the axis of the bench lily part 4 upstream of the bench lily part and approximately perpendicular to the axis of the bench lily part 4. Since the bypass passage 6 is opened, the rate at which carbon and oil droplets enter the bypass passage 6 can be significantly reduced.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a conventional air quantity detection device using a hot wire, Fig. 2 is a longitudinal sectional view of an air quantity detection device according to an embodiment of the present invention, and Fig. 3 is a plan view of Fig. 2. It is. DESCRIPTION OF SYMBOLS 1... Air valve body, 2... Intake passage, 3... Throttle valve, 4... Bench lily part, 4A... Projection part, 5...
... Airphone section, 5A... Land section, 6... Bypass passage, 6A... Inlet, 6B... Outlet, 7... Hot wire, 8... Detection circuit, 9... Pipe, 9A... Inlet.

Claims (1)

[Claims] 1. A throttle valve provided in the intake passage, a vent lily portion formed in the intake passage upstream of the throttle valve, a bypass passage communicating the upstream of the vent lily portion and the vent lily portion, a hot wire disposed in the bypass passage, and In an air amount detection device including a detection circuit that calculates the amount of air passing through the bench lily portion based on the output of the hot wire, a pipe is inserted into the bypass passage inlet, and the inlet of the pipe is connected to the air amount upstream of the bench lily portion. An air amount detection device having an opening that substantially coincides with the axis of the bench lily and is substantially perpendicular to the axis.