JPS6014181Y2 - Internal combustion engine air flow detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air flow rate detector for an internal combustion engine, and more particularly to a bypass type air flow rate detector suitable for a hot wire type.

A method of detecting the air flow rate by placing a temperature-dependent resistance, that is, a heat-sensitive resistance, in the intake air flow is described in Japanese Patent Publication No. 49-488.
As is known in Japanese Patent Application No. 93, etc., it is necessary to calculate the intake air amount by squaring or quadrifying the electric signal corresponding to the instantaneous value of the intake pulsation of the internal combustion engine and integrating it. This has the disadvantage that errors accumulate and accuracy decreases.

One possible way to solve this problem caused by intake pulsation is to install a surge tank in the intake passage itself, but there is a problem in that a large capacity surge tank is required in order to obtain sufficient damping effect. .

Further, there is a problem in that a surge tank having a fixed volume may not be able to provide sufficient damping effect depending on the operating conditions.

An object of the present invention is to provide an air flow rate detector that has a small volume and can obtain a sufficient damping effect even when operating conditions change.

The feature of this invention is that a heat-sensitive resistor is provided in the bypass passage that bypasses the intake passage, a surge tank is formed in this bypass passage, and the capacity of this surge tank is changed according to the opening degree of the throttle valve. .

An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, a bypass passage 4 is provided in a part of an intake passage 2 that connects an engine 1 and an air cleaner 3.

The entrance of the bypass passage 4 is upstream of the restriction 5 (orifice, nozzle, venturi, etc.), and the exit of the passage 4 is located upstream of the restriction 5 (orifice, nozzle, venturi, etc.).
Opens at the narrowest part or downstream from the narrowest part.

A heat sensitive resistor 8 is provided in the passage 4.

Restrictions 6 and 7 are provided at the entrance and exit of the passage 4, respectively.

Further, a surge tank 9 is provided in the middle of the aperture 6°7.

Now, if the capacity of the surge tank 9 is V, the pressure before and after the throttle 5, Pl, P2, and the pressure P of the surge tank 9
If the amount of air passing through the throttles 7 and 6 is G, G2, then G, = C1aI Pi P) γ1 - (1)
G2=C2a2j(P P2)')'
”・(2) Here, C□: Flow coefficient of throttle 7 a□: Cross-sectional area of throttle 7 C2: Flow coefficient of throttle 6 a2: Cross-sectional area of throttle 6 γ1. γ: Density to density: Constant relationship holds true.

If we linearize the above equation, we get = KIP1- to 1P- to 2P10 to 2P2 If we now set 1=to 2, ...(4) holds true.

Now, due to inspiratory pulsation, p, -p2:β5ina)
Assuming that a change in t occurs, ...(6) is obtained.

Solving equation (7) yields the following.

Here, as can be seen from equation (8), as ω and α become larger, the amplitude of P becomes smaller.

Here, α is the surge tank 9 as can be seen from the above formula.
The larger the capacity ■ and the smaller the cross-sectional area of the throttles 6 and 7, the more the pulsation of air in the bypass passage 4 is attenuated.

As is well known, the hot wire air flow rate detector has the following formula: RF = (A + Bju) (Tw - Ta) - (
9) Here, R: Resistance of the heat-sensitive resistor I: Current U of the heat-sensitive resistor: Air flow rate TW: Temperature of the heat-sensitive resistor Ta: Air temperature A, B, using the constant relationship, (Tw-Ta)/R= C as F=C(
A+Bju) ”・(1G or (Tw-Ta) /RI=C2, I=C2
(A0B ju) ... (11
), find U from the value of I.

In this case, the temporal average of ■ and the temporal average of U generally do not match if U varies over time.

However, by providing the above-mentioned surge tank 9 and suppressing the fluctuation of U as much as possible, it becomes possible to accurately detect the air amount when the intake pulsation width is large, and the signal corresponding to the above-mentioned I can be converted to A- The data can be input directly to the microcomputer 11 via the D converter 10.

The circuits 12 and 13 are circuits for making the above-mentioned C1 or C2 constant, and a known circuit can be used.

If the signal (2) fluctuates somewhat over time, a temporal averaging circuit may be provided before the A-D converter 10.

In the present invention, the surge tank 9 is configured as a variable capacity type.

That is, a variable capacity means (a diaphragm, a bellows, etc. may be used) such as a piston 14 is provided in the surge tank 9, and appropriate damping characteristics can be obtained over a wide range of motion.

The piston 14 is mechanically linked to the throttle valve 16 by a link 15, and the capacity of the surge tank 9 can be increased to ensure damping characteristics in an operating range where intake pulsation is large when the throttle valve 16 is fully open. .

Furthermore, the amount of air flowing in from the throttle 5 changes due to the movement of the piston 14, and when the throttle valve 5 is opened, a large air flow velocity is generated around the heating resistor 8, so that it is possible to increase the heating material during acceleration.

Furthermore, by utilizing the movement of the piston 14, a known flow velocity can be created around the heat-sensitive resistor 8, and changes in the heat-sensitive resistor 8 over time can be calibrated.

This can be done by detecting the movement of the piston 14 with a potentiometer or the like, inputting the signal to the microcomputer 11, and comparing it with the output of the heating resistor 8.

The heat-sensitive resistor 8 described above may be of the Thomas meter type.

As described above, according to the present invention, since a surge tank is provided in the bypass passage, a sufficient pulsation damping effect can be obtained with a small surge tank compared to the case where a surge tank is provided in the intake passage itself. Since the capacity of the tank is varied depending on the opening degree of the throttle valve, that is, the operating conditions, damping characteristics can be ensured even in areas where intake pulsation is large.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an air flow rate detector embodying the present invention, and FIG. 2 is a signal processing circuit diagram. 1...Engine, 2...Intake passage, 3
... Air cleaner, 4 ... Bypass passage, 8 ... Heat sensitive resistor, 9 ... Surge tank, 14. Curved Zeston.

Claims (1)

[Scope of utility model registration request] In an air flow sensor for an internal combustion engine, a bypass passage is provided in a part of the intake passage that connects the engine and the air cleaner, and a heat-sensitive resistor is provided in the bypass passage. An air flow rate detector for an internal combustion engine, comprising means for varying the capacity of the surge tank according to the opening degree of the throttle valve.