JPS62159015A - Measuring instrument for intake air quantity - Google Patents

Abstract

PURPOSE:To measure the intake air quantity with high accuracy without being influenced by dust, carbon, etc., by calculating a cross-correlation function of damped waveform signals by two light emitting photodetectors and a flying time of a fuel mist with respect to an interval of the peaks and measuring the intake air quantity. CONSTITUTION:A fuel feeder 2 is provided at the upstream side of a throttle valve 5 in an internal combustion engine. Two light sources 3 with small luminous fluxs are provided at a prescribed interval mutually with respect to the direction of the inlet flow on an inlet pipe between the feeder 2 and the valve 5 and the photodetectors 4 are arranged at the positions in opposition respectively. Then, the respective damped waveform signals generating by the passing of the fuel mist are inputted to a detected signal processing circuit 6 and the cross-correlation function of two damped waveform signals is calculated and a time lag between the signals of two photodetectors 4 with respect to the peak value is calculated. In this way, the flow velocity of the fuel mist is detected and the intake air quantity is calculated from the flow velocity of the fuel mist.

Description

[Detailed description of the invention]

[Industrial Application Field 1] The present invention relates to an intake air amount measuring device for an internal combustion engine for an automobile. [Prior Art] Conventionally, many means have been used as intake air amount measuring devices for air-fuel ratio control, and the ones currently in use include the L-JETRO as shown in Figure 6. Known current meters include the 7 Ratsupa method, the pressure measuring method such as the Nari-Jietro shown in Fig. 7, the hot wire method shown in Fig. 8, and the Karman vortex method shown in Fig. 9. . In the flapper system, seven flaps are rotated using the kinetic energy of the intake air, and a potentiometer is used to adjust the rotation angle according to the air flow rate. In addition, the pressure measurement method detects the intake pressure on the downstream side of the throttle valve, and uses the detected intake pressure to adjust the amount of air. Furthermore, in the hot wire method, one side of the hot wire of the Wheatstone bridge is inserted into the intake air flow, and the air velocity is detected by detecting a change in resistance depending on the degree of cooling. In the Karman vortex method, a vortex generating end is inserted into the intake pipe, and the frequency of the Karman vortex generated in its wake is detected by an ultrasonic detector or the like to measure the air velocity. Although turbine-type current meters and ion detection-type current meters are being developed, they have not yet been put into practical use.

[Problems to be solved by the invention]

In the conventional intake air amount measuring device as described above, the flapper method has a response delay due to the inertia of the flapper, and the pressure measurement method cannot respond to disturbances such as EGR, resulting in measurement errors. Further, in the hot wire method, the hot wire may break due to dust, dirt, etc., and may change over time. Furthermore, the Karman vortex type has a limited response, the turbine type has a response delay due to the inertia of the turbine blades, and the ion detection type increases power consumption due to corona discharge. As mentioned above, in the conventional intake air amount measuring device,
Each had their own problems. The present invention was made to solve the above-mentioned problems, and it improves the accuracy of air flow measurement, does not increase the flow path resistance of the intake system, and eliminates the influence of dust, carbon, etc. The purpose of this invention is to obtain an intake air amount measuring device that does not receive airflow.

[Means to solve the problem]

In order to achieve the above object, the present invention provides an internal combustion engine having a fuel supply device upstream of a throttle valve, in which two light sources with small luminous flux are installed in an intake pipe between the fuel supply device and the throttle valve. The two light sources are installed at a predetermined distance apart from each other in the flow direction, and light receivers are placed at positions facing each of the light sources, and the respective attenuated waveform signals generated by the passage of the fuel mist are input to the detection signal processing circuit.
Find the cross-correlation function φb2 of the two attenuated waveform signals, and find the time delay τ between the two optical receiver signals with respect to its peak value.
The present invention is characterized in that the fuel mist flow velocity is detected based on the calculated time delay τ, and the intake air amount is determined from the fuel mist flow velocity.

[For production]

In the intake air amount measuring device according to the present invention, when the fuel mist from the fuel supply device enters the light flux from the two light sources disposed in the intake pipe, a signal is sent to each of the light receivers disposed opposite to each other. A damped waveform is generated. This attenuated waveform signal has many same frequency components with a time delay τ between two receiver signals placed a predetermined distance apart, and the cross-correlation function φb2 of these two attenuated waveform signals is detected and signal processing is performed. The microcomputer in the circuit calculates the time delay τ between the attenuation waveform signals from both receivers with respect to the peak values of the cross-correlation functions φ1 and 2, and the flow velocity of the fuel mist is determined from the calculated time delay τ. , that is, the amount of intake air is detected.

【Example】

FIG. 1 is a system diagram showing an embodiment of the present invention. FIG. 2 is a detailed configuration diagram of the detection section. In these figures, reference numeral 1 is an air cleaner, 2 is a fuel supply device that injects fuel into the intake air flow, 3 is two light sources 3a and 3b installed on the intake pipe wall on the downstream side of the fuel supply device 2, and 4 is an air cleaner. Each light receiver receives the light flux emitted from the light sources 3a and 3b, and is composed of phototransistors 4a and 4b arranged opposite to the other side wall of the intake pipe. 5 is a throttle valve, 6 is a detection signal processing circuit, and amplifiers 7a and 7b.
, A/D converters 8a, 8b. and a microcomputer 9. 10 is an engine control unit (air-fuel ratio control device). Next, the operation of the intake air amount measuring device configured as described above will be explained. First, fuel mist supplied from the injection valve of the fuel supply bag @2 is sent to the engine through the throttle valve 5 in the intake pipe together with fresh air from the air cleaner 1. When this fuel mist enters the light beam from the light source 3 installed in the suction pipe, as shown in the third diagram),
An attenuated waveform occurs in the signal from the photoreceiver 4. Since the light sources 3a, 3b and the receivers 4a, 4b are installed a predetermined distance apart, this attenuation waveform is generated by changing the distance lll1tL from the upstream attenuation signal to the intake flow velocity V, as shown in () in Fig. 3. It also occurs in the downstream light receiver 4b with a delay of the divided time. Now, if the distance between the two light beams is relatively small, for example several m1Vl, the probability that the same mist will pass through the two light beams will be high, that is, the two light receivers 4a,
The signal 4b becomes an attenuated waveform signal having many same frequency components with a time delay τ. Therefore, the light receiver 4a. The signals 4b are each sent to the amplifier 7 of the detection signal processing circuit 6.
a, 7b, and A/D converters 8a, 8b.
The signal is A/D converted and input to the microcomputer 9. In this microcomputer 9, the light receiver 4a
, 4b, the cross-correlation function φ1,2 (7,) of the signal S1 (t >, S2 (t)) is determined by the following equation,
φI+2 = 1 'Lock (1/2T) f''5t(t)T~
Flash -- XSt (t+τ)dt... (1)φl
, 2 = 1 im ('/T) fooS 1(t
)τ~O XS2 (j+τ)dt... (2) However, in reality, the A/D converters 8a and 8b are
Because it is limited by the D conversion speed and buffer (memory),
Use an approximate formula. Now, the A/D conversion speed is Δt(SeG)
, if the buffer capacity is N (number of data), then N・Δt
During (SeC), N pieces of data will be captured. Therefore, each data is divided into dimensions Sl (t) = St [11, 81 [2]...S
t[N]Sz(t)=82[1],S
When expressed as t [2]...St [N],
The cross-correlation function between Sl (t) and 5t(t) can be approximated by the following formula. XSz [il... (3)n = 0.1
,2. ...N From this, by finding n', which indicates the maximum value of φ,,2[n], = Δt with the delay time of 81(t) and 5z(t)
-n= is determined by the control flow shown in FIG. 5, for example. In this program, first, the signals S1 . A/D convert Sz,
Next, in block B, the upstream signal S1 is approximated to a repetitive waveform, and the dimension address is moved by a step. Then, in block C, both signals S1 and Sz
Calculate the sum of the products. Then, in block D, obtain the cross-correlation functions φ, 2max from φ1, 2, and multiply the number of steps at this time by the data sampling interval (A/D conversion speed) to obtain the upper and downstream light reception at φ5□l1lax. device signal S1. The delay time τ between Sl is shown in Fig. 3 (C
). A block diagram of this processing flow is shown in FIG. The fine fuel mist sprayed from the fuel supply device 2 can be considered to flow at the same speed as fresh air without being affected by weight, so the amount of air intake Qa into the engine is: Qa = A - Va = A -Vd=A-L/τ... (4) Here, Vd: Mist flight speed ■a: Intake air flow rate [,: Distance between light beams -1 A: Determined by suction pipe cross-sectional area. The obtained intake air ff1Qa signal is sent to the control unit (air-fuel ratio control device) 10,
Here, a fuel injection amount that will provide a predetermined air-fuel ratio is calculated, and a drive signal with a pulse width corresponding to this result is sent to the fuel supply device 2 to optimally control the air-fuel ratio. The detection section of the intake air amount measuring device configured in this way is
There is no need for a bypass pipe for measurement, and the light source 3 and receiver 4 do not protrude into the intake pipe, so they do not increase the flow resistance of the intake system (and are free from dust, carbon, etc.) This mist does not affect the measurement. [Effects of the Invention] As explained above, the present invention calculates the cross-correlation function of the attenuated waveform signals from the two light emitters and receivers, and calculates the peak The delay time between both signals, that is, the flight time of the fuel mist, is determined, and the amount of intake air is measured based on this, so it is possible to increase the amount of intake air without being affected by dust or carbon. Since measurements can be made with high precision and the sensor can be made of a normal semiconductor element, the system can be constructed at low cost, and the effect is that no disturbance is caused to the intake system.

[Brief explanation of drawings]

Fig. 1 is a system diagram that does not show one embodiment of the present invention, Fig. 2 is a detailed configuration diagram of its detection section, and Figs. 3 (2) to 3 (
C) is a time chart of waveforms in the detection signal processing circuit, FIG. 4 is a flowchart showing the general operation of the detection signal processing circuit, FIG. 5 is a flowchart showing an example of its specific operation, and FIGS. FIG. 9 is a schematic diagram showing a conventional intake air amount measuring device. 2... Fuel supply device, 3... Light source, 4... Light receiver, 6... Detection signal processing circuit, 7a, 7b... Amplifier, 8a, 8b... A/D converter, 9...Microcomputer, 10...Control unit. Patent Applicant: Fuji Heavy Industries Co., Ltd. Agent, Patent Attorney: Makoto Kobashi, Patent Attorney: Susumu Murai, Figure 2-b, Figure 4, Figure 6 (L-Nitro J, Figure 6, Diagram-y) - Wa-suke] Figure 7 Figure 9 [Tsushinomumayu, 5th Sho]

Claims (1)

[Claims] In an internal combustion engine having a fuel supply device upstream of a throttle valve, two light sources with a small luminous flux are installed in an intake pipe between the fuel supply device and the throttle valve at a predetermined distance from each other in the direction of intake flow. , a light receiver is arranged at a position facing each of the light sources, and each attenuated waveform signal generated by passage of the fuel mist is inputted to a detection signal processing circuit, and a cross-correlation function φ_1 of these two attenuated waveform signals is obtained.
Find _, _2, calculate the time delay τ between the signals of the two light receivers with respect to their peak values, detect the flow velocity of fuel mist using this calculated time delay τ, and calculate the intake air amount from this fuel mist flow velocity. An intake air amount measuring device characterized by determining the amount of air.