JPS59136532A - Fuel control apparatus for internal-combustion engine - Google Patents

Abstract

PURPOSE:To execute optimum fuel control at all times, by using a heat-sensitive element as a means for detecting the vortex frequency of a vortex flow meter for detecting the quantity of intake air, detecting the mass flow rate from the output of said detecting means, and executing fuel calculation according to the operation zone judged from signals representing the operational conditions of an engine. CONSTITUTION:A vortex generator 6 is disposed in an intake pipe 16 on the downstream side of an air cleaner 1, and hot wires 4, 5 are provided for detecting the frequency of vortices generated by the vortex generator 6. These hot wires 4, 5 are connected to a detecting circuit 7 for a vortex flow meter. A frequency signal equivalent to the valume flow rate of intake air per unit time is obtained in the detecting circuit 7, and the frequency signal is afforded to a fuel control unit 11 together with the outputs of a sensor 3 for detecting the temperature of intake air, an engine-temperature sensor 12, an O2-sensor 13, a sensor 9 for detecting the opening of a throttle valve, an intake-pressure sensor 14, etc. With such an arrangement, a required quantity of fuel is calculated in the fuel control unit 11, and a pulse having a reference duration is applied to a fuel injection valve 8 in synchronism with the above frequency output or the frequecy obtained by frequency-dividing of the same.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fuel control device for an internal combustion engine that measures the intake air amount of the internal combustion engine using a vortex flowmeter and controls the operation of the internal combustion engine.

Generally, as air flowmeters for automobiles, Karman vortex type and swirl type vortex flowmeters are in practical use, and both output a frequency signal that is approximately proportional to the intake air amount or flow velocity. This frequency signal has a constant proportionality constant with the flow rate over a wide flow rate range, so the accuracy of flow rate measurement is good, and it also has an extremely fast response that follows transient changes in flow rate. However, on the other hand, since it is a volume flow meter, it has the disadvantage that it cannot measure mass flow rate.

For example, in a control device such as an automobile fuel injection system that calculates the amount of fuel proportional to the mass flow rate of the engine's intake air, the frequency output of the vortex flow meter is subjected to density correction due to temperature changes and density correction due to pressure changes. Otherwise, there is a drawback that the true mass flow rate cannot be calculated. In this case, a high-precision and inexpensive temperature sensor such as a thermistor can be easily used as a temperature sensor for measuring temperature, but a pressure sensor for measuring pressure has the disadvantage that it is expensive and cannot be easily used.

Next, when a vortex flowmeter is operated with a measuring load that only flows in one direction, the intake air flows backward due to intake pulsation (
This has the disadvantage that the frequency output is disturbed due to blowback) and measurement accuracy deteriorates.

As a means to solve these drawbacks, if a heat-sensitive element is used as a detection means for the frequency signal of the vortex, and a signal corresponding to the mass flow rate of intake air is simultaneously detected from among the control signals of the heat-sensitive element, the volume A frequency signal corresponding to the flow rate and the mass flow rate can be detected simultaneously. Therefore, by comparing these two signals, it becomes possible to measure the intake air flow rate with much higher accuracy.

By the way, one of the causes of the difference between these two signals is the density change component caused by changes in the intake air temperature and atmospheric pressure, and the speed of this density change is extremely slow. Therefore, this correction calculation can be performed with a slow time constant.

Another cause is a component generated by intake pulsation. This component occurs when the engine operating condition is under high load, and disappears instantly when this condition is removed, so high-speed responsiveness is required. Ru. In this way, when the intake air flow rate is determined by simultaneously and indiscriminately comparing two correction factors that originally have different properties, it is possible to calculate a stable intake air amount and to calculate the engine fuel amount based on this. The disadvantage was that it was not possible to perform calculations.

The present invention has been made in order to eliminate the above-mentioned drawbacks.It is possible to calculate the amount of fuel stably in any case regardless of the operating state of the engine, and to perform optimal fuel control of the engine. An object of the present invention is to provide a fuel control device for an internal combustion engine that can perform the following steps.

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 15 is an air conditioner, 16 is an intake pipe, 17 is an exhaust pipe, 1 is an air cleaner provided at the tip of the intake pipe 16, 2 is a cleaner element, 3 is an intake air temperature sensor that detects the intake air temperature, 4 and 5 are hot wires, and 6 is a vortex generator. The hot wires 4 and 5 and the vortex generator 6 are provided in the intake pipe 16 and constitute the main body of the vortex flowmeter. 7 is a detection circuit of a vortex flowmeter, 8 is a fuel injection valve, 9 is a throttle opening sensor that detects the opening of the throttle valve 10, 11 is a fuel control section, 12 is a temperature sensor that detects the temperature of @seki, 13 is an 02 sensor that detects the amount of oxygen in exhaust gas, and 14 is a pressure sensor that detects intake pressure.

Further, FIG. 2 shows details of the detection circuit 7, and the hot wire 4 is connected to the resistor 2.
3, 26, 27 and the arithmetic unit/width unit 21 form a Pritsuno circuit, and are controlled so that the difference between the temperature of the heat ffM4 and the temperature of the intake air is approximately constant. 35 and 36 are resistors, 39 is a transistor for current amplifying the output of the operational amplifier 21, and 65 is a resistor for stabilizing the output V1. Although this circuit portion is only for detecting the signal V1 of the one-sided Karman vortex street generated on the downstream side of the vortex generator 6, it constitutes the detection circuit of the hot wire flowmeter by itself.

Now, if the temperature coefficient of resistance of the hot wire 4 and the temperature coefficient of resistance of the resistor 27 are set equal, the temperature control in Meditation 4 will be performed by the so-called temperature difference change method using a hot wire anemometer, and the current IH flowing through the hot wire 4 will be the temperature of the intake air. In this case, the voltage value of V+ or V- of the operational amplifier 21 becomes a value corresponding to the mass flow rate, regardless of the change in pressure. Similarly, the temperature of the hot wire 5 is controlled by a temperature control circuit composed of resistors 24°29.30, 37, 38, 66, an operational amplifier 22, and a transistor 40 using the temperature difference change method of a hot wire anemometer. Then, the signal V2 of the other Karman vortex street is detected, and the signal V+ or V- of the operational amplifier 22 is detected.
The voltage value corresponds to the mass flow rate.

Also, capacitors 41, 44, resistors 42, 43°45.4
6, 47 and an operational amplifier 48 receives the signal V,
, V, is amplified to obtain output (3). Resistance 50~
53 and voltage comparator 49 is a waveform shaping circuit and obtains a frequency output V4.

The circuit consisting of the resistors 28, 31, and 32 is an adder circuit, which takes the average of V+ of the operational amplifier 21 and V+ of the operational amplifier 22, and obtains an output . The waveforms of the can outputs 1 to 1 V are shown in FIG.

In the above configuration, a symmetrical and regular Karman vortex street is generated downstream of the extraction body 6. The hot wire 4.5 is cooled by the average flow velocity of the intake air and alternately by the high frequency vortex frequency. Therefore, the control voltages V, , V2 for keeping the hot wires 4 and 5 at a desired temperature have components V, , V2 corresponding to the average flow velocity and components Δ■, corresponding to the change in flow velocity due to the Karman vortex.

It consists of △V. Since △V and △v2 have opposite polarities, a signal v3 is obtained from KIX (△V1-△V2), and a signal ■.

A frequency signal v4 is obtained by waveform shaping. The ratio between the frequency of the signal v4 and the flow rate of the intake air is approximately constant, and the frequency signal is equal to the volumetric flow rate of the intake air per unit time.
is obtained.

Next, by making the resistance temperature coefficients of the hot wire 4 and the resistor 27 and the hot wire 5 and the resistor 30 equal, the temperature difference between the hot wires 4 and 5 and the intake air will gradually increase as the temperature of the intake air increases. Controlled by the increasing temperature difference method of so-called hot wire anemometers. Therefore, the mass flow rate of the intake air can be detected regardless of the temperature and pressure of the intake air. This function of the mass flow rate is the control current of the thermal IVi14,5, and the terminal voltage of the fixed and stagnation resistor 23.24 is also a function of the mass flow rate. Therefore, the analog output V, in which the modulation caused by the vortex is canceled by the addition circuit, is V5-(A + Bu'& )q, where U is the mass flow ft(''/i, r), and the normal hot wire You can get the same analog output as a current meter.

The fuel control unit 11 shown in FIG. 1 includes a frequency output v4 and an analog output V3 in the detection circuit 7 of the vortex flow meter.
The output of the intake air temperature sensor 3, the output of the temperature sensor 12, the output of the 02 sensor 13, the output of the throttle opening sensor 9, the output of the pressure sensor 14, and although not shown, engine speed information, cranking signals, and other engine information. driving information is input. The fuel control unit 11 performs calculations based on these inputs to calculate the required amount of fuel for the engine, and sends a pulse with a standard time width to the fuel injection valve 8 in synchronization with the frequency output V4 or its frequency divided frequency. In addition, it supplies the required amount of fuel to the engine. In this way, the average fuel flow rate within a certain period of time can be controlled in accordance with the air flow rate taken into the engine per unit time. This is because the amount of fuel injected by one voltage pulse of a reference duration is constant, so the average fuel flow rate over a period of time is proportional to the frequency of that voltage pulse.

By the way, as mentioned above, the frequency output V4 is proportional to the volumetric flow rate of the engine's intake air, so in order to control the fuel flow rate required for the engine, the density must be corrected according to the temperature and pressure of the intake air. is necessary. The rate of change in this density is very slow compared to the rate of change in the amount of intake air, and the calculation speed for density correction may also be slow. On the other hand, the analog output V, is a value corresponding to the mass flow rate of the intake air, and the volume flow rate of the intake air obtained from the value of the mass flow rate of the intake air calculated back from the analog output V, and the frequency output V4 is used for fuel control. By comparing in section 11, information on the density of the intake air can be obtained. This comparison calculation can be performed slowly, so it only needs to be performed in a low-load, steady-state operating state where there are few fluctuations in the intake air of the engine. By changing the time width of the pulse applied to the fuel injection valve 8 in accordance with the density information obtained in this manner, it is possible to control the amount of injected fuel in accordance with the mass flow rate of intake air. In addition, the calculation for determining this density information is performed based on information on various other parameters that indicate the operating state of the engine, and the operating zone of the engine is determined to determine whether the engine is in a low-load steady operating state with little fluctuation in intake air. By performing the calculation only in the zone, it is possible to calculate the density correction more accurately.

Next, let us consider a case where the engine is operating in a zone where the engine speed is low, the load is high, and the intake pulsation is large. In this case, a backflow (blown back) of the intake air occurs, which has the disadvantage that the frequency output becomes more turbulent and fluctuates. Of course, the analog output (2) also outputs an output that is deviated from the true mass flow rate of intake air to the larger side due to the reverse flow, but no disturbance occurs in the frequency output V4.

In this case, the low rotation and high load operating zone is determined based on information on various other parameters that indicate the operating status of the engine, and within this operating zone, the flow rate information obtained from the analog output ■ and the frequency output v4 are determined. By comparing the obtained flow rate information and performing correction calculations to obtain the optimum fuel flow rate, it is possible to perform highly accurate engine fuel control calculations.

Further, by performing zone determination in this manner, adverse effects on other zones can be avoided, and the intake air flow rate can be calculated more accurately. Furthermore, output verification, re-correction and learning functions of the 02 sensor 13 can be controlled.

Further, it is sufficient for the purpose of density correction to determine the idle operating state as a representative point of low-load steady operation and to perform the correction calculation for the density correction.

As described above, in the present invention, a vortex flowmeter is used to detect the amount of intake air in the engine, and a heat-sensitive element is used as a means for detecting the vortex frequency of the vortex flowmeter, and the volumetric flow rate of the intake air is detected by the vortex frequency. The system detects the value of the mass flow cap from the electrical signal of the heat-sensitive element, determines the engine operating zone based on the input information indicating the engine operating status, and selectively performs fuel calculations according to this operating zone. I have to. For this reason,
Accurate density correction can be performed by performing density correction of the frequency signal in low-load steady operation conditions where there are few fluctuations in intake air, and in high-load operation zones where intake pulsation is large, the frequency signal generated in the zone turbulence can be effectively corrected, and optimal fuel control for the engine can be performed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the apparatus of the present invention, FIG. 2 is a block diagram of a detection circuit of a vortex flow meter according to the present invention, and FIG. 3 is a voltage waveform diagram of each part in the detection circuit shown in FIG. 3... Intake temperature sensor, 4, 5... Heat wire, 6... Vortex generator, 7... Detection circuit, 8... Fuel injection valve, 9...
...Throttle opening sensor, 11...Fuel control section, 1
2...Temperature sensor, 13...02 sensor, 14...
・Pressure sensor, 15... Engine, 16... Intake pipe, 1
7...Exhaust pipe. Note that the same reference numerals in the figures indicate the same or equivalent parts. Agent Shin Kuzuno − −1−−−−−−−−−−−−−−↑ 1. Indication of the incident Patent application No. 58-12483 2,
Name of the invention Fuel control device for internal combustion engine 3, Person making the amendment Representative Hitoshi Katayama Department 4, Agent 5 Column for detailed explanation of the invention in the specification to be amended. 6. Contents of correction Change rKIX(△Vl-△■2) in the 4th line of page 8 to ``K1
×(△■l−Δ■2)”. that's all

Claims (4)

[Claims] (1) Installed in the intake passage of the engine, which detects the flow velocity of the engine's intake air as a change in a fluid vortex, and detects the change in this vortex as a change in the frequency of a stain signal by at least one heat-sensitive element. , a means for outputting a frequency signal approximately proportional to the intake air flow velocity, and a means for outputting a signal corresponding to the mass flow rate of the intake air from among the electrical signals of the heat-sensitive element, and the output of these means and the operating status of the engine are In a fuel control system for an internal combustion engine that performs fuel calculation based on the input information that represents the engine and supplies fuel based on the calculation result, the input information that represents the operating status of the engine is the engine speed, acceleration, and cooling. The engine operating zone is determined according to at least one of the following elements: water temperature, intake pipe negative pressure, 02 sensor, and intake air temperature, and fuel calculation is selectively performed according to this operating zone. A fuel control device for an internal combustion engine. (2) The high-load operating zone of the engine is determined based on input information representing the operating status of the engine, and the 2. The fuel control device for an internal combustion engine according to claim 1, wherein disturbances in the frequency signal are corrected in accordance with the signal corresponding to the mass flow rate. (3) The low-load steady-state operating zone of the engine is determined based on input information representing the operating status of the engine, and changes due to the density of the frequency signal are corrected in accordance with the signal corresponding to the mass flow rate. A fuel control device for an internal combustion engine according to claim 1. (4) The fuel control system for an internal combustion engine according to claim 3, wherein the low load steady operation zone is an idle operation state.