JPH02230942A - Fuel feed control system for internal combustion engine - Google Patents

Abstract

PURPOSE:To invariably perform optimum combustion by analyzing the flow in a suction pipe based on the detected values of the air control valve opening, engine rotating speed, suction and exhaust states of cylinders, pressure and temperature of the atmospheric air, and calculating the suction air quantity. CONSTITUTION:A microcomputer 8 analyzes the flow in a suction pipe 2 based on the temperature and pressure of the atmospheric air, the valve opening of a throttle valve 4, the rotating speed of an engine 3, positions of pistons 15-18, and opened/closed states of suction valves 10-22 detected by detecting means 5, 6, 7, and 27 at the preset time step and determines the suction air quantity at a manifold section 10 by calculation. A controller 9 drives injectors 28-31 via a fuel injection quantity timing setting means 32 in response to the calculated suction air quantity value. The correct suction air quantity is invariably determined, and the fuel injection quantity and injection timing can be controlled for the optimum air-fuel ratio.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to fuel supply control, and the amount of intake air of an engine is determined from a theoretical calculation of the flow in the intake pipe, and from the result, the amount of fuel in each injector is determined. This article relates to a fuel supply control system for internal combustion engines that determines the injection amount and timing and can always achieve the optimum air-fuel ratio for each cylinder. [Prior Art] As engine performance increases and exhaust gas regulations become stricter, it has become necessary to accurately know the amount of intake air in order to constantly optimize engine combustion conditions. The conventional technology for flowmeters that measure the amount of intake air is as described in Japanese Utility Model Application Publication No. 56-126527, which measures the intake air flow rate in a part of the intake pipe using a hot wire, and calculates the amount of mass taken in. The flow rate was being calculated. In addition, as described in Japanese Patent Application Laid-Open No. 62-126243, the differential pressure is measured using pressure sensors installed on the upstream and downstream sides of the throttle valve, and the intake is determined based on the throttle valve opening information at that time. The method used was to calculate the flow velocity of the air flowing through the air and convert it into a mass flow rate using information from a separately installed temperature sensor. Furthermore, JP-A-56
As seen in Publication No. 9629, a strut is installed in the suction pipe, the frequency of the Karman vortex generated by the strut is detected to determine the intake air flow velocity, and the mass flow rate is calculated from the external temperature measured separately. Ta. And JP-A-57-70
As seen in Publication No. 926, when installed on the vehicle body, from the throttle valve opening and engine speed,
A method was devised in which a calibration map for calculating the intake air flow rate was prepared for one condition, and the intake air flow rate under all operating conditions was calculated from that calibration map.
Then, the fuel injection amount was determined by taking into account the air-fuel ratio from this measured mass flow rate. Due to the structure of devices that measure the intake air flow rate using hot wires, because the hot wire element for measurement is placed in the flow path, dust particles in the intake air and oil particles from the engine blowback may adhere to the hot wires. There was a problem that the element itself changed over time.6 Additionally, in systems that detect flow rate using a throttle valve (air control valve) and the differential pressure before and after it,
The flow rate measurement performance is greatly affected by variations in the accuracy of the pressure sensor during the manufacturing stage and the accuracy of the processing of the throttle valve, which forms the orifice, so detailed calibration is required for each completed flow rate measurement device. It had been.

Furthermore, the frequency of the Karman vortex is detected by a strain gauge,
In systems that measure flow velocity, there is a problem in that the unavoidable engine pulsation component affects the measured value. In addition, in the method of calculating the flow rate using a calibration map from the throttle valve opening and engine speed, the intake air flow rate is determined using a constantly calibrated map under various driving conditions of the car. , measurement errors due to pulsation amplitude in the intake pipe were essentially unavoidable.

[Problem to be solved by the invention]

In conventional fuel supply control systems for internal combustion engines, the measurement element itself has variations over time and accuracy, and the measured value of the intake air amount may need to be calibrated due to the processing accuracy of the air control valve. , measurement errors were essentially unavoidable because the engine pulsation component affected the measured values.

The purpose of the present invention is to always accurately calculate the intake air flow rate even in areas with large engine pulsation components without placing a measuring element in the intake pipe, and to always maintain the optimum air-fuel ratio based on this data. [Means for Solving the Problem] In order to achieve the above object, the present invention provides a fuel supply control system for an internal combustion engine that supplies fuel from an injector. The control system includes a detection means that detects air control valve opening, engine speed, atmospheric temperature, and atmospheric pressure at predetermined time steps, and at least one detection means that analyzes the flow in the intake pipe based on each detected value. and a control means for controlling the fuel injection amount and injection timing of at least one injector based on the output value of the calculation means. has been done.

The calculation means is formed by a digital computer or by a parallel computer consisting of a microcomputer provided corresponding to each cylinder. Alternatively, the intake pipe line may be replaced with an electrical equivalent circuit, and the calculation means may be formed by an analog computer. Furthermore, the calculation means may be formed by a hybrid computer that performs calculations by combining analog calculations and digital calculations.

[Effect]

According to the present invention, since the fuel supply control system for an internal combustion engine is provided with a detection means for detecting pressure, temperature, etc. at predetermined time steps, and a calculation means for calculating the intake air amount, each cylinder The amount of intake air is calculated at predetermined time steps, and the amount of intake air can be determined accurately without using a measuring element. Based on this value, the fuel injection amount and injection timing in the injector are determined so as to achieve the optimum air-fuel ratio.

〔Example〕

An embodiment of the present invention will be explained with reference to FIG. As shown in Figure 1, the air control valve opening (0,
) 6, engine rotation speed (N.) 7, atmospheric temperature (T0), and atmospheric pressure (PO) 5 at predetermined time steps. and at least one cylinder 11-1
A calculation means (microcomputer) 8 calculates the intake air amount of No. 4 in predetermined time steps, and the fuel injection amount and injection timing 32 of at least one of the injectors 28 to 31 are controlled based on the output value of the calculation means 8. It is configured to include control means (not shown). The calculation means 8 is formed by a digital computer or by a parallel computer (not shown) consisting of a microcomputer provided corresponding to each of the cylinders 11 to 14.

Alternatively, the intake pipe line 2 may be replaced with an electrically equivalent circuit, and the calculation means 8 may be formed by an analog computer (not shown). Furthermore, the calculation means 8 may be formed by a hybrid computer (not shown) that performs calculations by combining analog calculations and digital calculations.

Figure 1 shows the parts that form the air intake pipe of an internal combustion engine and the device (system) that detects the amount of intake air. External air A flows in from the intake section 1, passes through the intake pipe 2, and is supplied to the engine compartment 3. When the engine chamber 3 has four cylinders, there are four cylinders 11 to 14, each having a piston 15 to 18, an intake valve 19 to 22, and an exhaust valve 2.
3 to 26 are installed. Further, between the intake section 1 and the engine compartment 3, there is a throttle valve (air control valve) 4 that controls the amount of intake air.

Next, the operation of this embodiment will be explained. The flow of intake air into the engine occurs when the piston makes suction motion, changes the volume inside the cylinder, and the pressure inside the cylinder becomes negative compared to atmospheric pressure. The flow changes unsteadily in accordance with the movement of the piston and becomes a pulsating flow, and the amount of intake air is determined by the fluid loss characteristics of the entire intake pipe system and the opening degree of the air control valve.

Therefore, the intake system piping is modeled, and the boundary condition of the piping is that the upstream end is open to the atmosphere, that is, at atmospheric pressure.
On the downstream side, on the other hand, by assuming that the velocity of the air flow is equal to the velocity of the piston head, the flow in the entire intake pipe can be analyzed as an unsteady pulsating flow, and the flow rate can be determined. Note that the speed of the piston head is determined from the engine speed. The specific analysis method is described below.

The flow in the intake pipe is approximated by the following equation. Here, P: Pressure inside the pipe t represents differentiation.

Equation (1) is a continuity equation, and equation (2) is an equation of motion. The unknowns P and Q of the equation are obtained by combining these equations and using a characteristic curve method or the like.

To change the opening degree of the air control valve, use formula (2)
The average flow rate is determined by integrating the velocity over one period of the pulsating waveform in response to changing the frictional resistance coefficient f. These calculations are executed in real time by a computer (calculation means) built into the fuel supply control system. Therefore, by knowing the valve opening, engine speed, atmospheric pressure, and atmospheric temperature,
Analyzed by a computer in the intake pipe, the amount of intake air can be calculated without using a flow measurement sensor, and the constantly changing flow rate can be accurately measured without being affected by sensor measurement errors, variations, or changes over time. Based on this value, the fuel injection amount and injection timing at the injector can be determined to achieve the optimum air-fuel ratio.

Next, the system and operating state of the present invention will be explained.

The engine is running in the desired operating state, and now, at time T=
The pressure P (T0, χ) and flow rate Q ('re, χ) in the intake pipe 2 at T, are determined by the point (χnp n+1,
-N) is known, and the pressure in the intake pipe after T=T, +ΔTs is P(T0+ΔT s , χl'lL flow rate Q(
We will explain how to find T, +ΔTs, χn). first,
After ΔTs, engine speed (Nl,) 'i, throttle valve opening (0,) 6, outside temperature T. and atmospheric pressure (
po) 5. Sample the position of each piston and the opening/closing status 27 of the intake valve and enter it into the digital computer 8 for flow rate calculation. As a result, the cylinder speed VP of the piston in the suction state and the frictional resistance coefficient fv of the throttle valve 4 are determined. Then, using the boundary conditions that the upstream end is atmospheric pressure and the downstream end the fluid velocity is V p (t), the pressure P (To
+ΔT5, χn)l Find the flow rate Q(T0+ΔT5, χn). However, the time step ΔT when performing numerical calculations using the characteristic curve method is related to the number of divisions N, and usually ΔT<<Δ
Ts is ΔT《ΔTffi (time of one cycle). Therefore, the pressure P, flow rate Q, and density ρ are determined at intervals of Δt. The time-averaged mass flow rate Mi in each injector (28 to 31) is obtained by integrating one cycle, and if ΔTs is larger than the time ΔT1 of one cycle,
Sampling time T=T. +2ΔT. up to ΔTS
/ΔT is repeated once to obtain the mass flow rate. When the cylinder is in the suction state, both are calculated at the same time.

In addition, in order to reduce calculation time and perform parallel calculation processing, a parallel computer with a microcomputer associated with each cylinder is used to calculate the flow rate in a shorter calculation time than the actual time. Next, the fuel injection amount and injection timing for each injector are determined based on the flow rate value 9 of the injector section. The fuel injection amount is determined from the average mass flow rate during ΔTs, and the injection timing is determined by the unsteady mass flow rate P(t) Q(
It is determined from the calculated waveform value of t).

FIG. 2 shows a flowchart for determining the pressure, volumetric flow rate, and mass flow rate in the intake pipe.

Step 41 first sets time T to 0. Step 42 inputs the phase relationship of each piston in the case of a multi-cylinder engine, timing of opening and closing of the intake valve, and initial values of pressure P (t, χ) and flow rate Q (t, χ). The initial value is
Considering the state before the engine starts, it is normal to set the pressure to atmospheric pressure and the flow rate to zero. In step 43, time T is advanced by ΔTs so that T=T+ΔTs. And the valve opening degree at that time○. , engine speed N0, outside temperature T. , atmospheric pressure P0 are input in step 44. If this entry timing is matched to the reference position of engine rotation, the piston speed V p (t) of the cylinder in the suction state can be calculated in step 45 from the phase relationship of each piston.

Further, in step 46, a frictional resistance coefficient fν of the flow corresponding to the valve opening degree is determined. Now that the pipe resistance and boundary conditions at T=T+ΔTs have been determined, in step 47, 1=0 is set, and the pressure P(T, χsL flow rate at time T=T) is determined.

From (T, χN), Δmu is the time step in the characteristic curve #i method, and the pressure P and flow rate at T=T+ΔT.

is determined and output (steps 49 and 50). Further, step 51 calculates the density ρ from the above values.

This calculation is repeated, and in step 53, the average mass flow rate Mi in each injector section is determined by integrating the value of ρQ over one period ΔTt. If the time t is still smaller than the sampling time ΔTs, steps 49 to 53 are repeated until t becomes ΔTs. If this series of calculations is to be continued, the time is further advanced by ΔTs and the calculations are restarted from step 44.

FIG. 3 shows an example in which when calculating the flow in the intake pipe, the intake pipe system is replaced with an electrical equivalent circuit and the flow rate is determined by an analog computer 3o. According to this embodiment, since the intake air amount is determined without using a sensor for measuring the flow rate, the measurement error of the sensor,
Without being affected by scattering or even changes over time,
Accurate flow rate is always required, and the amount of fuel injected from the injector can be controlled to the optimal air-fuel ratio. Furthermore, according to this embodiment, since the flow rate, which changes from moment to moment, can be determined at each injector position, the injection timing can be precisely determined for each injector. Further, the calculation means may be formed by a hybrid computer that calculates by combining analog calculation and digital calculation, and according to each embodiment, the flow rate is calculated in advance, such as a hot wire air flowmeter or a Karman vortex flowmeter. There is no need to have a verification curve to calculate, and the assembly and adjustment process can be shortened. Furthermore, since there is no sensor for measuring the flow rate, the structure of the engine intake pipe is simplified.

〔Effect of the invention〕

According to the fuel supply control system for an internal combustion engine of the present invention, by knowing the air control valve opening, the engine speed, the intake/exhaust state of each cylinder, and the atmospheric pressure and temperature, the flow in the intake pipe is controlled. By analyzing this, the intake air amount at the manifold can be determined by calculation, eliminating measurement errors in the measurement element and always obtaining accurate flow rates. From this value, the fuel injection amount and injection timing for each injector can be calculated. The optimum air-fuel ratio can be determined, and engine combustion can always be kept in the optimum state.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing one embodiment of the present invention, and FIG.
FIG. 3 is a flowchart showing the calculation procedure, and FIG. 3 is a configuration diagram showing another embodiment of the present invention. 2... Intake pipe line, 5... Atmospheric temperature, atmospheric pressure, 6... Valve opening, 7... Engine rotation speed, 8... Calculating means (microcomputer), 11-1
4...Cylinder, 28-31...Injector. Figure 1

Claims (1)

[Claims] 1. Detection means for detecting air control valve opening, engine speed, atmospheric temperature, and atmospheric pressure at predetermined time steps, and analyzing the flow in the intake pipe based on each detected value. Calculating means for calculating the intake air amount of at least one cylinder in predetermined time steps; and control means for controlling the fuel injection amount and injection timing of at least one injector based on the output value of the calculating means. A fuel supply control system for an internal combustion engine, characterized in that: 2. The fuel supply control system for an internal combustion engine according to claim 1, wherein the calculation means is formed by a digital computer. 3. The fuel supply control system for an internal combustion engine according to claim 1, wherein the calculation means is formed by a parallel computer consisting of a microcomputer provided corresponding to each cylinder. 4. The fuel supply control system for an internal combustion engine according to claim 1, wherein the intake pipe is replaced with an electrically equivalent circuit, and the calculation means is formed by an analog computer. 5. The fuel supply control system for an internal combustion engine according to claim 1, wherein the calculation means is formed by a hybrid computer that performs calculations by combining analog calculations and digital calculations.