JPS6158946A - Air-fuel ratio control method for automobile - Google Patents

Abstract

PURPOSE:To have a control into optimum ignition timing by making correction of the zero point of a cylinder pressure sensor during the starting process of the engine and thereafter, by reference to the value determined by sampling prior to the start, every time sampling is made on the cylinder pressure sensor. CONSTITUTION:The pressure in the combustion chamber of an internal-combustion engine is sensed, and the ignition timing, fuel, etc. are controlled. Prior to start of the engine, sampling is made on a cylinder pressure sensor at Step 302. At Step 304, the zero point of this cylinder pressure sensor is stored in a memory. At Step 402, the zero point stored in the memory as at in Step 304 is subtracted from the sampling data for the cylinder pressure sensor, and by reference thereto the zero point correction for cylinder pressure sensor shall be performed. This will enhance accuracy in torque calculation as well as modification preciseness for the ignition timing, to ensure that the ignition timing is controlled optimum.

Description

Detailed Description of the Invention [Field of Application of the Invention] The present invention relates to the control of the fuel system and ignition system using a cylinder pressure sensor in an internal combustion engine, and in particular to the control of the fuel system and ignition system using a cylinder pressure sensor. This invention relates to a fuel ratio control method.

[Background of the invention]

Conventional devices are disclosed in Japanese Patent Application Laid-open No. 59-185945 and Japanese Patent Publication No. 59-1859.
No. 9-9743 describes means for sampling the pressure within a combustion chamber and calculating the indicated mean effective pressure and torque. However, no consideration was given to zero point fluctuations of the cylinder pressure sensor.

Automotive gasoline engines are equipped with a control device that uses a microcomputer to comprehensively control the operating conditions to improve exhaust gas conditions and improve fuel efficiency. The 02 sensor outputs output according to the oxygen concentration of the engine, and other sensors that provide various data indicating the operating status of the engine. 2. Description of the Related Art Engine control devices (hereinafter referred to as EECs), which perform control to always obtain optimal engine operating conditions, have come into use.

An example of a system applied to such an EECt-fuel injection type internal combustion engine is proposed in Japanese Patent Laid-Open No. 55-134721, and this conventional example will be explained with reference to FIGS. 1 and 2.

FIG. 1 is a partially sectional view schematically showing the entire engine control system. In the figure, intake air is supplied into a cylinder 8 through an air cleaner 2, a throttle chamber 4, and an intake pipe 6. The gas burned within the cylinder 8 passes through the exhaust pipe 10 from the cylinder 8 and is discharged into the atmosphere.

Throttle chamber 4 contains fuel ftpl! The fuel ejected from the injector 12 is atomized in the air passage of the throttle chamber 4 and mixed with intake air to form a mixture, and this mixture is injected into the intake air. Through the pipe 6, it is supplied to the combustion chamber of the cylinder 8 by opening the intake valve 20.

A throttle valve 14 is provided near the outlet of the injector 12. The throttle valve 14 is configured to be mechanically interlocked with the accelerator pedal and is reversely driven by the driver.

An air passage 22 is provided upstream of the throttle valve 14 of the throttle chamber 4, and a hot wire air flow meter made of an electric heating element, that is, a flow rate sensor 24 is disposed in this air passage 22, and the flow rate is adjusted according to the air flow velocity. A changing electrical signal AF is taken out. Since the flow rate sensor 24 made of this heating element (hot wire) is provided in the bypass air passage 22,
It is mined from the high-temperature gas generated during backfire from the cylinder 8, and is also protected from contamination by dust and the like in the intake air. The outlet of the bypass air passage 22 is opened near the narrowest part of the venturi, and the inlet thereof is opened on the upstream side of the venturi.

The injector 12 is constantly supplied with pressurized fuel from the fuel tank 30 via the 72-el pump 32, and when an injection signal from the control circuit 60 is given to the injector 12, the injector 12 Fuel is injected inside.

The air-fuel mixture taken in from the intake valve 20 is compressed by the piston 50 and combusted by a spark from an ignition plug (not shown), and this combustion is converted into kinetic energy. The cylinder 8 is cooled by cooling water 54. The temperature of this cooling water is measured by a water temperature sensor 56, and this measured value TW is used as the engine temperature.

At the gathering part of the exhaust pipe 10, there is a 0□ sensor 142 that operates on and off at the stoichiometric air-fuel ratio.

Further, the crankshaft (not shown) is provided with a crank angle sensor that outputs a reference angle signal and a position signal at every reference crank angle and at every fixed angle (for example, 0.5 degrees) in accordance with the rotation of the engine.

The output of the crank angle sensor, the output signal TW of the water temperature sensor 56, the output signal of the 02 sensor 142, and the electric signal AP from the heating element 24 enter a control circuit 60 consisting of a microcomputer, memory, etc. This is the input that controls the

Further, the throttle chamber 4 is provided with a bypass 26 that covers the throttle valve 14 and communicates with the intake pipe 6, and this bypass 26 is provided with a bypass valve 61 that is controlled to open and close.

This bypass valve 61 is made to face the bypass 26 provided by bypassing the throttle valve 14, and is controlled to open and close by a pulse current, and the cross-sectional area of the bypass 26 is changed depending on the soft amount, and this soft amount is controlled. The output of the circuit 60 drives and controls the drive section. That is, the control circuit 60 generates an opening/closing periodic signal for controlling the driving section, and the driving section adjusts the amount of softness of the bypass pulp 61 based on this opening/closing periodic signal.

The EGR control valve 90 controls the passage between the exhaust pipe 10 and the suction pipe 6, and the amount of EGR flowing from the exhaust pipe 10 to the suction pipe 6 is controlled.

Therefore, by controlling the injector 12 in FIG. 1, the air-fuel ratio (
A/F) control and fuel increase and decrease control can be performed, and the bypass pulp 61 and injector 12 can control the engine speed at idle (engine SC).
Furthermore, the amount of EGR can be controlled.

The cylinder pressure sensor is built into the spark plug and measures the pressure inside the combustion engine.

FIG. 2 is an overall configuration diagram of the control circuit 60 using a microcomputer, which includes a central grossenosing unit 102 (hereinafter referred to as CPU), a read-only memory 104 (hereinafter referred to as ROM), and a random access memory 1J106.
(hereinafter referred to as RAM) and an input/output circuit 108. The CPU 102 calculates input data from the input/output circuit 108 using various programs stored in the ROM 104, and transfers the calculation results back to the input/output circuit 108.
Return to 08. The intermediate memory required for these operations is RA.
Use M106. CPU102゜ROM104. R
AMl06. Transfer of various data between the input/output circuits 108 is performed by a path line 110 consisting of a data path and a control bust address path.

The input/output circuit 108 inputs a first analog-digital converter 122 (hereinafter referred to as ADC1), a 20th analog-digital converter 124 (hereinafter referred to as DC2), an angle signal processing circuit 126, and 1-bit information. Discrete input/output circuit 128 (hereinafter referred to as D) for outputting
(denoted as IO).

The ADCI includes a battery voltage detection sensor 132 (hereinafter referred to as VB).
8) and cooling water temperature sensor 56 (hereinafter referred to as TWS)
, Tsutsuuchi Danasensa 136 (hereinafter referred to as PS), 027sensa 142 (hereinafter referred to as 02S), and Scottor sensor 140
(hereinafter referred to as 0TH8) output is Multi-Zolexa 1
62 (hereinafter referred to as MPX), and MPX162 selects one of these to perform analog/digital
The signal is input to a conversion circuit 164 (hereinafter referred to as ADC).

AJ) The digital value that is the output of C164 is in register 1.
66 (hereinafter referred to as REG).

In addition, the flow rate sensor 24 (hereinafter referred to as AF'S) is an ADC
2.124, is digitally converted via an analog-to-digital conversion circuit 172 (hereinafter referred to as ADC), and is set in a register 174 (hereinafter referred to as REG).

The angle sensor 146 (hereinafter referred to as ANGLS) outputs a signal (hereinafter referred to as REF) indicating a reference crank angle, for example, a 180° crank angle (in the case of a 4-cylinder engine), and a signal (hereinafter referred to as REF) indicating a minute angle, for example, a 1 degree sink angle. (hereinafter referred to as PO8) is output and applied to the angle signal processing circuit 126, where the waveform is shaped.

DIO (128) has an idle switch 148 (hereinafter referred to as ID) that operates when the throttle valve 14 has returned to the fully closed position.
LE-8W) and top gear switch 150 (denoted as LE-8W)
(hereinafter referred to as TOP-8W) and starter switch 152
(hereinafter referred to as START-SW) is input.

Next, a pulse output circuit and a controlled object based on the calculation results of the CPU will be explained. Injector control circuit 1134
(hereinafter referred to as INGC) is a circuit that converts the digital value of the calculation result into a pulse output. Therefore, the pulse ING having a pulse width corresponding to the fuel injection amount is INGC11.
34 and is applied to the injector 12 via an AND gate 1136''i.

Ignition pulse generation circuit 1138 (hereinafter referred to as IGNC)
is a register that sets the ignition timing (hereinafter referred to as ADV)
and a register (hereinafter referred to as DWL) for setting the primary current supply start time of the ignition coil, and these data are set by the CPU.

Generates a pulse IGN based on the set data,
A to amplifier 62 for supplying primary current to the ignition coil
This pulse IGN is applied via the ND game) 1140.

The valve opening rate of the bypass pulp 61 is determined by the control circuit (hereinafter referred to as 15CC).
) 1142 through an AND gate 1144. l5OC1
142 is an EGR amount control pulse generation circuit 1178 (hereinafter referred to as EGRC) that controls the EGR control valve 90, which has a register l5CD for setting the pulse width and a register l5CP for setting the pulse period.
7' Register EGRD to set the value representing the knee
and a register EGR that sets a value representing the pulse period.
It has P. This EGRC output pulse EGR is applied to transistor 9o via AND gate 1156'i.

Further, the 1-bit input/output signal is controlled by the circuit DIO (128). The input signals are IDLE-SW signal, 5TART-8'W signal, and T.

There is a p-sw times signal. The output signal also includes a pulse output signal for pivoting the fuel pump.

This DIO is provided with a register DDRI')2 for determining whether a terminal is used as an input terminal, and a register DOUT 194 for latching output data.

The mode register 1160 is a register (hereinafter referred to as MOD) that holds instructions for commanding various states inside the input/output circuit 108.
), for example, by setting an instruction in this mode register 1160) AND gates 1136, 11
40,1144.1156 are all in operation state,
Put it in an inactive state.

By setting a command in the MOD register 1160 in this way, it is possible to control the stop and start of the output of INJC, IGNC, and 18CC.

A signal DIOI for controlling the fuel pump 32 is output to D'l0 (128).

Therefore, if such EC is applied, almost all controls related to the internal combustion engine, such as A/F control, can be appropriately performed, and the strict exhaust gas regulations for automobiles can be fully met.

By the way, in controlling the air-fuel ratio in such an EEC, for example, injector 120 control data is calculated from data AF24 representing the intake air amount and engine rotation speed data N, and the result is corrected by feedback control using data from the 02 sensor 142. However, it is well known that a predetermined air-fuel ratio is obtained.

In addition, the combustion status is monitored by the cylinder pressure sensor PS136.
It is also well known to perform learning control of air-fuel ratio fluctuations and ignition timing for each cylinder.

This type of control technology works effectively when the zero point of the cylinder pressure sensor does not fluctuate, but if the zero point of the cylinder pressure sensor shifts, an error occurs in the calculated torque.

This will result in a deviation in the ignition timing learning value, making it impossible to control the optimal ignition timing, causing deterioration in fuel efficiency, and an increase in harmful components in exhaust gas.

[Purpose of the invention]

An object of the present invention is to provide an air-fuel ratio control method for an internal combustion engine that solves the above-mentioned conventional problems.

[Summary of the invention]

To achieve this objective, the present invention samples the zero point of the cylinder pressure sensor before starting, constantly corrects the sampled zero point, and uses it for torque calculation 1 spark timing learning.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG. The hardware configuration of an embodiment of the present invention is shown in FIGS.

It is the same as the conventional EEC explained in FIG. 2, but the control operation by the control circuit 60 including a microcomputer is different.
Only a part of the program stored in the OM 104 is different.

FIG. 3 shows pre-start processing of the cylinder pressure sensor. Step 3
At 00, judgment is made before starting. If the engine has not yet started, the process proceeds to step 302, where the cylinder pressure sensor is sampled ($ points are included). In step 304, the zero point of the cylinder pressure sensor is stored in the memory, and in step 306, startup processing is performed. Through this process, the zero point of the cylinder pressure sensor is stored in the memory and used for zero point correction of the cylinder pressure sensor during and after startup.

FIG. 4 shows a processing routine for zero point correction of the cylinder pressure sensor. At step 400, sampling the in-cylinder pressure sensor;
At step 402, the zero point in the memory at step 304 (FIG. 3) is subtracted from the sampling data of the cylinder pressure sensor. As a result, the zero point of the cylinder pressure sensor is corrected, and torque is calculated in step 404. By performing this zero point correction, torque calculation can be performed with high precision.

In addition, if there is a cylinder pressure sensor for each cylinder, step 3
02 zero point acquisition is for the number of cylinders, step 304
It is sufficient to prepare memory for the number of cylinders.

[Effects of 4 shots and i] 1. According to the present invention, the zero point correction of the cylinder pressure sensor is always performed, so it is possible to compensate for variations in the cylinder pressure sensor and changes over time. Since it can be done easily, it has the effect of controlling the optimum ignition timing.

[Brief explanation of drawings]

Fig. 1 is a configuration diagram of an engine to which the present invention is applied, Fig. 2 is a diagram showing a control circuit, Fig. 3 is a flowchart for zero-point correction of the cylinder pressure sensor, and Fig. 4 is a flowchart for zero-point correction of the cylinder pressure sensor. show. 12... Injector, 24... Flow rate sensor, 60
...Control circuit, 136...Cylinder pressure sensor.

Claims (1)

[Claims] 1. In devices that detect the pressure in the combustion chamber of an internal combustion engine and control ignition timing, fuel, etc., the output of the cylinder pressure sensor is sampled before the engine starts, and stored in memory. 1. A method for controlling an air-fuel ratio of an automobile, the method comprising: correcting the zero point of a cylinder pressure sensor every time the cylinder pressure sensor is sampled after the engine is started, based on the sampling value before the engine is started.