JPS63195361A - Control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To make it possible to control an engine accurately, by computing the fuel feeding amount and the like related to the partial pressure of oxygen at a suction pipe, detecting the variation between solids and the variation with the time, of the value of an oxygen sensor, and arranging correction devices to eliminate the influences of these factors. CONSTITUTION:A control unit detects the partial pressure of oxygen of the suction gas including the EGR gas at the suction system 1A at the lower stream of a throttle valve 34 of an internal combustion engine 1 by an oxygen sensor 2, finds the fresh air amount in the suction air at first by an engine control factor value computing device 3 depending on the oxygen partial pressure, computes the engine control factors such as the fuel injection quantity and the ignition timing responding to the fresh air amount, and controls the operation condition of the internal combustion engine 1 through respective control devices 5. Furthermore, the engine control factor value computing device 3 corrects the detected oxygen partial pressure by the correction value of either the variation between solids or variation with the passage of time of the oxygen sensor 2 which is detected by a correction device 4. In such a way, an accurate engine control can be carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control device for an internal combustion engine, and can be suitably used for fuel injection control and ignition timing control.

[Conventional technology]

In the so-called D-J type fuel injection system for internal combustion engines, a pressure sensor is installed in the intake manifold (or surge tank) downstream of the throttle valve in the intake system of the internal combustion engine to detect intake pipe pressure as a load factor. Then, the amount of fresh air introduced into the cylinder bore is determined from the intake pipe pressure and engine speed, and the fuel injection amount to achieve a predetermined air-fuel ratio is calculated, and fuel is injected from the injector.
Compared to the air flow meter used in the so-called L-J type fuel injection system, the J type system has the advantage that the size of the sensor itself is smaller and the increase in intake resistance due to the installation of the sensor is smaller.

Unlike the air flow meter in the L-J type fuel injection system, in this DJ type fuel injection system, the amount of fresh air entering the internal combustion engine is determined by the intake pipe pressure. Therefore, when the intake pipe pressure changes due to exhaust gas recirculation (EGR), it becomes necessary to correct the sensor output value in order to know the amount of fresh air.
No. 5548 provides a differential pressure sensor that detects the pressure difference before and after a fixed orifice in the EGR passage, corrects the output of the pressure sensor based on the differential pressure signal from the differential pressure sensor, and makes it possible to determine the amount of fresh air related to EGR. I'm trying to make it possible.

[Problem that the invention seeks to solve]

In the conventional DJ type fuel injection system, the pressure sensor measures not only the amount of fresh air but also the flow rate of all gases introduced into the engine, such as EGR gas and blow-by gas. And E.G.
The amount of fresh air introduced into the engine is determined by detecting the contribution of R gas, blow-by gas, etc. to the intake pipe pressure and correcting it. Since the amount of fresh air is not directly measured, detection accuracy is poor, which may affect accurate air-fuel ratio control.

Therefore, the applicant has proposed that an oxygen sensor having a structure similar to a so-called lean sensor be disposed in the intake pipe to determine the oxygen partial pressure. In this case, the amount of fresh air itself can be determined from the oxygen partial pressure, but there is a problem that the output value of the oxygen sensor changes depending on whether the lid is opened or changes over time, causing the air-fuel ratio to deviate from the set value. This invention solves this problem.

[Means for solving problems]

In FIG. 1, the internal combustion engine control device of the present invention is installed in the intake system IA downstream of the throttle valve 34 of the internal combustion engine 1, and generates a signal having an output level according to the oxygen partial pressure of the intake air. An engine that calculates the value of an engine control factor that is controlled according to fresh air introduced into the internal combustion engine in relation to an oxygen partial pressure obtained based on the output of the fresh air amount detection means 2 and the fresh air amount detection means 2. control factor value calculation means 3; correction means 4 for correcting the engine control factor value calculated by the engine control factor value calculation means 3 so as to compensate for fluctuations in the detection value of the oxygen partial pressure detection means; and an engine control factor control means 5 for controlling the control factor of the internal combustion engine based on the engine control factor value corrected by 4.

[For production]

The fresh air amount detection means 2 detects the oxygen partial pressure in the intake air introduced into the internal combustion engine, and the engine control factor value calculation means 3 detects the fresh air amount introduced into the internal combustion engine in relation to the detected oxygen partial pressure. The value of a factor controlled depending on the air condition, such as the fuel supply amount, is calculated. The correction means 4 corrects the fuel supply amount etc. calculated by the engine control factor value calculation means 3 so as to compensate for fluctuations due to inter-individual fluctuations in the detected value of the fresh air amount detection means, changes over time, etc. The control means 5 controls the internal combustion engine 1 so that the factor controlled according to the fresh air of the internal combustion engine has a value corrected by the correction means 4.

〔Example〕

In FIG. 2, 10 is a cylinder block, 12 is a piston, 14 is a connecting rod, 16 is a cylinder head, 18 is a combustion chamber, 20 is a spark plug, 22 is an intake valve, 2
4 is an intake boat, 26 is an exhaust valve, 28 is an exhaust boat, 2
9 is a distributor, and 30 is an ignition device (consisting of an igniter 30a and an ignition coil 30b). The intake boat 24 is connected to the air cleaner 40 via an intake pipe 31 , a surge tank 32 , a throttle valve 34 , an intake pipe 36 , a compressor housing 38 a of a turbocharger 38 , and an intake pipe 39 . A fuel injector 42 is installed in the intake pipe 31 close to the intake boat 24. Exhaust boat 28 is connected to turbine housing 38b of turbocharger 38 via exhaust manifold 44. Note that the system may employ a mechanical supercharger instead of the turbocharger 38.

An exhaust gas recirculation passage (EGR passage) 45 is provided to connect the exhaust manifold 44 and the surge tank 32. An exhaust gas recirculation control valve (EGR valve) 46 is provided on the EGR passage 45 to control the exhaust gas recirculation rate (EGR rate). In this embodiment, an EGR valve 446 is provided with a negative pressure operated diaphragm mechanism 47. The diaphragm mechanism 47 is installed slightly upstream of the idle position of the throttle valve 34.
Connected to GR port 48. The pressure regulating valve 49 is connected by a pressure conduit 50 to a constant pressure chamber 52 formed downstream of the constant pressure throttle 51 in the EGR passage 45 . Therefore, the pressure regulating valve 49 is operated so that the pressure in the constant pressure chamber 52 is approximately constant.
The negative pressure introduced from the GR boat 48 to the negative pressure operating mechanism 47 of the EGR valve 46 is controlled. The diaphragm 49a of the pressure regulating valve 49 is connected to the negative pressure boat 53 slightly upstream of the EGR boat 48, and the negative pressure corresponding to the load acts on the diaphragm 49a to counteract the exhaust pressure, and the EGR rate is adjusted according to the load. control. Since the configuration and operation of this EGR device are well known, no further explanation will be provided. Furthermore, EG
The R device does not have to be of the type shown.

The control circuit 54 is configured as a microcomputer system and performs fuel injection control, ignition timing control, and other engine operation controls.

The control circuit 54 is a micro processing unit (M
PU) 54a, memory 54b, input boat 54c, and output boat 54d1. A bus 5 that connects these elements.
4e. The input boat 54c is connected to each sensor and receives engine operating condition signals. A crank angle sensor 56.5B is installed on the distributor 29.

The first crank angle sensor 56 is installed opposite the magnet piece 60 on the distributor shaft 29a, and generates a pulse signal as a reference signal every 7200 revolutions of the crankshaft, that is, every cycle of the engine. The second crank angle sensor 58 is installed opposite the magnet piece 62 on the distributor shaft 29a, and generates a signal every 30 degrees of the crankshaft, which serves as a trigger signal for fuel injection control and ignition timing control. The water temperature sensor 64 detects the temperature of the cooling water in the cooling water jacket 10a of the cylinder block 10. The intake air temperature sensor 66 can detect the temperature of intake air introduced into the engine through the intake pipe. Exhaust side oxygen sensor 68
is provided in the exhaust manifold 44.

This exhaust side oxygen sensor 68 is for air-fuel ratio feedback control, and is an oz sensor in a system that controls the air-fuel ratio to the stoichiometric air-fuel ratio, and a so-called lean sensor in a system that controls the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio. can do.

According to this invention, the intake side oxygen sensor 70 is installed in the surge tank 32. The intake side oxygen sensor 70 is used to detect the amount of fresh air introduced into the engine and calculate the fuel injection amount and ignition timing.

The intake side oxygen sensor 70 has a structure similar to a so-called lean sensor, and can extract a voltage that continuously changes depending on changes in the partial pressure of oxygen in the total intake air. In FIG. 3, the intake-side oxygen sensor 70 includes a bottomed cylindrical body 72 made of a solid electrolyte made of zirconia, and an air-permeable thin film platinum electrode 74-1 formed on the inner and outer surfaces of the cylindrical body 72.
．． 74-2, a diffusion layer 76 as a porous layer formed around the outer electrode 74-2 by plasma spraying of a ceramic material such as spinel, an outer case 78 formed of a porous plate, and a cylindrical The basic component is a ceramic heater 80 disposed in the central space of the body 72. Heater 80 is connected to power source E2 and can serve to activate sensor 70. The central space of the cylindrical body 72 is a heater 8
It is communicated with the atmosphere through a central passage 80a. Inner electrode 74-1 as an anode and outer electrode 7 as a cathode
4-2, a power source E is connected. O2 ions in the gas to be detected can flow from the outer electrode 74-2 toward the inner electrode 74-1 at a speed regulated by the diffusion layer due to the so-called pumping action, and at the voltage of the power source El, the ion current (limit Current) I/ is 1 1 - ((4Fx S x mouth Oz XP)/
(RxTx f))X(In(1/(1-Pot/P
))) j e H (1) Here, F: Faraday constant S: Electrode area 00 □: Gas diffusion constant R: Gas constant T: Temperature Il = Diffusion resistance layer effective length P: Total pressure PO! ? Expressed by oxygen partial pressure. Figure 4 shows the oxygen partial pressure relative to the total pressure,
The measured characteristics with the sensor output are shown. When the total pressure changes, the partial pressure changes, and the sensor output changes accordingly, making it possible to know the oxygen partial pressure from the sensor output.

The MPU 54a executes calculations according to the program and data stored in the memory 54b, and outputs the output data from the memory 54b.
Set to . The output port 54d is connected to the fuel injector 42, the igniter 30a, and other control devices, and a control signal is applied thereto.

The fuel injection control portion of the operation of the control circuit 54 will be explained below using a flowchart. FIG. 5 shows a fuel injection routine, and this routine is executed by detecting the crank angle before the fuel injection of the cylinder to which fuel is to be injected. For example, if fuel injection is to be performed during the intake stroke, it is executed by detecting 60'' before the intake top dead center.
This can be determined by the value of a counter that is cleared by the arrival of the 00CA signal and incremented each time the 30'CA signal from the second crank angle sensor 58 arrives.

In step 99, PO2 is obtained by multiplying the intake oxygen sensor output PO by the correction coefficient KPOz. KPO□
is a correction coefficient for calibrating the output of the sensor 70 over time, as will be described later.

In step 100, the basic injection time Tp is equal to the engine speed NE.
is calculated from the output value PO□ of the intake side oxygen sensor 70. Here, the basic injection time refers to the valve opening time of the injector 42 in order to obtain a fuel injection amount that makes the air-fuel ratio equal to the stoichiometric air-fuel ratio with respect to the amount of fresh air introduced into the internal combustion engine. and,
Since the intake efficiency changes depending on the rotation speed, in order to correct this, the fuel injection amount is determined by the combination of the fresh air amount and the rotation speed. In the conventional D-J system, the amount of fresh air is indirectly known by measuring the intake pipe pressure, and the basic fuel injection amount is determined from the combination of rotation speed and intake pipe negative pressure. In this invention, the basic fuel injection amount is determined based on the rotational speed and the output value of the intake side oxygen sensor 70.

The memory 54b includes a map of data of the basic fuel injection time Tp for obtaining the stoichiometric air-fuel ratio for each combination of the engine speed NE and the output value PO2 of the oxygen sensor 70. MPU54a is the second crank angle sensor 58
The current engine speed NE known from the interval of the 30" CA signal and the current output PO□O of the second oxygen concentration sensor 70.
A well-known interpolation calculation is performed based on the value, and the basic fuel injection time Tp is calculated thereby.

In step 102, the final fuel injection amount Tau is calculated using the following formula: Tau=TpXα+β. α and β are correction coefficients and correction amounts whose detailed explanations will be omitted because they are not directly related to this invention, and the feedback correction coefficient is calculated based on the signal from the intake oxygen sensor 68, and the water temperature correction coefficient is calculated based on the water temperature signal from the water temperature sensor 64. and various correction calculation processes added to the basic fuel injection time Tp such as acceleration correction.

In step 104, a fuel injection start time t is calculated. Although the fuel injection start timing is determined in various ways depending on the characteristics of the engine, for example, it is necessary to determine the fuel injection start timing so that the fuel injection ends approximately in synchronization with the end of the intake stroke. Therefore, the fuel injection start timing changes depending on the amount of fresh air and the rotation speed.

The memory 54b stores a data map of the crank angle from the intake top dead center at which fuel injection is started for the combination of the engine rotation @NE and the output POt of the intake side oxygen sensor 70. The MPU 54a outputs the output value PO of the intake side oxygen sensor 70! and 30'CA of the second crank angle sensor 58
The fuel injection start time 1. is calculated as the time from the current time t0 (see FIG. 8).

In step 106, the injection end time t0 is changed to the injection start time ti by the fuel injection time Ta calculated in step 102.
It is assumed that u is added. Step 108 indicates permission of the time coincidence interrupt routine, and step 110 sets fuel injection start time ti in a fuel injection control conveyor register (not shown).

FIG. 6 shows a time coincidence interrupt routine, which is started when the conveyor register determines that the current time coincides with the fuel injection start time of 1°. Step 114 indicates that interrupts are prohibited by the conveyor register, and in step 114, the fuel injection end time t is set in the conveyor register. Therefore, when the current time coincides with the fuel injection end time t, fuel injection by the injector 42 is stopped.

FIG. 7 shows a correction coefficient calculation routine for calibrating the output of the intake side oxygen sensor 70. This routine may be independent or may be combined with FIG. Figure 9 shows the relationship between the fresh air amount (oxygen partial pressure) POz and the limiting current. The fuel injection amount is determined by the output characteristic of the solid line m, which is the reference state. Due to inter-individual variation, the output may be more (dotted chain line n) or less. (dotted chain line n').

There is a routine shown in FIG. 7 to calibrate this. In step 120, it is determined whether the current operation is idling, where only fresh air is introduced, EGR is not being performed, and blow-by gas is not being introduced. Yes
If so, the process proceeds to step 122, where the actual measured value PO2 of the oxygen sensor 70 and the reference value PO8° (9th
The difference ΔPO□' from the point (on the straight line m in the figure) is calculated. This value corresponds to the deviation of the sensor value from the reference value. Furthermore, PO□.

The data is stored in advance in the memory 54 as a reference output during idle.
Assume that it is stored in b. In step 124, Δ
The correction coefficient Kpoz is calculated from po, '. This correction coefficient KPO1 is a proportionality constant for returning a shifted straight line like n or n' in Fig. 9 to the standard straight line m, and has the relationship shown in Fig. 10, and is calculated by interpolation from data stored in memory. can do. In step 126, the measured oxygen partial pressure PO□ is multiplied by the correction coefficient KPOz to calculate the oxygen partial pressure P08', which is calibrated for inter-individual variation and changes over time.

In the above example, D-J calculates Tp directly from oxygen partial pressure.
This invention was applied to a normal DJ type system in which a pressure sensor is installed in the intake pipe, and an oxygen partial pressure sensor is further added to the intake pipe pressure (PM) and rotational speed (NE
) is calculated from PO! detected by the oxygen partial pressure sensor. It can also be applied to things that need to be corrected. FIG. 11 shows the fuel injection amount routine of this embodiment. step 200
Then, Tp is calculated from NE and PM. Step 202
Then, the target oxygen partial pressure PO□ is calculated from NE and PM. In step 204, the oxygen partial pressure PO1' after calibrating the change over time is calculated by multiplying PO□ by POz, which is calculated in the same manner as in the routine of FIG. Step 20
6 is the oxygen partial pressure calibration value PO□' and the value po on the straight line m in FIG. The deviation amount ΔPOt is calculated from the difference between the two. In step 20B, the deviation amount ΔPO! From this, the fuel injection amount correction coefficient FPO□ is calculated. This correction coefficient FP(
h is used to optimally increase or decrease the fuel injection amount in response to the deviation of the sensor value from the reference value, and is multiplied by the basic fuel injection ITp.

FPO□ is calculated by interpolation from the straight line corresponding to m in FIG. 9 stored in the memory. In step 210, Tp is FPO
Corrected by □. In step 212, the injection start time tilJ is calculated from the PM-NE map. The following processing is the same as that in FIG.

In the embodiments, the present invention is applied to a vehicle equipped with an EGR device, but the EGR device does not necessarily need to be equipped. As an advantage of applying it to a vehicle equipped with an EGR device,
There is no need to correct the fuel injection amount according to the R rate, which has the advantage of simplifying fuel injection control. That is, in a normal DJ system, the fuel injection amount and the like are determined by a map of intake pipe pressure and rotational speed. When EGR gas enters, the amount of fresh air decreases even if the intake pipe pressure remains the same, so the amount of fuel must be reduced accordingly. However, in this invention, since the fresh air amount itself is detected in the same way as the air flow meter of the L-J system, there is basically no need to supplement the fuel injection amount. Strictly speaking, the measured value of the intake side oxygen sensor 70 has nonlinearity with respect to pressure, and in order to eliminate this influence and perform precise air-fuel ratio control, the fuel injection amount must be corrected according to the EGR rate. You can also do it. Even if the fuel injection amount is corrected according to the EGR rate, the influence of the intake pipe pressure on the measured value of the fresh air amount is small, so there is an advantage that the fuel correction based on the EGR rate can be extremely small. FIG. 11 shows the actually measured characteristics of the change in the fuel correction amount β for obtaining the set air-fuel ratio with respect to the EGR rate. According to the present invention, the fuel correction amount for the same EGR rate can be made smaller compared to the conventional one.

Although the present invention has been described in detail for fuel injection, the present invention can also be applied to ignition timing control. That is,
The basic ignition timing SAo is calculated from the engine speed NB and the output Pot from the intake side oxygen sensor 70. The basic ignition timing here refers to the ignition timing (MBT) at which the maximum torque is obtained for the amount of fresh air introduced into the internal combustion engine when the rotation speed is fixed.
) is expressed as an angle from compression top dead center. Even if the amount of fresh air is the same, the MBT will change if the engine speed changes, so the ignition timing to obtain the MBT is determined by the amount of fresh air and the engine speed. In the conventional DJ system, NE-
Although a SAG map was constructed for the PM combination, the present invention employs an SAO map for the NE-Pot combination instead. The routine for performing ignition control based on the SAG map is obvious to those skilled in the art, so a description thereof will be omitted.

〔Effect of the invention〕

According to the present invention, there is provided means for calculating the fuel supply amount, etc. in relation to the oxygen partial pressure in the intake pipe, detecting inter-individual fluctuations in sensor values and changes over time, and calibrating to eliminate these influences. By providing this, accurate engine control can be realized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention. FIG. 2 is an overall configuration diagram of an embodiment of the present invention. FIG. 3 is a cross-sectional view of the intake side oxygen sensor for measuring the amount of fresh air. FIG. 4 is a diagram showing the limiting current characteristics of the oxygen sensor shown in FIG. 3 with respect to oxygen partial pressure. 5 and 6 are flowcharts of the fuel injection routine. FIG. 7 is a flowchart of the oxygen sensor output calibration routine. FIG. 8 is a timing diagram illustrating how to form a fuel injection signal. FIG. 9 is a graph illustrating fluctuations in the output of the oxygen sensor. FIG. 10 is a graph showing the relationship between output fluctuation and a proportionality constant for calibrating the output fluctuation. FIG. 11 is a flowchart showing a fuel injection routine in a system that corrects the basic injection amount calculated by PM-NE using oxygen partial pressure. 18... Combustion chamber 20... Spark plug 30... Ignition device 31... Intake pipe 32... Surge tank 34... Throttle valve 38... Turbocharger 42... Fuel injector 44... ...Exhaust manifold 48...EGR valve 54...Control circuit 64...Water temperature sensor 66...Intake air temperature sensor 68...Exhaust side oxygen sensor 70...Intake side oxygen sensor

Claims (1)

[Claims] A control device for an internal combustion engine consisting of the following elements, which is installed in the intake system downstream of the throttle valve of the internal combustion engine, and generates a signal with an output level according to the oxygen partial pressure of intake air. means, engine control factor value calculation means for calculating the value of an engine control factor that is controlled according to fresh air introduced into the internal combustion engine in relation to the output of the oxygen partial pressure detection means; a correction means for correcting the engine control factor value calculated by the engine control factor value so as to compensate for fluctuations in the detection value of the oxygen partial pressure detection means; An engine control factor control means for controlling.