JPH0615844B2 - Control device for internal combustion engine - Google Patents

Description

The present invention relates to a control device for an internal combustion engine, which can be suitably used for fuel injection control and ignition timing control.

[Conventional technology]

In a so-called DJ type fuel injection system as a fuel injection system for an internal combustion engine, a pressure sensor is installed in an intake manifold (or surge tank) downstream of a throttle valve of an intake system of the internal combustion engine to detect an intake pipe pressure as a load factor. Then, a factor that is controlled according to the amount of fresh air introduced into the cylinder bore, for example, the basic fuel injection amount is calculated from the intake pipe pressure and the engine speed, and fuel injection is performed from the injector. The DJ type system has advantages that the size of the sensor itself is smaller than that of an air flow meter used in a so-called LJ type fuel injection system, and an increase in intake resistance due to mounting of the sensor is small. .

Unlike the air flow meter in the L-J type fuel injection system, in the D-J type fuel injection system, the amount of fresh air entering the internal combustion engine is controlled according to the control value of a factor calculated according to the intake pipe pressure. Is what you are trying to do. However,
The intake pipe pressure changes when exhaust gas circulation (EGR) or blow-by gas is introduced even with the same fresh air amount, and it is necessary to correct the sensor output value in order to perform engine control that correctly reflects the fresh air amount. Comes out. For example, JP-A-58-27
In No. 819, the correction coefficient is calculated according to the deviation from the reference value of the control amount in the air-fuel ratio feedback control by the oxygen sensor installed in the exhaust pipe, and the fuel injection amount is corrected.

[Problems to be solved by the invention]

In the prior art, the fuel injection amount is corrected by the sensor on the exhaust side, so that the air-fuel ratio cannot be corrected promptly due to factors such as delay. Further, since the correction by the sensor on the exhaust side can be performed only in a specific operation such as idling or steady state, there is a possibility that sufficient correction cannot be performed.

[Means for solving problems]

In FIG. 1, the engine speed detecting means (58) for detecting the speed of the internal combustion engine and the intake system (1A) downstream of the throttle valve (34) of the internal combustion engine are arranged to detect the intake pipe pressure (PM). Is installed in the intake system (2) and the intake system (1A) downstream of the throttle valve (34) of the internal combustion engine to detect the oxygen partial pressure (PO ₂ ) in all the gas drawn into the engine. A control device for an internal combustion engine comprising a detection means (4), wherein the rotation speed detection means (5
Control value calculation means (3) for calculating the control value of the control factor for controlling the internal combustion engine based on the engine speed detected by (8) and the suction pipe pressure detected by the intake pipe pressure detection means (2). ) And a reference oxygen partial pressure calculating means for calculating a value of the reference oxygen partial pressure assumed when a gas other than fresh air is not introduced into the engine, based on the engine speed and the intake pipe pressure.
(7) and the difference between the oxygen partial pressure (PO ₂₀ ) calculated by the reference oxygen partial pressure calculating means (7) and the actual oxygen partial pressure (PO ₂ ) detected by the oxygen detecting means (4). Correction means (5) for correcting the calculated control value based on the above, and control factor control means for controlling the control factor by the corrected control value
(6) A control device for an internal combustion engine including:

[Action]

The engine speed detecting means (58) detects the speed of the internal combustion engine,
The intake pipe pressure detecting means (2) detects the intake pipe pressure (PM), and the oxygen detecting means (4) detects the partial pressure of oxygen in all the gas sucked into the engine.
(PO ₂ ) is detected.

The control value calculating means (3) is an engine speed detected by the speed detecting means (58) and the intake pipe pressure detecting means (2).
The control value of the control factor for controlling the internal combustion engine is calculated based on the intake pipe pressure detected by.

The reference oxygen partial pressure calculation means (7) uses the engine speed detected by the engine speed detection means (58) as the value of the reference oxygen partial pressure assumed when no gas other than fresh air is introduced into the engine. It is calculated based on the intake pipe pressure detected by the intake pipe pressure detecting means (2).

The correction means (5) has a reference oxygen partial pressure value (PO ₂₀ ) calculated by the reference oxygen partial pressure calculation means (7) and an actual oxygen partial pressure (PO ₂ ) detected by the oxygen detection means (4). The control value calculated by the control calculation means (3) is corrected based on the difference between

The control factor control means (6) controls the control factor according to the control value corrected by the correction means (5).

〔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 port, 26 is an exhaust valve, 28 is an exhaust port, 2
Reference numeral 9 is a distributor, and 30 is an ignition device (comprising an igniter 30a and an ignition coil 30b). The intake port 24 is connected to an air cleaner 40 via an intake pipe 31, a surge tank 32, a throttle valve 34, an intake pipe 36, a compressor housing 38a of a turbocharger 38, and an intake pipe 39. A fuel injector 42 is installed in the intake pipe 31 near the intake port 24. The exhaust port 28 is connected to a turbine housing 38b of a turbocharger 38 via an exhaust manifold 44. A system that employs a mechanical supercharger instead of the turbocharger 38 may be used.

An exhaust gas recirculation passage (EGR passage) 45 is provided so as 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 for controlling the exhaust gas recirculation rate (EGR rate). In this embodiment, an EGR valve 44 negative pressure operating diaphragm mechanism 47 is provided. The diaphragm mechanism 47 is installed slightly upstream of the idle position of the throttle valve E
It is connected to the 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 adjusts the pressure E in the constant pressure chamber 52 so that the pressure is substantially constant.
The negative pressure introduced from the GR port 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 port 53 slightly upstream of the EGR port 48, and the negative pressure according to the load acts on the diaphragm 49a so as to resist the exhaust pressure. Control. The construction and operation of this EGR device is well known and will not be described further. EG
The R device does not have to be the illustrated type.

The control circuit 54 is configured as a microcomputer system and performs fuel injection control, ignition timing control and other engine operation control. The control circuit 54 includes a micro processing unit (MPU) 54a, a memory 54b, an input port 54c, and an output port 54.
d, and a bus 54e for connecting each of these elements.
The input port 54c is connected to each sensor and an engine operating condition signal is input. The intake pipe pressure sensor 55 is installed in the surge tank 32 and detects the intake pipe pressure PM downstream of the throttle valve 34. The crank angle sensors 56 and 58 are installed in the distributor 29. The first crank angle sensor 56 is installed opposite to the magnet piece 60 on the distributor shaft 29a, and generates a pulse signal every 720 ° rotation of the crank shaft, that is, every one cycle of the engine.
It becomes the reference signal. The second crank angle sensor 58 is installed opposite to the magnet piece 62 on the distributor shaft 29a, generates a signal for every 30 ° of the crank shaft, and serves as a trigger signal for fuel injection control and ignition timing control. The water temperature sensor 64 is the cooling water jacket 10a of the cylinder block 10.
The temperature of the cooling water inside is detected. Intake air temperature sensor 66
Can detect the temperature of the intake air introduced into the intake pipe. The exhaust side oxygen sensor 68 is connected to the exhaust manifold 44.
It is provided in. The exhaust side oxygen sensor 68 is for air-fuel ratio feedback control, is an O ₂ sensor in a system that controls the air-fuel ratio to the stoichiometric air-fuel ratio, and is a so-called lean sensor in a system that controls the air-fuel ratio to be leaner than the stoichiometric air-fuel ratio. Can be configured.

According to this invention, the intake oxygen sensor 70 is installed in the surge tank 32. The intake-side oxygen sensor 70 detects the partial pressure of oxygen in all the gases introduced into the engine, removes the influence of EGR gas or blow-by gas on the detection value of the intake pipe pressure sensor, as described later, This makes it possible to perform accurate control of factors (basic fuel injection amount, etc.) that are controlled according to the amount of air. The intake-side oxygen sensor 70 has the same structure as a so-called lean sensor, and can output a voltage that continuously changes due to a change 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 voltage electrolyte made of zirconia, and breathable thin film platinum electrodes 74-1 and 74-formed on the inner and outer surfaces thereof. 2, and a diffusion layer 76 as a porous layer formed by plasma spraying a ceramic material such as spinel around the outer electrode 74-2,
An outer case 78 formed of a perforated plate and a ceramic heater 80 arranged in the central space of the tubular body 72 are the basic components. The heater 80 is connected to the power supply E ₂ and can help activate the sensor 70. The central space of the cylindrical body 72 is communicated with the atmosphere by the central passage 80a of the heater 80. Inner electrode 74 as anode
-1 and the outer electrode 74-2 as the cathode, a power source E
₁ is connected. The outer electrode 74 by the so-called pump action
-2 to the inner electrode 74-1 can flow O ₂ ions in the gas to be detected at a speed regulated by the diffusion layer, and at a certain voltage of the power source E ₁ , the ion current (limit current) Il is , Il = ((4F × S × DO 2 × P) / (R × T × l)) × (1n (1 / (1-PO 2 / P))) ...... (1) here, F: Faraday Constant S: Electrode area DO ₂ : Gas diffusion constant R: Gas constant T: Temperature l: Effective length of diffusion resistance layer P: Total pressure PO ₂ : Represented by oxygen partial pressure. Fig. 4 shows the oxygen partial pressure relative to the total pressure,
It shows the measured characteristics with the sensor pressure, and when the total pressure changes, the partial pressure changes, and the sensor output changes accordingly, and the oxygen partial pressure can be known from the sensor output.

The MPU 54a executes an operation according to the program and data stored in the memory 54b, and sets it in the output port 54d. The output port 54d is connected to the fuel injector 4
2. Connected to the igniter 30a and other control devices to apply control signals.

Hereinafter, a portion of the fuel injection control in the operation of the control circuit 54 will be described with reference to a flowchart. FIG. 5 shows a fuel injection routine, and this routine is executed by detecting a certain crank angle before the fuel injection of the cylinder from which fuel is to be injected. For example, if fuel injection is performed during the intake stroke, it is executed by detecting 60 ° CA before the intake top dead center. This detection is performed by the 7th from the first crank angle sensor 56.
It can be known by the value of the counter that is cleared by the arrival of the 20 ° CA signal and is incremented each time the 30 ° CA signal from the second crank angle sensor 58 arrives. In step 100, the basic injection time Tp is calculated from the engine speed NE and the intake pipe pressure PM. 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 coverage the stoichiometric air-fuel ratio with respect to the amount of fresh air introduced into the internal combustion engine. Since the fresh air amount corresponds to the intake pipe pressure PM in a state where no gas other than fresh air having the EGR gas degree is introduced, the fuel injection amount is uniquely determined by the intake pipe pressure. The memory 54b is configured with a map of data of the basic control injection time Tp for obtaining the stoichiometric air-fuel ratio for each combination of the engine speed NE and the intake pipe pressure PM. The MPU 54a has a second crank angle sensor 58.
A known interpolating calculation is executed based on the current engine speed NE notified from the interval of the 30 ° CA signal and the value of the intake pipe pressure PM, whereby the basic fuel injection time Tp is calculated.

In step 101, the reference value of the oxygen partial pressure PO ₂ is calculated from the intake pressure PM and the rotational speed NE. When only fresh air is introduced into the engine and EGR gas is not contained, it can be assumed that the oxygen partial pressure has a certain value when the intake pipe pressure PM and the rotational speed NE are determined. In the memory, for many combinations of intake pipe pressure and rotational speed, the reference oxygen partial pressure PO assumed when no gas other than fresh air is introduced into the engine
The value of ₂₀ is stored, and the map value PC ₂₀ of the reference oxygen partial pressure corresponding to the combination of the intake pressure PM currently measured and the engine speed NE is calculated by interpolation calculation.

At step 102, partial pressure map value PC ₂₀ and oxygen sensor 7
A difference ΔPO ₂ from the actually measured current valve pressure value PO ₂ which is actually measured by 0 is calculated. This value corresponds to the amount of EGR gas or blow-by gas other than fresh air currently introduced into the engine. In step 103, the correction coefficient FPO _{2 for the} fuel injection amount is calculated from ΔPO ₂ . The correction coefficient FPO ₂ is for correcting the fuel injection amount according to the amount of gas other than fresh air and maintaining the air-fuel ratio at the set value regardless of these influences. The relationship between ΔPO ₂ and FPO ₂ is as shown in Fig. 7. The relationship is stored as a map in the memory, and the correction coefficient FPO ₂ is calculated according to the current oxygen partial pressure by the interpolated acid. Become.

In step 104, the final fuel injection amount Tau is calculated by the following equation: Tau = Tp × FPO ₂ × α + β. By multiplying this by FPO ₂ , the influence of EGR etc. will be eliminated. Since α and β are correction coefficients and correction amounts, which are not directly related to the present invention, detailed description thereof is omitted. Calculation of a feedback correction coefficient by a signal from the intake oxygen sensor 68 and a water temperature correction coefficient by a water temperature signal from the water temperature sensor 64 In addition, various correction calculation processes that are added to the basic fuel injection time Tp, such as acceleration correction, are shown.

In step 105, the fuel injection start time t _i is calculated. Although the fuel injection start timing is determined variously according to the characteristics of the engine, for example, it is necessary to determine the fuel injection start timing so that the fuel injection ends substantially in synchronization with the end of the intake stroke. Therefore, the fuel injection start timing changes depending on the fresh air amount and the rotation speed. The engine speed NE is stored in the memory 54b,
A data map of the crank angle from the intake top dead center at which fuel injection is started is stored in combination with the intake pipe pressure PM. The MPU 54a is the output P of the intake pipe pressure sensor 55.
And M, is calculated from the 30 ° CA pulse signal the engine speed NE to be measured from the distance of the second crank angle sensor 58, the fuel injection start time t _i as the time from the current time t _o (FIG. 8 reference).

In step 106, the injection end time t _e is the injection start time t _i and the fuel injection time Tau calculated in step 102.
Is added. Step 108 indicates the permission of the time match interrupt routine, step 110 in the fuel injection start time t _i is set to the fuel injection control compare register (not shown).

Figure 6 is a time match interrupt routine, the compare register is time now starts running and it is determined that matches the fuel injection start time t _i. The step indicates prohibition of interruption by the compare register, and in step 114, the fuel injection end time t _e is set in the compare register. Therefore, when the current time coincides with the fuel injection end time t _e , the fuel injection by the injector 42 is stopped.

Although the application of the present invention to fuel injection has been described above, the present invention can also be applied to ignition timing control. Measure
Basic ignition timing SA ₀ is engine speed NE and intake pipe pressure PM
It is calculated from Here, the basic ignition next period represents the ignition next period (MBT) at which the maximum torque is obtained with respect to the fresh air amount introduced into the internal combustion engine when the rotational speed is fixed, as an angle from the compression top dead center. When the fresh air amount changes due to EGR, the MBT differs even if the intake pipe pressure is the same. However, assuming that only fresh air gas is introduced, the oxygen partial pressure estimated from the intake pipe pressure and the engine speed is changed. The optimum ignition timing can be obtained by modifying the ignition timing according to the difference ΔPO ₂ between the value PC ₂₀ and the actually detected oxygen partial pressure PO ₂ . The method of ignition control is obvious to those skilled in the art, and therefore its explanation is omitted.

〔The invention's effect〕

According to the present invention, in the DJ system that calculates the control value of the control factor that is controlled according to the fresh air amount introduced into the engine, such as the fuel injection amount and the ignition timing, from the intake pipe pressure and the engine speed, the intake system The pipe is equipped with oxygen detection means for detecting the oxygen partial pressure, and when the gas other than fresh air is not introduced, it is actually detected as the value of the reference oxygen partial pressure assumed from the intake pressure and the engine speed. By correcting the control value based on the difference with the oxygen partial pressure value, it is possible to perform accurate engine control regardless of the influence of gases other than new gas.

[Brief description of drawings]

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 sectional view of an intake oxygen sensor for measuring the oxygen partial pressure in the intake pipe. FIG. 4 is a characteristic diagram of oxygen partial pressure with respect to the total pressure of the oxygen sensor of FIG. 5 and 6 are flowcharts of the fuel injection routine. FIG. 7 is a graph showing the relationship between the oxygen partial pressure and the fuel injection amount correction coefficient. FIG. 8 is a view for explaining the timing of fuel injection operation. 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 55 ... Intake pipe pressure sensor 64 ... Water temperature sensor 66 ... Intake air temperature sensor 68 ... Exhaust side oxygen sensor 70 ... Intake side oxygen sensor

Claims (1)

[Claims] Claim: What is claimed is: 1. An engine speed detecting means for detecting a speed of an internal combustion engine; an intake pipe pressure detecting means for detecting an intake pipe pressure, which is arranged in an intake system downstream of a throttle valve of the internal combustion engine; A control device for an internal combustion engine, which is arranged in an intake system downstream of a valve and has an oxygen detecting means for detecting an oxygen partial pressure in all gases sucked into the engine, the engine being detected by the rotational speed detecting means. Control value calculating means for calculating a control value of a control factor for controlling the internal combustion engine based on the rotational speed and the intake pipe pressure detected by the intake pipe pressure detecting means, and a gas other than fresh air is not introduced into the engine. A reference oxygen partial pressure calculation means for calculating the value of the reference oxygen partial pressure assumed based on the engine speed and the intake pipe pressure; and an oxygen partial pressure calculated by the reference oxygen partial pressure calculation means, Oxygen detection means Correction means for correcting the calculated control value based on the difference from the actual detected oxygen partial pressure, and control factor control means for controlling the control factor by the corrected control value. Control device for internal combustion engine.