JPH116436A - Control device for compression ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To properly control an ignition timing through self-ignition, in a compression ignition engine. SOLUTION: When compression ignition control to effect self-ignition through suspension of forced ignition by an ignition plug is indicated, a target ignition timing τTAGT is set (S92-S95) based on an engine running state and an ignition timing τA detected based on an ion current and the target ignition timing τTAGT are compared with each other (S96, S97). When the ignition timing τA is closer to the lead angle side than the target ignition timing τTAGT (τA<τTAGT-α), an GR factor by an EGR valve is controlled to a decrease (S98), and by reducing an intake air temperature, the temperature of air-fuel mixture in a combustion chamber is increased, and an ignition timing by a self-ignition is delayed. Further, when the ignition timing τA is closer to the delay angle side than the target ignition timing τTAGT (τA>=τTAGT+α), the EGR factor by the EGR valve is controlled to a decrease (S99), by increasing an intake air temperature, the temperature of air fuel mixture in the combustion chamber is increased, an ignition timing by self ignition is advanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for a compression ignition engine that performs self-ignition in a predetermined operating region without using spark ignition due to discharge of a spark plug, and more particularly, to appropriately control the ignition timing by self-ignition. The present invention relates to a control device for a compression ignition engine that can perform the control.

[0002]

2. Description of the Related Art Conventionally, a lean burn engine which operates at a lean air-fuel ratio to improve fuel economy by reducing pumping loss and improving theoretical thermal efficiency has been employed.
However, if the air-fuel ratio is further made lean and operation is performed with extremely lean combustion for the purpose of greatly improving fuel efficiency, thermal efficiency will deteriorate due to ignition mistake (misfire) or combustion delay.

To cope with this, the temperature of the air-fuel mixture in the combustion chamber is increased by increasing the compression ratio of the engine or by heating the intake air, etc., and in a predetermined operating region, spark ignition due to discharge of the spark plug, that is, forced ignition is performed. In addition, a compression ignition engine has been proposed which performs self-ignition at the end of the compression stroke or near the top dead center (so-called self-ignition) (Preprints 951 / 309-312 of the Society of Automotive Engineers of Japan / Academic Lecture Meeting).
Page "Study on 80 Gasoline Premixed Compression Ignition Engine"
(9534702) / Published May 1995, or
2-157220).

[0004]

However, in the above-mentioned compression ignition engine, the temperature of the air-fuel mixture in the engine combustion chamber, which determines the ignition timing at the time of self-ignition, largely depends on the engine operating conditions, atmospheric conditions, and the like.

[0005] Therefore, the optimum ignition timing is not always obtained at the time of self-ignition, and not only the thermal efficiency is reduced, but in an extreme case, knocking is caused to adversely affect the engine.

The present invention has been made in view of the above circumstances, and has as its object to provide a control device for a compression ignition engine capable of appropriately controlling the ignition timing by self-ignition.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, in a predetermined operating region, the compression stroke is not terminated at the end of the compression stroke or near the top dead center regardless of spark ignition caused by discharge of a spark plug. In a control apparatus for a compression ignition engine that performs self-ignition, as shown in the basic configuration diagram of FIG. Ignition timing detection means for detecting the timing, target ignition timing setting means for setting a target ignition timing based on the engine operating state,
An intake heating control means for controlling intake heating means for heating intake air according to a result of comparison between the ignition timing and the target ignition timing is provided.

According to a second aspect of the present invention, in the first aspect of the invention, the intake air heating means is interposed in the exhaust gas recirculation passage for recirculating exhaust gas of the engine to the intake system, and in the exhaust gas recirculation passage. An exhaust gas recirculation amount adjusting valve for adjusting the exhaust gas recirculation rate, wherein the intake air heating control means is configured to control the exhaust gas recirculation by the exhaust gas recirculation amount adjusting valve when the ignition timing is advanced from the target ignition timing. When the ignition timing is retarded from the target ignition timing, the exhaust gas recirculation rate by the exhaust gas recirculation amount adjusting valve is increased.

According to a third aspect of the present invention, in the second aspect of the present invention, the intake air heating control means uses the exhaust gas recirculation amount adjusting valve when the temperature of the recirculated exhaust gas or the exhaust gas reaches a predetermined temperature. The exhaust gas recirculation rate is increased by a predetermined amount to shift from spark ignition by discharge of the spark plug to self-ignition.

According to a fourth aspect of the present invention, in the second or third aspect of the present invention, the intake heating control means includes:
When the ignition timing is retarded from the target ignition timing and the valve opening of the exhaust gas recirculation adjusting valve reaches a limit value, the exhaust gas recirculation rate by the exhaust gas recirculation amount adjusting valve is reduced by a predetermined amount, It is characterized by shifting from self-ignition to spark ignition by discharge of a spark plug.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the intake air heating means includes a heat exchanger for performing heat exchange with exhaust gas or heat generated by the engine, and a part of intake air flowing through the intake system. A heated intake passage which is introduced into the heat exchanger and returns the heated intake air after the heat exchange by the heat exchanger to the intake system; and a flow rate of the heated intake air which is interposed in the heated air passage and flows through the heated intake passage. The intake air heating control means adjusts the ignition intake timing by decreasing the heating intake air flow rate by the heating intake air amount adjustment valve when the ignition timing is advanced from the target ignition timing. When the ignition timing is retarded from the target ignition timing, the heating intake air flow rate by the heating intake air amount adjusting valve is increased.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the intake air heating control means increases the heated intake air flow rate by the heated intake air amount adjusting valve when the engine temperature reaches a predetermined temperature. It is characterized in that a transition from spark ignition by discharge of a spark plug to self-ignition is made.

According to a seventh aspect of the present invention, in the fifth aspect or the sixth aspect, the intake air heating control means includes:
When the ignition timing is on the retard side of the target ignition timing and the valve opening of the heated intake air amount adjustment valve reaches a limit value, the heated intake air flow rate by the heated intake air amount adjustment valve is reduced, and ignition is performed from self-ignition. It is characterized by shifting to spark ignition by discharge of the plug.

According to an eighth aspect of the present invention, in the first aspect of the invention, the intake heating means is a heater interposed in an intake system, and the intake heating control means sets the ignition timing to a target ignition timing. When the ignition timing is more advanced than the target ignition timing, the amount of heat generated by the heater is decreased. When the ignition timing is more retarded than the target ignition timing, the amount of heat generated by the heater is increased.

According to a ninth aspect of the present invention, in the invention of the eighth aspect, when the engine temperature reaches a predetermined temperature, the intake heating control means increases the amount of heat generated by the heater.
It is characterized by shifting from spark ignition by discharge of the spark plug to self-ignition.

According to a tenth aspect of the present invention, in the invention of the eighth or ninth aspect, the intake heating control means is configured to determine that the ignition timing is on the retard side of the target ignition timing and the heater heat generation value is at a limit value. , The amount of heat generated by the heater is reduced to shift from self-ignition to spark ignition by discharge of the spark plug.

According to the eleventh aspect, in the fourth, seventh, and tenth aspects, the limit value is
It is set according to at least one of the engine load and the engine speed.

According to a twelfth aspect of the present invention, in the first to eleventh aspects, the target ignition timing is
It is set according to at least one of the engine load and the engine speed.

According to a thirteenth aspect of the present invention, in the first aspect of the invention, the target ignition timing is
It is characterized by being corrected according to the engine temperature.

That is, according to the first aspect of the present invention, the air-fuel mixture in the combustion chamber self-ignites, the ignition timing is detected based on the ion current flowing through the ions due to the presence of the ions of the combustion gas, and the engine operating state is detected. The target ignition timing is set based on. Then, according to the result of comparison between the ignition timing and the target ignition timing, the intake air heating means for heating the intake air is controlled to control the intake air temperature. Therefore, by controlling the intake air temperature, it is possible to obtain the temperature of the air-fuel mixture in the engine combustion chamber that is appropriate for obtaining the target ignition timing corresponding to the engine operating state. As a result, the engine operating conditions and atmospheric conditions change. Also, the ignition timing by self-ignition,
It is possible to control the target ignition timing, that is, the optimal timing, which matches the engine operating state.

In this case, according to the second aspect of the present invention, as the intake air heating means, an exhaust gas recirculation passage for recirculating exhaust gas of the engine to the intake system, and an exhaust gas recirculation rate interposed in the exhaust gas recirculation passage are provided. An exhaust gas recirculation device including an exhaust gas recirculation amount adjusting valve to be adjusted is employed. When the ignition timing is more advanced than the target ignition timing, the exhaust gas recirculation rate is controlled to decrease by the exhaust gas recirculation amount adjusting valve to lower the intake air temperature, thereby reducing the temperature of the air-fuel mixture in the engine combustion chamber. The ignition timing by self-ignition is retarded. Also, when the ignition timing is more retarded than the target ignition timing,
By increasing the exhaust gas recirculation rate by the exhaust gas recirculation amount adjusting valve to increase the intake air temperature, the temperature of the air-fuel mixture in the engine combustion chamber is increased, and the ignition timing by self-ignition is advanced.

According to the third aspect of the present invention, when the temperature of the recirculated exhaust gas or the exhaust gas reaches a predetermined temperature, the exhaust gas recirculation rate by the exhaust gas recirculation amount adjusting valve is increased by a predetermined amount, so that the ignition plug A transition is made from spark ignition by discharge to self-ignition.

Further, according to the present invention, when the ignition timing is retarded from the target ignition timing and the opening degree of the exhaust gas recirculation amount adjusting valve reaches a limit value, the exhaust gas recirculation amount is reduced. The exhaust gas recirculation rate by the regulating valve is reduced by a predetermined amount, and the mode is shifted from self-ignition to spark ignition by discharge of the spark plug.

According to a fifth aspect of the present invention, as the intake air heating means, a heat exchanger for exchanging heat with exhaust gas or heat generated by the engine, and a part of the intake air flowing through the intake system is introduced into the heat exchanger. A heated air intake passage for returning heated air after heat exchange by the heat exchanger to the intake system, a heated air intake amount adjusting valve interposed in the heated air passage and adjusting a flow rate of the heated air flowing through the heated air intake passage; An intake air heating device consisting of When the ignition timing is more advanced than the target ignition timing, the temperature of the air-fuel mixture in the engine combustion chamber is reduced by controlling the amount of heated intake air by the heated intake air amount adjusting valve to decrease the intake air temperature. The ignition timing by self-ignition is retarded. Further, when the ignition timing is retarded from the target ignition timing, the heating intake air flow rate is controlled to be increased by the heating intake air amount adjustment valve to increase the intake air temperature, thereby increasing the temperature of the air-fuel mixture in the engine combustion chamber, The ignition timing by self-ignition is advanced.

According to the sixth aspect of the present invention, when the engine temperature reaches a predetermined temperature, the flow rate of the heated intake air by the heated intake air amount adjusting valve is increased to shift from spark ignition by discharge of the spark plug to self-ignition. .

Further, in the present invention, when the ignition timing is on the retard side of the target ignition timing and the valve opening of the heated intake air amount adjustment valve reaches a limit value, the heated air intake amount adjustment valve , The flow rate of the heated intake air is reduced to shift from self-ignition to spark ignition by discharge of the spark plug.

According to the present invention, a heater interposed in the intake system is employed as the intake heating means. And
When the ignition timing is more advanced than the target ignition timing, the amount of heat generated by the heater is controlled to decrease to lower the intake air temperature, thereby lowering the temperature of the air-fuel mixture in the engine combustion chamber, and reducing the ignition timing due to self-ignition. Retard. When the ignition timing is more retarded than the target ignition timing, the amount of heat generated by the heater is controlled to increase to increase the intake air temperature, thereby increasing the temperature of the air-fuel mixture in the engine combustion chamber, and causing the ignition timing due to self-ignition. Is advanced.

According to the ninth aspect of the present invention, when the engine temperature reaches a predetermined temperature, the calorific value of the heater is increased to shift from spark ignition by discharge of the spark plug to self-ignition.

Further, in the invention according to claim 10, when the ignition timing is on the retard side of the target ignition timing and the calorific value of the heater reaches a limit value, the calorific value of the heater is reduced to reduce the self-ignition. Shift to spark ignition by discharge of the spark plug.

In the eleventh aspect, the limit value is set according to at least one of an engine load and an engine speed.

In the twelfth aspect, the target ignition timing is set in accordance with at least one of the engine load and the engine speed. In the invention according to claim 13, the target ignition timing is corrected according to the engine temperature.

[0032]

Embodiments of the present invention will be described below with reference to the drawings. 2 to 18 show a first embodiment of the present invention.

First, a schematic configuration of the compression ignition engine will be described with reference to FIG. Reference numeral 1 denotes a compression ignition engine for a vehicle such as an automobile as an example of the compression ignition engine. In the figure, a horizontal opposed 4-cycle 4-cylinder gasoline engine is shown.

In the present embodiment, the compression ignition engine (hereinafter simply referred to as "engine") 1 is an exhaust gas recirculation device 25 described below as an example of intake air heating means.
And a high compression ratio (for example, in the present embodiment, compression ratio = 11 to 12).
This raises the temperature of the air-fuel mixture in the combustion chamber, and performs self-ignition at the end of the compression stroke or near the top dead center in a predetermined operating region without spark ignition by discharge of the spark plug, that is, forced ignition. .

A cylinder head 2 is provided in each of the left and right banks of a cylinder block 1a of the engine 1. Each cylinder head 2 has an intake port 2a and an exhaust port 2b.

In the intake system of the engine 1, an intake manifold 3 is communicated with each intake port 2a, and a throttle chamber 5 is communicated with the intake manifold 3 via an air chamber 4 in which intake passages of respective cylinders are gathered. An air cleaner 7 is attached to the upstream side of the throttle chamber 5 via an intake pipe 6, and the air cleaner 7 is connected to the air intake chamber 8.

The throttle chamber 5 is provided with a throttle valve 5a linked to an accelerator pedal. The intake pipe 6 is connected to a bypass passage 9 that bypasses the throttle valve 5a.
At the time of idling, the bypass passage 9 depends on the valve opening.
An idle speed control valve (ISC valve) 10 for controlling the idle speed by adjusting the amount of bypass air flowing through the engine is provided.

Further, an injector 11 is disposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3. The injector 11 has a fuel supply path 12
The fuel tank 13 is provided with an in-tank type fuel pump 14. The fuel from the fuel pump 14 is pressure-fed to the injector 11 and the pressure regulator 16 via a fuel filter 15 interposed in the fuel supply passage 12, and is returned from the pressure regulator 16 to the fuel tank 13 to be returned to the fuel tank 13. The fuel pressure to 11 is regulated to a predetermined pressure.

On the other hand, an ignition plug 18 for exposing the discharge electrode 18a at the tip end to the combustion chamber 17 is attached to each cylinder of the cylinder head 2, and an ignition coil provided for each cylinder is attached to the ignition plug 18. An igniter 20 is connected via 19.

In the exhaust system of the engine 1, an exhaust pipe 22 is communicated with a collection portion of an exhaust manifold 21 which communicates with each exhaust port 2b of the cylinder head 2, and a catalytic converter 23 is interposed in the exhaust pipe 22. And is communicated with the muffler 24.

On the other hand, the engine 1 has an EGR device 2 for recirculating exhaust gas (hereinafter abbreviated as “EGR”).
5 are provided. The EGR device 25 is connected to an EGR passage 26 for recirculating exhaust gas from at least one of the exhaust ports 2b of the cylinder head 2 to the air chamber 4 downstream of the throttle valve 5a.
A stepping motor drive type EGR valve 27 driven by a built-in stepping motor is interposed as an example of the exhaust gas recirculation amount adjusting valve. The control amount of the EGR valve 27 is calculated by an electronic control unit 50 (see FIG. 18) described later. Then, the stepping motor operates according to the drive signal output from the electronic control device 50 in accordance with the control amount, and the valve opening of the EGR valve 27 is adjusted by the operation of the stepping motor.

In this embodiment, when the control amount is 00H, the EGR valve 27 is fully closed and the exhaust gas is recirculated, that is, EGR is stopped. When the control amount is FFH, the EGR valve 27 is fully opened. Becomes And the control amount is 00
H to FFH, and the valve opening of the EGR valve 27 is adjusted in accordance with the drive signal corresponding to the control amount.
The R amount, that is, the EGR rate is controlled.

Next, sensors for detecting the operating state of the engine will be described.

Reference numeral 30 denotes an absolute pressure sensor, which selectively communicates with the air chamber 4 and the atmosphere in accordance with switching of the intake pipe pressure / atmospheric pressure switching solenoid valve 31, and which is connected to the actual intake pipe downstream of the throttle valve 5a. As the pressure, the intake pressure in the air chamber 4 and the atmospheric pressure are detected by absolute pressure. Further, a thermal intake air amount sensor 32 using a hot wire or a hot film is interposed immediately downstream of the air cleaner 7 in the intake pipe 6, and a throttle valve 5a provided in the throttle chamber 5 is provided. A throttle sensor 33 having a built-in throttle opening sensor 33a and an idle switch 33b that is turned on when the throttle valve 5a is fully closed is provided in series.

The cylinder block 1a of the engine 1
A knock sensor 34 is attached to the cooling water passage 3 communicating the left and right banks of the cylinder block 1a.
5, a cooling water temperature sensor 36 is provided, and an O2 sensor 3 is provided upstream of the catalytic converter 23 as an example of an air-fuel ratio sensor.
7 are provided.

Further, an EGR gas temperature sensor 38 for detecting the temperature of the recirculated exhaust gas (hereinafter referred to as "EGR gas") flowing through the EGR passage 26 is provided in the EGR passage 26.

The crankshaft 39 of the engine 1
A crank angle sensor 41 is provided on an outer periphery of a crank rotor 40 which is axially mounted on the cam shaft 42. Further, a cam rotor 43 connected to a cam shaft 42 which makes a half rotation with respect to the crank shaft 39 has a cam angle for cylinder discrimination. A sensor 44 is provided opposite.

As shown in FIG. 15, the crank rotor 40 has projections 40a, 40b, and 40c formed on the outer periphery thereof, and these projections 40a, 40b, and 40c are connected to the cylinders (# 1 and # 2 cylinders). (# 3, # 4 cylinders) before compression top dead center (BTDC) θ1, θ2, θ3.
In the present embodiment, θ1 = 97 ° CA, θ2 = 65
° CA, θ3 = 10 ° CA.

As shown in FIG. 16, on the outer periphery of the cam rotor 43, protrusions 43a, 43b,
43c is formed, and the protrusion 43a is formed at a position θ4 after the compression top dead center (ATDC) of the # 3 and # 4 cylinders.
b is composed of three protrusions, and the first protrusion is A of the # 1 cylinder.
It is formed at the position of TDCθ5. Further, the projection 43c
Is composed of two projections, and the first projection is the AT of the # 2 cylinder.
It is formed at the position of DCθ6. In the present embodiment, θ4 = 20 ° CA, θ5 = 5 ° CA, θ6 = 20 °
CA.

As shown in the time chart of FIG. 11, the crank rotor 40 and the cam rotor 43 are rotated by the rotation of the crankshaft 39 and the camshaft 42 in accordance with the operation of the engine, and each projection of the crank rotor 40 is Detected by the angle sensor 41 and detected from the crank angle sensor 41 by θ1, θ2, θ3 (BTDC97
°, 65 °, 10 °) of the engine 1
Output every 1/2 rotation (180 ° CA). On the other hand, θ3
Each protrusion of the cam rotor 43 is detected by the cam angle sensor 44 between the crank pulse and the θ1 crank pulse, and the cam angle sensor 44 outputs a predetermined number of cam pulses.

Then, an electronic control unit 50 described later (FIG. 18)
), The engine speed NE is calculated based on the input interval time Tθ of the crank pulse output from the crank angle sensor 41, and the combustion stroke of each cylinder is determined (for example, # 1 cylinder → # 3 cylinder → # 2 cylinder → # 4 cylinder)
Based on the pattern of the cam pulse from the cam angle sensor 44 and the value counted by the counter, the cylinders such as the fuel injection target cylinder and the ignition target cylinder are determined.

In FIG. 14, reference numeral 45 indicates that when the air-fuel mixture in the combustion chamber 17 is ignited and the flame causes combustion gas ions to be present in the discharge gap between the discharge electrodes 18a of the ignition plug 18, this ion Is an ion current detection circuit for detecting an ion current flowing through the circuit. In the present embodiment, the ion current detection circuit 45 is provided only for a specific cylinder (for example, # 1 cylinder), but the ion current detection circuit is provided for all cylinders. Is also good.

As shown in FIG. 17, the ionic current detection circuit 45 uses a high voltage power supply 46 to supply a high voltage (for example, 50 V).
0V) is supplied to the high-voltage power supply 46.
Between the secondary side of the ignition coil 19 and the connection between the discharge electrode 18a of the ignition plug 18 and the ion current detection resistor R
And a diode D for backflow prevention is connected in series, and a voltage sensor 45a is connected in parallel to the ion current detection resistor R. In FIG. 17, reference numeral 60 denotes a power relay, which is turned on by turning on an ignition switch (indicated by IG in FIG. 17), and power is supplied to the electronic control unit 50, the ignition coil 19 and the like.

Here, when a DC voltage is applied to the ignition plug 18 from the high-voltage power supply 46 via the ion current detection circuit 45, normal ignition occurs and the flame causes ions of the combustion gas to be present between the discharge electrodes 18a of the ignition plug 18. Then, an ion current flows through the ions. Therefore, when the ion current flows, a potential difference is generated between both terminals of the ion current detection resistor R of the ion current detection circuit 45, and the ion current can be detected by detecting the potential difference with the voltage sensor 45a. .

Incidentally, this ion current detecting circuit is as follows.
It is well-known from Japanese Patent Application Laid-Open No. 6-241108.

FIG. 12 shows a time chart of the output voltage of the voltage sensor 45a of the ion current detection circuit 45, that is, the ion current detected by the ion current detection circuit 45. When an ignition signal having a pulse waveform is output from the electronic control device 50 via the igniter 20 (see FIG. 11),
A primary current flows through the primary side of the ignition coil 19. And
The fall of the ignition signal cuts off the primary current (dwell cut), induces a high-voltage secondary voltage on the secondary side of the ignition coil, and causes insulation breakdown between the discharge electrodes 18a of the ignition plug 18 to cause spark discharge (spark). Is performed. Then, an ionic current flows due to the ignition spark.

It should be noted that an ignition signal is not output during compression ignition control in which self-ignition is performed at the end of the compression stroke or near the top dead center regardless of spark ignition by discharge of the ignition plug 18, that is, forced ignition (FIG. 11). At this time, no ion current is generated by the ignition spark.

Then, when the air-fuel mixture in the combustion chamber 17 is ignited by spark ignition or self-ignition, and when the combustion gas ions are present between the discharge electrodes 18a of the ignition plug 18 by the flame, the combustion gas is ignited through these ions. Ion current flows.

Accordingly, this ion current is detected by the ion current detection circuit 45, and the output voltage of the voltage sensor 45a of the ion current detection circuit 45 is input to the electronic control unit 50.
By monitoring this voltage value in the electronic control unit 50, it is possible to determine the ignition timing.

Next, the circuit configuration of the electronic control system will be described.

Calculation of control amounts for actuators such as the EGR valve 27, the injector 11, the ignition plug 18, the ISC valve 10, etc., output of a drive signal corresponding to the control amounts, that is, EGR control including intake air temperature control, fuel injection Engine control such as control, ignition control, and idle speed control is performed by an electronic control unit (ECU) 50 shown in FIG.

The ECU 50 comprises a CPU 51, a ROM 5
2, RAM53, backup RAM54, counter
A timer group 55 and an I / O interface 56 are mainly configured by a microcomputer connected to each other via a bus line, and are connected to the constant voltage circuit 57 for supplying a stabilized power to each unit, and to the I / O interface 56. And a peripheral circuit such as an A / D converter 59.

The counter / timer group 55 includes various counters such as a free-run counter, a counter for counting the input of a cam angle sensor signal (cam pulse), a fuel injection timer, an ignition timer, and a timer for generating a periodic interrupt. A timer for periodic interruption, a timer for measuring an input interval of a crank angle sensor signal (crank pulse), a timer for measuring an elapsed time after starting the engine, a timer for measuring a post-start time, a timer for measuring an ignition timing for measuring an ignition timing, and Various timers such as a watchdog timer for monitoring a system abnormality are generically referred to for convenience, and other various software counter / timers are used.

The constant voltage circuit 57 is connected to a battery 61 via a first relay contact of a power relay 60 having two relay contacts, and a relay coil of the power relay 60 is connected to an ignition switch 62 by the battery 61.
Connected through. Further, the constant voltage circuit 57
Is connected directly to the battery 61. When the ignition switch 62 is turned on and the contact of the power supply relay 60 is closed, power is supplied to each part in the ECU 50, while the ignition switch 62 is turned on and off. Instead, the backup power is always supplied to the backup RAM 54. Further, the fuel pump 14 is connected to the battery 61 via a relay contact of a fuel pump relay 63. A power supply line for supplying power from the battery 51 to each actuator including the ignition coil 19 is connected to a second relay contact of the power supply relay 60.

The input ports of the I / O interface 56 are connected to the idle switch 33 b and the knock sensor 3.
4. A crank angle sensor 41, a cam angle sensor 44, a vehicle speed sensor 47 for detecting a vehicle speed, and a starter switch 48 for detecting a starting state are connected, and further via the A / D converter 59. And absolute pressure sensor 3
0, intake air amount sensor 32, throttle opening sensor 33
a, a coolant temperature sensor 36, an O2 sensor 37, an EGR gas temperature sensor 38, and a voltage sensor 45a are connected, and a battery voltage VB is input and monitored.

On the other hand, the output port of the I / O interface 56 is connected to the relay coil of the fuel pump relay 63, the ISC valve 10, the injector 11, the EGR valve 2
7, and the intake pipe pressure / atmospheric pressure switching solenoid valve 31 are connected via the drive circuit 58, and the igniter 20 is connected.

In accordance with the control program stored in the ROM 52, the CPU 51 processes the detection signals from the sensors and switches, which are input via the I / O interface 56, the battery voltage, and the like, and stores them in the RAM 53. Based on various data, various learning value data stored in the backup RAM 54, fixed data stored in the ROM 52, and the like, the control amount for the EGR valve 27, the fuel injection amount, the ignition timing, the duty of the drive signal for the ISC valve 10, A ratio is calculated to perform engine control such as EGR control including intake air temperature control, fuel injection control, ignition control, idle speed control, and the like.

In such an engine control system, EC
In U50, the air-fuel mixture in the combustion chamber 17 self-ignites, the ignition timing τA is detected based on the ion current flowing through the combustion gas due to the presence of the ions of the combustion gas, and based on the engine operating state. To set the target ignition timing τTAGT. Then, the EGR valve 27 is controlled according to the comparison result between the ignition timing τA and the target ignition timing τTAGT, and the intake air temperature is controlled by the recirculated exhaust gas. That is, by controlling the intake air temperature, it is possible to obtain the temperature of the air-fuel mixture in the engine combustion chamber 17 that is appropriate for obtaining the target ignition timing τTAGT corresponding to the engine operating state.
Even if the engine operating conditions, atmospheric conditions, and the like change, the ignition timing τA due to self-ignition can be controlled to the target ignition timing τTAGT suitable for the engine operation state, that is, the optimal ignition timing.

More specifically, in this embodiment,
When the ignition timing τA is more advanced than the target ignition timing τTAGT, the EGR rate is controlled by the EGR valve 27 to decrease the intake air temperature, thereby lowering the temperature of the air-fuel mixture in the combustion chamber 17, The ignition timing by ignition is retarded. When the ignition timing τA is on the retard side of the target ignition timing τTAGT, the EGR rate is controlled by the EGR valve 27 to increase the intake air temperature, so that the temperature of the air-fuel mixture in the combustion chamber 17 is increased. The ignition timing by self-ignition is advanced.

When the EGR gas temperature reaches a predetermined temperature and it is determined that it is possible to shift to self-ignition by increasing the intake air temperature by EGR, the EGR valve 27
Is increased by a predetermined amount, the intake air temperature is controlled to rise, the temperature of the air-fuel mixture in the combustion chamber 17 is raised, and the spark plug 18 discharges to shift from self-ignition to spark ignition.
That is, when the EGR gas temperature rises and the ignition timing τA at the time of self-ignition can be controlled by the intake air temperature control by the EGR, a transition is made from spark ignition by discharge of the spark plug 18 to self-ignition.

Further, at the time of self-ignition, when the ignition timing τA is on the retard side of the target ignition timing τTAGT and the opening degree of the EGR valve 27 reaches the limit value, the intake air temperature control by EGR becomes impossible and the self-ignition becomes impossible. When it is determined that it is no longer possible to control the ignition timing of the ignition, the RG by the EGR valve 27
The R rate is reduced by a predetermined amount, and the transition from self-ignition to spark ignition due to discharge of the spark plug 18 is made.

The target ignition timing τTAGT is set according to at least one of the engine load and the engine speed, and is further corrected and set according to the engine temperature.

The limit value is set in accordance with at least one of the engine load and the engine speed.

That is, the ECU 50 realizes the functions of the ignition timing detecting means, the target ignition timing setting means, and the intake heating control means according to the present invention.

Hereinafter, the control process according to the present invention executed by the ECU 50 will be described with reference to the flowcharts shown in FIGS.

First, the ignition switch 62 is turned on.
When the power is supplied to the ECU 50, the system is initialized, and each flag, each counter, and each timer, excluding data such as various learning values stored in the backup RAM 54, are initialized. Then, when the starter switch 48 is turned on and the engine is started, a cylinder discrimination / engine speed calculation routine shown in FIG. 2 is executed every time a crank pulse is input from the crank angle sensor 41.

In this cylinder discriminating / engine speed calculating routine, when the crank rotor 40 rotates in response to the engine operation and the crank pulse from the crank angle sensor 41 is input, first in step S1, the crank input at this time is input. Whether the pulse corresponds to the crank angle of θ1, θ2, or θ3 is identified based on the input pattern of the cam pulse from the cam angle sensor 44. In step S2, the current compression is determined based on the input pattern of the crank pulse and the cam pulse. The cylinders such as the stroke cylinders, that is, the cylinders to be ignited, the cylinders to be ignited, and the cylinders to be fueled are determined.

That is, as shown in the time chart of FIG. 11, for example, if there is a cam pulse input between the previous crank pulse input and the present crank pulse input, the current crank pulse is θ1 crank pulse. It can be identified as a pulse, and the crank pulse input next time can be identified as a θ2 crank pulse.

If there is no cam pulse input between the previous and current crank pulse inputs and there is a cam pulse input between the last and previous crank pulse inputs, the current crank pulse can be identified as the θ2 crank pulse, and The input crank pulse can be identified as a θ3 crank pulse. Further, when there is no cam pulse input between the previous and current times and between the last and last crank pulse inputs, the currently input crank pulse can be identified as the θ3 crank pulse, and the next input crank pulse is It can be identified as a θ1 crank pulse.

Further, three cam pulses are input between the previous and current crank pulse inputs (θ corresponding to the projection 43b).
(5 cam pulses), the next compression top dead center is # 3 cylinder, the current compression stroke cylinder (ignition target cylinder, ignition target cylinder) is # 3 cylinder, and the next fuel injection target cylinder is two cylinders later. # 4 cylinder. When two cam pulses are input between the previous and current crank pulse inputs (θ6 cam pulse corresponding to the projection 43c), the next compression top dead center is # 4 cylinder, and the current compression stroke cylinder, ignition target cylinder , The cylinder to be ignited can be determined to be the # 4 cylinder, and the cylinder to be fuel injected can be determined to be the # 3 cylinder.

One cam pulse is input between the previous and current crank pulse inputs (θ4 corresponding to the projection 43a).
When the previous compression top dead center determination is # 4 cylinder, the next compression top dead center is # 1 cylinder, and the current compression stroke cylinder, ignition target cylinder, and ignition target cylinder are # 1 cylinder. The fuel injection target cylinder can be determined to be the # 2 cylinder. Similarly, if one cam pulse is input between the previous and current crank pulse inputs and the previous compression top dead center determination is for cylinder # 3, the next compression top dead center is for cylinder # 2 and the current compression top dead center is for cylinder # 2. The compression stroke cylinder, ignition target cylinder, and ignition target cylinder are # 2 cylinders,
The fuel injection target cylinder can be determined to be the # 1 cylinder.

In the four-cycle four-cylinder engine 1 of the present embodiment, the combustion strokes are in the order of cylinders # 1, # 3, # 2, and # 4, and as shown in the time chart of FIG. Assuming that the current (current) compression stroke cylinder #n is the # 1 cylinder, the cylinders to be ignited and the cylinders to be ignited are similarly # n =
The # 1 cylinder, the fuel injection target cylinder at this time is # n-2 = # 2 cylinder, which is two cylinders behind the cylinder.

When the forced ignition control, that is, spark ignition by the spark plug 18 is selected, the ignition target cylinder #n is used in an ignition control routine shown in FIG.
The ignition timing for the corresponding cylinder #n is set in accordance with the determination result, and the ignition timing is controlled for each cylinder. When the self-ignition is selected by the compression ignition control, the setting of the ignition timing is stopped and the ignition plug 18 is stopped. To stop spark ignition. Further, in the θ2 crank pulse interrupt routine of FIG. 5 described later, in accordance with the determination result of the ignition target cylinder #n,
It is determined whether the cylinder is an ion current detection target cylinder, that is, an ignition timing detection target cylinder. Further, the determination result of the fuel injection target cylinder # n-2 is referred to in a fuel injection amount setting routine (not shown) executed every predetermined cycle, and the fuel injection amount is set for each cylinder.

Thereafter, the process proceeds from step S2 to step S3, in which the time from the previous crank pulse input to the present crank pulse input measured by the crank pulse input interval timer is used, that is, the crank pulse input interval time (θ1 crank pulse And the input interval time Tθ12 of the θ2 crank pulse, the input interval time Tθ23 of the θ2 crank pulse and the θ3 crank pulse, or the input interval time Tθ31 of the θ3 crank pulse and the θ1 crank pulse), and the crank pulse input interval time Tθ is detected.

Then, the process proceeds to a step S4, wherein the angle between the crank pulses corresponding to the crank pulse identified this time is read, and the current engine speed N is determined based on the angle between the crank pulses and the crank pulse input interval time Tθ.
E is calculated, stored at a predetermined address in the RAM 53, and the routine exits. Note that the angle between the crank pulses is known, and is previously stored as fixed data in the ROM 52. In the present embodiment, the angle between the θ1 crank pulse and the θ2 crank pulse is 32 ° CA, The angle between the θ2 crank pulse and the θ3 crank pulse is 55 ° CA, and the angle between the θ3 crank pulse and the θ1 crank pulse is 93 ° CA. Further, in consideration of the engine start, the engine speed NE is calculated at, for example, 150 rpm or more.

Then, in the compression ignition control condition determination routine shown in FIG. 3, which is executed every predetermined time (for example, 10 msec), each data such as the engine speed NE is read out, and the spark plug 18 is activated by spark ignition. A condition for switching from the forced ignition to the compression ignition control for performing the self-ignition is determined.

Next, the compression ignition control condition determination routine of FIG. 3 will be described.

In the compression ignition control condition determination routine, first, in step S11, the compression ignition control flag FCOMP
It is determined whether the forced ignition control by the spark ignition of the spark plug 18 is currently performed or the compression ignition control for causing the self-ignition has been selected.

The compression ignition control flag FCOMP is cleared at the time of system initialization, and forced ignition control is performed when FCOMP = 0. In this routine, the flag is set when the condition for switching from the forced ignition control to the compression ignition control is satisfied (FCOMP ← 1), and the process proceeds to the compression ignition control by setting the compression ignition control flag FCOMP. still,
After the transition to the compression ignition control with FCOMP = 1, FIG.
In the EGR control routine shown in FIG. 10, a condition for switching from compression ignition control to forced ignition control is determined, and when this condition is satisfied, the compression ignition control flag FCOMP is cleared, thereby shifting to forced ignition control.

Therefore, if FCOMP = 1 and compression ignition control for performing self-ignition has already been instructed, step S1
The program jumps to step S9, and stores the current engine speed NE and intake air amount Q as the previous values NEOLD and QOLD at predetermined addresses in the RAM 53 in steps S19 and S20, and then exits the routine.

Then, when FCOMP = 0 and the forced ignition control is currently selected and the forced ignition by the discharge of the spark plug 18 is being performed, the process proceeds to step S12, and the process for the compression ignition control is performed by the processes after step S12. It is determined whether the transition condition is satisfied.

At steps S12 and S13, the engine speed N
The change of E and the intake air amount Q is determined, and it is determined whether or not the engine is in a steady operation state. That is, in step S12, the current engine speed NE is read out, and the engine speed NE at the time of the previous execution of this routine is read from the engine speed NE.
By subtracting OLD and comparing the absolute value | NE−NEOLD | of the subtraction value with the set value NES, it is determined whether or not the engine speed region is substantially in the same region as the previous time. In step S13, the current intake air amount Q by the intake air amount sensor 32 is read, and the intake air amount QOLD at the time of execution of the previous routine is subtracted from the intake air amount Q, and the absolute value | Q of the subtraction value is obtained. By comparing -QOLD | with the set value QS,
It is determined whether or not the engine load region based on the intake air amount Q is substantially the same as the previous region.

When | NE-NEOLD |> NES or | Q-QOLD |> QS and the engine is in the transient operation state in which the engine operation range is changed by the engine speed NE and the engine load, the corresponding step is executed. S1
Jumping to 8, the condition duration count value CN for measuring the duration of satisfaction of the switching condition to the compression ignition control is cleared (CN ← 0), and in preparation for the next determination, in the following steps S19 and S20, The engine speed NE and the intake air amount Q are stored as the previous values NEOLD and QOLD at predetermined addresses in the RAM 53, respectively, and the routine exits to continue the forced ignition control by the spark ignition of the spark plug 18.

On the other hand, in steps S12 and S13, | N
When E-NEOLD | ≦ NES and | Q-QOLD | ≦ QS, and the engine is in the steady operation state in which the engine operation range based on the engine speed and the engine load is substantially the same, the process proceeds to step S14, and the cooling as an example of the engine temperature is performed. The engine coolant temperature TW is read by the coolant temperature sensor 36, and the coolant temperature TW is compared with a set value TWS to determine whether or not the engine warm-up is completed.

If the engine 1 has not been fully warmed up since TW <TWS, the routine jumps to step S18, exits the routine through steps S18 to S20, and sets TW ≧ TW.
When the engine has been warmed up in S, the process proceeds to step S15, in which the ignition timing TADV of the forced ignition by the spark plug 18 set in the ignition control routine of FIG. 4 described later and the ignition timing TADV in the ignition timing detection routine of FIG. The ignition timing τA detected based on the current is read out, and the ignition timing τA
Is subtracted from the ignition timing TADV, and the subtraction value (τA-TAD
By comparing V) with the set value TSET, it is determined whether self-ignition is possible at an appropriate time.

Although described later in detail, in the present embodiment, the ignition timing τA and the ignition timing TADV
As shown in FIG. 2, it is set as a time value based on the θ2 crank pulse input.

Here, as the engine temperature rises, the fluctuation in combustion decreases, the combustion state is stabilized, and the combustion speed increases, so that self-ignition can be performed at an appropriate time without using forced ignition by the ignition of the ignition plug 18. Becomes

Therefore, as a condition for shifting from forced ignition by ignition of the ignition plug 18 to self-ignition, the ignition timing TADV
And the difference between the ignition timing τA, that is, the subtraction value (τA−TAD)
V) is determined and compared with a predetermined value based on the set value TSET, thereby making it possible to determine the engine combustion state.
It is possible to appropriately determine the condition for shifting to self-ignition.

The set value TSET is determined by the ignition timing TADV, that is, by the discharge of the spark plug 18 in the combustion chamber 17 when the engine has been warmed up and the self-ignition is possible at an appropriate time. After the ignition of the air-fuel mixture in the air-fuel mixture, a period from the time when the combustion flame of the air-fuel mixture reaches between the discharge electrodes 18a of the spark plug 18 and the ionic current flows, that is, the time from the ignition until the ignition is detected based on the ionic current Is obtained in advance by simulation or experiment, and this time value is set as a set value TSET, and is stored in the ROM 52 as fixed data.

Therefore, when τA−TADV> TSET and the time interval between the ignition timing TADV and the ignition timing τA detected based on the ion current exceeds a predetermined time determined by the set value TSET, it is determined that self-ignition is impossible. Step S18 above
Through S20, the routine exits, and the forced ignition control by spark ignition of the spark plug 18 is continued.

On the other hand, at step S15, τA-TAD
When V ≦ TSET and the time interval between the ignition timing TADV and the ignition timing τA detected based on the ion current is reduced to a time within a predetermined value according to the set value TSET, the self-ignition can be performed at an appropriate timing. The process proceeds to step S16, and in steps S16 and S17, the EGR gas temperature condition is further determined, and it is determined whether or not intake temperature control by EGR is possible.

That is, in step S16, the ECU 50
Control amount E for the EGR valve 27 based on the
It is determined whether or not EGR is currently being performed when GRS is outside 00H. When EGR = 00H and the EGR valve 27 is fully closed and EGR is stopped, the EGR gas temperature cannot be detected. The routine exits from S18 to S20, and the forced ignition control by spark ignition of the spark plug 18 is continued.

Then, when EGR is performed with EGRS ≠ 00H, the process proceeds to step S17, where the EGR gas temperature TEGR by the EGR gas temperature sensor 38 is read out, and the EGR gas temperature TEGR is compared with the set value TEGRS to obtain It is determined whether the intake air temperature control using the EGR gas is possible.

The above-mentioned set value TEGRS is an EG that can appropriately control the intake air temperature by controlling the EGR rate by the EGR valve 27 when the temperature of the EGR gas rises to a predetermined value.
The R gas temperature is obtained in advance by simulation or experiment, and this temperature value is set as a set value TEGRS,
This is stored in the ROM 52 as fixed data.

Therefore, if TEGR <TEGRS and it is determined that the intake air temperature cannot be properly controlled by the EGR gas, the routine exits from the routine through steps S18 to S20, and the forced ignition control by the spark ignition of the spark plug 18 is performed. continue.

On the other hand, in step S17, TEGR ≧ TEG
At the time of RS, the EGR gas temperature TEGR rises to a predetermined temperature or more according to the set value, and the EGR valve 27
It is determined that the intake air temperature can be appropriately controlled by controlling the rate, and the process proceeds to step S21.

In this embodiment, the EGR gas temperature T
By comparing the EGR with the set value TEGRS, it is determined whether the intake air temperature control by the EGR is possible. However, for simplicity, an exhaust temperature sensor is provided in the exhaust system instead of the EGR gas temperature sensor 38. Then, in step S17, it may be determined whether the intake gas temperature control by EGR is possible by comparing the exhaust gas temperature detected by the exhaust gas temperature sensor with a set value. In this case, E
Step S16 for performing the GR determination can be omitted.

In step S21, the above steps S12 to S17
Is counted up (CN ← CN + 1), and the condition duration count value CN is set to the set value CSET in step S22. (For example, the number se
c equivalent value).

When CN <CSET, it is determined that the condition for switching to the compression ignition control is not yet satisfied, and the process proceeds to step S19. After steps S19 and S20, the engine speed NE and the intake The air amount Q is changed to the previous value NE
OLD and QOLD are stored at predetermined addresses in the RAM 53, and the process exits from the routine to continue the forced ignition control by spark ignition of the spark plug 18.

Further, in step S22, CN ≧ CSE
At T, when the continuation time of all the conditions satisfied in steps S12 to S17 reaches a predetermined time determined by the execution cycle of the present routine and the set value CSET, the process proceeds to step S23, and the compression ignition control flag FCOMP is reset. By setting (FCOMP ← 1), the forced ignition control by the spark ignition of the spark plug 18 is stopped, and the compression ignition control for performing the self-ignition is selected.

Then, in step S24, the condition duration time count value CN is cleared (CN ← 0), and in the following step S25, the current control amount EGRS for the EGR valve 27 is controlled.
Is set to a new control amount (EGRS ← EGRS + UPSET), and the routine exits.

That is, when the engine is in the transient operation state in which the engine operation range changes depending on the engine speed and the engine load, the time interval between the ignition timing TADV and the ignition timing τA detected based on the ion current is correspondingly changed. Therefore, the condition for switching to the compression ignition control cannot be properly determined based on this time interval, and an erroneous determination occurs.

In addition, since combustion fluctuations occur when the engine is not warmed up, self-ignition is not always performed even if the control shifts to compression ignition control, and the ignition timing detected based on the ignition timing TADV and the ion current When the time interval with τA exceeds a predetermined time, the combustion speed is low, and even if the process shifts to the self-ignition control, the self-ignition and combustion cannot be performed at a desired timing, and an ignition mistake (misfire) of the engine 1 may occur. In some cases, an appropriate ignition timing τA cannot be obtained in self-ignition, and abnormal combustion occurs, adversely affecting the engine, and deteriorating fuel consumption and exhaust emissions.

In the present embodiment, the intake air temperature is controlled by EGR during the self-ignition control to control the ignition timing τA due to the self-ignition to converge to the target ignition timing τTAGT set based on the engine operating state. , E
When the GR gas temperature TEGR is lower than the predetermined temperature at a low temperature of the EGR gas, the intake temperature cannot be sufficiently increased by the EGR gas. Even if the process shifts to the compression ignition control and the self-ignition is performed, the intake temperature control by the EGR is performed. Can not be performed, the ignition timing τA reaches the desired target ignition timing τTAGT.
Can not control.

Therefore, in the present embodiment, the engine operating region based on the engine speed NE and the intake air amount Q representing the engine load is in substantially the same region, and the engine is in the steady operation state and the engine warm-up is completed. , Ignition timing T
The time interval between ADV and the ignition timing τA detected based on the ion current is shortened to a time within a predetermined value according to the set value TSET, it is determined that self-ignition is possible at an appropriate time, and the EGR is executed. When the EGR gas temperature TEGR is equal to or higher than the predetermined temperature, the intake air temperature control by EGR can be appropriately performed, and the duration of satisfaction of all the above conditions reaches the predetermined time by the set value TSET, and the self-ignition control is started Is determined to be completely satisfied, that is, the self-ignition is possible and the ignition timing τ by the self-ignition
When A is obtained at an appropriate time, the compression ignition control flag FCOMP is set, the forced ignition control by spark ignition of the spark plug 18 is stopped, and the process shifts to compression ignition control for performing self-ignition.

This makes it possible to prevent erroneous determination of the condition for shifting to the compression ignition control, and to perform the shift from the forced ignition control by spark ignition of the spark plug 18 to the compression ignition control at an appropriate timing. Can be. As a result, the intake air temperature control by the EGR can be accurately performed in the compression ignition control, and the ignition timing by the self-ignition can be surely and appropriately controlled. Also,
Immediately after the transition to the compression ignition control, it is possible to perform self-ignition at an appropriate time, without causing a misfire (misfire) of the engine 1 and preventing abnormal combustion due to mismatch of the ignition timing τA in self-ignition. can do. Accordingly, it is possible to prevent adverse effects such as an adverse effect on the engine 1 due to abnormal combustion, and to improve the durability reliability of the engine 1. Further, since abnormal combustion due to misfire or ignition timing mismatch at the time of shifting to self-ignition is prevented, deterioration of exhaust emission can be prevented.

Then, the compression ignition control flag FCOMP
Is referred to in the ignition control routine of FIG. 4, the θ2 crank pulse interruption routine of FIG. 5, and the EGR control routine of FIGS. 9 to 10. In the forced ignition control of FCOMP = 0, the ignition timing TADV is set according to the engine operating state. Is set, the forced ignition by spark ignition of the spark plug 18 is performed, and the control amount EGRS for the EGR valve 27 is set according to the engine operating state, thereby performing the normal EGR control.

At the time of compression ignition control with FCOMP = 1,
The setting of the ignition timing TADV is stopped, the forced ignition by spark ignition of the spark plug 18 is stopped, and at the time of shifting to the compression ignition control (t1 in the time chart of FIG. 13).
), The control amount EGRS for the EGR valve 27 is increased by a predetermined amount based on the set value UPSET in the above-described step S25, and the valve opening degree of the EGR valve 27 is correspondingly increased by the predetermined amount, and the EGR amount, that is, the EGR rate is reduced. By increasing the intake air heating amount by the increase, the intake air temperature rises, whereby the temperature of the air-fuel mixture in the combustion chamber 17 rises, and the spark plug 18 discharge shifts from self-ignition to spark ignition.

After the transition to the compression ignition control, the EGR valve 27 is operated in accordance with the result of comparison between the ignition timing τA detected based on the ion current and the target ignition timing τTAGT set based on the engine operating state. , The intake air temperature is controlled such that the ignition timing τA converges to the target ignition timing τTAGT.

Next, the ignition control routine shown in FIG. 4 will be described.

This ignition control routine is executed at predetermined intervals after the system is initialized.
In step 1, referring to the compression ignition control flag FCOMP, whether the forced ignition control for performing spark ignition of the spark plug 18 is currently instructed, or the compression ignition control for performing self-ignition regardless of the forced ignition of the spark plug 18 is performed. Determine if you are instructed.

When the forced ignition control is instructed with FCOMP = 0, the routine proceeds to step S32, where the ignition timing TADV is set by the processing after step S32 in order to perform the forced ignition by the spark ignition of the spark plug 18. .

In the present embodiment, the ignition timing is controlled by a time control method, and as shown in FIG. 11, the energization start timing (dwell set) TDWL and the energization cutoff timing (dwell cut) to the ignition coil 19 are performed.
That is, the ignition timing TADV is set by the time based on the θ2 crank pulse input.

In step S32, the basic fuel injection pulse width Tp (which is calculated in a fuel injection amount setting routine, not shown) that indicates the engine load and determines the basic fuel injection amount.
p ← K × Q / NE; K is an injector characteristic correction constant) and sets the basic advance value ADVBASE by referring to the basic advance value table stored in the ROM 52 with interpolation calculation based on the engine speed NE. I do.

In the basic advance value table, the optimum ignition timing is previously determined by simulation or experiment for each engine operating region based on the engine speed NE and the basic fuel injection pulse width Tp.
Basic advance value ADVBASE that determines whether to ignite at A
Is set as a table using the engine speed NE and the basic fuel injection pulse width Tp as parameters.
These are stored in a series of 52 addresses.

Next, at step S33, knock sensor 34
Timing learning correction value ADV for learning the amount of retard or advance for each operation region according to the presence or absence of knock detected by
KR is calculated based on the engine speed NE and the basic fuel injection pulse width Tp.
Based on this, the ignition timing learning correction value table stored in the backup RAM 54 is set with reference to interpolation calculation.

Then, the flow advances to step S34 to perform learning correction by adding the ignition timing learning correction value ADVKR to the basic advance value ADVBASE, to set a control advance angle ADV that determines the ignition timing (ADV ← ADVBASE + ADVKR), and Steps
Proceed to S35.

In step S35, based on the control advance angle ADV, the power supply cutoff timing to the ignition coil 19 based on the θ2 crank pulse input, that is, the ignition timing T
Set ADV. As described above, the present embodiment employs the time control method, and the ignition timing TADV is set by time.

That is, since the control advance ADV is angle data (BTDC ° CA), it is necessary to convert the control advance ADV into the time from the input of the θ2 crank pulse to the ignition.
As shown in the time chart of FIG. 11, assuming that the latest crank pulse input interval time is Tθ and the crank pulse angle is θ, in the present embodiment, the ignition timing TADV is calculated based on θ2 crank pulse input by the following equation. Set by.

TADV ← (Tθ / θ) × (θ2−ADV) Next, the routine proceeds to step S36, where the energization time (dwell time) DWL for the ignition coil 19 is determined by referring to the table with interpolation calculation based on the battery voltage VB. Set. This energization time determines the optimum energization time of the coil primary current depending on the battery voltage VB, and an example of this table is shown in step S36. That is, when the battery voltage VB decreases, the energization time DWL is lengthened to secure ignition energy, and when the battery voltage VB increases, the energization time DW
L is shortened to prevent energy loss and heat generation of the ignition coil 19.

At the following step S37, the ignition timing TADV
The energization time DWL is subtracted from the above to set the energization start timing TDWL based on the θ2 crank pulse (TDWL ← T
ADV-DWL), in step S38, the ignition timing TADV is set in the ignition timing timer of the corresponding cylinder.
At 39, the energization start timing TDWL is set in the energization start timing timer of the corresponding cylinder, and the routine exits.

As a result, when FCOMP = 0, the spark plug 18
When the forced ignition control by spark ignition is selected, each timer is started by the θ2 crank pulse interruption routine of FIG. 5 which is started in synchronization with the input of the θ2 crank pulse, and the forced ignition by the spark plug 18 is performed.

On the other hand, in step S31, FCOMP =
1, when the compression ignition control for self-ignition is selected, the energization start timing TDWL and the ignition timing TA
The routine exits without setting the DV and setting the timer, whereby the spark ignition by the spark plug 18 is stopped during the compression ignition control.

Next, the θ2 crank pulse interruption routine shown in FIG. 5 will be described. The routine is started in synchronization with the θ2 crank pulse input, and the compression ignition control flag FCOMP is referred to in step S41.

When the forced ignition control for forcibly igniting with the spark plug 18 is instructed with FCOMP = 0, in step S42, the energization start timing timer of the cylinder to be ignited is started, and in step S43,
The ignition timing timer of the cylinder to be ignited is started, the process proceeds to step S44, and the ion current detection process is performed after step S44.

When the respective timers start and the energization start timing timer reaches the energization start timing TDWL, the routine shown in FIG. 6 is started by interruption. In step S51, the igniter is set by the dwell set of the cylinder to be ignited by the igniter. An energization signal for the corresponding cylinder is output to 20 (see the ignition signal at the time of the forced ignition control in FIG. 11), and energization (dwell) of the ignition coil 19 of the cylinder is started.

Thereafter, when the ignition timing reaches the ignition timing TADV as measured by the ignition timing timer, an interrupt routine shown in FIG. 7 is started, and in step S61, the dwell to the ignition coil 19 of the cylinder to be ignited is cut off.
9, a high secondary voltage is induced, and the discharge electrode 18a of the spark plug 18 of the cylinder to be ignited discharges.
A spark is generated between a and a mixture in the combustion chamber 17 is ignited by sparks and ignited and burned.

Therefore, when self-ignition is impossible or intake air temperature control by EGR is impossible, that is, at the time of forced ignition control with FCOMP = 0, the ignition timing T depends on the engine operating state.
ADV is set, and forced ignition by spark ignition of the ignition plug 18 is performed.

On the other hand, in step S41 of the θ2 crank pulse interruption routine of FIG. 5, when the compression ignition control is instructed at FCOMP = 1, the power supply start timing timer and the ignition timing timer are not started and step S41 is started. Then, the process jumps to step S44, and an ion current detection start process is performed from step S44.

That is, when the compression ignition control of FCOMP = 1 is selected, the ignition timing TAD
By stopping the setting of V and deactivating each of the timers, the forced ignition by spark ignition of the spark plug 18 is stopped.

In step S44, the current compression stroke cylinder (ignition target cylinder, ignition target cylinder) data is read out by the above-described cylinder discrimination / engine speed calculation routine, and the current compression stroke cylinder is provided with the ion current detection circuit 45. It is determined whether or not the cylinder is an ion current detection target cylinder (cylinder # 1 in this embodiment).

If the current compression stroke cylinder is outside the ion current detection target cylinder, the routine directly exits from the routine.
If the cylinder is the ion current detection target cylinder, proceed to step S45,
An ignition timing detection start process is performed in step S45 and subsequent steps.

In step S45, the timer value TMτ of the ignition timing timer in the counter / timer group 55 is read, and it is determined whether or not the timer value TMτ has been cleared.

Here, the ignition timing timer starts its timing in synchronism with the input of the θ2 crank pulse in step S48 to be described later, and the ignition timing detection timer shown in FIG. An ion current is detected in a routine, and when ignition of the corresponding cylinder is detected by the ion current, the count value TMτ is cleared.

Therefore, when TMτ ≠ 0, the timing of the ignition timing timer has been continued since the previous θ2 crank pulse input to the corresponding cylinder, and ignition has not been detected during two revolutions of the engine, ie, misfire. At this time, the process proceeds to step S46, and the timer value TMτ of the ignition timing timer, that is, the time required for two revolutions of the engine is stored as an ignition timing τA at a predetermined address of the RAM 53 (τA ← TMτ).

As a result, the upper limit of detection of the ignition timing τA is regulated, and at this time, when the self-ignition is performed by the compression ignition control, a comparison between the ignition timing τA and the target ignition timing τTAGT will be described later with reference to FIG. ~ EGR of FIG.
In the control routine, the compression ignition control flag FCOMP is cleared to perform the forced ignition control, and the process shifts to the forced ignition by the spark ignition of the ignition plug 18 to eliminate the misfire due to the inability to self-ignite.

In the following step S47, the timer value TMτ of the ignition timing timer is cleared (TMτ ←
0), and proceed to step S48.

On the other hand, in step S45, TMτ
When = 0 and the ignition timing τA is properly detected, the process jumps from step S45 to step S48.

Then, in step S48, the ignition timing timer is started to start timing of the ignition timing based on the input of the θ2 crank pulse of the corresponding cylinder. In step S49, the ignition timing detection inhibition flag Fτ is cleared. (Fτ ← 0), the detection of the ignition timing is permitted, and the routine exits.

As described above, the timing of the ignition timing τA is started based on the input of the θ2 crank pulse, and is executed for each A / D conversion input of the output voltage VION from the voltage sensor 45a of the ion current detection circuit 45 in FIG. The ignition timing τA is detected by the ignition timing detection routine.

Next, the ignition timing detection routine will be described. First, in step S71, the ignition timing detection prohibition flag Fτ is referred to, and when Fτ = 1, one cycle of the relevant cylinder (engine rotation: 720 ° CA rotation) has already been performed. When the ignition timing τA is detected and the detection of the ignition timing τA is prohibited, the routine exits from the routine. Also, Fτ
When = 0 and the detection of the ignition timing τA is not completed in one cycle of the cylinder and the detection of the ignition timing τA is permitted, the process proceeds to step S72.

In step S72, the compression ignition control flag FCOMP is further referred to. If FCOMP = 0 and the forced ignition control is currently selected, the process proceeds to step S73, where the timer value TMτ of the ignition timing timer and the ignition timing TADV by the ignition control routine are read, and the timer value TMτ is read. And a sum (TADV + TSE) obtained by adding the set value TSE to the ignition timing TADV.

Here, as shown in FIG. 12, in the forced ignition control in which the spark plug 18 performs spark ignition,
Not only the ion current due to the mixture ignition, but also the spark plug 1
The ion current due to the spark ignition of No. 8 is detected. That is, when an ignition signal having a pulse waveform is output from the ECU 50 via the igniter 20 (see the ignition signal at the time of the forced ignition control in FIG. 11), a primary current flows through the primary side of the ignition coil 19, and the ignition signal rises. The primary current is interrupted by the fall (dwell cut), and a high secondary voltage is induced on the secondary side of the ignition coil 19, and the discharge electrode 18 of the ignition plug 18 is discharged.
The insulation between the a is broken down, spark discharge (spark) is performed,
The ion current due to the ignition spark is detected by the ion current detection circuit 45, and an output voltage VION corresponding to the ion current due to the spark ignition is input to the ECU 50 from the voltage sensor 45a of the ion current detection circuit 45.

When the air-fuel mixture in the combustion chamber 17 is ignited by spark ignition, and the flame causes ions of the combustion gas to be present between the discharge electrodes 18a of the ignition plug 18, the ion current flowing through the ions is reduced. Detected by the ion current detection circuit 45, the voltage sensor 45a in the ion current detection circuit 45 detects
The output voltage VION is input in response to the ion current caused by the flame.

Therefore, in order to detect the ignition timing τA, it is necessary to exclude the ion current detection period due to spark ignition, and therefore, the time value TMτ of the ignition timing timer is used.
Is compared with an addition value (TADV + TSE) obtained by adding the set value TSE to the ignition timing TADV, thereby excluding the ion current detection period by spark ignition and preventing the ignition timing τA from being erroneously detected.

When TMτ <TADV + TSE, the routine exits as it is to prevent erroneous detection of ion current detection by spark ignition, and TMτ ≧ TADV + TS
In E, after the ion current period by spark ignition has elapsed, the process proceeds to step S74.

On the other hand, in step S72, FCOMP =
In step 1, when the compression ignition control is selected, the ignition signal is not output (see the ignition signal at the time of the compression ignition control in FIG. 11), and no ion current is generated by the ignition spark at this time.

Therefore, at this time, there is no need to determine the ion current due to spark ignition, and the process jumps from step S72 to step S74.

Then, in step S74, the output voltage VIO by the voltage sensor 45a in the ion current detection circuit 45 is output.
N is a determination value ION for determining the generation of an ion current.
If VION <ION, it is determined that no ionic current has occurred due to the flame, and the routine exits.

On the other hand, when VION ≧ ION, it is determined that an ion current has occurred due to the flame and ignition has occurred, and the flow advances to step S75 to set the clock value TMτ of the ignition timing timer as the ignition timing τA and store it at a predetermined address in the RAM 53. Then, in the next step S76, the count value TM of the ignition timing timer is set.
τ is cleared (TMτ ← 0), the operation of the ignition timing timer is stopped, and when the ignition timing τA in this cycle ends, the ignition timing detection inhibition flag Fτ is set in step S77 (Fτ ← 1), exit the routine.

Then, the ignition timing τA based on the θ2 crank pulse input is detected by the above-described processing, and FCOMP
At the time of the forced ignition control by spark ignition of the spark plug 18 of = 0, in the above-described compression ignition control condition determination routine,
The transition condition to the compression ignition control is determined based on the time interval between the ignition timing τA and the ignition timing TADV (step in FIG. 3).
After the shift to the compression ignition control for performing the self-ignition at FCOMP = 1, the target ignition set based on the ignition timing τA and the engine operating state in the EGR control routine shown in FIGS. The control amount EGRS for the EGR valve 27 is set according to the comparison result with the timing τTAGT,
By controlling the EGR amount by the EGR valve 27, that is, the EGR rate, the intake air temperature is controlled so that the ignition timing τA converges to the target ignition timing τTAGT.

Next, the EGR control routine shown in FIGS. 9 and 10 will be described.

This EGR control routine is executed every predetermined time (for example, 16 ms) after the system initialization, and in step S81, the compression ignition control flag FCOMP is referred to.

When FCOMP = 0 and the current forced ignition control is instructed, the process proceeds to step S82, and the control amount EGRS for the EGR valve 27 is set in accordance with the engine operating state by the processes of steps S82 to S91. Then, the normal EGR control is performed, and when the compression ignition control of FCOMP = 1 is instructed, the process proceeds to step S92, and the process proceeds to step S92.
In the subsequent processing, intake temperature control is performed by EGR control so that the ignition timing τA converges to the target ignition timing τTAGT in self-ignition.

First, the normal EGR control at the time of the forced ignition control with FCOMP = 0 will be described.
In this case, the post-engine start time TM measured by the post-start time timer in the counter / timer group 55
The AST is read and compared with the set value ASTEGR.

That is, when TMAST <ASTEGR, the time after the engine start TMAST has not reached the predetermined time determined by the set value ASTEGR, and the engine is not operating when the starter switch 48 is ON or immediately after the engine is started. It is in a stable state.
When performing GR, there is a possibility that engine stall will occur. Therefore, TMAS
When T <ASTEGR, it is determined that the EGR condition is not satisfied,
Jump to step S89 to stop EGR, TMAST ≧
When ASTEGR, the process proceeds to step S83, and the process proceeds to step S83.
In S88, the EGR condition is further determined.

That is, in step S83, the cooling water temperature TW
And the water temperature determination value TWEGR (for example, 50 ° C.)
In the engine warm-up completion state of TW ≧ TWEGR, and in steps S84 and S85, the basic fuel injection pulse width Tp is compared with the lower limit value LEGRL and the upper limit value LEGRH, respectively.
The lower limit side and the upper limit side of the EGR execution by the engine load are determined, and the basic fuel injection pulse width Tp representing the engine load is between the lower limit value LEGRL and the upper limit value LEGRH, that is, a so-called medium engine load state, and in step S86. , The engine speed NE is set to a high speed determination value NEGR (for example, 400
0 rpm), the engine speed NE is out of the high speed range when NE ≦ NEGR, and at step S87, the vehicle speed sensor 4
The vehicle speed VSP based on the vehicle speed determination value VEGR (e.g., 12
0 km / h), and only when VSP ≦ VEGR and the vehicle speed VSP is outside the high-speed running region, the process proceeds to step S88, and the operation state of the idle switch 33b is determined. Only when the idle switch 33b is OFF and not in the idle state, the EGR
When it is determined that the condition is satisfied, the process proceeds to step S91, and EGR is executed.

Here, when the engine is cold when TW <TWEGR, the combustion state of the engine is unstable.
When R is performed, the flammability deteriorates and the engine operability deteriorates remarkably. Further, when the engine is under low load operation where Tp <LEGRL, the intake amount of fresh air is small, and when EGR is performed, the combustibility of the engine deteriorates. In addition, during the engine high load operation of Tp> LEGRH, the engine output is required, and if the EGR is performed at this time, the engine output is reduced in spite of the output request. Further, when the engine is running at a high speed of NE> NEGR or at a high speed running of VSP> VEGR, an output request is also made. If the EGR is performed at this time, the engine output is reduced contrary to the output request.

Therefore, if any of the conditions is not satisfied in steps S82 to S88, it is determined that the EGR execution condition is not satisfied, and the process proceeds to step S89 from the corresponding step, where the control amount EGRS for the EGR valve 27 is fully closed. Is set to “00H”, and the control amount EGRS is set to
Set in step S90 and exit the routine.

As a result, a drive signal corresponding to the control amount EGRS is output from the ECU 50 to the EGR valve 27,
The EG is driven by the driving of the stepping motor built in the GR valve 27.
The R valve 27 is fully closed, and EGR is stopped.

On the other hand, when the EGR execution condition is satisfied, which satisfies all the conditions of steps S82 to S88, step S91 is executed.
To execute EGR. In step S91, the control amount table is referenced with interpolation calculation based on the engine speed NE at this time and the basic fuel injection pulse width Tp representing the engine load, and the control amount EGRS for the EGR valve 27 is determined.
Set.

The above control amount table indicates that the engine speed N
EGR for obtaining an appropriate EGR amount for each engine operating region based on E and the basic fuel injection pulse width Tp representing the engine load
The control amount EGRS for the valve 27 is obtained in advance by simulation or experiment, set as a table using the engine speed NE and the basic fuel injection pulse width Tp as parameters, and stored as a fixed data in a series of addresses in the ROM 52. Things. An example of this control amount table is shown in step S91.

In the present embodiment, as shown in step S91, the engine speed NE and the basic fuel injection pulse width T
p and 2,000 to 4,000 rpm, respectively, 3.0 to
Control amount EG having the largest value in a predetermined region of 4.0 ms
RS is stored. This is the NO in this region
x is high and NO is increased by increasing the EGR rate.
This is for suppressing generation of x. Then, as the engine speed NE or the basic fuel injection pulse width Tp deviates from the above range, the amount of generated NOx decreases. Accordingly, a control value EGRS of a small value is stored in order to correspondingly decrease the EGR rate. I have.

After setting the control amount EGRS, the process proceeds to step S90, where the control amount EGR set in step S91 is set.
Set S and exit the routine.

As a result, a drive signal corresponding to the control amount EGRS is output from the ECU 50 to the EGR valve 27,
By driving the stepping motor built in the GR valve 27, E
EG in which the degree of opening of the GR valve 27 matches the engine operating state
It is adjusted to a predetermined opening to obtain the R ratio.

On the other hand, in step S81, FCOMP =
In step 1, when the forced ignition by the spark ignition of the spark plug 18 is stopped and the compression ignition control for performing the self-ignition is instructed, the process proceeds to step S92, and by the processing after step S92, the ignition timing τA and the target ignition are set. The control amount EGRS for the EGR valve 27 is set by feedback control according to the result of comparison with the timing τTAGT to control the intake air temperature by EGR, so that the ignition timing τA due to self-ignition converges to the target ignition timing τTAGT.

In step S92, the basic target ignition angle table is referred to with interpolation calculation based on the engine speed NE and the basic fuel injection pulse width Tp representing the engine load, and the basic target based on the compression top dead center is referred to. Ignition angle ADVτ
Set BASE.

In the basic target ignition angle table, the optimum ignition timing (angle) in self-ignition is determined in advance by simulation or experiment for each engine operating region based on the engine speed NE and the basic fuel injection pulse width Tp.
This optimal ignition timing is set as a basic target ignition angle ADVτBASE that determines at what CA the BTDC is obtained,
It is stored in a series of addresses in the ROM 52.

The above basic target ignition angle table is stepped.
Shown in S92. In the basic target ignition angle table, a small value, that is, the basic ignition angle ADVτBASE on the retard side is stored in a high load region where the basic fuel injection pulse width Tp is large and a low rotation region where the engine speed NE is low. . Conversely, as the basic fuel injection pulse width Tp becomes smaller and the engine rotational speed NE becomes higher, that is, as the engine shifts to a low engine load high rotational speed region, the larger value, that is, the basic advance ignition angle ADVτBASE on the advance side is stored.

Here, the combustion period in the combustion stroke (expansion stroke) after ignition differs depending on the operating state of the engine. That is, in the low rotation region, the time required for one stroke is long, and the combustion period in one stroke is relatively short,
Similarly, in the high load region, the combustion period becomes relatively short due to the increase in the charging efficiency. Further, in the high rotation region, the time required for one stroke is short, and the combustion period in one stroke is relatively long. In the low load region, the combustion period is relatively long due to the decrease in the charging efficiency.

For this reason, when the ignition timing is fixed, the combustion ends quickly in the low rotation speed region and the high load region, and
In the high rotation region and the low load region, combustion is slow, and in any case, the thermal efficiency is reduced.

Accordingly, the higher the load and the lower the rotation, the more the basic target ignition angle ADVτBASE is retarded, so that the target ignition timing τTAGT set based on the basic target ignition angle ADVτBASE is retarded. The ignition timing τA is determined by the feedback control described later corresponding to the timing τTAGT.
Is retarded. As a result, the end timing of the combustion is relatively retarded, and the thermal efficiency at the time of high load and low rotation can be improved.

Further, as the load becomes higher and the engine speed becomes lower, the basic target ignition angle ADVτBASE is advanced, whereby the target ignition timing τTAGT is advanced, and ignition is performed by feedback control described later corresponding to the target ignition timing τTAGT. The timing τA is advanced. As a result, in the low-load, high-speed range,
The combustion period is relatively advanced and the combustion delay is suppressed,
Thermal efficiency can be improved.

As a result, it is possible to set an appropriate target ignition timing in accordance with the combustion period that differs for each engine operation region, and it is possible to improve the thermal efficiency in each region.

Although the controllability is poor, the basic target ignition angle ADVτBASE may be simply set using only the engine speed NE or the engine load as a parameter.

Further, in the present embodiment, the basic target ignition angle ADVτBA is used as angle data based on the compression top dead center.
Although SE is set, although the control accuracy slightly decreases,
Alternatively, the basic target ignition timing may be set as time data based on the θ2 crank pulse input by referring to a table based on at least one of the engine speed NE and the engine load. In this case, a later-described step S95 of converting the angle data into time is not required.

After setting the basic target ignition angle ADVτBASE in step S92, the flow advances to step S93 to read the coolant temperature TW as an example of the engine temperature, and to calculate a coolant temperature correction coefficient table based on the coolant temperature TW. With interpolation calculation, and a water temperature correction coefficient Kτ for correcting the basic target ignition angle ADVτBASE is set according to the engine temperature.

The water temperature correction coefficient table corrects the basic target ignition angle ADVτBASE for each engine temperature range based on the cooling water temperature TW to obtain an optimum target ignition timing (angle).
The water temperature correction coefficient Kτ is obtained by simulation or experiment in advance and stored in a series of addresses in the ROM 52.

One example of the water temperature correction coefficient table is shown in step S93. This water temperature correction coefficient table has a smaller value in the engine low temperature range where the cooling water temperature TW is low and the engine target high temperature range where the cooling water temperature TW is high, that is, the basic target ignition angle ADVτBASE as compared with the engine normal temperature range in the normal operation state. Is stored in memory.

That is, in the low engine temperature region where the cooling water temperature TW is low, the basic target ignition angle ADVτBASE is retarded by the water temperature correction coefficient Kτ, and the target ignition timing τTAGT
Is set, the target ignition timing τTAGT is retarded, and the ignition timing τA is retarded by feedback control described later corresponding to the target ignition timing τTAGT. As a result, the combustion temperature rises, and the warm-up of the engine 1 is promoted. At the same time, the engine exhaust temperature rises as the combustion temperature rises, and the catalyst temperature of the catalytic converter 23 installed in the exhaust system rises quickly. It is possible to heat the catalytic converter 2
By promoting the activity of No. 3, the catalytic action can be effectively exhibited, and the exhaust emission can be improved.

Further, even in the high-temperature region of the engine where the cooling water temperature TW is high, the ignition timing τA is retarded by setting the target ignition timing τTAGT by performing the retard correction using the water temperature correction coefficient Kτ. As a result, it is possible to relatively lower the combustion pressure, that is, the in-cylinder pressure, by retarding the ignition timing τA, and it is possible to prevent adverse effects on the engine 1 beforehand.

Then, the process proceeds to a step S94, wherein the basic target ignition angle ADVτBASE is corrected by the water temperature correction coefficient Kτ to set a target ignition angle ADVτTGT (ADVτT).
GT ← ADVτBASE × Kτ). Although the controllability decreases,
For simplicity, the setting of the water temperature correction coefficient Kτ in step S93 and the water temperature correction by the water temperature correction coefficient Kτ in step S94 may be omitted.

In the following step S95, the target ignition angle ADVτTGT based on the compression top dead center is converted to a time and θ2
The target ignition timing τTAGT is set based on the crank pulse input. In the present embodiment, the time control method is employed as described above, and the target ignition timing τTAGT is set by time.

That is, the target ignition angle ADVτTGT
Is the angle data (BTDC ° CA), it must be converted to the time from the input of the θ2 crank pulse to the ignition by self-ignition. As shown in the time chart of FIG. Time is Tθ,
Assuming that the angle between the crank pulses is θ, in the present embodiment, the target ignition timing τTAGT is set by the following equation based on the θ2 crank pulse input.

ΤTAGT ← (Tθ / θ) × (θ2−ADVτTGT) Then, the process proceeds to step S96, and the actual ignition timing τA detected in the above-described ignition timing detection routine and the target ignition timing by the processing after step S96. The control amount EGRS for the EGR valve 27 is set according to the comparison result with τTAGT, and the ignition timing τA is controlled by the intake air temperature control by EGR.
Is controlled so as to converge to the target ignition timing τTAGT.

In step S96, the latest ignition timing τA in the ignition timing detection routine is read out, and the target ignition timing upper limit (τTAGT + α) obtained by adding the set value α for defining the dead zone width to the ignition timing τA and the target ignition timing τTAGT. Compare with

When τA <τTAGT + α, the ignition timing τA
If is smaller than the target ignition timing upper limit (τTAGT + α), the routine proceeds to step S97, and further compares the ignition timing τA with the target ignition timing lower limit (τTAGT-α) obtained by subtracting the set value from the target ignition timing τTAGT.

As a result, when τA ≧ τTAGT−α, and the ignition timing τA is within the dead zone with respect to the target ignition timing τTAGT (τTAGT + α> τA ≧ τTAGT−α), the routine exits the routine and the current EGR valve 27 is exited. (Hereinafter, referred to as “EGR valve control amount”) EGRS.

In the above step S97, τA <τTA
GT-α, if the ignition timing τA is more advanced than the target ignition timing τTAGT outside the dead zone, step S98
To the EGR valve 27 by the stepping motor of the EGR valve 27.
In order to reduce the EGR amount by reducing the valve opening of the GR valve 27 by a predetermined amount, the set value DEGR is subtracted from the current EGR valve control amount EGRS to set a new control amount EGRS (E
GRS ← EGRS−DEGR), after the step S90, the new EGR valve control amount EG in the step S98.
Set RS and exit the routine.

As a result, a drive signal corresponding to the control amount EGRS is output from the ECU 50 to the EGR valve 27,
By driving the stepping motor of the GR valve 27, the valve opening degree of the EGR valve 27 is reduced by a predetermined amount determined by the above-mentioned set value DEGR, and the intake air temperature is lowered by the decrease of the EGR amount (EGR rate).

Therefore, in the compression ignition control in which the spark ignition of the spark plug 18 is stopped and the self-ignition is performed, when the ignition timing τA is more advanced than the target ignition timing τTAGT,
The intake air temperature decreases due to the decrease in the GR amount, and the temperature of the air-fuel mixture supplied into the combustion chamber 17 decreases along with the decrease in the intake air temperature, and the ignition timing τA due to self-ignition due to the decrease in the cylinder temperature during the compression stroke. Is retarded.

On the other hand, in step S96, τA ≧ τTA
When the ignition timing τA is on the retard side of the target ignition timing τTAGT as shown in FIG. 12 outside the dead zone, the routine proceeds to step S99, and the EGR valve 27 is controlled by the stepping motor of the EGR valve 27. In order to increase the EGR amount by increasing the valve opening by a predetermined amount, the EGR valve control amount E
The set value UEGR is added to GRS to obtain a new control amount EGRS.
Is set (EGRS ← EGRS + UEGR), and step S1 is set.
Go to 00.

In step S100, the upper limit table is referred to with interpolation calculation based on the engine speed NE and the basic fuel injection pulse width Tp representing the engine load, and EGR is performed.
An upper limit value EGRSMAX that sets an upper limit on the valve control amount EGRS is set.

The above upper limit value table indicates that the engine speed N
The appropriate upper limit value EGRSMA of the EGR valve control amount EGRS for each engine operation region based on E and the basic fuel injection pulse width Tp.
X is determined in advance by simulation or experiment, and R
This is stored in a series of addresses of the OM 52.

An example of the upper limit value table is described in step S100.
Shown inside. The upper limit value table includes a high load region where the basic fuel injection pulse width Tp is large, and an engine speed NE.
In a low rotation region where the engine speed is low, the upper limit value EGRSM of a small value
AX is stored. Conversely, the basic fuel injection pulse width Tp
Is smaller and the engine speed NE is higher, that is, as the engine shifts to the engine low load high speed region, the larger upper limit value EGRSMAX is stored.

That is, as described above, the higher the load, the lower the rotation, the longer the basic target ignition angle ADVτBASE is set to retard the target ignition timing τTAGT, so that the combustion period at the time of the high load, low rotation is performed. To improve thermal efficiency. Therefore, the target ignition timing τTAGT and the ignition timing τ
By lowering the upper limit value EGRSMAX of the EGR valve control amount EGRS set in accordance with the comparison with A correspondingly,
The upper limit can be set appropriately.

Further, the basic target ignition angle ADVτBASE is set to be advanced as the load decreases and the rotation speed increases, and the target ignition timing τTA
By advancing the GT, the combustion period is relatively advanced, and the delay in combustion during low-load high-speed rotation is suppressed to improve thermal efficiency. Quantity E
The upper limit value EGRSMAX of GRS is increased.

Thus, the EGR valve control amount EG corresponds to the target ignition timing τTAGT that differs for each engine operation region.
It is possible to set an appropriate upper limit value EGRSMAX for RS, and it is possible to appropriately set an upper limit allowable limit in each region.

It is to be noted that, simply, the upper limit value EG is set using only the engine speed NE or the engine load as a parameter.
RSMAX may be set.

Then, the process proceeds to a step S101, and the EGR valve control amount EGRS increased and corrected in the step S99 is compared with the upper limit value EGRSMAX set in the step S100.
If RS ≦ EGRSMAX, the EGR control amount EGRS is the upper limit EGR
If it is equal to or smaller than SMAX, the process jumps to step S90,
The EGR valve control amount EGRS corrected and increased in step S99 is set, and the routine exits.

As a result, a drive signal corresponding to the control amount EGRS is output from the ECU 50 to the EGR valve 27,
By driving the stepping motor of the GR valve 27, the opening degree of the EGR valve 27 is increased by a predetermined amount determined by the set value UEGR, and the intake air temperature is raised by the increase of the EGR amount (EGR rate).

Therefore, during the compression ignition control in which the spark ignition of the spark plug 18 is stopped and the self-ignition is performed, when the ignition timing τA is retarded from the target ignition timing τTAGT,
The GR amount is increased to increase the intake air temperature. With the increase in the intake air temperature, the temperature of the air-fuel mixture supplied into the combustion chamber 17 increases, and the ignition timing due to self-ignition due to the increase in the cylinder temperature during the compression stroke. τA is advanced.

As a result, the ignition timing τA due to self-ignition converges to the target ignition timing τTAGT suitable for the engine operating state.

On the other hand, in step S101, EGRS
> EGRSMAX, that is, since the ignition timing τA due to self-ignition is more retarded than the target ignition timing τTAGT,
As a result of sequentially increasing and correcting the GR valve control amount EGRS, the EGR
The control amount EGRS exceeds the upper limit value EGRSMAX and the EGR valve 2
When the valve opening degree of 7 reaches the limit value according to the engine operating state, the transition to the engine transient operation, or the intake air temperature control by EGR becomes impossible due to the system abnormality, etc., and the ignition timing τA by self-ignition is controlled. Judgment has been made impossible, or self-ignition itself has been disabled,
Proceed to step S102.

Then, in step S102, the compression ignition control flag FCOMP is cleared (FCOMP ← 0), and the subsequent step S1
03, the set value DWNS is calculated from the current EGR control amount EGRS.
By subtracting ET and setting a new EGR valve control amount EGRS (EGRS ← EGRS−DWNSET), the EG
The R valve control amount EGRS is returned to the initial state, and the routine proceeds to step S90.
Through the EGR valve control amount EGR in step S103.
Set S and exit the routine.

As a result, the compression ignition control flag FCOMP
When the ignition is cleared, the control shifts from the compression ignition control to the forced ignition control.
V, the setting of the energization start timing TDWL and the setting of each ignition timer are performed, and the forced ignition by the spark ignition of the ignition plug 18 is restarted.

The above control state will be described with reference to the time chart of FIG.

In the time chart of FIG. 13, at time t1, when the condition for shifting to the compression ignition control is satisfied by the above-described compression ignition control condition determination routine, the compression ignition control flag FCOMP is set (FCOMP ← 1), and The process shifts from the ignition control to the compression ignition control, and the setting of the ignition timing TADV and the setting of each ignition timer in the ignition control routine are stopped, so that the ignition spark by the spark plug 18 is stopped. At this time, the EGR valve control amount EGRS is increased by a predetermined amount based on the set value UPSET (step S2 in FIG. 3).
5) Correspondingly, the opening degree of the EGR valve 27 increases by a predetermined amount, and the intake air temperature rises due to the increase in the EGR amount (EGR rate). As a result, the temperature of the air-fuel mixture supplied into the combustion chamber 17 increases, and the ignition plug 18 shifts from forced ignition by spark ignition to self-ignition.

After shifting to the compression ignition control,
An actual ignition timing τA detected based on the ion current in the ignition timing detection routine, a target ignition timing upper limit (τTAGT + α) obtained by adding a set value α defining a dead zone width to a target ignition timing τTAGT set based on the engine operating state; The target ignition timing is compared with a target ignition timing lower limit (τTAGT-α) obtained by subtracting the set value α from the target ignition timing τTAGT.

When the ignition timing τA is within the range of the dead zone with respect to the target ignition timing τTAGT at the time from t1 to t2 (τTAGT + α> τA ≧ τTAGT-α), E
The GR valve control amount EGRS is maintained as it is.

After the time point t2, if the ignition timing τA deviates from the dead zone on the more retarded side than the target ignition timing τTAGT (τA ≧
τTAGT + α), the EGR valve control amount EGRS is gradually increased by a set value UEGR every time the EGR control routine is executed, that is, every calculation cycle, and the valve opening of the EGR valve 27 is increased by a predetermined amount determined by the set value UEGR. And
Due to the increase in the opening degree of the EGR valve 27, the EGR amount (E
(GR rate), thereby increasing the intake air temperature. As the intake air temperature increases, the temperature of the air-fuel mixture supplied into the combustion chamber 17 increases, and self-ignition occurs due to the increase in the cylinder temperature during the compression stroke. The ignition timing τA is advanced. As a result, the ignition timing τA due to self-ignition converges to the target ignition timing τTAGT suitable for the engine operating state.

At time t3, when the ignition timing τA converges within the range of the dead zone with respect to the target ignition timing τTAGT, the increase correction of the EGR valve control amount EGRS is stopped, and E
The GR valve control amount EGRS, that is, the valve opening of the EGR valve 27 is maintained as it is.

On the other hand, after the time point t4, if the ignition timing τA deviates from the dead zone on the advance side of the target ignition timing τTAGT (τA <τTAGT-α), E is executed every time the EGR control routine is executed.
The GR valve control amount EGRS is decreased by the set value DEGR,
The opening degree of the EGR valve 27 is decreased by a predetermined amount determined by the set value DEGR, and the EGR amount (EGR rate) is reduced. As a result, the intake air temperature is reduced due to the decrease in the EGR amount, and the temperature of the air-fuel mixture supplied into the combustion chamber 17 is reduced due to the decrease in the intake air temperature, and the self-ignition is caused due to the decrease in the in-cylinder temperature during the compression stroke. Is retarded, and the ignition timing τA due to self-ignition converges to the target ignition timing τTAGT suitable for the engine operating state.

As a result, the ignition timing τA is controlled so as to converge to the target ignition timing τTAGT suitable for the engine operation state even when the engine operating conditions, atmospheric conditions, and the like change. It is possible to improve fuel efficiency and reliability by improving the thermal efficiency, and it is possible to obtain the optimal ignition timing regardless of the difference in the engine operating state. Combustion can be avoided beforehand, and not only the adverse effect on the engine can be avoided, but also engine noise can be reduced.

At time t5, the ignition timing τ
When A converges within the range of the dead zone with respect to the target ignition timing τTAGT, the correction for decreasing the EGR valve control amount EGRS is stopped, and the EGR valve control amount EGRS, that is, the valve opening of the EGR valve 27 is maintained.

After the time point t6, the ignition timing τA
Deviates from the dead zone on the more retarded side than the target ignition timing τTAGT (τA ≧ τTAGT + α), the EGR valve control amount EGRS is gradually increased by the set value UEGR every time the EGR control routine is executed, and the EGR valve 27 is opened. Is the above set value UEGR
Is incremented by a predetermined amount.

The ignition timing .tau.A does not converge to the target ignition timing .tau.TAGT even by the correction for increasing the EGR valve control amount EGRS. At the time t7, the EGR valve control amount EGR
S is the upper limit value EG set based on the engine operating state
When it exceeds RSMAX (EGRS> EGRSMAX), that is, the ignition timing τA due to self-ignition becomes the target ignition timing τTAG.
Since the EGR valve control amount EGRS is successively increased and corrected for the retard side from T, the EGR control amount EGRS becomes the upper limit value EG.
When the valve opening degree of the EGR valve 27 exceeds RSMAX and reaches a limit value corresponding to the engine operating state, the intake temperature control by the EGR cannot be performed due to the transition to the engine transient operation or a system abnormality, and the self-ignition occurs. It is determined that the ignition timing τA cannot be controlled or the self-ignition itself has been disabled, and the compression ignition control flag FCOMP is cleared (FCOMP ← 0; step S102 in FIG. 10).

When the compression ignition control flag FCOMP is cleared, the control shifts from compression ignition control to forced ignition control.
In the above-described ignition control routine, the setting of the ignition timing TADV and the energization start timing TDWL and the setting of each ignition timer are performed, and the forced ignition by the spark ignition of the ignition plug 18 is restarted.

As a result, the transition to engine transient operation,
Alternatively, when the intake air temperature control by the EGR becomes impossible due to a system abnormality or the like, and the ignition timing τA by the self-ignition cannot be controlled, or when the self-ignition itself becomes impossible, the self-ignition and the ignition plug are started. It is possible to reliably shift to forced ignition by the ignition of No. 18. As a result, continuation of self-ignition in a state where the ignition timing τA due to self-ignition cannot be controlled is prevented, and deterioration of drivability can be prevented. Further, by preventing abnormal combustion and misfire due to continuation of self-ignition, deterioration of exhaust emission can be prevented and durability durability of the engine 1 can be improved.

At this time, the EGR control amount EGRS is reduced by a predetermined amount according to the set value DWNSET, and the initial state is restored. In response to this, the valve opening of the EGR valve 27 decreases by a predetermined amount, and returns to the normal EGR control.

In the present embodiment, the EGR control amount EGRS during the compression ignition control is set by integral control according to the result of comparison between the ignition timing τA and the target ignition timing τTAGT. The present invention is not limited to this, and may be set by proportional integral control (PI control) or proportional integral derivative control (PID control).

Also, in the present embodiment, the intake air amount Q or the basic fuel injection pulse width T is used as the engine load.
Although p is used as long as it represents the engine load, the present invention is not limited to this.

Further, the EGR valve is not limited to the stepping motor type EGR valve of the present embodiment. For example, a diaphragm actuator type EGR valve is employed, and the control pressure for operating the diaphragm actuator type EGR valve is adjusted. The intake heating control may be performed by controlling the control amount for the duty solenoid valve that regulates the pressure. In addition, a direct-acting EG using a duty solenoid valve
An intake valve heating control may be performed by employing an R valve and controlling a control amount for the duty solenoid valve.

Further, in the present embodiment, the EGR control is performed in accordance with the engine operating state even during the forced ignition control by the ignition of the spark plug 18, but the present invention is not limited to this. The EGR may be stopped during the forced ignition control, the EGR may be performed only during the compression ignition control by self-ignition, and the EGR may be used only for the intake air heating control. In this case, in the compression ignition control condition determination routine of FIG. 3, by comparing the exhaust gas temperature with the set value as described above, it is determined whether or not intake temperature control by EGR is possible. In the EGR control routine, steps S82 to S88 and S91 are omitted, and FCOMP
= 0, when the forced ignition control is instructed, step S8
From 1 the process proceeds to step S89 to stop EGR.

Next, a second embodiment of the present invention will be described with reference to FIGS.

In the first embodiment, the EGR device 25 is adopted as the intake air heating means. On the other hand, in the present embodiment, as shown in FIG.
A heat exchanger 70 that exchanges heat with exhaust gas, and a part of the intake air flowing through the intake passage 6 as an intake system is introduced into the heat exchanger 70, and the heated intake air after the heat exchange by the heat exchanger 70 is supplied to the intake system. A heated intake passage 71 returning to the air chamber 4 downstream of the throttle valve 5a, and a heated intake air amount adjusting valve 72 interposed in the heated air passage 71 and adjusting a flow rate of heated intake air flowing through the heated intake passage 71. Adopts an intake air heating device.

When the ignition timing τA is more advanced than the target ignition timing τTAGT, the heated intake air amount is controlled to be reduced by the heated intake air amount adjustment valve 72 to lower the intake air temperature, thereby reducing the engine combustion chamber 17. The temperature of the air-fuel mixture inside is lowered, and the ignition timing by self-ignition is retarded. Further, when the ignition timing τA is on the retard side from the target ignition timing τTAGT, the heated intake air flow rate is controlled to be increased by the heated intake air amount adjusting valve 72 to increase the intake air temperature, thereby increasing the temperature of the air-fuel mixture in the combustion chamber 17. And the ignition timing by self-ignition is advanced.

Also, a cooling water temperature TW representing the engine temperature
Reaches a predetermined temperature, the exhaust gas temperature rises sufficiently, and it is determined that it is possible to shift to self-ignition by increasing the intake air temperature by heat exchange with the exhaust gas, so that heating by the heated intake air amount adjusting valve 72 is performed. The intake air flow rate is increased, the intake air temperature is controlled to increase, the temperature of the air-fuel mixture in the combustion chamber 17 is increased, and the spark ignition caused by the discharge of the spark plug 18 shifts to self-ignition. That is, when the exhaust gas temperature rises and it becomes possible to control the ignition timing τA at the time of self-ignition by controlling the intake air temperature by controlling the flow rate of the heated intake air obtained by heat exchange with the exhaust gas, A transition is made from spark ignition by discharge to self-ignition.

Further, at the time of self-ignition, when the ignition timing τA is on the retard side of the target ignition timing τTAGT and the valve opening of the heated intake air amount adjusting valve 72 reaches the limit value, the intake air temperature control by heated intake air is performed. Is determined to be impossible and the ignition timing of the self-ignition cannot be controlled, the flow rate of the heated intake air by the heated intake air amount adjusting valve 72 is reduced, and the self-ignition is shifted to the spark ignition by the discharge of the spark plug 18. .

The same components as in the first embodiment,
The same steps are denoted by the same reference numerals, and a detailed description thereof will be omitted.

First, the intake air heating device of this embodiment will be described with reference to FIG.

In the exhaust manifold 21 of the exhaust system,
A heat exchanger 70 for exchanging heat with the exhaust gas is provided. In order to introduce a part of the intake air into the heat exchanger 70, an intake introduction passage 71 a communicating the intake pipe 6 and the heat exchanger 70, and a heated intake air that has been heat-exchanged with the exhaust gas by the heat exchanger 70 is taken in. In order to return to the system, a heating air supply passage 71b that connects the heat exchanger 70 and the air chamber 4 downstream of the throttle valve 5a forms a heating air passage 71.

The flow rate of the heated intake air flowing through the heated air supply passage 71b, that is, the supply rate of the heated air in the intake air (hereinafter referred to as the "heated air supply rate") is adjusted in the heated air supply passage 71b. And a duty solenoid valve type heating intake air amount adjusting valve 72 for controlling the intake air temperature. In addition, the heating intake air amount adjusting valve 7
2 may be interposed in the intake passage 71a.

A part of the intake air flowing through the intake pipe 6 is introduced into the heat exchanger 70 through the intake introduction passage 71a by the intake negative pressure generated downstream of the throttle valve 5a.
The heated intake air that has undergone heat exchange in the heat exchanger 70 is supplied to the air chamber 4 downstream of the throttle valve 5a via the heated air supply passage 71b.

Further, as shown in FIG. 22, the heating intake air amount adjusting valve 72 is connected to an output port of the I / O interface 56 of the ECU 50 via a driving circuit 58.

The control amount for the heated intake air amount adjusting valve 72, that is, the duty ratio DUTY of the drive signal is determined by the ECU.
50, and the opening degree of the heated intake air amount adjustment valve 72 is adjusted in accordance with the drive signal output from the ECU 50 in accordance with the duty ratio DUTY.

In the present embodiment, when the duty ratio DUTY is 15% or less and the heated intake air amount adjusting valve 72
Is completely closed, the supply of the heated intake air is stopped, and when the duty ratio DUTY is 90% or more, the heated intake air amount adjustment valve 72 is fully opened. Then, the duty ratio DUTY is 0% to 1
The heating air flow rate, that is, the heating air supply rate is controlled by adjusting the valve opening of the heating intake air amount adjusting valve 72 in accordance with the drive signal based on the duty ratio DUTY.

In the present embodiment, a compression ignition control condition determination routine shown in FIG. 19 is employed instead of the compression ignition control condition determination routine of FIG. 3 of the first embodiment, and FIGS. Instead of the EGR control routine of FIG. 10, an intake air heating control routine shown in FIG. 20 is employed.
Note that, for other routines, the routine of the first embodiment is employed as it is, and description thereof is omitted.

Hereinafter, the compression ignition control condition determination routine and the intake heating control routine of the present embodiment will be described. The same steps as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. .

The compression ignition control condition determination routine shown in FIG. 19 is executed every predetermined time (for example, 10 msec) after system initialization, as in the first embodiment, and at step S11, the compression ignition control flag FCOMP is set. If FCOMP = 1 and compression ignition control for self-ignition has already been instructed, the routine jumps to step S19, and in steps S19 and S20, the current engine speed NE,
Assuming the intake air amount Q as the previous value NEOLD, QOLD, RAM5
The program is stored at the predetermined address of No. 3 and the process exits from the routine.

On the other hand, when FCOMP = 0 and the forced ignition control is currently selected and the forced ignition by the discharge of the spark plug 18 is being performed, the process proceeds to step S12, and the process proceeds to steps S12 to S1.
5. In S22, it is determined whether a condition for shifting to compression ignition control is satisfied.

In steps S12 and S13, the engine speed N
The change of E and the intake air amount Q is determined, and it is determined whether or not the engine is in a steady operation state. And | NE-NEOLD |> NE
In the engine transient operation state of S or | Q-QOLD |> QS, the process jumps from the corresponding step to step S18 to clear the condition continuation time count value CN, and prepares for the next determination in steps S19 and S20. The above engine speed NE and intake air amount Q are respectively set to the previous values NEOLD and QO.
As LD, the routine exits and the forced ignition control by spark ignition of the spark plug 18 is continued.

In steps S12 and S13, | N
When the engine is in the steady operating condition of E-NEOLD | ≤NES and | Q-QOLD | ≤QS, the routine proceeds to step S14, where the engine coolant temperature TW is read out by the coolant temperature sensor 36 as an example of the engine temperature, and the coolant temperature TW is read. Is compared with the set value TWS to determine whether the intake air temperature control by the flow control of the heated air is possible.

In the present embodiment, the above set value TW
S indicates that when the warm-up of the engine 1 is completed and the exhaust gas temperature rises to a predetermined value, a high-temperature heated intake air is obtained by heat exchange with the exhaust gas. By controlling, a coolant temperature at which the intake air temperature can be appropriately controlled is obtained in advance by simulation or experiment, and this temperature value is set to a set value TWS.
And stored in the ROM 52 as fixed data.

Therefore, if TW <TWS and it is determined that the intake air temperature cannot be properly controlled by the heated air, the routine exits from the routine through steps S18 to S20, and the forced ignition control by spark ignition of the spark plug 18 is performed. continue.

In step S14, TW ≧ TWS
When the engine temperature reaches a predetermined temperature, the warm-up of the engine 1 is completed and the exhaust gas temperature rises sufficiently, and the intake air temperature rises sufficiently by the heated intake air after the heat exchanger 70 exchanges heat with the exhaust gas. It is determined that the intake air temperature can be properly controlled by controlling the heating air supply rate by the heating intake air amount adjustment valve 72, and
Proceed to S15.

In step S15, the ignition timing TADV of the forced ignition by the ignition plug 18 set in the above-described ignition control routine of FIG. 4 and the ignition timing τA detected based on the ion current in the ignition timing detection routine of FIG. Then, the ignition timing TADV is subtracted from the ignition timing τA, and the subtraction value is compared with a set value TSET to determine whether or not self-ignition is possible at an appropriate ignition timing.

When τA−TADV> TSET and the time interval between the ignition timing TADV and the ignition timing τA detected based on the ion current exceeds a predetermined time determined by the set value TSET, it is determined that self-ignition is impossible. Step S18 above
Through S20, the routine exits, and the forced ignition control by spark ignition of the spark plug 18 is continued.

On the other hand, at step S15, τA-TAD
When V ≦ TSET and the time interval between the ignition timing TADV and the ignition timing τA detected based on the ion current is reduced to a time within a predetermined value according to the set value TSET, self-ignition can be performed at an appropriate ignition timing. It proceeds to step S21 and counts up a condition continuation time count value CN that counts a continuation time of satisfaction of the switching condition to the compression ignition control under all the conditions of steps S12 to S15, and in step S22,
The condition duration time count value CN is compared with a set value CSET (for example, a value corresponding to several seconds).

When CN <CSET, it is determined that the condition for switching to the compression ignition control has not been satisfied, and the routine proceeds to step S19, exits the routine through steps S19 and S20, and sparks the spark plug 18. Continue the forced ignition control by ignition.

In step S22, CN ≧ CSE
At T, when the continuation time of all the conditions satisfied in steps S12 to S15 reaches a predetermined time determined by the execution cycle of this routine and the set value CSET, the process proceeds to step S23, and the compression ignition control flag FCOMP is reset. By setting (FCOMP ← 1), the forced ignition control by the spark ignition of the spark plug 18 is stopped, and the compression ignition control for performing the self-ignition is selected. Then, in step S24, the condition duration time count value CN is cleared, and in subsequent step S201,
The duty ratio of the drive signal to the heated intake air amount adjusting valve 72 is initialized by the initial value DINI (DUTY ← DIN
I) Exit the routine.

Then, the compression ignition control flag FCOMP
This is referred to in the above-described ignition control routine of FIG. 4, the θ2 crank pulse interruption routine of FIG. 5, and the intake heating control routine of FIG. 20, which will be described later. In the forced ignition control of FCOMP = 0, depending on the engine operating state. The ignition timing TADV is set, the forced ignition by spark ignition of the ignition plug 18 is performed, and the intake air heating is stopped. Here,
Also during the forced ignition control, the intake signal may be heated by setting the duty ratio DUTY of the drive signal for the heated intake air amount adjustment valve 72 in accordance with the engine operating state.

At the time of compression ignition control with FCOMP = 1,
The setting of the ignition timing TADV is stopped, the forced ignition by the spark ignition of the spark plug 18 is stopped, and the duty ratio DUTY of the drive signal to the heated intake air amount adjustment valve 72 in step S201 described above at the time of shifting to the compression ignition control.
Is increased by a predetermined amount based on the initial value DINI, the valve opening of the heated intake air amount adjusting valve 72 is increased by a predetermined amount, and the intake air heating is started by the increase of the heated intake air flow rate, that is, the heated air supply rate. As the amount is increased, the intake air temperature rises, whereby the temperature of the air-fuel mixture supplied into the combustion chamber 17 rises, and the ignition plug 18 shifts from forced ignition by spark ignition to self-ignition.

After the transition to the compression ignition control, the heating intake air amount is determined according to the result of comparison between the ignition timing τA detected based on the ion current and the target ignition timing τTAGT set based on the engine operating state. By controlling the regulating valve 72, the intake air temperature is controlled so that the ignition timing τA converges to the target ignition timing τTAGT.

Next, the intake air heating control routine shown in FIG. 20 will be described.

This intake heating control routine is executed every predetermined time (for example, 16 ms) after system initialization, and in step S81, the compression ignition control flag FCOMP is referred to.

If FCOMP = 0 and the forced ignition control is currently instructed, the process exits the routine and stops the intake air heating. At this time, as described above, the duty ratio DUTY of the drive signal for the heated intake air amount adjusting valve 72 may be set according to the engine operating state, and the intake air may be heated.

On the other hand, in step S81, FCOMP =
In step 1, when the forced ignition by the spark ignition of the spark plug 18 is stopped and the compression ignition control for performing the self-ignition is instructed, the process proceeds to step S92, and by the processing after step S92, the ignition timing τA and the target ignition are set. The duty ratio DUTY of the drive signal for the heated intake air amount adjustment valve 72 is obtained by feedback control according to the result of comparison with the timing τTAGT.
Is set and the intake air temperature is controlled by the heated intake air amount adjusting valve 72, and the ignition timing τA due to self-ignition is changed to the target ignition timing τTAG.
Control to converge to T.

In step S92, the basic target ignition angle table is referenced with interpolation calculation based on the engine speed NE and the basic fuel injection pulse width Tp representing the engine load, and the compression top dead center is used as a reference. Basic target ignition angle A
Set DVτBASE.

In this embodiment, the basic target ignition angle ADVτBASE may be simply set using only the engine speed NE or the engine load as a parameter. The basic target ignition timing may be set as time data based on the θ2 crank pulse input by referring to a table based on at least one of the engine speed NE and the engine load. In this case, step S95 for converting the angle data into time
Becomes unnecessary.

In the following step S93, the cooling water temperature TW as an example of the engine temperature is read out, and based on the cooling water temperature TW, the water temperature correction coefficient table is referred to with interpolation calculation. A water temperature correction coefficient Kτ for correcting the ignition angle ADVτBASE is set.

Next, proceeding to step S94, the basic target ignition angle ADVτBASE is corrected by the water temperature correction coefficient Kτ to set a target ignition angle ADVτTGT (ADVτT).
GT ← ADVτBASE × Kτ). Although the controllability decreases,
For simplicity, the setting of the water temperature correction coefficient Kτ in step S93 and the water temperature correction by the water temperature correction coefficient Kτ in step S94 may be omitted.

In the following step S95, the target ignition angle ADVτTGT based on the compression top dead center is converted to a time and θ2
Set the target ignition timing τTAGT based on the crank pulse input (τTAGT ← (Tθ / θ) × (θ2−ADVτTG
T)).

Then, the flow advances to step S96 to go to step S96.
By the subsequent processing, the duty ratio DUTY of the drive signal for the heated intake air amount adjustment valve 72 is set according to the comparison result between the actual ignition timing τA detected in the above-described ignition timing detection routine and the target ignition timing τTAGT, The intake air temperature is controlled by controlling the heating intake air flow rate (heating air supply rate), and feedback control is performed so that the ignition timing τA converges to the target ignition timing τTAGT.

In step S96, the latest ignition timing τA in the ignition timing detection routine is read out, and the target ignition timing upper limit (τTAGT + α) obtained by adding the ignition timing τA and the target ignition timing τTAGT to the set value α for defining the dead zone width. Compare.

If τA <τTAGT + α, and the ignition timing τA
If is smaller than the target ignition timing upper limit (τTAGT + α), the routine proceeds to step S97, and further compares the ignition timing τA with the target ignition timing lower limit (τTAGT-α) obtained by subtracting the set value from the target ignition timing τTAGT.

As a result, when τA ≧ τTAGT−α, and the ignition timing τA is within the dead zone with respect to the target ignition timing τTAGT (τTAGT + α> τA ≧ τTAGT−α), the routine exits as it is and the current heated intake air amount The duty ratio DUTY of the drive signal for the adjustment valve 72 is maintained as it is.

In step S97, τA <τTA
GT-α, outside the dead zone, and when the ignition timing τA is more advanced than the target ignition timing τTAGT, step S211
To the setting value DDI from the current duty ratio DUTY.
A new duty ratio DUTY is set by subtracting NT (DUTY ← DUTY−DDINT).

Then, the flow advances to step S217 to set a new duty ratio DUTY in step S211 and exit from the routine.

As a result, a drive signal based on the duty ratio DUTY is output from the ECU 50 to the heated intake air amount adjustment valve 72, and the valve opening of the heated intake air amount adjustment valve 72 is set to the set value D.
The intake air temperature is decreased by a predetermined amount determined by DINT, and the intake air flow rate (heated air supply rate) is decreased to decrease the intake air temperature.

That is, during compression ignition control in which spark ignition of the spark plug 18 is stopped to perform self-ignition, if the ignition timing τA deviates from the dead zone on the more advanced side than the target ignition timing τTAGT (τA <τTAGT−α). , The duty ratio D of the drive signal for the heated intake air amount adjusting valve 72 every time this routine is executed.
UTY is reduced by the set value DDINT, and the valve opening of the heated intake air amount adjusting valve 72 is reduced by a predetermined amount determined by the set value DDINT, thereby reducing the heated intake air flow rate (heated air supply rate). As a result, the intake air temperature decreases due to the decrease in the flow rate of the heated intake air, and the temperature of the air-fuel mixture supplied into the combustion chamber 17 decreases due to the decrease in the intake air temperature. Ignition timing by ignition τ
A is retarded, and the ignition timing τA due to self-ignition converges to the target ignition timing τTAGT suitable for the engine operating state.

The ignition timing τA is equal to the target ignition timing τTAG
When the value converges within the dead zone with respect to T, the correction of the decrease in the duty ratio DUTY is stopped, and the heating intake air amount adjusting valve 7 is stopped.
2, the duty ratio DUTY of the drive signal, that is, the opening degree of the heated intake air amount adjustment valve 72 is maintained as it is.

On the other hand, in step S96, τA ≧ τTA
GT + α, and if the ignition timing τA is on the retard side of the target ignition timing τTAGT outside the dead zone, step S212
To the current duty ratio DUTY and the set value UDIN
A new duty ratio DUTY is set by adding T (DUTY ← DUTY + UDINT).

Then, the flow proceeds to step S213, where the basic fuel injection pulse width T representing the engine speed NE and the engine load is displayed.
The upper limit value DUTYMAX that sets the upper limit of the duty ratio DUTY of the drive signal for the heated intake air amount adjustment valve 72 is set by referring to the upper limit value table with interpolation calculation based on p.

The above upper limit value table indicates that the engine speed N
E and the upper limit value DUTYMA of the duty ratio DUTY for each engine operation region based on the basic fuel injection pulse width Tp.
X is determined in advance by simulation or experiment, and R
This is stored in a series of addresses of the OM 52.

An example of the upper limit value table is shown in step S213.
Shown inside. The upper limit value table includes a high load region where the basic fuel injection pulse width Tp is large, and an engine speed NE.
In the low rotation region where the rotation speed is low, the upper limit value DUTY of the small value
MAX is stored. Conversely, the basic fuel injection pulse width T
The upper limit value DUTYMAX of a larger value is stored in memory as p is smaller and the engine speed NE is higher, that is, as the engine shifts to the engine low load high speed region.

That is, as described above, the higher the load, the lower the rotation, the longer the basic target ignition angle ADVτBASE is set to retard the target ignition timing τTAGT, so that the combustion period at the time of the high load, low rotation is performed. In order to improve the thermal efficiency appropriately, the upper limit value DUTYMAX of the duty ratio DUTY set according to the comparison between the target ignition timing τTAGT and the ignition timing τA is correspondingly reduced, The upper limit can be set appropriately.

Further, the basic target ignition angle ADVτBASE is set to be advanced as the load decreases and the engine speed increases, and the target ignition timing τTA
By advancing the GT, the combustion period is relatively advanced, and the delay in combustion during low-load high-speed rotation is suppressed to improve thermal efficiency. Accordingly, the duty ratio DU is correspondingly adjusted.
The upper limit value DUTYMAX of TY is increased.

Thus, the duty ratio DUT corresponding to the target ignition timing .tau.
It is possible to set an appropriate upper limit value DUTYMAX for Y, and it is possible to appropriately set the upper limit allowable limit in each region.

Note that, simply, the upper limit value DU is set using only the engine speed NE or the engine load as a parameter.
TYMAX may be set.

The flow advances to step S214 to compare the duty ratio DUTY increased and corrected in step S212 with the upper limit value DUTYMAX set in step S213.
When UTY ≦ DUTYMAX, the duty ratio DUTY of the drive signal for the heated intake air amount adjusting valve 72 is set to the upper limit value DUTYMA.
If the duty ratio DU is equal to or less than X, the process jumps to step S217, and the duty ratio DU increased and corrected in step S212.
Set TY and exit the routine.

As a result, a drive signal based on the duty ratio DUTY is output from the ECU 50 to the heated intake air amount adjustment valve 72, and the valve opening of the heated intake air amount adjustment valve 72 is set to the set value U.
The intake air temperature is increased by a predetermined amount determined by DINT, and the intake air flow rate (heating air supply rate) is increased to increase the intake air temperature.

That is, in the compression ignition control for performing the self-ignition, if the ignition timing τA deviates from the dead zone on the more retarded side than the target ignition timing τTAGT (τA ≧ τTAGT + α), the heating intake air amount adjusting valve 72 is set every time this routine is executed. , The duty ratio DUTY of the drive signal is gradually increased by the set value UDINT, and the valve opening of the heated intake air amount adjusting valve 72 is increased by a predetermined amount determined by the set value UDINT. The heating intake air flow rate (heating air supply rate) increases due to the increase in the valve opening degree of the heating intake air amount adjusting valve 72, whereby the intake air temperature rises and is supplied into the combustion chamber 17 as the intake air temperature rises. As the temperature of the mixture increases, the ignition timing τA due to self-ignition occurs due to the rise in cylinder temperature during the compression stroke.
Is advanced. As a result, the ignition timing τ due to self-ignition
A converges to the target ignition timing τTAGT suitable for the engine operating state.

The ignition timing τA is equal to the target ignition timing τTAG.
When it converges within the dead zone range for T, the increase correction of the duty ratio DUTY is stopped and the heating intake air amount adjusting valve 7 is stopped.
2, the duty ratio DUTY of the drive signal, that is, the valve opening degree of the heated intake air amount adjusting valve 72 is maintained as it is.

With the intake air temperature control described above, even if the engine operating conditions, atmospheric conditions, and the like change, the ignition timing τA converges to the target ignition timing τTAGT suitable for the engine operating conditions.
Is controlled, and the optimal ignition timing τ at the time of self-ignition is always
A can be obtained, and fuel efficiency and reliability can be improved by improving thermal efficiency.

Further, since it is possible to obtain the optimum ignition timing regardless of the difference in the engine operating state, abnormal combustion such as knocking can be avoided beforehand.
An adverse effect on the engine can be avoided beforehand, and engine noise can be reduced.

On the other hand, in step S214, the DUT
Y> DUTYMAX, the ignition timing τA does not converge to the target ignition timing τTAGT even by increasing and correcting the duty ratio DUTY, and the duty DUTY of the drive signal for the heated intake air amount adjustment valve 72 is set to the upper limit set based on the engine operating state. When the duty ratio DUTY exceeds the upper limit value DUTYMAX, the duty ratio DUTY exceeds the upper limit value DUTYMAX when the duty ratio DUTY exceeds the upper limit value DUTYMAX, that is, because the ignition timing τA due to self-ignition is retarded from the target ignition timing τTAGT. When the valve opening of the regulating valve 72 reaches a limit value according to the engine operating state, the transition to the engine transient operation or the intake air temperature control by adjusting the heated intake air flow rate (heating air supply rate) due to a system abnormality or the like. Becomes impossible, and it becomes impossible to control the ignition timing τA by self-ignition, or the self-ignition itself is impossible. We were in and the process proceeds to step S215.

Then, in step S215, the compression ignition control flag FCOMP is cleared (FCOMP ← 0), and the following step S2
At 16, the duty ratio DUTY of the drive signal for the heated intake air amount adjusting valve 72 is set to 0% (DUTY ← 0), and
In step S217, the duty ratio DUTY in step S216 is used.
To exit the routine.

As a result, the compression ignition control is shifted from the compression ignition control to the forced ignition control by clearing the compression ignition control flag FCOMP. In the above-described ignition control routine, the setting of the ignition timing TADV, the energization start timing TDWL, and the setting of each ignition timer are performed. Then, the forced ignition by the spark ignition of the spark plug 18 is restarted.

As a result, the transition to the engine transient operation,
Alternatively, the intake air temperature control by adjusting the heated intake air flow rate becomes impossible due to a system abnormality or the like, and the ignition timing τ due to self-ignition
When it becomes impossible to control A, or when the self-ignition itself becomes impossible, the ignition plug 1
Thus, it is possible to reliably shift to the forced ignition by the ignition of No. 8. As a result, also in the present embodiment, continuation of self-ignition in a state where the ignition timing τA due to self-ignition is uncontrollable is prevented, and deterioration of drivability can be prevented. Further, by preventing abnormal combustion and misfire due to continuation of self-ignition, deterioration of exhaust emission can be prevented and durability durability of the engine 1 can be improved.

At this time, the duty ratio DUTY is set to 0%, and the operation returns to the initial state. Corresponding to this, the valve opening of the heated intake air amount adjusting valve 72 decreases to be fully closed, and the intake air heating is stopped.

In the present embodiment, the duty ratio DUTY of the drive signal for the heated intake air amount adjusting valve 72 is set to 0% with the shift from the compression ignition control to the forced ignition control, and the heated intake control valve 72 is fully closed. Although the intake air heating is stopped, even in the forced ignition control, when performing the intake air heating by setting the duty ratio DUTY of the drive signal to the heated intake air amount adjusting valve 72 according to the engine operating state, In S216, the set value is subtracted from the current duty ratio DUTY to set a new duty ratio DUTY, thereby returning the intake heating control amount to the initial state.

Further, in the present embodiment, the duty ratio DUTY of the drive signal for the heated intake air amount adjusting valve 72 during the compression ignition control is set to the ignition timing τA and the target ignition timing τTAG.
Although it is set by integral control according to the result of comparison with T, the present invention is not limited to this, and may be set by proportional integral control (PI control) or proportional integral derivative control (PID control). .

The heating intake air amount adjusting valve 72 is not limited to the duty solenoid valve type heating intake air amount adjusting valve of the present embodiment, but may be of any appropriate type.

Further, in the present embodiment, the heat exchanger 70 is disposed in the exhaust system of the engine, and a part of the intake air flowing through the intake system is exchanged with the exhaust gas to heat the intake air. However, the present invention is not limited to this. For example, a heat exchanger is provided in the engine 1 itself, and a part of intake air is exchanged with heat generated by the engine to perform intake air heating. Is also good.

Next, a third embodiment of the present invention will be described with reference to FIGS.

In the present embodiment, as shown in FIG. 23, an electric heater 80 such as a well-known PTC heater is interposed in the intake system as the intake heating means.

When the ignition timing τA is on the advance side of the target ignition timing τTAGT, the calorific value of the heater 80 is controlled to be reduced to lower the intake air temperature, so that the temperature of the air-fuel mixture in the engine combustion chamber 17 is reduced. And the ignition timing due to self-ignition is retarded. When the ignition timing τA is on the retard side of the target ignition timing τTAGT, the amount of heat generated by the heater 80 is controlled to increase to increase the intake air temperature, thereby increasing the combustion chamber 1.
The temperature of the air-fuel mixture in 7 is raised, and the ignition timing by self-ignition is advanced.

The cooling water temperature TW representing the engine temperature
Reaches a predetermined temperature, the engine warm-up is completed, combustion is stabilized, and it is determined that it is possible to shift to self-ignition.
The temperature of the air-fuel mixture in the combustion chamber 17 is raised, and the ignition plug 1
The process shifts from spark ignition by the discharge of 8 to self-ignition.

Further, at the time of self-ignition, when the ignition timing τA is on the retard side of the target ignition timing τTAGT and the amount of heat generated by the heater reaches the limit value, the intake air temperature control by the heater 80 becomes impossible and the ignition of self-ignition is started. When it is determined that the timing cannot be controlled, the amount of heat generated by the heater is reduced, and a transition is made from self-ignition to spark ignition by discharging the spark plug 18.

Note that the same components as those in the above-described embodiments are denoted by the same reference numerals, and description thereof will be omitted.

First, the heater 80 of this embodiment will be described.

As shown in FIG. 23, the heater 80
An intake system is provided in an intake passage in the intake manifold 3 for each cylinder.

Further, as shown in FIG. 24, the power supply voltage to the heater 80 is made variable via the drive circuit 58 to the output port of the I / O interface 56 of the ECU 50, and the amount of heat generated by the heater 80 is adjusted by adjusting the power supplied to the heater. A well-known heater control module for adjusting (hereinafter, “HT
CM ”), and the HTC
The heater 80 is connected to M81. Then, the battery 61 is connected to the HTCM 81 via the ignition switch 62, and power is supplied.

The HTCM 81 changes the battery voltage VB from the battery 61 in accordance with the duty ratio DUTY of the duty signal output from the ECU 50, and supplies the converted voltage to the heater 80 as a power supply voltage. By adjusting the heater supply power by the HTCM 81, the amount of heat generated by the heater 80 is adjusted.

In the present embodiment, the duty ratio DUTY is 0%, and the
Is 0 V, that is, the power supplied to the heater becomes 0, and the heating of the heater is stopped. Also, the duty ratio D
When UTY is 100%, the heater 80
, The maximum voltage is applied, and the amount of heat generated by the heater becomes maximum.

Then, in the ECU 50, the duty ratio DUTY is set between 0% and 100%, and the HTC is set according to the duty signal based on the duty ratio DUTY.
The power supply voltage to the heater 80, that is, the heater supply power is adjusted by M81, and the heat generation amount of the heater 80 is adjusted.

In the present embodiment, the compression ignition control condition determination routine of FIG. 19 and the intake air heating control routine of FIG. 20 of the second embodiment are employed. However, the contents of the set values are different in some steps. The other steps are the same, and a detailed description thereof will be omitted.

Note that other routines (cylinder determination / engine speed calculation routine, ignition control routine, θ2 crank pulse interrupt routine, TDWL interrupt routine,
As for the TADV interruption routine and the ignition timing detection routine), the routine of the first embodiment is adopted as it is, and the description is omitted.

The compression ignition control condition determination routine and the intake heating control routine of this embodiment will be described below with reference to FIG.
And FIG.

First, the compression ignition control condition determination routine will be described with reference to FIG. 19. Referring to the compression ignition control flag FCOMP in step S11, compression ignition control for performing self-ignition has already been instructed when FCOMP = 1. In some cases, the process jumps to step S19, and in steps S19 and S20, the current engine speed NE and intake air amount Q are set to the previous value NEOL.
D and QOLD are stored in a predetermined address of the RAM 53, and the process exits from the routine.

On the other hand, when FCOMP = 0 and the forced ignition control is currently selected and the forced ignition by the discharge of the spark plug 18 is being performed, the process proceeds to step S12, and steps S12 to S1 are performed.
5. In S22, it is determined whether a condition for shifting to compression ignition control is satisfied.

At steps S12 and S13, | NE-NE
OLD |> NES or | Q-QOLD |> QS, when the engine is in the transient operation state, the corresponding step starts from step S18.
Then, the condition duration count value CN is cleared, and in subsequent steps S19 and S20, the engine speed NE and the intake air amount Q are set to the previous values NEOLD and QOLD, respectively, and the routine exits. Continue the forced ignition control by ignition.

In steps S12 and S13, | N
When the engine is in the steady operating condition of E-NEOLD | ≤NES and | Q-QOLD | ≤QS, the routine proceeds to step S14, where the engine coolant temperature TW is read out by the coolant temperature sensor 36 as an example of the engine temperature, and the coolant temperature TW is read. Is compared with the set value TWS to determine whether or not the engine warm-up is completed.

When the engine 1 has not been fully warmed up if TW <TWS, the routine jumps to step S18, exits the routine through steps S18 to S20, and sets TW ≧ TW.
When the warm-up of S is completed, the process proceeds to step S15.

In step S15, the ignition timing TADV and the ignition timing τA in the ignition control routine of FIG. 4 and the ignition timing detection routine of FIG.
The ignition timing TADV is subtracted from A, and this subtracted value is set to a set value TSE.
By comparing with T, it is determined whether self-ignition is possible. If τA−TADV> TSET and the time interval between the ignition timing TADV and the ignition timing τA exceeds a predetermined time determined by the set value TSET, it is determined that self-ignition is impossible, and the routine exits through the above steps S18 to S20. , Spark plug 1
The forced ignition control by the spark ignition of No. 8 is continued.

On the other hand, in step S15, τA-TAD
When V ≦ TSET and the time interval between the ignition timing TADV and the ignition timing τA is reduced to a time within a predetermined value according to the set value TSET, it is determined that self-ignition is possible at an appropriate ignition timing, and step S21 is performed. Then, the condition duration count value CN that counts the duration of satisfaction of the switching condition to the compression ignition control under all the conditions of steps S12 to S15 is counted up, and in step S22, the condition duration time count value CN is counted up.
Is compared with the set value CSET.

If CN <CSET, it is determined that the condition for switching to the compression ignition control is not yet satisfied, and the routine proceeds to step S19, exits the routine through steps S19 and S20, and sparks the spark plug 18. Continue the forced ignition control by ignition.

In step S22, CN ≧ CSE
At T, when the continuation time of all the conditions satisfied in steps S12 to S15 reaches a predetermined time determined by the execution cycle of this routine and the set value CSET, the process proceeds to step S23, and the compression ignition control flag FCOMP is reset. By setting (FCOMP ← 1), the forced ignition control by the spark ignition of the spark plug 18 is stopped, and the compression ignition control for performing the self-ignition is selected.

Then, in step S24, the condition continuation time count value CN is cleared.
Duty ratio DU of duty signal for TCM81
TY is initialized with an initial value DINI (DUTY ← D
INI), exit the routine.

The compression ignition control flag FCOMP
This is referred to in the above-described ignition control routine of FIG. 4, the θ2 crank pulse interruption routine of FIG. 5, and the intake heating control routine of FIG. 20, and at the time of the forced ignition control of FCOMP = 0, the ignition timing depends on the engine operating state. TADV is set to perform forced ignition by spark ignition of the spark plug 18 and stop intake air heating. Here, even in the forced ignition control, the HTCM 8 may be changed according to the engine operating state.
It is also possible to set the duty ratio DUTY of the duty signal with respect to 1 and control the amount of heat generated by the heater to perform intake air heating.

Also, at the time of compression ignition control with FCOMP = 1,
The setting of the ignition timing TADV is stopped, the forced ignition by spark ignition of the spark plug 18 is stopped, and at the time of shifting to the compression ignition control, the duty ratio DUTY of the duty signal with respect to the HTCM 81 is set to the initial value DINI in step S201. Is increased by a predetermined amount, and correspondingly HTC
The power supply voltage from M81 to the heater 80, that is, the heater supply power is increased by a predetermined amount, and the heating of the heater 80 is started, or the heating value of the heater is increased, so that the heating of the intake air by the heater 80 is started or the heating of the intake air by the heater 80 is started. As the amount increases, the intake air temperature rises, thereby increasing the temperature of the air-fuel mixture supplied into the combustion chamber 17 and causing the ignition plug 18
Is switched from forced ignition by spark ignition to self-ignition.

After the shift to the compression ignition control, the duty cycle for the HTCM 81 is determined according to the result of comparison between the ignition timing τA detected based on the ion current and the target ignition timing τTAGT set based on the engine operating state. By setting the duty ratio DUTY of the signal, adjusting the power supply voltage to the heater 80 by the HTCM 81 and controlling the heat generation amount of the heater 80, the ignition timing τA becomes equal to the target ignition timing τTAG.
Control the intake air temperature to converge to T.

Next, the intake air heating control routine will be described with reference to FIG. 20. In step S81, the compression ignition control flag FCOMP is referred to. Stop heating. As described above, in the present embodiment, at the time of the forced ignition control, the intake air heating by the heater 80 is stopped, but also at the time of the forced ignition control, the duty ratio DUTY of the duty signal to the HTCM 81 according to the engine operating state. May be set, and the heating value of the heater may be controlled to perform the intake air heating.

On the other hand, in step S81, FCOMP =
In step 1, when the forced ignition by the spark ignition of the spark plug 18 is stopped and the compression ignition control for performing the self-ignition is instructed, the process proceeds to step S92, and by the processing after step S92, the ignition timing τA and the target ignition are set. HTCM by feedback control according to the comparison result with time τTAGT
The intake temperature control by the heater 80 is performed by setting the duty ratio DUTY of the duty signal to 81, and control is performed so that the ignition timing τA due to self-ignition converges to the target ignition timing τTAGT.

In step S92, the basic target ignition angle ADVτBASE based on the compression top dead center is set by referring to a table based on at least one of the engine speed NE and the basic fuel injection pulse width Tp representing the engine load. In the following step S93, a coolant temperature TW as an example of the engine temperature is read, and a coolant temperature correction coefficient Kτ is set based on the coolant temperature TW by referring to a coolant temperature correction coefficient table.

Next, proceeding to step S94, the basic target ignition angle ADVτBASE is corrected by the water temperature correction coefficient Kτ to set the target ignition angle ADVτTGT (ADVτTGT
← ADVτBASE × Kτ) In step S95, the target ignition angle ADVτTGT based on the compression top dead center is converted to time to set the target ignition timing τTAGT based on the θ2 crank pulse input (τTAGT ← (Tθ / θ ) × (θ2-A
DVτTGT)).

Then, the flow advances to step S96 to go to step S96.
By the following processing, the duty ratio DUTY of the duty signal for the HTCM 81 is set in accordance with the comparison result between the actual ignition timing τA detected in the above-described ignition timing detection routine and the target ignition timing τTAGT, and the heater 8
The intake air temperature control is performed by controlling the heating value of 0, and the feedback control is performed so that the ignition timing τA converges to the target ignition timing τTAGT.

In step S96, the latest ignition timing τA is read out by the ignition timing detection routine, and the target ignition timing upper limit (τTAGT + α) obtained by adding the ignition timing τA and the target ignition timing τTAGT to the set value α defining the dead zone width. Compare.

If τA <τTAGT + α, the process proceeds to step S97, and the ignition timing τA is further reduced to the target ignition timing lower limit (τTA) obtained by subtracting the set value from the target ignition timing τTAGT.
GT-α).

As a result, when τA ≧ τTAGT−α, and the ignition timing τA is within the range of the dead zone for the target ignition timing τTAGT (τTAGT + α> τA ≧ τTAGT−α), the routine exits as it is and the duty for the current HTCM 81 is obtained. Signal duty ratio DUTY, that is, heater 8
The intake heating amount by 0 is maintained as it is.

In step S97, τA <τTA
GT-α, outside the dead zone, and when the ignition timing τA is more advanced than the target ignition timing τTAGT, step S211
To the setting value DDI from the current duty ratio DUTY.
A new duty ratio DUTY is set by subtracting NT (DUTY ← DUTY−DDINT).

Then, the flow advances to step S217 to set a new duty ratio DUTY in step S211 and exit from the routine.

As a result, a duty signal based on the duty ratio DUTY is output from the ECU 50 to the HTCM 81, and the power supply voltage to the heater 80 by the HTCM 81, that is, the heater supply power, decreases by a predetermined amount determined by the set value DDINT. As the amount decreases, the amount of intake air heating by the heater 80 decreases, and the intake air temperature decreases.

That is, during compression ignition control in which spark ignition of the spark plug 18 is stopped and self-ignition is performed, if the ignition timing τA deviates from the dead zone on the advance side of the target ignition timing τTAGT (τA <τTAGT−α). H every time this routine is executed
Duty ratio DU of duty signal for TCM81
TY is decreased by the set value DDINT, and the heater supply power, that is, the heat generation amount of the heater 80 is gradually reduced. Then, due to the decrease in the amount of heat generated by the heater, the amount of heating of the intake air by the heater 80 decreases, and the intake air temperature decreases. As the intake air temperature decreases, the temperature of the air-fuel mixture supplied into the combustion chamber 17 decreases. The ignition timing τA due to self-ignition is retarded due to the decrease in the in-cylinder temperature at the time, and the ignition timing τA due to self-ignition converges to the target ignition timing τTAGT suitable for the engine operating state.

The ignition timing τA is equal to the target ignition timing τTAG.
When the value converges within the dead zone range for T, the decrease correction of the duty ratio DUTY is stopped, and the duty ratio DUTY of the duty signal for the HTCM 81, that is, the amount of intake air heating by the heater 80 is maintained as it is.

On the other hand, in step S96, τA ≧ τTA
GT + α, and if the ignition timing τA is on the retard side of the target ignition timing τTAGT outside the dead zone, step S212
To the current duty ratio DUTY and the set value UDIN
A new duty ratio DUTY is set by adding T (DUTY ← DUTY + UDINT).

Then, the flow advances to step S217, where the engine speed NE and the basic fuel injection pulse width T representing the engine load are set.
The upper limit value DUTYMAX that sets the upper limit of the duty ratio DUTY of the duty signal for the HTCM 81 is set by referring to the upper limit value table with interpolation calculation based on p.

The upper limit value table indicates that the engine speed N
An appropriate upper limit value DUTYMAX of the duty ratio DUTY of the duty signal for the HTCM 81 is obtained in advance by simulation or experiment or the like for each engine operating region based on E and the basic fuel injection pulse width Tp, and is stored in a series of addresses in the ROM 52. .

As shown in step S213, as in the second embodiment, the upper limit value table includes a high load region where the basic fuel injection pulse width Tp is large and a low rotation region where the engine speed NE is low. , The upper limit value DUTYMAX of a small value is stored. Conversely, as the basic fuel injection pulse width Tp is smaller and the engine speed NE is higher, that is, as the engine shifts to the low engine load high speed region, the larger upper limit value DUTYMAX is stored.

That is, as described above, the higher the load, the lower the rotation, the longer the basic target ignition angle ADVτBASE is set to retard the target ignition timing τTAGT, so that the combustion period at the time of the high load, low rotation is performed. And the upper limit value DUTYMAX of the duty ratio DUTY of the duty signal with respect to the HTCM 81 which is set in accordance with the comparison between the target ignition timing τTAGT and the ignition timing τA.
Is correspondingly reduced, it is possible to appropriately set the upper allowable limit.

Further, as the engine speed becomes lower and the engine speed becomes higher, the basic target ignition angle ADVτBASE is advanced to set the target ignition timing τTA
By advancing the GT, the combustion period is relatively advanced, and the delay in combustion during low-load high-speed rotation is suppressed to improve thermal efficiency. Accordingly, the duty ratio DU is correspondingly adjusted.
The upper limit value DUTYMAX of TY is increased.

Thus, the duty ratio DUT corresponding to the target ignition timing .tau.
It is possible to set an appropriate upper limit value DUTYMAX for Y, and it is possible to appropriately set the upper limit allowable limit in each region.

Incidentally, simply, the upper limit value DU is set using only the engine speed NE or the engine load as a parameter.
TYMAX may be set.

Then, the flow advances to step S214 to compare the duty ratio DUTY increased and corrected in step S212 with the upper limit value DUTYMAX set in step S213.
When UTY ≦ DUTYMAX, the duty ratio DUTY of the duty signal with respect to the HTCM 81 is the upper limit value DUTYMAX
In the following cases, the process jumps to step S217, and the duty ratio DUTY increased and corrected in step S212.
To exit the routine.

As a result, a duty signal based on the duty ratio DUTY is output from the ECU 50 to the HTCM 81, and the power supply voltage to the heater 80 by the HTCM 81, that is, the heater supply power, increases by a predetermined amount determined by the set value UDINT. As the amount increases, the amount of intake air heating by the heater 80 increases, and the intake air temperature increases.

That is, in the compression ignition control for performing the self-ignition, if the ignition timing τA deviates from the dead zone on the more retarded side than the target ignition timing τTAGT (τA ≧ τTAGT + α), the duty of the duty signal to the HTCM 81 every time this routine is executed. The ratio DUTY is increased by the set value UDINT, and the heater supply power, that is, the heating value of the heater 80 is gradually increased. Then, due to the increase in the amount of heat generated by the heater, the amount of intake air heating by the heater 80 increases, and the intake air temperature rises. As the intake air temperature rises, the temperature of the air-fuel mixture supplied into the combustion chamber 17 increases, and the compression stroke The ignition timing τA due to self-ignition is advanced by the rise of the in-cylinder temperature at the time, and the ignition timing τA due to self-ignition converges to the target ignition timing τTAGT suitable for the engine operating state.

Then, the ignition timing τA is equal to the target ignition timing τTAG.
When it converges within the range of the dead zone for T, the increase correction of the duty ratio DUTY is stopped, and the duty ratio DUTY of the duty signal for the HTCM 81, that is, the amount of intake air heating by the heater 80 is maintained as it is.

Therefore, by the above intake air temperature control, the ignition timing τA is controlled so as to converge to the target ignition timing τTAGT suitable for the engine operation state even when the engine operation conditions, atmospheric conditions, etc. change. It is possible to always obtain the optimal ignition timing τA, and it is possible to improve fuel efficiency and reliability by improving thermal efficiency.

Also in the present embodiment, it is possible to obtain the optimum ignition timing regardless of the difference in the engine operation state, so that abnormal combustion such as knocking can be avoided beforehand. Adverse effects on the engine can be avoided beforehand, and engine noise can be reduced.

On the other hand, in step S214, the DUT
Y> DUTYMAX, the ignition timing τA does not converge to the target ignition timing τTAGT even after the increase correction of the duty ratio DUTY, and the duty DUTY of the duty signal for the HTCM 81 exceeds the upper limit value DUTYMAX set based on the engine operating state. That is, since the ignition timing τA due to self-ignition is retarded from the target ignition timing τTAGT, the duty ratio DUTY is sequentially increased and corrected. As a result, the duty ratio DUTY exceeds the upper limit value DUTYMAX, and the heat generation amount of the heater 80 becomes higher than the engine operation amount. When the limit value according to the state is reached, the transition to the engine transient operation or the system abnormality etc. makes it impossible to control the intake air temperature by adjusting the heater supply power (heater calorific value) and control the ignition timing τA by self-ignition. Or that self-ignition itself has been disabled. And, step
Proceed to S215.

Then, in step S215, the compression ignition control flag FCOMP is cleared (FCOMP ← 0), and the subsequent step S2
At 16, the duty ratio DUTY of the duty signal for the HTCM 81 is set to 0% (DUTY ← 0), and step S2
At 17, the duty ratio DUTY in step S216 is set, and the routine exits.

As a result, the compression ignition control is shifted from the compression ignition control to the forced ignition control by clearing the compression ignition control flag FCOMP. In the above-described ignition control routine, the setting of the ignition timing TADV, the energization start timing TDWL, and the setting of each ignition timer are performed. Then, the forced ignition by the spark ignition of the spark plug 18 is restarted.

As a result, the transition to the engine transient operation is performed,
Alternatively, the intake air temperature control by adjusting the amount of heat generated by the heater becomes impossible due to a system abnormality or the like, and the ignition timing τ due to self-ignition
When it becomes impossible to control A or when the self-ignition itself becomes impossible, the ignition plug 1
Thus, it is possible to reliably shift to the forced ignition by the ignition of No. 8. As a result, also in the present embodiment, continuation of self-ignition in a state where the ignition timing τA due to self-ignition is uncontrollable is prevented, and deterioration of drivability can be prevented. Further, by preventing abnormal combustion and misfire due to continuation of self-ignition, deterioration of exhaust emission can be prevented and durability durability of the engine 1 can be improved.

At this time, the duty ratio DUTY is set to 0%, and the operation returns to the initial state. In response to this, the heat generation amount of the heater 80 decreases, and the intake air heating is stopped.

In this embodiment, the duty ratio DUTY of the duty signal for the HTCM 81 is set to 0% and the intake air heating by the heater 80 is stopped with the shift from the compression ignition control to the forced ignition control. Even during the ignition control, the HTCM 81
When the intake air heating is performed by setting the duty ratio DUTY of the duty signal with respect to, the set value is subtracted from the current duty ratio DUTY in step S216 to set a new duty ratio DUTY, and thus the intake air by the heater 80 is set. Return the heating control amount to the initial state.

In the present embodiment, the duty ratio DUTY of the duty signal for the HTCM 81 during the compression ignition control is set to the ignition timing τA and the target ignition timing τTAGT.
Is set by integral control according to the comparison result with
The present invention is not limited to this. Proportional-integral control (PI control)
Or you may make it set by proportional integral derivative control (PID control).

Further, the heater 80 as the intake air heating means according to the present invention is not limited to the one in which the HTCM 81 of the present embodiment controls the amount of heat generated by the heater. Of course, an appropriate one may be adopted.

In each of the above embodiments, the ignition timing control and the ignition timing detection at the time of the forced ignition control are performed by a so-called time control method. However, the present invention is not limited to this. Of course, it may be adopted.

Further, in each of the embodiments, the ion current detection circuit 45 is provided only in the specific cylinder, and the ignition timing of this specific cylinder is detected. An ion current detection circuit may be provided to detect an ignition timing for each cylinder and control the intake air temperature based on the ignition timing.

[0371]

As described above, according to the first aspect of the present invention, the air-fuel mixture in the combustion chamber self-ignites and the ignition timing is determined based on the ion current flowing through the ions due to the presence of the ions of the combustion gas. At the same time, the target ignition timing is set based on the engine operating state. Then, according to the comparison result between the ignition timing and the target ignition timing, the intake air heating means for heating the intake air is controlled and the intake air temperature is controlled, so that it is appropriate to obtain the target ignition timing corresponding to the engine operating state. It is possible to obtain an appropriate mixture temperature in the combustion chamber. Therefore, even if engine operating conditions, atmospheric conditions, and the like change, the ignition timing by self-ignition can be controlled to the target ignition timing that matches the engine operating condition, that is, the optimal timing.

According to the second aspect of the present invention, as the intake air heating means, an exhaust gas recirculation path for recirculating exhaust gas from the engine to the intake system, and an exhaust gas recirculation rate interposed in the exhaust gas recirculation path are adjusted. An exhaust gas recirculation device comprising an exhaust gas recirculation amount adjusting valve to be used. When the ignition timing is more advanced than the target ignition timing, the exhaust gas recirculation rate is controlled to decrease by the exhaust gas recirculation amount adjusting valve to lower the intake air temperature, thereby reducing the temperature of the air-fuel mixture in the engine combustion chamber. The ignition timing by self-ignition is retarded. Also,
When the ignition timing is more retarded than the target ignition timing, the exhaust gas recirculation rate is controlled to be increased by the exhaust gas recirculation amount adjusting valve to raise the intake air temperature, thereby increasing the temperature of the air-fuel mixture in the engine combustion chamber, Since the ignition timing of self-ignition is advanced, the ignition timing is controlled so that it converges to the target ignition timing that matches the engine operating condition, even if the engine operating conditions or atmospheric conditions change, so that it is always optimal during self-ignition It is possible to obtain a proper ignition timing, and it is possible to improve fuel efficiency and reliability by improving thermal efficiency.

Further, since the optimum ignition timing can be obtained irrespective of the difference in the engine operating state, abnormal combustion such as knocking can be avoided beforehand.
This has the effect of not only preventing adverse effects on the engine, but also reducing engine noise.

According to the third aspect of the invention, when the temperature of the recirculated exhaust gas or the exhaust gas reaches a predetermined temperature, the exhaust gas recirculation rate by the exhaust gas recirculation amount adjusting valve is increased by a predetermined amount, so that the ignition plug Since the transition from spark ignition by discharge to self-ignition is made, in addition to the effect of the invention of claim 2,
When it is determined that it is possible to shift to self-ignition by raising the intake air temperature by the exhaust gas recirculation, the exhaust gas recirculation rate by the exhaust gas recirculation amount adjusting valve is increased by a predetermined amount to control the intake air temperature to rise, and combustion is performed. By raising the temperature of the air-fuel mixture in the room, it is possible to reliably shift to self-ignition. That is, when the temperature of the exhaust gas recirculation gas or the exhaust gas rises and the ignition timing at the time of the self-ignition can be appropriately controlled by the intake air temperature control by the exhaust gas recirculation, the operation is reliably shifted to the self-ignition. be able to. Therefore, it is possible to prevent the transition to the self-ignition in a state where the intake air temperature cannot be controlled, that is, in a state where the control to the target ignition timing cannot be performed, and the controllability can be improved. Further, there is an effect that abnormal combustion due to misfire or ignition timing mismatch at the time of shifting to self-ignition can be prevented, and deterioration of exhaust emission can be prevented.

According to the present invention, when the ignition timing is on the retard side of the target ignition timing and the opening degree of the exhaust gas recirculation amount adjusting valve reaches a limit value, the exhaust gas recirculation amount adjusting valve To reduce the exhaust gas recirculation rate by a predetermined amount and shift from self-ignition to spark ignition by discharge of the spark plug,
In addition to the effects of the invention described in claim 2 or 3,
When transition to engine transient operation or due to system abnormalities, intake air temperature control due to exhaust gas recirculation becomes impossible and it becomes impossible to control the ignition timing due to self-ignition, or self-ignition itself becomes impossible At times, it is possible to reliably shift from self-ignition to forced ignition by ignition of a spark plug. Therefore, continuation of self-ignition in a state where ignition timing cannot be controlled is prevented, and deterioration of drivability can be prevented. In addition, since abnormal combustion and misfire due to continuous self-ignition are prevented, deterioration of exhaust emission can be prevented, and the durability of the engine can be improved.

According to the fifth aspect of the present invention, as the intake air heating means, a heat exchanger for exchanging heat with exhaust gas or heat generated by the engine and a part of the intake air flowing through the intake system are introduced into the heat exchanger. A heat intake passage for returning the heated intake air after the heat exchange by the heat exchanger to the intake system, and a heated air intake amount interposed in the heated air passage and adjusting a flow rate of the heated intake air flowing through the heated intake passage. An intake heating device consisting of a valve is adopted. When the ignition timing is more advanced than the target ignition timing, the temperature of the air-fuel mixture in the engine combustion chamber is reduced by controlling the amount of heated intake air by the heated intake air amount adjusting valve to decrease the intake air temperature. The ignition timing by self-ignition is retarded. Further, when the ignition timing is retarded from the target ignition timing, the heating intake air flow rate is controlled to be increased by the heating intake air amount adjustment valve to increase the intake air temperature, thereby increasing the temperature of the air-fuel mixture in the engine combustion chamber, Since the ignition timing of self-ignition is advanced, the target ignition timing converges to the engine operation state even if the engine operating conditions or atmospheric conditions change, as in the effect of the second aspect of the present invention. The ignition timing is controlled as described above, and it is possible to always obtain the optimal ignition timing at the time of self-ignition, and it is possible to improve fuel efficiency and reliability by improving thermal efficiency. Further, since it is possible to obtain the optimal ignition timing regardless of the difference in the engine operation state, abnormal combustion such as knocking can be avoided beforehand, and as a result, adverse effects on the engine can be avoided beforehand. In addition, it has the effect of reducing engine noise.

In the invention according to claim 6, when the engine temperature reaches a predetermined temperature, the flow rate of the heated intake air by the heated intake air amount adjusting valve is increased to shift from spark ignition by discharge of the spark plug to self-ignition. Therefore, in addition to the effect of the fifth aspect of the present invention, when it is determined that it is possible to shift to self-ignition by increasing the intake air temperature by heat exchange with exhaust gas or heat generated by the engine, it is possible to adjust the heated intake air amount. By increasing the flow rate of the heated intake air by the valve, the intake air temperature is controlled to rise, the temperature of the air-fuel mixture in the combustion chamber is increased, and the self-ignition can be reliably shifted. That is, it is possible to appropriately control the ignition timing at the time of self-ignition by controlling the intake temperature by controlling the flow rate of the heated intake air obtained by heat exchange between the exhaust gas or the engine temperature and the heat exchange with the exhaust gas or the heat generated by the engine. When you can do it,
It is possible to reliably shift to self-ignition. Therefore, it is possible to prevent the transition to the self-ignition in a state where the intake air temperature cannot be controlled, that is, in a state where the control to the target ignition timing cannot be performed, and the controllability can be improved. Further, there is an effect that abnormal combustion due to misfire or ignition timing mismatch at the time of shifting to self-ignition can be prevented, and deterioration of exhaust emission can be prevented.

In the invention according to claim 7, when the ignition timing is on the retard side of the target ignition timing and the valve opening of the heated intake air amount adjusting valve reaches a limit value, the heating by the heated air intake amount adjusting valve is performed. Since the flow rate of the intake air is reduced to shift from self-ignition to spark ignition due to discharge of the spark plug, in addition to the effects of the invention described in claim 5 or 6, in addition to the transition to engine transient operation or system abnormality, etc. For this reason, when the intake air temperature control by heating intake air flow rate adjustment becomes impossible and it becomes impossible to control the ignition timing by self-ignition, or when the self-ignition itself becomes impossible, forced self-ignition by ignition of the ignition plug It is possible to reliably shift to ignition. Therefore, continuation of self-ignition in a state where ignition timing cannot be controlled is prevented, and deterioration of drivability can be prevented. In addition, since abnormal combustion and misfire due to continuous self-ignition are prevented, deterioration of exhaust emission can be prevented, and the durability of the engine can be improved.

According to the eighth aspect of the present invention, a heater interposed in the intake system is employed as the intake heating means. When the ignition timing is on the advance side of the target ignition timing,
By reducing the amount of heat generated by the heater to lower the intake air temperature, the temperature of the air-fuel mixture in the engine combustion chamber is reduced, and the ignition timing due to self-ignition is retarded. When the ignition timing is more retarded than the target ignition timing, the amount of heat generated by the heater is controlled to increase to increase the intake air temperature, thereby increasing the temperature of the air-fuel mixture in the engine combustion chamber, and causing the ignition timing due to self-ignition. In the same manner as the effect of the second or fifth aspect of the present invention, even if the engine operating conditions, atmospheric conditions, and the like change, the ignition timing converges to the target ignition timing suitable for the engine operating state. The ignition timing is controlled, so that it is possible to always obtain the optimal ignition timing at the time of self-ignition, and it is possible to improve fuel efficiency and reliability by improving thermal efficiency. Further, since it is possible to obtain the optimal ignition timing regardless of the difference in the engine operation state, abnormal combustion such as knocking can be avoided beforehand, and as a result, adverse effects on the engine can be avoided beforehand. In addition, it has the effect of reducing engine noise.

In the ninth aspect of the present invention, when the engine temperature reaches a predetermined temperature, the calorific value of the heater is increased to shift from spark ignition by discharge of the spark plug to self-ignition. In addition to the effects of the invention described in 8,
When it is determined that the engine temperature has reached a predetermined temperature and the engine has been fully warmed up and combustion has stabilized and it is possible to shift to self-ignition, the amount of heat generated by the heater is increased to control the intake air temperature to rise, and the temperature in the combustion chamber is increased. By raising the temperature of the air-fuel mixture, self-ignition can be reliably transferred. That is, when the engine temperature rises to a predetermined value and combustion stabilizes, and the ignition timing at the time of self-ignition can be properly controlled by the intake air temperature control by the heater heat generation amount control, the self-ignition is reliably performed. Can be transferred to. Therefore, it is possible to prevent the transition to the self-ignition in a state where the intake air temperature cannot be controlled, that is, in a state where the control to the target ignition timing cannot be performed, and the controllability can be improved. Further, there is an effect that abnormal combustion due to misfire or ignition timing mismatch at the time of shifting to self-ignition can be prevented, and deterioration of exhaust emission can be prevented.

According to the tenth aspect, when the ignition timing is on the retard side of the target ignition timing and the calorific value of the heater reaches the limit value, the calorific value of the heater is reduced, and the ignition plug is switched from self-ignition to the ignition plug. In addition to the effect of the invention described in claim 8 or 9, the intake air temperature control by adjusting the heater heating value due to the transition to the engine transient operation or the system abnormality, etc. When it becomes impossible to control the ignition timing by self-ignition, or when self-ignition itself becomes impossible, it is possible to reliably shift from self-ignition to forced ignition by ignition of the spark plug. Therefore, continuation of self-ignition in a state where ignition timing cannot be controlled is prevented, and deterioration of drivability can be prevented. In addition, since abnormal combustion and misfire due to continuous self-ignition are prevented, deterioration of exhaust emission can be prevented, and the durability of the engine can be improved.

In this case, according to the eleventh aspect of the present invention, the limit value is set according to at least one of the engine load and the engine speed. In addition to the effects of the above, the exhaust gas recirculation rate by the exhaust gas recirculation amount regulating valve, the heating air supply rate by the heated intake air amount regulating valve, or the heating value of the heater are determined according to the target ignition timing that differs for each engine operation region. The upper limit value of each control amount to be performed can be appropriately set, and the upper limit allowable limit can be appropriately set in each operation region.

In the twelfth aspect of the present invention, the target ignition timing is set according to at least one of the engine load and the engine speed.
In addition to the effects of the invention described in 1 above, it is possible to set an appropriate target ignition timing corresponding to a combustion period that differs for each engine operation region, and to improve the thermal efficiency in each engine operation region. Have.

According to the thirteenth aspect of the present invention, the target ignition timing is corrected in accordance with the engine temperature. Therefore, in addition to the effects of the first to twelfth aspects, the optimum ignition timing adapted to the engine temperature condition is provided. It is possible to obtain the ignition timing, and it is possible to improve the exhaust emission,
In addition, there is an effect that it is possible to prevent adverse effects on the engine due to mismatching of the ignition timing.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram of the present invention.

FIG. 2 is a flowchart of a cylinder discrimination / engine speed calculation routine according to the first embodiment of the present invention;

FIG. 3 is a flowchart of a compression ignition control condition determination routine;

FIG. 4 is a flowchart of an ignition control routine according to the first embodiment;

FIG. 5 is a flowchart of the θ2 crank pulse interruption routine.

FIG. 6 is a flowchart of a TDWL interrupt routine;

FIG. 7 is a flowchart of a TADV interrupt routine;

FIG. 8 is a flowchart of an ignition timing detection routine;

FIG. 9 is a flowchart of an EGR control routine according to the second embodiment;

FIG. 10 is a flowchart of an EGR control routine (continued)

FIG. 11 is a time chart showing a relationship among a crank pulse, a cam pulse, an ignition timing, and a fuel injection timing.

FIG. 12 is a time chart showing a relationship between a crank pulse and an ion current.

FIG. 13: As above, ignition timing, target ignition timing, and EGR
Time chart showing the relationship between the control amount and the valve

FIG. 14 is an overall schematic diagram of the engine.

FIG. 15 is a front view of the crank rotor and the crank angle sensor according to the first embodiment;

FIG. 16 is a front view of the cam rotor and the cam angle sensor according to the first embodiment;

FIG. 17 is an explanatory diagram of an ion current detection circuit according to the embodiment.

FIG. 18 is a circuit diagram of an electronic control system according to the first embodiment;

FIG. 19 is a flowchart of a compression ignition control condition determination routine according to the second embodiment of the present invention.

FIG. 20 is a flowchart of an intake heating control routine according to the second embodiment;

FIG. 21 is an overall schematic diagram of the engine.

FIG. 22 is a circuit diagram of an electronic control system according to the first embodiment;

FIG. 23 is an overall schematic view of an engine according to a third embodiment of the present invention.

FIG. 24 is a circuit diagram of an electronic control system according to the embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Compression ignition engine 3 Intake manifold (intake system) 4 Air chamber (intake system) 6 Intake pipe (intake system) 17 Combustion chamber 18 Spark plug 25 Exhaust gas recirculation device (EGR device; intake heating means) 26 Exhaust gas recirculation passage ( EGR passage) 27 Exhaust gas recirculation amount adjustment valve (EGR valve) 32 Intake air amount sensor 38 EGR gas temperature sensor 41 Crank angle sensor 45 Ion current detection circuit 45a Voltage sensor 50 Electronic control unit (ignition timing detection means, target ignition timing setting) Means, intake heating control means) 70 heat exchanger 71 heated intake passage 72 heated intake air amount adjusting valve 80 heater 81 heater control module (HTCM) τA ignition timing τTAGT target ignition timing EGRS EGR valve control amount (control amount for EGR valve) TEGR EGR gas temperature (temperature of exhaust gas recirculation gas) TEG RS set value (predetermined temperature) EGRSMAX upper limit value (upper limit value of EGR valve control amount; limit value) DUTY duty ratio (duty ratio of drive signal for heating intake air amount adjustment valve, duty ratio of duty signal for HTCM) TW Cooling water temperature (Engine temperature) TWS set value (predetermined temperature) DUTYMAX Upper limit value (Upper limit value of duty ratio; Limit value) Q Intake air amount (Engine load) Tp Basic fuel injection pulse width (Engine load) NE Engine speed

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301A 301N 301P F02M 25/07 550 F02M 25/07 550R 550F 31/04 31/04 31/07 31/12 311M 31/12 311 311P 31/06 F F02P 17/12 F02P 17/00 E

Claims (13)

[Claims] In a control apparatus for a compression ignition engine that performs self-ignition at the end of a compression stroke or near a top dead center without using spark ignition due to discharge of a spark plug under a predetermined operation range, the air-fuel mixture in a combustion chamber is self-ignited. Ignition timing detection means for detecting an ignition timing based on an ion current flowing through the ions due to the presence of the ions of the ignition and combustion gas; target ignition timing setting means for setting a target ignition timing based on an engine operating state; A control apparatus for a compression ignition engine, comprising: intake air heating control means for controlling intake air heating means for heating intake air in accordance with a result of comparison between an ignition timing and a target ignition timing. 2. An exhaust gas recirculation passage for recirculating exhaust gas of an engine to an intake system, an exhaust gas recirculation amount adjusting valve interposed in the exhaust gas recirculation passage for adjusting an exhaust gas recirculation rate. When the ignition timing is more advanced than the target ignition timing, the intake heating control means reduces the exhaust gas recirculation rate by the exhaust gas recirculation amount adjustment valve, and the ignition timing is later than the target ignition timing. 2. The compression ignition engine control device according to claim 1, wherein the exhaust gas recirculation rate by the exhaust gas recirculation amount adjusting valve is increased when the vehicle is on the corner side. 3. The intake heating control means, when the temperature of the recirculated exhaust gas or the exhaust gas reaches a predetermined temperature, increases the exhaust gas recirculation rate by the exhaust gas recirculation amount adjusting valve by a predetermined amount, and activates the ignition plug. 3. The control device for a compression ignition engine according to claim 2, wherein a transition is made from spark ignition by discharge to self-ignition. 4. The exhaust gas recirculation amount adjusting means when the ignition timing is on the retard side of the target ignition timing and the opening degree of the exhaust gas recirculation amount adjusting valve reaches a limit value. 4. The compression ignition engine control device according to claim 2, wherein the exhaust gas recirculation rate by the valve is reduced by a predetermined amount to shift from self-ignition to spark ignition by discharge of the spark plug. 5. The intake air heating means includes: a heat exchanger for exchanging heat with exhaust gas or heat generated by an engine; a part of intake air flowing through an intake system being introduced into the heat exchanger; A heated air intake passage for returning the heated air after replacement to the intake system, and a heated air intake amount regulating valve interposed in the heated air passage and adjusting a flow rate of the heated air flowing through the heated air intake passage. The heating control means reduces the heating intake flow rate by the heating intake air amount adjusting valve when the ignition timing is advanced from the target ignition timing, and when the ignition timing is retarded from the target ignition timing, the heating intake means 2. The control device for a compression ignition engine according to claim 1, wherein the flow rate of the heated intake air is increased by the amount adjusting valve. 6. The intake air heating control means, when the engine temperature reaches a predetermined temperature, increases the amount of heated intake air by the heated intake air amount adjusting valve to shift from spark ignition by discharge of a spark plug to self-ignition. 6. The method according to claim 5, wherein
A control device for a compression ignition engine according to any one of the preceding claims. 7. When the ignition timing is retarded from the target ignition timing and the valve opening of the heating intake air amount adjustment valve reaches a limit value, the intake air heating control means controls the heating air intake amount adjusting valve. 7. The control device for a compression ignition engine according to claim 5, wherein the flow rate of the heated intake air is reduced to shift from self-ignition to spark ignition by discharge of a spark plug. 8. The intake heating means is a heater interposed in an intake system, and the intake heating control means reduces the amount of heat generated by the heater when the ignition timing is advanced from a target ignition timing. 2. The control device for a compression ignition engine according to claim 1, wherein the amount of heat generated by the heater increases when the ignition timing decreases and the ignition timing is retarded from the target ignition timing. 9. The intake heating control means, when the engine temperature reaches a predetermined temperature, increases the heating value of the heater,
9. The control device for a compression ignition engine according to claim 8, wherein a transition is made from spark ignition by discharge of the spark plug to self-ignition. 10. When the ignition timing is on the retard side of the target ignition timing and the heater calorific value reaches a limit value, the intake heating control means reduces the heater calorific value, and sets the ignition plug to self-ignition. 10. The compression ignition engine control device according to claim 8, wherein the control is shifted to spark ignition due to the discharge of the compression ignition engine. 11. The compression ignition engine control device according to claim 4, wherein said limit value is set according to at least one of an engine load and an engine speed. 12. The compression ignition engine control device according to claim 1, wherein the target ignition timing is set according to at least one of an engine load and an engine speed. 13. The control apparatus for a compression ignition engine according to claim 1, wherein said target ignition timing is corrected in accordance with an engine temperature.