JPH0633819A - Intake air temperature predicting method - Google Patents

Abstract

PURPOSE:To carry out various control to an intake air temperature optimally by predicting hourly intake temperatures during engine operation. CONSTITUTION:An intake air temperature is calculated and predicted per specified time during engine operation by means of calculation parameters consisting of an intake efficiency constant decided by an engine speed and a throttle opening degree at the time of engine operation, a temperature correcting constant decided by the same engine speed and throttle opening degree, an intake pipe absolute pressure and an air weight per unit cycle. An air fuel ratio and an ignition timing are corrected according to predicted intake air temperature so as to prevent knocking and any wrong effect on a catalyst beforehand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an intake air temperature predicting method for predicting intake air temperature in a vehicle engine based on engine operating conditions.

[0002]

2. Description of the Related Art For example, a system equipped with an air-cooled intercooler for a turbocharged engine has been proposed. In this system, the compressed air from the turbocharger is forcibly cooled by the intercooler to improve the charging efficiency. Can be improved. By the way, in the case of an air-cooled intercooler, the intake air temperature is greatly affected by the vehicle speed. Further, the capacity of the intercooler changes due to the outside air temperature, the time-dependent change of the intercooler itself, the adhesion of dust, etc. Therefore, it is expected that the intake air temperature will change momentarily even under the same operating condition and running condition. Then, when the intake air temperature rises, the combustion temperature rises, knocking easily occurs, and the exhaust gas temperature rises, which adversely affects the catalyst. Therefore, in this type of engine, it is desired to detect the intake air temperature momentarily and perform control so as to prevent knocks and adverse effects on the catalyst.

As a method of detecting the intake air temperature, it is generally considered that the intake air temperature of the intake air is directly measured using an intake air temperature sensor. However, since this intake air temperature sensor has a large time constant of an output signal and poor responsiveness, it is not suitable for an engine whose intake air temperature changes momentarily such as a turbocharged engine. Therefore, it is required to quickly predict the intake air temperature by using various parameters during engine operation.

[0004] Conventionally, as for the prediction of the intake air temperature, there is, for example, the prior art of Japanese Patent Laid-Open No. 63-32145.
Since the water temperature when the engine is started is equal to the outside air temperature, the basic temperature coefficient is determined by this water temperature. Further, it is shown that the load coefficient for the basic air flow rate is determined, the intake air temperature coefficient is calculated by both of these, and the air flow rate is corrected.

[0005]

By the way, in the above-mentioned prior art, one intake temperature coefficient is obtained from the outside air temperature and the operating state during engine operation, and is uniformly corrected by this intake temperature coefficient. is there. Therefore, the intake air temperature during engine operation cannot be predicted moment by moment, and therefore various controls for the intake air temperature when operating and running conditions change cannot be performed with high accuracy.

The present invention has been made in view of this point, and an object thereof is to predict the intake air temperature during engine operation from moment to moment and optimally perform various controls for the intake air temperature.

[0007]

In order to achieve the above object, the present invention provides an intake efficiency constant based on engine speed and throttle opening during engine operation, and a temperature correction constant based on the same engine speed and throttle opening. , The intake pipe absolute pressure and the calculation parameter based on the air weight per unit cycle are used to calculate and predict the intake air temperature at predetermined time intervals during engine operation.

[0008]

By the above method, the intake efficiency constant and the temperature correction constant are set by various factors according to the operating state of the engine during operation, the calculation parameters are obtained, and the intake temperature is calculated based on the gas state equation. By doing so, it becomes possible to predict the intake air temperature with high accuracy every moment. Then, by correcting the air-fuel ratio and the ignition timing with respect to the predicted intake air temperature, the knock and the adverse effect on the catalyst can be prevented.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. Referring to FIG. 1, the overall configuration of a horizontally opposed engine equipped with a sequential turbocharger will be described. Reference numeral 1 denotes an engine body of a horizontally opposed engine, which is provided in the left and right banks 3 and 4 of the crankcase 2,
A combustion chamber 5, an intake port 6, an exhaust port 7, a spark plug 8, a valve mechanism 9 and the like are provided. Further, the primary turbo supercharger 40 and the secondary turbo supercharger 50 are respectively arranged immediately after the left and right banks 3 and 4 due to this engine shortening shape. Left and right banks 3, 4 as exhaust system
Is connected to the turbines 40a and 50a of both turbochargers 40 and 50, and the common exhaust pipe 10 from
The exhaust pipe 11 from 50a joins with one exhaust pipe 12, and is connected to the catalytic converter 13 and the muffler 14.

As an intake system, the intake pipes 16 and 17 branched from the air cleaner 15 are connected to the blowers 40b and 50b of the turbochargers 40 and 50, respectively, and the intake pipes 18 and 50 from the blowers 40b and 50b are connected to each other. 19 is communicated with the air-cooled intercooler 20. And the throttle body 2 which has the throttle valve 21 from the intercooler 20
7 to the chamber 22, and from the chamber 22 to the cylinders of the left and right banks 3 and 4 via the intake manifold 23. Further, as an idle control system, an idle control valve 25 and a check valve 26 that opens with negative pressure are provided in a bypass passage 24 between the downstream side of the air cleaner 15 and the intake manifold 23 to control the intake air amount during idle or during deceleration. It is supposed to do.

As a fuel system, an injector 30 is arranged near the port of the intake manifold 23, and the fuel pump 3
The fuel passage 33 from the fuel tank 32 having the fuel cell No. 1 is provided with the filter 34 and the fuel pressure regulator 35 and communicates with the injector 30. The fuel pressure regulator 35 adjusts according to the intake pressure, whereby the fuel pressure supplied to the injector 30 is constantly maintained at a constant height with respect to the intake pressure, and the fuel injection control is performed by the pulse width of the injection signal. It is possible to do. An ignition system is connected to the ignition plug 8 so that an ignition signal from the igniter 36 is input.

The operation system of the primary turbocharger 40 will be described. The primary turbocharger 40 uses the energy of the exhaust gas introduced to the turbine 40a to blower 40b.
It is driven to rotate and sucks and pressurizes air to always supercharge. A waste gate valve 41 having a diaphragm actuator 42 is provided on the turbine side. A control pressure passage 44 from directly downstream of the blower 40b communicates with the pressure chamber of the actuator 42 through an orifice 48 so as to open the waste gate valve 41 with good response when the supercharging pressure rises above a set value. It Further, the control pressure passage 44 communicates the supercharging pressure with a duty solenoid valve 43 that leaks to the upstream side of the blower 40b, and a predetermined control pressure is generated by the duty solenoid valve 43 to act on the actuator 42 to cause a waste gate valve. 41
The supercharging pressure is controlled by changing the opening degree of.
Here, for example, when the duty ratio is large, the control pressure is decreased due to the increase in the leak amount, the opening degree of the waste gate valve 41 is reduced, and the supercharging pressure is increased. On the contrary, when the duty ratio becomes small, the opening degree is increased by the high control pressure to reduce the supercharging pressure.

On the other hand, in order to prevent lowering of blower rotation and generation of intake noise when the throttle valve is closed rapidly, an intercooler 2 near the throttle valve 21 is provided downstream of the blower 40b.
The bypass passage 46 is connected between the outlet side of 0 and the upstream of the blower 40b. An air bypass valve 45 is provided in the bypass passage 46 so as to introduce a manifold negative pressure through a passage 47 and open when the throttle valve is rapidly closed, so that pressurized air trapped downstream of the blower is quickly leaked.

The operation system of the secondary turbocharger 50 will be described. Similarly, the secondary turbocharger 50 is one in which the turbine 50a and the blower 50b are rotationally driven by the exhaust gas to supercharge, and the actuator 5 is provided on the turbine side.
A waste gate valve 51 equipped with 2 is separately provided. A passage 67 immediately downstream of the blower 50b communicates with the pressure chamber of the actuator 52 via a duty solenoid valve 53 and a control pressure passage 54 that leak to the atmosphere, and when the boost pressure rises above a set value, the waste response is good. The gate valve 51 is opened, and a control pressure is generated by the duty solenoid valve 53 so that the boost pressure is similarly controlled. On the other hand, in the exhaust pipe 10 upstream of the turbine 50a, an exhaust control valve 55 equipped with a diaphragm type actuator 56 is provided.
Is provided, and an intake control valve 58 having a similar actuator 57 is provided downstream of the blower 50b.
A relief passage 59 having a boost pressure relief valve 60 is connected between the upper side and the lower side of 0b.

Explaining the pressure operation system of each of these valves, the passage 61 from the intake manifold 23 has a check valve 62 and is communicated with a surge tank 63 to store a negative pressure when the throttle valve is fully closed and a pulsating pressure. Is designed to buffer. A negative pressure passage 64 from the surge tank 63 and a positive pressure passage 65 downstream of the intake control valve 58 communicate with one spring chamber of the boost pressure relief valve 60 via a switching solenoid valve 70 and a passage 66. It Then, a negative pressure acts on the electric signal to open the boost pressure relief valve 60, and a positive pressure acts to close the boost pressure relief valve 60. In the actuator 57 of the intake control valve 58, a switching solenoid valve 71 for switching between negative pressure and atmospheric pressure is provided in the passage 6 in one spring chamber.
It is communicated via 8. Then, a negative pressure is applied by an electric signal to close the intake control valve 58, and the intake control valve 58 is opened by the spring force when the atmosphere is opened.

The exhaust control valve 55 is configured to open downstream, and a spring 56a is provided in one chamber of the actuator 56.
Is urged in the direction to close the exhaust control valve 55. Here, the spring force of the spring 56a is set equal to the force of the exhaust pressure in the preliminary rotation mode in the medium speed range. A second switching solenoid valve 74 for switching between atmospheric pressure and negative pressure is communicated with one chamber having the spring 56a of the actuator 56 through a passage 69, and the other chamber is switched between positive pressure and atmospheric pressure. The first switching solenoid valve 73 is connected via the passage 75. In the single turbo mode, the first and second switching solenoid valves 73 and 74 are operated by an electric signal to open both chambers to the atmosphere and fully close the exhaust control valve 55 by the spring force. When the waste gate valve 41 on the primary side fails and the exhaust pressure rises, it has a function of automatically opening and fail-safe. Further, even in the preliminary rotation mode, this state is maintained for a predetermined time, and the function of a pre-control valve is provided by opening a minute opening degree by the balance between the exhaust pressure and the spring force. Further, in the twin turbo mode, a negative pressure is applied to one chamber and a positive pressure is applied to the other chamber so that the exhaust control valve 55 is fully opened and is kept in the fully opened state.

Explaining various sensors, a differential pressure sensor 80 is provided so as to detect a differential pressure upstream and downstream of the intake control valve 58, and an absolute pressure sensor 81 is connected to the intake pipe pressure by a switching solenoid valve 76. It is provided to select and detect atmospheric pressure. Further, the engine main body 1 is provided with a crank angle sensor 82, a knock sensor 83, and a water temperature sensor 84, and the cam rotor 9 is connected to the cam shaft of the valve mechanism 9.
The cam angle sensor 85 is provided so as to face 0, and the exhaust pipe 10
Is provided with an O ₂ sensor 86, the throttle valve 21 is provided with a throttle opening sensor 87, and an intake air amount sensor 88 is provided immediately downstream of the air cleaner 15.

Further, the crank angle sensor 82 and the cam angle sensor 85 when applied to a four-cylinder engine will be described in detail with reference to FIG. 2. The crank angle sensor 82 is composed of an electromagnetic pickup or the like, and is mounted on the crankshaft. The three kinds of protrusions 91a, which are arranged on the outer periphery of the crank rotor 91, are arranged so as to face the rotor 91.
91c (or a slit) may be detected electrically. The protrusion 91a of the crank rotor 91 is for detecting the fuel injection start timing and the engine speed, and is set at a set angle θ1 of before compression top dead center (BTDC), for example, 97 degrees. The protrusion 91b detects the reference position of the ignition timing, and is set to a set angle θ2 of, for example, 65 degrees before the compression top dead center. The protrusion 91c is for detecting a fixed ignition timing,
It is set to a set angle θ3 of, for example, 10 degrees before the compression top dead center. As a result, when the engine is running, # 1 → # 3 → # 2 →
In the ignition sequence of # 4, a crank pulse as shown in FIG. 12 is generated for each cylinder.

The cam angle sensor 85, which is also composed of an electromagnetic pickup or the like, is arranged so as to face the cam rotor 90 mounted on the cam shaft, and is used for discriminating one to three cylinders formed on the outer circumference of the cam rotor 90. Protrusions 90a to 90c
(Slit is acceptable) is detected electrically. 3 protrusions 9
0b is set after compression top dead center (ATDC) of the # 1 cylinder, for example, at a set angle θ5 of 5 degrees, and one protrusion 90a is set angle after compression top dead center of the # 3 cylinder and the # 4 cylinder, for example, 20 degrees. is set to θ4, and the two protrusions 90c are set to a set angle θ6 of, for example, 20 degrees after the compression top dead center of the # 2 cylinder. As a result, when the engine is operating, a cam pulse is generated at a position where it does not overlap with the crank pulse as shown in FIG. 12, and it is possible to discriminate the cylinder from the number and generation state of the cam pulse.

Next, referring to FIG. 3, the overall structure of the electronic control system will be described. First, the control unit 100 including a microcomputer or the like includes an I / O 101, a CPU 1
02, RAM 103, backup RAM 104, RO
An M105 and a constant voltage circuit 106 are provided. When the ignition switch 90 is turned on, the relay 91 is turned on.
Then, electric power is supplied from the battery 92 to the constant voltage circuit 106 to execute various controls of the control unit 100, and the drive circuit 107 turns on the relay 93 to energize and drive the fuel pump 31. The CPU 102 inputs signals from the various sensors 80 to 88 and the vehicle speed sensor 89 from the I / O 101 on the basis of an arithmetic program stored in the ROM 105,
The arithmetic processing is performed based on the data stored in the RAM 103, the backup RAM 104, and fixed data such as maps stored in the ROM 105. Then, from the drive circuit 107, various switching solenoid valves 70, 71, 7
A switching signal is output to 3, 74 and 76, a duty signal is output to the duty solenoid valves 43 and 53 to perform sequential turbo control, and an injection signal is output to the injector 30 to control fuel injection. Further, an ignition signal is output to the igniter 36 to control the ignition timing, and a control signal is output to the idle control valve 25 to perform idle control.

Next, the intake air temperature predictive control will be described. First, the principle of intake temperature prediction will be described. The intake temperature T (absolute temperature; ° K) is the intake pipe absolute pressure P, the intake air volume V per unit cycle (in the case of a 4-cycle engine, two engine revolutions), the unit cycle. It is represented by the following equation of state of gas by the air weight m per unit and the gas constant R. PV = mRT (1) Therefore, the intake air temperature T is as follows. T = PV / mR (2) Here, if the intake air temperature T can be expressed as a function of P / m by the following equation, T = f (P / m) (3), the intake air temperature T can be predicted. It will be possible.

Then, when the relationship between the intake air temperature T and the calculation parameter P / m was measured by an experiment, it was as shown in FIG. 4 (a). As a result, a certain engine speed (4000 rp
It was found that the intake air temperature T and the calculation parameter P / m in the equation (3) except for m) are linear functions. Further, when the measurement points at an engine speed of 4000 rpm are arranged by the throttle opening, it becomes as shown in FIG. 7B, and the equation (3) may exist independently for each engine speed and each throttle opening. all right. That is, the equation (3) can be expressed as follows using the constants C1 and C0 that represent the engine characteristics. T = C1 (P / m) + C0 (4)

Here, C1 corresponds to V / R and is an intake efficiency constant indicating the intake efficiency in proportion to the intake air volume V per unit cycle. C0 is a temperature correction constant that is corrected when fresh air is sucked into the cylinder and part of it is blown into the exhaust system and further blowback gas is present. Therefore, these constants C1 and C0 are experimentally obtained from the relationship between the engine speed and the throttle opening, given by a map, and set with interpolation calculation. Also, the intake pipe absolute pressure P is determined by the absolute pressure sensor 8
The calculation parameter P / m can be obtained by measuring the signal No. 1 and calculating the air weight m per unit cycle from the intake air amount and the engine speed. Therefore, by using the signals of the engine speed, the throttle opening, the intake air amount, and the absolute pressure of the existing sensor, C1, C0, and P / m are calculated, and the intake temperature T is calculated from moment to moment by the equation (4). It is possible to make predictions with high accuracy.

Next, the operation of this embodiment will be described. First, when the engine is operating, for example, in the low-load low-medium speed single turbo mode, the control unit 100 outputs an open signal to the switching solenoid valve 70 to open the boost pressure relief valve 60, and the boost pressure downstream of the blower on the secondary side. Leak. At the same time, the first and second switching solenoid valves 73,
The exhaust signal is output to the secondary turbocharger 50 by outputting a close signal to the exhaust control valve 55 to close the exhaust control valve 55.
In addition, a closing signal is output to the switching solenoid valve 71 to close the intake control valve 58, whereby the secondary turbocharger 5
0 becomes inactive, and only the primary turbocharger 40 operates.

Next, when the twin turbo mode is entered due to an increase in vehicle speed or the like, the preliminary rotation mode is determined at the beginning of this mode. In the pre-rotation mode, first, a closing signal is output to the switching solenoid valve 70 to output the boost pressure relief valve 60.
Is closed, and then the exhaust control valve 55 is opened by a small opening due to the exhaust pressure, and the exhaust gas is introduced into the secondary turbocharger 50 to be preliminarily rotated. After that, the open signal is output to the first and second switching solenoid valves 73 and 74 to fully open the exhaust control valve 55, so that the secondary turbocharger 50 substantially operates and the differential pressure sensor 80 causes the secondary turbocharger 50 to operate. When the upstream pressure and the downstream pressure of the intake control valve 58 become substantially equal by the determination based on the detected differential pressure, an open signal is output to the switching solenoid valve 71 to open the intake control valve 58, which allows smooth operation. Switch to twin turbo mode.

Further, in each mode, the target boost pressure Pt
And the deviation Δp of the actual supercharging pressure Pb by the absolute pressure sensor 81 is calculated, and the correction amount according to the deviation Δp is determined. Therefore, in the single turbo mode, the duty solenoid valve 43 on the primary side outputs the duty signal corresponding to this correction amount.
And the supercharging pressure of the primary turbocharger 40 is controlled by the opening of the waste gate valve 41. Further, in the twin turbo mode, a duty signal based on the operation distribution of both turbochargers 40, 50 is output to the primary and secondary duty solenoid valves 43, 53, and both are controlled by the opening degree of the waste gate valves 41, 51. Feeder 4
The supercharging pressure of 0, 50 is controlled, and thus the feedback control is performed so that the actual supercharging pressure Pb always follows the target supercharging pressure Pt. The air having a predetermined supercharging pressure compressed by the primary turbo supercharger 40 and the secondary turbo supercharger 50 is cooled by the air-cooled intercooler 20, and the flow rate of the air is controlled by the throttle valve 21 to be higher than that of the engine body 1. It comes to be supplied with filling efficiency.

When the engine is operated by the sequential turbo, the intake temperature T is predicted by the sensor signal used in the turbo operation, and the intake temperature prediction routine executed by the control unit 100 will be described with reference to the flowchart of FIG. To do. This routine is executed every predetermined time. In step S1, a map search is performed using the engine speed N and the throttle opening Th to set the intake efficiency constant C1, and in step S2, the engine speed N and the throttle are similarly set. The map is searched by the opening Th to set the temperature correction constant C0. After that, the routine proceeds to step S3, the air weight m per unit cycle is obtained from the intake air amount Q and the engine speed N, and the intake pipe absolute pressure P is read from the signal of the absolute pressure sensor 81 at step S4. Then, in step S5, these intake efficiency constant C1 and temperature correction constant C
0, the intake air temperature T is calculated using the calculation parameter P / m. Thus, the intake air temperature T increases as the intake pipe absolute pressure P, that is, the supercharging pressure increases with respect to the air weight m per unit cycle during engine operation. Is predicted to be high.

Next, the case where the air-fuel ratio control is corrected by the intake air temperature T will be described with reference to the flowchart of FIG. This routine is executed every predetermined time, and in step S10, the basic injection amount (basic fuel injection pulse width) Tp is calculated by the intake air amount Q, the engine speed N, and the injector characteristic correction constant K, and by Tp = K · Q / N. calculate. After that, in step S11, the feedback correction coefficient α, the air-fuel ratio learning correction coefficient Kb, various correction coefficients COEF,
The voltage correction coefficient Ts is set.

In step S12, the intake temperature correction coefficient Kt is set by referring to the map based on the intake temperature T set by the intake temperature prediction routine. Here, in order to prevent knocking and the like with respect to the rise of the intake air temperature T, it is effective to correct the amount and cool the fuel. Therefore, as shown in FIG. 7, the correction coefficient Kt for the intake air temperature T is given as an increasing function after the predetermined temperature, and the intake air temperature correction coefficient Kt is set by this map. Then, in step S13, these basic injection amounts T
p, feedback correction coefficient α, air-fuel ratio learning correction coefficient K
b, various correction coefficients COEF, intake air temperature correction coefficient Kt and voltage correction correction Ts, the fuel injection amount (fuel injection pulse width) Ti is calculated by Ti = Tp · α · Kb · COEF · Kt + Ts. Thereafter, in step S14, this fuel injection amount Ti is set, and the fuel injection amount by the injector 30 is controlled.

Therefore, when the intake air temperature T is low due to the engine operating condition, the intake air temperature correction coefficient Kt is 1.0, and the air-fuel ratio is controlled near the stoichiometric air-fuel ratio. On the other hand, when the supercharging pressure becomes high on the high speed side and the intake air temperature T is predicted to be high, the fuel injection amount Ti is increased and corrected by the intake air temperature correction coefficient Kt, and rich air-fuel ratio control is performed. Therefore, in this case, the rich air-fuel mixture is used to cool the fuel to lower the combustion temperature, whereby knocking is suppressed and adverse effects on the catalyst are prevented.

A case in which the ignition timing control is corrected by the intake air temperature T will be described with reference to the flowcharts of FIGS. 8 to 10. The cylinder discrimination and engine speed calculation routine of FIG. 8 is executed by interruption by the input of crank pulse and cam pulse. Therefore, in step S20, the ignition target cylinder #i is determined based on the cam pulse, and step S2
The crank pulse is identified by 1. Further, in step S22, the crank angle sensor 82 detects the fuel injection start timing and the engine speed, and a θ1 pulse set at a set angle θ1 of before top dead center (BTDC), for example, 97 degrees,
In order to detect the reference position of the ignition timing, before the top dead center, for example, 65
The input interval time (cycle) Tθ12 with the θ2 pulse determined by the angle set angle θ2 is obtained. And step S23
Then, based on this pulse cycle Tθ12, the engine speed N
To calculate.

The ignition timing setting routine of FIG. 9 is executed every predetermined time. First, in step S30, the basic ignition timing map is referenced with interpolation calculation based on the basic injection amount Tp and the engine speed N. Then, the basic ignition timing ADVb of the angle data according to the engine operating state is set, the knock correction value ADVn according to the presence or absence of knocking is set at step S31, and then the process proceeds to step S32 to refer to the map and the intake air temperature The retard correction value ADVt is set.
Here, in order to prevent knocking or the like with respect to the rise of the intake air temperature T, it is effective to retard the ignition timing. Therefore, as shown in FIG. 11, the retard correction value ADVt for the intake air temperature T is given as an increasing function after the predetermined temperature.
Set t.

Then, in step S33, the control advance amount A as angle data is obtained by the basic ignition timing ADVb, the knock correction value ADVn, and the intake air temperature retard correction value ADVt.
DV is calculated by ADV = ADVb + ADVn-ADVt. Then, in step S34, the control advance amount A
DV is converted into ignition timing Tadv of time data based on the θ2 pulse. That is, the pulse input interval time T
The time per degree is calculated from θ12 and the difference between both set angles θ12, and the ignition timing Tad is obtained by subtracting the control advance amount ADV from this and the set angle of the θ2 pulse.
Find the time of v. Then, in step S35, the table is referenced with interpolation calculation based on the battery voltage to set the basic energization time Dwb, and in step S36, the rotation correction coefficient Kd is also set for the engine speed N.
In step 7, the energization time Dw is calculated from these. After that, proceeding to step S38, the energization (dwell) start timing Tdw at the energization start time based on the θ2 pulse is obtained by subtracting the energization time Dw from the ignition timing Tadv.

The energization / ignition routine of FIG. 10 is executed by interrupting each time the θ2 crank pulse is input. First, in step S40, the energization set timer TIM1 and the ignition set timer TIM2 start counting, and in step S41, the energization start timing Tdw is input after the θ2 crank pulse is input.
When the timing Tdw has passed, the process proceeds to step S42 to start energization of the ignition target cylinder #i, and the energization set timer TIM1 is reset in step S43. Thereafter, in step S44, it is determined whether the count value of the ignition set timer TIM2 has passed the ignition timing Tadv. When the timing Tadv has passed, the energization is cut off in step S45, and the ignition set timer TIM2 is reset in step S46.

As a result, an ignition signal is output to the igniter 36 as shown in FIG. 12, and a high voltage generated by the ignition coil or the like is applied to the ignition plug 8 of the cylinder #i at a predetermined timing to ignite. . When the intake air temperature T is low due to the engine operating condition, the intake air temperature delay angle correction value A
DVt is 0, and therefore (control advance amount) ignition timing A
The advance angle of the DV is properly controlled according to the engine operating state and the presence or absence of knocking. On the other hand, when the supercharging pressure becomes high on the high rotation side and the intake air temperature T is predicted to be high, the ignition timing ADV is retarded by the intake air temperature retardation correction value ADVt to lower the combustion temperature. In this way, knocking is likewise suppressed and an adverse effect on the catalyst is prevented.

Although the embodiments of the present invention have been described above, the present invention can be applied to engines other than the sequential turbo in the same manner. Of course, various other controls can be performed depending on the predicted intake air temperature.

[0037]

As described above, according to the present invention,
In a vehicle engine, it is a method of calculating the intake air temperature while using the engine speed, throttle opening, intake air amount, and intake pipe absolute pressure while operating the engine. It is possible to predict the intake air temperature every moment. The intake efficiency constant and the temperature correction constant are set, and the calculation parameters are obtained from the absolute pressure of the intake pipe and the air weight per unit cycle, and the intake temperature is calculated based on these equations of the gas state. The intake air temperature can be predicted with high accuracy.

In the air-fuel ratio control, correction is made so as to increase the amount of fuel with respect to a rise in intake air temperature, so that knocking and adverse effects on the catalyst can be effectively prevented by cooling the fuel. In the ignition timing control, the same effect can be obtained because the ignition timing control is corrected so as to retard the intake air temperature.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing a sequential turbo engine to which an intake air temperature prediction method of the present invention is applied.

FIG. 2 is a diagram showing a crank angle sensor and a cam angle sensor.

FIG. 3 is an overall circuit diagram of a control system.

FIG. 4 is a diagram showing an experimental result of intake temperature prediction.

FIG. 5 is a flowchart showing an intake air temperature prediction routine.

FIG. 6 is a flowchart showing an air-fuel ratio control routine.

FIG. 7 is a diagram showing a map of an intake air temperature correction coefficient.

FIG. 8 is a flowchart showing a routine for cylinder discrimination and engine speed calculation.

FIG. 9 is a flowchart showing an ignition timing setting routine.

FIG. 10 is a flowchart showing an energization / ignition routine.

FIG. 11 is a diagram showing a map of intake air temperature retardation correction values.

FIG. 12 is a time chart showing a state of ignition timing control.

[Explanation of symbols]

 1 Engine Main Body 20 Air-cooled Intercooler 40 Primary Turbo Supercharger 50 Secondary Turbo Supercharger 81 Absolute Pressure Sensor 82 Crank Angle Sensor 87 Throttle Opening Sensor 88 Intake Air Volume Sensor 100 Control Unit

Claims (2)

[Claims] 1. An intake efficiency constant based on engine speed and throttle opening during engine operation, a temperature correction constant based on the same engine speed and throttle opening, and a calculation parameter based on intake pipe absolute pressure and air weight per unit cycle. And an intake air temperature predicting method for calculating and predicting an intake air temperature every predetermined time during engine operation. 2. In the air-fuel ratio control, the correction coefficient is determined as an increasing function with respect to the predicted intake temperature, and in the ignition timing control the retard correction value is determined as an increasing function with respect to the predicted intake temperature. The intake air temperature predicting method according to claim 1, wherein