JPH0219635A - Control unit for engine - Google Patents

Abstract

PURPOSE:To make engine torque drawable to the maximum by controlling both of ignition timing and air-fuel ratio for feedback on the basis of output of a cylinder internal pressure detecting means at a high load area. CONSTITUTION:Load of an engine 1 is judged from an air quantity per rotation by each detected result of an air flow sensor 4 and an engine speed sensor 16 at a control unit 17. In brief, a stational state is judged from the absolute value of a deviation at each unit time of the air quantity per rotation. Then, in a stationary state of a high load area, ignition timing and fuel quantity are controlled so as to cause an illustrated mean effective pressure being operated from an output signal of a cylinder internal pressure sensor 13 to become the maximal value. With this constitution, such cylinder internal control that an air-fuel ratio is able to secure the maximum torque in a state of being rich.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an engine control device that controls the air-fuel ratio and ignition timing of an engine to optimal values based on the outputs of an air-fuel ratio sensor and an in-cylinder pressure sensor.

[Prior Art] In order to purify exhaust gas and improve engine output in a gasoline engine, it is necessary to accurately control the air-fuel ratio and ignition timing according to the operating conditions. Conventionally, a method of controlling the air-fuel ratio and ignition timing using a microcomputer has been widely used.

For example, in air-fuel ratio control using fuel injection (l), the intake air (Qa) of the engine is detected by an air flow sensor installed in the intake passage, and the engine rotation speed (No) is determined from the output of a rotation sensor attached to the crankshaft, etc. Find the air m per unit revolution (Q.

/N0) is calculated, and based on this air bottle (Q, /N0), a basic fuel injection amount for obtaining a target air-fuel ratio at each preset operating point is calculated. Then, the final fuel injection amount is determined by making corrections according to the output of a water temperature sensor, etc. that detects the temperature of the engine cooling water, and the injection pulse with a pulse width corresponding to the determined injection amount is used to control the engine rotation In synchronization with this, the injector is driven to open and fuel is injected into the engine. Furthermore, in light load and partial load regions, an air-fuel ratio sensor whose output changes suddenly around the stoichiometric air-fuel ratio is used to determine whether the actual air-fuel ratio is on the rich or lean side. , performs control to converge the engine air-fuel ratio to the stoichiometric air-fuel ratio by adding feedback correction to the fuel injection amount. By controlling the air-fuel ratio to always maintain the stoichiometric air-fuel ratio in this way, the three-way catalyst is able to purify exhaust gas with high efficiency.

In addition, in controlling the ignition timing, air @ (Qa/N
, ) and the rotational speed (No.), the ignition advance angle set in advance as a map is read out, and energization to the ignition coil is controlled by an ignition signal based on the ignition advance angle.

Incidentally, the ignition advance angle is normally set with the aim of achieving MBT (minimum ignition advance angle necessary to generate maximum shaft torque), but MBT is determined by variations in engine temperature, air-fuel ratio, and dimensional errors in the combustion chamber. , intake air temperature.

Since the ignition timing varies considerably depending on factors such as humidity, it is difficult to always obtain the optimum ignition timing by simply controlling the oven in this manner, which may lead to knocking or a decrease in torque.

Therefore, as described in JP-A No. 62-82273, for example, the cylinder pressure is detected and the ignition timing is feedback-controlled based on the detected value so that the shaft torque is maximized. has been proposed in the past. In this cylinder pressure feedback control, for example, a rotation sensor is configured to generate a pulse every 1 degree of crank angle, and each time this pulse is generated, the output value (po) of the cylinder pressure sensor that detects the pressure inside the cylinder is set. Read the cylinder volume (V) and stroke volume (V) corresponding to the crank angle at that time.
h), the indicated mean effective pressure (P,) is determined by the following formula.

Then, the ignition timing is feedback-controlled so that this Pl becomes the maximum value.

[Problems to be Solved by the Invention] As described above, conventional cylinder pressure feedback control is capable of obtaining the maximum torque by correcting the ignition timing so that the indicated mean effective pressure (pt) reaches its maximum value, for example. This is what I tried to do. However, in high load areas,
Since feedback of the air-fuel ratio is stopped and the control becomes open control, air-fuel ratio errors caused by variations in sensors, injectors, fuel properties, etc. directly appear as a decrease in torque. Therefore, even if cylinder pressure feedback control is performed by correcting the ignition timing, it has not been possible to extract the maximum torque from the engine.

The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to obtain an engine control device that can maximize engine torque even in a high load range by in-cylinder pressure feedback control. It is an object.

[Means for Solving the Problems] An engine control device of the present invention includes an air-fuel ratio control means for controlling the air-fuel ratio of the engine, an ignition timing control means for controlling the ignition timing of the engine, and an air-fuel ratio for detecting the air-fuel ratio of the engine. It is equipped with an air-fuel ratio detection means for detecting the engine load, a load detection means for detecting the engine load, and an in-cylinder pressure detection means for detecting the cylinder pressure of the engine, and also controls the ignition timing so that the engine torque is approximately maximized based on the cylinder pressure. first in-cylinder pressure feedback control signal generation means for outputting a feedback control signal to the means; and an air-fuel ratio for outputting a feedback control signal to the air-fuel ratio control means so that the air-fuel ratio converges to the stoichiometric air-fuel ratio in a light load to partial load range. It is equipped with a feedback control signal generation means and a second cylinder pressure feedback control signal generation means for outputting a feedback control signal to the air-fuel ratio control means so that the engine torque is approximately maximized based on the cylinder pressure in a high load range. In particular, in high-load ranges where air-fuel ratio feedback control is not performed, the engine is characterized by a structure in which the air-fuel ratio is also feedback-controlled in addition to ignition timing feedback, so that the engine torque is approximately at its maximum. .

1 Effect] In the light load to partial load range, the air-fuel ratio feedback control signal generating means operates to carry out feedback control of the air-fuel ratio based on the output of the air-fuel ratio detecting means.

As a result, the air-fuel ratio of the engine converges to approximately the stoichiometric air-fuel ratio. Furthermore, the ignition timing is feedback-controlled based on the output of the cylinder pressure detection means so that the engine torque is approximately at its maximum.

In the high load range, based on the output of the cylinder pressure detection means,
Both the ignition timing and the air-fuel ratio are feedback-controlled, and as a result, the in-cylinder pressure (combustion pressure) is controlled so that maximum torque can be obtained with a rich air-fuel ratio.

[Example] Examples will be described below based on the drawings.

FIG. 1 is an overall configuration diagram of an embodiment of an engine control device according to the present invention.

In this embodiment, an intake passage 2 of the engine 1 is provided with a throttle valve 3 for adjusting the amount of intake air, and an air flow sensor 4 for detecting the amount of intake air is provided on the second stream thereof. Further, an injector 6 for injecting fuel toward the combustion chamber 5 is installed in the intake passage 2 . An air-fuel ratio sensor (0, sensor) 8 is installed in the exhaust passage 7 of the engine 1, which detects the oxygen concentration in the exhaust gas and outputs a detection signal that changes significantly from the stoichiometric air-fuel ratio. Further, a water temperature sensor IO is attached to a tank 9 that stores cooling water for cooling the engine. The cylinder head II of the engine I is provided with an ignition plug 12 for igniting the air-fuel mixture in the combustion chamber 5, and is also provided with an in-cylinder pressure sensor 13 for detecting the pressure in the combustion chamber 5. The spark plug I2 is connected to an ignition coil 15 via a power distributor 14, and the power distributor 14 is provided with a rotation sensor I6 that detects engine rotation.

The injector 6 and the ignition coil 15 are controlled by a control unit 17. The control unit I7 includes an air flow sensor 4 degrees, a water temperature sensor lO1, a cylinder pressure sensor 13. Rotation sensor 16 and air-fuel ratio sensor 8
Each detection signal from is input. As shown in FIG. 2, the control unit 17 includes a CPU 100, an A/D converter 101 that converts various analog input signals into digital values and outputs data to the CPU 100, and an input for shaping the waveform of various pulse signals. The circuit 102 and the CPU
A ROM 103 in which 100 control procedures are stored in advance, and a C
RAM+04 used in the calculation process of PU I 00,
It is composed of output circuits 105 and 106 that output control signals to the injector 6 and the ignition coil I5, respectively.

FIG. 3 is an example of an acupressure diagram showing the relationship between combustion pressure (po) and crank angle, and FIG. 4 shows the combustion pressure P versus crank angle in FIG. The indicated mean effective pressure (
FIG. 4 is a characteristic diagram showing how the ignition timing (p+) changes as the ignition timing changes. In the present invention, control is performed with the crank angle at which P+ in FIG. Feedback control is performed.

In the control unit 17, the intake air! (Qa) and the engine rotational speed (N, ) are determined, and the load is determined based on Q, /N. Then, when the load is below a predetermined value,
In other words, in the region P shown in Fig. 5, normal fuel injection control is performed, and ignition timing feedback is performed based on the in-cylinder pressure so that the indicated mean effective pressure (P,) reaches its maximum value in a steady state. Control takes place. Moreover, when the load is larger than a predetermined value, that is, in the area E in FIG.
In a steady state, the ignition timing is feedback-controlled based on the in-cylinder pressure so that P reaches its maximum value, and
The fuel injection amount is also controlled based on the cylinder pressure so that Pl is maximized.

The control of this embodiment will be explained in more detail below with reference to the flowchart of FIG. Note that SI to SI3 indicate each step.

When starting, first, use Sl to determine the amount of intake air (Ql, )
Load. Here, the analog signal of the air flow sensor 4 is converted into a digital value by the A/D converter 101,
This value is averaged as necessary and the intake air f
Let it be l(Q,).

Next, in S2, the engine speed (No.) is read.

N8 is determined by reading and measuring the interval of the pulse signal of the rotation sensor 16.

Then, go to S3 and find the air per revolution corresponding to the engine load collapse! Calculate (Q, /N,).

Next, in S4, the output signal of the cylinder pressure sensor 13 is read every time the crank angle signal of the rotation sensor 16 is generated, and the indicated mean effective pressure (P,) is calculated based on the signal value in S5.

Next, at Sa, to judge the load, Q.

/N is larger than a predetermined value α1.

If Q, /N, is not larger than α8, it means that it is in the partial load region, and in this case, go to S7 and perform feedback control (Ot feedback control) of the air-fuel ratio based on the output signal of the air-fuel ratio sensor 8. Go.

Then, the process goes to S8, and it is determined whether or not the 02 feedback control is being performed. If YES, the process goes to S, and it is determined whether or not it is in a steady state. 0. To determine whether feedback control is in progress, check the water temperature condition, air-fuel ratio sensor (0, sensor)
This is a judgment condition that is used in normal fuel injection control. In addition, the steady state is determined by Q, /N, for each unit time,
Whether the absolute value of the deviation value of is less than the predetermined value (Q, /N,
It is also possible to use Q instead of ), that is,
This is a determination as to whether there are small changes in road conditions or accelerator operation amount.

If it is a steady state at S, then Sl. The ignition timing is controlled so that P reaches its maximum value. However, the ignition timing control has a lower limit A1 and an upper limit B1 of the variable range.
Perform within the range of.

No in SIl, that is, 0. When feedback control is not in progress, or when S is NO, that is, when the steady state is not present, the process returns to its original state.

Next, when Q,/N,>α1 in SI1, that is, it is a high load region, the process goes to S11 to determine whether or not it is in a steady state. This determination is the same as S.

Then, if it is a steady state, then S I
t, and the ignition timing is controlled so that Pi reaches its maximum value. In this case, the lower limit of the ignition timing variable range is At, and the upper limit is Bt. Note that air-fuel ratio feedback control is performed in the partial load range, whereas in the high-load range, the air-fuel ratio fluctuations are large, so the variable range of the ignition timing becomes smaller. The ignition timing variable range is, for example, -5° CA (A2
) to +5°CA (Bt), -10°CA in partial load range
(AI) to +10″cA(B, ).

Next, the process goes to S13, and the fuel amount is controlled so that Pi becomes the maximum. This fuel control uses A3 as the lower limit and S3 as the lower limit.
This is done within a variable range with the upper limit being .

In the above embodiment, the indicated mean effective pressure is determined from the detected value of the cylinder pressure, and this indicated mean effective pressure is taken as a value corresponding to the engine torque, and feedback control is performed based on this. Depending on the rotational speed and load range, it is also possible to feedback control the ignition timing and air-fuel ratio using the crank angle at which the in-cylinder pressure itself reaches its peak value as a reference parameter so that this becomes the crank angle that produces the maximum torque.

Further, in the above embodiment, the air-fuel ratio is controlled by controlling the fuel injection amount, but the air-fuel ratio control means is not limited to controlling the fuel injection amount.

The invention can be implemented in many different ways.

[Effects of the Invention] Since the present invention is configured as described above, even in a high load range where air-fuel ratio feedback control is not performed, in addition to feedback control of ignition timing based on in-cylinder pressure,
The engine torque can be maximized by feedback controlling the air-fuel ratio based on the cylinder pressure to obtain the maximum torque.

[Brief explanation of the drawing]

FIG. 1 is an overall configuration diagram of an embodiment of an engine control device according to the present invention, FIG. 2 is a block diagram of essential parts of the embodiment, and FIG.
5 to 5 are characteristic diagrams for explaining the control of the embodiment, and FIG. 6 is a flowchart for executing the control of the embodiment. l: Engine, 4: Air flow sensor, 6: Injector, 8: Air-fuel ratio sensor,! 3: cylinder pressure sensor, 15: ignition coil, 16 two-turn sensor, 17: control unit. No 5==! Crank fish and fire timing chart Engine rotor (Fig.

Claims (1)

[Claims] (1) air-fuel ratio control means for controlling the air-fuel ratio of the engine;
ignition timing control means for controlling the ignition timing of the engine; air-fuel ratio detection means for detecting the air-fuel ratio of the engine; load detection means for detecting the load of the engine; and in-cylinder pressure detection means for detecting the cylinder pressure of the engine; a first cylinder pressure feedback control signal that receives the output of the cylinder pressure detection means and outputs a first cylinder pressure feedback control signal to the ignition timing control means so that the output torque of the engine is approximately maximized based on the cylinder pressure; a load determining means for receiving the output of the load detecting means and determining whether the load of the engine is in the light load to partial load range or in the high load range; air-fuel ratio feedback control signal generation means for outputting an air-fuel ratio feedback control signal to the air-fuel ratio control means so as to converge the air-fuel ratio to the stoichiometric air-fuel ratio based on the output of the air-fuel ratio detection means when it is determined that the load is within the load range; When the load determination means determines that the load is in the high load range, a second cylinder pressure feedback control signal is sent to the air-fuel ratio control means so that the engine torque is approximately maximized based on the output of the cylinder pressure detection means. 1. An engine control device comprising second cylinder pressure feedback control signal generating means for outputting a second cylinder pressure feedback control signal.