JPS6315466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a combustion control device, and particularly to a combustion control device for maintaining good combustion in the cylinders of an automobile engine (compression ignition engine, spark ignition engine).

Currently, engine electronic control units using microprocessors, which are widely used today, use a control map stored in memory to determine the amount of operation to achieve the optimum air-fuel ratio and ignition advance angle. This type of control device is disclosed in, for example, Japanese Patent Laid-Open No. 159528/1983. However, each manipulated variable is based on the output value from each sensor such as the intake air flow meter and engine speed meter, and deterioration of these sensors can cause the air-fuel ratio and ignition advance angle to deviate from the optimal control values. It was the cause of this. In addition, deterioration of the engine, such as changes in compression ratio, has also been a factor causing combustion conditions to deviate from the optimum. Many structural and
Several methods have been considered, but all have been limited to partial treatment.

The purpose of the present invention is to measure the state of combustion in the cylinder and maintain it in a good state in response to changes in engine characteristics due to deterioration of the intake air flow meter, engine speed meter, etc., changes in the compression ratio, etc. The object of the present invention is to provide a combustion control device that can control combustion.

In order to achieve the above object, the present invention
As shown in the figure, a pressure pickup detects the pressure inside the cylinder, a crank angle sensor detects the rotation angle of the crank angle, and the indicated average effective pressure is calculated based on the detection signals from the pressure pickup and the crank angle sensor. an indicated average effective pressure calculation means that calculates the amount of fuel to the engine based on the engine rotation speed determined by the detection signal from the crank angle sensor and the valve opening time of the injection valve; Comparing the ratio of the indicated average effective pressure and the fuel amount with a predetermined value, and correcting at least one of the air-fuel ratio and the ignition timing based on the comparison result, and adjusting the ratio of the indicated average effective pressure and the fuel amount. It is characterized by comprising a control means for maintaining the predetermined value.

According to the above configuration, the indicated average effective pressure calculation means calculates the indicated average effective pressure from the pressure pickup and the detection signal from the crank angle sensor, and the fuel amount calculation means uses the detection signal from the crank angle sensor and the injection valve. Calculate the amount of fuel to the engine from the valve opening time. Then, the control means corrects the air-fuel ratio or the ignition timing, using the ratio between the indicated average effective pressure and the fuel amount as one variable, so that the value of this ratio is maintained at a predetermined value, Keep the engine in good condition.

Examples of the present invention will be described below.

FIG. 1 shows an embodiment of a combustion control device according to the present invention.

In the figure, 1 is a fuel tank, 2 is a methanol content sensor, 3 is a cylinder injection control device, 4 is an injection valve, 5 is a throttle valve, 6 is a throttle valve actuator, 7
is an air flow sensor, 8 is a microcomputer system for engine control, 9 is an accelerator pedal, 10 is an ignition control circuit, 11 is a spark plug and pressure pickup, 1
2 is a pressure signal processing circuit, 13 is a piston, 14 is an oxygen concentration sensor, 15 is an oxidation catalyst, 16 is an accelerator pedal position sensor, and 17 is a crank angle sensor.

The composition of the fuel contained in the fuel tank 1 is detected by a methanol content sensor 2, and the data is sent to the engine control microcomputer system 8.
Further, the in-cylinder injection control device 3 is used to maintain the pressure of fuel sent to the injection valve 4 at a constant level based on a signal from the engine control microcomputer system 8. The injection valve 4 also controls the flow rate of fuel injected into the cylinder.
It is used to adjust Gf, and its flow rate is adjusted by the width of the drive pulse to the injection valve 4. Further, the opening degree of the throttle valve 5 is adjusted by a throttle valve actuator 6. This throttle valve actuator 6 is driven by a feedback circuit using a pulse motor, and the opening degree of the throttle valve 5 is specified by an engine control microcomputer system 8. The air flow sensor 7 is a sensor that uses the cooling phenomenon of hot rays, or a type of sensor that opens and closes a movable plate depending on the intake air, and converts the degree of opening into an electrical signal. quantity is measured. Further, the oxygen concentration sensor 14 detects the oxygen concentration in the exhaust gas and generates an electric signal corresponding to the oxygen concentration. Further, a pressure pickup is mounted attached to the ignition plug 11, and detects the pressure inside the cylinder, converts this pressure into an electric signal, and outputs it to the outside. Further, the in-cylinder pressure signal detected by the pressure pickup 11 is input to the pressure signal processing circuit 12, and the indicated mean effective pressure Pi is calculated in the pressure signal processing circuit 12. A signal is generated. Further, in the present invention, the movement of the accelerator pedal 9 is not directly transmitted to the throttle valve 5, and the accelerator pedal position sensor 1
6 converts the position into an electrical signal and sends it to the engine control microcomputer system 8. The ignition control circuit 10 counts the pulse signals from the crank angle sensor 17 attached to the engine crankshaft based on the output results of the engine control microcomputer system 8, determines the ignition timing, and controls the power transistor and ignition. A power circuit using a coil converts it into a high voltage pulse and sends it to the spark plug 11. Also,
The oxidation catalyst 15 oxidizes incomplete combustion in the exhaust gas.
Change to _H2O , _CO2 .

In general, engines have output trends shown in FIGS. 2, 3, and 4. In other words, when the throttle valve 5 is fully opened and the engine speed is varied, the maximum torque will be reached at a certain engine speed (approximately 2800 rpm) as shown in Figure 2, and if the speed is increased beyond that, the torque will decrease. Changes to Furthermore, when the engine speed (and suction negative pressure) is kept constant and the ignition advance angle is changed while keeping the air-fuel ratio constant, as shown in Figure 3A, the value will change from that value around a certain ignition advance position Torque decreases whether it is increased or decreased. Further, the change in the maximum value of the cylinder pressure with respect to the ignition advance angle is as shown in FIG. FIG. 4 shows the torque characteristics when the air-fuel ratio is varied while keeping the throttle valve opening degree and engine speed constant. That is, as the air-fuel ratio is changed, the torque decreases around a certain air-fuel ratio value. Further, the relationship between compression ratio and torque is as shown in FIG. That is, if the compression ratio of the engine is increased, the output torque will also be increased. Conversely, if the engine deteriorates and the compression ratio decreases, no pressure will be produced.

The generally known engine output performance has been shown above, but the engine output torque changes depending on factors such as engine speed, air-fuel ratio, compression ratio, etc., and from these relationships, it can be calculated as an eccentric number that indicates the degree of combustion. It is extremely difficult to find out, and many attempts have been made. Among them DLStivender: Engine Air
Control-Basis of a Vehicular Systems
Control Hierarchy: SAE, 780346, P1~P36
(1978) or JPSoltan and KBSen.or;
Petrol Injection Control for Low Exhaust
Emissions: Lucas Engineering Keview, 6,
2 (1973-11) shows that there is a relationship between fuel weight and output torque per four cycles (intake, compression, explosion, exhaust) in a four-stroke engine as shown in Figure 6. . The relationship shown in Figure 3 is based on the data at the point where the air-fuel ratio is the highest and the ignition advance is the smallest among the ranges that give the maximum torque when the air-fuel ratio and ignition advance angle are varied in each operating state. This is the relationship obtained by plotting. Generally, the engine electronic control device currently in use is not adjusted so that the torque is maximized, but in the engine electronic control device of this embodiment, which applies the above relationship, the control map is adjusted so that the torque is maximized. It has been adjusted. In an engine equipped with an engine control device adjusted to maximize this torque, the shaft average effective pressure (or indicated average effective pressure) shown in Figure 7A and the
When the fuel weight ratio per four cycles shown in Figure B is determined, it remains approximately constant even if the engine speed and shaft torque change, as shown in Figure 7C.

This indicated mean effective pressure Pi is processed by a program as described below. In order to calculate the indicated mean effective pressure Pi, it is necessary to know the relationship (P-x diagram) between the cylinder pressure P and the piston position x. However, since it is difficult to directly measure the piston position x, it is common to calculate the piston position x from a relatively easy measurement of the crank angle θ. That is,
When the piston, connecting groove, and crankshaft are arranged as shown in Fig. 8, the distance between the piston position x and the crank angle θ is x=l ₁ cosθ+√ ₂ ² −( ₁ + ₃ ) ² −l ₂ + l ₁
......(1) There is a relationship. When calculating the indicated mean effective pressure Pi from the P-x diagram, Pi=(∫Pdx)/xs......(2) However, xs: Stroke length. Since direct measurement of the position x is avoided, it is necessary to find it from the relationship between the cylinder pressure P and the crank angle θ.

Equation (2) can be transformed as Pi = (∫Pdx/dθdθ)/xs (3), and in this equation (3), dx/dθ is found by differentiating equation (1) with respect to θ. . That is, It is. Therefore, the indicated average effective rate Pi can be determined from the P-θ diagram and the dx/dθ-θ diagram (equation (4)) using equation (3). The relationship between cylinder internal pressure P and crank angle θ in a 2-stroke or 4-stroke engine is shown in FIG. In FIG. 9, from the left are the exhaust cycle, intake cycle, compression cycle, and explosion cycle. Since the cylinder pressure P varies from cycle to cycle, it is necessary to calculate the average of several cycles when calculating the indicated mean effective pressure Pi. Also, by substituting specific numerical values into equation (1), x
When a -θ diagram is drawn, it becomes as shown in FIG. Further, by differentiating with respect to the crank angle θ, a dx/dθ-θ diagram is obtained, as shown in FIG. In this embodiment, data is processed discretely, so if equation (3) is converted into differential form, Pi={Σ(P×dx/dθ)}/xs (5).

The main parts of the indicated mean effective pressure measuring circuit according to this embodiment are shown in a block diagram as shown in FIG. That is, an A/D converter 20 is connected to a multiplexer 18 having a plurality of input terminals 27 via a sample-and-hold 19. An I/O converter 22 is connected to this A/D converter 20. This I/O converter 2
2 and the multiplexer 18 are connected to a channel address register 21. Further, a microprocessor 23 is connected to the I/O converter 22, and this microprocessor 23 has an I/O
Transducer 24 and program or data memory 2
6 is connected. Further, a keyboard 25 is connected to the I/O converter 24. In the indicated mean effective pressure measuring circuit constructed in this way, the in-cylinder pressure signal and crank angle pulse are taken in from the left side of FIG. 12 and processed by the microprocessor 23. That is, when the microprocessor 23 takes in the in-cylinder signal, the microprocessor 23 first
sends a data select signal to the channel address register 21. In response to this data select signal, a select signal is sent from the channel address register 21 to the multiplexer 18, and in response to this select signal, the multiplexer 18 selects one of the analog signals connected to the input terminal 27. and sends a selection signal to the sample-and-hold 19. This sample and hold 19 is for temporarily holding a selection signal, and the output of the sample and hold 19 is converted into a digital signal by an A/D converter 20 and sent to a microprocessor via an I/O converter 22. 23. I/O
The converter 24 and the keyboard 25 write an arithmetic program into a program or data memory 26 connected to the microprocessor 23,
This is for starting and stopping the microprocessor 23.

Next, the calculation processing procedure for the indicated mean effective pressure in this embodiment will be explained. This arithmetic processing procedure is performed according to the flowchart shown in FIG. The calculation program shown in FIG. 13 is for crank angle pulse 1.
Starts on every pulse. This crank angle pulse is configured to be input to an interrupt terminal of a microprocessor 23 shown in FIG. In this embodiment, for example, a crank angle sensor is used that outputs one pulse for every one degree of crank angle. The interrupt signal from this crank angle sensor causes the first step to be taken.
At step 28, the number of acquisition cycles is initialized. After initial setting is performed in step 28, pressure data is acquired in step 29. When the pressure data is taken in at step 29, an address for storage is selected at step 30, and the pressure data is stored at step 31. When the pressure data is stored in step 31, the storage address is updated in step 32. When the storage address is updated in step 32, it is determined in step 33 whether or not data for 720 degrees has been set. If the data has not been set, the process returns to step 29, and if it has been set, the acquisition cycle is started in step 34. Update numbers. When the number of capture cycles is updated in step 34, it is determined in step 35 whether or not 10 cycles' worth of data has been set. If 10 cycles' worth of data has not been set, the process returns to step 29 and the 10 cycles' worth of data is set. If it is determined that the value has been set, the process moves to step 36 in FIG. 13B. In step 36, the storage address is initialized. Once the storage address is initialized in step 36, the capture address is initialized in step 37. Next, in step 38, pressure data is fetched, in step 39, the pressure data fetched in step 38 is added to the previous pressure data, and in step 40, the fetch address is updated. When the import address is updated in step 40, the update is performed in step 41.
Determine whether or not 10 cycles have been added, and if it is determined that 10 cycles have not been added, step
Return to 38. If it is determined in step 41 that 10 cycles have been added, table address calculation is performed in step 42. When the address is calculated in step 42, reference is made to a predetermined table in step 43, and in step 44, the following calculation is performed: (total pressure data)/10×(table value). Once the calculation is performed in step 44, the data is set in step 45, and the storage address is updated in step 46. When the storage address is updated in step 46,
In step 47, it is determined whether or not 720 degrees worth of data has been processed, and if it is determined that the data has not been processed, the process returns to step 37. Also in step 47
If it is determined that 720 degrees worth of data has been processed, the process moves to step 48 in FIG. 13C. In this step 48, the fetch address is initially set, and in step 49, calculation data is fetched. When the calculation data is loaded in step 49, the calculation data is added to the previous data in step 50. Once added to the previous data in step 50, the fetch address is updated in step 51. When the import address is updated in step 51, it is determined in step 52 whether or not 720 degrees worth of data has been processed.
If it is determined that 720 degrees worth of data has not been processed, the process returns to step 49. If it is determined that 720 degrees worth of data has been processed, the calculation of summation data ÷ xs is performed in step 53, and the final calculation is performed in step 54. Data is output. In this way, in FIG. 13A, steps 28 to 35 include, for example, the process of taking in 10 cycles worth of pressure data P and storing it in the program or data memory 9.
In FIG. 13B, steps 37 to 41 are average processing of the pressure data P for 10 cycles, and steps 42 to 47 in FIG. The process of calculating, multiplying, and storing is further carried out in steps 48 to 48 of FIG. 13C.
52 is the process of multiplying the pressure data P by dx/dθ to obtain the sum, and steps 53 and 54 in FIG.
The process of dividing the sum of dx/dθ by the stroke length xs to obtain the indicated mean effective pressure Pi and outputting it to the outside is shown. With the program shown above, it is possible to obtain the indicated mean effective pressure Pi within a relatively short time.

In this implementation, as shown in Figures 6 and 7,
From the relationship of average effective pressure Pi to Gf/N, ΔPi/Δ
(Gf/N) is determined as shown in Fig. 14, and the fuel amount (air-fuel ratio) or ignition advance angle is controlled to maintain this value ΔPi/Δ(Gf/N) at a high value. . By doing this, even if Gf/N and Pi fluctuate as shown in Figure 7, ΔPi/Δ
(Gf/N) always remains on a straight line, and even when the operating conditions change, the optimum output torque can be obtained. Gf is determined from the opening time width of the injection valve 4 when the fuel pressure is constant. An example of the relationship between the opening time width of the injection valve and Gf is shown in FIG.
As shown above, the fuel weight flow rate Gf can be determined by monitoring the valve opening time width emitted from the control circuit.

The indicated average effective pressure Pi is determined from a certain time average value of the signal from the pressure pickup, and Gf is determined from a value corresponding to the valve opening time width Δt. This ΔPi/Δ
(Gf/N) is compared with the standard ΔPi/Δ(Gf/N) value stored in advance in the control circuit (microcomputer system), and the air-fuel ratio or ignition advance angle is corrected by the deviation. Standard ΔPi/Δ(Gf/N)
The value is uniquely determined by the type of engine.

In an actual engine, the combustion pressure waveform changes each time, depending on the operating conditions of the engine, as shown in FIG. This is because the combustion situation changes depending on the atomization state of the fuel within the cylinder, the distribution state of the fuel, and the ignition timing or injection timing. Particularly in a region where the engine speed is low or an operating region where the amount of air is small, the air density in the cylinder is low, so even when the spark plug is ignited, there is a time delay until the fuel actually ignites. Therefore, as shown in FIG. 16, the ignition delay time relative to the amount of air per unit time increases and the variation becomes larger as the amount of air decreases. Therefore, if the ignition timing or injection timing is controlled by detecting only the ignition delay time as in the past, true combustion control cannot be achieved because combustion is stochastic as described above. In this embodiment, main factors related to combustion are memorized in advance,
This stored value is compared with the actual driving situation, and a deviation from the stored value is detected to perform feedback control of the ignition timing. That is, by directly replacing the ignition delay time with respect to the amount of air per unit time (engine speed) as shown by the solid line A in Fig. 16, and comparing it with the actual value of the ignition delay time, this ratio can be calculated. The ignition timing or injection timing is controlled using the value of . As shown in FIG. 18, which is a partially expanded version of FIG. , calculate the differential value. The differential value is (+) at the pressure peak position as shown in Figure 19.
Changes from to (-). The top dead center of the piston 13 is detected in advance by the top dead center detector 17, and the time (crank angle may be used) between the signals calculated from the differential value of the pressure signal described above at this top dead center is calculated. Take it out. Letting this value be ΔθA, the control circuit 8 calculates the ratio K of the previously stored value Δθf [(=A・Ga+B) where A and B are constants] K = ΔθA/Δθf (5). 5) Correct the ignition timing or injection timing using K in equation.

Therefore, according to this embodiment, if the value of the ignition delay depending on the operating conditions such as the amount of air is stored in advance in the memory circuit (not shown) in the control circuit 8, the optimum value can be always obtained under any operating condition. Can maintain combustion.

It should be noted that another well-known method for detecting ignition delay is a method that utilizes ion conductivity using ions generated by a flame. In this method, a voltage of 1 to 5 kV is always applied to the spark plug 11, and when the spark plug ignites and the surrounding air-fuel mixture is ignited, the flame activates the air-fuel mixture and ionizes it, causing a current to flow temporarily. Voltage drops. By measuring the time it takes for this to fall, the ignition delay time can be determined. Furthermore, the amount of air per unit time can be calculated from the signal of the hot wire air flow meter or the pressure pickup signal in the cylinder.

As explained above, the present invention utilizes the fact that there is a proportional relationship between the indicated mean effective pressure when the maximum output is produced by changing the ignition timing, and the amount of fuel at that time. Therefore, according to the present invention, a control map having such a proportional relationship is stored in advance in the control means, and the ratio between the indicated average effective pressure and the fuel amount is set to a predetermined value on the control map. ,
By correcting the air-fuel ratio or ignition timing, it is possible to obtain the maximum output with the minimum amount of fuel.

[Brief explanation of the drawing]

Figure 1 is an overall configuration diagram showing an embodiment of the present invention, Figure 2 is a diagram showing the relationship between shaft average effective pressure and engine speed at full throttle, and Figure 3 is a diagram showing the relationship between engine speed and air-fuel ratio when the engine speed and air-fuel ratio are constant. Figure 4 is a diagram showing the relationship between ignition advance angle, shaft average effective pressure, and maximum combustion pressure in the following cases. Figure 4 is a diagram showing changes in torque when the air-fuel ratio is varied while keeping the throttle valve opening constant. Figure 5 is a diagram showing the relationship between average effective pressure and compression ratio;
Figure 6 shows the relationship between fuel weight and shaft average effective pressure per 4 cycles, and Figure 7 shows the relationship between Δ(Gf/N) and
A diagram showing how ΔP _BME and ΔP _BME /Δ(Gf/N) change over time. Figure 8 shows the positional relationship of the crankshaft, connecting rod, piston, and cylinder. Figure 9 shows the cylinder. Figure 10 is a diagram showing how the internal pressure changes over time.
Figure 11 is a diagram showing the relationship between dx/dθ and θ, Figure 12 is a configuration block diagram of a pressure signal processing circuit that calculates the indicated mean effective pressure, and Figure 13 is the diagram showing the indicated mean effective pressure. Figure 14 is a block diagram of the part that calculates ΔPi/Δ(Gf/N) from ΔPi and Δ(Gf/N), Figure 15 is a diagram showing the discharge characteristics of the injector. , 1st
Figure 6 is a diagram showing the relationship between air amount per unit time and ignition delay time, Figure 17 is a diagram to explain the method of measuring ignition delay time, and Figure 18 is an enlarged configuration of the part that measures ignition delay time. 19 is a diagram for explaining the method of measuring the ignition delay time, and FIG. 20 is a diagram corresponding to complaints. 11... Pressure pickup, 12... Pressure signal processing circuit, 15... Oxidation catalyst, 16... Accelerator pedal position sensor, 17... Crank angle sensor.

Claims (1)

[Claims] 1. A pressure pickup that detects the pressure in the cylinder, a crank angle sensor that detects the rotation angle of the crank angle, and an indicated average effective pressure that calculates the indicated average effective pressure based on the detection signals from the pressure pickup and the crank angle sensor. pressure calculation means;
a fuel amount calculation means for calculating the amount of fuel to be supplied to the engine based on the engine rotational speed determined by the detection signal from the crank angle sensor and the opening time of the injection valve; control means that compares the ratio with a predetermined value and corrects at least one of the air-fuel ratio and the ignition timing based on the comparison result to maintain the ratio of the indicated mean effective pressure and the fuel amount at the predetermined value; A combustion control device comprising: