JP6088209B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine mounted on a vehicle or the like.

  In a cylinder of an internal combustion engine, sometimes the combustion of fuel becomes unstable and a misfire may occur. In order to avoid engine stall in which the rotation speed of the crankshaft of the internal combustion engine decreases, it is determined whether the combustion of each cylinder is normal or defective (including misfire), and the engine is detected when a combustion failure is detected. It is desirable to implement correction control to increase the rotational torque.

  As a technique for detecting poor combustion that may cause engine stall, the average rotational speed of the internal combustion engine is calculated repeatedly, and it is determined that a defective combustion has occurred when the average rotational speed falls below the allowable amount. (For example, see the following patent document).

  However, with such a detection method, it takes time to know the occurrence of combustion failure, and the possibility that subsequent correction control will not be in time cannot be denied.

JP 2008-190433 A

  An object of the present invention is to make it possible to detect as soon as possible the occurrence of poor combustion or misfire that may cause engine stall.

In order to solve the above-described problem, in the present invention, the instantaneous value of the rotational speed of the internal combustion engine is measured at at least two times during the expansion stroke in the cylinder of the internal combustion engine, and the moving average value based on the instantaneous value is calculated . The difference obtained by subtracting the moving average value from the instantaneous value at the time point is compared with a determination threshold value, and when the difference falls below the determination threshold value, it is determined that the combustion of the cylinder is poor. The control apparatus for an internal combustion engine is characterized in that a determination threshold value to be compared with a difference at a later time point is set higher than a determination threshold value to be compared with a difference at an earlier time point during the expansion stroke.

  According to the present invention, it is possible to detect as soon as possible the occurrence of combustion failure or misfire that may cause engine stall.

The figure which shows the whole structure of the internal combustion engine for vehicles in one Embodiment of this invention. FIG. 3 is a circuit diagram of an electrical system of the vehicle in the same embodiment. The figure which illustrates transition of the instantaneous value and moving average value of the rotational speed of an internal combustion engine. The figure which calculated | required experimentally and calculated the magnitude | size of the difference of the instantaneous value of the rotational speed of an internal combustion engine in an expansion stroke, and a moving average value. The flowchart which shows the example of the procedure of the process which the control apparatus of the embodiment implements.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of an internal combustion engine for a vehicle in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type four-stroke engine and includes a plurality of cylinders 1 (one of which is shown in FIG. 1). In the vicinity of the intake port of each cylinder 1, an injector 11 for injecting fuel is provided. A spark plug 12 is attached to the ceiling of the combustion chamber of each cylinder 1. The spark plug 12 receives spark voltage generated by the ignition coil and causes spark discharge between the center electrode and the ground electrode.

  The intake passage 3 for supplying intake air takes in air from the outside and guides it to the intake port of each cylinder 1. On the intake passage 3, an air cleaner 31, a throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream. In addition, an idle speed control valve 36 that can adjust the opening degree of the flow path 35 is provided in the bypass flow path 35 that short-circuits the upstream side and the downstream side of the throttle valve 32 in the intake passage 3. .

  The exhaust passage 4 for discharging the exhaust guides the exhaust generated as a result of burning the fuel in the cylinder 1 from the exhaust port of each cylinder 1 to the outside. An exhaust manifold 42 and an exhaust purification three-way catalyst 41 are disposed on the exhaust passage 4.

  FIG. 2 shows a circuit 6 of the vehicle electrical system. The alternator 62 receives the rotation of the driving force from the crankshaft of the internal combustion engine, generates electric power, charges the in-vehicle battery 61, and / or supplies electric power to the various electric loads 51, 52, 53, 54. As an example of the electric load, a magnetic clutch 51 interposed between the crankshaft of the internal combustion engine and the compressor of the air conditioner, a condenser for the air conditioner refrigerant, and / or a radiator for cooling water is used for air cooling. Examples thereof include a fan motor 52 that drives a fan, a fan motor 53 that drives a blower fan for blowing air into a room, a vehicle headlamp, and other electric lamps 54.

  ON / OFF of energization to each electric load 51, 52, 53, 54 is switched via relay switches 63, 64, 65, 66 on the circuit 6, respectively.

  An ECU (Electronic Control Unit) 0 serving as a control device for an internal combustion engine according to the present embodiment is a microcomputer system having a processor, a memory, an input interface, an output interface, and the like.

  The input interface includes a vehicle speed signal a output from a vehicle speed sensor that detects the actual vehicle speed of the vehicle, a crank angle signal (N signal) b output from an engine rotation sensor that detects the rotation angle of the crankshaft and the engine speed, Accelerator opening signal c output from a sensor that detects the amount of depression of the accelerator pedal or the opening of the throttle valve 32 as an accelerator opening (engine output required by the driver, so-called required load), and the range of the shift lever are known. Intake temperature / intake pressure output from a temperature / pressure sensor for detecting the shift range signal d output from the sensor (shift position switch) for detecting the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33). Signal e, coolant temperature signal f output from a coolant temperature sensor that detects the coolant temperature of the engine, intake camshaft Is output from a cam angle signal (G signal) g output from a cam angle sensor at a plurality of cam angles of the exhaust camshaft, a battery voltage indicating a charging state of a vehicle-mounted battery, a battery current, and a battery temperature. Battery signal h or the like is input.

  From the output interface, an ignition signal i for the igniter of the spark plug 12, a fuel injection signal j for the injector 11, an opening operation signal k for the idle speed control valve 36, and an ON for the relay switch 63 (ie, , Energization) signal l, ON signal m for relay switch 64, ON signal n for relay switch 65, ON signal o for relay switch 66, power generation voltage for control circuit (IC regulator) of alternator 62 A signal p for instructing the magnitude of the signal is output.

  The processor of the ECU 0 interprets and executes a program stored in the memory in advance, calculates operation parameters, and controls the operation of the internal combustion engine. The ECU 0 acquires various information a, b, c, d, e, f, g, and h necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and is filled in the cylinder 1. Estimate the intake volume. Based on the engine speed, the intake air amount, and the like, various operating parameters such as required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, and ignition timing are determined. As the operation parameter determination method itself, a known method can be adopted. The ECU 0 applies various control signals i, j, k, l, m, n, o, and p corresponding to the operation parameters via the output interface.

  The ECU 0 of the present embodiment determines whether the combustion of fuel in each cylinder 1 is normal or defective (including misfire), and determines the rotational speed (engine speed) of the crankshaft of the engine in the expansion stroke of each cylinder 1. Judgment by reference. In addition, when a combustion failure that may cause an engine stall is detected, correction control is executed to increase the rotational torque of the engine.

The ECU 0 refers to the crank angle signal b and measures instantaneous values of the engine speed and calculates a moving average value of the engine speed at a plurality of times during the expansion stroke in the cylinder 1. The engine rotation sensor generates a pulse as a crank angle signal b every predetermined rotation angle, for example, every time the crankshaft rotates by 10 ° CA (crank angle). Based on the pulse train, the ECU 0 repeatedly measures the time required for the crankshaft to rotate by a predetermined angle as a value suggesting the rotational speed of the engine.

  The ECU 0 of this embodiment is measured at each of the time when the crankshaft after compression top dead center of the cylinder 1 in the expansion stroke rotates 90 ° CA, 120 ° CA, and 150 ° CA. Get the instantaneous value of the engine speed.

  Further, a moving average value of the engine rotation speed at each time point is calculated from the instantaneous value of the engine rotation speed repeatedly measured within the interval of each time point, that is, within a period of 30 ° CA. For example, the moving average value of the rotational speed at the time of 90 ° CA after the compression top dead center is the instantaneous value of the rotational speed measured at each of the 70 ° CA, 80 ° CA, and 90 ° CA after the compression top dead center. Is obtained by averaging.

  The respective time points of 90 ° CA, 120 ° CA and 150 ° CA after compression top dead center can be known from the pulse train (number of pulses) included in the crank angle signal b. The timing corresponding to each time point may be obtained by a timer or the like without being based.

  Thus, the ECU 0 obtains a difference obtained by subtracting the moving average value from the instantaneous value of the rotational speed of the engine for each time point of 90 ° CA, 120 ° CA, and 150 ° CA after the compression top dead center, and determines the difference as a determination threshold value. Compare with

FIG. 3 illustrates the transition of the instantaneous value and the moving average value of the rotational speed of the internal combustion engine. In FIG. 3, a thin solid line indicates an instantaneous value, and a thick broken line indicates a moving average value. t ₁ , t _2, and t ₃ are points at 90 ° CA, 120 ° CA, and 150 ° CA after the compression top dead center of the cylinder 1 when combustion is normally performed in the cylinder 1 in the expansion stroke. Each corresponds. When the combustion is normal, the rotational torque of the crankshaft increases during the expansion stroke and the engine is accelerated, and the difference between the instantaneous value of the rotational speed and the moving average value at each time t ₁ , t ₂ , t ₃ is positive. Become.

In turn, t ₄ , t _5, and t ₆ are 90 ° CA, 120 ° CA, and 150 ° after compression top dead center of the cylinder 1 when combustion is not normally performed in the cylinder 1 in the expansion stroke. Each corresponds to the time of CA. In the case of poor combustion, the crankshaft engine decelerates during the expansion stroke, so the difference between the instantaneous value of the rotational speed and the moving average value at each time point t ₄ , t ₅ , t ₆ is negative. By utilizing this fact, it is possible to quickly detect a combustion failure that may cause an engine stall.

  However, it is necessary to devise a judgment threshold value for poor combustion. FIG. 4 shows, for a specific cylinder 1, the difference between the instantaneous value of the engine rotational speed and the moving average value at the 90 ° CA, 120 ° CA, and 150 ° CA angles after compression top dead center is obtained a plurality of times. It is the result of the experiment. In FIG. 4, plot points not surrounded by a square frame indicate differences in normal combustion, and plot points α and β surrounded by a square frame indicate differences in the case of poor combustion.

  As shown in FIG. 4, the variation in the difference in rotational speed in the case of normal combustion is large at a relatively early time during the expansion stroke, that is, when the crank angle after compression top dead center is small. The variation tends to be smaller as the later time during the expansion stroke, that is, as the crank angle after the compression top dead center increases.

  The difference at 90 ° CA after compression top dead center varies significantly, and if the determination threshold value to be compared with this is set high, there is a high possibility that normal combustion will be erroneously determined to be defective. On the other hand, the difference at the time of 150 ° CA after compression top dead center has a much smaller variation (in other words, the S / N ratio is large). Therefore, in this embodiment, the determination threshold value to be compared with the difference at the 120 ° CA time point is set higher than the determination threshold value to be compared with the difference at the 90 ° CA time point. Furthermore, the determination threshold value to be compared with the difference at the time of 150 ° CA is set higher than the determination threshold value to be compared with the difference at the time of 120 ° CA. Thereby, it is possible to prevent erroneous determination while reliably detecting defective combustion.

  Further, as shown in FIG. 4, the rotational speed difference α when the cylinder 1 misfires for the first time is larger than the rotational speed difference β when the misfire continues several times continuously. Depressed. In other words, if the detection method of the present embodiment is adopted, this first misfire can be detected immediately, and correction control for increasing the rotational torque of the engine can be executed promptly. It greatly contributes to prevention.

  FIG. 5 shows a procedure example of processing executed by the ECU 0 when determining whether combustion is normal or bad in the cylinder 1 of the internal combustion engine. The routine shown in FIG. 5 is a situation where there is a risk of engine stall, for example, the vehicle speed is less than a predetermined value or the vehicle is stopped, the engine speed is less than a predetermined value, the engine is idling, etc. Execute if any of them apply. Even if a combustion failure occurs, such as when the engine speed is currently greater than or equal to a predetermined value, in a situation where the risk of engine stall is low, this routine is not executed, and the calculation load on the ECU 0 is allowed to be reduced.

  The ECU 0 measures the instantaneous value and moving average value of the rotational speed of the engine at 90 ° CA after the compression top dead center of the cylinder 1 in the expansion stroke (steps S1 and S2), and calculates the difference between the two ( In step S3), the difference is compared with a determination threshold value corresponding to a time point of 90 ° CA after the compression top dead center (step S4). If the difference is below the determination threshold, it is determined that the combustion in the expansion stroke of the cylinder 1 is poor.

  If the difference is equal to or greater than the determination threshold value in step S4, then the instantaneous value and moving average value of the engine speed at 120 ° CA after the compression top dead center of the cylinder 1 in the same expansion stroke are measured. (Steps S5 and S6), the difference between them is calculated (Step S7). And the difference is compared with the determination threshold value corresponding to the time of 120 degrees CA after compression top dead center (step S8). As already described, the determination threshold value in step S8 is higher than the determination threshold value in step S4. If the difference is below the determination threshold, it is determined that the combustion in the expansion stroke of the cylinder 1 is poor.

  If the difference is equal to or larger than the determination threshold value in step S8, the instantaneous value and moving average value of the engine speed at 150 ° CA after the compression top dead center of the cylinder 1 in the same expansion stroke are measured. (Steps S9 and S10), the difference between them is calculated (Step S11). And the difference is compared with the determination threshold value corresponding to the time of 150 degrees CA after compression top dead center (step S12). The determination threshold value in step S12 is higher than the determination threshold value in step S8. If the difference is below the determination threshold, it is determined that the combustion in the expansion stroke of the cylinder 1 is poor. Otherwise, it is determined that the combustion in the expansion stroke of the cylinder 1 is normal.

  The determination threshold values in steps S4, S8, and S12 are preferably raised or lowered according to the operating range of the internal combustion engine and / or the magnitude of the mechanical load acting on the internal combustion engine. The magnitude of the difference between the instantaneous value of the engine rotational speed and the moving average value differs between a low load region where the intake air amount and the fuel injection amount are small and a high load region where the intake air amount and the fuel injection amount are large. Even when the compressor 61 is compressing the refrigerant for the air conditioner, when the high voltage is generated by the power generation function of the alternator 62, and when it is not, the magnitude of the difference in rotational speed is different.

  In addition, the determination threshold values in steps S4, S8, and S12 are not necessarily the same for all cylinders 1. The determination threshold value may be different for each cylinder 1. This is because, in addition to the unequal intake amount distributed to each cylinder 1 from the intake passage 3, various characteristics are slightly different for each cylinder 1.

  When it is determined that the combustion in the expansion stroke of the cylinder 1 is poor, correction control is performed to increase the rotational torque of the engine in order to avoid engine stall (step S13). For example, in order to increase the intake (fresh air) amount and fuel injection amount filled in the cylinder 1, the opening of the idle speed control valve 36 is increased, or if the throttle valve 32 is an electronic throttle valve, the throttle valve 32 Or increase the opening. It is also conceivable to advance the ignition timing. When an exhaust gas recirculation device is attached to the internal combustion engine, an operation of reducing the opening of the EGR valve may be performed. Alternatively, the mechanical load acting on the internal combustion engine is reduced. If the magnet clutch 51 for transmitting the rotational torque of the crankshaft to the compressor is disconnected, it is possible to suppress a decrease in the rotational speed of the crankshaft. The same applies to reducing the voltage generated by the alternator 62.

In the present embodiment, it calculates the moving average value based on the instantaneous value while measuring at least the instantaneous value of the rotational speed of the internal combustion engine at two time points during the expansion stroke in the cylinder 1 of the internal combustion engine, from the instantaneous value at each time point The difference obtained by subtracting the moving average value is compared with a determination threshold value, and when the difference falls below the determination threshold value, it is determined that the combustion of the cylinder 1 is poor, and the difference at a later time point during the expansion stroke The control device 0 for the internal combustion engine is characterized in that the determination threshold value to be compared with is set higher than the determination threshold value to be compared with the difference at an earlier point in time during the expansion stroke.

  According to this embodiment, it is possible to detect the occurrence of a combustion failure or misfire that may cause an engine stall as quickly as possible, and to start correction control in a timely manner. As a result, the engine stall resistance is improved.

  The present invention is not limited to the embodiment described in detail above. For example, in the above embodiment, the difference between the instantaneous value of the engine rotational speed and the moving average value is calculated at three time points 90 ° CA, 120 ° CA, and 150 ° CA after the compression top dead center in the expansion stroke of the cylinder 1. Although these are respectively compared with the determination threshold values, the time points at which the difference in rotational speed is obtained are not limited to the above three time points. Differences in rotational speed are obtained for a plurality of arbitrary time points between 60 ° CA and 180 ° CA after compression top dead center, and these are respectively compared with determination thresholds to determine normality / badness of combustion of the cylinder 1 Can be done. In this case as well, it goes without saying that the determination threshold value to be compared with the difference at a later time point during the expansion stroke is set higher than the determination threshold value to be compared with the difference at an earlier time point during the expansion stroke. In order to achieve both early detection performance and false detection resistance at a higher level, the determination threshold value can be divided by the cylinder 1 (divided according to the hardware tendency).

  The number of times of calculating the difference in rotation speed and the number of times of comparison between the difference and the determination threshold may be two times or four times or more.

  The combustion failure detection method according to the present invention is particularly effective for a small-cylinder internal combustion engine such as a two-cylinder or a three-cylinder engine having a large interval between explosion combustions. Is possible.

  In addition, the specific configuration of each unit, the processing procedure, and the like can be variously modified without departing from the spirit of the present invention.

  The present invention can be used for controlling an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
1 ... Cylinder b ... Crank angle signal

Claims (1)

Measuring the instantaneous value of the rotational speed of the internal combustion engine at at least two points during the expansion stroke in the cylinder of the internal combustion engine and calculating a moving average value based on the instantaneous value ;
The difference obtained by subtracting the moving average value from the instantaneous value at each time point is compared with a determination threshold value, and when the difference is less than the determination threshold value, it is determined that the combustion of the cylinder is defective.
Control of an internal combustion engine characterized in that a determination threshold value to be compared with a difference at a later time point during an expansion stroke is set higher than a determination threshold value to be compared with a difference at an earlier time point during an expansion stroke apparatus.

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