JP5843546B2 - 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.

  It is known to constantly monitor the rotational speed of an internal combustion engine and detect misfire in a cylinder from fluctuations in the rotational speed (see, for example, the following patent document). As shown in FIG. 3, when the time taken for the crankshaft to rotate by a predetermined angle is taken on the horizontal axis, and the frequency of appearance of the required time is taken on the vertical axis, the distribution of the required time in the case of normal combustion without misfire. There is a difference between (represented by a solid line) and the required time distribution in a misfired case (represented by a broken line). Therefore, a determination value located between both distributions is set, and the time required for the crankshaft to rotate by a predetermined angle is measured and compared with this determination value to determine whether or not a misfire has occurred. Is possible.

  Misfire determination is difficult in a situation where there is no difference in engine speed between normal combustion and misfire. Accordingly, misjudgment is prevented by assuming that misfire determination is not performed in an operation region where the intake air amount or fuel injection amount per unit rotation is equal to or less than a predetermined threshold.

The engine output torque for a certain intake air amount or fuel injection amount varies depending on the properties of the fuel. For example, an E20 fuel blended with 20% ethanol for the purpose of reducing CO ₂ emissions has a higher oxygen content and a corresponding increase in output compared to a normal fuel.

  However, at present, the above threshold value, which is a condition for determining whether or not to make a misfire, is constant regardless of the properties of the fuel. When the threshold is set according to the fuel that generates a higher output torque such as E20 fuel, when normal fuel is used, the operation is low output so that the rotational speed does not fluctuate even if misfiring The misfire determination is performed in the region, and the chance of erroneous determination of the presence or absence of misfire increases.

JP 07-310586 A

  An object of the present invention is to reduce misjudgment of the presence or absence of misfire.

In the present invention, in the control device that determines whether or not the in-vehicle internal combustion engine has misfired, the misfire determination is performed on the condition that the intake air amount or the fuel injection amount per unit rotation is equal to or greater than a threshold value. During deceleration, when the driver depresses the accelerator pedal , the throttle valve or idle speed control valve is opened and operated while the torque transmission between the internal combustion engine and the axle is cut off. The amount of intake air or the amount of fuel injection per unit revolution and the engine speed so that the deceleration of the engine speed at that time is less than or equal to a predetermined value is obtained, and the threshold value is determined based on this. It was decided.

  According to the present invention, misjudgment of the presence or absence of misfire can be reduced.

The figure which shows the whole structure of the internal combustion engine in one Embodiment of this invention. The figure which shows the structure of the automatic transmission in the embodiment. The figure explaining the technique of misfire determination which the control apparatus of the embodiment implements. The figure explaining the method of learning of the threshold value which concerns on the judgment of the propriety of misfire judgment 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. This internal combustion engine is of a direct injection type, and includes a plurality of cylinders 1 (one of which is shown in FIG. 1), an injector 11 for injecting fuel into each cylinder 1, An intake passage 3 for supplying intake air to the cylinder 1, an exhaust passage 4 for discharging exhaust from each cylinder 1, an exhaust turbocharger 5 for supercharging intake air flowing through the intake passage 3, and an exhaust passage And an external EGR device 2 that recirculates EGR (Exhaust Gas Recirculation) gas from 4 to the intake passage 3.

  The intake passage 3 takes in air from the outside and guides it to the intake port of the cylinder 1. On the intake passage 3, an air cleaner 31, a compressor 51 of the supercharger 5, an intercooler 32, an electronic throttle valve 33, a surge tank 34, and an intake manifold 35 are arranged in this order from the upstream side.

  The exhaust passage 4 guides exhaust generated as a result of burning fuel in the cylinder 1 from the exhaust port of the cylinder 1 to the outside. An exhaust manifold 42, a drive turbine 52 for the supercharger 5, and a three-way catalyst 41 are disposed on the exhaust passage 4. In addition, an exhaust bypass passage 43 that bypasses the turbine 52 and a waste gate valve 44 that is a bypass valve that opens and closes the inlet of the bypass passage 43 are provided. The waste gate valve 44 is an electric waste gate valve that can be opened and closed by inputting a control signal l to the actuator, and a DC servo motor is used as the actuator.

  The exhaust turbocharger 5 is configured such that the drive turbine 52 and the compressor 51 are connected and linked in a coaxial manner. Then, the driving turbine 52 is rotationally driven by using the energy of the exhaust gas, and the compressor 51 is pumped by using the rotational force, whereby the intake air is pressurized and compressed (supercharged) and sent to the cylinder 1.

  The external EGR device 2 realizes a so-called high-pressure loop EGR. The inlet of the external EGR passage is connected to a predetermined location upstream of the turbine 52 in the exhaust passage 4. The outlet of the external EGR passage is connected to a predetermined location downstream of the throttle valve 33 in the intake passage 3, specifically to a surge tank 34. An EGR cooler 21 and an EGR valve 22 are also provided on the external EGR passage.

  FIG. 2 shows an example of an automatic transmission for a vehicle. This automatic transmission is a continuously variable transmission including a torque converter 7 and a belt type CVT 9. The rotational driving force output from the internal combustion engine is input from the crankshaft of the internal combustion engine to the pump impeller 71 on the input side of the torque converter 7 and transmitted to the turbine runner 72 on the output side. The rotation of the turbine runner 72 is transmitted to the drive shaft 94 of the CVT 9 via the forward / reverse switching device 8 using a planetary gear mechanism, and rotates the driven shaft 95 through a shift in the CVT 9. An output gear 101 is fixed to the driven shaft 95, and the output gear 101 meshes with a ring gear 102 of a differential device to rotate an axle and driving wheels (not shown).

  The torque converter 7 includes a lockup mechanism (not shown). The lockup mechanism is known in this field, and includes a lockup clutch that locks up the input side and the output side of the torque converter 7, and a lockup solenoid that controls the hydraulic pressure for driving the lockup clutch to connect and disconnect. A valve is an element. The lockup mechanism connects the lockup clutch and fastens the input side and the output side in a situation that does not involve a change in the gear ratio by the automatic transmission.

  In the forward / reverse switching device 8, the sun gear 81 communicates with the turbine runner 72 via the input shaft 73, and the ring gear 82 communicates with the drive shaft 94. Between the planetary carrier 83 that supports the planetary gear 831 and the transmission case, a forward brake 84 that is a hydraulic clutch that can be connected and disconnected is interposed. Further, a reverse clutch 85, which is a hydraulic clutch capable of switching connection and disconnection, is also interposed between the planetary carrier 83 and the sun gear 81 (or the input shaft 73).

  In the D range of the traveling range, the forward brake 84 is engaged and the reverse clutch 85 is disconnected. As a result, the rotation of the input shaft 73 is reversed and decelerated and transmitted to the drive shaft 94 for forward travel. In turn, in the R range, the reverse clutch 85 is engaged and the forward brake 84 is disconnected. As a result, the sun gear 81 and the planetary carrier 83 rotate integrally, and the input shaft 73 and the drive shaft 94 are directly connected to perform reverse travel. In the N range and P range, which are non-traveling ranges, the reverse clutch 84 and the forward brake 85 are both disconnected, and transmission of torque between the internal combustion engine and the axle is cut off. Note that the reverse clutch 84 and the forward brake 85 may be disconnected for an extremely short time even in the D range for the purpose of improving fuel efficiency and other purposes.

  The CVT 9 includes a driving pulley 91 and a driven pulley 92, and a belt 93 wound around the pulleys 91 and 92 as elements. The drive pulley 91 is disposed behind the movable sheave 912, a fixed sheave 911 fixed to the drive shaft 94, a movable sheave 912 supported on the drive shaft 91 via a roller spline so as to be displaceable in the axial direction. A hydraulic servo 913 is provided, and the gear ratio can be changed steplessly by operating the hydraulic servo 913 and displacing the movable sheave 912. The driven pulley 92 is disposed on the back of the movable sheave 922, a fixed sheave 921 fixed to the driven shaft 95, a movable sheave 922 supported on the driven shaft 95 via a roller spline so as to be axially displaceable. A hydraulic servo 923 is provided, and a belt thrust necessary for torque transmission is applied by operating the hydraulic servo 923 and displacing the movable sheave 922.

  An ECU (Electronic Control Unit) 0 that controls operation of the internal combustion engine and the CVT 9 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 vehicle speed, an engine rotation signal b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and an accelerator pedal depression amount (or , The opening degree of the throttle valve 33) as a required load, the accelerator opening degree signal c output from the accelerator opening degree sensor, the intake air temperature and the intake pressure (or supercharging) in the intake passage 3 (especially the surge tank 34). Intake temperature signal and intake pressure signal d output from the temperature / pressure sensor for detecting the pressure), shift position signal e output from the shift position switch for detecting the position (shift range) of the shift lever, and coolant temperature of the internal combustion engine The cooling water temperature signal f output from the water temperature sensor that detects the intake air, and the plurality of cam angles of the intake camshaft Exhaust cam signal g such that is output from the beam angle sensor is input. The engine rotation sensor generates a pulse signal b every 10 ° CA (crank angle). The cam angle sensor generates a pulse signal g at an angle obtained by dividing 720 ° CA by the number of cylinders, or every 240 ° CA for a three-cylinder engine.

  From the output interface, the fuel injection signal h for the injector 11, the ignition signal i for the ignition plug (ignition coil thereof), the opening operation signal j for the EGR valve 22, and the opening operation for the throttle valve 33. An opening operation signal l is output to the signal k and the waste gate valve 44, and a gear ratio signal m and the like are output to the CVT 9.

  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, and g necessary for operation control of the internal combustion engine via the input interface, knows the engine speed, and fills the cylinder 1 with the intake air amount. Is estimated. Based on the engine speed and intake air amount, the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, EGR rate (or EGR amount) And various operating parameters such as the opening degree of the EGR valve 22 and the gear ratio of the CVT 9 are determined. As the operation parameter determination method itself, a known method can be adopted, and the description thereof will be omitted. The ECU 0 applies various control signals h, i, j, k, l, and m corresponding to the operation parameters via the output interface.

  The ECU 0 as the control device of the present embodiment constantly monitors the rotational speed of the internal combustion engine, and detects misfire in the cylinder 1 from fluctuations in the rotational speed. As described above, the time taken for the crankshaft to rotate by a predetermined angle is plotted on the horizontal axis, and the frequency of occurrence of the required time is plotted on the vertical axis. The distribution of the required time in the case of normal combustion without misfiring (Fig. There is a difference between the required time distribution in the case of misfire (shown by the broken line in FIG. 3). It is possible to determine whether or not a misfire has occurred by setting a judgment value located between the two distributions, measuring the time required for the crankshaft to rotate by a predetermined angle and comparing it with this judgment value. Is possible.

  The ECU 0 repeatedly measures the time required for the crankshaft to rotate by a predetermined angle (for example, 30 ° CA) with reference to the signal b output from the engine rotation sensor, and determines the measured required time as a determination value. When the required time becomes larger than the determination value, that is, when the rotational speed decreases below the determination value, it is determined that misfire has occurred.

  However, the misfire determination is not performed when the intake air amount or the fuel injection amount per unit rotation (for example, one rotation) of the crankshaft is equal to or less than the threshold value. This is because when the amount of intake air and therefore the amount of fuel injection is small, the output torque of the engine generated by the combustion of fuel is small, and even if misfire occurs, no significant change appears in the engine speed.

  FIG. 4 shows the characteristics of the threshold value, which is a condition for carrying out the misfire determination. The horizontal axis represents the engine speed per fixed time, and the vertical axis represents the intake air amount or fuel injection amount per unit rotation. In the case where the fuel with the property that the output torque of the engine is relatively low is used (indicated by the solid line in FIG. 4), the fuel that has the property that the output torque is relatively high is used (as indicated by the broken line in FIG. 4). It is desirable to set the threshold value higher than that shown. Regardless of the nature of the fuel, the threshold value is increased as the engine speed increases in the operation range from medium to high. This is because the intake resistance and the like increase as the engine speed increases.

  In addition, the ECU 0 opens the throttle valve 33 and injects and burns fuel while the transmission of torque between the internal combustion engine and the axle is cut off. The amount or fuel injection amount is measured, and the threshold value that matches the fuel property is learned based on the measured amount or the fuel injection amount, and the threshold value is updated. Incidentally, the intake air amount is indirectly measured by estimating from the intake air pressure and the engine speed.

  The threshold value learning will be described in detail. The ECU 0 performs threshold value learning at the time of deceleration at which the driver depresses the accelerator pedal. In the case of deceleration in the D range, the reverse clutch 84 and the forward brake 85 that are clutches that connect the crankshaft and the axle of the internal combustion engine are temporarily disconnected. On the other hand, if the deceleration is in the N range, the clutches 84 and 85 are disengaged. Then, with the clutches 84 and 85 disconnected, the throttle valve 33 is opened at least once, fuel is injected from the injector 11 and burned in the cylinder 1, and fluctuations in the rotational speed of the engine are monitored.

  When the engine speed is higher than a certain level (fuel cut permission speed) or more, when the driver's foot leaves the accelerator pedal, it is customary to perform a fuel cut that stops the fuel supply. Even if it is in the middle, the threshold value learning is executed, and the throttle valve 33 is once opened to inject fuel, ignite and burn.

  What is needed to obtain a new threshold is that the engine speed is slowed down compared to the case where the fuel is not combusted (in other words, misfiring) as a result of burning the fuel, or the rotational speed Is the minimum intake air amount or fuel injection amount that increases. For this purpose, the ECU 0 continues to repeatedly measure the time required for the crankshaft to rotate at a predetermined angle (for example, 30 ° CA) for each predetermined angle. Then, referring to the time series of the measured required time, when the amount of change in the rotational speed per CA for a predetermined time or CA, that is, the deceleration is equal to or less than a predetermined value, the intake amount or fuel injection amount per unit rotation at that time In addition, the engine speed per fixed time is stored in the memory as a learning value.

  When the deceleration exceeds a predetermined value, the output torque of the internal combustion engine is insufficient and the vehicle is decelerating. Therefore, after increasing the opening degree of the throttle valve 33 and the fuel injection amount, combustion is performed again to reduce the deceleration. The intake air amount or fuel injection amount per unit rotation and the engine speed so that the speed becomes a predetermined value or less are obtained. Alternatively, the throttle valve 33 is gradually reduced in opening and the fuel injection amount is gradually reduced, and combustion is performed a plurality of times, and the minimum intake amount or fuel injection amount and the engine speed at which the deceleration does not exceed a predetermined value. You may know the number.

  Therefore, the threshold value, which is a condition for determining whether to perform misfire determination, can be updated from the learned intake air amount or fuel injection amount and engine speed. That is, as shown in FIG. 4, the threshold line (shown by a chain line in FIG. 4) is positioned at a level that passes through the learned intake air amount or fuel injection amount and the plot point of the engine speed (shown by a black circle in FIG. 4). . Thereafter, the ECU 0 determines whether or not to make a misfire determination using the threshold on the line as a determination criterion.

  It is preferable that the learning of the threshold value associated with the opening of the throttle valve 33, the fuel injection, and the combustion is performed immediately after the start of deceleration at which the driver depresses the accelerator pedal. This is because at the beginning of deceleration, it is difficult for the driver to feel uncomfortable even if combustion is performed for the purpose of threshold learning, and the increase in combustion noise is not noticeable.

  According to the present embodiment, in the control device 0 that determines whether or not a misfire has occurred based on fluctuations in the rotational speed of the in-vehicle internal combustion engine, misfire is performed on condition that the intake amount or fuel injection amount per unit rotation is equal to or greater than a threshold value. If the threshold is less than the threshold value, the misfire determination is not performed. In a state where the transmission of torque between the internal combustion engine and the axle is cut off, the throttle valve 33 is opened and fuel is injected and burned. Since the learning to determine the threshold value is executed based on the engine speed and the intake air amount or the fuel injection amount, the threshold value is set in consideration of the effects of fuel properties, lubricant deterioration, engine aging, etc. Therefore, it is possible to avoid performing the misfire determination in the low output operation region where the rotation speed does not change even if the misfire occurs. Therefore, the chance of misjudgment of the presence or absence of misfire is reduced, and the misfire judgment accuracy is improved.

  The present invention is not limited to the embodiment described in detail above. In learning the threshold value, in the above embodiment, the ECU 0 as the control device opens the electronic throttle valve 33. However, in an internal combustion engine equipped with an idle speed control valve, the idle speed control valve is opened. It is good as well. As is well known, the idle speed control valve is a flow control valve that opens and closes a bypass passage that communicates the upstream side and the downstream side of the throttle valve in the intake passage.

  The misfire determination method is not limited to the method that refers to fluctuations in the rotational speed of the engine, but other methods, such as those that detect ion current and perform misfire determination based on this, or use both rotation fluctuation and ion current together It does not matter if they are

  Other specific configurations of each part can be variously modified without departing from the spirit of the present invention.

  The present invention can be used to control an internal combustion engine mounted on a vehicle.

0 ... Control unit (ECU)
1 ... Cylinder 33 ... Throttle valve

Claims (1)

In a control device for determining whether or not an in-vehicle internal combustion engine has misfired,
A misfire determination is made on condition that the intake air amount or fuel injection amount per unit rotation is equal to or greater than a threshold, and the misfire determination is not performed below the threshold,
During deceleration when the driver depresses the accelerator pedal , the throttle valve or idle speed control valve is opened and fuel is injected and burned while torque transmission between the internal combustion engine and the axle is cut off. In addition, the intake air amount or fuel injection amount per unit rotation and the engine speed so that the deceleration of the engine rotation at that time is less than or equal to a predetermined value are obtained, and the threshold value is determined based on this. Control device for internal combustion engine.

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