JP2014109196A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize ignition timings for respective cylinders of an internal combustion engine.SOLUTION: Base ignition timings T1, T2, T3 are set for respective cylinders, and occurrence or not of knocking is detected each time expansion strokes take place in the respective cylinders. Individual delay correction amounts R1, R2, R3 for the respective cylinders, which are increased when the knockings occur in the cylinders and reduced when the knocking does not occur, are added to the base ignition timings T1, T2, T3 to determine ignition timings S1, S2, S3 for the next expansion strokes in the cylinders 1.

Description

  The present invention relates to a control device that controls the ignition timing of an air-fuel mixture in a cylinder of an internal combustion engine.

  There is a known knock control system that detects the occurrence of knocking in a cylinder, retards the ignition timing until knocking does not occur, and advances the ignition timing as long as knocking does not occur (see, for example, the following patent document). .

  Conventionally, the base ignition timing is commonly set for all cylinders of the internal combustion engine. The base ignition timing is set to a limit timing at which the cylinder having the highest risk of causing knocking does not cause knocking. Furthermore, the ignition timing retard correction amount by the knock control system is the same for all cylinders. Therefore, the ignition timing of each cylinder is consistently consistent.

JP 2000-073847 A

  However, the distribution of intake air, the state of combustion of the air-fuel mixture, and other conditions vary among cylinders. In particular, in an internal combustion engine attached with an exhaust gas recirculation device that recirculates a part of the combustion gas generated in the combustion chamber of the cylinder from the exhaust passage to the intake passage, each cylinder is filled. The amount of EGR gas mixed in the intake air varies greatly between the cylinders.

  Therefore, the limit ignition timing at which knocking does not occur differs for each cylinder. Nevertheless, since the ignition timing is common to all cylinders, the ignition timing of all cylinders must be retarded to prevent knocking in the cylinder where knocking is most likely to occur. It was supposed to lead to a decline.

  An object of the present invention is to optimize the ignition timing of each cylinder of an internal combustion engine.

  The present invention controls an internal combustion engine having a plurality of cylinders and having an exhaust gas recirculation device attached thereto, sets the base ignition timing of each cylinder, detects the presence or absence of knocking of each cylinder, and When the engine knocks at the cylinder, it increases and when the engine does not knock, it decreases for each cylinder. The internal combustion engine control apparatus is characterized in that the ignition timing is determined.

  According to the present invention, the ignition timing of each cylinder of the internal combustion engine can be optimized.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The figure explaining the method in which the control apparatus of the embodiment determines the ignition timing for each cylinder. The figure explaining the method in which the control apparatus concerning the modification of this invention determines the ignition timing for every cylinder.

  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 4-stroke gasoline 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 ignition coil is integrally incorporated in a coil case together with an igniter that is a semiconductor switching element.

  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, an electronic throttle valve 32, a surge tank 33, and an intake manifold 34 are arranged in this order from the upstream.

  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.

  An external EGR device 2 is attached to the internal combustion engine of the present embodiment. The external EGR device 2 realizes a so-called high-pressure loop EGR. The EGR device 21 communicates the upstream side of the catalyst 41 in the exhaust passage 4 and the downstream side of the throttle valve 32 in the intake passage 3, and the EGR passage 21. The EGR cooler 22 provided in the EGR passage and the EGR valve 23 that opens and closes the EGR passage 21 and controls the flow rate of EGR gas flowing through the EGR passage 21 are used as elements.

  The inlet of the EGR passage 21 is connected to the exhaust manifold 42 in the exhaust passage 4 or a predetermined location downstream thereof. The outlet of the EGR passage 21 is connected to a predetermined location downstream of the throttle valve 32 in the intake passage 3, specifically to a surge tank 33. Therefore, the EGR gas to be distributed to all the cylinders 1 once flows into the surge tank 33 and then travels to each cylinder 1 via the intake manifold 34.

  An ECU (Electronic Control Unit) 0 serving as a control device that controls operation of an internal combustion engine 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, An 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 (so-called required load), and the magnitude of vibration of the cylinder block that contains the cylinder 1 are detected. A knock signal d output from the knock sensor, an intake air temperature / intake pressure signal e output from the temperature / pressure sensor for detecting the intake air temperature and the intake pressure in the intake passage 3 (particularly, the surge tank 33), and cooling of the engine A cooling water temperature signal f output from a water temperature sensor for detecting the water temperature, a sensor for obtaining the shift lever range (or Shift range signal g outputted from the shift position switch), a cam angle signal (G signal output from the cam angle sensor at a plurality of cam angle of the intake camshaft or an exhaust camshaft) h or the like is input.

  From the output interface, the ignition signal i for the igniter of the spark plug 12, the fuel injection signal j for the injector 11, the opening operation signal k for the throttle valve 32, and the opening operation signal l for the EGR valve 23. Etc. are 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, etc., the required fuel injection amount, fuel injection timing (including the number of times of fuel injection for one combustion), fuel injection pressure, ignition timing, required EGR rate (or EGR rate) Various operating parameters such as volume). As the operation parameter determination method itself, a known method can be adopted. The ECU 0 applies various control signals i, j, k, and l corresponding to the operation parameters via the output interface.

Further, the ECU 0 refers to the knock signal d acquired via the knock sensor, and individually determines the presence or absence of knocking in the expansion stroke of each cylinder 1 for each cylinder 1. In determining whether knocking has occurred, the ECU 0 calculates a knock determination value in advance by statistical processing. Specifically, under the condition that knocking does not occur, the vibration of the cylinder block during the expansion stroke of the cylinder 1 is sampled through the knock sensor to obtain the knock signal d. Then, an average value, a standard deviation, and a knock determination value are calculated from a time series within a certain period of the sampling value of the knock signal d. When the average value is X and the standard deviation is σ, the knock determination value J is
J = X + Uσ
As required. The coefficient U in the above equation is set according to the operation region at that time, that is, the engine speed and the required load. The coefficient U may be changed according to the level of the air-fuel ratio, the required EGR rate, and the like.

  The knock determination value J may be obtained individually for each cylinder 1 or may be common to all cylinders 1. When the knock determination value J is individually set for each cylinder 1, when the knock determination value J is obtained for a certain cylinder 1, only the sampling value of the knock signal d detected during the expansion stroke of the cylinder 1 is used. Then, the average value X and the standard deviation σ are calculated and the values X and σ are substituted into the above equation. The ECU 0 stores the obtained coefficient U and knock determination value J in a memory.

  The ECU 0 then compares the current sampling value (current vibration intensity) of the knock signal d output from the knock sensor with the knock determination value J. That is, if the sampling value of the knock signal d detected through the knock sensor during the expansion stroke of the cylinder 1 exceeds the knock determination value J, it is determined that knocking has occurred in the cylinder 1. Conversely, if the sampling value of the knock signal d is equal to or less than the knock determination value J, it is determined that knocking has not occurred in the cylinder 1.

  Therefore, when determining the ignition timing for the air-fuel mixture filled in each cylinder 1, the ECU 0 of the present embodiment is based on the determination result of the presence or absence of knocking in each cylinder 1 based on the base ignition timing for each cylinder 1. Thus, the retardation correction (retard) amount of each cylinder 1 to be increased or decreased is taken into consideration.

  The base ignition timing is an ignition timing with no retardation correction, that is, the most advanced (limit) ignition timing. The base ignition timing is set according to the operation region [engine speed, load]. The load of the internal combustion engine is suggested by the accelerator opening, the fuel injection amount, the intake air amount filled in the cylinder 1, the pressure in the surge tank 33, and the like.

  FIG. 2 shows the relationship between the ignition timing and the torque output by the internal combustion engine when a certain intake air amount, fuel injection amount, and other operating parameters are assumed. The output torque is maximized when the ignition timing is set to an MBT (Minimum Advance for Best Torque) point after compression top dead center, and decreases as the ignition timing is retarded (or advanced) from the MBT point. Incidentally, in FIG. 2, only one characteristic curve and MBT point of ignition timing and engine torque are drawn, but this characteristic curve and MBT point are not necessarily the same for all cylinders 1.

  Depending on the operating region, when the ignition timing is set to the MBT point, knocking frequently occurs, and the internal combustion engine is damaged. Therefore, normally, in the operation region that causes knocking, the base ignition timing is set to a timing delayed to some extent from the MBT point.

  As shown in FIG. 2, in this embodiment, the base ignition timing is individually set for each cylinder 1. That is, the base ignition timing of each cylinder 1 is not always common. In FIG. 2, reference numeral T1 indicates the base ignition timing of the first cylinder 1, reference numeral T2 indicates the base ignition timing of the second cylinder 1, and reference numeral T3 indicates the third cylinder 1. Is the base ignition timing.

  These base ignition timings are determined based on the evaluation results after determining the ease of knocking of each cylinder 1 by conformity evaluation. These base ignition timings also take into account variations in the amount of EGR gas introduced into each cylinder 1.

  Note that, in an operation region where knocking is unlikely to occur, the base ignition timing is allowed to be set near the MBT point. In an operation region in which knocking does not occur almost reliably, the base timings of the cylinders 1 may gather near the MBT point and substantially coincide with each other.

  In the memory of the ECU 0 of the present embodiment, the EGR rate (or EGR gas amount) required for the operating region of the internal combustion engine and the intake air charged in the cylinder 1 and the base ignition timing for each cylinder 1 to be set are set in advance. Map data that defines the relationship between and is stored. The ECU 0 obtains the base ignition timing to be set for each cylinder 1 by searching the map using the current operation region and the required EGR rate as keys.

  Incidentally, the required EGR rate is basically set according to the required load of the internal combustion engine at that time. The required EGR rate is highest when the internal combustion engine is operating at a medium load, and decreases as the load decreases from a medium load to a higher load. The required EGR rate is zero during idling or during low load operation close to idling, or during high load operation where the accelerator opening is almost fully open. Further, the required EGR rate decreases when the internal combustion engine is warming up or when the load on an auxiliary machine (such as a generator or a compressor that compresses a refrigerant for an air conditioner) driven by the internal combustion engine is high.

  Then, the ECU 0 of the present embodiment knocks the retardation correction amount to be added to the next ignition timing in the cylinder 1 if knocking occurs in the cylinder 1 as a result of the knock determination for each cylinder 1. Increase by a predetermined amount until no more occurs. On the other hand, if knocking has not occurred, the retard correction amount to be added to the next and subsequent ignition timings in the cylinder 1 is decreased by a predetermined amount until just before knocking, thereby increasing the engine torque and fuel consumption. Pursuing improvement.

  In general, as shown in FIG. 2, the ignition timing of each cylinder 1 is obtained by adding an individual retardation correction amount for each cylinder 1 to an individual base ignition timing for each cylinder 1. In FIG. 2, the reference symbol R1 indicates the retardation correction amount of the first cylinder 1, the reference symbol R2 indicates the retardation correction amount of the second cylinder 1, and the reference symbol R3 indicates the third. This is the retardation correction amount of the cylinder 1. The ignition timing determined for the first cylinder 1 is S1, the ignition timing determined for the second cylinder 1 is S2, and the ignition timing determined for the third cylinder 1 is S3.

  In the present embodiment, an internal combustion engine having a plurality of cylinders 1 and having an exhaust gas recirculation device 2 attached thereto is controlled, and base ignition timings T1, T2, T3 are individually set for each cylinder 1, The presence or absence of knocking is detected every time the expansion stroke of each cylinder 1 is visited, and when the knocking occurs in the cylinder 1, the delay is corrected individually for each cylinder 1 that increases when the knocking does not occur and decreases when the knocking does not occur. An ignition timing S1, S2, S3 for the next expansion stroke in the cylinder 1 is determined by adding the amounts R1, R2, R3 to the base ignition timings T1, T2, T3. A control device 0 was configured.

  According to this embodiment, the ignition timing of each cylinder 1 of the internal combustion engine can be optimized. That is, it is possible to retard the ignition timing for the cylinder 1 that is relatively likely to cause knocking, and advance the ignition timing for the cylinder 1 that is relatively unlikely to cause knocking. Therefore, it is possible to avoid retarding unnecessary ignition timing while reliably suppressing knocking, and the engine torque is not sacrificed, and the efficiency and fuel efficiency are improved.

  The present invention is not limited to the embodiment described in detail above. For example, when setting the base ignition timing, the EGR gas amount flowing into each cylinder 1 is individually measured or estimated, and the base ignition timing of each cylinder 1 is determined according to the measured or estimated EGR gas amount for each cylinder 1. It is good also as what adjusts. In this case, map data defining the relationship between the operating region of the internal combustion engine and the EGR gas amount for each cylinder 1 and the base ignition timing for each cylinder 1 to be set is stored in the memory of the ECU 0 as the control device. The base ignition timing set for each cylinder 1 is obtained by searching the map using the current operation region and the EGR gas amount for each cylinder 1 as keys.

  Further, the means for detecting the presence or absence of knocking in the expansion stroke of each cylinder 1 is not limited to the vibration type knock sensor. It is also possible to employ a method of referring to the signal waveform of the ionic current flowing through the electrode of the spark plug 12 during the combustion of the air-fuel mixture or a method of referring to the pressure in the combustion chamber (cylinder pressure) of the cylinder 1.

  The base ignition timing of each cylinder 1 is not necessarily set individually for each cylinder 1 and may be common to all cylinders 1 as shown in FIG. The base ignition timing in this case is set to a timing TB at which the cylinder 1 having the smallest risk of causing knocking is advanced to the limit at which knocking does not occur (as close as possible to the MBT point). The base ignition timing TB is also set according to the current operating range of the internal combustion engine, the required EGR rate, etc., as in the above embodiment.

  In addition, the ECU 0 as a control device detects the presence or absence of knocking for each of the plurality of cylinders 1 for each expansion stroke, and increases when the knocking occurs and decreases when the knocking does not occur. The ignition timings S1, S2, and S3 for the next expansion stroke in each cylinder 1 are determined by adding the amounts R1, R2, and R3 to the base ignition timing TB. Even in such a case, the ignition timings S1, S2, and S3 can be optimized independently for each cylinder 1, and the thermomechanical conversion efficiency can be improved while preventing knocking, and the engine torque can be improved and / or Improved fuel economy.

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

  The present invention can be applied to ignition control of an internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
DESCRIPTION OF SYMBOLS 1 ... Cylinder 12 ... Spark plug R1, R2, R3 ... Delay angle correction amount S1, S2, S3 ... Decided ignition timing T1, T2, T3, TB ... Base ignition timing

Claims (1)

Controlling an internal combustion engine having a plurality of cylinders and attached with an exhaust gas recirculation device;
Set the base ignition timing for each cylinder,
The presence or absence of knocking in each cylinder is detected, and when the knocking occurs in the cylinder, an individual retardation correction amount is added to the base ignition timing for each cylinder that increases when knocking does not occur. An internal combustion engine control apparatus that determines an ignition timing for the next expansion stroke in the cylinder.

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