JP6161492B2 - Control device for spark ignition internal combustion engine - Google Patents

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.

  In the ignition control of the internal combustion engine, the timing for igniting the air-fuel mixture is basically determined according to the operating region of the internal combustion engine at that time. In a region where the load and temperature of the internal combustion engine are relatively low, knocking does not occur even if the ignition timing is set to the MBT (Minimum Advance for Best Torque) point. On the other hand, in a region where the load and temperature of the internal combustion engine are relatively high, knocking may be induced when the ignition timing is set to the MBT point, so the ignition timing is retarded from the MBT point.

  An ECU (Electronic Control Unit) that controls the internal combustion engine stores and holds map data that defines the relationship between the operating range of the internal combustion engine and the base ignition timing. The ECU searches the map using the current operation region as a key, sets a target ignition timing based on the acquired base ignition timing, and uses it for ignition control.

  In addition to this, a knock control system that detects the occurrence of knocking in the cylinder, increases the retard correction amount of the ignition timing until knocking does not occur, and decreases the retard correction amount unless knocking occurs. It is customary to use them together (for example, see the following patent document).

JP 2000-073847 A

  When the operating region of the internal combustion engine transitions, the base ignition timing and the target ignition timing change. However, the target ignition timing does not always coincide with the base ignition timing. If the target ignition timing is immediately changed to the base ignition timing corresponding to the driving region in response to the transition of the driving region, there is a concern that the magnitude of the engine torque changes suddenly and the engine speed may be greatly fluctuated. It is.

  Therefore, in general, when the base ignition timing varies with the transition of the operation region, the target ignition timing is gradually changed to follow the base ignition timing. As a result, the transition of the target ignition timing is delayed with respect to the transition of the base ignition timing.

  When the load of the internal combustion engine suddenly increases, the base ignition timing fluctuates to the retard side, and a divergence occurs between the base ignition timing and the target ignition timing. Since the base ignition timing is advanced to the limit where knocking does not occur in the cylinder, there is a risk of causing knocking if the target ignition timing is advanced from the base ignition timing. Rise.

  Since the knock control system increases the ignition timing retardation correction amount only after detecting the occurrence of knocking, it cannot contribute to prevention of knocking. Also, depending on the increment of the retardation correction amount, there is a possibility that knocking may be repeated a plurality of times before knocking is suppressed.

  In order to prevent knocking with certainty, it is conceivable to retard the base ignition timing corresponding to the operation region from the original. However, in a situation where the risk of knocking is not so high, the ignition timing is unnecessarily retarded, leading to a decrease in engine torque and a deterioration in fuel consumption performance.

  The present invention has been made by paying attention to the above-mentioned problem for the first time, and an object of the present invention is to optimize the control of the ignition timing of a spark ignition type internal combustion engine.

  In the present invention, the target ignition timing that is the reference of the actual ignition timing is made to follow the base ignition timing set according to the operating region of the internal combustion engine, and the target ignition timing is advanced from the base ignition timing. And a control device for a spark ignition type internal combustion engine that adds a temporary retardation correction to the actual ignition timing, on the condition that the difference between the two is greater than a threshold value.

  More preferably, when the amount of change in the load of the internal combustion engine is equal to or greater than the threshold value or the amount of change in the engine speed is equal to or greater than the threshold value, the temporary retardation correction is added.

  According to the present invention, it is possible to optimize the control of the ignition timing of the spark ignition type internal combustion engine.

The figure which shows schematic structure of the internal combustion engine in one Embodiment of this invention. The circuit diagram of the spark ignition device in the embodiment. The figure which shows each transition of the combustion pressure and the ionic current in the cylinder of an internal combustion engine. The figure which illustrates the ion current signal detected when knocking occurs in the cylinder of the internal combustion engine. The figure which shows each transition of the base ignition timing in ignition control, and a target ignition timing.

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

  FIG. 2 shows an electric circuit for spark ignition. The spark plug 12 receives spark voltage generated by the ignition coil 14 and causes spark discharge between the center electrode and the ground electrode. The ignition coil 14 is integrally incorporated in a coil case together with an igniter 13 that is a semiconductor switching element.

  When the igniter 13 receives an ignition signal i from the ECU 0 which is a control device for the internal combustion engine, the igniter 13 is first ignited and a current flows to the primary side of the ignition coil 14, and the igniter 13 is extinguished at the timing of ignition immediately thereafter. This current is cut off. Then, a self-induction action occurs, and a high voltage is generated on the primary side. Since the primary side and the secondary side share the magnetic circuit and the magnetic flux, a higher induced voltage is generated on the secondary side. This high induction voltage is applied to the center electrode of the spark plug 12, and a spark discharge occurs between the center electrode and the ground electrode.

  The ECU 0 detects an ionic current generated in the combustion chamber of the cylinder 1 during the explosion combustion of the fuel, and refers to the ionic current to determine the combustion state.

  As shown in FIG. 2, in this embodiment, a circuit for detecting an ionic current is added to the electric circuit for spark ignition. This detection circuit includes a bias power supply unit 15 for effectively detecting an ionic current and an amplification unit 16 that amplifies and outputs a detection voltage corresponding to the amount of the ionic current. The bias power supply unit 15 includes a capacitor 151 that stores a bias voltage, a Zener diode 152 for increasing the voltage of the capacitor 151 to a predetermined voltage, current blocking diodes 153 and 154, and a load that outputs a voltage corresponding to the ion current. A resistor 155. The amplifying unit 16 includes a voltage amplifier 161 typified by an operational amplifier.

  The capacitor 151 is charged during arc discharge between the center electrode and the ground electrode of the spark plug 12, and then an ion current flows through the load resistor 155 by the bias voltage charged in the capacitor 151. The voltage between both ends of the resistor 155 generated by the flow of the ionic current is amplified by the amplifying unit 16 and received by the ECU 0 as the ionic current signal h.

  FIG. 3 illustrates respective transitions of the ionic current (indicated by a solid line in the figure) and the combustion pressure in the cylinder 1 (in-cylinder pressure; indicated by a broken line in the figure) in normal combustion. The ionic current cannot be detected during the discharge for ignition. In the case of normal combustion, the ionic current decreases by a chemical reaction before the compression top dead center after the end of spark ignition, and then increases again by thermal dissociation. In addition, the ionic current reaches a maximum almost simultaneously with the peak of the combustion pressure.

  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.

  The ECU 0 of the present embodiment that controls operation of the 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 b output from an engine rotation sensor that detects the rotation angle and engine speed of the crankshaft, and depression of an accelerator pedal. Accelerator opening degree signal c output from a sensor that detects the amount or opening degree of throttle valve 32 as an accelerator opening degree (so-called required load), and the pressure of intake air in intake passage 3 (especially surge tank 33) are detected. An intake pressure signal d output from the pressure sensor, an intake air temperature signal e output from a temperature sensor that detects the temperature of intake air in the intake passage 3, and a water temperature sensor that detects the cooling water temperature of the internal combustion engine (indicating the temperature of the engine) Is output from the cam angle sensor at multiple cam angles of the cooling water temperature signal f output from the intake camshaft or exhaust camshaft. A cam angle signal g, the ion current signal h or the like to be output from the circuit for detecting an ion current caused by the combustion of the mixture in the combustion chamber are inputted.

  From the output interface, an ignition signal i is output to the igniter of the spark plug 12, a fuel injection signal j is output to the injector 11, an opening operation signal k is output to the throttle valve 32, and the like.

  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. The ECU 0 applies various control signals i, j, k corresponding to the operation parameters via the output interface.

  Further, the ECU 0 can determine the presence or absence of knocking in the cylinder 1 with reference to the ion current signal h acquired through a circuit for detecting the ion current.

  A knock determination with reference to the ion current signal h will be described. FIG. 4 illustrates the transition of the ion current when knocking occurs during the expansion stroke in the cylinder 1. When knocking occurs, intense combustion occurs at a high combustion speed in the combustion chamber of the cylinder 1. Therefore, as compared with the case of normal combustion shown in FIG. 3, the ion current peaks earlier and then decays quickly. Then, the vibration S generated due to knocking is superimposed on the waveform after the peak of the ion current signal h.

  Noise may be mixed in the ion current signal h. A typical noise is spike noise N induced in the ion current detection circuit when a relay switch operated to switch operation / non-operation of various auxiliary machines is turned on / off.

  In determining the presence or absence of knocking, the ECU 0 samples the ionic current flowing through the electrode of the spark plug 12 through the ionic current detection circuit during the combustion period after ignition. Further, the sampled ion current signal h is input to a band-pass filter that passes the frequency component of the signal S generated due to knocking, and the component of the signal S is extracted. The filter is a filter for reducing components other than the signal S caused by knocking, and passes a frequency component of, for example, 7 kHz to 11.5 kHz.

  Accordingly, the filtered signal h is time-integrated, that is, the time series of sampling values are integrated, and the obtained integrated value is compared with a predetermined knock determination value. If the integral value exceeds the knock determination value, it is determined that knocking has occurred in the cylinder 1. Conversely, if the integral value is equal to or less than the knock determination value, it is determined that knocking has not occurred in the cylinder 1. The knock determination value is stored and held in the memory of ECU0.

  The ion current detection circuit can detect the ion current flowing through each spark plug 12 mounted on each cylinder 1. That is, the ion current signal h can be acquired individually for each cylinder 1, and the presence or absence of knocking can be individually determined for each cylinder 1.

  The ECU 0 of the present embodiment determines the actual ignition timing from the base ignition timing in accordance with the operation region of the internal combustion engine [engine speed, load (accelerator opening degree, intake pressure, intake air amount or fuel injection amount charged into the cylinder 1)]. Ignition control for setting a target ignition timing that is a reference for the ignition timing is performed. The base ignition timing is determined to be a timing advanced to a limit near where no knocking occurs in the cylinder 1 in each operation region. In the operation region where knocking is unlikely to occur, the base ignition timing coincides with the MBT point. In an operation region where knocking is likely to occur, the base ignition timing is delayed from the MBT point.

  In the memory of the ECU 0, map data that defines the relationship between the operation region of the internal combustion engine and the base ignition timing is stored in advance. This map data may be determined through a conformance test or the like, or may be learned online during operation of the internal combustion engine. The ECU searches the map using the current operation region of the internal combustion engine as a key, and obtains the base ignition timing corresponding to the operation region.

  And the correction | amendment according to the present combustion chamber temperature, intake air temperature, etc. is added to the base ignition timing. Specifically, the base ignition timing is retarded as the temperature of the cooling water of the internal combustion engine or the temperature of the intake air flowing through the intake passage 3 is higher. This is because knocking is likely to occur in the cylinder 1 as the cooling water temperature and the intake air temperature are higher. However, it is not essential to correct the base ignition timing.

  In the ignition control, the target ignition timing is not always matched with the base ignition timing. When the operating range of the internal combustion engine changes greatly, the base ignition timing also fluctuates greatly. In response, if the target ignition timing is changed immediately to the base ignition timing, the torque at which the engine torque suddenly changes. There is a concern that a shock will occur, causing the engine speed to fluctuate significantly.

  Therefore, as shown in FIG. 5, when the base ignition timing fluctuates, the ECU 0 gradually changes the target ignition timing so as to follow the base ignition timing. In FIG. 5, a thin solid line represents the base ignition timing, and a thick broken line represents the target ignition timing. The target ignition timing is, for example, a moving average value of base ignition timing (in time series) at each of a plurality of past calculation opportunities. Since the transition of the target ignition timing is obtained by smoothing the transition of the base ignition timing, it is delayed with respect to the transition of the base ignition timing.

  The ECU 0 senses the occurrence of knocking for each cylinder 1 with reference to the ion current signal h, and individually corrects the ignition timing for each cylinder 1 based on the presence or absence of knocking. That is, for each cylinder 1, the retardation correction amount for the cylinder 1 is increased (by a predetermined increment every time the expansion stroke of the cylinder 1 comes) until knocking does not occur. The retard correction amount is decreased (by a predetermined decrement each time the expansion stroke of the cylinder 1 is visited).

In addition, the ECU 0 of the present embodiment temporarily corrects the ignition timing in a situation where there is a high risk of causing knocking in the cylinder 1 of the internal combustion engine. Examples of situations where the risk of causing knocking is high are listed below.
The target ignition timing is advanced with respect to the base ignition timing, and the difference ΔT between the two is large; Therefore, if the target ignition timing is advanced from the base ignition timing, the risk of causing knocking increases. The target ignition timing is advanced from the base ignition timing, that is, the base ignition timing fluctuates in the retarding direction when the load on the internal combustion engine increases or the engine speed decreases.
The amount of change (increase) per unit time of the load of the internal combustion engine is large; increasing the load of the internal combustion engine means increasing the temperature and pressure in the cylinder 1 and facilitating the occurrence of knocking.
-The amount of change (decrease amount) per unit time of the engine speed is large; lowering the internal combustion engine means delaying expansion of the combustion chamber volume in the expansion stroke of the cylinder 1, and it is also easy to cause knocking. To do.
-Knocking actually occurs in one of the cylinders 1; when knocking occurs in a certain cylinder 1, there is a high probability that knocking will occur in other cylinders 1 as well.

To sum up the above conditions:
(I) The target ignition timing is advanced with respect to the base ignition timing, and the difference ΔT between the two is greater than or equal to the threshold value. (II) The load change (increase) of the internal combustion engine is equal to or greater than the threshold value. (III) Engine rotation The number change amount (decrease amount) is equal to or greater than the threshold value (IV). The ECU 0 of the present embodiment assumes that at least (I) is satisfied, and in addition to this, if any of (II), (III), or (IV) is satisfied, the risk of knocking is high. Add temporary retard correction to ignition timing. This retardation correction is performed for the ignition timings of all the cylinders 1. The temporary retardation correction amount is larger as the difference ΔT between the target ignition timing and the base ignition timing is larger, as the amount of change (increase) in the load of the internal combustion engine is larger, and / or the amount of change in engine speed (decrease). The larger the amount, the more preferably it is increased.

Generally speaking, in ignition control,
(Actual ignition timing of each cylinder 1) = (target ignition timing) + (individual retardation correction for each cylinder 1 based on the determination result of knocking) + (temporary delay performed simultaneously for all cylinders 1) Corner correction)
It becomes.

  In the present embodiment, the target ignition timing that is the reference of the actual ignition timing is made to follow the base ignition timing set according to the operating region of the internal combustion engine, and the target ignition timing is advanced from the base ignition timing. The control device 0 of the spark ignition type internal combustion engine is configured to add a temporary delay correction to the actual ignition timing, on the condition that the angle is angular and the difference ΔT between the two is greater than a threshold value.

  According to the present embodiment, the ignition timing can be retarded only in a situation where there is a risk of knocking occurring in the cylinder 1, so that knocking can be prevented more reliably and unnecessary. The ignition timing does not need to be retarded, the engine torque does not decrease significantly, and fuel efficiency is improved.

  Further, when the amount of change in the load of the internal combustion engine is greater than or equal to the threshold value, or when the amount of change in the engine speed is greater than or equal to the threshold value, the temporary retardation correction is added, so that the ignition timing is retarded. It is possible to narrow down the opportunity to knock to a situation where the risk of knocking is high, which contributes to further improvement in fuel efficiency.

  The present invention is not limited to the embodiment described in detail above. In particular, for the above conditions (I), (II), and (III), the threshold value to be compared with the deviation ΔT between the target ignition timing and the base ignition timing, the amount of change in the load of the internal combustion engine, and the amount of change in the engine speed is The internal combustion engine temperature (cooling water temperature) at that time, the engine speed, and the like may be raised or lowered.

  Specifically, the higher the cooling water temperature of the internal combustion engine, the lower the threshold value, and the easier it is to generate the ignition timing retardation correction.

  And / or, the lower the engine speed, the lower the threshold value. In the low speed range, there is a large time difference between the time when the ignition timing is determined and the time when spark ignition is actually executed in the target cylinder 1. Therefore, there is a high possibility that the previously determined ignition timing does not match the situation in the combustion chamber of the cylinder 1 at the time of execution of spark ignition. Therefore, the threshold value is lowered to facilitate the ignition timing retardation correction, and knocking is reliably suppressed.

  The method for determining the presence or absence of knocking in each cylinder 1 is not limited to the method referring to the ion current signal h. For example, in an internal combustion engine in which a pressure sensor that detects the in-cylinder pressure for each cylinder 1 is mounted, the transition of the in-cylinder pressure measured through the in-cylinder pressure sensor (in particular, the expansion) The knock determination can be executed with reference to the maximum value of the in-cylinder pressure in the stroke and the time when the maximum value appears.

  Alternatively, in an internal combustion engine in which an in-cylinder temperature sensor that detects the in-cylinder temperature (combustion temperature) of the cylinder 1 is mounted, the in-cylinder temperature measured via the in-cylinder temperature sensor instead of the ion current signal h The knock determination can be performed with reference to the temperature transition (particularly, the maximum value of the in-cylinder temperature in the expansion stroke and the time when the maximum value appears).

  The internal combustion engine is mounted on a cylinder block having a plurality of cylinders 1 and mounted with a vibration type knock sensor that detects a cylinder block signal generated due to combustion or knocking during the expansion stroke of each cylinder 1. Thus, the knock determination can be executed with reference to the vibration signal output from the knock sensor.

  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 applied to control of a spark ignition type internal combustion engine mounted on a vehicle or the like.

0 ... Control unit (ECU)
1 ... Cylinder 12 ... Ignition plug h ... Ion current signal

Claims (2)

The base ignition timing set in accordance with the operating region of the internal combustion engine is made to follow the target ignition timing that is a reference for the actual ignition timing,
A control device for a spark ignition type internal combustion engine that adds a temporary retardation correction to the actual ignition timing on the condition that the target ignition timing is advanced with respect to the base ignition timing and the difference between the two is greater than a threshold value . The control device for a spark ignition type internal combustion engine according to claim 1, wherein the temporary retard correction is applied when a change amount of the load of the internal combustion engine is equal to or greater than a threshold value or when a change amount of the engine speed is equal to or greater than the threshold value.

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