JP2010248983A - Ignition timing control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ignition timing control device for an internal combustion engine, exactly correcting the ignition timing according to an operation state of a valve characteristic variable mechanism, even in the internal combustion engine in which a negative-valve-overlap-quantity becomes large according to an operation state of the valve characteristic variable mechanism. <P>SOLUTION: This internal combustion engine includes the valve characteristic variable mechanism 6 varying valve-overlap-quantity of an intake and an exhaust valve through a change in the valve timing of the intake valve. In the internal combustion engine, an electronic control unit 1 corrects the ignition timing according to the operation state of the valve-characteristic-variable-mechanism 6 only when valve overlap quantity is larger than an offset quantity set as negative value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an ignition timing control device that is applied to an internal combustion engine that includes a valve characteristic variable mechanism that changes a valve overlap amount of an intake / exhaust valve by changing a valve characteristic including at least a change in a closing timing of an intake valve. About.

  In recent years, the valve characteristics of intake and exhaust valves have been adjusted according to engine operating conditions for the purpose of improving intake efficiency, improving exhaust emissions by reducing NOx, and improving fuel efficiency by reducing pumping loss in response to the introduction of internal EGR. An internal combustion engine having a variable valve characteristic variable structure that is variable has been put into practical use. For example, in an in-vehicle internal combustion engine, a variable valve timing mechanism that makes the intake / exhaust valve open / close timing, that is, a valve timing variable, a variable valve lift mechanism that makes the valve lift amount of the intake / exhaust valve variable, and the like are widely used as variable valve characteristic mechanisms. It has been adopted. In an internal combustion engine equipped with such a variable valve characteristic mechanism, the valve overlap amount of the intake / exhaust valve is changed according to the operation of the variable valve characteristic mechanism.

  Incidentally, the valve overlap amount [° CA] is obtained as a value obtained by subtracting the valve opening timing [° CA] of the intake valve from the valve closing timing [° CA] of the exhaust valve. Therefore, when the valve closing timing of the exhaust valve is later than the valve opening timing of the intake valve and the valve opening periods of both valves overlap, the valve overlap amount takes a positive value. On the other hand, when the exhaust valve closing timing is earlier than the intake valve opening timing and the valve opening periods of both valves do not overlap, the valve overlap amount takes a negative value.

  In an internal combustion engine equipped with the valve characteristic variable mechanism as described above, the internal EGR amount existing in the cylinder increases or decreases in accordance with the change in the valve overlap amount of the intake and exhaust valves due to the operation of the valve characteristic variable mechanism. The change in the internal EGR amount has a non-negligible effect on the occurrence of knocking in the internal combustion engine. On the other hand, the ignition timing of the internal combustion engine is set in consideration of the occurrence of knocking. Therefore, in such an internal combustion engine, it is necessary to set the ignition timing in consideration of a change in the internal EGR amount according to the operation of the variable valve characteristic mechanism.

  Conventionally, an apparatus described in Patent Document 1 is known as an ignition timing control device for an internal combustion engine that sets an ignition timing in consideration of a change in an internal EGR amount in accordance with an operation of a variable valve characteristic mechanism. In the ignition timing control device for an internal combustion engine described in the same document 1, the square of the actual valve overlap amount with respect to the square value of the target valve overlap amount is added to the base ignition correction amount calculated according to the engine speed and the engine load. A value obtained by multiplying the ratio of the values is obtained as a correction amount of the ignition timing with respect to a change in the internal EGR amount according to the operation of the valve characteristic variable mechanism.

  The change in the internal EGR amount according to the operation of the variable valve characteristic mechanism occurs only when the valve overlap amount is a positive value. Therefore, the correction of the ignition timing with respect to the change in the internal EGR amount according to the operation of the valve characteristic variable mechanism as described above is performed only when the valve overlap amount is a positive value.

JP 2004-251183 A

  By the way, in an internal combustion engine having a variable valve characteristic mechanism for changing the closing timing of the intake valve, in addition to the change in the internal EGR amount accompanying the change in the valve overlap amount, the internal combustion engine accompanying the advancement of the intake valve closing timing An increase in the compression ratio also affects the occurrence of knocking. That is, if the closing timing of the intake valve is advanced, the compression stroke of the internal combustion engine starts earlier, and the compression ratio of the air-fuel mixture increases correspondingly, and knocking is likely to occur.

  However, in the above conventional ignition timing control device, only the change in the internal EGR amount due to the operation of the variable valve characteristic mechanism is considered, and the operation state of the variable valve characteristic mechanism is only in the positive region of the valve overlap amount. The ignition timing is corrected accordingly. Therefore, particularly in an internal combustion engine in which the negative valve overlap amount becomes large depending on the operating state of the valve characteristic variable mechanism, the optimal ignition timing may not always be set.

  The present invention has been made in view of such a situation, and the problem to be solved is that even in an internal combustion engine in which the amount of negative valve overlap becomes large depending on the operating state of the valve characteristic variable mechanism, An object of the present invention is to provide an ignition timing control device for an internal combustion engine that can accurately correct the ignition timing in accordance with the operating condition.

Hereinafter, means for solving the above-described problems and the effects thereof will be described.
In order to solve the above-mentioned problem, the invention according to claim 1 as an ignition timing control device for an internal combustion engine performs a valve characteristic change including at least a change in the closing timing of the intake valve, thereby providing a valve overlap of the intake and exhaust valves. An ignition timing control device applied to an internal combustion engine having a variable valve characteristic variable mechanism that makes the amount variable. The variable valve characteristic is variable only when the valve overlap amount is larger than the offset amount OFSET set as a negative value. The gist of the invention is to provide an ignition timing correction means for correcting the ignition timing in accordance with the operating state of the mechanism.

  In the above configuration, when the valve overlap amount is larger than the offset amount OFSET set as a negative value, the ignition timing is corrected according to the operating state of the valve characteristic variable mechanism. In such an ignition timing control device for an internal combustion engine, since the valve overlap amount is a negative value, the ignition timing is corrected according to the operating state of the valve characteristic variable mechanism. Therefore, it is possible to set the ignition timing in consideration of the influence of the increase in the compression ratio of the internal combustion engine accompanying the advancement of the intake valve closing timing when the valve overlap amount is negative on the occurrence of knocking. Therefore, according to the above configuration, even in an internal combustion engine in which the negative valve overlap amount increases depending on the operation state of the valve characteristic variable mechanism, the ignition timing can be accurately corrected according to the operation state of the valve characteristic variable mechanism. It becomes like this.

  The ignition timing correction by the ignition timing correction means is performed according to the overlap rate ekavvtb, which is the ratio of the actual valve overlap amount ovrpreal and the target valve overlap amount ovrptbi, as described in claim 2. Can do.

  Then, the overlap rate ekavvtb at this time may be calculated based on an equation “ekavvtb = (ovrpreal−OFSET) / (ovrptbi−OFSET)” as described in claim 3.

  Further, the ignition timing correction amount by the ignition timing correction means at this time is a multiplication value of the base ignition correction amount avvtb calculated based on the target valve overlap amount ovrptbi and the overlap ratio ekavvtb, as in claim 4. Can be set.

  Further, the offset amount OFSET is the valve overlap amount when the increase in the compression ratio of the internal combustion engine accompanying the advancement of the closing timing of the intake valve starts to affect the occurrence of knocking as described in claim 5. Can be set to that value.

The block diagram which shows typically the whole structure about one Embodiment of the ignition timing control apparatus of the internal combustion engine which concerns on this invention. The graph which shows an example of the setting aspect of the calculation map of the target overlap amount employ | adopted as the embodiment. The graph which shows an example of the setting aspect of the calculation map of the base ignition correction amount employ | adopted as the same embodiment. The graph which shows together the setting aspect of the overlap ratio in the same embodiment, and the setting aspect of the setting aspect of the overlap ratio in the conventional ignition timing control device.

  DESCRIPTION OF EMBODIMENTS Hereinafter, an embodiment of an ignition timing control device for an internal combustion engine according to the present invention will be described in detail with reference to FIGS. In the present embodiment, a case will be described in which the present invention is applied to an in-vehicle internal combustion engine provided with a variable valve characteristic mechanism that makes the valve timing of an intake valve variable.

  FIG. 1 shows the overall structure of an ignition timing control device for an internal combustion engine according to this embodiment. As shown in the figure, the ignition timing control device of the present embodiment is configured with an electronic control unit 1 as the center. The electronic control unit 1 that controls the overall control of the internal combustion engine includes a central processing unit (CPU) that performs various arithmetic processes related to engine control, a read-only memory (ROM) that stores programs and data for engine control, A random access memory (RAM) for temporarily storing calculation results, sensor detection results, and the like, and an input / output port (I / O) for exchanging signals with the outside are provided.

  The input port of the electronic control unit 1 detects a crank angle sensor 2 that detects the rotational phase of the crankshaft that is the engine output shaft, a cam angle sensor 3 that detects the rotational phase of the intake camshaft, and an accelerator operation amount. Sensors including the accelerator sensor 4 are connected. Connected to the output port of the electronic control unit 1 are a spark plug 5 for spark ignition of the air-fuel mixture in the combustion chamber of the internal combustion engine and a drive circuit for a valve characteristic variable mechanism 6 for varying the valve timing of the intake valve.

  Incidentally, the electronic control unit 1 calculates and calculates the engine rotation speed from the detection signal of the crank angle sensor 2. Further, the electronic control unit 1 calculates the rotational phase difference of the intake camshaft with respect to the crankshaft from the detection results of the crank angle sensor 2 and the cam angle sensor 3 and thus calculates the operating position of the valve characteristic variable mechanism 6.

  In the present embodiment configured as described above, the electronic control unit 1 performs the valve timing control of the intake valve by the operation of the valve characteristic variable mechanism 6 as part of the engine control. At this time, the electronic control unit 1 is set so that the target valve overlap amount ovrptbi and the actual valve overlap amount ovrpreal calculated from the map of the engine speed NE and the engine load KL as shown in FIG. The operating position of the variable valve characteristic mechanism 6 is controlled.

  The electronic control unit 1 also performs ignition timing control as part of engine control. The electronic control unit 1 at this time controls the ignition timing at a timing close to an MBT (Minimum Advance for Best Torque) point within a range in which the occurrence of knocking can be suppressed. The electronic control unit 1 corrects the ignition timing in accordance with the operating state of the valve characteristic variable mechanism 6 in such ignition timing control.

  When correcting the ignition timing, the electronic control unit 1 refers to a map based on the engine rotational speed NE and the engine load KL as shown in FIG. The base ignition correction amount avvtb, which is the base value of the correction amount, is calculated. In this base ignition correction amount avvtb, the ignition timing correction amount required when the valve overlap amount is the target valve overlap amount ovrptbi at the current engine speed NE and engine load KL is set to that value. .

  Subsequently, the electronic control unit 1 calculates an overlap rate ekavvtb. The overlap rate ekavvtb indicates the correction rate of the base ignition correction amount avvtb in accordance with the deviation between the target valve overlap amount ovrptbi and the actual valve overlap amount ovrppreal. The overlap rate ekavvtb is calculated for each case as follows according to the target valve overlap amount ovrptbi at that time.

(A) When the target valve overlap amount ovrptbi is smaller than the offset amount OFSET (ovrptbi <OFSET)
At this time, the electronic control unit 1 sets “0” to the value of the overlap rate ekavvtb. The offset amount OFSET is set to a negative value, and the valve overlap amount when the increase in the compression ratio of the internal combustion engine accompanying the advance of the closing timing of the intake valve starts to affect the occurrence of knocking is set as the offset amount OFSET. It is set to that value.

(B) When the target valve overlap amount ovrptbi is greater than or equal to the offset amount OFSET (ovrptbi ≧ OFSET)
At this time, the electronic control unit 1 sets the overlap rate ekavvtb based on the following equation (1). The overlap rate ekavvtb at this time indicates the ratio of the subtraction value of the offset amount OFSET from the actual valve overlap amount ovrpreal to the subtraction value of the offset amount OFSET from the target valve overlap amount ovrptbi.

ekavvtb = (ovrpreal-OFSET) / (ovrptbi-OFSET)
... (1)

After setting the overlap rate ekavvtb in this way, the electronic control unit 1 determines the final ignition correction amount as a multiplication value of the base ignition correction amount avvtb and the overlap rate ekavvtb as shown in the following equation (2). avvt is calculated. Thereafter, the electronic control unit 1 corrects the ignition timing by the ignition correction amount avvt thus calculated.

avvt = ekavvt × avvtb (2)

  FIG. 4 shows the relationship between the actual valve overlap amount ovrpreal and the overlap rate ekavvtb when the engine speed and the engine load are constant, that is, when the target valve overlap amount ovrpbi is constant. In the same figure, as the influence of the operating state of the variable valve characteristic mechanism 6 on the occurrence of knocking, the same relationship of the conventional ignition timing control device considering only the change in the internal EGR amount is also shown by a dotted line. Yes. As can be seen from the figure, in the case of the present embodiment, the overlap rate ekavvtb rises from when the valve overlap amount is negative, and the ignition timing is corrected according to the operating state of the valve characteristic variable mechanism 6. It has come to be. On the other hand, in the case of the conventional control device, the overlap rate ekavvtb has risen after the valve overlap amount becomes positive, and the operation state of the valve characteristic variable mechanism 6 is only when the valve overlap amount is positive. The ignition timing is not corrected according to the above.

In this embodiment, the electronic control unit 1 is configured to perform the processing as the ignition timing correcting means.
According to the ignition timing control device for an internal combustion engine of the present embodiment described above, the following effects can be obtained.

  In this embodiment, when the valve overlap amount is larger than the offset amount OFSET set as a negative value, the ignition timing is corrected in accordance with the operating state of the valve characteristic variable mechanism 6. In this embodiment, since the valve overlap amount is a negative value, the ignition timing is corrected in accordance with the operation status of the valve characteristic variable mechanism 6. Therefore, it is possible to set the ignition timing in consideration of the influence of the increase in the compression ratio of the internal combustion engine accompanying the advance of the intake valve closing timing when the valve overlap amount is negative on the occurrence of knocking. Therefore, according to the present embodiment, even in an internal combustion engine in which the negative valve overlap amount becomes large depending on the operating condition of the valve characteristic variable mechanism 6, the ignition timing is accurately corrected according to the operating condition of the valve characteristic variable mechanism. Will be able to.

In addition, the said embodiment can also be changed and implemented as follows.
In the above embodiment, the overlap rate ekavvtb is calculated by the above equation (1). However, when the absolute value of the offset amount OFSET is sufficiently small, the actual valve overlap amount ovrpreal and the target valve overlap amount ovrpbi May be set to the overlap rate ekavvtb as it is.

  In the above embodiment, the ignition correction amount avvt is set as a multiplication value of the base ignition correction amount avvtb calculated based on the target valve overlap amount ovrptbi and the overlap rate ekavvtb. The calculation logic is not limited to this and may be changed as appropriate. In any case, if the ignition correction amount avvt is set as the correction amount of the ignition timing with respect to the change in the internal EGR amount or the compression ratio according to the operating state of the variable valve characteristic mechanism, the ignition timing based on the ignition correction amount avvt is set. By performing this correction only when the valve overlap amount is larger than the offset amount OFSET set as a negative value, the same effect as in the above embodiment can be obtained.

  In the above-described embodiment, the case where the present invention is applied to an internal combustion engine including the variable valve characteristic mechanism 6 of the type that makes the valve timing of the intake valve variable has been described as an example. The present invention is also applicable to an internal combustion engine provided. For example, the present invention is also applied to an internal combustion engine equipped with a variable valve characteristic mechanism that changes the valve timing of the exhaust valve in addition to the intake valve, and a variable valve characteristic mechanism that changes the valve operating angle and valve lift amount of the intake valve. Can do. In any case, the present invention relates to the present invention as long as it is an internal combustion engine having a variable valve characteristic mechanism that changes the valve characteristic including at least the closing timing of the intake valve to vary the valve overlap amount of the intake and exhaust valves. The ignition timing control device can be applied in a manner according to the above embodiment.

  DESCRIPTION OF SYMBOLS 1 ... Electronic control unit, 2 ... Crank angle sensor, 3 ... Cam angle sensor, 4 ... Accelerator sensor, 5 ... Spark plug, 6 ... Valve characteristic variable mechanism.

Claims (5)

An ignition timing control device applied to an internal combustion engine including a valve characteristic variable mechanism that changes a valve characteristic including at least a change in valve timing of an intake valve to vary a valve overlap amount of the intake and exhaust valves,
An internal combustion engine comprising ignition timing correction means for correcting the ignition timing in accordance with the operating state of the valve characteristic variable mechanism only when the valve overlap amount is larger than the offset amount OFSET set as a negative value. Engine ignition timing control device. 2. The ignition of the internal combustion engine according to claim 1, wherein the ignition timing correction unit corrects the ignition timing in accordance with an overlap rate ekavvtb that is a ratio of an actual valve overlap amount ovrpreal and a target valve overlap amount ovrptbi. Timing control device. The ignition timing control device for an internal combustion engine according to claim 2, wherein the overlap rate ekavvtb is calculated based on an expression "ekavvtb = (ovrpreal-OFSET) / (ovrptbi-OFSET)". The correction amount of the ignition timing by the ignition timing correction means is set as a multiplication value of the base ignition correction amount avvtb calculated based on the target valve overlap amount ovrptbi and the overlap rate ekavvtb. An ignition timing control device for an internal combustion engine. The offset amount OFSET is set to a value of a valve overlap amount when an increase in the compression ratio of the internal combustion engine accompanying an early closing timing of the intake valve starts to affect the occurrence of knocking. The ignition timing control device for an internal combustion engine according to any one of claims 1 to 4.

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