JP3757738B2 - Ignition timing control device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ignition timing control device for an internal combustion engine, and more particularly, to an internal combustion engine that optimizes an ignition timing in consideration of a temporal change in the amount of EGR gas supplied to a combustion chamber in an internal combustion engine equipped with an exhaust gas recirculation device. The present invention relates to an ignition timing control device.
[0002]
[Prior art]
An exhaust gas recirculation device is known in which a predetermined amount of exhaust gas is recirculated during intake to burn an air-fuel mixture having a predetermined EGR rate. When this device is used, combustion of the air-fuel mixture in the combustion chamber is relatively Slower, NOx and oxide emissions are reduced, and exhaust gas can be improved. In addition, the intake amount is usually reduced by a predetermined amount in order for the engine to generate a predetermined torque.At this time, the downstream side of the throttle valve becomes negative pressure and causes a pumping loss, whereas when an exhaust gas recirculation device is used, By supplying nonflammable exhaust gas that does not contribute to output generation into fresh air, pumping loss can be reduced and fuel efficiency can be improved. When the exhaust gas recirculation device having such an advantage is used, a process of advancing the ignition timing in accordance with the change in the EGR rate (= EGR gas / fresh air) to cope with the relatively slow combustion of the air-fuel mixture. Is going.
[0003]
However, when the EGR rate is changed by adjusting the opening and closing of the EGR valve, the EGR rate in the combustion chamber does not immediately change to the EGR rate corresponding to the opening degree of the EGR valve due to the pressure accumulation effect of the intake system. The rate lag situation changes according to the intake passage structure downstream from the EGR valve, and then converges to an EGR rate corresponding to the EGR valve opening. For this reason, when the EGR rate corresponding to the EGR valve opening is regarded as the EGR rate of each cylinder as it is, and the ignition timing corresponding to the EGR rate is calculated and the ignition process is performed, the ignition timing does not match the actual situation. There is a possibility of misfire. Therefore, correction of the ignition timing with time after changing the EGR valve opening degree becomes a problem.
[0004]
For example, in the technique disclosed in Japanese Patent Laid-Open No. 9-242654, the opening / closing speed of the EGR valve is taken into account when correcting the basic ignition timing set according to the operating state in accordance with the target EGR rate. That is, the actual EGR rate is calculated from the target EGR rate using the ratio of the actual opening to the target opening, and the advance angle width per 1% of the EGR rate corresponding to the basic fuel injection amount and the engine speed is obtained. Is multiplied by the actual EGR rate to obtain the advance correction amount, and the final ignition timing is calculated from this and the basic ignition timing.
[0005]
Further, according to the technology disclosed in Japanese Patent Registration No. 2914192, when the EGR valve changes from the absence of EGR to a predetermined EGR rate in response to a change in the engine operating state, the ignition timing (basic ignition timing) in the absence of the EGR valve The time between the ignition timing and the ignition timing when there is smoothed by using a first-order lag filter, that is, the time constant of the delay response of EGR gas is calculated based on the rotational speed, charging efficiency, intake pipe volume, EGR valve opening, The ignition timing is moved by a moving average formula that reflects this time constant, so that the ignition timing can be accurately controlled even when the engine operating state changes and the EGR rate changes.
[0006]
[Problems to be solved by the invention]
However, the intake air (air mixture) mixed with the EGR gas flowing into the surge tank after passing through the EGR valve flows into the combustion chambers through the intake branches connected to the cylinders. In this case, even if the EGR valve changes, that is, even if the EGR rate changes, the mixture of the intake branch that holds the previous EGR rate flows into the combustion chamber of each cylinder. It is necessary to consider that there is a delay in reaching the target EGR rate corresponding to the EGR valve opening degree. In addition, after the flow delay, the correct change in the EGR rate cannot be considered unless the point where the mixture of the EGR rate regulated by the finite valve opening speed of the EGR valve sequentially flows in is taken into consideration. .
[0007]
In consideration of this point, for example, when a technique such as that of JP-A-9-242654 is used, the EGR rate in the intake pipe may be obtained by estimating or detecting the actual opening of the EGR valve. Although it is conceivable, especially in an internal combustion engine having a surge tank, there is an EGR mixture remaining in the surge tank, and this acts so as to make a transient value. There is a problem that it differs from the actual EGR rate in the surge tank according to the above, and there is a problem that the EGR rate according to the actual opening of the EGR valve cannot be simply applied.
[0008]
Furthermore, in the case of the technique of Japanese Patent Registration No. 2914192, only the time constant is set in inverse proportion to the EGR valve opening, that is, only the technical idea of optimizing the delay response, so that the EGR rate at the time of transition can be increased. Is not considered, and there is room for improvement in optimizing the ignition timing in the transient state. As described above, in each of the conventional examples, the EGR rate is corrected using a time constant or an approximate expression, but the flow delay of the intake air in the intake branch is not accurately taken into consideration, and an improvement is desired. .
The present invention provides an ignition timing control device for an internal combustion engine that corrects the basic ignition timing using the EGR rate of the intake air flowing into the cylinder and can perform appropriate ignition timing control even when exhaust gas recirculates based on the above-described problems. The purpose is to do.
[0009]
[Means for Solving the Problems]
In order to achieve the above-described object, according to the first aspect of the present invention, there is provided an EGR passage that recirculates a part of exhaust gas to an intake passage enlarged diameter portion provided in an intake system of an internal combustion engine or an upstream intake system thereof, and the EGR An EGR valve that is interposed in the passage and whose operation is controlled in accordance with the engine operating state; an instantaneous EGR rate deriving unit that derives an instantaneous EGR rate based on the latest opening degree of the EGR valve and the engine operating state; An enlarged-diameter EGR rate deriving unit that updates the EGR rate in the enlarged-diameter portion based on the EGR rate and a pre-calculated EGR rate in the enlarged-diameter portion of the intake passage enlarged portion, and a basic ignition timing based on the engine operating state The basic ignition timing setting means for setting the EGR rate, and the EGR rate in the enlarged diameter portion that is sequentially updated is stored. In addition, as the EGR rate of the intake air flowing into the cylinder, the EGR rate in the enlarged diameter portion before the number of strokes of the internal combustion engine adapted to the intake passage capacity between the enlarged diameter portion and the combustion chamber is used. Ignition timing correction means for correcting the basic ignition timing.
Since the EGR rate in the enlarged-diameter portion is sequentially updated based on the instantaneous EGR rate and the EGR rate in the enlarged-diameter portion calculated in advance, the air-fuel mixture containing the EGR gas staying in the intake passage enlarged portion and the newly introduced EGR gas The EGR rate in the enlarged diameter portion after the mixture is accurately obtained, and the EGR rate in the enlarged diameter portion that is sequentially updated is stored. In addition, as the EGR rate of the intake air flowing into the cylinder, the EGR rate in the enlarged-diameter portion that is the number of strokes before the internal combustion engine adapted to the intake passage capacity between the enlarged-diameter portion and the combustion chamber is used. Thus, the EGR rate of the intake air flowing into the cylinder can be accurately obtained.
[0010]
For this reason, by correcting the basic ignition timing based on the EGR rate, it is possible to appropriately set the ignition timing at the time of transition in which the EGR rate changes.
As a preferred embodiment of the present invention, the intake passage enlarged diameter portion may be a surge tank. In this case, in particular, the mixture containing the EGR gas staying in the surge tank and the newly introduced EGR gas are mixed, and the EGR rate when the mixture flows into the cylinder after passing through the intake branch is accurately obtained. It is possible to correct the advance angle according to the EGR rate, and to appropriately set the ignition timing at the time of transition in which the EGR rate changes.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an engine 1 equipped with an internal combustion engine ignition timing control device as one embodiment of the present invention. The engine 1 is a four-cylinder (see FIG. 2) in-cylinder injection engine and is equipped with an exhaust gas recirculation device 23 described later. A combustion chamber 3 is formed in a portion surrounded by the upper part of each cylinder 2 of the engine 1 and the cylinder head 20. One end of the crankshaft 4 of the engine 1 is provided with a unit crank angle signal θc, a reference signal θ, and a crank angle sensor 5 for detecting engine rotational speed Ne information based on the unit crank angle signal θc. The detection signal is output to 6) (denoted as ECU).
[0012]
An intake port 9 that is releasably closed to the intake valve V1 and an exhaust port 10 that is releasably closed to the exhaust valve V2 are formed on the upper inner wall surface of each cylinder 2. In addition, a spark plug 7 is provided at a substantially central position within a position where the valves do not interfere with both valves, and an injector 8 for fuel injection is provided at a side end position. The injector 8 is connected to an ECU 6 to be described later via an injector drive circuit 34, and is configured to inject fuel according to an injection signal of the ECU 6.
[0013]
An intake port 9 connected to the combustion chamber 3 is connected to an intake manifold (including an intake branch) 11, an intake branch of each cylinder, and a surge tank 12 that forms an intake passage diameter increasing portion, and an extension following the surge tank 12. The tube 13 and the air cleaner 14 are connected in this order. In the air cleaner 14, an air flow sensor 15 for obtaining intake air amount Qa information, an intake air temperature sensor 16 for outputting intake air temperature Ta information, and an atmospheric pressure sensor 17 for outputting atmospheric pressure Pa information are mounted. Is output. Further, a throttle valve 18 is provided in the extension pipe 13, and throttle opening θs information of the valve is output to the ECU 6 by a throttle opening sensor 19. Further, a water temperature sensor 21 for detecting the water temperature Tw information of the engine 1 is provided, and the detection signal is output to the ECU 6.
An exhaust manifold 22 and an exhaust pipe and a muffler (not shown) are connected to the exhaust port 10.
[0014]
An exhaust gas recirculation device 23 is disposed between the intake passage r1 and the exhaust passage r2 of the engine 1. The exhaust gas recirculation device 23 includes an exhaust gas recirculation path (hereinafter simply referred to as an EGR path) 24 that connects the exhaust manifold 22 on the exhaust path r2 side and the surge tank 12 on the intake path r1 side. A valve 25 is provided.
The EGR valve 25 includes a valve housing 26 partially integrated with the surge tank 12. A valve seat 28 that secures an EGR passage 24 is provided in the EGR valve 25. The valve seat 28 can be opened and closed by a valve member 29. Yes. The valve member 29 is connected to a stepper motor 30 supported on the upper portion of the valve housing 26 via a valve shaft 31. The stepper motor 30 is connected to an ECU 6 described later via a motor drive circuit 32, and the ECU 6 that outputs a control signal (number of steps) to the motor drive circuit 32 responds to the control signal (number of steps) to the current valve member 29. The opening degree (EGR actual opening degree) is determined.
[0015]
The spark plug 7 is connected to the ignition unit 33, and the ignition unit 33 is connected to the ECU 6. The ECU 6 controls the ignition operation of the spark plug 7.
The ECU 6 performs ignition control processing and EGR control processing in addition to known control processing such as fuel injection amount control of the engine 1 and throttle valve drive control.
In the EGR control process, the ECU 6 sets the EGR rate in the entire operation region using a preset EGR region map me (see FIG. 5). Here, the inflow amount of EGR gas with respect to the new air amount flowing into the surge tank, which is the intake passage enlarged diameter portion, is set as the EGR rate (= EGR gas amount / new air amount).
[0016]
This EGR range map me is set so as to ensure a high EGR rate q1 for supplying a large amount of EGR gas when the engine operating range is during operation on the medium speed / medium load range A1 side. That is, in this region, the high EGR rate (high step number) for moving the valve member 29 upward in the valve lift direction is set so as to increase toward the region center D1.
Further, when the engine operating range shifts to the high speed and high load range A2, the ECU 6 is set to reduce the flow of EGR gas. That is, in this region, the low EGR rate (low step number) for moving the valve member 29 downward in the closing direction is set, and the EGR rate is set to zero on the region outer peripheral side D2.
[0017]
Next, as shown in FIG. 4, the ECU 6 in the ignition control process includes an instantaneous EGR rate deriving unit E1, an in-diameter EGR rate deriving unit E2, a basic ignition timing setting unit E3, and an ignition timing correcting unit E4. Operates to perform its function.
Here, the instantaneous EGR rate deriving means E1 includes the latest opening degree (EGR actual opening degree) of the EGR valve 25, the latest engine operating state, the engine speed Ne and the fresh air amount (intake air amount Qa / Ne) EV. Based on the above, the instantaneous EGR rate (considering the opening degree during the mechanical displacement of the EGR valve, see the m line in FIG. 6) is derived as shown in the following equation (1). Here, the steady EGR opening degree he indicates the opening degree when the valve member 29 reaches a steady state when the valve member 29 secures a predetermined EGR rate.
[0018]
Instantaneous EGR rate = steady EGR rate × EGR actual opening / steady EGR opening ··················· (1) Note that FIG. 6 described above is a diagram illustrating the time-dependent change characteristic of the EGR valve opening, and t1 is EGR. The change point of the valve opening is shown, and the two-dot chain line U shows the static EGR valve opening change.
The in-diameter enlarged EGR rate deriving means E2 calculates the EGR rate in the in-diameter enlarged portion based on the instantaneous EGR rate and the EGR rate in the enlarged diameter portion of the surge tank (intake passage enlarged portion) 12 calculated in advance. And the update is repeated for each stroke of the engine. Note that symbol C is an EGR time constant, which is a capturing constant for taking a weighted average, and is set to 0, 3, for example, whereby the instantaneous EGR rate is smoothed, and the symbol n line in FIG. Will get.
[0019]
C x EGR rate in the expanded diameter part (n) + (1-C) x instantaneous EGR rate (2)
The basic ignition timing setting means E3 sets the basic ignition timing θb based on the engine rotational speed Ne and the fresh air amount (intake air amount Qa / Ne) EV in the engine operating state. Here, a basic ignition timing θb corresponding to the engine rotational speed Ne and the fresh air amount (intake air amount Qa / Ne) EV is set in advance in the basic ignition timing map m6.
[0020]
The ignition timing correction means E4 stores the diameter-increasing portion EGR rate that is sequentially updated, and uses the corresponding stored value at the timing at which the intake of the stored inside-expansion-portion EGR rate flows into the cylinder. In this case, the EGR rate (n) in the enlarged diameter portion of the surge tank (intake passage enlarged diameter portion) 12 is sequentially stored for each stroke of the engine. That is, in the next second stroke, the value of the EGR rate (n) in the enlarged diameter portion in the first stroke is pushed out into the storage area of the EGR rate (n-1) in the enlarged diameter portion, and similarly, it is equivalent to eight strokes (expanded diameter). The storage area values of the internal EGR rate (up to n-7) are sequentially stored, and each value can be updated by forward feeding. Here, the reason why the memory for eight strokes is stored is as follows.
[0021]
That is, as shown in FIGS. 3 and 4, the capacity of the intake branch (branch portion of the intake manifold) 11 between the surge tank 12 of the engine 1 and the combustion chamber 3 of each cylinder is twice the cylinder volume here. It is assumed that the air-fuel mixture in the surge tank 12 flows into the combustion chamber 3 after two intake strokes. For this reason, after fresh air and EGR gas are mixed in the surge tank 12, the intake air that is the air-fuel mixture passes through the intake branch 11 after 8 strokes and flows into the combustion chamber 3. A value for 8 strokes (up to EGR rate (n-7) in the enlarged diameter part is stored). The oldest value among the stored values for 8 strokes, that is, the EGR rate (n-7) in the enlarged diameter part is This is the accurate EGR rate of the intake air that flows into the cylinder next, and this value is expressed by the following equations (5) and (6), and is the amount EV ′ of the fresh air a1 supplied from the intake branch to the combustion chamber. Used for calculation.
[0022]
Next, a calculation formula for the amount EV ′ of fresh air a1 will be described.
Here, the inflow amount of EGR gas with respect to the fresh air is set to the EGR rate (= EGR gas amount / new air amount), so that this equation can be rewritten into the equation (3).
1 + EGR rate = (fresh air amount + EGR gas amount) / new air amount (3)
This is further converted into equation (4).
[0023]
(New air amount + EGR gas amount) = New air amount × (1 + EGR rate) (4)
The left side of this equation (new air volume + EGR gas volume) can be regarded as a value roughly proportional to the density (密度 internal pressure) of a manifold (surge tank or intake branch) with a constant volume. Air volume × (1 + EGR rate) is also regarded as a similar value.
[0024]
Here, it is assumed that the air-fuel mixture in the surge tank 12 passes through each intake branch after 8 strokes and flows into each combustion chamber 3, and the density of the air-fuel mixture flowing into the combustion chamber 3 this time (室 internal pressure) EV ′ (branch fresh air amount) × (1 + EGR rate (n−7)) and EV (surge tank fresh air), which is the density of the air-fuel mixture a1 flowing into the surge tank 12 (サ ー ジ internal pressure) this time. Suppose that (quantity) × (1 + EGR rate (n)) is equal and formula (5) is obtained.
EV ′ × (1 + EGR rate (n−7)) = EV × (1 + EGR rate (n)) (5)
This equation (5) can be converted to equation (6), and the amount EV ′ of fresh air a1 supplied from the intake branch to the combustion chamber can be calculated.
[0025]
EV ′ = EV × (1 + EGR rate (n)) / (1 + EGR rate (n−7)) (6)
Here, for example, if the current EGR rate is set to zero% and the EGR rate of the previous eight times is set to 10% and these values are substituted into the equation (6), fresh air supplied from the intake branch to the combustion chamber this time. The amount EV ′ of a1 is
EV ′ = 100 × (1 + 0) / (1 + 0, 1) ≈90%
Thus, EGR gas can be calculated as approximately 10%.
[0026]
Further, the ignition timing correction means E4 determines the timing at which the intake air from the surge tank (intake passage diameter increasing portion) 12 flows into the cylinder, and stores the stored EGR ratio in the expanded diameter portion, that is, the 8 strokes. Based on the previous value (the EGR rate (n-7) in the enlarged diameter portion), the ignition advance angle δθ during the EGR transition is obtained, and the basic ignition timing θb is corrected based on this value.
[0027]
In this case, based on the amount EV ′ of fresh air a1 supplied to the combustion chamber from the intake branch obtained by the above equation (6) and the engine speed Ne, the advance angle W / that is an advance value when EGR is not performed. Read the O value from the map m4, read the advance angle W / value, which is the advance value at the time of EGR, from the map m5, read the steady EGR rate from the map m2, respectively, and expand these values and the diameter before 8 strokes. By substituting the value of the in-portion EGR rate (the expanded-in-portion EGR rate (n-7)) into the following equation (7), the ignition advance angle δθ value during the EGR transition is calculated. As a result, an ignition advance δθ corresponding to the instantaneous EGR rate adapted to the latest amount EV ′ of fresh air a1 supplied from the intake branch 11 to the combustion chamber 12 is obtained.
[0028]
Ignition advance angle δθ = Advance angle W / O + (Advance angle W / −Advance angle W / O) × (EGR ratio in expanded diameter portion (n−7)) / (steady EGR ratio) (7)
Next, the ignition timing correction means E4 calculates the current corrected ignition timing θb ′ according to the equation (8) from the latest ignition advance angle δθ and the basic ignition timing θb obtained from the basic ignition timing map m6.
θb + δθ = θb ′ (8)
Thereafter, the ignition control means E5 executes an ignition process via the ignition unit 33 in accordance with the corrected ignition timing θb ′.
[0029]
Next, the operation of the engine ignition control device of this embodiment will be described with reference to the control block diagram of FIG. 4, the ignition control routine of FIG.
When the main switch (not shown) is turned on, the ECU 6 enters control in a main routine (not shown), and executes an injector injection process, an ignition control process, an EGR control process, and the like in the middle of the main routine.
In an injector injection amount calculation routine (not shown), the intake air amount Qa / Ne is calculated, the basic fuel pulse width Tf is calculated from the intake air amount Qa / Ne, and it corresponds to the current air-fuel ratio A / F taken in from the main routine side. The well-known control of calculating the target injector drive time based on the correction coefficient KAF, the correction coefficient KDT corresponding to the intake air temperature Ta, and the atmospheric pressure Pa is performed.
[0030]
When the EGR control process is reached, the engine temperature information, that is, the water temperature Tw information, the engine rotational speed Ne, and the fresh air amount EV (intake air amount Qa / Ne) are taken in here. If the water temperature Tw exceeds a predetermined EGR temperature value, the process proceeds to the following EGR rate control. If the water temperature Tw is not in the EGR range, the EGR control process is stopped. When proceeding to EGR rate control, here, using the EGR region map me (see FIG. 5), it is determined whether the current engine operating region is in the middle to middle load region A1 to the high speed and high load region A2. judge. Then, the EGR valve opening corresponding to this operating range is read, and the stepper motor 30 is output and driven so as to drive the stepper motor 30 only to eliminate the difference between the number of steps corresponding to the same value and the current number of steps. Ensure the EGR valve opening.
[0031]
As shown in FIG. 7, when the ignition control process is reached, first, in step s1, the latest opening (EGR actual opening θ1) of the EGR valve 25, the engine speed Ne, and the fresh air amount EV (intake air amount Qa). / Ne). After that, in step s2, the steady EGR opening degree he is read from the map m1 and the steady EGR rate α1 is read from the map m2. Then, in step s3, these values are substituted into the equation (1). The instantaneous EGR rate α2 of the intake air flowing into the surge tank is calculated.
[0032]
In step s4, the EGR rate (n) in the enlarged diameter portion of the surge tank 12 previously calculated and stored is read. Here, the initial value of the EGR rate (n) that has been calculated in advance is appropriately set. In step s5, the engine speed Ne and the fresh air amount EV (intake air amount Qa / Ne) are taken in, and the EGR time constant C is read from the map m3. In the subsequent step s6, the values obtained in steps s3 to s5 are substituted into the equation (2), the instantaneous EGR rate α2 is smoothed, and the current expanded EGR rate (n) is updated.
[0033]
In step s7, the previous expanded diameter EGR rate (n) read out in step s4 is forwarded to the storage area of the expanded diameter EGR rate (n-1) in the previous stroke, and the expanded diameter EGR in the expanded stroke before the seventh stroke. All values up to the rate (n-7) are sequentially updated and stored. Then, the EGR rate (n-7) in the enlarged diameter portion that has been memorized up to now, that is, the EGR rate in the surge tank 12 before 8 strokes, is regarded as the EGR rate of the intake air flowing into the cylinder in the current intake stroke. (Determine)
[0034]
Next, in step s8, the current expanded EGR rate (n) and the expanded EGR rate (n−7) before 8 strokes are substituted into the equation (6), and this time, the intake branch enters the combustion chamber. An amount EV ′ of the supplied fresh air a1 is calculated. Next, in step s9, the engine rotational speed Ne is taken, and then the advance value W / O value that is an advance value when EGR is not performed is mapped from the map m4 to the advance value that is the advance value when EGR is performed. Read from m5. Further, the steady EGR rate α1 is read from the map m2, and these values are substituted into the equation (7) to calculate the ignition advance δθ value at the EGR transition time.
In step s10, the engine speed Ne and the fresh air amount (intake air amount Qa / Ne) EV are taken in, and the basic ignition timing θb corresponding to the same value is calculated based on the map m6.
[0035]
Furthermore, in step s11, a corrected ignition timing θb ′ corresponding to the latest ignition advance angle δθ and basic ignition timing θb is calculated according to the equation (8), and the same value is output to the ignition unit 33, and this control cycle The process in is terminated.
Thereafter, the ignition unit 33 sparks the spark plug 7 in accordance with the corrected ignition timing θb ′, and can perform ignition processing with an appropriate ignition advance at the time of EGR transition.
[0036]
In this way, the EGR rate in the enlarged diameter portion after the mixture containing the EGR gas staying in the surge tank 12 and the newly introduced EGR gas are mixed is accurately obtained, and the intake air flowing into the combustion chamber 3 is determined. In the determination of the EGR rate, the EGR rate (n-7) in the enlarged diameter portion before 8 strokes was obtained as the EGR rate in the enlarged diameter portion of the intake air flowing into the combustion chamber in relation to the capacity of the intake branch. For this reason, the EGR rate of the intake air actually flowing into the combustion chamber 3 can be accurately obtained, and the basic ignition timing θb is advanced by the ignition advance angle δθ value corresponding to the EGR rate. In controlling the ignition timing of the internal combustion engine, the ignition timing at the EGR valve switching transition can be appropriately controlled.
[0037]
In the ignition timing control device for the internal combustion engine of FIG. 1, the surge tank 12 has been described as an intake passage enlarged portion. However, the present invention is not limited to this, and the intake passage enlarged portion here includes inflowing fresh air and EGR gas. It suffices to have a relatively large capacity part that enables mixing of the above.
In the ignition timing control device for the internal combustion engine of FIG. 1, when determining the EGR rate of the intake air flowing into the combustion chamber 3, the EGR rate (n-7) in the enlarged diameter portion before the eight strokes is applied to the determination. This value varies depending on the capacity of the intake passage between the surge tank 12 and the combustion chamber 3, and if other intake branches are employed, the EGR in the enlarged diameter portion before the number of strokes adapted to that case can be used. The rate may be adopted, and in this case, the same effect can be obtained. Further, the correspondence between the intake air flowing into the cylinder and the stored EGR rate in the enlarged diameter portion is not limited to the number of strokes, and may be made to correspond using the crank angle.
[0038]
In the ignition timing control device for the internal combustion engine of FIG. 1, the EGR passage 24 recirculates part of the exhaust gas to the surge tank 12, but in some cases, the EGR passage 24 recirculates part of the exhaust gas to the upstream side of the surge tank 12. In this case, the same effect can be obtained.
[0039]
【The invention's effect】
As described above, the invention of claim 1 The EGR rate in the enlarged diameter portion after the mixture containing the EGR gas staying in the intake passage enlarged portion and the newly introduced EGR gas is mixed is accurately obtained, and the EGR rate of the intake air flowing into the combustion chamber is determined. In the determination, in order to obtain the EGR rate in the enlarged diameter portion before the stroke according to the intake passage capacity as the EGR rate in the enlarged diameter portion of the intake air flowing into the combustion chamber, the EGR rate of the intake air actually flowing into the combustion chamber is accurately obtained. Can It is possible to appropriately set the ignition timing at the time when the EGR rate changes by correcting the advance angle according to the EGR rate, that is, when the EGR valve switching transition is transient.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an engine provided with an ignition timing control device for an internal combustion engine according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of intake flow characteristics in a plan view of the surge tank and intake branch in FIG. 1;
FIG. 3 is an explanatory view of intake flow characteristics in a side view of the surge tank and intake branch in FIG. 1;
4 is a flock diagram illustrating an ignition timing control process used in the internal combustion engine ignition timing control device of FIG. 1; FIG.
FIG. 5 is a characteristic diagram of an EGR region map used in the ignition timing control device for the internal combustion engine of FIG. 1;
6 is an explanatory diagram of EGR valve opening control characteristics used in the ignition timing control device for the internal combustion engine of FIG. 1; FIG.
7 is a flowchart of an ignition control routine used in the ignition timing control device for the internal combustion engine of FIG. 1;
[Explanation of symbols]
1 engine
3 Combustion chamber
12 Surge tank (intake channel diameter expansion part)
23 EGR valve
24 EGR passage
α2 Instantaneous EGR rate
E1 Instantaneous EGR rate deriving means
E2 EGR ratio deriving means in expanded diameter section
θb Basic ignition timing
E3 Basic ignition timing setting means
E4 ignition timing correction means
E5 ignition timing control means

Claims (1)

An EGR passage that recirculates a portion of the exhaust to the intake passage enlarged diameter portion provided in the intake system of the internal combustion engine or the upstream intake system thereof;
An EGR valve which is interposed in the EGR passage and whose operation is controlled according to the engine operating state;
Instantaneous EGR rate deriving means for deriving an instantaneous EGR rate based on the latest opening of the EGR valve and the engine operating state;
An enlarged-diameter EGR rate deriving unit that updates the EGR rate in the enlarged-diameter portion based on the instantaneous EGR rate and the EGR rate in the enlarged-diameter portion of the intake passage enlarged portion calculated in advance;
Basic ignition timing setting means for setting the basic ignition timing based on the engine operating state;
The EGR rate in the enlarged-diameter portion that is sequentially updated is stored , and the EGR rate of the intake air flowing into the cylinder is the previous number of strokes of the internal combustion engine that adapts to the intake passage capacity between the enlarged-diameter portion and the combustion chamber. An ignition timing control device for an internal combustion engine, comprising: an ignition timing correction unit that corrects the basic ignition timing using the EGR rate in the enlarged diameter portion .

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