JP2016031037A - Engine remaining gas rate estimation apparatus and ignition timing control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus capable of easy adaptation in a case of estimating a remaining gas rate.SOLUTION: An engine remaining gas rate estimation apparatus comprises: means (41) calculating a min (IVO, EVC) time remaining gas rate by a primary expression represented by min(IVO, EVC) time remaining gas rate=(min(IVO, EVC) time cylinder internal volume)×(gain 1)+segment using a cylinder internal volume at min(IVO, EVC) time, a gain 1, and a segment; means (41) calculating a remaining gas rate increment during the valve overlap; and means (41) calculating a sum of the calculated min(IVO, EVC) time remaining gas rate and the calculated remaining gas rate increment during the valve overlap as a remaining gas rate, the gain 1 is specified in response to an engine rotational speed and an engine load and the segment being specified in response to the engine load in a case of calculating the min(IVO, EVC) time remaining gas rate by the primary expression.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a residual gas rate estimating device and an ignition timing control device for an internal combustion engine (hereinafter referred to as “engine”).

  There is one that calculates the amount of residual gas in the combustion chamber by the equation: residual gas amount = in-cylinder gas amount at IVO + return gas amount during valve overlap (see Patent Document 1). In this case, in order to convert the residual gas amount into the residual gas rate, the residual gas rate = residual gas amount / (intake air amount + fuel injection amount) or the residual gas rate = residual gas amount / (intake air amount + fuel injection amount). The residual gas rate is calculated by the equation of “+ residual gas amount”.

JP 2007-255206 A

  By the way, in the technique of the said patent document 1, the cylinder internal gas amount m is calculated using the state equation m = PV / RT of gas. In the calculation, it is necessary to estimate P (cylinder pressure) and T (cylinder temperature) in the gas equation of state. There were a lot of constants to fit for the estimation, and it took time to fit.

  Therefore, an object of the present invention is to provide an apparatus that can simplify the adaptation in estimating the residual gas ratio.

  The present invention is premised on an engine residual gas rate estimation device having a mechanism for generating valve overlap in which the open periods of intake and exhaust valves overlap. And it comprises a residual gas rate calculating means at the time of min (IVO, EVC), a residual gas rate increase calculating means during valve overlap, and a residual gas rate calculating means.

  The min (IVO, EVC) remaining gas rate calculation means calculates the min (IVO, EVC) remaining gas rate by the following linear expression using the in-cylinder volume, gain 1 and intercept at min (IVO, EVC). To do.

Residual gas ratio at min (IVO, EVC) = In-cylinder volume at min (IVO, EVC)
× Gain 1 + Intercept Moreover, the above-mentioned residual gas rate calculation means at min (IVO, EVC) uses min (IVO, EVC) and three coefficients a, b, c, and min (IVO, EV) (EVC) The residual gas rate is calculated.

Residual gas ratio at min (IVO, EVC) = a × min (IVO, EVC) ^ 2
+ B × min (IVO, EVC) + c
The residual gas rate increase calculation means during the valve overlap calculates a residual gas rate increase during the valve overlap. The residual gas ratio calculating means calculates a residual gas ratio by the sum of the calculated residual gas ratio at min (IVO, EVC) and the calculated increase in the residual gas ratio during the valve overlap.

  Further, when calculating the remaining gas ratio at min (IVO, EVC) by the linear equation, the gain 1 is determined according to the engine speed and the engine load, and the intercept is determined according to the engine load.

  In addition, when calculating the residual gas ratio at min (IVO, EVC) by the secondary equation, the three coefficients a, b, and c are determined according to the engine speed and the engine load.

  In the present invention, not the residual gas amount but the residual gas rate can be directly calculated. Further, the residual gas amount at min (IVO, EVC) can be calculated from the gas equation of state (m = PV / RT), but in the present invention, in addition to calculating the cylinder volume V, the pressure P and temperature T are calculated. I don't do it. That is, in addition to the pressure P and the temperature T, a coefficient for converting the residual gas amount into the residual gas rate is also included and provided as a gain 1 map using the rotational speed and the engine load as parameters. Further, the residual gas amount when the gap volume is minimum can be similarly calculated from the gas state equation (m = PV / RT). However, in the present invention, the pressure P and the temperature T are not calculated. That is, in addition to the pressure P and the temperature T, a coefficient for converting the residual gas amount into the residual gas rate is included, and an intercept table with the engine load as a parameter is provided. As a result, since only the gain 1 map and the intercept table should be adapted, the adaptation when estimating the residual gas ratio can be easily performed.

It is a schematic block diagram of the gasoline engine of 1st Embodiment of this invention. It is a lift characteristic figure for demonstrating the estimation method of the residual gas rate of this invention. It is a characteristic view which shows the relationship between the cylinder internal volume at the time of min (IVO, EVC) and the residual gas rate at the time of min (IVO, EVC). It is a characteristic view which shows the relationship between the cylinder internal volume at the time of min (IVO, EVC) and the residual gas rate at the time of min (IVO, EVC). It is a timing chart which shows a simulation result when accelerating a vehicle from an idle state, maintaining a steady state, and then decelerating and returning to an idle state. It is a flowchart for demonstrating calculation of a residual gas rate. It is a characteristic diagram of gain 1. It is a characteristic figure of an intercept. It is a characteristic view for a basic residual gas rate increase. FIG. 6 is a characteristic diagram of gain 2. It is a flowchart for demonstrating calculation of an ignition timing command value. It is a characteristic view of basic ignition timing. It is a characteristic view of the ignition timing correction amount. It is a flowchart for demonstrating calculation of the residual gas rate of 2nd Embodiment. It is a characteristic figure of gain 3 of a 2nd embodiment. It is a flowchart for demonstrating calculation of the residual gas rate of 3rd Embodiment. It is a characteristic view of the coefficient a of 3rd Embodiment. It is a characteristic view of the coefficient b of 3rd Embodiment. It is a characteristic view of the coefficient c of 3rd Embodiment. It is a characteristic view which shows the relationship of the residual gas rate at the time of min (IVO, EVC) when there is no EVC and valve overlap.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a control device for a gasoline engine according to a first embodiment of the present invention.

  The engine 1 is a gasoline engine (hereinafter also simply referred to as “engine”). The engine 1 is mounted on a vehicle (not shown). The engine 1 includes an intake passage 4 and an exhaust passage 11. The intake passage 4 includes an intake pipe 4a, an intake collector 4b, and an intake manifold 4c.

  The intake pipe 4a immediately upstream of the intake collector 4b is provided with an electronically controlled throttle device that responds to the amount of depression of the accelerator pedal. The throttle device includes a throttle valve 5, a motor (rotary electric machine) 6 that drives the throttle valve 5, and a throttle sensor 7 that detects an actual throttle opening. The intake air is metered by the throttle valve 5 through the intake pipe 4a. The throttle valve opening is set according to the accelerator opening and the engine speed Ne. The metered air is stored in the intake collector 4b, and is distributed and supplied from the intake collector 4b to the combustion chamber 7 of each cylinder through the intake manifold 4c when the intake valve 8 is opened. Although the embodiment is an electronically controlled throttle device, the throttle valve and the accelerator pedal may be connected by a wire.

  The engine 1 includes an ignition device 13. The ignition device 13 includes an ignition plug 14 and an ignition coil 15 with a built-in power transistor. The spark plug 14 faces the combustion chamber 10 and the fuel injection valve 8 faces the combustion chamber 10 respectively.

  The engine controller 41 calculates a basic fuel injection pulse width Tp [ms] from the intake air amount Qa and the engine rotational speed Ne, and uses this Tp as a target equivalent ratio TFBYA [anonymous number] or an air-fuel ratio feedback correction coefficient α [anonymous number]. And the fuel injection pulse width Ti [ms] is calculated. By opening the fuel injection valve 8 by this Ti at a predetermined timing, the fuel is directly injected into the combustion chamber 10. On the other hand, the engine controller 41 calculates the basic ignition timing ADV0 [degCA (BTDC)] by referring to a predetermined map from the engine load and the rotational speed. Then, a spark is generated from the spark plug 14 by cutting off the primary current of the ignition coil 15 through the power transistor at a timing when the crank angle of the engine detected by the crank angle sensor 45 coincides with this ADV.

  The fuel injected into the combustion chamber 10 is mixed with the air metered by the throttle valve 5 after the intake valve 8 is closed to become a gas, and this gas is ignited by the spark plug 14 and burned. The combusting gas is discharged into the exhaust passage 21 when the exhaust valve 9 is opened after the work of pushing down the piston 11 sliding on the cylinder. The position where the fuel injection valve 12 is provided is not limited to the combustion chamber 10. A fuel injection valve may be provided in the intake manifold 4c (intake port).

  The engine 1 includes a variable valve timing mechanism 16 (hereinafter referred to as “intake VTC mechanism”) 16 that can variably adjust the phase of the operating angle center of the intake valve 8 relative to the cam shaft for the intake valve. Similarly, a variable valve timing mechanism (hereinafter referred to as “exhaust VTC mechanism”) 17 capable of variably adjusting the phase of the operating angle center of the exhaust valve 9 with respect to the cam shaft for the exhaust valve is provided. By using these two VTC mechanisms 16 and 17 (valve overlap generating mechanism), a valve overlap in which the open periods of the intake and exhaust valves 8 and 9 overlap (hereinafter simply referred to as “valve overlap”) is, for example, in a low load range. By doing so, the pumping loss of the engine is reduced. Thereby, the fuel consumption of the engine can be improved. An operating range in which valve overlap is generated is determined in advance, and the engine controller 41 instructs the two VTC mechanisms 16 and 17 to generate valve overlap when the operating range is reached. Specifically, the characteristics of IVO (intake valve opening timing) and EVC (exhaust valve closing timing) are determined in advance on a map using the engine load and the rotational speed Ne as parameters. The engine controller 41 refers to each map from the engine load and the rotational speed Ne to obtain IVO and EVC, and gives command values to the two VTC mechanisms 16 and 17 so that the obtained IVO and EVC can be obtained. Output.

The exhaust passage 21 includes an exhaust manifold 21a into which exhaust from the cylinder 10 of each cylinder flows, and an exhaust pipe 21b connected to a collective portion of the exhaust manifold 21a. Since the exhaust contains harmful three components of HC, CO, and NOx, a manifold catalyst 25 is provided at the assembly portion of the exhaust manifold 21a and a main catalyst 26 is provided at the exhaust pipe 21b downstream of the exhaust manifold 21a in order to purify all of them. Yes. The main catalyst 26 is provided, for example, under the floor of the vehicle. Each of these catalysts 25 and 26 is composed of, for example, a three-way catalyst. A muffler 27 is provided at the end of the exhaust pipe 21b. After the activation of the main catalyst 26, the engine controller 41 starts air-fuel ratio feedback control. In the air-fuel ratio feedback control, an air-fuel ratio feedback correction coefficient α [anonymous number] is calculated based on signals from the air-fuel ratio sensor 46 and the O ₂ sensor 47 so that the oxygen storage amount of the main catalyst 25 becomes a target value.

  The engine 1 includes an EGR device 31. The EGR device 31 includes an EGR passage 32, an EGR valve 33 (for example, a butterfly valve) that opens and closes the EGR passage 32, and a motor (rotary electric machine) 34 that drives the EGR valve 33. The EGR passage 32 is branched from the exhaust pipe 11b between the manifold catalyst 25 and the main catalyst 26, and merges with the intake manifold 4c. When the operating point of the engine is in the EGR region, the engine controller 41 performs EGR control by opening the EGR valve 33.

  Now, when the exhaust valve 9 is opened, the burned gas flows out from the combustion chamber 10 toward the exhaust port, while a part of the burned gas that has come out to the exhaust port blows back to the combustion chamber 10. This burned back burned gas remains inside the combustion chamber 10 when the exhaust valve 9 is closed. When the burned gas remaining in the combustion chamber 10 is defined as “residual gas”, the amount of residual gas is larger than that at high load, particularly at low load. The residual gas remaining in the combustion chamber 10 this time affects the combustion speed when the unburned gas is burned in the same combustion chamber 10 next time. If the amount of residual gas is large when the load is low, the combustion speed of unburned gas in the combustion chamber 10 becomes small and the combustion becomes unstable.

  Therefore, the remaining gas amount when there is no valve overlap is divided into the following equation (1), and the remaining gas amount when there is valve overlap is divided into the following equation (2). There is a conventional apparatus that calculates the residual gas ratio by the equation (3) or (4).

Residual gas amount when there is no valve overlap = In-cylinder gas amount at EVC (1)
Residual gas amount with valve overlap = In-cylinder gas amount at IVO
+ Blowing gas amount during valve overlap
... (2)
Residual gas ratio = residual gas amount / (intake air amount + fuel injection amount) (3)
Residual gas ratio = residual gas amount / (intake air amount + fuel injection amount + residual gas amount) (4)
In the conventional apparatus, the residual gas amount when there is no valve overlap is determined by EVC (exhaust valve closing timing) as in the above equation (1), and the in-cylinder gas amount during EVC is expressed as a gas state equation m = PV / RT Calculate using. For example, the pressure P of the gas state equation is calculated from the atmospheric pressure + pulsation estimated value, and the temperature T of the gas state equation is calculated from the correlation with the amount of exhaust heat.

  On the other hand, the amount of blow-back gas during the valve overlap of the second term on the right side of the equation (2) is calculated as follows. That is, the gas flow around the exhaust valve at the time of IVO, the crank angle at which the gas flow around the exhaust valve becomes 0 deg, and the gas flow around the exhaust valve at the crank angle after the valve overlap period elapses are estimated. Then, the amount of blown-back gas during valve overlap is calculated by approximating the time change of the gas flow rate around the exhaust valve with two straight lines and integrating between them.

  However, in the conventional apparatus, when calculating the in-cylinder gas amount m using the state equation of m = PV / RT, it is necessary to estimate P (in-cylinder pressure) and T (in-cylinder temperature) in the state equation. is there. There are many constants to be adapted for the estimation of P and T, and adaptation takes time. If it takes time to adapt, it will increase the development cost of the engine.

  Therefore, the inventor of the present invention has created a method for estimating the residual gas rate that requires less time for adaptation than the conventional apparatus. This will be described with reference to FIG. 2. The lift characteristics of the intake and exhaust valves 8 and 9 when there is no valve overlap (abbreviated as “O / L” in the figure) in the upper part of FIG. The lift characteristics of the intake and exhaust valves 8 and 9 when there is a valve overlap are shown. In the present invention, in order to convert the residual gas amount into the residual gas rate after obtaining the residual gas amount, the residual gas rate is not calculated using the above formula (3) or (4), but suddenly the residual gas rate is calculated. Think about what you want. First, when there is no valve overlap, it is considered that the residual gas ratio is determined by EVC as shown in the upper part of FIG. On the other hand, when there is a valve overlap, it is considered that an increase in the residual gas rate during the overlap is added to the residual gas rate determined by IVO (intake valve opening timing) as shown in the lower part of FIG. Instead of the above formulas (1) and (2), the following formula is adopted.

Residual gas rate when there is no valve overlap = Residual gas rate at EVC (5)
Residual gas rate when there is valve overlap = Residual gas rate at IVO
+ Increase in residual gas rate during valve overlap
... (6)
Here, EVC that defines the residual gas rate when there is no valve overlap and IVO that defines the residual gas rate when there is valve overlap are collectively defined as “min (IVO, EVC)”. At this time, it is as follows.

Min (IVO, EVC) = EVC when there is no valve overlap (7)
Min (IVO, EVC) = IVO when there is valve overlap (8)
Thus, “min (IVO, EVC)” means the smaller one of IVO and EVC. This employs [degCA (ATDC)] as a unit of IVO and EVC, so min (IVO, EVC) = EVC when there is no valve overlap, and min (IVO when there is valve overlap. , EVC) = IVO. The defined unit of min (IVO, EVC) is also the same [degCA (ATDC)] as the unit of IVO, EVC. [DegCA (ATDC)] represents the crank angle after compression top dead center.

Next, in order to determine the relationship between the in-cylinder volume [m ³ ] at the time of min (IVO, EVC) and the residual gas rate [%] at the time of min (IVO, EVC), a simulation test is performed. As shown in FIG.

  In FIG. 3, the upper three straight lines indicate that the engine speed Ne [rpm] is a first predetermined value N1 [rpm] and a second predetermined value N2 under the condition that the charging efficiency ηc [%] is constant (predetermined value η1 [%]). [Rpm] is different from the third predetermined value N3 [rpm]. In the upper three straight lines, the higher the Ne, N1, N2 and N3, the gentler the slope of the straight line. On the other hand, in the lower three lines in FIG. 3, the engine speed Ne is set to the first predetermined value N1 [rpm] and the second predetermined value under the condition that the charging efficiency ηc is constant (the predetermined value η2 [%] larger than the predetermined value η1). This is when N2 [rpm] is different from the third predetermined value N3 [rpm]. In the lower three straight lines, the slope of the straight line becomes gentler as Ne becomes higher as N1, N2, and N3. Further, when the charging efficiency ηc increases from the predetermined value η1 to the predetermined value η2, the residual gas ratio at min (IVO, EVC) decreases. In the present invention, the unit of filling efficiency is handled in [%], but it may be handled in [anonymous number].

  The fact that a linear characteristic is obtained means that the residual gas rate at min (IVO, EVC) can be expressed by a linear expression with the in-cylinder volume at min (IVO, EVC) as a variable. Note that, here, the cylinder volume at the time of min (IVO, EVC) excluding the gap volume is considered. However, the present invention is not limited to the one excluding the gap volume, and may include the gap volume although the accuracy is somewhat lowered.

  In this case, it is easier to consider using the TDC rather than the origin other than the TDC (compression top dead center). Therefore, if the position of the in-cylinder volume at the time of the TDC on the horizontal axis is shifted with respect to FIG. FIG. 4 is obtained. From FIG. 4, the residual gas rate at min (IVO, EVC) can be given by a linear expression using the in-cylinder volume at min (IVO, EVC) as a variable, that is, by the following expression.

Residual gas ratio at min (IVO, EVC) = In-cylinder volume at min (IVO, EVC)
X Gain 1 + intercept (9)
As shown in FIG. 4, the residual gas ratio at min (IVO, EVC) becomes the lowest when the cylinder volume at min (IVO, EVC) matches the cylinder volume at TDC, that is, min (IVO, EVC). This is when EVC) comes to TDC. The reason for this is that although the amount of residual gas can be calculated from the equation of state of gas (m = PV / RT), the in-cylinder volume V is the smallest at TDC and there is no temperature drop due to blow-back gas. This is because it becomes the highest. In the state equation of m = PV / RT, when the burned gas temperature T becomes the highest, the in-cylinder gas amount becomes the smallest (the residual gas ratio becomes the smallest).

  Next, as the in-cylinder volume at (IVO, EVC) becomes larger than the in-cylinder volume at TDC, that is, as min (IVO, EVC) moves to the retard side (BDC side) from TDC, min (IVO, EVC). The residual gas rate increases. There are two reasons for this. The first reason is that the in-cylinder volume increases. That is, when the cylinder volume V increases in the state equation of m = PV / RT, the cylinder gas amount m increases (the residual gas ratio increases). The second reason is that the amount of blown-back gas around the exhaust port increases as min (IVO, EVC) moves to the BDC side, but the burned gas releases heat to the atmosphere while it is in the vicinity of the exhaust port (heat dissipation). This is because the burnt gas temperature T is lowered. When the burnt gas temperature T decreases in the state equation of m = PV / RT, the in-cylinder gas amount m increases (the residual gas ratio increases).

  Up to this point, the residual gas rate at the time of min (IVO, EVC) (the residual gas rate when there is no valve overlap) has been described. In the first embodiment of the present invention, the residual gas ratio including not only the case where there is no valve overlap but also the case where there is a valve overlap is calculated by the following equation.

Residual gas rate = Residual gas rate at min (IVO, EVC)
+ Increase in residual gas ratio during valve overlap (10)
Here, qualitatively explaining the residual gas amount, when there is no valve overlap, the residual gas rate is determined by the amount of burnt gas blown back from the exhaust port to the combustion chamber 10. On the other hand, when there is a valve overlap, it can be considered the same as when there is no valve overlap. This is because the fresh air flows into the combustion chamber 10 from the intake port during the valve overlap, so that the burned gas does not often blow into the intake port. Even when there is a valve overlap, it is sufficient to consider the amount of burned gas that blows back from the exhaust port to the combustion chamber 10. That is, the increase in the residual gas rate during the valve overlap in the second term on the right side of equation (10) deals with the increase in the amount of burned gas that blows back from the exhaust port to the combustion chamber 10. Hereinafter, the formula (10) will be outlined. Details will be described with reference to the flowchart of FIG. The residual gas rate at the time of min (IVO, EVC) in the first term on the right side of the above equation (10) is calculated by the following equation that is the same as the above equation (9).

Residual gas ratio at min (IVO, EVC) = In-cylinder volume at min (IVO, EVC)
× Gain 1 + Intercept (11)
Here, the in-cylinder volume at the time of min (IVO, EVC) on the right side of the formula (11) is calculated from the bore diameter [m] of the cylinder and the piston stroke [m] at the time of min (IVO, EVC). The gain 1 [% / m ³ ] on the right side of the equation (11) is obtained by referring to a map using the engine speed Ne [rpm] and the charging efficiency ηc [%] as parameters. The intercept [%] on the right side of the equation (11) is obtained by referring to a map using the engine speed Ne and the charging efficiency ηc as parameters.

  The residual gas rate at min (IVO, EVC) will be further described. In the conventional apparatus, the residual gas amount at the time of min (IVO, EVC) was calculated from the gas state equation (m = PV / RT). On the other hand, in this embodiment, in addition to calculating the in-cylinder volume V during min (IVO, EVC), the pressure P and temperature T required when using the gas state equation are not calculated. That is, instead of the pressure P and the temperature T, a map of gain 1 having the rotational speed Ne and the charging efficiency ηc (engine load) as parameters is provided. This is because the pressure P and the temperature T differ depending on the engine operating point determined by the engine load and the rotational speed Ne, and therefore the engine load and the rotational speed Ne are used as parameters instead of the pressure P and the temperature T. It is because it can do. The coefficient for converting the residual gas amount into the residual gas rate can be simplified by including it in gain 1 instead of handling it with another gain.

  Further, the cylinder gas amount when the cylinder volume is minimum can be similarly calculated from the gas state equation (m = PV / RT), but in this embodiment, the pressure P and the temperature T are not calculated. . That is, instead of the pressure P and the temperature T, an intercept table using the charging efficiency ηc (engine load) as a parameter is provided. This is because the in-cylinder gas amount when the in-cylinder volume is minimum does not depend on the engine rotational speed Ne and can be given only by the charging efficiency ηc. The coefficient for converting the residual gas amount into the residual gas rate can also be simplified by including it in the intercept instead of handling it separately.

  As a result of such simplification, only the gain 1 map and the intercept table should be adapted in the present embodiment. As a result, the adaptation when estimating the residual gas rate at min (IVO, EVC) can be performed more easily than the conventional apparatus.

  Next, the increase in the residual gas rate during the valve overlap in the second term on the right side of the equation (10) is calculated by the following equation.

Increase in residual gas rate during valve overlap = increase in basic residual gas rate x gain 2
... (12)
Here, the basic residual gas rate increase [%] on the right side of Equation (12) is the residual gas rate increase when there is a valve overlap at the reference operating point (determined from Ne and ηc). The value of the increase in the basic residual gas rate is obtained in advance by making the valve overlap period [degCA] different at the reference operating point. The gain 2 [anonymous number] on the right side of the equation (12) is obtained by referring to a map using the engine speed Ne and the charging efficiency ηc as parameters. The reference operating point is not limited to one specific operating point. For example, what is necessary is just to set to the operating point from which the increase in the residual gas rate during overlap becomes relatively large.

  The increase in the residual gas rate during the valve overlap will be further described. In the conventional apparatus, the gas flow rate around the exhaust valve during the valve overlap is obtained by integrating the gas flow rate obtained by the orifice flow rate equation over the valve overlap period. Here, the orifice flow rate equation is the equation (19) described later. In this embodiment, the orifice flow rate type is not used as it is. Then, the relationship between the valve overlap period at the reference operating point and the increase in the residual gas rate during the valve overlap is simply used as a table. The difference in in-cylinder gas amount due to the differential pressure difference before and after the exhaust valve, and the coefficient for converting the remaining gas amount into the remaining gas rate are replaced with the charging efficiency ηc, and the difference in in-cylinder gas amount due to the valve overlap time [s] Replace with rotational speed Ne. Then, a gain 2 map using the charging efficiency ηc and the rotational speed Ne as parameters is introduced, and the increase in the residual gas rate during valve overlap is calculated from the product of the table value and the gain 2 map value.

  As a result of this simplification, what should be adapted in the present embodiment is a table representing the relationship between the valve overlap period at the reference operating point and the increase in the residual gas rate, and a gain 2 map. As a result, the adaptation when estimating the increase in the residual gas rate during the valve overlap can be made easier than when the orifice flow rate type is used as it is as in the conventional apparatus.

  As described above, the parameters for referring to the gain 1 and gain 2 maps are the rotational speed Ne and the charging efficiency ηc, and the parameters for referring to the intercept table are the charging efficiency ηc. Here, the filling efficiency ηc includes a target filling efficiency and an actual filling efficiency, either of which may be adopted. A method for calculating the target filling efficiency and the actual filling efficiency is known (see JP 2006-83804 A). The engine controller 41 has already calculated the target filling efficiency and the actual filling efficiency in other controls. Therefore, there is no need to newly calculate the target filling efficiency or the actual filling efficiency.

  Furthermore, in this embodiment, the charging efficiency is configured as a substitute value for the engine load. In the present embodiment, the case where the engine load substitute value is the charging efficiency will be described. However, the present invention is not limited to the case where the engine load substitute value is the charging efficiency. As a substitute value of the engine load, for example, volumetric efficiency ηv (target volumetric efficiency or actual volumetric efficiency), basic injection pulse width Tp, intake air amount Qa, accelerator opening, throttle valve opening, and engine torque are used. be able to.

  Next, FIG. 5 shows the result of a simulation test (simulation) when the accelerator pedal 43 is depressed a little to accelerate the vehicle from the idle state to maintain the steady state and then decelerate and return to the idle state. That is, FIG. 5 shows the residual gas rate at min (IVO, EVC) calculated by the method of calculating the residual gas rate created by the present inventor, the increase in the residual gas rate during valve overlap, and the total of these. The fifth stage, the sixth stage, and the seventh stage show how the residual gas ratio changes.

  First, the transition of the operating point will be described. As shown in the first stage of FIG. 5, the charging efficiency ηc gradually increases from the timing t2 when acceleration is started, becomes a constant value at the timing t6, and from the timing t7. It gradually decreases and returns to the idle value at the timing of t10. As shown in the second stage of FIG. 5, the engine rotational speed Ne gradually increases from the timing t3 slightly delayed from t2, and after reaching a peak at the timing t8, gradually decreases to the rotational speed in the idle state. doing.

  When the engine operating point determined by ηc and Ne changes in this way, as shown in the third stage of FIG. 5, IVO (see the thin solid line) and EVC (see the broken line) change. Due to these changes in IVO and EVC, valve overlap (abbreviated as “O / L” in FIG. 5) occurs when IVO becomes smaller than EVC, that is, in the period from t4 to t9 in FIG.

  Thus, when Ne, IVO, and EVC change due to the transition of the operating point, the remaining gas rate during min (IVO, EVC) and the increase in the remaining gas rate during valve overlap in this embodiment are shown in the fifth row of FIG. , As shown in the sixth row. That is, as shown in the fifth stage of FIG. 5, the residual gas rate at min (IVO, EVC) is large in the idle state up to t2, and becomes zero by acceleration from t2. Then, when returning to the idle state at t10 due to deceleration from t7, the residual gas ratio at min (IVO, EVC) becomes a large value again from zero. On the other hand, as shown in the sixth row of FIG. 5, the increase in the residual gas rate during valve overlap is greatly affected by the overlap period. That is, in the period from t4 to t5 when the valve overlap period is relatively large and the period from t7 to t9, the remaining gas ratio during valve overlap is longer than the period from t5 to t7 where the valve overlap period is relatively small. The increase is increasing. The reason why the value obtained by simply adding the fifth stage and the sixth stage is not the seventh stage is that the scale of the vertical axis is different between the fifth stage and the sixth stage. is there. As shown in the seventh stage, when the residual gas rate at min (IVO, EVC) is compared with the increase in the residual gas rate during valve overlap, it can be seen that the increase in the residual gas rate during valve overlap is larger.

  Thus, when the inventor tried the newly developed residual gas rate estimation method for various engines having different specifications, favorable results were obtained. According to the present embodiment, since the residual gas rate at min (IVO, EVC) and the increase in the residual gas rate during valve overlap are calculated with a simple configuration, the actual results are well traced. is there. In addition, since the conventional apparatus has a precise configuration, the accuracy of estimation of the residual gas rate is reduced when the Atkinson cycle is entered. However, when the simple configuration as in this embodiment is used, the Atkinson cycle is not used. However, it has also been found here that there is no problem level error. In the present embodiment, it can be said that robustness is obtained by the simple configuration.

As shown in FIG. 1, in addition to the EGR valve 33, an engine controller 41 is provided to control the ignition device 13 including the fuel injection valve 12 and the ignition plug 14. The engine controller 41 is configured as a computer unit including peripheral devices such as a microprocessor, ROM, and RAM. The engine controller 41 receives signals from the throttle sensor 7, the air flow meter 42, the accelerator sensor 44, the crank angle sensor 45, the air / fuel ratio sensor 46, and the O ₂ sensor 47. Here, the throttle sensor 7 detects the throttle valve opening. The air flow meter 42 detects the amount of air flowing into the intake pipe 4a. The accelerator sensor 44 detects the amount of depression (accelerator opening) of the accelerator pedal 43 and its change amount. The crank angle sensor 45 detects the actual crank angle that determines the piston position and the engine rotational speed Ne. The air-fuel ratio sensor 46 detects the air-fuel ratio of the exhaust upstream of the manifold catalyst 25. The O ₂ sensor 47 detects whether the air-fuel ratio of the exhaust downstream of the manifold catalyst is on the rich side or the lean side from the stoichiometric air-fuel ratio. The engine controller 41 performs the following control in addition to the fuel injection amount control and the air-fuel ratio control via the fuel injection valve 12 and the ignition timing control via the ignition device 13 as described above. That is, the remaining gas rate is calculated using the above equations (10) to (12), the basic ignition timing ADV0 is corrected to the advance side with the calculated remaining gas rate, and the ignition timing command value ADV is obtained. The ignition timing command value ADV is output to the power transistor of the ignition device 13.

  This control executed by the engine controller 41 will be described based on the following flowchart. First, the flow of FIG. 6 is for calculating the residual gas rate MBTRGR [%], and is executed at regular intervals (for example, every 10 ms).

In step 1, it is checked whether or not there is a valve overlap (abbreviated as “O / L” in FIG. 6). This can be known from the command value to the VTC mechanisms 16 and 17 by the engine controller 41. When there is a valve overlap, the process proceeds to step 2 to calculate the in-cylinder volume [m ³ ] at the time of IVO for one cylinder. The cylinder volume at the time of IVO is calculated from the bore diameter [m] of the cylinder and the piston stroke [m] at the time of IVO. The bore diameter of the cylinder can be determined from the engine specifications. The piston stroke at the time of IVO can be known by detecting the crank angle at the time of IVO by the crank angle sensor 45. The clearance volume is excluded from the in-cylinder volume at this IVO. The clearance volume can be known in advance from the engine specifications. The in-cylinder volume excluding the clearance volume is transferred to the in-cylinder volume [m ³ ] at min (IVO, EVC) in step 3.

On the other hand, when there is no valve overlap in step 1, the process proceeds to step 4. Step 4 is the same as step 2. That is, in step 4, the in-cylinder capacity [m ³ ] for one cylinder is calculated. The in-cylinder volume during EVC is calculated from the bore diameter [m] of the cylinder and the piston stroke [m] during EVC. The clearance volume is also removed from the EVC cylinder internal volume. The in-cylinder volume during EVC excluding the clearance volume is transferred to the in-cylinder volume during min (IVO, EVC) [m ³ ] in step 5. In FIG. 6, the in-cylinder volume at the time of min (IVO, EVC) is abbreviated as “volume at time of min (IVO, EVC)”.

In step 6, a gain of 1 [% / m ³ ] is calculated by referring to a map having the contents shown in FIG. 7 from the engine speed Ne [rpm] and the charging efficiency ηc [%]. As shown in FIG. 7, the gain 1 is larger as the rotation speed is lower and the charging efficiency is lower (low load), and is smaller as the rotation speed is higher and the charging efficiency is higher (high load). The reason why the gain 1 is increased as the rotational speed Ne is lower under the constant filling efficiency ηc is as follows. That is, the lower the rotational speed Ne, the longer the blow-back time. If the blowback time is long, the amount of heat released from the combustion chamber 10 to the atmosphere increases, so the burnt gas temperature T decreases. This means that the temperature T is lowered in the equation of state of m = PV / RT. When the temperature T decreases in the state equation of m = PV / RT, the in-cylinder gas amount m increases, so that the residual gas ratio at min (IVO, EVC) increases. This is because, in accordance with this tendency, the lower the Ne, the larger the inclination. Next, the gain 1 is increased as the filling efficiency ηc decreases under the condition that Ne is constant. The reason for this is unclear, but since such a feature was found, it was reflected.

  In step 7, an intercept [%] is calculated from the filling efficiency ηc by referring to a map having the contents shown in FIG. The intercept is a value for calculating the residual gas rate when (min (IVO, EVC) is at TDC. As shown in FIG. 8, the intercept is larger as the charging efficiency ηc is smaller (low load), and the charging efficiency is larger. The larger ηc (higher load), the smaller the reason for this is as follows: the residual gas rate when min (IVO, EVC) matches TDC (compression top dead center) is the charging efficiency. The reason why the higher the value of ηc is, the lower the burnt gas temperature is.In the state equation of m = PV / RT, when the burnt gas temperature T is high, the in-cylinder gas amount m is reduced (that is, the residual gas rate is reduced). It becomes smaller).

  On the other hand, in FIG. 8, only the charging efficiency ηc is used as a parameter, and the rotational speed Ne is not used as a parameter. The reason why Ne is not used as a parameter (there is no rotational speed sensitivity) is that the burned gas does not blow back in the TDC where the piston 11 stops, and therefore there is no heat release from the combustion chamber 10 to the atmosphere. Alternatively, the residual gas rate is a value defined by the equation of residual gas rate = residual gas amount / (new air amount + residual gas amount + fuel amount), but the denominator on the right side of this equation is determined by the charging efficiency ηc. This is because the residual gas ratio when min (IVO, EVC) coincides with TDC becomes a value determined by the charging efficiency ηc.

  In step 8, the cylinder volume at the time of min (IVO, EVC) is multiplied by gain 1, and the intercept is added to the multiplied value to obtain the remaining gas rate MBTRGRNO [%] at time of min (IVO, EVC). MBTRGRNO is calculated from the equation.

MBTRGRNO = min (IVO, EVC) volume x gain 1 + intercept
... (13)
Equation (13) is the same as equation (11) above.

  In step 9, as in step 1, it is determined whether or not there is a valve overlap. When there is a valve overlap, the process proceeds to step 10, and the valve overlap period (abbreviated as “O / L” in the figure) [degCA] is calculated from the following equation from EVC [degCA (BTDC)] and IVO [degCA (BTDC)]. To do. Here, the engine controller 41 can know EVC and IVO from command values to the VTC mechanisms 16 and 17.

Valve overlap period = EVC-IVO (14)
Since the valve overlap period of the equation (14) is a unit of the crank angle, it is a value that is not influenced by the engine rotational speed Ne. In step 11, the basic residual gas rate increase [%] is calculated by referring to the table having the contents shown in FIG. 9 from the valve overlap period. As shown in FIG. 9, the increase in the basic residual gas rate is a value that decreases as the valve overlap period decreases, and increases as the valve overlap period increases. The reason is as follows. That is, the longer the valve overlap period, the longer the burn-back time of the burned gas from the exhaust port into the combustion chamber 10 and the corresponding increase in the basic residual gas rate.

  Further, as shown in FIG. 9, the reason why the increase in the basic residual gas rate increases secondarily with respect to the valve overlap period is as follows. That is, the lift amount of the exhaust valve 9 increases secondarily during the valve overlap. When the lift amount of the exhaust valve 9 increases secondarily during the valve overlap, the increase in the basic residual gas rate also increases secondarily. In order to show that the increase in the basic residual gas rate depends on the lift amount of the exhaust valve 9, the increase in the basic residual gas rate is secondarily increased with respect to the valve overlap period.

  In step 12, a gain 2 [anonymous number] is calculated by referring to a map having the contents shown in FIG. 10 from the engine speed Ne and the charging efficiency ηc. Here, the gain 2 represents a gain for increasing the basic residual gas rate. As shown in FIG. 10, the gain 2 is a value that increases as the rotation speed decreases and the charging efficiency (low load) increases, and decreases as the rotation speed increases and the charging efficiency (high load) increases. The reason why the gain 2 increases as the rotational speed decreases under the condition that the charging efficiency ηc is constant is as follows. That is, even when the valve overlap period [degCA] is the same, the lower the rotational speed Ne, the longer the time [s] during the valve overlap. This is because the time during which the burned gas blows back into the combustion chamber 10 is increased by the amount of time during the valve overlap, and the increase in the basic residual gas rate is increased.

  On the other hand, the reason why the gain 2 becomes smaller as the filling efficiency ηc is higher under the condition where the rotational speed Ne is constant is as follows. That is, the higher the charging efficiency ηc, the higher the intake pressure and the lower the differential pressure from the exhaust pressure. This is because the amount of burned gas that blows back to the combustion chamber 10 (the increase in the residual gas rate) decreases as the differential pressure decreases.

  In step 13, the basic residual gas rate increase is multiplied by gain 2, that is, the residual gas rate increase MBTRGROL [%] during valve overlap is calculated by the following equation.

MBTRGROL = Increase in basic residual gas rate × Gain 2 (15)
Expression (15) is the same as the above expression (12).

  On the other hand, when there is no valve overlap in step 9, the routine proceeds to step 14 where zero is set in the remaining gas rate MBTRGRNO at the time of min (IVO, EVC).

  In step 15, the residual gas rate MBTRGR [%] is calculated by adding the remaining gas rate MBTRGRNO during min (IVO, EVC) calculated in step 8 and the increase amount of the residual gas rate during valve overlap MBTRGROL calculated in steps 13 and 14. calculate. That is, MBTRGR is calculated by the following equation.

MBTRGR = MBTRGRNO + MBTRGROL (16)
Expression (16) is the same as the above expression (10).

  The residual gas rate MBTRGR calculated in this way is stored in the memory. The charging efficiency ηc used in FIG. 6 is already calculated because the engine controller 41 has already been calculated for other control, and the calculated value is used. When the engine controller 41 has not calculated the charging efficiency ηc, a known calculation method may be used as described above.

  Next, the flowchart of FIG. 11 is for calculating the ignition timing command value ADV. The flow in FIG. 11 is executed following the flow in FIG. 6 at regular time intervals (for example, every 10 ms).

  In step 21, the basic ignition timing ADV0 [degCA (BTDC)] at which MBT is obtained is calculated from the engine load and the rotational speed Ne by referring to a map having the contents shown in FIG. The engine load may be the charging efficiency ηc described above, the basic fuel injection pulse width Tp, the intake air amount Qa, or the like.

  In step 22, the ignition timing correction amount HOS [degCA] is calculated by referring to a table having the contents shown in FIG. 13 from the residual gas ratio (already calculated by the flow of FIG. 6). The ignition timing correction amount HOS is a value for correcting the basic ignition timing ADV0 to the advance side. As shown in FIG. 13, the ignition timing correction amount HOS is a value that increases as the residual gas ratio increases from a predetermined value d (positive value). The predetermined value d is set by conformance. Explaining the reason for the characteristics shown in FIG. 13, the residual gas rate cannot be made zero, and there is a certain amount of residual gas rate. When the residual gas rate at this time is a predetermined value d, the basic ignition timing ADV0 is an ignition timing adapted to obtain MBT even when the residual gas rate is the predetermined value d. For this reason, as the residual gas ratio becomes larger than the predetermined value d, the combustion state of the unburned gas in the combustion chamber 10 becomes worse and the combustion speed decreases. Therefore, by correcting the basic ignition timing ADV0 to the advance side by the amount by which the residual gas ratio is larger than the predetermined value d, the residual gas ratio is predetermined in order to improve the combustion state and prevent the combustion speed from decreasing. The ignition timing correction amount HOS is increased as the value d becomes larger.

  In step 23, a value obtained by adding the ignition timing correction amount HOS to the basic ignition timing ADV0 is used as an ignition timing command value ADV [degCA (BTDC)], that is, the ignition timing command value ADV is calculated by the following equation.

ADV = ADV0 + HOS (17)
The reason why the ignition timing correction amount HOS is added to the basic ignition timing ADV0 in the equation (17) is as follows. That is, since the ignition timing command value ADV is a value [degCA (BTDC)] measured from TDC (compression top dead center) to the advance side, ADV0 is used to advance the basic ignition timing ADV with the ignition timing correction amount HOS. This is because it is necessary to add to.

  In a flow (not shown) provided in the engine controller 41, the ignition timing command value ADV calculated in this way is output to the power transistor of the ignition device 13. The power transistor is provided on the primary side of the ignition coil 15, and spark ignition is performed by the spark plug 14 by cutting off the primary side current of the ignition coil 15 at the timing of the ignition timing command value ADV.

  Here, the effect of this embodiment is demonstrated.

  The present embodiment is premised on an engine residual gas rate estimation device including VTC mechanisms 16 and 17 (a valve overlap generation mechanism that generates valve overlap in which the open periods of the intake and exhaust valves overlap). And it comprises a residual gas rate calculating means (41) at the time of min (IVO, EVC), a residual gas rate increase calculating means (41) during valve overlap, and a residual gas rate calculating means (41). The min (IVO, EVC) remaining gas rate calculating means (41) uses the in-cylinder volume, gain 1 and intercept at min (IVO, EVC), and min (IVO, EVC) according to the above equation (11) (primary equation). (EVC) The residual gas rate is calculated. The valve overlap increasing residual gas rate increase calculating means (41) calculates the remaining gas rate increasing increase during valve overlap. The residual gas rate calculating means (41) calculates the residual gas rate as a sum of the calculated residual gas rate at min (IVO, EVC) and the calculated increase in the residual gas rate during the valve overlap. Further, when calculating the remaining gas rate at min (IVO, EVC) by the above equation (11), the gain is set according to the engine speed Ne and the charging efficiency ηc (engine load), and the intercept is filled with the charging efficiency ηc (engine load). ) To determine each. In the present embodiment, the residual gas rate can be directly calculated instead of the residual gas amount. Further, the residual gas amount at the time of min (IVO, EVC) can be calculated from the gas equation of state (m = PV / RT), but in this embodiment, in addition to calculating the in-cylinder volume V, the pressure P, temperature T Is not calculated. That is, in addition to the pressure P and the temperature T, a coefficient for converting the residual gas amount into the residual gas rate is also included, and a gain 1 map having the rotational speed Ne and the charging efficiency ηc (engine load) as parameters is provided. ing. Further, the cylinder gas amount when the cylinder volume is minimum can be similarly calculated from the gas state equation (m = PV / RT), but in this embodiment, the pressure P and the temperature T are not calculated. . That is, in addition to the pressure P and the temperature T, a coefficient for converting the residual gas amount into the residual gas rate is included, and an intercept table having the charging efficiency ηc (engine load) as a parameter is provided. As a result of such simplification, only the gain 1 map and the intercept table should be adapted in the present embodiment. As a result, it is possible to perform adaptation in estimating the residual gas rate at min (IVO, EVC) more easily than the conventional apparatus.

  In the present embodiment, the increase in the residual gas rate during the valve overlap is calculated by the above equation (12), the increase in the basic residual gas rate is calculated according to the valve overlap period, and the gain 2 is set as the engine speed. And the charging efficiency ηc (engine load). The gas flow rate around the exhaust valve during valve overlap can be obtained by integrating the gas flow rate obtained by the orifice flow rate equation over the valve overlap period, but this is not the case in this embodiment. That is, in this embodiment, the relationship between the valve overlap period at the reference operating point and the increase in the residual gas rate during the valve overlap is simply used as a table. The difference due to the differential pressure difference before and after the exhaust valve and the coefficient for converting the residual gas amount into the residual gas rate are replaced with the charging efficiency ηc, the difference due to the valve overlap time (time) is replaced with the rotational speed Ne, and the charging efficiency ηc A gain 2 map using the rotational speed Ne as a parameter is introduced. Then, the residual gas rate increase during valve overlap is calculated by the product of the table value and the gain 2 map value. As a result of this simplification, what should be adapted in the present embodiment is a table representing the relationship between the valve overlap period at the reference operating point and the increase in the residual gas rate, and a gain 2 map. As a result, the adaptation when estimating the increase in the residual gas rate during the valve overlap can be made easier than when the orifice flow rate equation is used as it is as in the conventional apparatus.

  In this embodiment, the engine load is charging efficiency. When the engine controller 41 calculates the charging efficiency ηc such as the target charging efficiency and the actual charging efficiency, it is not necessary to calculate these charging efficiencies again, thereby suppressing an increase in cost.

  In this embodiment, the ignition device 13 includes a basic ignition timing calculation means (41), an ignition timing command value calculation means (41), and an output means (41). The ignition device 13 blows a spark into the combustion chamber. The basic ignition timing calculation means (41) calculates a basic ignition timing ADV0 at which MBT is obtained. The ignition timing command value calculating means (41) calculates the ignition timing command value ADV by correcting the basic ignition timing ADV0 to the advance side with the residual gas rate MBTRGR. The output means (41) outputs the calculated ignition timing command value ADV to the ignition device. As a result, even when there is a large amount of residual gas in the combustion chamber 10 particularly when accelerating from a low load to a partial load, good combustion is achieved without reducing the combustion rate of the unburned gas in the combustion chamber 10. Can be obtained.

(Second Embodiment)
The flow of FIG. 14 is for calculating the residual gas rate of the second embodiment, and is executed at regular intervals (for example, every 10 ms). The same parts as those in the flow of FIG. 6 in the first embodiment are denoted by the same reference numerals.

  The difference from the first embodiment will be mainly described. When there is a valve overlap in step 9, the process proceeds to step 10, and the valve overlap period [degCA] is calculated from EVC and IVO.

  In step 31, a gain 3 [% / degCA · kPa] is calculated by referring to a map having the contents shown in FIG. 15 from the engine speed Ne and the charging efficiency ηc.

  In step 32, the remaining gas rate increase MBTRGROL [%] during the valve overlap is calculated using the valve overlap period, the gain 3 and the intake pressure, that is, the remaining gas rate increase MBTRGROLL during the valve overlap is calculated by the following equation. .

MBTRGROL = Gain 3 × Intake pressure × Valve overlap period
... (18)
The intake pressure [kPa] on the right side of equation (18) is estimated by referring to a predetermined map from the throttle valve opening detected by the throttle sensor 7 and the atmospheric pressure. Alternatively, it may be detected by a pressure sensor provided in the intake collector 4b.

  The above formula (18) is a new simplification of the orifice flow rate formula by the present inventors. Explaining this, the conventional apparatus uses the orifice flow rate equation to calculate the blown back gas amount during the overlap, and calculates the blown back gas amount by the following equation.

Blowing gas amount = proportional constant x exhaust valve differential pressure x exhaust valve lift / exhaust temperature
... (19)
Then, the remaining gas amount during the valve overlap is calculated by integrating the blown back gas amount in (19), and the interval to be integrated is determined by the valve overlap period [degCA] and time (engine speed).

  Here, in the second embodiment, the exhaust valve lift amount on the right side of the equation (19) is substituted for the valve overlap period. If the pressure on the exhaust side of the exhaust valve 9 is assumed to be atmospheric pressure, the exhaust valve front-rear differential pressure on the right side of the equation (19) can be substituted with the intake pressure. Then, the above equation (19) which is the orifice flow rate equation is converted into the following equation.

Blow-back gas amount = proportional coefficient x intake pressure x valve overlap period / exhaust temperature
... (20)
The remaining considerations are the time, the exhaust temperature and the proportionality coefficient on the right side of equation (20), and the coefficient for converting the residual gas amount into the residual gas rate. In the second embodiment, these are included to obtain a gain of 3, and rewritten as in the above equation (18).

  The gain 3 in the equation (18) is expressed by a map of the engine rotational speed Ne and the charging efficiency ηc. In this way, the increase in the residual gas rate during valve overlap can be simply calculated from the above equation (18) and the gain 3 map using the engine speed Ne and the charging efficiency ηc as parameters. .

  Thus, in the second embodiment, the increase in the residual gas rate during the valve overlap is calculated by the above equation (18), and the gain 3 on the right side of the above equation (18) is calculated based on the engine speed Ne and the charging efficiency ηc ( Determine according to engine load. As a result, the increase in the residual gas rate during valve overlap can be easily calculated without performing complicated calculations such as integration as in the conventional apparatus.

  In the second embodiment as well, the charging efficiency ηc is configured as a substitute value for the engine load. As a substitute value of the engine load, for example, volumetric efficiency ηv (target volumetric efficiency or actual volumetric efficiency), basic injection pulse width Tp, intake air amount Qa, accelerator opening, throttle valve opening, and engine torque are used. be able to.

(Third embodiment)
The flow of FIG. 16 is for calculating the residual gas rate of the third embodiment, and is executed at regular time intervals (for example, every 10 ms). The same parts as those in the flow of FIG. 6 in the first embodiment are denoted by the same reference numerals.

The difference from the first embodiment will be mainly described. In steps 41, 42, and 43, by referring to the tables having the contents shown in FIGS. 17, 18, and 19 from the engine speed Ne and the charging efficiency ηc, the coefficient a [% / degCA ² ] and coefficient b [% / degCA] and coefficient c [%].

  In step 44, the remaining gas rate MBTRGRNO [%] at the time of min (IVO, EVC) is calculated by using the following equation using EVC [degCA (ATDC)] and the three coefficients a, b, c.

MBTRGRNO = a × EVC ² + b × EVC + c (21)
Here, the reason why the remaining gas rate MBTRGRNO at min (IVO, EVC) is given by a secondary expression of EVC (exhaust valve closing timing) as shown in the equation (21) will be described.

  In order to obtain the relationship between the EVC (exhaust valve closing timing) and the residual gas rate at min (IVO, EVC) when there is no valve overlap, a simulation test (simulation) is performed, as shown in FIG. A convex quadratic curve characteristic was obtained. In other words, the cylinder volume generally increases secondarily as the EVC goes to the bottom dead center side, which is the more retarded side than TDC (compression top dead center). The relationship between the EVC and the remaining gas ratio at min (IVO, EVC) can be expressed by a quadratic curve.

  Specifically, even if the charging efficiency ηc is a constant condition, when the upper four curve groups shown in FIG. 20 have a relatively low filling efficiency, the lower three curve groups shown in FIG. Is expensive. In any case, the burned gas is exhausted earlier as the rotational speed Ne is higher under the condition that the charging efficiency ηc is constant. Therefore, the crank angle (secondary) where the residual gas ratio becomes the smallest at min (IVO, EVC). The crank angle at the minimum point of the curve advances to the TDC side. Further, the higher the rotational speed Ne under the constant filling efficiency ηc, the more the gas is scavenged (the amount of blown-back gas is reduced), so the residual gas ratio at the minimum point becomes lower. On the other hand, comparing the case of the lower three curve groups having a relatively high filling efficiency ηc and the case of the upper four curve groups having a relatively low filling efficiency ηc, the lower three curve groups having a relatively high filling efficiency. The burnt gas temperature is higher in this case. When the burnt gas temperature T increases from the equation of state of m = PV / RT, the in-cylinder gas amount m decreases (the residual gas ratio decreases).

  Thus, the remaining gas rate at the time of min (IVO, EVC) is determined by the rotational speed Ne, the charging efficiency ηc, and EVC. Therefore, by expressing the three coefficients a, b, and c in the above equation (21) as a map using the engine speed Ne and the charging efficiency ηc as parameters, the remaining gas ratio at min (IVO, EVC) can be simply calculated. It became possible to calculate.

  The third embodiment is based on the assumption of an engine residual gas rate estimation device that includes VTC mechanisms 16 and 17 (a mechanism that generates valve overlap in which the intake and exhaust valve opening periods overlap). And it comprises a residual gas rate calculating means (41) at the time of min (IVO, EVC), a residual gas rate increase calculating means (41) during valve overlap, and a residual gas rate calculating means (41). The means for calculating the residual gas rate at the time of min (IVO, EVC) uses min (IVO, EVC) and three coefficients a, b, c, and min (IVO, EVC) according to the above equation (21) (secondary equation). Calculate the residual gas rate. The residual gas rate increase calculation means during the valve overlap calculates a residual gas rate increase during the valve overlap. The residual gas ratio calculating means calculates a residual gas ratio by the sum of the calculated residual gas ratio at min (IVO, EVC) and the calculated increase in the residual gas ratio during the valve overlap. Further, when calculating the remaining gas rate at min (IVO, EVC) by the above equation (21), three coefficients a, b, c are determined according to the engine speed Ne and the charging efficiency ηc (engine load). Since the map of the three coefficients a, b, and c should be adapted in the third embodiment, adaptation in estimating the residual gas rate at the time of min (IVO, EVC) is easily performed also in the third embodiment. Can be made.

  In the first embodiment, the in-cylinder volume is regarded as the minimum when min (IVO, EVC) matches TDC regardless of the difference in the rotational speed Ne. Actually, when the rotational speed Ne is high, the error level is slightly shifted. Therefore, in the second embodiment, even when the rotational speed Ne is high, a high estimation accuracy of the residual gas rate at min (IVO, EVC) can be obtained. In other words, the first embodiment corresponds to a quadratic curve approximated by a linear expression. Thus, when approximated by a linear expression, if the rotational speed Ne is not high, sufficient accuracy is obtained. On the other hand, according to the first embodiment, one map and one table are good, but according to the third embodiment, since three maps are required, the ROM capacity is increased as compared with the first embodiment. However, the estimation accuracy of the residual gas rate on the high rotation speed side is improved as compared with the first embodiment.

  In the third embodiment, the charging efficiency ηc is configured as a substitute value for the engine load. As a substitute value of the engine load, for example, volumetric efficiency ηv (target volumetric efficiency or actual volumetric efficiency), basic injection pulse width Tp, intake air amount Qa, accelerator opening, throttle valve opening, and engine torque are used. be able to.

  In the embodiment, the case where the engine 1 includes the intake VTC mechanism and the exhaust VTC mechanism has been described. However, the present invention is not limited to this case. If a variable valve mechanism that can variably adjust the operating angle of the intake valve 8 while maintaining the phase at the center of the operating angle of the intake valve 8 is defined as an “intake VEL mechanism”, the present invention can be applied to the following cases.

<1> For intake VTC only,
<2> For exhaust VTC only,
<3> When an intake VEL mechanism and an exhaust VTC mechanism are provided,
<4> When equipped with an intake VTC mechanism, an intake VEL mechanism, and an exhaust VTC mechanism,
Each of these four cases represents an aspect of the valve overlap generation mechanism.

DESCRIPTION OF SYMBOLS 1 Engine 4a Intake pipe 4b Intake collector 5 Throttle valve 12 Fuel injection valve 13 Ignition device 14 Spark plug 15 Ignition coil 16 Intake VTC mechanism (valve overlap generation mechanism)
17 Exhaust VTC mechanism (valve overlap generation mechanism)
21b Exhaust pipe 41 Engine controller (min (IVO, EVC) remaining gas rate calculating means, valve overlap remaining gas rate increase calculating means, remaining gas rate calculating means, basic ignition timing calculating means, ignition timing command value calculating means , Output means)

Claims (5)

In an engine residual gas rate estimation device including a valve overlap generation mechanism that generates valve overlap in which the open periods of intake and exhaust valves overlap,
Using min (IVO, EVC) in-cylinder volume, gain 1 and intercept,
Residual gas ratio at min (IVO, EVC) = In-cylinder volume at min (IVO, EVC)
X Gain 1 + by linear expression of intercept or using min (IVO, EVC) and three coefficients a, b, c
Residual gas ratio at min (IVO, EVC) = a × min (IVO, EVC) ^ 2
+ B × min (IVO, EVC) + c
A min (IVO, EVC) residual gas rate calculating means for calculating a residual gas rate at min (IVO, EVC) according to the quadratic equation of:
A residual gas rate increase calculation means for calculating a residual gas rate during the valve overlap;
A residual gas rate calculating means for calculating a residual gas rate as a sum of the calculated residual gas rate during min (IVO, EVC) and the calculated increase in the residual gas rate during the valve overlap,
When calculating the residual gas rate at min (IVO, EVC) by the primary equation, the gain 1 is determined according to the engine speed and the engine load, and the intercept is determined according to the engine load. (IVO, EVC) When calculating the residual gas rate, the three coefficients a, b, c are determined according to the engine speed and the engine load. The increase in the residual gas rate during the valve overlap,
Increase in residual gas rate during valve overlap = increase in basic residual gas rate x gain 2
And calculating with the formula
The increase in the basic residual gas rate is calculated according to the valve overlap period,
2. The engine residual gas rate estimating device according to claim 1, wherein the gain 2 is determined according to an engine speed and an engine load. The increase in the residual gas rate during the valve overlap,
Increase in residual gas rate during valve overlap = gain 3 x intake pressure
2. The engine residual gas rate estimating apparatus according to claim 1, wherein the gain 3 is determined according to an engine rotation speed and an engine load while being calculated by an equation of a valve overlap period.   The engine residual gas rate estimating apparatus according to any one of claims 1 to 3, wherein the engine load is charging efficiency. An ignition device that blows sparks into the combustion chamber;
Basic ignition timing calculation means for calculating basic ignition timing for obtaining MBT;
5. An ignition timing command value for calculating an ignition timing command value by correcting the basic ignition timing to an advance side with a residual gas rate estimated by the residual gas rate estimation device according to any one of claims 1 to 4. A calculation means;
An ignition timing control device comprising: output means for outputting the calculated ignition timing command value to the ignition device.

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