JP2010127134A - Cylinder egr ratio estimating device of engine, cylinder egr ratio estimating method, ignition timing control device and ignition timing control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for estimating the cylinder EGR ratio of an engine by accurately estimating the cylinder EGR ratio of a transition state, and to provide an ignition timing control device and a method for optimally controlling the ignition timing by using its cylinder EGR ratio. <P>SOLUTION: This EGR ratio estimating device is provided for estimating the cylinder EGR ratio with each cylinder of the engine having an EGR device for recirculating burnt gas exhausted from the engine and flowing in an exhaust passage, in the cylinder by recirculating in an intake passage, and includes storage means (#33111-#33114, #33121-#33124, #33211-#33214 and #33221-#33224) for storing a waste time and a primary delay of a cylinder EGR ratio change when transitionally operating the engine with each cylinder in response to a transitional operation state of the engine, and an each cylinder transitional EGR ratio estimating means (#3) for estimating the cylinder transitional EGR ratio with each cylinder based on the waste time and the primary delay stored with each cylinder. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an apparatus and method for estimating an in-cylinder EGR rate of an engine and an apparatus and method for controlling an ignition timing using the estimated in-cylinder EGR rate.

In order to ignite at an optimal timing, it is necessary to accurately estimate the in-cylinder EGR rate that affects the in-cylinder combustion speed. In Patent Document 1, the in-cylinder EGR rate in a steady state is calculated from the ratio of the intake throttle opening area calculated based on the opening degree of the intake throttle and the EGR valve opening area calculated based on the number of steps of the EGR valve. ing. The in-cylinder EGR rate in the transient state is calculated by correcting the dead time and the first-order lag with respect to the in-cylinder EGR rate in the steady state.
JP 2004-11619 A

  However, the present inventors have found that the desired characteristics cannot be obtained even if the in-cylinder EGR rate in the transient state is estimated as in the past and the ignition timing is controlled based on the estimated value.

  The present invention has been made paying attention to such conventional problems, and an in-cylinder EGR rate estimation device and an in-cylinder EGR rate estimation for an engine that can accurately estimate the in-cylinder EGR rate in a transient state. It is an object of the present invention to provide an ignition timing control device and an ignition timing control method capable of optimally controlling the ignition timing by using the in-cylinder EGR rate.

  The present invention solves the above problems by the following means. In addition, in order to make an understanding easy, although the code | symbol corresponding to embodiment of this invention is attached | subjected, it is not limited to this.

  The present invention provides an EGR rate estimation device that estimates an in-cylinder EGR rate for each cylinder of an engine, which includes an EGR device that recirculates burnt gas discharged from an engine and flowing through an exhaust passage to an intake passage and recirculates the in-cylinder. The storage means (# 33111 to # 33114, # 33121) stores the dead time and first-order lag of the in-cylinder EGR rate change when the engine is transiently operated for each cylinder according to the transient operation state of the engine. To # 33124, # 33211 to # 33214, # 33221 to # 33224) and cylinder-by-cylinder transient EGR for estimating the in-cylinder transient EGR rate for each cylinder based on the dead time and first-order delay stored for each cylinder. Rate estimation means (# 3).

  According to the present invention, the in-cylinder transient EGR rate for each cylinder can be accurately estimated by using the dead time and first-order delay of the in-cylinder EGR rate change when the engine stored in advance is transiently operated. Further, by controlling the ignition timing of each cylinder individually for each cylinder using the in-cylinder transient EGR rate for each cylinder, the ignition timing at the time of transition can be optimally controlled for all the cylinders.

  Hereinafter, the best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing an example of an engine that uses an in-cylinder EGR rate estimating apparatus for an engine according to the present invention.

  The engine 10 includes an exhaust gas recirculation (hereinafter abbreviated as “EGR”) device 40 to which an intake passage 20 and an exhaust passage 30 are connected. The engine 10 is an in-line four-cylinder engine that includes a first cylinder 11, a second cylinder 12, a third cylinder 13, and a fourth cylinder 14. The first cylinder 11 is a cylinder provided close to a crankshaft pulley 16 provided at the tip (left end in FIG. 1) of the crankshaft 15. The first cylinder 11 is provided with a first spark plug 51. The second cylinder 12 is a cylinder adjacent to the first cylinder 11. The second cylinder 12 is provided with a second spark plug 52. The third cylinder 13 is a cylinder adjacent to the second cylinder 12. The third cylinder 13 is provided with a third spark plug 53. The fourth cylinder 14 is a cylinder adjacent to the third cylinder 13. The fourth cylinder 14 is provided with a fourth spark plug 54. The ignition order of the engine 10 is first cylinder 11 → third cylinder 13 → fourth cylinder 14 → second cylinder 12.

  A first fuel injection valve 21 is provided in the first intake port of the intake passage 20. A second fuel injection valve 22 is provided in the second intake port. A third fuel injection valve 23 is provided in the third intake port. A fourth fuel injection valve 24 is provided at the fourth intake port. An intake throttle 25 is disposed upstream of the intake passage 20. The intake throttle 25 exists on the fourth cylinder side and is separated from the first cylinder 11. The opening degree of the intake throttle 25 is detected by an opening degree sensor. An intake throttle opening area is calculated based on this detection signal.

  The EGR device 40 includes an EGR passage 41 and an EGR valve 42.

  The EGR passage 41 connects the exhaust passage 30 and the intake passage 20. An EGR gas recovery port 43 is opened in the exhaust passage 30. In the intake passage 20, an EGR gas discharge port 44 is opened downstream of the intake throttle 25. During engine operation, the intake passage 20 has a negative pressure and the exhaust passage 30 has a positive pressure. Due to this differential pressure, a part of the exhaust gas flowing through the exhaust passage 30 is discharged to the intake passage 20 via the EGR gas recovery port 43 → EGR passage 41 → EGR gas discharge port 44.

  The EGR valve 42 is provided in the middle of the EGR passage 41. The EGR valve 42 is opened and closed by a stepping motor. The opening area of the EGR valve 42 can be calculated based on the number of steps of the stepping motor.

  The controller 70 calculates the intake throttle opening area based on the opening of the intake throttle 25. The controller 70 calculates the opening area of the EGR valve 42 based on the number of steps of the stepping motor. Then, the EGR rate for each cylinder is calculated based on these calculated values. Specific contents will be described later. The controller 70 includes a microcomputer having a central processing unit (CPU), a read only memory (ROM), a random access memory (RAM), and an input / output interface (I / O interface). The controller 70 may be composed of a plurality of microcomputers.

  FIG. 2 is a block diagram showing functions related to the estimation of the in-cylinder EGR rate of the controller.

  The controller 70 calculates the ignition timing correction opening area TEGRAR (# 1). More specifically, the controller 70 detects the intake throttle opening degree driven by the intake throttle drive control (# 11), and calculates the opening area ATPO1 based on the opening degree (# 12). The controller 70 detects the rotational load (# 13), and calculates the coefficient KQEGR based on the rotational load (# 14). Based on the opening area ATPO1 (# 12) and the coefficient KQEGR (# 14), the ignition timing correcting opening area TEGRAR is calculated (# 1).

  Next, the controller 70 estimates the actual EGR rate (# 2). More specifically, the controller 70 calculates the EGR valve opening area REGRAR (# 23) based on the number of steps of the stepping motor for EGR valve driven by the EGR valve drive control (# 22). Based on the EGR valve opening area REGRAR (# 23) and the ignition timing correction opening area TEGRAR (# 1), the actual EGR rate is estimated (# 2).

  Further, the controller 70 estimates the first cylinder actual EGR rate RATEGR1, the second cylinder actual EGR rate RATEGR2, the third cylinder actual EGR rate RATEGR3, and the fourth cylinder actual EGR rate RATEGR4 (# 3). More specifically, when the fuel cut execution flag FCCYL changes from 1 (stops fuel injection) to 0 (stops fuel cut, that is, starts fuel injection) (# 31), the controller 70 counts the number of cycles from that point. However, if the number of cycles is less than the predetermined value DCLEGFC # (# 331), referring to the characteristic map, the dead time immediately after the start of injection of the first cylinder (# 33111) and the first order delay immediately after the start of injection (# 331) 33121), a dead time immediately after the start of injection of the second cylinder (# 33112) and a primary delay immediately after the start of injection (# 33122), a dead time immediately after the start of injection of the third cylinder (# 33113), and a primary delay immediately after the start of injection (# 33123) In addition, the dead time immediately after the start of injection of the fourth cylinder (# 33114) and the first order delay (# 33124) immediately after the start of injection are obtained. The contents of the characteristic map will be described later.

  If the number of cycles is equal to or greater than the predetermined value DCLEGFC # (# 332), referring to the characteristic map, the dead time after the cycle of the first cylinder (# 33211), the first-order delay after the cycle (# 33221), the second Cylinder dead time after cycle elapse (# 33212) and first delay after cycle elapse (# 33222), third cylinder dead time after cycle elapse (# 33213), first cycle delay after cycle elapse (# 33223), and fourth cylinder The dead time after the elapse of the cycle (# 33214) and the first order delay (# 33224) after the elapse of the cycle are obtained.

  FIG. 3 is a diagram for explaining the gas flowing through the cylinder when the fuel injection is resumed after the fuel injection is stopped.

  For example, fuel injection is stopped when the driver returns the accelerator pedal while the vehicle is running. In this state, air (broken line) continues to be supplied to each cylinder of the engine 10 as shown in FIG. At this time, the gas discharged from each cylinder of the engine 10 and flowing through the exhaust passage 30 is also air. This air is discharged from the exhaust passage 30 to the intake passage 20 via the EGR passage 41.

  When the driver depresses the accelerator pedal, fuel injection is resumed. Then, the air-fuel mixture is supplied to each cylinder of the engine 10 and combusted. Then, as shown in FIG. 3B, burned gas (solid line) is discharged from each cylinder of the engine 10. However, immediately after resuming the fuel injection, the burned gas has not yet flowed through the EGR passage 41.

  When a certain amount of time elapses after the fuel injection is resumed, a part of the burned gas flowing through the exhaust passage 30 is released to the intake passage 20 through the EGR passage 41 as shown in FIG. . However, at the time shown in FIG. 3C, the EGR gas has not yet returned to each cylinder of the engine 10.

  When a sufficient time has elapsed after the fuel injection is resumed, as shown in FIG. 3 (D), the EGR gas released into the intake passage 20 returns to each cylinder of the engine 10 together with air.

  FIG. 4 is a diagram showing a result of simulating a change in the in-cylinder EGR rate of each cylinder of the engine when the fuel injection is stopped and then restarted. The time interval of the plot is 0.12 seconds.

  Until time t0, fuel injection is stopped. At this time, the state is as shown in FIG. 3A, and the in-cylinder EGR rate of each cylinder of the engine is zero.

  When fuel injection is resumed at time t0, burnt gas is discharged from each engine cylinder, but until a sufficient time has passed, the state of FIGS. 3 (B) and 3 (C) is maintained. The in-cylinder EGR rate remains zero.

  When sufficient time elapses and time t1 is exceeded, EGR gas recirculates to each cylinder of the engine, and the in-cylinder EGR rates of the fourth cylinder, the second cylinder, and the third cylinder increase. When the time t2 is exceeded, the in-cylinder EGR rate of the first cylinder increases. The time from the start of fuel injection until the in-cylinder EGR rate starts to change is a dead time. Further, the time from when the in-cylinder EGR rate starts to change until it converges is a first order lag. The dead time of the fourth cylinder, the second cylinder, and the third cylinder is the same because the time interval of the plot is relatively large at 0.12 seconds. That is, the dead time of the fourth cylinder, the second cylinder, and the third cylinder is a predetermined time from time t1 to time t2, and the dead time of the second cylinder is longer than the dead time of the fourth cylinder. The wasted time is long. However, since the time intervals of the plots are relatively large at 0.12 seconds, they all overlap the same time. If the time interval is shortened, the precision of dead time can be improved. The dead time of the first cylinder is a predetermined time from time t2 to time t2 plus 0.12 seconds.

  As described above, the ignition order of the engine 10 is as follows: first cylinder → third cylinder → fourth cylinder → second cylinder → first cylinder →. Therefore, the in-cylinder EGR rate is likely to change from the fourth cylinder → the second cylinder → the first cylinder → the third cylinder in the order of the intake stroke. However, actually, as shown in FIG. 4, the order changes in the order of the fourth cylinder → second cylinder → third cylinder → first cylinder. The order of the first cylinder and the third cylinder is switched. This is because the first cylinder is farther away from the EGR gas discharge port 44 than the third cylinder, so that the EGR gas discharged from the EGR gas discharge port 44 is ahead of the first cylinder regardless of the order of the intake stroke. This is because the air is sucked into the third cylinder.

  FIG. 5 is a diagram showing a result of simulating the change in the in-cylinder EGR rate of each engine cylinder when the EGR valve is increased from a very small opening degree for each engine speed, and FIG. The speed is 1000 rpm, FIG. 5B shows the engine rotation speed of 1600 rpm, and FIG. 5C shows the engine rotation speed of 3200 rpm.

  As shown in FIG. 5A, when the engine speed is 1000 rpm, the opening degree of the EGR valve is very small until time t0, and the in-cylinder EGR rate is about 2%. When the opening degree of the EGR valve is increased at time t0, the amount of EGR gas discharged from the EGR gas discharge port 44 to the intake passage 20 via the EGR valve increases. Does not reflux. When sufficient time elapses and time t11 is exceeded, the amount of EGR gas recirculated to each engine cylinder increases, and the in-cylinder EGR rates of the fourth cylinder, the second cylinder, and the third cylinder increase. When the time t12 is exceeded, the in-cylinder EGR rate of the first cylinder increases. The time from when the opening degree of the EGR valve is changed until the in-cylinder EGR rate starts to change is a dead time. Further, the time from when the in-cylinder EGR rate starts to change until it converges is a first order lag.

  As shown in FIG. 5B, when the engine speed is 1600 rpm, the opening of the EGR valve is expanded at time t0, and when a sufficient time has passed and time t21 is exceeded, EGR is returned to each engine cylinder. The gas amount increases, and the in-cylinder EGR rate of the fourth cylinder, the second cylinder, and the third cylinder increases. When the time t22 is exceeded, the in-cylinder EGR rate of the first cylinder increases. Compared to FIG. 5A, it can be seen that the dead time is reduced. It can also be seen that the first order lag is also reduced.

  As shown in FIG. 5C, when the engine rotation speed is 3200 rpm, the opening of the EGR valve is expanded at time t0, and when a sufficient time has passed and time t31 is exceeded, EGR is returned to each cylinder of the engine. The gas amount increases, and the in-cylinder EGR rate of the fourth cylinder, the second cylinder, and the third cylinder increases. When the time t32 is exceeded, the in-cylinder EGR rate of the first cylinder increases. It can be seen that the dead time is further reduced as compared with FIG. It can also be seen that the first-order lag is even smaller.

  FIG. 5 shows a change in the in-cylinder EGR rate of each cylinder of the engine when the EGR valve is increased from a very small opening degree. The tendency of the change is when the fuel injection is stopped and restarted. Is the same. That is, as the engine speed increases, the dead time and first-order lag decrease.

  3A when the fuel injection is stopped, and the burned gas is discharged from the cylinder after the fuel injection is restarted. Therefore, the time from when the fuel injection is restarted until the in-cylinder EGR rate starts to change. The dead time is long. That is, the dead time immediately after the start of fuel injection (# 33111, # 33112, # 33113, # 33114) immediately after resuming fuel injection is relatively large.

  On the other hand, after a certain cycle has elapsed since the fuel injection was resumed, a large amount of burned gas flows from the exhaust passage 30 to the EGR gas recovery port 43 and the EGR valve 42. However, the flow rate is reduced by the EGR valve 42 and the EGR gas flowing from the EGR valve 42 through the EGR gas discharge port 44 and the intake passage 20 is reduced. When the opening degree of the EGR valve 42 is increased from this state, the dead time, which is the time from when the opening degree of the EGR valve is changed to when the in-cylinder EGR rate starts to change, is relatively short, and the EGR gas is supplied to each cylinder. To reflux.

  The above-mentioned tendency is observed in the dead time and the primary delay depending on the operation state such as the elapsed cycle after restarting the fuel injection and the engine speed. Specific numerical values may be set through simulations and experiments and stored in the ROM as a characteristic map.

  Then, the effect by this embodiment is demonstrated. First, in order to facilitate understanding of the present embodiment, a comparative embodiment will be described with reference to FIG.

  Fuel injection is stopped until time t0, and fuel injection is resumed at time t0 (FIG. 7A). At this time, the actual in-cylinder EGR rate of each cylinder changes as shown by a thin solid line in FIG. On the other hand, in the comparative embodiment, only the in-cylinder EGR rate of the representative cylinder is estimated. In FIG. 7, the third cylinder is the representative cylinder, and the in-cylinder EGR rate of the third cylinder is estimated as indicated by a thick solid line. Based on the estimated EGR rate, the ignition timing of all cylinders is uniformly controlled. When the ignition timing is controlled in this way, the ignition timing of the third cylinder, which is the representative cylinder, matches the optimal ignition timing as shown in FIG. 7 (C-3). However, in the fourth cylinder, as shown in FIG. 7 (C-1), the optimum ignition timing indicated by the broken line is shifted to the retard side. Even in the second cylinder, as shown in FIG. 7 (C-2), the optimum ignition timing indicated by the broken line is shifted to the retard side. In the first cylinder, as shown in FIG. 7 (C-4), the optimum ignition timing indicated by the broken line is shifted to the advance side.

  FIG. 6 is a timing chart when the ignition timing is controlled by the in-cylinder EGR rate estimated in the present embodiment.

  The fuel injection is stopped until time t0, and the fuel injection is restarted at time t0 (FIG. 6A). At this time, the actual in-cylinder EGR rate of each cylinder changes as shown by a thin solid line in FIG. In contrast, in this embodiment, the in-cylinder EGR rate is estimated for each cylinder. Then, the ignition timing of each cylinder is individually controlled based on the estimated EGR rate for each cylinder. By doing so, as shown in FIGS. 7 (C-1) to 7 (C-4), the ignition timing of each cylinder coincides with the optimum ignition timing.

  Without being limited to the embodiments described above, various modifications and changes are possible within the scope of the technical idea, and it is obvious that these are also included in the technical scope of the present invention.

  For example, in the above description, the case where the opening degree of the EGR valve is increased is described as an example, but the same technical idea can be applied even when the opening is decreased.

  In the above description, the case where fuel injection is started from the stop has been described as an example, but the same technical idea can be applied even when the fuel is stopped from injection.

  Furthermore, the number of cylinders of the engine is merely an example, and a 6-cylinder engine or an 8-cylinder engine may be used.

It is a figure which shows an example of the engine which uses the in-cylinder EGR rate estimation apparatus of the engine by this invention. The function concerning in-cylinder EGR rate estimation of a controller is represented as a block diagram. It is a figure explaining the gas which flows through a cylinder, when fuel injection is restarted after stopping fuel injection. It is a figure which shows the result of having simulated the change of the in-cylinder EGR rate of each cylinder of an engine when fuel injection is stopped and restarted. It is a figure which shows the result of having simulated the change of the in-cylinder EGR rate of each cylinder of an engine when an opening degree of an EGR valve is increased from a minute opening degree for each engine speed. It is a figure which shows a timing chart when ignition timing is controlled by the in-cylinder EGR rate estimated in this embodiment. It is a figure explaining a comparative form.

Explanation of symbols

10 engine 40 exhaust gas recirculation (EGR) device 70 controller # 33111 to # 33114 dead time storage means immediately after injection start # 33112 to # 33124 first order lag storage means immediately after injection start # 33211 to # 33214 dead time storage means after cycle elapse # 33221 ~ # 33224 First-order lag storage means after elapse of cycle # 3 Transient EGR rate estimation means for each cylinder

Claims (7)

An EGR rate estimating device that estimates an in-cylinder EGR rate for each cylinder of an engine, which includes an EGR device that recirculates burnt gas discharged from an engine and flowing through an exhaust passage to an intake passage and recirculates it into the cylinder,
Storage means for storing, for each cylinder, the dead time and first-order lag of the in-cylinder EGR rate change when the engine is transiently operated, according to the transient operation state of the engine;
A cylinder-by-cylinder transient EGR rate estimation means for estimating an in-cylinder transient EGR rate for each cylinder based on the dead time and first-order delay stored for each cylinder;
An in-cylinder EGR rate estimation device for an engine having The in-cylinder EGR rate estimation device for an engine according to claim 1,
The storage means stores the dead time in the transient operation state in which the fuel injection is started from the stop as a larger value than the dead time in the transient operation state in which the opening degree of the EGR valve is changed while continuing the fuel injection.
An in-cylinder EGR rate estimation device for an engine characterized by the above. In the in-cylinder EGR rate estimation device for an engine according to claim 1 or 2,
The storage means stores the dead time and the first-order lag as small values as the engine rotation speed increases.
An in-cylinder EGR rate estimation device for an engine characterized by the above. The in-cylinder EGR rate estimation device for an engine according to any one of claims 1 to 3,
The storage means is in the case of being away from the EGR gas discharge port in the order of the first cylinder-second cylinder-third cylinder-fourth cylinder, and when the ignition order is 1-3-4-2. The cylinder-specific dead time is stored as a small value in the order of the fourth cylinder-second cylinder-third cylinder-first cylinder.
An in-cylinder EGR rate estimation device for an engine characterized by the above. An apparatus for controlling an ignition timing using a cylinder-by-cylinder transient EGR rate estimated by an in-cylinder EGR rate estimation device for an engine according to any one of claims 1 to 4,
Ignition timing control means for individually controlling the ignition timing of each cylinder according to the cylinder-by-cylinder transient EGR rate;
An ignition timing control device for an engine. An EGR rate estimation method for estimating an in-cylinder EGR rate for each cylinder of an engine including an EGR device that recirculates burnt gas discharged from an engine and flowing through an exhaust passage to an intake passage and recirculates the in-cylinder,
A storage step of storing, for each cylinder, the dead time and first-order lag of the in-cylinder EGR rate change when the engine is transiently operated, according to the transient operation state of the engine;
A cylinder-by-cylinder transient EGR rate estimation step of estimating a transient EGR rate for each cylinder based on the dead time and primary delay stored for each cylinder;
An in-cylinder EGR rate estimation method for an engine having A method for controlling ignition timing using a cylinder-by-cylinder transient EGR rate estimated by an in-cylinder EGR rate estimation method for an engine according to claim 6,
An ignition timing control step for individually controlling the ignition timing of each cylinder according to the cylinder-by-cylinder transient EGR rate;
An ignition timing control method for an engine.

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