JP2007002685A - Ignition timing control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To promote warm-up of a catalyst while sufficiently securing combustion stability. <P>SOLUTION: During catalyst warm-up, cylinder inner pressure P and a crank angle θ are obtained (step 110). Next, a heat generation rate dQ/dθ is determined based on the cylinder inner pressure P (step 112). The maximum value dQmax is then determined based on the heat generation rate dQ/dθ for one cycle (step 116). In a case where the maximum value dQmax is a prescribed value dQmaxthr or less, ignition timing SA is advanced (step 120). In a case where the maximum value dQmax is larger than the prescribed value dQmaxthr, the ignition timing SA is delayed (step 122). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ignition timing control device for an internal combustion engine, and more particularly to ignition timing control suitable for warming up a catalyst.

  It is desirable to complete the warm-up of the catalyst at an early stage when the internal combustion engine is cold started. Devices that delay the ignition timing and promote the temperature rise of the catalyst are known. Further, it is necessary to ensure combustion stability when the catalyst is warmed up. Specifically, it is necessary to keep combustion fluctuations (also referred to as “torque fluctuations”) within an allowable range. Thus, an ignition timing control device that retards the ignition timing to a limit determined based on angular velocity fluctuation data is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-107838 JP-A-8-86265 JP 59-136544 A JP 2004-332659 A

  However, as a factor that the angular velocity fluctuates, in addition to the above-described combustion fluctuation, tire rotation fluctuation can be considered. For this reason, it is difficult to accurately separate the factor of the combustion fluctuation from the fluctuation of the angular velocity. Therefore, the combustion state cannot be sufficiently grasped only by detecting the angular velocity fluctuation data. As a result, there may occur a situation where combustion stability cannot be sufficiently ensured when the catalyst is warmed up.

  The present invention has been made to solve the above-described problems, and an object thereof is to promote warm-up of a catalyst while sufficiently ensuring combustion stability.

In order to achieve the above object, a first invention is an ignition timing control device for an internal combustion engine,
In-cylinder pressure detecting means for detecting in-cylinder pressure;
A heat generation rate calculating means for calculating a heat generation rate based on the in-cylinder pressure detected by the in-cylinder pressure detecting means;
Maximum value calculating means for calculating the maximum value of the heat release rate in one cycle;
And ignition timing control means for retarding or advancing the ignition timing based on the maximum value of the heat generation rate calculated by the maximum value calculation means when the catalyst is warmed up.

The second invention is an ignition timing control device for an internal combustion engine,
In-cylinder pressure detecting means for detecting in-cylinder pressure;
A crank angle sensor for detecting the crank angle;
Based on the relationship between the in-cylinder volume and the in-cylinder pressure detected by the in-cylinder pressure detecting unit, a heat generation rate calculating unit that calculates a heat generation rate for each crank angle;
Maximum value calculating means for calculating the maximum value of the heat release rate in one cycle;
And ignition timing control means for retarding or advancing the ignition timing based on the maximum value of the heat generation rate calculated by the maximum value calculation means when the catalyst is warmed up.

  In a third aspect based on the first aspect, the ignition timing control means retards the ignition timing when the maximum value of the heat generation rate is larger than a predetermined value, and the maximum value is If it is less than the predetermined value, the ignition timing is advanced.

  According to the first and second aspects of the invention, when the catalyst is warmed up, the ignition timing is retarded or advanced based on the maximum value of the heat generation rate. The maximum value of the heat generation rate has a correlation with the combustion stability. Therefore, it is possible to promote the warm-up of the catalyst while ensuring sufficient combustion stability.

  According to the third invention, when the maximum value of the heat generation rate is larger than a predetermined value, the warm-up of the catalyst can be promoted by retarding the ignition timing. Further, when the maximum value of the heat generation rate is not more than a predetermined value, combustion stability can be sufficiently ensured by advancing the ignition timing. Therefore, both promotion of catalyst warm-up and sufficient securing of combustion stability can be achieved.

  Embodiments of the present invention will be described below with reference to the drawings. In addition, the same code | symbol is attached | subjected to the element which is common in each figure, and the overlapping description is abbreviate | omitted.

[Description of system configuration]
FIG. 1 is a diagram for explaining a system configuration according to an embodiment of the present invention. As shown in FIG. 1, the system according to the present embodiment includes an internal combustion engine 1. The internal combustion engine 1 includes a cylinder block 6 having a plurality of cylinders 2. FIG. 1 shows only one cylinder among a plurality of cylinders.

A piston 4 is provided inside each cylinder 2. The piston 4 is connected to the crankshaft 12 via a crank mechanism. A crank angle sensor 14 is provided in the vicinity of the crankshaft 12. The crank angle sensor 14 is configured to detect a rotation angle (hereinafter referred to as “crank angle”) CA (deg) of the crankshaft 12.
The cylinder block 6 is provided with a water temperature sensor 10. The water temperature sensor 10 is configured to detect the temperature Tw of the cooling water circulating through the internal combustion engine 1.

  A cylinder head 8 is assembled to the upper part of the cylinder block 6. A space from the upper surface of the piston 4 to the cylinder head 8 forms a combustion chamber 16. The cylinder head 8 is provided with a spark plug 18 that ignites the air-fuel mixture in the combustion chamber 16. An in-cylinder pressure sensor 17 is provided in the vicinity of the combustion chamber 16. The in-cylinder pressure sensor 17 is configured to detect a pressure (hereinafter referred to as “in-cylinder pressure”) P in the combustion chamber 16.

  The cylinder head 8 includes an intake port 20 that communicates with the combustion chamber 16. An intake valve 22 is provided at a connection portion between the intake port 20 and the combustion chamber 16. An intake passage 28 is connected to the intake port 20. An injector 26 for injecting fuel is provided near the intake port 20. A surge tank 30 is provided in the middle of the intake passage 28.

  A throttle valve 32 is provided upstream of the surge tank 30. The throttle valve 32 is an electronically controlled valve that is driven by a throttle motor 34. The throttle valve 32 is driven based on the accelerator opening AA detected by the accelerator opening sensor 38. In the vicinity of the throttle valve 32, a throttle opening sensor 36 is provided. The throttle opening sensor 36 is configured to detect the throttle opening TA. An air flow meter 40 is provided upstream of the throttle valve 32. The air flow meter 40 is configured to detect the intake air amount GA. An air cleaner 42 is provided upstream of the air flow meter 40.

The cylinder head 8 includes an exhaust port 44 that communicates with the combustion chamber 16. An exhaust valve 46 is provided at a connection portion between the exhaust port 44 and the combustion chamber 16. An exhaust passage 50 is connected to the exhaust port 44. A catalyst 54 is provided in the exhaust passage 50.
An air-fuel ratio sensor 52 is provided upstream of the catalyst 54. An oxygen sensor 56 is provided downstream of the catalyst 54. The air-fuel ratio sensor 52 is configured to detect the exhaust air-fuel ratio. The oxygen sensor 56 is configured to invert the output according to the presence or absence of oxygen. Further, the catalyst 54 is provided with a catalyst bed temperature sensor 55 for detecting the catalyst bed temperature.

Further, the system of the present embodiment includes an ECU (Electronic Control Unit) 60 as a control device.
An ignition plug 18, an injector 26, a throttle motor 34, and the like are connected to the output side of the ECU 60. On the input side of the ECU 60, a water temperature sensor 10, a crank angle sensor 14, an in-cylinder pressure sensor 17, a throttle opening sensor 36, an accelerator opening sensor 38, an air flow meter 40, an air-fuel ratio sensor 52, a catalyst bed temperature sensor 55, an oxygen sensor. 56 etc. are connected. The ECU 60 executes overall control of the internal combustion engine such as fuel injection control and ignition timing control based on the output of each sensor.
Further, the ECU 60 calculates the engine speed NE based on the output of the crank angle sensor 14.
Further, the ECU 60 calculates the load KL of the internal combustion engine 1 based on the accelerator opening AA detected by the accelerator opening sensor 38 and the like.
Further, the ECU 60 calculates a heat generation rate based on the in-cylinder pressure P detected by the in-cylinder pressure sensor 17 (described later). The ECU 60 includes a RAM (not shown). The RAM stores the calculated heat generation rate.

[Features of the embodiment]
When the internal combustion engine 1 is cold started, the ignition timing SA is retarded, so that the warm-up of the catalyst 54 can be completed early. However, when the catalyst is warmed up, it is necessary to promote the temperature rise of the catalyst bed temperature and to ensure combustion stability. Therefore, it is necessary to control the ignition timing SA so that the combustion stability is sufficiently ensured.

The present inventor has found that there is a correlation between combustion fluctuation (torque fluctuation) and the maximum value dQmax of the heat generation rate in one cycle. That is, it has been found that there is a correlation between the maximum value dQmax and the combustion stability. FIG. 2 is a diagram showing the relationship between the torque fluctuation value TQ and the maximum value dQmax of the heat generation rate. FIG. 3 is a graph showing the relationship between the ignition timing SA and the maximum heat generation rate dQmax.
As described above, in order to promote the temperature increase of the catalyst bed temperature, it is preferable to retard the ignition timing SA. As shown in FIG. 3, the maximum value dQmax decreases as the ignition timing SA is retarded. Further, as shown in FIG. 2, the torque fluctuation value TQ increases as the maximum value dQmax decreases. That is, the smaller the maximum value dQmax is, the larger the combustion fluctuation becomes, and the combustion becomes unstable.

Therefore, in the present embodiment, the ignition timing SA is controlled based on the maximum value dQmax. Specifically, when the maximum value dQmax is larger than the predetermined value dQmaxthr, the torque fluctuation value TQ is small. The predetermined value dQmaxthr is a value determined by the allowable limit of the torque fluctuation value TQ. Therefore, in this case, the ignition timing SA is retarded by giving priority to the promotion of catalyst warm-up.
On the other hand, when the maximum value dQmax is equal to or less than the predetermined value dQmaxthr, the torque fluctuation value TQ is large. Therefore, in this case, the ignition timing SA is advanced with priority given to ensuring combustion stability.

Here, the calculation method of the maximum value dQmax of the heat release rate described above will be described.
The heat generation rate dQ / dθ at a certain crank angle θ can be expressed as the following equation (1). That is, the heat release rate dQ / dθ at a certain crank angle θ can be calculated based on the relationship between the in-cylinder pressure P and the in-cylinder volume V.
dQ / dθ = {к / (к-1)} × P (dV / dθ) + {1 / (к-1)} × V (dP / dθ) (1)
In the above formula (1), к is a specific heat ratio, for example, about 1.4. This specific heat ratio к is obtained by dividing the constant pressure specific heat Cp by the constant volume specific heat Cv. In the above equation (1), P is the in-cylinder pressure, V is the in-cylinder volume, and θ is the crank angle.
According to the above equation (1), the heat generation rate dQ / dθ for one cycle, that is, the crank angle is 0-720 (deg) is calculated.
Then, the maximum value dQmax of the calculated heat release rate dQ / dθ for one cycle is calculated.

  Therefore, according to the first embodiment, the heat generation rate dQ / dθ is calculated based on the in-cylinder pressure P, and the maximum value dQmax of the heat generation rate dQ / dθ for one cycle is calculated. Then, based on the maximum value dQmax, the ignition timing SA is retarded or advanced. That is, the ignition timing SA is controlled based on the correlation between the maximum value dQmax and the combustion fluctuation (torque fluctuation value TQ). Thereby, combustion stability can be sufficiently ensured while promoting catalyst warm-up.

[Specific processing in the embodiment]
FIG. 4 is a flowchart showing a routine executed by ECU 60 in the present embodiment.
According to the routine shown in FIG. 4, first, the engine speed NE, the load KL, and the cooling water temperature Tw, which are the current operating state, are read (step 100). Here, the ECU 60 can calculate the engine speed NE based on the crank angle detected by the crank angle sensor 14.

  Next, it is determined whether or not the previous ignition timing SA is stored in the ECU 60 (step 102). In this step 102, when this routine is started last time, it is determined whether or not there is an ignition timing SA advanced or retarded in step 120 or 122 described later. If it is determined in step 102 that the previous ignition timing SA is stored, the previous ignition timing is set as the ignition timing SA (step 104).

  On the other hand, if it is determined in step 102 that the previous ignition timing SA is not stored, the standard ignition timing SAbse is set as the ignition timing SA (step 106). This standard ignition timing SAbse is not an increase in the catalyst bed temperature, but is an ignition timing determined in consideration of ensuring combustion stability (see FIG. 3). Therefore, even when the previous ignition timing SA is stored, sufficient combustion stability can be ensured.

  Next, it is determined whether or not the catalyst is warming up (step 108). In step 108, it is determined whether or not the coolant temperature Tw acquired in step 100 is lower than a predetermined temperature (for example, 60 ° C.). When the coolant temperature Tw is lower than the predetermined temperature, it is determined that the catalyst is warming up. If it is determined in step 108 that the catalyst is not warmed up, that is, if it is determined that the catalyst is warmed up, this routine is terminated.

On the other hand, if it is determined in step 108 that the catalyst is warming up, the in-cylinder pressure P and the crank angle θ are acquired (step 110).
Next, the heat release rate dQ / dθ at the crank angle θ is calculated according to the above equation (1) (step 112). In step 112, the heat generation rate dQ / dθ is calculated based on the relationship between the in-cylinder pressure P and the in-cylinder volume V. The ECU 60 can determine the in-cylinder volume V from the crank angle θ based on a map stored in the ECU 60 in advance. The heat release rate dQ / dθ calculated in step 112 is stored in the RAM in the ECU 60.

  Next, it is determined whether or not the heat generation rate dQ / dθ for one cycle has been calculated (step 114). That is, it is determined whether or not the heat generation rate dQ / dθ for one cycle is stored in the RAM. If it is determined in step 114 that the heat generation rate dQ / dθ for one cycle has not been calculated, the process returns to step 108. Thereafter, the crank angle θ is obtained, and the heat generation rate dQ / dθ is calculated.

  On the other hand, if it is determined in step 114 that the heat generation rate dQ / dθ for one cycle has been calculated, the maximum value dQmax of the heat generation rate dQ / dθ for one cycle is calculated (step 116). . After calculating the maximum value dQmax, the heat release rate dQ / dθ of each crank angle stored in the RAM is cleared.

  Next, it is determined whether or not the maximum value dQmax calculated in step 116 is larger than a predetermined value dQmaxthr (step 118). The predetermined value dQmaxthr is a value determined according to the allowable limit of the torque fluctuation value TQ, as shown in FIG. Therefore, in step 118, it is determined based on the maximum value dQmax whether or not the torque fluctuation value TQ is larger than the allowable range, that is, whether or not sufficient combustion stability can be ensured.

  If it is determined in step 118 that the maximum value dQmax is equal to or less than the predetermined value dQmaxthr, it is determined that the torque fluctuation value TQ is larger than the allowable limit (see FIG. 2). In this case, the ignition timing SA is advanced by a predetermined angle ΔSArtd (step 120). Thereby, priority is given to ensuring combustion stability rather than raising the catalyst bed temperature.

  On the other hand, if it is determined in step 118 that the maximum value dQmax is larger than the predetermined value dQmaxthr, it is determined that the torque fluctuation value TQ is smaller than the allowable limit (see FIG. 2). In this case, the ignition timing SA is retarded by a predetermined angle ΔSArtd (step 122). Thereby, priority is given to raising the catalyst bed temperature.

  When this routine is started after the next time, the heat generation rate dQ / dθ for one cycle is calculated, and the maximum value dQmax is calculated from the calculated heat generation rate dQ / dθ. The ignition timing SA is retarded or advanced based on the comparison result between the calculated maximum value dQmax and the predetermined value dQmaxthr.

As described above, according to the routine shown in FIG. 4, the heat release rate dQ / dθ is calculated based on the in-cylinder pressure P for each crank angle θ, and the maximum value dQmax of the heat release rate dQ / dθ for one cycle. Is calculated. When the maximum value dQmax is equal to or less than the predetermined value dQmaxthr, it is determined that the torque fluctuation value TQ is large, and the ignition timing SA is advanced. If the maximum value dQmax is larger than the predetermined value dQmaxthr, it is determined that the torque fluctuation value TQ is small, and the ignition timing SA is retarded. That is, the ignition timing SA is controlled based on the correlation between the maximum value dQmax and the combustion fluctuation (torque fluctuation value TQ). Thereby, both promotion of catalyst warm-up and securing of sufficient combustion stability can be achieved.
Further, the method for obtaining the heat generation rate dQ / dθ and its maximum value dQmax as in the present embodiment does not need to be sampled for many cycles, unlike the method for obtaining the variation rate as in the described prior art. For this reason, the ignition timing SA can be easily controlled.

By the way, in the system according to the present embodiment, the heat generation rate dQ / dθ for one cycle is calculated, but the crank angle at which the heat generation rate dQ / dθ is maximized is specified in advance. The heat generation rate dQ / dθ of the crank angle may be read as the maximum value dQmax. Thereby, in addition to the effects obtained in the above-described embodiment, the calculation load on the ECU 60 can be reduced.
In the present embodiment, the engine speed NE is calculated based on the crank angle CA, but it may be detected by an engine speed sensor.
In step 104, it is determined whether the catalyst is warming up based on the cooling water temperature Tw. However, it is determined whether the catalyst is warming up based on the catalyst bed temperature detected by the catalyst bed temperature sensor 55. May be. For example, when the catalyst bed temperature is lower than 400 ° C., it can be determined that the catalyst is warming up.
In steps 120 and 122, the ignition timing SA is uniformly advanced or retarded by a predetermined angle ΔSArtd. However, the ignition timing SA is advanced or retarded according to the difference between the maximum value dQmax and the predetermined value dQmaxthr. The angular amount may be determined.

  In the present embodiment, the ECU 60 executes the process of step 112 so that the “heat generation rate calculating means” in the first and second inventions executes the process of step 116 to execute the first and second steps. The “maximum value calculation means” in the second invention realizes the “ignition timing control means” in the first to third inventions by executing the processing of step 120 or 122, respectively.

It is a figure for demonstrating the system configuration | structure of embodiment of this invention. It is a figure which shows the relationship between the torque fluctuation value TQ and the maximum value dQmax of a heat release rate. It is a figure which shows the relationship between ignition timing SA and the maximum value dQmax of a heat release rate. 4 is a flowchart showing a routine executed by ECU 60 in the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 4 Piston 6 Cylinder block 8 Cylinder head 10 Water temperature sensor 12 Crankshaft 14 Crank angle sensor 16 Combustion chamber 17 In-cylinder pressure sensor 18 Spark plug 20 Intake port 22 Intake valve 26 Injector 28 Intake passage 30 Surge tank 32 Throttle valve 34 Throttle motor 36 Throttle opening sensor 38 Accelerator opening sensor 40 Air flow meter 42 Air cleaner 44 Exhaust port 46 Exhaust valve 50 Exhaust passage 52 Air-fuel ratio sensor 54 Catalyst 55 Catalyst bed temperature sensor 56 Oxygen sensor 60 ECU

Claims (3)

An ignition timing control device for an internal combustion engine,
In-cylinder pressure detecting means for detecting in-cylinder pressure;
A heat generation rate calculating means for calculating a heat generation rate based on the in-cylinder pressure detected by the in-cylinder pressure detecting means;
Maximum value calculating means for calculating the maximum value of the heat release rate in one cycle;
An internal combustion engine comprising: an ignition timing control means for retarding or advancing the ignition timing based on the maximum value of the heat generation rate calculated by the maximum value calculation means when the catalyst is warmed up. Ignition timing control device. An ignition timing control device for an internal combustion engine,
In-cylinder pressure detecting means for detecting in-cylinder pressure;
A crank angle sensor for detecting the crank angle;
Based on the relationship between the in-cylinder volume and the in-cylinder pressure detected by the in-cylinder pressure detecting unit, a heat generation rate calculating unit that calculates a heat generation rate for each crank angle;
Maximum value calculating means for calculating the maximum value of the heat release rate in one cycle;
An internal combustion engine comprising: an ignition timing control means for retarding or advancing the ignition timing based on the maximum value of the heat generation rate calculated by the maximum value calculation means when the catalyst is warmed up. Ignition timing control device. In the ignition timing control device according to claim 1 or 2,
The ignition timing control means retards the ignition timing when the maximum value of the heat generation rate is larger than a predetermined value, and advances the ignition timing when the maximum value is less than the predetermined value. An ignition timing control device for an internal combustion engine, comprising:

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