JPH11125141A - Method and device for detecting ignition timing of real fuel in engine and method and device for controlling fuel injection timing in engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent dispersion in ignition timing of each injector by computing heat generation rate from pressure data in a cylinder, calculating ignition timing from zero cross point of the heat generation rate and controlling a fuel injection timing so that it may agree with the aimed ignition timing. SOLUTION: The data of internal pressure Pc in a cylinder are stored in a scope of 360 deg. around top dead center in compression stroke of each cylinder (more than 540 and less than 180 in count value). The heat generation rate q in the cylinder is calculated from the internal pressure Pc in the cylinder to be detected successively based on the stored data, and volume in the cylinder to be computed successively and their change rates. Then, a zero cross point Td of the heat generation rate q is determined as an ignition timing for real fuel, and the fuel injection timing for injectors is controlled so that the ignition timing based on the following BTDC interruption signal may agree with the aimed ignition timing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a device for detecting the actual fuel ignition timing of an engine, and a method and a device for controlling the fuel injection timing of an engine.

[0002]

2. Description of the Related Art When fuel is injected into a combustion chamber by an injector, the combustible air-fuel mixture formed in the combustion chamber during the ignition delay starts combustion at a time, so that the pressure in the combustion chamber rapidly increases after the ignition delay. As the fuel burns rapidly and the temperature of the combustion gas becomes higher, the generation of NOx increases. Therefore, in order to reduce the amount of NOx generated, it is necessary to shorten the ignition delay period and lengthen the combustion period, or to increase the ignition delay. It is conceivable to reduce the amount of air-fuel mixture formed during the period.
However, with these measures, if the amount of fuel injected at a time is constant, if a large amount of air-fuel mixture is burned in the early stage of combustion, the amount of air-fuel mixture burned in post-combustion will decrease, and the amount of smoke generated will decrease. As a result, the combustion gas temperature increases, and the amount of NOx generated increases. On the other hand, if the amount of air-fuel mixture that burns in the early stage of combustion decreases, the temperature of the combustion gas is relatively suppressed, so
However, the amount of air-fuel mixture burned in the post-combustion increases and the amount of smoke increases. Therefore, taking into account these two conditions, an appropriate target ignition timing is determined, and the combustion injection timing is set and mapped in advance so that the actual ignition is performed at the target ignition timing. During operation, the fuel injection timing is determined based on this map during operation, and fuel is injected from the injector according to the determined timing.

Japanese Patent Application Laid-Open No. 59-37235 discloses a method or apparatus for controlling the fuel injection timing of a diesel engine, which calculates or detects the rate of change of in-cylinder pressure and controls the combustion injection timing of the engine. Kaisho 59-
There is one disclosed in JP-A-145334. JP 5
A fuel injection timing control method for a diesel engine disclosed in Japanese Patent Application Laid-Open No. 9-37235 detects a combustion pressure by a combustion pressure sensor attached to each cylinder of the diesel engine, and changes the combustion pressure per unit time for each cylinder. When the amount of change in the combustion pressure of one of the cylinders exceeds a predetermined value according to the operation state of the diesel engine, the fuel injection timing of the cylinder is retarded. By performing such a retard correction of the fuel injection timing, the change curve of the combustion pressure with the passage of the crank angle lowers its peak value for each cylinder and changes gradually, thereby lowering the engine noise level. It becomes possible to do.

In the fuel injection timing control apparatus for a diesel engine disclosed in the above-mentioned Japanese Patent Application Laid-Open No. Sho 59-145334, the timing at which a pressure peak occurs during combustion and the peak value are determined by simply reciprocating the piston without combustion. Focusing on the fact that it changes according to the ignition timing as compared with the compression pressure peak at the time of combustion, the piezoelectric element detects the change in pressure per hour during combustion, and if the pressure peak during combustion occurs, Detects the zero-cross timing when the pressure change changes from positive to negative in response to the pressure drop, compares the zero-cross timing with the peak compression pressure timing, and sets the interval between the two timings within a predetermined time. If it deviates, control is performed to advance or delay the fuel injection timing so that it falls within a predetermined time.

In a multi-cylinder engine in which the fuel injection timing is controlled by detecting the in-cylinder pressure, the target injection timing is determined in advance based on the operating state of the engine. The target injection timing is determined according to the operating state, and the drive timing to the injector is controlled so that the actual fuel injection timing becomes the target injection timing. However, it is difficult to inject fuel at the calculated target injection timing due to individual differences in the injectors provided for each cylinder, and the actual fuel ignition timing at which fuel actually ignites after the ignition delay is set to the target ignition timing. On the other hand, there is variation. This variation in the actual fuel ignition timing causes an increase in the amount of NOx or smoke contained in the exhaust gas. In particular, when the engine is in an idling operation state, the operation state of the engine is unstable because the engine speed is low, and the variation in the fuel injection timing greatly affects the variation in the actual fuel ignition timing. It also has a significant effect on performance.

[0006]

Therefore, the in-cylinder pressure of the cylinder of the engine is compared with the in-cylinder pressure when the compression and expansion without fuel injection are repeated, and the in-cylinder pressure by fuel injection and subsequent combustion is compared. From the standpoint that there is a relationship between the in-cylinder pressure of a cylinder and the actual fuel ignition timing because of the change in pressure, it is an object to determine the actual fuel ignition timing from the in-cylinder pressure of the cylinder. Another object is to correct the fuel injection timing so that when the actual fuel ignition timing is obtained, the actual fuel ignition is performed at the target ignition timing.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and to calculate a heat generation rate in a cylinder from a cylinder volume and a cylinder pressure of the engine by calculation.
A method and apparatus for detecting the actual fuel ignition timing from the heat release rate, and the fuel injection of the engine of the engine for correcting the fuel injection timing so that the target fuel ignition timing obtained from the operating state of the engine matches the actual fuel ignition timing It is an object of the present invention to provide a timing control method and an apparatus therefor.

The present invention relates to an engine in which fuel injected into a cylinder by an injector ignites and burns.
The pressure in the cylinder is sequentially detected, and the volume in the cylinder is sequentially calculated, and the heat generation rate in the cylinder fluctuated by the injection of the fuel into the cylinder and the combustion of the fuel in the cylinder. Is calculated from the sequentially detected pressure in the cylinder and the sequentially calculated volume in the cylinder and the rate of change thereof, and the time when the heat release rate changes from negative to positive is defined as the actual fuel ignition timing. The present invention relates to a method for detecting an actual fuel ignition timing of an engine, characterized in that it is determined.

Further, in the present invention, in an engine in which fuel injected into a cylinder by an injector ignites and burns, an in-cylinder pressure detecting means for sequentially detecting a pressure in the cylinder of the engine, and a capacity in the cylinder. An in-cylinder volume calculating means for sequentially calculating, a heat generation rate in the cylinder fluctuating due to the injection of the fuel into the cylinder and the combustion of the fuel in the cylinder being sequentially detected by the in-cylinder pressure detecting means; Heat generation rate calculation means for calculating from the calculated pressure in the cylinder and the volume in the cylinder sequentially calculated by the cylinder volume calculation means and a change rate thereof,
And an actual fuel ignition timing determining device for determining an actual fuel ignition timing at a time when the heat release rate changes from negative to positive.

Further, the present invention provides an engine in which fuel injected into a cylinder by an injector ignites and burns, a target fuel injection timing and a target fuel ignition timing which are predetermined based on an operation state of the engine. Calculating the target fuel injection timing and the target fuel ignition timing with respect to the operating state of the engine, sequentially detecting the pressure in the cylinder, and sequentially calculating the volume in the cylinder,
The heat generation rate in the cylinder, which fluctuates due to the injection of the fuel into the cylinder and the combustion of the fuel in the cylinder, is calculated based on the detected pressure in the cylinder and the sequentially calculated pressure in the cylinder. The actual fuel ignition timing is determined as the actual fuel ignition timing, and the time at which the heat release rate changes from negative to positive is determined from the deviation between the actual fuel ignition timing and the current target fuel ignition timing. A fuel injection timing control method for an engine, wherein the target fuel injection timing is corrected based on the corrected fuel injection timing correction amount.

Further, in the present invention, in an engine in which fuel injected into a cylinder by an injector ignites and burns, an in-cylinder pressure detecting means for sequentially detecting a pressure in the cylinder of the engine, and a capacity in the cylinder is determined. An in-cylinder volume calculating means for sequentially calculating, a heat generation rate in the cylinder fluctuating due to the injection of the fuel into the cylinder and the combustion of the fuel in the cylinder being sequentially detected by the in-cylinder pressure detecting means; Heat generation rate calculation means for calculating the pressure in the cylinder and the volume in the cylinder sequentially calculated by the cylinder volume calculation means and the rate of change thereof, wherein the heat generation rate changes from negative to positive Actual fuel ignition timing determining means for determining the time at which the engine is to run as actual fuel ignition timing, operating state detecting means for detecting the operating state of the engine, Target timing calculating means for calculating the target fuel injection timing and the target fuel ignition timing for the current operating state of the engine detected by the operating state detecting means from predetermined target fuel injection timing and target fuel ignition timing And a fuel injection timing correcting means for correcting the target fuel injection timing by a fuel injection timing correction amount obtained from a deviation between the actual fuel ignition timing and the target fuel ignition timing. The present invention relates to an injection timing control device.

In the method and the apparatus for detecting the actual fuel ignition timing of an engine according to the present invention, the in-cylinder pressure can be sequentially detected by the in-cylinder pressure detecting means, and the in-cylinder volume is sequentially calculated by the in-cylinder volume calculating means. Can be. Based on the detected and calculated in-cylinder pressure and in-cylinder volume, and the rate of change thereof, the rate of heat generation in the cylinder that fluctuates due to the injection of fuel into the cylinder and the combustion of fuel in the cylinder, It can be obtained by calculation. The time when the heat release rate changes from negative to positive can be regarded as the actual fuel ignition timing.

In the method and apparatus for controlling the fuel injection timing of the engine according to the present invention, the method for detecting the actual fuel ignition timing of the engine and the actual fuel ignition timing obtained by the apparatus are described below.
The target fuel ignition timing is compared with a predetermined target ignition timing based on the operating state of the engine, and a deviation between the two is obtained. A fuel injection timing correction amount is obtained from the deviation, and the target fuel injection timing is corrected by the fuel injection timing correction amount. The final fuel injection timing is determined. By doing so, the fuel injection timing is corrected so that the actual fuel ignition timing matches the target fuel ignition timing, and deterioration of the exhaust gas performance of the engine is prevented.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an engine fuel injection timing control device according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of an engine to which the fuel injection timing control device according to the present invention is applied. FIG. 2 is a diagram showing changes in in-cylinder pressure, fuel injection rate, and heat generation rate of the engine according to the passage of a crank angle. FIG. 3 is a graph showing an outline of a change in the in-cylinder pressure with the passage of the crank angle and a generation state of various signals in the fuel injection timing control device for the engine shown in FIG.

FIG. 1 shows an outline of an example of an engine to which the fuel injection timing control device according to the present invention is applied. In this example, the engine 1 is a four-cylinder engine.
The four cylinders # 1 to # 4 are respectively provided with injectors 31, 32, 33 and 34 (3 is used when collectively referred to) for injecting combustion into a combustion chamber (not shown) formed in the cylinder 2. Pressure sensors 41, 42, 43, 44 as pressure detecting means for detecting the pressure in the combustion chamber (in-cylinder pressure)
(When collectively referred to, 4 is used). A signal representing the in-cylinder pressure of each of the cylinders # 1 to # 4 detected by the pressure sensor 4 is sent to the engine controller 7 (which also controls the fuel injection timing in the present invention) via the pressure signal processing device 5. Further, an engine rotation sensor 6 is attached to the engine 1, and a signal related to rotation of the engine 1 detected by the rotation sensor 6 is also input to the engine controller 7.

FIG. 2 is a graph showing how the in-cylinder pressure Pc and the fuel injection rate Rf change with respect to the crank angle in each cylinder. The change in the in-cylinder pressure Pc when the fuel injection is not performed changes symmetrically with respect to the peak of the in-cylinder pressure Pc with the change in the crank angle θc, but the fuel injection is performed at time T0. When the injected fuel is ignited, the in-cylinder pressure Pc rises slightly moderately, and greatly increases by the subsequent ignition. It is difficult to accurately determine the crank angle from the rapidly increasing in-cylinder pressure Pc as the fuel ignition timing. The fuel injection rate R
f is controlled to have two peaks, an initial injection and a main injection.

The four graphs in the upper part of FIG. 3 show the in-cylinder pressure Pc with the passage of the crank angle of each of the cylinders # 1 to # 4.
Represents the change. Engine 1 has four cylinders,
Assuming that the cylinder numbers n are # 1 to # 4 according to the arrangement of the columns, the combustion order i is, as shown in Table 1, # 1 → # 3 → # 4 → #
The order is 2.

[Table 1] Each of the cylinders # 1 to # 4 sequentially undergoes a compression / explosion stroke in the order described above, and combustion is performed. When a certain cylinder passes through the explosion stroke, the next cylinder enters a compression stroke. Since the cylinder # 1 is a reference cylinder, a cylinder discrimination (REF) signal is output at 120 ° before the compression top dead center. Also, a BTDC signal is output at 60 ° before the compression top dead center of each cylinder. Since the engine is a four-cycle engine, the count value θ of the crank angle is 0 at the compression top dead center of the # 1 cylinder, and the cycle is completed by two rotations of the crankshaft, that is, the count value 719. # 1
As for the cylinder, when the count value is 180 ° before the compression top dead center to 180 ° after the compression top dead center, that is, when the count value is 540 or more and less than 180, the # 1 cylinder enters the compression / explosion stroke. The data of the in-cylinder pressure Pc that greatly changes is stored. Mention processing is calculated within a predetermined time from 180 ° after the compression top dead center based on the stored data, and injection valve driving processing of the injector 31 is performed based on the next BTDC interrupt signal.

FIG. 4 shows the relationship between various sensors mainly including the controller 7 of the engine and the injector 3. FIG. 4 is a block diagram showing an outline of an engine fuel injection timing control device, which receives detection signals from various sensors relating to engine rotation and a cylinder pressure sensor,
It outputs a control signal to each injector 3. The rotation sensor 6 of the engine 1 includes a reference cylinder among the cylinders # 1 to # 4, for example, a cylinder determination (REF) sensor 8 for determining the position of 120 ° before the top dead center of the cylinder # 1, and each of the cylinders # 1 to # 4. BTDC (bef) that detects 60 ° before top dead center of the # 4 explosion stroke
ore top dead center) sensor 9;
Crank angle sensor 1 that detects crank angle every 1 °
0. Since the engine 1 is a four-stroke engine, the cylinder discriminating sensor 8 and the BTDC sensor 9 operate so that the fuel pump emits four BTDC signals and one REF signal during two rotations of the crankshaft. It is arranged in connection with a drive shaft or a cam shaft for driving the intake and exhaust valves. A pressure sensor 4 for detecting the in-cylinder pressure Pc.
Is mounted facing the combustion chamber of each cylinder, and detects the in-cylinder pressure Pc as a relative pressure (gauge pressure) with the atmospheric pressure.

In the controller 7, in addition to the sensors 8 to 10 relating to the rotation of the engine 1, a fuel pressure sensor for detecting the pressure of an accelerator opening sensor 11, a common rail and the like is used to indicate the operating state of the engine 1. 12 and a detection signal from a water temperature sensor 13 for detecting the temperature of the cooling water for cooling the engine 1 are output from a central processing unit (C).
PU) 14. The detection signals detected and output by these various sensors are supplied to a DSP (digital signal processor) in parallel with the input to the CPU 14.
essor) 15. The DSP 15 can add / subtract the input signal at high speed.

The exchange of data between the CPU 14 and the DSP 15 is performed via a dual port memory 16 which is a common RAM readable and writable from both sides of the CPU 14 and the DSP 15. The CPU 14 and the dual port memory 16 are connected through a CPU bus 17, and the DSP 15 and the dual port memory 16 are connected through a DSP bus 18. In-cylinder pressure P
The in-cylinder pressure sensors 4 for detecting c are in-cylinder pressure sensors 41 to 44 provided corresponding to the cylinders # 1 to # 4, respectively. Analog signals of the in-cylinder pressure detected by the in-cylinder pressure sensors 41 to 44 are input to the AD converter 19, converted into digital signals, and sent to the DSP 15 through the DSP bus 18.

The CPU 14 controls the DSP 15 with respect to the information indicating the operating state of the engine 1 directly input from the sensors 8 to 13 and the in-cylinder pressure from the in-cylinder pressure sensors 41 to 44.
Is calculated based on the results and the like processed by
The control related to fuel injection such as fuel injection timing and fuel injection amount of the injectors 31 to 34 provided corresponding to 1 to # 4, respectively, is performed. The DSP 15 performs high-speed addition and subtraction processing of digital signals related to the in-cylinder pressure Pc. Because of the digital processing, the differentiation and integration of the in-cylinder pressure Pc can be similarly calculated at high speed. In addition, the CPU 15 is provided with a variable fuel pump 2 for controlling the pressure of the common rail.
0 in order to control the discharge rate of 0 and to control the exhaust gas circulation rate.
The GR valve 21 is controlled.

In the fuel injection timing control by the CPU 14, the target fuel injection timing is obtained from a predetermined map based on signals from the accelerator opening sensor 11 and the sensors 8 to 10 relating to the rotation of the engine 1.
According to the present invention, each of the injectors 31 to 34 is considered in consideration of the ignition delay so that the actual fuel ignition timing obtained from the in-cylinder pressure Pc detected by the in-cylinder pressure sensors 41 to 44 coincides with the target fuel ignition timing. Correct the fuel injection timing. Less than,
The correction of the fuel injection timing will be described.

The CPU 14 performs a main process as shown in FIG. FIG. 5 is a flowchart showing the main processing of the CPU in the fuel injection control of the engine shown in FIG. This main processing includes the following steps. (1) Initialization of the CPU 14 is performed (steps 1, S
Abbreviated as 1. same as below). (2) Process the sensor signal (S2). As shown in FIG. 4, processing of detection signals from various sensors input to the CPU 14 is performed. (3) Based on the information obtained in the signal processing performed in S2, the amount of fuel to be injected by each injector 3, that is, the fuel injection amount is calculated (S3). The calculation of the fuel injection amount is performed by obtaining a target fuel injection amount Qb corresponding to the current accelerator opening and the engine speed in an injection amount characteristic map determined in advance by the accelerator opening and the engine speed. (A final fuel injection amount may be obtained with a necessary injection amount correction amount). (4) Further, based on the information obtained in the signal processing performed in S2, the timing at which each injector 3 should inject fuel,
That is, the fuel injection timing is calculated (S4). A target fuel injection timing corresponding to the injection amount obtained in S3 and the current engine speed is obtained in an injection timing characteristic map determined in advance by the injection amount and the engine rotation speed. In the calculation of the fuel injection timing, the final fuel injection timing Tf is obtained based on the target fuel injection timing. The details of the calculation will be described later. (5) Further, the fuel is injected based on the information obtained in the signal processing performed in S2 and so that the fuel injection amount obtained in S3 can be injected at the fuel injection timing obtained in S4. The pressure, that is, the fuel injection pressure is calculated (S5).
The control of the fuel injection pressure is performed by obtaining a target injection pressure from the injection amount and the engine speed, and more specifically, by controlling a common rail pressure by controlling a flow control valve of a fuel pump. The fuel injection control includes the injection amount control, the injection timing control, and the injection pressure control as described above. The controller 7 controls each injector 3 and the common rail pressure so that the fuel is injected from each injector 3 under each injection condition described above. Perform control. CPU in S1
After the initialization of S14, S2 to S5 are sequentially executed for the injectors 3 to execute the fuel injection, and the above S2 to S5 are repeated for each injection.

On the rotary plate fixed to the pump shaft of the fuel pump 20 or the cam shaft for driving the intake and exhaust valves, one reference mark (missing tooth) is provided at an angular position corresponding to 120 ° before the compression top dead center of the reference cylinder # 1. May be formed), and the cylinder discriminating sensor 8
Outputs a REF signal once per rotation of the pump shaft by detecting this reference mark. When the cylinder discriminating sensor 8 outputs a REF signal, a RE signal as shown in FIG.
An F interrupt is performed. FIG. 6 is a flowchart showing an interrupt process when a cylinder discrimination signal is input in the main process shown in FIG. In this interrupt processing, a reset processing for setting the count value CNb of the signal before the compression top dead center to 0 is performed. That is, since the engine 1 has four cylinders, the count value CNb of the signal before the compression top dead center is 4
It can take two integer values. When the fuel injection and ignition in each cylinder makes a full cycle from the time when the count value CNb is 0, the rotation sensor 6 detects the reference mark before the count value CNb is incremented by 1 and becomes 4 so that the count value CNb becomes It is reset to 0 (S6).

On the rotating plate fixed to the pump shaft of the fuel pump 20, four pre-top-dead-center marks (may be missing teeth) at 90 ° at angular positions corresponding to 60 ° before the compression top dead center of each cylinder 4 are provided. The BTDC sensor 9 detects the mark before the top dead center, so that the number of B
A TDC signal is output (see the graph shown in the middle part of FIG. 3). When the BTDC signal is input to the CPU, the B signal in the processing of the CPU as shown in FIG.
TDC signal interruption processing is performed. FIG. 7 is a flowchart showing an interrupt process when a BTDC signal is input in the main process shown in FIG. (1) The rotation speed of the engine 1 is calculated (S10).
That is, the current BTD after detecting the previous BTDC signal
The number of revolutions of the engine 1 per unit time is calculated based on the time required until the detection of the C signal. (2) It is determined whether or not the count value CNb of the BTDC signal is 0 (S11). If the count value CNb is 0, the fuel injection process of the injector 31 provided in the cylinder (# 1) with the combustion order i = 1 (S2 to S5 and the subsequent fuel injection) is performed (S12). The timing of this injector processing is shown in the lowermost graph of FIG. (3) If the count value CNb is not 0 in the determination in S11, the process immediately proceeds to S13 to determine whether the count value CNb is 1 (S13). (4) If the count value CNb is 1, fuel injection processing (execution of S2 to S5 and subsequent fuel injection) of the injector 33 provided in the cylinder (# 3) of i = 2 is performed (S1).
4). (5) If the count value CNb is not 1 in the determination in S13, the process immediately proceeds to S15, and the same determination processing as described above and the injector fuel injection processing in the case of YES in the determination processing are performed (S15). ). (6) In S12, S14 or S15, # 1 to # 4
When the fuel injection processing of any of the injectors 3 is performed, the determination other than the determination of the corresponding count value CNb is always NO, so that the count value CNb which is increased by 1 in S16 is replaced with the new count value CNb. (S16)
This interrupt processing ends. Also in the next interrupt processing, the determination for the next count value CNb is made in S1.
YE in any of the similar determinations at S1, S13 or S15
It becomes S. When the count value CNb is sequentially increased and the count value CNb becomes 3, the reference mark is detected before the count value CNb becomes 4, and the count value CN is detected by S6.
b is reset to zero.

Next, regarding the main processing of the DSP 15,
A description will be given based on FIG. FIG. 8 is a flowchart showing the main processing of the DSP in the fuel injection control of the engine shown in FIG. (1) Initialize the DSP (S20). (2) When initialization is completed, in-cylinder pressure processing is performed (S2).
1). The in-cylinder pressure processing is processing of the detected in-cylinder pressure data of the cylinders # 1 to # 4. The in-cylinder pressure data processing is repeatedly performed for each of the corresponding cylinders # 1 to # 4 at every crank angle of 1 °.

In the DSP, the in-cylinder processing shown in S21 is premised on the AD conversion end interrupt processing shown in FIG. 9, the initialization of each crank included in the AD conversion end interrupt processing, and the in-cylinder pressure data. Are stored in the memory and the crank angle is updated. FIG.
9 is a flowchart showing interrupt processing at the end of AD conversion in the main processing of the DSP shown in FIG. Although the in-cylinder pressure of each cylinder is converted from analog to digital by the AD converter 19 at every crank angle of 1 °, the AD conversion end interrupt processing is performed every time the conversion by the AD converter 19 ends. (1) The AD conversion result ADr (i) of the in-cylinder pressure is read (S30). AD conversion result ADr (i) of each in-cylinder pressure
Is read as Pc (i) in the combustion order i (= 1 to 4). (2) Next, initialization of the crank angle is performed (S3).
1). (3) The in-cylinder pressure data is stored in the memory (S3
2). (4) The crank angle is updated (S33). Steps S31 to S33 will be described in detail below.

The initialization of the crank angle in S31 will be described with reference to the flowchart shown in FIG. FIG. 10 is a flowchart showing the process of initializing the crank angle in the interrupt process at the end of the AD conversion shown in FIG. The engine is a four-cylinder engine, and the fuel injection and ignition of each cylinder makes one cycle with two rotations of the crankshaft.
It is. The count value θ of the crank angle counts 1 at 1 °. The count value θ of the crank angle is set to 0 when the cylinder (# 1) having the combustion order i = 1 takes the position of the top dead center, and is set to 719 until the injection and ignition of the fuel of the four cylinders is completed.
Take the count value up to. (1) It is determined whether or not the initialization of the crank angle has already been completed (S40). If the initialization of the crank angle has already been completed, the routine immediately returns to the AD conversion end interrupt routine. If the crank angle initialization has not been completed,
The step moves to S41. (2) It is determined whether or not the REF signal output at 120 ° before the top dead center of a specific cylinder, i.e., the cylinder with i = 1 (# 1), has risen (S41). If the REF signal has not risen, the process immediately returns to the AD conversion end interrupt routine. (3) If the REF signal has risen in S41, the count number θ of the crank angle is set to 720 minus 12
It is set to 0 (ie, 600) (S42). 120 is
This corresponds to the mounting angle of the cylinder discrimination sensor. (4) When the setting in S42 ends, the initialization of the crank angle ends (S43).

Next, the process of storing the in-cylinder pressure data in the memory in S32 will be described with reference to the flowchart shown in FIG. FIG. 11 is a flowchart showing a process of storing the in-cylinder pressure data in the memory in the interrupt process at the end of the AD conversion shown in FIG. (1) The count number θ of the initialized crank angle is 54
0 or more and 720 (= 0) or 0 (= 72)
0) It is determined whether it is not less than 180 (S5).
0). If the count number .theta. Of the crank angle is not within this range, the flow shifts to S57. The range of the count number θ determined in S50 is a range in which the crank angle of the cylinder (# 1) of i = 1 is within 180 ° before and after the compression top dead center, and is a range from the compression stroke to the explosion stroke. The in-cylinder pressure during this time is important for ignition timing control and is adopted as data. (2) It is determined whether or not the count number θ of the crank angle is 540 (S51). This count number θ is 540
Is the starting point of the range of the count number θ, the cylinder-specific crank angle count number θc defined as the crank angle count number for the cylinder with i = 1
(1) is cleared to 0 (S52). 1 in parentheses
Indicates that it is the crank angle count number for the cylinder with i = 1. Therefore, θc (1) is from 0 to 3
Take values up to 59. (3) The in-cylinder pressure Pc (1) for the cylinder with i = 1 is
The in-cylinder pressure Pc (θc (1), 1) at the time of the cylinder-specific crank angle count number θc (1) is set (S53). (4) It is determined whether or not the cylinder-specific crank angle count number θc (1) for the cylinder with i = 1 is 359 (S54). That is, it is determined whether or not it is the end point of the data collection crank angle range for the cylinder with i = 1. (5) If θc (1) is 359, θc
Since (1) is after execution from 0 to 359, i
This means that the storage of the in-cylinder pressure data for the cylinder of = 1 has been completed (S55). (6) If θc (1) is not 359, θc (1)
Has not reached the end point yet, and in response to advancing the crank angle by 1 °, a value obtained by increasing the count of θc (1) by 1 is set as a new θc (1) (S5).
6).

(7) Next, the count number θ of the crank angle
Is greater than or equal to 0 and less than 360 (S5).
7). If the count .theta. Of the crank angle is not within this range, the flow shifts to S64. The range of the count number θ determined in S57 is a range in which the crank angle of the cylinder (# 3) with the combustion order i = 2 is within 180 ° before and after the compression top dead center, and the range from the compression stroke to the explosion stroke. It is. The in-cylinder pressure during this time is necessary for ignition timing control and is adopted as data. Therefore, when the count θ of the crank angle is not less than 0 and less than 180, i = 1
Of the cylinder (# 1) and the cylinder (# 3) with i = 2 are stored. (8) It is determined whether or not the count number θ of the crank angle is 0 (S58). If the count number θ is 0, it is the starting point of the range of the count number θ, and thus i =
Cylinder angle count number θc for each cylinder defined as the crank angle count number for the second cylinder (# 3)
(2) is cleared to 0 (S59). Therefore,
θc (2) for the cylinder with i = 2 also takes a value from 0 to 359. (9) The in-cylinder pressure Pc (2) for the cylinder of i = 2 at the time of the cylinder-specific crank angle count number θc (2) is set to the in-cylinder pressure Pc (θc (2), 2) (S60). (10) It is determined whether or not the cylinder-specific crank angle count number θc (2) for the cylinder with i = 2 is 359 (S61). (11) Assuming that θc (2) is 359,
Since c (2) is after executing from 0 to 359,
The storage of the in-cylinder pressure data for the cylinder with i = 2 ends (S62). (12) If θc (2) is not 359, θc
In (2), since the end point has not yet been reached, a value obtained by increasing the count number of θc (2) by 1 in response to advancing the crank angle by 1 ° is set as a new θc (2) (S63). ). (13) Thereafter, the same processing is performed for the cylinders of i = 3 and 4 (# 4 and # 2), and the in-cylinder pressure data is stored in the memory (S64).

Next, the process of updating the crank angle will be described.
This will be described with reference to the flowchart shown in FIG. FIG.
2 is a flowchart showing a crank angle update process in the interrupt process at the end of the AD conversion shown in FIG. An update S33 of the crank angle is executed for each increment of θc. (1) The count θ of the crank angle is increased by one and updated (S70). (2) It is determined whether or not the count number θ is less than 720 (S71). If the count number θ is less than 720, 4
Since the injection and ignition for one cylinder have not yet completed one cycle, the interrupt processing after the end of the AD conversion is continued. (3) If the count number θ is 720 or more, the count number θ is reset to 0 (S72).

Next, details of the in-cylinder pressure processing (S21) during the main processing of the DSP shown in FIG.
This will be described with reference to the flowchart shown in FIG. FIG.
9 is a flowchart showing in-cylinder pressure processing in the main processing of the DSP shown in FIG. 8. (1) Combustion order i = 1 performed in S55 of FIG.
It is determined whether the in-cylinder pressure data storage of the cylinder (# 1) has been completed (S80). If the storage of the in-cylinder pressure data of the cylinder (# 1) of i = 1 has not been completed, the flow shifts to S84 to determine whether the storage of the in-cylinder pressure data of the cylinder (# 3) of i = 2 has been completed. Is determined. (2) If it is determined in S80 that the storage of the in-cylinder pressure data of the cylinder with i = 1 has been completed, the data is subjected to a filtering process (S81). Since the in-cylinder pressure data greatly fluctuates, noise is removed by performing a filtering process such as taking a moving average to obtain a smooth in-cylinder pressure curve (see FIG. 2).

(3) From the obtained pressure curve, the heat release rate q
Is calculated (S82). The heat release rate q is obtained as follows. First, the in-cylinder volume Vθ is expressed by the following equation.

(Equation 1) Here, Vc is the clearance volume [m ³ ], S is the piston stroke [m], L is the connecting rod length [m], and θc is the crank angle [deg]. The in-cylinder volume Vθ and its differential value based on the crank angle θc are obtained in advance by calculation and are stored in a memory. In addition, the in-cylinder pressure Pc and its differential value based on the crank angle θc are detected by a sensor.
It is obtained by processing with a DSP. Heat release rate q = d
Q / dθ is obtained by the following equation.

(Equation 2) Here, assuming that the specific heat ratio κ is constant, the above equation is calculated in real time. (4) The fuel ignition timing Td (1) is calculated (S8).
3). Details of this calculation will be described later.

(5) If the in-cylinder pressure data storage of the cylinder (# 1) with the combustion order i = 1 has not been completed, is the in-cylinder pressure data storage of the cylinder (# 3) with i = 2 completed? It is determined whether or not it is (S84). Filter processing after S84 (S8
5), calculation of heat release rate q (S86), ignition timing Td
Steps in the calculation of (2) (S87) are described in S80 to S8.
3 and the description is omitted. Similarly, the same processing is performed for the cylinder (# 4) with i = 3 and the cylinder (# 2) with i = 4. Note that the processing in FIG. 11 is performed in a state where the in-cylinder pressure data for 10 combustion strokes of each cylinder has been stored due to the interruption of the crank angle, the filtering processing, the calculation of the heat release rate,
Each step of calculating the ignition timing Td (i) is performed.

Next, the calculation of the ignition timing Td (i) will be described with reference to the flowchart shown in FIG. FIG.
4 is the ignition timing Td in the in-cylinder pressure process shown in FIG.
It is a flowchart which shows the calculation process of (i). i is
This is a combustion number that can take a value of 1 to 4, and a common process is performed for each value of i. Θc is the compression of each cylinder.
It is a count value of the crank angle in the explosion process, and the crank angle in the range of 180 ° before and after the top dead center of the explosion stroke is 0 to 3
Count up to 59. This flowchart is performed in step S90.
Is executed when θ is 3 or more (S9).
0). It is assumed that the heat release rate q has already been determined in S82, S86, and the like. Also, reference is made to the graph of the heat release rate q with respect to the count value θc of the crank angle shown in FIG. (1) For the combustion order i at that time, q (i) (θc−
It is determined whether 3) is negative (S91). (2) If q (i) (θc-3) is negative, q (i) (θc-2) when the crank angle θ advances by one count
It is determined whether or not is negative (S92). (3) If q (i) (θc−2) is negative, q (i) (θc−) when the crank angle θ is further advanced by one count
It is determined whether 1) is positive (S93). (4) If q (i) (θc-1) is positive, q (i) (θc) when the crank angle θ is further advanced by one count
Is positive (S94).

(5) If q (i) (θc) is positive, the ignition timing Td (i) is assumed to be θc-2 (S9).
5). That is, as shown in FIG. 16, since the sign of the heat release rate q changes between θc-2 and θc-1, which are intermediate times, at the count values of four consecutive crank angles, ignition occurs. The timing Td (i) is regarded as θc-2. In fact,
Since the zero cross point is between θc-2 and θc-1,
The zero cross point may be obtained by interpolation. When the calculation accuracy is good, the time when the sign changes from negative to positive at two points before and after may be determined as the zero cross point. (6) When q (i) (θc-3) is positive in S91, S9
When q (i) (θc−2) is positive in step 2, q in step S93
(I) When (θc-1) is negative, and in step S94, q (i)
When (θc) is negative, the fuel ignition timing Td
(I) is the time when the crank angle count value is 0 (S9)
6). That is, the fuel ignition timing Td (i) is obtained in S95 only when the sign of q changes between θc-2 and θc-1, and in all other cases, the fuel ignition timing Td is obtained.
(I) is set to 0. (7) It is determined whether or not the fuel ignition timing Td (i) is 0, that is, the timing at which the crank angle count value is 0 (S9).
7). (8) If the fuel ignition timing Td (i) is 0, θ is increased by 1 (S98). (9) It is determined whether or not θc is 360 (S9)
9). That is, it is determined whether or not the count value is the last count value in the range that θc can take. If the range to be calculated still remains in θc, the process returns to S41 and the routine is executed again.

According to the flowchart shown in FIG.
When the fuel ignition timing Td (i) is obtained, the fuel injection timing in each injector is corrected so that the actual fuel ignition timing matches the target fuel ignition timing. The method of correction is described in the injector 3 provided in # 1 shown in FIG.
This will be described below taking 1 as an example. FIG. 15 is a flowchart showing a process of correcting the injection timing of the injector in the interrupt process when the BTDC signal shown in FIG. 7 is input. (1) In the main processing of the CPU shown in FIG. 5, since the target fuel injection pressure Pb, the target fuel injection amount Qb, and the target fuel injection timing Tb are obtained, these values are read (S
100). (2) It is determined whether or not the engine is in an idling operation state (S101). Whether or not the engine is in the idling state is determined by various sensors relating to the rotation of the engine, especially the BT.
It is obtained based on the engine speed calculated from the DC sensor 9, the detection output of the accelerator opening sensor 11, and the like. (3) The target fuel ignition timing Tr is read using data obtained in advance such as ignition timing delay (S102). (4) Fuel ignition timing Td (1) obtained in S95 and S10
From the target fuel ignition timing Tr read in 2, an ignition timing deviation ΔTe is obtained by the following equation (S 103). 1 in parentheses indicates the fuel ignition timing and the ignition timing deviation for the cylinder (# 1) with the combustion order i = 1. ΔTe (1) = Td (1) −Tr (5) The correction amount Δθ (1) of the fuel injection timing is obtained by the following equation (S104). Δθ (1) ← Δθ (1) + ΔTe × Gθ The ignition timing deviation ΔTe with respect to the previous correction amount Δθ (1).
Is corrected based on the current correction amount Δθ (1). Here, Gθ represents a gain. (6) Correction amount Δ of current fuel injection timing obtained in S104
Based on θ (1), the final fuel injection timing Tf (1) is obtained based on the following equation (S105). Tf (1) = Tb (1) + Δθ (1) × Gt That is, the target fuel injection timing Tb (1) is multiplied by the gain Gt multiplied by the current fuel injection timing correction amount Δθ (1). Then, the final fuel injection timing Tf (1) is obtained. (7) The injection pulse width PW is calculated from the target fuel injection amount Qb and the target fuel injection pressure Pb (S106). (8) The fuel injection timing and the injection pulse width are set in the drive pulse output counter (S107). That is, when and how long the solenoid valve for the injector 31 is
Decide whether to activate.

Referring again to FIG. 2, when the fuel injection is performed at time T0 and the injected fuel is ignited, the rise in the in-cylinder pressure Pc becomes slightly gentle, and increases greatly by the subsequent ignition. Although it has been difficult to accurately determine the crank angle from the rapidly rising in-cylinder pressure Pc, the actual fuel ignition timing can be accurately determined as described above by focusing on the heat release rate q. That is, when the fuel is injected into the combustion chamber at the fuel injection rate Rf shown in the middle graph of FIG. 2, as shown in the lower graph of heat release rate q, it once exhibits a negative heat release due to endothermic heat. , Then change to a positive heat release rate. The heat release rate q slightly decreases at the beginning of fuel injection (due to fuel vaporization), but the heat release rate q starts to increase due to ignition of the fuel, and the heat release rate q turns from negative to positive at a zero crossing time T1. Can be regarded as the fuel ignition timing Td. A period from time T0 to time Td corresponds to a fuel ignition delay period.

The contents of the above flow chart are summarized with reference to FIG. 3. The upper four graphs in FIG. 3 show changes in the in-cylinder pressure Pc as the crank angles of the cylinders # 1 to # 4 elapse. ing. The compression and explosion strokes take place one after another in the order of # 1, # 3, # 4, and # 2 cylinders. When one cylinder goes through an explosion stroke, the next cylinder is in a compression stroke. Since the # 1 cylinder is the reference cylinder, a cylinder discrimination signal is output at 120 ° before the compression top dead center. Also,
A BTDC signal is output at 60 ° before the compression top dead center of each cylinder. The count value of the crank angle is 0 at the compression top dead center of the # 1 cylinder, and since the engine is a four-cycle engine, it makes two revolutions of the crankshaft, that is, makes one cycle with the count value 719. # 1
For the cylinder, 180 ° before the compression top dead center, that is, the count value is 540 or more, and 180 ° after the compression top dead center, that is, the count value is less than 180, the in-cylinder pressure of the # 1 cylinder. Store the data. Based on the stored data, the main processing is calculated within a predetermined time from 180 ° after the compression top dead center, and the injection valve driving processing of the injector 31 is performed based on the next BTDC interrupt signal.

[0040]

The method and the apparatus for detecting the actual fuel ignition timing of the engine according to the present invention are constructed as described above, and have the following effects. That is, the method and apparatus for detecting the actual fuel ignition timing of an engine according to the present invention
The fuel injected into the cylinder by the injector ignites
In a burning engine, the pressure in the cylinder is sequentially detected and the volume in the cylinder is calculated sequentially, and the cylinder is varied by injection of the fuel into the cylinder and combustion of the fuel in the cylinder. Is calculated from the sequentially detected pressure in the cylinder, the sequentially calculated volume in the cylinder, and the rate of change thereof, and determines the time at which the rate of heat generation changes from negative to positive. The actual fuel ignition timing has been determined. Further, in the method and apparatus for controlling the fuel injection timing of the engine, even if there is an individual difference between the injectors provided for each cylinder, the actual fuel ignition timing is determined from the in-cylinder pressure of the cylinder according to the detection of the actual fuel ignition timing of the engine. When the actual fuel ignition timing is obtained, the fuel injection timing is corrected so that the actual fuel ignition is performed at the target ignition timing, so that the fuel can be injected at the target injection timing. Since there is no variation in the actual fuel ignition timing, it is possible to contribute to a reduction in the amount of NOx or smoke contained in the exhaust gas. In particular, when the engine is in the idling operation state, the operation state of the engine becomes unstable due to the low engine speed. However, according to the present invention, the actual fuel ignition timing is controlled by controlling the fuel injection timing. As a result, it is possible to stabilize the rotation of the engine, reduce engine noise, and improve exhaust gas performance.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of an engine to which a fuel injection timing control device according to the present invention is applied.

FIG. 2 is a graph showing how the in-cylinder pressure, the fuel injection rate, and the heat release rate change with the passage of the crank angle in the engine.

FIG. 3 is a graph showing an outline of a change in in-cylinder pressure with the passage of a crank angle and a generation state of various signals in the fuel injection timing control device for the engine shown in FIG.

FIG. 4 is a block diagram showing an outline of an engine fuel injection timing control device according to the present invention.

FIG. 5 is a flowchart showing main processing of a CPU of the fuel injection timing control device for the engine shown in FIG. 4;

FIG. 6 is a flowchart showing an interruption process when a cylinder discrimination signal is input in the main process shown in FIG. 5;

FIG. 7 is a flowchart showing an interrupt process when a BTDC signal is input in the main process shown in FIG. 5;

FIG. 8 is a flowchart showing a main process of a DSP of the fuel injection timing control device for the engine shown in FIG. 4;

9 is a flowchart showing an interrupt process at the end of AD conversion in the main process of the DSP shown in FIG. 8;

FIG. 10 is a flowchart showing a process of initializing a crank angle in an interrupt process at the end of AD conversion shown in FIG. 9;

FIG. 11 is a flowchart showing a process of storing in-cylinder pressure data in a memory in an interrupt process at the end of AD conversion shown in FIG. 9;

12 is a flowchart showing a crank angle update process in the interrupt process at the end of AD conversion shown in FIG. 9;

13 is a flowchart showing in-cylinder pressure processing in the main processing of the DSP shown in FIG. 8;

14 is a flowchart showing a process for calculating an ignition timing in the in-cylinder pressure process shown in FIG.

15 is a flowchart showing a process of correcting the injection timing of the injector in the interrupt process when the BTDC signal shown in FIG. 7 is input.

FIG. 16 is a graph illustrating the details of the ignition timing calculation process shown in FIG. 14;

[Explanation of symbols]

 Reference Signs List 1 engine 2 cylinder 3, 31-34 injector 4, 41-44 pressure sensor 5 pressure signal processing device 6 rotation sensor 7 controller 8 cylinder discrimination sensor 9 BTDC sensor 10 crank angle sensor 14 CPU 15 DSP Pc in-cylinder pressure CNb BTDC signal Count value θ Crank angle count value θc Cylinder-specific crank angle count value q Heat release rate Tb Target fuel injection timing Tr Target fuel ignition timing Td Actual fuel ignition timing Tf Final fuel injection timing Δθ Fuel injection timing correction amount

Claims (4)

[Claims] In an engine in which fuel injected into a cylinder by an injector ignites and burns, a pressure in the cylinder is sequentially detected, a volume in the cylinder is calculated sequentially, and a fuel is injected into the cylinder. The rate of heat generation in the cylinder, which is fluctuated by injection and the combustion of the fuel in the cylinder, is calculated by sequentially detecting the pressure in the cylinder, the volume calculated in the cylinder, and the rate of change thereof. And determining the time at which the heat release rate changes from negative to positive as the actual fuel ignition timing. 2. An engine in which fuel injected into a cylinder by an injector ignites and burns, an in-cylinder pressure detecting means for sequentially detecting a pressure in the cylinder of the engine, and a cylinder for sequentially calculating a volume in the cylinder. An internal volume calculating unit configured to sequentially detect, by the in-cylinder pressure detecting unit, a heat generation rate in the cylinder, which is changed by injection of the fuel into the cylinder and combustion of the fuel in the cylinder; The heat generation rate calculation means for calculating the pressure in the cylinder and the volume in the cylinder sequentially calculated by the cylinder volume calculation means and the rate of change thereof, and the time when the heat generation rate changes from negative to positive An actual fuel ignition timing detecting device for an engine, comprising an actual fuel ignition timing determining means for setting an actual fuel ignition timing. 3. An engine in which fuel injected into a cylinder by an injector ignites and burns, a target fuel injection timing and a target fuel ignition timing which are predetermined based on an operation state of the engine, and a current fuel injection timing of the engine. The target fuel injection timing and the target fuel ignition timing with respect to the operating state are obtained, the pressure in the cylinder is sequentially detected, and the volume in the cylinder is sequentially calculated, and the injection of the fuel into the cylinder and the injection in the cylinder are performed. The heat generation rate in the cylinder, which fluctuates due to the combustion of the fuel in the cylinder, is calculated from the sequentially detected pressure in the cylinder, the sequentially calculated volume in the cylinder, and the rate of change thereof, and The time at which the occurrence rate changes from negative to positive is determined as the actual fuel ignition timing, and the actual fuel ignition timing and the present target fuel ignition timing are used to determine the actual fuel ignition timing. A fuel injection timing control method for an engine, wherein the target fuel injection timing is corrected based on the obtained fuel injection timing correction amount. 4. An engine in which fuel injected into a cylinder by an injector ignites and burns, an in-cylinder pressure detecting means for sequentially detecting a pressure in the cylinder of the engine, and a cylinder for sequentially calculating a volume in the cylinder. An internal volume calculating unit configured to sequentially detect, by the in-cylinder pressure detecting unit, a heat generation rate in the cylinder, which is changed by injection of the fuel into the cylinder and combustion of the fuel in the cylinder; Heat generation rate calculation means for calculating the pressure in the cylinder and the volume in the cylinder calculated sequentially by the cylinder volume calculation means and the rate of change thereof, and the time when the heat generation rate changes from negative to positive. Actual fuel ignition timing determining means for determining the fuel ignition timing, operating state detecting means for detecting the operating state of the engine, and predetermined based on the operating state A target timing calculating means for calculating the target fuel injection timing and the target fuel ignition timing for a current operating state of the engine detected by the operating state detecting means from the target fuel injection timing and the target fuel ignition timing; A fuel injection timing control device for an engine, comprising: combustion injection timing correction means for correcting the target fuel injection timing by a fuel injection timing correction amount obtained from a deviation between an ignition timing and the target fuel ignition timing.