JP3879233B2 - Engine fuel injection timing control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an engine fuel injection timing control device that suppresses a rapid change in engine fuel injection timing.
[0002]
[Prior art]
Recently, as an electronically controlled fuel injection system for diesel engines, the engine characteristics including output and fuel efficiency and engine exhaust gas characteristics have been improved by enabling control of the fuel injection amount, fuel injection timing, and fuel injection pressure. Have been developed. The engine fuel injection system includes a needle valve that moves up and down in the main body to open and close the nozzle hole, and an electromagnetic valve that is supplied with a drive current that controls the pressure action of the working fluid to raise and lower the needle valve. The injection timing, the injection amount, and the injection pressure of the fuel injected from the injector into the combustion chamber are controlled by the controller in accordance with the operating state of the engine.
[0003]
In such an electronically controlled combustion injection system, with respect to the fuel injection timing, the basic injection timing is calculated by referring to a map determined in advance from the engine speed and the fuel injection amount. The final target injection timing is determined by performing various corrections based on the intake air temperature and the like. Therefore, if the engine speed and fuel injection amount change suddenly during acceleration / deceleration operation, the basic injection timing and the final target injection timing change suddenly, the engine combustion state and drivability change suddenly, and the driver feels uncomfortable. May give.
[0004]
In order to prevent such a change in the combustion state of the engine, there is a control that gradually advances the fuel injection timing to the target injection timing during acceleration operation, that is, a dumping control of the fuel injection timing (as an example) , Japanese Patent Publication No. 3-50899). In this publication, the degree of acceleration, that is, acceleration is detected, the advance speed of the fuel injection timing is increased during rapid acceleration, and the advance speed of the fuel injection timing is decreased during slow acceleration, so that the acceleration is slowed down. The fuel injection timing is controlled accordingly to reduce the amount of NOx and white smoke generated.
[0005]
In controlling the fuel injection timing, in order to determine the advance speed according to the stepwise acceleration such as sudden acceleration or slow acceleration, the optimum fuel injection timing is previously determined according to such acceleration. Therefore, it is necessary to store the fuel injection timing thus obtained in the memory of the controller. In order to obtain the optimal fuel injection timing in advance, it is necessary to repeat a number of experiments, which requires great effort and cost for engine development. Even if the advance angle is determined according to the stepwise acceleration, the fuel injection timing is controlled at the same advance angle for a certain range of acceleration. As a result, it is necessary to carry out many corrections of the fuel injection timing until the actual fuel injection timing reaches the target fuel injection timing. I can't do it.
[0006]
[Problems to be solved by the invention]
Therefore, instead of adopting a method of storing a large amount of fuel injection timing information in advance according to the acceleration and reading out the stored fuel injection timing and responding to the acceleration in stages, There is a problem to be solved in that the optimum fuel injection timing corresponding to the acceleration state is obtained by performing the optimum advance angle or retard angle control according to the acceleration condition for any acceleration.
[0007]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problem, and to obtain an optimal fuel injection timing by calculation no matter what degree of acceleration the acceleration / deceleration is when the engine is accelerated / decelerated. It is another object of the present invention to provide a fuel injection timing control device for an engine that can reduce the burden on the memory and CPU of the controller.
[0008]
In order to achieve the above object, a fuel injection timing control device for an engine according to the present invention comprises a basic injection timing calculation means for calculating a basic injection timing for injecting fuel according to an engine speed and a target fuel injection amount, An engine comprising difference calculating means for calculating a difference between the injection timing and the immediately preceding target injection timing, determination means for determining whether or not the difference exceeds a predetermined determination value, and damping correction injection timing calculation means in the fuel injection magnetic control device, the damping correction injection magnetic calculating unit, when the difference is determined to exceed the judgment value by the determination means, the injection timing correction quantity by multiplying a coefficient to the difference And calculating the next damping correction injection timing by correcting the immediately preceding target injection timing according to the injection timing correction amount, and the difference is If it is determined not to exceed the serial determination value, wherein the at the basic injection timing which the damping correction injection timing of the next.
[0009]
Further, in the fuel injection timing control apparatus of the engine, the coefficient is characterized by a value less than one. That is, the injection timing correction amount that is always smaller than the difference calculated by the difference calculating means is obtained.
[0010]
Since the present invention is configured as described above, it operates as follows. That is, the basic injection timing calculation means calculates the basic injection timing for injecting fuel according to the engine speed and the target fuel injection amount, which is the engine operating state at that time. The target fuel injection amount is usually determined based on data such as a map determined in advance corresponding to the engine speed and the accelerator depression amount. The difference calculating means calculates a difference between the basic injection timing calculated by the basic injection timing calculating means and the immediately preceding target injection timing calculated by the target injection timing calculating means. The determination unit determines whether or not the difference exceeds a predetermined determination value. When the difference exceeds the judgment value, the damping correction injection timing calculation means obtains an injection timing correction amount by multiplying the difference by a coefficient, and corrects the immediately preceding target injection timing according to the obtained injection timing correction amount to correct the next period. A damping correction injection timing is calculated. If the difference does not exceed the determination value, the basic injection timing calculated by the basic injection timing calculation means is set as the next damping correction injection timing. Therefore, if the difference between the basic injection timing and the immediately preceding target injection timing exceeds the judgment value, the injection timing correction amount can be obtained by multiplying the difference by a predetermined coefficient. And the damping correction injection timing is obtained only by the calculation using the coefficient.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an engine fuel injection timing control apparatus according to the present invention will be described with reference to the accompanying drawings. FIG. 4 is a schematic view of the entire system including an engine fuel injection system to which the engine fuel injection timing control device according to the present invention is applied. Although only one injector 11 is shown in FIG. 4, the engine 1 is a multi-cylinder four-cycle direct injection diesel engine such as four cylinders in order to obtain a high output. The engine 1 has a cylinder block 2 and a cylinder head 3, and the reciprocating motion of the piston 4 slidable in the cylinder liner formed in the cylinder block 2 and the rotational motion of the crankshaft 6 connect the two. It is converted via the connecting rod 5.
[0012]
The electronically controlled fuel injection system 10 of the engine 1 employs a hydraulically operated unitized injector 11. The injector 11 is disposed in the cylinder head 3, operates with engine oil as a working fluid, and injects the fuel directly into the combustion chamber 7 by increasing the pressure of the fuel to a predetermined fuel injection pressure. To do. The fuel boosted to a relatively low pressure by the fuel pump 12 is supplied to a pressure increasing chamber (not shown) formed inside the injector 11 through the fuel supply pipe 13. The engine oil is boosted to a high pressure by a high-pressure oil pump 14, accumulated in a high-pressure oil manifold (oil rail) 15, and supplied from the high-pressure oil manifold 15 to a pressure chamber (not shown) in each injector 11. The high-pressure engine oil supplied to the pressure chamber acts on a pressure-increasing plunger (not shown) to stroke the pressure-increasing plunger, and the fuel in the pressure-increasing chamber is increased in pressure and formed at the tip of the injector 11. It is injected from the nozzle hole.
[0013]
The electronic control fuel injection system 10 includes a controller 20 as an electronic control unit (ECM). The controller 20 receives detection signals from detection means for detecting the operating state of the engine 1, and the controller 20 Based on these detection signals, the high pressure oil pump 14, the flow control valve 16, the electromagnetic valve 17 of the injector 11 and the like are controlled.
[0014]
Specifically, the detection means for detecting the operating state of the engine 1 input to the controller 20 includes the following. A crank angle sensor 21 for detecting the rotational speed Ne of the engine 1 is fixed to the crankshaft 6 and rotates, and has a gear 8 (57 teeth at equal intervals) having a missing tooth (three teeth) 9 in a part of the periphery. It is comprised with the electromagnetic pick-up which detects. The rotational speed of the crankshaft 6 is obtained from the number of times that the missing tooth (three teeth) portion 9 is detected and the time required for the detection. The accelerator depression amount sensor 22 for detecting the accelerator depression amount (or accelerator opening) Ac is composed of a potentiometer that detects the depression stroke of the accelerator pedal. The engine temperature sensor for detecting the engine temperature is a water temperature sensor 23 (or an oil temperature sensor for detecting the lubricating oil temperature) that is provided in the cylinder head 3 and detects the cooling water temperature Tw circulating through the cylinder head 3. . The coolant temperature Tw can be used as a representative value of engine friction. Further, a pressure sensor 24 and a temperature sensor 25 are installed in the high pressure oil manifold 15 in order to detect rail pressure and oil temperature in the high pressure oil manifold 15.
[0015]
The intake pipe 26 of the engine 1 is provided with an intake pressure sensor 27 for detecting the intake pressure of the intake pipe 26 and an intake air temperature sensor 28 for detecting the intake air temperature. The opening degree of the intake throttle valve 29 provided in the intake pipe 26 is controlled by a control signal from the controller 20, and the throttle valve position is detected by a position sensor 30. In order to reduce NOx, an EGR (exhaust gas recirculation) pipe 32 that recirculates a part of the exhaust gas to the intake pipe 26 is connected between the exhaust pipe 31 and the intake pipe 26 of the engine 1. . The valve lift position of the EGR valve 33 provided in the middle of the EGR pipe 32 uses the negative pressure of a vacuum pump 34 as a vacuum source whose introduction is controlled by a pressure regulating valve (EVRV) 35 controlled by the controller 20. The valve lift position is detected by the pressure sensor 36 as a valve lift negative pressure. Further, the controller 20 also receives signals from a shift position sensor 37 of the automatic transmission, a warm-up switch 38 operated to promote warm-up of the engine 1, and an air conditioner switch 39 as an auxiliary machine.
[0016]
The injection pressure of the fuel injected from the injector 11 is determined by the pressure in the high pressure oil manifold 15, that is, the oil rail pressure. The oil rail pressure in the high-pressure oil manifold 15 is controlled by controlling the opening amount of the flow control valve 16 attached to the high-pressure oil pump 14 and controlling the amount of oil leaked from the flow control valve 16. The flow control valve 16 is a normally open or normally closed control valve, and the opening degree of the flow control valve 16 is controlled by, for example, a duty ratio of a control pulse current that is a control signal from the controller 20.
[0017]
The injector 11 is provided with an electromagnetic valve 17, and the electromagnetic valve 17 is disposed in an oil path from the high-pressure oil manifold 15 to the pressure chamber in the injector 11. By opening and closing the solenoid valve 17, the high pressure oil in the high pressure oil manifold 15 is controlled to be supplied to and discharged from the pressure chamber in the injector 11, and the high pressure oil supplied to the pressure chamber is increased in pressure. Pressure is applied to the plunger to increase the fuel in the pressure-increasing chamber and inject fuel.
[0018]
By controlling the operation of the solenoid valve 17 by the energization timing and energization period of the control current from the controller 20, the supply timing and the supply period of the high pressure oil to the pressure chamber in the injector 11 are controlled and injected from the injector 11. The fuel injection timing and the injection amount are controlled. That is, the controller 20 determines the energization period (pulse width) to the solenoid valve based on the target fuel injection amount determined by calculating the target fuel injection amount, and energizes the solenoid valve with this pulse width, The injection amount is controlled. The crank angle detected by the crank angle sensor 21 is set to the solenoid valve 17 together with a detection signal of each sensor for detecting that the reference cylinder or each cylinder has reached the compression top dead center or a predetermined position before the compression top dead center. It is used to control the energization start timing and energization period of the drive current to be driven. In addition, about the structure provided with the pressure increase plunger of the injector 11, and the fuel-injection system itself provided with this injector, what is disclosed, for example in Japanese translations of PCT publication No. 6-511526 etc. can be used. However, the fuel injection timing control device for an engine according to the present invention is not limited to the fuel injection system provided with the injector, but has a pressure control chamber to which high-pressure fuel is supplied, and the needle pressure is controlled by the fuel pressure. Of course, the present invention can be applied to a type of injector that moves up and down.
[0019]
FIG. 1 is a conceptual diagram of calculation of a target fuel injection timing applied to the fuel injection timing control device for an engine according to the present invention. The calculation of the fuel injection timing is performed by the controller 20. The basic injection timing calculation means 40 calculates the basic injection timing SOIbs by referring to data such as a predetermined map based on the engine rotational speed Ne and the target fuel injection amount Q which are the operating states of the engine at that time. (SOI; Start Of Injection). The target fuel injection amount Q is usually calculated with reference to data such as a predetermined map corresponding to the engine speed Ne and the accelerator depression amount Ac.
[0020]
The damping correction injection timing calculation means 41 is a calculation means for performing damping correction of the fuel injection timing in the present invention. The damping correction injection timing calculation means 41 is a difference ΔSOI between the basic injection timing SOIbs calculated by the basic injection timing calculation means 40 and the immediately preceding target injection timing SOIb calculated and output by the target injection timing calculation means 42 (described later). Is multiplied by a coefficient to obtain an injection timing correction amount, and the immediately preceding target injection timing SOIb is corrected according to this injection timing correction amount to calculate the next damping correction injection timing SOId that has been subjected to the damping correction. The coefficient is a predetermined value, and is set to a value smaller than 1. As the injection timing immediately before obtaining the difference ΔSOI from the basic injection timing SOIbs, the immediately preceding target injection timing SOIb calculated by the damping correction injection timing calculating means 41 may be employed instead of the immediately preceding target injection timing SOIb. .
[0021]
The target injection timing calculation means 42 performs various operations such as the cooling water temperature Tw detected by the water temperature sensor 23 and the intake air temperature Tboost detected by the intake air temperature sensor 28 using the damping correction injection timing SOId calculated by the damping correction injection timing calculation means 41. The final target injection timing SOI is calculated by correcting based on the state. The controller 20 repeatedly executes the calculation in each of the calculation means 40 to 42 at a constant time period. The controller 20 determines the energization timing of the drive current to the solenoid valve 17 of the fuel injection system 10 based on the target injection timing SOI obtained by the calculation performed as described above, and the energization determined in this way. The electromagnetic valve 17 is energized at the timing to control the fuel injection timing from the injector 11.
[0022]
FIG. 2 is a flowchart showing a calculation routine for obtaining a fuel injection timing at which fuel is injected in the fuel injection timing control device for an engine according to the present invention. This routine is executed by the damping correction injection timing calculation means 41 shown in FIG. This flowchart includes the following steps (S1 to S4).
(1) The difference between the basic injection timing SOIbs calculated by the basic injection timing calculation means 40 and the target injection timing SOIb immediately before calculated by the target injection timing calculation means 42 is obtained and substituted into ΔSOI (S1).
(2) It is determined whether or not the absolute value of the difference ΔSOI calculated in S1 exceeds a predetermined difference determination value, SOILv (S2).
(3) As a result of the determination in S2, if the absolute value of the difference ΔSOI calculated in S1 exceeds the determination value SOILv, the dumping correction should be performed because the change in the fuel injection timing is large. The corrected injection timing calculation means 41 corrects the immediately preceding target injection timing SOIb by adding the difference ΔSOI multiplied by a predetermined damping coefficient Kdmp (for example, 0.5) to the immediately preceding target injection timing SOIb. Thus, the next damping correction injection timing SOId is obtained (S3). The absolute value of the difference ΔSOI exceeds the predetermined difference level SOILv is an execution condition for correcting the injection timing by the damping correction injection timing calculation means 41.
(4) As a result of the determination in S2, if the absolute value of the difference ΔSOI calculated in S1 does not exceed the determination value SOILv, the change in the fuel injection timing is small and it is not necessary to perform the damping correction. The basic injection timing SOIbs calculated by the timing calculation means 40 is substituted into the next damping correction injection timing SOId (S4). The fact that the absolute value of the difference ΔSOI falls below the determination value SOILv is an escape condition for correcting the injection timing by the damping correction injection timing calculation means 41.
The final target injection timing SOI is calculated by the target injection timing calculation means 42 with respect to the damping correction injection timing SOId calculated by the above calculation routine. Note that the next target injection timing SOI becomes the immediately preceding target injection timing SOIb when the next calculation routine is executed.
[0023]
FIG. 3 is a graph showing how the target injection timing SOI changes with time when the fuel injection timing calculation routine shown in FIG. 2 is executed. Here, the target injection timing SOI is the time before compression top dead center (positive in the reverse direction), and the damping coefficient Kdmp is set to 0.5. The calculation time is executed every Δt. It is assumed that the basic injection timing SOIbs calculated by the basic injection timing calculation means 40 is increased stepwise at time t ₁ . A difference ΔSOI ₁ between the basic injection timing SOIbs and the immediately preceding target injection timing SOIb calculated by the target injection timing calculating means 42 is obtained (S1), and it is determined that the difference ΔSOI ₁ is larger than a predetermined determination value SOILv. since that (S2) calculating the damping correction injection timing calculation means 41, are multiplied by a damping coefficient Kdmp the difference DerutaSOI ₁ is added to immediately before the target injection timing SOIb, the result as damping correction injection timing SOID ₁ for the next (S3; provided that there is no correction by the cooling water temperature Tw and the intake air temperature Tboost).
[0024]
In the next operation time t _2, the routine shown in FIG. 2 is repeatedly executed. That is, the target injection timing SOID ₁ next to the immediately preceding, the difference DerutaSOI of the basic injection timing _{SOIbs 2 (= SOIbs-SOId 1} ) is larger than the still level SOILv (S2), a value obtained by multiplying the damping Kdmp to DerutaSOI ₂ SOId ₂ (= SOd ₁ + Kdmp × ΔSOI ₂ ) obtained by adding to SOId ₁ is set as the next damping correction injection timing (S3). Thereafter, the same processing is repeated until the difference between the target injection timing and the basic injection timing SOIbs becomes smaller than the level SOILv, and the target injection timing is gradually advanced. At time t _n, the difference DerutaSOI _n of the basic injection timing SOIbs is determined to be smaller than the level SOILv and (S2), damping correction injection timing SOID _n the next is set to the basic injection timing SOIbs (S4).
[0025]
In the above case, the injection timing control is performed when the basic injection timing SOIbs is greatly advanced stepwise. However, even when the basic injection timing SOIbs is greatly retarded stepwise, the target injection timing is the same as before the top dead center. The angle is gradually retarded at the angle of. FIG. 3 shows how the target injection timing changes when the basic injection timing SOIbs suddenly decreases stepwise at time t _m . The difference ΔSOI between the target injection timing and the basic injection timing SOIbs is a negative value, and the addition process in S3 is subtraction.
[0026]
As described above, in the control of the fuel injection timing according to the present invention, the injection timing correction amount for the next damping correction injection timing is obtained by multiplying the difference between the basic injection timing and the immediately preceding target injection timing by a predetermined coefficient. Therefore, the injection timing until the basic injection timing is reached, as seen in the case of correcting the advance speed stepwise by dividing the difference value into two steps, as in the conventional case, is required. The number of corrections does not increase or abrupt advance / retard angle control does not occur, and the target injection time is converged with an appropriate number of corrections. The damping coefficient Kdmp is set to 0.5 in the above embodiment, but is not limited to this. It can be changed depending on the value of the difference ΔSOI. That is, the injection timing correction width can be adjusted by reducing the damping coefficient Kdmp for ΔSOI that is too high. Further, in the calculation routine for obtaining the fuel injection timing, the determination value SOILv is fixed at S2, but the determination value when entering the correction of the injection timing after S3 is the determination value when exiting from the correction of the injection timing. It can also be set larger. Further, in the above embodiment, the damping coefficient Kdmp and the determination value SOILv are set to the same value when the injection timing is advanced and retarded, but may be set to different values.
[0027]
【The invention's effect】
The fuel injection timing control device for an engine according to the present invention is configured as described above, and the damping correction injection timing calculation means calculates the difference between the basic injection timing determined according to the operating state of the engine and the immediately preceding target injection timing. If the value exceeds the judgment value, the difference is multiplied by a damping coefficient to obtain the injection timing correction amount, the previous target injection timing is corrected according to the injection timing correction amount, and the next damping correction injection timing is calculated. If the above difference does not exceed the judgment value, the basic injection timing is set as the next damping correction injection timing. Therefore, the optimum advance angle corresponding to the degree of acceleration is calculated regardless of the degree of acceleration. Alternatively, it is possible to determine the fuel injection timing for retarding control, and it may take time to reach the target fuel injection timing, or rapid advance / retarding control may be performed. There is no. In addition, since a method of obtaining a large number of fuel injection timings step by step with respect to the degree of acceleration and storing them in the memory is not adopted, the burden on the memory and CPU of the controller can be reduced.
[Brief description of the drawings]
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a calculation conceptual diagram for obtaining a target injection timing applied to a fuel injection timing control device for an engine according to the present invention.
FIG. 2 is a flowchart showing a calculation routine for obtaining a target injection timing in an engine fuel injection timing control apparatus according to the present invention;
FIG. 3 is a graph showing an example of a change in target injection timing when an arithmetic routine for obtaining the injection timing of the engine shown in FIG. 2 is executed.
FIG. 4 is a diagram showing an example of an electronically controlled fuel injection system to which an engine fuel injection timing control device according to the present invention is applied.
[Explanation of symbols]
1 Engine 10 Electronically controlled fuel injection system 11 Injector 14 High pressure oil pump 15 High pressure oil manifold 17 Solenoid valve 20 Controller 40 Basic injection timing calculation means 41 Damping correction injection timing calculation means 42 Target injection timing calculation means Ne Engine speed Q Target fuel injection Quantity SOIbs Basic injection timing SOIb Target injection timing immediately before SOId Damping correction injection timing of the next period ΔSOI Difference SOILv Determination value Kdmp Damping coefficient

Claims (2)

Basic injection timing calculating means for calculating basic injection timing for injecting fuel according to engine speed and target fuel injection amount, difference calculating means for calculating a difference between the basic injection timing and the immediately preceding target injection timing, In a fuel injection timing control device for an engine, comprising: a determination unit that determines whether or not the difference exceeds a predetermined determination value; and a damping correction injection timing calculation unit.
Said damping correction injection timing calculation means, wherein when said difference by determining means is determined to exceed the judgment value determines the injection timing correction quantity by multiplying a coefficient to the difference, according to the injection timing correction amount Correcting the immediately preceding target injection timing to calculate the next damping correction injection timing, and if it is determined that the difference does not exceed the determination value, the basic injection timing is set to the next damping correction injection timing. An engine fuel injection timing control device characterized by the above . The engine fuel injection timing control apparatus according to claim 1, wherein the coefficient is a value smaller than one.

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