JP2764514B2 - Fuel increase correction amount control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for gradually decreasing a fuel increase correction amount in accordance with a surge torque generation level in an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, during warm-up operation of an internal combustion engine, the engine temperature is low, so that the flow rate of the fuel flowing on the inner wall of the intake passage increases due to the low temperature. Since the fuel sometimes adheres and is difficult to mix with the air, the water temperature is increased according to the engine cooling water temperature in order to secure the amount of fuel in the air-fuel mixture.

Incidentally, the conventional water temperature increase correction K _TW is set in consideration of the above points, and is basically set to an amount necessary for not deteriorating the combustion. Of the total water temperature increase correction for the minimum required amount (specifically, approximately 25% of the correction for the former) + 5%
(The latter correction) = A rich mixture of about 30% is supplied.

[0004]

Therefore, when a high-quality fuel having good vaporizability is used and the variation in the parts of the fuel system is at a normal level, an rich mixture is supplied.
This results in poor fuel economy and emissions. Therefore,
By detecting the surge torque in some way and setting the water temperature increase correction amount to the minimum necessary to keep the surge torque level below the specified level, it is possible to reduce fuel consumption and improve exhaust emissions. Attempted. In that case,
At first, the fuel used and environmental conditions are unknown, so the water temperature increase correction amount is set to a relatively large value, and the level of the surge torque is detected and gradually reduced within a range not exceeding a predetermined level. .

[0005]

By the way, the fuel supplied from the fuel injection valve or the like to the engine is delayed after it is supplied and burns to generate torque. This delay time is the sum of the time from when fuel reaches the combustion chamber via the intake passage and the time from when it is drawn into the combustion chamber to when it reaches the combustion explosion through the compression stroke. It is determined by the engine speed and the flow rate of the intake air, and the latter is determined by the engine speed, and therefore varies depending on the operating state.

Therefore, when the fuel increase correction amount is corrected to decrease, it is necessary to detect the torque state generated by the combustion explosion of the fuel whose decrease has been corrected, and then perform the following decrease correction. However, conventionally, the decrease correction of the fuel increase correction amount is made to gradually decrease with a constant time constant by the integral control having a constant integration constant, so that the above-mentioned requirement is satisfied and the delay time is the longest. Although it is set, naturally, there is a problem that the response delay becomes large during operation with a short delay time.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and it is desirable to appropriately set the decreasing speed of the fuel increase correction amount without being affected by a change in the operating state of the engine. It is an object of the present invention to provide a fuel increase correction amount control device for an internal combustion engine which can ensure a high response.

[0008]

Therefore, a fuel increase correction amount control device for an internal combustion engine according to the present invention, as shown in FIG. 1, detects a surge torque level of the engine.
Fuel increase correction for an internal combustion engine, comprising: a torque detection means; and an increase correction amount gradually decreasing control means for gradually decreasing a previously set fuel increase correction amount while maintaining the detected surge torque at a predetermined level or less. An operating state detecting means for detecting an operating state of the engine, and a torque estimating a delay time from when fuel is supplied to the engine based on the operating state of the engine to when the fuel generates torque by combustion. Generating delay time estimating means, and decreasing time constant setting means for setting a time constant of a decrease control of the fuel increase correction amount by the increase correction amount gradually decreasing control means based on the estimated delay time. A fuel increase correction amount control device for an internal combustion engine.

[0009]

[0010]

The fuel correction amount, which is set to a relatively large value, is gradually reduced so that the surge torque detected by the surge torque detection means is maintained at a predetermined level or less. It is set as follows by the decreasing time constant setting means.

That is, the torque generation delay time estimating means estimates the delay time from when fuel is supplied to the engine to when the fuel generates torque by combustion based on the operating state detected by the operating state detecting means. A time constant for the control for decreasing the fuel increase correction amount is set based on the estimated delay time. As a result, after the increase correction amount is reduced and corrected, the increase correction amount gradual decrease control means synchronizes with the corrected fuel immediately after a delay time in which torque is generated due to combustion explosion and synchronizes with the next torque state corresponding to the torque state. Since reduction correction can be performed, responsiveness can be ensured as much as possible without performing erroneous control.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. In FIG. 2 showing the configuration of the first embodiment, air is sucked into the internal combustion engine 1 through an air cleaner 2, an intake duct 3, a throttle chamber 4, and an intake manifold 5.

The intake duct 3 is provided with an air flow meter 6 for detecting an intake air flow rate Q. The throttle chamber 4 is provided with a throttle valve 7 interlocked with an accelerator pedal (not shown) to control the intake air flow rate Q. The intake manifold 5 is provided with an electromagnetic fuel injection valve 8 as a fuel injection means for each cylinder, and injects and supplies fuel which is fed from a fuel pump (not shown) and controlled to a predetermined pressure by a pressure regulator.

The crank angle phase difference of each cylinder of the engine (
For example, in the case of a four-cylinder engine, a crank angle sensor 9 that outputs a reference signal REF every 180 °, a water temperature sensor 11 that detects the temperature of cooling water of the engine, and a combustion engine of each cylinder that is fastened together with, for example, an ignition plug. A combustion pressure sensor 10 for detecting pressure (in-cylinder pressure) is provided, and a detection signal from these is output to a control unit 12 built in the microcomputer, and the control unit 12 generates a surge based on these detection signals as follows.・ Detect the torque and set the fuel water temperature increase correction coefficient K _TW .

The routine for setting the water temperature increase correction coefficient K _TW by detecting the surge torque will be described below with reference to FIG. Step (S in the figure; the same applies hereinafter) In step 1, an analog value of the combustion pressure detected by the combustion pressure sensor 11 mounted on the cylinder in the combustion stroke every predetermined minute unit time (for example, 12.8 μs) To a digital value.

In step 2, based on the detection signal from the crank angle sensor 9, it is determined whether or not the cylinder is within a predetermined crank angle range in the combustion stroke. And
If it is determined that the predetermined crank angle range, the converted sample values in step 1 proceeds to step 3, is stored as M _i in the memory M. In step 4,
Sum of the difference between the M _i and the previous _{M 1-i Σ (M i} -M
_1-i ) = ΔM is calculated.

In step 5, the ΔM obtained in step 4 is Fourier-transformed. As a result, the level of each frequency component whose sampling cycle is a unit cycle and each cycle is 1 to i times the cycle is obtained. In step 6, and stored in the memory A by selecting the level [Delta] P ₁ of predetermined frequency component f _n involved in the surge torque from the result of the Fourier transform. In this case, only one frequency component that is most involved in surge torque may be selected, or a plurality of frequency components may be selected and stored simply or weighted and averaged. .

Next, in step 7, reads the detection values M _i1 ~M _in the combustion pressure at the same crank angle timing of the same stroke each for each cylinder 1 to n. In step 8, obtained for between all cylinders difference (variation) .DELTA.M _i of the combustion pressure M _i1 ~M _in between the cylinders, and adds all these. As a result, the maximum variation in the combustion pressure between the cylinders is detected.

In step 9, ΔM _i is Fourier-transformed for all i in the predetermined crank angle range. In step 10, the level of a predetermined frequency component related to the surge torque is selected and stored in the memory B. In step 11, it is stored in the memory B to select the level [Delta] P ₂ of a predetermined frequency component f _m involved in the surge torque from the result of the Fourier transform. Also in this case, a value obtained by averaging the values of a plurality of frequency components simply or by adding weights may be stored.

After detecting the variation in the combustion pressure in the same cylinder and the variation in the combustion pressure between the cylinders in this way, the water temperature increase corresponding to the surge torque generation level is comprehensively taken into account. The reduction amount ΔK _TW of the correction coefficient K _TW is set. Here, at the start of warm-up, the generation level of surge torque is unknown. Therefore, with a margin, the water temperature increase correction coefficient K _TW is set to a high value as before, and the generation level of surge torque is detected. The water temperature increase correction coefficient K
_{The TW} is gradually reduced, and the reduction amount ΔK _TW for each time is set based on the detection of the variation in the combustion pressure in the same cylinder and the variation in the combustion pressure between the cylinders.

That is, based on the combustion pressure fluctuation ΔP ₁ in the same cylinder stored in the memory A and the combustion pressure variation ΔP ₂ between the cylinders stored in the memory B, a decrease corresponding to the surge torque generation level. The amount ΔK _TW is stored in the ROM in advance Δ
Reduction amount Δ stored with P ₁ and ΔP ₂ as parameters
_Calculated from K _TW . Here, in the low engine speed region, ΔP ₁ is more involved in the generation of surge torque,
In the high rotation region, ΔP ₂ is more involved in the generation of surge torque, so if one of them is large, or if the total value of both is below a predetermined level, the level of surge torque is small and the water temperature increase correction amount larger set of [Delta] K _TW as there is room to reduce the K _TW, the level of surge torque is set smaller [Delta] K _TW for the margin of decrease becomes smaller toward the limit. Therefore,
This step 11 is configured to include a surge torque detecting means.

Next, the reduction amount ΔK_TWDue to decrease
A water temperature increase correction amount K is set according to the time constant._TWAround
FIG. 4 is a flowchart showing a routine for correcting the decrease periodically.
Therefore, it will be described. This routine is executed at predetermined time intervals.
Is performed. In step 21, the value set in the routine
Water temperature increase correction amount K_TWReduction amount ΔK _TWRead.

In step 22, the time constant ΔI of the decrease by the decrease amount ΔK _TW according to the delay time from the supply of the fuel to the generation of the torque described above based on the engine speed N is previously experimentally or analytically determined. It is obtained by searching from the map obtained and stored in the ROM. Here, as the engine speed N increases, the time required for the fuel to reach _the combustion chamber and the time required for _the fuel to be sucked into _the combustion chamber and undergoing a combustion explosion through the compression stroke are both reduced, and the delay time is shortened. Δ
I is also set to be small. That is, step
Reference numeral 22 has the functions of torque generation delay time estimation means and decrease time constant setting means at the same time.

In step 23, the timer starts counting. In step 24, the count value _{Tc of the} timer is compared with the time constant ΔI. When the count value _{Tc of the} timer becomes equal to or more than ΔI, the process proceeds to step 25 to reset the count value _Tc, and then proceeds to step 26 to correct the water temperature increase correction amount K _TW by the decrease amount ΔK _TW . Update with values. The functions from step 23 to step 26 correspond to the increase correction amount gradual decrease control means.

With this configuration, the water temperature increase correction amount K is adjusted in accordance with the delay time until the generation of torque after fuel supply.
_Since the time constant of the decrease of _TW is set, after the change in torque due to the correction appears, the next decrease correction is immediately performed according to the torque state, so that responsiveness is ensured well even at high speed, and fuel consumption and Exhaust emissions can be improved. In the first embodiment, the decreasing time constant ΔI is set only by the engine speed N. However, as described above, the time until the fuel reaches the combustion chamber after the supply is determined by the flow rate of the intake air. The flow velocity changes depending on the intake air flow rate Q in addition to the engine rotation speed N.

Considering this point, the time constant Δ
A routine of the second embodiment for setting I with higher accuracy will be described with reference to FIG. In step 31, it reads the decrease amount [Delta] K _TW step 21 similar water temperature increase correction amount K _TW. Next, at step 32, based on the engine speed N and the intake air flow rate Q, the flow velocity v of the intake air is determined by searching a preset map or the like.

In step 33, a first delay time T ₀ from the fuel supply to the combustion chamber as a function of the flow velocity v of the intake air obtained in step 32 and the length of the intake passage from the fuel supply point to the combustion chamber. Ask for. Since the intake passage length is a constant value when the fuel supply point is constant, the function value may be directly set in a map corresponding to the engine speed N and the intake air flow rate Q.

In step 34, a second delay time T from the time when the fuel is sucked into the combustion chamber to the time when the combustion explosion occurs through the compression stroke.
₁ is obtained by searching the map based on the engine speed N. In step 35, the time constant ΔI of the decrease of the water temperature increase correction coefficient K _TW with respect to the total delay time T obtained by adding the first delay time T ₀ and the second delay time T ₁ is set by searching from a map or the like. I do. Here, ΔI is naturally set to increase in proportion to the increase of T.

In steps 36 to 39, the time constant Δ is set in the same manner as in steps 23 to 26 in FIG.
Every time I elapses, the water temperature increase correction coefficient K _TW is decreased by the decrease amount ΔK _TW . In this embodiment, since the delay time from the fuel supply to the generation of the torque can be grasped more accurately, the time constant ΔI corresponding to the delay time can be set with higher accuracy.

FIG. 6 shows a routine for learning the water temperature increase correction coefficient K _TW. After it is determined in step 41 that the ignition key switch is OFF, the water temperature increase correction coefficient K _TW corrected as described above is reduced in step 42 as described above. Backup R
The memory is stored in the AM, and then the power of the control unit 12 is cut off in step 43. With this configuration, at the next start of operation, by using the water temperature increase correction coefficient K _TW at the previous learning stored in the backup RAM as an initial value, the time until convergence by the decrease correction can be shortened, and fuel consumption can be reduced. _{Thus, the} effect of improving exhaust emissions can be enhanced as much as possible.

[0031]

As described above, according to the present invention, the time constant of the decrease when the fuel increase correction amount is reduced while the level of the surge torque is maintained at or below the predetermined level is set after the supply of fuel. Since the setting is made in accordance with the delay time until the torque is generated, the fuel increase correction amount can be converged to an appropriate value with the best possible response while preventing erroneous control, and the fuel consumption _and exhaust emissions are improved satisfactorily. You can do it.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 3 is a flowchart showing a routine for detecting a surge torque and setting a decrease amount of a water temperature increase correction coefficient by the detection according to the embodiment;

FIG. 4 is a flowchart showing a routine of a first embodiment for setting a time constant for decreasing the water temperature increase correction coefficient;

FIG. 5 is a flowchart showing a routine according to a second embodiment for setting a time constant for decreasing the water temperature increase correction coefficient.

FIG. 6 is a flowchart showing a routine for learning a water temperature increase correction coefficient;

[Explanation of symbols]

 1 internal combustion engine 9 crank angle sensor 11 combustion pressure sensor 12 control unit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F02D 41/06 F02D 41/16

Claims (1)

(57) [Claims] 1. A surge torque detecting means for detecting a level of a surge torque of an engine, and gradually decreasing a previously set fuel increase correction amount while maintaining the detected surge torque at a predetermined level or less. A fuel increase correction amount control device for an internal combustion engine, comprising: an operation state detection means for detecting an operation state of the engine; and a fuel supply to the engine based on the operation state of the engine. A torque generation delay time estimating means for estimating a delay time until the fuel generates torque by combustion; and a time constant of control for decreasing the fuel increase correction amount by the increase correction amount gradual decrease control means based on the estimated delay time. And a decreasing time constant setting means for setting a correction amount of fuel for the internal combustion engine.