JP2985506B2 - Fuel injection timing control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection timing control device for independently controlling the fuel injection timing of a fuel injection device provided for each cylinder in an internal combustion engine having an exhaust gas recirculation device. About.

[0002]

2. Description of the Related Art In exhaust gas recirculation, a part of the exhaust gas is recirculated to a combustion chamber, and the combustion temperature is reduced by the heat capacity of an inert gas which is a main component of the exhaust gas to reduce the amount of NOx generated. Things. On the other hand, since the exhaust gas recirculation involves a decrease in torque due to lean combustion, the ratio of the amount of exhaust gas to be recirculated to the entire air-fuel mixture in the combustion chamber is controlled in accordance with the operating state of the engine.

[0003] When the exhaust gas recirculation is stopped, better combustion is realized by making the mixture concentration in the combustion chamber uniform.
Since lean combustion occurs during the execution of exhaust gas recirculation, it is preferable that the higher concentration of the air-fuel mixture be formed in the upper part of the combustion chamber to achieve better combustion by improving ignitability.

Japanese Patent Application Laid-Open No. 63-253136 discloses a fuel injection timing control device that stratifies the air-fuel mixture and improves combustion by delaying the fuel injection timing when performing exhaust gas recirculation. Are listed.

[0005]

In the above-mentioned prior art, since there is an optimum degree of stratification depending on the ratio of the recirculated exhaust gas amount, the retard control of the fuel injection timing is performed by controlling the recirculated exhaust gas amount. The determination is performed based on the engine operating state for determining the ratio.

If the desired amount of exhaust gas is not recirculated due to a change over time in an exhaust gas amount control valve or the like provided in the exhaust gas recirculation passage, the timing of retarding the fuel injection timing is shifted to optimize the mixture. A high degree of stratification cannot be realized.

Accordingly, an object of the present invention is to provide a fuel injection timing control device which can always realize an optimum degree of stratification even if a desired amount of exhaust gas is not recirculated.

[0008]

In order to achieve the above-mentioned object, a fuel injection timing control device according to the present invention comprises a fuel injection device provided for each cylinder of an internal combustion engine having an exhaust gas recirculation device. In a fuel injection timing control device for independently controlling a fuel injection timing, an exhaust gas amount control valve of the exhaust gas recirculation device is controlled according to an initially set opening degree for each operation state in which exhaust gas recirculation is performed. An exhaust gas amount control means for controlling, and a delay of setting the fuel injection end timing to a more retarded side as the exhaust gas recirculation rate calculated based on the initially set opening degree of the exhaust gas amount control valve in each of the operating states is larger. Angle control means, monitoring means for monitoring torque fluctuations in a specific operating state during steady state of the engine that performs exhaust gas recirculation,
Opening control means for controlling the initially set opening in the specific operating state to a new opening so that the torque fluctuation is within an allowable range, wherein the specific operating state is calculated based on the calculated exhaust gas. When the gas recirculation rate is in an operating state equal to or higher than a predetermined value, and the opening degree control means controls the initially set opening degree in the specific operating state to the new opening degree, In an arbitrary operation state other than the specific operation state, the initial setting opening is corrected by a ratio between the initial setting opening and the new opening in the specific operation state, and a new opening is set based on the corrected opening. The exhaust gas recirculation rate is calculated, and the retard control means is implemented according to the new exhaust gas recirculation rate.

[0009]

The aforementioned fuel injection timing control device is a fuel injection timing control device for independently controlling the fuel injection timing of a fuel injection device provided for each cylinder of an internal combustion engine having an exhaust gas recirculation device. In, the exhaust gas amount control means controls the exhaust gas amount control valve of the exhaust gas recirculation device according to the initially set opening degree for each operating state performing the exhaust gas recirculation, the retard control means, In the operating state, the larger the exhaust gas recirculation rate calculated based on the initially set opening degree of the exhaust gas amount control valve, the more the fuel injection end timing is set to the retard side, and the monitoring means performs the exhaust gas recirculation when the engine is in a steady state. The torque change in the specific operation state is monitored, and the opening degree control means controls the initially set opening degree in the specific operation state to a new opening degree so that the torque fluctuation is within an allowable range. Calculated emissions If the gas recirculation rate is in an operating state equal to or higher than a predetermined value, and the opening degree control means controls the initially set opening degree in the specific operating state to a new opening degree, any operating state other than the specific operating state in each operating state In the operating state, the initially set opening is corrected by the ratio of the initially set opening and the new opening in the specific operating state, and a new exhaust gas recirculation rate calculated based on the corrected opening is obtained. The retard control means is implemented accordingly.

[0010]

1 is a sectional view of an internal combustion engine to which the present invention is applied. In FIG. 1, reference numeral 1 denotes a combustion chamber, and an intake passage 3 is provided through two intake valves 2 (one of which is not shown).
However, the exhaust passages 5 communicate with each other via two exhaust valves 4 (one is not shown). Intake passage 3
Is connected to an air cleaner 6 on the upstream side, branches off from a surge tank 7 provided on the way, and communicates with another cylinder. A throttle valve 8 is provided upstream of the surge tank 7.
However, an air flow meter 9 for measuring the amount of intake air is provided on the upstream side.

The intake passage 3 is bifurcated on the downstream side of the surge tank 7 and communicates with each intake valve 2. One is a helical port 3a having a hanging wall 10, and the other is a helical port 3a which can be closed. It is a straight port (not shown) provided with an intake control valve (not shown). A fuel injection device 11 for injecting fuel toward both intake valves 2 is provided for each cylinder on the partition wall of both ports.

The surge tank 7 and the exhaust passage 5 are communicated with each other by an exhaust gas recirculation passage 12.
2 is provided with an exhaust gas amount control valve 13 for controlling the amount of exhaust gas to be recirculated.

When the exhaust gas amount control valve 13 is opened, the exhaust gas flows into the surge tank 7 due to the negative pressure generated in the surge tank 7, and the exhaust gas is recirculated. At this time, by closing the straight port by the intake control valve, the intake air containing the exhaust gas is supplied to the combustion chamber 1 only through the helical port 3a, and a strong swirl is formed in the combustion chamber 1. Can be improved. The detailed control of the intake control valve will not be described.

The control of the fuel injection start and end timings of the fuel injection device 11 is performed by the control device 14 together with the opening and closing control of the exhaust gas amount control valve 13. The control device 14 is electrically connected to the above-described air flow meter 9, a combustion pressure sensor 15 attached to the combustion chamber 1, a rotation sensor 16 for detecting an engine speed, and the like.

When the engine operating state requires a high torque, such as at a high speed and a high load, the exhaust gas amount control valve 13 is closed and the exhaust gas recirculation is stopped. At this time, since better combustion can be obtained when the mixture concentration in the combustion chamber 1 is made uniform, the fuel injection is terminated at the start of the intake stroke.
This uniformization is realized.

However, when the exhaust gas amount control valve 13 is opened and the exhaust gas recirculation is executed, the mixture in the combustion chamber 1 becomes higher in the upper layer because the mixture becomes lean. Since better combustion can be obtained by improving stratification by stratification, the stratification is realized by retarding the fuel injection end timing.

Since the degree of stratification for obtaining optimum combustion varies depending on the ratio of the amount of recirculated exhaust gas to the total amount of intake air and recirculated exhaust gas (hereinafter referred to as EGR rate), the fuel injection end timing is retarded. Is controlled by the EGR rate. As shown in FIG. 2, this control increases the degree of retardation and increases the degree of stratification as the EGR rate increases. At this time, the ignition timing is delayed as the EGR rate decreases as shown in FIG.

FIG. 3 shows a case where the degree of retardation of the fuel injection end timing is fixed to that at the time of the maximum EGR rate (dotted line).
E in the case of decreasing by decreasing the R rate (solid line)
7 shows a comparison between a torque variation and a fuel efficiency rate with respect to a GR rate. In each case, the latter is superior.

Conventionally, the retard control of the fuel injection end timing with respect to the EGR rate has been performed based on the engine operating state which determines the EGR rate. As a result, if the desired EGR rate cannot be realized due to the change over time of the exhaust gas amount control valve 13 and the adhesion of the deposit to the intake system, the degree of retardation of the fuel injection end timing is shifted, and optimal combustion is obtained. The degree of stratification that is achieved is realized, and the combustion deteriorates.

Therefore, in order to solve this problem, the control device 14 of the present embodiment controls the exhaust gas amount control valve 13 and sets the fuel injection start and end timings of the fuel injection device 11 according to the flowchart shown in FIG. Do.

First, at step 101, the amount of change .DELTA.NE in the number of revolutions obtained from the rotation sensor and the amount of intake air per revolution obtained from the rotation sensor and the air flow meter 9 in the operating state in which exhaust gas recirculation is performed. Change Δ
It is determined whether G / N is less than respective predetermined values a and b indicating a steady state. If both are less than the predetermined value, the differential pressure ΔP between the surge tank 7 and the exhaust passage 5 is calculated in step 102. From the intake air weight Ga (g / s) per unit time obtained from the air flow meter 9, the pressure P1 in the surge tank 7 and the pressure P2 in the exhaust passage 5 are expressed by the following equations, respectively: P1 = αGa ² , P2 = From βGa ² , the differential pressure ΔP is obtained by the following equation. ΔP = (α−β) Ga ² = γGa ² (α, β, and γ are constants)

Next, in step 103, the optimum E in this operating state is determined by the current rotational speed NE and the intake air amount G / N per one rotation used as the current load.
The opening degree S of the exhaust gas amount control valve 13 so that the GR rate can be obtained.
The opening and closing of the exhaust gas amount control valve 13 is controlled according to a map (not shown) in which (the number of steps of the step motor for driving the exhaust gas amount control valve 13) is set.
Proceed to 4.

In step 104, it is determined whether or not the current operating state is in the operating range at the EGR rate at which the fuel efficiency becomes minimum. In this operating range, in step 105, based on the combustion pressure obtained from the combustion pressure sensor 15, The torque fluctuation DTRQ at this time is calculated, and this torque fluctuation DTRQ is calculated.
Is larger than the upper limit c of the allowable range.

This operating region is a region where a large torque fluctuation occurs unless the EGR rate is maintained at a required value. The amount of recirculated exhaust gas becomes excessive due to a change with time of the exhaust gas amount control valve 13, and the upper limit of the allowable range if the exceeding side c, the opening S _F of the exhaust gas amount control valve 13 at this time in step 106 1 is reduced. If the value does not exceed the upper limit c of the allowable range, the process proceeds to step 107, and it is determined whether the value is less than the lower limit d of the allowable range. If affirmative, the recirculation exhaust gas amount is insufficient, and step 108
The opening S _F of the exhaust gas amount control valve 13 at this time in 1
Is increased.

In any case, the process proceeds to step 109, the opening degree map of the exhaust gas amount control valve 13 used in step 103 is updated, and the process proceeds to step 111. If the result in Step 107 is negative, that is, the torque fluctuation D
Opening S _F when TRQ is within the allowable range is maintained, the process proceeds to step 110.

In step 110, the recirculated exhaust gas amount Ge at this time is calculated. Recirculated exhaust gas amount Ge
Is proportional to the differential pressure ΔP calculated in step 102 and the opening of the exhaust gas amount control valve 13, and is obtained by the following equation. Ge = K1 × S _F0 × ΔP (K1 is a constant) Here, K1 is a value set on the assumption that there is no change over time of the exhaust gas amount control valve 13 and no deposition of the intake system or the like has occurred. The actual opening of the exhaust gas amount control valve is S _F , but in the above equation, the initial set value S _F0
Is used.

If it is determined in step 104 that the current operating state is not in the operating range at the EGR rate at which the fuel efficiency becomes minimum,
After the opening degree map of the exhaust gas amount control valve 13 is updated in step 109, the recirculated exhaust gas amount Ge at this time is calculated in step 111. Step 11
Similarly to 0, the recirculated exhaust gas amount Ge is obtained from the differential pressure ΔP and the opening degree S of the exhaust gas amount control valve 13 at this time determined in step 103, and becomes the minimum fuel efficiency updated in step 109. is corrected by the opening S _F of the exhaust gas amount control valve 13 during operation of the EGR rate is obtained by the following expression. Ge = K1 × S _F0 / S _F × S × ΔP (K
(1 is a constant) In this equation, S _F0 is the minimum fuel consumption EG
This is the initial set value of the opening of the exhaust gas amount control valve 13 during operation at the R rate. This correction is performed in step 1 due to the change over time of the exhaust gas amount control valve 13 and the attachment of a deposit to the intake system.
It becomes effective after the update in 09 is performed.

Next, at step 112, the actual EG
The R rate W is calculated. The EGR rate W is obtained from the intake air amount Ga per unit time measured in step 102 and the recirculated exhaust gas amount Ge calculated in step 110 or 111 by the following equation as described above. W = Ge / (Ga + Ge)

Thus, the EGR rate W is obtained, and in step 113, the fuel injection end timing Injt is determined by using the EGR rate W by the following equation. Injt = K2 × W + Injt ₀ (K2 is a constant) In this equation, Injt ₀ is the fuel injection timing when the exhaust gas recirculation is stopped, and K2 × W is the retard time.

Next, at step 114, a fuel injection start timing Injt 'which is calculated back from the fuel injection end timing Injt and the required fuel amount in each engine operating state is set.

If the current operating state is not steady in step 101, a large torque fluctuation may occur even if the amount of recirculated exhaust gas does not increase or decrease due to aging.
Therefore, the process ends.

FIG. 5 is a graph showing the torque fluctuation with respect to the opening degree of the exhaust gas amount control valve 13 and the calculated value of the recirculated exhaust gas amount. Represents the time after the amount of recirculated exhaust gas changes with time to the increasing side.

As shown in the torque fluctuation graph, the minimum fuel
In the operation at the EGR rate which becomes expensive,
The opening degree S of the exhaust gas amount control valve set in the map_F0so
Set the torque fluctuation between the upper limit side c and the lower limit side d of the allowable range.
But the amount of recirculated exhaust gas increased due to aging.
When applied, the torque fluctuation becomes as shown by the solid line, and the opening S _F0
In this case, the torque fluctuation exceeds the upper limit c of the allowable range.
In order to achieve this, one-step opening
So that the torque fluctuation is within the allowable range.
You.

At all opening degrees of the exhaust gas amount control valve,
This means that the amount of recirculated exhaust gas increases at a similar rate, and the calculated value of the amount of recirculated exhaust gas Ge is S _F0 / (S _F0 −
Corrected by 1), an accurate recirculated exhaust gas amount shown by the solid line is obtained.

Since the retardation time of the fuel injection end timing is calculated based on this value, stratification that achieves optimal combustion without deviation is realized.

In the flow chart shown in FIG. 4, the updating of the opening of the exhaust gas amount control valve at the time of operation at the EGR rate that minimizes fuel consumption in step 109 is repeated at all times. Since it is unlikely that the amount of recirculated exhaust gas increases or decreases over time, the torque fluctuation can be kept within the allowable range by one step increase / decrease, but reliability is improved. To this end, it is possible to add a determination of the torque fluctuation immediately before updating the map, and when it is not within the allowable range, it is also possible to repeatedly increase and decrease the opening.

[0037]

When the amount of recirculated exhaust gas increases or decreases during the execution of exhaust gas recirculation due to a change with time of the exhaust gas amount control valve and a deposit on the intake system, the exhaust gas recirculation rate is reduced. In a specific operating state during steady state of the engine in which a large amount of exhaust gas is recirculated at a predetermined value or more, a large torque variation occurs particularly due to an increase in the amount of recirculated exhaust gas, so that the torque variation is within an allowable range. It is necessary to control the initially set opening of the exhaust gas amount control valve to a new opening. The present invention utilizes the opening degree control of the exhaust gas amount control valve in the specific operation state thus required, and in any operation state other than the specific operation state, sets the initially set opening degree of the exhaust gas amount control valve to: The actual exhaust gas recirculation rate is calculated on the basis of the corrected opening corresponding to the actually set opening and the new opening in the specific operating state. It has been found that, in each operating state, as the exhaust gas recirculation rate increases, the fuel injection end timing is set to the retard side, whereby optimal stratification is realized in the cylinder and combustion is improved, According to the present invention, since the retard control of the fuel injection timing is performed based on the accurate exhaust gas recirculation rate calculated in this manner, the actual exhaust gas is controlled by the change over time of the exhaust gas amount control valve and the deposition of the intake system. Optimum stratified good combustion can be realized even if the gas recirculation rate changes.

[Brief description of the drawings]

FIG. 1 is a sectional view of an internal combustion engine to which a fuel injection control device according to the present invention is applied.

FIG. 2 is a diagram showing a fuel injection end timing and an ignition timing with respect to an EGR rate.

FIG. 3 is a graph showing a torque variation with respect to an EGR rate, a fuel consumption rate, and a fuel injection end time. This shows the case where it is made faster with the decrease of

FIG. 4 is a flowchart for setting the injection start and end timings of the fuel injection device according to the present invention and controlling the opening and closing of the exhaust gas amount control valve.

FIG. 5 is a graph of the torque fluctuation with respect to the opening degree of the exhaust gas amount control valve and the calculated value of the recirculated exhaust gas amount, with the dotted line before the change over time and the solid line after the change over time on the increasing side of the recirculated exhaust gas amount. is there.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 3 ... Intake passage 5 ... Exhaust passage 8 ... Throttle valve 9 ... Air flow meter 11 ... Fuel injection device 12 ... Exhaust gas recirculation passage 13 ... Exhaust gas amount control valve 14 ... Control device 15 ... Combustion pressure sensor

Continuation of the front page (56) References JP-A-1-276551 (JP, A) JP-A-4-224254 (JP, A) JP-A-63-253136 (JP, A) JP-A-2-223853 (JP) , A) JP-A-63-68729 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02D 41/00-45/00 F02M 25/07

Claims (1)

(57) [Claims] 1. A fuel injection timing control device for independently controlling a fuel injection timing of a fuel injection device provided for each cylinder of an internal combustion engine having an exhaust gas recirculation device, wherein the exhaust gas recirculation is performed. An exhaust gas amount control means for controlling an exhaust gas amount control valve of the exhaust gas recirculation device according to an initially set opening degree for each operating state to be executed; and the initial state of the exhaust gas amount control valve in each operating state. A retard control unit that retards the fuel injection end timing as the exhaust gas recirculation rate calculated based on the set opening degree increases, and a torque fluctuation in a specific operating state during steady state of the engine that executes exhaust gas recirculation. Monitoring means for monitoring, and opening control means for controlling the initially set opening in the specific operating state to a new opening so that the torque fluctuation is within an allowable range, wherein the specific operating state is In the case where the calculated exhaust gas recirculation rate is in an operating state equal to or greater than a predetermined value, and the opening degree control means controls the initially set opening degree in the specific operating state to the new opening degree, In any operation state other than the specific operation state in each of the operation states, the initial setting opening is corrected by a ratio between the initial setting opening and the new opening in the specific operation state, and A fuel injection timing control device, wherein a new exhaust gas recirculation rate is calculated based on an opening degree, and the retard control means is implemented according to the new exhaust gas recirculation rate.