JP3412407B2 - Engine combustion fluctuation 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 an engine combustion fluctuation control device.

[0002]

2. Description of the Prior Art Improving engine fuel economy and at the same time NO
In order to reduce x, the fuel supply amount is controlled so that the air-fuel ratio, which is the ratio of air to fuel, becomes a lean air-fuel ratio that is leaner than the stoichiometric air-fuel ratio, and the combustion fluctuation amount of the engine during lean operation is the combustion fluctuation amount. When it becomes worse than the control target value of, the engine operating method that corrects the air-fuel ratio to the rich side (or corrects the ignition timing and the EGR rate to the side that stabilizes the combustion) to ensure the stability of combustion, It is proposed by Japanese Patent Publication No. 3-66505.

[0003]

However, in the conventional apparatus, when setting the control target value of the combustion fluctuation amount during lean operation, it is taken into consideration whether or not the drive wheels are in a slip state with respect to the road surface. Therefore, there is a limit to the effect of reducing fuel consumption and NOx emissions. For example, when traveling on a low μ road such as a snow road, it is difficult to transmit the engine rotation fluctuation due to the combustion fluctuation to the vehicle body because the reaction force received from the road surface is weakened due to the slip of the driving wheels (the occupant is accompanied by the combustion fluctuation. It becomes difficult to experience rotation fluctuations). At this time, it is possible to operate in a state where the combustion fluctuation is larger than in a state in which the drive wheels are not slipping, although it is within the combustion limit range of the engine. That is, when the drive wheels are slipping,
Although the leaner air-fuel ratio can be operated and the fuel consumption and NOx emission amount can be reduced accordingly, the conventional device does not consider whether or not the drive wheels are in the slip state.

Therefore, according to the present invention, the fuel consumption and the NOx emission amount in the lean burn system are further reduced by setting the control target value of the combustion fluctuation amount during lean operation according to whether or not the drive wheels are in the slip state. The purpose is to plan.

[0005]

In the first invention, the lean
The combustion fluctuation amount of the engine during operation is controlled by the combustion fluctuation amount.
Ensure fuel stability when worse than target
In the engine combustion fluctuation control device, as shown in FIG. 17, a means 21 for determining whether or not the drive wheel is in a slip state, and when the drive wheel is slipping from the result of this determination, the drive wheel is slipping. lean operation so that the amount of combustion variation of the control target value of the combustion fluctuation amount during lean operation and means 22 for setting the side to increase the combustion fluctuation amount during lean operation coincides with the control target value than when no Means 23 for controlling the amount of combustion fluctuation at the time.

In the second invention, the control target value of the combustion fluctuation amount during lean operation when the drive wheels are slipping in the first invention is a constant value.

In the third aspect of the invention, the means 21 for determining whether or not the drive wheel is in the slip state in the first or second aspect of the invention is as shown in FIG. 18 when the drive wheel is not slipping. Means 31 for setting the vehicle acceleration as the standard acceleration, means 32 for calculating the vehicle acceleration based on the signal from the vehicle speed sensor, and comparison of the vehicle acceleration based on the signal from the vehicle sensor with the standard acceleration When the absolute value of the vehicle acceleration based on the signal from the driving wheel is in the slip state when the absolute value is greater than the standard acceleration, and when the absolute value of the vehicle acceleration based on the signal from the vehicle sensor is less than the standard acceleration, the driving wheel is And a means 33 for determining that the vehicle is not in the slip state.

According to a fourth aspect of the invention, in any one of the first to third aspects of the invention, means for controlling the combustion fluctuation amount during lean operation so that the combustion fluctuation amount during lean operation matches the control target value. Reference numeral 22 denotes means 41 for calculating the basic control amount of the engine during lean operation, and correction amount for the basic control amount so that the combustion fluctuation amount during lean operation matches the control target value, as shown in FIG. Means 42 for calculating
And means 43 for correcting the basic control amount with this correction amount
And means 44 for controlling the torque generated by the engine during lean operation with this corrected control amount.

In the fifth aspect of the invention, the engine is operated during lean operation.
Combustion fluctuation amount of the engine is worse than the control target value of the combustion fluctuation amount
Then, in order to ensure the stability of the fuel, the combustion change of the engine
In the dynamic control device, as shown in FIG. 20, means 51 for detecting the respective rotational speeds (rotational speeds) of the drive wheels and the driven wheels,
52, a means 53 for calculating the rotational speed difference between the drive wheel and the driven wheel as a slip degree during lean operation, and a control target value of the combustion fluctuation amount during lean operation when the drive wheel slips as the slip degree. Means 54 for setting the combustion fluctuation amount to a larger value, and the drive wheel slips so that the combustion fluctuation amount during lean operation when the drive wheel slips matches the control target value. Means 55 for controlling the amount of combustion fluctuation during lean operation
And.

In a sixth aspect of the present invention, in the fifth aspect, when the control target value exceeds the combustion stability limit equivalent value during lean operation, the control target value is limited to this combustion stability limit equivalent value.

In a seventh aspect of the invention, the drive wheels are slipping so that the combustion fluctuation amount during lean operation when the drive wheels are slipping in the fifth or sixth aspect of the invention matches the control target value. The means 55 for controlling the amount of combustion fluctuation during lean operation at this time is the means 61 for calculating the basic control amount of the engine during lean operation when the drive wheels are slipping as shown in FIG. Means 62 for calculating a correction amount for the basic control amount so that the combustion fluctuation amount during lean operation during slipping matches the control target value, and means 6 for correcting the basic control amount by this correction amount.
3 and means 64 for controlling the torque generated by the engine during lean operation when the drive wheels are slipping with this corrected control amount.

In an eighth invention, in the fourth or seventh invention, the basic control amount of the engine is the air-fuel ratio, the ignition timing,
It is at least one of the EGR amounts.

In a ninth aspect of the invention, in any one of the first to eighth aspects of the invention, the combustion fluctuation amount during the lean operation is detected based on the engine rotation fluctuation amount.

[0014]

According to the first aspect of the invention, the air conditioner is operated during lean operation.
If the combustion fluctuation amount of the engine increases, the stability is secured.
Therefore, drivability is not impaired. On the other hand, in contrast to the conventional device that does not consider whether or not the drive wheels are in a slip state, in the first aspect of the invention, the control target value of the combustion fluctuation amount is non-slip when the drive wheels are slipping during lean operation. It is set to the side where the combustion fluctuation amount increases with time, and the air-fuel ratio is shifted to the lean side by the difference. When the drive wheels are slipping, the reaction force received from the road surface weakens, so engine speed fluctuations due to combustion fluctuations are less likely to be transmitted to the vehicle body (passengers are less likely to experience rotation fluctuations due to combustion fluctuations). At this time, it is possible to operate in a state where the combustion fluctuation amount is larger than that in a state where the drive wheels are not slipping (although it is within the combustion limit of the engine) (operation with a leaner air-fuel ratio). Fuel consumption and NOx emissions can be reduced accordingly.

In the second aspect of the invention, the set value of the control target value of the combustion fluctuation amount during lean operation when the drive wheels are slipping is a constant value and is not set in detail according to the road surface condition. Therefore, compared to the fifth invention described later, the fuel consumption and NOx reduction allowance are reduced, but a low μ like snowy road
This setting is sufficient for vehicle types that are expected to have few opportunities to drive on the road, and saves man-hours spent setting the control target value of the combustion fluctuation amount during lean operation when the drive wheels are slipping. it can.

According to the fifth aspect of the invention, the slip degree can be detected in real time even while the drive wheels are slipping, so that the slip degree can be calculated with high accuracy. Further, in the fifth invention, the control target value of the combustion fluctuation amount during lean operation when the drive wheels are slipping is set in detail by the continuous value according to the degree of slip, so that it can be used in various ways such as snow roads and icy roads. For vehicles that have many opportunities to drive on low μ roads, the fifth aspect of the invention allows the air-fuel ratio to be made lean to the limit corresponding to each road surface, which maximizes fuel consumption and NOx emissions during practical use. Can be reduced to

In the sixth aspect of the present invention, when the control target value exceeds the combustion stability limit equivalent value during lean operation, the control target value is limited to this combustion stability limit equivalent value, so combustion deteriorates and the engine becomes stable. It is possible to avoid making the air-fuel ratio lean so that it cannot be maintained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, reference numeral 1 is an engine body, and intake air is supplied from an air cleaner to an intake pipe 8 to a cylinder. The fuel is a control unit (C / U in the figure) so that it has a predetermined air-fuel ratio according to the operating conditions.
The fuel is injected from the fuel injection valve 7 toward the intake port of the engine 1 based on the injection signal from the fuel injection valve 7.

The control unit 2 includes a Ref signal from the crank angle sensor 4 (generated every 180 degrees for four cylinders and every 120 degrees for six cylinders) and a 1 degree signal, an intake air amount signal from the air flow meter 6, and a ternary signal. An air-fuel ratio (oxygen concentration) signal from an O ₂ sensor 3 installed upstream of the catalyst 10, a cooling water temperature signal from a water temperature sensor 11, a throttle valve 5 opening signal from a throttle sensor 12, a transmission gear position sensor A gear position signal from 13 and a vehicle speed signal from a vehicle speed sensor (not shown) are input, and the lean air-fuel ratio and the stoichiometric air-fuel ratio are controlled according to the conditions while determining the operating state based on these.

A three-way catalyst 10 is installed in the exhaust pipe 9 to reduce NOx in the exhaust gas and oxidize HC and CO with maximum conversion efficiency when operating at a stoichiometric air-fuel ratio. The three-way catalyst 10 oxidizes HC and CO when the air-fuel ratio is lean, but the NOx reduction efficiency is low.

However, the more the air-fuel ratio shifts to the lean side, the smaller the amount of NOx produced, and at a predetermined air-fuel ratio or higher, the NOx can be reduced to the same level as purification by the three-way catalyst 10, and at the same time, The fuel efficiency is improved as the lean air-fuel ratio is achieved. On the other hand, when operating with a lean air-fuel ratio, combustion tends to become unstable depending on operating conditions.

Therefore, the control unit operates at a lean air-fuel ratio in a predetermined operation region where the load is not so large, detects the combustion fluctuation amount of the engine at the same time, and if the combustion fluctuation amount of the engine increases during the lean operation, it becomes empty. The fuel ratio is shifted to the rich side to ensure stability,
That is, the feedback control of the combustion fluctuation amount at the lean air-fuel ratio is performed, and good fuel efficiency characteristics are maintained without impairing the stability of the engine.

When setting the control target value of the combustion fluctuation amount during lean operation, in the conventional example which does not take into consideration whether or not the drive wheels are in a slip state, fuel consumption and NO
Since the effect of reducing the x emission amount is limited, the present invention sets the control target value of the combustion fluctuation amount during lean operation according to whether or not the drive wheels are in the slip state, and thereby, the fuel consumption in the lean burn system is reduced. And further reduce NOx emissions.

The contents of this control executed by the control unit 2 will be described with reference to the following flow chart.

First, FIG. 2 shows a calculation of a fuel-air ratio correction coefficient Dml for feedback control to an air-fuel ratio necessary for stabilizing the engine while detecting the combustion fluctuation amount of the engine during operation with a lean air-fuel ratio. With a 4-cylinder engine, it is executed every 180 degrees (every 120 degrees for a 6-cylinder engine).

Since the combustion fluctuation amount of the engine has a very high correlation with the rotation fluctuation amount of the engine, the combustion fluctuation amount is estimated based on the rotation fluctuation amount in the embodiment. As will be described later, the cycle of the Ref signal is detected, and its statistical variation degree (that is, dispersion) is used as an index indicating the combustion fluctuation amount.

First, in step 1, the cycle TREF of the Ref signal for every 180 degrees is read from the signal of the crank angle sensor 4 and is stored in the memory TREF (new).

In step 2, it is judged whether the feedback (F / B) control of the combustion fluctuation amount is performed during the operation with the lean air-fuel ratio. For the determination of this feedback control condition, for example, the one disclosed in Japanese Patent Laid-Open No. 6-272591 may be used. Here, since it is not directly related to the present invention, a brief description is that it is a lean condition,
When the air-fuel ratio is not being switched, the engine speed and the load are in a predetermined feedback control region, and the like, it is determined that the feedback control condition is satisfied. Note that the lean condition will be described with reference to the flowcharts of FIGS. 6 and 7, which will be described later, performed as a background job.

When it is the feedback control condition, in step 3, the feedback correction rate, that is, the stabilized fuel-air ratio correction coefficient Lldm is followed according to the flowchart of FIG.
1 is updated and calculated.

In FIG. 3, in step 11, the old value of the Ref signal cycle TREF (i) (where i = 1 to N) is shifted, and in step 12, the memory TREF (ne).
The value of w) is transferred to the memory TREF (1). TREF
The shift of the old value of (i) is performed by, for example, the memory TREF (N
The value of -1) is stored in the memory TREF (N) and stored in the memory TREF (N).
The value of (N-2) is transferred to the memory TREF (N-1), ..., The value of the memory TREF (1) is transferred to the memory TREF (2) in that order.

Here, N is a predetermined number of samples. T
A total of N Ref signal periods TREF from the latest value are sampled in each memory from REF (1) to TREF (N). Each time the latest TREF is measured, the previous value of TREF (N) is discarded.

In steps 13 and 14,

[Equation 1] The N average value AVTREF of TREF is obtained by the formula of, and the average value AVTREF and the value of each memory are used.

[Equation 2] The dispersion of TREF is calculated according to the equation, and the calculated dispersion value is set as the surge index (combustion fluctuation amount) SRG.

In step 15, Lldml = Lldml (old) + G1 × (SRG-ISRG) (3) where ISRG: target surge index (control target value of combustion fluctuation amount) G1: constant Lldml (old): previous The stabilized fuel-air ratio correction coefficient Lldml is updated by the equation of Lldml.

Although omitted in the flow chart, this Ll
The range of dml is limited so that 1.0 ≦ Lldml ≦ LLDMMX # (where LLDMMX # is the maximum value of the preset stabilized fuel-air ratio correction coefficient), and this control operation is ended. Lldml is stored in memory,
It is constantly updated during feedback control.

Therefore, the stabilized fuel-air ratio correction coefficient Lldm
The larger the combustion fluctuation amount exceeds the control target value, that is, the larger the combustion deterioration, the larger l becomes.

Here, the calculation of the target surge index ISRG, which is the control target value of the combustion fluctuation amount, will be described with reference to the flowchart of FIG. The flowchart of FIG. 4 is shown in FIG.
Different from FIG. 3, the process is executed every constant time ΔT.

In step 21, a timer (initially set to 0 at the time of starting) T is compared with a preset gate time T1. When T <T1, in step 22, the timer T is incremented by the control period (that is, ΔT) in FIG. 4, and in step 23, it is checked whether the vehicle speed pulse (the pulse from the vehicle speed sensor) is reversed, and it is reversed. Only when this is done, the routine proceeds to step 24, where the vehicle speed pulse counter CVSP is incremented. This counts the number of edges of the vehicle speed pulse that has entered during the gate time T1.

If T ≧ T1 while repeating the increment of the timer T in step 22, the process proceeds from step 21 to step 25 and the vehicle speed pulse counter CVSP at that time is multiplied by the coefficient C1 to obtain the vehicle speed VSP. calculate. The vehicle speed sensor is attached to the drive shaft of the drive wheels and outputs a fixed number of vehicle speed pulses per one rotation of the drive shaft. Since the number of vehicle speed pulses per one rotation of the drive wheels is predetermined, the rotational speed of the drive shaft (that is, vehicle speed) can be calculated by counting the number of vehicle speed pulses within a predetermined time (gate time).

At step 26, ΔVSP = VSP−VSP (old) (4) where VSP (old): After the change amount of the vehicle speed per T1 (that is, vehicle acceleration) ΔVSP is calculated by the formula of VSP at the time of the previous calculation. In step 27, the vehicle speed pulse counter CVSP and the timer T are reset to 0 for the next calculation of the vehicle speed VSP and the vehicle acceleration ΔVSP. As a result, the vehicle acceleration ΔVSP at each gate time
Will be updated.

Next, at step 28, a map having the contents shown in FIG. 5 is searched from the basic injection pulse width Tp as the engine load and the vehicle speed VSP to find the acceleration when the drive wheels are in the non-slip state (this acceleration is called the standard acceleration). ) ACSTD
Ask for. When the driving wheels are in the non-slip state, the vehicle acceleration is determined by the driving force and the traveling load, of which the driving force is determined by the engine load Tp, and the traveling load is uniquely determined by the vehicle speed VSP (the greater the engine load, the greater the engine load). As the driving force increases and the vehicle speed increases, the running load also increases.) Therefore, the standard acceleration ACST is calculated from Tp and VSP.
It is possible to obtain D. ACSTD is shown in FIG.
As shown in, if the vehicle speed is constant, the driving force (that is, T
The larger p) is, the larger it is, and when the driving force is constant, the higher the vehicle speed VSP is, the smaller the ACSTD is.

In step 29, this standard acceleration ACST
D is compared with the absolute value | ΔVSP | of the acceleration ΔVSP obtained by the vehicle speed sensor, and when | ΔVSP | is ACSTD or more, it is determined that the drive wheels are slipping, and the routine proceeds to step 30 to set the target surge index ISRG. The slip-time corresponding value SLSRG # is entered, and when | ΔVSP | is smaller than ACSTD (when the drive wheels are not slipping), the routine proceeds to step 31, where the non-slip time corresponding value NMSRG # is entered in the target surge index ISRG.

When the vehicle acceleration is obtained by the vehicle speed sensor provided on the drive shaft and the drive wheels are slipping, the vehicle acceleration ΔVSP obtained by the vehicle speed sensor does not match the standard acceleration ACSTD, and | ΔV
Since SP | is larger than ACSTD, ACS
By comparing TD and | ΔVSP |, it is possible to estimate whether or not the drive wheels are slipping.

Here, the above slip-time corresponding value SLSR
G # is set to be larger than the non-slip corresponding value NMSRG #. When the drive wheels are slipping, it becomes difficult to transmit the rotation fluctuation due to the combustion fluctuation to the vehicle body. Therefore, the target surge index ISRG can be increased accordingly.
The stabilized fuel-air ratio correction coefficient Lldml can be made smaller than the conventional value by the amount of increase in the target surge index ISRG (that is, the air-fuel ratio can be shifted to the lean side).

The non-slip corresponding value NMSRG # may be set in the same manner as in the conventional case, and can be determined according to the engine load, the rotational speed, and the gear position.

Returning to FIG. 2, after the calculation of the feedback correction rate is completed in this way, the process proceeds to step 4 in FIG. 2 to calculate the target fuel-air ratio Tdml. Alternatively, the fuel-air ratio M set in the map of FIG.
This is calculated by searching for dml and then correcting it with the stabilized fuel-air ratio correction coefficient Lldml during feedback control. In this case, one of the maps is selected depending on whether or not the lean operation condition is satisfied.

Here, the determination of the lean operating condition will be described with reference to the flowcharts of FIGS. 6 and 7.

These operations are performed as a background job, and the lean condition is determined in step 41 of FIG. 6, and the specific contents for this are shown in FIG.
The lean condition is determined by checking the contents of steps 51 to 57 of FIG. 7 one by one. When all of the items are satisfied, the lean operation is permitted, and when any of them is contrary, the lean operation is prohibited. To do.

That is, step 51: the idle switch is not ON, step 52: the cooling water temperature Tw is within a predetermined range (TWL ≦ T
w ≦ TWH), Step 53: Load (Tp) is in a predetermined region (TPL ≦ T
Step 54: The rotation speed Ne is in a predetermined region (NEL ≦ Ne).
≦ NEH), Step 55: The throttle valve opening TVO is a predetermined value T
VOH or less, step 56: vehicle speed VSP is a predetermined value VSPL or more, step 57: when the vehicle speed change amount ΔVSP is a predetermined value DVH or less, lean operation permission flag FLEA in step 58
N is set to "1" (lean operation is permitted), and if not, the process proceeds to step 59 and lean operation permission flag F
Reset LEAN to "0" (prohibit lean operation). The above steps 51 to 57 are conditions for performing stable lean operation without impairing the operation performance. The regions where the lean operation is specifically permitted are shown in FIGS. 8, 9 and 10.

When the lean condition is determined in this way,
Returning to steps 43 and 44 in FIG. 6, when the lean condition is not satisfied, the map value of the stoichiometric air-fuel ratio or a richer air-fuel ratio (map fuel-air ratio) is calculated in step 43.
It is calculated by searching the map of the characteristics shown by the number of revolutions Ne and the load Tp. On the other hand, when the lean condition is satisfied, at step 44, the map fuel-air ratio of a value thinner than the theoretical air-fuel ratio by a predetermined range is obtained. Mdml is similarly searched according to the characteristic map shown in FIG. Since the numerical values shown in these maps are relative values with 1.0 at the stoichiometric air-fuel ratio, values larger than this indicate rich and lean values indicate lean.

Now, returning to step 4 of FIG. 2 again, of the map fuel-air ratio Mdml thus calculated,
The target fuel air ratio Tdml is calculated by multiplying Mdml under the lean condition by the stabilized fuel air ratio correction coefficient Lldml, that is, Tdml = Mdml × Lldml (5).

This target fuel-air ratio Tdml increases as the amount of rotation fluctuation of the engine increases, and thus Lldml increases, so that it increases as the amount of combustion fluctuation increases.
That is, the target fuel-air ratio is shifted to the rich side.

In the subsequent step 5 and subsequent steps, the sudden change of the torque is prevented by gently switching the air-fuel ratio in the process of damper operation at the time of switching the fuel-air ratio, and the stability of the operating performance is secured ( (See FIG. 13).

In step 5, Dml (old), which is the previous value of the fuel-air ratio correction coefficient Dml, is compared with Tdml calculated previously, and if Dml (old) <Tdml, empty in steps 6 and 7. In order to shift the fuel ratio to the rich side, a new Dml is obtained by adding Ddmlr corresponding to the air-fuel ratio changing speed to the rich side to the previous correction coefficient Dml (old). Then, the fuel-air ratio correction coefficient Dm
A limit is added to Dml so that 1 does not exceed the calculated target fuel-air ratio Tdml.

On the other hand, Dml (old) ≧ Tdml
If it is, in steps 8 and 9, a new fuel-air ratio correction coefficient Dml shifted to the lean side is obtained by subtracting Ddmll corresponding to the lean-side air-fuel ratio change speed from the held Dml (old). And further Dm
Limit Dml so that 1 does not fall below Mdml.

When the stoichiometric air-fuel ratio or the fuel-air ratio Mdml near the stoichiometric air-fuel ratio is calculated from the map shown in FIG. 12, the lean fuel condition is not shown, but the stabilized fuel-air ratio for the map fuel-air ratio Mdml in step 4 is not shown. Correction coefficient L
The fuel-air ratio correction coefficient Dml may be calculated by replacing Mdml with the target fuel-air ratio Tdml in step 5 without correction by ldml.

The fuel injection amount correction coefficient Dml thus calculated is used to calculate the fuel injection amount described below.

The flow chart of FIG. 14 shows the contents of the control operation for calculating and outputting the fuel injection pulse width using the fuel-air ratio correction coefficient Dml thus obtained. First, at step 61, the fuel-air ratio correction is performed. Using the coefficient Dml, the target fuel-air ratio equivalent amount Tfbya is calculated by the formula Tfbya = Dml + Ktw + Kas (6).

Here, Ktw is the fuel increase corresponding to the cooling water temperature, and Kas is the fuel increase immediately after the start. Next, in step 62, the output of the air flow meter is A / D converted,
The intake air flow rate Q is calculated by linearization. And
In step 63, this intake air flow rate Q and engine speed N
From e, the basic injection pulse width Tp at which the theoretical air-fuel ratio can be obtained is calculated as Tp = K × Q / N. Note that K is a constant.

Then, in step 64, based on this Tp, the fuel injection pulse width Ti for one time is calculated by the following equation: Ti = (Tp + Kathos) × Tfbya × (α + αm−1) × 2 + Ts (7) .

Here, Kathos is the transient correction amount, α is the air-fuel ratio feedback correction coefficient, αm is the air-fuel ratio learning correction coefficient, and Ts is the operation delay from when the injection valve receives the injection signal to when it actually opens. It is an invalid pulse width for performing. Further, since the expression (7) is an expression in the case of sequential injection (in four cylinders, injection is performed once every two rotations of the engine, in accordance with the ignition order of each cylinder), the numeral 2 is included.
However, under the lean condition, α and αm are fixed to predetermined values.

Next, at step 66, the fuel cut is determined, and at steps 67 and 68, if the fuel cut condition is satisfied, the invalid injection pulse width Ts is stored in the output register. Accordingly, the fuel injection is prepared at a predetermined injection timing.

As described above, the fuel injection amount is calculated, and therefore, during the feedback control of the combustion fluctuation amount in the lean operation, the surge index SRG is the target surge index ISRG (at this time When the slip corresponding value NMSRG #) is increased, the value of the stabilized fuel-air ratio correction coefficient Lldml is updated to a larger value (the air-fuel ratio is shifted to the rich side) accordingly, and the stability during lean operation is improved. Therefore, fuel efficiency and NOx are reduced without impairing drivability.

On the other hand, when the drive wheels are slipping even in the feedback control, the target surge index is switched from the non-slip corresponding value NMSRG # to the slip corresponding value SLSRG # (SLSRG # <NMSRG #). . In this case, the slip-time corresponding value SLSRG # is a value on the side where the combustion fluctuation amount is larger than the non-slip time corresponding value NMSRG #, and the stabilized fuel-air ratio correction coefficient Lldml is reduced by the difference. Here, since the target fuel-air ratio Tdml during lean operation becomes leaner as this value becomes smaller, the air-fuel ratio becomes leaner by the decrease of Lldml than when the drive wheels are not slipping. Be shifted. When the drive wheels are slipping, the reaction force received from the road surface is weakened, so that the rotation fluctuation due to the combustion fluctuation is less likely to be transmitted to the vehicle body (the occupant is less likely to experience the rotation fluctuation due to the combustion fluctuation). At this time, although it is within the combustion limit range of the engine, it is possible to operate in a state where the combustion fluctuation amount is larger than in a state where the drive wheels are not slipping (operation with a leaner air-fuel ratio). That is, fuel consumption and NOx emissions can be reduced accordingly.

In this embodiment, both the non-slip corresponding value NMSRG # and the slip corresponding value SLSRG # which define the target surge index ISRG are constant values. In this way, the target surge index ISRG is set to a binary value depending on whether or not the driving wheels are in a slip state, and is not set in detail according to the road surface condition. Therefore, fuel consumption and NOx are less than those in the second embodiment described later. However, the binary setting is sufficient for a vehicle model that is expected to have few opportunities to drive on low μ roads such as snow roads, and the man-hours spent for setting the target value are saved. it can.

The flowchart of FIG. 15 is the second embodiment and corresponds to FIG. The same step numbers are assigned to the same parts as in FIG.

In this embodiment, the difference in rotational speed between the drive wheels (front wheels for FF vehicles, rear wheels for FR vehicles) and driven wheels (rear wheels for FF vehicles, front wheels for FR vehicles) ( Rotation speed difference)
Is obtained as the degree of slip of the drive wheels.

Mainly explaining the parts different from FIG. 4, T <
When the driving wheel rotation pulse (pulse from the driving wheel rotation sensor) is reversed in step 61 at T1, it proceeds to step 62 only when it is reversed, and the driving wheel rotation pulse counter CVSP1 is driven. Whether or not the rotation pulse (a pulse from the driven wheel rotation sensor) is reversed is determined, and only when it is reversed, the routine proceeds to step 64, where the driven wheel rotation pulse counter CVSP2 is incremented.

On the other hand, when T ≧ T1, in step 65, the slip degree SLRATE of the drive wheels is calculated by the formula SLRATE = CVSP2-CVSP1 (8). If the driven wheel is not in the braking state, it can be considered that the driven wheel does not slip. Therefore, the difference in the number of rotations with the driving wheel indicates the slip degree of the driving wheel. In the braking state, the idle switch is normally turned on, and lean operation is prohibited (see FIG. 7). Therefore, it can be considered that the vehicle is not in the braking state during lean operation.

In step 66, the two rotation pulse counters CVSP1 and CVSP2 and the timer T are reset to 0 in order to calculate the next slip degree SLRATE.

On the other hand, in step 67, the target surge index ISRG is obtained by searching the table having the contents of FIG. 16 from the slip degree SLRATE. As shown in FIG. 16, the target surge index ISRG is the slip degree SLR.
The value increases as ATE increases. this is,
Operation with a larger amount of combustion fluctuation as the degree of slip of the drive wheels increases (operation with a leaner air-fuel ratio)
Therefore, the target surge index is increased according to the slip degree SLRATE.

However, the rotation fluctuation amount becomes very large,
After the value of ISRG reaches the combustion stability limit equivalent value, ISRG is limited to the combustion stability limit equivalent value so that the air-fuel ratio does not shift to the lean side until the engine cannot maintain the stable state. There is.

In the second embodiment, the slip degree SLRA
The calculation of TE is easier than in the first embodiment, and the slip degree SLRATE can be detected in real time even while the drive wheels are slipping, so the slip degree calculation accuracy is high.

Since the target surge index ISRG is set in detail by the continuous value according to the slip degree SLRATE, this target surge index ISRG is set for a vehicle type that has many opportunities to travel on low μ roads under various conditions such as snow roads and icy roads. By the embodiment, the air-fuel ratio can be made lean to the limit according to each road surface,
This makes it possible to reduce fuel consumption and NOx emissions to the maximum during practical use.

In the embodiment, the means for controlling the torque generated by the engine during lean operation is the air-fuel ratio control means, but the ignition timing control means and the EGR amount control means may be used. Further, the torque generated by the engine during lean operation may be controlled by using two torque control means or three torque control means out of the three torque control means mentioned here.

[Brief description of drawings]

FIG. 1 is a control system diagram of a first embodiment.

FIG. 2 is a flowchart of a 180-degree job.

FIG. 3 is a flowchart for explaining calculation of a feedback correction rate.

FIG. 4 is a flowchart for explaining calculation of a target surge index ISRG.

FIG. 5 is a characteristic diagram of standard acceleration ACSTD.

FIG. 6 is a flowchart of a background job.

FIG. 7 is a flowchart for explaining determination of lean conditions.

FIG. 8 is an explanatory diagram of a lean operation region.

FIG. 9 is an explanatory diagram of a lean operation region.

FIG. 10 is an explanatory diagram of a lean operation region.

FIG. 11 is a characteristic diagram showing the contents of a lean map.

FIG. 12 is a characteristic diagram showing the contents of a non-lean map.

FIG. 13 is a waveform diagram for explaining a damper operation when switching the air-fuel ratio.

FIG. 14 is a flowchart of a 10 msec job.

FIG. 15 is a flowchart for explaining calculation of a target surge index ISRG according to the second embodiment.

FIG. 16 is a characteristic diagram of a target surge index ISRG according to the second embodiment.

FIG. 17 is a diagram corresponding to claims of the first invention.

FIG. 18 is a diagram corresponding to a claim of the second invention.

FIG. 19 is a diagram corresponding to the claim of the fourth invention.

FIG. 20 is a diagram corresponding to the claim of the fifth invention.

FIG. 21 is a diagram corresponding to the claim of the seventh invention.

[Explanation of symbols]

1 engine body 2 control unit 4 Crank angle sensor 6 Air flow meter 7 Fuel injection valve

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 41/04 F02D 41/04 305J F02M 25/07 550 F02M 25/07 550G 550R 570 570A F02P 5/15 F02P 5/15 B ( 56) References JP-A-6-173742 (JP, A) JP-A-2-157440 (JP, A) JP-A-8-144803 (JP, A) JP-A-5-79389 (JP, A) Japanese Unexamined Patent Publication No. Hei 4-234572 (JP, A) Japanese Unexamined Patent Publication No. 6-213121 (JP, A) Japanese Unexamined Patent Publication No. 6-272591 (JP, A) Japanese Unexamined Patent Publication No. 6-221202 (JP, A) Japanese Unexamined Patent Publication No. 2-176136 (JP , A) Actual Kaihei 5-57336 (JP, U) Japanese Patent Publication 3-66505 (JP, B2) (58) Fields surveyed (Int.Cl. ⁷ , DB name) F02D 29/00-29/06 F02D 41/00-45/00 F02M 25/07 F02P 5/145-5/155

Claims (9)

(57) [Claims] 1. A combustion fluctuation amount of an engine is reduced during lean operation.
If the combustion fluctuation amount becomes worse than the control target value, the fuel becomes stable.
For combustion fluctuation control device of engine designed to ensure
Oite, means for determining whether the driving wheel is in a slipping state, the determination when the result from the driving wheel is slipping the combustion fluctuation amount during lean operation than when the drive wheels are not slipping Means for setting the control target value on the side where the combustion fluctuation amount increases and means for controlling the combustion fluctuation amount during lean operation so that the combustion fluctuation amount during lean operation matches the control target value A combustion fluctuation control device for an engine. 2. A combustion fluctuation control device for an engine according to claim 1, wherein the control target value of the combustion fluctuation amount during lean operation when the drive wheels are slipping is a constant value. 3. The means for determining whether or not the driving wheels are in a slipping state is based on a signal from a vehicle speed sensor and a means for setting a vehicle acceleration in a state where the driving wheels are not slipping as a standard acceleration. The driving wheel slips when the absolute value of the vehicle acceleration based on the signal from the vehicle sensor is equal to or higher than the standard acceleration by comparing the vehicle acceleration based on the signal from the vehicle sensor with the standard acceleration. 3. When the vehicle is in the state, and when the absolute value of the vehicle acceleration based on the signal from the vehicle sensor is less than the standard acceleration, the means for determining that the driving wheels are not in the slipping state is provided. A combustion fluctuation control device for an engine according to. 4. A means for controlling the combustion fluctuation amount during lean operation so that the combustion fluctuation amount during lean operation matches the control target value, means for calculating a basic control amount of the engine during lean operation, Means for calculating a correction amount for the basic control amount so that the combustion fluctuation amount during lean operation matches the control target value, means for correcting the basic control amount with this correction amount, and the corrected control amount 4. The combustion fluctuation control device for an engine according to claim 1, further comprising means for controlling a torque generated by the engine during lean operation. 5. The combustion fluctuation amount of the engine is reduced during lean operation.
If the combustion fluctuation amount becomes worse than the control target value, the fuel becomes stable.
For combustion fluctuation control device of engine designed to ensure
Oite, means for detecting each rotational speed of the drive wheels and the driven wheels, means for calculating the rotational speed difference of the drive wheels and the driven wheels during lean operation as the slip degree, lean when the drive wheel is slipping and means for setting the control target value of the combustion fluctuation amount during operation on the side where the combustion fluctuation amount as the slip degree increases increases, the control the combustion fluctuation amount during lean operation when the drive wheel is slipping A combustion fluctuation control device for an engine, comprising: means for controlling a combustion fluctuation amount during lean operation when the drive wheels are slipping so as to match a target value. 6. The combustion of an engine according to claim 5, wherein when the control target value exceeds the combustion stability limit equivalent value during lean operation, the control target value is limited to this combustion stability limit equivalent value. Fluctuation control device. 7. A combustion fluctuation amount during lean operation when the drive wheels are slipping is controlled so that a combustion fluctuation amount during lean operation when the drive wheels are slipping matches the control target value. The means calculates the basic control amount of the engine during lean operation when the drive wheels are slipping, and the combustion fluctuation amount during lean operation when the drive wheels are slipping matches the control target value. Means for calculating a correction amount for the basic control amount, means for correcting the basic control amount with this correction amount, and an engine during lean operation when the drive wheels are slipping with the corrected control amount. 7. The combustion fluctuation control device for the engine according to claim 5, further comprising a means for controlling the torque generated by the engine. 8. The combustion fluctuation control device for an engine according to claim 4, wherein the basic control amount of the engine is at least one of an air-fuel ratio, an ignition timing, and an EGR amount. 9. The combustion fluctuation control device for an engine according to claim 1, wherein the combustion fluctuation amount during the lean operation is detected based on an engine rotation fluctuation amount.