JPH0520582B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine control device that controls to soften the shock that occurs in engine output when the air-fuel ratio is switched from rich to lean or from lean to rich. .

(Prior Art) In terms of engine output, when power is required such as in a high-speed rotation range, the air-fuel ratio is changed to rich, and in a low-speed rotation range or when idling, the air-fuel ratio may be changed to lean.

When switching the air-fuel ratio as described above, when switching from lean to rich, a shock occurs in the upward direction of engine output, and when switching from rich to lean, a shock occurs in the downward direction of engine output. If such a shock occurs, it will reduce the product value, so as a means of alleviating the above-mentioned shock, there have conventionally been devices that steplessly change the air-fuel ratio (for example, Japanese Utility Model Publication No. 41227/1983).

However, in the case of this conventional device, although the above-mentioned shock can be alleviated, there is a problem in that it is disadvantageous in terms of exhaust gas purification.

As shown in the relationship diagram between the concentration of harmful components in exhaust gas and the air-fuel ratio in Figure 1, and the relationship diagram between the catalyst purification rate and the air-fuel ratio in Figure 2, the stoichiometric air-fuel ratio used during medium to high loads. (A/F = 14.7) If we look at the positions of rich zone A nearby and lean zone B, which is used during idling and low load, we find that rich zone A is a zone with relatively good purification rates for CO, HC, and NOx. And lean zone B is
Although the NOx purification rate has decreased slightly, there are no problems with the exhaust gas conditions in both zones because the amount of NOx emissions is small.

However, although NOx generation reaches its peak between the rich zone A and the lean zone B, the NOx purification rate is decreasing, so it is not preferable to set the air-fuel ratio there.

Therefore, it is possible to alleviate the shock by correcting the ignition timing in synchronization with the air-fuel ratio switching, but there is a problem in that the shock cannot be sufficiently alleviated depending on the direction of change in the air-fuel ratio.

In other words, when the air-fuel ratio is switched from lean to rich, the shock caused by the switch is in the direction of increasing engine output, so the engine's ignition timing is delayed in synchronization with this shock. It is possible to soften the shock by lowering the engine output and offsetting this output reduction with the above-mentioned output increase.

However, when the air-fuel ratio is switched from rich to lean, the engine output decreases, and the ignition timing of the engine normally operates at the optimum timing for maximum output, so the ignition timing By adjusting the retardation or advance angle, it is impossible to increase the engine output beyond the optimal timing, and the aforementioned shock at the time of downtime cannot be alleviated.

(Object of the Invention) An object of the present invention is to provide an engine control device that can alleviate the shock in the direction of output reduction that occurs when the air-fuel ratio is switched from rich to lean without deteriorating exhaust purification.

(Structure of the Invention) The present invention includes a fuel supply means for supplying fuel to an engine, an operating state detecting means for detecting the operating state of the engine, and a system that responds to the operating state by receiving the output of the operating state detecting means. an air-fuel ratio determining means for determining a basic air-fuel ratio; an ignition timing determining means for determining the ignition timing of the engine according to the output of the operating state detecting means; and an air-fuel ratio adjustment for adjusting the air-fuel ratio of the air-fuel mixture supplied to the engine. means, an ignition timing adjustment means for adjusting the ignition timing of the engine, and a basic air-fuel ratio that is leaner than the basic air-fuel ratio and thinner than the stoichiometric air-fuel ratio in the first operating state from the first operating state where the basic air-fuel ratio is rich. When the operating state changes to the second operating state, the ignition timing is gradually retarded by the ignition timing adjustment means, and this retardation amount is the basic air-fuel ratio of the second operating state and the ignition timing determined by the ignition timing determining means. After reaching a predetermined value under the engine output equivalent to that obtained at the timing, the air-fuel ratio adjustment means controls the air-fuel ratio to the air-fuel ratio corresponding to the second operating state, and the ignition timing is determined by the ignition timing determining means. and a control means for controlling an ignition timing adjusting means so as to achieve the desired ignition timing.

(Effects of the Invention) According to the present invention, the air-fuel ratio is switched from rich to lean all at once, and there is no combustion in the air-fuel ratio zone where a large amount of NOx is emitted, so a large amount of NOx is not emitted. Deterioration of exhaust gas purification is prevented.

Furthermore, when the air-fuel ratio is switched from rich to lean, before changing the air-fuel ratio, the engine's ignition timing is gradually retarded in the rich state to reduce the engine output, and the output after this reduction is equal to that of the lean one. When the engine output equivalent to that obtained under the conditions is reached, the air-fuel ratio is switched from rich to lean, and at the same time the engine's ignition timing is advanced to the required ignition timing in the lean conditions. Since the engine output at the lean angle and the engine output at the required ignition timing in the lean state can be approximately equal, the increase in output due to advance angle and the decrease in output due to switching the air-fuel ratio are offset, and the output decrease due to switching the air-fuel ratio is can relieve the shock of

Furthermore, since the aforementioned retardation of the ignition timing of the engine is carried out gradually, the driver is unaware of the retardation and does not feel uncomfortable.

(Example) An example of the present invention will be described in detail below based on the drawings.

The drawing shows an engine control device. In FIG. 3, an injector 3 for injecting fuel and a throttle valve 4 are provided in an intake passage 2 of an engine 1. Fuel is injected according to the amount of air under the control of the control unit 6. Note that the amount of intake air may be detected by ultrasonic waves or by means of detecting a plate that moves according to the amount of air.

Also, the throttle opening sensor 7 is connected to the throttle valve 4.
detects the degree of opening of the valve and outputs a signal corresponding to the degree of opening to the control unit 6. Crank angle sensor 8 is the top depth center (TDC) of the crankshaft.
Control unit 6 sends a crank angle signal indicating
Output to. An O ₂ sensor 10 as an air-fuel ratio sensor is provided in the exhaust passage 9 of the engine 1.
The O ₂ sensor 10 detects the air-fuel ratio and outputs a signal corresponding to the air-fuel ratio to the control unit 6.

The igniter 11 also controls the ignition timing of the engine 1 when the air-fuel ratio changes.

FIG. 4 shows a control circuit composed of the aforementioned control unit 6. The CPU 12 controls each circuit device according to a set program, and the crank angle sensor 8 detects the top depth center (TDC) of the crankshaft. The detected crank angle signal is waveform-shaped by a waveform shaping circuit 13 and input to the CPU 12.

The air floor sensor 14 provided in the air flow meter 5 converts an analog signal indicating the amount of air into a digital signal using an A/D converter 15 and inputs the digital signal to the CPU 12 .

It is determined whether the signal indicating the air-fuel ratio of the O ₂ sensor 10 is rich or lean based on the slice level set by the discrimination circuit 16. When the code signal is "0" (low level signal), the CPU1
Enter 2.

The throttle opening sensor 7 receives an analog signal indicating the throttle opening, which is converted into a digital signal by an A/D converter 17 and input to the CPU 12 .

The injector 3 is driven by a drive circuit 19 controlled by a time tJ set in a first timer 13 by the CPU 12 to inject fuel.

The igniter 11 determines the ignition timing at the time tG set in the second timer 20 by the CPU 12 and drives the ignition coil 21.
The spark plug 23 is driven via the ignition plug 23.

The oscillator 24 oscillates clock pulses to
12 and each timer 18, 20, 25
Also enter.

The third timer 25 measures time.

The operation of the engine control device configured as described above will be explained with reference to the flowchart of FIG.

In this embodiment, zone A where the stoichiometric air-fuel ratio λ=1 shown in FIGS. 1 and 2 is set as a rich zone, and zone B, which is permissible in terms of exhaust gas, is set as a lean zone.

In the first step 31, the CPU 12 initializes the necessary circuits such as memory, and in the second step 32, the CPU 12 initializes the crank angle sensor 8.
Crank angle signal that detected the top depth center of
Determine whether TDC is input or not, and if not input, wait until input.

When the above crank angle signal TDC is input,
In the third step 33, the CPU 12 uses the third timer 2.
5 reads the time _t2 at which the above-mentioned crank angle signal TDC was input.

Note that this input time _t2 is read and stored for each input.

In the fourth step 34, the CPU 12 controls the igniter 11 to start energizing, and at the same time sets the ignition timing tG or tSB calculated in the 18th step 48 or the 25th step 55, which will be described later, to the second timer 2.
Set to 0.

At the fifth step 35, the CPU 12 controls the injector 3 to start injection, and at the same time determines the injection time tJ corresponding to the fuel injection amount calculated at the 19th step 49, the 21st step 51, or the 24th step 54, which will be described later. The first timer 18 is set.

In the sixth step 36, the CPU 12 reads out the input time _t2 of the current crank angle signal TDC that has already been read and the previous input time _t1 , and determines the rotational speed of the engine ₁ from the difference between the two times t1 and _t2 . Calculate ne and convert time t ₁ to t ₂
to prepare for the next calculation of the rotation speed ne.

In the seventh step 37, the CPU 12 reads the intake air amount Qf from the air flow sensor 14, and in the eighth step 38 reads the throttle opening θTH from the throttle opening sensor 7.

The switching point between the air-fuel ratio λ=1 zone and the lean zone is set at the throttle opening θ ₀ , and this opening θ ₀ is set at the opening θ ₀ corresponding to the branching point between high speed and low speed or idle, for example. has been done.

At the ninth step 39, the CPU 12 determines whether the read throttle opening θTH is larger than the zone switching throttle opening θ ₀ , and if it is larger, the throttle opening θTH is
= 1 zone, i.e. rich zone processing,
When it is small, it is determined that processing is in the lean zone.

Furthermore, when it is determined that the zone is λ=1, the process is performed at the stoichiometric air-fuel ratio, so it is also a zone where feedback is applied by the O ₂ sensor.

If YES is determined in the ninth step 39, in the tenth step 40, the CPU 12 counts the basic injection amount tfB of fuel that will give the stoichiometric air-fuel ratio from the already read intake air amount Qf, and in the eleventh step, the CPU 12
Then, the air-fuel ratio indicated by the O ₂ sensor 10 is rich "1".
(high level) or lean "0" (low level).

If richness is determined to be “1”, proceed to step 4 of the 12th step.
In step 2, the CPU 12 decreases the feedback coefficient CF/B, and when lean "0" is determined, in step 43, the CPU 12 sets the feedback coefficient CF/B large.

At the 14th step 44, the CPU 12 calculates the engine speed ne calculated at the 6th step 36 and the 7th
The basic ignition timing tSB is calculated based on the intake air amount Qf read in step 37. Note that this basic ignition timing tSB is determined by the engine speed ne and intake air amount.
It is also possible to store a map determined by Qf in a memory in advance and read from this map.

In the 15th step 45, the CPU 12 determines whether the current process is a process when the lean zone is switched to the λ=1 zone, that is, a process to soften the upward shock of the engine, or a simple λ=1 process.
Determine whether feedback processing is for one zone.

In order to switch to the above-mentioned λ=1 zone, the necessary shock processing value TLRO to absorb the above-mentioned shock is set in advance, and this processing value TLRO
is assigned and stored in the 27th step 57, which will be described later.

Therefore, in the above-mentioned 15th step 45, it is determined whether the above-mentioned shock processing value TLR is zero or there is a remaining shock processing value, thereby determining whether the processing is for switching the λ=1 zone or the feedback processing. do.

When it is determined that it is time to switch as described above,
In the 16th step 46, the CPU 12 sets a small value ΔT to gradually restore the shock processing value TLR.
is updated by subtracting , and if it is determined that it is a simple fieldback process, the process of the 16th step 46 described above is skipped.

In the 17th step, the CPU 12 converts the necessary shock processing value TLRO when switching from rich to lean performed in lean zone processing to the shock processing value TLR.
be memorized as

At the 18th step 48, the CPU 12 calculates the ignition timing tG by adding the basic injection amount tSB calculated at the 10th step 40 and the shock processing value TLR determined at the 16th step 46.

At this time, when the above-mentioned shock processing value TLR is added, the ignition timing tG becomes larger than the basic ignition timing tSB, and as a result, it is retarded.

In the 19th step 49, the CPU 12 executes the injection based on the feedback coefficient CF/B determined in the previous 12th or 13th step 42, 43 and the basic injection amount tfB calculated in the 10th step 40. The time tJ is calculated, and when this calculation is completed, the process returns to the second step 32.

By repeating the above-mentioned routine, when the air-fuel ratio is switched from the lean zone to the λ=1 zone, the engine ignition time is greatly retarded, and the engine output increases when the switch is made. shock is softened by offsetting the reduction in engine output based on the retardation. Thereafter, each time the engine passes through the 16th step 46, the shock processing value TLR gradually decreases by the value ΔT, and the ignition timing is changed in the advance direction, and when the above-mentioned value TLR becomes zero, only the basic ignition timing tSB Therefore, only feedback processing is required.

In other words, the processing of the switching zone X portion shown in FIG. 6 has been executed.

Next, lean zone processing will be explained.

If it is determined in the above-mentioned ninth step 39 that the process is a lean zone process, in the 20th step 50,
The CPU 12 executes the shock processing value of the required shock processing value TRLO set in the previous 17th step 47.
Determine whether TRL is zero.

If the above-mentioned shock processing value TRL exists (TRL is not zero), it is the processing when switching from the λ = 1 zone to the lean zone, that is, the processing to soften the shock in the downward direction of engine output. If the processing value TRL is zero, it is determined that the processing is in a normal lean zone.

When it is determined that the process is for switching from the λ=1 zone to the lean zone, the process proceeds to the 21st step 51.
Then, the CPU 12 calculates the injection amount tJ at which λ=1, that is, the stoichiometric air-fuel ratio, from the intake air amount Qf read in the seventh step 37. Note that although this stage is lean zone processing, the air-fuel ratio of the λ=1 zone is maintained.

In the 22nd step 52, the CPU 12 reads the shock processing value TRL set in the 17th step 47, subtracts from this value TRL the value ΔT for one time for gradual retardation, and in the 23rd step 53 Engine speed calculated in 6 steps 36
ne and the intake air amount Qf read in the seventh step 37
The basic ignition timing tSB calculated based on
22 The subtracted value TRL in step 52 is subtracted from the required shock processing value TRLO, and the remaining value is added to calculate the ignition timing tG to be executed.

At this time, when the subtraction value TRL is added, the ignition timing
tG is larger than the basic ignition timing tSB by the value ΔT,
As a result, the angle is delayed.

By repeatedly executing the routines 51 to 53 in the 21st to 23rd steps, the retard amount gradually increases with the value ΔT, and the subtracted value TRL is increased in the 22nd step 52.
When becomes zero, the retard amount becomes maximum, and the added value in the 23rd step 53 becomes the required shock processing value TRLO.
Only.

Furthermore, in the above-mentioned 22nd step 52, the subtraction value TRL is calculated.
When the value TRL becomes zero, this routine is passed, and in the next repeating routine, it is determined that the shock processing value TRL is zero at the 20th step 50, and the process proceeds to the 24th step 50.
In step 4, the CPU 12 calculates the fuel injection amount tJ to make the air-fuel ratio lean based on the engine speed ne calculated in the sixth step 36 and the intake air amount Qf read in the seventh step 37. Furthermore, in the 25th step 55, the basic ignition timing tSB is calculated based on the engine speed ne and the intake air amount Qf, and the
In step 56, the above-mentioned basic ignition timing tSB is stored as the ignition timing tG.

Thereafter, in the 27th step 57, the CPU 12 executes λ=
The necessary shock processing value TLRO when switching from lean to rich in one zone processing is stored as the shock processing value TLR.

As a result, the ignition timing tG determined in the 26th step 56 described above is the basic ignition timing tSB in the lean zone process, so the ignition timing tG determined in the 26th step 56 is the basic ignition timing tSB in the lean zone process,
Routines 1 to 53 are executed repeatedly to determine the ignition timing.
The amount of retardation of tG is gradually increased, and then reaches the maximum value.In the first process, when the routine moves to the 24th to 26th steps 54 to 56, the basic ignition timing is changed all at once.
This means that the air-fuel ratio has advanced to tSB, and at the same time the air-fuel ratio has reached 21st.
~λ= maintained in the 23rd steps 51-53
The 1 zone will be switched to the lean zone.

When the engine is combusted at this time, the downward shock of the engine output is softened by the offset of the engine output increase based on the advance angle.

That is, the processing of the switching zone Y portion shown in FIG. 6 has been executed.

After that, only the normal lean zone processing is performed depending on the basic ignition timing tSB and the lean fuel injection amount tJ.

In summary, when shifting the air-fuel ratio from rich to lean (at step 50 in FIG. 5,
Prior to the air-fuel ratio transition, the ignition timing is retarded to the level equivalent to the engine output obtained in the lean state (see ΔT in Step 22 of Figure 5).
Then (step 50 in Figure 5)
(Refer to the NO judgment in the above)) By simultaneously shifting the air-fuel ratio from rich to lean (see 24th step 54) and canceling the retardation (see 25th step 55), the torque can be increased without causing an increase in _NOx . It has the effect of preventing shots.

In addition, in the above-mentioned embodiment, the air-fuel ratio λ=1
Although the zone is a rich zone, it may be a zone richer than the stoichiometric air-fuel ratio.

Further, even if feedback control is not performed using the O ₂ sensor, if the air-fuel ratio λ is in the 1 zone, anticipatory control may be performed using a fuel injection amount corresponding to the air-fuel ratio λ=1 zone.

In the correspondence between the configuration of the present invention and the above-described embodiments, the fuel supply means of the present invention corresponds to the injector 3 of the embodiment, and similarly, the operating state detection means corresponds to the throttle opening sensor 7.
and the air flow sensor 14, the air-fuel ratio determining means corresponds to each step 40, 54, and the ignition timing determining means corresponds to each step 48, 53,
56, the air-fuel ratio adjustment means corresponds to each step 51 and 54, the ignition timing adjustment means corresponds to the igniter 11, and the control means corresponds to the CPU 12. It is not limited only to the configuration.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a diagram showing the relationship between the concentration of harmful components in exhaust gas and the air-fuel ratio.
FIG. 2 is a diagram showing the relationship between purification rate and air-fuel ratio. FIG. 3 is a configuration diagram of the engine control device. FIG. 4 is a control circuit block diagram. FIG. 5 is a flowchart of control processing. FIG. 6 is a time chart showing zone switching. 1...Engine, 3...Injector, 7...
Throttle opening sensor, 11...Igniter, 1
2...CPU, 14...Air flow sensor, 40,
54...Air-fuel ratio determining means, 48, 53, 56...
Ignition timing determining means, 51, 54...Air-fuel ratio adjusting means.

Claims (1)

[Claims] 1. A fuel supply means 3 for supplying fuel to the engine 1; an operating state detecting means 7, 14 for detecting the operating state of the engine 1; and an output of the operating state detecting means 7, 14. air-fuel ratio determining means 40, 54 that determines a basic air-fuel ratio corresponding to the operating state based on the received information; and ignition timing determining means 48, 53 that determines the ignition timing of the engine 1 according to the output of the operating state detecting means 7, 14. , 56, air-fuel ratio adjusting means 51, 54 for adjusting the air-fuel ratio of the air-fuel mixture supplied to the engine 1, ignition timing adjusting means 11 for adjusting the ignition timing of the engine 1, and a first operation with a high basic air-fuel ratio. The ignition timing is gradually retarded by the ignition timing adjusting means 11 when changing from the state to the second operating state where the basic air-fuel ratio is leaner than the basic air-fuel ratio in the first operating state and thinner than the stoichiometric air-fuel ratio. After this retard amount reaches a predetermined value under the basic air-fuel ratio of the second operating state and the engine output equivalent to the ignition timing obtained by the ignition timing determining means, the air-fuel ratio adjusting means A control device for an engine, comprising: a control means 12 for controlling the air-fuel ratio to an air-fuel ratio corresponding to a second operating state, and for controlling an ignition timing adjusting means 11 so that the ignition timing becomes the ignition timing determined by the ignition timing determining means. .