JP3193103B2 - Engine 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 control device having a lean burn operation function.

[0002]

2. Description of the Related Art In recent years, there has been an increasing demand for lower fuel consumption of vehicle engines from the viewpoint of protecting the global environment along with the demand for resource saving.

[0003] setting as to meet this demand, generally stoichiometric engine air-fuel ratio A / F air-fuel ratio A / F = 14. 7 ( λ = 1) an air-fuel ratio leaner than, for example, A / F = 16 to 22 A so-called lean burn engine has been proposed (see, for example, JP-A-60-13953).

However, lean-burn engines do not mean that lean-burn operation can be performed over the entire engine operating range. In a high load region such as at full load or at full load, it is inevitable to shift to a rich region above the stoichiometric air-fuel ratio.

On the other hand, considering the NOx reduction effect of the combination of the O ₂ feedback control system for the air-fuel ratio and the three-way catalyst, the setting range of the lean air-fuel ratio is necessarily limited, and at least the amount of NOx generated Therefore, it is necessary to avoid setting the air-fuel ratio in the air-fuel ratio region (for example, A / F = around 16) where the reduction of Nox by the three-way catalyst is impossible.

Therefore, in the engine adopting the lean burn system as described above, at least the amount of NOx generated is generally large and it is impossible to reduce the amount as described in the above-mentioned publication. A lean side region and a rich side region as shown in FIG. 14 are set except for such an air-fuel ratio region, and, based on the operating condition, the lean side region and the stoichiometric air-fuel ratio (A / F = 14.7) An air-fuel ratio control system is adopted which appropriately uses (switches and controls) the region on the rich side centered at the center, thereby improving the overall fuel efficiency.

However, when such a lean / rich switching system is employed, the engine output changes suddenly when switching from the rich side to the lean side or from the lean side to the rich side as shown in FIG. There is a problem that a feeling of running anxiety due to an increase in acceleration or a torque shock due to deceleration is generated.

If the change in the air-fuel ratio is continuously changed steplessly, the torque shock as described above does not need to occur, but in such a case, the amount of NOx generated is large. In addition, the exhaust gas passes through a region where NOx reduction of the three-way catalyst cannot be performed, which causes a problem that the exhaust gas purification performance deteriorates.

Therefore, in the configuration of the prior art, as a means for solving the problem, when the air-fuel ratio is changed from lean to rich, the ignition timing of the engine is retarded in synchronization with the change to reduce the engine output. To reduce the uneasiness caused by unintended acceleration, while reducing the engine output by gradually retarding the ignition timing of the engine in a rich state in advance when changing the air-fuel ratio from rich to lean When the output down reaches a predetermined value, the air-fuel ratio is switched from rich to lean, and at the same time, the ignition timing of the engine is advanced to a predetermined position, thereby increasing the output by the advance and switching the air-fuel ratio. By canceling the output down, the torque shock at the time of the output down due to the switching of the air-fuel ratio is relieved.

[0010]

However, in the above-described configuration, the output performance itself is reduced particularly when the air-fuel ratio is switched from the lean or rich state to the rich or lean state, and eventually the original engine output itself is reduced. It will be bad. Further, since the ignition timing itself that affects the combustion performance is retarded, there is a problem that the combustion performance deteriorates and the fuel consumption performance at the corner becomes worse.

[0011]

SUMMARY OF THE INVENTION The inventions described in claims 1 to 4 of the present application have been made for the purpose of solving the above-mentioned conventional problems, and have the following structures. I have.

(1) Structure of the invention according to claim 1 The engine control device according to the invention according to claim 1 is an air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio, and the exhaust gas of the engine. And the target air-fuel ratio of the engine controlled by the air-fuel ratio control means is controlled to a lean side and a rich side according to the operating state while avoiding the air-fuel ratio region where the amount of NOx generated in the engine exhaust gas is largest. A variable valve timing means for increasing the output torque of the engine, comprising an engine having target air-fuel ratio setting means for setting the target air-fuel ratio in one of the two regions.
Synchronizing the torque assist means comprising variable intake means and the operation state of the torque assist means with the switching of the target air-fuel ratio set by the target air-fuel ratio setting means from the lean region to the rich region or from the rich region to the lean region. And torque assist control means for controlling the torque
The assist control means sets the target air-fuel ratio in the lean region.
When switching to the rich region, the torque assist means
Of variable valve timing means and variable intake means
After turning both off once, the throttle opening is
If so, the variable valve timing means and the variable suction
While the throttle means is turned on again,
When the opening is smaller than the set opening, the valve timing is
ON only one of the variable means and the variable intake means
And it is characterized in that it is configured to.

[0013] (2) The engine control apparatus of the present invention the arrangement according to claim 2, wherein the second aspect of the present invention includes a air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio, the exhaust gas of the engine And the target air-fuel ratio of the engine controlled by the air-fuel ratio control means is controlled to a lean side and a rich side according to the operating state while avoiding the air-fuel ratio region where the amount of NOx generated in the engine exhaust gas is largest. and the target air-fuel ratio setting means for setting the side one in the area, Barubuta to increase the output torque of the engine
An engine control device comprising: a torque assist means comprising an imming variable means and a variable intake means ; and a torque assist control means for turning on the torque assist means at least in a full load region of the engine. Turns on the torque assist means when the target air-fuel ratio set by the target air-fuel ratio setting means corresponds to the lean region, and sets the target air-fuel ratio set corresponding to the rich region ratio is intended to re-oN after once OFF in synchronization from the lean region to change to the rich region when is due switched from the lean region, and the upper
For switching the target air-fuel ratio from lean to rich
If the throttle opening is equal to or greater than the set opening,
Variable valve timing means and
And both the variable intake means and the throttle
The valve timing is smaller than the set opening.
Turn ON only one of the variable variable means and the variable intake means
And it is characterized in that it is configured such that.

[0014] (3) The engine control apparatus of the present invention the arrangement according to claim 3, wherein the invention according to claim 3, the basic structure of the arrangement of the invention described in claim 1, 2 or one of, the In the configuration, an ignition timing control unit is provided, and an ignition timing controlled by the ignition timing control unit is set to an optimum ignition timing capable of obtaining a maximum torque under the operation state in the target air-fuel ratio switching region. It is characterized by having such a configuration.

[0015] (4) The engine control apparatus of the present invention the arrangement according to claim 4, wherein the invention described in claim 4, the basic configuration of the structure of the invention according to the claim 1, 2 or one of, the The exhaust gas recirculation means for recirculating exhaust gas to the engine intake system and the exhaust gas recirculation state control means for controlling the recirculation state of the exhaust gas by the exhaust gas recirculation means are provided. The present invention is characterized in that reflux control is performed.

[0016]

According to the present invention, the engine control devices according to the first to fourth aspects of the present invention are configured as described above.
The following operation is achieved corresponding to each configuration.

(1) Operation of the engine control device according to the first aspect of the invention In the engine control device according to the first aspect, the air-fuel ratio control means controls the air-fuel ratio of the engine to a predetermined target air-fuel ratio. The three-way catalyst for purifying the exhaust gas of the engine and the target air-fuel ratio of the engine controlled by the air-fuel ratio control means are set to an operating state avoiding the air-fuel ratio region where the amount of NOx generated in the engine exhaust gas is the largest. And a target air-fuel ratio setting means for setting the target air-fuel ratio in either one of the lean side and the rich side according to the basic air-fuel ratio control system. Is possible.

[0018] Then, with respect to the basic system, a torque assist means for further increasing the output torque of the engine, and an operation state of the torque assist means are changed to a target air-fuel ratio set by the target air-fuel ratio setting means. Torque assist control means for controlling in synchronization with switching from the lean area to the rich area or from the rich area to the lean area is provided.For example, in the lean burn operation area, the torque assist means is turned ON to sufficiently generate torque. To improve driving performance.

On the other hand, at the time of switching from the lean region where the engine output becomes high to the rich region, the torque
The strike control means temporarily sets the torque assist means to OFF.
By controlling the state to the F state, the torque improving effect of the torque assist means is lost and the torque is reduced to a certain extent.
After that, it is configured to turn on again, so the degree of change in torque when shifting from the lean state to the rich state is
Output performance after shifting to the rich region.
You.

As a result, there is no accompanying deterioration in flammability as in the case where the ignition timing is retarded in a rich state in advance, and the fuel consumption performance does not need to be deteriorated.

Further, from the lean region to the rich region
When switched to, when the relative manner large throttle opening
Is the valve timing of the torque assist means
Turn on both the variable means and the variable intake means, and
When the opening is relatively small, the valve tie
Only one of the variable means and the variable intake means
Use two means, such as turning on
From the time of gentle acceleration to the time of sudden acceleration.
Torque when switching the air-fuel ratio in response to xel depression
Fluctuations can be eliminated.

[0022] (2) in the engine control system of the present invention acts according to claim 2, wherein the control apparatus for an engine of a second aspect of the present invention, the air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio The three-way catalyst for purifying the exhaust gas of the engine and the target air-fuel ratio of the engine controlled by the air-fuel ratio control means are set to an operating state avoiding the air-fuel ratio region where the amount of NOx generated in the engine exhaust gas is the largest. Target air-fuel ratio setting means for setting the engine to either the lean side or the rich side, torque assist means for increasing the output torque of the engine, and turning on the torque assist means at least in the full load area of the engine. A basic engine air-fuel ratio control system is provided with torque assist control means for controlling In the range, the torque assist means is operated to sufficiently increase the torque to improve the traveling performance as much as possible.

On the other hand, in the apparatus of the present invention, when the target air-fuel ratio of the engine shifts from the lean state to the rich state, the engine is once turned on in the lean state to increase the torque, and then the target air-fuel ratio is increased. Is turned off in synchronism with the change of the torque to prevent a sudden change in torque. Moreover, at this time, the invention of claim 1 and
Similarly, variable valve timing according to throttle opening
Means and variable intake means.
Various accelerator depressions from slow acceleration to rapid acceleration
Eliminates torque fluctuations when switching air-fuel ratios
be able to.

As a result, it is possible to reliably prevent a change in torque without deteriorating flammability as in the case where the ignition timing is retarded.

[0025] (3) in the engine control system of the present invention acts according to claim 3, wherein the control device of the engine of the invention of claim 3, wherein the preceding claims 1, 2 or one of the terms based on the basic structure In addition to the same operation as the invention described in (1), further provided is an ignition timing control means, and the ignition timing controlled by the ignition timing control means makes the maximum torque under the operating condition in the transition region of the target air-fuel ratio. Since the ignition timing is set to the optimum ignition timing that can be obtained, the flammability is good and the output and the fuel consumption do not deteriorate.

[0026] (4) in the engine control system of the present invention acts according to claim 4, wherein the control device of the engine of the invention of claim 4, wherein the preceding claims 1, 2 or one of the terms based on the basic structure In addition to the same operation as the invention described in the above, further comprising an exhaust gas recirculation means for recirculating exhaust gas to the engine intake system and an exhaust gas recirculation state control means for controlling the recirculation state of the exhaust gas by the exhaust gas recirculation means, Since the recirculation control of the exhaust gas is performed in the transition region of the target air-fuel ratio, the torque can be reduced by the recirculation of the exhaust gas, while the flammability is good and the fuel efficiency is not deteriorated. ,
In addition, the combustion temperature is reduced by the inert gas component and NOx
The reduction effect also increases.

[0027]

As described above, according to the first to fourth aspects of the present invention, unlike the related art, it is possible to prevent a torque fluctuation at the time of lean / rich switching without deteriorating fuel consumption. At the same time, the amount of generated NOx can be reduced as much as possible.

[0028]

Embodiment (1) First Embodiment FIGS. 2 to 6 show an air-fuel ratio control device for an engine having a torque assist mechanism according to a first embodiment of the present invention.

First, an outline of the engine air-fuel ratio control system according to the embodiment of the present invention will be described with reference to FIG. 2, and then, the flow chart of FIG. 3 and the characteristic diagrams of FIGS. The control operation of the unit will be described in detail.

In FIG. 2, reference numeral 1 denotes an engine body, and intake air is taken in from outside through an air cleaner 30, and thereafter, an air flow meter 2 in an intake passage is provided.
It is supplied into each cylinder via the throttle chamber 3 and the surge tank 39. Fuel is fuel pump 13
Is supplied from the fuel tank 12 to the engine body 1 side, and is injected by the fuel injector 5 in accordance with the measured value Q of the intake air amount of the air flow meter 2. The amount of air taken into the cylinder during normal running is determined by the throttle chamber 3.
The metering control is performed by a throttle valve 6 provided therein. The throttle valve 6 is operated according to the operation opening of the accelerator pedal.

The throttle chamber 3 is provided with a bypass intake passage 7 which bypasses the throttle valve 6. The bypass intake passage 7 has intake air for controlling the engine speed during idling. A current control type electromagnetic valve (ISC valve) 8 serving as an amount adjusting means is provided. Downstream of the surge tank 39 is a partition wall 3.
The first passage 34 is divided into two first and second passages 34 and 35, and a variable intake valve 33 is provided in the first passage 34. The variable intake valve 33 is driven to be opened and closed by a servomotor 36, and realizes an intake inertia supercharging action by, for example, changing an effective cross-sectional area of an intake passage of the engine, thereby improving an intake charge amount.

The variable intake valve 33 serves as a first torque assist mechanism for improving the output torque of the engine.
(First TAS).

Further, reference numeral 10 denotes an exhaust pipe of an engine provided with a three-way catalytic converter 11 for exhaust gas purification processing. The exhaust pipe 10 has an actual air-fuel ratio of the engine based on the oxygen concentration in the exhaust gas. It is O ₂ sensor 16 for detecting a is provided.

On the other hand, reference numeral 14 denotes an ignition plug provided on the cylinder head of the engine body 1 so that a predetermined ignition voltage is applied to the ignition plug 14 via a distributor 17 and an igniter 18. The ignition voltage application timing, that is, the ignition timing is controlled by an ignition timing control signal IGT supplied from the engine control unit 9 to the igniter 18. A boost pressure sensor 20 detects an engine boost pressure corresponding to an engine load and inputs the detected boost pressure to the ECU 9.

Reference numeral 37 denotes a variable valve timing mechanism (VVT) for adjusting the output torque of the engine by changing the phase relationship between the camshaft and the crankshaft by using an electromagnetic actuator to vary the valve timing of the engine. The operation state is controlled by the engine control unit 9. The variable valve timing mechanism 37 constitutes a second torque assist mechanism (second TAS) described later.

On the other hand, reference numeral 50 denotes an EGR passage, which recirculates a part of exhaust gas having more inert gas components than air in the atmosphere to the intake side to lower the combustion temperature and suppress the generation of NOx. In a predetermined area, the engine control unit 9 controls the EGR valve 51 so that the recirculation state is changed by controlling the EGR valve 51 as a torque reduction system for reducing engine torque.

The engine control unit 9 includes:
For example, with a microcomputer (CPU) serving as an arithmetic unit as the center, calculation of the fuel injection amount T and its injection control circuit (both closed / open control circuit), a servo motor control circuit of the variable intake valve 33, and a valve timing variable mechanism 37
, A control circuit for the EGR valve 51, a timer circuit, various data memories (ROM and RAM), an input / output interface (I / O) circuit, and the like. The interface circuit I of the ECU 9
/ O includes, in addition to the above detection signals, an engine start signal (ECU trigger) from a starter switch (not shown), a crank angle detection signal θ from the crank angle sensor 15, and an engine water temperature detection signal detected by the water temperature sensor Sw. Tw, various detection signals necessary for determining and controlling the operation state of the engine, such as a throttle opening detection signal TVO detected by the throttle opening sensor 4 and an intake air amount detection signal Q detected by the air flow meter 2. Are respectively input.

Next, the engine control unit 9
The details of the air-fuel ratio control and the accompanying torque assist control will be described in detail with reference to the flowchart of FIG.

That is, first, after the control is started, step S ₁
And the intake air amount Q, crank angle θ, throttle opening TVO,
Engine data detection signals such as the engine water temperature Tw and the O ₂ sensor output V _O2 are input.

[0040] Then, then in step S ₂ whether or not the lean lean burn area than the stoichiometric air-fuel ratio as described in the current operating region ahead (area to perform lean burn operation),
The determination is made in light of the target air-fuel ratio on the air-fuel ratio control map.

[0041] As a result, when YES (lean burn region), the output V _O2 of the O ₂ sensor 16 proceeds to step S ₃
While determining the current actual air-fuel ratio A / F on the basis of
At the time (non-lean burn region, ie, enrich or λ =
Referring first region.. 8), the process proceeds to the first, second torque assist mechanism (first 1TAS, actuation of the 2TAS) (ON) determined as described above in Step S _30, S ₃₁ (described later).

[0042] When the current air-fuel ratio A / F in step S ₃ is determined, followed by after determining the current engine speed Ne based on the output θ of the crank angle sensor at Step S _4, further steps S Proceed to ₅ and the current air-fuel ratio A /
The torque TRL (see FIG. 5) in the lean burn operation region is calculated from F and the engine speed Ne.

Next, the process proceeds to step S _6, further the stoichiometric air-fuel ratio under the present engine speed Ne lambda = 1
After calculating the engine torque TR (λ) in step S7, in the next step S7, the two torques TR (λ) and T
The difference ΔTR from the RL (ΔTR = TR (λ) −TRL) is calculated.

[0044] Then, in step S _8, the torque difference Δ
TR determines whether larger or not the first determination reference value deltaTR ₂ or more. The first determination reference value ΔTR ₂ is determined by the first torque assist mechanism (the first T
AS) and a variable valve timing type second torque assist mechanism (second TAS), which is a determination reference value for determining whether or not it is necessary to simultaneously use two sets of torque assist mechanisms to perform torque control.

On the other hand, if the result of determination in step S ₈ above is YES, the process further proceeds to step S ₉ to determine whether the actual air-fuel ratio λ of the engine has changed to λ = 1, that is, whether the air-fuel ratio whether determines a switching from the lean region to the lambda = 1 region, when the result is NO, the process returns to jump torque control operation of the steps S ₁₀ to S ₁₆ to be described later as it is.

Meanwhile, as a result of the determination in step S _9, A
/ F when is YES and changed to lambda = 1 (switching), first willing the first is ON at the lean burn during operation in a steady state in step S _10, the second torque assist mechanism (second First, the operating state of the second TAS) is turned off, and the torque is reduced by a considerable amount to reduce the amount of increase in torque associated with the A / F enrichment (see FIG. 6). Next, steps S ₁₁ and S
Then the throttle opening TVOA proceeds to _12, after sequentially determining an engine speed Ne, further for the determined throttle opening TVO is ON operation necessity determination of the first torque assist mechanism in step S ₁₃ Then, it is determined whether or not the first opening degree TVO ₁ (see FIG. 6) has changed greatly.

[0047] As a result, when YES, then the first torque assist mechanism (first 1TAS) to ON in step S ₁₄ is up a predetermined amount of torque, throttle opening TVO which is further the determination in step S ₁₅ The second set opening TV for determining whether or not the second torque assist mechanism needs to be operated.
O ₂ determines whether it has changed significantly over (see Figure 6).

[0048] As a result, ON the second torque assist mechanism (first 2TAS) in step S ₁₆ when YES, the end first, second two sets of torque assist mechanism (first, second
TAS) to sufficiently improve the engine torque and compensate for the lack of torque when the throttle opening change amount is large, such as during rapid acceleration.

As a result, low fuel consumption operation can be performed in the lean burn operation range, and the output performance can be maintained sufficiently high by the action of the torque assist mechanism. The torque fluctuation at the time of switching the air-fuel ratio due to the depression can be eliminated.
(See FIG. 4).

On the other hand, when it is determined NO in the determination in step S ₈ proceeds to step S _17, the same step S _17, in turn, the torque difference deltaTR (see FIG. 5) is first variable intake inertial system torque assist mechanism for determining whether to perform the control by the operation of the (first 1TAS), the first criterion value deltaTR ₂ is close to a small second than the deltaTR ₂ criterion value deltaTR ₁ or more It is determined whether (ΔTR ₂ > ΔTR ≧ ΔTR ₁ ). If YES, the process further proceeds to step S ₁₈ to determine whether the current actual air-fuel ratio λ of the engine has changed to λ = 1 in the same state. It determines whether (or is switched to the rich side), then the result is NO, as it jumps to (as required) return the operation of the steps S ₁₉ to S ₂₃ described later. ΔTR ₁ is a determination value when the torque reduction control is performed using only one of the first torque assist mechanism and the second torque assist mechanism.

Meanwhile, as a result of the determination in step S _18, A
/ F when is YES and changed to lambda = 1 (when switching) is, ON to lean burn during operation in a steady state go ahead step S ₁₉
The controlled first torque assist mechanism (first T
To reduce the torque in the temporarily OFF the operating state of the AS), then the routine proceeds to step S _20, S _21, then the throttle opening TVO, after sequentially determining an engine speed Ne, further the determination in step S ₂₂ It is determined whether or not the obtained throttle opening TVO is larger than a _first set opening TVO ₁ (an opening to be turned on) for determining whether or not the first torque assist mechanism is required.

[0052] As a result, when YES is first torque assist mechanism (first 1TAS) to ON in step S _23, to improve a degree torque only by the first torque assist mechanism (first 1TAS), the Λ from lean burn operation
= 1 The torque at the time of transition to the operating state is gradually increased to make the torque change gentle (see the broken line in FIG. 4).

As a result, low fuel consumption operation by lean burn operation in a sufficiently wide range can be achieved, and the output performance can be maintained high by torque assist. The accompanying torque shock at the time of air-fuel ratio switching can also be eliminated.

[0054] Further, when the calculated value deltaTR in step S ₇ is determined to be NO as smaller than the second criterion value deltaTR ₁ with torque difference determination in step S ₁₇ (deltaTR
<TR ₁ ), on the other hand, proceeds to step S ₂₄ to determine whether or not the actual air-fuel ratio λ of the engine has changed to λ = 1 (whether it is at the time of switching) as in step S _18. step S ₂₅ to S _29, and the result is NO, the described below as
Jump (return as unnecessary) with the torque control operation of.

On the other hand, the result of the determination in step S _24, A
/ F when is YES and changed to lambda = 1 (switching from lean to rich), first step S the second had been ON control in willing lean burn during operation in a steady state in ₂₅
Of the torque assist mechanism (second TAS) is turned off once
To reduce the torque by a predetermined amount, and then at step S ₂₆ ,
Throttle opening TVO at that time proceeds to S _27, after sequentially determining an engine speed Ne, further the determined throttle opening TVO second for raising determination the second torque assist mechanism in step S ₂₈ Set opening TVO
It is determined whether or not it is larger than ₂ (opening to be turned on).

[0056] As a result, the ON the second torque assist mechanism (first 2TAS) in step S ₂₉ when YES, the second
The torque is increased by a predetermined amount by the torque assist mechanism (second TAS), and gradually approaches the original required torque.

As a result, low fuel consumption operation by lean burn operation in a sufficiently wide range can be performed, and the output performance can be maintained high by torque assist. The torque fluctuation at the time of switching the air-fuel ratio can also be eliminated.

[0058] The above first in lean burn operation area, to the control of the second torque assist mechanism, when the other step S ₂ in the determination is NO non lean burn operation regions (rich region), previously as also mentioned, firstly the in step S ₃₀ the first torque assist mechanism (first 1TAS)
ON / OFF of the above the ON / OFF state, further the following step S ₃₁ second torque assist mechanism (first 2TAS)
The states are sequentially determined, and the first and second torque assist mechanisms are determined.
When both (first and second TAS) are ON, the throttle opening TVO and the engine speed N at that time are further increased.
After determining the e, whether the determined throttle opening TVO at step S ₃₂ is larger in the second set opening TVO ₂ or more for determining whether a main actuating said second torque assist mechanism judge.

As a result, when the result is NO, the second torque assist mechanism (second TAS) is viewed from the required torque at that time.
As there is no need to operate the up, the second torque assist mechanism in step S ₃₃ a (first 2TAS) and to OFF, the following additional steps S ₃₄ in the determined throttle opening TVO in turn the first also it determines whether the increases in the first set opening TVO ₁ or more for operation necessity determination of the torque assist mechanism.

[0060] Consequently, as there is no need for the operation of the first torque assist mechanism (second 1TAS) when NO, the even the first torque assist mechanism (first 1TAS) in step S ₃₅ O
The first and second two sets of torque assist mechanisms as FFs
(1st, 2nd TAS) The torque assist action is stopped. Thereafter, the routine proceeds further to step S _36, the actual air-fuel ratio lambda of the engine is also determined whether the change in lambda = 1, then the result is NO, to jump directly operation of step S ₃₇ To return.

On the other hand, if the result of the above determination is that the A / F has changed to the λ = 1 region, ie, if the air-fuel ratio has changed to YES, the routine proceeds to step _S37 , where the first and second torque assist mechanisms (first and second torque assist mechanisms) have been changed. 2TAS) is turned on at the same time, and a sufficient torque assist mechanism is exhibited to improve the engine torque.

In the above configuration, two sets of torque assist mechanisms, ie, a variable torque intake type first torque assist mechanism (first TAS) and a variable valve timing type second torque assist mechanism (second TAS) are used. In the case of an engine with a relatively small output torque, the first torque fluctuation alone is sufficient,
Needless to calculate and use the torque difference ΔTR as described above, for example, as shown in FIG.
By setting the ON region of the torque assist mechanism in the low rotation region below 3000 rotations, the output torque in the lean region is improved.

When the operating state of the engine changes as shown by arrows (A) and (B) in FIG. 8, first, as shown in FIG. 9, when the change in the air-fuel ratio becomes λ = 1, First
The engine torque is reduced by switching off the torque assist mechanism, and then, when the engine boost pressure becomes zero (the throttle is fully open), it is turned back on to improve the engine torque.

As a result, for example, as shown by the broken line in FIG. 7, the output torque of the engine has a smooth torque characteristic similar to that described above, and the torque fluctuation at the time of switching the air-fuel ratio from lean to rich. Is prevented.

The first torque assist mechanism of the variable intake system used in the above embodiment is not limited to the variable inertia supercharging system described above, but may be a variable resonance supercharging system. The same can be applied.

(2) Second Embodiment Next, FIGS. 10 to 12 show an engine control device according to a second embodiment of the present invention.

Recently, a part of the exhaust gas containing an inert gas component is recirculated to the intake side of the engine to reduce the combustion speed and reduce the amount of NOx emission (EGR).
Control) is common, but the slowing of the combustion speed means that the output (torque) of the engine also eventually decreases, so that the use of the EGR control is the same as in the first embodiment. Thus, a torque reduction control system corresponding to the change in the air-fuel ratio can be configured. In this embodiment,
It was invented from such a viewpoint.

That is, in the engine control apparatus of the present embodiment, for example, instead of the conventional general air-fuel ratio control region map shown in FIG. 14, the air-fuel ratio control of the rich theoretical air-fuel ratio λ = 1 as shown in FIG. "(Λ =
1) + EGR control region is set, and the engine engine torque is reduced by a predetermined amount by executing the EGR control particularly in the region where the lean state lower than the stoichiometric air-fuel ratio is shifted to the rich state higher than the stoichiometric air-fuel ratio. Then, by shifting to the λ = 1 region, for example, as shown in FIG. 12, a torque fluctuation reducing effect is realized as in the first embodiment.

In this case, the supplied EGR amount (the amount of exhaust gas recirculated to the intake side) is determined by, for example, the throttle opening (TV
If the value is changed corresponding to O), the drivability is further improved.

The EGR supply amount is, for example, as shown in FIG.
As shown in the figure, the EGR control region is subdivided in accordance with the torque value of the engine, and the EGR supply amount (EGR
(Ratio =%) may be set and placed on the map.

Further, similarly to the first embodiment, the difference ΔTR between the output torque TRL in the lean state and the output torque TR (λ) in the λ = 1 state is calculated, and ΔT is calculated according to the value. , The larger the EGR is, the larger the EGR supply amount may be.

According to the configuration of this embodiment, there is an advantage that the NOx reduction effect is enhanced simultaneously with the prevention of torque fluctuation.

This configuration may be combined with the variable torque system having the two sets of torque assist mechanisms of the first embodiment, or of course, as described above, the EGR control system alone may be used to reduce the torque as shown in FIG. A system may be configured.

[Brief description of the drawings]

FIG. 1 is a diagram corresponding to claims of the present invention.

FIG. 2 is a control system diagram of the engine control device according to the first embodiment of the present invention.

FIG. 3 is a flowchart showing the details of an air-fuel ratio and torque assist control operation by an engine control unit of the device.

FIG. 4 is a graph showing torque characteristics of an engine by the device.

FIG. 5 is a graph showing a relationship between an air-fuel ratio of an engine and an engine required torque in the same device.

FIG. 6 is a characteristic diagram showing a relationship between an operating state of a torque assist mechanism and an engine output torque at the time of air-fuel ratio switching corresponding to a change in throttle opening of the device.

FIG. 7 is a diagram showing the torque when only the first torque assist mechanism, which is a main part of the device, is used, and the torque is controlled by the engine load, acceleration, and air-fuel ratio instead of the engine speed. It is a characteristic diagram.

FIG. 8 is an explanatory diagram showing an engine operation region when the control method of FIG. 7 is adopted.

FIG. 9 is a torque characteristic diagram of the engine when the control method of FIG. 7 is employed.

FIG. 10 is a diagram showing an operating range of an engine control device according to a second embodiment of the present invention.

FIG. 11 is a diagram showing E according to the operation range of the device.
It is a GR map.

FIG. 12 is a diagram showing a torque characteristic of an engine by the device.

FIG. 13 is a torque characteristic diagram of an engine according to a conventional example.

FIG. 14 is an engine operating area diagram of a conventional example.

[Explanation of symbols]

1 engine body 6 throttle valve 9 engine control unit 10 exhaust pipe 11 three-way catalytic converter 16 O ₂ sensor 32 partition wall 33 variable intake valve 34 first passage 35 second passage 36 the servo motor 37 a variable valve timing mechanism 50 EGR passage 51 EGR valve

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FI F02D 13/02 F02D 13/02 J 41/14 310 41/14 310P F02M 25/07 550 F02M 25/07 550R F02P 5/15 F02P 5/15 B (72) Inventor Junichi Taga 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Inside Mazda Co., Ltd. (56) References JP-A-4-36052 (JP, A) JP-A-4-17755 ( JP, A) JP-A-2-286844 (JP, A) JP-A-60-13953 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02D 43/00 301 F02B 27 / 02 F02D 13/02 F02D 41/14 310 F02P 5/15

Claims (4)

(57) [Claims] 1. An air-fuel ratio control means for controlling an air-fuel ratio of an engine to a predetermined target air-fuel ratio, a three-way catalyst for purifying exhaust gas of the engine, and a target air-fuel ratio of the engine controlled by the air-fuel ratio control means The target air-fuel ratio setting means for setting the air-fuel ratio region where the NOx generation amount in the engine exhaust gas is the largest, in one of the lean side and the rich side depending on the operation state. A valve timing that increases the output torque of the engine
A torque assist means comprising a variable variable means and a variable intake means , and an operating state of the torque assist means from the lean region to the rich region or from the rich region to the lean region of the target air-fuel ratio set by the target air-fuel ratio setting means. Bei the torque assist control means for controlling in synchronism with the switching
For example, the torque assist control means, Lee said target air-fuel ratio
When switching from the
Valve timing variable means and variable among cyst means
After turning off both of the intake means once, the throttle opening
Is greater than or equal to the set opening, the valve timing variable means
And the variable intake means are turned on again,
When the tor opening is smaller than the set opening, the valve
Either of the variable immersing means or variable intake means
Control apparatus for an engine, characterized in that it is configured to only to ON. 2. An air-fuel ratio controller for controlling an air-fuel ratio of an engine to a predetermined target air-fuel ratio, a three-way catalyst for purifying exhaust gas of the engine, and a target air-fuel ratio of the engine controlled by the air-fuel ratio controller. Target air-fuel ratio setting means for setting the air-fuel ratio in either the lean side or the rich side according to the operating state, avoiding the air-fuel ratio region where the NOx generation amount in the engine exhaust gas is the largest, and the output torque of the engine Increase valve timing
A torque assist means comprising a grayed varying means and the variable air intake means, said torque assist device, a control device of an engine comprising a torque assist control means for ON operating at full load range of at least the engine, the torque assist control The means turns on the torque assist means when the target air-fuel ratio set by the target air-fuel ratio setting means corresponds to the lean area, and sets the target to be set corresponding to the rich area. When the air-fuel ratio is due to the switching from the lean region, the air-fuel ratio is turned off once and then turned on again in synchronization with the switching from the lean region to the rich region , and the lean region of the target air-fuel ratio is set. To rich areas
When switching, if the throttle opening is more than the set opening
For example, the valve timing of the torque assist means
While turning on both the variable means and the variable intake means,
When the opening of the rotary is smaller than the set opening,
Only one of variable timing means and variable intake means
A control device for an engine, wherein the control device is configured to turn ON . 3. An ignition timing control means, wherein the ignition timing controlled by the ignition timing control means is set to an optimum ignition timing capable of obtaining a maximum torque under the operating condition in the target air-fuel ratio switching region. the engine control apparatus according to claim 1, 2 or one of which is characterized by being configured to be set. 4. An exhaust gas recirculation means for recirculating exhaust gas to an engine intake system and an exhaust gas recirculation state control means for controlling a recirculation state of the exhaust gas by the exhaust gas recirculation means, wherein the target air-fuel ratio is switched in the target air-fuel ratio switching region. The engine control device according to any one of claims 1 and 2, wherein exhaust gas recirculation control is performed.