JPH05272397A - Engine control device - Google Patents

Abstract

PURPOSE:To realize lean burn operation in a wide range and prevent torque fluctuation at the time of switching lean/rich by controlling a target air-fuel ratio setting means by means of an air-fuel ratio control means so as to set a target air-fuel ratio at either of a lean side and a rich side in accordance with an operation state by avoiding an air-fuel ratio range where generation quantity of NOx in an exhaust gas becomes maximum. CONSTITUTION:The device is provided with an air-fuel ratio control means for detecting an air-fuel ratio of an engine to control it to a specified target air-fuel ratio; and a target air-fuel ratio setting means for setting a target air-fuel ratio in a range of either of a lean side and a rich side in accordance with an operation state by avoiding an air-fuel ratio range where a generation quantity of NOx in an exhaust gas becomes maximum. A torque assist control means is provided to control an operation state of a torque assist means for increasing output, in synchronization with switching of the target air-fuel ratio from the lean side to the rich side so that torque fluctuation can be prevented and generation of NOx can be reduced as far as possible.

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 Recently, from the viewpoint of resource conservation as well as global environmental protection, there is an increasing demand for low fuel consumption of vehicle engines.

In order to meet this demand, generally, the engine air-fuel ratio A / F is set to a leaner air-fuel ratio than the theoretical air-fuel ratio A / F = 14.2 (λ = 1), for example, A / F = 16 to 22. A so-called lean burn engine that operates is proposed (for example, see Japanese Patent Laid-Open No. 60-13953).

However, the lean burn engine does not mean that the lean burn operation can be performed over the entire engine operating range. For example, during acceleration with high output demand except during steady operation such as idling or partial load. In the high load region, such as at full load or at full load, there is no choice but to shift to the rich region above the theoretical air-fuel ratio.

On the other hand, considering the NOx reduction effect of the combination of the air-fuel ratio O ₂ feedback control system and the three-way catalyst, the lean side air-fuel ratio setting range is inevitably limited, and at least the amount of NOx produced is limited. However, it is necessary to avoid setting the air-fuel ratio in the air-fuel ratio region (for example, near A / F = 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 above-mentioned NOx production amount is large, and it is impossible to reduce the NOx production amount, as also shown in the above-mentioned prior art publication. Except for such an air-fuel ratio region, a lean side region and a rich side region as shown in FIG. 14 are set, and the lean side region and the theoretical air-fuel ratio (A / F = 14.7) are set on the lean side region and the rich side region. The air-fuel ratio control system is used so that the rich side region centered around is properly used (switching control), and thereby the total fuel efficiency is improved.

However, if such a lean / rich switching system is adopted, the engine output changes abruptly when switching from the rich side to the lean side or from the lean side to the rich side, as shown in FIG. 13, for example. There is a problem that driving anxiety due to increased acceleration or torque shock due to deceleration occurs.

If the change of the air-fuel ratio is continuously changed without any step, it is of course possible to avoid the above torque shock. However, if this is done, a large amount of NOx is generated. Moreover, the NOx reduction of the three-way catalyst passes through a region where NOx reduction is impossible, which causes a problem that exhaust purification performance deteriorates.

Therefore, in the configuration of the conventional example, as a means for coping with the problem, when the air-fuel ratio is changed from lean to rich, the engine ignition timing is retarded in synchronism with the change. To reduce the anxiety caused by unintentional acceleration, while reducing the engine output by gradually retarding the ignition timing of the engine in the pre-rich state 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 the ignition timing of the engine is advanced to a predetermined position at the same time. The output down is canceled to reduce the torque shock at the time of the output down due to the switching of the air-fuel ratio.

[0010]

However, in the above configuration, the output performance itself is reduced because the original engine output itself is eventually reduced when the air-fuel ratio is switched from the lean or rich state to the rich or lean state. It will be bad. Further, since the ignition timing itself, which influences the combustion performance, is retarded, there is a problem that the combustibility deteriorates and the fuel efficiency performance at the corner is also deteriorated.

[0011]

The invention described in each of claims 1 to 5 of the present application has been made for the purpose of solving the above-mentioned conventional problems, and is configured as follows. There is.

(1) Structure of the Invention According to Claim 1 The engine control apparatus according to the invention described in 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. A three-way catalyst for purifying the air-fuel ratio and a target air-fuel ratio of the engine controlled by the air-fuel ratio control means, avoiding the air-fuel ratio region where the NOx production amount in the engine exhaust gas is the largest, depending on the operating state, lean side and rich side. In an engine comprising target air-fuel ratio setting means set in either one of the two sides, torque assist means for increasing the output torque of the engine and the operating state of the torque assist means are set to the target air-fuel ratio setting means. Assist for controlling in synchronization with switching 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 means It is characterized in that provided a control means.

(2) Structure of the Invention According to Claim 2 The engine control device according to the invention of claim 2 is an air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio, and exhaust gas of the engine. A three-way catalyst for purifying the air-fuel ratio and a target air-fuel ratio of the engine controlled by the air-fuel ratio control means, avoiding the air-fuel ratio region where the NOx production amount in the engine exhaust gas is the largest, depending on the operating state, lean side and rich side. Target air-fuel ratio setting means to be set in any one of the regions, torque assisting means to increase the output torque of the engine, and the operating state of the torque assisting means to be set by the target air-fuel ratio setting means. An engine comprising torque assist control means for controlling the air-fuel ratio in synchronization with switching from the lean region to the rich region or from the rich region to the lean region. In the control device, the torque assist control means when the target air-fuel ratio set by the target air-fuel ratio setting means is changed from the lean region to the rich region once the torque assist means O
It is characterized in that it is configured to be turned on again after being turned to FF.

(3) Configuration of the Invention According to Claim 3 The engine control device according to the invention of claim 3 is an air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio, and exhaust gas of the engine. A three-way catalyst for purifying the air-fuel ratio and a target air-fuel ratio of the engine controlled by the air-fuel ratio control means, avoiding the air-fuel ratio region where the NOx production amount in the engine exhaust gas is the largest, depending on the operating state, lean side and rich side. Target air-fuel ratio setting means set in either one of the regions, torque assisting means for increasing the output torque of the engine, and torque assist control means for turning on the torque assisting means at least in the full load area of the engine. In the engine control device comprising: and the torque assist control means, the torque assist means is the target air-fuel ratio setting means. When the set target air-fuel ratio corresponds to the lean region, it is turned on. On the other hand, when the set target air-fuel ratio corresponding to the rich region is set by switching from the lean region. Is characterized in that it is configured to be turned off once and then turned on again in synchronization with the switching from the lean region to the rich region.

(4) Structure of the Invention According to Claim 4 The engine control device according to claim 4 is based on the structure of the invention according to any one of claims 1, 2 and 3 above. In the same configuration, an ignition timing control means is provided, and the ignition timing controlled by the ignition timing control means is an optimum ignition timing capable of obtaining a maximum torque under the operating condition in the target air-fuel ratio switching region. It is characterized in that it is configured to be set.

(5) Structure of the invention according to claim 5 The engine control device according to claim 5 is based on the structure of the invention according to any one of claims 1, 2 and 3 above. In the same configuration, an exhaust gas recirculation means for recirculating exhaust gas to the 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 are provided, and in the target air-fuel ratio switching region. It is characterized in that exhaust gas recirculation control is performed.

[0017]

Since the engine control device of the invention according to each of claims 1 to 5 of the present application is configured as described above,
The following operation is achieved corresponding to each of the configurations.

(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 of the invention, an air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio. , A three-way catalyst for purifying the exhaust gas of the engine and a target air-fuel ratio of the engine controlled by the air-fuel ratio control means are placed in an operating state while avoiding the air-fuel ratio region where the NOx production amount in the engine exhaust gas is the largest. A basic engine air-fuel ratio control system is configured with target air-fuel ratio setting means that is set in either the lean side or the rich side according to the lean burn operation in the widest possible area. Is possible.

With respect to the basic system, the torque assist means for further increasing the output torque of the engine, and the operating state of the torque assist means are set to the target air-fuel ratio set by the target air-fuel ratio setting means. Torque assist control means for controlling in synchronism with switching from the lean region to the rich region or from the rich region to the lean region is provided. For example, in the lean burn operation region, the torque assist means is operated to be turned on to provide sufficient torque. Improve and compensate for the lack of driving performance.

On the other hand, at the time of switching from the lean region to the rich region where the engine output becomes high, the torque assisting means is controlled to, for example, the OFF state, so that the torque improving action of the torque assisting means is eliminated, and the lean state is enriched. The torque does not change suddenly even when the state is changed.

As a result, it is possible to prevent deterioration of the fuel consumption performance without deteriorating the combustibility as in the case of retarding the ignition timing in the preliminarily rich state.

(2) Operation of the engine control device according to the second aspect of the invention: In the engine control device according to the second aspect of the invention, an air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio, , A three-way catalyst for purifying the exhaust gas of the engine and a target air-fuel ratio of the engine controlled by the air-fuel ratio control means are placed in an operating state while avoiding the air-fuel ratio region where the NOx production amount in the engine exhaust gas is the largest. Accordingly, the target air-fuel ratio setting means set within either one of the lean side and the rich side, the torque assisting means for increasing the output torque of the engine, and the operating state of the torque assisting means,
The basic air-fuel ratio of the engine provided with a torque assist control means for controlling the target air-fuel ratio set by the target air-fuel ratio setting means in synchronization with switching from the lean region to the rich region or from the rich region to the lean region. A control system is configured, and the same operation as the invention according to claim 1 is generated by the system.

Further, in the case of the device of the present invention, in addition to the above-mentioned basic structure, the torque assist control means, when the target air-fuel ratio set by the target air-fuel ratio setting means is switched from the lean region to the rich region, Since the torque assist means is turned off once to reduce the torque to some extent, and then turned on again,
The degree of change in torque is reduced, and the output performance after shifting to the rich region is improved.

(3) Operation of the engine control device according to the third aspect of the invention: In the engine control device according to the third aspect of the invention, an air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio. , A three-way catalyst for purifying the exhaust gas of the engine and a target air-fuel ratio of the engine controlled by the air-fuel ratio control means are placed in an operating state while avoiding the air-fuel ratio region where the NOx production amount in the engine exhaust gas is the largest. Accordingly, the target air-fuel ratio setting means to be set within either the lean side or the rich side area, the torque assist means for increasing the output torque of the engine, and the torque assist means are turned on at least in the full load area of the engine. A basic engine air-fuel ratio control system is provided with a torque assist control means for Improving running performance as much as possible to improve sufficiently torque by actuating said torque assist means in.

On the other hand, in the device of the present invention, in addition to that, when the target air-fuel ratio of the engine shifts from the lean state to the rich state, the engine is temporarily turned on in the lean state to increase the torque and then the target air-fuel ratio is increased. The torque is turned off in synchronism with the change to prevent the sudden change of the torque.

As a result, it becomes possible to reliably prevent the torque change without deteriorating the combustibility as in the case of retarding the ignition timing.

(4) Operation of the engine control device according to the fourth aspect of the invention The engine control device according to the fourth aspect of the present invention is based on the basic configuration thereof, and has any one of the above-mentioned first, second and third aspects. In addition to the operation similar to that of the invention described in the item 1, the ignition timing control means is further provided, and the ignition timing controlled by the ignition timing control means is maximum 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 at which the torque can be obtained, the combustibility is good and the output and the fuel consumption are not deteriorated.

(5) Operation of the engine control device according to the fifth aspect of the invention. In the engine control device according to the fifth aspect of the invention, any one of the above-mentioned first, second, and third aspects based on its basic configuration. In addition to the function similar to that of the invention described in Item 1, 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 exhaust gas recirculation state by the exhaust gas recirculation means are further provided. Since the exhaust gas recirculation control is performed in the transition region of the target air-fuel ratio, the torque can be reduced by the exhaust gas recirculation, while the combustibility is good and the fuel consumption is deteriorated. Without
Moreover, the combustion temperature is lowered by the inert gas component and NOx
The reduction effect is also high.

[0029]

Therefore, according to the invention described in each of claims 1 to 5 of the invention of the present application, unlike the prior art, it is possible to prevent the torque fluctuation at the time of lean / rich switching without causing deterioration of fuel consumption. At the same time, the amount of NOx produced can be reduced as much as possible.

[0030]

【Example】

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

First, an outline of the engine air-fuel ratio control system of the embodiment of the present invention will be described with reference to FIG. 2, and thereafter, the outline will be described with reference to the flowchart of FIG. 3 and the characteristic diagrams of FIGS. 4 to 6. The control operation of the unit will be described in detail.

In FIG. 2, reference numeral 1 is an engine body, intake air is sucked from the outside through an air cleaner 30, and then an air flow meter 2 in an intake passage,
It is supplied into each cylinder through 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 according to the measured value Q of the intake air amount of the air flow meter 2. The amount of intake air to the cylinder during normal traveling is determined by the throttle chamber 3
The throttle valve 6 provided in the inside controls the amount. Further, the throttle valve 6 is operated in correspondence with the opening degree of the accelerator pedal.

The throttle chamber 3 is provided with a bypass intake passage 7 that bypasses the throttle valve 6, and the bypass intake passage 7 is provided with intake air for controlling the engine speed during idling. A current control type solenoid valve (ISC valve) 8 serving as a quantity adjusting means is provided. Further, the partition wall 3 is provided downstream of the surge tank 39.
It is divided into two first and second passages 34 and 35 by 2, 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 servo motor 36, and for example, the intake inertia supercharging action is realized by changing the effective sectional area of the intake passage of the engine to improve the 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 equipped with a three-way catalytic converter 11 for exhaust gas purification processing, and the exhaust pipe 10 has an actual air-fuel ratio of the engine based on the oxygen concentration in the exhaust gas. An O ₂ sensor 16 for detecting is provided.

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

Next, reference numeral 37 is a valve timing variable mechanism (VVT) for varying the valve timing of the engine and adjusting the output torque of the engine by changing the phase relationship between the cam shaft and the crank shaft by an electromagnetic actuator. Yes, its operating state is controlled by the engine control unit 9. The variable valve timing mechanism 37 also 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 the exhaust gas having a larger amount of inert gas components than the air in the atmosphere to the intake side to lower the combustion temperature and suppress the generation of NOx. It is also used as a torque reduction system for reducing the torque of the engine in a predetermined region, and its recirculation state is changed by controlling the EGR valve 51 by the engine control unit 9.

The engine control unit 9 has
For example, with a microcomputer (CPU) as a calculation unit as the center, calculation of the fuel injection amount T and its injection control circuit (close / open control circuit), servo motor control circuit of the variable intake valve 33, variable valve timing mechanism 37
Control circuit of EGR valve 51, a timer circuit, various data memories (ROM and RAM), an input / output interface (I / O) circuit, and the like. Then, the interface circuit I of the ECU 9
In addition to the above-mentioned detection signals, for example, 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, for example, a throttle opening detection signal TVO detected by the throttle opening sensor 4, an intake air amount detection signal Q detected by the air flow meter 2, and other various detection signals necessary for determining and controlling the operating state of the engine. Are input respectively.

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 starting the control, step S ₁
, Intake air amount Q, crank angle θ, throttle opening TVO,
Each engine data detection signal such as engine water temperature Tw and O ₂ sensor output Vo ₂ is inputted.

Then, in step S ₂ , it is determined whether or not the current operating region is a lean burn region (a region in which lean burn operation should be performed) leaner than the stoichiometric air-fuel ratio described above.
The determination is made in light of the target air-fuel ratio on the air-fuel ratio control map.

As a result, if YES (lean burn region), the process proceeds to step S ₃ to output Vo _{2 of the} O ₂ sensor 16.
The current actual air-fuel ratio A / F is determined based on
When (in the non-lean burn region, that is, enriched or λ =
Region 1 (see FIG. 8) proceeds to the operation (ON) determination of the above-described first and second torque assist mechanisms (first TAS, second TAS) in steps S ₃₀ and S ₃₁ (described later).

When the current air-fuel ratio A / F is determined in step S ₃ , subsequently, the current engine speed Ne is determined based on the output θ of the crank angle sensor in step S ₄ , and then step S _Go to ₅ and above 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, in step S ₆ , the stoichiometric air-fuel ratio λ = 1 under the current engine speed Ne.
In the next step S ₇ of the engine torque TR (lambda) on computed, the shown in FIG. 5 the two torque TR and (lambda) T in
The difference ΔTR with RL (ΔTR = TR (λ) −TRL) is calculated.

Then, in step S ₈ , the torque difference Δ
It is determined whether TR is greater than or equal to the first determination reference value ΔTR ₂ . The first determination reference value ΔTR ₂ is the first torque assist mechanism (the first torque assist mechanism of the variable intake inertia supercharging system described above.
AS) and a variable valve timing second torque assist mechanism (second TAS) are two sets of torque assist mechanisms that are used at the same time for torque control.

On the other hand, if the result of the determination in step S ₈ is YES, the process proceeds to step S ₉ to see if the actual air-fuel ratio λ of the engine has changed to λ = 1, that is, 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.

On the other hand, as a result of the determination in step S ₉ above, 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 The operation state of (1st, 2nd TAS) is once turned off, and the torque is reduced by a considerable amount to reduce the amount of increase in torque due to A / F enrichment (see FIG. 6). Then steps S ₁₁ and S
_After proceeding to step ₁₂ and sequentially determining the throttle opening TVOA and the engine speed Ne at that time, the judged throttle opening TVO is further determined in step S ₁₃ to determine whether the first torque assist mechanism needs to be turned ON. It is determined whether or not the change has been larger than the first set opening degree TVO ₁ (see FIG. 6).

[0049] 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 A second set opening TV for determining whether or not the second torque assist mechanism should be operated
It is determined whether or not the change is larger than O ₂ (see FIG. 6).

As a result, if YES, the second torque assist mechanism (second TAS) is turned on in step S ₁₆ , and eventually the first and second two sets of torque assist mechanisms (first and second torque assist mechanisms) are turned on.
TAS) improves the engine torque sufficiently to compensate for the torque shortage when the amount of throttle opening change is large, such as during rapid acceleration.

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

Meanwhile, 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 A second determination reference value ΔTR ₁ or more that is close to the first determination reference value ΔTR ₂ but smaller than the ΔTR ₂ for determining whether or not the control by the operation of the torque assist mechanism (first TAS) should be performed. It is determined whether or not (ΔTR ₂ > ΔTR ≧ ΔTR ₁ ). If YES, the process proceeds to step S ₁₈ to see if 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. The 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
If / F has changed to λ = 1 and YES (when switching), proceed to step S ₁₉ and turn ON during lean burn operation during steady state.
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 the throttle opening TVO thus set is larger than a _first set opening TVO ₁ (opening to be turned on) for determining whether or not the first torque assist mechanism is required to be operated.

[0054] 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 Gradually increase the torque when shifting to the operating state to moderate the torque change (see the broken line in FIG. 4).

As a result, it is possible to realize a fuel-efficient operation by lean burn operation in a sufficiently wide range, and also to maintain high output performance by torque assist, and to depress the middle opening accelerator during normal acceleration. The torque shock at the time of switching the air-fuel ratio can be eliminated.

[0056] 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
On the other hand, <TR ₁ ) advances to step S ₂₄ , where it is determined whether or not the actual air-fuel ratio λ of the engine has changed to λ = 1 (whether or not the switching is being performed), as in step S ₁₈ described above. step S ₂₅ to S _29, and the result is NO, the described below as
The torque control operation of is jumped and returned (as unnecessary).

On the other hand, as a 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
The torque assist mechanism (2nd TAS) of
To reduce the predetermined amount of torque, then 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 Setting opening of TVO
₂ Determine if it is larger than (opening to be turned on).

As a result, if YES, the second torque assist mechanism (second TAS) is turned on in step S ₂₉ , and the second torque assist mechanism is turned on.
The torque assist mechanism (2nd TAS) improves the torque by a predetermined amount, and gradually approaches the original required torque amount.

As a result, it is possible to realize a fuel-efficient operation by lean burn operation in a sufficiently wide area, and also to maintain high output performance by torque assist, which accompanies depression of a low opening accelerator such as during slow acceleration. It is also possible to eliminate torque fluctuations when switching the air-fuel ratio.

On the other hand, in contrast to the above control of the first and second torque assist mechanisms in the lean burn operation region, when the non-lean burn operation region (rich region) is determined to be NO in step S ₂ above, first. as also mentioned, firstly the in step S ₃₀ the first torque assist mechanism (first 1TAS)
ON / OFF state of the second torque assist mechanism (second TAS) is further turned on in the subsequent step S _31.
The states are sequentially determined to determine the first and second torque assist mechanisms.
When both (1st and 2nd TAS) are ON, the throttle opening TVO and engine speed N at that time are further
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, in the case of NO, the second torque assist mechanism (second TAS) is seen 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 It is also determined whether or not the torque is larger than the first set opening TVO ₁ for determining whether or not the torque assist mechanism needs to be operated.

As a result, if NO, it is determined that the operation of the first torque assist mechanism (first TAS) is not necessary, and the first torque assist mechanism (first TAS) is also turned off in step S ₃₅ .
The first and second sets of torque assist mechanism as FF
The torque assist action by the (first and second TAS) 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, as a result of the above determination, when the A / F has changed to the λ = 1 region and the air-fuel ratio has changed to YES, the routine proceeds to step S ₃₇ , where the first and second torque assist mechanisms (first and second torque assist mechanisms). 2TAS) is turned on at the same time, and a sufficient torque assist mechanism is exhibited to improve engine torque.

In the above construction, two sets of torque assist mechanisms, that is, the first torque assist mechanism of the variable intake system (first TAS) and the second torque assist mechanism of the variable valve timing system (second TAS) are used. However, in the case of an engine having a relatively small output torque, the first torque fluctuation alone is sufficient,
There is no need to calculate and properly use the torque difference ΔTR as described above, and as shown in FIG. 7, for example, as shown in FIG.
The output torque in the lean region is improved by setting the ON region of the torque assist mechanism in the low rotation region of 3000 rpm or less.

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

As a result, the output torque of the engine, for example, as shown by the broken line in FIG. 7, draws the same smooth torque characteristic as in the above case, and the torque fluctuation when the air-fuel ratio is switched from lean to rich side. 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 the variable resonance supercharging system. It can be applied similarly.

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

Recently, by recirculating a part of the exhaust gas containing an inert gas component to the intake side of the engine, the combustion speed is slowed to reduce the NOx emission amount (EGR
Control) is generally used, but the fact that the combustion speed becomes slower means that the output (torque) of the engine also decreases. Therefore, by using the EGR control, the same as in the first embodiment. It is possible to configure a torque reduction control system that responds to changes in the air-fuel ratio. In this example,
It was invented from such a viewpoint.

That is, in the engine control system of this embodiment, instead of the conventional general air-fuel ratio control region map shown in FIG. 14, for example, as shown in FIG. 10, the air-fuel ratio control of the rich side theoretical air-fuel ratio λ = 1 is performed. In the lean side of the area, "(λ =
1) + EGR control ”region is set, and the original 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 equal to or higher than the stoichiometric air-fuel ratio. After that, by making the transition to the λ = 1 region, for example, as shown in FIG. 12, a torque fluctuation reducing action is realized as in the first embodiment.

In this case, the supplied EGR amount (exhaust gas recirculation amount to the intake side) is set to, for example, the throttle opening (TV
If it is changed according to (O), the drivability is further improved.

The EGR supply amount is, for example, as shown in FIG.
As shown in, the EGR control region is finely divided according to the torque value of the engine, and the EGR supply amount (EGR
(Rate =%) may be set and placed on the map.

Further, as in the case of 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 EGR supply amount may be increased as is larger.

According to the structure of the embodiment, there is an advantage that the NOx reducing action is enhanced at the same time as the torque fluctuation is prevented.

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

[Brief description of drawings]

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

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

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

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

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

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

FIG. 7 is a 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 in place of the engine speed. FIG.

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

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

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

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

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

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

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

[Explanation of symbols]

1 is an engine body, 6 is a throttle valve, 9 is an engine control unit, 10 is an exhaust pipe, 11 is a three-way catalytic converter, 16 is an O ₂ sensor, 32 is a partition wall, 33 is a variable intake valve, and 34 is a first passage. , 35 is the second passage, 3
6 is a servo motor, 37 is a variable valve timing mechanism,
Reference numeral 50 is an EGR passage, and 51 is an EGR valve.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location F02D 43/00 B 7536-3G N 7536-3G R 7536-3G 45/00 301 G 7536-3G F02M 25/07 550 R F02P 5/15 B G (72) Inventor Junichi Taga 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Mazda Motor Corporation

Claims (5)

[Claims] 1. An air-fuel ratio control means for controlling an engine air-fuel ratio to a predetermined target air-fuel ratio, a three-way catalyst for purifying engine exhaust gas, and a target air-fuel ratio for an engine controlled by the air-fuel ratio control means. Is the N in the engine exhaust gas
In an engine including target air-fuel ratio setting means for avoiding the air-fuel ratio region where the maximum amount of Ox generation is maximum and setting it in either one of the lean side and the rich side region depending on the operating state, the output torque of the engine is set. The torque assist means to be increased and the operating state of the torque assist means are controlled in synchronization 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 a torque assist control means for controlling the engine. 2. An air-fuel ratio control means for controlling the air-fuel ratio of the 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. Is the N in the engine exhaust gas
Target air-fuel ratio setting means for avoiding the air-fuel ratio area where the maximum amount of Ox is generated and setting it in either the lean side or the rich side area according to the operating state, and torque assist means for increasing the output torque of the engine. A torque assist control means for controlling the operating state of the torque assist means in synchronism 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. In the engine control device comprising:
An engine characterized in that when the target air-fuel ratio set by the target air-fuel ratio setting means is switched from the lean region to the rich region, the torque assist means is turned off once and then turned on again. Control device. 3. An air-fuel ratio control means for controlling the air-fuel ratio of the engine to a predetermined target air-fuel ratio, a three-way catalyst for purifying engine exhaust gas, and a target air-fuel ratio of the engine controlled by the air-fuel ratio control means. Is the N in the engine exhaust gas
Target air-fuel ratio setting means for avoiding the air-fuel ratio area where the maximum amount of Ox is generated and setting it in either one of the lean side and rich side areas according to the operating state, and torque assist means for increasing the output torque of the engine. A torque assist control means for turning on the torque assist means at least in a full load region of the engine, wherein the torque assist control means comprises:
The torque assist means is turned ON when the target air-fuel ratio set by the target air-fuel ratio setting means corresponds to the lean region, while the target air-fuel ratio set corresponding to the rich region is set to ON. An engine control device characterized in that when it is due to switching from the lean region, it is turned off once and then turned on again in synchronization with the switching from the lean region to the rich region. 4. The ignition timing control means is provided, and the ignition timing controlled by the ignition timing control means is an optimum ignition timing capable of obtaining a maximum torque under the operating condition in the target air-fuel ratio switching region. The configuration according to any one of claims 1, 2 and 3, characterized in that it is configured to be set.
The engine control device according to the paragraph. 5. 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 exhaust gas by the exhaust gas recirculation means are provided in the target air-fuel ratio switching region. Exhaust gas recirculation control is carried out.
The engine control device according to claim 1.