JPH07217472A - Control device for internal combustion engine having automatic transmission - Google Patents

Abstract

PURPOSE:To reduce the increase in the fluctuation of driving torque by prohibiting operation at a rich fuel-air ratio for regenerating an NOx absorbent during the power-on down shift operation of an automatic transmission. CONSTITUTION:An NOx absorbent 18 is laid in an engine exhaust passage 17 and an engine is normally operated at a lean air-fuel ratio, thereby causing the absorbent 18 to absorb NOx contained in exhaust gas. Also, an engine air- fuel ratio is selected at the rich side, when an NOx absorption amount increases, thereby regenerating the absorbent 18. In addition, an electronic control circuit 30 for controlling the engine is provided to prohibit the re-start of operation at a rich air-fuel ratio for regenerating the absorbent 18 over the preset time from the synchronization of the the rotation of transmission input and output shafts during the power-on down shift operation of an automatic transmission. Also, constitution is so made that the operation, if already under way at a rich air-fuel ratio, is stopped.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION This invention relates to a control apparatus for an internal combustion engine with an automatic transmission, air-fuel ratio of the exhaust gas flowing in detail absorbs NO _X in the exhaust gas when the lean, reduced exhaust oxygen concentration a control device for an internal combustion engine with an automatic transmission having an exhaust gas purification apparatus using the _the NO _X absorbent to release the absorbed NO _X when.

[0002]

2. Description of the Related Art NO of this kind_XInternal combustion engine using absorbent
As an exhaust gas purifying apparatus for the above, an international publication WO93-7
There is one described in No. 363. Exhaust gas purification device
Then, when the air-fuel ratio of the inflowing exhaust gas is lean,
NO_XIs absorbed, and the oxygen concentration in the inflowing exhaust gas has decreased.
NO absorbed at times_XReleases NO_XInternal combustion engine with absorbent
Located in the exhaust passage of the Seki
Driving in the above NO_XNO in exhaust gas to absorbent_XAbsorbed
Let Also, lean air-fuel ratio operation continues and NO_XAbsorption of absorbent
NO collected_XIf the amount exceeds the specified value,
The operating air-fuel ratio is changed from short-time lean air-fuel ratio to rich or theoretical air-fuel ratio.
The oxygen ratio in the exhaust gas is reduced by switching to the fuel ratio, and NO_X
NO absorbed from the absorbent_XAnd release this
NO issued_XDue to the components such as unburned HC and CO in the exhaust
(In the present specification, the above N
O_XNO from absorbent_XRelease, reduction and purification operations
"NO _XIt is called "regeneration operation of absorbent").

In the above device, the N absorbed by the NO _x absorbent is absorbed.
When O _X amount is somewhat increased, by switching the engine operating air-fuel ratio in a short time a rich air-fuel ratio from the lean air-fuel ratio NO
By reproducing the _X absorbent, NO in _the NO _X absorbent
By recovering the _X absorption capacity, the exhaust purification capacity of the NO _X absorbent is constantly maintained high. However, when applying the exhaust gas purifying device as described in the WO WO93-7363 the internal combustion engine with an automatic transmission, the rich for the automatic transmission of the transmission timing and _the NO _X absorbent regeneration Problems may occur due to the relationship with the timing of air-fuel ratio operation.

That is, in the above device, when the air-fuel ratio is switched from the lean air-fuel ratio to the rich air-fuel ratio for regeneration of the NO _x absorbent, the output torque of the engine increases with the enrichment of the air-fuel ratio. In addition, the regeneration operation of the NO _x absorbent is N
When the amount of NO _X absorbed by the O _X absorbent exceeds a predetermined value, it is executed regardless of whether or not the shift operation of the automatic transmission is performed. Therefore, the shift operation of the automatic transmission and the regeneration of the NO _X absorbent are performed. There is a case where the air-fuel ratio switching to the rich air-fuel ratio for is performed at the same time.

Since a driving torque fluctuation due to a gear shift occurs during a gear shifting operation of the automatic transmission, if the switching to the rich air-fuel ratio for regeneration of the NO _X absorbent and the gear shifting operation are simultaneously performed as described above, the rich air-fuel ratio is changed. In some cases, an increase in engine output torque due to switching to the fuel ratio and a driving torque fluctuation due to a gear shift operation may overlap with each other, resulting in an increase in driving torque fluctuation and deterioration of drivability (so-called riding comfort).

By the way, although it is not intended to increase the engine output torque by switching from the lean air-fuel ratio to the rich air-fuel ratio for the regeneration operation of the NO _x absorbent, it is disclosed in Japanese Patent Laid-Open No. 4-76216. In an internal combustion engine with an automatic transmission in which an intake control valve (swirl control valve) is provided in an intake passage, there is disclosed a control device that prohibits the opening / closing operation of the intake control valve during shifting of the automatic transmission. In an engine equipped with an intake control valve, the engine output torque increases when the intake control valve is opened, and the engine output torque decreases when the intake control valve is closed. Therefore, if the intake control valve is opened / closed during the shift operation of the automatic transmission, the engine output torque fluctuation caused by the opening / closing of the intake control valve and the torque fluctuation caused by the shift operation of the automatic transmission are overlapped with each other, thereby improving drivability. Getting worse. The engine of the above publication prevents the overlap of the torque fluctuations and prevents the deterioration of drivability by prohibiting the opening / closing operation of the intake control valve during the shift of the automatic transmission. .

[0007]

However, the above-mentioned NO
_In order to solve the problem of torque fluctuation due to the overlap of the rich air-fuel ratio operation for regeneration of the _X absorbent and the shift operation of the automatic transmission, as in the device of the above-mentioned JP-A-4-76216, simply automatic A problem may occur if only the air-fuel ratio switching operation between the lean air-fuel ratio operation and the rich air-fuel ratio operation is prohibited during the gear shift operation of the transmission. That is, if the switching to the rich air-fuel ratio is prohibited during the gear shift operation, if the rich air-fuel ratio operation for regeneration of the NO _X absorbent is started before the gear shift operation is started, the rich operation is started even if the gear shift operation is started. Since the air-fuel ratio operation is not stopped, the gear shift operation is performed while the engine output torque is increased by the rich air-fuel ratio operation.

Consider, for example, a case where the power-on downshift of the automatic transmission is performed while the rich air-fuel ratio operation for regenerating the NO _X absorbent is being performed. Here, the power-on downshift refers to a downshift operation of the transmission in the state where a positive torque is transmitted from the engine side to the transmission side. Before the shift down operation is started, the transmission input shaft rotates at a low rotation speed according to the gear ratio on the high speed side.However, this transmission input shaft rotation speed increases as the engine speed increases during the shift down operation. At the time when the gear shifts up and the shift down operation is completed, the rotation speed becomes equal to the rotation speed obtained by multiplying the transmission output shaft rotation speed by the gear ratio on the low speed stage side (that is, the transmission input / output shaft rotation speed is synchronized). Further, since the power-on downshift is executed with the accelerator pedal depressed, the engine output torque also increases after the downshift operation is completed.

As will be described later, the transmission output shaft torque (driving torque) at this time is once reduced after the start of the downshift operation, and then is rapidly increased when the rotation speed of the transmission input / output shaft is synchronized, and this drive is performed. After some fluctuation due to vibration of the drive system due to a rapid increase in torque, the output torque converges to a value obtained by multiplying the engine output torque by the low gear ratio (see FIG. 7). However, when the engine rich air-fuel ratio operation for _the NO _X absorbent regeneration when synchronizing the transmission input shaft speed is implemented, further rich spikes in the driving torque by the transmission input shaft speed synchronization Since the increase of the engine output due to the air-fuel ratio is added, the fluctuation of the driving torque becomes large, and the time until the driving torque converges after the downshift increases, which causes a problem that the drivability deteriorates.

The present invention, when the power-on downshift, the _the NO _X absorbent to prevent an increase in driving torque fluctuation due to the rich air-fuel ratio operation performed for reproduction, automatic capable to keep the drivability better shift It is intended to provide a control device for an engine equipped with an engine.

[0011]

According to the Summary of the Invention The present invention as set forth in claim 1, in which is disposed in an exhaust passage of an internal combustion engine, the air-fuel ratio of the exhaust gas absorbs NO _X in the exhaust gas when the lean exhaust Which releases the absorbed NO _x when the oxygen concentration in the
And O _X absorbent to control the air-fuel ratio of the internal combustion engine, by switching to the rich air-fuel ratio from the lean air-fuel ratio of the internal combustion engine under a predetermined condition, the NO _X absorbed from the _the NO _X absorbent In a control device for an internal combustion engine with an automatic transmission, which comprises an air-fuel ratio switching means for releasing and an automatic transmission connected to the internal combustion engine, rotation synchronization during power-on downshift operation of the automatic transmission is detected. During the predetermined time from the time when the rotation synchronization is detected and the rotation synchronization is detected, the switching of the engine to the rich air-fuel ratio by the air-fuel ratio switching means is prohibited and the rich air-fuel ratio operation already started is stopped. There is provided a control device for an internal combustion engine with an automatic transmission, characterized by comprising prohibiting means.

Further, according to the invention described in claim 2,
The control device for an internal combustion engine with an automatic transmission according to claim 1, further comprising: estimating means for estimating the NO _X amount absorbed by the NO _X absorbent, and start of a power-on downshift operation of the automatic transmission. When the NO _x absorption amount estimated by the estimating means when the power-on downshift operation start is detected is greater than or equal to a predetermined value, from the power-on downshift operation start to the rotation synchronization. In the meantime, a control means for performing the rich air-fuel ratio operation by the air-fuel ratio switching means may be provided.

According to the present invention as defined in claim 3,
The air-fuel ratio of the exhaust gas placed in the exhaust passage of the internal combustion engine is
NO in the exhaust when_XOxygen concentration in exhaust gas
NO absorbed when_XReleases NO_Xabsorption
Agent and the NO_XNO absorbed by the absorbent_XEstimate quantity
Estimating means for controlling the air-fuel ratio of the internal combustion engine,
Change the air-fuel ratio of Seki from lean air-fuel ratio to rich air-fuel ratio
Therefore, the NO _XNO absorbed from the absorbent_XLet go
The air-fuel ratio switching means to be output and the lean air-fuel ratio
The engine output torque after switching before switching
Torque reduction means to reduce the engine output torque of
Automatic transmission with an automatic transmission connected to the internal combustion engine
In a control device for an internal combustion engine with an engine, a part of the automatic transmission is
Synchronization to detect rotation synchronization during work-on downshift operation
The detection means and the estimation hand when the rotation synchronization is detected.
NO estimated by Dan_XIf the absorption amount is greater than
The engine is constituted by the torque reducing means and the air-fuel ratio switching means.
Lean-to-rich air-fuel ratio cutoff with reduced output torque
Automatic shifting, characterized by comprising:
A control device for an internal combustion engine with an engine is provided.

[0014]

According to the first aspect of the present invention, the inhibiting means is the NO _x by the air-fuel ratio switching means for a predetermined time from the time when the rotation synchronization of the transmission input / output shaft is detected during the power-on downshift operation. The start of the rich air-fuel ratio operation for regeneration of the absorbent is prohibited, and when the rich air-fuel ratio operation has already started, the rich air-fuel ratio operation is stopped.
Therefore, the rich air-fuel ratio operation for NO _X absorbent regeneration is not performed during the period in which the drive torque fluctuation occurs after the rotation synchronization during the power-on downshift operation, and the engine output torque increases due to the rich air-fuel ratio operation. Is not added to the driving torque fluctuation, and the increase of the driving torque fluctuation width and the fluctuation convergence time are prevented.

Furthermore, in the present invention as set forth in claim 2, and estimating means for estimating the NO _X absorption of _the NO _X absorbent in addition to claim 1, and detecting means for detecting a start power-on downshift operation When the estimated NO _x absorption amount is provided and is equal to or more than a predetermined value, switching to the rich air-fuel ratio for regeneration of the NO _x absorbent after the start of the power-on downshift operation is detected and before the rotation is synchronized. Is executed. The time from the start of the downshift operation to the completion of downshift (synchronization of the transmission input / output shaft rotation) is determined by the time required for the engine speed to rise to a high speed corresponding to the low gear ratio after the gear shift. However, by executing the rich air-fuel ratio operation for NO _X absorbent regeneration during the period from the start of the downshift operation to the rotation synchronization as described above, the engine output torque during this period increases and the engine speed The time required for climbing is shortened. Therefore, the time required for the shift-down operation is shortened while the NO _X absorbent is being regenerated.

In the present invention according to claim 3, NO
_X absorbent to reduce the engine output torque when performing the switching to the rich air-fuel ratio for playback, from the engine output torque of the lean air-fuel ratio during the operation of the before switching the engine output torque of the rich air-fuel ratio during operation after switching is provided with a torque reduction means to reduce, when the rotation synchronization of the power-on downshift operation is detected when NO _X absorption amount of the NO _X absorbent is higher than a predetermined value, the engine according to the torque reduction means The NO _x absorbent is regenerated by switching to the rich air-fuel ratio accompanied by the output reduction. Since the engine output torque after switching the air-fuel ratio is reduced by the torque reduction means, the increase in drive torque during rotation synchronization is suppressed to a small level even during power-on downshift, and the drive torque fluctuation range and fluctuation convergence during rotation synchronization are suppressed. Time becomes smaller. Thus, the relaxation of the drive torque fluctuation of the power-on downshift operation, and regeneration of _the NO _X absorbent is achieved at the same time.

[0017]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an overall view of an internal combustion engine with an automatic transmission to which the present invention is applied. In FIG. 1, reference numeral 1 is an internal combustion engine such as a gasoline engine that performs lean air-fuel combustion, and 3 is an engine 1.
Of the engine, 6 is an intake port of the engine, and 8 is an exhaust port. Each intake port 6 is connected to a surge tank 10 via an intake branch pipe 9, and a fuel injection valve 11 for injecting fuel into each intake port 6 is arranged in each branch pipe 9.

Further, the surge tank 10 is connected to an air cleaner 13 through an intake passage 12, and a throttle valve 14 having an opening corresponding to an operation of an accelerator pedal (not shown) by a driver is provided in the intake passage 12. It is arranged. Also,
The surge tank 10 is provided with an intake pressure sensor 15 that generates an output voltage proportional to the absolute pressure in the surge tank 10.

On the other hand, the exhaust port 8 of the engine 1 is connected to an exhaust passage 17 via an exhaust manifold 16, and the exhaust passage 17 is connected to a casing 19 containing a NO _x absorbent 18 described later. Further, reference numeral 40 in FIG. 1 denotes an automatic transmission connected to an output shaft (not shown) of the engine 1. The automatic transmission 40 includes a torque converter 41.
And a transmission 42, and the output shaft of the transmission 42 is connected to the drive wheels of the vehicle via a differential gear (not shown).

The transmission 42 is of a known type including a planetary gear train and a friction element, and the engagement state of the friction element (brake, clutch, etc.) is switched by switching the control hydraulic pressure to change the planetary gear train. A gear shift operation is performed by fixing and connecting each element. The torque converter 41 is of a known type including a pump directly connected to the engine output shaft and a turbine driven by the pump discharge fluid, and the turbine output shaft (hereinafter referred to as the converter output shaft) of the transmission 42. It is directly connected to the input shaft. The torque converter 41 has a known torque amplification action of amplifying the torque input from the engine output shaft and outputting it to the converter output shaft. The automatic transmission 40 includes a converter output shaft rotation speed sensor 22, which outputs a pulse signal having a frequency corresponding to the rotation speed of the converter output shaft (that is, the transmission 42 input shaft rotation speed), and the transmission 42.
The transmission output shaft speed sensor 23 that outputs a pulse signal having a frequency corresponding to the output shaft speed is provided.

Reference numeral 30 in FIG. 1 is an electronic control circuit of the engine 1. The electronic control circuit 30 includes a ROM (read only memory) 32, a RAM (random access memory) 3
3, CPU (microprocessor) 34, input port 3
5. A digital computer having a known structure in which the output ports 36 are connected to each other by the bidirectional bus 31.
In addition to performing basic control such as fuel injection amount control and ignition timing control of the engine 1, in this embodiment, an air-fuel ratio switching means for switching the engine operating air-fuel ratio to a rich air-fuel ratio for regeneration of the NO _X absorbent 18, power-on. It plays the role of each means described in the claims such as a synchronization detecting means for detecting the rotation input / output shaft rotation synchronization during the downshift operation, a prohibiting means for prohibiting the switching to the rich air-fuel ratio by the air-fuel ratio switching means, and the like. .

For the above purpose, the input port 35 of the control circuit 30 has a voltage signal from the intake pressure sensor 15 according to the intake pressure, a voltage signal from the throttle opening sensor 20 indicating the opening of the throttle valve 14, and , The voltage signals representing the vehicle traveling speed from the vehicle speed sensor 24 are respectively converted by the AD converter 37.
In addition to being input via the engine, a pulse signal representing the engine speed from an engine speed sensor 21 provided in a distributor (not shown) of the engine, the converter output shaft speed sensor 22 and the transmission output described above. Shaft speed sensor 23
The pulse signals from and are input respectively.

On the other hand, the output port 36 of the control circuit 30 is
The fuel injection valve 11 is driven through the corresponding drive circuit 38.
And the ignition plug 4 to control the fuel injection from the fuel injection valve 11 and the ignition timing of the engine, as well as to the control valve of the automatic transmission 40 to control the shift of the automatic transmission. There is. NO _X absorbent 1 contained in casing 19
Reference numeral 8 is a carrier such as alumina, on which potassium K, sodium Na, lithium Li, cesium Cs, alkali metals such as barium Ba, calcium Ca, lanthanum La, yttrium. At least one selected from rare earths such as Y and a noble metal such as platinum Pt are supported. This _the NO _X absorbent 18 absorbs NO _X in the case the air-fuel ratio of the exhaust gas flowing is lean, the oxygen concentration is carried out to absorbing and releasing action of the NO _X that releases NO _X when lowered.

The above-mentioned exhaust air-fuel ratio means here N
It means the ratio of the total amount of air and the total amount of fuel supplied to the exhaust passage on the upstream side of the O _X absorbent 18, the engine combustion chamber, the intake passage, and the like. Therefore, NO _X absorbent 1
When fuel or air is not supplied to the upstream exhaust passage 8 of No. 8, the exhaust air-fuel ratio becomes equal to the air-fuel ratio of the engine (air-fuel ratio in combustion in the engine combustion chamber).

In this embodiment, since an engine that burns lean air-fuel ratio is used, the exhaust air-fuel ratio during normal operation is lean, and the NO _X absorbent 18 absorbs NO _{X in} the exhaust gas. Further, when the air-fuel ratio of the engine is switched from the lean air-fuel ratio to the rich or stoichiometric air-fuel ratio and the oxygen concentration in the exhaust gas decreases, the NO _X absorbent 18 releases the absorbed NO _X.

There is a part where the detailed mechanism of this absorption and release action is not clear. However, it is considered that this absorbing / releasing action is performed by the mechanism shown in FIG. Next, regarding this mechanism, platinum P on the carrier
A case of supporting t and barium Ba will be described as an example, but other precious metals, alkali metals, alkaline earth metals,
The same mechanism can be achieved by using rare earths.

That is, the inflow exhaust becomes considerably lean.
And the oxygen concentration in the exhaust gas increased significantly, as shown in Fig. 2 (A).
As these oxygen O₂Is O₂ ^-Or O^2-In the form of
It adheres to the surface of platinum Pt. On the other hand, the NO in the exhaust gas is
This O on the surface of platinum Pt₂ ^-Or O^2-Reacts with N
O₂Becomes (2NO + O₂→ 2 NO₂ ). Then generated
NO₂Part of the inside of the absorbent while being oxidized on platinum Pt
While being absorbed by and bound to barium oxide BaO,
As shown in (A), nitrate ion NO₃ ^-Absorbent in the form of
Diffuse in. NO in this way_XIs NO_XAbsorbent 1
Absorbed in 8.

Therefore, NO ₂ is produced on the surface of platinum Pt as long as the oxygen concentration in the inflowing exhaust gas is high, and NO ₂ is absorbed in the absorbent as long as the NO _X absorption capacity of the absorbent is not saturated, and nitrate ion NO ₃ ^- is generated. Organization 1
When the air-fuel ratio of is switched to rich or stoichiometric air-fuel ratio,
The oxygen concentration in the inflowing exhaust gas decreases and the amount of NO ₂ produced decreases. Thus the reaction is reverse (NO ₃ ^- → NO ₂₎ proceeds, the nitrate ions NO in absorbent ₃ ^- are released from the absorbent in the form of NO _2. On the other hand, unburned HC, C
When components such as O are present, these components react with oxygen O ₂ ⁻ or O ²⁻ on the platinum Pt to be oxidized and consume oxygen on the platinum Pt. Further, NO ₂ released from the NO _x absorbent 18 is reduced by reacting with HC and CO as shown in FIG. 2 (B). In this way, NO is formed on the surface of platinum Pt.
_{When 2} is absent, the absorbent releases NO _{2 one} after another.

That is, HC and CO in the inflowing exhaust gas are first reacted with O ₂ ⁻ or O ²⁻ on platinum Pt immediately to be oxidized, and then O ₂ ⁻ or O ²⁻ on platinum Pt are consumed. If HC and CO still remain, the NO _X released from the absorbent by the HC and CO and the NO _X that flows in with the exhaust gas are reduced. In this embodiment, during normal lean-burn operation using the above together to absorb NO _X in the exhaust gas in the NO _X absorbent, short engine air when the absorbed amount of NO _X in _the NO _X absorbent is increased by switching the ratio to the rich or the stoichiometric air-fuel ratio is performed and reduction purification and release of the NO _X from _the NO _X absorbent. That is,
When the engine air-fuel ratio is switched to the rich or stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas sharply decreases, and the amounts of unburned HC and CO discharged from the engine greatly increase.
Therefore, by switching the engine air-fuel ratio to the rich or stoichiometric air-fuel ratio, the oxygen concentration in the exhaust gas is reduced and the amount of unburned HC and CO is increased, so that N
The regeneration of the _Ox absorbent 18 will be performed.

Next, the air-fuel ratio control of the engine of this embodiment will be described. In this embodiment, the above-mentioned International Publication WO No. WO is used.
Air-fuel ratio control similar to that of No. 93-7363 is performed. The air-fuel ratio control will be briefly described below. In the present embodiment, the fuel injection amount from the fuel injection valve 11, that is, the valve opening time (fuel injection time) T of the fuel injection valve 11 at the time of fuel injection
The AU is controlled by the control circuit 30, for example, TAU = TP × K
Is calculated as

Here, TP represents the fuel injection time required to bring the air-fuel ratio of the air-fuel mixture supplied into the engine combustion chamber to the stoichiometric air-fuel ratio, that is, the basic fuel injection time, which is detected by the intake pressure sensor 15. As a function of the absolute pressure PM in the surge tank 10 and the engine speed N obtained, it is obtained in advance by experiments or the like and stored in the ROM 32 of the control circuit 30 in the form of a numerical table as shown in FIG.

Further, K is a correction coefficient for controlling the engine air-fuel ratio, and when K = 1.0 is set, the engine air-fuel ratio becomes the stoichiometric air-fuel ratio. Further, if K> 1.0, the engine air-fuel ratio becomes smaller than the theoretical air-fuel ratio (that is, rich air-fuel ratio), and if K <1.0, the engine air-fuel ratio becomes larger than the theoretical air-fuel ratio (that is, lean air-fuel ratio). Becomes the fuel ratio). The value of the correction coefficient K is given as a function of the absolute pressure PM in the surge tank 10 and the engine speed N, for example, in the form shown in FIG. That is, as shown in FIG. 4, in the present embodiment, a region where the PM is relatively low (engine low / medium load operation region)
Then, the correction coefficient K is set to be smaller than 1.0, and the engine is operated at a lean air-fuel ratio. Further, in a region where PM is relatively high (engine high load operating region), the value of the correction coefficient K is 1.0, and the engine is operated at the stoichiometric air-fuel ratio. In addition, PM
In a high range (engine full load operation range), the value of the correction coefficient K is set to be larger than 1.0, and the engine is operated at the rich air-fuel ratio. In a vehicle engine or the like, a low-to-medium-load operation is usually most frequently performed, so these engines are operated at a lean air-fuel ratio for most of the period during operation.

[0033] As described above, NO NO _X absorbent engine absorbs NO _X in the exhaust gas when being operated at a lean air-fuel ratio, the engine is absorbed when being operated at a rich or stoichiometric air-fuel ratio _X To release. Therefore, if the operation of the rich or the stoichiometric air-fuel ratio is appropriately performed, NO _X absorption of the NO _X absorbent is not increased beyond a certain level, it is not necessary to perform special reproduction operation. However, when the engine operating conditions which may operated at a lean air-fuel ratio such that long-lasting, NO _X absorption of the NO _X absorbent increases,
There is a risk that the NO _x absorption capacity will be saturated.

[0034] Therefore, the electronic control circuit 30 in the present embodiment estimates the amount of NO _{X the} NO _X absorbent 18 is absorbed, when the estimated NO _X absorption amount becomes a predetermined amount or more, though the area of FIG. 4 not, short (e.g., time of about 0.5 to 1 second) driving the forcibly set to the engine a value of the correction coefficient K to 1.0 or rich or stoichiometric air-fuel ratio, of the NO _X absorbent NO _X absorbing capacity of the NO _X absorbent by performing reproduction operation is prevented from saturating.

[0035] Next, an embodiment of the estimation method of the NO _X absorption of the _the NO _X absorbent. Electronic control circuit 30 in this embodiment, in accordance with the engine operating state at predetermined time intervals, addition of the absorption amount counter representing the NO _X absorption of _the NO _X absorbent 18, by performing the subtraction, the absorption counter It estimates the NO _X absorption of the NO _X absorbent 18 from the value. That is, _the NO _X absorbent 18 when the engine is operated at a lean air-fuel ratio carried out absorption of the NO _X in the exhaust gas, NO _X absorption of the NO _X absorbent 18 increases. At this time, the NO absorbed by the NO _X absorbent 18 per unit time
_The amount of _X is considered to be proportional to the amount of NO _X emitted from the engine per unit time. On the other hand, the amount of NO _X discharged from the engine per unit time is determined by the engine load condition, and increases as the engine load (engine intake pressure) increases and the engine speed increases, for example. Therefore, in this embodiment, the NO _X emission amount of the engine is obtained as a function of the engine load and the engine speed in advance by actual measurement, and a value obtained by multiplying the NO _X emission amount by a constant coefficient is used as the NO _X absorbent per unit time. as of the NO _X absorption, it is stored in the form of a numerical table of the same format as FIG. 3 in ROM32 of the electronic control circuit 30. When the engine is operated with a lean air-fuel ratio, the electronic control circuit 30 calculates the NO _X absorption amount per unit time from the engine load (intake pressure) and the engine speed at regular time intervals using the above numerical table. Then, the value is added to the value of the NO _x absorption amount counter described above.

Further, when the engine is operating at the rich or stoichiometric air-fuel ratio, the NO _x absorbent 18 absorbs the absorbed N.
To release O _X, NO _X absorption of the NO _X absorbent 18 is reduced. Therefore, in the present embodiment, the electronic control circuit 30
When the engine is operated in a rich or stoichiometric air-fuel ratio, performs an operation of subtracting the constant value corresponding to the NO _X release amount per unit from the value of the NO _X absorption counter time at predetermined time intervals.

As a result, the above NO_XAbsorption amount counter
Is always NO_XAbsorbent 18 NO _XCorresponding to the amount absorbed
Since it becomes a value, NO_XNo from the value of the absorption counter_XSucking
NO of collecting agent 18_XIt is possible to estimate the absorption amount.
FIG. 5 is executed by the electronic control circuit 30 at regular intervals.
NO above_XThe flow chart of the absorption estimation routine is shown.
You

When the routine starts in FIG. 5,
In step 501, the engine intake pressure PM and the engine speed N are input from the intake pressure sensor 15 and the engine speed sensor 21, respectively. In step 503, the current lean air-fuel ratio operation is performed based on the value of the air-fuel ratio correction coefficient K described above. It is determined whether or not it is being performed. When the lean air-fuel ratio operation is currently being performed (when K <1.0) in step 503, the process proceeds to step 505, and a numerical value table stored in the ROM 32 using the intake pressure PM and the engine speed N. From this, the NO _X absorption amount α of the NO _X absorbent per unit time is calculated. Next, at step 507, the NO _X absorption amount counter C
The absorption amount α is added to the value of.

If the rich or stoichiometric air-fuel ratio operation is currently being performed (K ≧ 1.0) at step 503, the routine proceeds to step 509, where the value of the NO _X absorption amount counter C per unit time is changed. The constant value β corresponding to the NO _X release amount is subtracted. In this embodiment, the NO _x release amount β from the NO _x absorbent per unit time is a constant value, but the engine air-fuel ratio (K) and the engine load state (PM, N)
The value of β may be changed according to

Then, after the above steps are completed, step 5
No. 11 above_XThe value of the absorption counter C is the predetermined value C₀
It is determined whether or not the above, C <C₀In case of
End the routine. Also, C ≧ C₀If
Proceed to step 513, NO_XAbsorbent regeneration operation start flag
F is set (= 1). Where C₀The value of
NO_XMaximum NO that can be absorbed by the absorbent 18_XQuantity of 70
Is set to a value equivalent to_XSucking
NO of collecting agent_XWhen the absorption amount exceeds this value, the flag F
When executed, it is executed by the electronic control circuit 30 separately.
In the fuel injection routine, the value of K determined by FIG.
Not fixed time (eg 0.5 to 1 second)
The engine air-fuel ratio is switched to the rich air-fuel ratio and NO_Xabsorption
Regeneration of the agent 18 is performed. Also, after a certain period of time has passed
Is NO _XThe value of the absorption counter C is returned to zero and
The lag F is reset (= 0). It should be noted that FIG. 5 step
501 to 509 are the same as those described in claim 2 and claim 3.
It is equivalent to the determining means.

Next, the shifting operation of the automatic transmission of this embodiment will be described. In this embodiment, the shift operation of the automatic transmission 40 is performed based on the vehicle traveling speed and the throttle valve opening. That is, the electronic control circuit 30 inputs the vehicle traveling speed and the throttle valve opening from the vehicle speed sensor 24 and the throttle opening sensor 20, respectively, and performs the shift operation based on these values. FIG. 6 is a shift diagram showing an example of the relationship between the vehicle traveling speed, the throttle valve opening, and the shift operation. FIG. 6 shows shift characteristics of an automatic transmission having an overdrive (OD) mechanism and three-speed transmission gears. FIG. 6 shows the throttle valve opening TA on the vertical axis and the vehicle traveling speed SP on the horizontal axis. The solid line shows the timing of shifting from the low speed stage to the high speed stage (shift up), and the dotted line shows the timing of shifting from the high speed stage to the low speed stage (shift down). Also,
The hatched region in FIG. 6 indicates a region where the lockup clutch is engaged to directly connect the engine output shaft and the converter output shaft for operation.

The power-on downshift referred to in the present specification is different from the downshift at the time of deceleration, and is a downshift operation performed while the positive drive torque is being transmitted from the engine side to the transmission side. Say. Therefore, during the power-on downshift operation, the engine speed before and after the downshift (torque converter input shaft speed) is higher than the transmission input shaft speed (torque converter output shaft speed).

Next, the power-on downshift operation of the automatic transmission will be described with reference to FIGS. 7 (A) to 7 (C). FIG. 7 is a timing chart showing changes in general transmission output shaft torque, engine speed, and shift control hydraulic pressure during power-on downshift operation of an automatic transmission. 7 shows changes in the transmission output shaft torque (driving torque) during operation. Further, FIG. 7 (B) shows a change in the rotation speed of the converter output shaft (transmission input shaft rotation speed) during the power-on downshift operation, and FIG. 7 (C) shows a change in the automatic transmission control hydraulic pressure. . In FIGS. 7 (A) to 7 (C), for example, the relationship between the throttle valve opening and the vehicle traveling speed at the time of traveling is shown in the shift characteristic diagram of FIG.
If the shift line from the second speed to the second speed is passed, the electronic control circuit 30 outputs a shift command signal from the third speed to the second speed at a time point after a predetermined time has elapsed from the time point. After a lapse of a predetermined time from the time point, the shift command signal is output by a multiple shift operation (for example, immediately after the vehicle traveling condition crosses the shift line from the third speed to the second speed in FIG. In the case of crossing the shift line to the high speed, it is determined whether or not it is necessary to directly perform the shift operation from 3 → 1 instead of performing the shift operation from 3 → 2 → 1. This is because.

When the shift command signal is output at the time point, the control valve of the control hydraulic circuit of the automatic transmission is switched, and
As shown in (C), the switching hydraulic pressure that controls the shift clutch starts to decrease. Also, since the control hydraulic circuit is equipped with an accumulator to prevent sudden changes in hydraulic pressure, if the hydraulic pressure drops to a certain extent after switching, the speed at which the hydraulic pressure drops due to the operation of the accumulator decreases, and It gradually decreases (from Fig. 7 (C)).

Next, a change in the transmission output shaft torque (driving torque) when the switching hydraulic pressure changes as described above will be described with reference to FIG. 7 (A). Before the switching oil pressure starts to decrease (before the time), the drive torque is set to a value according to the gear ratio on the high speed side of the transmission (to be exact, engine output torque × converter torque amplification ratio × high speed side gear ratio). Has become. Next, when the switching oil pressure starts decreasing at a certain point and then decreases to some extent, the pressing force of the clutch decreases, causing slipping to occur in the transmission clutch that has been integrally engaged until now. Torque drops temporarily. Also, the engine speed increases due to the slip of this clutch (from Fig. 7 (B)). Next, at a time point, a one-way clutch, which will be described later, is activated (locked) and the rotation of the input / output shaft of the transmission is synchronized (FIG. 7 (A)). At this point in time, the engine speed is increasing and the engine output torque is increasing, so the drive torque rapidly increases due to the operation of the one-way clutch, and due to this sudden torque fluctuation, there is a transient in the drive system. Vibration occurs and the drive torque fluctuates after the transmission input / output speed is synchronized (from Fig. 7 (A)). Further, this drive torque fluctuation is attenuated with the passage of time, and when a certain amount of time has passed since the rotation speed was synchronized, the drive torque is a value corresponding to the gear ratio on the low speed side of the transmission (more precisely, the engine output torque). X converter torque amplification ratio x low speed side gear ratio) (Fig. 7 (A)).

Next, the power-on downshift operation will be specifically described by taking an actual transmission mechanism of an automatic transmission as an example. 8 (A) and 8 (B) are diagrams schematically showing the switching states of the transmission using the planetary gears between the third speed and the second speed, respectively. In FIGS. 8A and 8B, 71 is a transmission input shaft, 7
2 is an intermediate shaft connected to the transmission output shaft, 73, 74, 7
Reference numeral 5 denotes a sun gear, a pinion (planetary gear), and a ring gear, which form a planetary gear train. The intermediate shaft 72 is connected to the pinion carrier 76 and rotates at a speed equal to the revolution speed of the pinion. In addition, the one-way clutch 78 that allows only one direction of rotation of the sun gear (clockwise rotation when viewed from the input shaft side in FIG. 8) is applied to the sun gear 73.
Is provided. 79 and 80 are ring gears 7, respectively
5 is a direct clutch that directly connects the sun gear 73 to the input shaft 71. 8 (A) and 8 (B) are for showing the connection state of each element in the third speed and the second speed of the transmission, respectively.
All the elements necessary for connecting the other gears are omitted.

In the third speed operation of the transmission, as shown in FIG. 8A, both the clutch 80 connecting the sun gear 73 and the input shaft 71 and the clutch 79 connecting the ring gear 75 and the input shaft 71 are used. Are connected. Since the one-way clutch 78 described above allows clockwise rotation of the sun gear 73, in this state, as shown in FIG.
When 1 rotates clockwise, the sun gear 73 and ring gear 7
5, the pinion 74 rotates integrally with the sun gear 73 and the ring gear 75 while stopping its rotation. Therefore, the intermediate shaft (output shaft) connected to the pinion carrier 76 is directly connected to the input shaft 71 and rotates clockwise.

Further, in the second speed operating state shown in FIG. 8 (B),
The clutch 80 between the sun gear 73 and the input shaft 71 is disengaged, and only the ring gear 75 and the input shaft 71 are connected by the clutch 79. In this state, when the input shaft 71 rotates clockwise as shown in FIG. 8 (B), only the ring gear 75 is driven by the input shaft 71 to rotate clockwise, and as a result, the pinion 74 revolves clockwise. For,
A counterclockwise rotation torque due to the reaction force of the rotation of the pinion 74 is applied to the sun gear 73. However, as described above, the one-way clutch 78 prevents the sun gear 73 from rotating in the counterclockwise direction.
Does not rotate counterclockwise, but remains stationary.

Therefore, the pinion 74 revolves clockwise around the stationary sun gear 73, and the pinion carrier 76.
The intermediate shaft connected to rotates in the clockwise direction at a predetermined reduction ratio. The switching operation from the third speed to the second speed is performed by gradually reducing the switching hydraulic pressure applied to the clutch 80 from the third speed operating state to release the engagement of the clutch 80 (FIG. 7 (C)).

As described above, the sun gear 73 is operated during the third speed operation.
Is rotating integrally with the pinion 74 and the ring gear 73, but when the switching hydraulic pressure of the clutch 80 gradually decreases from this state, slippage occurs in the clutch 80 and the reaction force from the pinion 74 causes the sun gear 73 to move. The rotation gradually decreases. Further, while the rotation of the sun gear 73 continues to decrease, the sun gear 73 cannot give a sufficient reaction force to the pinion 74, so the sun gear 73
The transmission output shaft torque decreases as the rotation speed decreases (from Fig. 7 (A)). Further, since the load applied to the engine is temporarily reduced due to the reduction of the driving torque during this period, the engine speed is increased and the ring gear 75 connected to the input shaft 71 is increased.
The number of rotations of will also increase. On the other hand, since the pinion carrier 76 is connected to the drive system of the vehicle through the intermediate shaft 72 and continues to revolve at a constant rotation speed, there is a difference in rotation between the transmission input shaft and the output shaft. Is absorbed by an increase in the gear ratio due to a decrease in the rotation speed of the sun gear 73. When the rotation of the sun gear 73 decreases from this state and the rotation of the sun gear 73 starts to rotate counterclockwise from the stationary state, the one-way clutch 78 operates to fix the sun gear 73, so that the transmission is rapidly in the second speed operating state. And the rotation of the transmission input / output shaft is forcibly synchronized (Fig. 7 (B)).

Further, at this time, the fixing of the sun gear 73 causes the reaction force applied from the sun gear 73 to rapidly rise, so that the torque due to the revolution of the pinion 74 sharply rises, and the transmission output shaft torque (driving torque) changes to the above rotation. It will rise sharply with the synchronization (Fig. 7 (A)). Therefore, the greater the engine output torque (transmission input shaft torque), the greater the fluctuation of the drive torque during rotation synchronization, and the longer the time required for the fluctuation convergence. Therefore, when the rich air-fuel ratio operation for regeneration of the NO _X absorbent is performed and the engine output torque is in an increased state when the rotation is synchronized, as shown in FIG.
As indicated by the dotted line in (A), a large output fluctuation occurs, which causes a problem of deteriorating drivability.

In the above description, the power-on downshift operation from the 3rd speed to the 2nd speed of the transmission is described as an example. The same problem occurs when the rich air-fuel ratio operation for regeneration of the NO _X absorbent is performed during the rotation synchronization of the power-on downshift operation from the stage. In the embodiment corresponding to claim 1 of the present invention, for regeneration of the NO _x absorbent for a predetermined time (that is, from FIG. 7 to) from the time of rotation synchronization of the power-on downshift operation of the automatic transmission. By prohibiting the engine rich air-fuel ratio operation from being newly started, and by stopping the rich air-fuel ratio operation together with the rotation synchronization (Fig. 7,) when the rich air-fuel ratio operation has already been performed. This prevents an increase in drive torque fluctuation during power-on downshift operation.

FIG. 9 shows a flow chart of the inhibition control of the NO _X absorbent regeneration operation during the above power-on downshift operation. This routine is executed by the electronic control circuit 30 described above at regular intervals. When the routine starts in FIG. 9, in step 901, it is determined whether or not the rotation synchronization of the transmission input / output shaft occurs during the power-on downshift operation of the transmission. Whether or not the rotation synchronization occurs during the power-on downshift operation is determined by whether or not the following conditions are satisfied.

(1) The engine rotation speed detected by the rotation speed sensor 21 (that is, the converter input shaft rotation speed) is higher than the transmission input shaft rotation speed (converter output shaft rotation speed) detected by the rotation speed sensor 22. It is in a state (that is, a state where positive torque is transmitted from the engine side to the drive side), and the downshift gear shift command signal (FIG. 7) is output.

(2) In addition to the above (1), the rotation speed of the transmission input / output shaft is synchronized. Here, the determination of the rotation synchronization under the above condition (2) is made by determining the transmission input shaft rotation speed sensor (see FIG. 1,
22), the input shaft revolution speed NI and the output shaft revolution speed NO detected by the transmission output shaft revolution speed sensor (FIG. 1, 23) are equal to [NI ≧ NO × low speed gear ratio] This is done by detecting that the relationship has been met.

In step 901, if the rotation synchronization during the power-on downshift operation is not occurring, the above routine is terminated as it is, and if the rotation synchronization is occurring, in step 903, the rotation synchronization is performed. It is determined whether or not a predetermined time has elapsed since the occurrence of. Here, the predetermined time is set to be equal to the time required for the drive torque fluctuation to converge after the rotation is synchronized (time from FIG. 7A).

If it is determined in step 903 that the predetermined time has not elapsed, it is considered that the fluctuation of the drive torque has not yet converged, and therefore the routine proceeds to step 905, where the flag F is set.
Z is set (= 1) and the routine ends. Also,
If the predetermined time has elapsed in step 903, the flag FZ is reset (= zero) in step 907, and the routine ends.

When the flag FZ is set in step 905, the electronic control circuit 30 causes the rich air-fuel ratio for regeneration of the NO _X absorbent 18 regardless of the value of the flag F set in the above-mentioned flowchart of FIG. thereby prohibited to start a new operation, forcibly stops the rich air-fuel ratio operation when the rich air-fuel ratio operation for previously regeneration of _the NO _X absorbent is being carried out, normal air-fuel ratio Return to control (FIG. 4). Thus, the rich air-fuel ratio operation for _the NO _X absorbent regeneration during rotation synchronization in the power-on downshift operation is that there is no carried out, increase of the drive torque fluctuation is prevented.

[0059] Further, the flag FZ in step 907 is reset, the prohibition of the rich air-fuel ratio operation for _the NO _X absorbent regeneration is canceled, NO _X absorbent in accordance with the value of the flag F is set at 5 A rich air-fuel ratio operation for agent regeneration is performed. The step 901 corresponds to the synchronization detecting means described in claim 1, and the steps 903 to 907 correspond to the prohibiting means.

Further, in the above embodiment, when the rich air-fuel ratio operation for regeneration of the NO _X absorbent has already been carried out, this rich air-fuel ratio operation is stopped when the rotation is synchronized. In actual operation, since it takes a certain amount of time for the engine output torque to decrease after the rich air-fuel ratio operation is stopped, the rich air-fuel ratio operation may be stopped earlier than the rotation synchronization. In this case, for example, it is detected that the transmission input shaft revolution number NI has risen to some extent and is within a predetermined deviation with respect to the synchronous revolution number (output shaft revolution number NO x constant speed stage side gear ratio). The rich air-fuel ratio operation may be stopped.

Next, an embodiment corresponding to claim 2 of the present invention will be described. In the above-described embodiment, the rich air-fuel ratio operation for NO _X absorbent regeneration is prohibited during the rotation synchronization during the power-on downshift operation, and the drive torque fluctuation due to the engine output torque increase during the rotation synchronization is suppressed. It prevents the increase. However, in the power-on downshift operation, it may be preferable to increase the engine output torque.

FIGS. 10 (A) and 10 (B) show driving torque fluctuations during the power-on downshift operation and changes in the transmission input shaft speed, respectively, similar to FIGS. 7 (A) and 7 (B). It is a diagram. As described above, the transmission input shaft speed (engine speed) increases during the period from FIG. 10 (A) and (B) so that the transmission input shaft speed is synchronized with the output shaft speed. This is the time required to become (see FIG. 10 (B)). If the engine output torque is high, the engine speed increases in a short time. Therefore, if the engine output torque can be increased during the period after the start of the gear shifting operation (Fig. 10), the engine speed changes to Figs. 10 (A) and 10 (B). As shown by the dotted line, the time until the rotation synchronization (FIG. 10) is shortened, and the time required for the downshift operation can be shortened as a whole.

[0063] In this embodiment, NO if NO _X absorption amount of _X absorbent is equal to or greater than a predetermined amount, period actively NO _X to synchronously rotate the shift operation starts at the time of power-on downshift While performing the rich air-fuel ratio operation for regeneration of the absorbent, while regenerating the NO _x absorbent,
The shift operation time is shortened. FIG. 11 shows a flowchart of the NO _X absorbent regeneration control during the power-on downshift operation. This routine is also executed by the electronic control circuit 30 described above at regular intervals.

When the routine starts in FIG. 11, it is determined in step 1101 whether the power-on downshift gear shifting operation has been started (FIG. 10).
Here, whether or not the power-on downshift gear shift operation is performed is determined by whether or not the following conditions are satisfied at the same time. (1) The power-on downshift gearshift command is output (that is, the downshift command signal is output when the engine speed is higher than the transmission input shaft speed).

(2) After the above signal is output, the transmission input shaft speed NI and the output shaft speed NO become [NI> NO
X high-speed gear ratio] (that is, the transmission input shaft speed and the output shaft speed are out of synchronization, see FIG. 10 (B)). Step 1101
If the gear shifting operation has not been started, this routine is terminated as it is, and if the gear shifting operation has been started, the routine proceeds to step 1103, and whether rotation synchronization after downshifting (FIG. 10,) has occurred. It is determined whether or not. The occurrence of this rotation synchronization is judged by the fact that the relationship between the transmission input shaft revolution number NI and the output shaft revolution number NO is in the state of [NI = NO × low speed stage side gear ratio].

In step 1103, if the rotation synchronization is not generated, that is, the gear change operation is in the state shown in FIG. 10, the process proceeds to step 1105 and the flag FY is set (= 1). Here, when the flag FY is set, it is determined by a separately executed routine whether or not the value of the NO _X absorption amount counter C calculated according to FIG. 5 is a predetermined value C ₁ or more, and if C ≧ C ₁ . In some cases, NO _X regardless of the value of the flag F set by the routine of FIG.
The rich air-fuel ratio operation for regenerating the absorbent is started. Predetermined value C ₁ of the absorption, the flag F is set to a value smaller than the absorption amount C ₀ (Fig. 5 step 511) to be set, for example, corresponding to 30% of the maximum NO _X absorption of the NO _X absorbent Set to the value. The predetermined value C ₁ is set to be smaller than C ₀ because it is preferable to increase the engine output torque from the start of the speed change operation at the time of power-on downshift to the rotation synchronization, and therefore the NO _x absorbent regeneration operation is not normally performed. This is because the regeneration operation is performed earlier to shorten the time required to complete the gear shift operation even with a relatively small NO _x absorption amount.

On the other hand, as described in the above embodiment, if the engine output torque increases after the rotation synchronization, there is a problem that the fluctuation of the driving torque increases. Therefore, also in this embodiment, by the steps 1109 to 1113, new start of the rich air-fuel ratio operation for regeneration of the NO _X absorbent is prohibited and the rich air-fuel ratio operation is already performed for a predetermined time after the rotation synchronization. If so, the rich air-fuel ratio operation is stopped.

That is, if the rotation synchronization occurs in step 1103, it is determined in step 1107 whether or not the rotation synchronization predetermined time has elapsed. If the predetermined time has not elapsed, steps 1109 and 1111 are executed. This is executed, the flag FY is reset (= 0), and the flag FZ is set (= 1). When the flag FZ is set, new start of the rich air-fuel ratio operation for regeneration of the NO _x absorbent is prohibited and the rich air-fuel ratio operation currently being performed is stopped. Is the same as. If the predetermined time has elapsed after the rotation synchronization in step 1107, the flag FZ is determined in step 1113.
Are reset (= 0).

In the flowchart of FIG. 11, steps 1103 and 1105 correspond to the control means described in claim 2. As described above, according to the present embodiment, not only is it possible to prevent an increase in drive torque fluctuations during a power-on downshift, but it is also possible to shorten the time required for a downshift operation while executing regeneration of the NO _X absorbent. It will be possible.

Next, an embodiment corresponding to claim 3 of the present invention will be described. Aforementioned Figure 9, a rich air-fuel ratio for in order to prevent the drive torque fluctuation of the power-on downshift operation is increased in the embodiment of FIG. 11, the rotation synchronization time between the predetermined time _the NO _X absorbent regeneration I banned driving. However, since the prohibition of the rich air-fuel ratio operation is performed in order to prevent the engine output torque from increasing, if the engine output torque can be prevented from increasing after the rich air-fuel ratio is switched, the rich air-fuel ratio operation is not always required during the rotation synchronization. No need to ban. Further, if the engine output torque after switching the rich air-fuel ratio can be made lower than that during lean air-fuel ratio operation before switching, the sudden increase in the drive torque during rotation synchronization will be mitigated. It is preferable to carry out the air-fuel ratio operation.

In this embodiment, the electronic control circuit 30 uses NO _x.
Torque reduction means for reducing the engine output torque after switching the rich air-fuel ratio to a value lower than that during lean air-fuel ratio operation before switching by retarding the ignition timing when switching to the rich air-fuel ratio for regeneration of the absorbent. and functions as, by the revolution synchronization during power-on downshift operation performing the rich air-fuel ratio operation for _the NO _X absorbent play with aggressive engine output reduction, the driving of the power-on downshift operation The torque fluctuation is reduced.

FIGS. 12 (A) and 12 (B) show driving torque fluctuations during the power-on downshift operation and changes in the transmission input shaft rotation speed, respectively, similar to FIGS. 7 (A) and 7 (B), respectively. It is a diagram. As described above, the drive torque rapidly increases during the rotation synchronization () in FIGS. 12A and 12B, and the drive torque fluctuates due to the vibration of the drive system. However, as described above, by switching to the rich air-fuel ratio operation with ignition timing retardation at the time of rotation synchronization and lowering the engine output torque from before the switching, the rotation as shown by the dotted line in FIG. 12 (A). Since the sudden increase of the drive torque at the time of synchronization is mitigated, it is possible to reduce the fluctuation range of the drive torque after the rotation synchronization and the time until the fluctuation converges.

FIG. 13 shows a flow chart of the NO _X absorbent regeneration operation control during the above power-on downshift operation. This routine is executed by the electronic control circuit 30 described above at regular intervals. When the routine starts in FIG. 13, it is determined in step 1301 whether or not the rotation synchronization of the transmission input / output shaft during the power-on downshift operation of the transmission has occurred. The condition for determining whether or not the rotation synchronization occurs during the power-on downshift operation is as shown in FIG.
Since it is the same as step 901, its explanation is omitted here.

In step 1301, if the rotation synchronization during the power-on downshift operation is not occurring, the above routine is terminated as it is, and if the rotation synchronization is occurring, in step 1303, the above rotation synchronization is performed. It is determined whether or not a predetermined time has elapsed since the occurrence of. Here, the predetermined time is set to be equal to the time required for the drive torque fluctuation to converge after the rotation is synchronized (time from FIG. 12A).

If the predetermined time has not elapsed in step 1303, the process proceeds to step 1305 and the flag F
X is set (= 1) and the routine ends. Also,
If the predetermined time has passed in step 1303, the flag FX is reset in step 1307 (=
Zero) and terminate the routine. That is, the flag FX
Is set at the same time as the rotation is synchronized, and is reset when the predetermined time has elapsed.

When the flag FY is set in step 1305, it is determined by a routine that is separately executed whether the value of the NO _X absorption amount counter C calculated according to FIG. 5 is a predetermined value C ₂ or more, and C ≧ If a C ₂ regardless of the value of the flag F is set by the routine of FIG. 5 NO _X
The rich air-fuel ratio operation for regenerating the absorbent is started. Further, when the rich air-fuel ratio operation is switched, the ignition timing of the engine is significantly retarded, and the engine output torque after the switching is controlled to be lower than that before the switching.

Further, as in the embodiment of FIG. 11, the predetermined value C ₂ of the absorption amount is set to a value smaller than the absorption amount C ₀ (step 511 of FIG. 5) at which the flag F is set (eg NO _X).
As the value corresponding to 30% of the maximum NO _X absorption amount of the absorbent), rich opportunity to air-fuel ratio operation is carried out for regeneration of the NO _X absorbent during the rotation synchronization of the power-on downshifting increases To be

Thus, the power-on downshift operation is performed.
Sometimes NO with engine output torque reduction _XAbsorbent regeneration implemented
Then, as shown in FIG. 12, driving during downshifting
Reduced torque fluctuations and improved drivability
It On the other hand, in step 1303, a predetermined time has passed after the rotation synchronization.
If so, the flag FX is reset in step 1307.
(= 0). As a result, the ignition timing of the engine is a normal value.
To prevent the drive torque from decreasing after downshifting.
It Further, by resetting the flag FX, NO_XAbsorbent
Value is the value of the flag F set in the routine of FIG.
Will be executed accordingly.

In the flowchart of FIG. 13, steps 1303 and 1305 correspond to the control means described in claim 3. Further, in the above embodiment, the ignition timing is retarded as a torque lowering means for reducing the engine output torque at the time of switching the rich air-fuel ratio operation for NO _x absorbent regeneration, but the torque after switching is changed by other means. Can be reduced.For example, in an engine equipped with a sub-throttle valve whose opening can be controlled independently of the driver's operation of the accelerator pedal, the sub-throttle valve can be used when switching to rich air-fuel ratio operation. The engine output torque can also be reduced by reducing the opening.

[0080]

According to the present invention as set forth in claim 1, the rich air-fuel ratio operation for NO _x absorbent regeneration is prohibited for a predetermined time from the time of rotation synchronization during power-on downshift operation. As a result, the engine output torque does not increase during rotation synchronization, so it is possible to prevent an increase in drive torque fluctuation due to downshifting.

According to the present invention described in claim 2, further,
By performing the rich air-fuel ratio operation for regeneration of the NO _X absorbent from the start of the speed change operation to the rotation synchronization, it is possible to reduce the time required for the speed change operation while preventing an increase in the drive torque fluctuation. According to the present invention described in claim 3, during rotation synchronization during power-on downshift operation,
By performing the rich air-fuel ratio operation accompanied by the reduction of the engine output torque for the NO _X absorbent regeneration, it is possible to reduce the drive torque fluctuation during the downshift.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine with an automatic transmission showing an embodiment of the present invention.

[FIG. 2] NO _X used in the exhaust purification system of the embodiment of FIG. 1.
Absorbent is a diagram for explaining the absorbing and releasing action of NO _X.

FIG. 3 is a diagram showing a format of a numerical table used for determining a basic fuel injection amount.

FIG. 4 is a diagram showing a setting example of a fuel injection amount correction coefficient.

5 is a flowchart showing an example of the NO _X absorption estimation method of the NO _X absorbent.

FIG. 6 is a diagram showing an example of a shift diagram of an automatic transmission.

FIG. 7 is a diagram illustrating a power-on downshift operation of the automatic transmission.

FIG. 8 is a diagram illustrating a power-on downshift operation of the automatic transmission.

FIG. 9 is a flowchart for explaining the first embodiment of the present invention.

FIG. 10 is a view similar to FIG. 7 for explaining the power-on downshift operation of the second embodiment of the present invention.

FIG. 11 is a flowchart for explaining the second embodiment of the present invention.

FIG. 12 is a view similar to FIGS. 7 and 10 for explaining the power-on downshift operation of the third embodiment of the present invention.

FIG. 13 is a flow chart for explaining a third embodiment of the present invention.

[Explanation of symbols]

1 ... Internal combustion engine 17 ... Exhaust passage 18 ... NO _X absorbent 30 ... Electronic control circuit 40 ... Automatic transmission

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F02D 41/14 310 A

Claims (3)

[Claims] 1. Exhaust gas arranged in an exhaust passage of an internal combustion engine
NO in the exhaust when the air-fuel ratio is lean_XAbsorbs and exhausts
NO absorbed when the oxygen concentration in the inside decreased _XEmit
NO_XAn absorber and an air-fuel ratio of the internal combustion engine are controlled, and the internal combustion engine is operated under predetermined conditions.
Change the air-fuel ratio of Seki from lean air-fuel ratio to rich air-fuel ratio
Therefore, the NO_XNO absorbed from the absorbent_XLet go
An automatic transmission provided with an air-fuel ratio switching means for outputting the output and an automatic transmission connected to the internal combustion engine.
In a control device for an internal combustion engine with a speed changer, rotation of the automatic transmission during power-on downshift operation
Synchronization detection means for detecting synchronization, and the rotation synchronization is detected.
For a predetermined time from the
Seki's switch to rich air-fuel ratio is prohibited and already started
The prohibition means to stop the above rich air-fuel ratio operation
A control device for an internal combustion engine with an automatic transmission, characterized in that
Place 2. A control device for an internal combustion engine with an automatic transmission according to claim 1, further comprising: a estimating means for estimating an amount of NO _X absorbed in the _the NO _X absorbent, the power-on of the automatic transmission Detection means for detecting the start of a downshift operation, and the power-on downshift operation start when the NO _x absorption amount estimated by the estimation means when the power-on downshift operation start is detected is equal to or more than a predetermined value. From the time to the rotation synchronization, the control device for the internal combustion engine with an automatic transmission, comprising: a control means for performing a rich air-fuel ratio operation by the air-fuel ratio switching means. 3. Exhaust gas arranged in an exhaust passage of an internal combustion engine
NO in the exhaust when the air-fuel ratio is lean_XAbsorbs and exhausts
NO absorbed when the oxygen concentration in the inside decreased _XEmit
NO_XAn absorbent, and the NO_XNO absorbed by the absorbent_XEstimate quantity
Means for controlling the air-fuel ratio of the internal combustion engine to reset the air-fuel ratio of the internal combustion engine.
By switching from the air-fuel ratio to the rich air-fuel ratio,
Note NO_XNO absorbed from the absorbent_XAir-fuel ratio to release
Switching means and after switching when changing the air-fuel ratio from lean to rich
The engine output torque of the
Torque reduction means for controlling the internal combustion engine and an automatic transmission that is connected to the internal combustion engine.
In a control device for an internal combustion engine with a speed changer, rotation of the automatic transmission during power-on downshift operation
Synchronization detection means for detecting synchronization, and estimation by the estimation means when the rotation synchronization is detected
NO_XWhen the absorption amount is more than the specified value, the torque low
Of the engine output torque by the lower means and the air-fuel ratio switching means.
Control to switch lean-to-rich air-fuel ratio with drop
An internal combustion engine with an automatic transmission, characterized by comprising:
Control device.