JPH09193693A - Controller for automatic transmission - Google Patents

Abstract

PROBLEM TO BE SOLVED: To previously prevent deterioration in drivability by richening an air-fuel ratio and subsequently carrying out the upshift when reduction in a throttle opening to the extremely low opening is detected and the upshift in an automatic transmission is determined by means an upshift determining means. SOLUTION: An electronic throttle valve 23 is arranged in an intake duct in an engine 1, and an opening of the electronic throttle valve 23 is controlled by means of a controller 21 according to an actuating quantity of an accelerator pedal 20 via a throttle actuator 22. An airfuel ratio is richened if a throttle opening is extremely low, while a lean air-fuel ratio is attained if the throttle opening is larger than the extremely low opening. On the basis of the detection of reduction in the throttle opening to the extremely low opening, upshift in an automatic transmission 3 is determined, and if the upshift is determined, the air-fuel ratio is richened by means of an air-fuel ratio reducing means, and then, the upshift is carried out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for an automatic transmission for a vehicle, and more particularly to a control device for an automatic transmission connected to an internal combustion engine capable of lean burn operation with a large air-fuel ratio. .

[0002]

2. Description of the Related Art It is well known that it is strongly desired to improve fuel efficiency of an internal combustion engine in order to save energy and protect the environment. Therefore, for example, in a gasoline engine, a lean burn operation with a large air-fuel ratio is performed. The engine capable of is developed and put into practical use. This lean burn operation is an operation state in which a mixture of air-fuel ratio higher than the theoretical air-fuel ratio is sucked into the cylinder to cause combustion, so engine torque decreases and combustion becomes unstable, resulting in torque fluctuation. Is relatively large. Therefore, it is normally executed in a state where the vehicle speed is equal to or higher than a predetermined vehicle speed and the throttle opening is relatively low.

On the other hand, it is widely practiced to mount an automatic transmission in a vehicle together with an engine of this type. As is well known, an automatic transmission for a vehicle is configured to perform a gear shift based on a running state represented by an engine load represented by a throttle opening degree or a vehicle speed. Therefore, in a vehicle in which an automatic transmission is connected to a so-called lean burn engine, both the air-fuel ratio of the engine and the shift speed of the automatic transmission are changed in accordance with the change in the throttle opening.

For example, when the accelerator pedal is returned and the throttle opening is reduced while the vehicle is traveling with the air-fuel ratio set to rich, it is determined that the air-fuel ratio should be changed to lean and the automatic transmission is upshifted. The decision to make is established. Also, if the throttle opening is reduced while running with a lean air-fuel ratio, the automatic transmission will be upshifted with the air-fuel ratio kept lean, but the drive torque will decrease due to the reduction of the gear ratio accompanying the upshift. Therefore, when the accelerator pedal is depressed to increase the engine output, the air-fuel ratio is switched to rich by increasing the throttle opening.

As described above, the air-fuel ratio and the gear shift are judged simultaneously or continuously by the change of the throttle opening, and it is necessary to prevent the gear shift shock and the deterioration of the drivability which accompany the shift. An example is proposed by JP-A-63-176635. The device described in this publication is intended to prevent deterioration of drivability due to depression of the accelerator pedal after an upshift during lean burn operation, and upshift is performed during lean burn operation. In this case, the air-fuel ratio is set to stoichiometric or rich for a predetermined time after the upshift, thereby preventing the torque from decreasing immediately after the upshift.

[0006]

The device described in the above publication performs upshifting while keeping the air-fuel ratio lean and sets the air-fuel ratio rich during a predetermined time immediately after that. It is possible to prevent a reduction in the drive torque after the upshift, a depression of the accelerator pedal for compensating for the reduction, or aggravation of the shift shock due to the overlap between the upshift and the change of the air-fuel ratio.

However, as described above, when the air-fuel ratio is made lean, the combustion of the air-fuel mixture in the cylinder becomes unstable, so that the combustion is unsuccessful in the state where the throttle opening is a very small opening below a certain degree. The air-fuel ratio may be stoichiometric or rich in order to prevent it from becoming stable. If the conventional control described in the above-mentioned publication is executed in a vehicle in which an automatic transmission is connected to such an engine, the air-fuel ratio will be changed after the upshift. This is executed, and then the air-fuel ratio is changed to rich as the throttle opening decreases to an extremely low opening.
That is, in this control, the gear shift is performed in a state where the air-fuel ratio is lean, so there is a possibility that gear shift shock will deteriorate and drivability will deteriorate. That is, in the lean burn state, combustion is unstable and the engine torque fluctuates relatively, and the hydraulic pressure during gear shifting of the automatic transmission has characteristics that match the air-fuel ratio rich or stoichiometric state. Therefore, if shifting is performed in the lean burn state with the throttle opening extremely low, shift shock or drivability may be deteriorated due to fluctuations in input torque to the automatic transmission or incompatibility between input torque and hydraulic pressure. It was

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a control device capable of smoothly executing a shift accompanying a decrease in throttle opening to a so-called extremely low opening. It is intended.

According to the present invention, when the throttle opening is reduced to an extremely low opening and an upshift is judged, first, the air-fuel ratio is changed to rich including the stoichiometric condition, and then the upshift is executed. By doing so, the above object is achieved.

[0010]

In order to achieve the above object, the present invention sets the air-fuel ratio to a rich state including the stoichiometric air-fuel ratio when the throttle opening is extremely low, and has an extremely low air-fuel ratio. A vehicle in which an internal combustion engine that is controlled to make the air-fuel ratio lean when the throttle opening is larger than the opening is connected to an automatic transmission that executes a shift based on a change in a running state including a change in the throttle opening. And a power-off detection means for detecting that the throttle opening degree has decreased to an extremely low opening degree during traveling, and a power-off detection means that the throttle opening degree has decreased to an extremely low opening degree. Upshift determination means for determining an upshift in the automatic transmission based on the detection by the Air-fuel ratio reducing means for making the air-fuel ratio rich as the throttle opening degree decreases to an extremely low opening degree; and up-shift executing means for executing the up-shift after the air-fuel ratio reducing means makes the air-fuel ratio rich. It is characterized by having.

Therefore, in the present invention, when the throttle opening is reduced to an extremely low opening, the power-off detecting means detects the state, and the upshift determining means determines upshift of the automatic transmission based on the detected state. Further, the air-fuel ratio lowering means lowers the air-fuel ratio of the air-fuel mixture supplied to the internal combustion engine to bring it into a rich state including a stoichiometric state. When the air-fuel ratio is changed to rich due to the throttle opening being the extremely low opening, the upshift in the automatic transmission is thereafter executed by the upshift executing means. Therefore, when the throttle opening becomes extremely low, the air-fuel ratio is immediately switched to rich, and the upshift is performed in a state where the air-fuel mixture is rich, so that shift shock and drivability are improved.

[0012]

Next, the present invention will be described more specifically with reference to the drawings. First, an example of an automatic transmission targeted by the present invention will be described with reference to FIG. FIG.
In, the automatic transmission 3 is connected to the engine 1 via the torque converter 2. This torque converter 2
Is a pump impeller 5 connected to the crankshaft 4 of the engine 1, a turbine runner 7 connected to the input shaft 6 of the automatic transmission 3, and a lockup clutch that directly connects the pump impeller 5 and the turbine runner 7. 8
And a stator 10 that is prevented from rotating in one direction by a one-way clutch 9.

The automatic transmission 3 has two types of high and low.
It is provided with a sub-transmission unit 11 that switches the gears, and a main transmission unit 12 that can switch between a reverse gear and four forward gears. The auxiliary transmission unit 11 includes a sun gear S0, a ring gear R0,
And an HL planetary gear unit 13 composed of a pinion P0 rotatably supported by the carrier K0 and meshed with the sun gear S0 and the ring gear R0, and a clutch C0 and a one-way clutch provided between the sun gear S0 and the carrier K0. F0 and a brake B0 provided between the sun gear S0 and the housing 19 are provided.

The main transmission unit 12 includes a sun gear S1, a ring gear R1, and a first planetary gear unit 14 which is rotatably supported by a carrier K1 and comprises a pinion P1 meshed with the sun gear S1 and the ring gear R1.
A second planetary gear unit 15 including a sun gear S2, a ring gear R2, and a pinion P2 rotatably supported by the carrier K2 and meshed with the sun gear S2 and the ring gear R2, a sun gear S3, and a ring gear R3.
, And a third planetary gear unit 16 comprising a pinion P3 rotatably supported by the carrier K3 and meshed with the sun gear S3 and the ring gear R3.

The sun gear S1 and the sun gear S2 are integrally connected to each other, the ring gear R1, the carrier K2 and the carrier K3 are integrally connected to each other, and the carrier K3 thereof is connected.
Is connected to the output shaft 17. Also, the ring gear R2
Are integrally connected to the sun gear S3. A first clutch C1 is provided between the ring gear R2 and the sun gear S3 and the intermediate shaft 18, and a second clutch C2 is provided between the sun gear S1 and the sun gear S2 and the intermediate shaft 18.

As the braking means, the housing 19 is provided with a band-type first brake B1 for stopping the rotation of the sun gear S1 and the sun gear S2. Also, the sun gear S1 and the sun gear S2 and the housing 19
Between the first one-way clutch F1 and the brake B
2 are provided in series. This first one-way clutch F
1 is configured to be engaged when the sun gear S1 and the sun gear S2 try to reversely rotate in the direction opposite to the input shaft 6.

A third brake B3 is provided between the carrier K1 and the housing 19, and a fourth brake B4 and a second one-way clutch F2 are provided in parallel between the ring gear R3 and the housing 19. Has been. This second
The one-way clutch F2 is configured to be engaged when the ring gear R3 attempts to rotate in the reverse direction. The clutches C0, C1, C2, the brakes B0, B1, B2
, B3, B4 are hydraulic friction engagement devices in which friction materials are engaged by the action of hydraulic pressure.

In the above automatic transmission, it is possible to set five forward speeds and reverse speeds, and the engagement / release states of the friction engagement devices for setting these speeds are shown in FIG. It is shown in the operation table. In FIG. 2, the mark ◯ indicates the engaged state and the mark x indicates the released state.

FIG. 3 is a control system diagram of the engine 1 and the automatic transmission 3, and shows an accelerator pedal 20.
A signal corresponding to the amount of depression of the engine electronic control unit 2
It is input to 1. The intake duct of the engine 1 is provided with an electronic throttle valve 23 driven by a throttle actuator 22. The electronic throttle valve 23 changes from the control device 21 to the throttle actuator 22 according to the depression amount of the accelerator pedal 20. A control signal is output, and the opening degree is controlled according to the control amount.

An engine rotation speed sensor 24 for detecting the rotation speed of the engine 1, an air flow meter 25 for detecting the intake air amount, an intake air temperature sensor 26 for detecting the temperature of the intake air, and an opening degree of the electronic throttle valve 23. throttle sensor 27 for detecting θ, vehicle speed sensor 28 for detecting vehicle speed V from the rotational speed of output shaft 17, etc., engine 1
A cooling water temperature sensor 29 for detecting the cooling water temperature, a brake switch 30 for detecting the operation of the brake, an operation position sensor 32 for detecting the operation position of the shift lever 31, and the like are provided. Signals representing the engine speed NE, the intake air temperature Tha, the opening degree θ of the electronic throttle valve 23, the vehicle speed V, the engine cooling water temperature THw, the brake operating state BK, and the operation position Psh of the shift lever 31 are output from these sensors. It is adapted to be supplied to the engine electronic control unit 21 and the shift electronic control unit 33. It should be noted that the shift electronic control unit 33 is inputted with the signals of the opening degree θ of the electronic throttle valve 23, the vehicle speed V, the engine cooling water temperature THw, and the brake operating state BK.

Further, a signal representing the turbine rotation speed NT is supplied from the turbine rotation speed sensor 34 for detecting the rotation speed of the turbine runner 7 to the transmission electronic control unit 33. Further, a kick down switch 35 for detecting that the accelerator pedal 20 has been operated to the maximum operation position.
A signal representing a kick down operation is input to the electronic shift control device 33.

It is possible to manually set the sport mode for selecting each shift speed in a state where the engine brake is effective, and these signals based on the manual operation, that is, the sport mode signal and the plus (+) for the upshift are set. The signal and the minus (-) signal for downshift are input to the electronic shift control device 33.

The engine electronic control unit 21 is a so-called microcomputer provided with a central processing unit (CPU), a storage device (RAM, ROM) and an input / output interface. The CPU uses the temporary storage function of the RAM. Meanwhile, the input signal is processed according to a program stored in advance in the ROM, and various engine controls are executed. For example, the fuel injection valve 37 is controlled to control the fuel injection amount,
Controls the igniter 38 for ignition timing control, controls a bypass valve (not shown) for idle speed control, and controls all throttles including traction control.
The throttle actuator 22 controls and executes the electronic throttle valve 23.

The shift electronic control unit 33 is also a microcomputer similar to the engine electronic control unit 21 described above, and the CPU uses the temporary storage function of the RAM and receives the input signal according to the program stored in the ROM in advance. As well as processing, each solenoid valve or linear solenoid valve of the hydraulic control circuit 38 is driven.
For example, the electronic shift control device 33 includes the throttle valve 23.
The linear solenoid valve SLT for generating the output pressure PSLT having a magnitude corresponding to the opening of the valve, the linear solenoid valve SLN for controlling the accumulator back pressure, and the slip amount of the lockup clutch 8 are controlled, and the speed change is performed. The linear solenoid valves SLU are respectively driven to control the engagement pressure of a predetermined clutch or brake during transition in accordance with the progress of gear shifting and according to the input torque.

Further, the electronic shift control device 33 uses the basic throttle valve opening degree θ (throttle opening degree converted by a predetermined nonlinear characteristic with respect to the depression amount of the accelerator pedal), the vehicle speed V, and a shift line using these as parameters. Based on the drawing, the gear stage of the automatic transmission 3 and the lockup clutch 8
Of the hydraulic pressure control circuit 38 so that the determined gear and engagement state are obtained.
1 to No. 3 solenoid valves SOL1, SOL2, SOL
When driving 3 to generate engine braking,
o. 4 solenoid valve SOL4.

On the other hand, the lock-up clutch 8 is released at the first speed and the second speed of the automatic transmission 3, but at the third speed and the fourth speed, it is based on the basic throttle valve opening θ and the vehicle speed V. The lock-up clutch 8 is slip-controlled in the slip region, and engaged in the engagement region. This slip control is intended to suppress the rotational loss of the torque converter 2 as much as possible while absorbing the rotational fluctuation of the engine 1.

FIG. 4 shows the operating position of the shift lever 31. In the figure, a combination of six operation positions in the front-rear direction of the vehicle and two operation positions in the left-right direction of the vehicle allows the shift lever 31 to be operated at eight operation positions by a supporting device (not shown) so that the shift lever 31 can be operated. It is supported. And P is the parking range position, R
Is the reverse range position, N is the neutral range position,
D is a drive range position, "4" is a "4" range position for setting a gear up to the fourth speed, "3" is a "3" range position for setting a gear up to the third speed, and "2" is The "2" range position is used to set the gears up to the second speed, and L is the low range position where the upshift to the first or higher gears is prohibited. Further, a switch for selecting a sport mode, a plus switch for outputting an upshift signal and a minus switch for outputting a downshift signal in the sport mode are provided.

As shown in FIG. 2, the automatic transmission 3 described above is
The shift between the second speed and the third speed is a clutch-to-clutch shift in which both the engagement states of the third brake B3 and the second brake B2 are switched. In the shift control, it is necessary to control the friction engagement device involved in the shift to the underlap or overlap state according to the power on / off state and the shift up / down state. It is necessary to control the hydraulic pressure of the second brake B2 in accordance with the input torque, and the hydraulic pressure of the third brake B3 in accordance with the progress of the shift. Therefore, the hydraulic control circuit 38 incorporates the circuit shown in FIG. 5 in order to smoothly and quickly execute this shift, and its configuration will be briefly described below.

In FIG. 5, reference numeral 70 indicates a 1-2 shift valve, reference numeral 71 indicates a 2-3 shift valve, and reference numeral 72 indicates a 3-4 shift valve. The communication state of each port of these shift valves 70, 71, 72 at each shift speed is determined by the respective shift valves 70, 71, 7
2 as shown below. The numbers indicate the respective gears. A third brake B3 is connected via an oil passage 75 to a brake port 74 that communicates with the input port 73 at the first speed and the second speed among the ports of the 2-3 shift valve 71. An orifice 76 is interposed in this oil passage, and the orifice 76 and the third brake B3
A damper valve 77 is connected between and. The damper valve 77 sucks a small amount of hydraulic pressure to perform a buffering action when the line pressure is suddenly supplied to the third brake B3.

Reference numeral 78 denotes a B-3 control valve, which controls the engagement pressure of the third brake B3 directly by the B-3 control valve 78. That is, the B-3 control valve 78 includes a spool 79, a plunger 80, and a spring 81 interposed therebetween, and an oil passage 75 is connected to an input port 82 opened and closed by the spool 79. Output port 8 that is selectively communicated with input port 82
3 is connected to the third brake B3. Further, the output port 83 is connected to a feedback port 84 formed on the distal end side of the spool 79. On the other hand, among the ports 85 of the 2-3 shift valve 71, a port 86 that outputs the D range pressure at the third or higher speed is provided through a hydraulic passage 87 to the port 85 that opens at the place where the spring 81 is disposed. Are in communication. A lockup clutch linear solenoid valve SLU is connected to a control port 88 formed on the end side of the plunger 80.

Therefore, the B-3 control valve 78
Is configured such that the pressure regulation level is set by the elastic force of the spring 81 and the hydraulic pressure supplied to the port 85, and the elastic force of the spring 81 increases as the signal pressure supplied to the control port 88 increases. There is.

Further, in FIG. 5, reference numeral 89 is a 2-3 timing valve. The 2-3 timing valve 89 includes a spool 90 having a small diameter land and two large diameter lands and a first plunger. 91, a spring 92 arranged between them, and a second plunger 93 arranged on the opposite side of the first plunger 91 with the spool 90 interposed therebetween. An oil passage 95 is connected to an intermediate port 94 of the 2-3 timing valve 89.
Is the port 9 of the 2-3 shift valve 71 that is communicated with the brake port 74 at the third or higher speed.
6 is connected.

Further, the oil passage 95 is branched in the middle, and a port 97 is opened between the small land and the large land.
Is connected via an orifice. The port 98, which is selectively communicated with the port 94 at the intermediate portion, is the oil passage 9
9 is connected to the solenoid relay valve 100. The lock-up clutch linear solenoid valve SLU is connected to the port opened at the end of the first plunger 91, and the second brake B2 is passed through the orifice at the port opened at the end of the second plunger 93. Connected.

The oil passage 87 is for supplying and discharging hydraulic pressure to and from the second brake B2, and a small-diameter orifice 101 and an orifice 102 with a check ball are interposed in the middle thereof. Further, the oil passage 103 branched from the oil passage 87 has a large diameter orifice 10 provided with a check ball that opens when the pressure is exhausted from the second brake B2.
4 is interposed, and this oil passage 103 is connected to an orifice control valve 105 described below.

The orifice control valve 105 is a valve for controlling the speed of exhausting the pressure from the second brake B2.
The oil passage 103 is connected to a port 108 formed below the port 107 in the figure. A port 109 formed above the port 107 to which the second brake B2 is connected in the drawing is a port that is selectively communicated with the drain port, and the port 109 is connected to the port 109 via an oil passage 110. The port 111 of the B-3 control valve 78 is connected. The port 111 is a port that is selectively communicated with the output port 83 to which the third brake B3 is connected.

A control port 112 formed at the end of the port of the orifice control valve 105 opposite to the spring for pressing the spool 106 is connected to a port 114 of the 3-4 shift valve 72 via an oil passage 113. ing. The port 114 is a port that outputs the signal pressure of the third solenoid valve SOL3 at the shift speed of the third speed or lower, and outputs the signal pressure of the fourth solenoid valve SOL4 at the shift speed of the fourth speed or higher. Further, the orifice control valve 105 has an oil passage 11 branched from the oil passage 95.
5 is connected to selectively connect the oil passage 115 to the drain port.

In the 2-3 shift valve 71, the port 11 for outputting the D range pressure at the second or lower speed is selected.
6 through the oil passage 11 at the port 117 opening at the position where the spring 92 is arranged in the 2-3 timing valve 89.
8 are connected. Also 3-4 shift valve 72
Of these, a port 119, which is communicated with the oil passage 87 at a speed lower than the third speed, is connected to the solenoid relay valve 100 via an oil passage 120.

In FIG. 5, reference numeral 121 denotes an accumulator for the second brake B2, and the back pressure chamber thereof is supplied with the accumulator control pressure adjusted according to the hydraulic pressure output by the linear solenoid valve SLN. There is. The accumulator control pressure is controlled according to the input torque, and the linear solenoid valve SLN
The lower the output pressure of, the higher the pressure. Therefore, the transitional hydraulic pressure of the engagement / disengagement of the second brake B2 is changed to a higher pressure as the signal pressure of the linear solenoid valve SLN is lower. Further, by temporarily lowering the signal pressure of the linear solenoid valve SLU, the engagement pressure of the second brake B2 can be temporarily raised.

Reference numeral 122 denotes a C-0 exhaust valve, and reference numeral 123 denotes an accumulator for the clutch C0. C-0 exhaust valve 1
Numeral 22 operates to engage the clutch C0 to apply the engine brake only in the second speed in the second speed range.

Therefore, according to the hydraulic circuit described above,
If the port 111 of the B-3 control valve 78 communicates with the drain, the engagement pressure of the third brake B3 can be directly regulated by the B-3 control valve 78, and the regulation level can be adjusted by the linear solenoid valve. SLU
Can be changed by If the spool 106 of the orifice control valve 105 is in the position shown in the left half of the figure, the second brake B2 can be communicated with the oil passage 103 through this orifice control valve 105, so that the large diameter orifice 104 is used. Exhaust pressure is possible and therefore the drain speed from the second brake B2 can be controlled.

The engagement pressure of each friction engagement device in the automatic transmission 3 described above is a pressure determined by the line pressure controlled according to the throttle opening θ in the engine 1,
For example, the engagement pressure PB3 of the third brake B3 during the shift between the second speed and the third speed, which is a clutch-to-clutch shift.
Is controlled on the basis of the progress of the shift. For example, the second
In the case of an upshift from the third speed to the third speed, the second brake B2 and the second brake B2 are controlled so as to have a predetermined torque capacity so that the input speed is reduced to the synchronous speed of the third speed. Let On the contrary, when downshifting from the third speed to the second speed, the engagement pressure of the third brake B3 is maintained at a low pressure to control so-called underlap, and the input speed is set to the second speed. Promote the increase to the synchronous speed. Also, at the end of the downshift to the second speed, the engagement pressure of the second brake B2 that is finally released is temporarily increased to reduce the torque, so that the shock caused by the torsion torque is reduced. To prevent.

The engine 1 to which the automatic transmission 3 described above is connected is capable of lean burn operation in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio, and releases NOx from the NOx absorbent during lean burn operation. Therefore, it is configured to execute the rich spike that temporarily sets the air-fuel ratio to the rich side. Then, explaining the engine 1, FIG. 6 schematically shows an intake and exhaust system,
A spark plug 132 is arranged in a combustion chamber 131 formed on the top side of the piston 130. Further, the combustion chamber 131 has an intake port 134 having an intake valve 133.
And the exhaust port 136 having the exhaust valve 135 are in communication with each other.

The intake port 134 is connected to the surge tank 138 via the corresponding manifold 137,
A fuel injection valve 139 for injecting fuel into the intake port 134 is attached to each of the manifolds 137. Further, the surge tank 138 has an intake duct 140.
And the air cleaner 14 via the air flow meter 25.
1, the throttle valve 23 in the intake duct 140.
Is arranged.

On the other hand, the exhaust port 136 is connected to the NOx absorbent 1 through the exhaust manifold 142 and the exhaust pipe 143.
It is connected to a casing 145 containing 44, and the casing 145 is further connected to a catalytic converter 147 via an exhaust pipe 146. The catalytic converter 147 contains a three-way catalyst 148.

Electronic control unit 2 for controlling this engine 1
1 comprises a digital computer, a bidirectional bus 1
ROM (Read Only Memory) 150, RAM (Random Access Memory) 1 mutually connected by 49
51, a CPU (microprocessor) 152, an input port 153 and an output port 154. The air flow meter 25 generates an output voltage proportional to the intake air amount, and this output voltage is input to the input port 153 via the AD converter 155. Further, the input port 153 is connected to a rotation speed sensor 24 that generates an output pulse representing the engine rotation speed. On the other hand, the output port 154 is connected to the spark plug 132 and the fuel injection valve 139 via the corresponding drive circuits 156 and 157, respectively.

As described above, the engine 1 includes the fuel injection valve 1
The fuel is supplied from 39, and the fuel injection time TAU is calculated based on the equation TAU = TP × Kt. Where TP represents the basic fuel injection time,
Kt represents a correction coefficient. Basic fuel injection time T
P is the fuel injection time required to make the air-fuel ratio of the air-fuel mixture supplied to the cylinder of the engine 1 the stoichiometric air-fuel ratio.

The basic fuel injection time TP is previously obtained by an experiment, and the engine load and the engine speed NE are represented by the intake air amount Q / NE (Q is the intake air amount, NE is the engine speed) per revolution. Is previously stored in the ROM 152 in the form of a map as shown in FIG. The correction coefficient Kt is a coefficient for controlling the air-fuel ratio of the air-fuel mixture supplied into the engine 1, and Kt = 1.0.
If so, the air-fuel mixture supplied to the cylinder has the stoichiometric air-fuel ratio. On the other hand, when Kt <1.0, the air-fuel ratio of the air-fuel mixture supplied into the cylinder becomes larger than the stoichiometric air-fuel ratio, and the engine 1 is in lean burn operation. Further, if Kt> 1.0, the air-fuel ratio of the air-fuel mixture supplied into the cylinder becomes smaller than the stoichiometric air-fuel ratio, resulting in a so-called rich state.

In the engine shown in FIG. 6, normally, for example, K
Since t = 0.7 or 0.6 is maintained, lean burn operation is performed. FIG. 8 shows the combustion chamber 1
31 schematically shows the concentrations of typical components in the exhaust gas discharged from 31. As is known from FIG. 8, the concentration of unburned HC and CO discharged from the combustion chamber 131 increases as the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 131 becomes richer, and is discharged from the combustion chamber 131. The concentration of oxygen O2 in the generated exhaust gas increases as the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 131 becomes leaner.

NO stored in the casing 145
The x-absorbent 144 uses, for example, alumina as a carrier, and potassium K, sodium Na, lithium L
i, alkali metals such as cesium Cs, barium Ba
, Alkaline earth such as calcium Ca, lanthanum La
, At least one selected from rare earths such as yttrium Y, and a noble metal such as platinum Pt.

The ratio of air and fuel supplied into the exhaust duct upstream of the intake duct and the NOx absorbent 144 is determined to be "NO."
x air-fuel ratio of the exhaust gas flowing into the absorbent 144 ",
The NOx absorbent 144 absorbs NOx when the air-fuel ratio of the inflowing exhaust gas is lean, and when the oxygen concentration in the inflowing exhaust gas decreases, it performs the absorbing and releasing action of the NOx that releases the absorbed NOx.

When fuel or air is not supplied into the exhaust pipe upstream of the NOx absorbent 144, the air-fuel ratio of the inflowing exhaust gas matches the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 131. Therefore, in this case, the NOx absorbent 144 absorbs NOx when the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 131 is lean, and the oxygen concentration in the air-fuel mixture supplied to the combustion chamber 131 decreases. Then, the absorbed N
It will release Ox.

As described above, in the engine shown in FIG.
Normally, the air-fuel mixture supplied to the cylinder is kept lean (for example, Kt = 0.7), and the N generated at this time is generated.
Ox is absorbed by the NOx absorbent 144. However, if the lean air-fuel mixture continues to be burned, the NOx absorbent 144
The NOx absorption capacity due to is saturated and NOx cannot be absorbed by the NOx absorbent 144 after a while. Therefore, when the lean air-fuel mixture is continuously burned, the control device according to the present invention temporarily enriches the air-fuel mixture (Kt = Kt =) as shown in FIG.
KK) so that the NOx absorbed by the NOx absorbent 144 is released from the NOx absorbent 144.
That is, the rich spike is executed.

In this case, if the air-fuel mixture supplied to the cylinder is simply switched from the lean air-fuel ratio to the rich air-fuel ratio, the engine output torque fluctuates. Therefore, in order to prevent such a situation, the lean air-fuel ratio and the rich air-fuel ratio are prevented. And are set. That is, as shown in FIG. 10, the engine output torque decreases when the air-fuel ratio becomes lean with the output air-fuel ratio (11.0 to 12.0) as a boundary.
In addition, the engine output torque decreases even when the air-fuel ratio becomes rich.

Therefore, as shown in FIG. 10, there are the lean air-fuel ratio (KL) and the rich air-fuel ratio (KK) at which the engine output torque becomes equal. So combustion chamber 1
When the lean air-fuel mixture is to be burned in 31, the air-fuel ratio at that time is set to the lean air-fuel ratio (KL), and the combustion chamber 13
When the rich air-fuel mixture is to be burnt within 1, the air-fuel ratio at that time is set to the rich air-fuel ratio (KK) and the ignition timing is switched to a value corresponding to each air-fuel ratio. When the lean air-fuel ratio and the rich air-fuel ratio are predetermined in this way, when the lean air-fuel ratio is switched to the rich air-fuel ratio and when the rich air-fuel ratio is switched to the lean air-fuel ratio, fluctuations in engine output torque and shock Is suppressed.

In this embodiment, the lean air-fuel ratio (K
L) is preset to be equivalent to Kt = 0.7,
Therefore, the rich air-fuel ratio (KK) is set so that an output torque equal to the engine output torque when using this lean air-fuel ratio is obtained. In this case, this rich air-fuel ratio (KK) depends on the engine load Q / NE and the engine speed N.
It becomes a function of E and this rich air-fuel ratio (KK) is shown in FIG.
As shown in FIG. 5, it is stored in the ROM 150 in advance in the form of a function of the engine load Q / NE and the engine speed NE.

Further, the action of releasing NOx from the NOx absorbent 144 is such that when a certain amount of NOx is absorbed by the NOx absorbent 144, NOx is absorbed up to about 50% of the absorption capacity of the NOx absorbent 144. Sometimes done. N
The amount of NOx absorbed by the Ox absorbent 144 is proportional to the amount of exhaust gas discharged from the engine and the NOx concentration in the exhaust gas, in which case the amount of exhaust gas is proportional to the amount of intake air,
Since the NOx concentration in the exhaust gas is proportional to the engine load, the NOx amount absorbed by the NOx absorbent 144 can be accurately estimated from the cumulative value of the product of the intake air amount and the engine load, but the control For simplicity, the NOx amount absorbed in the NOx absorbent 144 may be estimated from the cumulative value of the engine speed.

Next, the rich spike control in the above engine will be described. FIG. 12 shows a routine executed by the electronic control unit 21 at regular intervals. First, in step 1, the basic fuel injection time T
Whether the correction coefficient Kt for P is smaller than 1.0,
That is, it is determined whether or not the lean burn operation is being performed. When Kt ≧ 1.0, that is, when the air-fuel mixture supplied to the cylinder has the stoichiometric air-fuel ratio or the rich air-fuel ratio, the routine exits without performing any control.

On the other hand, when Kt <1.0, that is, when the lean air-fuel mixture is being combusted, step 2
Then, the result of adding ΣNE to the current engine speed NE is taken as ΣNE. Therefore, ΣNE represents the cumulative value of the engine speed NE. Next, at step 3, it is judged if the cumulative rotational speed ΣNE is larger than a constant value SNE. This constant value SNE is NOx absorbent 14
4 shows the cumulative rotational speed at which it is estimated that 50% of the NOx absorption capacity of the NOx is absorbed. Σ
When NE ≤ SNE, the routine returns, and when ΣNE> SNE, that is, when it is estimated that the NOx absorbent 144 has absorbed 50% of the NOx absorption capacity of the NOx absorption capacity, the routine proceeds to step 4, where the NOx release flag is set To be done. When the NOx release flag is set, the air-fuel mixture supplied into the cylinder is switched to rich as described later, and the ignition timing is retarded according to the air-fuel ratio of the air-fuel mixture.

Next, at step 5, the count value C is 1
Is only incremented. Next, at step 6, it is judged if the count value C has become larger than the constant value C0, that is, if 0.5 seconds has elapsed, for example. C ≦
When C0, the routine returns, and when C> C0, the routine proceeds to step 7, where the NOx releasing flag is reset. NO
When the x release flag is reset, the air-fuel mixture supplied into the cylinder is switched from rich to lean as described later. Therefore, the air-fuel mixture supplied into the cylinder is richly controlled for 0.5 second. Next, at step 8, the cumulative rotation speed ΣNE and the count value C are cleared.

FIG. 13 shows a routine for calculating the fuel injection time TAU. This routine is executed by the engine electronic control unit 21 at regular intervals (or at constant crankshaft rotation angles). In FIG. 13, first, at step 10, the basic fuel injection time TP is calculated from the map shown in FIG. Next, at step 11, it is judged if the NOx releasing flag is set. When the NOx release flag is not set, steps 12 and 13
Then, the correction coefficient Kt is set to 0.7, for example, and then the process proceeds to step 14. In step 14, fuel injection time TA
U (= TP * Kt) is calculated. At this time, the air-fuel mixture supplied into the cylinder is made lean.

On the other hand, when it is determined in step 11 that the NOx releasing flag is set, step 1
Proceeding to step 5, KK is calculated from the relationship shown in FIG. Then, in step 16, the value of the correction coefficient Kt is set to KK,
Go to step 14. Therefore, at this time, the air-fuel mixture supplied into the cylinder has a rich air-fuel ratio.

By the way, the actual air-fuel ratio may deviate from the controlled air-fuel ratio due to aging of the engine or the like.
In such a case, for example, an air-fuel ratio sensor (not shown)
Is preferably installed in the exhaust port 136, and the control value is corrected based on the detected actual air-fuel ratio.

Further, when performing a rich spike for temporarily setting the air-fuel ratio to the rich side during lean operation, even if the air-fuel ratio of the mixture supplied to the cylinder is reduced, the combustion chamber 13
The air-fuel ratio of the air-fuel mixture within 1 may change with a delay.
This is because the wall surface of the intake port 134 is in a dry state during lean operation, and when a rich air-fuel ratio mixture is supplied to this, a part of the fuel contained in the mixture adheres to the wall surface of the intake port, This is because the amount of fuel in the air-fuel mixture in the cylinder decreases.

Therefore, the air-fuel ratio in the combustion chamber 131 becomes smaller after the start of the rich spike control. Therefore, if the ignition timing is changed at the same time when the rich spike control is started, it is conceivable that the air-fuel ratio and the ignition timing become transiently incompatible with each other and the fluctuation of the engine output torque becomes large. In order to avoid such a situation, when changing the air-fuel ratio from lean to rich, or when changing from rich to lean, the ignition timing is changed by delaying the change of the air-fuel ratio, or the ignition timing is gradually changed. It is preferable to change to. Alternatively, when changing the air-fuel ratio from lean to rich, the fuel injection amount is increased at the start of control so as to compensate for the adhesion of fuel to the wall surface, and when changing from rich to lean, rich due to the detachment of fuel from the wall surface. It is preferable to decrease the fuel injection amount at the start of the control so as to compensate for the change. The transient control when switching these air-fuel ratios is specifically described in Japanese Patent Laid-Open No. 6-193487.

The above lean burn operation is executed in a state where exhaust gas and riding comfort are not deteriorated, and therefore, the lean burn operation permission region is set for each shift speed of the second speed or higher. This permission area is for engine speed NE
And the throttle opening θ are set as parameters, and an example thereof is shown in FIG. 14 when the region for the second speed is illustrated. In FIG. 14, the hatched region is the region in which lean burn operation is performed, but in the state where the throttle opening θ is zero, that is, in the idling state, in order to prevent the engine rotation from becoming unstable, Set the fuel ratio to stoichiometric or rich. Therefore, this idling state is a state where the throttle opening degree is extremely low in the present invention, and this state can be detected by, for example, turning on the idle switch.

On the other hand, since the automatic transmission is constructed so that the shift speed is set based on the throttle opening and the vehicle speed, when the throttle opening θ changes to the extremely low opening as described above, Upshift is determined. That is, as shown in FIG. 15, when the throttle opening θ is closed during traveling in the second speed, the traveling state changes from the point A to the point B across the upshift line to the third speed. An upshift from the third speed to the third speed is determined. This shift is a so-called clutch-to-clutch shift in which the third brake B3 is released and the second brake B2 is engaged, as described above, and these friction engagements are performed by the hydraulic circuit shown in FIG. The hydraulic pressure of the device is controlled and executed.

When the throttle opening θ is changed from the so-called middle opening or low opening during lean burn operation to an extremely low opening for idling, it is necessary to change the air-fuel ratio and shift gears. The control device of the present invention executes the control of the air-fuel ratio and the shift as follows.

FIG. 16 shows an example of the control routine. After processing the input signal (step 20),
It is judged whether or not lean burn control is in progress (step 2).
1). This is a determination step similar to step 1 in FIG. 12 described above, and the correction coefficient Kt for the fuel injection time
Can be determined depending on whether or not is set to a value smaller than "1.0".

If the lean burn control is being performed, it is determined whether the drive (D) range is selected (step 22). This is because the shift lever 31 has D shown in FIG.
It is a judgment as to whether or not the range position is set, and FIG.
It can be determined based on the output signal of the operation position sensor 32 shown in FIG.

If the D range is selected, the second
It is determined whether the off-up from the third speed to the third speed is established (step 23). That is, the accelerator pedal 20
Is returned to enter the power-off state, and it is determined whether or not the upshift should be performed. Therefore, this step 23 corresponds to the upshift detecting means in this invention. As described above, this shift is a clutch-to-clutch shift, in which the input torque is estimated based on the intake air amount, the intake pipe negative pressure, and the like, and the linear solenoid valve SLU uses the third torque based on the estimated torque. By controlling the regulated value of the hydraulic pressure of the brake B3 or by controlling the back pressure of the second brake accumulator 121 by the linear solenoid valve SLN, the hydraulic pressure of the second brake B2 is controlled to reduce the shift shock.
Instead of controlling the hydraulic pressure based on the estimated input torque, the timing of engagement of the friction engagement device involved in gear shifting may be controlled.

If an affirmative decision is made in step 4, it is judged whether or not the idle switch has been turned on due to the decrease in the throttle opening θ, which is to judge the upshift to the third speed, that is, whether the idle switch is on. It is determined whether or not (step 24). This step 24 corresponds to the power-off detecting means of the present invention. As described above, in the so-called extremely low opening state in which the idle switch is turned on, it is necessary to stabilize the combustion of the air-fuel mixture in the engine, so the air-fuel ratio is set to rich. Therefore, if an affirmative decision is made in step 24, the air-fuel ratio is changed to rich including the stoichiometric air-fuel ratio in step 25. Specifically, the correction coefficient Kt is set to "1" or more (Kt≥1). This step 25
Corresponds to the air-fuel ratio lowering means of the present invention.

After changing the air-fuel ratio in this way, it is determined whether or not the elapsed time TFri since the enrichment of the air-fuel ratio has reached a preset reference time TA (step 26).
This reference time TA is the time required for the air-fuel ratio to stabilize at a value determined by the correction coefficient Kt after the increased amount of fuel has adhered to the wall surface, and after this reference time has elapsed, that is, the air-fuel ratio is After stabilizing in the rich state, the upshift from the second speed to the third speed is executed (step 27). This step 27 corresponds to the upshift executing means of the present invention. Since this shift is executed in the power-off state, first, the hydraulic pressure of the third brake B3 is reduced to a so-called underlap state to reduce the engine speed toward the third speed synchronous speed. After that, the hydraulic pressure of the second brake B2 is gradually increased to the third hydraulic pressure.
Control to achieve speed. The specific control can be executed by a control device that has already been applied for or is publicly known.

During lean burn operation, the engine speed and the counter C are integrated because NOx must be released every predetermined period, but the throttle opening θ is extremely low as described above. Since the air-fuel ratio is made richer with the opening, the NOx release flag, the engine speed integrated value ΣNE, and the counter value C are reset (step 28).

It should be noted that, when the negative judgment is made in step 21 because the lean burn control is not performed or when the off-up from the second speed to the third speed is not judged, the negative judgment is made in step 23. In case, step 2
The process immediately proceeds to step 8 to reset the NOx releasing flag, the engine speed integrated value ΣNE, and the counter value C.

On the other hand, when the negative determination is made in step 22 because the D range is not selected, it is determined whether or not the sports mode is selected (step 2).
9). This sports mode is a mode in which the gear is selected manually and the engine brake is applied at all gears, and it is executed by the driver operating the sports mode switch and the upshift switch or the downshift switch. It Therefore, this determination can be made based on whether or not the sports mode switch is ON.

If the determination in step 29 is negative because the sports mode has not been selected, this routine is exited without performing any particular control, and if the sports mode has been selected, the second speed is started. It is determined whether or not the off-up to the third speed is established (step 3
0). This is the same judgment as in step 23 described above.

If a negative decision is made in step 30,
If this routine is exited without performing any particular control, and if an affirmative determination is made, then it is determined whether or not the idle switch is ON (step 31).

Since the idle is on, step 3
In the case of a positive determination in 1, the upshift from the second speed to the third speed and the switching of the air-fuel ratio are executed. In the control device according to the present invention, first, the air-fuel ratio is enriched. (Rich switching) is prohibited (step 32).
In that state, the off-up from the second speed to the third speed is executed (step 33).

That is, the shift is executed with priority given to the improvement of drivability due to the enrichment of the air-fuel ratio. This is because in the sports mode, it is considered that the driver intentionally upshifts and wants to shift to the third speed. The third speed in this case is the third speed when the engine braking is effective.

In this way, the completion of the upshift from the second speed to the third speed, which is executed with priority, is judged from the data obtained by the timer or the rotation speed sensor (step 3
4) After the shift is completed, the air-fuel ratio is switched to rich (step 35). Then, the process proceeds to step 29, where NO
x The emission flag, the engine speed integrated value ΣNE, and the counter C are reset.

If a negative determination is made in step 31 because the engine is not idle-on, an off-up shift from second speed to third speed is immediately executed (step 36).
This is because the air-fuel ratio is kept lean.

If the idle switch is not ON even if it is determined that the second speed is off to the third speed, that is, if the determination in step 24 is negative, the second speed is immediately set.
A power-off upshift from the third speed to the third speed is executed (step 37).

Therefore, according to the above control, when it is judged that the throttle opening is switched to the extremely low opening and the off-up and the enrichment of the air-fuel ratio are judged, it is caused by the change of the running state in the D range. In the case of the shift, the air-fuel ratio is enriched prior to the off-up shift, so that it is possible to prevent deterioration of drivability due to instability of combustion of the air-fuel mixture in the engine.

In the above embodiment, the second speed to the third speed are used.
Although the description has been given by taking the off-up to the high speed as an example, the present invention is not limited to the above-described embodiment and can be applied to other off-up shifts. And in the case of off-up gear shifting that applies a one-way clutch,
Since there is no need to control the hydraulic pressure based on the input torque,
As in the case of the sport mode described above, the gear shift may be executed prior to the enrichment of the air-fuel ratio. The automatic transmission targeted by the present invention may have a gear train other than the gear train shown in FIG. 1 or a hydraulic circuit other than the hydraulic circuit shown in FIG. Further, the shift device for executing the sport mode is provided with a shift position corresponding to each shift stage in addition to a manually operated upshift switch and downshift switch, and a shift lever is provided at these shift positions. A known shift device such as a moving type or a type in which the up and down switches are turned on by a shift lever can be employed.

[0085]

As described above, according to the present invention,
When the throttle opening becomes extremely low and it is determined that the power-off / upshift and the enrichment of the air-fuel ratio have been made, the air-fuel ratio is changed prior to shifting, so the throttle opening is extremely low. It is possible to prevent a situation where the air-fuel ratio is kept lean even though the opening degree is low, and to avoid deterioration of drivability.

[Brief description of the drawings]

FIG. 1 is a skeleton diagram showing an example of a gear train of an automatic transmission targeted by the present invention.

FIG. 2 is a diagram showing an engagement operation table of a friction engagement device for setting each shift speed in the automatic transmission.

FIG. 3 is a control system diagram for the engine and the automatic transmission.

FIG. 4 is a diagram showing an arrangement of each range position in the shift device.

FIG. 5 is a diagram showing a part of a hydraulic circuit for controlling hydraulic pressures of second and third brakes that perform shift between clutch second and clutch third speeds. is there.

FIG. 6 is a diagram schematically showing an intake / exhaust system and an air-fuel ratio control system of an engine which is a target of the present invention.

FIG. 7 is a diagram showing a map of basic fuel injection time.

FIG. 8: Unburned H in exhaust gas discharged from the engine
It is a diagram which shows the concentration of C, CO, and oxygen roughly.

FIG. 9 is a diagram for explaining NOx release control.

FIG. 10 is a diagram for explaining the relationship between engine torque and air-fuel ratio.

FIG. 11 is a diagram showing a map of a correction coefficient KK.

FIG. 12 is a flowchart showing an example of NOx release control from a NOx absorbent.

FIG. 13 is a flowchart showing an example of fuel injection amount control.

FIG. 14 is a diagram schematically showing a lean burn region for the second speed.

FIG. 15 is a shift diagram showing only an upshift line for explaining an upshift from the second speed to the third speed.

FIG. 16 is a flowchart showing a control routine for changing the air-fuel ratio and changing gears when the throttle opening becomes extremely low.

[Explanation of symbols]

 1 Engine 3 Automatic Transmission 21 Electronic Control Device for Engine 33 Electronic Control Device for Shift

Claims (1)

[Claims] 1. The air-fuel ratio is controlled to a rich state including the stoichiometric air-fuel ratio when the throttle opening is extremely low, and is controlled to be lean when the throttle opening is larger than the extremely low opening. In an automatic transmission control device for a vehicle in which an internal combustion engine is connected to an automatic transmission that changes gears based on changes in the running state, including changes in the throttle opening, the throttle opening is extremely low during running. Power-off detection means for detecting that the throttle opening has fallen to an extremely low opening, and an up-shift for determining an upshift in the automatic transmission based on the fact that the power-off detection means has detected that the throttle opening has dropped to an extremely low opening. When the upshift is determined by the shift determining means and the upshift determining means, the air-fuel ratio is made rich when the throttle opening is reduced to an extremely low opening. A ratio reduction unit, the control system for an automatic transmission, characterized by comprising an up-shift executing means for executing the upshift after the air-fuel ratio is made rich by the air-fuel ratio decrease means.