JP3620131B2 - Engine and automatic transmission control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention controls an engine capable of executing lean burn operation with a large air-fuel ratio, and an automatic transmission connected to the engine and capable of selecting a shift based on manual operation and a shift based on the state of the vehicle. It is related with the apparatus for doing.
[0002]
[Prior art]
When the vehicle is heavily loaded with the accelerator pedal depressed, it is necessary to increase the engine output by supplying a large amount of fuel to the cylinder, especially when running at a constant vehicle speed above a predetermined speed. Since no acceleration force is required, it is preferable to reduce the fuel supplied to the cylinder while maintaining the engine speed. That is, it is desirable to perform lean burn by reducing the amount of fuel without changing the total amount of air-fuel mixture supplied to the cylinder at low load at so-called cruise speed. Recently, an engine capable of meeting such a demand has been developed and put into practical use.
[0003]
As described above, the lean burn operation is executed in a state where the vehicle speed is equal to or higher than a predetermined value and the engine load is low. The air-fuel ratio has also been changed to a larger value. In that case, the ignition timing suitable for the air-fuel ratio is used to prevent a decrease in torque and exhaust gas. One example is described in, for example, Japanese Patent Application Laid-Open No. 6-17732.
[0004]
On the other hand, recently, an automatic transmission has been frequently used as a transmission for a vehicle, but in order to more reflect the driver's intention in the shift, a shift mode in which the shift is executed based on a manual operation. An automatic transmission that can be selected has been developed and put into practical use. For example, an upshift signal and a downshift signal are selectively output based on a manual operation in a drive range state, and the upshift or downshift is performed one speed at a time based on these signals. This so-called manual shift mode (or direct mode, sport mode) is often selected for greater acceleration than in normal driving. Therefore, it is preferable to control the engine in accordance with the requirements, for example, In the invention described in Japanese Utility Model Laid-Open No. 5-26064, when the manual shift mode is selected, the engine output is controlled to increase.
[0005]
[Problems to be solved by the invention]
The execution of the lean burn operation described above is determined by the engine control device based on the traveling state of the vehicle such as the throttle opening and the vehicle speed. On the other hand, the selection of the manual shift mode described above in the automatic transmission is executed by the driver operating a switch or a shift device. Therefore, in a vehicle in which an automatic transmission capable of selecting the manual shift mode is connected to the engine capable of the lean burn operation, the lean burn operation and the manual shift mode are selected independently. In some cases, the manual transmission mode is selected in the automatic transmission while the engine is in lean burn operation.
[0006]
In such a case, although the driver is requesting a shift by selecting the manual shift mode, the engine has a relatively large output torque fluctuation in the lean burn state, and as a result, a shift shock may occur. was there.
[0007]
The present invention has been made against the background of the above circumstances, and provides a control device capable of improving fuel efficiency and reducing shift shock in a mode in which shift based on manual operation is executed. It is the purpose.
[0008]
According to the present invention, this object is achieved by prohibiting lean burn control in the engine in a state in which a mode in which a shift in the automatic transmission is performed based on a manual operation is selected.
[0009]
[Means for Solving the Problem and Action]
In order to achieve the above-mentioned object, according to the present invention, an engine capable of lean burn operation with a large air-fuel ratio is shifted based on a first shift mode in which a shift is executed based on manual operation and the state of the vehicle. In the engine and the automatic transmission control apparatus to which the automatic transmission capable of selecting the second shift mode to be executed is connected and the first shift mode for executing the shift based on the manual operation is selected. Does not allow lean burn operation with the engine.A means for stopping, and when switching from the lean burn operation to an operation state in which the air-fuel ratio is reduced as the first shift mode is selected and switched from the second shift mode to the first shift mode, And a means for switching to the first shift mode after a predetermined time has elapsed after switching from lean burn operation to an operation state with a reduced air-fuel ratio.Is.
Further, the present invention provides a first shift mode for executing a shift based on a manual operation and a second shift mode for executing a shift based on the state of a vehicle in an engine capable of lean burn operation with an increased air-fuel ratio. In the engine and the automatic transmission control apparatus to which the automatic transmission capable of selecting the transmission is connected, the second shift mode for executing the shift based on the state of the vehicle is selected, and the second shift mode is In a state where lean burn operation is performed, after the second speed change mode is selected and the first speed change mode is switched to the second speed change mode and a predetermined time elapses, the air fuel ratio is reduced. Means for switching to lean burn operation is provided.
[0010]
Therefore, in the present invention, when the mode for executing the shift based on the manual operation is selected as the shift mode in the automatic transmission, the air-fuel ratio in the engine is set smaller than in the lean burn operation, and the engine Since the torque is stable, shift shock can be reduced. Further, when switching from the first shift mode to the second shift mode and switching from lean burn operation to operation with a low air-fuel ratio, the change mode is switched after a predetermined time has elapsed after switching to operation with a low air-fuel ratio. .
Further, when switching from the second shift mode to the first shift mode and switching from the low air-fuel ratio operation state to the lean burn operation, after a predetermined time has elapsed after switching the shift mode in the low air-fuel ratio operation state, Switch to lean burn operation.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described more specifically based on the drawings. The engine that is the subject of this invention is an engine that performs lean burn operation based on the state of the vehicle such as the throttle opening and the vehicle speed, and the automatic transmission connected to this engine includes the throttle opening and the vehicle speed. This is an automatic transmission capable of selecting a shift based on the state of the vehicle and a shift based on a manual operation. First, an example of the automatic transmission will be described with reference to FIG.
[0012]
In FIG. 1, an automatic transmission 3 is connected to an engine 1 via a torque converter 2. The torque converter 2 includes 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 direct connection between the pump impeller 5 and the turbine runner 7. And a stator 10 that is prevented from rotating in one direction by a one-way clutch 9.
[0013]
The automatic transmission 3 includes a sub-transmission unit 11 that switches between two stages of high and low, and a main transmission unit 12 that can switch between a reverse gear stage and four forward stages. The subtransmission unit 11 is supported by the sun gear S0, the ring gear R0, and the carrier K0 and is rotatably supported by the sun gear S0 and the ring gear R0. A clutch C0 and a one-way clutch F0 provided between the sun gear S0 and the housing 19, and a brake B0 provided between the sun gear S0 and the housing 19.
[0014]
The main transmission 12 is supported by the sun gear S1, the ring gear R1, and the carrier K1 and is rotatably supported by the sun gear S1 and the ring gear R1, and the first planetary gear unit 14 comprising the pinion P1, the sun gear S2, the ring gear R2 , And a second planetary gear unit 15 comprising a pinion P2 rotatably supported by the carrier K2 and meshed with the sun gear S2 and the ring gear R2, and supported rotatably by the sun gear S3, the ring gear R3, and the carrier K3. A third planetary gear unit 16 comprising a pinion P3 meshed with the sun gear S3 and the ring gear R3.
[0015]
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, and the carrier K3 is connected to the output shaft 17. The ring gear R2 is 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.
[0016]
Further, a band-type first brake B1 for stopping the rotation of the sun gear S1 and the sun gear S2 is provided in the housing 19 as a brake means. A first one-way clutch F1 and a brake B2 are provided in series between the sun gear S1 and sun gear S2 and the housing 19. The first one-way clutch F <b> 1 is configured to be engaged when the sun gear S <b> 1 and the sun gear S <b> 2 try to reversely rotate in the direction opposite to the input shaft 6.
[0017]
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. . The second 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, and brakes B0, B1, B2, B3, B4 are hydraulic friction engagement devices in which a friction material is engaged when hydraulic pressure acts.
[0018]
In the above automatic transmission, five forward speeds and reverse speeds can be set, and the engagement / release states of the respective friction engagement devices for setting these shift speeds are shown in the engagement operation table of FIG. It is shown in In FIG. 2, a circle indicates an engaged state, and a cross indicates a released state.
[0019]
FIG. 3 is a control system diagram for the engine 1 and the automatic transmission 3, and a signal corresponding to the depression amount of the accelerator pedal 20 is input to the engine electronic control device 21. Further, an electronic throttle valve 23 driven by a throttle actuator 22 is provided in the intake duct of the engine 1, and this electronic throttle valve 23 is connected 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.
[0020]
Further, an engine rotation speed sensor 24 that detects the rotation speed of the engine 1, an air flow meter 25 that detects the amount of intake air, an intake air temperature sensor 26 that detects the temperature of intake air, and an opening θ of the electronic throttle valve 23 are detected. A throttle sensor 27 that detects the vehicle speed V from the rotational speed of the output shaft 17, a cooling water temperature sensor 29 that detects the coolant temperature of the engine 1, a brake switch 30 that detects the operation of the brake, and an operation by the shift device An operation position sensor 31 for detecting a position, a direct mode (DM) switch (sport mode switch) 32 for executing a shift based on a manual operation, a shift switch 33 for instructing a shift in the direct mode, and the like are provided. From these sensors, the engine speed N, the intake air temperature Tha, the intake air amount Q, 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 signals are output to the engine electronic control unit. 21 is input. A signal indicating the shift operation position Psh, a signal for selecting the direct mode, or a signal for instructing a shift in the direct mode is input to the shift electronic control unit 34. It should be noted that the shift electronic control unit 34 is inputted with signals of the opening degree θ of the electronic throttle valve 23, the vehicle speed V, the engine coolant temperature THw, and the brake operating state BK.
[0021]
Further, a signal representing the turbine rotational speed NT is supplied to the shift electronic control unit 34 from a turbine rotational speed sensor 35 that detects the rotational speed of the turbine runner 7. Further, a signal representing the kick-down operation is input to the shift electronic control device 33 from the kick-down switch 36 that detects that the accelerator pedal 20 has been operated to the maximum operation position.
[0022]
The engine electronic control device 21 is a so-called microcomputer provided with a central processing unit (CPU), a storage device (RAM, ROM), and an input / output interface. The input signal is processed in accordance with the program stored in, and various engine controls are executed. For example, the fuel injection valve 37 is controlled for fuel injection amount control, the igniter 38 is controlled for ignition timing control, a bypass valve (not shown) is controlled for idle speed control, and all throttles including traction control are controlled. The control is executed by controlling the electronic throttle valve 23 by the throttle actuator 22.
[0023]
The shift electronic control unit 34 is also a microcomputer similar to the engine electronic control unit 21 described above, and the CPU uses a temporary storage function of the RAM to process an input signal in accordance with a program stored in advance in the ROM. Each solenoid valve or linear solenoid valve of the hydraulic control circuit 39 is driven. For example, the shift electronic control unit 34 uses a linear solenoid valve SLT to generate an output pressure PSLT having a magnitude corresponding to the opening of the throttle valve 23, a linear solenoid valve SLN to control the accumulator back pressure, The linear solenoid valve SLU is driven in order to control the slip amount of the lock-up clutch 8 and to control the engagement pressure of a predetermined clutch or brake at the time of shifting transition according to the progress of shifting and according to the input torque.
[0024]
Further, the shift electronic control unit 34 is based on a basic throttle valve opening θ (throttle opening converted by a predetermined nonlinear characteristic with respect to the depression amount of the accelerator pedal), the vehicle speed V, and a shift diagram using these as parameters. The gear position of the automatic transmission 3 and the engagement state of the lock-up clutch 8 are determined, and No. 2 in the hydraulic control circuit 39 is set so that the determined gear position and engagement state can be obtained. 1 to No. When the solenoid valves SOL1, SOL2, and SOL3 of No. 3 are driven to generate engine brake, The fourth solenoid valve SOL4 is configured to be driven.
[0025]
On the other hand, the lockup clutch 8 is released at the first speed and the second speed of the automatic transmission 3, but is released based on the basic throttle valve opening θ and the vehicle speed V at the third speed and the fourth speed. Either the slip region or the engagement region is determined. If the slip region, the lock-up clutch 8 is slip-controlled, and if the slip region is engaged, the lock-up clutch 8 is engaged. This slip control is for suppressing the rotational loss of the torque converter 2 as much as possible while absorbing the rotational fluctuation of the engine 1.
[0026]
As described above, the automatic transmission 3 described above can select a direct mode for executing a shift based on a manual operation, and a shift device having the configuration shown in FIGS. 4 and 5 is provided to execute the direct mode. It has been. First, FIG. 4 shows the operation position selected by the shift lever. In the figure, the shift lever is supported by a support device (not shown) that supports the shift lever so that it can be operated to eight operation positions by combining six operation positions in the front-rear direction of the vehicle and two operation positions in the left-right direction of the vehicle. ing. P is the parking range position, R is the reverse range position, N is the neutral range position, D is the drive range position, “4” is the “4” range position for setting the gear stage up to the fourth speed, and “3” is the first position. "3" range position for setting up to 3rd speed, "2" for "2" range position for setting up to 2nd speed, L forbids upshifting to 1st or higher speed Indicates the low range position to be performed.
[0027]
These operation positions (range positions) are connected by a groove for guiding the shift lever. As shown in FIG. 5, the grip portion 41 of the shift lever 40 that can be moved by manual operation in the groove An upshift switch (+ switch) 42 and a downshift switch (−switch) 43 are provided. These switches 42 and 43 correspond to the shift switch 33, and each time the upshift switch 42 is turned ON, the shift electronic control device 34 outputs a command signal for upshifting one step, and the downshift Each time the shift switch 43 is turned ON once, the shift electronic control unit 34 outputs a command signal for downshifting by one step.
[0028]
The positions of these switches 42 and 43 in the front-rear direction of the vehicle are as shown in FIG. Further, in order to prevent an overrun in which the engine speed increases excessively, or to prevent an excessive shortage of acceleration performance, a shift prohibited area when the upshift switch 42 or the downshift switch 43 is turned on is provided. Setting is optional.
[0029]
FIG. 6 schematically shows another shift device, and the P range position, R range position, N range position, D range position, “3” range position, “2” range position, and L range position are linearly shown. These are connected by linear grooves 44, and an H-shaped groove 45 is intersected at the center at the D range position, and the four apex portions of the H-shaped groove 45 are the first to fourth speeds. The shift position sensors S1st, S2nd, S3rd, S4th corresponding to the shift switch 33 are arranged. These shift speed sensors S1st, S2nd, S3rd, and S4th are connected to the shift electronic control unit 34 and are turned on by a shift lever 46 that is moved in the grooves 44 and 45, respectively. The shift electronic control unit 34 is configured to output a command signal for setting the changed gear. Even in such a configuration, it is optional to prohibit the setting of a predetermined gear position according to the state of the vehicle.
[0030]
Although not specifically shown, a short straight groove branched from the D range position is formed in parallel with the straight groove 44 shown in FIG. 6, and an upshift switch and a downshift switch shown in FIG. It is also possible to employ a shift device provided with Further, the direct mode switch 32 described above may be attached to the shift levers 40 and 46, or in the shift device shown in FIG. 6, it is detected that the shift lever 46 has moved from the D range position to the H-shaped groove 45. May be a sensor that outputs.
[0031]
The engine 1 to which the automatic transmission 3 described above is connected can perform a lean burn operation in which the air-fuel ratio is larger than the stoichiometric air-fuel ratio, and in order to release NOx from the NOx absorbent during the lean burn operation, A rich spike for temporarily setting the air-fuel ratio to the rich side is configured to be executed. The engine 1 will be described below. FIG. 7 schematically shows an intake / exhaust system. A spark plug 132 is disposed in a combustion chamber 131 formed on the top side of the piston 130. The combustion chamber 131 communicates with an intake port 134 having an intake valve 133 and an exhaust port 136 having an exhaust valve 135.
[0032]
The intake port 134 is connected to a surge tank 138 via a corresponding manifold 137, and a fuel injection valve 139 that injects fuel into the intake port 134 is attached to each manifold 137. The surge tank 138 is connected to the air cleaner 141 via the intake duct 140 and the air flow meter 25, and the throttle valve 23 is disposed in the intake duct 140.
[0033]
On the other hand, the exhaust port 136 is connected to a casing 145 containing NOx absorbent 144 via an exhaust manifold 142 and an exhaust pipe 143, and the casing 145 is connected to a catalytic converter 147 via an exhaust pipe 146. The catalytic converter 147 includes a three-way catalyst 148.
[0034]
The electronic control device 21 for controlling the engine 1 is composed of a digital computer and includes a ROM (Read Only Memory) 150, a RAM (Random Access Memory) 151, and a CPU (Microprocessor) 152 connected to each other by a bidirectional bus 149. The input port 153 and the output port 154 are provided. The air flow meter 25 generates an output voltage proportional to the amount of intake air, and this output voltage is input to the input port 153 via the AD converter 155. The input port 153 is connected to a rotational speed sensor 24 that generates an output pulse representing the engine rotational speed. On the other hand, the output port 154 is connected to the spark plug 132 and the fuel injection valve 139 via corresponding drive circuits 156 and 157, respectively.
[0035]
As described above, the engine 1 is configured to be supplied with fuel from the fuel injection valve 139, and the fuel injection time TAU is:
TAU = TP × Kt
It is calculated based on the following formula. Here, TP represents the basic fuel injection time, and Kt represents a correction coefficient. The basic fuel injection time TP is a fuel injection time necessary for setting the air-fuel ratio of the air-fuel mixture supplied to the cylinder of the engine 1 to the stoichiometric air-fuel ratio.
[0036]
This basic fuel injection time TP is obtained in advance by experiments, and is calculated as a function of the engine load and engine speed N expressed by the intake air amount Q / N per rotation (Q is the intake air amount, N is the engine speed). It is stored in advance 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. If Kt = 1.0, the air-fuel mixture supplied into the cylinder becomes the stoichiometric air-fuel ratio. On the other hand, if 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 operated in lean burn. 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, and a so-called rich state is obtained.
[0037]
In the engine shown in FIG. 7, normally, for example, Kt = 0.7 or 0.6 is maintained, and therefore lean burn operation is performed. FIG. 9 schematically shows the concentration of typical components in the exhaust gas discharged from the combustion chamber 131. As is known from FIG. 9, 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 O 2 in the exhaust gas to be increased increases as the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 131 becomes leaner.
[0038]
The NOx absorbent 144 accommodated in the casing 145 uses, for example, alumina as a carrier, and an alkali metal such as potassium K, sodium Na, lithium Li, cesium Cs, barium Ba, calcium Ca, etc. on the carrier. At least one selected from alkaline earths, lanthanum La, rare earth such as yttrium Y, and a noble metal such as platinum Pt are supported.
[0039]
If the ratio of air and fuel supplied into the exhaust duct upstream of the intake duct and the NOx absorbent 144 is “the air-fuel ratio of the exhaust gas flowing into the NOx absorbent 144”, the NOx absorbent 144 When the air-fuel ratio of the exhaust gas is lean, NOx is absorbed, and when the oxygen concentration in the inflowing exhaust gas is below, the NOx absorption / release action is performed to release the absorbed NOx.
[0040]
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. In this case, the NOx absorbent 144 absorbs NOx when the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 131 is lean, and absorbs when the oxygen concentration in the air-fuel mixture supplied into the combustion chamber 131 decreases. The released NOx is released.
[0041]
If the NOx absorbent 144 is disposed in the exhaust pipe, the NOx absorbent 144 actually performs the NOx absorption and release action, but there are some unclear parts about the detailed mechanism of this absorption and release action. However, it is considered that this absorption and release action is performed by a mechanism as shown in FIG. This mechanism will be described by taking as an example the case where platinum Pt and barium Ba are supported on the carrier, but the same mechanism can be obtained by using other noble metals, alkali metals, alkaline earths, and rare earths.
[0042]
That is, when the inflowing exhaust gas becomes considerably lean, the oxygen concentration in the inflowing exhaust gas greatly increases, and as shown in FIG.₂ ⁻  Or O^2-It adheres to the surface of platinum Pt. On the other hand, NO in the inflowing exhaust gas is O on the surface of platinum Pt.₂ ⁻  Or O^2-Reacts with NO₂  (2NO + O₂  → 2NO₂  ).
[0043]
Next, 2NO generated₂  Is oxidized on platinum Pt while being absorbed in the absorbent 144 and combined with barium oxide BaO, as shown in FIG.₃ ⁻Is absorbed in the absorbent 144 in the form of In this way, NOx is absorbed into the NOx absorbent 144.
[0044]
NO on the platinum Pt surface as long as the oxygen concentration in the inflowing exhaust gas is high₂  As long as the NOx absorption capacity of the absorbent is not saturated₂  Is absorbed into the absorbent and nitrate ion NO.₃ ⁻Is generated. On the other hand, the oxygen concentration in the inflowing exhaust gas decreases and NO₂  When the amount of produced decreases, the reaction proceeds in the reverse direction (NO₃ ⁻→ NO₂  ) And, as a result, nitrate ion NO in the absorbent₃ ⁻Is NO₂  Is released from the absorbent in the form of That is, when the oxygen concentration in the inflowing exhaust gas decreases, NOx is released from the NOx absorbent 144. As shown in FIG. 9, if the oxygen concentration in the inflowing exhaust gas decreases, and therefore the degree of leanness of the inflowing exhaust gas is decreased, NOx is released from the NOx absorbent 144 even if the inflowing exhaust gas is lean. It will be.
[0045]
On the other hand, when the air-fuel ratio of the inflowing exhaust gas is made rich at this time, as shown in FIG. 9, a large amount of unburned HC and CO are discharged from the engine 1, and these unburned HC and CO are oxygen O on platinum Pt.₂ ⁻  Or O^2-It reacts with and oxidizes. Further, when the air-fuel ratio of the inflowing exhaust gas is made rich, the oxygen concentration in the inflowing exhaust gas extremely decreases, so that the NO from the absorbent.₂  Is released and this NO₂  As shown in FIG. 10B, it is reduced by reacting with unburned HC and CO. In this way, NO on the surface of platinum Pt.₂  NO from the absorbent to the next₂  Is released. Therefore, when the air-fuel ratio of the inflowing exhaust gas is made rich, NOx is released from the NOx absorbent 144 in a short time.
[0046]
That is, when the air-fuel ratio of the inflowing exhaust gas is made rich, first, unburned HC and CO are converted into O on platinum Pt.₂ ⁻  Or O^2-It immediately reacts and is oxidized, and then O on platinum Pt.₂ ⁻  Or O^2-If unburned HC and CO still remain after the consumption of NOx, NOx released from the absorbent and NOx discharged from the engine are reduced by the unburned HC and CO. Therefore, to reduce the total NOx released from the absorbent and the total NOx discharged from the engine when the air-fuel ratio of the inflowing exhaust gas is made rich, at least O on platinum Pt.₂ ⁻  Or O^2-Therefore, it is necessary to control the richness of the air-fuel ratio of the inflowing gas so that the amount of unburned HC and CO necessary to consume the fuel flows into the NOx absorbent 144.
[0047]
As described above, in the engine shown in FIG. 7, the air-fuel mixture supplied into the cylinder is normally maintained lean (for example, Kt = 0.7), and NOx generated at this time is absorbed by the NOx absorbent 144. Is done. However, if the lean air-fuel mixture continues to be burned, the NOx absorption capacity of the NOx absorbent 144 is saturated, and after a while, the NOx absorbent 144 cannot absorb NOx. Therefore, when the lean air-fuel mixture is continuously burned, the control device according to the present invention temporarily controls the air-fuel mixture supplied into the cylinder to be rich (Kt = KK) as shown in FIG. The NOx absorbed by the NOx absorbent 144 is released from the NOx absorbent 144. That is, rich spike is executed.
[0048]
In that case, the engine output torque fluctuates simply by switching the air-fuel mixture supplied into the cylinder from the lean air-fuel ratio to the rich air-fuel ratio. Therefore, the lean air-fuel ratio and the rich air-fuel ratio are set so that such a situation does not occur. Has been. That is, as shown in FIG. 12, the engine output torque decreases when the air-fuel ratio becomes leaner with the output air-fuel ratio (11.0 to 12.0) as a boundary, and the air-fuel ratio becomes richer. However, the engine output torque decreases.
[0049]
Therefore, as shown in FIG. 12, there are a lean air-fuel ratio (KL) and a rich air-fuel ratio (KK) at which the engine output torque becomes equal. Therefore, when the lean air-fuel mixture should be burned in the combustion chamber 131, the air-fuel ratio at that time is set to the lean air-fuel ratio (KL), and when the rich air-fuel mixture is to be burned in the combustion chamber 131, 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. Thus, when the lean air-fuel ratio and the rich air-fuel ratio are determined in advance, when the lean air-fuel ratio is switched from the lean 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.
[0050]
In this embodiment, the lean air-fuel ratio (KL) is set in advance to be equivalent to, for example, Kt = 0.7, so that an output torque equal to the engine output torque when using this lean air-fuel ratio is obtained. A rich air-fuel ratio (KK) is set. In this case, the rich air-fuel ratio (KK) is a function of the engine load Q / N and the engine speed N, and the rich air-fuel ratio (KK) is determined by the engine load Q / N and the engine speed as shown in FIG. It is stored in the ROM 150 in advance in the form of a function of N.
[0051]
By the way, the rich air-fuel ratio KK ′ in FIG. 11 is obtained when the air-fuel ratio of the air-fuel mixture supplied into the cylinder is switched from the lean air-fuel ratio (Kt = 0.7) to the rich air-fuel ratio (Kt = KK ′). O on Pt₂ ⁻  It shows the air-fuel ratio at which unburned components necessary to consume NOx and to reduce all NOx are generated. In the above engine, the rich air-fuel ratio (KK) at the time of the rich spike is set to an air-fuel ratio further richer than the rich air-fuel ratio (KK ′), so that the NOx absorbent 144 has no platinum on Pt. O₂ ⁻  As a result, unburned components necessary to consume NOx and reduce all NOx are supplied, and as a result, NOx is reduced well.
[0052]
However, in that case, surplus unburned components will be discharged from the NOx absorbent 144, and therefore, it is necessary to oxidize this surplus unburned components. Therefore, a catalytic converter 147 containing a catalyst 148 having a storage function is disposed in the exhaust pipe downstream of the NOx absorbent 144, and unburned components are oxidized by this catalyst.
[0053]
In other words, the catalyst 148 includes, for example, alumina as a carrier, and a noble metal, an alkaline earth such as calcium Ca, and cesium Ce are supported on the carrier. When cesium Ce is supported on the carrier in this way, the catalyst 148 adsorbs and holds oxygen contained in the exhaust gas when the air-fuel ratio of the exhaust gas flowing into the catalyst 148 is lean, and flows into the catalyst 148. When the air-fuel ratio of the fuel becomes rich, the unburned HC and CO take away the oxygen that has been adsorbed and retained.₂  It comes with a storage function. Therefore, such O₂  If the catalyst 148 having a storage function is disposed in the exhaust pipe downstream of the NOx absorbent 144, a large amount of oxygen is adsorbed and held by the catalyst 148 while the lean air-fuel mixture is burned, so that NOx absorption is achieved. Even when the air-fuel mixture supplied into the combustion chamber 131 is made rich to release NOx from the agent 144 and unburned HC and CO are discharged from the NOx absorbent 144, these unburned HC and CO are transferred to the catalyst 148. The absorbed oxygen is deprived and oxidized, and as a result, unburned HC and CO are prevented from being released into the atmosphere.
[0054]
The NOx releasing action from the NOx absorbent 144 is performed when a certain amount of NOx is absorbed by the NOx absorbent 144, for example, when NOx is absorbed to about 50% of the absorption capacity of the NOx absorbent 144. Is called. The amount of NOx absorbed by the NOx absorbent 144 is proportional to the amount of exhaust gas exhausted from the engine and the concentration of NOx in the exhaust gas. In this case, the amount of exhaust gas is proportional to the amount of intake air, Since the NOx concentration 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 in order to simplify the control Alternatively, the amount of NOx absorbed in the NOx absorbent 144 may be estimated from the accumulated value of the engine speed.
[0055]
Next, rich spike control in the engine will be described. FIG. 14 shows a routine executed by the electronic control device 21 at regular intervals. First, in step 1, it is determined whether or not the correction coefficient Kt for the basic fuel injection time TP is smaller than 1.0, that is, whether or not a lean burn operation is being performed. When Kt ≧ 1.0, that is, when the air-fuel mixture supplied into the cylinder is at the stoichiometric air-fuel ratio or rich air-fuel ratio, the routine exits without performing any particular control.
[0056]
On the other hand, when Kt <1.0, that is, when the lean air-fuel mixture is combusted, the routine proceeds to step 2 where the result of adding ΣNE to the current engine speed NE is taken as ΣNE. Therefore, ΣNE indicates the cumulative value of the engine speed NE. Next, at step 3, it is determined whether or not the cumulative rotational speed ΣNE is larger than a certain value SNE. This constant value SNE indicates the cumulative rotational speed at which it is estimated that the NOx absorbent 144 absorbs, for example, 50% of the NOx absorption capacity. When ΣNE ≦ SNE, the routine returns. When ΣNE> SNE, that is, when it is estimated that the NOx absorbent 144 has absorbed 50% of the NOx absorption capacity, the routine proceeds to step 4 where the NOx release flag is set. Is 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.
[0057]
In step 5, the count value C is incremented by one. Next, at step 6, it is determined whether or not the count value C has become larger than a certain value C0, that is, for example, whether or not 0.5 seconds have elapsed. When C ≦ C0, the routine returns. When C> C0, the routine proceeds to step 7 where the NOx releasing flag is reset. When the NOx release flag is reset, the air-fuel mixture supplied into the cylinder is switched from rich to lean as will be described later. Therefore, the air-fuel mixture supplied into the cylinder is controlled to be rich for 0.5 seconds. Next, at step 8, the accumulated rotational speed ΣNE and the count value C are cleared.
[0058]
FIG. 15 shows a routine for calculating the fuel injection time TAU, and this routine is executed by the engine electronic control device 21 at regular intervals (or at constant crankshaft rotation angles). In FIG. 15, 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 release flag is set. When the NOx release flag is not set, the routine proceeds to steps 12 and 13 where the correction coefficient Kt is set to 0.7, for example, and then the routine proceeds to step. In step 14, the fuel injection time TAU (= TP × Kt) is calculated. At this time, the air-fuel mixture supplied into the cylinder is lean.
[0059]
On the other hand, when it is determined at step 11 that the NOx release flag has been set, the routine proceeds to step 15 where KK is calculated from the relationship shown in FIG. In step 16, the value of the correction coefficient Kt is set to KK, and the process proceeds to step 14. Accordingly, at this time, the air-fuel mixture supplied into the cylinder is set to the rich air-fuel ratio.
[0060]
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, it is preferable to install an air-fuel ratio sensor in the exhaust port 136 and correct the control value based on the detected actual air-fuel ratio.
[0061]
Furthermore, when performing a rich spike that temporarily sets the air-fuel ratio to the rich side during lean operation, the air-fuel ratio of the air-fuel mixture in the combustion chamber 131 is delayed even if the air-fuel ratio of the mixture supplied to the cylinder is reduced. May change. 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 is reduced.
[0062]
Therefore, the air-fuel ratio in the combustion chamber 131 becomes smaller after the rich spike control start time. For this reason, if the ignition timing is changed simultaneously with the start of rich spike control, the air-fuel ratio and the ignition timing may become transiently incompatible and the fluctuation in engine output torque may increase. In order to avoid such a situation, when changing the air-fuel ratio from lean to rich, or changing from rich to lean, change the ignition timing by delaying the change of the air-fuel ratio, or gradually change the ignition timing. It is preferable to change to. Alternatively, when the air-fuel ratio is changed 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, and when changing from rich to lean, the rich due to fuel detachment from the wall It is preferable to reduce the fuel injection amount at the start of the control so as to compensate for the shift. The transient control for switching these air-fuel ratios is specifically described in Japanese Patent Laid-Open No. 6-193487.
[0063]
The above-described lean burn operation in which the air-fuel ratio is increased in the engine 1 is executed, for example, when the throttle opening θ is equal to or smaller than a predetermined value and the vehicle speed is equal to or larger than a predetermined value at the second speed to fifth speed. On the other hand, the direct mode in the automatic transmission 3 that executes a shift based on a manual operation is artificially executed by the driver operating the shift device described above. Therefore, the control device according to the present invention performs control that associates the artificial direct mode selection control with the lean burn operation control of the engine 1.
[0064]
FIG. 16 is a flowchart showing an example, and after processing the input signal (step 20), it is determined whether or not each of the sensors described above is normal (step 21). If there is an abnormality in the sensor, the actual state of the engine 1 and the automatic transmission 3 cannot be grasped, so the process returns without performing any particular control. On the other hand, if each sensor is functioning normally, it is determined whether or not the engine water temperature TE is equal to or higher than a predetermined reference temperature α (step 22). If an affirmative determination is made in step 22, it is determined whether or not the oil temperature TT of the automatic transmission 3 is equal to or higher than a predetermined reference temperature β (step 23).
[0065]
If an affirmative determination is made in step 23, warm-up of the engine 1 is completed, combustion in the engine 1 is stable, and shift control in the automatic transmission 3 is normally performed. Therefore, the precondition for performing lean burn operation is satisfied. Therefore, it is determined whether or not the D range is selected (step 24).
[0066]
If the D range is selected, lean burn control is executed for each gear position (step 25). Normally, it is executed at each of the second to fifth gears, and the throttle opening θ is set to a predetermined value or less for each gear, and the vehicle speed is set for each gear. The lean burn operation is executed when a condition such as a predetermined vehicle speed or higher is satisfied. The control details of the lean burn operation are as described above.
[0067]
On the other hand, if a negative determination is made in step 24 because the D range is not selected, it is determined whether or not the direct mode (DM) is selected (step 26). This is because, for example, the above-described upshift switch 42 or downshift switch 44 is turned on, or one of the shift position sensors S1st, S2nd, S3rd, S4th is on, or a direct mode (not shown) This can be determined based on the fact that the switch is turned on.
[0068]
When this direct mode is selected, even if the vehicle state such as the vehicle speed or the throttle opening changes, no gear shift occurs and the gear position at that time is maintained. In addition, the line pressure is increased during gear shifting to improve gear shifting responsiveness, and control such as increasing the amount of change in throttle opening relative to the amount of accelerator operation to improve acceleration. Is executed. The control in the direct mode is described in, for example, Japanese Patent Laid-Open No. 5-26064.
[0069]
As described above, in the direct mode, control for improving the traveling performance of the vehicle, such as acceleration, is executed. Therefore, when the direct mode is selected and an affirmative determination is made in step 26, the lean burn in which the engine torque decreases. Control is prohibited (step 27). That is, the operation is performed with the air-fuel ratio set to the stoichiometric air-fuel ratio or slightly richer than that. Therefore, the engine torque is maintained in a normal state and the engine torque is stabilized, so that deterioration of the shift shock can be prevented in advance. If a negative determination is made in step 26, the process returns without performing any particular control.
[0070]
Further, if the engine water temperature TE is lower than the reference value α and a negative determination is made in step 22, or if the oil temperature TT of the automatic transmission 3 is lower than the reference temperature β and a negative determination is made in step 23, the step Proceed to 28 to prohibit lean burn operation. This is because the combustion in the engine 1 is not stable, and the shift control in the automatic transmission 3 cannot always be performed stably due to the influence of oil viscosity.
[0071]
As described above, if the lean burn operation is prohibited in the direct mode, the switching from the normal automatic shift mode in which the automatic shift is performed to the direct mode occurs during the lean burn operation. Therefore, the lean burn control is changed to control that switches the air-fuel ratio to the rich side, such as normal stoichiometric control. On the other hand, when the direct mode is selected as the vehicle running state in a state where lean burn control is possible, the engine 1 is made lean as the manual operation is performed from the direct mode to the normal automatic transmission mode. It will be changed to burn operation. Such air-fuel ratio switching control accompanying the switching of the shift mode is executed as follows.
[0072]
FIG. 17 shows an example. First, input signal processing (step 30) is performed, and then it is determined whether or not the D range, which is the normal automatic transmission mode, is switched to the direct mode (DM) (step 31). ). When such shift mode switching is performed, it is determined whether lean burn control is being executed (step 32).
[0073]
If an affirmative determination is made in step 32 because the lean burn control is being performed, a control for prohibiting the lean burn operation is executed in order to prevent insufficient acceleration in the direct mode (step 33). The lean burn prohibition control is as described with reference to FIG. 16, and the air-fuel ratio of the engine 1 is changed to the rich side in accordance with this control. Next, it is determined whether or not the timer TMA has counted up the predetermined time TM1 (step 34). This timer TMA is a timer that counts the time from the time when the mode is switched to the direct mode or the time after execution of the lean burn prohibition in step 33, and the time TM1 counted by this timer TMA is a predetermined time TM1. When it exceeds, the mode is switched to the direct mode (step 35).
[0074]
That is, switching to the direct mode is executed after a predetermined time from the start of execution of the control for switching from lean burn operation to operation in which the air-fuel ratio is changed to the rich side.As a result, at the time of completion of switching to the direct mode, The operation state of the engine 1 is a stoichiometric operation state with a theoretical air-fuel ratio or an operation state in which the air-fuel ratio is set slightly richer than that. Therefore, the engine torque does not become insufficient at the time of switching to the direct mode, and the shift mode switching in the automatic transmission 3 and the air-fuel ratio switching in the engine 1 do not occur simultaneously. Therefore, these controls are facilitated, and a shock caused by a sudden change in torque can be prevented.
[0075]
If a negative determination is made in step 32 because the lean burn control has not been executed, the lean burn prohibition control (step 36) is executed, and then the routine proceeds to step 35 to switch to the direct mode. .
[0076]
On the other hand, if a negative determination is made in step 31 because the switching to the direct mode has not occurred, it is determined whether or not the switching from the direct mode to the D range in the automatic transmission mode has occurred (step 37). . If a negative determination is made in step 37, the process returns without performing any particular control, and if an affirmative determination is made, switching to the automatic transmission mode (auto mode) is immediately executed (step 38).
[0077]
Next, it is determined whether or not a condition for performing lean burn operation is satisfied at that time (step 39). Specifically, whether the gear set in the automatic shift mode at that time is a gear higher than the second speed, and whether the engine speed, throttle opening, etc. are values for performing lean burn operation, etc. Judgment is made. If a negative determination is made, there is no need to switch to the lean burn operation, so that the routine returns without performing any control, and if an affirmative determination is made conversely, whether or not the timer TMB has counted up the predetermined time TM2. Is determined (step 40). The timer TMB is a timer that counts the time from when the mode is switched to the auto mode, and when the time counted by the timer TMB exceeds a predetermined time TM2, switching to the lean burn operation is executed ( Step 41).
[0078]
Therefore, if it is determined that the direct burn mode is to be switched to the automatic shift mode when the conditions for lean burn operation are satisfied, the switch to the automatic shift mode is first executed, and the control is completed and the automatic shift mode is completed. When the mode is achieved, it is switched to lean burn operation. Therefore, the switching control of the air-fuel ratio in the engine 1 and the associated ignition timing and the switching of the shift mode in the automatic transmission 3 do not occur at the same time, and these controls are facilitated and the mode is switched to the automatic shift mode. When a shift occurs, the shift can be executed in a normal engine operating state in which the air-fuel ratio is set to stoichiometric or rich, so that the shift control is facilitated and a shock can be prevented.
[0079]
The present invention has been described with specific examples. However, the present invention is not limited to the above examples, and the automatic transmission targeted by the present invention has a gear train other than the gear train shown in FIG. There may be.
[0080]
【The invention's effect】
As described above, according to the present invention, when a mode for performing a shift accompanying manual operation is selected in the automatic transmission, control is performed so that the lean burn operation in the engine is not performed in association with the selected mode. The engine torque in the mode is stable and the shift shock can be prevented from deteriorating.. Further, in the present invention, when both the shift mode switching and the lean burn operation and the low air-fuel ratio operation are switched, the shift mode is switched in an operation state with a low air-fuel ratio, so that these controls are facilitated. In addition, it is possible to prevent a shock by suppressing the fluctuation of the torque, and this is the same when a shift occurs as the shift mode is switched, and the shift control becomes easy and a shift shock can be prevented. it can.
[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 gear position 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 schematic view showing an arrangement position of an upshift switch and a downshift switch provided on a shift lever in the shift device.
FIG. 6 is a diagram showing an arrangement of each range position and gear position switch in another shift device.
FIG. 7 is a diagram schematically showing an intake / exhaust system of an engine and an air-fuel ratio control system targeted in the present invention.
FIG. 8 is a diagram showing a map of basic fuel injection time.
FIG. 9 is a diagram schematically showing the concentrations of unburned HC, CO and oxygen in exhaust gas discharged from an engine.
FIG. 10 is a view for explaining the NOx releasing action.
FIG. 11 is a diagram for explaining NOx release control;
FIG. 12 is a diagram for explaining the relationship between engine torque and air-fuel ratio.
FIG. 13 is a diagram showing a map of a correction coefficient KK.
FIG. 14 is a flowchart showing an example of control of NOx release from the NOx absorbent.
FIG. 15 is a flowchart showing an example of fuel injection amount control.
FIG. 16 is a flowchart illustrating an example of a control routine for prohibiting lean burn operation in the direct mode.
FIG. 17 is a flowchart illustrating an example of a control routine that is executed in association with switching between the direct mode and the automatic transmission mode in the automatic transmission and the prohibition and permission control of the lean burn in the engine.
[Explanation of symbols]
1 engine
3 Automatic transmission
21 Electronic control unit for engine
33 Electronic control device for shifting

Claims (2)

An engine that can perform lean burn operation with a large air-fuel ratio and can automatically select a first shift mode in which a shift is performed based on a manual operation and a second shift mode in which a shift is performed based on the state of the vehicle In an engine to which a transmission is coupled and a control device for an automatic transmission,
When the first shift mode for executing the shift based on a manual operation is selected, and means for prohibiting the lean-burn operation in the engine,
When the first shift mode is selected and the second shift mode is switched to the first shift mode, the lean burn operation is switched to the operation state in which the air-fuel ratio is reduced. Means for switching to the first shift mode after a predetermined time has elapsed after switching to an operating state with a reduced fuel ratio;
A control device for an engine and an automatic transmission, comprising:   An engine capable of performing a lean burn operation with a large air-fuel ratio and automatically selecting a first shift mode for executing a shift based on a manual operation and a second shift mode for executing a shift based on the state of the vehicle In an engine to which a transmission is connected and a control device for an automatic transmission,
  When the second shift mode for executing a shift based on the state of the vehicle is selected and the lean burn operation is performed in the second shift mode, the second shift mode is selected and the first shift mode is selected. Control of an engine and an automatic transmission comprising means for switching from an operation state with a reduced air-fuel ratio to a lean burn operation after a predetermined time has elapsed after switching from the first shift mode to the second shift mode apparatus.

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