JP3239737B2 - Control device for multi-wheel drive vehicles - Google Patents

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 a vehicle equipped with an internal combustion engine capable of selectively performing lean burn operation with an air-fuel ratio larger than a stoichiometric air-fuel ratio.
It relates control apparatus for a multi-wheel drive vehicle that can be specifically modified torque distribution ratio front and rear wheels and left and right wheel or the like.

[0002]

2. Description of the Related Art It is well known that it is strongly desired to improve the fuel efficiency of an internal combustion engine in order to save energy and preserve the environment. For this reason, for example, in a gasoline engine, a lean burn operation with a large air-fuel ratio is required. Have been developed and put into practical use. This lean burn operation is an operation state in which an air-fuel mixture having an air-fuel ratio higher than the stoichiometric air-fuel ratio is sucked into the cylinder to generate combustion, so that the engine torque decreases and the combustion becomes unstable, causing torque fluctuation. Is relatively large, and therefore, the vehicle 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. Specifically, an area where the lean burn operation is performed is prepared by mapping the engine speed and the throttle opening as parameters, and it is determined whether the lean burn control is possible based on the traveling state detected during traveling. Then, lean burn control is executed according to a change in the running state.

[0003] Further, during lean burn control in which the air-fuel ratio is increased, the amount of NOx generated is large. Therefore, conventionally, a NOx absorbent is disposed in the exhaust system, and N2 exhausted from the engine is reduced.
Ox is being captured. However, since the capacity of the NOx absorbent gradually decreases with an increase in the amount of NOx absorbed, control for reducing NOx absorbed in the form of nitrate ions to nitrogen and releasing it to the atmosphere is executed at regular intervals. ing.
Specifically, this control is performed by increasing the fuel injection amount and temporarily lowering the air-fuel ratio. One example is described in JP-A-6-108824.

Further, in order to improve running stability and turning performance of a vehicle, a four-wheel drive device that distributes torque to front wheels and rear wheels is used. If torque is applied to the front and rear wheels of the vehicle to make all four wheels drive wheels, the running performance on uneven terrain is improved, but the turning performance of the vehicle changes depending on the magnitude of the torque between the front and rear wheels. Recently, control has been performed to change the torque distribution ratio to the front and rear wheels to set the torque distribution ratio according to the running state.

[0005]

The change of the torque distribution ratio to the front and rear wheels in a four-wheel drive vehicle is carried out in various forms according to the configuration of the four-wheel drive device. In a four-wheel drive device that is a moving device, the change is performed by changing the torque capacity of the differential limiting clutch. In this case, in a configuration in which the carrier is used as an input element and the ring gear is connected to the rear wheel output shaft, while the sun gear is connected to the front wheel output shaft, the torque TF transmitted to the front wheel and the torque TR transmitted to the rear wheel are reduced. Is represented by the following equation.

TF = ρ · Ti / (1 + ρ) + Tc / (1 + ρ) TR = (Ti−Tc) / (1 + ρ) where Ti is the input torque, Tc is the differential limiting torque, and ρ is the tooth between the sun gear and the ring gear. It is a ratio of numbers (gear ratio).

Therefore, the front wheel torque and the rear wheel torque of a four-wheel drive vehicle vary depending on the input torque. However, in a four-wheel drive vehicle equipped with an engine capable of lean burn operation, the change in the air-fuel ratio of the engine changes. As a result, the input torque to the four-wheel drive changes, so that the torque distribution ratio to the front and rear wheels may change. That is, as described above, the lean burn operation is executed based on the running state of the vehicle, so that the lean burn operation and the stoichiometric air-fuel ratio or an output air-fuel ratio richer than the stoichiometric air-fuel ratio are performed by changing the depression amount of the accelerator pedal or the engine speed. It is switched to the operation with. Further, during the lean burn operation, a rich spike is executed, and at that time, the air-fuel ratio is temporarily reduced, so that the engine torque increases. As a result, the engine torque increases or decreases with a change in the air-fuel ratio, and the input torque to the four-wheel drive changes, so that the torque distribution ratio to the front and rear wheels changes.

On the other hand, the distribution ratio of torque to the front and rear wheels is
Although the control is performed by controlling the differential limiting torque based on data such as the yaw rate, steering angle, and vehicle speed of the vehicle, when controlling the differential limiting torque to set the torque distribution ratio to a predetermined value, When the air-fuel ratio changes in the engine, the factors that determine the torque distribution change at the same time, making it difficult to set the torque distribution to the target value.

Further, since the engine torque is different between the case where the air-fuel ratio is set to lean and the case where the air-fuel ratio is set to rich, the torque distribution ratio of the front and rear wheels is controlled by the air-fuel ratio even in the same differential limiting state. It could be different depending on the state.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a control device capable of suppressing a deviation of a torque distribution ratio due to a change in an air-fuel ratio. This object is achieved by executing the air-fuel ratio switching control so as not to overlap with the torque distribution ratio change control.

[0011]

SUMMARY OF THE INVENTION In order to achieve the above object, an invention according to a first aspect of the present invention is directed to an internal combustion engine which can be operated by switching the air-fuel ratio at least between large and small, and a first engine. the control apparatus for tower drive vehicle having a torque distribution device for distributing torque to the wheel and a second wheel and change its torque distribution ratio, switching of the air-fuel ratio
Detection that change of torque and change of torque distribution ratio occur at the same time
Control means for detecting the air-fuel ratio
Change of torque and change of torque distribution ratio occur simultaneously.
Switching of air-fuel ratio and change of torque distribution ratio when detected
Prohibition means for prohibiting any one of
The door is to the feature.

Therefore, according to the first aspect of the present invention, the change of the torque distribution ratio for each drive wheel and the influence on the torque distribution ratio are affected.
Since the change in input torque does not overlap, the torque
When changing the ratio, control is performed with the input torque constant.
Therefore, the torque distribution can be set as intended.
Can be specified .

The simultaneous control detecting means in the present invention
Is connected to the first wheel and the second wheel as described in claim 2.
Whether the torque distribution ratio to the second wheel is under change control
By judging, the switching of the air-fuel ratio and the torque
It is configured to detect that a change in the distribution rate occurs at the same time.
Can be achieved.

Further, the prohibiting means according to the second aspect of the present invention.
Switches the air-fuel ratio as described in claim 3.
Can be configured to be prohibited. And billing
The prohibiting means in the invention of claim 3 is further described in claim 4
The air-fuel ratio is set to a value greater than the stoichiometric air-fuel ratio as
When lean control is set to
Fix the control and temporarily set the air-fuel ratio to the rich side.
Touch spikes can be configured to be prohibited.

[0015]

Next, the present invention will be described more specifically with reference to the drawings. First, an overall configuration including an engine 1, an automatic transmission 2, and a transfer 3 according to the present invention will be described. FIG. 4 is a control system diagram of the engine 1, the automatic transmission 2, and the transfer 3. A signal corresponding to the depression amount of the accelerator pedal 4 is input to the engine electronic control device 5. An electronic throttle valve 7 driven by a throttle actuator 6 is provided in an intake duct of the engine 1. The electronic throttle valve 7 is transmitted from the control device 5 to the throttle actuator 6 in accordance with an amount of depression of an accelerator pedal 4. A control signal is output, and the opening is controlled according to the control amount.

An engine rotational speed sensor 8 for detecting the rotational speed of the engine 1, an air flow meter 9 for detecting the amount of intake air, an intake air temperature sensor 10 for detecting the temperature of intake air, and an opening of the electronic throttle valve 7 a throttle sensor 11 for detecting θ, a cooling water temperature sensor 13 for detecting a cooling water temperature of the engine 1, a brake switch 14 for detecting an operation of a brake, an operation position sensor 16 for detecting an operation position of the shift lever 15, and the like. I have. From these sensors, the engine rotational speed NE, the intake air temperature Tha, the opening degree θ of the electronic throttle valve 7, the vehicle speed V, the engine coolant temperature THw, and the brake operating state B
K, a signal indicating the operating position Psh of the shift lever 15 is transmitted to the engine electronic control device 5 and the shift electronic control device 17.
It is supplied to. The shift electronic control device 17 receives signals of the opening degree θ of the electronic throttle valve 7, the vehicle speed V, the engine coolant temperature THw, and the brake operating state BK.

The automatic transmission 2 includes a torque converter, which is a type of fluid coupling, as will be described later. A turbine speed sensor 18 for detecting the rotation speed of a turbine runner in the torque converter detects a turbine rotation speed NT. Is supplied to the shift electronic control device 17. Further, a signal indicating a kick-down operation is input from the kick-down switch 19 for detecting that the accelerator pedal 4 has been operated to the maximum operation position to the shift electronic control device 17.

The engine electronic control unit 5 is a so-called microcomputer having a central processing unit (CPU), a storage unit (RAM, ROM), and an input / output interface. The CPU uses a temporary storage function of the RAM. While processing input signals in accordance with a program stored in the ROM in advance, various engine controls are executed. For example,
The fuel injection valve 20 is controlled for controlling the fuel injection amount, the igniter 21 is controlled for controlling the ignition timing, the bypass valve (not shown) is controlled for controlling the idle speed, and all the throttle controls including the traction control are performed. The electronic throttle valve 7 is controlled by the throttle actuator 6 and executed. These controls include lean-burn operation in which the air-fuel ratio is made larger than the stoichiometric air-fuel ratio, rich spike that temporarily lowers the air-fuel ratio during lean burn, and retard control of the ignition timing to suppress torque fluctuation. .

The shift electronic control unit 17 is also a microcomputer similar to the engine electronic control unit 5 described above.
An input signal is processed according to a program stored in the OM, and each solenoid valve or the linear solenoid valve of the hydraulic control circuit 22 is driven. For example, the shift electronic control device 17 includes a linear solenoid valve SLT for generating an output pressure PSLT having a magnitude corresponding to the opening of the electronic throttle valve 7, a linear solenoid valve SLN for controlling the accumulator back pressure, In addition, the linear solenoid valves SLU are respectively driven to control the slip amount of the lock-up clutch, and to control the predetermined clutch or brake engagement pressure during a shift transition in accordance with the progress of the shift and according to the input torque.

The transfer 3 connected to the output side of the automatic transmission 2 is for distributing the torque output from the automatic transmission 2 to the front wheel side and the rear wheel side. A differential limiting mechanism for limiting the differential action by the differential to change the torque distribution ratio to the front and rear wheels. The differential limiting mechanism is configured to operate by hydraulic pressure, and a solenoid valve SLC for controlling the hydraulic pressure is provided in the hydraulic control circuit 22.

A four-wheel drive (4WD) electronic control unit 23 is provided to control the torque distribution ratio to the front and rear wheels. The electronic control unit 23 is mainly composed of a microcomputer, similarly to the other electronic control units 5 and 17 described above, and includes front wheel rotation speed NF and rear wheel rotation speed NR as control data. Data such as the throttle opening and the gear position are input from the respective electronic control units 5 and 17. Although not specifically shown, a signal from a yaw rate sensor and a steering angle signal are input to the four-wheel drive electronic control device 23. , 17 are output.

The engine 1 is capable of lean-burn operation in which the air-fuel ratio is greater than the stoichiometric air-fuel ratio. In order to release NOx from the NOx absorbent during the lean-burn operation, the air-fuel ratio is temporarily increased. It is configured to execute a rich spike set on the side. The engine 1 will now be described. FIG. 5 schematically shows an intake / exhaust system. An ignition plug 32 is provided in a combustion chamber 31 formed on the top side of a piston 30. The combustion chamber 31 has an intake port 3 having an intake valve 33.
4 and an exhaust port 36 having an exhaust valve 35 are communicated.

The intake port 34 is connected to a surge tank 38 via a corresponding manifold 37. Each of the manifolds 37 is provided with a fuel injection valve 39 for injecting fuel into the intake port 34. . The surge tank 38 is connected to an air cleaner 41 via an intake duct 40 and an air flow meter 9, and the electronic throttle valve 7 is arranged in the intake duct 40.

On the other hand, the exhaust port 36 is connected via an exhaust manifold 42 and an exhaust pipe 43 to a casing 45 containing a NOx absorbent 44, and the casing 45 is connected to a catalytic converter 47 via an exhaust pipe 46. ing. The catalytic converter 47 has a built-in three-way catalyst 48.

An electronic control unit 5 for controlling the engine 1
Consists of a digital computer and has a bidirectional bus 49
(Read only memory) 50, RAM (random access memory) 51, C
A PU (microprocessor) 52, an input port 53 and an output port 54 are provided. The air flow meter 9 generates an output voltage proportional to the amount of intake air, and the output voltage is input to the input port 53 via the AD converter 55. The input port 53 is connected to a rotation speed sensor 8 that generates an output pulse representing the engine speed. On the other hand, the output port 54 is connected to the ignition plug 32 and the fuel injection valve 39 via corresponding drive circuits 56 and 57, respectively.

As described above, the engine 1 includes the fuel injection valve 3
The fuel injection time TAU is calculated based on the following equation: TAU = TP × Kt. Here, TP represents a basic fuel injection time, and Kt represents a correction coefficient. The basic fuel injection time TP is a fuel injection time required 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.

The basic fuel injection time TP is obtained by an experiment in advance, and the engine load and the engine speed NE are expressed by the intake air amount Q / NE per revolution (Q is the intake air amount, NE is the engine speed). Are stored in the ROM 52 in advance 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 to the engine 1. If Kt = 1.0, the air-fuel mixture supplied to the cylinder has 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, when 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 established.

In the engine shown in FIG.
t = 0.7 or 0.6 is maintained, so that the lean burn operation is performed. FIG. 7 shows the combustion chamber 3
1 schematically shows the concentrations of representative components in the exhaust gas discharged from FIG. As is known from FIG. 7, the concentration of unburned HC and CO discharged from the combustion chamber 31 increases as the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber 31 increases, and the concentration of the unburned HC and CO discharged from the combustion chamber 31 increases. The concentration of oxygen O2 in the exhaust gas increases as the air-fuel ratio of the mixture supplied to the combustion chamber 31 increases.

NOx contained in casing 45
The absorbent 44 uses, for example, alumina as a carrier, and has potassium K, sodium Na, lithium Li,
At least one selected from alkali metals such as cesium Cs, alkaline earths such as barium Ba and calcium Ca, and rare earths such as lanthanum La and yttrium Y, and a noble metal such as platinum Pt are supported.

The ratio between the air and fuel supplied into the intake duct and the exhaust pipe upstream of the NOx absorbent 44 is referred to as "NOx
Assuming that "the air-fuel ratio of the exhaust gas flowing into the absorbent 44", the NOx absorbent 44 absorbed NOx when the air-fuel ratio of the inflowing exhaust gas was lean, and absorbed it when the oxygen concentration in the inflowing exhaust gas decreased. An absorption / release operation of NOx that releases NOx is performed.

When no fuel or air is supplied into the exhaust pipe upstream of the NOx absorbent 44, the air-fuel ratio of the inflowing exhaust gas matches the air-fuel ratio of the air-fuel mixture supplied into the combustion chamber 31. Therefore, in this case, the NOx absorbent 44 absorbs NOx when the air-fuel ratio of the mixture supplied to the combustion chamber 31 is lean, and the oxygen concentration in the mixture supplied to the combustion chamber 31 decreases. Then, the absorbed NOx is released.

As described above, in the engine shown in FIG.
Normally, the air-fuel mixture supplied into the cylinder is kept lean (for example, Kt = 0.7), and the N
Ox is absorbed by the NOx absorbent 44. However, if the lean mixture continues to be burned, the NOx absorbing ability of the NOx absorbent 44 becomes saturated, and after a while
The x absorbent 44 cannot absorb NOx. Therefore, when the lean air-fuel mixture is continuously burned, the control device according to the present invention temporarily makes the air-fuel mixture supplied into the cylinder rich (Kt = Kt) as shown in FIG.
K), whereby the NOx absorbed by the NOx absorbent 44 is released from the NOx absorbent 44. That is, a rich spike is executed.

In this case, simply switching the air-fuel mixture supplied into the cylinder from the lean air-fuel ratio to the rich air-fuel ratio causes the engine output torque to fluctuate, so that such a situation does not occur. Is set. That is, as shown in FIG. 9, the engine output torque decreases as the air-fuel ratio becomes leaner from the output air-fuel ratio (11.0 to 12.0), and the engine output torque becomes richer as the air-fuel ratio becomes richer. Also, the engine output torque decreases.

Accordingly, as shown in FIG. 9, there are a lean air-fuel ratio (KL) and a rich air-fuel ratio (KK) at which the engine output torques are equal. So the combustion chamber 31
When the lean mixture is to be burned, the air-fuel ratio at that time is set to the lean air-fuel ratio (KL), and when the rich mixture is burned in the combustion chamber 31, the air-fuel ratio at that time is set to the rich air-fuel ratio (KK). At the same time, 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 determined in advance in this manner, when the lean air-fuel ratio is switched from the rich air-fuel ratio to the rich air-fuel ratio and when the rich air-fuel ratio is switched from the lean air-fuel ratio 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 set in advance, for example, to Kt = 0.7,
Therefore, the rich air-fuel ratio (KK) is set such that an output torque equal to the engine output torque when using this lean air-fuel ratio is obtained. In this case, the rich air-fuel ratio (KK) is determined by the engine load Q / NE and the engine speed N.
E, and this rich air-fuel ratio (KK) is shown in FIG.
As shown in (1), it is stored in the ROM 50 in advance in the form of a function of the engine load Q / NE and the engine speed NE.

The NOx releasing action from the NOx absorbent 44 is such that when a certain amount of NOx is absorbed by the NOx absorbent 44, for example, 50% of the absorption capacity of the NOx absorbent 44
This is performed when NOx is absorbed to the extent. The amount of NOx absorbed by the NOx absorbent 44 is proportional to the amount of exhaust gas discharged from the engine and the NOx concentration in the exhaust gas,
In this case, the exhaust gas amount is proportional to the intake air amount, and the NOx concentration in the exhaust gas is proportional to the engine load.
Although the amount of NOx absorbed by the absorbent 44 can be accurately estimated from the cumulative value of the product of the intake air amount and the engine load, in order to simplify the control, the NOx amount is calculated from the cumulative value of the engine speed. The amount of NOx absorbed in the absorbent 44 may be estimated.

Next, the control of the rich spike in the engine will be described. FIG. 11 shows a routine executed by the electronic control unit 5 at regular intervals. First, in step 1, the basic fuel injection time TP
It is determined whether the correction coefficient Kt is smaller than 1.0, that is, whether the lean burn operation is being performed. When Kt ≧ 1.0, that is, when the air-fuel mixture supplied to the cylinder has a stoichiometric air-fuel ratio or a rich air-fuel ratio, the routine exits from this routine without performing any particular control.

On the other hand, when Kt <1.0, that is, when the lean air-fuel mixture is being burned, step 2
The result of adding ΣNE to the current engine speed NE is set as ΣNE. Therefore, ΣNE indicates the cumulative value of the engine speed NE. Next, at step 3, it is determined whether or not the accumulated rotational speed ΣNE is larger than a fixed value SNE. This constant value SNE is the NOx absorbent 44
FIG. 5 shows the cumulative number of revolutions at which it is estimated that the NOx amount of, for example, 50% of the NOx absorption capacity is absorbed. ΣN
When E ≦ SNE, the routine returns. When ΣNE> SNE, that is, when it is estimated that 50% of the NOx absorption capacity of the NOx absorbent 44 has been absorbed by the NOx absorbent 44, 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.

Next, at step 5, the count value C is set to 1
Is only incremented. Then, in step 6, it is determined whether or not the count value C has become larger than the fixed value C0, that is, for example, whether or not 0.5 seconds have elapsed. C ≦
When C> C0, the process returns. When C> C0, the routine proceeds to step 7, where the NOx release 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 controlled to be rich for 0.5 seconds. Next, at step 8, the accumulated rotational speed ΣNE and the count value C are cleared.

FIG. 12 shows a routine for calculating the fuel injection time TAU. This routine is executed by the engine electronic control unit 5 at regular time intervals (or at regular rotational angles of the crankshaft). 12, first, at step 10, the basic fuel injection time TP is calculated from the map shown in FIG. Next, at step 11, it is determined whether or not 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, for example, 0.7, and then proceeds to step 14. In step 14, the fuel injection time TAU
(= TP × Kt) is calculated. At this time, the air-fuel mixture supplied into the cylinder is made lean.

On the other hand, if it is determined in step 11 that the NOx release flag has been set, then in step 1
Proceeding to 5, KK is calculated from the relationship shown in FIG. Next, at step 16, the value of the correction coefficient Kt is set to KK,
Proceed to step 14. Therefore, at this time, the mixture supplied to the cylinder is set to the rich air-fuel ratio.

Incidentally, 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 36, 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 the lean operation, even if the air-fuel ratio of the air-fuel mixture supplied to the cylinder is reduced, the combustion chamber 3
The air-fuel ratio of the air-fuel mixture within 1 may change with a delay.
This is because during lean operation, the wall surface of the intake port 34 is in a dry state, and when a mixture having a rich air-fuel ratio is supplied thereto, 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 31 becomes smaller at a time later than the start of the rich spike control. Therefore, if the ignition timing is changed at the same time as the start of the rich spike control, the air-fuel ratio and the ignition timing transiently become incompatible with each other,
It is conceivable that the fluctuation of the engine output torque becomes large. In order to avoid such a situation beforehand, when changing the air-fuel ratio from lean to rich, or from rich to lean, change the ignition timing later to change 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 surface. It is preferable to reduce the fuel injection amount at the start of control so as to correct the shift. The transient control for switching the air-fuel ratio is specifically described in Japanese Patent Application Laid-Open No. Hei 6-193487.

The above-described lean burn operation is performed in a state where the exhaust gas and the riding comfort are not degraded. Therefore, a lean burn operation permission region is set for each of the second and higher speeds. The permitted area is the engine speed NE
And the basic throttle opening TTA are set as parameters, an example of which is shown in FIG. FIG.
In FIG. 3, the hatched area is the area where the lean burn operation is performed.
In the state where TA is zero, that is, in the idling state, the air-fuel ratio is set to stoichiometric or rich in order to prevent the rotation of the engine from becoming unstable.

Next, the automatic transmission 2 connected to the engine 1 will be described. In FIG. 14, an automatic transmission 2 is connected to an engine 1 via a torque converter 60. The torque converter 60 is connected to the engine 1
A pump impeller 62 connected to a crankshaft 61 of
A turbine runner 64 connected to an input shaft 63 of the automatic transmission 2, and a lock-up clutch 65 directly connecting between the pump impeller 62 and the turbine runner 64
And a stator 67 which is prevented from rotating in one direction by a one-way clutch 66.

The automatic transmission 2 includes a high and a low 2
The transmission includes a subtransmission portion 68 for switching gears, and a main transmission portion 69 capable of switching between a reverse gear position and four forward speed positions. The auxiliary transmission unit 68 includes a sun gear S0, a ring gear R0,
A planetary gear set 70 comprising a pinion P0 rotatably supported by carrier K0 and meshed with sun gear S0 and ring gear R0;
C0 and a one-way clutch F0, a sun gear S0 and a housing 71 provided between the clutch 71 and the carrier K0.
And a brake B0 provided between them.

The main transmission section 69 includes a first planetary gear unit 72 comprising a sun gear S 1, a ring gear R 1, and a pinion P 1 rotatably supported by the carrier K 1 and meshed with the sun gear S 1 and the ring gear R 1.
A second planetary gear unit 73 comprising 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, a ring gear R3;
And a third planetary gear set 74 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, and the carrier K3
Is connected to the output shaft 75. 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 76, and a second clutch C2 is provided between the sun gear S1 and the sun gear S2 and the intermediate shaft 76.

A first brake B1 in the form of a band for stopping rotation of the sun gear S1 and the sun gear S2 is provided on the housing 71 as braking means. The sun gear S1 and the sun gear S2 and the housing 71
, A first one-way clutch F1 and a second brake B2 are provided in series. The first one-way clutch F1 has a sun gear S1 and a sun gear S2 connected to the input shaft 6.
It is configured to be engaged when trying to reversely rotate in the direction opposite to 3.

A third brake B3 is provided between the carrier K1 and the housing 71, and a fourth brake B4 and a second one-way clutch F2 are provided between the ring gear R3 and the housing 71 in parallel. Have 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 automatic transmission described above, five forward speeds and reverse speeds can be set, and the state of engagement and disengagement of each friction engagement device for setting these shift speeds is shown in FIG. It is shown in the joint operation table. In FIG. 15, a circle indicates an engaged state, and a cross indicates a released state.

The shift electronic control unit 17 calculates the basic throttle opening TTA (throttle opening obtained by converting the amount of depression of the accelerator pedal by a predetermined nonlinear characteristic), the vehicle speed V, and a shift diagram using these as parameters. Of the automatic transmission 2 and the lock-up clutch 6 based on the
No. 5 in the hydraulic control circuit 22 so as to obtain the determined shift speed and engagement state.
. 1 to No. 3 solenoid valves SOL1 and SOL2
, SOL3 to generate engine brakes. The fourth solenoid valve SOL4 is driven.

On the other hand, the lock-up clutch 65
Is released at the first speed and the second speed of the automatic transmission 2, but at the third speed and the fourth speed, the basic throttle opening TTA is released.
Any of the areas of release, slip, and engagement is determined based on the vehicle speed V and the vehicle speed V. If the area is the slip area, the lock-up clutch 65 is slip-controlled, and if the area is the engagement area, the lock-up clutch 65 is engaged. This slip control is for suppressing the rotation loss of the torque converter 60 as much as possible while absorbing the rotation fluctuation of the engine 1.

FIG. 16 shows the operating position of the shift lever 15. In FIG. 16, a combination of the six operation positions in the front-rear direction of the vehicle and the two operation positions in the left-right direction of the vehicle allows the shift lever 15 to be operably supported at the eight operation positions by a support device (not shown). Is supported. P is a parking range position, R is a reverse range position, N is a neutral range position, D is a drive range position, "4" is a "4" range position for setting the speed up to the fourth speed, and "3" is a third position. "3" range position for setting the speed up to the third speed, "2" is the second position
"2" range position for setting gears up to high speed, L is the first
The low range positions at which an upshift to a speed higher than the speed is prohibited are shown.

The transfer 3 that distributes and transmits the torque output from the transmission 2 to the rear wheel output shaft 80 and the front wheel output shaft 81 will be described. In FIG. 17, a differential device 82 composed of a simple planetary gear mechanism is arranged on an extension of the output shaft 75 of the automatic transmission 2 and its carrier 8
The output shaft 75 of the automatic transmission 2 is connected to 3. The ring gear 84 is connected to a rear wheel output shaft 80 disposed on the same axis as the output shaft 75 so as to rotate integrally therewith.

The sun gear 85 is integrated with a driving sprocket 86 arranged on the same axis on the outer peripheral side of the output shaft 75, and a driven sprocket 87 forming a pair with the driving sprocket 87 is arranged in parallel with the output shaft 75. A chain 89 is wound around these sprockets 86 and 87 while being attached to the front wheel output shaft 81.

The carrier 83 and the ring gear 84
And a wet multi-plate clutch 90 as a differential limiting mechanism. The differential limiting clutch 90 is configured to operate by hydraulic pressure, and the engagement hydraulic pressure is
It is controlled continuously or stepwise. That is, the output port 91 and the input port 92 are intermittently communicated by the spool, the output pressure is supplied to one end of the spool as feedback pressure, and the control pressure is supplied to the other end of the spool. A clutch hydraulic pressure control valve 93 is provided, and the differential limiting clutch 90 is connected to an output port 91 thereof. Input port 92
Is connected to a linear solenoid valve SLC for supplying a control pressure while supplying a line pressure PL.

The linear solenoid valve SLC is connected to a solenoid modulator valve 94 which regulates and outputs a line pressure PL. The linear solenoid valve SLC outputs a hydraulic pressure proportional to a current as a signal pressure. ing. Therefore, the clutch hydraulic control valve 9
3 changes according to the signal pressure of the linear solenoid valve SLC input as the control pressure, and as a result,
The engagement force of the differential limiting clutch 90, that is, the differential limiting torque Tc changes.

Depending on the magnitude of the differential limiting torque Tc, the torque distribution ratio to the front and rear wheels changes, and various control methods are conventionally known. For example, control for increasing the differential limiting torque Tc according to the difference between the rotational speeds of the front and rear wheels is generally performed.
It is also possible to calculate a target yaw rate based on the steering angle and the vehicle speed, and to control the differential limiting torque Tc so that the detected yaw rate matches the target yaw rate. This is based on the fact that the greater the torque of the rear wheel, the greater the turning performance.

As described above, the torque distribution ratio to the front and rear wheels changes according to the differential limiting torque Tc, but also changes according to the input torque Ti. The differential limiting torque Tc is controlled by the rotational speed difference between the front and rear wheels, the yaw rate, the steering angle, and the like.
Is controlled based on the engine speed NE and the throttle opening. As described above, since the control factor of the operation limiting torque and the control factor of the air-fuel ratio are independent of each other, there is a possibility that both controls are executed simultaneously. Therefore, the control device of the present invention performs the following control for stable control of the torque distribution ratio to the front and rear wheels.

FIG. 1 shows an example of the control routine. After the processing of the input signal (step 21),
It is determined whether or not the D range has been selected (step 22). This determination can be made based on the output signal of the operation position sensor 16 as to whether or not the shift lever is at the position D in the shift device shown in FIG.

When an affirmative determination is made in step 22 because the D range is selected, it is determined whether lean control for setting the air-fuel ratio to a value larger than the stoichiometric air-fuel ratio is being executed (step 23). ). This, for example, the basic fuel correction coefficient Kt for injection time Ru can be determined by whether it is set to "1" smaller value.

Step 23 is executed when the lean control is executed.
If the answer is affirmative, it is determined whether or not the change control of the differential limiting torque Tc is being performed (step 24). As described above, by changing the differential limiting torque Tc, the torque distribution ratio to the front and rear wheels changes, and the running characteristics of the vehicle, such as running ability and turning performance on uneven terrain, change. This is executed when the value exceeds a predetermined reference value or when a yaw rate occurs. This step 24
There corresponds to simultaneous control detection means definitive in claim 1.

If the differential limiting torque Tc is maintained at a constant value and a negative determination is made in step 24, the routine returns without performing any particular control. If the determination is affirmative, the air-fuel ratio control, that is, the lean control that is being executed at that time is fixed (step 25). Further, rich spikes are prohibited (step 26). That is, the change of the air-fuel ratio is prohibited . Therefore, the functional
The means correspond to the prohibited means in claims 3 and 4.
Hit.

Then, the output torque of the engine 1 in the state of the fixed lean control is estimated (step 27). As shown in FIG. 9 described above, since there is a certain correlation between the air-fuel ratio and the engine torque, the engine torque can be obtained from the air-fuel ratio at the time of the lean control based on FIG. 9, for example. Next, the differential limiting torque Tc is determined (step 28). That is, the differential limiting torque Tc is determined so that the required torque distribution ratio is obtained based on the rotational speed difference between the front and rear wheels and the yaw rate. In this case, since the input torque Ti to the transfer 3 is stable by fixing the air-fuel ratio, the differential limiting torque Tc and the accompanying torque distribution ratio of the front and rear wheels are determined as expected based on the yaw rate and the like. Can be set.

On the other hand, if a negative determination is made in step 23 because the lean control has not been executed, it is determined whether or not the change control of the differential limiting torque Tc is being performed as in step 24 (step 29). If a negative determination is made here, the control returns without performing any control. If an affirmative determination is made, the air-fuel ratio is set to the stoichiometric air-fuel ratio or an output air-fuel ratio richer than the stoichiometric air-fuel ratio (hereinafter referred to as these air-fuel ratios). The set state is described as a rich state (step 3).
0). Therefore, steps 25 and 30 correspond to the prohibiting means in claim 1 .

Then, the output torque of the engine 1 in the state of the fixed rich control is estimated (step 31). Also in this case, the engine torque can be obtained from the air-fuel ratio at the time of the rich control based on FIG. Next, the differential limiting torque Tc is determined (step 32). The differential limiting torque Tc is determined so that the required torque distribution ratio is obtained based on the difference between the rotational speeds of the front and rear wheels, the yaw rate, and the like. In this case, since the input torque Ti to the transfer 3 is stable by fixing the air-fuel ratio, the differential limiting torque Tc and the accompanying torque distribution ratio of the front and rear wheels are determined as expected based on the yaw rate and the like. Ru can be set.

The output torque of the engine 1 is determined to a predetermined value based on the air-fuel ratio, as shown in FIG. 9, and the air-fuel ratio is determined by a correction coefficient Kt for the basic fuel injection time. Therefore, the engine torque can be estimated because the air-fuel ratio can be known regardless of whether the air-fuel ratio is in the rich state, the lean state, or the execution of the rich spike. That is, since the torque input to the transfer 3 can be estimated in any case, the torque distribution ratio to the front and rear wheels, that is, the differential limiting torque Tc can be set according to the input torque.

The control routine shown in FIG. 2 is for determining the differential limiting torque Tc according to the control state of the air-fuel ratio. After the processing of the input signal (step 41), the D range is selected. (Step 4)
2) If a negative determination is made, the routine returns without performing any particular control. If an affirmative determination is made in step 42, it is determined whether or not the lean control is being performed as in step 23 (step 43).

If an affirmative determination is made during the lean control, it is determined whether or not there is a rich spike (step 44) . Since the rich spike as before mentioned is carried out for each predetermined period based on such an integrated value of the engine speed, it can be readily determined by those parameters. If an affirmative determination is made in step 44 due to the execution of the rich spike, the engine torque in consideration of the rich spike is estimated (step 4).
5). The rich spike is a control for temporarily increasing the fuel supply amount (injection amount). Since the air-fuel ratio is known, the engine torque can be estimated based on the known air-fuel ratio. Then, the differential limiting torque Tc is determined based on the engine torque (step 46).

The torque distribution ratio of the front and rear wheels is calculated based on the yaw rate and the like. Since the differential limiting torque Tc for achieving this is based on the engine torque, the torque distribution ratio is set as expected. Can be set to

On the other hand, if the result of the determination in step 44 is negative because the vehicle is not in the state of executing the rich spike,
The engine torque is estimated based on the air-fuel ratio during the lean control (step 47), and the differential limiting torque Tc is determined according to the estimated engine torque (step 48).
The control in steps 47 and 48 is performed in accordance with step 2 described above.
Ru same der and control of 7, 28.

If a negative determination is made in step 43 because the air-fuel ratio is rich, the engine torque is estimated based on the rich air-fuel ratio (step 4).
9) And, the differential limiting torque Tc is determined according to the engine torque (step 50). In this step 49,
The control at 50 is the same as the control at steps 31 and 32 described above.

Therefore, according to the control shown in FIG. 2, when the torque distribution ratio to the front and rear wheels is set to a target value, the differential limiting torque Tc is determined according to the input torque to the transfer 3, so that the lean control is performed. Irrespective of the presence or absence of the vehicle, the torque distribution ratio can be set almost accurately, and the running characteristics of the vehicle can be made as expected.

The differential limitation in the transfer 3 is performed when the rotational speed difference between the front and rear wheels is equal to or more than a predetermined reference rotational speed, when the yaw rate matches the target yaw rate, and the like. On the other hand, the switching of the air-fuel ratio in the engine 1 is executed based on the engine speed, the throttle opening, and the like, and the rich spike during the lean control is executed based on the accumulated value of the engine speed. . That is, since the control of the torque distribution ratio for the front and rear wheels and the control of the air-fuel ratio are independent of each other, there is a possibility that both controls are superimposed. Therefore, in the control shown in FIG. To prevent

That is, in FIG. 3, after the input signal processing (step 61) is performed, the rotational speed difference ΔN
It is determined whether FR detection and control based on the detection are performed (step 62). If the control is not performed, the routine returns without performing the control. If the control is performed, it is determined whether or not the lean control is being performed (step 63).

If the lean control is not being performed, it is determined whether or not there is a rich spike (step 64). If the rich spike is not executed, that is, if a negative determination is made in step 64, the air-fuel ratio is changed from the lean state to the rich state. Is determined (step 65). If the result of the determination in step 65 is negative due to the continuation of the lean control from the state of the engine speed and the throttle opening, the hydraulic pressure of the differential limiting clutch 90 is feedback-controlled (step 66) (Japanese Patent Laid-Open No. 6-107021). No.).

That is, if a negative determination is made in step 66, it means that the air-fuel ratio control is stable to the lean control. In this state, the differential limiting torque is feedback-controlled based on the difference between the rotational speeds of the front and rear wheels. The control of the torque distribution ratio for the front and rear wheels can be performed stably and accurately. In other words, since the control of the differential limiting torque that affects the torque distribution ratio of the front and rear wheels and the change of the input torque do not overlap, it is possible to prevent a deviation in the torque distribution ratio between the front and rear wheels.

On the other hand, when the affirmative determination is made in step 64 in the situation where the rich spike is executed, or when the affirmative determination is made in step 65 when the air-fuel ratio is switched from the lean state to the rich state. , The feedback control of the hydraulic pressure of the differential limiting clutch 90 is prohibited (step 67), and the forward control is executed (step 68). That is, since the torque input to the transfer 3 changes in accordance with the change in the air-fuel ratio, the differential limiting torque Tc is not controlled based on the rotational speed difference between the front and rear wheels, the yaw rate, and the like. Forward control is performed based on

This is for the following reason. In the feedback control of the hydraulic pressure of the differential limiting clutch 90, for example, the hydraulic pressure is changed so that the deviation between the target differential limiting torque and the actual differential limiting torque becomes zero. If the input torque fluctuates with the change, the torque distribution ratio changes, which makes the control of the hydraulic pressure of the differential limiting clutch 90 extremely complicated or difficult. Therefore, the feedback control is stopped so that the data fluctuating due to the change in the air-fuel ratio is not taken in as the control data, and the forward control is executed. As a result, the so-called interference with the change control of the change control and the differential limiting torque of the air-fuel ratio does not occur, Ru can be set torque distribution ratio between the front and rear wheels for the intended exactly.

If the rich control is being executed and a negative determination is made in step 63, the routine immediately proceeds to step 66 to execute the feedback control of the differential limiting clutch 90 because the engine torque is stable. .

In the above-described example, the differential device is constituted by the planetary gear mechanism and the differential is limited by the multi-plate clutch. However, the present invention is not limited to the above example. The present invention can also be applied to a device in which a transfer is constituted by a set of clutches, and the torque distribution ratio to the front and rear wheels is changed by increasing and decreasing the engagement force. Further, the control of the torque distribution ratio for the front and rear wheels can be performed by reading other parameters other than the rotational speed difference between the front and rear wheels, the yaw rate, and the steering angle. Further, in the above example, the pressure regulation level is changed by the output signal pressure of the linear solenoid valve to change the differential limiting torque and the accompanying torque distribution ratio, but the mechanism for controlling the torque distribution ratio is as described above. Various configurations other than the linear solenoid valve and the pressure regulating valve can be adopted as needed.

The present invention is, of course, not limited to the above-described embodiment, and therefore, the present invention can be applied to an engine or an automatic transmission other than the engine and the automatic transmission shown in the above-described drawings. . Further, the form of the lean burn control is not limited to the above-described embodiment. In short, it is sufficient that the air-fuel ratio of the air-fuel mixture is increased to operate the internal combustion engine. Further, in the above-described embodiment, a four-wheel drive vehicle that controls the distribution of torque to the front wheels and the rear wheels has been described as an example, but the present invention distributes the torque to the left and right wheels and controls the distribution ratio. The present invention can also be applied to a control device such as a two-wheel drive vehicle configured as described above.

[0085]

As described above , according to the present invention,
Change input torque to differential and torque to drive wheels
The change in the luck distribution rate does not occur at the same time
Causes the torque distribution ratio to deviate from the target value or cause a shock.
Can be prevented from occurring .

[0086]

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an example of a control routine for fixing an air-fuel ratio during control of a differential limiting torque.

FIG. 2 is a flowchart illustrating an example of a control routine for setting a differential limiting torque according to a control state of an air-fuel ratio.

FIG. 3 is a flowchart illustrating an example of a routine for performing switching of the control mode of the hydraulic pressure of the differential limiting clutch.

FIG. 4 is a control system diagram for an engine, an automatic transmission, and a transfer.

FIG. 5 is a diagram schematically showing an intake / exhaust system and an air-fuel ratio control system of an engine targeted by the present invention.

FIG. 6 is a diagram showing a map of a basic fuel injection time.

FIG. 7 shows unburned H in exhaust gas discharged from the engine.
FIG. 3 is a diagram schematically showing the concentrations of C, CO and oxygen.

FIG. 8 is a diagram for explaining NOx release control.

FIG. 9 is a diagram for explaining the relationship between engine torque and air-fuel ratio.

FIG. 10 is a diagram showing a map of a correction coefficient KK.

FIG. 11 is a flowchart showing an example of control for releasing NOx from a NOx absorbent.

FIG. 12 is a flowchart illustrating an example of fuel injection amount control.

FIG. 13 is a diagram schematically showing a lean burn control permission area for the second to fifth speeds.

FIG. 14 is a skeleton diagram showing an example of a gear train of the automatic transmission according to the present invention.

FIG. 15 is a diagram showing an engagement operation table of a friction engagement device for setting each shift speed in the automatic transmission.

FIG. 16 is a diagram showing an arrangement of each range position in the shift device.

FIG. 17 is a diagram schematically illustrating an example of a transfer and a differential limiting mechanism.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 engine 2 automatic transmission 4 engine electronic control device 16 shift electronic control device 23 four-wheel drive electronic control device

────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI F02D 41/02 305 F02D 41/02 305 45/00 368 45/00 368G (56) References JP-A-55-164742 (JP, A) JP-A-55-164743 (JP, A) JP-A-2-290732 (JP, A) JP-A-63-124846 (JP, A) JP-A-62-91321 (JP, A) JP-A-62 JP-A-82239 (JP, A) JP-A-6-213024 (JP, A) JP-A-58-124037 (JP, A) JP-A-61-192830 (JP, A) JP-A-6-108824 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B60K 41/00-41/28 B60K 17/28-17/36 F02D 29/00 F02D 41/02 F02D 45/00

Claims (4)

(57) [Claims] 1. A torque distribution device for distributing torque to an internal combustion engine operable by switching an air-fuel ratio at least in two directions, a first wheel and a second wheel, and changing a torque distribution ratio thereof. In the control device for a multi-wheel drive vehicle provided with the above, the switching of the air-fuel ratio and the change of the torque distribution ratio occur simultaneously.
Simultaneous control detecting means for detecting the
The output means switches the air-fuel ratio and changes the torque distribution at the same time.
Switching of the air-fuel ratio and torque
Means to prohibit either one of
Multiple wheel drive vehicle control apparatus characterized by comprising a. 2. The simultaneous control detecting means according to claim 1 , wherein
By determining whether the distribution ratio is under change control, the empty space is determined.
Switching of the fuel ratio and change of the torque distribution ratio occur simultaneously.
Is configured to detect
The control device for a multi-wheel drive vehicle according to claim 1. 3. The prohibition means prohibits switching of the air-fuel ratio.
3. The method according to claim 2, wherein
A control device for a multi-wheel drive vehicle as described in the above. 4. The prohibition means sets the air-fuel ratio to a stoichiometric air-fuel ratio.
If the lean control that sets the value larger than
In this case, lean control is fixed and the air-fuel ratio is temporarily set to the rich side.
Set to prohibit rich spikes
The control of a multi-wheel drive vehicle according to claim 3, wherein
Control device.