JPH04232125A - Differential limit control unit for four-wheel drive vehicle - Google Patents

Abstract

PURPOSE:To properly control the differential condition of right and left wheels in response to torque distribution to these wheels with a differential limit control unit for a four-wheel drive vehicle to control the differential limit of the right and left wheels of the four-wheel drive vehicle. CONSTITUTION:This device consists of an input torque setting means which computes torque input to wheels on a right and left wheel differential limit mechanism side in case that rotating speed difference occurs between front and rear wheels and in case that no difference occurs to select the larger one of these two input torque values, a right and left wheel differential limit force setting means 50 which sets differential limit force so that the differential limit force of the right and left wheel differential limit mechanism can be increased with the increase of the input torque set by the input torque setting means, and a differential limit control means 420 which controls the right and left wheel differential limit mechanism 23 so that the differential limit force set by the right and left wheel differential limit force setting means 560 can be obtained.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential limiting control device for a four-wheel drive vehicle, which controls differential limiting between left and right wheels of a four-wheel drive vehicle.

0002

[Prior Art] Between the left and right wheels of an automobile,
A differential mechanism is provided to allow for the differential movement that occurs when turning, etc., but with this differential mechanism, the load on one of the left and right wheels is stuck in the groove, and the coefficient of friction with the road surface is extremely small. In this case, only one of the wheels rotates while the other wheel hardly rotates, resulting in a situation where the drive torque cannot be transmitted to the road surface.

[0003] Therefore, a differential limiting mechanism (LSD = limited slip differential) has been developed that can limit the differential in such cases. Such a differential limiting mechanism for the left and right wheels includes a type that is proportional to the rotational speed difference between the left and right wheels, and a type that is proportional to the input torque. The left and right wheel rotation speed difference proportional type has a VC (VC) that uses the viscosity of the liquid.
There are viscous coupling type LSDs, etc., which have the advantage of improving the running stability of the vehicle. On the other hand, input torque proportional type devices include friction type devices such as the general LOM (Lock Automatic) type LSD, and TORSEN devices that utilize the frictional resistance of worm gears.
There are mechanical type LSDs such as the Torsen type LSD, which have the advantage of improving the turning performance of the vehicle.

0004

[Problems to be Solved by the Invention] Incidentally, there are cases where a rear wheel or front wheel of a four-wheel drive vehicle is provided with a differential limiting mechanism for left and right wheels. In this case, one of the elements that controls the differential limit between the left and right wheels.
In other words, this kind of torque distribution state is also considered to be effective.

The present invention was devised in view of the above-mentioned problems, and provides a differential for a four-wheel drive vehicle, which allows the differential state of the left and right wheels to be appropriately controlled according to the state of torque distribution to these wheels. An object of the present invention is to provide a motion restriction control device.

[0006]

[Means for Solving the Problems] Therefore, the differential limiting control device for a four-wheel drive vehicle of the present invention includes a front and rear wheel differential limiting mechanism that limits the differential state between the front and rear wheels of the vehicle, and a differential limiting mechanism for limiting the differential state between the front and rear wheels of the vehicle. In a four-wheel drive vehicle equipped with a left and right wheel differential limiting mechanism that limits the differential state between the left and right rear wheels or front wheels, the left and right wheel differential limiting mechanism is used when there is a difference in rotational speed between the front and rear wheels. Input torque setting means for calculating the input torque to the side wheels and the input torque to the side wheels of the left and right wheel differential limiting mechanism when the torque is not generated, and selecting the larger value of these two input torques; Left and right wheel differential limiting force setting means sets the differential limiting force of the left and right wheel differential limiting mechanism so that the differential limiting force of the left and right wheel differential limiting mechanism increases with an increase in the input torque set by the input torque setting means. and differential limiting control means for controlling the left and right wheel differential limiting mechanism so as to obtain the differential limiting force set by the left and right wheel differential limiting force setting means.

The left and right wheel differential limiting force setting means is configured to increase the differential limiting force of the left and right wheel differential limiting mechanism as the input torque set by the input torque setting means increases. Preferably, the differential limiting force is set to decrease as the difference in rotational speed between the left and right wheels increases.

[0008]

[Operation] In the differential limiting control device for a four-wheel drive vehicle of the present invention described above, the input torque setting means controls the input torque to the left and right differential limiting mechanism side wheels when there is a difference in rotational speed between the front and rear wheels. The left and right wheel differential limiting force setting means calculates the torque and the input torque to the side wheels of the left and right wheel differential limiting mechanism when no torque is generated, selects the larger value of these two input torques, and sets the left and right wheel differential limiting force setting means. The differential limiting force is set so that the differential limiting force of the left and right wheel differential limiting mechanism increases with an increase in the input torque set by the input torque setting means. Then, the differential limiting control means controls the left and right wheel differential limiting mechanism so that the differential limiting force set by the left and right wheel differential limiting force setting device is obtained.

The left and right wheel differential limiting force setting means is configured to increase the differential limiting force of the left and right wheel differential limiting mechanism as the input torque set by the input torque setting means increases. If the differential limiting force is set to decrease as the rotational speed difference between the left and right wheels increases, running stability and turning performance will be enhanced.

0010

[Embodiment] A left and right wheel differential control device as an embodiment of the present invention will be explained below with reference to the drawings. Fig. 1 is a block diagram showing its overall configuration, and Fig. 2 shows a drive equipped with the differential control device. The overall configuration of the torque transmission system is shown in FIG. 3. FIG. 3 is a sectional view showing the rear differential as a differential for the left and right wheels. FIGS. 6 is a block diagram showing the rear wheel torque gain correction section, FIG. 7 is a block diagram showing part of the input torque corresponding control section, and FIG. 8 is a block diagram showing the input torque corresponding control section. A configuration diagram showing a part of the control section, FIG. 9 is a configuration diagram of the part from the maximum value selection section to the control current output section,
FIG. 10 is a configuration diagram showing details of the steering angle detection means, and FIG.
1 is a configuration diagram showing details of the vehicle speed detection means, FIG. 12 is a plan view schematically showing the wheel condition for explaining the ideal rotation speed difference, and FIG. 13 is a diagram showing a map for setting the ideal rotation speed difference. Figure 14 is a diagram showing the rotation difference gain setting map, Figure 1
5(a) and 5(b) are diagrams each showing a differential clutch torque setting map, FIG. 16 is a diagram showing an example of the engine torque map, and FIG. 17 is a diagram showing an example of the transmission torque ratio map. Fig. 18 is a center differential input torque setting map, Fig. 19 is a flowchart showing the control flow of the entire vehicle including the device, Fig. 20 is a flowchart showing the control flow of the rear differential, and Fig. 21 is a correspondence to the rotation speed difference. 22 is a flowchart showing the flow of setting the clutch torque. FIG. 22 is a flowchart showing the flow of setting the clutch torque corresponding to the input torque.

First, the overall structure of the drive system of a vehicle equipped with this differentially adjustable front and rear wheel torque distribution control device will be described with reference to FIG.

In FIG. 2, reference numeral 2 denotes an engine, and the output of this engine 2 is transmitted to an output shaft 8 via a torque converter 4 and an automatic transmission 6. The output of the output shaft 8 is transmitted via an intermediate gear 10 to a planetary gear type differential device 12, which serves as an actuating device that distributes engine torque between front wheels and rear wheels as required.

The output of this planetary gear type differential device 12 is transmitted to a reduction gear mechanism 19 on one side and a differential gear mechanism 1 for front wheels on the other hand.
4 from the axles 17L, 17R to the left and right front wheels 16, 1
On the other hand, it is transmitted from axles 25L, 25R to left and right rear wheels 24, 26 via a bevel gear mechanism 15, a propeller shaft 20, a bevel gear mechanism 21, and a rear differential gear 22. Ru.

The planetary gear type differential device 12 includes a sun gear 121, a planetary gear 122 disposed outside the sun gear 121, and a ring gear disposed outside the planetary gear 122, as in the conventionally known one. 123,
The output of the output shaft 8 of the automatic transmission 6 is input to the carrier 125 that supports the planetary gear 122, and the sun gear 121
is interlocked with the front wheel differential gear device 14 via the front wheel output shaft 27 and the reduction gear mechanism 19, and the ring gear 123 is interlocked with the propeller shaft 20 via the rear wheel output shaft 29 and the bevel gear mechanism 15. .

The planetary gear type differential device 14 also controls the output torque of the engine between the front wheels and the rear wheels by restraining (or limiting) the differential between the front wheel side output section and the rear wheel side output section. A hydraulic multi-disc clutch 28 is provided as differential limiting means or differential adjusting means that can change the distribution.

That is, the hydraulic multi-disc clutch 28 includes a sun gear 121 (or ring gear 123) and a carrier 125.
The friction force is changed by the control pressure applied to its own hydraulic chamber, and the differential movement between the sun gear 121 (or ring gear 123) and the carrier 125 is restrained.

Therefore, the planetary gear type differential device 12 is as follows:
By appropriately controlling the hydraulic multi-disc clutch 28 from a completely free state to a locked state, the torque transmitted to the front and rear wheels can be adjusted from approximately 32:68 to 50:50. It is now possible to control between Front wheel in completely free condition: Rear wheel value: Approx. 32
:68 can be defined by setting the tooth ratio of the input gears on the front wheel side and the rear wheel side of the planetary gear, and here, when the pressure in the hydraulic chamber of the hydraulic multi-disc clutch 28 is zero and it is in a completely free state, approximately It is set to be 32:68.

[0018] Furthermore, the ratio in this completely free state (approximately 32
:68) changes depending on the load balance between the front wheel system and the rear wheel system, etc., but is usually a value like this. Further, when the pressure in the hydraulic chamber is set to the set pressure (9 kg/cm2) and the hydraulic multi-plate clutch 28 is in a locked state, and the differential restriction becomes substantially zero, the torque distribution between the front wheels and the rear wheels is as follows. 50:
50, resulting in a direct connection state.

Note that the rear differential 22 will be explained in detail later.

A steering wheel angle sensor 30 detects the rotation angle of the steering wheel 32 from the neutral position, that is, the steering wheel angle θ, and 34a and 34b detect the lateral accelerations Gyf and Gyr acting on the front and rear parts of the vehicle body, respectively. In this example, two detection data Gyf and Gyr are averaged to obtain lateral acceleration data, but one lateral acceleration sensor 34 is installed near the center of gravity of the vehicle body.
Only one sensor may be provided, and the detected value may be used as lateral acceleration data. 36 is a longitudinal acceleration sensor that detects the longitudinal acceleration Gx acting on the vehicle body; 38 is a throttle position sensor that detects the throttle opening θt of the engine 2; 39
is the engine key switch for engine 2, 40, 42, 4
4 and 46 are the left front wheel 16, the right front wheel 18, and the left rear wheel 2, respectively.
6. A wheel speed sensor that detects the rotation speed of the right rear wheel 28, and the outputs of these switches and each sensor are input to the controller 48.

Reference numeral 50 indicates an anti-lock brake device, and this anti-lock brake device 50 operates in conjunction with a brake switch 50A. That is, when the brake switch 50A is turned on when the brake pedal 51 is depressed, an anti-lock brake activation signal is output in conjunction with this, and the anti-lock brake device 50 is activated. Furthermore, when the anti-lock brake activation signal is output, a signal indicating the state is also sent to the controller 48 at the same time.
is configured to be input. Further, 52 is a warning light that lights up based on a control signal from the controller 48.

Note that the controller 48 includes a CPU, ROM, RAM, interface, etc., which are not shown, but are necessary for control described later.

Reference numeral 54 denotes a hydraulic power source, and 56 a pressure control valve system (hereinafter referred to as pressure control valve system) which is interposed between the hydraulic power source 54 and the hydraulic chamber of the hydraulic multi-disc clutch 28 and is controlled by a control signal from the controller 48. (abbreviated as control valve). In addition, this car is equipped with an automatic transmission, with a code of 16
0 is a shift lever position sensor (shift range detection means) that detects the selected shift range of the shift lever 160A of the automatic transmission, and this detection information is also sent to the controller 48.

Furthermore, the engine rotation speed N detected by the engine rotation speed sensor (engine rotation speed sensor) 170
e and the transmission rotation speed Nt detected by the transmission rotation speed sensor (transmission rotation speed sensor) 180 are also sent to the controller 48.

In this example, a traction control system 151 is also provided. In other words, the engine 2 includes a main throttle valve 152 whose opening degree is controlled according to the amount of depression of the accelerator pedal 162, and together with the accelerator pedal 162 and the connection mechanism, constitutes an accelerator pedal-based engine output adjustment device. .

A sub-throttle valve 153 serving as an engine output control means that is controlled independently of the accelerator pedal system engine output adjustment device is provided in series with the main throttle valve 152 in the intake passage of the engine 2. . The sub-throttle valve 153 is driven by a motor, and the motor is controlled based on detection results from rear wheel speed sensors 44, 46, front wheel speed sensors 40, 42, engine speed sensor 170, engine load sensor 172, and the like.

[0027]Then, the above-mentioned rear differential (
The rear differential) 22 is provided with a differential limiting mechanism 23, and is configured as shown in FIG.

That is, as shown in FIG.
is connected to the rear end of the propeller shaft 20, and a drive pinion gear 402 is supported by the input shaft 401 so as to rotate together with the input shaft 401. Further, the input shaft 401 is rotatably supported within the front part of the case 413 via a bearing 412.

A crown gear 403 meshes with the drive pinion gear 402.
The power transmission annular member 404 is connected to the power transmission ring member 404 by a bolt 431.
and first housing 405 are integrally coupled.

The rear differential 22 is a planetary gear type differential using a planetary gear mechanism, and is formed in a power transmitting annular member 404 and inside the annular member 404.
A ring gear 407 formed on the inner peripheral surface of the left wheel 24
a sun gear 408 spline-coupled with the axle 25L;
A carrier 409 spline-coupled to the axle 25R of the right wheel 26, and shafts 410a, 410b connected to the carrier 409.
Planetary gears 411a, 41 attached via
1b.

Therefore, the rotational torque input from the input shaft 401 passes through the drive pinion gear 402 and the crown gear 403, and then from the ring gear 407 of the annular member 404 to the planetary gears 411a, 411b and the carrier 40.
9 to the axle 25R of the right wheel 26, and the planetary gears 411a, 411b and the sun gear 40.
8 to the axle 25L of the left wheel 24.

Further, a second housing 406 is provided on the right side of the carrier 409, and this second housing 406 is connected to the annular support member 4 through a bearing 428.
It is supported by 18.

[0033] This rear differential 22 is provided with a differential limiting device 23, and this differential limiting device 23 has the following functions:
A multi-disc clutch 414 as a differential limiting mechanism, a drive device 417 that drives this multi-disc clutch, and this drive device 4
Rear differential control section 48 of controller 48 that controls 17
It is composed of a.

That is, the multi-disc clutch 414 is provided inside the annular member 404, and the holder portion 415a supporting one clutch disk 414a is connected to the shaft 410a,
The clutch disc 414a is coupled to the carrier 409 via the carrier 410b so as to rotate together with the carrier 409, and the holder part 415b supporting the other clutch disc 414b is formed on a hollow shaft 416 on which the sun gear 408 is provided. Clutch disc 4
14b rotates integrally with the sun gear 408.

Furthermore, the drive device 417 drives the carrier 40
9 and the second housing 406, and an electromagnetic clutch mechanism 430 that drives this force direction conversion mechanism 429. In addition,
This rear differential 22 uses an electromagnetic clutch mechanism to limit the differential.
D: Electro Magnetic Cont.
Rolled Differential).

The force direction conversion mechanism 429 includes a ball 421 interposed between the carrier 409 and the second housing 406, as shown in FIG. 3, and a ball 421, as shown in FIG. 4(a).
A diamond-shaped (or rectangular) chamber 42 that accommodates this ball 421
The chamber 425 consists of a groove 422 formed on the carrier 409 side, the carrier 409 and the second housing 40.
6 and a groove 424 formed in the annular member 423. The annular member 423 is interposed between the carrier 409 and the second housing 406 and is normally free in the rotational direction with respect to these members, but rotates integrally with the carrier 409 via the ball 421. However, the second housing 406 side (that is,
When the rotating torque of the crown gear 403 or the power transmission annular member 404 side is received, a differential rotation is generated with respect to the carrier 409, and the force due to this rotating torque is changed in direction and acts as a pressing force on the clutch 414. It is supposed to be done.

[0037] The second housing 406 is attached to the annular member 423.
It is the electromagnetic clutch mechanism 430 that applies the rotation torque on the side, and this electromagnetic clutch mechanism 430 acts on the annular member 423 and the second housing 406 side (crown gear 403 and power transmission annular member 404 side). It consists of a clutch 427 interposed between a member 426 and an electromagnetic clutch drive system including a magnet 419 and a solenoid (EMCD coil) 420 as differential limiting mechanism control means.

That is, the clutch 427 is disposed inside the second housing 406, the magnet 419 is disposed further inside the second housing 406, and the magnet 419 is disposed outside the second housing 406. , a solenoid 420 that can attract the magnet 419 is installed. As a result, when the solenoid 420 is actuated, the magnet 419
The clutch 416 is engaged by being attracted to the second housing 406 side and pressing the clutch 416 between the second housing 406 and the second housing 406 .

When the clutch 416 becomes engaged, the annular member 423 receives rotational torque from the second housing 406 and begins to rotate integrally with the second housing 406. . At this time, the second housing 406 side (therefore, the sun gear 407 side)
If there is a rotational speed difference (differential rotation) between the wheel and the carrier 409, that is, if there is a rotational speed difference between the left and right wheels,
The annular member 423 generates a differential rotation with respect to the carrier 409, and when the annular member 423 generates a differential rotation with respect to the carrier 409 in this way, the ball 421 and the grooves 422, 424 rotate as shown in FIG. 4(b). Through the inclined surface of is driven in the axial direction, and the multi-disc clutch 414 is pressed and engaged through the shafts 410a, 410b and the holder portion 415a.

The engagement force of the multi-disc clutch 414 corresponds to the rotational speed difference between the left and right wheels and the magnitude of the electromagnetic force generated by the solenoid 420.
By adjusting the current to the multi-disc clutch 414, the engagement force of the multi-disc clutch 414, and therefore the differential limiting force, can be controlled.

In order to control the differential limiting force by adjusting the current to the solenoid 420, the controller 48 is provided with a rear differential control section 48a.

The rear differential control section 48a will now be explained.

As shown in the block diagram of FIG. 1, the rear differential control section 48a controls each sensor (wheel speed sensors 40, 42,
44, 46, steering angle sensors 30a, 30b, 30c, lateral acceleration sensor 34, longitudinal acceleration sensor 36, throttle position sensor 38, engine speed sensor 170,
Based on the detection information from the transmission rotation speed sensor 180, shift position sensor 160, etc.), the clutch torque of the multi-disc clutch 414 is set, and the clutch torque is sent to the electromagnetic clutch mechanism 430 of the drive device 417 so as to obtain the target clutch torque. The supply current is controlled.

[0044] Among the data, ABS information, wheel speed,
Comprehensive communication (SCI communication: SCI=
Serial Communication In
Data such as surface (surface) are input digitally, and data such as longitudinal acceleration, lateral acceleration, accelerator opening, hydraulic control to the multi-disc clutch, 4WD control unit control, and current to the electromagnetic clutch of the rear differential are input analog.

In this device, the clutch torque of the multi-disc clutch 414 is set to an ideal differential state by focusing on the differential state between the left and right wheels (the difference in rotational speed, also expressed as the difference in rotational speed). The differential clutch torque Trn is set in proportion to the torque input to the rear wheels in order to suppress wheel slip during sudden starts and obtain large road surface transmission torque. One of the input torque proportional clutch torques Tra is selected from among the input torque proportional clutch torques Tra, and each of these clutch torques Trn,
The setting section of Tra will be explained in order.

The differential clutch torque Trn is a clutch torque for increasing control accuracy so that the vehicle behaves in accordance with the driver's intention when cornering, and also for avoiding tight corner braking phenomena. In other words, when turning, a geometric differential occurs between the left and right wheels and between the front and rear wheels due to the trajectory difference and the vehicle body posture.
It is desired to control the differential between the left and right wheels and between the front and rear wheels so that this differential can be appropriately tolerated.

By the way, when turning, the driver's intention is to
The available information is the driver's requested steering angle (pseudo steering angle) δr
ef and vehicle body speed (pseudo vehicle body speed) Vref, and based on these pieces of information δref and Vref, differential compatible clutch torque Trn is set.

Therefore, the differential compatible clutch torque Tv
As shown in FIG. 1, the parts involved in the setting include a left and right wheel actual rotational speed difference detection section 500 as an actual rotational speed difference detection means, and a left and right wheel ideal rotational speed difference setting section 510 as an ideal rotational speed difference detection means. and a differential compatible clutch torque setting unit 520 as differential limiting force setting means for setting clutch torque (differential limiting force) Trn' from the left and right wheel actual rotational speed difference ΔVrd and the right and left wheel ideal rotational speed difference ΔVhr, It is composed of a correction section (k3 correction section) 546 that corrects this clutch torque Trn' using a rear wheel torque gain k3.

The left and right wheel actual rotational speed difference detection section 500 is shown in FIG.
As shown in FIG. 2, it is configured to include filters 202c and 202d and a left and right wheel actual rotational speed difference calculation unit 506. Note that the filters 202c and 202d extract micro-vibration components of the data caused by disturbances, etc. from the rotational speed data signals RL and RR of the left rear wheel 26 and right rear wheel 28 detected by the wheel speed sensors 44 and 46, respectively. It is intended to remove. Further, the left and right wheel actual rotational speed difference calculation unit 506
Then, by subtracting the right rear wheel rotation speed Vrr from the left rear wheel rotation speed Vrl, we calculate the actual rotation speed difference between the left and right wheels [rotational speed difference between the left and right wheels (left and right rotation difference: this rotation difference is the rotation difference at the rear differential). )] ΔVrd is calculated.

The left and right wheel ideal rotational speed difference setting section 510 includes a driver-required steering angle calculation section (pseudo steering angle calculation section) 212 as a steering angle detection means, and a driver-required vehicle speed calculation section as a vehicle speed data detection means. section (pseudo vehicle speed calculation section) 216, and an ideal rotational speed difference setting section 5 as an ideal operating state setting section.
It is composed of 18.

As shown in FIG.
Based on the detection data θ1, θ2, and θn from the first steering angle sensor 30a, the second steering angle sensor 30b installed on the steering wheel, and the neutral position sensor 30c, the sensor-compatible steering angle δh[=f(θ1, θ2, θn
)] Sensor-compatible steering angle data setting unit 21 that calculates the value of
2a, a lateral acceleration data calculation unit 212b that calculates lateral acceleration data Gy by averaging the data Gyf and Gyr detected by the lateral acceleration sensors 34a and 34b, and the direction of the sensor-compatible steering angle δh and the direction of the lateral acceleration data Gy. and a driver requested steering angle setting section (vehicle speed data setting section) 212d that sets the driver requested steering angle δref according to the comparison result of the comparing section 212c. .

Note that the function δh=f(θ1, θ2, θn) for determining the sensor-compatible steering angle δh corresponds to the specifications of the steering wheel angle sensor. In addition, the steering angle δh corresponding to the sensor
and lateral acceleration data Gy, for example, both assume that the right turning direction is positive.

To compare the directions of these sensor-corresponding steering angle δh and lateral acceleration data Gy, a function SIG(x) regarding the following direction is set for the detected data x. When x>0, SIG(x)=1 When x=0, SIG(x)=0 When x<0, SIG(x)=-1 Then, the comparison unit 212c calculates the sensor-compatible steering angle δh. A comparison between the direction and the direction of the lateral acceleration data Gy is performed using SIG (
This is done by comparing δh) and SIG(Gy).

In the driver-required steering angle setting unit 212d, when the direction SIG(δh) of the sensor-compatible steering angle δh is equal to the direction SIG(Gy) of the lateral acceleration data Gy, the driver-required steering angle setting unit 212d sets the sensor-compatible steering angle δh to Set the requested steering angle (steering angle data) δref, and set the direction SI of the sensor-compatible steering angle δh.
G (δh) and direction SIG (Gy) of lateral acceleration data Gy
are not equal, 0 is set as the driver's requested steering angle δre
Set to f.

Direction SIG(δh
) is not equal to the direction SIG(Gy) of the lateral acceleration data Gy, setting 0 as the driver requested steering angle δref is because, for example, when the driver performs a steering wheel operation such as countersteering, the steering position and the steering wheel position are different. The actual steering angle (turning state) of the vehicle may differ, and in such a case, it is difficult to perform appropriate control if the steering angle of the vehicle is set from the steering position of the steering wheel.

Therefore, in order to eliminate such a problem, if the direction SIG(δh) of the sensor corresponding steering angle δh and the direction SIG(Gy) of the lateral acceleration data Gy are not equal, the steering angle requested by the driver is is set to 0.

In this way, the driver requested steering angle δref is
The steering angle δh, which is determined from the steering wheel angle, is a steering angle that reflects the driver's intention more than, for example, the steering angle δy based on the lateral acceleration Gy, and is used as the driver-required steering angle δref. Are suitable. For example, if the driver wants to make a larger turn than the current one, |δh|>|δ
y|, and by adopting the rudder angle value |δh|, the rudder angle value |
The magnitude of the ideal rotational speed difference (slip target value) can be made larger than by adopting δy|.On the other hand, if the driver wants to suppress the current turning, |δh|<|δy|, and the steering angle value By adopting |δh|, the magnitude of the ideal rotational speed difference (slip target value) can be made smaller than by using the steering angle value |δy|.

When the driver-required vehicle speed calculation unit 216 calculates the vehicle speed from the wheel speed when the wheels slip,
As shown in FIG. 11, wheel speed sensors 40, 42, 44,
Rotational speed data signals FL, FR, R of the left front wheel 16, right front wheel 18, left rear wheel 26, and right rear wheel 28 detected by 46
A wheel speed selection unit 216a that selects the second largest wheel speed data from the bottom (from the smallest) among L and RR, and a driver request that sets a driver-requested vehicle speed from the selected wheel speed data, etc. It consists of a vehicle speed calculation section 216c.

In particular, the driver-required vehicle speed calculation unit 216c uses wheel speed data SVW obtained by filtering the wheel speed data selected by the wheel speed selection unit 216a to remove noise components, and the wheel speed data SVW detected by the longitudinal acceleration sensor 36. Based on the longitudinal acceleration data Gx obtained by applying the filter 216d to the longitudinal acceleration obtained by removing noise components, the vehicle speed during the slip can be estimated from both data SVW and Gx at a certain point before the slip. . In other words, if the wheel speed data SVW at a certain point is V2 and the longitudinal acceleration data Gx is a, then the theoretical vehicle speed Vref after a time t from this point is Vref=V2+a
It can be calculated by t.

Further, instead of the longitudinal acceleration data Gx, the driver-required vehicle body acceleration V'ref obtained by time-differentiating the wheel speed data SVW or the driver-required vehicle body speed Vref may be used.

Note that the rotational speed data signals FL, FR, R
The reason why we use the second largest wheel speed data from the bottom among L and RR is because each wheel is often slipping toward the overspeed side, so normally we use the wheel speed that rotates at the lowest speed. Although it is desirable to do so, the second wheel speed from the bottom is used in consideration of the reliability of the data. The ideal rotational speed difference setting unit 518 then calculates the driver requested steering angle δref calculated by the driver requested steering angle calculation unit 212.
and the driver-required vehicle speed Vref calculated by the driver-required vehicle speed calculation unit 216, an ideal rotational speed difference ΔVhr is set in accordance with a map as shown in FIG.

In other words, regarding the steering angle, the larger the steering angle, the larger the rotation difference required between the left and right wheels, so the larger the steering angle data δref, the greater the ideal rotational speed difference ΔVh.
The value of r also increases; for example, as the steering angle data δref increases in the right turning direction, the value of the ideal rotational speed difference ΔVhr increases in the positive direction (in the direction where the left wheel has higher speed), and the steering angle data As δref increases in the left turning direction, the value of the ideal rotational speed difference ΔVhr increases in the negative direction (in the direction in which the speed of the left wheel is smaller). Regarding vehicle speed, when the vehicle speed is low, the value of the ideal rotational speed difference ΔVhr increases as the vehicle speed increases, but at high speeds, the tendency for the value of the ideal rotational speed difference ΔVhr to increase with respect to increase in vehicle speed becomes smaller. That is, at high speed, the ideal rotational speed difference ΔVhr between the left and right wheels is determined mainly according to the steering angle data δref.

The rotational speed difference ΔVhr between the left and right wheels due to the difference in orbit radius between the left and right wheels will be explained with reference to FIG. 12. The example shown in FIG. 12 is for a right turn, where the right wheel speed on the inside of the turn (turning inner wheel speed) is Vi, the left wheel speed on the outside of the turn (turning outer wheel speed) is Vo, and the center of the left and right wheels. The vehicle speed at that point is V, the turning radius of the vehicle (the turning radius at the center of the left and right wheels) is R, the distance between left and right wheels (tread) is Lt, the wheelbase is l, and the distance between the center of the front wheels and the center of gravity is lf, the distance between the center of the rear wheels and the center of gravity is lr, and the weight of the vehicle is m. If the vehicle body slip angle β is sufficiently small, cos β≈1, and sin β≈β, then the rotational speed difference ΔVhr between the left and right wheels can be expressed as follows. ΔVhr=Vo−Vi=(Lt/R)・V
...(1.1) In addition, R=(1+A・V2)・l/δ
...(1.2) However, A is the stability factor, where the front cornering power is kf and the rear cornering power is kr.
Then, A=-(m/2l2)・(lf・kf−lr・kr)/
(kf・kr)

[0064] Above formulas (1.1) (1.2)
As shown in the figure, the ideal rotational speed difference ΔVhr between the left and right wheels can be calculated from the vehicle speed V and the steering angle δ. However, the pseudo vehicle speed Vref and the driver requested steering angle δref are used as the vehicle speed V and the steering angle δ, respectively.

[0065] Then, the left and right wheel actual rotational speed difference detection section 500
The actual left and right wheel rotational speed difference ΔVrd detected by the right and left wheels ideal rotational speed difference ΔVhr set by the left and right wheel ideal rotational speed difference setting unit 510 is subtracted by a subtractor 522 (ΔVrd−
ΔVhr) and the resulting difference ΔVr (=ΔVrd−Δ
Vhr) and the ideal rotational speed difference ΔVhr between the left and right wheels are input as data to the differential compatible clutch torque setting section 520.

The differential compatible clutch torque setting section 520 is
Actual left and right wheel rotational speed difference ΔVrd and left and right wheel ideal rotational speed difference Δ
The clutch torque Trn' is set in accordance with the difference ΔVr (=ΔVrd−ΔVhr) from the left and right wheels, and the clutch torque Trn' is set depending on whether the left and right wheel ideal rotational speed difference ΔVhr is positive or negative.

(i) When ΔVhr≧0, in this case,
It is desired that the speed of the rear wheels be faster than that of the front wheels, and the clutch torque Trn' is set as shown in (1) to (2) below.

■If ΔVrd≧ΔVhr, the rear wheels are over-rotating and slipping, so a part of the engine torque that was largely distributed to the rear wheels is transferred to the front wheels to suppress the rear wheels from slipping. I want to. Therefore, the clutch torque T
Trn' = a x (ΔVrd - ΔVhr) = a x ΔV so that rn' increases in proportion to the magnitude of the difference ΔVr (ΔVrd - ΔVhr).
Set r...(1.3) (where a is a proportionality constant).

■If ΔVhr>ΔVrd>0, the front wheels are slipping, so if the clutch torque T
If rn' is increased, the engine torque distributed to the front wheels increases, which promotes slipping of the front wheels. For this reason, it is desirable to set the differential limit free and reduce the engine torque distributed to the front wheels. Therefore, in this case, the clutch torque Trn' is set to 0 to set a so-called dead zone region.

■ If 0≧ΔVrd, the front wheels are slipping, so it is desired to increase the distribution of engine torque to the front wheels to reduce the front wheel slips. Therefore, Trn'=-a×ΔVrd=-a×(ΔVr+ΔVhr
)...(1.4) (where a is a proportionality constant).

If such a relationship between Trn' and ΔVr is mapped, it will be as shown in FIG. 15(a). Using this map, the differential compatible clutch torque Trn can be calculated from the difference ΔVr and the ideal left and right wheel rotational speed difference ΔVhr. can be found.

Note that when ΔVhr=0, ΔVhr>
The dead zone region where ΔVrd>0 disappears.

(ii) When ΔVhr<0, in this case it is desired to make the speed of the front wheels faster than the speed of the rear wheels, and the clutch torque Trn' is set as shown in (1) to (2) below.

■If ΔVrd≧0, the rear wheels are over-rotating and slipping, so a part of the engine torque that was largely distributed to the rear wheels is transferred to the front wheels to suppress the rear wheels from slipping. I want to. Therefore, the clutch torque Trn'
Trn′ increases in proportion to the magnitude of ΔVrd.
=a×ΔVrd=a×(ΔVr+ΔVhr)
...(1.5) (where a is a constant of proportionality).

■If 0>ΔVrd>ΔVhr, the rear wheels are slipping, so if the clutch torque T
If rn' is increased, the engine torque distributed to the rear wheels will increase, which will promote rear wheel slippage. For this reason, it is desirable to set the differential limit free and reduce the engine torque distributed to the rear wheels. Therefore, in this case, the clutch torque Trn' is set to 0 to set a so-called dead zone region.

■ If ΔVhr≧ΔVrd, the front wheels are slipping, so it is desired to increase the distribution of engine torque to the front wheels to reduce the slip of the front wheels. Therefore, Trn'=-a×(ΔVrd-ΔVhr) so that the clutch torque Trn' increases in proportion to the magnitude of ΔVr(ΔVrd-ΔVhr).
=-a×ΔVr
...(1.6) (where a is a constant of proportionality). Trn like this
If the relationship between ' and ΔVr is mapped, the result will be as shown in FIG. 15(b). Using this map, the differential compatible clutch torque T
rn' can be obtained.

In this way, the differential compatible clutch torque Trn' obtained from ΔVr and ΔVhr by the differential compatible clutch torque setting unit 520 with reference to the map [FIGS. 15(a) and 15(b)] is , as shown in FIG.
6, the k3 correction is made so that the differential compatible clutch torque Trn can be obtained.

The correction unit 546 performs lateral acceleration correction by multiplying the differential compatible clutch torque Trn' by the rear wheel torque gain k3 to obtain the differential compatible clutch torque Trn. The wheel torque gain k3 is set by the rear wheel torque gain setting section 544 as follows.

That is, the rear wheel torque gain setting unit 544 receives the rear wheel shared torque Tre as the input torque calculated from the rear wheel shared torque calculating unit 560 as input torque setting means, and the rear wheel shared torque Tre as the input torque is sent to the rear wheel torque gain setting unit 544. From the map shown in block 544, a rear wheel torque gain k3 is set according to the rear wheel shared torque Tre.

This rear wheel torque gain k3 is a coefficient that is corrected according to the magnitude of the rear wheel shared torque Tre, and this rear wheel shared torque Tr is also applied to the differential compatible clutch torque Trn.
Taking into consideration the magnitude of e, when the rear wheel shared torque Tre is small, the differential compatible clutch torque Trn also becomes small, so that the differential compatible clutch torque Trn also decreases as the rear wheel shared torque Tre increases. It is intended to increase.

Note that the rear wheel shared torque Tre is Tre=T
rm, the rear wheel torque gain k3 becomes a constant value (k3=1), but Trm is the rear wheel shared torque assuming maximum acceleration driving on a dirt road, and Trm=μ[Wr+(h/ l)・W・Gx]・Rt
(1.7) where μ is the road surface friction coefficient, h is the height of the center of gravity, Gx is the longitudinal acceleration of the vehicle, and Rt is the tire radius.

Rear wheel shared torque proportional clutch torque Tra
is a set torque to prevent the initial slip of the rear wheels when the transmitted torque is expected to increase when suddenly starting from a stopped state, etc., and is calculated from the rear wheel shared torque Tre. It is obtained by finding the proportional torque Tra' and correcting it by k4.

In order to obtain such a rear wheel shared torque proportional clutch torque Tra and thereby control the clutch 414, a rear wheel shared torque calculating section 560 and a proportional torque calculating section 570 are used as shown in FIG. , a k4 correction section 572 as a proportional relationship adjustment means, and a switch 574a. Note that the proportional torque calculation section 570 and k
4 correction section 572 constitute differential limiting force setting means.

As shown in FIG. 7, the rear wheel shared torque calculating section 560 includes an engine torque detecting section 264 that detects the engine torque Te at a certain moment, and a torque converter torque ratio detecting section 266 that detects the torque converter torque ratio t at that moment. , a transmission reduction ratio detection unit 276 that detects the transmission reduction ratio ρm at that time, and a longitudinal acceleration Gx.
From center differential torque (center differential clutch torque) T
Respective information is sent from the center differential torque setting unit 562 that obtains c, and rear wheel shared torque Tre is calculated from these engine torque Te, torque converter torque ratio t, transmission reduction ratio ρm, and center differential torque Tc. is configured to do so.

In the engine torque detection section 264, the signal sent from the throttle position sensor 38 is sent to the filter 262.
Throttle opening data θth from which micro-vibration components caused by disturbances etc. have been removed through a filter 262b, and throttle opening data θth from which micro-vibration components from data caused by disturbances etc. have been removed from the engine speed sensor 170 through a filter 262b. From the rotation speed data Ne, for example, FIG.
The engine torque Te at that time is determined through an engine torque map as shown in FIG.

In the torque converter torque ratio detection section 266, the signal sent from the engine rotation speed sensor 170 is detected by the filter 262b.
The transmission torque ratio as shown in FIG. 17, for example, is determined from the engine rotation speed data Ne from which disturbance components have been removed through the filter 262c and the transmission rotation speed data Nt sent from the transmission rotation speed sensor 180 and from which disturbance components have been removed through the filter 262c. The transmission torque ratio t at that time is determined through the map.

Transmission reduction ratio detection section 276
Now, from the selected shift gear information from the shift position sensor 160, a shift gear-reduction ratio correspondence map (not shown) is created.
The reduction ratio ρm of the transmission is determined by referring to .

The center differential torque setting section 562 calculates the center differential torque Tc from the following equation based on the longitudinal acceleration Gx. Tc=(Z/Zr)・(Rt/ρrd)[(Wf-
Wa・Zs/Z)・Gx-h/l・Wa・Gx2]
...(2.1) However, Zs is the number of teeth of the sun gear, Zr
is the number of teeth of the ring gear, Wf is the front wheel shared load, Wa is the vehicle weight, ρrd is the final reduction ratio, and Z is Zs+Zr.

The rear wheel shared torque calculating section 560 calculates the rear wheel shared torque Tre based on the engine torque Te, torque converter torque ratio t, transmission reduction ratio ρm, and center differential torque Tc set as described above. , this calculation is based on the calculation results Tre1, Tr using the following two equations.
The larger value of e2 is adopted.

The calculation formula for calculating Tre1 is as follows:
This is a front-rear torque distribution formula assuming that the clutch 414 slips. Tre1=(Te・t・ρ1・ρm−Tc)・ρrd・
Zr/(Zr+Zs)

...(2.2)

00
[91] Also, the calculation formula for calculating Tre2 is the following formula,
This equation is based on the assumption that the clutch 414 does not slip, and the rear wheel shared torque Tre2 obtained thereby is the rear wheel shared torque at rest. Tre2=(Wr/W)・Te・t・ρ1・ρm・ρr
d...(2.4)

[0092] And Tre=MAX(Tre1, Tre2)
...(2.5), rear wheel shared torque Tr
Determine e.

[0093] The reason why the rear wheel shared torque Tre2 at rest is adopted as the rear wheel shared torque Tre as described above is because the value of Tre1 may be negative in the calculation formula for Tre1, and in such cases, etc. Rear wheel shared torque Tre when stationary
2 is adopted. Further, since the clutch control based on the rear wheel shared torque Tre is aimed at the time of starting the vehicle, it is suitable to employ the rear wheel shared torque Tre2 when the vehicle is stationary.

The proportional torque calculating section 570 calculates the clutch torque Tra' which is proportional to the rear wheel shared torque Tre mentioned above.
a′/Tre) is, for example, 0.8], and from Tre to Tr
Calculate a'.

k4 correction section 57 as proportionality adjustment means
2, the clutch torque Tra obtained in this way is
Correction (proportional relationship adjustment) is performed by multiplying ' by the rotation difference gain k4. Note that, as shown in FIG. 8, the rotation difference gain k4 is set in the rotation difference gain setting section 576 as follows.

In other words, the rotational speed difference gain k4 is intended to avoid the tight corner braking phenomenon, and is based on the ideal rotational speed difference ΔVhr set by the ideal rotational speed difference setting section 510.
is determined according to a map as shown in FIG. The rotation difference gain k4 in this map is the ideal rotation speed difference Δ
The relationship with Vhr is expressed by the following equation. K4=0.9×( |ΔVhrmax | |ΔVhr
|)/|ΔVhrmax |+0.1

...
(2.5) However, ΔVhrmax=MAX | ΔVhr
(δ=MAX) | Also, the coefficient 0.9 and constant 0.1 are
This is to set the lower limit of k2 to 0.1.

In this way, the rotational difference gain k linearly decreases as the ideal rotational speed difference ΔVhr increases.
By correcting according to 4, the ideal rotational speed difference Δ when turning, etc.
When Vhr increases, clutch torque Tra' is reduced so that turning performance (performance that can prevent tight corner braking) is given priority over sudden start performance.

[0098] Also, in order to obtain the clutch torque Tra,
The clutch torque Tra is set to have a proportional relationship with the ideal rotational speed difference ΔVhr, and this proportional coefficient is determined by the magnitude of the rear wheel shared torque Tre.The larger the rear wheel shared torque Tre is, the proportional coefficient [slope m' (=Tra/ΔV
hr)] may be provided.

Furthermore, the clutch 574a
74, when the vehicle speed is low (in this example, Vref
<20km/h), it is ON and the clutch torque T
a can be output as data, but if the vehicle speed becomes higher than this (Vref≧20 km/h), it turns OFF and outputs the value 0 as data of the rear wheel shared torque proportional clutch torque Tra. This is because the rear wheel shared torque proportional control tries to secure the torque transmitted to the road surface by preventing the wheels from slipping, and according to the rear wheel shared torque proportional clutch torque Tra, tight corner braking occurs. In order to avoid this, a condition has been established to perform this rear wheel shared torque proportional control only when the vehicle is running at a constant speed. -ing

The clutch torques of the differential clutch torque Trn and the rear wheel shared torque proportional clutch torque Tra are respectively set for each control cycle that is repeated at an appropriate timing, and sent to the maximum value selection section 580. This maximum value selection unit 580 selects the maximum value (
Let this clutch torque be Tr'). However, when the switch 574a is OFF, 0 is sent as the clutch torque Tra, so the maximum value selection section 58
At 0, clutch torque Trn is selected.

As shown in FIG. 9, the clutch torque Tr' selected in this manner is determined by the k5 correction section 584
Corrections will be made. This k5 correction is applied to clutch torque Tr' when traction control is performed.
This is a correction that reduces the
．． It is considered to be 0.

The clutch torque Tr thus corrected is sent to the torque-current converter 586, where it is converted into a clutch supply current I that provides the set clutch torque Tr. It has become so. Here, the map (see block 586 in Figure 9)
The clutch supply current I is calculated from the clutch torque Tr by
I am getting .

[0103] Once the clutch supply current I is obtained as described above, a current limiter 588 holds I at the limit value if the clutch supply current I exceeds the limit value (for example, 3A). It looks like this.

In this way, information on the clutch supply current I that has passed through the limiter 588 is taken into the peak hold filter 590. This peak hold filter 590 is a kind of limiter that prevents excessive sudden changes in current so that hunting does not occur in control due to sudden changes in current. 4A/s), and for the current fall, set a slightly lower limit speed (for example 5.2A/s).
/s) is set.

[0105] If information is sent about the clutch supply current I such that the speed of current change exceeds such a limit, the control current is kept at a value corresponding to this limit speed.

Furthermore, the control current I that has passed through the filter 590 passes through the switch 592a and is connected to the EMCD coil 42.
It is set to be sent to 0. Note that the switch 592
a is determined by the signal from the determining means 592 if ABS control (anti-lock brake control) is performed (O
If it is in the N state, it is turned OFF, and if ABS control is not being performed, it is turned ON. In other words, the signal of the control current I is sent on the condition that ABS control is not performed. This is because during ABS control, it is necessary to operate ABS reliably, and it is not preferable to control the torque distribution state between the left and right wheels at this time because it may interfere with ABS control.

[0107] The coil 420 generates a magnetic force in response to the control current I thus sent, and adjusts the connection state of the clutch 414.

Since this device is constructed as described above, differential adjustment is performed as follows.

First, the flow of the overall operation of the drive system is shown in Figure 1.
9, first, each control element is initialized (step a1), the steering angle neutral position is learned (step a2), and the clutch preload is learned (step a3). Front and rear wheel drive force distribution control is performed while controlling the clutch 28 according to the duty (step a4), and furthermore, the rear differential is controlled (step a5).

[0110] Then, in steps a7 to a11, slip control, trace control, torque selection, retard control calculation, SCI (Series Communication
Perform engine output control (traction control) such as communication control (Interface), turn on the torque distribution display lamp (step a12), and step a13.
Perform failure diagnosis. In step a14, it is determined whether a predetermined time (15 msec) has elapsed, and when the predetermined time (15 msec) has elapsed, a runaway check is performed by the watchdog (step a15), and the process returns to the above-mentioned step a2.
Repeat the series of controls from ~a13.

In other words, the above-mentioned front and rear wheel drive force distribution control, rear differential control, and engine output control are performed at a predetermined period (15
msec).

Among these, rear differential control (step a5
) will be explained with reference to the flowcharts of FIGS. 20 to 22.

As shown in FIG. 20, first, the wheel speeds FR,
FL, RR, RL, steering angle θ1, θ2, θn, lateral acceleration G
y, longitudinal acceleration Gx, throttle opening θth, engine rotational speed Ne, transmission rotational speed Nt, selected shift stage, etc., and from these data, driver-required vehicle speed Vref, driver-required steering angle δref, etc. is calculated (step j1).

[0114] Then, the ideal rotational speed difference ΔVhr between the left and right wheels is determined according to the map from the driver-required vehicle speed Vref and the driver-required steering angle δref (step j2), and this ΔV
A rotation difference gain k4 is set from hr according to the map (step j3).

Furthermore, two types of rear wheel shared torque Tre1,
Tre2 is calculated (steps j4, j5). and,
The larger one of the two types of rear wheel shared torque Tre1 and Tre2 is adopted as the rear wheel shared torque Tre (step j6
).

[0116] Also, the rear wheel torque gain k3 is determined from the rear wheel shared torque Tre according to the map (step j
7). Then, the differential compatible clutch torque Trn is determined from the actual left and right wheel rotation speed difference ΔVrd, the right and left wheel ideal rotation speed difference ΔVhr, and the rear wheel torque gain k3 (step j8).
.

On the other hand, the rear wheel shared torque proportional clutch torque Tra is determined from the rear wheel shared torque Tre and the rotational difference gain k4 (step j9).

Furthermore, in step j10, the larger of these clutch torques Trn and Tra is set as the set clutch torque Tr'.

Furthermore, in step j11, the clutch torque Tr' determined in this manner is determined based on the engine output state.
In other words, the clutch torque Tr is obtained by correcting k5 depending on whether traction control is being performed.

[0120] Subsequently, the clutch torque Tr thus corrected is subjected to torque-current conversion to obtain the clutch supply current I (step j12), and the clutch supply current I is set to a limit value (for example, 3A). ) (step j13), and if I exceeds the limit value, I is held at the limit value (step j14).

In this way, the clutch supply current I subjected to limiter processing is filtered by the peak hold filter 590 (step j15), and it is determined whether ABS control (anti-lock brake control) is being performed (step j16). If ABS control is being performed, the clutch supply current I is set to 0 (step j17).
, R/D control (rear differential control), that is, differential limiting control is performed through the EMCD coil 420 (step j18).
).

The above-mentioned differential clutch torque Trn is calculated as shown in FIG. 21.

First, from the right wheel speed Vrl, the left wheel speed V
Calculate the difference ΔVrd (=Vrl−Vrr) by subtracting rr (step k1), and from this difference (actual rotational speed difference between the left and right wheels) ΔVrd as described above (step j
(Refer to 3) The ideal rotational speed difference ΔVhr between the left and right wheels is subtracted to obtain the difference ΔVr (=ΔVrd−ΔVhr) (step k2).

[0124] Then, in step k3, it is determined whether the above-mentioned ideal rotational speed difference ΔVhr between the left and right wheels is greater than or equal to 0. If ΔVhr is greater than or equal to 0, the process proceeds to step k4, where ΔVhr is 0.
If it is less than that, proceed to step k5.

Proceeding to step k4, the map [FIG. 15 (
a)] to calculate the clutch torque Trn' from ΔVr.
Set.

Specifically, if ■ΔVr≧ΔVhr,
The clutch torque Trn' is the difference ΔVr (=ΔVrd−ΔV
Trn′=a increases in proportion to the size of
Set as ×(ΔVrd−ΔVhr)=a×ΔVr (where a is a proportionality constant).

[0127] Also, if ■ΔVhr>ΔVrd>0,
Clutch torque Trn' is set to 0 to set a so-called dead zone region.

Furthermore, ■If 0≧ΔVrd, Trn'=-a×ΔVrd=-a×(ΔVr+Δ
Vhr) (where a is a proportionality constant).

[0129] When ΔVhr=0, ΔVhr>Δ
The dead zone region where Vrd>0 disappears.

Proceeding to step k5, the map [FIG. 15 (
b)] to calculate the clutch torque Trn' from ΔVr.
Set.

Specifically, ■If ΔVrd≧0, set Trn'=a×ΔVrd=a×(ΔVr+ΔVhr) so that clutch torque Trn' increases in proportion to the magnitude of ΔVrd (however, a is a proportionality constant).

[0132] Also, if ■0>ΔVrd>ΔVhr,
Clutch torque Trn' is set to 0 to set a so-called dead zone region.

Furthermore, ■If ΔVhr≧ΔVrd, clutch torque Trn' is ΔVr(ΔVrd−ΔVhr)
Trn' = -a x (ΔVrd - ΔVhr) = -a x ΔV so that it increases in proportion to the size of
Set as r (where a is a proportionality constant).

[0134] In this way, the differential compatible clutch torque Trn' obtained in steps k4 and k5 is
By integrating the lateral G gain k1 in step 6, the lateral acceleration is corrected (step k6), and the differential compatible clutch torque Tr is
n is obtained.

[0135] Such differential compatible clutch torque Trn
By setting the above, the magnitude of the clutch torque Tr is appropriately set, and the vehicle can be made to behave in accordance with the driver's intention when turning while appropriately allowing the differential between the left and right wheels.

In particular, the direction SIG of the steering angle δh corresponding to the sensor
(δh) and the direction SIG(Gy) of the lateral acceleration data Gy are not equal, the driver-required steering angle is set to 0. Even if the steering position of the steering wheel differs from the actual steering angle (turning state) of the vehicle, inappropriate data will not be adopted, contributing to improved control performance.

Furthermore, as the driver requested vehicle speed Vref,
Since the wheel speed data with the second largest size from the bottom among the rotational speed data signals FL, FR, RL, and RR is adopted,
Data reliability is ensured.

As shown in the map (see FIG. 13), the setting of the ideal rotational speed difference ΔVhr increases as the steering angle increases, and at low vehicle speeds it increases as the vehicle speed increases, but at high speeds, the vehicle speed increases. Since the setting is made so that the tendency of increase becomes gradually smaller with respect to an increase in , the rear wheels tend to slip more easily at high speeds, and the responsiveness of the vehicle body attitude required at higher speeds is ensured. Regarding the steering angle, the greater the steering angle, the greater the rotation difference required between the front and rear wheels, which has the advantage of being appropriately tolerated and avoiding tight corner braking.

On the other hand, the above-mentioned rear wheel shared torque proportional clutch torque Tra is calculated as shown in FIG.

First, the rear wheel shared torque Tre is converted into a clutch torque Tra' proportional to this (step m1).
), the clutch torque Tra' is corrected by the rotational difference gain k4 to obtain the clutch torque Tra (step m2).
.

[0141] Further, based on the determination of whether the vehicle speed is low (Vref<20km/h in this example) by the determining means 574, the clutch obtained in step m2 described above is activated at low vehicle speed (Vref<20km/h). Torque Tra is used as a control signal, but if the vehicle speed is higher than this (Vref≧20k
m/h), and 0 is set as the control signal for the rear wheel shared torque proportional clutch torque Tra.

[0142] By using the rear wheel shared torque Tre and the rear wheel shared torque proportional clutch torque Tra that is proportional to the ideal rotational speed difference ΔVhr of the right and left wheels, the left and right wheels are This makes it possible to appropriately limit the differential of the vehicle and transmit high torque to the road surface, preventing tire slippage when starting or suddenly accelerating, and improving driving stability and turning performance. This can be achieved at the same time, improving driving performance and contributing to improving the durability of the drive system.

Note that this rear differential mechanism can be applied to vehicles other than four-wheel drive vehicles, and can also be applied to a front differential.

[0144]

As described in detail above, the differential limiting control device for a four-wheel drive vehicle of the present invention includes a front and rear wheel differential limiting mechanism that limits the differential state between the front and rear wheels of a vehicle; In a four-wheel drive vehicle equipped with a left and right wheel differential limiting mechanism that limits the differential state between the left and right rear wheels or front wheels of the vehicle, left and right wheel differential is applied when there is a difference in rotational speed between the front and rear wheels. Input torque setting means that calculates the input torque to the limiting mechanism side wheels and the input torque to the left and right wheel differential limiting mechanism side wheels when the torque is not generated, and selects the larger value of these two input torques. and a left and right wheel differential limiting force that sets the differential limiting force of the left and right wheel differential limiting mechanism so that the differential limiting force of the left and right wheel differential limiting mechanism increases with an increase in the input torque set by the input torque setting means. With a configuration including a setting means and a differential limiting control means for controlling the left and right wheel differential limiting mechanism so that the differential limiting force set by the left and right wheel differential limiting force setting means is obtained, or during sudden acceleration from low speed, etc.
It is now possible to appropriately limit the differential between the left and right wheels, allowing appropriate high torque to be transmitted to the road surface, preventing tire slippage when starting or sudden acceleration, and improving driving stability and turning performance. This simultaneously improves driving performance and contributes to improving the durability of the drive system.

[0145] The left and right wheel differential limiting force setting means is configured to increase the differential limiting force of the left and right wheel differential limiting mechanism as the input torque set by the input torque setting means increases. By setting the differential limiting force so as to decrease as the rotational speed difference between the left and right wheels increases, the above effects can be more reliably obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the overall configuration of a differential limiting control device for a vehicle as an embodiment of the present invention.

FIG. 2 is an overall configuration diagram of a drive torque transmission system equipped with a differential control device of this embodiment.

FIG. 3 is a sectional view showing a rear differential as a left and right wheel differential of this embodiment.

4(a) and (b) are both cross-sectional views taken along the line AA in FIG. 3. FIG.

FIG. 5 is a configuration diagram showing a rotation speed difference corresponding control section of the present embodiment.

FIG. 6 is a configuration diagram showing a rear wheel torque gain correction section of the present embodiment.

FIG. 7 is a configuration diagram showing a part of the input torque corresponding control section of the present embodiment.

FIG. 8 is a configuration diagram showing a part of the input torque corresponding control section of the present embodiment.

FIG. 9 is a configuration diagram of a portion from a maximum value selection section to a control current output section in this embodiment.

FIG. 10 is a configuration diagram showing details of the steering angle detection means of this embodiment.

FIG. 11 is a configuration diagram showing details of the vehicle speed detection means of this embodiment.

FIG. 12 is a plan view schematically showing a wheel state for explaining the ideal rotational speed difference of this embodiment.

FIG. 13 is a diagram showing a map for setting an ideal rotational speed difference according to the present embodiment.

FIG. 14 is a diagram showing a rotation difference gain setting map of this embodiment.

FIGS. 15(a) and 15(b) are diagrams each showing maps for setting differential clutch torque according to the present embodiment.

FIG. 16 is a diagram showing an example of an engine torque map according to the present embodiment.

FIG. 17 is a diagram showing an example of a transmission torque ratio map according to the present embodiment.

FIG. 18 is a center differential input torque setting map of this embodiment.

FIG. 19 is a flowchart showing the flow of control of the entire vehicle including the device of this embodiment.

FIG. 20 is a flowchart showing the flow of control of the rear differential according to the present embodiment.

FIG. 21 is a flowchart showing the flow of setting the clutch torque corresponding to the rotational speed difference in this embodiment.

FIG. 22 is a flowchart showing the flow of setting clutch torque corresponding to input torque in this embodiment.

[Explanation of symbols]

2 Engine 4 Torque converter 6 Automatic transmission 8 Output shaft 10 Intermediate gear (transfer idler gear) 12
Center differential (center differential) 14
Differential gear device 15 for front wheels Bevel gear mechanism 15A Bevel gear shaft 15a Bevel gears 16, 18 Front wheels 17L, 17R Front wheel side axle 19 Reduction gear mechanism 19a Output gear 20 Propeller shaft 21 Bevel gear mechanism 22 Rear as a differential gear device for rear wheels Differential (EMCD) 23 Differential limiting device 24 Left rear wheel 26 Right rear wheel 25L, 25R Rear wheel axle 27 Front wheel output shaft 27a Hollow shaft member 28 Differential limiting mechanism 29 Rear wheel output shaft 30, 30a, 30b, 30c Handle angle sensor 3
2 Steering wheel 34, 34a, 34b Lateral acceleration sensor 36 Longitudinal acceleration sensor 38 Throttle sensor 39 Engine key switch 40, 42, 44, 46 Wheel speed sensor 48 Controller 48a Rear differential control section 50 Anti-lock brake device 50A Brake switch 121 Sun gear 122 Planetary Pinion (planetary gear) 12
3 Ring gear 125 Planet carrier 160 Shift lever position sensor (shift range detection means) 160A Shift lever of automatic transmission 170 Engine speed sensor 180 Transmission speed sensor 202a~
202d Filter 212 Driver-required steering angle calculation unit (pseudo steering angle calculation unit) 212a Sensor-compatible steering angle data setting unit 212b
Lateral acceleration data calculation section 212c Comparison section 212d Driver requested steering angle setting section (vehicle speed data setting section) 216 Driver requested vehicle speed calculation section (pseudo vehicle speed calculation section) as vehicle speed data detection means 216a Wheel speed selection section 216c Driver-required vehicle speed calculation unit 216d Filter 218 Ideal rotational speed difference setting units 262a, 262b, 262c as ideal operating state setting units Filter 264
Engine torque detection section 266 Torque converter torque ratio detection section 276 Transmission reduction ratio detection section 401
Input shaft 402 Drive pinion gear 403 Crown gear 404 Power transmission annular member 405 First housing 406 Second housing 407 Ring gear 408 Sun gear 409 Carrier 410a, 410b Shafts 411a, 411b Planetary gear 412 Bearing 413 Case 414 Multiplex as differential limiting mechanism Plate clutch 414a
, 414b Clutch disc 415a, 145b
Holder portion 416 Hollow shaft 417 Drive device 418 Annular support member 419 Magnet 420 Solenoid (as differential limiting mechanism control means)
EMCD coil) 421 Ball 423 Annular member 424 Groove 425 Chamber 426 Second housing side member 427 Clutch 428 Bearing 429 Force direction conversion mechanism 430 Electromagnetic clutch mechanism (EMCD) 431
Bolt 500 Right and left wheel actual rotational speed difference detection section 506 as actual rotational speed difference detection means Right and left wheel actual rotational speed difference calculation section 510 Right and left wheel ideal rotational speed difference setting section 518 as ideal rotational speed difference detection means Ideal operating state setting section Ideal rotational speed difference setting section 520 Differential compatible clutch torque setting section (differential limiting force setting means) 522 Subtractor 546 Correction section (k3 correction section) 544 Rear wheel torque gain setting section 560 Rear wheel torque gain setting section 560 As input torque setting means Wheel sharing torque calculation section 562 Center differential torque setting section 570 Proportional torque calculation section (part of differential limiting force setting means) 572 k4 correction section as proportional relationship adjustment means (part of differential limiting force setting means) 574 Judgment Section 574a Switch 576 Rotation difference gain setting section 580 Maximum value selection section 584 k5 correction section 586 Torque-current conversion section 588 Current limiting section (limiter) 590 Peak hold filter 592 Judgment means 592a Switch

Claims (2)

[Claims] 1. A front and rear wheel differential limiting mechanism that limits the differential state between the front and rear wheels of a vehicle; and a left and right wheel differential limiting mechanism that limits the differential state between the left and right rear wheels or front wheels of the vehicle. 4 with
In a wheel drive vehicle, the input torque to the left and right wheel differential limiting mechanism side wheels when a rotational speed difference occurs between the front and rear wheels and the input torque to the left and right wheel differential limiting mechanism side wheels when there is no rotational speed difference. An input torque setting means that calculates and selects the larger value of these two input torques, and an increase in the input torque set by this input torque setting means to increase the difference between the left and right wheel differential limiting mechanisms. Left and right wheel differential limiting force setting means for setting the differential limiting force so that the dynamic limiting force increases; and left and right wheel differential limiting force setting means for setting the differential limiting force so that the differential limiting force increases, and 1. A differential limiting control device for a four-wheel drive vehicle, comprising differential limiting control means for controlling a wheel differential limiting mechanism. 2. The left and right wheel differential limiting force setting means is configured to increase the differential limiting force of the left and right wheel differential limiting mechanism in accordance with an increase in the input torque set by the input torque setting means. The differential for a four-wheel drive vehicle according to claim 1, characterized in that the differential limiting force is configured to be set to decrease as the rotational speed difference between the left and right wheels increases. motion limit control device.