JP3325347B2 - Driving force control device for four-wheel drive vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving force control apparatus for a four-wheel drive vehicle, and more particularly, to a torque characteristic having a plurality of physical quantities as parameters and a gain characteristic associated with each torque characteristic set in advance. The present invention relates to a system in which the engagement torque of the differential limiting clutch means can be appropriately set in consideration of the plurality of parameters comprehensively.

[0002]

2. Description of the Related Art Conventionally, a four-wheel drive vehicle is provided with a transfer device for distributing a driving force to a front wheel and a rear wheel. This transfer device usually has a differential gear mechanism having no differential limiting function. However, recently, in order to be able to control the driving force distribution to the four wheels, a differential limiting device including an electromagnetic multi-plate clutch is provided together with or instead of the differential gear mechanism. Provisions have also been made.

[0003] In a conventional differential limiting device, generally,
Although the configuration is such that the differential limiting torque is controlled based on one physical parameter (for example, the differential rotation speed), recently, the differential limiting torque is controlled based on a plurality of physical parameters. Technology is also being proposed. For example, Japanese Unexamined Patent Publication No. 1-145232 discloses that in a differential limiting device that limits the differential between the right and left rear wheels, the fastening torque of the differential limiting mechanism is set to a differential limiting set according to the accelerator opening. A vehicle differential limiting control device configured to control the total differential limiting torque of the torque and the differential limiting torque set according to the differential rotation speeds of the left and right rear wheels is disclosed. .

[0004]

By the way, as in the differential limiting control apparatus described in the above-mentioned publication, the differential limiting control is performed so that the total torque of the differential limiting torques independently obtained based on a plurality of parameters is obtained. When controlling the device, it is very difficult to properly control the differential limiting device. That is, assuming that the vehicle speed, the differential rotation speed, and the lateral acceleration are applied as the parameters, since the plurality of parameters are not mutually independent, the differential limiting torque is independently determined based on these parameters. If the differential limiting device is controlled to obtain the total torque, the differential stability may be too large or too small depending on the driving condition of the vehicle, resulting in steering stability. And the problem that runnability decreases. An object of the present invention is to enable the differential limiting torque of the differential limiting clutch means of a four-wheel drive vehicle to be appropriately controlled in consideration of the correlation between a plurality of physical parameters.

[0005]

According to a first aspect of the present invention, there is provided a driving force control apparatus for a four-wheel drive vehicle, wherein a driving force distribution to four wheels is distributed via a differential limiting clutch means capable of controlling a differential limiting torque. In the driving force control device for a four-wheel drive vehicle to be controlled, the wheel speed limited differentially by the differential limiting clutch means.
Difference and the yaw rate acting on the body of the four-wheel drive vehicle and the
Detector that detects each of the three physical quantities of the vehicle speed of a four-wheel drive vehicle
The step and one or two of the three physical quantities
Data of the fastening torque of the differential limiting clutch
A torque characteristic storage unit in which the torque characteristics are set in advance , a torque calculation unit that obtains a fastening torque by applying the three physical quantities detected by the detection unit to the plurality of torque characteristics, and a torque calculation unit that obtains the fastening torque. Torque addition means for adding a plurality of fastening torques to obtain a total fastening torque,
Control means for controlling the differential limiting clutch means so that the total engagement torque obtained by the torque adding means,

[0006] The torque characteristic storage means, as one or two parameters of said three physical quantities, at least one gain characteristic is previously set remembering correlation to the torque characteristics are stored, the The torque calculating means is:
The gain is obtained by applying the detected physical quantity to a gain characteristic,
The present invention is configured to multiply the fastening torque determined from the torque characteristic by the gain and output the result to the torque adding means.

[0007] Here, before Symbol torque characteristic storage means, dependent wheel speed difference remembering correlation torque characteristics and parameters, the vehicle speed and configuration that the gain characteristic is stored for a parameter the yaw rate (claim 1 Claim 2 ),

[0008] The torque characteristic storage means and remembering correlation torque characteristics of the wheel speed difference as a parameter, vehicle speed and configuration that the gain characteristic is stored for the wheel speed difference as a parameter (claims dependent on claim 1 Item 3 ), the torque characteristic storage means correlates a torque characteristic with a wheel speed difference as a parameter, and a gain characteristic with a vehicle speed and a yaw rate as parameters, and a gain characteristic with a vehicle speed and a wheel speed difference as parameters. claims but dependent on the stored configuration (claim 1
4), before Symbol torque characteristic storage means, vehicle speed and yaw rate remembering correlation torque characteristics as a parameter, the dependent claims wheel speed difference configurations gain characteristic is stored for a parameter (to claim 1 5 ) , etc.

[0009]

[0010]

In the driving force control apparatus for a four-wheel drive vehicle according to the first aspect, the differential limiting clutch is detected by the detecting means.
Between the wheel speed difference and the four-wheel drive vehicle
When three physical quantities, ie, the acting yaw rate and the vehicle speed of the four-wheel drive vehicle, are detected, the physical quantities are applied to the plurality of torque characteristics of the torque characteristic storage means, respectively, and the plurality of fastening torques are calculated by the torque calculation means. Is calculated, and the torque adding means
The plurality of calculated engagement torques are added to determine a total engagement torque, and the control means controls the differential limiting clutch means so that the total engagement torque is obtained.

[0011] Here, the torque characteristic storing means, and at least one gain characteristic remembering correlation torque characteristics, the gain characteristics of one or two parameters of said three physical quantities stored Then, the torque calculating means obtains a gain from the gain characteristic, multiplies the fastening torque obtained from the torque characteristic correlated with the gain characteristic by the gain, and outputs the result to the torque adding means. That is, at least one of the plurality of fastening torques is changed in gain by the gain obtained from the gain characteristic, and the total fastening torque is set by adding the changed fastening torque.

Therefore, if the gain characteristic is appropriately set, at least one of the fastening torques is changed in gain in consideration of the correlation between the three parameters, so that the total fastening torque is changed to the running state of the vehicle. The driving force can be appropriately distributed to the four wheels by setting the appropriate value without any excess or shortage and appropriately controlling the engagement torque of the differential limiting clutch means. Thereby, the steering stability and running performance of the four-wheel drive vehicle can be improved .

In the driving force control device according to the second aspect, the fastening torque according to the wheel speed difference can be changed by a gain according to the vehicle speed and the yaw rate, so that the wheel speed difference, the vehicle speed and the yaw rate can be changed. In consideration of the above, the total fastening torque can be appropriately set.

In the driving force control device according to the third aspect , since the fastening torque according to the wheel speed difference can be changed by a gain according to the vehicle speed and the wheel speed difference, the total torque is calculated in consideration of the vehicle speed and the wheel speed difference. The fastening torque can be set appropriately. Claim 4
In the driving force control device, the fastening torque according to the wheel speed difference can be changed between a gain according to the vehicle speed and the yaw rate, and a gain according to the vehicle speed and the wheel speed difference. The total fastening torque can be appropriately set in consideration of the torque and the yaw rate .

In the driving force control device according to the fifth aspect , since the fastening torque according to the vehicle speed and the yaw rate can be changed by the gain according to the wheel speed difference, the total is calculated by taking the vehicle speed, the yaw rate and the wheel speed difference into account. The fastening torque can be set appropriately .

[0016]

Embodiments of the present invention will be described below with reference to the drawings. The present embodiment is an example of a case where the present invention is applied to a four-wheel drive vehicle of a type in which front wheels are driven during normal running and the rear wheels are also driven in a running state in which differential limitation is required. First, a schematic overall configuration of the four-wheel drive vehicle MC will be described. As shown in FIG. 1, in a four-wheel drive vehicle MC, a left front wheel axle 5 and a right front wheel axle 6 are located between left and right front wheels 1 and 2.
A left rear wheel axle 8 and a right rear wheel axle 9 are provided between the left and right rear wheels 3 and 4, and the left front wheel axle 5 and the right front wheel axle 6 The left rear wheel axle 8 and the right rear wheel axle 9 are interlocked and linked by a front wheel differential device 7 that allows a differential.
The left and right rear wheels 3 and 4 are interlocked and linked by a rear wheel differential device 10 that allows a differential.

A power unit 11 comprising an engine and an automatic transmission directly connected to the engine is disposed in the front center of a vehicle body (not shown) in a front-rear direction. A front wheel driving force transmission system 13 that transmits driving force to the front wheel differential 7 and a rear wheel driving force transmission system 14 that transmits driving force from the output shaft 12 of the power unit 11 to the rear wheel differential 10 are provided. Have been.
The front wheel driving force transmission system 13 transmits a driving force from a gear 15 fixed to the output shaft 12 to a gear 16, and transmits the driving force of the gear 16 to the front wheel differential 7 via a front wheel driving shaft 17. It is configured to do so. The rear wheel driving force transmission system 14 includes a rear wheel drive shaft 1 operatively connected to the rear wheel differential 10.
8 and an electromagnetic clutch 19 provided between the output shaft 12 and the rear wheel drive shaft 18 and capable of controlling a differential limiting torque (this corresponds to a differential limiting clutch means). ing.

The electromagnetic clutch 19 includes a case 20 that rotates integrally with the output shaft 12, a plurality of clutch plates 21 disposed in the case 20 and rotating integrally with the case 20,
A plurality of clutch discs 22 disposed in the case 20 and integrally rotating with the rear wheel drive shaft 18, and electromagnets (which are formed by a coil 23 and a magnetic path forming a magnetic path on the plurality of clutch plates 21 and the clutch discs 22). And an electromagnet fixed to the vehicle body. When the coil 23 of the electromagnetic clutch 19 is not energized, the electromagnetic clutch 19 is in a disconnected state, and only the left and right front wheels 1 and 2 are driven, and the driving force is not transmitted to the rear wheel drive shaft 18. When energized, a drive torque equal to the fastening torque proportional to the magnitude of the coil current is transmitted to the rear wheel drive shaft 18, and the four-wheel drive state is established.

Next, the control system will be described. A power unit control device 30 for controlling the power unit 11,
ABS control device 31 for controlling a brake device (not shown)
(Control device for anti-skid control) and a clutch control device 32 for controlling the electromagnetic clutch 19 are provided. Further, as the sensors, the rotational speed N1 of the left front wheel 1 is set.
Is detected via a disk 33 which rotates integrally with the left front wheel axle 5 and a right speed which detects the rotation speed N2 of the right front wheel 2 via a disk 35 which rotates integrally with the right front axle 6. The front wheel speed sensor 36 and the rotational speed N3 of the left rear wheel 3 are transmitted to the disk 3 fixed to the left rear wheel axle 8.
7, a right rear wheel speed sensor 40 for detecting a rotation speed N4 of the right rear wheel 4 via a disk 39 that rotates integrally with the right rear wheel axle 9,
A brake switch 41, a steering angle sensor 43 for detecting a steering angle θh of a steering wheel 42, a neutral / inhibitor switch 44, a yaw rate sensor 45 for detecting a yaw rate ψv acting on the vehicle body, an idle switch 46 provided in the engine, A throttle opening sensor 47 and a crank angle sensor 48 are provided.

The wheel speed sensors 34, 36, 38, 40
The wheel speed signals N1, N2, N3, and N4 are input to the ABS control device 31, and the ABS signal and the wheel speed signals N1, N2, N3, and N4 that are turned on during execution of the anti-skid control are output from the ABS control device 31. Is supplied to the clutch control device 32. The switch signal BR from the brake switch 41, the steering angle signal θh from the steering angle sensor 43, and the yaw rate signal ψv from the yaw rate sensor 45 are directly input to the clutch control device 32.

The neutral / inhibitor switch 4
4, the switch signal ID from the idle switch 46, the throttle opening signal TVO from the throttle opening sensor 47, and the crank angle sensor 4.
5 is supplied to the clutch control device 32 via the power unit control device 30. The clutch control device 32 is configured to be able to output a coil current Iout to the coil 23 of the electromagnetic clutch 19. The clutch control device 32 is connected to a power source when the ignition switch is ON, and is connected to the ignition switch. Is turned off, the power is supplied from the backup battery 49, and the clutch control device 32 basically operates when the ignition signal IG input when the ignition switch is ON is input. Although it is configured as described above, it operates even when the ignition switch signal IG is OFF during tailing processing.

The clutch control unit 32 includes an A / D converter for A / D converting a detection signal as needed, a waveform shaping circuit for shaping the detection signal as needed, an input / output interface, a CPU and a ROM. The microcomputer includes a microcomputer including a RAM, a coil drive circuit that outputs a coil current Iout to the coil 23, and the like. In the ROM of the microcomputer, the fastening torque is controlled according to the running state of the four-wheel drive vehicle MC as described later.
A control program for driving force distribution control for controlling the driving force distribution to the wheels 1 to 4 and a plurality of maps and the like accompanying the control program are previously input and stored, and the RAM is required for arithmetic processing of the control. Various memories are provided.

Here, the outline of the control for the electromagnetic clutch 19 will be briefly described. As shown in FIG.
As the physical quantities (physical parameters) related to the running state and behavior of the four-wheel drive vehicle MC, the differential rotation speed ΔN of the front and rear wheels, the yaw rate ψv, and the vehicle speed V are mainly used. First, the detected differential rotation speed ΔN is applied to the map M1 to determine the fastening torque Tn, and the fastening torque Tn is calculated using the gain G1n obtained from the gain characteristic of the map M2 and the gain G2n obtained from the gain characteristic of the map M3. Then, the gain is changed, and the fastening torque Tn after the gain change is subjected to a hold process as necessary to obtain a differential rotation speed reflecting engagement torque T1.

In parallel with the above, the detected yaw rate Δv
The estimated lateral acceleration α obtained from the vehicle speed V (the speed of the four-wheel drive vehicle MC) is applied to the map M4 to determine the fastening torque Tψ, and the fastening torque Tψ is calculated as the gain G1ψ obtained from the gain characteristic of the map M5. Is changed to obtain the yaw rate reflection engagement torque T2. In parallel with the above, the detected vehicle speed V is applied to the map M6 to determine the engagement torque Tv to determine the vehicle speed reflecting engagement torque T3.

Next, the total fastening torque Tt obtained by adding the fastening torques T1, T2 and T3 is converted to a coil current I by applying the map to the map M7. The output coil current Iout is set by multiplying the gain Ga by the ABS processing and the gain Gt by the tailing processing, and the coil current Iout is output to the coil 23.

Here, each of the maps M1, M4 and M6 corresponds to a torque characteristic in which a characteristic of the fastening torque is set, and each of the maps M2, M3 and M5 is a characteristic of a gain multiplied by the fastening torque. Is equivalent to the gain characteristic in which. Next, the configuration of these maps M1 to M7 will be described. As shown in FIG. 3, the map M1 includes the engagement torque Tn using the differential rotation speed ΔN as a parameter.
The differential rotation speed ΔN is determined by the following equation as the difference between the detected maximum wheel speed and minimum wheel speed of the four wheels.

ΔN = Max [N1, N2, N3, N4] -min
[N1, N2, N3, N4] In the map M1, a solid line indicates a torque characteristic during acceleration, a dashed line indicates a torque characteristic during deceleration, and a = 80 to 12
0, b = 40 to 80, c = 400 to 500, etc. Some slippage is preferred when accelerating, but
At the time of deceleration, it is desirable to prevent locking of the wheels and to share the braking force with as many wheels as possible, so that a> b is set. Thereby, braking performance can be improved.

The map M2 shows the vehicle speed V as shown in FIG.
And the yaw rate ψv as parameters, and the characteristics of the gain G1n are set. The vehicle speed V is determined by the following equation by multiplying the detected minimum wheel speed by a constant. V = min [N1, N2, N3, N4] · 2π · rt · 60/10
00, where rt is the dynamic load radius of the tire. Since the minimum wheel speed is generated from the wheel gripping the road surface, the vehicle speed V is determined from the minimum wheel speed. In the map M2, in the area A1, the gain G1n is set to 1.0 in order to secure the straight running stability, and in the area A3, the gain G1n is set to 1.0 in order to prevent spin during a sharp turn. In the region A4, the gain G1n =
It is set to 1.0. In addition, d = 25-35, e = 70
１００100, f = 25-30, g = 40-60, etc.

Further, in the area A2, the gain G1n = 0 is set in order to improve the turning performance of turning in a tight corner. Also, when turning, the front wheels 1 and 2 have a large wheel load, and the rear wheels 3 and 4 have a small wheel load, so that the rear wheels 3 and 4 are likely to skid, resulting in an oversteer tendency. The body becomes easier to spin. Therefore, in the region A5, the driving force of the front wheels 1 and 2 is increased to decrease the grip force (tire lateral force) of the front wheels 1 and 2, and the grip force (tire lateral force) of the rear wheels 3 and 4 is increased. In order to cancel the oversteer tendency, the gain G
1n = 0 is set. The boundary line L1 is 0.4G
(However, G is a gravitational acceleration) is a line corresponding to the lateral acceleration, and the boundary lines L2 and L3 indicate that the yaw rate 減少 v decreases in accordance with the increase in the vehicle speed V. 4 can be distributed.

The map M3 shows the vehicle speed V as shown in FIG.
The characteristic of the gain G2n is set using the differential rotation speed ΔN as a parameter. The boundary line L4 is a line of the differential rotation speed ΔN corresponding to a case where the tire moving radius is reduced by 10% due to a decrease in tire air pressure or the mounting of a tempered tire. In order to ignore the influence of the differential rotation speed ΔN due to the mounting of the tire, the gain G2n is set to 0, and the area B2
Then, in order to correspond to the substantially generated differential rotation speed ΔN,
The gain G2n is set to 1.0. Note that h = 7, i
= 70 to 100, j = about 30 to 50, and h =
The value of 7 is the lowest vehicle speed that can be detected from the detection signals of the wheel speed sensors 34, 36, 38, 40.

As shown in FIG. 6, the hold process is a control for holding the engagement torque Tn for a predetermined time in order to prevent hunting. The engagement torque Tn ≧ the set torque Tno (this is 95% of the maximum engagement torque). Value). In this hold processing, Tn ≧ Tn
In the case of o, the fastening torque Tn is held for a predetermined hold time th while counting by a counter. After the predetermined time th has elapsed, the hold process is canceled and the fastening torque Tn is reduced at a predetermined reduction rate. However, if the engagement torque Tn ≧ the set torque Tno within a predetermined time tf after the release of the hold processing, the next hold processing is executed for a hold time 2th twice the previous hold time th, and the hold time After the lapse of 2th, the fastening torque Tn is reduced at a predetermined reduction rate as described above.

As shown in FIG. 7, the map M4 is obtained by setting the characteristic of the engagement torque Tψ using the estimated lateral acceleration α as a parameter. The estimated lateral acceleration α is determined by the following equation using the yaw rate Δv and the vehicle speed V as parameters. α = (V · 1000/3600) · (ψv · π / 10
0) In the map M4, when the estimated lateral acceleration α is equal to or more than a certain value, as shown in a line L5, the estimated lateral acceleration α is increased in order to enhance the running performance of the winding traveling and enable the power drift traveling. According to the fastening torque Tψ
To a certain value.

In the vicinity of the turning limit (the position of the estimated lateral acceleration α = m), the grip force of the rear wheels 3 and 4 decreases due to the small wheel load of the rear wheels 3 and 4, and the vehicle tends to oversteer. Increase the grip of the rear wheels 3 and 4 and the front wheels 1
In order to reduce the grip force of No. 2 and eliminate the oversteer tendency, the characteristic is set so that the fastening torque T # is gradually reduced along the line L6 above the turning limit. As described above, when the turning degree is equal to or larger than the turning limit, the characteristic is such that the fastening torque Tψ gradually decreases along the line L6. Since the grip force of the vehicle does not suddenly change, the steering stability in marginal turning can be ensured. In addition, k = 5.5-6.0, m =
6.5 to 7.0, n = 440 to 460, etc.

As shown in FIG. 8, the map M5 sets the characteristic of the gain G1ψ using the differential rotation speed ΔN as a parameter. This map M5 is used when the differential rotation occurs during the cornering. This is for improving the responsiveness.
Incidentally, p = 30 to 40 and q = 60 to 80, etc.

The map M6 sets the characteristics of the engagement torque Tv using the vehicle speed V as a parameter. The map M6 is for securing the straight running stability during high-speed running. Note that r = 60, s = 70 to 90, t = 100,
The value of the degree. The map M7 is a map in which the relationship between the total fastening torque Tt and the coil current I is set.
Taking into account the effect of hysteresis of No. 3, the total fastening torque T
When t increases, the coil current I is determined by the broken line L7, and when the total fastening torque Tt decreases, the coil current I is determined by the broken line L8.

The ABS corresponding process is a process of releasing the engagement torque of the electromagnetic clutch 19 in order to prevent the wheels from being locked by the ABS control device 31 during the execution of the ABS control. When the brake switch signal BR is ON, the gain Ga is set to 0,
In other cases, the gain Ga is set to 1.0.

The map M8 sets the characteristics of the gain Gt by the tailing process for preventing a shock due to a sudden change in the fastening torque when the vehicle shifts from the running state to the stop state. The characteristics are set so that the torque is gradually reduced. The tailing processing condition is executed when the conditions of the ignition switch signal IG = OFF, the crank angle signal CA = 0 (rpm), the vehicle speed V = 0, and the neutral / inhibitor signal NI = ON are satisfied.

Next, a description will be given of a control program of the driving force distribution control for the clutch control executed by the clutch control device 32 for appropriately setting the driving force distribution to the four wheels in accordance with the running state. I do. In the figure,
The symbol Si (i = 1, 2, 3,...) Indicates each step. When the ignition switch signal IG is turned ON, control is started, and first, various detection signals (N1 to N
4, BR, ABS, TVO, CA, NI, etc.) are read (S1), and then, using the read detection signal, the differential rotation speed ΔN, yaw rate ψv, vehicle speed V, and estimated lateral acceleration α Is calculated as described above (S2).

Next, the differential torque ΔN is applied to the map M1 to calculate the engagement torque Tn (S3).
And yaw rate ψv applied to map M2 to obtain gain G1
n is calculated (S4), and then the vehicle speed V and the differential rotation speed ΔN
Is applied to the map M3 to calculate the gain G2n (S5). Next, it is determined whether or not the holding process is necessary (S6). When the determination result is No, the fastening torque T is determined.
n is held unchanged (S7), and when the result of the determination in S6 is Yes, the fastening torque Tn is corrected by a hold process (S8). Note that the hold processing is as described above, and thus the description is omitted. Next, the differential rotation speed reflecting engagement torque T1 is calculated by the following equation (S9). T1 = Tn × G1n × G2n

Next, the estimated lateral acceleration α is applied to the map M4 to calculate the engagement torque Tψ (S10). Next, the differential rotation speed ΔN is applied to the map M5 to calculate the gain G1ψ (S11). Next, the yaw rate reflecting engagement torque T2
Is calculated by the following equation (S12). T2 = TψG1ψ

Next, the vehicle speed V is applied to the map M6 to calculate the engagement torque Tv (S13), and then the vehicle speed reflecting engagement torque T3 is calculated by the following equation (S12). T3 = Tv Next, a total fastening torque Tt obtained by adding the torques T1, T2, and T3 is calculated by the following equation (S15). Tt = T1 + T2 + T3

Next, at S16, the total fastening torque T
t is applied to the map M7 to calculate the coil current I. When the total fastening torque Tt increases, the map M
7 is calculated based on the line L7, and when the total fastening torque Tt decreases, the calculation is performed based on the line L8 of the map M7. Next, in S17, it is determined whether the ABS signal is ON and the ABS control is being executed, and the brake switch signal BR is ON and the brake is operating. When the determination result is No, the gain Ga is Ga
= 1.0 (S18), and when the determination result of S17 is Yes, the gain Ga is set to Ga = 0 (S19).

Next, in S20, it is determined whether or not the tailing process is necessary. This determination is made based on the ignition switch signal IG = OFF and the crank angle signal CA = 0 (r
pm), vehicle speed V = 0, neutral / inhibitor signal N
It is determined as Yes when the conditions of I = ON are satisfied, and is determined as No when the above conditions are not satisfied. When the determination result is No, the gain Gt is Gt
= 1.0 (S21), and the determination result is
If Yes, the gain Gt is calculated based on the time measured by the counter and the map M8 or the like (S22).

Next, in S23, the output coil current Iout to be output to the coil 23 is calculated by the following equation. Iout = I.times.Ga.times.Gt Next, in S24, the output coil current Iout is output to the coil 23, and thereafter, the process returns to S1 to S24.
Is repeatedly executed every predetermined minute time.

In this four-wheel drive vehicle MC, an auto mode in which the driving force distribution control is automatically executed, an FF mode in which only the front wheels are always driven, and an electromagnetic clutch 1
9 is connected and a 4WD mode for driving four wheels can be selectively set, and a high μ road traveling mode and a low μ road traveling mode can be selectively set. It is composed. The torque characteristics and the gain characteristics are characteristics based on a high μ road, and the above description relates to the case of the auto mode and the high μ road traveling mode. In addition, low μ
In the road running mode, substantially the same characteristics as the torque characteristics and the gain characteristics are applied, but the various values (a
To k, m, n, p to t) are appropriately changed in the slip suppression direction as needed, and the characteristics of the map M4 are such that the line L5 itself is changed to the left.

As described above, this four-wheel drive vehicle MC
In the driving force distribution control (differential limit control) executed by the clutch control device 32, the engagement torque Tn according to the differential rotation speed ΔN, the engagement torque Tψ according to the estimated lateral acceleration α, and the vehicle speed V The corresponding engagement torque Tv is obtained from the respective torque characteristic maps, and based on the total torque thereof, the differential limiting torque of the electromagnetic clutch 19 is controlled. Accordingly, it is possible to ideally execute the distribution of the driving force, the distribution of the driving force according to the yaw rate Δv during the turning, and the distribution of the driving force according to the vehicle speed V.

Further, the fastening torque Tn is calculated by using the gain G1 obtained from the map M2 based on the vehicle speed V and the yaw rate ψv.
Since the gain is changed by n, the engagement torque Tn can be appropriately set in consideration of the differential rotation speed ΔN, the vehicle speed V, and the yaw rate Δv comprehensively. In particular, in the map M2, the line L
2 and L3 are set so that 特性 v decreases as the vehicle speed V increases. Therefore , the torque distribution is in accordance with the increase in the lateral acceleration α, and the torque distribution in consideration of the limit of the tire lateral force. This makes it possible to prevent a sudden change in the tire lateral force and a sudden change in the steering characteristic during the cornering operation, thereby significantly improving the cornering performance.

In particular, in the map M2, the predetermined vehicle speed d
With respect to the following regions, the straight running stability can be improved by setting the gain G1n = 1.0 in the yaw rate minute region A1, and the tight corner can be achieved by setting the gain G1n = 0 in the yaw rate intermediate region A2. In the excessive yaw rate region A3, by setting the gain G1n = 1.0, spin can be prevented and steering stability can be improved.

Further, in the map M2, the line L2
And L3 are set so that ψv decreases as the vehicle speed V increases. Therefore , the torque distribution in accordance with the increase in the lateral acceleration α, and the torque distribution in consideration of the limit of the tire lateral force, is performed. This makes it possible to prevent a sudden change in the tire lateral force and a sudden change in the steering characteristic during cornering, thereby significantly improving cornering performance.

In particular, in the map M3, a line L4 separating the region B1 and the region B2 is a line indicating the differential rotation speed ΔN corresponding to the case where the tire moving radius is reduced by 10%, and the differential rotation speed ΔN is a line. In the region below L4, since the gain G2n is set to G2n = 0, the fastening torque Tn is reduced due to a decrease in tire air pressure or an erroneous differential rotation speed ΔN generated when a small-tempered tire is mounted. Is not controlled to increase, the accuracy and reliability of the differential limiting control can be improved. Further, since the fastening torque Tn is changed by the gain G2n obtained from the vehicle speed V and the differential rotation speed ΔN, the differential rotation speed ΔN and the vehicle speed V
The fastening torque Tn can be appropriately set in consideration of the correlation with

Further, the map M1 sets the torque characteristic at the time of acceleration shown by the solid line and the torque characteristic at the time of deceleration shown by the dashed line to be different from each other. Also, since the differential limiting effect is enhanced, differential limiting can be performed with appropriate characteristics at the time of acceleration and deceleration, respectively, and it is possible to ensure both drivability during acceleration and braking performance during deceleration. .

Further, the fastening torque Tψ is changed to the differential rotation speed ΔN
Since the gain is changed by the gain G1n obtained from the above, the engagement torque T # can be appropriately set in consideration of the yaw rate ψ, the vehicle speed V, and the differential rotation speed ΔN comprehensively. Further, since the fastening torque Tψ is changed by the gain G1n obtained from the differential rotation speed ΔN, the fastening torque Tψ is appropriately adjusted in consideration of the yaw rate ψ, the vehicle speed V, and the differential rotation speed ΔN. Can be set.

In particular, as shown in a map M4 shown in FIG. 7, when the lateral acceleration α is equal to or greater than a predetermined turning limit (position of α = m), the fastening torque Tψ is gradually reduced along the line L6. Therefore, the grip force (lateral force of the tires) of the front and rear wheels 1 to 4 does not suddenly change under a severe turning traveling condition exceeding the turning limit, and the effective driving force does not suddenly change. In addition, the stability of turning traveling can be ensured. Further, since the coil current I is determined based on the map M7 taking into account the hysteresis of the coil 23, the coil current I can be set with high accuracy. In addition to the above, the hunting can be suppressed by the hold processing, and the shock at the time of stopping the vehicle can be prevented by the tailing processing.

In the above embodiment, the three torque characteristics are set in advance in the maps M1, M4, and M6. However, some or all of these torque characteristics may be set in a table or an arithmetic expression. May be configured. Similarly, the three gain characteristics correspond to maps M2, M3, M
5, the gain characteristics may be set in advance in a table or an arithmetic expression. Further, regarding the map M4, the actual lateral acceleration acting on the vehicle body may be applied as a parameter of the horizontal axis. In this case, the actual lateral acceleration detected by the lateral acceleration detection sensor is applied to the map M4. Thus, the fastening torque Tψ is obtained. Note that the total engagement torque Tt may be determined without using the vehicle speed reflection engagement torque T3 as necessary, and the total engagement torque Tt may be determined using the yaw rate reflection engagement torque T2 as necessary. It may be configured so as to be obtained without using.

Next, a description will be given of another embodiment in which the present invention is applied to a four-wheel drive vehicle of a type in which the rear wheels 3 and 4 are constantly driven, which is different from the above embodiment. First, the overall configuration of the four-wheel drive vehicle MCA will be described with reference to FIGS. However, the same reference numerals are given to the same components as those in the above embodiment. As shown in FIG. 14, the four-wheel drive vehicle MCA has left and right front wheels 1 and 2 and left and right rear wheels 3 and 4.
A left front wheel axle 5; a right front wheel axle 6; a front differential 50 for interlocking the two axles 5 and 6;
, A right rear wheel axle 9, a rear differential device 51 interlockingly connecting the two axles 8, 9, a power unit including an engine 52 and an automatic transmission 53, and a driving unit interlockingly connected to the power unit to drive the front wheels 1, 2. Transfer device 54 for distributing the transfer device 54 to the front and rear wheels 3, 4; a front wheel drive shaft 17 for interlocking the transfer device 54 to the front differential device 50; and a rear wheel for interlocking the transfer device 54 to the rear differential device 51. Drive shaft 18 and the like are provided.

The transfer device 54 includes a driving force transmission mechanism for constantly transmitting the driving force from the power unit to the rear wheel driving shaft 18 and an electromagnetic multi-plate clutch 55 for limiting the driving force from the power unit to a differential. (A center differential device) to the front wheel drive shaft 17.

Here, the electromagnetic multi-plate clutch 55 will be described. As shown in FIG. 15, there is an input member 57 that rotates integrally with a shaft member 56 that is interlocked to the output shaft of the power unit via a gear train, and an outer shaft 58 that rotates integrally with the front wheel drive shaft 17. , A multi-plate clutch 59 is provided, an electromagnetic actuator 60 composed of a coil 61 and a magnetic path forming member 62 is fixed to the vehicle body side, a bearing 63 is mounted between the electromagnetic actuator 60 and the outer shaft 58, and an armature 64 is It is fixed to the outer shaft 58.

When the coil 61 of the electromagnetic actuator 60 is not energized, the electromagnetic multi-plate clutch 55 is OFF (disconnected state). When the coil 61 is energized, the electromagnetic multi-plate clutch 55 is turned ON (connected state). Thus, the differential limiting torque (that is, the front wheel drive torque) proportional to the coil current is transmitted to the front wheel drive shaft 17. The front differential device 50 is composed of a differential gear mechanism and an electromagnetic multi-plate clutch for limiting the differential as described above, and the rear differential device 51 is configured as a differential gear similar to the differential gear mechanism as described above. And a limiting electromagnetic multi-plate clutch.

Further, as a control system of the four-wheel drive vehicle MCA, a power unit controller 3
0, ABS control device 31, clutch control device 65, four wheel speed sensors 34, 36, 38, 40, brake switch 41, steering angle sensor 43, neutral inhibitor switch 44, yaw rate sensor 45, idle switch 46, throttle opening Sensor 47, crank angle sensor 4
8, etc., and various detection signals are supplied to the control devices 30, 31, 65 in the same manner as in the previous embodiment. Furthermore,
The clutch control device 65 is connected to a mode setting device 66 for selectively setting the auto mode, the C mode, the R mode, and the F mode.

In the auto mode, the electromagnetic multi-plate clutch of the front differential 50 is controlled to be in a free state, and the center differential 55 and the electromagnetic multi-plate clutch of the rear differential 51 are connected to the four-wheel drive vehicle MCA. It is automatically controlled according to the running state. In the C mode, the electromagnetic multi-plate clutch of the front differential 50 is controlled to a free state, the center differential 55 is controlled to a completely locked state, and the rear differential 5
One electromagnetic multi-plate clutch is automatically controlled according to the traveling state of the four-wheel drive vehicle MCA. In the R mode, the electromagnetic multi-plate clutch of the front differential 50 is controlled to be in a free state, and the center differential 55 and the electromagnetic multi-plate clutch of the rear differential 51 are controlled to be in a completely locked state. In the F mode, the electromagnetic multi-plate clutch of the front differential device 50, the center differential device 55, and the electromagnetic multi-plate clutch of the rear differential device 51 are each controlled to a completely locked state.

When automatically controlling the engagement torque of the electromagnetic clutch of the front differential device 50 in accordance with the traveling state of the four-wheel drive vehicle MCA, the engagement torque is set to the left and right front wheels 1 and 2 in the same manner as in the previous embodiment. The torque characteristics and the gain characteristics are set based on predetermined torque characteristics respectively set with the differential rotation speed between the two, the vehicle speed, and the yaw rate as parameters, and gain characteristics associated with each torque characteristic. Are set to predetermined characteristics different from those described above.

Next, various types of differential limiting control applied to the center differential device 55 and the rear differential device 51 in this alternative embodiment will be described. 1] The characteristics of control for automatically controlling the center differential device 55 according to the traveling state of the four-wheel drive vehicle MCA will be described with reference to FIGS. FIG. 16 is a map in which the torque characteristic of the fastening torque Tc of the center differential device 55 is set in advance using the differential rotation speed ΔN between the front and rear wheels as a parameter. It is determined as an absolute value of a difference between the average force of the wheel speeds N1 and N2 of the rear wheels 1 and 2 and the average force of the wheel speeds N3 and N4 of the rear wheels 3 and 4.

FIG. 17 shows the wheel speed sensors 34, 36, 3
Wheel speeds N1, N2, N3, N4 detected from 8, 40
16 is a map in which a gain characteristic of a gain G for changing the gain of the engagement torque Tc obtained by applying the differential rotation speed ΔN obtained from the map shown in FIG. 16 to the vehicle speed V and the yaw rate ψv is set in advance. Similarly to the map M2 in the above embodiment, the gain G = G in the region Z1 and the region Z3.
1.0, and in the area Z2, the gain G = 0.
Is set to

In the region Z4, the gain G is set to 0,
In the region Z5, the gain G is set to 1.0, but the lines L9 and L10 that define the region Z4
The characteristic is set so that the yaw rate Δv decreases with an increase in the yaw rate Δv. That is, in the region Z4, the rear wheel is in the driving state,
Oversteer tends to occur due to the sideslip of the rear wheels 3 and 4. However, as in the previous embodiment, the gain G starts when the yaw rate Δv that decreases as the vehicle speed V increases reaches the value of the lines L9 and L10. Is set to 1.0, the driving force is switched to the four-wheel drive state, the driving force of the front wheels 1 and 2 is increased, and the driving force of the rear wheels 3 and 4 is decreased, so that the grip force (tire lateral force) of the rear wheels 3 and 4 is reduced In order to increase and lower the grip force (tire lateral force) of the front wheels 1 and 2 and correct in the understeer direction, the line L
9 and 10 are set to the above characteristics. As a result, the same operation as in the above embodiment can be obtained, and the turning performance can be significantly improved.

The vehicle speed V and yaw rate obtained from the detection signal
v is applied to the map of FIG. 17 to determine a gain G, and the gain G is multiplied by the fastening torque Tc determined from FIG. 16 to determine the final fastening torque Tcf, which becomes the final fastening torque Tcf. Thus, the coil current I of the center differential limiting device 55 is controlled.

2] Differential limit control for automatically controlling the center differential device 55 according to the running state of the four-wheel drive vehicle MCA will be described (see FIG. 18). This differential limiting control is a control executed by the clutch control device 65, and reference symbols Si (i = 30, 31,...) In the figure indicate each step. After the start of the control, first, various detection signals (N1 to N4, Δv, etc.) are read from the sensors (S30), and then the differential rotation speed ΔN between the front wheels 1, 2 and the rear wheels 3, 4 is calculated, The vehicle speed V and the yaw acceleration ψa are calculated (S31). However, the differential rotation speed ΔN is different between the front wheels 1, 2
Of the wheel speeds N1 and N2 of the wheels and the wheel speed N of the high wheels 3 and 4
3, the vehicle speed V is calculated from the lowest wheel speed in the same manner as described above, and the yaw acceleration ψa is calculated as a time differential value of the yaw rate ψv.

Next, the center differential is calculated by applying the calculated differential rotation speed ΔN to a predetermined map (for example, a map similar to the map M1 of the above-described embodiment or another general map). The fastening torque Tc of the device 55 is calculated (S32), and then it is determined whether the vehicle speed V is equal to or higher than a predetermined vehicle speed V0 (for example, 25 to 35 km / h) (S3).
3) If the determination result is Yes, the process proceeds to S40. If the determination result is No, in S34, it is determined whether the yaw acceleration ψa is equal to or greater than a predetermined value C0,
When the determination result is Yes, the process proceeds to S40, but when the determination result is No, the process proceeds to S35.

Next, in S35, the yaw rate {v
Is smaller than or equal to a small predetermined value C1 (for example, a value of the order of 8.5 deg / s). If the determination result is Yes, a predetermined value ΔT1 is applied to the fastening torque Tc in S36.
Is added, and then the process proceeds to S40. As a result, in the small yaw rate area corresponding to the area A1 of the map M2 in the embodiment, the engagement torque Tc for limiting the differential is set high in order to improve the straight running stability. When the result of determination in S35 is No, in S37, the yaw rate ψv is a very large predetermined value C2 (for example, 50.0 de
g / s) or less, and if the result of the determination is Yes, a predetermined value ΔT2 is subtracted from the engagement torque Tc in S38.

Thus, in the yaw rate intermediate area corresponding to the area A2 of the map M2 of the above-described embodiment, similarly to the above-described embodiment, the fastening torque Tc is zero or very small in order to enhance the turning property of the tight corner. Will be set to the value. Then, the process proceeds from S38 to S40.

When the result of the determination in S37 is No, that is, when the yaw rate is excessive, a predetermined value ΔT1 is added to the engagement torque Tc in S39, and thereafter, the process proceeds to S40. As a result, in the excessive yaw rate region corresponding to the region A3 of the map M2 in the above-described embodiment, the differential limiting engagement torque Tc is set to be high in order to prevent spin and enhance steering stability. Next, in S40, the fastening torque Tc set as described above is set.
Is applied to a predetermined map, an arithmetic expression, or a table, and a coil current I to be supplied to the coil of the center differential device 55 is calculated. The control operation returns to S30
Steps S41 to S41 are repeatedly executed at predetermined small time intervals.

As described above, in the region where the vehicle speed V is equal to or lower than the predetermined vehicle speed V0, the engagement torque Tc is increased in the yaw rate minute region, the engagement torque Tc is set to zero or a small value in the yaw rate intermediate region, and the engagement torque Tc is set in the excessive yaw rate region. By increasing Tc, it is possible to improve the straight running stability in the small yaw rate area, increase the turning performance of tight corner turning in the middle yaw rate area, and improve the spin prevention and steering stability in the excessive yaw rate area, as in the above embodiment. it can.

3] Next, control for setting the engagement torque Tα of the electromagnetic clutch of the rear differential will be described (see FIGS. 19 and 20). As shown in FIG. 19, using the same estimated lateral acceleration α as a parameter, a map of the torque characteristic of the engagement torque Tα is set in advance and stored in the clutch control device 65, and the position of the lateral acceleration α = α3 is determined by a predetermined value. Corresponds to the turning limit of.

Next, as shown in the flowchart of FIG. 20, when the control is started, various signals (N1 to N4,.
v) is read (S30), and then the estimated lateral acceleration α is calculated (S31) as in the previous embodiment (S31).
When the lateral acceleration α is equal to or less than the set value α1 through the determinations of S2 to S38, the engagement torque Tα is set to 0 (S3
3) When the lateral acceleration α is larger than the set value α1 and equal to or smaller than the set value α2,
The engagement torque Tα is calculated (S35), and when the lateral acceleration α is larger than the set value α2 and equal to or smaller than the set value α3, the engagement torque Tα is set to the maximum engagement torque Tαm (S37), and the lateral acceleration α is set. When the set value α3 is larger than the set value α4 or less, the engagement torque Tα is calculated by the line 11 of the map (S39). When the lateral acceleration α is larger than the set value α4, the engagement torque Tα is set to 0. Is done.

Next, from the engagement torque Tα calculated as described above, a coil current I to be supplied to the coil of the electromagnetic clutch is calculated by a predetermined map or a calculation formula (S41).
Next, after outputting the coil current I to the coil, the control operation returns, and S30 to S42 are repeatedly executed at predetermined small time intervals. Based on the map in FIG. 19, when the turning degree is equal to or larger than the turning limit, the turning torque Tα is controlled by the line L11 so as to gradually decrease in accordance with the increase in the turning degree. There is no abrupt change in the grip force (tire lateral force) and the driving force acting on each of the rear wheels 3 and 4 in the severe turning operation exceeding the limit, and the stability of the turning operation can be secured.

In this embodiment, the estimated lateral acceleration α is applied as the turning degree. However, the lateral acceleration acting on the vehicle body may be detected by a sensor and the detected lateral acceleration may be applied. A change rate (yaw acceleration) of the yaw rate may be applied together with or instead of the lateral acceleration, or the steering angle θh and the vehicle speed detected by the steering angle sensor 43 together with or instead of the lateral acceleration. V may be applied.

4] The engagement torque Tr of the electromagnetic clutch of the rear differential 51 according to the running state of the four-wheel drive vehicle MCA.
FIGS. 21 to 24 show differential limiting control for automatically controlling
This will be described with reference to FIG.

The clutch control device 65 has the configuration shown in FIG.
A map shown in FIG. 22 and a control program for differential limiting control shown in FIGS. 23 and 24 are input and stored in advance. FIG.
The map shows the torque characteristic of the engagement torque Tr during acceleration. In this torque characteristic, the differential limiting effect is set so as to decrease as the acceleration β increases. Also,
The map in FIG. 22 shows the torque characteristics of the engagement torque Tr during deceleration. In the torque characteristics, the differential limiting action is set to increase as the deceleration γ increases.
In the drawing, ΔN1> ΔN2 with respect to ΔN1 and ΔN2.

Next, the differential limiting control will be described with reference to the flowcharts of FIGS. 23 and 24.
i (i = 30, 31,...) indicates each step. First, various detection signals (N1 to N4, Δv, etc.) are read (S30), and then, the differential rotation speed Δ between the left and right rear wheels 3, 4 is determined.
N, the estimated lateral acceleration α, the longitudinal acceleration β, and the longitudinal deceleration γ are calculated (S31). Note that the differential rotation speed ΔN is
The estimated lateral acceleration α is calculated from the difference between the wheel speeds N3, N4 of the left and right rear wheels 3, 4, and the estimated lateral acceleration α is calculated in the same manner as in the previous embodiment.
The longitudinal acceleration β and the longitudinal deceleration γ are calculated from the vehicle speed V obtained in the same manner as in the above embodiment.

Next, it is determined whether or not the vehicle is in a turning traveling state, that is, whether or not the estimated lateral acceleration α is positive (S32). If the vehicle is not in a turning traveling state, S33 to S40 are executed.
When the vehicle is turning, the process proceeds to S41. When the vehicle is not turning, it is determined whether or not the vehicle is accelerating, that is, whether or not β is positive (S33).
Through the determinations in S36 and S38, the fastening torque Tr is set based on the map of FIG. 21 as follows.

The acceleration β is Δβ corresponding to a predetermined dead zone.
In the following cases, the differential rotation speed ΔN is set to the characteristic L1 of the map.
0 is applied to calculate the engagement torque Tr (S35), and the acceleration β is larger than Δβ and the predetermined set value β
1 or less, the differential rotation speed ΔN
11 to calculate the fastening torque Tr (S37),
When the acceleration β is larger than β1 and equal to or less than the predetermined set value β2, the engagement torque Tr is calculated by applying the differential rotation speed ΔN to the characteristic L12 of the map (S3).
9) When the acceleration β is larger than β2,
The engagement torque Tr is calculated by applying the differential rotation speed ΔN to the characteristic L13 of the map (S40), and S35, S37, S
39, the process moves from S40 to S51.

On the other hand, if the torque characteristic is changed in the turning traveling state, the lateral force of the tires on the left and right rear wheels 3 and 4 may suddenly change and steering stability may be reduced. , S41, the differential torque ΔN is applied to the previous torque characteristic to calculate the engagement torque Tr.

If the vehicle is not in the accelerated state, the flow goes from S33 to FIG.
The process proceeds to S42 of 4 to determine whether or not the vehicle is in the deceleration state, that is, whether or not the deceleration γ is positive. As a result of the determination, when the vehicle is in the deceleration state, the engagement torque Tr is set based on the map of FIG. 22 as follows through the determinations of S43, S45, and S47. When the deceleration γ is equal to or smaller than Δγ corresponding to a predetermined dead zone, the differential rotation speed ΔN is changed to the characteristic L20 of the map.
Is applied to calculate the engagement torque Tr (S44), and the deceleration γ is larger than Δγ and the predetermined set value γ
1 or less, the differential rotation speed ΔN
The engagement torque Tr is calculated by applying the calculation to S21 (S46).

When the deceleration γ is larger than γ1 and equal to or smaller than a predetermined set value γ2, the differential rotation speed ΔN
Is applied to the map characteristic L22 to calculate the engagement torque Tr (S48). When the deceleration γ is larger than γ2, the differential rotation speed ΔN is applied to the map characteristic L23 to apply the engagement torque Tr. Tr is calculated (S49), and
If the result of determination in S42 is that the vehicle is not in a deceleration state, S50
, The differential rotation speed ΔN is applied to the previous torque characteristic to calculate the engagement torque Tr, and S44, S46, S4
8. The processing shifts from S49, S50 to S51 in FIG.

Next, in S51 of FIG. 23, the coil torque I to be supplied to the coil of the electromagnetic clutch is calculated by applying the fastening torque Tr to a predetermined map, calculation formula, or table. The coil current I is output to the coil, and thereafter, the control operation returns to S30
Steps S52 to S52 are repeatedly performed at predetermined small time intervals.

In the differential limiting control described above, during acceleration, differential limiting can be appropriately performed according to the magnitude of the acceleration, and during deceleration, differential limiting can be appropriately performed according to the magnitude of the deceleration. it can. Moreover, a predetermined dead zone (Δβ,
Δγ) is provided and when the acceleration / deceleration is within the dead zone, differential limiting is performed based on the torque characteristics of the base (characteristics L10 and L20), so that frequent switching of the differential limiting force does not occur. In addition, during turning, the torque characteristic is not changed and the previous torque characteristic is applied to limit the differential, so that the stability of turning can be ensured.

It is needless to say that the present invention can be similarly applied to a system provided with a hydraulic or pneumatic type differential limiting mechanism instead of the electromagnetic multi-plate clutch of the above embodiment. The present invention is not limited to the example, and may have a configuration in which various changes are added to the above-described embodiment by appropriately combining existing well-known techniques.

[Brief description of the drawings]

FIG. 1 is a schematic overall configuration diagram of a four-wheel drive vehicle according to an embodiment.

FIG. 2 is an explanatory diagram illustrating an outline of driving force distribution control of a four-wheel drive vehicle.

FIG. 3 is a map M1 showing a torque characteristic of a fastening torque Tn.
FIG.

FIG. 4 is a characteristic diagram of a map M2 that is a gain characteristic of a gain G1n.

FIG. 5 is a characteristic diagram of a map M3 which is a gain characteristic of a gain G2n.

FIG. 6 is an explanatory diagram illustrating a hold process.

FIG. 7 is a map M4 showing a torque characteristic of the fastening torque T #.
FIG.

FIG. 8 is a characteristic diagram of a map M5 which is a gain characteristic of a gain G1 #.

FIG. 9 is a map M6 showing a torque characteristic of the fastening torque Tv.
FIG.

FIG. 10 is a characteristic diagram of a map M7 for converting a total fastening torque Tt into a coil current I.

FIG. 11 is a characteristic diagram of a map M8 which is a gain characteristic of a gain Gt of the tailing process.

FIG. 12 is a part of a flowchart of driving force distribution control.

FIG. 13 is the remaining part of the flowchart of the driving force distribution control.

FIG. 14 is a schematic overall configuration diagram of a four-wheel drive vehicle according to another embodiment.

15 is a sectional view of the center differential of the four-wheel drive vehicle of FIG.

16 is a torque characteristic diagram of a fastening torque of the center differential of FIG. 14;

17 is a gain characteristic diagram for changing the gain of the fastening torque obtained from FIG.

FIG. 18 is a flowchart of differential limiting control for controlling the center differential of FIG. 14;

19 is a torque characteristic diagram of a fastening torque Tα of the rear differential shown in FIG.

FIG. 20 is a flowchart of a differential limiting control for setting the engagement torque Tα.

FIG. 21 is a map of a torque characteristic for limiting a differential of the rear differential shown in FIG. 14;

FIG. 22 is a map of a differential limiting torque characteristic of the rear differential of FIG. 14;

23 is a part of a flowchart of a differential limiting control for the rear differential shown in FIG. 14;

FIG. 24 is the remainder of the flowchart of the differential limiting control for the rear differential shown in FIG. 14;

[Explanation of symbols]

 MC 4 wheel drive vehicle 19 Electromagnetic clutch 32 Clutch control device 34, 36, 38, 40 Wheel speed sensor 45 Yaw rate sensor MCA 4 wheel drive vehicle 50 Front differential device 51 Rear differential device 55 Center differential device (electromagnetic multi-plate clutch) ) 65 Clutch control device

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-2-68226 (JP, A) JP-A-3-31030 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60K 17/28-17/36

Claims (5)

(57) [Claims] The method according to claim 1] driving force distribution for the four wheels, the driving force control apparatus for a four-wheel drive vehicle to control via the controllable differential limiting clutch means differential limiting torque in the differential limiting clutch means With differential speed limited wheel speed
Yaw rate acting on the body of the four-wheel drive vehicle and the four-wheel
Detecting means for detecting each of three physical quantities of the vehicle speed of the driving vehicle
And one or two of the three physical quantities as parameters
And a plurality of torques of the engagement torque of the differential limiting clutch means.
Torque characteristic storage means in which the torque characteristics are set in advance, torque calculation means for determining the fastening torque by applying the three physical quantities detected by the detection means to each of the plurality of torque characteristics, and torque calculation means for determining the fastening torque. A torque adding unit that adds a plurality of engagement torques to obtain a total engagement torque; and a control unit that controls a differential limiting clutch unit so that the total engagement torque obtained by the torque addition unit is obtained. the means, among the three physical quantity
One or two of the parameters are used as parameters, and at least one gain characteristic preset in correlation with the torque characteristic is stored. The torque calculating means obtains a gain by applying the detected physical quantity to the gain characteristic. A driving force control device for a four-wheel drive vehicle, wherein the driving torque control device is configured to multiply the fastening torque obtained from the torque characteristic by the gain and output the result to a torque adding means. The method according to claim 2, wherein the torque characteristic storage means, and remembering correlation torque characteristics of the wheel speed difference as a parameter, to claim 1 in which the gain characteristic is characterized in that stored for the vehicle speed and the yaw rate as a parameter A driving force control device for a four-wheel drive vehicle according to claim 1. 3. The torque characteristic storage means stores a gain characteristic using a vehicle speed and a wheel speed difference as a parameter by correlating a torque characteristic using a wheel speed difference as a parameter. The driving force control device for a four-wheel drive vehicle according to claim 1 . 4. The torque characteristic storage means correlates a torque characteristic using a wheel speed difference as a parameter, and a gain characteristic using a vehicle speed and a yaw rate as a parameter, and a gain characteristic using a vehicle speed and a wheel speed difference as a parameter. The driving force control apparatus for a four-wheel drive vehicle according to claim 1 , wherein The method according to claim 5, wherein the torque characteristic storage means, and remembering correlation torque characteristics to the vehicle speed and the yaw rate as a parameter, to claim 1 in which the gain characteristic is characterized in that stored for the wheel speed difference as a parameter A driving force control device for a four-wheel drive vehicle according to claim 1.