JPH0764218B2 - Driving force distribution clutch engagement force control device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a drive applied to a transfer clutch of a drive force distribution control device for a four-wheel drive vehicle, a differential limiting clutch of a vehicle differential limiting control device, and the like. The present invention relates to a fastening force control device for a force distribution clutch.

(Prior Art) As a conventional engagement force control device for a drive force distribution clutch,
For example, the following devices are known.

In Japanese Patent Laid-Open No. 62-198522, the yaw momentum of the vehicle is detected based on the vehicle speed and the steering angle signal, and the clutch engagement force command value is determined so that the detected yawing momentum value matches the yawing momentum target value. There is disclosed a device that realizes good turning performance without sudden changes in spin and steer characteristics during turning by controlling the clutch engagement force of a force distribution clutch or a limited slip differential clutch.

Japanese Patent Laid-Open No. 63-141831 detects the front and rear wheel rotation speed difference, which is wheel slip information, and the larger the front and rear wheel rotation speed difference, the higher the clutch engagement force command value becomes as the clutch engagement of the front and rear wheel drive force distribution clutch. There is disclosed a device that controls the force to change the distribution of the driving force to the four-wheel drive side when the occurrence of the driving wheel slip is large and to quickly suppress the driving wheel slip.

(Problems to be Solved by the Invention) However, such a conventional engagement force control device for a driving force distribution clutch has the following problems.

The device disclosed in Japanese Unexamined Patent Publication No. Sho 62-198522 has good controllability of the vehicle at the turning limit, but when traveling on low friction coefficient roads such as ice and snow roads or during intermediate acceleration on high friction coefficient roads, etc. When the steering angle is zero, the yawing momentum target value is also set to zero, and almost no clutch engagement force is applied.

Therefore, in the case of a four-wheel drive vehicle equipped with front and rear wheel drive force distribution clutches, the drive / acceleration performance is comparable to that of two-wheel drive.

Further, in the case of a vehicle equipped with a differential limiting clutch, the left and right drive wheels are allowed to be differential during straight running, so that straight running stability is poor and driving / accelerating performance is poor.

The device disclosed in Japanese Patent Laid-Open No. 63-141831 provides good drive / acceleration performance when traveling straight on a low friction coefficient road or during intermediate acceleration on a high friction coefficient road. If the lateral force characteristics with respect to tire slip change outside the preset values due to differences, tire wear, road surface temperature, vehicle weight, etc., the clutch engagement force will become excessive or excessive and the vehicle steering characteristics will be understeered or oversteered. Will change to.

The present invention has been made in view of the above problems, and a driving force distribution clutch engagement force control device for controlling torque distribution between front and rear wheels and left and right wheels by a clutch engagement force that is externally applied. The challenge is to achieve both improved drive / acceleration performance and improved controllability at the turning limit, while minimizing the effect of steer characteristics on external factors.

(Means for Solving the Problems) In order to solve the above problems, in the engagement force control device for the driving force distribution clutch according to claim 1, as shown in the claim correspondence diagram of FIG. Front and rear wheel drive force distribution clutch means a, which is provided in the middle of the engine drive system for distributed transmission to the front and rear wheels, and which can change the transmission torque by externally applied clutch engagement force, and front and rear wheels that detect the front and rear wheel rotational speed difference. A rotational speed difference detecting means b, a first calculating part c for determining a first clutch engagement force by a product of a front and rear wheel rotational speed difference detection value and a control constant, a yawing momentum detecting means d for detecting a yawing momentum of the vehicle, A yawing momentum target value setting means e for setting a yawing momentum target value based on the vehicle speed and the steering state, so that the yawing momentum detection value matches the yawing momentum target value. And a third calculation unit g that determines a second clutch engagement force, and a third calculation unit g that uses a value based on the sum of the first clutch engagement force and the second clutch engagement force as a clutch engagement force command value. It is a means characterized by that.

In order to solve the above-mentioned problems, in the engagement force control device for a drive force distribution clutch according to claim 2, as shown in the claim correspondence diagram of Fig. 1 (b), an engine drive system for distributing and transmitting the engine drive force to the left and right wheels. The left and right wheel drive force distribution clutch means h, which is provided in the middle of the vehicle and is capable of changing the transmission torque by the clutch fastening force applied from the outside, and the left and right wheel slip state quantity detection means for detecting the slip state quantity of the left and right drive wheels with respect to the road i, the left and right wheel slip state amount target value setting means j for setting the left and right wheel slip state amount target values for ensuring the driving performance and turning performance of the vehicle, and the left and right wheel slip state amount detection values for the left and right wheel slip state amount target values Based on the vehicle speed and the steering state, a first calculation unit k that determines the first clutch engagement force so as to match the first clutch engagement force, yaw momentum detection means m that detects the yaw momentum of the vehicle. A yawing motion amount target value setting means n for setting the yawing motion amount target value can, a second arithmetic unit o determining the second clutch engagement force as yawing motion amount detection value matches the yawing motion amount target value, the first
The third computing unit p has a clutch engagement force command value that is a value based on the sum of the clutch engagement force and the second clutch engagement force.

(Operation) The operation of the invention according to claim 1 will be described.

During traveling, the first calculation unit c determines the first clutch engagement force by the product of the front-rear wheel rotation speed difference detection value from the front-rear wheel rotation speed difference detection means b and the control constant, and the second calculation unit f The second clutch engagement force is determined so that the yawing momentum detection value from the yawing momentum detecting means d matches the yawing momentum target value set based on the vehicle speed and the steering state, and the third clutch g is engaged in the third computing unit g. A value based on the sum of the force and the second clutch engaging force is set as the clutch engaging force command value. Then, the clutch engagement force based on the clutch engagement force command value is applied to the front and rear wheel drive force distribution clutch means a, and the distribution ratio of the engine drive force to the front and rear wheels is controlled.

Therefore, when driving on a road with a low friction coefficient in which a large amount of drive wheel slip occurs, a large difference in front and rear wheel rotational speed is generated due to the occurrence of drive wheel slip, so that the first clutch engagement force corresponding to the front and rear wheel rotational speed difference is mainly used. As a result, the clutch engagement force is applied. Due to this clutch engagement force, part of the engine drive force transmitted to the slip generation drive wheel is distributed to the other wheel according to the magnitude of the clutch engagement force, and the occurrence of drive wheel slip due to excessive drive force transmission is suppressed. To be The responsiveness of the driving force distribution control due to the clutch engagement is determined by the magnitude of the control constant. As a result,
The drive transmission loss to the road surface due to the drive wheel slip is suppressed to a small level, and the drive / acceleration performance of the vehicle is improved.

In addition, since the yawing momentum is significantly generated during the critical turning traveling, the second yawing momentum corresponding to the second momentum is generated.
The clutch fastening force is mainly applied to the clutch fastening force. The clutch engagement force controls the driving force distribution ratio of the front and rear wheels, and adjusts the yawing momentum of the vehicle to a target value set based on the vehicle speed and the steering state.

The relationship between the driving force distribution ratio of the front and rear wheels and the yawing momentum is that the yawing momentum decreases as the driving force distribution ratio to the front wheels increases, and the yawing momentum increases as the driving force distribution ratio to the rear wheels increases. Will be a growing relationship.

As a result, controllability at the turning limit can be improved.

Further, since the value based on the sum of the first clutch engaging force and the second clutch engaging force is the clutch engaging force command value,
When the lateral force characteristics with respect to tire slip change due to external factors (for example, tire brand differences, tire wear, road surface temperature, etc.), the second clutch engagement force corresponding to yawing momentum corresponds to the first front / rear wheel rotational speed difference. It acts as a correction factor for the clutch engagement force, and the influence of steer characteristics on external factors can be suppressed to a small level.

This is because there is a corresponding relationship that the generation of yawing momentum also changes if the tire lateral force characteristics change.

For example, when a four-wheel drive vehicle with a rear wheel drive base in which the tire lateral force characteristics on the rear wheel side are deteriorated is turned, even if only the first clutch engaging force corresponding to the front-rear wheel rotational speed difference is applied, Since the lateral force generation value becomes small, the rear wheel is not supported and the steer characteristic tends to be oversteer. However, since the yawing momentum increases due to the oversteering tendency of the vehicle, the second clutch engagement force has a positive value in order to suppress the increase in the yawing momentum. Therefore, the total clutch engagement force is the first clutch engagement force plus the second clutch engagement force, and the oversteer characteristic due to the reduction of the tire lateral force on the rear wheel side is suppressed.

The operation of the invention according to claim 2 will be described.

During traveling, the left and right wheel slip state amount detection values from the left and right wheel slip state amount detection means i in the first computing unit k become the left and right wheel slip state amount target values set to ensure the driving performance and turning performance of the vehicle. The first clutch engagement force is determined so as to coincide with each other, and the yaw momentum detection value from the yawing momentum detection means m is coincident with the yawing momentum target value set based on the vehicle speed and the steering state in the second calculation unit o. The second clutch engagement force is determined and the third
In the calculation unit p, a value based on the sum of the first clutch engaging force and the second clutch engaging force is used as the clutch engaging force command value. Then, the clutch engagement force based on the clutch engagement force command value is applied to the left and right wheel drive force distribution clutch means h, and the distribution ratio of the engine drive force to the left and right wheels is controlled.

Therefore, during low-μ road acceleration turning, etc., the left and right wheel slip state amount detection values deviate from the target values set to secure the driving performance and turning performance of the vehicle due to large left and right driving wheel slips. Therefore, the clutch engaging force is applied mainly based on the first clutch engaging force corresponding to the left and right wheel slips, which is given according to the deviation between the target value and the detected value. A differential limiting force is applied between the left and right drive wheels by this clutch engagement force, differential rotation of the left and right drive wheels is suppressed, and the left and right wheel slip state amount approaches the target value. As a result, the drive transmission loss to the road surface due to the left and right wheel slips is suppressed to a small level, and the drive / acceleration performance of the vehicle is improved.

In addition, since the yawing momentum is significantly generated during the critical turning traveling, the second yawing momentum corresponding to the second momentum is generated.
The clutch fastening force is mainly applied to the clutch fastening force. The driving force distribution ratio to the left and right wheels is controlled by the clutch engagement force, and the yawing momentum of the vehicle is adjusted to a target value set based on the vehicle speed and the steering state.

The relationship between the driving force distribution ratio of the left and right wheels and the yaw momentum is that the yawing momentum decreases as the driving force distribution ratio to the turning inner wheel side increases, and the yawing moment increases as the driving force distribution ratio to the turning outer wheel side increases. When the outer ring rotation speed> the inner ring rotation speed, increasing the clutch engagement force decreases the yaw momentum due to the torque increase on the inner ring side, which is low rotation, and when the outer ring rotation speed ≦ the inner ring rotation speed, the momentum increases. When the clutch engagement force is reduced, the yaw momentum is reduced due to the torque reduction on the outer wheel side, which is low rotation.

As a result, controllability at the turning limit can be improved.

Further, since the value based on the sum of the first clutch engaging force and the second clutch engaging force is the clutch engaging force command value,
When the lateral force characteristics for tire slip change due to external factors (for example, tire brand differences, tire wear, road surface temperature, etc.), the second clutch engagement force corresponding to yaw momentum is the first clutch engagement corresponding to drive wheel slip. It acts as a force correction factor and suppresses the influence of the steer characteristic on external factors.

This is because, as described in the operation of the invention described in claim 1, there is a corresponding relationship that the generation of yawing momentum also changes if the tire lateral force characteristic changes.

(First Embodiment) First, the engagement force control device for a drive force distribution clutch of the present invention is applied to a transfer clutch of a drive force distribution control device for a four-wheel drive vehicle based on rear wheel drive. A first embodiment corresponding to the invention will be described.

To explain the configuration, FIG. 2 is a diagram showing an entire system of a drive force distribution control device for a four-wheel drive vehicle. The engine drive system of the four-wheel drive vehicle is an engine 10, a transmission 11, a transfer input shaft 12, a transfer 13 , A rear propeller shaft 14, a rear differential 15, a rear drive shaft 16, a rear wheel 17, a transfer output shaft 18, a front propeller shaft 19, a front differential 20, a front drive shaft 21, and a front wheel 22.

The transfer input shaft 12 and the rear propeller shaft 14 are directly connected, and a clutch engagement pressure P _C externally applied is provided between the transfer input shaft 12 and the transfer output shaft 18.
Thus, a transfer clutch 23 (front and rear wheel drive force distribution clutch means) having a wet multi-plate friction clutch structure capable of changing the transmission torque to the front wheels 22 side is incorporated.

Wherein the transfer clutch 23, as an external device, a hydraulic control unit 25 to produce a clutch engagement pressure P _C, the electronic control unit 30 for outputting a command to obtain the clutch engagement pressure P _C is provided.

Wherein the hydraulic control unit 25, the clutch engagement pressure P _C in accordance with working oil by the pump pressure from the hydraulic pump 26 to the command current value I _C
A hydraulic control solenoid valve 27 that regulates the pressure is provided.

The electronic control unit 30 is provided with a torque split control unit 31 having an internal circuit such as a microcomputer and a drive circuit, and input information means 32 for obtaining input information necessary for control calculation in the control unit 31. .

The input information means 32 includes a front wheel speed sensor 33 that detects the front wheel speed Nf, a rear wheel speed sensor 34 that detects the rear wheel speed Nr, and a lateral acceleration.
A lateral acceleration sensor 35 for detecting Yg, a vehicle speed sensor 36 for detecting a vehicle speed V, a steering angle sensor 37 for detecting a steering angle θ, a yaw rate sensor 38 for detecting a yaw rate, and the like are provided.

Then, the torque split control unit 31
Is a torque calculation unit (first calculation unit) that calculates the clutch torque TΔN (first clutch engagement force) corresponding to the rotational speed difference.
And a torque calculation unit (second calculation unit) that calculates the clutch torque T (second clutch engagement force) corresponding to the yawing momentum.
And a clutch engagement force calculation unit (third calculation unit) that calculates a clutch engagement force T (clutch engagement force command value) that is the sum of both clutch torques TΔN and T.

Next, the operation will be described.

FIG. 3 is a flowchart showing the flow of the driving force distribution control operation in the first embodiment, and each step will be described below.

In step 40, the front wheel speed Nf and the rear wheel speed Nf are sent from the respective sensors 33 to 38.
r, lateral acceleration Yg, vehicle speed V, steering angle θ, and yaw rate are read.

Steps 41 to 43 are steps for calculating the clutch engagement force TΔN corresponding to the rotational speed difference.

In step 41, the front-rear wheel speed difference ΔN is calculated from the front wheel speed Nf and the rear wheel speed Nr by the following equation.

ΔN = Nr−Nf In step 42, the control constant Kt is calculated from the lateral acceleration Yg.

The calculation formula is Kt = f ₁ (Yg), and specifically, 0 ≦ Yg
When <Y1, Kt = Ka, when Y1 ≦ Tg <Y2, Kt = Kb, and when Y2 ≦ Yg, Kt = Kc (where Ka>Kb> Kc), or Kt = A / It may be obtained by the formula of Yg (A; constant).

In step 43, the clutch engaging force TΔN corresponding to the rotational speed difference is obtained from the front / rear wheel rotational speed difference ΔN and the control constant Kt.

The arithmetic expression is TΔN = f ₂ (Kt, ΔN) = Nt * ΔN, and this relationship is shown in FIG. 4 as a characteristic diagram.

Steps 44 to 48 are steps for calculating the clutch torque T corresponding to the yawing momentum.

In step 44, the yaw angular acceleration is calculated from the yaw rate (yaw angular velocity).

The arithmetic expression is = d / dt.

In step 45, the target yaw rate * and the target yaw angular acceleration * are calculated by the following formulas based on the vehicle speed V and the steering angle θ.

* ＝ V / R, ＊ ＝ / R R ＝ Ks ・ L / tan (θ / N), ＝ dV / dt R; Turning radius; Vehicle acceleration Ks; Stability factor L; Wheel base N; Steering gear ratio where , *, * May be corrected so as to increase with an increase in steering angular velocity, accelerator depression speed, or the like.

In step 46, the actual yaw rate and the target yaw rate *
The yaw rate difference Δ, which is the difference between and, is calculated.

In step 47, the yaw angular acceleration difference Δ which is the difference between the actual yaw angular acceleration and the target yaw angular acceleration * is calculated.

In step 48, the yaw rate difference Δ and the yaw angular acceleration difference Δ
Thus, the yaw momentum-corresponding clutch torque T is calculated by taking these deviations as an example.

T = K ₃ * (Δ + K ₄ · Δ) That is, when Δ> 0 and> *, the clutch torque T increases. As a result, the driving force to the front wheels 22 is increased, the lateral force on the front wheels side is decreased, and a moment in the understeer direction is generated, so the yaw rate and yaw angular acceleration of the vehicle decrease and Δ decreases, and * matches. Direction.

In the case of Δ <0, <<, on the contrary, the clutch torque T decreases or has a negative sign. As a result, the driving force applied to the front wheels 22 is decreased, the lateral force on the front wheels is increased, and a moment in the oversteer direction is obtained, so that the yaw rate and the yaw angular acceleration of the vehicle increase, and the directions coincide with and.

 In the case of Δ> 0,> *, it is the same as.

 When Δ <0, <<, the same as.

In step 49, the clutch torque TΔN corresponding to the rotational speed difference
The clutch engagement force T is calculated by the sum of the yawing momentum-corresponding clutch torque ψ.

The clutch engagement force T is 0 or a positive value. on the other hand,
Since T has a positive or negative sign depending on the magnitude of the detected value and the target value, T _C = T when T <0 and TΔN <| T |
Since ΔN + T <0, T _C = 0 in this case.

In step 50, the control current for obtaining the clutch engagement force T
I _C is output from the drive circuit to the control solenoid valve 27.

By performing the front-rear wheel driving force distribution control as described above, the following traveling performance is exhibited.

(A) When a drive wheel slip occurs When the vehicle travels straight or turns on a low friction coefficient road such as a rain road or a snow / ice road, the grip force of the tire on the road surface becomes small, so that the drive wheel slip easily occurs.

Further, when the accelerator is suddenly stepped on at the time of starting or during intermediate acceleration, the excessive driving force of the engine is temporarily transmitted to the rear wheels 17, so that the driving wheel slip easily occurs.

Therefore, during traveling in which a large amount of drive wheel slip occurs, the clutch engagement force T is mainly determined by the rotational speed difference corresponding clutch torque TΔN, and the engine drive force is set to the front and rear wheels according to the degree of occurrence of drive wheel slip. Since the clutch torque is applied in the direction in which the vehicle is evenly distributed, the drive / acceleration performance of the vehicle can be improved.

(B) When large yawing momentum occurs During high-speed turning on a high friction coefficient road, large yaw rate and yaw angular acceleration occur.

Therefore, when a large yawing momentum is generated, the clutch engagement force T is determined mainly by the yaw momentum-corresponding clutch torque T, and the clutch torque is applied so as to match the target value based on the vehicle speed V and the steering angle θ. At times, there is no sudden change in spin or steer characteristics, and controllability at the turning limit is improved.

(C) When the lateral force characteristics of a tire change When the lateral force characteristics for tire slip change outside the preset values due to tire brand differences, tire wear, road surface temperature, vehicle weight, etc., the rotational speed difference The corresponding clutch torque TΔN becomes excessive or excessively small, and the vehicle steering characteristic changes to understeering or oversteering.

However, the clutch engagement force T depends on the clutch torque TΔN corresponding to the rotational speed difference and the clutch torque T corresponding to the yawing momentum.
Therefore, when the lateral force characteristic with respect to the slip of the tire changes due to an external factor as described above, the yawing momentum-corresponding clutch torque T acts as a correction factor for the rotational speed difference-corresponding clutch torque TΔN, and the steer characteristic The influence on external factors can be kept small.

That is, the change in the lateral force characteristic with respect to the slip of the tire and the generated amount of yawing momentum such as yaw rate and yaw angular acceleration have a correspondence relationship.

Therefore, for example, when the characteristics of the rear wheels are changed such that the lateral force against slip is reduced due to wear of the tires of the rear wheels, the clutch torque TΔN corresponding to the rotational speed difference is set according to the characteristics set in advance according to the generation amount of the drive wheel slip. Even if it is given, the lateral force generation value of the rear wheels is smaller than that in the initial state where the tire is not worn, so that there is an oversteer tendency and the yawing momentum increases. However, when the tire characteristics are changed so that the lateral force of the rear wheels becomes small and the yawing momentum increases, the clutch torque T corresponding to the yawing momentum T
Is a positive value, and the clutch torque T corresponding to the rotational speed difference is
Since the clutch engagement force T, which is the sum of ΔN, is set to be increased, the oversteer characteristic is suppressed.

Similarly, when the lateral force characteristic with respect to the slip of the tire changes so as to increase, the yawing momentum-corresponding clutch torque T becomes a negative value, which is the sum of the clutch torque TΔN corresponding to the rotational speed difference. It is corrected so as to decrease T, and the understeer characteristic is suppressed.

(Second Embodiment) First, the torque control device for a driving force distribution clutch according to the present invention is applied to a differential limiting clutch for a differential limiting control device for a rear-wheel drive vehicle. Examples will be described.

To explain the configuration, FIG. 5 is a diagram showing the entire system of the differential limiting control device for a rear-wheel drive vehicle. The engine drive system includes an engine 60, a transmission 61, a rear propeller shaft 62, a rear differential 63, and a rear drive shaft. It has 64,65 and rear wheels 66,67.

Incidentally, 68 and 69 are front wheels.

The rear propeller shaft 62 and the rear drive shaft 6
A differential limiting clutch having a wet multi-plate friction clutch structure capable of changing a transmission torque (differential limiting torque) by an externally applied clutch engaging force P _C is provided between each of the differential limiting clutches 4 and 65.
0,71 (right and left wheel driving force distribution control means) is built in.

Wherein the differential limiting clutch 71, as an external device, a hydraulic control unit 75 to produce a clutch engagement pressure P _C, the electronic control unit 80 for outputting a command to make the clutch engagement pressure P _C is provided.

Wherein the hydraulic control device 75, the clutch engagement pressure P _C in accordance with working oil by the pump pressure from the hydraulic pump 76 to the command current value I _C
A hydraulic control solenoid valve 77 for adjusting the pressure to is provided.

The electronic control unit 80 includes an LSD control unit 81 having a microcomputer, a drive circuit, etc. in its internal circuit.
And input information means 82 for obtaining input information necessary for control calculation in the control unit 81.

As the input information means 82, a vehicle speed sensor for detecting the vehicle speed V
83, steering angle sensor 84 for detecting steering angle θ, right rear wheel speed sensor 85 for detecting right rear wheel speed nr, left rear wheel speed sensor 86 for detecting left rear wheel n1, accelerator for detecting accelerator opening Acc An opening sensor 87, a lateral acceleration sensor 88 that detects a lateral acceleration Yg, a yaw rate sensor 89 that detects a yaw rate, and the like are provided.

The LSD control unit 81 includes a calculation unit (first calculation unit) for the clutch engagement force TΔn based on the outer wheel slip speed, a calculation unit for the tack-in countermeasure torque T _{T, and} a calculation unit for the torque T according to the yawing momentum ( Second calculation unit)
And a calculation unit (third calculation unit) for calculating the clutch engagement force T based on the sum of these torques.

Next, the operation will be described.

FIG. 6 is a flowchart of the main routine showing the flow of the differential limiting control operation in the second embodiment, and each step will be described below.

In step 100, the vehicle speed V, the steering angle θ, the right rear wheel speed nr, the left rear wheel speed n1, the accelerator opening Acc, and the lateral acceleration are detected from the sensors 83 to 89.
Yg and yaw rate are read.

In step 101, the clutch torque TΔn based on the outer wheel slip velocity is calculated according to the flow shown in FIG.

In step 102, the tack-in countermeasure torque T _T is calculated according to the flow shown in FIG.

In step 103, the torque T according to the yawing momentum is calculated according to the flow shown in FIG.

In step 104, the clutch engagement force T is calculated from the sum of the torques TΔn, T _T , T obtained by the above calculation.

In step 105, the control current I _{C with} which the clutch engagement force T is obtained is output from the drive circuit to the control solenoid valve 77.

Next, the calculation process of the clutch torque TΔn based on the outer wheel slip velocity will be described according to the flow shown in FIG.

This process calculates the slip target value ΔW _A (step 200) set according to the accelerator opening A _CC and the actual slip speeds ΔW _R and ΔW _L of the left and right wheels (step 201), and changes it according to the turning direction. Judgment of turning outer wheel, slip speed of turning outer wheel Δ
The speed required to match W _R or ΔW _L with the slip target value ΔW _A is determined (steps 202 to 208), and the clutch torque TΔn is set to the clutch torque TΔn _O one control cycle before by setting the set value A. It is calculated by increasing or decreasing (step 209 to step 214).

Next, the calculation process of the tack-in countermeasure torque T _T will be described according to the flow shown in FIG.

In this process, as the start condition of the tack-in control, the accelerator opening A _CC is less than the predetermined value A _O (step 305), the accelerator change speed A _CC is 0 or negative (step 306), and the accelerator change speed absolute value | When A _CC | exceeds the predetermined value A ₁ (step 307) and the lateral acceleration Yg is equal to or more than the predetermined value Y ₁ (step 308), when these conditions are satisfied, the tack flag TUCKFLG = 1 is set, and the step 310 As shown in
A tack-in countermeasure torque T _T that suppresses tack-in is calculated according to the vehicle speed V and the lateral acceleration Yg.

It should be noted that steps 300 to 303 are processing steps for setting the accelerator change speed flag A _CC FLG, step 304, step 311 and step 312 are release condition determination steps for tack-in suppression control, and when not controlled, step 313.
In step 314, the tack flag TUCKFLG is set to 0, and in step 314, the tack-in countermeasure torque T _T is set to 0.

Next, the calculation process of the torque T according to the yawing momentum will be described according to the flow shown in FIG.

Of these processes, steps 400 to 404 are steps corresponding to steps 44 to 48 of the first embodiment, and are steps for calculating torque from the difference between the target yawing momentum and the actual yawing momentum.

Then, steps 405 to 409 determine whether the vehicle is exerting a moment in the understeer direction or a moment in the oversteer direction by applying the differential limiting torque, and when the moment in the understeer direction is exerting, the yawing momentum is determined. The clutch engagement force T decreases in the decreasing direction, and increases the yawing momentum when a moment in the oversteering direction is generated.
Is the step of determining the increase or decrease of.

In step 405, the turning direction is determined, and steps 406 and 407
In, the inner and outer wheels during turning are identified, and the outer wheel rotational speed N _OUT and the inner wheel rotational speed N _IN are set respectively.

In step 408, it is determined whether the inner / outer wheel rotation speeds N _OUT and N _IN are large or small.

When N _OUT > N _IN , the outer wheel rotation speed N _OUT is faster than the inner wheel rotation speed N _IN. Therefore, if the differential limiting torque is reduced in this state, the moment in the understeer direction decreases. Therefore, in step 409, when the torque T> 0, the yawing momentum is larger than the target value, so the clutch torque is increased, the understeer moment is increased, and the yawing momentum is decreased.

Then, when N _OUT ≦ N _IN , inner wheel spin occurs due to acceleration, so increasing the differential limiting torque in this state increases the moment in the oversteer direction. Therefore, in step 410, when the torque T> 0, the yawing momentum is larger than the target value, so the clutch torque is reduced to reduce the oversteer moment and reduce the yawing momentum.

By performing the differential limiting control as described above, similarly to the case of the first embodiment, both the improvement of the driving / accelerating performance of the vehicle and the improvement of the controllability at the turning limit are achieved, and the steering characteristic is achieved. The influence on the external factors of can be suppressed to be small.

In addition, since the tack-in countermeasure torque T _T is added in determining the clutch engaging force T, the tack-in suppressing effect is also exerted.

Although the embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment.

Further, in the embodiment, the clutch by hydraulic engagement is shown as the driving force distribution clutch means, but another clutch such as an electromagnetic clutch or a viscous clutch may be used.

(Effect of the invention) In the engagement force control device for the driving force distribution clutch according to claim 1, a first calculation unit that determines the first clutch engagement force by the product of the front-rear wheel rotation speed difference detection value and the control constant. , A second computing unit that determines the second clutch engagement force so that the yaw momentum detection value matches the yawing momentum target value, and a value based on the sum of the first clutch engagement force and the second clutch engagement force In the vehicle in which the torque distribution to the front and rear wheels is controlled by the clutch engagement force externally applied, the drive / acceleration performance of the vehicle is improved and the turning limit is increased. It is possible to achieve both controllability improvement in
The effect that the influence of the steer characteristic on external factors can be suppressed to be small is obtained.

The engagement force control device for a driving force distribution clutch according to claim 2, wherein the first calculation unit determines the first clutch engagement force so that the detected value of the left and right wheel slip state amount matches the target value of the left and right wheel slip state amount. And a second calculation unit that determines the second clutch engagement force so that the detected yawing momentum value matches the yawing momentum target value, and a value based on the sum of the first clutch engagement force and the second clutch engagement force Since the device is provided with the third calculation unit for setting the command value, in a vehicle in which the torque distribution to the left and right wheels is controlled by the clutch engagement force applied from the outside, improvement of the drive / acceleration performance of the vehicle and turning It is possible to achieve both the improvement of controllability at the limit and the effect of suppressing the influence of steer characteristics on external factors to a small extent.

[Brief description of drawings]

FIG. 1 (a) is a claim correspondence diagram showing the engagement force control device of the driving force distribution clutch according to claim 1, and FIG. 1 (b) is the engagement force control device of the driving force distribution clutch according to claim 2. Claim correspondence diagram, FIG. 2 is an overall system diagram showing a first embodiment device applied to a transfer clutch of a driving force distribution control device for a four-wheel drive vehicle, and FIG. 3 is a torque split control unit in the first embodiment device. A flow chart showing the flow of front and rear wheel drive force distribution control operation performed in
FIG. 4 is a characteristic diagram of clutch torque corresponding to rotational speed difference, and FIG.
FIG. 6 is an overall system diagram showing a second embodiment device applied to a limited slip clutch of a vehicle limited slip control device, and FIG. 6 is a differential limit control operation performed by an LSD control unit in the second embodiment device. FIG. 7 is a flow chart of a main routine showing the flow of FIG. 7, FIG. 7 is a flow chart showing a flow of clutch torque calculation processing operation based on outer wheel slip velocity, and FIG.
FIG. 9 is a flow chart showing the flow of the calculation processing operation of the tack-in countermeasure torque, and FIG. 9 is a flow chart showing the flow of the calculation processing operation of the torque according to the yawing momentum. a: front and rear wheel driving force distribution clutch means b: front and rear wheel rotation speed difference detection means c: first calculation section d: yawing momentum detection means e: yawing momentum target value setting means f: second calculation section g ... Third computing unit h ... Left and right wheel driving force distribution clutch means i ... Left and right wheel slip state amount detecting means j ... Left and right wheel slip state amount target value setting means k ... First computing unit m ... Yawing Momentum detecting means n …… Yawing momentum target value setting means o …… Second computing unit p …… Third computing unit

Claims (2)

[Claims] 1. Front and rear wheel drive force distribution clutch means, which is provided in the middle of an engine drive system for distributing and transmitting the engine drive force to the front and rear wheels, and which can change the transmission torque by a clutch engaging force applied from the outside, and front and rear wheels. A front and rear wheel rotational speed difference detecting means for detecting a rotational speed difference; and a first product based on a product of the front and rear wheel rotational speed difference detection value and a control constant.
The first calculation unit that determines the clutch engagement force, the yawing momentum detecting unit that detects the yawing momentum of the vehicle, the yawing momentum target value setting unit that sets the yawing momentum target value based on the vehicle speed and the steering state, and the yawing momentum detection value are A second calculation unit that determines the second clutch engagement force so as to match the yawing momentum target value, and a third calculation unit that uses a value based on the sum of the first clutch engagement force and the second clutch engagement force as the clutch engagement force command value. An engagement force control device for a drive force distribution clutch, comprising: a computing unit. 2. A left and right wheel drive force distribution clutch means, which is provided in the middle of an engine drive system for distributing and transmitting the engine drive force to the left and right wheels, and which can change the transmission torque by an externally applied clutch engaging force, and a left and right drive. Left and right wheel slip state amount detecting means for detecting the slip state amount of the wheel with respect to the road surface, left and right wheel slip state amount target value setting means for setting the left and right wheel slip state amount target values for ensuring the driving performance and turning performance of the vehicle, The first clutch engagement force is determined so that the detected values of the left and right wheel slip state amounts match the left and right wheel slip state amount target values.
The calculation unit, the yawing momentum detecting means for detecting the yawing momentum of the vehicle, the yawing momentum target value setting means for setting the yawing momentum target value based on the vehicle speed and the steering state, and the yawing momentum detection value matches the yawing momentum target value. And a third calculation unit that determines a value based on the sum of the first clutch engagement force and the second clutch engagement force as a clutch engagement force command value. A drive force distribution clutch engagement force control device characterized by being provided.