JP2848107B2 - Vehicle differential limiting control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Between the right and left driving wheels of an automobile,
A differential mechanism is provided to allow the differential that occurs when turning, etc., but with this differential mechanism, the load on one of the left and right wheels is in the groove and the friction coefficient with the road surface is extremely small. Then, only one of the wheels rotates and the other wheel hardly rotates, so that a state where the driving torque cannot be transmitted to the road surface may occur.

Therefore, in such a case, a differential limiting mechanism (LSD = Limited Slip Differential) capable of limiting the differential has been developed. Such a left and right wheel differential limiting mechanism includes a type that is proportional to the rotational speed difference between the left and right wheels and a type that is proportional to the input torque. The right and left wheel rotation speed difference proportional type uses VC that utilizes the viscosity of the liquid.
(Viscous coupling) type LSD, etc.
There is an advantage that the running stability of the vehicle can be improved. On the other hand, the input torque proportional type includes a friction type such as a general LOM (lock automatic) type LSD, and a TORSE using a friction resistance of a worm gear.
There is a mechanical type such as an N (Truesen) type LSD, which has an advantage that the turning performance of the vehicle can be improved.

[0004]

Incidentally, in each of the differential limiting mechanisms (LSDs) as described above, the differential control characteristics are determined by physical properties and the like, so that the differential control mechanism can always always appropriately perform differential control. The differential control characteristics cannot be adjusted. Therefore, as a mechanism capable of positively adjusting the differential limiting state, for example, a mechanism using a multi-plate clutch is considered. In other words, a multi-plate clutch is interposed between the left-wheel rotation system and the right-wheel rotation system that generate a differential, and the engagement state of the multi-plate clutch is adjusted by, for example, hydraulic pressure or electromagnetic force adjusting means. In this manner, the differential limiting state can be positively adjusted through the adjusting means in accordance with a command from a controller (for example, a microcomputer).

[0005] Therefore, for example, the differential limiting state can be appropriately controlled according to the rotation difference (rotation speed difference) between the left and right wheels. FIG. 11 is a schematic block diagram showing the main configuration of such a differential limiting control device. A wheel speed sensor 104 is installed on the right wheel side and a wheel speed sensor 106 is installed on the left wheel side. A calculating means (subtractor) 116 for calculating a difference (for example, AB) between the right wheel rotation speed A from the wheel speed sensor 104 and the left wheel rotation speed B from the wheel speed sensor 106, and the rotation speed difference ( A differential limiting force setting means 126 'for setting a differential limiting force (= LSD restraining torque) corresponding to AB).

[0006] In the differential limiting force setting means 126 ', for example, the rotational speed difference (A-
The differential limiting force is set so as to be proportional to B). As a result, it becomes possible to limit the differential according to the difference in the number of revolutions, and it is possible to balance the allowance of the differential with the limit of the differential. Driving force can always be transmitted reliably.

However, in such a multi-plate clutch type differential limiting mechanism, the differential limit is adjusted while sliding the clutch. However, if the clutch continues to slide for a long time, durability of the clutch becomes a problem. For example, when the roads μ of the left and right wheels are started in different environments from each other (at the start of right and left splits), especially when traveling at a higher speed, the rotation difference between the left and right wheels is larger while restraining the multi-plate clutch. May continue and the clutch will be subjected to high load conditions for extended periods of time. For this reason, the clutch may be damaged, and vibration and noise may increase due to stick-slip of the clutch. Further, the clutch may be seized and smooth differential operation may not be performed, which may cause a tight corner braking phenomenon or the like.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and provides a vehicle differential limiting control device capable of controlling the differential limiting state of left and right wheels while increasing the durability of the device. With the goal.

[0009]

[0010]

Means for Solving the Problems] Therefore, vehicle differential limiting control apparatus of the present invention relates to claim 1, and the differential limiting mechanism for limiting a differential state between the right and left wheels of the vehicle, the differential limiting Control means for controlling a mechanism; and actual rotation speed difference detection means for detecting an actual rotation speed difference between the left and right wheels generated during the turning of the vehicle, wherein the control means is provided in accordance with the magnitude of the actual rotation speed difference. Differential limiting force setting means for setting the differential limiting force of the differential limiting mechanism, the differential limiting force setting means setting the differential limiting force when the vehicle is traveling at a low speed. A medium-to-low speed differential limiting force setting unit, including a high-speed differential limiting force setting unit that sets the differential limiting force during high-speed running of the vehicle, the medium-low speed differential limiting force setting unit, In order to increase the maximum value in proportion to the actual rotational speed difference, In addition to being configured to set the limiting force, the high-speed differential limiting force setting unit increases in proportion to the increase in the actual rotation speed difference until the actual rotation speed difference reaches a reference value. to set the differential limiting force so as to set the differential limiting force said actual rotational speed difference decreases with an increase in said actual rotational speed difference reaches the reference value as <br / > It is characterized by being structured like

According to a second aspect of the present invention, there is provided a differential limiting control apparatus for a vehicle according to the present invention , comprising: a differential limiting mechanism for limiting a differential state between left and right wheels of a vehicle; An actual rotational speed difference detecting means for detecting an actual rotational speed difference between the left and right wheels generated during the turning of the vehicle, wherein the control means includes: Differential limiting force setting means for setting a differential limiting force is provided, and the differential limiting force setting means is in proportion to the increase in the actual rotation speed difference until the actual rotation speed difference reaches a reference value. to set the differential limiting force as decreases with the increase to take as an increase in said actual rotational speed difference After setting the differential limiting force said actual rotational speed difference reaches the reference value I is urchin configuration, the smaller the value the reference value of the actual rotational speed difference the vehicle speed becomes faster It is characterized in that it is variably set corresponding to the vehicle speed so.

[0012]

[0013]

[0014]

[Action] In the vehicular differential limiting control apparatus of the present invention relates to claim 1 described above, when the actual rotational speed difference detecting means for detecting the actual rotational speed difference between the left and right wheels, the differential limiting force setting means of the control means the difference The differential limiting force of the motion limiting mechanism is set according to the speed.
In other words, when the vehicle is running at low speed, the differential limiting force setting unit for medium and low speed sets the differential limiting force so as to increase to a maximum value in proportion to the actual rotation speed difference. During high-speed running, the high-speed differential limiting force setting unit sets the differential limiting force so as to increase in proportion to the actual rotational speed difference until the actual rotational speed difference reaches the reference value. Is set, and when the actual rotation speed difference reaches the reference value, the differential limiting force is set so as to decrease as the actual rotation speed difference increases.

The differential limiting mechanism is controlled by the control means so as to be in the state of the differential limiting force. As a result, the differential state between the left and right wheels of the vehicle is generally limited by a greater differential limiting force as the actual rotation speed difference is larger, corresponding to the actual rotation speed difference between the left and right wheels. If the differential between them is large, the above-mentioned differential limiting force is set to a smaller value, so that the load applied to the differential limiting mechanism, which becomes a problem particularly at high speed running, is reduced, and this differential limiting mechanism is protected. Is done.

Further, in vehicle differential limiting control apparatus of the present invention relates to claim 2, when the actual rotational speed difference detecting means for detecting the actual rotational speed difference between the left and right wheels, the differential limiting force setting means of the control means the difference The differential limiting force of the motion limiting mechanism is set according to the speed. In other words, the differential limiting force setting means sets the reference value of the actual rotation speed difference corresponding to the vehicle speed so that the reference value becomes smaller as the vehicle speed increases, and until the actual rotation speed difference reaches this reference value. Sets the above-mentioned differential limiting force so as to increase in proportion to the increase in the actual rotation speed difference, and when the actual rotation speed difference reaches the reference value, decreases with the increase in the actual rotation speed difference. Set the differential limiting force so that

The differential limiting mechanism is controlled by the control means so as to be in the state of the differential limiting force. As a result, the differential state between the left and right wheels of the vehicle does not easily reach the reference value at low speed even if the actual rotation speed difference becomes large. The larger the speed difference is, the larger the differential limiting force is.
On the other hand, as the vehicle speed increases, the reference value is reached even if the actual rotation speed difference is not so large, and the differential limiting force decreases rather as the actual rotation speed difference increases. The load applied to the differential limiting mechanism, which becomes more problematic during high-speed running, is reduced, and the differential limiting mechanism is protected.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a vehicle differential limiting control apparatus according to a first embodiment of the present invention; FIG. FIG. 2 is a block diagram showing the overall configuration of the drive torque transmission system including the differential control device, FIG. 3 is a block diagram showing the overall configuration of the device, and FIG. 5 is a flowchart showing a main routine of the control, FIG. 6 is a flowchart showing a subroutine of another control, FIG. 7 is a flowchart showing a subroutine of another control, and FIG. FIG. 9 is a diagram illustrating a map relating to differential correspondence control, and FIG. 9 is a diagram illustrating a map relating to differential correspondence control of a vehicle differential limiting control device according to a second embodiment of the present invention. Figure 10 is a flowchart showing a subroutine related to differential response control of the vehicle differential limiting control apparatus of a third embodiment of the present invention.

First, the first embodiment will be described. The overall configuration of a drive system of a vehicle including the differential-adjustable front and rear wheel torque distribution control device will be described with reference to FIG. In FIG. 2, reference numeral 2 denotes an engine. The output of the engine 2 is transmitted to an output shaft 8 via a torque converter 4 and an automatic transmission 6. The output of the output shaft 8 is
Is transmitted to a planetary gear type differential device 12 as an actuating device for distributing the engine torque of the front wheels and the rear wheels to a required state.

On the other hand, the output of the planetary gear type differential device 12 is the reduction gear mechanism 19 and the differential gear device 1 for the front wheels.
4 through the axles 17L, 17R from the left and right front wheels 16, 1
And transmitted from the axles 25L, 25R to the left and right rear wheels 24, 26 via a bevel gear mechanism 15, a propeller shaft 20, a bevel gear mechanism 21, and a differential gear unit (rear differential) 22 for rear wheels. You.

The planetary gear type differential device 12 includes a sun gear 121, a planetary gear 127 disposed outside the sun gear 121, and a ring gear disposed outside the planetary gear 127, in the same manner as a conventionally known one. 123 and
The output of the output shaft 8 of the automatic transmission 6 is input to the carrier 125 that supports the planetary gear 127, and the sun gear 121
Is interlocked with the front wheel differential gear device 14 via the front wheel output shaft 27 and the reduction gear mechanism 19, and the ring gear 123 is interlocked with the propeller shaft 20 via the rear wheel output shaft 29 and the bevel gear mechanism 15. .

Further, the planetary gear type differential device 14 restricts (or limits) the differential between the front wheel side output portion and the rear wheel side output portion, thereby reducing the output torque of the engine between the front wheel and the rear wheel. A hydraulic multi-plate clutch 28 is provided as differential limiting means or differential adjusting means capable of changing the distribution. That is, the hydraulic multi-plate clutch 28 is interposed between the sun gear 121 (or the ring gear 123) and the carrier 125, the frictional force changes according to the control pressure applied to its own hydraulic chamber, and the sun gear 121 (or Ring gear 123)
And the carrier 125 is restricted.

Therefore, the planetary gear type differential 12 is
By appropriately controlling the hydraulic multi-plate clutch 28 from a completely free state to a locked state, the torque transmitted to the front and rear wheels can be reduced from about 32:68 to 50:50 for the front and rear wheels. It can be controlled between. Front wheel in completely free condition: rear wheel value: approx. 3
2:68 can be defined by setting the tooth ratio of the input gears on the front wheel side and the rear wheel side of the planetary gears. In this case, when the pressure in the hydraulic chamber of the hydraulic multi-plate clutch 28 is zero and completely free, It is set to be about 32:68.

The ratio in the completely free state (about 3)
2:68) changes depending on the load balance between the front wheel system and the rear wheel system and the like, but usually takes such a value. Further, when the pressure in the hydraulic chamber is set to the set pressure (9 kg / cm ² ) and the hydraulic multi-plate clutch 28 is in the locked state and the differential limit becomes substantially zero, the torque distribution between the front wheels and the rear wheels is reduced. , 50: 5
It becomes 0 and it is in a directly connected state.

The details of the rear differential 22 will be described later. Reference numeral 30 denotes a steering wheel angle sensor for detecting a rotation angle from a neutral position of the steering wheel 32, that is, a steering wheel angle θ, and reference numerals 34a, 34b denote lateral accelerations Gyf, G acting on a front portion and a rear portion of the vehicle body, respectively.
In this example, two pieces of detection data Gyf and Gyr are averaged to obtain lateral acceleration data. In this example, however, one lateral acceleration sensor 34 is provided near the center of gravity of the vehicle body.
Only one of them may be provided and this detected value may be used as the lateral acceleration data. 36 is a longitudinal acceleration sensor for detecting the longitudinal acceleration Gx acting on the vehicle body, 38 is a throttle position sensor for detecting the throttle opening θt of the engine 2, 39
Is the engine key switch of engine 2, 40, 42, 4
4 and 46 are the front left wheel 16, the front right wheel 18 and the rear left wheel 2, respectively.
6, wheel speed sensors for detecting the rotation speed of the right rear wheel 28, and the outputs of these switches and each sensor are input to the controller 48.

Reference numeral 50 denotes an anti-lock brake device, which operates in conjunction with a brake switch 50A. That is, when the brake switch 50A is turned on when the brake pedal 51 is depressed, an antilock brake operation signal is output in conjunction therewith, and the antilock brake device 50 is operated. Further, when the operation signal of the anti-lock brake is output, a signal indicating the state is simultaneously output to the controller 4.
8 is input. Reference numeral 52 denotes a warning lamp that lights based on a control signal from the controller 48.

The controller 48 includes a CPU, a ROM, a RAM, an interface, etc., which are not shown but are necessary for the control described later. Reference numeral 54 denotes a hydraulic pressure source, and 56 denotes a pressure control valve system (hereinafter, referred to as a pressure control valve) interposed between the hydraulic pressure source 54 and the hydraulic chamber of the hydraulic multi-plate clutch 28 and controlled by a control signal from a controller 48. (Abbreviated).
The vehicle is provided with an automatic transmission. Reference numeral 160 denotes a shift lever position sensor (shift range detecting means) for detecting a selected shift range of a shift lever 160A of the automatic transmission. 48.

Further, the engine speed N detected by the engine speed sensor (engine speed sensor) 170
e and the transmission rotation speed Nt detected by the transmission rotation speed sensor (transmission rotation speed sensor) 180 are also sent to the controller 48. In this example, the traction control system 1
51 is also available. That is, the engine 2 includes the main throttle valve 152 whose opening is controlled in accordance with the amount of depression of the accelerator pedal 162.
An accelerator pedal-based engine output adjusting device is constituted together with the engine 62 and the coupling measures. An auxiliary throttle valve 153 as engine output control means controlled independently of the accelerator pedal system engine output adjusting device is provided in series with the main throttle valve 152 in the intake passage of the engine 2. The auxiliary throttle valve 153 is driven by a motor, and this motor is connected to the rear wheel speed sensors 44 and 4.
6, front wheel speed sensors 40 and 42 and engine speed sensor 1
Drive control is performed based on the detection results of the engine 70, the engine load sensor 172, and the like.

The above-described rear differential (rear differential) 22 is configured as shown in FIG. , A left wheel driven pinion 22B and a right wheel side rotation shaft 25R connected to a left wheel side rotation shaft 25L.
And is distributed to the right wheel driven pinion 22C connected to the right wheel. In this example, the rear differential 22 is of a bevel gear type,
As the rear differential 22, a planetary gear type may be used.

A differential limiting mechanism 23 is attached to the rear differential 22.
As shown in the figure, the left wheel side rotation shaft 25L and the right wheel side rotation shaft 25
And a multi-plate clutch interposed between R and a state in which the multi-plate clutch is completely engaged from a completely separated state by a drive mechanism (not shown) (or a state in which the multi-plate clutch is engaged to a predetermined level). Up to this point, the engagement state can be continuously adjusted. Here, as the driving mechanism, an electromagnetic clutch mechanism that adjusts the pressing force of the multi-plate clutch to the clutch plate by magnetic force is used. For example, the pressing force of the multi-plate clutch to the clutch plate is adjusted by hydraulic pressure. A hydraulic multi-plate clutch mechanism that performs this operation is also considered.

The differential limiting force is controlled by adjusting the current to the solenoid of the electromagnetic clutch mechanism (or the hydraulic adjustment) of such a hydraulic multi-plate clutch mechanism. 48 is provided with a rear differential control unit 48a. Here, the rear differential control unit 48a will be described. As shown in the block diagram of FIG. 3, the rear differential control unit 48a includes a rear wheel sharing torque calculating unit 102 for calculating a rear wheel sharing torque, wheel speed detecting units 104 and 106 for detecting wheel speeds of left and right rear wheels. Vehicle speed detecting means 108 for detecting or calculating the vehicle speed (vehicle speed)
The clutch torque (LSD restraining torque) of the multi-plate clutch 23 is set based on the detection information from the above, and the supply hydraulic pressure or supply current of the drive mechanism is controlled so as to obtain the target clutch torque. . Note that the wheel speed detecting means 104 and 106 are provided with the wheel speed sensors 44 and 46 described above.
And a filter (not shown) for removing noise components in the output from the sensor.

In this device, the clutch torque of the multi-plate clutch 23 is set according to the differential state of the left and right wheels (the rotational speed difference, which is also referred to as the rotational speed difference). TRV, an input torque proportional clutch torque TRT set in proportion to the torque TA input to the rear wheels so as to obtain a large road surface transmission torque by suppressing the slip of the wheels at the time of sudden start or the like, and a multi-plate clutch. One is selected from the initial clutch torque TRI for setting the clutch torque 23 to a state immediately before engagement, and these clutch torques TRV, TR
The T and TRI setting units will be described in order.

The differential corresponding clutch torque TRV is a clutch torque for efficiently transmitting the driving force to the road surface while avoiding the tight corner braking phenomenon. For this reason, in the rear differential control unit 48a, FIG.
As shown in FIG. 3, an arithmetic processing unit (actual rotation speed difference detection means) which receives signals VRR and VRL from wheel speed detection means 104 and 106 and subtracts these signals to obtain a difference DVRD (= VRR-VRL). ) 116 and a clutch torque setting section (differential limiting force setting means) 126 for setting the clutch torque TRV using the map 3 based on the difference DVRD obtained in this manner.

Here, as shown in FIG. 3, the arithmetic processing unit 122 subtracts and corrects the difference DVRD output from the arithmetic processing unit 116 by a correction amount DVHR determined by the vehicle speed and the steering angle to obtain a value DVR. Is to be obtained. This correction amount DVHR is a value of a rotation difference that should occur between the left and right wheels when the vehicle turns, and this rotation difference (correction amount) DVH
R is determined by the vehicle speed VB and the steering angle TH. The vehicle speed VB increases with an increase in the vehicle speed VB, and the steering angle TH also increases with an increase in the steering angle TH.

Therefore, a vehicle-body-dependent rotation difference component setting section 118 for setting a rotation difference component DVHR1 corresponding to the vehicle speed VB detected by the vehicle speed detection means 108, for example, as shown in a map 5 in FIG. DVHR1 at steering angle T
A steering angle corresponding correction unit 120 that corrects according to H is provided. The correction by the steering angle correspondence correction unit 120 is performed by integrating the steering angle TH or a correction coefficient proportional to the steering angle TH into the rotation difference component DVHR1, thereby obtaining the rotation difference (correction amount) DVHR. I have. However,
During counter steer, DVHR is set to 0, and the subtraction correction processing in the arithmetic processing unit 122 is not substantially performed.

In the clutch torque setting section 126, a map 3 is set based on the difference value DVR corrected by the arithmetic processing section 122.
Is used to set the clutch torque TRV, and this setting is made by using two types of maps A and B depending on the vehicle speed. That is, a vehicle speed determination signal output unit 124 that determines whether the vehicle speed is in the middle or low speed state or the high speed state and outputs the signal to the clutch torque setting unit 126 is provided.
6 includes a medium / low speed differential limiting force setting unit 126A for setting a differential limiting force at the time of medium / low speed running, and a high speed differential limiting force setting unit 126 for setting a differential limiting force at the time of high speed running
B is provided.

The vehicle speed determination signal output unit 124 compares the reference value V ₀ which is previously set vehicle speed VB, and determines whether the vehicle speed VB is greater than the reference value V ₀ less than or reference value V _0. If the vehicle speed VB is equal to or lower than the reference value V _0, it can be determined that the vehicle is in the middle and low speed state, and if the vehicle speed VB is higher than the reference value V ₀ , it can be determined that the vehicle is in the high speed state. Then, a signal based on the determination result is output to the clutch torque setting unit 126.

When the clutch torque setting section 126 determines that the vehicle is in the middle / low speed state from the signal from the vehicle speed discrimination signal output section 124, the middle / low speed differential limiting force setting section 126A sets the differential limiting force. If it is determined from the signal from the determination signal output unit 124 that the vehicle is in the high speed state, the high speed differential limiting force setting unit 126B sets the differential limiting force. The medium / low speed differential limiting force setting unit 126A converts the differential limiting force (LSD restraining torque) to the actual rotation speed difference | A−B | (= DVR) as shown in the map in the block 126A of FIG. At a tilt angle θ ₁ )
The differential limiting force is set so as to increase in proportion to the maximum value (the differential limiting force for fully engaging the multiple disc clutch 23 or the differential limiting force for engaging to a predetermined level). When the rotational speed reaches the limit, the differential limiting force becomes constant even if the actual rotational speed difference increases.

In the high-speed differential limiting force setting unit 126B, the actual rotational speed difference | AB | (= DVR) is used as the reference value DV as shown in the block 126B of FIG. 1 and the map shown in FIG.
_{In an} area smaller than ₁ , the differential limiting force (LSD restraining torque) is set to increase in proportion to the actual rotation speed difference | AB | (= DVR) (at the inclination angle θ ₁ ) ( Reference numeral a in the map).

[0040] However, the actual rotational speed difference | A-B | the reference value in the area larger than DV _1, the actual rotational speed difference | A-B |
Is set so that the differential limiting force decreases (at the inclination angle θ ₂ ) as the value increases (see the portion indicated by the symbol “b” in the map).
Furthermore, the actual rotational speed difference | A-B | If becomes larger than the reference value DV _2, the differential limiting force is zero. Or is in the region larger than the reference value DV _1, since a large load consuming not on durability Preferably the clutch to the clutch, in this region, weaken the engagement of the clutch | This actual rotational speed difference | A-B Alternatively, the clutch can be released to protect the clutch. However, the reason why the differential limiting force is reduced at an appropriate inclination (inclination θ ₂ ) and is not suddenly set to zero as in the portion indicated by reference numeral b is that consideration is given to maintaining a good driving feeling of the vehicle. Things.

On the other hand, as the actual rotational speed difference | AB | that becomes larger as described above decreases, the actual rotational speed difference | AB
| Is until reduced to a predetermined value (the value of the small difference) DV ₃ are set so that a differential limiting force is maintained at 0 (see part of the code c in the map). This is the symbol a, b
This is because, for a clutch that has already been operated under severe conditions, such as the route indicated by と, it is desired to wait for the operation of the clutch until the clutch load becomes sufficiently small to reliably protect the clutch.

[0042] Then, the actual rotational speed difference | A-B | When becomes less further reduced than this value DV _3, (in inclination angle theta ₃₎ along with the differential limiting force to the decrease increases and It is set to be higher (see the part of the symbol d in the map). The reason for increasing the differential limiting force in this way is that when the actual rotation speed difference | AB | is sufficiently small, the load on the clutch when the clutch is engaged becomes sufficiently small.
This is because there is no need to protect the clutch, but rather, the clutch is engaged to effectively use the differential limiting control.

The above-mentioned inclination angles θ ₁ , θ ₂ , θ ₃ are appropriately set. As described above, in the high-speed differential limiting force setting unit 126B, the clutch is easily exposed to severe conditions during high-speed running, so that the differential limiting control is always performed while taking into consideration the protection of the clutch. If the actual rotation speed difference | AB | decreases in the middle of the symbol “b” in the map, that is, before the differential limiting force becomes zero, the differential limiting at this time is indicated by a chain line in the map. Means for maintaining the force or setting the differential limiting force so as to return to the straight line indicated by the symbol b can be considered. This sets with a margin reference value DV ₁ on the safe side (i.e., a relatively small set) that is, the actual rotational speed difference | A-B |
There in the vicinity of the reference value DV ₁ is give priority to the differential control than protection of the clutch, the actual rotational speed difference | A-B | is that Yuku gradually giving priority to the clutch protection Once beyond the reference value DV ₁ This is because it is considered that the clutch can be sufficiently protected.

It should be noted that the difference DVRD is given by DVRD = VRL-V
It may be defined as RR. On the other hand, the rear wheel shared torque proportional clutch torque TRT is a set torque for preventing the initial slip of the rear wheels when the transmission torque is expected to increase when the vehicle suddenly starts from a stopped state. It can be obtained by obtaining the proportional torque TRT1 from the rear wheel shared torque TA1 and performing a correction based on the steering angle and a correction based on the vehicle speed.

Therefore, the rear wheel shared torque calculating means 102
, A proportional clutch torque conversion unit 110, a steering angle correction unit 112, and a vehicle speed correction unit 114. The rear wheel shared torque calculating means 102 calculates the engine torque Te at a certain moment, the torque converter torque ratio t at that moment,
Information on the transmission reduction ratio ρm at that time and the center differential torque (center differential clutch torque) Tc obtained from the longitudinal acceleration Gx is sent, and these engine torque Te, torque converter torque ratio t, transmission reduction ratio ρm, The rear wheel shared torque TA1 is calculated from the center differential torque Tc.

At this time, the engine torque Te is determined from the throttle opening data and the engine speed data through an engine torque map (not shown). At this time, the torque converter torque ratio t is determined from the engine speed data Ne and the transmission speed data Nt through a transmission torque ratio map (not shown).

The transmission reduction ratio ρm is determined from the selected shift stage information of the transmission with reference to a shift stage-reduction ratio correspondence map (not shown). The center differential torque Tc is calculated from the following equation based on the longitudinal acceleration Gx. Tc = (Z / Zr) ・ (Rt / ρrd) (Wf-Wa ・ Zs / Z) ・ Gx-h / l ・ Wa ・ Gx ² where Zs is the number of teeth of the sun gear, Zr is the number of teeth of the ring gear, Wf Is the load shared by the front wheels, Wa is the vehicle weight, ρrd is the final reduction ratio, and Z is Zs + Zr.

The rear wheel shared torque TA1 is calculated based on the engine torque Te, the torque converter torque ratio t, the transmission reduction ratio ρm, and the center differential torque Tc set as described above. Next 2
Adopting the larger value among the calculation results TA1 _1, TA1 ₂ according to formula. Arithmetic expression for calculating the TA1 ₁ is a formula:
This is a torque distribution formula assuming a case where the clutch slips. TA1 ₁ = (Te · t · ρ ₁ · ρm−Tc) · ρrd · Z
r / addition (Zr + Zs), arithmetic expression for calculating the TA1 ₂ is the following formula, which is an expression which assumes the case where the clutch does not slip, wheel torque distributed TA1 ₂ After thus obtained is at rest rear wheel sharing Torque. _{TA1 2 = (Wr / W)} · Te · t · ρ 1 · ρm · ρrd By _{TA1 = MAX (TA1 1, TA1} 2), to determine a rear wheel allotted torque TA1.

[0049] Incidentally, as the rear wheel torque distributed TA1, to adopt a resting rear wheel torque distributed TA1 ₂ as described above, the arithmetic expression of TA1 ₁ may TA1 ₁ value becomes negative, thus Rear wheel sharing torque TA1 at rest
₂ is adopted. Further, since the clutch control based on the rear wheel torque distributed TA1 is something that is targeting at the start, to adopt a resting rear wheel torque distributed TA1 ₂ is suitable for this.

The proportional clutch torque converting means 110 is provided with a clutch torque T proportional to the rear wheel shared torque TA1.
RT1 is calculated, and for example, a proportional relationship [inclination m (= TRT1 / TRT) set as shown in Map 1 in FIG.
A1) calculates TRT1 from TA1 using, for example, 0.8]. However, the upper limit of TRT1 is clipped.

The steering angle correction means 112 sets the correction amount KRE from the steering angle according to the map 6 shown by the reference numeral 112A in FIG. Also, the vehicle speed correction means 114
The correction amount KVB2 is set based on the vehicle speed according to Map 2 as indicated by reference numeral 114A in FIG. These corrections are performed, for example, in order to avoid a tight corner braking phenomenon, and to allow a difference between the left and right wheels generated at the time of turning. In other words, in this case, the turning performance (the performance that can prevent the tight corner braking phenomenon) rather than the sudden start performance
Is corrected so that the clutch torque TRT1 decreases.

Further, the initial clutch torque TRI
The initial clutch torque setting means 128 sets the initial clutch torque TRI in accordance with the steering angle TH as shown in Map 7 in the figure. That is, the clutch is always kept in a state immediately before the start of engagement.

Each of the above-described differential corresponding clutch torque TRV, rear wheel shared torque proportional clutch torque TRT, and initial clutch torque TRI is set for each control cycle repeated at an appropriate timing, and the maximum value selection unit is provided. 130. The maximum value selecting section 130 selects the maximum value (this clutch torque is TRD) from the clutch torques TRV, TRT and TRI for each control cycle.

The clutch torque TRD selected in this way is sent to the torque-current conversion section 132, where it is converted into a clutch supply current IRD such that the set clutch torque TRD is obtained. Has become. Here, the clutch supply current IRD is obtained from the clutch torque TRD using a map (see the block 132 in FIG. 3).

As described above, the clutch supply current IR
When D is obtained, the rear differential electromagnetic clutch 2 is switched via the switch 134 and the current feedback means 136.
The third coil 138 is sent for control. The switch 134 is turned off by the signal from the judging means 134A if the ABS control (antilock brake control) is being performed (if it is in the ON state), and is turned on if the ABS control is not being performed. .
In other words, on condition that ABS control is not performed,
A signal of the control current IRD is sent. This is because it is necessary to reliably operate the ABS during the ABS control, and at this time, the torque distribution state of the left and right wheels is controlled because it interferes with the ABS control and is not preferable.

When the switch 134 is off, 0 is output as the control current IRD. Also, A
If there is no BS control device, a brake switch is provided, and based on information from the switch, the switch 134 is turned off during the operation of the brake, and turned on if the brake is not operated. The coil 138 generates a magnetic force in accordance with the control current I sent in this way to adjust the connection state of the rear differential electromagnetic clutch 23.

Since the apparatus of the first embodiment is configured as described above, differential adjustment is performed as follows. First, as shown in FIG. 5, the flow of the entire operation of the control of the rear differential electromagnetic clutch 23 is as follows. First, after each control element is initially set, various data are read (step M1), and the rear wheel is shared. The calculation of the torque proportional clutch torque TRT (Step M2), the calculation of the differential corresponding clutch torque TRV (Step M3), and the calculation of the initial clutch torque TRI (Step M4) are performed, and these clutch torques TRV, TRT, and TRI are calculated.
(Step M5).

Next, the clutch torque TRD is converted into the clutch supply current IRD (step M6). The determining means 134A determines whether the ABS control (antilock brake control) is operating (or whether the brake is operating) (step M7). If the ABS (or brake) is not operating, When the switch 134 is connected, the clutch supply current IRD set in step M6 is set.
However, if the ABS (or the brake) is operating, the routine proceeds to step M8, where the switch 134 is turned off to change the clutch supply current IRD to zero.

In this way, the actuator (coil 138 of the rear differential electromagnetic clutch 23) is driven based on the set clutch supply current IRD. by the way,
The calculation of the rear wheel shared torque proportional clutch torque TRT (step M2) can be performed, for example, according to a subroutine flowchart shown in FIG. That is, the proportional torque TRT1 is obtained from the rear wheel shared torque TA1 (step T1), and the proportional torque TRTR is calculated from the rear wheel shared torque TA1.
T1 is obtained and multiplied by a steering angle correction coefficient KRE and a vehicle speed correction coefficient KVB2 to calculate a rear wheel shared torque proportional clutch torque TRT (step T2).

The calculation of the differential corresponding clutch torque TRV (step M3) can be performed, for example, according to a flowchart of a subroutine shown in FIG. That is, the arithmetic processing unit (actual rotation speed difference detection means) 116 outputs signals VRR and VRL from the wheel speed detection means 104 and 106.
Receiving these signals, and subtracting these signals to obtain a difference DVRD (= V
(RR-VRL) is obtained (step V1).

Next, a rotation difference component setting unit 118 corresponding to the vehicle body.
In accordance with the map 5, the rotation difference component DV corresponding to the vehicle speed VB
HR1 is obtained, and the steering angle correspondence correction unit 120 multiplies and corrects the rotation difference component DVHR1 by the steering angle TH to obtain a rotation difference (correction amount) DVHR (step V2). Then, it is determined whether or not the counter steer is performed (step V3).
DVHR is set to 0 so that the subtraction correction process in 2 is not performed.
(Step V4). If it is not counter-steering, the rotation difference (correction amount) DVHR obtained in step V2 is used as it is.

Further, at step V5, the arithmetic processing unit 12
In step 2, the correction value DVHR is subtracted from the difference DVRD to determine a value DVR of the left and right wheel rotational speed difference as a control parameter.
Then, in step V6, it is determined whether the vehicle speed VB is the reference value V ₀ or less (less than or), if the vehicle speed VB is the reference value V ₀ below, the process proceeds to step V7, the value from the map A DV
The differential corresponding clutch torque TRV is set based on R. If the vehicle speed VB is not less than (less than) the reference value V ₀ , the routine proceeds to step V 8, where the differential corresponding clutch torque TRV is set from the map A based on the value DVR.

Further, the initial clutch torque TRI
(Step M4) can be performed, for example, according to a subroutine flowchart shown in FIG. That is, the initial clutch torque TRI is set from the map 7 according to the steering angle TH. Then, the above-described rear wheel shared torque proportional clutch torque TRT makes it possible to appropriately limit the differential between the left and right wheels at the time of starting or at the time of rapid acceleration from a low speed, etc., thereby transmitting a suitably high torque to the road surface. As a result, tire slippage during starting and sudden acceleration is prevented, driving stability and turning performance can be achieved at the same time, driving performance is improved, and driving system durability is also improved. .

The rear differential mechanism can be applied to a vehicle other than a four-wheel drive vehicle, or can be applied to a front differential. In addition, the above-described differential corresponding clutch torque TR
By setting V, the magnitude of the clutch torque TRD is appropriately set, and while the differential between the left and right wheels is appropriately allowed, the vehicle can behave in accordance with the driver's will during turning.

The correction amounts relating to the steering angle correction and the vehicle speed correction increase as the steering angle increases, and increase with increasing vehicle speed at low vehicle speed.
Since the rear wheel is set to have a gradually increasing tendency with an increase in the vehicle speed, the rear wheels easily slip at a high speed, and the responsiveness of the posture of the vehicle body required at a higher speed is secured. As for the steering angle, the larger the steering angle, the larger the difference in rotation required for the front and rear wheels, and this is appropriately allowed, and there is an advantage that the tight corner braking phenomenon can be avoided.

Then, the clutch torque TR corresponding to the differential
V configuration, the high speeds, since carried out based on the map B, the actual rotational speed difference | a is larger than the reference value DV ₁ region, the actual rotational speed difference | | A-B A-B | When increasing difference The dynamic limiting force decreases, and the actual rotational speed difference | AB
| Is larger than the reference value DV _2, the differential limiting force 0
become.

[0067] Thus, the actual rotational speed difference | A-B | in the area is larger than the reference value DV ₁ may protect the clutch and or releasing weaken the engagement of the clutch. Also, as indicated by the symbol b in the map, the differential limiting force is reduced at an appropriate inclination (inclination θ ₂ ) and is not suddenly set to zero, so that the steering feeling of the vehicle can be kept good. on the other hand,
If decreases, the actual rotational speed difference | | such actual rotational speed difference becomes larger as | A-B A-B | is up decreases to a predetermined value (the value of the small difference) DV ₃ Differential The limiting force is maintained at 0 (refer to the portion of the map with reference numeral c).

Thus, the protection of the clutch is reliably performed until the clutch load becomes sufficiently small. Then, actual rotational speed difference | A-B | When is it further reduced value DV ₃ below since it than, partial reference numerals d that was incubated with increasing (in the map along with the differential limiting force to the decrease ).

As a result, when the load on the clutch when the clutch is engaged is sufficiently reduced to eliminate the need for clutch protection, the clutch can be immediately engaged to effectively utilize the differential limiting control. Further, since the differential limiting force is increased at an appropriate inclination (inclination θ ₂ ), as shown by a portion indicated by reference numeral d in the map, the steering feeling of the vehicle can be kept good.

As described above, during high-speed running in which the clutch is easily exposed to severe conditions, the differential limiting control is always performed while taking into consideration the protection of the clutch. Next, a description will be given of a second embodiment. In this embodiment, some of the characteristics of one map are variably set according to the vehicle speed, instead of using different maps as in the above-described maps A and B depending on the vehicle speed. doing.

That is, in the vehicle differential limiting control device of this embodiment, the clutch torque setting unit (differential limiting force setting means) 126 and the vehicle speed discrimination signal output unit 124 are different from those of the first embodiment. The configuration is the same as that of the first embodiment. The clutch torque setting unit 126 receives the vehicle speed signal and sets the differential corresponding clutch torque TRV based on the actual rotation speed difference | AB | (= DVR) according to a map as shown in FIG. doing.

That is, as shown in FIG. 9, the portion corresponding to the straight line b in the map B of the first embodiment slides (translates) according to the vehicle speed. Here, the reference value DV _1, to reduce the vehicle speed VB is increased, so as to increase the vehicle speed VB is reduced. Therefore, if the vehicle speed is low, the reference value DV ₁
Very large and becomes substantially the same characteristics as the previous map A, as the vehicle speed becomes the constraint, the reference value DV ₁ is decreased, the actual rotational speed difference | A-B | (= DVR ) is a small area in so exceeds the reference value DV _1. Therefore, the differential limiting force is set to be smaller than the actual rotational speed difference | AB |.

This is because even at relatively high speeds, a relatively small actual rotational speed difference | AB | tends to apply a large load to the clutch, which is not desirable in terms of the durability of the clutch. In order to protect the clutch by weakening or releasing the clutch. Other than this,
Since the configuration is the same as that of the embodiment, the description is omitted.

Since the device of the second embodiment is constructed as described above, the differential-compatible clutch torque TRV is
Instead of the settings in steps V6 to V8 in the above, a vehicle speed signal is received, and according to a map as shown in FIG.
The differential corresponding clutch torque TRV is set based on the actual rotation speed difference | AB | (= DVR). Thereby, the first
Almost the same functions and effects as those of the embodiment can be obtained. In particular, there is an advantage that the clutch protection control at the differential corresponding clutch torque TRV is performed in detail according to the vehicle speed.

Next, a third embodiment will be described. In this embodiment, when the vehicle speed is high and the rotation difference between the left and right wheels is large, the differential corresponding clutch torque TRV is set to zero. That is, instead of the condition that the vehicle speed is high and the condition that the vehicle speed is high and the rotation difference between the left and right wheels is large in the first embodiment, a map of clutch torque TRV = 0 is prepared instead of the map B. Can be thought of.

However, the threshold value for determining whether the vehicle speed is high is the same for the protection control start condition and the protection control start condition (for example, V ₁
= V ₁ '= 10 km / h), but the threshold value for determining whether the rotation difference between the left and right wheels is large differs between the protection control start condition and the protection control start condition (for example, V ₂ = 25 km).
/ H, V ₂ ′ = 10 km / h). this is,
This is for the same reason as the characteristic line indicated by the symbol c in the first map B and the map of the second embodiment, and operates the clutch until the clutch load becomes sufficiently small for the clutch that has operated under severe conditions. To ensure the protection of the clutch.

Except for this, the configuration is the same as that of the first embodiment, and the description is omitted. Since the device of the third embodiment is configured as described above, the differential corresponding clutch torque TRV is set, for example, as shown in the flowchart of FIG. That is, the arithmetic processing unit (actual rotation speed difference detection means) 116 receives the signals VRR and VRL from the wheel speed detection means 104 and 106 and subtracts these signals to obtain a difference DVRD (= VRR-VRL). (Step V
1).

Next, a vehicle-body-dependent rotation difference component setting section 118
In accordance with the map 5, the rotation difference component DV corresponding to the vehicle speed VB
HR1 is obtained, and the steering angle correspondence correction unit 120 multiplies and corrects the rotation difference component DVHR1 by the steering angle TH to obtain a rotation difference (correction amount) DVHR (step V2). Then, it is determined whether or not the counter steer is performed (step V3).
DVHR is set to 0 so that the subtraction correction process in 2 is not performed.
(Step V4). If it is not counter-steering, the rotation difference (correction amount) DVHR obtained in step V2 is used as it is.

Further, in step V5, the arithmetic processing unit 12
In step 2, the correction value DVHR is subtracted from the difference DVRD to determine a value DVR of the left and right wheel rotational speed difference as a control parameter.
Then, in step V7, the differential corresponding clutch torque TRV is set based on the value DVR from the map A. In the following step V9, it is determined whether or not the control flag Frg is 1. This control flag Frg becomes 1 when the clutch protection control is being performed.

If the clutch protection control is not performed,
Since the control flag Frg is 0 and not 1, the process proceeds to step V10 to determine a clutch protection control start condition. That is, whether the rotational difference DVR of and left and right wheels by the vehicle speed VB is the threshold value V ₁ above is the threshold value V ₂ or more is determined. Rotational difference DV of and left and right wheels by the vehicle speed VB is the threshold value V ₁ or more
If R is the threshold value V ₂ or more, to start the clutch protection control. That is, the control flag Frg is set to 1 (step V11), and the differential corresponding clutch torque TRV is set to 0 (step V12).

[0081] On the other hand, unless the rotation difference DVR of and left and right wheels by the vehicle speed VB is the threshold value V ₁ above the threshold V ₂ or more, the clutch protection control is not started. When the clutch protection control is started, the control flag Frg is set to 1, so that in the subsequent control cycle, the process proceeds from step V9 to step V13 to determine the clutch protection control end condition. That is, it is determined whether the vehicle speed VB is equal to or less than the threshold value V ₁ ′ and the rotation difference DVR between the left and right wheels is equal to or less than the threshold value V ₂ ′.

If the vehicle speed VB is equal to or less than the threshold value V ₁ ′ and the rotation difference DVR between the left and right wheels is equal to or less than the threshold value V ₂ ′, the clutch protection control ends. That is, the control flag Frg is set to 0 (step V14), and the clutch torque T corresponding to the differential is set.
The RV set in step V5 is adopted. On the other hand, when the vehicle speed VB is equal to or less than the threshold value V ₁ ′ and the rotation difference D
If VR is not less than threshold value V ₂ ′, clutch protection control is continued. That is, the differential corresponding clutch torque TRV is set to 0 while maintaining the control flag Frg at 1 (step V15).

As a result, substantially the same operation and effect as those of the first embodiment can be obtained. In particular, control can be simplified and made more practical. In addition, since the end condition of the clutch protection control is stricter than the start condition, the protection of the clutch is reliably performed until the clutch load becomes sufficiently small.

[0084]

[0085]

As described above in detail , according to the vehicle differential limiting control device of the first aspect of the present invention, the differential limiting mechanism for limiting the differential state between the left and right wheels of the vehicle, and the differential limiting mechanism, Control means for controlling the motion limiting mechanism; and actual rotation speed difference detection means for detecting an actual rotation speed difference between the left and right wheels generated during the turning of the vehicle. Differential limiting force setting means for setting the differential limiting force of the differential limiting mechanism according to the differential limiting force setting means. A medium-to-low speed differential limiting force setting unit that sets the differential limiting force when the vehicle is traveling at high speed; Is increased to the maximum value in proportion to the actual rotational speed difference. The dynamic limiting force is set, and the high-speed differential limiting force setting unit increases in proportion to the increase in the actual rotation speed difference until the actual rotation speed difference reaches the reference value. to set the differential limiting force so as to set the differential limiting force said actual rotational speed difference decreases with an increase in said actual rotational speed difference reaches the reference value as going
It By the sea urchin structure, and improvement of the running performance of the vehicle by performing the control of the differential limited state of the left and right wheels and improve the durability of the apparatus balance may be achieved.

According to a second aspect of the present invention, there is provided a differential limiting control apparatus for a vehicle, the differential limiting mechanism for limiting a differential state between left and right wheels of a vehicle, and a control means for controlling the differential limiting mechanism. An actual rotational speed difference detecting means for detecting an actual rotational speed difference between the left and right wheels generated during the turning of the vehicle, wherein the control means includes: Differential limiting force setting means for setting a differential limiting force is provided, and the differential limiting force setting means is in proportion to the increase in the actual rotation speed difference until the actual rotation speed difference reaches a reference value. to set the differential limiting force as decreases with the increase to take as an increase in said actual rotational speed difference After setting the differential limiting force said actual rotational speed difference reaches the reference value I is urchin configuration, the smaller the value the reference value of the actual rotational speed difference the vehicle speed becomes faster A configuration that can be set variably according to the vehicle speed to improve the durability of the device while controlling the left and right wheel differential limiting state to improve the running performance of the vehicle with a more practical configuration Can be done.

[Brief description of the drawings]

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

FIG. 2 is an overall configuration diagram of a driving torque transmission system including a vehicle differential limiting control device as a first embodiment of the present invention.

FIG. 3 is a block diagram showing an overall configuration of a vehicle differential limiting control device as a first embodiment of the present invention.

FIG. 4 is a flowchart showing a subroutine relating to main control (differential correspondence control) of the vehicle differential limiting control device as the first embodiment of the present invention.

FIG. 5 is a flowchart showing a main routine for control of the vehicle differential limiting control device as the first embodiment of the present invention.

FIG. 6 is a flowchart showing a subroutine relating to another control of the vehicle differential limiting control device as the first embodiment of the present invention.

FIG. 7 is a flowchart showing a subroutine relating to another control of the vehicle differential limiting control device as the first embodiment of the present invention.

FIG. 8 is a diagram showing a map relating to differential correspondence control of the vehicle differential limiting control device as the first embodiment of the present invention.

FIG. 9 is a diagram showing a map relating to differential correspondence control of a vehicle differential limiting control device as a second embodiment of the present invention.

FIG. 10 is a flowchart showing a subroutine relating to differential correspondence control of a vehicle differential limiting control device as a third embodiment of the present invention.

FIG. 11 is a block diagram showing a main configuration of a vehicle differential limiting control device proposed in the process of devising the present invention.

[Explanation of symbols]

Reference Signs List 2 engine 4 torque converter 6 automatic transmission 8 output shaft 10 intermediate gear (transfer idler gear) 12 center differential (center differential) 14 differential gear device for front wheel 15 bevel gear mechanism 15A bevel gear shaft 15a bevel gear 16, 18 front wheel 17L, 17R front wheel Side axle 19 Reduction gear mechanism 19a Output gear 20 Propeller shaft 21 Bevel gear mechanism 22 Rear differential as differential gear for rear wheel 23 Differential limiter 24 Left rear wheel 26 Right rear wheel 25L, 25R Rear wheel axle 27 Front wheel Output shaft 27a Hollow shaft member 28 Differential limiting mechanism 29 Rear wheel output shaft 30, 30a, 30b, 30c Handle angle sensor 32 Steering wheel 34, 34a, 34b Lateral acceleration sensor 36 Forward / backward acceleration sensor 38 Slot Torque sensor 39 Engine key switch 40, 42, 44, 46 Wheel speed sensor 48 Controller 48a Rear differential control unit 50 Antilock brake device 50A Brake switch 102 Rear wheel shared torque calculating means 104, 106 Wheel speed detecting means 108 Vehicle speed detecting means 110 Proportional Clutch torque conversion means 112 Steering angle correction means 114 Vehicle speed correction means 116 Arithmetic processing unit (actual rotation speed difference detection means) 118 Vehicle body corresponding rotation difference component setting unit 120 Steering angle correspondence correction unit 122 Arithmetic processing unit 124 Vehicle speed discrimination signal output unit 126 Clutch torque setting section 128 Initial clutch torque setting section 126A Medium / low speed differential limiting force setting section 126B High speed differential limiting force setting section 130 Maximum value selecting section 132 Torque-current converting section 134 Switch 134A Judging means 136 Current feedback means 138 Coil of rear differential electromagnetic clutch 121 Sun gear 123 Ring gear 125 Planet carrier 127 Planetary pinion (planetary gear) 160 Shift lever position sensor (shift range detecting means) 160A Shift lever of automatic transmission 170 Engine speed sensor 180 Transmission speed Sensor

Claims (2)

(57) [Claims] 1. A differential limiting mechanism for limiting a differential state between left and right wheels of a vehicle, control means for controlling the differential limiting mechanism, and an actual rotational speed difference between the left and right wheels generated during turning of the vehicle. A differential limiting force setting means for setting a differential limiting force of the differential limiting mechanism in accordance with the magnitude of the actual rotational speed difference, the differential limiting force setting means comprising: A differential limiting force setting unit that sets the differential limiting force when the vehicle is traveling at a low speed; and a differential limiting force setting unit that determines when the vehicle is traveling at a high speed. A high-speed differential limiting force setting unit that sets the differential limiting force so that the medium-low speed differential limiting force setting unit increases to a maximum value in proportion to the actual rotation speed difference. And the high-speed differential limiting force setting unit is The differential limiting force is set so as to increase in proportion to the increase in the actual rotation speed difference until the actual rotation speed difference reaches the reference value. characterized in that it is by Uni configured to set the differential limiting force as decreasing with increasing rotational speed difference, vehicle differential limiting control apparatus. 2. A differential limiting mechanism for limiting a differential state between left and right wheels of a vehicle, control means for controlling the differential limiting mechanism, and an actual rotational speed difference between the left and right wheels generated during turning of the vehicle. A differential limiting force setting means for setting a differential limiting force of the differential limiting mechanism in accordance with the magnitude of the actual rotational speed difference, the differential limiting force setting means comprising: The differential limiting force setting means sets the differential limiting force so as to increase in proportion to the increase in the actual rotational speed difference until the actual rotational speed difference reaches a reference value. to set the differential limiting force as decreasing with increasing said actual rotational speed difference Once rotational speed difference reaches the reference value is urchin configuration, the reference value of the actual rotational speed difference is the vehicle speed It is variably set according to the vehicle speed so that the value becomes smaller as the speed increases A differential limiting control device for a vehicle.