JPS63112223A - Torque distributing device for four-wheel drive car - Google Patents

Abstract

PURPOSE:To improve running properties, by a method wherein either one of the input and output elements of plural central differential gear having different torque distribution ratios is made common, and a differential limit means is situated between the output elements of either central differential gear. CONSTITUTION:Torque from an engine is inputted to a transfer device 3 through an input gear 60. A sleeve 74 of a switching mechanism 70 is slid, for example, leftward, and after the torque is inputted to a carrier 44 of a first central differential gear 40, torque divided to the sun gear 41 side and the torque divided to the ring gear 45 side are outputted to a differential case 31 of a front wheel differential device 30 and an intermediate shaft 23 through first and third intermediate gears 61 and 63, respectively, and the switching mechanism 70. In this case, the torque inputted to the carrier 44 is properly divided according to a number of teeth ratio between the gears 41 and 45. According to a state available during cornering, a differential motion between the output elements of the central differential gears 40 and 50 is limited or allowed by means of a viscous coupling 90.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a torque distribution device for a four-wheel drive vehicle, particularly for a four-wheel drive vehicle equipped with a plurality of center differentials that allow differential movement between front and rear wheels. The present invention relates to a torque distribution device.

(Prior art) In a four-wheel drive vehicle in which the torque output from the engine via the transmission is divided to drive the front wheels and rear wheels respectively, in order to eliminate the so-called braking phenomenon during cornering, Sometimes equipped with a center differential. This center differential consists of an input element into which torque from the engine or transmission is input, and output elements for front wheels and rear wheels that divide the torque input to the element and transmit it to the front wheels and rear wheels, respectively. By performing differential operation between the output elements, the difference in rotational speed between the front and rear wheels during cornering is absorbed.

By the way, when a four-wheel drive vehicle is equipped with a center differential as described above, when one of the front or rear wheels slips, torque is not transmitted to the other, or when cornering suddenly, the rotational speed difference between the front and rear wheels increases. Excessive tolerance may cause problems such as unstable running conditions. To deal with this, a differential limiting means (for example, a viscous coupling) is provided to limit the differential operation of the center differential, and in the above case, the center differential is locked or brought close to the locked state, and the front and rear Torque is transmitted to both wheels, or the driving condition is stabilized during sharp cornering.

On the other hand, in order to improve the running condition of a four-wheel drive vehicle equipped with a center differential as described above, a plurality of center differentials may be provided as the center differential. As such, for example, according to JP-A-61-62641 and JP-A-61-94822, two or three planetary gear devices each having a different diameter or size of each part are provided as a center differential. , and a configuration in which a switching mechanism is provided for setting any one of these center differentials to a torque transmitting state. According to this, by switching each center differential according to the driving condition of the vehicle, it is possible to suitably change the distribution ratio of torque transmitted to the front wheels and the front wheels, and for example, it is possible to suitably change the distribution ratio of torque transmitted to the front wheels and the front wheels. It is expected that the vehicle will be able to ensure running performance according to one's preferences.

(Problems to be Solved by the Invention) However, even if the structure is provided with a plurality of center differentials as described above and changes the distribution ratio of torque transmitted to the front wheels and rear wheels, the sporty driving or normal driving of the car is difficult. It is still insufficient to obtain a torque distribution ratio that can be well adapted to various driving conditions such as driving, and even if the above-mentioned differential limiting means is added to such a configuration, the above-mentioned The question is how best to arrange them for multiple center differentials.

The present invention addresses the above-mentioned actual situation regarding the torque distribution device of a four-wheel drive vehicle, and by appropriately disposing differential limiting means such as a viscous coupling with respect to a plurality of center differentials, the present invention improves the running of the vehicle. The purpose of the present invention is to obtain a good differential limiting effect that is suitable for driving conditions in order to further improve performance, etc.

(Means for Solving the Problems) A torque distribution device for a four-wheel drive vehicle according to the present invention is characterized in that it is configured as follows to achieve the above object.

That is, an input element to which torque is input from the engine via the transmission, and a front wheel output element and a rear wheel output element that divide the torque from the input element and transmit it to the front wheels and rear wheels, respectively, are provided. In a four-wheel drive vehicle having a center differential, the center differential includes a plurality of center differentials each having a different torque distribution ratio, and the input element and the output element for either the front wheels or the rear wheels of these center differentials are made common. do. Then, when the rotational speed difference between the front and rear wheels is equal to or greater than a predetermined amount between the front wheel output element and the rear wheel output element in any one of the plurality of center differentials, the differential of the center differential is activated. It is characterized by providing differential limiting means for limiting the operation.

(Function) According to the above configuration, when a rotational speed difference occurs between the front wheels and the rear wheels, especially when this rotational speed difference exceeds a predetermined amount, both the front wheel and the rear wheel When the center differential (first center differential) with a differential limiting means interposed between the output elements is in a torque transmitting state, the differential limiting means also has a rotation equal to the difference in rotational speed between the front and rear wheels. Due to the speed difference, the relative rotation between the two output elements, that is, between the front and rear wheels is limited.

On the other hand, a center differential (second center differential) which shares input elements with the first center differential and also shares output elements for either the front wheels or the rear wheels with the first center differential generates torque. In the transmission state, when a rotational speed difference occurs between the front and rear wheels and an equal rotational speed difference occurs between the front and rear wheel output elements of the second center differential, A predetermined rotational speed difference also occurs between the input element in the second center differential and the shared output element. Furthermore, along with this, a difference in rotational speed occurs between the input element and output element of the first sender differential, which are respectively shared with the input element and output element of the second center differential, and the Man,
A predetermined difference in rotational speed will also occur between the front wheel and rear wheel output elements of the first center differential linked to the output element, and the relative rotation between them, that is, between the front and rear wheels will be the same as the above difference. The movement is limited by the action of the motion limiting means.

When the first center differential is in the torque transmitting state, the rotational speed difference between the front and rear wheel output elements of the first center differential and the rotational speed difference occurring in the differential limiting means are as described above. On the other hand, when the second center differential is in the torque transmission state, the rotational speed difference between the front and rear wheel output elements of the second center differential is different from the rotational speed difference between the front and rear wheel output elements of the second center differential. Occurs in restrictive means. Therefore, the first
By selectively putting the second center differential into the torque transmitting state depending on the driving state of the vehicle, it is possible to suitably change the differential limiting effect.

(Example) Examples of the present invention will be described below.

First, the overall configuration of the four-wheel drive vehicle according to this embodiment will be explained with reference to FIG. Equipped with a plant.

The engine 1 is arranged so that its output shaft 4 extends in the width direction of the vehicle body. Further, the transmission 2 is arranged such that an input shaft 6 connected to the engine output shaft 4 via a clutch 5 and an output shaft 1 parallel thereto extend in the vehicle width direction. , output @6.7, gear trains 81 to 8s for 1st to 5th speeds and reverse speed, which are selectively brought into a torque transmission state,
8r is provided, and an output gear 9 is provided at one end of the output shaft 7 for transmitting torque from the transmission 2 to the transfer device 3.

On the other hand, the transfer 5iffi3 divides the torque input from the transmission 2 to drive the left and right front wheels 10.11, and also divides the torque input from the transmission 2 to drive the left and right front wheels 10. The left and right rear wheels 1 are connected via rear wheel drive shafts 14°15 extending left and right.
6.17.

Next, to explain the internal structure of the transfer unit M3 with reference to FIG. 21, 22, an intermediate shaft 23 disposed parallel to the rear of these, and a rear wheel output shaft 24 disposed in the longitudinal direction of the vehicle body and protruding rearward, all of which are rotatably supported.

In this embodiment, the intermediate shaft 23 has a structure in which two shafts are connected. And the left and right front wheel drive shafts 21
．． 22 is connected to the front wheels 10.11 shown in FIG. 1, and a rear wheel output shaft 24 is connected to the propeller shaft 12, respectively.

Around the opposing ends of the left and right front wheel drive shafts 21 and 22, there is a bevel gear type front wheel differential 30 and a planetary gear type first differential. A second center differential 40.50 mm is arranged.

The front wheel differential device 30 includes left and right front wheel drive shafts 21 and 22.
A differential case 31 is rotatably fitted and supported on the top, a binion shaft 32 is installed within the case 31 in a direction perpendicular to the axis of the front wheel drive shaft 21, 22, and a differential case 32 is rotatably supported by the shaft 32. A pair of pinion gears 3
3.34, and a pair of left and right output gears 35.36 meshed with both pinion gears 33.34, and the ends of left and right front wheel drive shafts 21.22 are respectively connected to both output gears 35.36. There is.

On the other hand, the first center differential 40 is composed of a single and nion type planetary gear structure, and as shown in FIG.・42 and these pinion gears 42...42 are connected to the pinion shaft 43 respectively.
. . 43, and a ring gear 45 disposed outside of each pinion gear 42 . Further, the second center differential 50 is constructed with a double binion type planetary gear structure, and as shown in FIG.
A plurality of first pinion gears 52...52 arranged around and meshing with the first pinion gears 52...52, and these pinion gears 52...
- A plurality of second pinion gears 53 meshing with 52, respectively...
53 and 1st. Each second pinion gear 52...52.
53...53 respectively to the binion shafts 54...54
．． 55...55, and a ring gear 57 that is disposed outside the second pinion gears 53...53 and meshes with them.

As shown in FIG. 2, a lock V6o formed around the outer periphery of the ring gear 57 in the second center differential 50 is meshed with the output gear 9 of the transmission d, and the ring gear 45 of the first center differential 40 is engaged with the output gear 9 of the transmission d. and second
The carriers 56 of the center differential 50 each have a first. A second intermediate gear 61° 62 is integrally provided, and these gears 61° 62 are connected to a third intermediate gear rotatably supported on the intermediate shaft 23. They are meshed with fourth intermediate gears 63 and 64, respectively.

On the other hand, on the intermediate shaft 23, the first. 2nd center differential 4
A switching R mechanism 70 of 0.50 is provided. This switching mechanism 70 includes a spline member 71 coupled to the intermediate shaft 23.
The third . The first gear which is integrally provided with the fourth intermediate gears 63 and 64. Second
Splines having the same specifications are formed around the outer peripheries of the spline portions 72 and 73, and the sleeve 74 is slidably fitted over these splines. When the sleeve 74 is slid to the right as shown in the figure, the fourth intermediate gear r64 and the intermediate shaft 23 are connected via the spline member 71 and the second spline part 73, and the sleeve 74 is slid to the right as shown in the figure. If it is slid to the left from the position, the third intermediate gear 63 and the intermediate shaft 23 are connected via the spline member 71 and the first spline portion 72.

A bevel gear type rear wheel first output gear 81 is fixed to the end of the intermediate shaft 23, and the same bevel gear type first output gear 81 is integrally formed with the gear 81 and the rear wheel output shaft 24. The rear wheel second output gear 82 is meshed with the rear wheel.

However, in this transfer device 3, the first
1? A carrier 44 which is an input element of the differential differential 40 and a second
A ring gear 57, which is an input element of the center differential 50, is connected to the ring gear 57 so as to be integrally rotatable, and both center differentials 40
．． Sun gears 41 and 51, which are output elements of 50, are both integrally provided on the boss portion 31a of the differential case 31 in the front wheel differential device 30.

In addition to the above configuration, a viscous coupling 90 is provided on the left front wheel drive shaft 21 at one end of the transfer device @3, which is a differential limiting means for the 1°' second center differential 40.50. . This coupling 90 includes an outer case 91 coupled to a ring gear 45 (first intermediate gear 61) which is the rear wheel output element of the first center differential 40, and a first center differential 40. Sun gear 4 with 2nd sender Teff 40.50
1°51 (boss portion 31a of differential case 31), and a large number of plates 93...9 alternately engaged with both cases 91 and 92.
3, and the surroundings of the plates 93...93 are filled with viscous fluid.

When the rotational speed difference between the two cases 91 and 92 is small, their relative rotation is allowed, but when the rotational speed difference exceeds a predetermined amount, the relative rotation is restricted by the resistance of the viscous fluid.

Next, to explain the operation of this embodiment, the torque output from the engine 1 via the clutch 5 and the transmission 2 is input from the output gear 9 of the transmission 2 to the transfer device 3 via the input gear 60. . The switching mechanism 70 in the transfer device 3
When the sleeve 74 of is slid to the left, torque is input to the carrier 44 of the first center differential 40,
It is divided into a sun gear 41 and a ring gear 45, and
Torque divided to sun gear 41 side is front wheel differential fi1
30 differential case 31, the torque divided to the ring gear 45 side is the first one. The signals are output to the intermediate shaft 23 via the third intermediate gears 61 and 63 and the switching mechanism 70, respectively. Further, when the sleeve 74 in the switching mechanism 70 is slid to the right as shown in the figure, torque is input to the ring gear 57 of the second center differential 50 and is divided between the sun gear 51 and the carrier 56, and Similar to the 1 center differential 40, the torque divided to the sun gear 51 side is distributed to the differential case 31 of the front wheel differential 30, and the torque divided to the carrier 56 side is distributed to the 2nd. The signals are output to the intermediate shaft 23 via the fourth intermediate gears 62 and 64 and the switching mechanism 70, respectively. and,
In either case, the differential case 31 of the front wheel differential @30
The input torque is further divided into left and right, and drives the left and right front wheels 10.11 via the left and right front wheel drive shafts 21.22. Further, the torque output to the intermediate shaft 23 is applied to the rear wheel cylinder 1. Rear wheel output shaft 2 via second output gear 81.82
4, and further the propeller shaft 12 and the differential gear @ 13
and the left and right rear wheels 16.1 via the rear wheel drive shaft 14.15.
Drive 7.

In that case, when the torque is divided by the first center differential 40, the carrier 44 of the center differential 40
The torque input to the sun gear 41 and the ring gear 45 is, for example, 3; 7 depending on the ratio of the number of teeth of both gears 41.45.
Since the torque is transmitted from the sun gear 41 to the front wheels 1o and ii, the torque is transmitted from the ring gear 45 to the rear wheels 16.
The torque transmitted to the 17 side becomes larger, resulting in a so-called torque distribution that is biased toward the rear wheels and is suitable for sporty driving. On the other hand, when the torque is divided by the second center differential 50, if the ratio of the number of teeth between the sun gear 51 and the ring gear 57 is set to 1:2, for example, the ring gear 57
The torque input to the vehicle is divided equally between the sun gear 51 and the carrier 56, so that the torque is equally distributed to the front and rear wheels, which is suitable for normal driving.

In any case, during relatively gentle cornering, the viscous coupling 90 is connected between the sun gear 41 and the ring gear 45, which are the two output elements of the first center differential 40, or between the two output elements of the second center differential 50. Sun gear 51 and carrier 5, which are two output elements.
6 allows relative rotation and partial differential operation,
The difference in rotational speed caused by cornering between the front wheels 10.11 and rear wheels 16.17, which are respectively linked to these output elements, is absorbed, and the braking phenomenon is eliminated.

However, when the rotational speed difference between the front and rear wheels exceeds a predetermined amount, such as during sharp cornering or when either the front wheel 10°11 or the rear wheel 16.17 slips, The viscous coupling 90 limits the differential operation between the two output elements in the first center differential or the second center differential 50, but in that case, which one of the two center differentials 40. The differential limiting effect of the viscous coupling 90 differs depending on whether the transmission state is established. A concrete explanation of such an operation is as follows.

That is, the number of teeth ZS and the number of rotations (per unit time) Ns of the sun gear 41 in the first center differential 40 and the carrier 44
The meshing formula of the first center differential 40 is determined from the rotational speed NO, the number of teeth zr of the ring gear 45, and the rotational speed Nr as follows.

(Zr +Zs)-Nc-Zr-Nr +Zs-N
s Also, from the number of teeth Zs' and rotational speed Ns' of the sun gear 51 in the second center differential 50, the rotational speed Ncl of the carrier 56, and the number of teeth Zr' and the rotational speed Nr' of the ring gear 57, this second The meshing formula of the center differential 50 is determined as follows.

(Zr'-Zs')-Nc'-Zr-Nr-Zs'-
Ns' and the first. Focusing on the fact that both sun gears 41.51 of the second center differential 40.50 rotate integrally, both NS and Ns' are replaced with N1, and the carrier 44 of the first sender differential 40 and the second center differential 50
By paying attention to the fact that the ring gear 57 and the ring gear 57 rotate together and replacing both NO and Nr' with N2, the following simultaneous equations can be obtained.

Furthermore, by eliminating N2 from the above simultaneous equations, the following equation is obtained.

zr-zr'-(Nr-Nt) = (Zr+Zs)・(Zr'-Zs)・(Nc
'-N1) Then, set Zs / Zr to 1, and 7s'
If /zr' is 2 inputs, the above equation becomes Nr - N1 = (1 + 1 input) (1 - 2 people) (NO - N1) Beni).

Here, the torque distribution to the ring gear 45 side, that is, the rear wheel side in the first center differential 40 is xxi.

When it is assumed to be 0%, the relationship of X = Zr / (Zs + Zr) is established, so that x = 1/ (Input 1 + 1), and therefore the following formula (%) is obtained. In this case, X is 0, 5
It is set within the range <x <1, and is set to, for example, 0.7.

Furthermore, if the torque distribution ratio between the sun gear 51 side (front wheel side) and the carrier 56 side (rear wheel side) in the second center differential 50 is set to 50:50, and the torque is to be distributed equally between the front and rear wheels, then Zs'/Zr' = 1/2, so input 2 becomes input 2-1/2.

Then, input 1 and input 2 obtained in this way are ``the above (
I) By substituting into the formula, the following formula 2X・(Nr −N+
)=Nc'-N1・" (II) is obtained. In other words, the difference between the rotation speed Nr of the ring gear 45 and the rotation speed N1 of the sun gear 41 in the first sender gear 40 is 2×
The value obtained by multiplying by is equal to the difference between the rotation speed Nc' of the carrier 56 in the second center differential 50 and the rotation speed N1 of the sun gear 51.

Therefore, when the first center differential 40 is in the torque transmitting state, the rotational speed difference between the sun gear 41 and the ring wheel 45 of the differential 40 (the rotational speed difference between the front and rear wheels) is Case 91 and inner case 92
2nd center differential 5
0 is in the torque transmission state, the value obtained by multiplying the rotation speed difference between the carrier 56 of the differential 50 and the sun gear 51 (the rotation speed difference between the front and rear wheels) by 1/2x is the value obtained by multiplying the rotation speed difference between the carrier 56 of the differential 50 and the sun gear 51 by 1/2
This is equal to the difference in rotational speed between the outer case 91 and the inner case 92 of the motor.

Since the transmission torque of the viscous coupling 90 has the characteristics shown by the symbol (A) in FIG. The torque T corresponding to An becomes the transmission torque for the first center differential 40, and the torque T corresponding to the rotational speed difference An' (that is, Jn/2x) smaller than the above 4n
' is the transmission torque for the second center differential 50.

Furthermore, the transmission torque T regarding the first sender tension 40 is
is transmitted from the front wheel side to the rear wheel side or from the rear wheel side to the front wheel side with the same size via the viscous coupling 90. In other words, if the front wheels slip, for example, the transmission torque T is transmitted directly from the front wheels to the rear wheels. On the other hand, the transmission torque T' for the second center differential 50 is transmitted from the viscous coupling 90 through the second center differential 50 from the front wheel side to the rear wheel side or from the rear wheel side to the front wheel side. It is assumed to be T'/2X.

In other words, the transmission torque T' is further reduced and then transmitted to the front and rear wheels.

As described above, for the same rotational speed difference that occurs between the front wheels, when the first center differential 40 is in the torque transmission state, a relatively large torque is transmitted via the viscous coupling 90. , when the second center differential 50 is in the torque transmitting state, a relatively small torque is transmitted via the coupling 90. Therefore, when the coupling 90 restricts the differential operation of the first center differential 40, it acts to bring the differential 40 closer to the locked state, and the coupling 90 restricts the differential operation of the first center differential 50.
When the differential operation of the differential gear 50 is restricted, the differential operation of the differential gear 50 is kept away from the locked state. As a result, when performing sporty driving where the wheels are likely to spin due to frequent sudden starts or sudden accelerations, the first center differential 40 can be selected to limit the differential of the viscous coupling 90. This increases the force and reliably prevents the above-mentioned slipping, and when driving normally, by selecting the second center differential 50, the above-mentioned differential restriction becomes smaller and braking phenomena etc. are effectively eliminated. That will happen.

FIG. 6 shows a second embodiment of the present invention, and like the previous embodiment, this embodiment also has a case 2 of a transfer device 3'.
0' includes left and right front wheel drive shafts 21', 22' to which the differential case 31' of the front wheel differential 30' is fitted, an intermediate shaft 23' parallel to these, and a rear wheel connected to the propeller shaft. An output shaft 24' is rotatably supported. On the left front wheel drive shaft 21', a first gear is constructed of a single binion type planetary gear mechanism, including a sun gear 41', pinion gears 42'...42', a carrier 44', and a ring gear 45'. The center differential 40', the sun gear 51' and the first. Second pinion gear 53' (5
2') and a second sender gear 50' having a carrier 56' and a ring gear 57' and constituted by a double binion type planetary gear structure are respectively disposed. Further, on the intermediate shaft 23', a first. 2nd center differential 4
A switching mechanism 70' is provided that selectively puts 0' and 50' into a torque transmitting state.

Furthermore, also in this embodiment, the carrier 44' of the first center differential 40' and the ring gear 57' of the second center differential 50 are
The input gear 60' formed around the outer periphery of the ring gear 57' connects to the output gear 9' of the transmission.
Both center differentials 40' and 50
The sun gears 41' and 51' are both integrally provided on the boss portion 318' of the differential case 31'. Further, the ring gear 45' of the first center differential 40' and the carrier 56' of the second center differential 50' each have a first
Second intermediate gears 61', 62' are coupled to each other, and these gears 61', 62' are connected to a third intermediate gear rotatably supported on intermediate shaft 23'. They are meshed with fourth intermediate gears 63' and 64', respectively.

However, in this embodiment as well, the first. 2nd center differential 4
A viscous coupling 90' is provided as a differential limiting means for 0' and 50';
The outer case 91' is connected to the carrier 56' of the second center differential 50, and the inner case 92' is connected to the sun gears 41' and 51' of both center differentials 40' and 50'.

Therefore, the viscous coupling 90 in this example
' is the first center differential 40' or the second center differential 50'
In order to limit the differential operation of , the following limiting action is performed.

That is, when the second center differential 50' is set to the 1-herc transmission state by the selection operation of the switching mechanism 70', the rotational speed difference between the sun gear 51' and the carrier 56' of the differential 50' is determined by the viscous coupling 90'. Outer case 91'
is equal to the rotational speed difference between Differential 40' ring gear 45' and sun gear 41
' The value obtained by multiplying the rotational speed difference between the outer case 91' and the inner case 92 of the viscous coupling 90' by 2x is
It is equal to the difference in rotational speed from ′.

If a rotational speed difference of anl occurs between the front and rear wheels, the torque T1 corresponding to An+ shown in FIG.
0', and the above A
Rotational speed difference 1in1' (that is, Jt'
When the torque T1' corresponding to M'X2X) selects the first center differential 40', the viscous coupling 9
This is the transmission torque transmitted through 0'. Furthermore, while the transmission torque T1 for the second center differential 50' is transmitted unchanged from the front wheel side to the rear wheel side or from the rear wheel side to the front wheel side, the transmission torque T1 for the first center differential 40' is Torque T1' is set to 2x T' and is transmitted from the front wheel side to the rear wheel side, etc.

As a result, when the vehicle drives in a sporty manner, by selecting the first center differential 40', the differential suppression force of the viscous coupling 90' increases,
Also, when driving normally, the second center differential 5
By selecting 0', the differential limiting force of the coupling 90' becomes small, and a differential limiting effect suitable for sports driving and normal driving can be obtained.

(Effects of the Invention) As described above, according to the present invention, the differential limiting means for limiting the differential wJ operation of the center differentials is applied to a plurality of center differentials in which the torque distribution between the front and rear wheels is respectively set according to the driving condition. Since the differentials are properly distributed, each center differential can share the operation limiting means, and differential limiting effects suitable for driving conditions such as sports driving and normal driving can be obtained, thereby ensuring good driving performance. .

[Brief explanation of the drawing]

1 to 5 show a first embodiment of the present invention, and FIG. 1 is a schematic diagram showing the overall configuration of a four-wheel drive vehicle according to the embodiment;
FIG. 2 is a vertical cross-sectional view of the main part, and FIGS. A schematic diagram showing the configuration of the second center differential,
FIG. 5 is a graph showing the effects of this embodiment. Further, Fig. 6.7 shows a second embodiment of the present invention, and Fig. 6.7 shows a second embodiment of the present invention.
The figure is a vertical sectional view showing the main parts during four-wheel drive in this embodiment, and FIG. 7 is a graph showing the effects of this embodiment. 1...engine, 2...transmission, 40
．． 40'...1st center differential, 50.50'
...Second center differential, 90.90'...Differential limiting means (viscous coupling). Figure 3 Figure 4 Figure 5 Figure 7 Rotational aberration

Claims (1)

[Claims] (1) A center differential that has an input element into which torque is input from the engine via the transmission, and a front wheel output element and a rear wheel output element that divide the torque from the input element and transmit it to the front wheels and rear wheels, respectively. The four-wheel drive vehicle is equipped with a plurality of center differentials having different distribution ratios of torque output to the front wheels and torque output to the rear wheels, and input elements of these center differentials and input elements for the front wheels. Alternatively, one of the output elements for the rear wheels is made common, and the rotational speed difference between the front wheels and the rear wheels is adjusted between the output element for the front wheels and the output element for the rear wheels in one of the center differentials. A torque distribution device for a four-wheel drive vehicle, characterized in that a differential limiting means is provided for limiting the differential operation of the center differential when the torque is greater than a fixed amount.