JPH0825404B2 - 4 wheel drive transfer structure - Google Patents

Description

The present invention relates to a four-wheel drive vehicle in which front wheels and rear wheels are driven, and in particular, a four-wheel drive vehicle equipped with a center differential that absorbs a rotational speed difference between the front and rear wheels. The present invention relates to a transfer structure of a wheel drive vehicle.

(Prior Art) A four-wheel drive vehicle in which front wheels and rear wheels are driven by torque input from an engine via a transmission may include a so-called center differential.
The center differential has an input element to which the torque from the transmission is input and first and second output elements that divide and output the torque input to the element, and the first and second output elements are provided during cornering. The output element operates differentially to absorb the difference in rotational speed between the front and rear wheels, thereby eliminating a so-called braking phenomenon and enabling smooth cornering. The four-wheel drive vehicle equipped with this center differential includes a so-called full-time four-wheel drive vehicle that always operates the center differential, and a four-wheel drive state in which the center differential is operated or front and rear wheels without operating the center differential. There is known a two-wheel / four-wheel switching type four-wheel drive vehicle capable of switching a two-wheel drive state in which only one of the two is driven.

By the way, in a four-wheel drive state in which the center differential is operated, the center differential excessively allows the rotational speed difference between the front and rear wheels to make cornering unstable, and
When one of the rear wheels slips, the torque is not transmitted to the other wheel, which causes a problem that the slip state cannot be escaped. For such a problem, for example, a viscous coupling as disclosed in Japanese Utility Model Laid-Open No. 60-99333 may be provided as a center differential differential limiting means. In this viscous coupling, a large number of plates that are alternately coupled to these members are arranged between the input and output members, and the periphery of these plates is filled with a viscous fluid. If they are respectively coupled to the first and second output elements (or the input element and one output element), the differential operation of the center differential is restricted by the viscous resistance of the fluid, and the difference in rotational speed between the front and rear wheels is increased. Is suppressed, whereby traveling stability during cornering is improved, and when one wheel slips, torque is transmitted to the other wheel and escape from the slip state becomes possible.

On the other hand, Japanese Patent Laid-Open No. 60-172764 discloses a four-wheel drive vehicle using the above-mentioned viscous coupling as a power transmission means for varying transmission torque. This four-wheel drive vehicle has a structure in which the transmission output shaft is directly connected to the front wheels and the rear wheels are connected to each other via a viscous coupling. Since the viscous coupling does not transmit torque or transmits torque very little, the vehicle travels in a two-wheel drive state in which only the front wheels are driven, and when the rotational speed difference between the front and rear wheels becomes large. In accordance with the difference, the viscous coupling also transmits torque to the rear wheels, so that the state automatically shifts to the four-wheel drive state, and so-called full-auto four-wheel drive becomes possible. Further, according to this four-wheel drive vehicle, the same good fuel efficiency performance as that of the two-wheel drive vehicle can be obtained during normal traveling, and the viscous coupling can be used at the time of cornering or when the front wheels (driving wheels) slip. The torque is also transmitted to the rear wheels through the above, so that stable running performance can be obtained in these cases.

(Problems to be Solved by the Invention) By the way, a four-wheel drive vehicle including the center differential as described above and a viscous coupling as a differential limiting means thereof,
The four-wheel drive vehicle using the viscous coupling and the viscous coupling as a power transmission means for varying the transmission torque to one wheel has the advantages described above. If both driving modes are combined and switching between the two modes is possible, a four-wheel drive vehicle that always achieves traveling performance that meets the road surface condition and the driver's request can be realized. However, in the case of realizing such a four-wheel drive vehicle, there is a problem in how simple and compact the transfer device is configured.

In view of the above-mentioned situation regarding a four-wheel drive vehicle, the present invention enables switching between the two types of drive modes as described above, so that optimum traveling performance that is always adapted to traveling conditions such as road surface conditions can be obtained. In addition to realizing the transfer structure, it has a simple structure.
It is an object of the present invention to realize a wheel-four-wheel switching type four-wheel drive vehicle extremely easily by adding a part of the structure to the transfer structure.

(Means for Solving Problems) A transfer structure 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, a center differential having one input element and two output elements is arranged on the output shaft of the transmission, and is connected to the first output element of the center differential to reach either one of the front wheels or the rear wheels. 1 drive shaft and 2nd
Secondly connected to the output element in a detachable manner to reach the other wheel
And a drive shaft. Further, on the transmission output shaft, a state in which the respective elements of the center differential are separated and the second output element and the second drive shaft are connected, and at least two elements of the respective elements of the center differential are connected. Second
A switching mechanism is provided for switching between the output element and the second drive shaft. And in addition to these configurations,
The first and second parallel to the transmission output shaft
A power transmission shaft that connects the drive shaft via a viscous coupling is provided.

(Operation) According to the above configuration, when the elements of the center differential are separated by the switching mechanism and the second output element and the second drive shaft are connected, the center differential operates and is input to the input element. The torque is divided into the first and second output elements, and is transmitted to one and the other of the front and rear wheels via the first and second drive shafts respectively, and the front and rear wheels are always driven. A full-time four-wheel drive mode is obtained. Then, in this case, the viscous coupling provided between the first and second drive shafts by the power transmission shaft is interposed between the first and second output elements of the center differential, and the viscous coupling is The differential operation of the center differential is limited to prevent excessive difference in rotational speed between the front and rear wheels.

On the other hand, if the switching mechanism connects at least two elements of the center differential and disconnects between the second output element and the second drive shaft, the center differential is locked and the first output element of the center differential is separated from the first output element. Torque is output only to one of the wheels via the first drive shaft. At this time, the first drive shaft has the power transmission shaft, the viscous coupling on the shaft, and the second drive shaft. It will also be connected to the other wheel. Therefore, when there is no difference in rotational speed between the front and rear wheels, the two-wheel drive state in which only one of the wheels is driven is obtained, but if a difference in rotational speed occurs between the front and rear wheels,
According to the difference, the viscous coupling transmits torque to the other wheel and automatically shifts to the four-wheel drive state, so that a so-called full-auto four-wheel drive mode is obtained.

Further, according to the above configuration, such two four-wheel drive modes can be selectively set by one center differential, one viscous coupling, and one switching mechanism. A transfer device for a four-wheel drive vehicle is configured to be simple and compact, and in particular, a conventional two-wheel / four-wheel switching type transfer device in which a center differential and a switching mechanism are arranged on a transmission output shaft is added to a viscous cup. It can be realized very easily only by adding a power transmission shaft having a ring.

(Example) Hereinafter, the Example of this invention is described.

First, the overall configuration of a four-wheel drive vehicle according to this embodiment will be described with reference to FIG. 1. In this four-wheel drive vehicle, a power plant including an engine 1, a transmission 2, and a transfer device 3 at the front of the vehicle body. Is installed. The engine 1 is arranged so that its output shaft 4 extends in the front-rear direction of the vehicle body. In the transmission 2, the input shaft 6 connected to the engine output shaft 4 via the clutch 5 and the output shaft 7 on the same axis as the input shaft 6 are arranged in the vehicle front-rear direction. The output shaft 7 of the transmission 2 extends rearward and is projected into the transfer device 3.

On the other hand, the transfer device 3 has a rear wheel drive shaft 11 and a front wheel drive shaft 12 that output the torque input from the transmission output shaft 7. Of these drive shafts 11, 12, the rear wheel drive shaft 11 is disposed on the same axis as the transmission output shaft 7 and extends rearward, and extends rearward from the propeller shaft 13, the rear differential gear 14, and the rear differential gear 14. The left and right rear wheels 16, 16 are driven via the axles 15, 15, and the front wheel drive shaft 12 is disposed in parallel with the transmission output shaft 7 and extends forward, and extends toward the propeller shaft 17, the front differential 18, and the front differential 18. The left and right front wheels 20, 20 are driven via front axles 19, 19 extending from the left to the right.

Next, referring to FIG. 2, the internal structure of the transfer device 3 will be described. On the transmission output shaft 7 protruding into the device 3, a center differential 30 is provided at the rear end.
However, the drive mode switching mechanisms 40 are arranged in front of them, respectively, and further in front of them, the first gear for driving the front wheels.
51 is rotatably supported. The gear 51 is meshed with a second gear 52 fixed to the rear end of the front wheel drive shaft 12.

On the other hand, in the case of this embodiment, the center differential 30 is composed of a single pinion type planetary gear mechanism, and as shown in FIG. 3, a sun gear 31 and a plurality of pinion gears arranged around the sun gear 31 and meshing with the sun gear 31. 32, 32, a carrier 34 that supports these pinion gears 32, 32 via pinion shafts 33, 33, respectively, and a ring gear 35 that is arranged outside each of the pinion gears 32, 32 and meshes with them. . As shown in FIG. 2, the carrier 34 is connected to the rear end of the transmission output shaft 7 and the ring gear 35 is connected to the rear wheel drive shaft 11.

Further, the switching mechanism 40 has the first, second, and third spline members 41, 42, and 43 arranged in parallel on the transmission output shaft 7, and proudly slidably sleeves these members 41 to 43. With the configuration in which 44 is fitted, the first spline member 41 is coupled to the first gear 51 for driving the front wheels, and
The second spline member 42 is attached to the sun gear 31 of the center differential 30,
Third spline members 43 are respectively coupled to the carrier 34. When the sleeve 44 is slid forward as shown in the drawing, the sun gear that constitutes the center differential 30 is formed.
31, the carrier 34, and the ring gear 35 are separated from each other, and the sun gear 31 of the center differential 30 and the first gear 51 for driving the front wheels are coupled via the first and second spline members 41 and 42, and the sleeve is also provided. When 44 is slid rearward from the position shown in the figure, the sun gear 31 of the center differential 30 and the carrier 34 are coupled via the second and third spline members 42 and 43, and the sun gear 31 and the first gear 51 are connected. And are to be separated.

In addition to the above configuration, the transfer device 3 is provided with a power transmission shaft 60 parallel to the transmission output shaft 7 and rearward on the same axis as the front wheel drive shaft 12. The power transmission shaft 60 includes a power transmission first gear 53 fixed to the rear wheel drive shaft 11 and a power transmission second gear 54 fixed to the rear end of the transmission shaft 60. Rear wheel drive shaft 11
The front end portion of the power transmission shaft 60 is connected to
The front wheel drive shaft 12 is connected to the rear end portion (or the front wheel drive second gear 52) via a viscous coupling 70. Further, the viscous coupling 70 has an outer case 71, an inner case 72, and a large number of plates 73 ... 73 that are arranged between the two cases 71, 72 and are alternately coupled to these cases. … 73 is filled with viscous fluid. The outer case 71 is connected to the front wheel drive shaft 12, and the inner case 72 is connected to the power transmission shaft 60.

 Next, the operation of this embodiment will be described.

First, by sliding the sleeve 44 of the switching mechanism 40 forward as shown in FIG. 2, the sun gear 31 of the center differential 30 and the first gear 51 for driving the front wheels are driven through the first and second spline members 41 and 42. If the sun gear 31, the carrier 34, and the ring gear 35 of the center differential 30 are separated from each other, the center differential 30 operates, and the torque input from the transmission output shaft 7 to the carrier 34 is transmitted to the ring gear 35. It is divided into the sun gear 31. The torque divided on the ring gear 35 side is the rear wheel drive shaft.
11 is transmitted to the rear axles 15 and 15 via the propeller shaft 13 and the rear differential 14 shown in FIG. 1 to drive the left and right rear wheels 16 and 16. Further, the torque divided to the sun gear 31 side is transferred from the sun gear 31 to the first and second spline members 4 of the switching mechanism 40.
1, 42 and the first and second gears 51, 52 for driving the front wheels, which are transmitted to the front wheel drive shaft 12 and are further transmitted to the propeller shaft 17 shown in FIG.
Left and right front wheels 20, via the front differential 18 and front axles 19, 19.
Drive 20

In this way, when the sleeve 44 of the switching mechanism 40 is slid forward, the output torque from the engine 1 or the transmission 2 is divided by the center differential 30, and the left and right rear wheels 16, 16 and the left and right front wheels are divided. 20,20
To the full-time four-wheel drive state. In this case, the power transmission first and second gears 5
A viscous coupling 70 interposed between the power transmission shaft 60 that interlocks with the rear wheel drive shaft 11 via 3,54 and the front wheel drive shaft 12.
Is interposed between the sun gear 31 and the ring gear 35 that is each output element to the rear wheel side and the front wheel side of the center differential 30, and when a rotational speed difference occurs between these gears 35, 31, The inner case 72 and the outer case 71 of the viscous coupling 70 rotate relative to each other, and the differential operation of the center differential 30 is restricted by the resistance of the viscous fluid. As a result, when a rotation speed difference occurs between the front and rear wheels, an increase in the rotation speed difference is suppressed, and during cornering,
The instability of the running state due to excessive allowance of the rotational speed difference between the front and rear wheels is prevented, and when one of the front or rear wheels slips, torque is transmitted to the other wheel. Thus, it becomes possible to escape from the slip state.

On the other hand, the sleeve 44 of the switching mechanism 40 is slid rearward from the position shown in FIG. 2 to couple the sun gear 31 of the center differential 30 and the carrier 34 through the second and third spline members 42 and 43, and If the sun gear 31 and the first gear 51 for driving the front wheels are separated, the center differential 30
Is locked and the whole is integrally rotated, and the transmission of torque from the sun gear 31 of the center differential 30 to the front wheel drive first and second gears 51, 52 or the front wheel drive shaft 12 is blocked. Therefore, the transmission output shaft 7 to the center differential 30
The torque input to the carrier 34 is output as it is from the ring gear 35 without being divided by the center differential 30, and is transmitted only from the rear wheel drive shaft 11 to the rear wheels 16, 16. Therefore, in this case, basically the rear wheels 16,16
Only the two wheels are driven.

In this case, instead of disconnecting the sun gear 31 of the center differential 30 from the front wheel drive shaft 12, the ring gear 35 of the center differential 30 or the rear wheel drive shaft 11 and the front wheel drive shaft 12 are connected to each other for power transmission. 1, second gear 53, 54, power transmission shaft 6
0 and the viscous coupling 70. Therefore, there is a difference in rotational speed between the front and rear wheels,
When the outer case 71 and the inner case 72 of the viscous coupling 70 rotate relative to each other, the viscous coupling 70
Thus, a part of the torque output from the ring gear 35 of the center differential 30 to the rear wheel drive shaft 11 is transmitted to the front wheel drive shaft 12 side. In this way, from the two-wheel drive state in which only the rear wheels 16 and 16 are driven, the front wheels 20 and 20 are also driven in accordance with the rotational speed difference between the front and rear wheels, and the four-wheel drive state automatically shifts. A fully automatic four-wheel drive mode is obtained, fuel-efficient two-wheel drive traveling is performed during normal driving, and four-wheel driving is performed during cornering and when the rear wheels 16 and 16 slip. Driving performance will be improved.

In this embodiment, a single pinion type planetary gear mechanism is used as the center differential 30, and the torque input to the carrier 34 during full-time four-wheel drive is divided into the ring gear 35 and the sun gear 31. Will be divided according to the ratio of the diameters of the ring gear 35 and the sun gear 31, and therefore, in this embodiment, the torque distribution to the front and rear wheels is biased to the rear wheel side. On the other hand, if a double pinion type planetary gear mechanism is used as the center diff and torque is input to the ring gear and it is divided into a carrier and a sun gear, the diameter ratio of the ring gear and the sun gear is 2: By setting to 1, the torque can be evenly distributed to the front and rear wheels.

If the structure of the switching mechanism 40 is improved so that the sleeve 44 can simultaneously connect the first, second and third spline members 41 to 43, the center differential 30 can be locked and the center differential can be locked. The path from the sun gear 31 of 30 to the front wheels 20 and 20 through the first and second output gears 51 and 52 and the front wheel drive shaft 12 is also connected, and the front and rear wheels are both directly connected to the transmission output shaft 7 and driven. A direct-coupled four-wheel drive mode can be obtained. Further, if the first, second, and third spline members 41 to 43 of the switching mechanism 40 are configured so as not to be connected to each other at all, the transmission output shaft 7 and the rear wheels 16, 16 can be arranged.
It becomes possible to completely separate the front wheels 20 and 20 from each other.For example, when the front wheels 20 and 20 are towed, only the rear wheels 16 and 16 rotate freely and the traction resistance is increased. The effect of reduction is obtained. This switching mechanism 40
Is not limited to the mesh clutch type using the spline as described above, but may be configured using a hydraulic clutch or the like.

(Effects of the Invention) As described above, according to the transfer structure of the four-wheel drive vehicle according to the present invention, the full-time four-wheel drive mode having the center differential differential limiting function and the rotational speed difference between the front and rear wheels can be obtained. Accordingly, the full-auto four-wheel drive mode in which the two-wheel drive state automatically shifts to the four-wheel drive state can be selected. Therefore, by appropriately selecting these modes, the driving conditions such as the road surface state are always met. Optimal running performance will be obtained. In particular, according to the present invention, the transfer device capable of selecting two types of modes as described above is basically configured by only one center differential, a switching mechanism, and a viscous coupling, and the conventional center differential is provided. And a switching mechanism are arranged on the transmission output shaft, the transfer device of a two-wheel / four-wheel switching type four-wheel drive vehicle is configured by only adding a part of members such as a viscous coupling. As a transfer structure of this kind, a structure that is simple and compact and has excellent functionality can be easily realized.

[Brief description of drawings]

The drawings show an embodiment of the present invention. FIG. 1 is a skeleton diagram showing an overall configuration of a four-wheel drive vehicle, FIG. 2 is an enlarged skeleton diagram of an essential part thereof, and FIG. 3 is a schematic diagram showing a configuration of a center differential. It is a figure. 2 ... Transmission, 3 ... Transfer device, 7 ... Transmission output shaft, 11 ... First drive shaft (rear wheel drive shaft), 12 ... Second drive shaft (front wheel drive shaft),
30 …… Center differential, 31 …… Second output element (sun gear),
34: input element (carrier), 35: first output element (ring gear), 40: switching mechanism, 60: power transmission shaft, 70 ...
… Viscous coupling.

Claims (1)

[Claims] 1. A center differential having one input element and two output elements and arranged on an output shaft of a transmission for receiving torque from the transmission, and a center differential connected to a first output element of the center differential. A first drive shaft reaching either one of the front wheels or the rear wheels, a second drive shaft connecting to the second output element so as to be connectable / disconnectable to the other front wheel or the rear wheel, and the transmission output described above. Is arranged on the shaft to separate each element of the center differential and connect the second output element and the second drive shaft, or to connect at least two elements of each element of the center differential and A switching mechanism for switching between the output element and the second drive shaft in a shut-off state, and the first and second drive shafts in parallel with the transmission output shaft via a viscous coupling. Transportation structure of a four-wheel drive vehicle, wherein the power transmission shaft for binding is provided.