JPH0811497B2 - Vehicle four-wheel drive - Google Patents

Description

TECHNICAL FIELD The present invention relates to a four-wheel drive system for a vehicle.

(Prior Art) In a four-wheel drive vehicle, the drive mode is always
In addition to the constant four-wheel drive system in which both the front and rear wheels are driven, normally two-wheel drive is used, and only when necessary (for example, when the front wheels slip as in a sudden start in the front-wheel drive state).
There is a selective four-wheel drive system in which wheels are driven. In the case of this selective four-wheel drive system, when there is a speed difference between the front wheel side and the rear wheel side, it is sufficient to switch from two-wheel drive to four-wheel drive.
For automatically switching between four-wheel drive and four-wheel drive, for example, as disclosed in JP-A-60-172464, a center differential mechanism for distributing torque to front and rear wheels and a front or rear wheel. It is known that one of the wheels is provided with a known viscous coupling that utilizes the viscous resistance of fluid to transmit torque when a speed difference occurs between its input shaft and output shaft. Has been. That is, in this case, the viscous coupling functions as a clutch mechanism for selectively driving the front wheels in a four-wheel drive vehicle having a rear wheel drive base, for example.

On the other hand, in a four-wheel drive vehicle having a center differential mechanism, for example, when any one of the four wheels falls into the muddy state, all the power from the engine flows to the wheel side where the load is reduced. Since traveling becomes difficult, it is necessary to lock the operation of the center differential mechanism in such a case. Various structures have been proposed as the locking mechanism for the center differential mechanism. One of them is disclosed in, for example, Japanese Patent Laid-Open No. 60-236839. Since there is a speed difference between the two output members of the differential mechanism, the viscous coupling having the above-described structure is connected between the two output members to transmit the torque of the viscous coupling. There is a method of locking the sender differential mechanism by utilizing the action. That is, in this case, the viscous coupling functions as a brake mechanism.

In this way, by allowing the viscous coupling to function as a brake or a clutch, four-wheel running with different characteristics is possible.

However, when attempting to realize these two mechanisms in one four-wheel drive vehicle, a generally conceivable method is to incorporate a viscous coupling functioning as a brake and a viscous coupling functioning as a clutch into a transfer device. However, in such a case, the viscous coupling itself is relatively expensive, resulting in an increase in cost and an increase in the size of the apparatus, which is not preferable.

(Object of the Invention) The present invention is intended to solve the problems pointed out in the above-mentioned prior art, and is a four-wheeled vehicle configuration in which four viscous couplings of different patterns can be obtained by using one viscous coupling. The purpose of the present invention is to provide a wheel drive device.

(Means for Achieving the Object) As a means for achieving the above object, the present invention is designed to transmit a driving force transmitted through a main transmission to a front wheel and a rear wheel of a vehicle through a transfer device. In the four-wheel drive system for a vehicle, an input member connected to the output member of the main transmission, a first output member connected to the front wheel drive shaft, and a second output member connected to the rear wheel drive shaft. And a center differential mechanism in which a switching mechanism is installed in parallel, and a viscous coupling that transmits power using viscous resistance of fluid when a speed difference occurs between the two shafts. The connection state of the viscous coupling is a parallel connection state in which it is connected between the first output member and the second output member of the center differential mechanism, the center differential mechanism, the front wheel drive shaft, and the rear wheel drive shaft. Noi It is configured so that it can be selectively set to a serial connection state in which it is connected to either one of them.

(Operation) According to the present invention, by the above means, (1) when the viscous coupling is connected in parallel between the first output member and the second output member of the center differential mechanism, The coupling functions as a braking mechanism that locks the center differential mechanism by transmitting torque when there is a speed difference between the front and rear wheels, and limits the differential between the front and rear wheels for four-wheel drive. Maintain (realization of four-wheel drive running with the differential limiting function of the center differential mechanism), (2) Viscous coupling is in series between the center differential mechanism and one of the front wheel drive shaft and the rear wheel drive shaft. When the viscous coupling is connected by means of the above, when there is a speed difference between the second output member and the second output member, that is, there is a speed difference between the front wheels and the rear wheels of the vehicle. Only if It functions as a clutch mechanism that transmits power, and when there is no speed difference between the front and rear wheels, two-wheel drive with only the front wheels or the rear wheels is used, and there is a speed difference between the front and rear wheels. In this case, four-wheel drive with all front and rear wheels is realized (4 with automatic 2-4 switching function).
Realization of wheel drive traveling), etc. are obtained.

(Examples) Hereinafter, some preferred examples of the present invention will be described with reference to FIGS. 1 to 6.

(First Embodiment) FIG. 1 shows a four-wheel drive system for a four-wheel drive vehicle based on a rear-wheel drive of an engine transversely mounted according to a first embodiment of the present invention. This four-wheel drive system includes a multistage gear type main transmission 1 connected to an engine output shaft 14 via a clutch 8 and torque output from an output shaft 11 of the main transmission 1 on the front wheel side and the rear wheel side. And a transfer device 2 for distributing the same.

The transfer device 2 includes a ring gear 31 that meshes with an output gear 12 provided on the output shaft 11 of the main transmission 1 (corresponding to an input member in the claims), and a front wheel drive shaft 4.
A sun gear 32 fixed to a first rotating shaft 21 that is fitted to the outside of the shaft so as to be relatively rotatable, the ring gear 31 and the sun gear 32.
A planetary type center differential mechanism 3 including a plurality of pinion gears 33 which are located between
have.

On the first rotary shaft 21 to which the sun gear 32 is attached,
A first transmission gear 41 is provided, and the first transmission gear 41 is further provided.
A second transmission gear 42 which is connected to the rear wheel drive shaft 5 is meshed therewith (that is, in this embodiment, the first rotary shaft 21 is the second output member in the claims). Applicable). A sixth hub Z, which is a component of a switching mechanism 9 described later, is provided at one end of the first rotary shaft 21.

On the other hand, the carrier 34 that connects the pinion gears 33 of the center differential mechanism 3 to the second rotary shaft 22 that is fitted to the outside of the first rotary shaft 21 and the front wheel drive shaft 4 so as to be relatively rotatable. It is connected. Further, inside the second rotary shaft 22, a third rotary shaft 23 connected to an input gear 61 of the front wheel differential gear 6 is relatively rotatably fitted. The second rotating shaft 22 and the third rotating shaft 23 are provided with a second hub B and a first hub A provided at their respective shaft ends, and a switching mechanism 9 described later.
Is integrally connected to the front wheel drive shaft 4 through the front wheel differential 6 by being coupled by the sleeve 16 (i.e., the carrier 34 in this embodiment is the first in the claims). 1 corresponds to the output member).

Further, a fifth hub Y is provided at an axially intermediate portion of the second rotating shaft 22. Further, at an intermediate position between the fifth hub Y and the second hub B of the second rotary shaft 22,
A viscous cup provided with outer plates 72, 72, ... And inner plates 73, 73 .., acting to transmit torque by viscous fluid such as viscous fluid (for example, silicone oil) when the two rotate relative to each other. The inner plates 73, 73 ... Of the ring 7 are attached. on the other hand,
The casing 71 to which the outer plate 72 of the viscous coupling 7 is attached is connected to the fourth rotating shaft 24 which is fitted to the outside of the second rotating shaft 22 so as to be relatively rotatable. A third hub C and a fourth hub X are provided at both ends of the fourth rotating shaft 24, respectively.

The switching mechanism 9 includes a first hub group 51 composed of three hubs, the first hub A, the second hub B, and the third hub C, which are coaxially arranged on one side of the viscous coupling 7. The sleeve 16 and the viscous coupling 7
The fourth hub X arranged coaxially on the other side of the
A second hub group 52 composed of three hubs, a fifth hub Y and a sixth hub Z, is appropriately selected and coupled by a second sleeve 17, and the viscous coupling 7 and the center differential It acts so as to change the connection state with the mechanism 3, and the connection form thereof is set as follows.

Connection form a: The first hub A and the second hub B in the sleeve 16,
The second sleeve 17 connects the fourth hub X and the fifth hub Y, respectively.

Coupling b: Sleeve 16 with first hub A and second hub B
However, the second hub 17 connects the fourth hub X and the sixth hub Z, respectively.

Coupling c: Sleeve 16 with first hub A and second hub B
However, the second sleeve 17 couples the fourth hub X, the fifth hub Y, and the sixth hub Z, respectively.

Connection form d: Sleeve 16 with first hub A and third hub C
However, the fifth sleeve Y and the sixth hub Z are coupled by the second sleeve 17, respectively.

Coupling form e: Sleeve 16 with second hub B and third hub C
However, the fifth sleeve Y and the sixth hub Z are coupled by the second sleeve 17, respectively.

Coupling mode f: The fourth hub X, the fifth hub Y, and the sixth hub Z are coupled by the second sleeve 17.

Connection form g: Second hub B and third hub C with sleeve 16
However, the second hub 17 connects the fourth hub X, the fifth hub Y, and the sixth hub Z, respectively.

The functions of the transfer device 2 in each of the coupling configurations are shown in FIG. The function of the transfer device 2 in each of the coupling modes will be individually described with reference to FIG.

(Coupling form a) In this state, the second rotating shaft 22 and the third rotating shaft 22
23 and the fourth rotating shaft 24 are integrally connected. Therefore, the torque transmitted from the output shaft 11 side of the main transmission 1 to the center differential mechanism 3 side is equal to the second rotary shaft 22 and the third rotary shaft.
50% is distributed to the front wheel drive shaft 4 side via 23 and to the rear wheel drive shaft 5 side via the first rotary shaft 21 (this distribution ratio is set by the distribution value of the center differential mechanism 3). ) It is in a four-wheel drive state.

At this time, since there is no speed difference between the second rotary shaft 22 and the fourth rotary shaft 24, the viscous coupling 7
Is deactivated, and the center differential mechanism 3 is in a free state in which its pinion gear 33 can rotate and revolve. That is, a center differential free four-wheel drive state is realized.

(Coupling mode b) In this state, the second rotary shaft 22 and the third rotary shaft 22
23 with the sleeve 16 and also with the first rotary shaft 21 and the fourth
The rotary shafts 24 and 24 are connected by a second sleeve 17, respectively. Therefore, the torque transmitted from the output shaft 11 side of the main transmission 1 to the center differential mechanism 3 side is equal to the second rotary shaft 22.
And 50% are distributed and transmitted to the front wheel drive shaft 4 side via the third rotary shaft 23 and to the rear wheel drive shaft 5 side via the first rotary shaft 21, respectively, and the four-wheel drive state is achieved. .

At this time, the viscous coupling 7 is arranged and connected between the first rotary shaft 21 and the second rotary shaft 22 in parallel connection. Further, the center differential mechanism 3 is in a free state. Therefore, the viscous coupling 7 is fastened when a speed difference occurs between the second rotary shaft 22 and the fourth rotary shaft 24, that is, between the front wheel drive shaft 4 and the rear wheel drive shaft 5, and torque is generated. Transmission is performed to increase the torque on the low speed side and at the same time decrease the torque on the high speed side. That is, the differential limiting action of the center differential mechanism 3 is performed, and the viscous coupling 7 functions as a brake mechanism. As a result, four-wheel drive traveling with a differential limiting function is realized, and even if the front wheels fall into the muddy state, it is possible to easily get out of the muddy state due to the torque on the rear wheel side.

(Coupling form c) In this state, the first rotary shaft 21 and the second rotary shaft 21
The second rotary shaft 23, the third rotary shaft 23, and the fourth rotary shaft 24 are integrally connected. Therefore, the center differential mechanism 3 has a pinion gear.
The rotation of 33 is restricted and it becomes locked. Further, the viscous coupling 7 is deactivated. Therefore, the front wheel drive shaft 4 and the rear wheel drive shaft 5 are directly connected to the output shaft 11 side of the main transmission 1, and the direct connection four-wheel drive traveling is realized.

(Coupling form d) In this state, the third rotating shaft 23 and the fourth rotating shaft 24 are connected, and the first rotating shaft 21 and the second rotating shaft 22 are connected. The viscous coupling 7 is arranged and connected in series between the second rotary shaft 22 and the third rotary shaft 23 (that is, the front wheel drive shaft 4). Further, the center differential mechanism 3 is in a locked state. Therefore, in the state where there is no speed difference between the front wheel drive shaft 4 and the rear wheel drive shaft 5, the total amount of torque from the main transmission 1 side is the rear wheel drive shaft 5.
Is transmitted to the side, and two-wheel drive traveling of the rear wheel drive base is realized. On the other hand, when there is a speed difference between the front wheel drive shaft 4 and the rear wheel drive shaft 5 such as when the vehicle suddenly starts, the viscous coupling 7 is fastened and a part of the torque from the main transmission 1 side is removed. It is also transmitted to the front wheel drive shaft 4 side, and four-wheel drive traveling is realized. That is, in this case, the viscous coupling 7 is
It acts as a clutch mechanism that disconnects / contacts the torque transmission to the front wheel drive shaft 4 side, and four-wheel drive traveling with automatic 2-4 switching action is realized.

(Coupling form e) In this state, the first rotary shaft 21, the second rotary shaft 22, and the fourth rotary shaft 24 are integrally coupled, so that the viscous coupling 7 is deactivated. The center differential mechanism 3 is locked. Therefore, the front wheel drive shaft 4 is in a free state, and the entire torque input from the main transmission 1 side to the center differential mechanism 3 side is transmitted to the rear wheel drive shaft 5 side, and the rear wheel drive base is driven by two wheels. Is realized.

(Coupling Form f and Coupling Form g) In both cases, although the coupling forms of the hub are different, the same operation as that of the coupling form e can be obtained, and the description thereof will be omitted.

In addition to the above-mentioned examples, various combinations of the hubs can be made.

(Second Embodiment) FIG. 3 shows a four-wheel drive system for a four-wheel drive vehicle with an engine laterally mounted front wheel drive base according to a second embodiment of the present invention.

The transfer device 2 of this embodiment is a modification of the first embodiment, and is the sun gear 32 of the center differential mechanism 3.
Is connected not to the first rotary shaft 21 but to the second rotary shaft 22 side (that is, in this case, the second rotary shaft 22 corresponds to the second output member in the claims). , Pinion gear
33 is connected to the side of the third rotary shaft 23 instead of the second rotary shaft 22 via the carrier 34 (corresponding to the first output member in the claims), This is the same as the case of the embodiment.

Further, the coupling mode of the two hub groups 51, 52 of the switching mechanism 9 is as follows.

Coupling form a: The second hub B and the third hub C are coupled by the sleeve 16, and the fifth hub Y and the sixth hub Z are coupled by the second sleeve 17, respectively.

Connection form b: sleeve 16 with first hub A and third hub C
However, the fifth sleeve Y and the sixth hub Z are coupled by the second sleeve 17, respectively.

Coupling c: Sleeve 16 with first hub A and second hub B
However, the second hub 17 connects the fourth hub X, the fifth hub Y, and the sixth hub Z, respectively.

Connection form d: Sleeve 16 with first hub A and second hub B
However, the second hub 17 connects the fourth hub X and the sixth hub Z, respectively.

Connection form e: The first hub A, the second hub B, and the third hub C are connected by the sleeve 16.

Next, the transfer device 2 at the time of each of the coupling forms
The function of will be described with reference to FIG.

(Coupling form a) In this state, the first rotating shaft 21, the second rotating shaft 22, and the fourth rotating shaft 24 are integrally connected. Therefore, the viscous coupling 7 is deactivated, the center differential mechanism 3 is in a free state, and the torque transmitted from the main transmission 1 side is equal to the front wheel drive shaft 4 side at a ratio based on the distribution value of the center differential mechanism 3. Distribution is transmitted to the rear wheel drive shaft 5 side, and center differential free four-wheel drive traveling is realized.

(Coupling mode b) In this state, the fourth rotary shaft 24 and the third rotary shaft 23 are
The first rotary shaft 21 and the second rotary shaft 22 are connected to each other, and the center differential mechanism 3 is in a free state. At this time, the viscous coupling 7 is the carrier.
It is arranged and connected in parallel connection between 34 and the second rotary shaft 22. Therefore, the viscous coupling 7 functions as a brake mechanism that limits the differential of the center differential mechanism 3.
When there is a speed difference between the front wheel drive shaft 4 and the rear wheel drive shaft 5, the torque on the high speed side is reduced and the torque on the low speed side is increased. That is, in this case, four-wheel drive traveling having a differential limiting action is realized.

(Coupling form d) In this state, the second rotary shaft 22 and the third rotary shaft 23,
The first rotary shaft 21 and the fourth rotary shaft 24 are coupled to each other. Further, the viscous coupling 7 is arranged and connected between the carrier 34 and the first rotary shaft 21 in a serial connection state. Further, the center differential mechanism 3 is in a locked state. Therefore, in the state where there is no speed difference between the front wheel drive shaft 4 and the rear wheel drive shaft 5, the entire amount of torque from the main transmission 1 side is transmitted to the front wheel drive shaft 4 side, and the torque of the front wheel base 2 is
Wheel drive is realized. On the other hand, when there is a speed difference between the front wheel drive shaft 4 and the rear wheel drive shaft 5 as during a sudden start,
The viscous coupling 7 is fastened, and a part of the torque is transmitted from the main transmission 1 side to the rear wheel drive shaft 5 side.
Four-wheel drive traveling with four-switching action is realized.

(Coupling form e) In this state, since the second rotating shaft 22, the third rotating shaft 23, and the fourth rotating shaft 24 are integrally connected, the viscous coupling 7 is deactivated. The center differential mechanism 3 is locked. Therefore, the front wheel drive shaft 4 is in a free state, and the entire torque input from the main transmission 1 side to the sender differential mechanism 3 side is transmitted to the front wheel drive shaft 4 side, and two-wheel drive traveling based on the front wheel is realized. .

(Third Embodiment) FIG. 5 shows a four-wheel drive system for a four-wheel drive vehicle with an engine vertically mounted rear wheel drive base according to an embodiment of the present invention.

The output shaft 11 of the main transmission 1 is connected to a pinion gear 33 of the sender differential mechanism 3 via a carrier 34. The ring gear 31 of the center differential mechanism 3 is directly connected to the rear wheel drive shaft 5 via the first rotating shaft 27. Center differential mechanism 3
The sun gear 32 is connected to the second rotating shaft 28. The viscous coupling 7 is provided between the second rotary shaft 28 and the third rotary shaft 29 fitted to the outside of the second rotary shaft 28 so as to be relatively rotatable. Further, a first transmission gear 41 is attached to the fourth rotating shaft 30 which is fitted to the outside of the output shaft 11 so as to be relatively rotatable. Furthermore, this first transmission gear
A second transmission gear 42 coupled to the front wheel drive shaft is meshed with 41.

The first hub A and the second rotary shaft provided on the fourth rotary shaft 30.
The second hub B provided at one end of 28 and the third hub C provided at one end of the third rotating shaft 29 are coaxially arranged to form a first hub group 51. Further, a fourth hub X provided at the other end of the third rotary shaft 29, a fifth hub Y provided at an intermediate portion of the second rotary shaft 28, and a sixth hub Y provided at the first rotary shaft 27. Hub Z is
The second hub group 52 is arranged coaxially. Each hub A, B, C of this first hub group 51 is
Further, each hub X, Y, Z of the second hub group 52 has a second sleeve 17
Are combined in a suitable pattern. This first
The switching mechanism 9 is composed of the hub group 51, the second hub group 52, the sleeve 16 and the second sleeve 17. In this embodiment, the first rotating shaft 27 corresponds to the first output member in the claims and the second rotating shaft 28 corresponds to the second output member in the claims. Applicable

The coupling pattern of each hub of the switching mechanism 9 is as follows.

Coupling form a: sleeve 16 with fourth rotating shaft 30 and second rotating shaft
28, the second rotating shaft 28 and the third rotating shaft 29 are connected by the second sleeve 17, respectively.

Coupling form b: Sleeve 16 with fourth rotating shaft 30 and second rotating shaft
28 and the second sleeve 17 connects the third rotating shaft 29 and the first rotating shaft 27, respectively.

Coupling form c: sleeve 16 with fourth rotating shaft 30 and second rotating shaft
The second sleeve 17 connects the third rotating shaft 29, the second rotating shaft 28, and the first rotating shaft 27 to each other.

Coupling form d: sleeve 16 with fourth rotating shaft 30 and third rotating shaft
The second sleeve 17 connects the first rotating shaft 27 and the second rotating shaft 28 to each other.

Connection form e: First in both the sleeve 16 and the second sleeve 17
The rotary shaft 27 and the second rotary shaft 28 are coupled.

Coupling form f: The first rotating shaft 27, the second rotating shaft 28, and the third rotating shaft 29 are connected by the second sleeve 17, respectively.

Coupling form g: sleeve 16 with first rotary shaft 27 and second rotary shaft
The second sleeve 17 connects the first rotating shaft 27, the second rotating shaft 28, and the third rotating shaft 29 to each other.

Next, the transfer device 2 at the time of each of the coupling forms
The function of will be described with reference to FIG.

(Coupling mode a) In this state, since the second rotating shaft 28, the third rotating shaft 29, and the fourth rotating shaft 30 are integrated, the viscous coupling 7 is deactivated and the center of the viscous coupling 7 is deactivated. Differential mechanism 3
Is free. Therefore, the center differential free four-wheel drive state is adopted, and the torque transmitted from the main transmission 1 side is in accordance with the distribution value of the center differential mechanism 3 (in this embodiment, the ratio of the front wheels 3 to the rear wheels 7 is set. ) It is distributed and transmitted to the front wheel drive shaft 4 side and the rear wheel drive shaft 5 side.

(Coupling mode b) In this state, the first rotating shaft 27 and the third rotating shaft 29 are integrated, and the fourth rotating shaft 30 and the second rotating shaft 28 are integrated, so that the viscous The coupling 7 is arranged and connected in parallel between the first rotating shaft 27 and the second rotating shaft 28, and the center differential mechanism 3 is in a free state. Therefore, the torque transmitted from the main transmission 1 side is distributed and transmitted to the front wheel drive shaft 4 side and the rear wheel drive shaft 5 side to be in the four-wheel drive state, and at the same time, between the front wheel drive shaft 4 and the rear wheel drive shaft 5. When a speed difference occurs, the viscous coupling 7 is fastened to act as a brake mechanism, and the differential of the center differential mechanism 3 is limited. That is, four-wheel drive traveling having a differential limiting action is realized.

(Coupling mode c) In this state, the first rotary shaft 27, the second rotary shaft 28, the third rotary shaft 29, and the fourth rotary shaft 30 are integrated, so that the viscous coupling 7 does not operate. At the same time, the center differential mechanism 3 is locked, the main transmission 1 is directly connected to the front wheel drive shaft 4 and the rear wheel drive shaft 5, and direct connection four-wheel drive traveling is realized.

(Coupling form d) In this state, the third rotating shaft 29, the fourth rotating shaft 30, and the first rotating shaft 27 and the second rotating shaft 28 are integrated respectively, and the viscous coupling 7 is The first rotary shaft 27 and the fourth rotary shaft 30 are arranged and connected in series connection.
Further, the center differential mechanism 3 is in a locked state.
Therefore, in the state where there is no speed difference between the front wheel drive shaft 4 and the rear wheel drive shaft 5, the entire amount of torque from the main transmission 1 side is transmitted to the rear wheel drive shaft 5 side and the two wheels of the rear drive base. Drive running is realized.

On the other hand, when there is a speed difference between the front wheel drive shaft 4 and the rear wheel drive shaft 5, the viscous coupling 7 is fastened, and a part of the torque of the main transmission 1 side is transmitted to the front wheel drive shaft 4 side. Thus, four-wheel drive traveling is realized. That is, in this case,
The viscous coupling 7 functions as a clutch mechanism,
Four-wheel drive traveling with automatic 2-4 switching action is realized.

(Coupling form e) In this state, since the first rotating shaft 27 and the second rotating shaft 28 are integrated, the viscous coupling 7 is deactivated and the center differential mechanism 3 is locked. . Therefore, the entire amount of the torque from the main transmission 1 side is transmitted to the rear wheel side, and the two-wheel drive traveling of the rear wheel drive base is realized.

(Coupling Mode f and Coupling Mode g) In both cases, the hub coupling state is different from that in the coupling mode e, but since all the functions are the same as in the coupling mode e, description thereof will be omitted.

(Effects of the Invention) The present invention relates to a four-wheel drive system for a vehicle, wherein the driving force transmitted via the main transmission is transmitted to the front wheels and rear wheels of the vehicle via a transfer device. A center diff mechanism having an input member connected to the output member, a first output member connected to the front wheel drive shaft, and a second output member connected to the rear wheel drive shaft, and having a switching mechanism arranged in parallel. , A viscous coupling that transmits power using viscous resistance of the fluid when a speed difference occurs between the two axes, and the connection state of the viscous coupling is changed by operating the switching mechanism. A parallel connection state connected between the first output member and the second output member, and a series connection state connected between the center differential mechanism and any one of the front wheel drive shaft and the rear wheel drive shaft. Select and set to It is characterized in that it is configured to obtain.

Therefore, according to the four-wheel drive system for a vehicle of the present invention, the connection of the viscous coupling to the center differential mechanism is
By selecting the parallel connection state and the series connection state,
The viscous coupling functions as a clutch mechanism that is engaged and disengaged according to the speed difference between the front and rear wheels to drive four-wheel drive having an automatic 2-4 switching function, and the viscous coupling locks the center differential mechanism. It is possible to obtain the effect that four-wheel drive traveling having two different patterns of four-wheel drive traveling having a differential limitation function by functioning as a brake mechanism for performing differential limitation can be realized by using one viscous coupling.

[Brief description of drawings]

FIG. 1 is a skeleton diagram of a drive system of a four-wheel drive vehicle equipped with a four-wheel drive system according to a first embodiment of the present invention, and FIG.
FIG. 3 is an operation characteristic diagram of the four-wheel drive system shown in FIG. 3, FIG. 3 is a skeleton diagram of a drive system of a four-wheel drive vehicle equipped with the four-wheel drive system according to the second embodiment of the present invention, and FIG. FIG. 5 is an operation characteristic diagram of the four-wheel drive system shown in FIG. 3, FIG. 5 is a skeleton diagram of a drive system of a four-wheel drive vehicle equipped with the four-wheel drive system according to the third embodiment of the present invention, and FIG. FIG. 6 is an operational characteristic diagram of the four-wheel drive vehicle shown in FIG. 5. 1 ... Main transmission 2 ... Transfer device 3 ... Center differential mechanism 4 ... Front wheel drive shaft 5 ... Rear wheel drive shaft 6 ... Front wheel differential device 7 ... Viscous coupling 21 ... First Rotation shaft (second output member) 22 ... Second rotation shaft 23 ... Third rotation shaft 24 ... Fourth rotation shaft 27 ... First rotation shaft (First output member) 28 ... … Second rotary shaft (second output member) 29 …… Third rotary shaft 30 …… Fourth rotary shaft 31 …… Ring gear 32 …… Sun gear 33 …… Pinion gear 34 …… Carrier (First output Element)

Claims (1)

[Claims] 1. A four-wheel drive system for a vehicle, wherein a driving force transmitted through a main transmission is transmitted to front wheels and rear wheels of a vehicle through a transfer device, the output of the main transmission. A center differential mechanism that includes an input member that is connected to the member, a first output member that is connected to the front wheel drive shaft, and a second output member that is connected to the rear wheel drive shaft, and that has a switching mechanism arranged in parallel; A viscous coupling for transmitting power using a viscous resistance of a fluid when a speed difference occurs between the shafts, and the connection state of the viscous coupling is changed by operating the switching mechanism so that In a parallel connection state connected between the output member and the second output member, and in a serial connection state connected between the center differential mechanism and one of the front wheel drive shaft and the rear wheel drive shaft. As you can select and set Four-wheel drive system for a vehicle, characterized by being made.