JPH09109714A - Driving transmission of 4-wheel driving vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a front driving system into a small size by assembling a viscous coupling and an intermittent mechanism into the front driving system. SOLUTION: The driving transmission of the present 4-wheel driving vehicle is composed of a front driving system for transmitting the torque from an input shaft 1 to front wheels and a rear driving system for transmitting the torque to rear wheels. The torque distribution to the front driving system is set smaller than the torque distribution to the rear driving system by means of a viscous coupling 23 constructed in its no-humping characteristic provided in the front driving system. An inner case 25 is connected to a front drive shaft 2 and an outer case 24 is connected to a front drive gear 9 via an intermittent mechanism. The intermittent mechanism is constituted by intermittence between a dog gear 16 provided to the front drive gear 9 and a sleeve 10 provided in the outer case 24.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive transmission system for a four-wheel drive vehicle in which a front drive system is provided with a viscous coupling to transmit engine torque to front wheels.

[0002]

2. Description of the Related Art Conventionally, a drive transmission device for a four-wheel drive vehicle is a part-time type four-wheel drive vehicle, as shown in FIGS. 6 and 7, in which the engine torque is directly connected by gears and a front is provided by a distributor. The structure is such that the front wheels and the rear wheels are distributed at a ratio of 1: 1 through the drive system. The driving force or torque from the engine is transmitted to the input shaft 1 in the transfer 52 via the transmission. The input shaft 1 is rotatably supported by the transfer case 18 via bearings. In the transfer case 18, a front drive shaft 2 of a front drive system, a rear drive shaft 3 of a rear drive system, and a counter shaft 17 are rotatably supported in parallel to the input shaft 1 via bearings. . A high main gear 4 and a low main gear 7 are rotatably supported on the input shaft 1, respectively. Furthermore, the input shaft 1 has
The clutch hub 19 is fixed. High main gear 4
A dog gear 14 is attached to the low main gear 7, and a dog gear 15 is attached to the low main gear 7. Clutch hub 1
A sleeve 11 for switching between a four-wheel drive high speed stage and a four-wheel drive low speed stage is provided at 9. Sleeve 11
Is engaged with the dog gear 14, the high main gear 4 is rotated, and when the sleeve 11 is engaged with the dog gear 15, the low main gear 7 is rotated.

A high counter gear 5 meshing with the high main gear 4 and a low counter gear 8 meshing with the low main gear 7 are fixed to the counter shaft 17. A rear drive gear 6 is attached to the rear drive shaft 3, and a rear coupling 12 that connects the rear drive shaft 3 to the rear propeller shaft is attached. The rear drive gear 6 meshes with the high counter gear 5.

Further, the front drive shaft 2 has
The front drive gear 9 is rotatably supported, and the clutch hub 20 is fixed. A front coupling 13 that connects the front drive shaft 2 to the front propeller shaft is attached to the front drive shaft 2. The front drive gear 9 is provided with a dog gear 16. The clutch hub 20 is provided with a sleeve 10 for switching between a four-wheel drive stage that drives the front wheels and a two-wheel drive stage that releases the drive of the front wheels. Therefore, when the sleeve 10 meshes with the dog gear 16, the rotation of the front drive gear 9 is transmitted to the front drive shaft 2 via the clutch hub 20.

The above-described drive transmission device for a four-wheel drive vehicle has the above-mentioned structure, and when transmitting the torque from the input shaft 1 only to the rear drive shaft 3,
The sleeve 10 is operated to release the engagement between the sleeve 10 and the dog gear 16. Therefore, when the sleeve 11 is engaged with the dog gear 14, the torque from the input shaft 1 is applied to the high speed rear drive system, that is, the input shaft 1 → the clutch hub 19 → the sleeve 11 → the dog gear 14 → the high main gear 4 → the high gear. It is transmitted to the counter gear 5 → rear drive gear 6 → rear drive shaft 3 → rear coupling 12 → rear propeller shaft → rear differential → rear wheel. Alternatively, when the sleeve 11 meshes with the dog gear 15, the torque from the input shaft 1 is a low-speed rear drive system, that is, the input shaft 1 → the clutch hub 19 → the sleeve 11 →
Dog gear 15 → Low main gear 7 → Low counter gear 8
→ Counter shaft 17 → High counter gear 5 → Rear drive gear 6 → Rear drive shaft 3 → Rear coupling 12 → Rear propeller shaft → Rear differential → Transfer to the rear wheels.

When torque from the input shaft 1 is transmitted to both the rear drive shaft 3 and the front drive shaft 2 with a torque distribution of 1: 1, the sleeve 10 is actuated to move the sleeve 10 to the dog gear 16. Engage. Therefore, when the sleeve 11 is engaged with the dog gear 14, the input shaft 1
Torque is transmitted to the rear wheels through the high-speed rear drive system described above, and at the same time as the high-speed front drive system, that is, the input shaft 1 → the clutch hub 19 → the sleeve 11
→ dog gear 14 → high main gear 4 → high counter gear 5 → front drive gear 9 → dog gear 16 → sleeve 10 → clutch hub 20 → front drive shaft 2
→ Front coupling 13 → Front propeller shaft → Front differential → Front wheels are transmitted.
Alternatively, when the sleeve 11 meshes with the dog gear 15, the torque from the input shaft 1 is transmitted to the rear wheels through the low speed rear drive system, and at the same time, the low speed front drive system, that is, the input shaft 1 → Clutch hub 19 → Sleeve 11 → Dog gear 15 → Low main gear 7 → Low counter gear 8 → Counter shaft 1
7 → high counter gear 5 → front drive gear 9 → dog gear 16 → sleeve 10 → clutch hub 20 → front drive shaft 2 → front coupling 13 → front propeller shaft → front differential →
It is transmitted to the front wheels.

Further, Japanese Utility Model Laid-Open No. 62-103627 discloses a four-wheel drive type automobile. The four-wheel drive vehicle distributes and transfers the power from the engine to the front wheels and the rear wheels, and a center bearing member supported by the vehicle body allows an input side propeller shaft and an output side propeller shaft between front and rear wheel axles. Is rotatably supported, the center bearing member limits the differential between the input side propeller shaft and the output side propeller shaft, and absorbs the rotational difference when the output shaft side rotation exceeds the input shaft side rotation. It incorporates a motion limiting mechanism.

[0008]

However, in such a direct-coupled part-time four-wheel drive vehicle as described above, when the vehicle turns, a difference in turning speed occurs between the front and rear wheels due to the turning radius difference between the front and rear wheels. If the drive transmission device of the wheel drive vehicle has the direct coupling structure as described above, the difference in the rotational speeds of the front and rear wheels cannot be absorbed, so that the steer brake phenomenon occurs when the road surface friction coefficient is high.

Further, when the drive transmission device of the four-wheel drive vehicle has the direct coupling structure as described above, the front-rear drive force distribution, that is, the torque distribution is 50:50, so that the front drive system is almost the same as the rear drive system. Will be required. Increasing the strength of the front drive system not only makes it difficult to reduce the size and weight of the front drive system, especially the front differential, but also increases the passenger compartment height and deteriorates the occupant's ability to get in and out of the front suspension. Problems such as a reduction in stroke will occur, and the riding comfort will deteriorate.

Further, in the drive transmission system for a four-wheel drive vehicle as described above, the torque of the engine is distributed by the distributor to the front drive system and the rear drive system in equal proportions. In some cases, the difference in the shared load between the front and rear wheels may occur between when the vehicle is empty and when the vehicle is loaded, and the difference between the dynamic load radii of the front and rear wheels may increase. In this case, if the drive transmission device of the four-wheel drive vehicle has a direct coupling structure as described above, the rotation difference between the front and rear wheels cannot absorb the rotation difference between the front and rear wheels at all except slipping the tires. Problems such as deterioration of fuel consumption, tire wear, and drive system deterioration occur.

Further, like a light commercial vehicle, a vehicle whose load capacity changes greatly by loading a maximum load capacity (for example, 2000 kg) or leaving it empty (for example, Japanese Patent Laid-Open No. 61-191434). (See the official gazette),
When using a viscous coupling type four-wheel drive,
The amount of tire flexure varies depending on the difference in the shared load between the front and rear wheels between when the vehicle is empty and when the vehicle is loaded, and the torque in the viscous coupling is generated due to the difference in the rotational speeds of the front and rear wheels caused by the difference. At this time, the full-time four-wheel drive vehicle of the viscous coupling type, depending on the road surface friction coefficient and vehicle speed, is the same as the four-wheel drive vehicle of the direct coupling type,
Problems such as deterioration of fuel consumption, tire wear, and drive system deterioration occur.

Further, in a full-time four-wheel drive vehicle, all of the front drive system and the rear drive system of the four-wheel drive vehicle are rotating even when four-wheel drive such as traveling on a dry pavement is not necessary, and two-wheel drive Problems such as driving vehicle ratio, deterioration of fuel efficiency above weight increment, and noise increase occur.

By the way, as a front wheel suspension device for suspending the front wheels, those shown in FIGS. 3 and 4 are known.
The front wheel suspension device is configured as an independent suspension device, and the front drive system is configured to drive the front wheels 31 from the front differential 30 through the front drive shaft 35. An upper link 33 and a lower link 34 are attached to a knuckle 37 provided on the front wheel 31 via a king pin 38. Regarding the independent suspension device, the upper link 33 is attached to the vehicle body frame via the shock absorber 32, and the front differential 30 is supported and fixed to the floor of the vehicle. Further, the front wheel 31 is provided with a freewheel hub mechanism 54 on the axle. The freewheel hub mechanism 54 is the front wheel 3
It is a mechanism that can cut off the transmission of power from 1 to the front drive system.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, and a viscous coupling is incorporated in the front drive system so that the torque of the engine can be transmitted to the front wheels. It is possible to switch between two-wheel drive and four-wheel drive by an intermittent mechanism.In the case of two-wheel drive, the torque acting on the viscous coupling from the front wheels is eliminated, and the viscous coupling is not directly connected. It is configured so that the torque distribution to the front wheels is always smaller than the torque distribution to the rear wheels, and when drive conditions such as slip of the rear wheels occur, part of the engine torque is distributed to the front wheels. However, it is an object of the present invention to provide a drive transmission device for a four-wheel drive vehicle, which assists the smooth driving of the rear wheels and can improve fuel efficiency when driving two wheels. .

According to the present invention, an input shaft to which the torque of the engine is transmitted, a front drive system having a front differential for transmitting the torque from the input shaft to the front wheels, and the torque from the input shaft to the rear wheels. In a drive transmission device for a four-wheel drive vehicle including a rear drive system having a rear differential, a viscous coupling having a no-hump characteristic is provided in the front drive system, and the torque of the front drive system is provided by the viscous coupling. The distribution is set smaller than the torque distribution to the rear drive system,
The present invention relates to a drive transmission device for a four-wheel drive vehicle, wherein the front drive system is provided with an interrupting mechanism for interrupting torque transmission to the front wheels.

In the drive transmission system for a four-wheel drive vehicle, the front drive shaft of the front drive system is rotatably supported by a front gear connected to a main gear fixed to the input shaft via a counter gear. The inner case of the viscous coupling is connected to the front drive shaft, the outer case of the viscous coupling is connected to the front drive gear, and the disconnecting mechanism is provided on the outer case and the sleeve. It is configured by connecting and disconnecting with a dog gear provided on the gear.

Alternatively, in this four-wheel drive vehicle drive transmission system, the intermittent mechanism is constituted by a freewheel hub mechanism provided on the front wheels.

Alternatively, in the drive transmission system for a four-wheel drive vehicle, the connecting / disconnecting mechanism is composed of a two-wheel drive / four-wheel drive switching mechanism provided in the front drive system which can be operated via a switching means. There is.

In this four-wheel drive vehicle drive transmission system, the front wheel suspension system for suspending the front wheels is constructed as an independent suspension system.

In a commercial vehicle such as a truck, when the vehicle is empty or loaded, the load of the rear wheel changes drastically and the tire diameter of the rear wheel changes. If the balance with the front wheel is adjusted on either side during loading, in the other situation, there will be a difference in rotation speed between the front wheel and the rear wheel in the viscous coupling, even though there is no slip on the wheel. As a result, dragging occurs, heat is generated, and a force that transmits torque to the front wheels is exerted, which deteriorates fuel efficiency. However, the drive transmission of this four-wheel drive vehicle is
As described above, since the intermittent mechanism is incorporated in the front drive system, in such a case, if the torque transmission of the front drive system is interrupted by the intermittent mechanism, the undesirable phenomenon as described above will occur. Can be avoided.

Further, the viscous coupling is incorporated in the front drive system, and the viscous coupling is adjusted to be no hump which prevents the viscous coupling from being directly connected by a lock (that is, hump). Further, the viscous coupling is made to function as a torque limiter and a fluid clutch for torque distribution to the front wheels, and the torque distribution to the rear drive system through the viscous coupling is set to be larger than the torque distribution of the front drive system, that is, The torque distribution of the rear wheels can be set to a value that is always larger than the torque distribution of the front wheels, for example, a value of 5 to 8 times. Therefore, the front drive system does not require high strength, and can be significantly downsized as compared with the rear drive system. In particular, the front differential in the front drive system can be downsized and the front propeller shaft and The front drive shaft can be configured to have a small diameter, thereby achieving weight reduction, suppressing a rise in vehicle height, and reducing a passenger compartment height, thereby making it possible for passengers to get in and out of a vehicle close to a two-wheel drive vehicle. it can.

When the drive transmission device for a four-wheel drive vehicle is used and the front wheel suspension device for suspending the front wheels is configured as an independent suspension device, the floor base of the passenger compartment can be further lowered, and the four-wheel drive system can serve as a small cabover. The floor base of a wheel drive vehicle can be configured in the same way as the floor base of a two wheel drive vehicle, so that it can be accommodated in a small vehicle frame, and the stroke amount of the front suspension can be sufficiently secured to improve the riding comfort. .

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a drive transmission device for a four-wheel drive vehicle according to the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic explanatory view illustrating an embodiment of a drive transmission device for a four-wheel drive vehicle according to the present invention, and FIG. 2 is a sectional view showing an embodiment of a drive transmission device for a four-wheel drive vehicle according to the present invention. . In FIGS. 1 and 2, the same parts as those in FIGS. 3 to 7 are designated by the same reference numerals.

The drive transmission device for this four-wheel drive vehicle comprises a front wheel 3
Driving force, that is, torque from the engine 50 arranged on the first side is transmitted from the transmission 51 to the input shaft 1 in the transfer 52. In the transfer case 18, in order to distribute the torque from the engine 50 to the front drive system and the rear drive system, the main gear 21, the counter gear 22, and the counter gear 22, which constitute the transfer 52,
Front drive gear 9 and viscous coupling 23
Is housed. The drive transmission of this four-wheel drive vehicle is
The input shaft 1 to which the torque of the engine 50 is transmitted, the front drive system including the front differential 30 that transmits the torque from the input shaft 1 to the front wheels 31, and the torque from the input shaft 1 to the rear wheels 41.
It is composed of a rear drive system having a rear differential 40 for transmission to the.

In the drive transmission system of this four-wheel drive vehicle,
The torque transmitted to the input shaft 1 is
When there is no difference in rotational speed between the rear wheel 41 and the rear wheel 41 (for example, the rear wheel 41 is in a slip state), it is transmitted to the rear differential 40 through the rear propeller shaft 39, and the rear differential 40 transfers the rear drive shaft to the rear wheels 41 on both sides. Each is transmitted through 53. When a difference in the number of rotations of the front wheel 31 and the rear wheel 41 (for example, a slip state of the rear wheel 41) occurs in the torque transmitted to the input shaft 1, a part of the torque is part of the main gear 21, the counter gear 22, and the front gear. The torque transmitted to the drive gear 9 and transmitted to the front drive gear 9 is torque-distributed by the viscous coupling 23 and transmitted to the front drive shaft 2, and the torque distributed to the front drive shaft 2 is transmitted to the front propeller shaft 29 through the front. It is transmitted to the differential 30. The torque transmitted to the front differential 30 is transmitted to the front wheels 31 on both sides through the front drive shaft 35 and the joint 49.

The drive transmission device for a four-wheel drive vehicle is, in particular,
The front drive system is provided with a viscous coupling 23 having a no hump characteristic, and the viscous coupling 23 always sets the torque distribution of the front drive system to be smaller than the torque distribution to the rear drive system. The front drive system is completely shut off to prevent torque generation due to the rotation difference in the viscous coupling. That is, the viscous coupling 23 tunes the no-hump characteristic, has a function as a torque limiter and a fluid clutch, and is incorporated in series in the front drive system. Further, during two-wheel drive, the sleeve 10 is disengaged from the dog gear 16 and the difference in the viscous coupling 23 is cut off from the drive system.

In the drive transmission system for this four-wheel drive vehicle,
The input shaft 1, the counter shaft 17, and the front drive shaft 2 are rotatably supported by the transfer case 18 via bearings. A main gear 21 and a rear coupling 12 are fixed to the input shaft 1. The front drive gear 9 includes a dog gear 16 and is rotatably supported by the front drive shaft 2. An inner case 25 of a viscous coupling 23 is fixed to the front drive shaft 2. The sleeve 10 is slidably provided on the outer case 24 of the viscous coupling 23 so as to mesh with and release the dog gear 16. The sleeve 10 can function as an intermittent mechanism of the front drive system. Viscous coupling 23
Silicone oil 26 is enclosed in a chamber formed by the outer case 24 and the inner case 25, and an outer plate 27 erected on the outer case 24 and an inner plate 28 erected on the inner case 25 are arranged inside the chamber. ing.

The counter gear 22 fixed to the counter shaft 17 meshes with the main gear 21 and
It meshes with the front drive gear 9. The front drive shaft 2 in the front drive system is connected from a main gear 21 fixed to the input shaft 1 via a counter gear 22 to rotatably support the front drive gear 9, and the inner case 28 of the viscous coupling 23 is connected to the front. The outer case 24 of the viscous coupling 23 is connected to the drive shaft 2, and is connected to the front drive gear 9 via the sleeve 10 and the dog gear 16.

The torque transmission in the transfer 52 of the drive transmission system of the four-wheel drive vehicle is as follows. That is, when the sleeve 10 is not engaged with the dog gear 16 and is in the released state, in other words, when the sleeve of the intermittent mechanism is operated in the released state, the torque from the engine 50 is not distributed by the viscous coupling 23. , Not transmitted to the front drive system, but transmitted only to the rear drive system. Therefore, the torque from the engine 50 is transmitted to the rear wheel 41 through the route of the input shaft → the rear coupling 12 → the rear propeller shaft 39 → the rear differential 40 → the rear drive shaft 53 → the rear wheel 41. The drive transmission device of the four-wheel drive vehicle, that is, the vehicle is in a two-wheel drive state.

When the sleeve 10 meshes with the dog gear 16, in other words, when the sleeve of the disconnecting mechanism is operated in the connected state, the torque from the engine 50 is distributed by the viscous coupling 23, and the torque is distributed to the front drive system. It will be distributed to the rear drive system. During normal running of the vehicle in which there is no difference in rotation speed between the front wheels 31 and the rear wheels 41, the viscous coupling 23 includes an outer plate 27 fixed to the outer case 24 and an inner plate fixed to the inner case 25. A rotation difference is generated between the plate 28 and the silicone oil 26, no shearing force is exerted on the silicon oil 26, most torque is distributed to the rear drive system, and almost no torque is distributed to the front drive system. Is a two-wheel drive state.

In this drive transmission system for a four-wheel drive vehicle, when the rear wheel 41 exceeds the rotational speed of the front wheel 31 due to loading on the vehicle or the front wheel 31 or the rear wheel 41 slips, the rotational speed difference between them is increased. Occurs, a rotation difference occurs between the outer plate 27 and the inner plate 28 of the viscous coupling 23, and a shearing force acts on the silicone oil 26, causing the front drive system and the rear drive system of the viscous coupling 23 to move. The torque distribution function of is activated and the vehicle is in the four-wheel drive state. That is, the torque is transmitted in the rear drive system from the input shaft to the rear coupling 12
→ Rear propeller shaft 39 → Rear differential 4
It is transmitted to the rear wheel 41 through the path of 0 → rear drive shaft 53 → rear wheel 41. Further, torque transmission in the front drive system is performed by input shaft → main gear 21 → counter gear 22 → front drive gear 9 → dog gear 1
6 → sleeve 10 → viscus coupling 23 → front drive shaft 2 → front propeller shaft 29
→ Front differential 30 → Front drive shaft 35 → Joint 49 → Front wheel 31 through front wheel 4
1 is transmitted.

In the drive transmission system for a four-wheel drive vehicle, as described above, the viscous coupling 23 does not distribute the torque to the front drive system and is in a two-wheel drive state when the vehicle is in steady running. When the rear wheel 41 slips, the viscous coupling 23 exerts a torque distribution function between the front drive system and the rear drive system, and the front wheel 31
Therefore, the minimum required torque is distributed to the vehicle, and the four-wheel drive state is achieved, so that smooth running of the vehicle can be assisted. Further, when the relative rotation difference between the front wheel 31 and the rear wheel 41 is small, the shearing force of the viscous coupling 23 against the silicon oil 26 is also small,
The viscous coupling 23 will also act as a fluid clutch.

The drive transmission device for this four-wheel drive vehicle is
Although not shown, a front drive gear 9 can be fixed to the front drive shaft 2 of the front drive system, and the front drive gear 9 transmits torque from a main gear 21 fixed to the input shaft 1 through a counter gear 22. To be done. In this case, the viscous coupling 23 is incorporated in the front differential 30. As a result, in the drive transmission device of the four-wheel drive vehicle, the torque distribution to the rear drive system can be set to be larger than that of the front drive system by viscous coupling 23.

Next, another embodiment of the drive transmission device for a four-wheel drive vehicle according to the present invention will be described. In this embodiment, the free wheel hub mechanism 54 is used as an intermittent mechanism, and the front wheels 31
It is intended to prevent the torque of the above from being transmitted to the front drive system to generate torque in the viscous coupling 23. The front drive system near the front wheel 31 is shown in FIGS.
As shown in, the front wheels 31 are driven from the front differential 30 through the front drive shaft 35. An upper link 33 and a lower link 34 are attached to a knuckle 37 provided on the front wheel 31 via a king pin 38. An axle hub 57, to which a wheel 56 is fixed, is rotatably supported on an axle 55 of the front wheel 31, and a freewheel hub mechanism 54 is provided between the axle 55 and the axle hub 57. The freewheel hub mechanism 54 is a mechanism that can interrupt the transmission of power from the front wheels 31 to the axle 55 of the front drive system.

In this embodiment, the free wheel hub mechanism 54 is set in a state in which torque is transmitted from the axle 55 to the axle hub 57 during four-wheel drive. However, even when the viscous coupling 23 is in the cut-off state and the torque of the engine is not transmitted to the front drive system during two-wheel drive, the rotational force of the front wheels 31 is conversely transmitted from the axle 55 through the front drive system. The viscous coupling 23 acts on the coupling 23 to generate torque, which deteriorates fuel efficiency. Therefore, in this drive transmission device for a four-wheel drive vehicle, the free wheel hub mechanism 54 is used to drive the axle 55 from the axle hub 57.
A torque is not transmitted to the viscous coupling 23 so that the rotational force of the front wheel 31 does not act on the viscous coupling 23 to improve fuel efficiency.

Although not shown, in some cases, the drive transmission device of the four-wheel drive vehicle is provided with a front drive system, for example, a vacuum control unit, so that the rotational force from the front wheels 31 does not act on the viscous coupling 23. It is also possible to incorporate a clutch that can be actuated via a switching means such as a cable or cable, and use the clutch as an interrupting mechanism to switch between two-wheel drive and four-wheel drive.

Further, in the drive transmission system for this four-wheel drive vehicle, as shown in FIGS. 3 and 4, the front wheel suspension system for suspending the front wheels 31 is constructed as an independent suspension system 43. Further, FIG. 5 shows a cab 47 of the present invention and a conventional cab 48.
Is shown in a side view. FIG. 5A shows a cab-over type cab 47 in which the drive transmission device of the four-wheel drive vehicle is incorporated, and FIG. 5B shows a conventional cab 48. ing. In this four-wheel drive drive transmission system, the front differential 30 can be made smaller than the conventional front differential 42. Therefore, as shown in FIG. 1, the front differential 30 is installed in a space on the side of the engine 50. Yes, as shown in FIG. 5 (a), the height H ₁ of the passenger compartment base
Can be configured to be low, and the passenger seat can be seated for three people with a margin. On the other hand, in the conventional direct drive type drive transmission device for a four-wheel drive vehicle, as shown in FIG. 5B, the front differential has a large size due to its strength, and thus it is difficult to reduce the weight. In addition, the height H ₂ of the passenger compartment base becomes high, the passenger seat cannot be formed in the center, three passengers cannot be seated, the passenger's entry / exitability is deteriorated, and the stroke of the front suspension is reduced. Occurs.

[0038]

As described above, the drive transmission device for a four-wheel drive vehicle according to the present invention incorporates the viscous coupling having the no-hump characteristic into the front drive system so that the drive force of the front drive system can be applied to the rear drive system. By limiting the torque to be always smaller than the driving force, the front drive system can be downsized and reduced in weight. Since the front drive system can be downsized, the height of the occupant seat can be reduced while the vehicle is a four-wheel drive vehicle, the stroke of the suspension can be sufficiently ensured, and the rideability equivalent to that of the two-wheel drive vehicle can be ensured. Further, since the front drive system can be miniaturized, it is possible to provide a small vehicle frame, that is, a four-wheel drive vehicle capable of accommodating the total height of a vehicle, a three-seater, and a ton load. By viscous coupling having a function as a clutch,
It is possible to eliminate the steer brake phenomenon during turning during four-wheel drive.

In particular, the drive transmission device for this four-wheel drive vehicle is
Since an intermittent mechanism is provided in the front drive system and four-wheel drive and two-wheel drive can be arbitrarily switched, when four-wheel drive is unnecessary, the four-wheel drive is positively switched to the two-wheel drive, and the front drive is performed during the two-wheel drive. The drag does not occur in the viscous coupling through the system and torque is not generated, fuel consumption can be improved, and tire wear can be suppressed. Further, in the drive transmission device for a four-wheel drive vehicle, the viscous coupling acts as a fluid clutch, whereby tire wear during four-wheel drive traveling can be suppressed and fuel consumption can be improved. Moreover, in this drive transmission device for a four-wheel drive vehicle, the front differential can be made smaller in size than the direct drive transmission device for a conventional four-wheel drive vehicle, so that the front wheel suspension device for suspending the front wheels is independent. If it is configured as a suspension device, it is possible to allow a three-person ride with a margin due to the space of the front differential.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram illustrating an embodiment of a drive transmission device for a four-wheel drive vehicle according to the present invention.

FIG. 2 is a sectional view showing an embodiment of a drive transmission system for a four-wheel drive vehicle according to the present invention.

FIG. 3 is a partial rear view showing an independent suspension device of a front drive system applied to the drive transmission device of the four-wheel drive vehicle.

FIG. 4 is a partial cross-sectional view showing a front drive system applied to the drive transmission system of the four-wheel drive vehicle.

FIG. 5 is a side view showing a cab of the cab type and a conventional cab in which the drive transmission device of the four-wheel drive vehicle is incorporated.

FIG. 6 is a developed sectional view showing an example of a drive transmission device for a conventional four-wheel drive vehicle.

7 is an explanatory diagram showing a meshing relationship of gears in the drive transmission system of the four-wheel drive vehicle of FIG.

[Explanation of symbols]

 1 Input Shaft 2 Front Drive Shaft 9 Front Drive Gear 10 Sleeve 16 Dog Gear 21 Main Gear 22 Counter Gear 23 Viscous Coupling 24 Outer Case 25 Inner Case 27 Outer Plate 28 Inner Plate 30 Front Differential 31 Front Wheel 40 Rear Differential 41 Rear Wheel 43 Independent Suspension Device 50 Engine 54 Freewheel hub mechanism

Claims (5)

[Claims] 1. An input shaft for transmitting engine torque, a front drive system including a front differential for transmitting the torque from the input shaft to front wheels, and a rear differential for transmitting the torque from the input shaft to rear wheels. In a drive transmission device for a four-wheel drive vehicle including a rear drive system, a front drive system is provided with a viscous coupling having a no-hump characteristic, and the torque distribution of the front drive system is distributed by the viscous coupling. A drive transmission device for a four-wheel drive vehicle, which is set to be smaller than a torque distribution to the rear drive system, and which is provided with an interrupting mechanism for interrupting the transmission of torque to the front wheels in the front drive system. 2. The front drive shaft of the front drive system is connected to a main gear fixed to the input shaft via a counter gear to rotatably support the front drive gear, and the inner case of the viscous coupling is An outer case of the viscous coupling is connected to the front drive shaft, an outer case of the viscous coupling is connected to the front drive gear, and the disconnecting mechanism is configured by connecting and disconnecting a sleeve provided to the outer case and a dog gear provided to the front drive gear. The drive transmission device for a four-wheel drive vehicle according to claim 1, wherein 3. The drive transmission device for a four-wheel drive vehicle according to claim 1, wherein the intermittent mechanism is constituted by a freewheel hub mechanism provided on the front wheels. 4. The switching mechanism for switching between two-wheel drive and four-wheel drive, which is provided in the front drive system and can be operated via a switching means. Drive transmission for four-wheel drive vehicles. 5. The front wheel suspension device for suspending the front wheel is configured as an independent suspension device.
4. The drive transmission device for a four-wheel drive vehicle according to any one of 4 above.