JPH0444433Y2 - - Google Patents

Description

[Detailed explanation of the idea] <Industrial application field> The present invention relates to a power transmission device for a four-wheel drive vehicle.

<Prior art> Four-wheel drive vehicles that transmit engine power to the front and rear wheels have superior traversal performance on roads with a small coefficient of friction, such as muddy terrain and snow, compared to vehicles that drive only the front wheels or only the rear wheels. There is. However, in the case of direct-coupled four-wheel drive vehicles, where the power transmission system to the front wheels and the power transmission system to the rear wheels are directly connected, and the same amount of power is always transmitted to the front and rear wheels, when cornering, the front and rear wheels are connected directly. In addition, when driving straight at high speed on roads with a high coefficient of friction such as ordinary roads, there is a slight difference in the diameter of the tires, resulting in poor steering performance. There was a problem in that the difference in mileage could not be absorbed and unnecessary load was placed on the power transmission system.

Therefore, a so-called center differential type four-wheel drive vehicle has been developed, which transmits engine power to the front wheel power transmission system and the rear wheel power transmission system via a differential gear mechanism. In this case, the differential gear mechanism automatically provides a difference in rotational speed between the front wheels and the rear wheels to solve the above problem.

By the way, when the engine is installed horizontally, the driving force transmission device is often a two-shaft type consisting of an input shaft and an output shaft that is connected to this via a transmission mechanism and is approximately parallel to the input shaft. has been done.
In the case of this horizontal engine, the differential gear mechanism is provided with a planetary gear after final deceleration.

<Problems that the invention aims to solve> Center differential type four-wheel drive vehicles are a companion that can solve the problems of direct-coupled type four-wheel drive vehicles. The problem was that the wheels tend to slip due to this action, resulting in inferior running performance compared to the direct coupling type. In addition, especially in the case of a horizontally mounted engine, a differential gear mechanism with a planetary gear is provided after final deceleration, which increases the size and complexity of the device. Since it is disposed coaxially with either the front or rear wheels, the structure becomes complicated, making it difficult to form a unit, and there are problems in that maintainability also deteriorates.

The present invention has been developed in view of the above-mentioned conventional circumstances, and is intended to realize both the advantages of the direct coupling system and the advantages of the center differential system, as well as to reduce the size and simplicity of the device for use in four-wheel drive vehicles. The purpose is to provide a power transmission device.

<Means for Solving the Problems> The power transmission device for a four-wheel drive vehicle of the present invention connects an input shaft to the crankshaft of the engine substantially parallel to the crankshaft, and connects the input shaft to the crankshaft via a transmission mechanism. An intermediate shaft is connected substantially parallel to the input shaft, and first and second output shafts are disposed coaxially along an axis substantially parallel to the intermediate shaft and different from the axles of the front and rear wheels. A differential gear mechanism is disposed on the output shaft, and a differential case of the differential gear mechanism is connected to the intermediate shaft via a reduction mechanism, and a first side gear of the differential gear mechanism is connected to the first output shaft. a second side gear is connected to the second output shaft, the first output shaft is connected at one end thereof to a front wheel drive system including a first final reduction gear, and the first output shaft is connected to the front wheel drive system including a first final reduction gear; is connected to a rear wheel drive system including a second final reduction gear at an end on the same side as the one end, and a viscous clutch connects one of the output shafts to the differential case at the other end of both the output shafts. It is characterized by being connected via.

<Operation> A speed change mechanism is installed between the input shaft and the intermediate shaft, and a speed reduction mechanism is installed between the intermediate shaft and the output shaft.
A considerable space is formed around the output shaft, and a differential gear mechanism can be easily interposed between the speed reduction mechanism and the output shaft, thereby simplifying the device. Since the first side gear or second side gear of the differential gear mechanism and the differential case of the differential gear mechanism are connected via a viscous clutch, it can be used when the relative rotation difference between the front and rear wheels is not very large, such as when cornering or driving straight at high speed. , the viscous clutch does not operate, and the differential gear mechanism compensates for the rotational difference. In addition, if the relative rotational difference between the front and rear wheels becomes large, such as when one of the front and rear wheels slips, the differential gear mechanism is placed in front of the final reduction gear, so the rotational speed of the differential gear mechanism will change to that of the tire. It is faster than the rotational speed by the final reduction ratio, and similarly, the rotational speed difference between the front and rear wheels (differential rotational speed) detected by the viscous clutch is also faster, and the operating sensitivity is correspondingly higher. Furthermore, the differential limiting torque generated by the viscous clutch is amplified by the final reduction ratio via the final reduction gear and transmitted to the front and rear tires, resulting in an extremely efficient differential limiting function due to the synergistic effect. The viscous clutch operates to directly connect the front and rear wheels, improving off-road performance. Furthermore, in the first and second output shafts, which are separate from the axles for the front and rear wheels, a viscous clutch is arranged at the other end of each output shaft, which is opposite to the end where the output shaft is connected to the final reduction gear. Since the configuration is such that one of the output shafts is connected to the differential case,
The viscous clutch can be easily made into a unit, and maintainability is also improved.

<Example> Fig. 1 shows a schematic configuration of a power transmission device for a four-wheel drive vehicle according to an embodiment of the present invention, Fig. 2 shows a detailed structure of a viscous clutch and a center differential, and Fig. 3 shows a detailed configuration of a viscous clutch and a center differential. A graph representing the characteristics is shown.

In the figure, 1 is an engine, and an input shaft 4 is connected to the crankshaft 2 of the engine 1 through a clutch mechanism 3 in a substantially straight line with the crankshaft 2, and a transmission mechanism (speed gear group) 5 is connected to the input shaft 4. The intermediate shaft 6 is connected substantially parallel to the input shaft 4 via. An output shaft 8 is connected to the intermediate shaft 6 via a reduction gear 7 which is a reduction mechanism so as to be substantially parallel to the intermediate shaft 6 and separate from the axles of the front and rear wheels 9 and 10. A center differential 11, which is a differential gear mechanism that compensates for the rotational difference between the front wheels 9 and the rear wheels 10, is provided, and a differential case 12 of the center differential 11 is connected to the reduction gear 7. Center differential 11 is differential case 12
It includes differential pinions 13 and 14 that are pivotally supported, and the differential pinions 13 and 14 are engaged with a first side gear 15 and a second side gear 16 that are arranged opposite to each other. The first side gear 15 is connected to a final reduction gear 19 that transmits power to the front differential 18 via a tubular shaft 17 as a first output shaft, and the final reduction gear 19 is connected to a differential case 20 of the front differential 18. There is. In addition, front differential 1
8 compensates for the rotation difference between the left and right front wheels 9. The second side gear 16 is connected to the rear drive gear 22 via a shaft 21 serving as a second output shaft passing through the tubular shaft 17.
is connected via the reduction gear 23 and rear wheel drive system 24 to a known final reduction gear and rear differential (details not shown).
is connected to. Note that the rear differential compensates for the rotation difference between the left and right rear wheels 10.

On the other hand, the shaft 2 connected to the second side gear 16
1 extends to the outside of the differential case 12, and the shaft 2
1 and the differential case 12 are connected via a viscous clutch 25. Viscous clutch 25
As shown in FIG. 2, the inner shaft 26 includes an inner shaft 26 fixed to the second side gear 16, an outer case 27 coaxially and rotatably supported by the inner shaft 26 and fixed to the differential case 12, and an inner shaft 26. silicone oil 28 filled in a chamber defined by the outer case 27; a plurality of clutch plates 29 fixed to the inner shaft 26 and immersed in the silicone oil 28; The clutch plate 30 has a plurality of clutch plates 30 fixed to the outer case 27 and soaked in silicone oil 28. And this viscous clutch 25, as shown in FIG.
As the differential rotation speed △W between the inner shaft 26 and the outer case 27 increases, the differential limiting torque △
Since T increases, when a large relative rotation difference occurs between the inner shaft 26 and the outer case 27, both become locked and the relative rotation difference can be eliminated.

Although the above embodiment is applied to a vehicle based on front wheel drive, the present invention is not limited to the vehicle based on rear wheel drive. When the vehicle is based on rear wheel drive, the viscous clutch 25 is interposed between the first side gear 15 and the differential case 12.

Next, the operation of the power transmission device for a four-wheel drive vehicle having the above configuration will be explained.

The power from the engine 1 is transmitted to the front wheel drive system through a crankshaft 2, a clutch mechanism 3, an input shaft 4, a transmission mechanism 5, an intermediate shaft 6, a reduction gear 7, a first side gear 15 of a center differential 11, and a final reduction gear 19. The signal is transmitted to the front differential 18 via the front differential. In addition, power from the engine 1 is sent to the rear wheel drive system 24 through the center differential 1.
1 second side gear 16, rear drive gear 2
2. It is transmitted via the reduction gear 23. and,
When a small relative rotation difference occurs between the front wheels 9 and the rear wheels 10 during cornering, the rotation difference can be compensated for by the action of the center differential 11, and no braking phenomenon occurs. When a large relative rotation difference occurs between the front wheel 9 and the rear wheel 10, such as when a large slip occurs in the front wheel 9 or the rear wheel 10, the differential rotation speed between the inner shaft 26 of the viscous clutch 25 and the outer case 27 increases. When ΔW increases and the differential rotation speed ΔW increases, the differential limiting torque ΔT increases, and the inner shaft 26 and the outer case 27 become locked. When both are locked, front wheel 9 and rear wheel 1
0 becomes a direct connection state, and it is possible to obtain high running performance on a road surface with a small coefficient of friction. Therefore, the advantages of the center differential system and the direct connection system can be obtained automatically without any special operation. Furthermore, since the device has a simple configuration, there is no risk of it becoming larger.

<Effects of the invention> According to the invention, switching between the center differential system and the direct coupling system can be performed according to the driving condition of the vehicle by the action of the viscous clutch without any special operation. It is possible to realize a four-wheel drive vehicle that has both the advantages of the center differential system, such as maneuverability, and the advantages of the direct coupling system, such as high running performance on roads with a low coefficient of friction. Further, in the present invention, since the differential gear mechanism and the viscous clutch are arranged before the final reduction gear, the operating sensitivity is good and an extremely efficient differential limiting function can be achieved. Furthermore, since the viscous clutch is disposed at one end of the output shaft that is separate from the front and rear wheels, the unitization of the viscous clutch allows the device to be made smaller and simpler, and improves maintainability.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a power transmission system for a four-wheel drive vehicle according to an embodiment of the present invention, FIG. 2 is a detailed diagram of a viscous clutch, and FIG. 3 is a graph showing characteristics of the viscous clutch. In the drawing, 1 is an engine, 2 is a crankshaft, 4 is an input shaft, 5 is a transmission mechanism, 6 is an intermediate shaft, 7 is a reduction gear, 8 is an output shaft, 9 is a front wheel, 10 is a rear wheel, 11 is a center differential, 12 is a differential case, 15 is a first side gear, 16 is a second side gear, and 25 is a viscous clutch.

Claims (1)

[Scope of utility model registration request] An input shaft is connected to the crankshaft of the engine substantially parallel to the crankshaft, an intermediate shaft is connected to the input shaft substantially parallel to the input shaft via a transmission mechanism, and the front and rear wheels are substantially parallel to the intermediate shaft and are connected to the front and rear wheels. A first and a second output shaft are disposed coaxially along an axis different from the axle of the first and second axles, a differential gear mechanism is disposed on the output shaft, and a differential case of the differential gear mechanism is connected to the intermediate axle. A first side gear of the differential gear mechanism is connected to the first output shaft, a second side gear is connected to the second output shaft, and the first output the shaft is connected to a front wheel drive system including a first final reduction gear at one end thereof, and the second output shaft is connected to a rear wheel drive system including a second final reduction gear at an end on the same side as the one end; A power transmission device for a four-wheel drive vehicle, characterized in that one of the output shafts is connected to the differential case via a viscous clutch at the other end of the output shafts.