Power transmission device of all terrain vehicle

An all terrain vehicle comprising a V-belt continuously variable transmission and a gear-type transmission, being capable of transmitting drive torque from an engine with controlled engine braking but without loss of the torque, thereby giving a rider an improved driving feel. The V-belt continuously variable transmission and the gear-type transmission are placed in this order from upstream in a power transmission path from the engine to wheels. A one-way clutch for transmitting only the drive torque from the engine to the wheel and a torque limiter for transmitting the torque less than a predetermined value are arranged in parallel, between, e.g., a countershaft and forward intermediate gears fitted onto the countershaft.

Power transmission device diagram of all terrain vehicle

1. Field of the Invention

The present invention relates to a power transmission device of an all terrain vehicle (ATV). More particularly, the present invention relates to a power transmission device of an all terrain vehicle comprising a V-belt continuously variable transmission (CVT) and a gear-type transmission which are arranged in this order from upstream in a power transmission path from an engine to wheels, and an all terrain vehicle comprising the power transmission device.

2. Description of the Related Art

In the all terrain vehicle comprising the V-belt continuously variable transmission and the gear-type transmission, the V-belt continuously variable transmission is adapted to perform automatic speed change according to an engine speed and increase/decrease in load of wheels, and some gear-type transmissions are adapted to perform switching between forward and reverse, between forward high-speed and forward low-speed, and the like, by operation of a hand-operated shift lever.

In this all terrain vehicle, a braking effect of the engine is commonly produced by a friction force generated between a V belt and sheaves in the V-belt continuously variable transmission. Specifically, torque can be transmitted from wheel side to engine side while engine braking.

The all terrain vehicle travels over uneven roads, mountains, steep slopes, rough terrains, shores, and the like, and therefore, the engine brake is applied more frequently than those of general vehicles.

However, when the braking effect of the engine is produced by the friction force between the V-belt and the sheave of the V-belt continuously variable transmission as described above, because the coefficient of friction changes with wear of the belt, and changes in conditions of temperature, moisture, and the like, the braking effect of the engine varies, and excessive engine braking effect, for example, may result, which does not produce a comfortable driving feel.

On the other hand, where as a countermeasure to prevent excessive engine braking effect, an average braking effect of the engine is set relatively lower by lowering a belt pressing force of a movable sheave during engine braking, the engine braking effect is somewhat insufficient, which does not produce a comfortable driving feel.

As prior art directed to controlling the engine brake, a power transmission device is disclosed in Publication of Unexamined Patent Application No. Sho. 63-186043. In this power transmission device, power of the engine is transmitted from a transmission to right and left front wheels through a front-wheel differential unit. The power is further transmitted from bevel gears to a viscous clutch through a propeller shaft, and to rear wheels through a clutch device for controlling the engine brake and a rear-wheel differential unit.

in the clutch device for the engine brake, a one-way clutch and a multi-plate-friction-type limit clutch are provided in parallel between two rotational shafts provided in series on the side of the engine and on the side of wheels, respectively. It should be appreciated that this conventional all terrain vehicle does not employ the technique for producing the braking effect by the friction force between the belt and the sheave, because of absence the V-belt continuously variable transmission.

The one-way clutch and the limit clutch are located downstream of the transmission, the front-wheel differential unit, the propeller shaft, and the viscous clutch in a power transmission path from the engine . For this reason, the transmitted torque becomes larger as it goes from the engine toward the downstream in the power transmission path, and hence, the limit clutch of large friction capacity and the one-way clutch of large transmission capacity are needed. Consequently, the clutch device for controlling the engine brake becomes large-sized and its cost is increased.

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