FR2622517A1 - TRANSMISSION MECHANISM FOR AGRICULTURAL UTILITY VEHICLE - Google Patents

Abstract

Gearbox 3 is dimensioned for a lower input torque, compared to the higher torque of engine 1, and between clutch 2 and gearbox 3 an overload limiter 6 is installed that interrupts the transmission when this input torque is reached, with a one-way coupling 7 preventing backward rotation of the transmission line.

Description

The invention relates to a transmission mechanism for a motor vehicle.

  utility vehicle for agriculture with a torque transmission line from the engine via a clutch and a gearbox to the drive wheels and a PTO shaft driven by the

  motor independently of this torque transmission line.

  Such commercial vehicles, which are above all agricultural tractors, have to fulfill various functions. They are used on the one hand simply for the traction of various trailers or for plowing with a carried or towed plow, on the other hand they are able, due to the existence of the PTO, not only to tow machines work, but also to train work tools. For a simple towing a comparatively low power motor would be sufficient. But when a working machine is towed and has to be driven by the PTO shaft, more working power is required, in particular with working machines whose working width significantly exceeds the track of the vehicle. utility. The same is true when, in addition to the working machine, a trailer is also provided, when for example a harvester-chopper is coupled with a forage trailer and the latter is gradually filled. For a relatively low torque provided by the engine for a simple towing, a gearbox with a small dimension in correspondence would suffice as much as the higher torque required for the working machine with rotary working tools is transmitted by

  the shaft of the PTO independent of the gearbox.

  But until now, the gearbox is still produced according to the torque of the engine, which leads not only to a high weight of -The whole vehicle but obviously also to manufacturing and purchase costs higher. The object of the invention is therefore to eliminate this defect and to provide a transmission mechanism with which a reduction in the weight of the vehicle and in production costs can be obtained despite a relatively higher power.

of the motor.

  The invention achieves this object because the gearbox is dimensioned for a lower input torque in comparison with the higher torque of the engine and that on the torque transmission line is mounted between the clutch and the gearbox. speed an overload limiter cutting the transmission when this rotation input torque is reached with a unidirectional coupling or a similar member, preventing rotation behind the line of

torque transmission. -

  The vehicle can be equipped with an engine which provides the highest torque required by particularly large working machines or for the combined driving of a working machine and a trailer. However, in accordance with the invention, the gearbox is dimensioned only for an essentially lower torque since, as a general rule, for simple towing work, the observation of an essentially lower torque has been made. But, if for some reason a higher torque is transmitted through the gearbox

  lower dimensioned speed then the limiter of -

  overload would act and separate the gearbox from the engine

  without the driver having to take the corresponding measures.

  The smaller gearbox is therefore

  protected against deterioration due to trans-

  mission of a higher couple. It is true that the vehicle stops, but the engine and the PTO shaft continue to run and, when working a harvesting machine

  or similar, engorgement thereof is avoided.

  In this the invention stems from the knowledge that an overshoot of the admissible torque by the gearbox can only come each time from the transmission

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  on the engine side, but never on the thrust of a heavy trailer or similar machine, for example on a slope. This is due to the power transmission capacity by the drive wheels which is notably weaker in the case of traction operation. The higher force developed during training comes on the one hand from the increase in the load on the rear axle due to the nose up of the utility vehicle, on the other hand from the stability of the entire mobile system. On the other hand, during pushing operation, the braking moment on the rear wheels loads the rear axle and leads to the instability of the sliding system, to a lateral drift of the rear wheels and to a

  across the utility vehicle.

  In the latter case the circumferential force at the wheels decreases further, so that even in unfavorable conditions, that is to say when the driver does not apply the brake at all and the thrust is exerted only on the engine , the permissible input torque by the gearbox can never be reached from the drive wheels of the vehicle. But, usually, on rough roads the brakes are applied to maintain the stability of the pipe and thus the torque transmitted through the gearbox decreases further. It follows that it is more than sufficient to guarantee the gearbox by the overload limiter which precedes it, regardless of its type of construction, since it is always stressed in traction only and thus it

is fully protected.

  If the admissible input torque is exceeded due to an excessive trailer or an excessive traction force on flat ground, then, as

  as already mentioned, the utility vehicle simply stops

  plement. On the other hand, it would be critical that an interruption of the effort between the engine and the drive wheels occur on an uphill course in the mountains, because then the assembly could roll backwards and be damaged. According to the invention the overload limiter is therefore combined with the unidirectional coupling or a similar member preventing rotation in the reverse direction of the transmission line, which could be a freewheel or ratchet device. This unidirectional coupling or a similar member does not harm the rotation of the transmission line in the direction of rotation of the motor but prohibits at the time of opening of the overload limiter coupling, rotation in the opposite direction of the line of transmission and therefore reversing the

  utility vehicle, this also happens without inter-

  the driver and thus total operating safety is ensured. The one-way coupling could still be combined into a single construction unit

with the overload limiter.

  It is already known (DE-OS-2.902.557, GB-PS-1.599.941 DD-PS-16598 and DE-AS2.910.395) to provide an overload limiter on the PTO shaft or on the machine

  of work driven by the latter. But, this is uni-

  only to protect the driven working machine against deterioration by an overload due to too high a torque, which has nothing to do with a measure for the reduction

  sizing of the gearbox.

  We will now give a description of an example

  for producing a transmission mechanism in accordance with the invention for an agricultural utility vehicle. We are

  refer to the attached single figure which is a representation

  schematic statement of this mechanism.

  From the engine 1 a transmission line extends to the drive wheels 4 of the vehicle via

  a driving clutch 2 and a gearbox 3.

  Independently of this transmission line, there is a PTO driven by means of a device.

  disengageable coupling associated with the driving clutch.

  According to the invention an overload limiter 6 is placed in front of the gearbox 3 whose input torque is reduced compared to the highest torque of the motor and this limiter interrupts the transmission of rotation when this torque entry is reached. In addition, there is also provided in front of the gearbox 3 a one-way coupling 7, that is to say a freewheel or ratchet device, so that no rotation in reverse or backward direction of the part transmission line cannot occur.

Claims (1)

  Transmission mechanism for an agricultural utility vehicle with a transmission line   torque from the engine via a clutch   from a gearbox to the drive wheels and a PTO shaft driven by the engine independently of this torque transmission line, characterized in that the gearbox (3) is dimensioned for a torque of lower input rotation, in comparison with the higher torque of the engine, and there is installed on the torque transmission line between the clutch (2) and the gearbox (3) cutting overload limiter (6) the transmission when this rotation input torque is reached, with a unidirectional coupling (7) preventing rotation behind the torque transmission line.