FR2622159A3 - ELECTRONIC DEVICE FOR CONTROLLING FOUR-WHEEL DRIVE TRANSMISSION AND DIFFERENTIALS OF A TRACTOR - Google Patents

Abstract

The control device of the four-wheel drive unit 8 and of the front and rear differentials 4, 5 of a tractor 1 comprises means 10, 11, 12 detecting the operating conditions of the tractor and an electronic control unit 9 receiving the signals from the sensors and arranged to control electric actuators and being able to be set by means of selectors 13, 14, 15 in two modes of operation with manual control of the operations of engagement and disengagement of the unit 8 and of locking and unlocking the differentials 4, 5 and an automatic mode of operation in response to signals from the sensors. Application in particular to agricultural tractors.

Description

The present invention generally relates to

  tractors equipped with devices to engage and disengage the four-wheel drive and

  to lock and unlock the front and rear differentials

  Rière. These devices are normally active by means of

  electrical distributors, usually electromagnetic valves

  gniques, manually operated by the driver of

  tor. The selection of switching on or off of the four-wheel drive transmission and the locking and unlocking of differentials is linked in a certain manner.

  general principle of ensuring permanent traceability

  maximum extent during fieldwork and to facilitate

  maneuvering and moving operations.

  Since, as indicated, this series

  can be performed in a conventional manner only according to the driver's desire, it depends solely on his skill and can not always be optimal in relation to

  the operating conditions of the tractor.

  The object of the present invention is to avoid the

  indicated above and to provide a control device

  operationally associated with electric actuators

  the four-wheel drive and the four-wheel drive

  the tractor and regarding the possibility of

  manually, while being able to control the engagement

  and disengagement of the four-wheel drive

  drive and locking and unlocking the differentials

  the tractor in an automatic and optimal way.

  The control device according to the invention is characterized in that it comprises means for detecting the

  operating conditions of the tractor and a com-

  electronic control powered by signals from

  yens in the form of sensors and arranged to control

  electric actuators; the electronic control unit

  that can be set using selectors in three modes

  different types of operation, in two of which

  switching on and off of the transmission

  four-wheel drive are made manually,

  say that in the third mode the command unit

  of these functions in response to the signals delivered by the sensor-shaped means.

  These sensor-shaped means advantageously include.

  steering angle sensors, asymmetrical braking conditions and speed at which the tractor

moves.

  With these sensors, the electronic control unit

  that is able to detect the operating conditions of the tractors and therefore to control the electric actuators of the devices to engage and disengage the transmission four-wheel drive

  and locking and unlocking the differentials.

  For example, if the speed at which the tractor

  instead, exceeds a predetermined threshold value, the electronic unit causes the disengagement of the four-wheel drive transmission. In the case of wheel steering

  forward at a certain angle or during a unilateral

  the control unit automatically unlocks the differentials.

  In practice, the logical system of operation

  The electronic unit can be used to optimize the function of the tractors in a way that depends exactly on the different operating conditions, independently

the wishes of the driver.

  In addition, the device according to the present invention

  It also guarantees the possibility of manual

  if this proves necessary in particular circumstances

res.

  The invention will now be described in detail

  with reference to the attached drawing, indicated only at

  non-limiting example and showing a tractor in schematic form, with a schematic representation of a

  electronic control device according to the invention.

  In reference to the drawing, an agricultural tractor is de-

  signed by a majority of 1 and

  front wheels 2 and rear wheels 3, which are associated with

  cited respectively & a differential before and at a different

  rear end, schematically indicated by 4.5.

  The front wheels 2 are oriented in known manner by

  a steering wheel 6, and a braking circuit not shown action-

  born by means of the pedal device 7 is provided so as to allow symmetrical or asymmetrical braking of the wheels

2 and 3.

  The rear wheels 3 are driven continuously, while the front wheels 2 can be made motive

  to obtain a movement of the tractor with a trans-

  mission and four-wheel drive, thanks to a standard device

  8 transmission of four-wheel drive.

  In known manner, the two differentials 4 and 5 are

  equipped with respective locking and unlocking devices

  rusting, and the four-wheel drive transmission unit 8

  these comprises, also in a known manner, a device for

  latching and disengaging. For simplicity, these

  positive are not represented since they are well

  known to experts of this technique and are actuated normal-

  with the help of respective actuators, namely

  conventional electromagnetic valves controlled manually-

  is lying. According to the invention, the tractor 1 is equipped

  a control device which, while retaining the possibility of

  of a marine control, is arranged in such a way as to

  automatically send the electromagnetic valves

  positive to engage and disengage

  of the four-wheel-drive transmission unit 8 and the

  ratching and unlocking of differentials 4 and 5.

  This device consists of a control unit

  electronics 9 formed by a programmable microprocessor connected to a series of sensors installed on the tractor 1 and arranged to send to the control unit 9 signals indicative of actual operating conditions of the tractor. These sensors may comprise a sensor 10 of the steering angle, associated with the steering wheel 6, a sensor 11 of an asymmetric braking associated with the pedal device 7, and

  a sensor 12 of the tractor speed.

  The control unit 9 is arranged so as to function

  in three operating modes, using the same number of selector buttons 13, 14 and 15. The selector 13 allows a selection to be made between manual operation

  and automatic operation of the unit 9, and selections

  14 and 15 make it possible to manually control the

  ratcheting and unlocking the differentials 4 and 5 and

  the switching on or off of the transmission unit 8

  four-wheel drive mission, when button 13 is

in the "manual" position.

  When the selection button 13 is in the position

  "automatic" operation, the lock / unlock operations

  4.5 differential and interlocking / disengaging

  of the four-wheel drive transmission unit 8 are

  independent of the wishes of the operator, in accordance with the principle of ensuring

  maximum traction when working in the field and easily

  Automatically dispatch the maneuvering and moving operations, which require the differentials 4,5 to be unlocked and / or the transmission to be carried out in two

drive wheels.

  The electronic control unit "detects" the con-

  actual operating conditions of the tractor using the

  10 of the steering angle, the brake sensor 11 dis-

  symmetrical and sensor 12 of the wheel speed angle and for example causes the disengagement of the transmission unit 8 four-wheel drive if the speed exceeds a certain predetermined threshold value, or the unlocking of the differentials 4 and 5 in the case of wheel steering

  before a certain angle or in the case of

  one-sided braking.

  The logic operating system of the control unit 9 in the "automatic" operating mode can

  be illustrated by the following example.

  When the selector 13 is in the "auto-

  the transmission unit 8 is normally engaged and the differentials 4 and 5 are

locked.

  Differentials 4 and 5 are unlocked (

reversible) if:

  the speed of the tractor 1 is greater than one

  their predetermined threshold, or - an asymmetrical braking occurs, or - the steering takes place on an angle greater than a predetermined threshold value and the speed is simultaneously

  greater than a previously established threshold value.

  The four-wheel drive unit 8 is disengaged (reversibly) if: - the tractor speed is greater than the predetermined threshold speed (optionally)

  - the steering angle exceeds a pre-defined threshold angle

determined.

  Naturally the object of the present invention is

  models with the same utility, thanks to the same

me innovative concept.

  Thus, for example, additional processors can be provided to improve the system response in

  certain operating conditions. For example, in order to

  an abnormal unlocking due to an indiscriminate

  of the wheels, a protective system can be provided.

  The unlocking of the differentials 4 and 5 and the

  triggering of the four-wheel drive unit 8

  when the acceleration of the drive wheels is higher than

re to a predetermined threshold.

Claims (2)

  1. Tractor with devices for   latch and disengage a four-wheel   and lock and unlock front and rear differentials by means of respective electric actuators, characterized in that a control device is provided which   is operationally associated with the electronic actuators   devices for engaging and disengaging the four-wheel drive transmission (8) and locking and unlocking the differentials (4,5), and includes means (10,11,12) for detecting the conditions the tractor (1) and an electronic control unit (9) powered by signals from   means in the form of sensors (10, 11, 12) and arranged   to control the electric actuators; the unit of   electronic control (9) which can be adjusted by means of   readers (13,14,15k Bans three different modes of operation-   two of which the switching on and off operations of the four-wheel-drive transmission (8) and the locking and unlocking of the differential (5) are carried out manually, while in the third mode the unit comerns the automatic execution of these functions in   response to the signals delivered by the cap-shaped means tors (10,11,12).   Tractor according to Claim 1, characterized in that the sensor-shaped means comprise a sensor   (10) of the steering angle, an asymmetric brake   tramp (11) and a sensor (12) of the tractor speed (1).