Utility vehicle braking

Patent metadata

Field	Value
Publication number	US-11084529-B2
Application number	US-201816770455-A
Country	US
Kind code	B2
Filing date	Oct 26, 2018
Priority date	Dec 8, 2017
Publication date	Aug 10, 2021
Grant date	Aug 10, 2021

Abstract

A method of brake steering in a four-wheel drive utility vehicle having a driven front axle carrying at least two front wheels, a driven rear axle carrying at least two rear wheels, a powertrain delivering torque to the front axle via a first motor and to the rear axle via a second motor, a controlled clutch arrangement operable to couple the outputs of the first and second motors to vary the distribution of delivered torque between the front and rear axles, and independently operable service brakes on each of the front and rear wheels. The method includes determining a difference in wheel velocity between front and rear wheels; comparing the difference to a threshold value and, when exceeded, automatically engaging the controlled clutch arrangement. A determination is made as to whether or not the vehicle is performing a brake steering manoeuvre and the threshold value is adjusted accordingly. Additional braking force may be applied from independently operable park brakes on the rear wheels in inverse relationship to the level of service brake force applied.

First claim

The invention claimed is:

1. A method of brake steering in a four-wheel drive utility vehicle having at least two front wheels on a driven front axle, at least two rear wheels on a driven rear axle, a powertrain connected to the front and the rear axles, a first motor which drives the front axle, a second motor which drivees the rear axle, a controlled clutch arrangement connected to the first and the second motors, and independently operable service brakes on each of the front and the rear wheels, wherein the method comprises:
sensing when the vehicle is traveling in a substantially straight path, entering a driven turn, and entering a braking turn; determining a difference in wheel velocity between the front and the rear wheels;
comparing the difference in wheel velocity to a threshold value, wherein a first level of the threshold value is designated when the vehicle is traveling in a straight path, a second level of the threshold value is designated when the vehicle is entering a driven turn, and a third level of the threshold value is designated when the vehicle is entering a braking turn; engaging the controlled clutch arrangement when the difference in wheel velocity exceeds the designated threshold level, coupling an output of the first and the second motors, and varying distribution of delivered torque between the front and the rear axles based on the designated threshold level; and when the first level of the threshold value is designated, applying a corresponding first braking force to independently-operable service brakes on each of the front and rear wheels, when the second level of the threshold value is designated, applying a corresponding second braking force, higher than the first, to the service brakes on the front and the rear wheels, and when the third level of the threshold value is designated, applying a corresponding third level of braking force, higher than the second, to the service brakes on the front and the rear wheels adjacent to an inside of the turn.

2. The method of brake steering of claim 1 , further comprising:
with the vehicle entering the braking turn additionally applying a predetermined level of braking force to independently-operable parking brakes on each of the rear wheels adjacent to the inside of the turn.

3. The method of brake steering of claim 2 , wherein the level of braking force applied to the parking brakes of the rear wheels on entering the braking turn is substantially proportional to the level of braking force applied to the service brakes of the same rear wheels.

4. The method of brake steering of claim 1 , wherein the level of braking force applied to the service brakes during the braking turn is determined by the level of pressure exerted on a user-operable brake control of the vehicle.

5. The method of brake steering of claim 1 , wherein at least one of the second and third levels of the threshold value is determined at least partially by the vehicle wheelbase.

6. The method of brake steering of claim 1 , further comprising adapting at least one of the second and the third threshold levels in response to changes to a track width of the vehicle.

7. The method of brake steering of claim 1 , further comprising adapting at least one of the second and third threshold levels in response to changes to a maximum steering angle of the vehicle.

8. The method of brake steering of claim 1 wherein a ratio of the braking force applied to the service brakes of the front wheels and the breaking force applied to the service breaks of the rear wheels is controllably varied based on one or more factors comprising:
gross weight of the vehicle;
amount of front and/or rear ballasting carried by the vehicle;
weight of a towed or carried implement;
measured wheel-slip for the one or more wheels of the vehicle;
tyre pressure in one or more tyres on the respective wheels of the vehicle;
angle of the turn of the vehicle;
current speed of the vehicle;
ambient conditions external to the vehicle.

9. A driveline for a four-wheel drive utility vehicle comprising:
a driven front axle carrying at least two front wheels;
a driven rear axle carrying at least two rear wheels;
a powertrain delivering torque to the front axle via a first motor and to the rear axle via a second motor;
a controlled clutch arrangement configured to, when engaged, couple outputs of the first and the second motors and vary distribution of the delivered torque between the front and the rear axles;
independently operable service brakes on each of the front and the rear wheels;
first and second sensors respectively configured to determine the velocity of the front and the rear wheels;
a turn sensor configured to measure a turning angle of the vehicle;
a non-transitory data storage unit holding data defining a first, a second and a third level of a threshold value; and
a control system coupled with the powertrain, the sensors, the data storage unit, the clutch arrangement and the service brakes, configured to:
determine from the first and second sensors, a difference in wheel velocity between the front and the rear wheels;
determine from the turn sensor when the vehicle travels a substantially straight path, compare the difference in wheel velocity to the first level of the threshold value and when exceeded, engage the controlled clutch arrangement;
determine from the turn sensor when the vehicle enters a driven turn, compare the difference in wheel velocity to the second level of the threshold value, which second level is higher than the first and when exceeded, engage the controlled clutch arrangement; and determine at least partly from the turn sensor when the vehicle enters a braking turn, compare the difference in wheel velocity to the third level of the threshold value, which third level is higher than the second, and when exceeded, engage the controlled clutch arrangement and apply a corresponding braking force to the service brakes of the front and the rear wheels adjacent the inside of the turn.

10. The driveline of claim 9 , further comprising independently-operable parking brakes on the rear wheels, wherein the control system is configured to detect when the vehicle is entering the braking turn, and additionally apply a predetermined level of braking force, to the parking brake on the rear wheels adjacent to the inside of the turn.

11. The driveline of claim 10 , wherein the control system is configured to determine and apply a level of braking force to the parking brakes of the rear wheels of the vehicle entering the braking turn wherein, the applied braking force is substantially proportional to the level of braking force applied to the service brakes of the same rear wheels.

12. The driveline of claim 9 , comprising a user-operable brake control and sensor for determining applied pressure, wherein the control system is configured to set the level of braking force applied to the service brakes during a turn based on the level of pressure exerted on the user-operable brake control.

13. The driveline of claim 9 , wherein the control system includes an input for data and is configured to vary at least one of the first, second and third levels of the threshold value based on an input value for one or more factors comprising a vehicle wheelbase, a vehicle track width, and a maximum steering angle of the vehicle.

14. A utility vehicle comprising the driveline of claim 9 .

15. The utility vehicle of claim 14 , further comprising a geographical positioning system coupled with the control system, wherein the control system is configured to not implement brake steering on determination that the vehicle

Assignees

• Agco Int Gmbh

Inventors

• Brenninger Martin

Classifications

• B60T13/66

  Electrical control in fluid-pressure brake systems · CPC title

• B62D11/183

  Control systems therefor · CPC title

• B62D11/08 Primary

  using brakes or clutches as main steering-effecting means · CPC title

• B60T11/21

  with two pedals operating on respective circuits, pressures therein being equalised when both pedals are operated together, e.g. for steering (steering non-deflectable wheels or endless tracks by differentially driving ground-engaging elements on opposite vehicle sides using brakes as main steering effecting means B62D11/08) · CPC title