Differential lock control system responsive to a plurality of vehicle parameters

Claim 2

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means automatically causing the locking means to lock the differential in response to a predetermined condition of a steering system of the vehicle, the second means being inoperative to unlock a locked differential.

Claim 3

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential, the first means being responsive to vehicle braking to cause the locking means to unlock the differential when the vehicle is braked; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means automatically causing the locking means to lock the differential in response to a predetermined condition of a steering system of the vehicle, the second means being inoperative to unlock a locked differential.

Claim 4

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential, the first means being responsive to vehicle braking to cause the locking means to unlock the differential when the vehicle is braked; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means automatically causing the locking means to lock the differential in response to a predetermined condition of a steering system of the vehicle, the second means being inoperative to unlock a locked differential.

Claim 5

The invention of claim 2, wherein the control system comprises: a latching relay having a relay switch coupled between the locking means and a potential source, the first means comprising a brake-operated, normally closed switch coupled between the potential source and the relay switch, the second means comprising a steering-responsive switch coupled between the potential source and the relay and operable only to close the relay switch in response to said predetermined condition, the locking means locking the differential only when connected to the potential source.

Claim 6

The invention of claim 3, wherein the control system further comprises: a normally open, momentary contact, operator-controlled switch coupled between the potential source and the relay and operable only to cause the locking means to lock the differential in response to operator closing thereof.

Claim 7

The invention of claim 3, wherein the control system further comprises: an operator-controlled on/off switch coupled betwen the potential source and the steering-responsive switch and operable to prevent closing of the relay switch in response to operation of the steering-responsive switch.

Claim 8

The invention of claim 3, wherein the control system further comprises: a vehicle speed sensor and; a speed-responsive switch coupled in series with the brake-operated switches and operative to unlock the differential when vehicle speed exceeds a predetermined minimum speed.

Claim 9

The invention of claim 3, wherein the second means further comprises: a vehicle wheel slip sensor; and a slip-responsive switch coupled in series with the steering-responsive switch and operable to lock the differential when second wheel slippage is less than a predetermined mimimum slippage.

Claim 10

The invention of claim 3, wherein the second means further comprises: a draft sensor for sensing draft forces applied to the vehicle; and a draft-responsive switch coupled in series with the steering-responsive switch and the slip-responsive switch and operable to prevent locking of the differential when sensed draft force is below a predetermined draft force.

Claim 11

The invention of claim 3, wherein the second means further comprises: a vehicle wheel slip sensor; a slip-responsive switch coupled in series with the steering-responsive switch and operable to lock the differential when sensed wheel slippage is less than a predetermined minimum slippage; a draft sensor for sensing draft forces applied to the vehicle; and a draft-responsive switch coupled in series with the steering-responsive switch and the slip-responsive switch and operable to prevent locking of the differential when sensed draft force is below a predetermined draft force.

Claim 12

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means comprising pressure sensors for sensing fluid pressures in hydraulically-operated steering systems of the vehicle, and means coupled to the pressure sensors and to the locking means for locking the differential when pressures sensed by the pressure sensors are substantially equal.

Claim 13

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means comprising pressure sensors for sensing fluid pressures in hydraulically-operated steering systems of the vehicle, and means coupled to the pressure sensors and to the locking means for locking the differential when pressures sensed by the pressure sensors are substantially equal.

Claim 14

The invention of claim 10, wherein: the pressure sensors sense working pressures in steering actuators of the steering system.

Claim 15

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means comprising a pressure sensor for sensing fluid pressure in an hydraulically-operated steering actuator of the vehicle, a first relay coupled to the pressure sensor and changing between first and second states in response to changes in the sensed pressure, a potential source, and a second relay operable in response to operation of the first relay to control communication between the potential source and the locking means, the locking means locking the differential when communicated with the potential source.

Claim 16

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means comprising a pressure sensor for sensing fluid pressure in an hydraulically-operated steering actuator of the vehicle, a first relay coupled to the pressure sensor and changing between first and second states in response to changes in the sensed pressure, a potential source, and a second relay operable in response to operation of the first relay to control communication between the potential source and the locking means, the locking means locking the differential when communicated with the potential source.

Claim 17

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means comprising first and second pressure sensors, each sensing fluid pressure in a corresponding one of first and second hydraulically-operated steering actuators of the vehicle, a normally-closed (N.C.) dual solenoid-operated relay having a switch controlled by first and second solenoids, each solenoid being operatively coupled to one of the pressure sensors, at least one of the solenoids operating to open the switch when the sensed pressures in the actuators are unbalanced by a predetermined amount, a potential source, a first normally-open (N.O.) relay coupled between the potential source and the locking means, the locking means locking the differential when the first normally open relay is closed, and a second N.O. relay coupled between the N.C. relay and the first N.O. relay and operable to close the first N.O. relay in response to closing of the N.C. relay.

Claim 18

In a vehicle having a differential and locking means for locking and unlocking the differential, a differential lock control system comprising: first means coupled to the locking means and responsive to a first vehicle function and operable only to automatically unlock the differential; and second means coupled to the locking means and responsive to at least a second vehicle function and operable only to automatically lock an unlocked differential, the second means comprising first and second pressure sensors, each sensing fluid pressure in a corresponding one of first and second hydraulically-operated steering actuators of the vehicle, a normally-closed (N.C.) dual solenoid-operated relay having a switch controlled by first and second solenoids, each solenoid being operatively coupled to one of the pressure sensors, at least one of the solenoids operating to open the switch when the sensed pressures in the actuators are unbalanced by a predetermined amount, a potential source, a first normally-open (N.O.) relay coupled between the potential source and the locking means, the locking means locking the differential when the first normally open relay is closed, and a second N.O. relay coupled between the N.C. relay and the first N.O. relay and operable to close the first N.O. relay in response to closing of the N.C. relay.