Vehicle braking system
First Claim
1. A vehicle braking system comprising:
- (i) at least two wheel speed sensors which generate wheel speed signals indicative of the speed of rotation of the respective wheel;
(ii) a controller responsive to said wheel speed signals for sensing skid conditions of at least two wheels and for generating skid control signals;
(iii) a fluid pressure supply;
(iv) brake command means which when operated generate a brake operating signal;
(v) a plurality of wheel brakes responsive to fluid pressure supplied thereto;
(vi) a supply means, comprising a common supply valve, for supplying brake pressure to said brakes from said fluid pressure supply in accordance with said brake operating signal;
(vii) skid control means responsive to said skid control instructions for controlling said brake pressure in a plurality of cycles each of which comprises a pressure reduction phase and a pressure increase phase;
(viii) at least one comparison means selected from the group comprising;
(a) first comparison means arranged to compare the co-efficient of friction of the lower friction surface with a predetermined threshold, and(b) second comparison means arranged to compare the relative values of the co-efficients of friction of the surfaces with which at least two wheels are engaged; and
(ix) means to operate the skid control means in a select low mode if at least one condition is met from the group comprising;
(a) the co-efficient of friction of the lower friction surface is above said predetermined threshold; and
(b) the co-efficients of friction of the surfaces with which at least two wheels are engaged differ by less than a predetermined amount,and in a select high mode if at least one condition is met from the group comprising;
(a) the co-efficient of friction of the lower friction surface is at or below said predetermined threshold, and(b) the co-efficients of friction of the said surfaces differ by at least said predetermined amount.
1 Assignment
0 Petitions
Accused Products
Abstract
A vehicle braking system comprising a controller responsive to wheel speed signals from at least two wheel speed sensors for sensing skid conditions of at least two wheels and for generating skid control instructions; a plurality of wheel brakes responsive to fluid pressure, hereinafter referred to as brake pressure, supplied thereto; a supply device, comprising a common supply valve, for supplying brake pressure to the brakes from a fluid pressure supply in accordance with a brake operating signal; and a skid controller controlled by the skid control instructions for controlling the brake pressure in a plurality of cycles each of which comprises a pressure reduction phase and a pressure increase phase, and a first comparitor to compare the co-efficient of friction of the lower friction surface with a predetermined threshold, and/or a second comparitor to compare the relative values of the co-efficients of friction of the surfaces with which at least two of the wheels are engaged and a device to operate the skid controller in a select low mode if the comparitors determine that a) the co-efficient of friction of the lower friction surface is above a predetermined absolute level, and/or b) the co-efficients of friction of the surfaces with which at least two of the wheels are engaged differ by less than a predetermined amount, and in a select high mode if the comparitors determine that a) the co-efficient of friction of a lower friction surface is at or below a predetermined absolute level, and/or b) the co-efficients of friction of the surfaces differ by at least the predetermined amount.
16 Citations
19 Claims
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1. A vehicle braking system comprising:
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(i) at least two wheel speed sensors which generate wheel speed signals indicative of the speed of rotation of the respective wheel; (ii) a controller responsive to said wheel speed signals for sensing skid conditions of at least two wheels and for generating skid control signals; (iii) a fluid pressure supply; (iv) brake command means which when operated generate a brake operating signal; (v) a plurality of wheel brakes responsive to fluid pressure supplied thereto; (vi) a supply means, comprising a common supply valve, for supplying brake pressure to said brakes from said fluid pressure supply in accordance with said brake operating signal; (vii) skid control means responsive to said skid control instructions for controlling said brake pressure in a plurality of cycles each of which comprises a pressure reduction phase and a pressure increase phase; (viii) at least one comparison means selected from the group comprising; (a) first comparison means arranged to compare the co-efficient of friction of the lower friction surface with a predetermined threshold, and (b) second comparison means arranged to compare the relative values of the co-efficients of friction of the surfaces with which at least two wheels are engaged; and (ix) means to operate the skid control means in a select low mode if at least one condition is met from the group comprising; (a) the co-efficient of friction of the lower friction surface is above said predetermined threshold; and (b) the co-efficients of friction of the surfaces with which at least two wheels are engaged differ by less than a predetermined amount, and in a select high mode if at least one condition is met from the group comprising; (a) the co-efficient of friction of the lower friction surface is at or below said predetermined threshold, and (b) the co-efficients of friction of the said surfaces differ by at least said predetermined amount. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A vehicle braking system comprising:
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(i) at least two wheel speed sensors which generate wheel speed signals indicative of the speed of rotation of the respective wheel; (ii) a controller responsive to said wheel speed signals for sensing skid conditions of at least two wheels and for generating skid control signals; (iii) a fluid pressure supply; (iv) brake command means which when operated generate a brake operating signal; (v) a plurality of wheel brakes responsive to fluid pressure supplied thereto; (vi) a supply means, comprising a common supply valve for supplying brake pressure to said brakes from said fluid pressure supply in accordance with said brake operating signal; (vii) skid control means responsive to said skid control instructions for controlling said brake pressure in a plurality of cycles each of which comprises a pressure reduction phase and a pressure increase phase; (viii) comparison means arranged to compare the relative values of the co-efficient of friction of the surfaces with which at least two wheels are engaged and comprising means to control the brake pressure above a threshold for a limited time period; (ix) means to monitor the co-efficient of friction of the higher friction surface; (X) means to cause the controller to adopt a select high mode in response to the speed of the wheel engaged with the higher friction surface being above a threshold during the limited period; and (xi) means to cause the controller to adopt a select low mode in response to the speed of the wheel engaged with said higher friction surface being below the threshold during the limited time period. - View Dependent Claims (19)
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Specification