Brake pressure control system for motor vehicles

Claim 2

A brake pressure control system for a motor vehicle having wheels, comprising: skidding condition detecting means for detecting a skidding condition of at least one of the wheels based on at least a rotational speed of said at least one wheel and a speed of the motor vehicle in each of predetermined periodic cycles; control means for determining a continuous pressure-changing gradient according to a difference between said skidding condition detected by said skidding condition detecting means and a target skidding condition, said pressure-changing gradient representing one of a continuous pressure-increasing gradient and a continuous pressure-reducing gradient, and for increasing and reducing a braking pressure applied to said at least one wheel according to said pressure-changing gradient representing a continuous pressure-increasing gradient and said pressure-changing gradient representing a continuous pressure-reducing gradient, respectively, so that the skidding condition detected by said skidding condition detecting means will approach said target skidding condition; timer means for monitoring periods of time in which the braking pressure is continuously increased and reduced, respectively, by said control means, first correcting means for correcting said pressure-changing gradient representing a pressure-increasing gradient depending on said period of time, monitored by said timer means, in which the braking pressure is continuously increased; and second correcting means for correcting said pressure-changing gradient representing a pressure-reducing gradient depending on said period of time, monitored by said timer means, in which the braking pressure is continuously reduced.

Claim 3

A brake pressure control system according to claim 1, wherein said first correcting means comprises means for increasing the pressure-changing gradient representing a pressure-increasing gradient, in proportion to a period of time, monitored by said timer means, in which the braking pressure is continuously increased.

Claim 4

A brake pressure control system according to claim 1, wherein said second correcting means comprises means for increasing the pressure-changing gradient representing a pressure-reducing gradient, after the braking pressure has started being reduced by said control means.

Claim 5

A brake pressure control system according to claim 1, wherein said second correcting means comprises means for increasing the pressure-changing gradient representing a pressure-reducing gradient, in proportion to a period of time, monitored by said timer means, in which the braking pressure is continuously reduced, after said period of time has exceeded a predetermined period of time.

Claim 6

A brake pressure control system for a motor vehicle having a plurality of wheels, comprising: a plurality of wheel speed sensors for detecting rotational speeds of the wheels, respectively; first calculating means for calculating wheel speeds and wheel accelerations based on detected signals from said wheel speed sensors; second calculating means for calculating an estimated vehicle speed from the wheel speeds and also calculating an estimated vehicle deceleration from said estimated vehicle speed; reference speed calculating means for calculating a target reference speed from said estimated vehicle speed; deviation calculating means for calculating first deviations between said wheel speeds and said reference speed and second deviations between said wheel accelerations and said estimated vehicle deceleration; actuator means having a pressure-increasing position for increasing brake pressures applied to the wheels, a pressure-reducing position for reducing brake pressures applied to the wheels, and a pressure-holding position for holding brake pressures applied to the wheels; and control means for classifying pressure-reducing and pressure-increasing modes based on said first and second deviations calculated by said deviation calculating means, for applying a first control signal to said actuator means to actuate the actuator means with an actuation time ratio, represented by said first control signal, between said pressure-reducing position and said pressure-holding position depending on said first and second deviations in said pressure-reducing mode to control a pressure-changing gradient representing a pressure-reducing gradient of the brake pressures, and for applying a second control signal to said actuator means to actuate the actuator means with an actuation time ratio, represented by said second control signal, between said pressure-increasing position and said pressure-holding position depending on said first and second deviations in said pressure-increasing mode to control a pressure-changing gradient representing a pressure-increasing gradient of the brake pressures.

Claim 7

A brake pressure control system for a motor vehicle having a plurality of wheels, comprising: a plurality of wheel speed sensors for detecting rotational speeds of the wheels, respectively; first calculating means for calculating wheel speeds and wheel accelerations based on detected signals from said wheel speed sensors; second calculating means for calculating an estimated vehicle speed from the wheel speeds and also calculating an estimated vehicle deceleration from said estimated vehicle speed; reference speed calculating means for calculating a target reference speed from said estimated vehicle speed; deviation calculating means for calculating first deviations between said wheel speeds and said reference speed and second deviations between said wheel accelerations and said estimated vehicle deceleration; actuator means having a pressure-increasing position for increasing brake pressures applied to the wheels, a pressure-reducing position for reducing brake pressures applied to the wheels, and a pressure-holding position for holding brake pressures applied to the wheels; and control means for classifying pressure-reducing and pressure-increasing modes based on said first and second deviations calculated by said deviation calculating means, for applying a first control signal to said actuator means to actuate the actuator means with an actuation time ratio, represented by said first control signal, between said pressure-reducing position and said pressure-holding position depending on said first and second deviations in said pressure-reducing mode to control a pressure-changing gradient representing a pressure-reducing gradient of the brake pressures, and for applying a second control signal to said actuator means to actuate the actuator means with an actuation time ratio, represented by said second control signal, between said pressure-increasing position and said pressure-holding position depending on said first and second deviations in said pressure-increasing mode to control a pressure-changing gradient representing a pressure-increasing gradient of the brake pressures.

Claim 8

A brake pressure control system according to claim 5, further comprising: timer means for monitoring periods of time in which the braking pressures are continuously increased and reduced, respectively; and correcting means for correcting said pressure-changing gradient depending on said periods of time monitored by said timer means.

Claim 9

A brake pressure control system according to claim 6, wherein said correcting means comprises means for increasing said pressure-changing gradient representing a pressure-increasing gradient, in proportion to a period of time, monitored by said timer, in which the braking pressures are continuously increased.

Claim 10

A brake pressure control system according to claim 6, wherein said correcting means comprises means for increasing said pressure-changing gradient representing a pressure-reducing gradient, after the braking pressure has started being reduced by said control means.

Claim 11

A brake pressure control system according to claim 6, wherein said correcting means comprises means for increasing a pressure-changing gradient representing a pressure-reducing gradient, in proportion to a period of time, monitored by said timer means, in which the braking pressures are continuously reduced, after said period of time has exceeded a predetermined period of time.

Claim 12

A brake pressure control system according to claim 5, wherein said control means comprises means for calculating a quantity W indicative of skidding conditions of each of the wheels according to the equation: W=K.sub.A (V.sub.W =V.sub.S)+K.sub.A (G.sub.W -G.sub.S) K A , K S are constants, V W is the wheel speed, V S in the reference speed, G W is the wheel acceleration, and G S is the vehicle deceleration.

Claim 13

A brake pressure control system according to claim 10, wherein said control means comprises means for increasing said pressure-changing gradient in proportion to an absolute value of said quantity W indicative of skidding conditions of each of the wheels, means for calculating the pressure-changing gradient representing a pressure-increasing gradient for increasing the braking pressures when said quantity W is positive, and means for calculating the pressure-changing gradient representing a pressure-reducing gradient for reducing the braking pressures when said quantity W is negative.

Claim 14

A brake pressure control system according to claim 5, wherein said control means includes means for selecting said first and second actuation time ratios from a plurality of predetermined actuation time ratios.

Claim 15

A brake pressure control system according to claim 5, wherein said actuator means comprises three-position valves each having said pressure-increasing position, said pressure-reducing position, and said pressure-holding position.

Claim 16

A brake pressure control system for a motor vehicle having a wheel, comprising: skidding condition detecting means for detecting a skidding condition of the wheel based on at least a rotational speed of the wheel and a speed of the motor vehicle; calculating means for calculating a continuous pressure-reducing gradient according to the skidding condition when the skidding condition detected by said skidding condition detecting means exceeds a target slipping condition; pressure-reducing means for reducing a braking pressure to be applied to the wheel, according to said pressure-reducing gradient calculated by said calculating means; timer means for monitoring a period of time in which the braking pressure is reduced by said pressure-reducing means and correcting means for correcting said pressure-reducing gradient depending on said period of time monitored by said time means.

Claim 17

A brake pressure control system for a motor vehicle having a wheel, comprising: skidding condition detecting means for detecting a skidding condition of the wheel based on at least a rotational speed of the wheel and a speed of the motor vehicle; calculating means for calculating a continuous pressure-reducing gradient according to the skidding condition when the skidding condition detected by said skidding condition detecting means exceeds a target slipping condition; pressure-reducing means for reducing a braking pressure to be applied to the wheel, according to said pressure-reducing gradient calculated by said calculating means; timer means for monitoring a period of time in which the braking pressure is reduced by said pressure-reducing means and correcting means for correcting said pressure-reducing gradient depending on said period of time monitored by said time means.

Claim 18

A brake pressure control system for a motor vehicle having a plurality of wheels, said system comprising: skidding condition quantity detecting means for detecting a skidding condition quantity of at least one of the wheels based on at least a rotational speed of said at least one wheel and a speed of the motor vehicle in each of predetermined periodic cycles; control means for generating, based on the skidding condition quantity detected by said skidding condition quantity detecting means, a first control signal to increase a pressurechanging gradient representing a pressure-reducing gradient of brake pressures applied to the wheels as the skidding condition quantity varies in a direction from a target skidding condition amount toward a wheel locked condition, and for generating a second control signal to increase a pressure-changing gradient representing a pressure-increasing gradient of brake pressures applied to the wheels as the skidding condition quantity varies in a direction from said target skidding condition amount toward a wheel unlocked condition; and actuator means having a pressure-increasing position for increasing the brake pressures applied to the wheels, a pressure-reducing position for reducing the brake pressures applied to the wheels, and a pressure-holding position for holding the brake pressures applied to the wheels; wherein said actuator means is responsive to said first control signal for actuation with a first actuation time ratio represented by said first control signal to control said pressure-changing gradient representing a pressure-reducing gradient of the brake pressures when said actuator means is between said pressure-reducing position and said pressure-holding position; and said actuator means is responsive to said second control signal for actuation with a second actuation time ratio represented by said second control signal to control said pressure-changing gradient representing a pressure-increasing gradient of the brake pressure when said actuator means is between said pressure-increasing position and said pressure-holding position.

Claim 19

A brake pressure control system for a motor vehicle having a plurality of wheels, said system comprising: skidding condition quantity detecting means for detecting a skidding condition quantity of at least one of the wheels based on at least a rotational speed of said at least one wheel and a speed of the motor vehicle in each of predetermined periodic cycles; control means for generating, based on the skidding condition quantity detected by said skidding condition quantity detecting means, a first control signal to increase a pressurechanging gradient representing a pressure-reducing gradient of brake pressures applied to the wheels as the skidding condition quantity varies in a direction from a target skidding condition amount toward a wheel locked condition, and for generating a second control signal to increase a pressure-changing gradient representing a pressure-increasing gradient of brake pressures applied to the wheels as the skidding condition quantity varies in a direction from said target skidding condition amount toward a wheel unlocked condition; and actuator means having a pressure-increasing position for increasing the brake pressures applied to the wheels, a pressure-reducing position for reducing the brake pressures applied to the wheels, and a pressure-holding position for holding the brake pressures applied to the wheels; wherein said actuator means is responsive to said first control signal for actuation with a first actuation time ratio represented by said first control signal to control said pressure-changing gradient representing a pressure-reducing gradient of the brake pressures when said actuator means is between said pressure-reducing position and said pressure-holding position; and said actuator means is responsive to said second control signal for actuation with a second actuation time ratio represented by said second control signal to control said pressure-changing gradient representing a pressure-increasing gradient of the brake pressure when said actuator means is between said pressure-increasing position and said pressure-holding position.

Claim 20

A brake pressure control system according to claim 15, wherein said actuator means comprises three-position valves, each of said valves having said pressure-increasing position, said pressure-reducing position, and said pressure-holding position.

Claim 21

A brake pressure control system for a motor vehicle having a plurality of wheels, comprising: a plurality of wheel speed sensors for detecting rotational speeds of the wheels, respectively, and for generating detected signals responsive to said detected rotational speeds; first calculating means for calculating wheel speeds and wheel accelerations based on said detected signals from said wheel speed sensors; second calculating means for calculating an estimated vehicle speed from the wheel speeds and for calculating an estimated vehicle deceleration from said estimated vehicle speed; reference speed calculating means for calculating a target reference speed from said estimated vehicle speed; deviation calculating means for calculating first deviations between said wheel speeds and said reference speed and second deviations between said wheel accelerations and said estimated vehicle deceleration; control means for generating, based on the first and second deviations calculated by said deviation calculating means, a first control signal to increase a pressure-changing gradient representing a pressure-reducing gradient of brake pressures applied to the wheels as a wheel skidding condition corresponding to said first and second deviations means varies in a direction from a target skidding condition amount toward a wheel locked condition, and for generating a second control signal to increase a pressure-changing gradient representing a pressure-increasing gradient of brake pressures applied to the wheels as said wheel skidding condition varies in a direction from said target skidding condition amount toward a wheel unlocked condition; and actuator means having a pressure-increasing position for increasing the brake pressures applied to the wheels, a pressure-reducing position for reducing the brake pressures applied to the wheels, and a pressure-holding position for holding the brake pressures applied to the wheels; wherein said actuator means is responsive to said first control signal for actuation with a first actuation time ratio represented by said first control signal when said actuator means is between said pressure-increasing position and said pressure-holding position, thereby controlling said pressure-reducing gradient of the brake pressures, and said actuator means is responsive to said second control signal for actuation with a second actuation time ratio, represented by said second control signal when said actuator means is between said pressure-increasing position and said pressure-holding position, thereby controlling said pressure-increasing gradient of the brake pressures.

Claim 22

A brake pressure control system for a motor vehicle having a plurality of wheels, comprising: a plurality of wheel speed sensors for detecting rotational speeds of the wheels, respectively, and for generating detected signals responsive to said detected rotational speeds; first calculating means for calculating wheel speeds and wheel accelerations based on said detected signals from said wheel speed sensors; second calculating means for calculating an estimated vehicle speed from the wheel speeds and for calculating an estimated vehicle deceleration from said estimated vehicle speed; reference speed calculating means for calculating a target reference speed from said estimated vehicle speed; deviation calculating means for calculating first deviations between said wheel speeds and said reference speed and second deviations between said wheel accelerations and said estimated vehicle deceleration; control means for generating, based on the first and second deviations calculated by said deviation calculating means, a first control signal to increase a pressure-changing gradient representing a pressure-reducing gradient of brake pressures applied to the wheels as a wheel skidding condition corresponding to said first and second deviations means varies in a direction from a target skidding condition amount toward a wheel locked condition, and for generating a second control signal to increase a pressure-changing gradient representing a pressure-increasing gradient of brake pressures applied to the wheels as said wheel skidding condition varies in a direction from said target skidding condition amount toward a wheel unlocked condition; and actuator means having a pressure-increasing position for increasing the brake pressures applied to the wheels, a pressure-reducing position for reducing the brake pressures applied to the wheels, and a pressure-holding position for holding the brake pressures applied to the wheels; wherein said actuator means is responsive to said first control signal for actuation with a first actuation time ratio represented by said first control signal when said actuator means is between said pressure-increasing position and said pressure-holding position, thereby controlling said pressure-reducing gradient of the brake pressures, and said actuator means is responsive to said second control signal for actuation with a second actuation time ratio, represented by said second control signal when said actuator means is between said pressure-increasing position and said pressure-holding position, thereby controlling said pressure-increasing gradient of the brake pressures.

Claim 23

A brake pressure control system according to claim 17, wherein said actuator means comprises three-position valves, each of said valves having said pressure-increasing position, said pressure-reducing position, and said pressure-holding position.