Digital-type brake-control method and system

Claim 2

A digital-type brake-control method for controlling a hydraulic brake system in a vehicle, which method comprises: detecting the rotational state of at least one wheel of the vehicle to produce a detection output; converting said output into a pulse signal; comparing and calculating the difference between the number of pulses of said pulse signal counted from any first time instant for a specific and pRedetermined first time period and the number of said pulses counted from a time instant differing from said first time instant for a specific second time period; determining as to whether said difference pulse number is greater or less than a predetermined reference pulse number, by means of an output signal; and producing a pressure-reduction signal or pressure-increase signal in accordance with and represetnative of said output signal thereby to decrease or increase hydraulic pressure in said brake system.

Claim 3

A digital-type brake-control method as claimed in claim 1 in which said predetermined first time period is equal to said second time period.

Claim 4

A digital-type brake-control method as claimed in claim 1 in which said predetermined first time period is different from said second time period.

Claim 5

A digital-type brake-control system for controlling a hydraulic brake system in a vehicle, said brake-control system comprising: sensor means for detecting the rotational state of at least one wheel of the vehicle and producing a corresponding output signal; a conversion circuit for converting said output signal into a wheel pulse signal; an addition-subtraction circuit for determining the difference between the number of pulses of said wheel pulse signal counted from any first time instant for a specific first time period and the number of said pulses counted from a time instant differing from said first time instant for a specific second time period; AND circuits for sending the wheel pulse signal to said addition-subtraction circuit; a control circuit for producing control signals for controlling said AND circuits and the addition-subtraction circuit; a comparison circuit for comparing said difference between numbers of counted pulses with a predetermined number of pulses thereby to produce a pressure variation signal depending on the result of the comparison; a power amplifier circuit for amplifying said pressure variation signal; and an actuator for receiving said pressure variation signal thus amplified and varying the hydraulic pressure in said hydraulic brake system in accordance with said pressure variation signal.

Claim 6

A digital-type brake-control system for controlling a hydraulic brake system in a vehicle, said brake-control system comprising: sensor means for detecting the rotational state of at least one wheel of the vehicle and producing a corresponding output signal; a conversion circuit for converting said output signal into a wheel pulse signal; an addition-subtraction circuit for determining the difference between the number of pulses of said wheel pulse signal counted from any first time instant for a specific first time period and the number of said pulses counted from a time instant differing from said first time instant for a specific second time period; AND circuits for sending the wheel pulse signal to said addition-subtraction circuit; a control circuit for producing control signals for controlling said AND circuits and the addition-subtraction circuit; a comparison circuit for comparing said difference between numbers of counted pulses with a predetermined number of pulses thereby to produce a pressure variation signal depending on the result of the comparison; a power amplifier circuit for amplifying said pressure variation signal; and an actuator for receiving said pressure variation signal thus amplified and varying the hydraulic pressure in said hydraulic brake system in accordance with said pressure variation signal.

Claim 7

A digital-type brake-control system as claimed in claim 4 in which: said control circuit comprises a clock-pulse oscillator for continually transmitting a signal of a constant frequency, a free-running counter for counting said frequency to produce a corresponding output, and a decoder for control for generating said control signals in response to said putput, said control signals comprising a reset signal, an addition signal, a gate signal, a subtraction signal, and a set signal; said addition-subtraction circuit comprising: an addition counter which is reset by said reset signal, and in which addition of the number of the pulses of said wheel pulse signal is carried out when one of the AND circuits is placed in the open state by said addition signal, a gate circuit placed in the open state by said gate signal, a subtraction counter in which the result of said addition in the addition counter is set when the gate circuit is thus opened, and in which, moreover, the number of said wheel pulses is subtracted to determine the number of difference pulses relative to the result of the addition when the other AND circuit is opened by said subtraction signal, and a register circuit in which said number of difference pulses is set by said set signal, and which produces output pulses; and said comparison circuit comprising: a decoder circuit means for comparing the number of the output pulses from said register circuit with the predetermined number of pulses thereby to generate the pressure variation signal and a hysteresis circuit operating when the pressure variation signal from the decoder circuit means is applied thereto to continue transmitting the pressure variation signal of the instant state until the succeeding pressure variation signal is apPlied thereto.

Claim 8

A digital-type brake-control system as claimed in claim 4 in which said addition-subtraction circuit comprises a reversible counter which is reset by said reset signal and operates to add the number of wheel pulses when the addition signal is applied to an AND circuit and to subtract the number of wheel pulses when the subtraction signal is applied to the AND circuit thereby to determine the number of difference pulse relative to the result of the addition and a register circuit in which said number of difference pulses is set by said set signal.

Claim 9

A digital-type brake-control system as claimed in claim 4 in which said addition-subtraction circuit comprises an addition counter and a subtraction counter respectively operating to carry out simultaneously addition and subtraction of the wheel pulse signal from any time instant for a specific time period in response to the control signals, said subtraction counter being adapted to determine the difference pulse number relative to the result of the addition by the addition counter in the specific time period of the preceding divisional period of the said specific time period.

Claim 10

A digital-type brake-control system as claimed in claim 7 in which said addition-subtraction circuit comprises: a gate circuit opened by the gate signal of the control circuit; the subtraction counter in which the pulse count obtained by the addition counter is set when the gate circuit is opened; the addition counter which is reset by the reset signal of the control circuit, said addition counter and subtraction counter being adapted to carry out simultaneous addition and subtraction, respectively, of the number of wheel pulses when respective AND circuits are respectively opened by addition and subtraction signals generated simultaneously by the control circuit, whereby in the subtraction counter, the difference number of pulses relative to the set pulse count is determined; and a register in which said difference number of pulses is set by a set signal from the control circuit.

Claim 11

A digital-type brake-control system as claimed in claim 8 in which said control circuit comprises a clock-pulse oscillator for continually transmitting a signal of a constant frequency, a free-running counter for counting said frequency thereby to produce a corresponding output, and a decoder for control for transmitting said control signals in response to said output of the free-running counter, said free-running counter comprising a plurality of flip-flops controlled in ON-OFF operation by said signal transmitted by the clock-pulse oscillator to produce respective outputs, said decoder for control being adapted to generate simultaneously the addition and subtraction signals in accordance with the outputs of the flip-flops, the flip-flops being set in ON-OFF states in a manner such that the period of generation of the subtraction signal is longer than that of the addition signal.

Claim 12

A digital-type brake-control system as claimed in claim 4 in which said specific second time period is longer than said specific first time period of the addition-subtraction circuit.

Claim 13

A digital-type brake-control system as claimed in claim 10 in which: said control circuit comprises a clock-pulse generator for continually transmitting a signal of a constant frequency, a free-running counter for counting said frequency to produce a corresponding output, and a decoder for control for transmitting said control signals in response to said output, said control signals including an addition signal and a subtraction signal; and said addition-subtraction circuit comprises an addition counter for adding said number of wheel pulses when one of said AND circuits is opened upon transmission of said addition signal and a subtraction counter for subtracting the number of wheel pulses when the other AND circuit is opened upon transmission of said subtraction signal, said free-running couNter comprising a plurality of flip-flops controlled in ON-OFF operation by the signal transmitted by the clock-pulse generator and thereby producing an output, said decoder for control generating the addition signal and the subtraction signal in accordance with the output of the flip-flops, the flip-flops being set in ON-OFF states in a manner such that the period of generation of the subtraction signal is longer than that of the addition signals.

Claim 14

A digital-type brake-control system as claimed in claim 4 in which said sensor means comprises a plurality of sensors provided respectively with respect to a plurality of wheels of the vehicle and producing respective output signals corresponding to the rotational states of the respective wheels, and said conversion circuit is adapted to add electrically said output signals, to waveshape the resulting signal, and to convert the signal thus wave-shaped into the wheel pulse signal.

Claim 15

A digital-type brake-control system as claimed in claim 12 in which said conversion circuit comprises amplifier circuits for respectively amplifying the output signals of the plurality of sensors, differentiating circuits for respectively differentiating the outputs of the amplifier circuits and producing corresponding differentiated outputs, and NAND elements for generating the numbers of wheel pulses in response to said differentiated outputs.

Claim 16

A digital-type brake-control system as claimed in claim 12 in which said conversion circuit comprises amplifier circuits for respectively amplifying the output signals of the plurality of sensors, Schmitt circuits for operating in response respectively to the outputs of the amplifier circuits to produce, each, a pair of outputs in mutually opposite phase relationship, differentiating circuits for respectively differentiating the pairs of outputs of the Schmitt circuits, and NAND elements for generating the numbers of wheel pulses in response to the outputs of the differentiating circuits.