Drowsiness alarm system for a vehicle

Claim 2

A drowsiness alarm system for a vehicle for producing a warning in the event of driver drowsiness as determined from vehicle steering changes, comprising (a) a steering angle pulse generation circuit (1 and 2) which produces a clockwise steering angle pulse (2a) at one of two output terminals whenever the steering wheel is rotated clockwise through an angle equal to a predetermined angular increment and produces a counterclockwise steering angle pulse (2b) at the other output terminal whenever the steering wheel is rotated counterclockwise through an angle equal to the predetermined angular increment; (b) a first steering angle pulse counting circuit (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and 23) counting the clockwise and counterclockwise steering pulses only if the interpulse interval does not exceed a first predetermined period of time and outputting a first voltage signal (10a) whenever the counted number reaches a first predetermined number within a second predetermined period of time; (c) a second steering angle pulse counting circuit (31 and 32) which counts the number of both clockwise and counterclockwise steering angle pulses inputted thereto only if the interpulse interval does not exceed the first predetermined period of time and outputs a second voltage signal (31a) whenever the counted number reaches a second predetermined number within the second predetermined period of time; (d) a curved road detection circuit (30) which counts the respective numbers of the clockwise and counterclockwise steering angle pulses, (2a, 2b) separately, inputted thereto within the second predetermined period of time and outputs a first pulse whenever the counted number of either of the clockwise and counterclockwise steering angle pulses inputted thereto reaches a third predetermined number or whenever the difference of the counted numbers between the clockwise and counterclockwise steering angle pulses reaches a fourth predetermined number; (e) a signal switching circuit, (12, 27, 33-38) connected between said first and second steering angle counting circuit (3-12, 23 and 31, 32) and curved road detection circuit (30), which selectively enables the passage of either of the first and second voltage signals depending on whether said curved road detection circuit sends the output pulse thereto; and (f) an alarm section (28) which produces an alarm in a predetermined form in response to a pulse received when said signal switching circuit enables the passage of either of the first and second voltage signals.

Claim 3

A drowsiness alarm system as set forth in claim 1, characterized in that the second predetermined number of said second steering angle pulse counting circuit (31, 32) is greater than the first predetermined number of said first steering angle pulse counting circuit.

Claim 4

A drowsiness alarm system as set forth in claim 1, characterized in that said first steering angle pulse counting circuit comprises: (a) a first OR gate (3), connected to both two output terminals of said steering angle pulse generation circuit (1, 2), which takes logical OR of both clockwise and counterclockwise steering angle pulses from said steering angle pulse generation circuit; (b) a timer (4), connected to said first OR gate (3), which outputs a third voltage signal (4a) for the second predetermined period of time in response to the output signal of said first OR gate (3) so as to determine the reference time for counting clockwise and counterclockwise steering angle pulses; (c) a first AND gate (5), connected to said first OR gate (3) and timer (4), which enables the passage of the output signal (3a) of said first OR gate (3) while the third voltage signal (4a) is received from said timer (4); (d) a first reset circuit (6, 7 and 8), connected to said first AND gate (5), which produces a first reset pulse whenever the output signal of said first AND gate (5) is received at an interval exceeding a third predetermined period of time; (e) a second reset circuit (11 and 12), connected to said timer (4), which produces a second reset pulse (12a) whenever the third voltage signal (4a) outputted from said timer (4) drops to zero; (f) a second OR gate (9), connected to both first and second reset circuits, which takes logical OR of the first and second reset pulses fed from said first and second reset circuit; (g) a first counter (10), connected to said first AND gate (5), which counts the number of the clockwise and counterclockwise steering angle pulses passed through said first AND gate, outputs a second pulse (10a) whenever the-counted number reaches the first predetermined number, and is reset in response to the output pulse of said second OR gate (9); and (h) a first flip-flop (23), connected to said first counter (10) and to said second reset circuit (11, 12), which produces a fourth voltage signal (23a) until the second reset pulse of said second reset circuit is received in response to the second pulse outputted from said first counter.

Claim 5

A drowsiness alarm system as set forth in claim 1, characterized in that said second steering angle pulse counting circuit comprises: (a) a second counter (31), connected to said first AND gate (5), which counts the number of the clockwise and counterclockwise steering angle pulses (2a, 2b), outputs a third pulse (31a) whenever the counted number reaches the second predetermined number, and is reset in response to the output pulse of said second OR gate; and (b) a second flip-flop (32), connected to said second counter (31) and to said second reset circuit (11, 12), which outputs a fifth voltage signal (32a) in response to the third pulse outputted from said second counter (31) until the second reset pulse (12a) of said second reset circuit (11, 12) is received.

Claim 6

A drowsiness alarm system for a vehicle as set forth in either of claims 3 and 4, wherein said curved road detection circuit is characterized by: (a) a second AND gate (13), connected to said steering angle pulse generation circuit (1, 2) and to said timer (4), which enables the passage of the clockwise steering angle pulse from said steering angle pulse generation circuit while the third voltage signal from said timer is received: (b) a third AND gate (14), connected to said steering angle pulse generation circuit (1, 2) and to said timer (4), which enables the passage of the counterclockwise steering angle pulse while the third voltage signal from said timer is received; (c) an UP/DOWN counter (15), connected to said second and third AND gates (13, 14), which increments the count by one whenever the clockwise steering angle pulse passed through said second AND gate (13) is received, decrements the count by one whenever the counterclockwise steering angle pulse passed through said third AND gate (14) is received, outputs a fourth pulse (15a) whenever the difference between incrementally counted number and decrementally counted number reaches the fourth predetermined number, and is reset in response to the second reset signal (12a) from said second reset circuit (11, 12); (d) a third OR gate (17), connected to said third AND gate (14) and to said second reset circuit (11, 12), which takes logical OR of the counterclockwise steering angle pulse from said third AND gate (14) and second reset signal (12a) from said second reset circuit (11, 12); (e) a third counter (16), connected to said second AND gate (13), which counts the number of the clockwise steering angle pulse passed through said second AND gate, outputs a fifth pulse (16a) whenever the counted number reaches the third predetermined number, and is reset in response to the output pulse of said third OR gate (17); (f) a fourth OR gate (19), connected to said second AND gate (13) and to said second reset circuit (11,12), which takes logical OR of the clockwise steering angle pulse passed through said second AND gate (13) and the second reset signal (12a) from said second reset circuit (11, 12); (g) a fourth counter (18), connected to said third AND gate (14), which counts the number of the counterclockwise ' steering angle pulse passed through said third AND gate (14), outputs a sixth pulse (18a) whenever the counted number reaches the third predetermined number, and is reset in response to the output pulse of said fourth OR gate (19); and (h) a fifth OR gate (20 and 21), connected to said UP/DOWN counter (15), third, and fourth counters (16,18), which takes logical OR of the fourth (15a), fifth (16a), and sixth pulses (18a) of said UP/ DOWN counter (15), third, and fourth counters (16, 18).

Claim 7

A drowsiness alarm system for a vehicle as set fourth in any one of claims 3 through 5, wherein said signal switching circuit is characterized by: (a) a third flip-flop (40), connected to said curved road detection circuit (30) and to said second reset circuit (11,12), which outputs a sixth voltage signal in response to the output pulse from said curved road detection circuit (30), the sixth voltage signal being inverted by the second reset pulse (12a) fed from said second reset circuit (11, 12): (b) a fourth AND gate (33), connected to said first steering angle pulse counting circuit (... 10, 23) and to said third flip-flop (40), which enables the passage of the first voltage signal (23a) of said first steering angle pulse counting circuit in response to a seventh voltage signal (40b) from said third flip-flop (40) outputted when said third flip-flop does not produce the sixth voltage signal (40a); and (c) a fifth AND gate (34), connected to said second steering angle pulse counting circuit (... 31, 32) and to said third flip-flop (40), which enables the passage of the second voltage signal (32a) of said second steering angle pulse counting circuit when said third flip-flop (40) sends the sixth voltage signal (40a) thereto.

Claim 8

A drowsiness alarm system for a vehicle as set forth in any one of claims 3 through 6, wherein said alarm section is characterized by: (a) a first inverter (35 and 36), connected to said signal switching circuit (40, 33, 34), which inverts the level of the voltage signal selectively passed through said signal switching circuit; (b) a first monostable multivibrator (37), connected to said first inverter (36), which produces an eighth voltage signal for a fourth predetermined period of time when the output signal of said first inverter goes high so as to detect the falling edge of the voltage signal of either of said first and second steering angle pulse counting circuits fed through said signal switching circuit; (c) a sixth OR gate (35 and 38), connected to said signal switching circuit (40, 33, 34) and to said first monostable multivibrator (37), which takes logical OR of the voltage signal selectively passed through said signal switching circuit and the eighth voltage signal outputted from said first monostable multivibrator; (d) a sixth AND gate (27), connected to said sixth OR gate (35, 38) and to said second reset circuit (11, 12), which enables the passage of the second reset pulse (12a) fed from said second reset circuit when the output voltage signal (38a) of said sixth OR gate (38) is received; and (e) an alarm unit (28), connected to said sixth AND gate (27), which produces an alarm in a predetermined form in response to the second reset pulse passed through said sixth AND gate.

Claim 9

A drowsiness alarm system as set forth in claim 3, wherein said first reset circuit (6, 7, 8) is characterized by (a) a second monostable multivibrator (6), connected to said first AND gate (5), which produces a ninth voltage signal for the third predetermined period of time whenever the steering angle pulse passed through said first AND gate is received; (b) a second inverter (7), connected to said second monostable multivibrator (6), which inverts the level of the ninth voltage signal of said second monostable multivibrator; and (c) a first differentiator (8), connected to said second inverter (7), which produces the first reset pulse (8a) when the output voltage signal is received from said second inverter so as to detect the falling edge of the ninth voltage signal of said second monostable multivibrator.

Claim 10

A drowsiness alarm system for a vehicle as set forth in claim 3, wherein said second reset circuit (11, 12) is characterized by: (a) a third inverter (11), connected to said timer (4), which inverts the level of the third voltage signal fed from said timer; and (b) a second differentiator (12), connected to said third inverter (11), which produces the second reset pulse (12a) when the voltage signal is received from said third inverter so as to detect the falling edge of the third voltage signal outputted from said timer (4).