Control for automotive passive restraint system with seat adjust desensitizer

A passive restraint system includes a torso belt automatically securing a vehicle occupant by moving from a forward position along a track to a rearward position. A belt carrier carries one end of the torso belt along the track while the other end of the torso belt is retained on a belt retractor. Adjustment of the location of a vehicle seat during travel of the torso belt could cause inadvertent latching of the retractor latching mechanism which results in stalling of the belt carrier. The present invention inhibits torso belt movement whenever the seat is adjusted to prevent such latching. When the seat adjustment is completed, the torso belt movement is resumed.

BACKGROUND OF THE INVENTION 
The present invention relates in general to automotive passive restraint 
systems, and more particularly to a control circuit for a motorized 
passive restraint system. 
The passive restraint system in a motor vehicle is responsible for 
providing automatic seatbelt protection to the vehicle occupants. The 
operation of the system is defined according to certain conditions such as 
the open or closed position of a door and the occurrence of certain 
events, such as the turning on of the vehicle ignition switch. As 
required, a torso belt of the passive restraint system will travel along a 
track from a forward position to a rearward position to secure an 
occupant. Other conditions and events will cause the torso belt to travel 
to the forward position to allow an occupant to enter or leave the 
vehicle. 
The torso belt travels by means of a motor-driven carrier riding in a track 
along the door frame. As the belt carrier moves from the "A" pillar at the 
forward position toward the "B" pillar at the rearward position, the torso 
belt spools out of a retractor usually located at the base of the vehicle 
seat at the opposite side of the occupant from the door. The unspooling of 
the torso belt provides sufficient belt length to extend from the 
retractor, around the vehicle occupant, and to the rearward position of 
the belt carrier at the "B" pillar. 
The belt retractor normally includes a latch mechanism which prevents 
unspooling of the belt during large accelerations or decelerations, such 
as in a collision. In the event that the retractor latching mechanism 
becomes engaged during movement of the belt carrier toward the rearward 
position, the belt carrier may stall somewhere between the forward and 
rearward positions since there will be insufficient slack of the torso 
belt to allow further movement of the belt carrier. This unintended 
latching of the retractor can occur, for example, when the vehicle 
occupant adjusts the seat position during belt carrier movement. The 
sudden movement of the occupant and the seat causes the retractor to 
latch, and in turn causes the belt carrier to stall. This occurrence is 
especially possible when the seat has a manual adjustment mechanism, but 
is also possible with power seats. 
The belt carrier is driven by a reversible electric motor through a 
drivebelt which interconnects the belt carrier and the motor. In order to 
avoid overheating and possible damage to the electric motor during a stall 
condition, the motor control circuit includes a timer which limits the 
duration of time for which the motor is energized. A time period is 
selected which is longer than the normal amount of time required for 
travel of the belt carrier between opposite positions and is short enough 
to avoid motor damage in the event of a stalled condition. 
When a stall condition occurs due to the latching of the belt retractor, 
the motor timer can time out thereby removing power from the motor and 
leaving the belt carrier stalled somewhere between the forward and 
rearward positions. Warning lights or audible signals are typically 
activated to indicate that the belt carrier has not reached the intended 
position. 
In order to deactivate the warning signals in prior art systems, the 
vehicle occupant must reenergize the passive restraint system and bring 
the belt carrier into the proper position by either opening a vehicle door 
or turning the vehicle ignition off and on again. 
SUMMARY OF THE INVENTION 
It is a principal object of the present invention to provide a passive 
restraint system wherein the occurrence of a stall condition of the belt 
carrier is prevented. 
It is a further object of the invention to provide method and apparatus for 
ensuring proper operation of a passive restraint belt system even when the 
seat location is being adjusted. 
These and other objects are achieved by employing a carrier motor control 
circuit which includes a motor timer for determining an activation time 
for a belt drive motor. An adjustment sensor such as a contact switch 
detects the initiation of an adjustment of the seat location. In response 
to a signal from the sensor, a control logic circuit inhibits the motor 
timer stopping belt carrier movement. Thus, the torso belt will stop 
spooling out of the retractor while the seat is being adjusted, preventing 
inadvertent latching of the retractor mechanism. When the sensor signal 
indicates that the seat is no longer being adjusted, the control logic 
circuit retriggers the motor timer. The belt carrier is then driven to its 
proper location.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to FIG. 1, a vehicle generally designated as 10 has a passive 
restraint belt system including a torso belt 11. At one end of torso belt 
11 is a belt carrier 13. Belt carrier 13 is received for slidable movement 
in a track 14 which extends from the front or "A" pillar 15 to the rear or 
"B" pillar 16. Track 14 is affixed to the vehicle roof so that belt 
carrier 13 can be driven between a forward position at the "A" pillar and 
a rearward position at the "B" pillar as shown in phantom at 17. 
The other end of torso belt 11 is received within a latchable retractor 20 
which is secured to the floor of the vehicle near the bottom edge of a 
seat 21. Torso belt 11 is free to spool in or out from retractor 20 during 
movement of belt carrier 13 (except that belt 11 cannot spool out when 
retractor 20 becomes latched due to an acceleration exceeding a 
predetermined acceleration). With an occupant located in seat 21 and with 
belt carrier 13 moving from a forward to a rearward position, torso belt 
11 will be required to spool out from retractor 20 to provide sufficient 
length of the torso belt 11 to extend from retractor 20, around the 
occupant, and to the "B" pillar location of belt carrier 13. 
Belt carrier 13 is connected to a drivebelt 22 within track 14. Drivebelt 
22 extends through track 14 from belt carrier 13 to a motor 23 and engages 
a sprocket wheel 24 driven by motor 23. Thus, rotation of motor 23 in one 
direction causes movement of belt carrier 13 toward a rearward position 
and rotation of motor 23 in the opposite direction causes movement of belt 
carrier 13 toward a forward position. A pair of limit switches 25 and 26 
sense the presence of belt carrier 13 at the forward and rearward 
positions, respectively. 
The correct location of the passive restraint belt carrier at any moment is 
dependent on certain monitored conditions, including the state of an 
ignition switch 27 which may be either on or off. A door switch 28 
provides a signal which indicates the open or closed position of its 
respective vehicle door. Furthermore, movement of belt carrier 13 is 
dependent on the occurrence of a trigger event which initiates belt 
carrier movement. Following a trigger event, a time period of limited 
duration begins during which motor 23 is energized. 
Seat 21 is adjustable to a location desired by an occupant. As shown in 
FIG. 1, seat 21 may be a power seat in which seat adjustment motors (not 
shown) are controlled by power seat switches 30. Switches 30 include a 
contact switch or sensor which provides a seat adjust signal whenever the 
power seat is being adjusted. The seat adjust signal is transmitted to a 
control module as described below. As shown in FIG. 1A, seat 21 can 
alternatively be manually adjustable. In that embodiment, seat 21 includes 
a manual release lever 31 and a sensor switch 32 which senses the position 
of lever 31 to provide the seat adjust signal. 
In order to eliminate the possibility of a latched retractor mechanism 
causing a stalled belt carrier, the present invention provides means for 
deactivating motor 23 during adjustment of the position of seat 21. Once 
the seat adjustment is completed, the possibility of the belt retractor 
becoming latched is ended. Motor 23 is then reactivated and belt carrier 
13 moves to the proper position at the "B" pillar. 
Turning now to FIG. 2, control electronics 35 controls the operation of the 
passive restraint belt drive motors for the driver side and passenger side 
as shown. Control electronics 35 senses a plurality of predetermined 
monitored conditions over a group of sensing lines 36, senses trigger 
events over a group of sensing lines 37, and monitors the occurrence of a 
seat adjust signal over a signal line 38. 
The driver side of the passive restraint system includes a relay 40 
connected to be energized by control electronics 35 on a control line 42 
and a relay 41 connected to be energized by control electronics 35 on a 
control line 43. The outputs of relays 40 and 41 are connected to a driver 
side belt motor 44 which is a reversible dc motor, the direction of 
rotation depending on the energizing of the motor at its "A" input or its 
"B" input by relays 40 or 41, respectively. Motor 44 is mechanically 
connected to a driver side belt carrier 45 which engages limit switches 46 
depending on its position at either end of a track. The outputs of limit 
switches 46 are included in the monitored conditions sensed over sensing 
lines 36. 
In operation, the monitored conditions on signal lines 36 corresponding to 
the driver side of the passive restraint system causes control electronics 
35 to select the one of relays 40 or 41 which corresponds to the 
appropriate position of the belt carrier at either the "A" pillar or the 
"B" pillar. However, the selected relay is not energized unless a timer in 
control electronics 35 is activated by a trigger event over lines 37. 
During the limited time period initiated by a trigger, control electronics 
35 energizes the selected relay over corresponding control line 42 or 43 
causing the selected relay to output a voltage +V, supplied as shown, to 
energize motor 44. Movement of the belt carrier to the end of track at the 
desired position causes the opening of a corresponding limit switch which 
in turn causes control electronics 35 to deenergize the relay. 
In the event that the seat occupant adjusts the seat while the motor is 
energized, control electronics 35 receives a seat adjust signal on line 
38. The output of the timer is inhibited for as long as the seat adjust 
signal is being received. Therefore, the motor is deactivated during the 
seat movement. 
When the occupant releases the seat adjustment lever or switches, the seat 
adjust signal turns off. In response to the turning off of the seat adjust 
signal, control electronics 35 restarts or retriggers the motor timer to 
allow the belt carrier to move to the selected position. 
The passenger side of the passive restraint system is substantially 
identical to the driver side. Control electronics 35 is connected to a 
pair of relays 50 over control lines 47 and 48. Relays 50 are connected to 
an "A" input and "B" input of a passenger side belt motor 51 which 
provides motive power to a passenger side belt carrier 52. Limit switches 
53 are provided for contact with passenger side belt carrier 52 at its 
forward and rearward positions. 
The operation of the passive restraint system of FIG. 2 will be further 
described in connection with the flowchart in FIG. 3. In step 55, a relay 
has been selected and activated based on monitored conditions and a 
trigger event. Therefore, the belt motor is on and the belt carrier is in 
motion. In step 56, the seat occupant has initiated an adjustment of the 
seat position by turning a manual lever or by activating a power seat 
control. A seat adjust signal is generated so that the motor timer is 
turned off in step 57. Belt movement is inhibited until the lever or 
control is released by the occupant in step 58. The motor timer is 
retriggered in step 59. 
Referring to FIG. 4, the electrical portion of the passive restraint system 
of the present invention is shown in greater detail. Control electronics 
module 35 includes a timer trigger 65 which receives an IGNITION ON signal 
on a line 64 when the ignition switch of the vehicle is in its run or 
start position. Timer trigger 65 may include a monostable multivibrator, 
for example. The output of timer trigger 65 is connected to an input of a 
motor timer 66. Motor timer 66 provides an output signal at its outputs 
66a and 66b for a predetermined length of time (e.g., 7.5 seconds or some 
other period sufficient to allow full travel of the belt carrier) when it 
receives a trigger signal from timer trigger 65. 
A seat adjustment sensor 67 is actuated by a vehicle occupant when a seat 
is being adjusted. The output of sensor 67 is connected to a control logic 
circuit 68. Control logic circuit 68 provides an inhibit signal to motor 
timer 66 to deactivate the timer output whenever sensor 67 is active. When 
sensor 67 transistions from an active to a nonactive state, control logic 
68 provides a retrigger signal (by means of a monostable multivibrator, 
for example) to motor timer 66 to reactivate the timer output for the 
predetermined length of time. 
The driver side portion of the passive restraint system includes sensors 70 
to monitor the predetermined conditions for determining the direction and 
triggering of the driver side belt carrier. An "A" limit switch 90, a "B" 
limit switch 91, and a door switch 92 each have one side connected to 
ground and another side connected to a driver side logic block 71. Door 
switch 92 is further connected to timer trigger 65. 
Driver side logic 71 is connected to motor timer output 66a and has outputs 
connected to relays 72 and 73 which are connected to driver side belt 
motor 74. Driver side logic 71 has another output connected to a "B" 
detector 75 for determining the failure of the belt carrier to reach the 
rearward position at the "B" pillar. "B" detector 75 is connected to a 
warning indicator 76 for signaling a vehicle occupant that the belt 
carrier has failed to reach the "B" position. 
The passenger side portion of the passive restraint system includes sensors 
80, including a passenger door position switch 93, an "A" limit switch 94, 
and a "B" limit switch 95. Switches 93, 94, and 95 each have one side 
connected to ground and another side connected to passenger side logic 
block 81. Passenger door switch 93 is further connected to timer trigger 
65. Passenger side logic 81 is connected to motor timer output 66b. A 
relay 82 and a relay 83 receive output signals from passenger side logic 
81 and provide power to a passenger side motor 84. A "B" detector 85 
receives an input from passenger side logic 81 and provides an output to 
warning indicator 76. 
An inertia switch 87 for detecting large accelerations of the vehicle as 
would occur during a collision provides an inhibit signal to motor timer 
66. 
In operation, logic blocks 71 and 81 respectively select a belt carrier 
position at either the "A" pillar or the "B" pillar (i.e., one of the 
corresponding relays 72 or 73 and 82 or 83 are selected) based on the 
positions of their corresponding sensor switches 70 and 80. However, the 
selected relay is not energized unless a trigger event occurs and a signal 
is received from motor timer 66. Thus, when the ignition is turned on or 
when a door opens or closes, timer trigger 65 sends a signal to initiate 
the timing of motor timer 66. 
When either the appropriate limit switch is opened by the belt carrier or 
motor timer 66 times out, the logic block 71 or 81 turns off the relay 
which had been energized. If motor timer 66 times out without the opening 
of the appropriate limit switch, the appropriate logic block 71 or 81 
provides a signal to corresponding "B" detector 75 or 85. Upon receipt of 
the signal, "B" detector 75 or 85 energizes a warning indicator 76 until 
the stalled condition is corrected. 
Inertia switch 87 senses the occurrence of a collision and inhibits the 
operation of motor timer 66. Thus, during a collision, the belt carriers 
will not be allowed to move no matter what the sensed conditions are, thus 
protecting the vehicle occupants. 
While preferred embodiments of the invention have been shown and described 
herein, it will be understood that such embodiments are provided by way of 
example only. Numerous variations, changes, and substitutions will occur 
to those skilled in the art without departing from the spirit of the 
invention. Accordingly, it is intended that the appended claims cover all 
such variations as fall within the spirit and scope of the invention.