VEHICLE SEAT BELT SYSTEM

Abstract: A passive vehicle seat belt system includes measures to prevent overheating of the drive motor (9) and obstruction of system operation. Drive motor excess current demand is sensed by a sensor (41) to effect motor de-energization and/or disabling of latching means of a retractor (52; 62) included in the system and/or operation of an indicator light (17). The indicator light (17) can prompt manual motor de-­ energization. Disabling of retractor latching means can be effected by a belt movement command signal. Retractors with means (39,34) for signalling operation of latching means, with solenoid means (56,67) for disabling latching means, and with means (76,77) for indicating when a predetermined belt length has been received therein, are described.

Description: The invention relates to passive seat belt systems. Passive seat belt systems as used in road vehicles commonly include a seat belt which is moved between an operative and an inoperative position by means of an electric motor drive in response for example to the closing and opening of an adjacent vehicle door. One end of the belt may thus be fastened to a carriage which is reversibly moved along a track by the electric motor. The belt may be withdrawn from a retractor against a spring bias and such retractors commonly incorporate a latching mechanism which prevents belt withdrawal when a predetermined condition is sensed, typically one or both of belt or vehicle, and thus retractor, acceleration in excess of certain limits. One such system is disclosed in FR-A-2 439 595. Many vehicle acceleration sensitive latching mechanisms are capable of latching when the vehicle is parked on a steep hill and this condition prevents movement of the belt of a passive system where this movement requires belt withdrawal from the retractor, with possible consequential damage by overheating to the electric motor which has to be energized to effect this movement. Such damage could of course occur in any kind of passive system where a drive motor was unable to move the seat belt, for any reason. The invention thus provides a passive seat belt system comprising a belt movable between an operative position and an inoperative position, an electric motor which can be energised to move the belt between said positions, a retractor from which the belt is withdrawn against a retractive bias by energization of the motor, and a latch mechanism actuable to latch the retractor against belt withdrawal in response to a predetermined condition, characterized by protective means actuable to de-energize the motor in response to obstruction of belt movement by the latch mechanism. The protective means can be responsive to obstruction of belt movement, for example, by the latch mechanism. The retractor can comprise a spool journalled in a frame for releasably receiving the belt and the latch mechanism can comprise a ratchet wheel secured to the spool to rotate therewith, a pawl pivotably mounted on the frame for movement from an unlatching position to a latching position of engagement with ratchet wheel to thereby prevent unwinding of the belt from the spool, a member mounted on the frame for rotation from an inoperative position to an operative position to cause the pawl to engage the ratchet wheel, inertial acceleration sensing means operable in response to a predetermined acceleration condition to link the member to the spool whereby spool rotation effects the rotation of the member. The protective means can then comprise an electrical element arranged to change condition in response to the movement of the member to thereby signal the position of the pawl, for example, a switch engageable by the member. The protective means can instead comprise means responsive to excess current demand from the motor, and can in either instance include a switch to de-energize the motor. The invention also provides a passive seat belt system comprising a belt movable between an operative position and an inoperative position, an electric motor which can be energised to move the belt between said positions, a retractor from which the belt is withdrawn against a retractive bias by energization of the motor, and a latch mechanism actuable to latch the retractor against belt withdrawal in response to a predetermined condition, characterized by protective means actuable to de-activate the latch mechanism in response to energization of the motor to effect belt movement in the direction of withdrawal from the retractor. The retractor can then comprise a spool journalled in a frame for releasably receiving the seat belt, and the latch mechanism can comprise an inertial weight mounted for movement in response to the predetermined acceleration, a ratchet wheel rotatable with the spool, and a lever pivotably mounted for movement from a rest position to engage a first arm thereof with the ratchet wheel in response to the movement of the weight. The disabling means then comprises a second arm of the lever arranged to function as an armature for a solenoid coil, whereby the lever occupies its rest position during energization of the coil. The solenoid coil can be located with the axis thereof substantially at right angles to the axis of the spool. In another embodiment, the latch mechanism comprises a support supporting a hollow inertial weight for toppling movement thereon in response to the predetermined acceleration, and an elongate output member received within the weight and movable thereby from a rest position to effect the latching in response to the toppling of the weight. The disabling means can then comprise a solenoid coil mounted below the support with the solenoid coil axis substantially aligned with output member in the rest position thereof, an aperture in the support, an extension portion of the output member in the rest position thereof, an aperture in the support, an extension portion of the output member extending through the aperture towards the solenoid coil, and an armature carried by the output member extension portion for co-operation with the solenoid coil whereby the output member occupies the rest position thereof during energization of the solenoid coil. In yet another embodiment, the retractor comprises a spool journalled in a frame for releasably receiving a seat belt, and the protective means comprises an electrical element arranged to change condition in response to a predetermined change in the length of belt wound on the spool. The electrical element can comprise a switch and a lever having a first end operably engageable with the switch and a second end engageable with the seat belt wound upon the spool under a bias. The protective means can instead or as well comprise an indicator arranged to be energized in response to the sensed predetermined condition. Manually operable means for de-energizing the motor may then be provided. The invention is further explained below, by way of illustration, with reference to the accompanying schematic drawings, in which: Figure 1 is a partial perspective view of a road vehicle interior, showing a vehicle seat with which there is associated a passive seat belt system in accordance with the invention; Figures 2 and 3 are respectively axial and partial front views of a retractor for use in the system of Figure 1; Figure 4 is a schematic circuit diagram of the system of Figure 1; Figures 5 and 6 are like views of a second retractor for use in the system of Figure 1; Figure 7 is a schematic diagram of an alternative circuit for use in the system of Figure 1; Figures 8 and 9 are views similar to those of Figures 2 and 3 of a third retractor for use in the system of Figure 1; Figure 10 is a schematic diagram of a second alternative circuit for use in the circuit of Figure 1, with the retractor of Figures 8 and 9; Figures 11 and 12 are like views of a fourth retractor for use in the system of Figure 1 in place of the retractor of Figures 8 and 9; and Figure 13 is a fragmentary view of the interior of a fifth retractor in accordance with the invention. As shown in Figure 1, a road vehicle includes a passive seat belt system in which a shoulder belt 1 has its lower end received in a retractor 2 secured to the vehicle frame on the inboard side of a vehicle seat 4, the upper end being connected to a carriage 5 movable along a track 6 extending in the fore and aft direction of the vehicle above a window adjacent the seat. The carriage is movable along the track 6 by a cable 7 driven by a reversible electric motor 9. At its rearward end, the track 6 has a portion extending downwardly to a locking mechanism 10 with which the carriage 5 engages in the rearward, operative, position of the belt 1. A knee bolster 11 is located in front of the seat and/or an active lap belt 12 can be provided. The electric motor 9 is controlled by control circuitry 14 including limit switches responsive to the arrival of the carriage 5 at respective ends of the track, and a switch responsive to the position of the vehicle door, for example, the courtesy light switch. Any suitable control circuitry can be employed, for example that shown in Figure 1 of GB 1 388 382, the contents of which are incorporated herein by reference. When the vehicle door is opened, the door and limit switches effect energisation of the motor 9 so that the carriage 5 is moved forwardly from its rear, operative, position, carrying with it the belt 1 to an inoperative position in which it does not impede entry to the seat 4. When the door is closed again, with the seat occupied, the switches energising the electric motor to rotate in the opposite direction and bring the carriage 5 back into engagement with the lock device 10, with the belt in the operative position to restrain the occupant. It is to be understood that the passive seat belt system briefly described above is one only of a variety of such systems to which the present invention can be applied. The retractor 2 shown in Figures 2 and 3 can correspond generally to that disclosed in Patent Application EP 0 092 407, the contents of which are incorporated herein by reference. The retractor has a frame rotatably mounting a spring biassed spool for accommodating the belt and a locking mechanism including a lock cup 20 with a support 21 for a vehicle sensor 22, that is, an inertial device responsive to retractor acceleration, and thus to vehicle acceleration. The sensor 22 comprises a weight 24 which tilts in response to a predetermined acceleration to pivot an arm 25 also mounted on the lock cup 20 to engage with its free end a toothed wheel 23 driven by the spool to thereby cause rotation of the lock cup in the direction of the arrow 26 to a latched position in which further rotation of the spool in the belt unwinding direction is prevented. If the vehicle of Figure 1 were to be parked on a steep hill, such that the vehicle sensor weight 24 tilts sufficiently, the retractor becomes locked against belt withdrawal. Opening of the vehicle door will operate the control circuit so as to move the carriage 5 forwardly along the track 6. With the system as so far described, this movement will be promptly checked, because it requires withdrawal from the retractor 2 of a certain length of the belt 1, and the retractor has become locked against belt withdrawal. The occupant of the seat 4 can consequently remove himself from the vehicle only with considerable difficulty, or by use of a manual override, if provided, to render the belt inoperative and the motor 9 will remain energised so as to overheat and perhaps burn itself out. However, in accordance with the invention, the retractor 2 includes within its casing 27 a normally open microswitch 30 with an operating arm 31 located so as to be engaged by a portion of the lock cup 20 as this moves to the latching position. Closure of the microswitch 30 energises a relay to open a switch 15 in a circuit (Figure 4) including a power source 16, the motor 9, and the control circuitry 14, so as to de-energise the motor 9. Operation of a microswitch 30 preferably does not take place immediately, but only after the motor 9 has driven the carriage 5 through a certain distance, so the user of the system is made aware that it has not failed completely, but is merely being blocked by latching of the retractor 2. This situation is preferably also signalled to the user independently, conveniently by a warning light 17 on the dashboard which is energized through the switch 15 on de-energization of the motor 9. The user can then apply a manual override means to release the system, or the situation of the vehicle can be adjusted so that the vehicle sensor 22 no longer causes latching. In place of the retractor 2 shown in Figures 2 and 3, the retractor 32 of Figures 5 and 6 can be employed. This can resemble the retractor 2, but a normally open microswitch 34 is here mounted in the cover 27 so as to be actuated by the lock cup 20 at the beginning of the movement into the latching position. The motor 9 is thus de-energised after a smaller amount of belt movement than with the retractor 2. Whichever form of retractor is employed, the system provides protection for the motor 9 and an indication to the user as to why functioning of the system is blocked. Figure 7 schematically shows a control circuit for a passive seat belt system embodying the invention which can be generally in accordance with that of Figure 1 for example, and which can incorporate either the retractor 2 or the retractor 32, with or without the microswitch 30 and 34. The circuit of Figure 7 incorporates the motor 9, the control circuitry 14 and the power source 16, and in addition a current sensor 41 arranged to sense the current requirements of the motor. The sensor 41 is operatively linked with a switch 42 which is normally closed to allow operation of the system but which is arranged to be opened by the sensor when this senses that the motor current requirement exceeds a predetermined level, corresponding to the level that prevails under the most adverse operating conditions, as will occur when the motor 9 encounters the resistance to belt movement imposed by the latched retractor. Thus again the motor 9 is protected. The circuit again can include indicating means to alert the user of the system to the position, in the form of the warning light 17 which is energised on de-energization of the motor 9. In an alternative arrangement, the switch 42 is operated by the sensor 41 to energise the warning light 17 only, it being left to the user of the system to de-energise the motor 9 manually by means of a further switch such as the switch 43 of Figure 7. Also in accordance with the invention, a passive seat belt system such as that indicated in Figure 1 can incorporate the retractor 52, of Figures 8 and 9. The retractor 52 generally corresponds to the retractor 2, but the arm 25 is replaced by one arm 54 of a two-arm lever, of which the free end of the other arm 55 constitutes or carries an armature co-operating with a normally de-energised solenoid coil 56 secured within the retractor casing 57. As appears from Figure 10, the solenoid coil 56 is connected into a circuit including the motor 9, the control circuitry 14 and the power source 16 so as to be energised simultaneously with the electric motor 9, at least when such energization is to cause carriage movement in the direction to withdraw belt from the retractor 52, that is, to the forward position in the system of Figure 1. Energization of the solenoid coil 56 causes the lever to pivot in the counterclockwise direction (as shown in Figure 8) so that the free end of the arm 54 cannot engage with the wheel 23, or is withdrawn from such engagement. The weight 24 is thus held in or returned to its untilted position and the vehicle sensor 22 rendered ineffective. The arm 55 is so arranged that the balance and sensitivity of the arm 54 is the same as that of the arm 25. The arrangement of Figures 8 and 9 necessarily involves an increase in the axial dimension of the retractor as appears from Figure 9, and this can be avoided by use in place of the retractor 52, of the retractor 62 shown in Figures 11 and 12. This again generally corresponds to the retractor 2, but the weight 24 of the vehicle sensor 22 is hollow and rests on the support 21 by way of a circular rim. The weight acts by way of internal surfaces on a flange 64 carried by an upright central pin 65, the free upper end of which is received in a downwardly facing pocket at the outer end of the arm 25. When the weight 14 tilts under its own inertia, or because the retractor is tilted, the internal surfaces of the weight cause upward movement of the pin 65 and thus an upward pivoting of the arm 25 to engage the wheel 23. In the retractor 62 the lower end of the pin 65 protrudes through an aperture in the support 21 and carries an armature 66 co-operable with a solenoid coil 67, which is connected into the control circuitry in the same way as the coil 56. Energisation of the coil 67 thus acts on the armature 66 to hold the pin 65 in, or to draw it downwardly to, the position of Figure 8, in which the weight 24 is in its normal upright position, with the arm 25 spaced from the teeth of the wheel 23. Instead of being energised automatically on energisation of the motor 9, the solenoid coil 56 or 67 can be energised conditionally, for example, by closure of a switch controlled like the switch 42 by a sensor such as the current sensor 41 of Figure 7. Figure 13 illustrates schematically a retractor 72 incorporating switch means for sensing when a predetermined length of the belt 1 has been wound upon its spool. The retractor 72 can correspond generally to the retractors 2, 32, 52 or 62, but the retractor casing 74 incorporates a slot or elongate recess 75 extending parallel to the spool axis and pivotally mounting therein a lever 76 preferably by means of integrally moulded pivot pins. One end of the lever 76 can operate a microswitch 77 mounted in the casing 74, and the other end is biassed by a spring 79 to be engaged by the outer layer of the belt 2 when a predetermined length of the belt has been wound onto the spool. When the belt 1 is in its forward, inoperative position, sufficient of the belt is withdrawn from the retractor for the lever 76 to be out of contact with the belt. The microswitch 77 will then assume a first condition. The belt 1 is rewound onto the spool as the carriage 5 moves rearwardly along the track 6, and eventually the lever 76 is engaged by the belt and pivoted to change the condition of the microswitch. The signal obtained from the microswitch 77 can thus be used to indicate whether or not the belt 1 has been brought into use, as by way of an indicating device such as the light 17. The portions of the casing 74 adjacent the slot 75 are engageable by the belt and provide a limit for the length of the belt webbing that can be received on the spool.

Claims: A passive seat belt system comprising a belt (1) movable between an operative position and an inoperative position, an electric motor (9) which can be energised to move the belt between said positions, a retractor (2, 32, 52, 62) from which the belt is withdrawn against a retractive bias by energization of the motor (9), and a latch mechanism (23,25,54) actuable to latch the retractor against belt withdrawal in response to a predetermined condition, characterized by protective means (15,30;15,34;41,42) actuable to de-energize the motor (9) in response to obstruction of belt movement by the latch mechanism (23,24,25). A system as claimed in claim 1 wherein the retractor comprises a spool journalled in a frame for releasably receiving the belt (1), wherein the latch mechanism comprises a ratchet wheel (23) secured to the spool to rotate therewith, a pawl (25) pivotably mounted on the frame for movement from an unlatching position to a latching position of engagement with ratchet wheel to thereby prevent unwinding of the belt from the spool, a member (20) mounted on the frame for rotation from an inoperative position to an operative position to cause the pawl (25) to engage the ratchet wheel (23), inertial acceleration sensing means (22) operable in response to a predetermined acceleration condition to link the member (20) to the spool whereby spool rotation effects the rotation of the member (20), and wherein the protective means comprises an electrical element (30;34) arranged to change condition in response to the movement of the member (20) to thereby signal the position of the pawl (25). A system as claimed in claim 2 wherein the electrical element comprises a switch (30;34) engageable by the member (20). A system as claimed in claim 3 wherein the inertial acceleration sensing means comprises a weight (24) movable in response to a predetermined acceleration of the retractor and wherein the member (20) has a portion (21) mounting the weight, the switch (30) being engageable by the portion (21). A system as claimed in claim 1 wherein the protective means comprises means (41) responsive to excess current demand from the motor (9). A system as claimed in any preceding claim wherein the protective means comprises a switch (15;42) to de-energize the motor (9). A passive seat belt system comprising a belt (1) movable between an operative position and an inoperative position, an electric motor (9) which can be energised to move the belt between said positions, a retractor (2,32,52,62) from which the belt is withdrawn against a retractive bias by energization of the motor (9), and a latch mechanism (23,25,54) actuable to latch the retractor against belt withdrawal in response to a predetermined condition, characterized by protective means actuable to de-activate the latch mechanism in response to energization of the motor (9) to effect belt movement in the direction of withdrawal from the retractor. A system as claimed in claim 7 wherein the retractor comprises a spool journalled in a frame for releasably receiving the seat belt (1), wherein the latch mechanism comprises an inertial weight (24) mounted for movement in response to the predetermined acceleration, a ratchet wheel (23) rotatable with the spool, and a lever (54,55) pivotably mounted for movement from a rest position to engage a first arm (54) thereof with the ratchet wheel in response to the movement of the weight, and wherein the disabling means comprises a second arm (55) of the lever arranged to function as an armature for a solenoid coil (56), whereby the lever occupies its rest position during energization of the coil. A system as claimed in claim 8 wherein the solenoid coil (56) is located with the axis thereof substantially at right angles to the axis of the spool. A system as claimed in claim 7 wherein the latch mechanism comprises a support (21) supporting a hollow inertial weight (24) for toppling movement thereon in response to the predetermined acceleration, and an elongate output member (65) received within the weight and movable thereby from a rest position to effect the latching in response to the toppling of the weight, and wherein the disabling means comprises a solenoid coil (67) mounted below the support (21) with the solenoid coil axis substantially aligned with the output member (65) in the rest position thereof, an aperture in the support (21), an extension portion of the output member (65) extending through the aperture towards the solenoid coil (67), and an armature (66) carried by the output member extension portion for co-operation with the solenoid coil whereby the output member occupies the rest position thereof during energization of the solenoid coil (67). A system as claimed in claim 10 wherein the retractor comprises a spool journalled in a frame for releasably receiving a seat belt (1), and wherein the protective means comprises an electrical element (77) arranged to change condition in response to a predetermined change in the length of belt (1) wound on the spool. A system as claimed in claim 11 wherein the electrical element comprises a switch (77), and a lever (76) has a first end operably engageable with the switch and a second end engageable with the seat belt (1) wound upon the spool under a bias. A system as claimed in any preceding claim comprising an indicator (17) arranged to be energized in response to actuation of the protective means. A system as claimed in claim 13 wherein the protective means comprises manually operable means (43) for de-energizing the motor (9).

Inventors: PATTERSON, MICHAEL
Applicants: BSRD LIMITED
Application year: 1986
Main classification: B60R22
IPC codes: B60R22