FR2652908A1 - SPEED CHANGE DETECTOR WITH SPRING RECALL. - Google Patents

Abstract

An accelerometer for a passenger restraint system in a motor vehicle comprising a housing (18) with a path for an inertial element (46) and spring means (22) for biasing the inertial element towards a preselected position . When the vehicle decelerates to a degree greater than a predetermined degree, the ball moves away from the preselected position and forms electrical contact with a blade (24). A closed chamber can be used as a damping element for the inertial element.

Description

The present invention relates to a speed change detector or

  accelerometer, used in motor vehicles to detect sudden speed changes and to actuate in response a passenger restraint, such as an airbag. More particularly, this device comprises an element which

  moves to a predetermined position in response to a deceleration-

  sudden ration to close a pair of contact blades, this device also having a spring to return the element. Studies indicate that injuries resulting from motor vehicle accidents, especially at high speed,

  can be significantly reduced or eliminated by the use of

  tion of passenger restraint systems (the term "passenger" here also covers the driver of the vehicle). These systems include an inflatable balloon, usually called an air bag, which is normally stored in the dashboard or in the steering wheel. When the motor vehicle is subjected to sudden deceleration, the cushion

  pneumatic pneumatic is inflated and deploys automatically

  only in a condition that absorbs passengers, limits

  movement and prevents contact between them and the interior

  automobile, such as windshield, steering wheel

  tion, dashboard, etc. Of course, a crucial element of all these systems is the speed change detector or accelerometer which triggers the inflation and deployment of the airbags. The movement of the motor vehicle must be carefully and precisely controlled so that the air bags can deploy very quickly, before passengers risk

to be injured.

  US Patent No. 4,329,549 describes a speed change detector, issued to the present Applicant. This detector comprises a tubular sheath surrounding a metal housing, a metal ball and a magnet recalling the ball in the direction of a first end of the housing. Two electrical contact blades are arranged at the second end of the housing. The detector is arranged in the motor vehicle so that it is oriented so that when the vehicle decelerates beyond a predetermined level, the ball moves from the first end to the second end, making contact with the two blades. Because the blades and the ball are made of an electrically conductive material, when the ball comes into contact with the blades, it is established

  an electrical path between the two blades. This electric journey

  that is used to trigger a signal for deployment

pneumatic cushions.

  Because the contacts must have a certain flexibility

  intrinsic bility, they are normally made of steel, copper

  or alloy of these metals, while the ball is usual-

  gold plated to ensure good electrical contact

  between the ball and the contact blades. Due to the differ-

  Due to the electro-chemical activity between these materials, corrosion can occur due to electrolysis, which can form an insulating layer on the ball and / or the contact blades, thus causing the detector to malfunction. This problem is further compounded if the chamber containing the ball and contacts is not isolated from the atmosphere due to fumes and other contaminants

  from the automotive engine.

  Another problem encountered in the prior detector is that the restoring force on the ball is produced by a permanent magnet. Because the magnet must produce a relatively strong magnetic field, it is large

and wastes space.

  Given the aforementioned drawbacks of the prior art, it is an object of the present invention to produce a passenger restraint system in which an element

  inertial is recalled towards a preset position

  spring loaded, eliminating the need for a

permanent magnet.

  Another object is to provide a pass restraint system.

  gers with a detector in which the inertial element is not part of the electrical circuit used to actuate the airbag, which eliminates the need for a

  expensive coating on the element.

  Another object is to produce a pass restraint system.

  gers with a small and inexpensive accelerometer.

  Other objects and advantages of the invention will become apparent

  on reading the following description of the invention.

  In a first aspect, the invention provides an accelerometer used in a passenger restraint system in a

  motor vehicle, comprising a housing, an inert element

  tiel, a path defined in the housing for the inertial element

  tiel and a spring to return this inertial element towards a preselected position on the path, the path being carried out so as to allow the inertial element to move away from this preselected position

  in the presence of a deceleration of the motor vehicle.

  During a collision, deceleration causes the inertial element to move along this path and causes a change in the state of a pair of electrical contacts.

  coupled to an actuation circuit for actuating a device

  restraint such as an air bag. Preferably

  rence, the spring is part of one of the contacts, this

  which eliminates the need for a separate spring.

  In a second aspect, the invention provides a passenger restraint system for a motor vehicle comprising an air cushion arranged to retain a passenger when the vehicle undergoes a deceleration greater than a predetermined level, means for inflating the air cushion to inflate this cushion and an accelerometer for detecting deceleration and actuating the means for inflating the air cushion, this accelerometer being

  as defined above.

  The invention will be better understood on reading the description.

  detailed description, given below by way of example only, of several embodiments of the invention, in conjunction with the attached drawing, in which: - Figure 1 is a plan view of a detector for a restraint system passengers according to the invention; - Figure 2 is a side elevational view of the detector of Figure 1; - Figure 3 is a partial sectional view in side elevation of the detector of Figure 3, the inertial element being in an intermediate position;

  - Figure 4 shows the detector of Figure 3 with the element

  inertial in a terminal position; - Figure 5 is a partial side sectional view of another embodiment of the invention, with the ball in a first position or rest position; and - Figure 6 shows the detector of Figure 5 with the

ball in its final position.

  In what follows, terms such as top, bottom, above, below, vertical, horizontal, etc., are used simple-

  to facilitate the description of the invention. In se

  now referring to the figures, an accelerometer or detector

  gearshifter 10 made according to the invention is usually arranged in a housing mounted on the motor vehicle (not shown). The detector is connected by a cable 12, -with at least two conductors 14,16, to a control device for the deployment of the cushion

  pneumatic, described in more detail below.

  The detector has a generally tubular housing 18 in one

  non-conductive material, such as molded plastic

  ble and has a cylindrical side wall 20. Inside the casing are two contact blades 22, 24 having extensions generally perpendicular to the side wall 26. The blade 22 has a first extension

  28 and a second extension 30 offset from the first extension-

  ment by a curved section 32. The blades 22 and 24 are fixed to the bottom 36 of the housing by respective pins

38.38. -

  The housing 18 also has an upper wall 40. A multiplicity of ribs 42 extend downward from the wall 40. At their lower ends, the ribs have curved portions 44. An inertial element in the form of, for example a spherical ball 46 made of steel or any other relatively dense material, is disposed between the ribs 42. The ribs are arranged and produced so as to form a vertical tubular path

  (seen in Figures 3 and 4) for ball 46.

  The blades 22, 24 are made of a flexible conductive material, for example steel, copper or alloys of these metals. As can be seen in FIG. 2, the blade 28 is arranged in such a way that, under normal conditions, it exerts an upward biasing force on the ball 46 so as to manually

hold in a rest position.

  The detector is arranged so that it is oriented so that, when the vehicle is involved in a collision which causes a deceleration exceeding a predetermined level, the ball 46 overcomes the return force of the blade 22 and begins to move downward. along the path defined by the ribs 42. When the ball moves downward, it curves the blade 22 until it comes into electrical contact with the blade 24, as seen

  in Figure 3. The blades are part of an electrical circuit

  stick or other means of triggering the deployment of the cushion. For example, the blade 22 can be coupled to a battery 140 via the conductor 14, while the blade 24 can be coupled to a mechanism

  actuator 142 through the conductor 16.

  When the two blades 22 and 24 touch, a current flows from the battery 140 to the mechanism 142 to deploy

  the air bag 144 (see FIG. 3).

  After the two blades have come into electrical contact,

  if the deceleration of the vehicle is large enough, -

  the ball continues its downward movement by bending the two blades 22, 24 until it is stopped by the curved rib sections 44, as seen in FIG. 4. The combined force of the blades 22,24 slows down the ball in its last movement, which reduces the impact between ball 46 and case 18. As soon as the deceleration has disappeared, the ball is returned to its rest position

of Figure 2 by the blades.

  If the detector is placed in a relative environment-

  ment clean, such as the passenger compartment of the vehicle, it is not necessary that the interior of the housing 18 is hermetically sealed. Consequently, the detector of Figures 1 to 4 can be easily fabricated

  and inexpensively by standard molding techniques.

  A variant of the invention is shown in Figures and 6. The speed change detector 110, shown in these figures, has two blades 122,124 and a ball 146, made and arranged like the blades 22,24 and the ball 46 , respectively, Figures 1 to 4. However, in this embodiment, the ball 146 is arranged in a closed tubular chamber 148 with a narrow lateral slot 150. The blades 122,124 enter the chamber 148 through this slot 150. The diameter in section transverse

  of chamber 148 is substantially equal to or slightly higher than

  laughing at the diameter of the ball 146. Consequently, in this embodiment, in addition to the action of the blades, the movement of the ball is also affected by the air disposed in the chamber 148 which acts as a damper. When

  the detector 110 is arranged in an automobile, and in particular

  ment in the crushing zone thereof, in the presence of a sudden deceleration, the ball 146 moves downwards from the rest position shown in the figure, to an intermediate position in which the blade 122 touches the blade 124 and finally in a position

  final shown in figure 6. All other conditions

  being identical, the time interval from the moment when the ball 146 begins to move until the moment when the blades 122, 124 touch is slightly longer than for a detector produced according to FIGS. 1 to 4, from which it results in a slightly more precise detector

and free from error.

  Many modifications can obviously be made to the invention without departing from its scope as defined

in the appended claims.

Claims (19)

Claims   1. - Accelerometer (10), used in a passenger restraint system for a motor vehicle, characterized in that it comprises: - a housing (18), - an inertial element (46), - travel means arranged in the housing to define a path for the inertial element, and - spring means for returning the inertial element towards a preselected position on the path, this path being arranged and produced so as to allow the inertial element to move away from the preset position in the presence of a deceleration of the motor vehicle.   2. - Accelerometer according to claim 1, characterized in that it further comprises indication means arranged in the housing (18) to indicate the position   of the inertial element (46) in this path.   3. - Accelerometer according to claim 2, characterized in that these indication means comprise two electrical contacts having an open contact position and a closed contact position, these contact positions being   defined by the position of the inertial element.   4. - Accelerometer according to claim 1, characterized in that the path means comprise a closed chamber   (148) to house the inertial element.   5. - Accelerometer according to claim 4, characterized in that this chamber further comprises a gas for damping   the movement of the inertial element (146).   6. - Accelerometer according to claim 1, characterized in that these spring means comprise a blade (22) and a contact means (24), the first blade being arranged and arranged to push the ball towards its resting position and pivoting under the action of the displacement of the inertial element under the effect of deceleration to come into   contact with the contact means (24).   7. - Accelerometer for a passenger restraint system in a motor vehicle, characterized in that it comprises a housing (18), -   - an inertial element (46) disposed inside this casing, - path means for defining a path of movement of the inertial element, and - spring means disposed inside the casing to recall the inertial element to a first position   on the way, this inertial element moving in distance   gaining from its first position when the motor vehicle undergoes an acceleration.   8. - Accelerometer according to claim 7, characterized in that it comprises indication means for indicating   the position of the inertial element inside the housing.   9. - Accelerometer according to claim 7, characterized in that the spring means comprise a flexible blade (22) arranged to return the inertial element (46) to a rest position and a contact means (24), this blade coming into contact with the contact means when the inertial element moves by a preselected distance   away from the first position.   10. - accelerometer according to claim 9, characterized 11 in that the contact means is constituted by a second blade (24).   11. - Accelerometer according to claim 10, characterized in that the first blade and the second blade cooperate to slow the inertial element after the contact has   was established between the first blade and the second.   12. - Accelerometer according to claim 7, characterized   in that the path means comprise a tubular chamber   laire (148) containing the inertial element (146) and a gas   to dampen the movement of the inertial element.   13. - Passenger restraint system for a motor vehicle, characterized in that it comprises: (a) a pneumatic cushion arranged.and arranged to retain   a passenger when the motor vehicle decelerates   tion, (b) air bag inflating means for inflating the air bag; and (c) an accelerometer (10) for detecting this deceleration and actuating the means for inflating the airbag, this accelerometer comprising: (i) a housing (18), (ii) an inertial element (46) disposed in the housing,   (iii) path means for defining a movement path   ment of the inertial element inside the case, and (iv) spring means arranged in the case to return the inertial element towards a first   position in the absence of this deceleration.   14. - System according to claim 13, characterized in that the spring means comprise a first blade   (22) disposed in the housing and extending in the path.   15. - System according to claim 14, characterized in that it comprises a contact means disposed inside the housing to come into contact with the first blade when the inertial element moves from the first   position to a second position along this path.   16. - System according to claim 15, characterized in that the contact means is constituted by a second blade (24).   17. - System according to claim 13, characterized in   what the journey means are constituted by a multi-   plicity of ribs (42) extending inside the housing.   18. - System according to claim 13, characterized in that the path means comprise a closed chamber (148) for housing the inertial element and a gas for damping   the movement of the inertial element (146).   19. - System according to claim 18, characterized in that the chamber has a lateral slot (150) and in that the spring means extend in this chamber through slot.