Seat belt extension measuring device and system

Abstract

Seat belt extension measuring device, comprising the following: a rewind spring (46) having a first end connected to a middle coil (48) and a second end connected to a rewind spring housing (10); a dielectric material (62) having a first side adjacent to the rewind spring (46) forming a first layer; an electrolytic winding (60) whose two sides border the dielectric material (62), so that the rewind spring (46) is electrically insulated from the electrolytic winding (60); and a capacitive measuring device (90) comprising a first line (91) connected to the first end of the rewind spring (46) and a second line (93) connected to a first end of the electrolytic winding (60).

Description

BACKGROUND OF THE INVENTION

[0001] Occupant size is one of the most important considerations in vehicle design to comfortably and safely accommodate people of different sizes and shapes. Occupants traveling in an automobile are protected by various advanced technology and safety systems. These may include various advanced airbags, seatbelt systems with sensor-based pretensioning and load-limiting capabilities, and more. Seating systems such as airbags and seatbelts are typically optimized for the size of the occupant and their seating position. For example, some of these systems can be adjusted electronically or using pyrotechnics to provide optimal protection during a collision based on the occupant's size.

[0002] Current sizing methods include the use of weight sensors, seat track position, and visual measurements. Other methods include measuring the radius of the webbing on a retractor spool, connecting cable length sensors to the webbing, mounting various types of belt position sensors on the webbing, and using cameras, among others. All of these methods require additional components mounted externally to the retractor. Furthermore, these measuring devices add weight, increase cost, and require additional space to mount in a vehicle.

[0003] DE 10 2005 002 866 A1 discloses a safety belt device with a belt webbing partially wound onto a belt reel, the belt webbing having at least one electrical conductor extending at least over part of the length of the belt webbing, and a device for determining the extended length of the belt webbing. The device for determining the extended length of the belt webbing measures the capacitance and / or inductance of the electrical conductor. US 2008 015 79 40 A1 relates to a device for detecting the presence of objects in a vehicle. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of an exemplary pyrotechnic seat belt retractor pretensioner mechanism. Fig.Figure 2 shows an example of an anthropomorphic test device (ATD) that simulates the dimensions, weight proportions, and joints of the human body in a three-point seat belt. Fig. Figure 3A illustrates how an example seat belt appears when fastened. Fig. Figure 3B shows how the seat belt of Fig. 3A appears when stowed. Fig. 4 is a perspective view of an exemplary rewind spring when a seat belt is stowed. Fig. 5A is a perspective view of the rewind spring of Fig. 4 prior to movement (ie in a stowed condition) of a seat belt retractor. Fig. 5B is a perspective view of the rewind spring of Fig. 4 during initial use of the seat belt retractor. Fig.5C is a perspective view of the rewind spring of Fig. 4 during continued use of a seat belt retractor. Fig. 6 is a perspective view of a portion of the rewind spring of Fig. 4, which shows a layered structure of the rewind spring and a second winding forming a capacitive pull-out sensor. Fig. 7A is a perspective view of an exemplary spring of a retractor incorporating the capacitive sensor in a rewind spring housing. Fig. 7B is a perspective view of the spring of a retractor of Fig. 7A with the capacitive sensor before the seat belt is pulled out of the seat belt housing. Fig. 8A is a perspective view of an example of the capacitive sensor when a small-sized person is buckled up. Fig.8B is a perspective view of an example of the capacitive sensor when a person of average height is buckled up. Fig. 8C is a perspective view of an example of the capacitive sensor when a person of large size is buckled up. Fig. 9A is a perspective view of an example of the capacitive sensor and a capacitor measuring the electronics of an unwound seat belt retractor. Fig. Figure 9B is a perspective view of an example of the capacitive sensor and a capacitor measuring the electronics of a wound seat belt spring retractor. Fig. 9C is a perspective view of an example of the capacitive sensor and a capacitor measuring the electronics, with a first measuring lead connected to the rotation axis and a second test lead connected to an outer end of the rewind spring. Fig.9D is a perspective view of an example of the capacitive sensor and a capacitor measuring electronics, with a first measuring lead connected to an outer end of the rewind spring and a second measuring lead connected to the outer end of the second winding. Fig. 10 is a block diagram of a control subsystem for the occupant protection system. Fig. Figure 11A is a flow diagram of a capacitive measurement technique using a predetermined frequency. Fig. Figure 11B is a flow diagram of a capacitive measurement technique that uses a predetermined frequency in a controller. Fig. Figure 12A is a flow diagram of a capacitive measurement technique that uses a predetermined current. Fig. Figure 12B is a flow diagram of a capacitive measurement technique that uses a predetermined current in a controller. DETAILED DESCRIPTION

[0004] The disclosed subject matter is described in an illustrative manner, and it is understood that the terminology used is intended to be in the nature of words of description rather than limitation. Many modifications and variations of the present disclosure are possible in light of the above teachings, and the disclosure may be practiced otherwise than as specifically described herein.

[0005] A seated passenger in a vehicle should be offered some freedom of movement of the upper body within the vehicle compartment, but this movement should be restricted in the event of a collision. Most modern seat belts are stowed on spring-loaded reels called "retractors," which are equipped with inertial locking mechanisms that prevent the belt from unwinding or withdrawing from the reel during sudden deceleration, such as during a collision. The retractor clamps the seat belt in place in the event of an impact.

[0006] Disclosed herein are systems and methods for determining the approximate size of a vehicle occupant. Based on such determination, the extent and / or type of safety measures to be deployed in the event of a collision or sudden deceleration can also be determined.

[0007] Referring to the figures, wherein like numbers indicate like parts in the different views, Fig. 1 illustrates exemplary components of a pyrotechnic seat belt retractor 100. A rewind spring housing 10 is located adjacent to, e.g., mounted and / or abutting, a pyrotechnic pretensioner 12, which is located adjacent to, e.g., mounted and / or abutting, a first side of the seat belt housing 14. Retractable seat belt webbing 16 is retained within the housing 14. A pyrotechnic tensioning unit 18, of a known type, is also attached or mounted to a second side of the seat belt housing 14. A seat belt inertia trap buckle pocket 20 and mounting screw 22, also of a known type, are also illustrated. The pyrotechnic pretensioner 12 is activated in the event of a crash to "clamp" the seat belt-wearing occupant.

[0008] An extent of extension of the seat belt webbing 16 typically varies according to factors such as a seating position and a size of a seat occupant. Fig. 2 shows an exemplary anthropomorphic test device (ATD) 30 of known type and a placement of the seat belt webbing 16. A first end of the seat belt webbing 16 is attached to a first fixed point 33 near a left hip of the ATD 30. The seat belt webbing 16 leads over a lap portion of the ATD 30 into a buckle 19 and further over a midsection of the ATD 30 through a D-ring 44 and finally to the seat belt retractor 100 (not shown). The retractor 100 can be arranged as shown in the Fig. 3A and Fig. 3B, it may be attached to a vehicle frame 23, to a vehicle floor or to another rigid point.

[0009] A length of seat belt webbing 16 required to secure a vehicle occupant as represented by the ATD 30 varies depending on the size and body type of the ATD 30. Table 1 presents example lengths of unwound seat belt webbing 16 in millimeters (mm) to securely hold the ATD 30 for various occupant sizes. Specifically, the table presents unwound lengths of seat belt webbing 16 for three different body types by a percentage of the general adult population in the United States, arranged by body size, and for that of a hypothetical average 6-year-old. As can be seen, an unwound length of seat belt webbing 16 can vary by up to 550 mm due to varying occupant sizes. Table 1 ATD size Belt length (mm) 6 years old 670 5 percent of the population 900 50 percent of the population 1070 95 percent of the population 1220

[0010] Fig.3B shows an example of the seat belt in a stowed position. A typical total length of seat belt webbing 16 is approximately 3300 mm in one embodiment. The length of webbing from the seat belt retractor 100 to an anchor through the D-ring 44 varies from vehicle to vehicle. Typically, the amount of seat belt webbing 16 wound onto a spool (not shown) mounted on a central spool shaft 48 of the seat belt retractor 100 is approximately 1300 mm or more when the seat belt is in the stowed position.

[0011] Fig.4 illustrates an exemplary rewind spring 46 when the seat belt webbing 16 is stowed. The rewind spring 46 is arranged to draw excess seat belt webbing 16 onto the central spool 48. A first end of the rewind spring 46 is connected to a central shaft 48 that rotates about the axis 50 of the central spool shaft 48, and a second end of the rewind spring 46 is connected to a tab on the outer periphery of the rewind spring housing 10, as shown in Fig. 4. The spring winds up in the space between the outer circumference and the central spool shaft 48.

[0012] The rewind spring 46 is under tension (torsion) when the seat belt webbing 16 is stowed, as shown in Fig. 5A shown. Fig. Figure 5B shows that the rewind spring 46 has increased its tension as the seat belt webbing 16 is pulled from the retractor 100. The rewind spring 46 begins to wind toward the center spool 48. Fig.Figure 5C illustrates in more detail the tensioning and winding of the rewind spring 46 around the central spool 48 while the seat belt webbing 16 is further unwound or pulled out.

[0013] Now referring to the Fig. 6, Fig. 7A and Fig. 7B illustrates an electrolytic flexible coil 60 layered adjacent to a dielectric material 62, which is an electrical insulation barrier, to detect a length of seat belt webbing 16 unwound from seat belt retractor 100. Dielectric material 62 is attached to rewind spring 46 to form a flexible parallel-plate capacitor 75. A capacitor is a two-terminal electrical component used to electrostatically store energy in an electric field and includes two electrical conductors, e.g., rewind spring 46 and electrolytic coil 60, separated by an insulator, e.g., dielectric material 62. Fig.Figure 6 shows a view of the rewind spring 46, the electrolytic winding 60 and the dielectric material 62. The potential charges on the plates of the flexible parallel plate capacitor 75 are also shown as positive charges 64 and the negative charges 66 are in Fig. 6 to illustrate that the rewind spring 46 and the electrolytic winding 60 form the plates of a capacitor. The polarity of the charge may be reversed based on the polarity of the power source used to measure the capacitance.

[0014] When the seat belt 16 is in a stowed condition (see Fig.4) The flexible parallel-plate capacitor 75 has a specific capacitance value, which is measured by the capacitance measuring device 90. When the seat belt webbing 16 is extended (i.e., pulled out) from the seat belt housing 14, the rewind spring 46 and the electrolytic winding 60 begin to wind around the central spool shaft 48. Since the shape of the rewind spring 46 and the electrolytic winding 60 change as the seat belt webbing is extended, a capacitance value changes as the webbing is pulled out. Advantageously, this capacitance value can be used to determine a length of seat belt webbing 16 that is extended (i.e., pulled out).

[0015] Methods for measuring capacitance are known, and any one of several approaches, such as an oscillator circuit or a time-charge circuit, may be included in the device 90 to measure the capacitance between the spring 46 and the electrolytic winding 60. Furthermore, integrated circuits, such as a system on a chip (SOC), are known that have been designed to measure capacitance with high accuracy. SOCs are small and inexpensive and can be easily integrated into the rewind spring housing 10 with minimal impact on the overall package size.

[0016] The SOC is an integrated circuit (IC) that integrates all the components of a computer system into a single chip substrate, including a processor, memory for storing instructions, and registers for executing processor instructions. SOCs are useful because they can accommodate digital input and output (I / O) signals, analog I / O signals, and mixed-signal I / O, and support various communication port types, such as Controller Area Network (CAN), Ethernet, or Inter-Integrated Circuits (I / O). 2 C), all on a single chip. SOCs are very common in embedded systems and mobile electronics due to their size and low power consumption. Alternatively, the capacitance can be measured by a device connected to the spring 46 and the electrolytic winding 60 outside the retractor.

[0017] As explained above, the electrolytic winding 60 should be electrically insulated from the rewind spring 46. Therefore, a flexible dielectric material 62, as also mentioned above, is placed between the rewind spring 46 and the electrolytic winding 60. Since the rewind spring 46 and the insulated electrolytic winding 60 will slide against each other when the seat belt is extended and retracted, it is also important that this material has a low coefficient of friction. Materials such as Teflon, Mylar, polyvinyl chloride (PVC), polypropylene (PP), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or other similar materials can be used as the flexible dielectric material 62. The term coefficient of friction is well-known and is a dimensionless scalar value that describes the ratio of the normal force to the frictional force between two bodies and the force compressing them.

[0018] The electrolytic winding 60 may be made of the same material and thickness as the rewind spring 46, which is typically a spring steel or spring steel alloy. Alternatively, the electrolytic winding 60 may be aluminum, copper, or a malleable metal electrical conductor. In alternative embodiments, the electrolytic winding 60 may be a metal-like material, a metallized thin foil, or a metallized layer on dielectric plastic, and may have varying lengths and widths. The width of the conductive (electrolytic) winding 60 is equal to or less than the width of the spring 46 and can affect the capacitance of the capacitor 75 by changing the area adjacent to the rewind spring. A wider winding produces a capacitor with a higher capacitance.Depending on the selected material and the flexibility of the electrolytic winding 60, it may or may not affect the mechanical properties of the spring, and with a wider winding, it can increase the spring constant. The length of the winding determines the portion of the belt extension monitored by the capacitor. The winding can be lengthened or shortened to monitor only the portions of the belt extension of interest.

[0019] In yet another embodiment, the layer of dielectric material 62 and the electrolytic winding 60 are combined into a single dielectric-electrolytic layer and are attached to the rewind spring 46 to form the flexible parallel plate capacitor 75.

[0020] Fig. 7A shows a location of the flexible parallel plate capacitor 75 in the rewind spring housing 10, whereas Fig.7B shows a position of the flexible parallel plate capacitor 75 when it is not wound around the central spool shaft 48 and when a major portion of the flexible parallel plate capacitor 75 is closer to the outer periphery 47 of the rewind spring housing 10 than to the central spool shaft 48.

[0021] As stated above, a shape of the flexible parallel plate capacitor 75 varies depending on the size of a seat occupant. For example, the flexible parallel plate capacitor 75 is generally not wrapped around the center coil shaft 48, or a shorter length of the capacitor is wrapped around it when a smaller person is buckled in, as in Fig. 8A. The flexible parallel plate capacitor 75 generally has an increased length wrapped around the central coil shaft 48 when a person of average size is strapped in, as shown in Fig.8B. Furthermore, when additional webbing 16 is extended from the seat belt housing 14 for a larger person, the flexible parallel plate capacitor 75 generally has an increased length wrapped around the central coil 48, or it would be completely wrapped thereon, as in Fig. 8C. In general, the parallel plate capacitor moves closer to the coil center shaft 60 as the seat belt is extended.

[0022] With reference to the Fig.9A-9D, to measure the capacitance of the parallel-plate capacitor 75 in the illustrated embodiment, a first lead 91 of a capacitive measuring device 90 is attached to the rewind spring 46, and a second lead 93 of the capacitive measuring device 90 is attached to the electrolytic winding 60. The second lead 93 on the electrolytic winding 60 must be free to move within the rewind spring housing 10 to allow movement of the spring as it winds around the center shaft. Fig. Figure 9A shows the capacitive measuring device 90 connected to an unwound rewind spring 46, while Fig. Figure 9B shows the capacitive measuring device 90 connected to a wound rewind spring 46.

[0023] The electrolytic winding 60 can be positioned anywhere on the rewind spring 46. For example, Fig.9C, the rewind spring 46 and the electrolytic winding 60 are located near the central spool shaft 48 in contrast to the spring housing 10, and the capacitive measuring device 90 includes a measuring lead 93 connected to the rotational axis of the central spool shaft 48, one lead being electrically connected to the electrolytic winding 60, and the other lead 91 being connected to an outer end of the rewind spring 46.

[0024] In another embodiment (see Fig.9D), the first lead 91 of the capacitive measuring device 90 is connected to the electrolytic winding 60, the second lead 93 is connected to the rewind spring 46, and the flexible parallel-plate capacitor 75 is positioned near the outer peripheral region 47 of the rewind spring housing 10, as opposed to an inner peripheral region 49 closer to the central coil shaft 48. Furthermore, it should be understood that the attachment points of the leads 91 and 93 of the capacitive measuring device 90 may vary depending on the technology used, as well as space and design considerations.

[0025] The seat belt retractor 100 can be used as described above and as described in Fig.10 may include an impact sensing subsystem 118. The controller 122 of the impact sensing subsystem 118 generally includes a processor 124 and a memory 126. The memory 126 stores instructions executable by the processor 124 to detect a vehicle impact or collision event, e.g., in a known manner. The controller 122 is further generally programmed, upon detecting the impact, to cause the deployment of the deployment mechanism 11, which moves the occupant protection system or seat belt retractor 100 from the undeployed state to the deployed state and activates the pyrotechnic pretensioner 12 in response to an instruction from the deployment mechanism 11.

[0026] An impact sensor 78 of known type is typically connected to the controller 122 to transmit data to the controller 122. The impact sensor 78 may be of any suitable type, e.g., using accelerometers, radar, LiDAR, and / or a vision system. The vision system may include one or more cameras, CCD image sensors, and / or CMOS image sensors, etc. Based on data transmitted by the impact sensor 78, the controller 122 may trigger the triggering mechanism 11.

[0027] Communication between the controller 122, the impact sensor 128, the triggering mechanism 11, and / or other components in the vehicle 110 may be performed via a vehicle's communication bus 80, such as a controller area network (CAN) bus. The controller 122 may use information from the communication bus 80 to control the triggering of the triggering mechanism 11. The triggering mechanism 11 may be connected to the controller 122, or it may be Fig. 10 shown connected to the communication bus 80.

[0028] In one embodiment, the capacitance value obtained from capacitor 75 may be sent to an impact sensing subsystem 118 for use in calculating whether to activate pyrotechnic pretensioner 12 in the event of a collision or sudden deceleration (see Fig. 10). Fig.11A is a flowchart illustrating an exemplary process 200 for evaluating the capacitance of the flexible parallel-plate capacitor 75 by determining an unknown capacitance at a predetermined frequency 205. A signal of a predetermined frequency is generated in a block 210 and applied to the rewind spring 46 and the electrolytic winding 60 in a block 220. After a predetermined period of time, the voltage on the flexible parallel-plate capacitor 75 stabilizes in a block 230. The predetermined period of time is selected using the predetermined frequency and an estimate of the capacitance value. A voltage measurement is then taken in a block 240, and the length of the extended seat belt webbing is calculated in a block 250. The length information is sent to the impact sensing subsystem 118 in a block 260.

[0029] In an alternative embodiment, the voltage measurement may be sent directly to the impact sensing subsystem 118. Fig.11B is a flowchart illustrating an exemplary process 201 for evaluating the capacitance of the flexible parallel-plate capacitor 75 by determining an unknown capacitance at a predetermined frequency 206. A signal of a predetermined frequency is generated in a block 215 and applied to the rewind spring 46 and the electrolytic winding 60 in a block 225. After a predetermined period of time, the voltage on the flexible parallel-plate capacitor 75 stabilizes in a block 235. The predetermined period of time is selected using the predetermined frequency and an estimate of the capacitance value. A voltage measurement is then taken 245 and sent to the impact sensing subsystem 118 in a block 255, and the impact sensing subsystem calculates the unwound length of the seat belt in a block 265.

[0030] Fig.12A is a flowchart illustrating an example process 300 that includes an alternative technique for calculating capacitance using a predetermined current at a block 305. A signal having a predetermined current is then generated at a block 310 and applied to the flexible parallel-plate capacitor at a block 320. Next, voltages are measured over a period of time at a block 330, and the length of the extended seat belt webbing is calculated at a block 340. The predetermined period of time is selected using the predetermined current value and an estimate of the capacitance value. The calculated length is then sent to the impact sensing subsystem at a block 350.

[0031] In an alternative embodiment, the voltage over time measurements may be sent directly to the impact sensing subsystem 118. Fig.12B is a flowchart illustrating an exemplary process 301 for calculating capacitance using a predetermined current in a block 306. A signal having a predetermined current is then generated in a block 315 and applied to the flexible parallel-plate capacitor in a block 325. Next, voltages are measured over a period of time in a block 335, and the measurements are sent to the impact sensing subsystem 118 in a block 345. The predetermined period of time is selected using the predetermined current value and an estimate of the capacitance value. The length is then calculated by the impact sensing subsystem 118 in a block 355.

[0032] Other objects, advantages and outstanding features of the invention will be apparent to one skilled in the art from the following claims.

Claims

[1] Seat belt extension measuring device comprising: a rewind spring (46) having a first end connected to a central spool (48) and a second end connected to a rewind spring housing (10); a dielectric material (62) having a first side adjacent to the rewind spring (46) forming a first layer; an electrolytic winding (60) having both sides adjacent to the dielectric material (62) such that the rewind spring (46) is electrically insulated from the electrolytic winding (60); and a capacitive measuring device (90) having a first line (91) connected to the first end of the rewind spring (46) and a second line (93) connected to a first end of the electrolytic winding (60). [2] The device according to claim 1, wherein the electrolytic winding (60) and the rewind spring (46) are made of a same material. [3] The device of claim 1, wherein the electrolytic winding (60) is made of aluminum, copper or a malleable metal in the form of a flexible thin layer or foil. [4] The device of claim 1, wherein the electrolytic winding (60) is a metallized coating on a dielectric plastic layer. [5] The device of claim 1, wherein the dielectric material (62) and the electrolytic winding (60) are combined to form a dielectric-electrolytic layer. [6] The device of claim 1, wherein the electrolytic winding (60) has a length and width that are shorter than or approximately equal to the corresponding length and width of the rewind spring (46). [7] The device of claim 1, wherein a first end of the electrolytic winding (60) is closer to the outer periphery of the rewind spring housing (10) than to the central coil (48) in the rewind spring housing (10). [8] The device of claim 1, wherein the first end of the electrolytic winding (60) is closer to a central coil (48) in the rewind spring housing (10) than to the outer periphery of the rewind spring housing (10). [9] The device of claim 1, wherein the dielectric material (62) comprises Teflon, Mylar, polyvinyl chloride (PVC), polypropylene (PP), polyethylene naphthalate (PEN), polyethylene terephthalate (PET) or other suitable dielectric material (62). [10] System for clamping a seat belt in the event of an impact, comprising: a rewind spring (46) and an electrolytic winding (60) joined together to form a capacitor; a capacitive measuring device (90) connected to the rewind spring (46) and the electrolytic winding (60); a processor (124) for detecting the occurrence of an impact from the data from at least one impact sensor (78); a sensing subsystem for determining whether to activate a trigger mechanism to activate a pyrotechnic pretensioner (18) located in a seat belt assembly based on the belt extension calculated from the measured capacity; and a memory that stores instructions to be executed by the processor (124). [11] The system of claim 10, wherein the at least one impact sensor (78) is an accelerometer, a radar device, a LiDAR device, or a vision system. [12] The system of claim 10, wherein data transmission between the sensors and the impact detection subsystem (118) is effected by means of a controller area network bus. [13] The system of claim 10, wherein the capacitive measuring device (90) comprises a second processor (124) and a second memory for storing instructions to measure the capacitance.

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