KR20000057565A - Glass capsule enclosed shock sensor - Google Patents

Abstract

PURPOSE: A shock sensor is provided to extend the closure duration and increase the reliability. CONSTITUTION: A shock sensor (20) having some structural similarities to a reed switch, particularly in the use of a glass capsule (22) which hermetically seals the components of the shock sensor. The shock sensor employs a sensing mass (31) mounted on a metallic planar spring (32). Under the influence of a crash-induced acceleration, the sensing mass is driven against a fixed contact to close an electrical circuit. The contact surface (40) which is formed on the sensing mass is oriented at an angle of 60 degrees out of the plane containing the spring.

Description

Shock sensor {GLASS CAPSULE ENCLOSED SHOCK SENSOR}

Shock sensors are used in vehicles, including vehicles, to detect collisions in vehicles. In the event of a collision, the shock sensor triggers the electronics to activate one or more safety devices. Inflatable airbags, a type of safety device, are widely used by consumers because they improve the overall safety of the vehicle. Reliable deployment of airbags without unnecessary deployments includes actuation logic that can assess the nature and direction of a collision when a collision is occurring and determine whether the airbag is deployed based on pre-programmed logic. This is facilitated by employing a plurality of sensors in combination. However, solid state shock sensors tend to lose their sense of reality and may indicate that collisions are often occurring due to high frequency interference, electronic noise, crosstalk in electronic components, and the like. Mechanical shock sensors, when included as an integral part of an airbag deployment system, prevent unnecessary bag deployments that care about microelectronic problems. Because of this lack of sensitivity to mechanical interference, mechanical shock sensors are an important part of an airbag deployment system. Many shock sensor types employing reed switches are designed with a highly reliable electronic switch that can be configured to have the necessary dwell time required for reliable operation of vehicle safety equipment. There is a particular advantage when combining mechanical shock sensors. Reed switches have also been designed to be compact so that the switches are easily mounted to a particular part of the vehicle. The test shows that during a crash, a specific part of the vehicle receives a representative shock that indicates the amplitude of the crash. Therefore, shock sensors with small packaging dimensions are sensitive to proper placement of the shock sensor.

The shock sensor of the present invention has a structural similarity to the reed switch, in particular in the use of glass capsules which hermetic seal around parts of the shock sensor. However, while a reed switch functioning as a component of a shock sensor requires a moving magnetic mass, the shock sensor of the present invention employs a sensing mass mounted on a metal plane spring. Under the influence of acceleration due to a collision, the spring mounted mass is driven against a fixed contact to close the electrical circuit.

The sensing mass is formed using injection molded powder-metallurgy technology or metal stamping. The sensing mass is made to have a contact surface in the direction of 60 ° from the plane of the spring to extend the sealing duration. The sensing mass also has a structural property that allows the sensing mass to prevent undesirable movement of the mass. The sensor is oriented such that the acceleration force due to the collision is approximately perpendicular to the plane containing the spring. The orientation of the contact area on the sensing mass and similarly oriented fixed contact are sufficient to dissipate the energy to eliminate most splashing on the initial seal. The contact angle of 60 ° provides a more reliable and smaller noise shield signal in the presence of shock due to impact. The holding time of the initial contact seal is increased by 5-10 times due to the inclined contact, compared to the case of sensor closure with flat edges. The holding time for larger forces is similar to a collision detection device that is magnetically maneuvered in some cases. The stationary contact that the sensing mass contacts may also be a soft rod shape that reduces the sensitivity to manufacturing imperfections.

The present invention relates to a shock sensor, and more particularly to a shock sensor used for engaging or deploying a vehicle safety device.

1 is a side view of the shock sensor of the present invention;

2 is an end view of the shock sensor of FIG. 1 along line 2-2;

3 is a cross-sectional view of the shock sensor of FIG. 1 along line 3-3;

4 is an isometric view of the acceleration sensing mass mounted to the shock sensor of FIG.

5 is an isometric view of the shock sensor of FIG. 1 without an enclosed glass capsule, FIG.

6 is a schematic diagram showing comparative flexibility in tension of a U-shaped joint supporting the planar spring of the shock sensor of FIG. 1;

FIG. 7 is a schematic diagram showing comparative flexibility in vertical shear deformation of a U-shaped joint supporting the planar spring of the shock sensor of FIG. 1; FIG.

8 is a schematic diagram showing comparative flexibility in horizontal shear deformation of a U-shaped joint supporting the planar spring of the shock sensor of FIG. 1;

9 is an isometric view of another embodiment of the shock sensor of the present invention;

10 is a side view of another embodiment of the shock sensor of the present invention;

11 is an isometric view of the acceleration sensing mass of the shock sensor of FIG.

12 is a cross-sectional view taken along line 12-12 of the shock sensor of FIG. 10;

13 is a side view of another embodiment of the shock sensor of the present invention.

Reference is made to FIGS. 1-13 with the same reference numerals assigned to the same parts, in which a shock sensor 20 is shown. The shock sensor 20 consists of a glass capsule 22 defining an interior volume 24. The internal volume 24 may be filled with an inert gas or a gas having a high dielectric yield resistance value. The glass capsule 22 has a first end 23 formed around the short lead wire 26 and the long lead wire 28 and a second end 25 formed around the mounting lead wire 30. Electrical contact is made between the short lead wire 26 and the long lead wire 28 and the mounting lead wire 30 by an acceleration sensing mass 31 mounted on the planar spring 32.

The spring 32 has an attachment end 38 welded between the raised flange 36 formed at the end 39 of the long lead wire 28 and the tab 37 in the plane that is part of the mounting lead wire 30. The shock sensing mass 31 is welded to a spring 32 adjacent to the spring end 34 opposite the attachment end 38. The shock sensing mass 31 has a contact surface 40 oriented 60 ° from the plane of the spring 32. 4 shows the orientation of the spring 32 plane with respect to the contact surface 40 of the mass 31. As shown in FIG. 2, the contact surface 40 is engaged with the fixed contact surface 42 formed at the end 44 of the short lead wire 26. The short lead wire 26 has a deformation 46 defining a contact surface 42 which does not move.

In a typical shock sensor 20, the spring 32 may have a thickness of approximately 0.05 mm and a width of approximately 0.76 mm. The total length of the spring from end to end is approximately 10.7 mm. Thus, the spring is only flexible in the direction perpendicular to the plane defined by the spring 32 by its dimensions. The vertical direction of the spring 32 is aligned with the direction of acceleration desired to be sensed. In use, the sensor 20 may be mounted directly to a circuit board comprising some or all of the electrical components used to activate the airbag or similar device by the leads 30, 26, 28. The sensor may also be mounted in a package to facilitate orientation and mounting of the sensor to a specific portion of the vehicle determined through the testing and analysis to reliably indicate the direction and condition of the crash.

The shock sensor 20 utilizes manufacturing tools and techniques for making a reed switch to manufacture a shock sensor. Reed switch manufacturing processes have been developed around mass production of components such as lead wires and springs, and inexpensive and high precision contact. The reed switch manufacturing process also facilitates the assembly of the lead wires and the spring mass, thus automatically positioning them with high tolerances to weld seal the glass capsules around the switch components.

During manufacture, the hermetic glass capsule 22 is positioned around the shock sensor leads 26, 28, 30, and heated until the ends of the capsule are soft enough to seal the leads. The connection between the long lead wire 28 and the mounting lead wire 30 serves to accurately position and maintain the spring. However, as the glass shrinks as the glass capsule 22 cools, the ends 23 and 25 move towards each other. This shrinkage of the glass capsule results in a deformation sufficient for the capsule to rupture the sensor 20 or adversely affect its overall reliability. To overcome this shrinkage of the glass capsule, a strain relief U-shaped member 48 is included in the structure of the mounting lead wire 30 between the planar tab 37 and the shank of the mounting lead wire 30. Strain relief U-shaped members 48 are shown in FIGS. 1 and 5-8. FIG. 6 shows a considerable exaggeration in the ability of the U-shaped member to respond to the compressive force indicated by arrow 52. The direction of force shown in FIG. 6 is caused by the contraction of the glass capsule 22. 7 and 8 show the sheer force in the vertical direction indicated by the arrow 54 of FIG. 7 and the arrow 56 of FIG. 8. The vertical force shown in Figs. 7 and 8 is exaggerated, and in particular, very small movement can occur in the U-shaped member by the vertical force. As will be appreciated by those of ordinary skill in the mechanical arts, the U-shaped member is not flexible in vertical force and relatively flexible in compression. This is because the long lead wire 28 and the flat spring 32 mounted on the short mounting lead wire 30 are relatively firmly supported, but at the same time, the U-shaped member 48 prevents the compressive force generated by the cooling of the glass capsule 22. It means to accept.

By utilizing the technology of the reed switch manufacturer, the shock sensor 20 enables the benefits of the low cost and high reliability inherent in the reed switch to be achieved even with the shock sensor which can be suitably used in the vehicle's safety system.

In operation, the shock sensor 20 is mounted to a vehicle having a plane defined by a spring 32 perpendicular to the line of action that may be caused by a shock-induced accident or crash. The shock sensor 20 shown in FIGS. 2 and 3 is further inclined so as to move freely toward the arrow 58 indicating the direction in which the collision load decelerates the vehicle and the shock sensor 20 mounted on the vehicle. When the vehicle including the shock sensor 20 is subjected to a shock-induced collision, the vehicle is decelerated rapidly to decelerate the glass capsule 22 of the shock sensor 20. Since it is relatively unconstrained by the spring 32, the sensor mass 31 continues to move forward in accordance with Newton's first law so that the contact surface 40 of the sensing mass 31 is short from the lead wire 26. It makes contact with the firmly formed fixed contact surface 42.

Since the contact surface 40 of the sensing mass 31 and the fixed contact surface 42 of the short lead wire 26 are coupled at an angle α oriented 60 ° from the plane of the sensing mass 31 and the spring 32, the contact surface The close contact between 40 and 42 is smoother. Smooth contact is due to the contact surface 40 of the mass 31 sliding along the fixed contact surface 42, whereby a limited deflection of the spring 32 occurs in the plane of the spring. Sliding motion between the contact surface 40 and the fixed contact surface 42 of the sensing mass 31 creates a frictional bond between the contact surfaces 40, 42. Friction coupling helps to disperse energy and reduce splashing.

The spring 32 is much firmer in the plane of the spring than from the plane of the spring in that it is highly resistant to bending. Due to the closure of the switch made by the shock sensor 20, the inclined contact surfaces 40, 42 generate a deflection in some plane of the spring 32. When the contact surface 40 of the sensing mass 31 starts to rise from the contact surface 42 of the short lead wire 26 (due to the elastic bound), the friction between the contact surfaces 40, 42 is reduced or eliminated. Due to the reduction in friction between the contact surfaces 40, 42, the force due to the in-plane deflection of the spring 32 moves the shock sensing mass 31 towards the engaging portion 46 of the short lead wire 26. . Thus, the tendency for the contact surface of the switch to spring open when subjected to a sealing force is significantly reduced or eliminated by tilting the sealing surface relative to the sealing direction of the switch.

Indeed, an accurate kinetic analysis of the closure of the switch, due to manufacturing tolerances, which are the cause of the imperfection in the inclined contact surface alignment and the cross coupling between the spring constant of the spring 32 and its constant from the spring plane. Is complicated. Experience has shown that the configuration of the shock sensor 20 provides a smoother transition from weak point contact upon softer and mating contact surfaces when the contact surface rubs against the rigid line or surface contact and twists towards it. Incompleteness can actually improve the sealability of the switch.

The sensing mass 31 clearly shown in FIGS. 2-4 gives the ability to preload the spring in the unstarted state to control the overall movement of the sensing mass 31. As shown in FIG. 4, the sensing mass 31 has a wrist 62 having a slot 64 for receiving the spring end 34. The wrist portion 62 is welded by a weld portion 66 that penetrates the wrist portion 62 and welds the wrist portion to the spring 32. The welding may be electron beam welding, laser welding or resistance welding. The sensing mass has a thumb 68 extending from the body 70 of the sensing mass 31. The thumb portion 68 includes an upper surface 72 parallel to the plane of the spring, so that when sliding too far along the contact surface 42, the sensing mass 31 is engaged by engaging the lead wire 26. Prevent movement. The thumb portion 68 has an inner surface 74 that fixes one side 76 of the long lead wire 28. Similarly, the face 78 of the finger portion 80 extending from the body portion 70 secures the opposite side 82 of the long lead wire 28. The face 84 at the bottom of the body 70 supports the sensing mass 31 against the long lead wire 28. Face 84 acts as a stop member to allow the spring to be preloaded. By preloading the spring, the maneuvering force required to close the sensor can be controlled. The overall shock sensor 20 is approximately a reed switch size and has a length of approximately 1.9 cm-2.5 cm along the glass capsule. Therefore, the sensing mass 31 is very small.

One method of making the sensing mass 31 is in the field of injection molded powder metallurgy. Metal Injection Molding (MIM) technology is a wide range of alloys that allows the manufacture of highly granular metal parts at reasonable prices. The sensing mass 31 shown in FIGS. 1-5 is made from an alloy available from Ametek Inc., 88, Pennsylvania, USA. For example, it could be prepared using an AM 388 powder having an average particle size of 15 micrometers made by water to subdivide the alloy. The alloy powder was mixed with a polyoleofinie binder to obtain a feedstock with a shrinkage of 17%. This feedstock was used to injection mold the desired parts. In a process similar to injection molding of plastics, a heated mixture of metal powder and plastic binder is forced into the mold cavity under pressure where the mixture solidifies to form a green part. The molded parts are first separated in a solvent consisting of trichloroethylene. The separated parts were then sintered in a vacuum furnace with an argon partial pressure of approximately 2000 micrometers of the mercury manometer. The temperature was slowly raised to achieve a sintering temperature between about 870 ° C. and about 955 ° C., and the parts were held for 2 to 6 hours at the temperature mentioned above. Other parts were manufactured using P 729FMF, also available from Ametec Corporation.

Chemical composition of AM 388 (weight%)

C: 0.010 Ni: 7.71 Cr: Fe: Mo: Si:

Mn: Co: Cu: BAL W: S: Cb:

B: O: P: Sn: 5.70

Physical Properties of Powders (Size Distribution) Appearance Density: 4.17 g / cc

Microtrack Flow:

(Micron) (percent) Others: Tap Density-5.00g / cc

-62 100.0 Microtack

-44 100.0 90% 26.55

-31 97.5 50% 14.80

-22 82.3 10% 6.86

-16 56.3

-11 29.9

-5.5 5.7

-3.9 1.4

Chemical Composition of P729 (Weight%)

C: 0.008 Ni: 15.14 Cr: Fe: Mo: Si:

Mn: Co: Cu: BAL W: S: Cb:

B: O: 0.21 P: Sn: 8.17 N: 0.001

Physical Properties of Powders (Size Distribution) Appearance Density: 3.68 g / cc

Microtrack Flow:

(Micron) (percent) Others: Tap Density-5.33g / cc

-62 100.0 Microtack

-44 93.3 10% 6.01

-31 92.9 50% 15.55

-22 75.2 90% 29.51

-16 51.7

-11 32.6

-2.8 17.0

-5.5 8.0

A contact configuration 88 of a shock sensor of another embodiment is shown in FIG. 9. The contact arrangement 88 is similar to that shown in FIGS. 1-5, with the difference that the short lead 90, which corresponds to the short lead 26, utilizes a contact lead having a cylindrical contact surface 92. The cylindrical contact surface 92 is in contact with the contact surface 40 along the tangent 94 along the line 96 of the sensing mass 31. As disclosed in the reference to the shock sensor 20, the sealability may be sensitive to imperfections in manufacturing. Incomplete alignment of the inclined contact surface may in some cases improve the basic performance of the shock sensor 20, while in other cases the imperfection may not be sufficiently controlled. Cylindrical face 92 represents a tangent line 94 that reduces the complexity of the contact geometry. As a result, the contact arrangement 88 exhibits a sealing persistence and splashing characteristics similar to the average characteristics of the shock sensor 20, but is more robust and repeatable.

As another embodiment, a shock sensor 120 with a glass capsule 122 is shown in FIG. 10. The capsule has a first end 123 formed around the contact lead 126 and the support lead 128. The second end 125 is formed around the third lead wire 130. The third lead wire 130 has a planar tab 137 welded to the attachment end 138 of the planar spring 132. The spring 132 supports the acceleration sensing mass 131. The acceleration sensing mass 131 is shown enlarged in FIG. 11. The mass 131 is formed by stamping or coining. Stamping only includes bending and shearing, while casting involves, in this example, forging some parts from the metal blank. The mass 131 is composed of a copper alloy similar or identical to the alloy used to make the sensing mass 31 formed of powder metallurgy of the shock sensor 20.

The sensing mass 131 has a contact surface 140 that terminates at the stop surface 172. The mass 131 has a wrist portion 162 welded to the free end 134 of the planar spring 132. The first leg 168 and the second leg 180 extending from the wrist portion 162 place the sensing mass 131 on the positioning lead wire 128 so that the mass 131 can be in the plane of the spring 132. To prevent it from moving excessively. The preload position of the sensing mass is controlled by a flange 181 formed between the legs 168, 180. The flange 181 has a tapered portion 183 so that a single line contact is made with the positioning lead wire 128. In the configuration of the shock sensor 120, the first end 123 of the glass capsule 122 is formed around the contact lead wire 126 and the positioning lead wire 128. The sensing mass 131 together with the spring 132 is mounted to the third lead wire 130, and then the positioning lead wire 128 and the contact lead wire 126 to form a desired positive preload with respect to the positioning lead wire 128. Position is proportional to The second end 125 is then sealed about a third lead wire 130 that fixes the amount of reload between the sensing mass 131, the positioning lead wire 128, and the contact lead wire 126. The contact lead 126 extends through the contact surface 140 such that any burr formed when the lead wire is manufactured extends beyond the contact surface 140, such that the sensing mass 131 and the lead wire 126 are extended. Avoid contact due to rough parts between them.

As shown in FIG. 13, the shock sensor 220 of the present invention as another embodiment has a short lead wire 226, a long lead wire 228, and a glass capsule 222 formed around the mounting lead wire 230. Electrical contact is made between the short lead and the long lead by the spring 232.

The spring 232 generally has an attachment end 234 welded to the raised flange 236 of the free end 238 of the rigid long lead wire 228. The spring 232 has a shock sensitive upper mass 240 and a lower mass 242 welded to the spring 232 adjacent the contact end 244. The contact end 244 consists of a twisted portion 246 having a contact surface 248. Spring 232 defines plane and centerline 249. Twisted portion 246 is twisted about centerline 249 of spring 232 to bring contact flat portion 248 into a plane that is rotated approximately 60 ° relative to the plane of spring 232. The short lead wire 226 has a deformation 256 that defines a non-moving contact surface 258.

Since the contact surface 248 of the spring 232 and the fixed contact surface 258 of the short lead wire 226 are coupled at an angle α oriented 60 ° from the direction of movement of the spring 232, the sensing masses 240, 242, Contacts 248 and 258 are softer. The soft closure is because the contact 248 of the spring 248 slides along the fixed contact surface 258, causing a limited deflection of the spring 232 in the plane of the spring 232. Sliding motion between spring contact surface 248 and fixed contact surface 258 creates a frictional bond between faces 248 and 258. Friction coupling helps to disperse energy and reduce the bouncing shape.

The shock sensors 20 and 120 allow detection of the presence of a shock sensor in the circuit even when the shock sensor is not a starting condition. This allows the shock sensor to determine whether the shock sensor is properly included in the collision detection circuit. In the shock sensor 20, a check indicating the presence of the shock sensor 20 can be made consistent by passing a test current between the long lead wire 28 and the mounting lead wire 30. Since the shock sensor 120 has sufficient preload between the sensing mass 131 and the positioning lead 128, a test current will pass between the support lead 128 and the third lead 130.

Note that the molded acceleration sensing mass 131 can be used for the shock sensor 20, and that the sensing mass 31 made of powdered metal can be used for the shock sensor 120.

Also, while an angle of 60 ° is disclosed between the spring 32 and the contact surfaces 40, 42, the contact surface may be disposed at an angle greater than or less than 60 °.

Claims (10)

In the shock sensor, ① welded hermetic glass capsule (22), (Ii) a sufficiently rigid first conductor lead wire 26 extending into the capsule; ③ the second conductor lead wire 28 extending into the capsule; A flat spring 32 defining a plane having an end mounted to said second conductor lead and a movable end 34; ⑤ a sensing mass 31 installed adjacent to the movable end of the spring, ⑥ includes a contact surface 40 having a substantially planar portion tilted about 60 ° from the plane defined by the spring, ⑦ the movable end is movable from the first conductor lead towards the first conductor lead and the contact surface is formed at the movable end of the spring to close the circuit there when the movable end of the spring moves towards the first conductor lead To be coupled with the first conductor lead Shock sensor. The method of claim 1, The sensing mass 31 establishes the movable end 34 of the spring, and the contact surface 40 is formed on the sensing mass. Shock sensor. The method of claim 1, The contact surface 40 is formed by the twisted portion of the spring 32 Shock sensor. The method of claim 1, And further comprising a third conductor lead 30 extending into the capsule and engaging with the second conductor lead 28. Shock sensor. The method of claim 4, wherein The second conductor lead 28 includes means for receiving a compressive force between the second lead and the third lead 30. Shock sensor. The method of claim 5, The compressive force receiving means is a U-shaped portion 48 of the second lead wire 28. Shock sensor. The method of claim 2, And a third lead wire 30 extending into the capsule 22 in parallel with the first lead wire 26 at regular intervals, wherein the sensing mass 31 is positioned between the first lead wire and the third lead wire, The sensing mass is movable between a first position where the shock sensor is engaged with the third lead when the shock sensor is not shocked and a second position where the contact surface of the sensing mass engages with the first lead wire. Shock sensor. The method of claim 1, The first lead wire 26 has a contact surface 42 parallel to the movable end 34 of the spring 32 at regular intervals from the contact surface 40. Shock sensor. The method of claim 1, The first lead wire 26 has a cylindrical contact surface 42 which forms a contact line with the contact surface 40 at the movable end 34 of the spring 32. Shock sensor. The method of claim 7, wherein The sensing mass 31 extends toward the third lead wire 31 and the third lead wire is moved by the movable end of the spring 32 by fixing the third lead when the sensing mass moves approximately in the plane of the spring. 34) with parts to restrict Shock sensor.