JPH07182956A - Pressure switch device - Google Patents

Abstract

PURPOSE: To provide a pressure switch for an air bag device which checks pressure and leakage in a pressure container used for a safety air bag device of an automobile and always operates promptly with stability. CONSTITUTION: A pressure switch is filled with gas of the first pressure P1 and has a pressure container 12 to which gas is filled by the second pressure P2. The container responds to the difference of two kinds of pressures and has a flexible diaphragm 18 interacting with an electric circuit on the one side. Magnetic elements 16, 26 are operationally connected with the diaphragm. A wall part in the pressure container is made of non-magnetic material and is provided with a magnetic field induction switch element 40 facing to the diaphragm. A window element 13 of the magnetic material is located in the wall part of non-magnetic material matching with the magnetic element and the switch element. An armature can be used to concentrate a magnetic flux orbit. A magnetic curve can be adjusted with a bias magnet.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates generally to condition sensors and more particularly to sensors used to detect fluid pressure in automotive airbag safety systems.

[0002]

2. Description of the Prior Art In a device such as the one described above, a pressure switch device is typically housed in a pressure vessel filled with gas at a first pressure, such as a safety airbag for an automobile, and a second pressure device. A gas-filled pressure container having a flexible diaphragm on one side that is responsive to a difference in pressure between the two and interacts with an electrical circuit. Such a pressure device is described in US Pat.
049,935.

In the case of the known device described above, the pressure of the pressure vessel must be precisely monitored so that the normal operation of the pressure vessel is guaranteed for a long time, for example just before the deployment of a safety airbag in a motor vehicle. For this purpose, a gas-filled pressure container at a second pressure is arranged in the pressure container. A flexible diaphragm on one side of the pressure container moves or flips between positions on either side depending on the magnitude of the pressure difference between the first and second pressures. An element movable at right angles to the surface of the diaphragm and aligned with the center of the diaphragm then engages the movable arm of the two-way switch with one or the other stationary contact. The pressure switch detects the pressure in the main pressure vessel, its leakage,
And serves to monitor the pressure of the pressure container during the life of the device. A pressure container with a diaphragm and associated switch contacts is arranged in the pressure vessel, an electrical connection from said contacts extending through the wall of the pressure vessel and outside the pressure vessel, for example, an associated electrical connection for producing an audible alarm. Connected to the circuit. Electrical connections typically pass through the wall of the pressure vessel via a glass or plastic seal. The pressure in the pressure vessel is in the range of 200-400 bar at temperatures between -40 ° C and + 130 ° C, and the pressure in the pressure container needs to be maintained for an extremely long life (at least 10 years), so that the seal Doesn't seem reliable enough. Since this switch device is used to activate the aforementioned airbag in a vehicle,
The device must always be able to respond quickly and stably. Pressure loss due to leakage through unreliable seals in the wall is unacceptable.

[0004]

The object of the present invention is to overcome the aforementioned drawbacks of the prior art.

[0005]

SUMMARY OF THE INVENTION In summary, in the present invention, a pressure switch device of the type described above, known as an accumulator, is mounted near the wall of a pressure vessel and oppositely on one side. And a magnetic element operatively connected to the movable diaphragm. The wall portion of the pressure vessel is made of a non-magnetic material, and on the other side of the wall portion a magnetic field sensitive switching element or transducer is mounted opposite the magnetic element of the diaphragm.

According to the present invention, electrical leads through the seals in the walls of the pressure vessel are eliminated. The switching action takes place in the immediate vicinity of the wall by applying the magnetic field from the diaphragm magnet to a magnetic field sensitive switching element or transducer outside the wall of the pressure vessel.

In an advantageous embodiment, a window of magnetic material is located in the wall part of the non-magnetic material in alignment with the magnetic element and the switch element in order to achieve a more sensitive switching action.

The wall portion of non-magnetic material and the window of magnetic material therein are preferably made of materials having essentially corresponding coefficients of thermal expansion and easily welded together. Suitable materials include austenitic steel for non-magnetic materials and ferritic steel for magnetic materials.

In one embodiment, the magnetic element and the transducer are positioned in alignment with each other and with the south pole of the magnet facing the sensing surface of the transducer to form a unipolar head-on mode of operation. .

In an advantageous embodiment of the invention, the moveable magnetic element is telescopically received, for example by welding, on a skirt having a wall portion which is welded to the pressure vessel, and is suitable. The accumulator mounted on the end of the container is attached to the snap-acting diaphragm. Then, a transducer and associated electrical circuit that provides a digital or analog output is attached to the opposite or outer surface of the wall portion,
Eliminates the potential deleterious effects of heat associated with welding the wall portion to the pressure vessel.

In another embodiment, a high coercivity fixed bias magnet is used to adjust the characteristics of the magnetic curve, with its poles oriented in a coaxial relationship with the poles of the moving magnet.

In yet another embodiment, one end of the armature is adjacent to the moving magnet and the other end is adjacent to the transducer to penetrate the wall portion and concentrate the flux trajectory. The armature consists of two L-shaped members, which are aligned with each pole of the moveable magnet.

In another embodiment, an armature having two legs extends through the wall portion, a moveable magnet alternating north and south poles, and a magnet between the legs of the armature and It consists of first and second magnets positioned relative to each other to move therethrough and provide a bipolar, slide-by mode of operation.

In a preferred embodiment of the present invention, a circuit board is mounted on the outer wall of the pressure vessel to convert the three lead outputs from the Hall effect transducer into two lead outputs for normal operation. Each voltage level is provided to indicate an operating or fault condition.

The foregoing objects, as well as other objects and advantages which will become apparent hereinafter, are also included in the structure and operation described and claimed in detail below. Reference will now be made to the accompanying drawings in which like parts are designated with like reference numerals.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT In the prior art embodiment of the pressure switch described above and shown in FIG. 1, reference numeral 1 generally designates a gas container filled with gas at a first pressure. For example, the wall of a steel pressure vessel is shown at 2. The reference number 3 acts as part of the pressure switch and is filled with gas at the second pressure and indicates a pressure container mounted in a manner not shown in detail. The pressure container 3 is closed at one end by a flexible diaphragm 4. The diaphragm can move between a solid line and a dotted line by the action of the above-mentioned pressure. A motion transmitting element 5 is mounted on the diaphragm, which engages or disengages the movable contact 6 of the switch from one position to the other with the fixed contacts 7, 8 via the motion of the diaphragm. It can be. The contacts 7, 8 extend through a bush 9 in the wall of the pressure vessel and are connected to leads which are connected to an alarm or activation circuit not shown in detail. The connecting bush is entirely made of glass or plastic.

The pressure vessel can be used to supply pressure for a motor vehicle safety airbag. It is pyrotechnically actuated so that when the acceleration sensor measures the occurrence of a sudden large deceleration, the pressure vessel rapidly inflates the airbag and releases pressure to the airbag to form a safety device for the vehicle occupants. To do. The function of the pressure switch device is to constantly monitor the pressure in the main and pressure containers.

In the first embodiment of the pressure switch device made according to the invention shown in FIG. 2, reference numeral 1 generally designates a pressure vessel filled with gas at pressure P1 and reference numeral 12 at pressure P2. 1 shows a pressure container, also known as a gas filled accumulator assembly. The pressure container according to the invention is mounted close to the wall portion 14 of the wall 2 of the pressure container. The wall 14 is made of a non-magnetic material, i.e. a non-ferromagnetic material. The magnetic element 16 is operatively connected to the diaphragm 18 in any suitable manner, such as being secured with an adhesive. Diaphragm 1
8 is preferably a disc which is movable in the opposite direction between the dished concave and convex portions with a snap action. The outer edge 20 of the diaphragm 18 includes upper and lower support plates 22, which include a central portion that is dished outwardly to provide a void in which the diaphragm 18 can move between its opposite shapes. 24 flanges 2
It is sandwiched between 1 and 23. The support plate 2
2, 24 and end 20 are airtightly attached to each other in any suitable manner, such as by welding around the perimeter of flanges 21, 23 and end 20. The housing member 26 is generally cup-shaped and has an outwardly extending flange 28 formed at its open end, which is also airtightly attached to the lower support plate 24. The opening 30 of the support plate 24 communicates with the pressure of the accumulator assembly 12 on the lower side of the diaphragm 16, while the opening 32 of the upper support plate 22 communicates with the pressure in the pressure vessel 1 on the upper side of the diaphragm 18 and the magnetic element 16
To a position near wall portion 14. The housing member 26 is also formed with an opening 34 through the bottom wall which allows the accumulator to be filled with a selected pressure, preferably the same selected gas as in the pressure vessel 1. The accumulator 12 is then suitably gas tight welded, for example by welding the closure element 36 to the bottom wall.

Generally, the gas pressure P1 in the pressure vessel 1 is usually some value higher than the gas pressure P2 in the accumulator assembly 12. When this pressure difference (P1-P2) drops to a certain level below the selected value as a result of the pressure leak in the pressure vessel and / or the accumulator, the diaphragm 18 moves from the position indicated by the solid line to the position indicated by the dotted line.
The magnetic element 16 then moves to near the wall portion 14.

A magnetic field sensitive switch element 40, such as a Hall effect transducer, is aligned with the magnetic element 16,
And facing each other, on the opposite side of the outer wall of the pressure vessel. The switch element 40 has connecting leads 42, 4
4, connected to a suitable electrical circuit such as that shown in FIG. 5 and described below. The position and setting of the magnetic element 16 and the switch element 40 are in this case such that when the magnetic element 16 moves with the diaphragm 18 to the position indicated by the dotted line, the switch element 40 switches from the off state to the on state.

The magnetic element 16 is mounted on the diaphragm 18 with its south pole facing the wall portion 14 and moves in and out of the transducer 40 in a unipolar head-on mode of operation. As the magnet moves near wall portion 14, the Gaussian level changes its output voltage by increasing above the limit value or switching point of the transducer. Although it is convenient to use a digital output, ie on / off, it should be appreciated that using an analog output is also within the scope of the invention.

In the more sensitive embodiment of the switching action, a core or window 13 of magnetic or ferromagnetic material is provided in the wall portion 14 in alignment with the magnetic element 16 and the transducer 40. In this embodiment, the magnetic field lines emanating from the magnetic element 16 in the direction of the transducer extend more concentratedly through the window 13.

The wall portion 14 of non-magnetic material is preferably made of copper, aluminum or stainless steel. For example, if the wall portion 14 is made of austenitic steel, both types of steel have virtually the same coefficient of thermal expansion and can be easily welded together, for example by laser welding, so that the window 13 is made of ferritic steel. Is advantageous.

As shown in FIG. 3, the wall 2 of the pressure vessel may be provided with an opening 46 for receiving the switch assembly 100. The switch assembly 100 is composed of first and second subassemblies 102 and 104. Subassembly 102
Is a flange of the support plates 22 and 24 and a flange 28.
Attached to the skirt 108 extending below and below the base 106 by spot welding at several locations around the, leaving a suitable passage (not shown) between the interior of the container 1 and the hole 32 in the upper support plate 22. The pressure between the inside of the container 1 and the upper surface of the diaphragm 18 is surely equalized. Base or wall portion 106 is made of a non-magnetic or non-ferromagnetic material similar to wall portion 14 of the embodiment shown in FIG. The base 106 is then hermetically connected to the container 1 by welding its perimeter, as indicated at 110, for example. The magnetically responsive transducer 40 and its associated electronic components and mounting structure along with the housing 112 are included in the base 10.
The subassembly 104 can be conveniently formed on the upper side of the 6. Subassembly 104 can be attached to base 106 by any suitable means, such as by using a threaded fastener not shown. In this way, excess heat associated with welding the base 106 to the wall 2 can be isolated from the thermosensitive electronic components.

Another embodiment of the present invention is shown in FIGS. In this embodiment, the pressure assembly 200
Is a housing 202 formed of a non-magnetic material such as stainless steel and having a lower chamber 204 in which a spring 206 for properly mounting the magnetic element 16 is located.
including. A connecting pin 208 is operatively connected to the magnetic element 16 in any suitable manner so that it can move with the magnetic element. If desired, the pin 208 may be integrally formed with the magnetic element 16, but in any event the diaphragm 18 of the accumulator assembly 12 received in the chamber 204.
Extend to engage. The pressure sensing accumulator assembly 12 is telescopically received in the chamber 204, seats in the annular projection 210, and is locked by any suitable means, such as by squeezing the lower sidewall portion 212 of the housing 202.
An opening 205 is provided in the sidewall of the housing 202 to equalize the pressure between the upper surface of the diaphragm 18 and the pressure inside the pressure vessel. The spring 206 holds the magnet 26 apart from the wall portion 214 until the diaphragm 18 moves upward into a convex shape (not shown). If desired, by omitting the annular protrusion 210, the moveable magnetic element 16 can be telescopically inserted to any desired position to position it in an optimal position with respect to the magnetically responsive switch 40, thus accumulator assembly. 12 can be fixed to the housing 202 as in the embodiment of FIG.

A magnetically responsive switch 40, such as the Hall effect transducer described above, faces the magnetic element 16 and the wall 214.
Alternatively, it is located above wall portion 214 in longitudinal alignment with movement away therefrom. Magnetic element 1
6 is arranged such that its south pole faces the magnetic response switch 40.

In the embodiments of the invention described thus far, the magnetic element is constructed to move directly toward and away from the sensing surface of the magnetically responsive switch. As mentioned above, in this mode of operation the relationship between Gauss and the distance between the magnetic element and the switch is similar to the damping exponential curve. In order to take advantage of the steepness level of the Gaussian vs. distance curve, a second or bias magnetic element 216 has its south pole aligned with and facing the switch 40 and the switch 40 relative to the magnetic element 16.
It is located on the opposite side of. This reversal direction of the magnet is subtracted from the magnetic field of the moving magnet to create a bipolar mode so that the switch operates in the steep part of the curve such that even relatively small movements cause a relatively large change in magnetic field strength. . When using a bias magnet, it is preferable to use a magnet having a high coercive force, that is, a rare earth magnet, in order to eliminate the problem of partial demagnetization.

The housing 202 is hermetically attached to the wall 2 of the container, for example by welding the perimeter as indicated at 218. Preferably, after the housing 202 is attached to the container, the housing subassembly 220 is attached. Subassembly 220 includes circuit board 222 along with transducer 40 and bias magnet 216.

Honeywell's Microswitch Division (Microswitch Di)
Hall effect transducers, such as those commercially available from Vision, are three lead devices. Although the pressure sensing device can be used with three leads, it is preferable to provide a two wire device to reduce the equipment cost of the vehicle. The circuit board 220 including the circuit shown in FIG. 5 converts the three-lead device of the above-described converter into a two-lead device.

The circuit board 220 has an output current set resistor 22.
4, a bias current adjustment resistor 226, an input filter capacitor 228, and, if desired, a reverse voltage blocking diode 230 to prevent damage if the device is connected to the wrong battery terminal of the vehicle. Especially Figure 5
, The Hall effect converter has an open collector N
Used in current drop output mode of operation with PN transistor Q1. A resistor 224 connected to the output of the device minimizes the effects of small leakage currents from the output or electronic components with which the device is interfaced. Capacitor 2 connected in parallel with resistor 226
28 is used to filter any noise appearing on the battery line, while resistor 226 is used to adjust the bias current level. When the magnetic field is removed from the converter, its output is in a quiet normal high state and does not flow through the output transistor Q1 (except for minimal leakage current). When a magnetic field above the operating point is applied to the converter, a current flows through the transistor Q1 and the output voltage measured between the collector of Q1 and the negative terminal drops to ground potential, reducing the saturation voltage of transistor Q1. ignore.

Another advantageous modified embodiment of the invention is shown in FIG.
And shown in FIG. In FIG. 6, an armature 232 is used to concentrate the magnetic flux. Armature 2
32 includes first and second legs 234, 236 respectively located on each side of the magnetically responsive switch 240, each leg extending through an opening in the non-magnetic wall 238 and hermetically mounted. The legs 234, 236 are each located at their free distal ends in the vicinity of a magnet 240 operatively connected to the diaphragm 18 via a motion transmitting member 244.

FIG. 7 shows a pair of magnets 246, 248 vertically aligned so that their poles are aligned in opposite directions and slide in bipolar mode to move the end portions 250, 252 of the armature 254 in parallel. positioned. Such an arrangement offers the advantage that cheaper magnets can be employed, since partial demagnetization is not a problem.

The above discussion is considered to be illustrative of the principles of the present invention. Many modifications and variations will immediately occur to those skilled in the art, and the present invention is not limited to the exact construction and operation shown and described, but for all that fall within the scope of the appended claims. Appropriate modifications and equivalents are intended to be included in the present invention. For example, although the switch device has been described with respect to a pressure responsive device, the diaphragm is made of bimetal so that the same magnetic field sensitive switch device is employed to provide a response between selected concave and convex shapes in response to selected changes in temperature. It is also acceptable to be able to operate.

[Brief description of drawings]

1 is a cross-sectional view of a device according to the prior art.

FIG. 2 is a schematic cross-sectional view of a pressure switch device made according to the first embodiment of the present invention.

FIG. 3 is a sectional view of an advantageous embodiment of the present invention.

FIG. 4 is a sectional view of another embodiment of the present invention.

5 is a schematic diagram of an electric circuit used in the embodiment shown in FIG.

FIG. 6 is a diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing another embodiment of the present invention.

[Explanation of symbols]

 1 Pressure Vessel 3 Pressure Container 4 Diaphragm 5 Motion Transmission Element 12 Pressure Container 13 Window 14 Wall Part 18 Diaphragm 21,23 Flange 22,24 Support Plate 40 Switch Element 46 Opening 100 Switch Assembly 102 First Subassembly 104 Second Subassembly 200 Pressure assembly 202 Housing 216 Bias magnetic element 232,254 Armature

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shiro Calenda CIE Italy, Italy, Aversa, Parco Serimere (Fabbiar.C), Viale Olimpico (no address) (72) Inventor Carlton M. Cobb The Third Massasoite Sarkle, East Walpole, Massachusetts, USA 4 (72) Inventor Arnordas M. BROWELLS Weerden, The Netherlands, Europaring 245 (72) Inventor Roberto Novi-Cavaria Neapolivia, Italy. Longo, 50 (72) Inventor Edoardo Armenio Aversa (Icy), Italy, Via Giotto, 39 (72) Inventor Massimo Matsuola, Viale de Glio Leandri, Naples, Italy 13 (72) Inventor Daniel Morin United States Rhode Island North Providence, Smithfield Road 565, Number Sea 11 (72) Inventor Carl Earl. Abrahamson 87 Pine Street, Easton, MA, USA

Claims (11)

[Claims] 1. A pressure switch device adapted to be housed in a pressure vessel filled with gas at a first pressure, such as for a safety airbag of a motor vehicle, filled with gas at a second pressure. Pressure switch comprising a pressure container, said container being movable between two opposite shapes, having on one side a flexible diaphragm responsive to two types of pressure difference and interacting with an electrical circuit. In the apparatus, the container is mounted on one side adjacent to and opposite the wall portion of the pressure vessel and a moveable magnet is operatively connected to the diaphragm for movement therewith. The wall portion of is made of non-magnetic material,
A pressure switch device, characterized in that a magnetic field sensitive switch element is arranged in the vicinity of the other side of the wall portion, facing the movable magnetic element. 2. The pressure switch device according to claim 1, wherein the window element of magnetic material is located in the wall of the non-magnetic material in alignment with the moveable magnetic element and the switch element. 3. The wall portion is made of a non-ferrite material,
Pressure switch device according to claim 2, characterized in that the magnetic element is made of a ferrite material. 4. The pressure switch device according to claim 1, further comprising a fixed bias magnet disposed near the electric field sensitive switch element on a side remote from the moveable magnetic element. 5. The pressure switch device according to claim 4, wherein the movable magnetic element and the fixed magnet are formed of a rare earth material. 6. The device of claim 1, wherein the moveable magnetic element is attached to the diaphragm. 7. The switch device according to claim 1, further comprising a motion transmitting member disposed between the movable magnetic element and the diaphragm. 8. The pressure switch device of claim 1, further comprising an armature extending through the wall portion between the magnetic field sensitive switch element and the moveable magnetic element. 9. An opening is formed in the pressure vessel, the opening including first and second subassemblies, the first subassembly including a pressure container attached to an underside of the wall portion, the wall portion comprising: A flange is formed which fits into the opening of the pressure vessel for airtight attachment to the pressure vessel, the second subassembly being a magnetic field sensitive switch element and said wall to complete the assembly. A pressure switch device according to claim 1, including a housing attachable to the upper side of the part. 10. An opening is formed in the pressure vessel, a flange is formed in the wall portion to be hermetically fitted by fitting into the opening of the pressure vessel, and the wall portion has a member extending downward. 2. The pressure switch device according to claim 1, wherein the pressure container is attached to the downwardly extending member at a selected position with respect to the wall portion. 11. An armature extending through the wall portion, the armature having opposite end portions, one end portion disposed proximate to the magnetic field sensitive switch element and the other end portion in motion. A pressure switch device according to claim 1, characterized in that it is arranged adjacent to a movable magnetic element, the movable magnetic element being arranged to move in a direction parallel to the other end portion of the armature. .