Patent ID: 12259290

DETAILED DESCRIPTION

FIG.1Ais a perspective view of prior art pressure sensor10.FIG.1Bis a perspective view of damaged prior art pressure sensor10after a dynamic pressure event.FIG.2is a schematic cross-sectional side view of prior art pressure sensor10.FIGS.1A,1B, and2will be discussed together. Pressure sensor10includes isolator12with corrugations14, header16, and weld ring18. Header16includes dished isolator support20(shown inFIG.2) with hole22(shown inFIG.2) and cylindrical cavity24(shown inFIG.2). Pressure sensor10also includes first filler material26(shown inFIG.2), second filler material28(shown inFIG.2), pressure sensing element30, gap32(shown inFIG.2), and oil34(shown inFIG.2).FIG.1Balso includes area C and area P of isolator12.

Pressure sensor10has isolator12, which is a thin disc of metal stamped to include corrugations14. Header16acts as a housing for components of pressure sensor10. Header is made of metal. Isolator12is positioned over a top of header16. Isolator12and header16are welded together with weld ring18. Header16has dished isolator support20located at the top of header16under isolator12. Dished isolator support20is concave to isolator12such that a middle of dished isolator support20is farther away from isolator12than an edge of dished isolator support20. Header16includes hole22through dished isolator support20near the middle of dished isolator support20. Cavity24is a cylindrical space in header16.

First filler material26and second filler material28are positioned in cavity24. First filler material26and second filler material28can be adhered to one another and to header26. First filler material26has a central channel aligned with hole22. Second filler material28is designed to fit around pressure sensing element30, which is near a bottom of cavity24. Pressure sensing element30is electrically connected to other elements to transmit sensed pressure readings. Pressure sensing element30can be any appropriate pressure sensing element, including a strain gauge or a micro electro-mechanical systems (MEMS) device.

Pressure sensor10also has gap32between a bottom of isolator12and a top of dished isolator support20. Gap32is wider near the middle of dished isolator support20and narrower near the edge of dished isolator support20. Pressure sensor10is filled with oil34, including in gap32, hole22, the channel in first filler material28, and partially surrounding pressure sensing element30. Oil34can move between gap32, hole22, the channel in first filler material28, and around pressure sensing element30.

Pressure sensor10can be used to make pressure measurements of fluid in contact with isolator12. For example, pressure sensor10can be installed in a port of a hydraulic braking system such that hydraulic fluid in the braking system can interact with isolator12. Hydraulic brake systems can have pressures upwards of 4,000 PSI where pressure sensor10is located.

When pressure is exerted on isolator12(for example, by engaging the braking system), it moves from a neutral state to a depressed state. In the depressed state, isolator12is close to or touching dished isolator support20. In the neutral state (shown inFIG.2), isolator12is away from dished isolator support20and generally flat across the top of header16. Movement of isolator12moves oil34between gap32and cavity24. Hole22in dished isolator support20allows for oil34to move between gap32and cavity24through dished isolator support20. Pressure sensing element30registers pressure changes from oil34movement between gap32and cavity24. The pressure signal can then be transmitted from the pressure sensing element30.

Pressure sensor10operates in a wide range of temperatures. Isolator12has corrugations14that ensure repeatable and linear sensor behavior over multiple temperatures. Corrugations14accomplish this by allowing isolator10to move as oil34expands and contracts with temperature changes. First filler material26and second filler material28decrease the amount of oil34needed to fill pressure sensor10, which reduces volume changes with temperature fluctuations. This increases accuracy of temperature calibrations and allows for linear pressure measurements at multiple temperatures.

Dynamic pressure events can move isolator12against dished isolator support20. Dished isolator support20has a flat surface, which is mismatched with corrugations14on isolator12. The mismatched shapes cause crush and puncture damage during dynamic pressure events. Dynamic pressure events (pressure events that are high pressure and cause non-uniform pressure distribution on isolator12) can damage isolator12. Corrugations14on isolator12can crush, as shown in area C ofFIG.1B. Crushing damage includes deformation of corrugations14of isolator12. Isolator12can also be punctured, as shown in area P ofFIG.1B. Puncture damage can include a dimple or a perforation in isolator12. Crush and puncture damage occur when isolator12quickly and/or unevenly moves into the depressed state. Crush and puncture damage can also occur when isolator12collides with dished isolator support20. Damage, like crushing and puncturing, reduces performance of pressure sensor10, including decreased sensitivity, accuracy, and precision. If pressure sensor10experiences multiple dynamic pressure events, pressure sensor10will experience accumulated output degradation.

The curved shape of dished isolator support20allows for gap32to hold more oil34. Additional oil34theoretically cushions isolator12. However, the additional oil34in gap32reduces the accuracy of temperature calibration of pressure sensor10. This reduces performance of pressure sensor10at different temperatures. Further, isolator12still sustains crush and/or puncture damage at high pressures. Hole22, while necessary for pressure sending in pressure sensor10, allows for volumes of oil34to move beneath a center of isolator12and creates instability which can lead to puncture damage.

FIG.3is a perspective view of pressure sensor110.FIG.4is an exploded view of pressure sensor110.FIG.5is a schematic cross-sectional side view of pressure sensor110.FIGS.3-5will be discussed together. Pressure sensor110includes isolator112with corrugations114, header116with cavity118(shown inFIG.5), and weld ring120. Pressure sensor110also includes corrugated isolator support122(shown inFIGS.4-5), gap124(shown inFIG.5), filler material126(shown inFIGS.4-5), pressure sensing element128(shown inFIGS.4-5), plug130(shown inFIGS.4-5), electrical connections132(shown inFIG.5), s-pins134(shown inFIGS.4-5), and oil134(shown inFIG.5).

Pressure sensor110can be used, for example, with a hydraulic braking system on an aircraft. Isolator112is a foil disc stamped with corrugations114. Isolator112is approximately 0.001 inch thick. Isolator112is made of a metal. Isolator112is mounted on a top of header116, which is a housing for pressure sensor110. Within header116is cylindrical cavity118. Isolator112is held to the top of header116by weld ring120. Weld ring120, isolator112, and header116are all welded together.

Corrugated isolator support122is positioned inside cylindrical cavity118near a top of header116. Corrugated isolator support122has corrugations that align with corrugations114on isolator112. Corrugated isolator support122is made from a material with a low coefficient of thermal expansion (CTE). Example materials with a low CTE include polyetherimide, glass fibers, resin, plastic, and combinations thereof. Between isolator112and corrugated isolator support122is gap124. Gap124has a constant width between isolator112and corrugated isolator support122. The width of gap124is between 0.005 inches and 0.020 inches. The width of gap124is preferably 0.007 inches.

Filler material126, pressure sensing element128, and plug130are also positioned within cavity118below corrugated isolator support122. Filler material126is adhered to a bottom of corrugated isolator support122and a top of glass plug130. Filler material126is made of a material with a low CTE, for example, polyetherimide, glass fibers, resin, plastic, and combinations thereof. Filler material126has a generally cylindrical shape to fit tightly into cavity118. An inner portion of filler material126has a generally toroidal shape with an inner perimeter that matches pressure sensing element128. Pressure sensing element128is positioned inside filler material126. Pressure sensing element128is a strain gauge. Pressure sensor128can alternatively be a MEMS device or other stress sensor gauge. Plug130encloses a bottom of cavity118. Pressure sensing element128and filler material126are both adhered to plug130. Plug130is made of glass. Plug130is electrically insulating and hermetically seals cavity118. Other materials, for example resin, rubber, and plastic can be used to make plug130. Electrical connections132connect to pressure sensing element128and run through plug130to transmit information regarding the sensed pressure readings to other components. S-pins134are in a bottom of plug130to secure pressure sensor110.

Oil136fills gap124and portions of cavity118not filled by corrugated isolator support122, filler material126, pressure sensor128, and plug130. Oil136is silicone oil, but can be any other oil. Oil136can move between gap124and cavity118via a channel in a side of isolator112and/or a channel in filler material126.

Pressure sensor110uses isolator112to transmit external pressure to internal pressure sensing element128. When pressure is exerted on isolator112, isolator112moves to a depressed state and moves oil136into cavity118. The increased amount of oil136in cavity118is sensed by pressure sensing element128. Pressure sensing element128transmits electrical signals indicating the sensed pressure to other components through electrical connections132.

Filler material126and corrugated isolator support122reduce the volume of cavity118and the amount of oil134needed to operate pressure sensor110. Reducing the amount of oil134in cavity118and gap124reduces temperature-related volume fluctuations in pressure sensor110and makes calibration and pressure measurements more accurate.

Corrugated isolator support122protects isolator112from crush and puncture damage due to its shape matching corrugations114. A center of isolator112is designed to contact corrugated isolator support122first before permanent deformation of isolator112occurs. Corrugated isolator support122does not have a hole in the middle (like dished isolator support20shown inFIG.2), which supports the center of isolator112and reduces puncture damage. The center of isolator112is supported by the matching, flat surface of a center of corrugated isolator support. The corrugations on corrugated isolator support122match corrugations114on isolator112and support corrugations114from crush damage (as shown at C inFIG.1B). The matching shape of corrugated isolator support122with isolator112maximizes contact between isolator112and corrugated isolator support122. This prevents damage during dynamic pressure events by minimizing pressure exerted only on isolator112. Corrugated isolator support122can prevent damage to isolator112even when dynamic pressure events exert up to 11,000 PSI on pressure sensor110.

Further, the constant width of gap124protects isolator112from damage by acting as a hydrodynamic dampener. The constant width of gap124provides hydrodynamic resistance to prevent isolator112from being damaged during dynamic pressure events. The small size of the constant width of gap124also reduces the distance the center of isolator112must travel. By quickly contacting corrugated isolator support120, the middle of isolator112receives mechanical support prior to permanent deformation (for example, crush damage shown at C inFIG.1B) and is less likely to sustain puncture damage (for example, puncture damage shown at P inFIG.1B).

The combination of corrugated isolator support122and gap124reduce the likelihood of damage to isolator112during dynamic pressure events. This allows pressure sensor110to sense over its entire useful range even after multiple dynamic pressure events that would damage isolator12in pressure sensor10(as discussed in relation toFIGS.1A-2).

The following are non-exclusive descriptions of possible embodiments of the present invention.

DISCUSSION OF POSSIBLE EMBODIMENTS

A pressure sensor includes a header with a cavity, a pressure sensing element, an isolator, an isolator support, a damping gap, and oil. The pressure sensing element is in the cavity. The isolator has corrugations and is mounted to a top of the header. The isolator covers the cavity. The isolator support is in the cavity of the header above the pressure sensing element. The isolator support is corrugated. The corrugations of the isolator support align with the corrugations on the isolator. The damping gap is between the isolator support and the isolator. The damping gap has a constant width between the isolator support and the isolator. Oil fills the damping gap and the cavity in the header. The oil moves between the damping gap and the header cavity in response to external pressure changes moving the isolator.

The pressure sensor of the preceding paragraph can optionally include, additionally and/or alternatively, any one or more of the following features, configurations and/or additional components:

A further embodiment of the foregoing pressure sensor, and also including an isolator weld ring around an edge of the isolator and welded to the top of the header to mount the isolator onto the header.

A further embodiment of any of the foregoing pressure sensors, and also including a plug positioned in the header cavity to support the pressure sensing element and to seal the cavity. The plug is a glass plug with s-pins.

A further embodiment of any of the foregoing pressure sensors, electrical connections routed through the plug and connected to the pressure sensing element.

A further embodiment of any of the foregoing pressure sensors, wherein the plug electrically and hermetically seals the cavity.

A further embodiment of any of the foregoing pressure sensors, and also including filler material within the cavity of the header. The filler material has a cavity shaped to fit the pressure sensing element. The pressure sensor is positioned inside the filler material. The isolator support is adhered to a top of the filler material.

A further embodiment of any of the foregoing pressure sensors, wherein the cavity of the filler material is toroidal.

A further embodiment of any of the foregoing pressure sensors, wherein the filler material and the isolator support are made of a material with a low coefficient of thermal expansion chosen from the group consisting of polyetherimide, glass fibers, resin, plastic, and combinations thereof.

A further embodiment of any of the foregoing pressure sensors, wherein the oil is silicone oil.

A further embodiment of any of the foregoing pressure sensors, wherein the damping gap is between 0.005 inches (0.127 millimeters) and 0.020 inches (0.508 millimeters).

A further embodiment of any of the foregoing pressure sensors, wherein the damping gap is 0.007 inches (0.178 millimeters).

A further embodiment of any of the foregoing pressure sensors, wherein the pressure sensing element is a strain gauge.

A further embodiment of any of the foregoing pressure sensors, wherein the pressure sensing element is a micro electro-mechanical systems (MEMS) device.

A further embodiment of any of the foregoing pressure sensors, wherein the cavity is cylindrical.

A further embodiment of any of the foregoing pressure sensors, wherein the isolator is made of a metal foil.

While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalent embodiment(s) may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.