Patent Application
20140102210
This invention relates to pressure sensors for high pressure gasoline or diesel direct injection or braking systems and, more particularly, to a pressure sensor that employs welding to combine lower-cost individual parts so as to reduce the overall cost of the pressure sensor.
With reference to
Thus, there is a need to provide pressure sensor that has s simpler geometry, is easier to fabricate, uses less raw materials, and costs less than conventional sensors.
An objective of the invention is to fulfill the need referred to above. In accordance with the principles of an embodiment, this objective is achieved by a pressure sensor that includes a metal port member having a first closed end and a second opposing opened end. A metal shell surrounds a portion of the periphery of the port. A first weld connection joins the port to the shell. A metal base has upper and lower surfaces and a second weld connection joins the shell to the lower surface of the base. Sensing structure is associated with the closed end of the port member. The sensing structure is constructed and arranged to sense pressure changes at the closed end of the port member. A connector housing covers the sensing structure.
In accordance with another aspect of an embodiment, a method of joining portions of a pressure sensor is provided. The pressure sensor has a metal port member having a first closed end and a second, opposing opened end; a metal shell surrounding a portion of the periphery of the port; a metal base having upper and lower surfaces; and sensing structure associated with the closed end of the port member. The sensing structure is constructed and arranged to sense pressure changes at the closed end of the port member. The method includes the steps of welding the port member to the shell and welding the shell to the lower surface of the base.
Other objectives, features and characteristics of the present invention, as well as the methods of operation and the functions of the related elements of the structure, the combination of parts and economics of manufacture will become more apparent upon consideration of the following detailed description and appended claims with reference to the accompanying drawings, all of which form a part of this specification.
The invention will be better understood from the following detailed description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts, in which:
Sensing structure, generally indicated at 21, is associated with the closed end 16 of the port member 15 to sense pressure changes at closed end 16. In the embodiment, the sensing structure 21 includes a sensor element 22 mounted to the outer surface of the closed end 16 and a substrate 24 defining a circuit board that is electrically connected to the sensor element 22 by wire bonding in the conventional manner. The substrate 24 is preferably a PCB substrate having an application specific integrated circuit (ASIC) 23 thereon for processing and conditioning signals from the sensor element 22. The sensor element 22 is can be a semiconductor sensing device including strain gauges (not shown) that strain synchronously to change an electrical characteristic of the gauges when the closed end 16 strains due to the pressure to be measured. The sensor element 22 is preferably glass bonded on the outer surface 25 of the closed end 16 of the port member 15. The substrate 24 is electrically connected to terminals 26 via a metal springs 28, preferably coil springs. Only one spring 28 and associated terminal 26 is shown in
A metal base 30, preferably having a hexagonal shaped periphery for engagement by a tool, is joined at a bottom surface 31 thereof to the metal shell 18 by a second weld connection 32. A hollow metal tube structure 34 is joined at one end 36 to a top surface 33 of the base 30 by a third weld connection 38. The sensing structure 21 is preferably encapsulated and disposed within the tube structure 34. A connector housing 40, preferably of resin, is connected to a second end 42 of the tube structure 34, preferably by a tongue and groove seal connection 44. The connector housing 40 covers the sensing structure 21. The first, second and third weld connections can be achieved by laser or other welding techniques. The weld connections are preferred, but fasteners, adhesives or other similar joining methods can be used instead.
The port member 15, shell 18, base 30 and tube structure 34 comprise a four-piece port assembly, generally indicated at 46, having a simpler geometry than conventional sensors and thus is easier to manufacture. The pressure sensor 14 reduces the use of raw materials and is of lower cost than the sensor of the type shown in
The sequence of the assembly of the pressure sensor 14 can be performed in many ways since there is less constraint compared to the assembly of the pressure sensor of
With the pressure sensor 14, final welding between the base 30 and the tube structure 34 can be done when circuit is already encapsulated and protected. In the conventional two-piece pot assembly, welding the two pieces has to be done before wire-bonding, therefore exposing the bare die during welding.
The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the scope of the following claims.
