Transducers are used in many industrial applications. In automobile applications, sensor assemblies, which incorporate or include transducers are used to monitor such physical properties as oil pressure, oil temperature, and transmission fluid pressure. One example of a sensor assembly for detecting a gas pressure inside an internal combustion engine includes a hollow housing securable to a pressure port on the engine block, a base or integrated circuit substrate secured to the housing, and an elongated electrical connector having connector lead wires which connect to electrical terminals located on the base. A pressure transducer of the sensor assembly includes a flexible diaphragm that is attached to and covers one end of the housing, a strain sensing element mounted to the base, and an electric circuit portion.

The base is secured to the housing and isolates the transducer from the outside environment. Further, the transducer is electrically connected to the terminals on the base, and thereby electrically connects with the connector lead wires.

The diaphragm and the base forms an internal cavity that is filled with a pressure transmitting or transfer fluid such as a silicone gel. As the pressure in the engine increases, the diaphragm is caused to

flex in the direction of the internal cavity thereby increasing the pressure of the transmitting fluid therein. The increased pressure is sensed by the strain sensing element and causes the electrical circuit portion to generate an electrical signal functionally related to the pressure change. The electrical signal is then communicated through the terminals and the connector wires to an external control circuit.

In the sensor assembly, a signal conditioning circuitry may be electrically connected with the transducer to perform a signal conditioning function such as amplification. The signal conditioning circuitry is typically isolated from the transducer, however, since the transmitting fluid often contains contaminants which are harmful to the signal conditioning circuitry. This precludes the signal conditioning circuitry from being combined with the transducer and from being retained within the same cavity as the transducer.

The sensor assemblies described above are often installed in harsh operating environments. In automobile applications, for example, the engine block and the vehicle frame can generate substantial vibrational loads which can be transferred to the sensor assembly. Further, the sensor assembly may include a connector having long connector lead wires.

The connector lead wires extend outward from the sensor housing and may be routed around and, come in contact with, other components of the automobile. Through the connector, these components can transfer loads including, vibration, compression, and tension to the sensor housing, base, and transducer of the sensor assembly. Accordingly, the components of the sensor assembly must be sufficiently strong and adequately supported in order to have practical useful lives.

SUMMARY OF THE INVENTION A general object of the invention is to provide a sensor assembly that is particularly adapted to applications in operating environments wherein the sensor assembly is subject to a variety of loads including vibration, tension, and compression.

An important aspect of the aspect of the invention is a"floating connection" (as opposed to rigid or non- flexible) between the connector assembly and the fixedly securable components of the sensor assembly.

The floating connection allows the connector assembly to be movable relative to these components and also functions to minimize, if not eliminate, the loads which are transferred from these components to the connector assembly and from the connector assembly to these components. The floating connection can also compensate for misalignment and inaccuracies in the manufacturing and assembly process, and facilitate the ability of the sensor assembly to meet allowable tolerances.

In embodiment of the invention, the sensor assembly is for sensing a physical property (e. g., a pressure, temperature, density, etc. ) of a target fluid environment (e. g., inside an engine block, an oil pan, or transmission case) and is positioned (or positionable) between a fluid port that is in open communication with the fluid environment and a control circuit. The sensor assembly includes a sensor housing that is fixedly securable to the fluid port to define a sensing space that is in communication with the fluid environment. A transducer (e. g., pressure or temperature transducer) is positioned within the sensor housing in operable communication with the sensing space, such that the transducer is responsive to the fluid environment so as to generate an output signal (e. g., a voltage or current) indicative of a measurement of the physical property.

The sensor assembly also includes a conducting connector assembly connectible with the control circuit to communicate the output signal to the control circuit. In one embodiment, the connector assembly includes a preferably resilient signal conductor that is retained within the sensor housing and electrically interconnected with the transducer, and the signal conductor is secured to the sensor housing. In another embodiment, the signal conductor includes a signal conditioning circuit. Further, a connector body is retained substantially within the sensor housing by the sensor housing and includes at least one conducting connector terminal. The signal conductor is secured to the connector terminal and the connector body is movable within the sensor housing and\or shiftable with the signal conductor.

In one aspect of the invention, the sensor housing includes a connector housing that defines a connector space isolated from the sensing space. The connector body is retained by the connector housing and is movable within the connector housing. The connector housing may include a keyway through which the connector body extends, and the connector body may include a key portion that is engageable with the keyway to limit the rotational movement of the connector assembly. Preferably, the signal conductor is retained within the connector space and the connector body blocks the keyway to substantially enclose the connector space. In this way, the signal conductor and other components in the connector space are protected from the outside environment.

In one aspect of the invention, the connector body is rotatable relative to the sensor housing. Further, the connector housing may define a generally longitudinal axis, and the connector body and the signal conductor is shiftable in a direction generally transverse to said longitudinal axis. The connector body and the signal conductor may also be shiftable in

a direction generally parallel to the longitudinal axis. Further, the signal conductor may have a first conducting portion secured to the sensor housing and a second conducting portion secured to the connector body, wherein the second conducting portion is substantially movable relative to the sensor housing.

In one particular embodiment of the invention, the transducer of the sensor assembly includes a pressure sensing element and a diaphragm. The diaphragm is mounted in a transducer housing and is exposed to a pressure of the fluid environment. The diaphragm also forms a seal with the transducer housing to define a cavity between the diaphragm and the pressure sensing element. When the cavity is filled with a medium, the medium is adapted to communicate the pressure that is applied to the diaphragm to the pressure sensing element.

Other features and avantages of the invention will become apparent to those skilled in the art upon review of the following Detailed Description, Claims and Figures. However, before embodiments of the invention are explained in detail, it should be understood that the invention is not limited in its application to the details of the apparatus, composition or concentration of components, or to the steps or acts set forth in the following description.

For example, the invention is capable of embodiments other than those adopted particularly for automobile applications. Also, it should be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an exploded view of a sensor assembly according to the invention.

Figure 1A is a detailed view of the signal conditioning circuit in Figure 1.

Figure 2 is a sectional view of the pressure sensor assembly.

Figure 3 is a sectional view along line 3-3 in Figure 2.

DETAILED DESCRIPTION OF THE DRAWINGS The present invention is adapted to sensor assemblies of various alternate designs. The present invention is also adapted to sensor assemblies which incorporate different types of transducers, including transducers for measuring a pressure or a temperature.

One type of sensor assembly according to the invention is a sensor assembly 10 that incorporates a pressure transducer sub-assembly as illustrated in Figures 1 through 3 and generally designated by the reference numeral 10. It is emphasized, however, that the invention is not limited to a sensor assembly that includes a pressure transducer and that application of the invention to other types of sensor assemblies (e. g., a sensor assembly that includes a temperature transducer) will be apparent to one skilled in the art upon viewing the Claims, the Figures, and the Detailed Description provided herein.

For purposes of description, the sensor assembly 10 and each of the components which comprise the sensor assembly 10 are, hereinafter, referred to as having a leading end that is generally closest to the pressure port when the sensor assembly 10 is secured thereto, and a back end that is generally farther or away from the pressure port. Referring to the exploded view of Figure 1 and the vertical sectional view of Figure 2,

the leading end of the sensor assembly 10 is generally formed by a hydraulic interconnect or port housing 12 (also referred to as a transducer housing) that is securable to a pressure port or conduit (not shown) of a machine or structure (e. g., an engine block). An electrically-insulating base header 14 (or integrated circuit substrate) engages a back end or back surface 16 of the port housing 12 and retains a pressure transducer sub-assembly for sensing or detecting the gas pressure of the fluid environment within the pressure port. An elongated connector 18 is electrically interconnected with the pressure transducer sub-assembly through a flexible signal conductor 22 that is secured to the base header 14 and electrically connected with the pressure sensor sub- assembly. Four connector lead wires 62 extend outward from a can portion 64 of the connector 18 and is connectible with the appropriate external control circuit (not shown). Finally, a can housing 20 fits substantially over the connector 18 and is secured to the base header 14. The can housing 20 and the base header 14 may also be referred to as forming a housing for the connector 18 and signal conductor 22.

As will be described in further detail below, one aspect of the invention is the"floating connection" (as opposed to rigid or non-flexible) between the connector 18 and the fixedly securable components of the sensor assembly 10 (e. g., the port housing 12, base header 14, pressure sensor sub-assembly, and can housing 20). This floating connection allows the connector 18 to be movable relative to these components and also functions to minimize, if not eliminate, the loads which are transferred from these components to the connector 18 and from the connector 18 to these components. At the same time, the can housing 20 substantially encloses the signal connector 22 and adequately protects it and other components from the outside environment. Moreover, the floating connection

can compensate for misalignment and inaccuracies in the manufacturing and assembly process, and facilitate the ability of the sensor assembly 10 to meet allowable tolerances.

Referring to both Figures 1 and 2, the port housing 12 is preferably a stainless steel hollow case with a leading end that is generally formed by a protruding cylindrical portion 24. The protruding cylindrical portion 24 is engageable with and insertable into the pressure port, and an O-ring 26 is securable around the outer surface of the protruding portion 24 to seal the interface between the port housing 12 and the pressure port. Further, the protruding cylindrical portion 24 defines a longitudinal pressure passage 28 that opens into the pressure port on one end and into a pressure cavity 30 on the opposite end. The back end of the pressure cavity 30 defines a generally circular opening 76.

The base header 14 is generally disk-shaped and includes a leading surface 32 and a back surface 34.

The leading surface 32 mates with the back end 16 of the port housing 12 and substantially encloses the circular opening 76 of the pressure cavity 30. The leading surface 32 of the base header 14 also defines a central recess or internal cavity 36 wherein the pressure transducer sub-assembly is mounted (see Figure 2). The back surface 34, on the other hand, is a generally flat, circular surface bounded by a circumferential ledge 70.

The pressure transducer sub-assembly depicted in the Figures includes a flexible diaphragm 38 fixedly mounted on the leading surface 32 and a pressure sensing element 40. The pressure sensing element 40 may be an integrated circuit pressure sensing mechanism that includes a flexible strain detecting portion and an electric circuit. The diaphragm 38 is a convoluted, thin-plate membrane (preferably stainless steel) that is positioned between the port housing 12 and the base

header 14 to effectively separate the internal cavity 36 from the pressure cavity 30. Moreover, the internal cavity 36 is filled with a transmitting fluid or gel, and is completely sealed from the pressure cavity 30 and the outside environment.

While any integrated circuit pressure sensing mechanism is appropriate, one type suitable for the present invention is a mechanism including a fully integrated full-bridge configuration of two variable resistance pais-resistive elements (VAR) combined with two fixed resistance reference resistors (REF). Such a sensing bridge and its operation are described in U. S.

Patent Nos. 4, 744, 863, 4, 853, 669, and 4, 996, 082, each of which are incorporated herein by reference.

It should also be noted that the sensor assembly 10 according to the invention may incorporate another type of transducer sub-assembly. For example, instead of the pressure transducer sub-assembly described above, the sensor assembly 10 according to the invention may incorporate a temperature sub-assembly.

The modification required to incorporate another transducer sub-assembly into the sensor assembly 10 will be apparent to one skilled in the art upon viewing the Figures and reading the Claims and Description provided herein.

With specific reference to Figure 2, when the sensor assembly 10 is installed on a machine component, such as a cylinder head or a transmission case, gas pressure in the target fluid environment of the machine component is communicated via the pressure port and the passage 28 to the pressure cavity 30. An increase in the gas pressure in the pressure cavity 30 causes the diaphragm 38 to flex in the direction of the internal cavity 36 thereby increasing the pressure of the transmitting fluid therein. The increased pressure in the internal cavity 36 is sensed by the strain detecting portion of the pressure sensing element 40 and generates a voltage change in the electric circuit

portion. This voltage change is calibrated so as to be functionally related to the pressure applied to the diaphragm 38, and, in this way, the pressure in the pressure cavity 30 is detected.

Four rigid sensor terminals 48 are connected by bonding wire 82 to the pressure sensing element 82 (i. e., the electric circuit portion) and extend therefrom through the base header 14, and protrude outward from the back surface 34 of the base header 14.

The ends of the sensor terminals 48 are laser welded to and electrically connected with the signal conductor 22. As will be described in further detail below, the signal conductor 22 is electrically connected with the connector 18. Thus, an electrical signal may be communicated from the pressure sensing element 40 through the signal conductor 22 and the connector lead wires 62 and out to an external control circuit.

The signal conductor 22 depicted in the Figures is a flexible and resilient structure which includes a printed wiring circuit (not shown). As best shown in the detail view of Figure 4, the signal conductor 22 has a generally serpentine or multiply-folded shape formed from a plurality of generally horizontal plate portions 50a, 50b, 50c, 50d which are interconnected via vertical connecting portions 52a, 52b. This structure provides a spring-like quality which benefits the signal conductor 22 in terms of strength and resiliency on flexibility. In prior art sensor assemblies, the electrical or signal connection between the sensor terminals and/or the external control circuit is typically provided by a rigid rod-like conductor, or a wire. In contrast, the signal conductor 22 depicted in the Figures is formed from four generally horizontal plate portions 50a, 50b, 50c, 50d and two vertical connecting portions 52a, 52b. As will become further apparent below, compression loads transferred through the base header or through the connector 18 are first evenly distributed across the

relatively large surface areas of the plate portions 50a or 50d respectively. Moreover, the connecting portions 52a, 52b are substantially wider and have more mass than prior art signal conductors. The connecting portions 52a, 52b function to absorb bending stresses created by loads applied to the plate portions 50a, 50b, 50c, 50d. These stresses are distributed substantially uniformly across the width of the connecting portions 52a, 52b.

The plate portions 50a, 50b, 50c, 50d and the connecting portions 52a, 52b may be shaped from the same conductive material or formed from one or more pieces which are joined together (e. g., by welding).

In any case, the connection between plate portions 50a, 50b, 50c, 50d and the connecting portions 52a, 52b are preferably curved so as to minimize the potential for areas of stress concentration.

When the sensor assembly 10 is secured within the pressure port, the compactness and flexibility of the signal conductor 22 facilitates vertical (as viewed in Figure 2), lateral and rotational movement of the signal conductor 22 and the connector 18 relative to the fixed base header 14. This aspect of the sensor assembly is explained in more detail below.

Referring to Figures 1A and 2, a first plate portion 50a of the signal conductor 22 approximates the width and contour of the back surface 34 of the base header 14 and abuts adjacent the back surface 34. The four sensor terminals 40 extend through the four apertures 54 on the first plate portion 50a to electrically interconnect the pressure sensing element 40 with the signal conductor 22 and to secure the first plate portion 50a to the base header 14. As mentioned above, the sensor terminals 40 may be laser welded to the first plate portion 50a.

Preferably, a programmable application specific integrated chip 56 (ASIC) is mounted onto and electrically interconnected with a first or lower

intermediate plate portion 50c. As is known in the art, the ASIC is programmed to condition (e. g., amplify) the output signal from the pressure transducer. In this respect, the signal conductor 22 may also be referred to as a signal conditioning circuitry 22. Also, an upper or second intermediate plate portion 50b is provided immediately above the lower intermediate plate portion 50c. Prior to installation of the sensor assembly 10, a readily detachable edge connector 58 is connected to the upper intermediate plate portion 50b and is used to program the ASIC chip. Typically, the edge connector 58 is removed prior to final installation of the sensor assembly 10.

Returning to Figure 2, a back plate portion 50d of the signal conductor 22 approximates the width and contour of an inside surface 60 of the connector body 18 and abuts adjacent the inside surface 60. Four rigid connector terminals 62 extend outward from the inside surface 60 and through four apertures 94 on the back plate portion 50d. The connector terminals 62 may be laser welded to the back plate portion 50d. In this way, the signal conductor 22 is structurally secured to and electrically interconnected with the connector lead wires 62 of the connector 18.

The connector 18 includes a generally cylindrical plastic can portion 64 that fits substantially around the signal conductor 22 and a plastic key structure 66 extending from the back of the can portion 64. The connector terminals 62 extend from the back plate portion 50d of the signal conductor 22 and through the can portion 64 and the key portion 66 of the connector 18 (see also Figure 3). As best shown in Figure 2, the inside surface 60 of the can portion 64 is spaced from the signal conductor 22 and does not interfere with any lateral movement (e. g., during contraction or compression) of the signal conductor 22. Also, the can portion 64 of the connector 18 fits over the signal

conductor 22 but is spaced vertically from and, does not interface with, the back surface 16 of the base header 14. This space or vertical gap is designated in Figure 1 by the reference letter A. In the embodiment depicted in the Figures, the vertical gap A is preferably about 0. 50 mm. Accordingly, because of the vertical flexibility of the signal conductor 22, the connector 18 and the signal conductor 22 are vertically or longitudinally movable, or shiftable, (e. g., up to about 0. 50 mm) relative to the back surface 16 of the base header 14 without causing interference between the can portion 64 and the base header 14. Further, the connector 18 may be moved relative to the signal conductor 22 (as the signal conductor 22 extends or compresses) without interfering with the ASIC chip 56 or with the intermediate plate portions 50a, 50b, 50c, 50d and connecting portions 52a, 52b.

To provide additional cover for the signal conductor 22 from the outside environment, a stainless steel can housing 20 is fitted over the can portion 64 of the connector 18 and is secured to the base header 14. A generally circular rim 96 of the can housing 20 engages the circumferential ledge 70 on the back surface 34 of the base header 14 to substantially enclose the can portion 64 of the connector body 18 and the signal conductor 22. The can housing 20 fits substantially over and around the connector 18 and only engages a shoulder area 74 of the connector 18. The outside surface of the can portion 64, however, is spaced from an inside surface 86 of the can housing 20.

The resulting lateral or circumferential gap is designated in Figure 2 by the reference letter B. It should be noted that the circumferential gap B varies along the height of the can portion 18 and can housing 20. In the embodiment depicted in the Figures, the circumferential gap B is preferably about 0. 50 mm and allows the can portion 64 to be moved laterally about 0. 50 mm relative to the can housing 20. Accordingly,

because of the horizontal or lateral flexibility of the signal conductor 22, the connector 18 and signal conductor are shiftable or laterally movable relative to the can housing 20 without causing interference between the can portion 18 of the connector 18 and the can housing 20.

As best shown -in Figure 3, the four connector terminals 62 extend outward through an"H"-shaped opening 68 provided on a back surface 72 of the can housing 20. Now referring to both Figures 2 and 3, the key portion 66 of the connector 18 has an"H"-shaped structure defined by two opposite flanges 88 connected by a middle beam 90. Each of the two flanges 88 supports two oppositely-located connector lead wires 62 which extend outward from the key portion 66. The lateral dimensions (e. g., the width of the middle beam 90 and the length and width of the two flanges 88) of the"H"-shaped key portion 66 are conveniently smaller than corresponding dimensions of the"H"-shaped opening 68. In this way, the"H"-shaped key portion may be appropriately aligned with the"H"-shaped opening and conveniently extended through the"H"-shaped opening without interfering with the can housing 20. As discussed above, the shoulder area of the connector 18 may be designed to engage the can housing 20, however, to substantially enclose can portion 64 of the connector 18 as well as the signal conductor 22. This is especially helpful when the signal conductor 22 functions also as a signal conditioning circuitry and requires various components of the circuitry (e. g., the ASIC 56) to be substantially protected from the outside environment. To this end, the resilient signal conductor 22 is designed to be biased toward the "H"-shaped opening 68, thereby maintaining the "H"-shaped opening 68 to be normally, substantially closed off.

Referring to Figure 3, the"H"-shaped opening 68 defines, in the can housing 20, two key tabs 92 which

fit conveniently between the two flanges 88 of the key portion 66. The key tabs 92 and the key portion 66 are sized such that a first gap or inside gap C is provided between the key tab 92 and the flanges 88 and the middle beam 90. The key portion 66 and the"H"-shaped opening 66 are also sized relative to one another to provide a second gap or outside gap D between the flanges 88 of the key portion 66 and the can housing 20.

Because of the inside gap C and the outside gap D, as well as the flexibility of the signal conductor 22, when the sensor assembly 10 is assembled, the connector 18 may be rotated relative to the base header 14 and the can housing 20 and about a generally longitudinal axis through the base header 14 and the can housing 22.

The degree of rotation is limited by the size of the inside gap C and the outside gap D. Preferably, the inside gap C will close first such that rotational travel of the key portion 66 is stopped by the key tabs 92.

Thus, the sensor assembly 10 includes a connector 18 that is electrically interconnected with the pressure sensing element 40 of the pressure transducer sub-assembly but is vertically, laterally, and rotationally movable relative to the can housing 20, base header 14, and port housing 12. The can portion 64 of the connector 18 is, also, generally movable relative to the signal conductor. In this way, the operational loads (e. g., vibration, compression, and tensile loads) which the sensor assembly 10 is subjected to may be effectively absorbed and minimized by the flexible and resilient signal conductor.

While one embodiment of the present invention has been shown and described above, alternate embodiments will be apparent to those skilled in the art and are within the intended scope of the present invention.

Therefore, the invention is to be limited only by the following claims.