Pressure sensor device

Abstract

A pressure sensor device (1) has a pressure-sensitive element (10), which comprises a substrate to which a diaphragm bearing a sensing circuit is attached. The sensitive element (10) is housed in a chamber (C) with the diaphragm facing one end (5b) of a passage (5) for a fluid. A circuit arrangement (15) is provided at the upper face of the substrate, electrically connected to the detection circuit, and within the chamber (C) a reinforcing element (30) is provided, configured to extend above the circuit arrangement (15) and defining at least one reinforcing surface configured to abuts against a corresponding area of the upper face of the substrate.

Description

[0001] "Pressure sensor device"

[0002] DESCRIPTION TEXT

[0003] Field of invention

[0004] The present invention refers to pressure sensor devices, and has been developed with particular reference being paid to sensor devices that include pressure-sensitive elements formed in ceramic material.

[0005] Prior art

[0006] Pressure sensor devices for fluid media are widely known. Such devices typically include a pressure-sensitive element housed in a casing body having an inlet passage for a fluid. The sensitive element has an elastically deformable sensing diaphragm, facing one end of the aforementioned passage, in order to be reachable by the fluid. A side of the diaphragm not exposed to the fluid has a detection circuit associated thereto, typically including capacitive or resistive or piezo-resistive elements, suitable for detecting deformation or bending of the same diaphragm, which is representative of the value of the fluid pressure. Inside the device there is then a PCB, bearing a control circuit, which is connected to terminals protruding from the sensitive element, where a spacer element can be provided between the PCB and the sensitive element (see for example WO 2008 / 078184A2).

[0007] Miniature sensing elements formed with semiconductor material are known, typically obtained starting from a silicon die, but generally - for applications where greater robustness is required - it is preferable to use larger sensing elements, and generally formed in ceramic material, for example alumina, or in metallic material, for example stainless steel.

[0008] In a first type of solution involving the use of ceramic material, the sensitive elements have a sensor body that integrates a diaphragm, or to which a diaphragm is associated. These elements are typically robust and suitable for withstanding high fluid pressures, by virtue of their structure which usually comprises a body with a high thickness or significant dimensions in height, and also a thick diaphragm (see the aforementioned WO 2008 / 078184A2).

[0009] Sensitive elements of this first type are typically made with a circular shape, which is better suited to a perimeter seal by means of an annular gasket. The outer casing of the sensor device commonly operates in closing and compression over the entire perimeter or outer circular edge of the ceramic sensitive element. The circular shape is particularly suitable for the production of the single pressure sensor with high thickness, as it avoids internal tensions during corresponding sintering and firing. On the other hand, these sensitive elements have a high dimensional footprint and show a lower sensitivity in the detection of pressure. Their production is also relatively complicated, as each production step must be carried out on each individual sensor.

[0010] In a second type of solutions involving the use of ceramic material, the sensitive elements have a body that includes a ceramic substrate of reduced height or thickness, to which a ceramic diaphragm is attached, also typically of reduced height or thickness, and where a cavity is defined between the substrate and the diaphragm that allows the deformation of the same diaphragm. These sensitive elements of the second type are typically more sensitive to pressure detection than those of the first type mentioned above, and lend themselves to accurately detecting even small variations at low pressures. The sensitive elements of the second type can be produced in simpler and cheaper ways than the sensitive elements of the first type; In particular, their production may involve the use of large sheets of ceramic material, for example two sheets intended to be coupled together, on which respective parts of a plurality of sensitive elements are simultaneously made. The sheets are coupled and then cut or sheared, to obtain a plurality of individual sensitive elements that can be used individually.

[0011] In summary, electrically conductive tracks are deposited or screen-printed in advance on each sheet, and for each sensitive element to be obtained, and on the sheet intended to obtain the diaphragms, also resistive or piezo-resistive elements are deposited or screen-printed in advance; these steps carried out on the two sheets concern the set of the plurality of sensitive elements to be obtained.

[0012] The two sheets are then superimposed and fixed to each other, so that some parts deposited on one sheet are in positions corresponding to those deposited on the other sheet, and electrically connected to each other, for example through the use of sinterable materials. Subsequently, a plurality of pieces are cut from the semi-finished product including the two sheets fixed together, each corresponding to a single sensitive element. Typically, the individual sensors are sheared in a circular shape.

[0013] This processing technique allows the production of large volumes of sensing elements comparatively easier and more cost-effective than in the case of sensor elements of the first type mentioned above. However, this processing technique presupposes that the ceramic sheets intended to make the substrate and diaphragm of the sensitive elements to be obtained are relatively thin, so that they can be divided or cut after their assembly, as explained above.

[0014] The reduced thickness of the parts constituting these sensitive elements has the consequence that their use is limited to applications in which the nominal pressures of the fluids subject to detection are relatively low, or in any case the risks of high overpressures are very limited. On the other hand, where such a sensing element is used in areas where high overpressures, even momentary, may occur, there is a risk of breakage or bursting, particularly of the substrate. These high pressure variations may occur in a common hydraulic circuit, for example as a result of the well-known phenomenon commonly referred to as "water hammer", but much higher momentary pressure variations may be present in circuits for fluids on vehicles, for example circuits equipped with high-pressure pumps, such as the circuit for a fuel injected at high pressure.

[0015] In the event of overpressure, the diaphragm tends to bend considerably towards the inside of the aforementioned cavity of the sensing element. In this abnormal condition, the diaphragm may flex until it breaks, allowing the fluid to penetrate the cavity of the sensing element, which consequently pushes directly on the corresponding face of the substrate, or the diaphragm may flex until it comes into contact with the corresponding face of the substrate, transferring the thrust of the fluid to the substrate itself. In such cases, the pressure is almost entirely applied to the substrate, which, being relatively thin, can break, with the consequence that the fluid is free to penetrate inside the casing of the sensor device, and therefore in contact with electrical parts: in the event that the fluid subject to detection is a fuel, high risks of fire or explosion arise (see also what is described below with reference to figure 25).

[0016] Summary of the invention

[0017] In its general terms, an aim of the present invention is to obtain a pressure sensor device, provided with a pressure-sensitive element of simple and inexpensive construction, preferably of small size and / or high sensitivity in detection, which is reliable.

[0018] Another aim of the invention is to obtain a pressure sensor device, provided with a pressure-sensitive element, wherein the risks of possible malfunctions due to occasional high overpressures are eliminated or at least drastically reduced.

[0019] Another aim of the invention is to obtain a pressure sensor device wherein the risks of breakage of the sensitive element and / or the substrate thereof are reduced.

[0020] Another aim of the invention is to obtain a pressure sensor device wherein the risks of fluid leakage due to occasional high overpressures are reduced.

[0021] Another aim of the invention is to obtain a pressure sensor device that allows to prevent the risk of fire in the case of use of the device itself in combination with combustible or explosive fluids, such as a fuel, for example in vehicles.

[0022] One or more of the above aim, and still other aim which will become clearer later, are achieved according to the present invention by a pressure sensor device having the characteristics indicated in the claims. The claims form an integral part of the technical training provided here in connection with the invention.

[0023] Brief description of the drawings

[0024] Further aims, characteristics and advantages of the present invention will be clear from the detailed description that follows, made with reference to the attached schematic drawings, provided purely as a non-limiting example, wherein:

[0025] - Figure l is a perspective view of a pressure sensor device according to possible embodiments;

[0026] - Figures 2 and 3 are partially sectioned perspective views of a pressure sensor device according to possible embodiments;

[0027] - Figure 4 is a cross-sectional view of a pressure sensor device according to possible embodiments;

[0028] - Figures 5 and 6 are exploded views, from different angles, of a pressure sensor device according to possible embodiments;

[0029] - Figure 7 is detail of Figure 4 in a larger-scale;

[0030] - Figure 8 is a cross-sectional view similar to that of Figure 7, relating to a possible variant;

[0031] - Figure 9 is a perspective view of a pressure-sensitive element of a pressure sensor device according to possible embodiments, with an associated temperature-sensitive element;

[0032] - Figures 10 and 11 are perspective views, from different angles, of a reinforcing element of a pressure sensor device according to possible embodiments;

[0033] - Figure 12 is a perspective view of a reinforcing element and a sensitive element of a pressure sensor device according to possible embodiments, aimed at highlighting contact surfaces between these two elements;

[0034] - Figures 13-16 are perspective views of a reinforcing element according to Figures 10-11 coupled to a sensitive element according to Figure 9;

[0035] - Figures 17-21 are perspective views aimed at highlighting corresponding assembly phases of a pressure sensor device according to possible embodiments;

[0036] - Figures 22 and 23 are sectioned perspective views, from different angles, of a pressure sensor device according to possible embodiments;

[0037] - Figure 24 is a partial and schematic cross-sectional representation of a pressure sensor device according to possible embodiments;

[0038] - Figure 25 is a partial and schematic cross-sectional representation of a pressure sensor device of a traditional design;

[0039] - Figure 26 is a partial and schematic cross-sectional representation of some components of a pressure sensor device according to possible variant embodiments;

[0040] - Figure 27 is a perspective view of a component of a pressure sensor device according to possible variant embodiments; and

[0041] - Figure 28 is a cross-sectional view of a pressure sensor device equipped with the component of Figure 27.

[0042] Description of preferred embodiments of the invention

[0043] The reference to “an embodiment” within this description indicates that a particular configuration, structure, or characteristic described in relation to the embodiment is comprised in at least one embodiment implementation. Thus, phrases such as “in an embodiment” and the like, which may be present in different places in this description, do not necessarily refer to the same embodiment. In addition, particular conformations, structures or characteristics described or illustrated may be combined in any appropriate way in one or more embodiments, even if different from those depicted. Certain conformations, structures or characteristics described or illustrated by reference to “one embodiment” may be at least partially present or absent in other embodiments.

[0044] The references signs used herein are for convenience only and therefore do not define the scope of protection or the scope of the embodiments. Spatial references (such as “upper”, “lower”, “top”, “bottom”, etc.) used herein are for convenience only and refer to the examples as shown in the figures. In some figures, a sealing gasket described below is represented in such a way as to highlight its original shape, before its possible elastic deformation.

[0045] Initially referring to Figures 1-6, reference 1 designates as a whole a pressure sensor device according to possible embodiments. In preferential embodiments, the device 1 may also include a temperature-sensitive element, to allow both pressure sensing and temperature sensing of a fluid. In the following, assume that the device 1 is used for detecting the pressure (and possibly the temperature) of a fuel in a vehicle, in particular a diesel fuel. The device 1 can be configured - for example - to operate at nominal pressures of up to 12 bar, with a pressure measuring range between 1 and 10 bar. As it will be seen, however, the device is specially designed to withstand any abnormal pressure peaks, even up to 80 bar.

[0046] The device 1 has a casing body 2, which comprises at least two body parts 2a and 2b sealingly coupled together, to define a chamber C therebetween, in which a pressure-sensitive element is housed, indicated by 10 as a whole in Figures 3-6.

[0047] The body parts 2a and 2b, which define respective chamber parts, designated with 60 and 2b' for example in Figures 7 and 8, are preferably formed by moulding of plastic or polymer material, such as a polyphthalamide or polyamide PPA.

[0048] Body part 2a is intended for connection with a fluidic circuit in which the fluid whose pressure is to be measured (for example a fuel) is located, and has to this purpose at least one passage for the fluid. In the non-limiting example depicted, the body part 2a has a portion of fluidic coupling 3, protruding below, which preferably has a substantially cylindrical section and can be provided externally with a seat for an annular sealing element 4. Inside the fluidic coupling portion 3 a duct or passage 5 for the fluid extends, having a first end 5a that opens at a bottom of the same portion 3, and a second end 5b that opens at a bottom 60a (Figure 5) of the chamber C wherein the pressure-sensitive element 10 is housed. The end 5b can have an enlarged or flared shape, or in any case be shaped to better distribute the fluid subject to detection towards a diaphragm of a pressuresensitive element, described below.

[0049] In preferential embodiments, a housing 6 is also provided at the bottom of the fluidic connection portion 3, for a temperature-sensitive element, for example an NTC thermistor, designated by 40 in Figures 3-6. For this purpose, a passage 6a (Figures 3-4) is also defined within the portion 3 in which there extend the connecting conductors 41 of the pressure-sensitive element 40. Passage 6a also opens at the bottom 60a of the housing chamber C, in order to allow the connection of the conductors 41 to a control circuit (15, Figure 4), described below. In the case exemplified, the housing 6 is closed with respect to the outside, i.e., it is configured to keep the sensitive element 40 isolated from the fluid, with an indirect temperature detection; however, in other embodiments, particularly for use in combination with non-flammable media, the housing 6 and / or the passage 6a could be configured (for example by means of suitable seals) to allow direct temperature detection, with the sensitive element 40 at least partially in contact with the medium.

[0050] Body part 2b is intended for electrical connection with an external electrical circuit and has an electrical connector 7 to this purpose, and has closing functions with respect to body part 2a. Part 2b can also be configured to perform other functions, such as fixing of the device (in that case providing for example fixing eyelets) or taking an external reference pressure (in that case providing for example a passage that connects the housing chamber with the external environment).

[0051] The electrical connector 7 is preferably defined by a tubular part of the body part 2b, into which an external portion of respective electrical terminals extends. In Figure 1 the external portion of three of these terminals is partially visible, designated by 7a, 7b and 7c. It should be noted that, in preferential embodiments, at least four terminals are provided, for example one for connection to a positive power pole, one for connection to a negative power or ground pole, one for the signal relating to the pressure-sensitive element 10 and one for the signal relating to the temperature-sensitive element 40, the said signals being referred to said ground or negative power supply.

[0052] As can be seen, for example, in Figure 6, terminals 7a, 7b and 7c each have a shaped contact portion 7a', 7b', 7c', intended to be located within the housing chamber C, in particular at the bottom 2b" of the chamber part 2b' (in Figure 6, the contact portion 7d' of a fourth 7d terminal not visible in Figure 1 is also visible). For this purpose, the material that forms the body part 2b can be moulded over the electrical terminals, so as to leave the contact portions 7a' -7d' exposed. Again from Figure 6 it is possible to see how, in various embodiments, in the body part 2b, in particular in the chamber part 2b', reliefs, walls or surfaces 2c may be defined, intended to be settled on corresponding reliefs, walls or surfaces of body part 2a, in the assembled condition of device 1.

[0053] Referring to Figure 7, the sensitive element 10 comprises a substrate 10a, preferably of electrically insulating material, for example a ceramic material such as alumina, having an upper face and a lower face opposite to each other, where a diaphragm 10b is fixed to the lower face, the diaphragm being at least partly deformable in an elastic way, preferably formed with a material similar to that of the substrate 10a.

[0054] The diaphragm 10b is attached to the substrate 10a so that a cavity is defined therebetween, designated by 11 in Figure 7. In the case shown in Figure 7, for this purpose, the diaphragm 10b is glued to the lower face of the substrate 10a, which is flat, by means of a suitable peripheral annular layer of material 10c (for example a material or glue containing glass fibres or powder or frit), with this layer being sufficiently thick to determine the height of the cavity 11. In other embodiments, such as the one shown in Figure 8, a recess is defined at the lower face of the substrate 10a, such that between the lower face of the substrate 10a and the diaphragm 10b the aforementioned cavity is defined, here designated by 11'; in this case, the peripheral layer of material used to fix the substrate 10A and the diaphragm 10B together can have a much lower thickness than in the case of Figure 7; the substrate 10A and the diaphragm 10B can in any case be joined together by any bonding technique known in the field.

[0055] Preferably, the cavity 11 or 11' is a sealed cavity, i.e. not connected to the external environment, for the detection of an absolute pressure. However, in alternative embodiments, the cavity 11 or 11' can be connected with the external environment, for example by means of a through hole in the substrate 10a, for the detection of a relative pressure.

[0056] As will be seen, in preferential embodiments, the pressure-sensitive element 10 has a polygonal peripheral profile, preferably a square profile with sides having a length of between 12 and 16 mm, preferably 14 mm ± 10%, with a body or substrate 10a having a thickness of between 0.8 and 1.2 mm, preferably 1 mm ± 10%, and a diaphragm 10b having a thickness not exceeding 0.3 mm, preferably 0.2 mm ± 10%. Preferably, the diaphragm 10b has a flexible central portion (FP, Figures 7 or 8) with a diameter (inscribed in the square profile) of 5-7 mm, preferably 6 mm ± 10%, corresponding to an area of about 0.2 to about 0.39 cm2, preferably about 0.28 cm2± 10%, on which the fluid subject to detection operates in thrust. The sensitive element can be intended to work, in typical operating conditions, with pressures up to 10 bar, in which case a maximum force of about 2.8 kg acts on the aforementioned flexible portion of the diaphragm; in the event of abnormal pressure peaks at 80 bar, a force of about 22.5 kg could act on the same flexible portion of the diaphragm.

[0057] Referring to Figure 6, the side of the diaphragm 10b facing the cavity 11 or 11' has at least part of a detection circuit, designated as a whole by W, configured to detect bending of the diaphragm 10b depending on the fluid pressure. The detection circuit W can be of any type known in the field. For example, the circuit W can comprise resistive or piezo-resistive elements connected in a bridge configuration, in particular a Wheatstone bridge.

[0058] The sensitive element 10 is housed in the corresponding housing chamber C (Figures 2-4) in such a way that, for the purpose of pressure measurement, at least one flexible central region of diaphragm 10b is at least partially facing the end 5b of the passage 5, as can be seen, for example, in Figures 7 or 8, where this flexible part is designated by FP, to allow the fluid to reach the diaphragm itself. Preferably, the passage 5 has only one outlet end, here represented by end 5b, which is substantially concentric with respect to the aforementioned central flexible region FP of the diaphragm 10b.

[0059] In various embodiments, and referring for example to Figure 5, in the bottom of the aforementioned housing chamber C - here corresponding to the bottom 60a of the chamber part 60 - a sealing seat 61 is defined for an annular seal 20, intended to operate in seal with respect to the diaphragm 10b, or in seal between the body 2a and the sensitive element 10. The seat 61 preferably has a substantially cylindrical shape.

[0060] As can also be seen in Figures 7-8, the end 5b of the passage 5 for the fluid opens at the bottom of the aforementioned seat 61, in a region circumscribed by the annular seal 20. Preferably, this region circumscribed by the seal 20, or the internal passage of the same seal, has a diameter close to the diameter of the flexible portion FP of the diaphragm 10b, such as a diameter of about 6 mm ± 10%, corresponding to a fluid passage area of about 0.28 cm2.

[0061] Note that in Figures 4, 7-8, 22 and 26, the seal 20 is shown in a configuration that is not deformed in the axial direction, for the sake of clarity: however, in reality, in the assembled condition of the device 1, the seal 20 could be at least partially deformed axially, at least in a portion thereof provided with annular reliefs, with a peripheral region of the diaphragm 10b (in particular a region surrounding the area of the diaphragm where the detection circuit W is located) that is preferably resting relative to the bottom designated by 60a.

[0062] Referring in particular to Figure 9, in various embodiments, at least part of a circuit arrangement, designated as a whole by 15, is provided at the upper face of the substrate 10a, which is connected in signal communication with the detection circuit W.

[0063] Circuit arrangement 15 comprises at least one circuit component, preferably a plurality of circuit components, some of which are designated by 16a-16d (for example three-dimensional or thicker components such as chips, semiconductors, passive components, solid-state components, etc.) and tracks made of electrically conductive material which are substantially two-dimensional or thin in thickness, some of which are designated by 17, for connection of the circuit components 16a-16d.

[0064] In other embodiments, the circuit arrangement 15 might only include tracks 17 of electrically conductive material, with the circuit components 16a-16d placed elsewhere, such as on a PCB.

[0065] In various preferential embodiments, such as the one exemplified in the figures, the circuit arrangement 15 is associated with the upper face of a substrate 10a having a polygonal peripheral profile, such as a square or rectangular profile, or more generally a peripheral profile distinguished by the presence of angular regions with corners, possibly rounded corners, where at least part of the circuit arrangement, in particular part of its tracks of electrically conductive material, are arranged in positions corresponding to these angular regions.

[0066] The circuit arrangement 15, preferably comprising a control integrated circuit or a microcontroller 16d, is configured to implement the control functions required for operation of the sensor device 1, such control functions including, for example, power supply, detection and / or conditioning and / or transmission of the signal related to the pressure (and possibly temperature) measurement, and possibly protection against electrostatic charges (ESD protection) and / or filtering of electromagnetic disturbances (EMI filtering).

[0067] In preferential embodiments, such as the one exemplified, some of the tracks 17 are shaped, for example at a free end or in an intermediate area, so as to form contact pads 18, the function of which will be explained later. Preferably, at least some of these pads 18, or in any case the contact portions of some of the tracks 17, are located in position corresponding to the aforementioned corner regions of the upper face of substrate 10a. In fact, as already mentioned and as can be clearly seen from Figure 9, in preferential embodiments, the pressure-sensitive element 10 has a substantially polygonal peripheral profile, in particular quadrangular, preferably a substantially square peripheral profile.

[0068] Still referring to Figure 9, in various embodiments, the substrate 10a is provided with a plurality of metallized through holes 19 (i.e., holes made electrically conductive), for connection to the detection circuit W carried by the diaphragm 10b, according to a technique known in itself. For example, the holes 19 may be filled with, or have the surface covered with, an electrically conductive material (such as a metal or paste), with such material that, at one end of the holes 19, is in contact with a respective conductive track of the circuit arrangement 15, and at the other end of the holes is in contact with a respective conductive track, or a corresponding connection pad, of the detection circuit W.

[0069] In the case exemplified, the circuit arrangement 15 also includes contact elements M for connection of the conductors 41 of the temperature-sensitive element 40, from which respective tracks 17 extend.

[0070] In preferential embodiments, such as the one exemplified in the figures, the circuit arrangement is obtained on the upper face of the substrate 10a, which therefore acts directly as a circuit support. However, the case of a circuit arrangement 15 obtained on a respective circuit support, such as a PCB, which is constrained directly to the upper face of the substrate 10a, for example glued, is not excluded from the scope of the invention.

[0071] In particularly advantageous embodiments, the sensitive element 10 is obtained starting from a first sheet of ceramic material, intended to obtain a plurality of diaphragms 10b, and a second sheet of ceramic material, intended to obtain a plurality of substrates 10a, thicker than the first sheet. On the two sheets, respective circuit parts are made, such as the circuit W in the case of the first sheet, and the metallized holes 19 and the tracks 17 in the case of the second sheet. The two sheets are then mechanically joined to each other, such that each of the circuits W is electrically connected to respective metallized holes 19. Subsequently, the two sheets coupled together in an overlapping condition are cut, to obtain a plurality of individual sensitive elements 10. The circuits 15 can be completed with the components 16 before or after cutting the coupled sheets. Instead of being cut, at least one of the two sheets (in particular the one intended to obtain the substrate 10a) may be provided with incisions of predefined depth, to allow thereafter a calibrated break along these incisions, in order to obtain the separation of the sensitive elements.

[0072] To speed up and make the process economical, the cuts or incisions are made along linear stretches, which allow for the production of sensitive elements having a quadrangular profile. The quadrangular shape is advantageous because it allows more space to be available, compared to a circular shape, in the case of a sensitive element on which electronic components of a control circuit (e.g. chips, semiconductors, passive components, etc.) must also be mounted.

[0073] For example, on a first face of the first sheet (intended to be facing the second sheet) a plurality of detection circuits W can be obtained, each including the respective conductive tracks, with possible connection pads, and the respective detection elements (e.g. resistors or piezo-resistors). In the second sheet, at each substrate to be obtained, the holes 19 are formed, an electrically conductive material is deposited to form the conductive tracks 17, and the holes 19 are rendered conductive, as explained above, for connection to the tracks or the corresponding connection pads of the first sheet.

[0074] On the faces of the two sheets intended to be faced with each other, respective layers of electrical connection material - preferably suitable for sintering, such as an electrically conductive material, deposited above respective conductive tracks - are printed or deposited; sintering is preferably done by placing the two sheets in a sintering furnace.

[0075] On the same faces of the two sheets, respective layers of mechanical connection material, preferably of the sinterable type, are also printed, which are sintered in a sintering furnace, wherein the mechanical connection layers are electrically insulating and / or isolated from the electrical connection layers.

[0076] At this point, the two sheets are electrically and mechanically coupled, placing the first sheet on top of the second sheet, with the face of the first sheet bearing the circuits W facing the corresponding face of the second sheet. In this condition, the electrical connection layers and the mechanical connection layers of each sheet are fixed together or sintered in a furnace, in order to join together at least at each sensitive element to be obtained. The complex of mechanically and electrically coupled sheets is then divided as explained above, in order to obtain the individual sensitive elements 10. As mentioned, the circuits 15 for each sensing element 10 can be completed before or after the coupled sheets are cut.

[0077] As can be seen in Figures 3-4, according to a preferential embodiment, the temperature-sensitive element 40 and the corresponding housing 6 are in a lower position with respect to the pressure-sensitive element 10. For this reason, the connecting conductors 41 have an angled portion, with a generally horizontal section, facing or substantially parallel to the upper face of the substrate 10a, and a generally vertical section, for insertion in the passage 6a.

[0078] In accordance with the invention, within the housing chamber defined by the two chamber parts 2b' and 60 there is a reinforcing element of the pressuresensitive element 10. The reinforcing element is configured to extend at least partially above the circuit arrangement 15 and defines one or more reinforcing surfaces, each prearranged to rest on a corresponding area of the upper face of the substrate 10a, preferably a peripheral area and in the absence of constraints with respect thereto.

[0079] Preferably, a plurality of local reinforcing surfaces are provided, each designed to be abut directly for reinforcement purposes on a corresponding localized area of the upper face of the substrate 10a.

[0080] As will be clear later, the reinforcing element is configured to reinforce the sensitive element 10 by keeping it towards the bottom 60a of the housing chamber C, with the aforementioned reinforcing surfaces each abutting against a corresponding area of the upper face of substrate 10b, in particular to prevent breakage of the substrate 10b in the event of excessive fluid pressures.

[0081] A cited reinforcing element according to a possible embodiment is designated as a whole by 30 in the figures, and is visible in detail in Figures 10 and 11.

[0082] The reinforcing element 30 has a body shaped to define the aforementioned reinforcing surfaces, which is preferably formed of a polymer or a moulded plastic material, for example polyphenylene sulfide - PPS. However, the body of the reinforcing element 30 could be formed with a different material, such as a material with good resistance to deformation, for example a metal or a stamped alloy, possibly providing an appropriate layer of electrically insulating material with respect to electrically conductive tracks provided on the substrate 10a of the sensitive element 10.

[0083] In various embodiments, such as the one represented, the element 30 has a substantially polygonal peripheral profile, in particular quadrangular, preferably a substantially square peripheral profile, without prejudice to the possible presence of parts protruding from this profile. Preferably, the element 30 has a peripheral profile whose shape is at least approximately similar to that of the peripheral profile of the sensitive element 10.

[0084] Preferably, the plastic material that makes the reinforcing element 30 has a higher compressive strength than the plastic material that makes the body part 2a and / or 2b. Preferably, the material of the element 30 has a compressive strength approximately 25% greater than the material of the body part 2a and / or 2b. In this way, with the same resting area between the element 30 and the corresponding body part 2a, the element 30 is less subject to deformation than the casing body.

[0085] As mentioned, preferably, the parts 2a, 2b of body 2 are formed in PPA, while the reinforcement body is preferably formed in PPS. Advantageously, PPS is a material that lends itself more to making small parts with precise dimensions.

[0086] In various preferential embodiments, the reinforcing element 30 is configured as a separate part from the casing parts 2a, 2b, and therefore has smaller dimensions than these casing parts. The small size of the element 30 has the effect of avoiding or significantly reducing material shrinkage, with consequent advantages in terms of manufacturing precision, allowing to obtain reinforcing surfaces of appropriate shape, suitable for precisely coupling to the respective areas of the sensitive element 10. In addition, moulding of the reinforcing element 30 having reduced dimension allows the use of materials with better mechanical characteristics (these are generally more expensive materials) than the material used for the moulding of the more voluminous casing parts 2a, 2b. The reduced dimensions of the reinforcing element 30 also allows - if required - more complex moulding cycles and / or subsequent heat treatment cycles, to stabilise the dimensions after moulding.

[0087] In the case exemplified, the body of the reinforcing element 30 has a plurality of reinforcing portions, designated by 37a-37e, designed to settle on the upper face of the substrate 10a, in order to reinforce it.

[0088] Preferably, at least four reinforcing portions 37a-37d are provided at or near different corner and / or perimeter regions of the element 30; in the example, portions 37c and 37d are joined together by an intermediate reinforcing region 37 e, but this may be missing.

[0089] The reinforcing portions 37a-37e could be at least partially joined together by connecting portions of the element 30 which are free of reinforcing or resting surfaces with respect to substrate 10a, and therefore with such connecting portions not intended to couple with corresponding regions of the same substrate. However, these connecting portions can contribute to strengthening the reinforcing element 30 itself, for example by stiffening its structure. For example, in the case exemplified, between the reinforcing portions 37b and 37c there is an intermediate connecting portion 39, generally lowered with respect to the bottom surfaces of the portions 37a-37e.

[0090] Portions 37a-37e define, at the lower face of the element 30, corresponding reinforcing surfaces 37a'-37e', lying substantially according to the same plane.

[0091] Element 30 may also include one or more reinforcement portions in a more central or intermediate position, such as the portion indicated by 36 in Figure 11 (see also Figure 4), defining a corresponding reinforcing surface 36'; the at least one portion 36 is preferably located near the perimeter which defines the flexible portion FP of the diaphragm 10b, and in general in a position substantially closer, in the radial direction, to the center of the element 30, with respect to portions 37a-37e. The at least one portion 36 is preferably located in an intermediate position with respect to two corner portions 37a, 37b.

[0092] Preferably, the reinforcing element 30 is shaped to extend above the circuit arrangement 15, without however mechanically interfering with the latter, in particular with its three-dimensional circuit components (i.e., the components having a greater height footprint than the conductive tracks), such as electronic components (e.g. semiconductors, chips, transistors, capacitors, resistors) and electrical connectors. The reinforcing element 30 can instead extend on tracks or connecting pads, if these are suitable to be mechanically stressed, e.g. in compression, without being damaged.

[0093] To this purpose, in various embodiments, the element 30 is shaped to have portions intended not to rest on the substrate 10a, at which there are through openings or material cutouts or recesses at the lower face.

[0094] In this example, there are provided a recess 38a between the reinforcing portions 37a and 37b, a recess 38b between the reinforcing portions 37a and 37d, and a recess 38c between the reinforcing portions 37b and 37c.

[0095] Referring to the non-limiting example illustrated, the recesses 38a and 38b are designed to be located in positions corresponding to the circuit components designated by 16a and 16b in Figures 9 and 12, while the recess 38c is designed to be located in a position corresponding to the contacts M to which the conductors 41 of the temperature-sensitive element 40 are connected.

[0096] Again in order not to interfere with circuit components of the arrangement 15, the element 30 may include at least one through opening or a cutout or a recess in a generally central position; referring to the example, a central opening 34 is provided for this purpose, whose profile is shaped to avoid interference with the circuit component designated by 16d in Figures 9 and 12.

[0097] In addition to avoiding direct contact with components 16 of the circuit arrangement 15, the presence of the recesses 38a-38c and the opening 34 makes it possible to reduce the overall mass of the element 30 and that of the corresponding portions 36, 37a-37e, thus obtaining structural benefits, such as a reduction in shrinkage following moulding and / or greater dimensional accuracy. In this way, economic benefits can also be obtained, linked to a lower use of material.

[0098] Preferably, in the assembled condition of the device 1, at least one component of the circuit arrangement 15 may be substantially located between two reinforcing portions of the element 30, as for example in the case of the components 16a and 16b of Figure 12, which are intended to be at least partially interposed between the reinforcing portions 37a, 37b and between the reinforcing portions 37a, 37d, respectively.

[0099] Again referring to the assembled condition of the device 1, preferably at least one reinforcing portion of the element 30 may be substantially located between two circuit components, as is the case of the reinforcing portion 36 of Figure 12, which is intended to be at least partially interposed between the components 16b and 16d of the circuit arrangement 15.

[0100] Of course, the number and / or the position of the recesses 38a-38c and the at least one opening 34 may be different from the one exemplified, depending on the configuration of the circuit arrangement 15 and the profile of the sensitive element 10: for example, a recess of the exemplified type may be present between the reinforcing portions 37c and 37d.

[0101] Similarly, the number and the shape of the reinforcing portions 37a-37e could also be different, for example by providing a single reinforcing portion having an annular or circular or quadrangular shape, designed to completely surround or at least one area of the circuit arrangement 15; also in this case, the single reinforcing portion will preferably identify at least the surfaces 37a' -37c' intended to abut against the respective corner regions of the upper face of the substrate 10a.

[0102] In alternative embodiments, the circuit arrangement 15 could be located at least in part in a perimeter portion of the upper face of substrate 10a, in which case the layout of the same circuit arrangement could be organized in such a way as to leave local surfaces of the substrate exposed, for the reinforcing portions 37a-37e of the element 30 to rest on them.

[0103] In preferential embodiments, the reinforcing element 30 defines a plurality of seats or guiding and / or positioning and / or housing passages, preferably in the form of through seats or holes, which extend in the thickness direction (T, Figure 10) of the same element. These seats, designated by 32 in Figures 10-11, are intended to receive a corresponding plurality of springs or similar elastic elements of electrical contact, designated by 50 for example in Figures 5-6, preferably coil springs. In the following, reference will be made to contact springs for simplicity.

[0104] In the assembled condition of the device 1, each contact spring 50 has the two opposite ends thereof in contact with the first contact portion 7a' -7d' (Figure 6) of a respective electrical terminal of the body part 2b, on the one hand, and with a respective electrically conductive track 17, on the other hand, in particular with a corresponding pad 18 (Figure 9), of the sensitive element 10. The contact springs 50 are thus in a guided or positioned condition by means of the respective seat 32 of the reinforcing element 30. Preferably, each electrical contact spring 50 has the respective opposite ends which, at least in the uncompressed condition, extend beyond the thickness T of the reinforcing element 30.

[0105] From Figures 10 and 11 it can be seen that, preferably, at least some of the seats 32, preferably all the seats, each have an end that opens at a respective reinforcing surface 37a'-37d', here the lower surface of the reinforcement portions 37a-37d. The opposite end of the seats 32 can then open at the upper face of the same reinforcement portions 37a-37d. In the assembled condition of the device 1, the lower end of the seats 32 faces corresponding conductive tracks of the circuit arrangement 15 on the upper face of the substrate 10a, in particular at respective pads 18.

[0106] Referring again to Figures 10-11, in various preferential embodiments the reinforcing element 30 defines a plurality of peripheral coupling portions, designated by 31, which are configured for engagement with corresponding coupling seats defined in one of the body part 2a and the body part 2b, in particularly in peripheral or angular positions of the housing chamber C. As can be seen, each peripheral coupling portion 31 is preferably a protruding shaped portion of the reinforcing element 30, which extends in a generally radial direction (with respect to an imaginary central axis of the element 30). In this example, the coupling portions 31 protrude starting from the corner regions of the element 30, where the reinforcing surfaces 37a' -37d' are defined.

[0107] In the example, the coupling portions 31 have a respective roughly rhomboidal or square profile, but their shape can be different.

[0108] As mentioned, these portions 31 are designed to engage corresponding coupling seats of at least one of the two body parts 2a and 2b. In the example shown - see in particular Figures 17 and 18 - the body part 2a has on an upper face thereof a series of walls, some of which delimit the chamber part 60; other walls may be provided for the purpose of strengthening the body part 2a. As far as is of interest here, the seats - indicated by 64 - for the coupling portions 31 of the reinforcing element 30 are defined between walls or wall portions 62a-62h contiguous to each other of the body part 2b. In particular, in the example, between the successive wall portions 62a-62b, 62c-62d, 62e-62f and 62g-62h, interruptions or discontinuities are defined that obtain the seats 64, in which the coupling portions 31 are at least partially received to keep the reinforcing element 30 in a predefined position. It should be noted that the wall portions 62a-62g could be replaced by a substantially annular continuous wall, provided along its development with suitable coupling seats 64.

[0109] The body part 2a also defines the respective abutments surfaces 64a at the seats 64, on each of which the lower face of a respective coupling portion 31 abuts (see also Figure 22).

[0110] As mentioned, and as shown in the figures, the pressure-sensitive element 10 and the reinforcing element 30 preferably have a substantially polygonal peripheral profile. In such configurations, the reinforcing surfaces of the reinforcing member 30 comprise reinforcing surfaces 37a' -37d' defined at corner regions of the reinforcing member 30. On the other hand, the corresponding peripheral zones on which the surfaces 37a'-37d' are matched are defined at corner regions of the upper face of the substrate 10a.

[0111] The concept is shown in Figure 12, where references 137a'-137e' indicate the peripheral areas of the upper face of substrate 10a, on which the reinforcing surfaces 37a'-37e' of element 30 are designed to rest, and 136' indicates the radially more internal area in which the reinforcing surface 36' of the intermediate reinforcing portion 36 of element 30 is intended to rest.

[0112] As can be seen, for the purposes of the invention, the sensitive element 10 or its substrate 10a is appropriately prearranged with peripheral zones 137a'-l 37e' suitable for coupling with a reinforcing element, in particular with the reinforcing surfaces 37a'-37e' of the element 30.

[0113] It is preferable that the reinforcing surfaces of the element 30 abuts against on a substantial part of the upper surface of the substrate 10a, approximately between 25% and 40% ± 10% of this surface, in particular between 30% and 35% ± 10% of this surface, in order to increase the reinforcing effect. For example, in various embodiments, the area of the upper surface of substrate 10a is about 196 mm2± 10% (that is, the sensitive element 10 has a substantially square profile with sides of about 14 mm), and the bearing area between surfaces 37a' -37e', 36" and 137a'-l 37e', 136' is about 70 mm2± 10%.

[0114] Preferably, therefore, the reinforcing element 30 comprises a bearing area 36, 37a'-37e' which is between 25% and 40% ± 10% of the upper surface of the substrate 10a, in particular between 30% and 35% ± 10% of said surface, and the sensitive element 10 comprises a bearing area 136', 137a'-l 37e' which is between 25% and 40% ± 10% of the upper surface of substrate 10a, in particular between 30% and 35% ± 10% of said area. Advantageously, the sensitive element 10 or its substrate 10a comprises a plurality of zones or rest areas 136', 137a'-137e', which may be distinct from each other or interconnected, for example to form an open profile or a closed profile, possibly to form a substantially annular resting zone.

[0115] Figure 12 also shows that, at the corner areas of the above-mentioned upper face of the substrate 10a, there are the contact pads 18, which to which the seats 32 for the contact springs 50 are designed to face.

[0116] Figures 13-16 show, at different angles, the overlapping condition between the pressure-sensitive elementlO and the reinforcing element 30, with the various parts and surfaces resting on each other.

[0117] In various preferential embodiments, the reinforcing element 30 is configured as a separate part from the body parts 2a and 2b. In such embodiments, the element 30 may define at least one positioning part, configured to cooperate with a corresponding surface or positioning seat of at least one of the two body parts 2a and 2b, to identify a unique mounting location of the reinforcing member 30.

[0118] In the exemplified case, the element 30 defines two lateral positioning protrusions, denoted by 33a and 33b, which are preferably located on opposite parts or sides of the element 30. Referring to Figures 17 and 19, the protrusion 33a is designed to be coupled to a corresponding positioning seat 63a defined in one of the walls of the body part 2a that delimit the corresponding chamber part 60 (here the seat 63a is defined between the two wall portions designated by 62b and 62c); the protrusion 33b is instead designed to abuts against a positioning surface 63b, also defined in one of the walls of the body part 2a that delimit the corresponding chamber part 60 (here the surface 63b is contiguous to the wall portion designated by 62g).

[0119] In embodiments in which the element 30 is configured as a distinct part with respect to the body parts 2a and 2b, the element 30 can define a protruding part, preferably aimed at facilitating the orientation of the element itself during its automatic handling or manipulation during production, and / or suitable for protecting at least part of the electrical connections of the temperature sensor.

[0120] In the preferential case exemplified, the body of the element 30 has a shaped lateral protrusion, designated by 35, that extends downward with a shape which is substantially inclined or arched or L-shaped.

[0121] In the production phase, the elements 30 are preferably moved by means of vibrating conveyors, and the lateral protrusion 35 can be used in this phase to orient the pieces, in view of the subsequent assembly phase. The possible presence of the protrusion 35 is also advantageous for the assembly of device 1, as it creates a protective element, preferably superimposed on the bent area of the conductors 41 of the temperature-sensitive element 40, to protect this bent area, for example during the handling or manipulation of semi-finished products during production.

[0122] The assembly of the device can, for example, be carried out through the following phases, although different phases or sequences are not excluded; assembly is preferably carried out by means of automatic handling, even though a manual handling is not excluded.

[0123] After obtaining the body part 2a, preferably made by injection moulding of plastic material (preferably an overmoulding on the portions 7a', 7b', 7c', 7d' of the electrical terminals of the connector 7), the seal 20 is mounted inside the seat 61 provided on the bottom 60a of the chamber part 60, as schematized in Figure 17. The seal 20 can have peripheral reliefs or bosses, indicated by 20a, for example useful for centering purposes and / or to create an elastic interference in seat 61 and keep the seal in position during handling or manipulation in the assembly phases.

[0124] The seal 20 can also include a plurality of annular reliefs 12b at its two opposite major faces - in particular annular reliefs of reduced width, concentric to each other and oriented axially - which can allow a sealed assembly through a lower axial compression force, while guaranteeing a radial seal even in case of high pressure peaks.

[0125] On the assembly obtained in this manner, as schematized in Figure 18, the pressure-sensitive element 10 is mounted, previously obtained separately as a semi-finished product, preferably already equipped with the corresponding circuit arrangement 15 and the temperature-sensitive element 40 connected thereto. For this purpose, the conductors 41 of the sensitive element 40 are electrically connected (for example soldered) to the aforementioned contacts M; angled bending of the conductors 41 can be done before or after connection to the contacts M.

[0126] The assembly thus formed is mounted on the body part 2a, with the sensitive element 10 being inserted into the chamber part 60, so that the sensing element 40 and the corresponding part of the conductors 41 are also inserted into the passage 6a, until the sensitive element 40 reaches the corresponding housing 6. In this phase, the lower surface of diaphragm 10b rests on the seal 20, with the area corresponding to the detection circuit W facing the central passage of the same seal 20.

[0127] The reinforcing element 30 is then mounted on the body part 2a, as shown in Figure 19, so that the coupling portions 31 engage in their respective seats 64. The correct orientation of the element 30 with respect to the body part 2a is ensured by the positioning means represented by the projecting parts 33a and 33b, which cooperate with the positioning seats 63a and the positioning surface 63b, respectively. The substantially vertical part of the protrusion 35 results in being inserted in the passage 6a, above the bent part of the conductors 41, which can further contribute to positioning and / or protection.

[0128] Following this phase, the reinforcing surfaces 37a' -37e' of the reinforcing element 30 directly rest on the corresponding peripheral zones 137a'-137e' of the upper face of substrate 10a (Figure 12), and with also the intermediate reinforcing surface 36' of portion 36 abutting directly on the corresponding zone designated by 136' in Figure 12. As a result of this positioning, the seats 32 of the reinforcing element 30 are each located at a respective contact pad 18 (Figure 9) of the circuit arrangement 15, present on the upper face of substrate 10a. At this point, therefore, as schematized in Figure 20, the respective contact springs 50 are inserted into the seats 32.

[0129] In possible embodiments, the seats 32 could be configured to hold the contact springs 50 in place in the reinforcing element 30, for example in order to enable a preliminary assembly of the springs themselves in the element 30, and the subsequent automatic handling or manipulation of this assembly, during subsequent production phases of the sensor device 1. The reciprocal fixing or coupling between the seats 32 and the contact springs 50 could be obtained by mutual interference, for example by using springs 50 which provide at least a portion with a diameter slightly greater than the diameter of the seats 32, or by coupling, for example by providing reliefs within the seats 32 that couple with gaps between the coils of the springs 50.

[0130] In possible embodiments, the springs 50 could be made of an electrically conductive elastic polymer or elastomer, such as a polymer filled with an electrically conductive material, for example in the form of a powder or fibers of an electrically conductive material, such as carbon or a metal. Such electrically conductive polymer springs could be moulded separately and then assembled in the seats 32 in the reinforcing element 30, or they could be moulded in the seats 32, or co-moulded or overmoulded to the reinforcing element 30.

[0131] In possible embodiments, the springs 50 could be soldered or fixed to the tracks 17 or the pads 18 of the sensitive element 10, with subsequent assembly of the reinforcing element 30 such that the springs themselves are inserted into the seats 32.

[0132] Similarly, as an alternative, the springs 50 could be previously soldered to the shaped contact portions 7a' -7d' of the terminals 7, which are exposed inside the housing chamber C.

[0133] As already mentioned, instead of helical springs, elastic electrical contact elements of different shapes and types could be provided, such as shaped clips sheared from metal foil, for example bent substantially in the shape of an S or C. Elastic electrical contact elements of this different type could possibly be obtained by directly shaping the shaped contact portions 7a'-7d' of the terminals 7a-7d that are exposed inside the housing C.

[0134] As can be seen from the above, the reinforcing element and the sensing element are superimposed to each other in the absence of a reciprocal constraint, that is, the reinforcing surface or surfaces of the reinforcing element rests / rest directly on the sensitive element in the absence of an intermediate fixing material. However, in possible variants, the reinforcing element 30 could possibly be fixed to the sensing element 10, for example in order to protect it and / or obtain a preassembly that is easier to handle or manipulated during the production cycle; in the event that the fixing is made with an additional material, it is preferable to use a rigid fastening material, or substantially incompressible, or of reduced thickness, and more generally such as not to be subject to yielding or elastic deformations that could affect the function of the reinforcing element (i.e., to counteract any deformation of the sensitive element).

[0135] Finally, as schematized in Figure 21, the body part 2b is mounted on the body part 2a, previously obtained by plastic injection moulding, integrating the electrical terminals 7a-7d.

[0136] Following this positioning, the upper end of the springs 50 is in contact, or faces, the corresponding contact parts 7a' -7d' of the aforementioned terminals (Figure 6). The body part 2b is then placed in the final position on body part 2a, so that part 2b holds the reinforcing member 30 in place, and thus holds the pressure-sensitive member 10 towards the bottom 60a of the housing chamber, preferably until the peripheral region of the diaphragm rests on the bottom 60a, thereby determining the axial seal of the seal 20. The same movement causes the springs 50 to be in an elastically compressed condition between the contact pads 18, on one side, and the contact portions 7a' -7d' of the electrodes.

[0137] The two body parts 2a and 2b are then sealingly fixed together, for example by welding or gluing, in the condition shown, for example, in Figures 22- 23.

[0138] In the assembled condition, the body part 2b is in contact with the upper face of the reinforcing element 30, which is therefore kept in a stable position with respect to the sensitive element 10 and / or the body part 2a.

[0139] By means of the reinforcing surfaces 37a' -37e' and 36', abutting against the corresponding areas 137a'-137e' and 136' of the upper face of substrate 10b, mainly at the peripheral areas of the diaphragm 10a not subject to elastic deformation (in essence, radially outermost areas with respect to the cavity 11 or 11' of the sensing element 10 of Figures 7 or 8), the sensitive element 10 is kept in a sealed condition on the bottom 60a of the housing chamber C, reinforcing the structure of the sensitive element 10, i.e., reinforcing at least the structure of the substrate 10a, thus allowing greater resistance of said structure with respect to increases or high peaks in pressure of the fluid subject to detection present in the duct 5b. Given the functionality of the reinforcing element 30, it is preferable that no resilient or elastically deformable elements, such as elastomer elements, are interposed between the body part 2b and the same element 30.

[0140] As mentioned, in the assembled condition, the contact springs 50 ensure electrical conduction between the pads 18 of the circuit arrangement 15 and the contact parts 7a'-7d' of the connector terminals 7.

[0141] In normal operation, the fluidic connection portion 3 of the device 1 is coupled to a fluid passage, and the connector 7, i.e., its terminals 7a-7d, are electrically connected to an external system. The fluid can penetrate in the passage 5, in order to cause the elastic bending of the diaphragm 10b, the magnitude of which - representative of the pressure value - is detected by means of the circuit W (Figure 6). The temperature of the medium can also be determined by means of the possible temperature-sensitive element 40. The signals relating to pressure and possible temperature, processed through the circuit arrangement 15, can then reach the outside through the terminals of the connector 7.

[0142] In the event of an overpressure exceeding the nominal working range of the device 1, abnormal conditions might occur in a ceramic sensing element having the structure as described herein. For example, the diaphragm could flex until it comes into contact with the lower surface of the substrate, and in this case the fluid would push indirectly on the substrate itself, or the diaphragm could break, with the fluid pushing directly onto the substrate: these circumstances that can occur under high pressure conditions may determine flexures of the substrate which cause breakage thereof, or at least the formation of cracks in the substrate, with the consequent passage of the fluid towards the electrical parts of the sensor device (see Figure 25 cited below).

[0143] In both cases indicated above, the pressure of the fluid is in fact almost entirely discharged on the substrate: however, in the case of the invention, the substrate 10a cannot be lifted, thanks to the interference between the upper face of the reinforcing element 30 and the body part 2b (in particular the bottom 2b" of the chamber part 2b'). Thanks to the reinforcing surfaces 36', 37a' -37e' abutting against the corresponding areas 136', 137a'-137e' of the substrate 10a, it is possible to effectively counteract the effect of pressure, thus preventing possible breakage of the substrate itself.

[0144] The reinforcing portions 36, 37a-37e, or the reinforcing surfaces 37a'-37e', are for this purpose configured to counteract excessive or abnormal bending of the substrate 10a, that is, to avoid bending or deformation of such a magnitude as to cause irreversible damage to the sensitive element 10, in particular in a central region of the substrate 10a substantially corresponding to the flexible part FP of the diaphragm 10b, i.e. , the part thereof not affected by the annular fixing layer 10c. The presence of the aforementioned reinforcing surfaces has the effect of considerably reducing the area of the substrate subject to possible bending, with this reduced area therefore being intrinsically more robust.

[0145] For this purpose, the reinforcing surfaces 37a'-37e' are sufficiently large and / or positioned to counteract the aforementioned excessive or abnormal bending of the substrate.

[0146] It is preferable that the width in the radial direction of one or more of said surfaces is such that they overlap for a substantial part (e.g., at least half) of the width of the annular layer of the material (10c, Figure 7) used for fixing the substrate 10a and the diaphragm 10b together.

[0147] It is preferable that one or more of the reinforcing surfaces extend at least in a position substantially corresponding to a radially internal region of the layer of the fixing material, which is closer to the area FP of diaphragm 10b subject to bending in the presence of nominal fluid pressures.

[0148] The two concepts are schematically exemplified in Figure 24. Referring to the reinforcing portion indicated with 37x on the right in the figure, it can be seen that the corresponding reinforcing surface 37x' extends - with reference to the radial direction R - for almost the entire width of the fixing layer 10c, even in correspondence with a radially internal region Ri of said layer 10c.

[0149] The left part of Figure 24 also exemplifies the possible case of two distinct reinforcing portions 37y and 37 z, one in a peripheral region and the other in a radially more internal region of the reinforcing element 30.

[0150] The portions 37y and 37 z have a more reduced width with respect to the portion 37x, substantially set side-by-side in the radial direction R. As can be seen, the corresponding reinforcing surfaces 37y' and 37z' are superimposed on the whole in substantial part on the layer 10c (in the example, for more than half the width in the radial direction R of the layer 10c), and with the portion 37 z and its surface 37z' being substantially located at the radially internal region Ri of the layer 10c.

[0151] The effect of the portion indicated by 37z in Figure 24 is similar to that of the reinforcing portion previously indicated by 36: precisely by virtue of the radially more inner positioning of this portion 36, its effect helps to effectively counteract possible bending of substrate 10a, in combination with the other reinforcing portions 37a-37e. For this reason, the reinforcing element 30 could also include several portions of the type indicated by 36, depending on the design of the circuit arrangement 15.

[0152] The arrows P of Figure 24 are intended to represent the effect of a high pressure of the fluid, which in the case of the present invention does not cause bending of the substrate 10 such as to compromise its integrity.

[0153] Figure 25 shows instead schematically the already mentioned case of a traditional device with a sensitive element SE formed by a substrate S and a diaphragm M, bound by a joining material F, both obtained from relatively thin sheet material, as in the case of the present invention. The sensitive element SE is held tight on an underlying seal G by means of a traditional annular pusher T, which operates in a radially outermost area of the upper face of the substrate S of the sensitive element SE. As can be seen, in such a case, the pressure P pushes on the sensing element SE, which has a higher area subject to bending: in the case of high pressures, the ceramic of the substrate S is subject to risks of cracks C in several places.

[0154] Practical tests carried out by the Applicant, with a structure of the device 1 and reinforcing element 30 configured as described, and with a sensing element 10 of approximately 14 mm on each side (largest surface area of the substrate of approximately 196 mm2), with a thickness of the substrate 10a and of the diaphragm 10b of approximately 1 mm and approximately 0,2 mm, respectively, and with a rest area between the surfaces 37a'-37e' and 137a'-137e' of about 70 mm2, have made it possible to verify that the sensing element 10 effectively withstands pressures up to at least 80 bar.

[0155] From the description above the characteristics of the present invention are clear, as are its advantages.

[0156] The sensitive element 10 can be formed into two parts of ceramic material fixed together, using a technique that is particularly advantageous from a production and economic point of view, as explained above. The preferential polygonal profile of the sensitive elements, or the respective portions of the two sheets of ceramic material that obtains the substrate 10a and the diaphragm 10b, facilitates separation of the individual sensitive elements during the production phase, also significantly reducing the waste of ceramic material, unlike the production of circular sensitive elements sheared by the two coupled sheets, which implies greater difficulties and high scraps (scraps between the sheared circular areas). The polygonal shape of the sensitive element allows a circuit arrangement to be placed on the upper face of substrate 10a, while at the same time offering sufficiently large surfaces on which the reinforcing portions can abut against.

[0157] Despite the reduced height or thickness dimensions, the risk of breakage of the sensitive element 10 due to overpressure is virtually eliminated by the presence of the reinforcing element 30, which can itself be produced easily and cost-effectively, for example by means of common injection moulding techniques.

[0158] The invention has a preferred application for obtaining sensor devices that use absolute pressure-sensitive elements, as in the case exemplified in the figures, in which the substrate 10a is free of a through hole that connects the inside of the detection cavity 11 or 11' with the external environment, and consequently also the casing body 2 does not require one or more corresponding vent passages to have the reference ambient pressure available. In this perspective, the device according to the invention is particularly advantageous for use in combination with flammable fluids.

[0159] However, the invention could still be useful also in sensor devices whose casing body includes at least one opening to the external environment, as a reference for ambient pressure, and the sensitive element is intended for relative pressure measurements, with the substrate of the sensitive element which has a through-hole in communication with the corresponding detection cavity. Even in such cases, in fact, the strengthening of the substrate according to the invention could prevent it from bending and consequently could also avoid the rupture of the diaphragm: the absence of bending of the substrate 10a could in fact determine a correct support of the diaphragm 10b in the central region of the lower face of substrate 10a, when the diaphragm itself is at its maximum flexion.

[0160] In other words, even in the presence of excessive or abnormal fluid pressures, the flexible part FP of the diaphragm 10b can still flex only up to a predefined maximum value, making it intrinsically more robust.

[0161] It is clear that numerous changes are possible for the person skilled in the art to the device described as an example, without departing from the scope of the invention as defined by the attached claims.

[0162] In various embodiments, at least part of the upper face of the substrate 10a and / or the circuit arrangement 15 comprises a protective coating layer made of electrically insulating material. This protective layer can be advantageously capable of levelling or evening out the resting surfaces on the substrate 10a, so that they can better match with the reinforcing surfaces 36', 37a' -37e' of the lower face of the reinforcing element 30.

[0163] The concept is exemplified in Figure 26, where it can be seen the presence, on the upper face of the substrate 10a, of a pad 18 associated with a metallized hole 19 of the substrate itself. The lower end of the hole 19 is connected to an electrically conductive track 17' present on the inner face of diaphragm 10b, this track being part of the circuit W (Figure 6) for detecting diaphragm bending. As can be seen, the greater thickness of the layer of material 10c for fixing the diaphragm 10b to the substrate 10a makes it possible to compensate for the thickness of the track 17', ensuring that the non-flexible area of the diaphragm 10b (i.e., the annular area in correspondence with the layer 10c) is still substantially parallel to the lower face of the substrate 10a. A similar effect is achieved by the arrangement of the coating layer indicated by L, which makes it possible to compensate for the thickness of the pad 18, so that the upper face of the same layer L provides a flat surface against which the reinforcing surface 37' of the portion 37 of the element 30 can precisely abut.

[0164] The possible presence of such a coating layer made of electrically insulating material allows the use of a reinforcing element 30 made of electrically conductive material, such as a polymer reinforced with carbon fiber, or a metal or a metal alloy.

[0165] As previously indicated, it is preferable that the reinforcing element 30 be configured as a distinct part with respect to a corresponding part 2a, 2b of the casing body 2 (and also free of mutual constraint with respect to the sensitive element 10). In these embodiments, in fact, the body of the element 30 has small dimensions compared to said body parts, with obvious advantages in terms of moulding precision and lower shrinkage of the moulded material. However, in less advantageous embodiments, the element 30 could be formed in a single piece with a corresponding part of the casing body 2, or structurally bound to it.

[0166] Figures 27-28 show the case of a reinforcing element 30 formed in a single piece with the body part 2b, within the chamber part 2b', particularly at the bottom 2b" of the latter.

[0167] What has been described above in relation to the element 30 of Figures 1- 24 and 26 is equally valid in the case of the embodiment of Figures 27-28. In the case referred to in Figures 27-28, the element 30 could possibly be free of the coupling portions 31, and the body part 2a free of the corresponding positioning seats 64, delegating the function of a precise relative positioning of the parts to other positioning means defined between the body parts 2a and 2b. Also the lateral positioning protrusions 33a, 33b, and the corresponding seats or surfaces 63a, 63b on the body part 2a may be omitted. The same applies to the shaped lateral protrusion 35 of the previous embodiments.

[0168] In embodiments of the type shown in Figures 27-28, the material of the body part 2b may be different from that previously indicated, i.e. said body part may be made of a material having the characteristics described above for the material of the reinforcing member 30: for example, the body part 2b may be made of PPS, instead of PPA.

[0169] Furthermore, according to a variant not shown, the element 30 could be overmoulded or co-moulded to the body 2b, effectively creating a single piece but consisting of two respective materials (for example, a portion of the body corresponding to that designated by 2b in Figures 27-28 formed in PPA, and a portion of the body corresponding to that designated by 30 in Figures 27-28 formed in PPS); to this end, shapes could be envisaged that guarantee the mechanical coupling between the element 30 and the body 2b.

Claims

CLAIMS1. A pressure sensor device (1), having a casing body (2) which comprises at least one first body part (2b) and one second body part (2a) coupled to define therebetween a housing chamber (C) wherein a pressure-sensitive element (10) is housed, the first body part (2b) having an electrical connector (7) provided with terminals (7a-7d) each having a contact portion (7a1-7d') that extends within the housing chamber (C), and the second body part (2a) having at least one passage (5) for a fluid the pressure of which has to be detected, the at least one passage (5) having a first end (5b) which opens at the pressure-sensitive element (10), wherein the pressure-sensitive element (10) comprises a substrate (10a) made of ceramic material having an upper face and a lower face opposite to each other, the lower face of the substrate (10a) having a diaphragm (10b) fixed thereto, bearing at least part of a detection circuit (W), configured for detecting bending of a flexible part (FP) of the diaphragm (10b) depending on pressure of the fluid, between the lower face of the substrate (10a) and the diaphragm (10b) a cavity (11; 11') being defined, wherein the pressure-sensitive element (10) is housed in the housing chamber (C) in such a way that the diaphragm (10b) is facing the first end (5b) of the at least one passage (5), to enable the fluid to reach the diaphragm (10b), wherein, at the upper face of the substrate (10a), a circuit arrangement (15) is provided, electrically connected to the detection circuit (W), the circuit arrangement (15) comprising at least electrically conductive tracks made of an electrically conductive material (17, 18) and preferably one or more circuit components (16a-16d, M), characterized in that within the housing chamber (C) there is provided a reinforcing element (30) for reinforcing the pressure-sensitive element (10), configured for extending at least partly above the upper face of the substrate (10a) and comprising at least one reinforcing portion (37a-37e) that defines at least one reinforcing surface (37a'-37e'), the reinforcing element (30) being configured in such a way that the at least one reinforcing surface (37a'-37e') abuts against a corresponding area (137a1- 137e') of the upper face of the substrate (10a), in particular for preventing irreversible damages of the substrate (10b) in case of excessive pressure of the fluid.

2. The pressure sensor device according to claim 1, wherein thereinforcing element (30) moreover defines a plurality of first seats or passages (32) for a corresponding plurality of electrical -contact elastic elements (50), wherein preferably:- the electrical -contact elastic elements (50) are springs, and / or- the first seats or passages (32) extends in a thickness direction (T) of the reinforcing element (30), and / or- each electrical -contact elastic element (50) has respective opposite ends that extend beyond a thickness (T) of the reinforcing element (30), and / or- each electrical -contact elastic element (50) is in contact with the contact portion (7a'-7d') of a respective terminal (7a-7d) of the electrical connector (7) and / or with one said electrically conductive tracks (17, 18), and / or- each electrical-contact elastic element (50) is in a guided and / or positioned and / or fixed condition through a respective first seat or passage (32) of the reinforcing element (30), and / or- the first seats or passages (32) are through-holes.

3. The pressure sensor device according to claim 1 or claim 2, wherein the reinforcing element (30) moreover defines a plurality of coupling and / or positioning portions (31), in particular in peripheral positions of the reinforcing element (30), configured for engagement with corresponding coupling and / or positioning seats (64) defined in one of the first body part (2a) and the second body part (2b), in particular in peripheral positions of the housing chamber (C).

4. The pressure sensor device according to claim 3, wherein each of said coupling and / or positioning portions (31) is a protruding portion of the reinforcing element (30), which extends in a generally radial direction (R).

5. The pressure sensor device according to any one of claims 1-4, wherein at least some of the first seats or passages (32) each have an end that opens at one said reinforcing surface (37a'-37e').

6. The pressure sensor device according to any one of claims 1-5, wherein:- the pressure-sensitive element (10) has a substantially polygonal peripheral profile, and / or- the reinforcing element (30) has a substantially polygonal peripheral profile, and / or- the at least one reinforcing surface (37a'-37e') comprises reinforcing surfaces (37a'-37d') defined by corresponding reinforcing portions (37a-37d) that are at corner regions of the reinforcing element (30), and the at least onecorresponding area (137a'-137e') comprises peripheral areas (137a'-137d') defined at corner regions of the upper face of the substrate (10a), and / or- the pressure-sensitive element (10) and the reinforcing element (30) each have a substantially quadrangular peripheral profile.

7. The pressure sensor device according to claim 1, wherein- at least two reinforcing surfaces (37c1, 37d'), preferably reinforcing surfaces (37a'-37d') defined by reinforcing portions (37a'-37d') which are at corner regions of the reinforcing element (30), are joined to each other by an intermediate reinforcing portion (37e'), and / or- at least two reinforcing portions (37b, 37c) are joined to each other by at least one connection portion (39) of the reinforcing element (30), the at least one connection portion (39) having a lower height than the two reinforcing portions (37b, 37c).

8. The pressure sensor device according to claim 4, wherein the plurality of coupling and / or positioning portions (31) comprises shaped portion of the reinforcing element (30) that protrudes starting from corner regions of the reinforcing element (30).

9. The pressure sensor device according to any one of claims 1-8, wherein the reinforcing element (30) has at least one from among:- a reduction of thickness (38a, 38b, 38c) separating from one another two said reinforcing portions (37a-37c) or two said reinforcing surfaces (37a'-37d');- a through-opening (34) in a substantially central position;- a plurality of reinforcing portions (36, 37a-37d) that define corresponding reinforcing surfaces for local reinforcing (36', 37a'-37d'), each designed to abuts against a corresponding localized area (136', 137a'-l 37e') of the upper face of the substrate (10a);- one or more first reinforcing portions (36) or first reinforcing surfaces (36’) in a position substantially closer, in a radial direction (R), to a centre of the reinforcing element (30), with respect to one or more second reinforcing portions (37a-37e);- at least one through-opening (34) or a recess (38a-38c) at a lower face of the reinforcing element (30), within which there extends at least part of a circuit component (16a-16d, M) of the circuit arrangement (15);- at least two reinforcing portions (37a, 37b; 37a, 37d) between which a circuit component (16a; 16b) of the circuit arrangement (15) is at least partiallylocated;- at least one reinforcing portion (36) which is at least partly located between two circuit components (16b, 16d) of the circuit arrangement (15).

10. The pressure sensor device according to any one of claims 1-9, wherein the reinforcing element (30) is configured as a distinct part with respect to the first body part (2b) and the second body part (2a), and preferably defines at least one lateral protrusion (33a, 33b) configured for cooperating with a corresponding positioning surface or seat (63a, 63b) of one of the first body part (2b) and the second body part (2a), preferably to identify a unique mounting position of the reinforcing element (30).

11. The pressure sensor device according to any one of claims 1-10, wherein:- the pressure sensor device (1) also comprises a temperature-sensitive element (40), preferably comprising respective connection conductors (40a) connected to the circuit arrangement (15) on the upper face of the substrate (10a), and / or- the first body part (2b) has a further passage (6a) wherein a temperaturesensitive element (40) is housed and wherein there extends a corresponding part of connection conductors (41) of the temperature-sensitive element (40), the temperature-sensitive element (40) and the further passage (6a) being in particular in a lower position with respect to the pressure-sensitive element (10).

12. The pressure sensor device according to claim 11, wherein the temperature-sensitive element (40) has first connection conductors (41) associated thereto, having preferably an angle-bent portion, and the reinforcing element (30) defines a lateral projection (35) that extends above to at least a part of the first connection conductors (41), preferably above the corresponding angle-bent portion.

13. The pressure sensor device according to claim 3, wherein the coupling and / or positioning seats (64) are defined between adjoining walls or wall portions (62a-62h) of the one of the first body part (2b) and the second body part (2a).

14. The pressure sensor device according to claim 1, wherein in a bottom (60a) of the housing portion (C) a sealing seat (61) is defined for an annular seal (20) designed to sealingly operate with respect to the pressure-sensitive element (10), wherein the first end (5b) of the at least one passage (5) for the fluid opens at a bottom of the sealing seat (61), in a region circumscribed by the annular seal(20).

15. A pressure sensor device (1), having a casing body (2) which comprises at least one first body part (2b) and one second body part (2a) coupled to define therebetween a housing chamber (C) within which a pressure-sensitive element (10) is housed (10), the casing body (2) having an electrical connector (7) and a passage (5) for a fluid the pressure of which has to be detected, wherein the pressure-sensitive element (10) comprises a substrate (10a), preferably provided with a circuit arrangement (15) and / or at least one circuit component (16) and or tracks made of an electrically conductive material (17, 18), a flexible diaphragm (10b) being fixed to the substrate (10), bearing at least part of a detection circuit (W), characterized in that in the housing chamber (C) a reinforcing element (30) for reinforcing the pressure-sensitive element (10) is provided.

16. A pressure-sensitive element (10), configured for mounting in a casing body (2) of a pressure sensor device (1) which comprises at least one first body part (2b) and one second body part (2a), coupled to define therebetween a housing chamber (C), wherein the pressure-sensitive element (10) comprises a substrate (10a), preferably provided with a circuit arrangement (15) and / or at least one circuit component (16) and or tracks made of an electrically conductive material (17, 18), a flexible diaphragm (10b) being fixed to the substrate (10), bearing at least part of a detection circuit (W), characterized in that the substrate (10a) is prearranged to define, on an upper face thereof opposite to the diaphragm (10b), one or more areas (136’, 137a'-137e') configured for coupling with a reinforcing element (30) for reinforcing the pressure-sensitive element (10).

17. A reinforcing element (30), for mounting within a casing body (2) of a pressure sensor device (1) which comprises at least one first body part (2b) and one second body part (2a), coupled to define therebetween a housing chamber (C) within which a pressure-sensitive element (10) is arranged, characterized in that the reinforcing element (30) is prearranged for strengthening the pressuresensitive element (10).

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