Pressure Sensor

Abstract

To provide a pressure sensor that is provided, in a liquid seal chamber, with a shield member to cut off an undesired electric field for a signal processing electronic circuit unit of a sensor chip, and can further reduce the capacity of silicone oil filled into the liquid seal chamber.SOLUTION: A liquid-seal type pressure sensor comprises a pressure detection element, a liquid seal chamber, a diaphragm, a plurality of terminals electrically connected to the pressure detection element, and a stationary member for terminals that holds the plurality of terminals, and the liquid seal chamber is formed of the stationary member for terminals and the diaphragm. The pressure sensor further comprises an electric field cut-off member that is arranged between one end face of the pressure detection element and the diaphragm inside the liquid seal chamber and cuts off an electric field acting on the pressure detection element, and a spacer member that is arranged inside the liquid seal chamber. The plurality of terminals each have a projection that projects between opposite faces of the stationary member for terminals and the electric field cut-off member. The spacer member is arranged between the opposite faces of the stationary member for terminals and the electric field cut-off member in the liquid seal chamber.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a pressure sensor. [Background technology]

[0002] As shown in Patent Document 1, for example, the sensor unit built into a liquid-sealed semiconductor pressure sensor is composed of the following main elements: a metal diaphragm that separates the pressure chamber communicating with the port of the coupling member from a liquid-sealed chamber described below; a liquid-sealed chamber formed above the metal diaphragm on the inner periphery of the cylindrical housing and storing silicone oil as a pressure transmission medium; a sensor chip that is disposed within the liquid-sealed chamber and detects pressure fluctuations in the silicone oil via the metal diaphragm; a sensor chip mounting member that supports the sensor chip; hermetic glass that seals the periphery of the sensor chip mounting member on the inner periphery of the housing; and a group of input / output terminals that are fixed by the hermetic glass and that send output signals from the sensor chip and supply power to the sensor chip.

[0003] In addition to the above-described configuration, as shown in FIG. 1 of Patent Document 1, a shielding member is provided within the liquid-sealed chamber to block undesired electric fields from affecting the signal processing electronic circuitry of the sensor chip. A predetermined gap is formed between the gate-shaped cross-section of the shielding member, which covers the entire sensor chip, and the end face of the sensor chip. Two fixed ends of the gate-shaped cross-section of the shielding member are joined to one end face of a disc-shaped conductive plate in close proximity to the outer periphery of the sensor chip, thereby providing electrical continuity. The potential of the shielding member and the conductive plate is the same as that of the electronic circuitry mounted on the sensor chip.

[0004] In this configuration, the shield member with a gate-shaped cross section covers the entire sensor chip, resulting in a relatively large volume within the liquid-sealed chamber, and therefore the volume of silicone oil that can be filled into the liquid-sealed chamber. In such cases, there is a risk of changes in the output characteristics of the pressure sensor due to changes in the metal diaphragm caused by expansion and contraction of the silicone oil due to changes in ambient temperature. Therefore, as shown in Patent Document 2, for example, an annular member bonded to the conductive plate is provided within the liquid-sealed chamber to reduce the volume of silicone oil filled into the liquid-sealed chamber, thereby suppressing changes in the output characteristics of the pressure sensor due to changes in the metal diaphragm caused by expansion and contraction of the silicone oil due to changes in ambient temperature. In other words, the volume of silicone oil filled into the liquid-sealed chamber is smaller than the total internal volume of the liquid-sealed chamber formed by the shield member and the annular member and the inner periphery of the housing where the annular member is not located. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-100807 [Patent Document 2] Japanese Patent Application Publication No. 2019-100808 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-194401 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to further suppress changes in the output characteristics of the pressure sensor due to changes in ambient temperature, it is desired to further reduce the volume of silicone oil filled in the liquid-sealed chamber.

[0007] However, as shown in Patent Document 1, in a configuration in which the fixed end of the shielding member placed inside the liquid-sealed chamber is fixed to the end surface of a conductive plate supported on one end surface of the hermetic glass, the structure in which the shielding member covers the entire sensor chip from above the bonding wires requires the liquid-sealed chamber to be deep, which tends to increase the spatial volume inside the liquid-sealed chamber.Furthermore, the structures shown in Patent Documents 1 and 2 require a conductive plate to fix the shielding member, and furthermore, the liquid-sealed chamber needs to be deep, so there is a limit to how much the internal dimension of the liquid-sealed chamber along the axial direction of the input / output terminals can be further reduced while maintaining a predetermined gap between the metal diaphragm and the shielding member.

[0008] In consideration of the above problems, the present invention aims to provide a pressure sensor in which a shielding member is provided inside the liquid-sealed chamber to block undesired electric fields from being transmitted to the signal processing electronic circuit section of the sensor chip, and which can further reduce the volume of silicone oil filled inside the liquid-sealed chamber. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the pressure sensor of the present invention comprises a pressure detection element that detects pressure and sends a detection output signal, a liquid-sealed chamber in which the pressure detection element is disposed and a pressure transmission medium is sealed, a diaphragm that separates a pressure chamber facing the liquid-sealed chamber, a plurality of terminals electrically connected to the pressure detection element, and a terminal fixing member that holds the plurality of terminals, wherein the liquid-sealed chamber is a liquid-sealed pressure sensor constituted by the terminal fixing member and the diaphragm, and further comprises an electric field blocking member that is disposed between one end face of the pressure detection element in the liquid-sealed chamber and the diaphragm and blocks the electric field acting on the pressure detection element, and a spacer member that is disposed in the liquid-sealed chamber, wherein the plurality of terminals have protrusions that protrude between opposing surfaces of the terminal fixing member and the electric field blocking member, and the spacer member is disposed in the liquid-sealed chamber between the opposing surfaces of the terminal fixing member and the electric field blocking member.

[0010] In the pressure sensor according to the present invention, the spacer member is disposed farther away from the pressure detection element than the protruding portions of the plurality of terminals.

[0011] In addition, the pressure sensor according to the present invention is characterized in that the electric field blocking member is fixed to any one of the plurality of terminals.

[0012] The pressure sensor according to the present invention is characterized in that one end surface of the spacer member supports the electric field blocking member. [Effects of the Invention]

[0013] According to the pressure sensor of the present invention, at least one end of the electric field blocking member along the arrangement direction of the connection ends of the wiring members connected to the sensor chip in the shielding portion of the electric field blocking member is positioned closer to the center of the sensor chip than the position directly above the connection ends of the wiring members, so that the electric field blocking member is provided as a shield member within the liquid-sealed chamber to block undesired electric fields from the signal processing electronic circuit of the sensor chip, and the volume of silicone oil filled within the liquid-sealed chamber can be further reduced. As a result, the actual filling volume of silicone oil, i.e., the amount of pressure transmission medium such as silicone oil, can be reduced, so changes in the output characteristics of the pressure sensor caused by changes in the displacement of the metal diaphragm due to expansion and contraction of silicone oil caused by changes in ambient temperature can be suppressed, and the temperature characteristics of the pressure sensor output can be improved. [Brief explanation of the drawings]

[0014] [Figure 1] 1A is a partial cross-sectional view showing the main parts of a sensor unit used in an example of a pressure sensor according to the present invention together with a joint member, and FIG. 1B is an arrow view of an electric field shielding member disposed in a liquid-sealed chamber as seen from the direction indicated by arrow IB in FIG. 1A. [Figure 2] 1(B) is a cross-sectional view showing another example of a diaphragm used in the sensor unit shown in FIG. 1(A) together with a main part of the sensor unit. FIG. [Figure 3] 1(A) and 1(B) are cross-sectional views showing still another example of a diaphragm used in the sensor unit shown in FIG. 1(A), together with the main part of the sensor unit. [Figure 4] 10(A), 10(B), and 10(C) show examples of the chip mounting portion of the sensor chip / terminal fixing member. [Figure 5] 5(A) is a cross-sectional view showing a main part of a sensor unit used in another example of a pressure sensor according to the present invention, and FIG. 5(B) is an arrow view of an electric field shielding member disposed in a liquid-sealed chamber as seen from the direction indicated by arrow VB in FIG. 5(A). [Figure 6] 6(A) is a cross-sectional view showing a main part of a sensor unit used in yet another example of a pressure sensor according to the present invention, and FIG. 6(B) is an arrow view of an electric field shielding member arranged in a liquid-sealed chamber as seen from the direction indicated by arrow VIB in FIG. 6(A). DETAILED DESCRIPTION OF THE INVENTION

[0015] 1(A) and (B) show the main part of a sensor unit used in an example of a pressure sensor according to the present invention.

[0016] The pressure sensor, as shown in Patent Document 1, for example, is configured to include a coupling member 2 connected to a pipe through which a fluid whose pressure is to be detected is guided, and a sensor unit accommodating section that is connected to a base plate 4 of the coupling member 2 by brazing or the like, accommodates a sensor unit described below, and supplies a detection output signal from the sensor chip to a predetermined pressure measuring device.

[0017] 1(A), the metal coupling member 2 has an internal female thread 2fs that screws into the male thread of the connecting portion of the piping. The female thread 2fs is connected to a port 2a of the coupling member 2 that guides fluid supplied from the direction indicated by arrow P to a pressure chamber 4A (described later). One open end of the port 2a opens toward the pressure chamber 4A formed between the base plate 4 of the coupling member 2 and the diaphragm 32 of the sensor unit.

[0018] The outer shell of the sensor unit accommodating section is formed by a cylindrical waterproof case 6 that serves as a cover member. An opening is formed at the bottom end of the resin waterproof case 6. The peripheral edge of the base plate 4 of the joint member 2 engages with a stepped portion 6S on the inner periphery of the opening. Fluid pressure is introduced into the pressure chamber 4A through the port 2a of the joint member 2. The lower end surface of the sensor unit housing 12 is connected to the peripheral edge of the base plate 4 by welding.

[0019] As shown in Figure 1(A), the sensor unit detects the pressure in a pressure chamber 4A formed between the base plate 4 and a diaphragm 32 described later and sends out a detection output signal.The sensor unit is composed of the following main elements: a cylindrical metal housing 12, a metal diaphragm 32 that isolates the pressure chamber 4A from the inner periphery of the housing 12, a sensor chip 16 having multiple pressure detection elements and a signal processing electronic circuit that processes signals from the pressure detection elements, and a sensor chip / terminal fixing member 14 that supports the sensor chip 16 via an adhesive layer 50 within a recessed chip installation portion 14G and fixes a group of input / output terminals 40ai (i = 1 to 8) electrically connected to the sensor chip 16, and an oil filling pipe 44 (see Figure 1(B)) to the inner periphery of the housing 12.

[0020] The diaphragm 32 is supported on one lower end surface of the housing 12 facing the pressure chamber 4A. A diaphragm protective cover 34, which protects the diaphragm 32 disposed in the pressure chamber 4A, has a plurality of communication holes. The periphery of the diaphragm protective cover 34, together with the periphery of the diaphragm 32, is joined to the lower end surface of the housing 12 by welding. The housing 12, diaphragm 32, base plate 4, and coupling member 2 are connected and conductive, and therefore have the same potential. The input / output terminal group 40ai is held insulated from the housing 12 via a sensor chip / terminal fixing member 14 (insulator). The sensor chip / terminal fixing member 14 is formed of, for example, a resin material such as PPS or POE, hermetic glass, or ceramic.

[0021] The liquid-sealed chamber 13 formed between the metal diaphragm 32 and the opposing end faces of the sensor chip 16 and sensor chip / terminal fixing member 14 is filled with a pressure transmission medium PM, such as a predetermined amount of silicone oil or a fluorine-based inert liquid, via an oil filling pipe 44. After filling with oil, one end of the oil filling pipe 44 is crushed and closed.

[0022] The input / output terminal group 40ai (i = 1 to 8) is composed of two power supply terminals (one of which is a GND terminal: a terminal of zero (V)), one output terminal, and five adjustment terminals. Both ends of each terminal protrude from one end face of the sensor chip / terminal fixing member 14 described above toward the liquid-sealed chamber 13 along the central axis of the sensor chip / terminal fixing member 14, or protrude outward from the other end face of the sensor chip / terminal fixing member 14. Note that only four of the eight terminals are shown in FIG. 1(A). The input / output terminal group 40ai and the sensor chip 16, which will be described later, are connected by bonding wires Wi as wiring materials.

[0023] The sensor chip 16 has a plurality of pressure detection elements forming a bridge circuit on top of a silicon diaphragm portion, and is configured to include, for example, a semiconductor strain gauge portion formed of silicon in a substantially rectangular shape, and an electronic circuit portion formed around the pressure detection elements on the upper end surface of the semiconductor strain gauge portion and integrating an amplifier circuit for processing the output signal of the bridge circuit, a linear correction circuit, a temperature correction circuit, and a correction data holding circuit. Note that the semiconductor strain gauge portion and the electronic circuit portion may each be independent elements.

[0024] As shown in a partially enlarged view in FIG. 4(C), the sensor chip 16 is bonded, for example, via an adhesive layer 50, to the bottom of a chip mounting portion 14G in the sensor chip / terminal fixing member 14, which is located inside the liquid-sealed chamber 13. One end face of the sensor chip 16 protrudes from the chip mounting portion 14G toward the liquid-sealed chamber 13 beyond the end face of the sensor chip / terminal fixing member 14. The depth of the chip mounting portion 14G is set to, for example, approximately 0.3 mm. One end of the input / output terminal group 40ai, connected by bonding wires Wi, protrudes by, for example, approximately 0.2 mm. This positions the one end face of the input / output terminal group 40ai closer to the end face of the sensor chip / terminal fixing member 14 than the end face of the sensor chip 16.

[0025] 1(B), a shield member 20 serving as an electric field blocking member is provided between one end face of the sensor chip 16 and the diaphragm 32 within the liquid-sealed chamber 13. The shield member 20 blocks undesirable electric fields from being applied to the signal processing electronic circuit section of the sensor chip 16. The shield member 20 is made in a strip shape from a conductive metal material such as stainless steel, copper, or aluminum.

[0026] As shown in FIG. 1B, the strip-shaped shielding member 20 is composed of a shielding portion 20A located directly above the signal processing electronic circuit of the sensor chip 16, a fixed end portion 20B connected to one end of the shielding portion 20A, and a fixed end portion 20C connected to the other end of the shielding portion 20A. The width of the shielding portion 20A is set to be slightly smaller than one side of the sensor chip 16. As shown in a partially enlarged view in FIG. 4C, the shielding portion 20A is disposed between the ends of the bonding wires Wi connected to the sensor chip 16 that face each other in the width direction of the shielding portion 20A, and is located close to the surface of the sensor chip 16 with a predetermined gap therebetween. This predetermined gap is set to, for example, at least about 0.1 mm to prevent contact between the bonding wires Wi in the pressure transmission medium PM, the sensor chip 16, and the shielding portion 20A.

[0027] Regarding the relative positional relationship between the shield member 20, the input / output terminal group 40ai, and the sensor chip 16 relative to the sensor chip / terminal fixing member 14, the position of the surface of the sensor chip 16 facing the shielding portion 20A of the shield member 20 is closer to the shielding portion 20A than the position of the end face of the input / output terminal group 40ai protruding parallel to the central axis of the sensor chip 16 from the end face of the sensor chip / terminal supporting member 14.

[0028] As in Patent Document 1, conventionally, the shielding member covers the sensor chip 16 by straddling the bonding wires Wi so as not to interfere with the bonding wires Wi that are wired from the periphery of the sensor chip 16 to the sensor chip 16. In contrast, in the present structure, the shielding portion 20A of the shielding member 20 is positioned closer to the center of the sensor chip 16 than the apex Wit of the curved portion of the bonding wire Wi, as shown enlarged in Fig. 4(C), i.e., at a position that covers the sensor chip 16 corresponding to the inside of the curved portion of the opposing bonding wire Wi. The position of the widthwise end of the shielding portion 20A of the shielding member 20 is more preferably positioned closer to the center of the sensor chip 16 than the apex Wit of the curved portion of the bonding wire Wi, and close to the connection end Wie of the curved portion of the bonding wire Wi.

[0029] As a result, the shielding portion 20A is disposed at a position closer to the surface of the sensor chip 16 than the position of the apex Wit of the curved portion of the bonding wire Wi.

[0030] In addition, when the bonding wire Wi is wired on the surface of the sensor chip 16 in a gate-shaped state, the position of the end of the shielding portion 20A may be positioned closer to the connection end, which is spaced closer to the center of the sensor chip 16, than the apex located directly above the connection end of the bonding wire Wi.

[0031] An oil filling pipe 44 is inserted into a hole formed in the fixed end 20B. The fixed end 20C is soldered to one end of a conductor pattern 22 (described later) formed on the end surface of the sensor chip / terminal fixing member 14 so as to be positioned between two adjacent terminals of the input / output terminal group 40ai. The fixed end 20B is soldered to the other end of the conductor pattern 22. As shown in FIG. 1B , the conductor pattern 22, having a predetermined thickness, is formed by, for example, plating or metallizing, between the arrangement of one end of the input / output terminal group 40ai along the circumferential direction of the sensor chip / terminal fixing member 14 and the inner circumferential surface 12a of the housing 12, following the arrangement of one end of the input / output terminal group 40ai. The conductor pattern 22 is electrically connected to one of the input / output terminals 40ai, for example, via a bonding wire Wib connected to a GND terminal (zero (V) terminal). The GND terminal is connected to the sensor chip 16 via a bonding wire Wia. As a result, the shield member 20 has the same potential as the signal processing electronic circuit mounted on the sensor chip 16. Therefore, by disposing the shield member 20, which has the same potential as the sensor chip 16, between the diaphragm 32 and the signal processing electronic circuit of the sensor chip 16, the shield member 20 blocks the electric field acting on the sensor chip 16 due to the potential difference between the diaphragm 32, which has the same potential as the primary power supply (not shown) of the unit, and the control circuit (not shown). Furthermore, since the potentials of the shield member 20 and the sensor chip 16 are the same, no electric field is generated between them. Therefore, the potential difference between the sensor chip 16 and the diaphragm 32 does not act on the sensor chip 16, preventing any influence on the signal processing electronic circuit in the sensor chip 16. Furthermore, there is no conductive plate disposed within the liquid-sealed chamber 13 as shown in Patent Documents 1 and 2. Furthermore, the shielding portion 20A of the shield member 20 is positioned closer to the surface of the sensor chip 16 than the curved portion of the bonding wire Wi.As a result, the diaphragm 32 can be brought even closer to the sensor chip 16 arranged in the recessed chip installation portion 14G, and the depth along the central axis of the sensor chip / terminal fixing member 14 in the liquid-sealed chamber 13 formed in the inner periphery of the housing 12 can be made shallower. This makes it possible to reduce the amount of pressure transmission medium PM filled in the liquid-sealed chamber 13, thereby improving the temperature characteristics of the pressure sensor output. Note that the same effect can be obtained by simply covering at least the semiconductor strain gauge portion of the sensor chip 16 with the shield member 20 (shielding portion 20A).

[0032] In the above example, one end face of the sensor chip 16 protrudes from the chip mounting portion 14G toward the liquid-sealed chamber 13 beyond the end face of the sensor chip / terminal fixing member 14, but this is not limited to such an example. For example, as shown in FIG. 4(B), the depth of the chip mounting portion 24G of the sensor chip / terminal fixing member 24 may be set so that one end face of the sensor chip 16 is flush with the end face of the sensor chip / terminal fixing member 24. The fixed end of the shield member 20 is connected to the conductor pattern COL formed around the chip mounting portion 24G. This allows the depth of the sensor chip / terminal fixing member 24 along the central axis in the liquid-sealed chamber 13 formed on the inner periphery of the housing 12 to be made shallower.

[0033] 4(A), the depth of chip mounting portion 43G of sensor chip / terminal fixing member 43 may be set so that one end face of sensor chip 16 is positioned lower than the end face of sensor chip / terminal fixing member 43, and the entire sensor chip 16 is buried in the chip mounting portion. In FIG. 4(A), each fixed end (not shown) of shielding member 20 is connected to a conductor pattern COL formed around chip mounting portion 43G of sensor chip / terminal fixing member 43. In other words, each fixed end of shielding member 20 is formed on the same plane as shielding portion 20A.

[0034] This allows the depth along the central axis of the sensor chip / terminal fixing member 14 in the liquid-sealed chamber 13 formed on the inner periphery of the housing 12 to be made shallower, and the shielding portion and the fixing end of the shield member can be formed on a common plane, simplifying the configuration of the shield member 20. Note that in Figures 4(A) and (B), the same components as those in the example shown in Figure 4(C) are denoted by the same reference numerals, and redundant explanations will be omitted.

[0035] In the example shown in Figures 4(A), (B), and (C), the input / output terminal group 40ai is arranged at predetermined intervals along the circumferential direction of the entire periphery of the sensor chip 16, and is electrically connected by each bonding wire Wi to bonding pads formed in plurality at each end of the sensor chip 16.

[0036] Without being limited to such an example, for example, when the input / output terminal group is arranged only around one end of the sensor chip 16, that is, for example, when it is arranged within a range of 180° around the sensor chip 16, the input / output terminal group may be electrically connected to bonding pads formed in plurality only at one end of the sensor chip 16 by each bonding wire Wi.

[0037] In such a case, as a first variant, for example, the shielding portion of the cantilevered shielding member has one end fixed to the sensor chip / terminal fixing member, and the other end facing each bonding pad of the sensor chip 16 may be positioned as close as possible to the connection end of each bonding wire Wi connected to each bonding pad of the sensor chip 16 without contacting each bonding pad.

[0038] Furthermore, as a second modified example, each fixing end portion may be fixed to, for example, a sensor chip / terminal fixing member, at each of the short sides formed integrally with the shielding portion of the shielding member, which is perpendicular to the long side of the shielding portion that is aligned in the arrangement direction of the bonding pads of the sensor chip 16. In such a case, the position of the end portion of the long side of the shielding portion of the shielding member that faces each bonding pad of the sensor chip 16 in the shielding portion of the shielding member may be set as close as possible to the connection end of each bonding wire Wi that is connected to each bonding pad of the sensor chip 16, without coming into contact with each bonding pad.

[0039] In the example shown in FIG. 1(A), the gently undulating concentric recesses and projections in the cross section of the diaphragm 32 are formed relatively small, but this is not limited to such an example. For example, as shown in FIG. 2, relatively large recesses and projections may be formed concentrically around a flat portion of the cross section of the diaphragm 42 that faces the shielding portion 20A of the shield member 20 and protrude toward the liquid-sealed chamber 13. That is, the recesses and projections of the diaphragm 42 protrude more toward the liquid-sealed chamber 13 than toward the pressure chamber 4A from an imaginary plane defined by the outer periphery of the diaphragm 42. Desirably, the recesses and projections are formed to protrude toward the liquid-sealed chamber 13 but not toward the pressure chamber 4A. The recesses and projections of the diaphragm 42 are shaped so that when they protrude toward the liquid-sealed chamber 13, they do not interfere with the components inside the liquid-sealed chamber 13 (sensor chip, bonding wires, input / output terminal group, shield member, etc.).

[0040] As a result, the volume of the pressure transmission medium PM filled in the liquid-sealed chamber 13 is further reduced compared to the volume of the pressure transmission medium PM filled in the liquid-sealed chamber 13 in the example shown in Fig. 1(A). In Fig. 2, the same components as those in the example shown in Fig. 1(A) are denoted by the same reference numerals, and redundant explanations will be omitted.

[0041] 3(A), the position of the outer peripheral edge of the diaphragm 52 bonded to the housing 12 may be set at a position closer to the end face of the sensor chip / terminal fixing member 14 in the liquid-sealed chamber 13 than the position of the flat portion facing the shielding portion 20A of the shielding member 20 in the cross section of the diaphragm 52. Furthermore, for example, as shown in FIG. 3(B), the outer peripheral edge of the diaphragm 53 bonded to the housing 12 may be formed so as to be connected to the flat portion 53B by a conical surface 53F continuing to the flat portion 53B facing the shielding portion 20A of the shielding member 20 in the cross section of the diaphragm 53.

[0042] This allows the thickness of the housing 12 along the central axis of the sensor chip / terminal fixing member 14 to be made thinner.

[0043] 3(A) and 3(B), the same components as those in the example shown in FIG. 1(A) are denoted by the same reference numerals, and redundant explanations thereof will be omitted.

[0044] 5(A) and (B) show the main parts of another example of a sensor unit used in an example of a pressure sensor according to the present invention. In FIG. 5(A) and (B), the same components as those in the example shown in FIG. 1(A) and (B) are denoted by the same reference numerals, and redundant explanations will be omitted.

[0045] The sensor unit detects the pressure in the pressure chamber formed between the above-mentioned base plate and diaphragm 32 and sends out a detection output signal. It is composed of the following main elements: a metallic cylindrical housing 12; a metallic diaphragm 32 that isolates the pressure chamber from the inner periphery of the housing 12; a sensor chip 16 having multiple pressure detection elements and a signal processing electronic circuit that processes signals from the pressure detection elements; a metallic chip mount member 18 that supports one end of the sensor chip 16 via an adhesive layer 50; a group of input / output terminals 40ai (i = 1 to 8) electrically connected to the sensor chip 16; and hermetic glass 19 that fixes the group of input / output terminals 40ai and the oil filling pipe 44 between the outer surface of the chip mount member 18 and the inner surface of the housing 12.

[0046] A shield member 21 serving as an electric field shielding member is disposed between one end face of the sensor chip 16 and the diaphragm 32 in the liquid-sealed chamber 13 formed between the metal diaphragm 32 and the end faces of the sensor chip 16 and hermetic glass 19. The outer periphery of the shield member 21 is bonded to one end face of a spacer member 17 (described later). The shield member 21 shields undesired electric fields from being applied to the signal processing electronic circuitry of the sensor chip 16. The disk-shaped shield member 21 is made of a conductive metal material such as stainless steel, copper, or aluminum. Note that the outer periphery of the shield member 21 is bonded to one end face of the spacer member 17 (described later). However, this is not a limitation; for example, the outer periphery of the shield member 21 may be supported in a recess formed in one end of the spacer member 17.

[0047] 5(B), the shield member 21 has a hole 21a at a position corresponding to one of the input / output terminal group 40ai, for example, a GND terminal (zero (V) terminal). This allows the pressure transmission medium PM (for example, silicone oil) filled in the liquid-sealed chamber 13 to flow through the hole 21a between the inner periphery of the spacer member 17 covered by the shield member 21 and the portion formed between the diaphragm 32 and the shield member 21 in response to the displacement of the diaphragm 32.

[0048] The shield member 21 is grounded via a bonding wire Wib connected to one of the input / output terminals 40ai, for example, a GND terminal (zero (V) terminal). The GND terminal (zero (V) terminal) is connected to the sensor chip 16 via a bonding wire Wia. The shape of the shield member 21 is not limited to a disk shape, and may be, for example, a strip shape or an oval shape as shown in FIG. 1(B).

[0049] In addition to the hole 21a, the shield member 21 may have a hole or a communication passage such as a groove formed in the spacer member 17 that connects the inner surface of the spacer member 17 covered by the shield member 21 to the portion formed between the diaphragm 32 and the shield member 21.

[0050] The spacer member 17 is molded from an insulating material such as a resin material, a rubber material, or a ceramic material that has a lower coefficient of thermal expansion than the pressure transmission medium PM. This eliminates the need for a conductive plate disposed within the liquid-sealed chamber 13 to fix the shielding member, as shown in Patent Documents 1 and 2, and allows the depth along the central axis of the input / output terminal group 40ai in the liquid-sealed chamber 13 formed on the inner periphery of the housing 12 to be made shallower. This allows the internal spatial volume of the liquid-sealed chamber 13, i.e., the amount of pressure transmission medium PM enclosed, to be reduced, thereby improving the temperature characteristics of the pressure sensor output.

[0051] Note that, in cases where the cross-sectional shape of the internal space of the sensor device is rectangular, for example, as shown in Figure 1 of Patent Document 3, the spacer member 17 does not need to be annular, and may instead have, for example, a rectangular cylindrical cross-section. Furthermore, the shape of the spacer member can be any shape as long as it does not interfere with the sensor chip 16, bonding wire Wi, diaphragm 32, etc. inside the liquid-sealed chamber 13 and can fill the internal space volume of the liquid-sealed chamber 13 to the maximum.

[0052] When disposing the shield member 21 in the liquid-sealed chamber 13, first, for example, the input / output terminal group 40ai and the sensor chip 16 are connected via bonding wires, and then the spacer member 17 is fixed to the inner periphery 12a of the housing 12 by adhesive or welding, and the shield member 21 is joined to one end face of the spacer member 17, thereby integrating the spacer member 17 and the shield member 21. Next, the shield member 21 is connected to the GND terminal (zero (V) terminal) via the bonding wire Wib.

[0053] 6(A) and (B) show the main parts of yet another example of a sensor unit used in an example of a pressure sensor according to the present invention. In FIG. 6(A) and (B), the same components as those in the example shown in FIG. 5(A) and (B) are denoted by the same reference numerals, and redundant explanations will be omitted.

[0054] In the example shown in Figures 5(A) and (B), the shielding member 21 is connected to the GND terminal (terminal for zero (V)) via a bonding wire Wib, but instead, in the example shown in Figures 6(A) and (B), the shielding member 31 is connected to the GND terminal (terminal for zero (V)) by a terminal connection board 30 and a relay terminal 62 that is connected to the GND terminal (terminal for zero (V)) via the conductor pattern of the terminal connection board 30, for example.

[0055] The sensor unit detects the pressure in the pressure chamber formed between the above-mentioned base plate and diaphragm 32 and sends out a detection output signal. It is composed of the following main elements: a cylindrical metal housing 12; a metal diaphragm 32 that isolates the pressure chamber from the inner periphery of the housing 12; a sensor chip 16 having multiple pressure detection elements and a signal processing electronic circuit that processes signals from the pressure detection elements; a metal chip mount member 18 that supports one end of the sensor chip 16 via an adhesive layer 50; a group of input / output terminals 40ai (i = 1 to 8) electrically connected to the sensor chip 16; and hermetic glass 19 that fixes the group of input / output terminals 40ai and the oil filling pipe 44 between the outer surface of the chip mount member 18 and the inner surface of the housing 12.

[0056] A shield member 31, acting as an electric field shielding member, is disposed between one end face of the sensor chip 16 and the diaphragm 32 in the liquid-sealed chamber 13 formed between the metal diaphragm 32 and the end faces of the sensor chip 16 and hermetic glass 19. The outer periphery of the shield member 31 is bonded to one end face of the spacer member 17. The shield member 31 shields unwanted electric fields from the signal processing electronic circuitry of the sensor chip 16. The disk-shaped shield member 31 is made of a conductive metal material, such as stainless steel, copper, or aluminum. As shown in FIG. 6(B), the shield member 31 has two through-holes 31a and 31b at opposing locations. As a result, the pressure transmission medium PM (e.g., silicone oil) filling the liquid-sealed chamber 13 flows through the through-holes 31a and 31b between the inner periphery of the spacer member 17 covered by the shield member 31 and the portion formed between the diaphragm 32 and the shield member 31 in response to displacement of the diaphragm 32. The shape of the shield member 31 is not limited to a disk shape, and may be, for example, a strip shape or an oval shape as shown in Fig. 1(B). In such cases, the above-mentioned through holes are unnecessary. Furthermore, instead of through holes 31a and 31b in the shield member 31, a communication passage may be formed in the spacer member 17, which connects the inner periphery of the spacer member 17 covered by the shield member 31 with the portion formed between the diaphragm 32 and the shield member 31.

[0057] The shielding member 31 is fixed by soldering to the lower end of the relay terminal 62. The relay terminal 62 is disposed between two adjacent terminals of the input / output terminal group 40ai and is fixed by the hermetic glass 19. The relay terminal 62, the input / output terminal group 40ai (i=1 to 8), and the oil filling pipe 44 are each fixed within the hermetic glass 19 at equal intervals along the circumferential direction of the hermetic glass 19.

[0058] The upper end of the relay terminal 62 is soldered to one end of the conductor pattern of the terminal connection board 30. The other end of the conductor pattern of the terminal connection board 30 is connected to one of the input / output terminal group 40ai, for example, the GND terminal (zero (V) terminal). The terminal connection board 30 has a hole through which the upper end of the relay terminal 62 passes, and a plurality of holes through which the input / output terminal group 40ai and the oil filling pipe 44 pass, spaced at predetermined intervals along the circumferential direction. The terminal connection board 30 has a conductor pattern formed between the periphery of the hole through which the upper end of the relay terminal 62 passes and the periphery of the hole through which the GND terminal (zero (V) terminal) passes.

[0059] When placing the shielding member 31 in the liquid-sealed chamber 13, first, for example, the input / output terminal group 40ai and the sensor chip 16 are connected via bonding wires, and then the spacer member 17 is fixed to the inner periphery 12a of the housing 12 by adhesive or welding, and the shielding member 31 is joined to one end face of the spacer member 17. After that, one end of the conductor pattern of the shielding member 31 and the terminal connection board 30 is soldered and fixed to both ends of the relay terminal 62, respectively.

[0060] As a result, the shield member 31 is at the same potential as the signal processing electronic circuit mounted on the sensor chip 16 via the relay terminals 62 and the conductor patterns of the terminal connection board 30. Therefore, by disposing the shield member 31, which has the same potential as the sensor chip 16, between the diaphragm 32 and the signal processing electronic circuit section of the sensor chip 16, the electric field acting on the sensor chip 16 due to the potential difference between the diaphragm 32, which has the same potential as the primary power supply (not shown) of the unit, and the control circuit (not shown) side is blocked by the shield member 31. Furthermore, because the potential of the shield member 31 and the potential of the sensor chip 16 are the same, no electric field is generated between them. Therefore, the potential difference occurring between the sensor chip 16 and the diaphragm 32 does not act on the sensor chip 16, preventing it from affecting the signal processing electronic circuit in the sensor chip 16.

[0061] Furthermore, in the configuration of this embodiment, as in the above-described examples, the outer peripheral edge of the shield member 31 is directly joined to one end face of the spacer member 17 without an intervening conductive plate. Because there is no conductive plate disposed within the liquid-sealed chamber 13 to fix the shield member, as shown in Patent Documents 1 and 2, the depth along the central axis of the input / output terminal group 40ai in the liquid-sealed chamber 13 formed on the inner peripheral part of the housing 12 can be made shallower. This allows the internal spatial volume of the liquid-sealed chamber 13, i.e., the amount of pressure transmission medium PM enclosed, to be reduced, thereby improving the temperature characteristics of the pressure sensor output. [Explanation of symbols]

[0062] 12 Housing 14 Sensor chip / terminal fixing material 16 sensor chips 17 Spacer member 18 Chip mounting member 19 Hermetic Glass 20, 21, 31 Shielding members 30 Terminal connection board 32, 42, 52 diaphragm 40ai input / output terminal group 14G, 24G, 44G chip installation area 62 Relay terminal Wi, Wia, Wib bonding wire Wire connection end

Claims

1. A liquid-sealed pressure sensor comprising: a pressure detection element that detects pressure and sends out a detection output signal; a liquid-sealed chamber in which the pressure detection element is disposed and in which a pressure transmission medium is sealed; a diaphragm that separates a pressure chamber facing the liquid-sealed chamber; a plurality of terminals that are electrically connected to the pressure detection element within the liquid-sealed chamber; and a terminal fixing member that holds the plurality of terminals, wherein the liquid-sealed chamber is constituted by the terminal fixing member and the diaphragm; an electric field blocking member disposed between one end face of the pressure detection element and the diaphragm in the liquid-sealed chamber, for blocking an electric field acting on the pressure detection element; a spacer member disposed in the liquid-sealed chamber, the plurality of terminals have protrusions that protrude between opposing surfaces of the terminal fixing member and the electric field blocking member, A pressure sensor characterized in that the spacer member is arranged within the liquid-sealed chamber between the opposing surfaces of the terminal fixing member and the electric field blocking member, and between the pressure detection element and each of the protruding protrusions and the electric field blocking member so as to form a space in the direction of the central axis of the protrusion.

2. 2. The pressure sensor according to claim 1, wherein the spacer member is disposed at a distance from the pressure detection element greater than the projections of the terminals.

3. 3. The pressure sensor according to claim 1, wherein the electric field blocking member is fixed to one of the plurality of terminals.

4. 3. The pressure sensor according to claim 1, wherein one end surface of the spacer member supports the electric field blocking member.

5. 4. The pressure sensor according to claim 3, wherein one end surface of the spacer member supports the electric field blocking member.

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