Pressure detection device

Abstract

Pressure detection device (1) comprising: a metal housing including a deformation portion, the deformation portion being deformed by pressure received from a pressure medium; a detection element that detects the pressure by detecting the deformation of the deformation portion; a lead frame (8) electrically connected to the detection element; and a structure that holds the lead frame (8), where a first surface of the lead frame (8) and a second surface of the metal housing are arranged facing each other with a predetermined gap, while an insulator is arranged therebetween, an insertion portion (7c) is formed in the structure for inserting a connector terminal (5a) electrically connected to the detection element through the lead frame (8), and in the insertion portion (7c) the lead frame (8) and a pressing member which presses the connector terminal (5a) so that it abuts against the lead frame (8) are arranged.

Description

Technical FieldThe present invention relates to a pressure detection device.Background ArtIn order to achieve the environmental friendliness of a vehicle and to improve fuel consumption, a hydraulic system for generating oil pressure by an electric motor, a fuel injection system for injecting fuel by applying pressure to the fuel, and other systems are increasingly being applied. These systems include pressure sensors to detect the pressure. Generally, a pressure sensor is supported in a metal case to ensure strength reliability, and is fixed by bolts to a metal pipe through which a pressure medium as a measurement target, such as a working fluid and a liquid fuel, is measured. The metal pipe is fixed to a structure at a body potential GND, such as the body or the engine of the vehicle. Therefore, the potential of the metal case of the pressure sensor becomes the body potential GND similarly to the metal pipe.The pressure sensor is connected to an electronic control unit (ECU) mounted in the vehicle through a wire harness. If unnecessary electromagnetic waves are present around the wire harness, the wire harness serves as an antenna to easily receive the electromagnetic waves. Then, the electromagnetic waves flow into the pressure sensor as noise through the wire harness. A detection element for detecting the pressure in the pressure sensor is disposed facing the metal case with an insulating layer interposed therebetween. This configuration corresponds to that a parasitic capacitance having a relatively large capacitance is electrically connected between the detection element and the GND potential. Because the noise flowing from the wire harness into the pressure sensor is alternating, the noise can more easily flow from the pressure sensor to the metal housing as the parasitic capacitance is increased. At this time, if the noise flows on its way into a processing circuit, the processing circuit may cause a malfunction.A technique according to PTL 1 is known to solve the problem. In the technique disclosed in PTL 1, a chip capacitor is provided in a pressure sensor, and an electrode of the chip capacitor is electrically connected to a housing, so that the noise input to the pressure sensor is output to the housing 10 and a measurement object through the chip sensor to ensure the resistance of the pressure sensor to the noise.PTL 2 discloses an electronic device having a capacitor portion for removing noise electrically connected between a terminal and a metal case. The capacitor portion is made of an annular dielectric disposed along the end of a cylindrical side wall of the metal case in which a sensor chip and a substrate are disposed, and annular first and second electrodes disposed on both sides thereof.List of ReferencesPatent LiteraturePTL 1: JP 2005-257 442 APTL 2: JP 2014-232 025 ASUMMARY OF THE INVENTIONTechnical ProblemIn the technique disclosed in PTL 1, a substrate and the package are connected by a conductive adhesive, and the chip capacitor attached to a wiring pattern of the substrate and the package are electrically connected. Therefore, heterometal connection is produced between the wiring pattern or the case and the conductive adhesive. If the heterometal compound occurs, a potential difference is generated between the joined metals due to a difference in ionization tendencies of the metals. For example, if a closed circuit is formed due to moisture, corrosion may be caused by electroplating.The solution to the problemA pressure detection device according to the present invention includes a metal case including a deformation portion deformed by a pressure received from a printing medium, a detection element detecting the pressure by detecting the deformation of the deformation portion, a lead frame electrically connected to the detection element, and a structure holding the lead frame. A first surface of the lead frame and a second surface of the metal case are disposed facing each other with a predetermined gap while an insulator is interposed therebetween. In the structure, an insertion portion is formed to insert a connector terminal electrically connected to the detection element through the lead frame, and in the insertion portion, the lead frame and a pressing member pressing the connector terminal to abut on the lead frame are disposed.Advantageous Effects of the InventionAccording to the present invention, it is possible to improve the noise resistance of a pressure sensor while avoiding heterometal connection.Brief Description of the DrawingsFIG. 1 is a vertical cross-sectional view illustrating a configuration of a pressure detection device according to an embodiment of the invention. FIG. 2 is a view illustrating an outline of a connection member. FIG. 3 is a diagram for describing the formation of a capacitor using a parasitic capacitance. FIG. 4 is a diagram for describing an operation in a case where a parasitic capacitance Cic in a circuit and the Ct of the invention are added. FIG. 5 is a diagram illustrating a positional relationship of a lead frame and a metal case. FIG. 6 is a diagram illustrating a shape example of the connection member in a case where a parallel plate capacitor is formed using an adhesive. FIG. 7 is a diagram illustrating an example of an EMC test result with respect to the pressure detection device.DESCRIPTION OF THE EMBODIMENTSThe embodiments of the invention will be described below.FIG. 1 is a vertical cross-sectional view illustrating a configuration of a pressure detection device 1 according to an embodiment of the invention. The pressure detection device 1 is mounted on a vehicle, and includes a sensor element 2, a pressure terminal 3, a connector subassembly 5, a base member 6, a connector 7, a lead frame 8, and a press terminal 9.In the upper portion of the pressure port 3, a rectangular diaphragm 3a functioning as a pressure receiving surface of a pressure medium to be measured is provided. The upper surface of the diaphragm 3 a, i.e., a surface opposite to the pressure receiving surface, serves as a base surface 3 bwhere the sensor element 2 is disposed. The pressure port 3 supplies the pressure medium such as a working fluid and a liquid fuel to the pressure receiving surface of the diaphragm 3 a. In this configuration, the diaphragm 3a is deformed according to the pressure of the pressure medium, and deformation occurs. The sensor element 2 measures a change in resistance according to the deformation of the diaphragm 3 ato detect the amount of the change, i.e., the deformation of the diaphragm 3 a, and detects the pressure of the pressure medium.Both the pressure port 3 and the base member 6 are made of a metal such as SUS and joined together by welding. To the base member 6, the connecting member 7 is fixed by an adhesive or the like. Hereinafter, the combined body of the pressure terminal 3 and the base member 6 will be referred to as a "metal case". Further, the pressure terminal 3 and the base member 6 may be integrally formed as the metal housing, instead of connecting the pressure terminal 3 and the base member 6 to form the metal housing.A connector subassembly 5 includes a connector terminal 5a. A not-illustrated wire harness is connected to the connector terminal 5 a. The pressure detection device 1 is connected to an ECU of the vehicle through the wire harness to output a pressure detection result to the ECU. In the connector sub-assembly 5, a cover 11 is integrally formed to protect the sensor element 2 from the outside. Further, the cover 11 is formed in a hexagonal shape, for example.The connector 7 is a structure for supporting the lead frame 8, and an insertion portion is formed in the connector 7 to insert the connector terminal 5 a. In the insertion portion, one end of the lead frame 8 and the press terminal 9 are disposed. On the other end side of the lead frame 8, a connecting portion is provided to be connected to the sensor element 2 by wire bonding using a wire 10. The wire 10 may be formed of aluminum (Al) or gold (Au). The sensor element 2 and the ECU are electrically connected by the wire 10, the lead frame 8, the connector terminal 5 a, and the wire harness by inserting the connector terminal 5 ainto the insertion portion of the connector 7.When the pressure detection device 1 is assembled, the connecting member 7 having the lead frame 8 and the press terminal 9 assembled therein is disposed on the base member 6, and the sensor element 2 and the connecting portion of the lead frame 8 are connected by the wire 10. Thereafter, potting of a silicone gel 12 is applied to the surface of the sensor element 2 to protect the sensor element 2 from foreign matter. Then, in a state where the connector terminal 5 ais inserted into the insertion portion of the connection member 7, the cover 11 and the base member 6 are joined by welding to integrate the connector subassembly 5 into the metal housing. The pressure detection device 1 is configured with this configuration.The sensor element 2 is a pressure detection element having a one-chip configuration in which a deformation detection element and a processing circuit are integrally formed on a silicon substrate. Therefore, there is no need to provide a circuit substrate for arranging the processing circuit. An output signal generated by the sensor element 2 to the pressure received by the diaphragm 3 ais transmitted to the ECU through the wire 10, the lead frame 8, and the connector terminal 5 athrough the wire harness.Next, the detailed shapes of the connection member 7, the lead frame 8, and the press terminal 9 will be described with reference to FIG. 2. FIG. 2 is a diagram illustrating the outline of the connection member 7 with the lead frame 8 and the press terminal 9 assembled. In FIG. 2, the left drawing is a projected view of the connecting member 7, while the right drawing is a plan view.As illustrated in FIG. 2, an insertion portion 7 cis formed in the connection member 7. In the insertion portion 7 c, a connector contact portion 8 band the press terminal 9 are disposed on one end side of the lead frame 8. Further, on the other end side of the lead frame 8, a connection portion 8 ais provided to be wire-bonded to the sensor element 2. The press connection 9 has an elastic property. Therefore, when the connector terminal 5a is inserted into the insertion portion 7c, the press terminal 9 is deformed, pressing on the connector terminal 5a in the direction of the connector contact portion 8b. With this configuration, the connector terminal 5 acomes into secure contact with the connector contact portion 8 b, and the electrical connection between the connector portion 5 aand the lead frame 8 can be secured.In addition, an insertion guide 7 bis provided in the connector 7 for positioning the connection terminal 5 awhen inserted into the insertion portion 7 c. The position and the shape of the insertion guide 7 bare formed in accordance with the position and the shape of an unillustrated protrusion provided in the connector sub-assembly 5. If no insertion guide 7 bis provided, the position and direction of the connector terminal 5 amay deviate when the connector terminal 5 ais inserted into the insertion portion 7 c. There is a concern that the connector terminal 5 adoes not correctly abut on the connector contact portion 8 b. Then, with the insertion guide 7 bprovided in the connector 7 in this embodiment, the insertion guide 7 bis fitted to the protrusion of the connector subassembly 5 when the connector subassembly 5 is assembled, so that the connector terminal 5 ais positioned. When the connector terminal 5a thus positioned is inserted into the insertion portion 7c, the connector terminal 5a can properly abut on the connector contact portion 8b.Further, in the connector 7, a mounting portion 7a is provided to mount an electronic component such as a chip capacitor. The connection terminal 5a is formed by being pressed into a mold so as not to cause interference with the electronic component mounted on the mounting portion 7a when inserted into the insertion portion 7c so as not to cause a problem in mounting the electronic component on the mounting portion 7a. With this configuration, it is possible to remove the circuit substrate from the pressure detection device 1. The potting of the silicone gel 12 is applied to the mounting portion 7 aafter a required electronic component is mounted with the surface protected, similarly to the sensor element 2 (see FIG. 1 ).Next, the shape of a capacitor using a parasitic capacitance, which is a feature of this embodiment, will be described using FIGS. 3 and 4.FIG. 3 is a partially enlarged view of the pressure port 3 when the sensor element 2 is mounted. As illustrated in FIG. 3, the sensor element 2 is bonded to the pressure terminal 3 by an adhesive 4. As described above, the sensor element 2 is further configured by a chip, and the deformation detection element and the processing circuit are integrally formed. The adhesive 4 is an insulator such as an inorganic adhesive, and is coated extremely thinly as compared with the surface of the sensor element 2. Therefore, in the circuit including the sensor element 2, the connection portion between the sensor element 2 and the pressure terminal 3 with the adhesive 4 therebetween serves as a parasitic capacitance Cic having a relatively large capacitance.FIG. 4 is a diagram for describing an operation of the parasitic capacitance Cic in the circuit. FIG. 4( a) is a schematic diagram illustrating the circuit in a case where no noise suppression is considered. FIG. 4( b) is a schematic diagram of the circuit in a case where a capacitance Ct for noise suppression is provided. The IC and the protection circuit illustrated in these circuit diagrams illustrate the circuits configured by the sensor element 2 and the electronic components mounted in the mounting portion 7 aof the connector 7.In the case of FIG. 4( a) in which noise suppression is not implemented, when noise from the wiring connected to the IC is input through the protection circuit, the noise flows into the metal case at a body potential GND through the parasitic capacitance Cic provided between the IC and the metal case. At this time, because the noise passes through the IC, i.e., the processing circuit of the sensor element 2, there is a concern that the processing circuit causes a malfunction and the output of the sensor element 2 is abnormal.On the other hand, in the case of FIG. 4( b) in which the noise suppression is implemented, due to the capacitance Ct provided between the wiring and the metal case as a noise path, the input noise flows through the capacitance Ct into the metal case at the body potential GND without passing through the IC. Therefore, malfunction of the processing circuit caused by the noise can be avoided, and the output abnormality of the sensor element 2 can be prevented.In general, if the parasitic components such as the inductance and the low resistance are ignored by the capacitor, the impedance at the same frequency becomes smaller as the electrostatic capacitance is increased, and accordingly, the alternating current flows more easily. In other words, when the electrostatic capacitance of the capacitor is set to C [F], the impedance Z [Ω] of the capacitor is expressed as the following expression (1).In the above expression (1), ω [rad / s] represents a angular frequency of the alternating current flowing in the capacitor, and the following expression (2) is obtained using the frequency f [Hz] of the alternating current.As described above, in the alternating current having the same frequency, the impedance Z becomes smaller as the electrostatic capacitance C is increased, and accordingly, the alternating current flows more easily. Therefore, the noise flowing into the processing circuit can be suppressed by setting the value of the capacitance Ct larger than that of the parasitic capacitance Cic, and the noise resistance of the sensor element 2 can be improved.In this embodiment, with the connector 7, which is an insulator provided between the lead frame 8 and the metal case, the parasitic capacitance is caused between the lead frame 8 and the metal case. Using the parasitic capacitance as the above-described capacitance Ct, the noise resistance of the sensor element 2 is improved. Hereinafter, such a configuration will be described with reference to FIG. 5.FIG. 5 is a diagram illustrating a positional relationship of a lead frame 8 and a metal case. In order to assist in understanding the positional relationship between the lead frame 8 and the metal housing, the outline of the pressure detection device 1 is illustrated in FIG. 5 while the tip end of the connector terminal 5 ais removed from the connector subassembly 5 and the connector 7. In FIG. 5, the left drawing is a front view, while the right drawing is a plan view.As illustrated in a hatched portion on the right side of FIG. 5, in the portion between the connection portion 8 aand the connector contact portion 8 bin the lead frame 8, a parallel plate region is formed, which is a plate region formed parallel to the base member 6. The parallel plate portion is formed to have a width as wide as possible and is disposed as close to the base member 6 as possible. With this configuration, a parallel plate capacitor is formed by the lead frame 8 and the metal case, and the parasitic capacitance Ct serving as the noise path is actively generated.In a portion where the parallel plate capacitor is formed, the connection member 7 configured by an insulator such as a resin is disposed between the lead frame 8 and the metal case (the base member 6), while not illustrated in FIG. 5. Therefore, the parasitic capacitance Ct can be increased as much as a dielectric constant of the insulator as compared with the case of air. Further, the connecting member 7 and the base member 6 may be bonded with an insulating adhesive, wherein the adhesive may be such as to use the connecting member 7 and the base member 6 including the adhesive as a dielectric material of the parallel plate capacitor. With this configuration, the electrostatic capacitance of the parasitic capacitance Ct becomes larger than the parasitic capacitance Cic as described above, and the noise resistance of the sensor element 2 can be secured.In the prior art, a chip capacitor is used as a capacitor for the noise path. The chip capacitor is connected to the wiring and the metal case using a hetero metal for connection by soldering, and corrosion may occur. On the other hand, in the pressure detection device 1 of this embodiment, the surface on the lower side in the parallel plate region of the lead frame 8, i.e., the surface on the base member 6 side and the surface on the upper side of the base member 6 are disposed in the metal case so as to face each other with a predetermined gap therebetween while the resin and the adhesive of the connection member 7 which is an insulator are interposed therebetween. In this configuration, the parallel plate capacitor is formed between the lead frame 8 and the metal case, and the parasitic capacitance Ct caused by the parallel plate capacitor is used as the capacitor for the noise path. Therefore, it is possible to improve the noise resistance of the pressure detection device 1 while avoiding the heterometal connection. Further, because the chip capacitor is not used, it is possible to avoid the increase in the number of components.Further, in a case where the connection member 7 is configured as a molding resin, there is a minimum thickness for the member to be interposed between the lead frame 8 and the metal case due to a limitation at the time of molding. Therefore, a necessary electrostatic capacitance cannot be obtained in the parasitic capacitance Ct. Then, the resin of the connector cannot be disposed between the lead frame 8 and the metal case (the base member 6) using the connector having a shape different from the connector 7, so that the adhesive for connecting the connector and the base member 6 can be used as a dielectric material of the parallel plate capacitor.FIG. 6 is a diagram illustrating a shape example of the connection member in a case where a parallel plate capacitor is formed using an adhesive. In a connector 13 illustrated in FIG. 6( a), the lead frame 8 is fixed to the connector 13 in a state where the surface on the lower side in the parallel plate region of the lead frame 8, i.e., the surface on the base member 6 side from which the connector 13 is exposed. When the connector 13 to which the lead frame 8 is fixed is disposed on the base member 6, a portion of the lead frame 8, i.e., the surface facing the base member 6 of the lead frame 8, is exposed from the lower side, i.e., the surface of the connector 13 facing the metal case (the base member 6) of the connector 13. In this state, if the connector 13 is an insulating adhesive and is fixed to the base member 6, the adhesive serves as a dielectric material of the parallel plate capacitor, and the parasitic capacitance Ct is formed between the lead frame 8 and the metal case. At this time, a desired electrostatic capacitance in the parasitic capacitance Ct can be obtained by controlling the amount of the adhesive to adjust the thickness of the adhesive layer.In addition, a connecting member 14 illustrated in FIG. 6( b) may be used. On the lower side of the connecting member 14, a wall portion 14a formed along the outer edge and a filling portion 14b surrounded by the wall portion 14a are provided. The filling portion 14 bis recessed from the wall portion 14 awith respect to the lower side. Even in the connector 14 similar to the connector 13 of FIG. 6( a), the lead frame 8 is fixed to the connector 14 in a state where a surface on the lower side in the parallel plate region of the lead frame 8, i.e., the surface on the base member 6 side from which the connector 14 is exposed. When the connecting member 14 with the lead frame 8 fixed is disposed on the base member 6, the bottom surface of the wall portion 14 acomes in contact with the metal case (the base member 6). At this time, when the connector 14 is fixed to the metal case, the positioning can be performed by the wall portion 14 a. Further, a groove or step corresponding to the protruding shape of the wall portion 14 is formed on a side near the metal shell, the wall portion 14a being fitted to the groove or step, so that the positioning of the connecting member 14 can be performed. In addition, a portion of the lead frame 8, i.e., the surface facing the base member 6 of the lead frame 8, is exposed from the surface of the filling portion 14 bfacing the metal case (the base member 6). In this state, when an insulating adhesive is filled in the filling portion 14 band the connector 14 is fixed to the base member 6 similarly to the case of the connector 13, the adhesive serves as the dielectric material of the parallel plate capacitor, and the parasitic capacitance Ct is formed between the lead frame 8 and the metal case. The thickness of the adhesive layer at this time becomes the height of the wall portion 14 a, so that it is possible to suppress the variation in the distance between the lead frame 8 and the metal case. Therefore, by adjusting the height of the wall portion 14 a, a desired electrostatic capacitance in the parasitic capacitance Ct can be obtained with accuracy. Further, some of the lead frame 8 may not be exposed in the filling portion 14 b.Further, when the connection member 14 is fixed to the metal case, the metal case may be disposed so as to protrude into the filling portion 14 bfrom the lower side of the wall portion 14 atoward the lead frame 8. For example, when the protruding portion of the flat table-like upper portion is formed in the metal case and the connecting member 14 is fixed, the protruding portion can be inserted into the concave portion of the filling portion 14 bto realize the positioning described above. Alternatively, a groove corresponding to the protruding shape of the wall portion 14a may be provided in the metal case as described above, the wall portion 14a being fitted to the groove, so that the above positioning can be also realized. In this configuration, the metal case and the lead frame 8 may be disposed at a distance smaller than the minimum resin thickness due to a constraint at the time of molding as described above. Therefore, the parasitic capacitance Ct can be increased.Next, the distance between the lead frame 8 and the metal case will be described. In order to increase the electrostatic capacitance of the parasitic capacitance Ct as described above, the parallel plate portion of the lead frame 8 is provided as close to the metal case as possible. However, even in a case where a surge voltage of about several hundred volts [V] is input, there is a need to secure a distance to some extent so that insulation between the lead frame 8 and the metal case is secured to be non-conductive.It is generally known that dielectric breakdown of the air occurs when a potential gradient E [V / m] is equal to or greater than 3 [MV / m]. In a case where there is a defect such as a void in the insulator, the surrounding resin is carbonized when the dielectric breakdown occurs, resulting in a defect such as the conduction between the lead frame 8 and the metal case. Here, the value of surge voltage generally adopted in a surge test is about 300 [V]. Therefore, a minimum distance between the lead frame 8 and the metal case is calculated from these values as 0.1 [mm].In addition, as a result of the EMC test using the pressure detection device 1 of this embodiment, it is confirmed that an expected noise resistance is not shown if the parasitic capacitance Ct is less than 9 [pF]. Here, the capacitance C [F] of the parallel plate capacitor is obtained by the following expression (3) when the area of the plate is set to A [m 2] the plate pitch is set to d [m], and the dielectric constant is set to ε [F / m].In the above expression (3), the values corresponding to the pressure detection device 1 are substituted for A and ε, respectively, and the plate pitch d is calculated at C=9 [pF], where d=0.6 [mm] is obtained. Therefore, a maximum distance between the lead frame 8 and the metal case is obtained as 0.6 [mm].As described above, in the pressure detection device 1, the distance between the lead frame 8 and the metal housing is desirably set in a range of 0.1 [mm] to 0.6 [mm]. However, the maximum distance is not limited to 0.6 [mm] because the maximum distance varies according to the area of the parallel plate portion of the lead frame 8, the connector interposed between the lead frame 8 and the metal case, or the dielectric constant of the adhesive.In addition, in order to improve the noise resistance of the pressure detection device 1, it is effective to decrease the electrostatic capacity of the parasitic capacitance Cic instead of increasing the electrostatic capacity of the parasitic capacitance Ct. Specifically, for example, the adhesive 4 used to adhere the sensor element 2 to the pressure terminal 3 is made thicker, so that the electrostatic capacitance of the parasitic capacitance Cic can be reduced. In other words, it is apparent from the above expression (3) that the capacitance C of the parallel plate capacitor is decreased as the plate pitch d is increased. Therefore, the electrostatic capacitance of the parasitic capacitance Ct can be decreased to improve the noise resistance of the pressure detection device 1 by thickening the adhesive 4 within a range that does not affect the deformation detection performance of the sensor element 2 and setting a distance between the sensor element 2 and the pressure terminal 3.Further, in the pressure detection device 1, a position where the parasitic capacitance Ct is generated is desirably set as close as possible on the input side of the circuit illustrated in FIG. 4. In other words, the position is set on a side near the connector terminal 5 aof the mounting portion 7 awhere the electronic component such as the chip capacitor is mounted in the connector 7. In this case, the connection order from the viewpoint of the sensor element 2 becomes an order of the wire 10, the connection portion 8 aof the lead frame 8, the electronic component, and the parasitic capacitance Ct. In other words, in the lead frame 8, the electronic component mounted in the mounting portion 7 ais connected to an electrical path between the connection portion 8 aand the parallel plate region. With this configuration, the input noise can effectively flow from the parasitic capacitance Ct to the metal case, so that the noise resistance is even more improved.FIG. 7 is a diagram illustrating an example of an EMC test result regarding the pressure detection device 1. FIG. 7( a) illustrates an example of the EMC test result in a case where the noise suppressing structure described thus far is not provided. FIG. 7( b) illustrates an example of the EMC test result in a case where the structure for noise suppression is provided. By comparing Fig. 7(a) and Fig. 7(b), it can be seen that according to the noise suppressing structure of this embodiment, a good noise resistance is obtained over a wide frequency range.Next, another role of the press terminal 9 provided separately from the lead frame 8 constituting the parasitic capacitance Ct will be described. The press terminal 9 forms a spring for causing the connector terminal 5 ato abut on the connector contact portion 8 bin the insertion portion 7 cas described above. In addition, at the time of forming the connecting member 7, a plurality of press terminals 9 are integrally formed and separated into each press terminal 9 by a cutting process after forming. The press terminal 9 is disposed close to the metal housing similar to the lead frame 8. Therefore, the exposed portion close to the metal case is used to cause the press terminal 9 to serve as a discharge gap when an electrostatic force is applied.According to the above-described embodiment of the invention, the following operational advantages are obtained.(1) The pressure detection device 1 includes: a deformation portion, i.e., a metal case having the diaphragm 3 athat is deformed due to a pressure received from the pressure medium; a sensor element 2 that detects a pressure by detecting the deformation of the deformation portion; the lead frame 8 electrically connected to the sensor element 2; and a structure, i.e., the connection element 7, for holding the lead frame 8. A first surface of the lead frame 8, i.e., the surface on a side near the metal case in the parallel plate region, and a second surface of the metal case, i.e., the surface of the base member 6, sandwich at least one of the resin of the connection member 7 which is an insulator and the insulating adhesive, and are arranged to face each other with a predetermined gap therebetween. With such a configuration, the parasitic capacitance is generated between the lead frame 8 and the metal case, and the noise resistance of the pressure detection device 1, which is a pressure sensor, can be improved while avoiding the heterometal connection.(2) The electrostatic capacitance between the first surface and the second surface, i.e., the electrostatic capacitance of the parasitic capacitance Ct, is desirably larger than the electrostatic capacitance between the sensor element 2 and the metal case, i.e., the electrostatic capacitance of the parasitic capacitance Cic. With such a configuration, the noise flowing to the sensor element 2 is reduced, and malfunction of the sensor element 2 caused by the noise can be prevented.(3) The insertion portion 7 cis formed in the connector 7 to insert the connector terminal 5 awhich is electrically connected by the sensor element 2 and the lead frame 8. The pressing terminal 9, which is a pressing member, is disposed in the insertion portion 7 cto press the lead frame 8 and the connector terminal 5 ato abut on the lead frame 8. With such a configuration, the connector terminal 5 acomes into secure contact with the lead frame 8, and the electrical connection between the connector terminal 5 aand the lead frame 8 can be secured.(4) A guide portion, i.e., the insertion guide 7b, is formed in the connector 7 for positioning the connector terminal 5a when the connector terminal 5a is inserted into the insertion portion 7c. With such a configuration, the deviation in the position and direction of the connector terminal 5 acan be prevented, and the connector terminal 5 acan be brought into secure contact with the lead frame 8 through the press terminal 9.(5) The connector 7 is formed of a resin, and a portion of the connector 7 is formed as an insulator disposed between the first surface and the second surface. With such a configuration, a desired electrostatic capacity can be obtained using the portion of the connection member 7 as a dielectric material.(6) The first surface may be configured to be exposed from the surface of the structure facing the metal case, i.e., the bottom of the connector 13 and the connector 14. With such a configuration, the first surface can be approached to the metal case regardless of a constraint at the time of molding, and a desired electrostatic capacity can be obtained.(7) The connecting member 7, 13 or 14 is bonded to the metal case by the adhesive. The adhesive may be disposed between the first surface and the second surface as an insulator. With such a configuration, a desired electrostatic capacity can be obtained by controlling the amount of the adhesive to adjust the thickness of the adhesive layer.(8) The connecting member 14 includes a contact surface, i.e., a lower surface of the wall portion 14 athat abuts the metal shell, and the filling portion 14 bthat is recessed from the contact surface and filled with the adhesive. With the connecting member 14, a desired electrostatic capacity can be accurately obtained by adjusting the height of the wall portion 14 a.(9) The lead frame 8 includes a connection portion, i.e., the connection portion 8 aconnected to the sensor element 2 by wire bonding, and an electronic component is connected in an electrical path between the connection portion and the first surface. With such a configuration, the noise resistance is improved even more.(10) A predetermined gap between the first surface and the second surface is desirably set to be equal to or greater than 0.1 mm. With such a configuration, it is possible to prevent conduction between the lead frame 8 and the metal case due to the dielectric breakdown.(11) The metal housing includes the pressure port 3 that guides the pressure medium to the deformation portion and the base member 6 connected to the connection member 7. With such a configuration, it is possible to configure the pressure detection device 1 having high noise resistance.Further, in the above-described embodiment, the sensor element 2 has been described as a single-chip type element in which the deformation detection element and the processing circuit are integrated. However, the present invention is similarly applicable even to a sensor element other than the one-chip type in which a strain gage and the processing circuit are formed on separate substrates. In this case, since the strain gage is disposed in an insulating state at a location closest to the metal case, the parasitic capacitance having a large electrostatic capacitance is formed between the strain gage and the metal case. Therefore, because the noise passes through the processing circuit when it flows into the parasitic capacitance, there is a concern that a malfunction occurs in the sensor element. Accordingly, even in this case, the countermeasure is effective similarly to the embodiment.In addition, it has been described that the pressure detection device 1 in the embodiment is mounted on a vehicle to detect the pressure of the pressure medium such as the working fluid and the liquid fuel. However, the invention is similarly applicable to a pressure detection apparatus used for other purposes. As far as the sensor element is disposed close to the metal case in an insulated state and the metal case is at the GND potential, the effective improvement of the noise resistance according to the invention can be obtained in various types of pressure detection devices. For example, a large force is applied to a sensor that detects a load as a deformation. Therefore, the resin cannot be used to receive the pressure. In addition, the base of the sensor element is necessarily configured to be fixed. Therefore, the housing of such a sensor is necessarily configured of a metal to have a similar configuration to the pressure detection device 1 described in the embodiment, so that the noise resistance can be improved by similarly applying the invention.Further, the sensor element used in the sensor may be the one-chip type sensor element as described above in which the deformation detection element and the processing circuit are integrated. Alternatively, the deformation detection element and the processing circuit may be formed on separate substrates. In any case, the operational advantage similar to those in the embodiment can be obtained.The pressure detection device to which the invention is applied is not limited to the ring shape described in the embodiment, but may be formed in other shapes. If the technical elements described so far are combined, any shape may be adopted.In the application of the invention to the pressure detection device, the capacitor can be formed for a noise path without causing the hetero metal bonding as described above. Because the chip capacitor is not used, connection reliability can be improved, cost can be reduced, and space saving can be expected.The above-described embodiment and the various modifications have been described as merely exemplary. The invention is not limited to the contents as long as the features of the invention are not impaired. In addition, various embodiments and modifications have been described, but the invention is not limited to these contents. Other embodiments considered to be within a scope of the technical ideas of the invention may also be included in the scope of the invention.List of Reference Numerals1 Pressure detection device 2 Sensor element 3 Pressure terminal 3 a Membran 3 b Sockel surface 4 Adhesive 5 Connector subassembly 5 a Verbinder terminal 6 Base member 7 Connector 7 a Portion 7 bInsertion guide 7 cInsertion portion 8 Lead frame 8 aConnect portion 8 bConnection contact portion 9 Press terminal 10 Wire 11 Cover 12 Silicone gel

Claims

A pressure detection device (1) comprising: a metal case including a deformation portion, the deformation portion being deformed by a pressure received from a pressure medium; a detection element that detects the pressure by detecting the deformation of the deformation portion; a lead frame (8) electrically connected to the detection element; and a structure holding the lead frame (8), wherein a first surface of the lead frame (8) and a second surface of the metal case are disposed facing each other with a predetermined gap while an insulator is interposed therebetween, in the structure, an insertion portion (7c) is formed to insert a connector terminal (5a) electrically connected to the detection element through the lead frame (8), and in the insertion portion (7c), the lead frame (8) and a pressing member pressing the connector terminal (5a) to abut on the lead frame (8) are disposed.The pressure detection device (1) according to claim 1, wherein an electrostatic capacitance between the first surface and the second surface is larger than an electrostatic capacitance between the detection element and the metal case.The pressure detection device (1) according to claim 2, wherein a guide portion is formed in the structure to position the connector terminal (5a) when the connector terminal (5a) is inserted into the insertion portion (7c).The pressure detection device (1) according to any one of claims 1 to 3, wherein the structure is formed of a resin, and a portion of the structure between the first surface and the second surface is disposed as the insulator.The pressure detection device (1) according to any one of claims 1 to 3, wherein the first surface is exposed from a surface of the structure facing the metal case.The pressure detection device (1) according to claim 4 or 5, wherein the structure is bonded to the metal case by an adhesive, and wherein the adhesive is disposed between the first surface and the second surface as the insulator.The pressure detection device (1) according to claim 6, wherein the structure includes a contact surface abutting the metal case and a filling portion (14b) recessed from the contact surface and filled with the adhesive.The pressure detection device (1) according to any one of claims 1 to 7, wherein the lead frame (8) includes a connection portion (8a) connected to the detection element by wire bonding, and wherein an electronic component is connected in an electrical path between the connection portion (8a) and the first surface.The pressure detection device (1) according to any one of claims 1 to 8, wherein the predetermined gap is equal to or greater than 0.1 mm.The pressure detection device (1) according to any one of claims 1 to 9, wherein the metal case includes a pressure port (3) that guides the pressure medium to the deformation portion, and a base member (6) connected to the structure.

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