JP2010266210A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pressure sensor capable of enhancing the reliability, as compared to those of conventional types. <P>SOLUTION: The pressure sensor includes a cylindrical housing extending in its axial direction; a pressure-transmitting means housed in the tip side of the housing; a pressure detecting element which is housed in the housing and is pressed by the pressure-transmitting member; a base made up of an insulating material which is housed in the housing and holds the pressure-detecting element; a substrate which extends in the axial direction inside the housing and is arranged with its tip at a predetermined interval from the base; a plurality of conductor patterns formed on the substrate in the axial direction and electrically connected to the pressure detecting element; and an elastic member for displaceably holding the substrate with respect to the housing. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pressure sensor for measuring an in-cylinder combustion pressure of an internal combustion engine.

  Conventionally, a combustion state is controlled by measuring a combustion pressure in a cylinder of an internal combustion engine such as an automobile engine using a pressure sensor. In such a pressure sensor, a pressure detection element arranged on the pedestal and a pressure transmission member for pressing the pressure detection element are arranged on the front end side of the housing so as to penetrate the pedestal (hermetic pedestal). It is known that the pressure detection element is electrically drawn out to the rear end side of the housing by a pin terminal provided (see, for example, Patent Document 1).

JP-A-5-126667

  However, in the pressure sensor using the wiring structure with the hermetic pedestal and the pin terminal described above, since the pin terminal has a relatively large mass, it is easily affected by vibration and the pin length becomes long. There is a problem that the strength of the base (pedestal connecting portion) is insufficient, and there is a risk of damage due to vibration. Moreover, in order to prevent vibration of the pin, it is conceivable to perform molding by resin filling, but when measuring the combustion pressure in a cylinder of an automobile engine, the pressure sensor is exposed to an environment exceeding 300 ° C, It is difficult to perform resin molding. In addition, when using a hermetic pedestal, it is necessary to have a region for placing pin terminals, glass seals, etc. in addition to a region for placing pressure detection elements on the pedestal, making it difficult to reduce the area, and the entire pressure sensor It is difficult to reduce the size.

  The present invention has been made in response to the above-described conventional circumstances. The present invention seeks to provide a pressure sensor capable of improving reliability as compared with the prior art.

  A pressure sensor according to the present invention includes a cylindrical housing extending in the axial direction, a pressure transmission member housed on the distal end side of the housing, a pressure detection element housed in the housing and pressed by the pressure transmission member, A base made of an insulating material that is housed in the housing and holds the pressure detection element, and a substrate that extends along the axial direction in the housing and has a tip disposed at a predetermined interval from the base. A plurality of conductor patterns formed on the substrate along the axial direction and electrically connected to the pressure detecting element; and an elastic member that holds the substrate displaceably with respect to the housing. And

  In the pressure sensor of the present invention, without using a pin terminal by a hermetic pedestal, by a plurality of conductor patterns formed on a substrate extending in the axial direction in the housing and having a tip disposed at a predetermined distance from the pedestal. The pressure detection element can be electrically pulled out to the rear end side of the housing. For this reason, damage to the pedestal connecting portion of the pin terminal does not occur due to the influence of vibration, and reliability can be improved. Furthermore, by providing a predetermined gap between the tip of the substrate and the base and providing an elastic member that holds the substrate so as to be displaceable with respect to the housing, the difference in thermal expansion between the substrate and the housing can be absorbed. It becomes possible. Furthermore, since a predetermined interval is provided between the tip of the substrate and the pedestal, the pedestal does not press the substrate backward when the pressure detection element receives pressure.

  In the pressure sensor of the present invention, the conductor pattern can be configured to be electrically connected to the pressure detection element via a conductor provided on the pedestal and a bonding wire. As a result, the bonding wire is deformed, so that the substrate can be displaced relative to the base while maintaining the electrical connection state.

  In the pressure sensor of the present invention, it is preferable that the predetermined interval between the tip of the substrate and the pedestal is 1 mm or more and 2 mm or less. If the distance is less than 1 mm, the substrate and the pedestal may come into contact with each other due to thermal expansion difference or vibration. Moreover, when this space | interval becomes long exceeding 2 mm, the length of the bonding wire etc. for electrical connection arrange | positioned among these will become long, and the possibility of the disconnection etc. by vibration becomes high.

  In the pressure sensor of the present invention, the elastic member can be a metal terminal that is electrically connected to the conductor pattern and leads the pressure detection element to the rear end side. Accordingly, it is not necessary to provide an elastic member separately from the metal terminal, and the pressure sensor can be reduced in size and cost. In this case, the metal terminal can be configured to be elastic by bending a flat metal member. With such a configuration, it is possible to easily manufacture a metal terminal as an elastic member while suppressing an increase in the number of processes and the like, and to reduce costs. Furthermore, if the metal terminal and the conductor pattern are in contact with each other at two or more locations, a better electrical connection state can be maintained, and a more stable output can be obtained.

  In the pressure sensor of the present invention, a ceramic terminal holder is provided between the metal terminal and the housing, which is fixed to the base directly or via a relay member, and the metal terminal is elastically contacted. It can be configured. Accordingly, the metal terminal can be locked to the base (housing) with a simple configuration, and electrical insulation between the metal terminal and the housing can be performed.

  In the pressure sensor of the present invention, the conductor pattern can be formed on each of two opposing surfaces of the substrate. Thus, the two surfaces of the substrate can be used effectively, and the area of one conductor pattern can be increased, so that the electrical connection can be performed with a low resistance.

  ADVANTAGE OF THE INVENTION According to this invention, the pressure sensor which can aim at the improvement of reliability compared with the past can be provided.

The perspective view which shows typically the cross-sectional schematic structure of the pressure sensor which concerns on one Embodiment of this invention. The perspective view which shows typically the principal part schematic structure of the pressure sensor of FIG. The perspective view which shows typically the principal part schematic structure of the pressure sensor of FIG. The perspective view which shows typically the principal part schematic structure of the pressure sensor of FIG. The perspective view which shows typically the principal part schematic structure of the pressure sensor of FIG. The side view which shows typically the principal part schematic structure of the pressure sensor of FIG.

  Hereinafter, details of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view schematically showing a schematic cross-sectional configuration of a pressure sensor according to an embodiment of the present invention. As shown in FIG. 1, the pressure sensor 100 includes a sensor body 1 that extends in the axis X direction and is formed in a substantially cylindrical shape from metal or the like. A screw (not shown) is formed on the outer surface of the sensor body 1, and the pressure sensor 100 can be attached to an attachment hole provided in the engine head or the like by rotating the sensor body 1. Yes. The sensor body 1 is thinned so that the inner diameter thereof is about 4 mm, for example.

  A diaphragm 2 is provided at the tip of the sensor body 1 in the direction of the axis X (center axis of the sensor body 1). The diaphragm 2 is formed in a bottomed cylindrical shape, and the bottom plate portion of the diaphragm 2 serves as a pressure receiving portion that is disposed toward the combustion chamber of the engine. The pressure receiving portion bends according to the combustion pressure in the combustion chamber, so that the combustion pressure in the combustion chamber is transmitted to the pressure detection element 5 described later. Further, the rear end side of the tubular portion of the diaphragm 2 is inserted inside the sensor body 1 and is fixed to the sensor body 1 by welding or the like. The sensor body 1 and the diaphragm 2 constitute a housing 20.

  On the rear end side in contact with the pressure receiving portion of the diaphragm 2, a pressure transmitting member 3 configured to transmit a pressure and a hemispherical member 4 constituting a part of the pressure transmitting member are provided. A pressure detection element 5 is provided on the rear end side of the hemispherical member 4. The hemispherical member 4 is provided to prevent an uneven load on the pressure detecting element 5.

  A pedestal 6 made of an insulating material is provided on the further rear end side of the pressure detection element 5. The pressure detection element 5 is fixed and held on an element mounting surface 60 that is a surface on the tip side orthogonal to the axis X of the pedestal 6. A ring-shaped pedestal retainer 7 is provided around the pedestal 6, and the pedestal 6 is fixed to the rear end side of the cylindrical portion of the diaphragm 2 by welding or the like. It is fixed against.

  The pressure detecting element 5 is composed of a piezoresistive element such as an Si element or an SOI element, and an element configured to output an electric signal corresponding to strain when pressure is applied can be used. When such a pressure detection element 5 is configured, a structure in which an element such as an Si element or an SOI element is bonded to a substrate made of glass, metal, or the like can be used. A piezoresistor is formed on the surface of the pressure detection element 5, and the pressure is detected from a change in resistance value when the pressure detection element 5 is strained and deformed. The pressure detection element 5 is formed in a rectangular shape because of the relationship of being cut out from the silicon wafer by dicing. In addition to this, a piezoelectric element such as PZT or quartz can also be used as the pressure detection element 5.

  On the other hand, the base 6 is made of an insulating material, in this embodiment, alumina which is an insulating ceramic. A plurality of, for example, three electrical wiring layers (not shown) made of a conductive material are formed on the element mounting surface 60 of the base 6 and the side surface 61 of the base 6 orthogonal to the element mounting surface 60. Is formed.

  The electric wiring layer is configured to be capable of wire bonding, and is configured from a conductive metal such as Au or Al. This electrical wiring layer is configured to have a film thickness of several microns or more including the base. The electrical wiring layer having such a film thickness can be formed by a method such as printing, plating, vapor deposition, or sputtering.

  On the rear end side of the pedestal 6, a ceramic substrate 9 extending along the axis X direction is provided with a predetermined distance D (for example, an interval of about 1 to 2 mm) from the rear end of the pedestal 6. As shown in FIGS. 2 and 4, the ceramic substrate 9 is provided with conductor patterns 91, 92, and 93 for extracting the detection signal of the pressure detection element 5 to the rear end side. The conductor pattern 91 is formed to extend in the direction of the axis X at a substantially central portion of one surface of the ceramic substrate 9. The conductor patterns 92 and 93 are formed so as to extend in the axis X direction in parallel with a gap on the other surface of the ceramic substrate 9.

  Thus, by providing the conductor pattern 91 and the conductor patterns 92 and 93 on the two opposing surfaces of the ceramic substrate 9, the two surfaces of the ceramic substrate 9 can be effectively used. Since the width (area) of each conductor pattern can be increased, the electrical connection can be performed well with low resistance.

  The conductor patterns 91, 92, and 93 are configured so as to be capable of wire bonding, and are formed of a conductive metal such as Au or Al. These conductor patterns 91, 92, and 93 are configured to have a film thickness of several microns or more including the base. The conductor patterns 91, 92, and 93 having such a film thickness can be formed by a method such as printing, plating, vapor deposition, or sputtering.

  The conductor patterns 91, 92, 93 provided on the ceramic substrate 9 are the above-described electric wiring layers (not shown) formed on the base 6 with bonding wires 101, 102, 103 as shown in FIG. And are electrically connected. Further, these conductor patterns 91, 92, and 93 hold the metal terminals 111, 112, and 113 in a pressed state, respectively. The conductor patterns 91, 92, and 93 and the metal terminals 111, 112, and 113 are held. Are maintained in an electrically connected state.

  That is, the metal terminals 111, 112, and 113 are formed in a flat plate shape from a conductive metal, and have a structure having elasticity in the plane direction by being bent in a wave shape in the plane direction. And as shown in FIG. 6, it is comprised so that it may contact with the conductor patterns 91, 92, and 93 at two places (P1, P2 shown in FIG. 6) spaced apart in the longitudinal direction.

  Thus, by using the metal terminals 111, 112, and 113 as elastic members, there is no need to provide an elastic member separately from the metal terminals 111, 112, and 113, and the pressure sensor can be reduced in size and cost. Can do. Further, by using the metal terminals 111, 112, 113 imparted with elasticity by bending a flat metal member, the increase in the number of processes is suppressed and the metal terminals 111, 112, 113 can be manufactured, and cost reduction can be achieved. Further, by adopting a configuration in which the metal terminals 111, 112, 113 and the conductor patterns 91, 92, 93 are in contact with each other at two locations, it becomes possible to maintain a better electrical connection state, and more stable output. Obtainable.

  As shown in FIGS. 3 and 5, a terminal holder 10 formed in a cylindrical shape from ceramics or the like is provided around the ceramic substrate 9. The terminal holder 10 is provided with a rectangular substrate insertion hole 120 into which the ceramic substrate 9 is inserted along the axial direction thereof. In addition, metal terminal insertion grooves 121, 122, and 123 for inserting metal terminals 111, 112, and 113 are provided in the board insertion hole 120 so that the surface facing the ceramic substrate 9 is recessed. Yes.

  A small-diameter portion 130 whose outer diameter is smaller than other portions of the terminal holder 10 is provided on the distal end side of the terminal holder 10, and a step portion 131 is formed at the rear end of the small-diameter portion 130. ing. As shown in FIG. 1, the rear end side of the holding member 8 formed in a cylindrical shape is inserted and fixed to the small diameter portion 130, and the front end side of the holding member 8 is inserted into the rear stage side of the base presser 7. By being fixed, the terminal holder 10 is fixed to the base 6 (housing 20). A slight gap of, for example, about 0.1 mm is formed between the outer peripheral surface of the terminal holder 10 and the inner peripheral surface of the sensor body 1.

  The ceramic substrate 9 is inserted into the substrate insertion hole 120 in the terminal holder 10, and metal terminals 111, 112, and 113 are inserted into the metal terminal insertion grooves 121, 122, and 123, respectively. In other words, elastic metal terminals 111, 112, 113 are interposed between the ceramic substrate 9 and the terminal holder 10, and the metal terminals 111, 112, 113 press the ceramic substrate 9 and the terminal holder 10. . Thereby, the ceramic substrate 9 and the metal terminals 111, 112, and 113 are held with respect to the terminal holder 10 and the housing 20 in a displaceable state. Further, the metal terminals 111, 112, and 113 and the conductor patterns 91, 92, and 93 of the ceramic substrate 9 come into contact with each other in an elastically pressed state, so that electrical connection between them is performed. Yes.

  As described above, in this embodiment, the metal terminals 111, 112, 113 are elastically fixed to the base 6 (housing 20) via the holding member 8 between the metal terminals 111, 112, 113 and the housing 20. In this configuration, a ceramic terminal holder 10 is provided. As a result, the metal terminals 111, 112, 113 can be locked to the base 6 (housing 20) with a simple configuration, and electrical insulation between the metal terminals 111, 112, 113 and the housing 20 can be achieved. Can also be done. Note that the holding member 8 may be omitted and the terminal holder 10 may be directly fixed to the base 6.

  As described above, the ceramic substrate 9 and the metal terminals 111, 112, 113 are held with respect to the terminal holder 10 and the housing 20 in a displaceable state, and a predetermined amount is provided between the ceramic substrate 9 and the base 6. The distance D is provided so that the difference in thermal expansion between the metal housing 20 and the ceramic substrate 9 can be absorbed. In this case, it is preferable that the electrical connection between the pedestal 6 and the conductor patterns 91, 92, 93 of the ceramic substrate 9 is also made with some form of deformation such as bonding wires 101, 102, 103.

  As described above, in the pressure sensor 100 for detecting the pressure in the combustion chamber of the engine, the temperature rises to about 300 ° C. due to the influence of heat in the combustion chamber. For this reason, the difference in thermal expansion between members having different coefficients of thermal expansion (for example, a metal member and a ceramic member) becomes considerably large. In the present embodiment, such a difference in thermal expansion can be absorbed by adopting the above-described configuration. Here, the predetermined distance D between the tip of the ceramic substrate 9 and the base 6 is preferably 1 mm or more and 2 mm or less. If this distance is less than 1 mm, the ceramic substrate 9 and the pedestal 6 may come into contact with each other due to a difference in thermal expansion or vibration. Further, if the distance is longer than 2 mm, the lengths of the bonding wires 101, 102, 103 for electrical connection arranged therebetween are increased, and the possibility of disconnection due to vibration is increased.

  The rear end sides of the metal terminals 111, 112, 113 are electrically connected to an electric circuit for processing the detection signal of the pressure detection element 5. Such an electric circuit may be built in the housing 20 of the pressure sensor 100 or may be provided outside the housing 20. When the electric circuit is provided outside the housing 20, an electrode terminal for external connection and the electrode terminal and the metal terminal 111, 112, 113 are electrically connected to the rear end side of the metal terminal 111, 112, 113. A lead wire or the like for connection is provided.

  In the pressure sensor 100 of the present embodiment configured as described above, the pressure detection element 5 is electrically drawn out to the rear end side by the conductor patterns 91, 92, 93 formed on the ceramic substrate 9. Note that the pressure detection element 5 and the conductor patterns 91, 92, 93 include an electric wiring layer (not shown) formed on the base 6 for holding the pressure detection element 5 and the bonding wires 101, 102, 103. Are electrically connected. Therefore, since a member having a long length and a mass like a pin terminal using a hermetic pedestal is not used, the possibility of causing damage due to the influence of vibration can be reduced. In addition, the area for arranging the pin terminals, glass seals, and the like can be reduced as compared with the case where pin terminals using a hermetic pedestal are used, and the diameter of the sensor can be reduced.

  In the pressure sensor 100 configured as described above, when the pressure receiving surface of the diaphragm 2 receives the combustion pressure in the combustion chamber and bends, the pressure is transmitted to the pressure detecting element 5 via the pressure transmitting member 3 and the hemispherical member 4. The pressure detection element 5 generates an electrical signal corresponding to the pressure, and the electrical signal is drawn out to the rear end side through the bonding wires 101, 102, 103, the conductor patterns 91, 92, 93, etc. It is transmitted to the electric circuit to be processed, processed by this electric circuit and output. This pressure detection signal is input to a control device such as an ECU, and changes in combustion pressure in the engine are detected.

  As mentioned above, although the detail of this invention was demonstrated about embodiment, this invention is not limited to the said embodiment, Of course, various deformation | transformation are possible.

  DESCRIPTION OF SYMBOLS 1 ... Sensor body, 2 ... Diaphragm, 20 ... Housing, 3 ... Pressure transmission member, 4 ... Hemispherical member, 5 ... Pressure detection element, 6 ... Base, 60 ... Element mounting surface, 61 ...... Side, 7 ... Pedestal retainer, 8 ... Holding member, 9 ... Ceramic substrate, 10 ... Terminal holder, 91, 92, 93 ... Conductive pattern, 101,102,103 ... Bonding wire, 111, 112, 113 ... Metal terminal, 100 ... Pressure sensor.

Claims (8)

A cylindrical housing extending in the axial direction;
A pressure transmission member housed on the distal end side of the housing;
A pressure detecting element housed in the housing and pressed by the pressure transmission member;
A base made of an insulating material that is housed in the housing and holds the pressure detecting element;
A substrate extending in the axial direction in the housing and having a tip disposed at a predetermined distance from the pedestal;
A plurality of conductor patterns formed on the substrate along the axial direction and electrically connected to the pressure detection element;
A pressure sensor comprising: an elastic member that holds the substrate so as to be displaceable with respect to the housing.   2. The pressure sensor according to claim 1, wherein the conductor pattern is electrically connected to the pressure detection element via a conductor provided on the pedestal and a bonding wire.   The pressure sensor according to claim 1 or 2, wherein the predetermined interval is 1 mm or more and 2 mm or less.   4. The pressure sensor according to claim 1, wherein the elastic member is a metal terminal that is electrically connected to the conductor pattern and electrically leads the pressure detection element to a rear end side. 5. .   The pressure sensor according to claim 4, wherein the metal terminal is configured to be elastic by bending a flat metal member.   The pressure sensor according to claim 4, wherein the metal terminal and the conductor pattern are configured to contact at two or more locations.   A ceramic terminal holder is provided between the metal terminal and the housing, which is fixed to the pedestal directly or via a relay member and to which the metal terminal is elastically contacted. The pressure sensor according to claim 4.   The pressure sensor according to any one of claims 1 to 7, wherein the conductor pattern is formed on each of two opposing surfaces of the substrate.

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