JP2008082825A - Pressure sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce variations in sensor characteristics by reducing the size of low-melting-point glass to which a sensor chip is pasted. <P>SOLUTION: A metal stem 30 is provided with a recession part 30a, and the low-melting-point glass 51 is arranged in the recession part 30a. The sensor chip 50 is housed in the recession part 30a and joined to the metal stem 30 via the low-melting-point glass 51. Since the amount of movement of the sensor chip 50 is thereby restricted by the size of the low-melting-point glass 51 even if the sensor chip 50 moves within the low-melting-point glass 51, it is possible to reduce the amount of displacement of the sensor chip 50 from a center part of a distortion part 32 more than before. It is therefore possible to reduce variations in sensor characteristics such as sensitivity variations of each sensor. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pressure sensor having a pressure receiving surface for receiving a pressure to be measured, and is applied to a pressure sensor (combustion pressure sensor) that is attached to an engine and used to measure the pressure in a combustion chamber of the engine. Is preferred.

  Conventionally, as a pressure sensor of this type, a pressure receiving diaphragm having a pressure receiving surface for receiving pressure to be measured is provided at one end of the case, and the pressure receiving diaphragm receives pressure to be measured on the pressure receiving surface. When the strain is distorted, the strain is transmitted to the sensor chip on which the strain sensitive element is formed via the pressure transmission member, and the pressure to be measured is detected based on the change in the output of the strain sensitive element. (For example, refer to Patent Document 1).

Such a pressure sensor is attached, for example, by inserting it from one end side of the case, that is, the pressure receiving diaphragm side, into a mounting hole communicating with a combustion chamber provided in an automobile engine. Therefore, the pressure receiving diaphragm is exposed to the combustion chamber side so that the sensor chip on which the strain sensitive element is formed is not exposed to a high temperature, and the strain sensitive element is subjected to the pressure to be measured via the pressure transmission member described above. The structure is such that force can be applied.
JP-A-7-19981

  In the pressure sensor as described above, the inventors first attach a sensor chip to a strained portion of a metal stem provided with a thin strained portion, for example, and the strained portion is distorted by a force transmitted from the pressure transmitting member. Therefore, the sensor chip attached to the strained portion is also distorted, and a structure for detecting the pressure to be measured based on the output change of the strain sensitive element formed on the sensor chip is proposed (for example, Japanese Patent Application No. 2005-2005). 323444).

  FIG. 6 shows a mounting state of the sensor chip J2 on the metal stem J1 in the pressure sensor as described above, FIG. 6A is a cross-sectional view, and FIG. 6B is a top view.

  As shown in FIGS. 6A and 6B, a low melting point glass J4 as an adhesive material is printed on a strained portion J3 to which a force according to pressure is applied, and a sensor chip is formed on the low melting point glass J4. J2 is pasted. However, there is a limit to the printing formation of the low melting point glass J4, and for example, printing cannot be performed at φ 3.1 mm or less. For this reason, the sensor chip J2 having a smaller size moves on the low melting point glass J4 as indicated by an arrow in the figure, and the sensor chip J2 cannot be disposed at the center of the strained portion J3. There arises a problem that the sensor characteristics vary, such as variation.

  In view of the above points, an object of the present invention is to suppress variations in sensor characteristics by reducing the size of a low-melting glass to which a sensor chip is attached.

  In order to achieve the above object, in the present invention, a sensor chip (50) is attached, and a strain portion (32) that is displaced based on a force corresponding to a pressure to be measured applied from a pressure transmission member (60) is provided. A metal stem (30) and an adhesive (51) for attaching the sensor chip (50) to the strained portion (32) of the metal stem (30), and the sensor chip (50) of the metal stem (30). A concave portion (30a) is formed at a place where the concave portion (30a) is disposed, the adhesive (51) is filled in the concave portion (30a), and the sensor chip (50) is accommodated in the concave portion (30a). It is characterized by having.

  Thus, the metal stem (30) is provided with the recess (30a), and the adhesive (51) is disposed in the recess (30a). And a sensor chip (50) is accommodated in a recessed part (30a), and it joins to the metal stem (30) via the adhesive agent (51). For this reason, even if the sensor chip (50) moves in the adhesive (51), the amount of movement is limited by the size of the adhesive (51). The amount of displacement of the sensor chip (50) from the part can be reduced. This makes it possible to suppress variations in sensor characteristics, such as variations in sensitivity for each sensor.

  For example, the concave portion (30a) can be formed by partially denting a portion of the metal stem (30) that becomes the strained portion (32). Moreover, a recessed part (30a) can also be comprised by forming the projection part (30b) surrounding this recessed part (30a) in the surface in which a distortion | strained part (32) is formed among metal stems (30).

  Such a recess (30a) has, for example, a circular upper surface shape when viewed from the upper surface side of the sensor chip (50). In this case, if the sensor chip (50) is configured with a 1.7 mm square, the diameter of the circle formed by the recess (30a) may be 2.4 mm or more and less than 3.1 mm. it can.

  Moreover, as for the recessed part (30a), the upper surface shape when it sees from the upper surface side of a sensor chip (50) may be made into the polygon. In this case, if the sensor chip (50) is configured with a 1.7 mm square, the size of the sensor chip (50) accommodated in each side of the polygon formed by the recess (30a), And the length of the diagonal of this polygon can be made into less than 3.1 mm.

  The depth of the recess (30a) is set deeper than the film thickness of the adhesive (51). In addition, arrangement | positioning of the adhesive agent (51) to a recessed part (30a) can be performed by pouring an adhesive agent (51) in a recessed part (30a). As such an adhesive (51), for example, low-melting glass (51) can be used.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals in the drawings.

(First embodiment)
FIG. 1 is a schematic cross-sectional view showing a mounting structure of the pressure sensor 100 according to the first embodiment of the present invention to the engine 200. The pressure sensor 100 is a combustion for detecting the pressure in the combustion chamber 202 of the engine 200. It is applied as a pressure sensor.

  The pressure sensor 100 generally includes a case 1 and a connector portion 2 connected to the case 1. Further, the engine 200 is provided with a mounting hole 201 that communicates with the combustion chamber 202, and the case 1 of the pressure sensor 100 is inserted into the mounting hole 201 from one end (the lower end in FIG. 1) to It is in a state facing 200 combustion chambers 202.

  The case 1 has a pressure receiving diaphragm 10 as a pressure receiving portion at one end thereof. In this example, the case 1 has a cylindrical shape, and a bottomed cylindrical metal pipe 20, a cylindrical metal stem 30, and a cylindrical housing 40 are sequentially welded, brazed, and bonded from one end side thereof. Etc., which are connected and integrated. The connector portion 2 is connected to the other end portion of the case 1, that is, the housing 40.

  First, the housing 40 is made of a metal such as stainless steel. On the outer surface of the housing 40, a screw portion 41 is formed as an attachment portion for fixing the pressure sensor 100 to the attachment hole 201 of the engine 200. Although the mounting portion may have a configuration other than the screw portion 41, in this embodiment, the screw portion 41 that can be screw-coupled to the mounting hole 201 is used, and the screw between the screw portion 41 and the mounting hole 201 as the screw hole is used. The pressure sensor 100 is attached to the engine 200 by the coupling.

  The metal stem 30 is a member made of metal such as stainless steel processed into a hollow cylindrical shape, and has an opening 31 at the end on the metal pipe 20 side, and a thin distortion portion 32 with the end on the housing 40 side closed. It has become.

  The strained portion 32 of the metal stem 30 is distorted when the pressure P received by the pressure receiving diaphragm 10 is applied by a pressure transmission mechanism described later. The strain portion 32 is provided with a sensor chip 50 having a strain sensitive element that generates a signal based on the strain due to the pressure of the strain portion 32.

  FIG. 2 is a partially enlarged cross-sectional view of the metal stem 30 and the sensor chip 50. As shown in FIGS. 1 and 2, a recess 30a is formed on the end surface of the metal stem 30 on the side where the sensor chip 50 is provided, and the recess 30a is filled with, for example, a low-melting glass 51 as an adhesive. ing. The sensor chip 50 is bonded to the metal stem 30 through the low melting point glass 51.

The recess 30a is formed in a circular shape having a diagonal length of 2.4 mm (1.7 × 2 ^1/2 mm) or more and less than 3.1 mm, for example, of a sensor chip 50 configured by a 1.7 mm square. The size of the sensor chip 50 is accommodated in the recess 30a. The depth of the recess 30a is arbitrary, but is set larger than the film thickness of the low melting point glass 51 so that the end of the recess 30a plays a role as a stopper for restricting the movement of the sensor chip 50.

  The low melting point glass 51 is filled into the recess 30a by pouring. According to such pouring, compared to the case where the low melting point glass 51 is formed by printing, the degree of freedom in supplying the low melting point glass 51 is increased, and the size of the low melting point glass 51 can be reduced. In other words, when the low melting point glass 51 is formed by printing, the printable size is inevitably determined from the limit of the size of the mask used for printing. However, if the low melting point glass 51 is formed by pouring in this manner, there is no such restriction, and therefore the size of the low melting point glass 51 can be freely set. In the present embodiment, since the low-melting glass 51 is poured into the recess 30a, the size of the low-melting glass 51 is the size of the recess 30a, and the low-melting glass 51 is 2.4 mm or more and 3. It is composed of a circle of less than 1 mm.

  FIG. 3 is an enlarged perspective view showing a process of pouring the low melting point glass 51 into the metal stem 30 and attaching the sensor chip 50. As shown in FIG. 3B, the low melting point glass 51 is poured into the recess 30a as shown in FIG. 3B with respect to the metal stem 30 in which the recess 30a is formed as shown in FIG. Then, as shown in FIG. 3C, the sensor chip 50 is disposed so as to be accommodated in the recess 30 a, so that the sensor chip 50 is attached to the metal stem 30 via the low melting point glass 51. Thereby, the structure shown in FIGS. 1 and 2 is obtained.

  The sensor chip 50 is configured, for example, by forming a strain gauge made of a diffusion resistor or the like constituting a strain sensitive element on a semiconductor chip and forming a Wheatstone bridge circuit by this gauge.

  In addition, a tapered seal surface 33 projecting in a direction orthogonal to the peripheral surface is formed on the entire outer periphery of the metal stem 30. Further, the inner surface of the mounting hole 201 facing the seal surface 33 is a tapered seat surface corresponding to the seal surface 33.

  When the pressure sensor 100 is screw-coupled to the engine 200, the seal surface 33 of the case 1 and the inner surface of the mounting hole 201 of the engine 200 are brought into close contact with each other due to the axial force.

  The metal pipe 20 is made of metal such as stainless steel, and is fitted into and fixed to the opening 31 of the metal stem 30. The pressure receiving diaphragm 10 is joined to the end of the metal pipe 20 on the combustion chamber 202 side, that is, one end of the case 1.

  The pressure receiving diaphragm 10 is, for example, a metal circular plate such as stainless steel, and its one surface 11, that is, the one surface 11 facing the combustion chamber 202 receives the pressure P in the combustion chamber 202 as a pressure to be measured. It is a surface. Hereinafter, the one surface 11 is referred to as a pressure receiving surface.

  When the pressure sensor 100 is attached to the engine 200, the pressure P in the combustion chamber 202, which is the atmosphere to be measured, is located at one end of the case 1 as indicated by the white arrow in FIG. The pressure receiving diaphragm 10 is applied to the pressure receiving surface 11 of the pressure receiving diaphragm 10, and the pressure receiving diaphragm 10 is deformed and deformed by the application of the pressure P.

  A pressure transmission member 60 is provided in the space formed by the hollow portion of the metal stem 30 and the hollow portion of the metal pipe 20. The pressure transmission member 60 is made of, for example, a metal such as stainless steel or ceramics, and has a rod shape in this embodiment.

  Each end portion of the pressure transmission member 60 is in contact with the strained portion 32 of the metal stem 30 and the other surface of the pressure receiving diaphragm 10 opposite to the one surface 11 in a state where a load is applied, and the pressure P is The pressure receiving diaphragm 10 is applied to the strained portion 32 of the metal stem 30 through the pressure transmission member 60.

  In the case of the present embodiment, the pressure P received by the pressure receiving surface 11 of the pressure receiving diaphragm 10 is transmitted to the distorted portion 32 of the metal stem 30 by such a pressure detection mechanism, and the above described based on the distortion of the distorted portion 32. A signal is output from the sensor chip 50.

  Further, as shown in FIG. 1, a wiring substrate 42 made of a ceramic substrate or the like is provided inside the housing 40. An IC chip 43 is mounted on the wiring board 42 and is electrically connected to the wiring board 42 by a bonding wire (not shown). The IC chip 43 is formed with a circuit for amplifying and adjusting the output from the sensor chip 50.

  Further, as shown in FIG. 1, in the housing 40, the IC chip 43 and the sensor chip 50 are electrically connected by a wiring member 44 made of a lead wire, a flexible printed circuit board (FPC) or the like.

  The connector portion 2 is connected to the housing 40 via an O-ring 45. The connector portion 2 is made of resin or the like, and a metal terminal 2a is integrated with the connector portion 2 by insert molding or the like. The connector portion 2 is assembled to the housing 40 by caulking or the like with one end side being inserted into the opening of the housing 40, and is fixed integrally with the housing 40.

  In the housing 40, the terminal 2 a of the connector portion 2 is electrically connected to the wiring board 42. The terminal 2a can be electrically connected to an automobile ECU or the like, so that the pressure sensor 100 can exchange signals with the outside.

  The pressure sensor 100 configured in this manner operates by receiving power supply via the terminal 2a. When a signal is output from the sensor chip 50 according to the pressure P received by the pressure receiving diaphragm 10, the signal is transmitted to the IC chip 43 through the wiring member 44. Thus, after the signal processing is performed by the processing circuit or the like provided in the IC chip 43, the signal is output through the wiring board 42 and the terminal 2a.

  According to the pressure sensor 100 configured as described above, the metal stem 30 is provided with the recess 30a, and the low melting point glass 51 is disposed in the recess 30a. The sensor chip 50 is accommodated in the recess 30 a and bonded to the metal stem 30 via the low melting point glass 51. For this reason, even if the sensor chip 50 moves in the low melting point glass 51, the movement amount is limited to the size of the low melting point glass 51. It is possible to reduce the amount of deviation. This makes it possible to suppress variations in sensor characteristics, such as variations in sensitivity for each sensor.

(Second Embodiment)
A second embodiment of the present invention will be described. FIG. 4 is an enlarged perspective view of the metal stem 30, the sensor chip 50, and the low melting point glass 51 in the pressure sensor 100 of the present embodiment.

  In the first embodiment, the concave portion 30a formed in the metal stem 30 has a circular shape on the top surface, but the concave portion 30a may have a quadrangular shape (for example, a square shape) as in the present embodiment. .

(Third embodiment)
A third embodiment of the present invention will be described. FIG. 5 is an enlarged cross-sectional view of the metal stem 30, the sensor chip 50, and the low-melting glass 51 in the pressure sensor 100 of the present embodiment.

  In the first embodiment, the distorted portion 32 that is a thin-walled portion is formed by providing the recessed portion 30a in which the metal stem 30 is partially recessed, but the periphery of the distorted portion 32, specifically, the sensor chip 50 is formed. The concave portion 30a may be formed by forming the protruding portion 30b so as to surround the region in which the film is disposed. Note that the upper surface shape of the protrusion 30b may be a circle as shown in the first embodiment or a rectangle shown in the second embodiment.

(Other embodiments)
In each of the above-described embodiments, the upper surface shape of the recess 30a and the protrusion 30b has been described as an example of a circle or a quadrangle. However, these are only examples, and for example, the upper surface shape may be a polygon having a quadrangle or more. It may be oval or oval. When the upper surface shape of the recess 30a is a polygon, each side of the polygon is sized to accommodate the sensor chip 50, and the diagonal length of the polygon is less than 3.1 mm. Is set as follows.

It is a figure which shows the cross-sectional structure of the pressure sensor in 1st Embodiment of this invention. It is a partial expanded sectional view of the metal stem and sensor chip in the pressure sensor shown in FIG. It is the expansion perspective view which showed pouring of the low melting glass to a metal stem, and the affixing process of a sensor chip. It is an expansion perspective view of the metal stem in the pressure sensor of a 2nd embodiment of the present invention, a sensor chip, and low melting glass. It is an expanded sectional view of the metal stem in the pressure sensor of a 3rd embodiment of the present invention, a sensor chip, and low melting glass. The pressure sensor previously proposed by the present inventors shows the mounting state of the strain sensitive element on the metal stem, wherein (a) is a cross-sectional view and (b) is a top view.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Case, 2 ... Connector part, 10 ... Pressure receiving diaphragm, 11 ... Pressure receiving surface, 20 ... Metal pipe, 30 ... Metal stem, 31 ... Opening part, 32 ... Distortion part, 33 ... Sealing surface, 40 ... Housing, 42 DESCRIPTION OF SYMBOLS ... Wiring board, 43 ... Chip, 44 ... Wiring member, 50 ... Sensor chip, 51 ... Low melting glass, 60 ... Pressure transmission member, 100 ... Pressure sensor, 200 ... Engine, 201 ... Mounting hole, 202 ... Combustion chamber.

Claims (10)

One surface is a pressure receiving surface (11) that receives the pressure to be measured, and a pressure receiving diaphragm (10) that receives and distorts the pressure to be measured on the pressure receiving surface (11),
A pressure transmission member (60) whose one end is in contact with the other surface of the pressure receiving diaphragm (10) opposite to the pressure receiving surface (11);
The pressure transmission member (60) is provided on the other end side opposite to the one end portion, and a force corresponding to the pressure to be measured received by the pressure receiving diaphragm (10) is transmitted through the pressure transmission member (60). A pressure sensor including a sensor chip (50) on which a strain sensitive element that generates a signal corresponding thereto is formed,
A metal stem (30) provided with a strained part (32) to which the sensor chip (50) is attached and which is displaced based on a force corresponding to the measured pressure applied from the pressure transmitting member (60);
An adhesive (51) for attaching the sensor chip (50) to the strained part (32) of the metal stem (30);
A recess (30a) is formed in the metal stem (30) where the sensor chip (50) is disposed, and the recess (30a) is filled with the adhesive (51). The pressure sensor, wherein the sensor chip (50) is housed in the recess (30a). 2. The pressure sensor according to claim 1, wherein the concave portion (30 a) is formed by partially denting a portion of the metal stem (30) that becomes the strained portion (32). The said recessed part (30a) is comprised by forming the projection part (30b) surrounding this recessed part (30a) in the surface in which the said distortion | strained part (32) is formed among the said metal stem (30). The pressure sensor according to claim 1. The pressure sensor according to any one of claims 1 to 3, wherein the concave portion (30a) has a circular upper surface shape when viewed from the upper surface side of the sensor chip (50). The sensor chip (50) is composed of a 1.7 mm square,
5. The pressure sensor according to claim 4, wherein a diameter of the circle formed by the recess (30 a) is not less than 2.4 mm and less than 3.1 mm. The pressure sensor according to any one of claims 1 to 3, wherein the concave portion (30a) has a polygonal upper surface shape when viewed from the upper surface side of the sensor chip (50). . The sensor chip (50) is composed of a 1.7 mm square,
Each side of the polygon formed by the recess (30a) is sized to accommodate the sensor chip (50), and the diagonal length of the polygon is less than 3.1 mm. The pressure sensor according to claim 6. The pressure sensor according to any one of claims 1 to 7, wherein a depth of the recess (30a) is set deeper than a film thickness of the adhesive (51). The pressure sensor according to any one of claims 1 to 8, wherein the adhesive (51) is poured into the recess (30a). The pressure sensor according to any one of claims 1 to 9, wherein the adhesive (51) is a low-melting glass (51).

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