JP4381193B2 - Combustion pressure sensor - Google Patents

Description

  The present invention relates to a combustion pressure sensor that detects the pressure in a combustion chamber of an internal combustion engine.

  Conventionally, as disclosed in, for example, Patent Document 1, a diaphragm that deforms according to pressure, and a rod (punch as a pressure transmission portion that has one end abutting against the diaphragm and is displaced in the axial direction according to the deformation of the diaphragm. ) And a pressure detection element (sensor element) that abuts on the other end of the rod and outputs a detection signal corresponding to the displacement of the rod is known.

In this combustion pressure sensor, one end of a rod is welded to a diaphragm, and the other end having a conical shape is in contact with a pressure detection element. At least the end (contact surface) of the rod in contact with the pressure detection element is formed of a relatively soft material (for example, aluminum, brass, copper, plastic, etc.), and thereby the surface roughness of the rod end and The detection error of the pressure detection element due to non-flatness is reduced.
Japanese Patent No. 3190333

  However, in the case of the combustion pressure sensor, the pressure applied to the diaphragm is relieved by a relatively soft material when transmitted to the pressure detection element via the rod. That is, when a relatively soft material is applied, there is a problem in that pressure cannot be linearly transmitted from the diaphragm to the pressure detecting element, and sensor sensitivity is lowered.

  In the combustion pressure sensor, the rod and the diaphragm are welded in contact with each other in order to enable good and accurate pressure transmission. Therefore, if the contact surfaces of the rod and the diaphragm are not precisely machined (flat and surface roughness is small) and assembled, there will be a problem that, for example, contact with each other will occur, resulting in a large output variation for each sensor.

  On the other hand, in Patent Document 1, a force transmission member having a curved surface (for example, a hemisphere) on the side facing the rod is disposed between the pressure detection element and the rod, and the rod is always in contact with the force transmission member. There has also been proposed a configuration in which the pattern is substantially punctiform. However, since the force transmission member is provided separately from the rod or the pressure detection element, if the force transmission member is accurately positioned with respect to the pressure detection element and not fixed, there is a risk that output variations among sensors will increase. There is.

  In view of the above problems, an object of the present invention is to provide a combustion pressure sensor that can improve sensor sensitivity and reduce output variation.

In order to achieve the above object, the invention described in claim 1 includes a diaphragm that is deformed according to pressure, a rod that is one end abutting the diaphragm and is displaced in the axial direction according to deformation of the diaphragm, and abuts the other end of the rod, a pressure detecting element that outputs a detection signal corresponding to the displacement of the rod, comprises a an invention relates to a combustion pressure sensor for detecting the pressure in the combustion chamber of an internal combustion engine. The rod has a cylindrical shape, and spherical members are integrally provided at both ends of the rod. The rod is in contact with the pressure detection element and the diaphragm with the spherical member as a contact surface, and the inner diameter of the rod is spherical. The spherical member, which is smaller than the outer diameter of the member, is joined by laser welding in a state where the spherical member is in contact with an inner corner formed by an inner wall surface and an end surface of the rod .

Thus, according to the combustion pressure sensor of the present invention , the spherical member is integrally provided at both ends of the rod having a cylindrical shape, and the rod contacts the pressure detection element and the diaphragm with the spherical member as a contact surface . The contact with the pressure detection element and the diaphragm is almost a point contact. Therefore, output variations based on processing accuracy (surface roughness and flatness) and assembly accuracy of the contact surface can be reduced without applying a relatively soft material as in the prior art. According to this, since it is not necessary to apply a relatively soft material, it is possible to improve the sensor sensitivity as compared with the related art. Further, according to the present invention, the inner diameter of the rod is smaller than the outer diameter of the spherical member. Thereby, positioning of a rod and a spherical member can be made easy. Furthermore, in this invention, the spherical member is joined by laser welding in the state which contact | abutted to the inner corner | angular part of the rod. As described above, when the inner diameter of the rod is made smaller than the outer diameter of the spherical member, the position of the contact portion between the rod and the spherical member becomes the end surface of the rod, so the contact portion between the rod and the spherical member is The rod and the spherical member can be easily laser-welded as compared with the configuration in which the position is deeper than the end face of the rod in the axial direction.

As described in claim 2, the outer diameter of the rod is preferably smaller than the outer diameter of the spherical member. According to this, since the distance from the outer periphery of the rod to the contact portion is short as compared with the configuration in which the outer shape of the rod is larger than the outer shape of the spherical member, laser welding can be performed more easily.

According to a third aspect of the present invention, a piezoresistive element having a predetermined resistance value may be adopted as the pressure detecting element, and a bridge circuit may be configured by the piezoresistive element together with the wiring and the electrode.

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

(First embodiment)
FIG. 1 is a cross-sectional view showing a schematic configuration of a combustion pressure sensor 100 in the present embodiment. The combustion pressure sensor in this embodiment is suitable for detecting the combustion pressure of an internal combustion engine such as an automobile engine. In FIG. 1, for convenience, only the characteristic portion is hatched.

  The combustion pressure sensor 100 according to the present embodiment includes a diaphragm 10 that deforms according to pressure, a rod 20 that serves as a pressure transmission unit that is in contact with the diaphragm 10 at one end and is displaced in the axial direction according to deformation of the diaphragm 10, and a rod The sensor chip 30 includes a pressure detection element that abuts against the other end of the rod 20 and outputs a detection signal corresponding to the displacement of the rod 20. Each contact surface at both ends of the rod 20 in contact with the sensor chip 30 and the diaphragm 10 is a spherical surface.

  In FIG. 1, reference numeral 1 denotes a case for holding the rod 20 and the sensor chip 30 therein. In the present embodiment, in the assembled state, the first case 1a, the second case 1b, and the third case 1c. And the fourth case 1d are connected in this order to form the case 1. In addition, as a connection method of each case 1a-1d, well-known techniques, such as a fitting, welding, screw fastening, are applicable.

  The first case 1a is made of metal and has a cylindrical shape with both ends opened. A diaphragm 10 is disposed at an end facing the combustion chamber so as to be deformable when subjected to combustion pressure, and the rod 20 is held through in the hollow so that one end is in contact with the diaphragm 10. . Further, the hollow inner wall surface is provided so as to hold the rod 20 in a slidable state and prevent the rod 20 from swinging.

  Similarly to the first case 1a, the second case 1b is made of metal and has a cylindrical shape with both ends opened. Then, with the rod 20 penetratingly held inside the hollow, one end is connected to the first case 1a and the other end is connected to the third case 1c.

  Similarly to the first case 1a, the third case 1c is made of metal and has a cylindrical shape with both ends opened. Then, in a state where the metal stem 2 is contact-fixed inside the hollow of the third case 1c, one end is connected to the second case 1b and the other end is connected to the fourth case 1d.

  The metal stem 2 has, for example, a cylindrical hollow portion 2a inside by cutting or the like, and a support portion 2b that is a diaphragm surface on one end side of the hollow portion 2a. Then, with the metal stem 2 fixed in the hollow interior of the third case 1c, a part of the rod 20 is disposed in the hollow portion 2a, and the end of the rod 20 contacts the inner surface of the support portion 2b. It is configured. The sensor chip 30 is bonded and fixed to the outer surface of the support portion 2b, and one end of the rod 20 is in contact with the sensor chip 30 including the pressure detection element via the support portion 2b of the metal stem 2.

  The fourth case 1d is made of a heat-resistant resin (for example, polyphenylene sulfide), and the terminal 3 as an external output terminal is provided integrally with the fourth case 1d by insert molding. One end of the terminal 3 is connected to the third case 1c in a state where the terminal 3 is electrically connected to the sensor chip 30. The terminal 3 protrudes from the opening 4 provided on the side of the fourth case 1d that is not connected to the third case 1c, and constitutes a connector together with the fourth case 1d.

  The diaphragm 10 is made of a metal as a constituent material and is configured as a so-called cap diaphragm. Specifically, as shown in FIG. 1, the edge portion 11 is bent, and the edge portion 11 is welded and fixed in a state of being in contact with the outer peripheral surface of the end portion of the first case 1a. Accordingly, the bottom surface 12 of the diaphragm 10 is not in contact with the end surface of the first case 1a facing the combustion chamber, and can be freely deformed when combustion pressure is applied to the diaphragm 10 which is a pressure receiving surface. It has a configuration. In the present embodiment, the central portion of the bottom surface of the diaphragm 10 is recessed in the direction of the rod 20, and the recess 13 is in contact with the end of the rod 20.

  The rod 20 is made of metal, and one end is exposed from the opening of the first case 1a facing the combustion chamber and is in contact with the recess 13 of the diaphragm 10, and the other end is the third case 1c. It is in contact with a sensor chip 30 including a pressure detection element via a support portion 2b of the metal stem 2 fixed inside.

  Here, the present embodiment is characterized in that each contact surface of the rod 20 in contact with the diaphragm 10 and the sensor chip 30 is a spherical surface. Thus, if each contact surface of the rod 20 is a spherical surface, the contact state between the diaphragm 10 and the sensor chip 30 is almost point contact. Therefore, even if a relatively soft material is not applied as in the prior art, it is possible to reduce output variations for each sensor based on processing accuracy (surface roughness and flatness) of the contact surface and assembly accuracy. Further, since it is not necessary to apply a relatively soft material, the pressure can be transmitted linearly from the diaphragm 10 to the sensor chip 30. That is, the sensor sensitivity can be improved as compared with the conventional case. Further, since the end contact surface of the rod 20 is a spherical surface, positioning with respect to the diaphragm 10 and the sensor chip 30 is easy.

  As the rod 20 having such a form, for example, a rod having both ends processed into a spherical shape, or a separately prepared spherical member fixed to each end of the rod 20 and integrated can be applied. In the present embodiment, a cylindrical hollow rod is applied as the rod 20, and steel balls as the spherical member 21 are integrated at both ends by welding. In this case, since the spherical member 21 can be processed separately from the rod 20, it is easy to perform spherical processing. Accordingly, since the accuracy of the spherical surface can be improved, output variations among sensors can be further reduced.

  As a method for integrating the steel ball as the spherical member 21 into the end portion of the rod 20, for example, a welding method for connecting metals can be applied. In the present embodiment, as shown in FIG. 2, a steel ball that is the spherical member 21 is arranged on a hollow support portion 110 a provided at one end of a support member 110 that supports and fixes the spherical member 21, and the support member 110. Is held by the electrode 120. Then, with the rod 20 held between the electrodes 121, the end surface of the rod 20 is pressed against the spherical member 21 while being positioned with respect to the spherical member 21. In particular, in the present embodiment, the rod 20 is a hollow rod, and the inner diameter of the rod 20 is smaller than the outer diameter of the spherical member 21, so that the positioning (axis alignment) of the rod 20 and the spherical member 21 is easy. is there. FIG. 2 is a schematic diagram for explaining a method for connecting the spherical member 21 to the rod 20.

  And in a positioning state, the contact site | part of the rod 20 and the spherical member 21 is collectively joined by spot welding by applying a large voltage between both electrodes 120,121. By carrying out this process at both ends of the rod 20, the rod 20 integrally provided with the spherical member 21 at both ends can be formed. When the spot welding method is applied in this way, all the contact parts can be welded in a short time, so that productivity and processing accuracy can be improved.

  In addition, the sensor chip 30 includes four piezoresistive elements (not shown) having a predetermined resistance value as pressure detecting elements on a semiconductor substrate made of silicon, for example, and a bridge circuit together with wiring and electrodes (both not shown). It is formed so as to constitute. And it is adhesively fixed on the support part 2b of the metal stem 2 on the back side of the surface on which the piezoresistive element is formed.

  Therefore, in the combustion pressure sensor 100 according to the present embodiment, when the combustion pressure is applied to the diaphragm 10 that is the pressure receiving surface, the diaphragm 10 is elastically deformed according to the applied pressure and transmits the pressure to the rod 20 that contacts the diaphragm 10. The rod 20 is displaced in the axial direction. Then, the support portion 2b of the metal stem 2 is elastically deformed according to the displacement, and a resistance value change generated in each piezoresistive element of the sensor chip 30 due to the deformation is output as a voltage value change to detect an applied pressure. It has a configuration.

  Moreover, since the rod 20 as a pressure transmission part is arrange | positioned between the diaphragm 10 which is a pressure receiving surface, and the sensor chip 30, the sensor chip 30 can be kept away from a combustion chamber. That is, the heat load on the sensor chip 30 can be reduced.

  In FIG. 1, reference numerals 5 and 6 denote processing circuit substrates, and bonding wires and springs are provided between the sensor chip 30 and the processing circuit substrates 5 and 6 and between the processing circuit substrates 5 and 6. It is electrically connected by a terminal 7. Reference numeral 6 a denotes an amplifier mounted on the processing circuit board 6, and reference numeral 8 denotes a spacer for electrically connecting the processing circuit board 6 and the terminal 3. Therefore, the output signal of the sensor chip 30 is amplified by the amplifier 6a and then output from the terminal 3 to the outside. Reference numeral 9 denotes an O-ring for waterproofing between the third case 1c and the fourth case 1d.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various modifications can be made.

  The characteristic part of the present invention lies in the structure (spherical surface) of the contact surface of the rod 20 in contact with the diaphragm 10 and the sensor chip 30. Therefore, points other than the above-described structure shown in the present embodiment are not limited to the present embodiment.

  Moreover, in this embodiment, the example in which the steel ball which is the spherical member 21 was integrated with the rod 20 was shown. However, the spherical member 21 can be applied as long as the contact portion with at least the diaphragm 10 and the sensor chip 30 (the support portion 2b of the metal stem 2 in this embodiment) is a spherical surface.

  Moreover, in this embodiment, the spherical member 21 which is the edge part of the rod 20 showed the example of the structure which contacts the sensor chip 30 provided with a pressure detection element via the support part 2b of the metal stem 2. As shown in FIG. However, the spherical surface which is the contact surface of the rod 20 may be in direct contact with the pressure detection element.

  Moreover, in this embodiment, the example which applies a cylindrical hollow rod as the rod 20 was shown. However, the rod 20 is not limited to the above example. For example, a cylindrical rod 20 can be applied. In this case, as shown in FIG. 3, for example, a steel ball as the spherical member 21 is fixed to the fixing portion 131 on the rotatable table 130, and the rod 20 held by the fixing member 140 is positioned and positioned in a spherical shape. Contact the member 21. And in the said contact state, a contact part is laser-welded and joined, rotating the table 130. FIG. By carrying out this process at both ends of the rod 20, the rod 20 integrally provided with the spherical member 21 at both ends can be formed. However, when the rod 20 is not a hollow rod, positioning (axial alignment) between the rod 20 and the spherical member 21 becomes more difficult than when the rod 20 is a hollow rod. Further, in the case of the above method, since it is necessary to rotate the table 130 (the rod 20 and the spherical member 21) or the laser emitting device (not shown) when trying to weld all around, spot welding when a hollow rod is used. As a result, productivity and processing accuracy are reduced. Therefore, the hollow rod shown in this embodiment is preferably applied as the rod 20.

  In addition, an O-ring may be disposed between the first case 1 a, the second case 1 b, and the inner wall surface of the hollow portion 2 a of the metal stem 2 and the rod 20.

It is sectional drawing which shows schematic structure of the combustion pressure sensor 100 in this Embodiment. It is a schematic diagram for demonstrating the connection method of a rod and a spherical member. It is a schematic diagram which shows a modification.

Explanation of symbols

1 ... case 2b ... support part (diaphragm surface)
DESCRIPTION OF SYMBOLS 10 ... Diaphragm 20 ... Rod 21 ... Spherical member 30 ... Sensor chip 100 ... Combustion pressure sensor

Claims (3)

A diaphragm that deforms in response to pressure,
One end abuts against the diaphragm, and a rod as a pressure transmission part that is displaced in the axial direction in accordance with deformation of the diaphragm;
Abuts the other end of the rod, and a pressure detecting element that outputs a detection signal corresponding to the displacement of the rod, the combustion pressure sensor for detecting the pressure in the combustion chamber of an internal combustion engine,
The rod has a cylindrical shape;
A spherical member is integrally provided at both ends of the rod,
The rod is in contact with the pressure detection element and the diaphragm with the spherical member as a contact surface,
The inner diameter of the rod is smaller than the outer diameter of the spherical member,
The combustion pressure sensor , wherein the spherical member is joined by laser welding in a state of being in contact with an inner corner formed by an inner wall surface and an end surface of the rod . The combustion pressure sensor according to claim 1 , wherein an outer diameter of the rod is smaller than an outer diameter of the spherical member . The pressure detecting element is a piezoresistive element having a predetermined resistance value,
The combustion pressure sensor according to claim 1 or 2, wherein the piezoresistive element forms a bridge circuit together with wiring and electrodes .

Images