JP2018169255A - Pressure detector and method for manufacturing pressure detector - Google Patents

Abstract

To reduce an error of an output value that is attributable to the thermal expansion of a pressure receiving member that receives pressure.SOLUTION: A pressure detector comprises: an outside front housing 11 and an inside front housing 12 arranged in concentric circular form; a pressure receiving ring 14 for receiving pressure and heat from the outside and attached to the front side of the outside front housing 11 and inside front housing 12; and a pressure transfer ring 15 for transferring the pressure received by the pressure receiving ring 14 to a piezoelectric element group and arranged on the rear side of the pressure receiving ring 14 between the outside front housing 11 and the inside front housing 12. The outside front housing 11 and the pressure receiving ring 14 are connected by a second outside welding part 182 that penetrates the outside front housing 11, and the inside front housing 12 and the pressure receiving ring 14 are connected by a second inside welding part 192 that penetrates the inside front housing 12.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a pressure detection device and a method for manufacturing the pressure detection device.

  As a pressure detection device for detecting the pressure in a combustion chamber of an internal combustion engine or the like, a device using a piezoelectric element that outputs a signal corresponding to the received pressure has been proposed.

  Patent Document 1 discloses a cylindrical front outer casing, a front inner casing that is cylindrical and disposed inside the front outer casing, a rear surface of the front outer casing, and a rear surface of the front inner casing. A rear casing disposed across the front surface, the front surface of the front outer housing, and the front surface of the front inner housing, receiving pressure from the outside, and the front outer housing and the front inner housing A pressure detection device is described that includes a piezoelectric element group that is disposed in an internal space surrounded by a body, a rear housing, and a pressure-receiving ring, and outputs a charge corresponding to the received pressure. And in patent document 1, these are fixed by carrying out laser welding of a front outer housing | casing and a pressure receiving ring over a round, and carrying out laser welding of a front inside housing | casing and a pressure receiving ring over a round.

JP 2013-156114 A

  Here, when heat is applied together with pressure to the pressure receiving member that receives pressure from the outside and transmits the received pressure to the detection element, the pressure receiving member is deformed by thermal expansion, and the pressure transmitted from the pressure receiving member to the detection element is reduced. In other words, there is a situation where the size is increased or decreased compared to the size that should be transmitted. Then, the output value generated by the detection element increases or decreases compared to the size that should be output originally, and an error is included in the pressure obtained based on the output of the signal generation unit. End up.

  An object of the present invention is to reduce an error in an output value caused by thermal expansion of a pressure receiving member that receives pressure.

The pressure detection device of the present invention includes a detection element that outputs a detection signal corresponding to a received pressure, a cylindrical casing, and a pressure that is attached to one end of the casing and receives pressure from the outside. Including a pressure-receiving member that transmits the pressure-receiving member to the detection element, and a joint portion that is provided across the inner and outer sides of the housing over the entire circumference of the pressure-receiving member and joins the pressure-receiving member and the housing. .
In such a pressure detection device, the casing is housed inside, the pressure receiving member is attached to one end side, and a plurality of the other detection elements are disposed between the casing. And further including a housing and another joint portion that is provided across the inner and outer sides of the other housing over the entire circumference of the pressure receiving member and joins the pressure receiving member and the other housing. Can be a feature.
From another viewpoint, the present invention is attached to a detection element that outputs a detection signal corresponding to the received pressure, a cylindrical casing, and one end side of the casing, and applies pressure from the outside. A pressure detecting device comprising a pressure receiving member that receives and transmits the received pressure to the detection element, the pressure receiving member straddling the inside and outside of the casing over the entire circumference of the pressure receiving member, It has the process of welding the said housing | casing.
In such a method for manufacturing a pressure detection device, in the step of welding the pressure receiving member and the casing, welding is performed so as to fill a gap existing between the pressure receiving member and the casing. can do.
In addition, the pressure detection device accommodates the housing inside, the pressure receiving member is attached to one end side, and a plurality of other detection elements arranged in the cylinder between the pressure detection member And further comprising a step of welding the pressure receiving member and the other casing across the inner side and the outer side of the other casing over the entire circumference of the pressure receiving member. it can.
Furthermore, in the step of welding the pressure receiving member and the other casing, welding may be performed so as to fill a gap existing between the pressure receiving member and the other casing.

  According to the present invention, it is possible to reduce an error in an output value caused by thermal expansion of a pressure receiving member that receives pressure.

1 is a schematic configuration diagram of an internal combustion engine according to an embodiment. It is a perspective view of a pressure detection apparatus. It is III-III sectional drawing in FIG. It is IV-IV sectional drawing in FIG. It is an enlarged view of the V section in FIG. It is an enlarged view of the VI section in FIG. It is an enlarged view of the VII part in FIG. (A)-(d) is a figure for demonstrating the manufacturing method of the housing | casing structure of the front side.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
[Configuration of internal combustion engine]
FIG. 1 is a schematic configuration diagram of an internal combustion engine 1 according to the present embodiment.
The internal combustion engine 1 includes a cylinder block 2 having a cylinder 2a, a piston 3 that reciprocates in the cylinder 2a, a cylinder head 4 that is fastened to the cylinder block 2 and forms a combustion chamber C together with the cylinder 2a, the piston 3, and the like. It has. The internal combustion engine 1 is attached to the cylinder head 4 and ignites the fuel to explode the air-fuel mixture in the combustion chamber C. The internal combustion engine 1 is attached to the cylinder head 4 and injects fuel into the combustion chamber C. In addition, an injector unit 6 for detecting the pressure in the combustion chamber C is further provided. The cylinder head 4 is provided with two communication holes for communicating the combustion chamber C and the outside. One of the communication holes is a spark plug 5 and the other communication hole is an injector unit 6. It is attached in a penetrating state.

[Injector unit configuration]
The injector unit 6 includes a fuel injection device 7 that injects fuel into the combustion chamber C, and a pressure detection device 8 that is attached to the fuel injection device 7 and detects the pressure in the combustion chamber C. Here, the fuel injection device 7 includes a main body 71 disposed outside the combustion chamber C, and a columnar tip 72 extending outward from the main body 71. On the other hand, the pressure detection device 8 is attached to the distal end side of the distal end portion 72 of the fuel injection device 7. The part attached to the front end side in the front-end | tip part 72 of the fuel-injection apparatus 7 among the pressure detection apparatuses 8 is provided with the cylindrical shape which has a through-hole so that it may mention later. For this reason, the tip of the tip portion 72 of the fuel injection device 7, that is, the formation portion of the nozzle for injecting the fuel, is exposed in the combustion chamber C through the through hole. Note that a groove 72 a is formed along the longitudinal direction at the tip 72 of the fuel injection device 7.

[Configuration of pressure detector]
Next, the configuration of the pressure detection device 8 in the injector unit 6 will be described.
FIG. 2 is a perspective view of the pressure detection device 8. 3 is a cross-sectional view taken along the line III-III in FIG. 4 is a cross-sectional view taken along the line IV-IV in FIG. Furthermore, FIG. 5 is an enlarged view of a portion V in FIG. FIG. 6 is an enlarged view of a portion VI in FIG. Further, FIG. 7 is an enlarged view of a VII portion in FIG. In the following description, when the injector unit 6 is configured together with the fuel injection device 7, the side of the pressure detection device 8 facing the combustion chamber C (the back side in FIG. 2 and the bottom side in FIG. 3) The side facing the opposite side to the combustion chamber C (front side in FIG. 2, upper side in FIG. 3) is referred to as “back side”.

The pressure detection device 8 includes a sensor unit 10 having a function of detecting pressure, and a transmission unit 50 that transmits the pressure detected by the sensor unit 10 to the outside as an electric signal.
Among these, the sensor unit 10 has a cylindrical shape as a whole as described above, penetrates from the front side to the back side, and accommodates the front end side of the front end portion 72 in the fuel injection device 7 shown in FIG. A portion 10a (through hole) is provided. In the following description, the center line direction (shown by a one-dot chain line in FIG. 3) of the opening 10a having a cylindrical shape is simply referred to as a center line direction.
On the other hand, the transmission unit 50 extends along the center line direction, the end on the front side is accommodated in the sensor unit 10, and the other end on the back side is rearward from the end surface on the back side in the sensor unit 10. A transmission wire 51 that protrudes toward the sensor unit 10 and an attachment mechanism for attaching the transmission wire 51 to the sensor unit 10 are provided.

[Configuration of sensor unit]
First, the configuration of the sensor unit 10 will be described.
The sensor unit 10 includes a front outer casing 11 having a cylindrical shape, and a front inner casing having a cylindrical shape and disposed concentrically with the front outer casing 11 inside the front outer casing 11. 12. The sensor unit 10 has a cylindrical shape, a rear case 13 attached to the back side of the front outer case 11 and the front inner case 12, an annular shape, and the front outer case 11 and A pressure receiving ring 14 attached to the front side of the front inner housing 12 and receiving pressure from the outside is provided. In the sensor unit 10, a cylindrical inner space 10 b is formed in a portion surrounded by the front outer casing 11, the front inner casing 12, the rear casing 13, and the pressure receiving ring 14. The sensor unit 10 includes a pressure transmission ring 15 that has an annular shape in the internal space 10b and is disposed on the back side of the pressure receiving ring 14, and further transmits the pressure from the pressure receiving ring 14 to the back side. Yes. The sensor unit 10 is disposed between the back surface side of the pressure transmission ring 15 and the front surface side end surface of the rear housing 13 in the internal space 10b, and the pressure received from the pressure transmission ring 15 is an example of a detection signal. The piezoelectric element group 16 is converted to an electrical signal (a charge signal in this example). Here, the piezoelectric element group 16 in this example is provided with a first piezoelectric element 161, a second piezoelectric element 162, and a third piezoelectric element 163 provided at intervals of 120 ° in the circumferential direction on the back side of the pressure transmission ring 15. Including. In addition, the sensor unit 10 has a cylindrical shape as a whole and an L-shaped cross section, and includes an inner ring 17 attached to the inner peripheral surface on the front side of the front inner housing 12. Further, the sensor unit 10 includes an outer welded portion 18 formed by welding the front outer casing 11 and the pressure receiving ring 14 on the front side of the front outer casing 11, and a front inner side on the front side of the front inner casing 12. An inner welded portion 19 formed by welding the housing 12, the pressure receiving ring 14, and the inner ring 17 is provided.

Hereinafter, the constituent members of the sensor unit 10 will be described in detail.
(Front outer casing)
The front outer casing 11 as an example of another casing has a cylindrical shape as described above, and an outer projecting portion 14c (details are given in detail) on the inner side of the front end portion of the front casing. A notch for fitting a rear side end portion (described later) is formed (see also FIG. 8A described later).

(Front inner casing)
The front inner casing 12 as an example of the casing has a cylindrical shape as described above, and the outer diameter thereof is smaller than the inner diameter of the front outer casing 11 described above. Further, a notch for fitting a rear side end portion of an inner projecting portion 14d (details will be described later) of the pressure receiving ring 14 is formed outside the end portion on the front side of the front inner case 12, and the front inner case is formed. 12 is formed with a notch for fitting the inside of the front side end portion of the rear housing 13 (see also FIG. 8A described later).

(Rear housing)
The rear casing 13 is provided on the rear casing main body 13a having a cylindrical shape as a whole as described above, and an end surface on the front side of the rear casing main body 13a, and functions as a ground electrode of the piezoelectric element group 16. And a ground electrode layer 13b. Here, the rear casing body 13a includes a front stage 131 that is set to have the same outer diameter as the inner diameter of the front outer casing 11 on the front side, and an outer diameter of the front outer casing 11 on the rear side of the front stage 131. It has a middle step portion 132 set to substantially the same outer diameter, and a rear step portion 133 set to the same outer diameter as the inner diameter of the front outer casing 11 on the back side of the middle step portion 132. The ground electrode layer 13b described above is formed on the front side end face of the front stage 131 of the rear casing body 13a over substantially the entire circumference. In addition, a recess for fitting the outside of the rear end of the front outer casing 11 is formed on the outer side of the front end of the front stage 131 of the rear casing main body 13a by the middle stage 132. On the inner side of the front side of the front stage portion 131 of the body main body 13a, a protrusion is provided for fitting into a notch provided on the outer side of the rear side of the front inner housing 12.

  Furthermore, the front stage part 131 and the middle stage part 132 of the rear casing body 13a are each formed with one front side through-hole 13c that penetrates the rear casing body 13a along the center line direction, and the rear casing body 13a. The rear stage portion 133 is formed with one rear side through hole 13d penetrating the rear casing body 13a along the center line direction. Here, the front side through-hole 13c and the rear side through-hole 13d are provided at positions where they overlap each other when viewed from the center line direction, and the front-side through hole 13c includes the pressure transmission ring 15 and the piezoelectric element described above. The internal space 10b for accommodating the element group 16 is connected. A rectangular parallelepiped recess 13e is provided on the outer peripheral surface of the rear stage portion 133 in the rear casing body 13a between the formation portion of the front side through hole 13c and the formation portion of the rear side through hole 13d.

  The ground electrode layer 13b provided in the rear housing 13 is configured by laminating a single layer or a plurality of layers of a highly conductive metal thin film on the rear housing body 13a.

(About the housing)
Here, the front outer casing 11, the front inner casing 12, and the rear casing 13 (rear casing main body 13a) are located at a position facing the combustion chamber C or a position close to the combustion chamber C where the temperature can be high. Therefore, it is desirable to manufacture using a material that can withstand an operating temperature environment of at least −40 ° C. to 350 ° C. In this example, as will be described later, since the rear casing 13 (rear casing main body 13a) is used as a grounding target for the piezoelectric element group 16 and the transmission electric wire 51 constituting the sensor unit 10, at least the rear casing is used. The main body 13a is desirably manufactured using a conductive material. Specifically, the front outer casing 11, the front inner casing 12, and the rear casing 13 (rear casing main body 13a) are made of a stainless steel material having high heat resistance and conductivity, such as JIS standard SUS630, SUS316, It may be configured using SUS430 or the like.

  Then, the end of the rear side of the front outer casing 11 is laser-welded over the entire circumference in a state of being fitted into a notch provided on the outer end of the front side of the rear casing main body 13a. It is fixed. Further, the end on the back side of the front inner housing 12 is subjected to laser welding over one round in a state in which a protrusion provided on the inner side of the front side of the rear housing body 13a is fitted. It is fixed.

(Pressure ring)
The pressure receiving ring 14 as an example of a pressure receiving member is provided so as to close an annular gap formed on the front side by the front outer casing 11 and the front inner casing 12 arranged concentrically. The pressure receiving ring 14 has an annular shape and is exposed to the outside, that is, the combustion chamber C (see FIG. 1) side to receive pressure from the outside, and the pressure receiving portion 14a receives the pressure on the back side of the pressure receiving portion 14a. A transmission portion 14b that transmits the pressure to the pressure transmission ring 15, an outer protrusion 14c that has an annular shape and protrudes from the outer peripheral edge of the pressure receiving portion 14a to the back side, and an annular shape that is inward of the pressure receiving portion 14a. It has the inner protrusion part 14d which protrudes from the periphery to the back side (refer also to Fig.8 (a) mentioned later). 3 and 7 show a state after the outer welded portion 18 and the inner welded portion 19 are formed by welding, the pressure receiving portion 14a and the outer protruding portion 14c are connected to the outer welded portion 18 (more specifically, Specifically, the pressure receiving portion 14a and the inner protruding portion 14d are divided by the inner welded portion 19 (more specifically, the second inner welded portion 192 described later). Has been.

  And the transmission part 14b provided in the pressure receiving ring 14 is positioned with respect to both of the inner peripheral surface of the front outer housing 11 and the outer peripheral surface of the front inner housing 12 so as not to contact both. Note that the material constituting the pressure receiving ring 14 is made of an alloy having high elasticity and excellent durability, heat resistance, and corrosion resistance in consideration of being exposed to the combustion chamber C at high temperature and high pressure. For example, SUS630, SUS316, SUS430, SUH660, etc. can be used. However, considering that the front outer casing 11 and the pressure receiving ring 14 are fixed by the outer welded portion 18 and the front inner casing 12 and the pressure receiving ring 14 are fixed by the inner welded portion 19, these front outer casing 11 The front inner casing 12 and the pressure receiving ring 14 are preferably made of the same material.

(Pressure transmission ring)
The pressure transmission ring 15 is provided on the pressure transmission ring main body 15a having an annular shape as described above, and the end surface on the back side of the pressure transmission ring main body 15a, and for outputting a charge signal from the piezoelectric element group 16. And an output electrode layer 15b functioning as an output electrode. And the output electrode layer 15b is formed in the end surface of the back surface side in the pressure transmission ring main body 15a over the circumference.

  Here, the cross section of the pressure transmission ring main body 15 a is rectangular, the outer diameter of the pressure transmission ring main body 15 a is smaller than the inner diameter of the front outer casing 11, and the inner diameter of the pressure transmission ring main body 15 a is that of the front inner casing 12. It is larger than the outer diameter. In this example, the pressure transmission ring body 15a is made of a ceramic material such as alumina having heat resistance and insulation.

  The output electrode layer 15b provided on the pressure transmission ring 15 is configured by laminating a single conductive metal thin film or a plurality of layers on the pressure transmission ring main body 15a.

(Piezoelectric element group)
As described above, the piezoelectric element group 16 includes the first piezoelectric element 161, the second piezoelectric element 162, and the third piezoelectric element 163. Here, the first piezoelectric element 161 to the third piezoelectric element 163 have a common configuration, and each is formed on a piezoelectric body 16a processed into a rectangular parallelepiped shape and an end face on the front surface side of the piezoelectric body 16a. A front-side electrode 16b and a rear-side electrode 16c formed on an end surface on the back side of the piezoelectric body 16a are provided.

  Each of the first to third piezoelectric elements 161 to 163, each of which is an example of a detection element, has a piezoelectric body 16a that exhibits a piezoelectric action of the piezoelectric longitudinal effect. The piezoelectric longitudinal effect refers to an action in which charges are generated on the surface of the piezoelectric body 16a in the charge generation axis direction when an external force is applied to the stress application axis in the same direction as the charge generation axis of the piezoelectric body 16a. The first to third piezoelectric elements 161 to 163 according to the present embodiment are housed in the internal space 10b so that the center line direction is the direction of the stress application axis.

  Next, the case where the piezoelectric body 16a which shows a piezoelectric lateral effect is utilized for the 1st piezoelectric element 161-the 3rd piezoelectric element 163 is illustrated. The piezoelectric lateral effect is an action in which charges are generated on the surface of the piezoelectric body 16a in the direction of the charge generation axis when an external force is applied to the stress application axis at a position orthogonal to the charge generation axis of the piezoelectric body 16a. A plurality of piezoelectric bodies 16a that are thinly formed in a thin plate shape may be stacked, and by stacking in this way, charges generated in the piezoelectric body 16a can be efficiently collected to increase the sensitivity of the sensor. . Examples of the piezoelectric body 16a include use of a langasite crystal (a langasite, langagate, langanite, LTGA) having a piezoelectric longitudinal effect and a piezoelectric transverse effect, crystal, gallium phosphate, or the like. In the first piezoelectric element 161 to the third piezoelectric element 163 of the present embodiment, a langasite single crystal is used as the piezoelectric body 16a.

  On the other hand, the front-side electrode 16b and the rear-side electrode 16c are configured by laminating a single layer or a plurality of layers of a highly conductive metal thin film on the front end face and the rear end face of the piezoelectric body 16a.

  In each of the first piezoelectric element 161 to the third piezoelectric element 163, each front side electrode 16b is in contact with the output electrode layer 15b provided on the pressure transmission ring 15, and each rear side electrode 16c is connected to the rear casing 13. It contacts with the provided ground electrode layer 13b. In this example, the first piezoelectric element 161 to the third piezoelectric element 163 are joined to the output electrode layer 15b via the front side electrodes 16b. As a result, the pressure transmission ring 15 and the piezoelectric element group 16 are joined. Are integrated.

(Inner ring)
The inner ring 17 has a cylindrical shape as described above, and its cross section has an L shape. When the injector unit 6 is configured by attaching the pressure detection device 8 to the fuel injection device 7, the inner ring 17 and the opening 10 a of the sensor unit 10 in the pressure detection device 8 and the tip portion of the fuel injection device 7 are provided. 72 is filled in with the gap between the two.

  The material constituting the inner ring 17 is made of an alloy having high elasticity and excellent durability, heat resistance, and corrosion resistance in consideration of being exposed to the combustion chamber C at a high temperature and a high pressure. For example, SUS630, SUS316, SUS430, SUH660, etc. can be used.

(Outside weld)
The outer welded portion 18 includes a first outer welded portion 181 formed by welding a facing portion between an end surface on the front surface side of the front outer casing 11 and an end surface on the rear surface side of the outer protruding portion 14c of the pressure receiving ring 14; It has the 2nd outer side welding part 182 formed by welding the front outer side housing | casing 11 and the pressure receiving ring 14 in the front side rather than the outer side welding part 181. FIG. Here, the second outer welded portion 182 as an example of another joint portion includes a front surface side of the front outer casing 11, and an outer end portion of the pressure receiving portion 14a and a front surface side of the outer protruding portion 14c in the pressure receiving ring 14. It is constructed by welding. In this example, the second outer welded portion 182 straddles (penetrates) the inner side and the outer side of the front outer casing 11. And the outer side welding part 18 in this Embodiment is formed by the laser welding which fuse | melts and solidifies a base material by irradiating a laser beam, without using a welding rod (wire) etc. FIG. For this reason, the outer welded portion 18 is formed by the constituent material of the front outer casing 11 and the constituent material of the pressure receiving ring 14.

(Inner weld)
The inner welded portion 19 includes a first inner welded portion 191 formed by welding portions facing the front end surface of the front inner casing 12 and the rear end surface of the inner projecting portion 14d of the pressure receiving ring 14; The front inner housing 12, the pressure receiving ring 14, and the inner ring 17 are welded to the front inner side of the inner welded portion 191, and the second inner welded portion 192 is provided. Here, the second inner welded portion 192 as an example of the joint portion includes a front side of the front inner casing 12, an inner end portion of the pressure receiving portion 14a and a front side of the inner protruding portion 14d of the pressure receiving ring 14, and an inner ring. The front side of 17 is welded. In this example, the second inner welded portion 192 extends (penetrates) between the inner side and the outer side of the front inner casing 12. And the inner side welding part 19 in this Embodiment is formed by the laser welding which fuse | melts and solidifies a base material by irradiating a laser beam, without using a welding rod (wire) etc. FIG. For this reason, the inner welded portion 19 is formed by the constituent material of the front outer casing 11, the constituent material of the pressure receiving ring 14, and the constituent material of the inner ring 17.

[Configuration of transmission unit]
Next, the configuration of the transmission unit 50 will be described.
The transmission unit 50 is provided on the front side of the transmission wire 51 that transmits a charge signal from the sensor unit 10 toward the fuel injection device 7 (see FIG. 1), and the pressure transmission ring 15 of the sensor unit 10. The connection terminal 52 electrically connected to the output electrode layer 15b provided on the front surface of the transmission wire 51 and the rear surface of the connection terminal 52 from the transmission wire 51 are electrically connected. And a connection pipe 53 to be connected. The transmission unit 50 includes a protective tube 54 that protects the outer peripheral surface of the connection pipe 53, and a positioning tube 55 that covers the outer peripheral surface of the connection terminal 52 on the front side of the protective tube 54 and is used for positioning the connection terminal 52. The coil spring 56 is wound around the outer peripheral surface of the connection terminal 52 on the front side of the positioning tube 55 and pushes the connection terminal 52 toward the front side. Further, the transmission unit 50 is attached to the outer peripheral surface of the connection terminal 52 on the front side of the protective tube 54 and on the back side of the positioning tube 55, and is provided on the front side provided in the middle stage 132 of the rear casing body 13a. By contacting the inner wall surface of the through-hole 13c, the sealing portion 57 that seals the front side of the connection terminal 52 from the outside, and the outer peripheral surface of the transmission wire 51 is attached to the back side of the protective tube 54, and A fixing ring 58 that fixes the transmission wire 51 to the sensor unit 10 by contacting the inner wall surface of the rear side through-hole 13d provided in the rear stage portion 133 of the rear casing body 13a is provided.

Hereinafter, the constituent members of the transmission unit 50 will be described in detail.
(Transmission wire)
The transmission wire 51 is constituted by an insulated wire having a so-called coaxial structure. More specifically, the transmission wire 51 has a conductor part 51a made of a stranded wire of a metal wire, a resin insulating layer 51b made of an insulating resin and covering the outer periphery of the conductor part 51a, and semiconductive. And a resin semiconductive layer 51c made of resin and covering the outer periphery of the resin insulating layer 51b.

  When the pressure detection device 8 is mounted on the fuel injection device 7 to configure the injector unit 6, the portion of the transmission wire 51 that is exposed to the outside is the groove 72 a provided in the distal end portion 72 of the fuel injection device 7. Housed inside. Therefore, in the injector unit 6, the transmission wire 51 provided in the pressure detection device 8 has a configuration that is difficult to jump out of the injector unit 6.

(Connecting terminal)
The connection terminal 52 is composed of a metal rod-like body having heat resistance and conductivity, and a butting portion 52a that abuts against the output electrode layer 15b provided on the pressure transmission ring 15 by being located on the foremost side, The columnar part 52b located on the back side of the abutting part 52a and the connection part 52c located on the back side of the columnar part 52b are integrally configured. In the connection terminal 52, the outer diameter of the abutting portion 52a is smaller than the length of the inner space 10b in the radial direction, the outer diameter of the columnar portion 52b is smaller than the outer diameter of the abutting portion 52a, and the connecting portion 52c. Is smaller than the outer diameter of the columnar portion 52b.

(Connection pipe)
The connection pipe 53 is formed of a metal cylindrical body having heat resistance and conductivity, and the inner diameter of the through hole provided in the connection pipe 53 is the outer diameter of the conductor portion 51 a in the transmission wire 51 and the connection terminal 52. Is larger than the outer diameter of the connecting portion 52c. Further, the connection pipe 53 has an end portion on the front surface side of the conductor portion 51a in the transmission wire 51 from the back surface side of the through hole, and an end portion on the back surface side of the connection portion 52c in the connection terminal 52 from the front surface side of the through hole. Each is inserted. In this state, the connection pipe 53 is caulked from the outer peripheral surface side, whereby the connection pipe 53 electrically connects and fixes the conductor portion 51 a and the connection terminal 52.

(Protection tube)
The protective tube 54 is formed of a cylindrical body made of PFA, and all the outer peripheral surfaces of the connection pipe 53, the outer peripheral surface of the rear end side end of the columnar portion 52 b in the connection terminal 52, and the resin insulation in the transmission wire 51. The outer peripheral surface of the front side end of the layer 51b is covered.

(Positioning tube)
The positioning tube 55 is composed of a cylindrical body made of alumina ceramic, and includes a front side cylindrical portion 55a located on the front side and a rear side cylindrical portion 55b located on the back side of the front side cylindrical portion 55a. Have. Here, the outer diameter of the front side cylindrical part 55a in the positioning tube 55 is larger than the outer diameter of the rear side cylindrical part 55b, and smaller than the length of the inner space 10b in the radial direction. Further, the inner diameter of the positioning tube 55 is larger than the outer diameter of the columnar portion 52 b in the connection terminal 52.

(coil spring)
The coil spring 56 is disposed between the rear-side end surface of the abutting portion 52 a of the connection terminal 52 and the front-side end surface of the front-side tubular portion 55 a of the positioning tube 55. Here, the coil spring 56 is made of a heat-resistant metal, and the end portion on the front side abuts against the rear side end surface of the abutting portion 52 a of the connection terminal 52, and the end portion on the back side is the front of the positioning tube 55. It abuts against the front end face of the side tubular portion 55a. The inner diameter of the coil spring 56 is substantially equal to the outer diameter of the columnar portion 52 b in the connection terminal 52.

(Sealing part)
The sealing portion 57 includes a front-side O-ring 57a located on the rear side of the rear-side cylindrical portion 55b in the positioning tube 55, and a rear-side O located on the rear side of the front-side O-ring 57a and the front side of the protective tube 54. A ring 57b. Here, both the front O-ring 57a and the rear O-ring 57b are composed of PFA. Here, the outer diameters of the front-side O-ring 57a and the rear-side O-ring 57b are set to be larger than the inner diameters of the front-side through holes 13c provided in the rear housing body 13a, and the front-side O-ring 57a and the rear-side O-ring 57b. The inner diameter of the ring 57 b is set smaller than the outer diameter of the columnar part 52 b in the connection terminal 52.

(Fixing ring)
The fixing ring 58 is composed of a heat-resistant metal cylindrical body, and a reverse taper process is applied to an end portion on the front side thereof. The outer diameter of the fixing ring 58 is set to be slightly larger than the inner diameter of the rear side through hole 13d provided in the rear housing 13, and the inner diameter of the fixing ring 58 is the outer diameter (resin semiconductive) of the transmission wire 51. It is set to be approximately equal to or slightly smaller than the outer diameter including the layer 51c.

[Electrical connection structure in pressure detector]
Here, an electrical connection structure in the pressure detection device 8 of the present embodiment will be described.
First, the end face on the back side of each piezoelectric body 16a provided on the front side of the first piezoelectric element 161 to the third piezoelectric element 163 constituting the piezoelectric element group 16 is provided via a rear side electrode 16c provided on each. , And electrically connected to the ground electrode layer 13b provided in the rear housing 13. Here, the rear casing body 13a and the ground electrode layer 13b constituting the rear casing 13 are in an electrically connected state.

  On the other hand, the front end surface of each piezoelectric body 16a provided on the front side of the first piezoelectric element 161 to the third piezoelectric element 163 constituting the piezoelectric element group 16 is provided with the front side electrode 16b provided on the front side electrode 16b. And is electrically connected to the output electrode layer 15b provided on the pressure transmission ring 15. Here, the pressure transmission ring main body 15a and the output electrode layer 15b constituting the pressure transmission ring 15 are in an electrically insulated state. Further, the output electrode layer 15b is electrically connected to the connection terminal 52 via the abutting portion 52a. Furthermore, the connection terminal 52 is electrically connected to the conductor portion 51a in the transmission wire 51 through the connection pipe 53 from the connection portion 52c. The charge signal transmission path from the connection terminal 52 to the conductor portion 51a through the connection pipe 53 is an internal space 10b, a positioning tube 55, a sealing portion 57, and a protection tube 54 each made of an insulator. The front outer casing 11, the front inner casing 12, and the rear casing 13 (more specifically, the rear casing 13) are made of metal and electrically connected to each other by the resin insulating layer 51b of the transmission wire 51. It is electrically insulated from the housing body 13a). Since the position of the front side of the connection terminal 52 including the connection portion 52 c is regulated by the positioning tube 55, the connection terminal 52 is connected to the outer peripheral surface of the front outer housing 11 and the inner surface of the front inner housing 12. It does not touch the peripheral surface.

  Moreover, in the transmission wire 51, the conductor part 51a and the resin semiconductive layer 51c are electrically insulated by the resin insulating layer 51b. The resin semiconductive layer 51 c constituting the transmission wire 51 is electrically connected to the rear casing body 13 a in the rear casing 13 through a metal fixing ring 58.

  When the injector unit 6 configured using the fuel injection device 7 and the pressure detection device 8 is attached to the cylinder head 4 shown in FIG. 1, at least the front outer housing 11 is electrically connected to the metal cylinder head 4. Connected to. Since this cylinder head 4 is in an electrically grounded state, in the pressure detection device 8, the first piezoelectric elements 161 to 161 are disposed via the rear casing 13 (rear casing body 13 a) and the front outer casing 11. The front side of each of the third piezoelectric elements 163 and the resin semiconductive layer 51c of the transmission wire 51 are grounded.

[Pressure detection operation by pressure detector]
Next, the pressure detection operation of the pressure detection device 8 in the injector unit 6 attached to the internal combustion engine 1 will be described.

  The fluctuation of the combustion pressure generated in the combustion chamber C acts on the piezoelectric element group 16 sandwiched between the rear casing 13 and the pressure transmission ring 15 via the pressure receiving ring 14 and the pressure transmission ring 15. At this time, the vibration generated along with the fluctuation of the combustion pressure includes a frequency component of about several kHz at the maximum. In this example, the piezoelectric element group 16 includes a first piezoelectric element 161 to a third piezoelectric element 163 arranged at equal intervals in the circumferential direction, and each of the first piezoelectric element 161 to the third piezoelectric element 163 includes Electric charges are generated according to the fluctuation of the combustion pressure. The electric charges generated in the piezoelectric bodies 16a constituting the first piezoelectric element 161 to the third piezoelectric element 163 are transferred from the front end face of each piezoelectric body 16a through the front side electrodes 16b to the pressure transmission ring 15. Is transmitted to the output electrode layer 15b provided on the substrate. Thereafter, the charge signal transmitted to the output electrode layer 15b is transmitted from the connection terminal 52 to the conductor portion 51a of the transmission wire 51 via the connection pipe 53, and further, fuel injection is performed as a charge signal via the conductor portion 51a. Is transmitted to the device 7. The charge signal transmitted to the fuel injection device 7 is further transmitted to a control device (not shown) that controls the operation of the internal combustion engine 1.

  At this time, the end faces on the back side of the first piezoelectric element 161 to the third piezoelectric element 163 constituting the piezoelectric element group 16 are the rear casing 13 (the ground electrode layer 13b and the rear casing main body 13a) and the front outer casing 11. Are connected to the cylinder head 4 to suppress the mixing of noise with respect to the charges output from the first to third piezoelectric elements 161 to 163. At this time, the resin semiconductive layer 51 c in the transmission wire 51 is electrically connected to the cylinder head 4 via the fixing ring 58, the rear housing 13 (rear housing body 13 a), and the front outer housing 11. Thus, the noise is prevented from being mixed into the charge signal transmitted by the conductor 51a.

[Manufacturing method of front case structure]
Now, a method for manufacturing the front side housing structure of the pressure detection device 8 will be described. Here, the “front-side housing structure” in the present embodiment is an integrated body obtained by joining the front outer housing 11, the front inner housing 12, the pressure receiving ring 14, and the inner ring 17 by welding. Say.
FIG. 8 is a diagram for explaining a method of manufacturing the front side casing structure.

(Pressure ring installation process)
FIG. 8A is a diagram for explaining a pressure receiving ring mounting step that is executed first.
In the pressure receiving ring mounting step, first, the front outer casing 11 and the front inner casing 12 are arranged concentrically (the front outer casing 11 outside the front inner casing 12). At this time, a notch for the pressure receiving ring 14 (outer protruding portion 14c) provided in the front outer casing 11, and a notch for the pressure receiving ring 14 (inner protruding portion 14d) provided in the front inner casing 12. Are arranged facing upward. In this state, the front outer casing 11 and the front inner casing 12 are fixed with a jig (not shown).

  Next, the pressure receiving ring 14 is lowered from above the front outer casing 11 and the front inner casing 12 with the transmitting portion 14b, the outer protruding portion 14c, and the inner protruding portion 14d facing downward. Then, the outer protrusion 14c of the pressure receiving ring 14 is fitted into the notch positioned above the front outer casing 11, and the inner protrusion 14d of the pressure receiving ring 14 is inserted into the notch positioned above the front inner casing 12. Is inserted. As a result, the transmission portion 14 b of the pressure receiving ring 14 is disposed inside the front outer casing 11 and outside the front inner casing 12. At this time, the transmission portion 14 b of the pressure receiving ring 14 does not contact the inner peripheral surface of the front outer housing 11 and the outer peripheral surface of the front inner housing 12.

(First welding process)
FIG. 8B is a diagram for explaining a first welding process that is performed following the pressure receiving ring mounting process.
In the first welding step, first, the front outer casing is opposed to a portion of the front side end face of the notch located above the front outer casing 11 and the rear end face of the outer projecting portion 14c of the pressure receiving ring 14. The laser beam is irradiated over the entire circumference (one round or more) from the outside side as seen from the body 11. Then, the 1st outer side welding part 181 is formed in this part over the perimeter by melting and solidification accompanying laser irradiation. The penetration depth of the first outer welded portion 181 in this example is less than the thickness of the front outer casing 11. That is, the first outer welded portion 181 does not penetrate the front outer casing 11.

  Next, with respect to the facing portion between the front end face of the notch located above the front inner casing 12 and the rear end face of the inner projecting portion 14d of the pressure receiving ring 14, the interior is viewed from the front inner casing 12. Laser light is irradiated from the side over the entire circumference (one round or more). Then, the 1st inner side weld part 191 is formed in this part over the perimeter by fusion | melting and solidification accompanying laser irradiation. The penetration depth of the first inner welded portion 191 in this example is less than the thickness of the front inner casing 12. That is, the first inner welded portion 191 does not penetrate the front inner casing 12.

  Thus, the front outer casing 11, the front inner casing 12, and the pressure receiving ring 14 are integrated through the first outer welded portion 181 and the first inner welded portion 191. Hereinafter, the front outer casing 11, the front inner casing 12, and the pressure receiving ring 14 integrated in this way are referred to as a “front casing portion”.

Here, in FIG. 7, the outer appearances of the first outer welded portion 181 and the first inner welded portion 191 are flat, but in reality, a bead mark formed by forming irregularities along the circumferential direction remains. There are many cases.
In addition, although the 1st inner side welding part 191 is formed after forming the 1st outer side welding part 181 here, you may reverse order.

(Inner ring mounting process)
FIG.8 (c) is a figure for demonstrating the internal ring mounting process performed following the said 1st welding process.
In the inner ring mounting step, the inner ring 17 is fitted inside the inner projecting portion 14d of the pressure receiving ring 14 of the front casing obtained by the above-described procedure. And the internal ring 17 is positioned with respect to the front housing | casing part using the jig | tool which is not shown in figure.

(Second welding process)
FIG. 8D is a diagram for explaining a second welding process that is performed subsequent to the inner ring mounting process.
In the second welding step, first, the outer periphery 14c (front side of the first outer welded portion 181) of the pressure receiving ring 14 of the front housing portion is surrounded by the entire circumference (from the outer side and obliquely upward as viewed from the pressure receiving ring 14). Irradiate laser light over one or more rounds. Moreover, the irradiation amount per unit area (irradiation power × irradiation time) of the laser beam at this time is set larger than when the first outer welded portion 181 is formed. Then, the second outer welded portion 182 is formed over the entire circumference at this portion by melting and solidification accompanying laser irradiation. At this time, the second outer welded portion 182 is formed across the pressure receiving ring 14 and the front outer casing 11. Further, the second outer welded portion 182 fills a gap existing between the front end portion of the front outer casing 11 and the curved portion formed by the pressure receiving portion 14a and the outer protruding portion 14c in the pressure receiving ring 14. Formed. The penetration depth of the second outer welded portion 182 in this example is the thickness of the front outer casing 11. That is, the second outer welded portion 182 is provided so as to penetrate from the outer side of the front outer casing 11 to the inner side (strand). Thereby, the outer side welding part 18 containing the 1st outer side welding part 181 and the 2nd outer side welding part 182 is formed in the front side and the outer side (front outer side housing | casing 11 side) of a front housing | casing part. .

  Next, the pressure receiving ring is opposed to a portion of the pressure receiving ring 14 of the front housing portion facing the inner end surface of the inner protruding portion 14d and the outer end surface of the inner ring 17 (front side of the first inner welded portion 191). The laser beam is irradiated over the entire circumference (one round or more) from the inside and obliquely upward as viewed from 14. Further, the irradiation amount per unit area of the laser beam (irradiation power × irradiation time) at this time is set larger than when the first inner welded portion 191 is formed. Then, the second inner welded portion 192 is formed over the entire circumference at this portion by melting and solidification accompanying laser irradiation. At this time, the second inner welded portion 192 is formed across the pressure receiving ring 14, the inner ring 17, and the front inner casing 12. Also, the second inner welded portion 192 fills the gap that exists between the front end of the front inner casing 12 and the curved portion formed by the pressure receiving portion 14a and the inner protruding portion 14d of the pressure receiving ring 14. Formed. The penetration depth of the second inner welded portion 192 in this example is the thickness of the front inner casing 12. That is, the second inner welded portion 192 is provided from the outer side of the front inner casing 12 to the inner side (stranding). Thereby, the inner side welding part 19 containing the 1st inner side welding part 191 and the 2nd inner side welding part 192 is formed in the front side and inner side (front inner side housing | casing 12 side) of a front housing | casing part. .

  Here, in FIG. 7, the outer appearances of the second outer welded portion 182 and the second inner welded portion 192 are flat, but actually, the same as the first outer welded portion 181 and the first inner welded portion 191. In many cases, bead marks are formed by forming irregularities along the circumferential direction described above. Moreover, in FIG. 7, although each cross-sectional shape of the 2nd outer side welding part 182 and the 2nd inner side welding part 192 is a rectangular shape (rectangular shape), an actual shape is not restricted to this.

Here, the second inner welded portion 192 is formed after the second outer welded portion 182 is formed, but the reverse order may be used.
In addition, here, the outer welded portion 18 has a structure in which the first outer welded portion 181 and the second outer welded portion 182 are separated, but these may be integrated. Further, here, the inner welded portion 19 has a structure in which the first inner welded portion 191 and the second inner welded portion 192 are separated, but these may be integrated.

[Effect of penetrating second outer weld and second inner weld]
Heat is transmitted from the combustion chamber C of the internal combustion engine 1 to the pressure receiving ring 14 of the pressure detection device 8 in addition to the pressure accompanying combustion. Then, the pressure receiving ring 14 undergoes thermal expansion as heat is transmitted. When thermal expansion occurs in the pressure receiving ring 14, the piezoelectric element group 16 (the first piezoelectric element 161 to the third piezoelectric element 163) sandwiched between the pressure receiving ring 14, the pressure transmission ring 15, and the rear housing 13. A change occurs in the applied preload. In this way, when the preload applied to the piezoelectric element group 16 changes, the pressure received by the piezoelectric element group 16 via the pressure receiving ring 14 and the pressure transmission ring 15 also changes. As a result, the amount of charge output from the piezoelectric element group 16 is different from the amount that should be output, and an error occurs in the obtained pressure value.

  In the case of the present embodiment, a metal front outer casing 11 and a front inner casing 12 are connected to the metal pressure receiving ring 14, respectively, and the heat transferred to the pressure receiving ring 14 The signal is transmitted to the rear housing 13 via the housing 11 and the front inner housing 12.

  Here, in the present embodiment, the front outer casing 11 and the pressure receiving ring 14 are connected via a second outer welded portion 182 provided across the inner side and the outer side of the front outer casing 11. . For this reason, compared with the case where the front outer housing | casing 11 and the pressure receiving ring 14 are connected only by the 1st outer side welding part 181 which does not penetrate the front outer housing | casing 11, for example, while both can be joined firmly, both The contact area can be increased.

  Further, in the present embodiment, the front inner housing 12 and the pressure receiving ring 14 are connected via a second inner welded portion 192 provided across the inner side and the outer side of the front inner housing 12. For this reason, for example, compared with the case where the front inner housing 12 and the pressure receiving ring 14 are connected only by the first inner welded portion 191 that does not penetrate the front inner housing 12, the joint between the two can be strengthened. The contact area can be increased.

  As a result, since it becomes possible to increase the amount of heat transferred from the pressure receiving ring 14 to the front outer casing 11 and the front inner casing 12, thermal expansion of the pressure receiving ring 14 is less likely to occur, The rigidity of the pressure receiving ring 14 is increased. As a result, it is possible to reduce pressure error due to heat.

[Others]
In the present embodiment, the piezoelectric element group 16 provided in the pressure detection device 8 is composed of three piezoelectric elements. However, the present invention is not limited to this. In the present embodiment, the plurality of piezoelectric elements constituting the piezoelectric element group 16 are arranged at equal intervals in the circumferential direction. However, the present invention is not limited to this, and may be non-equal intervals. . In the present embodiment, the piezoelectric element group 16 is configured by a plurality of (here, three) piezoelectric elements (the first piezoelectric element 161 to the third piezoelectric element 163). However, a single piezoelectric element is used. May be used. In this case, it is desirable to use an annular piezoelectric element.

  In this embodiment, both the outer welded portion 18 and the inner welded portion 19 are formed by laser welding. However, the present invention is not limited to this, and various welding methods or various joining methods may be used. . However, when welding stainless steels, it is desirable to use laser welding.

  Further, in the present embodiment, an annular pressure receiving ring 14 is attached to the front side of the front outer casing 11 and the front inner casing 12 each having a cylindrical shape, and the front outer casing 11 and the front inner casing 12 are mounted. The cylindrical pressure detection device 8 in which the piezoelectric element group 16 is disposed on the back side of the pressure receiving ring 14 has been described as an example, but is not limited thereto. For example, the present invention may be applied to a device in which a circular pressure receiving plate (diaphragm) is attached to the front side of a cylindrical casing and a piezoelectric element is disposed inside the casing and on the back side of the pressure receiving plate. Absent. In this case, the present invention is applied to the connection portion between the housing and the pressure receiving plate.

  In the present embodiment, the case where the injector unit 6 is configured by combining the pressure detection device 8 with the fuel injection device 7 has been described as an example. However, the present invention is not limited to this. For example, an ignition plug unit may be configured by combining the pressure detection device 8 described above with the ignition plug 5 shown in FIG.

Furthermore, in this embodiment, the case where a piezoelectric element is used as a pressure detection element has been described as an example. However, the present invention is not limited to this, and for example, a strain gauge, a separated electrode, or the like may be used. .
In the present embodiment, the pressure detection target by the pressure detection device 8 is the internal combustion engine 1, but the present invention is not limited to this and may be other than the internal combustion engine 1.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Cylinder block, 2a ... Cylinder, 3 ... Piston, 4 ... Cylinder head, C ... Combustion chamber, 5 ... Spark plug, 6 ... Injector unit, 7 ... Fuel injection device, 8 ... Pressure detection device, DESCRIPTION OF SYMBOLS 10 ... Sensor unit, 10a ... Opening part, 11 ... Front outer case, 12 ... Front inner case, 13 ... Rear case, 14 ... Pressure receiving ring, 15 ... Pressure transmission ring, 16 ... Piezoelectric element group, 17 ... Inside Ring, 18 ... outer weld, 19 ... inner weld, 50 ... transmission unit

Claims (6)

A detection element that outputs a detection signal corresponding to the received pressure;
A cylindrical housing;
A pressure receiving member attached to one end of the housing, receiving pressure from the outside and transmitting the received pressure to the detection element;
A pressure detection device including a joint portion that is provided across the inner side and the outer side of the housing over the entire circumference of the pressure receiving member and joins the pressure receiving member and the housing. The casing is housed inside, the pressure receiving member is attached to one end side, and another cylindrical casing in which a plurality of the detection elements are disposed between the casing and the casing;
The pressure-receiving member is further provided across the inner periphery and the outer side of the other casing, and further includes another joining portion that joins the pressure-receiving member and the other casing. Item 2. The pressure detection device according to Item 1. A detection element that outputs a detection signal corresponding to the received pressure;
A cylindrical housing;
A pressure detecting device that is attached to one end of the housing and includes a pressure receiving member that receives pressure from the outside and transmits the received pressure to the detection element;
A method for manufacturing a pressure detecting device, comprising the step of welding the pressure receiving member and the casing across the inner and outer sides of the casing over the entire circumference of the pressure receiving member.   4. The manufacturing of the pressure detecting device according to claim 3, wherein in the step of welding the pressure receiving member and the casing, welding is performed so as to fill a gap existing between the pressure receiving member and the casing. Method. The pressure detection device accommodates the housing inside, the pressure receiving member is attached to one end side, and a plurality of other casings in which a plurality of the detection elements are arranged between the pressure detection device and the pressure detection device. Further comprising
5. The pressure according to claim 3, further comprising a step of welding the pressure receiving member and the other casing across the inner and outer sides of the other casing over the entire circumference of the pressure receiving member. A method for manufacturing a detection device.   6. The pressure according to claim 5, wherein, in the step of welding the pressure receiving member and the other casing, welding is performed so as to fill a gap existing between the pressure receiving member and the other casing. A method for manufacturing a detection device.

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