Pressure detection device

Abstract

To enable re-using of a first housing or a second housing when changing any of units partitioned by the first housing or the second housing.SOLUTION: There is provided a pressure detection device 5 comprising a detection unit 11 for detecting a pressure, a cable 90 for transmitting an output signal of the detection unit 11 and electrically connected to the detection unit 11, a first housing 41 for accommodating and supporting the detection unit 11 in the inside, and a second housing 42 for accommodating and supporting the cable 90 in the inside and secured to the first housing 41. The first housing 41 includes an opening provided with a step part 41e in the inside, the second housing 42 includes a connection part 42a that is insertable into the opening, with the connection part 42 inserted into the opening and the end of the connection part 42a butted against the step part 41e. The first housing 41 and the second housing 42 are fixed in position by joining the boundaries of the opening end of the opening and the connection part 42a.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a pressure detection device for measuring pressure, for example, in a combustion chamber of an internal combustion engine. [Background technology]

[0002] Patent Document 1 discloses a pressure detection device having a first housing that houses a pressure detection unit including a piezoelectric body, and a second housing that is fixed to the first housing by welding and houses a transmission wire for transmitting a charge signal from the piezoelectric body to the outside. The first and second housings of this pressure detection device are positioned by butting their respective members against each other, and are fixed by welding the butted parts. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-140045 A Summary of the Invention [Problem to be solved by the invention]

[0004] The transmission wire of the pressure detection device is installed, for example, near the internal combustion engine to transmit electric charge to the control device of the internal combustion engine, but due to the usage environment that causes problems with the transmission wire, such as bending or pressurizing the transmission wire for the installation, immersion in lubricating oil, etc., there are cases where the transmission wire needs to be replaced. Therefore, there is a demand to consider the first housing and the members contained therein and the second housing and the members contained therein as one unit and to replace at least one of them. However, if the first housing and the second housing are fixed by welding and the welded portion is also a positioning portion that determines the joining position of the two, for example, in the event of a malfunction in a portion related to the second housing that houses the transmission wire, even if the side including the malfunction is removed from the portion where it is fixed by welding, the first housing that did not include the malfunction cannot be reused because the butt portion is the welded portion. Therefore, an object of the present invention is to provide a pressure detection device that allows the first housing or the second housing to be reused when a malfunction occurs in either of the units separated by the first housing or the second housing and either of the units needs to be replaced. [Means for solving the problem]

[0005] The pressure detection device comprises a detection unit that detects pressure, a cable that is electrically connected to the detection unit and transmits an output signal of the detection unit, a first housing that houses and supports the detection unit, and a second housing that is fixed to the first housing and houses and supports the cable, wherein one of the first housing and the second housing has an opening with a stepped portion therein, and the other of the first housing and the second housing has a connecting portion that can be inserted into the opening, the connecting portion is inserted into the opening and an end of the connecting portion is abutted against the stepped portion, and the first housing and the second housing are fixed by joining at least the boundary between the opening end of the opening and the connecting portion. Furthermore, the device may be configured to include an electrical connection member that electrically connects the detection unit and the cable, and the electrical connection member may be non-detachably connected to one of the detection unit and the cable, and detachably connected to the other of the detection unit and the cable. The first housing or the second housing in which the connection portion is formed may be configured to have a protrusion at the connection portion that has a surface that faces the open end of the opening with a gap therebetween. Effect of the Invention

[0006] According to the present invention, a pressure detection device can be provided that enables reuse of the first housing or the second housing when replacing either of the units separated by the first housing or the second housing. [Brief description of the drawings]

[0007] [Figure 1] 1 is a schematic configuration diagram of an internal combustion engine according to an embodiment of the present invention; [Diagram 2] FIG. 2 is an enlarged cross-sectional view of a portion II in FIG. [Diagram 3] 4 is an enlarged cross-sectional view of a detection portion and a first housing of the sensor unit. FIG. [Figure 4] 4 is an enlarged cross-sectional view of a holding portion and a second housing of the sensor unit. FIG. [Diagram 5] 11A and 11B are diagrams illustrating a configuration of a conductive member in a holding portion. [Figure 6] FIG. 2 is a diagram for explaining a configuration of a transmission line. [Figure 7] 11A and 11B are diagrams for explaining a configuration of a press-in member in a holding portion. [Figure 8] FIG. 2 is a cross-sectional view of one end of a transmission wire that has been subjected to lead processing. [Figure 9] 1 is an exploded perspective view of a conductive member, a second insulating member, a front block ring, an O-ring, a rear block ring, and a press-fit member. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. Fig. 1 is a schematic configuration diagram of an internal combustion engine 1 according to this embodiment, and Fig. 2 is an enlarged cross-sectional view of a portion II in Fig. 1. This internal combustion engine 1 includes a cylinder block 2 having a cylinder 2a, a piston 3 that reciprocates within the cylinder 2a, and a cylinder head 4 that is fastened to the cylinder block 2 and defines a combustion chamber C together with the cylinder 2a and the piston 3. The internal combustion engine 1 also includes a pressure detection device 5 that is attached to the cylinder head 4 and includes a sensor unit 10 that detects the pressure within the combustion chamber C, and a control device 6 that controls the operation of the internal combustion engine 1 based on the pressure detected by the pressure detection device 5.

[0009] The cylinder head 4 is formed with a communication hole 4a that communicates the combustion chamber C with the outside. The communication hole 4a has a front side hole portion 4b exposed to the combustion chamber C side, and a back side hole portion 4c that is connected to the front side hole portion 4b and exposed to the outside and has a hole diameter larger than that of the front side hole portion 4b. In this embodiment, the outer diameter of the tip side of the sensor unit 10 close to the combustion chamber C is set to be larger than the inner diameter of the front side hole portion 4b and approximately equal to the inner diameter of the back side hole portion 4c. In addition, a male thread is formed on the outer peripheral surface of the tip side of the sensor unit 10, and a female thread into which the male thread is screwed is formed on the inner wall surface of the back side hole portion 4c of the communication hole 4a formed in the cylinder head 4. The pressure detection device 5 is fixed to the cylinder head 4 by screwing a male thread formed on the tip side of the sensor unit 10 into a female thread formed in the back side hole 4c of the communication hole 4a, and abutting the tip side of the sensor unit 10 screwed into the cylinder head 4 against a step formed in the boundary between the front side hole 4b and the back side hole 4c. Note that a seal member 7 for maintaining airtightness in the combustion chamber C may be provided between the cylinder head 4 and the sensor unit 10 at the boundary between the front side hole 4b and the back side hole 4c, and the tip side of the sensor unit 10 may abut against the seal member 7 arranged at the step formed in the boundary between the front side hole 4b and the back side hole 4c.

[0010] Next, the configuration of the pressure detection device 5 including the sensor unit 10 will be described. The pressure detection device 5 of this embodiment includes a sensor unit 10 that detects pressure, and a transmission wire 90 that is connected to the sensor unit 10 and transmits an electrical signal detected by the sensor unit 10 to the control device 6. The sensor unit 10 also includes a detection section 11 that includes a pressure detection element such as a piezoelectric element and generates an output signal corresponding to pressure received from the outside, a transmission wire 90 that is electrically connected to the detection section 11 and transmits the output signal of the detection section 11 to the outside, a holding section 12 that holds the transmission wire 90, and a housing 40 that houses the detection section 11 and the holding section 12 inside. Here, the housing 40 is cylindrical and has a structure in which a cylindrical hole is formed along the longitudinal direction.

[0011] The housing 40 is configured by connecting a first housing 41, which is provided at the front end side close to the combustion chamber C and mainly houses the detection unit 11, and a second housing 42, which is provided at the rear end side of the first housing 41 farther from the combustion chamber C than the first housing 41 and mainly houses the holding unit 12. The pressure detection device 5 is attached to the internal combustion engine 1 shown in Fig. 1 so that the detection unit 11 side (lower side in Fig. 2) faces the combustion chamber C (lower side in Fig. 1) and the holding unit 12 side (upper side in Fig. 2) faces the outside (upper side in Fig. 1). In the description of this embodiment, the center line direction of the housing 40 (shown by a dashed line in FIG. 2) is simply referred to as the "center line direction." Also, the direction perpendicular to the center line direction toward the center line is referred to as the "inner diameter side," and the direction perpendicular to the center line direction away from the center line is referred to as the "outer diameter side." Also, in FIG. 2, the side going downward in the figure is referred to as the "tip side" of the pressure detection device 5, and the side going upward in the figure is referred to as the "rear end side" of the pressure detection device 5. Here, in this embodiment, the "center line direction" is an example of the axial direction, the "tip side" is an example of one end side, and the "rear end side" is an example of the other end side.

[0012] FIG. 3 is an enlarged cross-sectional view of the tip side of sensor unit 10, that is, detection portion 11 and first housing 41. As shown in FIG. The detection unit 11 includes a diaphragm head 21 that receives pressure from the outside (for example, combustion chamber C), a piezoelectric element 22 that converts the pressure received through the diaphragm head 21 into an electric signal (charge signal in this example), and an electrode section 23 that functions as an electrode that outputs the charge signal from the piezoelectric element 22. The detection unit 11 also includes a first pressing member 24 that presses the piezoelectric element 22 against the diaphragm head 21 through the electrode section 23, a second pressing member 25 that presses the first pressing member 24 toward the tip side, a pressurizing member 26 that applies a predetermined pressure (pressurization) to the piezoelectric element 22 through the second pressing member 25, the first pressing member 24, and the electrode section 23, and a regulating member 27 that regulates the behavior of a coil spring 30 described later. In this example, the diaphragm head 21 has a function of receiving pressure from the outside, as well as a function as the other electrode of the piezoelectric element 22 that is paired with the electrode section 23. These members constituting the detection unit 11 are fixed directly or indirectly to the first housing 41, as described below.

[0013] Here, the components of the detection unit 11 will be described in detail. The diaphragm head 21 is provided so as to close an opening at the tip end in the center line direction of a cylindrical hole provided in the first housing 41. The boundary between the diaphragm head 21 and the first housing 41 is laser welded around the outer circumferential surface. When the diaphragm head 21 is attached to the first housing 41, the diaphragm head 21 has a protruding portion 21a that protrudes toward the rear end side, i.e., the piezoelectric element 22 side, in the first housing 41. The end face of the rear end side of the protruding portion 21a is processed to be flat. In addition, the material constituting the diaphragm head 21 is preferably made of an alloy that is highly elastic, has excellent durability, heat resistance, and corrosion resistance, and is further electrically conductive, in consideration of the fact that the diaphragm head 21 is exposed to the combustion chamber C that is at high temperature and high pressure, and functions as the other electrode of the piezoelectric element 22. For example, SUH660 or the like can be used.

[0014] The piezoelectric element 22 has a piezoelectric body that exhibits a piezoelectric action of the piezoelectric longitudinal effect. The piezoelectric longitudinal effect is an action in which, when an external force is applied to a stress application axis that is in the same direction as the charge generation axis of the piezoelectric body, a charge is generated on the surface of the piezoelectric body in the charge generation axis direction. The piezoelectric element 22 according to this embodiment is housed in the first housing 41 so that the center line direction is the direction of the stress application axis.

[0015] Next, a case where the piezoelectric transverse effect is used in the piezoelectric element 22 will be illustrated. The piezoelectric transverse effect refers to an action in which, when an external force is applied to a stress application axis at a position perpendicular to the charge generation axis of the piezoelectric body, a charge is generated on the surface of the piezoelectric body in the charge generation axis direction. A plurality of thin piezoelectric bodies formed in a thin plate shape may be laminated, and by laminating them in this way, the charge generated in the piezoelectric body can be efficiently collected and the sensitivity of the sensor can be increased. Examples of the piezoelectric body include Langasite-based single crystals (Langasite, Langatate, Langhanite, LGTA), quartz, and gallium phosphate, which have a piezoelectric longitudinal effect and a piezoelectric transverse effect. In addition, the piezoelectric element 22 of this embodiment uses a Langatate single crystal as the piezoelectric body.

[0016] The electrode portion 23 is disposed so that its tip end face contacts the rear end face of the piezoelectric element 22, and its rear end face contacts the tip end face of the first pressing member 24. Here, the outer diameter of the electrode portion 23 is smaller than the inner diameter of the first housing 41, and faces the inner wall surface of the first housing 41 with a gap. A cylindrical protrusion 23a is provided at the center of the rear end face of the electrode portion 23, protruding from the rear end face along the center line direction to the rear end side. The tip end face of the electrode portion 23 and the rear end face excluding the protrusion 23a are each flat and processed so that they are parallel to each other. In this example, the electrode portion 23 is made of the same material as the diaphragm head 21.

[0017] The first pressing member 24 has an annular shape and has a rectangular cross section. The first pressing member 24 is accommodated in a cylindrical hole provided in the first housing 41, so that the end face on the tip side of the first pressing member 24 is in surface contact with the end face on the rear side of the electrode portion 23, and the end face on the rear side of the first pressing member 25 is in contact with the end face on the tip side of the second pressing member 25. The protrusion 23a provided on the rear end side of the electrode portion 23 penetrates an opening provided in the center of the first pressing member 24. Here, the outer diameter of the first pressing member 24 is slightly smaller than the inner diameter of the first housing 41, and is larger than the outer diameter of the electrode portion 23 described above. The inner diameter of the first pressing member 24 is set to be larger than the outer diameter of the protrusion 23a. The first pressing member 24 is disposed in a cylindrical hole provided in the first housing 41, and the tip of the protrusion 23a protrudes further rearward than the first pressing member 24. A tip end of a coil spring 30, which will be described later, is attached to the tip end of the protrusion 23a of the electrode portion 23. In this example, the first pressing member 24 is made of a ceramic material having heat resistance and insulating properties, such as alumina.

[0018] The second pressing member 25 is a cylindrical member having a through hole from the rear end side to the front end side, and is disposed so that the end face on the front end side is in surface contact with the end face on the rear end side of the first pressing member 24 and the end face on the rear end side is in surface contact with the end face on the front end side of the pressurizing member 26 by being accommodated in a cylindrical hole provided in the first housing 41. Here, the outer diameter of the second pressing member 25 is slightly smaller than the inner diameter of the first housing and is substantially the same as the outer diameter of the first pressing member 24 described above. In addition, inside the through hole provided in the second pressing member 25, a coil spring 30 described later and a protrusion 23a (more specifically, a tip end of the protrusion 23a) of the electrode unit 23 to which the coil spring 30 is attached are located. In this example, the second pressing member 25 is made of a ceramic material having heat resistance and insulation, such as alumina, like the first pressing member 24 described above.

[0019] The pressurizing member 26 has a through hole formed from the rear end side toward the tip end side, and has a convex outer shape protruding from the rear end side toward the tip end side. A male thread is formed on the outer circumferential surface at the rear end side of the pressurizing member 26. The pressurizing member 26 is disposed so that the end face on the tip side thereof comes into surface contact with the end face on the rear end side of the second pressing member 25 by being housed in a cylindrical hole provided in the first housing 41. A female thread is formed on the inner wall surface (more specifically, intermediate hole portion 41c described later) on the rear end side of a cylindrical hole formed in first housing 41, and a male thread formed on the outer circumferential surface of pressurizing member 26 is screwed into this female thread, thereby fixing pressurizing member 26 to first housing 41, and by sandwiching piezoelectric element 22, electrode portion 23, first pressing member 24 and second pressing member 25 between pressurizing member 26 and diaphragm head 21 attached to first housing 41, these members are positioned relative to first housing 41, and a predetermined pressurization is applied to piezoelectric element 22. Pressurizing member 26 is made of an alloy material having heat resistance and durability.

[0020] The regulating member 27 is a cylindrical member having a through hole extending from the rear end side to the front end side, and is fixed to the inner wall of the through hole in the pressurizing member 26 by adhesion. Therefore, the pressurizing member 26 and the regulating member 27 are integrated with each other via an adhesive. Here, the regulating member 27 is attached to the pressurizing member 26 such that its end face on the front end side protrudes from the end face on the front end side of the pressurizing member 26 and its end face on the rear end side is at the same position as the rear end side of the pressurizing member 26. As a result, the front end side of the regulating member 27 attached to the pressurizing member 26 is located inside the through hole in the second pressing member 25 when the pressurizing member 26 is in contact with the second pressing member 25. However, in this state, the end face on the front end side of the regulating member 27 is located away from the end face on the rear end side of the first pressing member 24. Also, in this state, the protrusion 23a of the electrode portion 23 is partially inserted into the through hole in the regulating member 27. In this example, the regulating member 27 is made of a ceramic material such as alumina, which has heat resistance and insulating properties.

[0021] As shown in FIG. 3, a conductive member 31 provided in the holding portion 12, which will be described later, is inserted into the through hole in the regulating member 27, and a coil spring 30 is provided between the conductive member 31 and the protrusion 23a provided on the electrode portion 23 to transmit the charge signal output from the piezoelectric element 22 to the conductive member 31 via the electrode portion 23. The inner diameter of the coil spring 30 is larger than the outer diameter of each of the tip of the protrusion 23a of the electrode portion 23 and the bulge 31b (see FIG. 5, which will be described later) provided on the tip side of the conductive member 31, and the outer diameter of the coil spring 30 is smaller than the inner diameter of the through hole in the regulating member 27. The length of the coil spring 30 in the center line direction is larger than the length of the second pressing member 25 in the center line direction. The coil spring 30 is disposed between the electrode portion 23 and the conductive member 31 in a state compressed more than the original state by the electrode portion 23 and the conductive member 31, and a part of the coil spring 30 is accommodated inside the through hole of the regulating member 27, The entire coil spring 30 is accommodated inside the first housing 41. In this example, the coil spring 30 is made of an alloy having high elasticity and excellent durability, heat resistance, corrosion resistance, etc., and has a gold-plated surface.

[0022] Next, the first housing 41 will be described in detail. The first housing 41 is a cylindrical member, and has a columnar hole formed along its longitudinal direction. A male thread 41a is formed on the outer periphery of the front end side of the first housing 41, which is screwed with a female thread formed in the rear end hole 4c of the communication hole 4a. The columnar hole formed in the first housing 41 has a front end hole portion 41b located relatively on the front end side, a rear end hole portion 41d located relatively on the rear end side, and an intermediate hole portion 41c located between the front end hole portion 41b and the rear end hole portion 41d. The diameters of the front end hole portion 41b, the intermediate hole portion 41c, and the rear end hole portion 41d of the columnar hole formed in the first housing 41 are increased in this order, and a step portion 41e is formed between the intermediate hole portion 41 and the rear end hole portion 41, and is made of a surface that connects the intermediate hole portion 41 and the rear end hole portion 41 and is perpendicular to the center line direction. The intermediate hole portion 41c is provided with a female thread that screws together with a male thread formed on the outer circumferential surface of the pressurizing member . Here, the diaphragm head 21 is attached to the tip end of the first housing 1 so as to close the opening of the tip end hole 41b, and the components constituting the detection unit 11 are housed inside the tip end hole 41b and the intermediate hole 41c. Also, the tip end of the second housing 42 is inserted into the rear end hole 41d until it abuts against the stepped portion 41e. At this time, the stepped portion 41e functions as a positioning portion for the first housing 41 and the second housing 42.

[0023] Here, since the first housing 41 is located facing the combustion chamber C or close to the combustion chamber C, which may become hot, it is desirable to configure it using a material that can withstand an operating temperature environment of at least -40°C to 350°C. In this example, since the first housing 41 and the second housing 42 are used as grounding targets for the detection section 11 and the holding section 12 that configure the sensor unit 10 as described later, it is desirable to manufacture the first housing 41 and the second housing 42 using a material having electrical conductivity. Specifically, the first housing 41 may be configured using a stainless steel material that is highly heat resistant and electrically conductive, such as JIS standard SUS630, SUS316, SUS430, etc.

[0024] Next, the components of the holding portion 12 will be described in detail. Fig. 4 is an enlarged cross-sectional view of the rear end side of the sensor unit 10, that is, the holding portion 12 and the second housing 42. Here, Fig. 4 shows a state in which the holding portion 12 holds the transmission wire 90. 5A and 5B are diagrams for explaining the configuration of the conductive member 31 in the holding portion 12. Here, Fig. 5(a) shows a side view illustrating the appearance of the conductive member 31, and Fig. 5(b) shows a vertical cross-sectional view of the conductive member 31. 6 is a diagram for explaining the configuration of a transmission cable 90 which constitutes the pressure detection device 5 together with the sensor unit 10. Here, FIG. 6(a) shows a cross-sectional view of the transmission cable 90, and FIG. 6(b) shows a side view of the transmission cable 90. Furthermore, Fig. 7 is a diagram for explaining the configuration of the press-in member 37 in the holding portion 12. Here, Fig. 7(a) shows a diagram of the press-in member 37 seen from the tip side, Fig. 7(b) shows a diagram of the press-in member 37 seen from the side, and Fig. 7(c) shows a VIIC-VIIC cross-sectional view in Fig. 7(a).

[0025] Before describing the configuration of the holding portion 12, the configuration of the transmission cable 90 held by the holding portion 12 will be described first. A transmission wire 90 as an example of a cable is configured with an insulated wire having a so-called coaxial structure, as shown in Fig. 6. More specifically, the transmission wire 90 includes a conductor portion 91 made of twisted metal wires, a resin insulating layer 92 made of insulating resin and covering the outer periphery of the conductor portion 91, a resin semiconductive layer 93 made of semiconductive resin and covering the outer periphery of the resin insulating layer 92, a braided shielding layer 94 made of woven metal wires and covering the outer periphery of the resin semiconductive layer 93, a resin protective layer 95 made of insulating resin and covering the outer periphery of the braided shielding layer 94, and a braided protective layer 96 made of woven metal wires and covering the outer periphery of the resin protective layer 95 and exposed to the outside.

[0026] In the following description, the outer diameter of the conductor 91 is referred to as the conductor diameter D1, the outer diameter of the resin insulating layer 92 as the resin insulating layer diameter D2, the outer diameter of the resin semiconducting layer 93 as the resin semiconductor layer diameter D3, the outer diameter of the braided shielding layer 94 as the braided shielding diameter D4, the outer diameter of the resin protective layer 95 as the resin protective layer diameter D5, and the outer diameter of the braided protective layer 96 as the braided protective layer diameter D6. Here, the braided protective layer diameter D6 is the outer diameter of the transmission wire 90.

[0027] The configuration of the transmission cable 90 will be described in detail below. Conductor 91, which is an example of a transmission section, is formed by twisting together seven tin-plated soft copper wires with a diameter of 0.3 mm. Note that conductor 91 may be formed of a tin-plated copper alloy wire instead of the tin-plated soft copper wire. The resin insulating layer 92 is formed by covering the outer peripheral surface of the conductor portion 91 with perfluoroalkoxy fluorine resin (PFA) having a thickness of 0.075 mm by extrusion. The resin semiconductive layer 93 is formed by covering the outer peripheral surface of the resin insulating layer 92 with a 0.01 mm-thick layer of PFA containing carbon by extrusion. The braided shielding layer 94 is formed by braiding a plurality of tin-plated soft copper wires on the outer peripheral surface of the resin semiconductive layer 93 . Resin protective layer 95, which is an example of a covering portion, is formed by covering the outer peripheral surface of braided shielding layer 94 with PFA by an extrusion method. Braided protective layer 96, which is an example of a metal braided portion, is configured by braiding a plurality of stainless steel wires on the outer peripheral surface of resin protective layer 95. In this embodiment, braided protective layer 96 functions as an outer peripheral portion of the cable.

[0028] One end of the transmission wire 90 is attached to the holder 12 after being processed to expose the conductor 91, the resin insulating layer 92, the resin semiconductive layer 93, the braided shielding layer 94, the resin protective layer 95, and the braided protective layer 96 to the outside in that order (see also FIG. 8 described later). Meanwhile, the other end of the transmission wire 90 is attached to a connection part (not shown) such as a BNC connector after being processed to expose the conductor 91, the resin insulating layer 92, the resin semiconductive layer 93, the braided shielding layer 94, the resin protective layer 95, and the braided protective layer 96 to the outside in that order (see also FIG. 8 described later).

[0029] Next, the configuration of the holding portion 12 will be described. The holding portion 12 has a conductive member 31 that conducts the charge signal from the piezoelectric element 22 (see Figure 3) provided in the detection portion 11 to a conductor portion 91 of the transmission wire 90 held in the holding portion 12, a first insulating member 32 that positions the conductive member 31 relative to the second housing 42 and insulates the second housing 42 and the conductive member 31, and a second insulating member 33 that positions the portion of the transmission wire 90 where the resin insulation layer 92 is exposed relative to the second housing 42 and insulates the conductive member 31 and the braided shielding layer 94 in the transmission wire 90. The holding portion 12 further includes a front block ring 34 that sandwiches between the second insulating member 33 the front end side of the portion of the transmission wire 90 where the braided shielding layer 94 is exposed, an O-ring 35 that positions the portion of the transmission wire 90 where the resin protective layer 95 is exposed with respect to the second housing 42, and a rear block ring 36 that sandwiches the O-ring 35 between the front block ring 34 and the holding portion 12. The holding portion 12 further includes a press-in member 37 that has a through hole into which the transmission wire 90 covered up to the braided protective layer 96 is inserted, and is press-fitted from the rear end side of the second housing 42 into a cylindrical hole provided in the second housing 42, sandwiches the front end side of the braided protective layer 96 of the transmission wire 90 between the rear block ring 36, and fixes one end side of the transmission wire 90 to the second housing 42. The transmission wire 90 and the members constituting the holding portion 12 are attached directly or indirectly to the second housing .

[0030] The components of the holding portion 12 will be described in detail below. The conductive member 31 is attached to the tip end of the second housing 42, and its tip end protrudes forward beyond the tip end of the second housing 42, and this protruding portion is adapted to be inserted into a through hole of a regulating member 27 provided in the detection unit 11. 5, the conductive member 31 has a first columnar portion 31a having a columnar shape and located at the tip side, a bulging portion 31b bulging outward at the middle of the first columnar portion 31a, a second columnar portion 31c extending from the rear end side of the first columnar portion 31a and having a larger outer diameter than the first columnar portion 31a, a shoulder portion 31d expanding in an inverse tapered manner from the rear end side of the second columnar portion 31c, a third columnar portion 31e extending from the rear end side of the shoulder portion 31d and having a larger outer diameter than the second columnar portion 31c, and a rear end portion 31f extending from the rear end side of the third columnar portion 31e and having a larger outer diameter than the third columnar portion 31e. The conductive member 31 also has a hole portion 31g extending from the center of the end face on the rear end side of the rear end portion 31f toward the tip side. Here, hole 31g is provided inside rear end 31f and third columnar section 31e of conductive member 31. In this example, conductive member 31 can be made of an alloy having excellent durability, heat resistance, corrosion resistance, etc., with its surface plated with gold, or with nickel plating followed by gold plating.

[0031] In this example, when the sensor unit 10 shown in FIG. 2 and the like is constructed, the portion of the conductive member 31 extending from the first columnar portion 31a through the bulging portion 31b to the second columnar portion 31c is inserted into the through hole of the restricting member 27 provided in the detection unit 11. In addition, in this example, when the sensor unit 10 shown in FIG. 2 and the like is constructed, the coil spring 30 is wound around the first columnar portion 31a including the bulging portion 31b of the conductive member 31, and the other end of the coil spring 30 abuts against the boundary between the rear end of the first columnar portion 31a and the front end of the second columnar portion 31c. In addition, in this example, when the sensor unit 10 shown in FIG. 2 and the like is constructed, one end of the conductor portion 91 (see FIG. 6) of the transmission wire 90 is inserted into the hole portion 31g provided in the conductive member 31. Then, with the conductor portion 91 inserted into the hole portion 31g of the conductive member 31, force is applied from the outer peripheral surface of the third columnar portion 31e of the conductive member 31 to crush the third columnar portion 31e, thereby electrically connecting the conductive member 31 and the conductor portion 91.

[0032] The first insulating member 32 has a through hole extending from the rear end side to the front end side, and has a convex outer shape protruding from the rear end side to the front end side. The first insulating member 32 is accommodated in a cylindrical hole provided in the second housing 42, and is interposed between the inner wall of the front end side of the second housing 42 and the rear end 31f (see FIG. 5) of the conductive member 31, thereby positioning the conductive member 31 in the second housing 42 and insulating the second housing 42 from the conductive member 31. Here, the through hole of the first insulating member 32 has a first hole portion opening toward the front end side, and a second hole portion connected to the first hole portion and opening toward the rear end side, the hole diameter of which is larger than that of the first hole portion. The third columnar portion 31e of the conductive member 31 is accommodated in the first hole portion, and the rear end portion 31f of the conductive member 31 is accommodated in the second hole portion. In this example, the first insulating member 32 is made of a resin such as PFA having heat resistance and insulating properties.

[0033] The second insulating member 33 has an annular shape and has a rectangular cross section. The second insulating member 33 is accommodated in a cylindrical hole provided in the second housing 42, and is disposed so that the end surface on the front end side of the second insulating member 33 is in surface contact with the end surface on the rear end side of the first insulating member 32 and the end surface on the rear end side of the rear end portion 31f of the conductive member 31, respectively. Here, the outer diameter of the first insulating member 32 is substantially equal to the inner diameter of the second housing 42, and the inner diameter of the first insulating member 32 is slightly larger than the resin insulation layer diameter D2 of the transmission electric wire 90. In this example, the second insulating member 33 is made of a resin such as PFA having heat resistance and insulating properties, similar to the above-mentioned first insulating member 32.

[0034] The tip side block ring 34 has an annular shape and has a rectangular cross section. The tip side block ring 34 is accommodated in a cylindrical hole provided in the second housing 42, so that its tip side end face faces the rear end face of the second insulating member 33 across the braided shielding layer 94 of the transmission wire 90, and the rear end face is in contact with the O-ring 35 over the entire circumference. The outer diameter of the tip side block ring 34 is slightly smaller than the inner diameter of the second housing 42, and the inner diameter of the tip side block ring 34 is slightly larger than the diameter D5 of the resin protective layer of the transmission wire 90. In this example, the tip side block ring 34 is made of an alloy material that has heat resistance, durability, and electrical conductivity.

[0035] The O-ring 35 has an annular shape and has a circular cross section. The O-ring 35 is disposed so that its front end contacts the front end block ring 34 over the entire circumference and its rear end contacts the rear end block ring 36 over the entire circumference by being accommodated in a cylindrical hole provided in the second housing 42. Here, the outer diameter of the O-ring 35 is slightly larger than the inner diameter of the second housing 42, and the inner diameter of the O-ring 35 is slightly smaller than the diameter D5 of the resin protective layer of the transmission cable 90. Therefore, the O-ring 35 is accommodated in a cylindrical hole provided in the second housing 42, so that its inner peripheral surface contacts the outer peripheral surface of the resin protective layer 95 of the transmission cable 90 over the entire circumference and its outer peripheral surface contacts the inner wall surface of the second housing 42 over the entire circumference. In this example, the O-ring 35 is made of a resin such as PFA having heat resistance, water resistance, oil resistance, and insulation properties. The O-ring 35 is sandwiched between the front block ring 34 and the rear block ring 36, and also between the second housing 42 and the resin protective layer 95 of the transmission wire 90, so that the O-ring 35 is accommodated within the second housing 42 with its cross-sectional shape deformed from a circular shape (crushed state).

[0036] The rear block ring 36 has an annular shape and a rectangular cross section. The rear block ring 36 is accommodated in a cylindrical hole provided in the second housing 42, so that its end face on the front side is in contact with the O-ring 35 over the entire circumference, and its end face on the rear side is disposed to face the end of the front side of the press-fit member 37 across the braided protective layer 96 of the transmission wire 90. The outer diameter of the rear block ring 36 is slightly smaller than the inner diameter of the second housing 42, and the inner diameter of the rear block ring 36 is slightly larger than the diameter D5 of the resin protective layer of the transmission wire 90. In this example, the rear block ring 36 has the same shape as the front block ring 34 described above, and is made of an alloy material that has heat resistance, durability, and electrical conductivity.

[0037] The press-in member 37 is attached to the rear end of the second housing 42, with its rear end positioned outside the second housing 42 and its front end inserted into the through hole in the second housing 42 and abutting against the inner wall of the through hole. As shown in FIG. 7, the press-in member 37 has a base 37a having an annular shape, four legs 37b extending from the base 37a toward the tip end, and four projections 37c projecting outward from the outer circumferential surfaces of the four legs 37b. The tip end of each leg 37b is provided with an inclined portion 37d whose outer diameter gradually decreases from the projection 37c toward the tip end. The four legs 37b have a cylindrical shape as a whole, and four notches are formed along the center line direction at 90° intervals, so that each of the four legs 37b has an arc-shaped cross section. The projections 37c provided on each of the four legs 37b have an annular shape as a whole, and are divided into four in the circumferential direction by the four notches. When the press-in member 37 is attached to the second housing 42, the base 37a is exposed to the outside of the second housing 42, while the four legs 37b and the protrusions 37c attached to each leg 37b are embedded inside the through hole in the second housing 42.

[0038] The through hole of the press-fitting member 37 has a tip-side opening that opens toward the tip side, and a rear-end opening that is connected to the tip-side opening and opens toward the rear surface and has a larger diameter than the tip-side opening. Here, the rear-end opening has an inverse tapered shape in which the diameter gradually increases from the tip side toward the rear side.

[0039] In the following description, the outer diameter of the base 37a of the press-fit member 37 before being inserted into the second housing 42 is referred to as the base outer diameter Dao, the outer diameter of the two opposing legs 37b is referred to as the leg outer diameter Dbo, the outer diameter of the two protrusions 37c provided on the two opposing legs 37b is referred to as the protrusion outer diameter Dco, and the outer diameter of the two opposing legs 37b at the end on the tip side is referred to as the end outer diameter Ddo. In the following description, the inner diameter of the rear end side of the through hole in the press-fit member 37 is referred to as the base inner diameter Dai, and the inner diameter of the tip side of the through hole is referred to as the leg inner diameter Dbi.

[0040] Here, in the press-fit member 37, the relationship is: base outer diameter Dao>projection outer diameter Dco>leg outer diameter Dbo>end outer diameter Ddo, and the relationship is: base inner diameter Dai>leg inner diameter Dbi. Further, the base outer diameter Dao of the press-fitting member 37 is larger than the outer diameter at the rear end side of the through hole provided in the second housing 42, and the leg outer diameter Dbo of the press-fitting member 37 is smaller than the inner diameter at the rear end side of the through hole provided in the second housing 42. On the other hand, the projection outer diameter Dco of the press-fitting member 37 is larger than the inner diameter at the rear end side of the through hole provided in the second housing 42, and the end outer diameter Ddo of the press-fitting member 37 is smaller than the inner diameter at the rear end side of the through hole provided in the second housing 42. Furthermore, the base inner diameter Dai of the press-fit member 37 is larger than the braided protective layer diameter D6 of the transmission cable 90, and the leg inner diameter Dbi of the press-fit member 37 is slightly larger than or approximately the same as the braided protective layer diameter D6 of the transmission cable 90.

[0041] Next, the second housing 42 will be described in detail. The second housing 42 is a cylindrical member, and has a columnar hole along its longitudinal direction. The second housing 42 has a front end 42a that is coupled to the first housing 41, an intermediate portion 42b located on the rear end side of the front end 42a, and a rear end 42c located on the rear end side of the intermediate portion 42b. The front end 42a has an outer diameter smaller than that of the intermediate portion 42b, and the intermediate portion 42b has an outer diameter larger than that of the rear end 42c. Between the front end 42a and the rear end 42b, there is a step portion 42d that connects the front end 42a and the rear end 42b and is formed of a surface perpendicular to the center line direction. The columnar hole provided in the second housing 42 has a front end hole portion 42e on the front end side and a rear end hole portion 42f on the rear end side, and the diameters of the front end hole portion 42e and the rear end hole portion 42f increase in this order. Among the components of the holding portion 12, the tip side of the conductive member 31 (specifically, the shoulder portion 31d, the third columnar portion 31e, and the rear end portion 31f) and the tip side of the first insulating member 32 are housed in the tip hole portion 42e, while the tip side of the press-fit member 37, the rear end sides of the conductive member 31 and the first insulating member 32, and other components are housed in the rear end hole portion 42f. The rear end side of the press-fit member 37 (more specifically, the base portion 37a of the press-fit member 37) is provided so as to be exposed to the outside of the rear end side of the second housing 42.

[0042] Here, the tip portion 42a of the second housing 42 is set to be slightly smaller than the diameter of the rear end hole 41d of the first housing 41, and is inserted into the rear end hole 41d of the first housing 41 until the tip portion 42a of the second housing 42 abuts against the step portion 41e of the first housing 41. The first housing 41 and the second housing 42 are fixed to each other by laser welding the boundary between the end face on the rear end side of the first housing 41 and the outer circumferential surface of the second housing 42 around the circumference. The first housing 41 and the second housing 42 are fixed to each other such that a gap 100 is formed between the end on the rear end side of the first housing 41 and the step portion 42 located on the tip side of the intermediate portion 42b of the second housing 42.

[0043] Here, like the first housing 41, the second housing 42 is located in a position facing the combustion chamber C, which can become hot, or in a position close to the combustion chamber C, and since the first housing 41 and the second housing 42 are used as grounding targets for the detection section 11 and the holding section 12 that constitute the sensor unit 10, it is preferable to construct them using a stainless steel material that is highly heat resistant and conductive, such as JIS standard SUS630, SUS316, SUS430, etc.

[0044] Here, the electrical connection structure in the above-mentioned pressure detection device 5 will be described. First, the end face on the tip side of the piezoelectric element 22 is electrically connected to the metallic diaphragm head 21 via the protruding portion 21a. The diaphragm head 21 is electrically connected to the metallic first housing 41 by laser welding.

[0045] On the other hand, the rear end surface of the piezoelectric element 22 is electrically connected to the front end surface of the metallic electrode portion 23, and the electrode portion 23 is electrically connected to the metallic coil spring 30 via the protrusion portion 23a. The coil spring 30 is also electrically connected to the metallic conductive member 31, and the conductive member 31 is electrically connected to the metallic conductor portion 91 of the transmission wire 90. The transmission path of the charge signal from the electrode portion 23 to the conductor portion 91 via the coil spring 30 and the conductive member 31 is electrically insulated from the metallic housing 40 (the first housing 41 and the second housing 42) by the first pressing member 24, the second pressing member 25, the restricting member 27, the first insulating member 32, the second insulating member 33, and the resin insulating layer 92 of the transmission wire 90, each of which is made of an insulator.

[0046] In the transmission wire 90, the conductor portion 91 is electrically insulated from the resin semiconductive layer 93 and the braided shielding layer 94 by the resin insulating layer 92. In addition, the resin semiconductive layer 93 in the transmission wire 90 is electrically connected to the adjacent braided shielding layer 94, and the braided shielding layer 94 is electrically connected to the inner wall surface of the metal second housing 42 directly or via a metal tip block ring 34. Furthermore, the braided protective layer 96 in the transmission wire 90 is electrically connected to the inner wall surface of the metal second housing 42 via a metal press-in member 37. The second housing 42 is electrically connected to the metal first housing 41 by laser welding.

[0047] When the sensor unit 10 of the pressure detection device 5 is attached to the cylinder head 4 shown in FIG. 1, the first housing 41 is electrically connected to the metal cylinder head 4. Since the cylinder head 4 is electrically grounded, in the pressure detection device 5, the end face on the tip side of the piezoelectric element 22, the resin semiconductive layer 93 and the braided shielding layer 94 of the transmission wire 90, and the braided protective layer 96 of the transmission wire 90 are grounded via the first housing 41 and the second housing 42 provided in the sensor unit 10. Here, in this example, the structure is such that the side of the piezoelectric element 22 and the inner wall surface of the first housing 41 can come into contact with each other, but this does not pose a problem because the piezoelectric element 22 is made of an insulator and has an extremely large resistance value, and the electric charge generated in response to a pressure change is generated at the end face on the tip side and the end face on the rear side of the piezoelectric element 22.

[0048] Next, a pressure detection operation by the pressure detection device 5 mounted on the internal combustion engine 1 shown in FIG. 1 will be described. Fluctuations in the combustion pressure generated within the combustion chamber C act on the piezoelectric element 22 sandwiched between the diaphragm head 21 and the electrode portion 23 via the diaphragm head 21, causing an electric charge corresponding to the fluctuations in the combustion pressure to be generated in the piezoelectric element 22. The electric charge generated in the piezoelectric element 22 is then transmitted from the rear end face of the piezoelectric element 22 through the electrode portion 23, the coil spring 30 and the conductive member 31 to the conductor portion 91 of the transmission wire 90, and is further transmitted to the control device 6 via the conductor portion 91 as a charge signal.

[0049] At this time, the end face on the tip side of the piezoelectric element 22 is connected (grounded) to the cylinder head 4 via the diaphragm head 21 and the first housing 41, thereby suppressing the inclusion of noise components in the charge output from the piezoelectric element 22. At this time, the resin semiconductive layer 93 and the braided shielding layer 94 in the transmission wire 90 are connected (grounded) to the cylinder head 4 via the second housing 42 and the first housing 41, suppressing the intrusion of noise components into the charge signal transmitted by the conductor portion 91. Furthermore, at this time, the braided protective layer 96 in the transmission wire 90 is also connected (grounded) to the cylinder head 4 via the second housing 42 and the first housing 41, suppressing the intrusion of noise components into the charge signal transmitted by the conductor portion 91 and suppressing an increase in the potential of the braided protective layer 96 due to leakage current or the like.

[0050] Next, a procedure for assembling the pressure detection device 5 including the sensor unit 10 and the transmission wire 90 will be described. The pressure detection device 5 of this embodiment is obtained through a detection unit assembly process in which the diaphragm head 21 and the detection unit 11 are attached to the first housing 41, a holding unit assembly process in which the holding unit 12, in which the transmission cable 90 is held, is attached to the second housing 42, and an overall assembly process in which the first housing 41 to which the detection unit 11 and the diaphragm head 21 are attached and the second housing 42 to which the holding unit 12 and the transmission cable 90 are attached are connected and integrated via the coil spring 30.

[0051] Each step will be described in order below. <Assembly process of the detection unit 11> First, the diaphragm head 21 is attached to the opening on the tip side of the first housing 41 so that the protrusion 21a is positioned within the through hole of the first housing 41. Then, the boundary surface (outer periphery) of both is joined by laser welding.

[0052] Next, the piezoelectric element 22 is inserted into the through hole of the first housing 41 from the rear end side. Then, the electrode portion 23 is inserted into the through hole of the first housing 41 from the rear end side so that the protrusion 23a is at the rear end side, and the piezoelectric element 22 is sandwiched between the diaphragm head 21 (protrusion 21a) and the electrode portion 23. Next, the first pressing member 24 is inserted into the through hole of the first housing 41 from the rear end side, and the protrusion 23a of the electrode portion 23 is made to penetrate the opening of the first pressing member 24. At this time, the electrode portion 23 is set in a non-contact state with the first housing 41 as the position of the protrusion 23a is regulated by the opening of the first pressing member 24. Then, the second pressing member 25 is inserted into the through hole of the first housing 41 from the rear end side, and the end face of the tip side of the second pressing member 25 and the end face of the rear side of the first pressing member 24 are made to contact each other. Then, the pressure applying member 26 to which the restricting member 27 is adhered is inserted into the through hole of the first housing 41 from the rear end side.

[0053] Thereafter, with the first housing 41 fixed, the pressurizing member 26 is screwed toward the tip side, thereby moving the pressurizing member 26 to which the restricting member 27 is adhered toward the tip side, i.e., toward the side approaching the piezoelectric element 22. During this, the tip end face of the pressurizing member 26 comes into contact with the rear end face of the second pressing member 25, and the pressurizing member 26 applies pressure to the piezoelectric element 22 via the first pressing member 24 and the electrode portion 23. Then, when the pressure applied to the piezoelectric element 22 reaches a predetermined set value (pressure), the screwing of the pressurizing member 26 is stopped, and the pressurizing member 26 and the restricting member 27 are positioned relative to the first housing 41. At this time, a gap exists between the tip end face of the restricting member 27 integrated with the pressurizing member 26 and the rear end face of the first pressing member 24, and the first pressing member 24 and the restricting member 27 are maintained in a non-contact state. With the above, assembly of the detection unit 11 in the first housing 41 is completed.

[0054] <Assembly process of the holding portion 12> The holding portion assembly process is achieved through a transmission wire attachment process in which each component of the holding portion 12, except for the first insulating member 32, is attached to the transmission wire 90, and a holding portion attachment process in which each component of the holding portion 12, including the first insulating member 32, is attached to the second housing 42, thereby attaching the holding portion 12 holding the transmission wire 90 to the second housing 42. Each step will be described in order below.

[0055] [Installation process of transmission cable 90] First, one end of the transmission wire 90 is subjected to lead processing. FIG. 8 shows a cross-sectional view of one end of the transmission wire 90 that has been subjected to the lead-out process. At this time, the cut is performed so that the conductor portion 91, the resin insulating layer 92, the braided shielding layer 94, the resin protective layer 95, and the braided protective layer 96 are sequentially exposed on the one end of the transmission wire 90. However, as shown in FIG. 8, the resin semiconductive layer 93 is cut at a position that is closer to the rear end than the end of the braided shielding layer 94, so that the end of the braided shielding layer 94 is positioned closer to the tip than the end of the resin semiconductive layer 93. Also, as shown in FIG. 8, the resin protective layer 95 is cut at a position that is closer to the rear end than the end of the braided protective layer 96, so that the end of the braided protective layer 96 is positioned closer to the tip than the end of the resin protective layer 95. Note that a connector is attached to the other end of the transmission wire 90 in a separate process.

[0056] Next, the conductive member 31, the second insulating member 33, the front end block ring 34, the O-ring 35, the rear end block ring 36, and the press-fit member 37 are arranged in this order. 9 shows an exploded perspective view of the conductive member 31, second insulating member 33, front end block ring 34, O-ring 35, rear end block ring 36, and press-fit member 37, which are arranged in the above-mentioned order. At this time, hole 31g in conductive member 31 faces the openings in each of the front end block ring 34 to press-fit member 37, and base 37a in press-fit member 37 is positioned closer to the rear end than leg portion 37b.

[0057] 9, one end of the transmission wire 90 (see FIG. 8) that has been subjected to lead processing is inserted from the rear end side of the opening of the press-in member 37. Accordingly, the portion of the transmission wire 90 that is covered up to the braided protective layer 96 (the portion where the braided protective layer 96 is exposed) passes through the through hole of the press-in member 37, the portion of the transmission wire 90 that is covered up to the resin protective layer 95 (the portion where the resin protective layer 95 is exposed) passes through the openings of the rear end block ring 36, the O-ring 35, and the front end block ring 34, the portion of the transmission wire 90 that is covered up to the resin insulating layer 92 (the portion where the resin insulating layer 92 is exposed) passes through the opening of the second insulating member 33, and the portion of the transmission wire 90 where the conductor portion 91 is exposed enters the hole portion 31g provided in the conductive member 31. Therefore, the braided protective layer 96 of the transmission wire 90 faces the inner wall of the through hole in the press-fitting member 37, the resin protective layer 95 of the transmission wire 90 faces the inner wall of each opening in the rear-end block ring 36, the O-ring 35 and the front-end block ring 34, the resin insulating layer 92 of the transmission wire 90 faces the inner wall of the opening in the second insulating member 33, and the conductor portion 91 of the transmission wire 90 faces the inner wall of the hole 31g in the conductive member 31. In addition, the end side of the braided protective layer 96 of the transmission wire 90 does not pass through the opening of the rear-end block ring 36, but is disposed between the end face on the rear end side of the rear-end block ring 36 and the end faces on the front ends of the four legs 37b of the press-fitting member 37. At this time, the end side of the braided protective layer 96 is in a state of being expanded between the end face on the rear end side of the rear end block ring 36 and the end faces on the tip side of the four legs 37b of the press-fit member 37 due to the unraveling of the braid. Furthermore, the end side of the braided shielding layer 94 of the transmission wire 90 is disposed between the end face on the rear end side of the second insulating member 33 and the end face on the tip side of the tip side block ring 34 without passing through the opening of the second insulating member 33. At this time, the end side of the braided shielding layer 94 is in a state of being expanded between the end face on the rear end side of the second insulating member 33 and the end face on the tip side of the tip side block ring 34 due to the unraveling of the braid. Furthermore, the end side of the resin semiconducting layer 93 of the transmission wire 90 is disposed on the rear end side of the opening without entering the opening of the second insulating member 33.

[0058] Here, the inner diameters of the through holes in the press-fitting member 37 (the base inner diameter Dai and the leg inner diameter Dbi) are approximately the same as or slightly larger than the braided protective layer diameter D6 of the transmission electric wire 90, so that the press-fitting member 37 is unlikely to hinder the insertion of the transmission electric wire 90. Also, the inner diameters of the openings in the rear-end block ring 36 and the front-end block ring 34 are the same as or slightly larger than the resin protective layer diameter D5 of the transmission electric wire 90, so that the rear-end block ring 36 and the front-end block ring 34 are unlikely to hinder the insertion of the transmission electric wire 90. On the other hand, the inner diameter of the opening in the O-ring 35 is slightly smaller than the resin protective layer diameter D5 of the transmission electric wire 90, so that it may hinder the insertion of the transmission electric wire 90 to some extent, but since the O-ring 35 is made of a deformable resin, it does not actually hinder the insertion of the transmission electric wire 90 at all. Furthermore, since the inner diameter of the opening in the second insulating member 33 is slightly larger than the resin insulation layer diameter D2 in the transmission wire 90, the second insulating member 33 is unlikely to be an obstacle when inserting the transmission wire 90. Furthermore, since the inner diameter of the hole 31g in the conductive member 31 is slightly larger than the conductor portion diameter D1 in the transmission wire 90, the conductive member 31 is unlikely to be an obstacle when inserting the transmission wire 90.

[0059] Then, with the conductor portion 91 of the transmission wire 90 inserted into the hole portion 31g of the conductive member 31, force is applied from the outer peripheral surface of the third columnar portion 31e of the conductive member 31 to crimp the conductive member 31 and the conductor portion 91 together. With the above, the attachment of the transmission wire 90 to the holding portion 12 excluding the first insulating member 32 is completed.

[0060] [Attachment process of the holding part 12] First, the first insulating member 32 is inserted from the rear end side into the through hole of the second housing 42. Then, the shoulder portion of the first insulating member 32 abuts against the shoulder portion that connects the front end hole portion 42d and the rear end hole portion 42 of the second housing 42 and is provided between them, whereby the first insulating member 32 is positioned relative to the second housing 42.

[0061] Next, the holding portion 12 (excluding the first insulating member 32) to which the transmission electric wire 90 is attached, obtained in the above transmission electric wire attaching step, is inserted into the through hole of the second housing 42 from the rear end side, starting from the conductive member 31 side.

[0062] As a result of the above-mentioned insertion operation, the first columnar portion 31a, the bulging portion 31b, and the second columnar portion 31c of the conductive member 31 protrude to the outside (tip side) through the through hole of the first insulating member 32 attached to the second housing 42. In addition, the tip side end face of the rear end portion 31f provided on the conductive member 31 abuts against a flat surface provided on the rear end side of the through hole of the first insulating member 32, so that the conductive member 31 is positioned relative to the second housing 42 via the first insulating member 32. At this time, the third columnar portion 31e and the rear end portion 31f of the conductive member 31 are positioned within the through hole of the first insulating member 32.

[0063] Furthermore, through the insertion work up to this point, the second insulating member 33, the front end block ring 34, the O-ring 35 and the rear end block ring 36 are disposed in the through hole of the second housing 42. At this time, the end side of the braided shielding layer 94 of the transmission wire 90 is disposed between the second insulating member 33 and the front end block ring 34 in a state in which it spreads out toward the outside (the inner wall side of the second housing 42), and the end side of the braided protective layer 96 of the transmission wire 90 is disposed between the rear end block ring 36 and the press-in member 37 in a state in which it spreads out toward the outside (the inner wall side of the second housing 42).

[0064] On the other hand, at this time, the press-in member 37 cannot enter the through hole of the second housing 42 because the end outer diameter Ddo is smaller than the inner diameter of the through hole in the second housing 42, while the protrusion outer diameter Dco is larger than the inner diameter of the through hole, and so the press-in member 37 is positioned outside the rear end face of the second housing 42.

[0065] Then, with the second housing 42 fixed, the base 37a of the press-in member 37 is pressed from the rear end toward the through hole of the second housing 42. Then, as a force from the rear end toward the front end is applied to the four legs 37b of the press-in member 37, a force toward the inside is applied from the second housing 42 via the inclined portions 37d of each of the legs. As a result, the four legs 37b of the press-in member 37 are deformed toward the inside, and the end portions of the front ends of the four legs 37b are inserted into the through hole of the second housing 42. In addition, as the legs 37b are deformed, the protrusions 37c of each leg 37b also enter the through hole of the second housing 42. Then, the end face of the front end side of the base 37a of the press-in member 37 hits the end face of the rear end side of the second housing 42, and the press-in member 37 holding the transmission wire 90 is positioned with respect to the second housing 42.

[0066] During this time, the tip end surface of each leg 37b of the press-in member 37 moves from the rear end side to the tip side within the through hole in the second housing 42, pushing the conductive member 31 and the first insulating member 32 through the end side of the braided protective layer 96 of the transmission wire 90, the rear end block ring 36, the O-ring 35, the tip end block ring 34, the end side of the braided shielding layer 94 of the transmission wire 90, and the second insulating member 33. Then, when the tip end face of the base 37a of the press-in member 37 abuts against the rear end face of the second housing 42, the second insulating member 33, the end side of the braided shielding layer 94 of the transmission cable 90, the tip block ring 34, the O-ring 35, the rear block ring 36 and the end side of the braided protective layer 96 of the transmission cable 90 are sandwiched between the first insulating member 32 and the conductive member 31 already positioned in the second housing 42 and the press-in member 37 (each leg 37b of the press-in member 37) newly positioned in the second housing 42.

[0067] On the other hand, when the press-fitting member 37 is positioned in the second housing 42, each leg 37b of the press-fitting member 37 is deformed inward, so that the inner diameter of the opening of the press-fitting member 37 formed by each leg 37b becomes narrower than the leg inner diameter Dbi before fitting, and becomes smaller than the outer diameter of the transmission wire 90, i.e., the braided protective layer diameter D6. On the other hand, when the press-fitting member 37 is positioned in the second housing 42, a force (restoring force) that tries to expand to the original state, i.e., outward, acts on each leg 37b constituting the press-fitting member 37 due to its own elasticity. As a result, the transmission wire 90 is firmly fixed to the second housing 42 by the press-fitting member 37. Then, the boundary surface (outer peripheral surface) between the end on the rear end side of the second housing 42 and the end on the front end side of the base 37a of the press-fitting member 37 is joined by laser welding.

[0068] In addition, as the press-fit member 37 is positioned relative to the second housing 42, the second insulating member 33, the end side of the braided shielding layer 94 of the transmission wire 90, the front block ring 34, the O-ring 35, the rear block ring 36, and the end side of the braided protective layer 96 of the transmission wire 90 are also fixed in position within the second housing 42. At this time, the end side of the braided shielding layer 94 and the end side of the braided protective layer 96 of the transmission wire 90 are in contact with the inner wall surface of the second housing 42. At this time, the inner side of the O-ring 35 is in contact with the resin protective layer 95 of the transmission wire 90 over the entire circumference, and the outer side of the O-ring 35 is in contact with the inner wall surface of the second housing 42 over the entire circumference. With the above, the assembly of the holding portion 12 holding the transmission wire 90 to the second housing 42 is completed. In the following, the first housing 41 (see Figures 2 and 3) to which the detection portion 11 is attached is referred to as the "tip unit," and the second housing 42 (see Figures 2 and 4) to which the holding portion 12 that holds the transmission wire 90 is attached is referred to as the "rear end unit."

[0069] <Overall assembly process> First, the coil spring 30 is inserted from the rear end side into the through hole of the restricting member 27 of the tip unit. At this time, the tip side of the coil spring 30 inserted into the restricting member 27 covers the rear end side end of the protrusion 23a of the electrode unit 23 of the detection unit 11 and is in contact with the protrusion 23a.

[0070] Next, the rear end unit is attached to the front end unit to which the coil spring 30 is attached. Specifically, the rear end side of the front end unit is opposed to the front end side of the rear end unit, and the protruding parts of the conductive member 31 in the rear end unit (in this example, the first columnar portion 31a, the bulging portion 31b, and the second columnar portion 31c) are inserted into the through-hole of the restricting member 27 in the front end unit. The side of the conductive member 31 enters inside the coil spring 30 that has already been inserted into the restricting member 27 and comes into contact with the coil spring 30. As a result, the electrode portion 23 in the detecting unit 11 and the conductive member 31 are electrically connected via the coil spring 30. At this time, the coil spring 30 is in a more compressed state than before the conductive member 31 was inserted.

[0071] Thereafter, as the tip portion 42a of the second housing 42 is inserted into the rear end hole 41d of the first housing 41, the second housing 42 fits into the first housing 41, and the tip portion 42a of the second housing 42 abuts against the stepped portion 41e of the first housing 41, thereby positioning the rear end unit relative to the front end unit. Then, the boundary surface between the end portion on the rear end side of the first housing 41 and the second housing 42 is joined by laser welding. Through the above, the sensor unit 10 shown in FIGS. 2 to 4 is obtained.

[0072] As described above, in the pressure detection device 5 of the present embodiment, instead of butting the rear end of the first housing 41 against the front end of the second housing 42 as in the past and joining the boundary surface (outer periphery) by laser welding, the first housing 41 and the second housing 42 are positioned by butting the front end of the front end 42a of the second housing 42 against a step 41e in a cylindrical hole provided in the first housing 41, and the boundary surface (outer periphery) between the rear end of the first housing 41 (opening end of the rear end hole 41d) and the second housing 42 is joined by laser welding. In addition, at this time, a gap 100 is provided between the rear end of the first housing 41 and the step 42d of the second housing 42.

[0073] In this manner, in the pressure detection device 5 of the present embodiment, the positioning and joining of the first housing 41 and the second housing 42 are performed at different locations. In the conventional pressure detection device, for example, when a defect occurs only in the rear end unit and it is desired to replace the rear end unit, the joint portion of the first housing 41 and the second housing 42 is cut to separate the front end unit from the rear end unit. However, since the joint portion of the front end unit and the rear end unit is also a positioning portion, the positioning portion of the first housing 41 (the end portion on the rear end side of the first housing 41) is affected by the cutting, and the positioning of the replaced rear end unit cannot be performed accurately. However, in the pressure detection device 5 of the present embodiment, even if the joint portion of the front end unit and the rear end unit is cut, the positioning portion (the positioning portion of the first housing 41 and the second housing 42) is not affected by the cutting, so that the front end unit and the replaced rear end unit can be reliably positioned, and the front end unit can be reused.

[0074] Furthermore, in the pressure detection device 5 of the present embodiment, a gap 100 is provided between the rear end portion of the first housing 41 and the step portion 42d of the second housing 42. This prevents the rear end portion of the first housing 41 and the step portion 42d of the second housing 42 from interfering with the positioning of the first housing 41 and the second housing 42, making it possible to more reliably position the first housing 41 and the second housing 42.

[0075] In the pressure detection device 5 of this embodiment, the leading end of the conductive member 31 is detachably connected to the detection unit 11 via the coil spring 30, and the rear end is non-detachably connected to the transmission wire 90. Note that "detachably connected" here refers to a state in which the connected members can be attached and detached without plastic deformation or damage, and "non-detachably connected" refers to a state in which the connected members cannot be attached or detached without plastic deformation or damage. With this configuration, the conductive member 32 can be easily separated from the leading end unit, and since the conductive member 31 is integrally formed with the rear end unit, the labor required for separating and joining the units can be reduced.

[0076] In the present embodiment, the first housing 41 in which the piezoelectric element 22 is housed and the second housing 42 to which the transmission cable 90 is attached are each formed from a single member, but the present invention is not limited to this. For example, at least one of the first housing 41 and the second housing 42 may be formed by integrating two or more members into the first housing 41 or the second housing 42.

[0077] In the present embodiment, the front end portion 42a of the second housing 42 is inserted into the rear end hole 41d of the first housing 41, and the front end portion 42a of the second housing 42 is abutted against the stepped portion 41e of the first housing 41 to perform positioning, but the present invention is not limited to this. For example, a configuration may be adopted in which a stepped portion is provided in a front end side hole of a cylindrical hole provided in the second housing 42, and the rear end side of the first housing 41 is inserted into the hole of the second housing 42 and the rear end of the first housing 41 is abutted against the stepped portion provided in the second housing 42 to perform positioning. [Explanation of symbols]

[0078] Reference Signs List 1...internal combustion engine, 2...cylinder block, 2a...cylinder, 3...piston, 4...cylinder head, 5...pressure detection device, 6...control device, 7...sealing member, 10...sensor unit, 11...detection section, 12...holding section, 21...diaphragm head, 22...piezoelectric element, 23...electrode section, 24...first pressing member, 25...second pressing member, 26...pressurizing member, 27...regulating member, 30...coil spring, 31...conductive member, 32...first insulating section material, 33...second insulating member, 34...front block ring, 35...O-ring, 36...rear block ring, 37...press-fit member, 37a...base, 37b...leg, 37c...projection, 37d...inclined portion, 40...housing, 41...first housing, 42...second housing, 90...transmission wire, 91...conductor, 92...resin insulating layer, 93...resin semiconductive layer, 94...braided shielding layer, 95...resin protective layer, 96...braided protective layer, 100...gap

Claims

1. A detection unit that detects pressure; a cable electrically connected to the detection unit and transmitting an output signal from the detection unit; a first housing that accommodates and supports the detection unit therein; a second housing fixed to the first housing and accommodating and supporting the cable therein, One of the first housing and the second housing has an opening with a stepped portion therein, the other of the first housing and the second housing has a connection portion insertable into the opening, the connecting portion is inserted into the opening and an end of the connecting portion is abutted against the step portion, The pressure detection device, wherein the first housing and the second housing are fixed to each other by joining at least a boundary between an open end of the opening and the connecting portion.

2. The pressure detection device according to claim 1, further comprising an electrical connection member that electrically connects the detection unit and the cable, the electrical connection member being non-detachably connected to one of the detection unit and the cable and detachably connected to the other of the detection unit and the cable.

3. The pressure detection device according to claim 1 or 2, characterized in that the first housing or the second housing in which the connection portion is formed has a protrusion having a surface that faces the opening end of the opening with a gap at the connection portion.

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