JPWO2014034641A1 - Pressure detection device - Google Patents

Abstract

In a pressure detecting device configured in a cylindrical shape for detecting the internal pressure of a cylinder by being mounted on the outer periphery of the tip of a functional member facing an engine combustion chamber, a pressure receiving ring 14 that receives pressure from the outside, and a pressure receiving ring 14 A pressure transmission ring 15 for transmitting the pressure, a piezoelectric element 16 for contacting the pressure transmission ring 15 to detect pressure fluctuations, and a cylindrical casing having an opening 10a for supporting the piezoelectric element 16; 16 outputs an electric signal corresponding to pressure from two electrodes facing each other. One electrode of the piezoelectric element 16 abuts the piezoelectric element 16 on the casing to be a ground electrode, and the other electrode is connected via a connection terminal 52. The cable 60 is electrically connected, and the cable 60 is formed of a flexible printed circuit board. The cable 60 is configured to transmit an electric signal to an external device.

Description

  The present invention relates to a pressure detection device that is mounted on the outer periphery of a tip of a functional member facing an engine combustion chamber and detects the pressure in the combustion chamber.

  Conventionally, for example, a pressure detection device using a piezoelectric element has been proposed in order to detect the pressure in a combustion chamber attached to an engine. The pressure detection device includes an electrical transmission means for transmitting an electrical signal output from the piezoelectric element to the outside of the pressure detection device.

  As an electrical transmission means of this type, an insulating layer made of resin is formed around the conductor portion (center conductor), a shielding layer (outer conductor) made of, for example, a metal braid is formed around the insulating layer, and the shielding layer is further formed. A coaxial cable in which a protective layer made of a resin is formed around is known. In this cable structure, a coaxial cable formed by coating an electrolytic metal plating layer around an insulating layer instead of a metal braid is disclosed (for example, see Patent Document 1).

  In addition, a coaxial cable is disclosed in which an insulating coating made of resin is formed on the outer periphery of the central conductor, and a shield conductor is formed on the outer periphery of the insulating layer by electroless and / or electrolytic metal plating (see, for example, Patent Document 2).

JP 2007-48719 A JP 2005-149892 A

  By the way, a pressure detection device used in an engine or the like vibrates with a pressure change in the combustion chamber. And when such vibrations act on the electrical transmission means provided in the pressure detection device, in the coaxial cable as in the conventional example, cracking or peeling occurs in the shielding layer formed by metal plating, As a result, noise is superimposed on the electrical signal from the coaxial cable, and in the worst case, the coaxial cable may be disconnected.

  Further, when the pressure detection device is mounted on the tip of the functional member facing the combustion chamber of the engine, in order to extract an electrical signal (detection signal) from the pressure detection device, the tip of the functional member, that is, the combustion of the engine Electrical transmission means extending and connecting to the pressure detection device facing the chamber is essential. However, in the conventional coaxial cable, since the conductor portion and the insulating layer overlap each other, a predetermined thickness is required, and it is difficult to pass the coaxial cable through a slight gap inside the functional member. For this reason, it is necessary to widen the internal gap of the functional member so that the coaxial cable can be passed through to increase the outer diameter, or to place the pressure detection device in the combustion chamber independently of the functional member and connect the coaxial cable. was there. However, increasing the outer diameter of the functional member makes it difficult to reduce the size of the engine, and disposing the pressure detection device independently of the functional member also increases the communication holes of the cylinders that constitute the combustion chamber. That is not preferable.

  The object of the present invention is to solve the above-mentioned problems, and to be attached to the outer periphery of the tip of the functional member by providing an electrical transmission means that is strong against vibration and impact and is difficult to break and can be arranged in a slight gap of the functional member. It is to provide a pressure sensing device that can.

  In order to solve the above-described problem, a pressure detection device according to the present invention is a cylindrical pressure detection device configured to detect the internal pressure of a cylinder by being mounted on the outer periphery of the tip of a functional member facing the combustion chamber of the engine. , A pressure receiving member that receives pressure from the outside, a pressure transmission member that transmits pressure from the pressure receiving member, a piezoelectric element that abuts on the pressure transmission member to detect pressure fluctuations, and abuts on the piezoelectric element The piezoelectric element includes an electrode member and a cylindrical casing having an opening, and the piezoelectric element outputs an electrical signal corresponding to pressure from two opposing electrodes, and one electrode of the piezoelectric element supports the piezoelectric element. The other electrode is in contact with the electrode member provided between the pressure transmission member and the piezoelectric element, and the electrode member is electrically connected to the printed circuit board via the connection terminal. Electrically to the means Is continued, characterized by transmitting electrical signals to an external device by said electrical transmission means.

  In this case, according to a preferred aspect of the invention, one or a plurality of piezoelectric elements can be arranged along the circumferential direction inside the housing, and the piezoelectric elements can be alternately arranged via spacers. Further, the connection terminal can be connected to the electrical transmission means through the spacer and the through hole provided in the casing, and the connection terminal can be positioned by using the through hole provided in the casing. At this time, it is desirable to interpose a spring between the connection terminal and the electrode member. On the other hand, the housing can be provided with a fixing portion for fixing the electrical transmission means at a location where the connection terminal is exposed from the through hole. Note that a flexible printed circuit board is preferably used as the printed circuit board constituting the electrical transmission means. In addition, when the electrical transmission means is secured, a pair of opposing projections having a function of preventing the electrical transmission means from being detached can be formed on the end face of the securing portion. It has a letter-shaped stop portion, and the stop portion can be fitted into the fixing portion and hooked to the protrusion. Further, the electrical transmission means can be electrically and mechanically connected to the connection terminal by solder. At this time, the electric transmission means can be covered with the heat-resistant member and can be electrically shielded by the laminated structure of the insulating member and the conductive member.

  According to the pressure detection device according to the present invention having such a configuration, the following remarkable effects can be obtained.

  (1) In order to transmit an electrical signal from the pressure detection device to the outside, an electrical transmission means composed of a flexible printed circuit board that can be made extremely thin is used, so that the tip of the functional member facing the combustion chamber of the engine An electric signal from the pressure detection device to be mounted can be transmitted to the external device through a slight gap in the casing of the functional member. As a result, the pressure detecting device can be attached to the outer periphery of the tip end of the functional member without restricting the shape of the functional member. Therefore, the pressure that can be attached to the engine as a single functional member by integrating the functional member and the pressure detecting device. A detection device can be provided.

  (2) Solder the connection terminal of the pressure detection device and the flexible printed circuit board, and provide a fixing portion and a protrusion on the housing of the pressure detection device, and attach a T-shaped stopper to the tip of the flexible printed circuit board. By providing, the stopper can be hooked on the protrusion by fitting the stopper into the fixing portion of the housing. Thereby, even if the pressure detection device vibrates with the pressure change in the combustion chamber, it is possible to prevent the electrical transmission means formed of the flexible printed circuit board from being detached from the pressure detection device. Moreover, since the flexible printed circuit board is thin and excellent in flexibility, it is not damaged by vibration or impact. As a result, it is possible to provide a pressure detection device that is provided with an electrical transmission means that is strong against vibration and shock and is difficult to be disconnected, and that can realize electrical connection with an external device with high reliability.

  (3) According to a preferred embodiment, when a plurality of piezoelectric elements are arranged along the circumferential direction inside the housing, and the piezoelectric elements are alternately arranged via spacers, the pressure can be detected uniformly in a balanced manner, High-precision pressure detection is possible. Even if there is only one piezoelectric element, it is possible to accurately and easily incorporate the arrangement position with the spacer formed in the C shape, and there is no loss with respect to the piezoelectric element. Pressure transmission is possible. Further, by balancing the stress, no chipping or cracking of the piezoelectric element occurs, and the cost can be reduced by reducing the number of piezoelectric elements.

  (4) According to a preferred embodiment, the connection terminal is connected to the electrical transmission means through the spacer and the through hole provided in the housing, and the connection terminal is positioned using the through hole provided in the housing. If it does so, it can arrange | position, positioning the connection terminal connected to an electrical transmission means.

  (5) If a spring is interposed between the connection terminal and the electrode member according to a preferred embodiment, even if the positional relationship between the connection terminal and the electrode member varies due to external pressure, the spring is connected to the electrode member by the spring force of the spring. The terminals can be securely connected electrically.

  (6) According to a preferred aspect, if the housing is provided with a fixing portion for fixing the electrical transmission means at a location where the connection terminal is exposed from the through hole, the electrical transmission means is fixed to the fixing portion of the housing. Therefore, the electrical transmission means and the housing can be integrated. Further, since the fixing portion is disposed at a position where the connection terminal is exposed from the through hole, the electrical transmission means fixed to the fixing portion and the connection terminal can be easily connected.

  (7) According to a preferred embodiment, if a flexible printed circuit board is used as the printed circuit board that constitutes the electrical transmission means, the flexible printed circuit board is thin and flexible, so that it can be damaged by long-term vibration and impact. There is no. As a result, it is possible to provide a pressure detection device including an electrical transmission means that is strong against vibration and impact and is difficult to be disconnected.

  (8) According to a preferred embodiment, when the electric transmission means is fixed to the end face of the fixing portion, a pair of opposing protrusions having a function of preventing the electric transmission means from coming off is formed. Due to the protruding portion, the electric transmission means can be prevented from coming off from the fixing portion.

  (9) According to a preferred embodiment, when a substantially T-shaped stopper is provided at the tip of the electrical transmission means, and the stopper is fitted into the fixing portion and is hooked on the protrusion, The stop portion, which is a substantially T-shaped shape of the mechanical transmission means, is hooked on the protruding portion of the fixing portion, so that the electrical transmission means can be reliably prevented from coming off from the fixing portion.

  (10) According to a preferred aspect, when the electrical transmission means is electrically and mechanically connected to the connection terminal by solder, the electrical transmission means and the connection terminal are securely and electrically coupled to each other. it can.

  (11) If the electrical transmission means is covered with a heat resistant member according to a preferred embodiment, the electrical transmission means can be protected from the heat of the engine, and a pressure detection device excellent in heat resistance can be realized.

  (12) According to a preferred embodiment, if the electrical transmission means is electrically shielded by the laminated structure of the insulating member and the conductive member, the electrical noise from the outside is cut off and the S / N ratio is good. A simple electrical signal can be transmitted to an external device.

It is a schematic block diagram of the engine concerning the 1st-3rd embodiment. It is sectional drawing of the centerline direction of the pressure detection apparatus of 1st Embodiment. It is the expanded sectional view which expanded the area | region A of sectional drawing of FIG. It is the expanded sectional view which expanded the area | region B of sectional drawing of FIG. It is a perspective view for demonstrating the adhering part and projection part of the pressure detection apparatus of 1st Embodiment. It is a perspective view explaining the state which attached the cable which consists of a flexible printed circuit board to the pressure detection apparatus of 1st Embodiment. It is a top view explaining the state which attached the cable which consists of a flexible printed circuit board to the pressure detection apparatus of 1st Embodiment. It is sectional drawing which cut | disconnected the pressure detection apparatus of 1st Embodiment shown in FIG. 2 by the cutting line FF '. It is sectional drawing explaining the example of mounting to the fuel-injection apparatus of the pressure detection apparatus of 1st Embodiment. It is a block diagram explaining the pressure detection operation | movement of the pressure detection apparatus of 1st Embodiment. It is sectional drawing of the centerline direction of the pressure detection apparatus of 2nd Embodiment. It is a perspective view of the pressure detection apparatus of 2nd Embodiment. It is a top view of the cable which consists of a flexible printed circuit board of the pressure detection apparatus of 3rd Embodiment. It is sectional drawing of the cable which consists of a flexible printed circuit board of the pressure detection apparatus of 3rd Embodiment.

  1: engine, 2: cylinder block, 2a: cylinder, 3: piston, 4: cylinder head, 4a: communication hole, 4b: communication hole, 5: spark plug, 6: injector unit, 7: fuel injection device, 7b: Tip part, 10: Pressure detection device, 10a: Opening part, 11: Front outer casing, 12: Front inner casing, 13: Rear casing, 13c: Through hole, 13d: Adhering part, 13e: Protruding part, 13f : Protruding part, 14: Pressure receiving ring, 15: Pressure transmission ring, 16: Piezoelectric element group, 17: Electrode member, 52: Connection terminal, 56: Coil spring, 60: Cable, 60a: Stopping part, 61: Insulating film, 62: Conductive part, 63: Solder, 65: Amplifier circuit, 66: Control circuit, 70: Pressure detection device, 71: Heat-resistant member, 80: Cable, 80a: Stopping part, 81: Insulating film 82: conductive portion, 83: shielding member, 84: insulating member, 85: shielding member

  Hereinafter, various embodiments including the best embodiment according to the present invention will be given and described in detail with reference to the drawings.

  First, features of each embodiment will be described. A feature of the first embodiment is a basic configuration example of the present invention, in which an electrical signal from a pressure detection device used in an engine or the like is used with a cable formed of a flexible printed circuit board (hereinafter abbreviated as FPC). It is a pressure detection device that transmits to the outside. A feature of the second embodiment is a pressure detection device in which the heat resistance of a cable made of FPC is enhanced. A feature of the third embodiment is a pressure detection device in which an electrical shield structure is added to a cable made of FPC.

  First, a schematic configuration of an engine in which the pressure detection devices of the first to third embodiments of the present invention are incorporated will be described with reference to FIG. In addition, although the example which incorporates the pressure detection apparatus of 1st Embodiment is demonstrated here, the pressure detection apparatus of the 2nd and 3rd embodiment mentioned later can also be integrated similarly. In FIG. 1, reference numeral 1 denotes an engine in which the pressure detection device of the present invention is incorporated. The engine 1 includes a cylinder block 2 having a cylinder 2a, a piston 3 that reciprocates in the cylinder 2a, and 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. I have.

  The engine 1 is mounted on the cylinder head 4 and ignites the fuel to explode the air-fuel mixture in the combustion chamber C. The engine 1 is mounted on 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 4a has a spark plug 5 and the other communication hole 4b has an injector unit 6. Each is attached in a penetrating state.

  An injector unit 6 as a functional member for an engine includes a fuel injection device 7 that injects fuel into the combustion chamber C, and a pressure detection device 10 that is a first embodiment of the present invention that is attached to the fuel injection device 7. have. Here, the fuel injection device 7 includes a main body portion 7a disposed outside the combustion chamber C, and a columnar tip portion 7b extending from the main body portion 7a toward the combustion chamber C.

  On the other hand, the pressure detection device 10 has a function of detecting the pressure in the combustion chamber C (combustion pressure: arrow D), and is attached to the outer periphery of the tip portion 7 b of the fuel injection device 7. And this pressure detection apparatus 10 is comprised by the cylindrical shape which has the opening part penetrated so that it may mention later.

First embodiment

  Next, the structure of the pressure detection apparatus 10 of 1st Embodiment is demonstrated using FIGS. 2 is a cross-sectional view in the center line direction of the pressure detection device 10 of the first embodiment, FIG. 3 is an enlarged cross-sectional view of a region A in FIG. 2, and FIG. 4 is an enlarged cross-sectional view of a region B in FIG. It is. In the following description, when the injector unit 6 is configured together with the fuel injection device 7, the side facing the combustion chamber C in the pressure detection device 10 is referred to as the “front side” and is opposite to the combustion chamber C. The facing side is referred to as the “back side”. In addition, a region A in FIG. 2 indicates a piezoelectric element peripheral region for detecting pressure, and a region B indicates a connection terminal peripheral region for transmitting an electric signal. The cutting line FF ′ in FIG. 2 will be described later.

  Here, the pressure detection device 10 has a cylindrical shape as a whole, and is provided with an opening 10a that penetrates from the front side to the back side and accommodates the tip 7b in the fuel injection device 7 shown in FIG. . That is, the front end portion 7b of the fuel injection device 7 is accommodated in the opening 10a of the cylindrical pressure detection device 10, and a nozzle (described later) for injecting fuel provided in the front end portion 7b is used for pressure detection. It is exposed in the combustion chamber C through the opening 10 a of the apparatus 10.

  The structure of the pressure detection device 10 includes a front outer casing 11 having a cylindrical shape and a cylindrical shape, and is disposed concentrically with the front outer casing 11 inside the front outer casing 11. A front inner housing 12 having a cylindrical shape, a rear housing 13 attached to the rear side of the front outer housing 11 and the front inner housing 12, and an annular shape and the front outer housing 11. And a pressure receiving ring 14 as a pressure receiving member that is attached to the front side of the front inner housing 12 and receives pressure from the outside.

  Next, the casing of the pressure detection device 10 will be described in detail with reference to FIGS. As described above, the front outer casing 11 has a cylindrical shape, and a notch for fitting an outer end portion of a pressure receiving tip portion (described later) of the pressure receiving ring 14 into an inner end portion of the front surface side. 11a is formed (see FIGS. 3 and 4).

  As described above, the front inner casing 12 has a cylindrical shape, and the outer diameter thereof is smaller than the inner diameter of the front outer casing 11 described above. Further, a notch 12a for fitting the inner end portion of the pressure receiving tip portion of the pressure receiving ring 14 is formed on the outer side of the front end portion of the front inner housing 12 (see FIGS. 3 and 4). In addition, a notch 12b for fitting the inner side of the front side of the rear case 13 is formed on the outer side of the rear side of the front inner case 12 (see FIGS. 3 and 4).

  The rear housing 13 has a cylindrical shape, and is provided with a ground electrode layer 13b functioning as a ground electrode of the piezoelectric element group 16 on an end surface on the front surface side of the rear housing 13 (see FIG. 3). . Here, the rear casing 13 has 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 back side of the front stage 131. And the rear stage 133 set to the outer diameter substantially the same as the inner diameter of the front outer casing 11 on the back side of the middle stage 132 (FIG. 3). FIG. 4).

  The ground electrode layer 13b described above is formed on the front end surface of the front stage 131 of the rear housing 13 over substantially the entire circumference. In addition, a notch 131a for fitting the outer end of the rear side of the front outer casing 11 is formed on the outer side of the front end of the front step 131 by the middle step 132 (FIGS. 3 and 3). 4). Further, the inner side of the front portion of the front stage 131 has a structure that is fitted into the notch 12b provided on the outer side of the rear side of the front inner housing 12 described above.

  Here, the front outer casing 11, the front inner casing 12, and the rear casing 13 are present at a position facing the combustion chamber C or a position close to the combustion chamber C that can be at a high temperature. It is desirable to fabricate using a material that can withstand an operating temperature environment of from ℃ to 350 ℃. In this example, as will be described later, since the rear casing 13 is used as a grounding target for the cable including the piezoelectric element group 16 and the FPC, the rear casing 13 is manufactured using a conductive material. It is desirable. Specifically, the front outer casing 11, the front inner casing 12, and the rear casing 13 are made of stainless steel having high heat resistance and conductivity, such as JIS standard SUS630, SUS316, SUS430, or the like. Configure.

  Then, laser welding is performed over the entire circumference in a state where the rear end of the front outer casing 11 is fitted into a notch 131a provided on the outer end of the front end of the rear casing 13. It is fixed with. Further, the notch 12b on the back side of the front inner housing 12 is fixed by laser welding over the entire circumference in a state of being fitted to the front surface side of the rear housing 13. In this manner, the front outer casing 11 and the rear casing 13 are laser welded, and the front inner casing 12 and the rear casing 13 are laser welded to form an integrated casing.

  Thus, since the housing | casing of the integrated pressure detection apparatus 10 is cylindrical shape, the front-end | tip part 7b of the fuel injection apparatus 7 can be arrange | positioned in the opening part 10b in a housing | casing, and the fuel injection apparatus 7 and the pressure detection apparatus 10 can be arrange | positioned. Can be incorporated into the cylinder block 2 as one injector unit 6 (see FIG. 1). Thereby, it is not necessary to provide a new communication hole in the cylinder block 2 for the pressure detection device 10, and a pressure detection device excellent in space efficiency can be provided.

  Further, the ground electrode layer 13b provided on the end surface of the front portion 131 on the front side of 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 13. . As such a ground electrode layer 13b, an inner layer using, for example, Ti as an adhesion strengthening layer is stacked on the rear casing 13, and an intermediate layer using, for example, Pt as a diffusion preventing layer is stacked on the inner layer. For example, a laminate in which a bonding layer using, for example, Au is stacked on the uppermost layer can be used.

  Next, the internal space formed in the housing of the pressure detection device 10 will be described with reference to FIGS. In the pressure detection device 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 described above. The internal space 10b has an annular shape and is disposed on the back side of the pressure receiving ring 14, and a pressure transmission ring 15 as a pressure transmission member for transmitting the pressure from the pressure receiving ring 14 to the back side, and the pressure A piezoelectric element group 16 is provided between the back side of the transmission ring 15 and the end surface of the front stage 131 of the rear housing 13 and converts the pressure received from the pressure transmission ring 15 into an electrical signal. Details of the piezoelectric element group 16 will be described later.

  Next, details of the pressure receiving ring 14 will be described with reference to FIGS. The pressure receiving ring 14 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 is exposed to the outside, that is, the combustion chamber C (see FIG. 1) side, thereby receiving a pressure receiving tip 14a that receives the internal pressure of the combustion chamber C of the cylinder 2a, and a pressure receiving tip on the back side of the pressure receiving tip 14a. The transmission portion 14b that transmits the pressure received by the portion 14a to the pressure transmission ring 15 is integrally formed. Then, the outer end of the pressure receiving tip 14a of the pressure receiving ring 14 is laser welded over the entire circumference in a state where it is fitted into a notch 11a provided inside the front end of the front outer casing 11. Is fixed.

  The inner end of the pressure receiving tip 14a of the pressure receiving ring 14 is laser welded over the entire circumference in a state where the inner end of the pressure receiving ring 14 is fitted into a notch 12a provided on the outer side of the front side of the front inner housing 12. Is fixed. 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. 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, SUH660 or the like can be used.

  The pressure receiving ring 14 receives the combustion pressure from the combustion chamber C (arrow D in FIG. 3) by the pressure receiving tip portion 14a, and the combustion pressure D is transmitted to the pressure transmission ring 15 via the transmission portion 14b. It is transmitted to the piezoelectric element group 16 in contact with the ring 15 and converted into an electric signal described later.

  The pressure transmission ring 15 has an annular shape, and has a rectangular cross section. The outer diameter of the pressure transmission ring 15 is smaller than the inner diameter of the front outer casing 11, and the inner diameter is larger than the outer diameter of the front inner casing 12. . In addition, the pressure transmission ring 15 is good to comprise with ceramic materials, such as an alumina which has heat resistance and insulation.

  Further, an electrode member 17 that functions as an output electrode for outputting an electrical signal from the piezoelectric element group 16 is provided on the end surface on the back side of the pressure transmission ring 15. The electrode member 17 is annularly arranged on the end surface on the back side of the pressure transmission ring 15 over the entire circumference. That is, the electrode member 17 is provided between the pressure transmission ring 15 and the piezoelectric element group 16.

  As an example, the electrode member 17 includes an annular insulating film formed on one side of a highly conductive metal film that is a member different from the pressure transmission ring 15, and an end face on the back side of the pressure transmission ring 15 with an adhesive or the like. The electrode member 17 may be disposed in a fixed manner, or may be formed by directly forming a highly conductive metal film on the end face of the pressure transmission ring 15 so as to be integrated with the pressure transmission ring 15. In other words, the end surface on the back side of the pressure transmission ring 15 becomes a conductive electrode surface by providing the electrode member 17.

  Next, the through-hole formed in the rear housing 13 will be described with reference to FIG. In FIG. 4, the rear housing 13 is formed with a through hole 13 c that penetrates the rear housing 13 along the center line direction. The front side of the through-hole 13c is connected to the internal space 10b that accommodates the pressure transmission ring 15 and the piezoelectric element group 16 described above, and the back side of the through-hole 13c is connected to a later-described fixing portion formed in the rear housing 13. ing. The through-hole 13c has a function of positioning a connection terminal while inserting a connection terminal to be described later, exposing the connection terminal from the internal space 10b to the outside of the rear casing 13.

  Next, a fixing portion for fixing the electrical transmission means made of FPC, which is a feature of the present invention, to the housing will be described with reference to FIGS. 4 and 5, a fixing portion 13d for fixing a cable made of FPC, which will be described later, is formed on the back side of the through hole 13c, that is, the rear stage portion 133 of the rear casing 13 through which the through hole 13c passes. The The fixing portion 13d is formed at a location where the through hole 13c penetrates the rear stage portion 133 so as to cut out a part of the rear stage portion 133, and the bottom surface of the fixing portion 13d is flat. In addition, a pair of opposing protruding portions 13e and 13f are formed on the end surface on the back side of the fixing portion 13d.

  Next, the connection terminals will be described with reference to FIGS. The connection terminal 52 is formed of a metal rod-like body having heat resistance and conductivity, and has a butting portion 52a that abuts against the electrode member 17 provided on the end surface of the pressure transmission ring 15, and a back surface of the butting portion 52a. A stopper 52b having a diameter larger than that of the abutting portion 52a and a connecting portion 52c, which is located on the back side and becomes a tip portion, are integrally formed (see FIG. 4). The shape of the connection terminal 52 is not particularly limited. The connection terminal 52 is inserted into the through-hole 13c of the rear housing 13 from the inner space 10b side, and the connection portion 52c of the connection terminal 52 is exposed from the through-hole 13c located on the end surface on the front surface side of the fixing portion 13d (see FIG. 5).

  When the connection portion 52c of the connection terminal 52 is inserted into the through hole 13c, the connection portion 52 is inserted into the positioning tube 55 and positioned inside the through hole 13c (see FIG. 4). In addition, a coil spring 56 is provided which is wound around the outer peripheral surface of the abutting portion 52a of the connection terminal 52 and contacts the electrode member 17 to electrically connect the electrode member 17 and the connection terminal 52 (FIG. 4). reference). Due to the spring force of the coil spring 56, the end on the front side of the coil spring 56 contacts the electrode member 17, and the end on the back side of the coil spring 56 contacts the stopper 52 b of the connection terminal 52. Even if the positional relationship between the pressure transmission ring 15 to which the member 17 is fixed and the connection terminal 52 varies due to external pressure, the electrode member 17 and the connection terminal 52 are reliably electrically connected. In addition, it is not limited to a coil spring, Various springs, such as a leaf | plate spring and a conductive rubber, can be utilized.

  Next, the structure of the cable 60 as an electrical transmission means that is a feature of the present invention and is attached to the fixing portion 13d of the rear housing 13 will be described with reference to FIGS. Note that the cable 60 shown in FIG. 6 does not show the conductive portions and the like. Here, the cable 60 is made of FPC, has an elongated sheet shape, and is thin and flexible. For the insulating film 61 serving as the base of the cable 60, polyimide having excellent heat resistance is used. In addition, on the surface of the insulating film 61, a conductive portion 62 that passes an electrical signal along the longitudinal direction is formed. The conductive portion 62 is formed of a copper foil.

  The stopper 60a at one end of the cable 60 has a T-shape, and the stopper 60a is fitted into the fixing part 13d of the pressure detecting device 10 so that the stopper 60a is a pair of protrusions of the fixing part 13d. 13e and 13f are hooked. Further, the back surface of the stopper 60a of the cable 60 and the bottom surface of the fixing portion 13d are fixed with an adhesive having excellent heat resistance. As a result, the cable 60 is fixed to the fixing portion 13d, and even if a stress that pulls the cable 60 in the direction of arrow E (see FIG. 6) is generated, the cable 60 is hooked by the protruding portions 13e and 13f. The cable 60 can be prevented from being detached from the pressure detection device 10.

  Further, the end of the connection terminal 52 exposed from the through hole 13c of the rear housing 13 on the conductive portion 62 of the stop portion 60a of the cable 60 by the stopper portion 60a of the cable 60 being fitted into the fixing portion 13d. The connection part 52c of the cable 60 and the connection terminal 52c of the connection terminal 52 are close to or in contact with each other. In this state, the conductive portion 62 of the cable 60 and the connection portion 52c of the connection terminal 52 are soldered with the solder 63, whereby the conductive portion 62 of the cable 60 and the connection terminal 52 are electrically and mechanically connected. The pattern of the conductive portion 62 of the stopper 60a is desirably provided with a predetermined area for soldering.

  On the other hand, the external connection portion 60b (see FIG. 7), which is the tip of the cable 60 opposite to the T-shaped stop portion 60a, has a predetermined area for connection to an external device (not shown). An insulating film 61 and a conductive portion 62 are formed. In addition, the shape of the external connection part 60b is arbitrarily changed according to the specification of the external apparatus to connect. The insulating film 61 and the conductive portion 62 of the intermediate portion 60c between the T-shaped stopper 60a and the external connection portion 60b are desirably as thin as possible in order to ensure flexibility.

  As described above, the pressure detection device 10 of the present invention uses the cable 60 made of FPC to transmit an electrical signal that detects a pressure change to the outside, and solders the connection terminal 52 and the cable 60 of the pressure detection device 10. At the same time, a fixing portion 13d and a pair of protrusions 13e and 13f are provided on the rear casing 13 of the pressure detection device 10, and a T-shaped stopper 60a is provided at the tip of the cable 60, whereby the stopper 60a. Is fixed to the fixing portion 13d of the rear housing 13 and is hooked on the protruding portions 13e and 13f.

  With this structure, even if the pressure detection device 10 vibrates with the pressure change in the combustion chamber C of the engine 1, the cable 60 can be prevented from being disconnected from the pressure detection device 10. Further, since the cable 60 made of FPC is thin and flexible, it is not damaged by a long-term vibration or impact. As a result, it is possible to provide a pressure detection device including an electrical transmission means that is strong against vibration and impact and is difficult to be disconnected. In addition, the case where a non-flexible printed circuit board (PC) is used instead of FPC is not excluded. Therefore, when the external device is arranged in the vicinity of the pressure detection device 10 or when a general circular core type cable is connected (relayed) from the middle, a PC can be used. .

  Next, the piezoelectric element group 16 incorporated in the pressure detection device 10 will be described with reference to FIGS. 2, 3, and 8. FIG. 8 is a cross-sectional view of the vicinity of the piezoelectric element group 16 cut along the cutting line FF ′ in FIG. 2, 3, and 8, the piezoelectric element group 16 includes a cylindrical rear housing 13 in an internal space 10 b between the back surface of the pressure transmission ring 15 and the front surface of the rear housing 13. A plurality of elements are arranged along the circumferential direction, supported by the rear housing 13. In the present embodiment, the six piezoelectric elements 161 to 166 are arranged at substantially equal intervals, but the number of the piezoelectric element groups 16 may be less than six or more.

  Here, the piezoelectric elements 161 to 166 have a common configuration, and each of them has a piezoelectric body 16a processed into a rectangular parallelepiped shape, a front-side electrode 16b formed on the front end face of the piezoelectric body 16a, and a piezoelectric element. A rear-side electrode 16c formed on an end surface on the back side of the body 16a (see FIG. 3). The front-side electrode 16b and the rear-side electrode 16c are formed such that a highly conductive metal film is opposed to the piezoelectric body 16a.

  The piezoelectric body 16a can be exemplified by using a langasite crystal (a langasite, a langagate, a langanite, LGTA) having a piezoelectric longitudinal effect and a piezoelectric transverse effect, quartz, gallium phosphate, or the like. In the piezoelectric element group 16 of the present embodiment, a langasite single crystal is used as a piezoelectric body.

  In each of the piezoelectric elements 161 to 166, each front-side electrode 16 b abuts on an electrode member 17 provided on the end face of the pressure transmission ring 15, and each rear-side electrode 16 c is a ground electrode provided on the rear housing 13. It contacts the layer 13b.

  Spacers 171 to 176 are arranged in the gaps between the piezoelectric elements 161 to 166, and the piezoelectric elements 161 to 166 function so as to be arranged at substantially equal intervals. In addition, a spacer through hole 171 a for penetrating the connection terminal 52 is provided in a substantially central portion of the spacer 171, and the connection terminal 52 passes therethrough. The material of the spacers 171 to 176 is ceramic (alumina, zirconia) or the like, but the material is not limited as long as it is an insulating material. As described above, since the plurality of piezoelectric element groups 16 are arranged at equal intervals along the circumferential direction inside the casing, the pressure from the outside can be uniformly received in a balanced manner, and highly accurate pressure detection can be performed. It becomes possible.

  Note that the number of piezoelectric elements may be one. In this case, one piezoelectric element may be arranged together with the spacer formed in the C shape. When a single piezoelectric element is disposed, it is important to use a spacer that balances stress so that an offset load is not applied because a compressive load is applied by a diaphragm. Therefore, it is desirable that the shape of the spacer is a C shape in order to facilitate adjustment of the arrangement of the piezoelectric elements. That is, even with a single piezoelectric element, by using a spacer, it can be accurately and easily incorporated into the arrangement position, and pressure transmission without loss to the piezoelectric element is possible. Further, by balancing the stress, the piezoelectric element is not broken or cracked, and the cost can be reduced by reducing the number of piezoelectric elements.

  Next, an electrical connection structure of the pressure detection device according to the first embodiment will be described with reference to FIGS. 2 to 4 and 7. First, each rear electrode 16c provided on the back side of the piezoelectric elements 161 to 166 constituting the piezoelectric element group 16 is in contact with the ground electrode layer 13b provided in the rear casing 13 as described above. Electrically connected. Here, since the rear casing 13 is conductive, the rear casing 13 and the ground electrode layer 13b are in an electrically connected state (see FIG. 3).

  On the other hand, each front side electrode 16b provided on the front side of the piezoelectric elements 161 to 166 constituting the piezoelectric element group 16 is in contact with the electrode member 17 provided on the end face of the pressure transmission ring 15 to be electrically connected. Connected to. With such a configuration, the piezoelectric element group 16 is sandwiched between the ground electrode layer 13 b of the rear housing 13 and the electrode member 17 and is electrically connected.

  That is, the individual piezoelectric elements 161 to 166 of the piezoelectric element group 16 are connected in parallel between the ground electrode layer 13 b and the electrode member 17. For this reason, each electric charge generated by the pressure received by each of the piezoelectric elements 161 to 166 is averaged by parallel connection and output as one electric signal, so that there is a slight difference in the position of the piezoelectric elements 161 to 166. The pressure difference due to, the characteristic variation of each piezoelectric element, etc. are canceled by averaging, and high-precision pressure detection can be realized.

  Further, since the pressure transmission ring 15 has an insulating property as described above, the pressure transmission ring 15 and the electrode member 17 are fixed, but are electrically insulated. Is also insulated from the surrounding front outer casing 11 and front inner casing 12.

  On the other hand, the electrode member 17 is electrically connected to the connection terminal 52 via the coil spring 56 (see FIG. 4). Further, as described above, in the connection terminal 52, the connection portion 52 c is exposed to the fixing portion 13 d through the through hole 13 c, and the connection portion 52 c and the conductive portion 62 of the cable 60 are electrically connected by the solder 63. That is, the electrode member 17 that abuts on the front side electrode 16 b of the piezoelectric element group 16 and functions as an output electrode is electrically connected to the cable 60 via the connection terminal 52.

  As a result, the electrical signal from the piezoelectric element group 16 is transmitted to the conductive portion 62 of the cable 60, and the external connection portion 60b (see FIG. 7) of the cable 60 is connected to an external device (not shown) of the engine 1. Thus, an electrical signal can be transmitted to an external device.

  Further, the transmission path of the electrical signal from the connection terminal 52 to the cable 60 is a front outer casing made of metal and electrically connected to each other by the internal space 10b and the positioning tube 55 each made of an insulator. 11. It is electrically insulated from the front inner casing 12 and the rear casing 13. Further, since the position of the connection terminal 52 is regulated by the through hole 13 c and the positioning tube 55, the connection terminal 52 contacts the outer peripheral surface of the front outer casing 11 and the inner peripheral surface of the front inner casing 12. No (see FIG. 4).

  When the injector unit 6 configured using the fuel injection device 7 and the pressure detection device 10 of the present invention is attached to the cylinder head 4 shown in FIG. 1, at least the front outer casing 11 is made of a metal cylinder head. 4 is electrically connected. Since the cylinder head 4 is electrically grounded, each rear side electrode 16c on the back side of the piezoelectric elements 161 to 166 of the pressure detecting device 10 passes through the rear casing 13 and the front outer casing 11. Thus, it is connected to the ground electrode of the injector unit 6 and grounded. As a result, the rear side electrode 16c, which is one electrode of the piezoelectric element group 16, is connected to the ground electrode of the entire apparatus, so that the influence of electrical noise from the outside is cut off and high-precision pressure detection is performed. realizable.

  Next, a mounting example of the fuel injection device 7 which is an example of the pressure detection device 10 as a functional member, specifically, an example of mounting on the outer periphery of the tip portion 7b (see FIG. 1) of the fuel injection device 7 is shown in FIG. Will be described. 9 shows that the tip 7b of the fuel injection device 7 is incorporated in the opening 10a of the pressure detection device 10. In FIG. 9, the distal end portion 7 b of the fuel injection device 7 has a double structure of an inner casing 91 made of a substantially cylindrical metal and an outer casing 92 made of a substantially cylindrical metal that covers the outside of the inner casing 91. have.

  Here, the internal housing 91 is inserted into the opening 10 a of the pressure detection device 10, and the nozzle 7 c provided at the tip of the internal housing 91 is exposed from the front side of the pressure detection device 10. With this structure, the nozzle 7 c at the tip 7 b of the fuel injection device 7 can inject fuel into the combustion chamber C from the opening 10 a on the front side of the pressure detection device 10. Further, laser welding is performed on the entire circumference where the tip corner portion of the inner casing 91 and the front inner casing 12 of the pressure detection device 10 are in contact (welding location: G1).

  On the other hand, the outer casing 92 is fitted into the rear casing 13 of the pressure detection device 10, and laser welding is performed on the entire circumference where the tip of the outer casing 92 and the rear casing 13 are in contact (welding location). : G2). The pressure detection device 10 and the fuel injection device 7 are fixed and integrated by the welding locations G1 and G2.

  A narrow gap 93 is formed between the inner casing 91 and the outer casing 92, and the cable 60 from the pressure detection device 10 passes through the gap 93, and although not shown, the cable is connected to the electrode on the external apparatus side. The external connection part 60b (refer FIG. 7) of the front-end | tip of 60 is connected. In this way, the pressure detection device 10 and the external device are electrically connected, and an electrical signal from the piezoelectric element group 16 incorporated in the pressure detection device 10 can be transmitted to the external device.

  Here, if the cable 60 is composed of a coaxial cable as in the prior art, the coaxial cable needs to have a predetermined thickness as the outer diameter dimension because the conductor portion and the insulating layer overlap each other. For this reason, the gap 93 between the inner casing 91 and the outer casing 92 must be widened in accordance with the outer diameter of the coaxial cable. As a result, the outer diameter of the distal end portion 7b of the fuel injection device 7 is the clearance 93. Since it becomes thicker according to the spread, the diameter of the communication hole (see FIG. 1) of the cylinder block 2 through which the fuel injection device 7 passes is increased, which is not preferable because it hinders downsizing of the engine and the like.

  However, since the pressure detection device 10 of the present invention transmits an electric signal through the cable 60 made of a thin FPC, the width of the gap 93 of the tip end portion 7 b can be reduced to the minimum according to the thickness of the cable 60. As a result, the electrical signal from the pressure detection device 10 attached to the tip 7b of the fuel injection device 7 can be reliably transmitted to the external device without increasing the outer diameter of the fuel injection device 7. For this reason, since the pressure detection device 10 can be mounted on the outer periphery of the tip end portion 7b of the fuel injection device 7 without restricting the shape of the fuel injection device 7, the pressure detection device 10 and the fuel injection device 7 can be integrated, and the injector The unit 6 can be mounted on the cylinder block 2 through one communication hole 4b (see FIG. 1).

  The cable 60 is not directly connected to the fuel injection device 7, but will be described in detail later, but after passing through an amplifier circuit as an external device that converts the electrical signal of the pressure detection device 10, the fuel injection device 7 and others Connected to other devices.

  Next, the pressure detection operation of the pressure detection device 10 attached to the engine 1 will be described with reference to the block diagram of FIG. In addition, refer to FIGS. 2 to 8 for the configuration of the pressure detection device 10. In FIG. 10, the fluctuation of the combustion pressure (arrow D) as the internal pressure generated in the combustion chamber C in the cylinder block 2 of the engine 1 acts on the piezoelectric element group 16 via the pressure receiving ring 14 and the pressure transmission ring 15. At this time, the vibration generated with the fluctuation of the combustion pressure D includes a frequency component of about several KHz at the maximum.

  In this example, the piezoelectric element group 16 includes piezoelectric elements 161 to 166 arranged at equal intervals along the circumferential direction of the casing (see FIG. 8), and the piezoelectric elements 161 to 166 are substantially uniform. Electric charges corresponding to fluctuations in the combustion pressure D are generated. The electric charges generated in the piezoelectric bodies 16a constituting the piezoelectric elements 161 to 166 pass through the electrode members 17 provided on the end surfaces of the pressure transmission ring 15 as electric signals P1 from the front side electrodes 16b of the piezoelectric bodies 16a. To the connection terminal 52.

  Next, the electrical signal P <b> 1 transmitted to the connection terminal 52 is transmitted to the conductive portion 62 of the cable 60 connected to the connection terminal 52. Furthermore, the electrical signal P1 transmitted to the cable 60 is transmitted to an amplifier circuit 65 as an external device to which the cable 60 is connected. The amplifier circuit 65 includes an integrating circuit, integrates the electric signal P1 having a differentiated waveform, converts the electric signal P1 into a pressure signal P2, and transmits the pressure signal P2 to the control circuit 66 that controls the engine 1, whereby the fuel injection device 7 And the spark plug 5 is controlled.

  A rear side electrode 16c on the back side of the piezoelectric elements 161 to 166 constituting the piezoelectric element group 16 includes a cylinder block including the cylinder head 4 through the rear casing 13 and the front outer casing 11 from the ground electrode layer 13b. 2 is electrically connected to the ground electrode. As a result, the casing of the pressure detection device 10 and the entire cylinder block 2 are grounded, so that external electrical noise can be reduced. In this way, the pressure detection device 10 can detect the combustion pressure D generated in the combustion chamber C in the cylinder block 2 of the engine 1.

  And since the cable 60 is comprised by thin sheet-like FPC, it is possible to let the cable 60 pass only by providing a slight gap in the housing of the tip end portion 7b of the fuel injection device 7, and the fuel injection device. The electric signal from the pressure detection device 10 can be reliably transmitted without restricting the shape of 7. In addition, since the FPC has excellent flexibility, the cable 60 is not damaged even if it is repeatedly bent or vibrated. For this reason, the pressure detection device 10 provided with the cable 60 made of FPC is subject to vibration and impact from the engine 1 for a long time. A pressure detection device can be provided.

Second embodiment

  Next, the configuration of the pressure detection device according to the second embodiment will be described with reference to FIGS. 11 and 12. The pressure detection device of the second embodiment is a configuration in which the cable is covered with a heat-resistant member for the purpose of improving the heat resistance of the cable in the pressure detection device 10 of the first embodiment described above. Since it is the same as that of 1 embodiment, the same number is attached | subjected to the same element and the overlapping description is partially abbreviate | omitted.

  In FIG. 11 and FIG. 12, reference numeral 70 denotes the pressure detection device of the second embodiment. Similar to the pressure detection device 10 of the first embodiment, the pressure detection device 70 includes a front outer casing 11 having a cylindrical shape, a cylindrical shape, and an inner side of the front outer casing 11. A front inner housing 12 disposed concentrically with the front outer housing 11, and a rear housing 13 having a cylindrical shape and attached to the back side of the front outer housing 11 and the front inner housing 12. And a pressure receiving ring 14 which has an annular shape and is attached to the front side of the front outer casing 11 and the front inner casing 12 and receives pressure from the outside.

  Further, the pressure transmission ring 15 that further transmits the pressure from the pressure receiving ring 14 to the back surface side, and the pressure transmission ring 15 is disposed between the back surface side of the pressure transmission ring 15 and the front end surface of the rear housing 13. And a piezoelectric element group 16 for converting the pressure received from the electric signal into an electric signal. Since the configuration and function of each of these elements are the same as those in the first embodiment, detailed description thereof is omitted.

  Reference numeral 71 denotes a heat-resistant member having a cylindrical shape that is a feature of the second embodiment. The outer diameter of the heat-resistant member 71 is set slightly smaller than the outer diameter of the middle step portion 132 of the rear housing 13, and the inner diameter of the heat-resistant member 71 is set to be approximately the same as the outer diameter of the rear step portion 133 of the rear housing 13. Is done. The heat-resistant member 71 is fitted into the rear stage portion 133 of the rear housing 13, and the entire circumference of the heat-resistant member 71 is fixed by laser welding so that the heat-resistant member 71 and the rear housing 13 are integrated. As the material of the heat-resistant member 71, SUS, PBT resin (polybutylene terephthalate), or the like can be used.

  With the above structure, since the periphery of the connection terminal 52 and the cable 60 are covered with the heat-resistant member 71, a wall of the heat-resistant member 71 is formed between the combustion chamber C (see FIG. 1) as a heat source. As a result, since the heat from the combustion chamber C is shielded by the heat-resistant member 71, the temperature rise of the cable 60 and its surroundings is suppressed, and the cable 60 is prevented from being damaged or deteriorated by repeated heating. An excellent pressure detection device can be realized. In addition, the shape of the heat-resistant member 71, the length in the center line direction, and the like are not limited, and may be appropriately changed according to the specification of the pressure detection device 10, the shape of the fuel injection device 7, and the like.

  The mounting of the pressure detection device 70 of the second embodiment on the tip 7b of the fuel injection device 7 is the same as the mounting example shown in the first embodiment (see FIG. 9), and the description thereof is omitted. However, the heat-resistant member 71 has a structure that covers the cable 60 by being fitted inside the outer casing 92 of the distal end portion 7b. Note that the pressure detection device 70 of the second embodiment has many effects as in the first embodiment due to the characteristics of the cable 60 made of a thin sheet-like FPC.

Third embodiment

  Next, a pressure detection device according to a third embodiment, in particular, a cable configuration will be described with reference to FIGS. Here, FIG. 13 is a plan view of a cable made of FPC of the pressure detection device of the third embodiment, and FIG. 14 is an enlarged cross-sectional view cut along a cutting line GG ′ of FIG. The pressure detection device of the third embodiment has a configuration in which the cable of the pressure detection device of the first embodiment described above has a shield structure, and the basic structure of the pressure detection device itself is the first embodiment. Therefore, only the shielded cable will be described here.

  In FIG.13 and FIG.14, the code | symbol 80 is a cable as an electrical transmission means of the pressure detection apparatus of 3rd Embodiment. The cable 80 is made of FPC, has a sheet shape, and is thin and flexible. The stopper 80a at one end of the cable 80 has a T-shape, and the stopper 80a is fitted into the fixing part 13d (see FIG. 7) of the pressure detecting device 10, so that the stopper 80a is fixed. The pair of protrusions 13e and 13f of 13d are hooked. Thereby, it can prevent that the cable 80 remove | deviates from the pressure detection apparatus 10. FIG. In addition, the external connection portion 80b and the intermediate portion 80c, which are the ends opposite to the T-shaped stopper 80a of the cable 80, have the same structure as that of the cable 60 of the first embodiment. Omitted.

  For the insulating film 81 of the cable 80, polyimide having excellent heat resistance is used. The conductive part 82 on the insulating film 81 is made of copper foil. Further, a conductive shield member 83 that covers the entire back surface is formed on the back surface of the cable 80, that is, on the back surface of the insulating film 81. Further, a thin sheet-like insulating member 84 covering the entire conductive portion 82 is formed on the surface of the cable 80, that is, on the conductive portion 82 side, and a conductive shield member 85 is further formed on the surface of the insulating member 84. It is formed.

  Here, the upper and lower shield members 83, 85 are set slightly larger than the outer shapes of the insulating film 81 and the insulating member 84, and are portions protruding from the outer peripheries of the insulating film 81 and the insulating member 84 (broken lines in FIG. 14). ) Are fixed with a conductive adhesive or the like, so that the shield members 83 and 85 are in contact with each other and are electrically connected. With this structure, the conductive portion 82 of the cable 80 is electrically shielded by the laminated structure of the upper and lower shield members 83, 85, the insulating film 81, and the insulating member 84. Further, the upper and lower shield members 83 and 85 may be electrically connected by a through-hole penetrating the insulating film 81 and the insulating member 84 although not shown.

  The shield member 85 on the surface of the cable 80 has an opening 85a for exposing the conductive portion 82 at the position of the stop portion 80a and an opening 85b for exposing the conductive portion 82 at the position of the external connection portion 80b. have. Here, the opening 85a is a region for soldering the conductive portion 82 and the connection terminal 52, and the opening 85b is a region for connecting the conductive portion 82 and an external device.

  When the cable 80 is incorporated in the pressure detection device 10, it is fixed to the fixing portion 13d of the rear housing 13 (see FIG. 7), but the back surface of the cable 80, that is, the shield member 83 is attached to the bottom surface of the fixing portion 13d. By abutting, the rear housing 13 and the shield member 83 are electrically connected. Here, as described above, since the rear housing 13 is a conductive member and is connected to the ground electrode, the upper and lower shield members 83 and 85 that cover the cable 80 serve as the ground electrode.

  Therefore, the conductive portion 82 of the cable 80 is covered by the grounded upper and lower shield members 83 and 85, and the conductive portion 82 of the cable 80 is electrically shielded. As a result, since the electrical signal of the pressure detection device 10 passes through the electrically shielded cable 80, electrical noise from the outside is blocked and an electrical signal having a good S / N ratio is transmitted to the external device. I can do it.

  Moreover, you may attach the cable 80 of the shield structure shown in 3rd Embodiment to the pressure detection apparatus 70 of 2nd Embodiment. Thereby, it is possible to realize a pressure detection device that is excellent in heat resistance and excellent in noise resistance.

  Although various embodiments have been described in detail above, the present invention is not limited to such embodiments, and the detailed configuration, shape, material, quantity, and the like are within the scope that does not depart from the spirit of the present invention. , Can be changed, added and deleted arbitrarily. That is, it is not limited to the embodiment of the combustion pressure sensor described above, it is not necessary to perform all of them, and various modifications and omissions may be made within the scope of the contents described in the claims. I can do it.

  The pressure detection device according to the present invention can be used when measuring the pressure in the combustion chamber of the engine, particularly when detecting the combustion pressure by attaching it to the outer periphery of the tip of a spark plug, an injector or the like.

Claims (11)

In a pressure detection device configured in a cylindrical shape that detects the internal pressure of a cylinder by being mounted on the outer periphery of the tip of a functional member facing the combustion chamber of the engine,
A pressure receiving member that receives pressure from the outside, a pressure transmission member that transmits pressure from the pressure receiving member, a piezoelectric element that contacts the pressure transmission member to detect pressure fluctuations, and an electrode member that contacts the piezoelectric element And a cylindrical housing having an opening,
The piezoelectric element outputs an electrical signal corresponding to pressure from two opposing electrodes,
One of the electrodes of the piezoelectric element abuts the piezoelectric element on the housing and becomes a ground electrode,
The other electrode contacts the electrode member provided between the pressure transmission member and the piezoelectric element,
The pressure detecting device, wherein the electrode member is electrically connected to an electrical transmission means constituted by a printed circuit board via a connection terminal, and the electrical signal is transmitted to an external device by the electrical transmission means.   2. The pressure detecting device according to claim 1, wherein one or a plurality of the piezoelectric elements are arranged along a circumferential direction inside the casing, and the piezoelectric elements are alternately arranged via a spacer.   The connection terminal is connected to the electrical transmission means through the spacer and a through hole provided in the casing, and the connection terminal is positioned using the through hole provided in the casing. The pressure detection device according to claim 2.   4. The pressure detecting device according to claim 1, wherein a spring is interposed between the connection terminal and the electrode member.   5. The pressure detection device according to claim 1, wherein the housing has a fixing portion for fixing the electrical transmission means to a portion where the connection terminal is exposed from the through hole. .   The pressure detection device according to claim 1, wherein a flexible printed circuit board is used as the printed circuit board constituting the electrical transmission means.   6. The fixing part according to claim 5, wherein a pair of opposing protrusions having a function of preventing the electrical transmission means from being detached when the electrical transmission means is secured to an end face. 6. The pressure detection device according to 6.   8. The pressure detection according to claim 7, wherein a tip end of the electrical transmission means has a substantially T-shaped stop portion, and the stop portion is fitted into the fixing portion and hooked to the protrusion portion. apparatus.   The pressure detection device according to claim 1, wherein the electrical transmission unit is electrically and mechanically connected to the connection terminal by solder.   The pressure detection device according to claim 1, wherein the electrical transmission unit is covered with a heat-resistant member.   The pressure detection device according to claim 1, wherein the electrical transmission means is electrically shielded by a laminated structure of an insulating member and a conductive member.

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