JP5883691B2 - Internal combustion engine with combustion pressure detector - Google Patents

Description

  The present invention relates to an internal combustion engine with a combustion pressure detection device and a combustion pressure detection device.

In recent years, an internal combustion engine equipped with a combustion pressure detecting device for detecting the pressure in the combustion chamber is known. In such an internal combustion engine, it is necessary to suppress the leakage of combustion gas at the mounting portion of the combustion pressure detection device in the combustion chamber, or to prevent the inflow of combustion gas to the combustion pressure detection device.
For example, a combustion pressure detecting device described in Patent Document 1 includes a diaphragm at a front end portion of a main body formed in a cylindrical shape, and a sensor unit including a piezoelectric element disposed behind the diaphragm through a diaphragm. A combustion pressure sensor provided by being inserted into an insertion hole provided in the combustion chamber wall so that the combustion pressure in the acting combustion chamber can be detected is provided with a gas seal portion protruding in the radial direction at the front end portion of the main body, It is described that the gas seal portion is configured to be capable of being pressed against the inner wall surface of the insertion hole in the radial direction.

JP 2008-191059 A

Here, in the combustion pressure detection device, the temperature of the outer member rapidly rises due to the combustion gas flowing in from the gap between the internal combustion engine to which the combustion pressure detection device is attached. On the other hand, the temperature of the inner member of the combustion pressure detecting device is unlikely to rise immediately compared to the outer temperature. As a result, an expansion difference between the internal and external members due to a temperature difference between the inside and outside of the apparatus occurs, and the load acting on the detection unit that detects the pressure is affected by the expansion difference.
For example, when the outer member extends relative to the inner member, a member to which pressure is applied to the detection unit is pulled, and a gap is generated between the detection unit and the detection unit. In this case, the detection error that the pressure detected by the detection unit becomes small or the pressure is not detected even though the detection unit is under a load and the predetermined pressure should be detected. May occur. In order to suppress the occurrence of such detection errors, it is effective to suppress the inflow of combustion gas into the gap between the internal combustion engine and the combustion pressure detection device.

  An object of the present invention is to more reliably prevent an inflow of combustion gas into a gap between an internal combustion engine and a combustion pressure detection device attached to the internal combustion engine.

For this purpose, the present invention provides an internal combustion engine having a combustion chamber and an opening formed on a wall surface constituting the combustion chamber and leading to the combustion chamber and having a front side diameter wider than the side diameter. A cylindrical shape that can be inserted into the opening of the internal combustion engine, the tip end side in the insertion direction is narrow according to the diameter on the flange side of the opening, the rear end side is thick according to the diameter on the near side of the opening, and between the tip end side and the rear end side A combustion pressure having a housing having a shoulder portion, a diaphragm provided on a distal end side in the insertion direction of the housing, and a detection member that is disposed in the housing and is disposed behind the diaphragm and that detects pressure acting through the diaphragm comprising a detection device, a ring-shaped, having an opening cross section with opening shape, and the seal member for sealing the opening and the housing of the internal combustion engine at the shoulder of the housing of the combustion pressure detecting apparatus, a The housing is Has a stepped portion seal member is fitted, the seal member, the combustion pressure detector internal combustion engine with an opening edge of the opening of the sealing member, characterized in that it is held in the housing by engaging the step portion It is.

Here, the seal member can be characterized in that the opening of the seal member is in a state of being opened toward the combustion chamber.
Its to the detection member of the combustion pressure detector is provided at an end of the side facing the combustion chamber in the housing, the shoulder of the housing, by being formed in the position of the detecting member in the insertion direction For example, it is preferable in that the detection member is arranged on the combustion chamber side to improve the accuracy of pressure detection and to suppress the generation of detection errors due to thermal expansion.
In addition, it is preferable that the shoulder portion of the housing is a tapered portion having a diameter that gradually increases from the front end side toward the rear end side in that the combustion gas can be easily introduced into the opening .

Furthermore, it is possible to further include an outer seal member that is pressed in the same direction as the insertion direction in which the housing is inserted outside the opening of the internal combustion engine and seals between the housing and the combustion chamber.
The sealing member may have a horseshoe shape in cross section, and is provided along the inner wall of the opening of the internal combustion engine and the tapered portion of the housing.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to prevent more reliably the inflow of combustion gas to the clearance gap between an internal combustion engine and the combustion pressure detection apparatus attached to an internal combustion engine.

1 is a schematic configuration diagram of an internal combustion engine according to an embodiment. It is an enlarged view of the II section of FIG. It is a schematic block diagram of a pressure detection apparatus. It is sectional drawing of the IV-IV part of FIG. It is an enlarged view of the V section of FIG. It is a figure for demonstrating the 2nd sealing member of Embodiment 1. FIG. FIG. 5 is a diagram for explaining an internal combustion engine according to a second embodiment. FIG. 6 is a diagram for explaining an internal combustion engine according to a third embodiment.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
(Embodiment 1)
FIG. 1 is a schematic configuration diagram of an internal combustion engine 1 according to the present embodiment.
FIG. 2 is an enlarged view of a portion II in FIG.
As shown in FIG. 1, the internal combustion engine 1 includes a cylinder block 2 having a cylinder 2a, a piston 3 that reciprocates in the cylinder 2a, and a combustion chamber C that is fastened to the cylinder block 2 together with the cylinder 2a, the piston 3, and the like. And a cylinder head 4 to be formed. The internal combustion engine 1 is mounted on the cylinder head 4 to detect the pressure in the combustion chamber C, and a control device that controls the operation of the internal combustion engine 1 based on the pressure detected by the pressure detection device 5. 6, an electric signal is transmitted between the pressure detection device 5 and the control device 6, and between the pressure detection device 5 and the control device 6, which is interposed between the pressure detection device 5 and the cylinder head 4 and maintains the airtightness in the combustion chamber C. A transmission cable 8.

  As shown in FIG. 2, the cylinder head 4 is formed with a communication hole 4a as an example of an opening for communicating the combustion chamber C with the outside. The cross section of the communication hole 4a of this embodiment is circular. From the combustion chamber C side, the communication hole 4a has a hole diameter larger than the first hole part 4b, the inclined part 4c whose diameter gradually increases from the hole diameter of the first hole part 4b, and the hole diameter of the first hole part 4b. A large second hole 4d. A female screw 4e into which a male screw 332a of the housing 30 (described later) formed in the pressure detection device 5 is screwed is formed on the surrounding wall forming the second hole 4d.

Below, the pressure detection apparatus 5 is explained in full detail.
FIG. 3 is a schematic configuration diagram of the pressure detection device 5. 4 is a cross-sectional view taken along a line IV-IV in FIG. FIG. 5 is an enlarged view of a portion V in FIG.
As shown in FIG. 3, the pressure detection device 5 as an example of the combustion pressure detection device includes a sensor unit 100 having a piezoelectric element 10 that converts the pressure in the combustion chamber C into an electrical signal, and an electrical signal from the sensor unit 100. And a holding member 300 that holds the signal processing unit 200. When the pressure detection device 5 is mounted on the cylinder head 4, the diaphragm head 40 (described later) of the sensor unit 100 is inserted into the communication hole 4 a formed in the cylinder head 4 first.

First, the sensor unit 100 will be described.
As shown in FIG. 4, the sensor unit 100 includes a piezoelectric element 10 that converts received pressure into an electrical signal, and a cylindrical housing in which a cylindrical hole that accommodates the piezoelectric element 10 and the like is formed. 30.
In the following, the center line direction of the cylindrical hole formed in the housing 30 is simply referred to as the center line direction. In the following description, the left side of FIG. 4 is the front end side of the pressure detection device 5, and the right side is the rear end side of the pressure detection device 5.
The sensor unit 100 is provided so as to close the opening on the front end side of the housing 30, and the diaphragm head 40 on which the pressure in the combustion chamber C acts, and the first provided between the diaphragm head 40 and the piezoelectric element 10. 1 electrode part 50 and the 2nd electrode part 55 arrange | positioned with respect to the piezoelectric element 10 on the opposite side to the 1st electrode part 50 are provided.

  Further, as shown in FIG. 5, the sensor unit 100 is provided with an insulating ring 60 made of alumina ceramic that electrically insulates the second electrode unit 55 and a rear end side of the insulating ring 60. 200 includes a support member 65 that supports an end portion of a cover member 23 described later, and a coil spring 70 interposed between the second electrode portion 55 and a conductive member 22 described later.

  The piezoelectric element 10 has a piezoelectric body that exhibits the piezoelectric action of the piezoelectric longitudinal effect. The piezoelectric longitudinal effect refers to the action of generating charges on the surface of the piezoelectric body in the direction of the charge generation axis when an external force is applied to the stress application axis in the same direction as the charge generation axis of the piezoelectric body. The piezoelectric element 10 according to the present embodiment is housed in the housing 30 so that the center line direction is the direction of the stress application axis.

  Next, a case where the piezoelectric lateral effect is used for the piezoelectric element 10 will be illustrated. The piezoelectric transverse effect is an action in which charges are generated on the surface of the piezoelectric body in the direction of the charge generation axis when an external force is applied to the stress application axis at a position orthogonal to the charge generation axis of the piezoelectric body. A plurality of thinly formed piezoelectric bodies may be laminated, and by laminating in this way, the charge generated in the piezoelectric bodies can be efficiently collected to increase the sensitivity of the sensor. Examples of the piezoelectric body include the use of a langasite crystal (a langasite, langagate, langanite, LGTA) having a piezoelectric longitudinal effect and a piezoelectric transverse effect, quartz, gallium phosphate, and the like. In the piezoelectric element 10 of the present embodiment, a langasite single crystal is used as the piezoelectric body.

  Alternatively, the piezoelectric element 10 may be configured by laminating a plurality of piezoelectric bodies formed thinly in a thin plate shape. By doing in this way, the electric charge generated according to a combustion pressure can be collected efficiently, and the detection sensitivity can be raised. Further, by stacking a plurality of piezoelectric bodies into an integral block shape, the proof strength against a large combustion pressure generated in the combustion chamber C of the internal combustion engine 1 is increased. In addition, when the piezoelectric bodies formed in a thin plate shape are formed by being laminated, it has a rectangular parallelepiped shape whose end face is a flat surface in appearance.

As shown in FIG. 4, the housing 30 includes a first housing 31 provided on the front end side and a second housing 32 provided on the rear end side.
The first housing 31 is a thin-walled cylindrical member having a cylindrical hole 310 formed therein so as to have a diameter that gradually changes from the front end side to the rear end side. The hole 310 includes a first hole 311 and a second hole 312 having a diameter larger than the diameter of the first hole 311 formed in order from the front end side to the rear end side.

  In addition, the first housing 31 includes an end surface 31a that forms a part to which the diaphragm head 40 is attached, a side surface 31b that constitutes the outer peripheral surface, and a protruding portion 315 that is provided to protrude from the side surface 31b over the entire circumferential direction. I have. The projecting portion 315 has an inclined surface 315a as an example of a tapered shoulder portion having an outer diameter that gradually increases from the front end side toward the rear end side, and a rear end portion in the center line direction. And a vertical surface 315b. Further, in the present embodiment, a step portion 31bt which is a groove formed over the entire area in the circumferential direction is formed on the inclined surface 315a side of the side surface 31b.

The inclined surface 315a forms a seal (sealed) portion between the cylinder head 4 and a second seal member 72 described later. Specifically, in a state where the pressure detection device 5 is mounted on the cylinder head 4, an interval is formed in which the second seal member 72 is sandwiched between the inclined surface 315 a and the inclined portion 4 c of the cylinder head 4. . And between the cylinder head 4 and the pressure detection apparatus 5, the holding | maintenance which is a space which arrange | positions the 2nd seal member 72 by the inclined surface 315a and the side surface 31b, and the inner wall of the inclined part 4c and the 2nd hole 4d. A portion H is formed (see FIG. 6C described later). The cross section of the holding portion H of the present embodiment is formed in a rhombus shape because it includes the inclined portion 4c and the inclined surface 315a.
In addition, the holding portion H of the present embodiment is provided at a position (lateral) where the piezoelectric element 10 is provided in the central axis direction of the pressure detection device 5 (see FIG. 6C described later).

  As shown in FIG. 5, the vertical surface 315 b forms a contact portion between the first housing 31 and the second housing 32. Specifically, when connecting the first housing 31 and the second housing 32, the vertical surface 315 b of the first housing 31 corresponds to a vertical surface formed at the tip of the second housing 32. . The vertical surface 315b of the first housing 31 is in close contact with the tip of the second housing 32 so that they are connected.

  The step portion 31bt forms a portion that holds the second seal member 72, which will be described later, when the second seal member 72, which will be described later, is attached to the pressure detecting device 5. Specifically, a part of the second seal member 72 described later is fitted into the step portion 31bt. In the present embodiment, by attaching the second seal member 72 to the step portion 31bt in advance, the second seal member 72 is less likely to be displaced during the operation of the internal combustion engine 1, or the pressure detection device 5 is connected to the communication hole of the cylinder head 4. The workability when attaching to and detaching from 4a is improved.

The second housing 32 is a cylindrical member having a cylindrical hole 320 formed therein so that its diameter is gradually changed from the front end side to the rear end side. An outer peripheral surface 330 is provided so that the diameter is gradually changed toward the end side.
The hole 320 is formed in order from the front end side to the rear end side, and has a first hole 321, a second hole 322 having a smaller diameter than the first hole 321, and a larger diameter than the second hole 322. The third hole 323 includes a fourth hole 324 having a larger diameter than the third hole 323, and a fifth hole 325 having a larger diameter than the fourth hole 324.
The diameter of the first hole 321 is equal to or less than the diameter of the outer peripheral surface of the first housing 31 so that the front end of the second housing 32 is fitted (press-fit) to the rear end of the first housing 31 with an interference fit. It is set to be.

  The outer peripheral surface 330 has a first outer peripheral surface 331, a second outer peripheral surface 332 having an outer diameter larger than the outer diameter of the first outer peripheral surface 331, and an outer diameter of the second outer peripheral surface 332 from the front end side to the rear end side. A third outer peripheral surface 333 having a larger outer diameter, a fourth outer peripheral surface 334 having an outer diameter larger than the outer diameter of the third outer peripheral surface 333, and a fifth outer periphery having an outer diameter smaller than the outer diameter of the fourth outer peripheral surface 334 A surface 335. A male screw 332 a that is screwed into the female screw 4 e of the cylinder head 4 is formed at the tip of the second outer peripheral surface 332. A first seal member 71, which will be described later, is fitted into the third outer peripheral surface 333 with a clearance fit, and the dimensional tolerance between the outer diameter of the third outer peripheral surface 333 and the inner diameter of the first seal member 71 is, for example, from zero to 0.2 mm. Is set to be The rear end portion of the fourth outer peripheral surface 334 is formed as a regular hexagonal column having six chamfers at equal intervals in the circumferential direction. When the pressure detecting device 5 is fastened to the cylinder head 4, the portion formed in the regular hexagonal column is a portion into which a tightening tool is fitted and a rotational force applied to the tool is transmitted. A concave portion 335a that is recessed from the outer peripheral surface is formed over the entire circumference in the center portion of the fifth outer peripheral surface 335 in the center line direction.

  The second housing 32 is a transition portion from the fourth hole 324 to the fifth hole 325, and a tip portion of the fifth hole 325 is in a substrate covering portion 232 of a covering member 23 described later of the signal processing unit 200. An abutting surface 340 against which the end surface on the distal end side abuts is provided. The abutting surface 340 is formed with a pin recess 340a into which a second connection pin 21b of a printed wiring board 210 of the signal processing unit 200 described later is inserted.

  Since the first housing 31 and the second housing 32 exist at a position close to the combustion chamber C, it is desirable to manufacture the first housing 31 and the second housing 32 using a material that can withstand an operating temperature environment of at least −40 to 350 [° C.]. Specifically, it is desirable to use a stainless steel material having high heat resistance, for example, JIS SUS630, SUS316, SUS430 or the like of JIS standard.

As shown in FIG. 5, the diaphragm head 40 has a cylindrical cylindrical portion 41 and an inner portion 42 formed inside the cylindrical portion 41.
The rear end portion of the cylindrical portion 41 is fitted (press-fitted) with the front end portion of the first housing 31 of the housing 30 with an interference fit, and enters the inside of the front end portion, and the end surface 31a at the front end portion. And an abutting surface 41b against which the end surface 31a abuts when fitted.
The inner part 42 is a disk-shaped member provided so as to close the opening on the front end side in the cylindrical part 41, and a protruding part that protrudes from this surface to the piezoelectric element 10 side at the center part on the rear end side surface. 42a is provided.
The material of the diaphragm head 40 is preferably made of an alloy having high elasticity and excellent durability, heat resistance, touch resistance, and the like because it exists in the combustion chamber C at a high temperature and a high pressure. For example, SUH660 can be exemplified.

The first electrode unit 50 is a columnar member formed so as to have a stepwise difference in diameter from the front end side to the rear end side, and is larger than the outer diameter of the first columnar unit 51 and the first columnar unit 51. A second cylindrical portion 52 having an outer diameter. The outer diameter of the first cylindrical portion 51 is smaller than the inner diameter of the entry portion 41 a of the diaphragm head 40, and the outer diameter of the second cylindrical portion 52 is substantially the same as the hole diameter of the first hole 311 of the first housing 31. The end surface on the front end side of the first cylindrical portion 51 is in contact with the protruding portion 42 a of the inner side portion 42 of the diaphragm head 40, and the end surface on the rear end side of the second cylindrical portion 52 is in contact with the front surface side of the piezoelectric element 10. Are arranged as follows. When the outer peripheral surface of the second cylindrical portion 52 is in contact with the inner peripheral surface of the first housing 31 and / or the end surface on the distal end side of the first cylindrical portion 51 is in contact with the diaphragm head 40, the distal end of the piezoelectric element 10 is obtained. The part is electrically connected to the housing 30.
The first electrode portion 50 applies pressure in the combustion chamber C to the piezoelectric element 10, and the end surface on the rear end side of the second cylindrical portion 52, which is the end surface on the piezoelectric element 10 side, is the end surface of the piezoelectric element 10. It is formed in a size that can push the entire surface. Further, the first electrode portion 50 is formed in a smooth surface with both end surfaces in the center line direction being parallel (perpendicular to the center line direction) so that the pressure received from the diaphragm head 40 can be applied to the piezoelectric element 10 evenly. Has been.
Examples of the material of the first electrode unit 50 include stainless steel.

The second electrode portion 55 is a cylindrical member, and is arranged so that the end surface on the front end side contacts the end surface on the rear end side of the piezoelectric element 10 and the end surface on one end side contacts the insulating ring 60. The A columnar projecting portion 55 a that projects from the end surface to the rear end side is provided on the end surface on the rear end side of the second electrode portion 55. The protrusion 55a has a base end portion on the end face side and a tip end portion having an outer diameter smaller than the outer diameter of the base end portion. The outer diameter of the protruding portion 55a is set smaller than the inner diameter of the insulating ring 60, and the length of the protruding portion 55a is set longer than the width of the insulating ring 60 (the length in the center line direction). The tip is exposed from the insulating ring 60. The second electrode portion 55 is a member that acts so as to apply a certain load to the piezoelectric element 10 with the first electrode portion 50, and the end face on the piezoelectric element 10 side is the end face of the piezoelectric element 10. It is formed in such a size that the entire surface can be pressed, and is formed in a parallel and smooth surface. The outer diameter of the second electrode portion 55 is set to be smaller than the hole diameter of the second hole 312 of the first housing 31, and the outer peripheral surface of the second electrode portion 55 and the inner peripheral surface of the first housing 31 are set. There is a gap between them.
The material of the second electrode part 55 can be exemplified by stainless steel.

  The insulating ring 60 is a cylindrical member formed of alumina ceramic or the like, and the inner diameter (hole diameter at the center) is slightly larger than the outer diameter of the base end portion of the protruding portion 55a of the second electrode portion 55. The diameter is set to be substantially the same as the hole diameter of the second hole 312 of the first housing 31. The second electrode portion 55 is arranged such that the protruding portion 55a is inserted into the central hole of the insulating ring 60 so that the center position and the center of the second hole 312 of the first housing 31 are the same. Be placed.

The support member 65 is a cylindrical member in which a plurality of cylindrical holes 650 having different diameters are formed inside from the front end side to the rear end side, and the outer peripheral surface is the same.
The holes 650 are formed in order from the front end side to the rear end side, and have a first hole 651, a second hole 652 having a diameter larger than the diameter of the first hole 651, and a diameter larger than the diameter of the second hole 652. A third hole 653. The diameter of the first hole 651 is larger than the outer diameter of the base end portion of the protruding portion 55 a of the second electrode portion 55, and the protruding portion 55 a is exposed to the inside of the support member 65. The hole diameter of the second hole 652 is larger than the outer diameter of the distal end portion of the conductive member 22 of the signal processing unit 200 described later. The diameter of the third hole 653 is smaller than the outer diameter of the end portion of the covering member 23 of the signal processing unit 200 described later, and the covering member 23 is fitted to the surrounding wall forming the third hole 653 with an interference fit. The Thereby, the support member 65 functions as a member that supports the end portion of the covering member 23.

  The coil spring 70 has an inner diameter that is equal to or larger than the outer diameter of the distal end portion of the protruding portion 55a of the second electrode portion 55 and smaller than the outer diameter of the proximal end portion, and the outer diameter is smaller than the diameter of the insertion hole 22a of the conductive member 22 described later. Is also small. The distal end portion of the protruding portion 55a of the second electrode portion 55 is inserted inside the coil spring 70, and the coil spring 70 is inserted into an insertion hole 22a of the conductive member 22 described later. The length of the coil spring 70 is set to a length that can be interposed in a compressed state between the second electrode portion 55 and the conductive member 22. As a material of the coil spring 70, an alloy having high elasticity and excellent durability, heat resistance, touch resistance and the like may be used. Further, it is preferable to increase electrical conduction by applying gold plating to the surface of the coil spring 70.

Next, the signal processing unit 200 will be described.
As shown in FIG. 3, the signal processing unit 200 includes a circuit board unit 21 that at least amplifies an electric signal that is a weak charge obtained from the piezoelectric element 10 of the sensor unit 100, and a circuit that generates charges generated in the piezoelectric element 10. A rod-shaped conductive member 22 that leads to the substrate part 21, a cover member 23 that covers the circuit board part 21, the conductive member 22, and the like, and an O-ring 24 that seals the circuit board part 21 and the like are provided.

  As shown in FIG. 4, the circuit board unit 21 includes a printed wiring board 210 on which electronic components and the like constituting a circuit for amplifying a weak charge obtained from the piezoelectric element 10 of the sensor unit 100 are mounted. A first connection pin 21a for electrically connecting a rear end portion of the conductive member 22 and a second connection pin 21b for grounding and positioning are connected to the front end portion of the printed wiring board 210 by soldering or the like. Has been. In addition, three third connection pins 21c that are electrically connected to the control device 6 via the connector 8a at the front end of the transmission cable 8 are connected to the rear end of the printed wiring board 210 by soldering or the like. Yes. The three third connection pins 21 c are used to supply a power supply voltage and a GND voltage from the control device 6 to the printed wiring board 210 and to supply an output voltage from the printed wiring board 210 to the control device 6, respectively.

  As shown in FIG. 3, the conductive member 22 is a rod-shaped (columnar) member, and an insertion hole 22 a into which the distal end portion of the protruding portion 55 a of the second electrode portion 55 is inserted is formed at the distal end portion. Yes. The rear end portion of the conductive member 22 is electrically connected to the printed wiring board 210 of the circuit board portion 21 via a conductive wire. Examples of the material of the conductive member 22 include brass and beryllium copper. In this case, brass is desirable from the viewpoint of workability and cost. On the other hand, beryllium copper is desirable from the viewpoints of electrical conductivity, high temperature strength, and reliability.

  The covering member 23 includes a conductive member covering portion 231 that covers the outer periphery of the conductive member 22, a substrate covering portion 232 that covers the side and bottom surfaces of the printed wiring board 210 of the circuit board portion 21, and a third connected to the printed wiring board 210. A connector portion 233 that covers the periphery of the connection pin 21c and into which the connector 8a at the tip of the transmission cable 8 is fitted.

  As shown in FIG. 4, the conductive member covering portion 231 covers the center line direction so as to expose the front end portion of the conductive member 22, and the diameter gradually varies from the front end side to the rear end side. A formed outer peripheral surface 240 is provided. From the front end side to the rear end side, the outer peripheral surface 240 has a first outer peripheral surface 241, a second outer peripheral surface 242 having an outer diameter larger than the outer diameter of the first outer peripheral surface 241, and an outer diameter of the second outer peripheral surface 242. A third outer peripheral surface 243 having a larger outer diameter, and a fourth outer peripheral surface 244 having an outer diameter larger than the outer diameter of the third outer peripheral surface 243.

The diameter of the first outer peripheral surface 241 is larger than the hole diameter of the third hole 653 of the support member 65, and the distal end portion of the conductive member covering portion 231 is stuck to the surrounding wall forming the third hole 653 of the support member 65. Fitted (press-fit).
The diameter of the second outer peripheral surface 242 is formed smaller than the hole diameter of the second hole 322 of the second housing 32, and the diameter of the third outer peripheral surface 243 is formed smaller than the hole diameter of the third hole 323 of the second housing 32. Has been. In addition, the diameter of the fourth outer peripheral surface 244 is larger than the diameter of the fourth hole 324 of the second housing 32, and the rear end portion of the conductive member covering portion 231 forms the fourth hole 324 of the second housing 32. The wall is fitted (press-fit) with an interference fit. As a result, the conductive member covering portion 231 is supported by contacting at least both ends in the center line direction with the support member 65 and the second housing 32, respectively. The bad influence given to 22 can be suppressed, and it becomes possible to avoid the disconnection of the connection part of the conductive member 22, the poor contact, etc. resulting from the vibration.

  The substrate covering portion 232 is basically a cylindrical portion, and a rectangular opening 232a for installing the printed wiring board 210 therein is provided on the side surface thereof. Further, a ring groove 232b for the O-ring 24 for sealing the inside of the housing 30 and the printed wiring board 210 installation portion is formed on the rear end side of the substrate covering portion 232.

  The connector portion 233 is a thin portion that protrudes from the end surface 232 c on the rear end side of the substrate covering portion 232 and is formed so as to cover the periphery of the three third connection pins 21 c connected to the printed wiring board 210. The rear end portion of the connector portion 233 is open so that the connector 8a provided at the front end portion of the transmission cable 8 can be received therein. Further, a hole 233a that communicates the inside and the outside is formed on the rear end side of the connector portion 233, and a hook provided on the connector 8a of the transmission cable 8 is hooked into the hole 233a, so that the transmission cable The eight connectors 8a are prevented from dropping from the connector portion 233.

  The covering member 23 configured as described above is formed of an insulating material such as resin. The cover member 23 is integrally formed with the conductive member 22, the first connection pin 21a, the second connection pin 21b, and the three third connection pins 21c. More specifically, the cover member 23 is formed by pressing heated resin into a mold in which the conductive member 22, the first connection pin 21a, the second connection pin 21b, and the three third connection pins 21c are set. Is done.

  In order to unitize the signal processing unit 200, the printed wiring board 210 of the circuit board unit 21 is inserted from the opening 232 a of the formed covering member 23 and is installed at the center of the board covering unit 232. When installing the printed wiring board 210, the tips of the first connection pin 21a, the second connection pin 21b, and the three third connection pins 21c are passed through the through-holes penetrating in the plate thickness direction and soldered. Then, the 1st connection pin 21a and the conduction member 22 are connected using a conducting wire. Further, the O-ring 24 is attached to the ring groove 232 b of the substrate covering portion 232 of the covering member 23. The O-ring 24 is a well-known O-shaped ring made of fluorine-based rubber.

Next, the holding member 300 will be described.
The holding member 300 is a thin cylindrical member (see FIG. 3), and a protruding portion 300a protruding inward from the inner peripheral surface is provided at the rear end portion. After the holding member 300 is mounted on the second housing 32, the holding member 300 is caulked by pressurizing a portion corresponding to the concave portion 335 a provided in the fifth outer peripheral surface 335 from the outside. Thereby, the holding member 300 becomes difficult to move with respect to the housing 30, and the signal processing unit 200 is prevented from moving with respect to the housing 30.

The pressure detection device 5 configured as described above is assembled as shown below.
First, as shown in FIG. 5, the first housing 31 and the diaphragm head 40 are fitted (press-fitted) until the end surface 31a of the first housing 31 and the abutting surface 41b of the diaphragm head 40 come into contact with each other. Thereafter, a laser beam is applied to a portion where the end surface 31a of the first housing 31 and the abutting surface 41b of the diaphragm head 40 are in contact with each other in a direction intersecting the center line direction (for example, a direction orthogonal to the center line direction). The first housing 31 and the diaphragm head 40 are welded.

  Thereafter, the first electrode unit 50 and the piezoelectric element 10 are inserted from the opening on the rear end side in the first housing 31. Thereafter, the coil spring 70 is attached to the tip of the protruding portion 55 a of the second electrode portion 55 and the insulating ring 60 is inserted into the protruding portion 55 a of the second electrode portion 55. Insert from the opening on the end side. Thereafter, the support member 65 is inserted from the opening on the rear end side in the first housing 31.

Thereafter, in order to increase the sensitivity and linearity of the piezoelectric element 10, a predetermined load (preload) is applied to the piezoelectric element 10 in the first housing 31. That is, the support member 65 is pressed in the center line direction from the rear end side toward the front end side with a dedicated jig attached to the rear end portion of the support member 65. Then, pressure is applied until the amount of displacement in the center line direction of the end surface on the front end side in the inner portion 42 of the diaphragm head 40 reaches a predetermined length before the support member 65 is pressed. The support member 65 and the first housing 31 are fixed when the end face on the front end side of the inner side portion 42 of the diaphragm head 40 is displaced by a predetermined length. Examples of the fixing method include irradiation with a laser beam from a direction intersecting the center line direction (for example, a direction orthogonal to the center line direction). The laser beam may be applied to the entire circumference in the circumferential direction, or may be irradiated spotwise at equal intervals in the circumferential direction. After the support member 65 and the first housing 31 are fixed, the dedicated jig is removed. As a result, a preload is applied to the piezoelectric element 10 in the first housing 31.
In the pressure detection device 5 to which the present embodiment is applied, a state in which a preload is applied is set to a zero state that serves as a reference for pressure detection.

  Thereafter, the first housing 31 and the second housing 32 are fitted (press-fitted) until the vertical surface 315b of the protruding portion 315 of the first housing 31 and the end surface on the front end side of the second housing 32 come into contact with each other. Thereafter, a laser beam is irradiated from a direction intersecting the center line direction (for example, a direction orthogonal to the center line direction) to a portion where the vertical surface 315b of the first housing 31 and the end surface of the second housing 32 are in contact with each other. The first housing 31 and the second housing 32 are welded.

  Thereafter, as shown in FIG. 3, the signal processing unit 200 is moved to the second housing 32 until the end surface on the front end side of the substrate covering portion 232 of the covering member 23 of the signal processing unit 200 hits the abutting surface 340 of the second housing 32. Is inserted from the opening on the rear end side. At this time, as shown in FIG. 4, the coil spring 70 attached to the protruding portion 55 a of the second electrode portion 55 enters the insertion hole 22 a of the conductive member 22 of the signal processing portion 200 and the protrusion of the second housing 32. The signal processing unit 200 is inserted so that the second connection pin 21b connected to the printed wiring board 210 enters the pin recess 340a formed on the surface 340.

Thereafter, as shown in FIG. 4, the holding member 300 is fitted into the signal processing unit 200 from the rear end side until the protruding portion 300 a of the holding member 300 abuts on the end surface 232 c of the substrate covering portion 232 of the signal processing unit 200. Go. In a state where the end surface 232c of the signal processing unit 200 and the protruding portion 300a of the holding member 300 are in contact with each other, a portion corresponding to the concave portion 335a of the fifth outer peripheral surface 335 of the second housing 32 is pressurized. Thus, the holding member 300 is caulked to the second housing 32. Accordingly, the holding member 300 is difficult to move with respect to the housing 30, and the signal processing unit 200 is difficult to move with respect to the housing 30.
In this way, the pressure detection device 5 is assembled.

Here, the electrical connection structure in the pressure detection apparatus 5 mentioned above is demonstrated.
First, the end face on the front end side of the piezoelectric element 10 is electrically connected to the metal housing 30 via the metal first electrode portion 50 and the diaphragm head 40.

  On the other hand, the end surface on the rear end side of the piezoelectric element 10 is electrically connected to the metal second electrode portion 55, and the second electrode portion 55 is connected to the metal coil spring 70 via the protruding portion 55 a. Electrically connected. The coil spring 70 is electrically connected to the metallic conductive member 22, and the conductive member 22 is electrically connected to the printed wiring board 210. On the other hand, the outer diameter of the protrusion 55 a of the second electrode portion 55 is smaller than the hole diameter of the first hole 651 of the support member 65, and the outer diameter of the tip portion of the conductive member 22 is larger than the hole diameter of the second hole 652 of the support member 65. Is also small. That is, the second electrode portion 55, the coil spring 70, and the conduction member 22 are not electrically connected to the support member 65. Therefore, the transmission path of the charge signal from the second electrode portion 55 to the printed wiring board 210 via the coil spring 70 and the conductive member 22 is formed by the insulating ring 60 and the covering member 23 each made of an insulator. And electrically insulated from the metal housing 30.

When the pressure detecting device 5 configured as described above is attached to the cylinder head 4, the diaphragm head 40 of the sensor unit 100 is inserted into the communication hole 4a formed in the cylinder head 4 first, The male screw 332 a formed in the second housing 32 of the housing 30 is screwed into the female screw 4 e formed in the communication hole 4 a of the cylinder head 4.
By mounting the pressure detection device 5 on the cylinder head 4, the housing 30 is electrically connected to the metal cylinder head 4. Since the cylinder head 4 is in a state of being electrically grounded, in the pressure detection device 5, the tip portion of the piezoelectric element 10 is grounded via the housing 30. Here, in this example, the side surface of the piezoelectric element 10 and the inner wall surface of the housing 30 are in contact with each other, but the resistance value is extremely large because the piezoelectric element 10 is made of an insulator. The electric charge generated with the pressure change is generated at both ends of the piezoelectric element 10 in the center line direction.

  During the operation of the internal combustion engine 1, combustion pressure is applied to the inner portion 42 of the diaphragm head 40 of the sensor unit 100. When the combustion pressure applied to the diaphragm head 40 acts on the piezoelectric element 10 sandwiched between the first electrode portion 50 and the second electrode portion 55, an electric charge corresponding to the combustion pressure is generated in the piezoelectric element 10. The electric charge generated in the piezoelectric element 10 is applied to the circuit board portion 21 via the second electrode portion 55, the coil spring 70, and the conductive member 22. After the charge applied to the circuit board part 21 is amplified in the circuit board part 21, the voltage corresponding to the charge is applied to the third connection pin 21c connected to the circuit board part 21 and the transmission cable 8. To the control device 6.

Next, the seal part 7 will be described.
As shown in FIG. 2, the seal portion 7 includes an end surface 4 f in the tightening direction of the pressure detection device 5 on the surrounding wall forming the communication hole 4 a in the cylinder head 4, and a fourth outer peripheral surface 334 of the housing 30 of the pressure detection device 5. And a first seal member 71 that seals between the cylinder head 4 and the pressure detection device 5.
Further, the cylinder head is disposed in a holding portion H formed by the step portion 31bt and the inclined surface 315a of the first housing 31 and the end surface 4f and the inclined portion 4c of the communication hole 4a (see FIG. 6C described later). A second seal member 72 that seals between the pressure sensor 4 and the pressure detection device 5 is provided.

  The first seal member 71 can be exemplified as a metal gasket formed by punching a metal plate such as copper, stainless steel, or aluminum. The cross-sectional shape is preferably S-shaped or substantially rectangular. When the pressure detection device 5 is tightened to the cylinder head 4, the first seal member 71 is deformed so that the length in the tightening direction is shortened by receiving a force in the tightening direction, and the air tightness in the combustion chamber C is improved. Increase. That is, when the pressure detection device 5 is screwed into the cylinder head 4, the contact pressure generated between the first seal member 71 and the cylinder head 4, and between the first seal member 71 and the housing 30 of the pressure detection device 5. The contact pressure generated in the is increased. Thereby, the leakage of combustion gas from between the first seal member 71 and the cylinder head 4 and between the first seal member 71 and the housing 30 of the pressure detection device 5 is suppressed.

FIG. 6 is a view for explaining the second seal member 72 of the first embodiment.
6A shows an overall view of the second seal member 72, FIG. 6B shows a VIb-VIb cross section shown in FIG. 6A, and FIG. 6C shows the pressure applied by the second seal member 72. The state provided between the detection apparatus 5 and the cylinder head 4 is shown.
The second seal member 72 is a member that suppresses the inflow of combustion gas into the gap between the inner wall of the cylinder head 4 and the outer wall of the housing 30 of the pressure detection device 5. The 2nd seal member 72 is arrange | positioned at the holding | maintenance part H, as shown in FIG.6 (c). The holding portion H of the present embodiment is formed at the position (lateral) of the piezoelectric element 10 in the housing 30 central axis direction. Therefore, the second seal member 72 suppresses the inflow of combustion gas to the rear end side in the central axis direction from the position where the piezoelectric element 10 is provided in the gap between the cylinder head 4 and the pressure detection device 5.

As shown in FIG. 6A, the second seal member 72 is an annular (ring-shaped) member, and the inside is formed to be hollow. Furthermore, the 2nd seal member 72 has the opening part 72t which is the cyclic | annular cut formed in the one end side of a center axis direction over the perimeter.
The inner diameter of the second seal member 72 is slightly smaller than the outer diameter of the side surface 31b of the first housing 31 of the pressure detection device 5 (in this embodiment, the outer diameter of the step portion 31bt) before being attached. Is set. Further, the outer diameter of the second seal member 72 is set to be slightly larger than the inner diameter of the second hole portion 4 d in the communication hole 4 a of the cylinder head 4.
When the second seal member 72 is attached to the internal combustion engine 1, the inner peripheral portion of the second seal member 72 is in close contact with the outer periphery of the first housing 31, and the outer peripheral portion is in close contact with the inner periphery of the second hole portion 4d. To do.

Further, as shown in FIG. 6B, the cross section of the second seal member 72 has an opening shape by providing an opening 72t. The opening 72t is provided at one end in the central axis direction as shown in FIG. The opening 72t is formed so that the opening 72t is inclined with respect to the central axis. In the present embodiment, in the holding portion H, the gap N between the side surface 31b and the first hole portion 4b is located on the central axis side and the combustion chamber C side. Therefore, the opening 72t is inclined with respect to the central axis so that the opening 72t faces the gap N.
Further, the cross section of the second seal member 72 has a horseshoe shape when cut in the central axis direction. As shown in FIG.6 (c), the holding | maintenance part H in which the 2nd seal member 72 is arrange | positioned has a rhombus shape. And in this embodiment, the 2nd seal member 72 is formed in the horseshoe shape so that the cross-sectional shape of the holding | maintenance part H may be followed, and the adhesiveness with respect to the holding | maintenance part H is improved.

The second seal member 72 has a material thickness that can be deformed when the first seal member 31 is attached to the first housing 31 or when the combustion gas enters the inside from the opening 72t. Further, by configuring the second seal member 72 to be deformable, when the pressure detecting device 5 is mounted on the cylinder head 4, for example, the second seal member 72 can absorb a dimensional error in the central axis direction. Become.
In addition, metals, such as copper, stainless steel, and aluminum, can be used for the material of the 2nd seal member 72 of this embodiment. In addition, as a material of the second seal member 72 of the present embodiment, Teflon (registered trademark) or the like can be used.

  Then, as shown in FIG. 6C, the second seal member 72 is disposed in the holding portion H in a state where the pressure detection device 5 is mounted on the cylinder head 4. Moreover, in this embodiment, the 2nd seal member 72 is hold | maintained at the 1st housing 31 so that a part of inner peripheral side may be engage | inserted by the level | step-difference part 31bt. In the second seal member 72, the opening 72 t faces the gap N extending to the combustion chamber C. Therefore, the second seal member 72 is provided in a state where the opening 72 t is open toward the combustion chamber C.

Next, the operation of the sensor unit 100 of the pressure detection device 5 in the internal combustion engine 1 will be described.
In the internal combustion engine 1 configured as described above, when the pressure in the combustion chamber C is approximately atmospheric pressure and is negligibly small (initial state), for example, when no combustion pressure is generated, the diaphragm head 40 is Almost no deformation. In this state, a load corresponding to atmospheric pressure and a preload applied when the pressure detection device 5 is assembled are applied to the piezoelectric element 10. In this embodiment, the state in which only the preload acts is a state in which the pressure is zero.

  For example, in the internal combustion engine 1, after fuel and air are fed into the combustion chamber C, ignition is performed by the spark plug, whereby combustion pressure is generated in the combustion chamber C. Then, by receiving pressure through the diaphragm head 40, the first electrode unit 50 applies a load in the center line direction to the piezoelectric element 10. The piezoelectric element 10 is compressed and deformed by receiving a compressive force from the first electrode unit 50. Then, the electric charge generated by compressing and deforming the piezoelectric element 10 is transmitted to the signal processing unit 200 as an electric signal.

  Here, the combustion gas generated by the combustion in the combustion chamber C enters the gap N as shown in FIG. The combustion gas that has entered the gap N reaches the second seal member 72. Then, the second seal member 72 expands by entering the inside of the opening 72 t of the second seal member 72. The outer peripheral portion of the second seal member 72 is in close contact with the side surface 31b (stepped portion 31bt) and the inclined surface 315a of the first housing 31, and the second hole portion 4d and the inclined portion 4c of the cylinder head 4.

  In the present embodiment, the second seal member 72 is attached so as to be in contact with the inclined surface 315a of the first housing 31 constituting the holding portion H. Thus, when the second seal member 72 is pushed in the axial direction from the front end side to the rear end side in the central axis direction of the pressure detection device 5 by the combustion gas, the inclined surface 315a having a surface component in the axial direction. The second seal member 72 can be held. As the second seal member 72 is pushed toward the rear end side in the central axis direction, the degree of adhesion is further increased by the drag from the inclined surface 315a. In addition, the inflow of combustion gas to the gap on the rear end side from the second seal member 72 can be suppressed.

  Further, the inclined surface 315a of the first housing 31 is tapered so that the outer diameter gradually increases from the front end side toward the rear end side. Thereby, the opening 72t of the second seal member 72 can be easily arranged toward the gap N. Therefore, for example, compared with the case where the opening 72t of the second seal member 72 is directed in a direction orthogonal to the central axis direction of the pressure detection device 5, the combustion gas flowing in the central axis direction of the pressure detection device 5 is opened. 72t can be easily introduced into the inside.

If the pressure detection device 5 is exposed to combustion gas in a state where the temperature of the pressure detection device 5 is low, such as immediately after the internal combustion engine 1 starts combustion, the temperature of the outer housing 30 of the pressure detection device 5 rapidly increases. And in the front end side near the combustion chamber C of the pressure detection apparatus 5, the temperature inside and outside the housing 30 is likely to rise in a short time as the temperature rises. Therefore, on the tip side near the combustion chamber C of the pressure detection device 5, a difference in thermal expansion between the outer housing 30 and the inner member of the housing 30 hardly occurs.
On the other hand, on the side far from the front end side (combustion chamber C side) of the pressure detection device 5, the temperature of the member inside the housing 30 is unlikely to rise. Accordingly, on the side far from the combustion chamber C of the pressure detection device 5, the difference in thermal expansion between the outer housing 30 and the inner member of the housing 30 tends to increase. As a result, the amount of thermal expansion of the inner member is small, and the amount of thermal expansion of the outer housing 30 is relatively large. For example, a gap may be generated between the piezoelectric element 10 and the second electrode portion 55. There is. Then, in the pressure detection device 5, there is a possibility that a state in which the actual pressure cannot be accurately detected occurs and a detection error occurs.

  On the other hand, in the internal combustion engine 1 to which the present embodiment is applied, the combustion gas from the combustion chamber C of the pressure detection device 5 is suppressed by suppressing the inflow of the combustion gas into the gap on the rear end side with respect to the second seal member 72. On the far side, a rapid temperature rise is prevented from occurring only in the outer housing 30. Thereby, in the internal combustion engine 1 of the present embodiment, occurrence of pressure detection error due to thermal expansion is reduced.

  Further, in the pressure detection device 5 to which the present embodiment is applied, the piezoelectric element 10 is provided on the distal end side of the pressure detection device 5 and the piezoelectric element 10 is disposed closer to the combustion chamber C side. The detection accuracy of combustion pressure is improved. In the present embodiment, the holding portion H is formed in the vicinity (lateral) of the piezoelectric element 10, and the second seal member 72 is provided in the holding portion H. In this embodiment, the inflow of combustion gas to the rear end side in the central axis direction is suppressed from the position where the piezoelectric element 10 is provided. As described above, in the pressure detection device 5 of the present embodiment, the pressure detection due to the thermal expansion of the housing 30 is performed while detecting the pressure with high accuracy by arranging the piezoelectric element 10 closer to the combustion chamber C. The occurrence of errors is suppressed.

(Embodiment 2)
FIG. 7 is a view for explaining the internal combustion engine 1 according to the second embodiment.
In addition, about the thing similar to the internal combustion engine 1 which concerns on Embodiment 1, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.
7A shows an overall view of the second seal member 372, FIG. 7B shows a VIIb-VIIb cross section shown in FIG. 7A, and FIG. 7C shows the second seal of the second embodiment. A state in which the member 372 is provided between the pressure detection device 5 and the cylinder head 4 is shown.
As shown in FIG. 7C, in the internal combustion engine 1 according to the second embodiment, the protrusion 315 in the first housing 31 of the pressure detection device 5 is an example of a shoulder perpendicular to the center line direction at the tip. A second vertical surface 315c and a vertical surface 315b perpendicular to the center line direction at the rear end.
Further, the communication hole 4a of the cylinder head 4 according to the second embodiment includes, from the combustion chamber C side, the first hole 4b, the second hole 4d having a hole diameter larger than the hole diameter of the first hole 4b, and the first hole. A step 4e is provided between the portion 4b and the second hole 4d and forms a step perpendicular to the central axis direction.
The internal combustion engine 1 according to the second embodiment includes a second seal member 372 that seals between the cylinder head 4 and the pressure detection device 5.

  In the internal combustion engine 1 of the second embodiment, the second vertical surface 315c of the pressure detection device 5 and the cylinder head 4 are in a state where the pressure detection device 5 is attached to the cylinder head 4 as shown in FIG. A distance is provided so as to sandwich the second seal member 372 between the stepped portion 4e. In the internal combustion engine 1 of the second embodiment, the second seal member 372 of the second embodiment is held by the second vertical surface 315c, the side surface 31b (stepped portion 31bt), the second hole portion 4d, and the stepped portion 4e. The holding part H is formed. In the second embodiment, as shown in FIG. 7C, the holding portion H has a rectangular cross section.

  The second seal member 372 is a member that suppresses the inflow of combustion gas into the gap between the inner wall of the cylinder head 4 and the outer wall of the housing 30 of the pressure detection device 5. The second seal member 372 is disposed in the holding portion H as shown in FIG. The holding portion H of the present embodiment is formed at the position (lateral) of the piezoelectric element 10 in the housing 30 central axis direction. Accordingly, the second seal member 372 suppresses the inflow of combustion gas to the rear end side in the central axis direction from the position where the piezoelectric element 10 is provided in the gap between the cylinder head 4 and the pressure detection device 5.

As shown in FIG. 7A, the second seal member 372 is an annular member and has a hollow inside. Further, the second seal member 372 has an opening 372t that is an annular cut formed over the entire circumference on one end side in the central axis direction.
The inner diameter of the second seal member 372 is set to be slightly smaller than the outer diameter of the side surface 31b of the first housing 31 of the pressure detection device 5 (in this embodiment, the outer diameter of the step portion 31bt) before being attached. ing. Further, the outer diameter of the second seal member 372 is set to be slightly larger than the inner diameter of the second hole portion 4 d in the communication hole 4 a of the cylinder head 4. When the second seal member 372 is attached to the internal combustion engine 1, the inner periphery of the second seal member 372 is in close contact with the outer periphery of the first housing 31, and the outer periphery is the inner periphery of the second hole 4d. Close contact with.

Further, as shown in FIG. 7B, the cross section of the second seal member 372 has an opening shape by providing an opening 372t. The opening 372t is provided at one end in the central axis direction. Further, as shown in FIG. 7B, the opening 372t is directed obliquely with respect to the central axis so as to face the gap N located on the central axis side and the combustion chamber C side when attached. It has been.
Further, the cross section of the second seal member 372 has a circular shape when cut in the central axis direction. As shown in FIG. 7C, the holding portion H in which the second seal member 372 is disposed has a rectangular shape. In the present embodiment, the second seal member 372 is formed in a circular shape so as to follow the cross-sectional shape of the holding portion H, and the adhesion to the holding portion H is enhanced.

The second seal member 372 is set to a material thickness that can be deformed when the first seal member 372 is attached to the first housing 31 or when the combustion gas enters from the opening 372t to the inside.
In addition, metals, such as copper, stainless steel, and aluminum, can be used for the material of the 2nd seal member 372 of this embodiment. In addition, as a material of the second seal member 372 of the present embodiment, Teflon (registered trademark) or the like can be used.

  Then, as shown in FIG. 7C, the second seal member 372 is disposed in the holding portion H in a state where the pressure detection device 5 is mounted on the cylinder head 4. In the present embodiment, the second seal member 372 is held by the first housing 31 such that a part of the inner peripheral portion of the second seal member 372 is fitted into the step portion 31bt. The second seal member 372 is attached such that the opening 372t faces the gap N extending to the combustion chamber C. The second seal member 372 is provided in a state where the opening 372t is opened toward the combustion chamber C.

When the internal combustion engine 1 operates, the combustion gas generated by the combustion in the combustion chamber C enters the gap N as shown in FIG. The combustion gas that has entered the gap N reaches the second seal member 372. The second seal member 372 expands by entering the inside of the opening 372t of the second seal member 372. Accordingly, the second seal member 372 is in close contact with the side surface 31b (stepped portion 31bt) and the second vertical surface 315c, and the second hole portion 4d and the stepped portion 4e.
Then, the second seal member 372 suppresses the inflow of combustion gas toward the rear end side from the holding portion H where the second seal member 372 is provided. As a result, on the rear end side of the second seal member 372 of the pressure detection device 5, the occurrence of a sudden temperature difference between the inside and outside due to the temperature rise caused by the ingress of combustion gas is suppressed.

(Embodiment 3)
FIG. 8 is a diagram for explaining the internal combustion engine 1 according to the third embodiment.
In addition, about the thing similar to the internal combustion engine 1 which concerns on Embodiment 1, the same code | symbol is attached | subjected and the detailed description is abbreviate | omitted.
FIG. 8A shows an overall view of the second seal member 472, FIG. 8B shows a VIIIb-VIIIb cross section shown in FIG. 8A, and FIG. 8C shows the second seal of the second embodiment. The state where the member 472 is provided between the pressure detection device 5 and the cylinder head 4 is shown.
As shown in FIG. 8C, in the internal combustion engine 1 according to the third embodiment, the protrusion 315 in the first housing 31 of the pressure detection device 5 is an example of a shoulder perpendicular to the center line direction at the tip. A second vertical surface 315c and a vertical surface 315b perpendicular to the center line direction at the rear end.
Further, the communication hole 4a of the cylinder head 4 according to the third embodiment includes, from the combustion chamber C side, a first hole 4b, a second hole 4d having a hole diameter larger than the hole diameter of the first hole 4b, and a first hole. A step 4e is provided between the portion 4b and the second hole 4d and forms a step perpendicular to the central axis direction.
The internal combustion engine 1 according to the third embodiment includes a second seal member 472 that seals between the cylinder head 4 and the pressure detection device 5.

  In the internal combustion engine 1 according to the third embodiment, as shown in FIG. 8C, in a state in which the pressure detection device 5 is mounted on the cylinder head 4, the second vertical surface 315 c and the stepped portion 4 e are second. A distance is provided so that the seal member 472 is sandwiched therebetween. In the internal combustion engine 1 of the third embodiment, the holding portion H that holds the second seal member 472 of the third embodiment is formed by the second vertical surface 315c, the side surface 31b, the second hole portion 4d, and the stepped portion 4e. To do. And in Embodiment 3, as shown in FIG. 8, the cross section of the holding | maintenance part H becomes a rectangular shape.

  The second seal member 472 is a member that suppresses the inflow of combustion gas into the gap between the inner wall of the cylinder head 4 and the outer wall of the housing 30 of the pressure detection device 5. The second seal member 472 is disposed in the holding portion H as shown in FIG. The holding portion H of the present embodiment is formed at the position (lateral) of the piezoelectric element 10 in the housing 30 central axis direction. Therefore, the second seal member 472 suppresses the inflow of combustion gas to the rear end side in the central axis direction from the position where the piezoelectric element 10 is provided in the gap between the cylinder head 4 and the pressure detection device 5.

As shown in FIG. 8A, the second seal member 472 is an annular member and has an inner side that is hollow. Further, the second seal member 472 is an annular cut formed over the entire circumference of the inner peripheral surface at a substantially central portion in the central axis direction, and has an opening 472t facing the central axis side.
The inner diameter of the second seal member 472 is set to be larger than the outer diameter of the side surface 31b of the first housing 31 of the pressure detection device 5 before being attached. The outer diameter of the second seal member 472 is set to be slightly larger than the inner diameter of the second hole portion 4d in the communication hole 4a of the cylinder head 4. When the second seal member 472 is attached to the internal combustion engine 1, a gap is formed between the inner peripheral portion of the second seal member 472 and the outer periphery of the first housing 31, and the outer peripheral portion and the second It is in close contact with the hole 4d.

  The cross section of the second seal member 472 has a circular shape when cut in the central axis direction. As shown in FIG. 8C, the holding portion H in which the second seal member 472 is disposed has a rectangular shape. In this embodiment, the cross section of the second seal member 472 is formed in a circular shape so as to follow the cross sectional shape of the holding portion H, thereby improving the adhesion to the holding portion H.

The second seal member 472 is set to a material thickness that can be deformed when the first seal member 472 is attached to the first housing 31 or when the combustion gas enters the inside from the opening 472t.
In addition, metals, such as copper, stainless steel, and aluminum, can be used for the material of the 2nd seal member 472 of this embodiment. In addition, as a material of the second seal member 472 of this embodiment, Teflon (registered trademark) or the like can be used.

  Then, as shown in FIG. 8C, the second seal member 472 is disposed in the holding portion H in a state where the pressure detection device 5 is mounted on the cylinder head 4. The second seal member 472 is attached such that the opening 472t faces the central axis direction.

When the internal combustion engine 1 operates, the combustion gas generated by the combustion in the combustion chamber C enters the gap N as shown in FIG. Then, the combustion gas that has entered the gap N reaches the second seal member 472. Then, the combustion gas enters the inside of the opening 472t of the second seal member 472, so that the second seal member 472 expands in the central axis direction and the outer side in the circumferential direction. Accordingly, the second seal member 472 is in close contact with the second vertical surface 315c of the first housing 31, the second hole portion 4d and the step portion 4e of the cylinder head 4.
And the 2nd seal member 472 suppresses inflow of combustion gas toward the back end side from holding part H in which the 2nd seal member 472 is provided. As a result, on the rear end side of the second seal member 472 of the pressure detection device 5, the occurrence of a sudden temperature difference between the inside and outside due to the temperature rise caused by the ingress of combustion gas is suppressed.

  As described above, in the first to third embodiments, the second seal members 72 (372 and 472) each having an opening shape are provided on the shoulder portion that becomes the tapered portion or the step portion in the housing 30 of the pressure detection device 5. It is done. Therefore, even if the second seal member 72 (372, 472) expands and is pushed in the central axis direction, the combustion gas generated in the combustion chamber C is pushed by the shoulder portion having a surface facing the central axis direction. 72 (372, 472) is held by drag. And the sealing (sealing) property of the clearance gap between the pressure detection apparatus 5 and the cylinder head 4 improves.

  In the present embodiment, the piezoelectric element 10 is used as a detection member for detecting pressure, but the present invention is not limited to this. What is necessary is just to detect as a pressure by receiving force through the diaphragm head 40. For example, a strain sensor may be used as a detection member.

  In the present embodiment, the first seal member 71 and the second seal member 72 (372, 472) are used, but the present invention is not limited to this mode. For example, the opening between the pressure detection device 5 and the cylinder head 4 may be sealed using only the second seal member 72 (372, 472).

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Cylinder block, 3 ... Piston, 4 ... Cylinder head, 5 ... Pressure detection apparatus, 6 ... Control apparatus, 7 ... Seal member, 10 ... Piezoelectric element, 21 ... Circuit board part, 22 ... Conduction member 30 ... Housing, 40 ... Diaphragm head, 50 ... First electrode part, 55 ... Second electrode part, 60 ... Insulating ring, 65 ... Support member, 70 ... Coil spring, 71 ... First seal member, 72, 372, 472 ... Second seal member, 100 ... Sensor part

Claims (6)

An internal combustion engine having a combustion chamber and an opening formed on a wall surface constituting the combustion chamber and leading to the combustion chamber and having a wide diameter on the near side compared to the diameter on the heel side;
A cylindrical shape that can be inserted into the opening of the internal combustion engine, the tip end side in the insertion direction is narrow according to the diameter of the flange side of the opening, and the rear end side is thick according to the diameter of the front side of the opening. A housing having a shoulder portion between the rear end side, a diaphragm provided on a front end side in the insertion direction of the housing, and a pressure that is disposed behind the diaphragm and acts via the diaphragm in the housing A combustion pressure detection device having a detection member for detecting
A ring-shaped, having an opening cross section with opening shape, and the seal member for sealing the said opening and the housing of the internal combustion engine at the shoulder of the housing of the combustion pressure detecting device, the Prepared,
The housing has a stepped portion into which the seal member is fitted,
The internal combustion engine with a combustion pressure detecting device , wherein the sealing member is held by the housing by an opening edge of the opening of the sealing member being engaged with the stepped portion . 2. The internal combustion engine with a combustion pressure detecting device according to claim 1, wherein the seal member is in a state where the opening of the seal member is opened toward the combustion chamber. The detection member of the combustion pressure detection device is provided at an end of the housing facing the combustion chamber,
It said shoulder portion of said housing, a combustion pressure detecting apparatus with an internal combustion engine according to claim 1 or 2, characterized in that it is formed at a position of the detecting member in the insertion direction. The combustion pressure detecting device according to any one of claims 1 to 3 , wherein the shoulder portion of the housing is a tapered portion having a diameter that gradually increases from the front end side toward the rear end side. Internal combustion engine. The outer seal member that is pressed in the same direction as the insertion direction in which the housing is inserted outside the opening of the internal combustion engine to seal between the housing and the combustion chamber. An internal combustion engine with a combustion pressure detecting device according to any one of 1 to 4. 5. The internal combustion engine with a combustion pressure detecting device according to claim 4, wherein the seal member has a horseshoe shape in cross section, and is provided along an inner wall of the opening of the internal combustion engine and the tapered portion of the housing. organ.

Images