JP2018179894A - Pressure detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pressure detection device capable of highly accurate pressure measurement by preventing pre-injection due to a fuel gas leak under a cryogenic environment.SOLUTION: A pressure detection device comprises a gas seal section which is inserted into an internal combustion engine. The gas seal section is made up of: a first seal section arranged at a front edge side, a side closer to a combustion chamber, of the pressure detection device; and a second seal section arranged at a rear edge side of the pressure detection device. The first seal section has: a first groove section formed on an outer peripheral surface of the pressure detection device; and a first seal member arranged on the first groove section. The second seal section has: a second groove section formed on the outer peripheral surface of the pressure detection device; and a second seal member arranged on the second groove section. The first groove section and the second groove section have cross-sectional shapes different from each other.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pressure detection device for detecting a combustion pressure in a combustion chamber of an internal combustion engine, and more particularly to a combustion gas seal structure of the pressure detection device inserted and disposed in an insertion hole facing the combustion chamber.

  The conventional pressure detection device has a cylindrical front end portion inserted into an insertion hole provided in the wall of the combustion chamber, and the front end portion has a sensor unit for detecting a combustion pressure, a pressure detection device, and the insertion hole The gas seal portion is formed to prevent the combustion gas from leaking from the gap. A sensor part consists of a diaphragm and a piezoelectric element, transmits the displacement of the diaphragm by a combustion pressure to a piezoelectric element, converts it into an electrical signal with a piezoelectric element, and outputs it. The gas seal portion is formed of a groove formed in a ring shape along the outer periphery of the cylindrical front end portion, and a ring-shaped seal member fitted in the groove and protruding in the radial direction of the front end portion. The combustion gas is sealed by pressing the inner wall surface of the insertion hole.

  The diaphragm is located at the very tip of the front end of the pressure sensing device to enable highly accurate pressure measurement, and the gas seal is formed in the immediate vicinity of the most leading diaphragm to prevent the heating of the front end and burn the combustion gas An example is proposed in which the gas seal portion is doubled to prevent the leakage of combustion gas more reliably and prevent combustion gas leakage (see, for example, Patent Document 1).

  Further, as another prior art, as in Patent Document 1, the gas seal portion of the pressure detecting device is formed by a ring-shaped groove and a seal member formed on the cylindrical outer periphery of the front end portion. The side opposite to the combustion chamber is formed by a tapered surface which is inclined in a direction away from the combustion chamber from the bottom of the groove toward the opening side. Therefore, when the combustion gas pressure is generated in the combustion chamber, the seal member fitted in the groove is pushed by the pressure, and is deformed in a wedge shape along the inner wall surface of the insertion hole and the tapered surface of the groove to secure the seal. An example has been proposed (see, for example, Patent Document 2).

JP, 2008-191059, A (page 7, FIG. 7) Patent No. 5625366 (page 11, Figure 2)

  However, the gas seal of the conventional pressure detection device shown in Patent Document 1 has a structure in which a seal member having a circular cross-section is pressed and sealed between the inner wall of the insertion hole of the combustion chamber and the groove having a rectangular cross-section The contact surface of the seal portion where the groove and the groove directly contact is small, and has the disadvantage that the sealability between the pressure detection device and the insertion hole is unstable and lacks in reliability. Particularly in a cryogenic environment of about -40.degree. C., in addition to the instability of the seal location, the combustion gas is generated by the difference between the thermal expansion coefficient and the thermal conductivity of the combustion chamber wall of the internal combustion engine and the pressure detecting device. Leak easily.

  Furthermore, although the conventional pressure detection device shown in Patent Document 1 forms a double seal, since the gas seal portion is a gas seal portion formed of a seal member and a groove having the same structure, the defect of the same tendency is caused. When one side causes seal leakage in a cryogenic environment, the other side is likely to be generated, and combustion gas leakage is likely to occur even if it is configured at a double angle.

  Next, the prior art shown in Patent Document 2 will be described with reference to FIG. 5 (a) and 5 (b) are partially enlarged sectional views of the front end portion of the pressure detection device modified without departing from the scope of the invention in order to make the prior art disclosed in Patent Document 2 easy to understand the present invention. FIG.

  As shown in FIG. 5A, the front end portion 211 of the pressure detection device 200 is inserted into the insertion hole 321 of the combustion chamber wall 300. The front end portion 211 of the pressure detection device 200 is fitted in a sensor portion including the diaphragm 213, the piezoelectric element 214, and the electrode 215, a groove 240 formed in a ring shape on the cylindrical outer periphery of the front end portion 211, and the groove 240 And a gas seal portion composed of a rectangular ring-shaped seal member 212.

  The cross-sectional shape of the groove 240 is trapezoidal, and includes a bottom surface 241 of the groove and side surfaces 242 and 243 of the groove, and the side surface 243 on the side closer to the combustion chamber 20 is a surface perpendicular to the cylinder central axis Z of the front end portion 211 The other side surface 242 is formed of a tapered surface that is open in a direction away from the combustion chamber 20 from the bottom surface 241 toward the opening.

  Immediately after the pressure detection device 200 is attached to the internal combustion engine, the seal member 212 fitted in the groove 240 is pressure-contacted by the bottom surface 241 and the side surface 243 and the inner wall 322 of the insertion hole 321 to seal combustion gas. Do. Then, when the internal combustion engine is driven, the seal member 212 receives pressure from the combustion chamber 20 side by the combustion pressure in the combustion chamber 20 as shown by the arrow D.

  As a result, as shown in FIG. 5 (b), the seal member 212 is crushed following the tapered shape of the side surface 242 and deformed into a wedge shape, strongly in close contact with the inner wall 322 of the insertion hole, and the sealability is further ensured. Ru. Therefore, it is possible to reliably prevent the leakage of the combustion gas even in an environment such as a cryogenic temperature.

  However, when the seal member 212 collapses along the tapered side surface 242 at a high combustion pressure, a void 250 is formed between the side surface 243 and the seal member 212. Then, as indicated by an arrow E, the high-temperature and high-pressure combustion gas intrudes into the void 250.

  The bottom surface 241 of the groove 240, which is the inner circumferential portion of the gap 250, forms a base 251 supporting the diaphragm 213. When the gap 250 is exposed to high temperature combustion gas and the base 251 is thermally deformed, There is a problem that distortion occurs and the displacement makes it impossible to accurately measure the combustion pressure.

  In addition, when the combustion gas enters the space 250, the unburned gas may stay in the space 250, which may cause the occurrence of preignition. FIG. 6 is a known graph for explaining preignition, showing the combustion pressure at the time of preignition generation in the combustion chamber and the combustion pressure at the normal time, where the X axis is the crank angle and the Y axis is the combustion pressure. In the figure, a curve a shown by a solid line is a curve showing the combustion pressure at the normal time, and a curve b shown by a dotted line is a curve of the combustion pressure at the time of preignition occurrence. As apparent from this graph, the combustion pressure at the time of preignition occurrence is steeper than the combustion pressure at the normal time, and the peak value of the combustion pressure is also about 3 times, which may damage the engine. it is obvious.

  Then, in view of the above-mentioned subject, an object of the present invention is to provide a pressure detection device which can prevent a leak of a combustion gas effectively and can measure a pressure with high accuracy.

  The pressure detection device of the present invention adopts the following configuration in order to achieve the above object.

  A pressure detection device inserted and disposed in an insertion hole facing a combustion chamber of an internal combustion engine, the outer peripheral surface of the pressure detection device comprising a gas seal portion sealing between the inner wall surface of the insertion hole and the pressure detection device The first seal portion includes a first seal portion disposed on the tip side which is the combustion chamber side of the pressure detection device, and a second seal portion disposed on the rear end side of the first seal member. Is formed by a first groove portion formed in the outer peripheral surface of the pressure detection device and a first seal member disposed in the first groove portion, and the second seal portion is formed in the outer peripheral surface of the pressure detection device The second groove and the second seal member disposed in the second groove are formed, and the first groove and the second groove have different cross-sectional shapes.

  In the pressure detection device according to the present invention, in addition to the above configuration, a protrusion may be formed on the bottom surface of the first groove.

  In the pressure detection device according to the present invention, in addition to the above configuration, the projection formed on the bottom surface of the first groove may project from the bottom surface of the first groove toward the inner wall surface of the insertion hole.

  In the pressure detection device according to the present invention, in addition to the above configuration, the side surface of the second groove may be a tapered surface inclined with respect to a surface orthogonal to the pressure detection device.

  In the pressure detection device according to the present invention, in addition to the above configuration, the side surface on the rear end side of the second groove may be a tapered portion inclined from the bottom surface of the second groove toward the rear end.

  In the pressure detection device according to the present invention, in addition to the above configuration, the first seal member and the second seal member may have a rectangular cross section.

  In the pressure detection device according to the present invention, in addition to the above configuration, the first seal member and the second seal member may be a polymer material.

  According to the pressure detection device of the present invention, the first seal is formed by making the first groove for arranging the first seal member different from the second groove for arranging the second seal member. Part and the second seal part can be used as seal parts having different functions, and it is possible to effectively prevent leakage of combustion gas and provide a pressure detection device capable of measuring pressure with high accuracy Become.

It is a top view for explaining the appearance of one embodiment of the pressure sensing device concerning the present invention. It is sectional drawing of the front-end part corresponded to the A section of FIG. 1 before insertion to the internal combustion engine of one Embodiment of the pressure detection apparatus which concerns on this invention. It is sectional drawing of the front-end part shown to A part of FIG. 1 after insertion to the internal combustion engine of one Embodiment of the pressure detection apparatus which concerns on this invention. It is sectional drawing of the front-end part shown to A part of FIG. 1 for demonstrating the function of a 2nd seal part by one Embodiment of the pressure detection apparatus which concerns on this invention. It is sectional drawing of the front-end part for demonstrating the prior art shown to patent document 2. FIG. It is a graph explaining pre-ignition.

  The pressure detection device of the present invention is characterized in that it has at least two gas seals at its front end, and the cross-sectional shape of the groove of each gas seal differs.

  Hereinafter, the pressure detection device of the present invention will be described using the drawings. The embodiment to be described below will be described using an example of a pressure detection device inserted into an insertion hole of a combustion chamber wall of an internal combustion engine.

  The entire configuration of the pressure detection device will be described using FIG. 1, and the seal structure of the front end portion of the pressure detection device will be described using FIGS. 2 to 4. In each of the drawings, the same components are denoted by the same reference numerals and redundant description will be omitted.

[Description of Configuration of Embodiment of Pressure Detection Device: FIG. 1]
FIG. 1 is a plan view for explaining the overall configuration of a pressure detection device disposed and fixed by screwing in an insertion hole of a combustion chamber wall of an internal combustion engine.

  As shown in FIG. 1, the pressure detection device 1 is substantially cylindrical with the Z axis as a central axis, and has a front end portion 11, a main body 10, an external thread portion 101, and an output lead 102. It is inserted into the insertion hole 21 of the wall 2. The front end portion 11 has a sensor portion and a gas seal portion, the sensor portion includes a diaphragm 30 at the tip of the front end portion 11 and a piezoelectric element (not shown) inside, and the gas seal portion has a cylindrical outer periphery of the front end portion 11 A first seal portion 12 and a second seal portion 13 are formed on the rear side.

  The insertion hole 21 for disposing the pressure detection device 1 in the combustion chamber wall 2 has a female screw portion 22 and a tip hole 23, and the female screw portion 22 is screwed with the male screw portion 101 of the pressure detector 1. The pressure detection device 1 is inserted and fixed in the insertion hole 21. The tip hole 23 prevents the leakage of the combustion gas generated in the combustion chamber 20 by the inner wall and the first and second seals 12 and 13 of the front end 11 doing.

  The pressure detection device 1 is installed at a position where the diaphragm 30 at the front end 11 faces the combustion chamber 20, converts displacement of the diaphragm 30 due to combustion pressure into an electrical signal by a piezoelectric element (not shown), and outputs the output lead 102 It is output to the control circuit (not shown) of the internal combustion engine.

[Description of gas seal portion of one embodiment of pressure detection device: FIG. 2 to FIG. 4]
FIG. 2 is a cross-sectional view of the front end portion corresponding to A in FIG. 1 before the pressure detection device is mounted in the insertion hole of the combustion chamber wall, and is a view for explaining the structure of the seal portion at the front end. .
FIG. 3 is a cross-sectional view of the front end portion indicated by A in FIG. 1 and is a view for explaining the seal structure of the front end portion of the pressure detection device mounted in the insertion hole of the combustion chamber wall.
FIG. 4 is a cross-sectional view of the front end portion of the A portion similar to FIG. 3 and is a view for explaining the function of the second seal portion.

  As shown in FIG. 2, the front end portion 11 of the pressure detection device 1 of the present invention is provided with a diaphragm 30 at the end face of its tip, and the block-like end portion of the diaphragm 30 opposite to the combustion chamber 20 is a piezoelectric element 31 is in contact with one surface of the piezoelectric element 31, and the electrode section 32 is in contact with the other surface of the piezoelectric element 31 to form a sensor section. The pressure detected by the sensor section is converted into an electrical signal by the piezoelectric element 30 and output lead wire Output through 102 (see FIG. 1).

  A first seal portion 12 and a second seal portion 13 are formed on the outer periphery of the cylindrical front end portion 11 as a gas seal portion, and the first seal portion 12 has a first groove portion 14 and a first seal. The member 16 and the second seal portion 13 are constituted by the second groove portion 15 and the second seal member 17.

  The first groove portion 14 and the second groove portion 15 are formed in a ring shape coaxially with the central axis Z of the front end portion 11. The first groove portion 14 closer to the diaphragm 30 has both side surfaces 142 and 143 of the groove formed by surfaces perpendicular to the central axis Z, the cross section thereof is rectangular, and the bottom surface 141 of the groove is entirely The protrusion 144 is formed over the circumference.

  The second groove 15 on the rear end side far from the combustion chamber 20 side with respect to the first groove 14 has a trapezoidal shape, and one side 153 on the side closer to the first groove 14 has a first side. Similar to the side surfaces 142 and 143 of the groove of the groove portion 14, the side surface 152 perpendicular to the central axis Z is separated from the side surface 153 from the bottom surface 151 of the second groove portion 15 toward the opening side. It is formed as a surface inclined in a direction, in other words, a tapered portion inclined toward the rear end side.

  The first seal member 16 and the second seal member 17 fitted in the first and second groove portions 14 and 15 are preferably members having the same rectangular shape, and the material is a polymer material For example, perfluoroelastomers are desirable. Then, due to its elasticity, the first seal member 16 is fitted along the side surfaces 142 and 143 of the first groove portion 14 and the bottom surface 141, and the projection 144 of the bottom surface 141 forms a convex portion 161 in the radial direction. It is done. The second seal member 17 is fitted along the side surface 153 and the bottom surface 151 of the second groove portion 15. The outer diameters of the first and second seal members 16 and 17 fitted in the front end portion 11 are larger than the outer diameter of the diaphragm 30, and the pressure detection device 1 is inserted into the insertion hole 21 of the combustion chamber wall 2. The outer diameter (the outer diameter larger than the inner diameter of the distal end hole 23) is set such that the inner wall of the distal end hole 23 (see FIG. 1) and the bottom surface 141, 151 are in pressure contact when inserted.

  FIG. 3 is a cross-sectional view of a portion A of FIG. 1, in which the pressure detection device 1 is inserted into the tip end hole 23 of the insertion hole of the combustion chamber wall 2.

  As shown in FIG. 3, the first and second seal members 16 and 17 of the front end portion 11 are provided between the inner wall surface 231 and the bottom surfaces 141 and 151 of the distal end hole 23 of the insertion hole 21 (see FIG. 1). It is pressed. As described above, in the first seal member 16, the convex portion 161 (see FIG. 2) protruding in the outer peripheral direction by the protrusion 144 formed on the bottom surface of the first groove portion 14 is formed on the inner wall surface 231 of the tip hole 23. Strong pressure contact. Therefore, the actual seal location by the first seal member 16 is the projection 144 of the first groove 14 at the front end 11 of the pressure detection device 1 and the projection 144 on the inner wall surface 231 of the combustion chamber wall 2. With the convex portion 161 (see FIG. 2) of the first seal member 16, the actual seal position is clearly determined, and the gas seal is reliable.

  Further, in the first seal portion 12 positioned closer to the combustion chamber 2, the first seal member 16 is inserted into the first groove portion 14 without a gap so that the first seal member 16 is in the combustion chamber. Even when the pressure of the combustion gas from 20 is pushed as shown by arrow B in the figure, no air gap is generated between the side surface 143 of the first groove portion 14 and the first seal member 16, and a high temperature combustion is caused. Gas or unburned gas does not enter the bottom surface 141 of the first groove portion 14. That is, the base portion 301 that fixedly supports the diaphragm 30 is not exposed to the high temperature combustion gas, and distortion does not occur in the diaphragm 30, which enables accurate pressure measurement.

  The second seal member 17 is provided to ensure a seal when a seal leak occurs in the first seal member 16, and the inner wall 231 and the front end portion of the tip hole 23 of the combustion chamber wall 2 It is in pressure contact with the bottom surface 151 of the second groove portion 11.

  FIG. 4 is a view for explaining the function of the second seal member 17 when there is a situation where the combustion gas leaks from the first seal member 16.

  For example, when the combustion gas may leak from the first seal member 16 in a cryogenic environment or the like, the pressure of the combustion gas from the combustion chamber 20 reaches the second seal member 17 as shown by the arrow C. The second seal member 17 receives the pressure of the combustion gas and is pushed in the direction of the arrow C, and is pressed against the inner wall 231 and the tapered side surface 152 to be crushed and deformed in a wedge shape. That is, the wedge-shaped gap between the side face 152 and the inner wall 231 of the second seal member 17 is a real seal point, and the second seal member 17 is deformed and pressed into the wedge-like gap, which is very excellent. Has achieved a good seal.

  Then, when the seal member 17 is pushed into the wedge-shaped gap, the gap 18 is formed between the side surface 153 and the seal member 17. As a result, as shown by the arrow C, the high temperature / high pressure combustion gas or unburned gas infiltrates into the void portion 18, but the presence of the first seal portion 12 makes the void 18 have high temperature combustion gas or unburned gas The base 301 supporting the diaphragm 30 is separated from the air gap 18, and the amount of combustion gas and unburned gas entering can be reduced. Therefore, the effect of distortion of the base 301 supporting the diaphragm 30, or preignition Is configured to be able to suppress the occurrence of

  In the pressure detection device of this embodiment, the tip end side close to the diaphragm is the first gas seal portion, the groove cross section of the seal portion has a rectangular shape, and the far rear end side is the second gas seal portion, the seal portion The groove cross-sectional shape is formed in a trapezoidal shape, and is characterized in that the shape of each groove is different, and by changing the cross-sectional shape of the two grooves while having a double seal configuration, By making the seal characteristics different, it is possible to measure the combustion pressure with high accuracy, and the pressure detection device has a high response capability even in an environment such as cryogenic temperature.

  The pressure detection device is not limited to the above embodiment, and may be any device having a sensor unit, as long as the sensor unit receives a pressure and outputs a signal corresponding thereto. For example, instead of the piezoelectric element, it may be a pressure detection device that measures pressure from a change in resistance of a strain gauge or a change in capacitance generated between two electrodes.

  In the present embodiment, the combustion chamber of the internal combustion engine has been described as an example of the object to be measured. However, the pressure is not limited to the pressure measurement of the combustion chamber, and pressure for various uses such as exhaust pressure and fuel injection pressure. It goes without saying that it can be used for measurement.

  The present invention is not limited to the embodiments of the pressure detection device described above, and it is not necessary to perform all of them, and various changes and modifications may be made within the scope of the contents described in the respective claims of the claims. It goes without saying that omissions can be made.

DESCRIPTION OF SYMBOLS 1 pressure detection device 2 combustion chamber wall 10 main body 11 front end portion 12 first seal portion 13 second seal portion 14 first groove portion 15 second groove portion 16 first seal member 17 second seal member 18 gap portion DESCRIPTION OF SYMBOLS 20 combustion chamber 21 insertion hole 22 female screw part 23 tip hole 30 diaphragm 31 piezoelectric element 32 electrode part 101 male screw part 102 output lead wire 141, 151 bottom surface 142, 143, 152, 153 side surface 144 protrusion part 161 convex shape part 231 inside Wall 301 base

Claims (7)

In the pressure detection device inserted and disposed in the insertion hole facing the combustion chamber of the internal combustion engine,
The pressure detection device has a gas seal portion for sealing between the inner wall surface of the insertion hole and the pressure detection device on the outer peripheral surface of the pressure detection device,
The gas seal portion is formed of a first seal portion disposed on the front end side which is the combustion chamber side of the pressure detection device, and a second seal portion disposed on the rear end side of the first seal member. Become
The first seal portion is formed of a first groove portion formed on an outer peripheral surface of the pressure detection device, and a first seal member disposed in the first groove portion.
The second seal portion is formed of a second groove formed on an outer peripheral surface of the pressure detection device, and a second seal member disposed in the second groove.
A pressure detection device, wherein the first groove and the second groove have different cross-sectional shapes.   The pressure detection device according to claim 1, wherein a protrusion is formed on a bottom surface of the first groove.   The projection according to claim 1 or 2, wherein the projection formed on the bottom surface of the first groove projects from the bottom surface of the first groove toward the inner wall surface of the insertion hole. Pressure detection device.   The pressure detection device according to any one of claims 1 to 3, wherein a side surface of the second groove portion is a tapered surface inclined with respect to a surface orthogonal to the pressure detection device.   The side surface on the rear end side of the second groove portion is the tapered portion inclined from the bottom surface of the second groove portion toward the rear end side. The pressure detection device according to one of the preceding claims.   The pressure detection device according to any one of claims 1 to 5, wherein the first seal member and the second seal member have a rectangular cross section.   The pressure detection device according to any one of claims 1 to 6, wherein the first seal member and the second seal member are polymer materials.

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