JP2007198169A - Combustion pressure sensor and internal combustion engine with sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a low cost combustion pressure sensor of high combustion pressure detection performance, and an internal combustion engine with a sensor provided with such a combustion pressure sensor. <P>SOLUTION: The combustion pressure sensor 100 measures change of combustion pressure with a tip end side thereof inserted in a bottomed hole 221 in the internal combustion engine having the bottomed hole 221. The combustion pressure sensor 100 is provided with an intermediate shaft 130 fixed on a bottom surface 221b of the bottomed hole 221 and following displacement of the bottom surface 221b in an axial line BX direction of the bottomed hole 221, a fixed part 115 fixed on a part near an open edge 221c of the bottomed hole 221, and a sensor part 150 capable of detecting displacement in the axial line BX direction of the intermediate shaft 130 relative to the fixed part 115 generated by change of combustion pressure. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a combustion pressure sensor for measuring a change in combustion pressure in an internal combustion engine such as an automobile engine, and a sensor-equipped internal combustion engine in which such a combustion pressure sensor is attached to the internal combustion engine.

  Conventionally, a combustion pressure sensor for measuring the combustion pressure of an internal combustion engine is known. For example, Patent Literature 1 and Patent Literature 2 disclose such a combustion pressure sensor. A conventional combustion pressure sensor is used by providing a through hole leading to a combustion chamber in an engine block or an engine head and inserting the through hole into the through hole. For example, in the combustion pressure sensor of Patent Document 1, the pressure receiving surface (pressure-sensitive portion) is disposed in the combustion chamber through a through hole provided in the internal combustion engine, and a change in the combustion pressure is directly received by this pressure receiving surface to obtain the combustion pressure. Measure (refer to paragraph (0010) of FIG. 1 and FIG. 1). In general, in the combustion pressure sensor of Patent Document 2, a rod-shaped pressure transmission member (pressure-sensitive part) is inserted into a through hole provided in the engine block, and a change in combustion pressure is directly received by this pressure transmission member. The combustion pressure is measured (see FIG. 1 of Patent Document 2).

JP-A-5-332872 JP 2004-286617 A

  However, since such a conventional combustion pressure sensor is used by being inserted into a through hole communicating with the combustion chamber, the pressure sensitive part is exposed to the combustion chamber. For this reason, heat resistance, pressure resistance, corrosion resistance, and the like must be sufficiently ensured. Therefore, although it has high performance, it is inevitable that the cost is inevitably increased.

  The present invention has been made in view of the present situation, and provides a combustion pressure sensor having high combustion pressure detection performance and low cost, and a sensor-equipped internal combustion engine equipped with such a combustion pressure sensor. For the purpose.

  The solution is to measure the change in combustion pressure by inserting the tip side of the internal combustion engine with a bottomed hole with the bottom part closer to the combustion chamber than the opening edge of the part. A combustion pressure sensor that is directly or indirectly fixed to a fixed portion in the bottomed hole, and is configured to follow a displacement in the axial direction of the bottomed hole in the fixed portion. A first portion that is configured to be fixed to a portion of the internal combustion engine that is closer to the opening edge in the axial direction than the fixed portion; and the second portion that is generated in accordance with a change in the combustion pressure. And a sensor part configured to be able to detect relative displacement in the axial direction with respect to one part of the second part.

  The engine head or the like that forms the combustion chamber is distorted as the combustion pressure changes. More specifically, in the engine head or the like, the inner surface side exposed to the combustion chamber is greatly distorted as the combustion pressure changes. On the other hand, the outer surface exposed to the outside does not distort as much as the inner surface even if the combustion pressure changes. In particular, since the engine head has many cavities inside, the difference in distortion between the inner surface side and the outer surface side increases. By obtaining such knowledge, the present inventors devise the present invention, considering that the change in combustion pressure can be measured by detecting the difference in distortion between the inner surface side and the outer surface side of the engine head or the like. It came to.

As described above, the combustion pressure sensor of the present invention is fixed to a fixed portion in a bottomed hole provided in the internal combustion engine, and is configured to follow the displacement in the axial direction at the fixed portion. Have The combustion pressure sensor has a second portion configured to be fixed to a portion of the internal combustion engine that is closer to the opening edge side in the axial direction than the fixed portion. Of the engine head or the like that forms the combustion chamber, a portion close to the combustion chamber is greatly distorted due to a change in the combustion pressure, but a portion far from the combustion chamber causes only a relatively small distortion even if the combustion pressure changes. For this reason, the first part is greatly displaced as the combustion pressure is changed, but the second part is displaced only small.
Moreover, this combustion pressure sensor has a sensor part comprised so that detection of the relative displacement about the axial direction with respect to the 2nd part of the 1st part is possible. For this reason, a change in combustion pressure can be detected based on this relative displacement. As described above, the combustion pressure sensor according to the present invention can detect the combustion pressure with high accuracy in the same manner as the conventional combustion pressure sensor.

  In addition, since this combustion pressure sensor is used by being inserted into a bottomed hole of an internal combustion engine, the tip portion thereof is not exposed to the combustion chamber. For this reason, heat resistance, pressure resistance, corrosion resistance, etc. can be significantly reduced. Therefore, the cost of the combustion pressure sensor can be reduced, and an inexpensive combustion pressure sensor can be provided. In addition, since it is not necessary to make a through-hole leading to the combustion chamber in the internal combustion engine, there is an advantage that the combustion pressure can be measured without impairing the performance of the internal combustion engine.

  Here, the “bottomed hole” may be in a form in which the bottom is closer to the combustion chamber than the opening edge, and the shape and size thereof can be changed as appropriate. Moreover, the formation place should just select it suitably, for example, can form in an engine head or an engine block. As described above, the engine head is formed with a lot of cavities inside itself, and the difference in distortion between the inner surface side and the outer surface side becomes large, so that it is easy to detect a change in combustion pressure. For this reason, it is preferable to provide a bottomed hole in the engine head.

  As long as the “first part” can be fixed to the fixing portion in the bottomed hole as described above, for example, it may be fixed to the bottom of the bottomed hole, or fixed to the center in the axial direction of the bottomed hole. May be. The “bottom portion” includes the bottom surface of the bottomed hole and the vicinity of the bottom surface of the side surface (inner peripheral surface) of the bottomed hole. In addition, the “fixing” may be such that the first part and the fixing portion in the bottomed hole are not relatively displaced, and may be fixed by fixing them with welding or an adhesive. Then, they may be fixed by bringing them into contact, fitting, or screwing together.

  The “second part” only needs to be fixed to a portion of the internal combustion engine that is closer to the opening edge than the fixed portion as described above. For example, the “second portion” may be fixed near the opening edge of the bottomed hole. You may fix to an axial direction center part. The term “in the vicinity of the opening edge” refers to a portion of the internal combustion engine near the opening edge of the bottomed hole. Of the side surface (inner peripheral surface) of the bottomed hole, the portion near the opening edge or the opening of the bottomed hole. The peripheral portion of the edge (for example, the peripheral portion of the opening edge of the bottomed hole in the outer surface of the engine head) is included. Similarly to the above, this “fixing” may be performed as long as the second part and the portion of the internal combustion engine that fixes the second part are not displaced relatively, and the fixing form can be appropriately selected.

  The “sensor unit” only needs to satisfy the above-described requirements, and the configuration form and the formation location in the combustion pressure sensor can be appropriately selected. The “sensor unit” can be configured using, for example, a piezoelectric element or a piezoresistive element as described later. In addition, the “sensor unit” may be formed in a part disposed in the bottomed hole when in use, or may be formed in a part disposed outside the bottomed hole. It is suitable in terms of properties.

  Further, in the above combustion pressure sensor, the first part is configured to be fixed to the bottom part of the bottomed hole, and the second part is fixable to the vicinity of the opening edge of the bottomed hole. A combustion pressure sensor configured may be used.

  The combustion pressure sensor of the present invention is configured such that the first part can be fixed to the bottom part of the bottomed hole and the second part can be fixed to the vicinity of the opening edge of the bottomed hole. Since this combustion pressure sensor can take a particularly large distance from the fixed portion of the first part to the second part as compared with other cases, when this combustion pressure sensor is attached to the internal combustion engine, it is accompanied by a change in the combustion pressure. The relative displacement of the first part with respect to the second part also appears greatly. Therefore, the change in the combustion pressure can be detected particularly accurately.

  Furthermore, the combustion pressure sensor according to any one of the above, further comprising a housing including the second part, the housing covering at least a tip side of the first part with respect to the second part. A combustion pressure sensor is preferable.

Of the first part, the tip side of the second part is inserted into the bottomed hole of the internal combustion engine, and thus is exposed to a higher temperature than the outside of the bottomed hole. On the other hand, in this invention, since the front end side is covered with the housing rather than the 2nd part among 1st parts, compared with the case where there is no such housing, the 1st part is exposed to high temperature. Can be suppressed.
The housing only needs to cover at least the front end side of the first part, and may cover only the front end side of the second part, or may cover the entire first part. Good. Further, the housing may be configured to cover the sensor unit.

  Furthermore, in the combustion pressure sensor according to any one of the above, the sensor unit includes a piezoelectric element, changes a load applied to the piezoelectric element in accordance with the relative displacement, and charges corresponding to the change in the load. It is preferable to use a combustion pressure sensor configured to generate

In this way, by using the piezoelectric element to generate an electric charge corresponding to the relative displacement of the first part with respect to the second part, the sensor part can easily and accurately detect the change in the combustion pressure. Therefore, such a combustion pressure sensor can easily and accurately measure changes in combustion pressure.
As described above, the “piezoelectric element” is configured so that the load applied to itself changes according to the relative displacement of the first part relative to the second part, and generates electric charges according to the change. That's fine. Therefore, the load applied to the piezoelectric element may increase as the relative displacement increases, or the load applied to the piezoelectric element may decrease as the relative displacement increases.
A plurality of piezoelectric elements can be used by laminating them. In this case, all the piezoelectric elements can be configured to increase (or decrease) the load applied to the piezoelectric elements as the relative displacement increases. Alternatively, for some piezoelectric elements, the load applied to the piezoelectric element increases as the relative displacement increases, while for other piezoelectric elements, the load applied to the piezoelectric element decreases as the relative displacement increases. It is good also as a structure.

  Alternatively, in the combustion pressure sensor according to any one of the above, the sensor unit includes a piezoresistive element, and generates strain in the piezoresistive element in accordance with the relative displacement, and changes the strain. A combustion pressure sensor configured to generate a corresponding signal may be used.

  As described above, the sensor unit can easily and accurately detect the change in the combustion pressure by generating a signal corresponding to the relative displacement of the first part with respect to the second part using the piezoresistive element. Accordingly, such a combustion pressure sensor can also easily and accurately measure a change in the combustion pressure.

  Another solution is an internal combustion engine with a sensor in which a combustion pressure sensor for measuring a change in the combustion pressure is attached to the internal combustion engine, wherein the internal combustion engine has a bottom portion in the combustion chamber rather than its opening edge. The combustion pressure sensor has a bottomed hole in a close form, and the front end side of the combustion pressure sensor is inserted into the bottomed hole, and is directly or indirectly fixed to a fixing portion in the bottomed hole. A first portion configured to follow displacement in the axial direction of the bottomed hole in the fixed portion; and a portion of the internal combustion engine on the opening edge side in the axial direction with respect to the fixed portion. A second part fixed to the sensor, and a sensor part configured to detect relative displacement in the axial direction with respect to the second part of the first part caused by a change in the combustion pressure. It is an internal combustion engine with a sensor

  Since this sensor-equipped internal combustion engine includes the above-described combustion pressure sensor, it is possible to accurately detect a change in the combustion pressure based on the relative displacement of the first part with respect to the second part. Further, since the tip of the combustion pressure sensor is not exposed to the combustion chamber, the heat resistance, pressure resistance, corrosion resistance, etc. required for the combustion pressure sensor can be greatly reduced. Therefore, the cost of the combustion pressure sensor can be reduced, and an inexpensive combustion pressure sensor can be provided. As a result, an inexpensive internal combustion engine with a sensor can be provided. Furthermore, since it is not necessary to make a through-hole leading to the combustion chamber in the internal combustion engine, the combustion pressure can be measured appropriately without impairing the performance of the internal combustion engine.

  Furthermore, in the internal combustion engine with a sensor, the first part is fixed to the bottom part of the bottomed hole, and the second part is fixed to the vicinity of the opening edge of the bottomed hole. The internal combustion engine should be equipped.

  In the internal combustion engine with a sensor according to the present invention, the first part of the combustion pressure sensor is fixed to the bottom of the bottomed hole, and the second part is fixed near the opening edge of the bottomed hole. For this reason, since the distance from the fixing | fixed site | part of a 1st part to the 2nd part can be taken especially large, the relative displacement with respect to the 2nd part of the 1st part accompanying the change of a combustion pressure also appears large. Therefore, the change in the combustion pressure can be detected particularly accurately.

(Embodiment 1)
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a part of a combustion pressure sensor 100 according to Embodiment 1 and a sensor-equipped internal combustion engine 200 in which the combustion pressure sensor 100 is attached to an internal combustion engine 210. The combustion pressure sensor 100 measures changes in the combustion pressure of the internal combustion engine 210. Note that, in the combustion pressure sensor 100, the lower side in the figure is the distal end side, and the upper side in the figure is the proximal side.

The combustion pressure sensor 100 includes a cylindrical housing 110 extending in a direction along the axis AX (axis AX direction), a rod-shaped center shaft (first portion) 130 inserted inside the housing 110, and a base end of the housing 110. And a sensor unit 150 disposed on the side.
Of these, the housing 110 is made of carbon steel. The housing 110 includes a distal end portion 111, an insertion portion 113, a fixing portion (second portion) 115, and a hexagonal engagement portion 117, and is integrally formed.

The distal end portion 111 is located on the most distal end side of the housing 110 and is welded to a distal end portion 131 of the middle shaft 130 described later. When the tip 111 is attached to the internal combustion engine 210, the tip 111 is brought into contact with and fixed to the bottom surface (bottom, fixed portion) 221b of the bottomed hole 221.
The insertion portion 113 is positioned on the proximal end side of the distal end portion 111 and inserts the distal end side of the middle shaft 130. When the insertion portion 113 is attached to the internal combustion engine 210, the insertion portion 113 is inserted into the bottomed hole 221 via a side surface (inner peripheral surface) 221d of the bottomed hole 221 and a predetermined gap.

  The fixing portion 115 is located on the proximal end side of the insertion portion 113 and inserts the middle shaft 130 therein. When the fixing portion 115 is attached to the internal combustion engine 210, the fixing portion 115 is fixed to a portion of the side surface 221d of the bottomed hole 221 near the opening edge 221c. Specifically, a male screw portion 115f is formed on the outer side in the radial direction of the fixed portion 115, while a female screw portion 221g is formed in the vicinity of the opening edge 221c of the side surface 221d of the bottomed hole 221. The fixing portion 115 is fixed to the vicinity of the opening edge 221c in the side surface 221d of the bottomed hole 221 by screwing the both. Note that the female screw portion 221g in the vicinity of the opening edge 221c in the side surface 221d corresponds to a portion to which the second portion in the present invention is fixed.

  The hexagonal engagement portion 117 is located on the proximal end side of the fixed portion 115 and inserts the middle shaft 130. The hexagonal engagement portion 117 has a hexagonal column shape, and is used to engage a tool such as a wrench when the combustion pressure sensor 100 is attached to the internal combustion engine 210 (when screwed). The hexagonal engagement portion 117 is arranged outside the internal combustion engine 210 in a state of being attached to the internal combustion engine 210, unlike the tip portion 111, the insertion portion 113, and the fixing portion 115 described above.

  Next, the center shaft 130 will be described. The middle shaft 130 has a substantially elongated cylindrical shape (bar shape) and is made of carbon steel. The distal end side of the middle shaft 130 is inserted into the housing 110, and a part of the proximal end side protrudes from the hexagonal engagement portion 117 of the housing 110 toward the proximal end side. The tip 131 of the middle shaft 130 has a T-shaped cross section in which a disc is welded to the tip of the cylinder, and the tip of the cylindrical portion of the housing 110 is in contact with the peripheral portion of the disc. 130 and the housing 110 are welded. When the tip 131 of the intermediate shaft 130 is attached to the internal combustion engine 210, it is fixed in direct contact with the bottom surface 221 b of the bottomed hole 221 of the internal combustion engine 210. Further, the middle shaft 130 is loosely inserted into the housing 110 so as to be relatively displaced with respect to the housing 110 in the axis AX direction. For this reason, when the bottom surface 221b of the bottomed hole 221 of the internal combustion engine 210 is displaced in the axis BX (AX) direction, the middle shaft 130 is displaced following the bottom surface 221b.

  Next, the sensor unit 150 will be described. FIG. 2 shows the sensor unit 150. The sensor unit 150 has a substantially cylindrical shape having a circular distal end surface 151 and a proximal end surface 152. The sensor unit 150 has a metal case 154 that forms its outer shape. In this metal case 154, a base end side metal plate packing 155, a piezoelectric element 156, a metal electrode plate 157, a ceramic insulating plate 158 and a front end side metal plate packing 159 are laminated in order from the base end side to the front end side. ing. Moreover, the resin tube 160 is arrange | positioned inside these radial directions. The sensor unit 150 has a lead wire 153.

  Among these, the piezoelectric element 156 is made of lead zirconate titanate, is polarized in the direction of the axis AX, and generates positive or negative charges on both end surfaces based on a change in compressive stress in the direction of the axis AX. Specifically, when the compressive stress in the direction of the axis AX is reduced, the piezoelectric element 156 generates a positive charge on the tip side surface (upper surface in FIG. 2), while on the base end side surface (lower surface in FIG. 2). They are arranged to generate negative charges. The electric charge (output signal) generated by the piezoelectric element 156 is taken out of the combustion pressure sensor 100 through the metal electrode plate 157 and the lead wire 153 arranged on the tip side. In addition, the base end side metal plate packing 155, the metal case 154, etc. which are arrange | positioned at the base end side of the piezoelectric element 156 become a ground.

  In addition, the base end side metal plate packing 155 and the front end side metal plate packing 159 are buffer members when caulking the metal case 154 in the direction of the axis AX. Further, the ceramic insulating plate 158 is disposed between the metal electrode plate 157 and the front end side metal plate packing 159 to insulate them. Further, the resin tube 160 is disposed to insulate the metal case 154 from the piezoelectric element 156 and the metal electrode plate 157.

  The sensor unit 150 is disposed such that a distal end surface 151 thereof is in contact with a proximal end surface 118 of the hexagonal engagement portion 117 of the housing 110 (see FIG. 1). On the other hand, a nut 170 is disposed on the base end surface 152 of the sensor unit 150 via a spacer 175. The nut 170 is screwed to the proximal end side of the middle shaft 130 and is fixed to the middle shaft 130. The sensor unit 150 is sandwiched between the base end surface 118 of the hexagonal engagement portion 117 of the housing 110 and the spacer 175 in a state where a compressive load is applied in the direction of the axis AX.

  For this reason, when the middle shaft 130 is displaced relative to the fixed portion 115 of the housing 110 in the axis AX direction, the distance between the base end surface 118 of the hexagonal engagement portion 117 and the spacer 175 is displaced. Then, since the compressive load applied to the sensor unit 150 changes, an electric charge (output signal) is generated in the piezoelectric element 156 of the sensor unit 150 according to the change, and combustion occurs via the metal electrode plate 157 and the lead wire 153. It is taken out of the pressure sensor 100. And it inputs into control apparatuses, such as ECU, via the charge amplifier etc. which are not shown in figure, and the change of combustion pressure is detected.

  Such a combustion pressure sensor 100 is manufactured as follows. That is, the middle shaft 130 is inserted into the housing 110, and the cylindrical tip portion 131 of the housing 110 is brought into contact with the peripheral portion of the disk of the tip portion 131 of the middle shaft 130, and this portion is welded. In addition, the sensor unit 150 is disposed on the proximal end side of the housing 110. After that, if the spacer 175 is further disposed and screwed with a nut 170 from above, the combustion pressure sensor 100 is completed.

Next, a sensor-equipped internal combustion engine 200 in which the combustion pressure sensor 100 is attached to the internal combustion engine 210 will be described (see FIG. 1).
The internal combustion engine 210 is an automobile engine and has an engine head 211 that forms a combustion chamber NS. Further, other parts not shown in the figure have a known structure. A bottomed hole 221 for attaching the combustion pressure sensor 100 is formed in the engine head 211. The bottomed hole 221 has a form in which the bottom surface 221b is closer to the combustion chamber NS than the opening edge 221c. Specifically, the bottomed hole 221 is provided so as to go from the outer surface 213 side to the inner surface 212 side of the engine head 211 along the axis BX direction. A female screw portion 221g for screwing the combustion pressure sensor 100 is formed in the vicinity of the opening edge 211c in the side surface 221d of the bottomed hole 221. A plurality of cavities 215 such as a water jacket are formed in the engine head 211.

  In the internal combustion engine 200 with a sensor in which the combustion pressure sensor 100 is attached to such an internal combustion engine 210, the combustion pressure sensor 100 is provided so that its axis AX and the axis BX of the bottomed hole 221 of the internal combustion engine 210 coincide with each other. It is inserted into the bottom hole 221. Specifically, the combustion pressure sensor 100 is screwed to the bottomed hole 221 such that the tip 131 of the center shaft 130 of the combustion pressure sensor 100 contacts the bottom surface 221 b of the bottomed hole 221. In this state, the tip 131 of the middle shaft 130 of the combustion pressure sensor 100 is fixed to the bottom surface 221 b of the bottomed hole 221. Further, the fixing portion 115 of the housing 110 is fixed to the female screw portion 221g in the vicinity of the opening edge 221c of the side surface 221d of the bottomed hole 221.

  Next, the state during combustion of the sensor-equipped internal combustion engine 200 will be described with reference to FIG. When the combustion pressure rises as indicated by an arrow in the lower part of the figure, the engine head 211 is distorted. Specifically, since the portion closer to the inner surface 212 in the engine head 211 is more strongly affected by the combustion pressure, the portion closer to the inner surface 212 is more distorted as shown in the figure. Then, the bottom surface 221b of the bottomed hole 221 near the inner surface 212 is largely displaced toward the outer surface 213 in the axis BX direction. On the other hand, the portion near the outer surface 213 of the engine head 211 is less affected by the combustion pressure than the portion on the inner surface 212 side, so that the distortion generated is smaller than the portion on the inner surface 212 side. For this reason, the displacement in the direction of the axis BX generated at the opening edge 221c of the bottomed hole 221 located near the outer surface 213 is smaller than that of the bottom surface 221b.

  Since the tip 131 of the middle shaft 130 of the combustion pressure sensor 100 is directly fixed to the bottom surface 221b of the bottomed hole 221, when the bottom surface 221b is greatly displaced in the direction of the axis BX, the middle shaft 130 is also driven to the axis line. It is greatly displaced toward the base end side (upward in the figure) in the AX (BX) direction. Then, the nut 170 fixed to the proximal end side of the middle shaft 130 is also largely displaced together with the middle shaft 130 toward the proximal end side in the axis AX (BX) direction.

  On the other hand, in the combustion pressure sensor 100, the fixing portion 115 of the housing 110 is fixed to a female screw portion 221g in the vicinity of the opening edge 221c of the bottomed hole 221. In the vicinity of the opening edge 221c of the bottomed hole 221, since the distortion caused by the increase in combustion pressure is small, the fixing portion 115 of the housing 110 fixed to the female screw portion 221g is displaced only small. As a result, the insertion portion 113 of the housing 110 is compressed between the distal end portion 111 and the fixing portion 115 and deformed as shown in the drawing.

  Further, since the displacement generated in the fixing portion 115 of the housing 110 is small, the displacement generated in the hexagonal engagement portion 117 located on the proximal end side of the fixing portion 115 is also small. As described above, the nut 170 fixed to the middle shaft 130 is greatly displaced toward the base end side in the axis AX (BX) direction, and is thus sandwiched between the hexagonal engagement portion 117 and the nut 170 via the spacer 175. The sensor unit 150 is extended in the direction of the axis AX (BX). That is, the sensor unit 150 is extended in the direction of the axis AX (BX) in accordance with the relative displacement of the middle shaft 130 with respect to the fixed unit 115. Then, since the compressive stress applied to the sensor unit 150 is reduced, an output signal is generated from the sensor unit 150. This output signal is input to the control device via a charge amplifier (not shown) and the like, and a change in combustion pressure is detected.

  Thus, in the first embodiment, a change in the combustion pressure of the internal combustion engine 210 can be detected with high accuracy. In particular, since the middle shaft 130 is fixed to the bottom surface 221b of the bottomed hole 221 and the fixing portion 115 of the housing 110 is fixed near the opening edge 221c of the bottomed hole 221 (female screw portion 221g), the fixing portion of the middle shaft 130 is fixed. The distance between the (bottom surface 221b) and the fixing portion (the female screw portion 221g) of the fixing portion 115 of the housing 110 is particularly large. For this reason, the relative displacement between the middle shaft 130 and the fixing portion 115 of the housing 110 due to the change of the combustion pressure also appears greatly. Therefore, the change in the combustion pressure can be detected particularly accurately.

  In addition, since the combustion pressure sensor 100 is used by being inserted into the bottomed hole 221 of the internal combustion engine 210, the distal end portion 111 of the housing 110 and the distal end portion 131 of the middle shaft 130 are not exposed to the combustion chamber NS. For this reason, the heat resistance, pressure resistance, corrosion resistance, and the like required for the combustion pressure sensor 100 can be greatly reduced as compared with the prior art. Therefore, the cost of the combustion pressure sensor 100 can be reduced, and the combustion pressure sensor 100 can be provided that is inexpensive, durable, and highly reliable. In addition, since it is not necessary to make a through-hole leading to the combustion chamber NS in the internal combustion engine 210, there is an advantage that the combustion pressure can be measured without impairing the performance of the internal combustion engine 210.

Furthermore, the output value of the combustion pressure sensor 100 can be adjusted by changing the rigidity (material, thickness) of the insertion portion 113 of the housing 110.
In the first embodiment, since the combustion pressure sensor 100 is configured using the sensor unit 150 including the piezoelectric element 156, a change in the combustion pressure can be measured easily and accurately.

(Embodiment 2)
Next, a second embodiment will be described. Note that the description of the same parts as those in the first embodiment is omitted or simplified. FIG. 4 shows a part of the combustion pressure sensor 300 according to the second embodiment and a sensor-equipped internal combustion engine 400 in which the combustion pressure sensor 300 is attached to the internal combustion engine 210. In the combustion pressure sensor 300 as well, the lower side in the figure is the front end side, and the upper side in the figure is the base end side. In the second embodiment, the structure of the front end and the base end side of the combustion pressure sensor 300 is different from the combustion pressure sensor 100 of the first embodiment. Other than that, it is substantially the same as the first embodiment.

The combustion pressure sensor 300 is disposed on the base end side of the housing 310 having a bottomed cylindrical housing 310 extending in the direction of the axis AX, a rod-shaped central shaft (first portion) 330 inserted inside the housing 310. And a sensor unit 350.
Among these, the housing 310 includes a tip portion 311, an insertion portion 313, a fixing portion (second portion) 315, and a hexagonal engagement portion 317. Since the housing 310 has a bottomed cylindrical shape, the shape of the tip portion 311 is different from the tip portion 111 of the housing 110 of the first embodiment, but other parts have the same structure as the first embodiment. .

  The middle shaft 330 has an elongated cylindrical shape (bar shape) that is substantially the same as the middle shaft 130 of the first embodiment. However, unlike the first embodiment, the tip 331 of the central shaft 330 has a cylindrical shape. And this front-end | tip part 331 is accommodated in the housing 310 in the state contact | abutted to the bottom part of the housing 310 which makes a bottomed cylindrical shape. On the other hand, a part of the base end side protrudes from the hexagonal engagement portion 317 of the housing 310 to the base end side and is inserted into the sensor portion 350 as in the first embodiment. The middle shaft 330 is also loosely inserted into the housing 310 so that it can be displaced relative to the housing 310 in the direction of the axis AX. The front end 331 of the middle shaft 330 is in contact with the front end 311 of the housing 310 from the inside. For this reason, when attached to the internal combustion engine 210, the distal end portion 331 of the middle shaft 330 indirectly passes through the distal end portion 311 of the housing 310 and the bottom surface (bottom portion, fixed portion) of the bottomed hole 221 of the internal combustion engine 210. 221b is contacted and fixed. On the other hand, the base end portion 333 of the middle shaft 330 is in contact with an element support member 355 of the sensor unit 350 described later. Further, since the middle shaft 330 is loosely inserted so as to be able to be displaced relative to the housing 310, the middle shaft 330 follows the displacement in the direction of the axis BX (AX) in the bottom surface 221 b of the bottomed hole 221 of the internal combustion engine 210. To displace.

  Next, the sensor unit 350 will be described. The sensor unit 350 has a substantially cylindrical shape as an outer shape. The sensor portion 350 has a distal end surface 351 fixed to the proximal end surface 318 of the hexagonal engagement portion 317 of the housing 310. The sensor unit 350 includes an element support member 355 positioned on the distal end side thereof, a circuit support member 357 fixed to the proximal end side of the element support member 355, and a pair of lead wires 353. The element support member 355 and the circuit support member 357 have a U-shaped cross section and are open to the tip side.

  The base end portion 333 of the middle shaft 330 is inserted into the opening 355k of the element support member 355, and is in contact with the opening bottom portion 355b from the front end side. On the other hand, a piezoresistive element 361 is disposed in the opening 357k of the circuit support member 357 on the base end side of the opening bottom 355b. In addition, a circuit 363 for driving the piezoresistive element 361 is disposed on the distal end side of the opening bottom 357b in the opening 357k.

  In such a sensor unit 350, the base end portion 333 of the central shaft 330 is displaced toward the base end side in the axis AX direction, distortion occurs in the opening bottom portion 355b of the element support member 355, and the piezoresistive type disposed further thereon. When the element 361 is distorted, its resistance value changes and the output of the circuit 363 changes. This output is taken out of the combustion pressure sensor 300 via a pair of lead wires 353 and 353, and is input to a control device such as an ECU, and a change in the combustion pressure is detected.

  Such a combustion pressure sensor 300 is manufactured as follows. That is, the middle shaft 330 is inserted into the housing 310. Thereafter, when the sensor unit 350 is disposed and fixed on the proximal end side of the housing 310, the combustion pressure sensor 300 is completed.

Next, a sensor-equipped internal combustion engine 400 in which such a combustion pressure sensor 300 is attached to the internal combustion engine 210 will be described (see FIG. 4).
The internal combustion engine 210 is the same as that in the first embodiment. In the sensor-equipped internal combustion engine 400 in which the combustion pressure sensor 300 is attached to the internal combustion engine 210, the combustion pressure sensor 300 has a bottomed hole 221 such that the axis AX coincides with the axis BX of the bottomed hole 221 of the internal combustion engine 210. Has been inserted. Specifically, the combustion pressure sensor 300 is screwed to the bottomed hole 221 such that the tip 311 of the housing 310 of the combustion pressure sensor 300 abuts the bottom surface 221 b of the bottomed hole 221. In this state, the tip 331 of the middle shaft 330 of the combustion pressure sensor 300 is fixed to the bottom 221 b of the bottomed hole 221 through the tip 311 of the housing 310. The fixing portion 315 of the housing 310 is fixed to the female screw portion 221g in the vicinity of the opening edge 221c of the side surface 221d of the bottomed hole 221.

Next, the combustion state of the sensor-equipped internal combustion engine 400 will be described with reference to FIG. When the combustion pressure rises as indicated by an arrow in the lower part of the figure, the engine head 211 is distorted as described in the first embodiment.
Since the tip 331 of the middle shaft 330 of the combustion pressure sensor 300 is indirectly fixed to the bottom surface 221b of the bottomed hole 221, when the bottom surface 221b is displaced in the axis BX direction, the middle shaft 330 is driven. It is greatly displaced toward the base end side in the direction of the axis AX (BX). Then, the base end portion 333 of the middle shaft 330 presses the opening bottom portion 355b of the element support member 355 of the sensor portion 350 toward the base end side.

  On the other hand, in the combustion pressure sensor 300, the fixing portion 315 of the housing 310 is fixed in the vicinity of the opening edge 221c of the bottomed hole 221. In the vicinity of the opening edge 221c of the bottomed hole 221, the distortion caused by the increase in the combustion pressure is small, so that the fixing portion 315 of the housing 310 fixed in the vicinity thereof is displaced only small. As a result, the insertion portion 313 of the housing 310 is compressed between the distal end portion 311 and the fixing portion 315 and deformed as shown in the figure.

Further, since the displacement generated in the fixing portion 315 of the housing 310 is small, the displacement of the hexagonal engagement portion 317 located on the proximal end side of the fixing portion 315 is also small. For this reason, the displacement of the sensor part 350 fixed to the base end side of the hexagonal fixing part 317 is also small.
On the other hand, as described above, since the base end portion 331 of the middle shaft 330 is largely displaced toward the base end side, the opening bottom portion 355b of the element support member 355 is greatly distorted. That is, the opening bottom portion 355b of the element support member 355 is distorted according to the relative displacement of the middle shaft 330 with respect to the fixed portion 315. As a result, the piezoresistive element 361 is also distorted accordingly, the resistance value is changed according to the distortion, and the output of the circuit 363 is changed. And this output is input into a control apparatus, and the change of combustion pressure is measured.

  Thus, even in the sensor-equipped internal combustion engine 400 of the second embodiment, it is possible to accurately detect a change in the combustion pressure of the internal combustion engine 210. In particular, since the middle shaft 330 is fixed to the bottom surface 221b of the bottomed hole 221 and the fixing portion 315 of the housing 310 is fixed near the opening edge 221c (female screw portion 221g) of the bottomed hole 221, the fixed portion of the middle shaft 330 is fixed. The distance between the (bottom surface 221b) and the fixing portion (the female screw portion 221g) of the fixing portion 315 of the housing 310 is particularly large. For this reason, the relative displacement between the middle shaft 330 and the fixing portion 315 of the housing 310 accompanying the change in the combustion pressure also appears greatly. Therefore, the change in the combustion pressure can be detected particularly accurately.

  Further, since the combustion pressure sensor 300 is used by being inserted into the bottomed hole 221 of the internal combustion engine 210, the tip end portion 211 is not exposed to the combustion chamber NS. For this reason, heat resistance, pressure resistance, corrosion resistance, and the like can be greatly reduced as compared with the conventional case. Therefore, the cost of the combustion pressure sensor 300 can be reduced, and it is possible to provide the combustion pressure sensor 300 that is inexpensive, durable, and highly reliable. In addition, since it is not necessary to make a through-hole leading to the combustion chamber NS in the internal combustion engine 210, there is an advantage that the combustion pressure can be measured without impairing the performance of the internal combustion engine 210.

Further, in the second embodiment, the entire front end side of the middle shaft 330 with respect to the fixing portion 315 of the housing 310 is covered with the housing 310. For this reason, compared with the case where there is no housing 310, it can suppress that the intermediate shaft 330 is exposed to high temperature.
Further, the output value of the combustion pressure sensor 300 can be adjusted by changing the rigidity (material, thickness) of the insertion portion 313 of the housing 310.
In the second embodiment, since the combustion pressure sensor 300 is configured using the sensor unit 350 including the piezoresistive element 361, a change in the combustion pressure can be measured easily and accurately.
In addition, the same parts as those of the first embodiment have the same effects.

In the above, the present invention has been described with reference to the embodiments. However, the present invention is not limited to the above-described first and second embodiments, and can be applied with appropriate modifications without departing from the gist thereof. Needless to say.
For example, in the first embodiment, the case where the tip 131 of the middle shaft 130 is in direct contact with the bottom surface 221b of the bottomed hole 221 is shown. However, as in the second embodiment, the tip 131 of the middle shaft 130 is It can also be set as the form which contact | abuts to the bottom face 221b of the bottomed hole 221 indirectly.
Conversely, in the second embodiment, the case where the tip 331 of the middle shaft 330 is indirectly in contact with the bottom surface 221b of the bottomed hole 221 is shown. However, as in the first embodiment, the tip of the middle shaft 330 is shown. The portion 331 may be in direct contact with the bottom surface 221b of the bottomed hole 221.

  Further, in the first and second embodiments, the case where the whole or most of the front end side of the middle shafts 130 and 330 is covered with the housings 110 and 310 is shown. It can also be a protruding form. That is, for example, the front end portions 111 and 311 and the insertion portions 113 and 313 are eliminated from the housings 110 and 310 of the first and second embodiments, and the front end side of the middle shafts 130 and 330 extends from the fixing portions 115 and 315 of the housings 110 and 310. A protruding form or the like can also be used.

It is explanatory drawing which shows the combustion pressure sensor which concerns on Embodiment 1, and an internal combustion engine with a sensor. It is explanatory drawing which shows a sensor part among the combustion pressure sensors which concern on Embodiment 1. FIG. It is explanatory drawing which concerns on Embodiment 1 and shows the mode of the combustion pressure sensor and internal combustion engine at the time of combustion. It is explanatory drawing which shows the combustion pressure sensor which concerns on Embodiment 2, and an internal combustion engine with a sensor. FIG. 6 is an explanatory diagram illustrating a state of a combustion pressure sensor and an internal combustion engine during combustion according to the second embodiment.

Explanation of symbols

100, 300 Combustion pressure sensor 110, 310 Housing 115, 315 Fixed part (second part)
130,330 Middle shaft (Part 1)
150, 350 Sensor unit 156 Piezoelectric element 170 Nut 200, 400 Sensor-equipped internal combustion engine 210 Internal combustion engine 211 Engine head 221 Bottomed hole 221b Bottom surface (bottom, fixed part)
221c Open edge 361 Piezoresistive element AX (combustion pressure sensor) axis BX (bottom hole) axis NS Combustion chamber

Claims (7)

In an internal combustion engine having a bottomed hole with a bottom closer to the combustion chamber than its opening edge, a combustion pressure sensor for measuring a change in combustion pressure by inserting the tip of the bottom into the bottomed hole There,
A first part fixed directly or indirectly to a fixed part in the bottomed hole, and configured to follow displacement in the axial direction of the bottomed hole in the fixed part;
A second part configured to be fixed to a portion on the opening edge side in the axial direction with respect to the fixed portion of the internal combustion engine;
A sensor unit configured to be able to detect relative displacement in the axial direction with respect to the second part of the first part that occurs in accordance with a change in the combustion pressure;
A combustion pressure sensor. The combustion pressure sensor according to claim 1,
The first part is configured to be fixable to a bottom part of the bottomed hole,
The second part is a combustion pressure sensor configured to be fixed in the vicinity of an opening edge of the bottomed hole. The combustion pressure sensor according to claim 1 or 2,
A combustion pressure sensor comprising a housing including the second part, wherein the housing covers at least a tip side of the first part with respect to the second part. The combustion pressure sensor according to claim 1, wherein
The sensor unit is
Including a piezoelectric element,
A combustion pressure sensor configured to change a load applied to the piezoelectric element in accordance with the relative displacement and generate an electric charge in accordance with the change in the load. The combustion pressure sensor according to claim 1, wherein
The sensor unit is
Including piezoresistive elements,
A combustion pressure sensor configured to generate distortion in the piezoresistive element in accordance with the relative displacement and generate a signal in accordance with the change in the distortion. A sensor-equipped internal combustion engine in which a combustion pressure sensor for measuring a change in combustion pressure is attached to the internal combustion engine,
The internal combustion engine
It has a bottomed hole with a bottom closer to the combustion chamber than its own opening edge,
The combustion pressure sensor
The tip side of itself is inserted into the bottomed hole,
A first part that is fixed directly or indirectly to a fixed part in the bottomed hole, and is configured to follow displacement in the axial direction of the bottomed hole in the fixed part;
A second part of the internal combustion engine that is fixed to a portion on the opening edge side in the axial direction from the fixed portion;
A sensor-equipped internal combustion engine comprising: a sensor unit configured to be able to detect a relative displacement in the axial direction with respect to the second part of the first part that occurs in accordance with a change in the combustion pressure. An internal combustion engine with a sensor according to claim 6,
The first part is fixed to the bottom of the bottomed hole,
The second part is an internal combustion engine with a sensor, which is fixed in the vicinity of an opening edge of the bottomed hole.

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