JP5604890B2 - In-cylinder pressure sensor - Google Patents

Description

  The present invention relates to an in-cylinder pressure sensor that has a simple structure, can be easily replaced, and can avoid the influence of temperature.

  In order to increase the combustion efficiency of the internal combustion engine, it is desirable to appropriately control the fuel injection timing and the injection pressure. In order to detect in-cylinder pressure which is one of the elements used for such control, it is necessary to provide an in-cylinder pressure sensor in the internal combustion engine. When the in-cylinder pressure of the internal combustion engine is accurately detected by the in-cylinder pressure sensor, the internal combustion engine can be controlled more appropriately. For example, closed loop control of the internal combustion engine is possible, and deterioration of the internal combustion engine can be corrected. In particular, in the case of a diesel engine, the in-cylinder pressure can be used for correcting a change in the injection amount due to a secular change in the injection system, and can also be applied to correcting a measured value related to fuel consumption and exhaust gas. Further, the connection between the premixed combustion and the normal combustion and the power switching of the hybrid vehicle can be controlled more smoothly by the in-cylinder pressure. In-cylinder pressure can also be used for misfire diagnosis as defined in US regulations.

  As a prior art, an in-cylinder pressure sensor in which a pressure sensor is inserted into a cylinder is known.

  An in-cylinder pressure sensor in which a pressure sensor is incorporated in a glow plug or a spark plug is known.

  In-cylinder pressure sensors are known in which a strain gauge is attached to a cylinder liner that is an outer shell of a cylinder, the strain of the cylinder liner is detected, and the in-cylinder pressure is derived from the strain of the cylinder liner.

JP 2009-162893 A JP-A-8-50072

  However, if a pressure sensor is inserted into the cylinder, it will result in an increase in the surface area in the cylinder, and from the standpoint of thermal efficiency, the generated thermal energy will be taken away by the pressure sensor, resulting in a decrease in thermal efficiency. It is not preferable.

  Incorporating a pressure sensor into a glow plug or spark plug is not preferable because the structure of the engine becomes complicated and the durability and reliability of the engine are impaired.

  Compared to these two types of in-cylinder pressure sensors, the in-cylinder pressure sensor with a strain gauge attached to the cylinder liner does not affect the structure and characteristics of the engine, but the structure for waterproofing the strain gauge from cooling water is complicated, and This is not preferable because it is difficult to replace the strain gauge at the time of failure and the characteristics of the strain gauge fluctuate depending on the engine temperature and the coolant temperature.

  Therefore, an object of the present invention is to provide an in-cylinder pressure sensor that solves the above-described problems, has a simple structure, can be easily replaced, and can avoid the influence of temperature.

In order to achieve the above object, the present invention is attached by screwing into a screw hole of an engine having a cylinder block with a cooling water flow path outside a cylinder liner which is an outer shell of a cylinder in which a piston is accommodated. An in-cylinder pressure sensor for detecting an in-cylinder pressure, which is an atmospheric pressure in the cylinder, penetrating the cylinder block from the outside of the cylinder block, contacting the cylinder liner, and being displaced by the in-cylinder pressure; A displacement sensor that detects the displacement of the push rod in a sensor chamber formed in a recess in the head for rotating the screw disposed outside the cylinder block , and press-contacts the push rod to the cylinder liner. And a coil spring.

  The displacement sensor is arranged with a strain sensor pressed between one end of the push rod facing the outside of the cylinder block and a support member fixed to the cylinder block, and the strain sensor detects the displacement sensor. The strain may represent the displacement of the push rod.

  The displacement sensor has a generator mover pressed against one end of the push rod facing the outside of the cylinder block, the generator stator is fixed to the cylinder block, and the generator is generated. Electric power may represent the displacement of the push rod.

  The displacement sensor is disposed in such a manner that a piezoelectric sensor is in pressure contact between one end of the push rod facing the outside of the cylinder block and a support member fixed to the cylinder block, and the piezoelectric sensor is electrically The pressure to be detected may represent the displacement of the push rod.

  In the displacement sensor, a first electrode plate is pressed against one end of the push rod facing the outside of the cylinder block, and a second electrode plate facing the first electrode plate is fixed to the cylinder block. The capacitance between the first electrode plate and the second electrode plate may represent the displacement of the push rod.

  The present invention exhibits the following excellent effects.

  (1) The structure is simple.

  (2) Replacement becomes easy.

  (3) The influence of temperature can be avoided.

It is a fragmentary sectional view of the engine to which the cylinder pressure sensor of the present invention was attached. It is sectional drawing of the cylinder pressure sensor which shows 1st embodiment of this invention. It is sectional drawing of the cylinder pressure sensor which shows 2nd embodiment of this invention. It is sectional drawing of the cylinder pressure sensor which shows 3rd embodiment of this invention. It is sectional drawing of the cylinder pressure sensor which shows 4th embodiment of this invention.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  As shown in FIG. 1, in an engine 11 to which the in-cylinder pressure sensor 1 of the present invention is applied, a piston 12 is accommodated in a cylinder 13, and a cooling water flow path (outside of a cylinder liner 14 that is an outer shell of the cylinder 13 is provided. A cylinder block 16 is provided with a water jacket) 15 therebetween. A seat 17 for attaching the cylinder pressure sensor 1 to the engine 11 is formed on the cylinder block 16 so as to protrude outward from the cylinder block 16. The seat 17 is provided in a range between the top of the cylinder 13 and the top dead center of the piston 12. In the center of the seat 17, a screw hole 18 that penetrates the cylinder block 16 and passes from the outside of the cylinder block 16 to the cooling water passage 15 is formed.

  The in-cylinder pressure sensor 1 of the present invention includes a screw 3 screwed into the screw hole 18 and a head 4 for rotating the screw 3, and is attached to the engine 11 by screwing the screw 3 into the screw hole 18. . A sensor base 5 that forms a reference surface for detecting the displacement of the push rod 2 is fixed to the head 4. A connector cap 6 for fitting a wiring connector (not shown) is integrally formed on the sensor base 5.

  The cylinder pressure sensor 1 includes a push rod 2 that penetrates the cylinder block 16 from the outside of the cylinder block 16 and contacts the cylinder liner 14, and a displacement sensor that detects the displacement of the push rod 2 outside the cylinder block 16 (see FIG. Not shown; see FIG. 2 and subsequent figures). The push rod 2 extends along the extension of the diameter of the cylinder 13. When the cylinder liner 14 is displaced in the diameter direction of the cylinder 13, the push rod 2 is displaced in a direction along the extension of the diameter of the cylinder 13. Since the cylinder liner 14 is displaced in the diameter direction of the cylinder 13 by the in-cylinder pressure that is the atmospheric pressure in the cylinder 13, the in-cylinder pressure that is the atmospheric pressure in the cylinder 13 can be detected from the displacement of the push rod 2.

  As shown in FIG. 2, in the first embodiment of the present invention, the displacement sensor 201 used for the in-cylinder pressure sensor 1 is fixed to one end of the push rod 2 facing the outside of the cylinder block 16 and the cylinder block 16. A strain sensor (strain gauge) 203 is placed in pressure contact with the sensor base 5 as the support member 202. The displacement sensor 201 is configured such that the strain detected by the strain sensor 203 represents the displacement of the push rod 2.

  More specifically, a push rod passage 7 is formed at the center of the screw 3 of the in-cylinder pressure sensor 1 to hold the push rod 2 in a displaceable manner. The push rod 2 is inserted into the push rod passage 7. By rotating the head 4 and screwing the screw 3 into the screw hole 18 in FIG. 1, the in-cylinder pressure sensor 1 is fixed to the cylinder block 16 and the tip of the push rod 2 is brought into contact with the cylinder liner 14. .

  In the head 4, a sensor chamber 204 is formed that is recessed from the base end of the head 4 to the inside of the head 4. The support member 202 (sensor base 5) is fixed to the opening of the sensor chamber 204 so as to close the opening of the sensor chamber 204. One side of the strain sensor 203 is fixed to the support member 202. Two terminals 8 that penetrate into the connector cap 6 are electrically connected to the strain sensor 203.

  A pressing plate 205 that can be displaced in the sensor chamber 204 is provided to face the support member 202 so as to be sandwiched between the strain sensor 203 and the push rod 2. A coil spring (spring) 206 that is expanded and contracted by the displacement of the pressing plate 205 is inserted between the pressing plate 205 and the support member 202.

  The support member 202 is in contact with one side of the strain sensor 203, the pressing plate 205 is in contact with the opposite surface of the strain sensor 203, and the coil spring 206 is inserted between the pressing plate 205 and the support member 202. The force due to the displacement is received by the strain sensor 203 and the coil spring 206 through the pressing plate 205. At the same time, the push rod 2 is pressed against the cylinder liner 14 by the spring force of the coil spring 206.

  The operation of the in-cylinder pressure sensor 1 using the displacement sensor 201 of FIG. 2 will be described with reference to FIGS.

  When the piston 12 moves in the direction of compression in the cylinder 13 and the piston 12 is in the vicinity of the top dead center (position of an appropriate advance angle), the air-fuel mixture compressed in the cylinder 13 is ignited (gasoline engine Or the fuel injected during high-pressure intake in the cylinder 13 ignites (in the case of a diesel engine). Due to the explosion occurring in the cylinder 13, the in-cylinder pressure rapidly increases. For this reason, the cylinder liner 14 slightly expands and deforms between the top of the cylinder 13 and the piston 12. The displacement in the diameter direction of the cylinder 13 of the cylinder liner 14 is transmitted to the push rod 2 in contact with the cylinder liner 14. The push rod 2 is displaced in a direction along the extension of the diameter of the cylinder 13.

  The force due to the displacement of the push rod 2 is transmitted to the strain sensor 203 via the pressing plate 205. In the strain sensor 203, the electric resistance value changes according to the strain.

  An electric signal due to distortion generated in the distortion sensor 203 is transmitted from the terminal 8 to a processing circuit (not shown). The processing circuit detects the in-cylinder pressure based on the electrical signal from the strain sensor 203. The relationship between the in-cylinder pressure and the electrical signal of the strain sensor 203 may be obtained in advance by experiments, and a map may be set in an ECM (digital controller) or the like.

  As described above, the in-cylinder pressure sensor 1 of the present invention includes the push rod 2 that penetrates the cylinder block 16 from the outside of the cylinder block 16 and comes into contact with the cylinder liner 14. Displace. The cylinder pressure can be detected by detecting the displacement of the push rod 2 outside the cylinder block 16 by the displacement sensor 201.

  According to the above configuration, since the displacement sensor 201 is installed outside the cylinder block 16 outside the cooling water flow path 15, it is not immersed in the cooling water, and it is not necessary to waterproof the displacement sensor 201. The structure of the in-cylinder pressure sensor 1 is simplified.

  According to the above configuration, since the displacement sensor 201 is attached to the outside of the cylinder block 16, even if the displacement sensor 201 breaks down, replacement is easy. Further, since the push rod 2 is held in the push rod passage 7 in the screw 3, the push rod 2 is covered with the cylinder block 16 by the work outside the cylinder block 16 in which the in-cylinder pressure sensor 1 is attached to the seat 17. Therefore, the cylinder pressure sensor 1 can be attached to and detached from the cylinder liner 14 with ease.

  According to the above configuration, since the displacement sensor 201 is located outside the cylinder block 16, the influence of the engine temperature and the cooling water temperature is avoided, and the characteristics of the displacement sensor 201 depend on the engine temperature and the cooling water temperature. It does not fluctuate.

  Next, another embodiment of the displacement sensor used for the in-cylinder pressure sensor 1 will be described.

  As shown in FIG. 3, in the second embodiment of the present invention, the displacement sensor 301 used in the in-cylinder pressure sensor 1 has a generator mover 302 at one end 2 a facing the outside of the cylinder block 16 of the push rod 2. The generator stator 303 is fixed to the cylinder block 16 by pressure contact. The displacement sensor 301 is configured such that the electric power generated by the generator represents the displacement of the push rod 2.

  More specifically, a push rod passage 7 is formed at the center of the screw 3 of the in-cylinder pressure sensor 1 to hold the push rod 2 in a displaceable manner. The push rod 2 is inserted into the push rod passage 7. By rotating the head 4 and screwing the screw 3 into the screw hole 18 in FIG. 1, the in-cylinder pressure sensor 1 is fixed to the cylinder block 16 and the tip of the push rod 2 is brought into contact with the cylinder liner 14. .

  The head 4 is formed with a sensor chamber 304 that is recessed from the base end of the head 4 to the inside of the head 4. The sensor base 5 is embedded in the sensor chamber 304 and fixed to the head 4. The stator 303 is accommodated in the sensor base 5 and fixed to the sensor base 5. The mover 302 is close to the stator 303 and is held so as to be displaceable in the direction of displacement of the push rod 2.

  A displaceable pressing plate 305 is provided to face the sensor base 5 so as to be sandwiched between the mover 302 and the push rod 2. Between the movable element 302 and the sensor base 5, a coil spring (spring) 306 that is expanded and contracted by the displacement of the pressing plate 305 and the movable element 302 is inserted. The push rod 2 is pressed into contact with the cylinder liner 14 by the spring force of the coil spring 306 via the pressing plate 305 and the movable element 302.

  Here, the mover 302 is composed of a permanent magnet, and the stator 303 is composed of a winding wound around the permanent magnet. Two terminals 8 penetrating into the connector cap 6 are electrically connected to the winding.

  When the displacement sensor 301 of FIG. 3 is used, the displacement of the push rod 2 is transmitted to the mover 302 via the pressing plate 305. An induced current is generated in the winding that is the stator 303 of the generator in accordance with the displacement speed of the permanent magnet that is the generator movable element 302. The induced current is transmitted from the terminal 8 to a processing circuit (not shown). The processing circuit detects the in-cylinder pressure based on the electrical signal from the generator. The relationship between the in-cylinder pressure and the electrical signal of the generator is preferably obtained in advance by experiments and a map is set in the ECM or the like.

  Thus, even when the displacement sensor 301 is used, the in-cylinder pressure can be detected by detecting the displacement of the push rod 2 outside the cylinder block 16. Thereby, the same effect as the case where the displacement sensor 201 is used is obtained.

  As shown in FIG. 4, in the third embodiment of the present invention, the displacement sensor 401 used for the in-cylinder pressure sensor 1 is fixed to the one end 2 a of the push rod 2 facing the outside of the cylinder block 16 and the cylinder block 16. A piezoelectric sensor 403 is disposed in pressure contact with the sensor base 5 serving as the support member 402. The displacement sensor 401 is configured such that the pressure electrically detected by the piezoelectric sensor 403 represents the displacement of the push rod 2.

  More specifically, a push rod passage 7 is formed at the center of the screw 3 of the in-cylinder pressure sensor 1 to hold the push rod 2 in a displaceable manner. The push rod 2 is inserted into the push rod passage 7. By rotating the head 4 and screwing the screw 3 into the screw hole 18 in FIG. 1, the in-cylinder pressure sensor 1 is fixed to the cylinder block 16 and the tip of the push rod 2 is brought into contact with the cylinder liner 14. .

  In the head 4, a sensor chamber 404 is formed that is recessed from the base end of the head 4 to the inside of the head 4. The support member 402 (sensor base 5) is embedded in the sensor chamber 404 and fixed to the head 4.

  The piezoelectric sensor 403 has a structure in which a piezoelectric element 405 is sandwiched between a single electrode 406 and an opposite electrode 407. The push rod 2 is pressed against the one side electrode 406, and the opposite side electrode 407 is fixed to the support member 402. Two terminals 8 penetrating into the connector cap 6 are electrically connected to the one side electrode 406 and the opposite side electrode 407.

  A spring chamber 408 is formed by being recessed from the sensor chamber 404 into the screw 3. A flange plate 409 fixed to the push rod 2 is provided in the spring chamber 408 so as to face the one-side electrode 406. A coil spring (spring) 410 that is expanded and contracted by the displacement of the flange plate 409 is inserted between the flange plate 409 and the one-side electrode 406. The push rod 2 is pressed against the cylinder liner 14 by the spring force of the coil spring 410.

  When the displacement sensor 401 in FIG. 4 is used, the displacement of the push rod 2 is transmitted to the one-side electrode 406 of the piezoelectric element 405. In the piezoelectric sensor 403, a voltage is generated in the piezoelectric element 405 sandwiched between the one side electrode 406 and the opposite side electrode 407. The electrical signals of the one-side electrode 406 and the opposite-side electrode 407 are transmitted from the terminal 8 to a processing circuit (not shown). In the processing circuit, the in-cylinder pressure is detected based on the electric signal of the piezoelectric sensor 403. The relationship between the in-cylinder pressure and the electric signal of the piezoelectric sensor 403 may be obtained in advance by experiments and a map may be set in the ECM or the like.

  Thus, even when the displacement sensor 401 is used, the in-cylinder pressure can be detected by detecting the displacement of the push rod 2 outside the cylinder block 16. Thereby, the same effect as the case where the displacement sensor 201 is used is obtained.

  As shown in FIG. 5, in the fourth embodiment of the present invention, the displacement sensor 501 used for the in-cylinder pressure sensor 1 has a first electrode plate 502 at one end 2 a facing the outside of the cylinder block 16 of the push rod 2. The second electrode plate 503 that is in pressure contact with the first electrode plate 502 and is fixed to the sensor base 5 is fixed to the cylinder block 16. The displacement sensor 501 is configured such that the capacitance between the first electrode plate 502 and the second electrode plate 503 represents the displacement of the push rod 2.

  More specifically, a push rod passage 7 is formed at the center of the screw 3 of the in-cylinder pressure sensor 1 to hold the push rod 2 in a displaceable manner. The push rod 2 is inserted into the push rod passage 7. By rotating the head 4 and screwing the screw 3 into the screw hole 18 in FIG. 1, the in-cylinder pressure sensor 1 is fixed to the cylinder block 16 and the tip of the push rod 2 is brought into contact with the cylinder liner 14. .

  In the head 4, a sensor chamber 504 that is recessed from the base end of the head 4 to the inside of the head 4 is formed. The sensor base 5 is embedded in the sensor chamber 504 and fixed to the head 4.

  A gap chamber 505 is formed in the sensor base 5 on the side facing the push rod 2. In the gap chamber 505, a first insulating plate 506 that contacts the first electrode plate 502 by a surface, a second insulating plate 507 that contacts the second electrode plate 503 by a surface, and a first insulating plate 506, A spring 508 made of a non-conductor inserted between the second insulating plates 507 is accommodated. The spring 508 is not limited to a coil spring, and may be a silicon block, for example. The push rod 2 is pressed against the cylinder liner 14 by the spring force of the spring 508. The first electrode plate 502 is movable with respect to the sensor base 5 and pressed against the push rod 2. The second electrode plate 503 is fixed to the cylinder block 16 by being fixed to the sensor base 5. Two terminals 8 penetrating into the connector cap 6 are electrically connected to the first electrode plate 502 and the second electrode plate 503, respectively.

  When the displacement sensor 501 of FIG. 5 is used, the first electrode plate 502 is displaced by the displacement of the push rod 2. As the distance between the first electrode plate 502 and the second electrode plate 503 changes, the capacitance between the first electrode plate 502 and the second electrode plate 503 changes. Electrical signals from these two electrode plates 502 and 503 are transmitted from a terminal 8 to a processing circuit (not shown). In the processing circuit, the in-cylinder pressure is detected based on the electrical signals from the electrode plates 502 and 503. The relationship between the in-cylinder pressure and the electrical signals from the electrode plates 502 and 503 may be obtained in advance by experiments, and a map may be set in the ECM or the like.

  Thus, even when the displacement sensor 501 is used, the in-cylinder pressure can be detected by detecting the displacement of the push rod 2 outside the cylinder block 16. Thereby, the same effect as the case where the displacement sensor 201 is used is obtained.

DESCRIPTION OF SYMBOLS 1 In-cylinder pressure sensor 2 Push rod 3 Screw 4 Head 5 Sensor base 6 Connector cap 7 Push rod passage 8 Terminal 11 Engine 12 Piston 13 Cylinder 14 Cylinder liner 15 Cooling water flow path 16 Cylinder block

Claims (5)

An in-cylinder pressure, which is the atmospheric pressure in the cylinder, is attached to the outside of the cylinder liner, which is the outer shell of the cylinder in which the piston is accommodated, by screwing into a screw hole of an engine having a cylinder block with a cooling water flow path. An in-cylinder pressure sensor to detect,
A push rod penetrating the cylinder block from the outside of the cylinder block and coming into contact with the cylinder liner and being displaced by in-cylinder pressure;
A displacement sensor for detecting displacement of the push rod in a sensor chamber formed in a recess inside a head for rotating the screw disposed outside the cylinder block;
An in-cylinder pressure sensor comprising: a coil spring that presses the push rod against the cylinder liner.   The displacement sensor is arranged with a strain sensor pressed between one end of the push rod facing the outside of the cylinder block and a support member fixed to the cylinder block, and the strain sensor detects the displacement sensor. The in-cylinder pressure sensor according to claim 1, wherein the strain represents a displacement of the push rod.   The displacement sensor has a generator mover pressed against one end of the push rod facing the outside of the cylinder block, the generator stator is fixed to the cylinder block, and the generator is generated. The in-cylinder pressure sensor according to claim 1, wherein electric power represents displacement of the push rod.   The displacement sensor is disposed in such a manner that a piezoelectric sensor is in pressure contact between one end of the push rod facing the outside of the cylinder block and a support member fixed to the cylinder block, and the piezoelectric sensor is electrically The in-cylinder pressure sensor according to claim 1, wherein the pressure detected in the step represents the displacement of the push rod.   In the displacement sensor, a first electrode plate is pressed against one end of the push rod facing the outside of the cylinder block, and a second electrode plate facing the first electrode plate is fixed to the cylinder block. The in-cylinder pressure sensor according to claim 1, wherein a capacitance between the first electrode plate and the second electrode plate represents a displacement of the push rod.

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