JP2017116352A - Thermal strain measuring method and thermal strain measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To acquire change in pressure caused by thermal expansion of a diaphragm with an apparatus not being equipped to an actual pressure measurement target.SOLUTION: A thermal strain measuring apparatus 500 includes: an XYZ stage 510 that holds a pressure detector 5 having a diaphragm head for detecting a pressure; a laser irradiation section 520 that irradiates the diaphragm head of the pressure detector 5 held to the XYZ stage 510 with a laser beam Bm; a cover 530 over the XYZ stage 510; and a data analysis section 540 that analyzes an output signal (data) sent from the pressure detector 5 held to the XYZ stage 510 and calculates an irradiation pressure change amount corresponding to a thermal strain.SELECTED DRAWING: Figure 8

Description

  The present invention relates to a thermal strain measuring method and a thermal strain measuring apparatus for equipment using a pressure sensitive element.

Conventionally, in order to detect the pressure in a combustion chamber mounted on an internal combustion engine, a piezoelectric pressure detecting device using a piezoelectric element having a piezoelectric body as a pressure-sensitive element for measuring pressure, or a strain as a pressure-sensitive element. Piezoresistive pressure detectors using gauges, and capacitive pressure detectors using spaced electrodes as pressure sensitive elements are known.
For example, in Patent Document 1, a cylindrical housing, a diaphragm provided on the front end side of the housing, and an axial direction in the housing that is disposed on the rear end side of the diaphragm and detects pressure acting through the diaphragm. A pressure transmitting portion that is provided in contact with the piezoelectric element in the axial direction in the housing and between the diaphragm and the piezoelectric element, and that transmits the pressure acting through the diaphragm to the piezoelectric element; There is described a pressure detection device including a pressure member that applies a load to a piezoelectric element by being fixed to the housing so as to pressurize the portion in the axial direction of the housing.

JP 2013-205307 A

  Here, when a configuration is adopted in which the pressure received by the diaphragm is transmitted to the pressure sensitive element, when heat is applied to the diaphragm together with the pressure, the diaphragm is deformed by thermal expansion, and the pressure transmitted from the diaphragm to the pressure sensitive element is reduced. In other words, there is a situation where the size is increased or decreased compared to the size that should be transmitted. Then, the output that changes in accordance with the amount of deformation of the pressure-sensitive element will increase or decrease compared to the size that should be output, and there is an error in the pressure required based on the output of the pressure-sensitive element. Will be included.

  Such a phenomenon occurs in each device, but the magnitude of the change in pressure varies from device to device depending on the accuracy of components, the accuracy of component mounting, and the like. For this reason, the setting of the evaluation standard regarding the change of the pressure resulting from the thermal expansion of a diaphragm is calculated | required for every apparatus.

  An object of this invention is to acquire the change of the pressure resulting from the thermal expansion of a diaphragm in the state which does not mount an apparatus on the measurement object of an actual pressure.

For this purpose, the thermal strain measurement method of the present invention is a method for measuring a device having a diaphragm that is deformed by an external pressure and a pressure-sensitive element that generates an output corresponding to the pressure acting through the diaphragm. An irradiation step of irradiating the diaphragm with laser light, and a calculation step of calculating a pressure change generated in the pressure sensitive element using an output obtained from the pressure sensitive element irradiated with the laser light on the diaphragm. Including.
Here, in the irradiation step, the diaphragm may be irradiated with the focused laser beam at a position out of the focus of the laser beam.
Moreover, in the said irradiation process, it is good to irradiate a laser beam to the said diaphragm in the position far from the focus of a laser beam.
Further, in the irradiation step, the diaphragm may be irradiated with laser light at a position closer to the focal point of the laser light.
Furthermore, in the irradiation step, the diaphragm may be irradiated with the focused laser beam at the focal position of the laser beam.
And in the said irradiation process, it is good to irradiate the said diaphragm with the laser beam which exhibits a top hat pattern.
From another point of view, the thermal strain measuring device of the present invention includes a diaphragm that is deformed by receiving pressure from the outside, and a pressure-sensitive element that generates an output corresponding to the pressure acting through the diaphragm. A mounting part to which a device is mounted, an irradiation unit that irradiates laser light to the diaphragm of the device that is mounted to the mounting part, and an output obtained from the pressure-sensitive element in which the diaphragm is irradiated with laser light. And a calculating unit that calculates a change in pressure generated in the pressure sensitive element.
Here, the irradiation unit includes an oscillator that oscillates a laser, a light guide unit that guides laser light oscillated by the oscillator, and an emission that emits the laser beam guided by the light guide unit to the diaphragm of the device. Part.
Moreover, the said emission part is good to irradiate a laser beam to the said diaphragm in the position which remove | deviated from the focus of a laser beam while condensing a laser beam.
Further, the emitting unit may focus the laser beam and irradiate the diaphragm with the laser beam at a focal position of the laser beam.
Furthermore, the light guide section may be formed of a square fiber that outputs laser light having a Gaussian pattern as laser light having a top hat pattern.

  According to the present invention, it is possible to acquire a change in pressure caused by the thermal expansion of a diaphragm in a state where an actual pressure measurement target is not mounted.

It is a schematic block diagram of an internal combustion engine. It is an enlarged view of the II section of FIG. It is a schematic block diagram of a pressure detection apparatus. It is sectional drawing of the IV-IV part of FIG. It is an enlarged view of the V section of FIG. (A) is a figure which shows an example of the measurement result of the cylinder pressure by the pressure detection apparatus with which the internal combustion engine was mounted | worn, (b) is the pressure error obtained from the measurement result of the cylinder pressure shown to (a) It is a figure which shows an example of a calculation result. It is a figure for demonstrating the generation | occurrence | production mechanism of the thermal strain in the pressure detection apparatus of this Embodiment. It is a figure which shows the whole structure of the thermal-strain measuring apparatus of this Embodiment. It is a figure which shows the structure of the laser emission part in a thermal-strain measuring apparatus. (A), (b) is a figure for demonstrating the relationship between the laser beam in a thermal-strain measuring apparatus, and the diaphragm head of a pressure detection apparatus. (A)-(d) is a figure which shows the calculation result of the real machine pressure error obtained by mounting | wearing a common internal combustion engine with four different pressure detection apparatuses. (A)-(d) is a figure which shows the measurement result of the irradiation pressure variation | change_quantity obtained by mounting | wearing a common thermal strain measuring apparatus with four different pressure detection apparatuses. It is a figure for demonstrating the correlation with an actual machine pressure error measurement result and irradiation pressure variation | change_quantity measurement result when a laser output is made constant. It is a figure for demonstrating the correlation with an actual machine pressure error measurement result when a laser output is varied, and an irradiation pressure change amount measurement result.

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

  The cylinder head 4 is formed with a communication hole 4a that allows the combustion chamber C to communicate with the outside. The communication hole 4a includes, from the combustion chamber C side, a first hole 4b, an inclined portion 4c whose diameter gradually increases from the hole diameter of the first hole 4b, and a hole diameter of the first hole 4b. And a second hole portion 4d having a large hole diameter. A female screw 4e into which a male screw 332a of the housing 30 (described later) formed in the pressure detection device 5 is screwed is formed on the surrounding wall forming the second hole 4d.

Below, the pressure detection apparatus 5 as an example of an apparatus is explained in full detail.
FIG. 3 is a schematic configuration diagram of the pressure detection device 5. 4 is a cross-sectional view taken along a line IV-IV in FIG. FIG. 5 is an enlarged view of a portion V in FIG.
The pressure detection device 5 includes a sensor unit 100 having a piezoelectric element 10 that converts the pressure in the combustion chamber C into an electric signal, a signal processing unit 200 that processes an electric signal from the sensor unit 100, and a signal processing unit 200. Holding member 300. When the pressure detection device 5 is mounted on the cylinder head 4, the diaphragm head 40 (described later) of the sensor unit 100 is inserted into the communication hole 4 a formed in the cylinder head 4 first. In the following description, the left side of FIG. 4 is the front end side of the pressure detection device 5, and the right side is the rear end side of the pressure detection device 5.

First, the sensor unit 100 will be described.
The sensor unit 100 includes a piezoelectric element 10 that converts received pressure into an electrical signal, and a housing 30 that is cylindrical and in which a cylindrical hole that accommodates the piezoelectric element 10 and the like is formed. . Hereinafter, the center line direction of the cylindrical hole formed in the housing 30 is simply referred to as a center line direction.
The sensor unit 100 is provided so as to close the opening on the distal end side of the housing 30, and is provided between the diaphragm head 40 on which the pressure in the combustion chamber C acts, and between the diaphragm head 40 and the piezoelectric element 10. The first electrode unit 50 and the second electrode unit 55 disposed on the opposite side of the piezoelectric element 10 from the first electrode unit 50 are provided.

In addition, the sensor unit 100 is provided with an insulating ring 60 made of alumina ceramic that electrically insulates the second electrode unit 55 and a rear end side of the insulating ring 60, and a covering member described later of the signal processing unit 200. 23, and a coil spring 70 interposed between the second electrode portion 55 and the conductive member 22 described later.
The sensor unit 100 covers the outer periphery of the first electrode unit 50, the piezoelectric element 10, the second electrode unit 55, the insulating ring 60, the support member 65, and the like, and the surface on the distal end side of the first electrode unit 50. And a pressing member 80 that pressurizes the first electrode unit 50 in contact therewith.

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

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

The housing 30 includes a first housing 31 provided on the front end side and a second housing 32 provided on the rear end side.
The first housing 31 is basically a cylindrical member, and the outer peripheral surface is provided with a protruding portion 315 protruding from the outer peripheral surface in the central portion in the center line direction over the entire region in the circumferential direction. . The protrusion 315 has an inclined surface 315a whose diameter gradually increases from the front end side to the rear end side at the front end portion, and a vertical surface 315b perpendicular to the center line direction at the rear end portion. The inner peripheral surface of the first housing 31 is set so that its inner diameter is equal to or less than the diameter of the outer peripheral surface of the pressure member 80 so that the outer peripheral surface of the pressure member 80 is fitted (press-fitted) with an interference fit. Has been.

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

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

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

Since the first housing 31 and the second housing 32 exist in a position close to the combustion chamber C, it is preferable to manufacture the first housing 31 and the second housing 32 by using a material that can withstand at least a use temperature environment of −40 to 350 [° C.]. Specifically, it is desirable to use a stainless steel material having high heat resistance, for example, JIS standard SUS630, SUS316, SUS430, or the like.
Further, after the first housing 31 and the second housing 32 are fitted, they are further firmly fixed by welding.

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

The first electrode portion 50 is basically a columnar member, and the outer periphery on the tip side is chamfered. The end surface on the front end side is an end surface 42c provided on the protruding portion 42a of the inner portion 42 of the diaphragm head 40, and the end surface on the rear end side is the end surface 10a on the first electrode portion side that is the front end side surface of the piezoelectric element 10. It arrange | positions so that it may touch. The distal end portion of the piezoelectric element 10 is electrically connected to the housing 30 when the outer peripheral surface is in contact with the inner peripheral surface of the pressure member 80 and / or the end surface on the distal end side is in contact with the diaphragm head 40. .
The first electrode unit 50 applies the pressure in the combustion chamber C to the piezoelectric element 10, and the end surface on the rear end side which is the end surface on the piezoelectric element 10 side presses the entire end surface of the piezoelectric element 10. It is formed in a possible size. Further, the first electrode portion 50 has both end faces in the center line direction parallel (perpendicular to the center line direction) and smooth so that the pressure received from the diaphragm head 40 can be applied to the piezoelectric element 10 evenly. Is formed.
An example of the material of the first electrode unit 50 is stainless steel.

The second electrode portion 55 is a cylindrical member, and is arranged so that the end surface on the front end side contacts the end surface on the rear end side of the piezoelectric element 10 and the end surface on one end side contacts the insulating ring 60. Is done. A columnar projecting portion 55 a that projects from the end surface to the rear end side is provided on the end surface on the rear end side of the second electrode portion 55. The protrusion 55a has a base end portion on the end face side and a tip end portion having an outer diameter smaller than the outer diameter of the base end portion. The outer diameter of the protruding portion 55a is set smaller than the inner diameter of the insulating ring 60, and the length of the protruding portion 55a is set longer than the width of the insulating ring 60 (the length in the center line direction). The tip is exposed from the insulating ring 60. The second electrode portion 55 is a member that acts so as to apply a certain load to the piezoelectric element 10 with the first electrode portion 50, and the end face on the piezoelectric element 10 side is the surface of the piezoelectric element 10. It is formed in such a size that the entire end surface can be pushed and formed in a parallel and smooth surface. The outer diameter of the second electrode portion 55 is set to be smaller than the hole diameter of the hole provided in the pressure member 80, and the outer peripheral surface of the second electrode portion 55 and the inner periphery of the first housing 31 are set. There is a gap between the faces.
The material of the second electrode portion 55 can be exemplified by stainless steel.

  The insulating ring 60 is a cylindrical member formed of alumina ceramic or the like, and the inner diameter (hole diameter at the center) is slightly larger than the outer diameter of the base end portion of the protruding portion 55a of the second electrode portion 55, The outer diameter is set to be approximately the same as the hole diameter of the hole provided in the pressure member 80. The second electrode portion 55 is arranged such that the protruding portion 55 a is inserted into the central hole of the insulating ring 60, so that the center position and the center of the hole provided in the pressure member 80 are the same. Placed in.

The support member 65 is a cylindrical member in which a plurality of cylindrical holes 650 having different diameters are formed inside from the front end side to the rear end side, and the outer peripheral surface is the same.
The holes 650 are formed in order from the front end side to the rear end side, based on the first hole 651, the second hole 652 having a larger diameter than the first hole 651, and the hole diameter of the second hole 652. And a third hole 653 having a larger hole diameter. The hole diameter of the first hole 651 is larger than the outer diameter of the base end portion of the protruding portion 55 a of the second electrode portion 55, and the protruding portion 55 a is exposed to the inside of the support member 65. The hole diameter of the second hole 652 is larger than the outer diameter of the distal end portion of the conductive member 22 of the signal processing unit 200 described later. The hole diameter of the third hole 653 is smaller than the outer diameter of the end portion of the covering member 23 of the signal processing unit 200 described later, and the covering member 23 fits into the surrounding wall forming the third hole 653 with an interference fit. Combined. Thereby, the support member 65 functions as a member that supports the end portion of the covering member 23.
Further, on the outer peripheral surface of the support member 65, a male screw 65a to be screwed into a female screw 81a described later formed on the pressure member 80 is formed.

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

The pressing member 80 includes a cylindrical portion 81 that is a cylindrical portion that covers the outer periphery of the first electrode portion 50, the piezoelectric element 10, the second electrode portion 55, the insulating ring 60, the support member 65, and the like, and the cylinder. And an extending portion 82 extending inward from the tip portion of the shaped portion 81. A female screw 81 a into which a male screw 65 a formed on the outer peripheral surface of the support member 65 is screwed is formed on the inner peripheral surface on the rear end side of the cylindrical portion 81. Further, a through hole 82 a through which the protruding portion 42 a of the inner side portion 42 of the diaphragm head 40 passes is formed in the extending portion 82. Further, an end face 82 b is formed on the rear end side of the extending part 82. The tubular portion 81 may be a cylinder (round tube) or a square tube.
When the rear end portion of the cylindrical portion 81 of the pressure member 80 is cylindrical, the outer peripheral surface thereof is fitted (press-fitted) with the inner peripheral surface of the first housing 31 with an interference fit. The outer diameter is set to be equal to or larger than the diameter of the inner peripheral surface of the first housing 31. Then, after the pressurizing member 80 and the first housing 31 are fitted, they are further firmly fixed by welding.

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

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

  The conductive member 22 is a rod-shaped (columnar) member, and an insertion hole 22a into which the distal end portion of the protruding portion 55a of the second electrode portion 55 and the coil spring 70 are inserted is formed at the distal end portion. The rear end portion of the conductive member 22 is electrically connected to the printed wiring board 210 of the circuit board portion 21 via a conductive wire. Examples of the material of the conductive member 22 include brass and beryllium copper. In this case, brass is desirable from the viewpoint of workability and cost. On the other hand, beryllium copper is desirable from the viewpoints of electrical conductivity, high temperature strength, and reliability.

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

  The conductive member covering portion 231 covers the center line direction so as to expose the front end portion of the conductive member 22, and an outer peripheral surface 240 formed so that the diameter gradually changes from the front end side to the rear end side. Is provided. The outer peripheral surface 240 has a first outer peripheral surface 241, a second outer peripheral surface 242 having an outer diameter larger than the outer diameter of the first outer peripheral surface 241, and a second outer peripheral surface 242 from the front end side to the rear end side. A third outer peripheral surface 243 having an outer diameter larger than that of the third outer peripheral surface, and a fourth outer peripheral surface 244 having an outer diameter larger than the outer diameter of the third outer peripheral surface 243. The diameter of the first outer peripheral surface 241 is larger than the diameter of the third hole 653 of the support member 65, and the peripheral wall in which the distal end portion of the conductive member covering portion 231 forms the third hole 653 of the support member 65. It is fitted (press-fit) with a tight fit. The diameter of the second outer peripheral surface 242 is smaller than the diameter of the second hole 322 of the second housing 32, and the diameter of the third outer peripheral surface 243 is the third hole 323 of the second housing 32. It is formed smaller than the hole diameter. The diameter of the fourth outer peripheral surface 244 is larger than the diameter of the fourth hole 324 of the second housing 32, and the rear end portion of the conductive member covering portion 231 is the fourth hole of the second housing 32. It is fitted (press-fit) to the surrounding walls forming 324 with an interference fit. Accordingly, the conductive member covering portion 231 is supported by contacting at least both ends in the center line direction with the support member 65 and the second housing 32, respectively. The adverse effect on the member 22 can be suppressed, and it is possible to avoid disconnection of the connecting portion of the conductive member 22 and poor contact due to vibration.

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

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

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

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

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

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

  Thereafter, from the opening on the rear end side of the first housing 31, the pressurizing member 80, the end face 42 c on the rear end side of the protruding portion 42 a of the inner side portion 42 of the diaphragm head 40, and the extending portion of the pressurizing member 80 are disposed. 82 is inserted until the end surface 82b on the rear end side is on the same plane. At that position, the first housing 31 and the pressure member 80 are fixed. Examples of the fixing method include irradiating a laser beam from the outside of the first housing 31 from a direction intersecting the center line direction (for example, a direction orthogonal to the center line direction). The laser beam may be irradiated to the entire circumference in the circumferential direction, or may be partially irradiated at equal intervals in the circumferential direction.

  Thereafter, the first electrode unit 50 and the piezoelectric element 10 are inserted from the opening on the rear end side of the pressure member 80. Thereafter, the coil spring 70 is attached to the tip of the protruding portion 55a of the second electrode portion 55, and the insulating ring 60 is inserted into the protruding portion 55a of the second electrode portion 55. 31 is inserted through the opening on the rear end side. Thereafter, the support member 65 is inserted from the opening on the rear end side in the first housing 31.

  Thereafter, in order to increase the sensitivity and linearity of the piezoelectric element 10, a predetermined load (preload) is applied to the piezoelectric element 10 in the first housing 31. That is, the male screw 65a formed on the outer peripheral surface of the support member 65 is screwed into the female screw 81a formed on the pressurizing member 80, and the support member 65 uses the insulating ring 60, the second electrode portion 55, The piezoelectric element 10 and the first electrode unit 50 are pressurized in the center line direction from the rear end side toward the front end side. Then, pressure is applied until the amount of displacement in the center line direction of the end face on the distal end side in the inner portion 42 of the diaphragm head 40 reaches a predetermined length before being pressed by the support member 65. The support member 65 and the pressure member 80 are fixed when the end face on the front end side of the inner side portion 42 of the diaphragm head 40 is displaced by a predetermined length. Examples of the fixing method include irradiating a laser beam from the outside of the first housing 31 in a direction intersecting the center line direction (for example, a direction orthogonal to the center line direction). The laser beam may be applied to the entire circumference in the circumferential direction, or may be irradiated spotwise at equal intervals in the circumferential direction. When the support member 65 and the pressure member 80 are fixed, a preload is applied to the piezoelectric element 10 in the first housing 31.

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

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

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

Here, the electrical connection structure in the pressure detection apparatus 5 mentioned above is demonstrated.
First, the end face (first electrode part side end face 10a) of the piezoelectric element 10 is connected to the metal housing 30 via the metal first electrode part 50 and the diaphragm head 40 or the pressure member 80. Electrically connected.

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

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

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

Next, the seal member 7 will be described with reference to FIGS. 1 to 5.
The seal member 7 includes an end surface in the tightening direction of the sensor unit 100 on the surrounding wall forming the communication hole 4 a in the cylinder head 4, the third outer peripheral surface 333 and the fourth outer peripheral surface 334 of the housing 30 of the pressure detection device 5. The first sealing member 71 is disposed between the connecting surface and the connecting surface. The seal member 7 is a second seal member 72 disposed between the inclined portion 4 c of the communication hole 4 a of the cylinder head 4 and the inclined surface 315 a of the first housing 31 of the housing 30 of the pressure detection device 5. have.

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

  The second seal member 72 can be exemplified by a ring-shaped O-ring made of fluoro rubber (FKM) and having a circular cross section. When the pressure detection device 5 is fastened to the cylinder head 4, the second seal member 72 is formed by the inclined portion 4 c of the communication hole 4 a of the cylinder head 4 and the inclined surface 315 a of the first housing 31 of the housing 30. It is deformed by receiving a force in a direction crossing the tightening direction, and the airtightness in the combustion chamber C is enhanced. That is, when the pressure detection device 5 is screwed into the cylinder head 4, the contact pressure generated between the second seal member 72 and the inclined portion 4 c of the communication hole 4 a of the cylinder head 4, and the second seal member 72 The contact pressure generated between the housing 30 and the inclined surface 315a of the first housing 31 is increased. Thereby, it is suppressed that combustion gas leaks between the second seal member 72 and the cylinder head 4 and between the second seal member 72 and the housing 30 of the pressure detection device 5.

  FIG. 6A is a diagram illustrating an example of a measurement result of the in-cylinder pressure by the pressure detection device 5 attached to the internal combustion engine 1. FIG. 6B is a diagram illustrating an example of a calculation result of the pressure error obtained from the measurement result of the in-cylinder pressure illustrated in FIG.

  First, FIG. 6A shows the relationship between the crank angle θ of the internal combustion engine 1 and the in-cylinder pressure in the combustion chamber C (referred to as an actual in-cylinder pressure Pe) measured by the pressure detection device 5. Here, the rotation speed of the internal combustion engine 1 at the time of measurement is 3200 [rpm].

  For example, in a four-cycle internal combustion engine 1, four strokes of intake, compression, combustion (expansion), and exhaust are performed while the crank rotates twice (720 °). In the intake stroke, the actual in-cylinder pressure Pe becomes approximately 0 [MPa]. In the compression stroke following the intake stroke, the actual in-cylinder pressure Pe increases rapidly (in this example, from about 3.5 [MPa] to 5.0 [MPa]). Further, in the combustion (expansion) stroke after ignition following the intake stroke, the actual in-cylinder pressure Pe decreases rapidly. In the final exhaust stroke following the combustion (expansion) stroke, the actual in-cylinder pressure Pe returns to approximately 0 [MPa].

  Here, FIG. 6A illustrates three patterns (solid crank, 6 rotations) (solid line, broken line, and alternate long and short dash line). 6A shows that the variation (deviation) in the in-cylinder pressure Pe is larger in the combustion (expansion) stroke and the exhaust stroke than in the intake stroke and the compression stroke.

FIG. 6B shows the relationship between the crank angle θ of the internal combustion engine 1 and the pressure error (referred to as actual machine pressure error ΔPe).
Here, the actual machine pressure error ΔPe is the in-cylinder pressure in the combustion chamber C measured by the pressure detector 5 (actual machine in-cylinder pressure Pe shown in FIG. 6A) and a reference sensor (not shown). The difference (ΔPe = Pe−Ps) from the in-cylinder pressure in the same combustion chamber C (reference in-cylinder pressure Ps) measured by Here, although the pressure detection device 5 of the present embodiment does not include a cooling mechanism, a reference sensor (not shown) includes a cooling mechanism by water cooling. In this example, the maximum value of the variation R of the actual machine pressure error ΔPe in the combustion (expansion) stroke is approximately 0.6 [MPa].

  Here, in the actual machine pressure error ΔPe in the combustion (expansion) stroke shown in FIG. 6 (b), heat generated by the combustion of the internal combustion engine 1 is applied to the pressure detection device 5, which is generated in the pressure detection device 5. Included due to structural distortion. The phenomenon in which the output of the pressure detection device 5 is distorted due to the influence of heat due to combustion in this way is called “thermal strain”. However, in this example, the actual machine pressure error ΔPe is obtained from the actual machine in-cylinder pressure Pe (and the reference in-cylinder pressure Ps) measured by the pressure detection device 5 while the internal combustion engine 1 is operated. In addition to those caused by the thermal distortion, for example, errors caused by variations in combustion of the internal combustion engine 1 and other errors caused by the internal combustion engine 1 side (state changes caused by feedback control using various sensors, etc.) Resulting errors, etc.). As described above, the actual machine pressure error ΔPe in the combustion (expansion) process is included in a state in which the above-described plurality of error factors are superimposed, so that the variation R is considered to increase.

  In this example, as described above, the rotational speed of the internal combustion engine 1 at the time of measurement is set to 3200 [rpm], but the generation timing of the maximum value of the variation R of the actual machine pressure error ΔPe in the combustion (expansion) stroke. Is earlier than the time (10.4 msec) from which the crank angle θ is 0 ° (combustion start) to 200 ° (combustion end), and the time from which the crank angle θ is 0 ° (combustion start) to 100 ° ( Faster than 5.2 msec). That is, it is estimated that the thermal strain in the pressure detection device 5 attached to the internal combustion engine 1 is in the order of msec (up to about 10 to 20 msec) from generation to extinction.

FIG. 7 is a diagram for explaining a thermal strain generation mechanism in the pressure detection device 5 of the present embodiment.
When heat H is applied to the diaphragm head 40 in a state of being cooled to some extent from the surface, that is, the formation surface (referred to as the surface) side of the recess 42b, the surface of the diaphragm head 40 is indicated by a broken line in the figure due to thermal expansion. Deforms in the direction of opening. Along with this, the center of the inner portion 42 of the diaphragm head 40 is pulled to the front surface side, and is placed between the end surface 42c of the protruding portion 42a located on the back surface side of the center of the inner portion 42 of the diaphragm head 40 and the piezoelectric element 10. Load (preload) decreases. As a result, the output from the piezoelectric element 10 will be lower than the value that should be originally output as the preload is reduced. On the other hand, when the convex portion is provided on the surface of the diaphragm head 40, the output from the piezoelectric element 10 increases from the value that should be output due to the thermal expansion of the diaphragm head 40. There is also.

  The inventor has studied a method for evaluating the thermal strain generated in the pressure detection device 5 without being attached to the internal combustion engine 1. Then, the present inventor has focused on the laser as a heat supply source capable of supplying heat to the diaphragm head 40 of the pressure detection device 5 on the order of msec, and has developed a thermal strain measurement device described below.

FIG. 8 is a diagram showing an overall configuration of the thermal strain measuring apparatus 500 of the present embodiment.
The thermal strain measurement apparatus 500 includes an XYZ stage 510 that holds the pressure detection apparatus 5, a laser irradiation unit 520 that irradiates the pressure detection apparatus 5 held on the XYZ stage 510 with a laser beam Bm (an example of a laser beam), A cover 530 that covers the XYZ stage 510 and a data analysis unit 540 that analyzes an output signal (data) sent from the pressure detection device 5 held on the XYZ stage 510 are provided.

  First, an XYZ stage 510 as an example of an attachment portion is mounted on a base 511 loaded on an installation target (for example, an experimental bench) and the upper surface of the base 511, and is horizontal with respect to the base 511 (X direction and Y direction). XY stage 512 movably provided on the pedestal 511, and a Z stage 513 provided on the upper surface of the pedestal 511 and provided movably in the vertical direction (Z direction) with respect to the pedestal 511.

  The laser irradiation unit 520 as an example of the irradiation unit includes a laser oscillator 521 that outputs a laser beam Bm by laser oscillation, and an optical fiber cable that is connected to the laser oscillator 521 and guides the laser beam Bm output from the laser oscillator 521. 522 and a laser emitting unit 523 that is connected to the optical fiber cable 522 and emits the laser beam Bm guided by the optical fiber cable 522 to the outside.

  Here, the pressure detection device 5 is attached to the XY stage 512 in the XYZ stage 510, and the laser emission unit 523 in the laser irradiation unit 520 is attached to the Z stage 513 in the XYZ stage 510. At this time, the pressure detection device 5 is attached to the XY stage 512 so that the diaphragm head 40 faces vertically upward, and the laser emission unit 523 is attached to the Z stage 513 so that the emission surface of the laser beam Bm faces vertically downward. It is done.

  Here, the laser oscillator 521 as an example of the oscillator is not limited as long as it can output a laser beam Bm having a wavelength that is absorbed by the diaphragm head 40 of the pressure detection device 5 to be irradiated, and various lasers (solid laser, liquid laser, etc.). Gas laser, semiconductor laser) can be used. In this example, a semiconductor laser is used as the laser oscillator 521.

  In addition, as the optical fiber cable 522 as an example of the light guide unit, a rectangular fiber having a rectangular core shape is used. In the present embodiment, the beam profile of the laser beam Bm output from the laser oscillator 521 is a Gaussian pattern, but unevenness occurs in the intensity distribution of the laser beam Bm by passing through the optical fiber cable 522 made of a square fiber. A difficult top hat pattern (rectangular shape) is exhibited.

  The optical fiber cable 522 may be a circular fiber having a circular core shape instead of a square fiber. However, in this case, the beam profile of the laser beam Bm that has passed through the optical fiber cable 522 made of a circular fiber has a Gaussian pattern (circular), and the laser beam is compared with the case where the above-described rectangular fiber is used as the optical fiber cable 522. Unevenness is likely to occur in the Bm intensity distribution.

  Further, the laser emitting unit 523 as an example of the emitting unit includes an optical system for irradiating the laser beam Bm to the pressure detection device 5 in an appropriate range. The detailed configuration of the laser emitting unit 523 will be described later.

  The cover 530 covers the entire XYZ stage 510 on which the pressure detection device 5 and the laser emitting unit 523 are mounted. The cover 530 can be attached to and detached from the XYZ stage 510 when the pressure detecting device 5 is attached to and detached from the XYZ stage 510. The cover 530 is made of, for example, a transparent acrylic resin, and the XYZ stage 510 and the like disposed inside from the outside of the cover 530 can be observed with the cover 530 attached to the XYZ stage 510. It is said.

  The data analysis unit 540 as an example of a calculation unit includes a data logger 541 that sequentially accumulates and stores output signals (voltage values) sent from the pressure detection device 5, and an output signal (voltage value) acquired from the data logger 541. ) Is converted into pressure, and a PC (personal computer) 542 for calculating a pressure change amount (hereinafter referred to as an irradiation pressure change amount ΔPi) due to irradiation with the laser beam Bm is provided.

FIG. 9 is a diagram illustrating a configuration of the laser emitting unit 523 in the thermal strain measuring apparatus 500.
The laser emitting unit 523 of the present embodiment is arranged to face the emission surface of the laser beam Bm in the optical fiber cable 522, and emits the laser beam Bm whose beam diameter increases as it is emitted from the optical fiber cable 522. A collimator lens 523a that converts the light into parallel light and a laser beam Bm (parallel light) that is disposed below the collimator lens 523a and is opposed to the collimator lens 523a and passes through the collimator lens 523a is collected at the focal point F at a focal length f. And a condensing lens (plano-convex lens in this case) 523b. In addition, the laser emission unit 523 has a video camera (not shown) that captures the lower side from the emission surface side of the laser beam Bm.

  FIGS. 10A and 10B are diagrams for explaining the relationship between the laser beam Bm in the thermal strain measuring apparatus 500 and the diaphragm head 40 of the pressure detecting apparatus 5.

  FIG. 10A shows the relationship between the condenser lens 523b of the laser emitting portion 523, the laser beam Bm, and the diaphragm head 40 of the pressure detecting device 5 as viewed from the side of the XYZ stage 510 (upstream side in the Y direction). Show.

  In the present embodiment, when measuring the thermal strain of the pressure detection device 5 with the thermal strain measurement device 500, the irradiation distance L from the condenser lens 523b of the laser emitting unit 523 to the diaphragm head 40 of the pressure detection device 5 is It is set larger than the focal length f of the condenser lens 523b (L> f). Here, the irradiation distance L in the present embodiment is represented by the sum of the focal distance f and the defocusing distance fd (L = f + fd).

  10B is a cross-sectional view of the XB-XB portion of FIG. 10A, and shows the laser beam Bm and the diaphragm of the pressure detection device 5 as viewed from above the XYZ stage 510 (downstream in the Z direction). The relationship with the head 40 is shown.

  The outer diameter (diameter) of the diaphragm head 40 in the pressure detection device 5 varies depending on the model, but is usually selected from a range of 4 mm to 10 mm, for example. Here, in the present embodiment, the irradiation distance L (defocusing distance fd) is set so that the outer diameter of the irradiation region D of the laser beam Bm irradiated to the diaphragm head 40 is larger than the outer diameter of the diaphragm head 40. Is determined. Then, based on the determined irradiation distance L, positioning of the laser emitting unit 523 with respect to the pressure detection device 5 in the Z direction is performed.

  In the present embodiment, the pressure detection device 5 is positioned with respect to the laser emitting portion 523 in the X direction and the Y direction so that the entire surface of the diaphragm head 40 is included in the irradiation region D of the laser beam Bm. .

  Next, the thermal strain measurement procedure of the pressure detection device 5 using the thermal strain measurement device 500 of the present embodiment will be described. Here, in the initial state, it is assumed that the laser emission unit 523 of the laser irradiation unit 520 is attached to the Z stage 513 of the XYZ stage 510 and the XYZ stage 510 is covered with the cover 530.

(1) Attaching the pressure detection device 5 to the thermal strain measurement device 500 First, the cover 530 covering the XYZ stage 510 in the thermal strain measurement device 500 is removed. Subsequently, the pressure detection device 5 to be measured is attached to the XY stage 512 in the XYZ stage 510. At this time, the pressure detection device 5 is attached to the XY stage 512 so that the diaphragm head 40 in the pressure detection device 5 faces upward. The output end of the transmission cable 8 provided in the pressure detection device 5 is connected to the data logger 541.

(2) XY direction positioning of the pressure detection device 5 with respect to the laser emitting unit 523 Next, the XY stage 512 to which the pressure detection device 5 is attached is placed on the base 511 in the X direction or the −X direction, and the Y direction or − By moving in the Y direction, XY direction positioning is performed in which the diaphragm head 40 of the pressure detection device 5 is positioned directly below the laser emitting unit 523. At this time, it is preferable to perform positioning in the XY directions while referring to an image taken by a video camera (not shown) provided in the laser emitting unit 523. When the positioning in the XY directions is completed, the pressure detection device 5 is fixed on the pedestal 511 via the XY stage 512.

(3) Z-direction positioning of laser emitting portion 523 with respect to pressure detection device 5 Subsequently, the Z stage 513 to which the laser emitting portion 523 is attached is moved on the base 511 in the Z direction or the −Z direction, so that the laser Z-direction positioning is performed in which the distance from the condensing lens 523b provided in the emission unit 523 to the diaphragm head 40 of the pressure detection device 5 is set to the irradiation distance L. At this time, it is preferable to perform positioning in the Z direction while referring to an image taken by a video camera (not shown) provided in the laser emitting unit 523. Here, as described with reference to FIG. 10 and the like, the irradiation distance L is set so that the outer diameter of the irradiation region D of the laser beam Bm irradiated to the diaphragm head 40 is larger than the outer diameter of the diaphragm head 40. It is decided. When the positioning in the Z direction is completed, the laser emitting unit 523 is fixed on the pedestal 511 via the Z stage 513.

  Thus, the positioning of the laser emission unit 523 and the pressure detection device 5 in the thermal strain measurement device 500 is completed. Then, the XYZ stage 510 is covered with the cover 530 in a state where the positioning of the laser emitting unit 523 and the pressure detection device 5 is completed.

(4) Laser beam Bm irradiation and data collection (an example of irradiation process)
Then, the laser oscillator 521 is operated, and the laser beam Bm is output from the laser oscillator 521. The laser beam Bm is output from the laser oscillator 521 to the laser emitting unit 523 via the optical fiber cable 522, and is irradiated to the diaphragm head 40 of the pressure detecting device 5 from the laser emitting unit 523. During this time, the laser beam Bm having a Gaussian pattern output from the laser oscillator 521 passes through the optical fiber cable 522 made of a square fiber, so that its intensity distribution exhibits a top hat pattern. In addition, the laser beam Bm that has come to exhibit a top hat pattern by passing through the optical fiber cable 522 is converted into parallel light by passing through the collimator lens 523a at the laser emitting unit 523, and then the condenser lens. The light is collected by passing through 523b. However, in the present embodiment, the laser beam Bm that has passed through the condenser lens 523b is irradiated onto the diaphragm head 40 of the pressure detection device 5 at an irradiation distance L that is longer than the focal length f. As a result, the entire area of the surface of the diaphragm head 40 is irradiated with the laser beam Bm having a nearly uniform intensity. Then, the pressure detection device 5 transmits an output signal (voltage value) generated with the irradiation of the laser beam Bm to the data logger 541 via the transmission cable 8. The data logger 541 sequentially accumulates and stores output signals received from the pressure detection device 5.

(5) Data analysis (example of calculation process)
The PC 542 acquires an output signal (voltage value) from the data logger 541. Further, the PC 542 calculates the irradiation pressure change amount ΔPi by converting the acquired output signal into a pressure.

(6) Removal of pressure detection device 5 from thermal strain measurement device 500 After completion of laser beam Bm irradiation and data collection shown in (4) above (may be after data analysis shown in (5) above is completed) Then, the cover 530 covering the XYZ stage 510 in the thermal strain measuring apparatus 500 is removed. Subsequently, the pressure detection device 5 that is the measurement target is removed from the XY stage 512 in the XYZ stage 510. Further, the output end of the transmission cable 8 provided in the pressure detection device 5 is removed from the data logger 541.
Thus, the thermal strain measurement of the pressure detection device 5 using the thermal strain measurement device 500 is completed.

  FIG. 11 is a diagram showing a calculation result of an actual machine pressure error ΔPe obtained by mounting four different pressure detection devices 5 on the common internal combustion engine 1. Here, FIG. 11A shows the case where the first sample S1 is used as the pressure detection device 5, FIG. 11B shows the case where the second sample S2 is used as the pressure detection device 5, and FIG. 11 shows a case where the third sample S3 is used as the pressure detecting device 5, and FIG. 11D shows a case where the fourth sample S4 is used as the pressure detecting device 5.

  11A to 11D show the relationship between the crank angle θ of the internal combustion engine 1 and the actual machine pressure error ΔPe in the pressure detection device 5, respectively. Here, each of FIGS. 11A to 11D illustrates three patterns (solid line, broken line, and alternate long and short dash line). In addition, the rotation speed of the internal combustion engine 1 at the time of measurement is 3200 [rpm] similarly to the example shown in FIG.

  First, it can be seen from FIG. 11A that in the first sample S1, the actual machine pressure error ΔPe after the crank angle θ becomes 0 ° (combustion (expansion) stroke and exhaust stroke) is small. Further, from FIG. 11B, it can be seen that in the second sample S2, the actual machine pressure error ΔPe in the combustion (expansion) stroke and the discharge stroke is slightly smaller (larger than the first sample S1). Further, from FIG. 11C, it can be seen that in the third sample S3, the actual machine pressure error ΔPe in the combustion (expansion) stroke and the discharge stroke is slightly larger (larger than the second sample S2). Furthermore, from FIG. 11D, it can be seen that in the fourth sample S4, the actual machine pressure error ΔPe in the combustion (expansion) stroke and the discharge stroke is large (larger than the third sample S3).

  As described above, the actual pressure error ΔPe of the pressure detection device 5 obtained using the internal combustion engine 1 increases in the order of the first sample S1, the second sample S2, the third sample S3, and the fourth sample S4. Is understood. That is, the durability of the pressure detection device 5 and the actual machine pressure error ΔPe are in a contradictory relationship, and if the durability is improved, the actual machine pressure error ΔPe will increase, and the actual machine pressure error ΔPe will be reduced. Then, the durability will be lowered.

  FIG. 12 is a diagram illustrating a measurement result of the irradiation pressure change amount ΔPi obtained by attaching four different pressure detection devices 5 to the common thermal strain measurement device 500. Here, FIG. 12A shows a case where the first sample S1 is used as the pressure detection device 5, FIG. 12B shows a case where the second sample S2 is used as the pressure detection device 5, and FIG. Shows the case where the third sample S3 is used as the pressure detecting device 5, and FIG. 12D shows the case where the fourth sample S4 is used as the pressure detecting device 5.

  12A to 12D show the relationship between the (elapsed) time t and the irradiation pressure change amount ΔPi in the pressure detection device 5, respectively. Here, each of FIGS. 12A to 12D illustrates one (one time) pattern (solid line). In addition, the measurement conditions in the thermal strain measuring apparatus 500 were as follows.

[Measurement condition]
・ Laser beam Bm oscillation wavelength: 980 nm
-Core size of optical fiber cable 522: 0.6 mm x 0.6 mm (square)
-Focal length f of condensing lens 523b: 60 mm
・ Irradiation distance L: 75mm
・ Laser beam Bm irradiation time: 10 msec (once)
Laser beam Bm output (referred to as laser output): 10W

  First, it can be seen from FIG. 12A that in the first sample S1, the irradiation pressure change amount ΔPi after irradiation with the laser beam Bm is small. Also, from FIG. 12B, it can be seen that in the second sample S2, the irradiation pressure change amount ΔPi after irradiation with the laser beam Bm is slightly smaller (larger than the first sample S1). Further, from FIG. 12C, it can be seen that in the third sample S3, the irradiation pressure change amount ΔPi after irradiation with the laser beam Bm is slightly larger (larger than the second sample S2). Furthermore, from FIG. 12D, it can be seen that in the fourth sample S4, the irradiation pressure change ΔPi after irradiation with the laser beam Bm is large (greater than the third sample S3).

  Thus, the irradiation pressure change amount ΔPi of the pressure detection device 5 obtained using the thermal strain measurement device 500 increases in the order of the first sample S1, the second sample S2, the third sample S3, and the fourth sample S4. It is understood that

  FIG. 13 is a diagram for explaining the correlation between the actual machine pressure error ΔPe and the irradiation pressure change amount ΔPi when the laser output is constant. Here, FIG. 13 shows the relationship between the actual machine pressure error ΔPe shown in FIG. 11 and the irradiation pressure change amount ΔPi shown in FIG. Therefore, FIG. 13 shows the correlation between the actual machine pressure error ΔPe and the irradiation pressure change amount ΔPi when the laser output for each of the first sample S1 to the fourth sample S4 is set to 10 W. Here, all measurement conditions were set to be the same.

  FIG. 13 shows that when the laser output is constant at 10 W, the actual machine pressure error ΔPe and the irradiation pressure change amount ΔPi are in a substantially direct relationship. Here, when the correlation coefficient is obtained from the results shown in FIG. 13, the value of the correlation coefficient is 0.999, and there is a strong positive correlation between the actual machine pressure error ΔPe and the irradiation pressure change amount ΔPi. There was found.

  FIG. 14 is a diagram for explaining the correlation between the actual machine pressure error ΔPe and the irradiation pressure change amount ΔPi when the laser output is varied. More specifically, FIG. 14 differs from FIG. 13 above in that the actual machine pressure error when the laser output for each of the first sample S1 to the fourth sample S4 is set to 10 W, 25 W, 30 W and 40 W. The correlation between ΔPe and the irradiation pressure change amount ΔPi is shown. In addition, about the 4th sample S4, when the laser output was set to 30W and when it set to 40W, the output from the pressure detection apparatus 5 exceeded an allowable range, and the measurement could not be performed.

  Here, in the measurement of the irradiation pressure change ΔPi using the thermal strain measuring device 500, the output of the pressure detection device 5 is the laser output of the laser beam Bm and the irradiation distance L (the defocus distance fd which is the distance from the focus F). ) And the intensity (density of light energy) of the laser beam Bm irradiated to the diaphragm head 40. In the present embodiment, the irradiation conditions of the laser beam Bm are determined so that the diaphragm head 40 is not melted or laser marks are not formed on the surface of the diaphragm head 40 with the irradiation of the laser beam Bm. Yes.

  FIG. 14 shows that when the laser output is constant at 10 W, 25 W, 30 W, and 40 W, the actual machine pressure error ΔPe and the irradiation pressure change amount ΔPi are in a substantially direct relationship. Here, when the correlation coefficient is obtained from the results shown in FIG. 14, the correlation coefficient value exceeds 0.9 even under the condition of the laser output of 40 W having the weakest correlation, and the actual machine pressure error ΔPe and the irradiation pressure It was confirmed that there is still a strong positive correlation with the change amount ΔPi.

  Then, from the results shown in FIG. 13 and FIG. 14, the irradiation pressure change amount ΔPi of the pressure detection device 5 is measured using the thermal strain measurement device 500 shown in FIG. It can be seen that the actual machine pressure error ΔPe obtained in the mounted state can be estimated. Here, since the irradiation pressure change amount ΔPi is obtained by irradiating the pressure detection device 5 with the laser beam Bm, unlike the actual machine pressure error ΔPe, the variation in combustion of the internal combustion engine 1 and other internal combustion The error factor due to the engine 1 side is not included. As a result, by measuring the irradiation pressure change amount ΔPi, it is possible to evaluate the state of thermal strain caused by the configuration of the pressure detection device 5 itself.

  In particular, in the present embodiment, in the pressure detection device 5 attached to the internal combustion engine 1, the method of irradiating the surface of the diaphragm head 40 provided in the pressure detection device 5 with the laser beam Bm is adopted. An environment equivalent to that when heat was applied from the combustion chamber C to the surface side of the diaphragm head 40 could be created. Therefore, by using the method of the present embodiment, it is possible to evaluate the state of thermal strain caused by the configuration of the pressure detection device 5 in an environment equivalent to the state attached to the internal combustion engine 1. It became so.

  In this embodiment, the laser oscillator 521 generates the laser beam Bm by pulse oscillation, so that the irradiation time of the laser beam Bm is 10 msec. However, the present invention is not limited to this, and the laser beam Bm is shorter than 10 msec. It can be long or long. In this embodiment, the laser oscillator 521 generates the laser beam Bm by pulse oscillation. However, the present invention is not limited to this, and the laser beam Bm may be generated by continuous oscillation.

  Furthermore, in the present embodiment, the irradiation distance L is made longer than the focal distance f by making the irradiation distance L the sum of the focal distance f and the defocusing distance fd (L = f + fd) (L> f ) But not limited to this. For example, by setting the irradiation distance L as the difference between the focal distance f and the defocusing distance fd (L = f−fd), the irradiation distance L may be shorter than the focal distance f (L <f).

  Furthermore, in the present embodiment, the irradiation distance L is removed from the focal distance f, but the present invention is not limited to this. For example, when the diameter of the irradiation region D of the laser beam Bm at the focal distance f is larger than the outer diameter (diameter) of the diaphragm head 40, the irradiation distance L may be set as the focal distance f.

  In the present embodiment, the pressure detection device 5 that measures the combustion pressure in the internal combustion engine 1 will be described as an example for measuring the irradiation pressure change ΔPi corresponding to the thermal strain by the thermal strain measurement device 500. However, the object of measurement is not limited to this. That is, any device having a configuration that transmits the force received from the outside to the pressure-sensitive element via the diaphragm can be a measurement target by the thermal strain measuring apparatus 500. Here, examples of the pressure sensitive element other than the piezoelectric body include a strain gauge and spaced electrodes.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Cylinder block, 3 ... Piston, 4 ... Cylinder head, 5 ... Pressure detection apparatus, 6 ... Control apparatus, 7 ... Sealing member, 8 ... Transmission cable, 10 ... Piezoelectric element, 30 ... Housing, 40 DESCRIPTION OF SYMBOLS ... Diaphragm head, 50 ... 1st electrode part, 55 ... 2nd electrode part, 60 ... Insulating ring, 65 ... Supporting member, 70 ... Coil spring, 80 ... Pressurizing member, 100 ... Sensor part, 200 ... Signal processing , XYZ stage, 511, pedestal, 512, XY stage, 513, Z stage, 520, laser irradiation unit, 521, laser oscillator, 522, optical fiber cable, 523... Laser emitting section, 523 a. Collimator lens, 523 b. Condensing lens, 530... Cover, 540. Chromatography, 542 ... PC, Bm ... laser beam, C ... combustion chamber, D ... irradiation region, Pe ... actual cylinder pressure, Ps ... reference in-cylinder pressure, .DELTA.Pe ... actual pressure error, .DELTA.Pi ... radiation pressure change amount

Claims (11)

An irradiation step of irradiating a laser beam to the diaphragm of a device having a diaphragm that deforms in response to an external pressure and a pressure-sensitive element that generates an output corresponding to the pressure acting through the diaphragm;
And a calculation step of calculating a pressure change generated in the pressure sensitive element using an output acquired from the pressure sensitive element in which the diaphragm is irradiated with laser light.   The thermal strain measurement method according to claim 1, wherein, in the irradiation step, the diaphragm is irradiated with the focused laser beam at a position deviated from a focus of the laser beam.   3. The thermal strain measurement method according to claim 2, wherein, in the irradiation step, the diaphragm is irradiated with laser light at a position far from the focal point of the laser light.   3. The thermal strain measurement method according to claim 2, wherein, in the irradiation step, the diaphragm is irradiated with a laser beam at a position closer to the focal point of the laser beam.   2. The thermal strain measurement method according to claim 1, wherein in the irradiation step, the diaphragm is irradiated with the focused laser beam at a focal position of the laser beam.   6. The thermal strain measurement method according to claim 1, wherein, in the irradiation step, the diaphragm is irradiated with a laser beam exhibiting a top hat pattern. A mounting portion to which a device having a diaphragm deformed by receiving pressure from the outside and a pressure-sensitive element that generates an output corresponding to the pressure acting via the diaphragm is mounted;
An irradiation unit for irradiating a laser beam to the diaphragm of the device attached to the attachment unit;
A thermal strain measurement apparatus comprising: a calculation unit that calculates a change in pressure generated in the pressure sensitive element using an output acquired from the pressure sensitive element in which the diaphragm is irradiated with laser light.   The irradiation unit includes an oscillator that oscillates a laser, a light guide that guides laser light oscillated by the oscillator, and an emission unit that emits the laser light guided by the light guide to the diaphragm of the device. The thermal strain measuring device according to claim 7, comprising:   9. The thermal strain measuring apparatus according to claim 8, wherein the emitting unit condenses the laser beam and irradiates the diaphragm with the laser beam at a position deviated from a focal point of the laser beam.   9. The thermal strain measuring apparatus according to claim 8, wherein the emitting unit condenses the laser beam and irradiates the diaphragm with the laser beam at a focal position of the laser beam.   9. The thermal strain measuring device according to claim 8, wherein the light guide unit is formed of a square fiber that outputs laser light having a Gaussian pattern as laser light having a top hat pattern.

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