Cylinder internal-pressure sensor for engine

A cylinder internal-pressure sensor is provided with a housing unit 2 composed of an outer cylinder portion 2e and an inner cylinder portion 2i having elastic portions 2es and 2is having elasticity in an axial direction Fs formed on an intermediate portion Xm in the axial direction Fs; a pressure-receiving ring block portion 3 hermetically fixed between the outer cylinder portion 2e and the inner cylinder portion 2i located on the fronts of the elastic portions 2es and 2is and faced with the rear of the elastic portions 2e and 2i through the elastic portions 2e and 2i and having a front surface 3f as a pressure receiving surface; at least one or more pressure detection elements 5a, 5b, 5c, . . . in contact with one electrode portion 4 provided on a rear surface 3r of this pressure-receiving ring block portion 3, given the internal pressure Pc by the pressure-receiving ring block portion 3 and arranged at predetermined positions in a peripheral direction Ff; and a support ring block portion 6 fixed between the outer cylinder portion 2e and the inner cylinder portion 2i, having a front surface 6f as a support surface supporting the pressure detection elements 5a . . . and serving also as the other electrode 7.

TECHNICAL FIELD

The present invention relates to a cylinder internal-pressure sensor for an engine configured having a ring shape suitable in use during detection of an internal pressure of a cylinder.

BACKGROUND ART

In general, a cylinder internal-pressure sensor for an engine for detecting an internal pressure (combustion pressure) of a cylinder by being faced with a combustion chamber of an engine is known, but this type of cylinder internal-pressure sensor needs to be mounted independently with a highly hermetical structure in a through hole formed at a predetermined position of the cylinder. Thus, a cylinder internal-pressure sensor in which the cylinder internal-pressure sensor is configured having a ring shape and capable of being mounted integrally on an outer peripheral surface of a distal end portion of an ignition plug which is another functional component attached to the engine, so that the cylinder internal-pressure sensor can be mounted on the cylinder along with the ignition plug.

As a cylinder internal-pressure sensor configured having such ring shape, a combustion pressure sensor disclosed in Patent Literature 1, a pressure sensor disclosed in Patent Literature 2, and a spark plug incorporating a pressure sensor disclosed in Patent Literature 3 are known.

The combustion pressure sensor in Patent Literature 1 is a combustion pressure sensor having an insulating body formed around a center electrode and a washer member electrically connected to a side electrode and formed around the insulating body, and incorporated in an ignition plug, provided with a piezo-electric element formed of lithium niobate installed between the insulating body and the washer member and also in the vicinity of an ignition gap between the center electrode and the side electrode. Moreover, the pressure sensor in Patent Literature 2 is a pressure sensor joined to an attachment hole instead of a gasket of a spark plug, and this pressure sensor is configured such that a mounting surface of a housing is brought into pressure contact with a cylinder head, and a radiation fin is fastened to the housing. Furthermore, the spark plug incorporating a pressure sensor in Patent Literature 3 is provided with a seat portion facing a plug mounting surface provided in an internal combustion engine when being mounted on the internal combustion engine; an accommodating member incorporated in this seat portion and holding a plurality of piezo-electric elements at predetermined intervals in a peripheral direction of an inner wall surface of the seat portion; an electrode plate formed having a planar shape corresponding to this accommodating member and having a terminal with a notched portion bent upward and a notched portion formed by the bending being provided on an upper surface of the accommodating member in a state not overlapped with the piezo-electric elements; an insulating plate formed having a planar shape corresponding to this electrode plate having a notched portion formed and provided on the upper surface of the electrode plate in a state where a terminal of the electrode plate protrudes upward from the notched portion; and a taking-out member connected to the terminal protruding from the notched portion of this insulating plate and for taking out an output of the piezo-electric elements.

CITATION LIST

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. H4-34327

Patent Literature 2: Japanese Unexamined Patent Application Publication No. H11-94675

Patent Literature 3: Japanese Unexamined Patent Application Publication No. 2000-277233

SUMMARY OF INVENTION

Technical Problem

However, the above described prior-art cylinder internal-pressure sensor for an engine configured having a ring shape has the following problems.

That is, in this type of cylinder internal-pressure sensor, a pressure detection element to be used for detecting the combustion pressure of the engine is preferably a single crystal material having high heat resistance and favorable piezo-electric characteristics even in a high-temperature environment. On the other hand, since the single crystal material is highly fragile, a high level of machining technology is required for cutting the single crystal material and cutting out a pressure detection element having a ring shape as in the above described Patent Literatures 1 and 2, and manufacture is not easy. In the end, yield and mass productivity are lowered, and it can not be ignored as a cost-raising factor. Moreover, since the entirety needs to be formed having an elongated ring shape, it is concerned that nonconformity such as a crack might occur if it is attached to an engine with large vibration, and reliability is not necessarily high as a pressure detection element.

On the other hand, in Patent Literature 3, since the pressure detection element is configured to be formed as a cuboid chip body and a plurality of chip bodies are arranged in a ring shape, the above described problem in manufacture (machining) of the integrally formed ring shape does not occur. But on the contrary, variation in dimensions and angles of each chip body directly influences characteristics (performances) of the cylinder internal-pressure sensor, and as a result, there is a problem that deterioration of detection accuracy and product variation can easily occur.

Moreover, in either case, since the combustion pressure of the engine is detected, internal structures of the pressure detection element, the electrode and the like need to be protected as much as possible from severe temperature and vibration environments. However, they are not necessarily sufficient in the entire detection structure, and there is room for further improvement from a viewpoint of ensuring stable attachment and stable operation of the cylinder internal-pressure sensor.

The present invention has an object to provide a cylinder internal-pressure sensor which solves the problems in such prior-art technologies.

Solution to Problem

In order to solve the above described problems, the present invention is characterized by including, in constituting a cylinder internal-pressure sensor1for an engine formed having a ring shape for detecting an internal pressure Pc of a cylinder Ec by being attached to outer peripheral surfaces Mas and Mbs of distal end portions of functional components Ma and Mb faced with a combustion chamber Rb of the engine, a housing unit2composed of an outer cylinder portion2eand an inner cylinder portion2ihaving elastic portions2esand2is having elasticity in an axial direction Fs formed on an intermediate portion Xm in the axial direction Fs; a pressure-receiving ring block portion3hermetically fixed between the outer cylinder portion2eand the inner cylinder portion2ilocated on the fronts of the elastic portions2esand2isand faced with the rear of the elastic portions2eand2ithrough the elastic portions2eand2iand having a front surface3fas a pressure receiving surface; at least one or more pressure detection elements5a,5b,5c, . . . in contact with one electrode portion4provided on a rear surface3rof this pressure-receiving ring block portion3, given the internal pressure Pc by the pressure-receiving ring block portion3, and arranged at predetermined positions in a peripheral direction Ft and a support ring block portion6fixed between the outer cylinder portion2eand the inner cylinder portion2i, having a front surface6fas a support surface supporting the pressure detection elements5a. . . and serving also as the other electrode7.

In this case, according to a preferred mode of the invention, one or two or more spacers10a. . . ,10as. . . , and10at. . . in the peripheral direction Ff are preferably arranged on a portion in contact with a rear surface portion of the pressure receiving ring block portion3and excluding the pressure detection elements5a. . . . At this time, it is more preferable that the pressure detection elements5a. . . and the spacers10a. . . ,10as. . . , and10at. . . are alternately arranged in the peripheral direction Ff of the pressure-receiving ring block portion3, and a length in the axial direction Fs of each of the spacers10a. . . ,10as. . . , and10at. . . is selected in association with a length of each of the pressure detection elements5a. . . in the axial direction Fs. On the other hand, the elastic portions2esand2is can be provided by forming bent portions (or curved portions)11eand11iin the intermediate portion Xm of the outer cylinder portion2eand the inner cylinder portion2i. Moreover, the pressure-receiving ring block portion3can be constituted by a pressure receiving ring main body portion12disposed on the front side and an insulating block portion13brought into contact with the pressure receiving ring main body portion12by being disposed on the rear side, and a single crystal material can be used for the pressure detection elements5a . . . .

On the other hand, front surfaces5af. . . of the pressure detection elements5a. . . , a rear surface3rof the pressure-receiving ring block portion3, rear surfaces5ar. . . of the pressure detection elements5a. . . , and the front surface6fof the support ring block portion6can be coated with a bonding layer C formed of an inner layer Ci which becomes an adhesion reinforcing layer, an intermediate layer Cm which becomes a diffusion preventing layer, and an outer layer Ce which becomes a diffusion layer. Moreover, on the rear surface3rof the pressure-receiving ring block portion3, the front surface6fof the support ring block portion6, the front surfaces5af. . . of the pressure detection elements5a. . . or the rear surfaces5ar. . . of the pressure detection elements5a. . . , an alignment control layer14for the pressure detection elements5a. . . using a molten bonding layer having a predetermined thickness Ls can be provided. Furthermore, on a portion where there is no pressure detection elements5a. . . in the one electrode4, a connector portion16to which a lead15is to be connected can be provided, and at this time, a compressed spring17interposed between the lead15and the one electrode4can be provided in the connector portion16. For the functional components (Ma, Mb), an injector Ma for injecting fuel into the cylinder Ec or an ignition plug Mb for igniting the fuel in the cylinder Ec can be applied.

Advantageous Effects of Invention

According to the cylinder internal-pressure sensor1for an engine according to the present invention as above, the following marked advantages can be exerted.

(1) For the housing unit2composed of the outer cylinder portion2eand the inner cylinder portion2ihaving the elastic portions2esand2is having elasticity in the axial direction Fs formed on the intermediate portion Xm in the axial direction Fs, the pressure-receiving ring block portion3, the one electrode4, at least one or more pressure detection elements5a. . . , and the support ring block portion6serving also as the other electrode7are disposed sequentially from the front side between the outer cylinder portion2eand the inner cylinder portion2iin configuration. Thus, a pressure received by the pressure-receiving ring block portion3can be transmitted to each of the pressure detection elements5a. . . stably (uniformly) and reliably by the expanding/contracting elastic portions2esand2is, and highly accurate pressure detection can be made.

(2) At least one or more pressure detection elements5a. . . in contact with the one electrode portion4provided on the rear surface3rof the pressure-receiving ring block portion3having the front surface3fas the pressure receiving surface and arranged at equal intervals in the peripheral direction Ff are used. Thus, even if the cylinder internal-pressure sensor1is configured by using a single crystal material having large fragility for the pressure detection elements5a. . . , and having a ring shape to be attached to the outer peripheral surfaces Mas and Mbs at the distal end portions of the functional components Ma and Mb faced with the combustion chamber Rb of the engine, manufacture (machining) of the pressure detection elements5a. . . becomes easy, which can contribute to improvement of yield and mass productivity and moreover to cost down, prevention of nonconformity such as a crack, and reliability can be also improved.

(3) Since the entire detection structure such as the pressure detection elements5a. . . , the electrodes4and7and the like is covered by the cylindrical (ring-shaped) housing unit2, the entire detection structure can be effectively protected from the severe temperature and vibration environments when the combustion pressure of the engine is detected, stable attachment and stable operation can be ensured for the cylinder Ec, easy attachment to the various functional components such as the injector Ma, the ignition plug Mb and the like can be realized, and the cylinder internal-pressure sensor1with high usability can be obtained.

(4) According to the preferred mode, by arranging one or two or more spacers10a. . . ,10as. . . , and10at. . . in the peripheral direction Ff on a portion in contact with the rear surface portion of the pressure-receiving ring block portion3and excluding the pressure detection elements5a. . . , spaces between the pressure detection elements5a. . . can be filled with the spacers10a. . . ,10as. . . , and10at. . . . Thus, alignment control of the pressure detection elements5a. . . in assembling is assisted, and alignment control can be made accurately and easily as well as reliably and stably. In addition, mechanical strength can be improved, and contribution can be made to cost reduction accompanying quantity reduction of the pressure detection elements5a . . . .

(5) According to the preferred mode, by arranging the pressure detection elements5a. . . and the spacers10a. . . ,10as. . . , and10at. . . alternately in the peripheral direction Ff of the pressure-receiving ring block portion3, good stress balance can be obtained in assisting alignment control and a control action can be realized in the most preferable form from a viewpoint of stability.

(6) According to the preferred mode, by selecting the a length of the spacers10a. . . ,10as. . . , and10at. . . in the axial direction Fs in accordance with the length of the pressure detection elements5a. . . in the axial direction Fs, the action (function) by arranging the spacers10a. . . ,10as. . . , and10at. . . can be exerted most effectively.

(7) According to the preferred mode, by providing the elastic portions2esand2is by forming the bent portions (or curved portions)11eand11iin the intermediate portion Xm of the outer cylinder portion2eand the inner cylinder portion2i, they can be integrally formed of a part of the outer cylinder portion2eand the inner cylinder portion2i. Thus, easy and optimal form in terms of manufacture can be realized.

(8) According to the preferred mode, by coating the front surface5af. . . of the pressure detection elements5a. . . , the rear surface3rof the pressure receiving ring block portion3, the rear surfaces5ar. . . of the pressure detection elements5a. . . , and the front surface6fof the support ring block portion6with the bonding layer C formed of the inner layer Ci which becomes the adhesion reinforcing layer, the intermediate layer Cm which becomes the diffusion preventing layer, and the outer layer Ce which becomes the diffusion layer, the three components with different material qualities, that is, the pressure-receiving ring block portion3, the pressure detection elements5aand the support ring block portion6can be reliably bonded by interposition of the bonding layer C . . . .

(9) According to the preferred mode, by providing the alignment control layer14for the pressure detection elements5a. . . using the molten bonding layer having the predetermined thickness Ls on the rear surface3rof the pressure-receiving ring block portion3, the front surface6fof the support ring block portion6, the front surface5af. . . of each of the pressure detection elements5a. . . or the rear surface5ar. . . of each of the pressure detection elements5a. . . , appropriate alignment control can be made easily for each of the pressure detection elements5a. . . by using the rear surface3rof the pressure-receiving ring block portion3and the front surface6fof the support ring block portion6and moreover, the alignment control layer14. Therefore, even if at least one or more pressure detection elements5a. . . are used, variation in dimension or angle can be absorbed, and detection accuracy can be further improved.

(10) According to the preferred mode, by providing the connector portion16connecting the electrode4and the lead15to the portion where there are not pressure detection elements5a. . . in the one electrode4and by providing the compressed spring17interposed between the lead15and the electrode4in the connector portion16, connection of the lead15to the electrode4can be made reliably, and reliable connection can be realized.

REFERENCE SIGNS LIST

1: cylinder internal-pressure sensor for an engine,2: housing unit,2e: outer cylinder portion,2i: inner cylinder portion,2es: elastic portion,2is: elastic portion,3: pressure-receiving ring block portion,3f: front surface of pressure-receiving ring block portion,3r: rear surface of pressure-receiving ring block portion,4: one electrode portion,5a,5b,5c: pressure detection element,5af: front surface of pressure detection element,5ar: rear surface of pressure detection element,6: support ring block portion,6f: front surface of support ring block portion,7: the other electrode,10a: spacer,10as: spacer,10at: spacer,11e: bent portion (or curved portion),11i: bent portion (or curved portion),12: pressure receiving ring main body portion,13: insulating block portion,14: alignment control layer,15: lead,16: connector portion,17: spring, Ec: cylinder of engine, Ma: functional component (injector), Mb: functional component (ignition plug), Mas: outer peripheral surface at distal end portion of functional component, Mbs: outer peripheral surface at distal end portion of functional component, Pc: internal pressure, Fs: axial direction, Ff: peripheral direction, Xm: intermediate portion, Ci: inner layer, Cm: intermediate layer, Ce: outer layer, Ls: predetermined thickness, combustion chamber Rb of engine

DESCRIPTION OF EMBODIMENTS

Subsequently, a best embodiment according to the present invention will be described in detail on the basis of the attached drawings.

First, a configuration of a cylinder internal-pressure sensor1according to the present invention will be described by referring toFIGS. 1 to 8.

FIG. 1illustrates a configuration of an essential part of the cylinder internal-pressure sensor1. Reference numeral2denotes a housing unit and is provided with an outer cylinder portion2ehaving a large diameter and an inner cylinder portion2ihaving a small diameter. The outer cylinder portion2eand the inner cylinder portion2iare integrally formed of an alloy material or the like with excellent heat resistance, respectively, and elastic portions2esand2ishaving elasticity in an axial direction Fs are provided in an intermediate portion Xm in the axial direction Fs, respectively. Regarding the intermediate portion Xm, as illustrated inFIG. 1, a position closer to the front of the housing unit2or preferably a position on the rear by approximately several [mm] from a front end of the housing unit2is selected. InFIG. 1, a lower part is the front. Moreover, the elastic portions2esand2is are, as illustrated inFIG. 3, formed of bent portions11eand11i, respectively. That is, the elastic portion2esof the outer cylinder portion2eis formed of the bent portion11eformed by having an outer peripheral surface of the intermediate portion Xm swollen in the center direction, a recess groove having a trapezoidal (rectangular) section is provided in a ring shape in a peripheral direction Ff on the outer peripheral surface, and the elastic portion2is of the inner cylinder portion2iis formed of the bent portion11iformed by having an inner peripheral surface of the intermediate portion Xm swollen in the radial direction, and a recess groove having a trapezoidal (rectangular) section is provided in the ring shape in the peripheral direction Ff on the inner peripheral surface. In this case, the outer cylinder portion2eand the inner cylinder portion2iare formed thin from the intermediate portion Xm to the front end and elasticity (spring characteristics) in the axial direction Fs is given at least to the intermediate portion Xm. As a result, the elastic portions2esand2is each having a constricted shape (bellows shape) are provided on the intermediate portion Xm of the housing unit2. As described above, by providing the elastic portions2esand2is by forming the bent portions11eand11ion the intermediate portion Xm of the outer cylinder portion2eand the inner cylinder portion2i, they can be integrally formed of a part of the outer cylinder portion2eand the inner cylinder portion2i. Thus, there is an advantage that the invention can be put into practice in an easy and optimal form in terms of manufacture.

On the other hand, a pressure-receiving block portion3hermetically fixed between the outer cylinder portion2eand the inner cylinder portion2ilocated on the front of the elastic portions2esand2isand reaching the rear of the elastic portions2eand2ithrough the elastic portions2eand2iis provided. A pressure-receiving ring block portion3is composed of a pressure-receiving ring main body portion12disposed on the front side and an insulating block portion13brought into contact with the pressure-receiving ring main body portion12by being disposed on the rear side. As a result, a front surface of the pressure-receiving ring main body portion12becomes a front surface3fof the pressure-receiving ring block portion3, and this front surface3fbecomes a pressure receiving surface receiving an internal pressure Pc.

The pressure-receiving ring main body portion12is integrally formed having a ring shape from an alloy material excellent in heat resistance or the like in entirety and the section is formed having T-shape of a wide width portion and a narrow width portion, as illustrated inFIG. 3. The wide width portion in the pressure-receiving ring main body portion12is accommodated so as to fill a space between the outer cylinder portion2eand the inner cylinder portion2ilocated on the front of the intermediate portion Xm of the housing unit2and hermetically fixed to the inner peripheral surface of the outer cylinder portion2eand the outer peripheral surface of the inner cylinder portion2iby welded portions21and22using laser welding or the like, so that a combustion gas in a combustion chamber Rb does not go into the cylinder internal-pressure sensor1. At this time, the narrow width portion in the pressure-receiving ring main body portion12reaches the rear of the elastic portions2eand2ithrough between the elastic portions2eand2i.

Moreover, an insulating block portion13is integrally formed having a ring shape from an insulating material having rigidity and has a rectangular section. Therefore, a rear surface of the insulating block portion13becomes a rear surface3rof the pressure-receiving ring block portion3. Moreover, on the rear surface3rof the pressure-receiving ring block portion3, one electrode portion4is provided. In this case, as illustrated inFIG. 7, the rear surface3rof the pressure-receiving ring block portion3, that is, a rear surface of the insulating block portion13is coated with a bonding layer C made of an inner layer Ci using Ti (titanium) which becomes an adhesion reinforcing layer, an intermediate layer Cm using Pt (platinum) which becomes a diffusion preventing layer, and an outer layer Ce using Au (gold) which becomes a diffusion layer, and on this bonding layer C, an alignment control layer14which becomes a molten bonding layer having a predetermined thickness Ls using Au—Sn (gold-tin) is provided by coating. This alignment control layer14has an alignment control function for absorbing variation in dimensions, angles and the like of three pressure detection elements5a. . . which will be described later and also functions as the one electrode portion4of the pressure detection elements5a. . . . Therefore, for the thickness Ls of the alignment control layer14, a dimension which can absorb variation in dimensions, angles and the like of three (or at least one or more) pressure detection elements5a. . . is set.

Any one of Ni, Cr, Zr, In, Bi, Y and the like other than the above can be selected and used for the inner layer Ci which becomes the adhesion reinforcing layer, Cu, Sn, Ni, Fe, Cr, V, Ti and the like other than the above can be selected and used for the intermediate layer Cm which becomes the diffusion preventing layer, and Ag, Pd, Sn, Ge, Cu and the like other than the above can be selected and used for the outer layer Ce which becomes the diffusion layer, respectively. In this case, each of the layers Ci, Cm and Ce may be composed of a single element or may be composed of an alloy containing a single element. Moreover, any one of metal (alloy) having an eutectic phenomenon such as Ag—Cu—Sn, Au—Ge, Au—Pd, Ag—Pd, Ag—Sn, Cu—Sb and the like other than the above can be used for the alignment control layer14which becomes the molten bonding layer. Each of these layers may be used as solder or may be used as a brazing material. Therefore, the alignment control layer14which becomes a molten bonding layer and the outer layer Ce which becomes the diffusion layer needs combination. For example, if Au—Sn is used for the alignment control layer14, Au or Sn needs to be used for the outer layer Ce, and if Ag—Pd is used for the alignment control layer14, Ag or Pd needs to be used for the outer layer Ce. As such, the material of the diffusion layer (outer layer Ce) needs to be selected as a single material or a composite material in the materials constituting the alignment control layer14.

On the other hand,5a,5b, and5cindicate three pressure detection elements (piezo-electric elements). Each of the pressure detection elements5a. . . is manufactured by using a single crystal material having excellent heat resistance and spontaneous polarization without a Curie point, capable of obtaining stable piezoelectric conversion characteristics in a wide temperature range. Specifically, a single crystal material such as LNG, LGSA, LNGA, CAAS, CTGS and the like including a single crystal material LTG (La3Ta0.5Ga5.5O14), LTGA (La3Ta0.5Ga4.8Al0.2O14), and LGS (La3Ga5SiO14). Moreover, each of the pressure detection elements5a. . . is sandwiched between the above described insulating block portion13and the support ring block portion6which will be described later, and the front surface and the rear surface are bonded to the rear surface of the insulating block portion13(alignment control layer14) and the front surface of the support ring block portion6, respectively, thus, the front surfaces5af. . . and the rear surfaces5ar. . . of each of the pressure detection elements5a. . . are coated with the bonding layer C made of the above described inner layer Ci, the intermediate layer Cm, and the outer layer Ce, respectively, as illustrated inFIG. 7.

Then, when the pressure detection elements5a,5b, and5care to be assembled, as illustrated inFIG. 8A, the alignment control layer14provided on the rear surface3rof the insulating block portion13before heating treatment is set so as to be directed upward, and the three pressure detection elements5a,5b, and5care placed on this alignment control layer14at equal intervals as illustrated inFIG. 2. Then, the front surface6fof the support ring block portion6is abutted to the rear surface5ar(upper surface) of each of the pressure detection elements5a. . . , and each of the pressure detection elements5a. . . is pressurized from above with a uniform force, while being heated in a reflow continuous furnace set to a predetermined temperature environment. As a result, as illustrated inFIG. 8B, the front surfaces5af. . . (lower surfaces) of each of the pressure detection elements5a. . . enter the appropriately molten alignment control layer14, and the rear surfaces5ar. . . (upper surfaces) of each of the pressure detection elements5a. . . is brought into planar contact with the front surface6fof the support ring block portion6, respectively. That is, alignment control in which variation in dimensions, angles and the like of each of the pressure detection elements5a,5b, and5care absorbed by the alignment control layer14is executed. Moreover, at this time, the bonding layers C . . . provided on the front surfaces5af. . . of each of the pressure detection elements5a. . . are deposited on the alignment control layer14and also, the bonding layers C . . . provided on the rear surfaces5ar. . . of each of the pressure detection elements5ais deposited on the bonding layer C provided on the front surface6fof the support ring block portion6at the same time.

Therefore, after the alignment control layer14and the bonding layers C . . . are solidified, the insulating block portion13, each of the pressure detection elements5a. . . and the support ring block portion6are integrally bonded. That is, an alignment control process and an assembling process are performed together (at the same time). At this time, the front end portion of the support ring block portion6is accommodated between the rear end portions of the outer cylinder portion2eand the inner cylinder portion2iand fixed to the inner peripheral surface of the outer cylinder portion2eand the outer peripheral surface of the inner cylinder portion2iby welding portions23and24. By means of the above described assembling process, the support ring block portion6blocks the rear end between the outer cylinder portion2eand the inner cylinder portion2ias illustrated inFIG. 1, and the front surface6fof the support ring block portion6fixed to the rear end of the housing unit2becomes a support surface supporting each of the pressure detection elements5a,5b, and5c. The support ring block portion6also functions as the other electrode7(ground) of each of the pressure detection elements5a,5b, and5c.

As described above, by coating the bonding layer C made of the inner layer Ci, the intermediate layer Cm, and the outer layer Ce on the front surfaces5af. . . of the pressure detection elements5a. . . , the rear surface3rof the pressure-receiving ring block portion3, the rear surfaces5ar. . . of the pressure detection elements5a. . . , and the front surface6fof the support ring block portion6, the three components with different materials, that is, the pressure-receiving ring block portion3, the pressure detection elements5a. . . and the support ring block portion6can be reliably bonded by means of interposition of the bonding layers C . . . . Moreover, by providing the alignment control layer14for the pressure detection elements5a. . . using the molten bonding layer such as Au—Sn or the like having the predetermined thickness Ls on the rear surface3rof the pressure-receiving ring block portion3, accurate alignment control can be easily executed for each of the pressure detection elements5a. . . by using the rear surface3rof the pressure-receiving ring block portion3and the front surface6fof the support ring block portion6and moreover, the alignment control layer14. Therefore, even if the three (or at least one or more) pressure detection elements5a. . . are used, variation in dimensions and angles can be absorbed, and detection accuracy can be improved.

On the other hand, the alignment control layer14functions also as the one electrode portion4provided on the rear surface3rof the pressure-receiving ring block portion3. Therefore, a lead (shield cable)14leading out to the outside is connected to the solidified alignment control layer14(electrode4). In this case, the electrode4and the lead14are connected through a connector portion16.FIG. 4illustrates a connection structure between the lead15and the electrode4in an enlarged manner. The lead15leading in from the outside penetrates the support ring block portion6and has a distal end thereof faced with the electrode4. At this time, the lead15penetrating the support ring block portion6is held by a crimping pipe25and an insulating pipe26as illustrated inFIG. 4. Moreover, at a distal end of the insulating pipe26, a spring holding terminal27of the connector portion16to which the distal end of the lead15is connected is mounted. This spring holding terminal27is disposed in a space between the support ring block portion6and the insulating block portion13where the pressure detection elements5a. . . are not present and is faced with the electrode4, as illustrated inFIG. 2. One end of the spring17in a compressed state is attached to the spring holding terminal27and the other end of the spring17is brought into pressure contact with the upper surface of the electrode4. Therefore, by providing such connector portion16, connection of the lead15to the electrode4can be reliably realized, and reliable connection can be made.

As described above, the cylinder internal-pressure sensor1according to this embodiment has a basic structure in which it is brought into contact with the one electrode portion4provided on the rear surface3rof the pressure-receiving ring block portion3having the front surface3fas a pressure receiving surface and the three (or at least one or more) pressure detection elements5a. . . disposed at equal intervals in the peripheral direction Ff are used. Therefore, even if the cylinder internal-pressure sensor1having a ring shape using a single crystal material with large fragility and attached to the outer peripheral surface Mas on the distal end portion of the injector Ma attached to the cylinder Ec as will be described later is constituted as the pressure detection elements5a. . . , manufacture (machining) of the pressure detection elements5a. . . becomes easy, yield and mass productivity are improved, and contribution can be made to cost reduction. Moreover, nonconformity such as a crack hardly occurs and reliability can be improved.

Subsequently, a use method and an operation (function) of the cylinder internal-pressure sensor1according to this embodiment will be described by referring toFIGS. 1 to 8.

First, since the cylinder internal-pressure sensor1is covered by the housing unit2and the like having a cylindrical shape (ring shape) in entirety, as illustrated inFIG. 6, the entire detection structure of the pressure detection elements5a. . . , the electrodes4and7and the like can be effectively protected from the severe temperature and vibration environment when the combustion pressure of the engine is detected, and stable attachment to the cylinder Ec and a stable operation are ensured. Therefore, as indicated by a virtual line inFIG. 1, the cylinder internal-pressure sensor1can be easily attached to the outer peripheral surface Mas of the distal end portion of the injector Ma for injecting fuel into the cylinder Ec, while being faced with the combustion chamber Rb of the engine of an automobile and the like. That is, when the injector Ma is to be assembled to the cylinder Ec, the cylinder internal-pressure sensor1can be also assembled to the injector Ma together as a part of the injector Ma in a sense. That is, it is no longer necessary to form a separate through hole at a predetermined position of the cylinder Ec and to attach the sensor independently by a highly hermetical structure in this through hole.

On the other hand, at detection of the internal pressure Pc in the cylinder Ec, since the internal pressure Pc is applied to the pressure receiving surface (front surface3f) of the pressure-receiving ring block portion3, this internal pressure Pc acts on each of the pressure detection elements5a,5b, and5cthrough the pressure-receiving ring main body portion12and the insulating block portion13. At this time, since the pressure-receiving ring main body portion12constituting the pressure-receiving ring block portion3is supported by the expanding/contracting elastic portions2esand2is having elasticity in the axial direction Fs, displacement (pressure) of the pressure-receiving ring main body portion12caused by the internal pressure Pc is stably (uniformly) and reliably transmitted by the expanding/contracting elastic portions2esand2is to each of the pressure detection elements5a. . . , and highly accurate pressure detection is made. In addition, since each of the pressure detection elements5a,5b, and5cis alignment-controlled by the alignment control layer14, as illustrated, even if the three pressure detection elements5a. . . are used, variation in dimensions and angles is absorbed, and detection accuracy is further improved.

Subsequently, the cylinder internal-pressure sensor1according to a modified embodiment of the present invention will be described by referring toFIGS. 9 to 14.

In the modified embodiment illustrated inFIG. 9, the number of pressure detection elements5a. . . in use is changed. In the above described embodiment illustrated inFIG. 2, a case in which the three pressure detection elements5a. . . are used is illustrated, but in the modified embodiment illustrated inFIG. 9, six pressure detection elements5a,5b,5c,5d,5e, and5fare used and disposed at equal intervals in the peripheral direction Ff. As described above, in the cylinder internal-pressure sensor1according to the present invention, an arbitrary quantity of at least one or more pressure detection elements5a. . . can be used. In the case of an even number, it can be configured such that two pressure detection elements5a. . . are used and the remaining pressure detection elements are used as dummies having a matching size, and such dummies are also included in the quantity of the pressure detection elements5a . . . .

In a modified embodiment illustrated inFIG. 10, an application of the cylinder internal-pressure sensor1, that is, a functional component to which the cylinder internal-pressure sensor1is attached is changed. In the embodiment illustrated inFIG. 1, a case in which the cylinder internal-pressure sensor1is attached to the injector Ma for injecting fuel into the cylinder Ec is illustrated, but in the modified embodiment illustrated inFIG. 10, a case in which the cylinder internal-pressure sensor1is attached to an outer peripheral surface Mbs of a distal end portion of the ignition plug Mb for igniting fuel in the cylinder Ec is illustrated. If the shape of the cylinder internal-pressure sensor1with respect to the outer peripheral surface Mbs of the distal end portion of the ignition plug Mb is different, the shape of the inner cylinder portion2iof the housing unit2is changed so as to match the shape of the ignition plug Mb to which the cylinder internal-pressure sensor1is to be attached. As described above, the cylinder internal-pressure sensor1can be easily attached to various functional components such as the injector Ma, the ignition plug Mb and the like, and the highly usable cylinder internal-pressure sensor1can be obtained.

In a modified embodiment illustrated inFIGS. 11 to 13, a mounting form of the pressure detection elements5a. . . is changed, and as illustrated inFIG. 12, spacers10a. . . in the peripheral direction Ff are arranged on a portion in contact with the rear surface3rof the pressure-receiving ring block portion3, that is, a rear-surface portion of the insulating block portion13(including the alignment control layer14) and excluding the pressure detection elements5a. . . . By arranging such spacers10a. . . , as illustrated inFIG. 13, the space between the pressure detection elements5a. . . can be filled by the spacers10a. . . ,10as. . . , and10at. . . , and thus, alignment control of the pressure detection elements5a. . . in assembling is assisted so that alignment control can be made accurately and easily and moreover, reliably and stably.

Illustrated is a case in which three spacers10a,10b, and10cformed of a ceramic material are used. Moreover, a width of each of the spacers10ais substantially matched with the width of the pressure-receiving ring block portion3, and a length in the axial direction Fs is selected in accordance with the length in the axial direction Fs of each of the pressure detection elements5a. . . . In this case, the length in the axial direction Fs is preferably matched with the length in the axial direction Fs of each of the pressure detection elements5a. . . but does not necessarily have to be matched with that and can be changed depending on the thickness of the alignment control layer14or the material of the spacers10a. . . . Since a rigid body (ceramic material) is used for the material of the illustrated spacers10a. . . , the thickness of each of the spacers10a. . . (0.89 [mm]) slightly smaller than the thickness of each of the pressure detection elements5a. . . (0.9 [mm]) was selected. The material of the spacers10a. . . is not limited to the rigid body, and a material having elasticity to some degree may be used. Therefore, the thickness of each of the spacers10a. . . may be larger than the thickness of each of the pressure detection elements5a. . . as necessary. As described above, by selecting the length in the axial direction Fs of each of the spacers10a. . . in accordance with the length in the axial direction Fs of each of the pressure detection elements5a. . . , an action (function) realized by arranging the spacers10a. . . can be exerted most effectively. In addition, inFIG. 11, reference numeral10bhdenotes a through hole through which the spring holding terminal27and the spring17are inserted.

Furthermore, the pressure detection elements5a. . . and the spacers10a. . . are alternately arranged in the peripheral direction Ff of the pressure-receiving ring block portion3. By arranging as above, good stress balance can be obtained in assisting alignment control and the control action can be realized in the most preferable form from a viewpoint of stability. The pressure detection elements5a. . . and the spacers10a. . . are preferably arranged alternately but do not necessarily have to be arranged alternately, and the spacers10a. . . do not have to be present alternately between the pressure detection elements5a. . . as necessary.

In modified embodiments illustrated inFIGS. 14A and 14B, though spacers10asand10atsimilar to the spacers10a. . . illustrated inFIG. 11are used, the number of the pressure detection elements5a. . . is changed. InFIG. 14A, six pressure detection elements5a,5b,5c,5d,5e, and5fare used and arranged at equal intervals in the peripheral direction Ff, and six spacers10as,10bs,10cs,10ds,10es, and10fsare arranged alternately between the pressure detection elements5a. . . similarly toFIG. 11. Therefore, each of the spacers10as. . . can be manufactured similarly to the spacers10a. . . except that the length in the peripheral direction Ff is different. On the other hand,FIG. 14Billustrates a case in which the single pressure detection element5ais used and arranged at a predetermined position in the peripheral direction Ff. Even this case can be put into practice similarly toFIG. 11by using the single spacer10atformed having an entire shape of a C-shape. As described above, the present invention can be put into practice even with one pressure detection element5aby using the spacer10at. Thus, by using the spacers10a. . . ,10as. . . , and10at. . . , illustrated inFIGS. 11 to 14as above, mechanical strength when assembling the pressure detection elements5a. . . can be improved, and a cost can be reduced with the decrease in the number of the pressure detection elements5a. . . in addition to the above described advantages. InFIGS. 9 to 14, the same reference numerals are given to the same portions as inFIGS. 1 to 8in order to clarify the configuration, and detailed description will be omitted.

The best mode of embodiment and modified embodiments are described in detail, but the present invention is not limited to these embodiments and is capable of arbitrary change, addition, and deletion within a range not departing from the spirit of the present invention in the configuration of the details, shapes, materials, quantities, methods and the like.

For example, regarding the elastic portions2esand2is, the case in which they are provided by forming the bent portions11eand11iis illustrated, but they may be formed by semicircular curved portions or may be constituted by a combination of a plurality of bent portions (or curved portions)11e. . . and11i. . . as a bellows shape. Moreover, the cases in which the injector Ma and the ignition plug Mb are applied as the functional components are illustrated, but the cylinder internal-pressure sensor1can be also combined with other sensors (functional components) such as a temperature sensor and the like. On the other hand, the case in which the pressure-receiving ring block portion3is constituted by a combination of the pressure-receiving ring main body portion12and the insulating block portion13is illustrated, but it may be an integral type. Furthermore, it is preferable that a single crystal material is used for the pressure detection elements5a. . . , but use of other pressure detection elements having different detection principles such as a piezo element and the like is not excluded. On the other hand, the case in which the alignment control layer14for executing alignment control of each of the pressure detection elements5a. . . is provided on the rear surface3rof the pressure-receiving ring block portion3is illustrated, but this alignment control layer14may be provided on the front surface6fof the support ring block portion6instead of the rear surface3rof the pressure-receiving ring block portion3. Moreover, the case in which the alignment control layer14is provided on the upper surface of the bonding layer C is illustrated, but if the bonding layer C is not provided, it may be provided directly on the rear surface3rof the pressure-receiving ring block portion3or the front surface6fof the support ring block portion6. Furthermore, the alignment control layer14is preferably provided on the rear surface3rof the pressure-receiving ring block portion3or the front surface6fof the support ring block portion6, but provision on the front surfaces5af. . . of the pressure detection elements5a. . . or on the rear surfaces5ar. . . of the pressure detection elements5a. . . is not excluded. The alignment control layer14does not necessarily have to be provided if the pressure detection elements5a. . . whose variation in dimensions, angles and the like can be ignored due to improvement of machining accuracy are used. On the other hand, the structure of connecting the one electrode4and the lead15to each other is not limited to the illustrated configuration using the spring17but other connection structures are not excluded as long as the electrode4and the lead15can be connected to each other. Moreover, the ignition plug Mb includes various types of ignition plugs such as a spark plug, a glow plug and the like, and the functional components Ma and Mb faced with the combustion chamber Rb of the engine also includes a case of attachment to a piston in addition to the case of attachment to the cylinder Ec, as illustrated.

INDUSTRIAL APPLICABILITY

The cylinder internal-pressure sensor according to the present invention can be used when detecting an internal pressure of a cylinder constituting an internal combustion engine including an internal combustion engine represented by an engine of an automobile and other various applications.