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EP1687569A1 - Glow plug comprising a pressure sensor and motor equipped therewith - Google Patents

Glow plug comprising a pressure sensor and motor equipped therewith

Info

Publication number
EP1687569A1
EP1687569A1 EP04790815A EP04790815A EP1687569A1 EP 1687569 A1 EP1687569 A1 EP 1687569A1 EP 04790815 A EP04790815 A EP 04790815A EP 04790815 A EP04790815 A EP 04790815A EP 1687569 A1 EP1687569 A1 EP 1687569A1
Authority
EP
European Patent Office
Prior art keywords
sensor
finger
glow plug
pressure
housed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP04790815A
Other languages
German (de)
French (fr)
Inventor
Bernd Last
Michel Boucard
Cyrille Patri
Alain Ramond
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Continental Automotive France SAS
Original Assignee
Siemens VDO Automotive SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Siemens VDO Automotive SAS filed Critical Siemens VDO Automotive SAS
Publication of EP1687569A1 publication Critical patent/EP1687569A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/001—Glowing plugs for internal-combustion engines
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P19/00—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02P—IGNITION, OTHER THAN COMPRESSION IGNITION, FOR INTERNAL-COMBUSTION ENGINES; TESTING OF IGNITION TIMING IN COMPRESSION-IGNITION ENGINES
    • F02P19/00—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition
    • F02P19/02—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition electric, e.g. layout of circuits of apparatus having glowing plugs
    • F02P19/028—Incandescent ignition, e.g. during starting of internal combustion engines; Combination of incandescent and spark ignition electric, e.g. layout of circuits of apparatus having glowing plugs the glow plug being combined with or used as a sensor
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F23—COMBUSTION APPARATUS; COMBUSTION PROCESSES
    • F23Q—IGNITION; EXTINGUISHING-DEVICES
    • F23Q7/00—Incandescent ignition; Igniters using electrically-produced heat, e.g. lighters for cigarettes; Electrically-heated glowing plugs
    • F23Q7/001—Glowing plugs for internal-combustion engines
    • F23Q2007/002—Glowing plugs for internal-combustion engines with sensing means

Definitions

  • the present invention relates to a glow plug comprising a pressure sensor for measuring the pressure of an engine cylinder in which the spark plug is housed.
  • a glow plug is known comprising a pressure sensor adapted to measure the internal pressure of an engine cylinder in which the plug is housed, a body adapted to be fixed to the engine and a finger in which is housed a preheating electrode.
  • the senor is arranged between, on the one hand, the body on which it is supported and, on the other hand, a nut secured to the upper end of a core which transmits electrical energy to the preheating electrode and which extends the finger in the body and beyond by crossing the sensor.
  • the pressure inside the cylinder is felt by the finger of the spark plug and the pressure variations undergone by the finger are transmitted to the sensor via the core which is attached to it.
  • a candle has several drawbacks.
  • an overpressure exerted on the finger affects the sensor in the form of a reduction in pressure since the nut connecting the core (and consequently the finger) to the sensor is placed above this. latest.
  • the vibrations of the core due to the operation of the engine, cause a vibration of the sensor to which the core is secured by means of the nut, which causes interference in the measurement of the pressure.
  • the electrical connectors used to connect the sensor to the electrical circuit are also subjected to vibrations which interfere with the pressure measurement.
  • the present invention aims to solve at least some of the aforementioned problems by producing a spark plug comprising a pressure sensor which does not require prior stressing and whose intended operation is not disturbed by parasitic vibrations.
  • the sensor in the candle of the aforementioned type, the sensor is secured to the body by its upper face and bears against the finger, so that the pressure exerted on the finger compresses the latter against the body.
  • the compressions undergone by the finger correspond to compressions undergone by the sensor which therefore no longer needs to be prestressed.
  • the vibrations of the latter no longer generate parasites towards the sensor.
  • FIG. 1 represents a sectional view of a glow plug of the prior art
  • Figure 2 shows a view similar to Figure 1 of a candle according to the present invention
  • Figure 3 is an exploded perspective view of the spark plug illustrated in Figure 2
  • FIG. 4 is a perspective view of the spark plug illustrated in FIGS. 2 and 3.
  • a glow plug 1 here for an internal combustion engine 2 (typically a diesel engine, cylinder head 2a) comprises a body 10, a finger 20, a core 40 and a pressure sensor 90.
  • the body 10 is adapted to be fixed to the engine 2, for example by screwing to the cylinder head 2a.
  • Finger 20, inside which is housed the glow plug preheating electrode 1 is disposed in the body 10 and is crimped thereto.
  • the core 40 transmits electrical energy to the electrode located in the finger 20 and, therefore, is in contact with this electrode and is integral with the finger 20 which it extends inside the body 10, and at the beyond (its free end allowing its electrical connection to an electrical supply conductor protrudes from the body 10).
  • the pressure sensor 90 is adapted to measure the internal pressure of (one of) the cylinder (s) of the engine.
  • the sensor 90 comprises a piezoelectric element 74 which is disposed between two contact elements 72,76 made of electrically conductive material, and which is electrically isolated from the rest of the spark plug 1, in this case by two electrically insulating elements 70.78.
  • the elements 72, 76 each comprise a bent side tab of electrical connection 72a, 76a directed towards the free end of the core 40 and extending essentially parallel to the longitudinal axis 1a of the spark plug (cf. FIGS. 3 and 4 ).
  • the sensor 90 is secured to the body 10 by its upper surface and bears against the finger 20, so that the pressure exerted on the finger 20 compresses it against the body 10. It is perfectly understood that any compression of the finger 20 results directly in compression of the sensor 90 against the body 10. Thus, the sensor 90 no longer needs to be prestressed to measure the pressures prevailing in the engine. As can be seen in Figure 2, the core 40 passes through the sensor 90 but is not in contact with the latter. As a result, the vibrations of the core 40 are not transmitted to the sensor 90. Thus the core 40 essentially has only the function of transmitting the electric current to the preheating electrode of the finger 20, as in candles preheating without pressure sensor.
  • the senor 90 is supported on a spacer 80 which rests on the finger 20 and which is disposed in the body 10, without contact with the latter.
  • the spacer 80 which surrounds the core 40 is not in contact with the latter.
  • This spacer 80 allows, without changing the dimensions of the finger 20 and of the body 10, to accommodate the sensor 90 at the upper part of the spark plug 1, and not in the body 10 at the location of the upper end of the finger 20 what would generate additional constraints (obligation to use sensors of very small external diameter having lower sensitivities and exposure to higher temperatures generated by finger 20).
  • the sensor 90 is disposed in a cavity 100 formed at the upper end of the body 10, the upper end of the spacer 80 protruding beyond the bottom wall of the cavity 100 so that the sensor 90 does not rest on the body 10.
  • the location of the sensor 90 in the body 10 makes it easy to produce a plastic overmolding of the upper part of the spark plug 1, the overmolding making it possible to 'sealing and perfecting the electrical connection of electrical wires to the connectors of the sensor 90.
  • the spacer 80 is made of a material giving it good rigidity (given the dimensional constraints imposed by the internal diameter of the body 10, the external diameter of the core 40 and the respective lengths of the body 10 and the finger 20), and allowing it to have its own mode of vibration (clearly) beyond the bandwidth of the sensor 90 (thus, the spacer 8 0 is not itself subject to vibrations which can interfere with the measurements made by the sensor 90).
  • the spacer 80 is made of ceramic, this material having the various desired properties (insulation, rigidity, vibrations beyond the bandwidth and good mechanical strength at high temperatures).
  • a support piece 60 is interposed between the sensor 90 and the spacer 80 in order to distribute the pressure coming from the spacer 80 over the entire surface of the sensor 90.
  • the spark plug 1 also includes a nut 50 disposed on the sensor 10, and whose screwing to the body 10 causes the sensor 90 to be compressed against the finger 20 (by means of the spacer 80 and the support piece 60) and its attachment to the body 10
  • the nut 50 which is integral with the body 10 and which, of course, is not in contact with the core 40 makes it possible to notably dampen the vibrations of the electrical connectors of the sensor 90, by compressing this sensor.
  • the thread of the nut 50 is produced at its outer periphery and cooperates with a thread produced on the internal face of the side walls 110 of the cavity 100.
  • the production of the candle 1 according to the present embodiment is particularly simple: it consists of a stack of parts; no severe prestressing of the sensor 90 is necessary, it suffices to compress it slightly to immobilize it.
  • the core is no longer used to transmit the pressure variations to the sensor, it is possible to reduce its diameter and therefore to use a sensor 90 having relatively small internal and external diameters (for example an internal diameter 2.6 millimeters and an outer diameter of 8.5 millimeters).
  • relatively small internal and external diameters for example an internal diameter 2.6 millimeters and an outer diameter of 8.5 millimeters.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Measuring Fluid Pressure (AREA)
  • Spark Plugs (AREA)

Abstract

The invention provides a glow plug (1), comprising a pressure sensor (90), suitable for measuring the internal pressure of a motor cylinder in which said plug (1) is housed, a body (10) to be secured to the motor and a finger (20) in which a heater electrode is housed. According to said invention, the sensor (90) is firmly secured to the body (10) by the upper face thereof and rests on the finger (20), so that the pressure exerted on the finger (20) presses said sensor against the body (10).

Description

Bougie de préchauffaαe comprenant un capteur de pression et moteur ainsi équipé La présente invention concerne une bougie de préchauffage comprenant un capteur de pression permettant de mesurer la pression d'un cylindre de moteur dans lequel est logée la bougie. On connaît une bougie de préchauffage comprenant un capteur de pression adapté à mesurer la pression interne d'un cylindre de moteur dans lequel est logée la bougie, un corps adapté à être fixé au moteur et un doigt dans lequel est logée une électrode de préchauffage. Comme on peut le voir à la figure 1 (qui illustre une bougie de l'art antérieur vue en coupe), de façon à pouvoir mesurer la pression dans le cylindre sans apporter de modification importante à la structure de la bougie, le capteur est disposé entre, d'une part, le corps sur lequel il prend appui et, d'autre part, un écrou solidaire de l'extrémité supérieure d'une âme qui transmet l'énergie électrique à l'électrode de préchauffage et qui prolonge le doigt dans le corps et au-delà en traversant le capteur. La pression à l'intérieur du cylindre est ressentie par le doigt de la bougie et les variations de pression subies par le doigt sont transmises au capteur par l'intermédiaire de l'âme qui y est solidarisée. Toutefois une telle bougie présente plusieurs inconvénients. En premier lieu, une surpression exercée sur le doigt se répercute au capteur sous la forme d'une diminution de pression étant donné que l'écrou reliant l'âme (et par voie de conséquence le doigt) au capteur est disposé au dessus de ce dernier. Ainsi, il est typiquement nécessaire, lors de la réalisation de la bougie, de mettre le capteur sous contrainte par un serrage suffisant pour qu'il puisse mesurer toute la gamme attendue de pressions, mais sans atteindre une contrainte trop élevée qui risquerait d'endommager l'élément piézo électrique du capteur. En second lieu, les vibrations de l'âme, dues au fonctionnement du moteur, entraînent une vibration du capteur auquel l'âme est solidarisée par l'intermédiaire de l'écrou, ce qui provoque des parasites dans la mesure de la pression. En troisième lieu, les connecteurs électriques utilisés pour relier le capteur au circuit électrique sont eux aussi soumis à des vibrations qui parasitent la mesure de pression. La présente invention a pour but de résoudre au moins certains des problèmes précités en réalisant une bougie comportant un capteur de pression qui ne nécessite pas une mise sous contrainte préalable et dont le fonctionnement prévu n'est pas perturbé par des vibrations parasites. Selon l'invention, dans la bougie du type précité, le capteur est solidarisé au corps par sa face supérieure et prend appui contre le doigt, de sorte que la pression exercée sur le doigt comprime celui-ci contre le corps. Ainsi, aux compressions subies par le doigt correspondent des compressions subies par le capteur qui n'a donc plus besoin d'être précontraint. En outre, comme le capteur est disposé entre le corps et le doigt, il n'est plus en contact avec l'âme et, de ce fait, les vibrations de celle-ci ne génèrent plus de parasites vers le capteur. En outre, les vibrations parasites des connecteurs du capteur sont absorbées par le corps auquel le capteur est solidarisé. A noter que l'invention s'applique également à un moteur à combustion interne comprenant au moins un cylindre et une bougie de préchauffage telle que présentée ici, le capteur de pression étant donc adapté à mesurer la pression interne du cylindre dans lequel est logée la bougie et le corps de cette dernière étant fixé au moteur. D'autres particularités et avantages apparaîtront dans la description du mode de réalisation donné à titre d'exemple non limitatif et illustré par les figures annexées où : La figure 1 représente une vue en coupe d'une bougie de préchauffage de l'art antérieur ; La figure 2 représente une vue similaire à la figure 1 d'une bougie conforme à la présente invention ; La figure 3 est une vue en perspective éclatée de la bougie illustrée à la figure 2 ; et La figure 4 est une vue en perspective de la bougie illustrée aux figures 2 et 3. Comme on peut le voir aux figures 2, 3 et 4, une bougie de préchauffage 1 , ici pour moteur à combustion interne 2 (typiquement moteur diesel, culasse 2a) comprend un corps 10, un doigt 20, une âme 40 et un capteur de pression 90. De façon classique, le corps 10 est adapté à être fixé au moteur 2, par exemple par vissage à la culasse 2a. Le doigt 20, à l'intérieur duquel est logée l'électrode de préchauffage de la bougie 1 , est disposé dans le corps 10 et est serti à celui-ci. L'âme 40 transmet l'énergie électrique à l'électrode située dans le doigt 20 et, de ce fait, est en contact avec cette électrode et est solidaire du doigt 20 qu'elle prolonge à l'intérieur du corps 10, et au-delà (son extrémité libre permettant sa connexion électrique à un conducteur électrique d'alimentation fait saillie hors du corps 10). Le capteur de pression 90 est adapté à mesurer la pression interne du (d'un des) cylindre(s) du moteur. Dans le présent exemple, le capteur 90 comprend un élément piézo-électrique 74 qui est disposé entre deux éléments de contact 72,76 en matériau conducteur d'électricité, et qui est isolé électriquement du reste de la bougie 1 , en l'occurrence par deux éléments électriquement isolants 70,78. Les éléments 72,76 comprennent chacun une patte latérale coudée de connexion électrique 72a,76a dirigée vers l'extrémité libre de l'âme 40 et s'étendant essentiellement parallèlement à l'axe longitudinal 1a de la bougie (cf. figures 3 et 4). Selon l'invention, le capteur 90 est solidarisé au corps 10 par sa surface supérieure et prend appui contre le doigt 20, de sorte que la pression exercée sur le doigt 20 le comprime contre le corps 10. On comprend parfaitement que toute compression du doigt 20 se traduit directement par une compression du capteur 90 contre le corps 10. Ainsi, le capteur 90 n'a plus besoin d'être précontraint pour mesurer les pressions régnant dans le moteur. Comme on peut le voir à la figure 2, l'âme 40 traverse le capteur 90 mais n'est pas en contact avec ce dernier. De ce fait, les vibrations de l'âme 40 ne sont pas transmises au capteur 90. Ainsi l'âme 40 n'a essentiellement pour fonction que la transmission du courant électrique à l'électrode de préchauffage du doigt 20, comme dans les bougies de préchauffage sans capteur de pression. Dans le présent exemple, le capteur 90 prend appui sur une entretoise 80 qui repose sur le doigt 20 et qui est disposée dans le corps 10, sans contact avec ce dernier. Bien évidemment, l'entretoise 80 qui entoure l'âme 40, n'est pas en contact avec celle-ci. Cette entretoise 80 permet, sans modifier les dimensions du doigt 20 et du corps 10, de loger le capteur 90 à la partie supérieure de la bougie 1, et non pas dans le corps 10 à l'endroit de l'extrémité supérieure du doigt 20 ce qui engendrerait des contraintes supplémentaires (obligation d'utiliser des capteurs de très petit diamètre externe ayant des sensibilités plus faibles et exposition à des températures plus élevées générées par le doigt 20). Comme on peut le voir à la figure 2, le capteur 90 est disposé dans une cavité 100 réalisée à l'extrémité supérieure du corps 10, l'extrémité supérieure de l'entretoise 80 faisant saillie au-delà de la paroi de fond de la cavité 100 de sorte que le capteur 90 ne repose pas sur le corps 10. L'emplacement du capteur 90 dans le corps 10 rend aisée la réalisation d'un surmoulage en matière plastique de la partie supérieure de la bougie 1 , le surmoulage permettant d'assurer l'étanchéité et de parfaire la connexion électrique de fils électriques aux connecteurs du capteur 90. L'entretoise 80 est réalisée en un matériau lui conférant une bonne rigidité (étant donné les contraintes de dimensions imposées par le diamètre interne du corps 10, le diamètre externe de l'âme 40 et les longueurs respectives du corps 10 et du doigt 20), et lui permettant d'avoir un mode propre de vibration (nettement) au-delà de la bande passante du capteur 90 (ainsi, l'entretoise 80 n'est pas elle-même soumise à des vibrations pouvant parasiter les mesures effectuées par le capteur 90). De préférence, l'entretoise 80 est réalisée en céramique, ce matériau ayant les différentes propriétés désirées (isolation, rigidité, vibrations au-delà de la bande passante et bonne tenue mécanique aux fortes températures). Par ailleurs, dans le présent exemple, une pièce d'appui 60 est intercalée entre le capteur 90 et l'entretoise 80 afin de répartir la pression provenant de l'entretoise 80 sur toute la surface du capteur 90. La bougie 1 comprend également un écrou 50 disposé sur le capteur 10, et dont le vissage au corps 10 entraîne la compression du capteur 90 contre le doigt 20 (par l'intermédiaire de l'entretoise 80 et de la pièce d'appui 60) et sa solidarisation au corps 10. L'écrou 50 qui est solidaire du corps 10 et qui, bien évidemment, n'est pas en contact avec l'âme 40 permet d'amortir notablement les vibrations des connecteurs électriques du capteur 90, en comprimant ce capteur . Dans le présent exemple, le filetage de l'écrou 50 est réalisé à sa périphérie extérieure et coopère avec un taraudage réalisé sur la face interne des parois latérales 110 de la cavité 100. Ainsi, la réalisation de la bougie 1 selon le présent mode de réalisation est particulièrement simple : elle se compose d'un empilement de pièces ; aucune précontrainte sévère du capteur 90 n'est nécessaire, il suffit de le comprimer légèrement pour l'immobiliser. De plus, comme l'âme n'est plus utilisée pour transmettre les variations de pression au capteur, il est possible de réduire son diamètre et donc d'utiliser un capteur 90 ayant des diamètres interne et externe relativement faibles (par exemple un diamètre interne de 2,6 millimètres et un diamètre externe de 8,5 millimètres). Bien évidemment, il est possible d'apporter des modifications au présent mode de réalisation. The present invention relates to a glow plug comprising a pressure sensor for measuring the pressure of an engine cylinder in which the spark plug is housed. A glow plug is known comprising a pressure sensor adapted to measure the internal pressure of an engine cylinder in which the plug is housed, a body adapted to be fixed to the engine and a finger in which is housed a preheating electrode. As can be seen in Figure 1 (which illustrates a candle of the prior art seen in section), so as to be able to measure the pressure in the cylinder without making any significant modification to the structure of the candle, the sensor is arranged between, on the one hand, the body on which it is supported and, on the other hand, a nut secured to the upper end of a core which transmits electrical energy to the preheating electrode and which extends the finger in the body and beyond by crossing the sensor. The pressure inside the cylinder is felt by the finger of the spark plug and the pressure variations undergone by the finger are transmitted to the sensor via the core which is attached to it. However, such a candle has several drawbacks. Firstly, an overpressure exerted on the finger affects the sensor in the form of a reduction in pressure since the nut connecting the core (and consequently the finger) to the sensor is placed above this. latest. Thus, it is typically necessary, during the production of the spark plug, to put the sensor under stress by sufficient tightening so that it can measure the whole expected range of pressures, but without reaching a too high stress which would risk damaging the piezoelectric element of the sensor. Secondly, the vibrations of the core, due to the operation of the engine, cause a vibration of the sensor to which the core is secured by means of the nut, which causes interference in the measurement of the pressure. Thirdly, the electrical connectors used to connect the sensor to the electrical circuit are also subjected to vibrations which interfere with the pressure measurement. The present invention aims to solve at least some of the aforementioned problems by producing a spark plug comprising a pressure sensor which does not require prior stressing and whose intended operation is not disturbed by parasitic vibrations. According to the invention, in the candle of the aforementioned type, the sensor is secured to the body by its upper face and bears against the finger, so that the pressure exerted on the finger compresses the latter against the body. Thus, to the compressions undergone by the finger correspond to compressions undergone by the sensor which therefore no longer needs to be prestressed. In addition, as the sensor is disposed between the body and the finger, it is no longer in contact with the soul and, as a result, the vibrations of the latter no longer generate parasites towards the sensor. In addition, parasitic vibrations from the sensor connectors are absorbed by the body to which the sensor is attached. Note that the invention also applies to an internal combustion engine comprising at least one cylinder and a glow plug as presented here, the pressure sensor being therefore suitable for measuring the internal pressure of the cylinder in which the spark plug and the body of the latter being fixed to the engine. Other particularities and advantages will appear in the description of the embodiment given by way of nonlimiting example and illustrated by the appended figures where: FIG. 1 represents a sectional view of a glow plug of the prior art; Figure 2 shows a view similar to Figure 1 of a candle according to the present invention; Figure 3 is an exploded perspective view of the spark plug illustrated in Figure 2; and FIG. 4 is a perspective view of the spark plug illustrated in FIGS. 2 and 3. As can be seen in FIGS. 2, 3 and 4, a glow plug 1, here for an internal combustion engine 2 (typically a diesel engine, cylinder head 2a) comprises a body 10, a finger 20, a core 40 and a pressure sensor 90. Conventionally, the body 10 is adapted to be fixed to the engine 2, for example by screwing to the cylinder head 2a. Finger 20, inside which is housed the glow plug preheating electrode 1 is disposed in the body 10 and is crimped thereto. The core 40 transmits electrical energy to the electrode located in the finger 20 and, therefore, is in contact with this electrode and is integral with the finger 20 which it extends inside the body 10, and at the beyond (its free end allowing its electrical connection to an electrical supply conductor protrudes from the body 10). The pressure sensor 90 is adapted to measure the internal pressure of (one of) the cylinder (s) of the engine. In the present example, the sensor 90 comprises a piezoelectric element 74 which is disposed between two contact elements 72,76 made of electrically conductive material, and which is electrically isolated from the rest of the spark plug 1, in this case by two electrically insulating elements 70.78. The elements 72, 76 each comprise a bent side tab of electrical connection 72a, 76a directed towards the free end of the core 40 and extending essentially parallel to the longitudinal axis 1a of the spark plug (cf. FIGS. 3 and 4 ). According to the invention, the sensor 90 is secured to the body 10 by its upper surface and bears against the finger 20, so that the pressure exerted on the finger 20 compresses it against the body 10. It is perfectly understood that any compression of the finger 20 results directly in compression of the sensor 90 against the body 10. Thus, the sensor 90 no longer needs to be prestressed to measure the pressures prevailing in the engine. As can be seen in Figure 2, the core 40 passes through the sensor 90 but is not in contact with the latter. As a result, the vibrations of the core 40 are not transmitted to the sensor 90. Thus the core 40 essentially has only the function of transmitting the electric current to the preheating electrode of the finger 20, as in candles preheating without pressure sensor. In the present example, the sensor 90 is supported on a spacer 80 which rests on the finger 20 and which is disposed in the body 10, without contact with the latter. Obviously, the spacer 80 which surrounds the core 40 is not in contact with the latter. This spacer 80 allows, without changing the dimensions of the finger 20 and of the body 10, to accommodate the sensor 90 at the upper part of the spark plug 1, and not in the body 10 at the location of the upper end of the finger 20 what would generate additional constraints (obligation to use sensors of very small external diameter having lower sensitivities and exposure to higher temperatures generated by finger 20). As can be seen in Figure 2, the sensor 90 is disposed in a cavity 100 formed at the upper end of the body 10, the upper end of the spacer 80 protruding beyond the bottom wall of the cavity 100 so that the sensor 90 does not rest on the body 10. The location of the sensor 90 in the body 10 makes it easy to produce a plastic overmolding of the upper part of the spark plug 1, the overmolding making it possible to 'sealing and perfecting the electrical connection of electrical wires to the connectors of the sensor 90. The spacer 80 is made of a material giving it good rigidity (given the dimensional constraints imposed by the internal diameter of the body 10, the external diameter of the core 40 and the respective lengths of the body 10 and the finger 20), and allowing it to have its own mode of vibration (clearly) beyond the bandwidth of the sensor 90 (thus, the spacer 8 0 is not itself subject to vibrations which can interfere with the measurements made by the sensor 90). Preferably, the spacer 80 is made of ceramic, this material having the various desired properties (insulation, rigidity, vibrations beyond the bandwidth and good mechanical strength at high temperatures). Furthermore, in the present example, a support piece 60 is interposed between the sensor 90 and the spacer 80 in order to distribute the pressure coming from the spacer 80 over the entire surface of the sensor 90. The spark plug 1 also includes a nut 50 disposed on the sensor 10, and whose screwing to the body 10 causes the sensor 90 to be compressed against the finger 20 (by means of the spacer 80 and the support piece 60) and its attachment to the body 10 The nut 50 which is integral with the body 10 and which, of course, is not in contact with the core 40 makes it possible to notably dampen the vibrations of the electrical connectors of the sensor 90, by compressing this sensor. In the present example, the thread of the nut 50 is produced at its outer periphery and cooperates with a thread produced on the internal face of the side walls 110 of the cavity 100. Thus, the production of the candle 1 according to the present embodiment is particularly simple: it consists of a stack of parts; no severe prestressing of the sensor 90 is necessary, it suffices to compress it slightly to immobilize it. In addition, since the core is no longer used to transmit the pressure variations to the sensor, it is possible to reduce its diameter and therefore to use a sensor 90 having relatively small internal and external diameters (for example an internal diameter 2.6 millimeters and an outer diameter of 8.5 millimeters). Obviously, it is possible to make modifications to the present embodiment.

Claims

REVENDICATIONS 1. Bougie de préchauffage (1) comprenant un capteur de pression (90) adapté à mesurer la pression interne du cylindre d'un moteur dans lequel est logée la bougie (1), un corps (10) adapté à être fixé au moteur, et un doigt (20) dans lequel est logée une électrode de préchauffage, caractérisée en ce que le capteur (90) est solidarisé au corps (10) par sa face supérieure et prend appui contre le doigt (20) de sorte que la pression exercée sur le doigt (20) le comprime contre le corps (10). 2. Bougie de préchauffage (1) selon la revendication 1 , caractérisée en ce que le capteur (90) prend appui sur une entretoise (80) qui repose sur le doigt (20) et qui est disposée dans le corps (10), sans contact avec ce dernier. 3. Bougie de préchauffage (1) selon la revendication 2, caractérisée en ce que l'entretoise (80) est réalisée en un matériau dont le mode propre de vibration est au-delà de la bande passante du capteur (90). 4. Bougie de préchauffage (1) selon la revendication 3, caractérisée en ce que l'entretoise (80) est en céramique. 5. Bougie de préchauffage (1) selon l'une des revendications 1 à 4, caractérisée en ce qu'un écrou (50) est vissé au corps (10) et comprime le capteur (90) de façon à le solidariser au corps (10). 6. Bougie de préchauffage (1) selon la revendication 5, caractérisée en ce que le filetage de l'écrou (50) est réalisé à sa périphérie extérieure et coopère avec un filetage réalisé sur la face interne des parois latérales (110) d'une cavité (100) dans laquelle est logé le capteur (90). 7. Bougie de préchauffage (1) selon l'une des revendications 1 à 6, caractérisée en ce que le capteur (90) comprend un élément piézo-électrique (74) qui est disposé entre deux éléments de contact (72,76) et est isolé électriquement du reste de la bougie (1). 8. Moteur à combustion interne comprenant au moins un cylindre et une bougie de préchauffage (1) selon l'une des revendications précédentes, où le capteur de pression (90) est adapté à mesurer la pression interne du cylindre dans lequel est logée la bougie (1 ), et où le corps (10) est fixé au moteur. CLAIMS 1. Glow plug (1) comprising a pressure sensor (90) adapted to measure the internal pressure of the cylinder of an engine in which the spark plug is housed (1), a body (10) adapted to be fixed to the engine , and a finger (20) in which is housed a preheating electrode, characterized in that the sensor (90) is secured to the body (10) by its upper face and bears against the finger (20) so that the pressure exerted on the finger (20) compresses it against the body (10). 2. Glow plug (1) according to claim 1, characterized in that the sensor (90) is supported on a spacer (80) which rests on the finger (20) and which is arranged in the body (10), without contact with the latter. 3. Glow plug (1) according to claim 2, characterized in that the spacer (80) is made of a material whose proper mode of vibration is beyond the pass band of the sensor (90). 4. Glow plug (1) according to claim 3, characterized in that the spacer (80) is ceramic. 5. Glow plug (1) according to one of claims 1 to 4, characterized in that a nut (50) is screwed to the body (10) and compresses the sensor (90) so as to secure it to the body ( 10). 6. Glow plug (1) according to claim 5, characterized in that the thread of the nut (50) is made at its outer periphery and cooperates with a thread made on the inner face of the side walls (110) of a cavity (100) in which the sensor (90) is housed. 7. Glow plug (1) according to one of claims 1 to 6, characterized in that the sensor (90) comprises a piezoelectric element (74) which is disposed between two contact elements (72,76) and is electrically isolated from the rest of the spark plug (1). 8. Internal combustion engine comprising at least one cylinder and a glow plug (1) according to one of the preceding claims, wherein the pressure sensor (90) is adapted to measure the internal pressure of the cylinder in which the spark plug is housed. (1), and where the body (10) is fixed to the motor.
EP04790815A 2003-10-29 2004-10-25 Glow plug comprising a pressure sensor and motor equipped therewith Withdrawn EP1687569A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR0312682A FR2861836B1 (en) 2003-10-29 2003-10-29 PREHEATING CUP COMPRISING A PRESSURE SENSOR AND MOTOR THUS EQUIPPED
PCT/EP2004/012026 WO2005040681A1 (en) 2003-10-29 2004-10-25 Glow plug comprising a pressure sensor and motor equipped therewith

Publications (1)

Publication Number Publication Date
EP1687569A1 true EP1687569A1 (en) 2006-08-09

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ID=34429733

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EP04790815A Withdrawn EP1687569A1 (en) 2003-10-29 2004-10-25 Glow plug comprising a pressure sensor and motor equipped therewith
EP04805337A Withdrawn EP1690041A1 (en) 2003-10-29 2004-10-28 Preheater plug comprising a pressure sensor and engine fitted therewith

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Application Number Title Priority Date Filing Date
EP04805337A Withdrawn EP1690041A1 (en) 2003-10-29 2004-10-28 Preheater plug comprising a pressure sensor and engine fitted therewith

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US (2) US7759612B2 (en)
EP (2) EP1687569A1 (en)
JP (2) JP2007533943A (en)
KR (1) KR20060105762A (en)
CN (2) CN100498075C (en)
FR (1) FR2861836B1 (en)
WO (2) WO2005040681A1 (en)

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Also Published As

Publication number Publication date
JP2007533943A (en) 2007-11-22
US7759612B2 (en) 2010-07-20
KR20060105762A (en) 2006-10-11
FR2861836B1 (en) 2006-03-10
US20070163329A1 (en) 2007-07-19
FR2861836A1 (en) 2005-05-06
WO2005040681A1 (en) 2005-05-06
JP2007510123A (en) 2007-04-19
CN1902442A (en) 2007-01-24
CN1875221A (en) 2006-12-06
EP1690041A1 (en) 2006-08-16
CN100498075C (en) 2009-06-10
WO2005043039A1 (en) 2005-05-12
US20070062267A1 (en) 2007-03-22

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