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
• • 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
  • 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.
• a glow plug comprising a pressure sensor.
• an internal combustion engine in particular a diesel engine
• knowing the value of the pressure inside each cylinder makes it possible to better control the progress of combustion in this engine.
• This information is then used to regulate the injection of fuel into each of the cylinders. Pollutant emissions from the engine can thus be reduced and consumption optimized.
• each cylinder has a glow plug which makes it possible to heat the interior of the corresponding combustion chamber, in particular when the engine is started.
• This glow plug is arranged in a threaded bore which passes through the cylinder head of the engine. It is already known to those skilled in the art to integrate a pressure sensor with a glow plug.
• a glow plug generally comprises a tubular body having on its outer surface a threaded part allowing its fixing in a corresponding bore made in a cylinder head. Part of this body is then inside the combustion chamber and the other part outside of it. The part inside the combustion chamber has a finger inside which there is a heating electrode. This electrode is supplied by a core which crosses the tubular body of the spark plug. The part outside the combustion chamber is also called the spark plug head.
• FIG. 1 shows an embodiment of a glow plug of the prior art provided with a pressure sensor.
• the pressure sensor is disposed between, on the one hand the body of the glow plug on which it is supported and on the other hand a nut secured to the upper end of the core supplying electrical energy to the preheating electrode.
• the core passes through the sensor.
• Such a candle of the prior art makes it possible to measure the pressure exerted inside the combustion chamber on the finger of the glow plug.
• other signals are superimposed on the signal corresponding to the pressure measured.
• To make a good measurement of the pressure prevailing inside the combustion chamber of the cylinder in question it is necessary to be able to overcome the background noise disturbing the pressure measurement. This comes for example from deformations of the cylinder head in which is mounted the glow plug.
• the object of the present invention is therefore to provide a glow plug fitted with a pressure sensor for which the signal corresponding to the measured pressure is not disturbed by spurious signals.
• this glow plug offers a glow plug comprising: - a tubular body having means allowing it to be fixed in a bore, - a finger disposed inside the body of the plug and receiving a heating electrode, and - a sensor pressure.
• this glow plug further comprises an intermediate tubular part; the finger is disposed inside the intermediate tubular part; the intermediate tubular part is mounted in the tubular body; the sensor is secured by its face opposite the finger to the intermediate tubular part, and the face of the sensor facing the finger is supported on the latter.
• the pressure sensor can then measure the stresses resulting from the thrust exerted by the pressure prevailing in the corresponding combustion chamber without being hindered by stresses existing at the level of the bore in which the glow plug is fixed and which are retransmitted in part to the body of this candle.
• the invention also proposes that the intermediate tubular part be secured to the tubular body, for example near the end of the tubular body intended to be in the combustion chamber of the corresponding engine. This area of the tubular body is generally not subjected to external stresses and the tubular intermediate piece is then not subjected to such stresses.
• the intermediate piece is fixed to the tubular body by tight fitting. In this way, the attachment to the tubular body is excellent.
• the finger can be fixed to the intermediate piece by tight adjustment or by welding.
• the intermediate tubular part has a deformation zone between a first fixing zone in which the finger is secured to the intermediate tubular part and a second fixing zone in which the intermediate tubular part is secured to the tubular body.
• This deformation zone gives freedom of movement to the finger and avoids creating tension between the tubular intermediate piece and the finger which would be detrimental to the pressure measurement between these two pieces.
• a spacer is disposed between the finger and the corresponding face of the sensor inside the tubular intermediate piece. This spacer must be rigid in order to be able to transmit significant stresses.
• the spacer is for example made of a ceramic material.
• the spacer mentioned above can be in the form of an elongated tubular sleeve whose outside diameter is less than the inside diameter of the intermediate tubular part and ends on the side intended to come into contact with the pressure sensor by a zone frustoconical so as to have a bearing surface on the side of the sensor corresponding substantially to the surface of the sensor.
• a single piece is disposed between the finger and the sensor. This is of course favorable for good transmission of forces but also allows easier mounting of the glow plug.
• the senor is preferably placed in a housing provided for this purpose in the intermediate tubular part, near the end of this part opposite to that intended to receive the finger and the sensor is for example secured to the intermediate tubular part by a nut having a thread at its outer periphery engaged in a thread made at the inner end of the intermediate tubular part.
• the nut can come to tighten the sensor against this spacer.
• the present invention also relates to an internal combustion engine, in particular a diesel type engine, characterized in that it includes a glow plug as described above. Details and advantages of the present invention will emerge more clearly from the description which follows, given with reference to the appended diagrammatic drawing, in which: FIG.
• FIG. 1 represents a glow plug of the prior art
• FIG. 2 represents a glow plug according to the invention in side view
• Figure 3 shows the glow plug of Figure 2 in longitudinal section
• Figure 4 is an exploded perspective view of the candle shown in Figures 2 and 3.
• Figure 1 shows in longitudinal section of a glow plug of the prior art comprising a pressure sensor so as to be able to measure the pressure in an engine cylinder.
• This glow plug 2 is conventionally mounted in an engine 4, of the type Diesel, and more precisely in a cylinder head 6 of this engine. It comprises a body 8, a finger 10, a core 12 and a pressure sensor 14.
• the body 8 is adapted to be fixed to the motor 4 by screwing.
• the cylinder head 6 has a threaded bore passing through it and opening into a combustion chamber of said engine 4.
• the body 8 has meanwhile on its outer surface a thread 16 corresponding to the thread made in the cylinder head 6.
• a thread 16 cooperates with the threaded bore of the cylinder head 6, the spark plug 2 being in its position mounted in the engine 4, a part of the body 8 extends towards the inside of the engine 4, that is to say towards the combustion chamber, while another part extends towards the outside of the engine.
• the body 8 is a tubular steel body inside of which are housed in particular the finger 10 and the core 12.
• the finger 10 projects from the tubular body 8 inside the combustion chamber. It is tightened inside the body 8 and receives a preheating electrode (not shown).
• the core 12 transmits electrical energy to the electrode located in the finger 10 and, therefore, is in contact with this electrode and is integral with the finger 10 which it extends inside the body 8.
• a l opposite the finger 10, the free end of the core 12 allows its electrical connection to a supply conductor.
• the pressure sensor is a piezoelectric sensor. It comprises a piezoelectric element 18 disposed between two contact elements 20 of electrically conductive material, the sensor itself being electrically isolated from the rest of the spark plug 2 by electrically insulating elements 22.
• the pressure sensor 14 comes to take support by means of a support piece 24 on the body 8. The other face of the sensor bears against a nut 26 secured to the upper end of the core 12.
• the part of the glow plug 2 at which is the pressure sensor 14 and located outside the engine is also called the spark plug head.
• the body 8 has a gripping zone 28 used for mounting / dismounting the spark plug 2 relative to the cylinder head 6.
• this gripping zone 28 is cylindrical with a hexagonal cross section. In this way, using a key, accessing from outside the cylinder head 6, the mounting and dismounting of the glow plug 2 are possible.
• the diameter of this gripping zone 28 is, conventionally, greater than that of the rest of the body 8.
• Figure 2 shows, in external view a glow plug according to the invention. Compared to the candle of Figure 1, there is a body 8 having on its outer surface a thread 16. We also recognize on the side of the head of the body 8 a gripping area 28.
• the finger 10 ′ is very substantially smaller than the finger 10 in FIG. 1.
• the glow plug in FIGS. 2 to 4 also includes a pressure sensor 14. This is also a piezoelectric sensor here. which can be of the same type as the glow plug sensor shown in Figure 1. While in Figure 1 the finger 10 is adjusted in the body 8, in the embodiment of Figures 2 to 4, in accordance with l invention, a tubular intermediate piece 30 is provided between the body 8 and the finger 10 '.
• this tubular intermediate piece 30 is to isolate the finger 10 ′ from the body 8.
• An important difference between the sensors of the prior art and the sensor according to the invention described here is that the pressure sensor is no longer arranged between the body 8 and the finger 10 but is disposed between the finger 10 'and the tubular intermediate piece 30. This appears in particular from the sectional view of FIG. 3.
• the elements intended to be find on the side of the combustion chamber when the glow plug is fixed in the engine are at a lower level compared to elements located outside the combustion chamber, on the side of the head of the glow plug .
• the finger 10 ' is tightly adjusted to the lower end of the tubular intermediate piece 30.
• the intermediate tubular part 30 is itself fixed by adjustment with clamping at the lower end of the body 8 at a fixing zone 32.
• the tip of the candle is also sometimes called the candle cone.
• the tubular intermediate piece 30 extends freely inside the body 8. In its upper part, the tubular intermediate piece 30 widens and has a larger diameter area serving as a housing 34 for the sensor 14.
• this sensor 14 is then located at the head of the spark plug, that is to say in the upper part of the latter.
• the upper part of this housing 34 is tapped so as to be able to receive a nut 36 having an external thread.
• This nut 36 is designed to exert a support on the upper face of the sensor 14.
• the lower face of this sensor 14 rests on a spacer 38.
• the latter connects the finger 10 'to the sensor 14.
• the sensor 14 is for example a sensor of the type described with reference to FIG. 1. It is unnecessary to repeat the description of this sensor here.
• the important difference between the sensor 14 of FIG. 1 and that of FIGS. 2 to 4 is that in FIG. 1 the sensor 14 works in tension while in FIGS. 2 to 4 it works in compression.
• the spacer 38 is a tubular piece to allow in particular at its center the passage of the core 12.
• the outside diameter of the spacer 38 is adapted to the inside diameter of the tubular intermediate piece 30 so as to extend freely to the inside of it.
• the diameter of the spacer 38 is adapted to the diameter of the finger 10 '.
• the diameter of the spacer 38 is adapted to the diameter of the lower face of the sensor 14.
• the spacer has in its upper part a frusto-conical area 40 allowing to pass gradually of the diameter corresponding to the finger 10 'to that of the sensor 14.
• the pressure sensor 14 here measures only the stresses resulting from the pressure prevailing in the corresponding combustion chamber.
• the various stresses exerted on the cylinder head 6 in which the glow plug is mounted in particular those which are not proportional to the pressure prevailing in the combustion chamber, have no influence on the pressure measured by the sensor 14.
• the intermediate tubular part 30 is maintained in the body 8 at a region of the body which does not undergo the stresses linked to the deformation of the cylinder head 6 in which the glow plug 2 is screwed. Indeed, these deformations are found more at the level of the thread 16.
• the sensor 14 is mounted on the one hand between the tubular intermediate piece 30 and on the other hand the finger 10 '.
• care is taken in the design of the glow plug to provide a deformation zone 42 of the tubular intermediate piece 30.
• This deformation zone 42 is located between a on the one hand the zone in which the finger 10 'is tightly adjusted in the tubular intermediate part 30 and on the other hand the zone in which the tubular intermediate part 30 is adjusted in the body 8.
• This deformation zone 42 promotes the transmission of forces exerted by the pressure on the finger 10 'to the sensor 14.
• the role of the spacer 38 is important here and great attention must be paid to the manufacture thereof.
• the spacer 38 By retransmitting the forces exerted on the finger 10 ', the spacer 38 must not transmit parasitic forces. It should therefore be ensured that the spacer is not on the one hand in contact with the core 12 supplying the finger 10 'with electrical energy or on the other hand with the tubular intermediate piece 30. It should also be ensured that the own vibration mode of this spacer does not disturb the pressure measurement of the sensor 14. It is therefore necessary to ensure that the natural frequency of vibration of this spacer 38 is far from the bandwidth of the sensor 14. By choosing as material a ceramic to achieve this spacer 38, these problems can be solved. As shown in FIGS. 3 and 4, the head of the spark plug may include an overmolded piece 44 of synthetic material. This part can integrate the gripping zone 28 of the head of the spark plug.
• a glow plug 2 comprising a pressure sensor 14 such as the spark plug described above allows an excellent measurement of the pressure inside a combustion chamber .
• the measurement of this pressure is completely decoupled from parasitic noises which may disturb this pressure measurement.
• the pressure sensor mounted in a glow plug according to the invention makes it possible to overcome the deformations of the head of the cylinder head induced by the stresses exerted by these injectors.
• the deformation zone at the level of the intermediate tubular part makes it possible to obtain good sensitivity of the measurement carried out by the sensor. As is apparent in particular from FIG.
• the glow plug according to the invention remains easy to assemble. It is a stack of parts that are sealed by an overmolding of synthetic material at the head of the candle.
• the present invention is not limited to the preferred embodiment described above by way of nonlimiting example. It also relates to all the variant embodiments accessible to those skilled in the art. Thus for example the present invention is entirely possible with a conventional finger.
• the design of the glow plug must then be adapted to this larger finger but it remains of course possible to introduce a tubular intermediate piece to effect decoupling between the body of the candle and the finger thereof.
• the fastenings on the one hand of the finger in the intermediate tubular part and on the other hand of the tubular intermediate part in the body are provided above by tight fitting.
• Another method of attachment can be envisaged.
• An alternative to using a spacer can be considered.

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

Applications Claiming Priority (2)

Publications (1)

Family

ID=34945454

Family Applications (1)

Country Status (7)

Families Citing this family (11)

Citations (2)

Family Cites Families (20)

• 2004
  • 2004-04-27 FR FR0404463A patent/FR2869391B1/fr not_active Expired - Fee Related
• 2005
  • 2005-04-19 WO PCT/FR2005/000932 patent/WO2005111501A1/fr active Application Filing
  • 2005-04-19 JP JP2007510066A patent/JP4662981B2/ja not_active Expired - Fee Related
  • 2005-04-19 KR KR1020067024848A patent/KR20070043931A/ko not_active Application Discontinuation
  • 2005-04-19 US US11/587,659 patent/US7825352B2/en not_active Expired - Fee Related
  • 2005-04-19 CN CNB2005800131384A patent/CN100543370C/zh not_active Expired - Fee Related
  • 2005-04-19 EP EP05758221A patent/EP1747406A1/fr not_active Withdrawn

Patent Citations (2)

Non-Patent Citations (1)

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