|Title of Invention||
A GLOW PLUG FOR AN INTERNAL COMBUSTION ENGINE
|Abstract||A device for bearing on a pressure sensor mounted on a glow plug The device is a force transmitting device (38') for a pressure sensor (14) associated with a glow plug in an internal combustion engine, having the form of a tubular member of substantially circular section. it comprises a zone (40) in which its outer diameter increases towards one of its ends. Its front face corresponding to that flared end is a bearing face adapted to receive a piezoelectric pressure sensor (14). The invention also relates to a glow plug incorporating such a force transmitting device. Figure 5|
|Full Text||A da vice for bearing on a pressure sensor mounted on a glow plug
The present invention concerns a device for bearing on a pressure
sensor mounted on a glow plug,
It is known to integrate a pressure sensor in a glow plug in an internal combustion engine, in particular a diesel engine. This sensor makes it possible to measure the internal pressure of the engine. The knowledge of this pressure enables the progression of the combustion in that engine to be better controlled. Better efficiency of that engine is thus attained and limitation is achieved not only of its fuel consumption but also of its polluting emissions.
A glow plug generally comprises a tubular body having on its outer surface a threaded portion enabling it to be fixed into a corresponding bore formed in a cylinder head. One portion of that body Is located within the combustion chamber and the other portion outside it. The portion within the combustion chamber bears a finger within which is located a heater electrode. The latter is supplied by a core which passes through the tubular body of the glow plug, The portion outside the engine is also referred to as glow plug head. At that head, the core is connected to a source of electrical energy. It is also known to place the pressure sensor in that head,
One form of embodiment of such a glow plug has been provided in a patent application that has not yet been published at the time of filing the present application. This application was later published under the number FR 2 861 836. That embodiment is illustrated In Figure 1 appended hereto,
In the embodiment represented in Figure 1, and described in more detail later, the pressure sensor is mounted between a nut with an external screw thread screwed into a housing of the glow plug head, and a spacer bearing on the finger within which is located the heater electrode and mounted on the tubular body.
In this embodiment, the spacer is formed of ceramic and has a tubular circular cylindrical form, The spacer does not bear directly against the sensor but is separated therefrom by an electrically Insulating member as well as by a bearing part used
This solution has the drawback that at least three parts are situated between the finger and the glow plug and the pressure sensor. This implies a cost
both for the production of these different parts as well as for their assembly, Furthermore, it has bean noted that the presence of several contact surfaces (between the pressure sensor end the insulating member, between the insulating member and the bearing part and between the bearing part and the spacer) had a negative effect on the sensitivity of the pressure sensor.
The present invention thus concerns a glow plug equipped with a pressure sensor implementing a spacer for transmitting forces to the sensor but of which the production cost is less than the embodiment presented earlier. Preferably, the structure of this glow plug wili not weaken the sensitivity of the pressure sensor used.
To that end, it provides a force transmitting device for a pressure sensor associated with a glow plug in an Internal combustion engine, having the form of a tubular member of substantially circular section,
According tc the invention, the device comprises a zone In which Its outer diameter increases towards one of its ends, and the front face of the device corresponding to that flared end is a bearing fece adapted to receive a pressure sensor.
Such a force transmitting device is thus also adapted to service as a bearing part, it is possible in this way to eliminate a part between the origin of the force (pressure) to measure and the sensor.
in an advantageous embodiment, this force transmitting device is produced from a ceramic material. Thus, it may also serve as an electrically insulating member for the pressure sensor when this a piezo-electric sensor. This is because it may also be a resistive piazo-electric sensor or any other type of pressure sensor.
To enable the passage of a conductive cere, this device preferably has a central hole of substantially constant diameter.
The present invention also concerns a glow plug comprising a piezoelectric pressure sensor and characterized in that it comprises a force transmitting device as described above.
in such a glow plug, the flared end of the force transmitting device bears for example against a face of the pressure sensor and substantially corresponds to the surface of that sensor. In this way, the forces to transmit are perfectly so transmitted and the sensor can operate in good conditions.
The glow plug may in particular be of the type comprising at one of its ends a finger incorporating a heater electrode, and the force transmitting device is then for example disposed between that finger and the pressure sensor, In this embodiment, the finger may be fixed within a tubular part, at one end thereof, and that tubular part may have an interior shoulder against which the force transmitting device rests. The tubular part concerned here may be the body of the glow plug but It may also be another part, such as an intermediate part between the body and the finger of said glow plug.
in the case in which the finger is fixed into a tubular part, the outer diameter of the force transmitting device is preferably less than the inner diameter of the tubular part within which it is housed such that the force transmitting device is free at its periphery, in particular with respect to the tubular part, Thus the risk of transmitting extraneous forces is diminished.
Similarly, when a conductive core supplies the heater electrode of the
glow ptug with electrical energy, that core preferably passes freely within the fores transmitting device.
The present invention lastly concerns an internal combustion engine, in particular an engine of Diesel type, characterized In that it comprises at least one glow plug as described above,
Details and advantages of the present invention will appear more clearly from the following description, made with respect to the accompanying drawings in which;
Figure 1 shows a glow plug earlier than the present invention, in longitudinal cross-section.
Figure 2 ehowe an external view of a giow plug according to the invention,
Figure 3 Is a longitudinal cross-section of the glow plug of Figure 2,
Figure 4 is an exploded view of the various components of the giow plug of Figures 2 and 3,
Figure 6 illustrates the mounting of a spacer according to the invention in perspective and in cross-section,
Figure 6 shows a spacer according to the invention on which a piezoelectric sensor rests, and
Figure 7 is a view at a larger scale of the mounting of the piezo-electrlc
sensor of the preceding Figure viewed from a different angle.
Figure 1 represents a longitudinal cross-section of a glow plug of a model prior to the invention (but not disclosed at the time of the first filing of the present patent appiicetion), This glow plug comprises a pressure sensor so as to be able to measure the pressure in an engine cylinder. This glow plug 2 is mounted In a conventional manner in an engine 4, of Diesel type, and more particularly in a cylinder head 6 of that engine. It comprises a body 8, a finger 10, a core 12 and a pressure sensor 14.
The body 8 is adapted to by fixed to the engine 4 by screwing. To that end, the cylinder head 8 comprises a threaded bore passing through it and opening into a combustion chamber of said engine, Concerning the body 8, this has a screw thread 16 on its other surface corresponding to the bore formed in the cylinder head 6. When the screw thread 16 cooperates with the threaded bore of the cylinder head 6, the glow plug being in its mounted position in the engine 4, a portion of the body 8 extends Inwardly of the engine, that is to say towards the combustion chamber, whereas another portion extends outwardly the engine. The body 3 is a tubular body and is for example formed from steel.
!n this embodiment, the finger 10 is mounted within the tubular body 8, within which it has an interference fit, and projects into the combustion chamber. This finger 10 incorporates a heater electrode (not shown), The core 12 is adapted to supply that electrode with electrical energy and passes through the body 8 from the finger 10 as far as the opposite end of the body 8 from that at which the finger 10 projects. This core 12 Is then connected, by means not shown, to a supply conductor
The pressure sensor 14 is provided for measuring the pressure within the corresponding combustion chamber. In the embodiment of Figure 1, this pressure sensor 14 comprises a piezo-electric member 18 disposed between two contact elements 20 formed from an electrically conductive material. The sensor is then itself electrically isolated from the rest of the glow plug 2 by electrically insulating members 22.
In this embodiment, the pressure sensor 14 also comes to bear on the body 8 via a bearing part 24. The pressure sensor 14 is connected to the body 8 by its upper surface and bears against the finger 10 such that the pressure exerted on that finger compresses it against the body 8. To that end, the pressure sensor
14 bears on a spacer 38 which rests on the finger 10 and whloh is disposed In the body 8, without contact with the latter. This spacer 38 surrounds the core and is not in contact with It either.
The compression of the pressure sensor 14 against the finger 10 (via the spacer 38 end the bearing part 24) as well as its connection to the body 6 is provided by a nut with external screw threading 36. This nut is of course not in contact with the core 12 but cooperates with an internal thread formed on the internal face of the side wall 46 of a housing 34 formed In the body 8 for receiving the sensor 14.
In the embodimsnt of Figures 2 to 4, similar members take the same reference numbers as those used In Figure 1,
On the external view of Figure 2, there can be recognized on the outer surface of the glow plug body 8 s screw thread 16, and, In the vicinity thereof, adjacent the head of the glow plug 2, a gripping zone 28. In a conventional manner, this gripping zone 28 has a hexagonal cross-section.
In the example embodiment of Figures 2 to 4, the finger bears the reference 10'. This is a finger of a different type to that represented In Figure 1 since it is a ceramic finger. Another difference is that to Insulate the electrical connections and protect the sensor, the head of the glow plug has an overmoldlng 44 of synthetic material,
In Figures 2 to 4, a tubular intermediate part 30 Is provided between the body 8 and the finger 10' to ineuiate the finger 10' from the body 8,
Between the finger 10' and the pressure sensor 14 is a spacer 38'. There is no bearing part 24 to be found here, nor any electrically Insulating member 22 between the spacer 38' and the pressure sensor 14, or more specifically a contact element 20 of that sensor.
The spacer 38' is a tubular part which allows the core 12 to pass through its center. As In the embodiment of Figure 1, the spacer 38' is freely mounted around that core. Similarly, it is freely mounted in the tubular intermediate part 30 and its outer diameter is thus less than the inner diameter of that tubular intermediate part 30,
in its upper portion, the diameter of the spacer 38' is adapted to the diameter of the lower facs of the pressure sensor 14, Thus, the spacer 38' has, on Its upper portion, a frusto-ccnica! zone 40 enabling the outer diameter of the
spacer 38' to progressively pass from a diameter corresponding approximately to the diameter of the finger 10' to the diameter of the pressure sensor 14 on approaching the end of the spacer 38' against which the pressure sensor 14 bears,
As has just been seen, by virtue of its frusto-conlcal portion 40, the spacer 38" thus provides the function that is given by the bearing part 24 in the embodiment of Figure 1. in order for the spacer 38' also to be able to fulfill the function of the electrically insulating member 22 of Figure 1, the spacer 38' is formed from an electrically insulating material, such as a ceramic.
In the embodiment of Figures 2 to 4, the tubular intermediate part 30 has an interference fit with the iower end of the body 8, adjacent a fixing zone 32. Between that fixing 2one 32 and the zone in which the finger 10' has an interference fit within the tubular intermediate part 30, there is a deformation zone 42, The latter promotes the transmission of the forces exerted by the ambient pressure in the combustlon chamber on the finger 10' to the pressure sensor 14.
Figure 5 shows a third embodiment of a glow plug according to the invention. A spacer 38' according to the invention is again to be found in this glow plug. In this and the following Figures, the reference numerals of the preceding Figures are used for similar members.
The variant embodiment of Figure 5 may be considered as a combination of the embodiments of Figure 1 and of Figures 2 to 4. In this embodiment there is once again a body 8 bearing a finger 10 at one side and a pressure sensor 14 at another side. This sensor comprises a plezo-electric element 18 sandwiched between two contact elements 20. This sensor is located between a nut with an external screw thread 36 and a spacer 38'. A core 12 is oonnected to the finger 10 and passes through the spacer 38', the pressure sensor 14 and the nut with an external screw thread 36.
The spacer 38' is of the same type as that described with reference to Figures 2 to 4, It thus comprises a tubular circular cylindrical portion and ends with a frusto-conical portion 40 located adjacent the pressure sensor 14. It can be seen in Figure 5 in what way this spacer Is mounted in the body 8. Adjacent the pressure sensor 14, the spacer 38' has a bearing surface which substantially corresponds to the surface of the pressure sensor 14. This bearing surface is substantially perpendicular to the longitudinal axis of the spacer 38' and is of
annuier shape, The central recess of that annutus corresponds to the passage for the Gore 12.
At its other end, the spacer 38' comes to rest against a shoulder 50, The latter is formed In the vicinity of the and of the finger 10 located within the body 8, Thus, the opposite and of the spacer 38' to the frusto-conical zone 40 Is located doss to the finger 10 but does not rest thereon. The spacer 36' nevertheless passes on the forces exerted by the ambient pressure In the corresponding combustion chamber to the pressure sensor. This is because the body 8 has a deformation zone 42' located between the zone in which the finger 10 fits with an interference fit within the body 8 and the screw thread 16, It is considered that the screw thread is not deformable since It is mounted in the cylinder head 6 which is of high stiffness. As the shoulder 50 against which the spacer 38" rests Is located close to the finger 10 and to the zone In which that finger 10 has an interference fit with the body 8, it enables the pressure sensor 14 to nevertheless to experience the stresses exerted on the finger 10, This is because the pressure sensor 14 is located between the nut with an external screw thread 36 and the spacer 38'. The nut with outer screw thread 36 is fastened to the wall 46 which is fixed with respect to the cylinder head. This is because this wall Is situated to the exterior of the cylinder head and is not subject to any significant stress. If It is then considered that the ceramic material of the spacer 38' is stiff and does not deform, the forces exerted on the finger 10 are passed on to the pressure sensor 14 by the spacer 38",
As is apparent from the above description, adjacent the pressure sensor 14, the spacer 38" flares such that its outer diameter adapts itself to the diameter of the pressure sensor, Thus the spacer 38' may come to bear on the
whole surface of the pressure sensor 14. This flared form Is preferably produced close to the pressure sensor 14. This is because, in this way, the mass of the spacer 38' Is limited. Furthermore, this embodiment is adapted to the internal form of the body, or more gensraly of the tubular part, In which the spacer 38' Is found.
In the embodiment of Figures 3 and 4, it was considered that the flared zone of the spacer 38' was frusto-conlcal. The examples of Figures 6 and 7 show other embodiments,
in Figure 6, the flared form is a succession of frusto-conica! sections 52 of which the spray angle at the vertex increases on approaching the pressure
sensor 14. The apacer 38' ends adjacent the pressure sensor 14 with a circular cylindrical zone 54 (with a central hole for the passage of the core 12) of email thickness, in this way it is avoided to have a sharp angle on the upper edge of the spacer 38\ which is difficult to produce and is fragile.
In Figure 7, another non-fruito-conloal widening form is shown by way of example, hen the widening of the diameter is progressive and no intersection lines are found such ad those delimiting the frusto-conical sections 52 of Figure 6. However, there is again found here a circular cylindrical section 54 adjacent the pressure sensor for the same reasons as those given earlier.
As can be noted in the embodiments provided in Figures 2 to 7, no part other then the spacer 381 is situated between the finger of the glow plug described and its pressure sensor In this way the number of parts necessary to manufacture the glow plug provided with its pressure sensor is limited as is the number of interfaces in the transmission of the force exerted by the ambient pressure within the combustion chamber as far as the pressure sensor.
it is thus achieved to limit the production cost of the glow plug equipped with a pressure sensor and despite the reduction In cost, the sensor equipping that glow plug may have better sensitivity when making a pressure measurement.
The present invention is not limited to the embodiments described above by way of non limiting example, It concerns on the contrary all the variant embodiments accessible to the person skilled in the art.
Thus, for example, the spacer according to the invention could be produced from a material other than ceramic. An electrically conductive material may even be envisaged. To electrically insulate the sensor on the spacer side. when the sensor is for example a piezoelectric sensor, all means may be envisaged. A surface treatment may for example be suggested making It poesibie to render the bearing face of the spacer electrically insulating, on which face the pressure sensor rests.
The widening of the outer diameter of the spacer is preferably made m the immediate proximity of the pressure sensor, However, this widening may be made at another place on the spacer
The spacer according to the invention is described with respect to two different types of glow plug. Of course, this spacer may be used on other types of glow plug comprising a sensor, for example a piezoelectric sensor, and a spacer
for the transmission of forces towards that sensor.
1. A glow plug for an internal combustion engine comprising a plezo
electric pressure sensor as wall as a force transmitting device (38) having the
form of a tubular member of substantially circular section,
characterized in that the force transmitting device (38') comprises a zone (40) In which its outer diameter increases towards one of its ends, and in that the front face of the device corresponding to that flared end is a bearing face adapted to receive a pressure sensor (14).
2. A glow plug according to claim 1, characterized In that the force
transmitting device (38') Is formed from a ceramic material.
3. A glow plug according to one of claims 1 or 2, characterized in that
the force transmitting device (38!) has a central hole of substantially constant
4. A glow plug according to one of claims 1 to 3, characterized in that
the flared end of the force transmitting device (38') bears against a face of the
pressure sensor (14) and substantially corresponds to the surface of said sensor.
5. A glow plug according to one of claims 1 to 4, characterized in that it
comprises at one of its ends a finger (10, 10') incorporating a heating electrode,
and in that the force transmitting device (38') is arranged between said finger (10,
10') and the pressure sensor (14).
6. A glow plug according to claim 5, characterized in that the finger (10,
10') is fixed inside a tubular member (8), at one end of the tatter, and in that said
tubular member (8) has an inner shoulder (50) which the force transmitting device
(38') rests against.
7. A glow plug according to claim 6, characterized in that the outer
diameter of the force transmitting device (38') is less than the Inner diameter of the
tubular member (8,30) within which It is housed.
8. A glow plug according to one of claims 5 to 7, characterized In that it
comprises a conducting core (12) supplying the heating electrode of the glow plug
with electrical energy, and in that said core (12) passes freely within the force
transmitting device (38').
9. An internal combustion engine, in particular of the diesel engine type,
characterized in that it comprises a glow plug according to one of claims 1 to 8.
|Indian Patent Application Number||3948/CHENP/2006|
|PG Journal Number||18/2010|
|Date of Filing||27-Oct-2006|
|Name of Patentee||SIEMENS VDO AUTOMOTIVE|
|Applicant Address||1, AVENUE PAUL OURLIAC, 31036 TOULOUSE, FRANCE.|
|PCT International Classification Number||F23Q7/00|
|PCT International Application Number||PCT/FR05/00934|
|PCT International Filing date||2005-04-19|