WO2006131410A1

WO2006131410A1 - Sheathed-element glow plug having an integrated combustion chamber pressure sensor

Info

Publication number: WO2006131410A1
Application number: PCT/EP2006/061440
Authority: WO
Inventors: Christoph Kern; Steffen Schott; Pavlo Saltikov
Original assignee: Robert Bosch Gmbh
Priority date: 2005-06-07
Filing date: 2006-04-07
Publication date: 2006-12-14
Also published as: EP1891375A1; JP4644282B2; JP2008545918A; DE102005026074A1

Abstract

Information about the combustion chamber pressure in the combustion chamber of an internal combustion engine is required for efficient and low-pollutant engine control. An integrated combustion chamber pressure sensor is therefore proposed in the form of a sheathed-element glow plug (110) for a compression-ignition internal combustion engine. The sheathed-element glow plug (110) has a heating body (112) and a plug housing (116). Furthermore, the sheathed-element glow plug (110) has at least one force-measuring film element (126), the at least one force-measuring film element (126) being connected to the heating body (112) in such a way that a force (124) can be transmitted to the at least one force-measuring film element (126) via the heating body (112). In particular, the at least one force-measuring film element (126) can have at least one piezoelectric film (134), for example a piezoelectric film (134) made from highly polarized polyvinylidene fluoride (PVDF).

Description

Glow plug with integrated combustion chamber pressure sensor

The invention relates to a glow plug for self-igniting internal combustion engines with a combustion chamber pressure sensor integrated in the glow plug. The glow plug has as combustion chamber pressure sensor at least one force measuring foil element. With such integrated combustion chamber pressure sensors, in particular combustion chamber pressure signal-based engine controls for internal combustion engines can be realized.

State of the art

In the course of the constant tightening of the statutory emission regulations, in particular for diesel engines, the requirements for a reduced pollutant emission of internal combustion engines, in particular self-igniting internal combustion engines, are becoming more stringent. Modern engine management systems are to ensure low fuel consumption and at the same time have a long service life.

A combustion optimization in the combustion chamber of a diesel engine can be achieved in particular by the use of a regulated injection of fuel. In particular, this controlled injection can be controlled by electronic engine control devices which have already been established in modern motor vehicles. However, the successful execution of combustion chamber pressure signal-based engine control (CSC) depends on the availability of production-suitable pressure sensors, which have to meet high requirements in terms of price, reliability, accuracy and space.

At present, measuring devices are widely used that have so-called "stand-alone" sensors, which require a separate hole in the cylinder head wall, which means additional installation effort which is a considerable problem, especially in the case of four-valve engines, owing to the limited space available, and the price of such systems is generally comparatively high, and the lifetime of such systems is usually due to the high operating temperatures, significantly shorter than a typical vehicle life.

Accordingly, there are approaches in the prior art to integrate combustion chamber pressure sensors into already existing components of the cylinder head. An example of such an integration are spark plugs with integrated piezoelectric force measuring element, which are known for example from DE 694 05 788 T2. This document discloses a spark plug with built-in pressure sensor, wherein the pressure sensor has at least one pressure introduction channel, which connects the combustion chamber of an associated cylinder of the internal combustion engine with the pressure sensor.

Such sensor integration in already existing components of the cylinder head brings a significant price advantage and makes a large-scale production economically possible. Such systems eliminate the need for direct access to the combustion chamber. On the other hand, the signal quality of such combustion chamber pressure sensors depends strongly on the force curve in the entire mechanical composite and usually does not meet the requirements.

Also in the field of diesel engines such integration approaches are known. For example, DE 196 80 912 C2 discloses a glow plug with integrated pressure sensor. In this case, the pressure sensor between a fixing member and a heating portion of the glow plug is arranged. However, the device disclosed in DE 196 80 912 C2 has numerous disadvantages for practical implementation. In particular, these disadvantages consist in the fact that the pressure sensor used is technically located at an unfavorable position, since on the one hand it blocks a power supply to the heating section of the glow plug and on the other hand generally has no long service life due to high thermal load and high mechanical shock load. Furthermore, the fixation of the pressure sensor by means of the fixing member is complex and can easily lead to a malpositioning of the pressure sensor and thus to a malfunction during assembly.

Advantages of the invention

According to the invention, therefore, a glow plug for a self-igniting internal combustion engine is proposed, which avoids the disadvantages of the prior art described.

A basic idea of the present invention is to use at least one force measuring foil element, in particular a force measuring foil element which has at least one piezo foil, for measuring a combustion chamber pressure of an internal combustion engine. Zen. In this case, the force measuring foil element can be used in integrated combustion chamber pressure sensors, for example in combustion glow pressure sensors integrated in glow plugs or in spark plugs, or it can also be used in so-called stand-alone combustion chamber pressure sensors.

Another basic idea is to integrate at least one force measuring foil element into a glow plug which has a heating element and a plug housing. This force measuring foil element should be connected to the heating element in such a way that a force can be transmitted to the at least one force measuring foil element via the heating element. In particular, this at least one force measuring foil element can generate an electrical signal as a function of a force which is exerted on the at least one force measuring foil element via the heating body. Thus, when the glow plug is integrated into the cylinder head of an internal combustion engine, exerted by the combustion chamber pressure of the internal combustion engine, a force on the radiator of the glow plug. About the radiator, this force is transmitted to the at least one force measuring foil element, whereby an electrical signal can be generated, from which on the force and thus the pressure in the combustion chamber is rückschließbar.

In particular, the proposed force sensing foil element is characterized by its small thickness and high flexibility over conventional force sensing elements such as conventional pressure sensors (e.g., piezoceramics). In particular, the at least one force-measuring foil element may have at least one force measuring foil, which advantageously has a foil thickness in the range of 3-50 μm, preferably in the range of 5-100 μm and particularly preferably in the range of 8-30 μm. For example, this may be a piezo film, preferably a piezo film which has polyvinylidene fluoride. Such piezo films are typically commercially available with a thickness down to about 8-9 μm. However, any other materials of appropriate piezoelectric and mechanical properties can be used. Other types of force measuring foils can also be used in principle, which are not based on a piezo effect and which are known to the person skilled in the art, for example force measuring foils with strain gauges.

The at least one force measuring foil element can be used according to the invention in various ways, wherein preferably a transverse piezoelectric effect and / or a longitudinal piezoelectric effect and / or a piezoelectric shear effect is used. These effects can be exploited in various ways. To be particularly advantageous, it has been found that at least one force transmission element is used for transmitting power between the radiator and the at least one force measuring foil element. For example, this power transmission element can essentially chen be configured as a cylinder sleeve. The at least one force-measuring foil element can be used on a surface of the at least one force transmission element parallel to an axis of the glow plug or even on an end face perpendicular to this axis, whereby, for example, different piezoelectric effects (eg longitudinal and transverse piezoelectric effect) are utilized , The design of the at least one force-measuring foil element has the particular advantage that space inside the glow plug is optimally utilized, whereby, for example, sufficient space for a power supply to the radiator of the glow plug remains.

Furthermore, at least one insulating element may be arranged between the heating element and the at least one force measuring foil, for example at least one insulating sleeve, the at least one insulating element reducing heat transfer between the heating element and the at least one force measuring foil element relative to a construction without such an insulating element. In particular, this at least one insulating element may comprise a thermally insulating material. For example, the at least one insulating element between the radiator and the at least one force transmission element to be embedded.

The glow plug according to the invention has considerable advantages over the devices known from the prior art. Thus, in particular, the at least one force measuring foil element can be produced in virtually any dimensions and geometries. Furthermore, the at least one force measuring foil element is flexible and can therefore be used as a force sensor on almost any desired shaped surfaces. In general, such force measuring foil elements, in particular piezo foils, are suitable for the measurement of forces, pressures, bends, strains, accelerations, vibrations and / or shears. In this case, it is possible to make use of experiences from other areas of technology, so that in particular, for example, electronic circuits for controlling and evaluating such force measuring film elements can be adapted without great development effort.

The proposed construction of a glow plug thus also allows a simple design and installation taking advantage of the small space within a glow plug. As a result, in particular development and / or production costs are significantly reduced. Furthermore, the reliability of the glow plugs over conventional integrated pressure sensors is considerably improved, since in particular no fracture-prone pressure measuring elements made of piezoelectric ceramics or single crystals must be used. Nevertheless, the sensitivity of the pressure measurement compared to most known from the prior art solutions for Brennraumdruckmess- technology, such as quartz pressure sensing elements, significantly increased. The use of Force measuring foil elements further avoids or reduces the need for costly electrical and thermal insulation measures. Due to the advantageous use of space can also be dispensed with a construction with extremely thin-walled steel components with high tolerance requirements.

Specifically, the proposed solution, in which one or more sleeves, such as a sleeve made of steel or other metals, is used as a force transmission element, offers numerous advantages. Thus, the construction space is optimally utilized in particular by this construction. Furthermore, the Glühstromzuleitung can be passed through the inner opening of the sleeve. In this case, for example, as the Glühstromzuleitung a steel connection pin used in the prior art can be used, or it can be used according to the invention, a thin or flexible Drahtglühstromzuleitung. The sleeve-shaped force transmission element offers the advantage that due to a shielding effect through the sleeve, in particular the metallic sleeve (Faraday cage), the at least one force measuring foil element is protected against influences by electromagnetic fields of the glow current feed line. As a result, the signal characteristic and the susceptibility of the integrated combustion chamber pressure sensor is significantly improved.

drawing

Reference to the drawings, the invention will be explained in more detail below.

It shows:

Figure 1 shows a first embodiment of a glow plug according to the invention, in which a transverse piezoelectric effect is utilized;

FIG. 2 shows a perspective detailed representation of a force-measuring foil element of the exemplary embodiment according to FIG. 1;

Figure 2 A is a sectional view of the layer structure in the area A in Figure 2;

Figure 2B is a sectional view of the layer structure in region B in Figure 2;

FIG. 2C is a sectional view of the layer structure in region C in FIG. 2;

FIG. 2D is a sectional view of the layer structure in region D in FIG. 2; Figure 3 shows a second embodiment of a glow plug according to the invention, in which a longitudinal piezoelectric effect is utilized;

FIG. 4 shows a detailed representation of the force-measuring foil element used in the exemplary embodiment according to FIG. 3;

Figure 4A is a sectional view of the layer structure in the region E in Figure 4;

Figure 4B is a sectional view of the layer structure in the area F in Figure 4;

FIG. 4C is a sectional view of the layer structure in region G in FIG. 4; and

FIG. 4D is a sectional view of the layer structure in the region H in FIG. 4.

Exemplary embodiments

FIG. 1 shows a first, preferred exemplary embodiment of a glow plug 110 according to the invention. The glow plug 110 has a ceramic heater 112 which is mounted in a sealing cone 114 of a housing 116 of the glow plug 110. This attachment can preferably be carried out by soldering, but also by other attachment methods, such as gluing, welding or screwing. As a result, an inner space 118 of the glow plug 110 is sealed against a combustion chamber of an internal combustion engine.

The ceramic heater 112 has a combustion chamber facing the pressure surface 120, which is flat and perpendicular to an axis 122 of the glow plug 110 in this embodiment. Via the pressure surface 120, a pressure in the combustion chamber of the internal combustion engine is converted into a force F (reference number 124 in FIG. 1) parallel to the axis 122 on the ceramic heating element 112. By means of this force 124 on the ceramic heating element 112, a linear-elastic deflection of the parts of the glow plug 110 located in the force path is effected, which is typically in the range of a few micrometers for the occurring combustion chamber pressures. The force 124 and the associated with this force deflection of the glow plug 110 thus correlates directly with the combustion chamber pressure.

In principle, it is known from the prior art to measure this force 124 by fixing a force-measuring element in the glow plug 110 in such a way that it absorbs the force pulses of the heating body 112 via an end face facing the heating body 112. In the case of a piezoelectric force element is in a mechanical Load of this end face generates a charge and thus a voltage, which in turn can be tapped from surfaces of the force measuring element by means of a metallization and contacting. This electrical signal is led out via signal lines for evaluation. In this case, piezoelectric force measuring elements may be both ferroelectric piezoceramics (eg lead zirconate titanate, PZT) and monocrystalline materials such as quartz, langasite, lithium niobate, gallium orthophosphate or the like.

In contrast, in the first exemplary embodiment according to the invention according to FIG. 1, a force-measuring foil element 126 is used to detect the force 124. This force measuring element 126 generates an electrical signal which can be supplied via signal lines 128 via a plug connector 130 at the end of the glow plug 110 facing away from the combustion chamber to a corresponding evaluation electronics (not shown). For example, as mentioned above, this electrical signal can be supplied to an engine control unit in order to realize a combustion chamber pressure signal-based engine control (combustion signal based control system, CSC).

In principle, according to the invention, the force-measuring foil element 126 is used in such a way that it is connected to an element of the glow plug 110 via which the force 124 can be transmitted (in whole or in part) to the force-measuring foil element 126. The force measuring foil element 126 thus acts as a piezoelectric transducer. In the exemplary embodiment according to FIG. 1, the force-measuring foil element 126 is applied to an outer circumferential surface 133 of a rigid cylindrical transmission element 132 designed in the form of a cylindrical sleeve. Due to the flexibility of the force measuring foil element 126, this application to a curved surface 133 is easily possible.

FIG. 2 shows the force-measuring film element 126 in a perspective detail view. The force measuring foil element 126 has a piezo foil 134 as an essential element. This thin piezo foil 134 can have, for example, highly polarized polyvinylidene fluoride (PVDF) as the piezoelectric material. This material is commercially available in many embodiments and for many printing ranges, for example perpendicular to the film surface for a printing range of 10 ^"8 N / cm ² to 10 ⁵ N / cm ² , as well as in a frequency range for applications from 0.001 Hz to the gigahertz range Such piezo foils 134 are usually applicable at operating temperatures between -200 ° C and 160 ° C.

With modern manufacturing processes, commercial PVDF films can be produced down to the order of about 9 μm. Such low film thicknesses provide a great deal of leeway when used in extremely tight installation conditions. This is as described above. ben, for use in a Kraftmessfolienelement 126 in a glow plug 110 due to the low available installation space in the interior 118 of the glow plug 110 of particular advantage. Typically, the interior 118 of the glow plug 110 has a diameter of only about 5 mm. This available cross-sectional area with a diameter of 5 mm should be used for the Kraftmessfolienelement 126, its electrically insulated signal lines 128, and a Glühstromzuleitung 136 for charging the ceramic heater 112 with a glow current, and optionally for further required insulation and shielding measures, for example, for vibration isolation , In this case, a need for a centered positioning of a sensor element in the housing 116 of the glow plug 110 would make particularly disadvantageous, since such design variants often require the production of extremely thin-walled steel components and corresponding electrical insulation with costly coating processes required. The use of piezo films 134, in particular of the PVDF films mentioned, avoids these disadvantages.

According to the structure of the force measuring foil element 126 shown in FIG. 2, the piezo foil 134 in this exemplary embodiment is a central element of the force measuring foil element 126. This piezo foil 134 is sandwiched between two electrode layers 138, for example in the form of corresponding metallization layers 138, of which the perspective structure according to FIG 2, only the outermost electrode layer 138 is visible. These electrode layers 138 are contacted by means of the electrical signal lines 128. Finally, in order to protect the force measuring foil element 126, the sandwich of the electrode layers 138 and the piezo foil 134 is surrounded by a dielectric protective lamination 140, which protects the component against mechanical stresses and environmental influences, such as moisture. Part of the electrical signal lines 128 is also covered and protected by the dielectric protective lamination 140.

Shown in FIGS. 2A to 2D are layer constructions of the structure according to FIG. 2 in the regions indicated by A, B, C, D in FIG. 2, in a sectional representation. It can be seen in FIG. 2A that in region A the force transmission element 132 is covered only by the dielectric protective lamination. Thus, this area A serves only to mechanically stabilize and protect the edges of the force sensing foil member 126, but has no electrical function. The area B shown in FIG. 2B, on the other hand, is the actual force measuring area. Here, the electrode layer 138 - piezo film 134 - electrode layer 138 is applied to the force measuring element 132 of the sandwich structure described above, the sandwich structure being separated from the force measuring element 132 by the dielectric protective lamination 140. FIG. 2C shows the contacting region C, which fundamentally corresponds in construction to the region shown in FIG. 2B. In addition, however, it is shown here how the electrode layers 138 are electrically contacted by means of the electrical signal lines 128 in order to attack the piezoelectric signal and to move it outwards as a measuring signal. In this case, the electrical signal lines 128 are each covered on their side remote from the piezo foil 134 by the dielectric protective lamination 140 and thus electrically insulated. Finally, FIG. 2D shows how, in the area D (see FIG. 2), the electrical signal lines 128 embedded in the dielectric protective lamination 140 are led out of the force measuring element 126 perpendicular to the plane of the drawing.

Commercially available are such Kraftmessfolienelemente 126 with piezo films 134, which, including the electrode layers 138, corresponding contacts 142 of the electrode layers 138 and the outer dielectric Schutzlaminierung 140 have a thickness of only about 0.1 to 0.2 mm. Such force measuring foil elements 126 can be adapted to three-dimensionally curved surfaces, for example with the aid of hot drawing techniques. As a result, the space within the glow plug 110 can be optimally utilized. In the exemplary embodiment according to FIGS. 1 and 2, for example, the force-measuring foil element 126 is applied to the outer circumferential surface 133 of the sleeve-shaped, rigid force-transmitting element 132. In this exemplary embodiment, the force transmission element 132 has, for example, steel or ceramic as the material. The force transmission element 132 is arranged in the force path of the force 124 and thus exposed to a dynamic force by the combustion chamber pressure. The sleeve-shaped geometry of the force transmission element 132 has the advantage that the Glühstromzuleitung 136 can be performed centrally in the housing 116 of the glow plug 110 to the ceramic heating element 112, which currently makes commercially used manufacturing process for glow plugs 110 continue to use (with minor modifications). The use of steel as a material for the force transmission element 132 has the advantage that the probability of fracture is negligibly small in comparison with the prior art pressure measuring elements made of piezoelectric ceramics or single crystals. For thermal and / or electrical insulation of the sleeve-shaped force transmission element 132 against the ceramic heater 112, an insulating sleeve 144 or an insulating disk is used according to the invention in this embodiment shown in FIG. This may be, for example, a ceramic insulating sleeve 144 or a plastic sleeve.

In the arrangement of the force-measuring foil element 126 shown in FIG. 1 on the cylinder-sleeve-shaped force transmission element 132, in particular a transverse piezoelectric effect of the piezo foil 134 is utilized. In the case of such piezo foils, for example the above-mentioned PVDF foils, this transverse piezoelectric effect is increased by approximately one size. Stronger (eg PVDF: d ₃₁ = 23 pC / N) than common quartz pressure measuring elements.

A further advantage of the arrangement according to FIG. 1 is that the contacts 142 are not in line with the force path of the force 124. Thus, the contacts 142 are not directly exposed to the pressure effects, which could lead to impairment of the contact properties. Again, there is an advantage of the proposed arrangement over arrangements known in the art. Furthermore, an advantage of the device according to FIG. 1 is that the force transmission element 132, which, as described above, may for example comprise metallic materials, shields the glow current feed line 136. This minimizes the effect of the electromagnetic fields emanating from the glow current lead 136 on the force sensing foil element 126.

FIGS. 3 and 4 show an alternative embodiment to the exemplary embodiment according to FIGS. 1 and 2, in which a longitudinal piezoelectric effect is utilized. Of course, combinations of the embodiments with transversal and longitudinal piezoelectric effect are conceivable. A combination of force-measuring foil elements 126 with "conventional" force-measuring elements is also conceivable. In the exemplary embodiment according to FIG. 3, the glow plug 110 again has a ceramic heating body 112 and a housing 116, both components 112 and 116 basically being identical or identical to the exemplary embodiment according to FIG 2, a force measuring foil element 126 is used, which is arranged as an annular disc on an end face 146 of the force transmission element 132. This end face 146 is oriented perpendicular to the force 124 and thus to the axis 122. Also slight deviations from the Verticals are conceivable, for example deviations of up to 10 °.

FIG. 4 shows in perspective the force-measuring foil element 126 in detail. Again, the Kraftmessfolienelement 126 has a piezoelectric film 134 as a core element which is embedded on the end face 146 of the force transmission element 132 between two metallic electrode layers 138 in this embodiment, and is protected and insulated by a dielectric protective lamination 140 accordingly. The electrode layers can in turn be contacted by means of two contacts 142 and the electrical signal lines 128. The force measuring foil element 126, which is designed in the form of a circular ring, can be glued onto the end face 146, for example. The insulated electrical signal lines 128 are guided axially on the mantle surface of the sleeve-shaped force transmission element 132 to the plug connection 130. In FIGS. 4A to 4D, layer structures of the structure according to FIG. 4 are shown in a sectional view in the regions indicated by E, F, G, H in FIG. In the region E shown in FIG. 4 A, which lies in the region of the end face 146 of the force transmission element 132, there is a sandwich structure analogous to the layer structure described above in FIG. 2B, in which a piezo film 134 is embedded between two electrode layers 138 and from Power transmission element 132 is separated by the dielectric protective lamination 140. FIGS. 4B and 4C show the contacts 142 of the electrode layers 138 through the electrical signal lines 128. FIG. 4B shows the contacting of the upper electrode layer 138 (ie facing away from the force transmission element 132) in FIG 4 referred to as area G contacting the lower (ie the power transmission element 132 facing) electrode layer 138. Again, the e- lektrischen signal lines 128 each on their side facing away from the piezoelectric film 134 side of the dielectric protective lamination 140 covered and thus electrically isolated , The contacts 142, that is to say the regions F, G, lie in the region of the edges of the force transmission element at which the end face 146 merges into the lateral surface 133. Finally, in FIG. 4D, the regions marked H in FIG. 4 are shown in section. In these areas, analogous to FIG. 2D, the electrical signal lines 128 are embedded in the dielectric protective lamination 140 and led out of the force measuring film element 126 perpendicular to the plane of the drawing.

In the exemplary embodiment according to FIG. 3, the force-measuring foil element 126 is embedded between the insulating sleeve 144 and the sleeve-shaped force transmission element 132, which in turn is counteracted by a corresponding counter bearing 148 on the side of the glow plug 110 facing away from the combustion chamber. Thus, therefore, upon application of the force 124 to the ceramic heater 112, the force sensing foil member 126 is compressed between the force transmitting member 132 and the insulating sleeve 144. The insulating sleeve 144 thus forms in this embodiment, a part of the power transmission path from the ceramic heater 112 to the Kraftmessfolienelement 126. By this force on the Kraftmessfolienelement 126 in turn via the piezoelectric effect, a voltage is generated, which can be tapped by the electrical signal lines 128. In this embodiment, the longitudinal piezoelectric effect is utilized. The piezoelectric coefficient of said piezo film 134 of highly polarized polyvinylidene fluoride (PVDF) is, for example, for the longitudinal piezoelectric film.

It should be noted that numerous alternative to Figure 3 alternative embodiments are possible in which the longitudinal piezoelectric effect is used. For example, the insulating sleeve 144 and also the force transmission element 132 can be segmented from be designed, between a plurality of these segments force measuring foil elements 126 are embedded, the signals of which can be averaged, for example. Also, a configuration is possible in which the force sensing foil member 126 is located farther from ceramic heater 112 to minimize thermal effects on the force sensing foil member 126. For example, the force measuring foil element 126 could be arranged in the region of a thread 150, via which the glow plug 110 is screwed into a combustion chamber wall. There are comparatively low temperatures and temperature fluctuations.

LIST OF REFERENCE NUMBERS

110 glow plug

112 ceramic radiator

114 sealing cone

116 housing

118 interior

120 printing area

122 axis

124 power

126 force measuring foil element

128 electrical signal lines

130 plug connection

132 power transmission element

133 lateral surface

134 piezo film

136 Glühstromzuleitung

138 electrode layer

140 dielectric protective lamination

142 contacts of the electrode layers

144 insulation sleeve

146 face

148 counter bearing

150 threads

Claims

claims

1. glow plug (110) for a self-igniting internal combustion engine having a radiator (112) and a plug housing (116) and at least one force measuring foil element (126), wherein the at least one force measuring foil element (126) is so connected to the radiator (112), a force (124) can be transmitted to the at least one force-measuring film element (126) via the heating body (112).

2. glow plug (110) according to the preceding claim, characterized in that the at least one Kraftmessfolienelement (126) at least one piezo film

(134).

3. glow plug (110) according to the preceding claim, characterized in that the at least one piezo film (134) comprises polyvinylidene fluoride.

4. glow plug (110) according to any one of the preceding claims, characterized in that the at least one Kraftmessfolienelement (126) at least one Kraftmessfolie (134), wherein the force measuring film has a film thickness in a range of 3 microns to 500 microns, preferably in one area from 5 microns to 100 microns, and more preferably in a range of 8

Microns to 30 microns.

5. glow plug (110) according to one of the preceding claims, characterized in that the at least one Kraftmessfolienelement (126) generates an electrical signal in response to a force (124), wherein at least one of the following

Effects is used: transversal piezoelectric effect; longitudinal piezoelectric effect; piezoelectric shear effect.

6. glow plug (110) according to one of the preceding claims, characterized by at least one force transmission element (132), wherein the at least one

Power transmission element (132) with the at least one force measuring foil element (126) is in communication, wherein by means of the at least one force transmission element (132) a force (124) from the heating body (112) on the at least one force measuring foil element (126) is transferable.

7. glow plug (110) according to the preceding claim, characterized in that at least one Kraftmessfolienelement (126) with at least one substantially perpendicular to an axis (122) of the glow plug (110) arranged end face (146) of the at least one force transmission element (132) connected is.

8. glow plug (110) according to one of the two preceding claims, characterized in that at least one Kraftmessfolienelement (126) with at least one substantially parallel to the axis (122) of the glow plug (110) surface (133) of the at least one force transmission element (132) connected is.

9. glow plug (110) according to one of the three preceding claims, characterized in that the at least one force transmission element (132) is designed substantially as a cylinder sleeve.

10. glow plug (110) according to one of the preceding claims, characterized by additionally at least one insulating element (144), in particular at least one insulating sleeve (144), wherein the at least one insulating element (144) between the heating body (112) and the at least one force measuring foil element ( 126) is arranged and wherein the at least one insulating element (144) is designed such that it has a

Heat transfer between the radiator (112) and the at least one Kraftmessfolienelement (126) reduced.

11. Use of at least one force measuring foil element (126) for measuring a combustion chamber pressure of an internal combustion engine.

12. Use according to the preceding claim, characterized in that the at least one force measuring foil element (126) has at least one piezo foil (134).