JP2008541075A - Sheath type glow plug with combustion chamber pressure sensor - Google Patents

Abstract

  The present invention is directed to a sheath-type glow plug for a self-igniting internal combustion engine having an integrated combustion chamber pressure sensor for measuring the combustion chamber pressure for the purpose of engine control based on the combustion chamber pressure signal. 110). In the configuration of the present invention, such a sheath-type glow plug includes a heating body (112), a plug housing (114), and a plug axis (124), and the plug housing (114) includes the heating body (112). A receiving region (116) for receiving the body, a housing body (120), and at least one flexibility region (118) disposed between the housing body (120) and the receiving region (116). In addition, at least one force measuring element (136) is provided in the plug housing (114).

Description

  The present invention relates to a sheath-type glow plug incorporating a combustion chamber pressure sensor. Such a sheath-type glow plug is particularly used for measuring the combustion chamber pressure in a self-ignition internal combustion engine.

2. Description of the Related Art As exhaust gas regulations, particularly exhaust gas regulations for diesel engines, become increasingly strict, there is an increasing demand for reducing harmful substance emissions in self-igniting internal combustion engines. Today's engine management systems want to ensure low fuel consumption and at the same time have a long service life with low hazardous substance emissions. Combustion optimization in the combustion chamber of a diesel engine can be achieved in particular by the introduction of a controlled injection of fuel. This controlled injection can in particular be controlled by an electronic engine control device already established in today's automobiles. The effective configuration of a combustion signal based control system (CSC) based on the combustion chamber pressure signal, however, depends on the procurement of a pressure sensor suitable for manufacturing. High requirements regarding performance, accuracy and structural space must be met. Today, so-called “stand-alone” type sensors, ie measuring devices with independent sensors, are widespread. In order to use such a measuring device, it is necessary to provide a separate hole in the cylinder head wall, which is impossible in some cases for reasons of space, and if possible Installation cost or installation cost. Particularly in today's four-valve internal combustion engines, it is almost impossible to provide additional holes due to the very narrow space situation. Furthermore, usually the price of such systems is relatively expensive and the useful life of such systems is often significantly shorter than the typical vehicle useful life based on high operating temperatures.

  Therefore, in the prior art, an additional portion is provided for incorporating the combustion chamber pressure sensor into an existing cylinder head component. For example, there is an additional portion for incorporating a combustion chamber pressure sensor into a sheath-type glow plug. For example, DE 19680912C2 discloses an apparatus and method for detecting cylinder pressure in a diesel engine. This device has a pressure sensor, a heating section of a glow plug that is received in the inner chamber of a cylinder of a diesel engine and is loaded by the cylinder pressure, and a fixing member for fixing the heating section to the body of the glow plug. is doing. In this case, the pressure sensor is arranged between the heating section and the fixing member of the glow plug. The cylinder pressure is transmitted to the pressure sensor through the heating section.

  However, the device disclosed in DE 19680912C2 has many disadvantages in practice. In particular in this known device, the sheath of the glow glow plug is substantially tightly coupled to the cylinder head, whereas the heating section introduces a force and, to a slight extent, moves relative to the housing. Do. This can also cause friction and thus degrade the combustion chamber pressure signal, and in addition, a fixed sheath-type glow plug portion and a movable sheath-type glow plug portion (eg, tightly coupled to the cylinder head). This may cause carbon to adhere to the guide between the two. Another disadvantage of the device disclosed in DE 19680912C2 is that the housing and the component transmitting the force expand at different values. Due to the different expansions caused by the temperature difference when using the internal combustion engine and the difference in thermal expansion characteristics of the components involved, the preload of the inserted sensor will fluctuate greatly, which in terms of durability Problems can arise. Another disadvantage of the device disclosed in DE 19680912C2 is that the pressure sensor is in direct contact with the heating section and is thus exposed to high heat loads and temperature fluctuations. Furthermore, the assembly or assembly of such known devices is quite cumbersome and expensive.

Advantages of the invention The object of the present invention is therefore to provide a sheath-type glow plug for self-igniting internal combustion engines, which incorporates a combustion chamber pressure sensor and eliminates the above-mentioned drawbacks of known devices according to the prior art. Is to provide. In particular, the sheath-type glow plug according to the present invention, as described above, causes mechanical friction of the individual components of the sheath-type glow plug during operation, which causes problems in comparable devices of the prior art, Variations in sensor preload associated with temperature can be minimized. A sheath-type glow plug according to the present invention for a self-igniting internal combustion engine includes a heating element, a plug housing, and a plug axis. The basic idea of the invention is that a solid, stationary, preferably completely airtight connection between the plug housing and the heating element is produced. The function of the combustion chamber pressure sensor is obtained by the flexibility of the plug housing in the region between the threaded portion of the cylinder head and the end portion on the combustion chamber side.

  Accordingly, the sheath-type glow plug according to the present invention has a receiving region for receiving a heating body, a housing body, and at least one flexibility region disposed between the housing body and the receiving region. . In an advantageous configuration of the flexibility region, this flexibility region comprises at least one region in which the plug housing has a smaller stiffness in the direction parallel to the plug axis than in the region of the housing body. The arrangement of the invention further comprises at least one force measuring element in the plug housing, which in particular generates an electrical signal in relation to the force applied during the at least one force measuring element. It is a force measuring element that can. Basically, any force measuring element of any principle known to a person skilled in the art can be used, for example a piezoelectric force measuring element of almost any shape, a capacitive force measuring element or a strain gauge Force measurement using can be used. The at least one force measuring element is preferably received in the housing.

  The pressure in the combustion chamber must be transmitted as a force to at least one force measuring element. This force transmission can be effected directly, for example, from the heating element to the at least one force measuring element, or indirectly, for example via a plug housing or part of the plug housing. As an alternative or in addition, the sheath-type glow plug according to the invention is used for transmitting pressure, for transmitting the combustion chamber pressure to at least one force measuring element, in particular for measuring the force from the heating element to at least one force. There may be at least one separate force transmission element for transmitting to the element. This at least one separate force transmission element is, for example, a pressure rod, preferably a substantially cylindrical pressure rod, and / or a pressure sleeve, preferably a pressure sleeve that is substantially cylindrical. In this case, “substantially” can be a shape somewhat different from the cylindrical shape or the cylindrical sleeve shape. For example, the shape of the sheath-type glow plug or the shape of the inner chamber of the sheath-type glow plug is somewhat different. This means that a minute conical shape is also possible. The heating element enters the combustion chamber of the internal combustion engine, and is loaded with a pressure corresponding to the combustion chamber pressure on the pressure receiving surface, for example, the end surface. This pressure is converted by the heating body into a force transmitted from the heating body to the sheath-type glow plug. The at least one force measuring element then transmits this force directly or indirectly (ie without or through an additional intermediate element) from the heating body to the at least one force measuring element, where the force is It is converted into an electrical signal, which can be read by a corresponding electronic device and used, for example, for engine control. In this way, information regarding the combustion chamber pressure can be obtained.

  The at least one flexibility region can be configured in a wide variety of forms. The function of this flexibility area is mainly as follows. That is, in this case, when the heating element is loaded by the pressure of the combustion chamber based on the function of the flexibility region, all the front portions of the sheath type glow plug, that is, the receiving region and the heating body of the sheath type glow plug The part of the internal combustion engine that is directed to the combustion chamber can move along the plug axis and thus apply a corresponding force and thus a preload to at least one force transmission element. In contrast, the housing body in this case does not extend at all or hardly and remains substantially rigid during the elastic movement of the sheath-shaped glow plug front part. This pressure introduced into the sheath-type glow plug via at least one force transmission element can then be detected by at least one force measuring element. This pressure differs only slightly from the overall force introduced to the sheathed glow plug by the combustion chamber pressure, and is a nearly constant factor related to the rigidity of the plug housing in the flexibility region and the receiving region of the sheathed glow plug. Only the difference is. The stiffness of the at least one force transmission element is also included in this substantially constant factor.

  In a particularly advantageous configuration of the invention, the at least one flexibility region comprises at least one constriction or crease that is curved inwardly or outwardly in the elements described below, namely corrugations, plug housings. Have. Alternatively or additionally, the at least one flexibility region has at least one thin wall region of the plug housing, in particular a thin wall region relative to the adjacent region of the plug housing, or all remaining plugs. It can have a thin-walled area compared to the housing. Such a configuration also reduces the rigidity of the plug housing parallel to the plug axis in the flexibility region. Furthermore, alternatively or additionally, it is possible to use elastic elements such as spring elements, in particular coil springs or similar spring elements, or elastic elements made of metal material or plastic (for example elastomer) Such an elastic element ensures flexibility parallel to the plug axis in at least one flexibility region. In general, an element such as a material having a small elastic modulus can also be used. In this case, a small elastic modulus means in particular an elastic modulus smaller than that of the entire plug housing or the surrounding wall region.

  The heating element is preferably fixedly and firmly connected to the plug housing in the receiving area with a sealing action against pressure, preferably by a press fit. The plug housing is connected to the cylinder head, preferably by screwing. For this purpose, the sheath-type glow plug preferably additionally has at least one external thread for connecting the cylinder head of the internal combustion engine and the sheath-type glow plug. This at least one male thread is preferably a component of the housing body of the sheathed glow plug. At least one flexibility region is arranged, for example in the form of a metal bellows, between the receiving region for receiving the heating element and the connection to the cylinder head, in which the plug The housing has as little rigidity as possible in a direction parallel to the plug axis.

  The at least one force transmission element is advantageously supported on the plug housing as far forward as possible towards the combustion chamber or directly on the heating element. The at least one force transmission element is supported directly or indirectly at the opposite end by the at least one force measuring element, so that, as described above, the force is at least from the at least one heating body. It can be transmitted to one force measuring element. In the mounted state, the plug housing is preferably subjected to a tensile load, and at least one force transmission element is pressed. This load (preload) can be generated, for example, by means of screw housing or preferably by screwing or caulking of at least one force measuring element in the housing body. Advantages of the flexibility region according to the present invention include the following. In other words, by providing the flexibility region, the different thermal expansion of the plug housing and the at least one force transmission element can be compensated by the flexibility of the housing in the at least one flexibility region, and thus Variations in the preload applied to the force measuring element can be made relatively small. This improves the signal quality and avoids signal correction in various operating conditions of the internal combustion engine, which usually cause a corresponding temperature change. Furthermore, changes in the external temperature are also at least partially compensated. An axial force does not act on the heating element when the internal combustion engine is stopped, and the joint between the heating element and the plug housing is not loaded when the engine is stopped.

  As already mentioned above, in an advantageous configuration, at least one force transmission element is supported at one end directly or indirectly (for example via an intermediate element) on at least one force measuring element. In this case, the at least one force transmission element is supported at the other end directly on the heating element or alternatively or additionally on at least one flexibility region. The at least one force transmission element is supported, for example, in a corrugated part in the flexibility region directed towards the interior of the plug housing. As an alternative or in addition, the at least one force measuring element may be arranged in a plug housing area arranged between the at least one flexibility area and the at least one heating body. For example, at least one support element can be used therefor, such a support element serving to support at least one force transmission element on the plug housing in the region between the flexibility region and the heating element. For example, it is possible in this case to use a circular ring plate, which is connected at its periphery to the wall of the plug housing, for example by screwing or caulking. By being able to support at least one force transmission element in this way, the force transmission element is supported forward as far as possible towards the combustion chamber as described above, and thus configured, In the rigid area of the plug housing on the opposite side of the chamber, only as little stress as possible is produced. In this case, the at least one flexibility region is preferably supported directly on the heating element in the plug housing, or alternatively or additionally, an intermediate chamber between the heating element and the flexibility region. Is additionally filled with a filling material. If comprised in this way, too much flexibility will not arise in front of the force introduction part from a heating body to at least 1 force transmission element. To that end, the filling material is, for example, a material having a high rigidity and preferably a low thermal conductivity. Such a configuration allows as direct a force transmission as possible from the heating element to the at least one force transmission element. As a result, the force transmission function of the combustion chamber pressure to the at least one force measuring element is further improved.

  The current supply to the heating body can be performed using, for example, a steel connection pin extending in the middle in the vicinity of the plug axis. However, it is also possible to use a flexible wire feeder.

  A sheathed glow plug according to the present invention incorporating a combustion chamber pressure sensor has many advantages over previously known devices. One major advantage is that the combustion chamber pressure signal is not affected by the operating temperature of the internal combustion engine. This is because the sheath-type glow plug according to the invention is optimally compensated for temperature changes and the different expansions of the material associated therewith. Another advantage is that a nearly constant force transmission function is guaranteed. In particular, this means that the combustion chamber pressure is transmitted to the at least one force measuring element in the same or similar manner in almost all ranges of the combustion chamber pressure and thus in almost all operating ranges of the internal combustion engine. Means. In order to amplify the electrical signal of the at least one force measuring element and to infer the actual combustion chamber pressure from this signal, the force transfer coefficient used is therefore almost independent of the operating state of the internal combustion engine. This makes it possible to avoid additional corrections that are complicated and cumbersome and require, for example, a corresponding correction function or the like. As a result, the electrical signal of the at least one force measuring element can be applied directly or with a slight electronic post-processing for appropriate engine control, for example engine control based on the combustion chamber pressure signal. Can be used.

Drawings Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a view showing a first embodiment of a sheath type glow plug according to the present invention in which a combustion chamber pressure sensor is incorporated,
FIG. 2 is a graph simulating the course of the sensor signal of the force measuring element in comparison with the combustion chamber pressure at different crankshaft positions,
FIG. 3 is a view showing a second embodiment of the combustion chamber pressure sensor according to the present invention,
FIG. 4 is a view showing a third embodiment of the combustion chamber pressure sensor according to the present invention.

Embodiment FIG. 1 shows a first embodiment of a sheath-type glow plug 110 according to the present invention, and this sheath-type glow plug 110 incorporates a combustion chamber pressure sensor. The sheath type glow plug 110 includes a heating body 112 and a plug housing 114. In the illustrated embodiment, the plug housing 114 is combusted in three regions: a receiving region 116 directed to the combustion chamber for receiving the heating element 112, a flexibility region 118, and a sheathed glow plug 110. It is divided into a housing body 120 arranged on the side opposite to the chamber.

  The heating element 112 is configured as a ceramic heating element 112 in the illustrated embodiment. However, other configurations of the heating element 112 are possible. The heating element 112 is supplied with electrical energy by a steel connection pin 122 in the illustrated embodiment. In the embodiment shown in FIG. 1, the steel connection pin 122 is formed as a solid pin extending in the center and guided through the plug housing 114 in the axial direction along the plug axis 124. The sheath-type glow plug 110 has a threaded body 126 at the end opposite to the combustion chamber. The steel connection pin 122 is guided out of the plug housing 114 in the axial direction through this threaded body 126 and leads to a corresponding electrical energy supply device. Furthermore, the plug housing 114 has a male thread 128 on the housing body 120. The male thread 128 can be used to screw the sheath-type glow plug 110 into the cylinder head, whereby the heating element 112 enters the combustion chamber of the internal combustion engine. In the flexibility region 118, the plug housing 114 has a constricted portion 130. In the constricted portion 130, the plug housing 114 has a constricted portion inward. This constriction 130 thus acts like a metal bellows with a single fold and is smaller in the flexibility region 118 to the plug housing 114 in a direction parallel to the plug axis 124 than in the housing body 120. It will give rigidity.

  The heating element 112 is coupled to the plug housing 114 by a press fit 132 in the receiving area 116 in the illustrated embodiment. As a result, an airtight joint is formed in the receiving region 116, and as a result, the combustion gas can be reliably prevented from entering the inner chamber of the sheath-type glow plug 110. The heating element 112 is in this case pushed into the plug housing 114 in the receiving area 116. Accordingly, an intermediate chamber 134 exists between the heating body 112 and the constricted portion 130. In this case, it is advantageous if the intermediate chamber 134 is kept as small as possible, preferably if it has disappeared. In an alternative advantageous configuration, this intermediate chamber 134 is filled with a filling material having a high strength and / or a low thermal conductivity. In this way, the force transmission described below is further improved, and at the same time, the transfer of heat from the heating element 12 to other components in the inner chamber of the sheath-type glow plug 110 is prevented.

  Furthermore, in the housing body 120 of the plug housing 114, a ring-shaped force measuring element 136, in the form of a ring-shaped piezoelectric element in the illustrated embodiment, is received. The power supply body of the force measuring element 136 is not shown in FIG. 1 and is guided out of the plug housing 114 through the screw 126, for example, in the axial direction, for example, parallel to the steel connection pin 122. And connected to a corresponding electronic evaluation device. The force measuring element 136 is surrounded in this embodiment by two spacer sleeves 138, for example by cylindrical sleeve-shaped spacer sleeves, in particular by two spacer sleeves 138 made of a highly rigid material (for example steel). During assembly, the combustion chamber side spacer sleeve 138 is first introduced into the plug housing 114 from the end of the sheath-type glow plug 110 opposite the combustion chamber, then the force measuring element 136 is introduced, and then the second Two spacer sleeves 138 are introduced. Thereafter, the screw body 126 is screwed into the plug housing 114. As a result, a preload or preload is applied to the force measuring element 136.

  Further, a force transmission element 140 is inserted into the plug housing 114. The force transmission element 140 has a sleeve-like shape in the illustrated embodiment, and surrounds the peripheral surface of the steel connection pin 122 in the same manner as the force measurement element 136. In this embodiment, the force transmission element 140 is somewhat conical and has a somewhat smaller outer diameter on the combustion chamber side than on the opposite side of the combustion chamber. The force transmission element 140 is supported by the constriction 130 on the combustion chamber side, and is supported by the spacer sleeve 138 on the combustion chamber side on the side opposite to the combustion chamber. Thereby, the force transmission element 140 is indirectly supported by the force measuring element 136 in this embodiment.

  The heating element 112 has a hydraulic pressure receiving surface 142 on the side directed to the combustion chamber. The combustion chamber pressure is converted into a force F (indicated by reference numeral 144 in FIG. 1) acting on the heating element 112 via the pressure receiving surface 142. This force 144 is transmitted to the force measuring element 136 by the force transmitting element 140, where the force is converted into an electrical signal. The combustion chamber pressure can be estimated from this electrical signal. However, in this case, the force transmission of the force 144 from the heating element 112 to the force measuring element 136 is not complete, and it is necessary to multiply by a factor smaller than one. Ideally this transfer coefficient would be exactly 1. The fact that the transmission is not perfect is based on the fact that the force is received or absorbed by the plug housing 114. An advantage of the configuration of the sheathed glow plug 110 shown in FIG. 1 is that in this case the force 144 deforms the plug housing 114 to a negligible extent outside the flexibility region 118. Substantially the force 144 merely moves the receiving area 116 in the axial direction towards the housing body 120, in which case the plug housing 114 in the flexibility area 118 is compressed in a spring-elastic manner in the axial direction. This ensures that the force 144 is transmitted almost completely from the heating element 112 to the force measuring element 136. Furthermore, thermal stress is also absorbed by the constriction 130, so that only a substantially constant preload is applied to the force measuring element 136 at various operating temperatures.

  The transmission of the force 144 to the force measuring element 136 in the arrangement shown in FIG. 1 is shown in the form of simulation data in FIG. In the graph of FIG. 2, the x-axis indicated by φ indicates the crankshaft position in angle, the left y-axis indicates the combustion chamber pressure p in an arbitrary unit, and the right y-axis indicates in an arbitrary unit. The force F displayed by the force measuring element 136 is shown. For one particular situation, an operating point at 2000 U / min and a mean effective working pressure (PME) of 1 bar was assumed. In this case, the upper curve 210 associated with the left y-axis shows the course of the combustion chamber pressure. The lower curve 212 associated with the right y-axis shows the electrical signal of the force measurement element 136. As can be seen from FIG. 2, the sensor signal 212 can be multiplied by a suitable factor, from which the combustion chamber pressure 210 can be inferred. This factor mainly takes into account the material properties and configuration of the sheathed glow plug 110.

  FIG. 3 shows a second advantageous embodiment of a sheathed glow plug 110 according to the invention. The sheath-type glow plug 110 also has a plug housing 114, which is divided into a receiving area 116, a flexibility area 118, and a housing body 120. In the receiving area 116, the heating body 112 is fixed in the plug housing 114 by a press fit 132. As in the embodiment of FIG. 1, the sheath-type glow plug 110 also has a constricted portion 130 in the embodiment of FIG. 3. The configuration of the constricted portion 130 is basically similar to the configuration of the constricted portion 130 in the embodiment of FIG. An intermediate chamber 134 is formed between the constricted portion 130 and the heating body 112. Similarly to the embodiment of FIG. 1, in the embodiment of FIG. 3, the plug housing 114 has a male thread 128 for fixing the sheath-type glow plug 110 to the cylinder head.

  The difference between the embodiment shown in FIG. 3 and the embodiment shown in FIG. 1 lies mainly in the configuration of the force measuring element 136 and the configuration and support type of the force transmitting element 140. In the embodiment of FIG. 3, the force measuring element 136 is formed in the form of a cylindrical disc and is inserted into the housing body 120 at the end opposite to the combustion chamber. The force measuring element 136 is held and preloaded by the screw 126 in this embodiment as well. In the embodiment shown in FIG. 3, the spacer sleeve 138 is omitted.

  Further, in the embodiment of FIG. 3, the force transmission element 140 is formed in a rod shape, not a sleeve shape. The force transmission element 140 is in this case inserted into the plug housing 114 along the plug axis 124. The force transmission element 140 is supported at the center of the end surface of the force measuring element 136 on the combustion chamber side at the end opposite to the combustion chamber. The rod-shaped force transmission element 140 is supported by the wall of the intermediate chamber 134 at the end of the end surface on the combustion chamber side. For this purpose, an additional disc-shaped support element 310 is inserted in the receiving area 116. This support element 310 is connected to the wall of the plug housing 114 in the receiving area 116 by caulking or screwing, for example. In this case, other fixed formats are possible. The force is transmitted from the heating element 112 to the force measuring element 136 by means of the support element 310 via the wall of the plug housing 114 in the receiving area 116, the support element 310 and the rod-shaped force transmission element 140. The advantage of indirectly transmitting force from the heating element 112 to the force transmission element 140 via the support element 310 is mainly that heat is not directly transferred from the heating element 112 to the force transmission element 140. If heat is transferred to the force measuring element 136 through the force transfer element 140 (eg, made of metal), this heat transfer will cause a temperature change, for example, in the force measuring element 136 and thus to signal quality. It will have an adverse effect.

  In the embodiment of FIG. 3, the power supply to the heating body 112 is not shown. Since the region along the plug axis 124 is substantially filled in this embodiment by the rod-shaped force transmission element 140, there is no space for the steel connection pin 122 as in the embodiment of FIG. Instead, in the embodiment of FIG. 3, a wire feeder is used, which passes through a corresponding hole in the support element or a corresponding hole or groove in the wall of the plug housing 114 and elements 310 and 136. And is guided out through the threaded body 126.

  FIG. 4 shows a third embodiment of a sheath-type glow plug 110, which does not include a separate force transmission element 140. In this third embodiment, the force 144 is transmitted directly from the heating element 112 to the force measuring element 136. This force transmission is advantageously effected by means of a cylindrical extension 410 arranged on the side of the heating element 112 opposite to the combustion chamber. Other functions and structures of the sheath type glow plug 110 are the same as those of the embodiment shown in FIG.

It is a figure which shows 1st Example of the sheath type | mold glow plug by this invention incorporating the combustion chamber pressure sensor. 7 is a graph showing a simulation of the sensor signal progress of the force measuring element in comparison with the combustion chamber pressure at various crankshaft positions. It is a figure which shows the 2nd Example of the combustion chamber pressure sensor by this invention. It is a figure which shows the 3rd Example of the combustion chamber pressure sensor by this invention.

Claims (11)

  A sheath type glow plug (110) for an internal combustion engine of self-ignition type, comprising a heating body (112), a plug housing (114), and a plug axis (124), and the plug housing (114) is heated A receiving region (116) for receiving the body (112); a housing body (120); and at least one flexibility region (118) disposed between the housing body (120) and the receiving region (116). And at least one force measuring element (136) in the plug housing (114). A sheath type glow plug with a combustion chamber pressure sensor.   The sheath-shaped sheath of claim 1, wherein the sheath-shaped glow plug (110) further comprises at least one force transmitting element (140) for transmitting combustion chamber pressure to the at least one force measuring element (136). Glow plug.   The plug housing (114) in at least one region (130) in the at least one flexibility region (118) is less rigid in the direction parallel to the plug axis (124) than in the region of the housing body (120). The sheath-type glow plug according to claim 1 or 2, comprising:   At least one flexibility region (118) is provided with the following elements: corrugation, at least one constriction (130) or crease curved inside or outward of the plug housing (114), The sheath shape according to any one of claims 1 to 3, comprising at least one element of a thin wall region of the plug housing (114), an elastic element, and an element having a small elastic modulus. Glow plug.   The sheathed glow plug according to any one of the preceding claims, wherein at least one force measuring element (136) is received in the housing body (120).   At least one force transmission element (140) comprises at least one of the elements described below: a pressure rod, preferably a substantially cylindrical pressure rod, a pressure sleeve, preferably a substantially cylindrical sleeve-like pressure sleeve. The sheath-type glow plug according to any one of claims 1 to 5, having one element.   At least one force transmitting element (140) is supported at one end by at least one force measuring element (136) and at the other end, the element described below: heating element (112), at least one flexibility region (118) supported by at least one of the elements, such as the region of the plug housing (114) disposed between the flexibility region (118) and the at least one heating element (112), The sheath-type glow plug according to any one of claims 1 to 6.   At least one force transmission element (140) is supported at one end by at least one force measurement element (136) and at the other end at least one flexibility region (118) and at least one heating element (112). In order to support at least one force transmission element (140) on the plug housing (114), the sheath-type glow plug (110) being supported in the region of the plug housing (114) The sheath-type glow plug according to any one of the preceding claims, further comprising at least one support element (310).   In order to connect the sheath-type glow plug (110) and the cylinder head of the internal combustion engine, at least one external thread (128) is additionally provided, the at least one external thread (128) being the housing body ( The sheath-type glow plug according to any one of claims 1 to 8, which is a constituent part of 120).   The sheath-type glow plug according to any one of claims 1 to 9, wherein the at least one force measuring element (136) has a ring shape and / or a disk shape.   At least one force measuring element (136) is inserted into the plug housing (114), preferably connected to the plug housing (114) by screwing or caulking, the plug housing (114) being at least partially 11. A sheathed glow plug according to any one of the preceding claims, wherein the sheath is glow preloaded and at least one force transmission element (140) is pressure preloaded.

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