JP2011203103A - Piezoelectric module and glow plug including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric module having high responsiveness and a glow plug provided with the same.
A piezoelectric module 10 is attached to a through-hole 7 that communicates from the outside to a closed space, and has a columnar pressure transmission member 1 that transmits pressure received at a front end surface to a rear end surface, and a rear end surface of the pressure transmission member 1. A columnar pressure-sensitive element 2 that is in contact with one end surface and receives pressure from the pressure transmission member 1 and a support member that is attached to the through-hole 7 and has a tip surface that contacts and supports the other end surface of the pressure-sensitive element 2. 5, an inner cylinder 4 that is disposed so as to surround the pressure-sensitive element 2 from the rear end portion of the pressure transmission member 1 to the tip end portion of the support member 5, and an inner cylinder 4 that is disposed so as to be accommodated therein, The outer cylinder 3 whose end portion of the member 1 is fixed to the distal end portion of the support member 5, and at least the distal end side of the outer cylinder 3 between the outer cylinder 3, the pressure transmission member 1 and the inner cylinder 4 are filled, The inner cylinder 4 directly applies the pressure inside the closed space to the outer cylinder 3. Inhibit kicking contain a filler 6.
[Selection] Figure 1

Description

  The present invention relates to a piezoelectric module such as a pressure sensor for measuring a pressure of gas, liquid, etc., particularly a combustion pressure of an automobile engine, and a glow plug including the piezoelectric module.

  Conventionally, it is known that a pressure-sensitive element is used for a piezoelectric actuator or a piezoelectric sensor. For example, Patent Document 1 discloses a piezoelectric module including a pressure-sensitive element.

  The piezoelectric module described in Patent Document 1 has a pressure-receiving surface, a housing having a portion having a larger coefficient of thermal expansion than the other portions in a part of the side wall, and one end provided on the back side of the pressure-receiving surface. A pressure transmission member that is in contact with the surface, and a pressure-sensitive element that is provided inside the housing and provided at the other end of the pressure transmission member, and a portion having a large coefficient of thermal expansion when the housing is heated extends larger than other portions. This regulates the change in the positional relationship between the pressure sensitive element and the pressure receiving surface.

  With this configuration, a portion having a higher coefficient of thermal expansion than other portions is thermally expanded, whereby the pressure-receiving surface at the tip of the housing can be pulled toward the pressure-sensitive element side. As a result, it is possible to prevent a change in preliminary pressure due to thermal expansion and to realize a piezoelectric module having excellent temperature characteristics.

Japanese Patent Laid-Open No. 5-164643

  However, in the case of the piezoelectric module described in Patent Document 1, the purpose is to reduce the influence of thermal expansion, and the responsiveness when high-frequency pressure vibration of about several kHz to several tens kHz is applied is improved. Is not considered.

  For example, when a piezoelectric module is used as a combustion pressure sensor provided in an internal combustion engine such as an automobile, high pressure and high pressure pressure vibration of about several kHz to several tens kHz are applied to the pressure sensor, so that high responsiveness is obtained. Required.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a piezoelectric module having high responsiveness and a glow plug including the same.

  The piezoelectric module of the present invention is a piezoelectric module that is attached to a through-hole that communicates with the closed space from the outside and measures the pressure inside the closed space, and transmits the pressure received at the front end surface to the rear end surface. A columnar pressure transmission member, a columnar pressure-sensitive element that receives the pressure from the pressure transmission member with one end surface abutting against the rear end surface of the pressure transmission member, and a front end surface that is attached to the through-hole. A support member that supports the pressure-sensitive element in contact with the other end surface of the pressure-sensitive element, and is disposed so as to surround the pressure-sensitive element from a rear end portion of the pressure transmission member to a front end portion of the support member. An inner cylinder, an outer cylinder that is disposed so as to enclose the inner cylinder, and an end on the support member side is fixed to the distal end of the support member; the outer cylinder; the pressure transmission member; Between the inner cylinder And a filler that fills at least the distal end side of the outer cylinder and suppresses the inner cylinder from directly receiving the pressure inside the closed space from the outer cylinder. .

  The piezoelectric module of the present invention is characterized in that, in the above configuration, the filler is filled so as to surround the pressure sensitive element between the outer cylinder and the inner cylinder.

  Moreover, the piezoelectric module of the present invention is characterized in that, in the above-described configuration, the filler is filled in all regions between the inner cylinder and the outer cylinder.

  Here, it is preferable that the filler is made of an insulating material powder or an insulating material sheet.

  Furthermore, it is preferable that the insulating material is mainly composed of boron nitride or molybdenum disulfide.

  Furthermore, the glow plug of the present invention is characterized by including any one of the above piezoelectric modules.

  The piezoelectric module according to the present invention is formed so that, for example, when measuring the pressure inside a device such as an internal combustion engine that generates pressure (closed space such as a combustion chamber), the closed space of this device is communicated from the outside. A support member is screwed into a hole (through hole with a thread formed on the inner wall), and the outer cylinder functions as a positioning member that suppresses the penetration of the piezoelectric module from the desired mounting position. The tightening force for attaching to the through hole is not directly applied to the pressure sensitive element. Therefore, the clamping force and the pressure to be measured are separated from the pressure sensitive element, and the occurrence of pressure signal offset due to the clamping force is eliminated. Further, according to the piezoelectric module of the present invention, since the gap is provided between the outer cylinder, the pressure transmission member, and the inner cylinder, it is difficult for the vibration of the device to be transmitted to the pressure sensitive element, and the pressure signal Variations can be suppressed. Therefore, a piezoelectric module having high responsiveness can be realized.

  Further, according to the piezoelectric module of the present invention, at least the distal end side of the outer cylinder is filled between the outer cylinder, the pressure transmission member, and the inner cylinder, and the inner cylinder is supplied with pressure from the space between the outer cylinder and the inner cylinder. Because it contains a filler that suppresses direct contact, pressure is suppressed from being applied to the side of the inner cylinder or in the direction opposite to the pressure-sensitive direction (tip side) with respect to the pressure-sensitive element, resulting in high detection. Sensitivity can be maintained.

It is sectional drawing which shows an example of embodiment of the piezoelectric module of this invention. It is sectional drawing which shows the other example of embodiment of the piezoelectric module of this invention. It is sectional drawing which shows the other example of embodiment of the piezoelectric module of this invention.

  Hereinafter, embodiments of a piezoelectric module according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a cross-sectional view showing an example of an embodiment of a piezoelectric module of the present invention. The piezoelectric module 10 of the example shown in FIG. 1 is attached to a through-hole 7 that communicates from the outside in a closed space (positioned above, but not shown), and measures the pressure inside the closed space. It is. Specifically, a columnar pressure transmission member 1 that transmits the pressure received on the front end surface to the rear end surface, and a columnar shape in which one end surface abuts on the rear end surface of the pressure transmission member 1 and receives pressure from the pressure transmission member 1. The pressure sensitive element 2 is attached to the through hole 7, the front end surface is in contact with the other end face of the pressure sensitive element 2, the support member 5 that supports the pressure sensitive element 2, and the rear end portion of the pressure transmitting member 1. The inner cylinder 4 is disposed so as to surround the pressure-sensitive element 2 from the tip of the support member 5 to the support member 5, and is disposed so as to surround the inner cylinder 4, and the end on the support member 5 side is the tip of the support member 5. The outer cylinder 3 fixed to the portion, and at least the distal end side of the outer cylinder 3 between the outer cylinder 3 and the pressure transmission member 1 and the inner cylinder 4 is filled, and the pressure inside the closed space is between the outer cylinder 3 The piezoelectric module 10 includes a filler 6 that suppresses the inner cylinder 4 from being directly received from the inside.

  The pressure transmission member (pressure receiving pin) 1 is a columnar member for transmitting the pressure received at the front end surface to the rear end surface. For example, when the piezoelectric module 10 of the present invention is attached to a through-hole 7 provided in a cylinder (cylinder) forming a closed space (combustion chamber) of an automobile engine or the like, the tip surface of the pressure transmission member 1 is passed through the through-hole. 7 is attached so as to protrude from the combustion chamber. When measuring the pressure in the combustion chamber at such a high temperature (several hundred to 1000 ° C.), the pressure transmission member 1 is preferably made of a metal such as stainless steel having high heat resistance and corrosion resistance. However, the material for forming the pressure transmission member 1 is not necessarily limited to metals such as stainless steel, and may be resin or ceramics depending on the application. As shown in FIG. 1, it is preferable that a step having a reduced diameter is formed at the rear end of the pressure transmission member 1. According to this shape, stress during welding with the inner cylinder 4 to be described later is provided. Therefore, the center axis of the pressure transmission member 1 and the center axis of the inner cylinder 4 can be prevented from shifting.

The pressure-sensitive element 2 includes, for example, a piezoelectric body such as lead zirconate titanate (PZT: Pb (Zr _x , Ti _1-x ) O ₃ ) (x is about 0.525), and a pair of counter electrodes provided on the piezoelectric body (Not shown) having a configuration including The pressure-sensitive element 2 has, for example, a vertical, horizontal, and height (length in the pressure-sensitive direction) of about 1 to 5 mm, and one end surface abuts on the rear end surface of the pressure transmission member 1. The other end surface is in contact with the front end surface of the support member 5 described later. The pressure sensitive element 2 receives pressure from the rear end face of the pressure transmission member 1 and converts this pressure into electricity.

  The pressure-sensitive element 2 is adapted to take out an electric signal obtained by converting pressure from a pair of counter electrodes. For example, the pressure-transmitting element 1 is connected to the pressure transmission member 1 from one counter electrode provided on the end face of the pressure-sensitive element 2. An electric signal is taken out via the inner cylinder 4 and the support member 5, and the other counter electrode provided on the end surface on the rear end side of the pressure-sensitive element 2 passes through the inside of the support member 5 to define the support member 5. The insulated lead member 8 is connected, and an electric signal is taken out from the other counter electrode via the lead member 8.

  The pressure-sensitive element 2 is not limited to the above configuration, and a pair of external electrodes are provided on the side surface of a laminate in which piezoelectric layers made of lead zirconate titanate and the like and internal electrode layers made of silver and the like are alternately laminated. And each external electrode may be electrically connected to the internal electrode layer every other layer. In this case, an electric signal is taken out from the pair of external electrodes.

  The support member 5 supports the pressure-sensitive element 2 with its front end surface in contact with the other end surface of the pressure-sensitive element 2. Further, when the piezoelectric module 10 of the present invention is attached to the through hole 7 provided in the cylinder (cylinder) forming the closed space (combustion chamber), the support member 5 is engaged with and fixed to the through hole 7. Is. Examples of the method of engaging the support member 5 with the through hole 7 include a method of engaging the support member 5 by screwing using the support member 5 as a male screw and the through hole 7 as a female screw.

As a material for forming the support member 5, as in the case of the pressure transmission member 1, when measuring the pressure in the combustion chamber at a high temperature (several hundreds to 1000 ° C.), stainless steel having high heat resistance and corrosion resistance is used. It is preferably made of metal, and may be resin or ceramics depending on the application.

  In addition, as shown in FIG. 1, it is preferable that the front-end | tip part of the support member 5 is the shape formed in multiple steps, and since it is such a shape, the inner cylinder 4 and an outer part are attached to the front-end | tip part of the support member 5. The cylinder 3 can be arranged in a double manner.

  The inner cylinder 4 is disposed so as to surround the pressure sensitive element 2 from the rear end portion of the pressure transmission member 1 to the front end portion of the support member 5. The inner cylinder 4 is welded, for example, to the rear end portion of the pressure transmission member 1 and welded to the front end portion of the support member 5 to form a sealed space, and protects the pressure-sensitive element 2 disposed inside. This is to improve the durability of the pressure element 2. As the material for forming the inner cylinder 4, as with the pressure transmission member 1 and the support member 5, stainless steel having high heat resistance and corrosion resistance is used when measuring the pressure in the combustion chamber at a high temperature (several hundred to 1000 ° C.). It is preferably made of a metal such as steel, and may be a resin or ceramics depending on the application.

Moreover, it is preferable that the thickness of the inner cylinder 4 is 0.2-1 mm, and if it is this thickness, intensity | strength will fall and it will be suitable for elastic deformation by moderate thickness, without destroying. Moreover, it is preferable that the length of the inner cylinder 4 is 3-20 mm, and if it is this length, it will become a thing suitable for elastic deformation, without enlarging so much.

  In addition, as long as a pair of counter electrodes provided in the pressure-sensitive element 2 have a shape that does not short-circuit, the presence or absence of a gap between the pressure-sensitive element 2 and the inner cylinder 4 is not questioned, but the pressure-sensitive element In order to prevent the durability from being deteriorated by rubbing between the inner cylinder 4 and the inner cylinder 4, it is preferable that a gap of about 0.05 to 1 mm is provided between them.

  The outer cylinder 3 is disposed so as to surround the inner cylinder 4 so as to be accommodated therein. The end of the outer cylinder 3 on the support member 5 side is fixed to the tip of the support member 5. Here, the through hole 7 is provided with a step (a portion with a reduced diameter) on the tip side (combustion chamber side) of the region where the female screw is formed. And the end surface of the outer cylinder 3 opposite to the support member 5 side (front end side) comes into contact with this step and is locked, and the outer cylinder 3 includes the support member 5 (male screw) and the through hole 7 ( It functions as a positioning member that suppresses intrusion from the desired mounting position of the piezoelectric module 10 when the female screw is tightened. As a result, the clamping force is not directly applied to the pressure-sensitive element 2, and the clamping force and the pressure to be measured are separated from the pressure-sensitive element 2, so that no pressure signal offset is generated due to the clamping force. . In addition, the pressure sensitive element 2 that requires delicate handling is not damaged, and durability is improved. Such a configuration is also effective, for example, when the piezoelectric module 10 is assembled and removed and attached for maintenance.

  Further, a gap is formed between the outer cylinder 3, the pressure transmission member 1 and the inner cylinder 4. Thereby, the inner cylinder 4 is easily elastically deformed by the pressure to be measured. Further, the pressure sensing element 2 is less likely to transmit vibrations of a device (cylinder forming a combustion chamber) to which the piezoelectric module 10 is attached, and the fluctuation of the pressure signal can be suppressed. Therefore, a piezoelectric module having high responsiveness can be realized. The gap is preferably 0.01 to 1 mm from the viewpoint of elastic deformation of the inner cylinder 4.

  In addition, as a material for forming the outer cylinder 3, as in the case of the pressure transmission member 1, the support member 5, and the inner cylinder 4, when measuring the pressure in the combustion chamber at a high temperature (several hundred to 1000 ° C.), the outer cylinder 3 is heat resistant. It is preferably made of a metal such as stainless steel having high properties and corrosion resistance, and may be a resin or ceramics depending on the application.

Then, at least on the distal end side of the outer cylinder 3 between the outer cylinder 3 and the pressure transmission member 1 and the inner cylinder 4, the inner cylinder 4 receives the pressure inside the closed space directly from the outer cylinder 3. The filler 6 to be suppressed is filled.

  When a pressure in a closed space such as a combustion chamber is measured, if a gap is provided between the outer cylinder 3, the pressure transmission member 1, and the inner cylinder 4, Although pressure may be applied to the side or the direction opposite to the pressure-sensitive direction (tip side) and the detection sensitivity of the pressure-sensitive element 2 may be reduced, the filling material 6 is filled in this way. Since the pressure is suppressed from being applied to the side of the inner cylinder 4 or the direction opposite to the pressure sensitive direction (tip side), it is possible to prevent the detection sensitivity of the pressure sensitive element 2 from being lowered.

  Here, the filler 6 is preferably made of an insulating material powder or an insulating material sheet. By using an insulating material as the filler 6, even if the filler 6 enters the inner cylinder 4, there is no risk of the pressure sensitive element 2 shorting through the wall of the inner cylinder 4 via the filler 6. As a component of this insulating material, boron nitride or molybdenum disulfide is preferably a main component. Since these are materials having high insulation properties and excellent high-temperature stability and thermal conductivity, they can be expected to have an excellent effect in preventing a decrease in the detection sensitivity of the pressure-sensitive element 2 and a cooling effect described later. it can. When the filler 6 is made of a powder of an insulating material, it may be only an inorganic oxide powder, or may be a mixture of a resin such as epoxy or silicone. When the filler 6 is made of a sheet of an insulating material, for example, a rubber material such as silicone is mixed with boron nitride or molybdenum disulfide powder, and the sheet is formed into a sheet by a method such as direct pressure injection molding or injection molding Is preferred.

  Note that the piezoelectric module 10 of the present example has a columnar shape such as a columnar shape or a prismatic shape as a whole. Therefore, the pressure transmission member 1, the support member 5, and the pressure sensitive element 2 have a columnar shape such as a columnar shape or a prismatic shape as a whole. Further, the outer cylinder 3 and the inner cylinder 4 have a cylindrical shape such as a cylindrical shape or a rectangular tube shape as a whole.

  The piezoelectric module of the present invention is not limited to the form shown in FIG. 1, and the filler 6 surrounds the pressure sensitive element 2 between the outer cylinder 3 and the inner cylinder 4 as in the example shown in FIG. 2. It may be filled as follows. FIG. 2 is a cross-sectional view similar to FIG. 1, showing another example of the embodiment of the piezoelectric module of the present invention. In FIG. 2, the same parts as those in FIG.

  According to the configuration of this example, in addition to the effect of preventing the detection sensitivity of the pressure sensitive element 2 from being lowered, a cooling effect can also be expected. Since there is a gap (air layer) between the outer cylinder 3 and the inner cylinder 4, heat transfer becomes worse, and even if the engine block is cooled, the pressure sensitive element 2 cannot be cooled, and the temperature rises during combustion. Although the detection sensitivity may be lowered, if the filler 6 is filled in the gap between the outer cylinder 3 and the inner cylinder 4 in this way, the heat transfer performance is improved and the engine block is cooled. Since the pressure sensitive element 2 is cooled, it is possible to prevent a decrease in detection sensitivity. In particular, when the filler 6 is made of, for example, a powder or sheet of an insulating material mainly composed of boron nitride or molybdenum disulfide, it has excellent thermal conductivity, so that a cooling effect can be expected and excellent temperature characteristics can be obtained. A piezoelectric module having the same can be realized.

In the piezoelectric module of the present invention, it is preferable that the filler 6 is filled in all regions between the inner cylinder 4 and the outer cylinder 3 as in the example shown in FIG. In this case, the filling material 6 is filled in the entire region between the inner cylinder 4 and the outer cylinder 3, and the gap between the two is completely filled, so that the pressure during engine combustion is directly applied to the inner cylinder 4 In addition, it is effective in terms of cooling, and can further prevent a decrease in detection sensitivity. Furthermore, since the filler 6 is filled in the entire region between the inner cylinder 4 and the outer cylinder 3, the filler 6 is more stably filled, and the filler 6 spills from the gap even after long-term use. Since it does not come out, the piezoelectric module 10 is highly reliable and durable.

  In the above example, a combustion chamber of an automobile engine or the like is illustrated as a closed space, and an example in which the through hole 7 is provided in a cylinder (cylinder) that forms this combustion chamber is shown. This is an example in which the piezoelectric module 10 of the present invention is used as a combustion pressure sensor in an engine.

  An internal combustion engine has various devices such as a cylinder (cylinder), a piston, a spark plug, a glow plug, a fuel injection device, and a valve opening / closing device for a fuel supplied to the cylinder. Specifically, a gasoline engine, an alcohol-mixed gasoline engine, a diesel engine, an alcohol engine, a hydrogen gas engine, or the like used for a vehicle such as an automobile or a freight transport vehicle.

  The piezoelectric module of the present invention is installed in a combustion chamber (cylinder) of an internal combustion engine as a pressure chamber, and functions as a combustion pressure sensor that receives pressure due to combustion explosion of fuel and measures the pressure, and has high responsiveness. Therefore, the controllability of the combustion characteristics of the internal combustion engine can be enhanced, and the durability is excellent.

  Hereinafter, an example of a method for manufacturing a piezoelectric module of the present invention will be described.

  First, the pressure transmission member 1 and the inner cylinder 4 are joined and fixed in advance. Examples of the joining method include welding methods such as gas welding, laser welding, resistance welding, and electron beam welding. Bonding methods such as friction welding, brazing, and diffusion bonding may be used.

  Next, the pressure sensitive element 2 is disposed inside the inner cylinder 4. At this time, the pressure transmission member 1 and the pressure sensitive element 2 do not have to be joined.

  Next, the pressure-sensitive element 2 is sandwiched between the rear end surface of the pressure transmission member 1 and the front end portion of the support member 5 without a gap. Thereafter, the contact portion between the end of the inner cylinder 4 on the support member 5 side and the tip of the support member 5 is joined and fixed. Examples of the joining method include gas welding, laser welding, resistance welding, and electron beam welding. Also, a joining method such as friction welding, brazing or diffusion bonding may be used. At this time, the length of the inner cylinder 4 and the front end of the support member 5 are such that the position where the inner cylinder 4 and the support member 5 are in contact with each other is positioned on the side farther from the pressure chamber than the pressure sensitive element 2. Set the length of.

  Next, one end of the outer cylinder 3 is fixed to the front end portion of the support member 5 and the other end is locked to the step of the wall surface of the through hole 7 so that the pressure sensor 2 and the rear end portion of the pressure transmission member 1 are connected. Installed to cover. At this time, the position where the outer cylinder 3 and the support member 5 are fixed in contact with each other seems to be located on the side farther from the pressure transmission member 1 than the position where the inner cylinder 4 and the support member 5 are fixed in contact with each other. It is preferable to adjust to. In this case, there is an effect that the efficiency of separating the fastening force by screwing into the through hole 7 from the pressure to be measured with respect to the pressure sensitive element 2 is further increased.

  Examples of a method for fixing one end of the outer cylinder 3 and the tip of the support member 5 include welding methods such as gas welding, laser welding, resistance welding, and electron beam welding. Also, a joining method such as friction welding, brazing or diffusion bonding may be used. Further, it may be fixed by simply contacting one end of the outer cylinder 3 and the tip of the support member 5 and locking the other end of the outer cylinder 3.

And the filler 6 is filled from the clearance gap between the inner cylinder 4 and the outer cylinder 3, if the insulating material is a powder form. An insulating material powder may be mixed in advance with a resin such as epoxy or silicone and injected into the gap between the inner cylinder 4 and the outer cylinder 3 with a syringe. When the insulating material is in the form of a sheet, the sheet may be wound around the inner cylinder 4 in advance and the outer cylinder 3 may be fixed by this sheet.

  The piezoelectric module 10 obtained in this way receives pressure when the pressure transmission member 1 is exposed to the combustion chamber, the inner cylinder 4 is elastically deformed, and is sandwiched between the pressure transmission member 1 and the support member 5. The pressure sensitive element 2 senses the pressure and generates an electrical signal to measure the pressure, and has high responsiveness.

  The glow plug of the present invention is a glow plug provided with the above-described piezoelectric module. The glow plug of the present invention is a device that controls the temperature in a cylinder of, for example, a diesel engine. If the temperature in the cylinder is low, the engine starts poorly. Therefore, the glow plug provided in the cylinder before the engine starts. The plug is preheated to ensure fuel ignition and to improve startability. Accordingly, the glove lug of the present invention is provided with a tip that is a heat generating portion protruding in the combustion chamber of the diesel engine.

  The glow plug of the present invention is connected to a current-carrying resistor made of a metal such as iron (Fe) or nickel (Ni) having a large resistance change rate, and is connected to the tip of the current-carrying resistor, and has a large specific resistance and a resistance change rate. A heat transmission resistor made of an alloy such as iron-chromium (Fe-Cr) or nichrome (Ni-Cr), and a sheath tube covering the resistor, and a pressure transmission member in the piezoelectric module described above By adopting a configuration in which a heating resistor covered with a sheath tube is embedded in 1, a glow plug including the piezoelectric module of the present invention can be realized.

  Since the glow plug of the present invention includes the piezoelectric module of the present invention having high responsiveness and excellent durability, the controllability of the temperature in the cylinder of the internal combustion engine can be improved, and the durability can be improved. It is excellent.

1: Pressure transmission member 2: Pressure sensitive element 3: Outer cylinder 4: Inner cylinder 5: Support member 6: Filler 7: Through hole 8: Lead member
10: Piezoelectric module

Claims (7)

  A piezoelectric module that is attached to a through-hole that communicates from the outside to the closed space and measures the pressure inside the closed space, and a columnar pressure transmission member that transmits the pressure received at the front end surface to the rear end surface; One end face abuts on the rear end face of the pressure transmission member, is attached to the through-hole with a columnar pressure-sensitive element that receives the pressure from the pressure transmission member, and a front end face is the other of the pressure-sensitive elements. A support member that contacts the end surface and supports the pressure-sensitive element; an inner cylinder that is disposed so as to surround the pressure-sensitive element from a rear end portion of the pressure transmission member to a front end portion of the support member; and the inner cylinder Between the outer cylinder, the pressure transmission member, and the inner cylinder, and an outer cylinder in which the end on the support member side is fixed to the distal end of the support member. At least the tip of the outer cylinder The piezoelectric modules are filled, characterized in that it comprises a suppressing filler receive the inner cylinder is directly from between the pressure inside the closed space between the outer cylinder to.   2. The piezoelectric module according to claim 1, wherein the filling material is filled so as to surround the pressure-sensitive element between the outer cylinder and the inner cylinder.   The piezoelectric module according to claim 1, wherein the filler is filled in all regions between the inner cylinder and the outer cylinder.   The piezoelectric module according to claim 1, wherein the filler is made of a powder of an insulating material.   The piezoelectric module according to claim 1, wherein the filler is made of an insulating material sheet.   6. The piezoelectric module according to claim 4, wherein the insulating material is mainly composed of boron nitride or molybdenum disulfide.   A glow plug comprising the piezoelectric module according to claim 1.

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