A pressure sensor based on transverse piezoelectric effect

Abstract

The present invention discloses a pressure sensor based on the transverse piezoelectric effect, comprising an outer shell, a pressure-bearing body, a piezoelectric crystal and an electrode assembly. The pressure-bearing body is provided at the lower end of the outer shell, the lower end of the piezoelectric crystal receives the stress transmitted by the pressure-bearing body, and the upper end is connected to the electrode assembly. The piezoelectric crystal has an arched cylindrical structure, and n piezoelectric crystals are arranged in a circular array and are closely attached to each other in pairs to construct a piezoelectric assembly with a cylindrical structure. The outer arc surface of the piezoelectric crystal is one electrode, and the rectangular plane is another electrode. The sensor utilizes the transverse piezoelectric effect of the piezoelectric crystal for pressure detection, and the sensitivity can be improved by increasing the length of the piezoelectric crystal, so that the pressure sensor can be designed in a small size, which is conducive to its use in small, complex and precise engines. In addition, the pressure sensor has a simple overall structure, is easy to assemble, has good sealing, has high pressure sensitivity of the pressure-bearing body, has high detection accuracy, and has higher reliability when used in high-temperature and high-pressure environments in cylinders.

Description

Technical Field

[0001] The present invention relates to the technical field of internal combustion engine combustion pressure measurement, and in particular to a pressure sensor based on the transverse piezoelectric effect. Background Art

[0002] The function of the cylinder pressure sensor is to convert the pressure change in the cylinder of the internal combustion engine into an electrical signal. It is usually of strain gauge type and piezoelectric type. Piezoelectric pressure sensors have the advantages of good dynamic response (high frequency up to 400kHz), high mechanical strength, fatigue resistance, vibration resistance, corrosion resistance, high temperature resistance, small size, and long life. Quartz crystal is an ideal piezoelectric material because it has good stability within a temperature range of several hundred degrees Celsius. Therefore, quartz crystal is usually used to make cylinder pressure sensors in the cylinder pressure measurement of internal combustion engines.

[0003] Existing cylinder pressure sensors use the longitudinal piezoelectric effect to detect pressure. The piezoelectric element is formed by stacking several quartz wafers with a sheet structure. The stacked quartz wafers are connected in series by welding wires. The piezoelectric element of this structure has the following defects: 1. Under high temperature conditions in the cylinder, the wires are prone to unwelding, and the cylinder pressure sensor is not reliable enough; 2. The detection accuracy of the cylinder pressure sensor depends on the pressure-bearing surface area of ​​the quartz wafer, which limits the further reduction of the sensor size and reduces the usability of the cylinder pressure sensor in sophisticated and complex engines. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a pressure sensor based on the transverse piezoelectric effect to overcome one or more problems caused by the limitations and defects of the related art to a certain extent.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A pressure sensor based on the transverse piezoelectric effect, comprising an outer shell, a pressure-bearing body, a piezoelectric crystal, and an electrode assembly. The pressure-bearing body is disposed at the lower end of the outer shell. The piezoelectric crystal is vertically disposed within the outer shell, with its lower end receiving the stress transmitted by the pressure-bearing body and its upper end connected to the electrode assembly.

[0007] The number of piezoelectric crystals is n, n ≥ 3, and the piezoelectric crystal has an arched cylindrical structure with an arch angle of 360° / n. The n piezoelectric crystals are arranged in a circular array, and are closely attached to each other in pairs to form a piezoelectric component with a vertically placed cylindrical structure, which is assembled in an elastic sleeve. The pressure-bearing body seals the bottom of the elastic sleeve, and the upper end of the elastic sleeve is screwed to the electrode assembly. The outer arc surface of the piezoelectric crystal is an electrode. The electrode assembly applies an axial preload force on the upper end of the piezoelectric crystal to drive the elastic sleeve to stretch and deform, and its inner cylinder surface fits the outer arc surface to form electrical conduction. The rectangular plane of the piezoelectric crystal is another electrode. The edges on both sides of the piezoelectric crystal are flattened to form an assembly plane along its radial direction. The assembly planes of two adjacent piezoelectric crystals in the piezoelectric component fit together under the action of the preload force, and the assembly plane and the outer arc surface are transitioned by an insulating plane.

[0008] The upper end surface, outer arc surface, rectangular plane and assembly plane of the piezoelectric crystal are all provided with conductive coatings.

[0009] Furthermore, the pressure-bearing body is integrally formed with the elastic sleeve, and the pressure-bearing body includes a pressure-bearing circle, a secondary pressure ring, and a connecting ring. The pressure-bearing circle is connected to the secondary pressure ring of the outer ring through a first flexible structure transition, and the secondary pressure ring is connected to the lower end of the connecting ring through a second flexible structure transition. The upper end of the connecting ring encapsulates the lower end of the outer shell;

[0010] The lower end of the elastic sleeve is connected to the secondary pressure ring, the pressure-bearing circle is concentric with the elastic sleeve, and the pressure-bearing circle and the first flexible structure jointly cover the bottom port of the elastic sleeve.

[0011] Furthermore, it also includes a force transmission block for transmitting the stress of the pressure circle. The force transmission block can be slidably assembled in the elastic sleeve, its lower end face is fitted on the upper plane of the pressure circle, and its upper end face is fitted and pressed by the lower end combined plane of the piezoelectric component.

[0012] Furthermore, the force transmission block is a circular cylindrical structure, and the diameter of its inner ring hole should be equal to or smaller than the diameter of the inscribed circle of the piezoelectric component.

[0013] Furthermore, the elastic sleeve includes a deformation section and a guide section with different wall thicknesses, the force transmission block is arranged in the guide section, and the piezoelectric component is assembled in the deformation section.

[0014] Furthermore, the electrode assembly includes an electrode shell, a crystal terminal electrode, a negative electrode wire, an insulating ring, and a negative electrode lead terminal;

[0015] The crystal end electrode is arranged in the elastic sleeve and is positioned by the insulating ring. There is a gap between the crystal end electrode and the inner wall of the elastic sleeve. The insulating ring cooperates with the elastic sleeve.

[0016] The electrode shell is inserted and fixed in the electrode mounting hole of the outer shell, and its lower end is inserted into and threadedly connected to the elastic sleeve, so that a pre-tightening force is applied to the insulating ring when the threads are screwed together, and the electrode shell and the elastic sleeve are electrically connected;

[0017] A wire hole is provided through the middle of the electrode shell, which is connected to the annular hole of the insulating ring for passing the negative electrode wire; the lower end of the negative electrode wire is connected to the crystal end electrode, and the upper end is connected to the negative electrode lead-out terminal.

[0018] Furthermore, a cooling cavity is provided in the outer shell, and two water pipe joints are provided on the outer shell, and two cooling water holes are provided therein, which are connected to the water pipe joints and the cooling cavity respectively, for inputting and outputting circulating cooling water;

[0019] The elastic sleeve is arranged in the middle of the cooling cavity, and the pressure-bearing body covers the lower port of the cooling cavity;

[0020] The cooling cavity is connected to the electrode mounting hole. A sealing clip is provided near the lower end of the electrode shell. The sealing clip is clamped on the lower end surface of the electrode mounting hole. The electrode shell is also provided with a sealing member for sealing the cooling cavity.

[0021] Compared with the prior art, the pressure sensor based on the transverse piezoelectric effect of the present invention has the following beneficial effects:

[0022] Pressure detection is performed using the transverse piezoelectric effect of piezoelectric crystals. Since its sensitivity depends on the outer arc surface and rectangular plane area perpendicular to the pressure-bearing surface, it can be achieved by increasing the length of the piezoelectric crystal. This allows the pressure sensor to be designed with a small radial size while meeting the sensitivity requirements, which is beneficial for the use of pressure sensors in small, complex, and precise engines. There is no need to weld wires between the piezoelectric crystals. The elastic sleeve stretches and deforms under the action of the preload force, so that its inner cylinder wall is in close contact with the outer arc surface of the piezoelectric crystal. In the high-temperature and high-pressure cylinder environment, it has high structural strength, good reliability, stable detection performance, and high sensitivity. In addition, the pressure sensor has a simple overall structure, is easy to assemble, has good sealing, is highly sensitive to pressure on the pressure-bearing body, and has high detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a perspective view of the final assembly of the pressure sensor of the present invention;

[0024] Figure 2 Schematic diagram of the cross-sectional structure of the pressure sensor of the present invention;

[0025] Figure 3 for Figure 2 Schematic diagram of the combined structure of the medium-pressure piezoelectric crystal;

[0026] Figure 4 for Figure 3 A partial magnified view of the corners of a medium-voltage transistor;

[0027] Figure 5 for Figure 3 A three-dimensional diagram of the structure of a medium-pressure transistor.

[0028] In the figure: 1. Water pipe joint; 2. Electrode assembly; 21. Insulation head; 22. Negative electrode lead; 23. Negative electrode wire; 24. Electrode shell; 25. Sealing clamp circle; 26. Insulation ring; 27. Crystal end electrode; 3. Outer shell; 31. Joint mounting hole; 32. Cooling water hole; 33. Electrode mounting hole; 34. Cooling cavity; 4. Pressure-bearing body; 41. Elastic sleeve; 42. Pressure-bearing circle; 43. Secondary pressure ring; 44. Connecting ring; 5. Force transmission block; 6. Piezoelectric crystal; 61. Insulation plane; 62. Assembly plane. DETAILED DESCRIPTION

[0029] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only the best embodiments of the present invention, not all embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0030] This embodiment provides a pressure sensor based on the transverse piezoelectric effect, such as Figure 1-Figure 5 As shown, it includes an outer shell 3, a pressure-bearing body 4, a piezoelectric crystal 6 and an electrode assembly 2, wherein the piezoelectric crystal 6 uses the transverse piezoelectric effect for pressure detection. The piezoelectric crystal 6 is a long cylindrical structure with an arcuate cross-section. The arcuate cross-section is a minor arc that is smaller than a semicircle. The piezoelectric crystal 6 is placed vertically, with the lower end receiving pressure and the upper end connected to the electrode assembly 2, and the electrode assembly 2 applies a pre-tightening force. After the piezoelectric crystal 6 is compressed, charges are generated on the outer arc surface and the rectangular plane. The outer arc surface serves as a positive electrode and the rectangular plane serves as a negative electrode. Both surfaces are provided with a conductive coating and are respectively connected to the two electrodes of the electrode assembly 2;

[0031] The number of piezoelectric crystals 6 is n, where n ≥ 3, and their bow angle is 360° / n. Therefore, when n piezoelectric crystals 6 are arranged in a circular array and placed in pairs, they can form a piezoelectric component with a cylindrical structure. Since the sensitivity of the piezoelectric crystals 6 depends on the outer arc surface and the rectangular plane perpendicular to the pressure direction, the sensitivity can be improved by increasing the length of the piezoelectric crystals 6. Therefore, while meeting the sensitivity requirements, the radial dimension of the piezoelectric component can be designed to be very small, which facilitates the use of the pressure sensor in small, complex, and sophisticated engines.

[0032] Refer again to 3- Figure 5, respectively flatten the vertical edges of the piezoelectric crystal 6 on both sides to form assembly planes 62 on both sides, and the two vertical assembly planes 62 are respectively in the radial direction. In this way, under the action of the preload force, the assembly planes 62 of adjacent piezoelectric crystals 6 fit together to form a piezoelectric component with a stable structure. In addition, the assembly plane 62 and the outer arc surface are transitioned by an insulating plane 61. The insulating plane 61 and the lower end surface are not provided with a conductive coating for isolating the two electrodes on the piezoelectric crystal 6. The assembly plane 62 and the upper end surface are also provided with a coating, which is obtained by gold plating or platinum plating;

[0033] The prior art uses a pressure rod as a pressure-bearing element, but the sealing reliability of the pressure rod is insufficient and it is not suitable for use in a cylinder. In this embodiment, the pressure-bearing body 4 provided at the lower end of the outer shell 3 is a disc-shaped structure, which is welded to the lower end of the outer shell 3. The pressure-bearing body 4 has a certain thickness, and the lower end of the outer shell 3 is frustum-shaped. The upper end circle of the pressure-bearing body 4 coincides with the frustum end circle and is then laser welded. During testing, only the pressure-bearing body 4 as a whole extends into the cylinder to receive the direct effect of the cylinder pressure, and the outer shell 3 is clamped outside the cylinder mounting hole.

[0034] like Figure 1-Figure 2 As shown, the pressure-bearing body 4 and the elastic sleeve 41 are an integrally formed structure, and the pressure-bearing body is a disc structure constructed by a connecting ring 44, a pressure-bearing circle 42, and a secondary pressure ring 43. The pressure-bearing circle 42 is located in the center, and its outer ring is the secondary pressure ring 43. The pressure-bearing circle 42 is connected to the secondary pressure ring through a first flexible structure, and the secondary pressure ring is connected to the lower end of the connecting ring 44 through a second flexible structure. The first flexible structure and the second flexible structure are both formed by removing material on both side planes of the bottom surface of the disc structure to form a deformable annular thin structure. Therefore, the pressure-bearing circle 42 and the secondary pressure ring 43 can both be strained when subjected to the pressure in the cylinder. The setting of the secondary pressure ring 43 can further improve the sensitivity of strain and stress feedback. Under the action of the preload, the pressure-bearing circle 42 will synchronously and accurately feed back the pressure to the pressure after being compressed. On the electrical component; in order to improve the accuracy, an elastic sleeve 41 is integrally formed on the disc structure, and the lower port of the elastic sleeve 41 is connected to the secondary pressure ring 43, and the pressure-bearing circle 42 is connected to the elastic sleeve 41 through a first flexible structure. The piezoelectric component is gap-assembled in the elastic sleeve, and the upper end of the elastic sleeve 41 is screwed to the electrode assembly 2. One is used to support the elastic sleeve 41 and provide its rigidity, and the other is to simultaneously apply a pre-tightening force on the elastic sleeve 41. Under the action of the axial pre-tightening force, the elastic sleeve 41 stretches and deforms, and its inner cylinder wall fits with the outer arc surface to achieve electrical conduction; the pressure received by the pressure-bearing circle 42 is synchronously fed back to the piezoelectric component in the elastic sleeve 41. The pressure-bearing body 4, the elastic sleeve 41 and the piezoelectric component together form a combination that can sensitively sense pressure, thereby improving the detection accuracy;

[0035] Since the pressure received on the pressure circle 42 is fluctuating, in order to better synchronously transmit the detection pressure to the n piezoelectric crystals 6, a force transmission block 5 is slidably assembled in the elastic sleeve 41, and the lower end face of the force transmission block 5 is fitted on the upper plane of the pressure circle 42, and its upper end face is fitted by the lower end combined plane of the piezoelectric component, and they are pressed against each other under the action of the axial preload; in order to reduce the transfer of heat, the force transmission block 5 is a circular cylindrical structure, and the aperture of its inner ring hole should be equal to or smaller than the diameter of the inscribed circle of the piezoelectric component, and smaller than the diameter of the pressure circle 42; the elastic sleeve 41 includes a deformation section and a guide section with different wall thicknesses, and the guide section has a larger wall thickness and has greater rigidity, which is used to assemble and guide the force transmission block 5 therein, and the piezoelectric component is assembled in the deformation section, the deformation section has a small wall thickness, and is easy to deform and fit the piezoelectric component under the preload;

[0036] When assembling the pressure sensor, first assemble the electrode assembly 2 and the pressure-bearing body 4, and finally assemble the outer shell 3; refer to Figure 2 The electrode assembly 2 includes an electrode shell 24, a crystal terminal electrode 27, a negative electrode wire 23, an insulating ring 26, and a negative electrode lead-out terminal 22; the electrode shell 24 is connected to the elastic sleeve 41 and is used to conduct the positive electrode of the piezoelectric component, and the negative electrode of the piezoelectric component is conducted through the crystal terminal electrode 27, the negative electrode wire 23, and the negative electrode lead-out terminal 22;

[0037] The crystal end electrode 27 is arranged in the elastic sleeve 41, and a gap is set between it and the elastic sleeve 41. The gap is set by the insulating ring 26. The insulating ring 26 cooperates with the elastic sleeve 41. The crystal end electrode 27 is a stepped circular structure. Its lower end face is in contact with the upper end face of the piezoelectric component, and its upper small round end is inserted into the annular hole of the insulating ring 26 for positioning. The outer diameter of the large round end of the crystal end electrode 27 is smaller than the diameter of the elastic sleeve 41. After the insulating ring 26 performs center positioning, an insulating gap is formed between the large round end of the crystal end electrode 27 and the wall of the elastic sleeve 41.

[0038] The lower end of the electrode shell 24 is screwed into the elastic sleeve 41, and an axial pre-tightening force is applied to the insulating ring 26. After the electrode shell 24 and the pressure-bearing body 4 are assembled, the electrode shell 24 is fixedly installed on the electrode mounting hole 33 on the outer shell 3. The pressure-bearing body 4 is attached to the lower end surface of the outer shell 3 and then laser welded.

[0039] A wire hole is provided through the middle of the electrode shell 24, which is connected to the annular hole of the insulating ring 26. The negative electrode wire 23 led out from the small round end of the crystal end electrode 27 is pulled through the annular hole and the wire hole to the negative electrode lead-out terminal 22 at the upper end of the electrode shell 24. The negative electrode lead-out terminal 22 is fixedly mounted on the upper end opening of the electrode mounting hole 33 through the insulating head 21.

[0040] As a further technical solution, since the high temperature environment in the cylinder will affect the lateral piezoelectric effect of the piezoelectric crystal 6 and the pressure feedback accuracy of the pressure-bearing body 4, in order to ensure the detection accuracy, the pressure sensor needs to be cooled in time. A cooling cavity 34 and two cooling water holes 32 connected to the cooling cavity 34 are provided in the outer shell 3. Two connector mounting holes 31 connected to the cooling water holes 32 are provided on the outer shell 3 for mounting two water pipe connectors 1 and inputting and outputting circulating cooling water;

[0041] The lower end of the cooling chamber 34 is an open mouth, and the pressure-bearing body 4 covers the open mouth to facilitate cooling water to contact the cooling pressure-bearing body 4. The elastic sleeve 41 is arranged in the middle of the cooling chamber 34. Since the cooling chamber 34 is connected to the electrode mounting hole 33, the electrode mounting hole 33 needs to be sealed. A sealing clamp circle 25 is provided near the lower end of the electrode shell 24, and a sealing ring is provided on the outer axial surface near the sealing clamp circle 25, or a sealing gasket is provided between the sealing clamp circle 25 and the lower end surface of the electrode mounting hole 33. After the electrode shell 24 is tightened and connected to the outer shell 3, its sealing clamp circle 25 is clamped on the lower end surface of the electrode mounting hole 33, and the lower hole opening of the electrode mounting hole 33 is sealed by the sealing component.

[0042] The directional words such as "upper", "lower", "side", "end", "bottom", "inside" and "outside" mentioned in this article are based on the Figure 1-Figure 5 The orientations or positional relationships shown in the corresponding drawings are mainly used to better describe the present invention and its embodiments, and are not used to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation; in addition, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance;

[0043] Furthermore, some of the above terms may be used to express other meanings besides indicating a direction or positional relationship. For example, the terms "on" and "in" may also be used to express a dependency or connection relationship in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0044] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A pressure sensor based on the transverse piezoelectric effect, characterized in that: It includes an outer shell, a pressure-bearing body, a piezoelectric crystal and an electrode assembly. The pressure-bearing body is provided at the lower end of the outer shell. The piezoelectric crystal is vertically arranged in the outer shell, with its lower end receiving the stress transmitted by the pressure-bearing body and its upper end connected to the electrode assembly. The number of the piezoelectric crystals is n, n≥3, the piezoelectric crystal is an arched cylindrical structure, and its arch angle is 360° / n, and the n piezoelectric crystals are arranged in a circular array, and are closely attached to each other in pairs to form a piezoelectric component with a vertically placed cylindrical structure, and are assembled in an elastic sleeve, the pressure-bearing body seals the bottom of the elastic sleeve, and the upper end of the elastic sleeve is screwed to the electrode assembly; the outer arc surface of the piezoelectric crystal is an electrode, and the electrode assembly applies an axial preload force to the upper end of the piezoelectric crystal to drive the elastic sleeve to stretch and deform, and its inner cylinder surface fits the outer arc surface to form electrical conduction, and the rectangular plane of the piezoelectric crystal is another electrode; the edges on both sides of the piezoelectric crystal are flattened to form an assembly plane along its radial direction, and the assembly planes of two adjacent piezoelectric crystals in the piezoelectric component fit each other under the action of the preload force, and the assembly plane and the outer arc surface are transitioned by an insulating plane; The upper end surface of the piezoelectric crystal, the outer arc surface, the rectangular plane and the assembly plane are all provided with a conductive coating.

2. The pressure sensor based on the transverse piezoelectric effect according to claim 1, characterized in that: The pressure-bearing body is integrally formed with the elastic sleeve, and the pressure-bearing body includes a pressure-bearing circle, a secondary pressure ring, and a connecting ring. The pressure-bearing circle is connected to the secondary pressure ring of the outer ring through a first flexible structure transition, and the secondary pressure ring is connected to the lower end of the connecting ring through a second flexible structure transition. The upper end of the connecting ring encapsulates the lower end of the outer shell; The lower end of the elastic sleeve is connected to the secondary pressure ring, the pressure-bearing circle is concentric with the elastic sleeve, and the pressure-bearing circle and the first flexible structure jointly cover the bottom port of the elastic sleeve.

3. The pressure sensor based on the transverse piezoelectric effect according to claim 2, characterized in that: It also includes a force transmission block for transmitting the stress of the pressure circle. The force transmission block can be slidably assembled in the elastic sleeve, and its lower end face is fitted on the upper plane of the pressure circle, and its upper end face is fitted and pressed by the lower end combined plane of the piezoelectric component.

4. The pressure sensor based on the transverse piezoelectric effect according to claim 3, characterized in that: The force transmission block is a circular cylindrical structure, and the diameter of its inner ring hole should be equal to or smaller than the diameter of the inscribed circle of the piezoelectric component.

5. The pressure sensor based on the transverse piezoelectric effect according to claim 3, characterized in that: The elastic sleeve comprises a deformation section and a guide section with different wall thicknesses. The force transmission block is arranged in the guide section, and the piezoelectric component is assembled in the deformation section.

6. The pressure sensor based on the transverse piezoelectric effect according to any one of claims 2 to 5, characterized in that: The electrode assembly includes an electrode shell, a crystal end electrode, a negative electrode wire, an insulating ring and a negative electrode lead-out terminal; The crystal end electrode is arranged in the elastic sleeve, is positioned by the insulating ring, and has a gap with the inner wall of the elastic sleeve, and the insulating ring cooperates with the elastic sleeve; The electrode housing is inserted and fixed in the electrode mounting hole of the outer shell, and its lower end extends into and is threadedly connected to the elastic sleeve, so that a pre-tightening force is applied to the insulating ring when the threads are screwed together, and the electrode housing and the elastic sleeve are electrically conductive; A wire hole is provided through the middle of the electrode shell, which is connected to the annular hole of the insulating ring and is used to pass the negative electrode wire; the lower end of the negative electrode wire is connected to the crystal end electrode, and the upper end is connected to the negative electrode lead-out terminal.

7. The pressure sensor based on the transverse piezoelectric effect according to claim 6, characterized in that: A cooling cavity is provided in the outer shell, and two water pipe joints are provided on the outer shell, and two cooling water holes are provided therein, which are respectively connected to the water pipe joints and the cooling cavity, and are used for inputting and outputting circulating cooling water; The elastic sleeve is arranged in the middle of the cooling cavity, and the pressure-bearing body covers the lower port of the cooling cavity; The cooling cavity is communicated with the electrode mounting hole. A sealing clip is provided near the lower end of the electrode shell. The sealing clip is clamped on the lower end surface of the electrode mounting hole. The electrode shell is also provided with a sealing member for sealing the cooling cavity.

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