Capacitive displacement sensor

Abstract

The utility model provides a kind of capacitive displacement sensor, and the annular end face of mounting seat open end is arranged with accommodating cavity in circumferential interval, and the annular end face between adjacent accommodating cavity is equipped with protrusion, and the top surface of protrusion is attached with polar plate. The utility model mainly sets protrusion on annular end face, so that the distance between polar plate bottom surface and annular end face is the height of protrusion, which greatly reduces the contact area between polar plate and mounting seat, and further reduces the interference of thermal expansion and contraction on capacitance measurement value.

Description

Technical Field

[0001] This utility model relates to the field of precision measuring instrument technology, specifically to a capacitive displacement sensor. Background Technology

[0002] High-resolution capacitive displacement sensors can resolve and measure minute displacements as small as 0.5 mm between two opposing planes. Due to their high precision resolution and non-contact measurement advantages, capacitive displacement sensors are widely used in various precision manufacturing industries. The core component of a capacitive displacement sensor is the probe assembly, which mainly consists of measuring electrodes, a mounting base, and signal leads. The measuring electrodes are manufactured using a multilayer ceramic substrate with embedded metal electrode layers through a co-firing process. These electrodes are fixed to a metal mounting base and connected to an external controller via leads.

[0003] In existing technologies, capacitive sensors typically use epoxy resin to bond the metal mounting base and ceramic electrode surfaces together. However, due to the significant difference in the coefficients of thermal expansion (CTE) between metal and ceramic materials, when the ambient temperature fluctuates, the mounting base and electrode on both sides of the adhesive surface will undergo varying degrees of thermal expansion and contraction deformation. This causes positional drift of the measuring end in the displacement detection direction, and this drift is directly coupled to the measured value of the gap between the capacitor plates, becoming a bottleneck restricting the measurement accuracy of the sensor. Utility Model Content

[0004] The purpose of this invention is to provide a capacitive displacement sensor that reduces the impact of thermal expansion and contraction on the sensor's measurement accuracy by decreasing the contact area between the electrode plate and the mounting base.

[0005] To achieve the above objectives, the technical solution adopted by this utility model is as follows: a capacitive displacement sensor, wherein the annular end face of the top open end of the mounting base is circumferentially arranged with cavities for filling colloid, and a protrusion is provided on the annular end face between adjacent cavities, the top surfaces of the protrusions are coplanar, an electrode plate is attached to the top surface of the protrusion, and the electrode plate surface covers the open end of the mounting base.

[0006] This invention primarily involves creating a protrusion on the annular end face of the open end of the mounting base. The distance between the bottom surface of the electrode plate and the annular end face is the height of the protrusion, and the contact area between the electrode plate and the mounting base is the sum of the areas of the top of the protrusion. Compared to the traditional method of directly bonding the electrode plate to the end face of the mounting base, this method eliminates the need for adhesive between the contact surface of the electrode plate and the top of the protrusion. The electrode plate is only bonded to the mounting base at the accommodating cavity. This significantly reduces the contact area between the electrode plate and the mounting base, minimizing the slight bending or warping of the electrode plate relative to the mounting base due to thermal expansion and contraction. This results in minimal deformation of the measuring end in the measurement direction due to thermal expansion and contraction, thereby reducing the interference of thermal expansion and contraction on the capacitance measurement value. Attached Figure Description

[0007] Figure 1 This is a schematic diagram of a capacitive displacement sensor;

[0008] Figure 2 A schematic diagram of a capacitive displacement sensor after the electrodes have been removed;

[0009] Figure 3 This is a schematic diagram of another embodiment of the protrusion. Detailed Implementation

[0010] See Figures 1-3 The capacitive displacement sensor shown has circumferentially spaced cavities 20 for filling colloids on the annular end face 10 of the top open end of the mounting base 1. There are protrusions 30 on the annular end face 10 between adjacent cavities 20. The top surfaces of the protrusions 30 are coplanar. An electrode plate 40 is attached to the top surface of the protrusion 30. The surface of the electrode plate 40 covers the open end of the mounting base 1.

[0011] In the above scheme, the mounting base 1 is usually made of metal, while the electrode plate 40 is usually made of ceramic. When the ambient temperature changes, the mounting base 1 and the electrode plate 40 have significantly different coefficients of thermal expansion, resulting in different deformations. In the traditional scheme, the thermal expansion and contraction of the mounting base 1 with temperature changes is transmitted to the electrode plate 40 through a large-area adhesive layer. Due to the difference in deformation, the surface of the electrode plate 40 will be stretched or compressed by the adhesive layer, causing slight bending or warping, which directly changes the vertical gap between the electrode plate 40 and the measurement target. That is, the sensor measuring end drifts in the displacement detection direction, generating false signals. To address this, this scheme provides a cavity 20 for filling the adhesive, and the electrode plate 40 is attached to the top surface of the protrusion 30. The protrusion 30 serves as the contact point between the electrode plate 40 and the mounting base 1, and the distance between the bottom surface of the electrode plate 40 and the annular end face 10 is the height of the protrusion 30. The protrusion 30 reduces the contact area between the electrode plate 40 and the mounting base 1, while the cavity 20 reduces the bonding area between the electrode plate 40 and the colloid, significantly reducing heat transfer between them. The colloid also acts as a buffer between the mounting base 1 and the electrode plate 40 to mitigate thermal expansion and contraction, thereby improving the positional stability and flatness of the electrode plate 40. Simultaneously, it reduces sensor temperature drift and improves measurement accuracy. In this design, the cavity 20 is either a concave cavity with an open top or a groove radially penetrating the inner wall of the mounting base 1. The colloid filled in the cavity 20 is thermosetting epoxy resin. During assembly, the epoxy resin in the cavity 20 is placed at an ambient temperature of approximately 60°C, where it cures at high temperature, bonding the electrode plate 40 to the mounting base 1. During use, at an ambient temperature of approximately 20°C, the cured colloid firmly adheres the electrode plate 40 to the mounting base 1, pressing the bottom surface of the electrode plate 40 against the top surface of the protrusion 30.

[0012] As a preferred embodiment, the protrusions 30 are disposed adjacent to both sides of the circumferential direction of the receiving cavity 20 to shorten the distance between the top of the protrusions 30 and the colloid, thereby preventing the electrode plate 40 from being stretched or squeezed by the colloid and causing slight bending or warping. A further embodiment is that the sidewall of the protrusions 30 adjacent to the receiving cavity 20 shares the same wall as the inner wall of the receiving cavity 20.

[0013] To facilitate the installation of the electrode plate 40, the annular end face 10 is a stepped surface formed by a radially inwardly concave inner ring surface 11 and a radially outwardly convex outer ring surface 12. The accommodating cavity 20 and the protrusion 30 are both disposed on the inner ring surface 11. Preferably, the diameter of the electrode plate 40 is the same as the outer diameter of the inner ring surface 11, so that the stepped surface radially limits the electrode plate 40.

[0014] To improve the stability and reliability of the bonding between the colloid and the electrode plate 40 in the accommodating cavity 20, the accommodating cavities 20 are arranged circumferentially on the annular end face 10, and the number of accommodating cavities 20 is at least 3.

[0015] More specifically, the mounting base 1 is cylindrical, and the electrode plate 40 and the mounting base 1 form a closed cavity. The wire 50, which is electrically connected to the electrode plate 40, passes through the end cap hole 2 at the bottom of the mounting base 1, and the wire 50 is glued to the inner wall of the end cap hole 2. The closed cavity enclosed by the electrode plate 40 and the mounting base 1 is used to house the wire 50 and other components, and this closed cavity can also reduce the parasitic capacitance of the sensor.

[0016] Preferably, the mounting base 1 has a stepped portion on its peripheral wall near the top open end. The radius of the small-diameter section 3 between the stepped portion and the top of the mounting base 1 is R1, and the radius of the large-diameter section 4 between the stepped portion and the bottom of the mounting base 1 is R2, where R2 > R1. Since the electrode plate 40 is made of a relatively brittle material, when using an external clamp to hold and fix the capacitive displacement sensor, the clamp is held on the outer peripheral surface of the large-diameter section 4. The stepped portion can prevent the small-diameter section 3 from contacting the clamping surface of the clamp, thereby protecting the electrode plate 40 from damage caused by the mechanical stress of the clamp.

Claims

1. A capacitive displacement sensor, characterized in that: The annular end face (10) of the top open end of the mounting base (1) is circumferentially spaced with cavities (20) for filling colloid. The annular end face (10) between adjacent cavities (20) is provided with protrusions (30). The top surfaces of the protrusions (30) are coplanar. An electrode plate (40) is attached to the top surface of the protrusion (30). The surface of the electrode plate (40) covers the opening of the mounting base (1).

2. The capacitive displacement sensor according to claim 1, characterized in that: The protrusions (30) are located on both sides of the circumferential direction of the receiving cavity (20).

3. The capacitive displacement sensor according to claim 1 or 2, characterized in that: The sidewall of the protrusion (30) adjacent to the cavity (20) shares the same wall as the inner wall of the cavity (20).

4. The capacitive displacement sensor according to claim 1, characterized in that: The annular end face (10) is a stepped surface composed of a radially concave inner ring surface (11) and a radially outward convex outer ring surface (12). The accommodating cavity (20) and the protrusion (30) are both located on the inner ring surface (11).

5. The capacitive displacement sensor according to claim 4, characterized in that: The diameter of the electrode plate (40) is the same as the outer diameter of the inner ring surface (11).

6. The capacitive displacement sensor according to claim 1, characterized in that: The accommodating cavities (20) are arranged circumferentially on the annular end face (10), and there are at least 3 accommodating cavities (20).

7. The capacitive displacement sensor according to claim 1, characterized in that: The mounting base (1) is cylindrical, and the electrode plate (40) and the mounting base (1) form a closed cavity. The wire (50) electrically connected to the electrode plate (40) passes through the end cap hole (2) at the bottom of the mounting base (1) and the wire (50) is glued to the inner wall of the end cap hole (2).

8. The capacitive displacement sensor according to claim 1, characterized in that: The mounting base (1) has a stepped section on the peripheral wall near the top open end. The radius of the small diameter section (3) between the stepped section and the top of the mounting base (1) is R1, and the radius of the large diameter section (4) between the stepped section and the bottom of the mounting base (1) is R2, where R2 > R1.

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