KR100388375B1 - Metalized cylindrical capacitive sensor for measuring an orbit of the machine tool spindle and method of manufacturing the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic cylindrical capacitive sensor for measuring a shaft rotational trajectory of a machine tool using metallizing, and a method of manufacturing the same. The purpose of the present invention is to measure rotation precision of a precision spindle that is difficult to measure with a general displacement measuring sensor. The present invention provides a sensor for measuring only a motion component of an axis from which a shape error of an object is removed and a manufacturing method thereof.

The configuration of the present invention is a cylindrical sensor body manufactured by using alumina ceramic having excellent mechanical, thermal and electrical properties; A sensor electrode face and a guard electrode face formed on the inner or outer diameter surface of the cylindrical body by using metallization; A ceramic cylindrical sensor including a signal line connecting portion in which solder for connecting the electrode surface and a sensor signal line is fused, and a method of manufacturing the same are provided.

Description

Metallic cylindrical capacitive sensor for measuring an orbit of the machine tool spindle and method of manufacturing the same}

The present invention relates to a capacitive sensor for precisely measuring the axis rotational trajectory of a machine tool and a method of manufacturing the same, and more particularly, to form an electrode surface on a ceramic surface by metallizing after determining a shape with a ceramic material. It relates to a capacitive sensor and a manufacturing method thereof.

In order to measure the rotational trajectory of the machine tool spindle, a measuring object attached to the spindle itself or the spindle and rotating together is required.

If the test bar 3, which is the measurement target, is a complete circular cylinder without any shape error, as shown in FIG. 1, the rotational trajectory of the machine tool spindle 1 can be obtained through the displacement sensors 2 installed in the X and Y directions. have.

However, in the measurement of the spindle displacement trajectory in a real situation where surface roughness and roundness errors exist, if the shape error of the measurement surface is not smaller than the movement of the axis, a general displacement measurement system cannot measure only the axis movement. Because.

Figure 2 shows the operating characteristics of the capacitive sensor using a narrow surface and a wide surface, showing the difference between the two, using a larger area as the sensor surface than the general sensor (4) using a narrow area as the sensor surface In the case of the sensor 5, the shape errors having a high frequency component are canceled out by the averaging effect by the area integration.

2, 6 is a measurement object having a shape error, 7 is a motion error of a measurement object, and 8 is a sensor measurement signal.

Therefore, as shown in FIG. 3, a sensor system is required to cover the entire circumferential surface of the cylinder to be measured.

As such a large area sensor system, a capacitive sensor is most preferable, and displacement should be measured by detecting a change in capacitance formed in a gap between a cylinder surface to be measured and a sensor surface surrounding the sensor.

In order to achieve two-dimensional displacement through a cylindrical sensor system, several electrode faces must be formed on the sensor surface.

To this end, a method of fabricating a cylindrical sensor constituting the electrode surface through post-processing through a gap piece and molding for electrical separation between the electrode surfaces has been proposed. (Patent No. 0216987)

However, the disadvantage of the patent application is that the separation of the sensor and the guard in the cylindrical sensor through the epoxy molding and the grinding or grinding process for the separation of the sensor and the guard electrode, and the manufacturing method that produces the required shape precision is molding material and sensor And due to the different thermal properties of the guard material is not easy to process, there is a disadvantage that is vulnerable to deformation over a long period of time.

In FIG. 3, 9 is a capacitive sensor electrode surface, 10 is a capacitive guard electrode surface, 11 is a metal housing, 12 is an epoxy molding part, 13 is a sensor connection line, and 14 is an epoxy filled insulating gap. to be.

An object of the present invention for solving the above problems is to provide a sensor for measuring only the motion component of the shaft from which the shape error of the measurement object is removed, in order to measure the rotational accuracy of the precision spindle which is difficult to measure with a general displacement measuring sensor. To improve the durability and reliability of the sensor system.

The object as described above is a cylindrical sensor body manufactured by using alumina ceramic having excellent mechanical, thermal and electrical properties; A sensor electrode surface and a guard electrode surface formed on the surface of any one of an inner diameter or an outer diameter of the cylindrical sensor body by using metallization; It is achieved by providing a ceramic cylindrical sensor composed of a signal line connection portion in which solder for welding the electrode surface and the sensor signal line is fused.

Another object of the present invention is the step of turning and grinding after sintering the cylindrical ceramic sensor combined with the machine tool spindle exposed surface or chuck outer diameter or additionally mounted master cylinder or master ring; Metallizing the molybdenum paste on the surface of the cylindrical ceramic in accordance with the designed electrode surface; Plating a metal such as nickel on the metallized surface by brazing; Attaching solder to an electrode end to connect the plated electrode surface to a sensor signal line; It is achieved by providing a method of manufacturing a metallized ceramic cylindrical sensor, which comprises a step of removing a burr of a pattern boundary of the formed electrode surface.

1 is a view showing a rotation precision measurement using a general displacement sensor,

2 is a view showing the operating characteristics of the capacitive sensor using a narrow surface and a wide surface,

3 is a view showing the shape of a molded cylindrical capacitive sensor,

4 is a view showing the form before the metallization of the ceramic sensor according to the invention,

5 is a view showing a form produced by metallizing the inner diameter portion of the ceramic sensor according to the invention,

6 is a view showing a form produced by metallizing the outer diameter portion of the ceramic sensor according to the invention,

7 is an enlarged view illustrating electrode lines for connecting a sensor and a guard electrode surface to a signal line when metallizing is performed on an inner diameter portion of a ceramic sensor according to the present invention;

8 is an enlarged view illustrating electrode lines for connecting a sensor and a guard electrode surface to a signal line when metallizing is performed on an outer diameter portion of a ceramic sensor according to the present invention;

9 is a view showing the sensor and the guard form of a typical capacitive sensor,

10 is a diagram relating to impedance values between two conductors.

<Codes and explanations of the main parts of the drawings>

(1): machine tool spindle (2): displacement sensor

(3): test bar (4): narrow area displacement sensor

(5): displacement sensor of large area (6): measuring object with shape error

(7): Movement error of the measurement object (8): Sensor measurement signal

(9): Capacitive sensor electrode surface (10): Capacitive guard electrode surface

(11): metal housing (12): epoxy molding

(13): Sensor lead (14): Epoxy filled insulation gap

(15): Through hole for sensor housing (16): Sensor body made of ceramic

(17): solder for signal line connection (18): signal line connection

When described in detail with reference to the accompanying drawings, the configuration and the operation of the embodiment of the present invention to achieve the object as described above and to perform the task for eliminating the conventional drawbacks.

FIG. 4 is a view illustrating a shape before a metallization of a ceramic sensor according to the present invention, in which a plurality of through holes 15 for attaching a sensor housing are formed on the upper surface of the cylindrical ceramic sensor body 16.

5 is a view showing the inner diameter metallizing shape of the ceramic sensor according to the present invention, from the inside of the inner diameter portion of the ceramic sensor body 16 of FIG. An epoxy filled insulating gap 14 for enclosing and insulating the encapsulation, and a capacitive guard electrode surface 10 for enclosing the epoxy filled insulating gap 14 are formed in this order. In addition, the signal line connecting portion 18 for connecting the respective electrode surface and the signal line and the solder 17 for connecting the signal line are formed.

6 is a view showing the outer diameter metallizing shape of the ceramic sensor according to the present invention, the capacitive sensor electrode surface 9 and the epoxy wrapped around the electrode surface 9 in the outer diameter in the same manner as in FIG. The filled insulating gap 14 and the capacitive guard electrode surface 10 for enclosing the epoxy filled insulating gap 14 are sequentially formed. In addition, the signal line connecting portion 18 for connecting the respective electrode surface and the signal line and the solder 17 for connecting the signal line are formed.

7 is a view showing the inner diameter signal line connection of the ceramic sensor according to the invention in more detail showing the inner diameter portion of Figure 5, Figure 8 is a view showing the outer diameter signal line connection of the ceramic sensor according to the invention, the outer diameter of Figure 6 Wealth is shown in more detail.

The configuration of the sensor of the present invention comprises a cylindrical sensor body 16 manufactured by using alumina ceramic having excellent mechanical, thermal and electrical properties; Sensor electrode surface (9) and guard electrode surface (10) and sensor electrode surface (9) formed by using metallization on the surface of either the inner or outer diameter according to the capacitance formation direction according to the installation position of the cylindrical sensor body And an epoxy filled insulating gap 14 for insulating between the guard electrode surfaces 10; Each of the electrode surfaces 9 and 10 and the signal line connecting portion 18 to which the solder 17 for connecting the sensor signal lines is fused are formed.

Alumina ceramics are advantageous as an electrical material because they have high insulation strength and low leakage loss.

In addition, the mechanical strength and heat resistance is excellent, the impact of a sudden temperature change is generally less than the metal material used in the capacitive sensor.

The sensor system is manufactured by manufacturing the required shape with the ceramic material with the required precision and then forming the required electrode surface on the ceramic surface through metallizing.

Ceramics are metallized by the following method.

Paste molybdenum powder is coated on the surface of the ceramics and baked at about 1500 DEG C in a hydrogen atmosphere.

Then, the intermediate reaction layer is formed between the baked molybdenum layer and the ceramic, and their adhesive strength is considerably stronger and maintains high bonding strength even at high vacuum.

The necessary metallic parts are bonded by brazing in a hydrogen atmosphere.

The manufacturing process of the cylindrical ceramic sensor is as follows.

First, as shown in FIG. 4, a sintered ceramic is produced by manufacturing a mold considering a shape of a rough shape and a hole for fastening a bolt for assembling the ceramic powder.

At this time, the alumina Al ₂ O ₃ It is common to have a composition ratio of 90 ~ 96%, especially alumina ceramic for metallizing is preferably to have a composition of 94%.

In this case additional chemical components of 4% SiO ₃ , 1% CaO and 1% MgO are included.

The thermal expansion coefficient of the alumina ceramic having such a composition is about 7.9x10-6 / ° C in the range of 20 ° C to 1000 ° C and the temperature that can be used under no load is about 1,700 ° C.

In addition, the dielectric constant, which is an electrical property, shows a value of 8.9 at 1 MHz and 25 ° C. (誘 電 正 接, dissipation factor, tan d is 0.0001 at 1MHz and 25 ° C.)

The advantages of the ceramic sensor compared to the conventional method of manufacturing a cylindrical sensor by epoxy molding are as follows.

In the case of epoxy used for structural purposes, the coefficient of thermal expansion is very large, about 40x10-6 / ℃. At this time, the coefficient of thermal expansion of copper or brass used as the electrode surface of the molded sensor is 18-20x10-6 / ℃. Alternatively, epoxy is filled between the sensor electrode surface and the guard electrode surface made of brass to form the sensor shape, and then the required precision is obtained through internal diameter turning or grinding.

Due to the difference in behavior of the two materials due to the cutting heat caused during the cutting process, the residual stress remains large on the machining surface.

This causes the deformation of the workpiece after the completion of processing, there is a disadvantage that the production cost is very high when cutting and suppressing the temperature rise very much.

In addition, it can be pointed out that the shape accuracy of the epoxy material is changed due to the fluidity of the material when exposed to periodic temperature changes for a long time.

In particular, since it is applied to machine tools, there is a possibility of absorbing oil mist, moisture and the like.

On the other hand, the coefficient of thermal expansion of ceramic is 7.9x10-6 / ℃, which is lower than the coefficient of thermal expansion of steel, which is the main measurement object, 10 ~ 18x10-6 / ℃, and it is molded to 13x10-6 / ℃ of nickel plated by metallizing. Better thermal deformation than sensor material

In addition, since the sensor of the ceramic material is metalized and plated after finishing the processing to give the required precision, the possibility of residual stress due to the cutting process is low.

In the case of the sensor measurement surface, the roundness and the surface roughness of the measurement target portion of the master ring, the master cylinder or the main shaft, which is the measurement surface, are required to be below a certain level.

If the sensor resolution of about 0.1㎛ ~ 1㎛ is required, the measuring surface is required to be 5㎛ ~ 10㎛ or less, the general precision level of the spindle parts of the machine tool is usually more accurate. The sensor part is machined so that the precision of a sensor part may be about 10 micrometers about such a normal application object.

The capacitive sensor is inversely related to the measurement range and the sensitivity is inversely related to the narrow gap between the measurement surface and the sensor surface in order to increase the sensitivity.

In the case of illustration, it is assembled with radial clearance of 100 μm for high precision spindles such as air bearings and 200 μm to 300 μm for spindles using ball bearings in consideration of the measurement range. Consideration is given to the minimum precision required.

Hereinafter is a preferred embodiment of the present invention.

(Example)

For metallization, paste-type molybdenum powder is coated on the inner or outer diameter surface of the ceramics according to the electrode shape and baked at about 1500 ° C. in a hydrogen atmosphere.

To this end, a mask having an electrode-shaped penetrating portion is manufactured and used for paste coating.

The electrode surface can be formed in the ceramic inner or outer diameter according to the capacitance formation direction according to the sensor installation position.When measuring the capacitance with the main shaft part or the master cylinder, the master ring is installed in the ceramic inner diameter to refer to the ring inner diameter. As a result, when measuring capacitance, the sensor electrode surface is formed by metallizing the outer diameter portion of the ceramic, which has a shape as shown in FIGS. 5 and 6.

Molybdenum coated in the form of sensor electrodes forms an intermediate reaction layer on the surface of adjacent ceramics when baked at high temperatures, which increases the adhesion strength with the metal to be coated and maintains high bonding strength even at high vacuum. do.

The intermediate reaction layer formed at this time has a thickness of about 20 ㎛.

The metallic material required for the ceramic thus completed is bonded by brazing in a high temperature hydrogen atmosphere.

The surface of the sensor is nickel-plated in consideration of durability and its thickness is 50㎛ ~ 100㎛.

After plating, solder is welded to the end of the electrode surface formed for signal line connection to facilitate the connection of the sensor signal line to the electrode surface.

In the case of the inner diameter type sensor as shown in FIG. 7, a portion for connecting the signal line is installed by extending the electrode surface to the ceramic outer diameter, and in the case of the outer diameter type sensor, the same method as shown in FIG. 7 may be performed. When making the width of the ceramic sensor larger than the ring, a portion for connecting the signal line may be provided on the outer diameter surface.

The ceramic sensor completed as described above may have an ear around the electrode surface, and in this case, an operation of removing the corresponding area to be flattened using fine sandpaper more than 2000 times is performed.

The capacitive sensor generally has a shape as shown in FIG. 9, and a guard electrode for uniformly distributing an electric field of the sensor electrode surface 9 and the external noise shielding and the sensor electrode surface to form a capacitance with the measurement surface in the center. The surface 10 has a shape surrounding the sensor electrode surface, and has an insulating gap 14 filled with epoxy between the electrode surfaces.

Since the high frequency signal is applied to the electrode surface for the measurement of the sensor, when the impedance between the individual electrode surfaces is low, the adjacent electrode surfaces may affect each other's signals.

Impedance between adjacent electrodes can be calculated for various cases as shown in FIG.

If the shape-related parameters are constant, the impedance between the two conductors is inversely proportional to the square root of the permittivity. This is compared with the molded sensor and the ceramic sensor as follows.

In the case of a molded sensor, epoxy is filled between the sensor electrode surface and the guard electrode surface. In the case of a metal plated ceramic plated sensor, the electrode surface is separated by air.

The dielectric constant of air is 1.0 and has a value of 3.6 for epoxy and 8.9 for ceramic.

In this calculation, the impedance is approximately twice as large as the case of epoxy charging and air charging, and the signal and noise are less likely to flow between each electrode surface.

In addition, the ceramic material has a dielectric constant of 8.9 and maintains a high dielectric constant even for a high frequency signal. Thus, the ceramic material has excellent dielectric properties, and thus may be a desirable sensor material in an environment of a variety of ferroelectric noise machine tools.

The insulation between the sensor and the attachment is also about 1.57 times larger when the ceramic is made of ceramics than when epoxy is used.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

As described above, the present invention can measure the rotational trajectory of the precision spindle, which is difficult to measure with a general displacement measuring sensor as described above, and can improve sensor durability and reliability by using a ceramic material.

That is, the cylindrical sensor body manufactured by using alumina ceramic excellent in mechanical, thermal, and electrical properties; A sensor electrode surface and a guard electrode surface formed on the surface of any one of an inner diameter or an outer diameter of the cylindrical sensor body by using metallization; The ceramic cylindrical sensor system composed of the electrode line and the signal line connecting part fused with solder for connecting the sensor signal line realizes accurate rotation trajectory measurement, and is not only stable to temperature change due to the use of ceramic material, but also at high temperature. It can be applied to the main shaft of a machine tool, which increases the reliability, and enables the measurement of the trajectory of the rotating body in high temperature environment where the general sensor is not easy to apply. Are especially effective in contributing to.

Claims (7)

In the cylindrical capacitive sensor for measuring the shaft rotation accuracy of a machine tool, A cylindrical sensor body 16 manufactured using alumina ceramics; An epoxy-filled insulating gap insulating the sensor electrode surface 9 and the guard electrode surface 10 and the sensor electrode surface 9 and the guard electrode surface 10 formed by using metallization on the cylindrical sensor body surface ( 14); Ceramic cylindrical capacitance for measuring the axis rotation trajectory of the machine tool using metallizing, characterized in that the electrode line (9, 10) and the signal line connecting portion 18 is fused to the solder 17 for connecting the sensor signal line Type sensor. The method of claim 1, An epoxy-filled insulating gap insulating the sensor electrode surface 9 and the guard electrode surface 10 and the sensor electrode surface 9 and the guard electrode surface 10 formed by using metallization on the cylindrical sensor body surface ( 14); The signal line connecting portion 18 in which the solder 17 for connecting the electrode signal surfaces 9 and 10 and the sensor signal lines is fused is formed by metallizing the ceramic inner diameter portion during the capacitance measurement with the main shaft portion or the master cylinder. Ceramic cylindrical capacitive sensor for measuring the axis of rotation trajectory of the machine tool using metallization. The method of claim 1, An epoxy-filled insulating gap insulating the sensor electrode surface 9 and the guard electrode surface 10 and the sensor electrode surface 9 and the guard electrode surface 10 formed by using metallization on the cylindrical sensor body surface ( 14); The signal line connecting portion 18, to which the electrode surfaces 9 and 10 and the solder 17 for connecting the sensor signal lines are fused, has a master ring installed and metallized in the ceramic outer diameter when capacitance is measured based on the ring inner diameter. Ceramic cylindrical capacitive sensor for measuring the axis rotation trajectory of the machine tool using metallizing, characterized in that formed by. In the method for manufacturing a cylindrical capacitive sensor for measuring the axis rotation accuracy of a machine tool, Sintering and grinding the cylindrical ceramic sensor combined with the machine tool spindle exposed surface or the chuck outer diameter or the additionally mounted master cylinder or master ring; Metallizing the molybdenum paste on the surface of the cylindrical ceramic in accordance with the designed electrode surface; Plating a metal such as nickel on the metallized surface by brazing; Attaching solder to an electrode end to connect the plated electrode surface and a sensor signal line; The method of manufacturing a ceramic cylindrical capacitive sensor for measuring the axis rotational trajectory of a machine tool using metallizing, characterized in that it comprises a step of removing a burr of a pattern boundary of the formed electrode surface. The method of claim 4, wherein The ceramics used in the sintering molding of the cylindrical ceramic sensor are made of alumina ceramics, the composition of which is composed of 4% SiO ₃ , CaO 1%, MgO 1% and the rest of alumina (Al ₂ O ₃ ). A method of manufacturing a ceramic cylindrical capacitive sensor for measuring the axis rotational trajectory of a machine tool using metallization. The method of claim 4, wherein In the step of metallizing the molybdenum paste, a paste-like molybdenum powder is coated on the inner or outer diameter surface of the ceramics according to the electrode shape and baked in a hydrogen atmosphere at about 1500 ° C. to form an intermediate reaction layer between the molybdenum layer and the ceramic. A method of manufacturing a ceramic cylindrical capacitive sensor for measuring the rotational trajectory of a machine tool using metallizing, wherein the thickness is about 20 μm. The method of claim 4, wherein A method of manufacturing a ceramic cylindrical capacitive sensor for measuring the axis rotational trajectory of a machine tool using metallizing, wherein the thickness of the nickel plating is set to 50 µm to 100 µm in the step of plating the metal such as nickel by the brazing. .