JPS62156502A - Minute displacement measuring head - Google Patents

Abstract

PURPOSE:To execute a measurement more exactly and with a high accuracy by forming an arm by an insulator, providing an electric resistor on the arm, also converting the quantity of deflection to the quantity of electricity and detecting a minute displacement. CONSTITUTION:An arm 2 of a minute displacement measuring head is formed by an insulator of ceramic and plastic, etc. A comb tooth-shaped resistor 3 is provided on the upper face of the arm which is provided with a probe 1 consisting of a diamond on the tip, and the arm 2 is fixed to a supporting member 4. In case roughness of the surface is measured, the arm 2 is bent a little in accordance with a fine up-and-down motion of the probe 1, therefore, length in the long axis direction of the resistor 3 which is provided on the upper face of the arm 2 is varied and a resistance value is also varied. When the measurement is executed in a state that a prescribed voltage remains applied to the resistor 3, a current is varied by a variation of the resistance value of the resistor 3, the variation of this current is amplified by a general method, and by its signal waveform, roughness of the surface can be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a head for measuring minute displacements used in surface roughness measuring machines, coordinate measuring machine position sensors, and the like.

[Conventional technology]

The structure of the measuring head of the surface roughness measuring machine is shown in Figure 3 (a) and (b).
), a metal arm 2 having a diamond stylus l at its tip is supported by an arm support member 4,
It is provided at the rear end of arm 2. The magnet 2a was able to move up and down within the coil 4a. When the object to be measured 5 is slid in the direction of the arrow while the stylus 1 is in contact with the surface of the object to be measured 5, the arm 2 is moved by minute vertical movements of the stylus l depending on the roughness of the surface. Since the magnet 2a provided at the rear end moves up and down in the coil 4a, a current is generated in the coil 4a according to the movement of the magnet 2a due to electromagnetic induction. This current is detected through the conductor 4, amplified using a conventional method, and the surface roughness is measured based on the signal waveform.

Other measuring heads, such as coordinate measuring machines and position sensors, had a similar structure, and were designed to read minute movements of a stylus at the tip through an arm.

In either case, the arm must have rigidity, and if it bends, accurate measurements cannot be taken. Further, such a measuring head was able to perform accurate measurements even when magnified up to about 100,000 times in the vertical direction.

[Problems with conventional technology]

However, in the conventional minute displacement measurement head, the minute movement of the stylus 1 provided at the tip of the arm 2 is detected by the movement of the magnet 2a provided at the rear end of the arm 2. Due to the deflection, high-accuracy measurements resulted in large errors, and the limit was about 100,000 times. In addition, since arm 2 must have rigidity, arm 2
There was a problem in that the inner surface of a small hole or gap could not be measured because it could not be made thin or thin. Furthermore, the structure of the portion that detects the amount of displacement of the arm support member 4 is complicated, resulting in high costs.

Measures for Solving the Problem c] In view of the above, the present invention forms the arm of the minute displacement measuring head from an insulating material such as ceramic or plastic, arranges an electric resistor on the arm, and measures the amount of deflection. It is designed to detect minute displacements by converting them into electrical quantities.

〔Example〕

Embodiments according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a measuring head of a surface roughness measuring machine, in which a comb-shaped resistor 3 is arranged on the upper surface of an arm 2 equipped with a stylus 1 made of diamond at the tip. It is fixed to the support member 4. A certain voltage is applied to the resistor 3 inside the arm support member 4, and the current flowing through the resistor 3 at that time can be measured. When measuring surface roughness using a probe like this, arm 2 bends slightly in response to minute vertical movements of stylus 1. The length of the resistor 3 in the major axis direction changes, and the resistance value also changes. If measurement is performed with a constant voltage applied to the resistor 3, the current will change due to the change in the resistance value of the resistor 3. This change in current will be amplified using a general method, and the signal waveform will be used to determine the surface roughness. can be measured. Since this measurement head directly captures the minute vertical displacement of the stylus 1 as the amount of deflection of the arm 2, it can perform highly accurate measurements and is simple in structure.

In addition, as another embodiment, a U-shaped resistor 3 is disposed on the upper surface of an elongated arm 2 having a stylus 1 at the tip as shown in FIG. 2(a). 7d and the same figure (
A possible example is a clearance measuring head as shown in b) in which a comb-shaped resistor 3 is disposed on the upper surface of a thin plate-like arm 2 having a stylus 1 at its tip. Furthermore, as shown in FIG. 3(c), if resistors 3 are arranged on each of the two mutually perpendicular surfaces of the arm 2, which has a spherical stylus 1 at the tip, it is possible not only in the vertical direction ( Displacement in left/right and diagonal directions can also be measured.
Can be used for measurement heads such as coordinate measuring machines and position sensors.

In these examples, the material forming the arm 2 is
Possible materials include ceramic materials such as alumina, zirconia, silicon carbide, silicon nitride, and sapphire, as well as glass and plastics. It is suitable for arm 2 of the measuring head because it can perform measurements with a small amount of noise.

Furthermore, when measuring a relatively large amount of displacement, the arm 2 may be formed of highly elastic plastic. Furthermore, the measuring head according to the invention comprises arm 2
Since the rigidity of the arm 2 is not required, the arm 2 can be made thinner or thinner. For example, a rod-shaped arm 2 as shown in Figures 2(a) and (c) can be used even if the length is 6 mm and the wire diameter is 0.06 mm, and a thin plate as shown in Figure 2(b) can be used. The shaped arm 2 can be used even if it is a thin comb with a thickness of about 0.1 mm.

In addition, if the arm 2 is made of ceramic, the resistor 3 disposed on the upper surface of the arm 2 is made by printing a paste mixed with metal powder such as tungsten or molybdenum on unfired ceramic, and then firing the paste. When the arm 2 is made of glass or plastic, it is printed with a quick-drying paste similar to that described above. Alternatively, the resistor 3 may be formed by disposing a linear body of a high melting point metal on the surface of the arm 2 by adhering it or embedding it in a groove. The line width of such a resistor 3 can be reduced to about 30 μm in the case of printing and about 40 μm in the case of a linear body, so that it can be arranged even in a thin arm.

Next, the arm shown in FIG. 2(b) was formed from alumina with a width of 10+ nm and a length of 35 mm, and the surface was coated with 500 nm.
Using a measuring head prototyped by printing a resistor 3 of Ω,
When surface roughness was measured, there was little error even when magnified approximately 1 million times in the vertical direction, and accurate measurement was possible.

In addition, the shapes of the arm 2 and the resistor 3 and the method of measuring the amount of change in resistance value are not limited to those shown in the above embodiments.
It may be freely changed within the scope based on the idea of the present invention.

〔Effect of the invention〕

As described above, according to the present invention, the arm of the minute displacement measuring head is formed of an insulating material such as ceramic, resin, or plastic, and an electric resistor is disposed on the arm.
By converting the amount of deflection into an amount of electricity to detect minute displacements, not only can measurements be made with greater certainty and precision, but the cost is also lower due to the simple structure. Since the arm is not required, the arm can be made thin or thin, making it possible to measure the inner surfaces of small holes and gaps.If the arm is made of ceramic, it can transmit surrounding vibrations and It is possible to provide a high-performance micro-displacement measurement head that has many advantages such as less error.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a measurement head of a surface roughness measurement chamber according to the present invention, and FIGS. 2(a), (b), and (c) each represent other embodiments according to the present invention. FIG. Figures 3(a) and 3(b) respectively show the measurement throat of a conventional surface roughness measuring machine, with Figure 3(a) being a perspective view and Figure 3(b) being a cross section showing the internal structure. It is a diagram. ■...Stylus 2...Arm 3...Resistor 4...Arm support member

Claims (1)

[Claims] In the micro-displacement measuring head that measures the surface roughness, minute movement, etc. of the object to be measured by bringing a stylus provided at the tip of an arm with one end fixed into contact with the surface of the object to be measured by displacement of the stylus, For measuring minute displacements, the arm is made of an insulator such as ceramic or plastic, and an electric resistance is provided on the arm, and the amount of deflection is converted into an amount of electricity to detect minute displacements. head.