JPH0330084B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a detection device in a stylus type surface roughness measuring machine.

As is well known, the stylus type surface roughness measuring machine moves the detection device and the object to be measured relatively and traces the surface of the object with the stylus at the tip of the detection device, and measures the irregularities, that is, the roughness. is detected by a detector such as a differential transformer built into the detection device, converted into electricity, and then enlarged and recorded on a recorder or displayed on a meter.

Normally, a detection device has an arm rotatably supported inside by a pivot bearing, etc., a stylus at the tip, and a detector such as a differential transformer at the rear end across the fulcrum. is installed.

In such a roughness measuring machine, the arm holding the stylus is pivoted so that it can rotate even with a light measuring force so that the tip of the stylus can follow even minor irregularities of the object to be measured. In addition, it is required that the shaft support be stable without play, and that the measuring force be finely adjustable.

However, none of the conventional devices fully satisfies the above-mentioned technical requirements. For example, conventional devices have been proposed in which the fulcrum is a pivot bearing and a weight balance is used to apply the measuring force, or the fulcrum is a leaf spring and the spring pressure is used as the measuring force. However, in the former case, in order to reduce the measuring force, the support at the pivot bearing must be light enough to have a slight gap, but this will reduce the stability of the fulcrum, and conversely, in order to improve stability, If it is tightened strongly, it cannot be rotated with a weak force, and therefore the measuring force cannot be reduced. In addition, in the latter case, it is difficult to adjust the measuring force, and since the arm etc. must be supported, there is a limit to reducing the spring constant, making it impossible to reduce the measuring force. It was hot. In addition, as another example of the conventional device, a method has been proposed in which the fulcrum is a pivot bearing and the measuring force is applied by a coil spring installed at a position away from the fulcrum. It had the same drawbacks.

The present invention solves the above-mentioned drawbacks of the conventional device, supports the arm having the stylus in a rotatable and stable manner even with a light measuring force, and allows fine adjustment of the measuring force. The present invention provides a detection device that enables this. An embodiment of the present invention will be described below with reference to the drawings.

In FIGS. 1 and 2, 2 is an outer frame of the detection device 1, 3 is an arm having a stylus 4 that contacts the object W to be measured at its tip, 5 is an arm holder for holding the arm 4, and 6 is the arm holder for holding the arm 4. A pivot shaft is mounted through the arm holder 5, and 7 and 8 are pivot bearings that rotatably support the pivot shaft 6.
9 is a core of a differential transformer attached to the rear end of the arm holder 5, that is, the other end opposite to the attachment end of the arm 3 across the pivot shaft 6; 10 is fixed to the outer frame 2; A coil of a differential transformer engages with the core 9 to detect the amount of displacement of the stylus 4; 11 is a measuring force adjustment screw screwed into the outer frame 2 so that it can move forward and backward; 12 has one end connected to the It is attached to the tip of the measuring force adjustment screw 11, and the other end is attached to a selected one 13 of a plurality of pins installed on the side of the arm holder 5 slightly above the pivot shaft 6 in the figure. A coil spring is shown attached to bias the arm holder 5 upward in the figure.

In such a structure, when the detection device 1 is moved in the left-right direction in the figure by a drive mechanism (not shown),
The stylus 4 at the tip of the arm 3, which is rotatably supported around a pivot shaft 6, moves up and down following the irregularities of the object W to be measured, and its displacement is determined by the difference between the core 9 and the coil 10. It is detected by a dynamic transformer and recorded on a magnifying recorder (not shown) or the like. At this time, the arm holder 5 is always urged upward in the drawing by the coil spring 12, so even if the engagement between the pivot shaft 6 and the pivot bearings 7 and 8 is loosened a little to facilitate rotation, both It rotates while always maintaining the same contact state, thus ensuring a stable fulcrum without play.

Next, fine adjustment of the measuring force using this coil spring 12 will be explained. coil spring 12
The lower end of the pins 13 installed on the side of the arm holder 5 is used to measure the strength of the predetermined measurement pressure or the unbalance of the left and right weight around the pivot axis 6 due to the length of the arm 3, etc. It can be attached to an appropriate one with consideration. When the measuring force adjustment screw 11 is moved back and forth in this manner, the coil spring 12
The arm holder 5 is tilted leftward or rightward from the vertical position shown in the figure, and a force acts on the arm holder 5 to rotate it clockwise or counterclockwise about the pivot shaft 6. Therefore, a desired measuring force can be easily obtained by simply moving the measuring force adjusting screw 11 back and forth as appropriate.

Next, we will explain that the change in the measuring force is small relative to the amount of movement when the measuring force adjustment screw 11 is advanced or retreated, that is, the amount of movement of the upper end of the coil spring 12, and therefore fine adjustment of the measuring force can be easily performed. This will be explained using Figure 3. FIG. 3 is a geometrically enlarged view of the state in which the coil spring 12 is attached to the pin 13 almost directly above the pivot shaft 6. In the figure, the distance between the pivot shaft 6 and the stylus 4 is L, the distance between the pivot shaft 6 and the pin 13 is L1, and the pin ₁₃ and the measuring force adjustment screw 11.
When the distance from the tip of the coil spring 12 is L ₂ and the tension of the coil spring 12 in the vertical state is W, the measuring force adjustment screw 11
move back and forth to move the upper end of the coil spring 12 from point a to point b.
The tension W ₀ when the point is moved by the dimension l is W ₀ =k・(√ ² ₂ + ² −L ₂ )+W……(1) (k: spring constant) Also, the upper end of the coil spring 12 is at point b The distance ε between the extension line of the coil spring 12 and a line parallel to the extension line passing through the pivot shaft 6 when the coil spring 12 moves to , that is, the distance ε between the pivot shaft 6 and point C in the figure, is: The measuring force F is expressed as F=W ₀ ·ε/L (3).

As is clear from equation (2), if L ₁ is made smaller than L ₂ , even if l changes considerably, that is, even if the amount of movement of the measuring force adjustment screw 11 is somewhat large, the amount of change will remain the same. is small. Therefore, since L is set large, the amount of change in the lower part of equation (3) is also small. In other words, even if the amount of movement l of the measuring force adjustment screw 11 is large, the amount of change in the measuring force F is small, so that a minute adjustment of the measuring force can be easily made.

As detailed above, according to the present invention, the arm having the stylus can be rotated even with a light measuring force.
Moreover, it is possible to provide stable shaft support, and in addition to being able to finely adjust the measuring force, it also eliminates the need to precisely adjust the position of the two pivot bearings. It was also possible to achieve effects such as ease of assembly.

[Brief explanation of drawings]

FIG. 1 is a sectional side view of an embodiment of the present invention, FIG. 2 is a sectional view taken along the line -- in FIG. 1, and FIG. 3 is a geometric explanatory diagram of a measurement pressure adjustment function. 3: Arm, 4: Stylus, 5: Arm holder,
6: Pivot shaft, 7, 8: Pivot bearing, 11:
Measuring pressure fine adjustment screw, 12: Coil spring.

Claims (1)

[Claims] 1. An arm holder that has an arm that holds the stylus at one end and a detector that detects the amount of displacement when the stylus is displaced by following the unevenness of the object to be measured at the other end, and the arm holder. a bearing part that is rotatably supported; one end of the arm holder is attached to a position slightly apart from the bearing part; the other end is attached to a measuring pressure adjustment screw that is movably provided on the outer frame; A detection device for a surface roughness measuring machine, comprising a coil spring that always biases the arm holder in a certain direction.