Measuring and testing – Surface and cutting edge testing – Roughness
Reexamination Certificate
1999-08-26
2001-10-02
Larkin, Daniel S. (Department: 2856)
Measuring and testing
Surface and cutting edge testing
Roughness
C033S501040, C033S551000, C033S556000, C033S558000, C033S558400, C033S561000, C033S572000
Reexamination Certificate
active
06295866
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a surface-tracking measuring machine. More specifically, the present invention relates to a surface-tracking measuring machine for measuring a surface roughness and a profile of a workpiece by relatively moving both a tracer and the workpiece while abutting the tracer onto a surface of the workpiece.
2. Description of Related Art
A tracer-type surface roughness measuring machine is known as a measuring machine for measuring a surface roughness of the workpiece.
The tracer-type surface roughness measuring machine includes a main body, a probe swingably supported by the main body and having a tracer at an end thereof, a biasing device for biasing the tracer of the probe to touch the surface of the workpiece, a moving device for moving the probe in a direction approximately orthogonal with the tracer, and a displacement sensor for detecting a swing displacement amount of the probe.
In measuring the surface roughness of the workpiece, the probe is moved along the surface of the workpiece by the moving device while the tracer of the probe is in contact with the surface of the workpiece, and the swing displacement amount is detected by the displacement sensor. The surface roughness of the workpiece can be obtained by the swing displacement amount and the amount of movement of the probe.
Generally speaking, the following performance is required for the tracer-type surface roughness measuring machine.
First, a low measuring force for preventing scratch marks on the surface of the workpiece.
Second, good tracking ability for the tracer to accurately trace the sectional curve.
Third, high-resolution for detecting minute concave and convex features on the surface of the workpiece.
Conventionally, a spring is used as the biasing device for biasing the tracer of the probe to the surface of the workpiece. However, in order to lower the measuring force in accordance with the above first condition, the magnitude of the biasing device is limited.
Accordingly, in order to obtain the necessary tracking ability, the size and weight of the probe has to be reduced as much as possible. Further, the displacement sensor for detecting the swing displacement amount of the probe has to be selected from sensors, such as a differential transformer, a strain gauge, a capacitive sensor, and an optical lever, which applies less load for actuating the probe.
Ordinarily, the measurement range of the tracer-type surface roughness measuring machine is around 1 mm. According to a conventional arrangement, when the measurement range is to be solely widened, some kind of deterioration in performance such as deterioration of the resolution of the displacement sensor, deterioration of responsivity on account of increase of movable portion weight, and increased fluctuation of measuring force is inevitable, which results in difficulty in enlarging the measurement range.
Accordingly, the conventional tracer-type surface roughness measuring machine can not also be used as a profile measuring machine for measuring the profile of the workpiece. In other words, the surface roughness of the workpiece has to be measured by the surface roughness measuring machine and the profile of the workpiece has to be measured separately by the profile measuring machine.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the aforesaid disadvantages and to provide a surface-tracking measuring machine, in which a measurement range can be enlarged while keeping a measuring force, responsivity, and resolution for enabling surface-roughness measurement. A surface-tracking measuring machine according to the present invention is characterized in having: a main body movable relative to a workpiece; a probe displaceably supported by the main body and having a tracer at an end thereof; a measuring force controller for controlling a measuring force applied to the probe; a displacement detector for detecting a displacement of the probe; a measuring force detector for detecting the measuring force applied to the probe; and a controller for comparing a measuring force detected value detected by the measuring force detector and a previously commanded measuring force command value to control the measuring force detected value to be equal to the measuring force command value.
In the above, the probe may be supported by the main body to be linearly displaceable, or alternatively, may be swingably supported.
According to the above arrangement, when the main body and the workpiece relatively moves while the tracer of the probe is in contact with the surface of the workpiece, the tracer of the probe traverses the surface of the workpiece, so that the probe is displaced according to the surface roughness and the profile configuration of the workpiece. Then, the displacement is detected by the displacement detector and the surface roughness and the profile configuration of the workpiece can be measured by the detected value.
In the above, since the measuring force controller is controlled so that the measuring force detected value is equal to the previously commanded measuring force command value, the measuring force applied to the probe can be made constant (at a level of previously commanded measuring force command value) within the entire measurement range. Accordingly, since a detecting means having a heavy movable portion requiring a large driving force for moving thereof and high resolution in a wide measurement range can be used as the displacement detector for detecting the displacement of the probe, the measurement range can be enlarged while keeping high responsivity and high resolution. Accordingly, the surface roughness and the profile of the workpiece can be measured with a single measuring machine.
In the present invention, though any arrangement is possible for the probe, the probe preferably includes a first lever swingably supported by the main body through a first lever rotation shaft and a second lever swingably supported by the first lever at an intermediate portion thereof through a second lever rotation shaft disposed coaxially with the first lever rotation shaft, the second lever having the tracer at an end thereof, a rear end of the second lever and the first lever being connected by a connecting member.
According to the above arrangement, since the first lever rotation shaft and the second lever rotation shaft are disposed coaxially, a centroid position of the second lever is not moved by a swing movement of the first lever.
In the aforesaid arrangement having the first and the second lever, the second lever is preferably swingably supported by the first lever through the second lever rotation shaft at a centroid position thereof. Accordingly, a vertical and horizontal vibration acceleration from floor or a feeding mechanism is not converted into a rotation moment of the second lever.
Further, the measuring force applied only to the second lever can be accurately detected by using a strain gauge constituting the measuring force detector as the connecting member. In other words, since the strain gauge does not detect external vibrations, the sensitivity can be lowered against external vibrations.
In the present invention, though any configuration is possible as the measuring force controller as long as the measuring force controller can minutely change the measuring force applied to the probe, the measuring force controller preferably includes a movable member slidably provided to the main body and connected to the first lever and an actuator for sliding the movable member.
In the aforesaid arrangement having the first lever, the movable member, and the actuator, a link using a plate spring is preferably used for connecting the first lever and the movable member for transmitting the swing of the first lever accurately to the movable member. The actuator may be driven by any signal, such as electricity and fluid.
The displacement detector preferably has a scale attached to the movable member and a detector fixed to the main body o
Akaike Takenori
Yamamoto Takeshi
Larkin Daniel S.
Mitutoyo Corporation
Oliff & Berridg,e PLC
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