Measuring and testing – Vibration – Sensing apparatus
Reexamination Certificate
2001-05-15
2003-02-11
Williams, Hezron (Department: 2856)
Measuring and testing
Vibration
Sensing apparatus
C073S104000, C073S866500, C033S503000, C033S504000, C033S551000, C033S556000, C033S558000, C033S559000, C033S572000
Reexamination Certificate
active
06516669
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a vibration-type contact detection sensor and more particularly to a vibration-type contact detection sensor used to measure the configuration of a workpiece, etc., with a three-dimensional measuring machine, etc., for example.
2. Description of the Related Art
Hitherto, a height gauge (one-dimensional measuring machine), a three-dimensional measuring machine, a surface property measuring machine, a small-hole measuring machine, etc., has been known as a measuring machine for measuring the configuration and the dimension of a workpiece. Various probes are used for the measuring machines in order to detect the positional relation between the main unit of measuring machine and the workpiece. The probes are classified into non-contact probes and contact probes, and continuously measuring probes (or scanning probes) and trigger transmission probes (or touch probes), etc.
A vibration-type contact detection sensor
100
as shown in
FIG. 10
is known as a contact-type trigger transmission probe of a measuring machine as described above (refer to Japanese Patent Unexamined Publication No. 2000-55643). The vibration-type contact detection sensor
100
comprises a stylus holder
101
, a stylus
102
, and two piezoelectric elements
103
.
The stylus holder
101
comprises a fix part
111
and a stylus support portion
112
. The fix part
111
is attached to a move shaft of a measuring machine (not shown). The stylus support portion
112
bonds and fixes the stylus
102
therein. The stylus support portion
112
is bifurcated and the stylus
102
is supported along an axial direction at two points of the bifurcate tips. Each tip of the stylus support portion
112
is angular U-shaped in cross section and the stylus
102
is positioned in the opening of the tips of the stylus support portion
112
.
The stylus
102
is formed of a substantially column-shaped and is provided at a tip with a contact portion
121
for coming in contact with a workpiece.
The piezoelectric elements
103
vibrates the stylus
102
so that the stylus
102
is vibrated in the axial direction, and detects a change in the vibration state of the stylus
102
occurring when the contact portion
121
comes in contact with a workpiece. One piezoelectric element
103
is attached to the upper face and the other is attached to the lower face of the stylus support portion
112
across the bifurcate parts thereof. If the vibration conditions of the piezoelectric element
103
are adjusted so that the vibration of the stylus achieves resonance, the contact of the stylus with the workpiece can be detected with a high sensitivity.
Common electrodes are respectively formed on the lower face of the piezoelectric element
103
placed on the upper side and the upper face of the piezoelectric element
103
placed on the lower side in FIG.
10
. The upper face of the piezoelectric element
103
placed on the upper side in the figure is divided into two parts, a vibrator (more particularly, electrode parts of the vibrator)
131
and a detector
132
(more particularly, electrode parts of the detector) at the position corresponding to the center between the two support points of the stylus support portion
112
. In other words, the vibrator
131
and the detector
132
are implemented as a single solid-state component. The lower face of the piezoelectric element
103
placed on the lower side in the figure is also divided into two parts.
In such a structure, if the stylus
102
is vibrated by applying an alternating signal from electrodes of the vibrator
131
, it vibrates in a resonance state along the axial direction. In this state, if the contact portion
121
comes in contact with a workpiece, a change occurs in the resonance state of the stylus
102
. By measuring the change in the resonance state with an external detection circuit (not shown) via lead wire connected to electrodes of the detector
132
, the contact between the contact portion
121
and the workpiece can be detected.
In the vibration-type contact detection sensor
100
as described above, the piezoelectric elements
103
are attached to the upper face and the lower face of the stylus support portion
112
with relatively high rigidity of the stylus holder
101
and thus vibration of the stylus
102
and state change thereof are propagated via the stylus holder
101
, rather than directly to the detector
132
. Therefore, vibration of the stylus
102
and state change thereof are attenuated in the stylus support portion
112
before they are propagated to the detector
132
and, thus, it is feared that the detection sensitivity of the detector
132
may be degraded.
Particularly, if the aspect ratio of the stylus
102
is large or the stylus
102
is formed of a soft material, attenuation of vibration of the stylus
102
in the stylus holder
101
becomes noticeable. Thus, the possibility that the change in the resonance state of the stylus
102
cannot be detected also occurs depending on the configuration or materials of the stylus
102
.
Further, if the stylus
102
comes in contact with the workpiece from a direction orthogonal with the axial direction of the stylus, the stylus
102
is bent and the damage of the stylus
102
can be prevented. However, if the stylus
102
approaches and then comes in contact with the workpiece in the axial direction of the stylus, a relative movement of the stylus and the workpiece cannot be stopped instantaneously and, thus, the overrun occurs in the relative movement. In this case, excess stress is applied to the stylus
102
in the axial direction thereof due to the overrun and it is feared that the stylus
102
may sustain damage, such as plastic deformation or breakage; this is problem.
To circumvent such a problem, it is considered that limitations are imposed on the aspect ratio, the material, etc., of the stylus
102
. However, for example, if the vibration-type contact detection sensor
100
is used with a small-hole measuring machine, a stylus with a large aspect ratio is required for measuring a small hole with a large aspect ratio, namely, the object to be measured varies depending on the measuring machine using the vibration-type contact detection sensor
100
and, thus, the configuration and the material of the demanded stylus also varies. For this reason, if limitations are imposed on the configuration, the material, etc., of the stylus
102
, the number of types of measuring machines that can use the vibration-type contact detection sensor
100
and the number of types of objects to be measured are decreased; this is a problem.
Further, to circumvent the damage of the stylus by the contact of the stylus
102
with the workpiece in the axial direction of the stylus, a stylus axial direction escape mechanism is provided to prevent the stylus sustaining the damage. However, measurement accuracy is difficult to maintain due to the complicated structure and the cost of the whole sensor increases drastically.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a vibration-type contact detection sensor that can detect contact with a workpiece with high sensitivity without limiting the configuration, material, etc., of a stylus.
To the end, according to a first aspect of the invention, there is provided a vibration-type contact detection sensor comprising a column-shaped stylus provided with a contact portion to be contacted with a workpiece at a tip end thereof; a vibrator for vibrating the stylus in an axial direction of the stylus; a detector for detecting contact of the contact portion with the workpiece based upon a change in vibration state of the stylus occurring when the contact portion and the workpiece come in contact with each other; a holder provided with a support portion for supporting the stylus, the vibrator, and the detector with the support portion, wherein at least the vibrator of the vibrator and the detector is fixed on the support portion of the holder and at least the detector of the vibrator and the
Arai Masanori
Hidaka Kazuhiko
Matsuki Kaoru
Miller Rose M.
Mitutoyo Corporation
Rankin, Hill Porter & Clark LLP
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