Vibration detecting system of resilient body and vibrating contact detection probe

A stylus structure (40) integrally incorporating a stylus (2), a vibrator (4), a detector (6), a first secondary magnetic circuit (12) and a second primary magnetic circuit (21), and a stylus support (30) integrally incorporating a first primary magnetic circuit (11) and a second secondary magnetic circuit (22) are mutually fittable, thereby achieving signal transmission by the respective magnetic circuits using no electrical contact.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a vibration detecting system of resilient body for detecting vibration of resilient body having multiple vibration mode, and a vibrating contact detection probe used for a form measuring instrument for measuring a minute surface texture of a workpiece in accordance with the same principle as the vibration detecting system.

2. Description of Related Art

Conventionally, a height gauge (one-dimensional measuring instrument), a coordinate measuring machine, a surface texture measuring machine, a small hole measuring machine etc. have been known as measuring instruments for measuring form and dimension etc. of a workpiece. Some of the measuring instruments employ a contact probe, the contact probe detecting contact with the workpiece to sense coordinates value of the workpiece and positional relationship between the workpiece and the measuring instrument.

A so-called vibrating contact probe has been used as one of the contact probes. The vibrating contact probe vibrates a stylus and detects change in vibration of the stylus caused when the stylus touches the workpiece to sense whether the measuring probe has contacted the workpiece or not with high accuracy.

In order to detect contact by vibration, the vibrating contact probe has a stylus having a contact portion to be in contact with a workpiece at a distal end thereof, a vibrator for vibrating the stylus and a detector for detecting the vibrating condition of the stylus. A vibrating element and detecting element using, for instance, piezoelectric element is used as the vibrator and the detector.

According to thus constructed vibrating contact probe, the stylus is initially vibrated by the vibrator and the change in vibration of the stylus caused when the contact portion of the stylus and the workpiece are brought into contact is detected by the detector. Change in detection signal outputted by the detector is observed to recognize the change in vibration of the stylus.

Incidentally, in the vibrating contact probe, in order to vibrate the stylus at a predetermined vibrating condition, the stylus is ordinarily vibrated with a main vibration mode (e.g. primary vibration mode).

However, even when the stylus is vibrated with the main vibration mode, vibration of a multiple vibration mode as well as the main-vibration-mode vibration is generated to the stylus on account of the configuration of the stylus and influence of the mass of the element attached to the stylus.

Accordingly, the action of the multiple-vibration-mode vibration is reflected on the detection signal obtained by the detector in addition to the action of the vibration of the main vibration mode, the action of the multiple-vibration-mode vibration causing noise on the vibration of the main vibration mode to lower S/N ratio thereof. Further, the wider frequency range of the vibration capable of being detected by the detector catches the more noise, thereby further reducing S/N ratio.

A filter having the same transmission characteristics may be used for restraining noise of the detection signal. However, such filter having certain characteristics corresponding to the main vibration mode has complicated structure and is expensive.

On the other hand, in the above-described conventional contact probe, since a lot of minute electrical connections are provided to the vibrator and the detector, the size and configuration of ordinary connector which establishes electric connection through a plug and receptacle cannot be fitted to a minute stylus in order to prevent cross talk which is required in view of performance. Further, changing work of the electric connection each time the stylus is exchanged is in itself difficult, and causes great problems in view of workability and work speed.

On the other hand, the work can be facilitated and speeded up by exchanging the entire probe including the support side of the stylus not only the side of the stylus. However, such arrangement is extremely expensive.

SUMMARY OF THE INVENTION

An object of the present invention it to provide a vibration detecting system of resilient body capable of obtaining detection signal having improved S/N ratio and recognizing the vibration of the resilient body with a simple and inexpensive arrangement.

A vibration detecting system of a resilient body according to an aspect of the present invention is for detecting vibration of the resilient body, the system includes: a detector for detecting the vibration of the resilient body and outputting a detection signal in accordance with the vibration; and a magnetic circuit having a primary coil and a secondary coil, the primary coil and the secondary coil being in close electromagnetic connection, in which the vibration of the resilient body is detected using an output signal generated in the secondary coil when the detection signal from the detector is received by the primary coil.

According to the above aspect of the present invention, the detection signal from the detector is received by the primary coil of the magnetic circuit and the output signal generated in the secondary coil by mutual induction is used to detect the vibration of the resilient body. Since the coil has a tendency that impedance thereof becomes greater as the frequency of electric current is raised, the high frequency component of the detection signal corresponding to the multiple vibration mode as a noise can be substantially removed. Accordingly, since the output signal removing the noise from the detection signal can be generated in the secondary coil, the change in the output signal generated in the secondary coil can be sensed with high accuracy, so that, when outside force (such as contact with a workpiece) is applied to the resilient body, the change in the action of the vibration of the resilient body can be detected with high accuracy.

Further, since the primary coil and the secondary coil are in close electromagnetic connection in the magnetic circuit, voltage is generated in the secondary coil when the alternating current signal passes through the primary coil and no voltage is generated in the secondary coil when direct current signal having no change in electric current passes through the primary coil. Accordingly, even when static electricity is generated upon contact of the resilient body with the workpiece etc., since the static electricity is direct current, the influence on the voltage generated in the secondary coil can be avoided.

Since the winding number of the secondary coil is more than the winding number of the primary coil, the amplified amplitude of the output signal by boosting the amplitude of the detection signal received by the primary coil can be generated by the secondary coil.

Since the magnetic circuit enabling close electromagnetic connection between the primary coil and the secondary coil is used, the arrangement of the vibration detecting system can be easily and inexpensively constructed unlike the conventional arrangement using a filter of specific transmission characteristics.

In the above aspect of the present invention, the detector may preferably be attached to the resilient body and constructed of a piezoelectric element or a strain detecting element.

According to the above arrangement, since the detector is attached to the resilient body and is constructed of piezoelectric element or strain detecting element, the structure of the detector can be simplified and the production cost thereof can be reduced. The strain detecting element refers to an element for outputting electric potential in accordance with strain of an object such as a strain gauge.

The above word “attach” includes both of direct attachment of the piezoelectric element of the strain detecting element to the resilient body and indirect attachment through a member for holding the resilient body.

In the above aspect of the present invention, the detector may preferably be located around the resilient body and constructed of a non-contact detecting element for detecting the vibration of the resilient body in a non-contact manner.

According to the above aspect of the present invention, since the detector is constructed of a non-contact detecting element such as an optical fiber and a laser Doppler device, the influence on the vibration of the resilient body on account of contact between the resilient body and the detector can be eliminated, thereby improving the accuracy for detecting the vibration of the resilient body.

Another object of the present invention is to provide a vibrating contact detection probe capable of eliminating change of electric connection of the vibrator and the detector annexed to the stylus in exchanging the stylus. Specifically, in the vibrating contact detection probe according to the present invention, re-calibration after exchange including small stylus can be easily and rapidly conducted and trouble for changing electric connection of the vibrator and the detector annexed to the stylus can be eliminated while maintaining various conditions.

In exchanging the stylus, when only the stylus-side part is to be exchanged, possible action parameter to be updated is vibration frequency and detection gain. By commanding the data to the controller on the stylus support side in exchanging the stylus, the data can be appropriately adjusted to a computer of the controller, re-adjustment can be easily and rapidly conducted.

Mechanical dimension of the parts to be exchanged including the stylus can be independently calibrated in advance by a calibration means. When the position for attaching the exchanged part is reproduced in exchanging the stylus, mechanical re-calibration after exchange can be easily and rapidly conducted only by measuring minute mechanical value.

In view of the above, a vibrating contact detection probe according to the present invention uses close electromagnetic connection as in the above-described vibration detecting system to eliminate change of electric connection of the vibrator and the detector annexed to the stylus in exchanging the stylus.

A vibrating contact detection probe according to another aspect of the present invention includes: a shaft-shaped stylus having a contact portion to be in contact with a workpiece; a vibrator for causing resilient vibration to the stylus when electrical alternating current energy is applied thereto; a detector for detecting the action of the vibration changing in accordance with contact of the contact portion with the workpiece; a vibration energy transmitter for applying the electrical alternating current energy to the vibrator; a detection signal transmitter connected to the detector; and a stylus support and a stylus structure being mutually fitted, the vibration energy transmitter having a first primary magnetic circuit having a first primary coil connected to a vibration energy source and a first secondary magnetic circuit having a first secondary coil connected to the vibrator, the detection signal transmitter including a second primary magnetic circuit having a second primary coil connected to the detector and a second secondary magnetic circuit having a second secondary coil for fetching the detection signal, the stylus, the vibrator, the detector, the first secondary magnetic circuit and the second primary magnetic circuit being integrated on the stylus structure, the first primary magnetic circuit and the second secondary magnetic circuit being integrated on the stylus support, where, when the stylus structure and the stylus support are fitted, electromagnetic connection is established between the first primary magnetic circuit and the first secondary magnetic circuit and between the second primary magnetic circuit and the second secondary magnetic circuit and mechanical position of the stylus relative to the stylus support can be reproduced.

According to the above arrangement, since the stylus structure integrally incorporating the stylus, the vibrator, the detector, the first secondary magnetic circuit and the second primary magnetic circuit, and the stylus support integrally incorporating the first primary magnetic circuit and the second secondary magnetic circuit are mutually fittable, only the stylus structure is required to be exchanged in exchanging the stylus, so that re-calibration after exchange including small stylus can be easily and rapidly conducted, and trouble for changing electric connection of the vibrator and the detector annexed to the stylus can be eliminated while maintaining various conditions.

In the vibrating contact detection probe of the present invention, the second primary magnetic circuit and the second secondary magnetic circuit may preferably be disposed without being in electromagnetic connection with the other electromagnetic system of the stylus structure and the other electromagnetic system of the stylus support.

According to the above arrangement, since the second primary and the secondary magnetic circuits for transmitting the detection signal is not in electromagnetic connection with the other electromagnetic system on the side of the stylus structure and the stylus support, the S/N ratio of the detection signal, which is weak relative to the electromagnetic amount of the vibration energy, is not deteriorated.

In the vibrating contact detection probe of the present invention, the respective pairs of the first primary coil and the secondary coil and the second primary coil and the secondary coil may preferably be disposed coaxially along an axial direction of the stylus.

According to the above arrangement, since the respective pairs of coils are disposed coaxially along the axial direction of the stylus, the coils can be easily installed and the probe can be easily manufactured.

In the vibrating contact detection probe of the present invention, the first primary coil and the secondary coil and the second primary coil and the secondary coil may preferably be constructed of a toroidal coil.

According to the above arrangement, since the respective coils are constructed of toroidal coil, leakage of magnetic flux can be reduced.

In the vibrating contact detection probe of the present invention, the stylus structure and the stylus support may preferably be formed by a pair of structures fitted to form a cylinder or a polygonal tube which is separated in parallel with a central axis thereof.

According to the above arrangement, since the stylus structure and the stylus support are fitted to form a cylinder or a polygonal tube, the size of the probe can be reduced and the probe can be easily disassembled and re-fitted.

In the vibrating contact detection probe of the present invention, the stylus structure and the stylus support may preferably be formed by an inner and outer coaxial cylinders having a common axis or a pair of coaxial inner and outer polygonal tubes.

According to the above arrangement, the stylus structure and the stylus support can be fitted in the axial direction and can be easily fixed by, for instance, a setscrew.

In the vibrating contact detection probe of the present invention, an amplifier of the detector may preferably be provided, the amplifier being driven by a power generated by the first secondary coil using a part of electrical alternating current energy.

According to the above arrangement, when the detection signal is too weak for actual use, the detection signal can be amplified by the amplifier. Further, the amplifier can be driven by the first secondary coil using a part of the electric alternating current energy, thereby enabling efficient drive thereof.

In the vibrating contact detection probe of the present invention, an amplifier of the detector may preferably be provided, the amplifier being driven by a power generated using a part of electrical alternating current energy supplied by a third coil independent of the first primary and secondary coils and the second primary and secondary coils.

According to the above arrangement, when there is not sufficient amount in the transmission received by the first secondary coil, the amplifier can be driven by the electric alternating current energy supplied by the third coil independent of the first primary and secondary coils and the second primary and secondary coils.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

Preferred embodiments of the present invention will be described below with reference to attached drawings. Incidentally, the same reference numeral will be attached to the same components and description thereof is omitted or simplified in the following description of the embodiment.

FIG. 1shows a vibrating contact detection probe P1according to first embodiment. The vibrating contact detection probe P1has a stylus2, a stylus assembly1having a vibrator4and a detector6, a vibration energy transmitter10for applying electrical alternating current energy to the vibrator4, a detection signal transmitter20connected to the detector6, a stylus support30and a stylus structure40mutually fitted together, and an outer cylinder sleeve50composed of a magnetic body.

The stylus assembly1includes the stylus2having a contact portion2A to be in contact with a workpiece and having shaft-shape, a resilient element attaching body3holding an intermediate portion of the stylus2, the vibrator4composed of a piezoelectric element attached to one side of the resilient element attaching body3for causing resilient vibration (axial direction vibration of the stylus2: vibration in arrowed direction) by applying electrical alternating current energy, a vibrator electrically connecting lead wire5connected to the vibrator4, the detector6composed of a piezoelectric element for detecting action of the vibration changing in accordance with the contact of contact portion2A of the stylus2with the workpiece, and a detector electrically connecting lead wire7connected to the detector6.

The vibration energy transmitter10has a fist primary magnetic circuit11and a first secondary magnetic circuit12.

The first primary magnetic circuit11is composed of a primary coil11A connected to a vibration energy source, a yoke11B and a magnetic core11C.

The first secondary magnetic circuit12is composed of a secondary coil12A connected to the vibrator4through the vibrator electrically connecting lead wire5, a yoke12B and a magnetic core12C.

The detection signal transmitter20has a second primary magnetic circuit21, and a second secondary magnetic circuit22.

The second primary magnetic core21is composed of a primary coil21A connected to the detector6through the detector electrically connecting lead wire7, a yoke21B and a magnetic core21C.

The second secondary magnetic core22is composed of a secondary coil22A for fetching the detection signal, a yoke22B and a magnetic core22C.

In the stylus support30, the first primary magnetic circuit11and the second secondary magnetic circuit22are accommodated in an integrated manner. Specifically, the first primary magnetic circuit11and the second secondary magnetic circuit22are integrated by the stylus support30. Incidentally, the stylus support30also works as the yoke11B of the first primary magnetic circuit11and the yoke22B of the second secondary magnetic circuit22.

The stylus2, the vibrator4, the detector6, the first secondary magnetic circuit12and the second primary magnetic circuit21are accommodated in the stylus structure40in an integrated manner. In other words, the stylus2, the vibrator4, the detector6, the first secondary magnetic circuit12and the second primary magnetic circuit21are integrated by the stylus structure40. Incidentally, the stylus structure40also works as the yoke12B of the first secondary magnetic circuit12and the yoke21B of the second primary magnetic circuit21.

The stylus structure40and the stylus support30are mutually fitted to be a cylinder. Accordingly, the stylus structure40and the stylus support30respectively form a pair of structures divided in parallel with the central axis of the cylindrical body after being fitted.

When the stylus structure40and the stylus support30are fitted, the primary coil11A and the secondary coil12A of the first pair and the primary coil21A and the secondary coil22A of the second pair are mutually located coaxially along the axis direction (central axis of the stylus structure40and the stylus support30) of the stylus2.

When the stylus structure40and the stylus support30are fitted, an end surface11L of the first primary magnetic circuit11and an end surface12R of the first secondary magnetic circuit12, and an end surface21R of the second primary magnetic circuit21and an end surface22L of the second secondary magnetic circuit22are in close contact and a gap60is formed between the end surface12L of the first secondary magnetic circuit12and the end surface22R of the second secondary magnetic circuit22. Specifically, the pair of the first primary magnetic circuit11and the first secondary magnetic circuit12and the pair of the second primary magnetic circuit21and the second secondary magnetic circuit22are in close electromagnetic connection, and the first secondary magnetic circuit21and the second secondary magnetic circuit22are kept in coarse electromagnetic connection. Accordingly, the S/N ratio of the relatively weak detection signal as compared to the electromagnetism of the vibration energy is not deteriorated. In other words, the second primary and secondary magnetic circuits21and22(coil group21A,22A) are not electromagnetically connected to the other electromagnetic systems of the stylus structure40and the stylus support30.

Incidentally, in order to avoid electromagnetic cross talk, it is practically important that the vibrator electrically connecting lead wire5and the detector electrically connecting lead wire7are isolated by the magnetic body of the stylus structure and are mutually separated when being disposed in the same space. Accordingly, inFIG. 1, the lead wires on the outer end surface of the stylus structure40are spatially separated.

In assembly process, the stylus structure having the stylus2, the vibrator4, the detector6, the first secondary magnetic circuit12and the secondary primary magnetic circuit21is fitted with the stylus support30having the first primary magnetic circuit11and the second secondary magnetic circuit22. Subsequently, the outer cylinder sleeve50is attached on the outside thereof. Accordingly, mechanical position of the stylus2relative to the stylus support30can be reproduced with high accuracy.

On the other hand, in order to release fitting between the stylus structure40and the stylus support30, it is only necessary that the outer cylinder sleeve50is initially detached and the stylus structure40is detached from the stylus support30. The manipulation can be extremely easily and rapidly conducted and no electrical connection of the vibrator electrically connecting lead wire5and the detector electrically connecting lead wire7is required.

In other words, since it is only necessary to exchange the stylus structure40in exchanging the stylus2, re-calibration after exchange including minute stylus can be easily and rapidly conducted, so that trouble for changing electrical connection of the vibrator4and the detector6attached to the stylus2can be eliminated while maintaining various conditions.

FIG. 2shows a vibrating contact detection probe P2according to second embodiment of the present invention.

The vibrating contact detection probe has different form of primary coils11A and21A and secondary coils12A and22A constituting the first and the second magnetic circuits11,12,21and22as compared to the vibrating contact detection probe P1of the first embodiment. Specifically, when the stylus structure40and the stylus support30are fitted, the respective pairs of the first coils11A and12A and the second coils21A and22A are disposed orthogonal with the axial direction of the stylus2, not coaxial.

Further, the stylus30has a plane30A cutting a cylindrical body made of magnetic body with a plane parallel to central axis thereof, the plane30A also working as the end surfaces11L and22L. Accordingly, the magnetic circuits11and22disposed to the side of the stylus support30have no magnetic cores11C and22C.

Instead, in order to achieve electrically close connection with the stylus structure40, three portions of the stylus structure40are to be in close contact. Specifically, the plane30A is in close contact with the magnetic cores12C and22C of the stylus structure40and both sides sandwiching thereof (corresponding to the end surfaces12R and21R).

According to the second embodiment, since the cross section of the coil can be freely increased and decreased along the axial direction, great freedom of design can be achieved as long as the capacity of the transmitted vibration energy and the detection signal by the coil can be tolerated in view of the characteristics of the magnetic circuit.

However, when the stylus structure40is fitted to the stylus support30, the stylus support30and the stylus structure40form two components divided in parallel along the central axis of the cylindrical structure as in the first embodiment.

FIG. 3shows a vibrating contact detection probe P3according to third embodiment of the present invention.

In the vibrating contact detection probe P3, the stylus support30and the stylus structure40are composed of a pair of an outer cylinder and an inner cylinder of a coaxial inside and outside cylindrical structures having a common axis. In the present embodiment, the stylus support30is structured by an outer cylinder31and the stylus structure40is structured by an inner cylinder41.

The outer cylinder31is composed of a sleeve31A constructed of a magnetic body and a fitting member31B fitted to a base end of the sleeve31A. A first primary coil11A and a second secondary coil22A are disposed on the inner circumference of the sleeve31A mutually spaced apart by a predetermined interval.

The inner cylinder41is composed of two insert cylinders41A and41B, a spacer41C, and a connection bolt41D for integrating the components. On the outer circumference of the insert cylinder11A, a first secondary coil12A is disposed at a position corresponding to the first primary coil11A. On the outer circumference of the insert cylinder41B, a second primary coil21A is disposed at a position corresponding to the second secondary coil22A. The outer cylinder31and the insert cylinders41A and41B are made of magnetic body so that close electrical connection between the first and the second pairs of coils can be established. The spacer41C is composed of a non-magnetic material in order to provide the gap60.

Incidentally, the first primary coil11A and the secondary coil12A, and the second primary coil21A and the secondary coil22A are formed parallel and coaxial with a common axis in solenoid shape.

According to the third embodiment, since the stylus structure40is a cylinder coaxial with the stylus support30, the stylus structure40and the stylus support30can be fitted in axial direction and can be easily fixed in fixing the components.

Further, since the stylus support30also works as the outer cylindrical sleeve50, the number of components can be reduced, thereby reducing the production cost.

Incidentally, in the present embodiment, since the primary and the secondary coils of the respective coil pairs are parallel to the axis unlike the first and the second embodiments, though the axial length of the stylus support30is shortened with the same material and the same performance, diameter of the body tends to be increased.

[Modifications of First to Third Embodiments]

Though the stylus structure40and the stylus support30are constructed of a pair of structures fitted to form a cylinder which is divided in parallel with the central axis thereof in the first and the second embodiment, the stylus structure40and the stylus support30may be constructed of a pair of structures fitted to form a polygonal tube which is divided in parallel with the central axis thereof.

Though the stylus support30and the stylus structure40are formed of a pair of the outer cylinder31and the inner cylinder41of coaxial cylinder structure having a common axis in the third embodiment, the stylus support30and the stylus structure40of the third embodiment may be constructed of a pair of inner and outer coaxial polygonal tube.

The yoke and the magnetic core of the magnetic circuits11,12,21and22described in the respective first to the third embodiments are not restricted to the above arrangement, but may be, for instance, a toroidal core as shown inFIG. 4which is ordinarily of less magnetic flux leakage.

In the above respective embodiments, when the detection signal is excessively weak for practical use, an amplifier (integrated circuit driven by direct current) for amplifying the detection signal may preferably be connected between the detector6and the second primary coil21A.

At this time, the electrical alternating current of the medium which transmits the vibration energy is an alternating current of constant amplitude and constant frequency (normally belonging to radio frequency) corresponding to resilient vibration of the stylus2. However, when there is enough room in the transmission amount received by the first secondary coil12A, a predetermined direct current can be supplied to the amplifier by the integrated circuit for converting alternating current (AC) and direct current (DC) connected to the secondary coil12A in parallel with the vibrator4.

When not so much of transmission amount is received by the secondary coil12A, third magnetic circuit may be additionally annexed, where the primary coil thereof is provided to the stylus support30and the secondary coil thereof is provided to the stylus structure40, the integrated circuit for converting AC/DC being connected to the secondary coil, thereby supplying a predetermined direct current to the amplifier.

An arrangement for supplying power for the amplifier using the third magnetic circuit is shown, for instance, in FIG.5.

InFIG. 5, the same first and second magnetic circuits10and20as the second embodiment are provided between the stylus support30and the stylus structure40and the vibrator4and the detector6are provided to the stylus structure40.

Further, an integrated circuit4A is provided between the first secondary coil12A and the vibrator4and a third magnetic circuit70is located between the stylus support30and the stylus structure40. In the third magnetic circuit70, a primary coil71A is provided on the stylus support30and a secondary coil72A is provided on the stylus structure40. Incidentally, the respective coils71A and72A are the same as the above-described coils11A,12A,21A and22A. The integrated circuit4A is connected to the secondary coil72A. By supplying the power for the amplifier to the primary coil71A on the side of the stylus support30, the integrated circuit4A can be used as a power source for the amplifier through the third magnetic circuit70.

FIG. 6shows a vibration detecting system101according to fifth embodiment of the present invention. The vibration detecting system101has a vibration energy power source110, a contact probe120, a magnetic circuit130and a signal processor140. The vibration energy power source110provides a predetermined alternating current signal to a below-described vibrator122of the contact probe120.

As specifically shown inFIG. 7, the contact probe120has a stylus121as a resilient body of the present invention, a vibrator122for vibrating the stylus121, and a detector123for detecting the vibration of the stylus121.

The stylus121is formed in an approximate cylinder having a disk-shaped contact portion121A to be in contact with a workpiece on a distal end thereof and a counter balance121B on a rear end thereof, as necessary. The stylus121is held by a stylus holder124at the central portion thereof.

The stylus holder124has a fixing portion to be attached to a movement shaft of a measuring instrument (not shown: e.g. height gauge, coordinate measuring machine, surface texture measuring machine and small hole measuring machine), and a stylus attachment242for bonding and fixing the stylus121, the fixing portion241and the stylus attachment242being integrally formed. The stylus attachment242is branched in two parts, the two parts supporting the two points of the stylus121along the axial direction. The distal end of the stylus attachment242for the stylus121to be bonded is formed in a C-shaped cross section and the stylus121is located in the opening thereof.

The vibrator122and the detector123are respectively composed of a vibrating piezoelectric element and a detector piezoelectric element. Electrodes are formed on the top and bottom side of the two piezoelectric elements. The piezoelectric elements are disposed in an opposing manner, which are respectively attached on the upper and lower surface of the branch of the stylus attachment24spanning over the branch. Incidentally, alternating current signal from the vibration energy power source110is applied to vibrate the vibrator122.

As shown inFIG. 8, the magnetic circuit130has an approximately square frame core member133, a primary coil131and a secondary coil132wound respectively around opposing two sides of the core member133, thereby achieving close electromagnetic connection between the primary coil131and the secondary coil132.

Both ends of the primary coil131are respectively connected to both ends of the detector123of the contact probe120and electric charge generated on both ends of the detector123(detecting piezoelectric element) is applied to the primary coil131. In other words, voltage is applied to the primary coil131by the detector123.

On the other hand, the both ends of the secondary coil132are connected to the signal processor140. The signal processor140receives alternating current signal (output signal) from the secondary coil132and outputs a signal to the outside based on the analysis result of the alternating current signal.

In thus arranged magnetic circuit130, when the detection signal (voltage) from the detector123is applied to the primary coil131, the output signal (alternating current signal) is generated on the secondary coil132by mutual induction.

Coil has a general tendency that impedance is raised in accordance with the frequency of electric current, so that high-frequency electric current is difficult to flow through the coil. Accordingly, when high-frequency component is included in the detection signal from the detector123received by the primary coil131, an output signal from which the high-frequency component is substantially removed is generated on the secondary coil132.

The ratio of winding number of the primary coil131and the secondary coil132are determined at a predetermined ratio where the winding number of the secondary coil132is more than the winding number of the primary coil131. Accordingly, the amplitude of the output signal amplified by boosting the amplitude of the detection signal received by the primary coil131can be generated on the secondary coil132.

Next, a function of the present embodiment will be described below.

Initially, electric energy is applied to the vibrator122by the vibration energy power source110, in other words, voltage of a predetermined frequency is applied to the vibrating piezoelectric element to vibrate the stylus121with a main vibration mode (e.g. primary vibration mode).

At this time, multiple vibration mode including high-frequency component is generated on the stylus121in addition to the main vibration mode by virtue of the configuration of the stylus121, the mass of the stylus holder124for the stylus121to be attached, the vibrator122attached to the stylus121and the mass of the detector123.

The vibration of the multiple vibration mode of the stylus121is directly transferred to the detector123(detecting piezoelectric element) and the detector123is also vibrated with a multiple vibration mode as in the stylus121. Accordingly, the action of the vibration of the multiple vibration mode as well as the action of the vibration of the main vibration mode is reflected on the detection signal generated by the detector123.

When the detection signal (voltage) from the detector123is applied to the primary coil131, the output signal (alternating current signal) is generated on the secondary coil132by mutual induction. As described above, since the coil has a tendency of hindering flow of high-frequency electric current, when the high-frequency component is included in the detection signal from the detector123received by the primary coil131, the output signal from which the high-frequency component is substantially removed is generated on the secondary coil132. Accordingly, the noise of the action of the vibration of the main vibration mode can be substantially removed, thereby obtaining an output signal having improved S/N ratio.

By analyzing and processing the output signal highly accurately reflecting the action of the vibration of the main vibration mode with the signal processor140, the vibrating condition of the stylus121can be recognized with high accuracy.

Such vibration detecting system101is used for a contact touch trigger probe such as a coordinate measuring machine, for instance.

Specifically, when the stylus121is vibrated with a main vibration mode along axial direction by the vibrator122, the workpiece and the contact probe120are relatively moved. When the contact portion121A of the stylus121touches the workpiece, the vibration of the stylus121is restricted and the vibration of the main vibration mode of the stylus is damped.

Since the high-frequency component of the detection signal from the detector123is substantially removed by the magnetic circuit130, the damp of the vibration of the main vibration mode can be detected by the signal processor140with high accuracy. By setting the signal processor140to output a signal to the outside when the vibration of the main vibration mode is damped to a predetermined level, the contact between the stylus121and the workpiece can be securely detected and the measurement pressure by the coordinate measuring machine etc. can be made always constant.

According to the above-described present embodiment, following advantages can be obtained.(1) In the vibration detecting system101, since the detection signal from the detector123is received by the primary coil131of the magnetic circuit130and the vibration of the stylus121is detected using the output signal generated by the secondary coil132by mutual induction, the high-frequency component of the detection signal corresponding to multiple vibration mode as a noise can be substantially removed. Accordingly, the function of the external force applied on the stylus121(such as contact with the workpiece) can be recognized by the change in the output signal generated by the secondary coil132with high accuracy.

Further, since close electromagnetic connection is established between the primary coil131and the secondary coil132in the magnetic circuit130, voltage is generated on the secondary coil132when the alternating current signal runs through the primary coil131and no voltage is generated on the secondary coil132when direct current signal having no change in electric current runs through the primary coil131. Accordingly, even when static electricity is generated upon contact of the stylus121with workpiece etc., since the static electricity is direct current, the influence on the voltage generated by the secondary coil132can be avoided.(2) Since the vibrator122and the detector123are constructed by attaching the two piezoelectric elements on the stylus121, the structure of the vibration detecting system101can be simplified and the production cost thereof can be reduced. Incidentally, though the piezoelectric element is attached to the stylus121through the stylus attachment242in the present embodiment, the piezoelectric element may be directly attached to the stylus121, which is included in the scope of the present invention.(3) Since the winding number of the secondary coil132is more than the winding number of the primary coil131, the amplitude of the output signal amplified by boosting the amplitude of the detection signal received by the primary coil131can be generated in the secondary coil132.
[Sixth Embodiment]

FIG. 9shows a vibration detecting system102according to sixth embodiment of the present invention. The present embodiment differs from the above-described fifth embodiment in the arrangement of the detector for detecting the vibration of the stylus and the rest of the arrangement and function thereof are the same. Accordingly, the same reference numeral will be attached to the same structure and arrangement to omit or simplify the description thereof. Incidentally, in the present embodiment, illustration of a part of the vibration energy source and the contact probe is omitted.

InFIG. 9, the detector of the vibration detecting system102is composed of a laser Doppler device150as a non-contact detecting element located around the stylus121.

The laser Doppler device150utilizes Doppler effect and optical heterodyne method to detect vibration frequency and outputs a detection signal to the primary coil (not shown) of the magnetic circuit130in accordance with the detected vibration frequency.

In thus arranged vibration detecting system102, when vibration with the main vibration mode is applied on the stylus121is vibrated, the stylus121is vibrated with a multiple vibration mode including high-frequency component being influenced by the configuration thereof etc. The vibration of the stylus121is detected by the laser Doppler device150to output a detection signal in accordance with vibration to the primary coil of the magnetic circuit130. In the magnetic circuit130, since the high-frequency component of the detection signal from the detector123is substantially removed, the signal processor140can detect the vibration of main vibration mode with high accuracy.

According to the above-described present embodiment, following advantages as well as the advantages (1) and (3) of the fifth embodiment can be obtained.(4) Since the detector is constructed by the laser Doppler device150, the influence on the vibration of the stylus121on account of the contact between the stylus121and the detector can be eliminated, thereby detecting the vibration of the stylus121with higher accuracy.
[Modification of Fifth to Sixth Embodiments]

Though the laser Doppler device150is used as a non-contact detecting element constituting the detector in the sixth embodiment, an optical fiber displacement meter for detecting the vibration frequency by irradiating light irradiated from optical fiber to the stylus121and detecting the information on the reflected light and outputting detection signal in accordance with the detected vibration frequency may be used. In short, any element may be used as long as the vibration of the stylus121can be detected in a non-contact manner.

Though the detector123is constructed of a piezoelectric element in the fifth embodiment, the detector123may be constructed of a strain detecting element such as a strain gauge outputting electric potential in accordance with strain of an object, which is included in the scope of the present invention.

Though the vibration detecting systems101and102are used for a coordinate measuring machine, the vibration detecting system may be used for various measuring instruments such as a height gauge, surface texture measuring machine and small hole measuring machine, which is included in the scope of the present invention.