JP2000193404A - Measuring head and measuring feeler - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high-accuracy measurement by suppressing vibrations of a measuring head and a measuring feeler when measuring. SOLUTION: In order to suppress the vibrations of a measuring head 11 and a measuring feeler 13, a dynamic rigidity changing means 31 which changes the dynamic rigidity of the feeler 13 for suppressing the vibrations of the feeler 13 is attached to the feeler 13. The means 13 reduces the vibrations of the feeler 13 and head 11 at measuring to a level at which measurement is not affected or lower by improving the apparent dynamic rigidity of the feeler 13 by giving a vibration damping property to the feeler 13 and removing the resonance frequency of a measuring feeler system from a main vibration frequency range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring head for detecting contact with a workpiece and a displacement caused by the contact and a measuring feeler of the measuring head used in a coordinate measuring machine, a machine tool, and the like. The present invention relates to a measuring head and a measuring feeler provided with a means for suppressing vibration in the measuring head.

[0002]

2. Description of the Related Art A measuring head for detecting a contact with an object to be measured and a displacement after the contact is provided with a measuring feeler contacting the object to be measured, a feeler supporting portion for supporting the measuring feeler, and a displacement of the feeler supporting portion. And a detector that performs the measurement. The measurement feeler has a simple linear shape made of a homogeneous material such as metal, carbon, and ceramics. Also,
As the detector, there are a touch type using means such as a micro switch for detecting contact with an object to be measured, and a displacement measurement type using means such as a differential transformer for detecting displacement of a measurement feeler.

[0003] Such measuring heads are used in measuring machines for measuring two-dimensional and three-dimensional shapes. It is also possible to mount this measuring head on the spindle of the machine tool. In this case, the position reading device reads the x-axis, y-axis, and z-axis coordinates of the machine tool when it comes into contact with the workpiece, and reads the coordinates of the workpiece, for example, a processed workpiece. Measure the dimensions of In this case, the measured dimensions are used, for example, in order to process the insufficiently processed portion of the work again.

[0004] When a penetrating force is applied due to acceleration and stop during positioning or approaching operation during measurement, vibrations are generated in the measurement feeler and the measurement head. The amplitude of the vibration may be erroneously detected as contact or displacement by the detector of the measuring head. Therefore, in order to perform highly accurate measurement, it is necessary to take measures against this vibration.

[0005] One solution to such vibrations is:
The purpose is to attenuate the generated vibration to a level that does not affect the desired measurement accuracy. A displacement measuring device for attenuating vibration is disclosed in Japanese Patent Application Laid-Open No. 5-309551. In this displacement measuring device, the inside of the housing is filled with a liquid, a narrow gap is provided around the detection axis in the housing, and vibration is attenuated by viscous resistance when the fluid flows through the gap.

Another solution to vibration is to distinguish between deflection of the measuring feeler due to vibrations of the measuring or machine tool and deflection of the measuring feeler caused by contact. A signal processing circuit for discriminating deflection of a measurement feeler due to vibration and contact is disclosed in Japanese Patent Application Laid-Open No. 5-187808. In this signal processing circuit,
By setting two types of thresholds, a relatively low threshold and a relatively high threshold, for the signal for deflection,
The frequency of incorrect signal identification is reduced.

[0007]

With respect to the vibration generated in the measuring head, the above-mentioned solutions are known.
None of the measurement feelers has a function of suppressing vibration by itself, and in the case of a known measurement feeler, the vibration of the measurement feeler generated when performing positioning or approaching operation during measurement and the measurement feeler in the measurement head accompanying the vibration. Vibration of the support cannot be suppressed. For this reason, the measurement accuracy or reproducibility of the measurement head deteriorates, making it difficult to measure the measurement head with high accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to provide a measuring head and a measuring feeler which suppress vibrations generated in the measuring feeler during a measuring operation, thereby suppressing vibrations of the entire measuring head and enabling highly accurate measurement. It is to provide.

[0009]

SUMMARY OF THE INVENTION The present invention provides a measuring head and a measuring feeler having dynamic stiffness changing means for changing dynamic stiffness in order to suppress vibration during a measuring operation to a level that does not adversely affect the measurement. . The dynamic stiffness changing means improves the dynamic stiffness by adding vibration damping to the measurement feeler and removing the resonance frequency of the system of the measurement feeler from the range of the frequency generated at the time of measurement. To a desired level or less. The dynamic rigidity can also be increased by increasing the static rigidity.

Here, the dynamic stiffness is defined as F, which is a periodic excitation force acting on one point of application of an elastic body, and F at another point of the same elastic body.
Is the characteristic defined by X / F, where X is the displacement caused by That is, the dynamic stiffness means a property in which vibration due to a fluctuating load and an inertial force is unlikely to occur, and increasing the dynamic stiffness means reducing the amplitude for every frequency. The dynamic rigidity changes depending on the static rigidity, the resonance frequency, and the damping coefficient, and the dynamic rigidity increases as the static rigidity and the damping coefficient increase. Further, if the frequency of the generated vibration is out of the resonance frequency, the amplitude becomes small.

According to the present invention, there is provided a measuring head having a housing and a measuring feeler supported by the housing and in contact with an object to be measured, wherein the measuring feeler has a dynamic rigidity change comprising at least one of a mass, a spring element and a damping element. Means for changing the dynamic rigidity of the measuring head by changing a physical constant of the dynamic rigidity changing means.

Further, according to the present invention, in a measurement feeler supported by a housing of a measurement head and in contact with an object to be measured, a dynamic force comprising at least one of a mass, a spring element, and a damping element that changes the dynamic rigidity of the measurement feeler. A measurement feeler provided with a rigidity changing unit is provided.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a measuring head and a measuring feeler of the present invention will be described in detail with reference to embodiments. FIG.
1 is a schematic diagram illustrating the concept of an embodiment of a measuring head and a measuring feeler of the present invention. Although FIG. 1 shows a touch-type measuring head, it may be another type, for example, a displacement measuring type measuring head.

The measuring head 11 has a housing 15 and a measuring feeler 13 supported by the housing 15. The housing 15 includes a feeler support member 17 that supports the measurement feeler 13, a biasing unit 19 that biases the feeler support member 17, and a biased feeler support member 17.
Accommodates a fulcrum member 21 against which the sensor 23 abuts and a detector 23 for detecting displacement of the feeler support member 17. In the case of the touch-type measuring head 11 of FIG. 1, the detector 23 is a microswitch. In the case of the displacement measuring type measuring head 11, the detector 23 is a displacement measuring means such as a differential transformer.

The measuring feeler 13 according to the present invention comprises the spring element 2
5, a dynamic stiffness changing means 31 comprising a damping element 27 and a mass portion 29. The dynamic stiffness changing means 31 performs measurement including the measurement feeler 13 and the measurement feeler 13 and the urging means 19 of the measurement head 11. Changes the dynamic rigidity of the entire head. Specifically, at least one of the physical constants such as the spring constant of the spring element 25, the damping coefficient of the damping element 27, and the mass of the mass portion 29 may be changed.

In order to suppress the vibration of the measurement feeler 13 by changing the dynamic rigidity of the measurement head 11, it is necessary to add vibration damping to the system of the measurement feeler 13 or to measure the resonance frequency of the system of the measurement feeler 13. The vibration generated at the time of measurement may be reduced to a level which does not adversely affect the measurement accuracy by removing the vibration from the range of the frequency of the generated vibration. By removing the resonance frequency of the system of the measurement feeler 13 from the range of the frequency of the vibration generated at the time of measurement, the maximum amplitude in the range of the frequency that can be generated is reduced, and the apparent dynamic rigidity is improved. Further, the dynamic stiffness is proportional to the static stiffness under a constant condition. Therefore, by improving the static stiffness, the dynamic stiffness can be improved and the vibration of the system of the measurement feeler 13 can be suppressed.

Suppressing the vibration of the measuring feeler 13 leads to suppressing the vibration of the entire measuring head 11 including the measuring feeler 13 and the urging means 19. Therefore, by suppressing the vibration of the measurement feeler 13,
The measuring head 11 can perform highly accurate measurement. In the following, dynamic rigidity changing means 31 for suppressing vibration
A specific embodiment will be described with reference to the drawings.

In the following two embodiments, the dynamic rigidity changing means 31 changes the dynamic rigidity of the measurement feeler 13 and the measurement head 11 mainly by changing the vibration damping property of the measurement feeler 13. FIG. 2 is a side sectional view of the measurement feeler 13 showing the first embodiment of the dynamic rigidity changing means 31. In FIG. 2, a cavity 35 is provided inside the measurement shaft 33 of the measurement feeler 13, and a vibration damping material 37 is sealed in the cavity 35. In this case, as the vibration damping material 37, for example, oil, silicone grease,
Urethane or the like is used. Vibration damping material 3 in cavity 35
By enclosing 7, it is possible to change the vibration damping property of the measurement feeler 13 and further the measurement head 11 as a whole, and to provide the measurement feeler 13 and the measurement head 11 with desired vibration damping properties. For example, vibration is attenuated by oil fluid friction. In addition, the vibration damping material 37 is connected to the cavity 3
5, the mass and the internal damping of the measuring feeler 13 are changed, thereby changing the resonance frequency and the vibration amplitude.
1 can be changed.

FIG. 3 is a side view of the measuring feeler 13 showing a second embodiment of the dynamic rigidity changing means 31. In the embodiment shown in FIG. 3, a vibration damping member 41 is attached to a base end portion 39 of the measurement feeler 13 which is a joint with the feeler support member 17. In this case, as the vibration damping member 41, for example, rubber, plastic, or the like is used. By attaching the vibration damping material 41 to the joint between the feeler support member 17 and the measurement feeler 13, the vibration generated in the measurement feeler 13 is attenuated, and the dynamic rigidity of the measurement feeler 13 and the measurement head 11 is improved.

In order to change the dynamic rigidity of the measurement feeler 13, the resonance frequency of the measurement feeler 13 may be changed. In the following two embodiments, the dynamic rigidity changing means 31 mainly changes the resonance frequency of the measurement feeler 13. FIG. 4 shows a third embodiment of the dynamic rigidity changing means 31, in which a weight 43 is added to the measurement feeler 13 as the dynamic rigidity changing means 31. The weight 43 is the measurement feeler 13
Can be moved in the longitudinal axis direction 45. Preferably, the weight 43 further comprises fixing means 47 for movably fixing the weight at any position, for example, screws. By changing the mass and position of the weight 43, the resonance frequency of the measurement feeler 13 and the measurement head 11 changes. By changing the mass and position of the weight 43 so that the resonance frequency is out of the range of the main frequency of the vibration generated during the measurement operation in the measuring machine or machine tool to which the measuring head 11 is attached, the measuring feeler 13 and the measuring head are changed. 11 can be improved in dynamic rigidity.
Since the weight 43 can be made detachable, the weight can be freely replaced so that the resonance frequency deviates from a main frequency generated at the time of measurement by a measuring machine or a machine tool to which the measuring head 11 is attached. . Further, a weight 43 is added to the conventional measurement feeler 13 to
It is possible to easily change the resonance frequency of the measurement feeler 13 and the measurement head 11, that is, change the dynamic rigidity.

The weight 43 may be formed in an elongated cylindrical shape. By adopting an elongated cylindrical shape, the static rigidity of the measurement feeler 13 can be partially improved,
Thereby, the dynamic rigidity of the measurement feeler 13 can be further improved. The weight 43 may be composed of a plurality of parts and may be assembled together when attached to the measurement feeler 13.

FIG. 5 shows a fourth embodiment of the dynamic rigidity changing means 31. A cavity 49 is provided inside the measurement shaft 33 of the measurement feeler 13, and a thread is provided inside the cavity 49. In FIG. 5, the measurement shaft 33 of the measurement feeler 13 is detachable from the base end portion 39 of the measurement feeler 13, and the cavity 49 inside the measurement shaft 33 is provided at the end 5 of the measurement shaft 33.
1 is open. An internal screw 53 as the dynamic rigidity changing means 31 is inserted into the cavity 49 from the end 51 of the measuring shaft 33. The resonance frequency of the measurement feeler 13 and the measurement head 11 is changed by changing the position of the internal screw 53. As in the case of FIG. 4, the measurement is performed by changing the position of the internal screw 53 so that the resonance frequency is out of the range of the vibration frequency generated during the measurement operation in the measurement machine or the machine tool to which the measurement head 11 is attached. The dynamic rigidity of the feeler 13 and the measuring head 11 can be improved. Further, when the internal screw 53 is long, the static rigidity of the measurement feeler 13 is affected, and therefore, the effect of changing the dynamic rigidity by changing the static rigidity is also obtained.

In FIG. 5, it is also possible that no thread is provided in the cavity 49 provided inside the measurement feeler 13. In this case, what is inserted into the cavity 49 is a cylindrical body or a cylindrical body instead of the internal screw. Such a cylindrical or columnar body may be fixed in the cavity by frictional force. Changing the dynamic stiffness of the measurement feeler 13
It is also possible by changing the static rigidity by changing the mass distribution and the spring constant of the measurement feeler 13.

FIG. 6 shows one embodiment in which the static rigidity of the measurement feeler 13 is changed. In FIG. 6, the measurement feeler 13 has a measurement axis 33 of the measurement feeler 13 which is conventionally uniform in order to change the mass distribution and the spring constant.
Is tapered. With the tapered shape, for example, the mass distribution and the spring constant can be changed without changing the mass and length of the measurement feeler 13.

As described above, according to the present invention, it is possible to easily improve the measurement accuracy of the measurement head 11 by simply modifying the measurement feeler 13. The measuring feeler of the present invention not only suppresses the vibration generated in the measuring feeler, but also suppresses the vibration of the entire measuring head by applying the measuring feeler of the present invention to the measuring feeler portion of the existing measuring head. , Enables highly accurate measurement.

[0026]

According to the present invention, by providing the measuring feeler with dynamic rigidity changing means, the vibration of the measuring feeler or the vibration of the feeler supporting portion in the measuring head caused by the positioning and approaching operations during the measurement is attenuated or eliminated. Vibration suppression improves the measurement accuracy (reproducibility, degree of variation in measured values) of the measuring head, and enables high-speed, high-accuracy measurement.

Further, by using the measuring feeler of the present invention for a measuring head having no conventional damping or damping means, it is possible to improve the measuring accuracy of the conventional measuring head.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating the concept of an embodiment of a measuring head and a measuring feeler of the present invention.

FIG. 2 is a side sectional view of the measurement feeler showing a first embodiment of dynamic rigidity changing means for mainly giving vibration damping to the measurement feeler.

FIG. 3 is a side view of a measurement feeler showing a second embodiment of dynamic rigidity changing means for mainly giving a vibration damping property to the measurement feeler.

FIG. 4 is a side view of the measurement feeler showing a third embodiment of the dynamic rigidity changing means for changing the resonance frequency of the measurement feeler.

FIG. 5 is a side sectional view of a measurement feeler showing a fourth embodiment of dynamic rigidity changing means for changing a resonance frequency of the measurement feeler.

FIG. 6 is a side view of the measurement feeler showing one embodiment for changing the static stiffness of the measurement feeler.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Measuring head 13 ... Measuring feeler 15 ... Housing 25 ... Spring element 27 ... Damping element 29 ... Mass part 31 ... Dynamic rigidity changing means

Claims (2)

[Claims] 1. A measuring head comprising a housing and a measuring feeler supported by the housing and in contact with an object to be measured, wherein said measuring feeler includes a dynamic stiffness changing means comprising at least one of a mass, a spring element, and a damping element. A measuring head for changing the dynamic rigidity of the measuring head by changing a physical constant of the dynamic rigidity changing means. 2. A measuring feeler supported by a housing of a measuring head and in contact with an object to be measured, wherein a dynamic rigidity changing means comprising at least one of a mass, a spring element, and a damping element for changing the dynamic rigidity of the measuring feeler is provided. A measurement feeler characterized by comprising: