JPH01308902A - Contact sensor - Google Patents

Abstract

PURPOSE:To perform measurement with good reproducibility without generating errors even when the surface to be measured of an object to be measured is inclined by connecting a piezoelectric element to the base end of the contact element having forward and rearward with respect to the object to be measured. CONSTITUTION:A contact element 3 is formed in a suspended state at the central position of the lower surface of the bottom plate 2, which is fixed to the lower end opening part of a hollow cylindrical piezoelectric element 1. The piezoelectric element 1, the bottom plate 2 and the contact element 3 are unified and deformed as a whole when brought into contact with an object to be measured such as a work. An electrode plate 4 for detecting displacement quantity in an X-axis direction and an electrode plate 5 for detecting displacement quantity in a Y-axis direction are respectively bonded to the lower outer surface of the piezoelectric element 1 in directions crossing each other at a right angle on both sides thereof in the diameter direction. Further, an annular electrode plate 6 is bonded to the upper outer peripheral surface of the piezoelectric element 1 along the peripheral direction thereof and detects displacement quantity in a Z-axis direction. This sensor is allowed to advance toward the object to be measured until the leading end thereof impinges against the object to be measured and contact pressure is detected by the piezoelectric element 1 to stop the advance movement of the sensor, and the movement quantity of the sensor is measured.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a contact sensor, and more specifically, to a contact sensor capable of measuring the distance and inclination of a measurement point from a reference surface. It is something.

(Prior art) Conventionally, the height of a point on a workpiece placed on a reference surface (
For example, as a sensor that measures the distance between the reference surface and that point, there is a contact that comes into contact with the workpiece, and
- A mechanism that swings the contactor in a pendulum-like manner perpendicular to the contact surface with the workpiece on the Y plane (a plane parallel to the reference plane), and another mechanism that moves the contactor up and down along the Z-axis direction (direction perpendicular to the reference plane). There is a contact sensor with a mechanism of

In this contact sensor, the contact element is moved downward while swinging in a pendulum shape, and the X of the contact element is moved downward.

When the displacement in both the Y and Z directions becomes constant, a trigger is output to issue an instruction to read the coordinates, and the height is detected by reading the coordinates of the two axes at that time.

(Problem to be Solved by the Invention) However, in the conventional sensor described above, the lower end of the contact that comes into contact with the workpiece has no size and does not apply measurement pressure to the workpiece, which is an ideal point. However, in reality, it is not possible to manufacture such contacts.

Therefore, the lower end of the contact is made spherical with a constant radius, pressure is applied to the lower end of the contact at a certain point on the workpiece, and measurement is performed by detecting the pressure generated by the contact. . As a result, there is a problem in that the measured values vary and errors occur.

In other words, the lower end of the contact has a certain shape (not a point), and the frictional force generated between the lower end and the workpiece (as long as measurement pressure is applied, the generation of frictional force cannot be eliminated) causes contact. There is a risk that the child may contact the workpiece at an oblique angle rather than perpendicularly to the measurement point of the workpiece. When the contact is made at an angle, the difference (height) between the lower end and the upper end of the contact becomes shorter than the length of the contact, resulting in an error in the measured value. Furthermore, when the contactor is tilted, the lower end of the contactor comes into contact with a location different from the target point to be measured, which also causes an error.

This invention was made in view of the above-mentioned problems.
The purpose of this is to be able to measure with good reproducibility without causing errors even if the n1 constant plane of the object to be measured is inclined, etc., and also to be able to measure the inclination angle of the measurement plane. Provides contact sensors.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the contact sensor according to the present invention is capable of moving back and forth with respect to the fixed object 11111 and whose tip can come into contact with the fixed object 11111. with a contactor,
A piezoelectric element connected to the base end side of the contact and a means for detecting an electromotive force accompanying deformation of the piezoelectric element generated when the contact comes into contact with the object to be measured are provided.

(Operation) The contact sensor is advanced toward the object to be measured until the tip of the contact comes into contact with the object to be measured. Then, the contact pressure of the contact is detected by the piezoelectric element, and the forward movement of the contact sensor is stopped. By detecting the amount of movement of the contact sensor at that time, the distance of the measurement point from the reference plane is measured.

Further, the measurement point is inclined, and in order to measure the angle of inclination, the contact sensor is urged to move further from the above-mentioned state. Then, the tip of the sensor moves along the slope at the measurement point, and the amount of displacement is detected via the piezoelectric element, and by performing a predetermined correction calculation, the slope angle can be determined to be 7ip+.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of the invention.

As shown in the figure, in this embodiment, first, a disk-shaped bottom plate 2 having approximately the same diameter is fixed to the lower end opening of a hollow cylindrical piezoelectric element 1, and the bottom plate 2 is placed at the center position of the bottom surface of the bottom plate 2. The contact 3 is formed to hang down. These piezoelectric elements 1. Bottom plate 2
Further, the contactor 3 is integrated, and deforms as a whole when it comes into contact with an object to be measured such as a workpiece.

Further, on the lower outer circumferential surface of the piezoelectric element 1, X is provided on both sides in the radial direction.
A first electrode plate 4.4 for detecting the amount of displacement in the axial direction is attached. Further, second electrode plates 5, 5 are attached to the outer peripheral surface of the piezoelectric element 1 in a direction perpendicular to the first electrode plates 4, 4 for detecting the amount of displacement in the Y-axis direction. . Further, a third annular electrode plate 6 is attached to the upper outer peripheral surface of the piezoelectric element 1 along its circumferential direction, so that the amount of displacement in the Z direction can be detected.

Furthermore, specifically, an electrode plate (not shown) is also attached to the inner peripheral surface of the piezoelectric element 1, and the electrode plate and the above-mentioned first
- By detecting the potential difference generated between the third electrode plates 4 to 6, the displacement amount in each of the axial directions described above is detected.

The contact sensor 8 configured as described above is connected to a moving mechanism (not shown), and can be moved in three dimensions.

Next, the operation of this embodiment will be explained.

First, as shown in FIG. 2(A), a workpiece 10, which is an object to be measured, is placed on a reference surface 12. To explain the case where the measurement surface 10a of the workpiece 10 is parallel to the reference surface 12, the above-mentioned moving mechanism (not shown) is activated to move the contact sensor 8 to the exact position of the point on the workpiece 10 to be measured.
position it above.

Next, the contact sensor 8 is moved straight down, and when the downward movement is continued, the lower end of the contact comes into contact with the workpiece 10. Then, when the piezoelectric element 1 is operated to move further downward from this state, the piezoelectric element 1 contracts slightly in the vertical direction due to the contact pressure generated between the contactor 3 and the workpiece 10. Then, the contraction is detected via the third electrode plate 6 that detects displacement in the Z direction, and a stop command is issued to the moving mechanism (ideally, it would like to stop at the moment of contact, but in reality, the piezoelectric element (The stop command will be issued with a slight delay due to the detection ability of the robot.) Next, the height (distance from the reference plane 12) hl of the upper end of the piezoelectric element 1 at this time is measured. The length h2 of the contact sensor 8 (the length when the piezoelectric element 1 is not expanded or contracted) is known in advance,
Further, the amount of contraction a of the piezoelectric element 1 from the third electrode 6 described above is
h can also be detected. Therefore, the height h of the measurement point of the workpiece 10 is determined by h-hl-h2+, 6h...■.

In addition, even if the measurement surface is inclined, as shown in FIG. Since the contact sensor 8 maintains a straight state while the downward movement of the contact sensor 3 is stopped, the height can be determined using the correction formula described above. However, in this case, since the direction of the reaction force received from the n1 constant surface 10'a is perpendicular to the measurement surface, as the inclination angle increases, the first or second electrode 4.5
The contact of the contactor 3 is detected.

Next, a method for measuring the inclination angle when the measurement surface 10'a of the workpiece 10' is inclined as shown in FIG. 2(B) will be explained.

First, the basic operation is performed in the same manner as described above, and the contact sensor 8 is moved downward until the contactor 3 contacts the workpiece 10. When the contact sensor 8 is further lowered in this state, the lower end of the contactor 3 moves diagonally downward along the inclined surface of the workpiece 10. That is, positional deviations occur in the horizontal (X-Y) direction and the vertical (Z) direction with respect to the desired position (regular measurement point).

The amount of displacement 13x and Ay in the X-Y direction is the first . second electrode plate 4,
It can be measured by detecting through 5. The amount of displacement Jz in the height direction is determined when the lower end of the contactor 3 is on the measurement surface (specifically, point
) can be determined by measuring the distance traveled before stopping.

Moreover, as shown in FIG. 3, the displacement f in the height direction of the contactor 3
fi A z includes a difference Jzl caused by the rise of the lower end of the contactor 3 (when the contact sensor 8 rotates around its upper end and moves laterally), and a difference caused by the difference in height of the measurement point of the workpiece 12. There is dz2.

And 1. Since dzl is a value obtained by subtracting the length of side ab from the length h of the contact sensor 8 when a triangle abc is assumed, dzl is obtained as follows. Here, both zx and jy are displacement amounts in the XY plane from the regular measurement point to the point where the contactor 3 is actually in contact.

Therefore, 1lz2 is determined by 1, az 2-13 z -13z 1.

Then, considering a triangular bed, tanθ−,
dz2/7丙T〒77bow holds true, so that the inclination angle θ can be found from the 77bow.

Note that even while the contact moves along the inclined surface,
Since the piezoelectric element 1 is compressively deformed, it is desirable to make a correction in consideration of the amount of contraction, as shown in equation (2) above.

FIG. 4 shows a second embodiment of the invention.

In this embodiment, instead of the cylindrical piezoelectric element in the first embodiment described above, three prismatic piezoelectric elements 20a-
c is used. And these three piezoelectric elements 20
a - c are arranged so as to be orthogonal to each other,
Moreover, it is arranged along the x, y, and z axes. and,
A contactor 3 is formed to hang down from the lower surface of the intersection of each piezoelectric element 20a to 20C.

Further, although not shown, the tips of the piezoelectric elements 20a to 20c described above are immovably fixed to the measurement substrate, and the relative positions of the three fixed points remain substantially unchanged.

In this embodiment, each of the piezoelectric elements described above is a stack of a plurality of flaky piezoelectric elements.

Next, the operation of this embodiment will be explained. Similar to the first embodiment described above, the contact sensor 8' is moved downward until it comes into contact with the workpiece. When the measurement surface of the workpiece is flat, only the piezoelectric element 20c arranged in the Z direction contracts, so the height can be measured using the same correction formula as in the first embodiment.

Further, as shown in FIG. 5, the measurement surface 10a of the workpiece 10
If the lower end of the contactor 3 contacts the measurement surface and then moves downward, the lower end of the contactor 3 will rotate around the upper end Q of the piezoelectric element 20c arranged in the Z direction. Rotates along an inclined surface. Then, along with that rotation,
, the piezoelectric elements arranged in the Y-axis direction (in this example, only the piezoelectric element 20a in the X direction) are compressed. Thereby, it is possible to detect how far the lower end of the contactor 3 has been displaced in the X direction. Similarly, when the displacement of the contactor 3 has a component in the Y-axis direction, the piezoelectric element 20b arranged in the Y-axis direction also expands and contracts. As a result, the displacement mA x in the X-Y direction,
A y can be detected.

After measuring Jx and 4y in this way, the workpiece 10 is
The inclination angle of the 1lpj fixed point can be measured.

Furthermore, the above-mentioned 1. In the second embodiment, the case in which the height of the workpiece is measured has been described, but the present invention is not limited to this, and the present invention is not limited to this, but the present invention is not limited to this. However, by bringing it close to the object to be measured, it is possible to measure the distance (not limited to height) from any reference plane to the measurement point.

(Effects of the Invention) As described above, with the contact sensor according to the present invention, even if the measurement surface of the object to be measured is inclined or the like, it is possible to measure the object with good reproducibility without causing any error.

It is also possible to measure the inclination angle of the measurement surface.

Moreover, the object to be measured is not limited to the height of the object to be measured;
It becomes possible to measure the distance from the reference plane in any dimensional direction.

Furthermore, the contact sensor of the present invention only needs to be moved straight (in the -axis direction) relative to the DI object (there is no need to swing it in a pendulum shape as in the past), which simplifies the movement mechanism. .

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the first embodiment of the contact sensor according to the present invention, FIGS. 2 and 3 are diagrams explaining its operation, and FIG.
The figure is a perspective view showing the second embodiment, and FIG. 5 is a diagram illustrating its operation. 1...Piezoelectric element 3...Contactor 4...First electrode plate 5...Second electrode plate 6...First 3 electrode plate 8, 8'...
Contact sensor 10...Workpiece 12...Reference planes 20a to 20c...Piezoelectric element Patent applicant Fuji Electrochemical Co., Ltd. Agent Patent attorney - Ken Iro Interpolation
Patent Attorney Masatoshi Matsumoto Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] a contact that can move forward and backward relative to the object to be measured and whose tip can come into contact with the object to be measured; a piezoelectric element connected to the base end of the contact; A contact sensor comprising means for detecting an electromotive force caused by deformation of the piezoelectric element that occurs when the piezoelectric element comes into contact with the piezoelectric element.