Profile tolerance measuring rod mechanism

Abstract

The utility model discloses a profile tolerance measuring rod mechanism, which comprises a contact pin, a measuring rod, a fulcrum and a displacement sensor, the contact pin is mounted at the front end of the measuring rod, the tail end of the measuring rod is rotatably mounted on the fulcrum, and the displacement sensor is mounted in the middle of the measuring rod. According to the utility model, the arrangement structure of a traditional measuring rod is innovatively changed, the tail end of the measuring rod is rotatably mounted on the fulcrum, and the displacement sensor is mounted in the middle of the measuring rod, so that the error caused by the bearing clearance at the fulcrum can be greatly reduced, and the measurement resolution is not lost in the same structural space.

Description

Technical Field

[0001] The utility model relates to the technical field of precision measurement, in particular to a contour measuring rod mechanism. Background Art

[0002] like Figure 1 As shown, the traditional contour measuring rod mechanism includes a stylus 1, a measuring rod 2, a fulcrum 3 and a displacement sensor 4, and its structural setting relationship is as follows: the middle part of the measuring rod 2 is rotatably mounted on the fulcrum 3 (at B), the stylus 1 is mounted on the front end of the measuring rod 2 (at A), and the displacement sensor 4 is mounted on the rear end of the measuring rod 2 (at C).

[0003] The measurement principle is as follows: when the stylus 1 slides over the surface of an object, due to the unevenness of the object's surface, the measuring rod 2 rotates around the fulcrum 3, so that the displacement sensor 4 at the tail end detects the rotation amount of the measuring rod 2, and then restores the surface contour undulation of the object through an algorithm.

[0004] The fulcrum 3 generally uses a ball bearing as the center of rotation, but all bearings have a common feature that there is bearing clearance, that is, there is a radial gap X between the inner and outer rings of the bearing, such as Figure 2 As shown in the figure (exaggerated schematic diagram), this gap is generally at the um level. For ordinary applications, this gap can generally be ignored; however, the error caused by high-precision detection equipment such as contour accuracy cannot be ignored. Figure 3 As shown in the figure, the reason for the error caused by the gap is that when the stylus 1 measures the inclined surface, its force direction F1 is perpendicular to the contact surface, and this end of the measuring rod 2 is subjected to a rightward oblique force. The other end of the measuring rod 2 must be subjected to a leftward oblique force F2. This force must be generated by the support of the bearing outer ring on the inner ring. It can be deduced that the center of the bearing inner ring, that is, the rotation center of the measuring rod, has shifted. During the measurement process, it is assumed that the contact surface of the stylus 1 at the starting point is horizontal, and the stylus 1 at the end point is as follows: Figure 3 The motion process of the measuring rod can be decomposed into two parts. The first part is the rotation of the measuring rod around the theoretical center of the circle, and the second part is the rotation of the measuring rod around the needle tip to reach Figure 3 The first part of the movement is linear and will not produce errors; the second part is that the measuring rod produces an error of size X at point A. According to the conventional setting scheme, the length of the measuring rod AB section is twice that of the BC section, so the nonlinear error produced by the measuring rod at point C (where the displacement sensor is located) is 3 / 2*X. Utility Model Content

[0005] The technical problem to be solved by the utility model is to provide a contour measuring rod mechanism which can greatly reduce the error caused by the bearing clearance and does not lose the measurement resolution in the same structural space.

[0006] In order to solve the above technical problems, the technical solution of the utility model is: a contour measuring rod mechanism, including a stylus, a measuring rod, a fulcrum and a displacement sensor, the stylus is installed at the front end of the measuring rod, the tail end of the measuring rod is rotatably installed on the fulcrum, and the displacement sensor is installed in the middle of the measuring rod.

[0007] As a preferred technical solution, the distance from the front end of the measuring rod to the installation point of the displacement sensor is equal to the distance from the installation point of the displacement sensor to the fulcrum.

[0008] As a preferred technical solution, the displacement sensor is a grating ruler sensor.

[0009] Due to the adoption of the above technical solution, the utility model has at least the following beneficial effects: for the first time, the error problem caused by bearing clearance on high-precision detection equipment such as contour is discovered and proposed, and the layout structure of the traditional measuring rod is changed by innovation, the tail end of the measuring rod is rotated and installed on the fulcrum, and the displacement sensor is installed in the middle of the measuring rod. After this arrangement, the error caused by the bearing clearance can be greatly reduced, and the measurement resolution is not lost in the same structural space. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The following drawings are only intended to illustrate and explain the present invention, and do not limit the scope of the present invention.

[0011] Figure 1 It is a schematic diagram of the structure of a traditional profile measuring rod mechanism;

[0012] Figure 2 It is an exaggerated schematic diagram of the bearing clearance at the fulcrum;

[0013] Figure 3 This is a schematic diagram showing the effect of bearing clearance on the measurement error at point C in the traditional solution;

[0014] Figure 4 Schematic diagram of the main structure of the contour measuring rod mechanism in this embodiment;

[0015] Figure 5 Schematic diagram of the top view of the contour measuring rod mechanism in this embodiment;

[0016] Figure 6 Schematic diagram of the effect of bearing clearance on the measurement error at point C in this embodiment. DETAILED DESCRIPTION

[0017] The present invention is further described below in conjunction with the accompanying drawings and examples. In the following detailed description, only certain exemplary embodiments of the present invention are described by way of illustration. Needless to say, those skilled in the art will recognize that the described embodiments may be modified in various ways without departing from the spirit and scope of the present invention. Therefore, the drawings and descriptions are illustrative in nature and are not intended to limit the scope of protection of the claims.

[0018] like Figure 4 and Figure 5 As shown, the profile measuring rod mechanism includes a stylus 1, a measuring rod 2, a fulcrum 3 and a displacement sensor 4, wherein the displacement sensor 4 is preferably a grating ruler sensor; the stylus 1 is mounted on the front end of the measuring rod 2, the rear end of the measuring rod 2 is rotatably mounted on the fulcrum 3, and the displacement sensor 4 is mounted on the middle of the measuring rod 3. In this embodiment, the distance H1 from the front end (A) of the measuring rod 2 to the installation point (C) of the displacement sensor 4 is equal to the distance H2 from the installation point (C) of the displacement sensor 4 to the fulcrum 3 (B).

[0019] Similarly, a ball bearing is used as the center of rotation at the fulcrum 3, and the bearing clearance, that is, the radial clearance between the inner and outer rings of the bearing, is X. During the measurement process, it is assumed that the contact surface of the stylus 1 at the starting point is horizontal, and the stylus 1 at the end point is Figure 6 The motion process of the measuring rod is thus decomposed into two parts. The first part is the rotation of the measuring rod around the theoretical center of the circle, and the second part is the rotation of the measuring rod around the needle tip to reach the Figure 6 The first part of the movement is linear and will not produce errors; the second part is that the measuring rod produces an error of size X at point A. Since the distance H1 is equal to the distance H2, the nonlinear error produced by the measuring rod at point C (where the displacement sensor is located) is 1 / 2*X. It can be seen that this arrangement can greatly reduce the error caused by bearing clearance.

[0020] Moreover, this arrangement can maintain the same structural space without sacrificing measurement resolution. For example, assuming that the designed vertical range of point A is 50 mm, Figure 1 In the conventional solution of the prior art, the length of the AB segment is twice the length of the BC segment, and the effective measurement range of the C end is 25mm. In this solution, the length of the AC segment H1 is equal to the length of the BC segment H2, and the effective measurement range of the C end is also 25mm, that is, the measurement resolution is not lost in the same structural space.

[0021] In summary, by innovating and changing the layout structure of the traditional measuring rod, the tail end of the measuring rod is rotated and installed on the fulcrum, and the displacement sensor is installed in the middle of the measuring rod. This arrangement can greatly reduce the error caused by the bearing clearance, and does not lose the measurement resolution within the same structural space.

[0022] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any person skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A profile measuring rod mechanism, comprising a stylus, a measuring rod, a fulcrum and a displacement sensor, wherein the stylus is mounted at the front end of the measuring rod, and wherein: The tail end of the measuring rod is rotatably mounted on a fulcrum, and the displacement sensor is mounted on the middle part of the measuring rod.

2. The contour measuring rod mechanism according to claim 1, characterized in that: The distance from the front end of the measuring rod to the installation point of the displacement sensor is equal to the distance from the installation point of the displacement sensor to the fulcrum.

3. The contour measuring rod mechanism according to claim 1 or 2, characterized in that: The displacement sensor is a grating ruler sensor.

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