JPS6325284B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a displacement measuring device, and in particular, a displacement measuring device including a first sensing body attached to a first member, a second sensing body attached to a second member, and capable of reciprocating along the first sensing body together with the second member. a second sensing body,
A base end portion is attached to the second member, and a distal end portion presses the second sensing body against the first sensing body in a direction substantially perpendicular to the reciprocating direction, so that the first sensing body and the second sensing body are The present invention relates to an improvement in a displacement measuring device that measures the relative displacement of the first and second members from the relative movement with the body. 2. Description of the Related Art One type of length measuring device for measuring or adjusting the relative positions of two objects is one constructed as shown in FIGS. 1 to 3, for example. In the figure, an elongated case 1 has a substantially rectangular hollow cross section, is elongated in a direction perpendicular to the paper plane of FIG. A detection mechanism 3 as a moving member is brought into contact with the end face of the elongated case 1 on the opening 2 side via a sliding member 4, and is movable along the longitudinal direction of the elongated case 1. An arm portion 5 extending from the opening 2 into the elongated case 1 is integrally formed on the lower surface of the detection mechanism 3 . Further, a pair of magnets 6 are provided on the outer surface of the elongated case 1 near the opening 2 along the longitudinal direction of the elongated case 1, and the magnets 6 are made of a thin iron plate so as to cover the opening 2. The closing member 7 is attracted and prevents dust and the like from entering into the elongated case 1 through the opening 2. At this time, the closing member 7 of the portion of the detection mechanism 3 into which the arm portion 5 is inserted is provided in the detection mechanism 3 and is inserted into a side chevron-shaped groove 8 that is opened at both ends on the lower surface of the detection mechanism 3. The arm portion 5, which is straddled by the groove 8, can be inserted into the elongated case 1. The groove 9 provided in the longitudinal direction in the elongated case 1 is made of glass or the like, and has one side (scale surface).
The lower end side of the main scale 10 on which a vertically striped scale 10A (see FIG. 2) is formed is inserted into 10B and fixed with adhesive 11 or the like. The arm portion 5 of the detection mechanism 3 extends to the vicinity of the main scale 10, and a slider 13 is movably attached to the tip of the arm portion 5 via a connecting means 12. For example, the connecting means 12 has a triangular annular portion 12A integrally formed at its tip,
Attach the base end to the arm 5 with a washer 12B and a screw 12C.
It is composed of an elastic member of a linear cantilever spring 12 held by a cylindrical member, and a truncated cone 12E that is engaged with the annular portion 12A. The cantilever spring 12D is configured to press the slider 13 toward the graduation surface 10B of the main scale 10, which also serves as a first scanning reference surface, and to push the slider 13 perpendicularly to the graduation surface 10B of the main scale 10. Pressure is also applied to the end surface 10C, which is the second scanning reference surface. The slider 13 is screwed to a contact mounting member 13A formed from a plate material in a substantially L-shape and to a short side of the contact mounting member 13A bent at one end, and a scale 10A of the main scale 10 is formed thereon. A thick light-emitting element mounting member 13B facing the non-contact surface is screwed (not shown) to the other bent long side of the contactor mounting member 13A, and a scale face 10B of the main scale 10
and a thick light-receiving element mounting member 13C facing the. An index scale 14 having vertical striped scales (not shown) similar to the main scale 10 is fixed to a surface of the contact mounting member 13A of the slider 13 that faces the scale surface 10B of the main scale 10. . A light emitting element 15 as a light source and a light receiving element 16 are arranged with the index scale 14 and the main scale 10 sandwiched therebetween. In this case, the light emitting element 15 is fixed to the light emitting element mounting member 13B fixed to the short side of the L shape of the contact mounting member 13A, and the light receiving element 16 is fixed to the long side of the L shape of the contact mounting member 13A. Two of the light receiving element mounting members 13C are each fixed to the light receiving element mounting member 13C. On the L-shaped inner surface of the contact mounting member 13A, that is, on the surface opposite to the scale surface 10B, which is the first scanning reference surface of the main scale 10, and the end surface 10C, which is the second scanning reference surface orthogonal to this scale surface. A plurality of sliding pieces 17 and 18 each made of a resin with a low coefficient of friction such as polyacetal resin are fixed, and these sliding pieces 17 and 18 are attached to the main scale 1 by the biasing force of the cantilever spring 12D.
It is adapted to abut against the 0 scale face 10B and the end face 10C perpendicular to this scale face 10B. In such a configuration, either the elongated case 1 or the detection mechanism 3 as a moving member,
For example, the detection mechanism is attached to the object to be measured, and the other elongated case 1 is attached to the mounting surface 19 of the bed 19 of the machine.
When the object to be measured is moved while being fixed to A and 19B, a bright and dark striped pattern is generated between the scale 10A of the main scale 10 and the scale of the index scale 14, and this striped pattern is read by the light receiving element 16 and detected. It reads and measures the amount of movement of the object to be measured. In such a displacement measuring device, the gap, parallelism, etc. between the main scale 10 and the index scale 14 have a very serious effect on measurement accuracy. For example, in an optical measuring device having slits with a spacing of about 10 μm, the gap must be 20 μm in order to ensure a predetermined measurement accuracy. However, the opposing surfaces of the main scale 10 and the index scale 14 are not necessarily true planes and may have undulations or the like. Therefore, it is necessary for the main scale 10 and the index scale 14 to have extremely low sliding resistance with respect to each other, and for one to follow the other to maintain the gap constant. As a means for this purpose, in the displacement measuring device shown in FIGS. 1 to 3, the annular portion 12A at the tip of the cantilever spring 12D is loosely fitted into the truncated cone 12E on the index scale 14 side. . In another embodiment, as shown in FIG. 5, the tip of the cantilever spring 12D is made into a ball 12F, and the receiving side of the index scale 14 is formed into a V-shaped groove 12G.
There is something like that. Such a cantilever linear spring not only presses the main scale and index scale against each other, but also pushes the index scale toward one side of the object to be measured against sliding resistance when these scales move relative to each other in the longitudinal direction. This is to maintain it in a fixed position. Ideally, the cantilever spring 12D should be molded in advance along a bending curve as shown in FIG. 4, and in the attached state parallel to the moving direction of the main scale 10 as shown in FIG. As a result, even if the slider 13 and the index scale 14 integrated therewith are slid left and right, only a tensile or compressive load acts on the cantilever spring 12D, and the reciprocating motion of the slider 13 is measured. Avoid affecting accuracy. However, in reality, there are variations in the elastic modulus of the spring material constituting the cantilever spring 12D, errors with respect to the ideal deflection curve of the spring shape, and the cantilever spring 12D.
Other parts, elongated case 1, main scale 1
0. Due to variations in the dimensions of the detection mechanism 3, etc., and variations in the parallelism between the mounting surface of the machine tool and the mounting surface of the measuring device when the measuring device is attached to a machine tool, etc., for example, Fig. 6A, As shown in B, it becomes difficult to install the scale parallel to the main scale. Cantilever spring 12D installed in this condition
When sliding the slider 13 left and right,
In addition to the tensile and compressive loads, a bending moment acts, causing deflection in the sliding direction, which poses a problem in that measurement accuracy is adversely affected. The deflection λ of the cantilever spring 12D in the swinging direction is determined below. First, it can be assumed that the cantilever spring 12D in the actual installed state as shown in FIG. 6 is a curved beam having a radius of curvature R as shown in FIG. The pressing force of the slider 13 against the main scale 10 by the tip of the cantilever spring 12D is N = 240g, friction coefficient μ
=0.3, the distance from the base end to the tip of the cantilever spring is L
(mm), the material of the wire that forms the cantilever spring is SWP−
A, and its diameter is φ (mm), when the slider 13 moves relative to the main scale 10 in the direction of arrow A in the figure, the tips of the cantilever springs have F as shown in FIG. ₁ , F ₂ forces act. First, from Fig. 7, F ₁ = 2N ... (1) F ₂ = 2 μN ... (2) From formulas (1) and (2), F ₂ = μF ₁ ... (3) From Fig. 8, cantilever spring 12D The bending moment M due to F ₂ of _any mn cross section at a distance S measured from the fixed end of central angle,
θ indicates the central angle from the fixed end to the free end. ) The strain energy Us stored in this section is Us=1/2EIz∫ ^S ₀ M ² ds=1/2EIz∫〓 ₀ M ² Rdφ ……(5) (S is the distance from the fixed end to the mn cross section, E is The longitudinal elastic modulus, Iz, indicates the moment of inertia of area. Substituting equation (4) into equation (5), Us=1/2EIz∫〓 ₀ F ² ₂・R ² (cosφ−cosθ) ²・Rdφ = F ² / ₂・R ³ /2EIz∫〓 ₀ (cosφ−cosθ) ² dφ …(6) The displacement (λs) in the load direction (sliding direction) in this section is given by Casteliano's theorem, λs＝aUs／aF ₂ =F ₂ R ³ /EIz∫〓 ₀ (cosφ−cosθ) ² dφ
...(7) Therefore, considering the integration range, the displacement (λ) in the load direction (sliding direction) for the entire section (L) is λ=F ₂ R ³ /EIz∫〓 ₀ (cosφ−cosθ) ² dφ =F ₂ R ³ /EIz(θ/2+θcos ² θ−3/2sinθcosθ
)...(8) becomes. Note that the total displacement in the load direction (sliding direction) also takes into account the displacement in the direction opposite to the arrow A direction in Figure 7.
2λ. When the detection mechanism 3 is installed on a machine tool, etc., the slider 13 will be accurate to the scale surface even if the detection mechanism 3 varies to some extent three-dimensionally due to the installation accuracy and the straightness of the machine tool itself with respect to the sliding direction. Therefore, the wire diameter of the cantilever spring 12D needs to be such that it can form a certain degree of freedom of the slider 13 with respect to the detection mechanism 3. Also, considering the condition that the slider 13 does not rise from the scale surface due to the vibration of the machine tool itself, and also considering the size of the device, the linear φ of the cantilever spring 12D = 0.8 to 1.0 mm, and the length L = 30~50mm
Therefore, here, we adopted φ = 0.8 mm and L = 34.9 mm, which are considered appropriate in terms of shape. Also, the longitudinal elastic modulus of the cantilever spring material SWP-A is E=2.1×10 ⁴
Kg/ ^mm2 . It is also assumed that there is no play between the ball at the tip of the cantilever spring 12D and the ball bearing. This results in a large error in measurement accuracy as shown in Table 1 below. It has been confirmed that this agrees well with the experimental results.

[Table] In order to solve the above problems, it is possible to strengthen the rigidity of the cantilever spring, but in this case,
In order to strengthen the rigidity, if the length of the cantilever spring is not changed and the wire diameter is increased, the slider 1 for the detection mechanism 3
The degree of freedom of the sliding piece 18 shown in FIG.
This creates new problems such as increased wear. On the other hand, for example, the slider is supported on the arm while being pulled in the direction of the proximal end of the cantilever spring by a linear spring. A displacement measuring device designed to suppress the occurrence of such problems is conceivable. However, this displacement measuring device requires a separate biasing means to press the slider against the main scale, which increases the device size and cannot be miniaturized, and also because the slider moves following the surface of the main scale. In order to allow the slider to be displaced within the range of the undulations on the surface of the main scale, the linear spring must be configured to allow deflection, and therefore, the linear spring must be configured to allow deflection due to the force in the slider's movement direction. The problem remains that the measurement error cannot be made sufficiently small. This invention was made in view of the above-mentioned conventional problems, and it is possible to improve measurement accuracy by preventing sliding resistance caused by reciprocating movement of the scale from affecting the slider support member. The purpose of the present invention is to provide a displacement measuring device. Another object of the present invention is to provide a displacement measuring device that is small in size and can be miniaturized. Another object of the present invention is to provide a displacement measuring device in which a support member for supporting a slider and a biasing means for pressing the slider against a main scale can be easily attached. The present invention includes a first sensing body attached to a first member, and a second sensing body attached to a second member and capable of reciprocating along the first sensing body together with the second member. , a proximal end portion is attached to the second member, and a distal end portion connects the second sensing body to the first member.
A displacement measuring device that presses a sensing body in a direction substantially perpendicular to a reciprocating direction and measures the relative displacement of the first and second members from the relative movement between the first sensing body and the second sensing body. a high-rigidity member having one end rotatably engaged with the second member and the other end rotatably engaging with the second sensing body, thereby connecting the second member and the second sensing body; The above object is achieved by providing a biasing means for pressing the second sensing body against the first sensing body. Further, the present invention provides the displacement measuring device,
At least one of both ends of the high-rigidity member that engages with the second member and the second sensing body is spherical, and a seat is provided that has a shape corresponding to the spherical end and that fits therewith. Corresponding to the spherical end, the second
The above object is achieved by providing at least one of the member and the second sensing body. Further, the present invention provides the displacement measuring device,
In the case of the second member, the seat is opened in a direction substantially perpendicular to the reciprocating direction of the second sensing body and in a direction approaching the first sensing body, and The above object is achieved by opening in a direction substantially perpendicular to the reciprocating direction of the second sensing body and in a direction away from the first sensing body. Further, the present invention provides the displacement measuring device,
The above object is achieved by pivotally supporting the second member side end portion of the high rigidity portion to the second member via a pin shaft. Further, the present invention provides the displacement measuring device,
The above object is achieved by using the biasing means as a spring that acts in a direction that engages one end of the high-rigidity member with the second member and the other end with the second sensing body. Further, the present invention provides the displacement measuring device,
The above object is achieved by the urging means being mounted between the second member and the second sensing body and pressing the second sensing body against the first sensing body via the high rigidity member. be. Further, the present invention provides the displacement measuring device,
The above object is achieved by using the biasing means as a wire spring having one end attached to the second member and the other end attached to the second member side end of the high rigidity member from its outer end side. It is something. Further, the present invention provides the displacement measuring device,
The above object is achieved by attaching the wire spring to the end of the second member so as to be rotatable in the circumferential direction. Hereinafter, an embodiment in which the present invention is applied to a conventional displacement measuring device as shown in FIGS. 1 to 3 will be described. In this embodiment, the same or equivalent parts as those of the displacement measuring device shown in FIGS. 1 to 8 will be given the same reference numerals, and the explanation thereof will be omitted. In this embodiment, as shown in FIGS. 9 to 11, in a displacement measuring device similar to the conventional one, one end of the arm 5 is extended to the vicinity of the main scale 10 of the detection mechanism 3. To,
Further, the other end is rotatably engaged with the slider 13, thereby causing the arm portion 5 and the slider 1
A rod-shaped high-rigidity member 20 that connects the high-rigidity members 2 to 3 is mounted between the arm 5 side and the outer end of the high-rigidity member 20 on the arm 5 side.
A scale surface 10 where the slider 13 also serves as the first operation reference surface of the main scale 10 due to the tip of 0.
A wire spring 21 is provided as a biasing means for biasing the high rigidity member 20 so as to press the A side and the end surface 10C side, which is a second operation reference surface perpendicular to the scale surface 10B of the main scale 10. It is something. Also, instead of the conventional sliding piece, rollers 22A and 22B that roll into contact with the graduation surface 10B and the end surface 10C of the main scale 10 are installed on the slider 1.
It is attached to 3. The rollers 22A of the slider 13 that contact the graduation surface 10B of the main scale 10 include a pair on the front and rear ends of the slider 13 in the moving direction near the end surface 10C, and one roller 22A on the opposite side and at the center in the moving direction. , a total of three rollers 22B are attached, and a pair of rollers 22B are provided at the front and rear in the reciprocating direction of the slider 13, which roll in contact with the end surface 10C. Spherical end portions 20 are provided at both ends of the high rigidity member 20.
A, 20B are formed, and these spherical ends 20A,
20B is fitted into the cylindrical seat 5A formed at the tip of the arm portion 5 and the cylindrical seat 23 attached to the center of the slider 13, thereby forming a highly rigid member. The slider 13 is configured to be able to reciprocate in conjunction with the arm portion 5 via the arm portion 20. The catch seat 5A on the side of the arm portion 5 is attached to the slider 1.
The catch seat 23 has a cylindrical shape that is opened in a direction substantially perpendicular to the reciprocating direction of the slider 13 and in a direction approaching the main scale 10, and the bottom surface has a V-shaped groove shape in cross section. It has a cylindrical shape that is opened in a direction substantially perpendicular to the reciprocating direction of the scale and in a direction away from the main scale 10, and the bottom surface has a V-groove shape in cross section. To allow this, axial slits 5S and 23S are formed at opposite positions in the cylindrical wall. The wire spring 21 has a substantially hairpin shape, and its one end bent portion 21A is fitted into the hole 24 on the arm portion 5 side, and is separated from the slider 13 through the through hole 5B formed in the arm portion 5. From the outer end of the spherical end 20A, which protrudes in the direction of
It is inserted and fitted into a fitting hole 20C formed in 0A. In the free state, the wire spring 21 has its free end 21B in the direction in which the angle of the hairpin opens, as shown in FIG. 12, and in the attached state, as shown in FIG. The slider 13 is approximately parallel to the main scale 10, and at this time, the slider 13 can be pressed in the direction of the main scale 10 via the highly rigid member 20 by a predetermined spring force. The high-rigidity member 20 has such bending rigidity that it can transmit the spring force of the wire spring 21 to the slider 13 with almost no deflection. In this embodiment, the above-mentioned figures 1 to 8
The diameter was set to 2 mm under almost the same conditions as in the conventional displacement measuring device shown in the figure. The shape of the wire spring 21 is such that when its one end bent portion 21A is fitted into the hole 24 and in the set state, the spring force causes the spherical end 20A to be attached to the seat 5A, and the spherical end 20A to the spherical seat 23. It is formed so that it acts in the direction of pressing each. In addition, one end bent portion 21A of the wire spring 21 and the hole 2
4 and the other end 21B of the wire spring and the spherical end 20
The fittings A are loosely fitted. In this embodiment, the arm portion 5 on the detection mechanism 3 side
Since the slider 13 and the slider 13 are connected by the high-rigidity member 20 that hardly bends, the high-rigidity member 20 can be made parallel to the moving direction of the slider 13 in the set state, and the reciprocation of the slider 13 can be made parallel to the moving direction of the slider 13. Since the highly rigid member 20 hardly bends due to the force in the direction of movement during movement, measurement errors can be significantly reduced. For example, as can be seen from equation (8) above, the displacement λ in the load direction at the spherical end 20B of the high-rigidity member 20 is inversely proportional to the moment of inertia of the high-rigidity member 20. Wire diameter of cantilever spring 12B, which is a conventional connecting member shown in FIG.
0.8mm, high rigidity member 2 in this example
0, the cross-sectional moment of inertia is approximately 39 times greater. Therefore, the error in the reciprocating direction of the slider 13 in this embodiment is approximately 39 times that of the conventional displacement measuring device. This will result in a significant improvement. Also, generally, as in this embodiment, the slider 1
3 and the main scale 10, the frictional resistance is reduced and the load in the sliding direction is reduced, so the measurement error based on this load is reduced. However, there is a problem in that the displacement measurement device is affected by the acceleration of vibration in the sliding direction of the machine tool etc. to which it is attached, resulting in large measurement errors.
In the case of this embodiment, since the rigidity of the high-rigidity member 20 can be made sufficiently large, the high-rigidity member 20 hardly bends, and the vibrations of the machine tool etc. are transmitted to the slider 13.
It is possible to suppress the impact on That is, in the past, since the degree of freedom of the slider 13 had to be secured to a safe value, the rigidity of the cantilever spring in the sliding direction could not be made sufficiently large. Therefore, a roller with low resistance was used instead of the sliding piece. When installed, it was not possible to prevent the cantilever spring from being deflected in the sliding direction due to the acceleration of vibration in the sliding direction acting on the slider 13, but in this embodiment,
The highly rigid member 20 can prevent this deflection from occurring. In the embodiment described above, the slider 13 is pressed against the main scale 10 via the highly rigid member 20 by a wire spring having a substantially hairpin shape, but the present invention is not limited to this embodiment. The wire spring may be any wire spring as long as it can press the slider 13 in the direction of the main scale 10.
As shown in the figure, the wire spring 25 may have another shape, and as shown in FIG. 14 or 15, a tension coil spring 26A or a tension coil spring 26B and a compression coil spring 26C may be used. It may be a combination. However, in any of these cases, in the set state, the wire spring or coil spring is designed to press the spherical end 20A of the highly rigid member 20 against the seat 5A and the spherical end 20B against the seat 23, respectively. Its mounting position and shape must be selected accordingly. Further, the end portion of the high rigidity member 20 on the arm portion 5 side is
A spherical end 20A is formed, and this spherical end 20A is V.
By being pressed by the groove-shaped catch seat 5A,
The high-rigidity member 20 is configured to be able to swing around the seat 5A, but this is not limited to this embodiment. It may be pivoted freely. However, if the end of the high-rigidity member 20 is pivotally supported by a pin shaft, the installation work will be performed on the spherical end 20A.
This is more troublesome and has a more complicated structure than the case where the engagement with the catch seat 5A is used. Further, when the wire spring 21 or 25 is used as the biasing means, there is an advantage that setting is easy. Furthermore, although the high-rigidity member 20 is shaped like a round bar in the above embodiment, the present invention is not limited to this, and the high-rigidity member 20 may be an elongated member, for example, hollow. It may be in the shape of a pipe, etc. In the case of this pipe shape, a large moment of inertia of area can be obtained compared to its weight, so there is an advantage that it is more suitable than the above-mentioned embodiment. Furthermore, although the above embodiment adopts a so-called two-surface guide type in which the slider 13 is guided by two reference surfaces of the main scale 10, the present invention is not limited to this, and the slider 13 is guided by two reference surfaces of the main scale 10. For example, a guide surface may be formed on the elongated case 1 and used as a guide. Furthermore, although the above embodiment is a case where the present invention is applied to a displacement measuring device using an optical grating,
The present invention includes a first sensing body attached to a first member, and a second sensing body attached to a second member and capable of reciprocating along the first sensing body together with the second member. , biasing means for pressing the second sensing body against the first sensing body in a direction substantially perpendicular to the reciprocating direction, and the biasing means presses the second sensing body against the first sensing body in a direction substantially perpendicular to the reciprocating direction, and prevents the relative movement between the first sensing body and the second sensing body from moving. , which is generally applied to a displacement measuring device that measures the relative displacement of the first and second members. Therefore, as a displacement detection means, contact type, electromagnetic type, capacitance type, etc. are generally applied to displacement measuring devices that measure the relative displacement of two members from the relative movement of two sensing objects. be. Since the present invention is configured as described above, high rigidity is achieved by interlocking the second sensing body and the second member based on the influence of sliding resistance force and acceleration of vibration in the sliding direction when the two sensing bodies move relative to each other. It has the excellent effect of being able to eliminate or significantly reduce deflection of the member and measurement errors based on this deflection.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a conventional displacement measuring device, Fig. 2 is a sectional view taken along the - line in Fig. 1, Fig. 3 is a sectional view taken along the - line in Fig. 1, and Fig. 4 is a sectional view taken along the - line in Fig. 1. 5 is a schematic front view showing the shape of the cantilever spring in the displacement measuring device, FIG. 5 is a schematic front view showing the ideal usage condition of the same cantilever spring, and FIG. 6 is the actual usage condition of the same cantilever spring. FIG. 7 is a schematic front view showing an analytical model of the cantilever spring in actual use, and FIG. 8 shows the deformed state of the cantilever spring shown in FIG. 7. A schematic front view, FIG. 9 is a partially sectional front view showing an embodiment in which the present invention is applied to a displacement measuring device similar to that in FIG. 1, and FIG. 10 is a cross-sectional view taken along the - line in FIG. 11 is a sectional view taken along the line -- in FIG. 9, FIG. 12 is a front view showing the free state of the wire spring in the same embodiment, and FIGS. 13 to 15 are second to fourth embodiments of the present invention. It is a schematic front view which shows an example. DESCRIPTION OF SYMBOLS 1... Elongated case (first member), 3... Detection mechanism (second member), 10... Index scale (first detection object), 13... Slider (second detection object), 14... Index Tsukusu scale (second detection object), 20...High rigidity member, 20A, 20B...
Spherical end, 21, 25... wire spring (biasing means),
5A, 23... Seat, 26A to 26C... Coil spring (biasing means).

Claims (1)

[Claims] 1. A first sensing body attached to a first member, and a second sensing body attached to a first member.
a second member attached to the member and capable of reciprocating along the first sensing member together with the second member;
a sensing body and a proximal end attached to the second member;
The second sensing body is pressed against the first sensing body at the tip in a direction substantially perpendicular to the reciprocating direction, and from the relative movement between the first sensing body and the second sensing body, the first and second sensing bodies are In a displacement measuring device that measures the relative displacement of two members, one end is rotatably engaged with the second member and the other end is rotatably engaged with the second sensing body, whereby the second member and the second member are rotatably engaged. A displacement measuring device comprising: a highly rigid member that connects two sensing bodies; and a biasing means for pressing the second sensing body against the first sensing body. 2. At least one of both ends of the high-rigidity member that engages with the second member and the second sensing body is spherical, and has a shape corresponding to the spherical end,
2. The displacement measuring device according to claim 1, wherein a seat that fits therein is provided on at least one of the second member and the second sensing body in correspondence with the spherical end. 3. In the case of the second member, the seat is opened in a direction substantially orthogonal to the reciprocating direction of the second sensing body and in a direction approaching the first sensing body, and 3. The displacement measuring device according to claim 2, wherein the opening is in a direction substantially perpendicular to the reciprocating direction of the second sensing body and in a direction away from the first sensing body. 4. Claims 1, 2, or 4, characterized in that an end of the high-rigidity portion on the second member side is swingably supported on the second member via a pin shaft. 3. Displacement measuring device according to item 3. 5. The biasing means is a spring that acts in a direction such that one end of the high-rigidity member engages with the second member and the other end engages with the second sensing body. The displacement measuring device according to any one of Items 1 to 4. 6. The biasing means is mounted between the second member and the second sensing body, and the biasing means is mounted between the second member and the second sensing body, and
A displacement measuring device according to any one of claims 1 to 5, characterized in that the sensing body is pressed against the first sensing body. 7. A patent characterized in that the biasing means is a wire spring having one end attached to the second member and the other end attached to the second member side end of the high rigidity member from its outer end side. A displacement measuring device according to any one of claims 1 to 6. 8. The displacement measuring device according to item 7, wherein the wire spring is rotatably attached to an end of the second member in a circumferential direction.