JP4494425B2 - Ring laser gyro - Google Patents

Description

  The present invention relates to a ring laser gyro for detecting an angular velocity as an inertial reference device for an aircraft or other moving body, for example.

  A conventional ring laser gyro will be briefly described with reference to FIG. FIG. 8 is a cross-sectional view (hereinafter simply referred to as a cross-sectional view) cut along a cross section perpendicular to the input axis of the ring laser gyro. The block 11 is a polygon (a triangle in FIG. 8), and the reflecting mirrors 13a, 14 and 15 are provided at the apexes of the polygon in the block 11, so that a triangular blocking optical path 12 is formed. A laser medium is sealed in the blocking optical path 12, and anodes 16 and 17 are provided on two sides of the blocking optical path 12, and a cathode 18 is provided between the two sides. The optical path length control actuator 19 displaces the optical path length control reflecting mirror 15.

  In the block 11, a high voltage is applied between the anodes 16 and 17 and the cathode 18 to generate a plasma discharge to excite the laser medium and to pass through the blocking optical path 12 clockwise and counterclockwise. Laser light is oscillated. In this state, when an angular velocity centered on the axis (input axis) of the blocking optical path 12 is input to the block 11, an optical path difference is generated between the two laser beams, and the optical path difference generates an oscillation frequency difference between the two laser beams. Let

  The laser light is extracted through the reflecting mirror 13a. By superimposing the two extracted laser beams via the prism 29 and the reflecting mirror 13b, interference fringes are formed. The input angular velocity is detected by the photodetector 27 from the interference fringes.

  By the way, the ring laser gyro has a lock-in phenomenon that causes a state in which the angular velocity cannot be detected (gyro dead zone) when a low angular velocity is input. In order to avoid the lock-in phenomenon, there is a method of applying a dither angular vibration around the input shaft to the ring laser gyro so that a low angular velocity can be detected.

  A dither spring 21 is disposed near the center of the block 11 in order to apply dither angular vibration to the ring laser gyro. A circular through hole 28 is provided near the center of the block 11, and the dither spring 21 is inserted inside the through hole 28.

  Further, the block 11 is made of glass having a small coefficient of thermal expansion, whereas the dither spring 21 is metallic so that its coefficient of thermal expansion is larger than that of the block 11. As shown in Patent Document 1, a structure has been devised in which stress due to thermal expansion of the dither spring 21 is reduced from being transmitted to the block 11.

The dither spring 21 has an outer peripheral wall 26 and a plurality of arms 23 (three arms 23 in FIG. 1) extending radially from the center 24 thereof. A piezoelectric element 25, for example, PZT (lead zirconate titanate) is attached to both side surfaces of each arm 23. By applying an AC voltage to the piezoelectric element 25, a dither angular vibration is applied to the block 11. The mechanism that causes this dither angular vibration is called a dither mechanism. The angular velocity ω ₁ detected from the ring laser gyro is an angular velocity obtained by combining the angular velocity ω ₂ from the outside of the ring laser gyro and the angular velocity ω ₃ due to the dither angular vibration of the dither mechanism. Therefore, the external input angular velocity ω ₂ is obtained by subtracting the angular velocity ω ₃ by the dither mechanism from the detected angular velocity ω ₁ .

The error factors of the ring laser gyro include those caused by inaccuracy of values when subtracting the angular velocity ω ₃ by the dither mechanism, and those caused by instability of the amplitude and frequency of the dither angular vibration. The method of joining the dither spring and the block that transmits the dither angular vibration is related to the accuracy and stability of the dither angular vibration, and thus greatly affects the performance of the ring laser gyro.

  The outer peripheral wall 26 of the dither spring 21 and the arm 23 are connected by a connecting portion 31. In the outer peripheral wall 26, the intermediate portion between the adjacent connection portions 31 has no arm 23, so that the rigidity is low. A protruding portion 32 is formed radially outward from the outer peripheral surface of the outer peripheral wall 26 at an intermediate portion between the adjacent connecting portions 31.

  The dither spring 21 is attached to the through hole 28 of the block 11 and assembled. With the mounting, the projecting end surface (hereinafter referred to as a joining surface) 32 a of the projecting portion 32 is joined to the inner peripheral surface 35 of the through hole 28 of the block 11. As this joining method, an adhesive may be applied to the joining surface 32a for joining, or simply press-fitted.

FIG. 9 is an enlarged cross-sectional view of the vicinity of the protrusion 32. FIG. 9 shows a state in which the bonding surface 32 a and the inner peripheral surface 35 of the block 11 are bonded by the adhesive layer 33. A space 36 is formed between the inner peripheral surface 35 of the block 11 and the outer peripheral surface of the outer peripheral wall 26 of the dither spring 21 by the protruding length of the protruding portion 32. As a result, even if the dither spring 21 is thermally expanded, the stress due to the thermal expansion is transmitted to the block 11 through the joint surface 32a of the protrusion 32 having a low rigidity in the outer peripheral wall 26. The stress due to the thermal expansion of the spring 21 is relaxed.
Japanese Patent Publication No. 8-34326

  The direction of stress due to thermal expansion of the dither spring 21 is outward in the radial direction of the dither spring 21. In the outer peripheral wall 26, the connecting portion 31 where the outer peripheral wall 26 and the arm 23 are connected has high rigidity, and the protruding portion 32 joined to the block 11 is provided in an intermediate portion where the outer peripheral wall 26 has low rigidity. Therefore, the smaller the protrusion 32 is with respect to the entire circumference of the outer peripheral wall 26, that is, the smaller the area of the joint surface 32 a of the protrusion 32, the more relaxed the stress transmitted to the block 11. However, when the area of the joining surface 32a is reduced, the dither angle vibration direction of the dither spring 21 and the joining surface 32a are substantially parallel, so that sufficient adhesive strength or press-fitting with an adhesive against dither angle vibration is achieved. Insufficient bonding strength due to the above cannot be obtained and dither angular vibrations may not be transmitted.

  According to this invention, a reflecting mirror is provided at each vertex of the polygonal block to form a blocking optical path, and two laser beams are passed through the optical path in a clockwise direction and a counterclockwise direction, for example, by a photodetector. In order to apply dither angular vibration to the block for detecting the rotational motion and the ring laser gyroscope, the block is mounted in a circular through hole in the central portion of the block, and has a cylindrical outer peripheral wall and a center to the outer peripheral wall. And a dither spring having a plurality of arms extending radially in a ring laser gyro, and a linear convex portion parallel to an axis of the dither spring on the outer peripheral surface of the outer peripheral wall of the dither spring Or a groove provided between adjacent ones of the plurality of arms, and a straight line respectively fitted to the convex portion or the groove on the inner peripheral surface of the through hole of the block Groove or protrusion is provided.

  The ring laser gyro according to the present invention includes a convex portion that relieves stress due to thermal expansion of the dither spring transmitted to the block, and the joint surface between the dither spring and the block is substantially perpendicular to the dither angular vibration direction of the dither spring. Direction. For this reason, it is possible to obtain a bonding strength sufficient to transmit the dither angular vibration to the block.

  The best mode for carrying out the present invention will be described below.

  A cross-sectional view of a functional configuration example of the ring laser gyro according to the present invention is shown in FIG. The same parts as those in FIG. 8 are denoted by the same reference numerals, and redundant description is omitted. The same applies to the description of FIGS.

  A circular through hole 62 is provided at the center of the block 61. The dither spring 63 has a cylindrical outer peripheral wall 64 and a plurality of arms 68 extending in the radial direction from the central portion 65 toward the outer peripheral wall 64 (in the first embodiment, there are three arms 68, and so on). ing. In this embodiment, on the outer peripheral surface 64a of the outer peripheral wall 64 of the dither spring 63, a linear convex portion 66 parallel to the axis of the dither spring 63 is provided between the adjacent arms 68, preferably in the middle. It is done. Further, a linear groove 72 fitted to the convex portion 66 is provided on the inner peripheral surface 62 a of the through hole 62 of the block 61. By fitting the convex portion 66 and the groove 72, the dither angular vibration of the dither spring 63 is transmitted to the block 61 through the joint surface substantially perpendicular to the angular vibration direction of the dither spring 63.

  FIG. 2 shows an enlarged cross-sectional view of the vicinity of the convex portion 66. In Example 1 and Examples 2 and 3 below, the shape of the convex portion 66 is a cuboid, and the cross section perpendicular to the axis of the dither spring 63 is rectangular.

  A joint surface 66 a that intersects the circumferential direction of the outer peripheral wall 64 is formed by fitting the convex portion 66 and the groove 72. Dither angular vibration is transmitted from the dither spring 63 to the block 61 through the joint surface 66a. In this embodiment, the joint surface 66a is perpendicular to the dither angular vibration direction, and can sufficiently transmit the dither angular vibration even when the joint surface between the dither spring 63 and the block 61 is small.

  By the way, the direction of the thermal expansion stress of the dither spring 63 is a radial direction from the center of the dither spring 63, and when the projecting top surface 66b of the convex portion 66 of the dither spring 63 and the bottom surface 72b of the groove 72 of the block 61 are joined. The block 61 also receives stress due to thermal expansion of the dither spring 63 from this joint surface. Therefore, by providing the space 90 between the projecting top surface 66b of the convex portion 66 of the dither spring 63 and the bottom surface 72b of the groove 72 of the block 61, stress applied to the block 61 from the projecting top surface 66b can be prevented. . In the following description, this space is referred to as a stress relaxation space. Although a configuration in which the stress relaxation space 90 is not provided is conceivable, it is desirable to provide the stress relaxation space 90. The same applies to the following embodiments.

  As described above, the dither spring 63 is assembled by being mounted in the through hole 62 of the block 61. In mounting, an adhesive may be applied to the joint surface 66a of the convex portion 66, or may be simply press-fitted. The same applies to the following embodiments.

  FIG. 3 shows a cross-sectional view of a functional configuration example of the dither spring 63 of the second embodiment and parts related thereto. In the second embodiment, as shown in FIG. 3, a linear groove 80 parallel to the axis of the dither spring 63 is provided between the adjacent arms 68 on the outer peripheral surface 64 a of the outer peripheral wall 64 of the dither spring 63. It is done. Further, a linear convex portion 82 that fits into the groove 80 is provided on the inner peripheral surface 62 a of the through hole 62 of the block 61. FIG. 4 shows an enlarged cross-sectional view of the vicinity of the groove 80. In the second embodiment, a surface perpendicular to the dither angular vibration direction is formed by fitting the groove 80 and the convex portion 82, and this surface becomes the joint surface 80 a. In addition, it is desirable to provide the stress relaxation space 110 between the protruding top surface 82 b of the convex portion 82 and the bottom surface 80 b of the groove 80.

  In the second embodiment, the same effect as that of the first embodiment is obtained except that the linear protrusions that are fitted to each other are provided on the block 61 side and the groove is provided on the dither spring 63 side. It will be clear.

  FIG. 5 shows a cross-sectional view of the main part of the third embodiment. In the third embodiment, a straight groove 135 parallel to the axis is formed on the outer peripheral surface 64 a of the outer peripheral wall 64 of the dither spring 63, and the dither spring 63 is formed on the inner peripheral surface 62 a of the through hole 62 of the block 61. A straight groove 145 parallel to the axis is formed. Then, one half 131A of the joint member 130A having a rectangular parallelepiped shape and a rectangular cross section is fitted into the groove 135. The other half part 132 </ b> A protrudes and functions as the convex part 66. In this manner, the convex portion 66 may be provided using a separate member from the outer peripheral wall 64. Then, the convex portion 66 is fitted with the groove 145. In the case of Example 3, the surface intersecting the circumferential direction of the outer peripheral wall 64 formed by fitting the joint member 130A and the groove 135, and the inner peripheral surface 62a by fitting the joint member 130A and the groove 145. The surfaces intersecting the direction become the joint surfaces 130Aa.

  Further, it is desirable that the stress relaxation space 110 is provided between the bottom surface 135a of the groove 135 and the end surface 130Ab of the joint member 130A facing the bottom surface 135a. By providing the stress relaxation space 110, as with the stress relaxation space 90, stress due to thermal expansion of the dither spring 63 can be reduced.

  The block 61 is made of glass having a small coefficient of thermal expansion, and the dither spring 63 is also an invar having a small coefficient of thermal expansion. The material of the joint member 130 </ b> A is preferably a material having the same thermal expansion coefficient as that of the block 61 or the dither spring 63. The same applies to the material of the joint member described in the following embodiments.

  In the first to third embodiments, the case has been described in which the convex portion 66 of the dither spring 63 or the convex portion 82 of the block 61 has a rectangular shape when viewed in a rectangular parallelepiped, that is, a cross section perpendicular to the axis of the dither spring 63. The fourth embodiment is an example in which the convex portion is deformed from a rectangular shape to a trapezoidal shape, and FIG. 6 shows a cross-sectional view of the vicinity where the convex portion and the groove of the dither spring 63 and the block 61 are fitted.

  FIG. 6A is a cross-sectional view when the convex portion 140 of the dither spring 63 has a trapezoidal shape in which the cross section has a tapered surface. In this case, the convex portion 140 is fitted into the groove 150 of the block 61. A surface 140 a ′ in contact with the side surface of the groove 150 in the tapered surface 140 a becomes a bonding surface. Further, it is desirable that a stress relaxation space 142 is provided between the protruding top surface 140 b of the convex portion 140 and the bottom surface 150 a of the groove 150.

  6A, the area of the joint surface 140a for transmitting dither angular vibration from the dither spring 63 to the block 61 can be reduced as the slope of the trapezoidal taper surface of the convex portion 140 shown in FIG. The same applies to FIGS. 6B and 6C described below.

  FIG. 6B is a cross-sectional view when the convex portion 180 of the block 61 has a trapezoidal shape in which the cross section has a tapered surface 180a. In this case, the convex portion 180 is fitted into the groove 160 of the dither spring 63. A surface 180 a ′ in contact with the side surface of the groove 160 in the tapered surface 180 a becomes a bonding surface. Further, it is desirable that a stress relaxation space 182 is provided between the protruding top surface 180 b of the convex portion 180 and the bottom surface 160 a of the groove 160.

  FIG. 6C is a cross-sectional view in the case where the groove 190 having the inverted trapezoidal cross section is provided in the dither spring 63, and a protrusion 661 is formed by fitting a part of the joint member 130 </ b> B. . Further, the fitting between the groove 200 of the block 61 and the convex portion 661 is the same as that shown in FIG. 6A. In this embodiment, the trapezoidal shape fitted in the groove 190 of the joint member 130B and the trapezoidal shape fitted in the groove 200 are symmetrical with respect to the center line 130Bc of the cross section of the joint member 130B. Yes. By making the joint member 130B symmetrical, if the groove 190 and the groove 200 have the same shape, the effect that this embodiment can be carried out in any one half of the joint member 130B is obtained. Can do.

  In this case, a surface 130Ba where the joint member 130B contacts the groove 190 of the dither spring 63 and the groove 200 of the block 61 is a bonding surface. In this case as well, the stress relaxation space 92 is provided between the bottom surface 190a of the groove 190 and the end surface 130Bb of the joint member 130B facing the groove 190, and the bottom surface 200a of the groove 200 and the joint member 130B facing the surface 200B. It is desirable to provide a stress relaxation space 94 between the end face 130Bb ′.

  In the first to fourth embodiments, when the convex portion 66 of the dither spring 63 or the convex portion 82 of the block 61 is a rectangular parallelepiped, that is, when viewed in a cross section perpendicular to the axis line of the dither spring 63, or in a tapered shape. The case where the shape is a trapezoid having a surface has been described. However, in general, in the manufacturing process of a block made of a glass material, it is necessary to use a high level of technology and a long processing time to correctly form convex portions and grooves having a rectangular cross section or a trapezoidal cross section.

  In order to facilitate the processing of the convex portions and grooves, as shown in FIG. 7, the cross section perpendicular to the axis of the dither spring 63 of the convex portions and grooves can be formed into a semi-race track shape or a semi-elliptical shape. .

  FIG. 7A shows the case where the dither spring 63 has a convex portion 280 having a semi-race track shape in cross section, the block 61 has a groove 285 having a semi-race track shape in cross section, and the convex portion 280 and the groove 285 are fitted. It is sectional drawing. In this case, the surface where the convex portion 280 contacts the groove 285 becomes the bonding surface 280a. In addition, it is desirable that a stress relaxation space 290 is provided between the protruding top surface 280 b of the convex portion 280 and the bottom surface 285 a of the groove 285.

  FIG. 7B is a cross-sectional view showing that the block 61 has a convex portion 300 having a semi-race track shape in cross section and the dither spring 63 has a groove 305 having a semi-race track shape to be fitted to the convex portion 300. It is. In this case, the surface where the convex portion 300 and the groove 305 are in contact becomes the bonding surface 300a. Further, it is desirable that a stress relaxation space 310 is provided between the protruding top surface 300 b of the convex portion 300 and the bottom surface 305 a of the groove 305.

  In FIG. 7C, a joint member 130 </ b> C having a racetrack shape in cross section is used, and a half portion of the joint member 130 </ b> C is fitted into a groove 360 formed in the dither spring 63 to form a convex portion 662. 662 is a cross-sectional view in which 662 is fitted in a semi-race track shaped groove 370 formed in the block 61. FIG. In this case, the surface 130Ca where the joint member 130C, the groove 360, and the groove 370 are in contact with each other serves as a joint surface. Further, a stress relaxation space 324 is provided between the bottom surface 360a of the groove 360 and the end surface 130Cb of the joint member 130C facing this, and the bottom surface 370a of the groove 370 and the end surface 130Cb ′ of the joint member facing this A stress relaxation space 322 is preferably provided therebetween.

  5, 6C, and 7C, fitting members 130A, 130B, and 130C are fitted into grooves provided on the dither spring 63 side (groove 135 in FIG. 5, groove 190, groove 360 in FIG. 6C) and protruded. (The convex portion 66 in FIG. 5, the convex portion 661 in FIG. 6C, and the convex portion 662 in FIG. 7C) are provided, and the provided convex portion is a groove provided on the block 61 side (in FIG. 5, the groove 145 and FIG. 6C). Then, the procedure for fitting into the groove 200 and the groove 370 in FIG. 7C has been described. As a modification of the joining procedure of the joint members 130A, 130B, and 130C, the joint members 130A, 130B, and 130C are provided in the grooves provided on the block 61 side (the groove 145 in FIG. 5, the groove 200 in FIG. 6C, and the groove 370 in FIG. 7C). A convex portion is formed by fitting any one of the above, and the formed convex portion may be fitted into a groove on the dither spring 63 side (groove 135 in FIG. 5, groove 190, groove 360 in FIG. 6C). Good.

  Also, the groove on the dither spring 63 side (groove 135 in FIG. 5, groove 190, groove 360 in FIG. 6C) and the groove on the block 61 side (groove 145 in FIG. 5, groove 200 in FIG. 6C, groove 370 in FIG. 7C). Both may be provided, and the corresponding joint members may be simultaneously fitted into the groove on the dither spring 63 side and the groove on the block 61 side.

Sectional drawing cut | disconnected perpendicularly | vertically to the input axis line of the ring laser gyro of Example 1 of this invention (henceforth only sectional drawing). Sectional drawing which expanded the vicinity of the convex part 66 of Example 1 of this invention. Sectional drawing of the vicinity of the dither spring 63 of Example 2 of this invention. Sectional drawing which expanded the vicinity of the convex part 82 of Example 2 of this invention. Sectional drawing which shows that the half part 131A of the coupling member 130A of Example 3 of this invention is fitted by the groove | channel 135, the convex part 66 is formed, and the convex part 66 is fitted by the groove | channel 145. FIG. FIG. 6A is a cross-sectional view in which the vicinity of the convex portion 140 is enlarged, FIG. 6B is a cross-sectional view in which the vicinity of the convex portion 180 is enlarged, and FIG. 6C is a cross-sectional view showing Embodiment 4 of the present invention. It is sectional drawing which shows that the convex part 661 fitted and formed by the groove | channel is fitted by the groove | channel 200. FIG. 7A is a cross-sectional view in which the vicinity of the convex portion 280 is enlarged, FIG. 7B is a cross-sectional view in which the vicinity of the convex portion 300 is enlarged, and FIG. It is sectional drawing which shows that the convex part 662 fitted and formed in the groove | channel 370 is fitted. Sectional drawing of the conventional ring laser gyro. Sectional drawing which expanded the protrusion part 32 vicinity of the conventional ring laser gyro.

Claims (4)

A reflecting mirror is provided at each vertex of the polygonal block to form a blocking optical path,
The block that allows two laser beams to pass through the optical path in a clockwise direction and a counterclockwise direction;
To apply a dither angular vibration to the ring laser gyro, the cylindrical laser is mounted in a circular through hole in the center of the block, and a plurality of cylindrical outer walls extend radially from the center toward the outer wall. In a ring laser gyro provided with a dither spring having arms,
On the outer peripheral surface of the outer peripheral wall of the dither spring, linear protrusions or grooves parallel to the axis of the dither spring are provided between the adjacent arms, respectively.
A ring laser gyro characterized in that linear grooves or protrusions fitted into the protrusions or grooves, respectively, are provided on the inner peripheral surface of the circular through hole of the block. The ring laser gyro according to claim 1, wherein
A ring laser gyro characterized in that a space is formed between the protruding top surface of the convex portion and the bottom surface of the groove. The ring laser gyro according to claim 1 or 2,
One half of the joint member is fitted into a groove formed on the outer peripheral surface of the outer peripheral wall or the inner peripheral surface of the through-hole, and the other half of the joint member protruding constitutes the convex portion. A ring laser gyro characterized by In the ring laser gyro according to claim 3,
A ring laser gyro characterized in that a space is provided between a bottom surface of the groove and an end surface of the joint member facing the groove.

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