ROTATION STOP DEVICE

Abstract: A rotation stop device comprising a mechanism (121) for regulating a circumferential clearance (A) between an inner surface of a boss (114) and an outer surface of a spline shaft (120) by turning two-split first and second spline shaft members (116, 118) in the mutually opposite directions on the axes thereof.

Description: TECHNICAL FIELD The present invention relates to a rotation-preventive device as defined by the features of the preamble of claim 1 and known from US-A-4 473 317 which makes it possible to prevent, for example, a spline shaft from rotation in the circumferential direction by means of engagement of the spline shaft with a hole of a boss. BACKGROUND ART For example, a spline has been hitherto used to prevent a shaft member from rotation in the circumferential direction. As shown in FIG. 16, the spline 1 includes a spline shaft 4 which has a plurality of teeth 3a to 3h having a substantially trapezoidal cross section formed in the circumferential direction along the outer circumferential surface between adjoining grooves 2a to 2h separated from each other by a predetermined angle, and a boss 6 which is provided relatively slidably in the axial direction of the spline shaft 4 and which is formed with a hole 5 having a shape corresponding to the cross-sectional shape of the spline shaft 4 in a direction perpendicular to the axis. In this case, as shown in FIG. 17, a predetermined clearance A is formed between the teeth 3a to 3h of the spline shaft 4 in the circumferential direction and the inner wall surface of the hole 5 of the boss 6 corresponding to the teeth 3a to 3h. The clearance A is formed as follows. That is, the spline shaft 4 is formed, for example, by means of the thread rolling. The boss 6 is formed, for example, by means of the drawing. After that, the finishing machining is applied to the teeth 3a to 3h of the spline shaft 4 and the inner wall surface of the hole 5 of the boss 6. However, the spline 1 concerning the conventional technique as described above involves the following inconvenience. That is, the clearance A is dispersed due to any error in machining accuracy. Further, the teeth 3a to 3h of the spline shaft 4 are abraded due to the sliding friction with respect to the inner wall surface of the hole 5 of the boss 6, and the clearance A is increased to be larger than a preset predetermined value. As a result, any backlash is caused when the spline shaft 4 and the boss 6 make the relative sliding displacement in the axial direction. An electric actuator 10 has been hitherto used as a means for transporting a workpiece. As shown in FIG. 18, the electric actuator 10 comprises a motor 14 which is arranged at one end of a body 12 of the electric actuator 10, and a feed screw 18 which is coupled to a rotary shaft of the motor 14 and which is inserted into a hole 16 of the body 12. A feed nut 20 is meshed with the feed screw 18. The feed nut 20 is secured to one end of a cylindrical member 22. The other end of the cylindrical member 22 is secured to a movable member 24. A guide block 26 is secured to the movable member 24. The guide block 26 is slidably engaged with a guide rail 28. When the motor 14 is energized in the electric actuator 10, then the feed screw 18 is rotated to move the feed nut 20 in the axial direction of the feed screw 18, and the movable member 24, which is secured to the cylindrical member 22, is linearly displaced. In the electric actuator 10, the guide block 26, which is coupled to the movable member 24, slides along the guide rail 28 which is provided at the outside of the body 12. Thus, the rotation-preventive function is effected to prevent the movable member 24 from rotation together with the feed screw 18. An electric actuator 30 concerning another conventional technique is shown in FIG. 19. The electric actuator 30 comprises a movable member 32 which is secured to one end of a cylindrical member 22. One end of a guide shaft 34 is secured to the movable member 32 in parallel to the cylindrical member 22. On the other hand, an end plate 36 is secured to one end of a body 12. A bush 38 for inserting the guide shaft 34 therethrough is provided in the end plate 36. In the electric actuator 30, the guide shaft 34 is guided by the bush 38. Accordingly, the rotation-preventive function is effected to prevent the movable member 32 from rotation together with the feed screw 18. However, the electric actuators 10, 30 involve the following drawback. That is, the rotation-preventive mechanism for preventing the movable member 24, 32 from rotation is provided at the outside of the body 12. Therefore, the entire shape of the electric actuator 10, 30 becomes large. In order to realize a compact size, it is conceived that the rotation-preventive mechanism for preventing the movable member from rotation is provided at the inside of the body of the electric actuator. For example, as shown in FIG. 20, a ring-shaped guide member 42 is secured to one end of a cylindrical member 22 of an electric actuator 40. A groove 44 is defined on the guide member 42 so that the groove 44 is parallel to the axis of the cylindrical member 22. On the other hand, a rail section 48, with which the groove 44 is slidably engaged, is formed on the wall of a hole 46 of the body 12. When the groove 44 of the guide member 42 makes sliding movement along the rail section 48, the rotation-preventive function is effected to prevent the cylindrical member 22 from rotation. An electric actuator 50 concerning still another conventional technique is shown in FIG. 21. In the electric actuator 50, a guide member 54, which is formed with a spline 52, is secured to one end of a cylindrical member 22. A spline groove 58, with which the spline 52 is slidably engaged, is formed on the inner wall of a hole 56 defined in a body 12. In the electric actuator 50, the engagement between the spline 52 and the spline groove 58 effects the rotation-preventive function to prevent the cylindrical member 22 from rotation. An electric actuator 60 concerning still another conventional technique is shown in FIG. 22. The electric actuator 60 comprises a spline 64 which is formed over the entire outer circumference of a lengthy cylindrical member 62. An end plate 66 is secured to an end of a body 12. A spline groove 68, with which the spline 64 is slidably engaged, is formed on the end plate 66. In the electric actuator 60, the engagement between the spline 64 and the spline groove 68 effects the rotation-preventive function to prevent the cylindrical member 62 from rotation. However, the electric actuators 40, 50, 60, each of which is provided with the rotation-preventive mechanism at the inside of the body 12, require the exclusive part having the specified structure as the rotation-preventive mechanism to prevent the cylindrical member 22, 62 from rotation, including, for example, the guide member 42 formed with the groove 44, the guide member 54 with the spline 52 formed on the outer circumferential surface, and the cylindrical member 62 formed with the spline 64. Therefore, a problem arises in that the production cost of the electric actuators 40, 50, 60 is expensive. An object of the present invention is to provide a rotation-preventive device which makes it possible to conveniently and freely adjust the clearance in the circumferential direction between teeth of a spline shaft and an inner wall surface of a hole of a boss. Another object of the present invention is to provide an electric actuator having a rotation-preventive function which makes it possible to reduce the production cost by using parts hitherto used generally so that any exclusive part is unnecessary. DISCLOSURE OF THE INVENTION According to the present invention a rotation-preventive device comprises the features of claim 1 or 6. In particular, a first spline shaft member and a second spline shaft member, which are divided into two, are rotated and displaced in mutually opposite directions about a center of rotation of the axis. Thus, it is possible to freely adjust the clearance in the circumferential direction between an inner wall surface of a boss section and an outer wall surface of a spline shaft section. Further, a first boss member and a second boss member, which are divided into two, are rotated and displaced in mutually opposite directions about a center of rotation of the axis. Thus, it is possible to freely adjust the clearance in the circumferential direction between an inner wall surface of a boss section and an outer wall surface of a spline shaft section. Preferred embodiment of the present invention are evident from the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a partial longitudinal sectional view taken in the axial direction, illustrating a rotation-preventive device according to a first embodiment of the present invention. FIG. 2 shows, with partial cutout, a first spline shaft member and a second spline shaft member for constructing the rotation-preventive device shown in FIG. 1. FIG. 3 shows a view as viewed in a direction of the arrow X shown in FIG. 1. FIG. 4 illustrates the operation of a clearance-adjusting mechanism for constructing the rotation-preventive device shown in FIG. 1. FIG. 5 shows a longitudinal sectional view taken along the axial direction, illustrating the first spline shaft member and the second spline shaft member. FIG. 6 shows a vertical sectional view taken along a line VI-VI shown in FIG. 5. FIG. 7 shows a perspective view to illustrate the basic principle for adjusting the clearance. FIG. 8 illustrates the operation based on the basic principle for adjusting the clearance. FIG. 9 shows a magnified side view depicting principal parts to illustrate the operation of the clearance-adjusting mechanism. FIG. 10 shows a partial longitudinal sectional view illustrating a rotation-preventive device according to a second embodiment of the present invention. FIG. 11 shows a longitudinal sectional view illustrating a first boss member and a second boss member for constructing the rotation-preventive device shown in FIG. 10. FIG. 12 shows a perspective view to illustrate the basic principle for adjusting the clearance. FIG. 13 shows a perspective view to illustrate the basic principle for adjusting the clearance. FIG. 14 illustrates the operation based on the basic principle for adjusting the clearance. FIG. 15 shows a magnified side view depicting principal parts to illustrate the operation of the clearance-adjusting mechanism. FIG. 16 shows a front view illustrating a spline concerning a conventional technique. FIG. 17 shows a partial magnified view illustrating the spline shown in FIG. 16. FIG. 18 shows a longitudinal sectional view illustrating an electric actuator concerning a conventional technique. FIG. 19 shows a longitudinal sectional view illustrating an electric actuator concerning another conventional technique. FIG. 20 shows, with partial omission, a perspective view illustrating an electric actuator concerning still another conventional technique. FIG. 21 shows, with partial omission, a perspective view illustrating an electric actuator concerning still another conventional technique. FIG. 22 shows, with partial omission, a perspective view illustrating an electric actuator concerning still another conventional technique. BEST MODE FOR CARRYING OUT THE INVENTION With reference to FIG. 1, reference numeral 100 indicates a rotation-preventive device according to a first embodiment of the present invention. The rotation-preventive device 100 comprises a boss section 114 which has a substantially circular cross section and which is formed with a hole 112 penetrating in the axial direction, a spline shaft section 120 which is provided slidably along the hole 112 and which includes a first spline shaft member 116 and a second spline shaft member 118 divided into two and coaxially coupled to one another, and a clearance-adjusting mechanism 121 which adjust the clearance A (see FIG. 3) in the circumferential direction formed between the inner wall surface of the boss section 114 and the outer wall surface of the spline shaft section 120. As shown in FIG. 2, the first spline shaft member 116 includes a disk section 126 which has a plurality of first teeth 124 having a substantially trapezoidal cross section formed in the circumferential direction of the outer circumferential surface between adjoining grooves 122 separated from each other by a predetermined angle, and a shaft section 128 which protrudes outwardly from the center of the first plane of the disk section 126. The disk section 126 and the shaft section 128 are formed in an integrated manner. As shown in FIGS. 2 and 3, a recess 130 having a tapered cross section is formed on the shaft section 128. As shown in FIG. 2, the second spline shaft member 118 includes a cylindrical section 134 which is formed with a hole 132 for inserting and fitting the shaft section 128 of the first spline shaft section 116, and a flange section 136 which is formed at one end of the cylindrical section 134 in the axial direction. The cylindrical section 134 and the flange section 136 are formed in an integrated manner. A plurality of second teeth 140 having a substantially trapezoidal cross section are formed in the circumferential direction on the outer circumferential surface of the flange section 136 between adjoining grooves 138 separated from each other by a predetermined angle. The first spline shaft member 116 and the second spline shaft member 118 are coaxially coupled to one another by the aid of the shaft section 128 which is inserted and fitted to the hole 132. The diameter of the disk section 126 of the first spline shaft member 116 is substantially the same as the diameter of the flange section 136 of the second spline shaft member 118. In the first embodiment, the pitch is set to be substantially identical between the first teeth 124 and the second teeth 140 which are formed on the first spline shaft member 116 and the second spline shaft member 118 respectively. However, the present invention is not limited thereto. The pitch may be different between the first teeth 124 and the second teeth 140. As shown in FIG. 9, third teeth 142 and grooves 144, which have shapes corresponding to the plurality of grooves 122, 138, the first teeth 124, and the second teeth 140 of the first spline shaft member 116 and the second spline shaft member 118, are formed on the inner circumferential surface of the boss section 114. That is, the third teeth 142 and the grooves 144, which are meshed with the plurality of grooves 122 and the first teeth 124 formed on the outer circumferential surface of the disk section 126 of the first spline shaft member 116 and the grooves 138 and the second teeth 140 formed on the outer circumferential surface of the flange section 136 of the second spline shaft member 118 respectively, are formed on the inner circumferential surface of the boss section 114. The clearance-adjusting mechanism 121 is provided with a screw member 150 (see FIG. 3) with its forward end 148 which makes abutment against the recess 130 formed on the shaft section 128 of the first spline shaft member 116 by being screwed into a screw hole 146 formed through the cylindrical section 134 of the second spline shaft member 118. The forward end 148 of the screw member 150 is formed to have a tapered cross section. The forward end 148 of the screw member 150 is displaced in the direction of the arrow B along the inclined surface of the recess 130 (see FIG. 4) by increasing the screwing amount of the screw member 150. Accordingly, the first spline shaft member 116 can be rotated by a predetermined angle in the direction of the arrow C with respect to the second spline shaft member 118. As a result, the first teeth 124 of the first spline shaft member 116 make rotational displacement by the predetermined angle in the identical circumferential direction with respect to the second teeth 140 of the second spline shaft member 118. As shown in FIGS. 5 and 6, the first spline shaft member 116 and the second spline shaft member 118 are fixed in an integrated manner respectively by the aid of a bolt 154 which is engaged with a long hole 152 having a substantially elliptic configuration formed through the flange section 136. The rotation-preventive device 100 according to the first embodiment of the present invention is basically constructed as described above. Next, its operation, function, and effect will be explained. At first, as shown in FIG. 7, it is assumed that the spline shaft section 120 is set to be slidable in the axial direction (direction of the arrow D) with respect to the fixed boss section 114. On this assumption, explanation will be made for the basic principle for adjusting the clearance A between the teeth disposed on the side of the spline shaft section 120 and the teeth disposed on the side of the boss section 114. As clearly understood from FIG. 8, the spline shaft section 120 is divided into two, and the first spline shaft member 116 and the second spline shaft member 118, which are divided respectively, are allowed to make the rotational displacement by predetermined angles respectively in the mutually opposite circumferential directions (direction of the arrow E and direction of the arrow F) respectively. Thus, it is possible to freely adjust the clearance A between the teeth disposed on the side of the spline shaft section 120 and the teeth disposed on the side of the boss section 114. Next, explanation will be made for a case in which the clearance A is adjusted on the basis of the first embodiment. As shown in FIG. 4, the screwing amount of the screw member 150 is increased so that the forward end 148 of the screw member 150 presses the inclined surface of the recess 130, in the state in which the first spline shaft member 116 and the second spline shaft member 118 are coaxially coupled to one another by the aid of the shaft section 128. Accordingly, the first spline shaft member 116 can be rotated by a predetermined angle in the direction of the arrow C with respect to the second spline shaft member 118. Therefore, as shown in FIG. 9, the first teeth 124 disposed on the side of the first spline shaft member 116 make the rotational displacement by the predetermined angle in the identical circumferential direction (see two-dot chain lines) with respect to the second teeth 140 disposed on the side of the second spline shaft member 118. Accordingly, the clearance A in the circumferential direction can be freely adjusted with respect to the third teeth 142 formed on the inner wall surface of the boss section 114. As shown in FIG. 9, as for the clearance A in the circumferential direction between the first and second teeth 124, 140 of the spline shaft section 120 and the third teeth 142 of the boss section 114, it is possible to adjust the clearance A in any one of the positive and negative circumferential directions. As described above, in the first embodiment, the provision of the clearance-adjusting mechanism 121 makes it possible to avoid the dispersion of the clearance A which would be otherwise caused by any error of machining accuracy. Further, it is possible to avoid the backlash which would be otherwise caused by the sliding friction between the teeth 124, 140 of the spline shaft section 120 and the inner wall surface of the boss section 114. When the first spline shaft member 116, the second spline shaft member 118, and the boss section 114 are formed, for example, by means of extrusion molding based on the use of a material made of metal such as an aluminum material, then the production steps can be simplified, and the production cost can be reduced, by freely adjusting the clearance A generated between the sliding portions of the outer wall surface of the spline shaft section 120 and the inner wall surface of the boss section 114, by using the clearance-adjusting mechanism 121 described above. Next, a rotation-preventive device 160 according to a second embodiment of the present invention is shown in FIG. 10. The same constitutive components as those of the rotation-preventive device 100 shown in FIG. 1 are designated by the same reference numerals, detailed explanation of which will be omitted. The rotation-preventive device 160 according to the second embodiment comprises a boss section 168 which has a first boss member 162 and a second boss member 164 divided into two to be fitted coaxially by the aid of a shaft section 166, a spline shaft section 170, and a screw member 150 which functions as a clearance-adjusting mechanism 121. A first hole 172 and a second hole 174, which penetrate in the axial direction, are formed at the inside of the first boss member 162 and the second boss member 164. A plurality of grooves 122, 138, first teeth 124, and second teeth 140 are formed on the first hole 172 and the second hole 174 respectively (see FIG. 11). At first, as shown in FIG. 12, it is assumed that the boss section 168 is set to be slidable in the axial direction (direction of the arrow G) with respect to the fixed spline shaft section 170. On this assumption, explanation will be made for the basic principle for adjusting the clearance A between the teeth disposed on the side of the spline shaft section 170 and the teeth disposed on the side of the boss section 168. As clearly understood from FIGS. 13 and 14, the boss section 168 is divided into two, and the first boss member 162 and the second boss member 164, which are divided, are allowed to make the rotational displacement by predetermined angles respectively in the mutually opposite circumferential directions (direction of the arrow H and direction of the arrow I) respectively. Thus, it is possible to freely adjust the clearance A between the teeth disposed on the side of the spline shaft section 170 and the teeth disposed on the side of the boss section 168. Next, explanation will be made for a case in which the clearance A is adjusted on the basis of the second embodiment. The screwing amount of the screw member 150 is increased so that the forward end 148 of the screw member 150 presses the inclined surface of the recess 130, in the state in which the first boss member 162 and the second boss member 164 are coaxially coupled to one another by the aid of the shaft section 166. Accordingly, the first boss member 162 can be rotated by a predetermined angle in the direction of the arrow C with respect to the second boss member 164. Therefore, as shown in FIG. 15, the first teeth 124 disposed on the side of the first boss member 162 make the rotational displacement by the predetermined angle in the identical circumferential direction with respect to the second teeth 140 disposed on the side of the second boss member 164 formed on the inner wall surface respectively. Accordingly, the clearance A in the circumferential direction can be freely adjusted with respect to the third teeth 142 formed on the outer wall surface of the spline shaft section 170. In the first embodiment shown in FIG. 1, the clearance A is adjusted by rotating and displacing, by the predetermined angle, the first teeth 124 or the second teeth 140 provided on the outer wall surface of the spline shaft section 120. On the other hand, the second embodiment is different in that the clearance A is adjusted by rotating and displacing, by the predetermined angle, the third teeth 142 provided on the inner wall surface of the boss section 168. The other function and effect are substantially the same as those of the first embodiment described above, detailed explanation of which is omitted. INDUSTRIAL APPLICABILITY According to the present invention, the provision of the clearance-adjusting mechanism makes it possible to avoid the dispersion of the clearance which would be otherwise caused by the error of the machining accuracy. Further, it is possible to avoid the backlash which would be otherwise caused by the sliding friction between the spline shaft section and the boss section.

Claims: A rotation-preventive device for preventing rotation by making engagement between a boss section (114) which is formed with a hole (112) and a spline shaft section (120) which is inserted into said hole (112) and which is formed with spline grooves (122, 138), said rotation-preventive device comprising: a first spline shaft member (116) and a second spline shaft member (118) which are provided coaxially with each other and which are formed by dividing said spline shaft section (120) in a direction substantially perpendicular to an axis thereof; and characterised by a clearance-adjusting mechanism (121) for adjusting a clearance (A) in a circumferential direction between an inner wall surface of said boss section (114) and an outer wall surface of said spline shaft section (120) by rotating and displacing said first spline shaft member (116) and said second spline shaft member (118) in mutually opposite directions about a center of rotation of said axis. The rotation-preventive device according to claim 1, wherein: said first spline shaft member (116) has a disk section (126), and a shaft section (128) which protrudes from a flat surface of said disk section (126) in a direction substantially perpendicular thereto; said second spline shaft member (118) has a cylindrical section (134) which is formed with a hole (132) for inserting said shaft section (128) thereinto, and a flange section (136) which is formed at one end of said cylindrical section (134) in an axial direction; and a plurality of teeth (124, 140), which have a substantially identical diameter and which are separated from each other by a predetermined angle in said circumferential direction of outer circumferential surfaces, are formed on said disk section (126) and said flange section (136) respectively. The rotation-preventive device according to claim 2, wherein said clearance-adjusting mechanism (121) includes a recess (130) having a tapered cross section formed on said shaft section (128) of said first spline shaft member (116), and a screw member (150) for making abutment against said recess (130) by being screwed into a screw hole (146) formed in said cylindrical section (134) of said second spline shaft member (118), and one end (148) of said screw member (150) is formed to have a tapered configuration to make engagement with an inclined surface of said recess (130). The rotation-preventive device according to claim 3, wherein said clearance-adjusting mechanism (121) is provided adjustably for said clearance (A) in any one of positive and negative circumferential directions. The rotation-preventive device according to claim 1, further comprising a fixing means (154) for integrally fixing said first spline shaft member (116) and said second spline shaft member (118) adjusted for said clearance (A). A rotation-preventive device for preventing rotation by making engagement between a boss section (168) which is formed with a hole (172, 174) and a spline shaft section (170) which is inserted into said hole (172, 174) and which is formed with spline grooves, said rotation-preventive device comprising: a first boss member (162) and a second boss member (164) which are provided coaxially with each other and which are formed by dividing said boss section (168) in a direction substantially perpendicular to an axis thereof; and a clearance-adjusting mechanism (121) for adjusting a clearance (A) in a circumferential direction between an inner wall surface of said boss section (168) and an outer wall surface of said spline shaft section (170) by rotating and displacing said first boss member (162) and said second boss member (164) in mutually opposite directions about a center of rotation of said axis. The rotation-preventive device according to claim 6, wherein said first boss member (162) has a shaft section (166) which protrudes along an axis of said spline shaft section (170), and said first boss member (162) and said second boss member (164) are coupled coaxially and integrally with said shaft section (166). The rotation-preventive device according to claim 7, wherein said clearance-adjusting mechanism (121) includes a recess (130) having a tapered cross section formed on said shaft section (166) of said first boss member (162), and a screw member (150) for making abutment against said recess (130) by being screwed into a screw hole (146) formed in said second boss member (164), and one end (148) of said screw member (150) is formed to have a tapered configuration to make engagement with an inclined surface of said recess (130). The rotation-preventive device according to claim 8, wherein said clearance-adjusting mechanism (121) is provided adjustably for said clearance (A) in any one of positive and negative circumferential directions.

Inventors: NAGAI SHIGEKAZU, SHIRAI YOUSUKE, NAGAI, SHIGEKAZU, SHIRAI, YOUSUKE, NAGAI, Shigekazu c/o SMC K.K. Tsukuba Gijutsu Ctr., SHIRAI, Yousuke c/o SMC K. K. Tsukuba Gijutsu Ctr.
Applicants: SMC KK, SMC KABUSHIKI KAISHA
Application year: 1998
Main classification: F16H25
IPC codes: F16C29, F16H25, H02K7, F16D3