Motion conversion mechanism

Abstract

To provide a motion conversion mechanism that can miniaturize the whole mechanism and reduce the weight thereof and can increase a degree of freedom in installation location and use form.SOLUTION: A motion conversion mechanism 1 includes a flexible shaft 2 and a shaft guide 3. The flexible shaft 2 extends while penetrating an inner hole 3a of the shaft guide 3. A needle pin 11 is fitted to a pin guide 12 of the shaft guide 3 so as to be freely rotatable. One end of the needle pin 11 is fitted to a groove 2a of the flexible shaft 2 and the other end is held by a ball 13 and a screw 14 so as to be freely rotatable about an axis line of the needle pin 11.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a motion conversion mechanism that converts rotational motion into linear motion.

Background Art

[0002] Conventionally, as a motion conversion mechanism, the one described in Patent Document 1 is known. This motion conversion mechanism is of the ball screw type and includes a nut, a screw shaft, balls, etc. In this motion conversion mechanism, the balls are fitted into the screw grooves of the screw shaft and the nut. For example, when the screw shaft rotates around its rotation axis, as the balls roll along the screw grooves of the screw shaft and the nut, the nut moves linearly.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] According to the above conventional motion conversion mechanism, due to structural reasons, it is difficult to miniaturize the entire mechanism. In particular, in the balls and the screw grooves in which the balls roll, high machining accuracy is required, making it difficult to miniaturize them. Furthermore, since the nut moves on a linear screw shaft, the length and rigidity of the screw shaft are required. For the above reasons, the size of the entire mechanism increases and the weight increases. As a result, there is a problem that the installation location and usage form are restricted.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a motion conversion mechanism that can miniaturize and lighten the entire mechanism and improve the freedom of the installation location and usage form.

Means for Solving the Problems

[0006] To achieve the above objective, the invention according to claim 1 is a motion conversion mechanism 1 that converts rotational motion into linear motion, comprising: a first motion conversion member (flexible shaft 2, drive belt 2x) having an outer surface configured with a circular cross-section and a helical groove 2a extending along the extension direction formed on the outer surface; a second motion conversion member (shaft guide 3) having a first through hole (inner hole 3a) that penetrates in the axial direction and a second through hole (inner hole 12a) that extends radially between the first through hole and the outer surface, and which holds the first motion conversion member in a state in which the first motion conversion member penetrates the first through hole; a pin (needle pin 11) that is rotatably fitted into the second through hole of the second motion conversion member and has one end fitted into the groove of the first motion conversion member; and a holding member (ball 13, screw 14) that holds the other end of the pin rotatably around the axis of the pin. One end of the aforementioned pin is formed in a tapered shape, and a groove is formed along the circumferential direction on the tip side. The surface of the groove at one end is formed in such a shape that it is in close contact with the wall surface of the groove of the second motion conversion member. It is characterized by having this feature.

[0007] In this motion conversion mechanism, the first motion conversion member is held by the second motion conversion member while passing through the first through-hole of the second motion conversion member, and a pin is rotatably fitted into the second through-hole of the second motion conversion member. The pin has one end fitted into a groove in the first motion conversion member and is held by a holding member in a state where it can rotate around its axis.

[0008] As a result, for example, when the second motion conversion member rotates relative to the first motion conversion member, the pin rotates around its own axis due to friction with the groove of the first motion conversion member, while pressing the first motion conversion member in the axial direction of the second motion conversion member. Consequently, the first motion conversion member moves linearly relative to the second motion conversion member. In other words, the rotational motion of the second motion conversion member relative to the first motion conversion member is converted into linear motion of the first motion conversion member.

[0009] On the other hand, when the first motion conversion member rotates relative to the second motion conversion member, the pin rotates around its own axis due to friction with the groove of the first motion conversion member, and presses the second motion conversion member in the axial direction of the second motion conversion member. Consequently, the second motion conversion member moves linearly relative to the first motion conversion member. In other words, the rotational motion of the first motion conversion member relative to the second motion conversion member is converted into linear motion of the second motion conversion member.

[0010] As described above, this motion conversion mechanism, unlike conventional ball screws, does not use balls or screw grooves on which the balls roll. Instead, it uses a pin that fits into the groove of the first motion conversion member and the second through-hole of the second motion conversion member to convert rotational motion into linear motion. Compared to balls, the pin is easier to manufacture and can be made smaller, thus enabling miniaturization and weight reduction of the entire mechanism and improving the flexibility of installation location and usage.

[0011] In addition, the pin rotates around its own axis due to friction with the groove of the first motion conversion member, and presses the first motion conversion member in the axial direction of the second motion conversion member, thereby converting rotational motion into linear motion. This enables highly efficient torque transmission during the conversion operation.

[0012] The invention according to claim 2 is characterized in that, in the motion conversion mechanism described in claim 1, the first motion conversion member (flexible shaft 2, drive belt 2x) is configured so that the axis of the first motion conversion member can be elastically deformed in a curved shape.

[0013] According to this motion conversion mechanism, the first motion conversion member is configured so that its axis can be elastically deformed in a curved shape, allowing the three-dimensional shape of the first motion conversion member to be freely changed. As a result, the entire mechanism can be made smaller, and the degree of freedom in installation location and usage can be further improved.

[0014] The invention according to claim 3 is characterized in that, in the motion conversion mechanism described in claim 2, the first motion conversion member (drive belt 2x) is configured as an endless ring.

[0015] According to this motion conversion mechanism, since the first motion conversion member is configured in an endless ring shape, the operation of converting rotational motion to linear motion can be performed continuously and without limit. This ensures high versatility.

[0016] The invention according to claim 4 is a motion conversion mechanism according to any one of claims 1 to 3, wherein the second motion conversion member has one or more second through-hole groups, each consisting of a pair of second through-holes facing each other with respect to the central axis of the second motion conversion member, a pin fitted into the second through-hole of the one or more second through-hole groups, and a retaining member provided for each pin.

[0017] According to this motion conversion mechanism, since a retaining member is provided for each pin, two pins are fitted into a pair of second through holes that face each other across the central axis of the second motion conversion member. As a result, these opposing pins fit radially into the grooves of the first motion conversion member from both sides toward the center of the first motion conversion member, enabling stable motion conversion between the second motion conversion member and the first motion conversion member. For the same reason, when an axial force is applied between the first and second motion conversion members, the pair of pins are less likely to come out of the grooves of the first motion conversion member compared to when only one pin is fitted into the groove of the first motion conversion member, thus enabling stable motion conversion between the second and first motion conversion members.

[0018] Furthermore, since one or more groups of second through-holes are provided in the second motion conversion member, if multiple groups of second through-holes are provided in the second motion conversion member, the stability of motion conversion between the second motion conversion member and the first motion conversion member can be further improved accordingly. In this specification, "a pair of second through-holes facing each other" is not limited to a state in which the central axes of the pair of second through-holes coincide, but also includes a state in which the central axes of the two are slightly misaligned.

[0019] The invention according to claim 5 is characterized in that, in the motion conversion mechanism described in claim 4, the second motion conversion member is provided with a plurality of second through-hole groups, and each of the plurality of second through-hole groups is arranged to be spaced apart from one another along the central axis of the second motion conversion member.

[0020] In this motion conversion mechanism, each of the multiple second through-hole groups is arranged to be spaced apart from one another along the central axis of the second motion conversion member. As a result, at multiple positions along the central axis of the second motion conversion member, a pair of opposing pins engage with the grooves of the first motion conversion member from both sides toward the center of the first motion conversion member. Consequently, the stability of motion conversion between the second motion conversion member and the first motion conversion member can be further improved, and the torque transmission efficiency during the conversion operation can be further enhanced.

[0021] The invention according to claim 6 is characterized in that, in the motion conversion mechanism described in claim 4, the second motion conversion member is provided with a plurality of second through-hole groups, and the plurality of second through-hole groups include one or more second through-hole groups arranged to have rotational symmetry about the central axis of the second motion conversion member.

[0022] According to this motion conversion mechanism, the plurality of second through-hole groups include one or more second through-hole groups arranged to have rotational symmetry around the central axis of the second motion conversion member. Thereby, at a plurality of positions around the central axis of the second motion conversion member, a pair of opposing pins fit into the groove of the first motion conversion member from both sides in the radial direction toward the center of the first motion conversion member. As a result, the power transmission portions are dispersedly arranged at a plurality of rotationally symmetric locations along the circumferential direction of the second motion conversion member, so that the stability of the motion conversion between the second motion conversion member and the first motion conversion member can be further improved, and the torque transmission efficiency during the conversion operation can be further increased.

[0023] The invention according to claim 7 is characterized in that, in the motion conversion mechanism according to claim 5, the plurality of second through-hole groups are arranged to have rotational symmetry when projected onto a plane orthogonal to the central axis of the second motion conversion member.

[0024] According to this motion conversion mechanism, the plurality of second through-hole groups are arranged to have rotational symmetry when projected onto a plane orthogonal to the central axis of the second motion conversion member. Thereby, at a plurality of positions along the direction of the central axis of the second motion conversion member and at a plurality of rotationally symmetric positions along the circumferential direction of the second motion conversion member, a pair of opposing pins fit into the groove of the first motion conversion member from both sides toward the center of the first motion conversion member. Thereby, the power transmission portions are dispersedly arranged at a plurality of locations in the central axis direction of the second motion conversion member and at a plurality of rotationally symmetric locations along the circumferential direction of the second motion conversion member, so that the stability of the motion conversion between the second motion conversion member and the first motion conversion member can be further improved, and the torque transmission efficiency during the conversion operation can be further increased. The invention according to claim 8 is a motion conversion mechanism according to claim 1, characterized in that one end of the pin has a tapered shape with its central part protruding inward, and the surface of the one end is formed in a curved shape so as to be in close contact with the wall surface of the groove of the first motion conversion member. The invention according to claim 9 is a motion conversion mechanism according to claim 1, characterized in that one end of the pin is formed in a conical shape, and a gap is provided between the tip of the one end and the first motion conversion member.

Brief Description of the Drawings

[0025] [Figure 1] It is a perspective view showing the configuration of a motion conversion mechanism according to an embodiment of the present invention. [Figure 2]This figure shows a cross-section along the line II-II in Figure 1. [Figure 3] This is a cross-sectional view showing the pin mechanism. [Figure 4] This is an enlarged view of section A in Figure 3. [Figure 5] This diagram shows a linkage mechanism to which a motion conversion mechanism is applied. [Figure 6] This is a modified example of the arrangement of the output link and actuator section of a linkage mechanism. [Figure 7] This is another variation in the arrangement of the output link and actuator section of the link mechanism. [Figure 8] This is a cross-sectional view showing a modified needle pin. [Figure 9] This is an enlarged view of section B in Figure 8. [Figure 10] This is a cross-sectional view showing another variation of the needle pin. [Figure 11] This figure shows a modified example of a pin mechanism. [Figure 12] This figure shows another variation of the pin mechanism. [Modes for carrying out the invention]

[0026] The motion conversion mechanism according to one embodiment of the present invention will be described below with reference to the drawings. As shown in Figures 1 and 2, the motion conversion mechanism 1 of this embodiment includes a flexible shaft 2 and a shaft guide 3. In this embodiment, the flexible shaft 2 corresponds to the first motion conversion member, and the shaft guide 3 corresponds to the second motion conversion member.

[0027] The flexible shaft 2 is a round wire coil spring type, formed by tightly winding a round metal spring wire in a spiral shape, and has a single-layer structure. As a result, the flexible shaft 2 is configured to be elastically deformable in a curved shape along its axis, and a spiral groove 2a is formed along the entire outer surface of the flexible shaft 2 (see Figure 2).

[0028] The shaft guide 3 is a cylindrical metal structure with an internal bore 3a that penetrates axially (see Figure 2). This internal bore 3a is slightly larger in diameter than the outer shape of the flexible shaft 2, and the flexible shaft 2 extends through the shaft guide 3 while fitting into the internal bore 3a of the shaft guide 3. In this way, the flexible shaft 2 is held by the shaft guide 3. In this embodiment, the internal bore 3a corresponds to the first through-hole.

[0029] Furthermore, the shaft guide 3 has a total of 20 mounting holes 3b (only 6 are shown in Figure 2), and each of these 20 mounting holes 3b is provided with a pin mechanism 10. In other words, the shaft guide 3 is provided with a total of 20 pin mechanisms 10 (only 16 are shown in Figure 1).

[0030] Each mounting hole 3b has a circular cross-section and extends radially through the shaft guide 3 between the outer circumferential surface of the shaft guide 3 and the inner hole 3a. A female thread is formed on the circumferential surface of each mounting hole 3b for a predetermined length.

[0031] Furthermore, in the shaft guide 3, the four mounting holes 3b are arranged at equal intervals from one another along the circumferential direction of the shaft guide 3 at the same position in the axial direction of the shaft guide 3. That is, the four mounting holes 3b are arranged in a cross shape when viewed from the axial direction of the shaft guide 3. In addition, the shaft guide 3 is provided with a total of five mounting hole groups, with these four mounting holes 3b forming one mounting hole group.

[0032] These five mounting hole groups are arranged at equal intervals from each other in the axial direction of the shaft guide 3, and any two adjacent mounting hole groups are positioned with a 45° offset from each other around the axis of the shaft guide 3.

[0033] Furthermore, as shown in Figure 3, the pin mechanism 10 includes a needle pin 11, a pin guide 12, a ball 13, a screw 14, and a nut 15.

[0034] In this embodiment, the needle pin 11 corresponds to the pin, and the ball 13 and screw 14 correspond to the retaining members. In the following description of the pin mechanism 10, the radially inner side of the shaft guide 3 is referred to as the "inside," and the radially outer side of the shaft guide 3 is referred to as the "outside."

[0035] The needle pin 11 is made of metal and is formed in an elongated cylindrical shape. The inner end 11a of the needle pin 11 is formed in a conical shape and fits into the groove 2a on the outer surface of the flexible shaft 2.

[0036] Furthermore, a recessed area 11b, which is convex inward, is formed on the outer end face of the needle pin 11. The surface of this recessed area 11b is configured to have the same curved shape as the outer circumferential surface of the ball 13.

[0037] The pin guide 12 is formed in a cylindrical shape, and a male thread is formed on its outer circumferential surface. This male thread extends from a predetermined point closer to the inside of the outer end of the pin guide 12 to the inner tip of the pin guide 12. The pin guide 12 is attached to the shaft guide 3 by the male thread engaging with the female thread of the mounting hole 3b, so that there is a gap between its inner end and the flexible shaft 2.

[0038] A counterbore hole 3c concentric with the mounting hole 3b is formed on the outer circumferential surface of the shaft guide 3, and the nut 15 is tightened so that its female threads engage with the male threads on the outer circumferential surface of the pin guide 12 and are in contact with the bottom surface of the counterbore hole 3c. In this way, the pin guide 12 is firmly fixed to the shaft guide 3 via this nut 15 so that the screw connection between them does not loosen.

[0039] Meanwhile, the needle pin 11 is fitted into the inner hole 12a of the pin guide 12, and grease (not shown) is filled between the needle pin 11 and the pin guide 12. A female thread is formed on the outer part of the inner hole 12a of the pin guide 12. The screw 14 is attached to the pin guide 12 via a washer 16 by its male thread engaging with the female thread of the pin guide 12. The tip surface of this screw 14 is formed flat.

[0040] The ball 13 is made of metal and is sandwiched between the tip surface of the screw 14 and the recess of the pin guide 12, with its surface in contact with the tip surface of the screw 14 and the recess of the pin guide 12. This configuration allows the amount by which the inner end 11a of the needle pin 11 protrudes toward the flexible shaft 2 can be adjusted by changing the thickness of the washer 16 described above.

[0041] With the above configuration, in the pin mechanism 10, the needle pin 11 is held (supported) in a state where it can rotate freely around its axis by the pin guide 12, ball 13, and screw 14. Furthermore, in the case of a pair of pin mechanisms 10 provided in a pair of mounting holes 3b that face each other, the pair of needle pins 11 fit into the groove 2a at a position offset by one pitch of the flexible shaft 2, so the axes of the two are slightly misaligned.

[0042] Furthermore, as mentioned above, in the five mounting hole groups, two adjacent mounting hole groups are positioned so as to be offset from each other by 45° around the axis of the shaft guide 3, and a pin guide 12 is attached to each of the 20 mounting holes 3b. As a result, when the inner holes 12a of the 20 pin guides 12 are projected onto a plane perpendicular to the axial direction of the shaft guide 3, they exhibit rotational symmetry (8-fold symmetry).

[0043] In this embodiment, the pin guide 12 corresponds to the second motion conversion member, the inner hole 12a of the pin guide 12 corresponds to the second through hole, and the inner hole 12a of the pin guide 12 in the mounting hole group corresponds to the second through hole group.

[0044] Next, the operation of the motion conversion mechanism 1 configured as described above will be explained. First, when the axis guide 3 is rotated around its own axis while the flexible shaft 2 is held in a state where it can move only in the direction of its axis, the needle pin 11 moves along the groove 2a of the flexible shaft 2 as the axis guide 3 rotates.

[0045] In this process, the needle pin 11 contacts the wall surface of the groove 2a and presses the flexible shaft 2 in the axial direction while rotating around its own axis. Consequently, the flexible shaft 2 moves in the axial direction. In other words, the rotational motion of the shaft guide 3 can be converted into the linear motion of the flexible shaft 2.

[0046] On the other hand, if the flexible shaft 2 is rotated around its own axis while the shaft guide 3 is held in a state where it can move only in the direction of its axis, the needle pin 11 will be guided into the groove 2a of the flexible shaft 2 as the flexible shaft 2 rotates.

[0047] In this process, the needle pin 11 rotates around its axis while being pressed against the wall surface of the groove 2a. Consequently, the axis guide 3 moves in the direction of its axis. In other words, the rotational motion of the flexible shaft 2 can be converted into the linear motion of the axis guide 3.

[0048] As described above, the motion conversion mechanism 1 of this embodiment, unlike conventional ball screws, does not use balls or screw grooves on which the balls roll. Instead, it is possible to convert rotational motion into linear motion using a flexible shaft 2 having a groove 2a and a needle pin 11 fitted into the groove 2a. Here, the needle pin 11 is easier to manufacture and can be made smaller compared to balls, thus enabling miniaturization and weight reduction of the entire mechanism and improving the freedom of installation location and usage.

[0049] Furthermore, the needle pin 11, due to friction with the groove 2a of the flexible shaft 2, rotates around its own axis while pressing the flexible shaft 2 in the axial direction of the shaft guide 3, thereby converting rotational motion into linear motion. This enables highly efficient torque transmission during the conversion operation.

[0050] Furthermore, since the flexible shaft 2 is configured so that its axis can be elastically deformed in a curved shape, the three-dimensional shape of the flexible shaft 2 can be freely changed, which allows for a more compact overall mechanism and further improves the freedom of installation location and usage.

[0051] Furthermore, since the needle pins 11 of the four pin mechanisms 10 in one mounting hole group are arranged in a cross shape when viewed from the axial direction of the shaft guide 3, if a pair of opposing needle pins 11, 11 are considered as one needle pin group, the two needle pin groups are arranged in a cross shape when viewed from the axial direction of the shaft guide 3, and fit into the groove 2a of the flexible shaft 2 from both radial sides toward the center of the flexible shaft 2.

[0052] Furthermore, since the shaft guide 3 has five mounting holes provided at equal intervals in the axial direction of the shaft guide 3, two needle pin groups are fitted into the groove 2a of the flexible shaft 2 from both radial sides toward the center of the flexible shaft 2 at five locations in the axial direction of the shaft guide 3.

[0053] Furthermore, as mentioned above, the inner holes 12a of the 20 pin guides 12 exhibit rotational symmetry (8-fold symmetry) when projected onto a plane perpendicular to the axial direction of the axial guide 3. Consequently, the 20 needle pins 11 also exhibit rotational symmetry (8-fold symmetry) when projected onto a plane perpendicular to the axial direction of the axial guide 3.

[0054] With the above configuration, even when an impact or load is applied in the axial direction to either the shaft guide 3 or the flexible shaft 2, the engagement of the 20 needle pins 11 with the groove 2a of the flexible shaft 2 is less likely to disengage. As a result, as mentioned above, it is possible to improve the stability of motion conversion between the shaft guide 3 and the flexible shaft 2 while ensuring miniaturization and weight reduction of the entire mechanism and increased flexibility in installation location and usage, thereby improving torque transmission efficiency during conversion.

[0055] Next, with reference to Figure 5, an example of applying the motion conversion mechanism of the present invention to a link mechanism 50 will be described. This link mechanism 50 includes an output link 51 and an actuator section 52. Although not shown, the output link 51 and actuator section 52 are configured in a flat plate shape and are arranged parallel to each other.

[0056] The output link 51 is equipped with a guide pulley 51a, and the output link 51 and the guide pulley 51a are configured to rotate integrally around an axis extending in the depth direction in the figure. An axis guide 3 is fixed to this guide pulley 51a.

[0057] Furthermore, the actuator section 52 is equipped with two shaft guides 3, 3, a guide pulley 52a, and a motor mechanism 52b. The guide pulley 52a is provided on the actuator section 52 so as to be rotatable around an axis extending in the depth direction in the figure.

[0058] Furthermore, each of the two shaft guides 3, 3 is attached to the actuator unit 52 in a manner that allows it to rotate around its axis. The rotating shaft of the motor mechanism 52b extends in the left-right direction in the figure, and two rotating pulleys 52c, 52c are provided at both ends of this rotating shaft. These rotating pulleys 52c, 52c are connected to the two shaft guides 3, 3 via belts 52d, 52d.

[0059] The motor mechanism 52b combines a motor and a gear mechanism (neither of which are shown), and is configured such that when the motor is running, the two rotating pulleys 52c, 52c rotate in opposite directions at the same speed. As a result, when the motor mechanism 52b is running, the two shaft guides 3, 3 are driven by the motor mechanism 52b to rotate in opposite directions relative to each other.

[0060] Furthermore, in this link mechanism 50, the drive belt 2x (first motion conversion member) is wrapped around two guide pulleys 51a and 52a. This drive belt 2x is made up of a flexible shaft 2 configured as an endless ring, and it passes through the two shaft guides 3 of the actuator section 52 and the shaft guide 3 of the output link 51, and is wrapped around the two guide pulleys 51a and 52a via two small-diameter guide pulleys 53, 53.

[0061] With the link mechanism 50 configured as described above, the motor mechanism 52b drives the two shaft guides 3, 3 of the actuator unit 52 to rotate in opposite directions, and as a result, the drive belt 2x is driven to move in the axial direction by the two shaft guides 3, 3. This causes the drive belt 2x to rotate the guide pulley 51a via the shaft guide 3 of the output link 51, thereby rotating the output link 51.

[0062] In this case, since the drive belt 2x is configured as an endless ring, the operation of converting the rotational motion of the two shaft guides 3,3 into the linear motion of the drive belt 2x can be performed continuously and without limit.

[0063] Furthermore, since the drive belt 2x is configured to be elastically deformable, the arrangement and shape of the output link 51 and the actuator section 52 can be freely changed by providing several guide pulleys between the output link 51 and the actuator section 52.

[0064] For example, when viewing the output link 51 and actuator unit 52 from the side (up and down direction in Figure 5), it is also possible to arrange them so that they are orthogonal to each other, as shown in Figure 6. Furthermore, as shown in Figure 7, it is also possible to make the actuator unit 52 bend 90° relative to the output link 51, and then bend another 90°.

[0065] In the motion conversion mechanism 1, the needle pin 11A shown in Figures 8-9 may be used instead of the needle pin 11 of the embodiment. In the case of this needle pin 11A, only its inner end 11a is configured to differ from that of the needle pin 11. That is, the inner end 11a of this needle pin 11A is formed in a conical shape, similar to the needle pin 11, and a groove 11c is formed along the circumferential direction on its tip side. The surface of this groove 11c is configured to have the same curved shape as the wall surface (surface) of the groove 2a of the flexible shaft 2.

[0066] With the above configuration, the needle pin 11A has a larger contact area with the wall surface of the groove 2a of the flexible shaft 2 compared to the needle pin 11 of the embodiment. As a result, even when an impact or load is applied in the axial direction to either the shaft guide 3 or the flexible shaft 2, the engagement of the needle pin 11 with the groove 2a of the flexible shaft 2 becomes even less likely to come loose. Consequently, the stability of motion conversion between the shaft guide 3 and the flexible shaft 2 can be further improved, and the torque transmission efficiency during conversion can be further enhanced.

[0067] Alternatively, instead of the needle pin 11 of the embodiment, the needle pin 11B shown in Figure 10 may be used. In the case of the needle pin 11B, the center of the inner end 11d has a tapered shape that protrudes inward, and the surface of the inner end 11d is formed in a curved shape that adheres closely to the wall surface of the groove 2a of the flexible shaft 2.

[0068] As a result, in the case of this needle pin 11B, similar to the needle pin 11A described above, the contact area with the wall surface of the groove 2a of the flexible shaft 2 can be made larger than that of the needle pin 11 of the embodiment, and the same effects and advantages as described above can be obtained as with the needle pin 11A.

[0069] Furthermore, in the motion conversion mechanism 1, the pin mechanism 10C shown in Figure 11 may be used instead of the pin mechanism 10 of the embodiment. In the case of this pin mechanism 10C, as is clear from comparing Figure 11 and Figure 3, the ball 13 is omitted and the needle pin 11C is provided instead of the needle pin 11, which is different from the pin mechanism 10 of the embodiment.

[0070] In the case of this needle pin 11C, the differences from the needle pin 11 are that the outer end 11e is formed in a hemispherical shape and that this outer end 11e is in contact with the tip surface of the screw 14. In this case, the screw 14 corresponds to the retaining member.

[0071] With the above configuration, the needle pin 11C is held so as to be rotatable around its axis by the screw 14 and the pin guide 12. Therefore, even when using this pin mechanism 10C, the same effects and advantages as when using the pin mechanism 10 of the embodiment can be obtained.

[0072] Furthermore, in the motion conversion mechanism 1, the pin mechanism 10D shown in Figure 12 may be used instead of the pin mechanism 10 of the embodiment. In the case of this pin mechanism 10D, as is clear from comparing Figure 12 and Figure 3, the ball 13 is omitted and the needle pin 11D is provided instead of the needle pin 11, which is different from the pin mechanism 10 of the embodiment.

[0073] In the case of this needle pin 11D, the outer end 11f is formed in a conical shape, and this outer end 11f abuts against the tip surface of the screw 14. In this case, the screw 14 corresponds to the retaining member.

[0074] With the above configuration, the needle pin 11D is held rotatably around its axis by the screw 14 and the pin guide 12. Therefore, even when using this pin mechanism 10D, the same effects and advantages as when using the pin mechanism 10 of the embodiment can be obtained.

[0075] In this embodiment, the needle pin 11 is configured to fit into the inner hole 12a of the pin guide 12, which serves as the second through-hole. However, the needle pin 11 may be configured to fit directly into the second through-hole formed in the shaft guide 3.

[0076] Furthermore, although the embodiment uses a flexible shaft 2 as the first motion conversion member, the first motion conversion member of the present invention is not limited to this, and any member whose outer surface has a circular cross-section and whose outer surface has a helical groove formed on it so as to extend along the direction of extension may be used. For example, a rod-shaped member whose outer surface is cylindrical and whose outer surface has a helical groove formed on it so as to extend along the direction of extension may be used as the first motion conversion member.

[0077] Furthermore, although the embodiment uses a single-layer coil spring type as the flexible shaft 2, a two-layer or three-layer coil spring type may be used instead.

[0078] On the other hand, the embodiment is an example in which four pin mechanisms 10 are arranged at equal intervals (90° intervals) along the circumferential direction on the outer surface of the shaft guide 3 as a single pin mechanism group. Alternatively, an even or odd number of pin mechanisms 10 may be arranged at equal intervals along the circumferential direction on the outer surface of the shaft guide 3 as a single pin mechanism group.

[0079] Alternatively, the system may be configured to have only one pin mechanism 10 on the shaft guide 3. Furthermore, the system may be configured to have only one pin mechanism 10 on the shaft guide 3, with a projection positioned in the inner hole 3a of the shaft guide 3 so as to face the needle pin 11 of this pin mechanism 10, and the single needle pin 11 and the projection fitted into the groove 2a of the flexible shaft 2.

[0080] Alternatively, one pin mechanism 10 and one projection may be considered as one locking structure, and an even or odd number of locking structures may be arranged at equal intervals along the circumferential direction of the shaft guide 3 on the outer surface of the shaft guide 3. In addition to or instead of this, multiple locking structures may be arranged at intervals along the axial direction of the shaft guide 3. [Explanation of Symbols]

[0081] 1. Motion conversion mechanism 2. Flexible shaft (first motion conversion member) 2a groove 3-axis guide (second motion conversion member) 3a Inner hole (1st through hole) 11 Needle pins (pins) 12. Pin guide (second motion conversion member) 12a Inner hole (second through hole) 13. Ball (retaining member) 14. Screw (retaining member) 2x drive belts (first motion conversion member)

Claims

1. A motion conversion mechanism that converts rotational motion into linear motion, A first motion conversion member is formed on the outer surface such that its outer surface has a circular cross-section and a helical groove extends along the direction of extension, A second motion conversion member has a first through-hole that penetrates in the axial direction and a second through-hole that extends radially between the first through-hole and the outer circumferential surface, and holds the first motion conversion member in a state where the first motion conversion member is passing through the first through-hole, A pin that is rotatably fitted into the second through hole of the second motion conversion member, with one end fitted into the groove of the first motion conversion member, A retaining member that holds the other end of the pin so as to be rotatable around the axis of the pin, Equipped with, A motion conversion mechanism characterized in that one end of the pin is formed in a tapered shape, a groove is formed along the circumferential direction on the tip side, and the surface of the groove at the one end is formed in a shape that is in close contact with the wall surface of the groove of the second motion conversion member.

2. In the motion conversion mechanism described in claim 1, The motion conversion mechanism is characterized in that the first motion conversion member is configured so that its axis can be elastically deformed in a curved shape.

3. In the motion conversion mechanism described in claim 2, The motion conversion mechanism is characterized in that the first motion conversion member is configured in an endless ring shape.

4. In the motion conversion mechanism according to any one of claims 1 to 3, The second motion conversion member has one or more second through-hole groups, each consisting of a pair of second through-holes facing each other with respect to the central axis of the second motion conversion member. The pin is fitted into the second through hole of the one or more second through hole group. The motion conversion mechanism is characterized in that the holding member is provided for each of the pins.

5. In the motion conversion mechanism described in claim 4, The second motion conversion member is provided with a plurality of the second through-hole groups, A motion conversion mechanism characterized in that each of the plurality of second through-hole groups is arranged to be spaced apart from one another along the central axis of the second motion conversion member.

6. In the motion conversion mechanism described in claim 4, The second motion conversion member is provided with a plurality of the second through-hole groups, The motion conversion mechanism is characterized in that the plurality of second through-hole groups include one or more second through-hole groups arranged to have rotational symmetry about the central axis of the second motion conversion member.

7. In the motion conversion mechanism described in claim 5, The motion conversion mechanism is characterized in that the plurality of second through-hole groups are arranged such that they have rotational symmetry when projected onto a plane perpendicular to the central axis of the second motion conversion member.

8. In the motion conversion mechanism described in claim 1, The motion conversion mechanism is characterized in that one end of the pin has a tapered shape with its central part protruding inward, and the surface of the one end is formed in a curved shape so as to be in close contact with the wall surface of the groove of the first motion conversion member.

9. In the motion conversion mechanism described in claim 1, A motion conversion mechanism characterized in that one end of the pin is formed in a conical shape, and a gap is provided between the tip of the one end and the first motion conversion member.

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