Bidirectional torque limiter

Abstract

To provide a novel bidirectional torque limiter that has a small number of components and is easy to assemble, especially capable of changing the magnitude of a rotational torque at which rotation begins when the rotational torque is applied from one of two connected members, and the magnitude of a rotational torque at which rotation begins when the rotational torque is applied from the other member.SOLUTION: An inside coil spring 76 and an outside coil spring 82 are respectively mounted on an inner peripheral surface and outer peripheral surface of a common ring member 10.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a bidirectional torque limiter, and in particular to a bidirectional torque limiter that can change the magnitude of rotational torque at which rotation begins when rotational torque is applied from one of two connected members and the magnitude of rotational torque at which rotation begins when rotational torque is applied from the other member. [Background technology]

[0002] As an example of the bidirectional torque limiter described above, there is a bidirectional torque limiter as shown in the following Patent Document 1 by the applicant of the present application (hereinafter, this bidirectional torque limiter may be referred to as a "preceding bidirectional torque limiter"). The preceding bidirectional torque limiter includes a fixed housing, a one-side member, an other-side member, an outer ring, and an inner ring, which have a common central axis within the housing. The one-side member is formed with a one-side locking piece extending in the axial direction, and the other-side member is formed with a other-side locking piece extending in the axial direction, respectively, and the one-side locking piece and the other-side locking piece are combined and arranged so that there are two gaps in the circumferential direction. An outer coil spring is attached to the outer peripheral surface of the outer ring. The inner diameter of the outer coil spring in a free state is smaller than the outer diameter of the outer ring, and the outer coil spring is brought into close contact with the outer ring with a relatively small force. If the torque generated by the outer coil spring coming into close contact with the outer ring is called an outer holding torque, this outer holding torque is relatively small. The outer coil spring has two outer hook portions at different angular positions in the circumferential direction, and each of the two outer hook portions is inserted into each of the two gaps. The inner coil spring is attached to the outer peripheral surface of the inner ring. The inner diameter of the inner coil spring in a free state is smaller than the outer diameter of the inner ring, and the inner coil spring is brought into close contact with the inner ring with a relatively large force. If the torque generated by the inner coil spring coming into close contact with the inner ring is called the inner holding torque, this inner holding torque is relatively large. The inner coil spring has two inner hook portions at different angular positions in the circumferential direction, and each of the two inner hook portions is inserted into a hook groove formed on the inner peripheral surface of the outer ring.

[0003] When a rotational torque is applied to the one-side member, the one-side locking piece pushes one of the two outer hook portions in the direction in which the outer coil spring expands in diameter. Since the outer coil spring is attached to the outer peripheral surface of the outer ring, the outer ring tries to rotate together with the outer coil spring, and pushes one of the two inner hook portions of the inner coil spring in the direction in which the inner coil spring expands in diameter. At this time, since the outer holding torque is smaller than the inner holding torque, if the rotational torque applied to the one-side member is larger than the outer holding torque, the outer coil spring slips relative to the outer ring before the inner coil spring slips relative to the inner ring. In other words, before the inner coil spring starts to rotate relative to the inner ring, therefore, while the outer ring is held by the inner coil spring, the outer coil spring starts to rotate relative to the outer ring. Then, after the outer hook portion pushed by the one-side locking piece abuts against the other-side locking piece, the one-side locking piece pushes the other-side locking piece via the outer hook portion, and the one-side member, the outer coil spring, and the other-side member rotate together. In other words, the rotation applied to the member on one side is transmitted to the member on the other side. Note that if the rotational torque applied to the member on one side is smaller than the outer holding torque, the member on one side does not rotate and is held by the outer holding torque.

[0004] On the other hand, when a rotational torque is applied to the other-side member, the other-side locking piece pushes one of the two outer hook portions in the direction in which the outer coil spring contracts in diameter. This strengthens the contact between the outer coil spring and the outer ring, and the outer ring tries to rotate together with the outer coil spring. Since the outer coil spring is attached to the outer peripheral surface of the outer ring, the outer ring tries to rotate together with the outer coil spring, and pushes one of the two inner hook portions of the inner coil spring in the direction in which the inner coil spring expands in diameter. Therefore, if the rotational torque applied to the other-side member is greater than the inner holding torque, the inner coil spring slips relative to the inner ring. In other words, the inner coil spring starts to rotate relative to the inner ring, and the other-side member, the outer coil spring, the outer ring, and the inner coil spring rotate together relative to the inner ring. Then, after the outer hook portion pressed by the other-side locking piece comes into contact with the one-side locking piece, the other-side locking piece presses the one-side locking piece via the outer hook portion, and the other-side member, the outer coil spring, and the one-side member (and further the outer ring and the inner coil spring) rotate together. In other words, the rotation applied to the other-side member is transmitted to the one-side member. Note that if the rotational torque applied to the other-side member is smaller than the inner holding torque, the other-side member does not rotate and is held by the inner holding torque.

[0005] In other words, in the case of a leading bidirectional torque limiter, the magnitude of the rotational torque at which slippage, i.e., rotation, begins to occur when the rotational torque is transmitted from one side member to the other side member and when the rotational torque is transmitted from the other side member to the one side member differs, and is set smaller in the former case than in the latter case. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 6967687 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, the bidirectional torque limiter shown in Patent Document 1 has a large number of parts, and there is room for improvement in terms of the assembly process, weight, and cost. Also, alignment is required when inserting the inner hook portion of the inner coil spring attached to the outer peripheral surface of the inner ring into the hook groove formed on the inner peripheral surface of the outer ring, making the assembly process complicated.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and its main technical object is to provide a new bidirectional torque limiter which has a smaller number of parts and is easier to assemble than the previous bidirectional torque limiter by reviewing the structure of the previous bidirectional torque limiter. [Means for solving the problem]

[0009] According to the present invention, a bidirectional torque limiter that solves the above-mentioned main technical problem is provided, comprising a fixed housing, a one-side member, an other-side member, and a cylindrical ring member that have a common central axis within the housing, a one-side locking piece extending in an axial direction is formed on the one-side member, and an other-side locking piece extending in an axial direction is formed on the other-side member, and the one-side locking piece and the other-side locking piece are combined and arranged so that two gaps are present in a circumferential direction, an inner coil spring is attached to an inner peripheral surface of the ring member, an outer diameter of the inner coil spring in a free state is larger than an inner diameter of the ring member, the inner coil spring is brought into close contact with the ring member with a relatively small force, the inner coil spring has two inner hook portions at different angular positions in the circumferential direction, and each of the two inner hook portions is inserted into each of the two gaps; An outer coil spring is attached to the outer peripheral surface of the ring member, the inner diameter of the outer coil spring in a free state is smaller than the outer diameter of the ring member, and the outer coil spring is brought into close contact with the ring member with a relatively large force, the outer coil spring has two outer hook portions at different angular positions in the circumferential direction, and each of the two outer hook portions is inserted into a recess formed in the inner peripheral surface of the housing, When a rotational torque is applied to the one-side member, one of the two inner hook portions is pushed by the one-side locking piece in a direction in which the inner coil spring expands in diameter, and one of the two outer hook portions is pushed by the housing in the recess in a direction in which the outer coil spring expands in diameter, and the one-side member rotates integrally with the inner coil spring and the ring member against a relatively large braking torque applied by the outer coil spring to transmit the rotation to the other-side member, When a rotational torque is applied to the other-side member, one of the two inner hook portions is pushed by the other-side locking piece in the direction in which the inner coil spring contracts, and one of the two outer hook portions is pushed by the housing in the recess in the direction in which the outer coil spring expands, and with the ring member held by the outer coil spring, the other-side member rotates together with the inner coil spring relative to the ring member against a relatively small braking torque applied by the inner coil spring, transmitting the rotation to the one-side member, thereby providing a bidirectional torque limiter.

[0010] Preferably, the cross sections of the one-side locking piece and the other-side locking piece are both arc-shaped extending around the central axis. In this case, a notch is formed at each of the circumferential ends of both axial end portions of the one-side locking piece, and the circumferential end face of the one-side locking piece is divided into a notched end face where the notch is formed and a non-notched end face where the notch is not formed, and when the one-side member rotates, the notched end face presses one of the two inner hook portions and the non-notched end face presses the circumferential end face of the other-side locking piece, so that one of the two inner hook portions pressed by the notched end face moves away from the circumferential end face of the other-side locking piece, while when the other-side member rotates, the circumferential end face of the other-side locking piece presses the non-notched end face of the one-side member together with one of the two inner hook portions, and so that one of the two inner hook portions pressed by the other-side locking piece moves away from the notched end face of the one-side locking piece. The housing may be provided with an annular groove into which both axial ends of the ring member are loosely fitted. Preferably, the one-side member, the other-side member, the ring member, the inner coil spring, and the outer coil spring are made of metal, while the housing is made of synthetic resin.

[0011] The main technical problem is to provide a device that includes a fixed member, a one-side member, an other-side member, and a cylindrical ring member that have a common central axis, a one-side locking piece extending in an axial direction is formed on the one-side member, and an other-side locking piece extending in an axial direction is formed on the other-side member, and the one-side locking piece and the other-side locking piece are combined and arranged so that two gaps are present in a circumferential direction, an outer coil spring is attached to the outer peripheral surface of the ring member, the inner diameter of the outer coil spring in a free state is smaller than the outer diameter of the ring member, the outer coil spring is brought into close contact with the ring member with a relatively small force, the outer coil spring has two outer hook portions at different angular positions in the circumferential direction, and each of the two outer hook portions is inserted into each of the two gaps; an inner coil spring is attached to an inner peripheral surface of the ring member, an outer diameter of the inner coil spring in a free state is larger than an inner diameter of the ring member, the inner coil spring is brought into intimate contact with the ring member with a relatively large force, the inner coil spring has two inner hook portions at different angular positions in the circumferential direction, and each of the two inner hook portions can be engaged with an engaging means provided on the fixed member, When a rotational torque is applied to the one-side member, one of the two outer hook portions is pushed by the one-side locking piece in a direction in which the outer coil spring contracts in diameter, and one of the two inner hook portions is pushed by the locking means in a direction in which the inner coil spring contracts in diameter, and the one-side member rotates integrally with the outer coil spring and the ring member against a relatively large braking torque applied by the inner coil spring to transmit the rotation to the other-side member, This problem can also be solved by a bidirectional torque limiter in which, when a rotational torque is applied to the other-side member, one of the two outer hook portions is pushed by the other-side locking piece in the direction in which the outer coil spring expands in diameter, and one of the two inner hook portions is pushed by the locking means in the direction in which the inner coil spring contracts in diameter, and with the ring member held by the inner coil spring, the other-side member rotates together with the outer coil spring relative to the ring member against a relatively small braking torque applied by the outer coil spring, transmitting the rotation to the one-side member. Effect of the Invention

[0012] In the bidirectional torque limiter of the present invention, the inner coil spring and the outer coil spring are respectively attached to the inner peripheral surface and the outer peripheral surface of a common ring member. On the other hand, in the leading bidirectional torque limiter, the inner coil spring is respectively attached to the outer peripheral surface of the inner ring and the outer coil spring is respectively attached to the outer peripheral surface of the outer ring, that is, the inner coil spring and the outer coil spring are respectively attached to the outer peripheral surfaces of two different ring members. The ring member in the bidirectional torque limiter of the present invention is an integrated inner ring and outer ring in the leading bidirectional torque limiter, and this allows the bidirectional torque limiter of the present invention to reduce the number of parts by one compared to the leading bidirectional torque limiter. Furthermore, in the bidirectional torque limiter of the present invention, alignment between the outer coil spring and the inner coil spring and the ring member is not required, so the assembly process is simplified. In the leading bidirectional torque limiter, it is necessary to separately align the inner coil spring and the outer ring.

[0013] As a preliminary note, there is a bidirectional torque limiter in which an inner coil spring and an outer coil spring are respectively attached to the inner and outer peripheral surfaces of a common ring member, such as the bidirectional torque limiter disclosed in JP 2002-155973 A, which was filed by the applicant of the present application prior to the present application and has already been published (hereinafter, this will be referred to as the "reference bidirectional torque limiter"). However, this reference bidirectional torque limiter changes the magnitude of the rotational torque at which rotation begins in forward and reverse rotations, and is completely different in nature from the bidirectional torque limiter of the present invention and the preceding bidirectional torque limiter disclosed in the above-mentioned Patent Document 1. [Brief description of the drawings]

[0014] [Figure 1] 1 is a diagram showing the structure of a bidirectional torque limiter constructed according to the present invention; [Diagram 2] FIG. 2 is an exploded view of the bidirectional torque limiter shown in FIG. 1, with each component part arranged. [Diagram 3] FIG. 2 is a diagram showing the internal structure of the bidirectional torque limiter shown in FIG. 1 with the shield removed. [Figure 4] FIG. 2 is a view showing a housing of the bidirectional torque limiter shown in FIG. 1 by itself. [Diagram 5] FIG. 2 is a view showing one side member of the bidirectional torque limiter shown in FIG. 1 alone. [Figure 6] 2 is a view showing the other member of the bidirectional torque limiter shown in FIG. 1 alone. FIG. [Figure 7] 2 is a diagram showing a state in which a rotational torque is applied to one side member in the bidirectional torque limiter shown in FIG. 1; [Figure 8] 2 is a diagram showing a state in which a rotational torque is applied to the other-side member in the bidirectional torque limiter shown in FIG. 1. [Figure 9] 11A and 11B are diagrams showing modified examples of the bidirectional torque limiter according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, a bidirectional torque limiter constructed according to the present invention will be described in more detail with reference to the accompanying drawings showing a preferred embodiment of the bidirectional torque limiter.

[0016] Explaining with reference to FIGS. 1 to 3, the bidirectional torque limiter generally designated by the numeral 2 includes a fixed housing 4, and a one-side member 6, an other-side member 8, and a ring member 10, which have a common central axis o within the housing 4.

[0017] Explaining with reference to FIG. 4 together with FIG. 1 to FIG. 3, the housing 4 includes a housing body 12 shown in FIG. 4(a) and a shield 14 shown in FIG. 4(b). In the illustrated embodiment, the housing body 12 and the shield 14 are both integrally formed of an appropriate synthetic resin. The housing body 12 includes a circular end plate 16 arranged perpendicular to the axial direction, and a cylindrical outer peripheral wall 18 extending from the outer peripheral edge of the end plate 16 to one side in the axial direction. A bulging portion 20 having a circular cross section that bulges to the other side in the axial direction is formed in the center of the end plate 16. A circular recess 22 is provided in the center of one axial side of the bulging portion 20, and a circular hole 24 is formed in the center of the circular bottom surface of the recess 22, penetrating in the axial direction. A circular ring-shaped residual protrusion 26 is present on one axial side of the end plate 16, surrounding the outer peripheral edge of the recess 22, and a circular recess 28 is provided on the inside of the residual protrusion 26, and a circular ring-shaped groove 30 is provided on the outside of the residual protrusion 26. Six arc-shaped projections 32 protruding in the axial direction are arranged at equal angular intervals in the circumferential direction on the outer peripheral edge of the other axial side surface of the end plate 16. The housing 4 is fixed to a wall or the like (not shown) via the projections 32. A plurality of arc-shaped recesses 34 (six in the illustrated embodiment) are formed at intervals in the circumferential direction on the inner peripheral surface of the outer peripheral wall 18 by locally increasing the inner diameter. The recesses 34 extend in the axial direction. The circumferential lengths of the recesses 34 are not necessarily the same and are changed as appropriate. A step 36 extending in the circumferential direction is formed at the axially extending end of the inner peripheral surface of the outer peripheral wall 18 in the circumferential angle region where the recesses 34 are not formed. A plurality of arc-shaped extension pieces 38 (six in the illustrated embodiment) are formed at equal angular intervals in the circumferential direction on the axially extending end surface of the outer peripheral wall 18, which continue toward one axial side and further extend in the axial direction. In the illustrated embodiment, the extension piece 38 corresponds approximately to the circumferential angular region in which the recess 34 is formed. A locking protrusion 40 is formed on the inner peripheral surface of the extension piece 38 at the axially extending end portion thereof, extending in the circumferential direction.

[0018] The shield 14 includes a disk-shaped support wall 42 arranged perpendicular to the axial direction, and a cylindrical mounting wall 44 extending from the outer periphery of the support wall 42 to one side in the axial direction. A circular hole 46 is formed in the center of the support wall 42, penetrating in the axial direction. An outer rib 48 and an inner rib 50 are formed in the outer periphery of the other axial side of the support wall 42, surrounding the outer periphery of the hole 46, and an annular groove 51 is provided between the outer rib 48 and the inner rib 50. The outer diameter of the mounting wall 44 is larger than that of the support wall 42. An arc-shaped protrusion 52 is formed on the outer periphery of the mounting wall 44 by locally increasing the outer diameter. A plurality of protrusions 52 are formed corresponding to the number of extension pieces 38 formed on the housing body 12, i.e., six in the illustrated embodiment, and the plurality of protrusions 52 are arranged at equal angular intervals in the circumferential direction. The circumferential distance between two circumferentially adjacent protrusions 52 corresponds to the circumferential length of the extension piece 38. A circumferentially extending locking protrusion 54 is formed on the outer peripheral surface of the mounting wall 44 between two circumferentially adjacent protrusions 52. When the shield 14 is mounted on the housing body 12, the extension piece 38 of the housing body 12 is aligned between the two circumferentially adjacent protrusions 52, and then the shield 14 is forced in the axial direction toward the end plate 16 of the housing body 12, so that the locking protrusion 40 of the extension piece 38 elastically overcomes the locking protrusion 54. When the shield 14 is mounted on the housing body 12, the outer peripheral edge of the support wall 42 of the shield 14 abuts against the step 36 of the housing body 12, and the protrusion 52 of the shield 14 abuts against the axial end face (excluding the extension piece 38) of the outer peripheral wall 18 of the housing body 12.

[0019] The description will be continued with reference to FIG. 5 together with FIG. 1 to FIG. 3. In the illustrated embodiment, the one-side member 6 is made of metal and is integrally formed by powder metallurgy. The one-side member 6 includes a cylindrical one-side connection part 56 connected to either one of the driving side and the driven side external devices (such external devices are not illustrated), and a one-side locking piece 58 attached to the outer circumferential surface of the one-side connection part 56. The one-side connection part 56 penetrates in the axial direction, and a connecting internal tooth 60 such as a serration is formed on the inner circumferential surface. As shown in the AA cross-sectional view of FIG. 1, one axial end of the one-side connection part 56 is fitted into a recess 22 formed in the end plate 16 of the housing body 12 and rotatably supported. The one-side locking piece 58 extends from an axial middle part of the outer circumferential surface of the one-side connection part 56 beyond the other axial end of the one-side connection part 56 to the other axial side. The cross section of the one-side locking piece 58 is an arc shape extending around the central axis o. Notches 62 and 64 are formed at the circumferential ends of both axial ends of the one-side locking piece 58, and the circumferential end face of the one-side locking piece 58 is divided into a notched end face 65a where the notch 62 or 64 is formed and a non-notched end face 65b where the notch 62 or 64 is not formed. In the illustrated embodiment, the notch 62 is formed only at the downstream end in the clockwise direction in the left drawing of Fig. 5, and the notch 64 is formed only at the downstream end in the clockwise direction in the right drawing of Fig. 5. Therefore, when viewed from one axial direction, the notches 62 and 64 are located on opposite sides in the circumferential direction.

[0020] The description will be continued with reference to FIG. 6 together with FIG. 1 to FIG. 3. In the illustrated embodiment, the other-side member 8 is also made of metal and is integrally formed by powder metallurgy. The other-side member 8 includes a cylindrical other-side connection part 66 connected to the other of the external devices on the driving side and the driven side (such external device is not illustrated), a disk-shaped intermediate part 68 connected to one axial end of the other-side connection part 66, and an other-side locking piece 70 attached to the outer circumferential surface of the intermediate part 68. The other-side connection part 66 and the intermediate part 68 are commonly passed through in the axial direction. The outer circumferential surface of the other-side connection part 66 is formed with external connection teeth 72 such as serrations. As shown in the AA cross-sectional view of FIG. 1, the intermediate part 68 is disposed in a hole 46 formed in the support wall 42 of the shield 14 to support the one-side connection part 56 of the one-side member 6 in the axial direction. The other-side locking piece 70 extends from an axial intermediate part of the outer circumferential surface of the intermediate part 68 beyond one axial end of the intermediate part 68 to one axial side. The cross section of the other-side locking piece 70 is in the shape of a circular arc extending around the central axis o. Although not necessarily clearly shown, the other axial end face of the other-side locking piece 70 faces the support wall 42 of the shield 14, thereby preventing the one-side member 6 and the other-side member 8 from moving axially and falling off the housing 4. Here, as can be understood by referring to Fig. 3, the one-side locking piece 58 and the other-side locking piece 70 are arranged in combination so that two gaps 74a and 74b exist in the circumferential direction.

[0021] The description will be continued with reference to Figures 1 to 3. In the illustrated embodiment, the ring member 10 is made of metal and is a cylindrical rigid body having a required axial width and radial thickness (plate thickness). As shown in the AA cross-sectional view of Figure 1, one axial end of the ring member 10 is fitted (loosely fitted) into an annular groove 30 formed in an end plate 16 of the housing body 12, and the other axial end is fitted (loosely fitted) into an annular groove 51 formed in a support wall 42 of the shield 14, and the ring member 10 is supported by the housing 4 from both sides in the axial direction.

[0022] An inner coil spring 76 is attached to the inner peripheral surface of the ring member 10. In FIG. 3, the inner coil spring 76 is lightly marked for easy understanding (the same applies to FIG. 7 and FIG. 8 described later). In the illustrated embodiment, the inner coil spring 76 is made of a metal wire having a rectangular cross section. The inner coil spring 76 includes an inner winding portion 78 in which the wire is wound in a spiral shape, and two inner hook portions 80a and 80b in which the wire is bent radially inward at both axial ends of the inner winding portion 78. The outer diameter of the inner coil spring 76 in a free state, i.e., the outer diameter of the inner winding portion 78, is larger than the inner diameter of the ring member 10, and the inner coil spring 76 is brought into close contact with the ring member 10 with a relatively small force. When the inner coil spring 76 is attached to the ring member 10 and no force is acting on either of the two inner hook portions 80a and 80b, a torque generated by the inner coil spring 76 tightly contacting the ring member 10 is referred to as an inner holding torque, and this inner holding torque is relatively small. The two inner hook portions 80a and 80b are disposed at different angular positions in the circumferential direction, and each of the two inner hook portions 80a and 80b is inserted into each of the two gaps 74a and 74b described above, as shown in Fig. 3. A lubricant is applied to the inner coil spring 76.

[0023] An outer coil spring 82 is attached to the outer circumferential surface of the ring member 10. In FIG. 3, the outer coil spring 82 is also lightly marked for easy understanding (the same applies to FIG. 7 and FIG. 8 described later). In the illustrated embodiment, the outer coil spring 82 is positioned in alignment with the inner coil spring 76 in the axial direction. The outer coil spring 82 is also made of a metal wire having a rectangular cross section. The outer coil spring 82 includes an outer winding portion 84 in which the wire is wound in a spiral shape, and two outer hook portions 86a and 86b in which the wire is bent radially outward at both axial ends of the outer winding portion 84. The winding direction of the wire as viewed from one axial direction is the same for the inner coil spring 76 and the outer coil spring 82. In a free state, the inner diameter of the outer coil spring 82, i.e., the inner diameter of the outer wound portion 84, is smaller than the outer diameter of the ring member 10, and the outer coil spring 82 is brought into close contact with the ring member 10 with a relatively large force. When the outer coil spring 82 is attached to the ring member 10 and no force is applied to either of the two outer hook portions 86a and 86b, the torque generated by the outer coil spring 82 coming into close contact with the ring member 10 is called the outer holding torque, and this outer holding torque is relatively large. The two outer hook portions 86a and 86b are disposed at different angular positions in the circumferential direction, and each of the two outer hook portions 86a and 86b is inserted into two of the multiple recesses 34 formed on the inner peripheral surface of the outer peripheral wall 18 of the housing main body 12, as shown in FIG. 3. The outer coil spring 82 is also coated with a lubricant.

[0024] Next, the operation of the bidirectional torque limiter 2 will be described. First, a case where a rotational torque is applied to the one-side member 6 in the clockwise direction (as viewed from the right side of the AA cross section in FIG. 1; the same applies below) from one of the external devices not shown will be described with reference to FIG. 1, FIG. 3, and FIG. 7. In this case, the one-side locking piece 58 rotates in the clockwise direction, and its circumferential end face (more specifically, the circumferential end face on the downstream side in the clockwise direction) pushes the inner hook portion 80a of the inner coil spring 76 in the clockwise direction. In the illustrated embodiment, the notched end face 65a pushes the inner hook portion 80a. Since the outer coil spring 82 is also mounted on the outer peripheral surface of the ring member 10 to which the inner coil spring 76 is mounted, when the inner hook portion 80a is pushed in the clockwise direction and the ring member 10 tries to rotate in the clockwise direction together with the inner coil spring 76, the outer hook portion 86a is pushed in the counterclockwise direction by the housing 4 at the recess 34. Here, when the inner hook portion 80a is pressed clockwise, the inner coil spring 76, i.e., the inner wound portion 78, is expanded in diameter, and the contact between the outer peripheral surface of the inner wound portion 78 and the inner peripheral surface of the ring member 10 is strengthened. Therefore, the ring member 10 tries to rotate clockwise together with the inner coil spring 76. On the other hand, when the outer hook portion 86a is pressed counterclockwise, the outer coil spring 82, i.e., the outer wound portion 84, is expanded in diameter, and the contact between the inner peripheral surface of the outer wound portion 84 and the outer peripheral surface of the ring member 10 is weakened. For this reason, when the rotational torque applied to the one-side member 6 is larger than the relatively large outer holding torque, the ring member 10 slips relative to the outer coil spring 82. In other words, with the outer coil spring 82 held by the housing 4, the ring member 10 starts to rotate relative to the outer coil spring 82, and the one-side member 6, the inner coil spring 76, and the ring member 10 start to rotate clockwise together. Then, after the non-notched end surface 65b of the one-side locking piece 58 comes into contact with the circumferential end surface of the other-side locking piece 70 (more specifically, the circumferential end surface on the upstream side in the clockwise direction), the one-side member 6, the inner coil spring 76, and the ring member 10 rotate together with the other-side member 8 in the clockwise direction as a unit, as shown in Fig. 7. In other words, the clockwise rotation applied to the one-side member 6 is transmitted to the other-side member 8. At this time, the inner hook portion 80a moves away from the circumferential end surface of the other-side locking piece 70.When the rotational torque applied to the one-side member 6 is smaller than the relatively large outer holding torque, the one-side member 6 does not rotate and is held by the outer holding torque.

[0025] When the one-side member 6 rotates counterclockwise, the situation is the same as when the one-side member 6 rotates clockwise, except that the one-side locking piece 58 presses the inner hook portion 80b of the inner coil spring 76 and the housing 4 presses the outer hook portion 86b of the outer coil spring 82, so a detailed description will be omitted. In this case as well, the inner hook portion 80b and the outer hook portion 86b are both pressed in the direction in which the respective coil springs expand in diameter. The magnitude of the rotational torque at which the ring member 10 starts to rotate relative to the outer coil spring 82 is the same as that when the one-side member 6 rotates clockwise.

[0026] Next, a case where a rotational torque is applied to the other-side member 8 in the counterclockwise direction from the other external device (not shown) will be described with reference to Fig. 1, Fig. 3, and Fig. 8. In this case, the other-side locking piece 70 rotates in the counterclockwise direction, and its circumferential end face (more specifically, the circumferential end face on the downstream side in the counterclockwise direction) pushes the inner hook portion 80a of the inner coil spring 76 in the counterclockwise direction. Since the outer coil spring 82 is also mounted on the outer peripheral surface of the ring member 10 to which the inner coil spring 76 is mounted, when the inner hook portion 80a is pushed in the counterclockwise direction and the ring member 10 tries to rotate in the counterclockwise direction together with the inner coil spring 76, the outer hook portion 86b is pushed in the clockwise direction by the housing 4 at the recess 34. Here, when the inner hook portion 80a is pushed in the counterclockwise direction, the inner coil spring 76, i.e., the inner wound portion 78, is reduced in diameter, and the intimate contact between the outer peripheral surface of the inner wound portion 78 and the inner peripheral surface of the ring member 10 is weakened. Furthermore, when the outer hook portion 86b is pressed clockwise, the outer coil spring 82, i.e., the outer wound portion 84, is expanded in diameter, and the tight contact between the inner peripheral surface of the outer wound portion 84 and the outer peripheral surface of the ring member 10 is weakened. For this reason, when the rotational torque applied to the one-side member 6 is greater than the relatively small inner holding torque, the inner coil spring 76 slips relative to the ring member 10. In other words, with the ring member 10 held by the outer coil spring 82, the inner coil spring 76 starts to rotate relative to the ring member, and the other-side member 8 and the inner coil spring 76 start to rotate counterclockwise as a unit. 8, the circumferential end face of the other-side locking piece 70 (more specifically, the circumferential end face on the downstream side in the counterclockwise direction) together with the inner hook portion 80a comes into contact with the non-notched end face 65b of the one-side member 6 (the non-notched end face 65b is located on the upstream side in the counterclockwise direction) and pushes them in the counterclockwise direction, so that the other-side member 8 and the inner coil spring 76 rotate counterclockwise together with the one-side member 6. In other words, the counterclockwise rotation applied to the other-side member 8 is transmitted to the one-side member 6. At this time, the inner hook portion 80a is separated from the notched end face 65a of the one-side locking piece 58. Note that if the rotational torque applied to the other-side member 8 is smaller than the relatively small inner holding torque, the other-side member 8 does not rotate and is held by the inner holding torque.

[0027] When the other-side member 8 rotates clockwise, the situation is the same as when the other-side member 8 rotates counterclockwise, except that the other-side locking piece 70 presses the inner hook portion 80b of the inner coil spring 76 and the housing 4 presses the outer hook portion 86a of the outer coil spring 82, and therefore a detailed description thereof will be omitted. In this case as well, the inner hook portion 80b is pressed in a direction in which the inner coil spring 76 contracts in diameter, and the outer hook portion 86a is pressed in a direction in which the outer coil spring 82 expands in diameter. The magnitude of the rotational torque at which the inner coil spring 76 starts to rotate relative to the ring member 10 is the same as that when the other-side member 8 rotates counterclockwise.

[0028] In other words, in the bidirectional torque limiter 2, the magnitude of the rotational torque at which slippage, i.e., rotation, begins differs between when the rotational torque is transmitted from the one-side member 6 to the other-side member 8 and when the rotational torque is transmitted from the other-side member 8 to the one-side member 6, and is set to be larger in the former case than in the latter case. For this reason, if, for example, a hatchback, which is a driven external device, is connected to the one-side connecting portion 56 of the one-side member 6, and an electric motor, which is a driving external device, is connected to the other-side connecting portion 66 of the other-side member 8, the electric motor can open and close the hatchback with a relatively light load, while when the hatchback is fully open or in an intermediate angle position, the angular position of the hatchback is maintained without flapping under a relatively light load caused by disturbances such as wind. Therefore, the bidirectional torque limiter according to the present invention can also be used as an angular position maintaining device.

[0029] Among bidirectional torque limiters having such properties, in the bidirectional torque limiter of the present invention, the inner coil spring 76 and the outer coil spring 82 are respectively attached to the inner and outer circumferential surfaces of the common ring member 10, and therefore the number of parts can be reduced by one compared to, for example, a leading bidirectional torque limiter in which the inner coil spring and the outer coil spring are respectively attached to the outer circumferential surfaces of two different ring members (inner ring and outer ring). Furthermore, in the bidirectional torque limiter of the present invention, alignment between the outer coil spring and the inner coil spring and the ring member is not required, and therefore the assembly process is simplified. In the leading bidirectional torque limiter, it is necessary to separately align the inner coil spring and the outer ring.

[0030] Furthermore, in the illustrated embodiment, the one-side member 6, the other-side member 8, the ring member 10, the inner coil spring 76, and the outer coil spring 82 are made of metal, but the housing 4 is made of synthetic resin. Therefore, when the one-side locking piece 58 and the other-side locking piece 70 abut against the inner hook portion 80a or 80b of the inner coil spring 76, a sound is generated because of a collision between metals, but when the outer hook portion 86a or 86b of the outer coil spring 82 abuts against the housing 4, a sound is generated because of a collision between metal and synthetic resin. If the housing 4 is made of metal, the sound generated when the outer hook portion 86a or 86b collides with the housing 4 is added, and the above sound generated during operation becomes excessively large. It is possible to make the one-side member and the other-side member from synthetic resin, but since these members are connected to external members, relatively high strength is required, and it is preferable to form them from metal, particularly powder metallurgy.

[0031] Furthermore, in the illustrated embodiment, when the one-side member 6 rotates, the notched end face 65a presses one of the two inner hook portions 80a and 80b, and the non-notched end face 65b presses the circumferential end face of the other-side locking piece 8, so that one of the two inner hook portions 80a and 80b pressed by the notched end face 65a moves away from the circumferential end face of the other-side locking piece 70, while when the other-side member 8 rotates, the circumferential end face of the other-side locking piece 70 presses the non-notched end face 65b of the one-side member 6 together with one of the two inner hook portions 80a and 80b, and one of the two inner hook portions 80a and 80b pressed by the other-side locking piece 70 moves away from the notched end face 65a of the one-side locking piece 58. In other words, regardless of whether rotational torque is applied from the one-side member 6 or the other-side member 8, the inner hook portions 80a and 80b are not pinched by the circumferential end faces of the one-side locking piece 58 and the other-side locking piece 70, and the inner hook portions 80a and 80b are not positioned on the transmission path of the rotational torque from the one-side member 6 to the other-side member 8 or vice versa. Therefore, when the rotational torque is applied, force is prevented from concentrating on the inner hook portions 80a and 80b, and damage to the inner hook portions 80a and 80b is prevented.

[0032] The bidirectional torque limiter constructed according to the present invention has been described above in detail with reference to the attached drawings. However, the present invention is not limited to the above-described embodiment, and appropriate modifications and changes can be made without departing from the scope of the present invention. For example, in the above-described embodiment, the two inner hook portions 80a and 80b of the inner coil spring 76 are inserted into the two gaps 74a and 74b generated when the one-side locking piece 58 and the other-side locking piece 70 are combined, but instead, the two outer hook portions of the outer coil spring may be inserted. Such a modified example will be described with reference to FIG. 9. FIG. 9 is a view corresponding to FIG. 3. In FIG. 9, the same components as those in FIG. 3 are indicated by the same numbers with "'" and detailed description thereof will be omitted. In this modified example, the outer coil spring 82' is brought into close contact with the ring member 10' with a smaller force than the inner coil spring 76'. A locking means 88' having an arc-shaped cross section and extending linearly in the axial direction is formed in the center of the housing 4', which is the fixed member (therefore, the locking means 88' is fixed), and the inner coil spring 76' is disposed along the outer circumferential surface of the locking means 88'. When a rotational torque is applied to either the one-side member 6' or the other-side member 8' so that the inner coil spring 76' tends to rotate together with the ring member 10', one of the two inner hook portions 80a' and 80b' is pressed by the locking means 88', more specifically, its circumferential end face, in a direction in which the inner coil spring 76' contracts in diameter. Therefore, when a rotational torque is applied to the one-side member 6', one of the two outer hook portions 86a' and 86b' is pushed by the one-side locking piece 58' in the direction in which the outer coil spring 82' contracts in diameter, and one of the two inner hook portions 80a' and 80b' is pushed by the locking means 88' in the direction in which the inner coil spring 76' contracts in diameter, and the one-side member 6' rotates integrally with the outer coil spring 82' and the ring member 10' against the relatively large braking torque applied by the inner coil spring 76', transmitting the rotation to the other-side member 8'.On the other hand, when a rotational torque is applied to the other-side member 8', one of the two outer hook portions 86a' and 86b' is pushed by the other-side locking piece 70' in the direction in which the outer coil spring 82' expands in diameter, and one of the two inner hook portions 80a' and 80b' is pushed by the locking means 88' in the direction in which the inner coil spring 76' contracts in diameter, and in a state in which the ring member 10' is held by the inner coil spring 76', the other-side member 8' rotates together with the outer coil spring 82' relative to the ring member 10' against a relatively small braking torque by the outer coil spring 82', transmitting the rotation to the one-side member 6'. In this modified example, the locking means 88' does not necessarily need to be disposed in the housing 4' as long as it is fixed, and therefore the housing 4' may be omitted. When the housing 4' is omitted, the locking means 88' itself becomes a fixed member, or is provided as a part of a separate fixed member (not shown).

[0033] In the illustrated embodiment, the cross sections of the one-side locking piece and the other-side locking piece are both arc-shaped extending around the central axis and are each composed of a single member, but the one-side locking piece and the other-side locking piece may each be composed of two separate columnar members spaced apart in the circumferential direction. Depending on the intended use, all of the constituent members may be made of synthetic resin or metal. Furthermore, the cross sections of the wire material constituting the inner coil spring and the outer coil spring may be circular instead of rectangular. [Explanation of symbols]

[0034] 2: Bidirectional torque limiter 4: Housing 6: One-sided member 8: Other side member 10: Ring material 34: (Housing) recess 58: One-sided locking piece 70: Other side locking piece 74a and 74b: gap 76: Inner coil spring 80a and 80b: inner hook portion 82: Outer coil spring 86a and 86b: Outer hook parts

Claims

1. The device comprises a fixed housing, a one-side member, an other-side member, and a cylindrical ring member, the one-side member and the other-side member having a common central axis within the housing, a one-side locking piece extending in an axial direction is formed on the one-side member, and an other-side locking piece extending in an axial direction is formed on the other-side member, and the one-side locking piece and the other-side locking piece are combined and arranged so that two gaps are present in a circumferential direction, an inner coil spring is attached to an inner peripheral surface of the ring member, an outer diameter of the inner coil spring in a free state is larger than an inner diameter of the ring member, the inner coil spring is brought into close contact with the ring member with a relatively small force, the inner coil spring has two inner hook portions at different angular positions in the circumferential direction, and each of the two inner hook portions is inserted into each of the two gaps; An outer coil spring is attached to the outer peripheral surface of the ring member, the inner diameter of the outer coil spring in a free state is smaller than the outer diameter of the ring member, and the outer coil spring is brought into close contact with the ring member with a relatively large force, the outer coil spring has two outer hook portions at different angular positions in the circumferential direction, and each of the two outer hook portions is inserted into a recess formed in the inner peripheral surface of the housing, When a rotational torque is applied to the one-side member, one of the two inner hook portions is pushed by the one-side locking piece in a direction in which the inner coil spring expands in diameter, and one of the two outer hook portions is pushed by the housing in the recess in a direction in which the outer coil spring expands in diameter, and the one-side member rotates integrally with the inner coil spring and the ring member against a relatively large braking torque applied by the outer coil spring to transmit the rotation to the other-side member, When a rotational torque is applied to the other-side member, one of the two inner hook portions is pushed by the other-side locking piece in the direction in which the inner coil spring contracts, and one of the two outer hook portions is pushed by the housing at the recess in the direction in which the outer coil spring expands, and with the ring member held by the outer coil spring, the other-side member rotates together with the inner coil spring relative to the ring member against the relatively small braking torque applied by the inner coil spring, transmitting the rotation to the one-side member.

2. 2. The bidirectional torque limiter according to claim 1, wherein the cross sections of the one-side locking piece and the other-side locking piece are both arc-shaped extending around the central axis.

3. A notch is formed at each of the circumferential ends of both axial end portions of the one-side locking piece, and the circumferential end surface of the one-side locking piece is divided into a notched end surface where the notch is formed and a non-notched end surface where the notch is not formed, 3. The bidirectional torque limiter according to claim 2, wherein when the one-side member rotates, the notched end face presses one of the two inner hook portions and the non-notched end face presses the circumferential end face of the other-side locking piece, such that either of the two inner hook portions pressed by the notched end face moves away from the circumferential end face of the other-side locking piece, whereas when the other-side member rotates, the circumferential end face of the other-side locking piece presses the non-notched end face of the one-side member together with either of the two inner hook portions, such that either of the two inner hook portions pressed by the other-side locking piece moves away from the notched end face of the one-side locking piece.

4. 2. The bidirectional torque limiter according to claim 1, wherein the housing is provided with an annular groove into which both axial ends of the ring member are loosely fitted.

5. 2. The bidirectional torque limiter according to claim 1, wherein the one-side member, the other-side member, the ring member, the inner coil spring and the outer coil spring are made of metal, and the housing is made of synthetic resin.

6. The device includes a fixed member, a one-side member, an other-side member, and a cylindrical ring member, the one-side member and the other-side member having a common central axis, a one-side locking piece extending in an axial direction is formed on the one-side member, and an other-side locking piece extending in an axial direction is formed on the other-side member, and the one-side locking piece and the other-side locking piece are combined and arranged so that two gaps are present in a circumferential direction, an outer coil spring is attached to the outer peripheral surface of the ring member, the inner diameter of the outer coil spring in a free state is smaller than the outer diameter of the ring member, the outer coil spring is brought into close contact with the ring member with a relatively small force, the outer coil spring has two outer hook portions at different angular positions in the circumferential direction, and each of the two outer hook portions is inserted into each of the two gaps; an inner coil spring is attached to an inner peripheral surface of the ring member, an outer diameter of the inner coil spring in a free state is larger than an inner diameter of the ring member, the inner coil spring is brought into intimate contact with the ring member with a relatively large force, the inner coil spring has two inner hook portions at different angular positions in the circumferential direction, and each of the two inner hook portions can be engaged with an engaging means provided on the fixed member, When a rotational torque is applied to the one-side member, one of the two outer hook portions is pushed by the one-side locking piece in a direction in which the outer coil spring contracts in diameter, and one of the two inner hook portions is pushed by the locking means in a direction in which the inner coil spring contracts in diameter, and the one-side member rotates integrally with the outer coil spring and the ring member against a relatively large braking torque applied by the inner coil spring to transmit the rotation to the other-side member, When a rotational torque is applied to the other-side member, one of the two outer hook portions is pushed by the other-side locking piece in the direction in which the outer coil spring expands in diameter, and one of the two inner hook portions is pushed by the locking means in the direction in which the inner coil spring contracts in diameter, and with the ring member held by the inner coil spring, the other-side member rotates together with the outer coil spring relative to the ring member against the relatively small braking torque applied by the outer coil spring, transmitting the rotation to the one-side member.

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