Rotary damper

Abstract

The present invention provides a rotary damper that generates braking force during rotation of a rotor (20), the rotary damper comprising a clutch (30) having: an internal gear (31) that rotates simultaneously with the rotor; teeth (32) that mesh with the internal gear; a block (33) for which the teeth are formed; a recess (34) that holds the block in the circumferential direction; a flange (35) in which the recess is formed; a shaft (36) on which the flange is formed; and a spring (37) that radially supports the block.

Description

rotary damper

[0001] The present invention relates to a rotary damper having a clutch that transmits an external force to the rotor when the shaft of the clutch rotates in one direction, causing the rotor to rotate in one direction, and blocks the external force when the shaft rotates in the opposite direction, preventing the rotor from rotating in the opposite direction.

[0002] International Publication No. 2016-120835, which may be considered the prior art closest to the present invention, discloses a rotary damper that generates a braking force when a rotor rotates, the rotary damper including a clutch. The clutch includes an internal gear that rotates simultaneously with the rotor, teeth that mesh with the internal gear, a block on which the teeth are formed, a recess formed in the block, a protrusion movable within the recess, and a shaft on which the protrusion is formed. The outer surface of the block facing the internal gear has a portion on which the teeth are formed (portion A) and a portion on which the teeth are not formed (portion B). When the shaft rotates in one direction, the protrusion moves on an imaginary line connecting the center of the rotor and portion A, thereby engaging the teeth with the internal gear and rotating the rotor in one direction. On the other hand, when the shaft rotates in the reverse direction, the protrusion moves on an imaginary line connecting the center of the rotor and portion B, thereby disengaging the teeth from the internal gear. Therefore, the rotor does not rotate in the reverse direction.

[0003] However, in conventional clutches, the teeth continue to remain disengaged from the internal gear even after the shaft has stopped rotating in the reverse direction, resulting in a time lag between the start of the shaft rotating in one direction and the start of the rotor rotating in that direction.

[0004] International Publication No. 2016-120835

[0005] The problem that the present invention aims to solve is to make it possible to eliminate the time lag between the start of rotation of the clutch shaft in one direction after the shaft has finished rotating in the opposite direction and the start of rotation of the rotor in that direction.

[0006] In order to solve the above problem, the present invention provides a rotary damper that generates a braking force when a rotor rotates, comprising: an internal gear that rotates simultaneously with the rotor; teeth that mesh with the internal gear; a block on which the teeth are formed; a recess that holds the block circumferentially; a flange on which the recess is formed; a shaft on which the flange is formed; and a spring that supports the block radially, wherein the teeth mesh with the internal gear by the restoring force of the spring when the shaft is stationary, the pressure angle of a first tooth flank of the internal gear that faces one of the two tooth flanks of the teeth is set to an angle that allows the teeth to apply pressure to the first tooth flank when the shaft rotates in one direction, and the pressure angle of a second tooth flank of the internal gear that faces the other of the two tooth flanks of the teeth is set to an angle that allows the teeth to disengage from the internal gear when the shaft rotates in the opposite direction.

[0007] According to the present invention, when the shaft comes to a standstill after completing its reverse rotation, the teeth formed on the block mesh with the internal gear due to the restoring force of the spring that radially supports the block, and the pressure angle of the first tooth flank of the internal gear that faces one of the two tooth flanks of the teeth is set to an angle that allows the teeth to apply pressure to the first tooth flank when the shaft rotates in one direction, so that when the stationary shaft starts to rotate in one direction, the teeth simultaneously apply pressure to the first tooth flank, thereby rotating the internal gear and the rotor. Also, according to the present invention, if the shaft rotates in one direction immediately after completing its reverse rotation, the teeth mesh with the internal gear due to the restoring force of the spring immediately after disengaging from the internal gear, so that when the shaft starts to rotate in one direction, the teeth simultaneously apply pressure to the first tooth flank, thereby rotating the internal gear and the rotor. Therefore, according to the present invention, it is possible to eliminate the time lag between the start of rotation of the shaft in one direction and the start of rotation of the rotor in that direction after the shaft has finished rotating in the reverse direction. According to the present invention, the pressure angle of the second tooth flank of the internal gear, which faces the other of the two tooth flanks of the tooth, is set to an angle that allows the tooth to disengage from the internal gear when the shaft rotates in the reverse direction. Therefore, when the shaft rotates in the reverse direction, the tooth moves along the second tooth flank and disengages from the internal gear without applying pressure to the second tooth flank. The movement of the tooth is made possible by deformation of the spring. Therefore, according to the present invention, the internal gear and the rotor do not rotate when the shaft rotates in the reverse direction.

[0008] Fig. 1 is a cross-sectional view of a rotary damper according to an embodiment; Fig. 2 is an exploded perspective view of a rotary damper according to an embodiment; Fig. 3 is a diagram showing a block employed in the embodiment; Fig. 4 is a diagram showing a part of an internal gear employed in the embodiment; Fig. 5 is a diagram for explaining the operation of a clutch employed in the embodiment; Fig. 6 is a diagram for explaining the operation of a clutch employed in the embodiment.

[0009] The present invention is applied to a rotary damper that generates a braking force when a rotor rotates, and is characterized by including a novel clutch that rotates the rotor in only one direction. Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the technical scope of the present invention is not limited to the embodiments.

[0010] 1 and 2, the rotary damper according to the embodiment includes a casing 10, a rotor 20, and a clutch 30.

[0011] The casing 10 has a cylindrical peripheral wall 11 , a lid 12 that closes one end of the peripheral wall 11 , and a bottom wall 13 that closes the other end of the peripheral wall 11 .

[0012] The rotor 20 has a cylindrical peripheral wall 21. One end of the peripheral wall 21 is open. A bottom wall 22 is provided at the other end of the peripheral wall 21.

[0013] The rotor 20 is housed in the casing 10 .

[0014] An O-ring 70 is installed between the rotor 20 and the lid 12 to prevent the viscous fluid injected into the casing 10 from leaking out.

[0015] The outer peripheral surface of the rotor 20 (i.e., the outer peripheral surface of the peripheral wall 21) and the inner peripheral surface of the casing 10 (i.e., the inner peripheral surface of the peripheral wall 11) face each other.

[0016] The viscous fluid is injected into a gap formed between the outer circumferential surface of the rotor 20 and the inner circumferential surface of the casing 10 .

[0017] This viscous fluid generates shear resistance when the rotor 20 rotates inside the casing 10. The shear resistance of the viscous fluid acts as a damping force that attenuates the rotational force of the rotor 20.

[0018] The clutch 30 has an internal gear 31 that rotates simultaneously with the rotor 20, teeth 32 that mesh with the internal gear 31, a block 33 on which the teeth 32 are formed, a recess 34 that holds the block 33 circumferentially, a flange 35 on which the recess 34 is formed, a shaft 36 on which the flange 35 is formed, and a spring 37 that supports the block 33 radially.

[0019] The internal gear 31 is formed inside the peripheral wall 21 of the rotor 20. Therefore, the internal gear 31 rotates simultaneously with the rotor 20.

[0020] A plurality of teeth 32 are formed on the surface of the block 33 that faces the internal gear 31 .

[0021] The recesses 34 are formed in three equal areas of the circular flange 35, and the blocks 33 are disposed in the three recesses 34, respectively.

[0022] In the conventional technology, a member interposed between the block and the rotor is required to hold the block in the circumferential direction and support it in the direction perpendicular to the radial direction. In contrast, in the embodiment, the block 33 is held in the circumferential direction by the recess 34 and is directly supported in the direction perpendicular to the radial direction by the rotor 20 (i.e., the bottom wall 22 of the rotor 20), so it is not necessary to install a member interposed between the block 33 and the rotor 20. Therefore, the structure of the embodiment can result in a simplified structure and reduced manufacturing costs.

[0023] The shaft 36 protrudes outward from a hole 14 formed in the lid 12. The shaft 36 is also inserted into and supported by a hole 23 formed in the bottom wall 22 of the rotor 20.

[0024] The shaft 36 is connected to a drive source that rotates the rotor 20 .

[0025] The spring 37 is, but is not limited to, an arc-shaped torsion spring. The arc-shaped spring 37 can support all the blocks in the radial direction with a single spring, which can simplify the structure and reduce manufacturing costs.

[0026] In order to increase the damping force, the rotary damper according to the embodiment further includes an input shaft 24 protruding from the rotor 20, a plurality of rotating plates 40 connected to the input shaft 24, a plurality of fixed plates 50 connected to the casing 10 and arranged alternately with the rotating plates 40, and a plurality of spacers 60 arranged between the rotating plates 40 and the fixed plates 50. These elements are housed within the casing 10.

[0027] The input shaft 24 protrudes from the bottom wall 22 of the rotor 20. The input shaft 24 is hollow and is supported by a boss 15 formed on the bottom wall 13 of the casing 10.

[0028] The rotary plate 40 has a hole 41 into which the input shaft 24 is inserted and a protrusion 42 protruding from the hole 41. The rotary plate 40 is coupled to the input shaft 24 by fitting the protrusion 42 into a recess formed in the input shaft 24.

[0029] The fixed plate 50 has a hole 51 into which the input shaft 24 is inserted and a protrusion 52 formed on the outer periphery of the fixed plate 50. The fixed plate 50 is coupled to the casing 10 by fitting the protrusion 52 into a recess 16 formed in the peripheral wall 11 of the casing 10.

[0030] The spacer 60 has a hole 61 into which the input shaft 24 is inserted. The spacer 60 is arranged to form a gap between the rotating plate 40 and the fixed plate 50. In this embodiment, the spacer 60 is also arranged between the rotor 20 and the fixed plate 40 and between the rotating plate 40 and the casing 10.

[0031] The viscous fluid is injected into the gap formed between the rotor 20 and the fixed plate 40, the gap formed between the rotating plate 40 and the fixed plate 50, and the gap formed between the rotating plate 40 and the casing 10.

[0032] This viscous fluid generates shear resistance when the rotor 20, the input shaft 24, and the rotating plate 40 connected to the input shaft 24 rotate simultaneously. The shear resistance of the viscous fluid acts as a braking force that attenuates the rotational force of the rotor 20. Therefore, a braking force greater than the braking force generated between the rotor and the casing can be generated.

[0033] Referring to FIG. 3, the tooth 32 formed on the block 33 has two tooth surfaces (i.e., one tooth surface 32a and the other tooth surface 32b).

[0034] In the embodiment, the pressure angle α1 of one tooth flank 32a is smaller than the pressure angle α2 of the other tooth flank 32b, but the pressure angle α1 may be the same as or larger than the pressure angle α2.

[0035] Referring to Figure 4, the pressure angle α3 of the first tooth flank 31a of the internal gear 31, which faces one tooth flank 32a of the tooth 32, is set to an angle that allows the tooth 32 to apply pressure to the first tooth flank 31a when the shaft 36 rotates in one direction.

[0036] The pressure angle α3 is the same as or approximately the same as the pressure angle α1 of one tooth flank 32 a of the tooth 32 .

[0037] The pressure angle α4 of the second tooth surface 31b of the internal gear 31, which faces the other tooth surface 32b of the tooth 32, is set to an angle that allows the tooth 32 to disengage from the internal gear 31 when the shaft 36 rotates in the reverse direction.

[0038] The pressure angle α4 is the same as or approximately the same as the pressure angle α2 of the other tooth flank 32b of the tooth 32, but may be larger than the pressure angle α2.

[0039] The pressure angle α3 is smaller than the pressure angle α4.

[0040] Referring to FIG. 5, in the rotary damper according to the embodiment, when the shaft 36 is stationary, the teeth 32 of the block 33 are engaged with the internal gear 31 by the restoring force of the spring 37 .

[0041] When the stationary shaft 36 starts to rotate in one direction (clockwise in FIG. 5 ), the teeth 32 of the block 33 simultaneously apply pressure to the first tooth surface 31 a of the internal gear 31, causing the internal gear 31 and the rotor 20 to rotate simultaneously. Therefore, there is no time lag between when the shaft 36 starts to rotate in one direction and when the rotor 20 starts to rotate in that direction.

[0042] While the rotor 20 is rotating, shear resistance is generated by the viscous fluid injected between the rotor 20 and the casing 10. At the same time, shear resistance is generated by the viscous fluid injected between the rotating plate 40 and the fixed plate 50. As a result, a large braking force is applied to the rotor 20.

[0043] 6 , in the rotary damper according to the embodiment, when the shaft 36, which is stationary, starts to rotate in the opposite direction (counterclockwise in FIG. 6 ), the teeth 32 of the block 33 move along the second tooth flank 31 b of the internal gear 31 without applying pressure to the second tooth flank 31 b. This movement is made possible by the deformation of the spring 37 that supports the block 33 in the radial direction. That is, the block 33 can move in a direction approaching the shaft 36 due to the deformation of the spring 37. The spring 37 (an arc-shaped torsion spring) is subjected to a torsional moment by this movement of the block 33.

[0044] When the shaft 36 rotates in the reverse direction by a predetermined angle, the teeth 32 of the block 33 disengage from the internal gear 31, and immediately thereafter, they mesh with the internal gear 31 again due to the restoring force of the spring 37. The above-mentioned movement of the teeth 32 of the block 33 is repeated throughout the time that the shaft 36 is rotating in the reverse direction. Therefore, when the shaft 36 rotates in the reverse direction, no pressure is applied to the second tooth surface 31b of the internal gear 31, and therefore the internal gear 31 and the rotor 20 do not rotate.

[0045] When the shaft 36 stops rotating after the rotation in the reverse direction, the teeth 32 of the block 33 mesh with the internal gear 31 due to the restoring force of the spring 37. When the shaft 36 starts rotating in one direction immediately after the rotation in the reverse direction, the teeth 32 of the block 33 mesh with the internal gear 31 due to the restoring force of the spring 37 immediately after disengaging from the internal gear 31. Therefore, in either case, when the shaft 36 starts rotating in one direction, the teeth 32 of the block 33 simultaneously apply pressure to the first tooth flank 31 a of the internal gear 31, thereby rotating the internal gear 31 and the rotor 20. Therefore, the rotary damper according to the embodiment makes it possible to eliminate the time lag between the start of rotation of the shaft 36 in one direction and the start of rotation of the rotor 20 in that direction after the rotation of the shaft 36 in the reverse direction has ended.

[0046] DESCRIPTION OF SYMBOLS 10 Casing 11 Peripheral wall 12 Lid 13 Bottom wall 14 Hole 15 Boss 16 Recess 20 Rotor 21 Peripheral wall 22 Bottom wall 23 Hole 24 Input shaft 30 Clutch 31 Internal gear 31a First tooth surface 31b Second tooth surface 32 Teeth 32a One tooth surface 32b Other tooth surface 33 Block 34 Recess 35 Flange 36 Shaft 40 Rotating plate 41 Hole 42 Protrusion 50 Fixing plate 51 Hole 52 Protrusion 60 Spacer 61 Hole 70 O-ring

Claims

1. A rotary damper that generates a braking force when a rotor rotates, comprising: an internal gear that rotates simultaneously with the rotor; teeth that mesh with the internal gear; a block on which the teeth are formed; a recess that holds the block circumferentially; a flange on which the recess is formed; a shaft on which the flange is formed; and a spring that supports the block radially; wherein the teeth mesh with the internal gear due to the restoring force of the spring when the shaft is stationary; the pressure angle of a first tooth flank of the internal gear that faces one of the two tooth flanks of the teeth is set to an angle that allows the teeth to apply pressure to the first tooth flank when the shaft rotates in one direction; and the pressure angle of a second tooth flank of the internal gear that faces the other of the two tooth flanks of the teeth is set to an angle that allows the teeth to disengage from the internal gear when the shaft rotates in the opposite direction.

2. The rotary damper according to claim 1, wherein the spring is an arc-shaped torsion spring.

3. A rotary damper according to claim 1, wherein the block is directly supported on the rotor in a direction perpendicular to the radial direction.

4. The rotary damper according to claim 1, comprising: a casing that houses the rotor; and the following elements housed in the casing: an input shaft that protrudes from the rotor; a plurality of rotating plates that are connected to the input shaft; a plurality of fixed plates that are connected to the casing and arranged alternately with the rotating plates; spacers that are arranged between the rotating plates and the fixed plates; and a viscous fluid that is injected between the rotor and the casing and between the rotating plates and the fixed plates.

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