Speed reducer for walk assist apparatus

A reduction gear for a walking assistance system that, in order to assist walking movement by extending/bending a user's leg joint, reduces the speed of rotation of an input shaft (Si) driven by a motor (48) and transmits the rotation to an output shaft (So) connected to the leg joint, the reduction gear comprising:

• the input shaft (Si), the output shaft (So), a first planetary gear mechanism (P1), and a second planetary gear mechanism (P2) disposed coaxially on an axis (L), the second planetary gear mechanism (P2) being disposed so as to substantially overlap the radially outer side of the first planetary gear mechanism (P1), the rotation of the input shaft (Si) being reduced in speed by the first planetary gear mechanism (P1) and the second planetary gear mechanism (P2) and transmitted to the output shaft (So);
• the first planetary gear mechanism (P1) comprising a first sun gear (ZS1) provided on the input shaft (Si), a first ring gear (ZR1) rotatably disposed so as to surround the outer periphery of the first sun gear (ZS1), a plurality of first planetary gears (ZP1) meshing simultaneously with the first sun gear (ZS1) and the first ring gear (ZR1), and a first carrier (C1) rotatably supporting the first planetary gears (ZP1), and;
• the second planetary gear mechanism (P2) comprising a second sun gear (ZS2) provided on the outer periphery of the first ring gear (ZR1), a second ring gear (ZR2) disposed so as to surround the outer periphery of the second sun gear (ZS2), a plurality of second planetary gears (ZP2) meshing simultaneously with the second sun gear (ZS2) and the second ring gear (ZR2), and a second carrier (C2) rotatably supporting the second planetary gears (ZP2),
• wherein the first planetary gear mechanism (P1) is sandwiched between the first carrier (C1) and the second carrier (C2).

A reduction gear for a walking assistance system that, in order to assist walking movement by extending/bending a user's leg joint, reduces the speed of rotation of an input shaft (Si) driven by a motor (48) and transmits the rotation to an output shaft (So) connected to the leg joint, the reduction gear comprising:

• the input shaft (Si), the output shaft (So), a first planetary gear mechanism (Pl), and a second planetary gear mechanism (P2) disposed coaxially on an axis (L), the second planetary gear mechanism (P2) being disposed so as to substantially overlap the radially outer side of the first planetary gear mechanism (P1), the rotation of the input shaft (Si) being reduced in speed by the first planetary gear mechanism (P1) and the second planetary gear mechanism (P2) and transmitted to the output shaft (So);
• the first planetary gear mechanism (P1) comprising a first sun gear (ZS1) provided on the input shaft (Si), a first ring gear (ZR1) rotatably disposed so as to surround the outer periphery of the first sun gear (ZS1), a plurality of first planetary gears (ZP1) meshing simultaneously with the first sun gear (ZS1) and the first ring gear (ZR1), and a first carrier (C1) rotatably supporting the first planetary gears (ZP1), and;
• the second planetary gear mechanism (P2) comprising a second sun gear (ZS2) provided on the outer periphery of the first ring gear (ZR0, a second ring gear (ZR2) disposed so as to surround the outer periphery of the second sun gear (ZS2), a plurality of second planetary gears (ZP2) meshing simultaneously with the second sun gear (ZS2) and the second ring gear (ZR2), and a second carrier (C2) rotatably supporting the second planetary gears (ZP2), wherein the input shaft (Si), the first planetary gear mechanism (P1), the second planetary gear mechanism (P2), the motor are completely enclosed in a cylindrical casing, and the first carrier (C1) of the first planetary gear mechanism (P1) is fixed to a casing (41), the second ring gear (ZR2) of the second planetary gear mechanism (P2) is fixed to the casing (41), and the second carrier (C2) of the second planetary gear mechanism (P2) is connected to the output shaft (So).