A joint mechanism for a construction machine includes: a first member having a first facing surface; a second member rotatable around a rotation axis relative to the first member and having a second facing surface facing the first facing surface; a power transmission mechanism for transmitting power for rotation to the second member; a first wall protruding from the first facing surface and having an annular shape around the rotation axis; and a second wall protruding from the second facing surface and having an arc-like shape around the rotation axis. The power transmission mechanism is located on an inner side of the first wall in a radial direction around the rotation axis, and the second wall is located on an outer side of the first wall in the radial direction and overlaps at least partly with the first wall in a direction along the rotation axis.

A work vehicle includes an arm cylinder configured to raise an arm assembly. A front plate is attached to a vehicle body frame in front of the arm cylinder. A back plate is attached to the vehicle body frame in back of the arm cylinder. A side plate is attached to the front plate and the back plate opposite to the vehicle body frame with respect to the arm cylinder. A bottom plate is attached to the vehicle body frame and the side frame below the arm cylinder. The front plate extends in a reference direction in which the arm cylinder is directed when a work equipment attached to the arm assembly is grounded. The bottom plate includes a downward extending portion extending in the reference direction. The downward extending portion, the front plate, the side plate, and the vehicle body frame define an opening below the arm cylinder.

A speed reducer of one embodiment includes a first speed reduction unit and a second speed reduction unit. The first speed reduction unit includes a first carrier, a first case that surrounds the first carrier and is held rotatable relatively to the first carrier, and a first reduction gear portion having a first center shaft, which is a first input portion held by the first carrier and to which rotation is inputted from a drive shaft. The second speed reduction unit includes a second carrier, a second case that surrounds the second carrier and is held rotatable relatively to the second carrier, and a second reduction gear portion having a second center shaft, which is a second input portion held by the second carrier and to which rotation is inputted together with the first center shaft from the drive shaft.

An environment-friendly work machine is provided. A work implement includes a boom supported by a vehicular body frame, an arm coupled to the boom, and an attachment coupled to the arm. A boom foot pin rotatably couples the boom to the vehicular body frame. An arm motor is supported by the vehicular body frame. The arm motor generates drive force that moves the arm relatively to the boom. A motive power transmission apparatus mechanically transmits drive force generated by the arm motor to the arm. An arm gear member and a pivot member carry out rotational motion relative to the vehicular body frame as being concentric with the boom foot pin. An arm link transmits motive power to the arm as a result of the relative rotational motion.

A drive transmission device according to one embodiment of the disclosure includes a single differential unit to which rotation of a motor is transmitted and two speed reducers each having an operation output shaft that is coupled to the differential unit and a carrier that changes a speed of the rotation of the operation output shaft and outputs the rotation. The two speed reducers are arranged such that they are opposed to each other along a second rotation axis, and the operation output shaft and the carrier in each speed reducer are aligned in the second rotation axis direction.

This electric cylinder includes a motor that serves as a driving source, an output shaft that rotates in response to driving of the motor, a first rotor that is joined to the output shaft and rotates in response to rotation of the output shaft, and a second rotor that is adjacent to the first rotor and rotates in response to rotation of the first rotor. The first rotor has an open hollow portion capable of accommodating a lubricant therein.

A speed reducer according to an embodiment includes: a carrier; a first case encircling an outer circumferential surface of the carrier between two end surfaces of the carrier, the first case being held by the carrier so as to rotate relative to the carrier; a second case encircling the outer circumferential surface of the carrier and held by the carrier at a different position than the first case so as to rotate relative to the carrier; a first reduction portion including a first input portion held by the carrier and configured to receive rotation input from a first side toward which one of the two end surfaces of the carrier faces; and a second reduction portion including a second input portion held by the carrier and configured to receive rotation input from a second side toward which another of the two end surfaces of the carrier faces.