320C Excavator Hydraulic System – Swing Drive



Illustration 1 g00674518

Swing drive

(1) First stage planetary carrier

(2) First stage planetary gear

(3) Second stage planetary carrier

(4) Ring gear

(5) Second stage planetary gear

(6) Roller bearing

(7) Roller bearing

(8) Pinion shaft

(10) Shaft (swing motor)

(11) First stage sun gear

(12) Second stage sun gear

(14) Housing

(15) Bearing gear (swing gear)

The swing drive consists of a series of planetary gears. The planetary gears reduce the rotational speed of the swing motor. The swing motor is bolted to the top of the swing drive. The swing drive is bolted to the upper structure. The teeth of the swing drive output pinion shaft (8) engage with bearing gear (15) of the swing bearing. The pinion shaft (8) rotates around bearing gear (15). This causes the machine to swing. Bearing gear (15) is attached to the lower structure.

The swing drive is divided into the following two groups :

  • The first group is a double reducer of motor speed. The components of the first stage reduction are first stage sun gear (11), first stage planetary gears (2), ring gear (4) and first stage planetary carrier (1). The components of the second stage reduction are second stage sun gear (12), second stage planetary gear (5), ring gear (4) and second stage planetary carrier (3) .

  • The second group is the group for reduced output speed of the motor. The components of the second group are roller bearing (6), roller bearing (7) and pinion shaft (8). The roller bearings are installed in housing (14) and the roller bearings support pinion shaft (8) .

The swing speed is reduced by a ratio of teeth on the sun gear to ring gear teeth by planetary reduction. Since the sun gear is inside of the ring gear, the swing drive is more compact than reduction units with external teeth.




Illustration 2 g00721789

Operation of the first stage planetary assembly

(1) First stage planetary carrier

(2) First stage planetary gear

(4) Ring gear

(11) First stage sun gear

(16) Shaft (first stage planetary gear)

Swing motor output shaft (10) is splined to first stage sun gear (11). First stage planetary gears (2) of first stage planetary carrier (1) mesh with first stage sun gear (11). When first stage sun gear (11) rotates counterclockwise, first stage planetary gears (2) rotate in a clockwise direction on shafts (16). First stage planetary gears (2) move counterclockwise around ring gear (4). Ring gear (4) is bolted to housing (14). First stage planetary carrier (1) rotates counterclockwise.




Illustration 3 g00674912

Swing drive

(1) First stage planetary carrier

(2) First stage planetary gear

(3) Second stage planetary carrier

(4) Ring gear

(5) Second stage planetary gear

(6) Roller bearing

(7) Roller bearing

(8) Pinion shaft

(11) First stage sun gear

(12) Second stage sun gear

(17) Inner circumference of carrier

Splines on inner circumference (17) of first stage planetary carrier (1) engage with the splines on second stage sun gear (12). This causes second stage sun gear (12) to rotate counterclockwise when the first stage planetary carrier rotates. Second stage planetary gears (5) turn clockwise on the shafts and second stage planetary gears (5) move in a counterclockwise direction around ring gear (4). Second stage planetary carrier (3) turns counterclockwise around ring gear (4). The splines on the inner circumference of second stage planetary carrier (3) engage with the splines of pinion shaft (8). When the second stage planetary carrier turns clockwise, pinion shaft (8) rotates counterclockwise.




Illustration 4 g00766951

Rotation of pinion shaft

(8) Pinion shaft

(15) Bearing gear (swing bearing)

(18) Position of moving pinion shaft

Pinion shaft (8) engages with bearing gear (15) on the inner circumference of the swing bearing. Bearing gear (15) is bolted to the lower structure. As pinion shaft (8) rotates counterclockwise, pinion shaft (8) moves in a clockwise direction around bearing gear (15). The upper structure also rotates in a clockwise direction around bearing gear (15). This causes the upper structure to swing to the right (clockwise rotation).