TRANSMISSION
The power coming from the engine must be turned into useful power by controlling its speed, direction and force. Transmissions do this using either hydraulically engaged planetary clutches or hydrostatic/hydraulic drives. Each of these methods provides different characteristics of ground speed, torque, clutches maneuverability, and implement force.
Because of the wide variety of work they do, Caterpillar products use several types of transmissions, each designed to convert engine power into the exact combination of speed and force required by individual machines.
TORQUE CONVERTER
The power that is produced in the engine is multiplied in the torque converter and then transferred on to the transmission for use by the rest of the drive train components. Some Cat machines use a torque divider instead of the traditional torque converter, which divides the transmitted torque between the front and rear axles, with the rear receiving the majority. The three basic torque converter components include the impeller, the turbine, and the stator.
DRIVE SHAFT
The drive shaft is a means of connecting drive train components. It allows for misalignment in the drive. The output shaft connects to the transmission through a yoke and drive shaft or directly to the transmission input gear.
Caterpillar’s exact design for proper measurements and precise machining ensures proper gear alignment. Special heat treatment achieves proper surface hardness, core hardness, and hardened depth.
DIFFERRENTIAL
The differential decreases the speed and increases the torque as needed for each wheel’s motion adjustment. When a machine is turning, the differential supplies the needed adjustments to the wheels, allowing the outside wheel to move at a faster pace than the inside wheel.
The components of the differential are the differential case assembly, the pinion gears, the side gears, and the spider. The differential's key functions are:
- Transferring power coming from the transmission to the left and right axle shafts
- Balancing the power according to the demand of each wheel
- Further reducing the speed and increasing the torque to drive the rear wheels
FINAL DRIVE
The final drives are an important part of the drive train. They are the components that apply driving force to the wheels or tracks.
The final drives of a track-type tractor differ somewhat, but they perform the same function. They reduce rotating speed and increase torque. In fact, this is where the greatest torque rise occurs...in the gears. That allows these components ahead of the final drives to be smaller, which saves weight and space.
There are four types of final drives used in Caterpillar machines:
- Bull Gear Single Reduction
- Bull Gear Double Reduction
- Planetary Single Reduction
- Planetary Double Reduction
BRAKES
Brakes are the components that slow, stop or hold a machine stationary. On Caterpillar machines, they are located at the wheels of wheel-type machines. In track-type machines, they are located on the axle shafts.
Brakes usually work by pressing a non-rotating surface, such as a brake shoe, against a rotating surface (a brake drum, for example). The resulting friction stops the machine. At this point where the two meet, the inertial force of the machine is sometimes converted into bake-oven heat.
The braking requirements of various types of machines differ, chiefly because of differences in the work they do. To assure each type of machine has the braking system that best suits its needs, Caterpillar uses four types: Expanding Shoe, Caliper Disc, Wet Disc and Expander Tube. |
