Theory of Operation
The PTO feature provides constant engine speeds regardless of load. It can be used in a wide variety of applications that require the engine to provide power to auxiliary devices. The feature is designed to protect these devices by limiting torque and speed if necessary. It can also be setup to allow the operator to override speed control by use of the accelerator pedal.
PTO Engine Speed Limits
The PTO feature can be setup to operate within a desired engine speed range. The PTO Maximum and Minimum Engine Speed parameters will limit the engine speed during any operation where the PTO function is active.
PTO Speed Adjustment
The PTO feature has three pre-set speeds:
The PTO SET and RESUME speeds use the same cab switches as the Cruise Control feature. If the vehicle is traveling less than the customer programmable PTO Maximum Vehicle Speed, the switches are in PTO mode.
These switches are used to select one of the pre-set speeds and further adjust the engine speed to meet operational requirements while in PTO. When the operator uses the switches to adjust engine speed, the rate of speed adjustment is controlled by the PTO Engine Speed Accel/Coast Ramp Rate parameter. This ensures a smooth transition to the desired engine speed at the desired rate.
PTO is a "smart" feature. It can be setup to limit the torque output of the engine during PTO operation. This ensures that torque sensitive devices are not damaged. The PTO Maximum Engine Load parameter should be set at the maximum load rating of devices powered by the engine.
This parameter limits the torque output during ALL PTO operations, including accelerator override. If more torque than the maximum load parameter is required, the engine may not achieve the PTO maximum engine speed or vehicle speed parameters.
PTO Maximum Vehicle Speed
This is the maximum allowable vehicle speed when using PTO. The vehicle speed must be below this value to activate PTO and if the vehicle speed should exceed the PTO Maximum Vehicle Speed, PTO will be deactivated.
PTO Accelerator Override
The PTO feature can also be setup to allow the operator full use of the accelerator pedal. The PTO Accelerator Override Maximum Engine Speed parameter limits engine speed during the accelerator override event and may be set above the PTO Maximum Engine Speed parameter to allow higher engine speeds during the override condition. Remember, the engine torque output will still be limited by the PTO Maximum Engine Load parameters during accelerator pedal operation.
PTO Service Brake and Clutch Override
The PTO feature can be setup to allow the operator to disengage PTO operation with the use of the PTO Service Brake and Clutch Override features. If they are enabled the operator can disengage PTO by depressing the service brake or clutch pedals.