tailieunhanh - Cooling and Lubrication System Maintenance P2

Tham khảo tài liệu 'cooling and lubrication system maintenance p2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Lesson 3. FAN DRIVE METHODS LEARNING OBJECTIVES 1. Given a sentence discussing the operation of fan drive assemblies supply the missing key words. 2. Given a sentence listing the components that make up fan drive systems supply the missing key words. We said earlier that the fan is an essential part of the cooling system and that it is designed to pull a large volume of air through the radiator core so that engine heat can be dissipated effectively. A fan that operates continuously has a significant effect on the efficiency of the cooling system. There are many times such as during cold weather or when the vehicle is in motion that the fan may not be reguired. Controlling the operation of the fan makes the cooling system more efficient. Let s look at some of the methods used to control the operation of the fan. 1301. Conventional Fan Drive M809 series Older vehicles such as the M809 series use what is classified as the conventional fan drive method. This simply means that the fan is belt driven from the crankshaft. Since the fan operates off the crankshaft it remains in constant operation as long as the engine is in operation. The speed of the fan is also determined by the speed of the engine. If the engine speed increases the fan speed increases proportionally. This type of fan operation is not very efficient nor is it the most effective method used today. There are fan drive methods that are much more efficient. In the remainder of this lesson you will examine four of these fan drive methods. Let s take a look. 1302. Air Actuated Clutch Fan M939 series vehicles The M939 series vehicles uses an air actuated clutch to drive the fan. The clutch assembly connects and disconnects the fan when the cooling system is not required. 1-31 RADIATOR DRAINCOCK Fig 1-37. HMMWV fan drive system. 1-34 A time delay module fig 1-37 in the HMMWV fan drive system helps maximize the horsepower available for acceleration. When you move the accelerator to the full throttle position the