CHARGING SYSTEM - TM-10-3930-623-120043

TM 10-3930-623-12

4-39. Numerous models of similar 'appearing alternators

4-30. CHARGING SYSTEM.

4-31. The charging system includes the battery, alternator,

and regulators exist which have no practical

regulator, ammeter, and necessary wiring to connect these

interchangeability with original equipment, since their

components.

internal construction may differ in electrical values. In the

4-32. The continuous output alternator consists of two

course of maintenance, replace only with parts of identical

major parts, a stator and a rotor. The stator is composed of

part numbers as the original equipment.

a large number of windings assembled on the inside of a

4-40. TEMPERATURE COMPENSATION. Reference to

laminated core that is attached to the frame. The rotor

the test specifications in Section 2 of this manual will show

revolves within the stator on bearings located in each end

that the regulated voltage will decrease slightly with any

frame. Two brushes are required to carry current through

increase in temperature.

This design consideration

the two slip rings to the field coils wound concentric with the

presumes that both battery and regulator temperature will

shaft of the rotor. Six rectifier diodes are mounted in the

warm up at a similar rate as the truck engine warms up.

slip ring end frame and are joined to the stator windings at

Since a cold battery can be safely charged at a higher rate

three internally located terminals.

than a warm one, the initial charging voltage applied to a

4-33. Diodes are mounted in heat sinks to provide

cold battery is decreased as the truck engine and

adequate heat dissipation. The six diodes replace the

accessories warm up with operation. The thermistor in the

separately mounted rectifier as used in other types of

regulator is the temperature sensitive component which

application. The diodes change the alternating current to

controls this aspect of voltage regulation.

direct current.

4-41. CHARGING SYSTEM POLARITY. The components

4-34. The transistor regulator is an assembly composed

of the charging system are suitable for use only in a 12 volt

principally of transistors, diodes, resistors, a capacitor, and

system in which the battery negative terminal is grounded.

a thermistor to form a completely static voltage regulating

If a replacement battery, for example, is installed with file

unit in Combination with a field relay.

polarity reversed, (positive terminal grounded), the truck

4-35. The transistor is an electrical device which limits the

engine will start and run, but the solid state components of

alternator voltage to a preset value by controlling the

the charging system would probably be ruined before the

alternator field current. The diodes, capacitor and resistors

engine could be shut off. This also applies should it be

act together to aid the transistors in controlling the

necessary to connect a jumper battery to the truck for an

alternator voltage. This is the only function that the

emergency start. Always check battery polarity carefully

regulator performs in the charging circuit. The thermistor

before making connections.

provides a temperature-compensated voltage setting. A

4-42. DRIVE AXLE AND TRANSMISSION.

wiring diagram of this regulator's internal circuit is shown in

4-43. The drive axle (see figure 1-9) of the fork lift truck

Figure 4-3, on the wiring diagram for the truck.

includes an axle housing, differential assembly, two

4-36. The voltage at which the alternator operates is

axleshafts with integrally machined spur reduction gears,

determined by the regulator adjustment. The regulator

mating with internal sun) gears providing second rage of

voltage setting can be adjusted externally by removing a

speed reduction, and hydraulic self-adjusting brake

pipe plug in the cover and turning the adjusting arm inside

assemblies at the wheel ends.

the regulator. This procedure is explained in the following

4-44. DIFFERENTIAL ASSEMBLY. This item of the drive

section, and permits regulator adjustments

without

axle is similar in design and function to equipment found in

removing the cover.

the drive axle of practically all automotive equipment. The

4-37. The field relay in the regulator is a single pole, single

purpose of the differential is to provide equal power to each

throw normally open relay, the coil of which is energized at

driving wheel, while permitting the outside wheel in any

the time the ignition switch is turned ON. On closing, this

turning maneuver to travel further than the inside wheel.

relay connects the truck battery voltage to the alternator

This provision is necessary since the wheel on the outside

field circuit, energizing the field circuit. Note that the

of a turn must travel in a larger circle than the inside wheel.

alternator field has no residual magnetism, therefore the

4-45. CONSTRUCTION.

Figure 4-4 shows the

field cannot be self-excited, but depends on battery power

construction of a typical differential assembly schematically.

to function.

The pinion gear shown in the picture is actually the output

4-38. Self-discharge of the battery to ground through the

shaft of the transmission, and not part of the drive axle

alternator is prevented by the natural function of the

assembly, but must be considered to understand the power

alternator rectifiers, which permit current flow in the

flow to the wheels.

charging direction, but block reverse current flow quite

4-46. FUNCTION. The gears and shafts of the differential

effectively.

are carried in a housing or cage mounted between the two

shafts in the rear axle housing. Differential gearing can be

thought of as a special form of planetary gearing. The rear

4-5