Drive Motor - Maytag MAT12PDA Service Manual

General Information

DRIVE MOTOR

When the water level/pressure switch is satisfied circuits
are completed to the main drive motor. The drive motor is
a special high torque split-phase, four pole motor. Two
windings are used. The run winding is designed for full
time use in wash and spin. A second winding, called the
auxiliary or "start" winding is used to provide starting
torque and determine direction of rotation. A centrifugal
switch is mounted to the upper end bell of the motor and
serves to disconnect the start winding as the motor
reaches running speed.
Contact sets in a timer or in a motor reversing relay
provide proper connection to the motor to cause it to run
clockwise in agitate and counterclockwise in spin (viewed
from the top).
The motor drives the power unit by means of a special
design "V" belt. The belt has a "slip factor" designed to
act as a slip clutch.
TRANSMISSION
The helical drive shaft drives a pinion gear (which is
splined to the top of the drive shaft) at approximately 618
r.p.m. This drives the bevel gear at approximately 150
r.p.m.
The pivot pin of the yoke portion of the torque block and
yoke assembly is driven in a circular motion (orbit) around
an imaginary center point of the bevel gear center axis.
The yoke drives the torque block back and forth through
an arc of approximately 97 degrees at the rate of about
150 times per minute. Because this is a continuous
motion, the drive provides very smooth operation. The low
number of parts results in improved dependability. This
gear case can be serviced without removing it from the
washer.
HELICAL DRIVE
The helical drive mechanism used in the washer is simple
- not requiring a special device or linkage to shift the
washer from agitation to spin.
The drive mechanism utilizes a reversible motor and
helical (threaded) drive shaft. A pulley which is threaded
to the helical drive shaft moves either up or down the shaft
dependent upon the direction it is turned by the drive
motor by means of a drive belt.
AGITATION
When the pulley is turning counterclockwise (viewed from
the bottom) it moves down the helical drive shaft. As it
©2003 Maytag Appliances Company
rotates down the shaft, a lug on the pulley comes against
a drive lug which is splined to the helical drive shaft. At
this point the drive shaft turns with the pulley. The pulley
bearing which merely resting on top of the pulley also
rotates with the pulley, drive lug and helical drive shaft.
At the top of the drive shaft is a spined gear. As it rotates
it drives a series of gears causing the agitator to move
back and forth in an arc creating the water action for the
wash.
The tub and transmission are locked in place and cannot
turn because the brake rotor and brake shoe (which is
splined to the transmission ) is being held down against
the brake drum by the brake spring.
SPIN
When the motor reverses, the pulley will turn in a
clockwise (viewed from the bottom). This causes the
pulley and bearing to turn. The pulley climbs the threads
on the helical drive shaft overcoming the force of the brake
spring to lift the brake rotor and brake shoe off the brake
drum.
As the pulley climbs the shaft and overcomes the force of
the brake spring, there is a downward pull on the shaft.
Within the transmission there are two washers which act
as a spin clutch. This is a friction clutch consisting of a
bronze washer which is splined to and turns the drive
shaft. Between this washer and the pinion gear is a steel
washer which is locked to the transmission case.
As the helical shaft is pulled downward, the two clutch
washers under the pinion are forced together. This is
done rapidly and slippage occurs only during the first two
or three revolutions, until the film of oil between the two
clutch washers is forced out.
The drive occurs when the washers are forced together
and the pulley has climbed the shaft as far as it can. The
driving force has locked the pulley, brake rotor, drive tube
and gear case together and all will turn as a unit in the
same direction as the pulley is turning, causing the tube
to spin is a counterclockwise direction (as viewed from
the top).
Spin cycle completed:
When the washer reaches the end of the spin cycle, the
drive force is removed. Thus, there is no force supplied to
lock the components together or to compress the brake
spring. Therefore, the downward force of the brake spring
and the momentum of the spinning washbasket effectively
reverse all the actions outlined above.
16022842 Rev. 0 9