MTZ 952.2 - 5. Windscreen wiper; 5.1. Front windscreen wiper

Appendix
MTZ series 900
268
5. Windscreen wiper
5.1. Front windscreen wiper
The MTZ tractors are equipped with a
single-brush windscreen wiper with the
two-speed pantograph-type lever
mechanism with parking the brush:
• brush length: 650 mm;
• lever length: 600 mm;
• cleaning angle: 89-94 degrees;
• number of double strokes per minute:
a) Speed I: 34-46;
b) Speed II: 47-63.
The motor with a reduction gear consists of
the commutator-type motor, warm
reduction gear and rocker mechanism. The
second speed is provided at the cost of the
three brush in the commutator assembly of
the motor.
The windscreen operation modes are
switched over by a three-position key
switch (SA5) located in the shield of the
cab roof.
The electric circuits of the windscreen
wiper and washer are protected by a fuse
(4) (15 А). From their, the voltage is
applied permanently to the terminal "L" of
the switch (SA5) and to the terminal of the
end switch on the casing of the motor with
a reduction gear (wire Г) as well as to the
rear windscreen wiper (М5) and through
the switch (SA9) – to the windscreen
washer (М4).
One row of the contacts of the switch
(SA5) L, V and Н commutates the current
supplied to the motor brushes:
• Position І: the first speed: the contacts
L-V (wires Г-3) are closed;
• Position II: the second speed: the
contacts L-H (wires Г-К) are closed.
The second row of the contacts of the
switch (SA5) jointly with the end switch
serve for automatic stopping of the brush in
the parked position. The three contacts of
the end switch are mounted on the cover of
the motor with a reduction gear. Closing the
contacts in the required combination is
provided by the contact disk fastened to the
driven pinion of the reducing gear.
As the motor rotates, the terminal of the
end switch with the wire Б is connected
periodically with:
- terminal "+" (wire Г) – outside the parked
position;
- terminal "–" (wire Кч) – in the parked
position.
On setting the windscreen wiper switch to
the ON position, its contacts of the second
row (with the wires 3 and С) are closed and
the supply voltage is applied to the motor
through the closed contacts of the end
switch of the windscreen wiper and provide
the its operation in the first-speed mode
until the brush reaches the parked position.
As the brush enters the zone of the parked
position, the end switch breaks the power
supply circuit and then becomes connected
to the tractor body so that the motor is
short-circuited and its stop in the parked
position is accelerated due to the dynamic
braking.