Sharp R-267LST Uživatelský manuál stáhnout pdf (Strana 10)

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signal

valve

which

is‘positioned

with

hysteresis

in

an

upshift'ora

downshift

positionfdepe‘nding

on

the

signal

emitted

by

the

ratio

governor,

for

controlling the

ratio

range

shift

valves.

'

'_

' '

In

the

'ratio

governor,

the

set

speed

is

controlled

by

a

plurality

of

vehicle,

engine,

transmission,

and

brake

operation

signals,

and

the

rate‘of

change

of

the

advance

and

return

signals

is

controlled

for

improved governor

operatingcharacteristics

or

stability.

The

set

speed

is

varied

from

a

low

speed-such

as

engine

idle

speed,

to

a

high

or

maximum

engine

speed,

by

control

signals

pro

portional

to

each

of

leading

torque"

demand-such

as

the

degree

of

throttle

position;

steer

demand-such

as

the

degree

of

steer

lever

movement

from

straight

drive

position;

engine

power

or

substantially

simultaneous

torque

demand-such

as

compressor

discharge

pressure

from

a

gas

turbine

engine;

and

vehicle

brake

demand

such

as

vehicle

brake apply

pressure.

The

set

speed

will

be

the

highest

set

speed

called

for

by

any

one

of

these

control

signals.

In

drive

operation

during

acceleration,

increasing

throttle,

in

a

low-throttle

range,

will

increase

the

set

speed

to

an

intermediate

value.

Then,

as

engine

power

increases

to

a

high

or

maximum

value,

the

set

speed

is

increased

to

the

maximum.

As

throttle

is

decreased

for

deceleration,

the

lagging

decreasing

engine

power

sig

nal

controls

the

set

speed. Full

throttle

and

maximum

engine‘power

may

increase

the

set

speed

to

the

same

maximum

value.

The

steer

demand

increases

the

set

speed

to

a higher

value

to

maintain

higher

engine

speed,

even

though

throttle

and

engine

power

are

low,

to

maintain

a

greater

degree

of

steer

capability.

During

braking

in

higher

ratio

ranges,

the

brake

demand

in

creases

the

set

speed

to

a

higher

value

for

increased

engine

braking.

-

To

avoid

a

“stumble”

effect

as

the

vehicle

speed

slows

to

zero,

the

vehicle

brake apply

signal

is

fed

through

a

brake

signal

valve

which

blocks

feed

of

the

vehicle

brake apply

signal

to

the

ratio

governor

in

lst

ratio

range.

To

ensure

a

smooth

set

speed

transition

to

idle

as

lst

ratio

range

engages

during

a

vehicle

brake

stop,

the

lst

range

signal to

the

brake

signal

valve

is

fed

through

a

restriction

into

an

actuator

chamber

for

accu

mulator

operation

delaying

the

transition.

The

vehicle

brake

apply

signal

thus

has

a

modulated

transition

from

maximum

to

zero

signal

value

at

a

controlled

rate to

provide

a

smooth

set

speed

reduction.

During

normal

operation,

the

advance

and

return

signals

are

connected through

an

advance

cut-off

valve

and

a

rate

of

change

control

to

provide

ratio

governor

system

stability

and

smooth

ratio

change.

To

obtain

these

advantages,

the

return

signal,

which

is

provided

in

response

to

any

request

for

a

reduction

in

ratio,

is

sup

plied

rapidly

by

full-flow

lines

to

quickly

provide

full

pressure

for

fast

reduction

of

the

ratio

of

the

propulsion

drive

provided

by

the

propulsion

hydromechanical

transmission.

Also,

for

fast

reduction

of

ratio,

the

ad

vance

line

is

rapidly

exhausted

by

a

full-?ow

line.

When

the

advance

signal

is

provided

to

increase

ratio,

it

is

supplied

slowly

by

a

restricted

line

for

slowed

increase

of

the

ratio,

and

the

return

line

is

exhausted

slowly

by

a.

restricted

line.

-

Since

the

hydrostatic

ratio

change

in

lst

ratio

range

operation

provides

a

larger

percentage

change

in

speed,

5

20

35

45

55

4

further

decreased

by

including

a

second

restriction

in

the

advance

line.

This

system

provides

an

advance

sig

nal

rate

of

change

increasing

with

increasing

gear

speed

ratio

or

ratio

range.

The

transmission

has

the

capability

to

decrease

the

steering

radius

to

the

sharpest

turn,

pivot

steer,

and

the

steer

hydrostatic

transmission

has

a

large

power

capac

ity.

Since

a

steer

request

for

a

sharp

turn

at

low

engine

speed,

such

as

idle,

may

stall

the

engine,

the

steer

re

quest

controls

include

a

system

to

prevent

stalling

the

engine

at

low

input speed.

The

manual

steer

request

linkage

includes

a

steer

override

link

which,

when

sup

plied

with

fluid

pressure

by

a

steer

inhibitor

or

signal

valve,

transmits

steer

request

to

the

steer

servo

valve.

At

low

speeds,

the

steer

signal

valve

cuts

off

fluid

pres

sure

supply

to

the

steer

override

link

so

it

does

not

transmit

steer

request.

The

?uid

pressure

supply

to

the

steer signal

valve

is

cut off

by

a

regulator

valve

in

re

sponse

to

abnormally

low

minimum

charging

pressure

in

the

steer

hydrostatic

transmission

to

prevent

steering.

The

manual

control

for

neutral

controls

the

steer signal

valve

to

prevent

steer.

The

propulsion

hydromechanical

transmission

has

in

the

hydrostatic

transmission

portion,

an

overpressure

protection

system

for

limiting

high

hydrostatic

pressure

which

includes

a

stroke

limiter

control

operative

in

response

to

overpressure

of high

hydrostatic

pressure

to

limit

stroke

to

limit

high

hydrostatic

pressure

and

a

drive

control

operative

in

higher

ratio

ranges,

2nd

and

3rd,

in

response

to

overpressure

of

high

hydrostatic

pressure,

even

though

the

stroke

limiter

control

is

oper

ating,

to

an

overpressure

cut-off

valve

to

cut

off

the

mainline

feed

to

all

the

ratio-establishing

devices

to

place

the

transmission

in

neutral

and

to

lock

in

this

cut-off

mode

substantially

until

stroke

is

zero

and

out

put

governor

pressure

and

speed

are

zero

and

then

unlocking

so

operation

of

the

ratio

controls

may

be

resumed

with

normal

lst

ratio

range

starting

operation.

Also

in

this

cut-off

mode,

the

overpressure

cut-off

valve

provides

a return

demand

signal.

Also

lower

than

nor

mal

charging

or

low

kidney

pressure

in

the

propulsion

hydrostatic

transmission

also

provides

a

return

demand

signal.

Both

of

these

return

demand

signals

control

an

advance

cut-off

valve of

the

ratio

governor

to

cut

off

the

advance

signal

and

continuously

provide

a

return

signal.

These

and

other

features

and

advantages

of

this

in

vention

will

be

more

apparent

from

the

following

de

scription

and

accompanying

drawings.

BRIEF

DESCRIPTION

OF

DRAWINGS

FIG.

1

is

a

gear

schematic

of

the cross

drive

transmis

sion

on

line

1-1

of

FIG.

2.

FIG.

2

is

a

cross-sectional

view,

with

portions

broken

away,

of

the

cross

drive

transmission

gearing.

FIG.

3

is

a

block

diagram

showing

the

relative

posi

tions

of

FIGS.

3A,

3B,

3C,

3D,

3E,

and

3F.

FIGS.

3A,

3B,

3C,

3D,

3E,

and

SF,

when

arranged

as

.

shown

in

FIG.

3,

provide

a

diagrammatic

view

of

the

the

transmission

is

more

sensitive

to

rate

of

change

of

65

ratio.

Thus,

to

provide

optimum

ra'tio

change

stability

andl'shift

smoothness

in

lower

ratio

ranges‘

such

as

list

ratio

range,

the

rate

of

increase

in

the

advance

signal

is

propulsion

and

steer

controls

for

the

cross

drive

trans

mission.

FIG.

4

is

a

plot

of

pump

and

motor

displacement

relative

to

output

speed

for

the

propulsion

hydrostatic

transmission.

1 2 ... 5 6 7 8 9 10 11 12 13 14 15 ... 33 34

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