Sharp R-267LST Bedienungsanleitung PDF herunterladen (Seite 20)

4,309,917

23

to

1st

exhaust

413

to

close

the

leakage

path,

and

land

b

of

spool

407

has

a

large

overlap

of

2nd

port

410’ to

prevent

leakage.

When

pump

ring

370

moves

from

zero

stroke

(N)

position

in

the

other

or

opposite

direction,

mainline

112

is

similarly

connected

to

oppositely

dis

posed

and

similar

2nd

port

410’,

2nd

zero

stroke feed

line

411',

and

then

2nd

restricted

passage

412’

and 2nd

exhaust

413'

is

closed

by

land

b

of

spool

407,

and

the

large

overlap

of

land

a

of

spool

407

relative

to

1st

port

410

reduces

leakage.

The

1st

and

2nd

zero

stroke

feed

lines

411

and

411’

are

selectively

supplied

and

when

either

one

is

supplied

with

zero

stroke

indicator

signal

pressure,

the

zero

stroke

shuttle

valve

414

connects

the

zero

stroke

indicator

signal

pressure

to

zero

stroke

indi

cator

signal

line

416

whenever

pump

ring

370

is

not

in

zero

stroke

(N)

position.

Thus

zero

stroke

signal

pres

sure

at

zero

pressure

provides

the

zero

stroke

signal.

ADVANCE

TIME

DELAY

DEVICE

The

advance

time

delay

device

417 (FIG.

3B)

has

a

piston

418

slidable

in

a

bore

419

vented

by

exhaust

426

between

piston

418

and

end

wall

422.

Spring

421

seated

on

end

wall

422

engages

and

biases

piston

418

to

the

discharged

position

shown.

In

discharged

or

exhaust

position,

automatic

advance

line

266

is

exhausted

at

neutral

shift

valve

127

and

delayed

automatic

advance

line

423

is

connected

by

both

its

supply

port

424 and

exhaust

port

425

to

bore

419

and

via

bore

419

to

exhaust

426.

When

neutral

shift

valve

127

supplies

automatic

advance

line

266,

automatic

advance

signal

pressure

is

supplied

via

automatic

advance

line

266 through

restric

tion

427

to

expanding

chamber

428

in

bore

419

between

piston

418

and

end

wall

430

to

move

piston

418

against

the

bias

force

of

spring

421

during

a

predetermined

time

period

to

supply

position.

In

this

supply

position,

ad

vance

time

delay

device

417

connects

automatic

ad

vance

line

266 through

restriction

427

and

expanding

chamber

428

to

supply

port

424 and

delayed

automatic

advance

line

423

and

blocks

exhaust

port

425.

When

the

supply

port

424

is

fully

open,

piston

418

engages

stop

429

and

exhaust

426

continues

to

vent

the

bore

419

between

piston

418

and end

wall

422.

2-3

OVERPRESSURE

CUT-OF

F

VALVE

The

2-3

overpressure

cut-off

valve

431

(FIG.

3F)

has

a

spool

432

having

?ve

equal-diameter

lands

a,

b,

c,

d,

and

e,

and

a

piston

433

of

the

same

diameter,

both

slid

able

in

a

bore

434.

A

spring

436

seated

on

one

end

wall

437

in

a

spring

chamber

438

vented

by

exhaust

439,

engages

land

e

of

spool

432

to bias

spool

432

so

land

a

of

spool

432

abuts

piston

433

which,

in

turn,

abuts

the

other

end

wall

441

in

the

normal

position

shown.

In

this

normal

position,

the

2-3

overpressure

cut-off

valve

431

connects

range

feed

line

267

between

lands

c

and

d

of

spool

432

to

1st

range

supply

line

442

connects

over

pressure

signal

line

252

between

lands

d

and

e

of

spool

432

to

exhaust

443

and

blocks

lock

signal

line

444

be

tween

lands a

and

b

of

spool

432.

Also,

lock

chamber

446

between

piston

433

and

land

a

of

spool

432

is

con

nected

to

exhaust

448.

Thus

in

normal

position,

the

2-3

overpressure

cut-off

valve

431

functions

only

to

con

nect

range

feed

line

266

to

1st

range

supply

line

442.

The

output

or

2nd

governor

signal

pressure

line

157

and

zero

stroke

indicator

signal

line

416

are

connected

0

5

45

55

60

to

lock

shuttle

valve

445

which

supplies

the

higher of

65

2nd

governor

pressure

and

zero

stroke

indicator

signal

pressure

to

lock

signal

line

444.

When

there

is

high

hydrostatic

overpressure

as

described

below,

high

pres

24

sure

safety

signal

valve

451

(FIG.

3A)

connects

main

line

pressure

from

2-3

feed

line

283

to

high

pressure

signal

line

452.

High

pressure

signal

line

452,

in

2-3

overpressure

cut-off

valve

431,

is

connected

to

high

pressure

signal

chamber

453

between

end

wall

441

and

piston

433

to

act

on

piston

433

and

move

piston

433

and

spool

432

against

spring

436

to

the

cut-off

position

with

land

e

of

spool

432

abutting

stop

454.

The

2-3

overpres

sure

cut-off

valve

431

is

thus

moved

to

cut~off

position

only

in

2nd and

3rd

ratio

ranges

when

there

is

a

high

hydrostatic

overpressure.

The

2-3

overpressure valve

431,

in

cut-off

position,

provides

the

following

connections:

Range

feed

line

267

is

connected

between

lands

c

and

d

of

spool

432

to

overpressure

signal

line

252

which

is

connected

by

return

demand

shuttle

valve

251

to

supply

return

de

mand

signal

line

227

so

advance

return

signal

system

160

only

provides

a

return

signal

to

return

line

205,

as

explained

above.

The

1st

range

supply

line

442

is

con

nected

between

lands

b

and

c

of

spool

432

to

exhaust

448

to

disestablish

all

ratio

ranges,

1st

brake

65,

2nd

clutch

88,

and

3rd

clutch

72.

The

lock

signal

line

444

is

connected

between

lands

a

and

b

of

spool

432

to

lock

transfer

line

447

to

supply

lock

chamber

446

to

lock

2-3

overpressure

cut-off

valve

431

in

cut-off

position

until

the

high

pressure

signal

in

high

pressure

signal

line

452

is

discontinued

indicating

proper

high

hydrostatic

pres

sure,

until

the

zero

stroke

indicator

signal

pressure

line

416

is

exhausted

indicating

hydrostatic

pump

H1

is

at

substantially

zero

displacement,

a

displacement

not

greater

than

forward

and

reverse

bias

positions

(FB),

(RB),

and

until

output

governor

pressure

in

2nd

gover

nor

pressure

line

147

and

vehicle

speed

are

very

low

(e.g.,

5

mph),

so

lst

ratio

range

drive

can

be

smoothly

reestablished.

RATIO

RANGE

SHIFT

CONTROLS

Priority

Valve

The

ratio

range

shift

controls

460 (FIG.

3E)

are

sup

plied

by

lst

range

supply

line

442

which

is

connected

to

priority

valve

456

to

immediately

with

priority,

supply

2nd

range

supply

line

457 and

after

mainline

supply

requirements

are

met,

to

supply

3rd

range

supply

line

458.

Priority

valve

456

has

a

valve

spool

459,

slidable

in

a

bore

461

and

biased

by

a

spring

462

in

a

spring

chamber

463

vented

by

exhaust

464,

to

the

closed

position

shown

connecting

1st

range

supply

line

442

directly

for

full

flow

to

2nd

range

supply

line

457

and

through

restric

tion

466

to

3rd

range

supply

line

458.

Since

2nd

range

supply

line

457

is

only used

as

a

hold-pressure

in l-2

shift

valve

491

as

explained

below,

its

flow

requirements

are

not

signi?cant.

When

the

flow

requirements

of

mainline

112

are

met

at

a

proper

operating

pressure

(somewhat

less

than

mainline

pressure),

priority

valve

456

opens

to

provide

a

full-?ow

connection

to

-1

st

range

supply

line

442,

used

for

all

ratio

range

establishing

supply

and

exhaust

pressure

control

during

ratio

range

disestablishing.

RATIO

SHIFT

SIGNAL

VALVE

The

ratio

shift

signal

valve

257 (FIG.

3E)

has

a

valve

spool

468 having

five

equal-diameter

spaced

lands

a,

b,

c,

d,

and

e,

slidably

disposed

in

a

valve

bore

469,

1st

and

2nd

springs

471

and 472

seated

on

opposite

ends

of

valve

bores

469

and

centering

the

valve

spool

468

in

valve

bore

469.

Ratio

shift

signal

valve

257

also

has

lst

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