Sharp R-267LST Manual do Utilizador descarregar pdf (Página 15)

4,309,917

13

position

connects

restricted

line

243

via

its

restricted

branchline

245

to

advance

line

204.

Thus,

in

lst

range

the

supply of

advance

pressure

flow

is

restricted

by

two

restrictions

in

series-restricted

line

243

and

restricted

branchline

245.

So

the

delay

in

advance

pressure

flow

and

pressure

increase

in

lst

ratio

range

is

greater

than

in

higher

ranges

wherein

advance

flow

is

only

through

one

restriction,

restricted

line

243.

When

advance

pres

sure

decreases,

the

flow

is

from

advance

line

204

to

the

now

open

check

valved

line

242

which

by-passes

lst

range

advance

control

valve

123

for

flow

to

advance

connecting

line

217

to

exhaust

at

advance

cut-off

valve

122 or

ratio

governor

162.

The

return

connecting

line

218

is

connected

through

both

check

valve

247

and

restriction

248

of

check

valve

and

restriction

device

249

for

fast

flow

to

and

rapid

increase

of

return pressure

in

return

pressure

line

205.

When

return

pressure

decreases,

the

reverse

direction

?ow

is

only

through

restriction

248

and

via

advance

cut-off

valve

122

for

exhaust

at

ratio

governor

162

for

slow

decrease

of

return

pressure.

In

the

rate

of

ratio

change

controls

203,

normally

there

is

no

return

demand

signal

pressure

in

return

de

mand

signal

line

227,

so

the

return

demand

valve

124

supplies

operating

pressure

via

operating

line

211

to

position

advance

cut-off

valve

122

in

the

connecting

position

shown

(FIG.

3C)

for

connecting

advance

and

return

feed

lines

201

and

202

respectively

to

advance

and

return

connecting

lines

217

and

218.

Return

feed

line

202

and

connecting

line

218

are

connected

via

both

open

check

valve

247

and

restriction

248

for

rapid

sup

ply

to

return

line

205,

and

advance

line

204

is

connected

by

both

open

check

valved

line

242

and

restricted

line

243

for

rapid

exhaust

to

advance

connecting

line

217

and

feed

line

201

for

rapid

response

to

a

request

for

a

reduction

in

the

ratio

of

the

propulsion

drive.

Con

versely,

advance

pressure

is

supplied

with

delay

from

advance

connecting

line

217

only

through

one

restric

tion-restricted

line

243,

to

advance

line

204

for

delay

in

the

higher

ratio

drives

(2nd

and

3rd),

and

through

two

restrictions—restricted

line

243

and

restricted

ad

vance

branchline

245,

for

greater

delay

in

low

ratio

drive

(lst);

and

return

line

205

is

exhausted

only

via

restriction

248

for

delay

of

exhaust

of

return

line

205,

so

the

propulsion

hydrostatic

transmission

39

and

propul

sion

drive

13

have

a

delayed

response

to

a request

for

increase

in

drive

ratio.

In

lst

range

which

uses

lst

gear

ratio,

the

vehicle

is

accelerated

from

zero

speed, so

ratio

changes

represent

large

percentage

changes

in

speed.

The

drive

system

is

therefore

more

sensitive

to

rate

of

ratio

change

in

lst

range

than

it

is

in

higher

transmission

gear

ratios.

To

further

desensitize

ratio

change

in

propulsion

drive

13

in

lst

range,

lst

range

clutch

pressure

operates

on

1st

range

advance

control

valve

123

(as

explained

above)

and

provides

a

2nd

restriction,

restricted

advance

branchline

245

in

series

with

a

lst

restriction,

restricted

line

243,

in

the

advance

pressure feed

to

advance

line

204.

Therefore,

rate

of

ratio

change

controls

203

pro

vide

a

variable

advance

signal

pressure

rate

of

change

based

on

the

transmission

operating

ratio

range.

The

return

demand

signal

in

return

demand

signal

line

227

operates

return

demand

valve

124

to

exhaust

operating

line

211

quickly

through

full-flow

check

valve

232

to

quickly

move

advance

cut-off

valve

122

for

rapid

supply

of

return

pressure

from

mainline

112

to

return

line

205

and

rapid

exhaust

of

advance

pressure

from

advance

line

204.

The

restriction

and

check

valve

10

14

devices

233

and

249,

as

pointed out above,

provide

rapid

supply

of

return

pressure

and

exhaust

of

advance

pressure.

Mainline

112

is

used

to

supply

return

pressure,

so

this

supply

of

return

pressure

is

continuous

and

not

dependent

on

the

operation

of

ratio

governor

162.

The

return

demand

signal

line

227

is

supplied

by

return

demand

shuttle

valve

251

(FIG.

3F)

when

a

fluid

pres

sure

signal

is

supplied

by

either

or

both

overpressure

signal

line

or

low

charging

pressure

signal

line

253,

respectively,

indicating

excessive

high

control

or

kid

'

ney

pressure

and

less

than

normal

charging

or

low

kid

15

25

35

45

50

55

65

ney

pressure

in

propulsion

hydrostatic

transmission

39,

as

explained

below.

PROPULSION

RATIO

CONTROLS

The

advance

line

204

is

connected

to

neutral

shift

valve

127

(FIG.

3B).

The

return

line

205

is

connected

to

neutral

shuttle

valve

256

(FIG.

3B),

and

to

ratio

shift

signal

valve

257 (FIG.

3E).

These

and

the

other

compo

nents

of

propulsion

ratio

control

121

are

now

described.

MANUAL

RANGE

CONTROL

A

known

manual

control

254

(FIG.

3B),

having an

electric

supply,

manually

controlled

switches,

and

an

electric

circuit

having

a

connection

a

to

h

to

each

grounded

solenoid

valve

A

to

H,

as

shown

e.g.,

in

the

above

US.

Pat.

No.

3,640,157,

energizes

the

solenoid

valves

A

to

H

in

each

manual

range

position,

as

indi

cated

by

“X”

in

the

following

TABLE

I.

TABLE

I

SOLENOID

VALVES

MANUAL

RANGE

A

B

C

D

E

F

G

H

FORWARD

(F)

X

X X X

NEUTRAL

(N)

X

X X

X

PIVOT

STEER

(PS)

X

X

X X

REVERSE

(R)

X

X X X

Each

known

solenoid

valve

(A

to

H)

is

connected

to

an

associated

valve

operating

pressure

chamber,

as

ex

plained

below.

There

is

a

restricted

feed

to

each

operat

ing

chamber.

The

associated

solenoid

valve,

when

de

energized,

is

normally

closed

to

provide

pressure

in

the

associated

chamber,

and

when

energized,

opens

to

ex

haust

the

associated

chamber.

The

manual

range

control

254

controls

hydraulic

range

controls

255

which

includes

neutral

shift

valve

127,

inhibitor

valve

126,

disconnect

clutch

valve

125,

and

forward

and

reverse

signal

valves

128

and

129.

NEUTRAL

SHIFT

VALVE

The

neutral

shift

valve

127

(FIG. 38)

has

a

spool

258

having

five

equal-diameter

lands

a,

b,

c,

d,

and

e,

slid

ably

disposed

in

bore

259.

A

compression

spring

261,

in

lst

chamber

262

at

one end

of

bore

259,

engages

land

a

of

spool

258

and

urges

spool

258

to

the

right

so

that

land

e

of

spool

258

abuts

the

other

end

of

bore

259

which

encloses

2nd

chamber

263.

lst

and 2nd

chambers

262

and

263

are

closed.

The

lst

chamber

262

adjacent land

a

of

spool

258

is

connected

to

the

solenoid

valve

B,

and

the

2nd

chamber

263

adjacent

the

right

end

of

land

e

of

spool

‘258

is

connected

to

solenoid

valve

A.

Bore

259

is

connected

to

mainline

112,

a

neutral

advance

line

264,

automatic

advance

line

266,

advance

line

204,

range

feed

line

267,

lst

and

2nd

chamber

feed

lines

268

and

269,

and

exhausts

273, 274,

and

276.

The

lst

chamber

feed

line

268

is

connected

through

restriction

271

therein

to

solenoid

valve

B

for

pressure

control

and

to

1 2 ... 10 11 12 13 14 15 16 17 18 19 20 ... 33 34

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