Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
lV80Z~31
BACKGROUND OF THE INVENTION
It is known in prTor art brake booster to provide an accumulator
to a hydraulic brake booster so that when the power source faTls stored
pressurlzed fluid in the accumulator is available to asstst in actuating
braklng. For example, tf the fan belt on a motor vehicle breaks, the
power steering pump is disabled so that no source of fluid pressure is
avaTlable to actuate braktng unless a secondary pressure source Ts pro-
vided. Consequently, prior art brake boosters provide an accumulator
whTch is communicated with the brake booster pressure chamber when the
pressure source is disabled to actuate braking.
In vTew of the decreastng size of most motor vehicles in order to
compensate for fuel consumptton, englne compartments are also diminishing.
Wlth less space for ~ountlng a hydraulic brake booster, it is advantageous
to provtde a compact hydraulic brake booster for easier tnstallatton and
matntenance. However, the compact booster must tnclude a secondary pres-
sure source for assisting brake application when ttle main pressure source
Is rendered Inoperattve.
SUMMARY OF THE IN~ENTION
The present Inventlon provtdes a hydraultc brake booster tn whtch
a ptston deftnes a storage chamber for communtcatlng pressurlzed fluid theretn
wlth the pressure cha~ber to assist tn effecttng a brake appltcatton durtng
fatlure of the prtmary pressure source. The storage chamber ts charged with
pressurtzed fluTd durtng normal brake appltcatlons.
In particular, a brake booster houstng deflnes a pressure chamber
and slIdably carrles a spool valve and a ptston. An operator-controlled
actuatlng means Is responsive to brake pedal movement to actuate the spool
valve for communlcattng the pressure chamber wtth a pressure source so ~hat
tncreaslng pressure tn the pressure chamber moves the ptston to actuate a
master cyltnder for actuatlng braklng. A check valve tn the ptston communt-
cates the increaslng pressure tn the pressure chamber with the storage
- 2 - ~
~080Z~l
chamber and retains the pressurized fluid in the storage
when the pressure in the pressure chamber decreases following
a brake application.
When the pressure source is disabled, the operator-
controlled actuating means cooperates with the spool valve
to close the pressure chamber and, subsequently; cooperates
with the check valve to release the pressure in the storage
chamber into the pressure chamber for urging the piston
in a direction actuating the master cylinder.
As the piston in a hydraulic brake booster is re-
quired in order to actuate the brake master cylinder, the
provision of a storage chamber within the piston to form
an accumulator optimizes the compactness of the brake
booster. Therefore, installation is simplified due to the
size of the unit and the unit is compatible with the small-
er engine compartments resulting from smaller motor vehicles.
Thus, the present invention is defined as a
hydraulic brake booster comprising: a housing defining a
pressure chamber; a pressure responsive member movably disposed
in the housingj the member being movable relative to the housing
in response to pressure in the pressure chamber; the member
defining a storage chamber; the storage chamber communicating
with the pressure chamber when the pressure in the pressure
chamber is insufficient to move the pressure responsive member.
DES CRIPTI ON OF ~HE DRAWINGS
Figure 1 is a schematic illustration of a vehicle
hydraulic system with a hydraulic brake booster^of the
present invention, shown in cross-section.
Figure 2 is an enlarged fragmentary cross-sectional
view of the piston used in the hydraulic brake booster
- 3 -
rw/~
108028i
illustrated ln Figure 1.
DETAILED DESCRIPTION
~ eferrlng now to the drawings, the brake booster
generally indicated by the numeral 10 includes a housing
12 havlng an lnlet port 14~ an outlet port 16, and a return
or exhaust port 18. The inlet port 14 is communicated to
the outlet or high pressure side of the vehicle power steer-
ing pump 20, and the outlet port 16 is communicated to the
inlet of the vehicle power steering gear 22. The exhaust
10port 18 and the outlet of the gear 22 are each connected
to a reservoir (not shown) at the inlet or low pressure
side of the pump 20.
The housing 12 defines first and second bores 24 ~ '~
and 26 therewithin. A piston 28 is slidably mounted in
the bore 24 and is provided with :
-3a-
cbr/ d~
.i,~
108V;~
a connecttng rod 30 hhich transmits movement of the ptston 28 to a conven-
tional automotlve master cylTnder (not shown) which is mounted just to the
left of the houslng 12 vlewing Figure 1. Of course movement of the
piston 28 to the left generates pressure in the aforementioned n1aster
cylinder in the conventional manner. One end of another rod 32 Ts slidably
received tn a bore 34 In the piston 28 and the opposite end of the rod 32
Ts connected to a conventlonal brake pedal (not shown) mounted in the
vehicle operator s compartment. A bracket 36 is slidably mounted on the
rod 32 and Is urged into engagement with a stop ring 38 by a sprtng 40.
A first pivot 42 connects one end of lever means 44 to a bracket 46 which
is tntegral with the piston 28 and a second pivot 48 connects the inter-
mediate portlon of the lever means 44 with the bracket 36.
A spool valve generally indicated by the numeral 50 is slidably
mounted in the bore 26 and is adapted to control fluTd communicatlon Into
the booster pressure chamber 52. A secondary valve 54 is slidably mounted
on the end of the spool valve 56 extending into the pressure chamber 52
and a third plvot 56 connects the lever means 44 with the secondary valve 54.
A sprTng 58 yleldably urges the secondary valve 54 away from openlngs 60
in the body of the spool valve 50. Another spring 62 yieldably urges the
spool valve 50 tnto a ftrst or brake-released positton deftned by the engage-
ment of a stop 64 carrled on the spool valve 50 with a shoulder 66 provided
on the wall of the bore 26. The second or brake fully applied posltton of
the spool valve 50 is deftned by the engagement of the left hand end of the
spool valve 50 with a pl~Jg 68 whtch closes the bore 26.
The spool valve 50 and houstng bore 26 tnclude cooperatlng lands
and grooves such that in the ftrst posit10n illustrated in Ftgure 1 the
pressure chamber 52 is vented vta openings 60 passage 88 and openings 80
to the exhaust port 18. As the spool vatve 50 moves to the second posttton
wlth the left end of spool valve 50 abuttlng plug 68 the pressure chamber 52
Is communicated vla openTngs 60 passage 88 and openlngs 80 to the tnlet port 14.
10~3VZ~l
The piston 28, as Tllustrated more clearly In Flgure 2,
includes a plug 90 threadably engaging an open end of the plston. The
plug and piston cooperate to form a storage chamber 92 located intern-
~ h
ally of the piston. A diaphragm gK~ slidingly engages the inner wall ofthe storage chamber 92, and is biased to the right viewing the Figures
by a compresslble gas medlum on the left slde of the dtaphragm, to pres-
surize the fluid content of the storage chamber.
The plug 90 defines the bore 34 which slidingly receives the
rod 32. The rod 32 Is slotted at 114 to allow fluTd communtcation between
the rod 32 and bore 3~. A check valve 96 is centrally disposed in the plug
cooperates with bore 34 to define a passage commun7cating the storage
chamber 92 with the pressure chamber 52 when the pressure in the pressure
chamber is larger than the pressure in the storage chamber. A boss 112 on
the Inside of plug 90 is staked at its opening to retain the ball check valve ~6
within the plug. The plug 90 also carrtes a pressure relief valve 9~ opening
communication between the storage chamber and the pressure chamber when
the pressure In the storage chamber Is above a predetermTned value. This
rellef valve prevents bulldup of fluld pressure In the storage chambet above
that whlch is sultable for actuatlng braktng. Communlcatlon between the
storage and pressure chambers is also establIshed, when the pressure tn the
pressure chamber is below that in the storage chamber during a brake actua-
tton, by means of a projectlon 100 on the rod 32, whTch proJection engages
the check valve to unseat the ball of the check valve 96.
Seal means 102 and 104 are carrTed wlthln recesses on the plug
and dtaphragm, respectively, to seal the plug and piston and to slidlngly
seal the diaphragm to the Inner wall of the storage chamber.
A snap ring 106 retains the dTaph agm w1thln the storage chamber
and is mounted In a recess on the inner wall of the storage chamber.
MODE OF OPERATION
When the operator presses on the brake pedal, the rod 32 moves
1080~2ti 1
to the left vlewing Figures la and 2, thereby pivoting lever 44 about pTvot 42
to move the spool valve 50 to the left in the second position. In thls posi-
tion the spool valve 50 communlcates the inlet port 14 with the pressure
chamber 52. Increasing pressures in the pressure chamber from the inlet
port communicate with the storage chamber 92 via bore 34 and check valve 96,
whtle also urging the piston 28 to the left to eng~ge the connecting rod
with a master cylinder for actuating braking.
If the pressure source 2û Is disconnected from the hydraulic brake
booster 10 or disabled, no pressure is communlcated to the pressure chamber 52.
Moreover, no pressure is communicated to the pressure chamber 52 when the
spool valve sticks. Consequently, when the operator steps on the brake pedal
to shift the spool valve to the second position no movement of the plston
occurs. In accordance with the inventlon, further movement of the rod 32
pivots the lever 44 to move the valve 54 to the left on the spool valve 50
to close openings 60, whereupon projection 100 on the rod 32 engages check
valve 96 to communicate the storage chamber 92 on the rTght side of dia-
phragm 94 with the pressure chamber 52. ThTs communication increases the
pressure In the pressure chamber 52 to urge ptston 28 to the left thereby
actuating braklng.
WTth the pressure source disabled or dTsconnected from the hydraullc
brake booster, several brake applicatTons by the operator will exhaust the
pressurlzed fluld contaTned In the storage chamber. Thereafter, brake actu-
atTon proceeds as follows. SteppTng on the brake pedal moves the rod 32 to
the left to engage proJectTon 100 wTth check valve 96. Because the pres-
surtzed flutd Is spent in precedTng brake applTcations, no IncreasTng pres-
sures are communTcated to the pressure chamber. Consequently, further rod
movement Is required to actuate braklng. Such further movement pTvots
lever 44 about pivat 56 on spool valve 50 to move bracket 46 to the left.
Slnce bracket 46 Ts Integral wTth pTston 28, movement of the bracket moves
the ptston to operate the master cylTnder for actuatTng braklng.
~08()~81
The last-mentioned braking applicatTon, whlch proceeds without a
pressure source or a stored pressurlzed fluid tn the storage chamber, results
Tn a manual brake applIcatTon as the rod 32 mechanlcally urges the rod 30
in a direction actuating the master cyltnder.
Thus tt is apparent from the aforementioned descriptlon that the
present invention provides a compact hydraulic brake booster wlth a piston
defTning an accumulator whlch permits at least one safety braklng appllcatlon
after a pressure source for the booster has been disconnected. Thereafter,
with the pressure source disconnected, the operator manually actuates
braking.
WhTle the invention has been described in conjunction with a
speclflc embodiment thereof, ft ts evident that many alternatives, modifl-
cations, and variations are included within the broad scope of the appended
claims.
- 7
