CA1198965A - Hydraulic control apparatus for a servo-motor particularly for vehicle steerings - Google Patents

Abstract

A b s t r a c t In a hydraulic control apparatus for a servo-motor (11), particularly for vehicle steerings, there is a quantity setting device (4). This has in series between a pump connection (5) and the respective servo-motor connection (7) a quantity meter (18) and a supply throttle (12) which is adjustable in dependence on an actuating element (17) and the quantity meter (18). The pump connection (5) and the respective servo-motor connection (7) are connected by an amplifier line (22) which comprises in series an amplifier throttle (25) that is mechanically connected to the supply throttle (12) and adjustable proportionally thereto and a pressure regulating apparatus (24) that keeps the pressure drop at the amplifier throttle (25) equal to that at the supply throttle (12).
Single Figure.

Description

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Hydra~io control appara~1s for a servo-motox, p~rticularly ~or ~e~lcle s-teerinss ThQ in~ention relates to a hydrauli¢ control apparatu~ for a ser~motor, particularly or vshicle steering~, CO~pIiS~g a preerably direot~on~lly dependent ~uantlty settin~ de~ice having in ~eries b~th~een a pump connection and the respectiYe servo-motox connection a guan-tity meter and a ~upply throttle whioh ia ad~u3table in dep~ndPnce on an actuating el~m~nt ~nd the quantity meter.
Suo~ oontrol apparatuseq are or example known rom Dan~oss ~teerin~ unita Typee OSP~ and OSPB. qhe basio construotion col-le~onds to D~-PS 12 93 029 accoraing to ~lhich ~o concentrio ro~ary ~al~e sleeve~
are disposed in a hou~ing bore~ of whi¢h one i~ connected to the actuatin~ element and the other iB co~nected to the output cardan ~haft of a geax motor ~ervine aB a ~uantity metor ~nd with ~he aid of these xotaxy ~alve slee~s there ~8 ox~.ea the ~upply throttle~ ~ ~etu~n throttle, a direational ~lva and ~ diat~ibutin~ valYe for the gear motor. m e eervo-motor connection~ o~ tnl~ ~$eering ~lit can be conneated dixeo~ to the two sideq of tha servo-motor- ~y xaaron of the ratuxn flow eff~ated by th~ 6ear motor, adJu~ment o~ the ~e~o-motor is propox~ional ~o adju~tm~nt of the actuat~n~ ele~entO I~ th~ pump ror the pre~ure ~ediu~ fall~t tho g~ar motor can Ber~O a5 an aQxiliary pump ~o that ~mer~ncy op~ration i~ pos~3iblo. ~h~ t~rou~ut o~ a 8~365 L-quantity ~et~r ia limited. Conse~uently the speed of adJustmont of the se~ motor i~ limited.
To inc~eas~ tha ~p~ed of ad~us~nent, it i~ Xno~n ~dra~lioallY
to conn~ct two ~uantity meter~ in parallel ~nd to interconnect. theD
rechnn~oally (D~ OS 19 01 588), In thi~ ca~, the quatltity met~rs aot as a mete~ine pump~ qhe supply and retuln throttle~ axo adjust~d in dep~ndence on the metering pu~p p~e~u~ If the pr~ssu~ pump fails, a YalVe re~ponds which ~hort-cirouits the OnQ metering pu~p so t~at the other meterin~ pump now 8erving as an au2iliary pump oan ~till be ad~usted by manual foroe. ~o~evex, beoause of the BeCOnd motering p ~p, this require~ considexabla ædaitional e~pense~ ~kr~her, dul-lng emorgency operation~ on aotuation of the ~Lxil~ar~ pump the frlction ~nd the flow re~istanae o~ the inoperative meterin~ pt~mp ~u~t be oYQrcoms-Tb feed a ~erv~-motor, lt i8 al50 known ~E~OS 2~ 32 847) tQ
connect a co~trol oir¢ult ana an opexating oixcuit in parallol~ ~ho control cixoult conta~l~ a quantity ~ett~ng de-~ice with quant~ty meter snd ~upply tbrottle ln series w~th a GQntrol throttle~ ~he opar.~tlnæ
circuit contain~ the ~er~e~ clroult of ~ ohe~ vAlYe clo~n~ towards the p~s~re pump, a p~ re~ulat~l~ valve and an operating 1'hrottle~
~he contr~l thr~le ana opexatin~ throttle axe ~o~med on a commer~ val-va and have interproportional ox$f~ce oross-geotion~- Ihe valve at the ssme t~me form~ a pra~ule comp~rator whi¢h cont~ols the px~ssure~
regul~tin~ ralve and keep~ the pressur~ drop at the c:ontrol th~ottle ~ual to that at the operatln~ throttle, In thi8 way~ a oonsiaerably hi~er amount of pxe~f3u2~ ~ne~ium csn b~ suppliea to t~le sexvo-~motox ~th only one quant~ty m~ter becauso the ~moun~ of operating medium 9~5 --3, flowin~ thr~u~h ~he operatinæ circuit is ~roportional to th~ control oircuit quantity flowing ~hIou~h the control circult. ~owever, an additional Gontrol ~hrottl~ i9 required in th~ oontrol circ~t ~ld th~s leads to a hi~ler pres~uro drop. In a~dition, th3 valve of the pre3sur~
comparator has to be ~e~ e~ for a total of thr~e ~mction~.
~ h~ inV~ntiDn iB based on the p:coblem of providing a hydr~l~c ~ontl~l appar~tus of the aforementioned klnd which, with a very Pimple con~truotion9 maXe~ it po~sible to 6u~ply the se~ otor with a lar~or amount of pr~ssure fluid th~n that. colTespondln~ to the throu~hput c~paclt~ of the quantity meter~
qhis problem is solved acoordin~ to the inv~tion in that tho pump connection ænd tha respeotiY3 ~exYo~-motor connQotion ~r~ additionally connected by ~ ~pl~ ~ er linQ which comprises in 6eries an ~rllf~er throttle that i8 mechaaically co~neoted to the 9upply throttl~ ~d ad~usta~le propoxtion~lly thereto ana a ~re~sl~ro r~gulat~n~ appaxatus that ~eep~ the pres~ drop at the amplifier throttle equal to ~hat at tho ~upply throttle.
I~ this constructiont th~ q~uantity setti~g devlce oa~ a~ usual b~
lnst~llea bet~een the pump and ~ervo-motor becauso ~he ~mpli~ier llne is dis~os~d bet~een the ~ump connection and serv~-~otor co~nectio~0 Iha ~dditional e~pen~e f'or tha ~mp1~er thxottle ~s ~D~n~m~l becal~e~
by reaaon Or the mechanical conneotion to the supply throttle9 it oan be embodlcd b~ a ~imple expediant on the ~etting ~lem~nt of ~he ~uantity settin~ d~v~ce9 ~uch aa by a vilve. me ~x~Sure reeulatin~ a.ppa~a~ul need })Ol':~OXm only one function and can there~o~e li}cewiae be ~imply constructed. qho total e2pense ~or tho new co~trol ~ppa~tl~ ia thererorh ~ 9 low. In additlon9 the control is ve y Qxact because of t~e positive ~o~nection be~ween the ~upply and a~plifier throttles.
In n preferr~d ~bod1~1ont, the p7~e~sux~e reS~atin~ app~rat~D
oompri~o~ a throttlin5 position w~ch i~ co~lected to on~ siae of the amplifier throttle and ig cont~olled by a pre8SUra compa~ator ~ub~ected to the pressure on one side of th~ 8u~pl~ thx~ttle a~dt in the opponits direction, to the pr~sur~ on one si~e of tho ~mplifier throttle, the other ~ides of th~ supply and a~pllfier t~ttle~ ba~n~
~ntercol7nectea. ~y reason of the fact that ~he su~ply End am~ ier thxottles aIe ln~arconnected on one side, one can, with th~ a~d of a pr~7~ure comparison~ keep the pressu7~edrop on the other sidQs of ~oth throttle~ e~ual.
Xn æartioular, the ~h7rottling po~ition controlled by th~ pxes6uro comparator cEn be di~posed in i~ont of the ~mplifier throt~le and the qu~ltity meter in front of the ~r~ply thxottle~ and th~ ~rv~-motor conneotion ozn be oonneoted ~o the supply and P~ fier throttles.
~li8 ~ak~s it po~siblo to reta~l ~h~ p~ove~ Go~struction Or a particularly direotion~lly ~epond~nt qua~tity setting ae~ce in w}~oh the quantity ~eter precedcs the 6upply thr~ttl~.
~ he ~rl~ er line should b0 p~ovided with a che~; ral~o whiGh olo~e~ to~r~x~`the pump connection. It i~ open dur~n~ no~al operat~on but olo~es when, duI~n~ emex~ency operation, thQ qu~ntit~ mct~r i~
used as ~n aurilla~y pwmp.
A pr~f~rTed oxa~ple trill noW be des~ribed ln mox~ det~il with roferenca to thc dr.~win~ in which thf~ ~in~1~3 fig~re i~ ~ di~ mati¢

~pras~nta~ion of the control a~pa~atu~ a~cor~ln~ to th~ in~1tion.

~ pre~sure medium pump 1 suck~ pressur~ fluid fro~ a containor

2. Its ~R~-~ml~ pres~ure ls ~o~ernod by ~l ove.~press~re ~.~lve 30 A
qu~ntlty _et~ng de~ico 4 compr.ises a pum~) connection 5 and a ~ont.~inor conneot~on 6 a~ well as t~o servo~motor oonnootiona 7 ~nd 8~ ~he lattor are conneotcd to the two pr~s~ure chambera 9 ~nd 10 of a e~e~ motox llo Th~ qu~tity _ettinS de~ico 4 comprises threo throttle~ in known mannex~ In the illu~trated position in ~hich the piston o the Bervo-~otox 11 is mo~ea to the ri~lt~ the t~ ttle 12 se.rves as supply thl~ttleD the throttle 13 as xsturn throttle and the throttle 14 as bxpas~ throttle. Ihe latter iB b~dged by ~ oheck Yal~e 15 ~hich closes toward~ the conta;tner 2. ~he thIottlee 12, 13 and 14 are ad~usted i~ unlson by ~ contxol apparatu~ 16 il~ whic~ the position of ~n a~tuatlng Qlemsnt 17 ~nd of ~ m~tcrin~ motor 18 al~ compared ~ith ~ach other. ~he meterinæ ~otor 18 is disposed In the supply conduit 19 in sorl~e with the ~ply throttlo whllst ths return condult 20 1eadB
from tho r~t~rn throttle 13 direct to the con~ainer ccnnectlon 6. In the n~utr~l po~itlo~, the bypa~s throttle 14 i~ n~ly open whexeas $he thro Wl~s 12 and 13 are closed~ In the illustxated operating po~ition, tho throttle~ 12 and 13 are ~ntirely or partiR~ly op~n and, corres~
pon~n~y~ ths b~ps~ ~hxottl~ 14 is entiroly or partially clos~d~
On r~rer~ing the direetion o~ rntation of the &etuating el~m~nt 17~
tho throttlo 13 serYo~ ae supply thIo~tle nnd the th~o~t~ 12 aq r~xn throttlc, ~br thiq puxpo~, tha eonr.eetion ~ of the meterin~ mo~or 18 i~ eonneeted to polnt C ~nstead of point ~ o~ the eircuit and tha motor eonneetion ~ i~ connected t,o point, E ln8tP~d of point C9 ~urthex, th~ polnts ~ ana ~ are intereonn~ct~d.

~9~

~ ocording to the pres~lt invention, the qun~tity sotting device 4 iq suppl~mented b~ the circtlit ~)ortion 21. The latt~r compri~es an ampli~`ier line 22 ~hloh ~xtend~ betwee3l tho pt~p conncction 5 and one of the scrvo-motor co~lections, ~1 the pre~nt m~er o~
operatio~ the servo-~otor oonnection 7~ ~hQ ampli~i~r line comp~lso~
in eeries a ch~cX ~alve 23 closing toward~ th~ pump lt a pr~s~ure r~ulatin,g apparatus 24 ~nd ~n amp~fier throtttQ 25, Yhe lattex i~
~eoh~n~cally connected to the th~ee throttles 12, 13 a~d 14. I~
orifice cross~section ch~n~es proportion~lly to tbo oIlfico cross-~ection o~ the throttle 12.

~ho pXes3tlr~ re~ulat~ng z~?parat~ eeps tho pxes6ure drop at the ~ f~er ~hrottle 25 equal to ths p:reasurs drop ~t the uuppl~
throttlo 12. ~br th:iu pu~?o~e, a thr~ po~ on 27 ~ pro~d~d whioh iu controlled by a pres3~re co~parator 26 in -the form o~ a pi~to~, ~he piston i~ ~ub~ected a~ o~e ~d ~8 by the pre~re in a p~8USlU~3 ck~m~er 29 cOmrQmicating ~r~th the ~pply conduit~, ~Ehe other ond 30 i~ ~ub~ected to the pre~sure i~ 0~3mb~r ~1 cor~oted to one cide of the ampli~er tbrottle 25. ~ weak retu~ ~p~ 32 881:~9EI ~iO
olosa the throttlinæ position 27 ~1 th8 ab~e~ce o~ supply pre~6u~
On a chan~e in the d~l~ctlon of rotation o~ the actuatin~
elem~nt 17~ th~ upper connectln~ polnt ~ o~ the amr~ er lin~ 22 ~8 sepa~ted ~rom point H ~nd ~ppliea to po~nt ~. ~n a~di-tlon, thc pre~uro chamber 29 ~9 ~epa~ated from point B ~na applled to point ~0 In thi~
ca~e~ tha thlvttle 13 serve~ ~8 ~upply thlottle ~nd the pr~wro drop at the ampllf~er t~ottle 25 1~ k~pt eau~l to it~ pre~,~urQ drop.

~ lo quantity settin~ device 4 operates ln con~ntion~l manner, i.e. the qu~ntity mea~ured by the moter~ng motor 18 flow~ to tho sorvo-~otor 11. Since the pres~ dxop at the r~rl~er throttle 25 1~ o~ual to that at tho supply t~ottlc 12 and the cro6s~seotion~ of tho t~o t~ttlo3 vary proport.~on~ly~ tho $mount of pre~Dur~ fluia ~o~n~ throu~h the ~pli~ier l~o 22 i~ accurately proportional to tha~ flowing acro~s the meterln~ motor 18. It i~ ~her~o~e po~sible to opsrato th~ ~erYomotor 11 at a considerably higher sp~ed th~n. that corTesponding ~o the flow through the meterin~ motor 18 but ono neve~-theless obt2in3 very accur~te control.
If th~ englne-driv~n pump 1 fails, ths mate~inz motor la a¢ts as an a~ ry pump on rotation oi' the aotuatinS ~lem~t 17. Pre~sur~
fluid i8 sucked through the suotio~ valv~ 15 and passed to the sexvo-motor 11~ ~ ~hox~-oircuit acro~s the ~plif~er throttl~ 25 i~ ~ot pos~ible becal~ of thc ch~ck ~nlve 23. qhe deg~s~ o~ c~t~on c~n be a~leoted w~thout difficulty by choo~ing the oro6s~ectional asea.
ratio~ of ths ~upply throttle ana ~ pl~f~er tbl~ottle. In the pr~ctioal construction, ~or cxampla, the press~l~ rQgulatinæ app~lR 24 and the àhec~ ~al~e 23 san be combfned a~ a unlt~ pos~ibly together ~ith tho ovo~-pressure valve 3, ana applied to the out~id~ of the hou~ng block o~ the q~ant~g ~etting dev~oo 4 whi¢h i~ ~upplem~nted by tha ~mplifier throttle 25.
In the illu~tratea oon~truotio~ the pu~p oonneatio~ 5 ~nd cont~lner oonn~otion 6 axo short-circuited ~y th~ bypas~ throttle 14 (op~n centre) in the ncutxal position. ~lternativcly9 th~ pump connec-tion 5 and cont~nor con~ection 6 could bc block~d in ~1e ~leutral po~i~ion (closed cent~e). I~ tho illu~tr~ed ~bod~nent9 the two s ~~

servD-motor eonneation~ 7 and 8 ~r~ ~eparated from eaeh other (non-reaetion~ Iowever, they could also be interconneeted in the neutral po~ition (rec~etion). ~urther, it is possible to ha~e pu~p eontrol dcpend~nt on thc lo~d p~s~ule ~loacl E~nsing) an~or brc~kl~l~ whieh tako~ exte m al ~orees into ~ecot~nt (power bey~nd).

Claims (4)

Claims

1. A hydraulic control apparatus for a servo-motor particularly for vehicle steering, comprising a directionally dependent quantity setting device having in series between a pump connection and the respective servo-motor connection a quantity meter and a supply throttle which is adjustable in dependence on an actuating element and the quantity meter, characterised in that the pump connection (5) and the respective servo-motor connection (7, 8) axe additionally connected by an amplifier line (22) which comprises in series an amplifier throttle (25) that is mechanically connected to the supply throttle (12) and adjustable proportionally thereto and a pressure regulating apparatus (24) that keeps the pressure drop at the amplifier throttle equal to that at the supply throttle.

2. A control apparatus according to claim 1; characterised in that the pressure regulating apparatus comprises a throttling position (27) which is connected to one side of the amplifier throttle (25) and is controlled by a pressure comparator (26) subjected to the pressure on one side of the supply throttle (12) and, in the opposite direction, to the pressure on one side of the amplifier throttle, and that the other side of the supply and amplifier throttles are interconnected

3. A control apparatus according to claim 2, characterised in that the throttling position (27) controlled by the pressure comparator (26) is disposed in front of the amplifier throttle (25) and the quantity meter (18) is disposed in front of the supply throttle (12), and that the servo-motor connection (7) is connected to the supply and amplifier throttles.

4. A control apparatus according to one or claims 1 to 3, characteorised in that the amplifier line (22) is provided with a check valve (23) which closes towards the pump connection (5).