DK176119B1

DK176119B1 - Hydraulic actuation system for an exhaust valve in an internal combustion engine

Info

Publication number: DK176119B1
Application number: DK200000246A
Authority: DK
Inventors: Henning Lindquist
Original assignee: Man B & W Diesel As
Priority date: 2000-02-16
Filing date: 2000-02-16
Publication date: 2006-09-04
Also published as: JP2001254611A; CN1185404C; KR20010082083A; KR100498213B1; DK200000246A; JP3564074B2; CN1309231A

Description

i DK 176119 B1in DK 176119 B1

Opfindelsen angår et system til hydraulisk aktivering af en udstødsventil i en forbrændingsmotor, hvor et trykkammer i en ventilpumpe har en port, som ved hjælp af en styreventil kan forbindes skiftevis til en 5 højtrykskilde for hydraulikvæske eller til et tilbageløb, og hvor et servostempel i ventilpumpen adskiller trykkammeret fra et hydraulikvolumen, som via en trykledning står i forbindelse med et trykkammer i en hydraulisk aktuator anbragt i forbindelse med udlo stødsventilens spindel.BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a system for hydraulically activating an exhaust valve in an internal combustion engine, wherein a pressure chamber in a valve pump has a port which can be connected alternately by means of a control valve to a high pressure source of hydraulic fluid or to a reflux pump, and wherein a servo piston in the valve pump separates the pressure chamber from a hydraulic volume which is connected via a pressure line to a pressure chamber in a hydraulic actuator arranged in connection with the spindle of the thrust valve.

WO 98/57048 beskriver en hydraulisk aktiveret udstødsventil til en forbrændingsmotor, hvor en aktuator anbragt i forlængelse af udstødsventilens spindel har et trykkammer, som gennem en trykledning er for-15 bundet med en styreport på oversiden af en fordelerblok for højtryks hydraulikvæske. Styreporten kan ved hjælp af en on/off-styreventil monteret på fordelerblokken forbindes direkte med en forsyningsledning for hydraulikvæske, som fra en pumpestation leveres ved højt 20 tryk, såsom 125 til 325 bar. Det er i praksis endvidere kendt at indsætte en ventilpumpe med et servostempel i trykledningen mellem styreporten på fordelerblokken og udstødsventilens aktuator.WO 98/57048 discloses a hydraulically actuated exhaust valve for an internal combustion engine, wherein an actuator arranged in extension of the spindle of the exhaust valve has a pressure chamber which is connected through a pressure line to a control port on the upper side of a distributor block for high pressure hydraulic fluid. The control port can be connected directly to an hydraulic fluid supply line, which is supplied from a pump station at high pressure, such as 125 to 325 bar, by means of an on / off control valve mounted on the distributor block. It is also known in practice to insert a valve pump with a servo piston into the pressure line between the control port of the distributor block and the exhaust valve actuator.

De kendte systemer til aktivering af udstødsventi-25 ler har imidlertid vist sig at belaste såvel ventilak-tuatoren som de hydrauliske komponenter mellem denne og fordelerblokken i en sådan grad, at visse komponenter, såsom eksempelvis kontraventiler, tætninger og monteringsskruer for trykledningerne, nedslides uønsket 30 hurtigt.However, the known systems for activating exhaust valves have been found to load both the valve actuator and the hydraulic components between it and the distributor block to such an extent that certain components, such as, for example, check valves, seals and mounting screws for the pressure lines, are unwanted 30 quickly.

Den foreliggende opfindelse har til opgave at anvise et system til hydraulisk aktivering af en udstødsventil, hvor de ovenfor nævnte ulemper er afhjulpet, og hvor der samtidigt opnås en præcis 35 styring af ventilen.The object of the present invention is to provide a system for hydraulically activating an exhaust valve where the above-mentioned disadvantages have been remedied and at the same time precise control of the valve is obtained.

DK 176119 B1 2DK 176119 B1 2

Med henblik herpå er systemet ejendommeligt ved, at servostemplet omfatter et første servostempel og et i dette koaksialt forskydeligt andet servostempel, og at det andet servostempel i trykkammeret (30) har et 5 strømningsbegrænsende element (54), som i en udgangsstilling af servostemplet (33) er beliggende ved porten (29), således at det begrænser tilstrømningen af hydraulikvæske fra porten til trykkammeret.To this end, the system is characterized in that the servo piston comprises a first servo piston and a second servo piston displaceable in it, and that the second servo piston in the pressure chamber (30) has a flow limiting element (54) which in an initial position of the servo piston (33). ) is located at the port (29) so as to limit the flow of hydraulic fluid from the port to the pressure chamber.

For at løfte ventiltallerkenen i udstødsventilen 10 fra sit sæde kræves der en endog meget stor kraft, eftersom gastrykket på ventiltallerkenen i forbrændingskammeret skal overvindes. Ved at lade det første servostempel med større diameter medvirke ved en første del af ventilens åbningsbevægelse og samtidigt at lade 15 det strømningsbegrænsende element på det andet servostempel begrænse tilstrømningen af hydraulikvæske til trykkammeret i udgangsstillingen er det muligt at opnå en kontrolleret, men samtidig særdeles kraftig trykstigning i trykledningen fra ventilpumpen til 20 aktuatoren. Herved kan ulemperne fra ukontrollerede tryksvingninger i trykledningen og aktuatoren mindskes eller undgås, og der opnås derfor en væsentlig længere levetid af de hydrauliske komponenter. Udstødsventilen åbnes endvidere meget hurtigt, og åbningstidspunktet 25 kan styres meget nøjagtigt ved hjælp af enkle, meget hurtigt virkende styreventiler.In order to lift the valve plate in the exhaust valve 10 from its seat, an even very large force is required, since the gas pressure on the valve plate in the combustion chamber must be overcome. By allowing the first larger diameter servo piston to assist in a first part of the valve opening movement and at the same time allowing the flow restricting element on the second servo piston to limit the flow of hydraulic fluid to the pressure chamber in the initial position, it is possible to achieve a controlled, but at the same time extremely strong pressure rise. in the pressure line from the valve pump to the actuator. In this way, the disadvantages of uncontrolled pressure fluctuations in the pressure line and the actuator can be reduced or avoided, and therefore a significantly longer life of the hydraulic components is obtained. Furthermore, the exhaust valve opens very quickly and the opening time 25 can be controlled very accurately by simple, very fast control valves.

Under den første del af udstødsventilens åbning er det effektive areal af servostemplet i trykkammeret stort, hvilket resulterer i en stor åbningskraft i 30 udstødsventilen, men opbygningen af denne kraft sker imidlertid behersket, eftersom indstrømningen af hydraulikvæske til trykkammeret begrænses under en indledende fase af det andet stempels bevægelse, indtil dette har bevæget sig bort fra sin udgangsstilling.During the first part of the exhaust valve opening, the effective area of the servo piston in the pressure chamber is large, resulting in a large opening force in the exhaust valve, but the build-up of this force is controlled, however, since the flow of hydraulic fluid into the pressure chamber is limited during an initial phase of the second piston movement until this has moved away from its starting position.

DK 176119 B1 3 Så snart ventiltallerkenen er løftet fra sædet, kræves der kun en væsentlig mindre kraft til resten af åbningsbevægelsen. Det er derfor en fordel herefter at lade det andet servostempel med mindre diameter udføre 5 den resterende del af åbningsbevægelsen alene, idet det hydrauliske tryk, som påvirker aktuatoren, bliver mindre.GB 176119 B1 3 As soon as the valve plate is lifted from the seat, only a substantially smaller force is required for the rest of the opening movement. It is therefore advantageous thereafter to allow the second smaller diameter servo piston to perform the remaining portion of the opening movement alone, as the hydraulic pressure affecting the actuator is reduced.

I en fordelagtig udførelsesform rager det strømningsbegrænsende element aksialt ud fra det andet 10 servostempel og er i udgangsstillingen beliggende i porten. Ved at tilpasse den længde af det strømningsbegrænsende element, som i udgangsstillingen er beliggende i porten, kan varigheden af den indledende fase, hvor tilstrømningen af hydraulikvæske til trykkammeret 15 begrænses, afpasses således, at åbningskraften i aktuatoren stiger til sin maksimalværdi så hurtigt som det er muligt, uden at der opstår uønsket store tryksvingninger. Endvidere kan tværsnittet af det strømningsbegrænsende element udformes således i forhold til 20 tværsnittet af porten, at strømningen ind i trykkammeret tiltager tilpas hurtigt ved forskydning af det andet servostempel for et kontrolleret åbningsforløb af udstødsventilen.In an advantageous embodiment, the flow limiting member projects axially from the second servo piston and is located in the starting position in the gate. By adjusting the length of the flow limiting element located in the starting position in the gate, the duration of the initial phase, in which the flow of hydraulic fluid to the pressure chamber 15 is limited, can be adjusted so that the opening force in the actuator increases to its maximum value as fast as it is. possible without undesirably large pressure fluctuations. Furthermore, the cross-section of the flow limiting element can be designed in relation to the cross-section of the port so that the flow into the pressure chamber increases rapidly by displacing the second servo piston for a controlled opening of the exhaust valve.

I en yderligere fordelagtig udførelsesform udgøres 25 porten af en cylindrisk boring, og det strømningsbegrænsende element udgøres af en cylindrisk tap. Dette er en fremstillingsmæssig og montagemæssig enkel udformning, som giver et passende strømningsforløb under åbning af ventilen. Tværsnittet af den strøm-30 ningsbegrænsende passage mellem tappen og porten er på denne måde konstant så længe, at tappen befinder sig i porten, men længden af denne passage i tappens akseretning aftager under åbningen, og derfor aftager også den strømningsbegrænsende virkning. Strømningsforløbet kan DK 176119 B1 4 således afpasses ved ændring af tappens længde og diameterforskellen mellem tappen og porten.In a further advantageous embodiment, the port is constituted by a cylindrical bore and the flow limiting member is constituted by a cylindrical pin. This is a manufacturing and assembly simple design which provides a suitable flow flow during opening of the valve. In this way, the cross-section of the flow restricting passage between the pin and the port is constant so long as the pin is in the port, but the length of this passage in the axis direction of the pin decreases during the opening, and therefore the flow restricting effect also decreases. Thus, the flow course can be adjusted by changing the length of the pin and the diameter difference between the pin and the port.

Den cylindriske tap kan med fordel have en diameter, som er mindre end 0,7, og fortrinsvis mindre end 5 0,5 gange diameteren af servostemplets samlede effektive stempelflade i trykkammeret, og en længde, som er mindre end 0,7, og fortrinsvis mindre end 0,5 gange vandringen af det første servostempel.The cylindrical pin may advantageously have a diameter less than 0.7, and preferably less than 5 0.5 times the diameter of the total effective piston surface of the servo piston in the pressure chamber, and a length less than 0.7, and preferably less than 0.5 times the migration of the first servo piston.

I en yderligere fordelagtig udførelsesform er 10 porten udformet koaksialt i en bøsning, der er centreret i forhold til servostemplet i en endevæg af trykkammeret i ventilpumpen og er skruet ind i en fordelerblok for højtryks hydraulikvæske, og bøsningen har en rundtgående endeflade, som ligger tætnende an 15 mod en rundtgående flade i fordelerblokken. På denne måde kan der undgås separate tætningselementer, såsom tætningsringe, mellem forsyningskanalen for højtryks hydraulikvæske i fordelerblokken og portens udmunding i trykkammeret i ventilpumpen, og der opnås en længere 20 levetid af systemet. Når on/off-styreventilen på fordelerblokken åbnes, opstår der øjeblikkeligt en ekstrem trykstigning i dette område, eftersom det andet servostempel i sin udgangsstilling begrænser tilstrømningen af hydraulikvæske fra portmundingen til trykkam-25 meret, og der stilles derfor meget store krav til tætningsegenskaberne i dette område. Bøsningen har den yderligere fordel, at den holder ventilpumpehuset centreret i forhold til fordelerblokken. Da fordelerblokken er meget stor, er det enklere at bore et 30 gevindhul for bøsningen, end det ville være at udforme en reces på oversiden af blokken.In a further advantageous embodiment, the port is coaxially formed in a sleeve centered relative to the servo piston in one end wall of the pressure chamber of the valve pump and screwed into a distributor block for high pressure hydraulic fluid and the sleeve has a circumferential end face which seals close to one another. 15 toward a circumferential surface of the distributor block. In this way, separate sealing elements, such as sealing rings, can be avoided between the supply channel for high pressure hydraulic fluid in the distributor block and the outlet of the port in the pressure chamber in the valve pump, and a longer service life of the system is achieved. When the on / off control valve on the distributor block is opened, an extreme pressure rise in this area immediately occurs, since the second servo piston in its initial position limits the flow of hydraulic fluid from the port orifice to the pressure chamber, and therefore very high demands are made on the sealing properties therein. territory. The bushing has the additional advantage of keeping the valve pump housing centered relative to the distributor block. Since the distributor block is very large, it is easier to drill a 30 threaded hole for the bushing than it would be to design a recess on the top of the block.

En anden fordel ved bøsningen er, at den efter demontering af ventilpumpen rager et stykke op fra fordelerblokken og på denne måde danner en barriere 35 mellem porten og oversiden af fordelerblokken, hvor DK 176119 B1 5 eventuelt forurenet hydraulikvæske kan samle sig. Styreventilen, som står i forbindelse med porten, er forholdsvis følsom over for smuds. Ved stempeltrækning, som er en rutinemæssig arbejdsgang, fjernes trykled-5 ningerne til aktuatorerne og i nogle tilfælde også komponenter oven på fordelerblokken, såsom ventilpumperne, og det er her fordelagtigt, at portene og dermed styreventilerne er beskyttet mod forurening under arbej dsgangen.Another advantage of the bushing is that, after dismantling the valve pump, it protrudes a distance from the distributor block and in this way forms a barrier 35 between the port and the upper side of the distributor block, where any contaminated hydraulic fluid can collect. The control valve, which is connected to the gate, is relatively sensitive to dirt. In piston drawing, which is a routine operation, the pressure lines for the actuators and in some cases also components on the distributor block, such as the valve pumps, are removed, and it is advantageous here that the ports and thus the control valves are protected against contamination during the operation.

10 Det kan være en fordel, at der i det andet servo stempel og/eller i en væg af ventilpumpen er udformet en kanal, som muliggør begrænset gennemstrømning af hydraulikvæske fra porten til trykkammeret. En sådan kanal kan erstatte en spalte mellem et strømningsbe-15 grænsende element og porten eller kan kombineres med en sådan spalte. Ved at anvende en kanal i stedet for en spalte kan det opnås, at den strømningsbegrænsende virkning bliver i det væsentlige uafhængig af hydraulikvæskens viskositet og dermed uafhængig af væskens 2 0 temperatur.It may be an advantage that in the second servo piston and / or in a wall of the valve pump, a duct is provided which allows limited flow of hydraulic fluid from the port to the pressure chamber. Such a channel may replace a gap between a flow limiting element and the gate or may be combined with such a gap. By using a channel instead of a slit, it can be achieved that the flow limiting effect becomes substantially independent of the viscosity of the hydraulic fluid and thus independent of the temperature of the fluid.

Den strømningsbegrænsende kanal kan have et tragtformet afsnit, hvorved den strømningsbegrænsende virkning kan være afhængig af strømningsretningen i kanalen. Dette kan være en fordel, hvis der ønskes en 25 anden gennemstrømning ved lukning af ventilen end ved åbningen.The flow restricting channel may have a funnel-shaped section, whereby the flow restricting effect may be dependent on the flow direction in the channel. This can be advantageous if a different flow is desired in closing the valve than in the opening.

Opfindelsen vil i det følgende blive forklaret nærmere ved hjælp af eksempler på udførelsesformer under henvisning til den skematiske tegning, på hvilken 30 fig. 1 viser en skitse af en cylinder i en totakts krydshovedmotor, med et cylinderdæksel vist i tværsnit, fig. 2 til 4 et længdesnit gennem en ventilpumpe, idet servostemplerne er vist i tre forskellige arbejdsstillinger, og ventilpumpen samtidigt er vist i tre 35 forskellige snitplaner, DK 170119 B1 6 fig. 5 tryk- og positionskurver, der illustrerer åbningsforløbet for et kendt system til hydraulisk aktivering af en udstødsventil, og fig. 6 kurver svarende til de i fig. 5 viste for 5 et system ifølge den foreliggende opfindelse.The invention will now be explained in more detail by way of examples of embodiments with reference to the schematic drawing, in which FIG. 1 shows a sketch of a cylinder in a two-stroke cross-head motor, with a cylinder cover shown in cross section; FIG. 2 to 4 are a longitudinal section through a valve pump, the servo pistons being shown in three different working positions, and the valve pump being simultaneously shown in three different sectional planes, FIG. 17; 5 are pressure and position curves illustrating the opening process of a known system for hydraulically activating an exhaust valve; and FIG. 6 curves similar to those in FIG. 5 showed for 5 a system according to the present invention.

I fig. 1 ses en cylinder 1, der er af længdeskyllet type, og hvor en udstødsventil 2 er monteret centralt i toppen af cylinderen i et cylinderdæksel 3. Ved afslutningen af ekspansionsslaget åbner udstødsventilen 10 under overvindelse af kræfterne fra gastrykket i cylinderen 1. Der kan være tale om åbning mod eksempelvis omtrent 10 bars overtryk. Udstødsventilen lukker igen under stemplets opadgående bevægelse, idet den drives opad af en pneumatisk fjeder 4 eller en hydrau-15 lisk drivenhed.In FIG. 1 is a longitudinally flush type cylinder 1, in which an exhaust valve 2 is mounted centrally at the top of the cylinder in a cylinder cover 3. At the end of the expansion stroke, the exhaust valve 10 opens, under the control of the gas pressure forces in the cylinder 1. There may be talk about opening against, for example, about 10 bars overpressure. The exhaust valve closes again during the upward movement of the piston as it is driven upwards by a pneumatic spring 4 or a hydraulic drive unit.

Af hensyn til udstødsventilens holdbarhed og til en fordelagtig nøjagtig styring af forholdene i forbrændingskammeret og dermed af motorens virkningsgrad kan åbningen af ventilen 2 med fordel styres meget 20 præcist.In view of the durability of the exhaust valve and of an advantageously accurate control of the conditions in the combustion chamber and thus of the efficiency of the engine, the opening of the valve 2 can advantageously be controlled very precisely.

Forbrændingsmotoren har en cylinderboring i intervallet fra 210 til 1100 mm og kan være en mellemhastigheds firtaktsmotor, men er typisk en langsomt-gående totakts krydshovedmotor, der kan være frem-25 drivningsmotor i et skib eller en stationær drivenhed i et kraftværk. Motoren kan udformes i forskellige størrelser med ydelser per cylinder fra 400 kW til 5500 kW, og den kan have omdrejningstal ved fuldlast beliggende i intervallet fra 50 til 600 rpm, typisk højst 30 300 rpm.The internal combustion engine has a cylinder bore in the range of 210 to 1100 mm and can be a medium-speed four-stroke engine, but is typically a slow-moving two-stroke cross-head motor that can be a propulsion engine in a ship or a stationary drive unit in a power plant. The engine can be designed in different sizes with performance per cylinder from 400 kW to 5500 kW, and it can have full load rpm ranging from 50 to 600 rpm, typically at most 30 300 rpm.

Udstødsventilen 2 åbnes ved hjælp af en aktuator 5, der er hydraulisk drevet og kan have flere trin. Et trykkammer i aktuatoren 5 står via en trykledning 6 i forbindelse med en øvre tilslutning 7 på ventilpumpe 8.The exhaust valve 2 is opened by means of an actuator 5 which is hydraulically driven and can have several steps. A pressure chamber in the actuator 5 is connected via a pressure line 6 in connection with an upper connection 7 on the valve pump 8.

35 Ventilpumpen 8 er monteret på oversiden af en for- ! DK 176119 B1 7 delerblok 9, der er båret af en konsol 10, idet ventil-pumpen 8 er i forbindelse med en afgang for højtryks hydraulikvæske på fordelerblokken 9. Konsollen er tilsluttet en høj tryksledning 11 for hydraulikvæske, der 5 fra en ikke vist pumpestation forsynes med hydraulikvæske ved et tryk, der eksempelvis kan være beliggende i intervallet fra 125 til 325 bar. Trykket kan være fast, men er fortrinsvis regulerbart i afhængighed af motorens belastning. Pumpestationen kan forsynes fra 10 en lagertank og kan eksempelvis være en standard hydraulikolie, men det foretrækkes, at motorens smøreolie anvendes som hydraulikvæske, og at systemet fødes fra motorens oliesump. Da ventilpumpen 8 har et totrins servostempel, kan der med fordel anvendes en enkelt-15 trins standardaktuator for udstødsventilen 2.35 The valve pump 8 is mounted on the upper side of a front! DK 176119 B1 7 dividing block 9 carried by a bracket 10, the valve pump 8 communicating with an outlet for high pressure hydraulic fluid on the distributor block 9. The console is connected to a high pressure line 11 for hydraulic fluid 5 from a pump station not shown. is supplied with hydraulic fluid at a pressure which may, for example, be in the range of 125 to 325 bar. The pressure may be fixed, but is preferably adjustable depending on the load of the motor. The pump station may be supplied from a storage tank and may, for example, be a standard hydraulic oil, but it is preferred that the engine lubricating oil be used as hydraulic fluid and that the system be fed from the engine oil sump. Since the valve pump 8 has a two-stage servo piston, a single 15-stage standard actuator for the exhaust valve 2 can advantageously be used.

Hver cylinder på motoren er tilknyttet en elektronisk styreenhed 12, der modtager overordnede synkroniserings- og styresignaler gennem ledninger 13 og afgiver elektroniske styresignaler til blandt andet en 20 styreventil 14 gennem en ledning 15. Der kan være en styreenhed 12 per cylinder, eller flere cylindre kan være tilknyttet samme styreenhed. Styreenheden kan også modtage signaler fra mindst én overordnet styreenhed, der er fælles for alle cylindrene.Each cylinder of the motor is associated with an electronic control unit 12 which receives overall synchronization and control signals through wires 13 and outputs electronic control signals to, inter alia, a 20 control valve 14 through a conduit 15. There may be one control unit 12 per cylinder or several cylinders may be associated with the same controller. The controller can also receive signals from at least one parent controller common to all cylinders.

25 I konsollen 10 leder en afgrenet kanal 19 fra høj tryksledningen 11 den tryksatte hydraulikvæske frem til en højtryksport på styreventilen 14. Kanalen 19 er forsynet med et antal væskeakkumulatorer 16, der leverer hovedparten af væskemængden, når styreventilen 30 åbner, og efterfødes fra højtryksledningen, mens styreventilen er lukket. En styreport på styreventilen er via en kanal 17 i fordelerblokken 9 forbundet med den afgang på blokkens overside, som er i forbindelse med ventilpumpen 8. Styreventilen har endvidere en 35 lavtryksport for returnering af brugt hydraulikvæske.In the bracket 10, a branched duct 19 from the high pressure line 11 conducts the pressurized hydraulic fluid to a high pressure port on the control valve 14. The channel 19 is provided with a plurality of fluid accumulators 16 which supply most of the liquid quantity when the control valve 30 opens and is reborn from the high pressure line. while the control valve is closed. A control port on the control valve is connected via a channel 17 in the distributor block 9 to the outlet on the upper side of the block which is connected to the valve pump 8. The control valve further has a low pressure port for returning used hydraulic fluid.

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Styreventilen 14 kan være af enhver sædvanlig type, såsom en sædvanlig solenoideventil. For at opnå meget hurtige, præcise ventilindstillinger foretrækkes dog, at styreventilen 14 er sammensat af to ventiler, 5 nemlig en elektronisk aktiveringsventil 14a og en hovedventil 14b for ventilpumpen. Aktiveringsventilen 14a kan eksempelvis være af typen med magnetisk låsning i yderstillingerne, hvor ventilen aktiveres ved magnetisering af en af to spoler beliggende ved hver ende af 10 en ventilglider af ferromagnetisk materiale. Aktiveringsventilen kan i øvrigt være udformet som beskrevet i WO 98/57048, hvortil der henvises. Der henvises også til ansøgerens danske patent nr. 172961 for en detaljeret beskrivelse af en hydraulisk cylin-15 derenhed.The control valve 14 can be of any conventional type, such as a conventional solenoid valve. However, to achieve very fast, precise valve settings, it is preferred that the control valve 14 is composed of two valves, namely an electronic actuation valve 14a and a main valve 14b for the valve pump. For example, the actuating valve 14a may be of the magnetic locking type in the outer positions where the valve is actuated by magnetizing one of two coils located at each end of 10 a valve slider of ferromagnetic material. Furthermore, the actuating valve may be designed as described in WO 98/57048, to which reference is made. Reference is also made to Applicant's Danish Patent No. 172961 for a detailed description of a hydraulic cylinder unit.

Fig. 2 til 4 viser en ventilpumpe 8 ifølge opfindelsen. Ventilpumpen 8's hus 31 er sammensat af tre oven på hinanden beliggende blokke 20, 21, 22, hvoraf den nederste ligger an mod oversiden af fordelerblokken 20 9. Blokkene er spændt fast mod hinanden og fordelerblokken 9 ved hjælp af gennemgående stavbolte 23.FIG. 2 to 4 show a valve pump 8 according to the invention. The valve 31 of the valve pump 8 is composed of three superposed blocks 20, 21, 22, the lower of which abuts the upper side of the distributor block 20 9. The blocks are clamped to each other and the distributor block 9 by means of through-going bolts 23.

Det bemærkes, at ventilpumpen 8 kunne orienteres anderledes end vist, eksempelvis kunne den monteres mod en lodret side af fordelerblokken 9. Kanalen 17, som 25 forbinder styreporten på styreventilen 14 med ventilpumpen 8, udmunder i fordelerblokkens overside i et gevindhul 24, hvori er skruet en nedre del af en bøsning 25 med ydre gevind. Idet gevindhullet 24 har større diameter end kanalen 17, er der ved bunden af 30 gevindhullet i fordelerblokken en rundtgående flade 27, imod hvilken en nedre ringformet endeflade 26 af bøsningen 25 ligger tætnende an. En øvre del af bøsningen 25 uden gevind rager op over fordelerblokken 9 og er indsat centrerende i en boring i den nedre blok 35 22 af ventilpumpen 8.It should be noted that the valve pump 8 could be oriented differently than shown, for example, it could be mounted against a vertical side of the distributor block 9. The channel 17 connecting the control port of the control valve 14 with the valve pump 8 opens into the upper side of the distributor block in a threaded hole 24 which is screwed into it. a lower portion of an outer threaded bush 25. Since the threaded hole 24 has a larger diameter than the channel 17, at the bottom of the threaded hole 30 in the distributor block there is a circumferential surface 27 against which a lower annular end face 26 of the sleeve 25 seals. An upper portion of the sleeve 25 without threads protrudes over the distributor block 9 and is inserted centrally into a bore in the lower block 35 22 of the valve pump 8.

DK 176119 B1 9DK 176119 B1 9

En indre cylindrisk boring i bøsningen 25 danner en port 29, som via kanalen 17 er forbundet med styreventilen 14, og som udmunder i et trykkammer 3 0 i ventilpumpen 8. Trykkammeret 30 er afgrænset af huset 5 31 og af undersiden af det i huset forskydelige servostempel, som omfatter et første servostempel 32 og et i dette koaksialt forskydeligt andet servostempel 33.An inner cylindrical bore in the sleeve 25 forms a port 29 which, via the channel 17, is connected to the control valve 14 and opens into a pressure chamber 30 in the valve pump 8. The pressure chamber 30 is defined by the housing 5 31 and the underside of the housing displaceable in the housing. a servo piston which comprises a first servo piston 32 and a second servo piston 33 displaceable therein.

Det første servostempel 32 har et øvre cylindrisk afsnit 34, som er ført tætnende aksialt i en boring 36 10 i huset 31, og et nedre afsnit, som udgør en cylindrisk krave 35 med større diameter end det øvre afsnit 34.The first servo piston 32 has an upper cylindrical section 34 which is sealed axially in a bore 36 10 in the housing 31, and a lower section which constitutes a cylindrical collar 35 of greater diameter than the upper section 34.

Kraven 35 har en opadvendende rundtgående flade 37, som kan lægge an mod en nedadvendende flade 38 og derved definere et øvre anslag for den opadgående bevægelse af 15 det første servostempel 32. Fladen 38 danner i huset 31 overgang mellem boringen 36 og en neden under og koaksialt med denne udformet boring 39, som danner ydervæg i trykkammeret 30. Boringen 39 har et øvre afsnit 40, som kan slutte forholdsvis tæt med ydersiden 20 af kraven 35, således at den opadgående bevægelse af det første servostempel 32 kan nedbremses inden anslaget mellem fladerne 37, 38, idet der indesluttes hydraulikvæske på i sig selv kendt måde mellem kraven 35, fladen 38 og boringsafsnittet 40. Boringen 39 har 25 endvidere et nedre afsnit 41, som har lidt større diameter end det øvre afsnit 40, således at det første servostempel 32 kan bevæges op og ned uden bremsevirk-ning, så længe kraven 35 befinder sig ud for boringsafsnittet 41.The collar 35 has an upwardly facing circumferential surface 37 which can abut against a downwardly facing surface 38, thereby defining an upper stop for the upward movement of the first servo piston 32. The surface 38 forms in the housing 31 a transition between the bore 36 and one below and below. coaxially with this formed bore 39 which forms outer wall of the pressure chamber 30. The bore 39 has an upper section 40 which can connect relatively tightly to the outside 20 of the collar 35, so that the upward movement of the first servo piston 32 can be slowed down before the impact between the surfaces. 37, 38, enclosing hydraulic fluid in a manner known per se between the collar 35, the surface 38 and the bore section 40. The bore 39 further has a lower section 41 which is slightly larger in diameter than the upper section 40, so that the first servo piston 32 can be moved up and down without braking action as long as the collar 35 is off the bore section 41.

30 Det andet servostempel 33 har et nedre afsnit 42, som er koaksialt og tætnende forskydeligt i en boring 43 i det første servostempel 32, og et øvre afsnit 44, som har større diameter end det nedre afsnit 42 og er tætnende forskydeligt i en øvre boring 45, som i huset 35 31 er udformet med større diameter end boringen 36. Ved OK 1176119 B1 ίο overgangen mellem boringerne 36, 45 er der i huset udformet et ringkammer 46, som har større diameter end boringen 45 og er forbundet med en drænkanal 47, som er antydet med brudte linier i fig. 3. Oven over det andet 5 servostempel 33 er der i boringen 45 indesluttet et hydraulikvæskevolumen, som via tilslutningen 7 står i forbindelse med en væskesøjle i trykledningen 6, hvis anden ende er forbundet med trykkammeret i ventilaktua-toren 5.The second servo piston 33 has a lower section 42 which is coaxially and sealingly displaceable in a bore 43 of the first servo piston 32, and an upper section 44 which is larger in diameter than the lower section 42 and is sealingly displaceable in an upper bore 45, which is formed in the housing 35 31 with a larger diameter than the bore 36. At OK 117611, in the transition between the bores 36, 45, an annular chamber 46 is formed which has a larger diameter than the bore 45 and is connected to a drain channel 47. , which is indicated by broken lines in FIG. 3. Above the second servo piston 33, a hydraulic fluid volume is enclosed in the bore 45, which via the connection 7 communicates with a liquid column in the pressure line 6, the other end of which is connected to the pressure chamber in the valve actuator 5.

10 Via tilgangen 48, som er vist i fig. 2, og som i huset 31 står i forbindelse med tilslutningen 7, kan trykledningen 6 efterfyldes med hydraulikvæske gennem en ikke vist kontraventil. Efterfyldningen kan ske fra en lavtryksledning med et væsketryk på eksempelvis 4 15 bars overtryk, og sker for at kompensere for lækage mellem stempler og cylindre i aktuatoren 5 og ventilpumpen 8. I den i fig. 3 viste boring 49, som står i forbindelse med tilslutningen 7 og drænkanalen 47, er indsat en ikke vist ventil, som kan åbnes for tømning 20 af trykledningen 6 for væske ved demontage. Trykledningen 6 omfatter et inderrør 50 og et yderrør 51, således at der dannes et ringkammer mellem disse. Ringkammeret 52 står via den i fig. 3 viste kanal 53 i forbindelse med en ikke vist tryksensor, således at en 25 eventuel lækage af inderrøret 50 derved kan registreres .10 Via the access 48 shown in FIG. 2, and which in the housing 31 is connected to the connection 7, the pressure line 6 can be replenished with hydraulic fluid through a non-return valve. The backfill can be effected from a low-pressure line with a liquid pressure of, for example, 4 15 bar overpressure, and is done to compensate for leakage between pistons and cylinders in the actuator 5 and the valve pump 8. 3, which is in communication with the connection 7 and the drainage channel 47, is inserted a valve not shown, which can be opened for emptying 20 of the liquid pressure conduit 6 for disassembly. The pressure line 6 comprises an inner tube 50 and an outer tube 51, so that an annular chamber is formed between them. The annular chamber 52 is via the device shown in FIG. 3 in conjunction with a pressure sensor not shown, so that any leakage of the inner tube 50 can thereby be detected.

Den viste ventilpumpe 8 har et større effektivt stempelareal i boringen 45, end det effektive stempelareal i trykkammeret 30, således at eksempelvis et 30 hydrauliktryk på 210 bar i kammeret 30 kan resultere i et tryk på omkring 140 bar i boringen 45, hvilket kan være fordelagtigt, hvis der ønskes anvendt en standard-udstødsaktuator 5, som er udlagt til dette tryk, men servostemplerne kan udformes med andre stempelarealer, 35 alt efter det ønskede tryk ved aktuatoren 5.The valve pump 8 shown has a larger effective piston area in the bore 45 than the effective piston area in the pressure chamber 30, such that, for example, a hydraulic pressure of 210 bar in the chamber 30 can result in a pressure of about 140 bar in the bore 45, which can be advantageous. , if a standard exhaust actuator 5 applied to this pressure is desired, but the servo pistons can be formed with other piston areas, depending on the desired pressure at the actuator 5.

DK 176119 B1 11DK 176119 B1 11

Porten 29 i bøsningen 25 er centreret koaksialt i forhold til servostemplerne 32, 33, og det andet servos tempel 33 har en fra sin nedre ende koaksialt ' udragende tap 54 med et nedre konisk afsnit 55, Tappen 5 54 har lidt mindre diameter end porten 29 og ligger i udgangsstillingen af det andet servostempel 33 inde i porten 29, som vist i fig. 2.The port 29 of the sleeve 25 is centered coaxially relative to the servo pistons 32, 33, and the temple of the second servo 33 has a coaxially projecting pin 54 with a lower tapered portion 55, the pin 5 54 having a slightly smaller diameter than the port 29. and lies in the starting position of the second servo piston 33 within the port 29, as shown in FIG. 2nd

Når udstødsventilen skal åbnes, aktiverer et styresignal fra styreenheden 12 styreventilen 14 til 10 den stilling, hvor højtryksporten er forbundet med styreporten, så højtryksvæsken har fri adgang til porten 29 i ventilpumpen 8. Da tappen 54 ligger i porten 29, kan højtryksvæsken imidlertid kun umiddel- ( bart påvirke endefladen 56 af tappen 54, og da denne 15 flade 56 har væsentlig mindre areal end det samlede effektive stempelareal af servostemplerne 32, 33, giver dette kun anledning til en begrænset kraft på det andet servostempel 33. Der kan dog med begrænset hastighed strømme hydraulikvæske fra porten 29 til trykkammeret 20 30 via den ringformede passage mellem tappen 54 og porten 29, og der opstår derfor også et begrænset væsketryk på resten af det samlede stempelareal i trykkammeret 30. Følgeligt bevæger begge servostemplerne 32, 33 sig opad. Efterhånden som tappen 54 bevæges 25 ud af porten 29, mindskes længden af passagen mellem tappen 54 og porten 29, således at strømningsmodstanden bliver mindre, og stemplerne 32, 33's bevægelseshastighed tiltager. Når tappen 54 er helt ude af porten 29, har højtryksvæsken fri adgang til trykkammeret 30, og 30 bevægelseshastigheden tiltager væsentligt. Når det første servostempel 32 som ovenfor beskrevet lægger an mod sit øvre anlæg 38, som vist i fig. 3, bevæger det andet servostempel sig videre alene indtil sin topstilling, som er vist i fig. 4, og som svarer til fuldt 35 åben stilling af udstødsventilen 2.When the exhaust valve is to be opened, a control signal from the control unit 12 activates the control valve 14 to 10 to the position where the high pressure port is connected to the control port, so that the high pressure fluid has free access to the port 29 in the valve pump 8. However, the pin 54 is located in the port 29 only (notably affecting the end face 56 of the pin 54, and since this face 56 has substantially less area than the total effective piston area of the servo pistons 32, 33, this gives rise only to a limited force on the second servo piston 33. However, with limited hydraulic fluid flows from the port 29 to the pressure chamber 20 via the annular passage between the pin 54 and the port 29, and therefore a limited fluid pressure also arises on the remainder of the total piston area in the pressure chamber 30. Consequently, both the servo pistons 32, 33 move upward. as the pin 54 is moved 25 out of the port 29, the length of the passage between the pin 54 and the port 2 is reduced 9 so that the flow resistance becomes smaller and the speed of movement of the pistons 32, 33 increases. When the pin 54 is completely out of the port 29, the high pressure fluid has free access to the pressure chamber 30 and the speed of movement increases substantially. When the first servo piston 32, as described above, abuts its upper abutment 38, as shown in FIG. 3, the second servo piston moves on its own until its peak position shown in FIG. 4, which corresponds to the fully open position of the exhaust valve 2.

DK 176119 B1 12DK 176119 B1 12

Fig. 5 illustrerer åbningsforløbet for en udstødsventil i et kendt system som funktion af krumtapstillingen vist i grader efter stemplets topdød-punkt, idet kurven p viser hydrauliktrykket i trykled-5 ningen efter ventilpumpen angivet i bar, kurven v viser positionen af udstødsventilen angivet i millimeter, og kurven s viser positionen af servostemplet angivet i millimeter. Det fremgår, at hydrauliktrykket p i trykledningen først stiger næsten øjeblikkeligt til 10 cirka 120 til 130 bar og derefter falder drastisk til omkring nul igen, hvorefter det fortsætter med at svinge kraftigt op og ned, også efter at udstødsventilen har stabiliseret sig nogenlunde i åben stilling.FIG. 5 illustrates the opening flow of an exhaust valve in a known system as a function of the crank position shown in degrees after the piston's top dead point, the curve p showing the hydraulic pressure in the pressure line after the valve pump indicated in bar, the curve v showing the position of the exhaust valve indicated in millimeters, and curve s shows the position of the servo piston indicated in millimeters. It can be seen that the hydraulic pressure p in the pressure line first increases almost immediately to about 120 to 130 bar and then drops drastically to about zero again, after which it continues to swing strongly up and down, even after the exhaust valve has stabilized somewhat in the open position.

Disse kraftige tryksvingninger bevirker en negativ 15 påvirkning af hele det hydrauliske system fra ventilpumpen til udstødsaktuatoren, og navnlig kan de store trykfald give anledning til kavitation. Eksempelvis kan en kontraventil til efterfyldning af hydraulikvæske i trykledningen mellem ventilpumpen og aktuatoren tage 20 skade af tryksvingningerne. Hvis efterfyldningen eksempelvis sker fra en lavtryksledning med et overtryk på 4 bar, så vil de store negative trykstød i trykledningen få kontraventilen til at åbne, og de meget større positive trykstød vil få den til at lukke meget 25 voldsomt. Endvidere kan eventuelle kontraventiler i udstødsventilens aktuator påvirkes af trykstødene, ligesom trykledningen selv samt dennes monteringsbeslag kan tage skade.These strong pressure fluctuations adversely affect the entire hydraulic system from the valve pump to the exhaust actuator, and in particular, the large pressure drops can cause cavitation. For example, a check valve for replenishing hydraulic fluid in the pressure line between the valve pump and the actuator can damage the pressure fluctuations. For example, if the backfill occurs from a low pressure line with an overpressure of 4 bar, then the large negative pressure shocks in the pressure line will cause the check valve to open and the much larger positive pressure shocks will cause it to close very violently. Furthermore, any non-return valves in the actuator of the exhaust valve can be affected by the pressure shocks, and the pressure line itself and its mounting bracket can be damaged.

Fig. 6 illustrerer åbningsforløbet for udstødsven-30 tilen 2 i systemet ifølge den foreliggende opfindelse som funktion af krumtapstillingen vist i grader efter stemplets topdødpunkt, idet kurven p viser hydrauliktrykket i trykledningen 6 efter ventilpumpen 7 angivet i bar, kurven v viser positionen af udstødsven-35 tilen 2 angivet i millimeter, kurven si viser positio- DK 176119 B1 13 nen af det første servostempel 32 angivet i millimeter, og kurven S2 viser positionen af det andet servostempel 33 angivet i millimeter. Det fremgår, at hydrauliktryk-• ket p i trykledningen 6 først stiger til et tryk på 5 cirka 130 bar. Denne stigning sker hurtigt, men ikke nær så hurtigt som i det kendte system, og efter et kort og behersket indsvingningsforløb indtages der et konstant tryk på cirka 80 bar. Allerede ved cirka 125 grader efter topdødpunktet forekommer der ikke mere 10 voldsomme svingninger, hvor det kendte system til sammenligning stadig udviser kraftige svingninger ved 225 grader efter topdødpunktet. Efter den første trykstigning til cirka 130 bar forekommer der ingen tryksvingninger til under cirka 70 bar, og kontraventi-15 len til efterfyldning af trykledningen 6 vil derfor ikke åbne, og den udsættes følgeligt ikke for unødig belastning. Det fremgår endvidere, at udstødsventilen 2 i systemet ifølge opfindelsen åbner meget hurtigt, idet den ved mellem 125 til 150 grader er omtrent helt 20 åben, og at dens åbningskurve v er jævnt stigende og uden svingninger.FIG. 6 illustrates the opening flow of the exhaust valve 2 in the system of the present invention as a function of the crank position shown in degrees after the piston top dead-end, the curve p showing the hydraulic pressure in the pressure line 6 after the valve pump 7 indicated in the bar, the curve v showing the position of the exhaust valve 35 2 is shown in millimeters, the curve s1 shows the position of the first servo piston 32 indicated in millimeters, and the curve S2 shows the position of the second servo piston 33 indicated in millimeters. It can be seen that the hydraulic pressure p in the pressure line 6 first increases to a pressure of about 130 bar. This increase is rapid, but not nearly as fast as in the known system, and after a short and controlled oscillation process a constant pressure of about 80 bar is taken. Already at about 125 degrees after the peak deadlock, there are no more 10 violent swings, with the known system for comparison still exhibiting strong swings at 225 degrees after the peak deadlock. After the first pressure rise to about 130 bar, no pressure fluctuations occur below about 70 bar, and the counter-valve for filling the pressure line 6 will therefore not open and consequently it is not subjected to unnecessary load. Furthermore, it is seen that the exhaust valve 2 in the system according to the invention opens very quickly, at between 125 and 150 degrees it is approximately fully open and that its opening curve v is uniformly rising and without oscillations.

Når udstødsventilen 2 skal lukkes, aktiveres styreventilen til den stilling, hvor lavtryksporten er forbundet med styreporten, hvorved højtrykket i tryk-25 kammeret 30 drænes bort. Idet udstødsventilen er belastet mod sin lukkestilling af den pneumatiske fjeder 4, er der i trykledningen 7 et forholdsvist højt tryk, eksempelvis 80 til 100 bar, og for ved lukning af udstødsventilen 2 at undgå store tryksvingninger i 30 systemet er det andet servostempel 33 ved sin i boringen 45 beliggende overside forsynet med en strømnings-begrænsende tap 57, som i stemplets øvre stilling ligger i en port 58, som danner udmundingen af tilslutningen 7 i boringen 45, se fig. 4. Tappen 57 35 begrænser servostemplets nedadgående acceleration fra 14 ! DK 17611119 B1 den øvre udgangsstilling, og det hindres derved, at trykket i trykledningen 6 aflastes for pludseligt, hvilket kan føre til uønsket store tryksvingninger i systemet.When the exhaust valve 2 is to be closed, the control valve is activated to the position where the low pressure port is connected to the control port, whereby the high pressure in the pressure chamber 30 is drained away. As the exhaust valve is loaded against its closing position by the pneumatic spring 4, in the pressure line 7 there is a relatively high pressure, for example 80 to 100 bar, and in order to avoid large pressure fluctuations in the system, the second servo piston 33 is at its located on the upper side of the bore 45, provided with a flow-limiting pin 57, which in the upper position of the piston lies in a port 58 which forms the mouth of the connection 7 in the bore 45, see fig. 4. Pin 57 35 restricts the servo piston's downward acceleration from 14! DK 17611119 B1 the upper starting position, thereby preventing the pressure in the pressure line 6 from being relieved too suddenly, which can lead to undesirably large pressure fluctuations in the system.

5 Ved at tilpasse udformningen af tappen 54 kan åbningsforløbet optimeres, således kan diameteren og længden af tappen varieres, og eksempelvis kan et længere konisk afsnit 55 medføre, at den strømningsbegrænsende virkning af tappen 54 aftager mere gradvist.By adapting the design of the pin 54, the opening process can be optimized, thus the diameter and length of the pin can be varied, and for example, a longer conical section 55 can cause the flow limiting effect of the pin 54 to decrease more gradually.

10 Det er endvidere muligt at supplere eller erstatte passagen mellem tappen 54 og porten 29 med en kanal som delvist kortslutter tappens strømningsbegrænsende virkning. Kanalen kan udformes i tappen 54 eller i bøsningen 25 og eventuelt væggen af huset 31.It is further possible to supplement or replace the passage between the pin 54 and the port 29 with a channel partially shorting the flow limiting effect of the pin. The duct may be formed in the pin 54 or in the bush 25 and optionally the wall of the housing 31.

15 Tapperne 54, 57 medfører endvidere en passende opbremsning af det andet servostempel 33, inden det når henholdsvis sin nedre og øvre udgangsstilling, idet hydraulikvæske indesluttes i trykkammeret 30 eller i boringen 45 og presses ud gennem passagen mellem den 20 respektive tap 54, 57 og dennes tilhørende port 29, 58.The pins 54, 57 further provide a suitable braking of the second servo piston 33 before reaching its lower and upper starting positions, respectively, with hydraulic fluid being enclosed in the pressure chamber 30 or in the bore 45 and pressed out through the passage between the respective pins 54, 57 and its associated gate 29, 58.

Den ovenfor omtalte kanal til kortslutning af tapperne 54, 57's strømningsbegrænsende virkning kan endvidere omfatte et konisk afsnit, således at den strømningsbegrænsende virkning er afhængig af gennemstrømnings-25 retningen, og følgeligt er forskellig ved acceleration og deceleration af servostemplet.The above-mentioned channel for short-circuiting the flow limiting effect of the pins 54, 57 may further comprise a conical section such that the flow limiting effect is dependent on the flow direction and consequently differs in acceleration and deceleration of the servo piston.

Claims

A system for hydraulically activating an exhaust valve (2) in an internal combustion engine, wherein a pressure chamber (30) in a valve pump (8) has a port (29) which can be connected alternately to a valve (14) by means of a control valve (14). a high pressure source for hydraulic fluid or for reflux, and wherein a servo piston in the valve pump (8) separates the pressure chamber (30) from a hydraulic volume communicating via a pressure line (6) with a pressure chamber in a hydraulic actuator (5) with the spindle of the exhaust valve, characterized in that the servo piston comprises a first servo piston (32) and a second servo piston (33) displaceable therein, and the second servo piston (33) in the pressure chamber (30) has a flow restricting element (54), which is located in a starting position of the servo piston (33) at the port (29), so as to limit the flow of hydraulic fluid from the port (29) to the pressure chamber (30).

System according to claim 1, characterized in that the flow limiting element (54) projects axially from the second servo piston (33) and in the starting position of the servo piston (33) is located in the port (29).

System according to claim 2, characterized in that the port is constituted by a cylindrical bore (29) and the flow limiting element is constituted by a cylindrical pin (54).

System according to claim 3, characterized in that the cylindrical pin (54) has a diameter of less than 0.7, and preferably less than 0.5 times the diameter of the total effective piston surface of the servo piston in the pressure chamber, and a length. , which is less than 0.7, and preferably less than 0.5 times the migration of the first servo piston (32). DK 176119 B1

System according to one of the preceding claims, characterized in that the port (29) is formed coaxially in a sleeve (25) which is centered relative to the servo piston (32, 33) in an end wall of the pressure chamber (30). ) in the valve pump (8) and screwed into a distributor block (9) for high pressure hydraulic fluid, and that the bushing (25) has a circumferential end face (26) which seals against an annular surface (27) in the distributor block (9). .

System according to one of the preceding claims, characterized in that a duct is provided in the second servo piston (33) and / or in a wall of the valve pump (8) which permits limited flow of hydraulic fluid from the port (29) to pressure chamber (30).

System according to claim 6, characterized in that the channel has a funnel-shaped section. 20