DK173829B1

DK173829B1 - Hydraulically activated exhaust valve for an internal combustion engine

Info

Publication number: DK173829B1
Application number: DK199901284A
Authority: DK
Inventors: Erik Rosenlund Hansen
Original assignee: Man B & W Diesel As
Priority date: 1999-09-13
Filing date: 1999-09-13
Publication date: 2001-12-03
Also published as: DK199901284A

Description

i DK 173829 B1in DK 173829 B1

Opfindelsen angår en hydraulisk aktiveret udstødsventil til en forbrændingsmotor, med en hydraulisk aktuator omfattende mindst et første aktuatorstempel, som er anbragt koaksialt i forlængelse af udstødsventi-5 lens spindel og forskydeligt i en cylinder, således at der afgrænses et trykkammer for hydraulikvæske, som kan tilføres og bortledes gennem en hydraulikvæskekanal, hvorved udstødsventilen kan åbnes og lukkes.The invention relates to a hydraulically actuated exhaust valve for an internal combustion engine, with a hydraulic actuator comprising at least one first actuator piston which is arranged coaxially in extension of the spindle of the exhaust valve and displaceable in a cylinder, so as to define a hydraulic fluid pressure chamber which can be supplied and discharged through a hydraulic fluid passage allowing the exhaust valve to be opened and closed.

Ved udstødsventiler af denne art er bevægelsen af 10 et aktuatorstempel normalt dæmpet for at bremse ventilens lukkebevægelse. Ved driften af motoren kan der forekomme mærkbare længdeændringer af ventilspindlen fra den kolde starttilstand til den varme driftstilstand og/eller som følge af ventilslid. Disse uund-15 gåelige længdeændringer giver betydelig risiko for uønsket hårde ventillukninger, eftersom der ikke altid sker en konstant bremsning af ventilens lukkebevægelse.In exhaust valves of this kind, the movement of an actuator piston is usually attenuated to slow the valve closing movement. During operation of the engine, noticeable length changes of the valve spindle may occur from the cold start state to the hot operating state and / or due to valve wear. These undesirable longitudinal changes present a significant risk of unwanted hard valve closures, as the valve closing movement does not always slow.

Der er derfor i den kendte teknik blevet kompenseret herfor på forskellig vis.The prior art has therefore been compensated for this in various ways.

20 PCT/DK98/00219 beskriver en udstødsventil med en aktuator, som omfatter et første og et andet stempel, hvor det første stempel har en fast udgangsposition, idet det ved en dæmpet bevægelse lægger an mod ventilhuset under lukning af ventilen. For at kompensere for 25 længdeændringer mellem aktuatorstemplet og ventilens bevægelige sædeflade er der indsat en spillerumsudligner mellem aktuatoren og ventilspindlen. Spillerumsudligneren overfører den fulde spindelkraft ved åbning og lukning af udstødsventilen, og der er derfor tale om 30 en ekstra komponent af betydelige dimensioner.PCT / DK98 / 00219 describes an exhaust valve with an actuator comprising a first and a second piston, the first piston having a fixed initial position, abutting the valve housing during a damped movement during closing of the valve. To compensate for 25 length changes between the actuator piston and the movable seat surface of the valve, a clearance equalizer has been inserted between the actuator and the valve stem. The game room equalizer transmits the full spindle force when opening and closing the exhaust valve, and this is therefore an additional component of considerable dimensions.

DE 38 09 954 beskriver en ventil til en forbrændingsmotor, hvor et aktuatorstempel er stift forbundet med ventiIspindlen og ved lukning af ventilen føres ind i et udligningsstempel, som er sammensat af en cylin-35 dervæg og en bund, og som er forskydeligt i en cylinder DK 173829 B1 2 i ventilhuset. Ved åbning og ved opbremsningen under lukning af ventilen bærer udligningsstemplet imidlertid lige så stor en kraft som aktuatorstemplet og skal derfor have dimensioner af samme størrelse som dette, 5 hvilket navnlig ved store motorer er en ulempe. Det er endvidere en ulempe, at oliekammeret over udligningsstemplet aktivt skal efterfyldes med olie ved hver lukning af ventilen.DE 38 09 954 discloses a valve for an internal combustion engine in which an actuator piston is rigidly connected to the valve spindle and, when the valve is closed, is inserted into a compensating piston which is composed of a cylinder wall and a bottom and which is displaceable in a cylinder. DK 173829 B1 2 in the valve body. However, when opening and braking during the closing of the valve, the compensating piston carries as much force as the actuator piston and must therefore have dimensions of the same size as this, which is a disadvantage especially for large motors. Furthermore, it is a disadvantage that the oil chamber above the equalizing piston must be actively replenished with oil at each closing of the valve.

Den foreliggende opfindelse har til formål at 10 anvise en hydraulisk aktiveret udstødsventil, som ikke har de ovenfor nævnte ulemper, og hvor der opnås en ensartet dæmpning af ventilens lukkebevægelse.The present invention has for its object to provide a hydraulically actuated exhaust valve which does not have the disadvantages mentioned above, and where a uniform damping of the closing movement of the valve is obtained.

Med henblik herpå er ventilen ejendommelig ved, at et ventilelement er lejret forskydeligt i det første 15 aktuatorstempel i dettes akseretning og fjederbelastet bort fra aktuatorstemplet til anlæg mod mindst et positioneringselement, som ved forskydning i aktuatorstemplet i dettes akseretning kan ændre volumenet af et positioneringskammer i aktuatorstemplet, idet såvel 20 positioneringselementet (28) som aktuatorstemplet (19) har en flade, som afgrænser positioneringskammeret (42) i aktuatorstemplets (19) akseretning, at der mellem positioneringskammeret (42) og trykkammeret (21) er en begrænset strømningspassage, at positioneringselemen-25 tet (28) i udstødsventilens lukkede stilling kan ligge an mod et stationært anlæg i trykkammeret, og at hydraulikvæskekanalen udmunder i trykkammeret i en ventilåbning, der i det mindste delvist afspærres af ventilelementet ved forskydning af dette hen mod venti-30 låbningen.To this end, the valve is characterized in that a valve element is slidably mounted in the first actuator piston in its axis direction and spring-loaded away from the actuator piston to abutment against at least one positioning element, which, when displaced in the actuator piston in its axis direction, can change the volume of a positioning chamber in the actuator piston. both the positioning element (28) and the actuator piston (19) having a surface defining the positioning chamber (42) in the axial direction of the actuator piston (19) that there is a limited flow passage between the positioning chamber (42) and the pressure chamber (21). 25 (28) in the closed position of the exhaust valve may abut against a stationary system in the pressure chamber, and that the hydraulic fluid channel opens into the pressure chamber in a valve opening, which is at least partially blocked by the valve element by displacing it towards the valve opening.

En ventilåbning påbegyndes, når trykket stiger i hydraulikvæskekanalen, og ventilelementet presses herved tilbage og mod fjederbelastningen ind i aktuatorstemplet, hvorved ventilåbningen blotlægges, og 35 hydraulikvæsken kan strømme gennem denne og ind i DK 173829 B1 3 trykkammeret, hvor trykket derfor stiger, og aktuator-stemplet følgeligt åbner udstødsventilen. Når trykket i hydraulikvæskekanalen falder igen, presses aktuator-stemplet tilbage, eksempelvis som følge af en nedenfor 5 beliggende luftfjeder, som virker på ventilspindlen. I mellemtiden er ventilelementet af den tilhørende fjeder igen blevet presset et stykke ud af aktuatorstemplet, således at det ligger an mod positioneringselementet og derved holdes i stilling i forhold til aktuator-10 stemplet. Positioneringselementet holdes i stilling af den hydraulikvæske, som er indesluttet i positioneringskammeret. Dog strømmer der hele tiden lidt hydraulikvæske gennem den begrænsede strømningspassage mellem positioneringskammeret og trykkammeret, fordi 15 fjederen presser på ventilelementet, som så presser på positioneringselementet, hvorved den indesluttede hydraulikvæske i positioneringskammeret trykpåvirkes, hvilket uundgåeligt giver en vis lækage gennem den begrænsede passage, således at ventilelementet ganske 20 langsomt bevæger sig ud af aktuatorstemplet. Den begrænsede strømningspassage kan være dannet mellem en flade af positioneringselementet i glidende kontakt med en flade i aktuatorstemplet og er så også fordelagtig med henblik på smøring mellem de glidende flader. Når 25 udstødsventilen nærmer sig sin lukkede stilling, nærmer ventilelementet sig også ventilåbningen, som så lukkes gradvist. Herved stiger trykket i trykkammeret over aktuatorstemplet, og lukkebevægelsen bremses.A valve opening is initiated as the pressure rises in the hydraulic fluid duct and the valve element is thereby pushed back and against the spring load into the actuator piston, thereby exposing the valve opening and the hydraulic fluid can flow through it and into the pressure chamber where the pressure therefore rises and the plunger accordingly opens the exhaust valve. When the pressure in the hydraulic fluid duct drops again, the actuator piston is pushed back, for example as a result of an air spring located below 5 acting on the valve stem. In the meantime, the valve member of the associated spring has again been pressed out of the actuator piston so that it abuts against the positioning member, thereby being held in position relative to the actuator piston. The positioning element is held in position by the hydraulic fluid contained in the positioning chamber. However, little hydraulic fluid is constantly flowing through the restricted flow passage between the positioning chamber and the pressure chamber because the spring presses on the valve member which then presses on the positioning element, thereby pressurizing the enclosed hydraulic fluid in the positioning chamber, thus inevitably causing some leakage through the restricted passage. the valve member moves out of the actuator piston quite slowly. The limited flow passage may be formed between a face of the positioning member in sliding contact with a face in the actuator piston and is also advantageous for lubrication between the sliding faces. As the exhaust valve approaches its closed position, the valve member also approaches the valve opening, which is then gradually closed. Thereby the pressure in the pressure chamber rises above the actuator piston and the closing movement is slowed.

I forbindelse med lukningen vil der kunne ske en 30 justering af ventilelementets stilling i aktuatorstemplet. Hvis aktuatorstemplet står i samme højde i cylinderen som ved den foregående lukning, eller eventuelt nærmere ved cylinderens endevæg, vil positioneringselementet lægge an mod det stationære anlæg i 35 trykkammeret og blive presset et stykke tilbage, DK 173829 B1 4 hvorved volumenet af positioneringskammeret igen vil ændres, idet der lækkes hydraulikvæske. Hvis aktuator-stemplet derimod står længere væk fra cylinderens endevæg, end ved den foregående lukning, så vil posi-5 tioneringselementet muligvis ikke lægge an mod det stationære anlæg. Ved en af de følgende cykler vil det imidlertid nå til anlæg som følge af lækagen fra eller til kammeret. På denne måde justeres stillingen af positioneringselementet og dermed af ventilelementet i 10 aktuatorstemplet hele tiden i forhold til den aktuelle længde mellem aktuatorstemplet og udstødsventilens bevægelige sædeflade, hvilket sikrer en ensartet opbremsning af ventilens lukkebevægelse uafhængigt af denne længde.In connection with the closure, the position of the valve element in the actuator piston may be adjusted. If the actuator piston is at the same height in the cylinder as at the previous closure, or possibly closer to the end wall of the cylinder, the positioning element will engage the stationary abutment in the pressure chamber and be pushed back a little, thereby changing the volume of the positioning chamber again. , leaking hydraulic fluid. On the other hand, if the actuator piston is further away from the end wall of the cylinder than at the previous closure, then the positioning element may not engage the stationary system. However, on one of the following cycles, it will reach systems due to the leakage from or to the chamber. In this way, the position of the positioning element and thus of the valve element in the actuator piston is constantly adjusted relative to the actual length between the actuator piston and the movable seat surface of the exhaust valve, which ensures uniform braking of the valve closing movement regardless of this length.

15 Ved lukning af udstødsventilen opbremses aktuator stemplet som følge af trykstigningen i trykkammeret over stemplet, og ventilelementet og positioneringselementet skal derfor ikke bære den store bremsekraft i stemplets akseretning. Disse elementer kan være 20 forholdsvis små i forhold til aktuatorstemplet. Dette betyder endvidere, at positioneringselementet ikke har særlig stor masse, og ikke besidder stor bevægelsesmængde, når det lægger an mod det stationære anlæg i trykkammeret. Der sker derfor mindre slid og opnås en 25 mere ensartet lukning af ventilen.15 When the exhaust valve is closed, the actuator is braked due to the pressure increase in the pressure chamber above the piston, and the valve element and the positioning element must therefore not carry the large braking force in the piston's axis direction. These elements may be relatively small relative to the actuator piston. This also means that the positioning element does not have a very large mass and does not have a large amount of movement when it engages the stationary system in the pressure chamber. Therefore, less wear occurs and a more uniform closure of the valve is achieved.

I en fordelagtig udførelsesform kan positioneringskammeret yderligere stå i forbindelse med trykkammeret via en strømningspassage med en kontraventil. Som beskrevet ovenfor sker der konstant en 30 lækage, hvorved stillingen af positioneringselementet og dermed ventilelementet ændres langsomt i forhold til aktuatorstemplet. Når positioneringselementet lægger an mod det stationære anlæg i trykkammeret, kan det imidlertid være nødvendigt med en større gennemstrøm-35 ning af hydraulikvæske, end der kan ske ved denne DK 173829 B1 5 lækage, for i løbet af det korte øjeblik at opnå den nødvendige forskydning af positioneringselementet. Da denne gennemstrømning skal ske i modsat retning i forhold til den omtalte langsomme lækage, kan dette 5 opnås ved hjælp af en kontraventil.In an advantageous embodiment, the positioning chamber can further communicate with the pressure chamber via a flow passage with a check valve. As described above, a constant leakage occurs, whereby the position of the positioning element and thus the valve element changes slowly with respect to the actuator piston. However, when the positioning element abuts against the stationary system in the pressure chamber, a greater flow of hydraulic fluid than may occur in this leakage may be required in order to obtain the necessary displacement in the short time. of the positioning element. Since this flow must occur in the opposite direction to the said slow leakage, this can be achieved by means of a non-return valve.

Udstødsventilens aktuator kan være udformet således, at volumenet af positioneringskammeret kan øges ved anslag af positioneringselementet mod det stationære anlæg i trykkammeret, og at positionerings-10 kammeret kan modtage hydraulikvæske fra trykkammeret via kontraventilen.The actuator of the exhaust valve may be designed such that the volume of the positioning chamber can be increased upon impact of the positioning element against the stationary system in the pressure chamber and that the positioning chamber can receive hydraulic fluid from the pressure chamber via the check valve.

I en fremstillingsmæssig fordelagtig og særlig kompakt udførelsesform er ventilelementet cylindrisk og er ført koaksialt i positioneringselementet, som 15 ligeledes er cylindrisk og er ført koaksialt i det første aktuatorstempel, og hvis ud af stemplet vendende vægafsnit har mindst en gennemgang og en endeflade, som kan ligge an mod det stationære anlæg i trykkammeret, og ventilelementet har en nedre krave med en opadven-20 dende anlægsflade til anlæg mod en nedadvendende anlægsflade på positioneringselementet. Gennemgangen i det ud af stemplet vendende vægafsnit muliggør gennemstrømning af hydraulikvæske mellem ventilåbningen og trykkammeret, når positioneringselementet ligger an mod 25 det stationære anlæg, og endefladen kan derfor udformes som et ringformet anlæg, uden at gennemstrømningen kan blokeres af positioneringselementet.In a manufacturing advantageous and particularly compact embodiment, the valve member is cylindrical and is coaxially guided in the positioning member, which is also cylindrical and is coaxially guided in the first actuator piston, and if the wall portion facing out of the piston has at least one passageway and end surface which may lie abut the stationary abutment in the pressure chamber, and the valve member has a lower collar with an upwardly facing abutment surface for abutment with a downward abutment abutment on the positioning member. The passage in the wall section facing out of the piston allows the flow of hydraulic fluid between the valve opening and the pressure chamber when the positioning element abuts the stationary system and the end surface can therefore be designed as an annular system, without the flow being blocked by the positioning element.

I en yderligere fremstillingsmæssig fordelagtig udførelsesform med kort udstrækning i akseretningen har 3 0 positioneringselementet en nedre krave, som er ført i en cylinder i aktuatorstemplet, og positioneringskammeret er et omkring positioneringselementet beliggende ringkammer, som afgrænses nedadtil af kraven på positioneringselementet, og opadtil af et loft i 35 aktuatorstemplet.In a further manufacturing advantageous embodiment with a short extension in the axis direction, the positioning element has a lower collar which is inserted into a cylinder in the actuator piston, and the positioning chamber is a ring chamber located around the positioning element, which is delimited downwards by the collar on the positioning element, and upwards by a ceiling. in the actuator piston.

DK 173829 B1 6DK 173829 B1 6

Positioneringselementet og det stationære anlæg i trykkammeret kan være udformet således, at bevægelsen af positioneringselementet kan dæmpes, inden dette lægger an mod det stationære anlæg, eksempelvis ved at 5 et på positioneringselementet beliggende rundtgående vægafsnit med tilspidset tværsnit glider ind i en rundtgående rille i endevæggen i trykkammeret. Navnlig ved store byggestørrelser, hvor positioneringselementet har større masse, kan der herved opnås en mere præcis 10 positionering af ventilelementet, og følgeligt mere ensartede ventillukninger. Dette kan endvidere være en fordel, hvis ventillængden øges hurtigt som følge af hurtig temperaturstigning, da positioneringselementet så skal foretage en større forskydning i aktuator-15 stemplet ved anslaget mod det stationære anlæg.The positioning element and the stationary system in the pressure chamber can be designed so that the movement of the positioning element can be attenuated before it engages the stationary system, for example by sliding a circumferential wall section of the positioning element with a tapered cross-section into a circumferential groove in the end wall of the pressure chamber. Especially for large building sizes, where the positioning element has a larger mass, a more precise positioning of the valve element can be achieved, and consequently more uniform valve closures. Furthermore, this can be an advantage if the valve length is increased rapidly due to rapid temperature rise, since the positioning element must then make a larger displacement in the actuator-piston at the impact against the stationary system.

I en anden udførelsesform kan volumenet af positioneringskammeret mindskes ved anslag af positioneringselementet mod det stationære anlæg i trykkammeret, og positioneringskammeret kan afgive hydraulik-20 væske til trykkammeret via kontraventilen.In another embodiment, the volume of the positioning chamber may be reduced by impact of the positioning member against the stationary abutment in the pressure chamber, and the positioning chamber may deliver hydraulic fluid to the pressure chamber via the check valve.

I en fordelagtig udførelsesform er ventilelementets i aktuatorstemplet beliggende og bort fra ventilåbningen vendende areal blotlagt i et i aktuatorstemplet beliggende rum, som via en åbning i aktuator-25 stemplet står i forbindelse med trykkammeret. På denne måde er ventilelementet under lukningen af udstødsventilen påvirket af samme hydrauliske tryk i begge akseretninger, og fjederen, som holder ventilelementet i sin udskudte stilling, kan være mindre kraftig.In an advantageous embodiment, the area of the valve element in the actuator piston and away from the valve opening is exposed in a space located in the actuator piston which communicates with the pressure chamber via an opening in the actuator piston. In this way, the valve member during the closing of the exhaust valve is affected by the same hydraulic pressure in both axes, and the spring which holds the valve member in its extended position may be less powerful.

30 Endvidere kan positioneringselementet på denne måde også være påvirket af hydraulikvæske i begge akseretninger, og lækage fra eller til positioneringskammeret kan så også ske til dette rum i aktuatorstemplet.In addition, the positioning element in this way may also be influenced by hydraulic fluid in both axial directions, and leakage from or to the positioning chamber may then also occur to this space in the actuator piston.

Kontraventilen kan med fordel lukke ved hjælp af 35 en kugle, og ventilen kan være orienteret således, at DK 173829 B1 7 kuglen kun løftes fra sit sæde ved positioneringselementets anslag mod det stationære anlæg.The check valve can advantageously close by means of a ball, and the valve can be oriented such that the ball is only lifted from its seat by the positioning element's impact on the stationary system.

Ventilåbningen kan med fordel være en cylindrisk boring, og ventilelementet kan have et konisk afsnit, 5 som kan forskydes ind i ventilåbningen, hvorved dennes gennemstrømningsareal mindskes gradvist. På denne måde kan opnås et passende opbremsningsforløb for udstødsventilen.The valve opening may advantageously be a cylindrical bore and the valve member may have a conical section 5 which can be displaced into the valve opening, thereby gradually reducing its flow area. In this way, a suitable braking process for the exhaust valve can be achieved.

Positioneringselementet kan være belastet af en 10 separat fjeder i retning bort fra aktuatorstemplet.The positioning element may be loaded by a separate spring in the direction away from the actuator piston.

Dette kan være en fordel, hvis ventilelementet er ført i positioneringselementet, da en eventuelt for stor friktion mellem disse elementer vil kunne bevirke, at ventilelementet trækker positioneringselementet med ind 15 i aktuatorstemplet ved åbning af ventilen.This can be an advantage if the valve element is inserted into the positioning element, as a possible excessive friction between these elements could cause the valve element to pull the positioning element into the actuator piston upon opening the valve.

Opfindelsen vil i det følgende blive forklaret nærmere ved hjælp af eksempler på udførelsesformer under henvisning til den skematiske tegning, på hvilken fig. 1 viser et længdesnit gennem en hydraulisk 20 aktiveret udstødsventil, fig. 2 et delvist længdesnit gennem en hydraulisk aktuator til en udstødsventil ifølge opfindelsen, fig. 3 et udsnit af aktuatoren i fig. 2 under åbning af udstødsventilen, 25 fig. 4 et delvist længdesnit gennem en anden udførelsesform for aktuatoren, og fig. 5 til 7 udsnit af forskellige udførelsesformer for et positioneringselement i aktuatoren.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 is a longitudinal section through a hydraulically actuated exhaust valve; FIG. 2 is a partial longitudinal section through a hydraulic actuator for an exhaust valve according to the invention; FIG. 3 is a sectional view of the actuator of FIG. 2 during opening of the exhaust valve, FIG. 4 is a partial longitudinal section through another embodiment of the actuator; and FIG. 5 to 7 sections of various embodiments of a positioning element in the actuator.

I fig. l ses en udstødsventil 1 til en stor 30 totakts krydshovedmotor, med en spindel 2, som er lejret aksialt forskydeligt i et spindelstyr 3 monteret i udstødsventilens hus 4, og som ved sin nedre ende har en ventiltallerken 5, som vender mod den ikke viste motorcylinders forbrændingskammer og samvirker med et 35 bundstykke 6, der er fastgjort til undersiden af huset DK 173829 B1 8 4, som er monteret i det ikke viste cylinderdæksel.In FIG. 1, an exhaust valve 1 is shown for a large 30-stroke cross-head motor, with a spindle 2, which is mounted axially displaceable in a spindle guide 3 mounted in the exhaust valve housing 4 and which at its lower end has a valve plate 5 facing the engine cylinder not shown. combustion chamber and cooperates with a base piece 6 which is attached to the underside of the housing DK 173829 B1 8 4, which is mounted in the cylinder cover not shown.

Ventiltallerkenen 5 har en sædeflade 7, som samvirker med en modstående stationær sædeflade 8 på bundstykket 6. I ventilens ikke viste åbne stilling kan gasser fra 5 motorcylinderen strømme ud gennem en udstødskanal 9.The valve plate 5 has a seat surface 7 which cooperates with an opposing stationary seat surface 8 on the base 6. In the open position of the valve not shown, gases from the engine cylinder can flow through an exhaust duct 9.

Ved spindlens bort fra tallerkenen 5 vendte ende er anbragt en aktuator 11, som omfatter et hus 12, hvori der øverst befinder sig en hydraulisk aktuator 13 og mellem denne og ventilhuset 4 en såkaldt luftfjeder 10 14. Udstødsventilen 1 åbnes ved hjælp af den hydrauliske aktuator 13, idet hydraulikvæske ledes ind gennem en tilslutning 15 på aktuatoren 13. Hydraulikvæsken kan leveres gennem en elektronisk aktiveret styreventil, som skiftevis kan forbinde tilslutningen 15 med en 15 højtryksledning og et tilbageløb for hydraulikvæske. Hydraulikvæsken kan også leveres fra en kamaktiveret pumpecylinder. Udstødsventilen 1 lukkes ved hjælp af luftfjederen 14, som omfatter et på ventilspindlen 2 monteret fjederstempel 16 i en luftcylinder 17. I 20 stedet for at anvende en luftfjeder kunne hele aktuatoren 11 også udformes som en dobbeltvirkende hydraulisk aktuator.At the end facing away from the spindle from the plate 5, an actuator 11 is provided which comprises a housing 12 in which is located at the top a hydraulic actuator 13 and between this and the valve housing 4 a so-called air spring 10 14. The exhaust valve 1 is opened by means of the hydraulic actuator. 13, in that hydraulic fluid is fed through a connector 15 on the actuator 13. The hydraulic fluid can be delivered through an electronically actuated control valve, which can alternately connect the connection 15 to a 15 high-pressure line and a hydraulic fluid reflux. The hydraulic fluid can also be supplied from a cam-activated pump cylinder. The exhaust valve 1 is closed by means of the air spring 14, which comprises a spring piston 16 mounted on the valve stem 2 in an air cylinder 17. Instead of using an air spring, the whole actuator 11 could also be designed as a double acting hydraulic actuator.

I fig. 2 ses et aktuatorstempel 19 anbragt koaksi-alt med og i forlængelse af ventilspindlen 2, således 2 5 at spindlen 2 er forbundet drejeligt om sin akse med stemplet 19. Aktuatorstemplet 19 er forskydeligt i en hydraulisk cylinder 20 i aktuatorhuset 12, og et trykkammer 21 er afgrænset i cylinderen 20 over stemplet 19. En hydraulikvæskekanal 22 forbinder 30 hydrauliktilslutningen 15 på ydersiden af aktuatorhuset 12 med en ventilåbning 23 i form af en cylindrisk boring i en over for toppen af aktuatorstemplet 19 beliggende endevæg 24 i cylinderen 20. Ventilåbningen 23 er koaksialt beliggende i cylinderen 20 og kan af-35 spærres gradvist for gennemstrømning, idet et i aktua- DK 173829 B1 9 torstemplet 19 udragende ventilelement 25 har et øvre konisk afsnit 26, som kan glide ind i åbningen 23 ved forskydning af stemplet 19 i cylinderen 20. Ventilåbningen 23 og -elementet 25 kan også have andre udform-5 ninger, som tillader en gradvis lukning for gennemstrømningen, eksempelvis kunne ventilelementets overside være skråt afskåret eller have en langsgående fordybning med nedad aftagende tværsnit.In FIG. 2, an actuator piston 19 is arranged coaxially with and in extension of the valve spindle 2, so that the spindle 2 is pivotally connected about its axis with the piston 19. The actuator piston 19 is slidable in a hydraulic cylinder 20 in the actuator housing 12 and a pressure chamber 21 is delimited in the cylinder 20 above the piston 19. A hydraulic fluid channel 22 connects the hydraulic connection 15 on the outside of the actuator housing 12 with a valve opening 23 in the form of a cylindrical bore in an end wall 24 in the cylinder 20 opposite the top of the actuator piston 19. The valve opening 23 is coaxial. located in the cylinder 20 and can be gradually blocked for flow, a valve member 25 projecting in the actuator piston 19 having an upper tapered portion 26 which can slide into the opening 23 by displacing the piston 19 in the cylinder 20 The valve aperture 23 and element 25 may also have other designs which permit a gradual closure of the flow, e.g. For example, the upper side of the valve member may be obliquely cut or have a longitudinal depression with downward decreasing cross section.

Under sit koniske afsnit 26 har ventilelementet 25 10 en cylindrisk yderside 27, som er længdeforskydelig i et positioneringselement 28, som ligeledes har en cylindrisk yderside 41, der er længdeforskydelig i en cylindrisk boring 29 i aktuatorstemplet 19. Ved sin nederste ende har ventilelementet 25 en udadragende 15 krave 30, hvis overside i den i fig. 2 viste stilling ligger an mod underkanten af positioneringselementet 28. Ventilelementet 25 har en indre koaksial boring 31, som er afsluttet opadtil af en topvæg 32. Den ene ende af en trykfjeder 33 ligger an mod topvæggen 32, og dens 2 0 anden ende ligger an mod bunden i en udsparing i en bundvæg 40 i et indre rum 34 i aktuatorstemplet 19.Below its tapered section 26, the valve member 25 10 has a cylindrical outer face 27 which is longitudinally displaceable in a positioning member 28, which also has a cylindrical outer face 41 which is longitudinally displaceable in a cylindrical bore 29 in the actuator piston 19. At its lower end, the valve member 25 has a outwardly extending collar 30, the upper side of which is shown in FIG. 2 abuts the lower edge of the positioning member 28. The valve member 25 has an inner coaxial bore 31 terminated upwardly by a top wall 32. One end of a compression spring 33 abuts the top wall 32 and its other end abuts. toward the bottom of a recess in a bottom wall 40 in an inner compartment 34 of the actuator piston 19.

Rummet 34 i stemplet 19 står i forbindelse med trykkammeret 21 i cylinderen 20 via en eller flere gennemgange 35 i aktuatorstemplet 19. Positioneringselementet 28 25 har ved sin nedre ende en krave 36 med en ydre cylindrisk væg 38, som har større diameter end kraven 30 på ventilelementet 25, og som kan glide i en cylindrisk boring 37 i aktuatorstemplet 19. Kraven 36 på positioneringselementet 28 er på sin underside påvirket af den 3 0 ene ende af en trykfjeder 39, som har større indre diameter end kraven 30 på ventilelementet 25, og hvis anden ende ligger an mod bundvæggen 4 0 i rummet 34 i stemplet 19.The space 34 in the piston 19 communicates with the pressure chamber 21 in the cylinder 20 via one or more passageways 35 in the actuator piston 19. The positioning element 28 25 has at its lower end a collar 36 with an outer cylindrical wall 38 which has a larger diameter than the collar 30 of the valve member 25, which can slide into a cylindrical bore 37 in the actuator piston 19. The collar 36 of the positioning member 28 is, on its underside, affected by the one end of a compression spring 39 having a larger internal diameter than the collar 30 of the valve member 25, and the other end of which abuts the bottom wall 40 in the space 34 of the piston 19.

Oversiden af kraven 36 på positioneringselementet 35 28 afgrænser nedadtil et ringformet positionerings- DK 173829 B1 10 kammer 42 afgrænset sideværts af den cylindriske yderside 41 og af den cylindriske boring 37. Opadtil afgrænses positioneringskammeret 42 af en rundtgående topvæg 43, som forbinder væggene af de to cylindriske 5 boringer 29, 37 i aktuatorstemplet 19. Ved boringen 29 og/eller ved boringen 37 er positioneringselementet 28 ført med et vist spillerum, således at hydraulikvæske kan strømme ved lækage mellem positioneringskammeret 42 og trykkammeret 21. Der kan eventuelt være en separat 10 lækagekanal i aktuatorstemplet 19, hvis større lækage skulle være nødvendig. En kontraventil 44 i en strømningspassage i aktuatorstemplet tillader hydraulikvæske at strømme fra trykkammeret 21 til positioneringskammeret 42. Positioneringselementet 28 rager foroven 15 et stykke ud af aktuatorstemplet 19 og har en øvre flade 45, som i den i fig. 2 viste lukkede stilling af udstødsventilen 1 ligger an mod et stationært anlæg 46 på endevæggen 24 i cylinderen 20. I den ud af stemplet 19 ragende del af positioneringselementet 28's rundt-20 gående væg er der udsparinger 47, som tillader hydraulikvæske at passere mellem kanalen 22 i huset 12 og trykkammeret 21, når ventilelementet 25 er ført et stykke ind i aktuatorstemplet 19 under åbning eller lukning af udstødsventilen 1. I den viste udførelses-25 form deler udsparingerne 47 fladen 45, men de behøver ikke at være ført op til fladen 45, og så kan denne forløbe som en ubrudt rundtgående flade.The upper face of the collar 36 on the positioning element 35 28 defines downwardly an annular positioning chamber 42 bounded laterally by the cylindrical exterior 41 and by the cylindrical bore 37. Upwardly, the positioning chamber 42 is bounded by an annular top wall 43 connecting the walls of the two cylindrical 5 bores 29, 37 in the actuator piston 19. At the bore 29 and / or at the bore 37, the positioning element 28 is provided with a certain clearance so that hydraulic fluid can flow upon leakage between the positioning chamber 42 and the pressure chamber 21. There may optionally be a separate 10 leakage channel. in actuator piston 19 if major leakage is needed. A non-return valve 44 in a flow passage in the actuator piston allows hydraulic fluid to flow from the pressure chamber 21 to the positioning chamber 42. The positioning element 28 protrudes a portion out of the actuator piston 19 and has an upper surface 45, as in the FIG. 2, the closed position of the exhaust valve 1 abuts a stationary abutment 46 on the end wall 24 of the cylinder 20. In the wall 20 of the positioning element 28 extending around the piston 19 there are recesses 47 which allow hydraulic fluid to pass between the channel 22 in the housing 12 and the pressure chamber 21 when the valve member 25 is inserted a bit into the actuator piston 19 during opening or closing of the exhaust valve 1. In the embodiment shown, the recesses 47 divide the surface 45, but they do not have to be led up to the surface 45 , and then this can proceed as an unbroken circular surface.

Ved åbning af udstødsventilen 1 forsynes hydraulikkanalen 22 med tryksat hydraulisk væske, hvorved 3 0 ventilelementet 25 forskydes fra sin i fig. 2 viste stilling til omtrent den i fig. 3 viste stilling. Hydraulikvæsken kan så frit strømme ind i trykkammeret 21, og ventiIspindlen 2 forskydes nedad og løfter ventiltallerkenen 5 fra det stationære sæde 8.Upon opening of the exhaust valve 1, the hydraulic channel 22 is provided with pressurized hydraulic fluid, whereby the valve element 25 is displaced from its in FIG. 2 to approximately the position shown in FIG. 3. The hydraulic fluid can then freely flow into the pressure chamber 21, and the valve stem 2 is displaced downward and lifts the valve plate 5 from the stationary seat 8.

DK 173829 B1 11DK 173829 B1 11

Ved lukning af ventilen 1 aftager trykket i hydraulikkanalen 22, og hydraulikvæske presses tilbage i kanalen 22 fra trykkammeret 21, idet luftfjederen 14 presser ventilspindlen opad. Fjederen 33 har nu presset 5 ventilelementet 25 til dettes udskudte stilling i stemplet 19.When the valve 1 is closed, the pressure in the hydraulic duct 22 decreases and hydraulic fluid is pushed back into the duct 22 from the pressure chamber 21, with the air spring 14 pressing the valve stem upwards. The spring 33 has now pressed the valve member 25 to its extended position in the piston 19.

Under åbne- og lukkeforløbet lækker der lidt hydraulikvæske fra positioneringskammeret 42 til trykkammeret 21 gennem de ovenfor omtalte lækager, idet 10 fjedrene 33 og 39 påvirker positioneringselementet 28 med en opadrettet kraft. Fjederen 39 kan eventuelt udelades. Bortset fra en langsom opadgående bevægelse i aktuatorstemplet 19 holdes positioneringselementet 28 fast i stemplet af det volumen af hydraulikvæske, som 15 er indespærret i positioneringskammeret 42, og da kraven 30 på ventilelementet 25 under lukning af ventilen 1 ligger an mod positioneringselementet 28 som følge af påvirkningen fra fjederen 33, så holdes ventilelementet 25 i en sådan afstand i forhold til den 20 bevægelige sædeflade 7 på ventiltallerkenen 5, at opbremsningen af lukkebevægelsen begynder, når den bevægelige sædeflade 7 er i en passende afstand fra den stationære sædeflade 8. Hvis eksempelvis længden af ventilspindlen 2 udvider sig som følge af opvarmning, 25 så vil positioneringselementet 28 ved den endelige lukning af udstødsventilen 1 blive presset et stykke ind i aktuatorstemplet 19, idet den øvre flade 45 på positioneringselementet 28 lægger an mod det stationære anlæg 46 i trykkammeret 21. Herved vil noget hydrauli-30 kvæske strømme gennem kontraventilen 44 fra trykkammeret 21 ind i positioneringskammeret 42, og positioneringselementet 28 vil så blive fastholdt i en ny stilling. Hvis spindellængden derimod aftager, så vil positioneringselementet 28 som følge af den ovenfor 35 beskrevne langsomme opadgående bevægelse også indstille DK 173829 B1 12 sig i en hertil passende ny stilling, således at der opnås ensartede og præcise lukninger af udstødsventilen .During the opening and closing process, some hydraulic fluid leaks from the positioning chamber 42 to the pressure chamber 21 through the above-mentioned leaks, the springs 33 and 39 affecting the positioning element 28 with an upward force. The spring 39 may optionally be omitted. Except for a slow upward movement in the actuator piston 19, the positioning element 28 is held firmly in the piston by the volume of hydraulic fluid 15 trapped in the positioning chamber 42, and as the collar 30 of the valve element 25 abuts the positioning element 28 due to the actuation, from the spring 33, the valve member 25 is kept at such a distance from the movable seat surface 7 of the valve plate 5 that the slowing of the closing movement begins when the movable seat surface 7 is at a suitable distance from the stationary seat surface 8. If, for example, the length of the the valve spindle 2 expands due to heating 25, then the positioning element 28 will, upon final closing of the exhaust valve 1, be pressed a bit into the actuator piston 19, the upper surface 45 of the positioning element 28 abutting the stationary plant 46 in the pressure chamber 21. will some hydraulic 30 streams flow through the check valve 44 from the pressure chamber 21 into the positioning chamber 42, and the positioning element 28 will then be held in a new position. If, on the contrary, the spindle length decreases, then, due to the slow upward movement described above, the positioning element 28 will also adjust itself to a suitable new position for this, so that uniform and precise closures of the exhaust valve are obtained.

Kontraventilen 44 kan være orienteret således, at 5 kuglen bevæger sig i stemplet 19's akseretning, men den kan med fordel være orienteret anderledes, eventuelt radialt i stemplet, med henblik på at kuglen ligger fast an mod sit sæde, undtagen når positioneringselementet 28 forskydes ved anlæg mod det stationære anlæg 10 46 i trykkammeret 21, hvorved kuglen løftes fra sit sæde med henblik på passage af hydraulikvæske gennem kontraventilen. Der kan også anvendes andre typer af kontraventiler.The check valve 44 may be oriented such that the ball moves in the axis of the piston 19, but it may advantageously be oriented differently, possibly radially in the piston, so that the ball is firmly engaged with its seat, except when the positioning element 28 is displaced by abutment. against the stationary system 10 46 in the pressure chamber 21, thereby lifting the ball from its seat for passage of hydraulic fluid through the check valve. Other types of non-return valves can also be used.

Fig. 4 viser en anden udførelsesform for den 15 hydrauliske aktuator 13, hvor aktuatoren har et flertrinsstempel med et første stempel 19 og et sekundært stempel 48, som er længdeforskydeligt i det første stempel 19. Et sekundært trykkammer 49 oven over det sekundære stempel 48 er forbundet med et første tryk-20 kammer 21 via kanaler 50 i det første stempel 19, som svarer til stemplet 19 i den i fig. 2 viste udførelsesform, hvad angår ventilelementet 25's indretning i stemplet 19. Vandringen af det første stempel 19 er begrænset af et fremspring 51's anlæg mod et stationært 25 anslag 52 i det første trykkammer 21 efter en første forskydning af stemplet 19.FIG. 4 shows another embodiment of the hydraulic actuator 13, wherein the actuator has a multi-stage piston with a first piston 19 and a secondary piston 48 which is longitudinally displaceable in the first piston 19. A secondary pressure chamber 49 above the secondary piston 48 is connected to a first pressure chamber 21 via channels 50 of the first piston 19 which corresponds to the piston 19 of the embodiment shown in FIG. 2 in relation to the arrangement of the valve element 25 in the piston 19. The travel of the first piston 19 is limited by the abutment of a projection 51 against a stationary 25 stop 52 in the first pressure chamber 21 after a first displacement of the piston 19.

I fig. 5 ses en anden udførelsesform for positioneringselementet 28, hvor positioneringskammeret 42 har form af et ringkammer, som er afgrænset af positio-30 neringselementet 28 og radialt udadtil af aktuator-stemplet 19, men i aksial retning er ringkammeret afgrænset opadtil af positioneringselementet 28 og nedadtil af aktuatorstemplet 19. På denne måde kan positioneringskammeret 42 ved anlæg af positionerings-35 elementet 28's overside 45 mod det stationære anlæg 46 DK 173829 B1 13 i trykkammeret 21 mindske sit volumen ved forskydning af positioneringselementet 28 i stemplet 19, i modsætning til den i fig. 2 viste udførelsesform, hvor positioneringskammeret 42's volumen øges ved denne for-5 skydning. Det bemærkes, at den i fig. 2 viste kontraventil 44 her er udeladt, og hydraulikvæsken vil derfor lække mellem positioneringselementet 28 og aktuator-stemplet 19 ved reduktionen af positioneringskammeret 42's volumen.In FIG. 5, another embodiment of the positioning element 28 is shown, wherein the positioning chamber 42 is in the form of an annular chamber which is defined by the positioning element 28 and radially outwardly of the actuator piston 19, but in the axial direction the annular chamber is delimited upwards by the positioning element 28 and downwards by actuator piston 19. In this way, by positioning the upper side 45 of positioning element 28 against the stationary abutment 46 in the pressure chamber 21, the positioning chamber 42 can reduce its volume by displacing the positioning element 28 in the piston 19, in contrast to the positioning element 28 in FIG. 2 in which the volume of the positioning chamber 42 is increased by this displacement. It should be noted that the embodiment shown in FIG. 2, the hydraulic fluid will therefore leak between the positioning element 28 and the actuator piston 19 upon the reduction of the volume of the positioning chamber 42.

10 I fig. 6 ses en yderligere udførelsesform for positioneringselementet 28. Positioneringselementet 28 afgrænser her to positioneringskamre 42a, 42b på henholdsvis oversiden og undersiden af et radialt fremspring 55 på elementet 28, hvor det ene 42a øger sit 15 volumen ved det omtalte anslag, og det andet 42b mindsker sit volumen. Herved kan under visse omstændigheder opnås en mere stabil positionering af positioneringselementet 28. Det bemærkes endvidere, at positioneringselementet 28 her er udformet med et øvre vægafsnit 53, 20 hvis tværsnit aftager opad, og som ved den endelige lukning af ventilen 1 glider ind i en rundtgående rille 54 i endevæggen 24 i trykkammeret 21, hvorved bevægelsen af positioneringselementet 28 dæmpes inden elementet 28 lægger an mod det stationære anlæg 46, som her 25 ligger i bunden af rillen 54.10 In FIG. 6, a further embodiment of the positioning element 28 is seen. The positioning element 28 here defines two positioning chambers 42a, 42b on the upper and lower side respectively of a radial projection 55 on the element 28, whereby one 42a increases its 15 volume at said stop and the other 42b decreases. its volume. Hereby, under certain circumstances, a more stable positioning of the positioning element 28. can be achieved, it is further noted that the positioning element 28 is formed here with an upper wall section 53, 20 whose cross section decreases upwards and which, at the final closure of the valve 1, slides into a circumferential groove 54 in the end wall 24 of the pressure chamber 21, whereby the movement of the positioning element 28 is attenuated before the element 28 abuts the stationary abutment 46, which here 25 lies at the bottom of the groove 54.

I fig. 7 ses endnu en udførelsesform for positioneringselementet 28, som her er udformet som flere omkring ventilelementet 25 fordelte, cylindriske stempler 56, som er lejret i cylindre 57 i aktuator-30 stemplet 19 forskydeligt i dettes akseretning. Stemplet 56 er påvirket opad af trykfjederen 39 og afgrænser i sin cylinder 57 et positioneringskammer 42. Ved sin underside ligger stemplet 56 an mod kraven 30 på ventilelementet 25 og ved sin overside har det en 35 opadforløbende stødstang 57, som er ført med mulighed DK 173829 B1 14 for begrænset lækage gennem topvæggen af aktuator-stemplet 19, således at stangen 57's øvre ende kan lægge an mod det stationære anlæg 46 i trykkammeret 21, når ventilen 1 lukker, hvorved volumenet af positio-5 neringskammeret 42 øges. I stedet for flere stempler 56 kan der også anvendes et enkelt ringformet stempel med et tværsnit svarende til det i fig. 7 viste stempel 56 og med flere stødstænger 57.In FIG. 7, another embodiment of the positioning element 28, which here is formed as a plurality of cylindrical pistons 56 distributed around the valve element 25, which is mounted in cylinders 57 in the actuator 30 piston 19 is displaceable in its axis direction. The piston 56 is actuated upwardly by the compression spring 39 and defines in its cylinder 57 a positioning chamber 42. At its lower side, the piston 56 abuts the collar 30 on the valve element 25 and at its upper side it has an upwardly extending thrust bar 57, which is provided with option DK 173829 B1 14 for limited leakage through the top wall of the actuator piston 19 so that the upper end of the rod 57 can engage the stationary abutment 46 of the pressure chamber 21 as the valve 1 closes, thereby increasing the volume of the positioning chamber 42. Instead of multiple pistons 56, a single annular piston having a cross section similar to that of FIG. 7 with plunger 56 and with multiple thrust rods 57.

De viste udførelsesformer kan kombineres på 10 forskellige måder, ligesom systemet med ventilelementet 25 og positioneringselementet 28 kan indbygges i andre ventilaktuatorer med et eller flere stempler uden at bevæge sig uden for opfindelsens rammer.The embodiments shown can be combined in 10 different ways, just as the system of valve member 25 and positioning member 28 can be incorporated into other valve actuators with one or more pistons without moving outside the scope of the invention.

Claims

A hydraulically actuated exhaust valve (1) for an internal combustion engine, with a hydraulic actuator (13) comprising at least one first actuator piston (19) arranged coaxially in extension of the exhaust valve spindle (2) and slidable in a cylinder (20), so as to define a hydraulic fluid pressure chamber (21) which can be supplied and discharged through a hydraulic fluid channel (22), whereby the exhaust valve (1) can be opened and closed, characterized in that a valve element (25) is slidably mounted in the first actuator piston (19) in its axis direction and spring-loaded away from the actuator piston (19) to abut against at least one positioning element (28) which, by displacement in the actuator piston (19) in its axis direction, can change the volume of a positioning chamber (42) in the actuator piston (19), wherein both the positioning element (28) and the actuator piston (19) have a surface defining the positioning chamber (42) in the axial direction of the actuator piston (19) The positioning chamber (42) and the pressure chamber (21) are a limited flow passage, that the positioning element (28) in the closed position of the exhaust valve (1) can abut a stationary system (46) in the pressure chamber (21) and that the hydraulic fluid channel ( 22) opens in the pressure chamber (21) in a valve opening (23) which is at least partially blocked by the valve element (25) by displacing it towards the valve opening (23).

Hydraulically actuated exhaust valve (1) according to claim 1, characterized in that the positioning chamber (42) communicates with the pressure chamber (21) via a flow passage with a check valve (44).

Hydraulically actuated exhaust valve (1) according to claim 1 or 2, characterized in that the volume of the positioning chamber (42) can be increased by impacting DK 173829 B1 of the positioning element (28) against the stationary system (46) in the pressure chamber (21). ), and that the positioning chamber (42) can receive hydraulic fluid from the pressure chamber (21) via the check valve (44).

Hydraulically actuated exhaust valve (1) according to one of the preceding claims, characterized in that the valve element (25) is cylindrical and is coaxially inserted in the positioning element (28) which is also cylindrical and is coaxially inserted in the first actuator piston. (19), and if the wall portion facing out of the piston (19) has at least one passageway (47) and an end surface (45) which may abut against the stationary abutment (46) in the pressure chamber (21) and that the valve element (25) ) has a lower collar (30) with an upwardly facing abutment surface for 15 abutments against a downward abutting abutment surface of the positioning element (28).

Hydraulically actuated exhaust valve (1) according to one of the preceding claims, characterized in that the positioning element (28) has a lower collar (36) which is guided in a cylinder (37) in the actuator piston (19). and that the positioning chamber (42) is a ring chamber located around the positioning element (28), which is delimited downwardly by the collar (36) on the positioning element (28) and upwards by a ceiling in the actuator piston (19).

Hydraulically actuated exhaust valve (1) according to one of the preceding claims, characterized in that the positioning element (28) and the stationary system (46) in the pressure chamber (21) are designed so that the movement of the positioning element (28) can be damped, before this (28) abuts the stationary system (46), for example by sliding a circular wall section (53) of the positioning element (28) with tapered cross-section into a circular groove (54) in the end wall (24) in the pressure chamber (21). DK 173829 B1

Hydraulically actuated exhaust valve (1) according to claim 1 or 2, characterized in that the volume of the positioning chamber (42) can be reduced by impact of the positioning element (28) against the stationary system (46) in the pressure chamber (21), and that the positioning chamber (42) can deliver hydraulic fluid to the pressure chamber (21) via the check valve (44).

Hydraulically actuated exhaust valve (1) according to one of the preceding claims, characterized in that the valve element (25) located in the actuator piston (19) and away from the valve facing the opening (23) is exposed in an actuator piston (19). located (34), which communicates with the pressure chamber (21) via an opening (35) in the actuator piston (19).

Hydraulically actuated exhaust valve (1) according to one of claims 2 to 8, characterized in that the non-return valve (44) closes by means of a ball and the valve (44) is oriented such that the ball is only lifted from its seat by the positioning element. (28) 20 stops against the stationary plant (46).

Hydraulically actuated exhaust valve (1) according to one of the preceding claims, characterized in that the valve opening (23) is a cylindrical bore and the valve element (25) has a conical section (26) which can be displaced into the valve opening ( 23), thereby gradually reducing its flow area.

Hydraulically actuated exhaust valve (1) according to one of the preceding claims, characterized in that the positioning element (28) is loaded by a separate spring (39) in a direction away from the actuator piston (19). 35