EP0681092B1 - Ventiltriebvorrichtung für eine Brennkraftmaschine mit einem Stösselspielausgleichselement - Google Patents

Ventiltriebvorrichtung für eine Brennkraftmaschine mit einem Stösselspielausgleichselement Download PDF

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Publication number
EP0681092B1
EP0681092B1 EP95106560A EP95106560A EP0681092B1 EP 0681092 B1 EP0681092 B1 EP 0681092B1 EP 95106560 A EP95106560 A EP 95106560A EP 95106560 A EP95106560 A EP 95106560A EP 0681092 B1 EP0681092 B1 EP 0681092B1
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EP
European Patent Office
Prior art keywords
tappet
valve
cam
chamber
bush
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
EP95106560A
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English (en)
French (fr)
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EP0681092A1 (de
Inventor
Renato Filippi
Francesco Vattaneo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fiat Auto SpA
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Fiat Auto SpA
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Publication of EP0681092A1 publication Critical patent/EP0681092A1/de
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Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/12—Transmitting gear between valve drive and valve
    • F01L1/14—Tappets; Push rods
    • F01L1/16—Silencing impact; Reducing wear
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
    • F01L1/02—Valve drive
    • F01L1/04—Valve drive by means of cams, camshafts, cam discs, eccentrics or the like
    • F01L1/08—Shape of cams
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
    • F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
    • F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
    • F01L13/0031—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque by modification of tappet or pushrod length

Definitions

  • the present invention relates to a control device for a valve of an internal combustion engine, comprising:
  • Such a valve control device forms the subject of European Patent Application No. EP-A-0 574 867 which is to be considered as part of the present description.
  • the tappet clearance compensation device is constituted by a spacer pad of calibrated dimensions, interposed between the tappet and the valve. To adjust the tappet clearance, that is to say the relative position between cam and tappet, it is necessary to replace the spacer pad. Since such a system is subject to wear over time, which modifies the tappet clearance, it is necessary to perform periodic inspections for the purpose of checking if the tappet clearance is maintained within a predetermined range of values.
  • the principal object of the present invention is that of providing a valve control device for an internal combustion engine of more efficient type than previously known systems by the use of an automatic hydraulic tappet clearance compensation device.
  • the tappet clearance compensation device is of self adjusting hydraulic type and can be connected to the pressurised oil source of the hydraulic brake device by means of a first auxiliary duct formed in the body of the tappet and by a second auxiliary duct formed in the said bush, these auxiliary ducts being intended to assume a mutually aligned position in which the automatic compensation device and the hydraulic brake device are connected together, when the valve is in the said closure position, and positions out-of-alignment with one another, in which the automatic compensation device is isolated from the hydraulic brake device, when the valve is in a position other than the closure position.
  • the device according to the invention allows automatic adjustment of the tappet clearance compensation by utilising a single source of pressurised oil for supplying both the hydraulic brake device and the automatic tappet clearance compensation device, in this way making available a large volume for effectively damping shock waves which propagate in the pressurised oil circuit in consequence of different phases of operation of the hydraulic brake device.
  • the reference numeral 1 indicates a cylinder head of an internal combustion engine (only partially illustrated in the drawings).
  • the reference numeral 2 indicates an induction duct associated with one of the cylinders, the outlet opening of which is controlled by a valve 3 which in its closure position is disposed in contact with a seat 3a.
  • the valve 3 has a stem 4 displaceable axially along an axis D to control opening and closure of the duct 2.
  • the stem 4 is guided by a sleeve 4a of type known per se, associated with the cylinder head 1.
  • the displacement of the valve 3 is controlled cyclically by a cam 5 mounted on the internal combustion engine's camshaft, rotating in a direction indicated by the arrow E about the axis F of the camshaft.
  • a tappet 6 the body of which is substantially cup-shaped.
  • the tappet 6 is mounted axially slidably within a bush 8 coaxially of the axis D, connected rigidly to the cylinder head 1.
  • a spring cap (disc) member 10 of type known per se is axially fixed to the valve stem 4 and is engaged by a coil spring 11 concentric with the stem 4, the function of which is to maintain the valve 3 urged towards its closure position of the duct 2.
  • the tappet 6 includes a head 14 adjacent the cam 5, which has an active surface 15 cooperable with the cam profile 5.
  • This active surface 15 comprises a first flat portion 15a substantially orthogonal to the axis D and a second, curved portion 15b joined to the portion 15a and having a constant radius of curvature in such a way as to present a convex zone towards the cam 5.
  • the head 14, fixed to the tappet 6, is locked against relative rotation with respect to the bush 8 by means of a pair of guide shoulders 16 which have a shape corresponding to the shape of the adjacent edge of the head 14 and are formed on an element 16a rigidly connected to the cylinder head 1 by means of a screw 17 which also permits fixing of the bush 8 to the cylinder head 1.
  • the cam 5 comprises an asymmetric cylindrical member the base of which is defined by a curved line which comprises a portion 5a having a cam base circle of radius R 0 and a cam lobe 5b projecting from the base circle, serving as a thrust head for the tappet 6.
  • the curved line defines the profile of the cam 5 which is asymmetric with respect to a plane passing through the axis of rotation F and the apex of the lobe 5b, in such a way that the cam 5 has a "less steep" profile portion 5c and an opposite “steeper” profile portion 5d, where the term “steepness” means the variation of the radial coordinate with respect to the axis F for a given increment of the angular coordinate.
  • the angular displacement of the cam 5 is greater than the angular displacement of the cam necessary to take the valve to its closure position.
  • a predetermined threshold value for example corresponding to a speed of rotation of the engine of about 2500 revolutions per minute
  • the law of closure of the valve 3 is determined solely by the mass of the movable components, the thrust of the spring 11 and the inertial and damping actions to which the valve 3 is subject.
  • the active profile 15 of the tappet 6 is always in contact with the profile of the cam 5.
  • Each bush 8 is surrounded by a respective peripheral chamber 22 supplied by the pressurised oil utilised for lubrication of the engine.
  • annular chamber 26 forming part of a hydraulic brake device 23 the volume of which is variable in dependence on the position of the tappet 6 with respect to the bush 8.
  • the chamber 26 extends radially between the tappet 6 and the bush 8 and is delimited in the axial direction by a portion 6a of greater diameter than the tappet 6 and, on the opposite side, by a portion 8a of smaller diameter than the bush 8.
  • the chamber 26 therefore has a base area in the form of a circular ring concentric with the axis D and is delimited internally by a circumference of radius R 1 and externally by a circumference of radius R 2 .
  • Each bush 8 has radial holes 24 for connecting the peripheral chamber 22 to the annular chamber 26, having a relatively short length with respect to their diameter, or rather which achieve thin wall opening conditions in such a way that the flow of fluid through them produces a damping effect causing a hydraulic brake action to slow the stroke of the valve in the last part of its closure phase so as to avoid sharp contact between the tappet 6 and the cam profile 5 during "ballistic" operation.
  • exit apertures 28 close to the smaller diameter portion 8a, which extend between the chamber 22 and the chamber 26, the diameter of the holes 28 being significantly less than the diameter of the apertures 24 in such a way as to cause a more energetic damping action during the final phase of the closure of the valve 3, when the cylindrical outer wall of the tappet 6 closes the holes 24.
  • the tappet 6 further includes a hydraulic device for automatically adjusting the tappet clearance compensation.
  • This device generally indicated with the reference numeral 30, includes a cup-shaped member 32 mounted slidably along the axis D in a corresponding seat in the tappet 6 and substantially sealed in such a way that the bottom of the member 32 is disposed directly in contact with the end of the valve stem 4 closest to the cam 5.
  • a circlip 32a prevents accidental separation of the member 32 from the seat defined in the tappet 6.
  • the member 32 defines, with the inner wall of the cylinder head 14, a substantially cylindrical cavity 36 in which oil is present.
  • a sleeve 37 which has a dividing partition 38, orientated transversely with respect to the axis D, which allows the cavity 36 to be separated into an upper chamber 36a and a lower chamber 36b (with reference to the drawings).
  • a compression coil spring 48 is interposed between the partition 38 and the bottom of the cup-shaped member 32.
  • the partition 38 is provided with a central through hole 40 on the lower edge of which engages a ball 42 of a non-return valve.
  • the ball 42 is urged towards a position in which it closes the hole 40 by a conical coil spring 46 which rests on the bottom of a perforated cage 44 in such a way as to prevent the passage of the oil present in the chamber 36b towards the chamber 36a in normal conditions.
  • a conical coil spring 46 which rests on the bottom of a perforated cage 44 in such a way as to prevent the passage of the oil present in the chamber 36b towards the chamber 36a in normal conditions.
  • first auxiliary duct 50 which at one end is open to the exterior of the tappet and, at the opposite end, opens into the chamber 36a.
  • second auxiliary duct 52 passing therethrough, one end of which opens into the peripheral chamber 22, whilst the opposite end faces towards the tappet 6.
  • the ducts 50 and 52 can be disposed in a mutually aligned condition, illustrated in Figures 1 and 2, in which they put the peripheral chamber 22 into communication with the chamber 36 when the valve 3 is in its closure position closing the duct 2.
  • the ducts 50 and 52 are in positions which are not aligned with one another ( Figure 3) in such a way that the chamber 36a is isolated from the chamber 22.
  • the spring 48 automatically compensates for this clearance by separating the bottom of the member 32 from the partition 38 of the sleeve 37 and therefore from the head of the tappet 6 by a distance equal to the clearance which has arisen in the system.
  • a depression is caused within the chamber 36b which causes opening of the non-return valve against the action of the spring 46 causing the passage of oil under pressure from the chamber 36a to the chamber 36b until achieving an equilibrium condition in which the clearance is completely nullified and the ball 42 is returned into the position covering the hole 40 thereby closing the non-return valve.
  • the base area of the cavity 36 which corresponds to the area over which the pressure of the oil present in the peripheral chamber 22 is exerted when the ducts 50 and 52 are aligned with one another, corresponds to the area of a circular surface of radius R 3 , which is at least equal to but preferably greater than the base area of the annular chamber 26 defined by the difference between the areas of the circular surfaces defined by the radii R 2 and R 1 .
  • the resilient characteristic of the spring 48 is chosen in dependence on the force acting in the chamber 26 defined by the product of the base area of the chamber 26 and the pressure of the oil present in it, in such a way that this resultant force is of a magnitude which predominates over the resilient force of the spring 48. In this way, in the absence of any tappet clearance to be compensated, unwanted extension of the spring 48 during the "ballistic" operation of the system is prevented.
  • the cam 5 includes a pair of cylindrical abutment surfaces 7 the radius of which is equal to the radius of the base circle R 0 of the cam, disposed alongside and on opposite sides of the asymmetric cylindrical member of the cam 5.
  • Figure 7 shows the cylinder head 1 which has a plurality of valves 4 with respective tappets 6 and bushes 8, each of which is surrounded by a respective peripheral chamber 22.
  • the chambers 22 are supplied with pressurised engine lubrication oil via a common channel 20.
  • a plurality of cylindrical reservoirs 55 (only one of which is visible in Figure 7) are connected by service channels 54 to the channel 20 and each contains an elastically deformable cylindrical member 56 of type known per se.
  • the volume which each of the members 56 occupies within the respective reservoir 55 is variable as a function of the change of the oil pressure in the channels 20 and 54.
  • the hydraulic brake device 23 performs its action slowing the valve 3 during the final phase of its rising stroke.
  • the oil flows out from the chambers 26 in the contraction phase, through the respective apertures 24 and 28, accumulates in the reservoirs 55 to be returned to the chambers 26 during their subsequent phase of expansion which takes place simultaneously with opening of the valves 3.
  • the flow of oil exchanged between the chambers 26 and the reservoirs 55, caused by the cyclic expansions and contractions of the chambers 26, generates shock waves which propagate in the oil through the channels 20.
  • the volume of the reservoirs 55 and the channels 20 and 54 together with the additional volume defined by the ducts 50 and 52 is sufficiently great to minimise the effects of these shock waves and to render them negligible. Moreover, when the tappet clearance compensation devices 30 are connected to the peripheral chambers 22 by the ducts 50 and 52, these shock waves are effectively damped along the ducts 50 and 52 in such a way as not to propagate into the interior of the chambers 36a.
  • the invention it is possible to utilise the same pressurised oil circuit already intended to operate the hydraulic brake device 23 to supply oil under pressure to the cavity 36 of the device 30 so that the tappet clearance compensation can take place correctly even when, as a result of inevitable escapes of oil through the imperfect seals between the bush 37 and the cup-shaped member 32 and between the member 32 and its seat in the tappet 6, the volume of oil contained in the chamber 36b diminishes.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)
  • Valve Device For Special Equipments (AREA)

Claims (5)

  1. Einrichtung zurn Steuern des Ventils einer Brennkraftmaschine, welche umfaßt:
    - ein Ventil (3), welches zwischen einer Stellung, in der ein Kanal (2) geschlossen ist, und einer Stellung, in der ein Kanal (2) offen ist, bewegbar ist, wobei dieses Ventil (3) mit vorbelastenden Federmitteln (11), welche dieses zu seiner Verschlußstellung hin drücken, in Verbindung steht,
    - Ventilsteuermittel zum Bewegen des Ventils (3) zu seiner Offenstellung hin, wobel diese eine drehbare Nocke (5) umfassen, welche an einer akfiven Oberfläche (15) eines Stößels (6) anliegt, der zumindest während der Bewegung des Ventils zu seiner Offenstellung hin zwischen der Nocke (5) und dem Ventil (3) angeordnet ist,
    - eine hydraulische Bremseinrichtung zum Abbremsen der Bewegung des Ventils (3) im letzten Teil seines Verschlußtakts, wobei diese eine ringförmige Kammer (26) umfaßt, welche zwischen dem Stößel (6) und einer koaxial zum Stößel (6) und außerhalb des Stößels (6) befindlichen Buchse (8) ausgebildet ist, wobel diese Kammer (26) mit einer Quelle (22) unter Druck stehenden Öls in Verbindung steht und ein Volumen aufweist, weiches infolge des relativen Bewegens des Stößels (6) zur Buchse (8) variabel ist, und
    - eine Stößeispielausgleichseinrichtung (30), welche zwischen dem Stößel (6) und dem Ventil (3) angeordnet ist, dadurch gekennzeichnet, daß die Stößelspielausgleichseinrichtung (30) ein selbsteinstellender hydraulischer Typ ist und mit der unter Druck stehenden Ölquelle (22) der hydraulischen Bremseinrichtung mittels eines ersten im Körper des Stößels (6) ausgebildeten Hilfskanals (50) und
    durch einen zweiten in der genannten Buchse (8) ausgebildeten Hilfskanal (52) verbunden werden kann, wobei diese Hilfskanäle (50, 52) eine miteinander fluchtende Stellung einnehmen sollen, in welcher die automatische Ausgleichseinrichtung (30) und die hydraulische Bremseinrichtung (23) miteinander verbunden sind, wenn das Ventil in der genannten Verschlußstellung ist, und nicht miteinander fluchtende Stellungen einnehmen sollen, bei welchen dle automatische Ausgleichseinrichtung (30) von der hydraulischen Bremseinrichtung (23) getrennt ist, wenn sich das Ventil (3) in einer anderen Stellung als der Verschlußstellung befindet.
  2. Einrichtung nach Anspruch 1, dadurch gekennzeichnet, daß zwischen dem Stößel (6) und dem Ventil (3) ein kappenförmiges Element (32) eingefügt ist, welches bezüglich des Stößels (6) entlang der axialen Richtung (D) der Bewegung des Ventils (3) verschieblich ist, wobei dieses kappenförmige Element (32) mit dem Stößel (6) einen Hohlraum (36) begrenzt, in welchem eine bewegliche Trennwand (38) vorhanden ist, welche bezüglich der genannten axialen Richtung (D) quer angeordnet ist, um diesen Hohlraum (36) in eine erste Kammer (36a), in welche sich der genannte Hilfskanal (50) öffnet, und eine zweite Kammer (36b) zu unterteilen, in welcher zwischen der Trennwand (38) und dem kappenförmigen Element (32) eingefügte, federnde Druckmittel (48) vorgesehen sind, wobei die Trennwand (38) ein Rückschlagventil (40, 42, 46) umfaßt, um den Durchlaß eines in der zweiten Kammer (36b) vorhandenen Fluids in die erste Kammer (36a) zu verhindern.
  3. Einrichtung nach Anspruch 1 oder Anspruch 2, dadurch gekennzeichnet, daß die Querschnittsfläche des genannten Hohlraums (36) bezüglich der genannten axialen Richtung (D) gleich groß oder größer ist als die Querschnittsfläche der genannten ringförmigen Kammer (26).
  4. Einrichtung nach Anspruch 2 oder Anspruch 3, dadurch gekennzeichnet, daß die elastische Charakteristik der elastischen Druckmittel (48) derart ist, daß die durch den Druck in der ringförmigen Kammer (26) und durch Trägheits- und Reibungs- kräfte, welchen der Stößel (6) ausgesezt ist, bestimmten resultierenden Kräfte, die auf den Stößel (6) wirken, wenn dessen aktive Oberfläche (15) mit Abstand zur Nocke (5) liegt, die von den elastischen Druckmitteln (48) ausgeübte Druckkraft überwiegen.
  5. Einrichtung nach einem der Ansprüche 2 bis 4, dadurch gekennzeichnet, daß die mit einem asymmetrischen Profil ausgestattete Nocke (5) ein zylindrisches Element umfaßt, dessen Basis von einer gekrümmten Kurve festgelegt ist, welche einen von einem Basiskreis (Ro) der Nocke(5) abgegrenzten Basisabschnitt (5a) aufweist und von welcher sich eine asymmetrisch geformte Nockennase (5b) erstreckt, und ein Paar zylindrischer Oberflächen (7) umfaßt, welche durch einen dem Radius des Basiskreises (Ro) der Nocke (5) gleichen Radius außen abgegrenzt sind, wobei diese zylindrischen Oberflächen längsseits und an gegenüberliegenden Seiten des genannten zylindrischen Elements liegen.
EP95106560A 1994-05-06 1995-05-02 Ventiltriebvorrichtung für eine Brennkraftmaschine mit einem Stösselspielausgleichselement Expired - Lifetime EP0681092B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ITTO940369 1994-05-06
ITTO940369A IT1273185B (it) 1994-05-06 1994-05-06 Dispositivo di comando di una valvola di un motore a combustione interna con dispositivo di recupero del gioco della punteria

Publications (2)

Publication Number Publication Date
EP0681092A1 EP0681092A1 (de) 1995-11-08
EP0681092B1 true EP0681092B1 (de) 1997-02-26

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EP95106560A Expired - Lifetime EP0681092B1 (de) 1994-05-06 1995-05-02 Ventiltriebvorrichtung für eine Brennkraftmaschine mit einem Stösselspielausgleichselement

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EP (1) EP0681092B1 (de)
DE (1) DE69500161T2 (de)
IT (1) IT1273185B (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT1268193B1 (it) * 1994-12-22 1997-02-21 Fiat Auto Spa Dispositivo di comando di una valvola di un motore a combustione interna
DE102004048288A1 (de) * 2004-10-05 2006-05-04 Ina-Schaeffler Kg Variabler Ventiltrieb einer Brennkraftmaschine
GB2563064B (en) * 2017-06-02 2022-05-18 Camcon Auto Ltd Valve actuators
CN112267923B (zh) * 2020-09-28 2022-04-05 中国北方发动机研究所(天津) 一种发动机自供油蓄能型液压挺柱

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4035376C2 (de) * 1989-11-16 2000-04-27 Volkswagen Ag Betätigungseinrichtung für ein Hubventil
DE4317607A1 (de) * 1992-06-05 1993-12-09 Volkswagen Ag Variabler Ventiltrieb für ein Hubventil
IT1257904B (it) * 1992-06-19 1996-02-16 Fiat Ricerche Dispositivo di comando di una valvola di un motore a combustione interna.
DE4419768A1 (de) * 1993-06-26 1995-01-05 Volkswagen Ag Variabler Ventiltrieb für ein Hubventil

Also Published As

Publication number Publication date
DE69500161T2 (de) 1997-06-05
ITTO940369A0 (it) 1994-05-06
EP0681092A1 (de) 1995-11-08
ITTO940369A1 (it) 1995-11-06
DE69500161D1 (de) 1997-04-03
IT1273185B (it) 1997-07-07

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