EP1267044A2 - Système de distribution à soupapes - Google Patents

Système de distribution à soupapes Download PDF

Info

Publication number
EP1267044A2
EP1267044A2 EP02254154A EP02254154A EP1267044A2 EP 1267044 A2 EP1267044 A2 EP 1267044A2 EP 02254154 A EP02254154 A EP 02254154A EP 02254154 A EP02254154 A EP 02254154A EP 1267044 A2 EP1267044 A2 EP 1267044A2
Authority
EP
European Patent Office
Prior art keywords
valve
assembly
rocker arm
cam
lash adjuster
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.)
Granted
Application number
EP02254154A
Other languages
German (de)
English (en)
Other versions
EP1267044A3 (fr
EP1267044B1 (fr
Inventor
David Gerard Genise
Majo Cecur
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.)
Eaton SRL
Original Assignee
Eaton Automotive SpA
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Priority claimed from EP01830398A external-priority patent/EP1267043A1/fr
Application filed by Eaton Automotive SpA filed Critical Eaton Automotive SpA
Priority to EP02254154A priority Critical patent/EP1267044B1/fr
Publication of EP1267044A2 publication Critical patent/EP1267044A2/fr
Publication of EP1267044A3 publication Critical patent/EP1267044A3/fr
Application granted granted Critical
Publication of EP1267044B1 publication Critical patent/EP1267044B1/fr
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
    • F01L1/20—Adjusting or compensating clearance
    • F01L1/22—Adjusting or compensating clearance automatically, e.g. mechanically
    • F01L1/24—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically
    • F01L1/2405—Adjusting or compensating clearance automatically, e.g. mechanically by fluid means, e.g. hydraulically by means of a hydraulic adjusting device located between the cylinder head and rocker arm
    • 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
    • F01L1/18—Rocking arms or levers
    • F01L1/181—Centre pivot rocking arms
    • F01L1/182—Centre pivot rocking arms the rocking arm being pivoted about an individual fulcrum, i.e. not about a common shaft
    • 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
    • F01L1/18—Rocking arms or levers
    • F01L1/185—Overhead end-pivot rocking arms
    • 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
    • F01L1/20—Adjusting or compensating clearance
    • F01L1/22—Adjusting or compensating clearance automatically, e.g. mechanically
    • 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
    • F01L2303/00—Manufacturing of components used in valve arrangements
    • 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
    • F01L2305/00—Valve arrangements comprising rollers

Definitions

  • This invention relates to valve train assemblies, and particularly but not exclusively to assemblies which incorporate a rocker arm pivoted by a cam in order to operate a valve.
  • the valve train assembly 2 comprises the rocker arm 4 and a hydraulic lash adjuster 6.
  • One end 8 of the rocker arm 4 engages the stem 10 of a valve 11.
  • the other end 12 of the rocker arm is mounted for pivotal movement on the lash adjuster 6.
  • the rocker arm 4 is provided with a roller 14 mounted on an axle 16 carried by the rocker arm 4.
  • a cam 18 mounted on a cam shaft 15 has a lobe 17 which can engage the roller 14 and thus pivot the rocker arm 4 anti-clockwise as shown in the drawing. This depresses the valve stem 10 against the force of a valve spring (not shown) and thus opens the valve. As the cam continues to rotate, and the base circle 19 of the cam profile again engages the roller 14, the valve spring returns the valve and the rocker arm 4 to the position shown in Figure 1.
  • a hydraulic lash adjuster has an oil-containing chamber and a spring arranged to enlarge the chamber and thus extend the lash adjuster. Oil flows into the chamber via a one-way valve, but can escape the chamber only slowly, for example via closely-spaced leakdown surfaces.
  • the lash adjuster 6 of Figure 1 can extend to accommodate any slack in the valve train assembly, such as between the cam 18 and the roller 14. After it is extended, however, the oil-filled chamber provides sufficient support for the pivoting movement of the rocker arm 4.
  • the base circle 19 of the cam 18 It is important for the base circle 19 of the cam 18 to be concentric with respect to the axis of rotation of the cam shaft 15. Any slight eccentricity (“run-out”) could cause the valve to close later than it should, or open during the movement of the base circle past the roller 14.
  • the cam 18 is often formed by sintering and may not have, in its initial state, particularly accurate dimensions. Accordingly, it is conventional, before assembly, to grind either the outer surface, including the base circle 19, of the cam 18, or to grind the inner diameter which is fitted to the cam shaft 15, to ensure accurate concentricity of the base circle 19 relative to the axis of rotation of the cam shaft 15.
  • valve trains which provide "lift loss", that is, in which the initial movement caused by the cam is absorbed before further movement is transmitted to the valve. See for example US-A-6039017 and US-A-6170450.
  • lift loss that is, in which the initial movement caused by the cam is absorbed before further movement is transmitted to the valve.
  • a valve train assembly includes a rocker arm supporting a cam-engaging roller, wherein the roller, instead of having a rotation axis fixed with respect to the rocker arm, has an axis which is allowed to shift slightly against the force of a resilient biasing means, thereby providing lift loss when operating the valve, and thus accommodating movement of the valve towards its closing position in circumstances in which a lash adjuster has extended excessively.
  • the resilient biasing means is strong enough to prevent the lash adjuster from taking up the lost-motion connection in the valve train.
  • the lost-motion connection permits such movement to occur, without operating the valve, against the force of the spring.
  • the valve is operated. Subsequently, as the cam continues to rotate, the valve moves towards its closing position. After the valve is closed, the lost-motion connection is restored by the biasing means. Closing of the valve is thus guaranteed, because any required additional movement is accommodated by the lost-motion connection.
  • a lost motion connection such as that set out above means that the base circle radius variation of the cam no longer has to be minimised by grinding, allowing the use of net-shaped cam shaft technology instead of more expensive ground cams.
  • net-shaped is generally understood, and used herein, in the sense of having a shape and dimensions which are at least substantially the same as those resulting from the initial forming of the object. This does not exclude the possibility of small changes in dimensions which are a consequence of, for example, surface-treatment for the purpose of smoothing, as distinct from dimensional changes (e.g. by grinding) for the purpose of altering the function performed as a result of those dimensions.
  • the initial forming may, but is not necessarily, achieved by sintering.
  • valve assembly comprises a rocker arm pivoted at one end on the lash adjuster, with the other end operating the valve stem.
  • some aspects of the invention can also be embodied in other types of arrangements, such as centre-pivoted rocker arms, and indeed could be applied to arrangements which don't include a rocker arm, such as direct-acting tappets (see US-A-6170450), so long as the requisite lost motion connection is provided.
  • valve train assembly 2 shown here is similar to that of Figure 1 (and like reference numbers designate like elements) except in respect of the differences explained below.
  • the cam 18 of Figure 3 looks similar to that of Figure 1, and has also been formed by a sintering operation (but could alternatively be formed by other means, such as hydroforming or hot- or cold-forming). However, in this case, no additional grinding operation has been performed on either the outer surface of the base circle 19 or on the inner surface of the cam. Accordingly, the cam 18 is net-shaped and the base circle 19 is not necessarily accurately concentric with respect to the axis of rotation. (It may be desirable in some embodiments, such as alternatives which incorporate direct-acting cams, to have a surface treatment for the purpose of smoothing the exterior of the cam.)
  • axle 16 of the roller 14 is mounted and movable within an over-size hole, or aperture, 20 in the rocker arm 4, forming a lost-motion connection.
  • a spring 22 operates on the axle 16 so as to bias it towards the top of the hole 20.
  • the hydraulic lash adjuster 6 On start-up, the hydraulic lash adjuster 6 rapidly receives oil under pressure and expands to take up any slack in the valve train.
  • subsequent expansion of the engine components may result in the requirement for the lash adjuster to contract in order to permit closing of the valve. In prior art arrangements, this cannot occur quickly because the oil has to flow between leak-down surfaces, and the flow is thus slow, especially after start-up when the oil is still cold.
  • valve is still capable of being closed by the valve spring, because any additional movement required of the rocker arm is accommodated by the lost-motion connection.
  • the difference in desired versus actual lash adjuster position is taken up by the axle 16 not completely returning to the top portion of the hole 20.
  • Figure 4 illustrates that the rocker arm 4 can move from the dotted line position, which would preclude closing of the valve, to the solid line position which permits valve closing, by taking up some of the lost motion.
  • the spring 22 is specified so that the force it applies to the valve stem when it is fully extended is less than the pre-load force of the valve spring in the closed position. This ensures that the valve spring is sufficiently powerful to close the valve against the force produced by the spring 22. Also, the pre-load force of the spring 22 is calculated to be greater than the sum of the lash adjuster return spring and the oil pressure forces in the lash adjuster. In other words, the spring 22 is sufficiently powerful to prevent the lash adjuster 6 from expanding to take up the lost motion between the axle 16 and the hole 20.
  • any non-concentricity (run-out) of the base circle 19 (which in the Figure 1 arrangement would result in the valve being open during engagement of the base circle with the roller 14) will be accommodated by the lost motion connection, thus avoiding false opening.
  • the rocker arm is made of stamped sheet metal and has a part-spherical end 12 to permit pivoting about a part-spherical end of the lash adjuster 6.
  • the roller 14 is mounted on needle bearings 24 and supported on the axle 16.
  • the axle 16 is supported in holes 20 in respective side walls of the rocker arm 4, at least one and preferably both of the holes being oversized to permit lateral movement of the axle.
  • the axle 16 has circumferential grooves 26 at respective ends.
  • the end 8 of the rocker arm carries a member 28 having a surface 32 for engaging the end of the valve stem.
  • the spring 22 is generally U-shaped, having a central portion which locates over the end 8 of the rocker arm 4 and two arms which extend along the sides of the rocker arm, under the axle 16 and in the recesses 26 thereof.
  • the arms have ends which locate in the apertures 30 of the rocker arm 4 at the end 12 thereof.
  • the arms of the spring could instead extend through holes drilled through the axle 16.
  • FIGS 7 and 8 show an alternative arrangement.
  • the axle 16 of the roller 14 is tightly supported by the sides of a retainer 34 formed of stamped sheet metal with its sides fitted over and surrounding the rocker arm 4.
  • the axle again extends through over-sized holes 20 in the rocker arm 4.
  • the retainer 34 engages the rocker arm 4 at the end 8 thereof.
  • the opposite end of the retainer 34 is located over but biased away from the part-spherical end 12 of the rocker arm 4, by means of a conical spring 22.
  • the entire retainer 34 and the supported roller 14 and axle 16 are pivoted anti-clockwise by the force of the spring 22 such that, as in the earlier embodiments, the axle 16 is biased towards the top of the holes 20.
  • the valve opens later and closes sooner, in relation to the rotation of the cam, than in prior art arrangements.
  • the profile of the cam is altered as compared with prior art arrangements.
  • a further alteration to the profile is made in order to extend the ramp of the cam lobe to ensure that the axle 16 makes contact with the rocker arm 4 at a controlled velocity, rather than during the high-acceleration portion of the opening event. This reduces the impact force of the axle 16 against the rocker arm 4.
  • the sizes of the holes 20 define the maximum amount lost motion, and thus the maximum amount of lift loss.
  • the maximum amount of lift loss, as measured at any given location, should:
  • the sizes of the holes 20 are such as to provide lost motion of the axle 16 in the range of 0.1 mm to 0.3 mm, and more preferably in the range 0.15 mm to 0.25 mm.
  • the holes 20 may be oval-shaped or circular. If oval-shaped, each end radius is preferably substantially the same as the radius of the axle 16, the end radii being offset by the amount of the desired lost motion.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Valve-Gear Or Valve Arrangements (AREA)
EP02254154A 2001-06-15 2002-06-14 Système de distribution à soupapes Expired - Lifetime EP1267044B1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP02254154A EP1267044B1 (fr) 2001-06-15 2002-06-14 Système de distribution à soupapes

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
EP01830398A EP1267043A1 (fr) 2001-06-15 2001-06-15 Système de distribution à soupapes d'un moteur à combustion interne
EP01830398 2001-06-15
EP02254154A EP1267044B1 (fr) 2001-06-15 2002-06-14 Système de distribution à soupapes

Publications (3)

Publication Number Publication Date
EP1267044A2 true EP1267044A2 (fr) 2002-12-18
EP1267044A3 EP1267044A3 (fr) 2003-01-02
EP1267044B1 EP1267044B1 (fr) 2005-08-10

Family

ID=26077483

Family Applications (1)

Application Number Title Priority Date Filing Date
EP02254154A Expired - Lifetime EP1267044B1 (fr) 2001-06-15 2002-06-14 Système de distribution à soupapes

Country Status (1)

Country Link
EP (1) EP1267044B1 (fr)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5022361A (en) * 1989-11-11 1991-06-11 General Motors Corporation Valve-lash adjustment system
US5584267A (en) * 1995-12-20 1996-12-17 Eaton Corporation Latchable rocker arm mounting
US5669342A (en) * 1994-04-14 1997-09-23 Ina Walzlager Schaeffler Kg Device for simultaneous actuation of at least two gas exchange valves
EP0889206A1 (fr) * 1997-07-01 1999-01-07 Unisia Jecs Corporation Dispositif variable de commande de soupape
US6021751A (en) * 1999-02-18 2000-02-08 General Motors Corporation Hydraulic valve lifter with lash

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5022361A (en) * 1989-11-11 1991-06-11 General Motors Corporation Valve-lash adjustment system
US5669342A (en) * 1994-04-14 1997-09-23 Ina Walzlager Schaeffler Kg Device for simultaneous actuation of at least two gas exchange valves
US5584267A (en) * 1995-12-20 1996-12-17 Eaton Corporation Latchable rocker arm mounting
EP0889206A1 (fr) * 1997-07-01 1999-01-07 Unisia Jecs Corporation Dispositif variable de commande de soupape
US6021751A (en) * 1999-02-18 2000-02-08 General Motors Corporation Hydraulic valve lifter with lash

Also Published As

Publication number Publication date
EP1267044A3 (fr) 2003-01-02
EP1267044B1 (fr) 2005-08-10

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