GB2116631A

GB2116631A - I.c. Engine valve gear

Info

Publication number: GB2116631A
Application number: GB08307506A
Authority: GB
Inventors: Heinz Lemberger; Christoph Schausberger
Original assignee: Bayerische Motoren Werke AG
Current assignee: Bayerische Motoren Werke AG
Priority date: 1982-03-19
Filing date: 1983-03-18
Publication date: 1983-09-28
Also published as: FR2523643A1; IT8320113A0; GB8307506D0; DE3210165A1; IT1161118B

Abstract

The force transmitting connection between a pivoted rocker 1 and the end 4 of a valve stem includes a ball and socket joint 6, 7 and abutting flat surfaces 9, 11. One of the surfaces 9 has a cylindrical projecting wall 10 which limits relative sliding of the surfaces by cooperating with a cylindrical surface 12 associated with the other surface 11. The co-operating cylindrical wall and surface limit lateral rocker movement. <IMAGE>

Description

SPECIFICATION Valve drive This invention relates to a valve drive for an internal combustion engine, comprising a valve-actuating lever of the rocker or drag type arranged for pivotal movement on a ball-and-socket mounting, and a lateral guide which co-operates with an end portion of a valve stem.

In one particular valve drive of this construction, a valve-clearance adjusting element in the form of a set-screw bears against the end of the valve stem by way of a part-spherical surface (DE-PS 10 75 376. This results in substantially punctiform contact between the two high Hertz pressure as a consequence. The point of contact moves during the stroke ofthe valve so that heavy wear, which calls forfrequent adjust ment ofthe valve clearance, occurs in this zone.

Furthermore, an additional component in the form of a helical spring is required for the lateral guiding of the valve-actuating lever, which spring lies against the periphery of the set-screw and is centred in a circular recess in the helical spring plate in the zone of the end of the valve stem. Avalve drive that is reliable in operation cannot be achieved with this arrangement.

Another known valve drive (DE-OS 26 54 528) includes, as a valve-clearance adjusting element, an eccentric which is arranged between two clamping faces parts of which project beyond the eccentric and form lateral guide surfaces co-operating with the end ofthe valve stem. However, linearcontact with high Hertz pressure occurs between the eccentric and the end ofthevalve shaft, and heavywearconsequently takes place. In addition, the reduction ratio ofthe valve-actuating lever is altered when the eccentric is displaced.

The aim ofthe present invention isto provide a valve drive wherein the wear in the power-transmission zone between the valve-actuating lever and the valve stem is kept as low as possible and a simple, inexpensive and reliable lateral guiding ofthe valveactuating lever is ensured.

With this aim in view, a valve drive ofthe construction set forth in the opening paragraph of the specification has the following characteristic features (a) a slide element is arranged between the valveactuating lever and the end ofthevalve stem; (b) the slide element is mounted by means of a ball-and-socket joint on the valve-actuating lever or the stem; (c) a circular planar slide face on the slide element bears on a circular planarslideface on the stem of valve-actuating lever; (d) at least one of the slide faces is encircled by a cylindrical guidewallforming a lateral guide; and (e) the guide wail is spaced away from a cylindrical surface on the valve stem or valve-actuating lever, which cylindrical surfaceforms the periphery ofthe circular slide face on the valve stem or lever.

This arrangement enables the transmission power between the valve-actuating lever and the end of the valve stem to be achieved exclusively by means of components lying flat against each other, so that, if suitable material is selected, the wear in this zone is reducedto a minimum. Atthesametime, reliable lateral guiding of the valve-actuating lever is achieved by simple means and without additional components.

Although, in the case of rocker levers, it is known (from DE-Gm 1885 715and US 2,426,438) to form the valve-clearance adjusting elements as set-screws with slide elements which are linked bya ball-andsocket joint and which bear in a planar manneron the end of the valve stem by way of a slide face, these rocker levers are mounted on shafts and are laterally guided. In contrast, the valve-actuating levers of the valve drive in accordance with the invention are mounted by means of ball-and-socketjoints and have a guide edge on the slide face of the slide element or on the slide face co-operating therewith. The abovementioned publications do not suggest an arrangement ofthis kind.

Three examples of valve drives in accordance with the invention are illustrated in the accompanying drawings, in which Figure lisa cut-away illustration of a valve drive of an internal combustion engine, the Figure showing a valve-actuating lever, a mounting therefor, a drive cam, a slide element, and an end ofthe valve stem; Figure 2 illustrates an alternative form of slide element arranged between the valve-actuating lever and the end of the valve stem; and Figure 3 illustrates a two-partform of slide element.

The valve-actuating lever 1 shown in Figure 1 is designed as a drag ortrailing lever and pivots about a ball-and-socket mounting 2. It is driven by way of a cam 3 and acts on the end portion 4 of a valve stem The mounting 2 of the valve-actuating lever 1 comprises a socket formed in the valve-actuating lever 1 with the socket surface arranged to bear against a substantially spherical surface of a bolt or of an hydraulic valve-play adjusting element having a spherical head.

Atthe end of the valve-actuating lever 1 nearerthe valve stem there is a set-screw 5 forming a valve-play adjusting elementtowhich is securedaslide element 8 by means of a ball-and-socketjointformed bya substantially spherical surface 6 on the set-screw and a substantially spherical socket 7 in the slide element.

The slide element 8 has a flat, circular, slide face 9 which is encircled by a cylindrical guide wall 10. The slide face 9 of the slide element 8 bears in a planar manner against a second flat, circular, slideface 11 formed by the end face on the end portion 4 ofthe valve stem.The guide wall 10 accordingly surrounds the cylindrical surface 12 ofthe end portion 4 ofthe valve stem and is slightly spaced therefrom by an annular gap 13so asto permitlimitedtranslatory movement between the slide faces 9 and 11 which occurs as the result of the movements of the valve-actuating lever 1 The guide wall 10 prevents undesired lateral movements of the valve-actuating lever 1, i.e., movements substantially parallel to the cam shaft, and thus ensures thatthe valve-actuating lever 1 is laterally guided in a reliable manner.

The set-screw 5 has a differential or other irreversiblethread so that automatic displacement is pre cluded. For adjustment of the set-screw 5, it has a hexagonal recess 14atits upperendwhich isableto receive a correspondingly-shaped adjusting key or tool.

Figure 2 shows an alternative form of slide element 28 which is directly secured to the valve-actuating lever 21 by a ball-and-socket joint. The substantially spherical ball 26 is here provided on the slide element 28, wh ile the socket 27 is formed in the valveactuating lever. The slide element 28 has a flat, circular slide face 29 which bears against a flat, circular, slideface31 forming the end-face on the end portion 24 ofthe valve stem. The slide face 29 is surrounded buy a cylindrical guide wall 30 on the slide element, and this guide wall also surrounds the cylindrical surface 32 of the end portion 24 ofthe valve stem.It is, however, spaced therefrom by an annular gap 33 which permits the displaceinent of the slide faces 29 and 31 relatively to each other as is necessaryforactuation of the valve. The use of different slide elements 28 with differing distances between the ball-and-socket joint and the slide face 29 enables the valve clearanceto be adjusted.

In the modification shown i n in Figure 3, a valve- actuating lever, not illustrated, acts on the end portion 44 of the valve stem through atwo-partslide element 48 and a set-screw 45 which acts as a valve-clearance adjusting element. The two-part slide element 48 consists of an inner circular part 55 and an outer part 56 in the form of a sleeve. A flat slide surface 49 and a socket 47 for the ball-and-socketjoint are provided on the inner part 55, while the outer part 56 surrounds the inner part 55 and is firmly connected thereto. The outer part 56 also surrounds a substantially spherical ball 46 on the end portion ofthe set-screw 45 which is therefore so shaped as to form, in conjunction with the outer part 56, a ball-and socket joint. As a result, the outer part 56 is secured in an articulated mannerto the set-screw 45. The portion ofthe outer part 56 which projects beyond the slide face 49 of the inner part 55 forms a guide wall 50 which is spaced from the cylindrical end portion 52 of the stem by an annular gap 53.

The invention thereby ensures, in all three embodiments described above, reliable lateral guiding of the valve-actuating lever 1 as well as reduced wear on the slide faces. It also enables valve clearance to be adjusted in a simple fashion.

Claims

1. Avalve drive for an internal combustion engine, comprising avalve-actuating lever ofthe rocker or drag type arranged for pivotal movement on a ball-and-socket mounting, and a lateral guide which co-operates with an end portion of a valve stem, in which (a) a slide element is arranged between the valveactuating lever and the end of the valve stem; (b) the slide element is mounted by means of a ball-and-socketjoint on the valve-actuating lever or the stem; (c) a circular planar slide face on the slide element bears on a circular planar slideface on the stem or valve-actuating lever; (d) at least on of the slide faces is encircled by a cylindrical guide wall forming a lateral guide; and (e) the guide wall is spaced away from a cylindrical surface on the valve stem orvalve-actuating lever, which cylindrical surfaceformsthe periphery ofthe circularslideface on the valve stem or lever.

2. Avalve drive according to claim 1, in which (a) the slide element includes the socket of the ball-and-socket joint and incorporates the cylindrical guide wall; (b) the ball ofthe ball-and-socketjoint comprises a substantially spherical surface provided on the valveactuating lever; and (c) the slide face on the slide element cooperates with the end face on a cylindrical end portion of the valve stem, which end faceforms a further slide face.

3. Avalve drive according to claim 1, in which (a) the slide element includes the substatially spherical surface ofthe ball-and-socketjoint as well as one oftheslidefaces and the guide wall; (b) the socket ofthe ball-and-socketjoint is provided on the valve-actuating lever; and (c) theslideface on the slide elementcooperates with the end face on a cylindrical end portion of the valve stem, which end face forms a further slide face.

4. Avalve driveaccordingto anyone of claims 1-3, in which (a) the slide element comprises an inner part and an outer part; (b) one of the circular slide faces and a substantially spherical surface orsocketofthe ball-and-socketjoint are formed integrally with the inner part; and (c) the outer part is formed as a sleeve which constitutesthe guide wall and encloses the inner part.

5. Avalve drive according to claim 4, in which the outer part overlaps the equatorial line ofthe substantially spherical surface ofthe ball-and-socketjointto provide an articulated connection.

6. Avalve drive according to any preceding claim, in which the slide element is designed as an exchangeable element so that a different slide element having a different distance between the centre of the ball ofthe ball-and-socketjoint and the slide face, can befitted in orderto adjustthe valve clearance.

7. Avalve drive for an internal combustion engine substantially as described herein with reference to Figure 1, Figure 2 or Figure 3 of the accompanying drawing.