GB2115898A - A device for transmitting movement - Google Patents

Abstract

The device comprises a rocker arm 17 formed with a main bearing surface 18 mounted on a main bearing 16 and further bearing surfaces 23, 24 and 29, 30 which co-operate with the upper ends of exhaust and inlet valves 11, 12 and pushrods 13, 14 respectively. The bearing surfaces have pivotal centres V, W, X, Y, and Z which lie in a common plane P. Movement of pushrod 13 to open the inlet valve 12 will turn the rocker arm about an axis 32 passing through centres W, V and Z and movement of the pushrod 14 to open the exhaust valve 11 will turn the rocker arm about an axis 33 passing through centres X, V and Y. <IMAGE>

Description

SPECIFICATION A device for transmitting movement The invention relates to a devicefortransmitting movement and is particularly but not exclusively concerned with a device for transmitting movement between push rods and valves of an internal combustion engine.

On internal combustion enginesfittedwith a push rod system for operating overhead valves, motion is usually transmitted to the valves by one of thefollowing two methods: (i) By means of a rocker arm which rotates on a shaft whereby the push rod causes the rocker arm to pivotaboutthat shaft and thus push down the valve, or (ii) By means of a stamped steel bucket-type rocker whereby the rocker pivots on a spherical surface located by a central stud and nut.

In each ofthe above methods, two rocker arms are required, one for each valve.

Such arrangements can give rise to problems where the space available forthe rocker arms is somewhat limited. Also, the need to provide one rocker arm per valve complicates assembly.

An object ofthe present invention is to provide an improved devicefortransmitting movement such as movement from a pushrod to a valve.

According to one aspect ofthe invention there is provided a device fortransmitting movement from driving members to driven members comprising an arm arranged, in use, to engage the driving and driven members so that movement of one driving member will turn the arm about a first axis to transmit drive to one ofthe driven members, and movement of the other driving member will turn the arm about a second axis transverse to the first axis to transmit drive to the other driven member.

The arm may be mounted for pivotal movement on a main bearing co-operable with a main bearing surface which is preferably defined by an upper surface portion of the arm. Preferably the arm has further bearing surfaces on undersurface portions thereof arranged to co-operate with the driving and driven members. In such a case each of the first and second axes may passthroughthe pivotal centre of the main bearing surface and pivotal centres oftwo of the further bearing surfaces one of which further bearing surfaces co-operates with one of the driving members and the other of which co-operates with one of the driven members. Preferably all the pivotal centres lie in a common plane and the bearing surfaces may be spherical.

According to another aspect of the invention there is provided an internal combustion engine including driving members in the form of pushrods, driven membersintheform of inletand exhaustvalves and a device in accordance with either of the immediately preceding paragraphsfortransmitting movement from the pushrodsto the valves. With such an arrangement only one arm is necessaryto transmit movement from two pushrodsto inlet and exhaust valves associated therewith. As well as providing a cost saving by using a single arm,the single arm will take up less room than the two arms normally required.

A device in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which Figure lisa plan view of part of an internal combustion engine having a valve, push rod and rocker arm assembly in accordance with the invention, Figures 2 and 3 are cross-sections ofthe arrangement shown in Figure 1 on the lines A-Aand B-B respectively in Figure1 with the rockerarm in two different positions, and Figure 4 is a plan view of a reinforced rocker arm.

A cylinder head 10 carries exhaust and inlet valves 11,12 in known manner. Tubularpushrods 13,14 project upwardly through the cylinder head from a camshaft (not shown). A stud 15 is screwed into the cylinder head and carries a spherical main bearing 16 for a rocker arm 17 formed as a hollow metal pressing. The bearing 16 engages a spherical upper main bearing surface 18 on the rocker arm, the latter being formed with an aperture 1 9to enable the rocker to pivot on the bearing 16 without contacting the stud 15. The bearing 16is held in place bya nut 21.

The rocker arm has two fingers 20,22 formed on their undersurfaces with spherical bearing surfaces 23,24with locate respective valve activating elements 25,26. Each activating element has a spherical uppersurface 8 and a flat undersurface 9, the undersurface engaging the upper end of its associated valve.

The rocker arm has two further fingers 27,28 formed on theirundersurfaces with spherical bearing surfaces 29,30 which locate spherical upper ends (one end 31 of which is shown in Fig. 2) of the push rods 13,14.

The centres of curvature of the spherical uppersurface 18, the spherical bearing surfaces 23,24 on fingers 20,22 and the spherical bearing surfaces 29, 30 on fingers 27,28 are indicated respectively as V, W, X,Y and Z. The centres all lie in a common plane P and the centres W,V, Z and X, V, Y lie on axes 32 and 33 respectively.

In use, the inlet valve 12 is opened by upward movement of the pushrod 13 which causes the rocker arm to pivot about axis 32 on centres W, V, Z. At the same time, the exhaust valve 11 may be closing in which case the pushrod 14will be descending and the rocker arm will simultaneously pivot about axis 33 on centres X, V, Y. The exhaust valve 11 is subsequently opened by upward movementofthepushrod 14. It wilt be seen, therefore, that the single rocker arm 17 will enable movement to be transmitted from the two push rods 13, 14 (constituting the aforesaid driving members) to the two valves 11,12 (constituting the aforesaid driven members) by turning the rocker arm 17 about axes which are transverse to each other.

A plate 34 having birFurcations (one only of which is shown in Figure 2) is secured to the cylinder head 10 so that the pushrods 13,14 slidably locate in the birfurcations. Alternatively, a single birfurcation can be provided for locating one pushrod only. The plate 34 thereby inhibits rotary movement ofthe rocker arm 17 about the axis of the stud 15. Alternatively rotary movement can be inhibitedbyforming a recess in the undersurface 9 of one of the valve actuating snernbers Z9 which locates the upper end of the associated valve. Forces tending to rotate the rocker abouttI central stud are minimised by the alignment of each pushrod axis with its associated rocker axis 32,33 respectively.

The various bearing surfaces require lubrication which may simply take the form of an oil feed into the hollow rocker arm from the centre ofthe stud 15, or an oil feed from the tubular pushrods 13, 14. in the latter case, each pushrod terminates at a narrow bore 36 at its spherical upper end. The bore 36 communi- cates with the interior of the rocker arm through an inlet aperture 37 in the bearing surface 29. Lubricant flows on to surface 18 and outthrough the aperture 19.An aperture 38 isformed in each of bearing surfaces 23,24 for lubrication purposes and a small hole 39drilled through each of the valve activating elements provides lubrication di rectly to the upper surface of each valve if required.

By using valve activating elements 25,26 con tinuous face contact, rather than line contact, will be maintained with the upper ends of the valves, reducing the need for hardened contact faces. Also, the activators will compensate for movement of the rocker arm aboutthe axes 32,33. Alternatively the spherical bearing surfaces 23,24 could, if made convex, engage suitably hardenedflat upper ends of the valves.

To adjust the valve clearances, the push rods could be provided with mechanical length adjusters or the cam followers could be of known hydraulic type.

Alternatively, adjustment means could be provided on one pushrod, the second valve clearance being adjusted by varying the axial position of bearing 16 by means of nut 21.

A rocker cover40 can be held in position by a bolt 41 which scrnws into the upper end of the stud 15.

For mcre arduous conditions the rocker arm may Le resniorced as shown irt Fig. 4. Reinforcement may be effected by means of a stiffening ring 42 within the am which has a suitably shaped inner profile. Oil passages 43 through the stiffening ring allow transfer of oil between the interior 44 of the ring and resulting other compartments 45 - 48. Other methods of reintrceslizent and manufacture~(e.g. forging) of the rockerarm are possible.

Whilst specific reference Ras been made to a rocker arm for an internal combustion engine, the invention may be applied in other fields, e.g. the electrical field where switches are to be actuated by movement of actuating members.

Claims (1)

1. Adevicefortransmitting movementfrom driving membersto driven members comprising an arm arranged, in use, to engage the driving and driven members so that movement of one driving member will turn the arm about a first axis to transmit drive to one ofthe driven members and movement of the other driving memberwillturnthearmabouta second axis transverse to the first axis to transmit drive to the other driven member.

2. A device according to claim 1 in which the arm is mounted for pivotal movement on a main bearing co-operable with a main bearing surface on the arm.

3. A device according to claim 2 in which the main bearing surface is defined by an upper surface portion of the arm.

4. A device according to claim 2 or3 in which the arm has further bearing surfaces on underside portion thereof arranged to co-operate with the driving and driven members.

5. Adevice according to claim 4 in which each of the first and second axes passes through the pivotal centre ofthe main bearing surface and pivotal centres of two of the further bearing surfaces one of which further bearing surfaces co-operates with one ofthe driving members and the other of which co-operates with one of the driven members.

6. A device according to claim Sin which all the pivotal centres lie in a common plane.

7. A device according to claim 4,5 or6 in which all the bearing surfaces are spherical.

8. A device according to claim 7 in which each driven member includes an activating element which has a spherical bearing surface in contact with one of the further spherical bearing surfaces on the arm.

9. A device according to any of claims 4to 8 in which the arm is formed with lubricantfeed apertures in said further bearing surfaces.

10. A device according to any of claims 2 to 9 in which the arm is held in contact with the main bearing buy a retainer inciuding a retaining stud.

11. A deviceaccording to claim 10 in which means is provided to prevent rotation of the arm about the axis ofthe retaining stud.

12. A device according to any preceding claim in which the arm includestwofingersforengagement with respective said driven members, two further fingers for engagement with respective said driving members and a central section from which the fingers extend.

13. A device according to claim 12 in which the arm isformedasa metal pressing.

14. A device according to claim 12 or 13 in which the central section is reinforced by means of a stiffening ring.

15. Adevicefortransmitting movementfrom driving members to driven members constructed and arranged substantially as described herein with reference to the accompanying drawings.

18. An internal combustion engine including driv ing members in theforrn of pushrods, driven n .embers in the form of inlet and exhaust valves and a device in accordance with any preceding claim for transmitting movementfromthe push rods to the valves.