GB2182719A - I.C. engine valve gear rocker arm disconnecting mechanism - Google Patents

Abstract

One 16 of the intake valve rocker arms 14 and 16 on either side of the exhaust valve rocker arm 18 of each cylinder is operated under all load conditions and the other rocker arm 14 is brought into operation under heavy load by axially sliding a splined sleeve on the rocker shaft 10 to engage respective splines 26,30 on the rocker arm and sleeve. The sleeve is moved by a piston 38 within the shaft 10 subject on one end or the other to oil under pressure controllably supplied into shaft chambers 36. <IMAGE>

Description

SPECIFICATION A valve deactivation arrangement This invention relates to a valve deactivation arrangement for an internal combustion engine.

In some internal combustion engines, each cylinder is provided with two intake valves.

When the engine is under heavy load, both intake valves are open simultaneously for maximum performance, but when the engine is under light load or idling it is desirable to have only one valve opening, as this creates desirable swirl in the combustion chamber, leading to better fuel economy (swirl is not as important when the engine is operating at a high speed).

It is known for the rocker arm of one of the valves to be permanently engaged with a rocker arm drive, and for the rocker arm of the other of the valves to be driven from the first-mentioned arm. In a known arrangement, the rocker arms are coupled or decoupled by a connector which is remote from the rocker arm shaft. Such a connector is complex in operation and requires a considerable number of small parts. Its assembly is therefore costly and time consuming. Furthermore it imposes a considerable restraint on the engine designer, in that the valve arms of the two intake valves must be closely adjacent to one another to allow the connector to connect the arms.

According to the present invention, there is provided a valve deactivation arrangement for an internal combustion engine, the arrangement comprising a camshaft, a rocker arm shaft parallel with the camshaft and, for each cylinder, at least three rocker arms mounted for rocking movement on the rocker shaft, two of the arms being arranged to operate separate intake valves and one arm being arranged to operate an exhaust valve (with all three valves opening to one and the same cylinder), and coupling means on the rocker arm shaft, which coupling means can move in an axial direction to either couple together or to uncouple said two of the arms.

The provision of the coupling means on the rocker arm shaft means that a compact arrangement can be provided. The arms which operate the intake valves do not need to be side by side; in one particularly advantageous embodiment the exhaust valve rocker arm lies between two intake valve rocker arms.

Movement of the coupling means is preferably accomplished under hydraulic control.

The coupling means preferably comprises an externally splined sleeve surrounding the rocker arm shaft, and the two arms to be coupled then have internal splines arranged so that one arm is always coupled to the sleeve and the other arm is coupled to the sleeve in one position of the sleeve, but not in another position. The sleeve preferably moves between two end positions, in one of which coupling is effected and in the other of which uncoupling is effected.

In a preferred embodiment, hydraulic control is provided by making the rocker arm shaft hollow and dividing its internal space with internal plugs so as to define a separate hydraulic working chamber associated with each cylinder of the engine. Within each such chamber, a double-acting piston is mounted. This piston supports a transverse pin which projects radially, through windows in the rocker arm shaft wall, into the sleeve. When hydraulic pressure is applied into the chamber at one end, the piston is urged to the other end of the chamber and takes with it the externally splined sleeve. When hydraulic pressure enters the chamber from the other end, the piston moves in the opposite direction and takes the sleeve with it. Thus there is a positive drive mechanism both in the coupling as well as in the uncoupling direction.

The hydraulic pressure may be provided by an external oil pump which can operate continuously, and there may be a valve in the hydraulic circuit which can be switched from one position to another to alter the direction of oil flow, when influenced by an appropriate electronic signal which may, for example, come from an electronic engine management module.

The window in the rocker arm shaft wall preferably allows both longitudinal and rotational movement of the pin which passes through the window.

The invention also relates to an internal combustion engine including a valve deactivation arrangement as set forth above on one or more of its cylinders. It may be convenient for the coupling sleeves at opposite ends of the engine to move in opposite directions when moving to effect coupling or uncoupling.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a plan view of part of the valve gear of an internal combustion engine incorporating a valve deactivation arrangement in accordance with the invention; Figure 2 is a vertical section through a valve deactivation arrangement in accordance with the invention, in an uncoupled state; Figure 3 is a section corresponding to the section shown in Fig. 2 but with coupling effected; Figure 4 is a perspective view of part of the valve deactivation arrangement; and Figure 5 is a section through the arrangement on the lines V-V from Fig. 2.

Fig. 1 shows the valve gear for two cylinders of a four cylinder internal combustion engine, from above. A rocker shaft 10 is supported in blocks 12. Associated with each cylinder are two rocker arms 14 and 16 which operate intake valves and one rocker arm 18 which operates an exhaust valve. The valves themselves are not shown. The rocker arms, as is conventional, have cam followers 20 which run on cams 22 on a camshaft 24 (see Figs. 2 and 3). The rocker arms (14, 16, 18) are journalled about the shaft 10 and turn about the shaft as the camshaft 24 rotates and the cam followers 20 run on the respective cam profiles 22.

Figs. 2 and 3 show that, in fact, the cam profile 22 which corresponds to the left hand rocker arm 14 is 'flat', i.e. the profile is com pletely circular so that there is no action on the cam follower 20 of this rocker arm as the camshaft rotates. The cam follower on this rocker arm can in fact be dispensed with. The rocker arm 14 is however either coupled to or uncoupled from the rocker arm 16. When the two arms are coupled, rotational movement of the arm 16 will be directly transferred to the arm 14 and the two will move together.

When the arms are uncoupled, the arm 16 will move in response to rotation of the camshaft, but the arm 14 will remain stationary, keeping its associated valve closed.

The manner in which the rocker arms 14 and 16 are coupled and uncoupled with be described with reference to Figs. 2 and 3.

Both the rocker arms 14 and 16 have internal splines on their coilars which surround the rocker arm shaft, In the case of the arm 14, these splines are shown at 26 and occupy only a small axial length. In the case of the arm 16, the splines 29 extend across the full axial length of the arm. A sleeve 28 surrounds the shaft 10 and is freely rotatable and slidable on the shaft. The sleeve has external splines 30 at one end and external splines 32 at the other end. In the position shown in Fig.

2, the splines 29 and 32 mesh with one another whilst the splines 26 and 30 are out of mesh. In this position the arms 14 and 16 are disconnected. Movement of the arm 16 as its follower 24 follows the cam profile 22 will not be transferred to the arm 14.

The opposite end position is shown in Fig.

3. Here the sleeve 28 has been shifted to the left with the result that the splines 26 and 30 engage. Because of the length of the splines 29 and 32, these remain in engagement despite the axial shifting of the sleeve so that now the arms 14 and 16 are coupled to one another. The distance through which the sleeve 28 is shifted is suitably 5 mm.

The action of shifting the sleeve 28 is accomplished as follows: The shaft 10 is hollow and is sub-divided into a number of separate cylindrical chambers by means of plugs 34. One such chamber is indicated at 36. Within the chamber 36 is a piston 38 which carries a transverse pin 40.

The pin 40 is fixed in the piston 38 and extends radially from the piston, through opposite windows 42 in the wall of the shaft 10 and then into apertures in the sleeve 28. The outboard ends of the pin 40 are held fixed in the sleeve 28.

To move the piston 38 from the position shown in Fig. 2 to the position shown in Fig.

3, the right-hand side of the chamber 36 is pressurised which pushes the piston 38 to the left, and the pin 40 then pulls the sleeve 28 to the left at the same time. To reverse the procedure and to move from the position of Fig. 3 to the position of Fig. 2, the left-hand end of the chamber 36 is pressurised and the sequence is reversed.

In order to provide the motive power to move the pistons 38, the valve gear is connected in an hydraulic circuit. Above the rocker shaft are two parallel oil feed pipes 44 and 46. These are connected to opposite sides of a source of hydraulic fluid pressure (not shown in the figures). A movable valving component 48 decides which way the hydraulic fluid will flow along the pipes 44 and 46.

In the position shown in Fig. 1, the hydraulic fluid (oil) is pumped into a chamber 50 and flows along the pipe 44. The fluid then flows down galleries 52 into (see Fig. 1) the lefthand side of the chamber 36. It should be noted that the part of the valve gear shown in Fig. 1 (where the gear in respect of only two cylinders appears) is part of a four cylinder engine, and the valve gear for the other two cylinders will be a mirror image (reflected about the line A-A of the part shown. Thus the pistons 38 which serve the two cylinders which are not shown in the drawing will move in the opposite direction to those which serve the two cylinders which are shown. For this reason it will be seen that the gallery 52 at the left-hand side in Fig. 1 is open to both sides of the plug 34.

As oil under pressure enters the left-hand side of the chambers 36, the pistons 38 are moved to the right and the fluid which is present on the right-hand side of the pistons is expelled through galleries 54 and through a vent aperture 56 in the valve block 58. In this way, the rocker arms 14 and 16 will be coupled together in all the cylinders. The sleeves 28 which serve the two cylinders to the right of the plane of symmetry will move towards the right-hand side whereas the other two sleeves (which are not shown in Fig. 1) will move to the left.

To uncouple the rocker arms, the valve member 48 is rotated through 180O so that the passages in the member allow oil under pressure to flow in the opposite direction through the pipes 44 and 46.

When the engine is operating, the rocker arms 16 and 14 pivot about the axis of the shaft 10. Because the shaft itself is stationary, and because the sleeve 28 has to pivot with the rocker arms, the window 42 through which the ends of the pin 40 pass has to permit rotational movement of the pin in addi tion to the axial movement. For this reason the window 42 is shaped as shown in Figs. 4 and 5. The extent of the pivoting or oscillating movement is indicated in Fig. 5 by a doubleheaded arrow 60.

The rotation of the valving component 48 to either couple or uncouple the intake valve rocker arms and thus to activate or deactivate the second intake valve to each cylinder, can be done using a signal from an electronic engine management system which can, for example, activate a solenoid to change the setting of the valving component 48.

With this arrangement, there is no need for an extra cam profile to be provided on the camshaft 24 to operate the second intake valve. Furthermore because of the arrangement of the coupling means on the axis of the rocker arms, there is considerable flexibility in the positioning of the two intake valve rockers.

The invention is not limited to a configuration where there are two intake valves and one exhaust valve. In fact the invention can be applied in any instance where there are two valves which at times are to be operated together and at times are to be uncoupled from one another.

Claims (14)

1. A valve deactivation arrangement for an internal combustion engine, the arrangement comprising a camshaft, a rocker arm shaft parallel with the camshaft and, for each cylinder, at least three rocker arms mounted for rocking movement on the rocker shaft, two of the arms being arranged to operate separate intake valves and one arm being arranged to operate an exhaust valve (with all three valves opening to one and the same cylinder), and coupling means on the rocker arm shaft, which coupling means can move in an axial direction to either couple together or to uncouple said two of the arms.

2. An arrangement as claimed in Claim 1, wherein the exhaust valve arm is arranged on the rocker arm shaft between the two intake valve arms.

3. An arrangement as claimed in Claim 1 or Claim 2, wherein the axial movement of the coupling means is accomplished hydraulically.

4. An arrangement as claimed in any preceding claim, wherein the coupling means includes an externally splined sleeve surrounding the rocker arm shaft, and wherein the two arms to be coupled have internal splines arranged so that one arm is always coupled to the sleeve and the other arm is coupled to the sleeve in one position of the sleeve, but not in another position.

5. An arrangement as claimed in Claim 4, wherein the sleeve is movable between two end positions and said one position is one end position and said another position is the other end position.

6. An arrangement as claimed in Claim 4 or Claim 5, wherein the rocker arm shaft is hollow and is provided with internal plugs which define a separate, cylindrical working chamber associated with each cylinder of the engine, and with hydraulic fluid connections at either end of the cylinder.

7. An arrangement as claimed in Claim 6, wherein the hydraulic fluid connections extend through mounting blocks for the rocker arm shaft.

8. An arrangement as claimed in Claim 6 or Claim 7, wherein a double-acting piston is mounted within each working chamber, and this piston supports a transverse pin which projects radially through a window in the rocker arm shaft wall and into the sleeve.

9. An arrangement as claimed in Claim 8, wherein the window in the rocker arm shaft wall allows both longitudinal and rotational movement of the pin which passes through the window.

10. An arrangement as claimed in any one of Claims 6 to 9, wherein the hydraulic pressure is provided by an external oil pump.

11. An arrangement as claimed in Claim 10, wherein the pump is arranged to operate continuously, and there is a valve in the hydraulic circuit which can be switched from one position to another to alter the direction of fluid flow.

12. An internal combustion engine including a valve deactivation arrangement as claimed in any preceding claim on one or more of its cylinders.

13. An engine as claimed in Claim 11, wherein the coupling sleeves at opposite ends of the engine are arranged to move in opposite directions when moving to effect coupling or uncoupling.

14. A valve deactivation arrangement substantially as herein described with reference to the accompanying drawings.