GB2066403A

GB2066403A - Floating pivot rocker arm

Info

Publication number: GB2066403A
Application number: GB8040755A
Authority: GB
Original assignee: Thomson A J
Current assignee: Thomson A J
Priority date: 1979-12-21
Filing date: 1980-12-19
Publication date: 1981-07-08

Abstract

A rocker arm 5, which operates on valves 9 of an internal combustion engine, has an elongated hole 4 through which the rocker shaft 3 passes. Play is taken up by a spring loaded bucket 7 which may also take up some of the initial movement of the cam/pushrod 8 depending on the position of stop 1 which may be varied in accordance with engine conditions e.g. R.P.M. etc. A second spring loaded bucket (11) may be brought to bear on the rocker arm 5 due to movement of a piston (13) when valve lift is not sufficient (Fig 16 not shown). <IMAGE>

Description

SPECIFICATION Floating pivot rocker The floating pivot rocker consists of a rocker, with its pivot hole, through which the rocker shaft passes, elongated in the vertical plane parallel to the plane of movement of the valve. The play in the rocker due to this elongated hole is controlled by a spring loaded piston or bucket. The maximum movement of this piston is limited by a moveable stop, the position of the stop being varied during the operation of the engine.

As the camshaft or pushrod first operates against the rocker, the initial movement is taken up by the rocker sliding within the elongated hole against the spring loading of the piston, until the stop is reached. Once the stop is reached, any further depression/lift by the camshaft/pushrod, will cause the rocker to open the valve in the usual way. The spring controlling the piston must be strong enough to reduce the shock of the piston hitting the stop, but weak enough to compress before the valve spring starts to compress. With large movements of the rocker relative to the shaft, i.e. stop (1) further away from rocker, there may not be sufficient lift to the valve. This lift can be increased by the provision of stop (2), which may also be adjusted as required during operation.

As the rocker starts to lower the valve it then comes In contact with stop (2) causing the rocker to pivot around stop (2) and the original pivot hole to slide relative to the rocker shaft. This would cause the valve to open further.

Stop (1) moves nearer the rocker as the rev/min increases in order to allow the valve opening to follow the profile of the cam more closely.

Stop (2) moves nearer the rocker only at low rev/min when there is enough available play between the rocker and rocker shaft to avoid rocker shaft coming in contact with the bottom of the rocker at full lift position. Stop (2) may, if necessary, be slightly spring loaded to dampen shock.

Even at high speed setting with no opening the rocker should not quite be in contact with the rocker shaft at the absolute end of the hole's travel. This allows the spring to push the piston against the rocker which can then lightly maintain contact with both the valve and cam or pushrod.

Thus valve clearance adjustment is not required.

The use for this apparatus would be that an engine could utilise a camshaft with large dverlapping valve timing with considerable lift.

Such camshafts are normally applicable to high revving engines whose maximum torque and power outputs are developed at high rev/min. This apparatus would enable such camshafts to provide shorter valve overlap periods and less valve lift, by varying the position of the stops, thus enabling an engine with such a camshaft to produce adequate torque and power at much lower rev/min. This would make the engine much more flexible, and whilst the maximum power deveioped would remain unchanged, the fuel consumption and exhaust emissions at lower rev/min would be improved.

Fig. 1 (a) illustrates the low speed operation.

Drawing Fig. 1 (a) i shows the position of the rocker shaft (3) relative to the elongated hole (4) in the rocker (5). Spring (6) pushes bucket (7) against the rocker. (8) is the camshaft or pushrod.

(9) is the valve. (10) is a fixed part relative to the engine with a tube or cylinder through which (7), (6) and stop (1) slide. Stop (1) is a piston whose position is controlled depending upon the valve timing required.

Fig. 1 (a) ii indicates the position of the rocker shaft (3) to the elongated hole (4) as the valve is opened. Bucket (7) has been depressed and at very low speed operations may not quite have made contact with stop (1). Thus a certain amount of the valve lift has been used in allowing rocker arm (5) to move relative to shaft (3).

Fig. 1 (b) illustrates the action of assembly (2), a spring loaded domed bucket (11) whose contact to the rocker is dampened by spring (12) which acts against a piston (13) which can be retracted from the rocker as the rev/min increases. The assembly of (1 1), (12) and (13) known as stop (2) moves within a cylinder within part (10).

Fig. 2 (a) illustrates the high speed operation.

Stop (1) has been moved towards the rocker (8) so that as the cam or pushrod operates on the rocker, the rocker cannot compress bucket (7) and therefore must operate on the valve earlier.

Fig. 2 (b) shows the high speed operation with the valve closed. A small gap x still remains between (3) and (5) to avoid valve adjustment clearances which are taken up by the tension of spring (6).

Fig. 3 illustrates the same idea but this time with the cam/pushrod on the other side of the rocker shaft from the valve. This time the stops (1) and (2) are located on top of the rocker with stop (2), i.e. (11), (12) and (13) assembly, located between the rocker shaft and the cam/pushrod.

1. A rocker used for the operation of valve gear in an internal combustion engine has an elongated hole through which a round-sectioned rocker shaft passes. The exact location of the rocker relative to the shaft is controlled by a spring loaded bucket or piston acting externally upon the rocker to keep it in contact with both valve and cam/pushrod. The extent to which this bucket may be depressed is limited by the position of stop (1) whose position may be varied during engine operation. As stop (1) is retracted more of the lift from the cam/pushrod is absorbed by the bucket and spring.

2. The spring loaded bucket described in Claim 1 may be used to maintain contact between the rocker and the cam/pushrod, and between the rocker and the top of the poppet valve of the engine, thus avoiding the need for valve clearance adjustment.

3. By varying the position of stop (1) mentioned in Claim 1, a greater or lesser amount of the cam's lifting action may be transferred to the valve, thus enabling valve timing and valve lift to be altered

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Floating pivot rocker The floating pivot rocker consists of a rocker, with its pivot hole, through which the rocker shaft passes, elongated in the vertical plane parallel to the plane of movement of the valve. The play in the rocker due to this elongated hole is controlled by a spring loaded piston or bucket. The maximum movement of this piston is limited by a moveable stop, the position of the stop being varied during the operation of the engine. As the camshaft or pushrod first operates against the rocker, the initial movement is taken up by the rocker sliding within the elongated hole against the spring loading of the piston, until the stop is reached. Once the stop is reached, any further depression/lift by the camshaft/pushrod, will cause the rocker to open the valve in the usual way. The spring controlling the piston must be strong enough to reduce the shock of the piston hitting the stop, but weak enough to compress before the valve spring starts to compress. With large movements of the rocker relative to the shaft, i.e. stop (1) further away from rocker, there may not be sufficient lift to the valve. This lift can be increased by the provision of stop (2), which may also be adjusted as required during operation. As the rocker starts to lower the valve it then comes In contact with stop (2) causing the rocker to pivot around stop (2) and the original pivot hole to slide relative to the rocker shaft. This would cause the valve to open further. Stop (1) moves nearer the rocker as the rev/min increases in order to allow the valve opening to follow the profile of the cam more closely. Stop (2) moves nearer the rocker only at low rev/min when there is enough available play between the rocker and rocker shaft to avoid rocker shaft coming in contact with the bottom of the rocker at full lift position. Stop (2) may, if necessary, be slightly spring loaded to dampen shock. Even at high speed setting with no opening the rocker should not quite be in contact with the rocker shaft at the absolute end of the hole's travel. This allows the spring to push the piston against the rocker which can then lightly maintain contact with both the valve and cam or pushrod. Thus valve clearance adjustment is not required. The use for this apparatus would be that an engine could utilise a camshaft with large dverlapping valve timing with considerable lift. Such camshafts are normally applicable to high revving engines whose maximum torque and power outputs are developed at high rev/min. This apparatus would enable such camshafts to provide shorter valve overlap periods and less valve lift, by varying the position of the stops, thus enabling an engine with such a camshaft to produce adequate torque and power at much lower rev/min. This would make the engine much more flexible, and whilst the maximum power deveioped would remain unchanged, the fuel consumption and exhaust emissions at lower rev/min would be improved. Fig. 1 (a) illustrates the low speed operation. Drawing Fig. 1 (a) i shows the position of the rocker shaft (3) relative to the elongated hole (4) in the rocker (5). Spring (6) pushes bucket (7) against the rocker. (8) is the camshaft or pushrod. (9) is the valve. (10) is a fixed part relative to the engine with a tube or cylinder through which (7), (6) and stop (1) slide. Stop (1) is a piston whose position is controlled depending upon the valve timing required. Fig. 1 (a) ii indicates the position of the rocker shaft (3) to the elongated hole (4) as the valve is opened. Bucket (7) has been depressed and at very low speed operations may not quite have made contact with stop (1). Thus a certain amount of the valve lift has been used in allowing rocker arm (5) to move relative to shaft (3). Fig. 1 (b) illustrates the action of assembly (2), a spring loaded domed bucket (11) whose contact to the rocker is dampened by spring (12) which acts against a piston (13) which can be retracted from the rocker as the rev/min increases. The assembly of (1 1), (12) and (13) known as stop (2) moves within a cylinder within part (10). Fig. 2 (a) illustrates the high speed operation. Stop (1) has been moved towards the rocker (8) so that as the cam or pushrod operates on the rocker, the rocker cannot compress bucket (7) and therefore must operate on the valve earlier. Fig. 2 (b) shows the high speed operation with the valve closed. A small gap x still remains between (3) and (5) to avoid valve adjustment clearances which are taken up by the tension of spring (6). Fig. 3 illustrates the same idea but this time with the cam/pushrod on the other side of the rocker shaft from the valve. This time the stops (1) and (2) are located on top of the rocker with stop (2), i.e. (11), (12) and (13) assembly, located between the rocker shaft and the cam/pushrod. CLAIMS

3. By varying the position of stop (1) mentioned in Claim 1, a greater or lesser amount of the cam's lifting action may be transferred to the valve, thus enabling valve timing and valve lift to be altered during engine operation.

4. A further spring loaded bucket with rounded dome acted upon by a moveable piston (stop 2 in drawings) acts against the rocker when stop 1 (see Claim 1) is positioned further away from the rocker. As the rocker comes in contact with the stop (2) the rocker then pivots round stop (2) which will give greater lift than if it had pivoted about the rocker shaft. If the cam/pushrod is between the valve and the rocker shaft then stop (2) is positioned between the cam/pushrod and the rocker shaft on the other side of the rocker, i.e.

under the rocker (Fig. 2).

If the rocker shaft is between the valve and the cam/pushrod then stop (2) is positioned between the rocker shaft and the cam/pushrod on the other, i.e. the upper side of the rocker. This stop (2) is retracted away from the rocker as stop (1) moves nearer the rocker.

5. The springs controlling the bucket in Claim 1 and the bucket in Claim 4 dampen the shock as play is taken up between the rocker, the cam/pushrod and the valve head.

6. By using the apparatus described in C!aim 1 and Claim 4, greater lift for a greater time can be passed from the cam/pushrod directly to the valve as stop (1) is located nearer the rocker, this being done as engine rev/min increases.