GB2358453A

GB2358453A - Variable valve timing

Info

Publication number: GB2358453A
Application number: GB0001189A
Authority: GB
Inventors: Tendayi Sailas Machakaire
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-01-19
Filing date: 2000-01-19
Publication date: 2001-07-25
Also published as: GB0010251D0; GB0001189D0; GB2358358A

Abstract

A variable valve timing mechanism for a camshaft comprises a sleeve 1 mounted via straight splines 4 to a camshaft has external helical splines engaging within a camshaft timing belt 5 pulley 3. Axial sleeve movement 12 causes rotation of the camshaft relative to the crankshaft. Axial movement is caused by a vacuum cylinder 7 connected to the engine inlet manifold acting on a lever 9 via a fulcrum 10 and engaging a groove in sleeve hub 11. The cylinder may alternatively be directly connected to the sleeve (Fig. 2b). In an alternative arrangement straight splines are formed on a shaft (16) separate to the camshaft and connected thereto by a pulley (17), belt (5) and further pulley. An externally helically splined axially movable sleeve (15) meshes with a helical crankshaft gear (18).

Description

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Specification

Precision Variable Valve Timing System The invention relates to the method of changing the valve timing system of a four stroke combustion engine while the engine is running. The present systems applied do not vary the timing precisely. By this, meaning that the timing is varied in degrees and not minutes.

The present systems applied can either change the valve timing by applying a number of camshaft lobes on a single camshaft to open a single valve at a particular instance, or by using a hydraulic system that is not very efficient. Thus the changing of the valve timing is not precise to the engine speeds at each instant.

It is the object of this invention to mitigate this discrepancy of the present valve timing systems in use. The proposed invention applies a very simple, but precise method that can change the valve timing in precise response to the engine speeds. To achieve this, reference to the embodiments of the invention-are described by examples shown in the accompanying drawings.

Figures I and 2 show a system applied directly to the camshaft and camshaft gear.Yigures 3 and 4 show a system that uses an idler gear and -shaft to achieve similar results. The two concepts are based on sliding two helical gears together, while sliding at the same instant, one of the gears on a splined shaft.

Referring to Figure 1, a gear I with external helical grooves and internal splines, attached to a grooved hub 2, slides through the camshaft gear 3 which also has helical grooves internally. As gear 1 slides through the grooves in gear 3, it slides along the splines 4 on the camshaft gear.

As the gear I moves through the camshaft gear while sliding along the splines on the camshaft, it exerts a twisting motion between the camshaft and its gear. The camshaft gear is restrained from responding to the twisting motion by the timing belt 5 connected to the crankshaft gear 6.

The restrain on the camshaft gear forces the camshaft to respond to the twisting force. The sliding of the helical gear along the camshaft splines is indicated by the two headed arrow 12. The effect acted upon the camshaft by the sliding gear will in turn vary the opening of the engine valves.

Referring to Figure 2, in order for the movements of the helical gear to twist the camshaft so as to vary the valves opening with the variations of the engine speeds, a vacuum cylinder 7, is connected to the engine intake manifold by a metal or plastic pipe 8. The vacuum cylinder activates a lever 9 acting on a fulcrum 10 and the groove I I of the hub 2 attached to the helical gear.

Two spacers 13 in the camshaft gear housing 14, restrain the camshaft gear from sliding forwards and backwards, along the helical gear. The vacuum cylinder can be adapted to fit on the most suitable position, an example of this is shown in Figure 2B, where the vacuum cylinder is front of the helical gear and hub.

Another method of varying the valve timing using the helical gear principle is shown in Figures 3 and 4. Referring to Figure 3, an idler gear 15 with external helical and internal splines, slides along a splined shaft 16, attached to an idler gear 17. The sliding helical gear meshes with an elongated helical crankshaft gear 18. As the helical gear slides along the idler shaft while the crankshaft is turning, it varies the position of the idler gear in relation to the crankshaft gear. The idler gear is connected to the camshaft gear by the timing belt 5.

Claims

1. A variable valve timing system using a helical gear 1, attached to a hub 2, 4s I shown and described in Figure 1.

2. A variable valve timing system using helical gear as described in claim 1, meshing with the internal helical section of the camshaft gear 3.

3. A variable valve timing system using a helical gear with internal splines a described in claims I and 2, sliding on the splined camshaft 4.

4. A variable valve timing system as described and shown in Figure 2, using vacuum method 7 of activating a hub 2, and as claimed in claims I to 3,

5. A van able valve timing system as shown and described in Figure 3, using ti helical gear sliding on a shaft 16 attached to an idler gear 17.

6. A variable valve timing system as described in Figure 3, incorporating a slio ng helical gear, to mesh on an elongated helical crankshaft gear 18.

7. A variable valve timing system as shown and described in this patent specification and attached drawings.