CZ20022008A3 - Valve mechanism of spark ignition engine - Google Patents

Abstract

7)Annotation: The mechanism has rocker arms (7, 8), rotatably mounted on sliding calipers (12, 12'). The movement of the calipers with the rocker arms is controlled by eccentric shafts (13, 13'). The rocker arms are equipped with hydraulic elements (10, 10') for limiting the valve clearance. When transferring movement from the intake cam (3) to the intake valve (5), the intake rocker arm (7) rests on a movable support cam (19). By changing the relative position of the intake rocker arm (7), the intake cam (3) and the support cam (19), the time and phase of opening the intake valve (5) and its stroke from maximum to zero are changed. The intake valve thus serves to regulate engine power. When transferring movement from the exhaust cam (4) to the exhaust valve (6), the exhaust rocker arm (8) rests - on a fixed support (29). By changing the relative position of the exhaust rocker arm (8) and the exhaust cam (4), the opening phase of the exhaust valve (6) and thus the valve overlap time are changed. The support cam mechanism (19) used for both the intake and exhaust valves allows for zero lift

Description

Gasoline internal combustion engine valve mechanism

Technical field

Tooz 'Zoo /

The invention relates to a valve mechanism of a spark-ignition internal combustion engine with a variable stroke and valve timing.

BACKGROUND OF THE INVENTION

According to the preamble of the main claim, the invention is based on the arrangement published in SAE Trans., Vol. 77 on pages 1293-1303, entitled "Intake Valve Throttling (IVT) - A Sonic Throttling Intake Valve Engine". In this arrangement, the cam travel is transmitted to the valve by means of a rocker which is supported by the sliding support. When the position of this sliding support is changed, the gear ratio on the rocker arm and thus the valve stroke change.

A disadvantage of this known arrangement is that it does not allow to change the timing and opening time of the valves. The efficiency of a spark-ignition internal combustion engine can be greatly improved at a partial load by reducing the losses caused by the throttle. One option is to replace the throttle valve power control by varying the stroke and variable timing of the intake valves so that the engine only sucks in as much air as it needs for the currently required power.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a valve mechanism arrangement which permits for each engine operating mode to vary the stroke and opening time of the valves as well as the phase, i.e. the distance of the valve point.

An appropriate combination of these parameters will improve engine performance, efficiency and composition.

The drawbacks described in the prior art are overcome by the arrangement according to the invention, which is based on the meaning of the main claim, in that the rocker is movable perpendicular to the valve axis and tangential to the base circle of the cam.

Overview of the drawings

SUMMARY OF THE INVENTION

The following figures show some examples of the arrangement of the valve mechanism according to the invention.

Giant. 1 shows a cross-section of the internal combustion engine head in various planes; FIG. 2 shows a schematic representation of the valve mechanism at maximum and zero stroke of the intake valve; FIG. 3 schematically shows the partial stroke of the intake valve; Fig. 4 shows the various strokes of the intake valve depending on the angle of rotation of the engine crankshaft.

DETAILED DESCRIPTION OF THE INVENTION

In Fig. 1, a camshaft 2 with intake cams 3 and exhaust cams 4 rotating in a clockwise direction is mounted in the head 1 of the internal combustion engine. The head 1 is further provided with at least one inlet valve 5 and at least one exhaust valve 6.

The lift of the suction cam 3 is transmitted to the suction valve 5 by means of a suction lever 7 and 1 the exhaust cam lift is transmitted to the exhaust valve 6 by the exhaust rocker A

The rocker arms are provided with bells 9 and 9j for reducing frictional losses in contact with the intake and exhaust cams 3 and 4, and with hydraulic elements 10 and 10 'to define the valve clearance. The return spring 11 presses the suction rocker 7 against the suction cam 3. The rocker arms 8 and 8 are rotatably mounted in the yokes 12 and 12 '.

The displacement of the yokes with the rocker arms operating the eccentric shafts 13, 13 'rotatably mounted in the timing carrier 14 and driven by electric motors via a gear (not shown). The timing carrier 14 is firmly connected to the engine head 1 by screws 15, 15 '.

When the eccentric shaft 13 is rotated, the yoke 12 and with it the suction rocker 7 are moved. Similarly, when the eccentric shaft 13 is rotated, the yoke 12 and the exhaust rocker 8 are moved.

The direction of movement of the rocker arms 7, 8 is determined by the sliding of the hydraulic elements

10, 10 'by the valve caps 16, 16' and by rolling the bells 9, 9 'on the cams i' '

The channel 17 in the yoke 12 is connected through the passages in the eccentric shaft 13 g to the engine lubrication system (not shown) and supplies the hydraulic element 10 via the borehole i (not shown) in the suction arm 7 Similarly, the hydraulic element 10 'in the exhaust vahadle 8.

The suction arm 7 is supported by its contact surface 18 on the support cam 19 when transmitting movement from the suction cam 3 to the suction valve 5.

In the rest position of the suction arm 7, i.e. when the roller 9 is rolled on the base circle of the suction cam 3, the planar contact surface 18 lies perpendicular to the axis of the suction valve 5.

The support surface of the support cam 19 is composed of a base part 20 on the side adjacent to the suction valve 5, which is in contact with the suction arm 7

at its rest position, on the other hand, at its zero stroke position of the intake valve 5, and further from the opening portion 21 on the side adjacent to the cam 3 which is in contact with the rocker 7 when the valve is open. The base portion 20 is continuously connected to the opening portion 21 by a transition portion 22 over which the rocker arm 2 rolls during transition from the base portion 20 to the opening portion 21.

Upon changing the stroke of the intake valve 5 and the opening time and phase thereof, the support cam 19 is moved and rotated relative to the suction arm 9. These movements are provided by a shaft 23 with eccentric 24 and a slide 25 in a support cam 19 supported by a pin 26 fixed to the timing carrier 14. The shaft 23 is rotatably mounted in the timing carrier 14 and driven via a gear by an electric motor (not shown).

A mechanism similar to the suction side can be used to reduce the stroke of the exhaust valve 6 to zero. Zero stroke of the intake and exhaust valves is a suitable measure to eliminate some cylinders and thereby reduce throttle and friction losses at partial engine load.

The mechanism shown in Fig. 1 allows to change the opening phase of the exhaust valve 6 while maintaining a constant stroke.

As the exhaust rocker 8 is moved by the yoke 12 ', the support roller 27 rolls along the track 28 of the fixed support 29. The track 28 has the shape of an envelope of the individual positions of the support roller during its rolling.

By harmonizing the opening phases of the exhaust and intake valves in each operating mode, the engine properties can be significantly influenced. At idling and partial load, eliminating or reducing valve overlap can improve combustion stability and reduce fuel consumption and exhaust emissions. At higher and full load, with greater valve overlap, the fresh mixture can be diluted with exhaust gases to reduce the formation of nitrogen oxides. Alternatively, the arrangement according to the invention can only be used for intake valves.

* I · »» · i i i

On engines with separate intake and exhaust camshafts, possible timing of the exhaust valves can be achieved by rotating the respective camshaft relative to the crankshaft. The arrangement according to the invention is variable to such a wide extent that even when used only on the intake side and the rotation of the common camshaft, timing can be varied to an acceptable extent with both the intake and exhaust valves.

The bracket 12 in FIG. 2 keeps the suction arm 7 in the position shown of the eccentric shaft 13 in the rightmost position, when the opening phase of the suction valve 5 is greatest. At the maximum lift of the suction cam 3, the suction lever 7 rests with its contact surface 18 on the support cam 19 at the opening portion 21 of its support surface and the suction valve reaches its maximum stroke.

When the support cam 19 is pivoted, the suction lever 7 is supported only at the base part 20 of its support surface and the suction valve 5 remains closed even at the maximum lift of the suction cam 3.

In Fig. 3, the eccentric shaft 13 is rotated 180 ° from the position in Fig. 2 and the yoke 12 moves the suction rocker 7 to a position where the suction cam 3 opens and closes the suction valve earlier, that is, to a minimum phase position.

The shaft 23 with the eccentric 24 adjusts the support cam 19 so that the suction arm 7 gradually rolls over the base part 20 during the stroke of the suction cam 3 and passes to the transition portion 22 of the support surface of the support cam 19.

The curvature of the transition portion 22 is at least ten times less than the curvature of the opening portion 21, so that when the support cam 19 is in a suitable position, the suction valve 5 remains closed at the beginning of the transition portion 22 and opening time is shorter than in FIG.

The diagram in Fig. 4 shows one possible combination of strokes and phases of the intake valve of the valve mechanism of the invention shown in Figs. 1-3.

• this. It. This

to to · this to this ··

The maximum stroke curve 30 of the intake valve 5 with the maximum phase and opening time has its apex at point 31. The curve 32 connects the peaks of the stroke curves when the suction valve 5 is partially opened. The stroke curve 33 shows the stroke of the suction valve 5 at the rocker arm 7 19 shown in FIG. 3.

Claims (13)

PATENT CLAIMS A valve mechanism for an internal combustion engine having a rocker for transmitting cam movement to a valve supported by a support on a fixed part of the engine, characterized in that the rocker (7, 8) is displaceable perpendicular to the valve axis (5,6) and tangentially to the base circle the cams (3, 4). Valve mechanism according to Claim 1, characterized in that the rocker arm (7, 8) is rotatably supported on the caliper (12, 12 '). Valve mechanism according to claim 2, characterized in that the caliper (12, 12 ') is rotatably mounted on an eccentric shaft (13, 13') rotatably mounted in the timing carrier (14). j Valve mechanism according to claim 1, characterized in that the rocker arm (7, 8) is provided with a bell (9, 9 ') on the side adjacent to the cam (3, 4) and on the sj side _{in the} % side adjacent to the valve (5, 6). ) by a hydraulic element (10, 10 ') for limiting the valve clearance. Valve mechanism according to claim 1, characterized in that the valve (5, 6) is provided at its end with a valve cap (15, 15 ') which is in contact with the rocker (7, 8) as it moves perpendicular to the valve axis. . Valve mechanism according to claim 2, characterized in that the caliper (12, 12 ') is provided with a channel (17) for supplying oil to the hydraulic element (10, 10'). 9 4 4 4 4 4 4 3 4 4 4 4 4 4 4 4 44 4 4 · ^: ·· 4 4 Ί. Valve mechanism according to claim 1, characterized in that between the timing carrier (14) and the rocker arm (14). 7) the support cam (19) is rotatably and displaceably arranged. Valve mechanism according to claim 7, characterized in that the support surface of the support cam (19) is composed of a base part (20) on the side adjacent to the valve (5) that is in contact with the contact surface (18) of the rocker arm (7). ) in its rest position and in the zero-stroke position of the valve (5), further from the opening portion (21) on the side adjacent to the cam (3) in contact with the rocker (7) with the valve (5) open; the transition portion (22) connects the two parts continuously. Valve mechanism according to claim 8, characterized in that the transition portion (22) has at least ten times less curvature than the opening portion (21). ý 10. A valve mechanism according to claim 7, wherein the valve mechanism is: The support cam (19) is rotatably mounted on the cam (3) side on the eccentric (24) of the shaft (23) and on the side adjacent to the valve (5) is guided by a slide (25) on the pin (26), the shaft ( 23) is rotatably mounted and the pin (26) is fixed in the timing carrier (14). Valve mechanism according to claim 3, characterized in that, when the rocker arm (8) moves, the support roller (27) rolls along a track (28) of the fixed support (29) and that the track is in the form of an envelope of individual positions of the support roller . • 4 9 9 · 9 ·· 9 9Λ9 9? '9 9' 9 9 »9 9 9 9 9 9 9 9 9 9 9 · 9 9 9 9) 9 9 9 9 Valve mechanism according to claim 7, characterized in that it operates both the intake valves (5) and the exhaust valves (6). Valve mechanism according to claim 7, characterized in that it only operates the intake valves (5) and that the common camshaft (3) with both intake and exhaust cams or a separate camshaft with exhaust cams is provided with a device for pivoting them relative to the crankshaft.