EP0285877A1 - Valve control device - Google Patents

Abstract

In a valve control device of an exhaust valve (2) of an internal combustion engine of a motor vehicle with an exhaust flap brake, a throttle valve (4) in the exhaust is closed during braking operation. Valve clearance compensation should take place while driving, but not when braking. A hydraulic valve lash adjuster (11) is provided for this purpose, in which an adjusting piston (15) loaded with a return spring (19) is guided in a cylinder body (14). A control element (21) holds the readjusting piston (15) in relation to the cylinder body (14) in the readjustment position reached at the start of the braking operation in braking operation.

Description

The invention relates to a valve control device for an exhaust valve controlled by a camshaft of a cylinder of an internal combustion engine of a motor vehicle with an exhaust flap brake, an actuator closing a throttle valve in the exhaust of the cylinder to initiate the braking operation.

In known motor vehicle internal combustion engines with an exhaust flap brake (engine brake), the valve control device of the exhaust valves has no automatic valve play adjustment.

Hydraulic valve lash adjusters are known. In these, an adjusting piston loaded with a return spring is guided in a cylinder body. The valve clearance compensation element is arranged between the camshaft and a valve of an internal combustion engine.

Known valve lash adjusters cannot be used in internal combustion engines with an exhaust flap brake, because the exhaust valve flutters during braking. An adjustment would take place in the case of an automatic valve play compensation element.

However, this would have the consequence that the exhaust valve would no longer close completely during the subsequent driving operation. This would damage the exhaust valve

The object of the invention is to propose a valve control device of the type mentioned, by means of which an automatic valve lash adjustment is achieved in an internal combustion engine with an exhaust flap brake, without valve lash compensation taking place during braking operation.

According to the invention, the above object is achieved in a valve control device of the type mentioned at the outset in that a hydraulic valve clearance compensation element is arranged between the camshaft and the exhaust valve, in which an adjusting piston loaded with a return spring is guided in a cylinder body, and in that a control element is provided which is in the Braking operation holds the adjusting piston in relation to the cylinder body in the adjustment position reached at the beginning of braking operation.

It is thereby achieved that, while the valve lash adjuster is being adjusted according to the particular circumstances during driving, the valve lash adjuster is ineffective during braking operation.

In one embodiment of the invention, the control element acts in braking operation on the valve lash adjuster element with a force which is greater than or at least equal to the force of the return spring of the valve lash adjuster element and which is directed in the opposite direction. In braking operation, there is no change in the readjustment position of the readjusting piston.

If a push rod and a rocker arm are arranged between the valve clearance compensation element, then the control element preferably acts on the rocker arm or the push rod or the adjusting piston itself.

In another embodiment of the invention, the control element blocks the adjusting piston in relation to the cylinder body during braking operation. The control element is then preferably integrated in the valve clearance compensation element.

• Figur 1 eine Ventilsteuereinrichtung bei einem Verbrennungsmotor mit Auspuffklappenbremse, schematisch, wobei das Steuerelement einen Kipphebel beaufschlagt,
• Figur 2 eine Teilansicht eines weiteren Ausführungsbeispiels nach Figur 1,
• Figur 3 eine Teilansicht eines weiteren Ausführungsbeispiels nach Figur 1,
• Figur 4 eine Teilansicht eines weiteren Ausführungsbeispiels nach Figur 1,
• Figur 5 eine Teilansicht eines Ausführungsbeispiels, bei dem das Steuerelement an einer Stößelstange angreift,
• Figur 6 ein Ventilspielausgleichselement im Schnitt, in dem das Steuerelement integriert ist,
• Figur 7 ein weiteres Ausführungsbeispiel nach Figur 6 und
• Figur 8 ein weiteres Ausführungsbeispiel nach Figur 6.

Further advantageous embodiments of the invention result from the subclaims and the following description of exemplary embodiments. The drawing shows:

• FIG. 1 shows a valve control device in an internal combustion engine with an exhaust flap brake, schematically, the control element acting on a rocker arm,
• FIG. 2 shows a partial view of a further exemplary embodiment according to FIG. 1,
• FIG. 3 shows a partial view of a further exemplary embodiment according to FIG. 1,
• FIG. 4 shows a partial view of a further exemplary embodiment according to FIG. 1,
• FIG. 5 shows a partial view of an exemplary embodiment in which the control element acts on a push rod,
• FIG. 6 shows a valve clearance compensation element in section, in which the control element is integrated,
• Figure 7 shows another embodiment of Figure 6 and
• 8 shows a further exemplary embodiment according to FIG. 6.

An internal combustion engine has a cylinder (1) with an exhaust valve (2). A throttle valve (4) is arranged in an exhaust pipe (3). This can be operated by means of a pneumatic working cylinder (5). A compressed air reservoir (7) is connected to the working cylinder (5) via an engine brake valve (6).

A rocker arm (8) is associated with the outlet valve (2), with which a push rod (9) is coupled. A hydraulic valve lash compensation element (11) is displaceably mounted in the engine block (12) between the end of the push rod (9) facing away from the rocker arm (8) and a camshaft (10). This is connected to the engine's pressure oil via a bore (13).

The valve clearance compensation element (11) has a cylinder body (14) in which an adjusting piston (15) is guided. An oil pressure chamber (16) is formed in the adjusting piston (15) and is connected to the bore (13) and thus the oil pressure of the engine via channels (17). A check valve (18) and a return spring (19) are arranged between the adjusting piston (15) and the cylinder body (14) (cf. FIGS. 6 to 8). Such valve clearance compensation elements (11) are commercially available components.

The cylinder body (14) abuts the camshaft (10). The push rod (9) is fixed on the adjusting piston (15).

A control element (21) is provided on a cylinder head (20), under which the rocker arm (8) is arranged. The control element (21) according to FIG. 1 has a control piston (22) which is guided in a pressure chamber (23). The pressure chamber (23) is also connected to the engine brake valve (6). Between the Control piston (22) and the rocker arm (8), a compression spring (24) is arranged.

The operation of the described control device according to FIG. 1 is approximately as follows:

In Figure 1, the engine braking operation is shown. The engine brake valve (6) is actuated so that the throttle valve (4) actuated by means of the working cylinder (5) keeps the exhaust pipe (3) closed and the control piston (22) presses the compression spring (24) on the rocker arm (8) against the direction of force Return spring (19) presses.

The exhaust valve (2) flutters during braking. The rocker arm (8) does not follow this fluttering movement. It is actuated by the camshaft (10) via the valve lash adjuster (11) and the push rod (9). The force exerted on the rocker arm (8) via the compression spring (24) and the control piston (22) is so great that the return spring (19) cannot relax. This ensures that the readjustment position of the readjusting piston (15) with respect to the cylinder body (14) does not change compared to the state which was reached before the braking operation was switched on.

If the engine brake valve (6) is switched off, the throttle valve (4) opens. In addition, the control piston (2) is relieved and pushed back in the pressure chamber (23). The rocker arm (8) rests on the exhaust valve (2). The exhaust valve (2) is now controlled by the camshaft (10) via the valve lash adjuster (11), the push rod (9) and the rocker arm (8). The force of the compression spring (24) alone is less than the force of the return spring (19), so that the valve clearance compensation element (11) now works in the known manner when driving.

In the embodiment of Figure 1 is one of them assumed that the compression spring (24) is present on the rocker arm (8) even when driving. In contrast, in the exemplary embodiment according to FIG. 2, the compression spring (24) is designed such that it is applied to the rocker arm (8) only in braking operation, but not in driving operation. In Figure 2, the driving operation is shown. The compression spring (24) is lifted off the rocker arm (8) at least in the base circle phase. This simplifies the selection and dimensioning of the compression spring (24).

In the exemplary embodiment according to FIG. 3, an actuating arm (25) with a stop surface (26) is provided on the rocker arm (8). The stop surface (26) faces the control piston (22) of the control element (21). This is pressed into its rest position of the driving operation by a return spring (27), which is shown in FIG. 3. No spring is provided between the control piston (22) and the stop surface (26). In the case of braking operation, the pressure chamber (23) is acted upon pneumatically so that the control piston (22) hits the stop surface (26) and thus pressurizes the valve clearance compensation element (11) via the push rod (9) in such a way that the adjusting piston (15) compared to the cylinder body (14) under the action of the return spring (19) is unable to readjust. The pneumatic connection of the pressure chamber (23) acts here as a gas pressure spring, which allows the rocker arm (8) to move due to the camshaft (10) during braking.

In the exemplary embodiments according to FIGS. 1 to 3, the control element (21) acts directly on the rocker arm (8). In the exemplary embodiment according to FIG. 4, an angle lever (28) is provided between the control element (21) and the rocker arm (8) as an intermediate element, one arm (29) of which rests on the rocker arm (8) and the other arm (30) of the control element ( 21) is applied. In Figure 4, the control element (21) is pneumatic or hydraulic actuatable membrane arrangement (31) indicated. The arm (29) can also abut the rocker arm (8) with a roller with a sliding or roller bearing.

In the exemplary embodiment according to FIG. 5, a collar (32) is formed on the push rod (9). The upper end of the push rod (9) is held on a head (33) of the rocker arm (8). A pivotable fork (34), on which the control element (21) engages, rests on the collar (32) as an intermediate member. 5 shows an electromagnet (35) as the control element (21). The electromagnet (35) is dimensioned such that the force exerted by it in braking operation holds the readjusting position of the adjusting piston (15) achieved at the beginning of the braking operation with respect to the cylinder body (14).

The fork (34) can also be arranged so that it rests directly on the adjusting piston (15).

The arrangement of the control elements (21) and also that of the intermediate elements (28, 34) is designed according to the spatial conditions. Depending on the drive system provided for controlling the throttle valve (4), a pneumatically, hydraulically or electromagnetically operating control element (21) is used for the control system. If a purely mechanical drive of the throttle valve (4) is provided, a mechanical control element (21) is used accordingly.

In the embodiments according to FIGS. 6, 7 and 8, the control element (21) is integrated in the valve clearance compensation element (11).

The control element (21) does not act on the rocker arm (8) or the push rod (6) here, but acts directly between the adjusting piston (15) and the cylinder body (14).

In the exemplary embodiment according to FIG. 6, a raster pin (37) is slidably mounted in a transverse bore (36) of the adjusting piston (15). This has a tooth tip (38) at one end. On the inside of the cylinder body (14), a toothing (39) is provided, the length (L) of which is at least equal to the possible adjustment stroke of the adjustment piston (15) in the cylinder body (14). The transverse bore (36) is open via a ring channel (40) of the adjusting piston (15) and a bore (41) in the cylinder body (14) to a control oil line (42). The locking pin (37) is loaded by means of a compression spring (43) in the direction of a stop ring (44).

The control works as follows:

The control oil line (42) is depressurized when driving. Accordingly, the compression spring (43) presses the raster pin (37) against the stop ring (44), its tooth tip (38) not engaging in the toothing (39). If the engine brake valve (6) is actuated, the control oil line (42) is under pressure. The raster pin (37) is pressed against the force of the compression spring (43) with its tooth tip (38) into the toothing (39) so that the adjusting piston (15) can no longer move relative to the cylinder body (14). An adjustment position of the adjusting piston (15) reached before the braking operation is thus fixed in the cylinder body (14) as long as the braking operation continues. Depending on the readjustment position reached before braking operation, the tooth tip (38) engages in the toothing (39).

If the brake system is constructed in such a way that the oil pressure is eliminated in braking operation, the control element (21) according to FIG. 6 can be designed such that the tooth tip (38) of the locking bolt (37) in braking operation by means of the compression spring (43) into the toothing ( 39) pressed becomes. When driving, the raster pin (37) is then pushed out of the toothing (39) by the oil pressure.

In the exemplary embodiment according to FIG. 7, in comparison to the exemplary embodiment according to FIG. 6, no control oil line (42) is provided. In the adjusting piston (15) there is a blind bore (45) which is open towards the oil pressure chamber (16) and intersects the transverse bore (36). The raster pin (37) has an actuating surface (46) facing the blind bore (45). The compression spring (43) presses the tooth tip (38) of the locking pin (37) in the direction of the toothing (39).

As long as the oil pressure chamber (16) and thus the blind bore (45) are under pressure while driving, the raster pin (37) is held against its force against the force of the compression spring (43) via its actuating surface (46) so that its tooth tip (38) does not engage in the toothing (39). In braking mode, the oil pressure in the oil pressure chamber (16) is switched off. The compression spring (43) then presses the tooth tip (38) into the toothing (39), so that the adjusting piston (15) is blocked with respect to the cylinder body (14).

Even when the engine is switched off, the pressure in the oil pressure chamber (16) drops, so that the adjusting piston (15) is then also blocked with respect to the cylinder body (14). When the engine is switched off, the adjusting piston (15) cannot move in either direction. This reduces rattling noises when the engine is subsequently cold started.

In the embodiment according to FIG. 8, a clamping cam (48) is tiltably mounted on the adjusting piston (15) on a transverse axis (47). The clamping cam (48) is open with a side surface (49) to the oil pressure chamber (16). A compression spring (50) is in the clamping cam (48) arranged, which is supported against a side (49) opposite surface (51) of the adjusting piston (15). An end face (52) of the clamping cam (48) is part-circular and faces an inner surface (53) of the cylinder body (14).

When the engine is running, the oil pressure chamber (16) is under pressure. The side surface (49) of the clamping cam (48) is pressurized and the clamping cam (48) is held against the force of the compression spring (50) in the position shown in FIG. 8, in which the end surface (52) does not hold the inner surface (53) touched. The adjusting piston (15) is thus adjustable relative to the cylinder body (14).

In braking mode, the oil pressure in the oil pressure chamber (16) is switched off. The compression spring (50) then pivots the clamping cam (48) so that its end face (52) meets the inner surface (53). As a result, the adjusting piston (15) is blocked in its respective position with respect to the cylinder body (14) by self-locking. Only when pressure builds up again in the oil pressure chamber (16) is the adjusting piston (15) released relative to the cylinder body (14). The same applies in the event that the engine is switched off. Here too, as in the exemplary embodiment according to FIG. 7, rattling of the device on cold start is reduced. Compared to the control element (21) of FIGS. 6 and 7, the control element (21) of FIG. 8 works continuously.

If the direct pressurization of the side surface (49) is insufficient, an additional piston can be stored in the adjusting piston (15), which is pressurized by the oil pressure chamber (16) and acts on the side surface (49).

Claims (11)

1.Valve control device for an exhaust valve controlled by a camshaft of a cylinder of an internal combustion engine of a motor vehicle with an exhaust flap brake, an actuator closing a throttle valve in the exhaust of the cylinder to initiate braking operation, characterized in that between the camshaft (10) and the exhaust valve (2 ) a hydraulic valve lash adjuster (11) is arranged, in which an adjusting piston (15) loaded with a return spring (19) is guided in a cylinder body (14) and that a control element (21) is provided which, in braking operation, adjusts the adjusting piston (15) with respect to the cylinder body (14) in the adjustment position reached at the start of braking operation. 2. Valve control device according to claim 1, characterized in that the control element (21) in braking operation acts on the valve lash adjuster (11) with a force which is greater than or at least equal to the force of the return spring (19) of the valve lash adjuster (11) and which counteracts this is. 3. Valve control device according to claim 2, characterized in that the force acting on the valve clearance compensation element (11) is composed of a spring force (24) and a force activated in braking operation, the spring force being less than the force of the return spring (19) of the Valve clearance compensation elements (11). 4. Valve control device according to claim 2, characterized in that the spring force of the control element (21) is formed by a pneumatic chamber acting as a gas pressure spring. 5. Valve control device according to one of the preceding claims, characterized in that the control element (21) between an engine block fixed part (20) and a control part (rocker arm (8), push rod (9), adjusting piston (15)) of the control device is effective. 6. Valve control device according to claim 5, characterized in that the control element (21) is kept spaced from the control part during driving. 7. Valve control device according to one of the preceding claims, characterized in that an intermediate member (28, 34) is arranged between the control valve (21) and the control part (rocker arm (8), push rod (9), adjusting piston (15)). 8. Valve control device according to claim 1, characterized in that the control element (21) blocks the adjusting piston (15) of the valve lash adjuster element (11) against its cylinder body (14) in braking operation. 9. Valve control device according to claim 8, characterized in that the control element (21) has a locking pin (37) which can be displaced in the adjusting piston (15) and engages in a positive manner in a toothing (39) of the cylinder body (14) during braking operation. 10. Valve control device according to claim 8, characterized in that the control element (21) one in Adjustment piston (15) has pivotally mounted clamping cams (48), which rests against the cylinder body (14) during self-locking braking operation. 11. Valve control device according to one of the preceding claims 8 to 10, characterized in that the control element (21) is held in its non-blocking position by the oil pressure of the valve clearance compensation element (11) during driving operation and in braking operation by means of a spring (43, 50) its blocking position is brought.

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