Hydraulic valve clearance compensation element of an internal combustion engine

Abstract

Valve clearance compensation element of an internal combustion engine, with a piston (20) and a pressure chamber (36) and reservoir (34) for a hydraulic medium assigned to the piston (20), as well as a compression spring (50) arranged in the pressure chamber (36), wherein a one-way valve (38) is arranged in a connection (32) between the pressure chamber (36) and the reservoir (34), wherein means (46) are provided for supplying a medium which, if required, inhibits an adjustment movement of the piston (20), wherein the medium is a hydraulic medium which acts on the piston (20) at a corresponding point and a hydraulic blocking chamber (48) is provided for blocking a piston movement, which is in operative connection with the piston (20), wherein the blocking chamber (48) can be supplied with the hydraulic medium and can prevent a movement of the piston (20) and the blocking chamber (48) is connected to a controllable hydraulic line (46), characterized in that if necessary, a pressure can be set in the blocking chamber (48) which counteracts an actuating force of the compression spring (50) and thus prevents a movement of the piston (15) towards the valve (16).

Description

[0001] The invention relates to a hydraulic valve clearance compensation element of an internal combustion engine according to the preamble of claim 1.

[0002] It is known to provide valve lash adjusters in internal combustion engines to compensate for the play between a valve and a valve actuating device that applies a lifting and / or lowering movement to the valve. However, under certain operating conditions, readjusting the valve lash adjuster may be undesirable, for example during engine braking. The exhaust gases accumulating in the exhaust line upstream of the closed exhaust flap generate a counterforce on the valve springs via the exhaust valves, which counterforce can become so great that it can briefly cause the exhaust valves to open dynamically. This relieves the load on the adjuster within the valve train, causing it to adjust, with the disadvantage that the exhaust valves no longer close under load.

[0003] DE 101 29 729 A1 describes a hydraulic valve lash adjuster that can deactivate the adjustment function of the valve lash adjuster. In addition to a one-way valve, a shut-off valve is provided between a pressure chamber and a reservoir of the valve lash adjuster. This shut-off valve can separate the connection between the pressure chamber and the reservoir independently of the one-way valve. The piston moves inside a pot-shaped cylinder that is stationary relative to the piston. An adjusting spring is arranged between a base of the cylinder and the piston. This spring pushes the piston toward the valve as soon as there is clearance between the piston and the valve stem. The shut-off valve prevents unintentional adjustment.

[0004] DE 37 12 020 A1 discloses a hydraulic valve clearance compensation element for an internal combustion engine. This element contains a piston and a pressure chamber, with means for supplying a medium that inhibits the adjustment movement of the piston as needed.

[0005] The object of the invention is to provide a valve clearance compensation element which dispenses with such an additional shut-off valve between the pressure chamber and the storage chamber and can nevertheless prevent an adjustment function of the valve clearance compensation element if required.

[0006] The object is achieved according to the invention by the features of claim 1.

[0007] Advantageous embodiments are listed in the subclaims.

[0008] The valve clearance compensation element of an internal combustion engine according to the invention comprises a piston and a pressure chamber and reservoir for a hydraulic medium associated with the piston, as well as a compression spring arranged in the pressure chamber. A one-way valve is arranged in a connection between the pressure chamber and the reservoir, and means are provided for supplying a medium that inhibits an adjustment movement of the piston as needed. This allows clearance compensation to be specifically prevented during certain operating phases. The medium is a hydraulic medium that acts on the piston at the appropriate location.

[0009] According to the invention, a hydraulic blocking chamber is provided for blocking piston movement, which is operatively connected to the piston. The blocking chamber can be filled with a hydraulic medium and prevent any movement of the piston. The arrangement is simple to implement; no second shut-off valve is required in the piston.

[0010] Advantageously, the blocking chamber can be arranged at least partially on an outer side of the piston. This design is particularly inexpensive.

[0011] According to the invention, the blocking chamber is connected to a controllable hydraulic line as an additional means for supplying the medium. If necessary, a pressure can be set in the blocking chamber that counteracts the actuating force of the compression spring and thus prevents movement of the piston toward the valve. A clearance between the piston and the valve can be specifically maintained. This reliably prevents unwanted readjustment of the valve clearance compensation element. For this purpose, a pressure in the blocking chamber is preferably set at least equal to or greater than the actuating force of the compression spring.

[0012] According to a preferred embodiment, the piston is surrounded by the blocking chamber around its circumference. According to a further embodiment, the blocking chamber can also be arranged underneath the piston so that movement of the piston into the blocking chamber can be prevented as needed. A combination of the two embodiments is also possible, with the piston's underside partially immersed in the blocking chamber. "Underside" is to be understood as meaning that, in the event of an imaginary adjustment movement of the piston, it would move toward its underside.

[0013] The blocking chamber is expediently divided into a first and a second subchamber, with a radial extension of the piston being provided to separate the first and second subchambers. The extension can be arranged as an annular web on an outer circumference of the piston or underneath the piston. This is an easy-to-manufacture piston design.

[0014] A simple design for the valve lash adjuster is achieved when the pressure chamber and reservoir chamber are arranged in a recess within the piston. The arrangement is also compact. Conventional annular channels and / or leak lines can also be easily provided, allowing the pressure chamber to be drained in the usual way. Similar annular channels and / or leak lines can also be advantageously provided for the blocking chamber.

[0015] In a favorable further development, the storage space can be arranged in a pot-shaped inner part that is fixed with respect to the piston, wherein the one-way valve can expediently be arranged on a pot bottom of the inner part.

[0016] The compression spring can be arranged between the pot bottom and a stop in the interior of the piston.

[0017] The invention is explained in more detail below with reference to a drawing.

[0018] Showing: Fig. 1 a preferred embodiment of a valve clearance compensation element, Fig. 2 the valve clearance compensation element Fig. 1 with activated blocking space to prevent unwanted re-adjustment and Fig. 3 a further preferred embodiment of the valve clearance compensation element

[0019] In the figures, elements with the same functional effect are numbered with the same reference symbols.

[0020] A preferred embodiment of a valve clearance compensation element 10 of an internal combustion engine (not shown) according to the invention is shown in the Fig. 1 and Fig. 2, where Fig. 1 an adjustment of the valve clearance compensation element 10 is indicated and in Fig. 2 adjustment is blocked.

[0021] The valve lash adjuster 10 has a piston 20 with an outer side 54, which is associated with a valve actuating element 12, preferably a rocker arm or a bucket tappet or the like. The piston 20 is arranged within the valve actuating element 12. At its distal end 26, relative to the valve actuating element 12, the piston 20 has a pin with a spherical end 28 mounted in a matching receptacle, which is operatively connected to one end of a valve 60, more precisely its valve stem.

[0022] The piston 20 is cup-shaped, with the distal end 26 closed and the proximal end open toward the valve actuating element 12. A cup-shaped inner part 30 is arranged in its interior 24, the interior of which forms a reservoir 34. The reservoir 34 communicates with an opening 14 through which a hydraulic medium, for example, lubricating oil from the internal combustion engine, can be supplied.

[0023] Below the bottom 40 of the inner part 30, a pressure chamber 36 is arranged, in which a compression spring 50 is arranged between the bottom 40 and a stop 52 of the piston 20. Between the reservoir chamber 34 and the pressure chamber 36, a connection 32 is arranged, which can be opened or closed by means of a one-way valve 38, shown in simplified form as a ball.

[0024] If, under certain operating conditions, a gap 62 forms between the end 28 of the piston 20 and the valve 60, the compression spring 50 presses the piston 20 towards the valve 60 and reduces or closes the gap 62. The one-way valve 38 opens and hydraulic medium can flow through the connection 32 from the reservoir 34 into the pressure chamber 36. This is indicated by arrows in the Fig. 1. In the case of dynamic opening of an exhaust valve due to exhaust back pressure generated during engine braking, this can lead to an undesirably opened exhaust valve during normal operation, as described above.

[0025] The piston 20 is surrounded on its outer circumference by a blocking chamber 48, which is enclosed between a wall of the valve actuating element 12 and the outer side 54 of the piston 20. The axial height of the blocking chamber 48 is less than the axial height of the piston 20 in the valve actuating element 12. The blocking chamber 48 is divided into a lower subchamber 42 and an upper subchamber 44 by a radial extension 22 of the piston 20, designed, for example, as an annular web. The upper subchamber 44 is connected to the unpressurized oil chamber or reservoir chamber 34.

[0026] If necessary, conventional annular gaps and / or leakage lines (not shown) can be provided so that excess pressure in the pressure chamber 36 or in the blocking chamber 48 can be reduced.

[0027] A hydraulic line 46 opens into the lower subchamber 42, through which hydraulic medium can be supplied in a targeted manner, preferably in a controlled manner. This allows a counterforce to act on the piston 20, which counteracts the actuating force of the compression spring 50 and blocks the piston 20 in its axial deflection. This is Fig. 2 is indicated by arrows. Despite the gap 62, the piston 20 cannot be moved downward toward the valve 60. Undesired adjustment of the valve lash adjuster 10 is prevented, with the result that the valve 60 can now be closed during normal operation. The hydraulic line 46 thus serves as a brake pressure connection.

[0028] A further preferred embodiment of the valve clearance compensation element 10 is shown in Fig. 3. There, the blocking chamber 48 is arranged below the piston 20. In this case, a division into different subchambers can be omitted. If readjustment of the piston 20 is to be prevented, hydraulic medium is introduced into the blocking chamber 48 on the lower outer side 54 of the piston 20 via the hydraulic line 46. The piston 20 is, as in the embodiment of the Fig. 2, is subjected to a force acting against the actuating force of the compression spring 50 and held in place, so that a closing of the gap 62 can be specifically prevented.

Claims

[1] Valve clearance compensation element of an internal combustion engine, with a piston (20) and a pressure chamber (36) and storage chamber (34) for a hydraulic medium assigned to the piston (20), as well as a compression spring (50) arranged in the pressure chamber (36), wherein a one-way valve (38) is arranged in a connection (32) between the pressure chamber (36) and the storage chamber (34), wherein means (46) are provided for supplying a medium which, if required, inhibits an adjustment movement of the piston (20), wherein the medium is a hydraulic medium which acts on the piston (20) at a corresponding point and a hydraulic blocking chamber (48) is provided for blocking a piston movement, which is in operative connection with the piston (20), wherein the blocking chamber (48) can be supplied with the hydraulic medium and can prevent a movement of the piston (20) and the blocking chamber (48) is connected to a controllable hydraulic line (46), characterized by , that if necessary, a pressure can be set in the blocking chamber (48) which counteracts an actuating force of the compression spring (50) and thus prevents a movement of the piston (15) towards the valve (16). [2] Valve clearance compensation element according to claim 1, characterized by that the blocking chamber (48) is arranged at least in regions on an outer side (54) of the piston (20). [3] Valve clearance compensation element according to one of the preceding claims, characterized by that the piston (20) is circumferentially surrounded by the blocking chamber (48). [4] Valve clearance compensation element according to claim 3, characterized by that the piston has a radial extension (22) which separates the blocking chamber (48) into a first and second partial chamber (42, 44). [5] Valve clearance compensation element according to one of the preceding claims, characterized by that the blocking chamber (48) is arranged below the piston crown (52). [6] Valve clearance compensation element according to one of the preceding claims, characterized by that the pressure chamber (36) and the storage chamber (34) are arranged in a recess (24) within the piston (20). [7] Valve clearance compensation element according to claim 6, characterized by that the storage space (34) is arranged in a pot-shaped inner part (30) which is fixed with respect to the piston (20). [8] Valve clearance compensation element according to claim 7, characterized by that the one-way valve (38) is arranged on a pot bottom (40) of the inner part (30). [9] Valve clearance compensation element according to claim 8, characterized by that the compression spring (50) is arranged between the pot bottom (40) and a stop (52) in the interior (24) of the piston (20).

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