A reciprocating piston internal combustion engine working with the four stroke method and comprising a crankcase and at least one cylinder arranged in said crankcase, in which cylinder a piston is guided by a crankshaft, said engine further comprising at least one cylinder head closing said cylinder, inlet and outlet channels of said cylinder head being controlled in each case by at least one inlet and outlet valve loaded by a valve spring, said inlet and outlet valves being actuated by transmission elements driven by a camshaft, said engine further comprising a hydraulic valve lash adjusting element which is installed in at least one of said transmission elements or in a component which is installed in the transmission element between the camshaft and at least one inlet and/or outlet valve, said engine further comprising a hydraulic valve lash adjusting element comprising a working piston, a cylinder housing interacting with said working piston, a resetting spring arranged in between, and a non-return valve which delimits a high pressure chamber, and a valve closing body of said non-return valve corresponding to a valve seat on said working piston.
Reciprocating piston internal combustion engines with hydraulic valve lash adjusting elements of the generic type are well known. A problem of such engines is that, depending on the speed of rotation of the reciprocating piston, internal combustion engine and the lift height of the cams, the high pressure chamber of the valve lash adjusting elements is not capable of being sufficiently filled, so that a sinking of the hydraulic valve lash adjusting element can occur and this leads to enhanced or impermissibly large lash in the valve train. On the other hand, it is also possible that the hydraulic valve lash adjusting element gets excessively pumped up, so that valve lash falls short of the permissible value.
It is known, see DE 10 2007 014 248 A1, to provide stop and clamping devices on the hydraulic valve lash adjusting element that are externally activated and prevent both a pumping-up as also a sinking of the hydraulic valve lash adjusting element. Stop and clamping devices of this type are structurally very complex and cost intensive.
The problems are of particular importance when, in addition to the hydraulic valve lash adjusting elements, brake control devices or exhaust gas return devices are also used on the reciprocating piston internal combustion engine with provision of additional cam lobes in the region of the base circle of the cams.
It is therefore an object of the invention to eliminate the drawbacks of the aforesaid measures on hydraulic valve lash adjusting elements particularly with the aim that, both during normal operation, particularly in the case of large engines for utility vehicles, as also during operations with additional opening of the gas exchange valves for decompression or exhaust gas return purposes, no sinking of the hydraulic valve lash adjusting elements occurs. This should be achieved using simple means.
The invention achieves the above object by the fact that the valve closing body comprises a partial spherical surface in the region of the valve seat and that the ratio of the diameter of the working piston (8) to twice the radius of the partial spherical surface (13) is ≦2.
In this way, it is achieved that the valve seat, or the valve closing body, possesses a large opening in the region of the valve seat without the overall dimensions of the valve closing body being disproportionately large. This enables an adequate and rapid filling of the high pressure chamber, so that a sinking of the hydraulic valve lash adjusting element is prevented and this, even when additional lobes on the cam shorten the filling time considerably.
Adjoining the partial spherical surface, the valve closing body comprises a cylindrical peripheral surface starting from the edge of the spherical surface. Through this measure, the valve closing body has a light weight which, in contrast to usual valve closing bodies configured as balls, manifests a considerably smaller mass although the valve seat has a large diameter.
According to a further development of the invention, the valve closing body comprises following the cylindrical peripheral surface, a peg and this peg is surrounded by a valve closing spring that is further supported in an opening of a valve cap. In this way, an additional guidance is created for the valve closing body.
As proposed by the invention, a bore, preferably a stepped bore is arranged adjoining the opening in the valve cap, so that the high pressure chamber can get filled even along the valve closing spring, the peg and the stepped bore.
According to a further proposition of the invention, a pocket hole is arranged in the region of the partial spherical surface on the end of the valve closing body turned away from the peg. This pocket bore is a further contribution to a reduction of the mass of the valve closing body and an enlargement of the oil reservoir. The pocket hole also serves as a collecting pocket for contaminants in the oil.
In a further development of the invention, the radius of the closing spherical surface is larger than or equal to 2.5 mm.
In this case, the valve seat diameter is larger than or equal to 5.0 mm, and the diameter of the valve closing body is larger than or equal to 7.5 mm. This assures a complete filling of the high pressure chamber even in the presence of intermediate lobes in the region of the base circle of the cams.
This is based on the fact that the diameter of the working piston and that of the opening cross-section of the non-return valve are of special importance for the mode of functioning of the hydraulic valve lash adjusting element.
The valve cap is advantageously configured with a stepped inner diameter, and the large diameter surrounds the outer peripheral surface of the valve closing body, while the smaller diameter surrounds the valve closing spring.
Beads and openings are arranged on the valve cap in the region of the large diameter and extend from the high pressure chamber to the valve seat in order to assure an adequate and rapid filling of the high pressure chamber.
For a further elucidation of the invention reference will be made to the appended drawings in which one example of embodiment is shown in simplified illustrations.
As far as specifically illustrated in
On the free end of the rocker arm 1 is installed a hydraulic valve lash adjusting element generally identified at 5 that is supplied through a channel with oil from the reciprocating piston internal combustion engine and/or another oil supply unit.
The hydraulic valve lash adjusting element 5 comprises a cylindrical housing 7 that is guided for sliding in the rocker arm 1. Within the cylindrical housing 7 is installed a working piston 8 whose outward movement in the cylindrical housing 7 is limited by a spring ring. The working piston 8 is supported, as shown in
On the end of the valve closing body 12 turned away from the peg 15 is configured a pocket hole 22 through which the mass of the valve closing body is reduced, the reservoir 10 at the same time enlarged and a collecting pocket formed in which contaminants of the oil can get deposited.
Finally, it may be pointed out once again that, normally, the ratio of the diameter of the working piston to the diameter of the valve closing body, which is normally configured as a ball, is situated above a value of 3. In the present case, the ratio for a constant diameter of the working piston and a radius of the partial spherical surface of r=4 is ≦2.
Number | Date | Country | Kind |
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102010018208.7 | Apr 2010 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2011/055753 | 4/13/2011 | WO | 00 | 9/11/2012 |