Patent Application
20130025555
This patent claims priority from German Patent Application No. DE 10 2011 079 748.3, filed Jul. 25, 2011, which application is incorporated herein by reference in its entirety.
The invention relates to a valve drive for an internal combustion engine, with a rocker arm being arranged in its cylinder head, which can be pivoted by the cam of a cam shaft and is supported at one end at the valve shaft of a charge-cycle valve while it comprises a ball scraper at its other end, which rests on the spherical end section of a support element embodied as a hydraulic valve clearance compensation element.
A valve drive with a rocker arm of the type mentioned at the outset is known from the publication DE 42 34 868 A1. Here, the hydraulic valve clearance compensation element (hydraulic element) acting as a support element is installed in the cylinder head of the internal combustion engine and connected to its lubrication and hydraulic system. During operation of the internal combustion engine oil is ejected for lubrication and cooling via an oil ejection hole formed as a bore in the ball scraper of the rocker arm. Here, supported rotational at a rocker arm, a roller is lubricated and cooled, at which the cam rolls and here causes the deflection of the rocker arm.
Air is also inserted thereto, together with the oil to supply the hydraulic element, which can evacuate via the oil ejection hole. When in a valve drive an oil ejection hole is omitted in order to save and/or reduce the oil pumping performance and the lubrication and the cooling of the roller occurs in a different manner, depending on the design of the oil supply, a problem with noise may develop under certain operating conditions, e.g., in frequent motor starts or driving operation with very low average speeds. During start-up of the motor, the amount of air pumped together with the oil into the oil circuit and thus into the oil reservoir of the hydraulic valve clearance compensation element cannot evacuate quickly enough. Here, it is suctioned via the open return valve of the compensation element into its high-pressure chamber. This way, the compensation element becomes compressible, which leads to an elevated loss in stroke of the charge-cycle valve.
The closing speed of the valve increased here causes a noise, the so-called valve ticking. The leaking gap in the valve clearance compensation element between the top of the piston and the housing and/or the contact between the spherical end section of the support element and the ball scraper of the rocker arm prevent sufficient evacuation of air from the valve drive.
The invention is based on the objective to improve the valve drive such that during the pumping of oil into the valve clearance compensation element of the support element air entrained in the air can evacuate unhindered from the valve drive so that during operation the development of the valve ticking noise is avoided.
This objective is attained according to the invention such that in the contact area a groove-shaped ventilation channel is arranged between the ball scraper of the rocker arm and the spherical end section of the support element, via which the oil reservoir of the support element is opened towards the outside. This way, air entrained in the hydraulic oil of the valve clearance compensation element flows out of the oil reservoir, thus it is prevented from reaching the high-pressure chamber. The flow occurs through the ventilation channel according to the invention along the inner surface of the ball scraper of the rocker arm and the exterior surface of the spherical end section of the support element. Thus, the valve drive according to the invention can waive an additional opening of the ball scraper to evacuate air, as provided in the above-mentioned valve drive as an oil ejection hole.
The groove-shaped ventilation channel may be arranged in the ball scraper of the rocker arm or in the spherical end section of the support element. It is also possible to provide several ventilation channels in the contact area between the ball scraper and the end section, instead of only one ventilation channel.
In the following, exemplary embodiments of the invention are shown in the drawing and shall be described in greater detail in reference to a valve drive according to prior art. It shows:
The valve drive 1 of a piston-internal combustion engine of prior art according to
The rocker arm 4 may be produced as a formed sheet metal part, with it essentially showing a U-shaped cross-section. At its end 12, facing away from the ball scraper 11, the rocker arm 4 engages a valve shaft 13 of the charge-cycle valve 7. The charge-cycle valve comprises a valve plate 14 and is pre-stressed in the closed position by a valve spring 15, which is fixed in the axial direction by a spring plate 16 to the valve shaft 13. The roller 5 is guided via bolts 17 in the lateral walls 18, 19 of the rocker arm 4.
A needle bearing 20 serves for the rotary support of the roller 5 at the bolt 17, fastened in the lateral walls. During the rotation of the cam 3 the roller 5 rolls at the circumference of the cam.
A blind bore 21 is provided inside the ball scraper 11, with a dome 22 projecting beyond the exterior of the ball scraper. This dome is open towards the outside by a bore 23. By this bore acting as an oil ejection hole a fine beam of lubricant is applied at a tangential projection in reference to the roller 5 onto its running surface 24. A portion of the lubricant applied to the running surface reaches the faces of the roller 5 and therefrom into the needle bearing 20.
The support element 6 is shown in
Oil can enter the oil reservoir 34 as a pressure means from the pressure means bore 9, shown in
The valve drive 39 according to the invention comprises components shown in
The design of the support elements 42 and 43 is equivalent to that of the valve drives of prior art. They are embodied as valve clearance compensation elements, each comprising a housing 51 and a unit longitudinally displaceable therein. This unit forms an oil reservoir 54 together with a piston top 52 and a piston bottom 53. A ball valve 55 arranged at the lower end of the piston bottom 53 separates the oil reservoir 54 from the high-pressure chamber 56 of the valve clearance compensation element located underneath it, here forming the support element 42 and/or 43.
According to the invention, groove-shaped ventilation channels are arranged in the spherical end sections of the support elements, through which air can evacuate from the oil reservoir 54 of the support element. Here, at the support element 42 at the exterior surface of the spherical end section 44 two ventilation channels 57 are arranged extending in the radial direction, which start at a central lubrication channel 58 of the support element, while at the support element 43 at the exterior surface of the spherical end section 45 two ventilation channels 59 are arranged, starting at the respective lubrication channel 58, which extend in a helical (screw-like) direction.
Thus, based on the invention, air entrained in the lubrication and hydraulic oil can be guided out of the oil reservoir 54 of the respective support element 42 and/or 43 via its lubrication channel 58 and an adjacent blind bore 60 of the rocker lever-ball scraper 46, flowing into the ventilation channels 57 and/or 59, and guided thereby out of the valve drive.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102011079748.3 | Jul 2011 | DE | national |
