The invention concerns a valve train of an internal combustion engine comprising a tappet and a tappet pushrod that is actuated by said tappet, said tappet pushrod being at least partly hollow and comprising on one end, a first support for an at least indirectly contacting pressure piston of a hydraulic lash adjuster of said tappet that follows a periodic driving element, typically a cam, a second support for a follower member, typically a rocker arm, being arranged on a further end of the tappet pushrod, said first support comprising a passage for hydraulic medium that can be routed out of the pressure piston during operation of the internal combustion engine into an interior of the tappet pushrod.
A valve train of the pre-cited type is disclosed in U.S. Pat. No. 6,196,175 B1. The tappet of this valve train is configured as a switchable roller tappet and is installed in a relatively strongly restricted mounting space, so that only an inadequate quantity of hydraulic medium can be contained in its pressure piston. However, in various situations such as upon re-firing of the internal combustion engine after a longer standstill, “taxi operation” etc., this hydraulic medium proves to be insufficient for a proper lash adjusting operation of the lash adjuster. Therefore, a relatively high risk of a re-aspiration of air into the high pressure chamber of the lash adjuster exists with all the drawbacks, like rattling noises, wear etc., known in the technical field.
Moreover, it is usual in OHV trains comprising a roller tappet and a tappet pushrod to lubricate further components like rocker arms, cam-contacting surfaces etc. that are situated at a high geodetic level, through a hollow tappet pushrod. This is also disclosed in the pre-cited U.S. Pat. No. 6,196,175, while U.S. Pat. No. 3,908,615 likewise discloses a hollow tappet pushrod. Further, U.S. Pat. No. 5,351,662 shows a tappet configured as a roller tappet in which it can be seen that, for design reasons, the hydraulic lash adjuster can contain only a very small quantity of hydraulic medium.
It is an object of the invention to provide a valve train of the pre-cited type in which the aforesaid drawbacks are eliminated.
This and other objects and advantages of the invention will become obvious from the following detailed description.
The invention achieves the above objects by the fact that a one-way valve means is installed in the tappet pushrod for retaining, during a standstill of the internal combustion engine, a hydraulic medium column which, as viewed in gravity direction, is situated above the one-way valve means.
In this way, an additional volume of hydraulic medium is created. For this purpose, the invention has recourse to normally already used hollow tappet pushrods, and through the one-way valve means proposed by the invention, a larger part of the hydraulic medium transported through the tappet pushrod during operation is retained, so that, upon starting of the internal combustion engine, this quantity of hydraulic medium is available as an “additional oil supply” for the reservoir of the hydraulic lash adjuster.
The one-way valve bodies may be configured, for example, as balls, cones, plates or the like. These are held in a suspended state in the interior of the tappet pushrod during the passage of the hydraulic medium through the tappet pushrod during operation of the internal combustion engine. When the internal combustion engine is turned off and the pressure medium pressure thus decreases, the one-way valve means drops back into its seat due to the force of gravity and prevents a further re-flow of the hydraulic medium column situated above it.
Advantageously, the one-way valve means is configured together with an inner wall of the tappet pushrod as a choke for the hydraulic medium, so that, during the operation of the internal combustion engine, no unnecessarily high losses of hydraulic medium in the direction of the second support have to be feared. It is understood that the passages themselves may likewise comprise choking features.
The release of the hydraulic medium stored above the one-way valve means is caused by the vibrations occurring immediately after the internal combustion engine is started, for example, due to the reciprocating motion of the tappet pushrod.
The proposed floating body (ball, tapered cylinder etc.) that forms a part of the one-way valve means may be made of metal but likewise of a light-weight material like plastic, as a solid or a hollow construction. If the floating body is a ball, it extends with play relative to an inner wall of the tappet pushrod, so that, on the one hand, it cannot get clamped and, on the other hand, the desired choking effect can be achieved.
If a tapered body is used, that according to a further proposition of the invention may also be tapered at both ends, this body advantageously comprises longitudinal grooves on its outer peripheral surface for permitting a through-flow of the hydraulic medium.
According to still another proposition of the invention, the tappet pushrod is configured with quasi identical components (supports, passages, valve seats) on both sides of its central transverse plane. The floating body in this case can be a ball or a cylinder tapered at both ends. In this embodiment, the tappet pushrod can also be installed laterally reversed in the valve train which is advantageous for mounting purposes.
It is understood and proposed by the invention that the separate cylindrical part may also be arranged only in the region of the first support.
The proposed separately manufactured tappet pushrod has the advantage that it can be easily mounted in different kinds of internal combustion engines without complex modifications to any other parts.
Finally, the invention also proposes to configure the supports of the tappet pushrod in the form of ball heads. It is clear that other joint configurations, like, for example, pot or cylindrically arched shapes etc. can also be used for this purpose.
Although the scope of the invention is related particularly to OHV trains, this is not exclusive.
The invention will now be described more closely with reference to the appended drawing.
In the present case, the tappet pushrod 1 has a tubular configuration, and hydraulic medium from the pressure piston 5 can be routed through its interior 11 toward a follower member 2, configured here as a rocker arm. The follower member 2, in its turn, acts in lift direction on a gas exchange valve 32.
It can be further seen in
As described above, the quantity of hydraulic medium that can be contained or is contained in the pressure piston 5 is too small for some special cases of use. This is where the invention becomes effective. It is proposed, namely, to install a one-way valve means 12 in the tappet pushrod 1 to retain a hydraulic medium column, shown schematically in
As disclosed in
The tappet pushrod 1 of
According to
Looking at the lower part of
The ball 17 is designed such that it remains in a suspended state in the interior 11 of the tappet pushrod 1 when hydraulic medium pressure prevails. When the pressure drops after the internal combustion engine is turned off, the ball 17 sinks into its valve seat 19. This prevents the hydraulic medium that is situated thereabove from flowing-through in gravity direction. In this way, an additional hydraulic medium reservoir is created in the tappet pushrod 1. Due to the vibrations that occur upon a re-firing of the internal combustion engine, the ball 17 lifts off its seat 19. The quantity of hydraulic medium thus released flows into the reservoir of the pressure piston 5 and is additionally available for lash adjustment.
Because, as can be seen in
The floating body 16 of
The application claims the benefit of provisional patent application Ser. No. 60/637,274 filed Dec. 17, 2004.
Number | Name | Date | Kind |
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3144010 | Van Slooten | Aug 1964 | A |
4602597 | Rhoads | Jul 1986 | A |
7077090 | Sailer et al. | Jul 2006 | B2 |
7174870 | Rutsey | Feb 2007 | B2 |
Number | Date | Country |
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19 83 334 | Apr 1968 | DE |
19 92 038 | Aug 1968 | DE |
33 43 324 | Jun 1984 | DE |
10 2004 019 282 | Dec 2005 | DE |
Number | Date | Country | |
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20060169236 A1 | Aug 2006 | US |
Number | Date | Country | |
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60637274 | Dec 2004 | US |