Internal-combustion engines – Poppet valve operating mechanism – Tappet
Patent
1991-11-13
1992-07-14
Cross, E. Rollins
Internal-combustion engines
Poppet valve operating mechanism
Tappet
123 9052, 74569, F01L 124
Patent
active
051293749
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to hydraulic tappets for internal combustion engines, and more specifically to hydraulic tappets of the direct acting bucket type.
In the design of bucket tappets having an outer reservoir and an inner reservoir as exemplified by the tappets shown in U.S. Pat. No. 4,590,898 to Buente et al., it is important to prevent air bubbles present in the oil coming from the lubrication circuit from reaching the inner reservoir and finally the high pressure chamber, since this has a negative effect on the supply of oil to the inner reservoir and to the high pressure chamber and therefore on the adjustment of the play of the tappet when an internal combustion engine is restarted. There are already known hydraulic tappets substantially comprising a first outer part or body which engages the driving cam and has an outer annular reservoir where the oil collects, and a second inner part which slides telescopically inside the first one and is connected to the stem of a valve of the internal combustion engine, the inner reservoir and the high pressure chamber of variable capacity being provided by telescopic coupling of the first part inside the second one, said high pressure chamber communicating with the inner reservoir via a one way ball-valve.
As shown in U.S. Pat. No. 4,782,799 to Goppelt et al., it is known to provide within such a tappet a member which forces the oil to travel upward to the outer reservoir through a duct from an inlet port located in a low position relative to the outer reservoir, flow along a circular path through 180.degree. to a second duct which carries the oil from a low level of the outer reservoir to the inner reservoir, thus providing a circuitous oil path which aids in deaerating the oil.
The present invention is an improvement to the above design wherein the tappet includes structure which causes the oil to traverse a 360.degree. circular path and through two vertical levels in flowing from the inlet to the inner reservoir.
Initially, the oil flows along the upper level for 180.degree. and then descends to a lower level, where it flows for another 180.degree.. Hence it goes up a vertical channel to reach the inner reservoir. As air is lighter than oil, the air tends to stay in the upper part of the outer reservoir hence the oil in the lower area of the outer reservoir contains practically no air.
According to a first embodiment of the invention, there are provided two inserts forming a two-level outer reservoir and a guide for the telescopic parts of the tappet. Communication between the upper and lower levels of the inner annular reservoir is achieved via an opening provided between the two levels. The bottom of the lower level of the outer annular reservoir is formed by one of said inserts comprising a hub member including a web portion extending radially inwardly from the outer part or body of the tappet and an axially extending hub portion acting as a guide for the telescopically moving parts of the tappet.
According to another embodiment of the present invention, there is provided a single insert which forms the two-level outer reservoir, the hub member serving as a guide for the telescopic parts being provided by an axially-extending cylindrical extension of the end wall of the outer part.
The present invention will now be described in detail, with reference to the attached drawings, wherein:
FIG. 1 shows a vertical cross-section of the outer part of the tappet, according to a first form of embodiment; and
FIG. 2 shows a vertical cross-section of a second embodiment of the invention.
According to the first embodiment of the invention (see FIG. 1), the outer part 10 of the hydraulic tappet comprises a moulded or drawn cup-shaped member shaped as an upside-down bowl wherein there is inserted a first insert 12 preferably made of a plastic material and a second insert defining a hub member 14, preferably made of metal, which comprises an upper cylindrical hub portion 26 and a lower funnel-shaped web portion 28. The first insert 12, annular in shape and with a
REFERENCES:
patent: 4579094 (1986-04-01), Doppling et al.
patent: 4721076 (1988-01-01), Goppelt et al.
patent: 4745889 (1988-05-01), Speil
patent: 4782799 (1988-11-01), Goppelt et al.
patent: 4867114 (1989-09-01), Schaeffler
Cross E. Rollins
Eaton Corporation
Sajovec F. M.
Weilun Lo
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