вход по аккаунту


код для вставки
Dec. 3; 1946.
2,411,844 '
Filed Sept. 16, 1944
(7/0/06) .
Patented Dec. 3, 1946
2,411,844 ,
POPPET vanvnzliuNiiaéiimn ASSEMBLY
Walter B. Appel, Orchard Lake, Mich., assignor
to General Motors Corporation, Detroit, Mich”
a corporation of Delaware
Application September 16, 1944, Serial No. 554,355
3 Claims. (Cl. 123-188)
The use of high octane leaded fuel in internal
combustion engines has created a problem which .
this invention aim-s to solve. The problem arises
from the very considerable deposits of lead prod
ucts on and in the vicinity of the exhaust poppet
valves. These valves are opened positively by
cam action but close under the influence of
springs. The deposit frequently causes the valve
sults may be had from the use of a counter
bored guide this invention makes use of a guide
with a uniform bore through which slides a two
dimension stem. Among the reasons‘ for select
ing the second of these expedients are the fol
lowing. The length of annular chamber is con
stant when one counterbores the guide whereas
with the two dimension stem the guiding portion
of the guide increases in length as the valve
~ stems to become so stuck in the valve guides that
opens. Also there is no provision for- removing
' the springs cannot overcome the resistance and 10 ..the deposit on the inner wall of the counter
close the valves. Thereupon the combustion
chamber gases pass around the valve heads, burn
bored guide.v On the contrary, the shoulder be
tween the two parts of the two dimension stem
the heads and stems and soon the valves must
scrapes the deposit from the walls of the guide
be replaced. In the ‘case of lower octane fuels
due to the positive action of the cam. There is
similar but lessserious sticking occurs and in
another and very important reason for selecting
such cases the difficulty has been to some extent
the second of the two expedients. The hot gases
lessened'by the use of counterbored guides or
from around the valve head build up deposits
reduced valve stem diameters within the ‘ends
along the stem. . Near the head the more intense '
of the guides.
heat burns these to a kind of film but a, little way
The present invention has taken cognizance of 20 down the stem, where the heat is somewhat less,
these prior expedients adopted to overcome the
there is found a bulbous deposit of some appre- '
effects of carbon deposits from relatively low
ciable size. This bulbous deposit, if it gets within
octane fuels but it has been found that a mere
the counterbore of a guide necessitates an other-.
unscienti?cally counterbored guide or a two di
wise needlessly large counterbore to prevent
ameter stem is not enough to solve the present
sticking. With a reduced dimensioned stem hav
. ing less heat conducting metal the critically» hot
Very brie?y stated, the problem has’been solved
region is nearer the valve head and hence the
by resort to a. two dimension valve stem movable
bulbous region at the lower end of the critically
in a'valve guide having‘ a bore of uniform diam
hot region is further from the end of_ the guide.
eter, the partsbeing so dimensioned relative to 30 Since it is‘ nearer the head it is well above the‘
the position of the valve head and its seat and
end of the guide and ‘does not cause sticking be
the stroke of the cam that the shoulder between
cause of contact with the guide. A deposit does
the parts of the stem shall always be within the
collect on the end of the guide, and just within
guide and shall approach but not reach the end
the end. Therefore the shoulder which is within
of the guide as the valve opens. The best re 35 the guide should be so located that, invalve posi
sults also require that the radial dimension of
tion, it will not contact this deposit. As a mat
the annular space between the reduced dimen
'ter of fact the deposit at the guide opening is
sion part of the stem and the wall of the guide
of use in that it partly closes the annular space
shall be such as to permit the collection of a
within the guide and around the stem thus seal
moderate coating of lead deposit on the stem
ing off this space to such an extent as to prevent
but that it shall not be so large as to permit a
the lead deposits being carried into the space
turbulence of gas within the space and conse
by the turbulent gases outside. vThere are there
quently the‘ carrying of much of the lead deposit
fore many reasons for reducing the stem diam
into this chamber. The axial dimension should
eter rather than counterboring the guide. The
not be extended unduly else the stem will not be 45 experiments have shown that very good results
properly guided and the valve will not seatas it
are obtained with a valve having a 13-32 inch
stem reduced to 11-32 inch from the valve head
The structure which is believed to bethe best
for a distance of about 1% in. the shoulder being
to carry out the inventive idea is shown on the
accompanying drawing, in which:
Fig. 1 is a view in elevation of a conventional
valve assembly.
Figs. 2‘ and 3 are similar views of my new as
50 always in the guide and the movement being
such that, when the valve. is opened by the cam,
the shoulder shall be about ya in. from the end
of the guide. This will avoid the danger of the
large diameter part» sticking to the deposit just -
sembly with the valve in two different positions.
While with certain valve dimensions good re 55 within the guide opening. I1’, too; the radial
dimension of the annular'space is between 1752
and 3/;4 in., the space has been found to be su?i
cient to accommodate the slight collection. of
deposit on the stem which will occur in spite of
the nearly ‘closed annular space. As explained
above, any deposit on the inner wall of the guide
except that adjacent the opening beyond the ‘_
limit of outward movement of the shoulder on
the stem is scraped off by the shoulder.
Fig. 2 toward the open end of the guide and
scrapes on.’ any deposit which may form on the
wall of the guide. However, as shown by Fig. 3,
when the valve reaches its open position the
shoulder is still a little Way from the end vof the
guide and does not engage and stick to the
deposit I5 which forms at the end of and extends
just a little way into the guide. It will also be
It is believed that the invention will be under 10 seen that this deposit l5 partially closes the an
nular chamber at the end of the guide so that
stood from the description above. The drawing
the turbulence outside may not extend thereinto
serves to illustrate it. On the drawing, the old
and carry an undue quantity of carbon or lead
type of valve assembly is shown by Fig. 1. Here .. products
into the chamber.
the valve guide 5 has a uniform bore and the
I claim:
valve stem.'l is also of uniform diameter.
The ,
valve head 9 is showniseated. As explained
above, the tendency to collect a deposit on the
stem adjacent the end of the guide is indicated
by a bulbous formation marked I I (exaggerated).
It will be readily seen that the deposit may cause
the valve to stick at the end of the guide so that
the releasing spring may be unable to break it
away. Fig. 2 shows the same valve guide 5 but
my improved valve with its stem 1' reduced in
diameter as at [3 from the head to a point 25
marked a which is well within the guide when
the valve is seated. Also the reduced diameter
of the valve stem 1' has ‘caused the bulb II’ to
form further from the end of the guide than
before, so that it cannot cause sticking. The .30
shoulder at a moves from the position shown by
v 1. A valve and guide assembly, said valve hav
ingan integral stem with parts of two different
diameters forming a shoulder therebetween, the
parts being so, proportioned that the shoulder is
always within the guide and that the shoulder
approaches but does not reach the end of the
guide- on the valve opening movement.
2. The invention de?ned by claim 1, the dif
ference in diameter being such as to permit only
a slight deposit within the space around the stem
within theguide.
3. The invention de?ned by claim 1, the open
ing movement of the valve carrying the shoulder
to a limit at. about one-eighth of an inch from
the end of the guide.
Без категории
Размер файла
255 Кб
Пожаловаться на содержимое документа