Note: Descriptions are shown in the official language in which they were submitted.
1056241
This invention relates to internal combustion engines
` having adjustable valve gear.
Conventional engines have fixed valve timing for normal
R.P.M. and load conditions which are experienced during its
lifetime.
This fixed valve timing is optimal for a small spectrum
of normal operating conditions.
As a result when the engine is operating outside the
optimal valve timing spectrum, the engine is inefficient and
causes above average pollution. The thermal efficiency of
; the engine suffers and is diminished.
' Variable valve timing has been theoretic`ally known fora number of years. However, in order to implement such variable
valve timing the previously proposed measures have been both
complex and expensive to instal.
- Mechanisms are known where valve dwell, or period of
opening, is controlled but valve overlap still remains fixed.
Conversely when valve overlap is controlled, the actual period
the valve is open remains fixed. So far as is known the prior
mechanisms do not control both the period of valve opening and
valve overlap and also do not control the effective rate of
valve lift.
; It is an object of the present invention to provide a
mechanism in an internal combustion engine which will allow
control of both valve overlap and duration of opening and also
vary the rate of valve lift so as to improve the thermal
efficiency of the engine under a wider spectrum of operating
conditions and also to control the pollutant emission.
According to the~invention there is provided an internal
combustion engine having a valve and a mechanism for controlling
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1056241
valve operation comprising means for actuating said valve,
a non-interchangeable cam for controlling said valve actuating
means, a pair of pivotable timing lever arms with inner ends
interposed for contact engagemen-t by the cam for control of
said valve actuating means, and two separate adjustment
control means disposed for engagement with the outer end of
each said timing lever arm for adjustment of the position of
the respective arm during operation of the engine.
, Generally this invention is most easily applied to four
stroke engines, but it may also readily be used with a two
stroke poppet valve engine.
The invention will be further described, by way of
example, with reference to the accompanying drawings, in
which:
Figures 1 to 3 illustrate preferred valve gear of
engines embodying the invention.
Turning now to Figure 1, two timing levers 2 and 3 are
- situated between a cam shaft 1 and a rocker arm 4.
These levers have a pivot point 5 connecting the rocker
arm 4 and the timing levers 2 and 3.
, When a change in valve timing is required the timing
levers 2 and 3 are angularly adjusted about the pivot 5 to a
new position by movement of vertically movable control lever
setting bars 6 and 7.
When the bar 6 is raised from the idling position shown
in Figure 1 the flank of the cam 1 rotates through fewer
degrees before coming into contact with lever 2. As the flank
of the cam 1 exerts pressure upon the timing lever 2, the
timing lever itself exerts pressure in turn upon the pivot
30 point 5 and the rocker arm 4.
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1056241
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; The rocker arm 4 then starts to depress valve 8. AS a
result the valve 8 starts to open earlier in the four stroke
cycle than at idling speed. How much earlier valve 8 starts
to operate depends on how much the control lever setting bar
; 6 is lifted.
As~the lobe of cam 1 passes from timing lever 2 it begins
to bear onto timing lever 3. This lever controls the closing
of valve 8, aided by the valve spring 9.
; The point at which valve 8 actually closes depends on
; 10 the position of control lever setting bar 7.
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10 is the rocker arm pivot post. 11 and 12 are timing
lever springs which ensure that the timing levers 2 and 3
are always in contact with the timing lever setting bars 6
and 7. 13 is a rocker arm spring which biases the levers
upwardly into engagement with the cam. 14 is the cylinder
head of the internal combustion engine. As will be appreciated
adjustment of the position of the timing lever arms 2 and 3
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is provided by movement of the setting bars 6 and 7.
Regarding Figure 2. The construction is the same as
~ 20 Figure 1 except the rocker arm 4 and rocker arm pivot post
- 10 are replaced by a bucket tappet 4a.
Concerning Figure 3, this mechanism operates in a manner
similar to the mechanisms of Figures 1 and 2 except that
instead of having the pivot 5 connecting the levers 2 and 3
the levers 2 and 3 are pivoted at 5a and 5_ to the control
lever setting bars 6a and 7a.-
- Timing lever springs lla and 12a connect the control
lever setting bars 6a and 7a with the timing levers 2 and 3
respectively to urge the overlapping ends of the timing levers
2 and 3 downwardly onto bucket tappet 4a for sliding engagement
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1056;Z41
therewith. As the cam 1 rotates the lobe first comes into
contact with timing lever 2 depressing it onto the bucket
tappet 4a which then depresses valve 8. Timing levers 2 and
3 always maintain contact with bucket tappet 4a by reason of
timing lever springs lla and 12a.
As the lobe of cam 1 rides off timing lever 2 it begins
- to ride onto timing lever 3. Timing levers 2 and 3 are con-
trolled by control lever setting bars 6a and 7a which are
adjusted vertically to set the timing levers 2 and 3 for most
desirable valve timing of the engine while the engine is in
~, operation.
In a further mechanism not shown in a drawing, the variable
valve timing mechanism, as described in Figure 3, is associated
' with the rocker arm of Figure 1. Here the timing levers 2a and
3a have their overlapping ends bearing down upon the rocker arm
and the cam 1 operates as previously described.
As described in Figure 1, the timing lever arms 2 and 3
have a common pivot 5. In an alternative embodiment lever arms
2 and 3 may have separate pivots connectèd by a bridge fixed
to the rocker arm or bucket tappet. This enables the cam to
move of f timing lever arm 2 on to the bridge and then to pass
on to timing lever arm 3.
Another application of this invention is to utilize a
hydraulic system which is controlled generally as described
above except that the action of the timing levers causes
depression of a piston into a hydraulic system. The pressure
within the hydraulic system then activates another piston
situated above the valve which depresses the valve.
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