Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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VALVE OPERATING MECE~ANISM FOR INTERNAL COMBUSTIO~ AND
LIKE-VALVED ENGINES
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This invention relates to a valve operating mechanism
for internal combustion and like-valved engines.
10 It has for some time been real ized that the
requirements for engine valve timing in an internal
combustion engine are variable depending upon the speed
of the engine when optimum operation is desired. Thus
in the use of the usual mechanically operated valve
15 system, operated by means of a camshaft, selection is
dependent upon the maximum engine power at high speed
operation, minimum exhaust emissions at low speed
part-load operation, or on some form of compromise
between the twoO Considerable research has been
20 undertaken on thls subject which have 1 argely produced
the conclusion that, ideally, full control over every
parameter of valve movement is required; and these
parameters need to be varied in response to the
operating conditions of the engine at any particular
25 time. As a result of this research, various
modifications have been proposed for existing camshaft
install ations, and in different ways in dependence ~pon
the particul ar objectives which have been considered in
the particular research involvedO Nevertheless, no
30 modification has been found which is capable of
providing a full optimum control of the valve operation
over the whole of the operating conditions of the
engine, and, as a result, any proposed system is
effectively only a compromise.
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The present invention seeks to pnovide a valve operating mechanism for an
internal combustion, or like-valved engine in whichl the operating mechanism
enables a substantially full control to be exercised over all parameters for
each of the valves of ~he eng me.
Gen~rally speaking, the present invention may be considere~ as providing a
valve operating n~chanism for ~n internal combustion engine comprising: a
piezo-electric actuating device arranged to drive an engine valve opening
directly into a combustion cha~ber by the expansion of the piezo electric
actuatLny devics such that expansion of the piezo-electric actuating device
provides the sole motive force for opening the valve; and control means to
control an electrical feed to the pieæo-electric actuating device in
accordance with parameters o~ engine operation fed to it.
In a first form of the invention, the piezo-electric device is coupled to
the engine valve through an amplifying mechanical linkage.
In a second form of the invention, ~he piezo-electric device is connected to
~he engine valve through a fluid linkage including an hydraulic or pneumatic
piston and cylinder arrangement for directly driving the valve.
Control of the piezo-eleetrie deviee is preferably carried out with a
feedback loop control circuit, the control circuit being fed with
instructions by a mieroprocessor with associate~d memory which in turn is fed
by values representing engine operating parameters. Such parameters may
include crankshaft position, engine speed, mixture information, and exhaust
information.
The inventio~ will now be described in greater de~ail, by way of example,
which referenee to the drawings, in which:
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Figure 1 is a diagrammatic view of a valve operating mechanism in accordance
with the invention, with mechanical linkage between the piezo-electric
device, and the valve.
Figure 2 is a diagrammatic view of a valve operating mechanism in accordance
with the invention, in which two piezo-electric devices ac-t as fluid/gas pumps.
Figure 3 shows an alternate embodiment of Fig. 2 utilizing a single piezo-
electric device.
Figures 4 and 4a show an alternate control for the piston.
Figure 5 is a block circuit diagram showing a typical proposal for the
circuitry of the control means for control of the piezo-electric devices
as shown in Figures 1 and 2.
Referring firstly to Figure 1, there is shown a mechanical vers.ion of the
valve operating mechanism. In this figure, the piezo-electric device is
;~ indicated as 1 and comprises a stack of piezo-electric discs or rings 2
to which a voltage can be applied by a means not shown. One end of the
stack of discs or rings 2 is fixedly mounted at 3 in a housing 4 while the
other end of the stack is freely movable. At this end of the stack,
there is provided, an operating pin 5 which engages an operating lever arm
6 pivo-ted at 7 and carried by a carrier 8 mounted on the engine block 9.
m is lever arm 6 is connected at 10 to the actuating rod 11 of the valve
12. As will be seen, the relatively small movement of the piezo-electric
device 1 is converted by the lever arm 6 into a considerably larger movement
for actuating the valve 12.
: In this embodiment, the voltage supplied to the piezo-electric devices acts
by direct mechanical linkage on the valve 12, and the valve 12 will move thus
in accordance with the voltage supply to the piezo-
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electric device 1. While in this embodiment no motion
sensor has been provided for clarity, in order to
enable operation with a feedback loop, a suitable
sensor would be mounted to sense the movement of the
v~ ve.
Figure 2 shows a second ~orm of the invention, where
two piezo-electric devices, 13 and 14, generate and
control ~he pressure of the fluid/gas, and hence
control the movement of the valve 15 of an internal
combustion engine. The ~wo piezo-electric devices
suitably comprise a number of piezo-electric discs or
rings, 16 and 17, to which a voltage can be applied by
a means not shown. One end of the stack of discs or
15 rings, 16, 17 is fixedly mounted at 18, 19 in a housing
20, 21, while the other ends of the stacks are freely
movable. Where rings are used, ~he free ends could be
; attached to a bolt which passes through the stack from
one end to the other At these ends of the stacks,
there are connections 22, 23, which lead, through
valves 22a and 22b operated by any derived means and
controlled by the operating system to a control ram 24,
~or actuating the valve 15. This ram comprises a
cylinder 25 in which lie the piston 26 carried by a rod
27 which is suitably an extension of the rod 28 of the
valve 15. Connections 29, 30, are provided which are
connected to the connections 22, 23, respectively, and
provide for the feed or exhaust of fluid/gas from
either side of the piston 25. ~he end of the rod 27 is
suitably provided with a motion sensor, indicated
; schematically in the variable resistor 31. The system
can be closed in that the same fluid/gas is used
repeatedly, and connections 32, 33 are not needed, or,
alternatively, connections 32, 33 can lead to
connections 34, 35 through which extra fluid/gas can be
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suppiied from the reservoir 36 under the control of the
one-way valves 37, 38. These one-way valves co~ld be
controlled electrically or mechanically, by a means not
shown. The reservoir could be press~rised, if
required.
In operation, voltages are applied to the stacks of
piezo-electric discs or rings 16, 17, (the magnitude
and orm of the voltage depending upon ~he required
parameters of valve ~ovement of the valve 15). This
voltage can be converted into an expanding longitudinal
movement of one or more 'strokes' so as to feed
fluid/~as under pressure to one side of the control ram
24. Alternatively, the voltage can be converted to a
contracting longitudinal movement of one or more
'strokes' so as to control the flow of fluid/gas being
exhausted from the control ram 24. Thus the actuating
piston 26 will be moved longitudinally in the cylinder
25 in response to the voltages appl~ed to the piezo-
electric devices 13 and 14, and will open and close thevalve in a controlled way. Feedback of the movement
carried out is provided by the movement sensing device
31, and this information is fed back to control
apparatus, as will be seen hereafter, in order to
provide a control loop for control of the piezo-
electric devices 13 and 14.
In some circumstances, particularly in these
embodiments, it may be desirable to provide a damper
for the operation of the engine valve. This could take
the form of a piston and dashpot connected to the end
of the valve operating rod, suitably at the position
indicated for the motion sensor. The motion sensor
could then be suitably relocated.
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Figure 5 is a block diagram of a suita-~le electronic
control arrangement for operating the valves of an
internal combustion engine, and provide for control of
the piezo-electric devices as shown in Fi~ures 1 and 2.
In the arrangement of Figure 5, all the valves of an
internal combustion engine are to be contr~lled by a
single microprocessor or computer and it's associated
memory indicated at 91. In this figure, two groups of
piezo- electric control devices are shown, indicate~ 92
and 92n~ each group having one, (see Figures 1 & 37~ or
two, (see Figure 2), piezo-electric devices associated
~ith one motion sensing transducer, 93 and g3n, which
~eeds information into a piezo-electric feedback loop
control circuit, 94 and 94n.
The loop control circuit 94 and 94n provides a signal
to a high-voltage interface, 95/ 95n, which feeds it's
associated group of piezo-electric devices9 92, 92n
This part of the circuit provides for a loop control
system so that the movement transmitted by the piezo-
electric device(sJ to the valve is sensed and any
dPviation from the correct movement is corrected by
means of the control circuit. In addition to this
loop, instructions are. also fed into the piezo-electric
feed-back loop control circuit, 94, 94n, by way of a
; data bus 96, which transmits instructions from the
microprocessor and its associated memory 91, to the
control circuit. The microprocessor unit is fed with
the necessary input data providing information as to
30 the operational state of the en~ine. In the partlcular
example shown, this information is provided at two
inputs 97 and 98.
The input 97 is provided with a value indicating the
35 crankshaft position, which ~ay be detected by an
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optical or magnetic sensor. The input 98 is provided
with values representing the engine load, and can be
determined by an optical or magnetic sensor on a
roadbearing wheel. Other inform~tion which can be
included in the information presented to the
microprocessor include engine speed, mixture, inlet
conditions, and exhaust conditions.
The microprocessor or computer is programmed to convert
the information which is provided by it's inputs, 97
and 98, into instructions which indicate the optimal
operation of the valve in question. These instructions
modify the loop control circuit of the individual
piezo-electric devices, 92 and 92n, so that optimum
operation of the valves results~ Thus the processor
output data may represent timing, lift position and
velocity profile for the operation of the associated
valves.
Addition~ functions of the ~icroprocessor or computer
can control the valve to provide a number of different
effects. Firstly, admitted fuel-air mixture could be
increased so as to make starting of the engine easier.
Secondly, the engine could be used as a brake by
causing the inlet valves to remain shut during intake
strokes of the engine, and in this way cause an
increase in deceleration of the vehicle to which it is
connected. Thirdly, the lift of the inlet valve can be
varied in such a fashion as to increase the pressure
drop at the intake port~ In this way, the velocity in
Reynolds Number of the incoming mixture can be
increased. Thus, the thermal efficiency of the engine
can be increased, and it is possible to use very lean
fuel-air ratios where there is only a part-load. It is
also possible to dispense with, entirely, the
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carburettor butterfly, and rely entirely on valve
control. This piezo-electric valve operating system
can also easily cope with the extra demands of a
turbocharger-supercharger installation; and in the
hydraulic mode of the system, can provide valuable
cooling to help cope with the increased heat genera~ed.
Considering the construction of the piezo-electric
stack itself, a typical piezo~electric material which
would be suitable, is that known as PXE5 manufactured
by Phillips, which provides an e~tension of 616 x 10-12
meters/volt. If a construction of 1 to 200 discs were
used, each disc say lOmm diameter, and over 5mm thick,
ade~uate operation will be provided for the hydraulic
system outlined in Figure 2. For the mechanical
arrange~ent such as shown in Figure 1, an even more
responsive piezo-electric device would be needed, to
obviate the necessity of having an over large
mechanical ratio.
In a typical situation, an operating voltage of between
500 and 2000 volts could be used. The current supply
into the piezo-electric device would be of the order of
milliamps, the power needed for driving the piezo-
electric devices of an eight cylinder engine forexample, would be very approximately the order o~ l
H.P.
It will be appreciated that various modifications may
be made to the above described embodiments without
departing from the scope of the invention. For
example, the loop control circuit could be omitted,
only direct control of the piezo-electric device being
provided. The hydraulic control could be replaced by a
simple pneumatic control. Instead of providing a
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double-acting ram for the actual operation of the
valve, this could be replaced by a single-acting ram
with a return spring. Where the hydraulic control is
used, the hydraulic control apparatus could all be
housed together at a position spaced from the actuating
cylinders of the valves, so that in this way a single
control function limit is formedO
From the above described embodiment, it will be seen
that there is provided a valve operating mechanism
which, with sufficient control functions, can control
the operation of the valves of an internal combustion
engine in respect of all their parametees of movement.
