WO2000057035A1

WO2000057035A1 - Hydraulic valve actuation means

Info

Publication number: WO2000057035A1
Application number: PCT/GB2000/001072
Authority: WO
Inventors: Colin Andrews
Original assignee: Csa Performance Ltd.
Priority date: 1999-03-23
Filing date: 2000-03-21
Publication date: 2000-09-28
Also published as: AU3311700A; GB9906504D0

Abstract

Internal combustion engine inlet and exhaust valve (11) actuation means including a cam (1) for providing a force and a hydraulic means including an enclosed space (7) for transmitting a force to a valve actuator (10) by way of an hydraulic fluid disposed in the enclosed space. The hydraulic fluid is introduced to the enclosed space (7) by way of a fluid feed (15). A fluid drain (17) is provided through which fluid may flow from the enclosed space (7). A valve means is disposed in the fluid drain to control the flow of fluid through the drain. Opening the valve means enables a valve being operated by the actuator to be closed earlier, than the cam would otherwise permit.

Description

HYDRAULIC VALVE ACTUATION MEANS

The present invention relates to an inlet and exhaust valve actuation

means for an internal combustion engine.

Most modern internal combustion engines employ poppet type inlet

and exhaust valves. They are biassed towards the closed position by valve

springs and actuated by way of a rotating cam. Rather than the cam acting

directly on the valve stem there is usually provided an intermediate means

for transmitting the action of the cam to the valve. The nature of this

means varies, depending on engine configuration. However, in general it

comprises some form of tappet.

One known arrangement involves the use of a so-called hydraulic

tappet. In this arrangement the mechanical force generated by the rotating

cam is transmitted via a hydraulic fluid, typically engine oil, to the valve.

The hydraulic fluid is retained in an enclosed space. To ensure that the

enclosed space is maintained full of hydraulic fluid during operation and to

allow for tolerances in the system there is usually provided a hydraulic fluid

feed, typically from the engine lubrication system, and a leak path.

Both the feed and leak path are usually dimensioned so that the

volume of fluid in the enclosed space remains substantially constant during

valve operation. Essentially, the feed and leak path are sufficiently

restricted and the hydraulic fluid sufficiently viscous so that very little or no

fluid flows out of the space during valve operation. A recent development in engine technology is the introduction of

variable valve operation to enable the timing and for the degree of opening

of the valves to be varied to take account of engine operating conditions.

To date, though, these systems have been expensive, complex and have

only provided for relatively small variation in valve operation.

Another, relatively, recent development in engine technology is the

widespread use of electronic engine control.

It is an object of the present invention to provide a simple, reliable

and cost effective means for providing variable valve operation in an internal

combustion engine. It is a further object of the invention to allow for

electronic control of valve operation.

According to the present invention there is provided inlet and exhaust

valve actuation means comprising a cam for providing a force, a hydraulic

means comprising an enclosed space for transmitting the force to a valve

actuator by way of a hydraulic fluid disposed in the enclosed space, the

hydraulic means further comprising a fluid feed through which fluid may be

introduced into the enclosed space, a fluid drain through which fluid may

flow from the enclosed space and a valve means disposed in the fluid drain

to control the flow of fluid through the drain.

Preferably the fluid drain is sufficiently dimensioned to allow the

volume of fluid in the enclosed space to be varied during valve operation,

by allowing some fluid to leak away. This enables the opening and closing of the inlet and exhaust valves of an internal combustion engine to be varied

by operation of the valve means. More preferably the hydraulic means and

fluid drain are arranged so that sufficient fluid may flow through the fluid

drain to prevent operation of the valve actuator.

The hydraulic means is preferably arranged so that when the valve

means is closed the volume of fluid in the enclosed space remains

substantially constant during valve operation.

The fluid feed preferably includes a non-return valve to prevent fluid

flowing from the enclosed space via the feed. The fluid is preferably

engine oil, the supply of fluid to the feed is preferably filtered.

The hydraulic means preferably includes a cam follower which may

be a roller type cam follower. The cam follower preferably comprises a

piston. The piston is preferably disposed in a cylinder which is in

communication with the enclosed space. The cam follower is preferably

biassed towards the cam.

The valve actuator preferably also comprises a piston disposed in a

cylinder in communication with the enclosed space.

The valve actuator is preferably linked, directly or indirectly to a

valve, the valve is preferably biassed towards a closed state.

The valve means is preferably electrically operated. More preferably

the valve means is a solenoid operated spool valve. Alternatively, however

the valve means could be mechanically operated. Preferred types of valve have two states, open or closed, although

variable valves could be used

The valve means is preferably under the control of an electronic

control means, which means is preferably an engine control unit (ECU).

With the valve means closed, the valve actuation means will operate

in the manner of a conventional valve actuation means with hydraulic

tappets. The volume of fluid in the enclosed space will remain substantially

constant.

However, by opening the valve means at any time when an inlet or

exhaust valve is open, or about to be opened, the operation of the valve can

be modified. By opening the valve means to allow hydraulic fluid to escape

from the enclosed space it is possible to limit the amount of opening of a

valve, to allow the valve to close earlier than the cam would otherwise

allow or to prevent the valve from opening at all. The effect is as if the

profile of the cam had been altered.

Since valve operation can only be modified by allowing fluid to

escape it is desirable for the cam profile to include large opening period,

with a steadily rising ramp and a short closing period. The valve could be

closed at any time by opening the valve means.

The fluid drain may comprise a drain port located in the cylinder in

which the valve actuator piston is disposed.

A second fluid drain may also be provided, the second fluid drain comprising a drain port located in the cylinder in which the valve actuator

piston is disposed.

The valve actuation means is preferably comprised in an internal

combustion engine.

In order that the invention may be more clearly understood

embodiments thereof will now be described, by way of example, with

reference to the accompanying drawings in which:

Figure 1 shows a simplified schematic view of a valve actuation means

according to the invention;

Figures 2 show the valve actuation means of Figure 1 in various

to 16 operational states;

Figure 17 shows a simplified schematic view of a modified version of the

valve actuation, means of Figure 1 ; and

Figure 18 shows an alternative modified version of the valve actuation

means of Figure 1.

Referring to Figure 1 the valve actuation means comprises a cam

shaft 1 having a cam lobe 2 mounted thereon. The cam profile provides a

large opening period, with a steadily rising ramp, the closing period being

shorter.

The cam 2 is in contact with a cam follower 3. The cam follower

comprises a roller 4 and a piston 5. A roller type cam follower is thought

suitable for the preferred type of cam profile, but a conventional cam follower could be employed. The piston 5 is slidably mounted within a

cylinder 6 defined by a housing which also defines an enclosed space 7.

The cam follower 3 is biassed towards the cam 2 by a helical spring 8, to

maintain contact between the cam 2 and follower 3.

The housing also defines a second cylinder 9 in which there is

slidably mounted a valve actuator 10 which comprises a piston. The valve

actuator 10 is connected to the stem of an engine valve 1 1 (the whole valve

is not shown). The valve 1 1 could be an inlet or exhaust valve. The valve

stem runs in a valve guide 12. The valve 1 1 is biassed towards the closed

position by helical valve spring 13 which acts between the piston 10 and

a support 14 which is fixed relative to the housing. There may be benefits

of using a different size piston 10 to the cam follower 3 to utilise the

hydraulic advantage available. One cam follower could be used to drive

more than one valve.

The enclosed space 7 forms a working chamber. Hydraulic oil,

typically engine oil, is supplied to the working chamber via an oil feed 15 by

way of the engine's lubrication system. The oil feed 15 includes a non¬

return valve 16 which ensures that the oil will not flow out of the chamber

via the feed route.

Although not shown, the oil feed 15 could also include a filter and

pressure and temperature sensing means, which parameter may be required

by an engine control unit (ECU). The chamber 7 also includes an oil drain 17 closed by a spool valve

18 operated by a solenoid 19. Oil flowing through the drain 17 is returned

to the engine sump. The oil drain 17 and spool valve 18 are sufficiently

dimensioned so as to allow a sufficient flow of oil so that when the valve

18 is open operation of the cam 2 will not cause operation of the piston 10.

Thus it will be appreciated that, whilst it is desirable to keep the chamber

7 as small as possible to minimise valve train flexibility, there must be a

sufficient clearance between the cam follower 3 and piston 10 so that the

cam 2 may rotate without actuating the valve. For efficient operation the

chamber 7 must be free of air or other contaminants.

The solenoid 19 has a powerful, fast response and the valve 18 is

capable of quick operation to allow accurate control of the amount of oil

allowed to drain from the chamber 7.

The solenoid 19 is under the control of an electronic engine

management system 20 arranged to trigger valve 18 operation at

predetermined times and for predetermined periods to obtain the desired

engine valve operation.

The actuation means enables the opening and closing of the inlet and

exhaust valves of an internal combustion engine to be varied by the control

signals from an electronic engine control unit (ECU), to provide variable

valve timing and lift. It also offers the possibility of throttle-less operation

of petrol engines. To further illustrate the invention, Figures 1 to 14 in which the same

reference numerals are used to indicate corresponding components, show

the actuation means in various different operational states. Figures 1 to 6

show a cycle of operation when an engine is operating at full load as

follows:

Figure 1 The cam 2 is on its dwell period. Filtered oil is fed into

chamber 7 via the non-return valve 16. The oil flows through

chamber 7 and straight out, through the open spool valve 17

to the drain. The engine valve 1 1 is closed.

Figure 2 The cam 2 is just starting on its ramp. The solenoid 19

operates to close the spool valve 18. Filtered oil is fed into

chamber 7 via the non-return valve 16. The oil is trapped in

chamber 7 by the closed spool valve 18. The engine valve 1 1

is closed.

Figure 3 The cam 2 moves further up its ramp, moving the follower 3

against its spring 8 and the hydraulic load. The non-return

valve 16 is closed against the pressure build-up in chamber 7.

The follower piston 5 displaces a given volume of oil, moving

the piston 10 by a distance equivalent to a similar

displacement, subject to a small amount of oil compression.

The engine valve 1 1 begins to open.

Figure 4 The cam 2 is at its maximum lift, with the follower 3 at its maximum displacement. The piston 10 is at its maximum

displacement. The engine valve 1 1 is at its maximum lift.

Figure 5 The cam 2 continues round on the closing ramp. The follower

3 maintains contact with the cam 2 thus reducing the

displacement. The piston 10 and valve 1 1 close, by the spring

13 load, maintaining the trapped hydraulic oil volume.

Figure 6 The cam 2 is on its dwell period. The solenoid 19 operates to

open the spool valve 18. The oil flows from chamber 7

through the open spool valve 18 to the drain 17. Filtered oil

is fed into chamber 7 via the non-return valve 16. The engine

valve 1 1 is closed.

Figures 7 show a cycle of operation when an engine is operating at light

to 13 load.

Figure 7 The cam 2 is on its dwell period. Filtered oil is fed into

chamber 7 via the non-return valve 16. The oil flows through

chamber 7 and straight out, through the open spool valve 18

to the drain 17. The engine valve 1 1 is closed.

Figure 8 The cam 2 moves up its ramp, moving the follower 3 against

its spring 8. Filtered oil is fed into chamber 7 via the non-

return valve 16. The oil flows through chamber 7 and straight

out, through the open spool valve 18, to the drain 17. The

follower piston 5 displaces a given volume of oil, which also flows out, through the open spool valve 18 to the drain 17.

The engine valve 1 1 is closed.

Figure 9 The solenoid 19 operates to close the spool valve 18. Filtered

oil is fed into chamber 7 via the non-return valve 16. The oil

is trapped in chamber 7 by the closed spool valve 18. The

engine valve 1 1 is closed.

Figure 10 The cam 2 moves further up its ramp, moving the follower 3

against its spring 8 and the hydraulic load. The non-return

valve 16 is closed against the pressure build-up in chamber 7.

The follower piston 5 displaces a given volume of oil, moving

the piston 10 by a distance equivalent to a similar

displacement, subject to a small amount of oil compression.

The engine valve 1 1 begins to open.

Figure 1 1 The solenoid 19 operates to open the spool valve 18. The oil

flows from chamber 7 through the open spool valve 18 to the

drain 17. The engine valve 1 1 begins to close.

Figure 12 The cam 2 is at its maximum lift, with the follower 3 at its

maximum displacement. The piston 10 and valve 1 1 close by

the spring 13 load, as the oil drains through the spool valve

18. Filtered oil is fed into chamber 7 via the non-return valve

16. The oil flows through chamber 7 and straight out, through

the open spool valve 18 to the drain 17. Figure 13 The cam 2 continues round on the closing ramp, to its dwell

period. The follower 3 maintains contact with the cam 2.

Filtered oil is fed into chamber 7 via the non-return valve 16.

The oil flows through chamber 7 and straight out, through the

open spool valve 18 to the drain 17. The engine valve 1 1 is

closed.

Figures 14 show a cycle of operation when an engine is operating with

to 16 no load.

Figure 14 The cam 2 is on its dwell period. Filtered oil is fed into

chamber 7 via the non-return valve 16. The oil flows through

chamber 7 and straight out, through the open spool valve 18

to the drain 17. The engine valve 1 1 is closed.

Figure 15 The cam 2 is at its maximum lift, with the follower 3 at its

maximum displacement. The follower piston 5 displaces a

given volume of oil, which flows out, through the open spool

valve 18 to the drain 17. Filtered oil is fed into chamber 7 via

the non-return valve 16. The oil flows through chamber 7 and

straight out, through the open spool valve 18 to the drain 17.

The engine valve 1 1 is closed.

Figure 16 The cam 2 continues round on the closing ram, to its dwell

period. The follower 3 maintains contact with the cam.

Filtered oil is fed into chamber 7 via the non-return valve. The oil flows through chamber 7 and straight out, through the open

spool valve 18 to the drain 17. The engine valve 1 1 is closed.

The system uses a trapped volume of oil to open the engine valves.

This trapped volume is a variable, controlled by an ECU. The engine valve

1 1 moves a distance which is a function of the volume of oil trapped. The

engine valve moves in time as a function of the timing of the opening and

closing of the spool valve 18. Therefore, the valve lift/timing profile is

controlled by the ECU 20. Since a "no load" position is obtainable, where

no air is permitted to enter the engine, it follows that the function of the

throttle can be fully performed by the valve control.

Figure 17 shows a possible modification to the valve actuation means

of Figure 1. Referring to Figure 17 an additional drain 21 is provided from

the working chamber 7. Tjie drain 21 is closed by means of a pressure

relief valve 22 arranged to allow fluid to pass out of the chamber via the

drain when the pressure of fluid in the chamber reaches a predetermined

level.

Provision of a pressure relief valve 22 arranged to allow fluid to

escape from the working chamber 7 when a suitably chosen fluid pressure

is reached can serve to protect the apparatus from damage due to excess

pressure build up, for example as a result of the valve 1 1 or spring 13

reaching its maximum travel. Allowing fluid to escape from the working

chamber 7 will effectively modify the cam profile, changing the relationship between duration and lift of the valve 1 1 .

Figure 18 shows a number of other possible modifications to the

valve actuation means of Figure 1 . Referring to Figure 18 three additional

drains 23,24 and 25 are provided from the working chamber. Each drain

runs from a port in the cylinder 9 for the valve actuation piston 10. The

ports are spaced apart in a direction parallel to the direction of movement

of the piston 10 in the cylinder 9.

The port leading to drain 23 is located closest to the valve end 1 1 of

the cylinder 10 of the three ports such that it is normally closed by the

piston 9. If the piston travels towards the valve 1 1 more than is normal the

port will be uncovered allowing fluid to drain from the cylinder 9, and hence

working chamber 7, via drain 23.

This provides protection against damage to the apparatus. In

particular, the apparatus requires a long duration rising ramp on the cam

profile 2 to offer a range of valve control options. This could lead to the

apparatus locking up with consequent apparatus and/or engine damage as

the maximum travel of valve 1 1 or spring 13 is reached. Provision of drain

23 prevents locking up by allowing fluid to escape from the cylinder 9 and

working chamber 7 rather than creating excess valve travel or fluid

pressure. Drain 23 could be provided as an alternative, or in addition to the

pressure relief valve 22 shown in Figure 17.

Drain 23 also permits greater valve control by allowing for full valve lift to be obtained for a long duration.

Ports for drains 24 and 25 are located at positions in the cylinder 9

where the piston 10 would normally be expected to uncover them during

operation. Drains 24 and 25 are each closed by means of electrically

operable valves 26. The valves allow drains 24 and 25 to be brought into

operation when required, to allow for greater flexibility in valve control and,

in particular, to provide two optional limits of travel for the piston. Thus,

fixed lift of the valve 1 1 can be obtained at which the duration can be

modified, greatly increasing control options at part load.

The above embodiments are described by way of example only, many

variations are possible without departing from the invention.

Claims

1 . Inlet and exhaust valve actuation means comprising a cam for

providing a force, a hydraulic means comprising an enclosed space

for transmitting the force to a valve actuator by way of a hydraulic

fluid disposed in the enclosed space, the hydraulic means further

comprising a fluid feed through which fluid may be introduced into

the enclosed space, a fluid drain through which fluid may flow from

the enclosed space and a valve means disposed in the fluid drain to

control the flow of fluid through the drain.

2. Valve actuation means as claimed in claim 1 , wherein the hydraulic

means comprises a cam follower which comprises a piston and the

piston is disposed in a cylinder which is in communication with the

enclosed space.

3. Valve actuation means as claimed in either claim 1 or 2, wherein the

valve actuator comprises a piston disposed in a cylinder in

communication with the enclosed space.

4. Valve actuation means as claimed in claim 3, wherein the fluid drain

comprises a drain port located in the cylinder in which the valve

actuator piston is disposed.

5. Valve actuation means as claimed in either claim 3 or 4, wherein a

second fluid drain is provided, the second fluid drain comprising a

drain port located in the cylinder in which the valve actuator piston is disposed.

6. Valve actuation means as claimed in any preceding claim, wherein

the valve means is electrically operated.

7. Valve actuation means as claimed in claim 6, wherein the valve

means is a solenoid operated spool valve.

8. Valve actuation means as claimed in any preceding claim, wherein

the valve means is under the control of an electronic control means.

9. Valve actuation means as claimed in any preceding claim, wherein

the cam has a large opening period with a steadily rising ramp, and

a short closing period.

10. Valve actuation means as claimed in any preceding claim, wherein a

pressure relief valve is provided to allow hydraulic fluid to escape

from the enclosed space when a predetermined fluid pressure is

reached.

1 1 . An internal combustion engine comprising a valve actuation means

as claimed in any preceding claim.

12. A method of controlling an inlet or exhaust valve of an internal

combustion engine using a valve actuation means as claimed in any

of claims 1 to 10 comprising the steps of rotating the cam to cause

the inlet or exhaust valve to open and opening the valve means to

allow fluid to flow through the drain to allow the valve to close

and/or prevent further opening.

3. A method of controlling an inlet or exhaust valve of an internal

combustion engine using a valve actuation means as claimed in any

of claims 1 to 10 comprising the steps of opening the valve means

to prevent the inlet or exhaust valve opening.