WO2011058504A1

WO2011058504A1 - Flow control device

Info

Publication number: WO2011058504A1
Application number: PCT/IB2010/055103
Authority: WO
Inventors: Charles Lovell Freeman; Ryan Lipke; Clinton Pierre Bemont; Linduyise Hlophe; Hamresin Archary
Original assignee: University Of Kwazulu-Natal
Priority date: 2009-11-10
Filing date: 2010-11-10
Publication date: 2011-05-19

Abstract

This invention relates to a flow control device, and more particularly, but not exclusively, to a flow control device that can be used as a valve system for a cylinder of a reciprocating engine or compressor, and alternatively also as a valve actuator for use in controlling flow of a hydraulic fluid to a hydraulically actuated valve. The flow control device includes a flow distribution device having a distribution aperture, the distribution aperture being in continuous flow communication with an inlet; and a flow control assembly having a flow control passage provided therethrough. The flow control assembly and the flow distribution device are displaceable relative to one another, in order for the distribution aperture and the flow control passage to be displaceable between an at least partially aligned condition in which the inlet is in flow communication with an outlet; and an offset condition in which the flow control assembly prevents flow between the inlet and the outlet. The flow control passage has an effective length that is adjustable in order to adjust a period of the aligned condition.

Description

FLOW CONTROL DEVICE

BACKGROUND TO THE INVENTION

THIS invention relates to a flow control device, and more particularly, but not exclusively, to a flow control device that can be used as a valve system for a cylinder of a reciprocating engine or compressor, and alternatively also as a valve actuator for use in controlling flow of a hydraulic fluid to a hydraulically actuated valve.

Engine technology has improved over the years in order to increase fuel efficiency and performance, whilst simultaneously reducing harmful emissions. One aspect that contributes to achieving the above goals is the ability to change the valve timing.

A four stroke internal combustion engine typically comprises a number of cylinders inside which pistons reciprocate. Valves are provided to regulate flow to and from the cylinders. In a four stroke internal combustion engine the intake valve opens as the piston moves down in the cylinder for the intake stroke. At the end of this stroke, the inlet valve closes, for simplifiedanalysis. Clearly in an Atkinson Cycle engine this does not apply and the need for variable valve timing is increased. The piston moves to top dead center during the compression stroke, after which the power stroke takes place, forcing the piston back down. At bottom dead center, the exhaust valve opens and allows the burned gas to exit the cylinder during the exhaust stroke. In effect, this is a simplified version of what actually happens. At relatively low engine speeds, the above is reasonably accurate. However, at higher engine speeds it is preferable for the closing of the intake valve to be delayed. This is because the intake of air and fuel represents an inertial mass. Therefore, by keeping the intake valve open longer extra air, and hence fuel, can be forced into the cylinder, allowing a greater power output. The Atkinson Cycle also keeps the inlet valve open longer, for an increase in the power to compression stroke ratio.

Various valve arrangements are known in the art, including pressure differential driven valves, cam driven valves, solenoid driven valves, and hydraulically and/or pneumatically operated valves.

Pressure differential valves open or close based on a pressure differential between their inlet and outlet ports. One example is a reed valve, which essentially consists of a valve port and thin reeds of a flexible but strong material positioned over the valve port. If the pressure on the inside of the valve is greater than the outside then the reed is displaced away from the port to allow gas to pass. If the pressure difference is reversed, the reed is pressed against the port, thus preventing gas flow through the valve. While very simple in operation, there are some severe drawbacks to pressure differential operated valves. They typically require some sort of restoring force, which allow them to close quicker when the pressure differential changes. The larger the restoring force, the faster they operate, which is good. The drawback is that the larger the restoring force, the greater the resistance to gas flow through the valve. This may waste a fair amount of energy depending on the flow rate of gas and repetition rate of the valve. These valves are also not controllable to achieve variable valve timing.

Cam driven valves are the most common technology encountered in reciprocating engines and compressors as they are relatively simple, effective and reliable. Because the valve movement can be accurately determined from the cam lobe shape, fast activation of the valve can be achieved without the valve slamming into the valve seat. It is for this reason mainly that this technology has dominated the manufacturing scene for so long. Of course, there are many associated disadvantages. Firstly, the cam and camshaft has to be strong to avoid bending, which leads to a heavy and large construction. Also the cam shape cannot be modified on the fly, thus leading to performance, efficiency and emissions variations as a function of engine speed and load.

Variable valve timing can to some extent be achieved using cam driven valves. In one method the camshaft is allowed to advance and retard. However, while the leading edge of the cam can be moved, this also moves the trailing edge, producing undesirable effects. A further solution that partially overcomes the above disadvantage is to have two interchangeable cams, so that one operates at lower engine speeds, and the other operates at higher engine speeds. While this is an improvement, it is still not optimal, and it also renders the configuration complex and expensive.

A further type of valve that is used to a limited extent are solenoid actuated valves. Solenoid actuated valves represent true continuously variable valve timing. Essentially an electrical signal displaces a solenoid armature which changes the valve position. As the electrical system is independent from the engine state, the valve may be opened and closed at any time. While this is a great advantage, solenoid actuated valves tend to either be too slow or too high in power consumption for automotive valve actuation applications. There are solenoid valves in production that have sufficient speed, but they tend to consume too much power and are relatively large.

Further technology exists where a high pressure medium, such as oil or air, is used to actuate the valve, and the flow of oil or air is controlled by a smaller, fast, lower powered solenoid or piezoelectric actuator. Although closer to the end goal, the solenoid valves are still not fast enough at the flow rates required. Faster piezoelectric actuators are available and have the required speed, but they don't have adequate flow rate requirements. This results in a piezoelectric stack being used instead of a single layer, which in turn increases cost and complexity. It is accordingly an object of the invention to provide a valve or a valve actuator that will, at least partially, alleviate the above disadvantages.

It is also an object of the invention to provide a valve or a valve actuator for use in a reciprocating gas machine, which will at least partially alleviate the disadvantages associated with existing valves or valve actuators.

It is also an object of the invention to provide a valves or valve actuators that will be a useful alternative to existing valves or valve actuators.

It is also an object of the invention to provide a means to control the air flowing into and out of one or more cylinders of a compressed air engine, where such engine may operate as an air compressor in regenerative braking mode or a compressed air engine during acceleration of a vehicle or mode of transport.

SUMMARY OF THE INVENTION

According to the invention there is provided a flow control device for controlling flow of a pressurized fluid, the device including:

a housing assembly having an inlet for receiving a pressurized fluid, and an outlet for discharging the pressurized fluid;

a flow distribution device including a distribution aperture, the distribution aperture being in continuous flow communication with the inlet; and

a flow control assembly having a flow control passage provided therethrough;

the flow control assembly and the flow distribution device being displaceable relative to one another, in order for the distribution aperture and the flow control passage to be displaceable between an at least partially aligned condition in which the inlet is in flow communication with the outlet; and an offset condition in which the flow control assembly prevents flow between the inlet and the outlet; the flow control passage having an effective length that is adjustable in order to adjust a period of the aligned condition.

The fluid flow controlling device may be in the form of a valve actuator for controlling flow of a pressurized medium to a valve. There is also provided for the fluid flow controlling device to be in the form of a valve.

Preferably the flow distribution device is in the form of a flow distribution disc having an aperture provided therethrough, and the flow control assembly also Includes a flow control disc, the flow distribution disc and the flow control disc assembly being rotatable relative to one another.

There is provided for the flow control assembly to comprise two adjacent discs, with each disc having a slot provided therein, and wherein the arcuate slots define the flow control passage when at least partially overlying one another.

There is also provided for the two flow control discs to be independently displaceable in order to adjust the position of the slots relative to one another, and therefore the effective length of the flow control passage defined by the overlying slots.

There is also provided for the actuator to include a flow receiving disc having a receiving aperture provided therethrough.

The flow receiving disc is located adjacent the outlet in order for the receiving aperture to be in flow communication with the outlet irrespective of the rotational position of the flow receiving disc.

There is further provided for the flow distribution disc and the flow receiving disc to be rotationally coupled. Preferably, the flow distribution disc and the flow receiving disc are driven by a crankshaft of an engine or compressor with which the valve or valve actuator is used. More preferably, the flow distribution disc and the flow receiving disc are stationary mounted on a rotating shaft, whereas the flow control discs are rotatable relative to the shaft.

The two flow control discs may be independently driven. Preferably the two flow control discs are driven by stepper motors, but may be driven or gripped by any other means, such as a controlled frictional surface, magnetic engagement or servo motor.

There is also provided for the flow the flow control discs to be in the form of spur gears, in which an external gear driven by a stepper motor engages the peripheral gear teeth of the flow control discs.

According to a further aspect of the invention there is provided a flow control system including a fluid flow control device as described above.

The flow control system may include two flow control devices mounted on a single cylinder, one in use being an inlet valve, and the other being an outlet valve, with interchangeable operation functions.

The flow control system may include stepper motors for driving the flow control discs.

The flow control system may include pressure sensing means for sensing pressure inside a cylinder on which the flow control system is mounted, in order to, in use, be able to determine the maximum efficiency of an engine or compressor utilizing the flow control system. BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described by way of non-limiting examples, and with reference to the accompanying drawings in which:

Figure 1 is a schematic illustration, and in particular an exploded perspective view from the outlet end, which illustrates the operating principle of the flow control device in accordance with the invention;

Figure 2 shows an exploded perspective view of the flow control of

Figure 1 from the inlet end;

Figures 3 to 8 show a valve system that incorporates an embodiment of the flow control device of Figures 1 and 2, and in particular:

Figure 3 is a perspective view of a head plate to which the valve system is secured, and which links the valve system to a cylinder (not shown);

Figure 4 is an enlarged perspective view of an inlet / outlet formed in the head plate, and which also shows a lower end of a shaft which is rotatably secured to the head plate;

Figure 5 is a perspective view of two flow control devices (similar but not identical to that shown in Figures 1 and 2) having been mounted on the head plate, and in particular mounted on the shaft extending from the head plate, with one flow control device having been covered by a valve cylinder, which is effectively the distribution aperture; Figure 6 is a perspective view of the partially assembled valve system, but which omits the bearing plates and pressure sensor;

Figure 7 shows the valve system of Figure 6 with the bearing plates and pressure sensor installed; and

Figure 8 is a perspective view of the fully assembled valve system inside a valve system housing.

DETAILED DESCRIPTION OF INVENTION

Referring to the drawings, in which like numerals indicate like features, a non-limiting example of a flow control device forming part of a valve or valve actuator in accordance with the invention is indicated by reference numeral 10, and comprises an inlet disc 20, a flow distribution disc 40, two flow control discs 60, 70, a flow receiving disc 50 and an outlet disc 30.

The inlet disc 20 and the outlet disc 30 are stationary discs, and in this embodiment define a housing assembly of the valve actuator 10. At the outset, it should however be noted that the inlet disc 20 may be of many different configurations, and may for example not be in the form of a disc at all, but may be defined by the valve cylinder covering the flow control device or a cylinder of an engine or compressor to which the flow control device is operatively secured. Referring to the present embodiment, the inlet disc 20 has an inlet aperture 21 provided there through for introducing a pressurized fluid into the valve actuator 10. An annular distribution channel 22 is provided in an operatively inner surface of the inlet disc. The fluid distribution disc 40 is located adjacent the inlet disc 20, and is rotatable relative to the inlet disc 20. More particularly, in this embodiment the fluid distribution disc 40 is in the form of a spur gear having gear teeth 42, and which is driven by a crankshaft (not shown) of a engine with which the valve actuator is used. A distribution aperture 41 is provided in the flow distribution disc, and is in continuous flow communication with the distribution channel 22 in the inlet disc 20, and thus with the pressurized fluid. It should be noted that the fluid distribution disc may also be mounted on a central shaft (not shown) of the device, in which case the gear teeth will not be required. The essential feature is however that the fluid distribution disc rotates at a fixed speed relative to the rotational speed of the crankshaft.

An outlet disc 30 and a flow receiving disc 50 are provided on an opposing end of the valve actuator 10, and are inversely configured to the inlet disc 20 and the flow distribution disc 40. Importantly, the flow receiving disc 50 also includes a receiving aperture 51 which is in continuous flow communication with a receiving channel 32 of the outlet disc 30, which is in turn in flow communication with an outlet 31. The outlet disc are also stationary, whilst the flow receiving disc 50 is rotatable relative to the outlet disc 30. The flow distribution disc 40 and the flow receiving disc 50 are rotationally coupled, and is configured in order for the distribution aperture 41 and the receiving aperture 51 to be aligned concentrically at all times.

A flow control assembly, in the form of two flow control discs, 60 and 70, are sandwiched between the flow distribution disc 40 and the flow receiving disc 50, and regulates flow between the distribution aperture 41 and the receiving aperture 51 , and hence between the inlet 21 and the outlet 31 of the flow control device 10. Each flow distribution disc includes an arcuate slot 61 , 62 which is in the same radial plane as the distribution aperture 41 and the receiving aperture 51. The two slots 61 , 71 define a fluid transfer passage when they at least partially overlie one another. It will be appreciated that an effective length of such fluid transfer passage will be at a maximum when the slots 61 , 71 are fully aligned, and will be of reduced length when the slots only partially align. The flow control discs 60, 70 are independently displaceable by way of stepper motors, and the effective length of the fluid transfer passage can therefore be adjusted while the valve actuator is in an operative condition.

In use, the inlet 21 of the inlet disc 20 is in flow communication with a pressurized fluid, which may be a pneumatic or hydraulic fluid, and enters the distribution channel 22. The flow distribution disc 40 rotates relative to the stationary inlet disc 20, and is continuously driven by the crankshaft of the engine or compressor. The flow distribution disc 40 is linked to the crankshaft in a 1 :1 ratio in the case of an air compressor or a compressed air motor, and in a 1 :2 ratio if the engine is a four stroke internal combustion engine. The rotating distribution aperture 41 in the distribution disc 40 is continuously in flow communication with the pressurized fluid due to the presence of the annular distribution channel 22.

The flow control assembly controls flow of the pressurized fluid from the distribution aperture 41 to the receiving aperture 51. More particularly, the distribution aperture 41 is in flow communication with the receiving aperture 51 during a part of the rotation of the distribution disc wherein the distribution aperture 41 , and hence the receiving aperture 51 , is aligned with the transfer passage defined by the overlying slots 61 , 71 in the flow control discs 60, 70. As soon as the distribution aperture 41 or the collection aperture 51 is displaced beyond an end of at least one of the slots 61 , 71 the transfer passage is effectively closed, and prevents any further flow of pressurized fluid through the actuator 0. The duration of the open condition is therefore directly proportional to the effective length of the transfer passage, and thus the degree to which the slots 61 , 71 overlie one another. An important feature of this invention is that this parameter is adjustable, in that the two control discs can be selectively and independently displaced while the actuator, and thus the engine or compressor, is in operation, which allows for the flow characteristics of the actuator to be adjustable in accordance with a particular operational state of the engine or compressor.

It is therefore foreseen that the new valve actuator will provide variable valve timing functionality in a manner that is accurate yet practical to implement.

It should be noted that the example described above is directed to the use of the flow control device as a valve actuator. However, the device may also be used as a valve for controlling fluid flow, and more particularly, but not exclusively, to a valve for controlling the flow of a fluid into and out of a cylinder of an engine or a compressor. An embodiment in which the flwo control device is used as part of a valve system 100 in this manner will now be described with reference to Figures 3 to 8, which shows a valve system that incorporates two of the flow control devices 10 described above. In this case the flow control devices 10 effectively directly bolts onto a top of a cylinder, and is in addition covered by its own housing, thus negating the need for the inlet and outlet discs as described in the embodiment of Figures 1 and 2.

Referring now to the figures, a head plate 101 of the valve system 100 is shown in Figure 3. The head plate 101 is configured to bolt onto the body of a single reciprocating cylinder (not shown). A lower surface 102 of the head plate mates with an upper surface (not shown) of the cylinder. The valve system 100 is mounted on an upper surface 103 of the head plate 101 . Various apertures 104 defining bearing housings are provided for receiving bearings (not shown) that will in use receive shafts forming part of the valve system. An inlet 105 and an outlet 106 are provided, which are interchangeable in operation, and is in flow communication with an internal volume of the cylinder (not shown). The inlet 105 and the outlet 106 are always in inverse operation, but their timing may be independently adjusted by way of the valve system. Figure 4 shows a shaft 107 located inside the aperture 04 in the inlet 105. The shaft 107, in use, is driven by the crankshaft in a predetermined ratio - i.e. the phase of the shaft is fixed relative to that of the crankshaft. Keyed sections 108 are provided for receiving the flow distribution disc 40 and the flow receiving disc 50, which consequently rotate with the shaft 107. A cylindrical section 109 allows the two flow control discs 60, 70 to be rotatable independently of the shaft 107, thus allowing stepper motors 122 in Figure 6 to determine the position^' of these discs. Significantly, flow control discs 60 and 70 are adjusted independently (as described in more detail above) in order to adjust the effective length of the flow passage, and therefore the opening and closing time of the valve.

In Figure 5, valve housings 1 10 are fitted over the discs in order to house the discs, whilst also forming an airtight seal. An inlet / outlet port is provided anywhere on the cylindrical or other surface of the valve housing so as to enable air or other working fluid to flow either into or out of the valve housing, the discs and then the compressor or engine. A suitable seal (not shown) is used to seal the shaft 107 relative to the housing.

Referring now to Figure 6, stepper motors 122 are provided to displace the flow control discs (60, 70) to required positions relative to one another. Each stepper motor 122 is mechanically linked to a disc by way of two gears (120, 121 ). In particular, the use of offset gears increases the torque imparted by the stepper motor. In total two stepper motors are used for each valve sub-assembly, one to drive the first control disc 60, and one to drive the second control disc 70.

Springs 125 are provided for applying a downwardly directed force to hold down the valve housings 1 10. A bolt (not shown) through each spring is mounted in the head plate 101 , and a nut is used to compress the spring, By applying a specified maximum torque to the nut a specified is applied by the spring to the valve housing. Not shown, but a possible addition to reduce friction during higher pressure operation, a lower force spring could be used with an additional variable force applied by another means, for example, the pressurized fluid being transported.

A sleeve 126 is provided on the stepper motor shaft, and contains a magnet 127. The magnetic axis is perpendicular to the stepper motor shaft so that it can be used with a magnetic shaft encoder. This is needed to determine the signals to send to the stepper motors in order to drive them (or let them slip) to a particular position.

A printed circuit board 128 is provided for controlling each stepper motor, and contains electronics to measure the stepper motor shaft position and drive the stepper motor to a position determined by an external electronic controller. A plate 1 10 made from mild steel or a high magnetic permeability material is located below each PCB 128 so that the magnetic fields generated by the stepper motors and other stray fields from below, do not interfere with the individual magnetic encoders on each PCB. There are other means such as optical or electrical encoding that could be used for this function.

Figure 7 shows the bearing plates 30 that are used to hold the ends of the shafts for the gears. This is required to reduce radial forces or wear on the bearings and shafts. Bosses 131 are furthermore provided to hold bearings on the other end of the shafts.

The valve system 100 also includes a pressure sensor 140 with a fast response time, sufficient to measure the immediate pressure inside of the compressor/engine cylinder. This is required to increase the efficiency of the system. For this purpose an inner hole is provided in the head plate, which is small enough so as to maintain a negligible additional volume to the compressor/engine cylinder, but large enough so as to not interfere with the pressure measurements. Finally, the enclosed valve system 100 is shown in Figure 8, with a valve box 150 covering the valves, and encoder boxes covering the PCB's in order to provide magnetic shielding from external fields, as well as from adjacent magnets on adjacent shafts.

It will be appreciated that the above are only two embodiments of the invention and that there may be many variations without departing from the spirit and/or the scope of the invention.

Claims

CLAIMS:

1. A flow control device for controlling flow of a pressurized fluid, the device including:

a flow control assembly having a flow control passage provided therethrough;

the flow control assembly and the flow distribution device being displaceable relative to one another, in order for the distribution aperture and the flow control passage to be displaceable between

an at least partially aligned condition in which the inlet is in flow communication with the outlet; and

an offset condition in which the flow control assembly prevents flow between the inlet and the outlet; the flow control passage having an effective length that is adjustable in order to adjust a period of the aligned condition.

2. The flow control device of claim 1 in which the flow distribution device is in the form of a flow distribution disc having an aperture provided therethrough, and in which the flow control assembly also includes a flow control disc, the flow distribution disc and the flow control disc assembly being rotatable relative to one another.

3. The flow control device of claim 2 in which the flow control assembly comprises two adjacent discs, with each disc having a slot provided therein, and wherein the slots define the flow control passage when at least partially overlying one another.

4. The flow control device of claim 3 in which the two flow control discs are independently displaceable in order to adjust the position of the slots relative to one another, and therefore the effective length of the flow control passage defined by the overlying slots.

5. The flow control device of claim 4 in which the flow control discs are displaceable by way of stepper motors.

6. The flow control device of claim 5 in which each flow control disc is provided with gear teeth at a periphery thereof, in order for the flow control disc to be engageable by a gear that is driven by the stepper motor.

7. The flow control device of any one of the preceding claims including a flow receiving disc having a receiving aperture provided therethrough.

8. The flow control device of claim 7 in which the flow receiving disc is located adjacent the outlet in order for the receiving aperture to be in flow communication with the outlet.

9. The flow control device of claim 7 or claim 8 in which the flow distribution disc and the flow receiving disc are rotationally coupled.

10. The flow control device of claim 7, 8 or 9 in which the flow distribution disc and the flow receiving disc are driven by a crankshaft of an engine or compressor with which the valve or valve actuator is used.

1 1 . The flow control device of any one of the preceding claims in which the flow control device is in the form of a valve actuator for controlling flow of a pressurized medium to a valve, in order to contro\ the operation of the valve.

12. The flow control device of any one of claims 1 to 10 in which the flow control device is in the form of a valve.

13. The flow control device of claim 1 , substantially as herein described with reference to the accompanying figures.

14. A flow control system including at least one flow control device as claimed in any one of claims 1 to 13.

15. The flow control system of claim 14 including two flow control devices mounted on a single cylinder, one in use being an inlet valve to the cylinder, and the other being an outlet valve to the cylinder.

16. The flow control system of claim 14 or 15 including stepper motors for displacing the flow control discs of the flow control device.

17. The flow control system of claim 14, 15 or 16 including pressure sensing means for sensing pressure inside the cylinder on which the flow control system is mounted, in order to, in use, be able to determine the maximum efficiency of an engine or compressor utilizing the flow control system.

18. The flow control system of claim 14 substantially as herein described with reference to the accompanying figures.