This invention relates to a pressure regulator which may be used, for example, to supply a gaseous fuel to an internal combustion engine.

In an internal combustion engine operating with a gaseous fuel supply, such as an LPG or CNG gaseous fuel supply as is preferred for environmental reasons in India and many other parts of the world, the gas pressure regulator controls the pressure and quantum of gas delivered to the engine in accordance with engine operating conditions. When vacuum in an intake manifold to the engine is high, reflecting high engine load conditions, a higher quantum of gas is supplied to the engine, which reduces with the level of vacuum in the intake manifold such that, at idle, the delivered gas volume is least.

A typically used gas pressure regulator, of diaphragm type, comprises of a regulator body which has an inlet port to receive high pressure gas from a gas fuel tank and an outlet port to deliver lower pressure gas to the engine. A valve or orifice controls flow of the gas between the inlet port and outlet port through use of a valve element which moves in setting in accordance with the movement of a diaphragm assembly comprising a diaphragm and lever, movement of the diaphragm being constrained by a spring with pre-determined - though typically adjustable -compression. The setting of the valve element is therefore dependent on the movement or flexion of a diaphragm, against the bias of the spring, in accordance with the pressure variations in the engine.

The movement or flexion of the diaphragm is caused by the pressure differential across it. That is, one side of the diaphragm is subjected to engine side vacuum which varies with engine demand. On the other side of the diaphragm is a breather chamber which ideally is maintained at a constant atmospheric pressure through connection of the chamber to atmosphere through a breather. When the regulator is tuned, at the factory, there is relatively little pressure fluctuation in the breather chamber. While there may be some variation in atmospheric pressure, this will not usually affect proper operation of the gas pressure regulator even when at its idle or "lowest operating pressure" setting. That is, there are no wind streams or currents around the breather opening. Tuning is straightforward.

Experience is different when the gas pressure regulator is used in the moving vehicle. In this case, the breather opening is subjected to a wind stream, typically of variable speed. This changes the atmospheric pressure on the side of the diaphragm which is supposed to be at a constant reference atmospheric pressure. This in turn causes a change in pressure differential across the diaphragm resulting in excess or less gas supply than the required amount. This will result in engine instability.

The problem is particularly acute when the engine is operating in an idle condition where the gas pressure differential across the diaphragm of a diaphragm type gas pressure regulator is, in any case, at a minimum. Under idle operating condition, wind stream induced pressure functuations in the breather chamber and correspondent fluctuations in diaphragm movement result in venations in the pressure of gas delivered to the engine, potentially very small gas pressure or flow across the orifice and consequent unstable engine idling. Alternatively, in some circumstances, excessive flow of fuel to the engine will result this also leading to unstable engine idling.

This situation may be hazardous in traffic conditions. For example, a driver of a gas fuelled vehicle may seek to cruise to a turning position in idle. There is a real prospect that the instability of idle could cause the engine to stall, this being hazardous in certain circumstances. For example, if the turn has to be made quickly to avoid oncoming traffic, there is obvious danger in an engine stalling. The problem is aggravated if the driver expects the engine to remain idling.

Other situations may be envisaged where operation of a gas pressure regulator may be adversely affected by pressure fluctuations in the breather or atmospheric pressure chamber.

It is an object of the present invention to provide a gas pressure regulator less subject to adverse effects caused by pressure fluctuations in the breather chamber, especially - but not exclusively - in the case of automotive applications.

With this object in view, the present invention provides a gas pressure regulator for controlling pressure and quantity of a gas delivered by the regulator comprising a regulator body having an inlet port; an outlet port; a valve having a valve seat; a valve element moveable relative to the valve seat for controlling gas flow through the regulator from the inlet port to the outlet port; and a diaphragm assembly comprising a diaphragm and lever for adjusting position of the valve element relative to the valve seat, the diaphragm being exposed on one side to a breather chamber connected to atmosphere by a breather wherein the breather is configured to reduce the effect of pressure fluctuations in said breather chamber on said diaphragm and pressure of gas delivered from the outlet port of the regulator.

Such a gas pressure regulator has advantageous application in a gas fuel supply system for a vehicle engine. In this application, the gas may be any suitable fuel gas, for example LPG or CNG. Other applications, outside of the automotive industry, may also be envisaged.

The breather may be configured in a number of ways to reduce the effect of pressure fluctuations, most typically caused by significant air motion past an opening of the breather. The breather may take the form of, or include, a passage connecting the breather chamber with the atmosphere. This breather passage could be connected to open to atmosphere in a location less subject to wind motion and consequential pressure fluctuations, here defined as a quiescent location. In a three wheeler passenger vehicle, the breather passage may open to atmosphere at a location behind a passenger seat or bench.

The quiescent location may be selected to minimise the effects of pressure fluctuations in the breather chamber even when a vehicle using the regulator is moving at high speed. The breather passage may therefore be connected to this quiescent location by a duct or tube which may be a flexible tube to facilitate connection with the quiescent location. This duct or tube may be a readily replaceable part. The breather passage may be provided with a connection means or fitting to co-operate with a complementary connection means or fitting on the duct or tube.

The breather passage may be formed with particular geometry to minimise risk of pressure fluctuations in the breather chamber. The breather passage may, in such case, be formed as a nozzle. Alternatively, the nozzle may be fitted into the breather passage of a conventional gas pressure regulator. Advantageously, the nozzle has a predefined inner diameter which is fixed in place of a conventional small breather opening, this predefined inner diameter being selected to minimise or stabilise pressure fluctuations in air passing into the breather chamber.

The breather passage may include a flow restrictor such as an orifice to minimise pressure fluctuations due to air motion past the breather opening. The orifice may be selected having regard to a desired reduction in pressure fluctuations in the breather chamber. This may be determined empirically with particular regard being pad to need for reduction of pressure fluctuations under idling conditions.

In another aspect, the present invention provides a gas fuelled engine comprising:

(a) a gaseous fuel supply system for supplying a gaseous fuel to the engine; and

(b) a gas pressure regulator for controlling pressure of gaseous fuel supplied from the gaseous fuel supply system to the engine, said regulator comprising a regulator body having an inlet port; an outlet port; a valve having a valve seat; a valve element moveable relative to the valve seat for controlling gas flow through the regulator from the inlet port to the outlet port; and a diaphragm assembly comprising a diaphragm and lever for adjusting position of the valve element relative to the valve seat, the diaphragm being exposed on one side to a breather chamber connected to atmosphere by a breather wherein the breather is configured to reduce the effect of pressure fluctuations in said breather chamber on said diaphragm and pressure of gas delivered from the outlet port of the regulator.

The gas pressure regulator and gas fuelled engine may be usefully employed in a range of vehicle types, but is especially suitable for inclusion in a two or three wheeled vehicle having an LPG fuel system for commuting, for example about urban areas. The engine may be any suitable gas fuelled engine.

The gas pressure regulator and gas fuelled engine may be more fully understood from the following description of a preferred embodiment thereof made with reference to the accompanying drawings in which:

Figure 1 is a schematic side section view of a gas pressure regulator in accordance with the prior art;

Figure 2 is a detail A taken from the schematic of the gas pressure regulator shown in Figure 1;

Figure 3 is a detail of the breather for a gas pressure regulator in accordance with a preferred embodiment of the present invention;

Figure 4 shows a schematic side view of a vehicle having an gas pressure regulator and engine in accordance with a preferred embodiment of the present invention.

Referring now to Figures 1 and 2, there is shown a gas pressure regulator 10 which delivers LPG or CNG fuel to the engine of a three wheel commuter vehicle. Gas pressure regulator 10, which has a body comprising two co-operating halves, is mounted to the frame of the vehicle by rigid or flexible mounts. Gas pressure regulator 10 has a high pressure gas chamber 11 which is connected to a gas fuel supply tank (not shown) of conventional form and containing the LPG or CNG fuel gas. High pressure gas chamber 11 is selectively communicated to an engine side vacuum chamber 12, itself connected to the intake manifold of the .engine, through an orifice 13. The opening and closing of the orifice 13, which is dependent on the LPG or CNG gas flow required to operate the engine of the vehicle, is controlled with a valve element in the form of a rubber pad 14 which is attached to a valve element actuating lever 15 around its midpoint. The position of the rubber pad 14 at the orifice 13 controls the flow area for gas fuel to flow into the engine and thus the amount of gas fuel supplied to the engine when it is operating.

Lever 15 is pivoted, at lever pivot 16, by a predetermined spring load through a spring 17. The predetermined load of spring 17 is adjustable as required by the engine specification. The predetermined spring load biases the valve element 14 closed when the engine is not running (ENGINE OFF condition).

One end of actuating lever 15 is connected to a diaphragm assembly which comprises, as its main component, a diaphragm 18 made of a flexible material such as rubber material with a fabric lining. This is a readily deformable construction which provides greater sensitivity of diaphragm 18 to variations in differential pressure across it. The diaphragm 18 is clamped, at the outer portion edge of its circumference between the two halves of the body of gas pressure regulator 10. The central portion of diaphragm 18 is arrested between thin metal sheets 33 which, in turn, are connected to the lever end through an arrester 32.

One side of the diaphragm 18 is exposed to a chamber 12 having variable pressure due to variable engine vacuum pressure during engine operation. This reflects the pressure fluctuations in the intake manifold of the engine. The other side of diaphragm 18 is exposed to a chamber 20 having atmospheric or near atmospheric pressure due to its connection to the surrounding air through a breather 21.

Movement of the diaphragm 18 is caused by changing differential pressure between pressure in chamber 12 reflecting the changing vacuum generated in the engine due to throttle movement (or engine load) while the engine is running or in ON condition and pressure in atmospheric pressure chamber 20. The movement of diaphragm 18, during such engine operation, causes movement of actuating lever 15 so as to move the valve element 14 upwardly against the predetermined load exerted by spring 17, The predetermined load is so adjusted as to ensure that the required amount of gas fuel flows through orifice 13 with respect to engine vacuum, that is, engine load.

The idling condition puts an especially high demand on the proper functioning of diaphragm 18, It is under idling conditions, when engine vacuum and load is at its lowest, that the differential pressure across diaphragm 18 is also very low. if there is insufficient or incorrect pressure differential, there may be sufficient variance from the desired flow area of orifice 13 for efficient running of the engine that engine instability due to insufficient or over-fuelling results. Variable differential pressure may also interfere with the supply of fuel to the engine under idling conditions. Tuning of the engine is intended to take real running conditions into account. However, engine tuning in a factory or service setting does not take account of all "on-road" conditions.

In particular, engine idling is set or tuned with the vehicle in stationary condition. There are no wind streams or currents, let alone variable speed wind streams or currents, around the breather opening 21, Tuning with the vehicle in stationary condition ensures a steady state atmospheric pressure in the atmospheric pressure chamber 20 on one side of the diaphragm 18. The spring force for spring 17 for idling is therefore set under more or less steady state atmospheric conditions.

In reality, when the vehicle is running, breather 21 has its opening subjected to a wind stream 22 as indicated by the arrows in Figure 2, As a result, air pressure in atmospheric pressure chamber 20, rather than being constant or near constant, becomes variable. This variability also causes a change, in pressure differential across the diaphragm 18 causing variance from the tuned flow area of orifice 13 for idling such that excess or less gas supply than the preset amount is supplied to the engine.

Figures 3 and 4 show how a conventional gas pressure regulator 10, as described with reference to Figures 1 and 2 above, may have a breather which is configured to reduce such undesirable pressure fluctuations in atmospheric pressure chamber 20.

A fitting in the form of nozzle 23 may be fitted into breather opening 21. Nozzle 23, which is illustrated in the form of an elbow which enables convenient fitting to the regulator, may include a bore 23a of relatively wider inner diameter and a bore 24 of controlled inner diameter. That is, the inner diameter of bore 24 is selected to provide a restriction to flow of air into the atmospheric pressure chamber 20. The inner diameter of bore 24 may also be calculated with reference to achieve desired changes in CO emissions present in the engine exhaust under various engine operating conditions.

When nozzle 23 is fitted into the breather port 21, by push fitting of spigot 26 into the breather opening, bore 24 is communicated, through the breather port 21 to atmospheric pressure chamber 20.

At the other end of nozzle 23 may be fitted a rubber hose 25, this rubber hose being routed to a quiescent location 26. As shown in Fig. 4, quiescent location 26 is located behind passenger seat or bench 27 of the three wheeler vehicle. At this location, the breather opening is not exposed to wind stream 22 even though it may be seen that the gas pressure regulator 10 is exposed to such wind stream 22.

By combination of breather portion 21, nozzle 23 and rubber hose 25 opening in the quiescent location 26, the breather is configured to reduce the effect of pressure fluctuations in atmospheric pressure 20 chamber on diaphragm 18 and pressure of gas delivered from the outlet port of the gas pressure regulator 10. This provides much greater engine stability under idling condition though stability benefits may be achieved under other engine operating conditions as well.

Modifications and variations to the gas pressure regulator and engine of the present invention may be apparent to the skilled reader of this disclosure. Such modifications and variations are deemed within the scope of the present disclosure.

WE CLAIM:

1. A gas pressure regulator for controlling pressure and quantity of a gas delivered by the regulator comprising a regulator body having an inlet port; an outlet port; a valve having a valve seat; a valve element moveable relative to the valve seat for controlling gas flow through the regulator from the inlet port to the outlet port; and a diaphragm assembly comprising a diaphragm and adjustment means for adjusting position of the valve element relative to the valve seat, the diaphragm being exposed on one side to a breather chamber connected to atmosphere by a breather wherein the breather is configured to reduce the effect of pressure fluctuations in said breather chamber on said diaphragm and pressure of gas delivered from the outlet port of the regulator.

2. A gas pressure regulator according to claim 1 wherein the breather takes the form of, or includes, a breather passage connecting the breather chamber with the atmosphere.

3. A gas pressure regulator according to claim 2 wherein said breather passage is connected to open to atmosphere in a quiescent location.

4. A gas pressure regulator according to claim 3 wherein, in a three wheeler passenger vehicle, the breather passage opens to atmosphere at a location behind a passenger seat or bench.

5. A gas pressure regulator according to claim 3 or claim 4 wherein said quiescent location is selected to minimise the effects of pressure fluctuations in the breather chamber even when a vehicle using the regulator is moving a high speed.

6. A gas pressure regulator according to any one of claims 3 to 5 wherein said breather passage is connected to said quiescent location by a duct or tube.

7. A gas pressure regulator according to claim 6 wherein said duct or tube is flexible.

8. A gas pressure regulator according to claim 7 wherein said breather passage is provided with a connection means or fitting to co-operate with a complementary connection means or fitting on the duct or tube.

9. A gas pressure regulator according to any one of claims 2 to 8 wherein said breather passage is formed as a nozzle.

10. A gas pressure regulator according to any one of claims 2 to 8 wherein said nozzle is fitted into said breather passage.

11. A gas pressure regulator according to claim 9 or claim 10 wherein said nozzle has a predefined inner diameter selected to minimise or stabilise pressure fluctuations in air passing into the breather chamber.

12. A gas pressure regulator according to any one of claims 2 to 11 wherein said breather passage includes a flow restrictor to minimise pressure fluctuations due to air motion past the breather opening.

13. A gas pressure regulator according to claim 12 wherein said flow restrictor is an orifice.

14. A gas fuelled engine comprising a gas pressure regulator according to any one of the preceding claims.

15. A vehicle comprising a gas fuelled engine according to claim 14.

16 A gas pressure regulator substantially as hereinbefore described.

17. A gas fuelled engine substantially as hereinbefore described.