FIELD OF THE INVENTION

The present invention provides an automatic valve for the inlet manifold of an internal combustion engine,

BACKGROUND ART

The principle of "air bleed" has been known for many years. This principle states that allowing a small amount of additional air into the inlet manifold of an internal combustion engine at times of particularly low pressure (high vacuum), for example during moments of acceleration or deceleration of the engine, will allow significantly more efficient fuel burning within the engine. This should, in theory, reduce the emission of pollutants such as carbon monoxide (CO) and unbumt hydrocarbons (HC).

Early examples of this principle can be found in GB496409 from 1937 and GB690635 from 1950. Such devices do not appear to have become common in the field.

GB 2129869 and GB 2213875 propose arrangements in which a ball bearing-based non-return valve is arranged to supply bleed air to the inlet manifold. The ball bearing is biased towards a valve seat by a spring. However, the response time of these versions are lower than desirable, and in addition the CO and HC reductions achieved are disappointing, even taking into account the lower response time.

In recent times, attention has been principally directed to computer based engine management systems (EMS), These are essentially microprocessors supplied with data from a number of sensors distributed around the engine. The EMS notes this data and compares it with preset data and/or algorithms and actively manages certain variables in order to optimise the fuel burning characteristics. However, such a system will inevitably be reactive, in that an imbalance must first be detected and then corrected after it has existed for a certain period. Thus, the efficiency of such systems is inherently limited by their processing times. Recent attention has therefore been directed to providing ever better response times for an existing EMS.

To the knowledge of the inventor, the only commercially viable embodiment of the air bleed principle that has been produced is that described in his earlier application W096/34194. This publication describes a device with a lightweight conical valve fitting into a valve seat, which achieves the necessary reaction time to keep up with the variations in vacuum in the inlet manifold - typically of the order of tens of milliseconds.

SUMMARY OF THE INVENTION

The device of W096/34194 is however open to improvement. In practice, the geometry of the device is difficult to fit in an OE (original equipment) context, and the necessary adjustment steps described in W096/34194 are time-consuming, skilled, and require a special tool.

The present invention therefore provides a valve for the air inlet manifold of an internal combustion engine, comprising a housing having an internal chamber, an air inlet and an air outlet, each communicating with the internal chamber, a valve closure and a valve seat located within the chamber to selectively close the air inlet, the valve seat being a distinct element from the housing and abutting against an internal face of the housing. The fact that the valve seat is a distinct element which abuts against an internal face of the housing allows it to be one seat selected from a plurality of such seats, chosen to fit the already-determined requirements of a specific model of engine. Thus, the time-consuming and difficult step of tuning the device to a particular engine need only be done once, after which the correct dimensions of the valve seat for the specific engine design under test can be determined, and that size of valve seat thereafter used for that engine type.

In W096/34194, the device was made tunable by setting the valve seat in a threaded bore; rotation of the valve seat therefore moved it bodily along the bore. Such movement of the valve seat had the effect of adjusting the degree of bias of the valve closure toward the seat and therefore adjusting the pressure differential at which the valve opened, thereby tuning it to the requirements of a specific engine. According to the present invention, this can be done instead by the simpler step of selecting the valve seat with a correct thickness. The valve of the present invention is therefore suited to the OE manufacturing environment in which assembly time is limited and each individual step is ideally unskilled.

The valve seat is preferably annular and locatable around the air inlet. The valve closure can be biased toward the valve seat, such as by a spring or the like. The valve closure can be of a convex conical shape, and the valve seat of a concave conical shape, to correspond. To provide a valve closure with a sufficiently low mass (and therefore inertia), the valve closure can be of a plastics material. Ideally, the valve seat is also of a plastics material to limit wear on the valve closure. More preferably, the valve seat and the valve closure are each of a different plastics material, to prevent the seat and closure from welding together.

The housing is preferably formed of two parts that are mutually separable. This allows the chamber to be defined by a pair of recesses, each recess being formed in each part of the housing.

The outlet can be a conduit extending into the housing. This provides a convenient location to seat the spring that biases the valve closure. The conduit can then be adjustable relative to the housing, to allow for fine adjustment of the spring bias.

The present invention also relates to a kit of parts for assembly into a valve for the air inlet manifold of an internal combustion engine, comprising the parts necessary to make up a valve as defined above, together with at least one additional valve seat having a different dimension to the first valve seat. Such a kit can be applied to a plurality of engines by selecting the appropriate valve seat.

Alternatively, the kit of parts can be defined as comprising at least two housing sections, each having recesses that define an internal chamber when the housing sections are assembled to form a housing, one housing section having an air inlet communicating with the recess of that section, one housing section having an air outlet communicating with the recess of that section, a plurality of valve seats having different dimensions, and a valve closure.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way of example, with reference to the accompanying figures in which;

Figure 1 shows a side view of an embodiment of the invention;

Figure 2 shows a top view of the embodiment of figure 1;

Figure 3 shows a section through the embodiment of figure 1, along line

ΠΙ-ΠΙ;

Figure 4 shows the device of figure 3 in a closed state;

Figure 5 shows the device with an first alternative valve seat in place; and

Figure 6 shows the device with a second alternative valve seat in place. DETAILED DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows a side view and Figure 2 a top view of a valve 1 according to embodiments of the present invention.

The valve 1 comprises primarily two parts: a first part 2, connected to an air outlet 4; and a second part 3, connected to an air inlet 5, In operation, the first and second parts 2, 3 are coupled together to form a housing, and the outlet 4 is connected to an air inlet manifold of a combustion engine (not illustrated).

Both parts comprise external gripping aids 6, 7 and 8, 9 to facilitate rotation of the one part relative to the other by a user and to allow for retention of the device within a suitable clamp. These may be formed from protruding circumferential ridges, as illustrated. However, alternative structures relatively high friction properties will be familiar to those skilled in the art.

To eliminate the requirement of a tuning tool, the outlet tube 4 of the external body is threaded to enable finer settings of spring tension on the internal components. This allows for the device to be fitted as a retro fit with no tuning tool required. The adjustable outlet tube, once set, can be locked by the external lock nut 10. In an alternative embodiment intended purely for OEM use, the first part 2 and the outlet tube 4 could be formed as a single item with no relative movement and the relevant dimensions fixed at the settings required for the intended use of the device.

Figure 3 is a cross-section through the line III— III in Figure 2.

It can be seen that the first and second parts 2, 3 fit together by means of an engagement 12. Each part 2, 3 has a recess which, when the parts are coupled together, communicate to form an internal chamber 13. In one embodiment, the engagement 12 is threaded such that rotation of the first and second parts relative to one another adjusts the axial length of the internal chamber 13 and, ultimately, may disengage the first part 2 from the second part 3. It is preferred, however, for the two parts to be an interference fit and/or to be welded together in an airtight manner and for any adjustment to be achieved via the outlet tub e 4.

The air outlet 4 comprises a conduit fitted within a bore in the first part 2 by means of a screw thread 15 that engages with a corresponding screw thread on the inner face of the bore in the first part 2. Once the longitudinal position of the air outlet 4 is set relative to the first part 2, it can then be fixed in that position using the locking nut 10. This fine adjustment allows the valve 1 to be retrofitted to the air inlet manifolds of existing vehicles, The outlet conduit 4 extends through the first part 2 into communication with the internal chamber 13.

The inner extremity of the outlet conduit 4 has a flared section 17 that is oversized relative to the bore in the first section 2. This prevents the outlet conduit 4 from being unscrewed too far from the first section 2, which prevents third parties from damaging the device or rendering it inoperable through misunderstanding or incorrect adjustment. To fit the outlet conduit 4 in the first place, it can be screwed into the first section 2 from the inside, prior to fitting the first section 2 to the second section 3,

Likewise, the air inlet 5 also comprises a conduit extending through the second part 3 into communication with the internal chamber 13.

At one end of the internal chamber 13, located around the air inlet 5, there is provided a valve seat 18, having a shaped contact surface. A valve closure 14 has a form that is complementary to that of the valve seat contact surface so that, when the two components are engaged with one another, the valve is closed. In the illustrated embodiment, the valve seat 18 is annular and has a concave conical shape. In this embodiment, therefore, the valve closure 14 has a convex conical shape that fits into the recess defined by the valve seat and closes the air inlet. However, those skilled in the art will appreciate that substantially any pair of complementary shapes may be employed, although we prefer the illustrated conical shape for the reasons set out in W096/34194. The valve seat 18 is a separate and distinct component from either of the first and second parts 2, 3. This allows it to be easily replaced for purposes of tuning, to be discussed in greater detail below. It can be fitted into the second section 3 by heating the second section 3 to an elevated temperature, placing the valve seat 18 in place, and allowing the second section 3 to cool and contract around the valve seat 18.

Both the valve seat 18 and the valve closure 14 may be manufactured from plastics and, in one embodiment, from different plastics material.

Plastics material is advantageous in this circumstance because the resultant lower weight of the closure element reduces the inertia of that element and thereby increases the reaction speed. A suitable plastics material for one of the elements is nylon 66, and it is particularly preferred if the seat is formed of this material. However, the use of identical plastics materials for both the seat and closure has been found to result in unacceptably high rates of wear.

A particularly suitable material for the closure element is a PTFE/acetal mixture. The PTFE component is preferably between 90 and 98%, balance acetal. A particularly preferred composition is about 96% PTFE and about 4% acetal. This material is preferred because the PTFE gives an especially low friction surface which increases the reaction speed, whilst the acetal ensures that the element has a sufficient strength.

Such a low friction surface for the valve gives surprisingly better response times. It is thought that this is because it reduces the tendency of the valve closure to "stick" temporarily whilst travelling to the closed position. In extreme circumstances, it is possible for the valve closure to sit in an open position, held in place by friction alone. Such a situation can lead to increased fuel consumption and engine wear,

A biasing member 16 is provided to bias the valve closure 14 towards the valve seat 18, i.e. towards a position in which the valve is closed. For example, in the illustrated embodiment, a coiled spring under compression provides the necessary bias. However, again, a skilled person may think of alternatives without departing from the scope of the present invention.

Usefully, the biasing member 16 may be connected between the air outlet 4, which extends slightly into the internal chamber 13, and the valve closure 14. This allows for self-alignment between the outlet 4, chamber 13, and valve closure/seat. The biasing member 16 is seated on the flared part 17 of the air outlet 4, around a suitably-sized ridge 19. Thus, as the air outlet 4 is adjusted via the screw thread 15, the degree of compression of the spring 16 is adjusted correspondingly. Alternatively, the biasing member may be coupled between the valve closure 14 and the walls of the internal chamber 13 provided by the first part 2.

Figure 3 shows the valve 1 in its rest position. That is, the biasing member 16 forces the valve closure 14 into the valve seat 18, closing the valve and preventing air flowing from the inlet 5 to the outlet 4 and into the manifold.

As previously mentioned, occasionally the air inlet manifold will undergo periods of low pressure (i.e. vacuum) which lead to inefficient fuel burning in the engine, and increased generation of pollutants. The valve 1 according to embodiments of the present invention compensates for these periods of low pressure by allowing a small amount of air into the manifold. Figure 4 shows the valve in its open state, during such a period of low pressure.

The low pressure in the manifold is transferred to the air outlet 4 and the internal chamber 13. The pressure difference between the air inlet 5 and the internal chamber is sufficient to overcome the bias provided by the biasing member 16 and force the valve closure 14 out of the valve seat 18. This creates an opening that allows a small amount of air into the chamber 13, and hence into the air outlet 4 and manifold, from the inlet 5. In a matter of milliseconds, the pressure in the chamber 13 increases and the force provided by the biasing member is sufficient to force the valve closure 14 into its seat 18, closing the valve 1. Thus it is important that the level of bias provided by the biasing member 16 be accurately set for proper operation of the valve 1. If the bias is set too low, the valve 1 will open too easily and too much air will be provided to the manifold. If set too high, the valve 1 will be too difficult to open and insufficient amounts of air will reach the manifold to compensate for the vacuum. In general, the level of bias that is required will vary from engine to engine. Embodiments of the present invention provide several mechanisms for setting the bias of the biasing member.

As previously mentioned, the device can be subjected to a fine adjustment by rotating the air outlet tube 4 within its screw thread 15. Alternatively, the axial length of the internal chamber 13 may be adjusted via a threaded engagement 12 by rotation of the first and second parts 2, 3 relative to one another. By altering the length of the internal chamber 13 in the direction of applied bias, the compression of the spring 16 and so the magnitude of bias can be adjusted. A fine-pitched thread allows commensurate fine adjustment of the bias.

A third mechanism for adjustment is provided by appropriate selection of the valve seat 18. According to embodiments of the present invention, the valve 1 may be provided in a kit of parts, with a plurality of alternative valve seats, each having generally similar circumferential shapes and contact surfaces, but a different thickness in the direction of the applied bias (i.e. in the axial direction of the illustrated embodiment). A relatively thicker or thinner valve seat 18 offsets the valve closure 14 from the end of the chamber and therefore applies relatively greater or weaker bias, respectively.

Figure 5 shows a valve 1 having a relatively thick valve seat 18', and therefore relatively high bias. Thus, this valve may be suitable for combustion engines in which relatively little air should be allowed into the manifold.

Figure 6 shows a valve 1 having a relatively thin valve seat 18", and therefore relatively low bias. Thus, this valve may be suitable for combustion engines in which a relatively large amount of air should be allowed into the manifold.

As the valve seat rests against an Internal face of the housing, its thickness determines the location of the seat face. In the illustrated embodiment, the valve seat rests against the rear face of the housing, but other faces could be used, or an internal ledge within the housing could define a face against which at least part of the valve seat could abut.

Once the bias has been adjusted appropriately, by any combination of the mechanisms described above, the valve 1 may be sealed to prevent later adjustment (i.e. tampering) by users of the engine. For example, in an embodiment where the first and second parts are manufactured from plastics material, ultrasonic welding may be used to join them together and create a solid state weld.

The present invention therefore provides a valve, and a kit of parts for making a valve, for application to the air inlet manifold of a combustion engine. The valve van be retrofitted to existing engines or used in original equipment manufacture. Further, the valve can be set to apply a range of biases and so is suitable for use with many different engines.

It will of course be understood that many variations may be made to the above-described embodiment without departing from the scope of the present invention.