Compressor valve arrangement

Details Compressor valve arrangement Compressor valve arrangement

2000-08-11

2003-02-04

Rivell, John (Department: 3753)

Fluid handling

Line condition change responsive valves

Direct response valves

C137S854000, C137S856000, C418S015000

Reexamination Certificate

active

06513544

ABSTRACT:

BACKGROUND OF THE INVENTION
Field of the Invention
The present invention is directed to compressor valve arrangements, and is particularly applicable to gas compressors which are used on or with internal combustion engines. The present invention will in the main be described with respect to compressor discharge valves. It is however to be appreciated that the invention is also applicable to compressor intake valves.
Compressor valves generally control the flow of to and from the compression chamber of a compressor. Compressor valves of the type having a flexible valve member in the form of a valve disc or a series of valve petals are commonly used as intake and discharge valves in small capacity compressors. The single flexible valve disc, flexible valve petals, or any other flexible valve arrangement close off a number of intake or discharge ports in a seat or valve plate of the compressor valve. Compressed gas exits though the discharge ports and is admitted through the intake ports by deflecting the valve member away from the ports.
The periodic deflection of the valve member due to the operation of the compressor causes the valve member to vibrate in different modes. Under certain conditions, the vibration of the valve member can generate a significant amount of noise. For example, where the compressor is a gas compressor for supplying pressurised air to a dual fluid fuel injection system of an internal combustion engine, the discharge valves are often a source of an annoying high pitched “chirping noise” during low speed operation of the compressor. Where the compressor is driven off a crankshaft of the engine, this typically equates to idle and low speed engine operation and as such may be particularly objectionable to the operator.
Where the valve member is a single flexible disc or plate, it has been found that when the member is vibrated in an axi-symmetric mode, it can be idealized as a monopole sound source which is an efficient sound radiator. In this mode of vibration, different elements of the surface of the member vibrate together at least substantially in phase. Therefore, the pressure waves produced by the different elements of the member reinforce each other as they are in phase. A similar effect occurs where the valve member includes a series of valve petals when the petals vibrate together at least substantially in phase thereby also behaving as an efficient sound radiator. The vibration of the valve member in the above described manner can result in the generation of sound at relatively high levels and at particular frequencies.
The sound produced by the vibration of the valve member is however significantly reduced when, in the case of the flexible disc, the various areas of the disc are vibrating in a non-axi-symmetric mode, with the disc surface separated into areas moving at least substantially out of phase with respect to each other. In this mode of vibration, the valve disc can be idealised as a dipole sound source which is an inefficient sound radiator. This is because the pressure waves produced by the vibration of the various elements of the disc area generally cancel each other out when they are out of phase. A similar effect occurs where the valve member includes a series of valve petals when the petals do not vibrate in phase.
As the noise generated by a vibrating valve member can be particularly annoying to people close to the compressor, and may contribute to increasing the overall noise level of the compressor and/or the machine or engine to which it is operatively connected, it would be advantageous to be able to minimise or eliminate such noise.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to reduce or eliminate noise generated by a compressor valve due to valve member vibration.
With this in mind, according to the present invention, there is provided a compressor valve comprising at least one valve port opening and a flexible valve member located over the at least one valve port for controlling gas flow therethrough, wherein the compressor valve is adapted to cause elements of the valve member to vibrate at least substantially out of phase during operation of the compressor valve.
The elements of the valve member may be constituted by a plurality of individual valve portions which are joined or which together define the valve member. Alternatively, the valve member may be a single structure wherein the elements thereof are constituted by different points of the surface of said structure. Accordingly, where the valve member comprises a plurality of individual valve elements, the compressor valve may be adapted to cause these separate valve elements to vibrate substantially out of phase with respect to each other. Alternatively, where the valve member is a single structure, the compressor valve may be adapted to cause different elements of the surface of said structure to vibrate substantially out of phase with respect to each other.
The out of phase movement of the valve member may be induced by modifying or controlling the airflow around the vibrating valve member. As one possibility, the nature of the forcing air which acts to urge the valve member off its seat may be modified by way of the design and configuration of the ports and any associated passages which deliver air to the valve member. As an alternative possibility, the nature of the cushioning air or effect which acts on the other side of the valve member may be modified in a manner which results in the elements of the valve member vibrating at least substantially out of phase with respect to each other.
In yet a further alternative possibility, the physical characteristics of the valve member or the means by which it is operatively retained could be selected such as to induce the out of phase vibration of elements of the valve member. Such characteristics may include the shape, construction and/or properties of the valve member.
For example, the valve member may comprise elements of varying stiffness such that the elements of the valve member vibrate with different phases with respect to each other during operation of the compressor valve. Alternatively, separate means may be provided to vary the stiffness distribution in different elements of the valve member.
Alternatively, the valve member may be mounted in a manner so as to limit the movement of some of the elements of the valve member such that they are forced to vibrate at least substantially out of phase with respect to one another by virtue of the air flow through the compressor valve.
It is also envisaged that the compressor valve may include a combination of the above described features to induce phase difference in the vibration of the elements of the valve member. Hence, the compressor valve arrangement is effectively preventing the occurrence of the modes of vibration which are efficient at radiating sound and/or supporting those modes of vibration which are inefficient at radiating sound and which will hence promote sound cancellation and the elimination or reduction of noise generation.
Conveniently, the valve member may be in the form of a single flexible disc or any other planer element, such as a rectangular plate. Alternatively, the valve member may comprise a plurality of valve petals. The compressor valve may be of the type where the valve member is located in a gap provided between a valve seat or valve plate and a guide member.
According to a preferred embodiment of the present invention, the compressor valve may include a flexible valve disc, a valve seat, and a guide member, the valve disc being supported at a central portion thereof within a gap provided between the valve seat and the guide member, the valve seat having at least one port extending therethrough, the valve disc closing off the at least one port, wherein the at least one port is located relative to areas of the disc such that the areas of the valve disc are adapted to vibrate at least substantially out of phase with respect to each other during operation of the compressor valve.
A single port may be located

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