GB2356020A

GB2356020A - Pressure wave damping device for use in a hydraulic system, eg a fuel injection system

Info

Publication number: GB2356020A
Application number: GB0026410A
Authority: GB
Inventors: Philippe Legrand
Original assignee: Delphi Technologies Inc
Current assignee: Delphi Technologies Inc
Priority date: 1999-11-02
Filing date: 2000-10-27
Publication date: 2001-05-09
Also published as: GB0026410D0; GB9925803D0

Abstract

The pressure wave damping device comprises a first chamber 22, eg a fuel injector needle control chamber, which communicates with a bore or drilling 24 having an enlarged diameter region 24a. An insert member 28 is located in the bore 24, the insert member having a blind bore 30 defining a (Helmholtz) resonance chamber 32 which is sealed by a closure member 26 received in the enlarged diameter portion 24a. The outer surface of the insert member 28 has a helical groove 34 which defines, with bore 24, a restricted passage 36 such that fuel in chamber 22 can flow into resonance chamber 32 only at a low rate. The passage 36 may have a length of about 25mm and a diameter of about 0.5mm. Compared to a conventional straight restricted passage of the same length and diameter, the helical passage 36 of the invention occupies less space and the groove 34 is easier to produce than a narrow drilling.

Description

2356020 DAMPING DEVICE The invention relates to a device for damping

pressure waves in a hydraulic system. In particular, the invention relates to a device for damping pressure waves in a fuel injection system.

Known fuel injection systems commonly comprise a high pressure fuel pump which delivers fuel under high pressure to a plurality of fuel injectors forming part of the injection system. In use, pressure waves can arise within the fuel injectors and other parts of the fuel system which can result in damage being caused to the components thereof.

To overcome this problem, it is known to provide the fuel injection system with a device for damping pressure waves in order to prevent.or reduce the risk of damage being caused to the components of the system. Figure I is a schematic diagram of a part of an injection system including a conventional Helmholtz resonator device for damping pressure waves within a chamber 12 for fuel. The fuel injection system includes a housing 10 within which the chamber 12 is defined, the chamber 12 communicating with a resonance chamber 14 which is defined within the housing 10 by means. of a passage 16. The passage 16 is of relatively long length, typically about 25 nim, and of restricted diameter, typically about 0.5 mm. As pressure waves are able to escape from the chamber 12 to the resonance chamber 14 along the passage 16, any resonance of pressure waves within the chamber 12 will be damped. Within the resonance chamber 14, pressure wave energy is dispersed through the walls of the chamber 14 to the housing 10. By damping pressure waves in this way, the risk of damage being caused to the various components of the fuel injection system is reduced.

Conventional Helmholtz resonator devices of this type are, however, difficult and expensive to manufacture as the passage 16 between the chamber 12 and the resonance chamber 14 must be machined with a small diameter and must have a relatively long length. Furthermore, the housing 10 must be relatively large in order to accommodate the length of the passage 16.

It is an object of the present invention to provide a device for damping pressure waves within a hydraulic system wherein the aforementioned disadvantages are alleviated or removed.

According to a first aspect of the present invention, there is provided a pressure wave damping device for use in a hydraulic system having a first chamber for fluid, the device comprising a bore within which an insert member is received, the insert member and the bore together defining a restricted passage for fluid between the first chamber and a resonance chamber such that, in use, pressure waves within the first chamber are transmitted through the passage to the resonance chamber resulting in damping thereof.

Conveniently, the insert member is provided with a groove or recess which defines, together with the bore within which the insert member is to be received, the restricted passage. For example, the insert member may be provided with a groove or recess of helical form to define a restricted passage of helical form.

The invention provides the advantage that, as the restricted passage is defined by an insert member received within the bore, the need for machining a narrow diameter bore within the device housing is removed. Additionally, by forming an appropriately shaped groove or recess on the outer surface of the insert member, a relatively long restricted passage can be defined with an insert member of only relatively short length. The device therefore occupies a reduced space within the device housing.

The bore is conveniently formed within a housing which may take the form of one or more housing parts.

Conveniently, the insert member may be provided with a further bore, the further bore defming, at least in part, the resonance chamber. This provides the additional advantage that a further reduced,housing space is required to accommodate the device.

Alternatively the resonance chamber may be defined within the housing.

The device may further comprise a closure member for the resonance chamber.

According to a further aspect of the present invention, there is provided an insert member for use in a damping device as herein described, the insert member being provided with a groove on its outer surface which defines, together with the bore within which it is to be received in use, the restricted passage for fluid.

Preferably, the insert member may be provided with a bore, the bore defining, at least in part, the resonance chamber.

According to a further aspect of the present invention, there is provided a fuel injector forming part of a fuel injection system, the fuel injector comprising a damping device as herein described for damping pressure waves within the fuel injector.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which:- Figure 1 is a schematic diagram of a part of a fuel injection system including a conventional Helmholtz resonator device for damping pressure waves within the fuel injection system; Figure 2 is'a schematic diagram of a part of a fuel injection system including a device in accordance with an embodiment of the present invention; and Figure 3 is an enlarged schematic diagram of an insert member forming part of the device in Figure 2.

Referring to Figure 2, there is shown a part of a fuel injection system comprising a housing 20 defining a first chamber 22 for fuel. The housing 20 is provided with a bore or drilling 24, one end of which communicates with the chamber 22, the bore 24 including an enlarged diameter region 24a. The chamber 22 may take the form of a control chamber for fuel, fuel pressure within the control chamber 22 controlling movement of a valve needle of a fuel injector forming part of the injection system. It will be appreciated, however, that the chamber 22 may be arranged anywhere within the fuel injection system or the fuel system for supplying fuel under high pressure to the injection system.

An insert member 28 is located within the bore 24, the insert member 28 itself being provided with a blind bore 30, as indicated by the dashed line, which defines a resonance chamber 32. The bore 30 is sealed, at its end remote from the chamber 22, by a closure member 26 received in the enlarged diameter region 24a of the bore 24 such that the resonance chamber 32 forms a substantially enclosed chamber.

The outer surface of the insert member 28 is provided with a groove or recess 34 of helical form such that, when the insert member 28 is received within the bore 24, the groove 34 defines, together with the bore 24, a restricted passage 36 of helical form. One end of the passage 36 communicates with the chamber 22 and the other end of the passage 36 communicates with the resonance chamber 32 such that, in use, fuel within the chamber 22 is only able to flow through the passage 36 into the resonance chamber 32 at a relatively low rate. Any resonance of pressure waves within the chamber 22 is therefore damped as pressure waves therein can escape through the passage 36 to the resonance chamber 32 where energy is dispersed through the insert member 28 to the housing 20.

As the passage 36 providing communication between the chamber 22 and the resonance chamber 32 is of helical form the passage 36 occupies a reduced space within the housing 20. Furthermore, as the groove 34 is provided on the outer surface of the insert member 28, the groove 34 can be machined more easily than the narrow bore or drilling required in conventional Helmholtz resonator devices. Typically, the groove 34 provided on the insert member 28 is arranged so as to provide a restricted passage 36 having a length of approximately 25 mm and a diameter of approximately 0. 5 mm.

It will be appreciated that the groove 34 provided on the surface of the insert member 28 need not be of helical form but may take the form of any suitable formation providing a restricted passage 36 of sufficient length to achieve adequate damping of pressure waves. For example, the groove 34 may be a substantially linear groove formed along the longitudinal axis of the insert member 28. This also provides a manufacturing advantage as the groove can be easily machined on the outer surface of the insert member 28, although the bore 24 and the insert member 28 will need to be of longer length than in the embodiment shown in Figures 2 and 3.

In a further alternative embodiment of the invention (not shown), the insert member 28 is not provided with the bore 30 and, instead, the end of the passage 36 remote from the chamber 22 communicates with a resonance chamber defined within the housing 20. In this case, the resonance chamber may be completely defined within the housing 20 such that the need for the closure member 26 is removed. Alternatively, a closure member may be used to close the resonance chamber, the resonance chamber being defined, in part, by a recess formed in an end face of the housing 20. This embodiment of the invention does, however, occupy a larger accommodation space within the injection system.

In any of the embodiments described herein, it will be appreciated that the housing 20 may comprise one or more housing parts. It will further be appreciated that the chamber 22 described hereinbefore need not form part of a fuel injection system but may form part of any hydraulic system where it is desirable to damp pressure waves. Thus, the chamber 22 need not be supplied with fuel, in use, but may be supplied with any fluid.

Claims

1. A pressure wave damping device for use in a hydraulic system having a first chamber for fluid, the device comprising a bore within which an insert member is received, the insert member and the bore together defining a restricted passage for fluid between the first chamber and a resonance chamber such that, in use, pressure waves within the first chamber are transmitted through the passage to the resonance chamber resulting in damping thereof.

2. A damping device as claimed in Claim 1, wherein the insert member is provided with a groove or recess which defines, together with the bore within which the insert member is to be received, the restricted passage.

3. A damping device as claimed in Claim 2, wherein the insert member is provided with a groove or recess of helical form to defme a restricted passage of helical form.

4. A damping device as claimed in any of Claims 1 to 3, wherein the bore is formed within a housing.

5. A damping device as claimed in Claim 4, wherein the housing comprises at least one housing part.

6- A damping device as claimed in Claim 4 or Claim 5, wherein the insert member is provided with a further bore, the further bore defining, at least in part, the resonance chamber.

7. A damping device as claimed in Claim 5, wherein the resonance chamber is defined within the housing.

8. A damping device as claimed in any of Claims I to 7, further comprising a closure member for the resonance chamber.

9. An insert member for use in a damping device as claimed in any of Claims I to 8, the insert member being provided with a groove on its outer surface which defines, together with the bore within which it is to be received in use, the restricted passage for fluid.

10. A fuel injector forming part of a ftiel injection system, the fuel injector comprising a damping device as claimed in any of Claims 1 to 8 for damping pressure waves within the fuel injector.

11. A damping device substantially as herein described with reference to the accompanying Figures 2 and 3.

12. An insert member for use in a damping device substantially as herein described with reference to the accompanying Figures 2 and 3.

13. A fuel injector forming part of a fuel injection system, the ftiel injector comprising a damping device substantially as herein described with reference to the accompanying Figures 2 and 3.