GB2187539A

GB2187539A - Constant-pressure device

Info

Publication number: GB2187539A
Application number: GB08704802A
Authority: GB
Inventors: Roberto De Concini
Original assignee: Weber SRL
Current assignee: Weber SRL
Priority date: 1986-03-04
Filing date: 1987-03-02
Publication date: 1987-09-09
Anticipated expiration: 2007-03-02
Also published as: FR2595413A3; FR2595413B3; GB8704802D0; IT207880Z2; IT8653064V0; GB2187539B; DE8703065U1

Abstract

A device for maintaining substantially constant the pressure of a liquid in a hydraulic circuit comprises a chamber 2 inside which the liquid is circulated and which communicates with a drain hole 4; the passage of the liquid through the hole is controlled by member 16 having a substantially flat active surface 17 designed to rest on an annular surface portion 15 coaxial with the hole; the member 16 is thrust against the annular surface portion by a spring 8 acting on a deformable diaphragm 7 constituting a wall of the chamber; a ball 19 is located between the diaphragm and the member 16, which presents a concave surface opposite the active surface 17 designed to constitute a supporting seat for the surface of the ball, so as to enable the member 16 to move in relation to the ball, about any axis through the centre of the ball and so provide for substantially uniform supporting pressure between the active surface 17 and the annular surface portion 15. <IMAGE>

Description

SPECIFICATION Device for maintaining substantially constant the pressure of a liquid in a hydraulic circuit, in particular, a fuel injection system circuit on an internal combustion engine The present invention relates to a device for maintaining substantially constant the pressure of a liquid in a hydraulic circuit, in particular, the fuel circuit of a fuel injection system on an internal combustion engine.

Devices of the aforementioned type substantially comprise a chamber inside which a liquid is circulated, and which communicates with a drain hole the opening of which is controlled by an on-off member having a substantially flat active surface designed to rest on an annular surface portion coaxial with the said hole. The said on-off member is thrust against the said annular surface portion by a spring, which acts on a deformable diaphragm constituting a wall of the said chamber. The on-off member also presents a substantially spherical surface opposite the said active surface and designed to rest on a conical surface formed on an element supporting the on-off member and fitted directly on to the diaphragm.The connection between the spherical surface portion of the on-off member and the conical surface of the seat inside which the on-off member rests allows the said on-off member to oscillate so as to provide for substantially uniform supporting pressure between the active surface of the on-off member and the said annular surface portion.

On other devices, the on-off member consists of a circular disc, one surface of which defines the said active surface, and a ball welded on to the other surface of the disc. In this case also, the surface of the ball rests on a conical surface of the seat formed in the onoff member support, for enabling the on-off member to oscillate, in relation to the said support, about any axis through the centre of the ball.

When the pressure of the liquid circulating inside the chamber on the aforementioned devices exceeds a given value, as determined by the initial setting of the device, the diaphragm is deformed against the action exerted by the spring, and the active surface of the on-off member is detached from the said annular surface portion, so as to allow the liquid to flow out through the drain hole. Devices of the type briefly outlined above present a number of drawbacks.

Firstly, construction of the components on the said devices requires numerous high-pressure operations, which obviously results in fairly high manufacturing cost. In fact, in the case of an on-off member comprising a spherical surface portion, this requires extremely accurate machining, which can only be performed on special machines.

If, on the other hand, the said member is formed by welding a ball on to a metal disc, welding must be performed with extreme care to prevent distortion of the disc, Furthermore, the surface on which the on-off member rests in the supporting member cavity requires highly accurate finishing, and surface treatment for rendering the surface particularly hard.

Such operations are also rendered difficult by virtue of the said surface being inside the cavity on the supporting element. Furthermore, for enabling the said operations and surface treatment to be performed, the various components involved must be manufactured using high-cost materials.

Finally, due to the difficulty involved in performing the aforementioned operations, dimensional and geometrical tolerances may be fairly wide. thus impairing operation of the finished device.

The aim of the present invention is to provide a device of the aforementioned type, but involving none of the aforementioned drawbacks, i.e. a device comprising a small number of components of straightforward design, which may be machined highly accurately, but with no need for special machinery or tooling.

With this aim in view, according to the present invention, there is provided a device for maintaining substantially constant the pressure of a liquid in a hydraulic circuit, in particular, the fuel circuit on a fuel injection system of an internal combustion engine, said device substantially comprising a chamber inside which the said liquid is circulated and which communicates with a drain hole; passage of the said liquid through the said hole being controlled by an on-off member having a substantially flat active surface designed to rest on an annular surface portion coaxial with the said hole; the said on-off member being thrust against the said annular surface portion by a spring acting on a deformable diaphragm constituting a wall of the said chamber; characterised by the fact that it comprises a ball located between the said diaphragm and the said on-off member; the said on-off member presenting a concave surface opposite the said active surface and designed to constitute a supporting seat for the surface of the said ball, so as to enable the saidon-off member to oscillate, in relation to the said ball, about any axis through the centre of the said ball, and so provide for substantially uniform supporting pressure between the said active surface of the said on-off member and the said annular surface portion.

The present invention will be described, by way of example, with reference to the attached drawing, which shows an axial section of the device according to the present invention.

The device according to the present invention is designed for use on a hydraulic circuit, in particular, the fuel circuit of a fuel injection system on an internal combustion engine, for maintaining the pressure of the said fuel at a substantially constant given value.

The said device substantially comprises a body 1 inside which is formed a chamber 2 in which is circulated the liquid in the said circuit; which liquid is supplied by one of pipes 3 and drained through the other.

Chamber 2 communicates with a drain hole 4, in turn, communicating with the hole of an end bush 5. Between body 1 and cover 6, there is gripped a deformable diphragm 7 subjected to the action of a helical spring 8 located between a first plate 9 resting on diaphragm 7 and a second plate 10 secured to the bottom end of a pin 11. Pin 11 is driven inside a corresponding hole on cover 6, and may be adjusted axially in relation to cover 6 for adjusting preloading of spring 8. The chamber formed inside cover 6 communicates with outside atmosphere through a hole 12 formed in pin 11.

Bush 5 presents a substantially flat annular surface portion 15 on which rests an on-off member 16. The said on-off member 16, which is substantially in the form of a disc, presents a substantially flat active surface 17 designed to contact the said annular surface portion 15, and, on the opposite side, a concave, conveniently conical surface8 coaxial with the said disc.

The device also comprises a ball 19 housed inside a cavity 20 on a supporting element 21 secured to deformable diaphragm 7. Cavity 20 may be of any suitable shape for supporting ball 19, and comprise, as shown in the attached drawing for example, a cylindrical surface portion and conical bottom surface portion. Ball 19 may be housed inside the said cavity by simply resting on the said conical bottom surface, or it may be locked inside the cavity, for example, by permanently deforming the edge portions of the cavity itself.

Ball 19 is designed to rest on concave surface 18 of on-off member 16, as shown clearly in the attached drawing, and a helical spring 22 is provided for holding on-off member 16 against ball 19.

The device as described above operates as follows.

Under normal operating conditions of the device, the liquid flows through chamber 2 from one of pipes 3 and out through the other. When, on the other hand, the pressure of the liquid exceeds a given value, as determined by the preload on the spring and the elastic and geometrical characteristics of deformable diapragm 7, the sum of the pressures exerted on diaphragm 7 produces a substantially axial resultant capable of overcoming the preload on spring 8 and, therefore, of deforming diaphragm 7. Consequently, supporting element 21 moves upwards, so as to detach active surface 17 of on-off member 16 from annular surface portion 15 and so allow a given quantity of liquid to flow through drain hole 4. Upon normal pressure being restored inside chamber 2, on-off member 16 is restored by spring 8 to its initial position, thus cutting off the flow of liquid through hole 4.

When restored to the said closed position, on-off member 16 is allowed to oscillate, in relation to ball 19, about any axis through the centre of the said ball, by virtue of the connection between the spherical surface of the ball and the conical surface 18.

The connection between the said surfaces obviously provides for a substantially spherical coupling enabling on-off member 16 to move into the most appropriate position for ensuring substantially uniform supporting pressure between active surface 17 and annular surface portion 15. As a result, the said on-off member also provides for highly efficiently sealing.

Furthermore, during displacement of on-off member 16, spring 22 ensures that is is held permanently against respective ball 19.

The device according to the present invention also presents a highly straightforward structure, as well as component parts of straightforward design, which may be produced to strict machining tolerances. On-off member 16, in fact, presents no more than a pair of opposite surfaces, one flat and the other conical, which may be machined rapidly on standard machines and to a high degree of precision, by virtue of being totally accessible and of very simple design, Furthermore, ball supporting element 21 is also of very simple design, requiring neither precision machining nor the use of high-cost materials. Cavity 20 provided on supporting element 21, and which serves for housing ball 19, requires no precision machining, due to the absence of any movement between the ball and the cavity, which serves solely for supporting the said ball. As shown clearly in the attached drawing, even in the event of the cavity axis not being strictly coaxial with the axis of hole 4 on body 1, this would in no way impair the sealing performance of on-off member 16, which would merely be shifted in the plane of mating surfaces 15 and 17 on which sealing performance depends. Furthermore, as no surface treatment is required on any of the surfaces of supporting element 21, this may be made using iow-cost materials.

Finally, ball 19 is a widely used, low-cost component, with an extremely fine finish and precise machining tolerances.

To those skilled in the art it will be clear that changes may be made to the form and arrangement of the component parts of the device as described and illustrated herein with out, however, departing from the scope of the present invention.

Claims

1) - A device for maintaining substantially constant the pressure of a liquid in a hydraulic circuit, in particular, the fuel circuit on a fuel injection system of an internal combustion engine, said device substantially comprising a chamber inside which the said liquid is circulated and which communicates with a drain hole; passage of the said liquid through the said hole being controlled by an on-off member having a substantially flat active surface designed to rest on an annular surface portion coaxial with the said hole; the said on-off member being thrust against the said annular surface portion by a spring acting on a deformable diaphragm constituting a wall of the said chamber; characterised by the fact that it comprises a ball located between the said diaphragm and the said on-off member; the said on-off member presenting a concave surface opposite the said active surface and designed to constitute a supporting seat for the surface of the said ball, so as to enable the said onoff member to oscillate, in relation to the said ball, about any axis through the centre of the said ball, and so provide for substantially uniform supporting pressure, between the said active surface of the said on-off member and the said annular surface portion.

2) - A device as claimed in Claim 1, characterised by the fact that the said ball is housed in a cavity on a ball supporting element secured to the said deformable diaphragm.

3) - A device as claimed in one of the foregoing Claims, characterised by the fact that the said concave surface is conical.

4) - A device as claimed in one of the foregoing Claims, characterised by the fact that it comprises a second spring acting on the said on-off member and designed to hold the said on-off member against the said ball.

5) - A device as claimed in one of the foregoing Claims, characterised by the fact that the said annular surface portion is formed on a bush fitted into the body of the device.

6) - A device as claimed in one of the foregoing Claims, characterised by the fact that the said ball is locked inside the cavity.

7) - A device as claimed in one of the foregoing claims, characterised by the fact that the said supporting element for the said bail comprises an annular projection secured to the said deformable diaphragm.

8) - A device for maintaining substantially constant the pressure of a liquid in a hydraulic circuit, substantially as described and illustrated herein with reference to the attached drawing.