WO1998027412A1

WO1998027412A1 - A pressure sensor inlet adapter

Info

Publication number: WO1998027412A1
Application number: PCT/GB1997/003464
Authority: WO
Inventors: Stephen Gresty
Original assignee: Genrad Ltd
Current assignee: Teradyne Diagnostic Solutions Ltd
Priority date: 1996-12-19
Filing date: 1997-12-17
Publication date: 1998-06-25
Anticipated expiration: 1999-06-19
Also published as: AU5328398A; GB9626365D0

Abstract

A pressure sensor inlet adapter comprises a body provided with an inlet bore and an outlet bore with a constriction between the two.

Description

A PRESSURE SENSOR INLET ADAPTER

The present invention relates to a pressure sensor inlet adapter for use in connecting a source of variable pressure to a pressure sensor. Particularly, but not exclusively, the invention provides an adapter for connecting a pressure transducer to a tube connected to a throttle valve of an internal combustion engine.

It is conventional to monitor the conditions within a internal combustion engine using computer controlled electronic equipment. Such equipment is widely used in fault diagnosis. For instance, many cars and motor cycles have fuel supply systems incorporating more than one carburettor or throttle valve. For example, high performance motor cycle engines often have a separate carburettor for each cylinder. To achieve optimum performance it is necessary to balance the pressure at each of the throttle valves/carburettors. It is therefore known to use electronic diagnostic equipment to monitor the pressures produced at the throttle valves of a combustion engine either for initial set up of the engine or as part of a fault diagnosis procedure.

Such known systems essentially comprise a series of pressure transducers each of which is in use connected to a respective throttle valve of an engine. For this purpose each transducer is provided with an inlet nipple onto which a tube can be fitted, the other end of the tube being connected to the throttle valve housing. Pressure at the throttle valve is transmitted through the tube to the transducer, where it is measured and converted into an electronic signal which is then processed appropriately.

A problem with such existing diagnostic systems is that the transducers used are relatively fragile and thus vulnerable to sudden high changes of pressure. This is a particular problem for fault diagnostic equipment since by definition the engine being monitored will be suffering from some form of fault. For instance, a backfiring engine will produce very high pressure surges at the throttle valves which can damage the transducers.

It is an object of the present invention to obviate or mitigate the above disadvantage. According to a first aspect of the present invention there is provided a pressure sensor inlet adapter comprising a body provided with an inlet bore and an outlet bore, wherein there is a constriction between the inlet bore and the outlet bore.

The combination of the constriction and the larger sized outlet bore attenuates shock fronts but does not affect normal pressure measurement. The adapter therefore effectively functions as an acoustic low pass filter preventing large shock fronts from reaching and therefore damaging the pressure sensor.

Preferably at least a portion of the outlet bore has a greater volume per unit length than the inlet bore to thereby define an expansion chamber. This enhances the affect of the adapter.

The adapter is preferably provided with a removable member (preferably fabricated from a resilient material) which seats within the outlet bore and provides means for connecting the adapter to a pressure sensor. For instance, the connecting member may define a bore therethrough to receive the inlet of the pressure sensor.

In preferred embodiments of the invention the adapter further comprising a pressure release valve.

For instance, the pressure release valve may comprise at least one pressure release channel communicating laterally with the inlet bore and/or the outlet bore (preferably the inlet bore only) and opening at an external surface of the body, and a resilient valve member which covers said opening to seal the or each pressure release channel but which deflects to vent the or each channel when the pressure therein exceeds a threshold level.

The resilient valve member may, for instance, comprise a sleeve of resilient material which seats around said body.

According to a second aspect of the present invention there is provided a pressure sensor inlet adapter comprising a body defining a fluid transmission bore and provided with a pressure release valve communicating laterally with the fluid transmission bore.

The pressure release valve may for instance, be of the type discussed above. Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is a side view of a pressure sensor connector according to a preferred embodiment of the present invention;

Fig. 2 is a perspective view of the adapter of Fig. 1 ;

Fig. 3 is a cross section of the adapter of Figs. 1 and 2 taken on the line A-A of Fig. 2; and

Fig. 4 is a cross section of the adapter of Figs. 1 and 2 taken on the line B-B of Fig. 2.

Referring to the drawings, the illustrated pressure sensor inlet adapter comprises a generally cylindrical body 1 having a relatively small diameter inlet end la and a relatively large diameter outlet end lb. Between the inlet end la and the outlet end lb the body is provided with a screw threaded portion lc (adjacent outlet end lb) and an annually recessed portion I d (between screw threaded portion lc and inlet end la).

The body 1 is provided with an axial through-channel comprising an inlet bore 2, a constriction 3 and an outlet bore 4. The diameter of the constriction 3 is substantially less than that of the inlet bore 2 and the diameter of the outlet bore 4 is substantially greater than that of the inlet bore 2.

The opening of the outlet bore 4 is sealed with a rubber connecting plug 5 which is provided with a narrow diameter bore 6 through its centre. The connecting plug 5 both seals the bore 4 and provides means for connecting the adapter to a transducer as mentioned further below.

A pair of diametrically opposed pressure release bores 7 extend from the inlet bore 2 and open to the annually recessed portion 1 d of the body 1. The openings of the bores 7 are covered by a resilient elestomeric sleeve 8 which seats in the annually recessed portion Id. In the illustrated example the sleeve 8 is formed from a transparent elastomer. The bores 7 and sleeve 8 together define a pressure release mechanism as is described in more detail below. The adapter is designed to be fitted to a transducer (not shown) by pushing the outlet end lb onto the inlet of the transducer (not shown) which is received within the bore 6 provided by the plug 5. It will thus be appreciated that the plug 5 is designed to allow simple connection of the adapter to a transducer. In the illustrated example the plug is designed to receive a relatively narrow transducer inlet (or nipple) such as, for example, is provided by the conventional transducer available from Sensor Technics (product serial number- SX15 GD2).

The screw threaded portion lc of the body 1 is provided to enable the adapter to be secured to a housing (not shown) which houses the transducer and associated circuitry, with the inlet end la protruding therefrom.

In use, an appropriate tube (not shown) is connected to a throttle valve to be monitored and to the inlet end la of the adapter body 1 . The inlet end la is provided with tapered portions to facilitate easy and secure fitting of a rubber or similar tube in a conventional manner. Variations in pressure at the throttle valve are then transmitted to the transducer via the tube and adapter. The operation of the transducer and processing of the transducer signal is entirely conventional. However, in contrast to existing systems the adapter according to the present invention provides a means of preventing sudden large increases in pressure from being transmitted to the transducer. The adapter achieves this in two ways.

Firstly, the constriction 3 and large diameter bore 4 (which in effect provides an expansion chamber immediately downstream of the constriction 3) together provide an effective acoustic low pass filter which prevents large shock fronts from reaching the transducer.

Secondly, the bores 7 and sleeve 8 provide a pressure release mechanism to limit the maximum pressure at the inlet side of the constriction 3. That is, if the pressure in the inlet bore exceeds a certain threshold, the resilient sleeve 8 will be deflected away from the openings of bores 7 to vent pressure from the inlet bore la. The threshold pressure level can effectively be pre-determined by appropriate selection of the characteristics of the resilient sleeve 8. It will be appreciated that many modifications could be made to the details of the adapter described above. For instance, the resilient plug 5 could be replaced by a fitting which is a screw fit within the end of the outlet bore 4 rather than a push fit. Similarly, the detail of the plug 5 could be varied as appropriate to facillate connection to different designs of transducer inlet.

In addition, details of the pressure release mechanism could be varied. For instance the bores 7 and sleeve 8 could be replaced with some other conventional form of pressure relief valve.

It will also be appreciated that while it is advantageous for a single adapter to include both a constriction and a pressure release valve this need not necessarily be the case. For instance, an adapter comprising either one of these features will have advantages over the prior art.

It will further be understood that whilst adapters according to the present invention are particularly suited for connection to pressure transducers incorporated in diagnostic equipment to measure the variations in pressure at the throttle valves/carburettors of a combustion engine, adapters according to the present invention could be used for connection in-line between any pressure sensor and pressure source.

Other possible modifications will be readily apparent to the appropriately skilled person.

Claims

1. A pressure sensor inlet adapter comprising a body provided with an inlet bore and an outlet bore, wherein there is a constriction between the inlet bore and the outlet bore.

2. An adapter according to claim 1, wherein at least a portion of the outlet bore has a greater volume per unit length than the inlet bore to thereby define an expansion chamber.

3. An adapter according to claim 2, wherein said expansion chamber is immediately downstream of said constriction.

4. An adapter according to any preceding claim, wherein the adapter is provided with a removable member which seats within the outlet bore and provides means for connecting the adapter to a pressure sensor.

5. An adapter according to claim 4, wherein said connecting member defines a bore therethrough to receive the inlet of the pressure sensor.

6. An adapter according to claim 4 or claim 5, wherein said connecting member is received within said expansion chamber.

7. An adapter according to anyone of claims 4 to 6, wherein said connecting member is fabricated from a resilient material which is a push fit within the outlet bore and forms a gas tight seal with the wall of the outlet bore.

8. An adapter according to any preceding claim, further comprising a pressure release valve.

9. An adapter according to claim 8, wherein said pressure release valve comprises at least one pressure release channel communicating laterally with the inlet bore and/or the outlet bore and opening at an external surface of the body, and a resilient valve member which covers said opening to seal the or each pressure release channel but which deflects to vent the or each channel when the pressure therein exceeds a threshold level.

10. An adapter according to claim 9, wherein said resilient valve member comprises a sleeve of resilient material which seats around said body.

11. An adapter according to claim 9 or claim 10 wherein the or each pressure release channel extends from the inlet bore.

12. A pressure sensor inlet adapter comprising a body defining a fluid transmission bore and provided with a pressure release valve communicating laterally with the fluid transmission bore.

13. An adapter according to claim 12. comprising a pressure release valve as defined in claim 9 or claim 10.

14. A pressure sensor inlet adapter, substantially as hereinbefore described, with reference to the accompanying drawings.