IE43437B1

IE43437B1 - Improvements relating to fluid regulating systems

Info

Publication number: IE43437B1
Application number: IE1475/75A
Authority: IE
Original assignee: Laser Grade Ireland Ltd
Priority date: 1976-01-03
Filing date: 1976-01-03
Publication date: 1981-02-25
Also published as: ES454774A1; DK677A; IE43437L; DE2657604A1; JPS52145623A; ATA944676A; AU2078976A; AT355877B; AU505505B2; FR2337256A1; FR2337256B1; SE7614084L; GB1565706A; SE425871B; CH609789A5; NZ182901A; NL7614126A

Abstract

Pipe (81) leads a liquefied natural gas to the pressure regulator (2). The gas passes through a proportional-flow solenoid valve (3) and arrives at the injection nozzle (4) placed in the air intake of a petrol carburetter (50) above the venturi (5). The solenoid (3a) of the valve (3) is linked to the output of an electronic control assembly (6) on which acts a pressure sensor (7) comprising a diaphragm (9) and an HF coil (10) sensitive to the movement of a stud mounted on the diaphragm (9). Negative pressure in the pipe (11a) measures the requirement of the engine and constitutes a demand signal. Positive pressure in the pipe (11b) measures the flow rate. The combined pressures move the diaphragm (9), which reacts on the control device (6) of the valve (3).

Description

This invention relates to fluid regulating systems for regulating the flow rate of a gaseous fluid along a supply line.

Such systems comprise basically a sensing arrangement for sensing the relationship between an existing flbw rate condition and a demand signal, and a regulating device controlled by an output from said sensing arrangement for regulating flow rate if it departs from a predetermined relationship with the demand signal whereby to restore said predetermined relationship.

The fluid regulating system of the invention is intended to have particular, but not exclusive, application in supplying vaporised hydrocarbon fuel (knoxvn as LPG liquidfied petroleum gas) such as propane, to internal combustion engines.

In this application the demand signal can be caused to manifest itself continuously as a negative fluid pressure related to the engine running condition and throttle setting, for example by use of a venturi in the inlet to the engine upstream of the throttle.

The primary object of the invention is to provide an electro-fluidic regulating system suitable for regulating the supply of LPG to internal combustion engines.

According to one aspect of the invention there is provided a fluid regulating system for regulating the flow rate of a' gaseous fluid along a supply line, said system comprising a pressure detecting and summing arrangement which produces a fluid control pressure as the resultant of summing a first pressure indicative of the existing flow rate along said supply line and a second negative pressure which is indicative of a demanded flow rate, a control chamber in which said fluid control pressure acts in opposition to a bias pressure on a movable control member carrying a proximity device which forms 43497 ,i transducer with ari >·]>>·I r i.r? si-uuor for sunsinq the instantaneous position of said proximity device, whereby an electrical output representative of the instantaneous position of said proximity device is continuously produced and a regulating device arranged to be controlled by said electrical output and to vary the said flow rate whereby to maintain said fluid control pressure for any given demand pressure at a substantially constant value.

According to another aspect of the invention there is provided a fluid regulating system for regulating the flow rate of a gaseous fluid along a supply line, especially for regulating the supply of gaseous fuel to the carburation system of an internal combustion engine, comprising: a) a regulating device connected in the supply line, b) a first feed-back line leading from the supply line and providing a first, positive, pressure indicative of the actual flow rate, c) a second feed-back line connected to a demand detecting device and providing a second, negative, pressure indicative of the demanded flow ratez d) a junction between said first and second feedback lines at which said first and second pressures are summed to provide a resultant fluid control pressure in a third line leading from said junction, and e) a control arrangement having i) a control chamber divided into sub-chambers by a control member in the form of a diaphragm, said third line leading to one of said sub-chambers so that 484®*? said control pressure acts on one side of said diaphragm in opposition to a bias pressure acting on the other side of said diaphragm, and ii) a diaphragm position sensor comprising a proximity device carried by the diaphragm, and an electric sensor whose output controls said regulating device, the electrical output of said electric sensor varying In dependence upon the proximity of said device to it to vary the setting of said regulating device.

Preferably said control member comprises a flexible diaphragm whose elastic rate is substantially constant, so that its deflection from a rest position is proportional to the applied differential pressure across it.

Said proximity device and said electric sensor· may form part of an impedance device, for example an inductive or capacitive device which modulates an alternating current wave-form Ln dependence upon the position of said control member to provide said electrical output. Λ detector circuit would then convert ;he modulated wave-form to an analogue representation.

Alternatively said proximity device and said electric sensor may :omprise an electro-optical device, which operates With DC and >roduces the analogue representation directly. Said analogue representation may then be used to control the energisation of a iolenoid operated proportional flow controller constituting aid regulating device.

In applying the regulating system of the invention to he carburation system of an internal combustion engine using PG in order to regulate the volume flow of LPG, said fluid ontrol pressure can be derived by relating a negative pressure erived from a venturi upstream of a carburettor throttle - 4 43437 positive pressure in the LPG supply line. This can be effected by detecting directly the pressures in the venturi and supply line. Alternatively the supply line may be connected to the carburettor in such manner that the required fluid control pressure is automatically set up in the supply line.

As will be appreciated from the ensuing description, petrol carburation systems can be adapted by a simple conversion for use with LPG using the regulating system of the invention, and where the ability to still operate with petrol as an alternative fuel source is preserved.

The invention will now be further described by way of example with reference to the accompanying drawings, in which:Figure 1 is a schematic diagram of a fluid regulating system in accordance with the invention and as applied to the conversion of a conventional petrol carburettor for use with LPG, Figure 2 is a schematic diagram showing how tlie system of Figure I is applied to the conversion of a compound petrol carburettor for use with LPG, Figure j is a schematic diagram of a fluid regulating system in accordance with the invention as applied to an LPG carburettor, Figure 4, is a schematic diagram of a further fluid regulating system in accordance with the invention, Figure 5 shows a block circuit diagram of the electronic part of the regulating system which is common to the systems of Figures 1 to 4, Figure 6 is an exploded view showing the mechanical design of the regulating system, and Figure 7 is a cross section showing the mechanical - J 434S5? design of the sensing arrangement.

Referring to Figure 1, a supply line 81 is arranged to feed LPG from a storage tank (not shown) to a primary pressure regulator· ?. From the regulator 2 the LPG flows through a proportional flow solenoid valve 3 und into a supply line 1. which has at its outlet an injection nozzle 4 which is positioned in the normal air intake of a petrol type carburettor 50 above the carburettor venturi 5.

The solenoid 3a of the valve 3 is connected to the output of an electronic control unit 6 which in turn is controlled by a control arrangement 7 (see also Figure 7) comprising a control chamber 8, a control member in the form of a low silicone rubber diaphragam 9 mounted in the chamber 8 under slight tension and an electric sensor in the form of a sensing coil 10 which senses the distance from it of the proximity device in the form of a slug 51 mounted at the centre of the diaphragm 9· By use of a low-silicone rubber a constant elasticity, i.e. a constant rate diaphragm, can he provided.

The diaphragm 9 divides the chamber 8 into sub-chambers 8a and 8b. The sub-chamber 8a is vented to atmosphere, thus providing a bias or reference pressure acting on one side of the diaphragm. The chamber 8b is connected to line 11 which contains a damping jet 49 and branches into lines 11a and lib containing jets 52 and 53 which may he of equal or different size. The line Ila leads via a small drilling into the waist of the carburettor venturi 5 and the line lib leads into the gas supply line 1. Thus a negative pressure is created in line 11a related to the negative pressure at the waist of the venturi 5 and a positive pressure is created in line lib related to the pressure in supply line 1. The negative pressure in line 11a is a measure of engine demand since it is dependent upon engine - 6 43437 running condition and the setting of throttle 54 and hence constitutes a demand signal. The positive pressure in line lib is a measure of volume flow in relation to the demand signal. The negative and positive pressures are summed effectively at point A and the resultant pressure is fed via line 11 to subchamber 8b and hence acts on the diaphragm in opposition to the bias pressure in sub-chamber Qa.

Referring now to Figure 2, this shows an adaptation of the system of Figure 1 to a compound carburettor, in which the throttle 56 is fully opened before the throttle 57 is opened. In this case the line 11 has an additional branch 11c leading via a small drilling into the waist of the second venturi 58 and containing a jet 59. Otherwise the system of Figure 2 is the same as that of Figure 1, Referring now to Figure 3, this shows a carburation system designed for use solely with LPG. In this system the supply line 1 leads to the waist of the carburettor venturi 61 and contains a main mixture screw 62 which together with the pressure in line 1 determines the idling mixture.

The line 11 is not branched but leads directly into the supply line 1. Thus a pressure is created in the line 11 which is related to the pressure in line 1 and is therefore indicative of the existing relationship between the demand signal us determined by the negative pressure in the venturi 61 and the volume supply along line 1. Otherwise the system is the same as Figure 1.

Referring to Figure 4 this shows a modification of the system of Figure 1, in that the demand signal is measured in the air inlet to the carburettor upstream of an air cleaner 63 by the provision of a separate venturi 64. Otherwise the system is the same as that of Figure 1. - 7 34 37 Referring now to Figure 5, this shows a block circuit diagram of the control unit 6 and the associated control arrangement 7 and solenoid 3a of valve 3· The sensing coil 10 forms part of an RF oscillator 70 whose output is modulated in dependence upon the spacing of the slug 51 from the coil 10. If the slug is of certain metals this will cause amplitude modulation and if of ferrite will cause frequency modulation since it will vary the inductance of the coil 10 rather than its Q. The output from the RF oscillator is fed to a detector 71 which converts the modulated output from the oscillator 70 to an analogue representation.

The output from the detector 71 is fed to an integrator 72 whose purpose is to provide the necessary integration of the analogue signal to maintain stability of the elctro-fluidic loop of which it forms part. The output of the integrator is fed to a power amplifier 73 for providing the necessary level of energisation for the solenoid coil 3a. The biasing unit 55 is shown controlling the RF oscillator and will thus control the level of modulation for a given spacing of the slug 51 from the coil 10. The bias control 55 is in turn controlled by a temperature control unit 74 so that its applied bias to oscillator 70 is also dependent upon temperature. This is advantageous in very cold starting conditions for the engine.

The regulating system thus comprises an electro-fluidic loop in which the difference between the pressures in the subchambers 8a and 8b is in proportion to the bias setting of bias control 55 and the open loop gain of the electro-fluidic loop. - 8 43437 The engergisation circuit (not shown) of the control unit 6 is for example from the engine battery. A line 76 leads from a contact breaker contact 75 of the engine distributor to an enhancement circuit 77 whose output is fed to the integrator 72. The circuit 77 provides a pulse of short duration to the integrator upon the commencement of pulses from the engine distributor. This short duration pulse in turn causes the output of the integrator effectively to increase the energisation of the solenoid 3a momentarily and therefore increase the gas supply along supply line 1 in the form of a puff of gas at nozzle 4. This is very advantageous for engine starting.

The line 76 from the contact 75 also leads to a disable circuit 78, so that energisation of the solenoid is turned off in the absence of pulses from the engine distributor, thus providing a positive shut down of the LPG supply.

In operation of the regulating system, the open loop gain is very high i.e. for a very small deflection of the diaphragm the change in output from the power amplifier is relatively very large. Hence for any given demand signal the diaphragm will be set in an equilibrium position which is for practical purposes always the same so that the pressure at point A remains constant.

In setting up the regulating system the size of the injection nozzle 4 is selected to have a desired relationship with the cross-sectional area of the waist of the venturi 5 and the size of the jets 52 and 55 are selected to have a predetermined relationship with each other and with the size of the injection nozzle 4 to determine the main air/fuel mixture.

The bias unit 55 is set with the engine idling so that an air/ fuel ratio of the idling mixture is set producing a desired low CO emission exhaust from the engine. It will be appreciated - 9 3437 that this will set the pressure at point A at a certain value.

If the demand signal varies for example by adjustment of the throttle 54, this will cause a variation in the pressure at point A which will cause a change in the differential pressure between chambers 8a and 8b and the diaphragm 9 will move in response to this change. Since the movement is damped hy the damping jet 49, the rate of movement is determined by the change in pressure. The movement of the diaphragm and hence of the slug 51 causes a variation in modulation of the RF output from oscillator 70 and this in turn will cause the integrator 72 to change its state of.charge and thus change the energisation current of solenoid 3a to vary the flow of gas in the sense to return the pressure at A towards its original value. As this original pressure is approached the diaphragm will be returned to almost its original position and the integrator will now hold its new charge value as long as the demand signal remains the same.

Referring now to Figures 6 and 7 these show the mechanical design of the solenoid control valve and the associated control arrangement and control unit. On a main support block 12 is mounted the primary pressure regulator 2 and the proportional flow solenoid valve 3. The sensing coil 10 of the sensing arrangement 7 and the electronic control unit 6 except for the power amplifier 73 form an assembly referenced generally 41. The main support block 12 of necessity incorporates a portion of the gas supply line 1 and of the line 11.

The primary pressure regulator 2 is of substantially conventional construction and comprises a ball valve 13, lo 43437 plunger 16, spring 15 and retaining cap 16. The plunger 14 ia not however, of conventional construction and is provided with seating for 0 ring 17 which instead of having conventional rectangular construction is undercut on its trailing side to 5 allow the 0 ring to move somewhat in the groove thus reducing wear on the 0 ring and the mechanical hysterisis of the plunger 14.

The proportional flow solenoid valve 3 comprises an armature 18 biased by a spring 19 having a cap 20. The armature 18 is housed within a coil 21 wound on former 22.

The assembly Is retained in position by a solenoid base 23, solenoid outer housing 24 and solenoid top 25. The armature is recessed at its lower end to receive a disc-type rubber sealing member 26.

The solenoid base 23 is provided with a pair of threaded holes 27 for engagement with bolts (not shown) which project through holes 28 in the main support block 12.

A chamber 29 is provided in the support block 12 and has inlet port 31. A valve seating 30 surrounds the outlet orifice of the .part 31. The chamber 29 is provided with an outlet port 32. The chamber 29 is fed with LPG from the main gas supply line 81 (Figure 1) which passes through the primary pressure regulator 2 and into the chamber 29 through the port 31. The gas exits into the supply line 1 through the port 32. A set screw not shown is mounted in a threaded hole 35 in the solenoid top 25 and engages the cap 20 for adjustment of the bias spring 19.

The Kintrol arrangement 7 has a cover 36 (see Fig. 7) which clamps the diaphragm 9 around its periphery to the main ll 343? support block 12 over a chamber provided in the block which thus constitutes sub-chamber 8b. The diaphragm 9 is of convoluted shape and is provided with an inner portion'in which is encased a metal washer forming the slug 51· The diaphragm 9 is stretched when it is clamped in position so that it is biased towards a central position. The sensing coil 10 which is of conventional construction is mounted within a casing 39 in the cover 36.

The proportional flow solenoid valve 3 operates as follows. In the unenergised condition of the solenoid the armature is pressed downwardly by the bias spring 19 so that the sealing member 26 engages the seating 30 to close the port 31. When the solenoid is energised from control unit 6 it lifts the armature 18 against the bias spring 19· As the armature 18 lifts, gas passes under the armature 18 from the port 31 and into the chamber 29.

The volume of gas flowing will depend upon the spacing of the armature from the port 31 and this in turn will depend upon the level of energisation of the solenoid.

An electric heater unit 79 is mounted on the support block 12 to provide a source of heat for vaporising LPG from the liquid state.

Claims

1. A fluid regulating system for regulating the flow rate of a gaseous fluid along a supply line, said system comprising a pressure detecting and summing arrangement which produces a fluid control pressure as the resultant of summing a first pressure indicative of the existing flow rate along said supply line and a second negative pressure which is indicative of a demanded flow rate, a control chamber in which said fluid control pressure acts in opposition to a bias pressure on a movable control member carrying a proximity device which forms a transducer with an electric sensor for sensing the instantaneous position of said proximity device, whereby an electrical output representative of the instantaneous position of said proximity device is continuously produced and a regulating device arranged to be controlled by said electrical output and to vary the said flow rate whereby to maintain said fluid control pressure for anygiven demand pressure at a substantially constant value.

2. A fluid regulating system for regulating the flow rate of a gaseous fluid along a supply line, especially for regulating the supply of gaseous fluid to the carburation system of an internal combustion engine, comprising: a) a regulating device connected in the supply line; h) a first feed-back line leading from said supply line and providing a first, positive, pressure indicative of the actual flow rate; c) a second feed-back line connected to a demand detecting device and providing a second, negative, pressure indicative of the demanded flow rate; d) a junction between said first and second feed-back lines at which said first and second pressures are summed to provide a resultant fluid control pressure in a third line leading from said junction; - 13 43437 and (c) a control arrangement having i) a control chamber divided into sub-chambers by a control member in the form of diaphragm, said third line leading to one of said sub-chambers so that said control pressure acts on one side of said diaphragm in opposition to a bias pressure acting on the other side of said diaphragm, and ii) a diaphragm position sensor comprising a proximity device carried by the diaphragm and an electric .sensor whose output controls said regulating device, the electrical output of said electric sensorvarying in dependence upon the proximity of said device to it to vary the setting of said regulating device.

3. A fluid regulating system according to .aim 1 or 2, wherein said regulating device comprises a solenoid >erated proportional flow controller whose electrical energisation ; controlled hy said electrical output.

4. A fluid regulating system according to claim 1, or 3 wherein said bias pressure is at a substantially constant Llue.

5. A fluid regulating system according to-claim 3, lerein said bias pressure is atomospheric pressure.

6. A fluid regulating system according to any receding claim, wherein said control member comprises a flexible .aphragm whose elastic rate is substantially constant.

7. A fluid regulating system according to any eceding claim, wherein said proximity device and said electric 14 43437 sensor form part of an impedance device which is arranged to modulate an alternating current wave-form in dependence upon the position of said control member to provide said electrical output.

8. A fluid regulating system according to claim 7, wherein said impedance device comprises an inductance whose characteristic is varied in dependence upon the proximity of said control member to modulate the alternating wave-form of an R.F. oscillator.

9. A fluid regulating system according to claim 7 or 8, wherein the modulated alternating current waveform is arranged to be fed to a detector to provide an analog output representative of the position of said control member.

10. A fluid regulating system according to claim 9, wherein the output from said detector is arranged to be fed to an integrator.

11. A fluid regulating system according to claim 10, wherein the output from said integrator is arranged to control the output level of a power amplifier whose output is arranged to energise said regulating device.

12. A fluid regulating system according to any of claims 7 to 11, wherein a bias unit is provided whereby for a given position of said control member, the level of modulation of said alternating current wave-form can be adjusted.

13. A fluid regulating system according to claim 1, wherein said transducer comprises an electro-optical device.

14. A regulating system according to any preceding - 15 <3437 claim in combination with the carburation system of an internal combustion engine arranged to be supplied with LPG, said regulating device being arranged to control the flow rate of LPG along a supply line leading into the carburation system and said fluid control pressure being derived by relating a negative pressure derived from a venturi with a positive pressure derived from the supply line.

15. A fluid regulating system according to claim 14, wherein said carburation system has a carburettor which is also suitable for use with petrol, and said supply line for LPG leads to a nozzle in the air intake of the carburettor.

16. A fluid regulating system according to claim 15, wherein a drilling is made in the venturi of the carburettor for detecting the negative pressure in the venturi.

17. A fluid regulating system according to claim 15 wherein said negative pressure is detected in an air supply line upstream of an air cleaner connected to the carburettor and the supply line for LPG leads to a nozzle in the air cleaner.

18. A fluid regulating system according to claims 1 and 14 wherein said supply line for LPG leads to a venturi and said fluid control pressure is derived from the pressure existing at a point in said supply line down-stream of said venturi.

19. A fluid regulating system according to any one of claims 14 to 18, wherein said engine is a spark ignition engine, controlled from a distributor, and wherein an enhancement circuit is provided which at the initiation of distributor pulses is arranged to temporarily modify said electrical output to cause a puff of LPG to be fed into the carburation system.

20. Λ fluid regulating system according to any of claims 14 to 19, wherein said engine is a spark Ignition engine controlled from a distributor, and wherein a disable circuit is provided, which is arranged to shut down 5 said regulating device in the absence of distributor pulses.

21. Λ fluid regulating system substantially as hereinbefore described with reference to Figures 1, 5, 6 and 7 of the accompanying drawings.

22. A fluid regulating system in combination 10 with the carburation system of an internal combustion engine and substantially as hereinbefore described with reference to Figures 1, 5, 6 and 7, or as modified by Figure 2 or Figure 3 or Figure 4 of the accompanying drawings.